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Biomedical subjects

N Cohen

Publications and source records attributed to N Cohen.

At least 289 records · Page 16Linked to original sources
PubMed1984

A flow cytometric analysis of the embryonic origin of lymphocytes in diploid/triploid chimeric Xenopus laevis.

Quantitative flow cytometry was used to examine the embryonic origin of lymphocytes in Xenopus laevis. Reciprocal head/body transplants were made between diploid (2N) and triploid (3N) embryos of the same developmental stages ranging from neural plate to tail bud stages. Thymuses and spleens were removed from postmetamorphic chimeras. Cell suspensions were stained with the fluorescent DNA stain, mithramycin, and the ploidy (relative fluorescence intensity) of the cells was then determined by flow cytometry. All lymphocytes in the chimeras were derived from the posterior portion of the embryo. In other experiments, various regions of the lateral plate or ventral mesoderm were grafted from triploid to diploid embryos. Only transplants that included middorsal mesoderm gave rise to lymphocytes.

Animals↗
PubMed1984

Analogs of arachidonic acid methylated at C-7 and C-10 as inhibitors of leukotriene biosynthesis.

The syntheses and biological activity of (all Z)-7,7-dimethyl-5,8,11,14- eicosatetraenoic acid, (all Z)-7,7,-dimethyl-5,8,11-eicosatrienoic acid, (Z,Z)-7,7-dimethyl-5,8-eicosadienoic acid, (all Z)-10,10-dimethyl-5,8,11,14-eicosatetraenoic acid, (all Z)-10,10-dimethyl-5,8,11-eicosatrienoic acid, and rac.-(Z,Z)-15-hydroxy-7,7-dimethyl-5,8-eicosadienoic acid are described. These arachidonic acid analogs are all inhibitors of ionophore-induced SRS-A biosynthesis in rat peritoneal cells. Their mode of action may involve inhibition of phospholipase A2 rather than delta 5-lipoxygenase. These compounds failed to exhibit significant activity in an in vivo model designed to detect inhibitors of antigen-induced, leukotriene-mediated bronchoconstriction in sensitized guinea pigs.

Animals↗
PubMed1984

HLA-D clusters associated with DR2 and the definition of HLA-D"AZH": a new DR2 related HLA-D specificity in Israel.

In order to investigate the HLA-D clusters associated with DR2 in Israeli Jews, 40 DR2 positive unrelated individuals were studied with a panel of DR2 associated homozygous typing cells (HTC's) which detect the lymphocyte defined specificities HLA-Dw2, Dw12, Dw9 and D-WJR. The results confirmed the existence of two distinct HLA-D clusters associated with the same serologically defined DR2. Of 40 individuals 22.5% (9/40) were Dw2 and 50% (20/40) were Dw12 carriers. Yet, no HLA-D specificity could be assigned to the remaining 11 DR2 positive individuals. In the present study we have defined a unique DR2-associated Dw specificity, HLA-D"AZH". The donor of the HTC was of Moroccan origin and an offspring of a first cousin marriage. This cell was not typeable with the known DR2-associated homozygous typing cells nor with other HTC's which define the well established HLA-Dw1 to Dw11 specificities. It was shown to segregate with DR2 positive HLA haplotypes in family analysis and in a population study, typed out 7 of 11 unrelated DR2 positive, Dw blank individuals, thus identifying a unique and new HLA-D cluster provisionally designated D"AZH".

Epitopes↗
PubMed1984

HLA-linked SB antigens in Israel. Population study, analysis of homozygous typing cells and generation of local SB reagents.

In the present study we have investigated the HLA-SB antigen distribution in 65 unrelated Israeli Ashkenazim and non-Ashkenazim and in a panel of 18 local homozygous typing cells (HTC). Two locally derived SB reagents, anti-SB2 and SB3, were also studied. The HLA-SB allele frequencies in the Israeli sample ranged from 0.02 for SB1 to 0.47 for SB4 while SB5 was absent. SB3 had a higher frequency in non-Ashkenazim (0.11) as compared to Ashkenazim (0.06) but this difference was not significant. On the whole, the allele frequencies for the 5 HLA-SB antigens studied were in the range observed in non-Jewish Caucasoid populations with some minor variations. Two of eighteen local HTC's were found heterozygous for SB, demonstrating that homozygosity for HLA-A, B, C, D and DR does not indicate homozygosity for HLA-SB. The local anti-SB2 and SB3 typing reagents gave concordant results when compared with the NIH reference typing cells in population studies.

