bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDURANCE TRAINING EFFECTS ON THE CONTRACTILE ACTIVATION CHARACTERISTICS OF SINGLE MUSCLE FIBRES FROM THE RAT DIAPHRAGM
Authors: Lynch Gordon S. , Duncan Noel D. , Campbell Siun P. , Williams David A.
Published: June 2007

1. Considerable debate exists as to whether the properties of diaphragm muscles can be modified by training. As the diaphragm is chronically activated during normal respiration, it is of interest to determine whether this muscle is resistant to further modification by exercise. The aim of this study was to investigate the contractile activation characteristics of single skinned muscle fibres from the diaphragm of both CONTROL and TRAINED rats.

2. Male rats were subjected to a 20 week high‐intensity endurance exercise training programme that consisted of running on a motorized treadmill, 5 days/week, 90–120 min/day, 27–30 m/min, up a 20° incline. At the conclusion of training, rats were killed with an overdose of ether and costal regions of the diaphragm were removed and stored in a glycerol‐based skinning solution at—20° C.

3. Single skinned (membrane‐permeabilized) diaphragm muscle fibres were attached to a sensitive force transducer and activated in Ca2+‐ and Sr2+‐buffered solutions in order to determine relative force‐pCa and force‐pSr characteristics. Fibres were allocated into discrete groups (population I, population II, intermediate, mixed) on the basis of their physiological (contractile) properties.

4. Population I (slow‐twitch) fibres from the diaphragm of TRAINED rats exhibited a reduced sensitivity to Ca2+ (indicating a rightward shift of the force‐pCa relationship) compared to those diaphragm fibres from CONTROL animals. An increased number of population II (fast‐twitch) fibres were sampled from TRAINED rats, however, training did not affect the activation properties of these fibres.

5. The fact that training‐induced alterations in the contractile characteristics did occur in one group of fibres indicates that the intensity of training was sufficient to induce some modifications to the costal fibres of the diaphragm muscle. However, the lack of alterations to the contractile characteristics of the population II (fast‐twitch) fibres may also suggest that the overall properties of the diaphragm are relatively resistant to modification despite high‐intensity training.
HYBRID GENE OR HYBRID STEROIDS IN THE DETECTION AND SCREENING FOR FAMILIAL HYPERALDOSTERONISM TYPE I
Authors: Stowasser Michael , Bachmann Anthony W. , Jonsson Julie R. , Tunny Terry J. , Klemm Shelley A. , Gordon Richard D.
Published: June 2007

1. Early diagnosis of Familial Hyperaldosteronism Qpe I (FH‐I, glucocorticoid‐suppressible hyperaldosteronism) in asymptomatic, affected individuals is essential if death from stroke is to be prevented.

2. In 21 patients with FH‐I (presence of the causative hybrid 11β‐hydroxylase/aldosterone synthase gene confirmed by Southern blot testing), various biochemical parameters were compared as possible screening tests. Hypokalaemia and elevated plasma aldosterone each detected only two (10%) of the affected individuals.

3. Plasma renin activity 19 (90%) and aldosterone/renin ratio 18 (86%) were more reliable but not free from false negatives.

4. Levels of the urinary ‘hybrid’ steroid, 18‐oxocortisol, were elevated (P <0.01) in all 15 patients tested (138.2 ± 17.4 μg/g creatinine, range 41.6–281.0 μg/g) with no overlap when compared with 11 normals (9.7 ± 1.3μg/g, range 2.8–17.4 μg/g).

5. We conclude that measurement of urinary ‘hybrid’ steroids is probably the most rapid and reliable biochemical screening test currently available for FH‐I, with confirmation dependent on demonstration of the hybrid gene by genetic techniques.
HYPERTENSION MANAGEMENT: A COMPARISON OF URBAN VERSUS RURAL GENERAL PRACTITIONERS IN WESTERN AUSTRALIA
Authors: Yapp Caroline K. , Taylor Lynette S. , Ow Cherynne Y. , Jamrozik Konrad , Puddey Ian B.
Published: June 2007

1. We have conducted a survey of 75 rural and 75 urban randomly selected general practitioners (GPs) in Western Australia to ascertain how closely current practice mirrors published Australian guidelines for the management of hypertension.

2. Fifty‐one rural and 49 urban GPs completed the 19 item questionnaire. The two groups were well matched in terms of age and years in general practice. An assessment of the criteria utilized to diagnose hypertension revealed a tendency for much greater scatter in the cut points used to define systolic compared to diastolic hypertension, but no systematic difference between urban and rural GPs.

3. After an initial finding of mild hypertension the follow‐up time to the next check‐up was significantly longer for rural patients compared to urban patients (72 ± 13 and 36 ± 5 days respectively, P < 0.01). Urban GPs reviewed established hypertensive patients more commonly at 1–3 monthly intervals (89%) while rural GPs reviewed more commonly at 3–6 monthly intervals (86%).

4. In terms of target blood pressure (BP) for BP reduction, 67% rural compared to 83% urban GPs aimed for a systolic BP of < 140mmHg (P= 0.06), while 95% of both groups aimed for diastolic BP < 90mmHg.

5. The profile of first line antihypertensive agents most commonly used was also similar in both groups with 46% preferring angiotensin converting enzyme inhibitors, 18.5% diuretics, 18.5% beta blockers, 16% calcium entry blockers and 1% prazosin.

6. This study demonstrates a clear preference for the newer anti‐hypertensive agents. Otherwise there was self‐reported broad compliance with Australian guidelines for hypertension management in this randomly selected GP population. Urban and rural practices were more notable for their consistency rather than any systematic differences in approach.
MUTATIONS IN THE FIRST INTRON OF THE SHR RENIN GENE DISRUPT PUTATIVE REGULATORY ELEMENTS
Authors: Yu H. , Nicolantonio R. Di , Lan L. , Wilks A.
Published: June 2007

1. Four single base mutations unique to the spontaneously hypertensive rat (SHR) were identified in the first 1100 base pairs of its renin gene first intron when compared to that of Wistar‐Kyoto and Sprague‐Dawley normotensive rats.

