Biomedical subjects
Publications and source records attributed to J M Johnson.
The author describes the process used to develop a patient classification system in a large multi-specialty ambulatory care facility. The process involved identifying critical indicators for each specialty area, validating the instruments, and calculating the workload. The approach to sampling and the problems encountered for relatively short visits are discussed.
Skin blood flow (SkBF) in humans is controlled by a noradrenergic active vasoconstrictor system and an active vasodilator system of an uncertain neurotransmitter. Understanding how these systems interact would be aided if the vasodilator system could be studied in the absence of effects of the vasoconstrictor system. To accomplish this we combined laser-Doppler velocimetry (LDV) with the local iontophoresis of bretylium in 10 studies with eight healthy subjects. Each subject had two forearm sites (0.64 cm2) treated with bretylium to block local norepinephrine release. LDV was monitored at those sites and at two untreated sites during 3-4 min of cold stress, 35-45 min of heat stress, and a final cold stress to verify blockade. In five studies, local temperature was raised to 39 degrees C at the LDV sites before the final cold stress. Whole body skin temperature was controlled by water-perfused suits. Mean arterial pressure (MAP) was measured noninvasively. Heart rate and internal temperature were also recorded. Cutaneous vascular conductance (CVC) was calculated as LDV/MAP. During the initial cold stress, performed 130 min after bretylium treatment, CVC at treated sites fell by an average of 0.3 +/- 3.2% (P greater than 0.10) and at untreated sites by 29.2 +/- 4.1% (P less than 0.001 between sites). During heat stress, CVC at treated sites rose by 419 +/- 66% and at control sites, by 517 +/- 90% (P greater than 0.10 between sites). The internal temperature threshold for cutaneous vasodilation was not statistically different between sites (P greater than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)
The role of thermoregulatory background in the baroreceptor reflex control of the tail circulation was investigated 1) in anesthetized rats with a constant flow technique and 2) in conscious rats by measuring tail blood flow (venous occlusion plethysmography). In series I, during normothermia, systemic intravenous phenylephrine infusion increased mean arterial pressure (MAP) by 61.0 +/- 3.6 mmHg and induced a reflex decrease in tail perfusion pressure (TPP) from 105.0 +/- 6.3 to 84.2 +/- 4.4 mmHg (P less than 0.005). Hyperthermia decreased TPP to 66.5 +/- 5.1 mmHg (P less than 0.001) and abolished the TPP response to increased MAP (P greater than 0.05). Increases in MAP via systemic infusion of whole blood caused reductions in TPP during normothermia but failed to reduce TPP further during hyperthermia. Graded decreases in MAP during both normothermia and hyperthermia caused tail vasoconstriction. The increase in TPP was greater (P less than 0.025) during hyperthermia. In series II, conscious animals showed similar responses to hemorrhage. Graded decreases in MAP produced graded decreases in tail vascular conductance (TVC, ml.100 ml-1.min-1.100 mmHg-1). The slope of the TVC-MAP relationship averaged 0.011 +/- 0.003 TVC U/mmHg during normothermia and was markedly steeper (P less than 0.01) during hyperthermia (1.99 +/- 0.39 TVC U/mmHg). Thus the participation of the cutaneous vasculature of the rat in baroreceptor reflexes depends on thermal status, probably through the level of background sympathetic vasoconstrictor nerve activity.
Cutaneous vascular responses to dynamic exercise have been well characterized, but it is not known whether that response pattern applies to isometric handgrip exercise. We examined cutaneous vascular responses to isometric handgrip and dynamic leg exercise in five supine men. Skin blood flow was measured by laser-Doppler velocimetry and expressed as laser-Doppler flow (LDF). Arterial blood pressure was measured noninvasively once each minute. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure. LDF and CVC responses were measured at the forearm and chest during two 3-min periods of isometric handgrip at 30% of maximum voluntary contraction and expressed as percent changes from the preexercise levels. The skin was normothermic (32 degrees C) for the first period of handgrip and was locally warmed to 39 degrees C for the second handgrip. Finally, responses were observed during 5 min of dynamic two-leg bicycle exercise (150-175 W) at a local skin temperature of 39 degrees C. Arm LDF increased 24.5 +/- 18.9% during isometric handgrip in normothermia and 64.8 +/- 14.1% during isometric handgrip at 39 degrees C (P less than 0.05). Arm CVC did not significantly change at 32 degrees C but significantly increased 18.1 +/- 6.5% during isometric handgrip at 39 degrees C (P less than 0.05). Arm LDF decreased 12.2 +/- 7.9% during dynamic exercise at 39 degrees C, whereas arm CVC fell by 35.3 +/- 4.6% (in each case P less than 0.05). Chest LDF and CVC showed similar responses.(ABSTRACT TRUNCATED AT 250 WORDS)
Calcium metabolism has been reported to be disturbed in some forms of affective disorder. We studied concurrently a battery of calcium measures in 29 unipolar, 14 bipolar depressed, 11 manic, and 10 healthy control subjects. In addition to measures of extracellular calcium, we studied intracellular calcium concentration in platelets and measures that reflect cellular capability to maintain a low intracellular Ca++ concentration in red blood cells (RBCs) and platelets. Plasma calcium was lower in unipolar and manic patients than in control subjects. Platelet calcium concentration was lower in unipolar than bipolar depressed patients. RBC Ca++ adenosine triphosphatase (ATPase) was lower in unipolar and control subjects than in bipolar depressed and manic patients. Platelet Ca++ ATPase and Ca++ uptake were inversely correlated with severity of illness in unipolar patients. In bipolar depressed patients, RBC Ca++ ATPase and platelet Ca++ uptake were inversely correlated with severity. In addition to indicating abnormalities in calcium activity in affective disorders, the data suggest that unipolar and bipolar patients differ in several measures and may have different pathophysiological disturbances in calcium metabolism.
