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Biomedical subjects

S Davies

Publications and source records attributed to S Davies.

At least 325 records · Page 18Linked to original sources
PubMed1986

Ultrafast chemical repair of DNA single and double strand break precursors in irradiated V79 cells.

The fast kinetics of reactions of free radical precursors of DNA single strand breaks (ssb) and double strand breaks (dsb) have been determined in Chinese hamster V79 cells by fast mixing and irradiation methods using the alkaline unwinding technique to assay breaks. Fast chemical repair of oxygen-dependent ssb and dsb precursors was observed and approached completion within 10-20 ms of irradiation. Treatment of cells with the glutathione synthesis blocking agent, buthionine sulphoximine, showed that approximately half of the chemical repair was attributable to intracellular non-protein thiols. The nature of the residual repair is obscure, but it is apparently not attributable to non-protein thiols. Similar repair rates and thiol dependences were also found for cell kill. With all three endopoints, oxygen competes with and blocks the chemical repair.

Animals↗
PubMed1986

Helper and suppressor activities of an autoreactive mouse thyroglobulin-specific T-cell clone.

An autoreactive T-cell clone, MTg9B3, specific for mouse thyroglobulin, has been characterized. This clone has properties consistent with it an being autoreactive T helper cell. It is I-A restricted, with a surface phenotype of Thy 1+, L3T4+, Ly2-, and produces a number of non-specific lymphokine activities following specific triggering with antigen. Furthermore, antigen-stimulated clone cells were capable of providing bystander help in SRBC-specific antibody responses. Surprisingly, MTg9B3 cells had a profound suppressive effect on thyroglobulin autoantibody responses in vitro.

Animals↗
PubMed1985

The substance P innervation of the rat hippocampal region.

The distribution of substance P (SP) immunoreactive nerve cell bodies and preterminal processes was studied in the rat brain by using several anti-SP-antibodies in combination with immunohistochemical techniques. In normal rats and in rats pretreated with colchicine, SP immunoreactive preterminal processes were found in the hippocampal region, but SP positive cellbodies could be detected only after colchicine pretreatment. Medium-sized to large, multipolar cells immunoreactive for SP were found in stratum oriens of the hippocampal subfield CA 3 and in the hilus of the area dentata. Medium-sized to small, round or fusiform cells were detected in the pyramidal layer of the ventral subiculum and in layers III-VI of the ventral entorhinal area. The SP stained preterminal processes were of two types. Numerous fine, varicose axons were stained in different parts of Ammon's horn, while in the retrohippocampal structures, the SP immunoreactivity was present in small distinctly stained puncta. These frequently formed pericellular arrangements around unstained cells, indicative of axosomatic contacts between SP terminals and cells in the hippocampus. In Ammon's horn, the densest SP innervation was found in strata oriens, radiatum and moleculare of subfields CA 3a and CA 2. Scattered fibers were also present in the stratum oriens of CA 3a-c and in the hilus, in particular at ventral levels. In retrohippocampal structures, the SP innervation predominated in the deep pyramidal layer of the subiculum, the second layer of the presubiculum and in layers VI and IV of the medial and lateral entorhinal area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Platelet monoamine oxidase activity in patients with panic disorder.

Preliminary reports have indicated that platelet monoamine oxidase (MAO) activity is elevated in patients with anxiety disorder. We compared MAO activity in 20 drug-free patients with panic disorder with 20 age- and sex-matched normal controls. MAO activity in patients was significantly higher than in normals. MAO activity was not correlated with age or plasma catecholamine levels. The authors speculate about the possible significance of elevated MAO activity in patients with panic disorder.

Adult↗
PubMed1985

Potentiation of a nucleolytic activity in Bacillus subtilis.

In several strains of Bacillus subtilis extensive breakdown of chromosomal DNA may be potentiated by osmotic lysis of protoplasts. At its most severe, in strains originating from Farmer & Rothman's thymine auxotroph, the rate of DNA breakdown was greater than 50% per hour at 40 degrees C. The rate of DNA breakdown in most other strains tested was approximately 5% per hour except for SP beta- strains, in which the rate of DNA breakdown was only 0.3%. DNA degradation was attributed to relaxation of control of a nuclease specified by the prophage of SP beta or a related phage. The most potent nuclease in lysates was an ATP-activated protein of Mr 280 000. Derivatives of Farmer and Rothman's strain containing integrated plasmids had the highest rate of DNA degradation. Although the chromosome was completely destroyed, covalently closed circular plasmids were generated from the integrated sequence. These showed massive deletions of the B. subtilis part of the integrated plasmid but the vector sequence remained intact. The nucleolytic activity therefore appears to recognize specific sequences in B. subtilis DNA. We suggest that activation of SP beta genes during development of competence may be a cause of deletion of cloned genes in the early stages of establishment of cloned sequences.

