bluuebunny/crossref_metadata_2025_split huggingface dataset:
BASIC INFORMATION PROCESSING AND HIGHER COGNITION: DOES THE MAMMALIAN CEREBRAL CORTEX DEAL WITH THEM AT DIFFERENT HIERARCHICAL LEVELS?
Authors: Vidyasagar TR 
Published: June 2007

SUMMARY1. The primary visual cortex has been generally considered as a feature processing area where the neurons code for basic stimulus attributes, such as orientation, colour and direction of movement. Higher cognitive functions, such as attention and memory, were believed to be mediated by extrastriate regions at higher levels in a hierarchy of visual areas. However, the experiments reported here suggest that the function of the primary visual cortex is more than basic information processing in at least two respects.2. First, significant modulation of visual responses occur in the primary visual cortex (V1) of the monkey depending upon attentional factors. There appears to be a feedback to V1 from extrastriate regions that facilitates neuronal responses in areas of attention and suppresses responses in other regions of the visual field.3. Second, one would expect a region that is concerned with coding basic stimulus features to be rather resistant to plastic changes, as cells need to be reliable feature detectors for meaningful behaviour by the organism. However, the experiments on anaesthetized cats reported here show that a subset of neurons in visual area 17 of the cat have a potential for synaptic plasticity. Their response properties can undergo longterm changes under certain circumstances. To induce these changes, specific visual stimuli were combined with iontophoretic administration of NMDA and the GABA antagonist, bicuculline, which are believed to provide the molecular milieu for long‐term potentiation and long‐term depression.
LIMITS OF PARALLEL PROCESSING: EXCITATORY CONVERGENCE OF DIFFERENT INFORMATION CHANNELS ON SINGLE NEURONS IN STRIATE AND EXTRASTRIATE VISUAL CORTICES
Authors: Dreher B. , Wang C. , Burke W. 
Published: June 2007

SUMMARY1. It has been postulated that the distinct parallel retinogeniculo‐cortical information channels characterizing visual pathways of virtually all mammals are selectively linked to parallel motion, colour and/or form information processing ‘streams’ distinguishable within the primary visual cortices, extrastriate cortical areas of occipital lobes and the temporal and parietal visual cortices.2. Using selective pressure‐blocking of the large‐fibre channel (the so‐called Y‐channel) in the optic nerve of the cat, we have experimentally examined the ‘selective excitatory parallel links’ hypothesis. We conclude that the majority of neurons in the primary visual cortices (areas 17, 18) as well as in the two ‘higher order’ visual areas, area 21a and posteromedial lateral suprasylvian (PMLS) area, constituting, respectively, part of the ‘form’ and part of the ‘motion’ processing streams, receive their excitatory inputs from both Y‐ and non‐Y‐information channels. In areas 17, 18 and 21a (but not in PMLS area), there are, however, subpopulations of cells that apparently receive excitatory inputs from only one information channel.3. Review of the relevant work on the macaque monkey suggests that the situation is similar in the primate: that is, there is a substantial degree of excitatory convergence of different retino‐geniculo‐cortical information channels on single neurons in the primary visual cortices and the extrastriate cortices constituting parts of the form/colour or the motion processing streams.4. Despite this high degree of excitatory convergence of different information channels, the large‐fibre channels (the Y‐channel in the cat and the magnocellular or Y‐like channel in macaque), are in both carnivores and primates the principal contributors to the motion processing cortical streams.
PARALLEL ORGANIZATION OF SOMATOSENSORY CORTICAL AREAS I AND II FOR TACTILE PROCESSING
Authors: Rowe MJ , Turman AB , Murray GM , Zhang HQ 
Published: June 2007

