bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences in Transcription and Translation of Long and Short GSα, the Stimulatory G-Protein, in Human Atrium
Authors: Monteith M. Susan , Wang Tao , Brown Morris J.
Published: August 2015

1. We have previously reported the relative mRNA and protein level of the long and short splice variants of Gsα (GsαL and GsαS) in human atrium. We have now measured the relative proportions of the serine+ and serine− variants of GsαL and GsαS in human atrium, and assessed, indirectly, whether their differential expression may (i) regulate Gsα phosphorylation, and (ii) be regulated by atrial cyclic AMP levels.

2. The serine+ and serine− variants of GsαL and GsαS were estimated by single nucleotide primer extension in 36 right atrial strips of which half were from β-adrenoceptor-blocked patients. The ratio of serine+ to serine− variants was 0.06 ± 0.12 for GsαL, compared with 8.04 ± 12.16 for GsαS (P < 0.001).

3. Isoelectric points of GsαL and GsαS in the atria of four β-adrenoceptor-blocked and four non-β-adrenoceptor-blocked patients were estimated by two-dimensional gel electrophoresis. Two-dimensional gel analysis gave a consistent pattern with several spots for both GsαL and GsαS; however, the isoelectric points of GsαS were more acid (5.18 ± 0.24) than those of GsαL (5.87 ± 0.17, P < 0.001).

4. No significant difference in either the serine variants or isoelectric point value was observed between β-adrenoceptor-blocked and non-β-adrenoceptor-blocked patients.

5. In conclusion, all four Gsα variants were expressed in human atrium, but GsαL is almost entirely of the serine− form. GsαS has a more acidic isoelectric point than GsαL, indicating a possible post-translational modification. The lack of difference in our results between β-adrenoceptor-blocked and non-β-adrenoceptor-blocked patients suggests indirectly that cyclic AMP is an unlikely candidate for regulating splicing or post-translational modification of Gsα in vivo.
Effects of Fish Oil Supplementation on Atherosclerosis in Different Regions of the Aorta of Rabbits with Diet-Induced Hypercholesterolaemia
Authors: Chen Ming-Fong , Hsu Hsiu-Ching , Lee Yuan-Teh
Published: August 2015

1. The effects of fish oil supplementation on atherosclerosis in different regions of the aorta in rabbits with diet-induced hypercholesterolaemia were studied. Control and experimental rabbits were fed a 1% cholesterol-enriched diet with or without 10% fish oil supplementation (seven in each group), and were killed after 2 weeks of feeding. The ascending, descending and abdominal aortas as well as the pulmonary artery were harvested for analyses of prostanoid production, malondialdehyde, superoxide dismutase activity and cholesterol levels. The tissues from the other seven rabbits of each group were obtained after 6 weeks of feeding for the identification of atherosclerotic lesions by a Sudan IV stain.

2. The cholesterol-fed rabbits had a significantly higher thromboxane B2 production, a lower 6-keto-prostaglandin1α/thromboxane B2 ratio and a higher malondialdehyde level than the other two groups in the ascending and abdominal aortas as well as the pulmonary artery; this finding paralleled the severity of atherosclerotic lesions. These manifestations were most prominent in the ascending aorta. The fish oil-supplemented rabbits had the most beneficial aortic prostanoid production, attenuated lipid peroxidation and significantly suppressed atherosclerosis.

3. These results suggest that a high-cholesterol diet induces more atherosclerotic lesions, especially on the ascending aorta, in rabbits. A fish oil supplement favours prostanoid production and attenuates lipid peroxidation on all four regions of the great arteries, thus suppressing atherosclerosis in diet-induced hypercholesterolaemic rabbits.
Cardiomegaly and Vasoactive Hormones in Rats with Chronic Myocardial Infarction: Long-Term Effects of Chlorothiazide
Authors: Kohzuki Masahiro , Kanazawa Masayuki , Yoshida Kazunori , Tsutsumi Eikatsu , Yasujima Minoru , Abe Keishi , Johnston Colin I. , Sato Tokutaro
Published: August 2015

1. The effects of prolonged chlorothiazide treatment of left ventricular failure on cardiac hypertrophy, circulating vasoactive hormones and exchangeable body sodium were examined in rats with chronic myocardial infarction induced by left coronary artery ligation. Chlorothiazide therapy commenced either immediately or 2 weeks after infarction. For 4 weeks, the rats were given either chlorothiazide (50 mg day−1 kg−1) in their drinking water or drinking water alone.

2. Cardiac weight increased in untreated rats with infarction in comparison with sham-operated controls, indicating the presence of chronic left ventricular dysfunction, although exchangeable body sodium, plasma renin activity, plasma vasopressin and plasma osmolality remained unchanged.

3. Chlorothiazide raised haematocrit and plasma renin activity equally in rats with and without infarction, although exchangeable body sodium, plasma vasopressin and plasma osmolality were not changed by the treatment. Plasma atrial natriuretic peptide was 2-fold higher in rats with infarction and this response was not affected by chlorothiazide treatment. Chlorothiazide therapy did not prevent or reverse cardiac hypertrophy.

4. Chronic diuretic therapy in this experimental model of heart failure did not reduce extracellular sodium, plasma vasopressin or the extent of ventricular hypertrophy, possibly because the condition was associated with activation of the renin—angiotensin system.
Differences in Microvascular Fluid Permeability between Long-Duration Type 1 (Insulin-Dependent) Diabetic Patients with and without Significant Microangiopathy
Authors: Jaap Alan J. , Shore Angela C. , Tooke John E.
Published: August 2015

1. To further investigate the role of microvascular functional changes in the pathogenesis of diabetic microangiopathy in type 1 diabetes, microvascular fluid permeability was measured in nine patients with a long disease duration and no or minimal (background retinopathy alone) microangiopathy, nine age-, sex- and duration-matched patients with microalbuminuria and nine control subjects. Microvascular fluid permeability was assessed by determination of the forearm capillary filtration coefficient using a sensitive strain-gauge plethysmographic technique.

