bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Fetal Kidney Morphometry during Gestation and the Relationship between Weight, Kidney Morphometry and Plasma Active Renin Concentration at Birth
Authors: Konje Justin C. , Bell Stephen C. , Morton James J. , De Chazal Richard , Taylor David J.
Published: August 2015

1. This study was designed to examine the changes in kidney morphometry during gestation in fetuses that were either appropriate or small for gestational age and the relationship between umbilical vein plasma active renin and kidney morphometry.

2. Serial ultrasound measurements of various morphometric and renal indices were performed in a cohort of 87 singleton fetuses from 22 to 38 weeks gestation. Blood was collected from the umbilical vein at delivery and active renin was measured from the plasma based on angiotensinogen I generated during incubation with plasma and ox renin substrate.

3. Growth in the longitudinal plane of fetal kidneys was similar in the small- and appropriate-for-gestational age groups; however, growth in the anterio-posterior, transverse and circumference planes of the kidneys was significantly slower in the small-for-gestational-age group after 26 weeks gestation. Differences in growth rate in the two groups were most marked between 26 and 34 weeks and persisted until delivery when the anterior-posterior diameter was significantly larger (P < 0.00001) in the appropriate-for-gestational-age group (26.1 ± 2.5 mm compared with 19.8 ± 2.6 mm). The mean umbilical vein active plasma renin concentration at delivery was significantly higher (P < 0.05) in the small-for-gestational-age group (274.4 ± 32.9 μ-units/ml plasma) than in the appropriate-for-gestational-age group (164.9 ± 28.3 μ-units/ml plasma). In addition, there were statistically significant inverse correlations between renin concentration and birthweight (r = − 0.55, P < 0.001) and between renin concentration and kidney anterior-posterior diameter (r = −0.67, P < 0.001).

4. Fetal renal growth was slower in small than in appropriate-for-gestational-age fetuses. The period of 26–34 weeks gestation was that during which maximum fetal renal growth occurred. Umbilical vein plasma renin levels were higher in small-for-gestational-age fetuses. The findings of slow fetal renal growth rate and associated high renin concentrations seen in small-for-gestational-age fetuses could be implicated in an irreversible reno-vascular pathology leading to adult hypertension. We suggest that 26 to 34 weeks could be the ‘critical period’ during which the insult that leads to in-utero programming for the development of adult hypertension occurs.
Renal Metabolism and Effects of the Glutamyl Derivatives of l-Dopa and 5-Hydroxytryptophan in Man
Authors: Wa T. C. Li Kam , Freestone S. , Samson R. R. , Johnston N. R. , Lee M. R.
Published: August 2015

1. Equimolar amounts of y-l-glutamyl-l-3,4-dihydroxyphenylalanine (gludopa) and γ-l-glutamyl-5-hydroxy-l-tryptophan were infused separately and together in eight healthy, salt-replete male subjects in a placebo-controlled, cross-over study to investigate whether the administration of one amine precursor affects the renal metabolism of the other and to determine whether dopamine or 5-hydroxytryptamine would be generated preferentially. The overall effect on sodium excretion was also measured when both precursors were administered simultaneously.

2. Administration of gludopa was associated with marked increases in the urinary excretion of l-dopa, dopamine and 3,4-dihydroxyphenylacetic acid, together with a rise in the urinary excretion of sodium. γ-l-Glutamyl-5-hydroxy-l-tryptophan, on the other hand, produced marked increases in the urinary excretion of 5-hydroxy-l-tryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid, and this was accompanied by a slight, but non-significant, reduction in sodium excretion. About 27% of the infused dose of gludopa (on a molar basis) was recovered in the urine as dopamine whereas 15% of the given dose of γ-l-glutamyl-5-hydroxy-l-tryptophan was excreted as 5-hydroxytryptamine.

3. The urinary excretion values of l-dopa, dopamine and 3,4-dihydroxyphenylacetic acid after the simultaneous infusion of gludopa and γ-l-glutamyl-5-hydroxy-l-tryptophan were not significantly different from those observed after infusion of gludopa only. Similarly, the urinary excretion values of 5-hydroxy-l-tryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid during the co-infusion were similar to those measured after administration of γ-l-glutamyl-5-hydroxy-l-tryptophan only. The net effect of the concomitant infusion of both glutamyl derivatives was an increase in urinary sodium excretion.

4. Our study in salt-replete individuals suggests that dopamine rather than 5-hydroxytryptamine was preferentially produced when equimolar amounts of their precursors were provided and that the natriuretic effect of dopamine, generated intrarenally from gludopa, was greater than the sodium retaining action of 5-hydroxytryptamine derived from γ-l-glutamyl-5-hydroxy-l-tryptophan. Comparison of the urinary metabolite data after the separate and concomitant infusion of the two glutamyl compounds provided no evidence of competitive inhibition of synthesis of either amine.
Presence of the NHE3 Isoform of the Na+/H+ Exchanger in Human Gallbladder
Authors: Colombani V. , Silviani V. , Marteau C. , Lerique B. , Cartouzou G. , Gerolami A.
Published: August 2015

1. In man and in various animal species, absorption of NaCl from bile by the gallbladder mucosa is associated with luminal proton secretion. A similar absorption of NaCl in small intestine, colon and renal tubule is related, at least in part, to the presence of the NHE3 isoform of the Na+/H+ exchanger. This work was designed to find out whether NHE3 is also present in human gallbladder.

