The parathyroid hormone-related protein associated with malignancy is secreted by neuroendocrine tumors

We have demonstrated the production of the PTH-related protein (PTHrP) associated with hypercalcemia of malignancy by human neuroendocrine cell lines that also produce calcitonin gene products and chromogranin A. PTHrP was demonstrable in the cells by immunocytochemistry and immunoassay and Northern analysis of the cells revealed the presence of multiple mRNAs for PTHrP. The cell lines also secreted PTHrP in a regulated fashion, with the most potent secretagogue being phorbol. Thus, PTHrP is secreted by neuroendocrine cells and it may have neuroectodermal lineage. The coexpression of calcitonin gene products and chromogranin A, also neuroendocrine, with PTHRP may influence its secretion and ultimate biological effects in vivo.     

Phylogeography of the leaf beetle Chrysolina virgata in wetlands of Japan inferred from the distribution of mitochondrial haplotypes

The genetic differentiation among populations of the leaf beetle Chrysolina virgata living in wetlands of Japan was studied based on the sequence data of the mitochondrial cytochrome oxidase subunit I gene region (750 bp). Two distinct lineages of mitochondrial haplotypes were found: one (clade A) consisted of 26 haplotypes distributed over the distribution range of C. virgata between north‐east Honshu and Kyushu, whereas the other (clade B) was monotypic and confined to a small region in north‐east Honshu where it coexisted with clade A. Nested clade analysis for these haplotypes suggested that range expansion and following differentiation due to isolation by distance might have resulted in the present distribution pattern of the haplotypes in clade A. We discuss the evolutionary process leading to the occurrence of two distinct haplotype clades in Japan in terms of repeated colonization from the continent and range expansion and contraction during climatic changes.     

Glycyrrhizic acid and its hydrolysate as mineralocorticoid agonist

Mineralocorticoid activity of glycyrrhetinic acid (GR) was studied in vivo (electrical potential difference in rat rectum) and in vitro (brush border Mg2+-HCO3- ATPase in rat small intestine, kidney cytosol binding of GR with and without RU-28362, anti-glucocorticoid compound) in order to clarify the mechanism of mineralocorticoid-like activity of GR. Scatchard analysis of [3H]aldosterone showed that Kd of higher affinity site (type I) 6.0 X 10(-9) M, Bmax 1.0 X 10(-14) mol/mg protein, and Kd of lower affinity site (type II) 1.6 X 10(-7) M, Bmax 7.5 X 10(-14) mol/mg protein. GR competed for [3H]aldosterone binding sites in kidney cytosol at the concentration of 10(4) times as that of unlabeled aldosterone. RU-28362 displaced aldosterone binding curve, whereas GR binding kinetic was not affected by this compound. Adrenalectomy caused a significant fall in brush border Mg2+-HCO3- ATPase activity (75% reduction compared with the initial level) which was not restored by GR administration. Electrical potential differences in the adrenalecomized rats were significantly lower than those in the control rats, which did not increase after GR administration.     

Molecular cloning and nucleotide sequence of cDNA encoding the entire precursor of rat liver medium chain acyl coenzyme A dehydrogenase

cDNA encoding the precursor of rat liver medium chain acyl-CoA dehydrogenase (EC 1.3.99.3) was cloned and sequenced. The longest cDNA insert isolated was 1866 bases in length. This cDNA encodes the entire protein of 421-amino acids including a 25-amino acid leader peptide and a 396-amino acid mature polypeptide. The identity of the medium chain acyl-CoA dehydrogenase clone was confirmed by matching the amino acid sequence predicted from the cDNA to the NH2-terminal and nine internal tryptic peptide sequences derived from pure rat liver medium chain acyl-CoA dehydrogenase. The calculated molecular masses of the precursor medium chain acyl-CoA dehydrogenase, the mature medium chain acyl-CoA dehydrogenase, and the leader peptide are 46,600, 43,700, and 2,900 daltons, respectively. The leader peptide contains five basic amino acids and only one acidic amino acid; thus, it is positively charged, overall. Cysteine residues are unevenly distributed in the mature portion of the protein; five of six are found within the NH2-terminal half of the polypeptide. Comparison of medium chain acyl-CoA dehydrogenase sequence to other flavoproteins and enzymes which act on coenzyme A ester substrates did not lead to unambiguous identification of a possible FAD-binding site nor a coenzyme A-binding domain. The sequencing of other homologous acyl-CoA dehydrogenases will be informative in this regard.     

