Differential expression of cytoplasmic proteins during yeast bud and germ tube formation in Candida albicans

Changes in the identity and quantity of proteins synthesized during morphogenesis may result from alterations in gene expression in the dimorphic yeast Candida albicans. Stationary phase yeast cells, upon resuming growth at 25 degrees C, form budding yeast and at 37 degrees C form germ tubes. In order to identify proteins associated with morphogenesis, we compared cytoplasmic proteins synthesized during germ tube and bud formation. Proteins synthesized during this period were labeled at four intervals with either [3H]leucine or [35S]methionine and separated by two-dimensional polyacrylamide gel electrophoresis. This study shows that, of the 230 proteins resolved on each gel, 5 were specific to the yeast morphology and 2 proteins showed reduction in net synthesis in the mycelial phase. There were, however, no mycelium-specific proteins at any labeling period. The majority of proteins were common to both morphologies and showed no major shift in number during resumption of growth. The observations reported here suggest that differential gene expression occurs during morphogenesis of C. albicans.     

Toward a molecular paleontology of primate genomes

Families of related, but nonidentical repetitive DNA sequences, termed the alphoid DNAs, have been identified and characterized in representative species from seven major primate Families. The sequences appear as old as the primate Order itself: they are found in a prosimian (lemur), in a New World monkey, and in all Old World primates examined, including man. The alphoid DNAs are uniquely primate sequences and they may represent the most abundant repetitive DNAs in the primate genome. — A classification scheme for two major families of alphoid DNAs is proposed that is based upon restriction enzyme analysis and Southern blotting with radioactive probes prepared from component DNA (Maio, 1971) and from the human EcoRI dimer sequences (Manuelidis, 1976). The family of alphoid DNAs that hybridizes readily with component is termed the HindIII family of alphoid DNAs. This family shows an almost universal distribution among present-day primates. The family of DNA sequences that hybridizes readily with the human EcoRI dimer probe is termed the EcoRI dimer family of alphoid DNAs. This family may be restricted to the great apes and man. The two probes permitted the discrimination of different, but related alphoid families in present-day primates. Multiple alphoid sequence families are found within the genomes of individual primates and the major primate taxa can be characterized by the representations of the various alphoid DNAs within their genomes. — An Appendix is presented (Brown et al., 1981) indicating that competition hybridization effects may influence the autoradiographic banding patterns, and hence, the interpretations of Southern filter-transfer hybridizations when dealing with related repetitive sequences such as the alphoid DNAs that are present in abundance in eukaryotic genomes.     

Induction of tyrosine aminotransferase by pyridoxine in Drosophila hydei

Salivary glands incubated in various concentrations of pyridoxine (Vitamin B₆) show increasing tyrosine aminotransferase (TAT) activity at concentrations up to 10^–5 M and then decreasing activity up to 10^–2 M but in all cases the activity is greater than that of the controls. This increase in activity is demonstrable for up to 6 h, the longest period tested, and is dependent on the synthesis of new mRNA. A similar increase in TAT activity is observed in salivary glands subjected to heat shock. Antibodies prepared against purified tyrosine aminotransferase precipitate a peptide of the same molecular weight (40 KD) as that induced by pyridoxine.     

Possible link between converting enzyme inhibition and renomedullary interstitial cells

The kidney exerts both prohypertensive and antihypertensive functions. Part of the anti-hypertensive function of the kidney is mediated by the renomedullary interstitial cells (RIC), as an endocrine-type function. Six experimental models of hypertension and their relation to the antihypertensive function of the RIC are discussed. It is proposed that the anti-hypertensive function of the RIC may be deficient by the three mechanisms: 1) absence of the cells (as in the renoprival state); 2) severe damage to the cells (as in partial nephrectomy-salt hypertension of the rat and late malignant hypertension of the rabbit); and 3) constraint of the function of these cells (as in angiotensin-salt hypertension due to a lower salt intake). The constraint may result from excessive angiotensin, either by a direct effect or via a hemodynamic mechanism. The converting enzyme inhibitors (CEI) fail to exert their antihypertensive function when the RIC are absent or damaged. Conversely, the CEI are effective in those models associated with intact RIC. CEI appear to exert their antihypertensive action partly through an effect on RIC.     

Alternate mechanism for amino acid entry into Neurospora crassa: extracellular deamination and subsequent keto acid transport

The growth of the pm nbg mutant strain of Neurospora crassa was inhibited by the amino acid analog para-fluorophenylalanine despite the fact that none of the three constitutive amino acid permeases is functional in this strain. This observation led to the detection of both a deaminase which was released into the growth medium in response to para-fluorophenylalanine and a keto acid transport system which allowed entry of the resulting keto acid into the cell. The transported keto acid was recovered in cellular protein, suggesting its regeneration as the amino acid. The cooperative activity of these two systems represents an additional mechanism for the intracellular accumulation of amino acids, which is distinct from the known amino acid permeases.     