SUMMARY1. The two principal tactile processing areas in the cerebral cortex, somatosensory areas I and II, receive direct projections from the thalamus and, as well, are linked through intracortical reciprocal connections. Tactile information may therefore be conveyed to SII, for example, over either a direct path from the thalamus or an indirect, or serial, path from the thalamus via SI.2. Reports in recent years that tactile responsiveness within the hand area of SII was abolished by surgical ablation of the hand area of the postcentral, or SI, area of cortex in the macaque and marmoset monkeys indicated that a serial processing scheme may operate, at least in primates.However, as the surgical ablation is clearly irreversible and precludes examination of individual SII neurons in both the control and test circumstances, that is, when SI is intact and when it is inactivated, we have examined in the cat, the rabbit and the marmoset monkey the behaviour of SII neurons before, during and after the selective, rapidly‐reversible inactivation of SI by means of localized cooling.3. The results demonstrate that in the cat and rabbit, SII responsiveness is never abolished and infrequently affected by SI inactivation and that tactile inputs to SII therefore traverse a direct path from thalamus, organized in parallel with that to SI. In the marmoset (Callithrix jacchus), in contrast to earlier studies based on ablation of SI we found that with reversible inactivation of SI, SII responsiveness was unaffected in 25% of neurons and, although reduced in the remainder, was rarely abolished (<10% of SII neurons).4. The results indicate that there is substantial direct thalamic input to SII, even in this simian primate, and therefore necessitate revision of the hypothesis that tactile processing at the thalamocortical level in simian primates is based on a strict serial scheme in which tactile information is conveyed from the thalamus to SI and thence to SII.
INSIGHTS INTO MOTOR PERFORMANCE AND MUSCLE FATIGUE BASED ON TRANSCRANIAL STIMULATION OF THE HUMAN MOTOR CORTEX
Authors: Gandevia SC 
Published: June 2007

SUMMARY1. Direct cortical stimulation of motor and sensory areas of the cortex in experimental animals and some neurosurgical patients has provided much useful physiological information. Some of the benefits of this approach can be provided in awake volunteer subjects using new techniques which activate the motor cortex thorough the skull (i.e. transcranial electrical or magnetic stimulation).2. Both electrical and magnetic transcranial stimulation produce complex descending corticospinal volleys which usually contain a direct component (via corticofugal axons) and an indirect trans‐synaptic component. Changes in cortical ‘excitability’ can affect the evoked corticofugal volleys and the electromyographic responses which they involve.3. Apart from its diagnostic applications to patients with neurological disorders, transcranial stimulation has been applied to the study of a range of aspects of human motor control ranging from apparent cortical ‘plasticity’ to the changes in cortical behaviour produced by exercise.
THE HIPPOCAMPUS, LONG‐TERM POTENTIATION AND MEMORY
Authors: Redman Stephen 
Published: June 2007

SUMMARY1. The induction of long‐term potentiation (LTP) at excitatory synapses on CA1 pyramidal neurons occurs partly through an increase in the quantal AMPA current. It is also accompanied by an increase in the number of active sites. Any presynaptic modification, requiring the presence of a retrograde messenger, remains uncertain.2. There are no definitive data that establish a causal link between LTP and the formation of memories. Pharmacological blockage of NMDA and m GLU receptors and genetic mutants with proteins deleted that are thought to be involved in LTP induction or maintenance or in the formation of memories have all linked deficits in LTP with impairments to behavioural learning, but these links are not necessarily causal. The development of tissue‐ and time‐specific lesions of gene expression for multiple gene products may overcome the present limitations of gene deletion experiments and provide more revealing insights into the relationship between LTP and memory.
PHOSPHODIESTERASE INHIBITORS AND ENDOTHELIN AS MODULATORS OF RESPIRATORY NEUROTRANSMISSION
Authors: Fernandes LB 
Published: June 2007

SUMMARY1. Airway smooth muscle receives cholinergic, adrenergic and non‐adrenergic, non‐cholinergic (NANC) neural input. In guinea‐pig airways cholinergic and NANC nerves provide contractile innervation, while adrenergic and NANC nerves provide nerves provide relaxant pathways. In contrast, the major relaxant innervation in human airways is NANC in nature.2. The present review describes the effects of selective phosphodiesterase (PDE) inhibitors on NANC relaxant and contractle responses in guinea‐pig trachea as well as on NANC relaxations in human bronchus.3. The effects of endothelin‐1 on cholinergic contractile responses obtained in a variety of species are also assessed.
ILLUMINATION OF THERAPEUTICS BY TOXICOLOGY: A PERSONAL VIEW*
Authors: Pond Susan M. 
Published: June 2007

SUMMARY1. My specialties are therapeutics and toxicology. When we think in classical terms about drugs, therapeutics refers to curative healing, toxicology to the capacity to produce harm. However, they are not opposite disciplines, but rather reflect a continuum along the dose‐response curve of a drug or toxin. Since antiquity, the study of toxicology has underpinned and illuminated therapeutics. Even the most potent toxins, such as botulinum and ricin, are used for therapeutic purposes.2. In the case of one of my favourite research topics, the herbicide paraquat, I illustrate how investigating methods to treat patients poisoned by it has led to important advances in knowledge in medicine and therapeutics. Studying paraquat has launched my own research group on a path towards elucidating the mechanisms of the chronic neurological side effects of the antipsychotic drug, haloperidol, which is used widely to treat schizophrenia. In tracing these tortuous paths, the roles that serendipity and creativity play in research and their implications for education and funding policies are highlighted.
POTASSIUM CHANNELS AND THE CEREBRAL CIRCULATION
Authors: Faraci Frank M. , Sobey Christopher G. 
Published: June 2007

