Lysis of bacterioids in the vicinity of the host cell nucleus in an ineffective (fix-) root nodule of soybean (Glycine max)

In nodules of Glycine max cv. Mandarin infected with a nod ⁺fix^- mutant of Rhizobium japonicum (RH 31-Marburg), lysis of bacteroids was observed 20 d after infection, but occurred in the region around the host cell nucleus, where lytic compartments were formed. Bacteroids, and peribacteroid membranes in other parts of the host cell remained stable until senescence (40d after infection). With two other nod⁺ fix^- mutants of R. japonicum either stable bacteroids and peribacteroid membranes were observed throughout the cell (strain 61-A-165) or a rapid degeneration of bacteroids without an apparent lysis (strain USDA 24) occurred. The size distribution of RH 31-Marburg-infected nodules exhibited only two maxima compared with four in wild-type nodules and nodule leghaemoglobin content was found to be reduced to about one half that of the wild type. The RH 31-Marburg-nodule type is discussed in relation to the stability of the bacteroids and the peribacteroid membrane system in soybean.     

The transition of the thick ascending limb of Henle's loop into the distal convoluted tubule in the nephron of the rat kidney

Summary Examination of serial semithin sections of rat kidney cortex and a subsequent electron microscopic study of selected areas revealed that the characteristic epithelium of the cortical part of the thick ascending limb of Henle extends for a varying distance beyond the macula densa. The transition from the relatively thin epithelium of the thick ascending limb at this site to the three -or even four-fold thicker epithelium of the convoluted part of the distal tubule is sharply defined and occurs without the interposition of an intermediate cell type.The position of the macula densa at the end but still clearly within the ascending limb of Henle's loop is functionally interpreted to guarantee the separation of the sensor point macula densa from disturbing influences which might arise from the secretory activity of the subsequent tubular portion.Investigations supported by the Deutsche Forschungsgemeinschaft. The skillful technical assistance of Mrs. Saliha Sabanovic is gratefully acknowledged     

Inhibition of compensatory kidney hypertrophy by hypothyroidism in the rat. Measurement of the mean diameter of glomeruli and proximal tubules]

The body, heart and kidney weights are reduced in the hypothyroid rat. In this animal, the diameter of the proximal tubule is significantly smaller than in euthyroid controls. The glomerular diameter is not affected by hypothyroidism. 21 days after uninephrectomy, the weight of the remaining kidney and the diameter of the proximal tubule increase significantly both in the hypothyroid and the euthyroid rats. But this compensatory renal hyperthrophy is definitely impaired in the hypothyroid animals.     

Germination dimorphism and developmental flexibility in the ruderal weed Heterotheca grandiflora

Summary Heterotheca grandiflora Nutt. (Asteraceae, tribe Astereae) is one of the few native Californian plant species increasing its range as a weed. The production of dimorphic seed, together with flexible development in either the annual or biennial habit, may contribute to its range expansion. Well dispersed disc achenes germinate rapidly to high percentages while poorly dispersed ray achenes show considerable dormancy, germinating at a much lower rate to lower final percentages. Ray achenes appear more sensitive to environmental factors and have more specific germination requirements than do disc achenes. Thus, germination is distributed in space and time. Plants growing as annuals have one flowering period while those acting as biennials may flower up to three times, although seed production differs greatly among the stages. These factors aid in forming the general purpose genotype so frequently encountered in weedy species.     

Effects of methylazoxymethanol given at different stages of postnatal life on development of the rat brain. Comparison with those of thyroid deficiency

Newborn rats were treated at different stages of their development with low doses of methylazoxymethanol acetate. The postnatal increase of the DNA content of the cerebrum did not differ from that of controls. In the cerebellum, the DNA content was transitorily reduced, but later, the external granular layer became thicker and DNA deposition increased in comparison with controls; finally, the cerebellar DNA returned to a normal value. Morphological abnormalities of the cerebellum, abnormal orientation of migrating cells, scattering of Purkinje cell bodies within the internal granule cells and specially striking abnormalities of the morphology and orientation of Purkinje cell dendrites were noted in rats treated with MAM from birth to day 3. The effects on the Purkinje cell morphogenesis persisted but were much less marked when MAM was given from 4 to 7 or from 8 to 11 days. Neonatal thyroid deficiency, as MAM-treatment between days 0 and 3, leads to an abnormal position of Purkinje cell bodies within the cerebellar cortex; it also leads to morphological abnormalities of their dendritic arborization which closely resemble those observed after MAM-treatment during the second postnatal week. It also alters the cell formation in the cerebellum. Thyroid deficiency probably exerts its effect on cell formation earlier than previous biochemical studies have shown. On another hand, the morphological abnormalities of Purkinje cell arborizations in the thyroid-deficient animals may be partly due to the perturbations of cell formation which persist later in the cerebellum.     

