Coral diversity and disease in Mexico.

Field studies and empirical tests of the 'diversity-disease hypothesis' demonstrate the effects of species richness on disease transmission and severity in plant systems. Yet the converse, i.e. effects of disease on diversity, is rarely considered in either relatively well-studied plant systems or marine ecosystems. We investigated these effects along the Mexican Yucatan Peninsula to (1) quantify the relationship between disease prevalence and coral diversity, (2) test the hypothesis that octocoral and scleractinian disease prevalence are associated with one another, and (3) establish a long-term dataset. Aspergillosis of sea fans and 6 scleractinian diseases were documented. Prevalence of aspergillosis declined from 12.85% in 2002 to 5.26% in 2004, while prevalence of scleractinian diseases remained relatively constant at 5.7 +/- 0.8% in 2002 and 7.96 +/- 0.7% in 2004. Sites were relatively rich (71 species of octocoral and scleractinian corals) and even (E5 > 0.5). Sea fan disease prevalence was not associated with scleractinian disease prevalence, nor were there consistent associations between disease and measures of diversity. However, the most abundant octocoral and scleractinian species are susceptible to infection with several diseases, and disease may alter coral diversity in complex ways. These data represent the first in what will become a long-term dataset monitoring disease prevalence and associated changes in coral diversity.

Regulation of hypothalamic neuropeptide expression by peripheral metabolism.

The mechanisms of appetite and body-weight regulation by peripheral signals are highly complex in vertebrates and remain poorly understood. It is intuitively apparent that such regulation must involve interactions between peripheral metabolic status and the brain, but what are the signals recognized by the brain to initiate feeding? The hypothalamus has long been recognized as central in "recognition" of peripheral nutrient and metabolic signals (and, perhaps, body weight status) and in "regulation" of hunger and satiety responses and, therefore, is a logical site on which to focus research aimed at understanding interactions between and regulation of the periphery and central nervous system. Recent studies demonstrating modulation of hypothalamic neurotransmitter expression by peripheral metabolic status may yield insights into regulation of appetite and metabolism in obesity and aberrant metabolic homeostasis. This review concentrates on summarizing data regarding regulation of expression of neuropeptide Y and growth hormone-releasing hormone as model peptide systems for addressing questions relating peripheral metabolism and hypothalamic neuropeptide expression.

Covalent labeling of the somatostatin receptor in rat anterior pituitary membranes.

The molecular characteristics of the somatostatin (SRIF) receptor were investigated by covalently cross-linking [125I-Tyr11]SRIF to rat anterior pituitary membranes using three heterobifunctional cross-linking agents, N-5-azido-2-nitrobenzoyloxysuccinimide, N-hydroxysuccinimidyl-4-azidobenzoate, and N-succinimidyl-6-(4'-azido-2'-nitrophenylamino) hexanoate, and the homobifunctional agent disuccinimidyl suberate. Sodium dodecyl sulfate-gel electrophoresis followed by autoradiography revealed two SRIF-binding proteins with apparent mol wt (Mr) of 69,000 and 66,000 that were selectively labeled by the four cross-linking agents. When cross-linking was performed with N-5-azido-2-nitrobenzoyloxysuccinimide, both proteins migrated as a broad band centered at 68,000; however, with N-hydroxysuccinimidyl-4-azidobenzoate, the band was resolved into 69,000 and 66,000 Mr components. N-Succinimidyl-6-(4'-azido-2'-nitrophenylamino) hexanoate covalently labeled the 69,000 Mr protein and a minor species with a Mr of 45,000-47,000. Cross-linking with disuccinimidyl suberate labeled only the 66,000 Mr band. Labeling of both bands was specific, since affinity labeling with each of the four agents was abolished when 1 microM cyclic SRIF was included in the binding reaction. Binding of [125I-Tyr11]SRIF to membranes and labeling of the 69,000 and 66,000 Mr SRIF-binding species were similarly inhibited in a dose-dependent manner by unlabeled SRIF. Radiolabeling of both proteins was specifically displaced by 1 microM SRIF-28 and [D-Trp8,D-Cys14]SRIF, but not by oxytocin. Moreover, the extent of radiolabel incorporation into both components was dependent on the concentration of [125I-Tyr11]SRIF in the binding reaction. These results demonstrate the presence of two SRIF-binding proteins in rat anterior pituitary membranes that show characteristics of the SRIF receptor.

