Search PubMed⌕ Search

Biomedical subjects

P Nathan

Publications and source records attributed to P Nathan.

At least 55 records · Page 3Linked to original sources
PubMed1980

Anti-HLA specificity determined by serum absorption with antigen-masked lymphocytes.

Lymphocyte or platelet absorption of multispecific sera is frequently used to establish HLA antibody specificity. Absorption of such sera with cells containing the desired antigenic combinations is often limited by the availability and the HLA characteristics of fresh or frozen cell panels. The method described permits improved absorption of specific HLA antibody with a preparation of cells containing a predetermined single HLA antigen. The procedure involves the screening of the patient's active sera against a panel of frozen cells. Analysis of the positive and negative reactions allows tentative assessment of recipient serum specificities. Cells with a single available HLA antigen type are prepared for serum absorption by suspending the cells in selected antisera to block (mask) HLA surface antigens while leaving just one type of antigen free for monospecific absorption. Following absorption of the test serum with the masked cells, the absorbed serum is then retested against the original panel of frozen cells. Should the results of this screen show a loss of a single HLA activity, the suspected specificity is assigned to the recipient's serum. The use of HLA antigen-masked lymphocytes has proven useful in the definition of HLA antibody specificity.

Absorption↗
PubMed1980

Removal of contaminating polymorphonuclear leukocytes to prepare purified lymphocytes for cytotoxicity testing.

Human polymorphonuclear leukocytes (PMN) die, apparently nonspecifically, in the standard tissue typing assay. When the cell preparation contains more than 20% PMN, proper evaluation of the histocompatibility assay is difficult. PMN were noted to aggregate when normal rabbit serum was added as the complement source. Based on the latter observation, a simple technique was developed which reduces the PMN contamination in the suspension of test cells and returns high yields of lymphocytes. Removal of the PMN lowers the high background of dead cells and permits precise evaluation of the microcytotoxicity test results.

Absorption↗
PubMed1980

Delivery of the topical antimicrobial agents silver sulfadiazine, gentamicin and nystatin to infected burn wounds in rats from preloaded synthetic dressings.

1. A synthetic burn dressing made from polyethylene glycol - 400 (PEG) and poly-2-hydroxyethyl methacrylate (PHEMA) can be prepared to contain topical antimicrobial agents. 2. Sheets of these antimicrobial loaded dressings may be applied to the wounds or alternatively, the synthetic dressing incorporating the active drugs may be formed directly on the burn wound from the PEG-PHEMA drug mixture. 3. The antimicrobials (silver sulfadiazine, gentamicin and nystatin) are continuously and effectively released from the solid dressing over 2-11 days.

Animals↗
PubMed1979

Rat thymic dihydrotestosterone receptor: preparation, location and physiochemical properties.

Castration in the male rat has been shown to produce enlargement of the thymus gland while treatment with dihydrotestosterone (DHT) results in a decrease in thymic size in these animals. To determine if these changes might be receptor mediated, thymus tissue from castrate male rats was removed and homogenized in buffer and centrifuged to produce cytosol. By Scatchard plot analysis, it was shown that a specific DHT receptor was present at a concentration of 0.24 +/- 0.02 pmoles/g tissue and it possessed a KA of 2.51 +/- 0.45 x 10(9)M-1. This thymic DHT receptor sedimented on 5--20% sucrose gradients in the 8s region. By competition analysis it was found that testosterone only partially competed (25%) for this receptor, with virtually no binding noted for estradiol, progesterone, and cortisol. The receptor was found to be localized in the reticuloepithelial matrix of the thymus and was not present in the thymic lymphocyte fraction.

Animals↗
PubMed1979

A micromethod for prospectively testing lymphocyte-mediated cytotoxicity (LMC) using fresh or frozen cells labelled with a fluorescent dye.

