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Biomedical subjects

P Nathan

Publications and source records attributed to P Nathan.

At least 73 records · Page 4Linked to original sources
PubMed1976

Proteolytic enzyme activity in the granulation tissue of the human burn wound.

A procedure for adsorbing enzymes from the human burn wound onto solid sheets of substrate is described. Using this technique, low levels of enzyme activity with chymotrypsin-like specificity can be demonstrated in the wound approximately 2 weeks after injury. This activity disappears at about 5 weeks after the burn. The enzyme activity corresponds with the clinical experience for the time course of natural loss of the burn eschar. A trypsin-like enzyme of very low level activity is present in the wound. No collagenase was detected in the human burn wound. Preliminary evidence shows an additional leucine-specific enzyme in the human burn wound. A more detailed analysis of enzymes in the human burn wound should permit the development of a useful artificial debriding agent. Presently these preparations must be used with caution.

Adolescent↗
PubMed1976

Burn wounds: selection and preservation of skin, natural products, blood, and blood products for burn therapy.

Skin allografts and xenografts are routinely used as dressings to control infection, pain and fluid loss from the burn wound. The procedure for preparing and storing grafts will be reviewed and suggested indications for use will be considered. A method for preparing porcine xenograft will be discussed in some detail. Skin banking by low temperature preservation including conditions and processing necessary for obtaining viable grafts will be discussed. The use of tissue typing matching procedures for obtaining prolonged survival will be considered. Possible harmful effects of grafts will be reviewed. The use of blood and blood products for resuscitation of burn patients is of primary importance in burn patients. The literature will be reviewed concerning a variety of blood and blood products including a consideration of washed cells, single donoplasma, serum albumin and purified blood components for treatment of burned patients. The use and indications for hyper-immune serum and gammu-globulin will be considered. Coagulopathy syndromes, burn wound sepsis, and support of immunologically deficient patients will be discussed on the basis of current literature.

Adolescent↗
PubMed1976

A new biomaterial for the control of infection in the burn wound.

A synthetic dressing has been developed that isolates the burn wound to protect patients from microbial contamination. This dressing is unique as it is formed from a 2-component system directly on the wound, leaving no voids for microbial proliferation. The synthetic cover, HYDRON Burn Dressing, adheres to the entire wound surface so that additional dressings are not required. It is sufficiently flexible to permit patient mobility. The components used to form the dressing are an ultra-pure, high molecular weight form of HYDRON, a hydrophilic polymer, poly (2-hydroxyethyl methacrylate) and Polethylene Glycol-400. The dressing is intended to be applied directly to the wound immediately post-burn, prior to sloughing or removal of the eschar, a period in the burn therapy regimen for which satisfactory alternative dressings are not readily available. Decreased frequency of dressing changes compared to conventional procedure provides an additional benefit with a corresponding reduction in pain to the patient. Gross examination of the wounds under the dressing has shown that the healing process proceeds similarly to that of wounds under conventional treatment. There is no evidence of fluid accumulation or maceration or desiccation of the eschar. In our series of 32 patients the barrier dressing formed on the wound has offered a new, effective procedure for treatment of the burn wound.

Acrylic Resins↗
PubMed1975

In situ production of a synthetic barrier dressing for burn wounds in rats.

We describe the in situ production of a burn wound dressing applied to eschar that completely isolates burned tissue from contamination with Pseudomonas aeruginosa. Anesthetized, adult rats were subjected to a scald burn over 10% of their body surfaces. One-half hour later a test dressing presumed to be a barrier to bacterial contamination of the wound was applied to the burned surface. Tannic acid, vaseline, ethyl linoleate, collodion, and polyhydroxethylmethacrylate (PHEMA) were evaluated. Each agent was applied directly to the burned surface. A solid film of the PHEMA was produced on the eschar by addition of solvent and a powdered form of the polymer. The surface of each synthetic dressing was contaminated 30 min after application by the addition of 10(8) P. aeruginosa. Also, a control set of rats was burned and their eschars were directly contaminated without application of the test dressing. Seven days later the contaminated muscle under the burned area in 10 control rats had P. aeruginosa counts of 10(7) to 10(8) per g of muscle (wet weight). Of the materials tested, only PHEMA consistently acted as an effective barrier dressing, reducing bacteria in the muscle to undetectable levels in 11 of 14 tests. It was also possible to treat contaminated eschar through this synthetic dressing by topical application of antibiotics to the barrier surface. The results suggest a novel clinical approach in which a barrier dressing could be used to isolate a burn eschar from environmental and subject contamination until the wound site is ready for grafting.

Acrylic Resins↗
PubMed1974

Methionine accumulation in villi isolated from maturing rat intestine.

