Regulation of meiotic recombination and prophase I progression in mammals.

Meiosis is the process by which diploid germ cells divide to produce haploid gametes for sexual reproduction. The process is highly conserved in eukaryotes, however the recent availability of mouse models for meiotic recombination has revealed surprising regulatory differences between simple unicellular organisms and those with increasingly complex genomes. Moreover, in these higher eukaryotes, the intervention of physiological and sex-specific factors may also influence how meiotic recombination and progression are monitored and regulated. This review will focus on the recent studies involving mouse mutants for meiosis, and will highlight important differences between traditional model systems for meiosis (such as yeast) and those involving more complex cellular, physiological and genetic criteria.     

Homeostatic control of presynaptic release is triggered by postsynaptic membrane depolarization.

Homeostatic mechanisms regulate synaptic function to maintain nerve and muscle excitation within reasonable physiological limits. The mechanisms that initiate homeostasic changes to synaptic function are not known. We specifically impaired cellular depolarization by expressing the Kir2.1 potassium channel in Drosophila muscle. In Kir2.1-expressing muscle there is a persistent outward potassium current ( approximately 10 nA), decreased muscle input resistance (50-fold), and a hyperpolarized resting potential. Despite impaired muscle excitability, synaptic depolarization of muscle achieves wild-type levels. A quantal analysis demonstrates that increased presynaptic release (quantal content), without a change in quantal size (mEPSC amplitude), compensates for altered muscle excitation. Because morphological synaptic growth is normal, we conclude that a homeostatic increase in presynaptic release compensates for impaired muscle excitability. These data demonstrate that a monitor of muscle membrane depolarization is sufficient to initiate synaptic homeostatic compensation.     

Maternal or fetal origin of rhesus monkey (Macaca mulatta) amniotic fluid leukocytes can be identified by polymerase chain reaction using the zinc finger Y gene.

Leukocytes can be found in substantial numbers within the intrauterine tissues and amniotic fluid of women, and play a central role in the pathophysiology of infection-related preterm labor by their production of proinflammatory mediators. It remains unclear whether these leukocytes represent a fetal immune response, a maternal response, or a combination of the two. The objective of this study was to develop a test in the rhesus monkey (Macaca mulatta) suitable for determining the percentage of male fetal cells present in a population of leukocytes recovered from blood or amniotic fluid. We found inadequate specificity for rhesus monkey cells using commercial human Y-chromosome paint kits (fluorescence in situ hybridization (FISH)). Human-specific primers for the repetitive Y chromosome DYZ-1 locus employed in the polymerase chain reaction (PCR) produced an unacceptable percentage of false positives. However, we successfully developed a PCR-based test using rhesus-specific primers for the zinc finger Y (ZFY) locus. Densitometry of PCR products from known ratios of male and female adult peripheral leukocytes generated a linear standard curve which provided quantitative results and required only 400 cells per sample. The rhesus beta globin (RBG) gene served as an internal control. The PCR test correctly discriminated the sex of peripheral leukocytes in 20 adult males, 20 adult females, two male fetuses, and one female fetus. Serial samples of amniotic fluid from four chronically catheterized rhesus monkeys bearing male fetuses were used to confirm the utility of this assay for quantifying fetal cells in amniotic fluid. In conclusion, we have developed a PCR test which is suitable for distinguishing male from female cells in adult and fetal blood and in amniotic fluid, which lends itself to a variety of diagnostic and biologic applications in the rhesus monkey and potentially in other nonhuman primates.     

Active compounds in Populus nigra L. wilted leaves responsible for attracting Helicoverpa armigera (Hübner) (Lep., Noctuidae) and new agaropectin formulation

Abstract:  The leaf extracts of Populus nigra were collected and identified by steam distillation, air entrainment and gas chromatographic–mass spectrometric analysis. Electroantennograms were recorded from Helicoverpa armigera adults in response to the chemicals identified. Both aromatic compounds and green-leaf volatiles elicited strong responses. Field experiments revealed that the active compounds responsible for attracting H. armigera moths are mainly short-side-chain aromatic alcohols and aldehydes. We, for the first time, used agaropectin as the controlled-release matrix of insect attractants. A five-component lure containing all the aromatics without phenolics, mixed in the proportions as found in the steam distillate of the leaves collected in August, produced the best trap catch. The results showed that the volatiles of wilted leaves of P. nigra can attract H. armigera adults by feeding attraction.     

