Extramacrochaetae,a trans-acting gene of the achaete-scute complex of Drosophila involved in cell communication

Summary Phenotypic analyses of genetic combinations involving the gene extramacrochaetae (emc) reveal its participation in the differentiation of both sensory elements and wing veins. The study of near-amorphic alleles of emc in mitotitc recombination clones indicates that it also affects cell proliferation. These clones show abnormal sizes, shapes and spatial distribution. They differentiate extra sensory elements as well as extra veins. A gain of function mutation in the gene causes opposite phenotypes in both differentiation systems. The effects of the mutant on proliferation and patterning are consistent with the emc gene being involved in the transfer of information between neighbouring cells, which leads to the spatial expression of the achaetescute gene complex and genes involved in vein formation.     

Experimental aflatoxin production in Manchego-type cheese

Manchego-type cheese, a typical Spanish cheese, was inoculated in various ways with an aflatoxigenic organism, Aspergillus parasiticus NRRL 2999, to study the production of aflatoxin. When the original milk was contaminated with a spore suspension, aflatoxin was not detected in paraffin-covered cheeses although it was present in the top layer of non-paraffin-covered cheeses after ripening at 15°C for 60 d. When the cheese surface was inoculated, no aflatoxins were detected in paraffin-covered cheeses after ripening for 60 d although they were found when the cheeses were ripened for 30 d. In non-paraffin-covered cheeses aflatoxins were detected only in the top layer and in the second 10 mm layer when cheeses were incubated after the normal ripening at 28°C for 30 d. When the centre of the cheese was inoculated, no aflatoxins were detected although Aspergillus grew slightly along the inoculation area. When cheese portions were inoculated, fungal growth was evident after incubation at 28° and 15°C for 6 d but there was no growth at 10°C after 50 d. At 28°C aflatoxins were detected at a concentration of 132 μg/g after 13 d, the highest level obtained. In cheese paste at 28° and 15°C, growth was intense, but the level of aflatoxins detected was lower than in cheese portions. At 10°C the growth was heavy, but aflatoxins were not detected.     

Lesion and regeneration in the medial cerebral cortex of lizards.

The cerebral cortex of Squamate reptiles (lizards and snakes) may be regarded as an archicortex or "reptilian hippocampus". In lizards, one cortical area, the medial cortex, may be considered as a true "fascia dentata" on grounds of its anatomy, connectivity and cyto- chemo-architectonics of its main zinc-rich axonal projection. Moreover, its late ontogenesis and postnatal development support this view. In normal conditions, it shows delayed postnatal neurogenesis and growth during the lizard's life span. Remnant neuroblasts in the medial cortical ependyma of adult lizards seasonally proliferate. The late-produced immature neurocytes migrate to the medial cortex cell layer where they differentiate and give off zinc-containing axons directed to the rest of cortical areas. This results in a continuous growth of the medial cortex and its zinc-rich axonal projection. Perhaps the most important characteristic of the lizard medial cortex is that it can regenerate after having been almost completely destroyed. Recent experiments in our laboratory have shown that chemical lesion of its neurons (up to 95%) results in a cascade of events; first, those related with massive neuronal death and axonal-dendritic retraction and, secondly, those related with a triggered neuroblast proliferation and subsequent neo-histogenesis, and the regeneration of an almost new medial cortex that shows itself undistinguishable from a normal undamaged one. This is the only report to our knowledge that an amniote central nervous centre may regenerate by new neuron production and neo-histogenesis. Perhaps the medial cortex of lizards may be used as a model for neuronal regeneration and/or transplant experiments in mammals or even in primates.     

Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes.

A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways.     

Alarm reaction and alert state inGambusia Affinis (Pisces,Poeciliidae) in response to chemical stimuli from injured conspecifics

We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to mechanical and visual fright stimuli.     

HLA gene and haplotype frequencies in galicia (NW Spain)

The genetic structure of six populations of Iran (Turks, Kurds, Lurs, Zabolis, Baluchis and Zoroastrians) was examined using data on blood groups, serum proteins and cell enzymes. Our results show conclusively that there are genetic differences among the six populations and the analysis of superimposed R and S matrices defined by Harpending & Jenkins (1973) show that the dispersion of some of the alleles correspond to the dispersion of the populations. The F_ST estimates are not large enough to favour selection on any of the loci studied. The F_IT and F_IS estimates are positive and moderately high suggesting that the genetic differentiation to some extent is influenced by inbreeding.     

In vivo regulatory phosphorylation site in c(4)-leaf phosphoenolpyruvate carboxylase from maize and sorghum

Reversible seryl-phosphorylation contributes to the light/dark regulation of C₄-leaf phosphoenolpyruvate carboxylase (PEPC) activity in vivo. The specific regulatory residue that, upon in vitro phosphorylation by a maize-leaf protein-serine kinase(s), leads to an increase in catalytic activity and a decrease in malate-sensitivity of the target enzyme has been recently identified as Ser-15 in ³²P-phosphorylated/activated dark-form maize PEPC (J-A Jiao, R Chollet [1990] Arch Biochem Biophys 283: 300-305). In order to ascertain whether this N-terminal seryl residue is, indeed, the in vivo regulatory phosphorylation site, [³²P]phosphopeptides were isolated and purified from in vivo ³²P-labeled maize and sorghum leaf PEPC and subjected to automated Edman degradation analysis. The results show that purified light-form maize PEPC contains 14-fold more ³²P-radioactivity than the corresponding dark-form enzyme on an equal protein basis and, more notably, only a single N-terminal serine residue (Ser-15 in maize PEPC and its structural homolog, Ser-8, in the sorghum enzyme) was found to be ³²P-phosphorylated in the light or dark. These in vivo observations, combined with the results from our previous in vitro phosphorylation studies (J-A Jiao, R Chollet [1989] Arch Biochem Biophys 269: 526-535; [1990] Arch Biochem Biophys 283: 300-305), demonstrate that an N-terminal seryl residue in C₄ PEPC is, indeed, the regulatory site that undergoes light/dark changes in phosphorylation-status and, thus, plays a major, if not cardinal role in the light-induced changes in catalytic and regulatory properties of this cytoplasmic C₄-photosynthesis enzyme in vivo.     

Microbial transformation of neutral fraction and upgraded neutral fraction of Polish tall oil

Summary Microbial transformations of neutral fraction (NF) and upgraded neutral fraction (UNF) of Polish tall oil byMycobacterium sp. MB 3683 were performed. Final metabolites and yields were compared to bioconversion of pure -sitosterol. Additionally, origin of a new metabolite —5-androsta-3,6,17-trione was proved by transformation of UNF in the presence of labeled -sitosterol.