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Biomedical subjects

S A Gregory

Publications and source records attributed to S A Gregory.

71 records · Page 4Linked to original sources
PubMed1985

Cloning of a restriction-modification system from Proteus vulgaris and its use in analyzing a methylase-sensitive phenotype in Escherichia coli.

A 4.84-kilobase-pair plasmid was isolated from Proteus vulgaris (ATCC 13315) and cloned into the plasmid vector pBR322. Plasmid pBR322 contains substrate sites for the restriction endonucleases PvuI and PvuII. The recombinant plasmids were resistant to in vitro cleavage by PvuII but not PvuI endonuclease and were found to cause production of PvuII endonuclease or methylase activity or both in Escherichia coli HB101. The approximate endonuclease and methylase gene boundaries were determined through subcloning, Bal 31 resection, insertional inactivation, DNA-dependent translation, and partial DNA sequencing. The two genes are adjacent and appear to be divergently transcribed. Most E. coli strains tested were poorly transformed by the recombinant plasmids, and this was shown by subcloning and insertional inactivation to be due to the PvuII methylase gene. At a low frequency, stable methylase-producing transformants of a methylase-sensitive strain were obtained, and efficiently transformed cell mutants were isolated from them.

Bacteriophage lambda↗
PubMed1985

Tissue factor induction in human monocytes. Two distinct mechanisms displayed by different alloantigen-responsive T cell clones.

One component of the cellular immune response to antigens is the expression of procoagulant activity (PCA) by monocytes and macrophages. Induction of human monocyte PCA in response to alloantigenic stimulation requires the collaboration of HLA-DR-responsive T cells. In mixed lymphocyte cultures (MLCs), the induction of monocyte tissue factor appears to be mediated exclusively by a T cell-derived lymphokine. We have used a soft agar cloning method to generate alloantigen-responsive T cell clones from MLCs between irradiated Daudi lymphoblastoid cells and human peripheral blood mononuclear cells. Developing clones were screened for the ability to induce PCA in fresh autologous monocytes in response to Daudi stimulator cells. PCA induction was observed with some, but not all, proliferating T cell clones and two modes of induction were apparent. Some T cell clones mediated PCA induction exclusively by lymphokine production, whereas other clones delivered induction signals by direct cellular collaboration with the monocyte effector cells. These two inductive pathways were represented in distinct, non-inclusive functional subsets of T cell clones. Constitutive production of soluble inducer signals was not observed in T inducer clones. The magnitude of the monocyte PCA response increased in response to an increase in the allogeneic stimulator/T clone responder ratio, and third-party allogeneic cells were unable to elicit the PCA-inducing lymphokine signals from T inducer clones. Both modes of induction were shown to generate tissue factor protein activity in monocytes. Collectively, these results suggest that PCA induction can be initiated in response to alloantigens through collaboration with certain OKT3+, OKT4+, OKT8-, OKM1- T inducer clones, and that induction can be mediated by at least two different functional subsets of human T cells. Stimulation with the appropriate alloantigen may elicit both lymphokine and T cell-contact pathways of induction of tissue factor in human monocytes.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1984

Resistance of bovine colostral anti-cholera toxin antibody to in vitro and in vivo proteolysis.

Pregnant cows immunized with cholera enterotoxin produce an immunoglobulin G class 1 antibody that enters the colostrum in high titer. After exposure to intestinal enzymes, this antibody remains immunologically reactive and inhibits intestinal fluid secretion in infant and adult rabbits exposed to cholera enterotoxin. Specific bovine colostral antibodies may be a source of passive immune protection for human infants and adults at risk for cholera and other enteric diseases.

Animals↗
PubMed1984

Intracranial meningioma unmasked by elective general anesthesia: report of three cases.

