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Biomedical subjects

R Schafer

Publications and source records attributed to R Schafer.

16 recordsLinked to original sources
PubMed1992

Induction of a cellular immune response to a foreign antigen by a recombinant Listeria monocytogenes vaccine.

A recombinant strain of Listeria monocytogenes that stably and constitutively expresses Escherichia coli beta-galactosidase was used as a live vaccine vector. BALB/c mice were immunized orally or parenterally with the recombinant L. monocytogenes, and their cellular and humoral immune responses to beta-galactosidase were measured. Spleen cells taken 1 week after oral inoculation or 5 weeks after oral or parenteral inoculation (with a boost at 4 weeks) showed beta-galactosidase-specific CTL responses. The CTL line derived from mice immunized i.p. was also shown to be class I restricted and Thy-1.2+, CD8+, and TCR alpha beta+. All mice immunized with the recombinant L. monocytogenes had positive delayed-type hypersensitivity responses to heat-killed L. monocytogenes, but only 15% had a positive delayed-type hypersensitivity reaction to beta-galactosidase. Individual serum samples from mice immunized i.p. or i.v. were tested for antibody to beta-galactosidase. Approximately 11% had low positive titers for beta-galactosidase antibodies. These results demonstrate that both oral and parenteral immunization with recombinant L. monocytogenes results in a cellular immune response to the foreign protein, which is primarily a specific CD8+ CTL response.

Animals↗
PubMed1992

Forcing expression of a soybean root glutamine synthetase gene in tobacco leaves induces a native gene encoding cytosolic enzyme.

Glutamine synthetase (GS; EC 6.3.1.2) is present in different subcellular compartments in plants. It is located in the cytoplasm in root and root nodules while generally present in the chloroplasts in leaves. The expression of GS gene(s) is enhanced in root nodules and in soybean roots treated with ammonia. We have isolated four genes encoding subunits of cytosolic GS from soybean (Glycine max L. cv. Prize). Promoter analysis of one of these genes (GS15) showed that it is expressed in a root-specific manner in transgenic tobacco and Lotus corniculatus, but is induced by ammonia only in the legume background. Making the GS15 gene expression constitutive by fusion with the CaMV-35S promoter led to the expression of GS in the leaves of transgenic tobacco plants. The soybean GS was functional and was located in the cytoplasm in tobacco leaves where this enzyme is not normally present. Forcing this change in the location of GS caused concomitant induction of the mRNA for a native cytosolic GS in the leaves of transgenic tobacco. Shifting the subcellular location of GS in transgenic plants apparently altered the nitrogen metabolism and forced the induction in leaves of a native GS gene encoding a cytosolic enzyme. The latter is normally expressed only in the root tissue of tobacco. This phenomenon may suggest a hitherto uncharacterized metabolic control on the expression of certain genes in plants.

Base Sequence↗
PubMed1992

Natural killer cells mediate protection induced by a Salmonella aroA mutant.

We have previously shown that an avirulent strain of Salmonella typhimurium, SL3235, blocked in aromatic synthesis, confers high levels of resistance to challenge with virulent Salmonella as early as 3 days postvaccination. In the present studies, it was found that immunization with SL3235 resulted in high levels of natural killer (NK) cell activity in the spleens and peritoneal cavities of C3H/HeJ mice, as measured by cytotoxicity against YAC-1 targets. NK cell activity was at its maximum 2 to 4 days after immunization and was ablated by in vivo or in vitro treatment with anti-asialo GM1. In vivo treatment with anti-asialo GM1 during the first week after immunization with SL3235 depleted NK cell activity and markedly increased mortality in mice challenged with a virulent Salmonella strain. These results are compatible with a role for NK cells as one important component in the resistance against virulent Salmonella infection induced by a live, attenuated vaccine.

Animals↗
PubMed1989

Abnormal typical pattern of platelet function and thromboxane generation in unstable angina.

