Influence of venous emptying on the reactive hyperemic blood flow response

Background

Previous research indicates that venous emptying serves as a stimulus for vasodilation in the human forearm. This suggests the importance of recognizing the potential influence of venous volume on reactive hyperemic blood flow (RHBF) following occlusion. The purpose of this study was to examine the influence of venous emptying on forearm vascular function.

Methods

Forearm RHBF, venous capacitance and venous outflow were examined in 35 individuals (age = 22 ± 2 years), using mercury in-Silastic strain gauge plethysmography, at rest and following five minutes of upper arm occlusion using standard procedures (Control). In addition, the same measures were obtained following five minutes of upper arm occlusion preceded by two minutes of passive arm elevation (Pre-elevation).

Results

Average resting arterial inflow was 2.42 ± 1.11 ml·100 ml^-1·min^-1. RHBF and venous capacitance were significantly greater during Pre-elevation compared to Control (RHBF; Pre-elevation: 23.76 ± 5.95 ml·100 ml^-1 ·min^-1 vs. Control: 19.33 ± 4.50; p = 0.001), (venous capacitance; Pre-elevation: 2.74 ± 0.89 % vs. Control: 2.19 ± 0.97, p = 0.001). Venous outflow did not differ between the two conditions.

Conclusion

Venous emptying prior to upper arm occlusion results in a significant greater RHBF response and venous capacitance. Recognition of the influence of venous volume on RHBF is particularly important in studies focusing on arterial inflow, and also provides further evidence for the interplay between the venous and arterial system.

     

Localization of selected pathogens of cotton within the southern green stink bug

Southern green stink bugs, Nezara viridula (L.) (Hemiptera: Pentatomidae), are pests of cotton recently shown to ingest, retain, and introduce some pathogens of cotton into bolls. The objective of this study was to determine where pathogen colonization occurs in N. viridula after ingestion. Laboratory‐reared adult N. viridula were fed sterile green beans soaked in water (control) or beans previously soaked in a suspension of one of three opportunistic bacterial pathogens [Pantoea agglomerans (Ewing & Fife), Pantoea ananatis (Serrano) Truper & De’Clari, or Klebsiella pneumoniae (Schroeter)] or a yeast [Nematospora coryli (Peglion)]. The insect rostrum, head, and alimentary canal were subsequently processed to determine the presence of pathogenic organisms. Overall, the alimentary canal exhibited significantly more bacterial colony forming units per g tissue (mean ± SEM = 4 806.3 ± 397.2) than the head (443.4 ± 397.2) and rostrum (46.0 ± 397.2); concentrations in the head and rostrum did not differ significantly. All four pathogens were detected in the alimentary canal, but only P. agglomerans and N. coryli were detected in the rostrum and head. Although P. ananatis and K. pneumoniae were only detected in the alimentary canal, their ranges of concentrations were similar to those of P. agglomerans and N. coryli in this tissue. Non‐selective media indicated that other bacterial fauna was also detected in all study insects. Thus, N. viridula does not discriminate with regard to ingestion of pathogens. The observed distribution pattern of tested bacteria and yeast in certain tissues of N. viridula clarifies the propensity for transmission of P. agglomerans and N. coryli. Results are discussed in relation to future research avenues examining selective colonization of certain pathogens and frequency of host infection by adults harboring the pathogenic organisms.     

Pesticide exposure: the hormonal function of the female reproductive system disrupted?

Some pesticides may interfere with the female hormonal function, which may lead to negative effects on the reproductive system through disruption of the hormonal balance necessary for proper functioning. Previous studies primarily focused on interference with the estrogen and/or androgen receptor, but the hormonal function may be disrupted in many more ways through pesticide exposure. The aim of this review is to give an overview of the various ways in which pesticides may disrupt the hormonal function of the female reproductive system and in particular the ovarian cycle. Disruption can occur in all stages of hormonal regulation: 1. hormone synthesis; 2. hormone release and storage; 3. hormone transport and clearance; 4. hormone receptor recognition and binding; 5. hormone postreceptor activation; 6. the thyroid function; and 7. the central nervous system. These mechanisms are described for effects of pesticide exposure in vitro and on experimental animals in vivo. For the latter, potential effects of endocrine disrupting pesticides on the female reproductive system, i.e. modulation of hormone concentrations, ovarian cycle irregularities, and impaired fertility, are also reviewed. In epidemiological studies, exposure to pesticides has been associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy, spontaneous abortion, stillbirths, and developmental defects, which may or may not be due to disruption of the female hormonal function. Because pesticides comprise a large number of distinct substances with dissimilar structures and diverse toxicity, it is most likely that several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining the role of pesticide exposure in ovarian cycle disturbances, ultimately leading to fertility problems and other reproductive effects. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both in toxicological and epidemiological settings.     

