The effect of kainate on protein kinase C,GABA, and the uptake of serotonin in the rabbit retina in vivo

The purpose of this study was to investigate the effect of kainate on protein kinase C (PKC), -aminobutyrate (GABA) and serotonin uptake in the rabbit retina. Kainate when injected into the vitreous humour produces a change in the GABA immunoreactivity within 6 hours. After 3 days, remnants of the normal GABA immunoreactivity still persist and additionally astrocyte and microglia-like elements stain positively for GABA. After 7 days exposure to kainate none of the normal GABA immunoreactivity is apparent, instead a number of round-shaped elements which may be reactive astrocytes and/or microglia stain positively for GABA. During these stages kainate does not affect the PKC immunoreactivity associated with the on-bipolar cells. Six hours following kainate treatment the ability of certain GABA amacrine cells to take up exogenous serotonin is unaffected. After three days only a few of these cells can still take up exogenous serotonin and then not avidly. After seven days the GABA/serotonin amacrine cells cannot take up exogenous serotonin suggesting that all of these neurons are irreversibly damaged. One hour after treatment with kainate both calcium-dependent and-independent PKC species are translocated from the cytosolic to membrane compartments. After 5 hours and 7 days there was also evidence from the enzyme assay experiments that kainate caused the calcium-dependent and-independent PKC enzymes to be translocated but because the total enzyme activity was reduced due perhaps to down-regulation of the enzyme this was difficult to assess precisely. However, the electrophoresis/blotting experiments of tissues exposed for 5 hours (but not one hour) to kainate established clearly that , , and PKC are translocated from cytosolic and membrane compartments.     

A general-purpose system for characterizing medically important bacteria to genus level

A computer program and accompanying data matrix have been prepared for bacteria of medical interest, to assist the assignment of an unidentified bacterium to the most likely genus. The results on a set of relatively simple tests are entered. The program prints the more likely genera, followed by a list of diagnostic tables in Cowan & Steel (1974) and Buchanan & Gibbons (1974). Where available, identification matrices for further computer-assisted study, are presented. This program may be of particular help in laboratories where a wide range of bacteria have to be identified.     

Clinical implications of developments in in vitro fertilisation.

During February 1979 to December 1983, 831 infertile couples were treated by in vitro fertilisation and embryo transfer. The problems they faced included deciding on the number of oocytes to be collected at laparoscopy, the numbers to be donated or fertilised, the numbers of embryos to be transferred and frozen, and whether abnormal embryos should be used for research or discarded. The 831 patients received a total of 1530 treatment cycles. Of the 763 patients for whom complete data were available, 136 (17.8%) became pregnant. The rate of pregnancy, however, increased dramatically from 7.4% when only one embryo was transferred to 21.1% and 28.1% when two and three embryos were transferred, respectively. The chance of multiple pregnancy also increased with the number of embryos transferred, but the risk (2% for twins) was far outweighed by the relatively poor result after transferring a single embryo. Out of 40 embryos freeze-thawed, 23 survived thawing and were transferred; of these, 4 (17%) resulted in pregnancy. Thirty four transfers of donor oocyte embryos also resulted in four pregnancies (12%), but two of these ended in abortion. Neither microscopy nor any other available test can determine the potential of an oocyte to result in pregnancy, so that discarding oocytes that may look abnormal simply reduces the chances of conception--both for the patient and for any prospective recipient of donor oocyte embryos. In any case, abnormal embryos tend to die when growth is allowed to continue in vitro. Probably all oocytes harvested from a patient should be inseminated and the utilisation of the embryos decided once the number developed is known.     

Isolation and characterization of recombinant clones containing the chicken adult beta-globin gene.

We have isolated and characterized two independent clones containing the chicken adult beta-globin gene. Each clone contains a 6.2-kilobase-pair Eco RI restriction fragment of chicken erythrocyte DNA inserted into the vector, lambda gtWES . lambda B. The orientation of the inserted fragment is opposite in the two clones. Characterization of the clones by electron microscopic R-loop studies, by restriction enzyme mapping, and by filter hybridization shows that the adult beta-globin gene is interrupted by at least one small and one large intervening sequence. In addition to the complete adult beta-globin gene, at least part of a second beta-globin-like gene was identified about 2.7 kilobase pairs from the 3'-end of the adult gene. The two independent clones, while very similar, do differ at two Msp I restriction endonuclease sites in regions flanking the adult beta-globin gene.     

Attachment of tail fibers in bacteriophage T4 assembly: role of the phage whiskers.

