Changes of receptor mRNAs for oxytocin and estrogen during the estrous cycle in rat uterus

Oxytocin receptor (OTR) mRNA levels increase dramatically near term and is potently stimulated by estrogen because increased OTR mRNA levels result from estrogen treatment in ovariectomized rat uterus. In this study, OTR, estrogen receptor (ER) alpha and ERbeta mRNA levels in the rat uterus during the estrous cycle were examined by quantitative RT-PCR. OTR mRNA levels during the estrous cycle began to increase on diestrus (P<0.05, vs value on estrus), reached maximal increase both in the morning (1000-1130 hr) and afternoon (1600-1630 hr) on proestrus (P<0.01, vs metestrus, diestrus and estrus) and then declined on estrus. In contrast ER alpha mRNA levels began to decrease on diestrus, reached statistical significance both in the morning and the afternoon on proestrus (P<0.01, vs metestrus, diestrus and estrus) and returned to the value of metestrus on estrus. ERbeta mRNA levels were low in the morning and the afternoon on proestrus (P<0.01, vs metestrus and estrus) and also returned to metestrus values on estrus. Treatments with estrogen for 3 days significantly decreased both ERalpha and ERbeta mRNA levels. It can be concluded from these results that during the estrous cycle, OTR mRNA levels in rat uterus predominantly increase at proestrus with a decrease in ERalpha and ERbeta mRNA levels, which is probably due to the increased estrogen levels in circulation before ovulation.     

Suppressive effect of liquid potassium silicate on powdery mildew of strawberry in soil

A soil drench of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of strawberry in soil for 2 years in a vinyl house under growers' conditions on two cultivars: very susceptible Toyonoka and slightly susceptible Sachinoka. Soluble silicon suppressed the disease more effectively as a preventive control than as a control to reduce initial incidence. The suppressive effect against this disease was more effective for Toyonoka than for Sachinoka. The control value of soluble potassium silicate was 85.6% for Toyonoka in the first year and 60.2% in the second year, while for Sachinoka it was 58% in the first year and 40.6% in the second year. Strawberry leaf hardness was measured for the control and silicate-treated leaves. Although silicate-treated leaves seemed to be harder than control leaves, leaf hardness did not vary significantly between controls and silicate-treated leaves in either of the 2 years, and the mode of preventive action of liquid potassium silicate remains unknown. A factor other than a physical action may be involved.     

Generation and alteration of norlignans in a transition zone during the drying of a Cryptomeria japonica log

Sugi (Cryptomeria japonica D. Don) produces secondary metabolite norlignans in xylem. Several norlignans are involved in the coloration of heartwood and defense of sapwood against microbial invasion. Their biosynthetic process should be well understood so that their properties can be exploited to improve the quality and utility of C. japonica wood. Unfortunately, information on the norlignan biosynthesis is limited because norlignans are mainly synthesized in a particular season in the transition zone (TZ) along with the heartwood formation, and is difficult to study. Although the generation of two norlignans of C. japonica, agatharesinol and (E)-hinokiresinol, has been reported, systems for producing other norlignans are not yet known. To establish a novel norlignan generating system, we examined the changes occurring in norlignans in a TZ during the process of drying a C. japonica log. On the day of felling, the TZ contained agatharesinol and (E)-hinokiresinol, which increased until they reached a maximum on day 40 after felling. Sequirin-C appeared on day 40 and increased to day 70. The generation of sequirin-C in the TZ can be used to investigate the biosynthetic process of heartwood norlignans. This study describes for the first time the changes that occur in the composition of norlignan during the drying of the TZ.     

Effects of low pH on the reproductive behavior of salmonid fishes

In northern Europe and America, the acidification of lakes and rivers induced by acid precipitation has damaged fish populations. At present, rapidly expanding industrial activities in East Asia have led to continuous increases in the quantity of emission of acidic pollutants, and rain of acidic levels of pH4 has precipitated throughout Japan. In this way, the effects of acid rain on fish populations have also been manifested in Japan. In order to examine the effects of low pH on the reproductive behavior of salmonids which are known to be acid-sensitive species, changes in the frequency of upstream behavior and spawning-related female nest-digging behavior in response to changes in pH were observed in mature hime salmon (land-locked sockeye salmon) Oncorhynchus nerka, brown trout Salmo trutta and Japanese char Salvelinus leucomaenis. Digging and upstream behavior were significantly inhibited in weakly acidic water of pH 5.8–6.4 formulated using sulfuric acid. Land-locked sockeye salmon was the most sensitive to changes in pH among the three species.     