Adenosine Diphosphate↗
PubMed1985

Specificity of lactate infusions in social phobia versus panic disorders.

Lactate infusions produced panic attacks in one of 15 patients with social phobia, four of nine with agoraphobia, and 10 of 20 with panic disorder in a blind study. The proportion of patients with social phobia who panicked in response to lactate was significantly lower than that of patients with agoraphobia or panic disorder. These findings lend validity to the DSM-III classification of anxiety states. They also suggest that the pathophysiology of social phobia differs from that of disorders characterized by spontaneous panic attacks.

Adult↗
PubMed1985

Characterization of a family of nuclear and chromosomal proteins identified by a monoclonal antibody.

A monoclonal antibody (3C5) isolated from a mouse immunized with human chromatin stained the nuclei of all cultured cell types tested by indirect immunofluorescence. Experiments with HeLa and PtK1 cells demonstrated striking cell-cycle-related changes in the staining properties of the target antigen. A rapid increase in nuclear fluorescence was seen in prophase, with antigen located between the condensing chromosomes. In metaphase and anaphase cells antigen was present throughout the cytoplasm with the chromosomes apparently unstained. However, isolated metaphase chromosomes showed intense, peripheral staining. In telophase cells immunofluorescent staining was most intense among the decondensing chromosomes and by early G1 staining was predominantly nuclear. Nuclear fluorescence faded as cells progressed through interphase. By protein blotting and immunostaining, 3C5 recognized protein bands with subunit molecular weights of 130, 73, 50, 38, 32 and 22 to 25 kDa. These bands were present in all human and rodent cultured cell types tested. All bands were extracted by 6 M urea or 1% sodium dodecyl sulfate (SDS) but not by Triton X-100. Our results provide evidence against the involvement of a common carbohydrate moiety, in vitro proteolysis or non-specific cross reaction in this multi-banded pattern. The same family of proteins was detected in mitotic and interphase cells, suggesting that the changes in immunofluorescent staining through mitosis are due to changes in antigen accessibility. Subcellular fractionation experiments showed that all major bands were present in the nuclear fraction. Only two (50 and 32 kDa) were detected also in the post-nuclear membrane fraction and none were present in the soluble cytoplasmic fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

A monoclonal antibody identifies a 215 000-dalton nuclear envelope protein restricted to certain cell types.

The monoclonal antibody, AGF2.3, was isolated from mice immunised with the human promyeloid cell line HL60. By immunofluorescence and immunoelectron microscopy the antibody was shown to bind to the nuclear envelope in uninduced HL60 cells. Immunofluorescent staining was reduced to very low levels in HL60 cells induced to mature to monocytes or neutrophils by addition of 12-0-tetradecanoylphorbol-13-acetate or dimethyl sulfoxide respectively. Blood neutrophils did not express the antigen. Weak immunofluorescent staining of cell nuclei was observed in peripheral blood lymphocytes and in sections of normal human kidney, tonsil and skin epithelium. The AGF2.3 antigen was strongly expressed on the nuclei of 21/21 haemopoietic cell lines and 21/25 permanent non-haemopoietic cell lines representing various cell types. In contrast, the antigen was not expressed by any of six primary (untransformed) cell cultures. These included fibroblasts, endothelial cells and keratinocytes. The antigen was expressed in the Q10 SV-40 transformed cell line derived from a non-expressing primary fibroblast culture. AGF2.3 antibody precipitated a protein with an apparent subunit molecular weight of approximately 215 kDa from Triton X-100 extracts of HL60 and HeLa cells labelled with 35S-methionine. This protein was not detectable in extracts of primary skin fibroblasts prepared in parallel. We conclude that AGF2.3 antibody recognises a previously undescribed protein associated with the nuclear envelope which is expressed at high levels in most transformed cell lines but which is weakly expressed or absent in normal tissues and primary cell cultures.

Animals↗
PubMed1984

Effect of blood transfusion on iron status in sickle cell anaemia.