2. These mutations were found to fall within the consensus sequences for a number of transcription factors and thus may alter the affinity of these putative transcription factor binding sites.

3. The reported overexpression of the renin gene in the SHR may therefore result from these structural abnormalities and, in turn, result in a tissue angiotensin‐dependent hypertension in this strain.
PAF ANTAGONISTS BLOCK INDUCTION OF NITRIC OXIDE SYNTHASE IN CULTURED MACROPHAGES AND VASCULAR SMOOTH MUSCLE CELLS
Authors: Arthur Jane F. , Shahin Susan , Dusting Gregory J.
Published: June 2007

1. Nitric oxide (NO) synthase inhibitors and Paf antagonists abrogate hypotension in septic shock. The latter may act by blocking intracellular transduction mechanisms in vascular smooth muscle cells and inflammatory cells. We examined the effect of Paf antagonists on expression of inducible NO synthase.

2. A murine macrophage cell line (J774.2) and rat vascular smooth muscle cells (VSMC) were stimulated with lipopoly‐saccharide (LPS), either alone or in combination with Paf or Paf antagonists, BN 50739 or E‐6123.

3. NO synthase activity in 5774.2 was measured by the conversion of [3H]l‐arginine to [3H]l‐citrulline. Nitrite accumulation was measured in the culture medium of J774.2 and VSM.

4. BN 50739 (10 μmol/L) and E‐6123 (1 μmol/L) both reduced the expression of calcium‐independent NO synthase activity and nitrite accumulation, while Paf alone had no effect.

5. Inhibition of NO synthase induction by Paf antagonists might afford therapeutic benefits in the management of septic shock and possibly other cardiovascular disorders.
PARTICIPATION OF THE RENIN‐ANGIOTENSIN SYSTEM IN REGULATING THE EXCRETORY RESPONSE TO ACUTE SODIUM INGESTION
Authors: Duggan K. A. , Jones D. M. , MacDonald G. J.
Published: June 2007

1. A gastric sodium monitor has been proposed, based upon greater urinary sodium excretion after gastric, compared with intravenous, sodium loading. However, this difference has only been demonstrated in animals and humans on a low sodium diet prior to study. This suggests involvement of a system activated by decreased sodium intake. As the renin‐angiotensin system is the most active of these, this study sought to determine whether angiotensin II (AII) might act as a humoral mediator for this gastric sodium monitor.

2. Male New Zealand white rabbits with a gastrostomy tube in situ were placed on a low sodium diet (0.008% NaCl) for 7 days. To determine if differences in plasma AII might explain the different natriuretic responses AII was measured 0, 5,10, 30, 60 and 120 min after a 1.5mmol/kg sodium load given gastrically or intravenously. To determine whether the AII response was specific to low salt diets the gastric salt load was given after equilibration on normal (2.2% NaCl) and high (4.4% NaCl) sodium diets.

3. In rabbits on the low sodium diet plasma AII decreased significantly at 5 min after both gastric (P < 0.025) and intravenous (P < 0.05) sodium and returned to baseline by 10 min in the latter. In contrast after gastric sodium AII remained less than in controls throughout (120 min, P < 0.05). In the rabbits on the normal and high sodium diets plasma AII concentration increased non‐significantly after gastric sodium administration.

4. We conclude that circulating AII may participate as a mediator of the gastric sodium monitor. Its concentration was reduced and remained persistently lower after gastric but not intravenous sodium. Further, this change was not apparent on sodium diets in which differences in sodium excretion have not been demonstrated previously.
PCR‐SSCP ANALYSIS OF THE ANGIOTENSIN II TYPE 1: RECEPTOR GENE IN PATIENTS WITH ALDOSTERONE‐PRODUCING ADENOMAS
Authors: Klemm S. A. , Ballantine D. M. , Tunny T. J. , Stowasser M. , Gordon R. D.
Published: June 2007

1. In patients with primary aldosteronism due to angiotensin‐responsive and andotensin‐unresponsive aldosterone‐producing adenomas, no differences in the coding region of the angiotensin II type 1 (AT1) receptor gene were observed compared to normal subjects in peripheral blood leucocyte DNA.

2. Furthermore, no differences in the AT1 receptor gene were observed in DNA extracted from tumour tissue of either subgroup.

3. Genotypic and allelic frequencies for an RFLP detected in the coding region of the AT1 receptor gene were not significantly different between normal subjects and patients with aldosterone‐producing adenomas as a group, nor between normal subjects and patients of either subgroup when compared with each other.

4. In those patients heterozygous in peripheral blood at the RFLP site, tumour DNA showed the same allelic pattern.

5. In patients with aldosterone‐producing adenomas either responsive or unresponsive to the renin‐angiotensin system, no differences were detected using SSCP analysis in the coding region of the AT1 receptor gene in peripheral blood or tumour tissue.
PLASMA ALDOSTERONE RESPONSE TO ACTH IN SUBTYPES OF PRIMARY ALDOSTERONISM
Authors: Stowasser Michael , Klemm Shelley A. , Tunny Terry J. , Gordon Richard D.
Published: June 2007

1. Aldosterone responsiveness to ACTH was compared in eleven patients with angiotensin‐unresponsive (AII‐U) aldosterone‐producing adenomas (APA), 16 with AII‐responsive (AII‐R) APA and 19 with bilateral adrenal hyperplasia (BAH).

2. After overnight recumbency, aldosterone levels were highest in AII‐U APA and lowest in BAH. Following 2h of upright posture, however, levels were similar among the three groups.

3. During ACTH infusion, aldosterone levels in AII‐U and AII‐R APA were similar, and higher than those in BAH. Because of the higher basal level, the percentage rise in aldosterone was lower in AII‐U APA compared with the other groups, as was the ratio of per cent aldosterone rise to per cent cortisol rise.

4. Slightly but significantly reduced plasma cortisol levels observed in the AII‐R APA group may reflect secretion by AII‐R APA of a cortisol‐like substance that is capable of suppressing ACTH and thus adrenal cortisol production.

