scholarly journals Glutamine gluconeogenesis in the small intestine of 72 h-fasted adult rats is undetectable

2006 ◽  
Vol 401 (2) ◽  
pp. 465-473 ◽  
Author(s):  
Guy Martin ◽  
Bernard Ferrier ◽  
Agnès Conjard ◽  
Mireille Martin ◽  
Rémi Nazaret ◽  
...  
Keyword(s):  
Small Intestine ◽  
Glucose Production ◽  
Sprague Dawley ◽  
Adult Rats ◽  
Concentration Difference ◽  
Adult Rat ◽  
Nutrition And Diabetes ◽  
Glucose Synthesis

Recent reports have indicated that 48–72 h of fasting, Type 1 diabetes and high-protein feeding induce gluconeogenesis in the small intestine of adult rats in vivo. Since this would (i) represent a dramatic revision of the prevailing view that only the liver and the kidneys are gluconeogenic and (ii) have major consequences in the metabolism, nutrition and diabetes fields, we have thoroughly re-examined this question in the situation reported to induce the highest rate of gluconeogenesis. For this, metabolically viable small intestinal segments from 72 h-fasted adult rats were incubated with [3-13C]glutamine as substrate. After incubation, substrate utilization and product accumulation were measured by enzymatic and NMR spectroscopic methods. Although the segments utilized [13C]glutamine at high rates and accumulated 13C-labelled products linearly for 30 min in vitro, no substantial glucose synthesis could be detected. This was not due to the re-utilization of [13C]glucose initially synthesized from [13C]glutamine. Arteriovenous metabolite concentration difference measurements across the portal vein-drained viscera of 72 h-fasted Wistar and Sprague–Dawley rats clearly indicated that glutamine, the main if not the only gluconeogenic precursor taken up, could not give rise to detectable glucose production in vivo. Therefore we challenge the view that the small intestine of the adult rat is a gluconeogenic organ.

Effects of hypophysectomy and subsequent FSH and testosterone treatment on inhibin production by adult rat testes

1985 ◽  
Vol 105 (1) ◽  
pp. 1-6 ◽  
Author(s):  
C. L. Au ◽  
D. M. Robertson ◽  
D. M. de Kretser
Keyword(s):  
Seminiferous Tubule ◽  
Hormonal Control ◽  
Human Chorionic Gonadotrophin ◽  
Experimental Conditions ◽  
Adult Rats ◽  
Adult Rat ◽  
Fluid Production ◽  
Tubule Fluid

ABSTRACT The hormonal control of inhibin production by adult rat testes was investigated using an in-vitro inhibin bioassay validated for the measurement of inhibin activity in charcoal-treated rat testicular extracts. The effect of hypophysectomy examined at 16 h, 3, 7 and 42 days after surgery showed a decrease in testicular inhibin content and seminiferous tubule fluid production by 7 days and a decrease in inhibin production by 42 days. Serum FSH and LH were suppressed 3 days after surgery. In 30-day chronically hypophysectomized adult rats treated for 3 days with twice daily s.c. injections of (a) human FSH (hFSH, 22 i.u./rat per day), (b) testosterone (5 mg/rat per day), (c) hFSH + testosterone (same doses as a and b), or (d) human chorionic gonadotrophin (hCG, 12 i.u./rat per day), hFSH or hFSH and testosterone stimulated an increase in testicular inhibin content but not in inhibin production or tubule fluid production. Testosterone and hCG had no effect on these parameters. It is concluded that in vivo, FSH alone stimulates an increase in testicular inhibin content. The failure to observe an increase in inhibin production in vivo is attributed to the suppression of seminiferous tubule fluid production under the same experimental conditions. J. Endocr. (1985) 105, 1–6

Effect of glucocorticoid treatment on glucose and glutamine metabolism by the small intestine of the rat