Regulation of rat hypothalamic preprogrowth hormone-releasing factor messenger ribonucleic acid by dietary protein.

To further evaluate nutrient regulation of GRF synthesis, we measured hypothalamic preproGRF messenger (m) RNA in food-deprived rats refed diets varying in nutrient composition by nuclease protection analysis. Adult male Sprague-Dawley rats were allowed free access to food (Fed), food deprived for 72 h (72-h FD), or 72 h FD then refed for 72 h with either a normal (NF) diet or isocaloric diets containing no protein (PF), carbohydrate (CF), or fat (FF). Seventy-two-hour FD rats displayed the expected 80% reduction in hypothalamic preproGRF mRNA. Upon refeeding, levels were normalized in rats refed NF, CF, or FF diets. In contrast, preproGRF mRNA in rats refed a PF diet was similar to that in 72-h FD rats. Rats refed a PF diet failed to gain weight and consumed less food than animals refed NF, CF, or FF diets. However, the lack of the GRF response to the PF diet was due to protein deprivation rather than caloric restriction, since hypothalamic preproGRF mRNA returned to 66% of Fed values in rats refed an equivalent amount (grams per day) of a NF diet. In 72-h FD rats refed isocaloric diets containing 4%, 8%, or 12% protein, preproGRF mRNA was restored to Fed values in a protein concentration-dependent manner being completely restored by the 12% diet. A lack of dietary protein was sufficient to regulate hypothalamic preproGRF mRNA since feeding rats a PF diet without prior food deprivation resulted in 70% reduction in preproGRF mRNA, whereas CF and FF diets were without effect. These data indicate that decreased hypothalamic preproGRF mRNA expression in 72-h FD rats occurs as a result of dietary protein deprivation.

Dexamethasone regulates somatostatin receptor subtype messenger ribonucleic acid expression in rat pituitary GH4C1 cells.

Ligand binding studies have shown that glucocorticoids down-regulate somatostatin receptor (sst) concentration in several endocrine target cells and cell lines including GH4C1 cells. However, it has not been determined whether this decrease in sst number occurred via transcriptional and/or posttranscriptional events. In the present study, we have investigated the effect of dexamethasone (Dex) treatment (1 microM) of GH4C1 cells for up to 48 h on the steady state level of messenger RNA (mRNA) for sst1, sst2, and sst3, the predominant isoforms expressed in this cell line, by solution hybridization-nuclease protection analysis. Exposure of GH4C1 cells to Dex for 2 h increased sst1 mRNA levels 2.5-fold and sst2 1.5-fold compared with controls (Con). Prolonged exposure, however, resulted in a decrease in mRNA levels of sst1 to 50% and sst2 to 30% of Con by 24-48 h. In contrast, sst3 mRNA levels were unchanged at 2 h, decreased to 30% of Con by 6 h, and remained decreased for up to 24 h. Longer exposure resulted in a dramatic increase in expression, reaching 350% of Con by 48 h. The Dex effect on expression of all subtypes was dose dependent, maximal at 10 nM. Steroid hormone regulation of sst mRNA expression in GH4C1 cells proved to be complex. Exposure to Dex for 24 h, as expected, decreased expression of all subtypes. Progesterone, however, increased sst1 mRNA levels, decreased sst3 levels, but was without effect on sst2; treatment with estrogen and testosterone increased expression of all three subtypes. Nuclear run-on assays indicated that the Dex-induced changes in sst1 and sst2 mRNA levels were associated with congruent changes in the transcription rate of sst genes. Thus, glucocorticoids regulate sst expression in GH4C1 cells, at least in part, by controlling the rate of transcription of sst genes.

Tissue distribution of somatostatin receptor subtype messenger ribonucleic acid in the rat.

