bluuebunny/crossref_metadata_2025 huggingface dataset:
HYPERTENSION AND INSULIN RESISTANCE: ROLE OF PEROXISOME PROLIFERATOR‐ACTIVATED RECEPTOR γ
Authors: Itoh Hiroshi , Doi Kentaro , Tanaka Tokuji , Fukunaga Yasutomo , Hosoda Kiminori , Inoue Gen , Nishimura Haruhiko , Yoshimasa Yasunao , Yamori Yukio , Nakao Kazuwa
Published: March 2003

1. Insulin resistance has been highlighted as a common causal factor for hypertension, hyperlipidaemia, diabetes mellitus and obesity, all of which are recognized to occur simultaneously, and a distinct clinical entity is defined as ‘multiple risk factor syndrome’.

2. Recently, a new class of antidiabetic agents, thiazolidinediones (TZD) has been developed and has been shown to improve insulin resistance by binding and activating a nuclear receptor, peroxisome proliferator‐activated receptor (PPAR)γ.

3. cDNA of rat PPARγ1 and γ2 were cloned and gene regulation of PPARγ in rat mature adipocytes was examined. Hydrogen peroxide, an oxygen radical, which is recognized to be the common intracellular signal for multiple risk factors, potently down‐regulated PPARγ mRNA expression in rat mature adipocytes.

4. Tumour necrosis factor (TNF)‐α, which is considered to play a role in obesity‐induced non‐insulin‐dependent diabetes mellitus and to augment oxidative stress, also suppressed PPARγ expression.

5. Thiazolidinediones dose‐dependently recovered TNF‐α‐induced down‐regulation of PPARγ mRNA expression.

6. The modulation of PPARγ expression by TZD can be one mechanism for the improvement of insulin resistance by TZD.

7. Vascular tone and remodelling are controlled by several vasoactive autocrine/paracrine factors produced by endothelial cells in response to several vascular injury stimuli, including hypertension. The PPARγ gene transcript was detected in cultured endothelial cells.

8. The administration of TZD stimulated the endothelial secretion of type‐C natriuretic peptide, which is one of the natriuretic peptide family and is demonstrated by us to act as a novel endothelium‐derived relaxing peptide.

9. Concomitantly, TZD significantly suppressed the secretion of endothelin, a potent endothelium‐derived vasoconstricting peptide.

10. Thiazolidinediones can affect vascular tone and growth by modulating the production of endothelium‐derived vasoactive substances to influence occurrence and progression of hypertension and atherosclerosis.
CIGARETTE SMOKE AND ITS EXTRACT DELAYS ULCER HEALING AND REDUCES NITRIC OXIDE SYNTHASE ACTIVITY AND ANGIOGENESIS IN RAT STOMACH
Authors: Ma L , Chow JYC , Liu ESL , Cho CH
Published: March 2003

1. The purpose of the present study was to examine whether cigarette smoke and its extract could affect ulcer healing, angiogenesis and nitric oxide synthase (NOS) activity in the gastric mucosa.

2. Ulcerated rats were either exposed to cigarette smoke or given smoke extract once daily for 3 days. Rats were killed and stomachs were removed for the measurement of ulcer size, angiogenesis and NOS activity.

3. Angiogenesis and constitutive NOS activity were concomitantly and dose‐dependently reduced by cigarette smoke or its extract. The same treatments also delayed ulcer healing.

4. These results indicate that cigarette smoke and its extract repress the processes of new blood vessel formation and NOS activity during tissue repair in the gastric mucosa. These could, in turn, retard the healing process in the gastric mucosa.
Effects Of Resistance Training On Bone Parameters In Young And Mature Rats
Authors: Bennell Kim , Page Carolyn , Khan Karim , Warmington Stuart , Plant David , Thomas David , Palamara Joseph , Williams David , Wark John D
Published: March 2003

1. Osteoporosis is a major public health problem that is predicted to worsen over the next decade and preventative strategies that increase bone strength have become the focus of substantial research.

2. Although mechanical load is a primary factor in the acquisition and maintenance of skeletal tissue, the type of exercise used and when in life it is most effectively prescribed remain inconclusive.

3. The present study compared 10 weeks of resistance training in both young and mature female Sprague‐Dawley rats and measured bone density and body composition by dual energy X‐ray absorptiometry and biomechanical properties by three point bending tests of the tibia and femur.

4. No significant differences were observed for any of the bone parameters when comparing exercise and control groups at either age. This was despite using a comparable training protocol to that in humans and using loads of approximately 150% bodyweight.

5. The present study concludes that more intensive work programmes of resistance training or different outcome measures are required when using animal models for skeletal research.
Skeletal Muscle Metabolism During Exercise In Humans
Authors: Hargreaves Mark
Published: March 2003

1. Contracting skeletal muscle is able to use a number of intra‐ and extramuscular substrates to generate ATP during exercise. These include creatine phosphate (CP), muscle glycogen, blood‐borne glucose, lactate and free fatty acids (FFA), derived from either adipose tissue or intramuscular triglyceride stores.

2. During high‐intensity short‐duration exercise, CP degradation and the breakdown of muscle glycogen to lactate are the major energy yielding pathways, although oxidative metabolism can make a significant contribution. The ‘anaerobic’ substrates are also important fuels during the transition from rest to steady state exercise.