1988 ◽  
Vol 75 (1) ◽  
pp. 93-100 ◽  
Author(s):  
M. Salleh M. Ardawi ◽  
May F. Majzoub ◽  
Eric A. Newsholme
Keyword(s):  
Small Intestine ◽  
Glucose Utilization ◽  
Citrate Synthase ◽  
Glutamine Metabolism ◽  
Dexamethasone Treatment ◽  
Glucocorticoid Treatment ◽  
Concentration Difference ◽  
Oxoglutarate Dehydrogenase

1. The effect of dexamethasone (30 μg day−1 100 g−1 body wt.) on the metabolism of glucose and glutamine was studied in the small intestine of rats after 9 days of treatment. 2. Dexamethasone treatment resulted in negative nitrogen balance (P < 0.001), and produced increases in the concentrations of plasma glucose (22%, P < 0.05), alanine (32%, P < 0.001) and insulin (127%, P < 0.001), but a decrease in the plasma concentration of glutamine (20%, P < 0.05). 3. Portal-drained visceral blood flow increased by approximately 22% (P < 0.001) in dexamethasone-treated rats, and was accompanied by a decrease in the arteriovenous concentration difference of glucose (43%, P < 0.001) and an increase in that of lactate (22%, P < 0.05), glutamine (35%, P < 0.01), glutamate (33%, P < 0.01) and alanine (21%, P < 0.05). 4. Enterocytes isolated from dexamethasone-treated rats showed decreased and increased rates of glucose and glutamine utilization, respectively. 5. The maximal activities of hexokinase, 6-phosphofructokinase, citrate synthase and oxoglutarate dehydrogenase were decreased (30–64%, P < 0.001) in intestinal mucosal scrapings of dexamethasone-treated rats, whereas the activity of glutaminase was increased (35%, P < 0.001). 6. It is concluded that glucocorticoid administration decreases the rate of glucose utilization but increases that of glutamine (both in vivo and in vitro) by the epithelial cells of the small intestine. This may be caused by changes in the maximal activities of key enzymes in the pathways of glucose and glutamine metabolism in these cells.

Postovulatory steroidogenesis after PMS-induced ovulation in immature female rats

1981 ◽  
Vol 241 (3) ◽  
pp. E221-E225 ◽  
Author(s):  
K. Taya ◽  
G. S. Greenwald
Keyword(s):  
Serum Levels ◽  
Female Rats ◽  
Corpora Lutea ◽  
Adult Rats ◽  
Rat Serum ◽  
Follicular Maturation ◽  
Adult Rat ◽  
Serum Lh

Thirty-day-old rats given a single subcutaneous injection of 5 IU pregnant mare serum gonadotropin (PMS) at 0900 h ovulated on the morning of day 33 (= estrus). However, the second ovulation did not occur until 9.4 days later. To determine the mechanism responsible for the delay in the second ovulation, in vivo and in vitro determinations of steroid and peptide hormones were compared between PMS-primed immature rats and adult cyclic rats. In PMS-primed rats, the corpora lutea (CL) produced progesterone for 2 days longer (until day 36) than the CL of the adult rat. Serum levels of 20 alpha-dihydroprogesterone, testosterone, and estradiol in PMS-primed rats were significantly lower than the corresponding values in adult rats. Serum LH was consistently lower in the PMS-primed rats. An increase in serum FSH occurred on days 36–37, which may be responsible for maturation of the follicles destined to ovulate at the second ovulation. On day 37, the nonluteal ovary of the PMS-primed rats also began to produce in vitro appreciable amounts of testosterone and estradiol. These findings suggest that the greater levels of prolactin and/or low levels of luteinizing hormone during estrus in PMS-primed rats may be responsible for the prolonged secretion of progesterone by the CL. This in turn inhibits follicular maturation, indirectly by lowering serum LH, which is reflected in reduced ability of the follicles in vitro to produce testosterone and estradiol until the CL regress.

