CA1055843A - Non-antigenic, non-thrombogenic infection-resistant grafts from umbilical cord vessels and process for preparing and using same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Flexible segments of mammalian umbilical cord vessels which are non-antigenic and non-thrombogenic are disclosed for use as protheses in mammals. The flexible segments are prepared by separation and removal of principal blood vessels from an umbilical cord, hardening of the blood vessels by means of a reagent, preferably formaldehyde, glutaraldehyde, dialdehyde starch or glyoxal, and shaping of the vessels.

Description

NON-ANTIGENIC, NON-THRO~BOGENIC INFECTION-RESISTANT
I~:RAFTS FROM U~IBILICAL CORD VESSELS AND PROCESS FOR
PREPARING AND USING SAME

A major problem in vascular reconstructive surgery is the provision of blood to organs and tissues the blood vessels of which are inade~uate either as the result of congenital defects or acquired disorders such as trauma, arterial sclerosis or other diseases. Initially, arterial homografts ~human arteries) were used to restore continuity but lirnited supply, inadequate size ranges, development of aneurysms and athero-sclerosis necessitated the search ~or a bet~er substitute.
Artificial grafts of porous and pliable plastic cloth have been made but these suffer from the following problems:
1. Infection in a foreign body graft is catastrophic, often leading to hemorrhage, sepsis and death.

2. The inner lining is throm~ogenic, predispoæed to clotting of the gra~ and distal embolism of the clot.

3. The rigidity of cloth grafts may resul~ in twisting and kinking, especially in areas of crossing a joint.

4. Because of clotting difficulties, smaller caliber artificial grafts are frequently unsuccessful.
Other types o~ grafts which have been testedl with --1-- ?

10 5 5 ~ ~ 3 grea~er or le~ser degrPes of success are bo~ine heterogra~s, collagen tube~ created within the recipient patient, saphenous veins both as autograf~s where the patilent i9 the dGnor and as allografts or h~ografts where another human is the donor.
These variou~ substitutes also give ris~e to problems of unavail-ability9 small size, non-uniform caliber, time required or harve~ting, intraluminal valves, easy twisting leading to occlu~ion and taper in the wrong direction. Thi3 las~ problem is particularly acute where saphenous veins are used since the veins must be reversed as to the direction of flow o~ blood .:
therethrough when substituted for arteries. In view of the difficulties encountered, it is evident that there is pressing need for ~ vascular prosthesis which is free of the problems enumer.ated ab~ve. In addition, it would be highly desirable that such prostheses could be stored and kept .at hand.in a ..
wide var~ety of size~ and shape~ immediately available for use.

SUMMARY OF THE INVENTION
_ TKe human umbilical cord contains structures which may be use~ ~or grafts in the vascular system or other body condults in ~ nals including man. The umbilical cord contains a vein and t~ arteries surrounded by ~arton's Jelly. Both arteries an~ the vein are suitable for use in surgery. Composite 1 0 5 5 ~ 4 3 grafts and patches can be made in various sizes and shapes.
Arteries and veins removed from umbilical cords may be used fresh or as a stored homograft in elther frozen or chemically preserved form. Treatment with antibiotics ~r other means for sterilization may be carried out. Although the antigenicity of these members is low, treatment with enzymes may be carried out to eliminate any antigenic substances.
In general, the cord is somewhat coiled and the artèrles therein are twisted around the veln. Consequently, mechanical or chemical techniques to stralghten out the vein and arteries may be necessary.
In preparation or use of the vein and arteries, Wharton's jelly may be removed either manually or by flushing out wi~h saline solution. A mandrel, which may be shaped, a preferred shape be~ng a taper, ~ay be inserted into the vein after which the vein and the arteries may be dissected readily out of the umbilical cord itself. As aforenoted, the vein and the arteries may be used fresh or frozen. In addition, a tanning treatment as with an aldehyde can be used to stifen the material, one advantage of such tr~eatment being that the tanned member will retain the shape of the mandrel. Glùtaraldehyc e is a preferred tanning agent. Prior to use of the ~anned mem~er, .

