Spironolactone, but not Eplerenone, Impairs Glucose Tolerance in a Rat Model of Metabolic Syndrome

Although some clinical studies have suggested that spironolactone (SPL), a mineralocorticoid receptor (MR) antagonist, appears to increase the blood glucose levels, experimental studies have not supported this notion. Here, we investigated the effect of SPL on blood glucose levels in SHR/NDmcr-cp(cp/cp) (ND) rats, an animal model of metabolic syndrome, in comparison with that of eplerenone (EPL), another MR antagonist. At the same dose of 100 mg/kg, SPL and EPL increased the urinary sodium-to-potassium ratio to a comparable extent, indicating that both agents have similar renal MR antagonistic efficacy in ND rats. Interestingly, SPL but not EPL significantly increased the level of blood glucose. The oral glucose tolerance test revealed that treatment with SPL led to glucose intolerance. The levels of serum insulin and adiponectin, regulators of the blood glucose level, were virtually unaffected by treatment with SPL. On the other hand, SPL induced a marked increase in the blood level of aldosterone, known to be a risk factor for insulin resistance. These results demonstrate that in comparison with EPL, SPL characteristically impairs glucose tolerance in an animal model of metabolic syndrome, in association with a higher blood level of aldosterone.     

Age related decreases in neural sensitivity to NaCl in SHR-SP

To determine whether neurophysiological taste responses of young and old rats are different, recordings were made from the whole chorda tympani nerve which innervates taste buds on the anterior tongue. SHR-SP (Stroke-Prone Spontaneously Hypertensive Rats) in two age groups were studied. Chemical stimuli included single concentrations of 250 mM NH(4)Cl, 100 mM NaCl, 100 mM KCl, 500 mM sucrose, 20 mM quinine-hydrochloride, 10 mM HCl, 10 mM monosodium glutamate (MSG), 10 mM L- glutamic acid (L-Glu) and an NaCl concentration series. The magnitude of the neural response (response ratio) was calculated by dividing the amplitude of the integrated response by the amplitude of the spontaneous activity that preceded it. Substantial neural responses to all chemicals were obtained at both ages. The responses to KCl, sucrose, quinine-hydrochloride, HCl, monosodium glutamate (MSG) and glutamic acid (Glu) did not change with age, but the response to NaCl did decrease significantly. The profile of the response/concentration function for NaCl differed with age. In particular, the responses to solutions more concentrated than 100 mM NaCl were significantly weaker in aged than in young SHR-SPs. We also observed that recovery from amiloride treatment on the tongue of SHR-SPs was faster in aged rats than in young ones, suggesting that there is some functional difference in the sodium-specific channels on the taste cell. These results suggest that aged SHR-SP may be less able than young SHR-SPs to discriminate among higher concentrations of NaCl solutions.     

Quantitative in vivo measurement of central benzodiazepine receptors in the brain of cats by use of positron-emission tomography and [11C]flumazenil

OBJECTIVE: To map central benzodiazepine receptors (BZRs) in the brain of cats by use of positron-emission tomography (PET) and [11C]flumazenil. ANIMALS: 6 male cats that weighed between 2.0 and 3.6 kg. PROCEDURE: Brain images obtained by PET evaluation of [11C]flumazenil were superimposed on T2-weighted magnetic-resonance imaging (MRI) scans of the same cats. Detailed anatomic regions, such as the cerebral cortex, striatum, thalamus, midbrain, and cerebellum, on the PET images were evident by PET-MRI registration. Regional binding of [11C]flumazenil to BZRs was quantitatively measured by use of a model with 2 tissue compartments and 4 variables. RESULTS: The highest value for distribution volume was observed in the cerebral cortex, and the lowest value was found in the midbrain of cats. CONCLUSIONS AND CLINICAL RELEVANCE: Binding of [11C]flumazenil to BZRs in the brain of cats can be quantitatively measured by use of PET with the aid of PET-MRI registration. It is difficult to diagnose changes in these neuroreceptors within the field of current veterinary science. In the future, PET should prove useful for investigating and diagnosing brain disorders in animals in clinical settings.     

A meningioma with hyperintensity on T1-weighted images in a dog

A male six-year-old Pomeranian showed recurrent seizures and progressive left hemiparesis. MRI revealed a mass in the right paramedian frontal-temporal region with hyperintensity on T1-weighted (T1W) and mixed-intensity on T2-weighted (T2W) images. After gadolinium enhancement, the mass was enhanced homogenously and demonstrated the dural tail sign. Surgical resection of mass was performed and its histological diagnosis was meningioma. The meningioma of this case had a high cellular density with some lipid contents and intra- and extra-tumor hemorrhage, however, calcification was not found. These cellular characteristics may contribute to a higher signal intensity on T1W imaging.     

Disentangling density‐dependent effects on egg production and survival from egg to recruitment in fish

Understanding of density‐dependent effects is key to achieving sustainable management of self‐regulating biological resources such as fish stocks. Traditionally, density‐dependent effects on population abundance in fish have been considered to occur from hatching to recruitment, based on the paradigm of proportionality between spawning stock biomass and total egg production. Here, we demonstrate how the existence of intraspecific and interspecific density dependence in egg production changes the current understanding of density‐dependent processes in the life history of fish, by disentangling density‐dependent effects on egg production and survival from egg to recruitment, using sardine (Sardinops melanostictus, Clupeidae) and anchovy (Engraulis japonicus, Engraulidae) as model species. For sardine, strong intraspecific density‐dependent effects occurred in egg production, but no density‐dependent effects occurred or if any they were weak enough to be masked by environmental factors from hatching to recruitment. In contrast, for anchovy, interspecific density‐dependent effects occurred in egg production. In the survival after hatching, anchovy experienced stronger intraspecific density‐dependent effects than currently recognized. This analysis could overturn the current understanding of density‐dependent effects in the life history, highlighting contrasts between the effects on individual quality and population abundance and between the model species. We propose to reconsider the basis of fisheries management and recruitment studies based on the revised understanding of density‐dependent effects in the life history of the respective species.     

