bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of [K+]O on Regional Differences in Electrical Characteristics of Ventricular Myocytes in Guinea‐Pig
Authors: Wan Xiaoping , Bryant Simon M. , Hart George
Published: May 2004

Altering [K+]o might have different effects on action potential duration (APD) in myocytes from different regions. Therefore, the effects of [K+]o on regional differences in action potential characteristics were investigated in sub‐endocardial, mid‐myocardial and sub‐epicardial myocytes isolated from the base of guinea‐pig left ventricular free wall using three different [K+]o (2.7, 5.4 and 8.1 mM KCl). Action potentials were recorded using the switch‐clamp technique at 0.5 Hz. Increasing [K+]o from 2.7 to 8.1 mM shortened the action potential duration to 90% repolarization (APD90; mean APD90 values in sub‐endocardial, mid‐myocardial and sub‐epicardial myocytes were, respectively, 295 +‐ 9, 286 +‐ 9 and 266 +‐ 8 ms in 2.7 mM [K+]o, 270 +‐ 7, 255 +‐ 7 and 215 +‐ 7 ms in 5.4 mM [K+]o, 234 +‐ 7, 212 +‐ 10 and 155 +‐ 8 ms in 8.1 mM [K+]o), depolarized the resting potential, and reduced the amplitude of the action potential. The effect of increasing [K+]o on action potential characteristics was more pronounced in sub‐epicardial myocytes than in sub‐endocardial and mid‐myocardial myocytes. The regional differences in APD90 in 5.4 mM [K+]o were increased in 8.1 mM [K+]o and abolished in 2.7 mM [K+]o. In conclusion, changing [K+]o produces more pronounced effects on action potentials in sub‐epicardial myocytes than in sub‐endocardial myocytes, modifying the normal heterogeneity of action potentials. The differences in the response of sub‐epicardium and sub‐endocardium to [K+]o may contribute to the flattening or inversion of the T wave commonly seen in patients presenting with hypokalaemia and the upright and tall T waves observed in electrocardiograms recorded during hyperkalaemia, although the underlying ionic currents remain to be determined.
Development of an Improved Technique for the Perfusion of the Isolated Caudal Lobe of Sheep Liver
Authors: Ali A. M. , Rossouw H. C. , Silove M. , Van Der Walt J. G.
Published: May 2004

The study was designed to develop an improved technique for perfusing the isolated caudal lobe of sheep liver. Twenty caudal lobes were perfused for 3‐4 h, in a non‐recirculating mode, with Krebs‐Henseleit bicarbonate buffer. The perfusion system was designed to give a constant flow. The hepatic viability and functional normality of the perfused lobe were assessed by measuring the perfusion flow rate, pH, K+ efflux, O2 uptake, substrate uptake, gluconeogenesis from propionate and amino acids, and ureagenesis from ammonia and amino acids. Liver tissue was sampled for histological examination, as well as for the determination of liver glycogen and wet: dry weight ratio. The perfusion flow rate and pH were both stable throughout the perfusion. The potassium concentration in the effluent perfusate did not increase during the perfusion, suggesting that there was no loss of viability or hypoxia. The perfused lobe extracted more than 50% of the O2 supply. The rate of oxygen consumption was comparable to the rate reported in vivo. The initial glycogen content was reduced by about 40% after 4 h perfusion. The wet: dry weight ratio was 3.6, consistent with the absence of tissue oedema. Urea production was stimulated when NH4Cl (0.3 mM) was added to the medium but there was no significant increase in urea release when alanine (0.15 mM), glutamine (0.2 mM) or lysine (0.2 mM) was added. Urea production, however, increased by about 171% when a physiological mixture of amino acids was added. Propionate (0.5 mM), alanine and glutamine stimulated glucose production but not lysine or the complete amino acid mixture. Glutamine release was lower than that reported in the rat liver. Changing the direction of flow also revealed an apparent difference between livers from sheep and rats in their metabolism of ammonia. The improved technique offers a simple practical and inexpensive approach to many problems in ruminant physiology and nutritional biochemistry.
Ageing Modulates some Aspects of the Non‐Specific Immune Response of Murine Macrophages and Lymphocytes
Authors: Ortega E. , Garcia J. J. , De la Fuente M.
Published: May 2004

The deterioration of the immune system with ageing, which leads to an increased morbidity and mortality from infections, appears to be related to decreases in specific lymphocyte functions. However, the alteration of non‐specific immunity is a more controversial subject. Our purpose was to investigate the age‐related changes of different functions of the non‐specific immune response in peritoneal macrophages (adherence to tissues, mobility directed to a chemical gradient from an infectious focus or chemotaxis, phagocytosis of foreign agents and destruction of these agents by superoxide anion production) and in lymphocytes (adherence and chemotaxis) from peritoneum, axillary lymph nodes, spleen and thymus. We used young (12 weeks), adult (22 weeks), mature (48 weeks) and old (72 weeks) female BALB/c mice. The adherence capacity of macrophages and lymphocytes was greater in adult and old mice than in young animals. The chemotaxis of macrophages showed higher values in cells from young mice than in those from adult mice, increasing again in macrophages from mature and old animals. A similar behaviour was shown by phagocytosis, which reached its highest values in old animals. Anion superoxide production increased with age and again the highest values were obtained in the oldest mice. Conversely, chemotaxis of lymphocytes was higher in the adult and mature animals than in the young and old animals. We conclude that, although there is a decrease in lymphocyte chemotaxis in old animals, the non‐specific immune response of macrophages instead of decreasing, may increase in aged mice with respect to the values seen in adult mice.
The Preoptic Area in the Hypothalamus is the Source of the Additional Respiratory Drive at Raised Body Temperature in Anaesthetised Rats
Authors: Boden A. G. , Harris M. C. , Parkes M. J.
Published: May 2004