2. Microvascular fluid permeability was significantly higher in the patients with microalbuminuria [8.5 (6.8–15.2) × 10−3 ml min−1 100 g−1 of tissue mmHg−1; median (range)] than in the patients with no or minimal complications [5.2 (3.6–7.0) × 10−3 ml min−1 100 g−1 of tissue mmHg−1, P < 0.001]. There was, however, no significant difference in microvascular fluid permeability between the patients with no or minimal complications and control subjects [4.5 (3.2–5.7) × 10−3 ml min−1 100 g−1 of tissue mmHg−1, P = 0.31]. Blood pressure and glycaemic control were similar in the two groups of diabetic patients.

3. These results provide further evidence that changes in microvascular permeability are found in other vascular beds in patients with incipient nephropathy, whereas no such changes are found in patients with a long disease duration and little evidence of microangiopathy.
Action of Endothelin-1 on Glomerular Haemodynamics in the Dog: Lack of Direct Effects on Glomerular Ultrafiltration Coefficient
Authors: Heller Jiri , Kramer Herbert J. , Horacek Vladislav
Published: August 2015

1. Although numerous studies have demonstrated the potent vasoconstrictor effect of endothelin-1 on the renal vasculature, it is difficult to differentiate in vivo between indirect and direct actions of endothelin.

2. In the present study we therefore performed micropuncture experiments in 14 anaesthetized dogs after the administration of endothelin-1 into the renal artery (i.r.a.) for 15 min at a dose of 2.78 ng min−1 kg−1 which did not affect blood pressure or contralateral kidney function.

3. In seven dogs on a ‘normal’ sodium diet (3.5 mmol of NaCl day−1 kg−1) endothelin-1 resulted in decreases in renal blood flow and glomerular filtration rate with a rise in filtration fraction from 0.24 ± 0.01 to 0.35 ± 0.01. Similar changes were seen at the single-nephron level. An increase from 0.11 ± 0.01 to 0.23 ± 0.02 (+ 109 ± 11%) in efferent, and from 0.15 ± 0.01 to 0.24 ± 0.02 mmHg min−1 μl−1 (+58 ± 4%) in afferent arteriolar resistance was observed. The ultrafiltration coefficient, Kf, decreased from 4.75 ± 0.14 to 3.67 ± 0.14 μl min−1 mmHg−1 (P<0.01).

4. In another group of seven dogs, the same endothelin-1 infusion was given after an administration into the renal artery of a ‘cocktail’ designed to block the receptors of α- and β-adrenergic agonists, thromboxane A2, leukotrienes and angiotensin II together with intravenous cyclo-oxygenase inhibition. Under these conditions, the vasoconstrictor action of endothelin-1 was reduced by more than 30%. The increase in vascular resistance was now relatively similar in both arterioles, i.e. +44 ± 5% in the afferent and 66 ± 6% in the efferent arterioles (no significant difference). No change in Kf was seen after the ‘cocktail’-blockade (9.4 ± 0.4 versus 10.1 ± 0.1 μl min−1 mmHg−1).

5. In conclusion, in anaesthetized dogs on a ‘normal’ salt diet, the vasoconstrictor effect of endothelin-1 is more pronounced on the efferent than on the afferent arteriole. This is accompanied by decreases in glomerular filtration rate and water, urea and electrolyte excretion. Part of the vasoconstrictor action of endothelin seems to be mediated by other autacoids. Endothelin-1 itself contributes only partly to pre- and post-glomerular vasoconstriction and has no direct effect on the glomerular ultrafiltration coefficient Kf.
Central and Peripheral Haemodynamic Responses to High Carbohydrate and High Fat Meals in Human Cardiac Transplant Recipients
Authors: Kearney M. T. , Cowley A. J. , Stubbs T. A. , Perry A. J. , MacDonald I. A.
Published: August 2015

1. Patients with autonomic dysfunction and elderly people with an age-related decline in autonomic function can suffer from a fall in blood pressure after eating. While the cardiovascular changes after eating and the effect of meal composition on these changes are well established, the underlying mechanisms are less clear.

2. This study assessed the cardiac, circulatory and humoral responses to ingestion of isoenergetic (2.5 MJ) high carbohydrate and high fat meals in nine orthotopic cardiac transplant recipients, who before transplantation had significant circulatory, metabolic and autonomic abnormalities and after transplantation had complete or partial extrinsic cardiac denervation, and compared them to the responses seen in nine healthy age-matched control subjects.

3. All variables were measured non-invasively. Cardiac transplant recipients, despite cardiac denervation, showed a normal heart rate response to high carbohydrate and high fat meals (maximal increase at 30 min postprandially +7.8 ± 1.1 and +6.3 ± 1.4 beats/min respectively), a normal cardiac output response to the high carbohydrate meal (maximal increase at 30 min +1.16 ± 0.25 l/min), but a significantly attenuated cardiac output response to the high fat meal. Cardiac transplant recipients had attenuated superior mesenteric artery blood flow responses after both meals (P < 0.05) and an attenuated calf vascular resistance response after the high fat meal (P < 0.01). Throughout the study after both meals, cardiac transplant recipients maintained blood pressure.