This paper describes a method for routinely checking the accuracy of individual cerrobend compensators made for use with the Varian Clinicomp-100. The Reduction Ratios (for a given beam energy) are provided for select depth of compensation and field size. It is important to check each compensator before commencing treatment to identify possible operation error and ensure proper filling of the styrofoam with cerrobend. This verification process involves: (1) choosing several points at which the tissue deficit is known; (2) exposing a ready-pack film (Kodak XV-2) in a polystyrene phantom at a suitable depth, both with and without the compensator in place (the dose to which the film is exposed is within the initial linear range of the H and D curve); (3) determining the optical density at the above chosen points; and (4) comparing the O.D. ratios corresponding to the compensated and uncompensated conditions to the Tissue Maximum Ratios (TMRs) for the proper depths at these points. The method of this technique is also incorporated into the quality control check of other compensators, for example, acrylic, brass c-wedges, etc.
Neurochemistry of the base and body of the rat urinary bladder was compared for both adrenergic and cholinergic parameters using Fischer 344 rats. In bladder base and body, respectively, the concentration (pmol./mg. wet weight) of norepinephrine was 23.4 and 2.16, of acetylcholine was 26.7 and 18.3, and of choline was 96.7 and 199. The activity (nmol./mg. protein/hour) of tyrosine hydroxylase was 422 and less than 50, of monoamine oxidase was 80.6 and 126, of choline acetyltransferase was 17.4 and 11.5, and of acetylcholinesterase (nmol./mg. wet weight/hour) was 485 and 165. Treatment with alpha-methyl-p-tyrosine did not alter norepinephrine concentration in bladder base but decreased it by 27% in bladder body. Studies were also done to determine whether age-related changes exist in the adrenergic and cholinergic neurochemistry of the rat urinary bladder. Bladders from rats of 6-7, 15-17, and 22-24 mo. of age were examined. The only age-related differences noted were a progressive decrease in level of monoamine oxidase activity in both bladder regions and an increase in bladder base norepinephrine concentration from 6-7 to 15-17 mo. followed by a decrease at 22-24 mo. Overall, the results show marked regional variations in bladder neurochemistry which remain remarkably stable as the animals grow old.
In 1982, the Centers for Disease Control, the Food and Drug Administration, and the manufacturer created a surveillance system to monitor spontaneous reports of adverse events occurring after inoculation with the new plasma-derived hepatitis B vaccine (Heptavax-B, Merck Sharp and Dohme, West Point, PA). In the three years between June 1, 1982 and May 31, 1985, an estimated 850,000 persons received the vaccine. During that period, a total of 41 reports were received for one of the following neurologic adverse events: convulsions (five cases), Bell's palsy (10 cases), Guillain-Barré syndrome (nine cases), lumbar radiculopathy (five cases), brachial plexus neuropathy (three cases), optic neuritis (five cases), and transverse myelitis (four cases). Half of these occurred after the first of three required vaccine doses. There were no deaths. Calculation of the relative risks of these illnesses after hepatitis B vaccination was highly dependent on diagnostic classification of the cases, estimates of the size of the vaccinated population, background incidence of the diseases, and the length and distribution of the hypothetical at-risk interval used in the analysis. Other factors important in judging the results of the study could not be measured, including underreporting. In some analyses, Guillain-Barré syndrome was reported significantly more often than expected (p less than 0.05, Poisson probability distribution). However, no conclusive epidemiologic association could be made between any neurologic adverse event and the vaccine. Even if such an association did exist, the preventive benefits of the vaccine in persons at high risk for hepatitis B would unequivocally outweigh the risk of any neurologic adverse event.
