Biomedical subjects

L A Brown

Publications and source records attributed to L A Brown.

At least 37 records · Page 2Linked to original sources

PubMed2000

Adenovirus-mediated transfer of an Na+/K+-ATPase beta1 subunit gene improves alveolar fluid clearance and survival in hyperoxic rats.

Pulmonary edema is cleared via active Na(+) transport by alveolar epithelial Na(+)/K(+)-ATPases and Na(+) channels. Rats exposed to acute hyperoxia have a high mortality rate, decreased Na(+)/K(+)-ATPase function, and decreased alveolar fluid clearance (AFC). We hypothesized that Na(+)/K(+)-ATPase subunit gene overexpression could improve AFC in rats exposed to hyperoxia. We delivered 4 x 10(9) PFU of recombinant adenoviruses containing rat alpha(1) and beta(1) Na(+)/K(+)-ATPase subunit cDNAs (adalpha(1) and adbeta(1), respectively) to rat lungs 7 days prior to exposure to 100% O(2) for 64 hr. As compared with controls and ad alpha(1), AFC in the adbeta(1) rats was increased by >300%. Permeability for large solutes was less in the ad beta(1) than in the other hyperoxia groups. Glutathione oxidation, but not superoxide dismutase activity, was increased only in the adbeta(1) group. Survival through 14 days of hyperoxia was 100% in the adbeta(1) group but was not different from hyperoxic controls in animals given adalpha(1). Our data show that overexpression of a beta(1) Na(+)/K(+)-ATPase subunit augments AFC and improves survival in this model of acute lung injury via antioxidant-independent mechanisms. Conceivably, restoration of AFC via gene transfer of Na(+)/K(+)-ATPase subunit genes may prove useful for the treatment of acute lung injury and pulmonary edema.

Adenoviridae↗

PubMed2000

Application of cDNA microarrays in determining molecular phenotype in cardiac growth, development, and response to injury.

BACKGROUND: Normal myocardial development and the tissue response to cardiac stress are accompanied by marked changes in gene expression; however, the extent of these changes and their significance remain to be fully explored. We used cDNA microarrays for gene expression profiling in rat cardiac tissue samples to study developmental transitions and the response to myocardial infarction (MI). METHODS AND RESULTS: Microarrays with rat cDNAs for 86 known genes and 989 anonymous cDNAs obtained by molecular subtraction (representational difference analysis) of mRNA from sham-operated and 6-week post-MI samples were used in 2-color hybridization experiments. Twelve known genes previously associated with myocardial development were identified together with 10 uncharacterized expressed sequence tags and 36 genes not previously associated with cardiac development. After MI, genes associated with myocardial stress and wound healing exhibited differences in magnitude and expression kinetics, and 14 genes not previously associated with MI were identified. In situ hybridization revealed mRNA localization characteristic of wound healing and vascular and cardiomyocyte reactivity. CONCLUSIONS: Tissue analysis of gene expression with cDNA microarrays provides a measure of transcriptional or posttranscriptional regulation and cellular recruitment. Our results demonstrate the complexity of gene regulation in the developing myocardium and show that cDNA microarrays can be used to monitor the evolution of the cardiac stress-inducible phenotype.

Animals↗

PubMed2000

Digital analysis of light microscope immunofluorescence: high-resolution co-localization of synaptic proteins in cultured neurons.

A protocol is presented for determining the subcellular distribution of fluorescently labeled proteins in neurons using deconvolved images gathered with a wide-field microscope. The protocol includes optimal settings for the numerical algorithm used to deconvolve the images and an objective method for thresholding the deconvolved images to retain only high-intensity, specific labeling. The effectiveness of the protocol is demonstrated using a fluorescent antibody stain directed towards the alpha1 subunit of the GABA(A) receptor in cultured neurons. We also show, using an antibody against the presynaptic vesicular protein synaptophysin, that the technique can detect presumptive regions of synaptic contact between neurons. Double-labeling with the anti-alpha1 and anti-synaptophysin antibodies in a cultured neuron reveals regions of both synaptic and non-synaptic alpha1 labeling. Thus, numerical postprocessing of wide-field images can be used to efficiently locate receptor proteins in neurons in relation to functionally important structures. This confocal-like functionality is attained without the excessive bleaching and phototoxicity associated with the intense laser excitation light used in confocal techniques.

