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Biomedical subjects

J C Russell

Publications and source records attributed to J C Russell.

At least 19 recordsLinked to original sources
PubMed2007

Synergistic effects of conjugated linoleic acid and chromium picolinate improve vascular function and renal pathophysiology in the insulin-resistant JCR:LA-cp rat.

AIMS: Conjugated linoleic acid (CLA) is a natural constituent of dairy products, specific isomers of which have recently been found to have insulin sensitizing and possible antiobesity actions. Chromium is a micronutrient which, as the picolinate (CrP), has been shown to increase insulin sensitivity in animal models, including the JCR:LA-cp rat. We tested the hypothesis that these agents may have beneficial synergistic effects on the micro- and macrovasculopathy associated with hyperinsulinaemia and early type 2 diabetes. METHODS: Insulin-resistant cp/cp rats of the JCR:LA-cp strain were treated with mixed isomers of CLA (1.5% w/w in the chow) and/or CrP at 80 microg/kg/day (expressed as Cr) from 4 weeks of age to 12 weeks of age. Plasma insulin, lipid and adiponectin levels, aortic vascular function, renal function and glomerular sclerosis were assessed. RESULTS: CLA administration reduced food intake, body weight and fasting insulin in JCR:LA-cp rats. Plasma adiponectin levels were significantly elevated in rats treated with both CLA and CrP. Aortic hypercontractility was reduced and the relaxant response to the nitric oxide-releasing agent acetylcholine (Ach) was increased in CrP-treated rats. Striking reductions were also observed in the level of urinary albumin and the severity of glomerular sclerosis in rats treated specifically with CLA. CONCLUSIONS: CLA and CrP have beneficial effects ameliorating several of the pathophysiologic features of an insulin-resistant rat model. These supplements may be useful adjuncts in the management of patients with the metabolic syndrome and warrant further study.

Adiponectin↗
PubMed2006

Impaired postprandial apolipoprotein-B48 metabolism in the obese, insulin-resistant JCR:LA-cp rat: increased atherogenicity for the metabolic syndrome.

AIM: Postprandial lipaemia is a significant contributor to the development of dyslipidaemia and cardiovascular disease, which has more recently been shown as a potential risk factor for obesity and pre-diabetes. Clinically however, the diagnosis of early insulin-resistance remains confounded due to the fact that aberrations in lipid metabolism are not often readily identified using classic indicators of hypercholesterolemia (i.e. LDL). METHODS: In this study, we assessed the metabolism of apolipoprotein-B48 (apoB48)-containing lipoproteins in an animal model of obesity and insulin-resistance, the JCR:LA-cp rat. The contribution of lipoproteins from the intestine was assessed by measuring plasma apoB48 concentration in the postprandial period following an oral fat load. Plasma apoB48 was measured by improved enhanced chemiluminescent detection and other biochemical parameters measured by established analysis. RESULTS: Fasting concentrations of plasma apoB48, postprandial apoB48 area under the curve (AUC), as well as incremental-AUC (iAUC), were all significantly greater in the obese phenotype compared to lean controls. Fasting apoB48 correlated significantly with apoB48-iAUC, triglyceride (TG)-iAUC and insulin-iAUC. In addition, there was a highly significant association with fasting insulin and the postprandial ratio of TG:apoB48, a relationship not often detected in humans during insulin-resistance. CONCLUSIONS/INTERPRETATION: We conclude that the JCR:LA-cp rat can be used as a model of postprandial lipemia to explore chylomicron metabolism during the onset and development of insulin-resistance, including the increased cardiovascular complications of the metabolic syndrome.

Animals↗
PubMed2005

A novel complex of arginine-silicate improves micro- and macrovascular function and inhibits glomerular sclerosis in insulin-resistant JCR:LA-cp rats.

