Regulation of the elemental composition of the epididymal fluids in the tammar, Macropus eugenii

Micropuncture, microanalytical and microelectrode techniques were used to study electrochemical aspects of 7 elements and fluid in the ductuli efferents and ductus epididymidis of the tammar. Rete testis fluid was isosmotic with blood and had a lower pH. It also contained lower concentrations of bicarbonate, sodium, calcium, magnesium, phosphorus and sulphur and higher concentrations of potassium and chloride than blood. The luminal fluid was acidified further during passage through the sperm ducts and all of the elements which were studied moved in or out of the lumen, usually against an electrochemical gradient. The ductuli efferents reabsorbed 87% of the fluid leaving the testis without changing the intraluminal concentrations of sodium, potassium and calcium, but the concentrations of magnesium, phosphorus and sulphur increased. The caput epididymidis reabsorbed about half the fluid entering it: sodium concentrations decreased and those of potassium and phosphorus increased. There was also some fluid reabsorption and an increase in the values of potassium and phosphorus in the corpus epididymidis. There was little net transport of fluid in the cauda epididymidis; sodium, chloride, magnesium and phosphorus concentrations decreased and potassium values increased. Studies involving filtration through a dialysis membrane of blood and fluid from the rete testis and cauda epididymidis showed that, whilst some of the calcium, magnesium, phosphorus and sulphur was associated with high molecular weight compounds in blood, the association was not significant in the reproductive fluids.     

Prolonged decrease in cardiac volumes after maximal upright bicycle exercise

Sequential exercise-gated cardiac blood pool scintigrams provide a noninvasive technique for evaluating the effect of therapeutic interventions on cardiac volumes and function only if both exercise periods are equivalent in the absence of an intervention. To assess whether they are indeed equivalent, 14 healthy subjects underwent gated blood pool scintigraphy during two maximal upright exercise periods separated by 60 min without changing position. Although resting cardiac output and blood pressure returned to base-line values 60 min after the first exercise period, mean resting heart rate was markedly higher (89.4 +/- 2.7 vs. 66.5 +/- 2.5 beats/min, P less than 0.001) and upright cardiac volumes lower [39.1 +/- 4.9 vs. 56.3 +/- 6.0 ml, P less than 0.001, for end-systolic volume (ESV) and 112.6 +/- 8.0 vs. 144.9 +/- 9.0 ml, P less than 0.001, for end-diastolic volume (EDV)] than before the first exercise period. These differences persisted during low levels of the subsequent exercise but not at high and maximum work loads. Cardiac volumes and heart rate 60 min after an identical exercise protocol in a second group of 22 subjects who received propranolol, 0.15 mg/kg iv, after their initial exercise, however, were the same as those preexercise. Thus higher sympathetic tone may be responsible for the persistently higher heart rate and decreased cardiac volumes after exercise, and the assumption that cardiac volumes and function are similar during two closely spaced sequential exercise studies is not always valid.     

Efficiency clustering for low-density microarrays and its application to QPCR

Background  

Pathway-targeted or low-density arrays are used more and more frequently in biomedical research, particularly those arrays that are based on quantitative real-time PCR. Typical QPCR arrays contain 96-1024 primer pairs or probes, and they bring with it the promise of being able to reliably measure differences in target levels without the need to establish absolute standard curves for each and every target. To achieve reliable quantification all primer pairs or array probes must perform with the same efficiency.     

Cardiovascular responses to lower body negative pressure in trained and untrained older men.

To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59-73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects (C) (VO2 max = 31.0 +/- 2.9 ml.kg-1 x min-1). Cardiac volumes were determined from gated blood pool scintigrams by use of 99mTc-labeled erythrocytes. During lower body negative pressure (0 to -50 mmHg), left ventricular end-diastolic and end-systolic volume indexes and stroke volume index decreased in both groups while heart rate increased. The decreases in cardiac volumes and mean arterial pressure and the increase in heart rate between 0 and -50 mmHg were significantly less in A than in C. For example, end-diastolic volume index decreased by 32 +/- 4 ml in C vs. 14 +/- 2 ml in A (P < 0.01), mean arterial pressure declined 7 +/- 5 mmHg in C and increased by 5 +/- 3 mmHg in A (P < 0.05), and heart rate increased 13 +/- 3 beats/min in C and 7 +/- 1 beats/min in A (P < 0.05). These data suggest that increased VO2 max among older men is associated with improved orthostatic responses.     

