Development of neurochemical separation of ON and OFF channels at retinal ganglion cells

Anatomical and physiological segregation of neurons into ON (brightening detector) and OFF (darkening detector) channels in the retina and subsequent visual system ensure the high sensitivity required for contrast detection and spatial discrimination. This segregation is finest at the visual axis. Neurochemically, ON and OFF ganglion cells at the visual axis seem to be distinguished by different inhibitory transmitters but not excitatory transmitters. Microiontophoretic studies of inhibitory transmitters on the retinal ganglion cells in kittens and adult cats suggest that this neurochemical distinction is poor in immature ganglion cells at the visual axis. Initially both ON and OFF cells seem to be supplied by GABAergic, glycinergic, and catecholaminergic amacrine cells, but in adults, ON cells remain supplied only by GABAergic amacrines, while OFF cells are supplied by glycinergic amacrines. Postnatal elimination of multiple inputs and strengthening of the appropriate inputs, as seen in the central nervous system, also seem to occur at the retinal neurotransmitter synapses during development.     

Body fat in normal adults estimated by oxygen-18- and deuterium-dilution and by anthropometry: a comparison

We estimated body fat in 20 normal adults (10 males and 10 females) from 18O- and 2H-dilution spaces and from the equations of Durnin & Womersley and Pollock, Schmidt & Jackson based on skinfold thickness measurements. Differences between methods for body fat estimation were found to be sex-dependent: subsequent analyses indicated significant differences between methods within each sex. Regardless of sex, the highest fat estimates were obtained with the 18O-dilution method, followed by those obtained with the 2H-dilution method or the Durnin & Womersley equation. The lowest fat estimates were obtained using the Pollock, Schmidt & Jackson equation. The 18O-dilution method and the Durnin & Wormersley anthropometric method are both suitable and appropriate for body fat estimation in adults studied under field conditions.     

The effects of running and meditation on beta-endorphin, corticotropin-releasing hormone and cortisol in plasma, and on mood

The relations between three hormones of the hypothalamic-pituitary-adrenocortical (HPA) axis, beta-endorphin (β-EP), corticotropin-releasing hormone (CRH) and cortisol, and mood change were examined in 11 elite runners and 12 highly trained meditators matched in age, sex, and personality. Despite metabolic differences between running and meditation, we predicted that mood change after these activities would be similar when associated with similar hormonal change. Compared to pre-test and control values, mood was elevated after both activities but not significantly different between the two groups at post-test. There were significant elevations of β-EP and CRH after running and of CRH after meditation, but no significant differences in CRH increases between groups. CRH was correlated with positive mood changes after running and meditation. Cortisol levels were generally high but erratic in both groups. We conclude that positive affect is associated with plasma CRH immunoreactivity which itself is significantly associated with circulating β-EP supporting a role for CRH in the release of β-EP. Increased CRH immunoreactivity following meditation indicates, however, that physical exercise is not an essential requirement for CRH release.     

Venous disease: investigation and treatment,fact or fiction?

This review looks at some clinical and experimental methods and treatments used in venous disease, and attempts to dispel some myths which have been associated with it. Over the last century numerous techniques have been introduced to aid the understanding of the physiology of normal legs and the pathophysiology of those with venous disease. Tourniquet testing along with clinical examination remains the only method of venous assessment in most hospitals. Venous ulceration in the past has been associated with deep vein incompetence, but the newer, non-invasive techniques of Doppler ultrasound and duplex examination are now identifying patients with leg ulceration who have superficial venous insufficiency and therefore a surgically correctable condition. Perforating veins and their possible role in the aetiology of venous ulceration along with invasive and non-invasive methods for their detection is reviewed. Some of the conservative compression treatments and dressings available for the treatment of venous ulceration are discussed. It is concluded that adherence to sound surgical principles remains the mainstay of the successful management of patients with venous disease.     

Male infertility and its treatment: A review of over 4700 patients treated for male related infertility

Changes in semen parameters are presented for 4708 patients treated for infertility. The largest group comprised patients with oligoasthenozoospermia of various grades (57.7%). Improvement in the seminal state was noted in 70.3%. The percentage of achieved normospermia increased proportionally to the initial semen state. Pregnancy rate also increased proportionally to the initial seminal state. Among the patients' wives 20.4% conceived: 28.2% of these pregnancies had occurred after having achieved normospermia, while in 71.8% the seminal states were still below the accepted normal values.     

The effects of inhibitors of arachidonate metabolism on spontaneous and evoked endplate potentials at normal and crotoxin-treated frog neuromuscular junctions

Aspirin (1 mM), a selective cyclooxygenase inhibitor, decreased endplate potential (e.p.p.) amplitude but did not affect either the biphasic changes in m.e.p.p. frequency or triphasic changes in e.p.p. amplitude induced by crotoxin. Nordihydroguaiaretic acid (30 microM), a dual inhibitor of cyclooxygenase and lipoxygenase pathways, increased e.p.p. amplitude but did not affect the characteristic changes in m.e.p.p. frequency and e.p.p. amplitude in response to crotoxin. The incidence of giant m.e.p.p.s was reduced by aspirin and increased by NDGA. Arachidonate metabolism is not a major factor in the induction of neurotoxicity by crotoxin at the frog neuromuscular junction.     

Evaluation of Tenidap (CP-66,248) on human neutrophil arachidonic acid metabolism, chemotactic potential and clinical efficacy in the treatment of rheumatoid arthritis

Ten patients with rheumatoid arthritis (RA) were evaluated in a placebo-controlled, double-blind study examining the clinical efficacy of a novel nonsteroidal anti-inflammatory agent: Tenidap (CP-66,248). RA patients receiving active drug therapy (n = 6) demonstrated clinically significant improvements in observer assessment of pain (p less than 0.025), painful joint count (p less than 0.010), and overall clinical assessment as based on a modified rheumatoid activity index, MRAI (p less than 0.025). In parallel laboratory assays, Tenidap was found to exhibit a significant in vitro dose-dependent inhibition of ionophore-stimulated neutrophil production of the 5-lipoxygenase product: [3H]leukotriene B4 (LTB4). Although more importantly, Tenidap was also found to exhibit an in vitro dose-dependent inhibition (IC50 20 microM) of the ionophore-stimulated release (deacylation) of the precursor [3H]arachidonic acid (AA) from membrane phospholipids. In further studies, Tenidap did not have any effect on fMLP-induced neutrophil chemotactic response. These results suggest that one of the possible mechanisms for the clinical effectiveness of this agent, may be through its effect at inhibiting the release of free AA from membrane phospholipids and therefore limiting its further metabolism into certain biologically-active inflammatory lipids.