Animals↗

PubMed2000

Insights into early vasculogenesis revealed by expression of the ETS-domain transcription factor Fli-1 in wild-type and mutant zebrafish embryos.

Fli-1 is an ETS-domain transcription factor whose locus is disrupted in Ewing's Sarcoma and F-MuLV induced erythroleukaemia. To gain a better understanding of its normal function, we have isolated the zebrafish homologue. Similarities with other vertebrates, in the amino acid sequence and DNA binding properties of Fli-1 from zebrafish, suggest that its function has been conserved during vertebrate evolution. The initial expression of zebrafish fli-1 in the posterior lateral mesoderm overlaps with that of gata2 in a potential haemangioblast population which likely contains precursors of blood and endothelium. Subsequently, fli-1 and gata2 expression patterns diverge, with separate fli-1 and gata2 expression domains arising in the developing vasculature and in sites of blood formation respectively. Elsewhere in the embryo, fli-1 is expressed in sites of vasculogenesis. The expression of fli-1 was investigated in a number of zebrafish mutants, which affect the circulatory system. In cloche, endothelium is absent and blood is drastically reduced. In contrast to the blood and endothelial markers that have been studied previously, fli-1 expression was initiated normally in cloche embryos, indicating that induction of fli-1 is one of the earliest indicators of haemangioblast formation. Furthermore, although fli-1 expression in the trunk was not maintained, the normal expression pattern in the anterior half of the embryo was retained. These anterior cells did not, however, condense to form blood vessels. These data indicate that cloche has previously unsuspected roles at multiple stages in the formation of the vasculature. Analysis of fli-1 expression in midline patterning mutants floating head and squint, confirms a requirement for the notochord in the formation of the dorsal-aorta. The formation of endothelium in one-eyed pinhead, cyclops and squint embryos indicates a novel role for the endoderm in the formation of the axial vein. The phenotype of sonic-you mutants implies a likely role for Sonic Hedgehog in mediating these processes.

Amino Acid Sequence↗

PubMed2000

Cognitive influence on postural stability: a neuromuscular analysis in young and older adults.

BACKGROUND: Previous literature indicates that attentional resources are required for recovery of postural stability. Previous studies have also examined the effect of aging on the performance of a static postural task while a secondary cognitive task is being conducted. This study describes the effect of a cognitive task on the neuromuscular response characteristics underlying reactive balance control in young versus older adults. METHODS: The attentional demand on the neuromuscular system was examined in 14 young and 12 healthy older adults by analysis of the integrated electromyography activity while the adults were performing a dual-task paradigm. The primary task involved standing platform perturbations and the secondary task was a math task that involved subtraction by threes. Integrated electromyography activity was compared between the cognitive (math and balance) task versus control (balance only) task. RESULTS: For both groups of subjects, onset latency of postural muscle responses did not change under dual-task conditions. In contrast, the amplitude of postural muscle activity was significantly affected by performance of a secondary task. When electromyography data were combined for both young and older adults, there was a decrease in muscle response amplitude in both agonist (gastrocnemius) and antagonist (tibialis anterior) muscles when the cognitive math task was performed. This was apparent at 350-500 milliseconds from plate onset for the gastrocnemius and between 150 and 500 for the tibialis anterior. When young and older adults were compared, an age by task interaction effect was seen in muscle response amplitude for the agonist (gastrocnemius) muscle between 350 to 500 milliseconds, with older adults showing a significantly greater reduction than young adults. CONCLUSION: The decline of muscle activity when the secondary task was performed suggests that less attentional processing capacity was available for balance control during the dual-task paradigm. The results also indicate that the dual-task activity has a greater impact on balance control in the older adults than in the young adults.

Adult↗

PubMed2000

Focal bacterial nephritis (lobar nephronia) presenting as renal mass.

A focal infection of the kidney can cause a diagnostic dilemma by mimicking a neoplasm. We describe a case of focal bacterial nephritis (acute lobar nephronia) caused by Escherichia coli in which the diagnosis was confirmed only after surgical exploration. Although the patient had fever on admission, urine and blood cultures were negative and fine needle aspiration of the kidney could not rule out a well-differentiated carcinoma.