1055~

residual traces of glutaraldehyde are removed by trea~ment wi~h appropriate chemical reagents, a preferred reagent being glutamic acid. It has been ound that such treatment with a tanning agert and a reagent to remove residual traces of same yield a product of low antigenicity and thrombogenicity.
The advantages of the umbilical vessels, whether fresh or preserved, for use as a conduit or a patch or rein-forclng member are as follows:
1, Ready availability.
2. High 1exibility with freedom from tendency to kink.
3. Marked strength, particularly in the smaller diameter vessels.
4. Highly smooth, natural inner lining with extremely low clotting tendency.

- 5. Low tendency to become infected.

6. Low antigenicity.

7. Controllable diameter.

8. Size selec~ion available for bo~h large and small vessels.

9, Sufficient length for virtually any use.

10, Adaptability to a wide variety of shapes including both tapers and curves.

11. Compatability with an outer support in ~he form of a mesh for reinforcement of larger vessels , to be used under pulsatile condition

12. Use as a coating Eor promotlng ~he healing of sur~ace trauma such as wounds and burns.

A~cordingly, an object of the present lnvention is an improved material for use as a vascular prosthesis, a rein-forcement for organs in the form of patches, for reinforcement .
of a~asto~ases, and for promoting the healing of surface trauma.
. kno~her object of the present invention is a method o~
emplo!ying the vein and arteries from an umbilical cord in surg~cal procedures.
A.further ob~ect of the present inventioll i8 a method of s~aping ve~ns and arteries rom an umbil~cal cord in preparation for usa in surgical proceduresO ~.
An important object of the present invention is a method of pr.eparing and preserving veins and arteries from umbilical cords, so that they ~ay be stored in readiness for use in surgical procedures.
~ .s~gnificant ob~ect o~ the present Lnvention is a material in the shape of conduits or patches using veins and . arteries fro~ umb~lical cords as the source of same, said mater.~al ~aving low antigenicity. low thro~bogenicity and being highly resistant to in~ection.

~ O 5 S 8 ~ 3 Still other objects and advantages of ~he invention will in par~ be obvious and will in part be aLpparent from ~he specification.
~ he invention accordingly comprlses the scveral steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the ~eatures, properties, and the relat~on of elements, which are exemplified in ~he following detailed disclosure, and the scope of thP
invention will be i~dicated in the claims.

BRIET oEsoRIPrloN OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:
Flg. 1 is a view in perspecti~e of an umbilical cord prior to treatment;
Fig. 2 is a sectional view of an umbilical cord vessel on a cylindrical mandrel;
Fig. 3 is a view in partial section of an umbilical cord vessel pressed against the interior of a mold hydraulically;
Fig. 4 is a sec~ional view of an umbilical cord vessel on a tapered mandrel;
Fig, 5 is a view in perspective of a segment o~ an umbilical cord;

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l~S5~3 Fig. 6 is a side view of a vessel reinforced at a seam by a segment in the shape of a patch;
Fig. 7 is a sectional view of an anastamosis reinfarced by a segment in the form of a strip; and Fig. 8 is a view in perspective of an eyeball wherein the region of attachment of a retina to the interior of an eyeball ~8 reinforced by an eye sling, the sling being formed af an umbiliral eord vessel in ac~ordance with ~he present invention, DESCRIPTION OF THE PREFERRED EMBODIMENTS
. __ . The following example illustrates the t~chnique of vascular surgical interposition of an u~bilical cord vessel derived ~rom the human into the abdominal aorta of an animal.
The animal, in ~his case a baboon, was prepared under general anesthesia and sterile conditions for making an abdominal incision The baboon was prepared and shaved and a longitudinal incision was made in the midline of the abdomen. The incision extended ro~ the xythoid to the pubic area and was carried down through the midline and into the peritoneal cavity, Bleeding vessels were clamped and ligated with 3-0 polyglycollic acid sutures.
The peritoneal cavity was entered and the viscera and bowel were explored for any other dis~ases. ~he animal was found to be n 1. m e bowel and viscera were walled off with cloth pads _7_ . ' ~ .