Induction of centrum defects in amberjack Seriola dumerili by exposure of embryos to hypoxia

ABSTRACT:   Artificially hatched Seriola species have the problem of malformation, mainly in their vertebrae, head, and mouth parts. To clarify the cause of vertebral malformation, the effects of hypoxia during embryogenesis on the induction of centrum defects was investigated in artificially hatched amberjack Seriola dumerili . Firstly, 7-somite stage embryos were exposed to waters of 0, 12.5, 25, 50, and 100% dissolved oxygen (DO) for 0.5, 1, 2, 3, 4, and 5 h to confirm the effective dose (DO concentration and duration of exposure) of hypoxia that induces somitic disturbances in newly hatched larvae. Exposure of embryos to 12.5% DO concentration for longer than 0.5 h induced somitic disturbances. Following this result, centrum defects in juveniles were investigated by an induction experiment with embryos exposed to 12.5% DO for 2 h at the gastrula, 1- or 2-somite, 10-somite, 15-somite, or heart beating stage. This experiment revealed that centrum defects were induced only during somitogenesis, and somitic disturbances were the premonitory symptom of centrum defects. These results indicate hypoxia during somitogenesis as a possible cause of centrum defects in amberjack.     

Effect of water temperature and light intensity on swim bladder inflation and growth of red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis> larvae

This study aimed to examine the effect of different water temperatures and light intensities on swim bladder inflation (SBI) and growth of red sea bream Pagrus major larvae to improve rearing techniques for this species. Two sets of experiments were conducted: different rearing temperatures were used in experiment 1 (19, 21, 23, and 25 °C), and different light intensities in experiment 2 (250, 1000, 4000, and 16,000 lx). Water temperature did not affect SBI frequency, but SBI initiation was accelerated at higher temperature, i.e., it was initiated on 3 days post-hatching (dph) at 25 °C and on 6 dph at 19 °C, suggesting that the promotion period for SBI, which needs a surface skimmer to be  run, also accelerated with increasing temperature in red sea bream larviculture. A higher temperature also significantly promoted larval growth, although the notochord of larvae at SBI initiation was shorter at higher temperatures. Light intensity had no effect on either the initiation or the frequency of SBI. However, light intensity of 250 lx significantly reduced early larval growth compared to light intensities higher than 1000 lx. These results indicate that light at an intensity greater than 1000 lx at the water surface is suitable for the early larviculture of red sea bream.     

Age validation,growth and annual reproductive cycle of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> off the waters of northern Kyushu and in the East China Sea

The age and growth of chub mackerel Scomber japonicus collected from the East China Sea and the northern waters off Kyushu between June 2000 and June 2001 were determined by observing the otolith surface after dipping it in xylene. The translucent and opaque zones on the otolith surface were identified, and the number of translucent zones was counted. Monthly changes in the frequency of fish with translucent zones on the otolith margin, and in the marginal increments, indicated that the translucent zones were formed between April and June. The seasonal pattern of annulus formation on the otolith became clear by observing the otoliths of fish with known ages, and the otolith formation in wild fish was consistent with that of fish with known ages. The mean gonadosomatic index of male and female fish was high from March to May, and spawning females were observed from mid-March to mid-May. The estimated ages were 1–5 years for males and 1–6 years for females. The von Bertalanffy growth parameters did not significantly differ between male and female. The model was obtained as FL _t=406×{1−exp[−0.372×(t+1.68)]     

Purification and characterization of an angiotensin I‐converting enzyme inhibitory peptide derived from porcine troponin C

To search for a novel angiotensin I‐converting enzyme (ACE) inhibitory peptide, porcine skeletal troponin was hydrolyzed with pepsin. This hydrolysate showed ACE inhibitory activity, and was applied to various kinds of chromatography to separate an active peptide. Analysis using a protein sequencer identified this peptide as RMLGQTPTK (9mer). This sequence was estimated to occur at the 44–52 position of troponin C, and its 50% inhibitory protein concentration (IC₅₀) was 34 µM. RMLGQTP (7mer), a partial peptide of 9mer, showed activity with an IC₅₀ of 503 µM. RP‐HPLC analysis of a reaction mixture of 9mer and ACE showed that 9mer was slowly hydrolyzed by ACE. On the other hand, 7mer was rapidly hydrolyzed by ACE. Activity of 9mer was reduced as its hydrolysis by ACE proceeded. To estimate the resistance of 9mer to digestive proteases after oral administration, it was reacted with pepsin, α‐chymotrypsin, or trypsin. In each of these reaction mixtures, a significant amount of 9mer remained as a substrate after digestion. Remaining ACE inhibitory activity was close to that of 9mer. These results suggest that 9mer might not be digested after oral administration, because of its relatively high resistance to digestive proteases. Therefore, 9mer might be expected to work well in vivo as an ACE inhibitor.