Moulting interval and growth of juvenile Antarctic krill (Euphausia superba) fed different concentrations of the diatom Phaeodactylum tricornutum in the laboratory

Summary Juvenile Antarctic krill (Euphausia superba) were fed the diatom Phaeodactylum tricornutum at concentrations ranging from 0.0–5.0 mgCl^-1. Intermoult period (IP) decreased, but an increment of body length per moult (BL) of juvenile krill increased, up to a concentration of 1.0 mgCl^-1. No further effect of food concentrations on IP or BL was seen at concentration beyond 1.0 mgCl^-1. IP plateaued at 23.8 days and BL, 1.14 mm. The maximum daily growth rate (BL/IP) of juvenile krill was calculated to be 0.047 mm day^-1. BL and IP were correlated and the relationship is expressed as BL=-0.0066IP+2.47 (r=0.58, n=141, P<0.01). Growth conditions of krill in the Southern Ocean are discussed in terms of available food concentration in there.     

Effect of beta-hydroxybutyrate and acetoacetate on insulin and glucagon secretion from perfused rat pancreas

To elucidate the physiological significance of ketone bodies on insulin and glucagon secretion, the direct effects of beta-hydroxybutyrate (BOHB) and acetoacetate (AcAc) infusion on insulin and glucagon release from perfused rat pancreas were investigated. The BOHB or AcAc was administered at concentrations of 10, 1, or 0.1 mM for 30 min at 4.0 ml/min. High-concentration infusions of BOHB and AcAc (10 mM) produced significant increases in insulin release in the presence of 4.4 mM glucose, but low-concentration infusions of BOHB and AcAc (1 and 0.1 mM) caused no significant changes in insulin secretion from perfused rat pancreas. BOHB (10, 1, and 0.1 mM) and AcAc (10 and 1 mM) infusion significantly inhibited glucagon secretion from perfused rat pancreas. These results suggest that physiological concentrations of ketone bodies have no direct effect on insulin release but have a direct inhibitory effect on glucagon secretion from perfused rat pancreas.     

Rapid formation of myometrial gap junctions during parturition in the unilaterally implanted rat uterus

Summary In uterine smooth muscles, gap junction plaques rapidly form during the final stages of gestation. To investigate the related mechanisms, regional differences in myometrial gap junction development in rat uterus were examined quantitatively during delivery, using thin-section and freeze-fracture techniques in combination with light- and electron microscopy.Examination of implanted and nonimplanted horns in the unilaterally ligated rat bicornuate uteri, revealed no differences in the occurrence of gap junction plaques, but after 2 to 4 pups had been delivered, the contracted segments contained more gap junction plaques than did noncontracted segments examined immediately before delivery. In all segments, gap junctions were found more frequently in the circular muscle layers than in the longitudinal muscle layers. Gap junctions ranged in size from 0.002 m² to 0.52 m², but two-thirds were less than 0.1 m². The frequency of small gap junction plaques (less than 0.1 m²) was higher in the noncontracted segment.These results suggest that gap junctions are dynamic structures, and that their formation is controlled not only by general hormonal factors, possibly involved in gap junction increases in the myometrium before delivery, but also by local factors, possibly related to the contraction, that may accelerate an increase in gap junction formation during delivery.     

Isocitrate dehydrogenase kinase/phosphatase

In Escherichia coli, isocitrate dehydrogenase (IDH) is regulated by phosphorylation. This phosphorylation cycle is catalyzed by an unusual, bifunctional protein:IDH kinase/phosphatase. IDH kinase/phosphatase is expressed from a single gene, aceK, and both activities are catalyzed by the same polypeptide. The amino acid sequence of IDH kinase/phosphatase does not exhibit the characteristics which are typical of other protein kinases, although it does contain a consensus ATP binding site. The available evidence suggests that the IDH kinase and IDH phosphatase reactions occur at the same active site and that the IDH phosphatase reaction results from the back reaction of IDH kinase tightly coupled to ATP hydrolysis. The function of the IDH phosphorylation cycle is to control the flux of isocitrate through the glyoxylate bypass. This pathway is essential for growth on acetate because it prevents the quantitative loss of the acetate carbons as CO2 in the Krebs' cycle. IDH kinase/phosphatase monitors general metabolism by responding to the levels of a wide variety of metabolites, many of which activate IDH phosphatase and inhibit IDH kinase. The ability of IDH kinase/phosphatase to monitor general metabolism allows. the IDH phosphorylation cycle to compensate for substantial perturbations of the system, such as a 15-fold overproduction of IDH. The significance of the cellular level of IDH kinase/phosphatase has also been evaluated. The level of this protein is in great excess of that required for steady-state growth on acetate. In contrast, IDH kinase/phosphatase is, in some cases, rate-limiting for the dephosphorylation of IDH which results when preferred carbon sources are added to cultures growing on acetate.