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Biomedical subjects

B Martin

Publications and source records attributed to B Martin.

At least 415 records · Page 23Linked to original sources
PubMed1982

Cimetidine does not stimulate human T lymphocyte functions in vitro.

Cimetidine, an H2-receptor antagonist had no immunoproliferative or immunostimulative effect on in vitro T cell functions of normal human peripheral blood lymphocytes. This was shown by adding Cimetidine to mitogen, alloantigen and xenoantigen-stimulated cultures. Generation of helper and cytotoxic T cells was not modified in a full kinetic experiment. These data failed to confirm previous reports showing an increase of cell-mediated immunity under Cimetidine therapy.

Cells, Cultured↗
PubMed1981

Size at birth of infants born at term to coloured primiparas in Cape Town.

An in-depth study was made on the size and body proportions of infants born at term to Coloured primiparas in Cape Town. The infants were lighter and shorter than has been found in most comparative studies, but had some sparing of head growth with normal weight/length proportions. This report provides a standard which will facilitate further studies of fetal growth determinants in this community.

Black or African American↗
PubMed1981

An evaluation of prostaglandin E2 administered intrarectally to induce labour.

Prostaglandin E2 (PGE) 4 mg administered as an intrarectal suppository failed to induce labour in 70% of patients with a favourable cervical score. This may indicate that intravaginally administered PGE, which is effective in inducing labour in 70% of patients, acts at least in part directly on the cervix.

Evaluation Studies as Topic↗
PubMed1981

Cell junctions in explanted tissues from early chick embryos.

Hypoblast and definitive endoblast derived from young chick embryos were explanted and grown for 24 h in culture. The junctional complexes which characterise these tissues were studied on freeze-fracture replicas and thin sections. Cell membranes of the hypoblast displayed tight junctions only, disposed in randomly arranged strands or narrow belts which included many discontinuous strands. The definitive endoblast showed tight and gap junctions as well as desmosomes in close association with the tight junctions. It is suggested that the differences between the two types of tissue may be related to cell cohesiveness, which appears to be relatively low in the hypoblast and high in the definitive endoblast.

Animals↗
PubMed1981

The permeability barrier in the epidermis of the grass snake during the resting stage of the sloughing cycle.

Tracer and freeze-fracture replication techniques show that there are two morphologically and topographically distinct permeability barriers in the epidermis of the grass snake. Tight junctions interconnect the apico-lateral plasma membranes of the uppermost living cells, establishing an ionic or osmotic gradient between the stratum germinativum and alpha layer. The second barrier is formed by intercellular lipid sheets in the overlying mesos layer, which are very similar to the barrier found in the stratum corneum of mammals.

Animals↗
PubMed1981

Associated particle aggregates in juxtaparanodal axolemma and adaxonal Schwann cell membrane of rat peripheral nerve.

Freeze-fracture observations have been made on unfixed cryoprotected, and glutaraldehyde-perfused and cryoprotected rat sciatic nerve. In the juxtaparanodal region of the internode, numerous particle clusters were observed on the axolemmal E face and rings of particles of uniform size on the P face of the adaxonal Schwann cell membrane. Both of these particle aggregates were concentrated in the internodal region immediately adjacent to the paranode (juxtaparanodal). The findings provide evidence for a close association between the two particle formations, suggesting a unitary structure forming links between the axolemma and Schwann cell membrane. Figures are given for the density distribution of these particles at the juxtaparanodal region. They were rarely observed on membrane fracture faces of the general internodal regions. It is possible that these particle formations may represent potassium channels or that they could provide channels for other metabolic communication between the Schwann cell and the axon.

Animals↗
PubMed1981

Lack of effects of beta sympathetic blockade on the metabolic and respiratory responses to carbohydrate feeding.

