Axonal patterns of disc-shaped cells in the central nucleus of the cat inferior colliculus

The axonal patterns of disc-shaped cells (Dsc) and their distribution within the central nucleus (Cn) of the inferior colliculus was studied in young cats with the rapid Golgi method. Dsc were subdivided in three main cell varieties according to their axonal branching pattern. The first type possesses local axonal collaterals inside the lamina of origin but also gives collaterals and probably terminals to adjacent lamina. The second variety is characterized by a dense axonal plexus with a restricted zone of arborization. The third axonal pattern is distributed in a radiate fashion. These results demonstrate that Dsc contribute to the intrinsic axonal system of the Cn to a larger degree than previously supposed. Axon terminals of Dsc probably establish axo-dendritic contacts with medium sized Stc which probably establish contacts with neighbouring Dsc. This suggests that reciprocal connections between Dsc and Stc could exist in the Cn.     

Effect of epinephrine on the synthesis of glyceride glycerol in adipose tissue in vitro.

In order to study the effect of epinephrine on the rate of esterification of fatty acids in adipose tissue, pieces of epididymal fat pad were incubated in KRB in the presence of purified albumin, glucose and either 1-14C-glycerol, 1-14C-glucose or 6-14C-glucose. Epinephrine enhances the production of glycerol but reduces the uptake of 1-14C-glycerol by the tissue and its conversion to 14CO2, 14C-fatty acids and 14C-glyceride glycerol. When the change in specific activity of the tracer is taken into account the effect of epinephrine on the utilization of glycerol by the tissue is only observed in the reduction of glyceride glycerol synthesis. When 14C-labelled glucose was used as tracer, epinephrine enhances both the production of 14CO2 from 6-14C-glucose and the synthesis of 14C-glyceride glycerol from 1-14C and 6-14C-glucose. The contrasting effects of epinephrine on the glyceride glycerol formation from glycerol and from glucose can explain the difficulties found in observing any change in the net rate of esterification of fatty acids by adipose tissue.     

Different efficiency of UmuDC and MucAB proteins in UV light induced mutagenesis in Escherichia coli

Summary Two multicopy plasmids carrying either the umuDC or the mucAB operon were used to compare the efficiency of UmuDC and MucAB proteins in UV mutagenesis of Escherichia coli K12. It was found that in recA ⁺ uvr ⁺bacteria, plasmid pIC80, mucAB ⁺mediated UV mutagenesis more efficiently than did plasmid pSE117, umuDC ⁺. A similar result was obtained in lexA51(Def) cells, excluding the possibility that this was due to a differential regulation by LexA of the umuDC and mucAB operons. We conclude that some structural characteristic of the UmuDC and MucAB proteins determines their different efficiency in UV mutagenesis. This characteristic could be also responsible for the observation that in the recA430 mutant, pIC80 but no pSE117 can mediate UV mutagenesis. In the recA142 mutant, pIC80 also promoted UV mutagenesis more efficiently than pSE117. In this mutant, the recombination proficiency, the protease activity toward LexA and the mutation frequency were increased by the presence of adenine in the medium. In recA ⁺ uvrB5 bacteria, plasmid pSE117,umuDC caused both an increase in UV sensitivity as well as a reduction in the mutation frequency. These nagative effects resulting from the overproduction of UmuDC proteins were higher in recA142 uvrB5 than in recA ⁺ uvrB5 cells. In contrast, overproduction of MucAB proteins in excision-deficient bacteria containing pIC80 led to a large increase in the mutation frequency. We suggest that the functional differences between UmuDC and MucAB proteins might be due to their different dependence on the direct role of RecA protease in UV mutagenesis.     

Characterization of cell ion exchange in the sea anemoneCondylactis gigantea

Summary Maintenance of intracellular ion contents and their relations to transmembrane potential were studied in tentacles ofCondylactis gigantea. Tentacles leached at 2°C in 10 mMK⁺ and 2 mM K⁺ artificial seawaters (10K ASW and 2K ASW) with and without 2 MM ouabain, and in 0K ASW, lost cell K⁺ and gained Na⁺. Rewarming to 25°C in 10K ASW resulted in a marked accumulation of K⁺ and extrusion of Na⁺ in tentacles leached in 10K ASW and in 0K ASW. Initial rate of Na⁺ extrusion was twice the initial rate of K⁺ accumulation, suggesting a pump coupling ratio of 2. In tentacles leached and rewarmed in 2K ASW, no net reaccumulation of K⁺ and little net extrusion of Na⁺ was observed; i.e., the pump just kept pace with the leaks. Ouabain inhibited K⁺ reaccumulation and Na⁺ extrusion. This effect was less marked in 10K ASW than in 2K ASW confirming, in anemone tentacles, the well documented ouabain-K⁺ antagonism observed in other systems. In no case did K _i ⁺ /K ₀ ⁺ equal Cl ₀ ^– /Cl _i ^– ; therefore, the distribution of these ions did not fit a Donnan distribution. Transmembrane potential difference was –22±3 mV in 10K ASW at 25°C. It fitted a modified Nernst equation which includes the pump coupling ratio and a Na⁺ to K⁺ permeability ratio of 0.31.A moderately high permeability of the cell membrane to Na⁺, and a ouabain and K⁺ sensitive ion pump, exchanging 2 Na⁺ for 1 K⁺, appear to be responsible for the observed ionic distribution and transmembrane potential in anemone cells.     

New role for photoreversible pyrimidine dimers in induction of prototrophic mutations in excision-deficient Escherichia coli by UV light.

UV mutagenesis to His+ in certain recA441 lexA51 bacteria was not photoreversible, indicating that pyrimidine dimers are not target lesions. Photoreversibility was observed in recA+ lexA51 bacteria, showing that pyrimidine dimers are needed to activate the recA+ protein (unlike the recA441 protein) to perform a function in UV mutagenesis distinct from cleavage of the lexA repressor.     

Evolutionary aspects on the construction of the first optic neuropil (lamina) in Crustacea

Summary A Golgi study of the neuronal morphology of the first optic neuropil (lamina) in three anostracan species revealed a close similarity in the lamina construction and neuron types. The lamina architecture of decapod and mysid crustacean species, as revealed by the Golgi method, conformed to previous studies and differed from the anostracans. The comparison was made at the level of resolution comprising retinal projection on the lamina, structural entities such as columns and layers and neuron position, branching pattern and terminal fields. It was shown that different types of compound eyes and variation in the habitat of the animals were of less importance for the lamina design than common descent as expressed in the present taxonomic groups.     

Effect of stress and sampling site on metabolite concentration in rat plasma

The effect of mild stress on various plasma metabolites in the rat has been studied. Mild stress resulted in significant decreases in liver size and glycogen content, as well as in an increase of blood glucose. In addition, plasma lactate, insulin, glycerol and urea, as well as a number of amino acids were altered by stress. These data indicate that minimal stress can have major effects upon the composition of blood, and suggest the need for strict precautions on the handling of animals during blood sampling. The site of blood extraction--tail tip vs. neck--was also found to have a significant effect on plasma lactate, glucose and urea concentrations. In stressed animals the differences between tail- and neck blood composition were increased.