Longitudinal, lateral, vertical and temporal thermal heterogeneity in a large impounded river: implications for cold-water refuges.

Dam operations can affect mixing of the water column thereby influencing thermal heterogeneity spatially and temporally. This occurs by restricting or eliminating connectivity in longitudinal, lateral, vertical and temporal dimensions. We examined thermal heterogeneity across space and time and identified potential cold-water refuges for salmonids in a large impounded river in inland northwestern USA. To describe these patterns, we used thermal infrared (TIR) imagery, in situ thermographs, and high-resolution 3-D hydraulic mapping. We explained the median water temperature and probability of occurrence of cool-water areas using generalized additive models (GAMs) at reach and sub-catchment scales, and we evaluated potential cold-water refuge occurrence in relation to these patterns. We demonstrated that (1) lateral contributions from tributaries dominated thermal heterogeneity; (2) thermal variability at confluences was approximately an order of magnitude greater than of the main stem; (3) potential cold-water refuges were mostly found at confluences; and (4) the probability of occurrence of cool areas and median water temperature were associated with channel geomorphology and distance from dam. These findings highlight the importance of using multiple approaches to describe thermal heterogeneity in large impounded rivers and the need to incorporate these types of rivers in the understanding of thermal riverscapes because of their limited representation in the literature.

Esophageal dysmotility and acid sensitivity in patients with mitral valve prolapse and chest pain.

Mitral valve prolapse (MVP) patients often experience non-cardiac chest pain. The aims of this study were to determine, in patients with non-cardiac chest pain: (i) whether esophageal dysmotility is more common in patients with MVP than in patients without MVP; and (ii) if acid sensitivity is an important cause of the chest pain in MVP patients. Esophageal manometry and acid perfusion testing were performed in 277 consecutive patients with non-cardiac chest pain. Patients with MVP (13 female, one male; mean age 49 years) were more likely (P = 0.01) to have esophageal dysmotility, while acid perfusion was less likely (P < 0.05) to provoke their chest pain, than in patients without MVP. The most common esophageal motor abnormalities detected in patients with and without MVP were diffuse esophageal spasm (prevalence, 57%) and non-specific motor disorder (prevalence, 9%), respectively. This study, the first large prospective series examining possible esophageal sensorimotor correlates of chest pain in MVP patients, demonstrates that in the absence of a cardiac cause for chest pain, a specific esophageal motility disorder should be excluded, rather than assuming the chest pain is likely to be due to acid sensitivity.

Localization of agonist- and antagonist-binding domains of human corticotropin-releasing factor receptors.

The CRF receptors, CRFR1 and CRFR2, are members of the G protein-coupled receptor superfamily. Despite their considerable sequence similarity, CRFR1 and CRFR2 have quite different affinities for the peptide ligand rat/human CRF. Previous studies using chimeric receptors between human CRFR1 and CRFR2 have identified three potentially important regions in the second and third extracellular domains of CRF receptor for the binding of rat/human CRF. The present report further demonstrates that these same three regions also affect the binding of urocortin and sauvagine, two other members of the CRF peptide family, albeit to different extents. We also show that a fourth region in the third extracellular domain, Asp254, has been identified to be important for sauvagine but not CRF or urocortin binding. Thus, the three peptide ligands not only interact with a different set of regions on CRFR1 and CRFR2 but also differentially interact with some of the same regions. These data could, at least in part, account for the much higher affinity of CRFR2 for urocortin and sauvagine compared with rat/human CRF. We have also identified two amino acid residues, His199 in the third transmembrane domain and Met276 in the fifth transmembrane domain, that are important for binding the non-peptide high-affinity CRFR1 antagonist NBI 27914. Mutations of His199 and Met276 to the corresponding amino acids in CRFR2 each decreased the binding affinity of NBI 27914 for CRFR1 by 40- and 200-fold, respectively. This suggests that the transmembrane regions are critically important in forming the binding pocket for the nonpeptide antagonist.

Corticotropin-releasing factor-binding protein ligand inhibitor blunts excessive weight gain in genetically obese Zucker rats and rats during nicotine withdrawal.

