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W D Currie

Publications and source records attributed to W D Currie.

10 recordsLinked to original sources
PubMed1992

Calbindin-D9k mRNA is tightly regulated during the estrous cycle in the rat uterus.

Calbindin-D9k (CaBP-9k) is a cytosolic calcium binding protein with a molecular weight of 9000. CaBP-9k is mainly expressed in intestine, uterus and placenta, with intestinal levels controlled by vitamin D and uterine levels controlled by estrogens. CaBP-9k mRNA levels were measured in rat uterus throughout the estrous cycle. On the morning of proestrus, estrus and diestrus animals were sacrificed. Serum 17 beta-estradiol concentrations were determined using a radioimmunoassay. Whole uterus was used for preparation of total RNA. Northern blot analysis was performed to quantify CaBP-9k and beta-actin mRNA. CaBP-9k levels were highest at proestrus, dropped 10-fold at estrus and were not detectable at diestrus. beta-Actin levels did not change significantly throughout the estrous cycle. Peak 17 beta-estradiol concentrations coincided with maximum CaBP-9k mRNA expression at proestrus. Despite minimal concentrations of 17 beta-estradiol at estrus, CaBP-9k mRNA was still present at 10% of the proestrus level. At diestrus, CaBP-9k mRNA was not detectable despite increasing 17 beta-estradiol. It is concluded that CaBP-9k is subject to 17 beta-estradiol regulation during the estrous cycle. Correlation between CaBP-9k mRNA and 17 beta-estradiol levels indicates a lag period for CaBP-9k induction in diestrus following a rise in steroid hormone levels.

Animals↗
PubMed1992

Cytosolic free calcium increased by prostaglandin F2 alpha (PGF2 alpha), gonadotropin-releasing hormone, and angiotensin II in rat granulosa cells and PGF2 alpha in human granulosa cells.

Cytosolic [Ca2+]i was measured using a microspectrofluorimetric technique. Prostaglandin F2 alpha (PGF2 alpha, 10(-6) M) transiently increased the concentration of free cytosolic Ca2+ ([Ca2+]i) in individual rat and human granulosa cells. In a study examining a total of 170 individual rat and human granulosa cells, approximately 100% of rat granulosa cells and 80% of human granulosa cells tested responded to PGF2 alpha (10(-6) M). In a dose-response trial, the magnitude of the [Ca2+]i response did not vary, although a decreasing number of cells responded to decreasing PGF2 alpha concentrations (10(-5) to 10(-9) M). PGE2 (10(-4) to 10(-6) M) did not affect [Ca2+]i in rat or human granulosa cells. GnRH (10(-6) M) increased [Ca2+]i in rat but not human granulosa cells. Over 90% of rat granulosa cells tested responded. Angiotensin II (ANG II, 10(-5) M) increased [Ca2+]i in approximately 25% of rat, but not human granulosa cells. Individual rat granulosa cells which responded to GnRH responded to PGF2 alpha and vice versa. Individual rat granulosa cells which responded to ANG II responded to PGF2 alpha and GnRH. Conversely, less than 30% of individual rat granulosa cells which responded to PGF2 alpha and GnRH responded to ANG II. Desensitization (pretreatment) of rat granulosa cells by continuous hormone perifusion suggested that effects of PGF2 alpha, GnRH, and ANG II on [Ca2+]i were receptor specific. However, the effects of combined hormone treatments on [Ca2+]i were not additive. The transient increase in [Ca2+]i in response to PGF2 alpha or GnRH, alone, may be maximal. Results of this study suggested that effects of PGF2 alpha, GnRH, and ANG II receptor-ligand interactions may be at least partially mediated by transient increases in [Ca2+]i in rat granulosa cells. Similarly, effects of PGF2 alpha, but not GnRH or ANG II, receptor-ligand interactions may be mediated by transient increases in [Ca2+]i in human granulosa cells.

Angiotensin II↗
PubMed1992

Luteinizing hormone-releasing hormone (LHRH)- and (hydroxyproline9)LHRH-stimulated human chorionic gonadotropin secretion from perifused first trimester placental cells.