4. This study demonstrates that cardiac transplant recipients, despite partial or complete cardiac denervation, have a normal chronotropic response to food and a normal cardiac output response to a high carbohydrate meal. The attenuated cardiac output response to a high fat meal did not compromise blood pressure, due at least in part to decreased splanchnic vasodilatation.
Platelet 5-Hydroxytryptamine is Decreased in a Preliminary Group of Depressed Patients Receiving the 5-Hydroxytryptamine Re-Uptake Inhibiting Drug Fluoxetine
Authors: Menys V. C. , Smith C. C. T. , Lewins P. , Farmer R. D. T. , Noble M. I. M.
Published: August 2015

1. In view of the importance of 5-hydroxytryptamine in coronary thrombosis, we wanted to know whether a potentially protective decrease in platelet 5-hydroxytryptamine could be achieved by treatment with an inhibitor of 5-hydroxytryptamine uptake, fluoxetine.

2. We studied 15 patients treated for psychiatric indications with fluoxetine, and compared the findings with those obtained with blood from 18 patients treated with amitriptyline and 13 controls previously treated for affective disorders.

3. Platelet-rich plasma 5-hydroxytryptamine levels were significantly decreased in the fluoxetine group (P > 0.005) but not in the amitriptyline group compared with the control group.

4. Collagen-induced aggregation in whole blood anti-coagulated with hirudin was measured by sequential single platelet counting. The contribution of 5-hydroxytryptamine was assessed from the effect of adding the 5-hydroxytryptamine specific antagonist ICI 170809. This contribution was significantly decreased in the fluoxetine group but not in the amitriptyline group compared with the control group.

5. It is concluded that platelet 5-hydroxytryptamine is indeed decreased by fluoxetine, and we would predict a protective effect of fluoxetine against coronary thrombosis.
Effects of Adrenaline Infusion on the Interstitial Environment of Subcutaneous Adipose Tissue as Studied by Microdialysis
Authors: Samra J. S. , Simpson E. J. , Clark M. L. , Forster C. D. , Humphreys S. M. , MacDonald I. A. , Frayn K. N.
Published: August 2015

1. Adrenaline was infused at a rate of 25 ng min−1 kg−1 into seven healthy volunteers and its effects on adipose tissue were studied by microdialysis.

2. Adrenaline infusion led to a rapid rise in plasma adrenaline concentration from a basal value of 0.15 ± 0.03 nmol/l to a peak value of 1.82 ± 0.15 nmol/l within 30 min (analysis of variance: P < 0.001). Plasma noradrenaline levels increased from the basal value of 1.48 ± 0.21 nmol/l to 1.78 ± 0.20 nmol/l within 30 min of infusion (analysis of variance: P < 0.05). Once the infusion was stopped the plasma adrenaline and noradrenaline levels returned to basal values within 15 min.

3. The arterialized blood glycerol concentration increased from the basal value of 47 ± 6μmol/l to 101 ± 8 μmol/l (analysis of variance: P < 0.001), and the interstitial glycerol concentration increased from 181 ± 17 μmol/l to 350 ± 47μmol/l (analysis of variance: P < 0.001) within 30 min of adrenaline infusion. Thereafter the concentrations declined gradually towards basal values. When the infusion was discontinued the levels declined further, below the basal value.

4. Adrenaline infusion caused a significant increase in the plasma glucose and blood lactate concentration (analysis of variance: P < 0.001 and P < 0.001), but no such effect was observed in the interstitial concentrations.

5. The basal dialysate concentrations of adrenaline and noradrenaline were 43 ± 37 pmol/l and 1170 ± 430 pmol/l respectively. There were difficulties in estimating the absolute interstitial concentrations of adrenaline and noradrenaline which are discussed. The dialysate adrenaline concentration increased to a peak value of 112 ± 48 pmol/l (analysis of variance: P < 0.05) within 30 min. The dialysate noradrenaline concentration increased to a peak value of 2830 ± 1470 pmol/l, but the rise was not significant.

6. These results show that the interstitial concentrations of metabolites and hormones can be significantly different from those of blood and plasma and these differences reflect tissue specialization.
Blood Transfusion Enhances Production of T-Helper-2 Cytokines and Transforming Growth Factor β in Humans
Authors: Gafter Uzi , Kalechman Yona , Sredni Benjamin
Published: August 2015

1. Blood transfusion confers immune suppression with improved allograft survival. The aim of this study was to evaluate the effect of blood transfusion on the production of T-helper-2 cytokines and transforming growth factor β, which are associated with suppression of allograft rejection. An additional aim was to try to identify which blood cell type is mostly responsible for the blood transfusion effect. Production of interleukin-4, interleukin-10 and transforming growth factor β by peripheral blood mononuclear cells isolated from patients with end-stage renal disease was measured in vitro. These assays were performed before, and 4 h, 4, 7 and 14 days after a single blood transfusion and the transfusion of one unit of leucocyte-free erythrocytes.

2. Blood transfusion stimulated a significant rise in the production of all three cytokines measured. Transfusion of erythrocytes had no effect on the production of interleukin-4 or interleukin-10.

