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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucocorticoids act upon the hypothalamic paraventricular nucleus (PVN) and anterior pituitary in a classic negative feedback loop to regulate ACTH biosynthesis and secretion. Evidence exists to indicate that glucocorticoid feedback may be attenuated during late gestation in the sheep fetus to allow the preterm rise in fetal plasma cortisol necessary for parturition in this species. The present studies were undertaken to determine the effect of glucocorticoids placed adjacent to the fetal PVN on messenger RNA (mRNA) for CRH in the PVN and mRNA for POMC in the anterior pituitary during late gestation. We performed our studies at two critical stages during late gestation to determine if gestational age related changes occur in the efficacy of negative feedback regulation of expression of CRH and subsequently POMC. Dexamethasone (DEX) implants were placed bilaterally 2 mm lateral to the fetal PVN at 105 to 107 days gestational age (dGA; group I, n = 4) and 121-123 dGA (group II; n = 4). Gestational-age matched, sham implanted fetuses were used as controls (CONT) for both groups (n = 4 per group). Fetuses were recovered at 126-128 (group I) and 136 dGA (group II). Fetal PVN were isolated by micropunching, and the anterior pituitary was separated from neurointermediate and posterior lobes after necropsy. Total RNA was subjected to Northern analysis using specific complementary DNA probes to CRH and POMC, and specific message was normalized to actin mRNA content in each individual sample. Anterior pituitary POMC mRNA was not different in DEX fetuses compared to CONT for either group I (78 +/- 26% of CONT; mean +/- SEM) or group II (84 +/- 17% of CONT). PVN CRH mRNA content was lower in DEX fetuses in group I (28 +/- 14% of CONT; P less than or equal to 0.01) and group II (65 +/- 12% of CONT; P less than or equal to 0.01). The degree to which DEX suppressed mRNA for CRH was greater in group I compared to group II (P less than or equal to 0.05). We conclude that 1) CRH expression in the PVN of fetal sheep is suppressible by glucocorticoids; 2) suppression can occur directly at the level of the PVN and 3) that the efficacy of negative feedback decreases with increasing gestational age. Furthermore, the lack of effect of hypothalamic administration of DEX on anterior pituitary POMC mRNA indicates that basal expression of POMC in fetal sheep may be independent from support from the PVN at this stage of gestation.
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PMID:Effect of implantation of dexamethasone adjacent to the paraventricular nucleus on messenger ribonucleic acid for corticotropin-releasing hormone and proopiomelanocortin during late gestation in fetal sheep. 154 33

In the ovine fetus, adrenalectomy at 90-120 days gestational age (dGA) results in a gradual increase in basal concentrations of fetal plasma ACTH beginning at approximately 122 dGA. Bilateral adrenalectomy at 116-119 dGA also results in an increase in POMC mRNA in the fetal pituitary. It is not known whether both the paraventricular nuclei (PVN) of the hypothalamus and the anterior pituitary of the ovine fetus are responsive in late gestation to the removal of cortisol negative feedback. The purpose of this study was to determine the subsequent effect of fetal adrenalectomy at 118-121 dGA on the CRH mRNA content in fetal PVN and on POMC mRNA in the fetal anterior pituitary at 134 dGA. Mature Rambouellet-Columbia cross-bred ewes (n = 10), bred on a single occasion only and carrying fetuses of known gestational ages, were used. Both fetal adrenal glands were exposed via a retroperitoneal approach and removed [adrenalectomized (ADX); n = 5]. In control fetuses (CONT; n = 5) adrenal glands were exposed and isolated, but not removed. At 134 dGA, fetal plasma cortisol concentrations were significantly greater in CONT fetuses (7.2 +/- 2.5 ng/ml) than in ADX fetuses (mean +/- SD, 1.97 +/- 0.9 ng/ml; P less than 0.025). At 134 dGA the fetal PVN was removed by micropunching, and the anterior pituitary was separated from neurointermediate and posterior lobes after necropsy. Total RNA was prepared by the guanidium isothiocyanate-cesium chloride method and subjected to Northern analysis using specific cDNA probes to CRH and POMC. After autoradiography, quantification of mRNA was performed by scanning densitometry. Quantities of specific hybridization signal for POMC and CRH were normalized to the content of actin mRNA in each individual sample. RNA prepared from PVN exhibited a single specifically hybridizing band for CRH of approximately 1300 nucleotides. RNA prepared from anterior pituitary exhibited a single specifically hybridizing band for POMC at approximately 1300 nucleotides. Anterior pituitary POMC mRNA was significantly increased (P less than 0.025) in ADX fetuses (236 +/- 32% of CONT). CRH mRNA in PVN was greater in ADX fetuses than in CONT fetuses (P less than 0.05; mean +/- SEM, 179 +/- 21% of CONT). Adrenalectomy in fetal sheep significantly increased expression of CRH and POMC. We conclude that the increased levels of mRNA for CRH and POMC indicate that both the fetal PVN (CRH) and the anterior pituitary (POMC) are responsive to removal of the primary source of circulating glucocorticoid at this gestational age.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of fetal adrenalectomy on messenger ribonucleic acid for proopiomelanocortin in the anterior pituitary and for corticotropin-releasing hormone in the paraventricular nucleus of the ovine fetus. 203 73

