A circadian rhythm of luteinizing hormone secretion in ovariectomized rats

Lawton, IE; Nb, Schwartz

doi:10.1152/ajplegacy.1968.214.2.213

Cited by 11 publications

(9 citation statements)

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“…At the time of this study (11), very little was known about the nature of LH secretion at times other than the preovulatory LH surge. Great strides had been made, however, toward identifying the key factors (ovarian steroids, a hypothalamic releasing factor, and the circadian clock) that control the ovulation-inducing LH surge.…”

Section: Historical Backgroundmentioning

confidence: 99%

“…Although significant progress had been made in characterizing the LH surge at the time of the study of interest (11), LH secretion at other times of the female cycle was poorly understood. While a hypothalamic releasing factor for LH had been identified (14), the pulsatile nature of its secretion, as well as the pulsatile nature of LH secretion, would not be discovered for quite some time.…”

Section: Historical Backgroundmentioning

confidence: 99%

“…Even though the precise nature of tonic LH secretion was yet to be discovered at the time that Dr. Schwartz's laboratory conducted the study of interest [LH secretion at times other than proestrus was thought to be "constant" rather than pulsatile (11)], the role of ovarian steroids in regulating the tonic secretion of both LH and follicle-stimulating hormone (FSH) was fully recognized. Dr. Schwartz's laboratory (21) as well as others (16) had demonstrated that at times of the cycle other than proestrus, gonadal steroids exert a negative feedback action on the secretion of LH and FSH and that removal of the gonads resulted in an elevation of plasma LH and pituitary LH content.…”

Section: Historical Backgroundmentioning

confidence: 99%

“…In the study of interest (11), the ovarian ascorbic acid depletion assay was used to assess whether plasma LH levels and pituitary LH content exhibit a circadian pattern in female rats. Figure 1 shows results from experiments assessing pituitary LH content across a 24-h period.…”

Section: Teaching Pointsmentioning

confidence: 99%

“…The study (11), entitled "A circadian rhythm of luteinizing hormone secretion in ovariectomized rats," was published in the American Journal of Physiology in 1968, and is useful for encouraging students to think about the complex interplay of regulatory mechanisms that govern pituitary luteinizing hormone (LH) secretion. The primary objective of the study was quite simple: to determine whether tonic (pulsatile) LH secretion exhibits a circadian rhythm or 24-h periodicity.…”

mentioning

confidence: 99%

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Using a classic paper by I. E. Lawton and N. B. Schwartz to consider the array of factors that control luteinizing hormone production

Bauer-Dantoin

Hanke

2007

Advances in Physiology Education

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Two significant benefits derived from reading and discussing classic scientific papers in undergraduate biology courses are 1) providing students with the realistic perspective that science is an ongoing process (rather than a set of inarguable facts) and 2) deepening the students' understanding of physiological processes. A classic paper that is useful in both of these regards is by I. E. Lawton and N. B. Schwartz (A circadian rhythm of luteinizing hormone secretion in ovariectomized rats. Am J Physiol 214: 213-217, 1968). The primary objective of the study is to determine whether tonic (pulsatile) secretion of luteinizing hormone (LH) from the pituitary gland exhibits a circadian rhythm. While this hypothesis seems relatively straightforward, its in vivo investigation necessitates an awareness of the multitude of factors, in addition to the circadian clock, that can influence plasma LH levels (and a consideration of how to control for these factors in the experimental design). Furthermore, discussion of the historical context in which the study was conducted (i.e., before the pulsatile nature of LH secretion had been discovered) provides students with the realistic perspective that science is not a set of facts but rather a systematic series of attempts by scientists to understand reality (a perspective that is difficult to convey using a traditional textbook alone). A review of the historical context in which the study was conducted, and a series of discovery learning questions are included to facilitate classroom discussions and to help deepen students' understanding of the complex nature of pituitary hormone regulation.

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Section: Historical Backgroundmentioning

confidence: 99%

Section: Historical Backgroundmentioning

confidence: 99%