In mammals that use the ventilatory system as the principal means of increasing heat loss, raising body temperature causes the adoption of a specialised breathing pattern known as panting and this is mediated by the thermoregulatory system in the preoptic area of the hypothalamus. In these species an additional respiratory drive is also present at raised body temperature, since breathing can reappear at low Pa,CO2 levels, when stimulation of chemoreceptors is minimal. It is not known whether the preoptic area is also the source of this additional drive. Rats do not pant but do possess this additional respiratory drive at raised body temperatures. We have therefore tested whether the preoptic area of the hypothalamus is the source of this additional respiratory drive in rats. Urethane anaesthesia and hyperoxia were used in eleven rats to minimise behavioural and chemical drives to breathe. The presence of the additional respiratory drive was indicated if rhythmic diaphragmatic EMG activity reappeared during hypocapnia (a mean Pa,CO2 level of 21 ± 2 mmHg, n = 11), induced by mechanical ventilation. The additional respiratory drive was absent at normal body temperature (37°C). When the temperature of the whole body was raised using an external source of radiant heat, the additional respiratory drive appeared at 40.6 ± 0.5°C (n = 3). In two further rats this drive was induced at normal body temperature by localised warming in the preoptic area of the intact hypothalamus. The additional respiratory drive appeared at similar temperatures to those in control rats in three rats following isolation of the hypothalamus from more rostral areas of the brain. In contrast, the additional respiratory drive failed to appear at these temperatures in three rats after isolating the hypothalamus from the caudal brainstem, by sectioning pathways medial to the medial forebrain bundle. Since the preoptic area is known to contain thermoreceptors and to receive afferents from peripheral thermoreceptors, the results show that this area is also the source of the additional respiratory drive at raised body temperature in anaesthetised rats.
Humoral Pathway for Local Transfer of the Priming Pheromone Androstenol from the Nasal Cavity to the Brain and Hypophysis in Anaesthetized Gilts
Authors: Stefanczyk‐Krzymowska S. , Krzymowski T. , Grzegorzewski W. , Wasowska B. , Skipor J.
Published: May 2004

It is generally accepted that pheromones act by stimulating of the dendritic receptors of the olfactory neurones massed in the olfactory epithelium. This study was designed to ascertain whether it is possible for the boar pheromone androstenol (5alpha‐androst‐16‐en‐3‐ol) to be transported from the nasal cavity of anaesthetized gilts to the brain and hypophysis via local transfer from the blood in the perihypophyseal vascular complex. The experiment was performed on days 18‐21 of the porcine oestrous cycle (crossbred gilts, n = 6). Tritiated androstenol (3H‐A; total amount 108 d.p.m. (758 ng)) was applied for 1 min onto the respiratory part of the nasal mucosa, 4‐6 cm from the opening of the nares. Arterial blood samples from the aorta and from the carotid rete were collected every 2 min during the 60 min period following administration of the steroid. Total radioactive venous effluent from the head was removed and an adequate volume of homologous blood was transfused into the heart through the carotid external vein. At the end of the experiment gilts were killed and tissue samples of the hypophysis and some brain structures were collected to measure radioactivity. In addition, corresponding control tissues were collected from three untreated gilts and from three heads of gilts 60 min after 3H‐A was applied post mortem into the nasal cavity. The concentration of 3H‐A was significantly higher (P < 0.0001) in the arterial blood of the carotid rete than that of aorta. The mean rate of 3H‐A counter current transfer from venous to arterial blood in the perihypophyseal vascular complex, expressed as the ratio of the 3H‐A concentration in arterial blood of the carotid rete to the 3H‐A concentration in blood sampled simultaneously from the aorta, was 1.96 ± 0.1. The concentration of 3H‐A in plasma from the venous effluent from the head ranged from 1.3 to 1.8 pg ml‐1. During the 60 min period of the experiment, 0.68% of the total applied dose of 3H‐A was resorbed from the nasal cavity into the venous blood. Moreover, we found that 3H‐A was present in the olfactory bulb (P < 0.01), amygdala, septum, hypothalamus, adenohypophysis, neurohypophysis (P > 0.05) and perihypophyseal vascular complex (P < 0.01). These results demonstrate that, in anaesthetized gilts, the boar pheromone androstenol may be resorbed from the nasal mucosa, transferred in the perihypophyseal vascular complex into arterial blood supplying the brain and hypophysis, and then arrested in the hypophysis and certain brain structures. We suggest that in addition to the standard neural pathway for signalling pheromones, another pathway exists whereby androstenol, as a priming pheromone, may be resorbed from the nasal cavity into the bloodstream and then pass locally from the perihypophyseal vascular complex into the arterial blood supplying the brain and hypophysis, thus avoiding the first passage metabolism in the liver.
Angiotensin‐Converting Enzyme Genotype Affects the Response of Human Skeletal Muscle to Functional Overload
Authors: Folland Jonathan , Leach Ben , Little Tom , Hawker Kate , Myerson Saul , Montgomery Hugh , Jones David
Published: May 2004