The tissue distribution of mRNA encoding five somatostatin receptor subtypes, SSTR1, SSTR2, SSTR3, SSTR4, and SSTR5, was determined in adult rat tissues by solution hybridization/nuclease protection analysis using sequence-specific cRNA probes. In the central nervous system, SSTR1 and SSTR2 mRNA were expressed widely, with highest levels in hippocampus, hypothalamus, cortex, and amygdala and expression of both isoforms in cerebellum and spinal cord. Expression of SSTR3 was also widespread, occurring in all brain regions examined, with the highest level of expression in the cerebellum. SSTR4 mRNA was detected in most brain regions, with highest levels occurring in the hippocampus, cortex, and olfactory bulb. No detectable levels were found in cerebellum. SSTR5 showed a unique pattern of expression in the central nervous system, being found primarily in the hypothalamus and preoptic area. In peripheral tissues, high levels of SSTR1 and SSTR2 mRNA were found in pituitary and spleen. SSTR1 mRNA was also found in the heart and intestine, SSTR2 was detected in pancreas, and both isoforms were expressed in stomach. Expression of SSTR3 was noted in heart, liver, stomach, intestine, kidney, spleen, and pituitary. The patterns of expression were similar for SSTR4 and SSTR3 mRNA; however, SSTR4 was not expressed in liver. SSTR5 was expressed predominantly in the pituitary, but detectible levels were observed in spleen and intestine. Thus, the SSTR subtype mRNA showed both a tissue-specific and overlapping pattern of expression. Taken together with SSTR-specific signal transduction systems, this probably explains the diverse physiological actions of somatostatin.

Regulation of hypothalamic preprogrowth hormone-releasing factor messenger ribonucleic acid expression in food-deprived rats: a role for histaminergic neurotransmission.

To determine the component(s) of dietary protein that regulates GH-releasing factor (GRF) synthesis, we measured hypothalamic prepro-GRF mRNA by solution hybridization/nuclease protection analysis in food-deprived rats refed protein-free diets (PF) supplemented with individual amino acids. Adult male Sprague-Dawley rats were allowed free access to food (Fed), food deprived for 72 h (FD), or FD then refed for 72 h with a normal (NF) diet, a protein-free (PF) diet, or PF diets containing tyrosine, tryptophan (Trp), glutamic acid, or histidine (His). Food-deprived rats displayed the expected 80% reduction in hypothalamic prepro-GRF mRNA. Upon refeeding, levels were normalized in rats refed a normal diet, but not in those refed a PF diet alone or with tyrosine, Trp, or glutamic acid. In contrast, prepro-GRF mRNA was restored to 70% of Fed values by a PF diet with His. Supplementing a PF diet with His was sufficient to maintain hypothalamic prepro-GRF mRNA expression, as 3 days of feeding replete rats with PF diet or PF diet with added Trp resulted in a 50% reduction in prepro-GRF mRNA, whereas levels were reduced 25% by feeding animals a PF diet with His. Groups of rats allowed free access to food were treated for 72 h with two daily injections of 100 mg/kg alpha-fluoremethylhistidine, a specific irreversible inhibitor of histidine decarboxylase, to determine if the effect of His on prepro-GRF mRNA depended on neural conversion to histamine. alpha-Fluoremethylhistidine-treated rats showed a 40% reduction in hypothalamic prepro-GRF mRNA, with no concomitant change in preproneuropeptide-Y or preprosomatostatin. These data indicate that decreased hypothalamic prepro-GRF mRNA in FD rats is due in part to the lack of dietary and provide clear evidence for a role of the histaminergic neural system in the regulation of hypothalamic GRF expression.

Estrogen regulates somatostatin receptor subtype 2 messenger ribonucleic acid expression in human breast cancer cells.