3. It is suggested that blood transfusion enhances the production of interleukin-4, interleukin-10 and transforming growth factor β. These cytokines may inhibit production of T-helper 1 and pro-inflammatory cytokines, deactivate cytotoxic cells and thereby suppress allograft rejection. It is further suggested that the leucocyte is the transfused cell type which is mostly associated with induction of this immunosuppressive response.
Weanling Rats Exposed to Maternal Low-Protein Diets during Discrete Periods of Gestation Exhibit Differing Severity of Hypertension
Authors: Langley-Evans Simon C. , Welham Simon J. M. , Sherman Rachel C. , Jackson Alan A.
Published: August 2015

1. In the rat, hypertension is induced by fetal exposure to maternal low-protein diets. The effect on blood pressure of undernutrition before conception and during discrete periods in early, mid or late pregnancy was assessed using an 18% casein (control) diet and a 9% casein diet to apply mild protein restriction.

2. The offspring of rats fed 9% casein developed raised blood pressure by weaning age. Feeding a low-protein diet before conception was not a prerequisite for programming of hypertension.

3. Hypertension was observed in rats exposed to low protein during the following gestational periods: days 0–7, days 8–14 and days 15–22. Blood pressure increases elicited by these discrete periods of undernutrition were lower than those induced by feeding a low-protein diet throughout pregnancy. The effect in early gestation was significant only in male animals. Post-natal growth of male rats exposed to low-protein diets was accelerated, but kidneys were small in relation to body weight.

4. Biochemical indices of glucocorticoid action in liver, hippocampus, hypothalamus and lung were elevated in rats exposed to low-protein diets in utero. The apparent hypersensitivity to glucocorticoids was primarily associated with undernutrition in mid to late gestation.

5. Plasma renin activity was elevated in rats exposed to 9% casein over days 15–22 of gestation. Animals undernourished over days 0–7 and 8–14 produced pups with lower plasma angiotensin II concentrations at weaning.

6. Fetal exposure to maternal low-protein diets for any period in gestation may programme hypertension in the rat. Alterations to renal structure, renal hormone action or the hypothalamic—pituitary-adrenal axis may all play a role in the programming phenomenon, either independently or in concert.
α-Adrenoceptor Mechanisms of Thermoregulation during Cold Challenge in Humans
Authors: Frank Steven M. , El-Gamal Nader , Raja Srinivasa N. , Wu Peter K.
Published: August 2015

1. Previous studies on the thermoregulatory effects of α-adrenoceptor antagonists have been performed primarily in animals and the findings have been inconsistent. There is evidence for thermoregulatory impairment by α-adrenergic antagonists in humans not exposed to cold, but the effects of α-adrenergic blockade during cold challenge have not been investigated.

2. Fourteen healthy human volunteers (seven elderly, aged 55–68 years and seven young, aged 19–27 years) were studied on three separate days and received three randomly assigned treatments: (i) control (no drug), (ii) low-dose phentolamine, and (iii) high-dose phentolamine. On each day cold intravenous saline (4°C) was given until both vasoconstriction and shivering were triggered or a maximum fluid volume (40 ml/kg) was delivered. Core temperature, peripheral vasoconstriction and metabolic heat production were measured.

3. The α-adrenoceptor antagonist caused a dose-dependent inhibition of vasoconstriction in the elderly but did not impair vasoconstriction in the young subjects at the doses that were given. Shivering and metabolic heat production were unaffected by α-adrenergic blockade in the elderly or in the young.

4. These findings illustrate the selective inhibition of vasoconstriction (but not shivering) by α-adrenoceptor antagonism in elderly individuals. Compared with the young, the elderly are more sensitive to the effects of α-antagonists, perhaps due to downregulation of the α-adrenoceptor. These findings lead us to conclude that thermoregulatory vasoconstriction is α-adrenergically mediated, and this response is attenuated by α-adrenoceptor blockade in elderly humans.
Na+,K+-ATPase of Human Placenta during Gestational Hypertension: A Biochemical—Biophysical Study
Authors: Rabini Rosa A. , Zolese Giovanna , Staffolani Roberto , Lucarelli G. , Amler E. , Cester Nelvio , Mazzanti Laura
Published: August 2015

1. Na+,K+-ATPase is the membrane enzyme catalysing the active transport of Na+ and K+ across the plasma membrane of animal cells. A reduced activity of Na+,K+-ATPase has been described in gestational hypertension in a variety of cell types, in agreement with the hypothesis that gestational hypertension can induce membrane transport modifications similar to those reported for essential hypertension. The causes of the reduced Na+,K+-ATPase activity are still debated.

2. The aim of the present work was to investigate the molecular mechanism of the reduced enzymic activity in gestational hypertension using as a model Na+,K+-ATPase purified from human placenta. Na+,K+-ATPase obtained from term placentas of eight healthy pregnant women and eight age-matched women with gestational hypertension was purified as previously described.

3. We observed in gestational hypertension: (i) a significant increase in the activation energies above transition temperature; (ii) a significant decrease in the fluorescence polarization of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (i.e. increased fluidity) and an increase in the mean lifetime (modified hydrophobicity); (iii) a lower Kq, suggesting an enzymic structural modification; and (iv) an increased mean lifetime and rotational relaxation time of pyrene isothiocyanate, indicating a modified ATP binding site.
Understanding the Molecular Basis of Cell Migration; Implications for Clinical Therapy in Multiple Sclerosis
Authors: Milner Richard
Published: August 2015

1. Multiple sclerosis is characterized by areas of demyelination spread throughout the central nervous system, in which the myelin sheaths surrounding axons are destroyed. While therapies aimed at suppressing the autoimmune response, such as β-interferon, may prevent further damage, they cannot repair or replace the lost myelin. To this end, an additional therapy has been proposed, which involves transplanting cells of the oligodendrocyte lineage into the central nervous system.