1. This study compares the absorption rates of methionine in 15-day-old rats (preweaned) and 30-day-old rats (post-weaned), and the effect of varying initial substrate concentration on the absorption rate of methionine in tissue removed from specific sites in the small intestine.2. The experiments utilize a new in vitro method, the villus technique, permitting evaluation of the mucosal (villus) absorptive cells separated from the relatively non-transporting muscle and connective tissue components (non-villus tissue).3. When the villus technique was used in a comparative age study of absorption by jejunal and duodenal tissue, it was found that at initial methionine concentrations below 1.0 mM, no difference in the transport rate between preweaned and post-weaned animals was observed.4. However, in preweaned animals, methionine transport is faster in the ileum than in the jejunum or duodenum.5. With initial methionine concentration greater than 1.0 mM, duodenal and jejunal villi from preweaned animals transport methionine better than villi from older animals.6. At these higher methionine concentrations there is a slightly better transport by ileal villi from 30-day-old rats than in the younger group.7. With increasing initial concentration of methionine, physiological changes are shown to occur during maturation because transport rates into villi of mature duodenal and jejunal tissues are slower than into similar tissue from preweaned rats.8. The underlying physiological changes responsible for the transport rate differences are not known.9. The results reported indicate that following maturation, the absorbing mucosal cells from the duodenum, jejunum and ileum have an equal capacity for methionine accumulation.10. The apparent localization of the major amino acid transport to the ileum as reported by others may be an artifact reflecting the inclusion of an undetermined amount of non-absorbing muscle mass in the calculation of intestinal transport.

Age Factors↗
PubMed1974

Effect of a synthetic dressing formed on a burn wound in rats: a comparison of allografts, collagen sheets, and polyhydroxyethylmethacrylate in the control of wound infection.

Allograft dressings to control Pseudomonas wound infections in rats were studied on surgical wounds and escharectomized burn wounds. The effects of allografts were compared with a collagen sheet (Aviderm) and a synthetic dressing, polyhydroxyethylmethacrylate (Hydron), formed on the wound by mixing the polymer and the solvent. The results indicated that infections in surgical wounds were more easily controlled by dressings than similar contaminations in burn wounds. A procedure was described for the formation of a synthetic dressing directly on the wound from a mixture of polymer and solvent. This type of preparation completely filled the wound area and sealed the edges, preventing further contamination, and gave excellent coverage of the wound. With 24 h of coverage of escharectomized burn wounds, allografts provided the best dressing for reduction of wound organisms. At 96 h of coverage, Hydron and Aviderm produce significant reductions in the Pseudomonas resident in the burn wound. The results support the thesis that suitable dressings promote local host defense processes which kill the contaminating bacteria.

Acrylates↗
PubMed1973

Control of surface wound infection: skin versus synthetic grafts.

Auto-, iso-, or xenografts of skin and synthetics placed on surface wounds freshly contaminated with Pseudomonas aeruginosa stabilizes the wound bacterial population in rats over a 24-h period. When these wounds contained a bacterial contamination established for 24 h prior to grafting, only skin and the synthetic polyhydroxyethylmethacrylate were effective in lowering the initial bacterial concentration. Polyurethane foam and nylon velour were not effective in the established infection model. Skin placed on a contaminated wound for 2 h or longer appeared to equilibrate with the underlying muscle so that the bacterial count per milligram of skin was similar to that of the muscle. It was suggested that this preparation would be useful to obtain an estimate of surface contamination without biopsy of the infected muscle. Skin grafts in place for 2 h significantly lowered the bacterial count in a wound with an established infection. A second decrease occurred between 4 and 24 h after grafting. Histological studies of contaminated and exposed panniculus muscle showed that leukocytes tend to migrate from the muscle surface to its base. Skin grafts and polyhydroxyethylmethacrylate appear to reverse the white cell migration so that the cells move toward the surface of the muscle with preservation of normal staining characteristics in the muscle. It is suggested that this alteration in cell movement after graft application might modify the white cell function and result in a greater bactericidal activity. Apparently, grafts lower bacterial levels in an established infection by modifying the host response to the surface contamination.

Acrylates↗
PubMed1973

Effect in mice of injection of viable Candida albicans and a cell-free sonic extract on circulating platelets.

The ability of intravenously injected Candida albicans to cause thrombocytopenia and clotting disorders was tested. Mice injected in this manner showed a decrease in circulating platelets and a shortening of clotting time within hours after challenge. Treatment with heparin changed the death distribution pattern, but did not increase overall long-term survival. A cell-free sonic extract prepared from viable C. albicans cells was shown to cause aggregation of platelets in vitro, and injection of the cell-free extract into mice caused a decrease in circulating platelets similar to that observed when viable organisms were injected.

Animals↗
PubMed1972

Infected surface wound: an experimental model and a method for the quantitation of bacteria in infected tissues.

Methods for the quantitation of bacteria in infected tissues must be rigidly standardized to insure uniformity of results. In this communication we report on a laboratory animal model for the study of surface wound infection and the development of a standardized method for the quantitative estimation of bacteria in infected surface wound tissue by mechanical tissue homogenization and serial dilution. Parallel comparative studies demonstrated that a moist-swab sampling procedure detected only 10% of the bacteria recoverable by a surface-wash procedure. Either tissue homogenization or surface-wash procedures recovered significantly more bacteria from contaminated surface wounds than were obtained by surface-swab sampling techniques.

Animals↗