The response to strength training varies widely between individuals and is considerably influenced by genetic variables, which until now, have remained unidentified. The deletion (D), rather than the insertion (I), variant of the human angiotensin‐converting enzyme (ACE) genotype is an important factor in the hypertrophic response of cardiac muscle to exercise and could also be involved in skeletal muscle hypertrophy – an important factor in the response to functional overload. Subjects were 33 healthy male volunteers with no experience of strength training. We examined the effect of ACE genotype upon changes in strength of quadriceps muscles in response to 9 weeks of specific strength training (isometric or dynamic). There was a significant interaction between ACE genotype and isometric training with greater strength gains shown by subjects with the D allele (mean ± S.E.M.: II, 9.0 ± 1.7%; ID, 17.6 ± 2.2%; DD, 14.9 ± 1.3%, ANOVA, P 0.05). A consistent genotype and training interaction (ID DD II) was observed across all of the strength measures, and both types of training. ACE genotype is the first genetic factor to be identified in the response of skeletal muscle to strength training. The association of the ACE I/D polymorphism with the responses of cardiac and skeletal muscle to functional overload indicates that they may share a common mechanism. These findings suggest a novel mechanism, involving the renin‐angiotensin system, in the response of skeletal muscle to functional overload and may have implications for the management of conditions such as muscle wasting disorders, prolonged bed rest, ageing and rehabilitation, where muscle weakness may limit function.
Variations in Regional Sweat Composition in Normal Human Males
Authors: Patterson Mark J. , Galloway Stuart D. R. , Nimmo Myra A.
Published: May 2004

This project aimed to quantify the regional distribution of sweat composition over the skin surface and to determine whether sweat constituent concentrations collected from regional sites can estimate whole‐body concentrations. Ten males cycled for 90 min in a 20°C (50% relative humidity) environment at 45% peak aerobic power. Sweat was collected from eleven skin regions and the whole body, using a wash‐down technique. Strong relationships were evident between the regional and whole‐body sweat [Na+] and [Cl‐], such that the thigh and calf exhibited greater correlation coefficients than area‐weighted means derived from four and eight skin regions. Therefore, in this particular protocol the whole‐body sweat [Na+] and [Cl‐] could be predicted from regional sweat collections. Relationships between sweat constituents were evident for sweat [Na+] and pH, and sweat [K+] and [lactate] when data were pooled between skin regions and subjects. To our knowledge this is the first investigation to report a positive relationship between sweat [K+] and [lactate]. The exact mechanism responsible for the positive relationship between sweat [K+] and [lactate] is uncertain although it is speculated to occur at the secretory coil.
Renal Haemodynamic Effects of B2 Receptor Agonist Bradykinin and B2 Receptor Antagonist HOE 140 in Conscious Lambs
Authors: Patel Avni , Smith Francine G.
Published: May 2004

The present study was designed to test the hypothesis that the high renal vascular resistance characteristic of the newborn results from age‐dependent changes in the responsiveness of the renal vasculature to kinins. Two studies were carried out in conscious, chronically instrumented lambs aged 1 and 6 weeks. Firstly, we measured the renal blood flow response to intra‐arterial injection of the B2 receptor agonist bradykinin over the range of doses 0‐800 ng kg‐1. The ED50 renal blood flow response to bradykinin was 50 ng kg‐1 in both age groups of lambs. Secondly, we measured the effects of intravenous administration of 12.5 μg kg‐1 of the specific B2 receptor antagonist HOE 140; this dose attenuated the renal blood flow response to 50 ng kg‐1 of bradykinin in both age groups. HOE 140 administration was associated with an age‐dependent increase in mean arterial pressure, with little effect on heart rate or renal vascular resistance. This study provides new information regarding the effects of kinins in modulating renal haemodynamics during postnatal maturation. We reject our hypothesis and conclude that the high renal vascular resistance of the newborn does not appear to result from age‐dependent changes in the responsiveness of the renal vasculature to endogenous kinins.
Nerve‐Evoked Secretion of Immunoglobulin a in Relation to other Proteins by Parotid Glands in Anaesthetized Rat
Authors: Proctor G. B. , Carpenter G. H. , Anderson L. C. , Garrett J. R.
Published: May 2004

Secretion of fluid and proteins by salivary cells is under the control of parasympathetic and sympathetic autonomic nerves. In a recent study we have shown that, in the rat submandibular gland, autonomic nerves can also increase the secretion of IgA, a product of plasma cells secreted into saliva as SIgA (IgA bound to Secretory Component, the cleaved poly‐immunoglobulin receptor). The present study aimed to determine if parotid secretion of SIgA is increased by autonomic nerves and to compare SIgA secretion with other parotid proteins stored and secreted by acinar and ductal cells. Assay of IgA in saliva evoked by parasympathetic nerve stimulation immediately following an extended rest period under anaesthesia indicated that it had been secreted into intraductal saliva in the absence of stimulation during the rest period. The mean rate of unstimulated IgA secretion (2.77 ± 0.28 μg min‐1 g‐1) and the 2.5‐fold increase in IgA secretion evoked by parasympathetic stimulation were similar to results found previously in the rat submandibular gland. Sympathetic nerve stimulation increased SIgA secretion 2.7‐fold, much less than in the submandibular gland. SDS‐PAGE and Western blot analysis with anti‐IgA and anti‐Secretory Component antibodies confirmed that SIgA was the predominant form of IgA in saliva. Acinar‐derived amylase and ductal‐derived tissue kallikrein were more profoundly increased by parasympathetic and particularly sympathetic stimulation than SIgA. Overall, the results of the present study indicate that SIgA forms a prominent component of unstimulated parotid salivary protein secretion and that its secretion is similarly increased by stimulation of either autonomic nerve supply. The secretion of other parotid salivary proteins that are synthesized and stored by acinar or ductal cells is upregulated to a much greater extent by parasympathetic and particularly sympathetic stimulation.
Insulin Sensitivity and Glucose Effectiveness Estimated by the Minimal Model Technique in Spontaneously Hypertensive and Normal Rats
Authors: Natalucci Silvia , Ruggeri Piero , Cogo Carla Emilia , Picchio Viviana , Burattini Roberto
Published: May 2004