3. The oxidative metabolism of carbohydrate and lipid supplies most, if not all, of the ATP during prolonged submaximal exercise. Muscle glycogen, blood glucose and FFA are the key fuels. The relative importance of the various substrates for exercise metabolism is primarily determined by exercise intensity and duration, although training status, dietary manipulation and environmental factors can modify the metabolic response to exercise.
Carotid Artery Intima–Medial Thickness Is Increased In Chronic Renal Failure
Authors: Zoungas Sophia , Ristevski Sonya , Lightfoot Paul , Liang Yu‐Lu , Branley Pauline , Shiel Louise M , Kerr Peter , Atkins Robert , McNeil John J , McGrath Barry P
Published: March 2003

1. Chronic renal failure (CRF) is associated with rapidly progressive atherosclerotic vascular disease. In the present study, carotid arterial intima–medial thickness (IMT) was assessed in a large cohort of patients with CRF and matched controls and related to risk factors.

2. A total of 159 subjects with CRF (serum creatinine ≥ 0.40 mmol/L) aged > 50 years (mean (±SD) 63.8±7.7 years) and 159 healthy controls matched for age, sex and smoking status were studied.

3. The IMT was determined using B‐mode ultrasound measurements of the far wall of both common carotid arteries and presented as the mean IMT. Fasting plasma homocysteine (tHcy) was measured in the CRF group.

4. Intima–medial thickness was significantly greater in CRF patients than controls (0.89±0.17 vs 0.73±0.13 mm, respectively) after matching for age, sex and smoking status. Heart rate and pulse pressure were also significantly increased. The tHcy was increased two‐fold in the CRF group (27.7±11.3 μmol/L; normal < 13.0 μmol/L) and did not correlate with carotid IMT.

5. Compared with controls after adjusting for traditional risk factors, patients with CRF exhibit significantly increased IMT.
Fluvastatin Normalizes The Decreased Turnovers Of Glutathione And Ascorbic Acid In Watanabe Heritable Hyperlipidaemic Rabbits
Authors: Suzumura Kuniharu , Kasahara Emiko , Ohnishi Yasuyo , Chien Kuang‐Chang , Inoue Masayasu
Published: March 2003

1. Fluvastatin, a 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitor, has been reported to decrease the oxidizability of plasma lipids in hyperlipidaemic subjects. In order to elucidate one of the mechanisms of this in vivo, we investigated the effects of fluvastatin and pravastatin on the decreased turnovers of reduced glutathione (GSH) and ascorbic acid (AA) in Watanabe heritable hyperlipidaemic (WHHL) rabbits.

2. These drugs (30 mg/kg per day) equally decreased plasma levels of lipids after a 4 week treatment period. However, only fluvastatin significantly decreased thiobarbituric acid‐reactive substances, which were increased in the plasma of WHHL.

3. Although these drugs did not affect the steady state levels of total glutathione and low molecular weight thiols in the liver and kidney, fluvastatin markedly normalized the rate of GSH turnover in these tissues, as determined by using L‐buthionine‐(
S,
R)‐sulphoximine, a specific inhibitor of GSH synthesis.

4. Fluvastatin also increased the clearance of AA from the circulation in WHHL.

5. These results suggest that, in addition to its hypolipidaemic action, fluvastatin has the potential to improve the turnover of anti‐oxidants, which is closely related to the amelioration of the redox status in the body.
Anticardiolipin Antibodies In Spontaneously Hypertensive Rats (Shr), Stroke‐Prone Shr And Normal Wistar Rats
Authors: Todorova M , Baleva M , Nikolov K , Higashino H , Kamenov Z
Published: March 2003

1. Anticardiolipin antibodies (ACA) can be detected in the serum of patients with autoimmune disturbances, ischaemic heart disease, myocardial infarction, neurological disorders and other medical conditions. Elevated values of these autoantibodies can be associated with recurrent fetal loss, arterial and venous thrombosis and thrombocytopenia.

2. In the present study, we investigated the presence of ACA in three rat strains, namely normal Wistar rats (WR), spontaneously hypertensive rats Okamoto‐Aoki (SHR) and stroke‐prone SHR (SHRSP). All animals were examined at four ages: 1, 4, 10 and 12 months of age. Anticardiolipin antibodies were determined by ELISA.

3. Anticardiolipin antibody levels in normal WR, which were used as controls, were lowest at 1 month and increased significantly from the 4th month on. At the prehypertensive age (1 month), ACA levels in SHR and SHRSP were significantly higher compared with control WR, decreased with age and were significantly lower at 4, 10 and 12 months compared with age‐matched WR.

4. These differences may be a result of immunological disorders in SHR.
Dexmedetomidine And Haemodynamic Responses To Acute Central Hypovolaemia In Conscious Rabbits
Authors: Blake Dw , Ludbrook J , Leeuwen Af Van
Published: March 2003

1. Effects of the α2‐adrenoceptor agonist dexmedetomidine on vasoconstrictor and heart rate (HR) responses to acute central hypovolaemia were studied in eight chronically instrumented rabbits. We compared intravenous (i.v.) and fourth ventricular (V4) dexmedetomidine (0.1–10 μg/kg) and the reversal of effects by the α2‐adrenoceptor antagonist idazoxan and the opioid agonist alfentanil.

2. Gradual inflation of an inferior vena cava (IVC) cuff reduced cardiac index (CI) by 8%/min, with progressive vasoconstriction and increased HR. In control rabbits, at approximately 40% baseline CI, there was sudden decompensation with failure of vasoconstriction and a fall in mean arterial pressure (MAP).

3. Dexmedetomidine (i.v. and V4) reduced resting MAP and HR and caused an earlier decompensation during central hypovolaemia. Intravenous dexmedetomidine (3 and 10 μg/kg) also reduced the slope of the initial vasoconstrictor response and the maximum HR.

