Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

In vitro biological activities of the E6 and E7 genes vary among human papillomaviruses of different oncogenic potential.

Human papillomavirus type 16 (HPV-16) and HPV-18 are often detected in cervical carcinomas, while HPV-6, although frequently present in benign genital lesions, is only rarely present in cancers of the cervix. Therefore, infections with HPV-16 and HPV-18 are considered high risk and infection with HPV-6 is considered low risk. We found, by using a heterologous promoter system, that expression of the E7 transforming protein differs between high- and low-risk HPVs. In high-risk HPV-16, E7 is expressed from constructs containing the complete upstream E6 open reading frame. In contrast, HPV-6 E7 was efficiently translated only when E6 was deleted. By using clones in which the coding regions of HPV-6, HPV-16, and HPV-18 E7s were preceded by identical leader sequences, we found that the ability of the E7 gene products to induce anchorage-independent growth in rodent fibroblasts correlated directly with the oncogenic association of the HPV types. By using an immortalization assay of normal human keratinocytes that requires complementation of E6 and E7, we found that both E6 and E7 of HPV-18 could complement the corresponding gene from HPV-16. However, neither E6 nor E7 from HPV-6 was able to substitute for the corresponding gene of HPV-16 or HPV-18. Our results suggest that multiple factors, including lower intrinsic biological activity of E6 and E7 and differences in the regulation of their expression, account for the low activity of HPV-6, in comparison with HPV-16 and HPV-18, in in vitro assays. These same factors may, in part, account for the apparent difference in oncogenic potential between these viruses.     

Detection of novel sequence heterogeneity and haplotypic diversity of HLA class II genes

Nucleic acid sequences of the second exons of HLA-DRB1, –DRB3/4/5, –DQB1, and –DQA1 genes were determined from 43 homozygous cell lines, representing each of the known class II haplotypes, and from 30 unrelated Caucasian subjects, comprising 60 haplotypes. This systematic sequence analysis was undertaken in order to a) determine the existence of sequence microheterogeneity among cell lines which type as identical by methods other than sequencing; b) determine whether direct sequencing of class II genes will identify the presence of more extensive sequence polymorphism at the population level than that identified with other typing methods; c) accurately determine the molecular composition of the known class II haplotypes; and d) study their evolutionary relatedness by maximum parsimony analysis. The identification of seven previously unidentified haplotypes carrying five new allelic amino acid sequences suggests that sequence microheterogeneity at the population level may be more frequent than previously thought. Maximum parsimony analysis of these haplotypes allowed their evolutionary classification and indicates that the higher mutation rate at DRB1 compared to DQB1 loci in most haplotypic groups is inversed in specific haplotype lineages. Furthermore, the extent and localization of gene conversions and point mutations at class II loci in the evolution of these haplotypes is significantly different at each locus. Identification of additional HLA class II molecular microheterogeneity suggests that direct sequence analysis of class II HLA genes can uncover new allelic sequences in the population and may represent a useful alternative to current typing methodologies to study the effects of sequence allelism in organ transplantation.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M35890 through M35953.     

On the effect of temperature and pH on the settling behaviour of a flocculent strain ofZymomonas mobilis

Summary In this paper the effect of temperature and pH on the settling behaviour of a flocculent strain ofZymomonas mobilis is studied by using the old fashioned batch settling technique. Plots are given to show the influence of the above mentioned parameters on the settling curve behaviour.     

Nucleosomal organization of chromatin in sperm nuclei of the bivalve mollusc Aulacomya ater

The sperm nuclei of Aulacomya ater, family Mitylidae, contain three proteins (X, Aa5 and Aa6) which are specific to this cell type coexisting with a set of five somatic-type histones. Information about the chromatin structure resulting from this kind of association is scarce. Therefore, we have probed the structure of this sperm chromatin through digestion with micrococcal nuclease in combination with salt fractionation. The data obtained have allowed us to propose a nucleosomal arrangement for this chromatin. However, two types of nucleosomes would be present in agreement with their protein components.     

Accuracy and direction of error in the sexing of the skeleton: implications for paleodemography

Determinations of sex by subjective assessment of the skulls from a skeletal series of known sex were compared to fully independent assessments based on pelves of the same specimens. Within-sex correlations of cranial and pelvic morphologies measured on an android-gynecoid scale were smaller than expected. Subjective assessment by means of the skull compared favorably to that of the linear discriminant functions of Giles and Elliot; however, the direction of error was similar for both procedures. Of course, estimations based on the pelves were generally superior to both in terms of frequency and overall bias of error. The bias of sex estimation for paleodemographic purposes is contingent upon completeness of skeletal remains.     

Glucocorticoids Potentiate the Prostaglandin E1-Mediated Cyclic AMP Formation by a Cultured Murine Neuroblastoma Clone

The effect of steroid hormones on the prostaglandin E1 (PGE1)-mediated cyclic AMP formation by murine neuroblastoma clone N1E-115 was studied. Dexamethasone at submicromolar concentrations and corticosterone at micromolar concentrations (steroids with glucocorticoid activity) were able to modify the PGE1-mediated response whereas testosterone, progesterone, and estradiol each at 10 microM had no effect. Glucocorticoids added to the culture medium of N1E-115 cells produced an increase in the maximal response to PGE1 only after long-term (greater than or equal to 4 h) incubation with the hormone. Inhibitors of protein and RNA synthesis blocked this effect of glucocorticoids. Basal activity of adenylate cyclase in treated cells was twofold higher than that in control cells, and this enzyme seemed to be the primary target for the hormone action, since the activity of 3':5'-cyclic AMP phosphodiesterase and the binding of [3H]PGE1 to its receptors were not altered by glucocorticoid treatment. Our results indicate that glucocorticoids modulate receptor-mediated responses in cells of neural origin through a mechanism that involves induction of protein synthesis.     

Rhodotorula nothofagi sp. nov., isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

An unusual Rhodotorula isolated from decayed wood of Nothofagus obliqua (Mirb.) Blume is described and illustrated. This species differs from all accepted Rhodotorula species (1–7, 10) to warrant its establishment as a new species, Rhodotorula nothofagi sp. nov.Postgraduate student from the Instituto de Ecología y de Evolución, Universidad Austral de Chile, Valdivia.