5. The tendency of aldosterone to follow the diurnal rhythm of ACTH in AII‐U APA may thus represent an unmasking of the normal ability of ACTH to regulate aldosterone, secondary to the loss of AII responsiveness, rather than an enhancement of ACTH effect.
EFFECTS OF ISOTONIC SALINE LOADING ON RENAL TUBULAR AND NEUROGENIC DOPAMINE RELEASE IN CONSCIOUS RABBITS
Authors: Akama Hiroyoshi , Noshiro Takao , Sane Naoki , Watanabe Toshiya , Trigg Lisbeth , Kotsonis Peter , Majewski Harry , McGrath Barry P. , Miura Yukio , Abe Keishi
Published: June 2007

1. This study was designed to investigate the effects of isotonic saline loading on renal tubular and neurogenic dopamine (DA) in conscious rabbits.

2. Isotonic saline loading did not affect mean arterial pressure, heart rate or renal blood flow but markedly increased urine volume, sodium excretion and DA excretion.

3. Renal DA spillover was not affected by venous emptying, while renal noradrenaline (NA) spillover tended to decrease during saline loading. The ratio of % renal DA spillover to % renal NA spillover increased to 2.3 ± 0.6 (P < 0.05) 3h after saline loading.

4. Isotonic saline loading increased renal tubular DA production but had little effect on neurogenic DA release.
THE INFLUENCE OF THE RENIN ANGIOTENSIN SYSTEM ON ABNORMAL EXPRESSION OF NERVE GROWTH FACTOR IN THE SPONTANEOUSLY HYPERTENSIVE RAT
Authors: Jeffreson S. , Rush R. , Zettler C. , Frewin D. B. , Head R. J.
Published: June 2007

1. The levels of the neurotrophic factor, nerve growth factor (NGF) in the mesenteric vascular bed of the spontaneously hypertensive rat (SHR) were greater than those in the corresponding vascular bed of normotensive Wistar‐Kyoto rats (WKY).

2. Administration of angiotensin II (200 ng/kg per min, by minipump) for 2 weeks to juvenile WKY rats increased the levels of NGF in the mesenteric vasculature to those seen in untreated SHR.

3. Administration of the angiotensin II receptor antagonists losartan (30 mg/kg per day, p.o.) or PD144277 (10 mg/kg per day, p.o.) to juvenile SHR for 4 weeks reduced the levels of NGF such that they were indistinguishable from the values obtained for normotensive WKY rats.

4. The results confirm the elevated level of NGF in the mesenteric vasculature of the SHR and suggest that angiotensin II may play a role in regulating the abnormal concentrations of the protein in this tissue.
ANALYSIS OF THE RENIN GENE IN PATIENTS WITH ALDOSTERONE‐PRODUCING ADENOMAS BY POLYMERASE CHAIN REACTION‐SINGLE STRANDED CONFORMATIONAL POLYMORPHISMS AND LONG POLYMERASE CHAIN REACTION
Authors: Ballantine Donna M. , Klemm Shelley A. , Tunny Terry J. , Stowasser Michael , Gordon Richard D.
Published: June 2007

1. Angiotensin‐responsive aldosterone‐producing adenomas (AII‐R‐APA) have increased expression of renin mRNA compared with angiotensin‐unresponsive aldosterone‐producing adenomas (AII‐U‐APA) or normal adrenals.

2. Further, significant associations between the Bgl I, Taq I and Hinf I RFLP and aldosterone responsiveness to the renin‐angiotensin system of the two subgroups of patients have been reported.

3. Using the polymerase chain reaction based technique single stranded conformational polymorphism, we detected no alterations in exon 1 of the renin gene in peripheral blood leucocyte DNA from normal AII‐U‐APA and AII‐R‐APA subjects.

4. Using long‐PCR, we amplified a fragment of the renin gene consisting of a region covering 500 bp upstream of exon 1, exon 1 and intron A. No gross changes in this area of the renin gene were found in the three groups of subjects studied. However this does not exclude small alterations in this area.
FUNCTIONS OF THE RENIN‐ANGIOTENSIN SYSTEM DURING DEVELOPMENT
Authors: Lumbers E. R.
Published: June 2007

1. From studies in chronically catheterized fetal sheep and other species, it can be shown that the renin‐angiotensin system (RAS) is active during intra‐uterine life. Levels of angiotensin II (AII) in fetal sheep are similar to maternal.

2. The fetal RAS plays a role in maintenance of arterial pressure. The extent to which it does so depends on the level of activity of the system.

3. The distribution of renin within the fetal rat kidney is much more widespread than in the adult. The fetal kidney, like other vascular beds has high levels of the AT2 angiotensin receptor subtype. With maturation the proportion of the AT1 receptor subtype increases.

4. Blockade of the fetal RAS with angiotensin converting enzyme (ACE) inhibitors or with the non‐peptide AII antagonist (losartan) caused a fall in fetal glomerular filtration rate (GFR) and a rise in renal blood flow (RBF). AII reverses the fall in GFR even though RBF decreases.

5. The fraction of the filtered sodium load reabsorbed by the proximal tubule was not affected when the fetal RAS was blocked by captopril or losartan. High doses of infused AII had no effect on renal reabsorption of sodium, in the short term, but in the long term depressed fractional proximal reabsorption.

6. Only in high doses does AII stimulate the secretion of aldosterone from the fetal adrenal.

7. Since the fetal RAS is responsible for maintenance of GFR and physiological levels of AII do not stimulate either proximal tubular sodium reabsorption nor aldosterone secretion, it is proposed that during intra‐uterine life the fetal RAS maintains the renal excretion of sodium and water into the amniotic cavity, thus ensuring an adequate volume of amniotic fluid for normal growth and development.
HYPOXIC INHIBITION OF BREATHING AND MOTOR ACTIVITY IN THE FOETUS AND NEWBORN
Authors: Walker David W.
Published: June 2007

