An activated S6 kinase in regenerating rat liver

S6 kinase activity was increased in the regenerating liver 5 h after partial hepatectomy compared with sham-operated liver. The protein kinase activity was eluted from DE-52 column at approximately 250 mM NaCl and was not affected by known regulators of protein kinases. The S6 kinase was further purified by chromatography on peptide R1A13-Sepharose 4B and Sephadex G-150. The molecular weight of the enzyme was estimated to be 4.5 X 10(4) by gel filtration. The enzyme catalyzes the phosphorylation of whole histone, mainly H2B histone, at 75 mM Mg2+. These properties are similar to those of a proteolytically modified Ca2+/phospholipid-independent form of protein kinase C.     

Autonomic innervation of the arteriovenous anastomoses in the dog tongue

Summary The innervation of the arteriovenous anastomoses in the dog tongue has been investigated. At the lightmicroscopic level, the vessels were found to be densely supplied with adrenergic and AChE-positive nerve plexuses and less densely with the quinacrine-binding nerve plexus. At the electron-microscopic level, at least two apparently different types of axon profiles were identified: 1) Small vesicle-containing axons, characterized by many small granular vesicles, variable numbers of small clear vesicles and large granular vesicles. Storage of endogenous amines and uptake of exogenous amines into most small granular vesicles and many large granular vesicles was demonstrated. These axons stained only lightly with reaction products for AChE activity and thus seemed to be adrenergic in nature. Some axons contained numerous large granular vesicles, whose cores occasionally stained with uranyl ions; this suggests a co-localization of ATP or peptides as neurotransmitters. 2) Small granular vesicle-free axons, containing small clear vesicles and large granular vesicles in variable ratio. Most cores of these large granular vesicles were heavily stained with uranyl ions. No storage or uptake of amine into the synaptic vesicles was detected. Some axons appeared to be typically cholinergic, some, typically non-adrenergic, noncholinergic, and the rest, intermediate between the two. All axons stained heavily with reaction products for AChE activity, suggesting their cholinergic nature.     

A fragile X female with Down syndrome

Summary Clinical and cytogenetic aspects of a female infant with trisomy 21 and the fragile X [fra (X)] chromosome are reported. Most of the facial characteristics of the patient are those observed in Down syndrome, but some features such as long face with prominent forehead and lower jaw, and large ears are related to the fra (X) syndrome. The origin of an additional chromosome 21 may be ascribed to maternal first meiotic nondisjunction in our case. It has been suspected that female carriers of the fra (X) chromosome may be predisposed to meiotic nondisjunctional events. However, there is probably no relationship between the two chromosomal abnormalities in our case because of the maternal age at the delivery.     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

Effect of UV-B (290–320 nm) irradiation on growth and metabolism of cucumber cotyledons

Cucumber ( Cucumis sativus L. cv. Natsusairaku 3) seedlings were grown in a growth cabinet under UV-B (290–320 nm) irradiation (equivalent to the UV-B radiation normally incident at Tokyo, 36°N latitude, during clear sky conditions in mid-april on a weighted daily fluence basis) and a UV-B-free control condition. UV-B irradiation inhibited the growth of the cotyledons, i.e. the increase in area, and increase in fresh and dry weights of the cotyledons. The greatest inhibition rate was observed in the increase in area, causing a significant increase in specific leaf weight (the ratio of weight to area). UV-B irradiation had no significant effect on DNA and RNA contents in the cotyledons, but decreased protein content slightly. In contrast, the irradiation reduced the amounts of organic acids and soluble sugars, indicating that primary carbon metabolism was very sensitive to UV-B radiation. UV-B irradiation lowered the photosynthetic activity in the cotyledons without any effect on chlorophyll content and respiratory activity. These results indicate that UV-B radiation at the ambient level may act as a physiological stress in some UV-sensitive plants.     

Comparison of growth properties of carrot hairy root in various bioreactors

Summary Growth properties of carrot hairy root cells in various bioreactors were investigated. A turbine-blade reactor and an immobilized rotating drum reactor were found to be advantageous for the hairy root culture because of a high oxygen transfer coefficient (k in L a). After 30 days of culture, 10 g/l of dry hairy root cells were obtained in both bioreactors and maximum growth rates (V _m ) were found to be 0.63 and 0.61 g/l per day for the turbine-blade reactor and immobilized rotating drum reactor, respectively. Specific growth rates () at various cultivation times were observed to be linearly proportional to X/k _l a for both bioreactor configurations where X is the cell concentration. The estimated specific oxygen uptake rate of 0.34 mmol O₂/g dry cells per hour compares fairly well with an experimental value of 0.3.     