The iron status of 31 patients with sickle cell anaemia (Hb SS) and balanced globin chain synthesis was studied. Twelve patients (group I) had never been transfused; 14 had received up to 4 units of blood in the past (group II) and five had been hypertransfused for 6 months to 2 years (group III). The hypertransfused group had significantly higher MCV and MCH than the nontransfused one, and significantly lower total iron binding capacity and higher serum ferritin concentration than either groups I or II. The serum ferritin concentration was lower than normal in eight patients (five in group I and three in group II), and higher than normal in seven patients (four in group III and three in group II). The remaining 16 patients had normal serum ferritin concentrations. Our results indicate that iron overload is uncommon in adults with Hb SS who have not been transfused, and that a proportion of patients have lower than normal serum ferritin concentrations. Transfused patients, even 6 months after the last transfusion, show increased haemoglobin content of red cells, which may have an adverse effect on the frequency and severity of sickle crises.

Adult↗
PubMed1984

Therapy of Waldenström's benign hypergammaglobulinaemia by regular plasmapheresis.

A patient with a 20-year history of Waldenström's hypergammaglobulinaemic purpura has over that time developed increasingly troublesome clinical symptoms of purpura and joint swelling, associated with a progressive increase in the level of polyclonal IgG. These symptoms have been controlled by the use of a regular plasmapheresis regime and associated with a reduction in IgG levels.

Adolescent↗
PubMed1984

Ethanol suppresses hepatic glutathione synthesis in rats in vivo.

Ethanol-induced depletion of hepatic glutathione has been construed as evidence supporting the hypothesis that reactive oxygen intermediates generated during the metabolism of ethanol lead to glutathione oxidation and lipid peroxidation and are responsible for the toxic effects of ethanol. However, the evidence for a pathogenetic role of lipid peroxidation in ethanol-induced liver injury is indirect and a decreased synthesis might well account for the glutathione depletion produced by large doses of ethanol. In order to determine whether a decreased synthesis or an increased consumption of glutathione is responsible for the ethanol-induced glutathione depletion, hepatic glutathione turnover, plasma glutathione and the biliary excretion of glutathione and its disulfide were measured in rats. The administration of 5 g/kg of ethanol p.o. resulted in a decreased incorporation of labeled cysteine and labeled methionine into the hepatic glutathione pool and decreased the hepatic concentration of glutathione from 3.7 +/- 0.1 to 2.7 +/- 0.2 mumol/g. Kinetic analysis of the specific activity-time curves revealed that ethanol decreased significantly the rate of influx of cysteine into the glutathione pool but did not stimulate the rate of consumption of glutathione. Moreover, the plasma concentration of glutathione and the biliary excretion of glutathione disulfide and reduced glutathione decreased after the administration of ethanol, indicating that ethanol does not increase the efflux of glutathione from the liver. Our data demonstrate that a large dose of ethanol does not produce an oxidative stress, which would increase glutathione consumption, but rather impairs glutathione synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effects of a 1,5-benzodiazepine derivative upon performance in an experimental stress situation.

Psychological performance tasks were given to normal subjects under different conditions of experimental stress: high stress (being filmed on video), or low stress (tested without filming); and after different pharmacological treatments: clobazam 20 mg (an anxiolytic 1,5-benzodiazepine derivative), or placebo. On all five performance assessments (choice reaction times, serial subtraction times, critical flicker fusion values), there was a consistent tendancy for clobazam performance to be comparatively better under high stress, and for placebo performance to be comparatively better under low stress. From these, and previous similar findings, it seems that the level of experimental "stress" under which subjects are tested, can have important influences upon the psychopharmacological performance levels obtained.

Adult↗
PubMed1983

Iron deficiency in sickle cell anaemia.

Thirty-seven patients with SCD were studied: 24 were diagnosed as homozygous Hb S on the basis of their haematological findings, and alpha:non-alpha globin chain ratios were found to be balanced in all. Thirteen patients were thought to have alpha or beta thalassaemia interaction with Hb S on the basis of low MCV and MCH, family history and/or presence of Hb A on electrophoresis. Six of them had abnormal alpha:non-alpha ratio (one had a ratio of 0.72 suggestive of alpha thalassaemia, and five had ratios between 1.4 and 1.9, compatible with beta thalassaemia interaction). The remaining seven patients with microcytosis had balanced globin chain synthesis and five were found to be iron deficient. Five additional patients (3 with Hb SS and 2 with Hb S/beta thalassaemia) had lower than normal serum ferritin concentration. The analysis of case histories disclosed that peptic ulceration, recurrent epistaxis and multiple pregnancies could account for iron loss in seven patients. These findings indicate that iron deficiency may be common in SCD and should be excluded as a cause of microcytosis. Microcytosis, in the absence of conclusive family studies and/or presence of Hb A on electrophoresis, is an unreliable indicator of alpha or beta thalassaemia interaction with Hb S.

Adolescent↗