. , , ' ~ ~ S ~ ~ 3 and re~ra tors. The peritoneum overlying the aorta was inclsed and the aorta immobilized by sharp and blunt dissectlon. Lumbar arteries were individually clamped and liga~ed with 3-0 silk suture so that the segment o abdomirlal ~orta extend~ng fro~
the infra-renal arteries to the bifurcat:ion of the aorta was immobilized. The entire segmen~ of abdominal aorta was thus made available for transplant of the umbilical cord. Dur~ng preparation o~ the abdominal aorta of the baboon, another investigator had taken the umbilical cord o an infant (human) that had been born two hours prior to the 5urgical intervention of the baboon. Th~ cord had been delivered and taken in it9 entirety and transported in sterile saline solution, packed in ice The purpose of freezing the umbilical cord in ice was ~o prevent any further decomposition of the cord structure. The cordg prior to insertion, was washed and irrigated numerous times with sterile Collins solutlon with antibiotics, in this particuLar lnstance, 1% cephalosporln solution and 25,000 units of bacitracin per liter of solution. The blood was thoroughly washed out from within the vessels of the cord and the cord was also irrigated wi~h a 1% heparin anticoagulant solution. Follow~ng this thorough cleansing of ~he cord, one end of the um~ilical vein wi~in the cord which was to be used as the transpl ~ was clamped . , .
_~_' ~' lOS51~143 with a clamp and ~hrough the other end a red rubber catheter, No~ 1~ French, was introduced and the vein was distended. At this point a suitable segment of umbilical graft, approx~mately 5 centimeters in length, was selected for excision. A mandrel was placed in the vein and the remainder of the cord was CUt away.
This segment o~ ~in was then s~erilely handled and placed into the operating fiel~. At this point the animal was heparinized with 2,500 units of aqueous heparin given in~ravenously. The abdominal aorta was then clamped proximally and distally to the segment to be resected. A segment o~ approximately 3 centimeters in ~ength was resected rom the abdominal aorta and an end-to-end anastomosis was performed between host aorta and donor umbilical vein, first using continuous 6-0 prolene suture which is a nylon monof~lament suture. The distal anasto~os~s was then performed following flushing of the aorta to r~d it of any ~lot material and debris. Following completion of anastomosis t~e distal and then the proximal clamps were removed. It was noted that there was no bleeding between the inte~stices of the sutures, which is unusual, and is ~elt ~o be du~ to the streng~h and self-sealing gelatinous quali~ies of t~e cord str~c~ure. Excellent pulses were noted to be presen~ in the gr~ft as well as the distal iliac vessels. The . ~.
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~l~S5`~343 area was lavaged with saline and suctionecl. The retroperitoneum was closed with interrupted 3-0 pol~cJlycollic acid sutures ancl the vis-cera was replaced. The animal, -throughout the procedure thus far, was stable; the respiration and vital SigtlS were normal. The ab-dominal wall was then closed in layers using continuous 0 silk for j' the posterior fascia and peritoneum and interrupted 2-0 silk sutures for the anterior fascia. The skin was approxlmated with continuous 3-0 nylon suture. The anesthesia used in this procedure was nembu-tal. The blood loss estimated during the procedure was approximate-ly 50 to 75 cc. The animal tolerated the procedure well and awokewithin 30 minutes. Postoperatively on the following day the animal was sitting and walking in its cage, and on the third postoperative day was eating its regular diet and was allowed out of its cagé to roam around and climb up and down the walls, and appeared to be in excellent health. The legs were warm and pulses were intact in the extremities.
A number of procedures will become apparent to those s~illed in the art. If desired or necessary, the vein or artery of the umbilical cord may be split longitudinally and formed into com-posites of larger diameter. The umbilical cord vessel or a portionthereof whether tanned or fresh may be used to reinforce, support or seal a weakened area or defect of any body structure, such as the heart, the heart valves or urinary bladder, or to cover a surface trauma to promote healing thereuncler. Such procedures are included . . . . . .. . .

