Search PubMed⌕ Search

Biomedical subjects

K H Lu

Publications and source records attributed to K H Lu.

At least 73 records · Page 4Linked to original sources
PubMed1980

Biological effects of various doses of conjugated equine estrogens in postmenopausal women.

To determine which dosage of estrogen might provide physiological replacement and also avoid possible harmful side effects, 21 postmenopausal women were studied before and after the oral administration of conjugated equine estrogens. The dosages studied were 0.15, 0.30, 0.625, and 1.25 mg/day, with each being given for 6 weeks. Fifteen premenopausal women were also studied, and their values were presumed to reflect normal physiological function. Variable responses of the different biochemical and biological markers of the action of estrogen were observed. Both LH and FSH levels showed stepwise decreases with increasing amounts of estrogen, but even 1.25 mg/day did not suppress these hormones to the range found in premenopausal women, suggesting a subphysiological response. The lower dosages of conjugated estrogen had minimal effects on vaginal cytology, with only the 1.25-mg dose changing the maturation index to values similar to those found in premenopausal subjects. The 0.3-mg dose of conjugated estrogen was the lowest amount that resulted in a significant reduction (P < 0.05) of the urinary calcium to creatinine ratio (an index of bone resorption). Liver protein synthesis was the most sensitive parameter to the action of estrogen. Hepatic resoponses were variable depending on which protein was assessed. These data indicate that the oral administration of conjugated equine estrogens results in inconsistent effects. All doses exerted subphysiological, physiological, and pharmacological responses at the different sites of action.

Animals↗
PubMed1980

Effect on dental caries of a stannous fluoride-calcium pyrophosphate dentrifice in an adult population: one-year results.

The first year of a two-year double-blind clinical trial of the anticaries effectiveness of a stannous fluoride-calcium pyrophosphate (SnF2-CPP) dentifrice as compared to a placebo control dentifrice involved 1,337 adult subjects, 18 to 78 years of age. Adult subjects were examined for dental caries at a baseline examination and after one year of ad lib dentifrice usage by an experienced clinical examiner using a visual-tactile examination and a radiographic evaluation. Results of the study after one year indicate a significant (P < 0.05) 33.3% difference in new caries formation with use of the SnF2-CPP dentifrice as compared to the placebo control based on the DMFS score.

Adolescent↗
PubMed1979

Altered neuroendocrine status of middle-aged rats prior to the onset of senescent anovulation.

The incidence of senescent anovulation (constant estrus) in female rats increases sharply in the age interval 10--14 months. We have compared the neuroendocrine status of 12-month-old rats, which were still cycling, with that of 6-month-old rats in the reproductive prime. Norepinephrine content in the median eminence of the hypothalamus and circulating levels of FSh and androstenedione were significnatly higher in middle-aged rats (12 months old) than in young controls (6 months old). These increases were selective, in that ten other neuroendocrine parameters measured were unchanged. These results indicate that changes occur at multiple levels of the neuroendocrine system during the transitional phase prior to the onset of senescent anovulation.

Age Factors↗
PubMed1979

LH, FSH and skin temperaure during the menopausal hot flash.

Six postmenopausal women, who were experiencing frequent hot flashes, had an 8 h continuous recording of skin temperature over the dorsum of the finger as an objective index of hot flashes. Frequent blood samples were obtained during the time of the recording for the measurement of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels. During the 48 h of recording 34 significant temperature elevations were recorded and 32 were associated with a subjective hot flash. 3l pulses of LH release were also observed with 26 occurring simultaneously with the temperature rises. Correlation analysis of simultaneous skin temperature and circulating LH levels showed a significant positive correlation (p less than 0.01). FSH levels showed no consistent relationship with skin temperature. These data suggest that LH or the factors that trigger its pulsatile release are related to the mechanism responsible for the initiation of hot flashes.

Climacteric↗
PubMed1978

Hypothalamic-pituitary-ovarian interactions during reproductive senescence in the rat.