Adult↗

PubMed2000

Ethanol ingestion via glutathione depletion impairs alveolar epithelial barrier function in rats.

We determined that rats fed a liquid diet containing ethanol (36% of calories) for 6 wk had decreased (P < 0.05) net vectorial fluid transport and increased (P < 0.05) bidirectional protein permeability across the alveolar epithelium in vivo compared with rats fed a control diet. However, both groups increased (P < 0.05) fluid transport in response to epinephrine (10(-5) M) stimulation, indicating that transcellular sodium transport was intact. In parallel, type II cells isolated from ethanol-fed rats and cultured for 8 days formed a more permeable monolayer as reflected by increased (P < 0.05) leak of [(14)C]inulin. However, type II cells from ethanol-fed rats had more sodium-permeant channels in their apical membranes than type II cells isolated from control-fed rats, consistent with the preserved response to epinephrine in vivo. Finally, the alveolar epithelium of ethanol-fed rats supplemented with L-2-oxothiaxolidine-4-carboxylate (Procysteine), a glutathione precursor, had the same (P < 0.05) net vectorial fluid transport and bidirectional protein permeability in vivo and permeability to [(14)C]inulin in vitro as control-fed rats. We conclude that chronic ethanol ingestion via glutathione deficiency increases alveolar epithelial intercellular permeability and, despite preserved or even enhanced transcellular sodium transport, renders the alveolar epithelium susceptible to acute edematous injury.

Administration, Oral↗

PubMed2000

The effects of chronic alcohol abuse on pulmonary glutathione homeostasis.

The incidence and severity of the acute respiratory distress syndrome (ARDS) is increased in critically ill patients with a prior history of chronic alcohol abuse; however, the specific mechanisms responsible for this association are unknown. Recently, we determined that chronic ethanol ingestion in rats decreased the alveolar epithelial lining fluid (ELF) concentration of the antioxidant glutathione (GSH), which is a characteristic finding in patients with ARDS. However, the effects of chronic alcohol abuse on the human alveolar epithelium are essentially unknown. Therefore, as a first step we asked if chronic alcohol abuse, independent of other comorbid conditions, decreases the concentration of GSH in the human lung. We determined that otherwise healthy chronic alcoholics had significantly decreased ELF concentrations of GSH compared with nonalcoholic control subjects (79 micromol [48 to 118 micromol] versus 576 micromol [493 to 728 mmol], p < 0.001). Furthermore, the percentage of GSH in the oxidized form was higher in the chronic alcoholics (9.8% [2.2 to 14.8%] versus 2.8% [0.4 to 4.0%] p = 0.05), indicative of increased utilization of GSH. This is the first report that chronic alcohol abuse alters GSH homeostasis in the human lung, and suggests a potential mechanism by which chronic alcohol abuse predisposes susceptible patients to develop ARDS.

Alcoholism↗

PubMed2000

Mitochondrial glutathione replacement restores surfactant synthesis and secretion in alveolar epithelial cells of ethanol-fed rats.

BACKGROUND: Chronic alcohol abuse increases the incidence and severity of acute lung injury in critically ill patients. Previously we determined that ethanol ingestion in rats dramatically decreased alveolar epithelial cellular levels of glutathione and surfactant synthesis and secretion in vitro. Previous studies in alcoholic liver disease suggest that mitochondrial glutathione levels, and not cellular levels per se, are involved in the pathogenesis of ethanol-mediated hepatotoxicity. Therefore, we hypothesized that alveolar epithelial mitochondrial glutathione depletion mediates the observed defects in surfactant synthesis and secretion in ethanol-fed rats. METHODS: Male Sprague-Dawley rats were fed the Lieber-DeCarli liquid diet with or without ethanol (36% of total calories) for 6 weeks. In some experiments, ethanol-fed rats were then switched to the control diet for 1 week, with or without glutathione supplementation with either N-acetylcysteine (NAC) or procysteine (PRO). Alveolar epithelial type II cells were then isolated and glutathione levels (cytosolic and mitochondrial) and surfactant production (synthesis and secretion) were determined. RESULTS: Ethanol ingestion decreased (p < 0.05) mitochondrial and cytosolic levels of glutathione, and surfactant synthesis and secretion in isolated type II cells when compared to cells from control-fed rats. NAC treatment restored (p < 0.05) cytosolic but not mitochondrial glutathione levels (p > 0.05), and had no effect (p > 0.05) on surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats. In contrast, PRO treatment restored (p < 0.05) cytosolic and mitochondrial glutathione levels, and normalized (p < 0.05) surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats. CONCLUSIONS: These results suggest that mitochondrial, and not simply cytosolic, replacement of glutathione is necessary to improve surfactant function in critically ill patients with a history of alcohol abuse.