Local Circuit Properties Underlying Cortical Reorganization

2002 ◽  
Vol 88 (3) ◽  
pp. 1288-1301 ◽  
Author(s):  
Peter W. Hickmott ◽  
Michael M. Merzenich
Keyword(s):  
Cortical Reorganization ◽  
The Novel ◽  
Adult Rats ◽  
Postsynaptic Potentials ◽  
Local Circuit ◽  
Adult Rat ◽  
The Times ◽  
Stimulation Of

Peripheral denervation has been shown to cause reorganization of the deafferented somatotopic region in primary somatosensory cortex (S1). However, the basic mechanisms that underlie reorganization are not well understood. In the experiments described in this paper, a novel in vivo/in vitro preparation of adult rat S1 was used to determine changes in local circuit properties associated with the denervation-induced plasticity of the cortical representation in rat S1. In the present studies, deafferentation of rat S1 was induced by cutting the radial and median nerves in the forelimb of adult rats, resulting in a rapid shift of the location of the forepaw/lower jaw border; the amount of the shift increased over the times assayed, through 28 days after denervation. The locations of both borders (i.e., original and reorganized) were marked with vital dyes, and slices from the marked region were used for whole-cell recording. Responses were evoked using electrical stimulation of supragranular S1 and recorded in supragranular neurons close to either the original or reorganized border. For each neuron, postsynaptic potentials (PSPs) were evoked by stimulation of fibers that crossed the border site (CB stim) and by equivalent stimulation that did not cross (NCB stim). Monosynaptic inhibitory postsynaptic potentials (IPSPs) were also examined after blocking excitatory transmission with 15 μM CNQX plus 100 μMdl-APV. The amplitudes of PSPs and IPSPs were compared between CB and NCB stimulation to quantify effects of the border sites on excitation and inhibition. Previous results using this preparation in the normal (i.e., without induced plasticity) rat S1 demonstrated that at a normal border both PSPs and IPSPs were smaller when evoked with CB stimulation than with NCB stimulation. For most durations of denervation, a similar bias (i.e., smaller responses with CB stimulation) for PSPs and IPSPs was observed at the site of the novel reorganized border, while no such bias was observed at the suppressed original border site. Thus changes in local circuit properties (excitation and inhibition) can reflect larger-scale changes in cortical organization. However, specific dissociations between these local circuit properties and the presence of the novel border at certain durations of denervation were also observed, suggesting that there are several intracortical processes contributing to cortical reorganization over time and that excitation and inhibition may contribute differentially to them.

scholarly journals Effects of burn injury on myocardial signaling and cytokine secretion: possible role of PKC

2007 ◽  
Vol 292 (2) ◽  
pp. R887-R896 ◽  
Author(s):  
Jing Tan ◽  
David L. Maass ◽  
D. Jean White ◽  
Jureta W. Horton
Keyword(s):  
Burn Injury ◽  
Total Body Surface Area ◽  
Cytokine Secretion ◽  
Sprague Dawley ◽  
Inhibitory Peptide ◽  
Adult Rat ◽  
Pkc Isoforms ◽  
Major Burn

This study examined the effects of major burn injury on the cellular distribution of several PKC isoforms in adult rat hearts and examined the hypothesis that PKC plays a regulatory role in cardiomyocyte cytokine secretion. Burn trauma was given over 40% total body surface area in Sprague-Dawley rats. An in vitro model of burn injury included addition of burn serum, 10% by volume, to primary cardiomyocyte cultures (collagen perfusion). In vivo burn injury produced redistribution of PKCδ, PKCε, and PKCα from the cytosol (soluble) to the membrane (particulate) component of the myocardium. This activation of the PKC isoforms was evident 2 h after burn injury and progressively increased over 24 h postburn. Addition of burn serum to isolated myocytes produced similar PKC isoform redistribution from the soluble to the particulate compartment, promoted myocyte Ca2+ and Na+ loading, and promoted robust myocyte secretion of inflammatory cytokines similar to that reported after in vivo burn injury. Pretreating cardiomyocytes with either calphostin or PKCε inhibitory peptide, a potent inhibitor of PKCε, prevented burn serum-related redistribution of the PKCε isoform and prevented burn serum-related cardiomyocyte secretion of TNF-α, IL-1β, IL-6, and IL-10. These data suggest that the PKCε isoform plays a pivotal role in myocardial inflammatory response to injury, altering cardiac function by modulating cardiomyocyte inflammatory cytokine response to injury.