AIMS/HYPOTHESIS: The metabolic syndrome, with associated vasculopathy, is a major cause of cardiovascular disease and nephropathy. Impaired nitric oxide (NO) metabolism and endothelial function is an important component of the disease process. Increasing the availability of arginine, the precursor of NO, might enhance vascular function and protect against end-stage disease. MATERIALS AND METHODS: Insulin-resistant JCR:LA-cp rats were treated with arginine-silicate-inositol complex or arginine-HCl at 1.0 g kg(-1) day(-1) (expressed as arginine-HCl) from 8 to 13 weeks of age. The contractile/relaxant function of thoracic aortae and coronary arteries was assessed in vitro. Kidneys were assessed for severity of glomerular sclerosis. RESULTS: Arginine-silicate complex, but not arginine-HCl, normalised the hypercontractile response of the aorta to phenylephrine via an NO-dependent pathway. Coronary artery function, as indicated by reactive hyperaemia to warm ischaemia, was enhanced by both arginine compounds. In addition, the arginine-silicate complex increased coronary vasodilatation in response to bradykinin. Glomerular sclerosis was significantly reduced in rats treated with the arginine-silicate complex. CONCLUSIONS/INTERPRETATION: Treatment with exogenous arginine, in an efficiently absorbed form, improves vascular function and reduces nephropathy in an animal model of insulin resistance and cardiovascular disease, via mechanism(s) independent of insulin concentration. Enhancement of NO metabolism through increased availability of the precursor arginine appears to offer protection against micro- and macrovascular disease associated with the metabolic syndrome and insulin resistance.

Acetylcholine↗
PubMed2005

Insulin-sensitizing and cardiovascular effects of the sodium-hydrogen exchange inhibitor, cariporide, in the JCR: LA-cp rat and db/db mouse.

The effects of the sodium-hydrogen (Na/H) exchange inhibitor cariporide (HOE642), on insulin sensitivity and vascular function were studied in the JCR:LA-cp rat and the db/db mouse. In the insulin-resistant rat, cariporide reduced fasting insulin levels (42%, P < 0.02) and insulin response in a meal tolerance test (50%, P < 0.01), indicating increased insulin sensitivity. The ACE inhibitor, ramipril, used as a reference agent, reduced the insulin response to the meal, but not fasting levels. The EC50 for acetylcholine-mediated relaxation of phenylephrine-precontracted aortic rings was significantly lower in cariporide-treated rats (P < 0.002), but not in ramipril-treated rats. Flow response of the coronary circulation to bradykinin was significantly greater in both cariporide- and ramipril-treated rats, (3-fold decrease in the EC50, P < 0.05). Cariporide-treated hearts were smaller, slower beating, with greater developed LVP. In the obese db/db mouse, chronic treatment with cariporide obviated vascular hypercontractility and improved endothelial function. Thus, cariporide had beneficial effects on the abnormal insulin metabolism and associated vascular dysfunction in the JCR:LA-cp insulin-resistant rat, which develops advanced cardiovascular disease and ischemic myocardial lesions. It also improved vascular function in a similar mouse model of insulin resistance. These effects were markedly greater than those of ramipril.

Acetylcholine↗
PubMed2004

Leptin and the control of respiratory gene expression in muscle.

Leptin plays a central role in the regulation of fatty acid homeostasis, promoting lipid storage in adipose tissue and fatty acid oxidation in peripheral tissues. Loss of leptin signaling leads to accumulation of lipids in muscle and loss of insulin sensitivity secondary to obesity. In this study, we examined the direct and indirect effects of leptin signaling on mitochondrial enzymes including those essential for peripheral fatty acid oxidation. We assessed the impact of leptin using the JCR:LA-cp rat, which lacks functional leptin receptors. The activities of marker mitochondrial enzymes citrate synthase (CS) and cytochrome oxidase (COX) were similar between wild-type (+/?) and corpulent (cp/cp) rats. In contrast, several tissues showed variations in the fatty acid oxidizing enzymes carnitine palmitoyltransferase II (CPT II), long-chain acyl-CoA dehydrogenase (LCAD) and 3-hydroxyacyl-CoA dehydrogenase (HOAD). It was not clear if these changes were due to loss of leptin signaling or to insulin insensitivity. Consequently, we examined the effects of leptin on cultured C(2)C(12) and Sol8 cells. Leptin (3 days at 0, 0.2, or 2.0 nM) had no direct effect on the activities of CS, COX, or fatty acid oxidizing enzymes. Leptin treatment did not affect luciferase-based reporter genes under the control of transcription factors involved in mitochondrial biogenesis (nuclear respiratory factor-1 (NRF-1), nuclear respiratory factor-2 (NRF-2)) or fatty acid enzyme expression (peroxisome proliferator-activated receptors (PPARs)). These studies suggest that leptin exerts only indirect effects on mitochondrial gene expression in muscle, possibly arising from insulin resistance.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2002