2. At surgery, 100–200 mg of the gallbladder wall was obtained from patients treated by cholecystectomy for gallstones. After isolation of the mucosa, total RNA was extracted and submitted to reverse transcription—polymerase chain reaction with two primers: 5′-AAGCCICTGGTGCAGTGGCTGAAGG-3′ and 5′-GGAGTCCTTIAAGTCGGCIAAGCTGGGC-3′, designed to amplify a sequence of 645 bp of rabbit NHE3 mRNA (642 bp in man). RNA from human liver and from rabbit heart, neither of which contain NHE3, and human ileal RNA, which does contain NHE3, were used as controls.

3. RNA extracted from the mucosal moiety of the gallbladder wall gave an amplification product of about 645 nucleotides. Controls gave the expected negative or positive results. Sequencing of the amplified RNA showed it was almost identical to previously determined sequences of NHE3 in other human tissues.

4. It is concluded that the mucosa of human gallbladder contains the mRNA of NHE3 isoform. This isoform could therefore play a role in sodium absorption from bile.
Regulation of Pancreatitis-Associated Protein (HIP/PAP) mRNA Levels in Mouse Pancreas and Small Intestine
Authors: McKie Andrew T. , Simpson Robert J. , Ghosh Simon , Peters Timothy J. , Farzaneh Farzin
Published: August 2015

1. In the present study we have examined the expression of pancreatitis-associated protein mRNA in mouse pancreas and small intestine and determined the effect of a number of factors on the steady-state level of the RNA.

2. The normally low level of pancreatitis-associated protein mRNA in pancreas increased severalfold after 6 h of hypoxia, reaching peak levels (approximately 10-fold greater than normal) after 24 h hypoxia. After 3 days' hypoxia pancreatitis-associated protein mRNA levels were again undetectable.

3. In the pancreas the level of pancreatitis-associated protein mRNA was also increased by alcohol and iron overload, but not by paracetamol.

4. In the small intestine expression of pancreatitis-associated protein mRNA was higher in normal ileum than in duodenum. In the ileum pancreatitis-associated protein mRNA levels were increased 7 to 15-fold after 6 h hypoxia, reaching peak levels by 24 h. Levels declined after 3 days' hypoxia, but remained higher than normal.

5. In the ileum long-term (4 weeks) dietary iron deficiency reduced pancreatitis-associated protein mRNA levels compared with control fed mice, whereas parenteral iron overload increased pancreatitis-associated protein mRNA levels.

6. The data presented suggest regulation of pancreatitis-associated protein gene expression by both oxygen tension and iron status.
Total Energy Expenditure and Physical Activity Measured with the Bicarbonate-Urea Method in Patients with Human Immunodeficiency Virus Infection
Authors: Paton N. I. J. , Elia M. , Jebb S. A. , Jennings G. , MacAllan D. C. , Griffin G. E.
Published: August 2015

1. Our objectives were to measure total energy expenditure, the daily variation in total energy expenditure and the physical activity level in a group of HIV-positive subjects using the bicarbonate-urea method. The study also aimed to assess the practicalities of using the bicarbonate-urea technique in free-living conditions.

2. Total energy expenditure was measured with the bicarbonate-urea method over 2 consecutive days (1 day in one subject) in 10 male patients with HIV infection (median CD4 count = 30). Resting energy expenditure was measured by indirect calorimetry. Physical activity level (total energy expenditure/resting energy expenditure) was calculated from these measurements and from activity diaries.

3. Resting energy expenditure was found to be 7.46 ± 0.87 MJ/day, 5% higher than predicted values. Total energy expenditure was 10.69 ± 1.95 MJ/day with an intra-individual day-to-day variation of 6 ± 6%. The measured physical activity level was 1.42 ± 0.14, higher than the diary estimate of 1.34 ± 0.16 (P = 0.029), and there were large inter-method differences in individual values. The subcutaneous infusion of bicarbonate was well tolerated and did not seem to restrict normal activities.

4. Total energy expenditure was not elevated in the group of HIV-positive subjects when compared with reference values for normal subjects. The physical activity level of the patients in this study was lower than that measured using other techniques in healthy young men, but was compatible with that expected for people leading a sedentary lifestyle. Reductions in physical activity in patients with HIV are likely to contribute to the wasting process and physical activity level may thus be a clinically useful measure. This study has also provided the first tracer estimate of the day-to-day variation in total energy expenditure. The bicarbonate-urea method represents an important new investigative tool for measuring total energy expenditure which has previously only been possible within the confines of a whole-body calorimeter or using the expensive doubly labelled water method.
Rates of Bone Loss in Peri- and Postmenopausal Women: A 4 Year, Prospective, Population-Based Study
Authors: Young R. , May H. , Murphy S. , Grey C. , Compston J. E.
Published: August 2015

1. Age-related bone loss is well established but reported rates of bone loss in the spine and femur vary widely. The aim of the present study was to investigate changes in bone mineral density in the lumbar spine and proximal femur in healthy postmenopausal women.

2. One hundred and thirty-eight population-based women, aged 45–65 years, recruited from general practice registers in 1990, were assessed at baseline; 108 returned for repeat assessment 4 years later, of whom 31 had taken hormone replacement therapy for 12 months or more of the 4-year study period. Bone densitometry of the lumbar spine and proximal femur was performed by dual-energy X-ray absorptiometry. Serum 25-hydroxyvitamin D and oestradiol were measured by RIA and serum intact parathyroid hormone by radio-immunometric assay.