Platelet aggregation (PA), platelet thromboxane B2 (TXB2) generation and 14C 5-hydroxytryptamine (5HT) release were studied in 13 patients with unstable angina, and compared to 14 patients with stable angina and 16 healthy controls. A typical pattern, distinct in 4 aspects from stable angina patients or controls, was observed in the unstable angina patients. ADP or collagen induced shape change was 3-4 times greater, the extent of epinephrine induced PA was nil or very low, the extent of collagen induced 14C 5HT release was also reduced while collagen induced platelet TXB2 generation was increased in spite of a reduced extent of PA. The extent of ADP or collagen induced PA was also significantly reduced. These results indicate a platelet membrane abnormality occurring presumably during contact of the circulating platelets with a non-occlusive thrombus observed at sites of ruptured plaques in unstable angina patients. Since also the pattern (20-30% overlap with control values) was distinct from that of stable angina patients, it might indicate an active thrombotic process. Plasma beta-thromboglobulin (beta TG) and TXB2 levels and serum TXB2 generation were also studied in the cardiac patients and controls and in another 10 patients with advanced peripheral occlusive arterial disease (POAD). Plasma beta TG and TXB2 levels were slightly elevated in the unstable angina patients and markedly elevated in the POAD patients. Serum TXB2 generation was, however, elevated in the stable angina patients (p less than 0.002) and more so in the unstable angina patients (p less than 0.001) compared to controls or to POAD patients. This was presumably mediated through enhanced thrombin generation. These results suggest that the measured plasma beta TG variable in the unstable angina patients is not useful in the assessment of in vivo platelet activation. It is presumably reflecting the sum of local enhanced platelet activation (at sites of ruptured plaques) and of reduced function of the "defective" circulating platelets. The ability of the platelets of unstable angina patients to generate large amounts of TXB2 if occurring in vivo might induce an intense coronary vasospasm.

Adult↗
PubMed1977

The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. IV. electrophysiological study of attractant specificity and its determination by juvenile hormone.

The antennae of male Periplaneta americana acquire a large number of olfactory receptors at the adult stage. Electrophysiological methods (single unit and electroantennogram recording) show that a portion of the receptors added at the adult ecdysis are sex attractant receptors. Sex attractant receptors are not present in large numbers on larval and adult female antennae. The differentiation of pheromone receptors is inhibited during normal larval development by juvenile hormone. Topical application of juvenile hormone-mimic to male antennae during the terminal larval instar inhibits their development. Comparative electrophysiological studies indicate a high degree of cross-reactivity of the P. americana sex attractant among four other species within the genus Periplaneta.

Action Potentials↗
PubMed1977

Psychoanalytic methodology in Helene Deutsch's the psychology of women.

Although Helen Deutsch's The Psychology of Women contains a wealth of descriptive material about women's problems, the methodology employed by Deutsch in reaching her conclusions about femininity is marred in several ways. Her evolutionary-adaptational bias and natural science approach led to the attribution of questionable biological bases to behavior and to the neglect of social factors and learning. Her concepts and language reveal an unquestioning adoption of Freud's metapsychology and lead to a perception and interpretation of psychological events according to the specific cast of that approach. She confuses her values with definition and observation. A re-examination of the thought of Deutsch seems fitting in these days of ever more extensive reconsideration of the views of Freud and other major psychoanalytic thinkers on the psychology of women. In addition to furthering our understanding of her insights, the study of Deutsch's methodology and its pitfalls contributes to a more critical understanding of the values and preconceptions that influence popular thinking about women and to a deeper grasp of problems inherent in psychoanalytic methodology.

Adaptation, Psychological↗
PubMed1976

The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. I. Sexual dimorphism in the distribution of antennal sense organs in five species.

Sexual dimorphism in the distribution of antennal sense organs is common among adults of the genus Periplaneta. In three out of the four strains of Periplaneta americana examined, adult males had more contact chemoreceptros than females. In the fourth strain of P. americana and in P. australasiae, P. brunnea, P. fuliginosa, and P. japonica, no statistically supportable sexual dimorphism of contact chemoreceptors was found. However, in all strains and species of Periplaneta examined, sexual dimorphism was found in the total number and/or density of olfactory sensilla. Male adults had nearly twice as many olfactory sensilla as female adults. These observations are consistent with the behavioral observation that males within the genus Periplaneta rely on the reception of an airborne pheromone for the initiation of courtship behavior. In P. americana, where sexual dimorphism was found in the contact chemoreceptors, contact stimuli release the full wing raising display and presentation in males during courtship.

Animals↗