Developmental changes in adipose and muscle lipoprotein lipase activity in the atherosclerosis-prone JCR:LA-corpulent rat.

OBJECTIVE: To characterize the developmental changes in adipose and muscle lipoprotein lipase (LPL) activity in the atherosclerosis-prone JCR:LA-corpulent rat, and to test the hypothesis that tissue-specific abnormalities in LPL activity precede the establishment of obesity. DESIGN: Lean (+/?) and obese cp/cp male JCR:LA rats were studied at 4, 5 and 8 weeks of age, that is at the onset of obesity, and at a time when obesity is well established. Assessment was made of plasma variables related to glucose and lipid metabolism and of LPL activity in several adipose depots, skeletal muscles and the heart. RESULTS: At week 4, body weights were identical in both genotypes and began to diverge at week 5. Eight-week-old cp/cp rats weighed 35% more than their lean counterparts. Perirenal and epididymal adipose depot weights were also identical in both genotypes at week 4 and began to increase in cp/cp rats at week 5, whereas the subcutaneous depot of 4-week-old cp/cp rats was slightly enlarged. At week 4, the cp/cp rats were hyperinsulinemic (5-fold), hyperleptinemic (30-fold) and hypertriglyceridemic (3-fold) compared to their lean counterparts, and their liver contained twice as much triglyceride. The 4-week-old cp/cp rats displayed 2-7-fold higher LPL specific activity in the various adipose depots compared to lean rats, and enzyme activity remained higher in obese than in lean rats at all subsequent ages. In contrast, LPL activity in the vastus lateralis, gastrocnemius and heart muscles of 4-week-old obese rats was approximately half that observed in lean animals. CONCLUSION: Profound, persistent alterations in the tissue-specific modulation of LPL activity are established in the JCR:LA cp/cp rat prior to the development of frank obesity. The increase in adipose tissue LPL activity and its decrease in muscle tissues are likely to be related to the concomitant alterations in insulinemia and triglyceridemia, respectively. The pre-obesity, tissue-specific alterations in LPL activity may be considered as an integrated adaptation to increased lipid flux aimed at driving lipids toward storage sites and limiting their uptake by triglyceride-laden muscles.

Adipose Tissue↗
PubMed2002

The physiology and clinical applications of vasopressin in critical illness.

OBJECTIVE: To present the physiology of vasopressin, and review published data on its use in critically ill patients. DATA SOURCES: A review of articles on the clinical use of vasopressin in critical care medicine up to 2002 and identified through a MEDLINE search. SUMMARY OF REVIEW: Vasopressin (antidiuretic hormone) acts via vasopressinergic receptors to maintain osmotic and baroreceptor homeostasis. It has complex and varying effects depending on serum levels, coexisting disease states and organs studied. Synthetic vasopressin is available for clinical use. In large doses (e.g. 40 U) it has vasoconstrictor effects comparable to epinephrine during cardiopulmonary resuscitation. The use of much lower "replacement" doses (e.g. 0.04 U/min) may have a marked vasopressor effect in clinical states associated with vasopressin deficiency; for example sepsis, the organ donor and after cardiopulmonary bypass. These doses are much lower than those leading to cardiovascular effects in healthy patients and may avoid the adverse vasoconstrictor effects seen at "pharmacological" doses. The use of vasopressin to reduce portal pressure and bleeding in oesophageal varices is well established. CONCLUSIONS: Vasopressin has widespread effects throughout the body and has several important clinical applications in the critically ill patient.