Europe↗
PubMed1984

HLA-DR2 and DR4 further defined by two new HLA-D specificities (HTC) derived from Israeli Jewish donors: comparative study in Caucasian, Korean, Eskimo and Israeli populations.

Two newly-identified HLA-D antigens were characterized by testing selected homozygous typing cells (HTC) against responder panels derived from Caucasian, Korean, Alaskan Eskimo and Israeli Jewish populations. The first specificity, defined by typing cell "AZH", is associated with DR2 haplotypes and is detected primarily in Israelis. The second specificity, defined by HTC "TAS", is associated with DR4 haplotypes and is detected with relatively high frequency in Koreans and Alaskan Eskimos. The data indicate that HTC-AZH and -TAS can be used to identify previously undefined splits or variants of lymphocyte-defined (LD) determinants associated with DR2 and DR4 haplotypes. Further, the study demonstrates the utility of comparative population analysis in identifying and characterizing alleles encoded by the HLA-D region and provides additional evidence of heterogeneity within the family of serologically-defined HLA-DR haplotypes.

HLA-DR Antigens↗
PubMed1984

Materials management in multi-facility systems: a case study.

Although the problems of managing materials in a health care institution are formidable, these problems increase when the institution is part of a multi-facility system. There are many issues of organization, standardization, centralization (or decentralization) of authority, reporting, and monitoring faced by the multi-facility system, which are not issues relevant to the single institution. The state of New York operates a centralized supply purchasing, warehousing, and distribution system through its Office of General Services. This system serves a number of state organizations, including the focus of this report, the Office of Mental Retardation and Developmental Disabilities (OMRDD), which is responsible for 20 residential facilities as well as day programs and community residences. Faced with the recognition that the cost of supplies ("commodities" in the official nomenclature) was becoming a significant and vulnerable part of the operating budget, OMRDD engaged Friesen International, Inc. to assist in analyzing and improving its commodity distribution system, with the object of holding the line on operating costs. This article describes the methods and results of the ensuing study, which began as a review of the procedures in place, and ended with on-site assistance in implementing changes at each of the component facilities. Neither HPM nor the authors suggest that any other system could, or should, proceed in exactly the same manner; however, apart from the specific information about particular commodities which can be gleaned from this report, there may be value for others in seeing how the task proceeded, and the authors' self-critical analysis of how well the employed methods worked.

Materials Management, Hospital↗
PubMed1984

Induction of T cell differentiation in early-thymectomized Xenopus by grafting adult thymuses from either MHC-matched or from partially or totally MHC-mismatched donors.

The effect of grafting thymuses from major histocompatibility complex (MHC)-matched and mismatched (either partially or totally) adult donors on the restoration of T-cell dependent immune responses of Xenopus adults that were thymectomized (txd) during early larval life was examined. Four to 5 month-old diploid (or triploid) frogs of defined MHC haplotypes that had been txd on day 4 or 5 postfertilization were each grafted subcutaneously with a pair of thymuses from a triploid (or diploid) MHC-defined frog. Regardless of the donor-host combination, thymus grafts restored in vivo acute skin allograft rejection capacities and antibody responses to SRBC and in vitro proliferative responses of spleen cells to the T cell mitogens, PHA and Con A. Txd frogs that were grafted with MHC-mismatched thymus did not reject skin grafts with the MHC haplotype of the thymus donor. Nevertheless, their spleen cells could proliferate, in one way MLC, in response to irradiated stimulator cells with the thymus donor MHC haplotype. Ploidy analyses of mithramycin-stained thymic and splenic lymphocytes (DNA quantitation by flow cytometry) demonstrated that in certain donor-host combinations, cells from totally or partially MHC-mismatched donors as well as from MHC-matched donors persisted in the thymus grafts and/or the spleens of txd hosts. Chimerism lasted for at least 1 year after thymus grafting. In other donor-host combinations, however, (txd isogenic cloned LG15 frogs grafted with allogeneic thymus from MHC-homozygous triploid J strain frogs), no donor cells could be detected 7 months after thymus grafting. Chromosome counts of PHA-induced metaphases of spleen cells from these and other thymus-grafted frogs revealed host cells in metaphase. This suggests that thymus grafts can promote the differentiation of host precursor cells along a T cell pathway.