3. The mean age at follow-up was 62 years (mean of 13.6 years after menopause). Lumbar spine bone mineral density was significantly higher in women who had received hormone replacement therapy for more than 12 months during the study period than in those who had not (P < 0.01). There was no difference between these two groups in the femoral neck or trochanteric bone mineral density. In the lumbar spine, the annual change in bone mass in untreated women was −0.39% (95% confidence intervals −0.60 to −0.09; P < 0.02) whereas there was a small gain in women receiving hormone replacement therapy [+0.36% (−0.12 to 0.84; P not significant)]. The annual change in bone mass in the femoral neck and trochanter was −0.51 and −0.45 respectively in untreated women (P < 0.01 and P < 0.02), and −0.16 and −0.15 in those receiving hormone replacement therapy (P not significant).

4. Our results demonstrate relatively low rates of bone loss in the spine and proximal femur in these healthy, population-based peri- and postmenopausal women. Hormone replacement therapy appeared to be associated with a significant protective effect on spinal, but not femoral, bone mineral density.
Plasma Ionized Magnesium during Acute Hyperventilation in Humans
Authors: Hafen Gaudenz , Laux-End Regula , Truttmann Anita C. , Schibler Andreas , McGuigan John A. S. , Peheim Edgar , Bianchetti Mario G.
Published: August 2015

1. Respiratory alkalosis accompanies the clinical syndrome of tetany, precipitates cardiac arrhythmias and predisposes to coronary vasoconstriction. Magnesium plays a critical role in the maintenance of membrane function, and magnesium depletion is often associated with cardiac arrhythmias or vasoconstriction.

2. As technology for detecting circulating ionized magnesium (the most interesting form with respect to physiological and biological properties) is now available in the form of new magnesium-selective electrodes, the effect of respiratory alkalosis induced by voluntary overbreathing for 30 min on circulating ionized magnesium was studied in eight healthy subjects.

3. The total plasma magnesium concentration was not modified by hyperventilation. On the contrary, hyperventilation was associated with a significant reduction in the ionized magnesium concentration of 0.05 (0.02–0.15) mmol/l (median and range) and in the free magnesium fraction of 0.06 (0.01–0.19). During hyperventilation the relative intravascular magnesium mass, calculated from changes in total plasma magnesium concentration and haematocrit, decreased significantly.

4. It is concluded that acute overbreathing reduces the circulating ionized magnesium concentration and the intravascular magnesium mass. It is therefore conceivable that extracellular magnesium deficiency is at least a subsidiary cause of the syndrome of tetany and the cardiac complications that are precipitated by hyperventilation.
Human Erythrocyte Choline Uptake in Uraemia: The Role of Intracellular Substrate and An Investigation into the Effects of Haemodialysis
Authors: Flanagan G. J. , O'kelly J. , Rae C. , Winearls C. G. , Ellory J. C.
Published: August 2015

1. Erythrocyte choline transport was studied in 10 haemodialysis patients immediately before and after a haemodialysis session and in 10 control subjects. Choline uptake was measured in erythrocytes from normal and uraemic patients after washing in vitro and subsequent incubation in autologous plasma. Amines present in uraemic plasma were examined for their effect on choline transport in normal erythrocytes.

2. NMR spectroscopy was used to measure choline, trimethylamine and dimethylamine in erythrocyte extracts from nine control subjects, 32 subjects with renal impairment and nine samples from haemodialysis patients.

3. The increased choline influx in uraemic erythrocytes is significantly decreased by prior haemodialysis (mean Vmax pre-dialysis 146±20 μmol h−1 I−1, postdialysis 113±13 μ/mol h–1 I−1 (P < 0.005). After in vitro washing there is a fall in Vmax, and no longer any significant difference between pre- and post-dialysis samples. There remains a significant difference in the erythrocyte choline Vmax between samples from patients with chronic renal failure and from normal subjects (P < 0.005).

4. Human plasma was found to contain factors capable of increasing choline uptake. Trimethylamine and dimethylamine were found to inhibit choline uptake. Trimethylamine and trimethylamine-N-oxide transstimulated choline efflux, but the major transport substrate present in erythrocyte extracts from all groups was choline, which was higher in those with renal impairment (71 ± 10 μmol/l) than in haemodialysis patients (47 ± 10 μmol/l) and control subjects with normal renal function (40 ± 9 μmol/l).

5. Our data suggest that erythrocyte choline transport is increased in uraemia as a consequence of increased transporter number or activity, rather than the presence of intracellular substrate.
Reproducibility of Heart Rate Variability Measures in Patients with Chronic Heart Failure
Authors: Ponikowski Piotr , Piepoli Massimo , Amadi Aham A. , Chua Tuan Peng , Harrington Derek , Volterrani Maurizio , Colombo Roberto , Mazzuero Giorgio , Giordano Amerigo , Coats Andrew J. S.
Published: August 2015

1. In patients with chronic heart failure, heart rate variability is reduced with relative preservation of very-low-frequency power (< 0.04 Hz). Heart rate variability has been measured without acceptable information on its stability and the optimal recording periods for enhancing this reproducibility.

2. To this aim and to establish the optimal length of recording for the evaluation of the very-low-frequency power, we analysed 40, 20, 10 and 5 min ECG recordings obtained on two separate occasions in 16 patients with chronic heart failure. The repeatability coefficient and the variation coefficient were calculated for the heart rate variability parameters, in the time-domain (mean RR, SDRR and pNN50), and in the frequency-domain: very low frequency (< 0.04 Hz), low frequency (0.04–0.15 Hz), high frequency (0.15–0.40 Hz), total power (0–0.5 Hz).

3. Mean RR remained virtually identical over time (variation coefficient 8%). The reproducibility of time-domain (variation coefficient 25–139%) and of spectral measures (variation coefficient 45–111%) was very low. The stability of the heart rate variability parameters was only apparently improved after square root and after log transformation.