In fetal animals hypoxia of rapid onset causes cessation of breathing movements, electro‐ocular activity and decrease of muscle tone. These effects last several hours and are in contrast to the hypernoea and behavioural activation which occurs during hypoxia soon after birth and in the adult. Transection and lesion studies in fetal sheep suggest that hypoxia activates a descending inhibition of respiratory and other motor activities which either originates in the pons or is conveyed to medullary and spinal levels of the neuraxis by fibres through the pons in the region of the Kolliker‐Fuse nucleus. Recently, using FOS immunohistochemistry we have identified cells in the medial parabrachial complex which are activated by hypoxia in fetal sheep, but not newborn lambs. It is proposed that these cells have descending inhibitory connections with respiratory and spinal motor pathways, but the precise anatomy and neuro‐chemistry of such pathways is unknown. It is not known if the parabrachial cells are directly sensitive to low P o2 or receive input from other centres or peripheral receptors which monitor arterial P o2 in the foetus. Nor is it known why these cells are not activated by low P o2 after birth.
REGULATION OF NEURAL PRECURSOR DIFFERENTIATION IN THE EMBRYONIC AND ADULT FOREBRAIN
Authors: Bartlett P. F. , Richards L. R. , Kilpatrick T. J. , Talman P. S. , Bailey K. A. , Brooker G. J. F. , Dutton R. , Koblar S. , Nurcombe V. , Ford M. , Cheema S. S. , Likiardopoulos V. , Murphy M.
Published: June 2007

1. Precursors form the neuroepithelium of the developing cortex and also from the adult sub‐ventricular zone, can be cloned in vitro after stimulation with fibroblast growth factor (FGF)‐2 and have the potential to give rise to both neurons and glia. The generation of neurons from these clones can be stimulated by either a factor derived from an astrocyte‐precursor line, Ast‐1, or FGF‐1.

2. Neuronal differentiation stimulated by FGF‐1 can be inhibited by diacylglycerol‐lipase inhibitor and mimicked by arachidonic acid, suggesting that the neuronal differentiation is signalled through the PCLγ pathway.

3. The sequential expression of FGF‐2 and FGF‐1 within the developing forebrain neuroepithelium fits with the different functions the two FGF play in precursor regulation.

4. We have shown that the precursor response to FGF‐1 is regulated by a heparan sulphate proteoglycan (HSPG) expressed within the developing neuroepithelium. Precursors restricted to the astrocyte cell lineage can be stimulated by epidermal growth factor or FGF‐2; however, the differentiation into GFAP positive astrocytes appears to require a cytokine acting through the leukaemia inhibitory factor β receptor.
DEVELOPMENTAL SIGNALLING
Authors: Hendry I. A. , Johanson S. O. , Heydon K.
Published: June 2007

1. In investigating the communication paths between target tissue and neurons we have been led to propose two classes of neurotrophic factors. One comprises the factors which transport themselves, the other factors relying on the transport of a second messenger. The former may have labile second messenger systems necessitating the translocation of agonist and receptor from the nerve terminal to the cell body and the latter must possess a stable second messenger system that itself is sufficiently robust to survive the transport to the cell body.

2. One such class of stable messengers may be the GTP‐binding protein family and it has been shown that the alpha subunits of both Giα and Gzα can be retrogradely transported in the mouse sciatic nerve.

3. Examination of the cell bodies in the dorsal root ganglia revealed that Gα accumulated in the nucleus of cells with intact axons but that 24 h after axonal ligation this immunoreactivity decreased.

4. It is suggested that Gzα is activated at the nerve terminal and it, or at least its alpha subunit, undergoes retrograde transport to the cell body where it accumulates in the nucleus.
SCHWANN CELLS AND THE REGROWTH OF AXONS IN THE MAMMALIAN CNS: A REVIEW OF TRANSPLANTATION STUDIES IN THE RAT VISUAL SYSTEM
Authors: Harvey A. R. , Plant G. W. , Tan M. M. L.
Published: June 2007

1. We have used peripheral nerve transplants or cultured Schwann cells grafted in association with different types of polymer to study axonal regrowth in the rat visual system. In some instances the glia were co‐grafted with fetal tectal tissue.

2. The studies have two main aims: (i) to determine whether retinal axons can be induced to regrow at a site distant from their cell soma, that is, after damage to the brachial region of the optic tract; (ii) to determine whether retinal axons exposed to Schwann cells retain the ability to recognize their appropriate target neurons in CNS tissue.

3. In brachial lesion studies, Schwann cells were placed in the lesion site in association with nitrocellulose papers, within polycarbonate tubes in the presence or absence of a supporting extracellular matrix (ECM), or within polymer hydrogel scaffolds. Autologous sciatic nerve grafts were also used. Immuno‐histochemical studies revealed the presence of regenerating axons within all polymer bridges. Regrowth of retinal axons was also seen, however, growth was not extensive and was limited to the proximal 1–1.5 mm of the implants.

4. In target innervation experiments, two surgical paradigms were developed. In one experiment, a segment of sciatic nerve was autografted onto the transected optic nerve in adult rats and the distal end of each graft was placed adjacent to fetal tectal (target) tissue implanted into the frontal cortex. To date, we have not been able to demonstrate selective recognition of target regions within tectal transplants by retinal axons exiting the sciatic nerve implants.

5. In the second experiment, Schwann cells were mixed with fetal tectal cells and co‐grafted to the midbrain of newborn host rats. Schwann cells altered the characteristic pattern of host retinal growth into tectal grafts; in some cases axons were induced to grow away from appropriate target areas by nearby co‐grafted Schwann cells.

6. In summary, Schwann cell/polymer scaffolds may provide a useful way of promoting the regrowth of damaged axons in the CNS, however: (i) in adults, at least, their effectiveness is reduced if they are located at a distance from the cell bodies giving rise to regenerating axons; (ii) in some circumstances exposure to a peripheral glial environment may affect the capacity of regenerating axons to recognize appropriate target cells in the CNS neuropil.
EFFECTS OF SODIUM DEPLETION ON TISSUE CONCENTRATIONS OF THE NATRIURETIC HORMONE VASOACTIVE INTESTINAL PEPTIDE
Authors: Duggan K. A. , Ye V. Z. C.
Published: June 2007

1. Variations in dietary sodium intake have been shown to affect the plasma concentration, the metabolic clearance rate and secretion rate of vasoactive intestinal peptide (VIP). In this study we sought to determine the effect of sodium depletion on the concentration of VIP in plasma and in three tissues, namely heart, lung and kidney.