Animals↗
PubMed1984

Effect of thyroxine on induction of Lucké renal adenocarcinomas in Lucké tumor herpesvirus-infected leopard frog tadpoles.

The incidence of Lucké renal adenocarcinomas and premalignant kidney lesions in leopard frog tadpoles (Rana pipiens) was determined at specified ages and metamorphic stages following embryonic infection with the Lucké tumor herpesvirus. Tumor incidence increased with time elapsed after virus infection but was not strictly correlated with advanced metamorphic stages. When the rate of tadpole development was altered by thiourea or thyroxine treatment, the onset of tumor development was unchanged. These results show that neither increased nor decreased thyroxine levels affect the induction of Lucké tumors.

Adenocarcinoma↗
PubMed1984

Acquisition and extinction of conditioned suppression of a graft-vs-host response in the rat.

Injection of rats with cyclophosphamide (CY) after their consumption of a novel saccharin-flavored drinking solution results in a conditioned aversion to saccharin and a conditioned suppression of immune responses. In this study, female Lewis X Brown Norwegian F1 rats were conditioned by pairing saccharin with 50 mg/kg CY. Seven weeks later (day 0), a graft-vs-host response (GvHR) was induced in these animals by injecting splenic leukocytes from Lewis donors into a rear footpad. At this time, some conditioned animals were reexposed to saccharin, the conditioned stimulus. During the 7-wk interval between conditioning and immunization, subgroups of conditioned rats were given 0, 4, 9, or 18 extinction trials (saccharin followed by saline injections). Animals receiving 4, 9, or 18 extinction trials showed a greater preference for saccharin on day 0 than did animals receiving no extinction trials, but these groups did not differ among themselves; all conditioned groups showed a lower preference for saccharin than placebo-treated animals. There was a clear effect of number of extinction trials on the GvHR. Animals receiving 9 or 18 extinction trials did not differ from controls, whereas animals receiving 0 or 4 trials had a milder GvHR than did conditioned rats that were not reexposed to saccharin at the time of immunization. These results confirm a previous report of conditioned suppression of a GvHR, demonstrate that conditioned immunopharmacologic responses are subject to experimental extinction, and indicate that conditioned immunosuppression can be dissociated from conditioned taste aversion.

Animals↗
PubMed1984

During frog ontogeny, PHA and Con A responsiveness of splenocytes precedes that of thymocytes.

The in-vitro proliferation of splenocytes and thymocytes from Xenopus laevis-gilli (hybrid clone LG-15) to the T cell mitogens, concanavalin A (Con A) and phytohaemagglutinin-P (PHA), were examined at specific stages of larval development (stages 51-66 of Nieuwkoop & Faber, 1967) and at 2 months post-metamorphosis. The responses of splenic lymphocytes to each mitogen were significant at all stages with stimulation indices ranging from 1.9 to 50.5 and 2.6 to 45.5 for PHA and Con A, respectively. Stage-related differences in responses of splenocytes to both mitogens suggest two waves of emergence of proliferative activity during development, divided by periods of diminished responsiveness during the metamorphic crisis. In contrast to the responses observed with splenocytes, proliferation of thymocytes cultured with either mitogen was barely detectable, with stimulation indices ranging from 1.2 to 6.9 and 1.4 to 2.9 for PHA and Con A, respectively. These minimal responses were observed only when thymocytes were cultured at relatively high cell density (5 X 10(5) cells/ml); they were not improved by increased or decreased concentrations of mitogen or by increased concentrations of fetal calf serum (5 or 10%) in the medium. Co-culture of larval thymocytes with autologous splenocytes and each mitogen did not consistently increase thymocyte responses suggesting that the defect in thymocyte responsiveness is not due to lack of accessory cells. These findings suggest that if PHA- and Con A-reactive cells are present in the thymus, they are present in relatively low numbers at all stages of larval development. The pattern of early mitogen responsiveness in the spleen at a time when the thymus is unresponsive contrasts with that observed in mammalian development in which thymocytes become responsive to mitogens in fetal stages and mitogen responsiveness appears in the spleen only around the time of birth. The apparent inactivity of larval thymocytes may reflect a population of cells that can become tolerant to those neo-self-antigens that arise during and after metamorphosis. If so, the larval amphibian thymus may provide a model to study the early events of thymocyte 'education' and differentiation in a broader time framework than is possible with fetal mammals.

