PubMed Health⌕ Search

Biomedical subjects

S Larson

Publications and source records attributed to S Larson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Cerebral glucose metabolism in the Lennox-Gastaut syndrome.

We used positron emission tomography with fluorine 18-labeled 2-deoxyglucose to study cerebral glucose metabolism in 10 patients with Lennox-Gastaut syndrome who had normal neuroradiological studies. The scans showed decreased metabolic rates relative both to those in the caudate nucleus and to normal control values in 3 patients whose seizures began before the age of 1, as well as in a patient with hyperprolinemia. No patient had a region of persistent focal hypometabolism. Metabolic rates increased in parallel with increased electroencephalographic discharges in 1 patient; 3 patients had lower metabolic rates when the electroencephalogram showed epileptiform discharges and while the patients were taking barbiturates.

Adolescent↗
PubMed1987

125I-iodinated benzazepines bind to melanin: implications for the noninvasive localization of pigmented melanomas.

Both the 5-R and the 5-S enantiomers of [125I]2,3,4,5-tetrahydro-8-iodo-3-methyl-5-phenyl-1H-3-benzazepin- 7-ol bind to melanin. The interaction between the 5-R enantiomer and melanin permits visualization of melanomas in mice with a noninvasive imaging procedure. Two lines of evidence suggest that the interaction between iodinated ligands and melanin is not related to the D-1 dopamine receptor, a known target for the 5-R enantiomer: first, melanin binds both enantiomers of the 125I-iodinated benzazepine while the D-1 receptor binds only the 5-R enantiomer; second, the melanin binding site displays only a 5-fold difference in affinity towards the R- and S-enantiomers of SCH 23390 while the D-1 receptor displays a 100-fold difference in affinity towards these two molecules. Because both enantiomers of the iodinated benzazepine bind to a human pigmented melanoma, we propose that such compounds may be of use in the diagnosis of pigmented melanoma: in addition, we discuss the possible application of these molecules as a supplement to existing technology for the localization of pigmented melanomas.

Animals↗
PubMed1987

Erythrocyte Na+-K+ ATPase activity in childhood: regulation by genetic factors independent of body weight.

A number of previous investigations in obese and normal-weight adults suggested a link between (usually) lower than normal erythrocyte Na+-K+ ATPase activity and obesity, although more recent studies have disputed this link. Developmental patterns of ATPase activity in children have not been studied. Infants of diabetic mothers show an increased incidence of macrosomia and such infants are at risk for later development of obesity. These children provide an ideal group to study the link (if any) between this enzyme and obesity, as well as changes in the level of the enzyme which may occur with age and/or the onset of obesity. The Na+-K+ ATPase levels in erythrocytes from 87 normal children and 27 infants of diabetic mothers were therefore studied by an ouabain-binding method. The study populations contained representatives of three ethnic groups (black, Caucasian and Hispanic) and individuals of normal body weight, as well as overweight and obese individuals. The ATPase activities were not correlated with body weight, sex, or age, nor was umbilical cord red cell ATPase correlated with birthweight. Several children who are being followed have shown considerable variation in percentage ideal body weight (IBW); however their ATPase levels have remained unchanged. There were, however, significant differences among the ethnic groups, with Caucasians having the highest values (0.443 +/- 0.012 pmol ouabain bound/10(9) cells). These data demonstrate the importance of matching study groups by race when investigating factors affecting this enzyme. The differences among the ethnic groups suggest a genetic component in the determination of the activity of this enzyme. This link was further investigated in 14 families and revealed considerable heterogeneity within a given ethnic group, with family members generally having similar enzyme activities, thus supporting a genetic basis for the different enzyme levels. Thus erythrocyte Na+-K+ ATPase in childhood is primarily regulated by genetic factors which are generally independent of body weight.

Black People↗
PubMed1986

Effect of phenytoin on human cerebral glucose metabolism.

We used serial positron emission tomography scans with [18F]2-deoxyglucose to study the effect of phenytoin on human cerebral glucose metabolism in 10 patients with seizure disorders. Local CMRglu for each patient was measured in 10 regions of interest. EEGs were performed during each procedure to match scans for state of consciousness and exclude data from scans with ictal activity. Serial scans without a drug change were performed in six control patients. Metabolic rates were significantly lower in two cortical regions while patients were taking phenytoin. No significant changes on repeat scan were seen in the control population. Measured across all regions of interest, metabolic rates were 13% higher when patients were off phenytoin (p less than 0.02).

Adult↗
PubMed1986

Positron emission tomography in Alzheimer's disease.

Twenty-one patients with a clinical diagnosis of dementia of the Alzheimer's type (DAT) and 29 healthy, age-matched controls were studied using positron emission tomography (PET) and [18F]2-fluoro-2-deoxy-D-glucose to measure regional cerebral glucose consumption in the resting state. Reductions in ratio measures of relative metabolism in some parietal, temporal, and frontal regions were found in mild, moderate, and severe DAT groups. A significant increase in right/left metabolic asymmetry, particularly in parietal regions, also was seen in mild and moderate groups. Only in the severely demented patients was the absolute cerebral metabolic rate reduced significantly from control values. Fourteen patients had repeated PET studies, but only those patients with moderate to severe dementia showed a decline in IQ over 6 to 15 months. There were no significant changes in metabolic measures over time. PET is useful in quantifying regional cerebral dysfunction in DAT, even in the early stages of the disease.

Aged↗
PubMed1985

Sexual dimorphism in the postcranial skeleton of New World primates.