2. Male Sprague‐Dawley rats were placed on low or normal sodium diets and drinking water ad libitum. A third group was placed on a low salt diet and in addition were given frusemide, 1 mg/kg per day in the drinking water. After 7 days the rats were killed, a blood sample collected and tissues harvested. VIP concentrations were determined by radio‐immunoassay on unextracted plasma and in tissue after extraction.

3. There were significant differences between the three groups in the Concentration of VIP in the lung (P< 0.0005), kidney (P< 0.005) and plasma (P< 0.025) but not the heart. In the group that received frusemide and the low sodium diet, VIP in the lung was significantly lower than the low sodium (P< 0.005) and normal sodium (P< 0.0001) groups. Similar differences were noted in the kidney (frusemide vs low sodium, P< 0.001; frusemide vs normal, P< 0.01) and plasma (frusemide vs low sodium P< 0.001, frusemide vs normal P< 0.05).

4. We conclude that sodium depletion decreases the concentration of VIP in plasma and in its metabolizing tissues.
EFFECTS OF CAPTOPRIL ON [3H]‐NOREPINEPHRINE RELEASE IN RAT CENTRAL NERVOUS SYSTEM
Authors: Tsuda Kazushi , Tsuda Seiko , Nishio Ichiro , † Yoshiaki Masuyama , Goldstein Menek
Published: June 2007

1. The present study was performed to investigate the effects of captopril (an angiotensin converting enzyme inhibitor, ACE‐I) on noradrenergic transmission in the rat central nervous system.

2. Slices of rat hypothalamus and medulla oblongata were prepared and prelabelled with [3H]‐norepinephrine. Slices were continuously superfused with Krebs‐Ringer solution, and electrical stimulation (1 Hz) was performed.

3. Captopril significantly inhibited the stimulation‐evoked [3H]‐norepinephrine release from rat hypothalamic slices in a dose‐dependent manner (S2/S1 ratio: control 0.904 ± 0.025, n= 6, captopril l × 10‐5 mol/L 0.617 ± 0.043, n= 6,P<0.05, captopril 5 ×10‐5 mol/L 0.547±0.037, n= 6, P<0.05). However, the basal release of [3H]‐norepinephrine was not affected by captopril.

4. Captopril also reduced the stimulation‐evoked [3H]‐nor‐epinephrine release in the medulla oblongata (S2/S1 ratio: control 0.878 ± 0.018, n= 6, captopril 3.3 × 10‐5 mol/L 0.624 ± 0.046, n= 6, P<0.05).

5. These results show that captopril might inhibit the stimulation‐evoked norepinephrine release in rat hypothalamus and medulla oblongata. Although the precise mechanisms underlying the neurosuppressive effect of captopril are still uncertain, the finding suggests that the inhibition of noradrenergic transmission might be related to the central action of the ACE‐I.
COMPARISON OF RESPONSES TO AMINOGUANIDINE AND Nω‐NITRO‐L‐ARGININE METHYL ESTER IN THE RAT AORTA
Authors: Yen Mao‐Hsiung , Chen Shiu‐Jen , Wu Chin‐Chen
Published: June 2007

1. We have compared the effect of aminoguanidine with that of Nω‐nitro‐L‐arginine methyl ester on isolated thoracic aortic rings obtained either from endotoxin (lipopolysaccharide, 10 mg/kg, i.v. for 3 h) or vehicle (saline) treated rats.

2. Administration of endotoxin for 3h resulted in a hypo tension and a significant reduction of pressor responses to nor‐epinephrine (1 μg/kg, i.v.) in the anaesthetized rat.

3. In intact rings obtained from vehicle treated rats, amino guanidine (0.3 and 1mmol/L) had no significant effect on acetylcholine‐induced relaxation (10‐9–10‐5mol/L), whereas Nω‐nitro‐L‐arginine methyl ester (0.3mmol/L and 1mmol/L) abolished that response, suggesting that aminoguanidine does not inhibit the activity of constitutive nitric oxide synthase.

4. Relaxation induced by L‐arginine (10‐6–10‐2mol/L) was competitively inhibited by both aminoguanidine (0.3 mmol/L) and Nω‐nitro‐L‐arginine methyl ester (0.3 mmol/L) in endo thelium‐denuded aortic rings obtained from endotoxin treated rats.

5. Three hours of endotoxaemia was associated with an impairment of contraction to norepinephrine (10‐9–10‐6 mol/L) in the endothelium‐denuded aorta ex vivo. This hyporeactivity to norepinephrine was partially restored by treatment of the vessels either with aminoguanidine (0.3 mmol/L) or with Nω‐nitro‐l‐arginine methyl ester (0.3 mmol/L) in vitro.

6. These results in isolated thoracic aortae of the rat reinforce that aminoguanidine is a selective inhibitor of the inducible nitric oxide synthase, whereas Nω‐nitro‐L‐arginine methyl ester is a non‐selective inhibitor of both the inducible and constitutive nitric oxide synthase.
FUNCTIONAL AND STRUCTURAL CHARACTERISTICS OF EXPERIMENTAL FK 506 NEPHROTOXICITY
Authors: Andoh Takeshi F. , Burdmann Emmanuel A. , Lindsley Jessie , Houghton Donald C. , Bennett William M.
Published: June 2007

1. FK 506 (Tacrolimus, Prograf®) is a novel Immunosuppressant which is effective in solid organ transplantation and autoimmune diseases. The lack of a suitable animal model has hindered the study of the nephrotoxicity of the drug which has emerged as a common adverse effect in clinical trials. We report both acute and chronic nephrotoxicity with tacrolimus (FK) in which renal structure and function are worsened by sodium depletion.

2. Pair fed male Sprague‐Dawley rats were given FK (3 or 6 mg/kg, p.o.) or vehicle for 7, 21 and 42 days on low salt or normal diet. The FK whole blood trough levels achieved (3–10ng/mL) were similar to those observed in FK treated transplant patients.