2. The cell of interest for transplantation is the oligodendrocyte precursor because, unlike the differentiated cell, it is an intrinsically migratory and proliferative cell. In order to optimize the transplant strategy we have investigated the molecular mechanisms that control migration in vitro, so that these mechanisms might be upregulated to maximize cell migration in vivo. We have focused on the integrin family of cell adhesion molecules, known to play a fundamental role in the regulation of migration in other cell types.

3. These studies show that oligodendrocytes express a limited repertoire of integrins consisting of α6β1 and three different αv integrins. α6β1 is expressed throughout development but αv integrins show developmental regulation; differentiation is accompanied by loss of αvβ1 and upregulation of αvβ5.

4. Function-blocking studies show that oligodendrocyte precursor migration in vitro is mediated primarily by the developmentally regulated αvβ1 integrin, but not α6β1 or αvβ3. Taken together with previous evidence that cell migration can be regulated by altering integrin expression, this work suggests that modifying expression levels of αvβ1 on oligodendrocyte precursors may increase the migratory capacity of these cells. If so, this would support a future therapeutic strategy aimed at transplanting genetically modified oligodendrocyte precursors to repair widespread demyelinated lesions.
Role of Nitric Oxide towards Vasodilator Effects of Substance P and ATP in Human Forearm Vessels
Authors: Shiramoto Masanari , Imaizumi Tsutomu , Hirooka Yoshitaka , Endo Toyonari , Namba Takashi , Oyama Jun-Ichi , Hironaga Kiyoshi , Takeshita Akira
Published: August 2015

1. It has been shown in animals that substance P as well as acetylcholine releases endothelium-derived nitric oxide and evokes vasodilatation and that ATP-induced vasodilatation is partially mediated by nitric oxide. The aim of this study was to examine whether vasodilator effects of substance P and ATP are mediated by nitric oxide in humans.

2. In healthy volunteers (n = 35), we measured forearm blood flow by a strain-gauge plethysmograph while infusing graded doses of acetylcholine, substance P, ATP or sodium nitroprusside into the brachial artery before and after infusion of NG-monomethyl-l-arginine (4 or 8 μmol/min for 5 min). In addition, we measured forearm blood flow while infusing substance P before and during infusion of l-arginine (10 mg/min, simultaneously), or before and 1 h after oral administration of indomethacin (75 mg).

3. Acetylcholine, substance P, ATP or sodium nitroprusside increased forearm blood flow in a dose-dependent manner. NG-Monomethyl-l-arginine decreased basal forearm blood flow and inhibited acetylcholine-induced vasodilatation but did not affect substance P-, ATP-, or sodium nitroprusside-induced vasodilatation. Neither supplementation of l-arginine nor pretreatment with indomethacin affected substance P-induced vasodilatation.

4. Our results suggest that, in the human forearm vessels, substance P-induced vasodilatation may not be mediated by either nitric oxide or prostaglandins and that ATP-induced vasodilatation may also not be mediated by nitric oxide.
Gene Therapy for Diabetes Mellitus
Authors: Docherty Kevin
Published: August 2015

1. This review describes experimental approaches to test the feasibility of using gene therapy to administer insulin to type 1 and type 2 diabetic patients. Two approaches, i.e. ex vivo and in vivo transfer of the insulin gene, are described.

2. Substantial progress has been made in recent years in engineering glucose-responsive β-cell lines that have been genetically engineered to proliferate or differentiate in response to appropriate extracellular signals.

3. Non-β-cell lines have been engineered to constitutively secrete insulin at a constant rate. These cells may improve glycaemic control in patients over longer periods when used in combination with insulin injections. Engineering glucose-stimulated insulin secretion in such cells has proved extremely difficult and several genes may be required.

4. In vivo transfer of the insulin gene to animals results in improved control of diabetes. However, for safety reasons this approach may have limited use in the treatment of diabetes in humans.
Fractal Component of Variability of Heart Rate and Systolic Blood Pressure in Congestive Heart Failure
Authors: Butler Gary C. , Ando Shin-Ichi , Floras John S.
Published: August 2015

1. There is a substantial non-harmonic or fractal component to the variability of both heart rate and blood pressure in normal subjects. Heart rate is the more complex of these two signals, with respect to the slope, β, of the 1/fβ relationship. In congestive heart failure, heart rate spectral power is attenuated, but the fractal and harmonic components of heart rate and systolic blood pressure variability have not been characterized.

2. Two groups, each comprising 20 men, were studied during 15 min of supine rest and spontaneous respiration: one with functional class II—IV heart failure (age 52 ± 2 years; mean ± SEM) and a second group of healthy men (age 46 ± 2 years).

3. Total spectral power for heart rate was significantly reduced in heart failure (P < 0.02), whereas total spectral power for systolic blood pressure was similar in the two groups. In both heart failure and normal subjects, 65–80% of total spectral power in these two signals displayed fractal characteristics.

4. In heart failure, the slope of the 1/fβ relationship for heart rate was significantly steeper than in normal subjects (1.40 ± 0.08 compared with 1.14 ± 0.05; P < 0.05), indicating reduced complexity of the fractal component of heart rate variability. There was no significant difference in the 1/fβ slope for systolic blood pressure variability between these two groups, but the blood pressure signals were less complex than heart rate variations in both heart failure (2.31 ± 0.15; P < 0.006) and normal subjects (2.47 ± 0.15; P < 0.0001).

5. Parasympathetic nervous system activity, as estimated from heart rate variability was reduced (P < 0.01) in patients with heart failure, whereas trends towards increased sympathetic nervous system activity and decreased non-harmonic power were not significant.