Plasmin can degrade fibronectin and laminin, two important components of the extracellular matrix facilitating cell sliding and healing following a wound. In this study we investigated the relationship between the tear fluid level of plasmin and plasminogen activator and the healing of a corneal wound. Anterior keratectomy (AKE) was performed for seven rabbits (11 eyes). Eight eyes were rewounded after re-epithelialization. Tear fluid samples were collected with capillaries before wounding and during wound healing. Plasmin and plasminogen activator (PA) activities were determined using radial caseinolysis procedures. After AKE the plasmin concentrations increased rapidly, from a mean (+/- SEM) of 3.9 +/- 0.9 micrograms/ml to a mean of 37.9 +/- 7.8 micrograms/ml (p less than 0.01), and decreased during wound healing. Rewounding also resulted in an increase in plasmin concentration in the tear fluid (from a mean of 2.9 +/- 0.6 micrograms/ml to a mean of 5.0 +/- 1.1 micrograms/ml; p greater than 0.05). The PA activity showed an inverse trend as it decreased after AKE from a mean of 2.0 +/- 0.6 IU/ml to a mean of 0.3 +/- 0.1 IU/ml (p less than 0.001). During wound healing and re-epithelialization, the PA activity increased again, to 2.1 +/- 0.3 IU/ml (p less than 0.001). Abrasion of the newly grown epithelium in eight eyes caused a second elevation of PA activity which was not significant. This study demonstrates a close association between the healing of corneal wounds and changes in the plasmin and PA activities in tear fluid. Determination of the activity of these enzymes may therefore be useful for monitoring corneal wound healing.
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PMID:Plasmin and plasminogen activator activities in tear fluid during corneal wound healing after anterior keratectomy. 253 68

The present study investigated the integrity of the rat gastric mucosa after 6 hours of vagotomy without drainage. Transection vagotomy was employed to ensure complete gastric vagal denervation. Vagotomy without drainage produced gastric distension and mucosal injury confined to the glandular part. Anterior truncal vagotomy produced injury in 70% of rats, whereas truncal or transection vagotomy produced injury in all rats. The injury score with transection vagotomy was significantly higher than that with anterior truncal (21.2 mm2 +/- 1.6 vs. 8 mm2 +/- 2.7, mean +/- SEM, n = 10, p less than .01) or truncal vagotomy (21.2 mm2 +/- 1.6 vs. 15.6 mm2 +/- 1.4, mean +/- SEM, n = 10, p less than .05). Histologic examination of the mucosal injury revealed necrosis involving the epithelium and lamina propria. Cholestyramine, pyloroplasty, or gastric diversion protected the stomach against the vagotomy-induced mucosal injury. The results demonstrate in the rat that vagotomy without drainage produces within 6 hours injury of the gastric mucosa, which increases as vagal denervation is rendered more complete. Because cholestyramine protects the rat stomach against vagotomy-induced acute gastric mucosal injury, reflux of duodenal contents appears to be the principal factor behind this injury. Pyloroplasty prevents gastric distension but probably not duodenal contents refluxing, suggesting that this distention also may have a role in the mechanism of the said injury.
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PMID:The mechanism of vagotomy-induced acute gastric mucosal injury in the rat. 273 40

Servocontrol of skin temperature for the critically ill premature neonate nursed on a radiant warmer bed has been assumed to be analogous to skin temperature control for infants nursed in convection-warmed incubators. There are significant differences between these two warming techniques, and no definitive data exist to aid the clinical specialist in governing radiant warmer control. Eighteen low birth weight premature infants less than 2 weeks of age were studied under powerful overhead radiant warmers to determine the optimal skin temperature for servocontrol of radiant heater output. Anterior abdominal wall temperature was servocontrolled at 35.5 degrees, 36.5 degrees, and 37.5 degrees C in a randomized fashion for three periods of 90 minutes each after thermal equilibrium was established. Oxygen consumption was measured during the entire 90-min sample period at each temperature by a computerized metabolic apparatus to determine the optimal thermal neutral control temperature defined as minimal oxygen consumption with normal body temperature. Skin, deep rectal, and environmental temperature measurements, as well as behavior assessments, were made concurrently. Oxygen consumption was significantly elevated at 35.5 degrees C (8.62 +/- 0.73 mL/kg/min, mean +/- SEM) compared with 36.5 degrees C (7.30 +/- 0.55 mL/kg/min). Changing servocontrol temperature to 37.5 degrees C produced no further significant decrease in oxygen consumption (7.41 +/- 0.70 mL/kg/min), and nine infants manifested supranormal deep rectal temperatures (greater than 37.5 degrees C). Optimal abdominal skin temperature control at 36.5 degrees C (slightly warmer than previously reported but less than 37.5 degrees C) is recommended for premature neonates nursed on radiant warmer beds.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Optimal thermal management for low birth weight infants nursed under high-powered radiant warmers. 379 70