3. In salt depleted animals treated for 7 days, FK (6 mg/kg) decreased renal blood flow and glomerular filtration rate (1.8 ± 0.1 and 0.2 ± 0.1 mL/min per 100g vs 2.9 ± 0.2 and 1.1 ± 0.1 mL/min per 100 g in the vehicle group, P<0.01).

4. After 21 days of treatment of FK on low salt diet but not normal salt, FK induced focal collapse and vacuolization in proximal tubules and discrete or confluent zones of tubulointerstitial oedema and mononuclear cell infiltration.

5. After 42 days in salt depleted rats, there was significant tubulointerstitial scarring that was associated with an increased plasma renin activity (PRA) (64 ± 10 vs 30 ± 4 ng AI/mL per h in the vehicle group, P< 0.05). Animals given normal salt diets did not develop significant histological lesions even up to 42 days.

6. Sodium depletion is critical for the development of FK induced progressive striped tubulointerstitial fibrosis associated with an increase in PRA. These data suggest a role for the renin‐angiotensin system in the pathogenesis of functional and structural changes of chronic FK nephrotoxicity.
OPIOID MECHANISMS CONTROLLING RENAL FUNCTION
Authors: Kapusta Daniel R.
Published: June 2007

1. Over the past 50 years considerable evidence has been reported suggesting that endogenous opioids participate in the control of renal function.

2. Exogenous administration of opioids produces profound changes in the renal excretion of water and sodium.

3. Opioids produce changes in urine output and urine sodium excretion by multiple integrated neural and hormonal mechanisms within the periphery, central nervous system and kidneys.

4. Although opioid antagonist administration does not consistently reveal an action of endogenous opioid systems on renal function, this may result from the quiescent nature of the endogenous opioid system under basal conditions.

5. Manipulations that activate endogenous opioid systems have begun to reveal important, previously unrecognized mechanisms that control kidney function and can enhance renal tubular sodium reabsorption in normal and potentially pathological states.
ANGIOTENSIN CONVERTING ENZYME (ACE) INHIBITORS AND KININ METABOLISM: EVIDENCE THAT ACE INHIBITORS MAY INHIBIT A KININASE OTHER THAN ACE
Authors: Campbell Duncan J.
Published: June 2007

1. Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II, and also metabolizes bradykinin‐(1–9) to bradykinin‐(1–7) and bradykinin‐(1–7) to bradykinin‐(1–5). Increases in endogenous kinin levels may contribute to the therapeutic effects of ACE inhibitors.

2. ACE inhibitors increase vascular levels of both bradykinin‐(1–9) and its ACE cleavage product bradykinin‐(1–7), at doses below the threshold for ACE inhibition, leading to the proposal that ACE inhibitors may also inhibit a non‐ACE kininase which cleaves both kinin peptides; this non‐ACE kininase may be the major pathway of kinin metabolism in the vasculature and some other tissues.

3. In support of this proposal, ACE inhibitors potentiate bradykinin‐(1–9) effects at doses which have little or no effect on ACE activity, as indicated by angiotensin I conversion to angiotensin II. ACE inhibitors also potentiate the actions of ACE‐resistant kinin analogues, which may be susceptible to metabolism by a non‐ACE kininase.

4. Identification and characterization of the putative non‐ACE kininase which is inhibited by ACE inhibitors may reveal novel approaches to the tissue‐specific modulation of kinin levels.
LONG‐TERM OUABAIN ADMINISTRATION DOES NOT ALTER BLOOD PRESSURE IN CONSCIOUS SPRAGUE‐DAWLEY RATS
Authors: Li Ming , Martin Allison , Wen Cheng , Turner Steven W. , Lewis Lynley K. , Whitworth Judith A.
Published: June 2007

1. We tested the ability of ouabain to cause chronic hyper tension by continuously infusing ouabain for 28 days (mini‐osmotic pump implantation; i.p.). The blood pressure and metabolic effects of sham (150 mmol/L NaCI; n= 12) or ouabain infusion (10 μg/kg per day; n= 14; 100 μg/kg per day; n = 14) were examined in conscious Sprague‐Dawley rats.

2. Plasma ouabain concentrations measured after 28 days of ouabain infusion were as follows: sham, not detectable (n= 11); ouabain 10 μg/kg per day, 0.60 ± 0.07 nmol/L (n= 14); and ouabain 100 μg/kg per day, 7.17 ± 0.57 nmol/L (n= 14; P < 0.001).

3. Sham or ouabain infusion did not alter food intake, bodyweight, water intake or urine output in conscious rats.

4. Blood pressure was not altered by sham treatment. Ouabain at 10 μg/kg per day or 100 μg/kg per day did not produce consistent rises in blood pressure. Ouabain at 10 μg/kg per day increased blood pressure on treatment day 12 only (+ 6mmHg; P < 0.05), while at 100μg/kg per day blood pres sure increased on treatment days 16 (+ 9 mmHg; P < 0.05) and day 18 (+ 8mmHg; P < 0.05) only. There was no significant difference in blood pressure between sham and ouabain groups.

5. Renal blood flow was decreased in rats infused with ouabain at 10 μg/kg per day (2.0 ± 0.3 mL/min per 100 g body‐weight; n= 5; P < 0.01) and 100 μg/kg per day (2.2 ± 0.4 mL/ min per 100 g bodyweight; n= 7; P < 0.05) compared with sham treatment (3.5 ± 0.2 mL/min per 100 g bodyweight; n= 6). Renal vascular resistance was increased in rats treated with ouabain at 10 μg/kg per day (65.5 ± 12.6 mmHg/mL per min per 100 g bodyweight; n= 5; P < 0.01) and 100 μg/kg per day (66.0 ± 15.6 mmHg/mL per min per 100 g bodyweight; n= 7; P < 0.05) compared with sham treatment (32.6 ± 2.5 mmHg/mL per min per 100 g bodyweight; n= 6).

6. High plasma concentrations of ouabain do not cause consistent increases in blood pressure in conscious Sprague‐Dawley rats.
TRANSCRIPTIONAL CONTROL AND THE REGULATION OF ENDOCRINE GENES
Authors: Zajac J. D. , Chilco P. J.
Published: June 2007

1. Endocrine genes are regulated at a number of levels during their expression. Regulation can occur during transcription, mRNA splicing, mRNA degradation, translation, or post‐translational processing of protein precursors.