ATL-derived factor (ADF), an IL-2 receptor/Tac inducer homologous to thioredoxin; possible involvement of dithiol-reduction in the IL-2 receptor induction.

HTLV-I transformed T cells not only express a large number of interleukin-2 receptors [IL-2R/p55(Tac)], but also produce a factor named ATL-derived factor (ADF) that augments the expression of IL-2R/p55(Tac). Based on a partial N-terminal amino acid sequence, complementary DNA (cDNA) clones for human and mouse ADF were isolated and sequenced. Recombinant ADF produced by COS-7 monkey kidney cells showed IL-2R/Tac inducing activity on YT cells, which are sensitive for ADF. ADF mRNA was strongly expressed in HTLV-I(+) T cells lines, but not in inactivated cells (THP-1, unstimulated PBMC). Furthermore, in normal human peripheral blood mononuclear cells, the expression of ADF mRNA was enhanced by mitogens or phorbol myristate acetate, suggesting a possible involvement of ADF in the lymphocyte activation. Homology analysis revealed an unexpected relationship between ADF and dithiol-reducing enzyme, thioredoxin, involved in many important biological reactions such as the conversion of ribonucleotides into deoxyribonucleotides, or the stabilization of glucocorticoid receptors. The biological significance of the generation of a redox potential in lymphocyte activation, and the possible involvement of dithiol reduction in the induction of IL-2R/Tac are discussed.     

Overt diabetes induced by overeating in neonatally STZ-treated impaired glucose tolerant mice: long-term follow up study

This study has investigated the effect of a long period of overeating on the glycemic control and pancreatic beta-cell function in neonatally streptozocin treated impaired glucose tolerant mice. Neonatally streptozocin (60 mg/kg) treated male ICR mice with 150-200 mg/dl of fed blood glucose levels were divided into two groups at 6 weeks of age. One group was maintained on a cafeteria diet (SZC) and the other on ordinary mouse chow (SZ) until 30 weeks of age. Normal male ICR mice were divided into a cafeteria diet group (CC) and an ordinary chow group (Cont). SZC and CC consumed 134-124% of the caloric intake in SZ and Cont throughout the study. Marked elevation of the fed blood glucose level was observed and the glucose tolerance was progressively impaired in SZC. On pancreas perfusion at 30 weeks of age, insulin secretion to 30 mM glucose in SZC was significantly decreased compared with that in SZ. That in CC was slightly decreased compared with that in Cont. The pancreatic insulin concentration in SZC was significantly less than that in SZ. We conclude that chronic hyperglycemia, induced by the long period of overeating, accelerated the selective loss of beta-cell sensitivity to glucose. Even in normal mice that did not have marked hyperglycemia, insulin secretion to glucose was suppressed, probably by chronic stimulation of the beta-cell due to the long period of dietary excess.     

A pertussis toxin-sensitive GTP-binding protein plays a role in the G0-G1 transition of rat hepatocytes following establishment in primary culture

Acute spontaneous c-myc gene expression and sustained increase of a GTP-binding protein(s) (G-protein) which is sensitive to islet-activating protein (IAP), pertussis toxin, occurred early during primary culture of adult rat hepatocytes. Following these earlier events, DNA synthesis was demonstrated in response to EGF and insulin. Addition of IAP immediately after plating of primary cultures inhibited c-myc expression and the hormone-induced DNA synthesis. Addition at 24 h or later following cell inoculation, however, produced only weak effects on DNA synthesis, even though the IAP-sensitive G-proteins were completely inactivated. We conclude that the IAP-sensitive G-protein(s) plays a role in the earlier process(es) of the G0-G1 transition, which is essential for the initiation of growth factor-dependent DNA synthesis.     

Endothelin-induced mobilization of Ca2+ and the possible involvement of platelet activating factor and thromboxane A2

Endothelin (ET) caused transient and sustained elevations of cytosolic free Ca2+ concentrations ([Ca2+]i) in cultured rat and rabbit vascular smooth muscle cells (VSMC). Specific platelet activating factor (PAF) antagonists (CV-6209 and WEB-2086) and arachidonic acid (AA) cascade blockers (chlorpromazine, indomethacin, CV-4151 and AA-2414) potently inhibited the ET-induced increase in [Ca2+]i. Additionally, these compounds inhibited the PAF-induced increase in [Ca2+]i. These results suggest that PAF and thromboxane A2 (TXA2) may be involved in the mechanism of ET-induced mobilization of Ca2+ in cultured rat and rabbit VSMC.