Isotonic, neutral buffered solutions of benzalkonium chloride or chlorhexidine digluconate were applied topically to one eye of rabbits or human subjects. Contralateral control eyes received phosphate buffered saline as placebo. One-half hour later, the tear film of both eyes was loaded with nonpreserved sodium fluorescein. Anterior chamber fluorescence levels were measured at 1 hr intervals to determine corneal permeability changes attributable to preservative action. In rabbits, corneal permeability increased with rising preservative concentration. Benzalkonium chloride 0.01% increased anterior chamber fluorescence level 1.8 (+/- 0.2 SEM) times over control eyes, while chlorhexidine digluconate 0.01% caused 1.5 (+/- 0.2 SEM) to one ratio of fluorescence in treated/untreated eyes. In human subjects, neither preservative produced significant permeability change at 0.01% concentration. However, benzalkonium chloride 0.02% caused 1.23 (+/- 0.08 SEM) permeability increase. The results support the hypothesis that rabbits are more sensitive to single-dose applications of preservatives than humans.
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PMID:Preservative alteration of corneal permeability in humans and rabbits. 651 Dec 30

The concentrations of dopamine (DA) in pituitary stalk plasma and the number of DA D-2 receptor sites in the anterior pituitary gland were evaluated in ovariectomized (OVX) rats treated for 48-78 h with estradiol (E2) or vehicle and for 2-30 h with progesterone (P) or vehicle. Only the combined administration of E2 for 72-78 h and P for 24-30 h altered the release of DA into pituitary stalk blood and the number of dopaminergic binding sites in the anterior pituitary gland. The DA concentrations in pituitary stalk plasma 72 h after initiation of treatment were 1.9 +/- 0.3 (mean +/- SEM), 2.6 +/- 0.2, and 2.4 +/- 0.3 ng/ml in OVX rats treated with vehicle, E2, and P alone, respectively, and were increased significantly to 4.3 +/- 0.4 ng/ml in E2- and P-treated rats. The binding of [3H] spiperone to DA D-2 receptors was measured by a single point assay in homogenates of the individual anterior pituitary glands obtained from the same rats. Anterior pituitary tissue was incubated with 0.4 nM [3H]spiperone in the presence or absence of 10(-6) M (+)butaclamol. Binding was similar in all animals except those treated with E2 and P, in which a significant increase occurred. Three days after initiation of treatment, binding was equivalent to 49.8 +/- 5.8, 51.3 +/- 5.1, and 55.4 +/- 4.9 fmol/mg protein in OVX rats treated with vehicle, E2, and P, respectively. In contrast, a significant increase in binding to 83.7 +/- 4.6 fmol/mg protein was observed in rats given E2 and P. No differences in either parameter were apparent 48 h after starting the steroid/vehicle treatment, nor were there any differences between morning and afternoon values in any single group. Scatchard analyses were made on the binding kinetics of DA receptors in anterior pituitary glands obtained from additional rats, and 1.5- to 2-fold increases in the density of sites were observed in animals that had received both E2 and P, while the apparent affinity of the receptors was unchanged. We conclude that treatment with the combination of E2 and P is required to increase the release of DA into hypophysial portal blood and that it also increases the density of DA receptors within the anterior pituitary gland.
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PMID:Ovarian steroids modulate the release of dopamine into hypophysial portal blood and the density of anterior pituitary [3H]spiperone-binding sites in ovariectomized rats. 672 85

Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) is a neuropeptide related to vasoactive intestinal peptide-secretin-glucagon which stimulates adenylate cyclase in cultured rat pituitary cells and stimulates LH and FSH release in vitro and in vivo. Because the cAMP-protein kinase-A pathway regulates the gonadotropin subunit messenger RNAs (mRNAs) and modulates GnRH-stimulated gonadotropin secretion in vitro, we examined the effects of PACAP38 on gonadotropin secretion and subunit mRNA levels. Anterior pituitary cells were prepared from 7-week-old male rats castrated at 5 weeks of age. In monolayer cultures stimulated with GnRH, 0.1-10 nM PACAP38 decreased (P < 0.05) the EC50 for GnRH dose-dependently without affecting the maximum LH secretory response. Cells were next stimulated with 1-min pulses of 2.5 nM GnRH every hour for 9 h in the absence or presence of 10 nM PACAP38, which was perifused continuously. The amplitude of GnRH-induced LH, FSH, and alpha-subunit secretory episodes from PACAP38-treated cells rose (P < 0.01) gradually to 233 +/- 54%, 197 +/- 44%, and 378 +/- 104%, respectively (mean +/- SEM; n = 5 experiments), of the value for control cells lacking PACAP38. This enhancement was sustained for at least 3 h after PACAP38 was removed from the perifusion medium. With PACAP treatment, interpulse secretion of LH and alpha-subunit increased gradually (P < 0.01) to 174 +/- 21% and 212 +/- 64% of the value for chambers stimulated with GnRH alone (control), respectively, whereas interpulse secretion of FSH declined (P < 0.001) to 75 +/- 7% of the control value. In contrast to the gradual effect of PACAP38 to enhance GnRH-induced hormone secretion, PACAP38 alone produced a transient burst of gonadotropin secretion. At the completion of the perifusions, total RNA was extracted and gonadotropin subunit mRNA levels were determined by Northern analysis. GnRH increased (P < 0.01) FSH beta mRNA to 438 +/- 52% of the level in cells stimulated with medium alone (control). Adding PACAP38 to the perifusion medium partially blocked (P < 0.01) the effect of GnRH (178 +/- 20% of the control value), and PACAP38 alone reduced (P < 0.01) FSH beta mRNA levels to 31 +/- 3% of the control value. By contrast, alpha-subunit mRNA levels were increased by both PACAP38 (143 +/- 4% of the control value; P < 0.01) and GnRH (121 +/- 2% of the control value; P < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effects of pituitary adenylate cyclase-activating polypeptide on gonadotropin secretion and subunit messenger ribonucleic acids in perifused rat pituitary cells. 791 30

We studied the healing response of a devitalized anterior cruciate ligament to a treatment of initial anterior-posterior joint translation in goats. Devitalization and devascularization were achieved by five successive freeze-thaw cycles. Anterior-posterior translation was surgically altered by an osteotomy of the tibial attachment of the devitalized ligament and its reattachment either in the anatomical position or in a position 5 mm posterior. Six weeks after the first surgery, the same procedure was performed on the contralateral limb, except that the ligament was reattached in the alternate position. Six months after the initial surgery, femur-anterior cruciate ligament-tibia specimens were tested to determine their structural and mechanical material properties. Anatomic ligament placement resulted in reduced anterior-posterior translation (p < 0.05) and greater anterior joint stiffness (p < 0.05). Maximum load (p < 0.05) and ligament stiffness (p < 0.01) also were greater for the anatomically placed anterior cruciate ligaments. The maximum load for anatomically placed ligaments averaged 1.625 +/- 211 N (SEM). The strength of the posteriorly placed anterior cruciate ligament, 895 +/- 164 N was similar to results of historical anterior cruciate autograft reconstructions. Ligament failure occurred near the tibial insertion in the posteriorly placed ligaments more often than in the anatomically placed ligaments (four of five times compared with one of five times). Ligament failure near the tibial insertion occurred with lower mean maximum load than failure at the midsubstance or by bone avulsion (796 compared with 1.592 N: p < 0.05). These data support the hypothesis that ligament laxity is important to the healing and remodeling of anterior cruciate ligament grafts.
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PMID:Effect of tibial attachment location on the healing of the anterior cruciate ligament freeze model. 876 61

The purpose of this study was to determine whether there are changes in anterior and posterior glenohumeral translation after arthroscopic, nonablative, thermal capsuloplasty with a laser. Two anteriorly and two posteriorly directed loads were sequentially applied to the humerus of nine cadaveric glenohumeral joints, and anterior and posterior translation of the humerus on the glenoid was measured. The glenoid was rigidly fixed, and the glenohumeral joint was positioned simulating 90 degrees of shoulder abduction and 90 degrees of external rotation. Using the holmium:yttrium-aluminum-garnet laser, thermal energy was then applied to the anterior capsuloligamentous structures and anterior and posterior translation measurements were then repeated. The results showed a significant reduction in anterior and posterior translation after laser anterior capsuloplasty. Anterior translation decreased from 10.9 +/- 2.0 mm (mean +/- SEM) to 6.4 +/- 1.5 mm with the 15-N load; and from 13.4 +/- 2.1 mm to 8.9 +/- 1.8 mm with the 20-N load. Posterior translation decreased from 7.2 +/- 1.2 mm to 4.4 +/- 0.6 mm with the 15-N load and from 10.4 +/- 1.4 mm to 6.5 +/- 0.9 mm with the 20-N load. These results indicate that the holmium:yttrium-aluminum-garnet laser can be used to decrease glenohumeral joint translation and may be an effective treatment for glenohumeral joint instability.
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PMID:Glenohumeral joint translation after arthroscopic, nonablative, thermal capsuloplasty with a laser. 968 66


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