Stimulations of arachidonate release and inositol-1,4,5-triphosphate formation are mediated by distinct G-proteins in human platelets

Addition of fluoroaluminate to human platelet suspension stimulated thromboxane synthesis and inositol-1,4,5-triphosphate formation in a time and dose dependent manner. Neomycin inhibited markedly fluoroaluminate induced inositol-1,4,5-triphosphate formation without significantly affecting thromboxane synthesis. Preincubation of platelets with PGE1, also inhibited significantly inositol-1,4,5-triphosphate formation with modest reduction of thromboxane synthesis. On the contrary, pretreatment of platelets with pertussis toxin inhibited fluoroaluminate stimulated thromboxane synthesis without affecting inositol-1,4,5-triphosphate formation. Similarly, preincubation of platelets with phorbol ester, PMA, inhibited markedly thromboxane synthesis with modest reduction of inositol-1,4,5-triphosphate formation. These results indicate that inositol-1,4,5-triphosphate formation and arachidonate release and thromboxane synthesis are controlled separately and are mediated by different G-proteins which are coupled to phospholipase C and phospholipase A2 respectively in platelets.     

Hypoxanthine guanine phosphoribosyltransferase deficiency: nucleotide substitution causing Lesch-Nyhan syndrome identified for the first time among Japanese

Summary A previously undescribed nucleotide substitution at codon 51 (CGA to TGA) has been identified using the polymerase chain reaction technique in hypoxanthine guanine phosphoribosyltransferase (HPRT) cDNA; this is the first molecular evidence for a point mutation in a Japanese patient with Lesch-Nyhan syndrome. The present mutation is the 19th nucleotide substitution identified as a germ-line mutation at this locus and the second mutation generating a stop codon. The position of the nucelotide substitution is exactly the same as a previously described mutation HPRT_Toronto, indicating for the first time that nucleotide substitutions at the same position in the sequence of HPRT can generate different mutant alleles, one causing a partial deficiency and the other a complete deficiency. Although the type of nucleotide substitution is different between the two cases, a single base position has twice become the target of a mutation. However, the calculation of the probability of finding substitution mutations at the same base position in the coding region of hprt indicates that there is no evidence for the presence of a hot spot for substitution mutations in the human hprt germ line.     

Statistical models of the overdispersed molecular clock

The most commonly used statistical model to describe the rate constancy of molecular evolution (molecular clock) is a simple Poisson process in which the variance of the number of amino acid or nucleotide substitutions in a particular gene should be equal to the mean and henceforth the dispersion index, the ratio of the variance to the mean, should be equal to one. Recent sequence data, however, have shown that the substitutional process in molecular evolution is often considerably overdispersed and have called into question the generality of using a simple Poisson process. Several efforts have been made to develop more realistic models of molecular evolution. In this paper, I will show that the spatial (site-specific) variation in the rate of molecular evolution is an improbable cause of the overdispersion and then review various statistical models which take the temporal variation into account. Although these models do not immediately specify what the mechanisms of molecular evolution might be, they do make qualitatively different predictions and give some insight into their inference. One way to distinguish them is suggested. In addition, effects of selected substitutions that presumably occur after a major change in a molecule are quasi-quantitatively examined. It is most likely that the overdispersion of molecular clock is due either to a major molecular reconfiguration (fluctuating neutral space) led by a series of subliminal neutral changes or to selected substitutions fine-tuning a molecule after a major molecular change. Although the latter possibility, of course, violates the simplest neutrality assumption, it would not impair the neutral theory as a whole.     

Binding of mibolerone to androgen receptor of benign hypertrophic human prostate. Comparison with R1881

The binding nature of mibolerone in cytosols and nuclear extracts from hypertrophic human prostate was examined in comparison with that of R 1881. The binding of mibolerone in the cytosol and nuclear extract was single and of high affinity when evaluated by the method of Scatchard (1949). Binding of mibolerone with testosterone-binding globulin was not detected. The sedimentation coefficients of the binder for mibolerone in the cytosol and nuclear extract were 10.6 S and 3.6 S, respectively. When triamcinolone acetonide was induced in the binding medium, inhibition of mibolerone binding in the cytosol by testosterone and dihydrotestosterone was potentiated and this may imply that the binding observed in the presence of triamcinolone acetonide was responsible for the binding of the androgen receptor. In the nuclear extract, the binding was attributable mainly to the androgen receptor irrespective of the presence or absence of triamcinolone acetonide. These properties of the binding observed in the hypertrophic human prostate were almost same as those of the binding with R 1881. Although maximum binding sites measured using mibolerone were correlated with those using R 1881 in the cytosols as well as in the nuclear extracts, the values obtained with mibolerone were slightly greater than those with R 1881. Thus, mibolerone seems to be a suitable ligand for measuring the androgen receptor, but when compared with R 1881 no special merits in using mibolerone were detected.     

Gene Genealogy and Variance of Interpopulational Nucleotide Differences

A mathematical theory is developed for computing the probability that m genes sampled from one population (species) and n genes sampled from another are derived from l genes that existed at the time of population splitting. The expected time of divergence between the two most closely related genes sampled from two different populations and the time of divergence (coalescence) of all genes sampled are studied by using this theory. It is shown that the time of divergence between the two most closely related genes can be used as an approximate estimate of the time of population splitting (T) only when T identical to t/(2N) is small, where t and N are the number of generations and the effective population size, respectively. The variance of Nei and Li's estimate (d) of the number of net nucleotide differences between two populations is also studied. It is shown that the standard error (Sd) of d is larger than the mean when T is small (T much less than 1). In this case, Sd is reduced considerably by increasing sample size. When T is large (T greater than 1), however, a large proportion of the variance of d is caused by stochastic factors, and increase in the sample size does not help to reduce Sd. To reduce the stochastic variance of d, one must use data from many independent unlinked gene loci.     