Elevation of the neuropeptide corticotropin-releasing factor (CRF) in the brain is associated with a reduction of food intake and body weight gain in normal and obese animals. A protein that binds CRF and the related peptide, urocortin, with high affinity, CRF-binding protein (CRF-BP), may play a role in energy homeostasis by inactivating members of this peptide family in ingestive and metabolic regulatory brain regions. Intracerebroventricular administration in rats of the high-affinity CRF-BP ligand inhibitor, rat/human CRF (6-33), which dissociates CRF or urocortin from CRF-BP and increases endogenous brain levels of "free" CRF or urocortin significantly blunted exaggerated weight gain in Zucker obese subjects and in animals withdrawn from chronic nicotine. Chronic administration of CRF suppressed weight gain nonselectively by 60% in both Zucker obese and lean control rats, whereas CRF-BP ligand inhibitor treatment significantly reduced weight gain in obese subjects, without altering weight gain in lean control subjects. Nicotine abstinent subjects, but not nicotine-naive controls, experienced a 35% appetite suppression and a 25% weight gain reduction following acute and chronic administration, respectively, of CRF-BP ligand inhibitor. In marked contrast to the effects of a CRF-receptor agonist, the CRF-BP ligand inhibitor did not stimulate adrenocorticotropic hormone secretion or elevate heart rate and blood pressure. These results provide support for the hypothesis that the CRF-BP may function within the brain to limit selected actions of CRF and/or urocortin. Furthermore, CRF-BP may represent a novel and functionally selective target for the symptomatic treatment of excessive weight gain associated with obesity of multiple etiology.

Ethanol self-administration restores withdrawal-associated deficiencies in accumbal dopamine and 5-hydroxytryptamine release in dependent rats.

Basal forebrain dopamine (DA) and 5-HT neurotransmission has been implicated in the mediation of the acute reinforcing actions of ethanol. Neuroadaptation theories predict that compensatory changes in neurochemical systems that are activated by alcohol acutely may underlie symptoms of withdrawal after chronic administration. To test this hypothesis, the release of DA and 5-HT was monitored by microdialysis in the nucleus accumbens of dependent male Wistar rats at the end of a 3-5 week ethanol (8.7% w/v) liquid diet regimen, during 8 hr of withdrawal, and during renewed availability of ethanol involving (1) the opportunity to operantly self-administer ethanol (10% w/v) for 60 min, followed by (2) unlimited access to the ethanol-liquid diet. Results were compared to control groups pair-fed with ethanol-free liquid diet and trained to self-administer either ethanol or water. In nondependent rats, operant ethanol self-administration increased both DA and 5-HT release in the NAC. Withdrawal from the chronic ethanol diet produced a progressive suppression in the release of these transmitters over the 8 hr withdrawal period. Self-administration of ethanol reinstated and maintained DA release at prewithdrawal levels but failed to completely restore 5-HT efflux. 5-HT levels recovered rapidly, however, within 1 hr of reexposure to ethanol liquid diet. These findings suggest that deficits in accumbal monoamine release may contribute to the negative affective consequences ethanol withdrawal and, thereby, motivate ethanol-seeking behavior in dependent subjects.

Increase of extracellular corticotropin-releasing factor-like immunoreactivity levels in the amygdala of awake rats during restraint stress and ethanol withdrawal as measured by microdialysis.

Previous research has suggested a role for corticotropin-releasing factor (CRF) in the anxiogenic effects of stressful stimuli and ethanol withdrawal. This hypothesis was explored in a series of experiments using intracranial microdialysis to monitor CRF-like immunoreactivity (CRF-IR) in the extracellular compartment of the rat amygdala. The synaptic origin of CRF-IR release in the amygdala was determined in vitro by assessing the Ca2+ dependency of 4-aminopyridine stimulated CRF-IR release from tissue preparations of rat amygdala. In vivo experiments were performed in awake rats after the placement of microdialysis probes in the amygdala. In the first experiment, transient restraint stress (20 min) produced an increase of CRF-IR release (basal levels, 1.19 +/- 0.15 fmol/50 microliters; stress levels, 4.54 +/- 1.33 fmol/50 microliters; p < 0.05) that returned to basal values within 1 hr. When 4-aminopyridine (5 mM) was added to the perfusion medium, it consistently increased CRF-IR release (4.83 +/- 0.92 fmol/50 microliters, p < 0.05). In the second experiment, CRF-IR release was measured during ethanol withdrawal in rats previously maintained for 2-3 weeks on a liquid diet containing ethanol (8.5%). Basal CRF-IR levels were 2.10 +/- 0.43 fmol/50 microliters in ethanol exposed rats and 1.30 +/- 0.19 fmol/50 microliters in control rats. During withdrawal, a progressive increase of CRF-IR levels over time was observed, reaching peak values at 10-12 hr after the onset of withdrawal (10.65 +/- 0.49 fmol/50 microliters vs 1.15 +/- 0.30 fmol/50 microliters of control rats, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive value of symptom profiles in patients with suspected oesophageal dysmotility.

