PubMed Health⌕ Search

Biomedical subjects

J A Adam

Publications and source records attributed to J A Adam.

10 recordsLinked to original sources
PubMed2002

Decreased plasma orexin-A levels in obese individuals.

Orexin-A and -B stimulate appetite and food intake in rats. Orexins and orexin receptors are present in the hypothalamus as well as the enteric nervous system, the pancreas and the gut. The presence of orexins in peripheral blood, however, has not yet been reported. To determine whether orexin-A is present in human plasma and is related to body weight, we measured plasma orexin-A and leptin levels in a population with a body mass index (BMI) range from 19.8 to 59 kg/m(2). Plasma orexin-A levels correlated negatively and plasma leptin levels correlated positively with BMI. In obese and morbidly obese individuals, orexin-A levels were significantly lower and leptin levels were significantly higher when compared to normal. Our results support previous data suggesting that orexin-A acts also in a peripheral manner. The fact that lower levels of plasma orexin-A are present in obese individuals suggests that it is involved in the regulation of human energy metabolism.

Body Mass Index↗
PubMed2000

Postprandial refilling and turnover: specific gallbladder motor function defects in patients with gallstone recurrence.

BACKGROUND AND AIMS: Impaired gallbladder motor functions are important in the pathogenesis of primary cholesterol gallstones, and possibly in the pathogenesis of recurrent gallstones. By using ultrasonography and cholescintigraphy simultaneously, we recently defined new parameters of gallbladder motor function (postprandial refilling and turnover in addition to emptying), which were markedly impaired in gallstone patients. The aim of this study was to assess the value of these new parameters in distinguishing patients with from those without gallstone recurrence. METHODS: We studied 11 patients with gallstone recurrence, 11 without gallstone recurrence (at least 40 months after complete dissolution by oral bile acids) and 11 healthy controls. Simultaneous measurements of gallbladder volume (ultrasound) and gallbladder counts (gamma-camera scintigraphy) were carried out in the fasting state and at 10 min intervals following meal ingestion, for a period of 90 min. Gallbladder refilling, turnover of bile and turnover index were calculated, as well as gallbladder emptying by both cholescintigraphy and ultrasound. RESULTS: Patients with gallstone recurrence had reductions in gallbladder emptying, postprandial refilling and gallbladder bile turnover. They also had a significant reduction in the turnover index (1.7 +/- 1.4) compared to controls (3.5 +/- 0.3, P < 0.01) and to patients without gallstone recurrence (3.1 +/- 1.5, P < 0.05). Patients without gallstone recurrence had only a small reduction in emptying and no reduction in postprandial refilling or turnover compared to controls. CONCLUSIONS: We conclude that impairment of gallbladder emptying persists in all patients after gallstone dissolution, albeit to a more pronounced extent in patients with recurrence; but that impairment of postprandial refilling and turnover are specific defects in patients with recurrence.

Adult↗
PubMed1996

Mathematical models of prevascular spheroid development and catastrophe-theoretic description of rapid metastatic growth/tumor remission.

A brief survey is provided of deterministic models of tumor growth and development over the last three decades. The evolution of these models has proceeded from basic phenomenological and empirical descriptions, through both time-dependent and time-independent diffusion models (largely within the diffusive equilibrium approximation). This includes a study of the diffusion of growth inhibitors. The stability of spheroid models to small perturbations is discussed, and also recent applications of nonlinear elasticity theory and differential geometry to possible staging and grading of cancers. Finally, an excursion is made into catastrophe theory, wherein it is suggested that the cusp catastrophe (in particular) may provide a qualitative description of rapid, almost spontaneous (i) growth of metastases, or (ii) tumor remission (both occurring under certain restrictive conditions).

Animals↗
PubMed1995

Postprandial gallbladder motor function: refilling and turnover of bile in health and in cholelithiasis.

BACKGROUND & AIMS: Impaired gallbladder emptying is implicated in gallstone disease. Ultrasonography and scintigraphy have shown conflicting results because the former is influenced by postprandial refilling, whereas the latter is not influenced by refilling. The aim of this study was to measure postprandial refilling and turnover of bile by combining the two techniques. METHODS: Simultaneous scintigraphy and ultrasonography were used in 14 patients with gallstones and 11 healthy controls. Measurements were performed while the patients were fasting and at 10-minute intervals after a standard meal for 90 minutes, and the measurements were used to calculate postprandial refilling, turnover of bile (in milliliters), and turnover index. RESULTS: Ultrasonography and scintigraphy provided different gallbladder emptying patterns. Compared with controls, patients with gallstones had impaired emptying by both scintigraphy (P < 0.0001) and ultrasonography (P < 0.01). Postprandial refilling and turnover were both reduced between 60 and 90 minutes (P < 0.05), and the turnover index was markedly reduced (1.8 vs. 3.5; P < 0.001). CONCLUSIONS: Simultaneous scintigraphy and ultrasonography provide a new model of gallbladder motor function showing that refilling begins immediately postprandially. In healthy controls, the gallbladder postprandially handles up to six times its basal volume within a period of 90 minutes, but this turnover of bile is markedly reduced in cholelithiasis causing a reduced washout effect of the gallbladder contents, including cholesterol crystals.

Analysis of Variance↗
PubMed1993

Equilibrium model of a vascularized spherical carcinoma with central necrosis--some properties of the solution.

Properties of the solutions of a nonlinear time-independent diffusion equation are studied. The equation arises in a model of a spherically symmetric vascularized carcinoma with a central necrotic core. The boundary value problem as posed possesses a constant solution when the nutrient consumption rate and deposition rate (from the vascular network) are equal. This solution can lose uniqueness at a critical tumor dimension which corresponds to the onset of instability with respect to deviations from that uniform equilibrium state.

Cell Division↗
PubMed1990

Diffusion regulated growth characteristics of a spherical prevascular carcinoma.

Recently a mathematical model of the prevascular phases of tumor growth by diffusion has been investigated (S.A. Maggelakis and J.A. Adam, Math. Comput. Modeling, in press). In this paper we examine in detail the results and implications of that mathematical model, particularly in the light of recent experimental work carried out on multicellular spheroids. The overall growth characteristics are determined in the present model by four parameters: Q, gamma, b, and delta, which depend on information about inhibitor production rates, oxygen consumption rates, volume loss and cell proliferation rates, and measures of the degree of non-uniformity of the various diffusion processes that take place. The integro-differential growth equation is solved for the outer spheroid radius R0(t) and three related inner radii subject to the solution of the governing time-independent diffusion equations (under conditions of diffusive equilibrium) and the appropriate boundary conditions. Hopefully, future experimental work will enable reasonable bounds to be placed on parameter values referred to in this model: meanwhile, specific experimentally-provided initial data can be used to predict subsequent growth characteristics of in vitro multicellular spheroids. This will be one objective of future studies.

Animals↗
PubMed1989

Mathematical models of tumor growth. IV. Effects of a necrotic core.

Two mathematical models for the control of the growth of a tumor by diffusion of mitotic inhibitor are presented. The inhibitor production rate is taken to be uniform in a necrotic core for the first model and in the nonnecrotic region for the second model. Regions of stable and unstable growth are determined, and conclusions are drawn about the limiting peripheral widths of stable tissue growth for both models. Comparisons of the results from the two models indicate that the models are sensitive to the source distributions of inhibitor production.

Diffusion↗