The neuroendocrine status of Long-Evans female rats was evaluated at several key stages of reproductive senescence. Young (4-8 mo), middle-aged (10-14 mo) and old (24-30 mo) animals were studied according to reproductive state. The reproductive states studied were (1) regularly cycling, (2) constant estrus and (3) pseudopregnant, as determined by vaginal smear cytology. Neuroendocrine parameters at the levels of the hypothalamus, pituitary and steroid-producing organs were compared between each group. DA3, E and NE concentrations in the median eminence of the hypothalamus were determined by a highly sensitive radioenzymatic assay. LRF content in the median eminence was measured by radioimmunoassay. Circulating levels of LH, FSH, PRL and six steroids were determined. Changes in hormone and neurotransmitter concentrations were deomonstrated in association with the various stages of reproductive senescence and with age advancement. These changes involved the hypothalamic, pitiutary and steroid systems. NE content in the median eminence, FSH in serum and circulating androstenedione were all significantly increased in middle-aged, cyclic rats prior to the onset of senescent anovulation. DA concentration in 24 mo. old constant estrous rats (30.7 +/- 7.7 pg/microgram, N = 6) and in 30 mo. old pseudopregnant rats (27.5 +/- 7.1 pg/microgram, N = 6) was significantly reduced compared to young (6 mo. old), cyclic controls on proestrous (55.0 +/- 4.7 pg/microgram, N = 12). This DA reduction was associated with a 3-fold increase in circulating prolactin. The results are discussed in terms of a regulatory cascade model of female reproductive senescence (Finch, 1976).

Aging↗
PubMed1977

Relation of gonadotropin secretion by pituitary grafts to spermatogenesis in hypophysectomized rats.

In hypophysectomized male rats, 2 anterior pituitary (AP) grafts placed underneath the kidney capsule partially prevented atrophy of the testes and ventral prostate during a 17 day post-implantation period. Spermatogenesis was partially maintained as revealed by histological examination of the testes. The AP grafts released small amounts of LH and FSH and substantial amounts of prolactin as determined by radioimmunoassay. Serum LH and FSH were undetectable in the hypophysectomized rats with no AP grafts. Inhibition of prolactin release by daily injections of ergocornine methanesulfonate (ERG) did not significantly alter serum levels of FSH and LH, spermatogenesis or testes and ventral prostate weights, indicating that circulating levels of prolactin were not responsible for the partial maintenance of spermatogenesis and prostate weight in these rats. Daily injections of ovine prolactin also had no effect on spermatogenesis or prolactin also had no effect on spermatogenesis or prostate weight in the hypophysectomized rats, and there was no change in the histological appearance of the testes and prostate. These observations indicate that secretion of gonadotropins and not prolactin by AP grafts accounts for the partial maintenance of spermatogenesis and prostate weight in hypophysectomized, AP-grafted male rats during the experimental period studied.

Animals↗
PubMed1976

Reduced luteinizing hormone release by synthetic luteinizing hormone-releasing hormone (LHRH) in postpartum lactating rats.

The ability of the pituitary to release LH in response to synthetic LHRH was tested in lactating female rats on days 7 and 17 post partum, and compared with that of normal cycling female rats on diestrous day 2 (controls). Three consecutive injections of LHRH (100 ng/100 g BW, sc), each 50 min apart, were given to each rat and sequential blood samples were collected at 25-min intervals by cardiac puncture under light ether anesthesia. In all 3 groups, the 2nd and 3rd injections of LHRH produced much greater increases in serum concentrations of LH than the 1st injection. However, this self-priming effect of LHRH on LH response was markedly attenuated in the postpartum lactating rats (PPL), compared with the normal cycling female rats on diestrous day 2. Three consecutive injections of LHRH produced significantly less LH release in PPL rats than in normal cycling female rats on diestrous day 2. Both day 7 and day 17 PPL rats released equally small amounts of LH in response to LHRH administration. The total amount of LH released by anterior pituitaries (APs) during a 5 h incubation in medium-199, from day 7 or day 17 in PPL rats, was significantly less than that released by the APs from normal cycling female rats on diestrous day 2. APs from day 7 and day 17 PPL rats also released less LH in vitro in response to LHRH (50 ng) stimulation than APs from normal cycling female rats. When APs from normal cycling female rats on diestrous day 2 were incubated with LHRH, the increments in LH release were greater at the end of the 2nd and 3rd h than after the 1st h of incubation. However, such increments in LH release were relatively small when APs from day 7 or day 17 PPL rats were similarly incubated with LHRH.

