Variability of colonial morphology in benomyl-induced morphological mutants from Candida albicans

Abstract Colonies of Candida albicans wild-type strain 1001 were white and glossy, and this character was rather stably maintained. In contrast, 2 benomyl (methyl benzimidazole-2-yl-carbamate)-induced mutant strains, B17 and B14, that grew as long filamentous forms and displayed a rough-wrinkled colonial phenotype, switched to other colonial morphologies at significant frequencies. Clonal populations of B17 segregated smooth or sectored (rough/smooth) colonies at a frequency of 1.85%, when plated in nutrient-agar. Strains derived from these rough or smooth segregants switched back to one or the other phenotype at similar frequencies. Colonial variability in C. albicans B14 was not restricted to spontaneous switching from rough to smooth or vice versa, but eventually other types of variants, characterized as 'wavy' and 'fuzzy' were obtained, and shown to have their own capacity to switch. Smooth variants, derived from B14, were essentiallt unicellular, whereas fuzzy strains consisted only of long thin filaments, wavy and rough clones apparently being intermediate in their degree of filamentation. It is concluded that the capacity for colonial variation shown to exist in natural isolates could be activated by benomyl in others, such as 1001, which are quite stable and do not switch colonial morphology spontaneously.     

G2 effects of DNA-repair inhibitors on chromatid-type aberrations in root-tip cells treated with maleic hydrazide and mitomycin C

In recent years the existence of a DNA-repair process in G2 has been proposed to explain the potentiating effects of DNA-repair inhibitors given in G2 on chromatid aberrations (CA) induced by S-dependent as well as S-independent DNA-damaging agents. In the present report, root-tip cells of Allium cepa were exposed to maleic hydrazide (MH) or mitomycin C (MMC) and post-treated in G2 with caffeine (Caff) and various inhibitors of DNA synthesis. No enhancement of chromosome damage was observed when Caff was present in G2, but hydroxyurea (HU) or 5-fluorodeoxyuridine (FdUrd) potentiated the frequencies of CA. A slight additional increase of CA frequencies was observed following treatment with Ara C and excess thymidine in G2. When MH-damaged cells were pulse-treated with Caff earlier during recovery, the yield of CA was enhanced. The earlier Caff was present following MH treatment, the stronger was the potentiation.     

A chromosomal genetic map of Rhizobium sp. NGR234 generated with Tn5-Mob

Summary Rhizobium sp. NGR234 in a fast-growing Rhizobium strain with a broad host range. The location and role of chromosomal genes involved in cellular metabolism or in the legume symbioses is unknown. We isolated a series of auxotrophic and antibiotic resistant mutants of NGR234 and utilized a chromosome mobilization system based on Tn5-Mob and pJB3JI; Tn5-Mob donor strains behaved like Hfr strains, transferring the chromosome polarly at high frequency from a fixed point of insertion. The use of four different strains with Tn5-Mob located at different nutritional loci in crosses with double auxotrophic recipients, allowed us to build up a circular linkage map of NGR234 based on relative recombination frequencies. Also, symbiotically important genes identified by site-directed mutagenesis, such as hemA and ntrA, could be located and mapped on the chromosome.Abbreviations Tc tetracycline - Sp spectinomycin - Rif rifampicin - Km kanamycin     

Aging and cerebral aminopeptidase activity

A comparative study of brain aminopeptidase activity between 18 month old male rats and young adults of 3 months has been carried out utilizing the arylamides Leu-, Arg-, Lys-, Tyr- and Asp-beta-naphthylamide as substrates. Statistical analysis of results showed no significant differences either in areas studied or for enzymatic activities detected when both ages were compared. Two different patterns of regional distribution of enzymatic activity were observed: One came to be as a result of the use of Lys-, Arg-, Leu- or Tyr-beta-naphthylamide and the other as a result of the use of Asp-beta-naphthylamide.     

Cytochemical localization of calcium in renal sac nephrocytes of Helix aspersa

In renal sac nephrocytes of Helix aspersa, intracellular calcium has been localized using the oxalate-pyroantimonate (OPA) and phosphate-pyroantimonate (PPA) methods. Pyroantimonate precipitates are preferentially localized in the excretory spherule and in vesicles located in the basal and lateral regions of the nephrocyte. Such vesicles appear to release their content into the excretory vacuole. Calcium may interact with diverse types of molecules present in the excretory vacuole, thus favouring stabilization and packaging of the excretory spherule.     

Comparative effects of tumour necrosis factor-alpha (cachectin), interleukin-1-beta and tumour growth on amino acid metabolism in the rat in vivo. Absorption and tissue uptake of alpha-amino[1-14C]isobutyrate.

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.     

Acetyl-cholinesterase and fluoride-resistant acid phosphatase activities in dorsal root ganglia in the rat

Acetylcholinesterase and fluoride-resistant acid phosphatase activities were contrasted in alternative serial sections of rat dorsal root ganglia. The morphometric analysis demonstrated no correlation between cellular size and enzymatic activity. Differences with previous works in this area are discussed.     

Algesia and local responses induced by neurokinin A and substance P in human skin and temporal muscle

Neurokinin A (NKA), substance P (SP) and the two peptides combined (SP + NKA) were injected intracutaneously on the forearm and into the temporal muscle of healthy volunteers. Pain intensity, cutaneous wheal and flare responses and tenderness of the temporal muscle were quantitated. SP but not NKA induced cutaneous pain. This relates the algesic effect of SP to the specific N-terminal amino acid sequence of the peptide, not shared by NKA. NKA, however, potentiated the algesic effect of SP as SP + NKA induced a significantly prolonged cutaneous pain sensation. Both peptides induced wheals, but only SP induced flare. These results confirm previous studies relating wheal formation to the identical C-terminal amino acid sequence of the two peptides and flare reaction to the N-terminal part of SP. Injections into the temporal muscle did not cause pain or tenderness.     

Effect of prenatal exposure to alcohol on membrane-bound enzymes during astrocyte development in vivo and in primary culture

In the present work we have analyzed the effect of prenatal ethanol exposure on the activity of several glial marker and functional enzymes during the development of astrocytes isolated from rat brain as well as in primary culture. The activity of marker enzymes glutamine synthetase and butylcholinesterase showed no differences between isolated astrocytes from 15 and 70 day old control rats. However, the activity of the membrane-bound enzymes (Na+K)ATPase and 5'-nucleotidase was higher in astrocytes from 70 day old control rats than in those from 15 day old animals. Although the pattern found in astrocytes from alcohol-exposed rats was similar to that of controls, the levels of activity of the enzymes were lower in alcoholic than in control animals. When control astrocytes in primary culture were used, the activity of (Na+K)ATPase and 5'-nucleotidase increased throughout the entire culture period. In contrast, the maximal activity of glutamine synthetase was found at 7 days of culture. Ethanol also induced a decrease in the activity of all enzymes, which was more evident at the end of the culture period. These results indicate that the activity of the enzyme markers analyzed increased mainly during the first weeks of life and remained constant after this period. By contrast, the membrane-bound enzymes studied showed a progressive increase with age. In conclusion, since these astrocyte enzymes are important in the regulation of several neuronal functions through the control of the composition of extracellular fluid, the effect of ethanol on their activities could explain some of the neuronal alterations reported in children and animals exposed to ethanol during development.