Journal Article↗
PubMed2001

Mg2+-dependent ATPase activity in cardiac myofibrils from the insulin-resistant JCR:LA-cp rat.

There is a great deal of information presently available documenting a cardiomyopathic condition in insulin-deficient models of diabetes. Less information is available documenting a similar status in non insulin-dependent models of diabetes. We have studied the functional integrity of the myofibrils isolated from hearts of JCR:LA rats. The JCR:LA rat is hyperinsulinemic, hyperlipidemic, glucose intolerant and obese. As such, it carries many of the characteristics found in humans with non insulin-dependent diabetes mellitus. These animals also have many indications of heart disease. However, it is not clear if the hearts suffer from vascular complications or are cardiomyopathic in nature. We examined Mg2+-dependent myofibrillar ATPase in hearts of JCR:LA-cp/cp rats and their corresponding control animals (+/?) and found no significant differences (P> 0.05). This is in striking contrast to the depression in this activity exhibited by cardiac myofibrils isolated from insulin-deficient models of diabetes. Our data demonstrate that myofibrillar functional integrity is normal in JCR:LA-cp rats and suggest that these hearts are not in a cardiomyopathic state. Insulin status may be critical in generating a cardiomyopathic condition in diabetes.

Animals↗
PubMed2001

Laparoscopic cholecystectomy does not demonstrably decrease survival of patients with serendipitously treated gallbladder cancer.

BACKGROUND: The purpose of this study was to evaluate the possibility that laparoscopic cholecystectomy has worsened the prognosis of patients with resected gallbladder cancer; particularly for patients whose cancer was accidentally resected. STUDY DESIGN: We conducted a retrospective review of Connecticut Tumor Registry data and data extracted from individual patient records at 15 of 30 hospitals in Connecticut reporting data to the Registry, at two separate time points, 1985-1988 (immediate prelaparoscopic era) and 1992-95 (laparoscopic cholecystectomy well established). There were 194 and 208 patients in each 3-year period, respectively. Additional information was extracted from hospital records in 82 and 91 patients, respectively. Twenty-five percent of patients in both data sets presented with "local" or Tis, T1, T2 disease. RESULTS: Three-year survival for localized disease was 29% in the prelaparoscopic period and 34% once laparoscopic cholecystectomy was established. But analysis of individual patient records indicated that 36% of patients from the laparoscopic period did not actually undergo a laparoscopic procedure. Fifty-nine patients had their gallbladder cancer discovered in the specimen postoperatively (serendipitously treated). A higher proportion of cancers were discovered postoperatively in the laparoscopic era (44% versus 24%). Three-year survival for these patients was 25%. If the data from the two eras are grouped according to whether or not the cancer-bearing gallbladder was manipulated laparoscopically, 24 of 59 patients (41%) turned out to be at risk for the possibility of increased laparoscopic dissemination of tumor. Survival of these patients (11-month median survival) was not statistically different from survival of patients whose serendipitously discovered gallbladder cancer was never manipulated laparoscopically (16-month median survival); p = 0.54 by log rank test. CONCLUSIONS: The widespread adoption of laparoscopic cholecystectomy did not worsen the survival of patients with gallbladder cancer, and patients with serendipitously treated gallbladder cancers did not have a worse survival after laparoscopic manipulation than after a standard open cholecystectomy. The laparoscopic aspects of operative manipulation of a gallbladder with cancer in it do not appear to be a proximate cause of the poor prognosis in this disease.

Aged↗
PubMed2001

Protection of vascular wall function in insulin-resistant rats from copper oxidative stress.

