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Biomedical subjects

J M Miles

Publications and source records attributed to J M Miles.

At least 73 records · Page 4Linked to original sources
PubMed1988

A new immunoperoxidase marker for microglia in paraffin section.

We tested antisera against monocytic and lymphocytic lineages on 27 formalin-fixed, paraffin-embedded brains, obtained at autopsy, using the avidin-biotin-complex immunoperoxidase method. Patients ranged from one day to 69 years with 12 cases under the age of two. LN-1-positive microglia were present in 22 brains. LN-1 did not stain any other glial or neuronal cells. Five negative brains included two irradiated gliomas, two cases of multiple sclerosis and one normal case. Immunostaining was confined to cells with bipolar processes and rod-shaped nuclei recapitulating the characteristic features of microglia in silver-impregnated sections. LN-1-positive microglia were most prominent in the grey matter and in the grey-white junction with fewer positive cells seen in the white matter. Double immunostaining with LN-1 and glial fibrillary acidic protein (GFAP) clearly distinguished LN-1-positive microglia and GFAP-positive astrocytes. The expression of LN-1, a B-lymphocyte antigen, by microglia contradicts the macrophage derivation theory and supports data indicating a functional role of microglia in immune processes. LN-1, while not specific for microglia, should be considered a useful marker, more reliable than silver impregnation, for detecting microglia in paraffin section.

Adult↗
PubMed1988

Choice of infusion-sampling mode for tracer studies of free fatty acid metabolism.

To determine the preferred infusion-sampling mode for isotopic studies of free fatty acid (FFA) metabolism, tracer [( 14C]palmitate) was infused into the left ventricle of five anesthetized dogs, and tracee ([3H]palmitate) was infused into three separate peripheral veins of each dog. The [14C]palmitate specific activity (SA) was lower in mixed venous than arterial blood, and [3H]palmitate SA was equal in both sites. The actual infusion rate of [3H]palmitate [2.15 +/- 0.31 X 10(5) disintegrations/min (dpm).kg-1.min-1] could be accurately predicted (2.14 +/- 0.32 X 10(5) dpm.kg-1.min-1) using the known [14C]palmitate infusion rate and the arterial plasma [14C]-to-[3H]palmitate ratio. In contrast, the mixed venous [14C]-to-[3H]palmitate ratio resulted in overestimates (P less than 0.05) of the actual [3H]palmitate infusion rate. In summary, venous tracer infusion with arterial blood sampling for FFA tracer studies provides the most accurate estimates of tracee rate of appearance.

Animals↗
PubMed1988

Preservation of insulin effects on glucose production and proteolysis during fasting.

To determine whether fasting alters the ability of insulin to suppress endogenous glucose production or proteolysis, isotopic flux measurements of glucose, leucine, alpha-keto-isocaproate, and alanine were made in 13 normal volunteers after a 14-h (day 1) and an 84-h (day 4) fast. Using the "pancreatic clamp" technique, we achieved small increments in plasma insulin concentrations, as well as constant and identical plasma hormone and glucose concentrations, on both study days in seven subjects. The remaining six subjects were infused with saline and served as controls. Leucine rate of appearance (an index of proteolysis) was greater on day 4 than on day 1 (P less than 0.001), but decreased to equal values during the pancreatic clamp on each study day. During the pancreatic clamp, endogenous glucose production decreased to lesser (P less than 0.005) values on day 4 than on day 1. In conclusion, insulin suppresses proteolysis equally well before and after brief fasting, and endogenous glucose production is more completely suppressed by insulin after brief fasting than after an overnight fast.

Adult↗
PubMed1987

Treatment of severe accidental hypothermia using the Clinitron bed.

Two cases of severe accidental hypothermia (core temperature less than 28 degrees C) rewarmed employing the Clinitron system are described. The physiological changes during hypothermia and rewarming are discussed and the current concepts of rewarming (active external versus internal) outlined. It is suggested that severely hypothermic patients can be successfully treated by rapid external rewarming using the Clinitron heated fluidised-bead bed. This method combines the advantages of rapid rewarming, minimal physiological disturbance and is non invasive.

Aged↗
PubMed1987

The effect of two new alpha-glucosidase inhibitors on metabolic responses to a mixed meal in normal volunteers.