Evolutionary Consequences of DNA Mismatch Inhibited Repair Opportunity

Double strand breaks (DSBs) are often repaired via homologous recombination. Recombinational repair processes are expected to be influenced by nucleotide heterozygosity through mismatch detection systems. Unrepaired DSBs have severe biological consequences and are often lethal. We show that natural selection due to inhibition of recombinational repair associated with polymorphisms could influence their molecular evolution. The main conclusions from this analysis are that, for increasing population size, mismatch detection leads to a limit on average heterozygosity of otherwise selectively neutral polymorphism, an excess of rare variants, and a slowing down of the rate of neutral molecular evolution. The first two results suggest that mismatch detection may account for the surprisingly narrow range of observed average heterozygosities, given the great variation in population size between species.     

Differences in the In Vitro and In Vivo 5-Hydroxytryptamine Extraction Performance Among Three Common Microdialysis Membranes

The present study summarizes the results of an in vitro and in vivo comparison of the apparent 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid, and 3,4-dihydroxyphenylacetic acid dialysis performance of three types of membrane frequently used in intracerebral microdialysis experiments. The dialysis fiber types examined were a regenerated cellulose Cuprophan (GF), a proprietary polycarbonate ether (CMA), and a polyacrylonitrile/sodium methallylsulfonate copolymer (HOSPAL). The experiments unexpectedly revealed that the HOSPAL membrane-equipped probes displayed clearly aberrant 5-HT diffusion dynamics compared with GF and CMA probes, demonstrable not only in vitro, but also in in vivo experiments. In vitro, the GF and CMA membrane-equipped probes exhibited maximum relative recovery for 5-HT already in the first 20-min sample, whereas the 5-HT recovery of HOSPAL probes increased in a very slow and protracted manner over a period of a little less than 2 h. The GF and CMA probes further displayed an immediate washout of 5-HT when the probes were subsequently transferred to artificial CSF only-containing medium (no 5-HT), whereas approximately 2 h was required to yield near-total extinction of dialysate 5-HT with the standard HOSPAL probes. In vivo, the rat ventral hippocampal dialysate 5-HT output responses to K+ (100 mM) infusion, to Ca2+ omission, and to systemic 8-hydroxy-2-(di-n-propylamino)tetralin injection were all markedly retarded and blunted when HOSPAL instead of GF membrane-equipped probes were used. However, the 5-hydroxyindoleacetic acid and 3,4-dihydroxyphenylacetic acid extraction in vitro and in vivo were comparable using either of the membrane types.(ABSTRACT TRUNCATED AT 250 WORDS)     

Subtype of muscarinic receptor coupled to the attenuation of hormone-stimulated cAMP accumulation in NG108-15 neuroblastoma x glioma hybrid cells.

The subtype of muscarinic receptor which mediates cAMP attenuation is not established. Therefore, several selective muscarinic antagonists were used to characterize the subtype of muscarinic receptor coupled to the inhibition of hormone-stimulated cAMP accumulation using NG108-15 neuroblastoma x glioma hybrid cells. These cells were prelabeled with [2-3H]-adenine, washed, and resuspended in a culture medium containing the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.5 mM). The labeled cells were preincubated with the different antagonists 12-15 min. before they were challenged with agonists. The formation of [3H]-cAMP was activated by PGE1 (1 microM) or forskolin (1 microM). In all cases, [3H]-cAMP formed was separated and measured. Carbachol (100 microM) and McN-A343 (10 mM) were used as standard muscarinic agonists. These studies gave the following results: a) McN-A343 (10 mM), an M1 receptor agonist, was only a partial agonist causing 40% inhibition of cAMP accumulation indicating that this effect was not mediated by an M1 receptor; b) The M1-selective antagonist, pirenzepine, exhibited low affinity (pA2 6.2) further suggesting that an M1 receptor was not coupled to the attenuation of cAMP accumulation; c) Two selective M2 antagonists (AF-DX 116 and methoctramine) and M3 antagonist (HHSiD) were used to further characterize these muscarinic receptors. The order of all antagonists based on their affinities (pA2 values) could be arranged in the following order: atropine (9.0) > methoctramine (7.6) > HHSiD (6.9) > AF-DX 116 (6.6) > pirenzepine (6.2). HHSiD exhibits the same degree of affinity to M2 receptors of other tissues as it does to those of NG cells.(ABSTRACT TRUNCATED AT 250 WORDS)