(Hydroxyproline9)LHRH [(Hyp9)LHRH] has been isolated from human, sheep, rodent, and frog hypothalamus. (Hyp9)LHRH is the major LHRH moiety in fetal rat hypothalamus. This study compared 1) synthetic LHRH-stimulated hCG secretion from term trophoblast vs. first trimester placental cells and 2) the ability and specificity with which synthetic LHRH and (Hyp9)LHRH could stimulate hCG secretion from 8- to 12-week gestation placenta. Physically dissociated cells from multiple placentae were pooled, plated on microcarrier beads, and perifused in 1.5-ml chambers (1.5 x 10(6) cells/chamber). Effluent fractions were analyzed for hCG. Each chamber was its own control. Basal hCG secretion did not depend upon exogenous LHRH stimulation. The amplitude of LHRH-stimulated hCG pulses was greater from first trimester placental than term trophoblast cells (mean +/- SEM, 6.99 +/- 1.47 vs. 0.50 +/- 0.05 mIU/ml perifusate; peak minus basal; n = 4 chambers; P less than 0.01). LHRH and (Hyp9)LHRH (10(-9) M) increased hCG secretion from first trimester placental cells (5.02 +/- 1.29 vs. 8.64 +/- 1.61 and 4.36 +/- 0.58 vs. 7.44 +/- 1.01 mIU/ml; n = 15 and 9, respectively; P less than 0.01). At the concentrations used, LHRH and (Hyp9)LHRH seemed to stimulate hCG secretion equipotently (P greater than 0.05). Simultaneous perifusion with an LHRH antagonist, (Nal-Glu)LHRH blocked the hCG secretory response to LHRH or (Hyp9)LHRH (equimolar 10(-9) M concentrations; n = 5; P less than 0.05). (Nal-Glu)LHRH alone (10(-9) M) did not affect hCG secretion (n = 5; P greater than 0.05). The results suggested that first trimester placental cells are more responsive to LHRH than are term trophoblast cells. (Hyp9)LHRH is a potential physiological secretagogue of hCG.

Chorionic Gonadotropin↗
PubMed1992

Rapid stimulation of human chorionic gonadotropin secretion by interleukin-1 beta from perifused first trimester trophoblast.

Placental trophoblast has been implicated as a major source of interleukin-1 beta (IL-1 beta), a cytokine that mediates immunological responses in the body. This study evaluated the effect of IL-1 beta on hCG secretion from 8- to 12-week-old placental trophoblast. Physically dissociated trophoblast cells collected from multiple placentae were cultured on carrier beads and loaded into chambers in a perifusion system. Medium was perifused through the chambers, and effluent was collected and assayed for hCG. Basal hCG secretion was not dependent on exogenous IL-1 beta or GnRH, but varied between mixed placental preparations and increased with duration of culture. Therefore, hCG secretion was expressed as a percentage of mean basal hCG secretion for any given chamber. IL-1 beta (10(-9) M) stimulated a rapid and transient hCG secretory response. hCG release increased by approximately 150% (P less than 0.05; n = 5) in response to the cytokine, but lower concentrations (10(-10) and 10(-11) M) were ineffective (P greater than 0.05; n = 3 each). GnRH stimulated hCG secretion by approximately 80% (P less than 0.05; n = 6). The hCG secretory profiles in response to IL-1 beta and GnRH were similar. Combined treatment with equimolar (10(-9) M) IL-1 beta and GnRH increased hCG secretion by approximately 150% (P less than 0.05; n = 5), stimulating hCG secretion as effectively as either hormone alone (P greater than 0.05). The stimulatory effect of GnRH on hCG secretion was blocked by the concomitant presence of a GnRH antagonist, Nal-Glu-GnRH (P less than 0.05; n = 5). However, simultaneous treatment with IL-1 beta and Nal-Glu-GnRH did not affect IL-1 beta-stimulated hCG secretion (100.5 +/- 3.6 vs. 162.9 +/- 10.2%; P less than 0.05; n = 7). The data suggest that IL-1 beta and GnRH stimulated a near-maximal physiological hCG secretory response, possibly through different receptor types. Alternatively, these two hormones may share a common signal transduction pathway, or IL-1 beta may influence a step distal to the coupling of GnRH to its receptor in the placental trophoblast.

Cells, Cultured↗
PubMed1992

Effects of time after ovariectomy, season and oestradiol on luteinizing hormone and follicle-stimulating hormone secretion in ovariectomized ewes.

During the breeding season, five groups of three ewes were implanted at ovariectomy with 0.36, 0.5, 1.0 and 6.0 cm oestradiol implants or implants containing no steroid. Eleven days after receiving implants, blood samples were taken every 10 min for 6 h; implants were then removed. Treatments were repeated three times during each of two consecutive breeding seasons and four times during the intervening anoestrus. In ovariectomized ewes without steroid treatment, luteinizing hormone (LH) pulse frequency increased from early to mid-breeding season, decreased to a minimum at mid-anoestrus and increased to reach a maximum at the mid-point of the second breeding season, subsequently declining. LH pulse amplitude was inversely related to frequency. Basal serum LH concentrations decreased gradually from the first breeding season to reach a minimum at mid-anoestrus and gradually increased to reach a maximum at the end of the second breeding season. Mean serum LH and follicle-stimulating hormone (FSH) concentrations were higher at the end of the second breeding season compared with the beginning of the first breeding season. All parameters of gonadotrophin secretion were decreased much more by oestradiol during the anoestrus than during the breeding season. LH pulse frequency was decreased during anoestrus and at high oestradiol concentrations during the first breeding season. Apart from LH pulse amplitude, the decreases in all parameters of gonadotrophin secretion were less during the second compared with the first breeding season. The minimum effective dose of oestradiol required to decrease mean and basal serum concentrations of LH during anoestrus was lower than in the breeding season. The minimum effective dose of oestradiol required to decrease mean serum concentrations of FSH was lower in the first compared with the second breeding season. Oestradiol depression of LH pulse amplitude and mean serum concentrations of LH and FSH showed a dose dependency during the breeding season. During anoestrus dose dependency was seen for basal concentrations of LH and mean serum concentrations of LH and FSH. We conclude that significant chronic changes in gonadotrophin secretion occur in the ewe with time after ovariectomy. Sensitivity to oestradiol also changes, and the effects of oestradiol are not always dose dependent. We suggest that the circannual pattern of LH pulse frequency and basal LH secretion are directly linked to the circannual cycle of photoperiod.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Independence of progesterone blockade of the luteinizing hormone surge in ewes from opioid activity at naloxone-sensitive receptors.