4. Very-low-frequency values derived from 5 and 10 min intervals were significantly lower than those calculated from 40 and 20 min intervals (P < 0.005). Discrete very-low-frequency peaks were detected in 11 out of 16 patients on the first 40, 20 and 10 min recording, but only in seven out of 16 when 5 min segments were analysed.

5. The reproducibility of both time or frequency-domain measures of heart rate variability in patients with chronic heart failure may vary significantly. Square root or log-transformed parameters may be considered rather than absolute units in studies assessing the influence of management on heart rate variability profile. Recordings of at least 20 min in stable, controlled conditions are to be recommended to optimize signal acquisition in patients with chronic heart failure, if very-low-frequency power in particular is to be studied.
Visualizing Signal Transduction: Receptors, G-Proteins, and Adenylate Cyclases
Authors: Dessauer Carmen W. , Posner Bruce A. , Gilman Alfred G.
Published: August 2015

1. The first glimpses of heterotrimeric G-proteins came with the discoveries of the ubiquitous adenylate cyclase activator, Gs, and the specialized retinal cGMP phosphodiesterase activator, Gt or transducin. The model that evolved for regulation of adenylate cyclase activity by G-proteins soon proved to be a general paradigm for a large number of signalling pathways. Although many different G-proteins interact with a diverse array of receptors and effectors, each is composed of a guanine-nucleotide-binding α-subunit and a tightly associated complex of a β- and a γ-subunit.

2. Receptors catalyse the activation of G-proteins by promoting exchange of GDP for GTP, while G-proteins catalyse their own deactivation as a result of their intrinsic GTPase activity. Crystallographic analysis has described several of the various conformational states that G-proteins undergo as they are activated and deactivated and has provided great insight into the kinetic models of G-protein-mediated signal transduction.

3. The regulation of adenylate cyclase has proven to be intriguing and complex. Gsα activates all forms of mammalian adenylate cyclase; other G-proteins (Gi, Go and Gz) inhibit certain isoforms of the enzyme. The discovery of new isoforms of adenylate cyclase has revealed synergistic and conditional mechanisms of regulation. These include activation or inhibition by the G-protein βγ-subunit complex, activation by Ca2+-calmodulin, and phosphorylation by protein kinases. The large number of receptors, G-proteins and adenylate cyclases provides a complex signalling network that integrates and interprets a multitude of convergent inputs.
T-Cell Autoimmunity in Primary Biliary Cirrhosis
Authors: Jones David E. J.
Published: August 2015

1. Primary biliary cirrhosis is a chronic cholestatic liver disease with an autoimmune aetiology. The classical histopathological lesion, of portal tract biliary epithelial cell damage, is accompanied by a T-cell-rich mononuclear cell infiltrate and upregulation of cell surface markers suggestive of local T-cell activation and cytokine release. This suggests that T-cell mediated mechanisms play an important role in tissue damage in primary biliary cirrhosis.

2. CD4+ T-cells specific for the E2 component of human pyruvate dehydrogenase complex (PDC-E2), a highly conserved enzyme which plays a critical role in intermediate metabolism, are present in the peripheral repertoire of the majority of patients with primary biliary cirrhosis. These cells are almost entirely absent from normal and chronic liver disease control subjects. The observations that peripheral blood PDC-E2-specific cells are most commonly seen in early stage disease, when active bile duct damage is occurring, and that PDC-E2-specific cells can be found in the portal tract infiltrate at times when this damage is occurring, suggest that these autoreactive cells may have a role to play in the aetiology of primary biliary cirrhosis.

3. T-cells specific for the whole PDC and its E1 component are seen in significant numbers of normal control subjects as well as patients with primary biliary cirrhosis. Retention of potentially autoreactive cells in the normal T-cell repertoire has been reported for a number of other autoantigens.

4. T-cell epitopes appear to be widely distributed throughout PDC-E2. This is in contrast to the B-cell epitopes which are highly restricted to the inner lipoyl binding domain of the protein.
Effects of High External Concentrations of K+ on 86Rb+ Efflux in Human Platelets: Evidence for Na+/K+/2Cl− Co-Transport
Authors: De Silva H. A. , Carver J. G. , Aronson J. K.
Published: August 2015

1. Na+/K+/2Cl− co-transport mediates a bidirectional symport of Na+, K+ and Cl−. The important properties of the co-transport system are its requirement for Na+, K+ and Cl− and its inhibition by loop diuretics such as bumetanide. This co-transporter has been described in a number of animal and human tissues. However, its presence in human platelets, although inferred, has not been demonstrated directly.

2. We have studied the efflux of 86Rb+ (a marker for K+) from Rb+-loaded platelets, and have defined their response to stimulation by high concentrations of external K+.

3. KCl (30–120 mmol/l) stimulated a concentration-dependent increase in 86Rb+ efflux from the platelets. This efflux was completely inhibited by bumetanide (10 μmol/l) but was insensitive to ouabain and R(+)-[(dihydroindenyl)oxy]alkanoic acid. It also required Cl− in the external medium, but did not depend on the presence of extracellular Na+.

4. These observations suggest that 86Rb+ efflux from platelets stimulated by external K+ occurs via Na+/K+/2Cl− co-transport acting in a K+/K+ (K+/Rb+) exchange mode.

