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Biomedical subjects

C F Wang

Publications and source records attributed to C F Wang.

64 records · Page 4Linked to original sources
PubMed1976

The functional changes of the pituitary gonadotrophs during the menstrual cycle.

Submaximal doses of LRF, administered over a period of several hours, either by repeated pulses (10 mug at 2 h intervals X 5) or by constant infusion (0.2 mug/min X 4 h), have permitted the assessment of changes in the releasable gonadotropin during the menstrual cycle. Quantitations in the acute releasable and ultimately releasable gonadotropins were made which represent, respectively, the sensitivity and reserve of the gonadotrophs. The functional expression of these two components of gonadotropin release exhibited profound changes during the menstrual cycle and were in synchrony with the cyclicity of ovarian steroid levels; during the early follicular phase, both sensitivity and reserve were at a minimum, but with increasing levels of E2, a preferential increase in reserve over sensitivity (P less than 0.005) was found. Although both sensitivity and reserve increased dramatically near the midcycle, the relative change in these two components was reversed from the late follicular phase to the midcycle surge. The presence of this phenomenon may be causally related to the development of a self-priming effect of LRF at this time, as evidenced by an augmentation of gonadotropin release to the 2nd pulse of LRF. Thus, a build-up in pituitary store consequent to the greater increase in reserve than in sensitivity, together with the appearance of the self-priming effect of LRF induced by progressively rising levels of E2, may constitute the essential dynamics required for the development of the midcycle gonadotropin surge. Pituitary sensitivity and reserve continued to be high during the early luteal phase but reduced progressively thereafter. In all studied, FSH responses were less obvious but showed remarkable parallelism to the pattern of LH responses. We have concluded that the functional capacity of the gonadotrophs exhibits a remarkable cyclic change and that the adenohypophysis represents a critical feedback site in the development of pre-ovulatory gonadotropin surge.

Adult↗
PubMed1976

Assessments of the functional capacity of the gonadotrophs in men: effects of estrogen and clomiphene.

Serum LH and FSH responses to serial injections of LRF with small (10 mug x 5), large (150 mug x 5), decremental (300 to 10 mug), and incremental (10 to 300 mug) doses at 2-hour intervals were assessed in eugonadal men. At constant doses, pulses of LRF induced pulsatile LH release which was qualitatively similar but quantitatively greater for the large than for the small dose of LRF. There were no periods of refractoriness or augmentation of subsequent responses from prior exposure to LRF when administered at 2-hour intervals. LH responses to incremental and decremental doses of LRF resulted in corresponding measurable changes in the magnitude of pituitary LH release. The FSH responses to pulses of LRF at all doses tested were uniformly small. These data suggest that analyses of the initial and integrated release (10 h experiment) to pulses of LRF may disclose the functional capacity of the gonadotrophs and that small variations in the endogenous LRF delivered may represent a significant factor in the control of LH release. The small dose (10 mug x 5) of pulses of LRF was utilized in the assessment of estrogen and clomiphene treatments on the functional capacity of the gonadotrophs in normal men. Compared with the pretreatment results, both constant doses of ethinyl estradiol (50 mug/day x 7 days) and incremental doses of estradiol benzoate (100 to 400 mug, twice daily injections x 4 d) induced an attenuation of the initial release as well as of the integrated response 10 h) to pulses of LRF. Clomiphene treatment (100 mg/day x 5 d), likewise, resulted in a reduction of gonadotropin release to all pulses of LRF. These data suggest that circulating estrogen in intact men may have both a negative and a positive feedback effect on the gonadotrophs and that the testicular estrogen secretion as well as the extraglandular sources of estrogen, may play a critical role in the regulations of gonadotropin secretion in man.

Adult↗
PubMed1975

Direct evidence of estrogen modulation of pituitary sensitivity to luteinizing hormone-releasing factor during the menstrual cycle.

To delineate the role of estradiol in the augmented pituitary gonadotropin responsiveness to synthetic luteinizing hormone releasing factor (LRF) seen during high-estrogen phases of the ovulatory cycles (late follicular and midluteal phases), the anti-estrogenic effect of clomiphene citrate (Clomid) on pituitary response to LRF was evaluated during different phases of the ovulatory cycle. Clomid administration (100 mg/day times 5 days) completely negates the augmented gonadotropin responses to LRF (150 mug) during late follicular and midluteal phases observed during the control studies. Thus, a quantitatively and qualitatively similar pituitary sensitivity to LRF during three distinct phases of the menstrual cycle was induced by Clomid treatment that resembles the LRF responsiveness of themale pituitary. The present study demonstrates the pituitary component of the estrogen-induced changes in the sensitivity to LRF. From this and previous data, we conclude that the increases of estradiol secretion associated with the follicular maturation and corpus luteum formation represent a major component of the feedback signal in the modulation of cyclic gonadotropin release occasioned in a large measure by the augmented pituitary sensitivity to LRF.