Abstract 15601: On the Mechanisms of Accelerated Calcification of Bioprosthetic Heart Valve Biomaterials in Juvenile Animal Models

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Yingfei Xue ◽  
Alexander Kossar ◽  
Gaetano THIENE ◽  
Robert LEVY ◽  
Giovanni Ferrari
Keyword(s):  
Pediatric Patients ◽  
Calcium Deposition ◽  
Collagen Structure ◽  
Adult Rats ◽  
Rat Serum ◽  
Juvenile Rats ◽  
Adult Rat ◽  
Circulating Markers

Objective: Bioprosthetic heart valves (BHV) are subject to accelerated structural valve degeneration (SVD) in pediatric patients. Prior literature has reported differences in circulating markers of mineralization in pediatric patients compared to adults. Here we test the hypothesis that calcification-related circulating markers are differentially expressed in juvenile vs adult animals, and these markers functionally drive the accelerated SVD in juvenile animals in vitro and in vivo . Methods: Serum calcium (Ca 2+ ), phosphate (PO 4 - ), alkaline phosphatase (ALP), and osteopontin (OPN) levels of juvenile (3 week-old; n=5) and adult (8 month-old; n=5) Sprague-Dawley rats were measured by commercially-available assay kits. Glutaraldehyde-fixed bovine pericardial discs (BP) were incubated in juvenile or adult rat serum in vitro for 4 or 8 weeks. BP were subcutaneously implanted in juvenile or adult rats for 7 or 30 days (4-6 discs/rat). Pericardial transcatheter valves were implanted in juvenile Dorset sheep for 150 days (n=3). Alizarin Red staining, Von Kossa staining, and a quantitative assay were used for calcium analyses. Second harmonic generation imaging visualized collagen structure. Results: Serum Ca 2+ (p<0.05), PO 4 - (p<0.05), ALP (p<0.01), and OPN (p<0.01) were all increased in juvenile rats compared to adult rats. BP incubated in juvenile rat serum resulted in higher calcium deposition (p<0.05) and more disruption to collagen structure as evidenced by reduced alignment coefficient (p<0.01) as compared to those incubated in adult rat serum. Similarly, BP explanted from juvenile rats had higher calcium deposition (p<0.01) and more disrupted collagen structure in terms of collagen alignment and crimp period (p<0.01). Results in progress in juvenile sheep implantation model further confirmed the in vitro and in vivo findings that BHV explants had substantial calcium deposition and collagen disalignment. Conclusion: Calcium accumulates within BHV biomaterials more prominently in juvenile rats; increased serum markers of mineralization may explain the increased susceptibility to SVD in pediatric patients. Future studies will investigate novel strategies for the prevention and mitigation of accelerated SVD in pediatric patients.

Cardiac fibrogenesis in magnesium deficiency: a role for circulating angiotensin II and aldosterone

2006 ◽  
Vol 291 (1) ◽  
pp. H436-H440 ◽  
Author(s):  
S. Sapna ◽  
S. K. Ranjith ◽  
K. Shivakumar
Keyword(s):  
Angiotensin Ii ◽  
Magnesium Deficiency ◽  
Cardiac Fibroblasts ◽  
Control Diet ◽  
Sprague Dawley ◽  
Adult Rats ◽  
Serum Factors ◽  
Significant Difference

