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Biomedical subjects

J Smahel

Publications and source records attributed to J Smahel.

At least 19 recordsLinked to original sources
PubMed1991

Viability of skin subjected to deep partial skin thickness thermal damage: experimental studies.

Secondary tissue loss in burn wounds (due to necrosis in the zone of stasis) is interpreted as a sequel of progressive vascular occlusion and dehydration of thermally damaged tissue. In this study on rats, delayed healing represented an additional factor in determining the fate of tissue that had sustained deep partial skin thickness burns. Early revascularization induced by excision and subsequent replantation of the burned skin resulted in survival of a large part of the corium. Replantation reduced the loss of full thickness skin seen in controls left to heal spontaneously to partial loss in treated wounds. The experiments substantiate the theory that deep partial skin thickness thermal damage is at least partly reversible and indicate that with tangential excision of dermal burns a viable part of the corium is sacrificed. This deeper part of the corium can be saved by early excision and replantation.

Animals↗
PubMed1991

Spontaneous anastomosis of transected vessels.

Experiments were performed on rats to establish the capacity for spontaneous repair of transected arteries and veins. The tests were done on the femoral vessels, with transection effected in a number of modifications. Veins proved capable of bridging even a triple transection within 2 weeks. Not a single artery, however, anastomosed. Vascular repair was on the basis of adventitial and perivascular networks. Explanations of arterial incapacity for spontaneous repair can presently be only speculative. The observations add to our knowledge concerning the revascularization of free grafts, and also indicate that in veins, spontaneous anastomosis can be induced by loosely approximating the stumps.

Animals↗
PubMed1989

Experimental implantation of adipose tissue fragments.

The healing of small adipose tissue implants was evaluated in experimental studies on rats. Adipose tissue of approximately 0.5 ml volume was obtained by resection of parauterine fat pads. The tissue was divided into fragments that were 1-3 mm in size and implanted under the dorsal skin. The implantation of adipose tissue in fragments offered no biological advantage and the healing process terminated in extensive necrosis of fat cells. The results are analysed and considered in relation to the implantation of adipose tissue fragments obtained by liposuction.

Adipose Tissue↗
PubMed1988

[Blood supply of free skin flaps].

This article discusses the factors which determine the blood supply of free skin flaps. The method of free transfer consists of three steps, namely, the elevation of the flap, its transfer to the target area with microvascular anastomosis, and the healing of the flap on the recipient site. During the first two steps the flaps meet with a diminished blood supply and, in addition, their tissues undergo a period of ischemia. The flaps are usually able - within certain limits - to tolerate these disturbances of blood circulation. The healing of the flap begins with the proliferation of capillaries in the recipient site, which is stimulated by the relative hypoxia of the transferred tissues. The first capillary links between the recipient site and the flap can usually be observed on the third day after the transfer. On the sixth day after the operation, the anastomoses are quite numerous and can take over the blood supply to the flap. The progress of this dynamic process depends on the functional ability of the anastomosed vascular pedicle. The development of a new blood supply to the flap leads to profound remodelling of its original vascular system and the axial character of the flap is usually lost.

Humans↗
PubMed1988

[Stimulating effect of isolated nerve segments on the regeneration of peripheral nerves].

The present paper concerns observations in two series of experiments in which the effect of isolated nerve segments on nerve regeneration was studied. Bridging of a nerve defect with a tube was used as an experimental model--a model often used in studies on nerve regeneration today. In the first series of experiments performed on rats, 14 mm of the femoral nerve were removed and the gap bridged with the femoral vein. A 2-mm nerve segment was inserted at the center of the vein in one group of the animals. In the second experimental series performed on rabbits, 40-45 mm of the peroneal nerve was resected. Up to three segments were introduced into the lumen of the bridging vein. The experiments demonstrated the promoting effect of nerve segments on nerve regeneration and indicated the probable mode of their action: the nerve segments serve as an additional source of Schwann cells and of neurofibroblasts, contributing substantially to the formation of the guiding structures for the axons. The nerve segments are apparently able to develop a similar nerve structure to that formed by the distal nerve stump. However, this ability also appears to be limited to a distance of 10 mm as is the case with distal nerve stumps. These conclusions do not exclude a possible neurotropic action of the nerve segments.

Animals↗
PubMed1987

Glueing of peripheral nerves with fibrin: experimental studies.

Experiments were carried out on rats to compare fibrin glueing of nerves with suturing. For this purpose, the sciatic nerve was transected and the cut ends were joined, either by glueing with Tissucol or with an epineural suture. Assessment of the two methods was based on clinical and histologic examination and electrophysiologic measurement (latency and amplitude of compound action potentials). Reconstruction with fibrin glue proved to be the simpler method, requiring considerably less time than nerve suture. Separation of the glued nerve stumps did not occur in any instance. The fibrin glue was completely absorbed after a maximum interval of one week following the operation. It had no negative effect on nerve regeneration, which was the same for both groups. The histologic variability found to be characteristic of both glued and sutured nerves reflected differences in the way the nerve repair was effected, rather than in the method used. The electrophysiologic measurements did not show statistically significant differences between the two methods of nerve repair.

Action Potentials↗
PubMed1987

A training model for the stereomicroscopic evaluation of flap survival.

The stereomicroscopic appearance of the vasculature and circulation of groin flaps, with their epigastric pedicles divided at various time intervals, is an early diagnostic indication of flap viability. A simple and comprehensive training model, with characteristic vascular and flow changes within a single flap, is provided in rats, with pedicles transected at three to four days after the flap is raised.

Animals↗
PubMed1986

Stimulation of peripheral nerve regeneration by an isolated nerve segment.

