Biomedical subjects

J R Wingfield

Publications and source records attributed to J R Wingfield.

5 recordsLinked to original sources

PubMed1979

Development of a reversible vas deferens occlusive device. VI. Long-term evaluation of flexible prosthetic devices.

Fifty-three dogs received implants of several types of flexible devices containing valving mechanisms. These devices were constructed entirely of silicone rubber with the exception of the valve stem, which was made of stainless steel. Generally, the devices were (1) implanted in the open mode and left this way for 27 to 44 months, (2) implanted in the closed mode and kept this way for 11 to 12 months before the valves were reopened, (3) implanted in either the closed or open mode and cycled to the opposite mode every 3 months (four or five cycles), or (4) implanted in either the closed or open mode and cycled to the opposite mode every 6 months (two or three cycles). Different implant methods were also evaluated. Semen analyses were regularly performed on all of the dogs, and a number of the animals were bred during the experiments. It can be concluded that (1) the devices can be opened and closed successfully over long periods, respectively allowing and preventing sperm transport; (2) the breeding ability of the animals is not impaired while the devices are in the open mode, independent of the type of device; (3) the devices do not result in an enhanced incidence of congenital abnormalities in the offspring; and (4) the success rate of device performance does not depend on the method of implanatation used. Thus, the results clearly indicate that the basic mechanism of a soft, reversible valve is a feasible approach to conception control.

Animals↗

PubMed1976

New studies with intravasal devices. The soft valve.

In contrast to the results that were obtained with rigid ended prosthetic devices, effective sperm transport occurred for prolonged periods of time through the IITRI Vas-Valve, which had soft silicone rubber flexible end tubes when implanted in the vasa deferentia of dogs. Such transport could be halted by device occlusion with stainless steel springs or with shuttle stem valves. Opening the devices resulted once more in the passage of spermatozoa as well as the production of offspring, indicating that these devices have the potential for being useful as a human male contraceptive method. More research needs to be performed to determine why there is an over-all decrease in sperm output after device implantation and to evaluate and adverse side effects of such devices. The presence of Dacron velour-covered suture rings on the devices permitted effective tissue ingrowth and prevented leakage or recanalization in all cases.

Animals↗

PubMed1976

A prosthetic vas deferens.

Six dogs were implanted with the synthetic vas deferens device as part of our continuing research into the development of a reversible occlusive device for implant in the transected vas deferens. The experimental objectives were to assess the effects of sperm path length and duration of aspermia on total sperm count and motility by implanting three different lengths of the device in animals with different degrees of aspermic duration induced by bilateral vasectomy. Device lengths varied from 1.55 cm to 4.3 cm including the pilot tubes. The prosthesis is fabricated entirely of silicone rubber with Dacron velour tissue ingrowth material bonded to the outside surface of the ring to which vas ends are sutured. The pilot tubes extend 4 mm beyond the suture rings and are 0.6 mm OD with a 0.3 mm ID that extends through the entire length of the device. The flexible pilot tubes are an important feature of this design and insert into the vas lumen ensuring alignment between the device and the vas deferens while maintaining the necessary resiliency to adapt to the inherent movements of the vas without perforation. All animals included in these experiments were carefully selected and conditioned before implant. The evaluation of performance was based on semen samples collected at one week intervals. Sperm subsequently appeared in the ejaculate of all 6 dogs, demonstrating that the restoration of sperm transport can be restored after bilateral vasectomy through the implantation of a prosthetic vas deferens. The potential application of this device to the human male for the restoration of fertility appears excellent.

Animals↗

PubMed1975

Development of reversible vas deferens occlusive device: IV. Rigid prosthetic devices.

Different types of rigid, reversible, vas deferens occlusive devices were developed and evaluated in 14 unilaterally vasectomized dogs. All prosthetic devices had molded silicone rubber bodies, and rigid inflow and outflow tubes. Various techniques for the removal of the vas luminal epithelium, and for the preparation of porous ceramic and etched stainless steel surfaces to encourage tissue ingrowth into the prosthetic device end tubues were attempted. The devices differed in their methods of achieving occlusion. One device used a "rotary stem valve" which had a C-section rotating mechanism; the others used the "shuttle stem valve" which possessed an occlusive element that moved transverse to the axis of flow in the device, thus occluding the device when the stem was depressed. The rotarystem valve was implanted by means of a longitudinal incision. The remaining 13 shuttle stem devices were placed in the vas using either a longitudinal or a transverse implantation. Inno case was sperm transport through the prosthetic devices obtained for more than a few ejaculations.

Animals↗

PubMed1975

Development of reversible vas deferens occlusive device: V. Flexible prosthetic devices.

In contrast to the results with rigid-ended prosthetic devices implanted in the vas deferens of the dog, effective sperm transport was obtained for prolonged periods of time with flexible-ended (all soft) devices. Such transport could be halted by device occlusion with clips or shuttle stem valves. Opening the devices resulted once again in the passage of spermatozoa, indicating that these devices may be potentially useful as reversible male contraceptives. More research is necessary to determine the cause of an overall decrease in sperm output after device implantations and to evaluate any adverse side effects of such devices. Dacron velour-covered suture rings on the devices permitted effective tissue ingrowth and prevented leakage or recanalization.

Animals↗