Characterisation of the arrestment responses of Trichogramma evanescens

Summary Contact kairomones and oviposition in a host egg stimulated arrestment behaviour in Trichogramma evanescens, characterised by a reduction in walking speed and increased turning. Previous oviposition experience did not influence a parasitoid's response to contact kairomones, but successive encounters with kairomone patches resulted in parasitoids habituating to the contact chemical. Oviposition on a kairomone patch did not reverse this habituation effect. It was concluded that contact kairomones and host eggs will both contribute independently to the duration of a patch visit. The selection of patches by T. evanescens will depend on its response to kairomones. Results from this study indicate that the application of contact kairomones to field crops will not necessarily increase the probability of parasitoids finding hosts.     

tert–butylhydroperoxide—Induced toxicity in isolated hepatocytes: Contribution of thiol oxidation and lipid peroxidation

Incubation of isolated rat hepatocytes with tert-butylhydroperoxide resulted in marked cytotoxicity preceded by intracellular glutathione depletion and extensive lipid peroxidation. Addition of antioxidants delayed, but did not prevent, this toxicity. A significant decrease in protein-free sulfhydryl groups also, occurred in the presence of tert-butylhydroperoxide; direct oxidation of protein thiols and mixed disulfide formation with glutathione were responsible for this decrease. The involvement of protein thiol depletion in tert-butylhydroperoxide–induced cytotoxicity is suggested by our observation that administration of dithiothreitol, which caused re-reduction of the oxidized sulfhydryl groups and mixed disulfides, efficiently protected the cells from toxicity. Moreover, depletion of intracellular glutathione by pretreatment of the hepatocytes with diethyl maleate accelerated and enhanced the depletion of protein thiols induced by tert-butylhydroperoxide and potentiated cell toxicity even in the absence of lipid peroxidation.     

Effect of pressure on [3H]GABA release by synaptosomes isolated from cerebral cortex

High hydrostatic pressure has been shown to produce neurological changes in humans which manifest, in part, as tremor, myoclonic jerks, electroencephalographic changes, and convulsions. This clinical pattern has been termed high-pressure nervous syndrome (HPNS). These symptoms may represent an alteration in synaptic transmission in the central nervous system with the inhibitory neural pathways being affected in particular. Since gamma-aminobutyric acid (GABA) transmission has been implicated in other seizure disorders, it was of interest to study GABAergic function at high pressure. Isolated synaptosomes were used to follow GABA release at 67.7 ATA of pressure. The major observation was a 33% depression in total [3H]GABA efflux from depolarized cerebrocortical synaptosomes at 67.7 ATA. The Ca2+-dependent component of release was found to be completely blocked during the 1st min of [3H]GABA efflux with a slow rise over the subsequent 3 min. These findings lead us to conclude that high pressure interferes with the intraterminal cascade for Ca2+-dependent release of GABA.     

Reconstitution of catecholamine-stimulated adenylate cyclase activity using three purified proteins

beta-Adrenergic receptors, the GTP-binding regulatory protein that stimulates adenylate cyclase (Gs), and adenylate cyclase were each purified and reconstituted into unilamellar vesicles composed of phosphatidylethanolamine and phosphatidylserine (3:2, w/w). The molar ratio of receptor:Gs:adenylate cyclase was estimated to be about 1:10:1. Adenylate cyclase activity in the vesicles was stimulated up to 2.6-fold by beta-adrenergic agonists. Stimulation was dependent on the presence of guanine nucleotide, displayed appropriate beta-adrenergic selectivity and stereoselectivity for agonists, and was blocked appropriately by beta-adrenergic antagonists. Therefore, while additional proteins may modulate adenylate cyclase activity in native membranes, these results show that these three proteins are sufficient for the expression of hormone-stimulated adenylate cyclase.     

Gibberellins in immature seeds and dark-grown shoots of Pisum sativum

Gibberellins (GAs) A₁₇, A₁₉, A₂₀, A₂₉, A₄₄, 2OH-GA₄₄ (tentative) and GA₂₉-catabolite were identified in 21-day-old seeds of Pisum sativum cv. Alaska (tall). These GAs are qualitatively similar to those in the dwarf cultivar Progress No. 9 with the exception of GA₁₉ which does not accumulate in Progress seeds. There was no evidence for the presence of 3-hydroxylated GAs in 21 day-old Alaska seeds. Dark-grown shoots of the cultivar Alaska contein GA₁, GA₈, GA₂₀, GA₂₉, GA₈-catabolite and GA₂₉-catabolite. Dark-grown shoots of the cultivar Progress No.9 contain GA₈, GA₂₀, GA₂₉ and GA₂₉-catabolite, and the presence of GA₁ was strongly indicated. Quantitation using GAs labelled with stable isotope showed the level of GA₁ in dark-grown shoots of the two cultivars to be almost identical, whilst the levels of GA₂₀, GA₂₉ and GA₂₉-catabolite were significantly lower in Alaska than in Progress No. 9. The levels of these GAs in dark-grown shoots were 10²- to 10³-fold less than the levels in developing seeds. The 2-epimer of GA₂₉ is present in dark-grown-shoot extracts of both cultivars and is not thought to be an artefact.Abbreviations cv cultivar - GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatographymass spectrometry - HPLC high-pressure liquid chromatography - KRI Kovats retention index - MeTMSi methyl ester trimethylsilyl ether     

