Low levels of beta hexosaminidase A in healthy individuals with apparent deficiency of this enzyme.

Appreciable beta hexosaminidase A (hex A) activity has been detected in cultured skin fibroblasts and melanoma tissue from healthy individuals previously reported as having deficiency of hex A activity indistinguishable from that of patients with Tay-Sachs disease (TSD). Identification and quantitation of hex A, amounting to 3.5%-6.9% of total beta hexosaminidase activity, has been obtained by cellulose acetate gel electrophoresis, DEAE-cellulose ion-exchange chromatography, radial immunodiffusion, and radioimmunoassay. Previous family studies suggested that these individuals may be compound heterozygotes for the common mutant TSD gene and a rare (allelic) mutant gene. Thus, the postulated rate mutant gene appears to code for the expression of low amounts of hex A. Heterozygotes for the rare mutant may be indistinguishable from heterozygotes for the common TSD mutant. However, direct visualization and quantitation of hex A by the methods described may prevent false-positive prenatal diagnosis of TSD in fetuses having the incomplete hex A deficiency of the type described in the four healthy individuals.     

Sulfated homologues of heparin inhibit hepatitis C virus entry into mammalian cells

The mechanism of entry of hepatitis C virus (HCV) through interactions between the envelope glycoproteins and specific cell surface receptors remains unclear at this time. We have previously shown with the vesicular stomatitis virus (VSV)/HCV pseudotype model that the hypervariable region 1 of the HCV E2 envelope glycoprotein helps in binding with glycosaminoglycans present on the cell surface. In this study, we have examined the binding of HCV envelope glycoproteins with chemically modified derivatives of heparin. Furthermore, we have determined the functional relevance of the interaction of heparin derivatives with HCV envelope glycoproteins for infectivity by using a human immunodeficiency virus (HIV)/HCV pseudotype, a VSV/HCV pseudotype, and cell culture-grown HCV genotype 1a. Taken together, our results suggest that the HCV envelope glycoproteins rely upon O-sulfated esters of a heparin homologue to facilitate entry into mammalian cells.     

Genomic prediction in biparental tropical maize populations in water-stressed and well-watered environments using low-density and GBS SNPs

One of the most important applications of genomic selection in maize breeding is to predict and identify the best untested lines from biparental populations, when the training and validation sets are derived from the same cross. Nineteen tropical maize biparental populations evaluated in multienvironment trials were used in this study to assess prediction accuracy of different quantitative traits using low-density (~200 markers) and genotyping-by-sequencing (GBS) single-nucleotide polymorphisms (SNPs), respectively. An extension of the Genomic Best Linear Unbiased Predictor that incorporates genotype × environment (GE) interaction was used to predict genotypic values; cross-validation methods were applied to quantify prediction accuracy. Our results showed that: (1) low-density SNPs (~200 markers) were largely sufficient to get good prediction in biparental maize populations for simple traits with moderate-to-high heritability, but GBS outperformed low-density SNPs for complex traits and simple traits evaluated under stress conditions with low-to-moderate heritability; (2) heritability and genetic architecture of target traits affected prediction performance, prediction accuracy of complex traits (grain yield) were consistently lower than those of simple traits (anthesis date and plant height) and prediction accuracy under stress conditions was consistently lower and more variable than under well-watered conditions for all the target traits because of their poor heritability under stress conditions; and (3) the prediction accuracy of GE models was found to be superior to that of non-GE models for complex traits and marginal for simple traits.     

Experimental investigation of the origin of fynbos plant community structure after fire

Background and aims

Species in plant communities segregate along fine-scale hydrological gradients. Although this phenomenon is not unique to fynbos, this community regenerates after fire and therefore provides an opportunity to study the ecological genesis of hydrological niche segregation.

Methods

Following wildfires at two field sites where we had previously mapped the vegetation and monitored the hydrology, seeds were moved experimentally in >2500 intact soil cores up and down soil-moisture gradients to test the hypothesis that hydrological niche segregation is established during the seedling phase of the life cycle. Seedling numbers and growth were then monitored and they were identified using DNA bar-coding, the first use of this technology for an experiment of this kind.