The main aim of the study was to determine prospectively, in patients referred for oesophageal manometry, whether certain combinations of oesophageal symptoms are more likely than others to predict the presence of oesophageal dysmotility or a positive response to acid perfusion testing. In 524 consecutive patients, presenting predominantly with (non-cardiac) chest pain (n = 277), dysphagia (n = 186), or heartburn (n = 61), a standardized symptom assessment was completed before oesophageal manometry and acid perfusion testing. Half the patients in each group reported additional ('secondary') oesophageal symptoms as well as the predominant symptom. Oesophageal dysmotility was categorized in accordance with standard manometric criteria for achalasia, diffuse oesophageal spasm, nutcracker oesophagus, hypertensive lower oesophageal sphincter, or non-specific oesophageal motility disorder. In the predominant chest pain group, the prevalence of abnormal manometry was 33%; in the presence of secondary symptoms, especially dysphagia rather than heartburn, however, the prevalence was significantly (p < 0.01) increased. Also in the predominant chest pain group the prevalence of positive acid perfusion testing (44%) was significantly greater (p < 0.05) in those with than in those without secondary symptoms. In the predominant dysphagia group, the prevalence of abnormal manometry was higher than in the other two groups (56%; p < 0.001) but was not affected by the presence or absence of secondary symptoms; this latter finding was also true for the predominant heartburn group. The distribution of specific manometric disorders in any group was not related to the presence or type of secondary symptoms, although a combination of dysphagia and chest pain discriminated achalasia from other manometric disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

Psychological symptom profiles in patients with chest pain.

Five-hundred and thirty-two patients with ischaemic-like chest pain referred for symptom-limited exercise thallium myocardial perfusion studies, were assessed on a range of psychosocial measures. Three groups of patients were identified on the basis of their perfusion studies: (1) normal thallium perfusion; (2) current myocardial ischaemia; and (3) past myocardial infarction (but no current ischaemia). There were no significant psychological differences between these groups on a wide range of measures which included depression, state and trait anxiety, Type A behaviour, personality, suppression of affect, locus of control, alexythymia, and hypochondriasis. Significant differences were identified, however, on measures of anger and coping style. Subjects with no current ischaemia (normal thallium perfusion and those with past myocardial infarction) had higher scores on 'immature coping' and 'anger in', than subjects with current myocardial ischaemia. These findings are discussed in the light of other published research.

Oral alcohol self-administration stimulates dopamine release in the rat nucleus accumbens: genetic and motivational determinants.

Dopaminergic neurotransmission in the nucleus accumbens may be an important factor in ethanol reinforcement and genetically determined ethanol preference. This hypothesis was tested by measuring dopamine (DA) release by intracranial microdialysis during voluntary oral ethanol self-administration in alcohol-preferring (P) and genetically heterogeneous Wistar rats. The animals were trained to respond for ethanol (10% w/v) or water in a free-choice operant task. Extracellular DA levels in the nucleus accumbens were subsequently monitored during 30-min self-administration sessions and a 15-min "waiting period" before session onset. Ethanol self-administration in all animals was followed by a significant, dose-dependent rise in DA release with maximal effects at approximately 15 min after peak intake. Dose-effect functions revealed significantly steeper slopes for the DA-releasing effects of ethanol in P than in genetically heterogeneous Wistar rats. Over an identical range of ethanol doses and blood alcohol levels, increases in DA efflux ranged from 143% to 459% of basal levels in P rats but only from 142% to 212% in Wistar rats. To differentiate the pharmacological effects of ethanol from the effects of operant responding, additional groups of P and Wistar rats were tested during self-administration of saccharin (0.05% w/v). By contrast with ethanol, saccharin did not substantially elevate extracellular DA levels. A significant, transient increase in DA efflux was, however, observed in both strains of rats during the presession waiting period in the absence of ethanol or saccharin availability.(ABSTRACT TRUNCATED AT 250 WORDS)

High intracerebral levels of CRH result in CRH receptor downregulation in the amygdala and neuroimmune desensitization.