Clomiphene↗
PubMed1975

The role of estrogen in the modulation of pituitary sensitivity of LRF (luteinizing hormone-releasing factor) in men.

The role of estradiol in modulating pituitary gonadotropin release in the human male was studied by evaluating the effects of clomiphene on the pituitary gonadotropin response to synthetic LRF (150 mug) in 6 eugonadal men. Administration of clomiphene (100 mg single daily dose time 5 days) induced a significant elevation of the basal levels of LH, FSH, estradiol and testosterone. However, the pituitary release of LH and FSH in response to LRF was markedly diminished by the clomiphene treatment. This finding suggests that in men, as in women, endogenous estradiol provides feedback regulation of gonadotropin output by the pituitary.

Adult↗
PubMed1975

The effects of estrogen and progesterone on the functional capacity of the gonadotrophs.

The functional capacity of the gonadotrophs under the influence of exogenous estrogen and progesterone was assessed by repeated stimulation with submaximal doses of LH-releasing factor (LRF) (10 mug at 2-h intervals) of subjects during the early follicular phase of the cycle and of hypogonadal women. The initial increment of peak serum LH and FSH concentrations after the first administration of LRF, was used to describe the pituitary sensitivity, and the integrated release during the 10 hours of LRF-stimulated pulses was utilized to approximate the pituitary gonadotropin reserve. During the early follicular phase, response to LRF stimulations was relatively stable with corresponding release of LH and FSH. An augmentation of sensitivity, as well as the reserve, for both LH and FSH was elicited by an incremental change in circulating estradiol levels, a change imposed by daily administration of estradiol benzoate for 4 days during the early follicular phase. Under the same conditions, the addition of progesterone (10 mg, im) at the end of the estradiol benzoate treatment induced a marked amplification of the estrogen-augmented pituitary gonadotropin sensitivity and reserve. The pituitary sensitivity, relatively higher than the reserve in hypogonadal subjects, was reversed by the administration of ethinyl estradiol (20-50 mug/day) for 7 days. These data indicate that the functional capacity of the gondotrophs is profoundly modulated by estrogen through relative changes in pituitary sensitivity and reserve, and that progesterone in low doses exhibited an amplifying effect on estrogen-primed gonadotrophs in both the pituitary sensitivity and the reserve.

Estradiol↗
PubMedDate not supplied

Immediate and long-term outcomes of stent implantation for unprotected left main coronary artery disease.

Left main coronary artery (LMCA) disease is now uniformly treated with coronary artery bypass grafting (CABG). However, some patients with LMCA disease do not receive CABG because of high operative risks. The advent of stent implantation has permitted a non-operative improvement in myocardial blood flow in many patients with single- and multi-vessel coronary artery disease. However, the outcomes of stent implantation for unprotected LMCA disease are still unclear. Stent implantation was performed for unprotected LMCA disease in 13 patients; eight patients had high operative risk and five patients had refused CABG. The primary success rate was 100% (13/13 patients). One patient (8%) developed a non-Q-wave myocardial infarction after LMCA stenting. Repeat angiography was obtained in five patients (38%) with recurrent angina, and three patients (23%) received repeated percutaneous transluminal coronary angioplasty (PTCA) for LMCA restenosis. In the follow-up period of 18+/-3 months, 12 patients (92%) remained in satisfactory condition with no further need for surgical intervention. One patient (8%) ultimately required CABG, and she died after CABG at 3 months after LMCA stenting. In conclusion, although CABG remains the standard treatment for LMCA disease, the present study demonstrates that stent implantation is a safe and clinically beneficial revascularization procedure for unprotected LMCA disease in patients who have high operative risk as well as those who refuse CABG.

Aged↗
PubMedDate not supplied

Patch testing in the detection of cutaneous reactions caused by carbamazepine.

Carbamazepine is a widely used antiepileptic drug associated with various side effects including skin eruptions. Peroral provocation test with any suspected drug is a reliable method of investigating the etiology: however, it is both laborious and potentially dangerous to the patient. Patch testing has been reported with variable success in skin drug reactions. Four cases (one male, three females) with epileptic seizures were reviewed; all had received carbamazepine therapy with appropriate dosage, then suffered from various cutaneous reactions including maculopapular exanthema, exfoliative dermatitis, erythema multiforme and Stevens-Johnson syndrome after the initial therapy for two weeks to one month. Skin patch test was done with 1% and 10% carbamazepine in petrolatum applied on the back, then read at 48 and 72 hours. All four patients had positive allergic patch test reactions to carbamazepine. One patient had extreme (+3), one had strong (+2) and another two had weak (+) reactions. There were no any skin reaction to vehicle and control cases. This limited study demonstrates that patch testing may be useful in the detection or confirmation of any type of exanthematous eruption caused by carbamazepine.

Adolescent↗