5. Non-stimulated efflux of 86Rb+ from the platelets (i.e. in the presence of 5 mmol/l K+) had the characteristics of Na+/K+/2Cl− co-transport acting in normal mode.
Changes in the Period of No Respiratory Sensation and Total Breath-Holding Time in Successive Breath-Holding Trials
Authors: Nishino Takashi , Sugimori Kunio , Ishikawa Teruhiko
Published: August 2015

1. Immediately after breath-holding at end-expiratory level, there is a certain period of no particular respiratory sensation which is terminated by the onset of an unpleasant sensation and followed by progressive discomfort during breath-holding. This period, defined as the time from the start of voluntary breath-holding to the point where the onset of an unpleasant sensation occurs, is designated ‘the period of no respiratory sensation’. Although it has been shown that the maximum breath-holding performance is improved with successive trials, it is not clear whether this training effect exerts a similar influence on the period of no respiratory sensation during breath-holding.

2. Since the training effect seems to be associated with the stresses of breath-holding, we hypothesized that the initial period of no respiratory sensation during breath-holding might be less influenced by the training effect.

3. We studied 13 normal subjects who performed repeated breath holds while continuously rating their respiratory discomfort using a visual analogue scale. In addition, we measured the hypercapnic ventilatory response of each individual and obtained the relationship between the slope of the hypercapnic response curve and breath-holding periods.

4. Our results showed that there was little training effect on the period of no respiratory sensation and that the period of no sensation during breath-holding is inversely related to the slope of the hypercapnic ventilatory response curve.

5. The period of no respiratory sensation was also measured in eight patients with chronic obstructive pulmonary disease. The values of the period of no respiratory sensation in patients with chronic obstructive pulmonary disease were apparently lower than those obtained in normal subjects.

6. These findings suggest that measurement of the period of no respiratory sensation can be a useful clinical test for the study of genesis of dyspnoea.
Regulation of Adipose Cell Number in Man
Authors: Prins Johannes B. , O'rahilly Stephen
Published: August 2015

1. Adipose tissue mass is dependent on both the average volume and the number of its constituent adipocytes. Significant alteration in body mass involves alteration in both adipocyte volume and number.

2. Increases in adipocyte number occur via replication and differentiation of preadipocytes, a process which occurs throughout life. Decreases in adipocyte number occur via preadipocyte and adipocyte apoptosis, and possibly adipocyte dedifferentiation.

3. Overall regulation of adipose mass involves endocrine, paracrine and possibly autocrine systems. Hypothalamic centres appear to control appetite, metabolic rate and activity levels in a co-ordinated manner. Within the hypothalamus, known weight regulatory molecules include glucagon-like peptide-1, neuropeptide Y and leptin. Leptin is a major afferent signal from adipose tissue to the hypothalamus, providing information on overall adipose tissue mass. However, the precise means by which the hypothalamus signals to adipose tissue is less well understood.

4. In adipose tissue, known molecular regulators of adipose cell number include insulin, ligands for the peroxisome proliferator activated receptor-γ, retinoids, corticosteroids and tumour necrosis factor-α. The net effect of these and other regulators is to effect a concerted alteration in adipocyte volume and number. This review largely focuses on the control of fat cell acquisition and loss and the influence of these processes on adipose tissue mass and regional distribution.
Cardiovascular Pharmacology of Purines
Authors: Rongen Gerard A. , Floras John S. , Lenders Jacques W. M. , Thien Theo , Smits Paul
Published: August 2015

1. This review focuses on the extracellular actions of ATP and adenosine, and in particular their role in cardiovascular regulation.

2. ATP serves as a co-transmitter within the sympathetic nervous system, and is also released from endothelium and aggregating thrombocytes. ATP acts on P2x purinoceptors on vascular smooth muscle cells to induce vasoconstriction. Stimulation of P2y purinoceptors on endothelial cells releases endothelium-derived relaxing factors and causes vasodilatation. This dual action of ATP may have pathophysiological importance by inducing vasospasm at sites of impaired endothelial function and thrombus formation.

3. Adenosine is generated by enzymic degradation of ATP. Its formation is enhanced during ischaemia. Adenosine inhibits noradrenaline release from sympathetic nerve endings, causes vasodilatation via endothelium-dependent and endothelium-independent actions, has important anti-arrhythmic properties and prevents deleterious sequelae of ischaemia. In humans, adenosine evokes a sympatho-excitatory reflex mediated by chemically sensitive receptors and afferent nerves in the kidney, heart and forearm. This reflex may be active during exercise and ischaemia and, because of its potential adverse consequences, it should be considered when developing new therapies to potentiate the anti-ischaemic actions of endogenous adenosine in humans. Adenosine appears to mediate ischaemia-induced pain; a reduced sensitivity to adenosine may underlie silent ischaemia.

4. New drugs that interact with adenosine formation or degradation or with adenosine receptors are under development. These have potential therapeutic application in the treatment of ischaemia and other circulatory disorders.
Effects of Silicon, Citrate and the Fasting State on the Intestinal Absorption of Aluminium in Rats
Authors: Drüeke Tilman B. , Jouhanneau Philippe , Banide Hélène , Lacour Bernard , Yiou Françoise , Raisbeck Grant
Published: August 2015

1. The effect of silicon (Si) contained in drinking water and solid food on the intestinal absorption of aluminium (Al) remains a matter of debate. The present study was designed to readdress this issue in the experimental animal, and to examine concomitantly the effects of citrate and the fasting state, respectively.

2. Three groups of young, non-fasted rats (n = 8 per group) were gavaged by solutions containing 3.8 ng of 26Al, 63 ng of 27Al, and either distilled water (<0.1 mg/l Si) or commercial mineral water with a medium (6 mg/l) or high (14 mg/l) Si concentration.

3. Two other groups of eight non-fasted rats each received the same distilled water or high-Si gavage solution, respectively, together with a high citrate concentration (62 g/l). In each case the animals had free access to drinking water for 5 days before and 2 days after the gavage, containing the same Si concentration as in the gavage solution. A sixth group of eight rats was gavaged by low-Si, Al and distilled water in the fasted state.

