Changes in sensitivity to histamine of guinea pig cardiac muscles during postnatal development

Histamine stimulates the heart by interacting with cardiac histamine receptors. We investigated the postnatal changes in histamine sensitivity with spontaneously beating right atria and electrically driven left atria and right ventricular papillary muscles from 0-, 5-, and 10-day-old and adult guinea pigs. The positive chronotropic response to histamine in right atria was antagonized by cimetidine but not by chlorpheniramine at any age. Chlorpheniramine did not antagonize the positive inotropic effect of histamine and 2-(2-pyridyl)ethylamine in the immature left atria but it blocked the positive inotropic effect in the adult; cimetidine had no effect. The positive inotropic effect of histamine in right ventricular muscles was not affected by chlorpheniramine in immature right ventricular muscles but was antagonized in the adult. These results suggest that, in immature left atria and right ventricular muscles, there is no H1-receptor system mediating the positive inotropic effect of histamine and that, as age advances, this system begins to mediate the positive inotropic effect. In immature left atria, non-H1 and non-H2 receptors exist and mediate the positive inotropic effect of histamine.     

Utilization of Polyphenyl and Polyphenyl-related Compounds by Microorganisms. Part I

Two hundreds and fifty eight strains of microorganisms have been isolated from 526 samples (soil, leaf and river water gathered from 17 prefectures) by repeating liquid enrichment culture techniques in the medium containing biphenyl, diphenylmethane, diphenylethane or terphenyl, as the sole source of carbon.

In the course of investigation, several strains were found to produce a large amount of γ-benzoylbutyric acid from biphenyl. Furthermore these strains utilized p-Cl-biphenyl and produced p-Cl-benzoic acid in good yield.

Microorganisms obtained were almost short rod, motile bacteria, and fungi were also found from the screening medium of diphenylethane.     

Thiol-disulfide Transhydrogenase from Baker’s Yeast and a New Method for the Direct Assay of an Enzyme-catalyzed Thiol-disulfide Interchange Activity

This paper presents a study on the enzyme reduction of the disulfide bond and the following results have been found.

In enzyme preparation, antioxidants showed a stability effect and EDTA appeared to have both enzyme stabilization and solubilization. On the distribution of the enzyme activity in subcellular fractions, the water soluble fraction appeared to contain the major released enzyme activity. The enzyme was inhibited with several metals. Hg²⁺ and transition metals were the most toxic. The substrate specificity of this enzyme was wide for the low molecular substrates, but the protein disulfide reducing activity was not detected in this preparation. It was assumed that the thiol-disulfide transhydrogenase was coupled with glutathione reductase and the disulfide substrates were reduced by the system involving the two enzymes. A new method for the direct recording of an enzyme-catalyzed thiol-disulfide interchange using diphenyl disulfide and p,p-dinitro diphenyl disulfide was devised.     

Potential Costs of Selecting Good Sites For Offspring: Increased Risk of Drowning And Negative Effects on Egg Production

Many studies have shown the benefits of selecting suitable sites for offspring survival and growth. However, costs of selecting suitable sites have been little covered. If the female's costs associated with selecting suitable sites exceed the benefit from improvement of offspring performance, selecting such sites can have a negative effect on the ongoing reproductive success for ovipositing females. We investigate the potential costs of selecting suitable sites in the water strider Aquarius paludum insularis. Where there exists a risk of egg parasitism, the female A. paludum will submerge and select a deep site, more suitable for offspring survival, for oviposition. By forcing A. paludum underwater once a day for 10 d, we investigated the potential costs associated with oviposition at deep sites, firstly relating to the performance of submergence (latency to asphyxiation or proportion of buoyancy loss) and, secondly, in the number of eggs laid. Buoyancy became weaker and the latency to asphyxiation became shorter with the number of submergences. The number of eggs laid in the period of forced submergence was smaller than both before and after the period. Selecting deep sites can therefore increase the mortality risk of ovipositing females and also decrease the number of eggs laid in their lives. Selecting suitable sites in all the oviposition bouts can decrease ovipositing females' reproductive success. Costs, not only benefits, should be taken into consideration for understanding oviposition site selection during the lifespan of an ovipositing female.     