Effects of aging on cell cooperation and lymphocyte responsiveness to cytokines

Functional activities and cell cooperation of macrophages (Mphi), T cells, and B cells of young and old Lewis rats were compared. Splenic M phi from young and old rats provided accessory help for T cell mitogenesis and B cell mitogenesis, provided accessory help for generation of PFC, and produced IL 1 equally well as measured in costimulator assays. Splenic T cells of aged Lewis rats, however, were poorly responsive in mitogen assays and did not respond to supplemental IL 2 and antigen with blast transformation and with increased help for B cells to produce PFC. "Old" B cells did not respond in vitro to mitogens with help from M phi and T cells, nor did they respond to B cell helper factor with increased PFC. The data indicate that hyporesponsiveness of the immune system, especially of B cells, in aged rats is due in part to defective reactivity to interleukins and cytokine(s) and to defective cell-cell cooperation.     

Immunological Studies on Dermatophytes IV. Chemical Structures and Serological Reactivities of Polysaccharides from Microsporum praecox, Trichophyton ferrugineum, Trichophyton sabouraudii, and Trichophyton tonsurans

The chemical structures and serological specificities of polysaccharides isolated from four species of dermatophytes, Microsporum praecox, Trichophyton ferrugineum, T. sabouraudii, and T. tonsurans, were investigated. Each of these species yielded a mixture of crude polysaccharides which could be separated into three water-soluble, neutral polysaccharides free of nitrogen. These were grouped as galactomannan I, galactomannan II, and glucan. The galactomannans I were quite similar in chemical structure. When measured by complement fixation, their serological cross-reactivities were similar with rabbit antisera to each of these species except T. sabouraudii. The differences in their relative reactivities with this antiserum could be correlated with differences in structure and specificity of this antiserum for galactofuranose end groups. The galactomannans II differed both in chemical structure and in their serological reactivities with antisera to each of these species. The galactomannan II from T. ferrugineum differed most in chemical structure and was the least reactive serologically. The glucans also differed in both structure and serological reactivities.     

CHLOROPLAST DEVELOPMENT IN OCHROMONAS DANICA

When dark-grown cells of Ochromonas danica are placed in the light, the amount of chlorophyll a per cell increases 82-fold; the content of carotenoid pigment, 24-fold. Concomitantly with this increase in chlorophyll and carotenoid pigment, the small proplastid of dark-grown cells develops into a large lamellate chloroplast. During the first 12 hours in the light, vesicles appear within the loose clusters of dense chloroplast granules, enlarge, align themselves into rows (plates in three dimensions), and fuse into discs. Double discs may form from the more or less simultaneous fusion of two adjacent plates of vesicles or by the addition of vesicles to an already formed single disc. Three-disc bands arise by the addition of a disc to an already formed two-disc band through the approach and fusion of more vesicles. After 24 hours in the light, most of the chloroplast bands contain three discs, but the chloroplasts are still small. After 48 hours in the light, almost all the cells contain full-sized chloroplasts with a full complement of three-disc bands. However, at this time the amount of chlorophyll a and carotenoid pigment is only one-half of maximum. During the next 3 days in the light, as the number of chlorophyll and carotenoid molecules per chloroplast approximately doubles, there is a compression of the discs in each band (from 180 to 130 A) and a precise alignment of their membranes. Changes also occur in the nucleus when dark-grown cells are placed in the light. There is an increase in the number of small nucleolar bodies, many of which lie directly against the nuclear envelope, and in a few cells a dense mass of granules is seen between the two membranes of the nuclear envelope.     

An electron microscopic study of the cerebral blood vessels of the opossum

Summary Blood vessels of the opossum brain are paired, artery and vein, and end in a closed loop. Both anatomically and physiologically they are true end-arteries. The two limbs are enclosed within a single basement membrane and are separated from each other by an intercapillary cell thought to be analogous to the usual capillary pericytes. The similarity of this vascular arrangement to that in the rabbit placenta and in the medulla of the kidney is discussed in relation to the counter-current multiplier system.This work was supported in part by the Beaumont-May Institute of Neurology and by a grant, B-425, from the United States Public Health Service.Research Fellow of the National Multiple Sclerosis Society.     

FINE STRUCTURE OF THE NEUROHYPOPHYSIS OF THE OPOSSUM (DIDELPHIS VIRGINIANA)

The neurohypophysis of the opossum (Didelphis virginiana) was studied by electron microscopy in order to amplify Bodian''s classic light microscopic observations in which he demonstrated a definite lobular pattern. The lobule of the opossum neurohypophysis is divided into three regions: a hilar, a palisade, and a septal zone. The hilar portion contains bundles of nerve fibers, the extensions of the hypothalamo-hypophyseal tract containing neurofilaments but few neurosecretory granules. In the opossum, pituicytes have a densely fibrillar cytoplasm. Herring bodies are prominent in the hilar region. They are large bodies packed with neurosecretory granules that have been described as end bulb formations of axons. From the hilar region, axons fan out into a palisade zone where the nerve terminals packed with neurosecretory granules, mitochondria, and microvesicles abut upon basement membranes. The neurosecretory granules are similar to those present in the neurohypophysis of other mammals, except for an occasional huge granule of distinctive type. Material morphologically and histochemically resembling glycogen occurs as scattered particles and as aggregates within nerve fibers. The septal zone, containing collagen, fibroblasts, and numerous small capillaries, is separated from the adjacent glandular tissue by a basement membrane.