:~5~ 3 within the scope of the claims.
Before removal ~rom the umbilical cord, the vessels, especially the vein, appear to be almost closed and quite small as can be seen in Fig. 1 which is a perspec-tive view in enlarged scale of a portion of an umbilical cord. The umbilical cord vein carries the reference numeral 11 and -the arteries the reference numeral 12.
These vessels are surrounded by Wharton's jel;Ly, as aforenoted.
Moreover, the arteries 12 are twis-ted and coiled about vein 11 and also contain the valves of Hoboken. These are some of the factors which have made it unobvious to use these vessels as tubular grafts. Mention has already been made of the fact that the insertion of a mandrel into the vein 11 facilitates the removal of the remainder of the umbilical cord. However, arteries 12 can also be carefully ciissected from the umbilical cord and mounted upon mandrels. When this is done and they are properly tanned, the valves of Hoboken are eli.minated and vessels smaller than 1 mm in inside diameter can readily be prepared and permanently shaped by the use of appropriate tanni.ny solution. The umbilical cord vein is substantially larger than the arteries and can be stretched on a mandrel so that vessels as large as 1 cm in inside diameter can be prepared. Such vessels can, of course, be cut open and laid out flat in which condition they are suitable as ~L~S~i~343 patches for reinforcement of organs, for supplementation of anastomoses and Eor coverings OVeL surface trauma.
After dissecting out the desired vessel or vessels and clearing of resldual blood, they are irrigated for several minutes with a hardening agent, preferably 3 - 10 minutes. This step effects partial elimination of Hoboken's valves from the arteries. The hardening agent found mos-t suitable is the class of aldehydes. Examples are formaldehyde, glyoxal, dialdehyde starch and glutaraldehyde, with glutaraldehyde being the best from the standpoints of elimination of any traces of an-tigenicity and thrombogenicity and convenience, with a solution of dialdehyde starch being next best. The concentra-tion of the glutaraldehyde solution should be between about 0.15~ and 0.7~. The concentration of dialdehyde starch should be between about 0.5 and 2.0~ by weight. At lower concentrations the glutaraldehyde solut:ion does not render the material non-antigenic, while at higher concentra-tions the reaction is too rapid and embrittles the wall of the vessel.
After irrigating a vessel with a hardening solution, the vessel is slipped onto a mandrel of appropriate shape. The vessel on the mandrel is then placed in a tank (not shown) of hardening solution for about 15 to ~5 minutes, during which time the vessel conforms to the shape of the manclrel. A preferred ~ ~ S 5 ~ 4 3 solution for hardening the vessel is 0.5% glutaraldehyde buffered with 1% sodium bicarbonate so lthat ~he pH of the solution is between 7.5 and 8.5. The hardening agent causes the vessel to conorm to the shapP of the mandrel and also increases the strength of the vessel material, A vein 11 i8 shown on a cylindrical mandrel 15 in Fig. 2.
Another means of shaping a vessel is shown in Fig. 3 in which a vein 11 is inserted in a tubular mold 18, end 19 of vein 11 being closed with stopper 21. The other end 22 of vein 11 is connected to hose 23 ~or introduction of harden-ing solution 16 under moderate pressure, The pres~ure o~ the hardening solution 16 forces vein 11 against the interior of mo~d 18 to con~orm to said interior. This process results in a vessel having a smoothed exterior.
The practice of shrinking a vein or artery onto a cylindrical mandrel 15 as in Fig. 2 or a tapered mandrel 25 as in Fig. 4 has the advantage that any internal `
irregularities such as the valves of Hoboken are eliminated, the reference numeral 24 indicating a vessel segment where the vessel may be either a vein or an artery. Ar~eries of 11 diameter a e particula-ly valuable for replacement

