Evolution of four human Y chromosomal unique sequences

Four cloned unique sequences from the human Y chromosome, two of which are found only on the Y chromosome and two of which are on both the X and Y chromosomes, were hybridized to restriction enzyme-treated DNA samples of a male and a female chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and pig-tailed macaque (Macaca nemestrina); and a male orangutan (Pongo pygmaeus) and gibbon (Hylobates lar). One of the human Y-specific probes hybridized only to male DNA among the humans and great apes, and thus its Y linkage and sequence similarities are conserved. The other human Y-specific clone hybridized to male and female DNA from the humans, great apes, and gibbon, indicating its presence on the X chromosome or autosomes. Two human sequences present on both the X and Y chromosomes also demonstrated conservation as indicated by hybridization to genomic DNAs of distantly related species and by partial conservation of restriction enzyme sites. Although conservation of Y linkage can only be demonstrated for one of these four sequences, these results suggest that Y-chromosomal unique sequence genes do not diverge markedly more rapidly than unique sequences located on other chromosomes. However, this sequence conservation may in part be due to evolution while part of other chromosomes.     

Phosphorylation of Tyrosine Hydroxylase by Cyclic GMP-Dependent Protein Kinase

Tyrosine hydroxylase purified from rat pheochromocytoma was phosphorylated and activated by purified cyclic GMP-dependent protein kinase as well as by cyclic AMP-dependent protein kinase catalytic subunit. The extent of activation was correlated with the degree of phosphate incorporated into the enzyme. Comparable stoichiometric ratios (0.6 mol phosphate/mol tyrosine hydroxylase subunit) were obtained at maximal concentrations of either cyclic AMP-dependent or cyclic GMP-dependent protein kinases. The enzymes appeared to mediate the phosphorylation of the same residue based on the observation that incorporation was not increased when both enzymes were present. The major tryptic phosphopeptide obtained from tyrosine hydroxylase phosphorylated by each protein kinase exhibited an identical retention time following HPLC. The purified phosphopeptides also exhibited identical isoelectric points. These data provide support for the notion that the protein kinases are phosphorylating the same residue of tyrosine hydroxylase.     

A single amino acid substitution deregulates a bacterial lactate dehydrogenase and stabilizes its tetrameric structure

We have engineered a variant of the lactate dehydrogenase enzyme from Bacillus stearothermophilus in which arginine-173 at the proposed regulatory site has been replaced by glutamine. Like the wild-type enzyme, this mutant undergoes a reversible, protein-concentration-dependent subunit assembly, from dimer to tetramer. However, the mutant tetramer is much more stable (by a factor of 400) than the wild type and is destabilized rather than stabilized by binding the allosteric regulator, fructose 1,6-biphosphate (Fru-1,6-P2). The mutation has not significantly changed the catalytic properties of the dimer (Kd NADH, Km pyruvate, Ki oxamate and kcat), but has weakened the binding of Fru-1,6-P2 to both the dimeric and tetrameric forms of the enzyme and has almost abolished any stimulatory effect. We conclude that the Arg-173 residue in the wild-type enzyme is directly involved in the binding of Fru-1,6-P2, is important for allosteric communication with the active site, and, in part, regulates the state of quaternary structure through a charge-repulsion mechanism.     

Life history adaptations of Gasterosteus aculeatus in a Mediterranean wetland

Synopsis The life cycle of leiurus-type Gasterosteus aculeatus occurring in a Mediterranean coastal wetland is described. Fish have a low number of lateral plates, short spines and marked sexual dimorphism in size. The life cycle is strictly annual, adults dying shortly after breeding. Adult fish migrate into seasonally-flooded freshwater marshes to breed, and the young migrate back to brackish water to pass the summer and autumn. Breeding occurs in March at water temperatures of about 10°C, the season lasting about 50 days. Growth of fish occurs throughout the year, but differs from year to year, resulting in variable adult size. Maximum gonadal investment of male fish is in autumn, whereas that of females is in spring. Gonadal investment of female fish, as measured by gonado-somatic index and fecundity, is higher than in other studied leiurus populations, but the number of clutches produced in a season is probably low. These differences in life history from other studied populations of sticklebacks are seen as adaptations to a mediterranean-type climate (high summer temperatures, seasonality of water bodies) and to heavy predation by fish-eating birds.     

