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Biomedical subjects

W Campbell

Publications and source records attributed to W Campbell.

At least 73 records · Page 4Linked to original sources
PubMed1986

Cervical motion assessment: a new, simple and accurate method.

Accurate assessment of head motion can be a useful tool in clinical studies. Since the head moves on a combination of axes in the cervical spine, evaluation of neck motion is difficult. Assessment of cervical mobility is further complicated because of inadequate reference points on the head from which to measure. Hence, numerous methods for approximating cervical range have been devised. These methods include visual estimation, radiographic analysis, schematography, photography, and a variety of goniometer devices. Disadvantages of these techniques are lack of accuracy and objectivity, radiation exposure, expense, time consumption, and equipment availability. To measure cervical mobility, a standard gravity goniometer with spirit level and head adapter was used, which allowed stabilization. The gravity goniometer can be obtained in a variety of sizes at most hardware stores. The head adapter consists of a wood block into which an arc is carved and elastic straps suspended for securing on the head. The reliability of this instrument was tested and compared to the universal goniometer, and correlation coefficients were determined. When two experienced examiners used the universal goniometer to assess cervical motion, significant intraclass correlation coefficients (ICC) were found with three of the six criteria measures (p less than 0.05). When one experienced and one novice examiner used the gravity goniometer with head adapter, highly significant ICC values were found for all six criteria measures (p less than 0.01). A single experienced examiner comparing both instruments on the same subjects produced significant ICC values in four of the six criterion measures (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cervical Vertebrae↗
PubMed1985

Cardiovascular deconditioning produced by 20 hours of bedrest with head-down tilt (-5 degrees) in middle-aged healthy men.

Cardiovascular deconditioning after prolonged bedrest has been attributed to inactivity. To examine the role of the altered distribution of body fluids, 5 healthy men, aged 41 to 48 years, were studied before, during and after a 20-hour period of bedrest with head-down tilt (-5 degrees). This intervention produces a marked central shift of intravascular and interstitial fluid, but the short duration minimizes the effects of inactivity. Central venous pressure, cardiac output and stroke volume all increased significantly (p less than 0.05) from supine baseline mean values; central venous pressure from 8.6 to 12.6 cm H2O, cardiac output from 6.9 to 7.9 liters/min, and stroke volume from 104 to 113 ml after 15 minutes of tilt, but all values returned to baseline within 20 hours. Supine central venous pressure after tilt was 7.4 cm H2O, cardiac output 5.7 liters/min and stroke volume 84 ml. Blood volume decreased 0.51 liters. After tilt, orthostatic stress produced a higher heart rate (90 +/- 18 vs 68 +/- 12 beats/min). Maximal oxygen consumption decreased (2.36 +/- 0.41 vs 2.62 +/- 0.48 liters/min), mainly owing to reduced stroke volume (87 +/- 22 vs 107 +/- 18 ml, p less than 0.05). Thus, tilt produced a transient increase in central venous pressure, stroke volume and cardiac output, but supine mean values were below baseline levels after 20 hours. The post-tilt state was qualitatively and quantitatively similar to that seen after 2 to 3 weeks of bedrest or several days of spaceflight. These results are also similar to those from a previously studied group of ten 20- to 30-year-old normal men.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1985

Dopamine autoreceptors and the effects of drugs on locomotion and dopamine synthesis.

Criteria for distinguishing dopamine autoreceptor agonism from other mechanisms of inhibiting locomotion were examined, together with the relationship between inhibition of locomotion and dopamine synthesis. ED50 potencies to inhibit locomotion of mice were established for drugs from a number of categories. Spiperone 0.02 mg kg-1 significantly (P less than 0.05) reversed inhibition of locomotion by known dopamine agonists but not that by the other types of drug. Idazoxan antagonized inhibition of locomotion due to alpha 2-agonists but not dopamine agonists. RU 24926 (N-propyl-N,N-di[2-(3-hydroxyphenyl)ethyl]amine) was antagonized by both spiperone and idazoxan. Only for dopamine agonists was there good correlation (r = 0.97) between potencies to inhibit locomotion in mice and L-dihydroxyphenylalanine (L-DOPA) accumulation in the nucleus accumbens of rats treated with gamma-butyrolactone and 3-hydroxybenzylhydrazine. The specific dopamine D1-agonist, SK&F 38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine), was inactive in both tests at doses up to 10 mg kg-1. The mixed dopamine agonist/antagonist, (-)-3-(3-hydroxyphenyl)-N-propylpiperidine, commonly known as (-)-3-PPP, acted as a dopamine agonist in both tests but inhibited locomotion more potently than L-DOPA accumulation. The inhibitory effects of dopamine agonists on locomotion were not prevented by alpha-methyl-p-tyrosine pretreatment. The data suggest that spiperone-reversible inhibition of locomotion in mice is a good criterion for dopamine autoreceptor agonists. The receptors involved are affected by low doses of both dopamine agonists and antagonists and seem similar to those involved in the autoreceptor mediated inhibition of dopamine synthesis. However, inhibition of locomotion is not due simply to suppression of dopamine release brought about as a secondary consequence of effects on synthesis; a separate mechanism for inhibiting dopamine release is probably involved.

Animals↗
PubMed1984

Distribution of P2 antigen in neural and non-neural bovine tissues.

Rabbit antisera to bovine nerve preparations were used to study the tissue distribution in the ox of P2, an antigen specific for the peripheral nervous system. Double diffusion gel precipitation tests were able to demonstrate P2 in spinal nerves, trigeminal nerve, spinal cord, medulla oblongata, and pons, but not in higher centers of the CNS, optic nerve, or non-neural tissues. A highly sensitive inhibition of enzyme immunoassay was developed to detect and quantitate low levels of P2. By this assay, P2 was found to be most concentrated in peripheral nerves, with decreasing amounts found in the spinal cord, medulla oblongata, pons, cerebellum, and cerebral peduncle. No P2 was found in the thalamus, cerebrum, or optic nerve; however, low levels of P2 were detected in the adrenal medulla, a non-neural tissue composed largely of cells derived from the embryonic neural crest region.

