Reciprocal changes of plasma glucose and ketone bodies in fasted and acutely diabetic rats after CNS stimulation

To assess the effect of chemical stimulation of the central nervous system (CNS) on ketogenesis, we injected neostigmine (5 x 10(-8)mol) into the third cerebral ventricle in normal rats fasted for 48 h and fed rats with diabetes induced by streptozotocin (STZ, 80 mg/kg). The hepatic venous plasma levels of ketone bodies (3-hydroxybutyrate and acetoacetate), free fatty acids (FFA), and glucose were measured for 120 min after the injection of neostigmine under pentobarbital anesthesia. In the normal rats, plasma glucose levels were significantly increased but neither ketone bodies nor FFA were affected by CNS stimulation with neostigmine. In contrast the plasma levels of ketone bodies and FFA were significantly increased in STZ-diabetic rats, while glucose levels remained unchanged. The intravenous infusion of somatostatin (1.0 microgram/kg/min) suppressed the increase in plasma ketone bodies following CNS stimulation in STZ-diabetic rats. These findings suggest that CNS stimulation with neostigmine may accelerate ketogenesis by promoting the lipolysis, which may be induced by glucagon, in fed diabetic rats but not in normal fasted rats.     

Sex pheromone of the butterbur borer, Ostrinia zaguliaevi

The sex pheromone blend of the butterbur borer, Ostrinia zaguliaevi (Lepidoptera: Pyralidae) was analyzed by means of gas chromatography-electroantennographic detection (GC-EAD), GC-mass spectrometry and a series of wind-tunnel bioassays. Four EAD-active compounds were detected in the female sex pheromone gland extract, and these were identified as tetradecyl acetate (14:OAc), (Z)-9-tetradecenyl acetate (Z9-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc) and (Z)-11-tetradecenyl acetate (Z11-14:OAc). The average amounts ± s.d. of the four compounds in a single sex pheromone gland were 7.9±3.7 ng, 10.1±3.2 ng, 1.1±0.5 ng and 11.6±5.1 ng, respectively. In a wind-tunnel bioassay, the ternary blend of Z9-, E11- and Z11-14:OAc at a ratio found in the sex pheromone gland (45:5:50) elicited the same behavioral responses from the males as did virgin females and pheromone gland extract. Removal of any single compound from the ternary blend significantly diminished the pheromonal activity, whereas addition of 14:OAc to the ternary blend had no effect on the males' behavioral responses. Therefore, it was concluded that the sex pheromone blend of O. zaguliaevi is composed of Z9-14:OAc, E11-14:OAc and Z11-14:OAc at a ratio of 45:5:50.     

Equilibrium and kinetics of the thermal unfolding of yeast 5S ribosomal RNA.

The equilibrium and kinetics of thermal unfolding of yeast 5S ribosomal RNA have been studied by optical methods, in a low ionic strength environment without Mg2+, to follow the disruption of the secondary structure base pairs in the molecule. The equilibrium results demonstrated that all of the helical regions melted simultaneously, and the kinetics of the thermal unfolding were first order. These findings suggest the validity of the two-state approximation for the unfolding reaction under the present conditions. The total number of secondary structure base pairs estimated from our experiment was consistent with that contained in the conformational model based on the Raman spectrum rather than that in the one derived by the enzymic digestion method. Taking our results on the kinetic behavior of the thermal unfolding overall, we propose that the 5S RNA has a partly melted secondary structure under the solvent conditions used.     