6. The non-harmonic components of cardiac frequency are reduced in heart failure. Non-harmonic power is not attenuated, but the complexity of the heart rate signal is less than in subjects with normal ventricular function. A reduction in parasympathetic modulation appears to contribute to this loss of complexity of heart rate. Consequently, the heart rate signal comes to resemble that of blood pressure. In contrast, the variability and complexity of the systolic blood pressure signal is similar in heart failure and normal subjects. This reduced complexity of heart rate variability may have adverse implications for patients with heart failure.
Determination of Appropriate Recording Force for Non-Invasive Measurement of Arterial Pressure Pulses
Authors: Driscoll M. Darcy , Malcolm J. , Arnold O. , Marchiori Gordon E. , Harker Linda A. , Sherebrin Marvin H.
Published: August 2015

1. Non-invasive recording techniques of the arterial pressure pulse will distort the arterial wall and may alter pulse wave measurements. We hypothesized that intersubject variability of these measurements would be reduced if recording forces were normalized to reflect individualized arterial occlusion forces.

2. In 10 normal male subjects (age 24 ± 1 years), brachial, radial and finger arterial pressure pulses were recorded simultaneously using volume displacement pulse transducers (Fukuda TY-303) and a finger pressure monitoring system (Finapres, Ohmeda 2300) and were made at 2, 5 and 10–100% (10% increments) of the brachial arterial force associated with marked distortion of finger pulsations. Forces were applied at the brachial site in a randomized order while a constant 1.8 N force was applied at the radial artery site. Pressure pulses were analysed using the discrete fast Fourier transform.

3. Pulse amplitude, contour, wave velocity and relative transmission ratios remained relatively constant until the brachial artery recording force exceeded 59.9 ± 0.3% of the largest recording force used in each subject (7.14 ± 0.75 N). The finger pulse pressures (P < 0.0001), radial pulse amplitudes (P < 0.0001) and contours (harmonics 2–6, P < 0.003), pulse wave velocity (P < 0.021) and relative transmission ratios (harmonics 3–7, P < 0.01) then decreased with higher recording forces.

4. To avoid distortion, non-invasive recordings of arterial pressure pulse amplitude, contour, pressure wave velocity and relative transmission ratios along a peripheral arterial segment should use recording forces of less than 60% of the force associated with marked distortion of finger pulsations.
Determination of Urea Kinetics by Isotope Dilution with [13C]Urea and Gas Chromatography–isotope Ratio Mass Spectrometry (GC–IRMS) Analysis
Authors: Kloppenburg W. D. , Wolthers B. G. , Stellaard F. , Elzinga H. , Tepper T. , De Jong P. E. , Huisman R. M.
Published: August 2015

1. Stable urea isotopes can be used to study urea kinetics in humans. The use of stable urea isotopes for studying urea kinetic parameters in humans on a large scale is hampered by the high costs of the labelled material. We devised a urea dilution for measurement of the distribution volume, production rate and clearance of urea in healthy subjects and renal failure patients using the inexpensive single labelled [13C]urea isotope with subsequent analysis by headspace chromatography—isotope ratio MS (GC—IRMS) of the [13C]urea enrichment.

2. The method involves measurement of the molar percentage excess of [13C]urea in plasma samples taken over a 4 h period after an intravenous bolus injection of [13C]urea. During the sample processing procedure, the plasma samples together with calibration samples containing a known molar percentage excess of [13C]urea are acidified with phosphoric acid to remove endogenous CO2, and are subsequently incubated with urease to convert the urea present in the plasma samples into CO2. The 13C enrichment of the generated CO2 is analysed by means of GC—IRMS. This method allows measurement of the molar percentage excess of [13C]urea to an accuracy of 0.02%.

3. Reproducibility studies showed that the sample processing procedure [within-run coefficient of variation (CV) <2.8% and between-run CV <8.8%] and the GC—IRMS analysis (within-day CV <1.3% and between-day CV <1.3%) could be repeated with good reproducibility.

4. In clinical urea kinetic studies in a healthy subject and in a renal failure patient without residual renal function, reproducible values of the distribution volume, production rate and clearance of urea were determined using minimal amounts of [13C]urea (25–50 mg).

5. Because only low [13C]urea enrichments are needed in this urea dilution method using GC—IRMS analysis, the costs of urea kinetic studies are reduced considerably, especially in patients with renal failure.
Fermentable Dietary Fibre, Intestinal Microflora and Plasma Hormones in the Rat
Authors: Ghatei M. A. , Ratcliffe B. , Bloom S. R. , Goodlad R. A.
Published: August 2015

1. Conventional and germ-free rats were fed a fibre-free elemental diet with or without the addition of fermentable dietary fibres. We have previously reported that fibre was associated with greatly increased epithelial cell proliferation, but only in the conventional group, implying that it is the breakdown of fibre by the colonic microflora that is the main determinant of mucosal proliferation in the hind gut. The relationship of these changes to various plasma hormones implicated in intestinal growth control are described in this paper.

2. The most dramatic finding was that plasma levels of enteroglucagon and peptide YY were greatly increased in the germ-free groups. The response of these rats to fibre differed in that fibre decreased levels of enteroglucagon and peptide YY in the germ-free animals, but increased them in the conventional rats. Gastrin and insulin levels were significantly lowered in the fibre-supplemented groups, but were not affected by the microflora.