Somatostatin (SRIF) and its analogs exhibit antiproliferative effects that are mediated by SRIF receptors (sst) present in responsive normal and neoplastic tissue including breast cancer. However, information regarding regulation of sst gene expression in cancer cells and modulation of SRIF binding is limited. In the present study we have determined the pattern of sst subtype messenger RNA (mRNA) expression in human breast cancer cells. Furthermore, we investigated the effect of 17beta-Estradiol (E2) treatment on steady state levels of sst mRNA by solution hybridization/nuclease protection analysis and on SRIF binding to membranes of treated cells by receptor binding assay. sst2 mRNA was highly expressed in T47D, ZR75-1, and MDA MB231 cells. Transcripts for sst1 were also detected at very low levels in ZR75-1 cells, whereas sst5 mRNA was expressed at low levels in MCF-7 cells. No sst subtype was detected in MDA MB 435s cells. When the estrogen receptor (ER)(+) cell lines T47D and ZR75-1 were cultured in phenol red-free media plus CS-FCS, sst2 mRNA levels decreased by 60-80% compared with complete serum controls. Adding E2 restored sst2 mRNA levels to control in both cell lines. Moreover, the effect of E2 on sst2 gene expression in T47D and ZR75-1 cells was dose- and time-dependent. In contrast, neither culturing in phenol red-free media plus CS-FCS nor E2 influenced sst2 expression in the ER(-) cell line MDA MB231. E2-induced regulation of SRIF binding and sst2 mRNA expression occurred in a parallel manner in T47D cells but were dissociated in ZR75-1 cells. The pure antiestrogen ICI 182 780 inhibited E2-induced sst2 expression in both cell lines. The antiestrogen 4OH tamoxifen showed strong estrogen-like effects on sst2 mRNA expression in T47D cells, while acting as a potent antiestrogen in ZR75-1 cells. Thus, these data suggest that E2 regulates sst2 expression in human breast cancer cell lines through the ER. The human breast cancer cell lines provide a useful model to examine the molecular mechanisms involved in E2 regulation of sst2 expression.

Pituitary and hypothalamic somatostatin receptor subtype messenger ribonucleic acid expression in the food-deprived and diabetic rat.

Prolonged food deprivation (FD) and streptozocin-induced diabetes (STZ diabetes) in the rat result in abolition of GH secretory episodes. We have previously shown that hypothalamic prepro-GRF messenger RNA (mRNA) expression is markedly reduced in the hypothalamus of FD and STZ diabetic rats, with no change in prepro-somatostatin (SRIF) mRNA and suggested that reduced GRF and increased SRIF tone explained the loss of GH secretion in FD and STZ diabetes. Altered SRIF peptide expression has been implicated in many physiological and pathological states; however, information on the regulation of SRIF receptor (SSTR) expression is lacking. Therefore, we examined the expression of mRNA for the five recently cloned SSTR subtypes in the pituitary and hypothalamus of FD and STZ diabetic rats. In addition, we measured SRIF binding to pituitary membranes of FD rats. SSTR1, SSTR2, and SSTR3 mRNA expression was reduced 80% in the pituitary of FD rats vs. fed controls, whereas pituitary levels of SSTR4 and SSTR5 mRNA were unaffected. The pituitary plasma membrane SSTR concentration was reduced over 50% in FD vs. fed animals. However, hypothalamic levels of the five isoforms were unchanged. In STZ diabetes, pituitary SSTR1, SSTR2, and SSTR3 mRNA expression was reduced 50-80%, with levels of SSTR1 partially restored by insulin, whereas SSTR4 mRNA was unchanged. In contrast to the effect of FD, SSTR5 mRNA levels were reduced 70% in the pituitary and 30% in the hypothalamus of STZ diabetic rats, with complete restoration by insulin. Thus, SSTR subtype mRNA expression is differentially regulated in two models of GH deficiency in the rat, FD and STZ diabetes. As chronic exposure to SRIF results in desensitization of transfected SSTR2 and SSTR3, and SSTR binding is decreased in FD and STZ diabetic rats, the possibility exists that the pituitary changes result from continued exposure to SRIF. In the hypothalamus, however, regulation appears more complex. These data support a role of increased SRIF with decreased GRF in mediating the loss of GH secretion in FD and diabetes.

Pituitary insulin-like growth factor-I content and gene expression in the streptozotocin-diabetic rat: evidence for tissue-specific regulation.

