Biphasic perimicrovillar membrane production following feeding by previously starved Dysdercus peruvianus (Hemiptera: Pyrrhocoridae)

The development of perimicrovillar membranes (PMM) from midgut cells of starved and fed Dysdercus peruvianus was studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and assays for specific enzymatic markers of the perimicrovillar membranes (alpha-glucosidase), perimicrovillar space (aminopeptidase) and microvillar membranes (beta-glucosidase). High activities of these enzymes were observed 6h post-feeding and significant production of membranes was observed at 30 h post-feeding. In the gut cells of starved insects, the rough endoplasmic reticulum was organized in concentric bundles, with a greater number of mitochondria in the cellular apex. The presence of electron dense double-membrane vesicles and the production of PMM were not observed in this condition. Thirty hours post-feeding, a disorganization of the rough endoplasmic reticulum was observed, and it was possible to see double-membrane vesicles close to the cell apex. The membrane system formation was evident with a significant development of PMM in the midgut lumen. The luminal surface of the midgut during starvation and up to 48 h post-feeding was monitored using SEM. It was demonstrated that in the starved condition, the PMM was virtually absent from gut cells, except at the base of the microvilli. At 6h post-feeding, the microvilli were already completely covered with PMM, but with a maximum of PMM formation seen at 30 h post-feeding. Signals of PMM degradation were observed 48 h after pulse feeding.     

Effects of 24 weeks of progressive resistance training on knee extensors peak torque and fat-free mass in older women

This study examined the effects of resistance training (RT) on knee extensor peak torque (KEPT) and fat-free mass (FFM) in older women. Seventy-eight volunteers (67.1 ± 5.9 years old) underwent 24 weeks of progressive RT (RTG) while 76 (67.4 ± 5.9 years old) were studied as controls (CG). Dominant knee extension peak torque was assessed using an isokinetic dynamometer (Biodex System 3) and FFM measurements were performed by dual-energy x-ray absorptiometry. Muscle strength and FFM were evaluated before and after the intervention in all volunteers. Participants in the RTG trained major muscle groups 3 times per week during 24 weeks. Training load was kept at 60% of 1 repetition maximum in the first 4 weeks, 70% in the following 4 weeks, and 80% in the remaining 16 weeks, with repetitions, respectively, decreasing from 12, 10, and 8. A Split-plot analysis of variance was performed to examine between- and within-group differences, and the level of significance was accepted at p ≤ 0.05. It was observed that the RTG showed significant increases in KEPT (from 89.9 ± 21.8 to 102.8 ± 22.6 N·m; p < 0.05) and FFM (from 36.4 ± 4.0 to 37.1 ± 4.2 kg, p < 0.05). Appendicular FFM was also significantly increased after the intervention period in the RTG (13.9 ± 1.8 to 14.2 ± 1.9 kg, p < 0.05). None of these changes were observed for the CG. Consistent with the literature, it is concluded that a progressive RT program promotes not only increases in muscle strength, as evaluated by an isokinetic dynamometer, but also in FFM as evaluated by the DXA, in elderly women.     

A preliminary fish assemblage index for a transitional river–reservoir system in southeastern Brazil

Large river–reservoir systems are some of the most difficult aquatic ecosystems to assess because: (1) they typically lack minimally disturbed reference sites; (2) the reservoirs are not natural systems to begin with; and (3) reservoirs with high exchange rates are transitional systems between rivers and lakes. These features are further complicated in Brazil where fish species taxonomy is incomplete (let alone fully described ecologically), where waters naturally have high organic and thermal loadings, and where dams and reservoirs provide most of the nation's electricity and water supplies. As a first step towards generating a biological tool for assessing the effects of reservoirs on rivers, we developed a preliminary River–Reservoir Fish Assemblage Index (RRFAI) in a transitional river–reservoir system in southeastern Brazil. To do so, we gill-netted fish monthly between October 2006 and September 2007 (excluding May and July 2007) immediately upriver of the reservoir, in the upper reservoir, in the lower reservoir, and immediately downriver of the reservoir. In developing our RRFAI we sought fish assemblage metrics to represent ecological characteristics including richness, habitat, trophic, tolerance, and resilience guilds. Despite clear differences in fish assemblage composition between river and reservoir sites, we found 9 metrics common to both systems that were nonredundant and had low sampling variability (number of native species, number of characiform species, number of siluriform species, % omnivorous individuals, % invertivorous individuals, % non-native carnivorous individuals, % intolerant individuals, % tolerant individuals, number of tolerant species). Fish assemblage condition was significantly and consistently lower in the lower reservoir. There was no significant difference between the dry and wet season in RRFAI scores, suggesting that a single season sample should usually suffice. Further research is needed along distinct disturbance gradients in multiple river–reservoir systems in Brazil to confirm the sensitivity of our preliminary RRFAI for assessing the physical and chemical habitat disturbances common to such systems.     

Distribution of digestive enzymes among the endo- and ectoperitrophic spaces and midgut cells of Rhynchosciara and its physiological significance

Determinations of carbohydrases, proteases, carboxylesterases and phosphatases in the midgut cells and in the luminal spaces outside and inside the peritrophic membrane of Rhynchosciara americana larvae have been carried out. The data show that alpha-amylase, cellulase and proteinases are present in cells, ecto- and endoperitrophic spaces; aminopeptidases and trehalase in cells and ectoperitrophic space; and finally disaccharidases (except trehalase), carboxypeptidases, dipeptidases, carboxylesterases and phosphatases only in cells. The results support the conclusion that digestion takes place in three spatially organized steps. The first one occurs inside the peritrophic membrane and comprises the dispersion and/or decrease in molecular weight of the food molecules. The second is the hydrolysis of the polymeric food molecules in the ectoperitrophic space to dimers and/or small oligomers. Finally, terminal digestion occurs in the midgut caeca and posterior ventriculus cells by enzymes presumed to be plasma membrane bound. The existence of two extracellular sites for digestion in R. americana is considered to be an adaptation to conserve secreted enzymes, since only those penetrating the endoperitrophic space are lost quickly in the faeces.     