3. These results corroborate our previous findings that the effects of fibre and its fermentation are dynamically complex, and demonstrate that, like proliferation, direct effects and indirect fermentation-derived effects on plasma hormones also coexist.
Plasma Immunoreactive Leptin Concentration in End-Stage Renal Disease
Authors: Howard Jane K. , Lord Graham M. , Clutterbuck Elaine J. , Ghatei Mohammad A. , Pusey Charles D. , Bloom Stephen R.
Published: August 2015

1. Leptin is thought to be an inhibitor of appetite. As the kidney helps clear several polypeptide hormones, plasma leptin may accumulate in end-stage renal disease.

2. Plasma immunoreactive leptin was measured in four groups of subjects: haemodialysis, continuous ambulatory peritoneal dialysis and renal transplant patients and a group of healthy controls. Leptin was also measured before and after a single dialysis session.

3. There was a strong correlation between plasma immunoreactive leptin and body mass index in all groups except female haemodialysis patients. Leptin was higher in females than in males in all groups when controlled for body mass index. Mean plasma leptin [mean (SD)] was significantly higher in all renal groups [haemodialysis, 15.1 (3.6) ng/ml; continuous ambulatory peritoneal dialysis, 25.4 (4.3) ng/ml; transplants, 11.6 (2.6) ng/ml] compared with controls [5.3 (2.3) ng/ml]. There was a significant difference in the regression equations relating leptin and body mass index (dialysis > transplants > controls), even when controlled for gender. Leptin correlated modestly with serum creatinine in non-dialysis subjects. Plasma leptin immunoreactivity was slightly reduced by haemodialysis, but post-dialysis leptin was still significantly higher than that found in controls.

4. Chromatographic characterization of the high level of leptin immunoreactivity found in haemodialysis subjects showed a single elution peak corresponding to that of the highly purified human leptin standard.

5. In conclusion, leptin is higher than expected for body mass index in end-stage renal disease. Hyper-leptinaemia could contribute to the anorexia and poor nutritional status commonly seen in renal failure.
Site of Insulin Resistance after Surgery: The Contribution of Hypocaloric Nutrition and Bed Rest
Authors: Nygren Jonas , Thorell Anders , Efendic Suad , Nair K. Sree , Ljungqvist Olle
Published: August 2015

1. Insulin resistance after surgery has been shown to be related to several important derangements in protein and fat metabolism. However, mechanisms of impaired glucose tolerance after surgery remain ill-defined.

2. Insulin sensitivity and glucose kinetics (6,62H2-glucose) were studied in seven patients before and after elective surgery (surgery group), by two step-hyperinsulinaemic (0.3 and 0.8 munits kg−1 min−1), normoglycaemic (4.5 mmol/l) clamps. Six healthy subjects were studied, using the same protocol, before and after a similar period of bed rest and hypocaloric nutrition (fast/bed rest group) to delineate the effects of surgery per se.

3. Basal endogenous glucose production and whole-body glucose disposal was higher after surgery (P < 0.001), whereas no change was found after fast/bed rest. During glucose clamps, the glucose infusion rates required to maintain normoglycaemia and whole-body glucose disposal decreased (P < 0.001) after surgery, while endogenous glucose production increased (P < 0.001). In the control subjects, levels of endogenous glucose production remained unchanged after fast/bed rest. In contrast, glucose infusion rates and whole-body glucose disposal during glucose clamps also decreased after fast/bed rest (P < 0.01). However, the relative decrease in both these parameters was greater after surgery compared with after fast/bed rest (P < 0.01).

4. After surgery, energy expenditure and fat oxidation increased (P < 0.001), whereas glucose oxidation decreased (P < 0.05). No significant change was found in glucose utilization postoperatively. After fast/bed rest, no change was found in energy expenditure. However, fat oxidation increased (P < 0.01), whereas glucose oxidation and glucose utilization decreased (P < 0.05).

5. In conclusion, impaired glucose tolerance develops after surgery as a result of decreased insulin-stimulated whole-body glucose disposal as well as increased endogenous glucose release. Despite the increase in endogenous glucose production, the reduction in endogenous glucose production with each elevation of insulin was unaffected by surgery. Perioperative bed rest and/or hypocaloric nutrition contribute to the decrease in insulin-stimulated whole-body glucose disposal in the postoperative state, whereas these factors have no effects on endogenous glucose production.
Timing of Administration of Dexamethasone or the Nitric Oxide Synthase Inhibitor, Nitro-l-Arginine Methyl Ester, is Critical for Effective Treatment of Ischaemia-Reperfusion Injury to Rat Skeletal Muscle
Authors: Zhang Baimeng , Knight Kenneth R. , Dowsing Bruce , Guida Elizabeth , Phan Long H. , Hickey Michael J. , Morrison Wayne A. , Stewart Alastair G.
Published: August 2015

1. The effects of the nitric oxide synthase (NOS) inhibitors, NG-nitro-l-arginine-methyl ester (l-NAME), nitroiminoethyl-l-ornithine and S-methylisothiourea on skeletal muscle survival following 2 h of tourniquet ischaemia and 24 h of reperfusion were compared with those of the antiinflammatory steroid, dexamethasone.

2. Administration of each of the NOS inhibitors or dexamethasone 30 min before reperfusion reduced the degree of skeletal muscle necrosis 24 h after reperfusion.

3. The influence of timing of drug administration was investigated. l-NAME administered 30 min before reperfusion, at 3 h after reperfusion, but not thereafter, significantly improved muscle survival compared with saline-treated controls. Dexamethasone administered 30 min before, or at 3 or 8 h after reperfusion, but not at 16 h, significantly improved muscle survival, but neither agent had protective effects when administered before ischaemia.

