Neonatal rat hepatocytes in primary tissue culture free from density-dependent regulation of growth

Summary Studies employing [³H]thymidine and radioautography as well as colchicine and Feulgen staining of DNA showed that up to 19-fold increases in the degree of cell crowding in vitro, i.e. from 1.45 to 27.55×10⁴ cells per specimen, did not change the rates of entry into DNA synthesis and mitosis of cultivated primary neonatal rat hepatocytes.     

A first molecular phylogenetic analysis of Passiflora (Passifloraceae)

Passiflora, a genus with more than 400 species, exhibits a high diversity of floral and vegetative structures and a complex taxonomy, which includes 23 subgenera and many sections and series. To better understand Passiflora's variability and interspecific relationships, the phylogeny of 61 species, classified in 11 of 23 suggested subgenera, was investigated. Three molecular markers were used, the nuclear ribosomal internal transcribed spacers (nrITS), the plastid trnL-trnF spacer regions (～1000 bp), and the rps4 plastid gene (～570 bp). Three major clades were highly supported, independent of the marker and phylogenetic method used; one included the subgenera Distephana, Dysosmia, Dysosmioides, Passiflora, and Tacsonioides, a second, the subgenera Adopogyne, Decaloba, Murucuja, and Pseudomurucuja, and a third, the subgenus Astrophea. We call these the Passiflora, Decaloba, and Astrophea clades, respectively. The position of subgenus Deidamioides is undefined. The monophyly of Passiflora could not be statistically corroborated, and the relationships among the major clades and of these clades with the related genera remain unresolved. Our results indicate that a reevaluation of the monophyly of Passiflora and its infrageneric classification is necessary.     

Diversification and distinctive structural features of S-RNase alleles in the genus <Emphasis Type="Italic">Solanum</Emphasis>

The multigenic and multiallelic S-locus in plants is responsible for the gametophytic self-incompatibility system, which is important to prevent the detrimental effects of self-fertilization and inbreeding depression. Several studies have discussed the importance of punctual mutations, recombination, and natural selection in the generation of allelic diversity in the S-locus. However, there has been no wide-ranging study correlating the molecular evolution and structural aspects of the corresponding proteins in Solanum. Therefore, we evaluated the molecular evolution of one gene in this locus and generated a statistically well-supported phylogenetic tree, as well as evidence of positive selection, helping us to understand the diversification of S alleles in Solanum. The three-dimensional structures of some of the proteins corresponding to the major clusters of the phylogenetic tree were constructed and subsequently submitted to molecular dynamics to stabilize the folding and obtain the native structure. The positively selected amino acid residues were predominantly located in the hyper variable regions and on the surface of the protein, which appears to be fundamental for allele specificity. One of the positively selected residues was identified adjacent to a conserved strand that is crucial for enzymatic catalysis. Additionally, we have shown significant differences in the electrostatic potential among the predicted molecular surfaces in S-RNases. The structural results indicate that local changes in the three-dimensional structure are present in some regions of the molecule, although the general structure seems to be conserved. No previous study has described such structural variations in S-RNases.     

The Association of Low-To-Moderate Alcohol Consumption with Breast Cancer Subtypes Defined by Hormone Receptor Status

Background

Alcohol is a well-established risk factor for breast cancer, but pathways involved in alcohol-related breast carcinogenesis are not clearly defined. We examined the association between low-to-moderate alcohol intake and breast cancer subtypes by tumor hormone receptor status.

Materials and Methods

A hospital-based case-control study was performed in 585 cases and 1,170 controls. Information on alcohol intake and other risk factors was collected via a questionnaire. Logistic regression was used for analyses. All statistical tests were two-sided.

Results

The odds ratio of breast cancer was 1.75 (95% confidence interval [CI]: 1.21–2.53) in women who consumed ≤5 drinks/week, and 3.13 (95% CI: 1.81–5.43) in women who consumed >5 drinks/week, both compared with non-drinkers for ≥10 years, after adjustment for age and other confounders. The association of alcohol intake with estrogen receptor-positive breast cancer was stronger than with estrogen receptor-negative: the odds ratio per 1 category increase was 2.05 (95% CI: 1.49–2.82) and 1.29 (95% CI: 0.85–1.94) (P-heterogeneity = 0.07). There was no evidence of an interaction between alcohol intake and menopausal status (P = 0.19) in overall group; however, it was significant in estrogen receptor-positive breast cancer (P = 0.04).

Conclusions

Low-to-moderate alcohol intake is associated with the risk of estrogen receptor-positive breast cancer with the strongest association in postmenopausal women. Since alcohol intake is a modifiable risk factor of breast cancer, every woman should be informed and advised to control alcohol use.     