Fifteen ovariectomized ewes were treated with implants (s.c.) creating circulating luteal progesterone concentrations of 1.6 +/- 0.1 ng ml-1 serum. Ten days later, progesterone implants were removed from five ewes which were then infused with saline for 64 h (0.154 mol NaCl l-1, 20 ml h-1, i.v.). Ewes with progesterone implants remaining were infused with saline (n = 5) or naloxone (0.5 mg kg-1 h-1, n = 5) in saline for 64 h. At 36 h of infusion, all ewes were injected with oestradiol (20 micrograms in 1 ml groundnut oil, i.m.). During the first 36 h of infusion, serum luteinizing hormone (LH) concentrations were similar in ewes infused with saline after progesterone withdrawal and ewes infused with naloxone, but with progesterone implants remaining (1.23 +/- 0.11 and 1.28 +/- 0.23 ng ml-1 serum, respectively, mean +/- SEM, P greater than 0.05). These values exceeded circulating LH concentrations during the first 36 h of saline infusion of ewes with progesterone implants remaining (0.59 +/- 0.09 ng ml-1 serum, P less than 0.05). The data suggested that progesterone suppression of tonic LH secretion, before oestradiol injection, was completely antagonized by naloxone. After oestradiol injection, circulating LH concentrations decreased for about 10 h in ewes of all groups. A surge in circulating LH concentrations peaked 24 h after oestradiol injection in ewes infused with saline after progesterone withdrawal (8.16 +/- 3.18 ng LH ml-1 serum).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of naloxone on circulating gonadotrophin concentrations in prepubertal heifers.

The pattern and opioidergic control of the secretion of gonadotrophins in prepubertal heifer calves were examined. Ten age-matched Hereford heifer calves were weighed and a blood sample was taken every 2 weeks from 2 to 25 weeks of age and then weekly until 60 weeks of age. At 60 weeks, a fertile bull was introduced and at 75 weeks of age pregnancy diagnosis was performed by transrectal ultrasonography. At 4, 12, 18, 24 and 32 weeks of age, the opioid antagonist naloxone was injected (i.v., n = 5; 1 mg kg-1 body weight) each hour for 12 h. Control heifers received sterile saline at the same ages. Blood samples were collected every 12 min for the 12 h treatment and serum samples were analysed for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Samples taken once every 2 weeks from 2 to 60 weeks were analysed for LH, FSH and oestradiol, and weekly samples were taken for progesterone determination. There was no effect of naloxone on the age at puberty, which was 56.2 +/- 0.7 weeks at a body weight of 388.5 +/- 8.0 kg. The mean age at conception was 63.4 +/- 0.5 weeks. On the basis of samples taken every other week, serum concentrations of LH were high at 10 weeks and between 40 and 60 weeks of age. From the periods of intensive blood collection, the early rise in mean serum concentrations of LH appeared later at 12 and 18 weeks of age and was caused by a rise in LH pulse amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1979

Protection of mitochondrial function during ischemia by potassium cardioplegia: correlation with ischemic contracture.

The effect of potassium cardioplegia on mitochondrial function was evaluated in the ischemic isolated rat heart. Mitochondrial function as well as adenosine triphosphate (ATP) levels were determined at the initiation of ischemic contracture, at the completion of ischemic contracture, and 20 minutes following contracture completion. Group I received no cardioplegia prior to ischemia, while Group II received potassium cardioplegia prior to the onset of ischemia. The respiratory control index (RCI), which is the primary measure of the intactness of mitochondrial function, was calculated with both a NAD (nicotinamide adenine dinucleotide)-linked substrate and a FAD (flavin adenine dinucleotide)-linked substrate. Potassium cardioplegia significantly delayed ischemic contracture initiation and completion. Although the RCI and ATP levels decreased significantly at successive levels of contracture, there was no difference in the RCI or ATP content between Group I and Group II at contracture initiation or completion. Unlike previous investigations that have used a time-base to examine mitochondrial function and acute cardiac ischemic injury, we correlated mitochondrial function with the measurable physiologic event ischemic contracture. The data indicated that potassium cardioplegia preserved ATP content and mitochondrial function, and that contracture initiation and completion correlate well with specific ATP levels and mitochondrial respiratory control. The relationship between mitochondrial function and ATP content indicates that the beneficial effect of potassium cardioplegia on mitochondrial function may be secondary to the preservation of high-energy phosphate levels which provide energy for mitochondrial maintenance.

Adenosine Triphosphate↗