4. After 8 h of reperfusion of ischaemic skeletal muscle, cell-free homogenates contained Ca2+-independent (inducible) NOS activity which was reduced in dexamethasone-treated (2.5 mg/kg) rats. Furthermore, inducible NOS mRNA levels, as detected by reverse transcriptase-PCR, were increased after 8 h of reperfusion in saline, but not in dexamethasone-treated rats.

5. These data suggest a significant deleterious effect of endogenous NO which may be restricted to the first 3 h of the reperfusion phase of ischaemia-reperfusion injury, and raise the possibility of effective treatment of incipient reperfusion injury, even after several hours of reperfusion.
Enrichment in Urinary Ammonia and Urea with Hourly Oral Doses of [15N]glycine: Evidence for a Step Function and a Circadian Rhythm in Protein Turnover
Authors: Jackson A. A. , Soares M. J. , Grove G. , Waterlow J. C.
Published: August 2015

1. The present study sought to determine the possible existence of a pool of proteins which turn over with life-time kinetics. The pattern of enrichment of ammonia and urea in hourly samples of urine was determined in normal adults to whom oral doses of [15N]glycine were given hourly for 36 h. The subjects received hourly meals throughout, and in six the study commenced at 06.00 hours, in five at 12.00 hours and in two at 18.00 h.

2. A plateau level of enrichment was achieved in urinary ammonia within 4–6 h. Regardless of the time at which the study started this plateau was held until about midnight, at which time there was an increase in enrichment, with a second higher plateau 5–6 h later. The second plateau was held to the end of the study. For urinary urea the rate of rise in enrichment was slower and smoother, because of the slow turnover of the urea pool.

3. Protein synthesis, derived from the first ammonia plateau, 179 mg h−1 kg−1, was significantly higher than that derived from the second plateau, 118 mg h−1 kg−1. Using the plateau in urea towards the end of the 36 h, the estimate of protein synthesis was 153 mg h−1 kg−1.

4. The results are considered to provide evidence of a pool of proteins for which degradation takes place in harmony with a circadian rhythm.
Activation of Two Inward Chloride Transport Systems in Rat Femoral Arterial Smooth Muscle in Deoxycorticosterone Acetate/Salt Hypertension
Authors: Harper Alexander A. , Davis Julian P. L. , Chipperfield Alan R.
Published: August 2015

1. Intracellular [Cl−] ([Cl−]i) was measured with ion-selective microelectrodes in rat femoral arterial smooth muscle in normotensive controls and after the induction of deoxycorticosterone acetate/salt hypertension.

2. Linear regression of [Cl−]i and time after the induction of hypertension showed good correlation (r = 0.96) for 5–6 weeks, as [Cl−]i increased from 30 ± 1 mmol/l (mean ± SD, n = 16), to 49 ± 2 mmol/l (n = 9, P < 0.0001).

3. Arterial systolic blood pressure also increased linearly (r = 0.97) for 5–6 weeks as hypertension developed from 122 ± 1 mmHg (n = 20) to 187 ± 7 mmHg (n = 14): there was consequently a linear relationship between [Cl−]i and arterial systolic blood pressure (r = 0.96).

4. The increase in [Cl−]i was partly because Na+−K+−Cl− co-transport activity, estimated from the fall in [Cl−]i caused by bumetanide, was greater in hypertension (18 mmol/l) than in normotension (10 mmol/l). This finding, and the depolarization of the membrane potential in hypertension (−56 ± 3 mV compared with −64 ± 4 mV in normotension; P < 0.0001), confirms previous studies.

5. The increase in [Cl−]i was also partly due to greater activity of an Na+- and HCO3−-independent, acetazolamide-sensitive inward Cl− transport system; thus acetazolamide reduced [Cl−]i by 7 mmol/l in normotension and by 16 mmol/l in hypertension.

6. In Cl−-free media, the membrane potential in normotension (−59 ± 5 mV) was not significantly different from that in hypertension (−60 ± 4 mV).

7. The role of [Cl−]i in the depolarization of the membrane potential in hypertension is discussed.
Maternal Carbenoxolone Treatment Lowers Birthweight and Induces Hypertension in the Offspring of Rats Fed a Protein-Replete Diet
Authors: Langley-Evans Simon C.
Published: August 2015

1. In the rat low birthweight and raised systolic blood pressure are the consequence of fetal exposure to maternal low protein diets. Nutritional down-regulation of the placental isoform of 11β-hydroxysteroid dehydrogenase, which may increase exposure of the fetus to maternal glucocorticoids, has been suggested to underlie effects of low protein diets on fetal growth and blood pressure.

2. Pregnant rats were fed control (18% casein) or low protein (9% casein) diets throughout gestation. Animals fed the control diet were injected with carbenoxolone, an inhibitor of 11β-hydroxysteroid dehydrogenase. Injections were administered either throughout pregnancy (days 0–22), or targeted to specific periods in early (days 0–7), mid- (days 8–14) or late (days 15–22) gestation.

3. Exposure to a low protein diet reduced birthweight and at 4 weeks of age systolic blood pressure was significantly elevated in the rats exposed to low protein. These hypertensive animals had small kidneys in proportion to body weight.

4. Fetal exposure to carbenoxolone at any period in gestation resulted in lower weight at birth. In rats exposed to the inhibitor over days 8–14, 15–22 or 0–22 systolic blood pressure at 4 weeks was significantly higher than in control animals. The greatest elevation of pressure was associated with carbenoxolone treatment in late (days 15–22) gestation. Animals with carbenoxolone-induced hypertension did not exhibit evidence of retarded renal growth.

5. Increased fetal exposure to maternal glucocorticoids impairs fetal growth and programmes elevated blood pressure in later life.