4. The effects of dexmedetomidine were reversed by the antagonist idazoxan, which prevented the decompensation phase. Intravenous alfentanil was also effective in restoring the vasoconstrictor response and delaying decompensation with hypovolaemia after dexmedetomidine. Combining dexmedetomidine with an opioid, such as alfentanil, may provide the benefit of reduced sympathetic tone without increased risk of cardiovascular collapse.
Localization Of Tachykinin Receptors And Fos‐Like Immunoreactivity Induced By Substance P In Guinea‐Pig Brain
Authors: Yip Jane , Chahl Loris A
Published: March 2003

1. In the present study, a comparison was made between the distribution of tachykinin NK1 and NK3 receptor immunoreactivity and the distribution of Fos‐like immunoreactivity induced by the tachykinin agonist substance P (SP) in the guinea‐pig brain.

2. In agreement with results from previous studies in rat brain, NK1 receptor‐immunoreactive neurons were found to be widely distributed throughout the brain in the striatum and in diencephalic and mesencephalic structures, while NK3 receptor‐immunoreactive neurons were mainly in telencephalic structures. Considerable overlap was observed between NK1 and NK3 receptor distributions.

3. Substance P induced Fos‐like immunoreactivity (Fos‐LI) in extensive areas of the guinea‐pig brain. The induction of Fos‐LI was markedly inhibited in many areas by pretreatment with the NK1 receptor antagonist SR 140333. The NK3 receptor antagonist SR 142801 reduced Fos‐LI staining in fewer areas, although a reduction was observed in the cortex, striatum and hypothalamus.

4. In general, tachykinin receptors were located at sites corresponding to areas of functional activation by SP, as shown by Fos‐LI. These results extend previous studies by adding a functional dimension to tachykinin receptor localization studies.
Glutathione Metabolism In Cyclosporine A‐Treated Rats: Dose‐ And Time‐Related Changes In Liver And Kidney
Authors: Jiménez R , Galán AI , González de Buitrago JM , Palomero J , Muñoz ME
Published: March 2003

1. We investigated the simultaneous effects of cyclosporine A (CsA) treatment in rats on glutathione metabolism, oxidative status and their interorgan relationship in the liver and kidney.

2. Reduced and oxidized glutathione (GSH and GSSG, respectively), lipid peroxidation and the activity of several enzymes of the glutathione cycle were evaluated in adult Wistar rats treated daily (i.p.) with saline, CsA vehicle (olive oil) or CsA (10 and 20 mg/kg per day) for either 1 or 4 weeks (short‐ and long‐term treatments, respectively).

3. Cyclosporine A treatment elicited a significant depletion in liver GSH content and a decrease in the GSH/GSSG ratio that was unrelated to either the time of treatment or the dose used; these effects were already evident after 1 week of treatment. Renal GSH levels remained unaffected or increased, while those of GSSG increased markedly in all CsA‐treated rats, leading to decreases in the GSH/GSSG ratio, except in rats treated in the short term with the lower dose of CsA. These changes in the GSH/GSSG ratio were time and dose dependent. Short‐term CsA treatment using the higher dose and long‐term treatment with both doses of CsA progressively enhanced lipid peroxidation, which was reflected by increased levels of thiobarbituric acid‐reactive substances in both hepatic and renal homogenates. Hepatic γ‐glutamylcysteine synthetase activity was increased after long‐term treatment with both doses of CsA, whereas the activity of GSH hepatic peroxidase and GSH transferase was not significantly modified in any of the experimental groups. In contrast, renal γ‐glutamyl transpeptidase activity decreased in a progressive fashion, with the magnitude of this decrease being dose and time dependent. The plasma levels of total glutathione increased only in rats treated in the long term, regardless of the dose of CsA used, and remained unaltered in animals treated in the short term.

4. In summary, the data collected indicate that CsA treatment alters the interorgan homeostasis of glutathione and the oxidative status of the rat liver and kidney, which is associated with increases in lipid peroxidation in both organs, and also induces modifications in the activity of some enzyme related to the glutathione cycle.
Sunlight, Immunosuppression And Skin Cancer: Role Of Histamine And Mast Cells
Authors: Hart Prue H , Grimbaldeston Michele A , Finlay‐Jones John J
Published: March 2003

1. The development into tumours of skin cells transformed by ultraviolet (UV) B radiation of wavelengths 290–320 nm is enhanced by the ability of UVB to suppress an immune response that would otherwise destroy them. Ultraviolet B‐induced immunomodulation may be by multiple mechanisms, but generally manifests in an antigen‐presenting cell defect and an altered cytokine environment in the draining lymph nodes.

2. Immune responses to microbial or self‐antigens may be dysfunctional by similar mechanisms following UVB exposure.

3. Earliest‐acting intermediates in the initiation of UVB‐induced immunosuppression are the UVB absorbers (photoreceptors) of the skin, notably DNA resulting in immunoregulatory cytokine production, and trans‐urocanic acid (UCA), which, upon isomerization to its cis isomer, signals downstream immunosuppressive events.

4. In mice, dermal mast cells are critical to UVB‐induced systemic immunomodulation. In mice, there is a functional link as well as a linear relationship between the prevalence of histamine‐staining dermal mast cells and the log of the dose of UVB required for 50% immunosuppression. Studies with histamine receptor antagonists support histamine as the main product of mast cells involved. Histamine acts in large part via a prostanoid‐dependent pathway.