The effects of oxidative stress on vascular function in the insulin-resistant state were assessed in mesenteric resistance arteries of obese, insulin-resistant (cp/cp) and lean, normal (+/?) JCR : LA-cp rats. Nitric oxide-mediated relaxation of noradrenaline-contracted arteries in response to acetylcholine was impaired after 2 h of incubation with Cu(2+) in both genotypes, with or without the continuing presence of Cu(2+). Relaxation was enhanced on initial exposure to Cu(2+), and post-incubation removal of the Cu(2+) resulted in a greater impairment of relaxation. Arteries from cp/cp rats were less impaired in function by Cu(2+) incubation than were those of +/? controls. Sodium nitroprusside-mediated relaxation was impaired by exposure to Cu(2+), with an accompanying increase in EC(50). The impairment in acetylcholine-mediated relaxation in the arteries from both cp/cp and +/? rats was completely inhibited by co-incubation with copper-zinc superoxide dismutase and catalase, confirming that the impairment associated with Cu(2+) incubation was due to oxidative stress. The impairment appears to involve both smooth muscle and the endothelium. The cp/cp rats showed greater resistance to the effects of oxidative stress on arterial function, possibly due to an adaptation to oxidative stress on arterial function associated with the insulin-resistant state.

Analysis of Variance↗
PubMed2001

Effects of LY117018 and the estrogen analogue, 17alpha-ethinylestradiol, on vascular reactivity, platelet aggregation, and lipid metabolism in the insulin-resistant JCR:LA-cp male rat: role of nitric oxide.

The JCR:LA-cp rat is obese and insulin resistant and develops a major vasculopathy, with associated ischemic damage to the heart. Male rats were treated with 17alpha-ethinylestradiol (EE), LY117018, and/or the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME). LY117018 decreased plasma cholesterol esters, with a 40% reduction in total cholesterol. EE increased triglyceride levels and modestly decreased cholesterol esters. L-NAME increased blood pressure and aortic contractile sensitivity to phenylephrine and inhibited acetylcholine-induced relaxation. LY117018 decreased the force of contraction. The L-NAME-mediated increase in force of contraction and decrease in response to acetylcholine was inhibited by LY117018. L-NAME-induced hypertension was prevented by LY117018. Platelet aggregation was not different between obese and lean rats and was unaffected by L-NAME. LY117018, both in the absence and presence of L-NAME, inhibited platelet aggregation. The effects of LY117018 are apparently mediated through both NO-dependent and -independent mechanisms. The changes induced by EE and LY117018 may reflect the activation of multiple mechanisms, both estrogen receptor-dependent and -independent. The changes induced by LY117018 are significant and may prove to be cardioprotective in the presence of the insulin resistance syndrome.

Animals↗
PubMed2001

High glucose concentrations induce oxidative damage to mitochondrial DNA in explanted vascular smooth muscle cells.

Oxidative stress is considered to be one of the mechanisms leading to atherosclerosis. It occurs in response to injury or to altered metabolic state. Alterations in cell growth (proliferation or apoptosis) can also contribute to the pathogenesis of atherosclerosis and is influenced by oxidative stress. Smooth muscle cells (SMC) from aortic explants of JCR:LA-cp homozygous cp/cp corpulent rats who are genetically predisposed to develop atherosclerosis exhibit increased SMC proliferation, which can be attenuated by exercise and food restriction. This study was conducted to characterize the effects fo oxidative stress and high glucose media on cell growth and its relationship to mitochondrial DNA integrity and gene expression in explanted aortic SMC from corpulent and lean JCR:LA-cp rats. The results show that SMC from the cp/cp rat appear to be resistant to oxidant-induced cell death and that they accumulate mitochondrial DNA mutations, probably as a result of a reduction in apoptosis. These data suggest that susceptibility to age- and glucose-related atherosclerosis may be related to alterations in redox signaling.

Animals↗
PubMed2001

Reduction and prevention of the cardiovascular sequelae of the insulin resistance syndrome.