Mechanisms underlying cardiac fibrogenesis in magnesium deficiency are unclear. It was reported earlier from this laboratory that serum from magnesium-deficient rats has a more pronounced stimulatory effect on cell proliferation, net collagen production, and superoxide generation in adult rat cardiac fibroblasts than serum from rats on the control diet. The profibrotic serum factors were, however, not identified. This study tested the hypothesis that circulating angiotensin II may modulate cardiac fibroblast activity in hypomagnesemic rats. Male Sprague-Dawley rats were pair-fed a magnesium-deficient (0.0008% Mg) or -sufficient (0.05%) diet for 6 days, and the effects of serum from these rats on [3H]thymidine and [3H]proline incorporation into cardiac fibroblasts from young adult rats were evaluated in the presence of losartan, an angiotensin II type 1 (AT1) receptor antagonist, and spironolactone, an aldosterone antagonist. Losartan and spironolactone markedly attenuated the stimulatory effects in vitro of serum from the magnesium-deficient and control groups, but the inhibitory effects were considerably higher in cells exposed to serum from magnesium-deficient animals. Circulating and cardiac tissue levels of angiotensin II were significantly elevated in magnesium-deficient animals (67.6% and 93.1%, respectively, vs. control). Plasma renin activity was 61.9% higher in magnesium-deficient rats, but serum angiotensin-converting enzyme activity was comparable in the two groups. Furthermore, preliminary experiments in vivo using enalapril supported a role for angiotensin II in magnesium deficiency. There was no significant difference between the groups in serum aldosterone levels. The findings suggest that circulating angiotensin II and aldosterone may stimulate fibroblast activity and contribute to a fibrogenic response in the heart in magnesium deficiency.

Comparison of the effects on purified Leydig cells of four hormones (oxytocin, vasopressin, opiates and LHRH) with suggested paracrine roles in the testis

1987 ◽  
Vol 113 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. M. Sharpe ◽  
I. Cooper
Keyword(s):  
Leydig Cells ◽  
Interstitial Fluid ◽  
Adult Rats ◽  
Adult Rat ◽  
Clear Cut ◽  
Testosterone Production ◽  
Time Period ◽  
High Doses

ABSTRACT Four hormones have been identified by various authors as possible paracrine regulators of testicular Leydig cells. The aim of this study was to evaluate their effects on purified adult rat Leydig cells under various conditions in vitro, and then to assess whether comparable effects occurred in vivo. In agreement with previous findings, an LHRH agonist (LHRH-A) exerted clear-cut effects on testosterone secretion by Leydig cells both in vitro and in vivo. On its own, LHRH-A stimulated testosterone production by Leydig cells for up to 24 h in culture but inhibited testosterone production stimulated by human chorionic gonadotrophin (hCG) between 24 and 72 h of culture. In-vivo, unilateral intratesticular injection of adult rats with 1 ng LHRH-A resulted 5 h later in a significant increase in testosterone concentrations in testicular interstitial fluid (IF). Vasopressin exerted effects in vitro which were similar to those of LHRH-A. On its own, vasopressin stimulated testosterone production for up to 5 h of culture, but not thereafter, while in the presence of hCG, vasopressin inhibited testosterone production beyond 24 h of culture. The initial stimulatory effect of vasopressin on testosterone production occurred with concentrations of 1 nmol/l and higher, but the magnitude of stimulation (threefold or less) was considerably less than that induced by LHRH-A (ninefold) over the same time period. In contrast to LHRH-A, unilateral intratesticular injection of vasopressin in high doses (20 and 2 ng) had no effect on IF testosterone levels 5 h later. When Leydig cells were cultured in the presence of testicular IF, to approximate in-vivo conditions, there was marked stimulation of testosterone production, but the effects of vasopressin and LHRH-A in the presence of IF were comparable to those observed in its absence. Neither morphine nor oxytocin at concentrations of 0·1 μmol/l had any effect on testosterone production under any of the conditions of culture, and unilateral intratesticular injection of oxytocin, morphine or naloxone was without effect on the IF levels of testosterone. It is concluded that opiates and oxytocin are probably not involved in the paracrine regulation of Leydig cells, whereas vasopressin may play such a role. However, as the stimulatory effects of vasopressin were small in relation to those of LHRH-A and were not evident in vivo, the physiological significance of the effects of vasopressin are uncertain. J. Endocr. (1987) 113, 89–96

Degradation of IGF-I in the adult rat gastrointestinal tract is limited by a specific antiserum or the dietary protein casein