Three cases of intracranial meningioma unmasked by elective general anesthesia are reported. In each case, the meningioma was either asymptomatic or so subtly symptomatic that no suspicion of intracranial tumor had been entertained preoperatively. Each patient presented with failure to wake up after routine general anesthesia for a nonneurosurgical procedure. The management of unexplained failure to wake up after uncomplicated general anesthesia is discussed. Early computed tomographic scanning and neurosurgical consultation are suggested in such situations.

Aged↗
PubMed1980

Uracil mustard in the treatment of thrombocytosis.

Uracil mustard was used for the treatment of thrombocytosis in 14 patients, eight who had polycythemia vera and six who had essential thrombocytosis. Intermittent treatment with 1 to 2 mg/day for 14 days was used for most patients, and continuous treatment was used for three patients. The nadir of the platelet count occurred during a mean period of five to seven weeks, and the mean duration between courses was seven months. The drug selectively depressed the platelet count, with a minimal effect on leukocytes and erythrocytes. Uracil mustard is an effective drug for the control of thrombocytosis.

Administration, Oral↗
PubMed1977

Chronic lymphocytic leukemia: correlation of clinical course and therapeutic response with in vitro testing and morphology of lymphocytes.

Forty-two patients with chronic lymphocytic leukemia (CLL) were studied for morphology of lymphocytes by light and electron microscopy (EM), in vitro responses of lymphocytes to a battery of physical and chemical agents, overall clinical status, immunologic status, course, and response to therapy. CLL lymphocytes could be classified by EM into four groups on the basis of cell size and nuclear contour and by light microscopy into two groups, small cells and large cells (lymphosarcoma cells). Patient survival did not vary with cell size or morphology as determined by light or electron microscopy. In vitro testing of CLL lymphocytes following exposure to X-ray, PHA, DMSO 2 hr at 43 degrees C, prednisolone, glutaminase, and asparaginase permitted a separation of patients into categories of normal and abnormal in vitro responses. A normal in vitro response predicted a good response to therapy but an abnormal in vitro response did not preclude a good response to therapy. Following therapy, normalization of abnormal EM morphology and in vitro response was seen in some patients. Most patients tested had decreased serum immunoglobulins and abnormal PHA responses. There was a high incidence of infections and second neoplasms. Immunologic deficits could not be correlated with variations in lymphocyte morphology or in vitro response.

Asparaginase↗
PubMedDate not supplied

The myelodysplastic syndromes in 1996: complex stem cell disorders confounded by dual actions of cytokines.

Based upon recent studies of apoptosis, proliferation, cytokines and genic abnormalities, a new hypothesis regarding the pathology of myelodysplastic syndromes is being proposed. The transforming abnormality which affects an early progenitor hemopoietic stem cell is poorly defined so far but confers a growth advantage on this cell eventually leading to monoclonal hemopoiesis at least affecting the non-lymphoid bone marrow cells. Several cytokines confound the picture by exerting dual effects of stimulating the proliferation of immature cells while inducing the apoptosis in their maturing progeny thereby producing the clinical syndrome of cytopenias despite cellular marrows. Since a number of these offending cytokines share the same common lipid intracellular signalling pathway, interfering with the generation of specific phospholipid second messengers should hypothetically result in a dual effect as well. Alleviation of cytopenias (due to attenuation of apoptosis) should be accompanied by a decrease in the progeny of the transformed stem cell (due to suppression of proliferation) eventually allowing for resumption of polyclonal hemopoiesis.

Acute Disease↗
PubMedDate not supplied

Audiological deficits in brain-injured children and adolescents.

A retrospective chart review of 62 children aged 2 to 18.5 years admitted over a 4-year period to a brain injury rehabilitation unit was performed. Glasgow Coma Scales were not always recorded at the referring institutions, but all but three of the children in the series experienced a period of unresponsiveness to the environment for a period of at least one hour. Available Glasgow Coma scores at the time of injury ranged from 3 to 13. Maximum coma duration was 3 months. All children received an audiological evaluation. Sixteen per cent of the children had conductive hearing losses, 13% had sensorineural hearing loss, and 16% had central auditory processing problems. Three of these children were found to have combined losses, one with both conductive and sensorineural hearing loss, and two with sensorineural hearing loss and central auditory processing problems. Of the five patients with the most severe injuries and prolonged comas, none had hearing deficits. Twenty-five of the 62 patients, or 40%, had hearing deficits, of which 15 are known to persist.

