Salsolinol is present in the bovine posterior pituitary gland and stimulates the release of prolactin both in vivo and in vitro in ruminants

The aims of the present study were to determine whether salsolinol (SAL), a dopamine-related compound, is present in the bovine posterior pituitary (PP) gland, and to clarify the effect of SAL on the secretion of prolactin (PRL) in ruminants. SAL was detected in extract of bovine PP gland using high-pressure liquid chromatography with electrochemical detection (HPLC-EC). A single intravenous (i.v.) injection of SAL (5 and 10mg/kg body weight) significantly and dose-dependently stimulated the release of PRL in goats (P<0.05). Plasma PRL levels reached a peak 10min after the injection, then gradually returned to basal values in 60-80min. The PRL-releasing pattern was similar to that in response to sulpiride (a dopamine receptor antagonist). The intracerebroventricular (i.c.v.) injection of 1mg of SAL had no significant effect on the release of PRL in calves, however, 5mg significantly stimulated the release (P<0.05) with peak values reached 30-40min after the injection. Moreover, SAL significantly stimulated the release of PRL from cultured bovine anterior pituitary cells at doses of 10(-6) and 10(-5)M, compared to control cells (P<0.05). Taken together, our data clearly show that SAL is present in extract of the PP gland of ruminants, and has PRL-releasing activity both in vivo and in vitro. Therefore, this endogenous compound is a strong candidate for the factor having PRL-releasing activity that has been previously detected in extract of the bovine PP gland.     

The effects of l‐DOPA and sulpiride on growth hormone secretion at different injection times in Holstein steers

The effects of l ‐DOPA, a precursor of dopamine (DA), and sulpiride, a D₂‐type DA receptor blocker, on growth hormone (GH) and prolactin (PRL) secretion were investigated in steers. Eight Holstein steers (212.8 ± 7.8 kg body weight) were used. Lighting conditions were 12:12 L:D (lights on: 06.00–18.00 hours). Blood samplings were performed during the daytime (11.00–15.00 hours) and nighttime (23.00–03.00 hours). Intravenous injections of drugs or saline were performed at 12.00 hour for the daytime and 00.00 hour for the nighttime, respectively. Plasma GH and PRL concentrations were determined by radioimmunoassay. l ‐DOPA did not alter the GH secretion when it was injected at 12.00 hour (spontaneous GH level at its peak). On the other hand, l ‐DOPA increased GH secretion at 00.00 hour (GH level at its trough). Injection of sulpiride suppressed GH secretion at 12.00 hour but did not affect GH levels at 00.00 hour. l ‐DOPA inhibited and sulpiride stimulated PRL release during both periods. These results suggest that dopaminergic neurons have stimulatory action on GH secretion and inhibitory action on PRL secretion in cattle. In addition, injection time should be considered to evaluate the exact effects on GH secretion due to its ultradian rhythm of GH secretion in cattle.     

Molecular phylogenetic analysis of Theileria species detected from Japanese serows (Capricornis crispus) in Iwate Prefecture, Japan

In the present study, we tried to detect DNA for ribosomal RNA genes of piroplasma parasites from the liver or blood of 43 Japanese serows (Capricornis crispus) in Iwate Prefecture of Japan by polymerase chain reaction. Approximately 500-bp amplicons were obtained in 35 (81.4%) of the 43 samples by amplification for V4 hyper-variable regions of the 18S rRNA gene, and the amplicons were considered to be DNA of Theileria species. The complete nucleotide sequences (1,700 or 1709 bp) of the 18S rRNA gene were determined in 20 samples and were divided into 5 genotypes that were phylogenetically separated into two different lineages showing a polyphyletic relation. The Theileria DNAs of the two different lineages were considered to be those of distinct species.     

Termiticidal activity of wood vinegar, its components and their homologues

The termiticidal activity of wood vinegar, its components, and their homologues have been studied. Three kinds of wood vinegar made from the mixed chips ofCryptomeria japonlca andPseudotsga menziesii (wood vinegar A),Quercus serrata (wood vinegar B), andPinus densiflora (wood vinegar C) exhibited high termiticidal activities againstReticulitermes speratus. Acetic acid, which is the largest content of wood vinegar, exhibited high termiticidal acitivity. The contents of organic fraction of wood vinegars and acetic acid might be responsible for the differences in termiticidal activities among these wood vinegars. The structure and termiticidal activity relations of phenols were studied. Phenol with some substituents revealed higher termiticidal activity than benzene derivatives, which have no hydroxyl group; an ortho substituent of phenol plays an important role in termiticidal activity. It has become apparent that high termiticidal activity cannot be obtained by a phenolic hydroxyl group alone; it can be obtained, however, by some substituents, especially an ortho substituent in addition to a phenolic hydroxyl group. The bulkiness of the substituent at the ortho position participates in termiticidal activity; activity decreases as the size of an ortho substituent increases. It is thought that the interaction at the receptor site of termites is affected by the increased size of the ortho substituent.     

Effects of citric acid on the viscoelasticity of cornstarch pastes

The effects of citric acid on the rheological properties of cornstarch pastes were studied by steady shear and dynamic oscillatory viscoelasticity, intrinsic viscosity measurements and microscopic observation. The pH of cornstarch dispersion was adjusted between 6.0 and 3.0. The viscosity of the pastes was increased by lowering the pH (between 5.5 and 3.6), while the viscosity of samples with pH below 3.5 decreased further than that of the control (pH = 6.3). Citric acid promoted the collapse of starch granules; however, adding excessive citric acid led to the hydrolysis of glucose chains. No decrease in the viscoelasticity was observed for cornstarch pastes by adding acid at 25 degrees C after gelatinization.     