Insulinopenic diabetes mellitus in the rat is associated with reduced circulating levels of insulin-like growth factor-I (IGF-I), resulting primarily from decreased IGF-I synthesis in liver and extrahepatic sites. Plasma GH levels in these animals are also suppressed, with loss of episodic secretion and decreased pituitary synthesis. Intrapituitary IGF-I has been postulated to exert local autocrine/paracrine negative feedback regulation on GH synthesis and secretion. The present studies were designed to examine regulation of pituitary IGF-I peptide content and gene expression in insulinopenic streptozotocin (STZ)-diabetic rats compared to that in liver and testis. Serum IGF-I levels were reduced by 86% in STZ-diabetic rats together with reduction of IGF-I content in liver (53%) and testis (74%; all P less than 0.001 vs. control). Concomitantly, liver and testicular IGF-I mRNA levels were reduced by 90% (P less than 0.001 vs. control). Insulin treatment restored IGF-I peptide levels in serum, liver, and testis toward normal, with a partial but significant increase in liver IGF-I mRNA. In contrast, pituitary IFG-I peptide content increased by 69% in STZ-diabetic rats (P less than 0.001 vs. control), with no change in IGF-I gene expression. Insulin treatment completely reversed the rise of pituitary IGF-I peptide content. These results demonstrate a novel discordance in the regulation of IGF-I gene expression and peptide content between pituitary and other tissues in STZ-induced diabetic rats. Elevated IGF-I levels in the pituitaries of these animals may partly explain the suppressed GH synthesis and secretion seen in STZ-diabetic rats and provide further evidence for a potential autocrine or paracrine role of pituitary IGF-I in GH regulation.

Influence of food deprivation in the rat on hypothalamic expression of growth hormone-releasing factor and somatostatin.

Food deprivation in the rat is associated with a reduction in serum GH levels characterized by suppression of high amplitude GH bursts and a decrease in the duration of secretory episodes. The mechanism(s) mediating this response is unknown. The present studies were designed to evaluate the role of hypothalamic factors potentially responsible for abnormal GH dynamics in food-deprived rats by measuring hypothalamic prepro-GH-releasing factor (GRF) and preprosomatostatin (SRIF) mRNA and peptide levels in adult male Sprague-Dawley rats after 72 h of food deprivation or free access to food. Hypothalamic prepro-GRF mRNA was reduced 80% in food-deprived rats compared to that in fed controls (P less than 0.001), while GRF content was unchanged. Levels of prepro-SRIF mRNA in food-deprived rats were similar to those in controls, as was hypothalamic SRIF content. The time course of hypothalamic prepro-GRF mRNA reduction was determined in groups of rats food-deprived for 24, 48, or 72 h and revealed a significant (30%) reduction of prepro-GRF mRNA (P less than 0.05 vs. fed) by 24 h, with maximal reduction (80%) by 48 h. Refeeding groups of animals for up to 72 h after they had been food-deprived for 72 h resulted in restoration of prepro-GRF mRNA levels to 50% of control levels by 24 h (P less than 0.05 vs. fed) and a return to control values by 48 h. These data suggest that decreased GRF gene expression and possibly GRF release play a major role in the loss of pulsatile GH secretion seen in this model of nutrient deprivation.

Altered pituitary growth hormone (GH) regulation in streptozotocin-diabetic rats: a combined defect of hypothalamic somatostatin and GH-releasing factor.

