Sex steroid levels and leydig cell ultrastructure of the male common sheath-tail bat, taphozous georgianus

Male sheath-tail bats were collected from central Queensland over a 12-month period. Plasma testo­sterone levels peaked in August, coincident with an increase in the volume of the accessory glands and ampulla/seminal vesicle secretion. Peak spermatogenesis occurred in summer and autumn and declined in the face of maximal testosterone levels in winter. Levels of androstenedione and 5a-dihydrotesto- sterone were high compared with testosterone levels and showed no significant seasonal changes. Ultrastructural examination of Leydig cell cytoplasm revealed numerous lipid droplets and mitochondria, and an abundant smooth endoplasmic reticulum. There were no seasonal changes in Leydig cell ultrastructure. The anomalous reproductive pattern in this species is consistent with the imposition of a cold-induced winter spermatogenic shutdown, on a framework of continuous spermatogenesis, with spring peaks in testosterone and accessory gland activity

Prolonged epididymal sperm storage, and the temporal dissociation of testicular and accessory gland activity in the common sheath-tail bat, Taphozous georgianus, of tropical Australia

Peak spermatogenic activity of the common sheath-tail bat occurs in autumn, declines over winter and ceases in spring. Accessory glands enlarge in spring when mating occurs, but are regressed at other times of the year. Spermatozoa are stored in the cauda epididymidis throughout the year, and their numbers increase progressively from early summer to late autumn. Sperm storage permits asynchrony of male and female cycles and allows each to be optimally timed in relation to environmental conditions. The temporal separation of primary and secondary sexual functions in the male enables the insemination of females close to ovulation and is a consequence of the burden of sperm storage being placed upon the male

Testicular migration, spermatogenesis, temperature regulation and environment of the sheath-tail bat, Taphozous georgianus

The testes of the common sheath-tail bat of tropical Australia undergo a seasonal migration between the abdomen and the scrotal pouches, while each cauda epididymidis is permanently maintained in the scrotal pouch. Straps of smooth muscle attach to both the cranial and caudal poles of the testes, and these extend cranially to the diaphragm and caudally to the cauda epididymidis. The testicular arteries are not coiled. Among the environmental factors investigated, maximum temperature correlated most significantly with testicular descent, and the number of spermatogonia per bat also correlated most significantly with maximum temperature. Body temperature of a captive bat ranged from 25 to 38 degrees C and this was closely related to body weight and ambient temperature. It seems likely that the scrotal pouch provides a temperature slightly below that of the body and so facilitates sperm storage in the permanently scrotal cauda epididymidis. Migration of the testes probably serves to ameliorate the seasonal temperature fluctuations to which they are exposed while the relatively high correlation between maximum environment temperature and spermatogonial numbers suggests that temperature may be a proximate influence on reproduction in the sheath-tail bat

Nerve cord repair in 3-dimensional collagen gels

No abstract available

Intracellular injection of antisense oligonucleotides into identified leech neurons regenerating in 3-D cultures

No abstract available

The morphology and behaviour of axons and microglia in 3-dimensional collagen gel cultures of isolated leech ganglia

No abstract available

Simultaneous multisite recordings and stimulation of single isolated leech neurons using planar extracellular electrode arrays

Planar extracellular electrode arrays provide a non-toxic, non-invasive method of making long-term, multisite recordings with moderately high spatial frequency (recording sites per unit area). This paper reports advances in the use of this approach to record from and stimulate single identified leech neurons in vitro. A modified enzyme treatment allowed identified neurons to be extracted with very long processes. Multisite extracellular recordings from the processes of such isolated neurons revealed both the velocity and direction of action potential propagation. Propagation in two cell types examined was from the broken stump towards the cell body (antidromic). This was true for spontaneous action potentials, action potentials produced by injecting current into the cell body and extracellular stimulation of the extracted process via a planar extracellular electrode. These results extend previous findings which have shown that the tip of the broken stump of extracted neurons has a high density of voltage-activated sodium channels. Moreover they demonstrate the applicability of extracellular electrode arrays for recording the electrical excitability of single cells