Using co-occurrence network structure to extract synonymous gene and protein names from MEDLINE abstracts

Background  

Text-mining can assist biomedical researchers in reducing information overload by extracting useful knowledge from large collections of text. We developed a novel text-mining method based on analyzing the network structure created by symbol co-occurrences as a way to extend the capabilities of knowledge extraction. The method was applied to the task of automatic gene and protein name synonym extraction.     

An IGF-I promoter polymorphism modifies the relationships between birth weight and risk factors for cardiovascular disease and diabetes at age 36

BACKGROUND: Biochemical testing for pheochromocytoma by measurement of fractionated plasma metanephrines is limited by false positive rates of up to 18% in people without known genetic predisposition to the disease. The plasma normetanephrine fraction is responsible for most false positives and plasma normetanephrine increases with age. The objective of this study was to determine if we could improve the specificity of fractionated plasma measurements, by statistically adjusting for age. METHODS: An age-adjusted metanephrine score was derived using logistic regression from 343 subjects (including 33 people with pheochromocytoma) who underwent fractionated plasma metanephrine measurements as part of investigations for suspected pheochromocytoma at Mayo Clinic Rochester (derivation set). The performance of the age-adjusted score was validated in a dataset of 158 subjects (including patients 23 with pheochromocytoma) that underwent measurements of fractionated plasma metanephrines at Mayo Clinic the following year (validation dataset). None of the participants in the validation dataset had known genetic predisposition to pheochromocytoma. RESULTS: The sensitivity of the age-adjusted metanephrine score was the same as that of traditional interpretation of fractionated plasma metanephrine measurements, yielding a sensitivity of 100% (23/23, 95% confidence interval [CI] 85.7%, 100%). However, the false positive rate with traditional interpretation of fractionated plasma metanephrine measurements was 16.3% (22/135, 95% CI, 11.0%, 23.4%) and that of the age-adjusted score was significantly lower at 3.0% (4/135, 95% CI, 1.2%, 7.4%) (p < 0.001 using McNemar's test). CONCLUSION: An adjustment for age in the interpretation of results of fractionated plasma metanephrines may significantly decrease false positives when using this test to exclude sporadic pheochromocytoma. Such improvements in false positive rate may result in savings of expenditures related to confirmatory imaging.     

Characterization of a membrane-bound aminopeptidase purified from Acyrthosiphon pisum midgut cells. A major binding site for toxic mannose lectins

A single membrane-bound aminopeptidase N (APN) occurs in the pea aphid (Acyrthosiphon pisum Harris) midgut, with a pH optimum of 7.0, pI of 8.1 and molecular mass of 130 kDa. This enzyme accounts for more than 15.6% of the total gut proteins. After being solubilized in detergent, APN was purified to homogeneity. The enzyme is a glycoprotein rich in mannose residues, which binds the entomotoxic lectins of the concanavalin family. The internal sequence of APN is homologous with a conservative domain in APNs, and degenerated primers of highly conserved APN motifs were used to screen a gut cDNA library. The complete sequence of APN has standard residues involved in zinc co-ordination and catalysis and a glycosyl-phosphatidylinositol anchor, as in APNs from Lepidoptera. APN has a broad specificity towards N-terminal amino acids, but does not hydrolyze acidic aminoacyl-peptides, thus resembling the mammalian enzyme (EC 3.4.11.2). The kcat/Km ratios for different di-, tri-, tetra-, and penta-peptides suggest a preference for tripeptides, and that subsites S1, S2' and S3' are pockets able to bind bulky aminoacyl residues. Bestatin and amastatin bound APN in a rapidly reversible mode, with Ki values of 1.8 microM and 0.6 microM, respectively. EDTA inactivates this APN (k(obs) 0.14 M(-1) x s(-1), reaction order of 0.44) at a rate that is reduced by competitive inhibitors. In addition to oligopeptide digestion, APN is proposed to be associated with amino-acid-absorption processes which, in contrast with aminopeptidase activity, may be hampered on lectin binding.     

Relationships between newly synthesized proteins and DNA puff patterns in salivary glands of Rhynchosciara americana

An asymmetrical pericentric inversion in the onion fly, Hylemya antiqua was studied. Somatic pairing was studied in young eggs from test-and sibcrossed inversion heterozygous females which gave four and seven distinguishable karyotypes respectively. From these seven, three are balanced: the normal type, the inversion heterozygote and homozygote, and four are unbalanced recombinant karyotypes descending from crossovers in the loop. In all types at all mitotic stages the centromeres are paired. The telomeres only show association during prophase but this decreases from mid to late prophase. Quantitative analysis of the four different cross-over products as produced by inversion heterozygous females showed the presence of nonrandom disjunction. A significant disparity was observed, viz. the normal chromosome was taken up preferentially into the functional gamete compared to the inverted chromosome. Dragging of long chromatids in the asymmetric dyad during M I-A I is a possible explanation of this feature.