Conserved energy for Robertson-Walker spacetimes with scalar fields.
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Journal Article↗
Biomedical subjects
J Katz
Publications and source records attributed to J Katz.
Zonation of glycogen and glucose syntheses, but not glycolysis, in rat liver.
We have investigated the cause of defective glycogen synthesis in hepatocyte preparations enriched with cells from the periportal or perivenous zones obtained by the methods of Lindros & Penttila [Biochem. J. (1985) 228, 757-760] and of Quistorff [Biochem. J. (1985) 229, 221-226]. A modified procedure which yields hepatocytes capable of consistent rates of glycogen synthesis is described, and the rates of glucose and glycogen syntheses and of glycolysis in hepatocytes from the two zones are compared. Glycogen synthesis in cells was greatly impaired by very low concentrations (0.01-0.05 mg/ml) of digitonin, which had little effect on glucose and protein syntheses and Trypan Blue exclusion. Cells exposed to such low concentrations of digitonin lose all their synthetic capacity and ability to exclude Trypan Blue when incubated with EGTA, which does not affect cells not exposed to digitonin. With a modified procedure based on this phenomenon, our study reveals that hepatocyte preparations enriched with cells from the periportal zone synthesized glucose from lactate and alanine at rates twice those by cells from the perivenous zone, whereas the rate of glycogen synthesis from C3 precursors in periportal cells was 4 times that in the perivenous preparations. With substrates entering the pathway at the triose phosphate level, gluconeogenesis in periportal-cell preparations was 20% higher, and glycogen synthesis was twice that in perivenous preparations. Glycolysis was studied by the formation of 3HOH from [2-3H]glucose, the yield of lactate, and the conversion of [14C]glucose into [14C]lactate. In cell preparations from both zones glycolysis by all criteria was negligible at 10 mM-glucose, but was substantial at higher concentrations. However, there was no difference between the zones. We confirm that the capacities for glucose and glycogen syntheses in periportal cells are higher than in perivenous cells, but that at physiological glucose concentrations there is negligible glycolysis in liver parenchyma in both zones. The metabolic pattern in the perivenous cells is not glycolytic.
Animals↗
Left ventricular mass as determined by magnetic resonance imaging in male endurance athletes.
Although many studies of the effect of dynamic exercise training on left ventricular (LV) mass have been reported, controversy continues to exist. Previous work has been criticized because of the techniques used for measuring LV mass, the variable level of training of the subjects recruited and the methods used to normalize the data. In an attempt to resolve this controversy, LV mass was determined using the very accurate and reproducible technique of magnetic resonance imaging (MRI). Highly trained competitive athletes including cross-country skiers, endurance cyclists and long distance runners (VO2max = 77 +/- 1, 72 +/- 2 and 75 +/- 2 ml (kg X min)-1, respectively) were examined. The data were normalized for body weight, body surface area and lean body mass. LV mass was significantly greater in skiers (239 +/- 9 g), runners (244 +/- 10 g) and cyclists (258 +/- 11 g) when compared with nonathletic control subjects (189 +/- 6 g) (p less than 0.001), which represents percent differences of 26, 29 and 37%, respectively. LV mass remained greater in the athletes, regardless of the method used to normalize the data. In addition, there was a good correlation between LV mass and VO2max (r = 0.80, p less than 0.001). It was concluded that LV mass is significantly greater in highly trained competitive endurance athletes and that normalizing LV mass with respect to body weight, body surface area or lean body mass does not alter this relation.
Adult↗
Effects of supine and lateral positions on cardiac output and intracardiac pressures.
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Adult↗
The specific activity of hexose 6-phosphates in liver.
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Hexosephosphates↗
The zonation of liver and the distribution of fructose 2,6-bisphosphate in rat liver.
Livers of starved rats refed for 2 h were perfused in situ by a modification of the dual digitonin pulse technique of Quistorff and Grunnet (Quistorff, B., and Grunnet, N. (1987) Biochem. J. 243, 87-95). A pulse of digitonin (2 mg/ml) was infused first antegrade through the portal vein followed retrograde through the vena cava, or in reverse order, 13 mg of digitonin per zone. Microscopic examination showed that this procedure permeabilized the periportal and perivenous zones of the liver without overlap, with a narrow unaffected band of hepatocytes between the zones. The distribution pattern between periportal and perivenous zones ratio for alanine transaminase, lactate hydrogenase, fructose-1,6-bisphosphatase, and phosphoenolpyruvate carboxykinase ranged from 1.5 to 3. Glucokinase activity was higher in the perivenous zone (periportal/perivenous ratio of 0.7) and glutamine synthetase was exclusively present in that zone. Fructose 2,6-bisphosphate concentration was nearly equal in the two zones.