A specific binding protein for 1 alpha,25-dihydroxyvitamin D in the chick embryo chorioallantoic membrane

A 3.7 S binding protein for the steroid hormone and vitamin D metabolite 1 alpha-25-dihydroxyvitamin D (1,25-(OH)2-D) was observed in high salt cytosol extracts of chick embryo chorioallantoic membrane. The binding protein was characterized after partial purification of cytosol extracts by ammonium sulfate fractionation. The binding of 1,25-(OH)2-D was saturable, had a high affinity (Kd = 0.16 nM), and was specific for hormonally active vitamin D metabolites. Analysis of the displacement of [3H]1,25-(OH)2-D by unlabeled analogues showed the affinities of vitamin D metabolites to be in the order of 1,25-(OH)2-D = 1,24R,25-(OH)3-D much greater than 25-OH-D = 1-OH-D greater than 24R,25-(OH)2-D. Hormone binding was sensitive to pretreatment with sulfhydryl-blocking reagents. The chorioallantoic membrane 1,25-(OH)2-D-binding protein associated with the chromatin fraction after homogenization of membranes in low salt buffer, and bound to DNA-cellulose columns, eluting as a single peak at 0.215 M KCl. These findings support identification of this 1,25-(OH)2-D-binding protein as a steroid hormone receptor, with properties indistinguishable from 1,25-(OH)2-D receptors in other chick tissues. The chorioallantoic membrane functions in the last third of embryonic development to reabsorb calcium from the eff shell for deposition in embryonic bone. 1,25-(OH)2-D binding activity in the chorioallantoic membrane increased 4- to 5-fold from day 12 to day 16 of incubation, immediately preceding the onset of shell reabsorption. This finding suggests that 1,25-(OH)2-D may act to regulate shell mobilization and transepithelial calcium transport by the chorioallantoic membrane. Finally, the similarity of shell mobilization to bone resorption, which is also stimulated by 1,25-(OH)2-D, suggests that the chorioallantoic membrane is a useful alternate model for the study of 1,25-(OH)2-D action on bone mineral metabolism.     

Sur une flore a Glossopteropsida et Lycopsida de Namibie (Sud-Ouest Africain)

The study of imprints of fossil plants collected in the Permian from the country of Hammanskraal (Namibia) leads to the following identifications: Glossopteris sp., Gangamopteris sp., Noegerrathiopsis sp., Gondwanidium sp., Asterotheca sp. and Lycopodiopsis derbyiB. Renault, Lycopodiopsis costilatus n. sp., Brasilodendron pedroanum(W. Carruthers) W.G. Chaloner & alii, Brasilodendron africanum n. sp. This flora has affinities with some fossil floras from South Africa and from Brazil, and is, probably, of upper Permian age.     

Revision du genre LycopodiopsisB. Renault, 1890

The study of imprints of Lycopsida from Permianof the Gondwana has permitted to specify the organisation of the leaf cushions and their variation in the genus LycopodiopsisB. Renault. The presence of a ligula is showed off. The invalidity of the genera Cyclodendron and Lycopodiophloios is demonstrated, and the species refered to these genera must be refered to the genus Lycopodiopsis for which an emended diagnosis is proposed.     

The estradiol-stimulated lipoprotein receptor of rat liver. A binding site that membrane mediates the uptake of rat lipoproteins containing apoproteins B and E

Hepatic catabolism of lipoproteins containing apolipoproteins B or E is enhanced in rats treated with pharmacologic doses of 17 alpha-ethinyl estradiol. Liver membranes prepared from these rats exhibit an increased number of receptor sites that bind 125I-labeled human low density lipoproteins (LDL) in vitro. In the present studies, this estradiol-stimulated hepatic receptor was shown to recognize the following rat lipoproteins: LDL, very low density lipoproteins obtained from liver perfusates (hepatic VLDL), and VLDL-remnants prepared by intravenous injection of hepatic VLDL into functionally eviscerated rats. The receptor also recognized synthetic lamellar complexes of lecithin and rat apoprotein E as well as canine high density lipoproteins containing apoprotein E (apo E-HDLc). It did not recognize human HDL or rat HDL deficient in apoprotein E. Much smaller amounts of this high affinity binding site were also found on liver membranes from untreated rats, the number of such sites increasing more than 10-fold after the animals were treated with estradiol. Each of the rat lipoproteins recognized by this receptor was taken up more rapidly by perfused livers from estrogen-treated rats. In addition, enrichment of hepatic VLDL with C-apoproteins lowered the ability of these lipoproteins to bind to the estradiol-stimulated receptor and diminished their rate of uptake by the perfused liver of estrogen-treated rats, just as it did in normal rats. The current data indicate that under the influence of pharmacologic doses of estradiol the liver of the rat contains increased amounts of a functional lipoprotein receptor that binds lipoproteins containing apoproteins B and E. This hepatic lipoprotein receptor appears to mediate the uptake and degradation of lipoproteins by the normal liver as well as the liver of estradiol-treated rats. The hepatic receptor bears a close functional resemblance to the LDL receptor previously characterized on extrahepatic cells.     

Assignment to chromosome 16 of a gene necessary for the expression of human mitochondrial glutamate oxaloacetate transaminase (aspartate aminotransferase) (E.C. 2.6.1.1.)

A gene necessary for the expression of human mitochondrial glutamate oxaloacetate transaminase (GOT-2) has been assigned to chromosome 16 on the basis of an immunochemical analysis of human-mouse somatic cell hybrids. Mitochondrial GOT cosegregates with adenine phosphoribosyl transferase (E.C. 2.4.2.7.).