An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.     

Renal cortical intermediary metabolism in the recovery phase of postischemic acute renal failure in the dog.

Renal metabolism has been studied in eight dogs before and 48 hr after a 60-min period of renal ischemia induced by clamping the left renal artery with the simultaneous removal of the right kidney, and in 12 sham-operated animals. The study involved the measurement of renal uptake and production of lactate, glutamine, glutamate, alanine, ammonium, and oxygen, and the measurement of the tissue concentrations of ATP, glutamine, lactate, alpha-ketoglutarate, aspartate, and alanine in the renal cortex. Two days after a temporary renal ischemia, the remaining kidney showed a 22% decrease in glomerular filtration rate (GFR) and a 25% decrease in renal plasma flow. Fractional sodium and potassium excretions were similar to those of control dogs. Renal production or extraction of glutamine, glutamate, alanine, ammonium, and oxygen (all expressed by 100 ml of GFR) was not significantly different in basal conditions or 2 days after ischemia, but lactate extraction was reduced in postischemic kidneys (-101 +/- 29 vs -204 +/- 38 mumol/100 ml GFR in control dogs). The cortical concentrations of glutamine and glutamate were lower in postischemic than in control kidneys. No differences were found in cortical concentration of alpha-ketoglutarate, aspartate, lactate, pyruvate, or ATP, but total nucleotides and inorganic phosphate were decreased in postischemic kidneys. It is concluded that in the recovery phase of the ischemia, a decreased lactate uptake is the main metabolic change, and total ATP production is adapted to the decrease of GFR and sodium reabsorption.     

Additional Characters to Distinguish the Nymphs of the Perlid Genera from Southeastern Brazil (Insecta,Plecoptera)

Six additional characters are proposed to distinguish the nymphs of the perlid genera from Southeastern Brazil, and a practical key is provided.     

Force to Divide: Structural and Mechanical Requirements for Actomyosin Ring Contraction

One of the unresolved questions in the field of cell division is how the actomyosin cytoskeleton remains structurally organized while generating the contractile force to divide one cell into two. In analogy to the actomyosin-based force production mechanism in striated muscle, it was originally proposed that contractile stress in the actomyosin ring is generated via a sliding filament mechanism within an organized sarcomere-like array. However, over the last 30 years, ultrastructural and functional studies have noted important distinctions between cytokinetic structures in dividing cells and muscle sarcomeres. Myosin-II motor activity is not always required, and there is evidence that actin depolymerization contributes to contraction. In this Review, the architecture and contractile dynamics of the actomyosin ring at the cell division plane will be discussed. We will report the interdisciplinary advances in the field as well as their integration into a mechanistic understanding of contraction in cell division and in other biological processes that rely on an actomyosin-based force-generating system.     

Complex regulation of nucleoside transporter expression in epithelial and immune system cells

Nucleoside transporters have a variety of functions in the cell, such as the provision of substrates for nucleic acid synthesis and the modulation of purine receptors by determining agonist availability. They also transport a wide range of nucleoside-derived antiviral and anticancer drugs. Most mammalian cells coexpress several nucleoside transporter isoforms at the plasma membrane, which are differentially regulated. This paper reviews studies on nucleoside transporter regulation, which has been extensively characterized in the laboratory in several model systems: the hepatocyte, an epithelial cell type, and immune system cells, in particular B cells, which are non-polarized and highly specialized. The hepatocyte co-expresses at least two Na+-dependent nucleoside transporters, CNT1 and CNT2, which are up-regulated during cell proliferation but may undergo selective loss in certain experimental models of hepatocarcinomas. This feature is consistent with evidence that CNT expression also depends on the differentiation status of the hepatocyte. Moreover, substrate availability also modulates CNT expression in epithelial cells, as reported for hepatocytes and jejunum epithelia from rats fed nucleotide-deprived diets. In human B cell lines, CNT and ENT transporters are co-expressed but differentially regulated after B cell activation triggered by cytokines or phorbol esters, as described for murine bone marrow macrophages induced either to activate or to proliferate. The complex regulation of the expression and activity of nucleoside transporters hints at their relevance in cell physiology.     

A new species of Nicon Kinberg, 1866 (Polychaeta,Nereididae) from Ecuador,Eastern Pacific,with a?key?to?all known?species?of the genus

A new species of Nicon Kinberg, 1866 from the east Pacific coast of Ecuador is described. The new species is characterized by a long, thin dorsal ligule on median and posterior parapodia and infracicular sesquigomph falcigers in the neuropodia. A key to all species of Nicon is provided.     

Inborn errors of complex II--unusual human mitochondrial diseases.

The succinate dehydrogenase consists of only four subunits, all nuclearly encoded, and is part of both the respiratory chain and the Krebs cycle. Mutations in the four genes encoding the subunits of the mitochondrial respiratory chain succinate dehydrogenase have been recently reported in human and shown to be associated with a wide spectrum of clinical presentations. Although a comparatively rare deficiency in human, molecularly defined succinate dehydrogenase deficiency has already been found to cause encephalomyopathy in childhood, optic atrophy or tumor in adulthood. Because none of the typical housekeeping genes encoding this respiratory chain complex is known to present tissue-specific isoforms, the tissue-specific involvement represents a quite intriguing question, which is mostly addressed in this review. A differential impairment of electron flow through the respiratory chain, handling of oxygen, and/or metabolic blockade possibly associated with defects in the different subunits that can be advocated to account for tissue-specific involvement is discussed.     

Immunolocalization of a novel annexin‐like protein encoded by a stress and abscisic acid responsive gene in alfalfa

We report here on the isolation and characterization of a full-length cDNA clone from alfalfa termed AnnMs2 encoding a 333 amino acid long polypeptide that shows 32–37% sequence identity with both mammalian and plant annexins, and has four tandem repeats. While other plant annexins exhibit a high level of sequence similarity to each other (up to 77% identity at amino acid level), AnnMs2 appears to be a distinct type of plant annexins. All the four endonexin folds contain the conserved eukaryotic motif within this alfalfa protein, but this element is considerably different in the second repeat. The AnnMs2 gene is expressed in various tissues of alfalfa with elevated mRNA accumulation in root and flower. This gene is activated in cells or tissues exposed to osmotic stress, abscisic acid (ABA) or water deficiency. The recombinant AnnMs2 protein is able to bind to phospholipid in the presence of Ca²⁺. Indirect immunofluorescence studies using affinity purified rabbit anti-AnnMs2 peptide antibody show mainly nucleolar localization, but the protein sequence lacks the usual nuclear localization signal. The potential role of this novel annexin-like protein in the basic and stress-induced cellular functions is discussed.