The relationship between the size of yellow water traps and catches of aphids

Yellow water traps are often used for sampling populations of flying aphids. This note suggests that the size and probably the shape of traps should be standardised, because trapping efficiency (nos. caught/unit area), and the relative attractiveness of traps to different species, depends on trap size. Aphidologists using water traps to compare mixed populations of flying aphids, should therefore compare catches from different traps with caution.Traps of three sizes were made up from individual trays, each 29×21.5×5cm, and painted Hansa yellow inside; 1 tray alone, 4 arranged in a 2×2 rectangle, and 9 in a 3×3 rectangle, gave trapping surfaces of approx. 625, 2500 and 5700 cm² respectively. The traps were half-filled with water plus a drop of detergent, placed on bare land and daily catches collected on 19 days in June and July 1966.     

Epitopes recognized by the neutralizing antibodies of an HIV-1-infected individual.

Sera from individuals infected by HIV-1 usually neutralize multiple viral isolates. To determine the extent to which these neutralizing antibodies recognize a principal neutralizing determinant in the V3 region of the envelope protein gp120 (amino acids 308-332), one broadly neutralizing serum was fractionated by affinity chromatography on immobilized peptide columns. Antibodies that neutralize one isolate (HTLV-IIIMN) were substantially but not completely absorbed by the peptide corresponding to a portion of its V3 determinant, whereas the antibodies that neutralize two other isolates (HTLV-IIIB and HTLV-IIIRF) were not absorbed by homologous peptides corresponding to their neutralizing determinants. Neutralizing antibodies also failed to be absorbed by full length envelope protein gp160 and by two other envelope peptides previously reported to be broadly neutralizing epitopes (amino acids 254-274 and 735-752). We conclude that the infected individual had raised a type-restricted neutralizing response targeted at a linear epitope in the V3 region, and that broad neutralization resulted from recognition of epitopes not yet identified.     

Endogenous Benzodiazepine Receptor Ligands in Human and Animal Hepatic Encephalopathy

The role of endogenous benzodiazepine receptor ligands in the pathogenesis of hepatic encephalopathy was studied in humans and in rat models of hepatic encephalopathy. Endogenous benzodiazepine ligands were extracted from rat brain and human CSF by acid treatment and purification by HPLC. Detection and partial characterization of these endogenous benzodiazepine ligands were carried out using both radioreceptor binding assays and radioimmunoassays with anti-benzodiazepine antibodies. Four different benzodiazepine receptor ligands were identified in human and rat tissue, two of which may be diazepam and desmethyldiazepam, based on elution profiles and anti-benzo-diazepine antibody reactivity. Human CSF and serum from patients with hepatic encephalopathy contained approximately 10 times more endogenous benzodiazepine receptor ligand than CSF from controls or nonencephalopathic patients with liver disease. The levels of brain benzodiazepine receptor ligand compounds were also increased approximately 10-fold in rats suffering from fulminant hepatic failure, but not in rats with portacaval shunts, a model of chronic hepatic disease. The increased concentrations of these substances could be behaviorally significant and may contribute to the pathogenesis of hepatic encephalopathy.     

ATP hydrolysis by ischemic mitochondria

Cellular ATP levels are determined by the rates of ATP production and ATP hydrolysis. Both phenomena are affected by ischemia. Mitochondrial enzymes are damaged, inhibiting this organelle's ability to make ATP. Mitochondria are also uncoupled by ischemia and have the ability to hydrolyze ATP. We designed a series of experiments to determine whether decreased production or increased hydrolysis of ATP was the primary effect of mitochondrial damage. Rat hearts were subjected to 45 min of warm ischemia in order to induce irreversible cell damage. ATP or ADP was injected into cuvettes containing mitochondria isolated from normal myocardium or myocardium damaged by ischemia. Luciferin-luciferase, which fluoresces in the presence of ATP, was also added to the tubes as an indicator of ATP levels. Mixtures of uncoupled and coupled mitochondria were made and compared with the mitochondria damaged by ischemia. The results showed that mitochondria damaged by prolonged ischemia hydrolyze ATP more rapidly than normal mitochondria; however, normal mitochondria can easily compensate for increased ATP hydrolysis when in mixture with equal amounts of uncoupled mitochondria. These data suggests that the low cellular levels of ATP following irreversible ischemia are primarily due to decreased ATP synthesis and not to increased hydrolysis.     

Aging and sex influence the permeability of the blood-brain barrier in the rat

The aim of the present study was to investigate the existence of aging- and sex-related alterations in the permeability of the blood-brain barrier (BBB) in the rat, by calculating a unidirectional blood-to-brain transfer constant (Ki) for the circulating tracer [14C]-alpha-aminoisobutyric acid. We observed that: a) the permeability of the BBB significantly increased within the frontal and temporo-parietal cortex, hypothalamus and cerebellum in 28-30 week old rats, in comparison with younger animals; b) in several brain areas of female intact rats higher Ki values (even though not significantly different) were calculated at oestrus than at proestrus; c) in 1-week ovariectomized rats there was a marked increase of Ki values at the level of the frontal, temporo-parietal and occipital cortex, cerebellum and brain-stem. One can speculate that aging- and sex-related alterations in the permeability of the BBB reflect respectively changes in brain neurochemical system activity and in plasma steroid hormone levels.