2. Transcription is controlled by an increasingly well studied and enlarging family of transcription factors that bind to basal control DNA sequences (promoters) and transcriptional activator sequences (enhancers).

3. Steroid receptors act as transcription factors, as do the proteins involved in the gene regulation by cyclic AMP. Parathyroid hormone related protein is typical of many endocrine genes in that it is regulated by multiple agonists including glucocorticoids and hormones activating the cyclic AMP cascade.
MICROCOMPUTER STATISTICS PACKAGES FOR BIOMEDICAL SCIENTISTS
Authors: Ludbrook John
Published: June 2007

1. There are hundreds of commercially available microcomputer statistics packages, ranging from the very cheap and elementary to the very expensive and complex, and from the very general to the very specialized. This review covers only those that appear to be popular with biomedical investigators who deal with fairly small sets of data but may wish to use relatively complex analytical techniques.

2. It is highly desirable, if not essential, that biomedical investigators who use microcomputer statistics packages have access to a spreadsheet program. These provide sample statistics and simple statistical analyses but, more importantly, they are often the best way of entering data into the files of the statistics packages proper.

3. A vital component of any statistics package is its manual. This should be easy to follow, but at the same time it must provide full documentation of, and references to, precisely how the various statistical tests are performed.

4. Some packages are elementary and offer only a narrow range of test procedures (mini‐packages). Some are designed to be used as statistical libraries and programming tools for professional statisticians. Between these extremes are the general purpose packages (mid‐range, maxi‐ and supermaxi packages) that constitute the main body of this review.

5. All the packages reviewed have some shortcomings or flaws. It is argued that the ideal package for biomedical investigators should have the following features: (i) it should provide a wide range of test procedures for analysing continuous, rank‐ordered, and categorical data; (ii) the way in which these tests are carried out should be clearly stated in the manual; and (iii) lastly, although not unimportantly, the package should be easy to use.

6. It is recommended that biomedical investigators purchase a package that provides many more statistical routines than they use in their everyday practice. Provided the manual is a good one and the package itself has no serious flaws, this is an excellent stimulus to continuing education in statistical techniques.
NAFAMOSTAT ENHANCES IBMX AND SECRETIN‐STIMULATED WATER AND BICARBONATE SECRETION IN THE ISOLATED, BLOOD‐PERFUSED DOG PANCREAS
Authors: Horiuchi A. , Iwatsuki K. , Chiba S.
Published: June 2007

1. The effect of nafamostat mesilate, a synthetic protease inhibitor, on pancreatic exocrine secretion was investigated in isolated, blood‐perfused dog pancreas.

2. Intra‐arterial injections of nafamostat (2–10 gmol) dosedependently enhanced water and bicarbonate secretion stimulated by 3‐isobutyl‐1‐methylxanthine (IBMX) or secretin, although nafamostat alone did not affect the basal secretion.

3. In the nafamostat‐enhanced pancreatic juice, bicarbonate concentrations were increased dose‐dependently as compared with the control, while protein concentrations were not significantly changed.

4. These results indicate that nafamostat enhances IBMX and secretin‐stimulated water and bicarbonate secretion, which may be mediated through CAMP activation.
EFFECT OF HAEMORRHAGE ON THE POWER OF LOW FREQUENCY BLOOD PRESSURE FLUCTUATIONS IN YOUNG SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Eliash S. , Oz O. , Akselrod S. , Cohen S.
Published: June 2007

1. Before the onset of hypertension low frequency (0.04– 0.1 Hz) MAP fluctuations are reduced in SHR when compared to WKY. We studied the effect of haemorrhage under α1 blockade or angiotensin converting enzyme inhibition (CEI) on the power spectra (PS) of each strain.

2. MAP was recorded from the caudal artery in conscious, 1 month old SHR and WKY. Three groups of rats were studied. Group 1, acute 2 mL haemorrhage; groups 2 and 3, injection of prazosin (0.25–2.5 mg/kg) or captopril (O.5–4 mg/kg), followed by haemorrhage, as in group 1. The PS was divided into 3 frequency bands, 0.004–0.04,0.04–0.07 and 0.07–0.1 Hz.

3. In SHR, although the baseline MAP levels were similar to those of WKY, the PS was significantly damped in each of the 3 frequency bands.

4. Haemorrhage induced a similar MAP fall in both strains accompanied by an increase in the slow MAP fluctuations. However, in SHR the PS response was significantly greater than in WKY. The biggest response was in the slowest (0.004–0.04 Hz) frequency band, 8.7 ± 1.7 vs 1.5 ± 0.4 times baseline levels, respectively.

5. The difference between the two strains in the PS response to haemorrhage was eliminated by α1 blockade. The exaggerated response observed in haemorrhaged, unblocked SHR was reduced in the 3 frequency bands.

6. Captopril reduced the PS response to haemorrhage in SHR to the level observed in WKY in all 3 frequency bands.

7. The enhanced amplification of the MAP fluctuations in haemorrhaged SHR may indicate that SHR requires greater recruitment of control mechanisms than WKY to maintain MAP at a similar level to WKY.
DEVELOPMENT OF POLYURIA IN TSUKUBA HYPERTENSIVE MICE CARRYING HUMAN RENIN AND ANGIOTENSINOGEN GENES
Authors: Uehara Sayuri , Mino Nobuyuki , Tsuchida Minoru , Nishikibe Masaru , Fukamizu Akiyoshi , Murakami Kazuo , Ikemoto Fumihiko
Published: June 2007

1. Tsukuba hypertensive mice (THM) carry both human renin and angiotensinogen genes, and develop hypertension. The animal has high levels of renin activity and angiotensin II concentration in the plasma.

2. Urinary excretion in THM was greater than in the control animal, non‐transgenic C57/BL/6j. THM showed a greater amount of daily water intake. The osmolality of 24 h urine was lower than that of the control animal.