1. alpha-Glucosidase inhibitors delay carbohydrate absorption and have been proposed as adjunctive therapy for diabetes mellitus. 2. To determine the effects of two new alpha-glucosidase inhibitors, Bay-m-1099 and Bay-o-1248, on meal carbohydrate and lipid tolerance, plasma glucose, insulin and triglyceride levels were measured at 15-60 min intervals over 12 h after ingestion of a standard breakfast, lunch and dinner of identical composition in 31 normal volunteers. 3. The volunteers were randomized to receive either Bay-m-1099 (50 or 25 mg) or placebo prior to each meal, or the single administration of Bay-o-1248 (20 or 10 mg) or placebo prior to breakfast. 4. Only Bay-m-1099 at the 50 mg dose reduced significantly the postprandial increase in plasma insulin levels after each meal when compared with placebo (25, 36, 54% at breakfast, lunch, and dinner, respectively; P less than 0.05). Both drugs were well tolerated, with side effects limited to complaints of flatulence. 5. Thus, with the dosage schedule employed, Bay-m-1099, but not Bay-o-1248, significantly reduced postprandial increments in plasma insulin.

1-Deoxynojirimycin↗
PubMed1987

Validation of a new method for determination of free fatty acid turnover.

The accuracy of tracer methods for estimating free fatty acid (FFA) rate of appearance (Ra), either under steady-state conditions or under non-steady-state conditions, has not been previously investigated. In the present study, endogenous lipolysis (traced with 14C palmitate) was suppressed in six mongrel dogs with a high-carbohydrate meal 10 h before the experiment, together with infusions of glucose, propranolol, and nicotinic acid during the experimental period. Both steady-state and non-steady-state equations were used to determine oleate Ra ([3H]oleate) before, during, and after a stepwise infusion of an oleic acid emulsion. Palmitate Ra did not change during the experiment. Steady-state equations gave the best estimates of oleate inflow approximately 93% of the known oleate infusion rate overall, while errors in tracer estimates of inflow were obtained when non-steady-state equations were used. The metabolic clearance rate of oleate was inversely related to plasma concentration (P less than 0.01). In conclusion, accurate estimates of FFA inflow were obtained when steady-state equations were used, even under conditions of abrupt and recent changes in Ra. Non-steady-state equations, in contrast, may provide erroneous estimates of inflow. The decrease in metabolic clearance rate during exogenous infusion of oleate suggests that FFA transport may follow second-order kinetics.

Animals↗
PubMed1987

Lipolysis during fasting. Decreased suppression by insulin and increased stimulation by epinephrine.

These studies were designed to determine whether the insulin resistance of fasting extends to its antilipolytic effects and whether fasting enhances the lipolytic effects of adrenergic stimulation independent of changes in plasma hormone and substrate concentrations. Palmitate flux was determined isotopically ([1-14C]palmitate) before and during epinephrine infusion in normal volunteers after a 14-h (day 1) and an 84-h (day 4) fast. Using a pancreatic clamp, constant plasma hormone and glucose concentrations were achieved on both study days in seven subjects. Six subjects were infused with saline and served as controls. During the pancreatic clamp, palmitate flux was greater (P less than 0.01) on day 4 than day 1, despite similar plasma insulin, glucagon, growth hormone, cortisol, epinephrine, norepinephrine, and glucose concentrations. The lipolytic response to epinephrine was greater (P less than 0.05) on day 4 than day 1 in both groups of subjects. In conclusion, lipolysis during fasting is less completely suppressed by insulin and more readily stimulated by epinephrine.

Adult↗
PubMed1986

The roles of diet and exercise in the management of patients with insulin-dependent diabetes mellitus.

Current dietary recommendations for patients with diabetes are similar to those for the US population in general, including a moderate intake of sucrose. Awareness of the carbohydrate content of meals will allow adjustments of the dose of meal-related short-acting insulin when the size of the meal is altered; thus, meal planning can be flexible without sacrificing glycemic control. Although exercise may have potential benefits for patients with diabetes, it is also associated with greater risk in these persons than in their nondiabetic counterparts and frequently complicates the management of their disease. If there are no contraindications to regular, vigorous exercise and the patient desires to participate, careful self-monitoring of blood glucose, combined with snacks and insulin dose adjustment, should enable the intensively treated patient to exercise safely.

Absorption↗
PubMed1986

Complications of insulin-dependent diabetes mellitus: management of insulin reactions and acute illness.