Diabetes mellitus in the rat is associated with loss of pulsatile GH secretion. An interplay between hypothalamic GH-releasing factor (GRF) and inhibitory factor [somatostatin (SRIF)] secretion is thought to account for episodic pituitary GH release. An increase in SRIF tone/action or a decrease in GRF release/response in diabetic rats could account for the suppressed GH levels. Pituitaries from streptozotocin-diabetic rats contained less GH than controls (15.9 +/- 2.5 vs. 29.5 +/- 4.6 micrograms/mg; P less than 0.05) despite normal somatotrope representation, as demonstrated using immunofluorescence studies. Basal GH secretion from monolayer culture of dispersed anterior pituitary (AP) cells from diabetic rats was proportionately decreased (150 +/- 10 vs. 103 +/- 10 ng/10(5) cells; P less than 0.005). GRF (10(-11)-10(-8) M)-induced release of GH from AP cells was decreased in diabetic rats (maximum response to 10(-8) M GRF, 401 +/- 60 vs. 618 +/- 41 ng/10(5) cells; P less than 0.01); however, sensitivity to GRF was unchanged (EC50, 79 +/- 41 vs. 128 +/- 67 pM). By contrast, SRIF (10(-7)-10(-10)-induced inhibition of GRF (10(-8) M)-mediated GH release was impaired in AP cells of diabetic rats compared to that in controls (IC50, 112 +/- 33 vs. 55 +/- 31 pM; P less than 0.05) associated with a decrease in AP plasma membrane SRIF receptor concentration (63.4 +/- 15.6 vs. 160.3 +/- 13.7 fmol/mg protein; P less than 0.05), with no change in affinity. These findings are consistent with chronic exposure to increased hypothalamic SRIF influence. GH synthesis has been shown to be independent of SRIF regulation; however, insulin-like growth factor-I and GRF inhibit and stimulate GH synthesis, respectively. In diabetic rats insulin-like growth factor-I levels were decreased, appropriate to low GH status, in serum (290 +/- 66 vs. 1662 +/- 92 ng/ml; P less than 0.001) and hypothalamus (6.8 +/- 1.0 vs. 13.0 +/- 0.4 pg/mg wet wt; P less than 0.001) and, thus, did not seem to account for the low AP GH content. Hypothalamic GRF content in diabetic rats (1.11 +/- 0.10 ng/hypothalamus) did not differ from that in controls (1.16 +/- 0.17 ng/hypothalamus). GRF mRNA levels, however, were reduced by 80% in diabetic rats compared to controls. Taken together these data support a combined role for decreased hypothalamic GRF and increased SRIF in mediating alterations of GH synthesis and secretion in streptozotocin-induced diabetes.

Growth hormone-releasing factor expression is discordantly regulated in the hypothalamus and testis of streptozotocin-diabetic rats.

Growth hormone-releasing factor (GRF) mRNA expression in male rats occurs predominantly in the hypothalamus (mainly in the arcuate nucleus), and among extraneural sites primarily in the testis. Hypothalamic GRF is the physiological tropic stimulus to growth hormone secretion. However, the role of GRF in the testis is unknown. We have shown previously that hypothalamic GRF mRNA expression is significantly reduced in streptozotocin (STZ)-diabetic rats. This reduction is confined to the arcuate nucleus and probably accounts for the suppression of growth hormone pulsatility. The present studies were performed to evaluate GRF expression in the testis of streptozotocin (STZ)-diabetic rats. Diabetes was induced by injection of STZ (100 mg/kg i.p.). Seventeen to twenty days later diabetic rats were hyperglycemic compared with vehicle-injected controls and demonstrated growth failure. Insulin treatment reduced the glycemia and increased body weight towards normal. Total RNA was extracted from the hypothalamus and testis, and GRF mRNA levels estimated by solution hybridization/nuclease protection assay. Levels of hypothalamic somatostatin mRNA were measured to serve as control values. GRF mRNA was significantly (P < 0.001) decreased in the hypothalamus of STZ-diabetic rats (0.2 +/- 0.07 mean relative densitometric units, n = 8) compared with controls (1.0 +/- 0.19, n = 8) with no change in somatostatin mRNA expression. In contrast, testicular GRF mRNA was increased 70% (P < 0.05) in STZ-diabetic rats. Insulin treatment resulted in normalization of hypothalamic GRF mRNA levels (1.1 +/- 0.17, n = 5) with no effect on testicular GRF mRNA expression. In conclusion GRF gene expression is discordantly regulated in tissues of male STZ-diabetic rats. While reduced GRF expression may account for the low growth hormone state in this model, increased testicular GRF mRNA (with the previously reported reduction of insulin-like growth factor-I mRNA) resembles the response seen in growth hormone-sensitive tissue (especially the hypothalamus) to this growth hormone-deficient state.

Characterization of the promoter region of the human somatostatin receptor subtype 2 gene and localization of sequences required for estrogen-responsiveness.