Corticotropin-releasing hormone (CRH) acts at the pituitary level to increase ACTH secretion and, within the central nervous system, to stimulate the sympathoadrenomedullary axis and behavioral activity. In addition, the central administration of CRH has been reported to reduce cellular immunity in the periphery. This study investigated the temporal relationship between CRH receptor regulation and the changes in splenic natural killer (NK) cell and pituitary-adrenocortical hormone responses to a single intracisternal (IC) CRH challenge (acute CRH) 24 h after chronic CRH pretreatment (5 nmol/day IC CRH for 4 days). Chronic CRH significantly decreased by 44.2 +/- 7.8% (P < 0.01) the CRH receptor concentration (beta max) in the amygdala. In contrast, the CRH receptor concentration of the anterior pituitary in the chronic CRH group was similar to the pituitary CRH receptor concentration in chronic saline controls. The immunoreactive-CRH concentration of the amygdala measured 24 h after the last IC CRH injection was not different from brain CRH levels in controls receiving chronic saline pretreatment. Consequently, the downregulation of amygdala CRH receptors occurred after transient increases in intracerebral CRH levels and did not result from ex vivo receptor occupancy by residual exogenous CRH sequestrated in brain tissue at the time of the CRH binding assay. Pretreatment with chronic CRH completely abolished the ability of a central CRH injection to suppress splenic NK activity; whereas, pituitary-adrenal responses to a superimposed acute CRH challenge were not significantly altered by chronic CRH pretreatment. These results suggest that the desensitization of the brain processes mediating CRH-induced suppression of splenic NK cytotoxicity is temporally correlated with CRH receptor downregulation in the amygdala but independent of pituitary-adrenal activation. These findings represent the first in vivo demonstration of homologous downregulation of extrahypothalamic CRH receptors and provide further evidence for the role of central CRH in the modulation of immune function.

Pituitary-adrenal axis responses to acute amphetamine in the rat.

After acute administration of amphetamine (AMPH), a characteristic behavioral response occurs in the rat, involving increased locomotion and stereotyped licking, grooming, and biting. AMPH administration also activates several neuroendocrine systems, including the pituitary-adrenal axis. Because recent evidence has supported a role for glucocorticoids in modulating the behavioral response to AMPH, the purpose of the present study was to examine the relationship between behavioral and hypothalamic-pituitary-adrenal (HPA) responses to AMPH and determine the physiological substrates responsible for the AMPH-induced release of adrenal steroids. AMPH administration produced the often-reported "inverted-U" shaped behavioral response. Specifically, locomotion was increased by low doses (0.5-1.0 mg/kg, SC) significantly more so than by the highest dose (5.0 mg/kg, SC), which instead elicited intense focused stereotyped movements. Plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone were increased by AMPH in a monotonic dose-response function, with highest levels measured in rats exhibiting the most intense stereotyped behaviors. Plasma ACTH levels then declined 10-30 min after AMPH administration, while AMPH-induced locomotion and stereotyped behavior persisted well beyond this period. In a parallel study, AMPH failed to elevate plasma levels of vasopressin, an important ACTH secretagogue, and AMPH reduced levels of corticotropin-releasing factor (CRF) immunoreactivity in the median eminence, providing indirect evidence of CRF release from this region. AMPH-stimulated ACTH and corticosterone release were prevented by immunoneutralization of CRF.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional gastrointestinal disorders in unselected patients with non-cardiac chest pain.

Patients with non-cardiac chest pain (NCCP) (n = 387) and cardiac chest pain (CCP) (n = 93) were compared with community controls (n = 81), using a symptom questionnaire that assessed the presence of irritable bowel syndrome (IBS), functional dyspepsia, and oesophageal dysfunction and chest pain characteristics. A significantly (p < 0.05) increased prevalence of symptoms compatible with IBS occurred in NCCP patients when compared with those with CCP and with controls. Dysphagia was more frequent in both those with non-cardiac and cardiac chest pain than in controls; this was not apparent, however, when patients with concomitant IBS were excluded. The presence of oesophageal or gastrointestinal symptoms did not enable discrimination with regard to the chest pain characteristics. We conclude that unselected referred patients with documented NCCP are more likely to have IBS and that the presence of oesophageal symptoms such as dysphagia may merely reflect the spectrum of the 'irritable gut'.

