Biomedical subjects
Publications and source records attributed to J M Walker.
A 41-year-old man who habitually slept in a car park presented with a culture-negative endocarditis. Serological tests indicated infection with both Coxiella burneti and Chlamydia psittaci. He was treated with doxycycline and clindamycin and required aortic valve replacement. Culture of the excised value for both agents was negative but electron microscopy was suggestive of coxiella endocarditis.
Clinicians continue to focus attention on the sacroiliac joint (SIJ) as one cause of low back pain. Considerable literature now exists to support the contention that symptoms arise from the sacroiliac region. In the last couple of decades, studies with quantitative data, often using sophisticated methods, have added to our knowledge from earlier descriptive reports of SIJ morphology and motion. The unique morphology of the SIJ, together with its location, makes study of the SIJ complex. All reported studies have limitations such as small sample size or lack of randomization or methodology. The purpose of this article is to review the literature to determine the support for current beliefs, opinions, and theories on joint morphology, life-span changes, and motion. Clinicians should provide well-documented clinical case-study series if we are to understand what occurs with treatments designed to affect the SIJ.
The effect of transtracheal oxygen administration by means of a 9-French (2.7 mm) percutaneous catheter was assessed in five patients with severe obstructive sleep apnea. We hypothesized that the delivery of oxygen below the site of airway obstruction should reduce the arterial oxygen desaturation during apneas and hypopneas, thereby increasing respiratory stability. Standard sleep and respiratory measurements were recorded in these subjects with all-night polysomnography on nonconsecutive nights during four experimental conditions: room air (BL), nasal continuous positive airway pressure (CPAP), nasal O2 (NC O2), and transtracheal O2 (TT O2). In three of these subjects, room air was infused (TT RA) at flow rates comparable to TT O2. Compared with baseline room air measurements, TT O2 not only significantly increased the SaO2 nadir from 70.4 percent to 89.7 percent (p less than 0.01), but it also reduced the frequency of sleep apnea/hypopnea from 64.6 to 26.2/h sleep (p less than 0.01). NC O2 ameliorated desaturation during apnea/hypopnea (mean SaO2 nadir, 86.2 percent; p less than .01) but did not significantly alter frequency (59.0/h sleep). Nasal CPAP was the most effective means of reducing sleep apnea/hypopnea (13.8/h sleep) but did not abolish desaturations when apneas occurred (mean SaO2 nadir, 80.0 percent). Compared with oxygen, transtracheal infusion of room air appeared to be somewhat effective; however, the small number of studies with TT RA precluded statistical analysis. We believe that TT O2 is superior to NC O2 for some patients with obstructive sleep apnea because continuous oxygen flow below the site of airway obstruction more reliably prevents alveolar hypoxia and respiration is stabilized. Infusion of air or oxygen through the tracheal catheter flow may also increase mean airway pressure and reduce obstructive apnea similar to nasal CPAP. We conclude that TT O2 may be an effective alternative mode of therapy for some patients with severe sleep apnea/hypopnea when nasal CPAP is not tolerated or when combined oxygen and nasal CPAP are required.
A novel class of compounds with very high affinity and selectivity for sigma receptors has been discovered. BD614 [(+/-)-cis-N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1- pyrrolidinyl)cyclohexylamine] and its optically pure 1S,2R-(-)-[BD737] and 1R,2S-(+)-[BD738]enantiomers bound to sigma receptors of guinea pig brain with Ki = 2.0 +/- 0.4, 1.3 +/- 0.3 and 6 +/- 3 nM, respectively. These compounds exhibited little or no affinity for dopamine-D2, kappa opiate or phencyclidine receptors and displayed high biological efficacy in assays of sigma receptor function, ability to produce alterations in motor behavior and inhibition of the muscarinic cholinergic phosphoinositide response. Microinjection of BD614 into the rat red nucleus or substantia nigra produced a dose-dependent alteration in head position and contralateral circling, respectively. BD614, BD737 and BD738 inhibited stimulation of inositol phosphate production by carbachol or oxotremorine-M in a dose-dependent manner. Thus, N-substituted cis-2-(1-pyrrolidinyl)cyclohexylamines may prove useful in studies of sigma receptor structure and function.
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Dobutamine has favorable properties for the pharmacologic manipulation of myocardial oxygen demand in the provocation of ischemia during the investigation of coronary artery disease. The value of dobutamine infusion for thallium myocardial perfusion tomography was assessed in 50 patients with exertional chest pain undergoing coronary arteriography. Dobutamine was infused in 5-min stages at incremental rates from 5 to 20 micrograms/kg per min or until limited by symptoms. The myocardium was divided into nine segments for analysis of perfusion. Thirty-nine of 40 patients with coronary artery disease had a reversible perfusion defect demonstrated by dobutamine thallium tomography (sensitivity 97%) and 8 of 10 patients with normal coronary arteries had normal myocardial perfusion (specificity 80%). These values were significantly better than the sensitivity and specificity of exercise electrocardiography (78% and 44%, respectively; p less than 0.01). There was a significant relation between the mean number of segments with abnormal perfusion and the number of diseased coronary vessels (0.6, 2.6, 4.4 and 6 segments in zero-, one-, two- and three-vessel disease, respectively; p less than 0.001). There was also a significant relation between the maximal tolerated dose of dobutamine and the treadmill exercise time (r = 0.56, p less than 0.001), but a wide range of exercise times was achieved in the 15- and 20-micrograms/kg per min groups, principally because of exercise limitation by noncardiac symptoms. Dobutamine infusion was well tolerated in all patients, including six with asthma. There were no significant arrhythmias or limiting symptoms other than chest pain.(ABSTRACT TRUNCATED AT 250 WORDS)
The role of the red nucleus (RN) in nociception was investigated in this study. Extracellular recordings from spontaneously active RN neurons were conducted in the rat while noxious pressure was delivered to the hindpaws or tail. Cells in the RN were predominantly inhibited by the stimuli. The units were most responsive when noxious pressure was applied to the contralateral hindpaw. Furthermore, more cells in the magnocellular division of the RN responded to the stimuli than cells in the parvocellular division. Delivery of a graded pressure stimulus to the contralateral hindpaw revealed 4 cell types in the RN: non-responsive cells; cells only responsive during the early, non-noxious portion of the stimulus; cells only responsive during the later, noxious portion of the stimulus; and cells that showed an initial response during the non-noxious part of the stimulus and a second, later response during the noxious portion of the stimulus. To further examine the putative role of the RN in nociception, oxotremorine, gamma-aminobutyric acid (GABA), serotonin, glutamate, and morphine were unilaterally microinjected into the RN and the responses of the animals in the tail flick test were assessed. Only morphine produced a significant antinociception in the animals following intrarubral microinjection. However, it is unclear whether this alteration was mediated through the RN because an antinociception of equal magnitude could be elicited from the reticular formation surrounding the RN and lesions of the RN did not alter the antinociception produced by systemic administration of morphine. Although other explanations cannot be ruled out, it appears that the RN may be involved in coordinating the motor response to pain rather than modulating sensory transmission.