SUMMARY1. Hyperpolarization of vascular muscle in response to activation of potassium channels is a major mechanism of vasodilatation.2. In cerebral blood vessels, two potassium channels have received considerable study recently: ATP‐sensitive and calcium‐dependent potassium channels. Activation of these potassium channels appears to play a major role in the relaxation of cerebral arteries and arterioles in response to diverse stimuli, including receptor‐mediated agonists, intracellular second messengers, reactive oxygen species and hypoxia.3. The functional influence of ATP‐sensitive and calcium‐dependent potassium channels may be altered in disease states, including hypertension, diabetes and subarachnoid haemorrhage.
EXPERIMENTAL BASIS FOR REALISTIC LARGE‐SCALE COMPUTER SIMULATION OF THE ENTERIC NERVOUS SYSTEM
Authors: Furness JB , Bornstein JC , Kunze WAA , Bertrand PP , Kelly H. , Thomas EA 
Published: June 2007

SUMMARY1. The enteric nervous system is perhaps the most accessible part of the mammalian nervous system in which it is feasible to attempt large scale computer simulation that is based closely on experimentally determined data. Here we summarize the data obtained for simulation of motility reflexes in the guineapig small intestine.2. The chemistry, morphology and connectivity of each type of neuron involved in intrinsic reflexes have been investigated and most classes of neurons are physiologically well characterized. This includes primary sensory neurons, ascending and descending interneurons and motor neurons to circular and longitudinal muscle.3. The responses of primary sensory neurons and the physiology of synaptic transmission from sensory neurons to interneurons and motor neurons, from interneurons to interneurons and from interneurons to motor neurons have been recorded during reflexes and in some cases the pharmacology of transmission has also been investigated.4. Computer simulation, in which the activities of up to 30000 neurons are modelled, produces patterns of activity that closely mimic those recorded in physiological experiments.
CYCLOSPORINE A IMMUNOSUPPRESSION IN SHEEP WITH RESPONSE ENHANCEMENT BY CONCOMITANT KETOCONAZOLE
Authors: O'Donoghue HL , Penhale WJ , Manning LS , Reynoldson JA , Turner JH 
Published: June 2007

SUMMARY1. The pharmacokinetics of a single dose of Cyclosporine A (CsA) administered to sheep by intravenous (i.v.) route were examined.2. Concomitant administration of ketoconazole was found to increase the area under the blood CsA concentration‐time curve (AUC) and was effective when adminstered by the oral or intraperitoneal route.3. The effects of CsA and ketoconazole on the immune system of sheep were also assessed.4. A single dose of CsA 5mg/kg resulted in abrogation of in vitro lymphocyte function manifest at 24h after injection of CsA. Normal responsiveness recovered in 48‐72h. Numbers of T lymphocytes in peripheral blood were elevated transiently at 48h although no other significant alteration in lymphocyte subsets was observed with this treatment.5. Concomitant ketoconazole administration enhanced the CsA‐induced suppression of in vitro lymphocyte responses. Blood levels of CsA (AUC values to 24h) were significantly elevated with concomitant ketoconazole administration and depression of lymphocyte responses to mitogens were also significantly enhanced. An increase in the proportion of T4 positive cells in the blood was observed at 48h and at 7 days after administration of CsA with ketoconazole.6. These findings indicate that CsA effectively abrogates immunocompetence in the sheep and this immunosuppressive effect is enhanced by concomitant administration of ketoconazole.
RENAL KALLIKREIN IN CHRONIC HYPOXIC RATS
Authors: Chen Chau‐Fong , Chen Li‐Wen , Chien Chiang‐Ting , Wu Ming‐Shieu , Tsai Tun‐Jun 
Published: June 2007