Adolescent↗
PubMedDate not supplied

The use of T cell subtyping to distinguish rheumatoid arthritis from systemic lupus erythematosus.

The use of T cell subtyping to distinguish rheumatoid arthritis (RA) from systemic lupus erythematosus (SLE) was evaluated. We determined the distribution of IgG Fe receptor T cells (TG), IgM Fc receptor T cells (TM), and T cells lacking Fc receptors (Tnull) in 17 patients with RA and 7 patients with SLE. All RA patients including 3 antinuclear antibody positive-rheumatoid factor negative cases had normal numbers and percentages of TG, TM, and Tnull, whereas all SLE patients had a relative and absolute deficiency of TG. This TG lymphopenia was a better discriminator for SLE (7 of 7 SLE, 0 of 17 RA) than anti-DNA antibodies, hypocomplementemia, circulating immune complexes or total number of T cells.

Antibodies, Antinuclear↗
PubMedDate not supplied

Two in situ labeling techniques reveal different patterns of DNA fragmentation during spontaneous apoptosis in vivo and induced apoptosis in vitro.

BACKGROUND: Two new enzymatic reactions were described recently to detect apoptotic cell death in situ viz in situ end labeling (ISEL) and terminal deoxynucleotidyl transferase mediated UTP nick end labeling (TUNEL) of fragmented DNA. A comparative study was conducted to detect in vivo and in vitro apoptotic death using these two techniques. Experimental design; Spontaneous apoptous cell death was detected in plastic embedded tumor biopsies from patients with non-Hodgkin's lymphoma (NHL), head and neck squamous cell carcinomas (HNSCC), and breast cancer using these two in situ methods. Uninvolved normal tissues adjacent to breast tumors and a lymph node metastasis of breast tumor were also studied. Furthermore, apoptotic death induced by different doses of etoposide (VP16) was also studied in HL60 cells by in situ methods and by agarose gel electrophoresis. RESULTS: Interestingly, whereas NH1 and HNSCC biopsies showed comparable levels of detectability with the two techniques, the breast tissues be it neoplastic, normal or metastatic, revealed apoptosis detectable only by TUNEL and not by ISEL. Similarly in HL60 cells, the percentage of apoptotic cells or apoptotic index (AI) determined by TUNEL was significantly higher than that determined by ISEL. A double labelling of these HL60 cells for ISEL and TUNEL also revealed a higher proportion of cells labeled positively for TUNEL as compared to those labeled for ISEL. Agarose gel electrophoresis revealed characteristic DNA laddering only at 35 microM dose of VP 16. No smearing of DNA was found in any group ruling out the necrotic death. In vivo, in one HNSCC specimen apoptosis and necrosis could be differentiated by the difference in staining intensity. Both methods stained necrotic chromatin fragments very lightly. The DNA fragments generated during apoptosis could be of unique lengths (ie 180-200 bp or multiples) but have differently staggered ends. These fragments may be 3' recessed, 5' recessed or blunt ended. While TUNEL can label all three types, ISEL labels only those with 3' recessed ends. CONCLUSIONS: Thus our data show that the DNA fragments formed during spontaneous apoptosis in breast tissues and preferentially during VP16 induced apoptosis in HL60 cells are either 5' recessed or blunt ended, being distinctly different from 3' recessed fragments seen in NHL and HNSCC or with a lesser frequency in VP 16 treated HL60 cells. Specific fragmentation patterns could be a result of activation of different endonucleases which as indicated by our data could be tissue specific and may be differentially activated by different chemotherapeutic agents. Therefore, screening for the presence of specific endonucleases in different tissues and for agents specifically activating them would have major clinical implications.

Apoptosis↗