Increases in extracellular dopamine in the nucleus accumbens by cocaine are inversely related to basal levels: effects of acute and repeated administration.

Repeated administration of cocaine enhances several of the behavioral and neurochemical responses to subsequent cocaine injections, an effect that has been attributed, in part, to decreased somatodendritic autoreceptor sensitivity of mesocorticolimbic dopamine (DA) neurons. Such changes in autoregulation may not only modify the direct effects of cocaine on extracellular DA levels but also result in tonically increased basal DA release in the terminal areas of the mesocorticolimbic DA system. The present study was therefore designed to investigate the effects of repeated cocaine administration on basal extracellular DA concentrations in the nucleus accumbens (NAC) using in vivo microdialysis procedures in halothane-anesthetized rats. We subsequently examined the relationship between basal DA levels and the increase in extracellular DA produced by an acute injection of cocaine, and determined whether this relationship was altered by prior, repeated exposure to cocaine. Rats received one daily intraperitoneal injection of cocaine (30 mg/kg) or its vehicle (saline) for 10 consecutive days. On days 1, 3, or 7 after termination of the repeated cocaine treatment, extracellular DA levels in the NAC were determined under basal conditions and following a single intraperitoneal cocaine challenge injection (10 mg/kg) in separate groups of rats. Repeated cocaine administration produced a substantial increase in basal DA release in the NAC that was most prominent on day 1 post-cocaine (mean +/- SEM: 10.7 +/- 2.55 nM vs 3.55 +/- 0.56 nM) but was no longer apparent on day 7 post-cocaine. Higher extracellular DA levels were also observed after cocaine challenge in rats that received repeated cocaine treatments. Similar to the increase in basal release, this effect was most pronounced on day 1 post-cocaine (23.6 +/- 4.36 nM vs 12.61 +/- 1.76 nM) but did not persist through day 7 post-cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)

Basal extracellular dopamine levels in the nucleus accumbens are decreased during cocaine withdrawal after unlimited-access self-administration.

The effects of withdrawal from cocaine on extracellular dopamine (DA) levels in the nucleus accumbens (NAC) were examined by intracranial microdialysis in awake rats after periods (9.5-21.75 h) of unlimited-access, intravenous cocaine self-administration. Cocaine withdrawal was associated with significant reductions in basal DA overflow that persisted up to 12 h. Maximal inhibition of DA release (mean +/- S.E.M. 66.15 +/- 3.30 percent of basal levels) was observed between 4-6 h after cessation of cocaine intake and was positively correlated (r = 0.88) with the duration of the preceding self-administration episode. The results suggest that suppression of basal DA release in the NAC is an adaptive consequence of sustained cocaine exposure and may in part underlie the post-cocaine anhedonia observed in behavioral models of cocaine withdrawal.

CRF receptor regulation and sensitization of ACTH responses to acute ether stress during chronic intermittent immobilization stress.

The relationship between corticotropin releasing factor (CRF) receptors and pituitary-adrenal responses was determined after chronic intermittent immobilization (2.5 h restraint/day) to examine the hypothesis that CRF receptor regulation is involved in the sensitization of the pituitary-adrenocortical axis to novel stimuli during repeated stress. Following the 11-fold stimulation of ACTH secretion on the first day of restraint stress, a desensitization of the pituitary ACTH response to immobilization was observed over the next 9 days of chronic intermittent stress. In contrast, the magnitude of the restraint-stimulated release of corticosterone on the 2nd and 4th day of stress was similar to the day 1 adrenocortical response. Furthermore, the significant stimulation of corticosterone secretion by restraint stress persisted to the 16th day of immobilization (P less than 0.001), even though significant increases in plasma ACTH were absent. The concentration of anterior pituitary CRF receptors was unchanged after a single period of restraint; however, a down-regulation of anterior pituitary CRF receptors was observed following 4 days (P less than 0.001) and 10 days (P less than 0.005) of repeated immobilization stress. CRF receptors in the olfactory bulb were unchanged following acute or chronic restraint stress, consistent with previous observations that brain CRF receptors are neither changed by adrenalectomy, glucocorticoid administration, nor 18-48 h of continuous restraint stress. The concentration of CRF receptors in the intermediate lobe of the pituitary also was not influenced by immobilization stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoids and 1,25-dihydroxyvitamin D3 regulate parathyroid hormone stimulation of adenosine 3',5'-monophosphate-dependent protein kinase in rat osteosarcoma cells.