Animals↗
PubMed1983

Specific in vivo and nonspecific in vitro alloreactivities of adult frogs (Xenopus laevis) that were thymectomized during early larval life.

Thymectomy of very young Xenopus larvae abrogated in vitro proliferative responses to phytohemagglutinin (PHA) and allogeneic leukocytes. Thymectomized (Txd) frogs, however, still rejected first-set skin allografts chronically and second-set grafts (but not third-party grafts) more rapidly. The specific second-set rejection reaction by Txd frogs was transferable in vivo to secondary Txd hosts (with major histocompatibility complex identical to the cell donor) by the subcutaneous injection of a mixture of splenic and peripheral blood leukocytes. Spleen cells used in this adoptive transfer experiment (i.e., immune cells) were responsive to allogeneic cells from the original donor strain as well as from unrelated donors in mixed leukocyte culture in vitro but were still unreactive to PHA. The results are consistent with an extrathymic pathway of alloreactive cell differentiation in this species, although the physiological significance of such a pathway is not clear.

Animals↗
PubMed1983

Carcinoma of the thyroglossal duct.

Seven patients with carcinoma in a thyroglossal duct cyst have received treatment over a 15 year period. Findings in all of these patients reflect the likelihood of carcinoma arising within thyroglossal duct tissue. In each patient there was sufficient histologic evidence of the presence of a thyroglossal duct cyst and carcinoma arising within an intimate admixture of normal thyroid tissue in the cyst wall. In the absence of a history of irradiation and with separation of the carcinoma from the pyramidal lobe of the thyroid, excision of the thyroglossal cyst alone by traditional means seems appropriate. Our experience as well as a review of reported cases to date indicate that distant metastases are extremely rare and the prognosis excellent.

Adenocarcinoma↗
PubMed1983

Mitogenic responses of frog lymphocytes to crude and purified preparations of bacterial lipopolysaccharide (LPS).

We have compared in vitro mitogenic responses of frog (Xenopus laevis and Rana pipiens) lymphocytes to various preparations of lipopolysaccharide (LPS). Commercial LPS prepared from E. coli (phenol extraction) and from S. abortus-equi (phenol and TCA extraction procedures) was mitogenic for frog lymphocytes. After reextraction of these LPS preparations with phenol-water, the remaining LPS was either considerably less mitogenic or not mitogenic. Purified E. coli 055:B5 LPS, prepared by phenol water extraction, enzyme treatment and column chromatography, was not mitogenic. Frog cells proliferated poorly or not at all with all concentrations of reextracted or purified LPS tested (0.5-400 micrograms/ml) and at all culture periods examined (days 1-7). All LPS preparations used were mitogenic for CAF1 mouse lymphocytes, whereas reextracted and purified LPS preparations were not mitogenic for lymphocytes from C3H/HeJ cells. Xenopus were also not susceptible to toxicity induced by parenterally administered LPS in concentrations which killed CAF1 mice.

Animals↗
PubMed1983

Human growth hormone but not ovine or bovine growth hormones exhibits galactopoietic prolactin-like activity in organ culture from bovine lactating mammary gland.

Explants from the mammary gland of 6 lactating cows were cultured in M-199 medium containing insulin (1.0 micrograms/ml) and hydrocortisone (0.5 micrograms/ml) and supplemented with bPRL (0.2-1.0 micrograms/ml) or oGH (0.1, 0.5 and 2.5 micrograms/ml) or bGH or hGH (0.2 and 1.0 micrograms/ml). It was found that neither oGH nor bGH significantly increased (P less than 0.05) the casein and fat synthesis and alpha-lactalbumin secretion above the control level. A significant and almost equal increase was, however, observed in the presence of bPRL and hGH, but was not influenced by the simultaneous addition of oGH to bPRL-containing medium (both at 0.5 micrograms/ml). Various hormonal treatments did not affect casein secretion and glucose uptake. High correlations (r = 0.89-0.97) were found between the mean values for casein and fat synthesis and alpha-lactalbumin secretion. Our results suggest that (a) the in vivo galactopoietic activity of bGH does not result from a direct effect of synthetic capacities on the mammary gland, and (b) hGH is a potent lactogen in the organ culture of bovine lactating mammary tissue.

Animals↗