Honeydew amino acids in relation to sugars and their role in the establishment of ant-attendance hierarchy in eight species of aphids feeding on tansy (Tanacetum vulgare)

Abstract. The ratio of the concentration of honeydew total amino acids to total sugars in the honeydew of eight species of aphids, all feeding on tansy, Tanacetum vulgare (L.), was determined and correlated with honeydew production and ant‐attendance. The honeydew of the five ant‐attended aphid species [Metopeurum fuscoviride (Stroyan), Trama troglodytes (v. Hayd), Aphis vandergooti (Börner), Brachycardus cardui (L.), Aphis fabae (Scopoli)] was rich in total amino acids, ranging from 12.9 to 20.8 nmol µL^?1 compared with the unattended aphid Macrosiphoniella tanacetaria (Kalt.) with only 3 nmol µL^?1. Asparagine, glutamine, glutamic acid and serine (all nonessential amino acids) were the predominant amino acids in the honeydew of all species. The total concentration of amino acids in the phloem sap of tansy was much higher (78.7 nmol µL^?1) then in the honeydew samples, and the predominant amino acids were glutamate (34.3%) and threonine (17.7%). A somewhat unexpected result was the finding that those aphid species with the highest total amino acid concentration in the honeydew always had the highest concentration of sugars. The lowest amino acid–sugar combined value was 104–28.8 nmol µL^?1 in the non ant‐attended species M. tanacetaria, and the highest value was an average of 270–89.9 nmol µL^?1 for the three most intensely attended aphid species M. fuscoviride, A. vandergooti and T. troglodytes. There is no evidence that any single amino acid or group of amino acids in the honeydew acted as an attractant for ant‐attendance in these eight aphid species. The richness of the honeydew (rate of secretion × total concentration of sugars), along with the presence of the attractant sugar melezitose, comprised the critical factors determining the extent of ant‐attendance of the aphids feeding on T. vulgare. The high total amino acid concentration in sugar‐rich honeydews can be explained by the high flow‐through of nutrients in aphids that are particularly well attended by ants.     

Candidate mechanical stimuli for hypertrophy during volume overload.

A myocyte system that senses and responds to mechanical inputs might be activated by any number of features of the time-varying length or force signals experienced by the myocytes. We therefore characterized left ventricular volume and wall stress signals during early volume overload with high spatial and temporal resolution. Left ventricular pressure and volume were measured in open-chest isoflurane-anesthetized male Sprague-Dawley rats 4 and 7 days after surgical creation of an infrarenal arteriovenous fistula or sham operation. Mean wall stresses were calculated by using a simple thick-walled ellipsoidal model. Consistent with previous reports, this surgical model produced a 66% increase in cardiac output and a 10% increase in left ventricular mass by day 7. A number of features of the time-varying volume signal (maximum, mean, amplitude, rates of rise and fall) were significantly altered during early volume overload, whereas many other proposed hypertrophic stimuli, including peak systolic wall stress and diastolic strain, were not. Treating hemodynamic variables more generally as time-varying signals allowed us to identify a wider range of candidate mechanical stimuli for hypertrophy (including some not previously proposed in the literature) than focusing on standard time points in the cardiac cycle. We conclude that features of the time-varying ventricular volume signal and related local deformations may drive hypertrophy during volume overload and propose that those features of the volume signal that also change during pressure overload might be the most interesting candidates for further exploration.     

Silent mutations in secondary Shine-Dalgarno sequences in the cDNA of human serum amyloid A4 promotes expression of recombinant protein in Escherichia coli.

The serum amyloid A (SAA) superfamily comprises a number of differentially expressed genes with a high degree of homology in mammalian species. SAA4, an apolipoprotein constitutively expressed only in humans and mice, is associated almost entirely with lipoproteins of the high-density range. The presence of SAA4 mRNA and protein in macrophage-derived foam cells of coronary and carotid arteries suggested a specific role of human SAA4 during inflammation including atherosclerosis. Here we underline the importance of ribosome binding site (rbs)-like sequences (also known as Shine-Dalgarno sequences) in the SAA4 cDNA for expression of recombinant SAA4 protein in Escherichia coli. In contrast to rbs sequences coded by the expression vectors, rbs-like sequences in the cDNA of target protein(s) are known to interfere with protein translation via binding to the small 16S ribosome subunit, yielding low or even no expression. Here we show that PCR mutations of two rbs-like sequences in the human SAA4 cDNA promote expression of considerable amounts of recombinant SAA4 in E.coli.     

Cervical screening in Luxembourg: 1990–1999

For quality assurance purposes, the results of the 1990's obtained by the National Cervical Cancer Screening Programme (NCCSP) launched in 1962 were reviewed. The positive cytodiagnosis, the histologically verified in situ and invasive cervical cancers and the mortality rates were reported.