Animals↗

PubMed1999

Molecular characterization of a zebrafish TCF ETS-domain transcription factor.

The ternary complex factor (TCF) subfamily of ETS-transcription factors represent key nuclear targets of the MAP kinase pathways. Members of this subfamily are classified by the presence of several conserved domains for DNA binding, interaction with SRF, interaction with MAP kinases and transcriptional activation. In this study we have isolated a further member of this subfamily (TCF-1) from zebrafish. The protein product of zebrafish TCF-1 (zTCF-1), shares sequence similarity with the mammalian TCFs in all four conserved domains, with highest overall similarity to SAP-1. Zebrafish TCF-1 is expressed throughout zebrafish embryonic development and exhibits typical TCF DNA binding characteristics, with the B-box being required for interaction with SRF. Of the mammalian TCFs, its DNA binding specificity resembles Elk-1. zTCF-1 is a target for both the growth factor/mitogen-activated and stress-activated MAP kinase cascades in vitro and in vivo. However, differential targeting occurs, with the profile of its activation closely resembling that of mammalian SAP-1. Together, our results demonstrate that the TCFs have been functionally conserved during vertebrate development.

Amino Acid Sequence↗

PubMed1999

Bio-imaging of nitric oxide-producing neurones in slices of rat brain using 4,5-diaminofluorescein.

4,5-Diaminofluorescein (DAF-2) was used to identify individual nitric oxide (NO)-producing neurones in brain slices in vitro. Coronal slices of midbrain or hippocampus, 300 microm thick from young adult rats, were incubated for 30 min in 1 microM DAF-2 diacetate (DAF-2 DA) and maintained in ACSF at 33 degrees C. Illumination at 450-490 nm revealed punctate fluorescence in neurones in the lateral tegmental nucleus, dorsal raphe nucleus, dorsolateral periaqueductal grey matter, deep collicular layers and cortical areas. Neurones in the hippocampal pyramidal cell layer, molecular layer of the dentate gyrus and the hilus fluoresced also. The fluorescence was abolished by pre-incubation of slices with L-NAME (100 microM-1 mM), the inhibitor of constitutive nitric oxide synthase (NOS), but not by D-NAME (100 microM) or L-NIL (5-50 microM), an inhibitor of inducible NOS. In some superficially located arterioles, there were small regions of bright fluorescence close to the outer smooth muscle wall and diffuse fluorescence within the adjacent smooth muscle cells. A diffuse fluorescence was also seen in some superficially located capillaries. Basal production of NO was not seen within deeper blood vessels. DAF-2 DA offers a sensitive indicator for visualising basal production of NO with high spatial resolution and could provide a means of identifying NOS-containing neurones in brain slices in vitro prior to neurophysiological study.

Animals↗

PubMed1999

Effects of exogenous nitric oxide and hyperoxia on lung fibroblast viability and DNA fragmentation.