Structure-activity relationships of endothelin: importance of the C-terminal moiety

The vasoconstrictor activities of various forms of derivatives of endothelin (ET) were characterized in vitro by measuring the contraction of porcine coronary artery strips. The removal of the C-terminal Trp21 reduced the molar potency of the peptide by nearly 3 orders of magnitude. The removal of amino acid residues from the C-terminus of ET(1-20) further attenuated the activity. Replacement of Trp21 with D-Trp, reduction and carboxamidomethylation of the four Cys residues, or cleavage at Lys9 by lysyl endopeptidase all lowered the potency approximately 200 fold. While both native ET and [D-Trp21]ET induced a very slow and sustained vasoconstriction, the other derivatives of ET listed above showed a much more rapid kinetics of vasoconstriction. These results indicate that the C-terminal Trp of ET is especially important for the potent and extremely long-lasting vasoconstrictor activity characteristic to ET.     

Complete primary structure and tissue expression of chicken pectoralis M-protein.

M-Protein (165 kDa) is a structural constituent of myofibrillar M-band in striated muscle. We generated a monoclonal antibody which recognized a 165-kDa protein from chicken pectoralis muscle in immunoblot analysis and stained the M-band under immunofluorescence microscopy. By screening a lambda gt11 cDNA library from chicken embryonic pectoralis muscle with this antibody, we isolated a cDNA clone encoding the M-protein. Northern blot analysis showed that M-protein mRNA is expressed in pectoralis and cardiac muscle but not in gizzard smooth muscle or non-muscle tissues. Moreover, the anterior latissimus dorsi muscle, which consists almost exclusively of slow fiber types, contains no detectable levels of the mRNA. The full-length cDNA sequence predicted a 1,450-amino acid polypeptide with a calculated molecular weight of 163 x 10(3). The encoded protein contains several copies of two different repetitive motifs: five copies of fibronectin type III repeats are in the middle part of the predicted molecule, and two and four copies of the immunoglobulin C2-type repeats are located toward the NH2-terminal and COOH-terminal regions, respectively. This indicates that M-protein, along with other thick filament-associated proteins such as C-protein, twichin, and titin, belongs to the superfamily of cytoskeletal proteins with immunoglobulin/fibronectin repeats.     

Arbuscular mycorrhizal fungi (Glomeromycota) communities in tropical savannas of Roraima,Brazil

Savanna vegetation in the northern region of Brazil is jeopardized by several anthropogenic activities including cattle ranching and extensive agriculture, and soil biota of these ecosystems is virtually unknown. The soils in savannas are poor in nutrients, very acidic, and subject to drought, and under these conditions, arbuscular mycorrhizal fungi (AMF) are likely to play a key role on plant nutrition and improving soil structure. In this study, we surveyed AMF communities in five savanna locations in Roraima state, Northern Brazil. AMF species were identified using two approaches: field collected spores and trap cultures. Twenty-three AMF species were identified, including 21 species in field samples, 8 species in trap cultures, of which 15 and 2 were unique to field and trap culture samples, respectively. Gigaspora margarita, Dentiscutata heterogama, and Glomus sp1 were the most frequent species recovered from all locations. AMF communities were dominated by members of Gigasporaceae that accounted for 50 to 87% of the total species richness within each location. Spore numbers differed across locations and ranged from 5 to 25 spores 100 cm^?3 soil. Redundancy analysis indicated that soil organic matter was the only selected predictor among soil parameters and correlated positively with occurrence of Glomus heterosporum. We conclude that savannas in Roraima harbor a high sporulating AMF species richness with communities dominated by members of Gigasporaceae and that organic carbon is an important edaphic factor influencing AMF community composition in this ecosystem.     

Mycorrhizae ofMonotropastrum globosum growing in aFagus crenata forest

The achlorophyllousMonotropastrum globosum was found growing in aFagus crenata forest. Samples ofM. globosum and their interpenetrating root systems ofF. crenata were collected to investigate the mycorrhizal association.Monotropastrum globosum mycorrhizae showed thick sheaths, invasion of the epidermal cells by fungal pegs, and Hartig nets, which reached only the first layer of cortical cells. TheF. crenata mycorrhizae also showed thick sheaths, but Hartig nets penetrated deep into the cortex and intracellular hypha were seen in the outer cortical cells. The similarities observerd in the mantle inner plan view and emanating hypha suggest that both mycorrhizae are formed by the same fungus.