5. Approximately 50% of humans and greater than 90% of patients with non‐melanoma skin cancer are UVB susceptible for suppression of a contact hypersensitivity response. Neither cytokine polymorphisms nor UVB‐induced levels of cis‐UCA in irradiated skin have been linked to UVB susceptibility. Patients with basal cell carcinomas (BCC) have an increased dermal mast cell prevalence in non‐sun‐exposed buttock skin. We propose that mast cells function in humans, as in mice, by initiating immunosuppression and, thereby, allowing a permissive environment for BCC development.
Sites of Epidermal Growth Factor Synthesis and Action in the Pituitary: Paracrine and Autocrine Interactions
Authors: Childs Gwen V , Armstrong Jennifer
Published: March 2003

1. Epidermal growth factor (EGF) is produced by growth hormone (GH) cells and gonadotropes in normal pituitary cell populations. The studies were initiated to determine whether EGF is a paracrine or autocrine regulator of gonadotrope function.

2. The first group of studies tested for the presence of EGF receptors in gonadotropes from cycling female rats by immunolabelling. Expression varied with the stage of the cycle. At the highest point (metoestrus), only a few EGF target cells are gonadotropes, identified by their content of luteinizing hormone (LH)‐β mRNA. Expression by gonadotropes then increased to reach a peak of 50% of cells during pro‐oestrus.

3. Studies investigating the regulation of expression of EGF receptor (R) showed that all culture conditions (in media with or without serum) and EGF itself both stimulated expression of the receptor by gonadotropes in populations from oestrus or metoestrus rats. Gonadotropin‐releasing hormone (GnRH) also stimulated EGFR expression in follicle‐stimulating hormone (FSH) gonadotropes from oestrus animals. Additional tests of expression of immediate early genes (c‐fos) showed that, after 15 min, EGF stimulated expression in cells with FSH antigens.

4. Epidermal growth factor also stimulated gonadotrope proliferation, as detected by the MTT cell growth/cell death assays and bromodeoxyuridine uptake by gonadotropes during the S phase (DNA synthesis) of the cell cycle.

5. Epidermal growth factor and GnRH both stimulated a significant increase in the percentage of mitotic gonadotropes. Epidermal growth factor may be an autocrine or a paracrine growth factor to maintain and develop the gonadotrope population and EGF may also be involved in early differentiation events that prepare cells to support the LH surge.
Cardiac Output In Mice Overexpressing β2‐Adrenoceptors Or With Myocardial Infarct
Authors: Gao Xiao‐Ming , Lambert Elisabeth , Dart Anthony M , Du Xiao‐Jun
Published: March 2003

1. The aims of the present study were to characterize cardiac output (CO) in transgenic mice that overexpress the β2‐adrenoceptor and to evaluate ultrasonic flowmetery for continuous CO measurement in the mouse in vivo.

2. Under conditions of anaesthesia, open chest and positive ventilation, CO was determined with a transonic flowmeter at baseline and during dobutamine administration and intravenous volume loading in wild‐type mice (n = 17) and β2‐adrenoceptor transgenic (n = 9) and wild‐type mice with chronic myocardial infarct (n = 16).

3. Compared with wild‐type mice, β2‐adrenoceptor transgenic mice with markedly enhanced ventricular contractility had a significantly higher CO, heart rate (HR) and maximal acceleration of aortic flow. Both dobutamine and volume loading increased CO in the two groups and higher levels of CO were measured in transgenic mice during the interventions. At baseline or during interventions, stroke volume was similar between β2‐adrenoceptor transgenic and wild‐type mice. Infarcted mice with impaired cardiac function had a significantly lower CO under basal and stress conditions.

4. Thus, β2‐adrenoceptor transgenic mice revealed higher CO that was largely attributable to a significantly higher HR but not to an increase in stroke volume. Transonic flowmetery can detect differences in CO among mice in various functional states and is suitable for evaluation of cardiac functional reserve in mice in vivo by continuous monitoring of CO responses to different interventions.
Multiple Inert Gas Elimination Technique For Determining Ventilation/Perfusion Distributions In Rat During Normoxia, Hypoxia And Hyperoxia
Authors: Alfaro V , Roca‐Acín J , Palacios L , Guitart R
Published: March 2003

1. The use of the multiple inert gas elimination technique (MIGET) in quantifying ventilation/perfusion distributions (V•A/Q•) in small animals, such as the rat, may cause results to be biased due to haemodilution produced by the large volume of liquid infused intravenously.

2. We tested two methods of administering inert gases in rats using the MIGET: (i) standard continuous intravenous administration of inert gases (method A); and (ii) a new method based on the physicochemical properties of each inert gas (method B). This method included acute simultaneous inert gas administration using three pathways: inhalation, intravenous infusion and rectal infusion. Both MIGET methods were applied to obtain data while breathing three different inspiratory fractions of oxygen (FIO2): normoxia, hypoxia and hyperoxia.

3. Inert gas levels obtained from blood or expired air samples were sufficient for chromatographic measurement, at least during a 2 h period. The V•A/Q• distributions reported using both methods were acceptable for all the physiological conditions studied; therefore, the alternative method used here may be useful in further MIGET studies in rats because haemodilution resulting from continuous intravenous infusion of less‐soluble gases can be avoided.

4. Normoxic rats showed lower mean values of the V•A/Q• ratio of ventilation distribution and higher mean values of the V•A/Q• ratio of perfusion distribution with the usual method of inert gas administration (method A). These non‐significant differences were observed under almost all physiological conditions studied and they could be caused by haemodilution. Nevertheless, the effect of interindividual differences cannot be discarded. An additional effect of the low haematocrit on cardiovascular changes due to low FIO2, such as pulmonary vasoconstriction or increased cardiac output, may explain the lower dispersion of perfusion distributions found in group A during hypoxia.
Endothelium‐Dependent Changes In Arterial Diameter In Old Normotensive Rats
Authors: Safar Me , Duriez M , Corman B , Levy Bi
Published: March 2003

1. In normotensive rats, removal of carotid artery endothelium results in an acute increase in diameter. This finding, observed in young animals, has not been investigated in old animals. The present study was undertaken to assess the contribution of endothelial function in the regulation of arterial stiffness in aged rats.