Occasional mild hypoglycemia is an unavoidable and usually acceptable side effect of intensive insulin therapy. Patients with insulin-dependent diabetes mellitus may have impaired glucose counterregulation, which may increase the risk of hypoglycemia and justify less ambitious glycemic goals. A conservative but flexible approach to the treatment of insulin reactions is appropriate in order to avoid hyperglycemia. Insulin requirements are often increased during acute illness, and frequent self-monitoring of blood glucose concentrations is necessary to determine the need for supplementation with regular insulin. Frequent supplementation, together with modification of diet and maintenance of fluid intake, should not only minimize the need for hospitalization but also prevent severe deterioration in glycemic control.

Acute Disease↗
PubMed1986

A dual-isotope technique for determination of in vivo ketone body kinetics.

"Total ketone body specific activity" has been widely used in studies of ketone body metabolism to circumvent so-called "isotope disequilibrium" between the two major ketone body pools, acetoacetate and beta-hydroxybutyrate. Recently, this approach has been criticized on theoretical grounds. In the present studies, [13C]acetoacetate and beta-[14C]hydroxybutyrate were simultaneously infused in nine mongrel dogs before and during an infusion of either unlabeled sodium acetoacetate or unlabeled sodium beta-hydroxybutyrate. Ketone body turnover was determined using total ketone body specific activity, total ketone body moles % enrichment, and an open two-pool model, both before and during the exogenous infusion of unlabeled ketone bodies. Basal ketone body turnover rates were significantly higher using [13C]acetoacetate than with either beta-[14C]hydroxybutyrate alone or the dual-isotope model (3.6 +/- 0.5 vs. 2.2 +/- 0.2 and 2.7 +/- 0.2 mumol X kg-1 X min-1, respectively, P less than 0.05). During exogenous infusion of unlabeled sodium acetoacetate, the dual-isotope model provided the best estimate of ketone body inflow, whereas 14C specific activity underestimated the known rate of acetoacetate infusion by 55% (P less than 0.02). During sodium beta-hydroxybutyrate infusion, [13C]-acetoacetate overestimated ketone body inflow by 55% (P = NS), while better results were obtained with 14C beta-hydroxybutyrate alone and the two-pool model. Ketone body interconversion as estimated by the dual-isotope technique increased markedly during exogenous ketone body infusion. In conclusion, significant errors in estimation of ketone body inflow were made using single-isotope techniques, whereas a dual-isotope model provided reasonably accurate estimates of ketone body inflow during infusion of exogenous acetoacetate and beta-hydroxybutyrate.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1986

Trioctanoin infusion increases in vivo leucine oxidation: a lesson in isotope modeling.

We have reported that infusion of trioctanoin in conscious dogs had little effect on leucine oxidation but decreased the rate of appearance (Ra) and interconversion of leucine and its alpha-keto acid, alpha-ketoisocaproate (KIC). To verify that these conclusions were independent of the leucine tracers and isotope models employed, the studies were repeated using [1-14C]leucine and [4,5-3H]KIC rather than [1-14C]KIC and [4,5-3H]leucine. In the present study, leucine oxidation calculated using the plasma [14C]leucine or [14C]KIC specific activities (SA) increased nearly twofold (P less than 0.001) during trioctanoin infusion in direct contrast to our previous results. When the data from either study were analyzed using the plasma SA of the leucine moiety reciprocal to the infused tracer as a potential indicator of the intracellular leucine SA, similar conclusions were obtained from either study: trioctanoin infusion in conscious dogs appears to increase whole-body leucine oxidation and does not decrease proteolysis. These studies challenge the validity of previously used isotope models of leucine metabolism and suggest that the plasma KIC SA during infusion of labeled leucine may most accurately reflect changes in whole-body leucine metabolism.

Animals↗
PubMed1986

Inverse relationship of leucine flux and oxidation to free fatty acid availability in vivo.