SUMMARY1. We have studied the role of kallikrein (KK) in the maintenance of renal function in chronic hypoxic rats (high altitude; HA), compared with control rats kept at sea level (SL). Hypoxia was induced by placing female Wistar rats (198‐290 g) in an altitude chamber (5500m) 15 h/day for 4 weeks. Experiments were also conducted to study the interaction of KK with renal nerve activity and endothelin (ET), two parameters previously shown to be altered in this model.2. It was found that renal cortex tissue KK activity (TKA) was not significantly different in 10 SL and 10 HA rats. However, the urinary KK activity (UKA) was reduced nearly to half (from 35.2±4.6 to 18.5±1.7 pkat/min) in HA rats after 4 weeks of chronic hypoxia.3. Acute renal denervated diuresis was accompanied by a significant increase in UKA (from 9±2 to 14±2 pkat/min in HA and denervated HA rats, respectively; P < 0.05) in HA rats. Intrarenal arterial pretreatment of aprotinin reduced the denervated diuresis.4. Endothelin (600 ng/kg per h) reduced urine flow, sodium and potassium excretion in the ipsilateral kidney in another 10 SL and 10 HA rats. The extent of the drop of these parameters was significantly less in HA rats. Urinary KK activity was correlated significantly with the measured renal functional parameters (r ranging from 0.472 to 0.612) in SL rats, but was insignificant in HA rats (r ranging from 0.032 to 0.192).5. We have demonstrated that chronic exposure to hypoxia decreases urinary KK excretion and that KK is involved in acute renal denervated diuresis generated in these animals. The present study suggests that KK plays a partial role in the maintenance of renal function in chronic hypoxic rats.
MAGNOLOL REDUCES INFARCT SIZE AND SUPPRESSES VENTRICULAR ARRHYTHMIA IN RATS SUBJECTED TO CORONARY LIGATION
Authors: Hong CY , Huang SS , Tsai SK 
Published: June 2007

SUMMARY1. Magnolol is an active component of Magnolia officinalis. It is 1000‐times more potent than α‐tocopherol in inhibiting lipid peroxidation in rat heart mitochondira. In the present study, the in vivo antiarrhythmic and anti‐ischaemic effects of magnolol in coronary ligated rats were investigated.2. Male Sprague‐Dawley rats were anaesthetized with urethane. Magnolol, at dosages of 10−7, 10−8 and 10−9 g/kg, was adminstered intravenously 15 min before ligation of the coronary artery.3. The incidence and duration of ventricular tachycardia and ventricular fibrillation during 30 min coronary ligation were significantly reduced by magnolol. Ventricular arrhythmias during 10 min reperfusion after the relief of coronary ligation were also reduced.4. In rats subjected to 4h coronary ligation, 10−7 and 10−8 g/kg magnolol significantly reduced infarct size.5. We conclude that magnolol may protect the myocardium against ischaemic injury and suppress ventricular arrhythmia during ischaemia and reperfusion.
LOSS OF NITRIC OXIDE PRODUCTION IN THE CORONARY CIRCULATION AFTER THE DEVELOPMENT OF DILATED CARDIOMYOPATHY: A SPECIFIC DEFECT IN THE NEURAL REGULATION OF CORONARY BLOOD FLOW
Authors: Zhao Gong , Shen Weiqun , Zhang Xiaoping , Smith Carolyn J. , Hintze Thomas H. 
Published: June 2007

SUMMARY1. The aims of our study were to determine the role of nitric oxide (NO) in cholinergic reflex dilation of the coronary circulation in normal healthy conscious dogs and after the development of pacing‐induced dilated cardiac myopathy and overt congestive heart failure.2. Dogs were instrumented using sterile surgical techniques under general anaesthesia and allowed to fully recover. The Bezold‐Jarisch reflex was stimulated by the intra‐atrial injection of veratrine or the intravenous injection of PGI2, while the carotid chemoreflex was stimulated by the intracarotid injection of nicotine. Experiments were performed before and after the development of overt congestive heart failure (HF) caused by rapid left ventricular pacing for 4 weeks.3. The release of NO, or NO‐mediated vascular relaxation following administration of acetylcholine (ACh) may have little physiological significance since as ACh is released from nerve endings in vivo. Stimulation of the Bezold‐Jarisch or carotid chemoreflex resulted in typical vagal cholinergic reflex coronary vasodilation, an increase in coronary blood flow and a decrease in coronary vascular resistance, which was substantially reduced following NO synthesis inhibition with nitro‐L‐arginine.4. After the development of severe congestive HF, the production of NO by sieved coronary microvessels from the heart was markedly reduced accompanied by a 60‐80% reduction in both the mRNA (northern blot) and protein (western blot) for endothelial NO synthase in the aorta.5. After the development of severe pacing‐induced HF, activation of the Bezold‐Jarisch or carotid chemoreflex no longer resulted in coronary vasodilation due to the disappearance of NO production from the coronary circulation.6. Therefore, cholinergic reflex coronary vasodilation is mediated by NO. Because coronary blood vessels lose the ability to produce NO after the development of HF, reflex cholinergic coronary vasodilation is markedly altered, uncovering a previously undiscovered specific defect in the integrated control of the coronary circulation in the failing heart.
PROBING EXCITATION‐CONTRACTION COUPLING IN TRACHEALIS SMOOTH MUSCLE WITH THE MYCOTOXIN CYCLOPIAZONIC ACID
Authors: Amoako Daniel , Qian Yun , Kwan Chiu‐Yin , Bourreau Jean‐Pierre 
Published: June 2007

