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P N Humphreys

Publications and source records attributed to P N Humphreys.

16 recordsLinked to original sources
PubMed1975

Ultrastructure of the budgerigar testis during a photoperiodically induced cycle.

Spermatogenesis in the Budgerigar can be arrested by reducing the birds' photoperiod to 8 hours of daylight or less. When this occurs, Sertoli cell cytoplasm shows a great increase in the size and number of residual bodies, while the smooth endoplasmic reticulum is reduced. If the bird is kept at 8 hours of daylight for some weeks large lipid droplets are seen in Sertoli cytoplasm, and degenerated spermatids are apparently phagocytosed. The interstitium shows fewer active Leydig cells, a paucity of lipids and occasional ovoid mitochondria. The basal lamellae of the tubule which are thick and convoluted before and during spermatogenesis become thinner and straighter. It is thought that these morphological changes reflect changes in metabolic activity.

Animals↗
PubMed1975

The differentiation of the acrosome in the spermatid of the budgerigar (Melopsittacus undulatus).

The development of the acrosome of the budgerigar spermatid was studied under the electronmicroscope. The acrosome arises from a granule derived from the Golgi apparatus which interacts with the nucleus to form a cone shaped acrosomal cap and a perforatorium. A quanity of cytoplasm and plasma membrane is captured from the cell periphery and incorporated into the substance of the acrosome. The possible significance of the developmental phases and comparative avian spermatology is discussed.

Animals↗