Phylogeny of the Drosophila saltans species group based on combined analysis of nuclear and mitochondrial DNA sequences

Nucleotide sequences from two nuclear loci, alcohol dehydrogenase and internal transcribed spacer-1 of the nuclear ribosomal DNA repeats, and two mitochondrial genes, cytochrome oxidase I and cytochrome oxidase II, were determined from nine species in the Drosophila saltans species group. The partition homogeneity test and partitioned Bremer support were used to measure incongruence between phylogenetic hypotheses generated from individual partitions. Individual loci were generally congruent with each other and consistent with the previously proposed morphological hypothesis, although they differed in level of resolution. Since extreme conflict between partitions did not exist, the data were combined and analyzed simultaneously. The total evidence method gave a more resolved and highly supported phylogeny, as indicated by bootstrap proportions and decay indices, than did any of the individual analyses. The cordata and elliptica subgroups, considered to have diverged early in the history of the D. saltans group, were sister taxa to the remainder of the saltans group. The sturtevanti subgroup, represented by D. milleri and D. sturtevanti, occupies an intermediate position in this phylogeny. The saltans and parasaltans subgroups are sister clades and occupy the most recently derived portion of the phylogeny. As with previous morphological studies, phylogenetic relationships within the saltans subgroup were not satisfactorily resolved by the molecular data.      

Phylogenetic analysis supports horizontal transfer of P transposable elements

Nucleotide sequence comparisons were used to investigate the evolution of P transposable elements and the possibility that horizontal transfer has played a role in their occurrence in natural populations of Drosophila and other Diptera. The phylogeny of P elements was examined using published sequences from eight dipteran taxa and a new, partial sequence from Scaptomyza elmoi. The results from a number of different analyses are highly consistent and reveal a P-element phylogeny that contradicts the phylogeny of the species. At least three instances of horizontal transfer are necessary to explain this incongruence, but other explanations cannot be ruled out at this time.      

Population patterns of Mexican corn rootworm (Coleoptera: Chrysomelidae) adults indicated by different sampling methods

The Mexican corn rootworm, Diabrotica virgifera zeae Krysan & Smith, is a serious pest of corn, Zea mays L., in several areas of Texas. Recent demonstrations of areawide adult control suggest this tactic has promise for rootworm management, but additional information regarding treatment thresholds and sampling methodology is needed. In 2000 and 2001 we examined the influence of distance into the field on rootworm captures by CRW and Pherocon AM traps, the fidelity of trap captures to population estimates from visual counts of beetles on plants (whole plant samples), and the seasonal population patterns indicated by each sampling method. Only the CRW trap consistently indicated reduced trap captures at the field margin compared with other distances. However, trends for the AM trap and whole plant samples suggested sampling on the field margin should be avoided. Population estimates at other distances into the field (2-30 m) were usually statistically similar. Thus, monitoring does not require trap placement far into the field. Both trap types indicated population peaks after flowering in corn, whereas plant samples indicated peak populations during tasseling and flowering. Both the CRW trap and plant samples showed the proportion of female beetles increased as the season progressed, but the CRW trap underestimated the proportion of females until after flowering. Regressions relating captures by traps to counts from plant samples indicated efficiency of both traps increased with increasing plant development. Our findings should increase acceptance of the CRW trap by producers and consultants and provide a rationale for development of improved, plant growth stage-specific treatment thresholds.     

Electron paramagnetic resonance study of the migratory ant Pachycondyla marginata abdomens

Electron paramagnetic resonance was used to investigate the magnetic material present in abdomens of Pachycondyla marginata ants. A g congruent with 4.3 resonance of high-spin ferric ions and a very narrow g congruent with 2 line are observed. Two principal resonance broad lines, one with g > 4.5 (LF) and the other in the region of g congruent with 2 (HF), were associated with the biomineralization process. The resonance field shift between these two lines, HF and LF, associated with magnetic nanoparticles indicates the presence of cluster structures containing on average three single units of magnetite-based nanoparticles. Analysis of the temperature dependence of the HF resonance linewidths supports the model picture of isolated magnetite nanostructures of approximately 13 nm in diameter with a magnetic energy of 544 K. These particles are shown to present a superparamagnetic behavior at room temperature. The use of these superparamagnetic particle properties for the magnetoreception process of the ants is suggested.     

Differences in growth and water relations among Phaseolus vulgaris cultivars in response to induced drought stress

Relatively little ecophysiological research has been conducted to determine the responses to drought of Phaseolus vulgaris. Four bean cultivars (cvs.) from Brazil, A320, Carioca, Ouro Negro and Xodó were submitted to an imposed water deficit in order to evaluate the importance of some adaptive mechanisms of drought resistance through the analysis of growth parameters, water status, gas exchange and indicators of tolerance mechanisms at the cellular level. During the drought treatment, relative growth rates were more reduced for A320 and Xodó than Carioca and Ouro Negro. A320 closed its stomata very rapidly and complete stomatal closure was obtained at Psi(w)=-0.6 MPa, in contrast to the other cvs. where stomata were fully closed only at Psi(w)=-0.9 MPa. Net assimilation rates were closely related to stomatal conductances. Mechanisms at the cellular level appeared to be mostly important for higher tolerance. Carioca and Ouro Negro, when compared to A320 and Xodó, were characterized by having better drought tolerance mechanisms and higher tissue water retention capacity leading to a better growth under water deficits. The leaf dehydration rates of those cvs. were slow whereas those of the drought sensitive cvs. were rapid. The results were confirmed by the electrolyte leakage test and leaf osmotic potential measurements, which indicated higher membrane resistance and osmotic adjustment in the two tolerant cvs. Carioca and Ouro Negro. It appears from this study that despite being cultivated in the same geographical region, the four cvs. of P. vulgaris displayed somewhat different drought adaptive capacities for prolonged drought during the vegetative phase.