This study was performed to compare glucose metabolism in anaesthetised spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) in an attempt to clarify whether this animal model of hypertension approximates the insulin‐resistant state seen in human hypertension. With this aim the minimal model of glucose kinetics was applied to glucose and insulin data derived from a 12‐sample, 120 min intravenous glucose tolerance test (IVGTT) performed in ten SHR and nine WKY rats under pentobarbital anaesthesia. This method provided two metabolic indices: the glucose effectiveness, SG, which quantifies the ability of glucose per se to enhance its rate of disappearance and to inhibit hepatic glucose production, and the insulin sensitivity, SI, which measures the ability of insulin to enhance plasma glucose disappearance and to inhibit hepatic glucose production. Systolic and diastolic arterial pressures in the SHR group were significantly higher (P < 0.0005) than in the WKY group. Mean SG and SI estimates from the SHR group (SG = 16.2 (± 2.0) × 10‐2 dl min‐1 kg‐1 and SI = 12.5 (± 1.9) × 10‐4 dl min‐1 kg‐1 (μU ml‐1)‐1) were not significantly different (P > 0.05) from mean estimates that characterised the WKY group (SG = 13.1 (± 1.5) × 10‐2 dl min‐1 kg‐1 and SI = 15.8 (± 4.3) × 10‐4 dl min‐1 kg‐1 (μU ml‐1)‐1). This result is in contrast with reported findings from humans in which insulin sensitivity is significantly reduced in the presence of hypertension.
Differential Effect of Frusemide on Renal Medullary and Cortical Blood Flow in the Anaesthetised Rat
Authors: Dobrowolski Leszek , Badzynska Bozena , Sadowski Janusz
Published: May 2004

In addition to its known effect on renal tubular transport, frusemide (furosemide) has been shown to affect renal circulation. This study in the anaesthetised rat examined the influence of frusemide (bolus 0.25 or 0.5 mg kg‐1 I.V., then infusion delivering the same dose over 1 h) on renal cortical and medullary circulation measured as laser‐Doppler blood (cell) flux. The responses were compared with simultaneously measured changes in renal excretion and in the tissue admittance, an index of medullary ionic hypertonicity of the interstitium. Renal vascular responses to frusemide were significant but not dose dependent. During low‐dose frusemide infusion cortical flux decreased 11.5 ± 0.9% and medullary flux decreased 32.3 ± 3.5% (difference significant at P < 0.001). During high‐dose infusion the decreases were by 13.5 ± 1.4 and 29.3 ± 3.8%, respectively (difference significant at P < 0.001). Sodium excretion increased 15‐fold (by 3.7 ± 0.4 μmol min‐1) and 30‐fold (by 5.9 ± 1.1 μmol min‐1) during low‐ and high‐rate infusion of frusemide, respectively. By contrast, medullary tissue admittance decreased similarly with the two doses: maximally by 13.4 ± 1.4 and 10.9 ± 0.9%, respectively. The observations that an exaggerated post‐frusemide decrease in blood flow within the medulla coincided with decreasing tissue admittance in this zone and that neither medullary blood flow nor admittance changes were related to the dose suggest a causal relationship between interstitial ionic hypertonicity and vascular resistance. We propose that the post‐frusemide decrease in medullary tissue NaCl depressed medullary circulation by inhibiting local generation of vasodilator prostaglandins.
Modelling the Influence of Fat‐Free Mass and Physical Activity on the Decline in Maximal Oxygen Uptake with Age in Older Humans
Authors: Amara Catherine E. , Koval John J. , Johnson Patrick J. , Paterson Donald H. , Winter Edward M. , Cunningham David A.
Published: May 2004

The purpose of this study was to use an allometric model (maximal oxygen uptake (V̇O2,max) = FFMb1 × PAb2 × exp(b0 + b3 age + b4 sex) ×ε) to determine the influence of fat‐free mass (FFM), physical activity (PA), sex and age on V̇O2,max in older men (n = 152) and women (n = 146) aged 55‐86 years. V̇O2,max was measured during a fatigue‐limited treadmill test, FFM was determined from skinfold thickness and physical activity by the Minnesota Leisure Time Physical Activity questionnaire. The model was linearised by taking the natural logarithm of V̇O2,max, FFM and physical activity. Variables were selected using multiple linear regression (P < 0.05). The sex variable was not significant (P = 0.062). The model explained 72.1% of the variance in V̇O2,max. Significant individual coefficients were incorporated into the model yielding the following expression: V̇O2,max= FFM0.971 × PA0.026 × exp(‐2.48 – 0.015age). Therefore, FFM and physical activity were significant factors contributing to the changes in V̇O2,max with age. In addition, controlling for FFM and physical activity abolished sex differences in V̇O2,max. The rate of decline in V̇O2,max (after accounting for FFM and physical activity) with age, was approximately 15% per decade.
Equine Uteroplacental Metabolism at Mid‐ and Late Gestation
Authors: Fowden Abigail L. , Forhead Alison J. , White Kate L. , Taylor Polly M.
Published: May 2004