Effective lung repair after acute injury requires elimination of proliferating mesenchymal and inflammatory cells without inducing an acute inflammatory response or disturbing concomitant repair of lung microvasculature. Previous studies have shown that endogenous NO regulates programmed cell death in fibroblasts and can modulate wound fibroblast synthetic function. We hypothesized that exposure of human lung fibroblasts to NO gas would decrease viability and induce apoptotic cell death. Primary cultures of normal human lung fibroblasts were exposed for 4 h to room air (RA), 80% oxygen, NO (at either 20 or 50 ppm) blended with RA, or NO blended with 80% O(2), then incubated for 24 to 72 h. Cell viability was determined by fluorescence viability/cytotoxicity assay and DNA fragmentation by TUNEL assay. Peroxynitrite formation was assessed using immunoblotting for S-nitrosotyrosine. NO plus O(2) induced significant cell death at 20 and 50 ppm NO when compared to either RA or O(2) alone at both 24 and 72 h (p < 0.05). Incubation with superoxide dismutase (SOD), catalase (CAT) or SOD + CAT significantly decreased cell death in fibroblasts treated with NO(20)/O(2) and NO(50)/O(2) compared with controls (p < 0.05). NO(20)/O(2) and NO(50)/O(2) exposure significantly increased TUNEL mean fluorescence intensity (MFI), consistent with increased DNA fragmentation, compared to RA at 24 and 72 h (p < 0.05). Antioxidants decreased MFI in cells exposed to NO(20)/O(2) (CAT and SOD + CAT) compared to controls at 24 h (p < 0.05). Western blot analysis for S-nitrosotyrosine showed increased signal intensity in fibroblasts exposed to NO at 20 and 50 ppm plus O(2) compared to RA or O(2) alone. Incubation with SOD + CAT reduced signal intensity for peroxynitrite in cells exposed to NO(20)/O(2). We conclude that NO in hyperoxic conditions induces fibroblast cell death and DNA fragmentation, which could be partially mediated by peroxynitrite synthesis.

Antioxidants↗

PubMed1999

Differential expression of alpha1, alpha2, alpha3, and alpha5 GABAA receptor subunits in seizure-prone and seizure-resistant rat models of temporal lobe epilepsy.

Temporal lobe epilepsy remains one of the most widespread seizure disorders in man, the etiology of which is controversial. Using new rat models of temporal lobe epilepsy that are either prone or resistant to develop complex partial seizures, we provide evidence that this seizure susceptibility may arise from arrested development of the GABAA receptor system. In seizure-prone (Fast kindling) and seizure-resistant (Slow kindling) rat models, both the mRNA and protein levels of the major alpha subunit expressed in adult brain (alpha1), as well as those highly expressed during development (alpha2, alpha3, and alpha5), were differentially expressed in both models compared with normal controls. We found that alpha1 subunit mRNA expression in the Fast kindling strain was approximately half the abundance of control rats, whereas in the Slow kindling strain, it was approximately 70% greater than that of controls. However, Fast rats overexpressed the alpha2, alpha3, and alpha5 ("embryonic") subunits, having a density 50-70% greater than controls depending on brain area, whereas the converse was true of Slow rats. Using subunit-specific antibodies to alpha1 and alpha5 subunits, quantitative immunoblots and immunocytochemistry revealed a concordance with the mRNA levels. alpha1 protein expression was approximately 50% less than controls in the Fast strain, whereas it was 200% greater in the Slow strain. In contrast, alpha5 subunit protein expression was greater in the Fast strain than either the control or Slow strain. These data suggest that a major predispositional factor in the development of temporal lobe epilepsy could be a failure to complete the normal switch from the GABAA receptor alpha subunits highly expressed during development (alpha2, alpha3, and alpha5) to those highly expressed in adulthood (alpha1).

Animals↗

PubMed1999

Transient expression of GABAA receptor subunit mRNAs in the cellular processes of cultured cortical neurons and glia.

In this study, we have studied by in situ hybridisation histochemistry the expression and intracellular distribution of the GABAA receptor subunit mRNAs in cultured neurons obtained from postnatal day 1-3 rats in order to determine how neurotransmitter receptor expression may be regulated during development of the nervous system. In postnatal cortical cells, we found that GABAA receptor subunit mRNAs coding for alpha2, alpha5, beta2, beta3 and gamma2 subunits were transiently expressed in the cellular processes and growth cones after 1-3 days in culture. These observations indicate that GABAA receptor subunit mRNAs are transported (or trafficked) into the cellular processes of early postnatal cortical cells. These selective localisations were rarely observed after 5 days in culture and only in cells which had not made cell-to-cell contact. The localisation of subunit mRNAs in the processes was more effectively maintained up to 5 days or even longer if cell-to-cell contact was avoided by culturing the cells at low density or by inhibiting neurite sprouting pharmacologically with the GABA receptor channel antagonist TBPS. Finally, immunocytochemistry revealed the expression of GABAA receptors in the growth cones of pyramidal neurons in culture. Thus, the expression of mRNA correlates to the expression of protein. These results suggest that the selective trafficking of GABAA receptor subunit mRNAs during synaptogenesis may be regulated by synapse formation and/or glial-neural communication.