Insulin resistance and hyperinsulinemia are the critical characteristics of the metabolic syndrome that is associated with abdominal obesity and are the early manifestations of its progression to type 2 diabetes. These metabolic abnormalities are becoming recognized as a major contributor to cardiovascular disease. The experimental studies required to elucidate the underlying mechanisms and to develop effective preventative strategies will require the use of appropriate animal models and these are available. The evidence from such research indicates that a wide range of interventions (including peroxisome proliferator activator receptor agonists, insulin-sensitizing agents, statins, fibrates, angiotensin-converting enzyme inhibitors, estrogen receptor modulators, lipid-based nutriceuticals, and ethanol) can markedly reduce or prevent vasculopathy and ischemic cardiac lesions in animal models. Overall, the results suggest that early damage to the vascular wall, both in function and presenting as atherosclerotic lesions, is secondary to long-term hyperinsulinemia and, especially, to postprandial peaks in plasma insulin levels, and is exacerbated by the accompanying hyperlipidemia. Effective treatment will, of necessity, be preventative and will necessitate diagnostic approaches that can identify asymptomatic individuals at high risk for vascular damage and eventual progression to type 2 diabetes. Therapeutic targets in this population include insulin sensitivity and the associated signal transduction pathways, the peroxisome proliferator activator receptor-alpha and -gamma systems, and the complex pathways leading from acetyl CoA and the citric acid cycle to the synthesis of fatty acid and the storage of triglyceride. These pharmacological approaches offer the prospect of preventing a significant proportion of cardiovascular disease.

Animals↗
PubMed2001

Adenocarcinoma of the stomach in an adolescent presenting as pneumoperitoneum: a brief report.

BACKGROUND: Adenocarcinoma of the stomach is rare in children and adolescents. A unique case, presenting as an acute abdomen with pneumoperitoneum, is discussed. METHODS: Case presentation and literature review. RESULTS: A 13-year-old girl with perforated gastric adenocarcinoma treated by wedge resection developed metastatic disease within two months and died within six months despite chemotherapy. CONCLUSION: Frozen section of all perforated gastric ulcers, with resection/postoperative chemotherapy for adenocarcinoma. SUMMARY: A 13-year-old girl with gastric adenocarcinoma presented with pneumoperitoneum. Within two months of wedge resection widespread metastatic disease was documented by computerized tomography scan and laparoscopy and despite chemotherapy, the patient died within six months. Frozen section of all perforated gastric ulcers, even in children, and definitive formal gastrectomy with postoperative chemotherapy, offer the only chance of cure.

Adenocarcinoma↗
PubMed2001

Increased hepatic VLDL secretion, lipogenesis, and SREBP-1 expression in the corpulent JCR:LA-cp rat.

The corpulent JCR:LA-cp rat (cp/cp) is a useful model for study of the metabolic consequences of obesity and hyperinsulinemia. To assess the effect of hyperinsulinemia on VLDL secretion in this model, we measured rates of secretion of VLDL in perfused livers derived from cp/cp rats and their lean littermates. Livers of cp/cp rats secreted significantly greater amounts of VLDL triglyceride and apolipoprotein, compared with lean littermates. The content of apoB, apoE, and apoCs in both perfusate and plasma VLDL was greater in the cp/cp rat, as was the apolipoprotein (apo)C, apoA-I, and apoA-IV content of plasma HDL. Triglyceride content was also greater in cp/cp livers, as was hepatic lipogenesis and expression of lipogenic enzymes and sterol regulatory element binding protein-1 (SREBP-1). Hepatic mRNAs for apoE, and apoA-I were higher in livers of cp/cp rats. In contrast, the steady state levels of apoC-II, apoC-III, and apoB mRNAs were unchanged. Thus, livers of obese hyperinsulinemic cp/cp JCR:LA-cp rats secrete a greater number of VLDL particles that are enriched in triglyceride, apoE, and apoC. Greater secretion of VLDL in the cp/cp rat in part results from higher endogenous fatty acid synthesis, which in turn may occur in response to increased expression of the lipogenic enzyme regulator SREBP-1c.

Animals↗