Increases in metabolic rate, heart rate and ventilation occur following carbohydrate feeding or during beta sympathetic stimulation. Furthermore, insulin secretion and hypokalemia are features common to both which raises the question as to whether these effects of carbohydrate depend upon an intact sympathetic nervous system. Accordingly, in the present study, we measured the effects of carbohydrate feeding (250 gram meal) before and after chronic beta sympathetic blockade in sex normal men. Before blockade metabolic rate (O2 consumption) rose (P less than 0.05) from a fasting mean of 248 +/- 19.7 (SEM) ML O2/min to 292 +/- 15.2 at 1 hr. 269 +/- 13.7 at 2, and 262 +/- 18.0 at 3 hr following the meal. During blockade (oral propranolol 80 mg p.o. Q 6 h for 3 days) the post-prandial increase in O2 consumption was also significant (P less than 0.05) and almost identical to that found before blockade. A similar pattern was found for ventilation, heart rate, insulin secretion and hypokalemia, where the significant postprandial changes were not altered by blockade. A transient increase in serum triiodothyronine from a mean of 92 +/- 8.4 microgram/ML to 109 +/- 9.4 occurred at 1 hr (P less than 0.05) only during blockade. No other changes in thyroid hormonal concentrations occurred as a result of the meal. We conclude that although similarities exist between beta sympathetic stimulation and carbohydrate feeding, the post-prandial effects studied do not depend on intact beta sympathetic receptors.

Dietary Carbohydrates↗
PubMed1981

Impairment of photosynthesis by chilling-temperatures in tomato.

Chilling of attached tomato leaves (cv. Rutgers) in the dark for 16 hours at 1 C decreased both photosynthesis and transpiration. To separate the effects of chilling on stomatal CO(2) conductance from more direct effects of chilling on the chloroplasts' activities, measurements of photosynthesis and transpiration were made at atmospheric and saturating CO(2) levels. At atmospheric CO(2), the inhibition of photosynthesis was approximately 60%, of which about 35% was attributable to the impairment of chloroplast function and about 25% was attributable to decreased stomatal conductance. However, the affinity of the photosynthetic apparatus for CO(2) was not changed by chilling, since the dependence of the relative rate of photosynthesis on the intercellular CO(2) concentration was unaltered. The apparent quantum requirement for CO(2) reduction also was identical in chilled and unchilled plants. This observation contradicts the widely held notion that the chilling-induced inhibition of photosynthesis is caused by an impairment of the water oxidation mechanism. The impairment of chloroplast activity was not a consequence of an unfavorable water status within the leaf, since chilling caused only a small drop (1 bar) in water potential. A small loss of chlorophyll resulted as a secondary effect of chilling, but this loss of chlorophyll was eliminated as a cause of the inhibition of photosynthesis.No recovery of chloroplast activity occurred during the subsequent light period after chilling. The recovery seemed to be inhibited by light or to require both a light period and a dark period or to occur after a considerable lag period. After a period of both light and dark, restoration of stomatal conductance occurred more slowly than did the recovery of chloroplast activity.

Journal Article↗
PubMed1981

Binding of steroids by proteins in follicular fluid of the human ovary.

Steroid-protein interactions were studied in the antral fluid of preovulatory follicles of the human ovary. Two high affinity binding systems are described. These steroid-binding proteins do not differ from those identified in the plasma of women (transcortin and sex binding protein), as indicated by similar specificity, binding affinity, and electrophoretic pattern. Their concentrations in the fluid are either similar to or lower than those in plasma. Since the steroid concentrations in antral fluid are approximately 20- to 100-fold higher than the binding capacities of the specific steroid binders, the buffer role that many authors attribute to the proteins which bind steroids is unlikely in antral fluid.

Body Fluids↗
PubMed1981

Effects of whole-body vibrations on sensory motor system performance in man.

The effects of whole body vibration (WBV) were studied on subjects trained to perform on tasks involving blindfolded arm positioning (proprioceptive tasks), tracking of visual targets and control of static and dynamic torques. Subjects were vibrated in a seated position by means of a hydraulic jack. The vibration used (0.1 G at floor level and 18 Hz) was that occasionally encountered on medium-size cruising helicopter. The seat was that of a heliccopter pilot whose foam cushion was 6 cm thick with a density of 26 kg/m3. Systematic past-pointing was observed for both arm flexion and extension. Foot and arm visual tracking precision, as determined by position and velocity errors, increased in both directions. Static and dynamic control, rated by torque holding stability and torque amplitude precision, were also significantly altered compared to pre-stimulus readings. The results are interpreted in relation to current knowledge of the effects of vibration induced at spinal, vestibular, and central nervous system levels. It is concluded that the proprioceptive system through which vibration-induced afferents enter the neurological networks is the common denominator for the observed alterations of the position, velocity, and force controls. Our observations suggest that particular care should be taken in helicopters and other vibrating vehicles to prevent vibration from reaching muscular masses, especially those involved in motor tasks.

Adolescent↗