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~ ',' ' ' ~. ~
, 5 ~ ~ 3 of ~lood vessels in the body. In this context, the umbilical l~ cords of the larger mammals, while not so readily available as those of humans, contain larger vessels so that larger and thicker-walled vessels and patches become available throu~h use ~'of vessels from such sources. Also, the small mammals provide vessels of smaller diameter, such vessels being needed for ~pecialized applications such as in fingers and toes.
It should be noted that for use o~ segments treated in accordance with the present invention in pulsatile blood vessels smaller than abou~ 2 mm internal diameter, rein-~orcement with artiflcial mesh Ls unnecessary. This follows not only from the fact that tubes of smaller diameter can wi~hstand higher pressure, in genPral, but from the fact that in collapsing the vessels, the wall thickness is increased. Soaking the vessel ¦
~in alcohol prior to the aldehyde treatmen~ results in a stiffer ~'vessel. ' j ' After hardening the vessel, it is rinsed to remove most of the hardener. A 1% solution of NaHC03 may be used. It is then desirable to tre~t the vessel or segment for a period of 30 - 45 minutes wi~h a reagent which reacts with residual aldehyde.
'Suitable materials are amino acids, alkali salts thereof and oxidizing agents in dilute ~orm such as peroxides, peracids and hypcchlorites. The amino acids as sodium salts, and preferably of 'L-sodium glutamate, L-sodium alanine 9 L-sodium phenylalanine and L-cyst'eine are partîcularly sui~able for this purpose l ;

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, ~ 1055843 because they are antitllrombogenic, the best of the above being the glutamate. The mechanism is believed to depend on condensation of the amine group of the a~inoacid with the carbonyl group of aldehydes. This leave~ the carboxyl group of the condensate free to ionize and impart a negative charge to the surface of the vessel. Negatively charged surfaces are known to be antithrombogenic.
Although the preferred method of storage subsequent to hardening and shaplng of the vessel is in a dllute solution of aldehyde, it is advantageous to treat the vesseL with an amino-acid ater hardening to eliminate aldehyde as lndicate~.
A suitable method of storage of tanned vessel segments is in a dilute solution of aldehyde, 0,5% glutaraldehyde being preferred. Some further hardening of the segment takes place over a period of 4 - 6 days. However, the extent of hardening during s~orage is small and can readily be compensated for in the principal hardening stage.
In preparation or implantation, after storage, the segmen~ is rinsed, as in sterile saline or 1% NaHC03 solution, It is preferably treated again wi~h sodium L-glutamate or one of the other aforenoted co~pounds to eliminate residual aldehyde.

105584;3 An alterna~e method of storage is in a solution of 40 - 50~/O aqueous alcohol containing about 1% of propylene oxide.
Treatment of segments stored by this method wIth reagent to remove aldehyde is, of course, unnecessary.
As will be recognized, a substantlal number of variations on the procedures outlined above are Eeasible Thus, after flushing out the vein in the umbilical cord, a mandrel, either tapered or straight, may be inserted into the vein, the cord frozen, ~he mandrel placed in a chuck and all elements other than the vein cut away on a lathe In the process, the exterior of the vein may be cut 80 that the wall thickness becomes uniform or, tapered, if so desired As would be expected, the vessel or segment must be rendered sterile after subjection to such manipulation. Conventional non-destructive techniques such as radiation, antibio~ics and elevated temperature are used. ~lso, elevation of the temperature up to as high as 60C during ~he tanning reaction increases the rate of tanning. The same technique can be used ¦for removal of residual traces of tannlng agent.
~ nother ~ariation ls to slit the vein open and lay ~t out flat. The use of a flat mandrel facilitates the formation Qf 1at segments. The vessel may then be cut into !

isegments ~0 of any desired size as shown in Fig. 5, such ~segments to be ysed as reinforcements or patches. One use of such a patch is shown in Fig. 6 wherein a vessel 26, which may llbe a portion of a bowel which has been sewn together to form lla seam 27, using sutures 28. This repair of the vessel 26 can ,be reinforced by placing a segment 29 as a patch over seam 27 I!and suturing the patch over vessel 26.
li The function of such a patch is greater than mere reinforcement. As is well known, in stitching together j portions of walls of o~gans in the body, it is necessary that 'the sutures not be pulled too tight and ~hat the stitches not be too close, else the blood supply to the wall of the organ may be cut off in which case gangrene may supervene. As a result, ~using standard techniques, there may be leakage through the , suture line in the wall. It is for this reason that drains are so commonly used. Reinforcing the seam with a patch as shown in Fig. 6, greatly decreases i~ not completely eliminates this danger. -- Another version o~ the use of a segment prepared in accordance with the present invention is shown in Fig. 7 which represents an anastamosis in a bowel 31. In accordance with the usual surgical procedure, the two ends 32 and 33 of bowel 31 are turned inward and the ends are then sewn together with suture 34. A segment 36 is then sèwn around '~