Animals↗

PubMed1999

Comparison of pathological and biological features of symptomatic and mammographically detected ductal carcinoma in situ of the breast.

To determine whether the ductal carcinoma in situ (DCIS) detected mammographically or presenting clinically is the same or differs, pathological and biological (c-erbB-2 and p53 detection) features of 79 cases of pure DCIS, 5 cases with microinvasion and 8 cases with 1 to 2 mm of invasion, all detected by mammography, have been compared with 59 cases of pure DCIS, 8 cases with microinvasion and 7 cases with 1 to 2 mm invasion, all of which presented clinically. Half of the mammographically detected group were smaller than 20 mm, and there was a higher incidence of these being low grade, whereas 30% of the symptomatic cases were smaller than 20 mm, and more of this group were larger than 50 mm. For the pure DCIS, there were less high-grade and more intermediate-grade cases in the mammographically detected group, although the incidence of low grade was similar between the two groups. There were more cases with a micropapillary pattern in the symptomatic group. C-erbB-2 protein was detected in 42% of the mammographically detected cases, whereas 59% of the symptomatic cases had c-erbB-2 reactivity. P53 detection was similar for both groups (33.0% and 37.0%). There were more symptomatic cases with invasion, and these were predominantly high grade, whereas the mammographically detected cases were both high and intermediate grade. Twelve of the 15 symptomatic cases with invasion expressed c-erbB-2, in comparison with 4 of the 13 mammographically detected cases, with half of the high-grade lesions in the latter group being negative. This study has shown that although there is overlap of pathological and biological features between DCIS presenting clinically and that detected mammographically, there can be differences in extent, grade, and invasion. The impact of this, however, can be determined only by clinical follow-up.

Adult↗

PubMed1999

Neurovascular relationships in hippocampal slices: physiological and anatomical studies of mechanisms underlying flow-metabolism coupling in intraparenchymal microvessels.

Experiments were carried out to investigate the functional and anatomical relationships between neuronal elements and cerebral microvessels in 300-350-microm thick coronal hippocampal slices maintained at 33-35 degrees C, obtained from 150-200 g male Wistar rats. Cerebral arterioles (9-22 microm in diameter) were visualized in situ and pre-constricted by 22.0+/-6.6% by the addition of the thromboxane A2 agonist U46619 (75 nM), to the bathing medium. The glutamate agonist N-methyl-D-aspartate (0.01-1 mM) produced a dose-related increase in luminal diameter of pre-constricted vessels. In the presence of 4 microM haemoglobin to scavenge nitric oxide from the extravascular environment of the slice, the increase in diameter evoked by 0.1 mM N-methyl-D-aspartate was significantly reduced from 17.5+/-4.6% to 4.8+/-1.7% indicating that N-methyl-D-aspartate-induced vasodilatation of cerebral microvessels is mediated via a mechanism which involves neuronally-derived nitric oxide. In a parallel anatomical study, beta-nicotinamide adenine dinucleotide phosphate-dependent diaphorase staining was used to reveal the enzyme nitric oxide synthase in vascular endothelium and neurons in slices. A small subpopulation (< 11 cells per slice) of darkly-stained multipolar neurons, 21-32 microm in diameter was observed to give rise to a dense network of fine diaphorase-reactive nerve fibres that ramified throughout the whole of the hippocampus and appeared to come into close apposition with arterioles. Morphometric analysis of the relationship between cerebral microvessels, beta-nicotinamide adenine dinucleotide phosphate, reduced form-dependent diaphorase-reactive neuronal elements and individual pyramidal layer neurons, identified by filling with biocytin, revealed that for a given point on a pyramidal layer neuron, the proximity of the nearest diaphorase-reactive nerve fibre was less than 10 microm, whilst the distance to the nearest arteriole (the smallest functional unit for controlling blood flow) was in excess of 70 microm. Such a distance would probably preclude diffusion of vasoactive metabolites in effective concentrations from the area of increased neuronal activity. We therefore propose that the diaphorase-reactive nerve network constitutes the functional link. It is possible that during periods of increased neuronal activity, spillover of glutamate from synapses may activate the diaphorase-reactive network. Release of nitric oxide from the network in the vicinity of local cerebral arterioles may then produce relaxation of the vascular smooth muscle, enabling increased blood flow into the capillary network supplying the region of increased metabolic activity. This study has shown that the process whereby increases in neuronal activity elicit a local change in cerebral blood flow remains functionally intact in hippocampal slice preparations. Nitric oxide of neuronal origin appears to be involved in mediating the coupling between neurons and cerebral arterioles. Stereological analysis of the relationship between neuronal and vascular elements within hippocampal slices suggested that a small subpopulation of nitric oxide synthase-containing neurons which give rise to a diffuse network of fine nitric oxide synthase-containing nerve fibres that lie in close apposition to cerebral arterioles may provide the anatomical substrate for coupling of blood flow to metabolism.