3. When water was deprived for 12h and then loaded with 0.25mL/10g bodyweight, the osmolality of urine at the first 0–3 h period was the same in THM and control, but significantly lower in THM at the following 3–6 h period, indicating that the urine concentrating activity is insufficient in THM compared with the control animal.

4. Urinary excretion of vasopressin was significantly higher in THM. Plasma aldosterone concentration and urinary excretion of aldosterone were also higher in THM. Plasma potassium level was significantly low.

5. The mechanism underlying the pathophysiology of polyuria is not totally explained; however, hypokalaemia, which was probably the result of hyperaldosteronism, may be at least partially involved, since hypokalaemia is considered to be a factor hampering the action of vasopressin for concentration of urine at the site of the collecting duct of the kidney.
ROLE OF NITRIC OXIDE IN IMPAIRED CORONARY CIRCULATION AND IMPROVEMENT BY ANGIOTENSIN II RECEPTOR ANTAGONIST IN SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Fujita Hiroshi , Takeda Kazuo , Nakamura Kame , Uchida Atsushi , Takenaka Ken , Itoh Hiroshi , Nakata Tetsuo , Sasaki Susumu , Nakagawa Masao
Published: June 2007

1. To determine whether coronary flow regulation by nitric oxide (NO) is impaired in the hypertensive heart (HTH), coronary perfusion was measured in isolated rat hearts using NO synthesis inhibitor L‐NG‐monomethyl arginine (L‐NMMA) in Wistar‐Kyoto (WKY) rat and spontaneously hypertensive rat (SHR) with and without chronic Nω‐nitro‐L‐arginine‐methylester (L‐NAME) treatment. Moreover, the effect of angiotensin 11 receptor antagonist (AT1 receptor antagonist) (TCV‐116) on the impaired coronary circulation in HTH was examined.

2. Coronary flow (CF) was decreased in HTH accompanied with cardiac hypertrophy. The decreased response of CF to L‐NMMA infusion was diminished in HTH. It is suggested that NO production was reduced in coronary vasculature in HTH.

3. In chronic L‐NAME treated SHR, blood pressure and cardiac hypertrophy were accelerated. Although coronary flow resistance (CFR) was increased, the increased response of CFR to L‐NMMA infusion was not altered.

4. The AT1 antagonist improved total minimal coronary flow resistance (MCFR) restoring CFR response in SHR, although it did not recover CFR response in chronic L‐NAME treated SHR.

5. Taken together the findings suggest that NO production was exhausted in the coronary artery even in the developing stage of hypertension and this exhaustion could contribute to the impairment of coronary circulation of HTH.
A ROLE OF LYSINE‐43 IN THE INACTIVATION OF RAT PRORENIN
Authors: Suzuki Fumiaki , Tosaki Ikuko , Shiratori Yasuhiko , Nagai Miyuki , Murakami Kazuo , Nakamura Yukio
Published: June 2007

1. Lysine‐43 (Lys43) in the prosegment region was located within 3 × 10−1 of catalytic sites, Asp81 and Asp266, in a stereo structure model of rat prorenin.

2. A mutant prorenin, Lys43Leu, was produced to elucidate a role of Lys43 in the inactivation of prorenin. Lys43Leu as well as the wild type were inactive at a neutral pH, and activated at an acidic pH. Its acid‐activation speed was three times higher than that of the wild type. The mutant prorenin was more labile than the wild type at 55°C and a neutral pH.

3. These results indicate that Lys43 forms ionic bonds with Asp81 and Asp266 to inactivate and stabilize prorenin.
HAEMODYNAMIC EFFECTS OF NO‐SYNTHASE INHIBITORS, NG‐MONOMETHYL‐L‐ARGININE, NG‐NITRO‐L‐ARGININE AND NG‐NITRO‐L‐ARGININE METHYL ESTER, AND NO‐DONOR, GLYCERYL TRINITRATE, IN CONSCIOUS SHRSP AND WKY
Authors: Higashino H. , Simeonova K. , Lambev I. , Suzuki A.
Published: June 2007

1. The experiments were carried out by an ordinary and a microsphere method in order to clarify the effects of three nitric oxide‐synthase inhibitors and ‐donor on the circulating system between SHRSP and WKY.

2. Intravenous administration of each compound possessing the nitric acid‐synthase inhibiting action markedly elevated the systolic blood pressure both in SHRSP and WKY, but more prominently in the former.

3. The hypotensive and tachycardic responses to glyceryl trinitrate were more enhanced after treatment with NO‐nitro‐L‐arginine and NG‐nitro‐L‐arginine methyl ester but not with NG‐monomethyl‐L‐arginine compared with the non‐treated one.

4. All peripheral organs except the brain decreased their regional blood flow after administration of NG‐nitro‐L‐arginine, indicating a crucial involvement of nitric oxide in the peripheral circulation.

5. It was suggested that the nitric oxide system worked more sensitively and actively in SHRSP than in WKY in order to maintain the peripheral blood flow and systemic blood pressure.
VASCULAR ENDOTHELIAL GROWTH FACTOR: TISSUE DISTRIBUTION AND SIZE OF MULTIPLE mRNA SPLICE FORMS IN SHR AND WKY
Authors: Lan L. , Wilks A. , Morgan T. O. , Di Nicolantonio R.
Published: June 2007

1. We have determined the optimal polymerase chain reaction (PCR) conditions for the amplification and detection of mRNA for a new vascular growth factor—vascular endothelial growth factor (VEGF)–‐and determined its size and tissue distribution in genetically normotensive and hypertensive rats.

2. Multiple VEGF mRNA subtypes were obtained which were 625, 520 and 480 base pairs in length.

3. All three species of VEGF mRNA were found in heart, kidney, aorta, adrenal and brainstem and the size and tissue distribution of VEGF mRNA subtypes were not different between spontaneously hypertensive rats (SHR) of the Okamoto strain and normotensive Wistar‐Kyoto (WKY) controls.

4. Thus multiple forms of VEGF mRNA can be readily detected by PCR in a variety of tissues. While these preliminary results suggest no difference in size and tissue distribution between SHR and WKY, sequencing and quantitative studies will be required to confirm this.