Purine Ribonucleosidase g from Aspergillus foetidus

Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.     

Cloning of the mgtE Mg2+ transporter from Providencia stuartii and the distribution of mgtE in gram-negative and gram-positive bacteria.

The MM281 strain of Salmonella typhimurium possesses mutations in each of its three Mg2+ transport systems, requires 100 mM Mg2+ for growth, and was used to screen a genomic library from the gram-negative bacterium Providencia stuartii for clones that could restore the ability to grow without Mg2+ supplementation. The clones obtained also conferred sensitivity to Co2+, a phenotype similar to that seen with the S. typhimurium corA Mg2+ transport gene. The sequence of the cloned P. stuartii DNA revealed the presence of a single open reading frame, which was shown to express a protein with a gel molecular mass of 37 kDa in agreement with the deduced size of 34 kDa. Despite a phenotype similar to that of corA and the close phylogenetic relationship between P. stuartii and S. typhimurium, this new putative Mg2+ transporter lacks similarity to the CorA Mg2+ transporter and is instead homologous to MgtE, a newly discovered Mg2+ transport protein from the gram-positive bacterium Bacillus firmus OF4. The distribution of mgtE in bacteria was studied by Southern blot hybridization to PCR amplification products. In contrast to the ubiquity of the corA gene, which encodes the dominant constitutive Mg2+ influx system of bacteria, mgtE has a much more limited phylogenetic distribution.     

Homologous chromosome pairing.

Commonly accepted precepts are challenged: (1) that homologous chromosome pairing is normally mediated by nuclear envelope attachment sites; (2) that crossover site establishment awaits synaptic completion; and (3) that it is the function of the synaptonemal complex to hold homologues in register so that equal crossing over can occur, and perhaps to provide machinery for the crossover process. Although these views may eventually be shown to be true, it is felt that currently available evidence does not warrant their full acceptance, and that alternatives should be considered. As examples of alternatives the following ideas, with some supporting evidence, are suggested: (1) homologous chromosome pairing (in non-haplont organisms) may be accomplished by chance meeting of homologue segments (followed by establishment of invisible, elastic connectors) at congression for a mitotic metaphase (in many cases perhaps the premeiotic mitosis); (2) crossover sites may be established before, during, or immediately following initiation of synapsis; and (3) the synaptonemal complex may somehow function in the crossover process at the inception of its formation, but its complete deployment throughout each normal bivalent may serve some other role, such as mediation of the binding of sister chromatids apparently required for chiasma maintenance until anaphase I.     

Effect of counselling on the psychiatric morbidity associated with mastectomy.

A controlled trial was conducted to determine whether counselling by a specialist nurse prevented the psychiatric morbidity associated with mastectomy and breast cancer. Seventy-five patients were counselled by the nurse and monitored during follow-up, while 77 patients received only the care normally given by the surgical unit. Counselling failed to prevent morbidity, but the nurse''s regular monitoring of the women''s progress led her to recognise and refer 76% of those who needed psychiatric help. Only 15% of the control group whose condition warranted help were recognised and referred. Consequently, 12 to 18 months after mastectomy there was much less psychiatric morbidity in the counselled group (12%) than in the control group (39%). These findings highlight the high degree of psychiatric morbidity in patients who have undergone mastectomy and indicate the need to find ways of reducing this morbidity.     

Direct cytological evidence for true terminalization of chiasmata in maize

Equational and disjunctional separation of heterozygous heterochromatic regions was observed relative to chiasma positions at diakinesis. Equational separation of heterozygous knobs was frequently observed and always accompanied by a chiasma distal to the knob. This is considered evidence that in these cases a crossover had occurred in a position proximal to the knob and had terminalized to a position distal to the knob by the time of fixation for observation.     

Pulmonary metabolism of epoxides.

Activities of epoxide hydrase (EH) and glutathione S-transferase (GST) have been measured in pulmonary tissue from several species. On the basis of total organ activity, pulmonary tissue has less capacity than liver tissue to metabolize epoxides. Pulmonary EH and GST appear to be refractory to induction by typical agents. Rat pulmonary GST will conjugate a variety of epoxides, but K-region epoxides are metabolized at lower rates than alkene oxides. In the isolated perfused rabbit lung, benzo (a) pyrene-4,5-oxide (BPO) is metabolized by EH and GST at similar initial rates, but EH activity is lost after a few minutes, apparently owing to inadequate local substrate levels. GST from rabbit lung cytosol has been separated by chromatographic methods into six peaks of enzymic activity (toward 1-chloro-2,4-denitrobenzene). Of these peaks, all six metabolized BPO and two metabolized styrene oxide. Although EH and GST are less active in lung than in liver, pulmonary metabolism of epoxides is important because this tissue must be able to protect itself from arene oxides generated by pulmonary oxidative metabolism of polycyclic aromatic hydrocarbons.     

Clustering of specific crossovers in maize microsporocytes

Analysis of systematic scan data from microsporocyte smear preparations suggests that cells with a crossover in a specific region tend to be geographically clustered to some extent within anthers. Crossover classes observed include single crossovers within a heterozygous inversion, three-strand double crossovers within and proximal to the inversion, and four-strand double crossovers within the inversion. Evidence for clustering within scans of cells of the first two classes is reported, but results are inconclusive for the third class. No evidence for within-scan correlation of frequencies of any two of the crossover classes was found. It is inferred that a large part of the variability in crossover frequency observed is probably due to factors which alter crossover interference. Implications related to the frequency and distribution of crossover sites are discussed.     

Representations of specific acoustic patterns in the auditory cortex and hippocampus

Previous behavioural studies have shown that repeated presentation of a randomly chosen acoustic pattern leads to the unsupervised learning of some of its specific acoustic features. The objective of our study was to determine the neural substrate for the representation of freshly learnt acoustic patterns. Subjects first performed a behavioural task that resulted in the incidental learning of three different noise-like acoustic patterns. During subsequent high-resolution functional magnetic resonance imaging scanning, subjects were then exposed again to these three learnt patterns and to others that had not been learned. Multi-voxel pattern analysis was used to test if the learnt acoustic patterns could be ‘decoded’ from the patterns of activity in the auditory cortex and medial temporal lobe. We found that activity in planum temporale and the hippocampus reliably distinguished between the learnt acoustic patterns. Our results demonstrate that these structures are involved in the neural representation of specific acoustic patterns after they have been learnt.     

Comparative analyses of <Emphasis Type=Italic>Astacus leptodactylus</Emphasis> morphological characteristics from Croatia and Armenia

Narrow-clawed crayfish, Astacus leptodactylus is a native European freshwater crayfish species, also distributed in Croatian freshwater systems belonging to the Black Sea drainage. Its taxonomical status is still in the process of change and discussion, and the data on morphological, molecular, ecological and zoogeographical characteristics of this species are scarce. Therefore, comparative analyses of morphological characteristics were applied with the aim to contribute to the knowledge on the morphometrical and meristical characteristics of A. leptodactylus. Recent research proved that measurements of a large number of morphometrical characteristics, in combination with multivariate statistical analysis, could provide a good instrument for identification and differentiation between populations. In this research altogether 143 animals were analysed (121 from two Croatian populations and 22 from Armenia). 22 morphometrical characteristics and 4 meristical characteristics, per crayfish, were measured. It was found that males and females differ between populations in measured meristical and morphometrical characteristics. None of recorded meristical characteristics proved itself to be reliable characteristic for distinguishing populations. From measured morphometrical characteristics the most discriminant characteristics for separating males from different populations were those describing carapace shape and for females those that describe shape of the claws.