Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

Pituitary receptors for gonadotropin-releasing hormone in relation to changes in pituitary and plasma luteinizing hormone in ovariectomized-hypothalamo pituitary disconnected ewes. I. Effect of changing frequency of gonadotropin-releasing hormone pulses

Studies were undertaken to determine if changes in the amplitude of luteinizing hormone (LH) pulses that occur in response to changes in the frequency of gonadotropin-releasing hormone (GnRH) pulses are due to an alteration in the number of GnRH receptors. Ewes were ovariectomized (OVX) and the hypothalamus was disconnected from the pituitary (HPD). Ewes were then given pulses of GnRH at a frequency of 1/h or 1/3 h. Two control groups were included: OVX ewes not subjected to HPD, and HPD ewes that were not OVX. At the end of one week of treatment, blood samples were collected to determine the amplitude of LH pulses. The treated ewes were killed just before the next scheduled pulse of GnRH, and the content of LH and number of GnRH receptors were measured in each pituitary. The amplitude of LH pulses was highly correlated with the amount of LH in the pituitary gland (r = 0.71, p less than 0.01), and both LH content and pulse amplitude (mean + SEM) were higher in ewes receiving GnRH once per 3 h (189.7 +/- 39.3 microgram/pituitary, 10.3 +/- 1.1 ng/ml, respectively) than in ewes receiving GnRH once per h (77.8 +/- 11.4 microgram/pituitary, 5.2 +/- 1.3 ng/ml). The pituitary content of LH was highest in the OVX ewes (260.2 +/- 57.4 micrograms/pituitary) and lowest in the nonpulsed HPD ewes (61.7 +/- 51.2 micrograms/pituitary). The number of GnRH receptors was similar in all groups, and was not correlated with any other variable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of exogenous melatonin and altered day length on reproductive performance of Polypay ewes

Two experiments were designed to evaluate postlight treatment use of melatonin as a method of overcoming photorefractory response by measuring the lambing percentage of early-postpartum Polypay ewes bred either late in the breeding season or during anestrus. In Trial 1, pregnant ewes (n = 140) were assigned to one of three groups: 1) ambient photoperiod (control), 2) extended light (20 h) from October 21 to December 27, and 3) extended light as in Group 2, followed by supplemental feeding of 10 mg melatonin/head (hd) daily until April 6. Breeding started on February 3 and ended April 9. A greater percentage of ewes given extended light plus melatonin (54%) and extended light alone (45%) lambed than controls (24%) (P = 0.06). In Trial 2, pregnant ewes (n = 158) were assigned to groups as in Trial 1, except extended light was given to Groups 2 and 3 from January 1 to March 11, and Group 3 ewes were supplemented with 10 mg melatonin daily from March 12 to June 10. Breeding started April 18 and ended June 10. Lambing percentage was increased (P < 0.01) by extended light plus melatonin (54%) compared to controls (6%) or ewes given only extended light (10%). The shift from artificially extended light to the shorter ambient light with or without melatonin enhanced the lambing percentage of early postpartum ewes on an accelerated lambing program during breeding late in the season. However, only the more pronounced shift from long days to short days, accomplished with extended light plus melatonin, was effective in inducing out-of-season breeding in Polypay ewes.     

Measurement of messenger RNA for luteinizing hormone beta-subunit and alpha-subunit during gestation and the postpartum period in ewes

Pituitary content of luteinizing hormone (LH) and mRNAs for LH beta-subunit (LH beta), alpha-subunit, prolactin, and growth hormone were measured in ewes on Days 50 and 140 of gestation and on Days 2, 13, 22, and 35 postpartum. Content of LH in dissociated anterior pituitary cells declined (P less than 0.05) between Days 50 and 140 of gestation and remained low at 2 days postpartum. By 22 days postpartum, pituitary concentrations of LH were comparable to concentrations in normally cycling ewes. During gestation concentrations of mRNA for LH beta and alpha-subunit paralleled changes in cellular content of LH, reaching minimal levels on Day 140. By Day 2 postpartum, pituitary concentrations of mRNAs for LH beta and alpha-subunit began to increase; they reached maximum levels by Day 13 postpartum. There appeared to be a gradual linear increase in mRNA for prolactin through gestation and the postpartum period. No changes in mRNA for growth hormone were noted during the prepartum or postpartum periods. These data suggest that the decline in pituitary concentrations of LH during gestation is due to a decrease in cellular mRNA for LH beta and alpha-subunit. The increase in mRNA for LH beta and alpha-subunit appears to precede an increase in cellular content of LH in the postpartum ewe by several days.     

Levels of lutenizing hormone, estradiol and progesterone in serum during the estrous cycle and pregnancy in the beagle bitch (38491).

Levels of luteinizing hormone (LH), estradiol-17 beta and progesterone were determined by specific radioimmunoassays in sera obtained from Beagle bitches during proestrus, estrus and diestrus. Concentrations of LH (expressed as NIH-LH-SI equivalents) were 2.8 plus or minus 0.1 ng/ml in proestrus, 35.5 plus or minus 10.0 ng/ml during early estrus and 2.2 plus or minus 0.1 ng/ml in early diestrus. Peak levels of estradiol-17beta (68.9 plus or minus 11.0 ng/ml) were detected 24 hr prior to the LH peak, declined rapidly and reached basal levels (17.8 plus or minus 6.3 ng/ml) by five days following the LH peak. Levels of progesterone were 1.7 plus or minus 0.3 ng/ml during proestrus, 3.5 plus or minus 0.3 ng/ml during early estrus and 23.3 plus or minus 2.8 ng/ml on day 5 after the LH peak . Progesterone levels remained elevated through day 28 of diestrus and pregnancy. A significant decrease (p smaller than 0.05) in levels of prosgesterone occurred between day 28 of pregnancy and one day prior to shelping (3.3 plus or minus 1.2 ng/ml, with a further decrease on the day of whelping (1.1 plus or minus 0.2 ng/ml). Levels of estradiol-17beta and LH did not change significantly (p smaller than 0.0k) during diestrus or pregnancy.     

The effect of exogenous progestins on endogenous progesterone secretion in pregnant mares

Twenty-four pregnant, light horse mares were used in a study to determine if an exogenous progestin or progesterone would alter serum concentrations of progesterone. On day 40 of gestation, mares were randomly assigned to one of three administration groups: 1) 250 mg of progesterone in oil every other day, 2) 22 mg of Altrenogest (Regumate, American Hoechst, Somerville, NJ 08876) orally every day, or 3) 10 ml of neobee oil (control) orally every day. The treatment period was from day 40 to 105. Pregnancy status was monitored on days 40, 60, 80, 100 and 105 and a single jugular blood sample was obtained daily from days 40 to 46, 69 to 75 and 99 to 105. Serum concentrations of progesterone were determined by radioimmunoassay. Concentrations of progesterone were similar (P>0.05) among groups at each sampling period. Overall concentrations of progesterone increased (P<0.001) from days 40 to 46. Injection of 250 mg of progesterone in oil failed (P>0.05) to maintain concentrations of progesterone in serum above baseline for 24 hr. Thus higher doses and/or more frequent injections would be needed in order to increase concentrations of progesterone above those seen in untreated controls. In summary, Altrenogest was found to be a nonstressful, convenient method of administering progestins to pregnant mares without altering their endogenous secretion of progesterone.