Somatostatin receptor (sst) subtype 2 mRNA is potently regulated by 17beta-estradiol (E2) in a time and dose-dependent manner in the estrogen receptor (+) human breast cancer cell line T47D. To explore the mechanism involved in E2 regulated expression of sst2, we isolated and characterized a genomic clone containing over 5.3 kilobase pairs (kb) of the 5' flanking region of the human sst2 gene. The 5'-flanking region lacks both TATA and CCAAT boxes. Primer extension and RNAase protection analysis revealed the existence of two transcriptional start sites, located within an initiator-like sequence, 85 and 82 bp upstream of the translational initiation methionine. The 5.3-kb 5'-flanking region was an active promoter in T47D cells but was inactive in MDA MB 435s cells, a human breast cancer cell line that does not express sst2. Deletion analysis identified both positive and negative regulatory elements within the 5.3-kb fragment. Furthermore, transcriptional regulation by E2 was mediated by a distal 1.5-kb fragment located 3.8 kb from the transcriptional start sites. Determining the precise ERE will provide important insights into the complex regulation of sst2 expression in normal and neoplastic tissue.

Pituitary and hypothalamic insulin-like growth factor-I (IGF-I) and IGF-I receptor expression in food-deprived rats.

The present study was designed to evaluate a possible role for the insulin-like growth factor-I (IGF-I) system in mediating the suppression of growth hormone (GH) secretion observed in food-deprived rats by measuring IGF-I mRNA, receptor concentration and receptor mRNA in neuroendocrine tissues (hypothalamus and pituitary). Rats were deprived of food (food-deprived) for 72 h or had free access to food (fed). Tissues were processed for measurement of steady-state levels of: (a) IGF-I and IGF-I receptor mRNA (by solution hybridization/RNase protection assay); (b) IGF-I in serum and tissue extracts (by RIA) and (c) IGF-I displaceable [125I]IGF-I binding to plasma membrane preparations. Food deprivation resulted in decreased serum and liver levels of IGF-I. Kidney IGF-I mRNA levels were reduced 80% in food-deprived rats with a concomitant increase in IGF-I receptor concentration and mRNA levels. Refeeding of food-deprived rats fully normalized these perturbations. Pituitary IGF-I content was reduced 50% in food-deprived rats while IGF-I mRNA levels were unaffected. A modest increase was seen in pituitary IGF-I receptor concentration; however, IGF-I receptor mRNA levels were not changed. Hypothalamic IGF-I mRNA content was reduced in 72 h food-deprived rats while IGF-I receptor binding capacity and mRNA were unaffected. In conclusion, IGF-I mRNA levels are decreased in liver, kidney and hypothalamus together with a reduction in plasma IGF-I in food-deprived rats but is unaffected in anterior pituitary. IGF-I receptor gene expression and binding capacity are coordinately regulated in kidney and hypothalamus, but not in the pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

Intensity and duration effects of exercise on heart cAMP, phosphorylase, and glycogen.

Glycogen, phosphorylase, and adenosine 3',5'-cyclic monophosphate (cAMP) were determined in rat heart following an acute exercise bout. Intensity and duration of exercise were varied to gain further insights into the mechanism regulating myocardial glycogenolysis during exercise. Groups of rats were run at either 15 or 30 m/min for 0, 5, 10, 15, or 30 min and immediately killed. Heart glycogen degradation was influenced by intensity and duration of exercise and was independent of cAMP levels and activation of phosphorylase to its a form. cAMP levels were increased in the heart, dependent on intensity and duration of exercise. Phosphorylase in the a form increased at the onset of exercise, independent of intensity, and remained elevated throughout the exercise despite little or no glycogenolysis. Absolute phosphorylase a activity was also increased with exercise and was independent of intensity of exercise. Compared with resting levels, total phosphorylase activity was decreased at all times at the lower exercise intensity, whereas total phosphorylase activity declined at the higher intensity only after glycogenolysis had occurred. These data suggest that myocardial glycogen degradation during exercise can occur independently of cAMP and that the percentage of phosphorylase in the a form is not a good indicator of glycogenolytic rate.

Intensity and duration of exercise effects on skeletal muscle cAMP, phosphorylase, and glycogen.

