PubMed Health⌕ Search

Biomedical subjects

J Simmons

Publications and source records attributed to J Simmons.

14 recordsLinked to original sources
PubMed1992

Electrophysiological effect of the maze procedure on canine sinoatrial node function.

The maze procedure is an operation that has had great initial success in curing atrial fibrillation. This procedure includes several right atrial incisions that may interrupt the integrity of the sinoatrial node or its arterial supply. To assess the effect of the maze procedure on sinus node function (SNF), the following studies were performed: sinus node recovery times (SNRT), corrected SNRT (CSNRT), CSNRT under autonomic blockade maximal heart rate and intrinsic heart rates. Thirty-four dogs underwent a right thoracotomy with cardiopulmonary bypass (CPB). The dogs were divided into three groups. Group 1 (n = 9), the sham group, underwent CPB without any incisions. Group 2 (n = 8) underwent CPB and one of the right atrial incisions. Group 3 (n = 18) underwent CPB and all three of the right atrial incisions. SNF was determined before and after the procedure. Groups 1 and 2 had no significant difference in measured SNF acutely after the procedure. In Group 3 the mean SNRT increased from 552 msec to 1,984 msec (P = 0.005). Sinus node dysfunction was corroborated by all studies. In the chronic studies, a trend toward recovery of SNF was observed. The maze procedure results in significant acute sinus node dysfunction. This dysfunction may resolve spontaneously over the ensuing months. Modifications of the maze procedure that avoid the sinus node or its blood supply area may reduce procedure related sinus node dysfunction.

Animals↗
PubMed1992

From obstructive sleep apnea syndrome to upper airway resistance syndrome: consistency of daytime sleepiness.

Some patients with excessive daytime sleepiness who do not present the features of obstructive sleep apnea syndrome (OSAS) present a sleep fragmentation due to transient alpha EEG arousals lasting between three and 14 seconds. These transient EEG arousals are related to an abnormal amount of breathing effort, indicated by peak inspiratory esophageal pressure (Pes) nadir. In the studied population, these increased efforts were associated with snoring. Usage of nasal CPAP, titrated on Pes nadir values, for several weeks eliminated subjective daytime sleepiness and improved Multiple Sleep Latency Test scores from baseline evaluations. Patients suspected of CNS hypersomnia should be asked about continuous snoring, and their clinical evaluation should include a good review of maxillo-mandibular and upper airway anatomy.

Airway Obstruction↗
PubMed1989

Non-Alzheimer-type pattern of brain cholineacetyltransferase reduction in dominantly inherited olivopontocerebellar atrophy.

We recently reported reduced activity of the cholinergic marker enzyme cholineacetyltransferase (ChAT) in several brain regions of patients with dominantly inherited olivopontocerebellar atrophy (OPCA). To document the regional extent of these changes we performed a comprehensive examination of the behavior of ChAT throughout both cerebral cortical and subcortical brain areas in 5 patients from one large OPCA pedigree. As compared with the controls, mean ChAT activities in OPCA were reduced by 39 to 72% in all (n = 27) cerebral cortical areas examined and in several thalamic subdivisions, caudate head, globus pallidus, red nucleus, and medial olfactory area. In contradistinction to findings in Alzheimer's disease (AD), mean ChAT levels in OPCA amygdala and hippocampal subdivisions were either normal or only mildly reduced. The lack of severe disabling dementia in our OPCA patients compared with AD patients having a similar cortical cholinergic reduction could be explained by an absence of either a marked cholinergic loss in amygdala or hippocampus or significant loss of noncholinergic cerebral cortical and limbic neurons as occurs in AD brain. We suggest that this and other OPCA pedigrees having a cortical cholinergic reduction represent a unique model for the study of behavioral consequences of a more selective cerebral cortical cholinergic lesion rather than a limbic cholinergic lesion.

Adult↗
PubMed1988

Brain acetylcholinesterase activity is markedly reduced in dominantly-inherited olivopontocerebellar atrophy.

The activity was measured of the acetylcholine catabolising enzyme acetylcholinesterase (AChE) in brain after necropsy of seven patients from one established pedigree with dominantly-inherited olivopontocerebellar atrophy (OPCA), a cerebellar ataxia disorder in which neuropathological changes are assumed to be primarily restricted to cerebellum, lower brain stem and spinal cord. Mean AChE activity was significantly reduced in cerebral (-51% to 65%) and cerebellar (-47%) cortex with a less severe change (-37%) in the hippocampus. The magnitude of the enzyme reduction in cerebral cortex was equal to or greater than that reported in brain of demented Alzheimer's and Parkinson's disease patients having loss of AChE-containing nucleus basalis cholinergic neurons. It is concluded that the data provide additional biochemical evidence suggesting a cerebral cortical cholinergic denervation in OPCA.

