K J de Neef

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During a 28-month period, data were collected on physiological parameters and sociosexual behavior of 13 adult male members of a large mixed-sex group of stumptail macaques living in an outdoor cage. Monthly measurements of plasma testosterone, testis size, and body weight revealed no systematic seasonality. Seasonal variations did occur in branch shaking(More)
Physiological changes around the time of puberty were studied in a longitudinal manner in male and female stumptail macaques. In the male, testicular descent (mean age 3.3 years) is an early sign of puberty, which coincides with onset of the pubertal spurt in body weight and testis growth and precedes the pubertal rise in plasma testosterone. In the female(More)
Sexual interactions were studied in a large, well-integrated group of stumptail macaques, continuously living together. Copulations with the highest-ranking male and with young males were equally distributed over the ovarian cycle. Copulations with other adults males also occurred during all cycle phases, but were most frequent peri-ovulatory. This was most(More)
The morphological and physiological features of the rabbit vagus nerve were studied at different ages after birth. The total fibre count is about 37,500 of which at birth 1-2% and in the adult animal approximately 10% are myelinated. In the postnatal period the cross-sectional area of the vagus grows to 5 times its perinatal size due to an increase of(More)
Behavioral changes before and around the time of puberty were studied in a longitudinal manner in male and female stumptail monkeys. Around the time of testicular descent (mean age: 3.3 years) males started to become more aggressive towards adult males. Within two years following testicular descent males rose in rank with the support of others and reached(More)
Agonistic behaviors of pregnant female stumptail monkeys, members of a large, well-integrated group continuously living together, were studied during 480 observation hours (over 32 months). A total of 28 pregnancies of 20 females occurred, resulting in 12 male and 16 female live infants. The main finding was a significant decline in aggression, both(More)
Monthly blood samples were collected for more than two years from adult stumptail macaques living in a large captive group. The social organization, feeding pattern, and food composition were stable throughout the study period. No seasonal variability was observed for any of the 30 blood variables studied. It appeared that for each variable, within-animal(More)
In the adult rabbit, both myelinated and nonmyelinated efferent fibers travel from the cervical vagus nerve to the sinoauricular node. The myelinated fibers convey the negative chronotropic effect. The influence of the nonmyelinated fibers was studied. Stimulation (4/sec) of the myelinated fibers, while the compound action potential was monitored(More)
The effects of supramaximal vagus nerve stimulation on heart rate were studied in newborn rabbits, cats and guinea pigs. The analysis of the stimulus-effect curve revealed that the earlier proposed relationship: log If/IO = H.f (IO is the steady state PP-interval before and If during stimulation, f is the stimulus frequency, and H the slope of the line)(More)
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