4. The animals were killed 48 h after gavage, and blood, tissue and urine samples were collected for 26Al measurements by accelerator mass spectrometry.

5. We found that the fraction of absorbed 26Al retained in the skeleton (0.025–0.030%) was of the same order of magnitude as the fraction excreted in the 48 h urine (0.035-0.037%). High Si concentrations in the drinking water failed to depress the 26Al fraction absorbed, as estimated on the basis of skeletal accumulation and urinary excretion.

6. The administration of citrate-containing fluid enhanced 26Al absorption 5- to 10-fold (P < 0.005), but again the Si content of drinking water did not interfere. Finally, the intestinal absorption of 26Al was approximately 15 times higher in the fasted than in the non-fasted state.

7. In conclusion, the provision of large amounts of Si in the drinking water failed to modify physiological intestinal Al absorption under basal conditions or after its stimulation by citrate. However, a prolonged fast greatly enhanced Al absorption, compared with the non-fasted state.
Brisk Walking Reduces Calcaneal Bone Loss in Post-Menopausal Women
Authors: Brooke-Wavell Katherine , Jones Peter R. M. , Hardman Adrianne E.
Published: August 2015

1. This study examined the influence of brisk walking on skeletal status in post-menopausal women.

2. Subjects were 84 healthy women aged 60–70 years who were previously sedentary and at least 5 years post-menopausal. Subjects were randomly assigned to walking (n = 43) and control (n = 41) groups. Walkers followed a 12-month, largely unsupervised programme of brisk walking. The bone mineral density of the lumbar spine, femoral neck and calcaneus and broadband ultrasonic attention of the calcaneus were measured at baseline and after 12 months.

3. Forty control subjects and 38 walkers completed the study. Walkers built up to 20.4 ± 3.8 min/day (mean ± SD) of brisk walking. Body mass increased in control subjects relative to walkers [mean change (SE) ± 0.9 (0.3) and −0.1 (0.3) kg respectively; P = 0.04]. Predicted maximum oxygen uptake increased in walkers by 2.1 (0.9) ml min−1 kg−1 (P = 0.02). Bone mineral density in the lumbar spine and calcaneus fell in control subjects [–0.005 (0.004) and −0.010 (0.004) g/cm2, respectively] but not in walkers [+0.006 (0.004) and +0.001 (0.004) g/cm2]. The difference in response between groups was significant in the calcaneus (P = 0.04) but not in the lumbar spine (P = 0.08). Mean femoral neck bone mineral density did not change significantly in either group, although changes in walkers were related to the amount of walking completed (r = 0.51, P = 0.001). The change in broadband ultrasonic attenuation of the calcaneus differed between groups [control subjects, −3.7 (0.8); walkers, −0.7 (0.8) dB/MHz; P = 0.01].

4. Walking decreased bone loss in the calcaneus and possibly in the lumbar spine. It also improved functional capacity and enabled walkers to avoid the increase in body mass seen in control subjects.
Comparison of Forearm Vasodilatation to Substance P and Acetylcholine: Contribution of Nitric Oxide
Authors: Newby David E. , Boon Nicholas A. , Webb David J.
Published: August 2015

1. Forearm blood flow responses to incremental challenges of acetylcholine and substance P, administered via the brachial artery, were measured by venous occlusion plethysmography in eight subjects in the presence of saline, the nitric oxide synthase inhibitor, NG-monomethyl-l-arginine, and a control vasoconstrictor, noradrenaline.

2. Substance P and acetylcholine caused dose-dependent increases in forearm blood flow (P < 0.001). When separated by 30 min saline infusions, repeated responses did not undergo tachyphylaxis.

3. Noradrenaline caused a mean reduction in basal blood flow of 34–51% (P < 0.001), and augmented the percentage increases in blood flow with both substance P (P = 0.05) and acetylcholine (P = 0.03) infusions.

4. NG-Monomethyl-l-arginine caused a mean reduction in basal blood flow of 42–45% (P < 0.001) and significantly inhibited the responses to both substance P (P < 0.001) and acetylcholine (P = 0.05).

5. In comparison with saline responses, NG-monomethyl-l-arginine caused a mean inhibition of 69 ± 8% for substance P-induced vasodilatation and 40 ± 5% for acetylcholine-induced vasodilatation. However, comparing responses with those to the control vasoconstrictor noradrenaline, NG-monomethyl-l-arginine caused a mean inhibition of 81 ± 5% for substance P responses and 58 ± 3% for acetylcholine responses. Inhibition by NG-monomethyl-l-arginine of the response to substance P was significantly greater than inhibition of the response to acetylcholine (P = 0.02).

6. Hence, in healthy men, a greater proportion of the forearm vasodilatation to substance P than to acetylcholine appears to be nitric oxide-mediated. Given its greater stability, substance P may be more suitable as a pharmacological tool in the investigation of stimulated nitric oxide production and endothelial cell function.
Transfection of Cardiac Muscle: Effects of Overexpression of c-myc and c-fos Proto-Oncogene Proteins in Primary Cultures of Neonatal Rat Cardiac Myocytes
Authors: Green Nicola K. , Franklyn Jayne A. , Ohanian Vasken , Heagerty Anthony M. , Gammage Michael D.
Published: August 2015

1. Studies of cells transfected with specific expression vectors allow functions of specific gene products to be investigated. We first established optimum conditions for transfection of neonatal cardiac myocytes in primary culture. Increased proto-oncogene expression has been implicated in the development of cardiac hypertrophy; we therefore wished to examine the effects of overexpression of the c-myc and c-fos proto-oncogenes induced by cell transfection on cell growth.