Uptakes of oxygen, glucose and lactate by the gravid uterus, fetus and uteroplacental tissues were measured in chronically catheterized pregnant ponies and their fetuses at mid‐ and late gestation (term 335 days). Rates of O2 uptake by the gravid uterus, fetus and uteroplacental tissues were significant at both gestational ages and were 2‐ to 3‐fold higher in late gestation than the mid‐gestation values of 3338 ± 794, 1352 ± 258 and 2035 ± 602 μmol min‐1, respectively (n = 4). Similarly, there were significant uptakes of glucose by the gravid uterus, fetus and uteroplacental tissues at both mid‐ and late gestation. However, unlike O2 uptake, glucose uptake by the uterus and uteroplacental tissues did not increase between mid‐ and late gestation. No significant uptakes or outputs of lactate were observed by the uterus or uteroplacental tissues at either gestational age, although there was a significant umbilical uptake of lactate in late but not mid‐gestation. There was no change in the distribution of uterine O2 uptake between the fetus and uteroplacental tissues with increasing gestational age. The uteroplacental tissues accounted for about 50% of the uterine O2 uptake at both gestational ages. In contrast, the proportion of the uterine glucose uptake used by the uteroplacental tissues decreased from 73.2 ± 2.1% (n = 5) at mid‐gestation to 61.1 ± 1.9% (n = 4, P < 0.02) in late gestation. The gestational changes in uteroplacental carbohydrate metabolism in the mare differ from those seen in the ewe and may have important consequences for the duration and outcome of pregnancy in the mare.
No Protection of the Porcine Kidney by Ischaemic Preconditioning
Authors: Behrends Matthias , Walz Martin K. , Kribben Andreas , Neumann Till , Helmchen Udo , Philipp Thomas , Schulz Rainer , Heusch Gerd
Published: May 2004

One or more episodes of sublethal ischaemia and reperfusion delay infarct development during subsequent, sustained ischaemia in the heart and skeletal muscle. The present study tested whether or not such ischaemic preconditioning (IP) also protects the kidney. Enflurane‐anaesthetized pigs underwent 60 min of right renal vessel occlusion (RVO), followed by 8 h of reperfusion without (placebo group, n = 8) or with three preceding cycles of 10 min RVO and 10 min reperfusion (IP group, n = 8). After 8 h of reperfusion, kidneys were oliguric in both groups (placebo group: 23 ± 21 ml h‐1, IP group: 24 ± 27 ml h‐1). A transient polyuric phase occurred in the IP group at 2 h reperfusion. The reperfused kidneys did not excrete inulin, creatinine or urea in both groups, although renal blood flow during reperfusion was similar to baseline. Morphological damage ranged in both groups from single cell necrosis to disseminated patchy necrosis; the number of pyknotic cells tended to be higher in the IP group than in the placebo group (27.0 ± 7.1 vs. 15.6 ± 5.6%, n.s.). In anaesthetized pigs, IP did not therefore attenuate renal dysfunction and morphological damage resulting from 60 min of renal normothermic ischaemia followed by 8 h of reperfusion.
Regional Distribution of Potassium Currents in the Rabbit Pulmonary Arterial Circulation
Authors: McCulloch K. M. , Kempsill F. E. J. , Buchanan K. J. , Gurney A. M.
Published: May 2004

The response of pulmonary arteries to hypoxia varies as a function of vessel diameter. Small intrapulmonary resistance arteries are thought to be the main site of hypoxic pulmonary vasoconstriction (HPV), with hypoxia causing minimal contraction or even dilatation in large, conduit vessels. This has been proposed to reflect a differential distribution of morphologically and electrophysiologically distinct pulmonary artery smooth muscle (PASM) cells. We investigated longitudinal heterogeneity in smooth muscle cells isolated from five regions of the rabbit pulmonary vasculature and could find no evidence of morphological heterogeneity at the level of the light microscope. PASM cells from main (8 mm outer diameter) and branch (5 mm) arteries and large (400 m) intrapulmonary arteries (IPA) were similar in shape and size, as indicated by cell capacitance (25 pF). PASM cells from medium (200‐400 m) and small (200 m) IPA were significantly smaller (15 pF), but had the same classical spindle shape. Cells from all five regions also had similar resting membrane potentials and displayed voltage‐activated K+ currents of similar amplitude when recorded in standard physiological solution. Longitudinal heterogeneity in K+ current became apparent when tetraethylammonium ions (TEA; 10 mM) and glibenclamide (10 M) were added. The remaining delayed rectifier current (IK(V)) doubled in amplitude upon moving down the pulmonary arterial tree from the main artery (9 pA pF‐1 at 40 mV) to the large IPA (17 pA pF‐1), but remained constant throughout the intrapulmonary vasculature. The O2‐sensitive, non‐inactivating K+ current (IK(N)) showed a similar trend, but was significantly reduced in the smallest IPA, where its amplitude was comparable with the main artery. Thus the IK(N)/IK(V) ratio was relatively constant, at around 0.14, from the main pulmonary artery to medium IPA, but fell by 50% in the smallest vessels. The amplitude of the TEA‐sensitive K+ current was similar (16 pA pF‐1 at 40 mV) at all levels of the pulmonary arterial tree, except in the medium sized vessels where it was 50% smaller. These variations in K+ current expression correlate with reported variations in sensitivity to hypoxia and may contribute to the regional heterogeneity of HPV in the rabbit lung.
Book Review
Authors: Montani Jean‐Pierre , van Vliet Bruce N.
Published: May 2004