The maturation of the salmon GnRH system and its regulation by gonadal steroids in masu salmon

Pituitary gonadotropin (GTH) secreting cells and brain gonadotropin-releasing hormone (GnRH) secreting neurons are known to be subjected to feedback control by gonadal steroid in teleosts. In masu salmon, Oncorhynchus masou, salmon GnRH (sGnRH) neurons in the ventral telencephalon (VT) and the preoptic area (POA) are involved in the control of GTH cells because sGnRH synthesis in these areas is activated with gonadal maturation. In this study, we attempted to clarify mechanisms of feedback control of sGnRH neurons by gonadal steroids. We examined the effects of 17-methyltestosterone (MT) on sGnRH synthesis in yearling and 2-year-old female fish (which were immature during experimentation in May), and the effects of castration on sGnRH synthesis in underyearling precocious male fish in August. sGnRH synthesis in the POA, but not in the VT, was increased by MT administration in 2-year-old females only, indicating higher sensitivity to MT in the preoptic sGnRH neurons. Castration increased sGnRH synthesis in the VT but not in the POA. These results suggest that sGnRH neurons in the VT and those in the POA are differentially regulated by gonadal steroids.     

Recording cerebellar neuron activities in swimming goldfish

ABSTRACT:   Neuronal activities were investigated in the cerebellum of immobilized and swimming goldfish Carassius auratus . Extracellularly recorded neural activities of the cerebellum in immobilized goldfish were characterized and classified into five types. Based on the waveforms and recording depths, these five neural activity types were estimated to originate from three identified classes of cerebellar neurons: Purkinje cells, eurydendroid cells, and granule cells. Chronic recording of cerebellar neuron activities in unrestrained goldfish was performed for more than 100 h. During the chronic recordings, a submersible amplifier attached to the goldfish head, and a multielectrode array developed for the present study were used. Neuronal activities in the cerebellum of free-swimming fish could also be classified into five types as in the immobilized condition. Firing patterns of two neurons identified as Purkinje cells and eurydendroid cells were analyzed during turning movements of the goldfish. The firing patterns of these neurons changed in relation to turning movements. Although some improvements are required, the chronic recording method developed in the present study can be applied to further investigations concerning the direct relationship between brain neural activities and certain behavior.     

Activities of mesencephalic nucleus neurons during fictive swimming of the carp Cyprinus carpio

ABSTRACT:   Fish swim by undulatory contractions of the axial trunk musculature. It has been presumed that a descending signal from the brainstem activates central pattern generators in the spinal cord to make the swimming rhythm. In the carp the electrical or chemical stimulation of a mesencephalic nucleus, the nucleus fasciculi longitudinalis medialis (Nflm), could initiate swimming. However, it has not been established what signals originate from the Nflm in order to make the fish swim. The activity of the Nflm neurons was therefore examined electrophysiologically during fictive swimming in paralyzed carp. Three types of neuronal activities closely related to the swimming rhythms were obtained. The first type was a continuous tonic firing throughout an episode of fictive swimming. Neurons involved in this tonic activity may project to the spinal cord and contribute to the activation of spinal neurons to initiate fish swimming. The second type was accompanied by continual phasic firings occurring in rhythm with the activity of spinal motoneurons. Supposing that the swimming rhythm originates in the spinal cord, the synchronous activity in the brain neurons may suggest that in the nucleus there is a relay neuron conveying the rhythm information from the cord to other neurons there or in the brain. The third type exhibited reduced firing rates during fictive swimming. It is possible that the neurons engaged in this activity may be inhibitory and suppress the activities of other neurons in the nucleus and spinal cord during rest or during decelerating swimming.     

Structural unit of xylans from sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) and hinoki (<Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>)

Arabinoglucuronoxylans (AGXs) isolated from the holocellulose of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) contained one 4-O-methyl-d-glucopyranosyluronic acid (4-O-Me-d-GlcAp) residue per 6.2 d-xylopyranose (d-Xylp) residues and one 4-O-Me-d-GlcAp residue per 3.8 d-Xylp residues. These AGXs were subjected to partial acid hydrolysis. Analyses by size exclusion chromatography and electrospray-ionization mass spectroscopy of the neutral sugar fractions in the hydrolysates showed the presence of xylooligosaccharides having a degree of polymerization of 2-8 in addition to d-Xyl, suggesting that the AGXs from sugi and hinoki contained unsubstituted chains consisting of at least eight d-Xyl residues. The acidic sugars in the hydrolysates were separated into two series of aldouronic acids composed of 4-O-Me-d-GlcAp and d-Xylp by ion-exchange chromatography. The first series included aldouronic acids from aldobiouronic acid (4-O-Me-d-GlcAp-Xyl) to aldopentaouronic acids (4-O-Me-d-GlcAp-Xyl₄). The second series were aldouronic acids composed of two 4-O-Me-d-GlcAp residues and 2-4 d-Xyl residues. In these acidic sugars, the uronic acid side chains were located on two contiguous d-Xyl residues. These facts indicated that AGXs from sugi and hinoki had a structural unit containing two 4-O-Me-d-GlcAp residues on two contiguous d-Xyl residues as well as AGXs from spruce and larch.