Animals↗

PubMed1999

GABA(A) receptor subunit messenger RNA expression in the enteric nervous system of the rat: implications for functional diversity of enteric GABA(A) receptors.

GABAergic neurons occur in the myenteric plexus and submucosa and their innervations of the gut, where GABA stimulates motor neurons, and non-neural cells via "central type" GABA(A) receptors. These receptors occur on half of the neurons in the rat intestine. The GABA(A) receptor is a ligand-gated chloride channel constructed from different subunit families (alpha, beta, gamma, delta, epsilon). In rat these exist as subtypes, alpha1-6, beta1-3, gamma1-3 and delta, defining the clinically relevant pharmacological features of GABA(A) receptors. However, the identity, distribution, and abundance of enteric GABA(A) receptor subunits are unknown. To identify and map the regional expression of GABA(A) receptor subunit messenger RNAs in the enteric nervous system, we assayed enteric RNA from the ileum of Sprague-Dawley rats by reverse transcription-polymerase chain reaction for alpha1-6, beta 1-3, gamma1-3, and delta subunit messenger RNAs. Subunit messenger RNA localization, was probed by in situ hybridization. Reverse transcription-polymerase chain reaction analysis of RNA from myenteric and submucosal nerve layers revealed the expression alpha1, alpha3, beta2, beta3, gamma1 and gamma3 subunit messenger RNAs. Little alpha4 and alpha6 and no alpha2, beta1, gamma2 or delta subunit messenger RNA were detected. In situ hybridization revealed that transcripts for alpha1, alpha3, alpha5 and beta2 subunits occur in both myenteric and submucous ganglia. However, beta3 messenger RNA was found only in myenteric plexus. The gamma1 subunit messenger RNA was also restricted to the cells in the myenteric plexus while gamma3 was found in cells of both nerve layers. In this study of the subunit messenger RNA expression profile of GABA(A) receptors within the enteric nerve layers we show an abundant, diverse and widespread distribution that is unique in comparison to the CNS. The distinctive and heterogeneous distribution of enteric GABA(A) subunits may be important in the integration of neural control of gut function.

Animals↗

PubMed1999

Attentional demands and postural recovery: the effects of aging.

BACKGROUND: Cognitive demands associated with balance and locomotion may contribute to the incidence of falling among older adults. This study addressed issues related to the effects of aging on the attentional demands of recovering from an external disturbance to balance. This research also investigated whether performing a secondary cognitive task differentially affects postural recovery in young versus older adults. METHOD: Fifteen young and 10 healthy older adults were exposed to a series of balance disturbances. Attentional demands were assessed using a dual task paradigm where postural recovery served as the primary task, and counting backwards served as a concurrent secondary cognitive task. The effect of the counting task was assessed by comparing kinematic variables related to feet-in-place and stepping recovery strategies. RESULTS: Recovering upright stance was found to be attentionally demanding in both age groups. The type of recovery strategy did not influence attentional demands in young adults; however, a hierarchy of increasing attentional demands between the ankle strategy and compensatory stepping was apparent among older adults. In addition, stepping appears to be more attentionally demanding for older adults than for younger adults. Counting backwards did not affect the type of strategy used; however, it did affect the kinematics of stepping. For both age groups, steps occurred when the center of mass was located in a more central location within the base of support when the secondary task was added. CONCLUSIONS: The ability to recover a stable posture following an external perturbation is more attentionally demanding for older adults than for younger adults. This would suggest that for some older adults, an increased risk for loss of balance and falls may result if sufficient attentional resources are not allocated to the task of postural recovery.

Accidental Falls↗