2. In normotensive female WAG/Rij rats, isobaric (100 mmHg transmural pressure) carotid diameter was measured in vitro in situ, using a previously described arterial preparation associated with a high‐resolution echotracking technique allowing non‐invasive diameter measurements under baseline conditions, after removal of the endothelium and after total relaxation of vascular smooth muscle by potassium cyanide. Histomorphometry of the carotid wall was studied after pressure fixation (100 mmHg) of the arteries.

3. Compared with younger animals (10 months), older animals (30 months) had the same baseline carotid isobaric diameter but significantly higher values of wall thickness and collagen content. In older animals, whereas total relaxation by potassium cyanide was associated with a slight but significant increase of isobaric diameter, no increase was observed after endothelium removal.

4. The results of the presnt study provide evidence that, in old normotensive rats, endothelium‐dependent increases in isobaric carotid diameter are blunted. This endothelium alteration may contribute to the age‐dependent increase in isobaric carotid stiffness observed in old rats.
Nitric Oxide Reduces Pressor Responsiveness During Ovine Hypoadrenocorticism
Authors: Orbach Pini , Wood Charles E , Keller‐Wood Maureen
Published: March 2003

1. Hypoadrenocorticism frequently results in critical hypotension, hypovolaemia, hyponatraemia and hyperkalaemia. Perhaps even more important, hypoadrenocorticoid humans experience decreased vasoconstriction in response to exogenous administration of vasoconstrictors, such as noradrenaline.

2. We studied chronically adrenalectomized adult sheep to test the hypothesis that the reduction in pressor responsiveness is the result of increased production of nitric oxide (NO) during hypoadrenocorticism.

3. Withdrawal of steroid replacement resulted in reduced blood pressure, reduced pressor responsiveness, as well as hyperkalaemia and hyponatraemia.

4. Inhibition of NO production by NG‐nitro‐L‐arginine methyl ester in the hypoadrenocorticoid ewes restored mean arterial pressure and pressor responsiveness response to normal values.

5. The results of these experiments support the hypothesis that reduced pressor responsiveness in the hypoadrenocorticoid state is mediated by the overproduction of NO.
Effect of epomediol on ethinyloestradiol‐induced changes in bile acid and cholesterol metabolism in rats
Authors: Cuevas María J , Mauriz José L , Almar Mar , Collado Pilar S , González‐Gallego Javier
Published: March 2003

1. Epomediol is a terpenoid compound that has been reported to stimulate bile acid synthesis and to reverse 17α‐ ethinyloestradiol‐induced cholestasis. The aim of the present study was to investigate the contribution of changes in bile acid and cholesterol metabolism to the protective effects of epomediol in ethinyloestradiol‐treated rats. Animals received epomediol for 5 days at 100 mg/kg daily, i.p., ethinyloestradiol for 5 days at 5 mg/kg, s.c., or a combination of both drugs.

2. When compared with control animals, epomediol treatment resulted in a significant increase in bile flow (+42%) and in the secretion of bile acids (+74%) and cholesterol (+42%). Ethinyloestradiol administration caused a significant decrease in bile flow (–43%), bile acid secretion (–37%) and cholesterol secretion (–45%). Bile flow, bile acid secretion and cholesterol secretion were significantly increased in animals receiving ethinyloestradiol plus epomediol compared with ethinyloestradiol‐treated rats (+13, +29 and +31%, respectively).

3. Both cholesterol 7α‐hydroxylase and hydroxy‐3‐ methylglutaryl coenzyme A reductase activities were significantly increased in epomediol‐treated rats (+30 and +96%, respectively). Cholesterol 7α‐hydroxylase activity was significantly reduced by ethinyloestradiol (–22%) and did not differ from control values in animals receiving epomediol plus ethinyloestradiol. Levels of cholesterol 7α‐hydroxylase mRNA were elevated (+41%) by epomediol, but were not significantly modified by ethinyloestradiol or ethinyloestradiol plus epomediol.

4. It is concluded that epomediol enhances bile acid secretion by increasing the expression of cholesterol 7α‐hydroxylase. Changes in bile acid metabolism contribute to the effects of epomediol in rats with ethinyloestradiol‐induced cholestasis.
Large Artery Stiffness: Structural And Genetic Aspects
Authors: Kingwell Bronwyn A , Medley Tanya L , Waddell Tamara K , Cole Timothy J , Dart Anthony M , Jennings Garry L
Published: March 2003

1. Large artery stiffness is a principal determinant of pulse pressure and both are related to cardiovascular mortality independently of other major risk factors. A clearer understanding of the structural and genetic processes that contribute to large artery properties may provide novel approaches to therapy.

2. Age, atherosclerosis and gender are three important factors that contribute to large artery stiffening. Each influences the artery elastic matrix and its relationship to medial smooth muscle cells. Genetic and hormonal modulation of the extracellular matrix proteins and their regulators, including matrix metalloproteinases (MMPs), may account for some interindividual differences.

3. In a study of 213 healthy individuals and 105 patients with coronary artery disease (CAD), we examined whether stromelysin‐1 (MMP‐3) genotype, determined by the 5A/6A promoter polymorphism, influences large artery stiffening. In healthy individuals, the 5A/5A genotype was linked with stiffer large arteries and higher systolic blood pressure compared with other genotypes.