Lanthanide ion catalysis of the trans-cis isomerization of trans-bis(oxalato)-diaquochromate(III) and trans-bis(malonato)diaquochromate(III) [1]

The lanthanide ion catalyzed trans-cis isomerizations of trans-bis(oxalato)diaquochromate(II) and trans-bis(malonato)diaquochromate(III) have been studied. A linear free energy relationship was found correlating the catalytic rate constants for the oxalate reaction with the corresponding formation constants of complexes formed between simple monocarboxylic acids and the light (LaGd) members of the lanthanide series. The results indicates that for this portion of the series, the reaction mechanism is related to the formation of monocarboxylate complex intermediates. When the ionic radius of the lanthanide ion decreases below a particular value (as in the latter half of the series), the metal ion remains coordinated to both carboxylates of the oxalate ion rather than simply binding to only one carboxylate. In either situation, isomerization to the cis product eventually occurs, and the lanthanide ion is released.The reaction rates associated with the trans-bis(malonato)diaquochromate(III) reaction were found to be significantly slower than those of the corresponding oxalate system. However, in the malonate system, no linear free energy relationship was found relating the catalytic rate constants with the corresponding formation constants of monocarboxylic acids. One does find a linear relationship between the catalytic rate constants for the malonate reaction and the log K₁ values for the corresponding lanthanide/malonate complexes. During the course of the trans-cis isomerization, the lanthanide ion chelates the dissociated malonate group of a pentavalent Cr(III) intermediate. In the mechanism the lanthanide ion does not aid in ring opening, and neither does it singly bond to the intermediate     

Dynamics of amino acids in the conditioning film developed on glass panels immersed in the surface seawaters of Dona Paula Bay

The conditioning film developed on glass panels immersed in surface seawater over a period of 24 h was analysed for total organic carbon (OC), total organic nitrogen (ON), and total hydrolyzable amino acid (THAA) concentrations and composition. The concentrations of C and N and THAA increased, whereas the C/N ratio decreased over the period of immersion. The amino acid-C and N accounted for 3.7-6.7% and 10.3-65.3% of OC and ON, respectively. The relative contribution of glycine plus threonine and serine to the total amino acids decreased while that of valine, phenylalanine, isoleucine and leucine increased over the period of immersion. Principal component analysis (PCA) based on mole% amino acid composition showed that the degradation indices (DI) for the conditioning film organic matter increased over the period of immersion. A high C/N ratio, a low %THAA-C, % THAA-N and DI values and the abundance of glycine plus threonine and serine in the conditioning film organic matter during the first few hours following immersion imply that the adsorbed organic matter was mostly derived from degraded organic matter.     

Molecular modeling of pathogenesis-related proteins of family 5

The family of pathogenesis-related (PR) 5 proteins have diverse functions, and some of them are classified as thaumatins, osmotins, and inhibitors of α-amylase or trypsin. Although the specific function of many PR5 in plants is unknown, they are involved in the acquired systemic resistance and response to biotic stress, causing the inhibition of hyphal growth and reduction of spore germination, probably by a membrane permeabilization mechanism or by interaction with pathogen receptors. We have constructed three-dimensional models of four proteins belonging to the Rosaceae and Fagaceae botanical families by using the technique of comparative molecular modelling by homology. There are four main structural differences between all the PR5, corresponding to regions with replacements of amino acids. Folding and the secondary structures are very similar for all of them. However, the isoelectric point and charge distributions differ for earch protein.     

Neuronal typology of the thalamic area triangularis of Gallotia galloti (reptilia,sauria)

In a Golgi study of the area triangularis (AT), a rostral nucleus of the ventral thalamus of Gallotia galloti, we have identified four major neuronal types on the basis of their morphological characteristics: medium-sized fusiforms with two processes, medium-sized fusiforms with three or four processes, small bipolars, and small and medium-sized multipolars. These neurons are characterized by a simple morphology and radial arrangement. Cell size varies from small to medium, and all axons project laterally. These characteristics distinguish AT neurons from those of neighboring nuclei. In addition, we found some evidence of differential topographic distribution of each neuronal type within the nucleus. Medium-sized fusiform neurons with two processes are located in the most ventral part, where they constitute the ventral nuclear limit. Small multipolar neurons prevail in the dorsal and ventromedial parts, and in the rest of the nucleus medium-sized neurons, including both fusiform with three or four processes and multipolar types, are normally found. Finally, we discuss a putative homology of the reptilian AT with a part of the mammalian zona incerta.     

Multiple introductions and gene flow in subtropical South American populations of the fireweed,Senecio madagascariensis(Asteraceae)

Non-indigenous plants exhibit different attributes that make them aggressive competitors with indigenous plants and serious threats to biodiversity.Senecio madagascariensis (fireweed, Asteraceae), a native from southern Africa, is a strong competitor in agricultural activities and has toxic alkaloids that may result in high cattle mortality. In Brazil, this weed was collected for the first time in 1995 and has since spread quickly throughout the Pampas region. To better understand the invasion of the fireweed in South America, we used a genetic characterization with internal transcribed spacer (ITS) and microsatellite markers. Based on the ITS data, the southern Brazil populations of S. madagascariensis shared genetic homology with samples taken from the Hawaiian Islands and South Africa. Microsatellite analysis showed the genetic diversity split in two clusters, perhaps intimating the independent introduction of each species into South America. Although fireweed was introduced recently in southern Brazil, the considerable levels of genetic diversity, gene flow, and inbreeding may indicate success in the species establishment in this environment.