Acetylcholinesterase↗
PubMed1985

Construction of the mycoplasma evolutionary tree from 5S rRNA sequence data.

The 5S rRNA sequences of eubacteria and mycoplasmas have been analyzed and a phylogenetic tree constructed. We determined the sequences of 5S rRNA from Clostridium innocuum, Acholeplasma laidlawii, Acholeplasma modicum, Anaeroplasma bactoclasticum, Anaeroplasma abactoclasticum, Ureaplasma urealyticum, Mycoplasma mycoides mycoides, Mycoplasma pneumoniae, and Mycoplasma gallisepticum. Analysis of these and published sequences shows that mycoplasmas form a coherent phylogenetic group that, with C. innocuum, arose as a branch of the low G+C Gram-positive tree, near the lactobacilli and streptococci. The initial event in mycoplasma phylogeny was formation of the Acholeplasma branch; hence, loss of cell wall probably occurred at the time of genome reduction to approximately to 1000 MDa. A subsequent branch produced the Spiroplasma. This branch appears to have been the origin of sterol-requiring mycoplasmas. During development of the Spiroplasma branch there were several independent genome reductions, each to approximately 500 MDa, resulting in Mycoplasma and Ureaplasma species. Mycoplasmas, particularly species with the smallest genomes, have high mutation rates, suggesting that they are in a state of rapid evolution.

Base Sequence↗
PubMed1978

Lack of visualization of the portal venous tree in cirrhosis of the liver: a computed tomography finding with possible diagnostic significance.

During computed tomography (CT) scanning of the liver, the inferior vena cava can be identified as a separate structure of lesser density adjacent to the caudate lobe in two-thirds of patients without known hepatocellular disease. In patients with alcoholic (portal) cirrhosis of moderate to severe degree, intrahepatic portal veins may not be identified on CT scans, even though their inferior vena cavas can be definitely distinguished from the caudate lobe. Portal cirrhosis causes distortion and obliteration of the portal triads, which is presumably reflected by lack of visualization of intrahepatic portal veins during CT scanning.

Humans↗
PubMed1975

Responses to cold in the midbrain sonar center of hibernating and tropical bats.

The central gray matter of the bat midbrain, when electrically stimulated, causes the animal to produce a string of species-specific biosonar cries. Changes in this response with progressive cooling were studied in tropical homeothermic bats and in temperate hibernating bats. The species of hibernators chosen often move between hibernacula in the winter, flying and echolocating at low body temperatures (Tb). It was found that the midbrain "sonar center" exhibits a differential response to cooling that depends on the thermal propensities of the animal and its natural environment. Tropical bats followed a Q10 similar to that reported for other nonhibernating mammals and ceased responding at Tb 14-15 degrees C. Temperate zone-hibernating bat brains showed a relative insensitivity to temperature change and still responded at Tb 4-5 degrees C. Individual sonar cries within a string showed that duration was correlated with temperature but amplitude was unaffected. The study provides data for the functional separation of some parameters of biosonar and gives further evidence for differential nervous function in eurythermal versus stenothermal animals.

Adaptation, Physiological↗
PubMedDate not supplied

High performance liquid chromatographic analysis of six conjugated and unconjugated estrogens in serum.

Six estrogens-estrone, equilin, estradiol, sodium estrone sulphate, sodium equilin sulphate and sodium 17-alpha-dihydroequilin sulphate in dog serum were successfully separated and quantified by a high performance liquid chromatographic method developed in our laboratories. The mobile phase was optimized by studying the effects of an organic modifier (acetonitrile) and an ion pairing reagent (tetrabutylammonium hydroxide). The serum sample work-up procedure was designed to recover both conjugated and unconjugated estrogens. The optimum method involved acetonitrile to precipitate serum proteins/peptides and extract estrogens. Residues were reconstituted in 50% acetonitrile in water for injection. The detection limits for these six estrogens via UV detection ranged from 0.5 to 5 ng on-column with a signal-to-noise ratio (S/N) of 10 for a 20 microL injection and via fluorescence 0.1 ng on-column for 17-beta-estradiol. Validation data are included for all six estrogens.

Acetonitriles↗