Role of cardiac renin-angiotensin system in sarcoplasmic reticulum function and gene expression in the ischemic-reperfused heart

The aim of this study was to explore the possible participation of cardiac renin-angiotensin system (RAS) in the ischemia-reperfusion induced changes in heart function as well as Ca²⁺-handling activities and gene expression of cardiac sarcoplasmic reticulum (SR) proteins. The isolated rat hearts, treated for 10 min without and with 30 M captopril or 100 M losartan, were subjected to 30 min ischemia followed by reperfusion for 60 min and processed for the measurement of SR function and gene expression. Attenuated recovery of the left ventricular developed pressure (LVDP) upon reperfusion of the ischemic heart was accompanied by a marked reduction in SR Ca²⁺-pump ATPase, Ca²⁺-uptake and Ca²⁺-release activities. Northern blot analysis revealed that mRNA levels for SR Ca²⁺-handling proteins such as Ca²⁺-pump ATPase (SERCA2a), ryanodine receptor, calsequestrin and phospholamban were decreased in the ischemia-reperfused heart as compared with the non-ischemic control. Treatment with captopril improved the recovery of LVDP as well as SR Ca²⁺-pump ATPase and Ca²⁺-uptake activities in the postischemic hearts but had no effect on changes in Ca²⁺-release activity due to ischemic-reperfusion. Losartan neither affected the changes in contractile function nor modified alterations in SR Ca²⁺-handling activities. The ischemia-reperfusion induced decrease in mRNA levels for SR Ca²⁺-handling proteins were not affected by treatment with captopril or losartan. The results suggest that the improvement of cardiac function in the ischemic-reperfused heart by captopril is associated with the preservation of SR Ca²⁺-pump activities; however, it is unlikely that this action of captopril is mediated through the modification of cardiac RAS. Furthermore, cardiac RAS does not appear to contribute towards the ischemia-reperfusion induced changes in gene expression for SR Ca²⁺-handling proteins.     

Bovine milk lactoferrin modulates the proliferative lymphocyte response to phytohemagglutinin

Bovine milk lactoferrin (2 to 20 g ml^–1) changed enhancement of [³H]thymidine incorporation by phytohemagglutinin-stimulated rat spleen lymphocytes into suppression as their lactoferrin-withdrawal incorporation increased to greater than 10000 cpm culture^–1 under the present isotope-labeling conditions. The enhancement disappeared by 15-min delayed addition of lactoferrin after addition of lectin. There was no lactoferrin effect when the cells were stimulated with 12-O-tetradecanoylphorbol-13-acetate plus ionomycin. Thus, lactoferrin has a certain extracellular effect on lymphocyte proliferation in response to the lectin.     

Enzyme reactions and genes in aflatoxin biosynthesis

Aflatoxins are highly toxic and carcinogenic substances mainly produced by Aspergillus flavus and Aspergillus parasiticus. Sterigmatocystin is a penultimate precursor of aflatoxins and also a toxic and carcinogenic substance produced by many species, including Aspergillus nidulans. Recently, the majority of the enzyme reactions involved in aflatoxin/sterigmatocystin biosynthesis have been clarified, and the genes encoding the enzymes have been isolated. Most of the genes constitute a large gene cluster in the fungal genome, and their expression is mostly regulated by a product of the regulatory gene aflR. This review will summarize the enzymatic steps and the genes in aflatoxin/sterigmatocystin biosynthesis.     

Invertase and phosphatase of yeast in a phosphate-limited continuous culture

Summary Deficiency of inorganic phosphate caused the hyper production of invertase and the derepression of acid phosphatase in a continuous culture ofSaccharomyces carlsbergensis. The specific invertase activity was 40,000 enzyme units per g dry cell weight at a dilution rate lower than 0.05 h^–1 with a synthetic glucose medium of which the molecular ratio of KH₂PO₄ to glucose was less than 0.006. This activity is eight fold higher than in a batch growth and 1.5 fold as much as the highest enzyme activity observed so far in a glucose-limited continuous culture.For the hyper production of invertase, it is necessary to culture the yeast continuously by keeping the Nyholm's conservative inorganic phosphate concentration at less than 0.2 m mole per g dry weight cell. The derepression of acid phosphatase brought about by phosphate deficiency, was similar in both batch and continuous cultures.Nomenclature D dilution rate of continuous culture (h^–1) - E_i invertase concentration in culture (enzyme unit l^–1) - E_p acid phosphatase concentration in culture (enzyme unit l^–1) - P inorganic phosphate concentration in culture (mM) - S glucose concentration in culture (mM) - X cell concentration in culture (g dry weight cell l^–1) Greek Letter specific rate of growth (h^–1) Suffix f feed - 0 initial value     

Role of three chitin synthase genes in the growth of Candida albicans.