The production-to-respiration ratio and its implication in Lake Biwa,Japan

Production-to-respiration (P:R) ratio was estimated at an offshore site of Lake Biwa in order to examine whether the plankton and benthic community is subsidized with allochthonous organic carbon, and to clarify the role of this lake as potential source or sink of carbon dioxide. The respiration rate of protozoan and metazoan plankton was calculated from their biomass and empirical equations of oxygen consumption rates, and that of bacterioplankton was derived from their production rate and growth efficiency. In addition, the carbon mineralization rate in the lake sediments was estimated from the accumulation rate of organic carbon, which was determined using a ²¹⁰Pb dating technique. On an annual basis, the sum of respiration rates of heterotrophic plankton was comparable to net primary production rate measured by the ¹³C method. However, when the mineralization rate in the lake sediments was included, the areal P:R ratio was 0.89, suggesting that Lake Biwa is net heterotrophic at the offshore site with the community being subsidized with allochthonous organic carbon. Such a view was supported by the surface water pCO₂ that was on average higher than that of the atmosphere. However, the estimate of net CO₂ release rate was close to that of carbon burial rate in the sediments. The result suggests that the role of Lake Biwa in relation to atmospheric carbon is almost null at the offshore site, although the community is supported partially by organic carbon released from the surrounding areas.     

The electron microscopic observation of haustoria of Erysiphe graminis hordei

The fine structure of haustoria ofErysiphe graminis hordei was studied using samples fixed with 3 per cent KMnO₄ or 2 per cent OsO₄. The cell wall of the infected leaves of barley seedlings was extremely electron-dense around the penetration point of this fungus. This may be due to chemical change of components in cell wall by the enzymatic action of the fungus. The cell wall was invaginated towards the cytoplasm at the point of penetration and formed a sheath around the infection hypha. Unknown electron-dense substances were accumulated around the infection hypha outside the sheath. The haustorial cell wall was surrounded with encapsulation and distinguished clearly from the cytoplasm of epidermal cell. The cell wall of the haustorium was very thin and electron-transparent, when compared with that of conidia and hyphae. A septum with a septal pore was observed between the infection hypha and the haustorium. Besides the nucleus, mitochondria, endoplasmic reticula and the like, many kinds of vesicles and specific coiled membraneous structure were found in the haustorium. The origin and the function of the encapsulation remain obscure.

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Zusammenfassung Die Feinstruktur von Haustorien vonErysiphe graminis hordei war untersucht, indem Stücke mit 3 % KMnO₄ oder 2 % OsO₄ fixiert worden sind. Die Zellwand der infizierten Blätter der Gerstenkeimlinge war elektron-dicht um die Eindringungsstelle des Pilzes. Dies mag die Folge der chemischen Veränderung der Komponenten in der Zellwand durch die enzymatische Wirkung des Pilzes sein. Die Zellwand war an der Eindringungsstelle zum Zytoplasma gebogen und hat eine Hülle um die Infektionshyphe gebildet. Unbekannte, elektron-dichte Substanzen waren um die Infektionshyphe außerhalb der Hülle angesammelt. Die Haustorialzellwand war abgegrenzt und war vom Zytoplasma der Epidermalzelle unterscheidbar. Die Zellwand des Haustoriums war dünn und elektron-durchsichtig im Vergleich mit denen der Konidien und Hyphen. Ein Septum mit einer Septalpore war zwischen der Infektionshyphe und dem Haustorium beobachtet. Neben dem Nucleus, Mitochondrien, endoplasmatischen Netz sind mancherlei Blister, spezifische, eingerollte Membranstruktur im Haustorium gefunden worden. Die Herkunft und die Funktion dieser Strukturen blieb ungeklärt.

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Contribution No. 232     

Discovery of ciliates reproducing in the gut of Antarctic krill

During a recent Antarctic research cruise (December 1994/February 1995), dissection of fresh Antarctic krill (Euphausia superba) on board ship revealed live motile ciliates in the gut of krill. Further observation of gut samples by scanning electron microscopy indicated that the ciliates were symbionts located within the gut. We inferred that the ciliates may have enabled the krill to digest a wider range of food items, and as a consequence, this had became an important strategy for Antarctic krill's survival in the Antarctic ecosystem. Received: 1 August 1996 / Accepted: 1 December 1996     

Long α helices projecting from the membrane as the dimer interface in the voltage-gated H+ channel