Cloned trypanosomal calmodulin was expressed in Escherichia coli and purified to homogeneity using hydrophobic interaction chromatography on phenyl-Sepharose. The purified protein was subjected to NMR analysis which allows detailed changes to be observed when, firstly, calcium, and secondly, the drug calmidazolium bind. These spectral changes are the result of conformational changes in the protein and proximity effects due to the drug.
Rats were treated twice daily either with saline or d-amphetamine (5 mg/kg) for 5 days. When challenged approximately 15 days later with an injection of 0.5 mg/kg amphetamine, the chronic amphetamine animals showed (1) an augmented release of dopamine in the caudate nucleus in vivo and (2) an increase in stereotyped behavior compared to the chronic saline animals. These results suggest that an increase in dopamine release from the caudate may contribute to amphetamine-induced behavioral sensitization.
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The early development of the limbs, the skeletal and muscular systems, and the joints and early changes in joint mobility are reviewed. The musculoskeletal system is vulnerable to failures of specific morphogenetic processes in the embryonic period. Congenital anomalies and postural deformities also may arise in the fetal period. Awareness of prenatal and postnatal events and their timing will assist health care workers in management of pediatric clients.
This study deals with age changes in the anulus fibrosus of the lumbar intervertebral discs of human individuals 21-83 years of age. The anular laminas from individuals less than 40 years of age consisted of obliquely orientated collagen fibers exhibiting a pennate arrangement. These fibers were intensely argyrophilic after silver nitrate impregnation. The fibers and surrounding substance appeared light pink after exposure to the periodic-acid-Schiff (PAS) reaction and blue with alcian blue complex. Beginning during middle age and continuing into the eighth decade, there was a progressive degeneration of the laminas. The breakdown of the intact laminas was characterized by the fraying, splitting, and loss of collagen fibers. The newly formed spaces became filled with intense PAS-positive material. In addition, there was a continual deposition of chondroid substance in the anuluses of the aging discs. This phenomenon was not seen in the young disc. These age related changes lead to a loss of integrity to the disc, which may be a factor in disc pathology.
Two hundred and one whiptail lizards, Cnemidophorus spp., from Texas and Colorado (USA), were examined for Mesocestoides sp. tetrathyridia. Eleven (5%) were infected, including three of 58 (5%) C. dixoni, six of 70 (9%) C. gularis septemvittatus, one of 35 (3%) C. marmoratus, and one of 34 (3%) C. tesselatus; four C. inornatus heptagrammus were not infected. In addition, 41 non-cnemidophorine lizards from the same study area were not infected. Free tetrathyridia were found in the body cavity of lizards and encapsulated tetrathyridia were observed in the heart, liver, stomach, mesenteries, ovaries, intestines, and lungs. None of the Mesocestoides sp. exhibited any evidence of asexual proliferation such as multiple scoleces or buds. This note, the fifth in a series of reports on helminths of Cnemidophorus spp., represents the first time Mesocestoides sp. has been reported from these four taxa, and Colorado is a new geographic locality record for this parasite.
The case of a 12-year-old girl with retroperitoneal fibrosis and a horseshoe kidney is presented. This is a relationship that has not previously been described. An in-depth review of the literature of childhood retroperitoneal fibrosis is undertaken with accompanying discussion on the etiology, symptoms, pathology, radiographic findings, treatments and prognosis of the disease.
41 short normal children were randomly allocated either to daily injections of growth hormone (rhGH) at 30 IU/m2 per week or to no treatment. 6 months of rhGH therapy produced up to 76% loss of fat mass and up to 25% increase in lean body mass (LBM). These changes were significantly different from those in the untreated group. LBM was the main determinant of resting energy expenditure (REE) expressed as kJ/24 h. REE expressed as kJ/kg LBM per 24 h correlated negatively with height, which was responsible for 66% of the variance in REE kJ/kg LBM per 24 h. Short children therefore expend more energy than tall children in fulfilling basic metabolic needs. After 6 months REE kJ/24 h increased significantly in treated children. However, treated children did not differ significantly from untreated children in REE kJ/kg LBM per 24 h. rhGH does not therefore seem to have a specific effect upon REE. The possibility that rhGH produces profound metabolic effects should limit its use in otherwise healthy children until the mechanism of action is more clearly elucidated.