Key Results

At the site where niche segregation among Restionaceae had previously been found, the size of seedlings was significantly greater, the wetter the location into which they were moved, regardless of the soil moisture status of their location of origin, or of the species. Seedling weight was also significantly greater in a competition treatment where the roots of other species were excluded. No such effects were detected at the control site where niche segregation among Restionaceae was previously found to be absent.

Conclusions

The finding that seedling growth on hydrological gradients in the field is affected by soil moisture status and by root competition shows that hydrological niche segregation could potentially originate in the seedling stage. The methodology, applied at a larger scale and followed-through for a longer period, could be used to determine whether species are differently affected by soil moisture.     

Effects of habitat loss and limitation on effective population size and inbreeding rates of Walia ibex (Capra walie) in Ethiopia

The effects of habitat loss and limitation on effective population size and inbreeding rates of Walia ibex (Capra walie) were assessed at Simien Mountains National Park. Total direct census was conducted in 2009. Historical data were obtained from park offices and literatures. Effective population sizes (N_e), inbreeding rates (ΔF) and heterozygosity losses to the whole and subdivided population per habitat were estimated. Correlations (r) between the two repeated direct censuses were positive (r = 0.99, P < 0.01). The mean N_e and ΔF (%/year) per study sites were 65.34 ± 59.45 and 0.0286 ± 0.032, respectively. The ΔF of the whole population of C. walie was 0.228 ± 0.011. The ΔF was negatively correlated with N_e (r = ?0.799, P < 0.05). The mean ΔF per fragmented habitat ranged from 0.3 (Cheneck) to 7.7% (Buait ras). The highest ΔFs per year were observed in Buait ras (7.7%), Adarmaz (7.4%) and Sankaber (4.5%). The mean heterozygosity loss per total population was 0.235 ± 0.42, which was about 23.5%. The differences in N_e and ΔF among the population per habitat were the results of habitat limitation, which in turn reduce the genetic variability and foster losses of heterozygosity.     

Epilithic diatoms as indicators in tropical African rivers (Lake Victoria catchment)

We investigated epilithic diatoms in rivers draining to the Nyanza Bay in Lake Victoria (Kenya) with the aim of determining environmental gradients in the assemblages and testing the usefulness of diatom metrics from temperate regions. Spatial and temporal variations of assemblages were studied in 12 sites of three rivers. Kibos, Nyando, and Kisat rivers contained 224 diatom taxa collected on seven sampling occasions over 4 years. Species richness showed a marginal decrease downstream and was the lowest at sites with high conductivity and ammonia–nitrogen levels. Two-Way Indicator Species Analysis and Canonical Correspondence Analysis revealed two major groups of river sites. Conductivity, alkalinity, turbidity, dissolved oxygen, and silicate were the most important variables influencing species distribution. Ecological diatom metrics of temperate regions and the Specific Pollution sensitivity Index showed good relationships with environmental variables. Both diatom assemblages and averaged indicator values were strong in predicting sites of ecological deterioration and in differentiating an upstream site of better quality (drinking water supply of Kisumu), thereby confirming epilithic diatoms as suitable water quality indicators in equatorial rivers. The use of metrics initially designed for temperate rivers, however, appears less valuable in good quality tropical rivers because potential indicators are not considered.     

Efect of emergency oral contraceptive use on condom utilization and sexual risk taking behaviours among university students, Northwest Ethiopia: a cross-sectional study

ABSTRACT: BACKGROUND: Young people between the ages of 15 and 24 years are both the most at risk of HIV and the greatest hope for turning the tide against HIV/AIDS. Although various surveys have been done on sexual behaviour of youth in Ethiopia, studies assessing the effect of emergency oral contraceptives on condom utilization of university students are lacking. METHODS: A cross-sectional study was conducted in two major universities of Ethiopia from January to May 2011 using structured self administered questionnaire with the aim to assess the effect of introducing oral emergency contraceptive pills on condom utilization and sexual risk taking behaviours among female university students. Study participants were selected by simple random sampling using the list from the associate registrars of each University. Data were entered, cleaned and analyzed using SPSS version 17.0. Bivariate and multiple logistic regression analyses were used to determine factors associated with condom utilization. RESULTS: a total of 623 students out of 660 were included giving response rate of 94.4%. A total of 103(16.5%) had history of sexual intercourse and nearly half (45.6%) of them had sex before the age of 20 years. Forty (6.4%) students had history of sexually transmitted infections (STI). Sixty seven percent of students had heard about emergency oral contraceptives. One hundred and ninety one (45.7%) of students believe that EOC is effective in preventing pregnancy. Believing that EOC is effective in preventing pregnancy (adjusted Odds ratio, AOR = 0.22 95% CI 0.06, 0.87), condom prevents STI (AOR = 10.37, 95%CI 1.73, 62.24) and younger age below 20 years (AOR = 11.68 95% CI 1.25, 109.19) were statistically significantly associated with condom use. CONCLUSION: a significant number of students had history of sexual intercourse and used emergency contraception. The belief in the effectiveness of EOC negatively affects condom use. The preference for the pill may make teenagers less prepared to practice STI protective behaviours in specific situations. Therefore, there is an urgent need to educate young people in universities about reproductive health and family planning and skills on how to prevent HIV/STIs including unwanted pregnancy.     