Adrenal Medulla↗
PubMed1982

Detection of invasiveness of mammalian cells by Escherichia coli: collaborative study.

In a collaborative study of 2 standard procedures (Procedure I, presented in J. Assoc. Off. Anal. Chem. 60, 546-562 (1977) and Procedure II in the Bacteriological Analytical Manual, 1978), 7 laboratories evaluated the invasive potential of Escherichia coli. Monolayers of HeLa cultures were infected with E. coli (infectivity ratio 100 bacteria/mammalian cell) suspended in 2 menstrua: heat-inactivated fetal bovine serum (Procedure I) and 0.2% bovine albumin Fraction V dissolved in Earle's buffered salts (Procedure II). After uptake of the bacteria, intracellular growth, and differential staining, the percentages of HeLa cells containing a minimum of 5 bacteria were determined microscopically. All laboratories correctly identified invasiveness of E. coli by Procedure I; 5 of 6 laboratories recognized invasiveness by Procedure II. Although Procedure I was more reproducible than Procedure II, repeatability did not differ significantly. Procedure I was adopted official first action for presumptive recognition of invasiveness in E. coli.

Bacteriological Techniques↗
PubMed1979

Constriction of the fetal ductus arteriosus after administration of indomethacin to the pregnant ewe.

The prostaglandin synthetase inhibitor indomethacin was given orally or intravenously to pregnant ewes. This resulted in the fetal pulmonary to systemic arterial mean blood pressure difference across the ductus arteriosus rising significantly, presumably secondary to constriction of the ductus arteriosus. The pressure difference was due to pulmonary arterial hypertension, and not due to a fall in systemic arterial mean blood pressure. Fetal arterial blood gas tensions and pH values were normal throughout. In five experiments the pressure difference could be promptly but temporarily reversed by the administration of PGE1 into the fetal inferior vena cava. Indomethacin was present in fetal blood, and maternal plasma prostaglandin levels were suppressed. Indomethacin administration during pregnancy causes constriction of the fetal ductus arteriosus and fetal pulmonary arterial hypertension which, if severe, may cause rapid fetal death. It is possible that this mechanism may be one cause of persistent pulmonary hypertension or tricuspid insufficiency or both in the newborn infant.

Animals↗
PubMed1979

Autonomic dysfunction in women with mitral valve prolapse syndrome.

Autonomic cardiovascular regulation was evaluated in 35 women, 19 with mitral valve prolapse and 16 healthy controls. Heart rate responses to the diving reflex and to phenylephrine infusion were diminished in patients. Noninvasive measures of cardiac output, heart rate, blood pressure, forearm flow and leg volume during lower body negative pressure (LBNP) showed that patients had less lower extremity pooling of blood and had lower forearm conductance. Blood pressures during LBNP rose or remained unchanged despite decreases in cardiac output of 20--25%. These data indicate that mitral valve prolapse patients have an increased venous and arterial vasoconstrictor activity. Cardiac output at rest and echocardiographic indices of contractility were normal. Patients with a history of significant ventricular arrhythmias had higher heart rates and lower forward stroke volumes than the other patients or controls. The combined data demonstrate autonomic dysfunction in women with the mitral valve prolapse syndrome and suggest decreased parasympathetic, increased alpha- and normal beta-adrenergic tone and responsiveness.

Adult↗
PubMed1978

The pharmacokinetics of slow-release procainamide.

Procainamide was given to 20 patients with normal renal function as an i.v. bolus of 500 mg followed by 1.0 or 1.5 g eight-hourly by mouth in the form of a slow release preparation (Durules). 97.6 +/- 27.1 (SD)% of the oral procainamide was absorbed, the absorption half life being 1.54 h. The elimination half life following the oral formulation was 6.0 +/- 0.8 h, compared to a mean of 3.4 +/- 0.4 h following i.v. administration. Elimination half life following i.v. administration was slightly related to acetylator status, being 2.75 +/- 0.9 h in fast acetylators, and 4.4 +/- 2.4 h in slow acetylators. This dependence on acetylator status was not seen in half life following oral administration. Total body clearance, steady state plasma procainamide and N-acetylprocainamide were not significantly dependent on acetylator status, although a few patients who are slow acetylators had unexpectedly low clearance and high steady state procainamide concentrations when given the higher dose.

Biological Availability↗
PubMed1978

Role of cardiac output in the pressor responses to graded muscle ischemia in man.

Ten men repeatedly performed leg exercise (100-150 W) for 7 min with 30-min recovery periods interspersed. Both legs were made ischemic by total occlusion (OCCL), first for 3 min immediately after exercise and second for 30 s before exercise ended and 3 min into recovery. In addition legs were occluded for 3 min at rest (seated). OCCL at rest increased mean arterial pressure (MAP) by 9 Torr but did not affect cardiac output (CO) or heart rate (HR). OCCL at the end of exercise significantly raised MAP and HR above control values during 3-min recovery but CO was unaffected. OCCL 30 s before the end of exercise further increased MAP and HR significantly during recovery; MAP, CO, and HR were significantly increased above control values (CO by 2.1 1-min-1) during the 3rd min of recovery. We conclude that a strong reflex from ischemic legs maintains normal or elevated CO during leg OCCL. Thus CO was too high relative to total vascular conductance so that MAP was elevated.

Blood Pressure↗