Simultaneous utilization of glucose and xylose byCandida curvata D in continuous culture

Summary Of ten, mainly oleaginous, yeasts examined for the ability to use glucose and xylose simultaneously, only one,Candida curvata D, was found which could do so. This yeast was examined further in a single-stage chemostat wherein it produced similar biomass yields, lipid contents and fatty acids on glucose plus xylose mixed in varying proportions. This oleaginous yeast would therefore be capable of growing on hydrolysed wood and straw wastes as a potential source of single cell oil.     

Centrifugation of 2-cell mouse ova: cytoplasm stratification and recovery

Summary Two-cell mouse ova, which were centrifuged for l h at 70 000–90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres. Cleavage, compaction and blastulation were not prevented by centrifugation. Treatments with colcemid or cytochalasin D delayed but did not impair recovery. These results suggest that a resilient cytoskeletal structure may be involved in this kind of embryonic regulation.     

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.     

Évaluation de la toxicité deBacillus thuringiensis surSpodoptera frugiperda

Résumé Cinquante deux souches deB. thuringiensis appartenant à 13 sérovars ont été testées sur des chenilles néonates deSpodoptera frugiperda en contaminant la surface du milieu semi-synthétique d'élevage. Deux souches du sérovarkenyae et une autre du sérovartolworthi provoquent le plus de mortalité, suivies par les souches des sérovarsaizawai etkurstaki. Les souches les moins actives appartiennent aux sérotypesalesti, dendrolimus, sotto etcolmeri. L'action des souches sur le développement larvaire a aussi été abordée. Les souches des sérovarskenyae, aizawai etkurstaki ont ralenti le développement des chenilles, tandis que les souches des sérovarsalesti, sotto etcolmeri n'ont eu aucun effet.      

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.     

Structure-function analysis of hepatocyte growth factor: identification of variants that lack mitogenic activity yet retain high affinity receptor binding.

Hepatocyte growth factor (HGF) is a potent mitogen for parenchymal liver, epithelial and endothelial cells. Structurally, it has similarities to kringle-containing serine proteases, although it does not possess proteolytic activity. A structure-activity relationship study of human HGF was performed by functional analysis of HGF substitution and deletion variants. Analysis of HGF variants was accomplished by defining their ability to induce DNA synthesis on hepatocytes in primary culture and to compete with wild-type HGF for binding to a soluble form of the HGF receptor. Three groups of variants were made: (i) substitutions at the cleavage site, (ii) substitutions within the protease-like domain and (iii) deletions of the beta-chain and/or kringle domains. Our results show that: (i) single-chain HGF is a zymogen-like promitogen in that cleavage into a two-chain form is required for biological activity, however, the single chain form of HGF still retains substantial receptor binding capacity; (ii) certain mutations in the protease-like domain result in variants that are completely defective for mitogenic activity, yet exhibit apparent receptor binding affinities similar to wild-type HGF (Kd approximately 50-70 pM); and (iii) a variant containing the N-terminal 272 residues of mature HGF showed only a 4-fold increase in Kd when compared with wild-type HGF indicating that a primary receptor binding determinant is located within this sequence.     

Agrobacterium-mediated transformation of tomatillo (Physalis ixocarpa) and tissue specific and developmental expression of the CaMV 35S promoter in transgenic tomatillo plants

A protocol for the Agrobacterium-mediated transformation of tomatillo was developed. Up to 40 transgenic plants could be obtained in experiments using 60 cotyledon expiants. The transformed nature of the regenerated plants was confirmed by NPT II and Southern blot hybridization analysis. Using the b-glucuronidase system the tissue specific and developmental patterns of expression of the Cauliflower Mosaic Virus 35S promoter were determined in transgenic tomatillo plants. It was found that this promoter is developmentally regulated during fruit and seed formation.     

Facial clefts in Saudi Arabia: an epidemiologic analysis in 179 patients

One hundred and seventy-nine consecutive cases of facial clefts that were treated at the King Khalid University Hospital, in Riyadh, Saudi Arabia, were analyzed for an epidemiologic study. Isolated cleft lip was present in 38 percent, cleft of lip and palate in 37.4 percent, and cleft of the posterior palate in only 22.4 percent. There was a male preponderance in all types. In cases of cleft lip with or without cleft palate, the more commonly affected side was the left, followed by bilateral cases. Associated malformations were present in 13.4 percent. A positive family history was found in 26.8 percent of cases. A significant number of patients (7.8 percent) were first seen at more than 10 years of age. The incidence of facial clefts at this hospital was 0.3 per 1000 live births, computed over a period of 6 years. This incidence is significantly lower than that reported from European and Far Eastern countries.     

Characterization of DNA sequences that mediate nuclear protein binding to the regulatory region of the Pisum sativum (pea) chlorophyl a/b binding protein gene AB80: identification of a repeated heptamer motif

Two protein factors binding to the regulatory region of the pea chlorophyl a/b binding protein gene AB80 have been identified. One of these factors is found only in green tissue but not in etiolated or root tissue. The second factor (denominated ABF-2) binds to a DNA sequence element that contains a direct heptamer repeat TCTCAAA. It was found that presence of both of the repeats is essential for binding. ABF-2 is present in both green and etiolated tissue and in roots and factors analogous to ABF-2 are present in several plant species. Computer analysis showed that the TCTCAAA motif is present in the regulatory region of several plant genes.     

An ATP-dependent Na/Mg countertransport is the only mechanism for Mg extrusion in squid axons

The components of magnesium efflux in squid axons have been studied under internal dialysis and voltage clamp conditions. The present report rules out the existence of an ATP-dependent, Na₀- and Mg₀-independent Mg²⁺ efflux (ATP-dependent Mg²⁺ pump) leaving the Mg²⁺---Na⁺ exchange system as the only mechanism for Mg²⁺ extrusion. The main features of the Mg²⁺ efflux are: (1) The efflux is completely dependent on ATP. (2) The efflux can be activated either by external Na⁺ (forward Mg²⁺---Na⁺ exchange) or external Mg²⁺ (Mg²⁺---Mg²⁺ exchange). (3) The mobility of the Mg²⁺ exchanger in the Na₀⁺-loaded form is greater than that in the Mg²⁺-loaded one. (4) In variance with the Na⁺---Ca²⁺ exchange mechanism, Mg²⁺---Mg²⁺ exchange is not activated by external monovalent cations. (5) ATPγS replaces ATP in activating Mg²⁺---Na⁺ exchange suggesting that a phosphorylation/dephosphorylation process regulates this transport mechanism.