An experimental model in rats was used to assess the stimulant effect of an isolated nerve segment on peripheral nerve regeneration. In a first group of animals, 14 mm of the femoral nerve was removed unilaterally and the gap was bridged with femoral vein taken from the other side. In a second group, the intervention differed in that a 2-mm nerve segment was introduced at the center of the bridging vein. Histological examination was done three months after the operation. In the first group, a newly formed nerve structure was found in the proximal part of the vein, with incipient myelination of nerve fibers. The frequency of nerve fibers decreased with the distance from the proximal nerve stump, with no fibers present in the distal part of the vein. In the second group, a well-developed nerve structure was noted in both the proximal and the distal parts of the bridging vein, with myelination well advanced. Possible reasons for the positive effect of an isolated nerve segment in bridging nerve gaps are discussed.

Animals↗
PubMed1986

Adipose tissue in plastic surgery.

In this article I review the present state of knowledge about adipose tissue as it is relevant to the practical purposes of plastic surgery. Fat cells are normal constituents of loose connective tissue. Large numbers of fat cells organized into lobules are classified as adipose tissue. Adipose tissue is a special form of reticular connective tissue. The lobules are both morphologically and angiologically independent units. They are seen as well-vascularized structures supplied with blood through a pedicle. Severance of the lobule normally results in necrosis. The subcutaneous fat layer derives from the "primitive organs" identifiable in the hypodermis from the fourth fetal month onward. The primitive organs are the basis for individual fat lobules. The development of adipose tissue continues until physical growth is complete. The disposition of the subcutis to develop adipose tissue shows great variation in different regions of the body. The in-situ mechanical resistance of adipose tissue is provided by the supporting structures. The development, structural characteristics, and physiology of adipose tissue can provide an explanation for many of the observations plastic surgeons have made on this tissue. The processes involved in healing, grafting, and reduction of adipose tissue are analyzed and considered in relation to the clinical picture.

Adipose Tissue↗
PubMed1985

New disposable microvascular clamp.

A new design for a plastic microvascular clamp is described. The clamp consists of two flat blades, with eyes permitting application and removal of the clamp with cross-forceps. Closure is effected by the elasticity of a rubber ring placed around the blades, obviating the need for an articular joint or a spring mechanism. The new design simplifies production of the clamp, which is intended to be disposable, i.e., for once-only use.

Animals↗
PubMed1985

[Pathophysiology of the burn wound].

The thermal injury produced by the first, second and third degree burn is defined. The degree of thermal damage is characterised by the zones of coagulation, stasis and hyperaemia. The zone of coagulation is definitely lost and the pathophysiological changes in the zone of hyperaemia are spontaneously reversible. The zone of stasis although not immediately destroyed converts to necrosis during the first week after injury owing to a fatal combination of several factors. The healing of a burn wound proceeds from the zone of hyperaemia and follows the same course as in a surgical wound. Modifications of the healing process are produced by the graded nature of the thermal injury and by the presence of coagulated tissue acting as a foreign body. Attempts to reduce the secondary tissue loss concentrate on the zone of stasis the damage to which is considered as potentially reversible. Therapeutic measures positively influencing the pathophysiological processes in a burn wound are discussed.

Burns↗
PubMed1985

[Morphology and topography of valves of the superficial venous system of the forearm and dorsum of the foot (a microsurgical dissection study using scanning electron microscopy].

Microsurgical dissection technique revealed an astonishingly large number of valves in the superficial venous system of the dorsum of the foot and the palmar aspect of the forearm. The distribution and special positioning of these valves are demonstrated. As a result of the anatomical distribution it seems logical to differentiate between segmental and orificial valves. The superficial venous system of the dorsum of the foot consists of two layers, one of which is in particular suitable as a donor for small vein grafts. The venous arcades are given special consideration.

Adult↗
PubMed1979

Foreign material in the capsules around breast prostheses and the cellular reaction to it.

Thirteen capsules which had formed around breast prostheses were examined, using the technique of splitting the capsule wall. A foreign material in droplet form was present in all the capsules. The foreign material was taken up by phagocytes, and the cytological evidence is that it has cytotoxic activity. It was shown that the material migrates to the vessels in the outer layer of the capsule and may reach the lumen of those vessels. On the basis of the microscopic appearance and the results of infrared spectrum analysis, the foreign material in the capsules was assumed to be silicone.

Breast↗
PubMed1979

Resurfacing denuded areas of the beard with full thickness scalp grafts.

Reconstruction of a beard-bearing area, such as the upper lip, necessitates hair-bearing grafts no thicker than a full thickness skin graft, in order to allow for normal movement. In the normal scalp, however, most of the follicles reach into the subcutaneous fat. By preoperative epilation it seems possible to induce the catagen phase of the hair cycle during which the follicles migrate into the corium and thus will be transplanted as complete morphological units. The clinical results support this concept.

Adolescent↗
PubMed1978

Fibrous reactions in the tissues which surround silicone breast prostheses.

Fibrotic reactions in adipose tissue, in the pectoral muscle and in the mammary gland are described. These were provoked by trauma to those tissues during implantation. Such reactions cause thickening of the capsule around the implant, and may be contributory factors in constrictive fibrosis.

Adipose Tissue↗
PubMed1978

Tissue reactions to breast implants coated with polyurethane.

The histological features noted in the capsules from 7 polyurethane coated silicone breast prostheses are described. The polyurethane provoked a definite foreign body reaction and was slowly degraded, with some particles ejected from the capsule into the surrounding tissues. Separation of the polyurethane coating from the silicone prosthesis and the degradation of the polyurethane took about two years. Another much more resistant foreign material was found to occur in conjunction with the polyurethane in the capsules. It may be an adhesive or flakes off the silicone shell. Vacuolated spaces were noted in the inner layers of 3 capsules; it was assumed that they contained liquid silicone.

Breast↗