4. Genetic variation in the extracellular matrix protein fibrillin‐1, using a pentanucleotide repeat polymorphism, was assessed as a potential determinant of large artery stiffness in patients with CAD. The 2–3 genotype was associated with stiffer large arteries, higher pulse pressure and more severe CAD than other genotypes.

5. Females experience a greater increase in large artery stiffness with age than males, with a time‐course suggestive of sex steroid modulation. The mechanisms mediating such gender differences have not been established, but the known regulatory role of sex steroids with respect to MMPs likely contributes.

6. The demonstration that genetic and hormonal modulation of extracellular matrix components and MMPs contributes to age, atherosclerotic and gender‐related differences in large artery mechanical properties suggests these proteins may be important targets for therapy.
Large Artery Stiffness: Implications For Exercise Capacity And Cardiovascular Risk
Authors: Kingwell Bronwyn A
Published: March 2003

1. Large artery stiffness, or its inverse, compliance, determines pulse pressure, which, in turn, influences myocardial work capacity and coronary perfusion, both of which impact on exercise capacity and cardiovascular risk.

2. In support of a role for arterial properties in exercise performance, aerobically trained athletes (aged 30–59 years) have lower arterial stiffness than their sedentary counterparts. Furthermore, in healthy older subjects (aged 57–80 years), time to exhaustion on treadmill testing correlated positively with arterial compliance.

3. Arterial stiffness is more closely linked to exercise capacity and myocardial risk in patients with coronary disease where, independently of degree of coronary disease, those with stiffer proximal arteries have a lower exercise‐induced ischaemic threshold.

4. Moderate aerobic training elevates resting arterial compliance by approximately 30%, independently of mean pressure reduction, in young healthy individuals but not in isolated systolic hypertensive patients. Rat training studies support a role for exercise training in structural remodelling of the large arteries.

5. High‐resistance strength training is associated with stiffer large arteries and higher pulse pressure than matched controls.

6. Large artery stiffness is an important modulator of the myocardial blood supply and demand equation, with significant ramifications for athletic performance and ischaemic threshold in coronary disease patients. Moderate aerobic training, but not high‐resistance strength training, reduces large artery stiffness in young individuals whereas older subjects with established isolated systolic hypertension are resistant to such adaptation.
Opioid Signalling In The Rat Rostral Ventrolateral Medulla
Authors: Guyenet Patrice G , Stornetta Ruth L , Schreihofer Ann M , Pelaez Nicole M , Hayar Abdallah , Aicher Sue , Llewellyn‐Smith Ida J
Published: March 2003

1. The present article reviews several aspects of opioid signalling in the rostral ventrolateral medulla (RVLM) and their implications for the neural control of blood pressure.

2. In the RVLM, preproenkephalin (PPE) mRNA is expressed by bulbospinal cells that are strongly barosensitive. These putative presympathetic neurons includes C1 and non‐C1 neurons.

3. In the RVLM, PPE mRNA is also present in GABAergic neurons that do not project to the thoracic spinal cord.

4. Rostral ventrolateral medulla presympathetic cells receive enkephalinergic inputs and express μ‐opioid receptors (MOR). Some of their synaptic inputs also contain MOR.

5. Pre‐ and post‐synaptic modulation of RVLM presympathetic neurons by MOR agonists has been demonstrated in slices of neonate brain. The post‐synaptic effect is inhibitory (increased gK). Presynaptic effects include disfacilitation (reduction of glutamate release) and possibly dishinhibition (reduction of GABA release).

6. In conclusion, opioid signalling plays a pervasive role in the medullospinal network that controls sympathetic tone and arterial pressure. Opioid peptides are made by the presympathetic, presumably excitatory, cells of the RVLM and by local GABAergic inhibitory neurons. In addition, RVLM presympathetic neurons are also controlled by opioid peptides at the pre‐ and post‐synaptic level. μ‐Opioid receptors
are found post‐synaptically, whereas presynaptic receptors probably include both
μ and δ subtypes. Conditions that trigger the release of opioid peptides by presympathetic neurons or by inputs to these cells are not fully understood and may include decompensated haemorrhage and certain types of peripheral sensory stimulation related to acupuncture.
Heterogeneity In The Distribution Of Vascular Gap Junctions And Connexins: Implications For Function
Authors: Hill CE , Rummery N , Hickey H , Sandow SL
Published: March 2003

1. Gap junctions, which are comprised of members of a family of membrane proteins called connexins (Cx), permit the transfer of electrical and chemical information between adjacent cells in a wide variety of tissues. The aim of the present study was to compare the expression of Cx37, 40 and 43 in the smooth muscle and endothelium of a large elastic artery and two smaller muscular arteries of the rat. Serial section electron microscopy was also used to determine the presence of pentalaminar gap junctions in the smooth muscle and the incidence of myoendothelial gap junctions between the smooth muscle and endothelial cells in muscular arteries of different size.

2. Using immunohistochemistry, Cx37, 40 and 43 were found in the endothelium of the aorta, caudal and basilar arteries, with Cx43 being the least abundant. Connexin 43 was readily observed throughout the muscle layers of the aorta, but was not detected in the media of the caudal or basilar arteries. Connexin 40 was not detected in the media of any of the arteries, while very fine punctate staining was observed with Cx37 antibodies in the media of the caudal and basilar arteries, but not in the aorta.

3. Real‐time polymerase chain reaction showed that the expression of mRNA for Cx43 was 15‐fold greater in the aorta than in the caudal artery of the rat.

4. At the ultrastructural level, small pentalaminar gap junctions (< 100 nm) were found between the fine processes of adjacent smooth muscle cells and also between the smooth muscle and endothelial cells. The incidence of myoendothelial gap junctions in the mesenteric vascular bed and in the caudal artery increased as vessel size decreased.