Glucocorticoids increase and 1,25-dihydoxyvitamin D3 [1,25-(OH)2D3] decreases the activity of PTH-responsive adenylate cyclase, altering intracellular cAMP in a rat osteoblast-like cell line (ROS 17/2.8). This study was undertaken to measure the subsequent activation of the cAMP-dependent protein kinase (PKA). Pretreatment of ROS cells for 2 days with the glucocorticoid triamcinolone acetonide (TRM), shifted the dose-response curve for PKA activation by PTH upward compared to the control value. Basal PKA activity was enhanced 50% by TRM, and the PTH concentration required for maximal activation of PKA decreased from 1.0 to 0.05 ng/ml. At the lowest effective PTH concentration (0.05 ng/ml) the mean PKA activity ratio increased to 0.73 in TRM-treated cells compared with 0.45 in untreated cells. Pretreatment with 1,25-(OH)2D3 had opposite effects, shifting the dose-response curve for PKA activation by PTH downward and to the right, decreasing the basal activity ratio from 0.26 to 0.16, and increasing the PTH concentration required for maximal activation to 10 ng/ml. 1,25-(OH)2D3-treated cells stimulated with 0.5-1 ng/ml PTH consistently had lower PKA activity ratios than untreated cells. Simultaneous treatment with 1,25-(OH)2D3 reversed the effect of TRM. There were no differences in total PKA activity (2.57 +/- 0.09 pmol 32P/min.micrograms protein) between treatment groups, suggesting that TRM and 1,25-(OH)2D3 do not alter the cellular PKA concentration. In control experiments exogenous PKA was added to sonication buffer of PTH-stimulated cells to verify that the TRM and 1,25-(OH)2D3 shifts in PKA activation at low PTH doses occur before sonication. cAMP-dependent protein kinase activation was also studied by measuring the progressive occupation of regulatory subunit-binding sites by hormonally stimulated endogenous cAMP. [3H] cAMP binding was expressed as the percent change in bound [3H]cAMP per microgram protein compared to that in unstimulated cells not steroid treated. [3H]cAMP binding to all cytosol fractions decreased as PTH increased over the concentration range predicted by our PKA activation experiments. TRM treatment shifted the curve for [3H]cAMP binding to regulatory subunit downward and to the left, and 1,25-(OH)2D3 treatment shifted it upward and to the right. In cells treated with both TRM and 1,25-(OH)2D3, the curve was similar to control curve. Sonicating unstimulated cells in buffer containing comparable concentrations of added cAMP did not alter [3H]cAMP binding. These and the previous controls suggest that changes in PKA activation at low doses of PKA reflect cellular events occurring before cell disruption.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth of rat osteoblast-like cells in a lipid-enriched culture medium and regulation of function by parathyroid hormone and 1,25-dihydroxyvitamin D.

To examine the role of lipid metabolism in the growth and function of osteoblast-like cells, we studied ROS 17/2.8 osteosarcoma cells and primary cultures of rat calvarial osteoblasts during growth in a serum-free medium supplemented by purified human lipoproteins or by liposomes. Increase in ROS cell number was measured in sparse (1-5 X 10(3)/cm2) cultures over 6-8 days. Liposomes (0-300 micrograms/ml) and high (HDL), low (LDL), and very low density (VLDL) lipoprotein fractions (0-300 micrograms apoprotein) markedly stimulated cell growth. Cells plated at 5 X 10(3)/cm2 achieved growth rates in the presence of LDL or HDL comparable to 10% fetal bovine serum. Serum-free culture with exogenous lipid maintained the response of cell cyclic AMP accumulation to parathyroid hormone. Cyclic AMP response to parathyroid hormone was enhanced by glucocorticosteroid, and was attenuated by 1,25-dihydroxyvitamin D (1,25(OH)2D) with an EC50 (10(-10) M) comparable to that previously observed in serum-cultured cells (J. Biol. Chem. 258:736, 1985). 1,25(OH)2D also increased the alkaline phosphatase activity in ROS cells cultured in lipid-supplemented serum-free culture. Lipoproteins or liposomes also markedly enhanced the proliferative response of sparse cultures of normal rat osteoblasts to polypeptide mitogens.