SdhE is a conserved protein required for flavinylation of succinate dehydrogenase in bacteria

Conserved uncharacterized genes account for ~30% of genes in both eukaryotic and bacterial genomes and are predicted to encode what are often termed "conserved hypothetical proteins." Many of these proteins have a wide phylogenetic distribution and might play important roles in conserved cellular pathways. Using the bacterium Serratia as a model system, we have investigated two conserved uncharacterized proteins, YgfY (a DUF339 protein, renamed SdhE; succinate dehydrogenase protein E) and YgfX (a DUF1434 protein). SdhE was required for growth on succinate as a sole carbon source and for the function, but not stability, of succinate dehydrogenase, an important component of the electron transport chain and the tricarboxylic acid cycle. SdhE interacted with the flavoprotein SdhA, directly bound the flavin adenine dinucleotide co-factor, and was required for the flavinylation of SdhA. This is the first demonstration of a protein required for FAD incorporation in bacteria. Furthermore, the loss of SdhE was highly pleiotropic, suggesting that SdhE might flavinylate other flavoproteins. Our findings are of wide importance to central metabolism because SdhE homologues are present in α-, β-, and γ-proteobacteria and multiple eukaryotes, including humans and yeast.     

Predator Presence and Vegetation Density Affect Capture Rates and Detectability of Litoria aurea Tadpoles: Wide-Ranging Implications for a Common Survey Technique

Trapping is a common sampling technique used to estimate fundamental population metrics of animal species such as abundance, survival and distribution. However, capture success for any trapping method can be heavily influenced by individuals’ behavioural plasticity, which in turn affects the accuracy of any population estimates derived from the data. Funnel trapping is one of the most common methods for sampling aquatic vertebrates, although, apart from fish studies, almost nothing is known about the effects of behavioural plasticity on trapping success. We used a full factorial experiment to investigate the effects that two common environmental parameters (predator presence and vegetation density) have on the trapping success of tadpoles. We estimated that the odds of tadpoles being captured in traps was 4.3 times higher when predators were absent compared to present and 2.1 times higher when vegetation density was high compared to low, using odds ratios based on fitted model means. The odds of tadpoles being detected in traps were also 2.9 times higher in predator-free environments. These results indicate that common environmental factors can trigger behavioural plasticity in tadpoles that biases trapping success. We issue a warning to researchers and surveyors that trapping biases may be commonplace when conducting surveys such as these, and urge caution in interpreting data without consideration of important environmental factors present in the study system. Left unconsidered, trapping biases in capture success have the potential to lead to incorrect interpretations of data sets, and misdirection of limited resources for managing species.     

Heterogeneous binding of high mobility group chromosomal proteins to nuclei

A dramatic difference is observed in the intracellular distribution of the high mobility group (HMG) proteins when chicken embryo fibroblasts are fractionated into nucleus and cytoplasm by either mass enucleation of cytochalasin-B-treated cells or by differential centrifugation of mechanically disrupted cells. Nuclei (karyoplasts) obtained by cytochalasin B treatment of cells contain more than 90 percent of the HMG 1, while enucleated cytoplasts contain the remainder. A similar distribution between karyoplasts and cytoplasts is observed for the H1 histones and the nucleosomal core histones as anticipated. The presence of these proteins, in low amounts, in the cytoplast preparation can be accounted for by the small percentage of unenucleated cells present. In contrast, the nuclei isolated from mechanically disrupted cells contain only 30-40 percent of the total HMGs 1 and 2, the remainder being recovered in the cytosol fraction. No histone is observed in the cytosol fraction. Unike the higher molecular weight HMGs, most of the HMGs 14 and 17 sediment with the nuclei after cell lysis by mechanical disruption. The distribution of HMGs is unaffected by incubating cells with cytochalasin B and mechanically fractionating rather than enucleating them. Therefore, the dramatic difference in HMG 1 distribution observed using the two fractionation techniques cannot be explained by a cytochalasin-B-induced redistribution. On reextraction and sedimentation of isolated nuclei obtained by mechanical cell disruption, only 8 percent of the HMG 1 is released to the supernate. Thus, the majority of the HMG 1 originally isolated with these nuclei, representing 35 percent of the total HMG 1, is stably bound, as is all the HMGs 14 and 17. The remaining 65 percent of the HMGs 1 and 2 is unstably bound and leaks to the cytosol fraction under the conditions of mechanical disruption. It is suggested that the unstably bound HMGs form a protein pool capable of equilibrating between cytoplasm and stably bound HMGs.     

Invasion status of Florida bass Micropterus floridanus (Lesueur, 1822) in South Africa

Largemouth bass Micropterus salmoides are a popular North American angling species that was introduced into South Africa in 1928. To enhance the largemouth bass fisheries, Florida bass Micropterus floridanus were introduced into KwaZulu Natal, South Africa, in 1980. Knowledge on the status of M. floridanus in South Africa is required, because it lives longer and reaches larger sizes than M. salmoides, which may result in heightened impacts on native biota. Because M. floridanus are morphologically similar, but genetically distinct from M. salmoides, the distribution of this species was assessed by genetically screening 185 Micropterus sp. individuals sampled from 20 localities across South Africa using the mitochondrial ND2 gene. Individuals with mitochondrial DNA matching M. salmoides were recovered from 16 localities, whereas M. floridanus mitochondrial DNA was recovered from 13 localities. At nine localities (45%), the mitochondrial DNA of both species was detected. These results demonstrate M. floridanus dispersal to multiple sites across South Africa.