The Cardiovascular System at a Glance. Edited by P. I. Aaronson and J. P. T. Ward.
Effect of Nitric Oxide Synthase Inhibition on Renal Circulation and Excretory Function in Anaesthetized Rats
Authors: Tost Hilda , Hably Csilla , Lengyel Milena , Gógl A. , Lendvai A. , Bartha J.
Published: May 2004

The effects of nitric oxide synthase (NOS) inhibition (effected using L‐NAME, 14 mg (kg body mass (BM))‐1, administered intravenously) on systemic and renal circulation and renal excretory function has been investigated in anaesthetized Wistar rats subjected to one of two different degrees of isotonic extracellular (EC) volume expansion (40 and 60 ml kg‐1 (240 min)‐1). The administration of L‐NAME resulted in an increase in mean arterial blood pressure and total peripheral vascular resistance (TPR), and a significant reduction in cardiac output (CO) and the kidney fraction of CO in both experimental groups. The total renal blood flow (RBF) dropped from 557 ± 43.4 to 149 ± 13.1 ml min‐1 (100 g BM)‐1 and from 592 ± 45.9 to 191 ± 16.3 ml min‐1 (100 g BM)‐1 in the 40 and 60 ml kg‐1 (240 min)‐1 experimental volume expansion groups, respectively. A redistribution of the intrarenal circulation from the medulla of the kidney toward the cortex may have occurred. The NOS inhibition induced a significant decrease in the glomerular filtration rate (GFR; from 1.18 ± 0.10 to 0.53 ± 0.08 ml min‐1 (100 g BM)‐1 and from 1.26 ± 0.07 to 0.73 ± 0.08 ml min‐1 (100 g BM)‐1 in the 40 and 60 ml kg‐1 (240 min)‐1 experimental volume expansion groups, respectively), and the filtration fraction increased. The urine excretion dropped in parallel with the GFR, while the reduction in sodium and potassium excretion was more marked than that of the GFR, raising the possibility of a direct effect on the kidney tubules. The difference in EC volume expansion (the calculated increases in the EC volume in the last 90 min were 1.30 and 5.44% in the two time control groups and 3.66 and 7.45% in the two L‐NAME‐treated groups) did not induce any significant modification of the L‐NAME effect.
The Neurogenic Vasodilator Response to Endothelin‐1: A Study in Human Skin In Vivo
Authors: Katugampola Ruwani , Church Martin K. , Clough Geraldine F.
Published: May 2004

We have investigated the mediators and mechanisms underlying the vasodilator effects of the potent vasoactive peptide, endothelin‐1 (ET‐1) and its isomers ET‐2 and ET‐3 in human skin, in vivo, using cutaneous microdialysis to quantify the release of mediators within the dermal response and scanning laser Doppler imaging to measure changes in blood flux. The effects of local anaesthesia, inhibition of nitric oxide synthase (NOS) by L‐NAME and ET receptor blockade on the ET‐induced vascular response were also investigated. ET‐1, ‐2 and ‐3 all caused a dose‐dependent area of pallor surrounded by a long‐lasting flare which was accompanied by a short‐lived burning pruritus. The concentration of nitric oxide (NO) in dialysate collected within the pallor response to 5 μM ET‐1 (1.43 ± 0.64 μM, n = 5) was not significantly different from baseline levels collected prior to injection (0.86 ± 0.38 μM) whilst that in the flare increased to reach a peak value of 2.28 ± 0.61 μM at between 4 and 10 min after intradermal injection (P < 0.004). Pretreatment with local anaesthetic slowed the development of the flare and significantly reduced its size by up to 52% at 20 min after injection (P < 0.05) but had no significant effect on the central pallor. L‐NAME, delivered by dialysis also caused a significant reduction in the ET‐1‐induced flare (P < 0.005). Bosentan, the non‐selective ETA/ETB antagonist, when given by dialysis at the site of injection, reduced the area of both the ET‐1‐induced pallor and surrounding flare by 41 and 26%, respectively. No significant increase in tissue histamine was measured within either the pallor or flare response to ET‐1, ‐2 or ‐3. Together these data confirm that the vasodilator response to endothelin‐1 in human skin is neurogenic in origin and that it is in part mediated by the local release of nitric oxide. There appears to be little evidence for the involvement of mast cell‐derived histamine in the initiation or modulation of ET‐induced vasodilatation, in vivo.
Neuroinvasion of Prions: Insights from Mouse Models
Authors: Brandner Sebastian , Klein Michael A. , Frigg Rico , Pekarik Valdimir , Parizek Petra , Raeber Alex , Glatzel Markus , Schwarz Petra , Rülicke Thomas , Weissmann Charles , Aguzzi Adriano
Published: May 2004

The prion was defined by Stanley B. Prusiner as the infectious agent that causes transmissible spongiform encephalopathies. A pathological protein accumulating in the brain of scrapie‐infected hamsters was isolated in 1982 and termed prion protein (PrPSc). Its cognate gene Prnp was identified more than a decade ago by Charles Weissmann, and shown to encode the host protein PrPC. Since the latter discovery, transgenic mice have contributed many important insights into the field of prion biology, including the understanding of the molecular basis of the species barrier for prions. By disrupting the Prnp gene, it was shown that an organism that lacks PrPC is resistant to infection by prions. Introduction of mutant PrP genes into PrP‐deficient mice was used to investigate the structure‐activity relationship of the PrP gene with regard to scrapie susceptibility. Ectopic expression of PrP in PrP knockout mice proved a useful tool for the identification of host cells competent for prion replication. Finally, the availability of PrP knockout mice and transgenic mice overexpressing PrP allows selective reconstitution experiments aimed at expressing PrP in neurografts or in specific populations of haemato‐ and lymphopoietic cells. The latter studies have allowed us to clarify some of the mechanisms of prion spread and disease pathogenesis.
Germ Line Transformation of Mammals by Pronuclear Microinjection
Authors: Rülicke T. , Hübscher U.
Published: May 2004