Corticotropin-releasing factor receptors and pituitary adrenal responses during immobilization stress.

The regulation of pituitary and brain CRF receptors and corticotroph responses during stress were studied in rats subjected to prolonged immobilization. Plasma ACTH levels showed the characteristic biphasic changes, with a rapid 23-fold increase in 15 min, followed by a decrease to about twice the basal levels after 6-h immobilization. In contrast, plasma corticosterone levels were markedly elevated throughout the duration of the stress. Pituitary CRF receptor content, measured by binding of [125I]Tyr-ovine CRF to pituitary membrane-rich fractions, was unchanged after 2.5 h, but was reduced by 28 +/- 2.7% (+/- SE) and 47.6 +/- 1.1% after 18 and 48 h of immobilization, respectively. These results were confirmed by autoradiography in slide-mounted frozen pituitary sections. In contrast, no changes in CRF receptor content were observed in brain areas, including olfactory bulb, frontoparietal cortex, hippocampus, amygdala, and lateral septum. A concomitant decrease in immunoreactive (ir) CRF content in the median eminence of rats immobilized for 48 h is consistent with the hypothesis that increased release of CRF into the portal circulation occurs during chronic stress. Despite pituitary CRF receptor loss and reduced in vitro responses to CRF, the increases in plasma ACTH and corticosterone in vivo after ether exposure or CRF injection were greater and more prolonged in rats immobilized for 48 h than in nonimmobilized controls. The decrease in pituitary CRF receptors was accompanied by decreased CRF-stimulated cAMP and ACTH release in cultured pituitary cells from 48-h restrained rats. However, concomitant incubation of cells with CRF and vasopressin restored cAMP and ACTH responses to control levels, suggesting that the simultaneous release of both regulators from the hypothalamus determines the plasma ACTH level. These findings indicate that the decrease in plasma ACTH during the adaptation phase to stress is accompanied by decreases in pituitary CRF receptors. However, the enhanced pituitary response to a superimposed stress or CRF injection implies that the decrease in plasma ACTH levels during prolonged stress may be due to adaptive changes at the central level. These findings emphasize the importance of the integrated actions of CRF and other regulators in the control of the pituitary adrenal-axis during stress.

Surgery for recurrent peptic ulceration.

Sixty-six patients having surgery for recurrent peptic ulcers over a 10-year period are reviewed. The majority of the patients were male and developed their initial ulcers at an early age. Bleeding was the most common presenting symptom. Seventy-one percent of the recurrences occurred within three years. Barium meal X-ray examination plus endoscopy gave the correct diagnosis in 96% of cases. The causes of the recurrent peptic ulcers were: (1) incomplete vagotomy; (2) inadequate gastric resection; (3) inappropriate surgery; (4) Zollinger-Ellison syndrome; (5) gastric outflow obstruction; and (6) bile reflux. Other factors such as alcohol, analgesic abuse and psychiatric disorders were found to be common associations. Resection plus vagotomy was the summation of primary and secondary surgery in 85%. The operative mortality was 3%. Eighty-five percent of patients had a Visick grading of I or II. Only one patient had a further recurrent ulcer and this healed on medical treatment.

Selective vagotomy for duodenal ulcer: a five-year follow-up.

The results for the first 101 consecutive patients who had selective vagotomy and a drainage procedure performed for duodenal ulceration between 1967 and 1971 are presented. Seventy-four patients were followed up for five to nine years, 13 patients were lost to follow-up for part of the five-year period, and 14 patients died during follow-up. Six patients developed recurrent ulcers. Five of these recurrent ulcers were observed in patients in whom the vagotomy was not tested for completeness during the operation; this represents a recurrence rate of 10%. One patient, in whom testing was used at operation, developed a recurrent ulcer; this represents a recurrence rate of 2%. There was a statistically significant difference in the rate of recurrence between the group tested during operation and that not tested.