SUMMARY1. Muscarinic stimulation‐induced tonic contraction of airway smooth muscle is independent of membrane potential. This contraction is not sensitive to inhibition by voltage‐operated Ca2+ channel blockers or by K+ channel openers.2. Cyclopiazonic acid (CPA) inhibits Ca2+ loading of internal stores but does not affect maximal tonic contraction induced by acetylcholine (ACh) in steady state conditions.3. After depletion of internal Ca2+ stores with CPA, AChinduced tonic contraction becomes dependent upon values of membrane potential. The contraction is then sensitive to voltage‐operated Ca2+ channel blockers and to K+ channel openers.4. Treatment of trachealis muscle with CPA potentiates the M2‐mediated component of ACh stimulation, but this potentiation is not entirely responsible for the switch in excitation‐contraction (E‐C) coupling.5. It is proposed that depletion of internal Ca2+ stores with CPA and promotion of M2‐stimulation can lead to a switch in E‐C coupling in trachealis smooth muscle from pharmaco‐ to electromechanical mode, perhaps by targeting a plasma membrane K+ channel.
SLOW PRESSOR EFFECT OF ANGIOTENSIN II IN NORMOTENSIVE RATS WITH RENAL ARTERY STENOSIS
Authors: Melaragno Matthew G. , Fink Gregory D. 
Published: June 2007

SUMMARY1. We have shown previously that renal artery stenosis in rats causes enhanced responsiveness to the slow pressor effect of angiotensin II (AngII) and suggested that two‐kidney, one clip (2K1C) hypertension may depend, in part, on changes in responsiveness to the peptide.2. The present experiment was performed in order to investigate whether a degree of renal artery stenosis that was insufficient to raise blood pressure was able to enhance responsiveness to the slow pressor effect of AngII.3. Two to four weeks after placement of a 0.2 mm clip over the left renal artery (2K1C) or a sham operation, some 2K1C rats were normotensive. These rats and the sham rats then received an intravenous infusion of AngII (4 ng/min) for 10 days.4. AngII caused the 2K1C rats to attain significantly higher mean arterial pressure than the sham rats (152 ± 7 vs 133 ± 7 mmHg) and did not result in water or electrolyte retention in the 2K1C rats.5. These results indicate that normotensive 2K1C rats exhibit enhanced responsiveness to the slow pressor effect of AngII and that the arterial pressure response to renal ischaemia may depend on both AngII formation and responsiveness to the chronic actions of the peptide.
HIGH POTASSIUM DIETS REDUCE ENDOTHELIAL PERMEABILITY IN STROKE‐PRONE SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Ishimitsu Toshihiko , Tobian Louis 
Published: June 2007

SUMMARY1. High potassium (K) diets are known to prevent hypertensive arterial lesions and reduce stroke incidence without affecting blood pressure.2. To elucidate the mechanism of this beneficial effect, we studied the effect of K supplementation on the extravasation of plasma albumin in high NaCl‐fed stroke‐prone spontaneously hypertensive rats (SHRSP). Increased permeability of the endo‐thelium to macromolecules is assumed to be an early manifestation of vascular injury.3. The disappearance of intravenously injected [125I]‐albumin was examined in SHRSP rats fed high NaCl diets containing either 0.5% normal K or 2.1% high K for 5 weeks.4. The bodyweight, blood pressure, plasma volume and urinary protein excretion were not significantly different between the two SHRSP groups.5. The high K SHRSP showed a slower plasma albumin disappearance rate than the normal K SHRSP (10.3 vs 14.7%/h, P<0.004). The albumin radioactivity remaining in the aortic wall and in the brain after removing blood after perfusion was lower in the high K SHRSP than in the normal K SHRSP (aorta, ‐ 20%, P<0.02; brain, ‐ 26%, P<0.04).6. These results suggest that the high K diet reduced the endothelial permeability to albumin in high NaCl‐fed SHRSP rats. High K diets may have a protective effect against endothelial dysfunction and thereby contribute to the reduction of vascular lesion formation and stroke incidence.