Embryonic Development and Postnatal Changes in Free d-Aspartate and d-Serine in the Human Prefrontal Cortex

Abstract: We have analyzed free chiral amino acids (aspartate and serine) in the human frontal cortex at different ontogenic stages (from 14 weeks of gestation to 101 years of age) by HPLC with fluorometric detection after derivatization with N-tert -butyl-oxycarbonyl- l -cysteine and o -phthaldialdehyde. Exceptionally high levels of free d -aspartate and d -serine were demonstrated in the fetal cortex at gestational week 14. The ratios of d -aspartate and of d -serine to the total corresponding amino acids were also high, at 0.63 and 0.27, respectively. The concentration of d -aspartate dramatically decreased to a trace level by gestational week 41 and then remained very low during all postnatal stages. In contrast, the frontal tip contained persistently high levels of d -serine throughout embryonic and postnatal life, whereas the d -amino acid content in adolescents and aged individuals was about half of that in the fetuses. Because d -aspartate and d -serine are known to have selective actions at the NMDA-type excitatory amino acid receptor, the present data suggest that these d -amino acids might play a pivotal role in cerebral development and functions that are related to the NMDA receptor.     

Histological studies on male sterility of hybrids between laboratory and wild mouse strains

In this study the cellular mechanisms of male sterility in F1 hybrids (BNF1) between BALB/c and wild-derived M.MUS-NJL (NJL) was investigated. Cell proliferation and differentiation in the sterile testis were examined by bromodeoxyuridine-labeling and use of germ cell stage-specific antibodies. In BNF1 testes, spermatogonia actively proliferated with a seminiferous epithelial cycle, and were retained in the basal layer of the tubules. However, preleptotene, leptotene and zygotene spermatocytes moved to the adluminal region. Immunohistological data with germ cell stage-specific antibodies indicated the presence of few, if any, pachytene spermatocytes in BNF1 testes. Thus, spermatogenesis seemed to be blocked at the zygotene stage. For examination of germ cell-Sertoli cell interactions, testes of aggregation chimeras between BNF1 and C3H/HeN were analyzed immunohistologically with C3H-specific antibody. Results showed that spermatogenesis of C3H-germ cells was normal, even when these cells in contact with BNF1-Sertoli cells. Differentiation of BNF1-germ cells progressed from zygotene to pachytene stage spermatocytes when these cells were surrounded by C3H-Sertoli cells, but never proceeded beyond the pachytene stage. These observations suggest that at least two different cellular factors may be involved in spermatogenesis, one acting in the germ cells and the other mediated by Sertoli cells. Furthermore, mating experiments revealed that the degree of spermatogenesis varied in different F1 hybrids, and that the major sterility factor was closely linked to the T -locus on chromosome 17.     

Interrelationship between lignin deposition and the activities of peroxidase isoenzymes in differentiating tracheary elements of Zinnia

In a culture system in which single cells isolated from the mesophyll of Zinnia elegans L. differentiate to tracheary elements (TEs), two inhibitors of phenylalanine ammonia-lyase (EC 4.3.1.5), L-α-aminooxy-β-phenylpropionic acid (AOPP) at 10 μM inhibited lignification without reducing the number of TEs formed. These inhibitors caused intracellular changes in peroxidase (EC 1.11.1.7) activities. The inhibitors increased the activity of peroxidases bound to the cell walls and especially the activity of peroxidase bound ionically to the cell walls. In contrast, the activity of extracellular peroxidase decreased. There were five isoenzymes, P1-P5, in the ionically bound peroxidase of cultured Zinnia cells. Among the isoenzymes, P4 and P5 appeared to be specific for TE differentation. Treatment with AOPP and AIP resulted in increases in the activities of P2, P4 and P5 isoenzymes, with the most prominent increase in P5 activity. The addition of lignin precursors, including coniferyl alcohol, to the AOPP-treated cells restored lignification, and suppressed the alteration of peroxidase isoenzyme patterns caused by AOPP. The relationship between the wall-bound peroxidases and lignification during TE differentiation is discussed in the light of these results.     

Effects of body and head positions on bilateral difference in tympanic temperatures

We have examined the nonparallel changes in tampanic membrane temperatures (T _ty) from the two ears in response to various changes in body and head positions. Upon assuming a lateral recumbent position, the T _ty on the lower side increased while that on the upper side decreased. Pressure application over a wide area of the lateral chest only caused inconsistent and obscure asymmetric changes in T _ty. A lateral flexion of the head with the subject sitting upright and a rotation of the head to the side in a supine position induced an increase in the T _ty on the lower side compared to that on the upper side. The temperature and blood flow of the forehead often decreased on the lower side and increased on the upper side, although such responses were not always concomitant with the asymmetric changes in T _ty. A dorsal flexion of the head with the subject in a reclining position caused a slight increase in the T _ty, whereas raising the head upright induced a slight decrease in them. Two additional experiments were carried out with single photon emission computed tomography using ^99mTc-hexamethylpropyleneamine oxime as tracer, and a slight, relative decrease in counts was noted in the right hemisphere during rotation of the head to the right. These results would strongly suggest that unilateral increases and decreases in T _ty could have been caused by one-sided decreases and increases, respectively, in blood flow to the brain and/or the tympanic membrane, induced by a vasomotor reflex involving vestibular stimulation.     