The collar and whiskers of bacteriophage T4 extend outward from the top of the tail and play a role in regulating retraction of the tail fibers (Conley &; Wood, 1975). The collar and whiskers also are required for efficient tail fiber attachment during phage assembly. The structural gene for the collar/whisker protein is called wac. In vitro, infected-cell extracts that contain tail fibers activate whiskerless (wac) tail fiberless particles and ordinary (wac⁺) tail fiberless particles at equal rates if the extracts contain the wac⁺ gene product. However, extracts that contain tail fibers but no wac⁺ gene product activate wac particles about ten times more slowly. In vivo, whiskers are not essential for plaque formation, but a wac mutation causes a delay in the appearance of intracellular phage and a fivefold decrease in the burst size of infectious particles.The effect of the whiskers on tail fiber attachment is due to an interaction between the whisker and the distal half of the tail fiber, similar if not identical to the interaction that controls tail fiber retraction in complete phage. The following observations support this view: a slow rate of in vitro tail fiber attachment similar to that described above is seen with wac⁺ particles when they are pretreated with anti-whisker serum, or when the tail fibers carry a mutational alteration in gp36, a structural protein in the distal half fiber near the central kink. Lack of whiskers does not affect the slow rate of attachment of proximal half fibers to the baseplate of fiberless particles, but lack of whiskers greatly decreases the rate at which particles with attached proximal half fibers are activated by addition of distal half fibers. Since whiskers normally are attached to the phage only after head—tail union (Coombs &; Eiserling, 1977; Terzaghi et al., 1978), these findings explain why tail fibers do not attach efficiently to the baseplates of free tails.     

Effects of temperature on respiration and acid-base balance in a monitor lizard

Summary Ventilation, gas exchange, blood gas tensions and arterial pH were measured simultaneously in monitor lizards,Varanus exanthematicus. In contrast to previously studied poikilotherms, the arterial pH is independent of body temperature within the normally encountered temperature range (Fig. 1). This exception to the relative alkalinity concept (Rahn, 1966) is correlated with the finding thatV. exanthematicus maintains a constant ratio of ventilation to oxygen uptake (and CO₂ production) at different temperatures (Fig. 3). The increase in arterial (Fig. 1) is related to an increase in physiological dead space; i.e., alveolar ventilation increases less with temperature than total ventilation (Fig. 4). This may result from the increased frequency of breathing which results in a reduced breath holding time (Fig. 2). Varanid lizards have a higher oxygen requirement than other reptiles. This is reflected in the control of ventilation, the specialized lung morphology, the high arterial saturation due to low intracardiac shunting, pH regulation and other mammal-like features ofVaranus.     

Unusual thick and thin filament packing in a crustacean muscle

The proximal accessory flexor (PAF) of the myochordotonal organ (MCO) in the meropodite of crayfish walking legs contains two populations of muscle fibers which are distinguishable by their diameters. The large accessory (LA) fibers are 40-80 micrometer in diam and are similar in ultrastructure to other slow crustacean fibers. The small accessory (SA) fibers are 1-12 micrometer in diam and have a unique myofilament distribution at normal body lengths. There is extensive double overlap of thin filaments at these lengths, and some of them form bundles that may extend the length of the sarcomere. In the middle of the sarcomeres, thick and thin filaments are totally segregated from each other. When the fibers are stretched to lengths beyond double overlap length, the myofilament patterns are conventional. The segregated pattern is reestablished when stretched fibers are allowed to shorten passively. The length-tension relationship of the SA fibers is described by a linear ascending branch, a plateau, and a linear descending branch. The ascending branch encompasses normal body lengths from slack length (Ls) with maximum double overlap to the length at which double overlap ceases (1.8 X Ls). The descending phase is comparable to that of other skeletal muscles. That is, tension decreases in proportion with the reduction in thick-thin filament interdigitation (2 X Ls to 3 X Ls).     

Predation by Megaponera foetens (Fabr.) (Hymenoptera: Formicidae) on termites in the Nigerian southern Guinea Savanna

Summary At Bakers Hill, differential winter mortality of juvenile slowgrowing Amphibolurus ornatus is correlated with the incidence of frosts (Bradshaw, 1971). The present study shows that the probability an individual will spend the night in a refuge that is safe from the lethal effect of a frost is directly related to the individual's size. Thus should frosts occur during any particular winter, juvenile slow-growers, will suffer a higher mortality than juvenile fast-growers. At Tuttanning, animals do not segregate according to size, and consequently juvenile slow-growers do not suffer increased mortality during frosty winters.