Animals↗
PubMed1976

Relation between prolactin and gonadotrophin secretion in post-partum lactating rats.

In post-partum lactating rats, sucking by the young was associated with high prolactin release and maintenance of lactation but severe inhibition of LH and FSH release and suspension of oestrous cycles. Shortly after the pups were removed on day 22 post partum LH and FSH release returned to normal and oestrous cycles resumed. Twice-daily injections of ergocornine methanesulphonate (ERG) into mothers beginning at 5 or 7 days post partum, resulted in sustained inhibition of prolactin release and diminished mild secretion. By frequent exchange of pups between control and ERG-treated mothers, it was possible to maintain vigorous sucking and almost normal pup growth despite low serum prolactin levels and diminished lactation. In these rats, serum levels of LH remained low during 11 or more days of treatment with ERG, but serum FSH was consistently higher than in untreated control mothers. After 11 or more days of ERG treatment, most rats showed a return to normal LH and FSH release and resumption of oestrous cycles. These results suggest (a) that the sucking stimulus rather than high prolactin levels in the circulation is mainly responsible for inhibition of LH and FSH release during the first 11 days post partum, (b) that the sucking stimulus acts to increase prolactin and inhibit LH release by separate hypothalamic mechanisms, and (c) that administration of ERG results in diminished prolactin release and lactation, and in increased release of FSH and subsequently of LH with earlier resumption of oestrous cycles.

Animals↗
PubMed1975

Surgical disconnection of the medial basal hypothalamus and pituitary function in the rhesus monkey. II. GH and cortisol secretion.

Eighteen female rhesus monkeys subjected to complete or anterior disconnection of the medial basal hypothalamus (MBH) were studied to assess the effects of these deafferentation procedures on GH and cortisol secretion. Basal serum levels of GH were not disturbed or were slightly elevated following complete or anterior MBH disconnection. GH secretion in response to vasopressin administration or insulin hypoglycemia, however, was abolished by complete isolation of the MBH. In contrast, the elevations in serum cortisol concentrations observed in response to these noxious stimuli were not noticeably affected. The normal diurnal rhythm in cortisol secretion remained fully evident following anterior deafferentation, but was severely attenuated or abolished when all neuronal inputs to the MBH were transected. Such observations suggest that the central components of the neuroendocrine systems which regulate basal GH secretion and which subserve stress-induced elevations in cortisol secretion are resident within the MBH-hypophysial unit. In addition, these data indicate that the mechanisms underlying the diurnal rhythm in cortisol secretion, as well as those mediating the discharges of GH in response to vasopressin administration and insulin hypoglycemia, are dependent on the integrity of neuronal connections between the MBH and other hypothalamic and/or extrahypothalamic areas.

Animals↗
PubMed1975

Surgical disconnection of the medial basal hypothalamus and pituitary function in the rhesus monkey. IV. Prolactin secretion.

The effects of anterior and complete hypothalamic deafferentation on prolactin secretion in the rhesus monkey have been assessed. Complete disconnection ofthe medial basal hypothalamus (MBH) had no apparent effect on serum prolactin concentrations, in either intact or ovariectomized monkeys, nor did it diminish the stimulation of prolactin secretion induced by sodium pentobarbital anesthesia. Anterior disconnection of the MBH in intact females was also without effect on prolactin secretion. When the MBH was inadvertently damaged during the complete disconnection procedure, serum prolactin levels increased approximately 5-fold in otherwise intact animals while remaining unchanged in ovariectomized monkeys, thereby suggesting that ovarian hormones may modulate the secretion of prolactin in response to a reduction of hypothalamic inhibitory influences. In contrast, basal serum prolactin concentrations were not notably influenced by ovariectomy or estrogen administration nor were the patterns of prolactin secretion related to the phases of the menstrual cycle. The results of these studies suggest that the consequences of complete MBH disconnection on prolactin secretion are essentially the same in the rhesus monkey and in the rat, although major differences exist between these species with regard to the influence of estrogen on the production of this hormone.

Animals↗