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.     

Target antigens in malaria transmission blocking immunity

Malaria transmission blocking immunity has been found to operate against two distinct phases of development of malaria parasites in the mosquito midgut: (i) against the extracellular gametes and newly fertilized zygotes shortly after ingestion by a mosquito of parasitized blood and (ii) against the zygotes during their subsequent development into ookinetes. Immunity is antibody-mediated and stage-specific. A set of three proteins, synthesized in the gametocytes, expressed on the surface of the gametes and newly fertilized zygotes and subsequently shed during later transformation of the zygotes, has been identified as the target antigens of anti-gamete fertilization blocking antibodies. A single protein, synthesized and expressed on the zygote surface during its development to ookinetes, has been identified as the target of antibodies which block the development of the fertilized parasites in the mosquito. Immunization of human populations against gamete or zygote antigens, while not directly protecting an immunized individual from inflection, would reduce the transfer of malaria within the population. Such immunity, in addition to reducing the overall rate of malaria transmission, would, if combined with a vaccine against the asexual (disease-causing) stages, reduce the chance of selection of parasites that are resistant to the asexual vaccine by preventing their entry into the mosquito population.     

Characterization of the collagen synthesized by cultured human smooth muscle cells from fetal and adult aorta.

Smooth muscle cells were grown from explants of the tunica media of fetal and adult human aorta. Collagen was isolated after incubation with [14C]glycine and was characterized by ion-exchange chromatography. All cells investigated synthesized two types of collagen: Type I (chain composition [alpha1(I)]2alpha2) and type III (chain composition [alpha1(III)]3). The collagen made by cells from adult donors contained approximately 70% type I and 30% type III collagen. This corresponds to the collagen composition in teh original tissue. No age-relate change in the type I/type III ratio was found with cells from donors between 9 and 67 years of age. On the other hand, the type III portion of the collagen made by fetal cells was markedly less (about 15-20% of total collagen).     

Ribosomal protein S20 purified under mild conditions almost completely inhibits its own translation

Summary The efficiency of ribosomal protein S20 to act as repressor of its own synthesis in an in vitro system was found to depend greatly on the procedures employed to purify this protein. Whilst conventionally purified r-protein S20 inhibited its own synthesis by some 30%, up to 90% inhibition was observed if milder purification conditions were used. Evidence is presented that the latter preparation shows also a higher binding affinity to 16S rRNA.     

Structure of the murine leukemia virus envelope glycoprotein precursor.

The glycosylated env gene precurosr (Pr80env) of Moloney murine leukemia virus has been isolated by selective immunoprecipitation. Use of the drug tunicamycin to inhibit nascent glycosylation or specific cleavage with endoglycosidase H demonstrated that the precursor contained an apoprotein with a molecular weight of 60,000. The finished virion glycoprotein (gp70) was largely resistant to the action of endoglycosidase H. Chromatography of the glycopeptides of Pr80env in conjunction with endoglycosidase H digestion studies suggested that the precursor contained two distinct major glycosylation sites. Analysis of partial proteolytic cleavage fragments of Pr80env before and after endoglycosidase H treatment placed the two glycosylation sites within a 30,000-dalton region of the apoprotein sequence. Kinetic experiments showed that carbohydrate processing as well as proteolytic cleavage are late steps in the maturation of Pr80env.     

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.