This study examines sexual dimorphism in 24 dimensions of the postcranial skeleton of four platyrrhine species: Callithrix jacchus, Saguinus nigricollis, Saimiri sciureus, and Cebus albifrons. The two callitrichid species show a relatively small amount of variation in the degree of sexual dimorphism among the different dimensions. Variation is considerably higher in the two cebid species as reflected by a mosaic pattern of sexual dimorphisms with males being significantly larger than females in some dimensions, and females significantly larger than males in others. In dimensions of the pectoral girdle and limb bones, males and females in each of the two cebid species are essentially scaled versions of each other, with males being peramorphic compared to females. This pattern is primarily the result of time hypermorphosis, i.e. an extension of the growth period in time in males. Rate hypermorphosis, i.e. an increase in the rate of growth in time in males, appears to play an additional role, however, in S. sciureus. By contrast, in dimensions of the true pelvis, sex differences in shape are dissociated from those in size. They are interpreted as the result of acceleration, i.e. increase in rate of shape change in females, as an adaptation to obstetrical functions. Interspecific analyses indicate positive allometry of mean degree of postcranial dimorphism with respect to body size. This coincides with previous findings by Leutenegger and Cheverud [1982, 1985] on the scaling of sexual dimorphism in body weight and canine size, and thus supports their model which posits selection on body size as the prime mover for the evolution of sexual dimorphism.

Aging↗
PubMed1984

Regulation of glutamine synthetase and glutaminase activities in cultured skeletal muscle cells.

Glutamine is synthesized in skeletal muscle, released to the circulation, and transported to other tissues, where it may provide important substrate for gluconeogenesis, ammoniagenesis, and energy-yielding pathways. With the ultimate goal of delineating the factors that control glutamine production and release by skeletal muscle, we have studied the regulation of two key enzymes, glutamine synthetase and glutaminase, in the L6 line of rat skeletal muscle cells grown in monolayer culture. The cultured myotubes were found to have glutamine synthetase and phosphate-dependent glutaminase activities. Glutamine synthetase activity was increased following incubation (1) in glutamine-free medium (threefold); (2) in medium containing high glutamic acid concentrations (fourfold); and (3) in medium supplemented with dexamethasone (threefold). In each case the increase in glutamine synthetase activity required several hours to reach a maximum and was prevented by cycloheximide, suggesting that the change occurred through increased enzyme biosynthesis. No substances tested were found to affect glutaminase activity. We conclude that glutamine synthetase in cultured skeletal muscle is responsive to substrate, product, and hormonal regulation.

Animals↗
PubMed1980

Effect of electrical current on temperature and pH in cerebellum and spinal cord.

Electrical currents similar to those used for relief of pain and spasticity were applied to the spinal cord and cerebellum of monkeys and cats. Direct coupled monopolar pulses increased pH at the tissue surface near a negative electrode and correspondingly decreased the pH near a positive electrode. Cerebrospinal fluid (CSF) circulation around the electrodes neutralized these changes. Capacitively coupled currents up to a 10 mA peak and 2.5 mucoul per peak failed to change tissue pH measurably. Current levels with power densities of 100 mW per cm2 did not cause any change in tissue temperature.

Animals↗
PubMed1976

Acquired resistance to parathyroid hormone.

Studies are presented in a patient with pseudohypoparathyroidism who showed a partial response to parathyroid extract. Resistance to the extract was observed after its short-term administration for the gourth time. Serum from the patient contained antibodies of the gamma G globulin class which bound 125I-labelled bovine parathyroid hormone. Prior incubation of parathyroid hormone with the serum prevented the activation in vitro of adenylate cyclase from pork renal cortex. The antibodies were directed primarily toward the C-terminal portion of the molecule. Thus, clinical resistance to parathyroid hormone is attributed to specific antibodies.

Adenylyl Cyclases↗
PubMed1976

Simple radiometric techniques for rapid detection of herpes simplex virus type 1 in WI-38 cell culture.

Two radiometric techniques were developed for detecting the presence of herpes simplex virus type 1 in stationary monolayers of the diploid cell line WI-38. The time of detection was compared to that obtained from visual examination for cytopathic effects in the same cell line. Oxidation of 14C-1-glucose in infected and uninfected cells was determined by 14CO2 production, measured by an ionization chamber, and DNA synthesis was determined by 3H-thymidine incorporation, measured by scintillation counting. Compared to uninfected cells, infected cells showed a 23-26% reduction in 14C-1-glucose oxidation and a 355-498% increase in DNA synthesis 4-6 hr after infection. These changes in cellular metabolism were observed 14 hr before visible signs of cytopathic effects. The increase in DNA synthesis was completely inhibited by viral neutralization with herpes simplex antiserum. Increased DNA synthesis was observed 5 hr after infection with 10,000-3,200,000 TCID50 units of virus. These radiometric methods for the detection of viral effect on cellular metabolism are simple, fast, and objective.

Carbon Radioisotopes↗
PubMed1973

Chloroplast maintenance and partial differentiation in vitro.

Tissue homogenates, etioplasts, and developing chloroplasts were prepared from cucumber (Cumucis sativus L.) cotyledons in tris-sucrose. They were incubated aerobically in the dark or in the light at pH 7.7 in the presence or absence of a cofactor mixture containing coenzyme A, glutathione, potassium phosphate, methyl alcohol, magnesium, nicotinamide adenine dinucleotide, and adenosine triphosphate. These cofactors were previously shown to be essential for protochlorophyll and chlorophyll biosynthesis. Ultrastructural changes were monitored by electron microscopy. The following observations were made. (a) Crude homogenates contained agents which degraded etioplasts and developing chloroplasts. (b) Added cofactors were essential for the maintenance of the membrane structure; they were also implicated in the transformation of the prolamellar body in the absence and presence of light. (c) Light pretreatment of the cotyledons improved the maintenance of the developing chloroplast membranes during subsequent in vitro incubation. (d) In the presence of the cofactors, grana formation appeared to take place in the absence of nuclear-cytoplasmic control.

Journal Article↗