Control of ion transport by the sperm duct epithelium of brook trout (Salvelinus fontinalis)

The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na⁺ (measured as the short-circuit current, I_sc) and secretes K⁺ (measured using⁸⁶Rb⁺ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na⁺ uptake and K⁺ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.     

Volume regulation in glutathione-treated brook trout (Salvelinus fontinalis) erythrocytes

Brook trout erythrocytes that were washed with and suspended in Ringer's solution with reduced glutathione (1.0 mM) maintained steady state cell volume for up to 24h, while those without the thiol-protective agent steadily shrank. Changes in cell volume (measured as packed cell volume, PCV) were evoked by acidic media (Ringer's at pH 6.8), hypoosmotic solutions (or both) and intracellular K⁺ and Cl⁻ concentrations were monitored over 4h. Acid-swollen cells failed to volume regulate or release K⁺ but had significantly elevated intracellular Cl⁻ Osmotically-swollen cells at pH 7.8 but not at pH 6.8 underwent regulatory volume decrease (RVD) and returned to initial levels in 2h, accompanied by release of K⁺ and Cl⁻ In contrast, osmotically-shrunken cells did not show regulatory volume increase. The regulatory volume decrease and concomitant K⁺ release were dependent on Cl⁻ implying a direct or indirect coupling of K⁺ to Cl⁻ transport in volume regulation. RVD was partially blocked by 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS, 0.1 mM), an anion exchange blocker, but was unaffected by amiloride (1.0 mM) which blocks Na⁺/H⁺ exchange. Amiloride and DIDS prevented the swelling response to low pH but had no effect on control cells, suggesting involvement of Na⁺/H⁺ and Cl⁻/HCO₃ ⁻ exchanges in acid-induced cell swelling. Quinine (1.0 mM) a known blocker of K⁺ channels, exacerbated the osmotically-induced swelling but had little effect on the subsequent RVD and release of KCl. The results suggest that low extracellular pH inhibits neutral C⁻-dependent K⁺ release and the resultant regulatory volume decrease in osmotically-swollen cells.     

Efficacy of clavulanate-potentiated amoxycillin in experimental and clinical skin infections

The efficacy of clavulanate-potentiated amoxycillin was compared with amoxycillin alone in experimental staphylococcal infection in dogs and in a controlled trial in clinical cases of skin infection in dogs and cats. The experimental infection was produced by subdermal inoculation with beta-lactamase producing (amoxycillin resistant) staphylococci absorbed in cotton dust. This produced discrete, localised lesions with no systemic involvement. In a cross over study, six animals were randomly allocated to treatment with either amoxycillin alone (10 mg/kg, dosed twice daily) or a formulation of clavulanate-potentiated amoxycillin (12.5 mg/kg, of a 1:4 ratio, dosed twice daily). The lesions of the animals treated with clavulanate-potentiated amoxycillin resolved more quickly than those treated with amoxycillin alone. The difference was significant (P less than 0.05) for both lesion diameter and inflammation score after day 6 of treatment. A trial was carried out in clinical cases of skin disease which were randomly allocated to twice daily treatment with either amoxycillin alone (10 or 20 mg/kg), or with clavulanate-potentiated amoxycillin (12.5 or 25 mg/kg of a 1:4 ratio). The required duration of treatment was shorter (P less than 0.5) for the potentiated amoxycillin treatments, and the success rate (judged by cure or substantial improvement) was higher (P less than 0.05) for this group, especially (P less than 0.01) where amoxycillin resistant organisms were isolated. It was concluded that clavulanate-potentiated amoxycillin was an effective treatment of skin infections both under experimental and clinical conditions.     

按胚胎温度进行孵化

传统上 ,孵化机都是设计成机内各处都保持均匀一致的温度。为使现代高产肉鸡的孵化能够取得最佳结果 ,这一概念有其局限性     

Height,competition and yield potential in winter wheat

Summary A monogenic dominant male sterility is used for hybrid production in autumn and winter cauliflower. The ratio of male sterile plants in the backcross progenies of autumn cauliflower was 1:1 over five years (1987–1991). However, a significant deficit of male sterile plants was observed in the winter type over the same period.The influence of the temperature on the male sterile phenotype was studied within backcross progenies planted inside polythene tunnels. Six classes of phenotype were defined during the flowering period (from May to November). At low temperature, some male sterile plants developed partial to complete male fertility, whereas at high temperature, male fertile plants became male sterile.Segregation among the progenies of self-pollinated unstable male sterile plants did not deviate from the expected 3:1 ratio. Plants homozygous for the male sterility allele have been revealed by test crosses with a male fertile plant.For use in seed production, stable male sterile plants are vegetatively maintained; however, crossing lines isogenic except at the MS locus would allow male sterile plants to be raised from seed.     

Improvement of large-seeded common bean cultivars under sustainable cropping systems in Spain

Approaches are needed to broaden the genetic base and improve earliness and yield potential of large-seeded beans under sustainable cropping systems. The objective of this research was to develop adapted dwarf bean populations having a commercial seed quality and yield suitable for the production in the South of Europe. The original base populations were produced from crosses between genotypes within each Mesoamerica, Nueva Granada and Peru races, and between Peru and Nueva Granada, and Mesoamerica and Nueva Granada races. Visual mass selection for plant performance was practised in the F₂ and F₃ generations. In the F₄ and F₅, single plants were harvested under two cropping systems (sole cropping and intercropping with maize). From F₄, selection was based on precocity, combined with seed yield and seed commercial type. The F_4:7 selected lines from each original population were compared with their parents and five checks at four environments and two cropping systems. Differences among environments, populations, parents and checks were observed for all traits. Under intercropping with maize, there was a 50% reduction in seed yield. Yield of parents and checks belonging to Andean South American races, intraracial (Nueva Granada × Nueva Granada) and interracial (Nueva Granada × Peru) populations, was higher than that of those of Middle American origin. Intraracial crosses within large-seeded Andean South American (Peru race) and Middle American gene pools (Mesoamerica race) did not produce lines yielding more than the highest yielding parent. Only two large-seeded lines selected from crosses between small- and large-seeded gene pools out-yielded the best parent and check cultivar.