Alanine Transaminase↗
Reliability indexes of automated perimetric tests.
The "reliability" of a subject's automated perimetric test result is generally assessed by three measures: fixation loss and false-positive and false-negative rates. These reliability criteria were examined for 76 glaucomatous and 248 normal subjects who underwent visual field testing (C-30-2 program; Humphrey Visual Field Analyzer, Allergan Humphrey, San Leandro, Calif). Of the examination results, 45% in glaucomatous subjects and 30% in normal controls were considered unreliable with the use of the manufacturer's reliability criteria. Most test results were unreliable because they failed to meet the criterion for fixation loss. The greater rejection rate among glaucomatous subjects was entirely due to their higher rate of false-negative responses. Factors such as age, pupil diameter, and visual acuity did not explain the difference between the false-negative rates of glaucomatous patients and normal subjects.
Diagnosis, Computer-Assisted↗
On the measurement of lactate turnover in humans.
It has been shown in studies of turnover in vivo of lactate and several amino acids that the specific activity in blood depends on the site of tracer administration and of sampling. Theoretical and experimental studies have established that to obtain valid estimation of turnover in vivo for these compounds, tracers should be administered into the left heart, ideally the ventricle, and blood sampled from the right heart, ideally the pulmonary artery. Alternately, tracer may be infused into the pulmonary artery and blood sampled from the right ventricle. The insertion of such in-dwelling catheters for turnover studies is difficult in small animals and not justified on ethical grounds in humans. We describe here a method to calculate valid turnover rates when the tracer is administered in a peripheral vein and blood sampled from any peripheral artery. In humans, infusion into a hand vein and sampling from the contralateral heated hand vein can be used. The true turnover rate can then be calculated if the cardiac output is determined. Several noninvasive methods for the determination of cardiac output are available. Thus a correct estimate, avoiding major catheterization, for turnover for many blood-borne compounds is possible.
Alanine↗
Gadolinium-DTPA-enhanced nuclear magnetic resonance imaging of reperfused myocardium: identification of the myocardial bed at risk.
Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced nuclear magnetic resonance (NMR) imaging can be useful in the identification of reperfused myocardium. However, the effects of dose and the time of administration and the relation of the extent of the region of enhancement to the myocardial bed at risk have not been evaluated. In this study, dogs were given Gd-DTPA (0.1 mM/kg body weight [n = 21] or 0.34 mM/kg [n = 7]) or saline solution (n = 5) after various periods of occlusion and reperfusion. Twenty-five dogs were killed after 1 or 2 h of reperfusion and the excised hearts were imaged. Images were analyzed for presence, intensity and extent of a region of increased signal. All images in dogs given Gd-DTPA had easily identifiable regions of increased signal in the distribution of the reperfused myocardial bed. Analysis of the extent of these regions in spin-echo images of excised hearts when Gd-DTPA was administered after 5 min of reperfusion demonstrated a correlation coefficient of 0.72 with the bed at risk as determined postmortem with a dye perfusion technique. These images consistently overestimated the infarct size. Signal intensity of the reperfused myocardium increased to a maximum of 1.67 times control (p less than 0.05) in spin-lattice relaxation time (T1)-weighted sequences as the dose of Gd-DTPA increased. This was due to a higher concentration of Gd-DTPA in the reperfused myocardium with resultant shortening of the T1 relaxation time. When Gd-DTPA was given after 90 min of reperfusion, NMR images did not identify the bed at risk.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Effect of the Trendelenburg position on the distribution of arterial air emboli in dogs.