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Biophysical profile scoring was the principal technique of antepartum fetal surveillance in 238 well-controlled diabetic pregnancies. Fifty insulin-dependent diabetics had twice-weekly testing, and 188 gestational diabetics had weekly testing. Intervention was not pursued unless there were maternal or fetal complications. There were no stillbirths and three neonatal deaths, all resulting from congenital anomalies, giving a corrected perinatal mortality rate of 0. The incidence of abnormal biophysical profile scores, eight of 238 (3.3%) overall, was low, with no significant difference between types of diabetics. In those with an abnormal score, intervention was mandated; the cesarean section rate was 50% and the rate of intensive care nursery admissions was high. Of the 230 fetuses with a normal biophysical profile score, 200 (87%) were delivered at term with minimal maternal or neonatal morbidity. Amniocentesis for phospholipid profile was performed in only 33 cases (13.9%). Hyaline membrane disease was confined to five premature neonates (incidence 2.1%). We conclude that antepartum fetal surveillance using the biophysical profile score permits safe expectant management in the diabetic pregnancy, yielding significant clinical advantages to both mother and fetus.
The cutaneous vascular conductance-esophageal temperature (CVC-Tes) relationship was examined at five work loads (75-200 W) in each of four men to find whether there is a role for exercise intensity in the control of skin blood flow (SkBF). Several factors contributed to our evaluation of the CVC-Tes relationship during work. Laser-Doppler velocimetry (LDF) provided a continuous measure of SkBF that is not influenced by underlying muscle blood flow. Local warming to 39 degrees C at the site of measurement of SkBF provided a consistent skin temperature and facilitated observation of changes in LDF. Mean arterial pressure was measured noninvasively once per minute to calculate CVC. Supine exercise minimized baroreceptor-induced cutaneous vasoconstriction. Our major finding was that the internal temperature at which CVC began to rise during exercise (CVC threshold) was graded with work load beyond 125 W (P less than 0.05). In that range the CVC threshold increased by 0.16 degrees C for every increment of 25 W. The CVC threshold was never reached at the highest work load in three of the four subjects. There was no consistent effect of work load on the slope of the CVC-Tes relationship or on the internal temperature at which sweating began during exercise (sweat rate threshold). We conclude that the level of work beyond 125 W affects the CVC-Tes relationship in a graded fashion, principally through shifts in threshold.
To find whether the measurement of skin blood flow (SkBF) by laser-Doppler flowmetry (LDF) is influenced by blood flow to underlying skeletal muscle, five subjects performed mild forearm exercise to induce a metabolic hyperemia in muscle in both forearms. This exercise consisted of alternative opening and closing of both hands at a frequency of approximately 1/s for a duration of 3 min. This exercise was performed twice by each subject. Forearm blood flow (FBF) by plethysmography increased from 2.64 +/- 0.49 (rest) to 31.11 +/- 9.95 ml.100 ml-1.min-1 (immediately after exercise) (P less than 0.001). No statistically significant postexercise increase was observed in LDF measured on the dorsal (110 +/- 21 to 105 +/- 21 mV) or ventral surface (266 +/- 113 to 246 +/- 77 mV) of the forearm. LDF measured from the chest also showed no significant change, indicating that the exercise was too mild to have reflex effects on SkBF. Moreover, the slope of the logarithmic linear regression and the half-time for recovery during the postexercise period for FBF were not reflected in LDF measurements from any of the three sites. We conclude that LDF measured from the skin surface is not influenced by blood flow to underlying skeletal muscle.
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A prospective analysis of 296 carotid arteries in 293 asymptomatic patients was undertaken using real-time B-mode ultrasonography. All patients had carotid bifurcation disease and were followed for an average of 46 months. The endpoint for follow-up was a transient ischemic attack or stroke. Patients were categorized according to degree of stenosis (greater or less than 75 percent) and morphologic plaque characteristics (calcified, dense, or soft). Patients with hemodynamically significant stenosis were at greater risk of transient ischemic attack or stroke than their counterparts with less than 75 percent stenosis. However, even patients with less than 75 percent stenosis were at risk if the plaque was less organized (dense or soft). Patients with hemodynamically significant stenosis and morphologically soft plaque were at the greatest risk of transient ischemic attack or stroke. Those patients with calcified plaque and less than 75 percent stenosis had the lowest risk of transient ischemic attack or stroke. Morphologic plaque characteristics, as well as degree of stenosis, is important in determining which patients are candidates for carotid endarterectomy.
Saccharides of known standard solutions of high purity are analyzed on a carbohydrate high-performance liquid chromatographic (HPLC) column. Standards filtered through membranes with wetting agents and other additives have different compositional results from those filtered through membranes without additives. The selection of a filter membrane to remove insolubles from the sample prior to HPLC analysis of saccharides is an important consideration of the analysis.
Effects of varying temperature (26, 32, 38 degrees C) on age-related differences in inotropic and chronotropic sensitivities were investigated on electrically stimulated left atria and spontaneously beating right atria isolated from newborn and adult rabbits. Adult tissue had significantly greater sensitivity (low ED50) than newborn tissues to isoproterenol-induced inotropic responses at 26 and 32 degrees C (p less than 0.01), but not at 38 degrees C. The chronotropic sensitivity of adult tissues was significantly greater than the newborn at 26 degrees C (p less than 0.01), but not different at 32 or 38 degrees C. It is concluded that age-related differences in inotropic and chronotropic responses in vitro are more pronounced at low temperatures and tend to disappear at physiological temperatures.
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