5. In summary, heterogeneity exists within the vascular system with regard to the distribution of gap junctions and their constituent Cx. Such variation will have important consequences for the coordination and propagation of vascular responses. In muscular arteries, in comparison with elastic arteries, Cx37 may be more important than Cx43 for cell coupling within the smooth muscle layers. The correlation between the incidence of myoendothelial gap junctions and the role of endothelium‐derived hyperpolarizing factor, relative to nitric oxide, in vasodilatory responses suggests that myoendothelial gap junctions play an important physiological role in the regulation of vascular tone.
Effect Of Training On Activation Of Extracellular Signal‐Regulated Kinase 1/2 And P38 Mitogen‐Activated Protein Kinase Pathways In Rat Soleus Muscle
Authors: Lee Jong Sam , Bruce Clinton R , Spurrell Brian E , Hawley John A
Published: March 2003

1. The effect of a chronic programme of either low‐ or moderate‐to‐high‐intensity treadmill running on the activation of the extracellular‐signal regulated protein kinase (ERK1/2) and the p38 mitogen‐activated protein kinase (MAPK) pathways was determined in rat muscle.

2. Sprague‐Dawley rats were assigned to one of three groups: (i) sedentary (NT; n = 8); (ii) low‐intensity training (8 m/min; LIT; n = 16); and (iii) moderate‐to‐high‐intensity training (28 m/min; HIT; n = 16). The training regimens were planned so that animals covered the same distance and had similar glycogen utilization for both LIT and HIT exercise sessions.

3. A single bout of LIT or HIT following 8 weeks of training led to a twofold increase in the phosphorylation of ERK1/2 (P = 0.048) and a two‐ to threefold increase in p38 MAPK (P = 0.005). Extracellular signal‐regulated kinase 1/2 phosphorylation in muscle sampled 48 h after the last exercise bout was similar to sedentary values, while p38 MAPK phosphorylation was 70–80% lower than sedentary. One bout of LIT or HIT increased total ERK1/2 and p38 MAPK expression, with the magnitude of this increase being independent of prior exercise intensity or duration. Extracellular signal‐ regulated kinase 1/2 expression was increased three‐ to fourfold in muscle sampled 48 h after the last exercise bout irrespective of the prior training programme (P = 0.027), but p38 MAPK expression was approximately 90% lower than sedentary values.

4. In conclusion, exercise‐training of different intensities/ durations results in selective postexercise activation of intracellular signalling pathways, which may be one mechanism regulating specific adaptations induced by diverse training programmes.
Toxic marine dinoflagellates in Singapore waters that cause seafood poisonings
Authors: Holmes Michael James , Teo Serena Lay Ming
Published: March 2003

1. The present paper reviews the toxic dinoflagellates found in Singapore waters that produce toxins that can accumulate through marine food chains to cause seafood poisonings.

2. Singapore waters contain dinoflagellate species linked to three types of seafood poisoning: paralytic shellfish poisoning, diarrhetic shellfish poisoning (DSP) and ciguatera.

3. Paralytic shellfish poisoning and DSP occur by eating bivalve shellfish contaminated with saxitoxins and okadaic acid analogues, respectively. Shellfish accumulate these toxins from filter feeding on a number of species of (mostly) planktonic dinoflagellates.

4. In contrast, benthic species of dinoflagellates of the genus Gambierdiscus produce the ciguatoxins that are bioaccumulated into finfish to cause ciguatera.

5. Paralytic shellfish poisoning and DSP are the major concern for local and regionally produced seafood. To the best of our knowledge, ciguatera poisoning in Singapore only originates from imported reef fish.
Autonomic effects of some scorpion venoms and toxins
Authors: Gwee Matthew CE , Nirthanan Selvanayagam , Khoo Hoon‐Eng , Gopalakrishnakone Ponnampalam , Kini R Manjunatha , Cheah Li‐Sam
Published: March 2003

1. The autonomic effects of venoms and toxins from several species of scorpions, including the Indian red scorpion Mesobuthus tamulus, the Chinese scorpion Buthus martensi Karsch and the Israeli scorpion Leiurus quinquestriatus quinquestriatus, all belonging to Buthidae, and the Asian black scorpions Heterometrus longimanus and Heterometrus spinifer, belonging to Scorpionidae, are reviewed.

2. The effects of the venoms of M. tamulus and L. q. quinquestriatus on noradrenergic and nitrergic transmission in the rat isolated anococcygeus muscle revealed that both venoms mediated their pharmacological effects via a prejunctional mechanism involving the activation of voltage‐sensitive sodium channels with consequent release of neurotransmitters that mediate target organ responses, similar to the effects mediated by other α‐scorpion toxins.

3. Two new toxins, Makatoxin I and Bukatoxin, were purified to homogeneity from the venom of B. martensi Karsch. Determination of their complete amino acid sequences confirmed that both toxins belonged to the class of α‐scorpion toxins. The effects of both toxins on noradrenergic and nitrergic transmission in the rat anococcygeus muscle provided firm evidence that their pharmacological actions also closely resembled those mediated by other α‐scorpion toxins on neuronal voltage‐sensitive sodium channels.

4. The venoms of H. longimanus and H. spinifer were found to have high concentrations of noradrenaline (1.8 ± 0.3 mmol/L) and relatively high concentrations of acetylcholine (79.8 ± 1.7 µmol/L) together with noradrenaline (146.7 ± 19.8 µmol/L), respectively, which can account for their potent direct cholinergic and noradrenergic agonist actions in the rat anococcygeus muscle.