We examined the effects of buoyancy on the distribution of arterial gas bubbles using in vitro and in vivo techniques in dogs. A simulated carotid artery preparation was used to determine the effects of bubble size and vessel angle on the velocity and direction of bubble movement in flowing blood. Because buoyancy tends to float bubbles away from dependent areas, bubble velocity would be expected to decrease as the vessel angle increased. We found that larger bubbles increased in velocity in the same direction as the blood flow at 0-, 10-, and 30-degree vessel angles and decreased when the vessel was positioned at 90 degrees. Smaller bubbles did not change velocity from 0 to 30 degrees and increased in velocity in the same direction as blood flow at 90 degrees. In 10 anesthetized dogs, we studied the effects of 0-, 10-, 15-, and 30-degree Trendelenburg's position on carotid artery distribution of gas bubbles injected into the left ventricle or ascending aorta. Regardless of the degree of the Trendelenburg position, the bubbles passed into the carotid artery simultaneously with passage into the abdominal aorta. We conclude that the forces of buoyancy do not overcome the force of arterial blood flow and that the Trendelenburg position does not prevent arterial bubbles from reaching the brain.
Animals↗
A self-limited febrile illness produced in guinea pigs associated with oral administration of Legionella pneumophila.
The presumed route of human infection by Legionella pneumophila is inhalation. We investigated possible oral transmission of legionellosis in guinea pigs. Fifty-six guinea pigs (group 1) were given virulent L. pneumophila, serogroup 1, in drinking water. Fifty-nine guinea pigs (group 2) were inoculated with L. pneumophila via gastric intubation. Nineteen guinea pigs (group 3) were given heat-killed L. pneumophila in drinking water. Twenty-four guinea pigs (group 4, positive control) were inoculated intraperitoneally with L. pneumophila. Twenty-seven guinea pigs (group 5, negative control) were either intubated gastrically with phosphate-buffered saline or given drinking water without L. pneumophila. Sixty-six of 115 (57%) of the guinea pigs orally inoculated with viable L. pneumophila (groups 1 and 2) had a temperature greater than or equal to 103 degrees F and 8 of 115 (7%) had diarrhea, compared with 0 of 19 (0%) and 0 of 19 (0%), respectively, in group 3 and 1 of 27 (4%) and 0 of 27 (0%), respectively, in group 5. There were no fatalities in groups 1, 2, 3, and 5 compared with 15 of 24 (63%) in group 4. Groups 1, 2, and 4 consistently showed pneumonitis and splenitis. The pneumonitis of groups 1 and 2 was mild, predominantly interstitial, and mainly composed of macrophages; neither gross nor microscopic evidence of aspiration was seen. In group 1, 4 of 29 (14%) guinea pigs tested seroconverted to L. pneumophila compared with 0 of 7 (0%) in group 3 and 0 of 10 (0%) in group 5. In groups 1 and 2 combined, L. pneumophila was isolated from the lung of 5 of 57 (11%) guinea pigs and spleen of 5 of 47 (11%) guinea pigs compared with 0 of 14 guinea pigs in group 5. We conclude that viable L. pneumophila administered orally produces a self-limited febrile illness in guinea pigs.
Administration, Oral↗
Intraobserver and interobserver agreement in measurement of optic disc characteristics.
Reliable measures of optic nerve status are important parameters for epidemiologic and clinical studies of glaucoma. Stereo fundus photography has been used to reduce interobserver variation, but little data have been reported quantifying the level of agreement in these situations. This article examines chance-corrected intraobserver and interobserver agreement for horizontal and vertical cup:disc ratios and width of the narrowest remaining neuroretinal rim on stereo, color, fundus photographs. Intraobserver agreement was substantial to almost perfect for both readers (kappas between 0.82 and 0.86 for horizontal and vertical cup:disc ratios and 0.71 for the neuroretinal rim). Interobserver agreement was also substantial (kappas of 0.71 for horizontal cup:disc ratio, 0.74 for vertical cup:disc ratio, and 0.58 for the neuroretinal rim). Both intraobserver and interobserver agreement were best for glaucoma patients followed by ocular hypertensives and controls. Dichotimizing cup:disc ratios into suspicious or not suspicious using a range of cutoff points (greater than or equal to 0.5, greater than or equal to 0.6, and greater than or equal to 0.7 disc diameters [DD]) had little effect on agreement levels. Estimation of the status of the optic nerve is complex, requiring judgment about the shape and structure of the cup. Agreement is optimized by using stereo photographs, using the same observer and, when evaluating progression, comparing photographs from different points in time at a single sitting.
Glaucoma↗
Effects of inhalation anaesthetics on filtration of venous gas emboli by the pulmonary vasculature.
