On the Control of Gonadotropin Secretion in the Rhesus Monkey

Knobil, E.

doi:10.1016/b978-0-12-571130-2.50005-5

Cited by 242 publications

(164 citation statements)

References 49 publications

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“…Although the mechanisms by which this reversal occurs remain elusive, comparisons between diurnal and nocturnal species may provide insight into how circadian control is accomplished in humans (i.e., a diurnal species). Studies in rhesus initially indicated that the LH surge could be induced at any circadian phase in primates (Knobil, 1974). However, frequent urinary LH monitoring of women with regular menstrual cycles suggests a pronounced influence of circadian timing on the preovulatory LH surge, with most exhibiting the LH surge between midnight and 8:00 AM (Cahill et al, 1998;Edwards, 1981) (Fig.…”

Section: Neural Scn Output and Estrus Regulationmentioning

confidence: 99%

The regulation of neuroendocrine function: Timing is everything

Kriegsfeld

Silver

2006

Hormones and Behavior

129

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Hormone secretion is highly organized temporally, achieving optimal biological functioning and health. The master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates the timing of circadian rhythms, including daily control of hormone secretion. In the brain, the SCN drives hormone secretion. In some instances, SCN neurons make direct synaptic connections with neurosecretory neurons. In other instances, SCN signals set the phase of "clock genes" that regulate circadian function at the cellular level within neurosecretory cells. The protein products of these clock genes can also exert direct transcriptional control over neuroendocrine releasing factors. Clock genes and proteins are also expressed in peripheral endocrine organs providing additional modes of temporal control. Finally, the SCN signals endocrine glands via the autonomic nervous system, allowing for rapid regulation via multisynaptic pathways. Thus, the circadian system achieves temporal regulation of endocrine function by a combination of genetic, cellular, and neural regulatory mechanisms to ensure that each response occurs in its correct temporal niche. The availability of tools to assess the phase of molecular/cellular clocks and of powerful tract tracing methods to assess connections between "clock cells" and their targets provides an opportunity to examine circadian-controlled aspects of neurosecretion, in the search for general principles by which the endocrine system is organized. KeywordsCircadian; Diurnal; Endocrinel; Neurosecretion; Clock genes; Suprachiasmatic Circadian aspects of reproductionThe importance of circadian (about a day) timing in hormone production/secretion has been known since the 1950s when Everett and Sawyer determined that a stimulatory signal occurring during a narrow temporal window on the afternoon of proestrus is necessary for induction of ovulation later that night (Everett and Sawyer, 1950). Such close temporal organization is important for successful reproduction, as numerous hormone-dependent behavioral and physiological processes must be coordinated. If optimal temporal relationships are disrupted, pronounced deficits in fertility can result. For example, ovulation, behavioral estrus, fertilization, and pregnancy maintenance require a specific

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Section: Neural Scn Output and Estrus Regulationmentioning

confidence: 99%

The regulation of neuroendocrine function: Timing is everything

Kriegsfeld

Silver

2006

Hormones and Behavior

129

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“…Hampton & Hampton (1978) 15-5 ± 1-5 Leucocyte alkaline 14-6 ± 1 -6 phosphatase monkeys, Macaca mulatta: Knobil, 1974; lowland gorillas, Gorilla gorilla gorilla: Nadler, Graham, Collins & Gould, 1979 (Table 2). Similarly, there are varying estimates of the ovarian cycle length in common marmosets, with a longer cycle length documented when urinary oestrogens are the primary measure.…”

Section: Discussionmentioning

confidence: 99%

Cyclic excretion of urinary oestrogens in female tamarins (Saguinus oedipus)

French¹,

Abbott

Scheffler

et al. 1983

Reproduction

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Summary. Urine was collected from 6 female cotton-top tamarins (Saguinus o. oedipus) and urinary oestrone and oestradiol concentrations were measured by radioimmunoassay. Oestrone was excreted at 50-fold higher concentrations than oestradiol. Five females showed patterns of regular oestrone cyclicity, with a mean peak-to-peak oestrone cycle of 23\m=.\6\m=+-\1\m=.\2days. Levels of oestradiol tended to vary with levels of oestrone excretion, but peaks were less pronounced and more variable. The sixth female, diagnosed as having 'wasting marmoset syndrome', had very low levels of excreted oestrogens, suggesting infertility. We suggest that urinary oestrone provides a good index to ovarian cyclicity in female cotton-top tamarins.

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“…Nonhuman primates, notably the rhesus macaque, are excellent models for human reproduction that have led to new drugs, medical procedures, and devices. One of the reasons is that the GnRHR of the rhesus macaque, like that of other primates, is sensitive to a complex signal, with both amplitude-and frequency-modulated components from the releasing hormone (Knobil, 1974). This is probably one of the mechanisms by which the cell is able to respond to one ligand with multiple different endpoints, [YS amino-terminal motif; E(X) , the Arg-X-Arg retention motif, the NxS/T consensus for N-glycosylation (Tan et al, 2004;Dong et al, 2007), the AFNGT motif (present in the gonadotropin receptors that comprise the NxT consensus for glycosylation) (Huhtaniemi and Themmen, 2005), the BBxxB or BBxB motifs [involved in G protein activation (Okamoto and Nishimoto, 1992) (Gether and Kobilka, 1998;Rovati et al, 2007) (Crowley et al, 1985).…”

Section: A Frequency Modulation Among Primate Gonadotropin-releasingmentioning

confidence: 99%

“…The GnRHR is located in the pituitary gonadotrope and is bathed by the circulation of the (closed) hypothalamicpituitary portal system, which transfers pulsatile signals of the hypothalamic decapeptide, GnRH (shown). The gonadotrope cell responds with a concomitant pulsatile release of the gonadotropins, LH, and FSH (Santen and Bardin, 1973;Knobil, 1974). These enter the peripheral circulation and regulate gonadal steroidogenesis, along with maturation of eggs and sperm.…”

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confidence: 99%