To gain further insights into the mechanisms regulating skeletal muscle glycogenolysis during exercise, glycogen, phosphorylase, and adenosine 3',5'-cyclic monophosphate (cAMP) were determined in fast-twitch white (FTW) and fast-twitch red (FTR) muscle from groups of rats that ran for 0, 5, 10, 15, or 30 min at either 15 or 30 m/min. Glycogen degradation demonstrated an intensity and duration response in both fiber types. cAMP increased in both fiber types by 5 min and remained elevated at all times measured. FTW muscle cAMP levels were independent of both intensity and duration of exercise. FTR muscle cAMP levels were higher from 10 to 30 min at the 30-m/min intensity compared with the 15-m/min intensity. The ratio of the activity of phosphorylase in the presence of 2 mM AMP X 100 (phosphorylase a%) remained elevated at 20-22% independent of intensity and duration in FTW muscle; however, phosphorylase a% demonstrated an intensity and duration effect in FTR muscle. Glycogenolytic rates decreased with time, even though both cAMP and phosphorylase a% remained elevated in both fiber types. These data suggest that cAMP and phosphorylase a activation can be maintained during exercise in skeletal muscle but indicate a dissociation of these factors from glycogenolysis.

Patch-size dependent habitat modification and facilitation on New England cobble beaches by Spartina alterniflora.

Most marine habitats are generated by the presence of habitat-modifying species. However, little is know about many aspects of this process, such as how individual- and population-level traits of habitat modifiers affect their ability to reduce environmental stress and thus facilitate other species. An important habitat modifier in New England is the intertidal grass Spartina alterniflora which facilitates the establishment and persistence of cobble beach plant communities by reducing wave-related disturbance. The objectives of this study were to (1) quantify the modification of cobble beach habitats by S. alterniflora, (2) determine how this process is related to S. alterniflora bed traits, and (3) determine why small patches of S. alterniflora generally remain unoccupied by cobble beach plants. Our results demonstrate that S. alterniflora substantially reduces flow-related physical disturbance on cobble beaches. Behind S. alterniflora, mean flow velocity was reduced by 40-60% and substrate stability was dramatically increased compared to portions of the shoreline not bordered by this species. These comparative results were supported by a S. alterniflora shoot removal experiment, which resulted in a 33% increase in average flow velocity and an 85% increase in substrate instability relative to control areas. There was a strong inverse logarithmic relationship between bed length and both average flow velocity and substrate instability behind S. alterniflora. Most S. alterniflora beds were small and bed length was significantly related to the presence of one or more cobble beach plant species. Only 13% of beds <25 m and 40% of beds 30-40 m in length were occupied, in contrast to an occupancy rate of 87% for beds >40 m long. Seeds of two annual cobble beach species (Suaeda linearis and Salicornia europaea) were added to plots behind large (>100 m in length) and small S. alterniflora (<25 m) beds with and without a substrate stabilization manipulation. Seedlings of both species only emerged and established behind small beds when the substrate was stabilized. These results indicate that smaller S. alterniflora patches are usually unoccupied because they do not stabilize the substrate to a degree that meets the establishment requirements of seedlings. Thus, both habitat modification and facilitation by S. alterniflora are patch-size dependent. The conditionality of this facilitation appears to generate a pattern of patchy yet predictable population and community distribution at a landscape spatial scale.

Connective tissue graft technique assuring wide root coverage.

Gingival recession related to periodontal disease or developmental problems can result in root sensitivity, root caries, and esthetically unacceptable root exposures. Consequently, root restorations are performed that often complicate, rather than resolve, the problems created by exposed roots. This article presents a predictable procedure for root coverage on areas of wide denudation in the maxilla and the mandible.

Histology of a human biopsy section following the placement of a subepithelial connective tissue graft.

This case report histologically examines the type of attachment that can occur after root coverage of a long-standing facial recession defect on a maxillary premolar with a subepithelial connective tissue graft. Histologic findings suggest that various types of tissue attachment, including periodontal regeneration, may occur over a recession defect after placement of a subepithelial connective tissue graft. In the present case, it was noteworthy that after 1 year the greatest area of exposed root surface was covered by a connective tissue attachment (adhesion), which had remained intact during orthodontic movement and distal drifting of the tooth.