The voltage-gated H⁺ channel (Hv) is a H⁺-permeable voltage-sensor domain (VSD) protein that consists of four transmembrane segments (S1–S4). Hv assembles as a dimeric channel and two transmembrane channel domains function cooperatively, which is mediated by the coiled-coil assembly domain in the cytoplasmic C terminus. However, the structural basis of the interdomain interactions remains unknown. Here, we provide a picture of the dimer configuration based on the analyses of interactions among two VSDs and a coiled-coil domain. Systematic mutations of the linker region between S4 of VSD and the coiled-coil showed that the channel gating was altered in the helical periodicity with the linker length, suggesting that two domains are linked by helices. Cross-linking analyses revealed that the two S4 helices were situated closely in the dimeric channel. The interaction interface between the two S4 and the assembly interface of the coiled-coil domain were aligned in the same direction based on the phase angle calculation along α helices. Collectively, we propose that continuous helices stretching from the transmembrane to the cytoplasmic region in the dimeric interface regulate the channel activation in the Hv dimer.     

Characterization of Plasmodium falciparum calcium-dependent protein kinase 4

In Plasmodium berghei, the orthologous gene of P. falciparum calcium-dependent protein kinase 4 (PfCDPK4) was reported to be essential for the exflagellation of male gametocytes. To elucidate the role of PfCDPK4 in P. falciparum gametogenesis, we characterized the biological function of PfCDPK4 in vitro. PfCDPK4 was purified as a fusion protein that was labeled with [γ-³²P]ATP; this labeling was then eliminated by phosphatase. Phosphorylation activity of PfCDPK4 was eliminated when its putative catalytic lysine residue was replaced with alanine. In biochemical analyses, PfCDPK4 was found to have characteristics that were similar to those of homologous proteins from plants. PfCDPK4 phosphorylation was activated when experimental conditions were changed from those characteristic of human blood (37 °C, pH 7.4) to those of the mosquito bloodmeal (at least 5 °C below 37 °C, pH 7.6, with xanthurenic acid (XA)). PfCDPK4 was overexpressed in day 15 gametocytes exposed to XA or human serum. Thus, PfCDPK4 phosphorylation is activated by an increase in Ca²⁺ concentration or pH and by a decrease in temperature, and is associated with the Ca²⁺ signals that facilitate P. falciparum gametogenesis.     

Elevated Na+/K+-ATPase responses and its potential role in triggering ion reabsorption in kidneys for homeostasis of marine euryhaline milkfish (Chanos chanos) when acclimated to hypotonic fresh water

The milkfish (Chanos chanos) is an economic species in Southeast Asia. In Taiwan, the milkfish are commercially cultured in environments of various salinities. Na⁺/K⁺-ATPase (NKA) is a key enzyme for fish iono- and osmoregulation. When compared with gills, NKA and its potential role were less examined by different approaches in the other osmoregulatory organs (e.g., kidney) of euryhaline teleosts. The objective of this study was to investigate the correlation between osmoregulatory plasticity and renal NKA in this euryhaline species. Muscle water contents (MWC), plasma, and urine osmolality, kidney histology, as well as distribution, expression (mRNA and protein), and specific activity of renal NKA were examined in juvenile milkfish acclimated to fresh water (FW), seawater (SW 35‰), and hypersaline water (HSW 60‰) for at least two weeks before experiments. MWC showed no significant difference among all groups. Plasma osmolality was maintained within the range of physiological homeostasis in milkfish acclimated to different salinities, while, urine osmolality of FW-acclimated fish was evidently lower than SW- and HSW-acclimated individuals. The renal tubules were identified by staining with periodic acid Schiff’s reagent and hematoxylin. Moreover, immunohistochemical staining showed that NKA was distributed in the epithelial cells of proximal tubules, distal tubules, and collecting tubules, but not in glomeruli, of milkfish exposed to different ambient salinities. The highest abundance of relative NKA α subunit mRNA was found in FW-acclimated milkfish rather than SW- and HSW-acclimated individuals. Furthermore, relative protein amounts of renal NKA α and β subunits as well as NKA-specific activity were also found to be higher in the FW group than SW and the HSW groups. This study integrated diverse levels (i.e., histological distribution, gene, protein, and specific activity) of renal NKA expression and illustrated the potential role of NKA in triggering ion reabsorption in kidneys of the marine euryhaline milkfish when acclimated to a hypotonic FW environment.