5. Our studies confirmed that the rat anococcygeus muscle is an excellent nerve–smooth muscle preparation for investigating the effects of bioactive agents on noradrenergic and nitrergic transmission, as well as the direct agonist actions of these agents on post‐synaptic α‐adrenoceptors and M3 muscarinic cholinoceptors. Although many studies, including our own, have documented that scorpion venoms and toxins mediate their primary effects via a prejunctional mechanism that leads to the marked release of various autonomic neurotransmitters, our studies have shown that there are exceptions to this generally accepted phenomenon. In particular, we have provided firm evidence to show that the venoms from H. longimanus and H. spinifer do not have such a prejunctional site of action but, instead, the venoms mediate their autonomic effects through direct agonist actions on post‐junctional muscarinic M3 cholinoceptors and α‐adrenoceptors.
Association of the SULT1A1 R213H polymorphism with colorectal cancer
Authors: Wong Chung Fai , Liyou Nancy , Leggett Barbara , Young Joanne , Johnson Anthony , McManus Michael E
Published: March 2003

1. Sulphotransferases are a superfamily of enzymes involved in both detoxification and bioactivation of endogenous and exogenous compounds. The arylsulphotransferase SULT1A1 has been implicated in a decreased activity and thermostability when the wild‐type arginine at position 213 of the coding sequence is substituted by a histidine. SULT1A1 is the isoform primarily associated with the conversion of dietary N‐OH arylamines to DNA binding adducts and is therefore of interest to determine whether this polymorphism is linked to colorectal cancer.

2. Genotyping, using polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) analysis, was performed using DNA samples of healthy control subjects (n = 402) and patients with histologically proven colorectal cancer (n = 383). Both control and test populations possessed similar frequencies for the mutant allele (32.1 and 31%, respectively; P = 0.935). Results were not altered when age and gender were considered as potential confounders in a logistic regression analysis.

3. Examination of the sulphonating ability of the two allozymes with respect to the substrates p‐nitrophenol and paracetamol showed that the affinity and rate of sulphonation was unaffected by substitution of arginine to histidine at position 213 of the amino acid sequence.

4. From this study, we conclude that the SULT1A1 R213H polymorphism is not linked with colorectal cancer in this elderly Australian population.
A diet supplemented with thiolic anti‐oxidants improves leucocyte function in two strains of prematurely ageing mice
Authors: Guayerbas N , Puerto M , Ferrández MD , De la Fuente M
Published: March 2003

1. According to previous studies, Swiss mice of the same age showed striking interindividual differences in behaviour when exposed to a T‐maze test, with a slow performance being linked to an impaired immune function, hyperemotional response to stress and a shorter life span compared with mice that quickly explore the maze.These facts led us to propose the slow mice as a model of prematurely ageing mice (PAM).

2. In the present study, we investigated whether this prematurely ageing model could be found in other strains of mice, such as BALB/c mice, by analysing several lymphocytes functions, such as adherence, chemotaxis, proliferative response to the mitogen concanavalin A (Con A), interleukin (IL)‐2 release and natural killer (NK) activity. In addition, we tested the probable beneficial effects on these functions of dietary supplementation with thioproline (TP) plus N‐acetylcysteine (NAC; 0.1% w/w of each anti‐oxidant) in female Swiss and BALB/c mice.

3. Our model of premature ageing, previously reported in Swiss mice, has also been reproduced in the inbred BALB/c mouse strain, in which PAM showing an immunosenescence in several lymphocyte functions, such as lower chemotaxis, proliferative response to Con A, IL‐2 release and NK activity, as well as higher adherence, were observed. A short‐term (5 week) ingestion of TP + NAC by female Swiss and BALB/c mice improved leucocyte function, increasing chemotaxis, the proliferative response to Con A, IL‐2 release and NK activity and decreasing the adherence of lymphocytes.These effects are greatest in cells from PAM of both strains.

4. In conclusion, our model of premature ageing has been reproduced in an inbred strain. In addition, the ingestion of a diet supplemented with two thiolic anti‐oxidants, such as NAC and TP, has been shown to be beneficial to the immune response in PAM.
Effect of creatine manipulation on fast‐twitch skeletal muscle of the mouse
Authors: Robinson Dean M , Loiselle Denis S
Published: March 2003

1. The effect of short‐term, reversible alteration of muscle total creatine content (Crtot) on force development was sought in fast‐twitch extensor digitorum longus (EDL) muscles of female mice.

2. Three in vivo interventions were investigated: 1% creatine‐supplementation, treatment with the creatine‐uptake inhibitor β‐guanidino propionic acid (β‐GPA; 1%) or β‐GPA treatment followed by creatine supplementation for 5 days.

3. The Crtot of isolated muscles, determined using reverse‐phase high‐performance liquid chromatography, was 133 ± 38 mmol/kgdry in 11 EDL control muscles and was not significantly affected by dietary creatine‐supplementation (152 ± 25 mmol/kgdry; n = 8). Significant creatine depletion was observed in the β‐GPA‐fed group (65 ± 6 mmol/kgdry; n = 9) and this was reversed by 5 days of creatine supplementation (133 ± 21 mmol/kgdry; n = 10).

4. Creatine depletion did not affect maximum tetanic stress. However, when muscle creatine was restored by creatine supplementation, a substantial increase in tetanic stress was observed. Significant correlations were observed between Crtot and maximum tetanic stress (r = 0.56) and relaxation rate (r = 0.43). The enhancement of force was not due to effects of creatine on muscle fibre type because neither mechanical tests of fibre characteristics nor the fibre types of the muscles were affected.

5. We conclude that, in muscles that contain large numbers of fast‐twitch fibres, maximum tetanic stress is determined, in part, by muscle creatine stores.