The most popular approach for generating transgenic mammals is the direct injection of transgenes into one pronucleus of a fertilized oocyte. In the past 15 years microinjection has been successfully applied in laboratory as well as in farm animals. The frequency of transgenic founders, although highly different between the species, is efficient enough to render this technique applicable to a wide range of mammals. The expression levels and patterns of a transgene are initially influenced by the construction of the transgene. However, the overall phenotype of a transgenic organism is influenced by several genetic and environmental factors. Due to the features of this technique not all of the genetic factors can be experimentally controlled by the scientist. In this article we will emphasize some peculiarities which have to be taken into account for the successful performance of transgenesis by pronuclear microinjection
Transgenic Animal Models for Virus‐Induced Autoimmune Diseases
Authors: Ludewig Burkhard , Zinkernagel Rolf M. , Hengartner Hans
Published: May 2004

In the pathogenesis of autoimmune diseases, tolerance against self‐determinants is lost and autoreactive lymphocytes are activated leading to pathological damage of single or multiple organs. Viral and other microbial infections have been implicated in these processes. Viruses may induce immunopathological damage by maintaining a chronic immune response against the locally persisting infectious agent. Alternatively, viruses may help to initiate anti‐self immunoreactivity, e.g. by induction of an inflammatory milieu needed to overcome tolerance against self‐antigens. Presentation of viral antigens and/or previously immunologically ignored self‐antigens in secondary lymphoid organs is most probably the key event in the initiation of autoimmune diseases. Translocation of antigens to secondary lymphoid organs and primary induction of T cell responses is primarily mediated by dendritic cells (DCs). We discuss here two transgenic models of autoimmune diseases where DC‐mediated antigen transport initiated autoimmune responses against microbial neoself antigens. In the first model, dose and timing of antigen delivery by DCs and turnover of antigenic peptides presented by DCs are the main parameters regulating the outcome of autoimmune diabetes. In the second model, chronic stimulation of organ‐specific immune responses via DCs leads to severe cardiovascular immunopathology with arteritis, myocarditis and eventually dilated cardiomyopathy. Taken together, transgenic mouse models are valuable tools for delineating basic pathogenic mechanisms and evaluating therapeutic strategies to interfere with early detrimental processes that lead to manifest autoimmune diseases.
Large‐Scale N‐Ethyl‐N‐Nitrosourea Mutagenesis of Mice – from Phenotypes to Genes
Authors: Rathkolb Birgit , Fuchs Edith , Kolb Helmut J. , Renner‐Müller Ingrid , Krebs Ottheinz , Balling Rudi , de Angelis Martin Hrabé , Wolf Eckhard
Published: May 2004

The most important tool for obtaining insight into the function of genes is the use of mutant model organisms. Homologous recombination in embryonic stem cells allows the systematic production of mouse mutants for any gene that has been cloned. Gene trap strategies have been designed to interrupt even unknown genes which are tagged by the inserted vector and can be characterised structurally and functionally. Complementary to such ‘gene‐driven’ approaches, ‘phenotype‐driven’ approaches are necessary to identify new genes or gene products through a search for mutants with specific defects, uncovering the function of genetic pathways in physiological and pathological processes. Mutagenesis using the alkylating agent N‐ethyl‐N‐nitrosourea (ENU) is a powerful approach for the production of such mouse mutants. Since ENU induces mainly point mutations in premeiotic spermatogonia, this strategy allows the production of multiple alleles of a particular gene, which is pivotal for a fine tuned analysis of its function.
Dissecting the Behaviour of Transgenic Mice: Is it the Mutation, the Genetic Background, or the Environment?
Authors: Wolfer David P. , Lipp Hans‐Peter
Published: May 2004

Increasingly sophisticated and precise molecular genetic tools are applied to mice in order to study the cellular mechanisms underlying higher brain functions, including learning and memory. However, several studies have produced unclear or conflicting results. One reason for this is that performance in the behavioural tests used to assess learning and memory is influenced by various non‐cognitive phenomena and can thus easily be affected by mutations through mechanisms unrelated to memory function. We conducted principal component analysis on data from 3003 mice tested using a standardized protocol to demonstrate this for the Morris swimming navigation test, one of the most widely used paradigms to assess memory and hippocampal function. In addition, we present a meta‐analysis showing that genetic background and environment alone produce sufficient variation to span the range of most, if not all, behavioural variables and can thus easily mask or fake mutation effects if genetic studies are not designed properly. We suggest that the chance of obtaining useful results is maximized if behavioural deficits are differentiated by combining complementary behavioural protocols and by analysing multiple complementary parameters in each of them. Mutation effects must be contrasted statistically against the influences of genetic background and environment. In many situations, this is most efficiently achieved if (i) mutations are backcrossed to and maintained in one or (preferably) two well‐characterized, commonly available inbred strains and (ii) if mutant and wild‐type littermates are analysed on a hybrid or mixed genetic background, that is in F1 or F2 generations derived from the inbred stocks
Transgenic Animals in Cardiovascular Disease Research
Authors: Bader Michael , Bohnemeier Holger , Zollmann Frank S. , Lockley‐Jones Ora E. , Ganten Detlev
Published: May 2004