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the join between bowel ends 32 and 33, thereby eliminating or greatly reducing the danger of seepage of bowel contents into the abdomen. Needless to say, although Fig. 7 shows only a single turn of segment about the bowel, two or more turns about the bowel could also be taken.
A plurality of segments may be used in certain applications such as for lining the pericardium o~ ~he heart, or a heart valve, or for covering an arti~icial implant such as a pacemaker. Segments may also be used in plastic surgery as an inert reconqtructive material, Although the tensile strength of a hardened vessel is only moderate, it has other characteristics which make it highly desirable for use surgically. These are the afdrenoted non-antigenicity and non-thron~ogenlcity as well as characteristic flexibility, slipperyness and complete compatibllity with body organs and ves~els.
There i8 a wide variety of surgical procedures in wh~ch cord segments can be used to great advantage. It .

~3 Ihas already been mentioned that a segment can be used to reinforce a seam and an anastamosis.' ]:t can also be used to reinforce a weak portion or a defect in the wall of an organ ¦suc~ as an urinary bladder. A segment can be shaped to form an artificial conduit between the urinary,bladder and the skin.
A most important use is as a retinal eye sling, The need for a sling arises in the surgical procedure for repairing a detached !¦retina. The way in which an eye sling- is used is shown in Fig. 8¦
wherein the reference numeral 47 generally indicates an eyeball.
The pupil 48 of the'eyeball 47 i8 shown and the area where a repair llas been e~fected surgically is shown at 49. Th~ region of repair mus~ be held under pressure until the retLna attaches itself permanently to the eyeball. For this purpose a sling 51 !
is wrapped around the eyeball so that the eyeball is compressed aga~nst the retlna in the ;nterior thereof. This generally requires that the internal pressure in the eyeball be increased by about 30 mm of mercury.
Up to ~he present time retinal eye slings have been made ~ silicone plastic or fascia lata. The Eormer . . .
~' can erode the eyeball and precipitate infection. Consequently, a certain fraction ,of such procedures fail andp in suc~ cases, ' blindness can result. Use of fascia lata, on the other hand, I necessitates a prior operation in order to obtain the material.
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loSS~3 ' I
Substitution of a segment prepared in accordance with the present invention eliminates these diE~iculties. The material is completely compatiblP with the body and has no tendency to erode the eyeball.
Another important use for patches derived from umbilical cord vessels is in connection with skin grafting.
a patch can be placed in position ovar a burned or tra~atized area, even in the presence o infection. In many cases even a dressing is not needed. The patch "takes" quickly. Healing, including clearing of underlying inection,proceeds rapidly under the patch and with no need for the usual change oE
surgical dressings. The patch sloughs of~ when healing is sufficiently advanced. Of major importance, these grafts -will persist for several months while healing proceeds.
The use of umbilical cord vessels, whether from humans or from other mammais, as can be seen from the above, presents numerous advan~ages. The supply is virtually unLimlted and the treatment needed for rendering the vessels appropriate for use in surgery is simple. Also, many variations are possible in order to meet specific and varied needs. As a result, steriLe cord vessel segments can be produced in unlimited supply and at relatively low cost. They can be stored indefinitely and in a variety of shapes and ~hicknesses to meet ', .