A possible role of central serotonin in L‐tryptophan‐induced GH secretion in cattle

To clarify the role of serotonin (5‐HT) in the regulatory mechanism of L‐tryptophan (TRP)‐induced growth hormone (GH) secretion in cattle, changes in 5‐HT concentrations in the cerebrospinal fluid (CSF) in the third ventricle (3V) and GH in plasma before and after the peripheral infusion of TRP were determined simultaneously. The direct effect of TRP on GH release from the dispersed anterior pituitary cells was also assessed. A chronic cannula was placed in 3V by stereotaxic surgery, then CSF and blood were withdrawn under physiological conditions. TRP (38.5 mg/kg BW) was infused through an intravenous catheter from 12.00 to 14.00 hours and CSF and blood sampling were performed from 11.00 to 18.00 hours at 1‐h intervals. The concentration of 5‐HT in CSF was determined by high‐performance liquid chromatography with electrochemical detection. GH, melatonin (MEL), and cortisol (CORT) concentrations were measured by radio‐immunoassay and enzyme‐immunoassay. Concentrations of 5‐HT were increased by TRP infusion. The TRP infusion significantly increased GH release. On the other hand, TRP did not stimulate GH release from the bovine pituitary cells. MEL and CORT concentrations were not altered by TRP infusion. These results suggest that TRP induced GH release via the activation of serotonergic neurons in cattle.     

Light exposure during night suppresses nocturnal increase in growth hormone secretion in Holstein steers

To understand the regulatory mechanism of the secretory rhythm of GH and the involvement of melatonin (MEL) in GH regulation in cattle, daytime and nighttime profiles of GH secretion and the effect of a photic stimulation on nocturnal GH and MEL secretion were investigated in Holstein steers. Steers were kept under a constant lighting condition of 12 h of light (LIGHT; 500 lx, 0600 to 1800 h):12 h of dark (DARK; 10 lx, 1800 to 0600 h). In Exp. 1, blood was taken for 4 h at 15-min intervals during LIGHT (1100 to 1500 h) and DARK (2300 to 0300 h), respectively. The sampling was also performed from 0500 to 0900 h, with the usual light transition (light onset at 0600 h; morning sampling). In Exp. 2, steers were exposed to light (500 lx) for 1 h from 0000 to 0100 h. Plasma GH and MEL concentrations were determined by RIA and enzyme immunoassay, respectively. Both GH (P < 0.05) and MEL (P < 0.01) concentrations in plasma for 4 h during DARK were greater than those during LIGHT. On the other hand, although MEL concentrations were decreased after the light onset at 0600 during the morning, GH release was not altered. Increased GH secretion during DARK was suppressed (P < 0.01) by the 1 h of light exposure, as were MEL concentrations (P < 0.05). Pineal MEL, which was affected by the photic condition, may play an important role in the secretory rhythm of GH secretion in cattle.     

Development of biosensor for measuring oxidative stress of fish

Fisheries Science - To elucidate the dynamics of oxidative stress in fish, it is necessary to know the concentration of superoxide anions as a precursor to various reactive oxygen species in the...     

Two novel QTLs regulate internode elongation in deepwater rice during the early vegetative stage

Deepwater rice possesses internode elongation ability to avoid drowning under deepwater conditions. Previous studies identified three QTLs regulating internode elongation ability on chromosomes 1, 3 and 12 using different populations. However, these QTLs only induce internode elongation in response to deepwater conditions from the 7-leaf stage and not during the early leaf stage. In this study, we detected two novel QTLs, qTIL2 and qTIL4 regulating deepwater response at the early leaf stage using an F₂ population derived from the cross between NIL1-3-12 carrying the three QTLs regulating deepwater response in T65 (O. sativa ssp. japonica) genetic background and C9285 (O. sativa ssp. indica, deepwater rice). Plants of the BC₂F₂ population derived from NIL1-3-12/C9285 and the RILs of T65/Bhadua (O. sativa ssp. indica, deepwater rice) possessing these QTLs as well as the three QTLs previously identified also showed internode elongation during the early leaf stage. These results indicate that qTIL2 and qTIL4 regulate early internode elongation and function in coordination with the three major QTLs under deepwater conditions. The results presented here would not only help define the mechanism of deepwater response in rice but also contribute in the breeding of deepwater tolerant rice that is adapted to various water depths.     

Effect of intracerebroventricular injections of prolactin‐releasing peptide on prolactin release and stress‐related responses in steers

Some evidence suggests that there might be a species difference in the effect of intracerebroventricularly administered (ICV) prolactin‐releasing peptide (PrRP) between rodents and sheep. We compared the levels of cortisol (CORT) and prolactin (PRL), rectal temperature (RT) and behavioral responses to ICV bovine PrRP (bPrRP) in steers. ICV bPrRP (0.2, 2 and 20 nmol/200 µL) tended to evoke a dose‐related increase in CORT concentrations and 0.2 nmol of bPrRP induced transient increase in PRL concentrations. A significant time–treatment interaction was observed for the percent change of CORT (P < 0.05) and PRL (P < 0.05) from pre‐injection value. The time–treatment interaction for changes in RT was not significant (P = 0.50). There tended to be a difference among the four treatments in terms of maximum change in RT from the pre‐injection value between 0 and 90 min (P < 0.1). Stress‐related behavioral signs were not observed in the present experiment. These findings indicate that ICV bPrRP increased CORT and PRL levels, suggesting that central PrRP might participate in controlling the hypothalamo‐pituitary‐adrenal axis and PRL release in cattle, unlike sheep. In contrast, central PrRP is unlikely to be involved in controlling the behavior of this species because ICV bPrRP did not induce marked changes in their behavior.