Absorção e utilização do fósforo pelas culturas da soja e do feijão e por plantas daninhas Absorption and use of phosphorus by soybean and common bean crops and by weeds

A aplicação de fertilizantes pode, em determinadas situações, beneficiar mais as plantas daninhas do que as próprias culturas. O manejo de fertilizantes em sistemas agrícolas pode ser um importante componente em programas de manejo integrado das culturas. O objetivo deste trabalho foi avaliar a eficiência na absorção e utilização do P pelas culturas da soja e do feijão e por espécies de plantas daninhas. O experimento foi realizado em casa de vegetação, no período de agosto a novembro de 2002. O delineamento experimental utilizado foi o de blocos casualizados com três repetições; os tratamentos originaram-se de esquema fatorial 6 x 4, sendo seis espécies vegetais: soja (Glycine max), feijão (Phaseolus vulgaris), dois biótipos de Euphorbia heterophylla (suscetível e resistente aos herbicidas inibidores de ALS), Bidens pilosa e Desmodium tortuosum; e quatro doses de P (0,00 12,00; 24,00 e 48,00 mg dm-3), aplicadas na semeadura sob a forma de superfosfato simples. A soja foi a espécie que revelou maior aumento na sua massa seca de raízes com o incremento do fornecimento de P. D. tortuosum, soja e B. pilosa apresentaram maior resposta à adição de doses crescentes de P em relação ao acúmulo de massa seca. O maior teor de P foi constatado para o feijão, independente da dose de P aplicada, contudo D. tortuosum foi a única espécie a ter seu teor de P aumentado em quase três vezes, quando cultivado com o dobro da dose aplicada (48,00 mg dm-3), com base nas necessidades da cultura do feijão. Até a avaliação realizada no início do florescimento, as plantas de soja e D. tortuosum foram as espécies que acumularam a maior quantidade de P em seus tecidos, porém, durante a fase reprodutiva foi D. tortuosum a qual, juntamente com feijão, apresentaram variações quanto à eficiência de suas raízes em absorver P, de acordo com a dose desse nutriente, enquanto as demais espécies mantiveram a mesma eficiência radicular, independente do teor de P do solo. A eficiência na utilização do P absorvido, observado para D. tortuosum, soja e feijão, diminuiu com o aumento da dose. Nos biótipos de E. heterophylla e no feijão, foi verificado baixo desempenho quanto ao uso eficiente do P disponível no solo. A maior porcentagem de recuperação do P aplicado até à fase de formação de propágulos foi constatada nas plantas de D. tortuosum.<br>This work aimed to evaluate the absorption and use of phosphorus (P) by soybean and common bean crops and by weeds. The experiment was carried out in a greenhouse from August to November 2002. I was adopted a randomized block design with three replications, in a 6 x 4 factorial scheme. Six vegetal species (soybean (Glycine max), common bean (Phaseolus vulgaris), two Euphorbia heterophylla biotypes (susceptible and resistant to ALS inhibitor herbicides), Bidens pilosa and Desmodium tortuosum) and four doses of P (0.00 12.00; 24.00 and 48.00 mg dm-3), applied at sowing in the form of single super phosphate, were evaluated. The soybean root biomass was increased by the higher P supply and soybean, D. tortuosum, and B. pilosa accumulated more biomass in response to the increasing P doses. The highest P concentration was observed in the bean plants, independent of the applied P level, while D. tortuosum was the only specie in which the P content nearly tripled when cultivated with a P dose (48.00 mg dm-3) that was twice as high as that recommended for common bean. The highest P content in the plant tissues was accumulated by soybean and D. tortuosum until the beginning of flowering, and by D. tortuosum during the reproductive phase. In relation to the P uptake efficiency of roots, D. tortuosum and common bean presented variations according to the applied P level. The other species maintained the same root efficiency, independent of the P availability in the soil. The efficiency in the use of absorbed P by D. tortuosum, soybean and common bean decreased with the increase of the P dose. The E. heterophylla biotypes and common bean performed worst in relation to the efficient use of available P in the soil. Until the reproductive phase, D. Tortuosum presented the highest percentage of recovery of applied P