In situ detection of early replication phases of a gemini virus in legume protoplasts

Protoplasts of Phaseolus vulgaris L. (Top Crop), infected with bean golden mosaic virus, were isolated and fixed by various methods for in situ hybridization. An iodine-125 labeled probe was made from the replicative form of the virus. The localization and quantitation was done by autoradiography. Cell wall removal lowered the background and allowed a more accurate analysis. RNase was used to eliminate the possibility of hybrids to RNA. The evidence suggests a sequence of virus movements starting from rough endoplasm reticulum, moving to the nuclear membrane, and finally with the highest concentration inside the nucleus.Abbreviations BGMV bean golden mosaic virus - rfBGMV or rfDNA replicative double-stranded DNA virus - ssDNA single-stranded virus     

Use of latex balls labelled by lectins in the demonstration of Salmonella-Schistosoma mansoni receptor sites

Surface tegumental membrane of adult stage Schistosoma mansoni were examined using the latex sphere coated with Concanavalin A (Con A). Wheat germ agglutinin (WGA) and Protein A (PA). Competitive saccharide inhibitors glucose, mannose and methyl alpha-D-glucopyranoside were used for Con A.     

EXTERNAL MORPHOLOGY AND PIGMENTATION OF THE VAQUITA, PHOCOENA SINUS (CETACEA: MAMMALIA)

The vaquita, Phocoena sinus , is a porpoise in the family Phocoenidae that lives only in the Gulf of California. The external appearance of P. sinus was unknown until 13 fresh specimens were recently examined. The most obvious morphological feature distinguishing P. sinus from its two congeners is the proportionately higher dorsal fin. The most striking features of the pigmentation pattern are the large black eye patches and the black upper and lower lip patches. In both areas, the pigmentation contrasts sharply with the surrounding light gray coloration. The total lengths of the specimens ranged from 70.3 cm (a neonate) to 143.5 cm (an adult female).     

Methods for determination of lipid peroxidation in biological samples

Interest in the pathological consequences of lipid peroxidation has led to the development of a number of analytical approaches to the quantitation of products. However, the various analytical methodologies employed often do not measure the same chemical classes of products, and apparent discrepencies have been observed, particularly in studies of lipid peroxidation in biological systems. This review provides a brief discussion of some of the strengths and weakness of methods currently used for the determination of lipid peroxidation in biological tissues.     

β-Adrenergic receptor-coupled adenylate cyclase

Beta-adrenergic receptor-coupled adenylate cyclase is regulated by both amplification and desensitization processes. Desensitization of adenylate cyclase is divided into two major categories. Homologous desensitization is initiated by phosphorylation of the receptors by a beta-adrenergic receptor kinase. This reaction serves to functionally uncouple the receptors and trigger their sequestration away from the cell surface. These sequestered receptors can rapidly recycle to the cell surface or, with time, become down regulated, being destroyed within the cell. Dephosphorylation of the receptors is accomplished in the sequestered compartment of the cell, which may functionally regenerate the receptors and allow their return to the cell surface. In heterologous desensitization, receptor function is also regulated by phosphorylation, but in the absence of receptor sequestration or down regulation. In this case, phosphorylation serves only to functionally uncouple the receptors, that is, to impair their interactions with the guanine nucleotide regulatory protein Ns. Several protein kinases are capable of promoting this phosphorylation, including the cAMP-dependent kinase and protein kinase C. In addition to the receptor phosphorylation, heterologous desensitization is associated with modifications at the level of the nucleotide regulatory protein Ns and perhaps Ni. Adenylate cyclase systems are also subject to amplification that involves a protein kinase C-mediated phosphorylation of the catalytic unit of the enzyme. Phosphorylation of the catalytic unit enhances its catalytic activity and results in amplified stimulation by the regulatory protein Ns. Other receptor/effector systems exhibit qualitatively similar regulatory phenomena, suggesting that covalent modification (phosphorylation) may represent a general mechanism for regulating receptor function.