To determine the effect of fatty acid availability on leucine metabolism, 14-h fasted dogs were infused with either glycerol or triglyceride plus heparin, and 46-h fasted dogs were infused with either nicotinic acid or nicotinic acid plus triglyceride and heparin. Leucine metabolism was assessed using a simultaneous infusion of L-[4,5-3H]leucine and alpha-[1-14C]ketoisocaproate. Leucine, alpha-ketoisocaproate (KIC), and totalleucine carbon (leucine plus KIC) flux and oxidation rates were calculated at steady state. In 14-h fasted animals, infusion of triglyceride and heparin increased plasma free fatty acids (FFA) by 0.7 mM (P less than 0.01) and decreased leucine (P less than 0.01), total leucine carbon flux (P less than 0.02), and oxidation (P less than 0.05). The estimated rate of leucine utilization not accounted for by oxidation and KIC flux decreased, but the changes were not significant. During glycerol infusion, leucine and KIC flux and oxidation did not change. In 46-h fasted dogs, nicotinic acid decreased FFA by 1.0 mM (P less than 0.01) and increased (P less than 0.05) the rate of leucine and total leucine carbon flux, but did not affect KIC flux. Leucine oxidation increased (P less than 0.01) by nearly threefold, whereas nonoxidized leucine utilization decreased. Infusion of triglyceride plus heparin together with nicotinic acid blunted some of the responses observed with nicotinic acid alone. In that changes in oxidation under steady state condition reflect changes in net leucine balance, these data suggest that FFA availability may positively affect the sparing of at least one essential amino acid and may influence whole body protein metabolism.

Animals↗
PubMed1986

Insulin dose-response characteristics for suppression of glycerol release and conversion to glucose in humans.

To compare the dose-response characteristics for suppression of lipolysis and suppression of glucose production by insulin, 13 normal nonobese individuals were infused with insulin at rates of 0.1, 0.2, 0.4, 0.8, and 1.6 mU X kg-1 X min-1 while normoglycemia was maintained with the glucose clamp technique. Glucose appearance and glycerol appearance (taken as index of lipolysis) were measured isotopically with simultaneous infusions of 3-[3H]glucose and U-[14C]glycerol. Baseline glucose and glycerol rates of appearance were 14 +/- 0.5 and 1.7 +/- 0.2 mumol X kg-1 X min-1, respectively. Approximately 3% of plasma glucose originated from glycerol, and this accounted for approximately 50% of glycerol disposal. During the insulin infusions, arterial insulin (basal, 9.8 +/- 0.6 microU/ml) increased to 14 +/- 0.5, 20 +/- 0.5, 31 +/- 1, 58 +/- 2, and 104 +/- 6 microU/ml; calculated portal venous insulin (basal, 24 +/- 2 microU/ml) increased to 26 +/- 1, 32 +/- 3, 70 +/- 4, and 115 +/- 6 microU/ml. The rate of glucose appearance was suppressed 100%, whereas the rate of appearance of glycerol was maximally suppressed only 85%. Nevertheless, the insulin concentration that produced half-maximal suppression of glucose appearance was twice as great as that required for half-maximal suppression of glycerol appearance (26 +/- 2 vs. 13 +/- 2 microU/ml, P less than .001). Insulin decreased both the absolute rate of glycerol conversion to plasma glucose and the percent of glycerol disposal appearing in plasma glucose (both P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Use of t-butyldimethylsilylation in the gas chromatographic/mass spectrometric analysis of physiologic compounds found in plasma using electron-impact ionization.

The use of N-methyl-N-(t-butyldimethylsilyl)trifluoroacetamide to prepare the t-butyldimethylsilyl derivatives of a number of organic compounds (selected amino acids, alpha-keto acids, ketone bodies, free fatty acids, urea, glycerol, lactate, and pyruvate) is reported. These derivatives are particularly useful for gas chromatographic/mass spectrometric analysis involving the use of stable isotopes and selected ion monitoring, since a peak of sufficient abundance at 57 mass/charge units below the molecular ion was always present, and was the result of the loss of one t-butyl group. In each case, this fragment contained the entire skeleton of the original compound, which permitted easy analysis using electron-impact ionization of these compounds alone or when labeled with stable isotopes in any nonexchangeable position.

Amino Acids↗
PubMed1984

Determination of ketone body turnover in vivo with stable isotopes, utilizing gas chromatography/mass spectrometry.

JH imple and reliable method for the determination of ketone body turnover in vivo using a primed, continuous infusion of [3,4-13C2]acetoacetate is described. Mole percent enrichment of beta-[13C2]hydroxybutyrate and [13C2]acetoacetate is determined by gas chromatography/mass spectrometry using electron-impact ionization and selected ion monitoring. Ketone body flux data are provided from preliminary dog experiments. The method is readily applicable to the study of ketone body metabolism in both laboratory animals and humans.

3-Hydroxybutyric Acid↗