2. Neonatal rat ventricular myocytes were transfected by electroporation, voltage and capacitance settings were optimized and these conditions were then used to transfect expression vectors encoding MYC and FOS proteins into this cell type. Effects on cell number, DNA synthesis and protein content were determined.

3. Increased expression of c-myc and c-fos in cells transfected with proto-oncogene expression vectors was confirmed by Northern and Western blotting. Increases in cardiac myocyte cell number, DNA synthesis and total cellular protein were observed in cells transfected with either c-myc or c-fos expression vectors compared with cells transfected with non-coding vectors.

4. Overexpression of MYC and FOS proteins results in hyperplastic rather than hypertrophic growth of the neonatal rat heart, providing evidence for a role of these proteins in the control of myocardial growth.
Down-Regulation of the Acute-Phase Response in Patients with Pancreatic Cancer Cachexia Receiving Oral Eicosapentaenoic Acid is Mediated via Suppression of Interleukin-6
Authors: Wigmore Stephen J. , Fearon Kenneth C. H. , Maingay Jean P. , Ross James A.
Published: August 2015

1. Weight loss in pancreatic cancer is associated with persistent elevation of the acute-phase protein response. The effect of oral administration of eicosapentaenoic acid on the regulation of the acute-phase response in weight-losing patients with pancreatic cancer was investigated in vitro and in vivo.

2. Oral supplementation with eicosapentaenoic acid, in patients with cancer cachexia, resulted in a significant reduction in the serum concentration of the acute-phase protein C-reactive protein (11.0 ± 4.8 mg/l before eicosapentaenoic acid compared with 0.8 ± 0.8 mg/l after 4 weeks of eicosapentaenoic acid, P < 0.05), but no significant reduction in the serum concentration of the hepatocyte-stimulating cytokine interleukin-6. Production of interleukin-6 by peripheral blood mononuclear cells isolated from patients was significantly reduced after supplementation with eicosapentaenoic acid (interleukin-6 production by peripheral blood mononuclear cells exposed to 10 μg of lipopolysaccharide/ml: 10.2 ± 2.1 ng/ml before supplementation with eicosapentaenoic acid compared with 3.5 ± 1.7 ng/ml after supplementation, P < 0.05) and supernatants from these cells had reduced potential to stimulate C-reactive protein production by isolated human hepatocytes (hepatocyte C-reactive protein production in response to supernatants from peripheral blood mononuclear cell cultures exposed to 10 μg of lipopolysaccharide/ml: 150.4 ± 18.6 ng/ml before eicosapentaenoic acid versus 118 ± 14.9 ng/ml after 4 weeks of eicosapentaenoic acid, P < 0.05). The potential of lipopolysaccharide-stimulated peripheral blood mononuclear cell supernatants to stimulate C-reactive protein production by hepatocytes could be attenuated by neutralizing anti-interleukin-6 antibody in control subjects and in patients before, but not after, treatment with eicosapentaenoic acid.

3. In conclusion, eicosapentaenoic acid can down-regulate the acute-phase response in patients with pancreatic cancer cachexia and this process is likely to involve suppression of interleukin-6 production.
Nitric Oxide is Involved in the Inhibitory Neurotransmission and Endothelium-Dependent Relaxations of Human Small Penile Arteries
Authors: Simonsen ULF , Prieto Dolores , Delgado Jose Angel , Hernández Medardo , Resel Luis , De Tejada Iñigo Saenz , García-Sacristán Albino
Published: August 2015

1. Alteration in the flow of blood to the penis is thought to be the most frequent organic cause of erectile dysfunction or impotence. However, information concerning the penile small arteries (helicine arteries) which control blood flow between the arterial systemic circulation and the cavernous sinusoids is scarce. Therefore, the purpose of the present study was to investigate the involvement of nitric oxide, which is considered to be the main neurotransmitter in corpus cavernosum, in both the non-adrenergic non-cholinergic inhibitory neurotransmission and the endothelium-dependent responses in human penile small arteries.

2. Penile small arteries (lumen diameter 200-700 μm), which were branches of the human deep penile arteries obtained either from patients undergoing penile surgery or from organ donors, were mounted in microvascular myographs for isometric tension recording and electrical field stimulation was performed in the presence of guanethidine and atropine to block adrenergic neurotranmission and muscarinic receptors, respectively.

3. In phenylephrine-contracted penile small arteries, electrical field stimulation (0.5–32 Hz) induced frequency-dependent relaxations of both endothelium-intact and -denuded preparations. The inhibitor of nitric oxide synthase, NG-nitro-l-arginine (3 × 10−5 mol/l), abolished the relaxations at the lowest frequencies, while slow-developing relaxations were still observed at high frequencies (16 and 32 Hz). The inhibitory effect of NG-nitro-l-arginine was reversed in the presence of l-arginine (3 × 10−3 mol/l). Tetrodotoxin totally abolished the relaxations to electrical field stimulation. In contracted small penile arteries in the presence of NG-nitro-l-arginine, the nitrovasodilator sodium nitroprusside induced potent relaxations.

4. The endothelium-dependent vasodilator acetylcholine induced relaxations of penile small arteries, which were only partially reduced in the presence of NG-nitro-l-arginine. In contrast, the relaxations to acetylcholine of trabecular corpus cavernosum preparations were almost abolished in the presence of NG-nitro-l-arginine.