The CHS2 and CHS3 genes of Candida albicans were disrupted. The double disruptant was still viable. Assessment of chitin and of calcofluor white resistance shows that CHS1 is responsible for septum formation and CHS3 is responsible for overall chitin synthesis otherwise. There were only small differences in virulence to immunocompromised mice of homozygous chs2 delta amd chs3 delta null mutants.     

Putative functions of nucleoside diphosphate kinase in plants and fungi

The putative functions of NDP (nucleoside diaphosphate) kinases from various organisms focusing to fungi and plants are described. The biochemical reactions catalyzed by NDP kinase are as follows. (i) Phosphotransferring activity from mainly ATP to cognate NDPs generating nucleoside triphosphates (NTPs). (ii) Autophosphorylation activity from ATP and GTP. (iii) Protein kinase (phosphotransferring) activity phosphorylating such as myelin basic protein. NDP kinase could function to provide NTPs as a housekeeping enzyme. However, recent works proved possible functions of the NDP kinases in the processes of signal transduction in various organisms, as described below. By use of the extracts of the mycelia of a filamentous fungus Neurospora crassa blue-light irradiation could increase the phosphorylation of a 15-kDa protein, which was purified and identified to be NDP kinase (NDK-1). By use of the etiolated seedlings of Pisum sativum cv Alaska and Oryza sativa red-light irradiation of intact plants increased the phosphorylation of NDP kinase. However, successive irradiation by red–far-red reversed the reaction, indicating that phytochrome-mediated light signals are transduced to the phosphorylation of NDP kinase. NDP kinase localizing in mitochondria is encoded by nuclear genome and different from those localized in cytoplasm. NDP kinase in mitochondria formed a complex with succinyl CoA synthetase. In Spinicia oleraceae two different NDP kinases were detected in the chloroplast, and in Pisum sativum two forms of NDP kinase originated from single species of mRNA could be detected in the choloroplast. However, the function of NDP kinases in the choloroplast is not yet known. In Neurospora crassa a Pro72His mutation in NDP kinase (ndk-1 ^Pro72His ) deficient in the autophosphorylation and protein kinase activity resulted in lacking the light-induced polarity of perithecia. In wild-type directional light irradiation parallel to the solid medium resulted in the formation of the perithecial beak at the top of perithecia, which was designated as light-induced polarity of perithecia. In wild-type in darkness the beak was formed at random places on perithecia, and in ndk ^Pro72His mutant the perithecial beak was formed at random places even under directional light illumination. The introduction of genomic DNA and cDNA for ndk-1 demonstrated that the wild-type DNAs suppressed the mutant phenotype. With all these results except for the demonstration in Neurospora, most of the phenomena are elusive and should be solved in the molecular levels concerning with NDP kinases.     

A highly efficient construction of GM1 epitope tetrasaccharide and its conjugation with KLH

GM1 epitope tetrasaccharide was synthesized by a condensation of sialyl-alpha(2-3)-gal acceptor and gal-beta(1-3)-GalN donor in a highly efficient manner. After introduction of mercaptohexanol to the tetrasaccharide, it was coupled to maleimide-activated KLH carrier protein to give the desired GM1 epitope-KLH conjugate.     

Extensive polymorphism of ABO blood group gene: three major lineages of the alleles for the common ABO phenotypes

Polymorphism of the ABO blood group gene was investigated in 262 healthy Japanese donors by a polymerase chain reactions-single-strand conformation polymorphism (PCR-SSCP) method, and 13 different alleles were identified. The number of alleles identified in each group was 4 for A¹ (provisionally called ABO*A101, *A102, *A103 and *A104 according to the guidelines for human gene nomenclature), 3 for B (ABO*B101, *B102 and *B103), and 6 for O (ABO*O101, *O102, *O103, *O201, *O202 and *O203). Nucleotide sequences of the amplified fragments with different SSCP patterns were determined by direct sequencing. Phylogenetic network analysis revealed that these alleles could be classified into three major lineages, *A/*O1, *B and *O2. In Japanese, *A102 and *13101 were the predominant alleles with frequencies of 83% and 97% in each group, respectively, whereas in group O, two common alleles, *O101 (43%) and *O201 (53%), were observed. These results may be useful for the establishment of ABO genotyping, and these newly described ABO alleles would be advantageous indicators for population studies.