Vapor Phase Deposition, Structure, and Plasmonic Properties of Polymer-Based Composites Containing Ag–Cu Bimetallic Nanoparticles

Nanocomposite (NC) thin films with noble metal nanoparticles embedded in a dielectric material show very attractive plasmonic properties due to dielectric and quantum confinement effects. For single component nanoparticles (NPs), the plasmon resonance frequency can only be tuned in a narrow range. Much interest aroused in bimetallic nanoparticles (BNPs), however many wet chemical approaches do not allow large variation of the NP alloy composition and filling factor. Here, we report a vapor phase co-deposition method to produce polymer–metal NCs with embedded Ag_1 − x Cu _x alloy particles. The method allows production of NPs with controlled alloy composition (x), metal filling (f) and nanostructure in a protecting Teflon AF matrix. The nanostructure size and shape were characterized by transmission electron microscope. Energy dispersive X-ray spectroscopy was used to determine x and f. The optical properties and the position of surface plasmon resonances were studied by UV–Vis spectroscopy. The plasmon resonances can be tuned over a large range of the visible spectrum associated with the change in x, f, and nanostructure. For low filling factors and small particle sizes, only one resonance peak was observed. This is attributed to enhanced miscibility at the nanoscale. Double plasmon resonances were seen for larger particle sizes in accord with phase separation expected from the bulk phase diagram and were explained in terms of the formation of core-shell structures with Cu core and Ag shell. Changes upon annealing at 200 °C are also reported.     

Nucleotide-Dependent Isomerization of Glutamate Dehydrogenase in Relation to Total RNA Contents of Peanut

The physiological function of glutamate dehydrogenase (GDH) was investigated by treating germinating peanut (Arachis hypogaea L.) seeds with nucleoside triphosphate (NTP) solutions in order to alter the isoenzyme distribution patterns. The free nucleosides and nucleotides of the GTP-treated peanut were the highest [8.7 μmol g⁻¹(f.m.)], and they decreased through the ATP-treated peanut [5.8 μmol g⁻¹(f.m.)], and CTP-treated peanut [5.5 μmol g⁻¹(f.m.)], to the UTP-treated peanut [4.1 μmol g⁻¹(f.m.)]. The combination of 4 NTPs induced 20 % higher content of Pi [173 nmol g⁻¹(f.m.)] than in the control, but the combined ATP+UTP treatment induced the lowest (93.0 nmol g⁻¹(f.m.)] Pi. The 4 NTP treatment also induced the highest number of GDH isoenzymes (28) followed by the purine NTP treatments (15 to 20), but the pyrimidine NTP treatments and the combined purine + pyrimidine NTP treatments induced the lowest numbers (<15) of isoenzymes. The deamination/amination ratios were generally higher in the UTP (0.11), and CTP (0.06) treated peanuts than in the GTP (0.04), and ATP (0.07) treated peanuts. There were mutual relationships between higher numbers of GDH isoenzymes present in the GTP-, and ATP-treated peanuts and higher RNA (236.5 and 239.4 μg g⁻¹, respectively) contents on one hand, and between the lower numbers of isoenzymes in the CTP-, and UTP-treated peanuts and lower RNA (162.0 and 152.5 μg g⁻¹, respectively) contents. The recurrent relationships of the effects of the NTP treatments of peanut were UTP > ATP > CTP > GTP. This revised version was published online in July 2006 with corrections to the Cover Date.