1995 ◽  
Vol 146 (2) ◽  
pp. 215-225 ◽  
Author(s):  
C J Xian ◽  
C A Shoubridge ◽  
L C Read
Keyword(s):  
Receptor Binding ◽  
Dietary Protein ◽  
Half Life ◽  
Structural Integrity ◽  
Binding Activity ◽  
Adult Rats ◽  
Adult Rat ◽  
Igf I

Abstract To investigate the potential of IGF-I peptides as therapeutics in the gut, the survival profiles of a bolus of 125I-labelled IGF-I (8·6 ng) in vivo in various ligated gut segments of fasted adult rats have been examined. The intactness of IGF-I tracer in the flushed luminal contents was estimated by trichloroacetic acid precipitation, antibody and receptor binding assays. It was found that IGF-I was degraded very rapidly in duodenum and ileum segments with a half-life (t1/2) of 2 min by all three methods. IGF-I was slightly more stable in the stomach (t1/2=8, 5 and 2·5 min by the above three methods), and considerably more stable in the colon (t1/2=38, 33 and 16 min as judged by the three methods). Rates of degradation in gut flushings in vitro were similar to the in vivo rates except for the colon, where IGF-I was proteolysed more rapidly in vivo. As a means of developing gut-stable and active forms of IGF-I, several approaches were examined for their effectiveness in prolonging IGF-I survival in the upper gut. It was found that the extension peptide on the analogue, LR3IGF-I did not protect IGF-I, nor did association with IGF-binding protein-3. However, an IGF-I antiserum was effective in prolonging IGF-I half-life in duodenum fluid by 28-fold. Charge interaction between IGF-I and heparin could also protect IGF-I in the stomach but not in duodenum flushings. Furthermore, casein (a non-specific dietary protein) and to a lesser extent, BSA and lactoferrin, were effective in preserving IGF-I structural integrity and receptor binding activity in both stomach and duodenum fluids. It can be concluded that IGF-I cannot be expected to retain bioactivity if delivered orally because of rapid proteolysis in the upper gut, but the use of IGF antibodies and casein could represent useful approaches for IGF-I protection in oral formulae. Journal of Endocrinology (1995) 146, 215–225

Preparation of cultured astrocytes for x-ray microanalysis

1989 ◽  
Vol 47 ◽  
pp. 988-989
Author(s):  
N.K.R. Smith ◽  
K.E. Hunter ◽  
P. Mobley ◽  
L.P. Felpel
Keyword(s):  
Cultured Cells ◽  
Elemental Content ◽  
Elemental Distribution ◽  
Sprague Dawley ◽  
X Ray ◽  
Cultured Astrocytes ◽  
Freeze Dried ◽  
Ultimate Objective

Electron probe energy dispersive x-ray microanalysis (XRMA) offers a powerful tool for the determination of intracellular elemental content of biological tissue. However, preparation of the tissue specimen , particularly excitable central nervous system (CNS) tissue , for XRMA is rather difficult, as dissection of a sample from the intact organism frequently results in artefacts in elemental distribution. To circumvent the problems inherent in the in vivo preparation, we turned to an in vitro preparation of astrocytes grown in tissue culture. However, preparations of in vitro samples offer a new and unique set of problems. Generally, cultured cells, growing in monolayer, must be harvested by either mechanical or enzymatic procedures, resulting in variable degrees of damage to the cells and compromised intracel1ular elemental distribution. The ultimate objective is to process and analyze unperturbed cells. With the objective of sparing others from some of the same efforts, we are reporting the considerable difficulties we have encountered in attempting to prepare astrocytes for XRMA.Tissue cultures of astrocytes from newborn C57 mice or Sprague Dawley rats were prepared and cultured by standard techniques, usually in T25 flasks, except as noted differently on Cytodex beads or on gelatin. After different preparative procedures, all samples were frozen on brass pins in liquid propane, stored in liquid nitrogen, cryosectioned (0.1 μm), freeze dried, and microanalyzed as previously reported.

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