Two Types of Apoptotic Cell Death of Rat Central Nervous System-Derived Neuroblastoma B50 and B104 Cells: Apoptosis Induced During Proliferation and After Differentiation

Abstract: We describe here two types of apoptotic cell death observed in the rat CNS-derived neuroblastoma B50 and B104 cells. One type was induced by dibutyryl cyclic AMP (DBcAMP) after differentiation, and the other was induced by treatment of proliferating cells with cycloheximide. When B50 and B104 cells were treated with 1 m M DBcAMP in the presence of 0.5% fetal calf serum, they began to extend neurites within 12 h and differentiated into neurons at 24 h, as reported previously. However, further cultivation with DBcAMP for up to 72 h led to flotation and, finally, death. Death was by apoptosis as shown by chromatin condensation and DNA fragmentation. Addition of a protein kinase A inhibitor or removal of DBcAMP after differentiation suppressed apoptosis, indicating the involvement of cyclic AMP and protein kinase A in apoptotic cell death. Cell death was also induced in proliferating cells without neurite outgrowth by treatment with cycloheximide. The death was also judged to be by apoptosis based on chromatin condensation and apoptotic body formation, although DNA fragmentation into small sizes was not detected. Both types of cell death showed similar responses to inhibitors for protein kinases and protein phosphatases.     

Natural disturbance and tree species coexistence in an old-growth beech - dwarf bamboo forest,southwestern Japan

Abstract. The structure and composition of a cool-temperate old-growth beech (Fagus crenata) - dwarf bamboo (Sasa spp.) forest, partially affected by landslide disturbance, in the Daisen Forest Reserve of southwestern Japan, were investigated in relation to forest floor and canopy conditions. All stems ≥ 4 cm DBH were mapped on a 4-ha plot and analyses were made of population structure, spatial distribution and spatial association of major tree species. The dominant species, F. crenata, which had the maximum DBH among the species present, had the highest stem density. However, for other species, larger-sized species had lower stem density with few smaller stems or saplings, while smaller-sized species had higher stem density with many smaller stems or saplings. Canopy trees of F. crenata were distributed randomly in the plot, while its stems in the other layers and all other species were distributed patchily. Small patches represent gap-phase regeneration. Larger patches correlate with landslide disturbance, difference in soil age, or the presence/absence of Sasa. Cluster analysis for spatial associations among species and stems in the different layers revealed that the forest community consists of several groups. One main group was formed on sites not covered with Sasa. This group contained a successional subgroup (from Betula grossa to Acer mono and/or F. crenata) initiated by landslide disturbance and a subgroup of tree species that avoid Sasa. Another group was formed on sites with mature soils covered largely with Sasa. This contained associations of canopy trees of F. crenata and smaller-sized tree species such as Acanthopanax sciadophylloides and Acer japonicum. It is found that the community of this old-growth beech forest is largely organized by natural disturbance and heterogeneous conditions of the forest floor (difference in soil age and presence/absence of Sasa). The existence of these different factors and the different responses of species to them largely contribute to the maintenance of tree species diversity in this forest.; Keywords: Cluster analysis; Fagus crenata; Forest dynamics; Gap; Landslide; Spatial pattern.     

Evaluation of the Sensitivity and Specificity of Polymerase Chain Reaction Test Kit,AMPLICOR Chlamydia trachomatis

The sensitivity and specificity of the polymerase chain reaction (PCR) test kit, AMPLICOR Chlamydia trachomatis, were examined by the use of purified elementary bodies (EBs), cells having inclusions containing reticulate bodies alone and 20 clinical isolates. The numbers of EB and inclusion of C. trachomatis at the detection limit were determined to be approximately 2 to 4 EBs and one inclusion per assay, respectively. No reaction occurred for C. psittaci and C. pneumoniae. All clinical isolates were positively reacted in the PCR assay.     

Characterization of a Chlamydia pneumoniae Strain Isolated from a 57-Year-Old Man

The isolation of Chlamydia pneumoniae, especially from elderly persons, is generally not easy. Recently, we succeeded in isolating a chlamydial strain, which was designated KKpn-15, from a 57-year-old man suffering from acute bronchitis. It was compared with well established strains of C. pneumoniae, C. trachomatis and C. psittaci, and its biological properties, such as the morphology of elementary bodies (EBs) and inclusions, and the immunochemistry of EB proteins, were investigated. Based on the results obtained in the present study, it was confirmed that the new chlamydial strain, KKpn-15, is a member of the C. pneumoniae strain and that the organisms of KKpn-15 are useful as an antigen for the serodiagnosis and epidemiology of C. pneumoniae infection.     

Effective population size,genetic diversity,and coalescence time in subdivided populations

A formula for the effective population size for the finite island model of subdivided populations is derived. The formula indicates that the effective size can be substantially greater than the actual number of individuals in the entire population when the migration rate among subpopulations is small. It is shown that the mean nucleotide diversity, coalescence time, and heterozygosity for genes sampled from the entire population can be predicted fairly well from the theory for randomly mating populations if the effective population size for the finite island model is used.