Spatially resolved cytosolic calcium response to angiotensin II and potassium in rat glomerulosa cells measured by digital imaging techniques

The response of cytosolic calcium [Ca2+]i to angiotensin II (AII) and potassium (K+) in individual rat glomerulosa cells was determined using the calcium-sensitive fluorescent dye, fura-2 and digital imaging. Control (4 mM K+) cytosolic calcium levels were generally in the 80-120 nM range and increased monotonically as [K+] was increased from 4 to 12 mM. There was no delay in the onset of the response. In most cells the [Ca2+]i decreased from its peak after 3-4 min, even in the presence of superfusate containing elevated K+. The time course of the change in [Ca2+]i in response to AII stimulation, on the other hand, was more variable. It was most often characterized by an early decrease followed by a large delayed increase. The response also was observed to decline during sustained AII stimulation. The majority of the cells showed some response to one or the other secretagogue with a sizeable minority (25%) having an increase in [Ca2+]i in excess of 200%. While the majority showed a response, the cell to cell variation was substantial. Finally, the pattern of cytosolic calcium increase sometimes showed a marked dependence on the secretagogue used, with different regions of the same cell being more strongly affected by one agent or the other. A few cells (10%) responded to AII only at one pole, establishing a large concentration gradient of calcium across the cell. Because of differences in time course, pattern, and degree of responsiveness, it is likely that the mechanisms underlying the Ca2+ elevation with K+ and AII are different.     

Controlled trial of methylprednisolone pulses and low dose oral prednisone for the minimal change nephrotic syndrome.

In a multicentre, randomised, prospective trial 89 patients (67 children and 22 adults) with the minimal change nephrotic syndrome were treated with three intravenous pulses of methylprednisolone followed by low dose oral prednisone for six months (group given methylprednisolone) or with high dose oral prednisone for four weeks followed by low dose oral prednisone for five months (control group). Five patients in the group given methylprednisolone and one in the control group did not respond initially. The time to response was shorter in children treated with methylprednisolone. No significant differences between the two groups were observed in the number of patients who relapsed or number of relapses per patient per year. Patients given methylprednisolone tended to relapse earlier than patients in the control group. Side effects related to treatment were significantly fewer in the group given methylprednisolone than in the control group. These data suggest that a short course of methylprednisolone pulses followed by low dose oral prednisone is only marginally less effective than a regimen of high dose oral steroids but can improve the ratio of risk to benefit associated with treatment of the minimal change nephrotic syndrome.     

Nucleic acid relationships among Acholeplasma species.

3H-labeled Acholeplasma DNA probes were generated in vitro by the nick-translation method and used to determine the nucleotide sequence homology among the type strains of the eight currently recognized species of Acholeplasma. Very little nucleotide sequence homology (less than or equal to 18%) was found among the eight species, with heteroduplexes showing at least 12% or more mismatching as determined by thermal elution midpoints. The small amount of nucleotide sequence homology among the eight species indicates that these species are quite distinct and are not closely related to each other genomically.     

Monosomy 21: a new case confirmed by in situ hybridization

Summary A new case of total monosomy 21 in a newborn is described. The diagnosis was first made using the cytogenetic data; it was then confirmed by the dosage of copper-superoxide dismutase (SOD-1) which showed a 50% decrease. In situ hybridization with a probe previously assigned to chromosome 21 was used to rule out the possibility of a partial monosomy with an unbalanced reciprocal translocation.     

Genetic mapping of the G101 bacteriophage (Pseudomonas aeuruginosa by temperature-sensitive mutations

Temperature-sensitive (ts) mutations of the G101 phage were isolated after mutagenesis with hydroxylamine. A complementation analysis of 61ts mutants showed that these mutants may be divided into at least 12 complementation groups. Twots mutants probably originated in genes which control lytic functions of the G101 phage. It was shown by three factor crosses that all of the 12ts mutations tested are localized on that side of the “c” region where the probablecI repressor gene is positioned. Sevents mutations is closely linked to thecI ₂₆ clear marker, three exhibit a closer linkage and two do not exhibit any linkage withcI. All mutations isolated until now can be arrange linearly. According to the present knowledge the preliminary genetic map of the G101 phage is linear.     

Polyphyly of Asian Tree Toads,Genus Pedostibes Günther, 1876 (Anura: Bufonidae), and the Description of a New Genus from Southeast Asia

The Asian Tree Toad genus Pedostibes, as currently understood, exhibits a conspicuously disjunct distribution, posing several immediate questions relating to the biogeography and taxonomy of this poorly known group. The type species, P. tuberculosus and P. kempi, are known only from India, whereas P. hosii, P. rugosus, and P. everetti are restricted to Southeast Asia. Several studies have shown that these allopatric groups are polyphyletic, with the Indian Pedostibes embedded within a primarily South Asian clade of toads, containing the genera Adenomus, Xanthophryne, and Duttaphrynus. Southeast Asian Pedostibes on the other hand, are nested within a Southeast Asian clade, which is the sister lineage to the Southeast Asian river toad genus Phrynoidis. We demonstrate that Indian and Southeast Asian Pedostibes are not only allopatric and polyphyletic, but also exhibit significant differences in morphology and reproductive mode, indicating that the Southeast Asian species’ are not congeneric with the true Pedostibes of India. As a taxonomic solution, we describe a new genus, Rentapia gen. nov. to accommodate the Southeast Asian species.     

Genes for the biosynthesis of spinosyns: applications for yield improvement in Saccharopolyspora spinosa

Spinosyns A and D are the active ingredients in an insect control agent produced by fermentation of Saccharopolyspora spinosa. Spinosyns are macrolides with a 21-carbon, tetracyclic lactone backbone to which the deoxysugars forosamine and tri-O-methylrhamnose are attached. The spinosyn biosynthesis genes, except for the rhamnose genes, are located in a cluster that spans 74 kb of the S. spinosa genome. DNA sequence analysis, targeted gene disruptions and bioconversion studies identified five large genes encoding type I polyketide synthase subunits, and 14 genes involved in sugar biosynthesis, sugar attachment to the polyketide or cross-bridging of the polyketide. Four rhamnose biosynthetic genes, two of which are also necessary for forosamine biosynthesis, are located outside the spinosyn gene cluster. Duplication of the spinosyn genes linked to the polyketide synthase genes stimulated the final step in the biosynthesis — the conversion of the forosamine-less pseudoaglycones to endproducts. Duplication of genes involved in the early steps of deoxysugar biosynthesis increased spinosyn yield significantly. Journal of Industrial Microbiology & Biotechnology (2001) 27, 399–402. Received 31 May 2001/ Accepted in revised form 09 July 2001