Venous gas emboli are prevented from reaching the systemic circulation by filtration in the pulmonary vasculature. This filtration can be overwhelmed by exceeding certain critical rates of venous air infusion. To characterize further these filtration phenomena, the effects of pentobarbitone, isoflurane and halothane anaesthesia on the incidence of spillover of venous bubbles into the arteries were studied in groups of nine dogs. Venous air was infused at rates of 0.25, 0.30, and 0.35 ml kg-1 min-1. Spillover of venous bubbles into the arteries was detected with a Doppler ultrasonic probe located over the suprarenal aorta. At the lowest venous air dose (0.25 ml kg-1 min-1), no bubbles were detected in the systemic circulation in the pentobarbitone- or halothane-anaesthetized dogs, while arterial bubbles were detected in two with isoflurane anaesthesia. At 0.30 ml kg-1 min-1 air, one, four and two dogs had arterial bubbles detected with pentobarbitone, halothane or isoflurane anaesthesia, respectively, while at 0.35 ml kg-1 min-1 spillover of bubbles occurred in four, five and three, respectively. The spillover of venous bubbles into the arteries was dose-related for the pentobarbitone- and halothane-anaesthetized dogs.
Anesthesia, Inhalation↗
Village and household clustering of xerophthalmia and trachoma.
The clustering of xerophthalmia in villages and in households was assessed among preschool children surveyed in the Lower Shire Valley, Malawi, and in Aceh province, Indonesia. Trachoma clustering was similarly assessed among the same children in Malawi. Trachoma clustered much more than xerophthalmia among villages and among households. The impact of xerophthalmia clustering on sample size considerations for future surveys or interventions was similar in Malawi and Indonesia. Village clustering of xerophthalmia would necessitate a twofold increase in sample size. Household clustering in the absence of village clustering would have almost no impact on sample size. Village clustering of trachoma would necessitate a ninefold increase in sample size. Household clustering would increase sample size requirements by 26%.
Child, Preschool↗
Balloon aspiration of tracheal secretions.
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Airway Obstruction↗
Health belief model intervention to increase compliance with emergency department patients.
The effects on compliance of clinical and telephone intervention, based on the Health Belief Model (HBM), were investigated for 842 Emergency Department (ED) patients. The influence of mediating variables on compliance was also examined. Compliance was defined operationally as follow-through on a recommended referral originating in the ED. The study design was a 2 X 2 X 11 factorial design, in which the first factor was the HBM clinical intervention, the second was the HBM telephone intervention, and the third was the type of presenting problem. Patients were randomly assigned to one of four intervention groups, with all nursing care, interventions, and follow-up telephone calls being done by the research nurse. The HBM clinical, telephone, and combination clinical/telephone interventions were strongly associated with increased compliance in the 11 presenting problems. Availability of child care, knowledge of presenting problem, nature and duration of the illness, and demographic variables (such as age of the patient) were also related to compliance.
Attitude to Health↗
Compliance for low-back pain patients in the emergency department. A randomized trial.
A randomized trial was used to evaluate two forms of a Health Belief Model (HBM) intervention aimed at increasing compliance among low-back pain (LBP) patients visiting an Emergency Department (ED). Patients who received an HBM clinical intervention administered in the ED, HBM phone intervention made 1 to 2 days post-ED visit, or both interventions were much more likely than control patients to both schedule and keep a follow-up referral appointment. Both the phone and clinical interventions were designed to increase patients' perceived susceptibility to complications of the LBP, seriousness of the complications, and benefits and costs of action through a follow-up referral appointment. Other factors predicting compliance included persistence of pain symptoms, previous treatment of LBP by a health care provider, and an unmet need for child care.
Adult↗
A comparison of different methods of lubrication of glass syringes used to identify the epidural space.
Measurement of loss of resistance in glass syringes is a method widely used to locate the epidural space in epidural anaesthesia. Static and dynamic forces were measured under four experimental conditions in new glass syringes: unpolished, dry; polished, dry; unpolished, saline lubricated; and polished, saline lubricated. The unpolished saline lubricated syringes had a mean (SD) static force of 53.18 (15.0) g and dynamic force of 40.88 (15.2) g. These values were significantly greater than for polished dry syringes where the values were 5.27 (2.1) g and 4.38 (0.94) g, respectively. The results show that the least amount of resistance to plunger movement is obtained by dry polishing glass syringes.
Anesthesia, Epidural↗