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virtu~lly any need. Assuming they are stored in dilute glutaral~ehyde solution, they need only be rinsed ln sterile water cr saline solution or dilute NaHC03 preparatory to u~e.
If desired, they can be further rinsed in sodium-L-glutamate to eliminate any residual aldehyde.
In preparation for tanning and shaping, cleansing, rinsing or irrigating solutions may be passed through the vein and arteries of the umbilical cord, solutions which may be employed including water, sterile saline solution, E~inger's lactate solution, hydrogen peroxlde, sodium ~icarbonate solution, alcohol, and transplantation perfusate solutions, Antithrombo-genic agents which may be used to treat the graft include L-sodium glu~amate, L-alanine, L-phenylalanine, L-cysteine and L-lysine. These compounds are also suitable for treating vessel segments after tanning in order to remove residues of the tanning agent.
Wharton's ~elly may be removed mechanically or chemically using hyaluronidase to dissolve the hyaluronic acid which comprises the jelly. Moreover, saline solution -ls also effecti~e for this purpose.
Mandrels used for shaping vessels may be of glass, silicone plastic, stainless steel or any other material inert to the graft vessel and the chemicals used in the process. The mandrel may be straight or curved, solid or hollow, cylindrical or tapered and smooth or rough on its surface, as desir~d.

1 0 5 5~ 4 3 Among aldehydes suitable for tanning agents are glutaraldehyde, dialdehyde starch and formaldehyde, as well anhydrous alcohol, glyoxal and chromic oxide.
In addition to the am~no ~cids listed above for rem~ing residues of aldehyde tanning agents, mild oxidizing agents can also be effecti~e. Examples of such agents are ~ilute hypochlorite solution and dilute peroxide.
Particularly where the larger vessels are to be used, especially those over about 5 mm in inside diameter, it is desirable to reinforce the vessel. In general the vessels are reinforced by the use of an exterior coating o~ a mesh support,. Both polyesters and fluorocarbon plastics can be used, with the polyesters being preferred. ~o~nercially available Mers1ene m~sh having wide interstices (0.5 - 2.0 mm) may be wound around the vessel in order to gi~e the grat added streng~.h and support, the mesh actually embedding itself into the outer watl of the graf~. A pre~erred form o the mesh is a~ a preformed ~leeve. '', &rafts reinforced by mesh can 'be tes~ed for leaks and strength by attaching them to a pulsa~ing machine and passing solu~ion therethrcugh at a pressure of 150 to 300 mm of mercury.
It will thus be seen that the objects set forth above, among ~hose made apparent from the preceding descrip~'ion, are efficiently attained and, since certain changes may be made in carrying out the above process and in ~he article set . .
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orth without departing from the spirit: and scope of the ~nvention, it is intended that all matter contained in the above description and shown in the accompanying drawlngs shall be interpreted as illustrative and not in a limiting sense.
It is al80 to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.

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Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flexible segment of a mammalian umbilical cord vessel for use as a prosthesis in mammals, said segment being in a shapel and hardened state and being non-antigenic and non-thrombogenic.

2. The flexible segment as defined in claim 1 wherein said vessel used as a prosthesis is within said umbilical cord.

3. The flexible segment as defined in claim 1 wherein said segment is tubular in shape and is reinforced by a pliable, plastic cloth mesh around the exterior thereof.

4. A process for preparing a flexible segment of an umbilical cord for use as a prosthesis, comprising the steps of (a) separating and removing at least one of the principal blood vessels from an umbilical cord, (b) hardening said blood vessel by means of a reagent, (c) shaping said vessel.

5. The process as defined in claim 4 wherein said segment is hardened by one of the aldehydes, glutaraldehyde, formaldehyde, dialdehyde starch and glyoxal.

6. The process as defined in claim 4 wherein said segment is hardened by bringing same in contact with a solution of glutaraldehyde at a concentration of from 0.15% to 0.6% by weight for a period of about 15 to 45 minutes.

7. The process as defined in claim 6 further comprising the steps of washing the aldehyde-treated segment with water, saline, or dilute sodium bicarbonate to remove aldehyde and then with a reagent to re-move any residual aldehyde, said reagent being an amino acid, an alkali salt of an amino acid, an amine, a hydroxylamine, a peracid, a peroxide, or a hypochlorite.

8. The process as defined in claim 4 further comprising the step of storing said segment in a sterile sealed container.