Worldwide, the highest morbidity and mortality results from such cardiovascular diseases as hypertension, myocardial infarction, cardiac and renal failure, as well as stroke. Since the cardiovascular system and its regulation is quite complex, study of these disorders has been grossly limited to whole organism models. As a result, in recent years, transgenic technology has played a significant role in the discovery of specific gene products for cardiovascular regulation and disease aetiology. Genetic manipulation in rats and mice has altered the expression of numerous genes. In this review, some of the important new genetically modified animals (i.e. transgenic models) with alterations in hormone and second messenger systems involved in cardiovascular regulation are summarized.
The Role of Perforin in Infections and Tumour Surveillance
Authors: van den Broek Maries F. , Hengartner Hans
Published: May 2004

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are able to lyse suitable target cells. CTLs recognize a specific peptide epitope presented by major histocompatibility complex (MHC) class I molecules on the target cells, whereas NK cells lyse targets that express no or low MHC class I molecules. Using perforin‐deficient mice, we provide evidence that both NK cells and CTLs exclusively use perforin‐dependent cytolysis as an effector mechanism in vitro, as well as in vivo. This review summarizes the most important role of perforin‐dependent cytolysis in a wide variety of bacterial and viral infections, in tumour surveillance, in immunopathology and in autoimmunity.
Mouse Genetics in Cell Biology
Authors: Mansuy Isabelle M. , Suter Ueli
Published: May 2004

Genetic methodologies have provided powerful means for investigating the cellular and molecular mechanisms of biological functions. Cell‐cell and cell‐extracellular matrix interactions in particular have been studied in different functional systems with genetically modified animals. In the peripheral and central nervous system, many aspects of specific processes based on such interactions, including myelination, synaptic transmission and plasticity, have been elucidated at the cellular and molecular level. Importantly, genetic approaches have greatly advanced the understanding of pathologies resulting from impaired cellular interactions in the brain and the periphery. In this review, some of the most relevant genetic mouse models in cell biology and the methodologies employed for their production will be described. In addition their usefulness for studies of the mechanisms of hereditary neuropathies, learning and memory, and tumorigenesis will be illustrated.
Genetically Modified Mouse Models in Studies on Cutaneous Wound Healing
Authors: Scheid Annette , Meuli Martin , Gassmann Max , Wenger Roland H.
Published: May 2004

Genetically modified mice have become an invaluable tool in modern biomedical and basic research. This review provides an overview of knockout and transgenic mice studied with regard to their cutaneous wound healing properties. In addition, several gene transfer studies are briefly introduced, which have further highlighted our knowledge on individual gene function in wound healing
Embryoid Bodies: An In Vitro Model of Mouse Embryogenesis
Authors: Desbaillets Isabelle , Ziegler Urs , Groscurth Peter , Gassmann Max
Published: May 2004

Embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of blastocysts. ES cells are able to differentiate into the three primitive layers (endoderm, mesoderm and ectoderm) of the organism, including the germline. To study early stages of development, as well as to investigate the impact of a gene knock‐out in vitro, ES cells are differentiated into three‐dimensional structures called embryoid bodies, because of their ability to mimick post‐implantation embryonic tissues. This review summarises the work on ES cell differentiation into haematopoietic and vascular cells, neuronal and glial cells, myocytes, and adipocytes, using this in vitro model of early embryogenesis. We also present the potential of this method to analyse the impact of genetic alterations in vitro
Embryonic Stem Cells and Gene Targeting
Authors: Ledermann Birgit
Published: May 2004

The development of gene targeting technology, the exchange of an endogenous allele of a target gene for a mutated copy via homologous recombination, and the application of this technique to murine embryonic stem cells has made it possible to alter the germ‐line of mice in a predetermined way. Gene targeting has enabled researchers to generate mouse strains with defined mutations in their genome allowing the analysis of gene function in vivo. This review presents the essential tools and methodologies used for gene targeting that have been developed over the past decade. Special emphasis has been laid on the available embryonic stem cell lines and the importance of the genetic background. Also, the state‐of‐the art of gene targeting approaches in species other than mice will be discussed.
Transgenic Technology in Farm Animals – Progress and Perspectives
Authors: Wolf Eckhard , Schernthaner Wolfgang , Zakhartchenko Valeri , Prelle Katja , Stojkovic Miodrag , Brem Gottfried
Published: May 2004

Current applications of gene transfer in farm animals include the improvement of product quality and quantity, disease resistance, the production of valuable proteins in the mammary gland or other organs, the genetic modification of pigs for xenotransplantation and the generation of new animal models in cases where rodent models are not sufficient for studying the problem under evaluation. Although DNA microinjection into pronuclei of zygotes from various farm animal species has happened since 1985, the efficiency of this method is low. Further drawbacks are related to the random integration process which may cause mosaicism, insertional mutations and varying expression due to position effects. Sperm‐mediated gene transfer is not routinely established yet, although the mechanisms of binding and internalisation of DNA by sperm cells is becoming increasingly clearer. New protocols for the use of retroviral vectors to infect metaphase II oocytes which are subsequently fertilised resulted in efficient production of transgenic cattle. In spite of extensive efforts to establish pluripotent stem cells from farm animal species, no germ‐line competent cells have been reported in mammalian species other than mouse so far. However, recent success in cloning sheep, cattle, goats and pigs from cultured cells provides an alternative route for efficient and targeted genetic modifications of farm animals.