A direct, specific and rapid method has been developed to prospectively evaluate lymphocyte mediated cytotoxicity (LMC) for kidney transplant recipients. Donor lymphocytes, labeled with fluorescein diacetate, were incubated in a microtest plate for 2 h with recipients' effector cells. The percentage of fluorescent cells in each well was estimated relative to controls using an inverted phase fluorescence microscope. Lymphocytes obtained from seven of 12 recipients post-transplantation exhibited positive reactions, fluorescence of labeled donor cells was reduced to 30-65% of that observed in controls, and these reactive patients required nephrectomies. The responses of the remaining five patients were negative. Tests with their donor cells showed 80-95% control fluorescence, with favorable transplant results. Six of 21 recipients evaluated prospectively required nephrectomies within 34 days post-transplantation. Three of these subjects showed 15-65% control fluorescence, a positive LMC response; the other three yielded negative LMC responses but required nephrectomies possibly due to renal ischemia prior to transplantation. The remaining 15 patients demonstrated 85-90% control fluorescence with graft function continuing for 17 to 270 days. The results from direct LMC tests with a fluorescent label indicate that the system is of value in predicting early rejection of renal allotransplants.

Cytotoxicity Tests, Immunologic↗
PubMed1979

Immune adherence of platelets to sensitized leukocytes: a model of hyperacute rejection.

Specifically hypersensitized recipients of canine renal allotransplants demonstrate an accumulation of host platelets in the transplanted kidney within minutes following implantation. Transplant function is ra,idly lost. The present work describes an in vitro model of this hyperacute rejection mechanism. Renal donor leukocytes sensitized with host serum are incubated with donor platelets. Within a few minutes the platelets adhere to the sensitized leukocytes to form rosettes. Serum complement is required for platelet rosette formation. Platelets act as indicators in this reaction and they may be obtained from any dog. Donor platelets were used to avoid the transfer of specific antibody to the test mixture. The in vitro model supports the view that hyperacute rejection in the dog is a specific example of the immune adherence reaction in which platelets bind to antigen-antibody-complement complexes.

Animals↗
PubMed1978

Effect of exposure to lead on maturation of intestinal iron absorption of rats.

The influence of lead on iron absorption was investigated at various stages of development in rat pups exposed to lead first through mothers' milk and later in their solid diet. Hematocrit, hemoglobin, iron absorption, and tissue iron concentration were measured on d 14, 20, 23, 29, 35, 42, and 63 after birth. Both hematocrit and hemoglobin in the lead-exposed group were significantly below control levels at all periods earlier than d 42 and 63, respectively. Absorption of iron ([59Fe]-ferrous citrate in 10(-4)M FeSO4) from intestinal loops measured over 1/2 h remained at preweaning levels (10-12% of total activity added to the loop) for at least 1 wk after weaning in the lead-exposed rats, whereas in control animals iron absorption fell to adult levels (3-4%) at weaning. Spleen weight was significantly elevated in lead-exposed rats compared with control rats at all ages beyond d 14. However, spleen iron content (micrograms of Fe per gram of tissue) was not significantly elevated in the lead-exposed group before d 42. The results indicate that exposure to lead does not reduce iron absorption from the intestinal tract; thus alteration of intestinal iron absorption does not contribute to lead-induced anemia. Indeed, lead-exposed rats demonstrated increased iron uptake.

Aging↗
PubMed1977

The use of pooled sera for HLA cytotoxicity crossmatching.

A two-stage procedure is described for cytotoxicity tests in which three different sera from a prospective kidney recipient are pooled in each well of a standard microcytotoxicity test plate. The results are reproducible and as sensitive as those obtained with single sera tests. The technique permits a reduction in time required for a test and the number of wells that must be evaluated to screen a series of sera. It enables a laboratory to run all available sera on patients for cadaver kidney crossmatching and to eliminate hyperacute rejections. Serum pooling may also be used for screening of many sera against random cell panels.

Cytotoxicity Tests, Immunologic↗
PubMed1976

The effect of a collagen dressing on contaminated surgical wounds in rats.

In maintaining the rat, the collagen dressings, Aviderm Amine and Aviderm, are as effective as skin in low bacterial levels in contaminated surgical wounds. In the scald-burn wound in the rat the effect of skin dressing is confirmed. Also, 48 h after collagen dressing in the wound the bacterial contamination was the same as that seen under autograft dressings. We have elsewhere suggested that skin and some other dressings modify the local host defense by their effect on the accumulated white blood cells. We believe that collagen, as well as some synthetics, can alter the local environment permitting the destruction of invading bacteria by the accumulated white blood cells.

Animals↗