5. The present study suggests that relaxations of human intracavernosal small penile arteries induced by non-adrenergic non-cholinergic nerve stimulation partially involve nitric oxide and also another inhibitory transmitter causing relaxations resistant to nitric oxide synthase blockade. In addition, endothelium-dependent relaxations in human small penile arteries are mediated by both nitric oxide and a factor resistant to NG-nitro-l-arginine.
Combination Oral Antioxidant Supplementation Reduces Blood Pressure
Authors: Galley Helen F. , Thornton Judith , Howdle Peter D. , Walker Barry E. , Webster Nigel R
Published: August 2015

1. Hypertension affects 30% of adults and low intakes of antioxidants have been associated with increased risk of hypertension and cardiovascular disease. To investigate the effect of short-term high-dose antioxidant supplementation on blood pressure in hypertensive and normotensive outpatients, we undertook a randomized, double-blind, crossover design placebo-controlled study.

2. Forty subjects were recruited from medical outpatient clinics, of whom 38 completed the study. Twenty-one were attending for treatment of hypertension and 17 were normotensive, attending for minor gastrointestinal complaints. Subjects were randomly assigned to receive either 8 weeks placebo followed by 2 weeks washout then 8 weeks antioxidants or vice versa. The combination of antioxidants consisted of 200 mg of zinc sulphate, 500 mg of ascorbic acid, 600 mg of α-tocopherol (sodium succinate salt) and 30 mg of β-carotene daily.

3. Systolic blood pressure fell at the end of the antioxidant phase compared with the placebo phase both in subjects receiving anti-hypertensive therapy (P < 0.01) and those who were normotensive (P = 0.067). Circulating levels of β-carotene and α-tocopherol increased in all subjects during supplementation (P < 0.01) and urine nitrite increased in hypertensive patients (P < 0.05).

4. Short-term oral high-dose combination antioxidant therapy reduces blood pressure, possibly via increased availability of nitric oxide. This study may have implications for the innovative use of antioxidants as an adjunct to anti-hypertensive therapy.
The Steroid Vitamin D3 Reduces Cell Proliferation in Human Duodenal Epithelium
Authors: Thomas M. G. , Sturgess R. P. , Lombard M.
Published: August 2015

1. The active metabolite of vitamin D3, 1,25-dihydroxyvitamin D3, controls calcium absorption in the human duodenum, an effect that is mediated by mucosal vitamin D receptor expression. Functional vitamin D receptor signalling in the human colon is suggested by the reduced colonic mucosal cell proliferation seen in response to 1,25-dihydroxyvitamin D3. Thus 1,25-dihydroxyvitamin D3 might be expected to reduce cell proliferation in the small-bowel epithelium.

2. We have used an organ-culture system combined with the metaphase arrest technique to study the effects of 1,25-dihydroxyvitamin D3 on human duodenal mucosal proliferation. To validate our technique, multiple human mucosal explants were established in organ culture and vincristine (0.6μg/ml) was added at 10 h. Explants were removed sequentially from 10 to 15 h and metaphase arrest figures were demonstrated by using the Feulgen reaction. The mean number of metaphase arrest figures was plotted against time in culture to show a linear accumulation of metaphases between 11 and 15 h (correlation coefficient = 0.93, r2 = 0.87, P < 0.0001). The mean crypt cell production rate was 2.01 (0.27) cells/h per crypt.

3. Paired normal duodenal mucosal biopsies from six patients were then established in organ culture with or without 10−10 mol/l (100 pmol/l) 1,25-dihydroxyvitamin D3. The crypt cell production rate was determined between 12 and 15 h after vincristine-induced metaphase arrest. 1,25-Dihydroxyvitamin D3 reduced the median crypt cell production rate from 2.42 (1.15–4.82) to 1.41 (0.03–2.05) cells/h per crypt (P < 0.05). Thus, vitamin D3 reduces human duodenal epithelial cell proliferation.
Intestinal Absorption of Trace Amounts of Aluminium in Rats Studied with 26Aluminium and Accelerator Mass Spectrometry
Authors: Schönholzer K. W. , Sutton R. A. L. , Walker V. R. , Sossi V. , Schulzer M. , Orvig C. , Venczel E. , Johnson R. R. , Vetterli D. , Dittrich-Hannen B. , Kubik P. , Suter M.
Published: August 2015

1. Until recently studies of intestinal aluminium absorption used pharmacological amounts of stable 27Al.

2. To examine the intestinal absorption of trace amounts of different chemical compounds of aluminium, in the present study we have employed the long half-life isotope of aluminium, 26Al, and accelerator mass spectrometry. Trace amounts of 26Al (2.7–12.1 ng) as the hydroxide, citrate, citrate plus 1 mmol/kg sodium citrate, or maltolate respectively, were administered to four groups of rats (n = 9 per group) by gavage. Blood and urine samples were collected for 5 h and the 26Al content (as a percentage of the administered dose) determined by accelerator mass spectrometry.

3. The 5 h urinary 26Al excretion amounted to 0.1 ± 0.02, 0.7 ± 0.2, 5.1 ± 1.5 and 0.1 ± 0.1% of administered dose in the four groups respectively. There was a strong positive correlation between peak plasma 26Al (r = 0.98) and urinary 26Al excretion in individual animals (P < 0.001).

4. We conclude that the fractional intestinal absorption of trace oral doses of aluminium hydroxide is at least 0.1% (compared with the previous estimate of 0.01% using large 27Al oral loads). Absorption of aluminium citrate given alone is significantly greater (0.7%) and is further increased to 5% by the accompanying sodium citrate, consistent with an enhancing effect of added citrate upon mucosal aluminium permeability. Aluminium maltolate absorption approximates that of aluminium hydroxide (0.1%).