A new snailfish of the genus Careproctus (Cottoidei: Liparidae) from the Pacific coast of southern Japan

Ichthyological Research - A new snailfish, Careproctus tomiyamai, is described on the basis of four specimens collected from Suruga Bay, Tosa Bay, and the Hyuga-nada Sea, southern Japan...     

Prostaglandin E2 is a Potential Mediator of Extracellular ATP Action in Osteoblast-Like Cells

Extracellular ATP dose dependently stimulated ⁴⁵Ca²⁺ influx even in the presence of nifedipine, a Ca²⁺ antagonist that inhibits voltage-dependent Ca²⁺ channel, in osteoblast-like MC3T3-E1 cells. ATP stimulated arachidonic acid release and the synthesis of prostaglandin E₂ (PGE₂). However, the ATP-induced arachidonic acid release was significantly reduced by chelating extracellular Ca²⁺ with EGTA. On the other hand, ATP induced DNA synthesis of these cells in a dose-dependent manner in the range between 1μM and 1 mM. The pretreatment with indomethacin, a cyclooxygenase inhibitor, suppressed both ATP-induced PGE₂ synthesis and DNA synthesis in these cells. The inhibitory effect by 50μM indomethacin on the DNA synthesis was reversed by adding 10μM PGE₂. These results strongly suggest that extracellular ATP stimulates Ca²⁺ influx resulting in the release of arachidonic acid in osteoblast-like cells and that extracellular ATP-induced proliferative effect is mediated, at least in part, by ATP-stimulated PGE₂ synthesis.     

Effects of vitamin D3 on signaling by prostaglandin E2 in osteoblast-like cells

We investigated the effects of vitamin D₃ on the signaling pathways by prostaglandin E₂ (PGE₂) in osteoblast-like MC3T3-E1 cells. The pretreatment with 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃), an active form of vitamin D₃, significantly inhibited cAMP accumulation induced by 10 μM PGE₂ in a dose-dependent manner in the range between 1 pM and 1 nM. This effect of 1,25-(OH)₂D₃ was dependent on the time of pretreatment up to 8 h. 1,25-(OH)₂D₃ also inhibited the cAMP accumulation induced by NaF, a GTP-binding protein activator, or forskolin which directly activates adenylate cyclase. On the other hand, 1,25-(OH)₂D₃ significantly inhibited PGE₂-induced IP₃ formation in a dose-dependent manner between 10 pM and 1 nM. However, 1,25-(OH)₂D₃ had little effect on NaF-induced IP₃ formation. The pretreatment with 24,25-dihydroxyvitamin D₃, an inactive form of vitamin D₃, affected neither cAMP accumulation nor IP₃ formation induced by PGE₂. These results strongly suggest that 1,25-(OH)₂D₃ modulates the signaling by PGE₂ in osteoblast-like cells as follows: the inhibitory effect on the cAMP production is exerted at a point downstream from adenylate cyclase and the inhibitory effect on the phosphoinositide hydrolysis is exerted at the point between the PGE₂ receptor and GTP-binding protein, probably G_i2.     

Population dynamics,productivity and biomass allocation ofZizania latifolia in an aquatic-terrestrial ecotone

The population and production ecology of aZizania latifolia stand at a sheltered shore of the Hitachi-Tone River were investigated. Shoot emergence was observed twice a year; the fist was a synchronized shoot emergence in April and the second was from August to October. Aboveground biomass was mostly occupied by leaves and peaked at 1500 g dry weight m⁻² in August. The belowground biomass also reached its peak, 750 g dry weight m⁻², in August. The secondary shoots were small in spite of their high density. Leaves were produced continuously throughout the season. The leaf life span was as short as 55.6 days for cohorts that emerged from May through to September. Total annual net production ofZ. latifolia could be more than 3400 g dry weight m⁻². Shoot clusters of several centimeters were observed in April. The following self-thinning caused a regular distribution of the remaining shoots in August. Most shoots produced in August to October were found near a shoot persisting since April. They showed more concentrated distribution than shoots in April. A large biomass allocation to leaves and the ability to produce many clump shoots during the late growing period may facilitate dominance ofZ. latifolia in relatively sheltered sites.