UV irradiation of polycyclic aromatic hydrocarbons in ices: production of alcohols, quinones, and ethers.

Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis.

Role of brain insulin receptor in control of body weight and reproduction.

Insulin receptors (IRs) and insulin signaling proteins are widely distributed throughout the central nervous system (CNS). To study the physiological role of insulin signaling in the brain, we created mice with a neuron-specific disruption of the IR gene (NIRKO mice). Inactivation of the IR had no impact on brain development or neuronal survival. However, female NIRKO mice showed increased food intake, and both male and female mice developed diet-sensitive obesity with increases in body fat and plasma leptin levels, mild insulin resistance, elevated plasma insulin levels, and hypertriglyceridemia. NIRKO mice also exhibited impaired spermatogenesis and ovarian follicle maturation because of hypothalamic dysregulation of luteinizing hormone. Thus, IR signaling in the CNS plays an important role in regulation of energy disposal, fuel metabolism, and reproduction.

Evidence-based dentistry for everyday practice.

Busy practitioners can easily implement evidence-based dentistry with the use of technology and electronic evidence-based dentistry resources.

Tetraspanin CD82 regulates bone marrow homing of acute myeloid leukemia by modulating the molecular organization of N-cadherin.

Communication between acute myeloid leukemia (AML) and the bone marrow microenvironment is known to control disease progression. Therefore, regulation of AML cell trafficking and adhesion to the bone marrow is of significant interest. In this study, we demonstrate that differential expression of the membrane scaffold CD82 modulates the bone marrow homing of AML cells. By combining mutational analysis and super-resolution imaging, we identify membrane protein clustering by CD82 as a regulator of AML cell adhesion and bone marrow homing. Cluster analysis of super-resolution data indicates that N-linked glycosylation and palmitoylation of CD82 are both critical modifications that control the microdomain organization of CD82 as well as the nanoscale clustering of associated adhesion protein, N-cadherin. We demonstrate that the inhibition of CD82 glycosylation increases the molecular packing of N-cadherin and promotes the bone marrow homing of AML cells. In contrast, we find that the inhibition of CD82 palmitoylation disrupts the formation and organization of N-cadherin clusters and significantly diminishes bone marrow trafficking of AML. Taken together, these data establish a mechanism where the membrane organization of CD82, through specific posttranslational modifications, regulates N-cadherin clustering and membrane density, which impacts the in vivo trafficking of AML cells. As such, these observations provide an alternative model for targeting AML where modulation of protein organization within the membrane may be an effective treatment therapy to disrupt the bone marrow homing potential of AML cells.

Functional interactions between melanin-concentrating hormone, neuropeptide Y, and anorectic neuropeptides in the rat hypothalamus.

A growing body of evidence indicates that a number of peptides expressed in the mammalian hypothalamus are involved in the regulation of food intake and energy balance. Among these, melanin-concentrating hormone (MCH) and neuropeptide Y (NPY) are potent appetite stimulants, whereas alpha-melanocyte-stimulating hormone (alpha-MSH), neurotensin, and glucagon-like peptide (GLP)-1(7-36) amide have appetite-suppressing properties. However, the functional interactions between pathways involving these neuropeptides remain incompletely understood. In the current study, we describe the functional interactions between orexigenic (appetite-stimulating: MCH and NPY) and anorectic (appetite-suppressing: alpha-MSH, neurotensin, and GLP-1) peptides after intracerebroventricular (i.c.v.) administration in the rat. The i.c.v. administration of GLP-1 completely prevents the orexigenic effects of both MCH and NPY. However, i.c.v. administration of alpha-MSH prevents only the orexigenic effect of MCH, as we have previously shown, but does not prevent the effect of NPY on food intake. Similarly, i.c.v. administration of neurotensin prevents only the orexigenic effect of MCH, but does not prevent the appetite-stimulating effect of NPY. Thus, our study suggests that the functional interactions between these neuropeptides are specific, although the underlying mechanisms are as yet unexplored.

An integrated approach to the study of chemically reactive metabolites of acetaminophen.

I have examined in mice the kinetics of covalent binding of a metabolite of acetaminophen, as well as the binding to target tissue (and hence toxic reactions). At low doses, the chemically reactive metabolite seems to be converted to a glutathione conjugate that is ultimately excreted as a mercapturic acid. High acetaminophen doses that deplete available glutathione in the liver lead to toxic reactions. Manipulation of the system with agents that affect either glutathione availability or activity of the operative enzyme system has suggested that a chemically reactive acetaminophen metabolite is the active agent in hepatotoxic reactions from the drug. The chemically reactive intermediate seems to be short lived; it reacts with glutathione and is easily reduced by ascorbic acid. Acetylcysteine prevents liver necrosis caused by acetaminophen, and some possible mechanisms are discussed.

Estradiol metabolism by complementary deoxyribonucleic acid-expressed human cytochrome P450s.

Twelve forms of human cytochrome P450 were synthesized in human hepatoma Hep G2 cells by means of cDNA-directed expression using vaccinia virus. The cDNA-expressed enzymes were tested for their ability to oxidize estradiol. Incubation of [14C]estradiol with cell lysates containing P450 IA2 resulted in the production of 2-hydroxy and 4-hydroxy metabolites with substrate turnovers of 2.74 and 0.27 min-1, respectively. P450s IIIA3 and IIIA4 yielded the same metabolites at about one third the rate of P450 IA2. Low levels of estradiol hydroxylation were also catalyzed by P450s IIC9, IIIA5, and IVB1. Six other P450 forms yielded no detectable metabolism. The roles of P450s IA2, IIA3, and IIIA4 were further established by immunoinhibition using antirat P450 antibodies. Antibody that specifically binds to P450 IIIA3 and IIIA4 inhibited 60-70% of estradiol hydroxylation, and antibody against P450 IA2 inhibited 20-40% of the estradiol hydroxylase activity in microsomes from two human liver specimens, suggesting that these enzymes constitute the major forms catalyzing estradiol oxidation in human liver. Immunoinhibition results also suggest that 2-hydroxy- and/or 4-hydroxycatechol estrogens are further metabolized to other yet uncharacterized metabolites by P450s IIIA3 and IIIA4.

Effect of spironolactone on sex hormones in man.

Administration spironolactone at a dosage of 400 mg/day to healthy male volunteers for 5 days resulted in a significant rise in plasma progesterone and 17alpha-hydroxyprogesterone which persisted throughout the study. A transient increase in plasma FSH and LH concentration was observed after the second but not the third or fifth days of drug administration. There was no change in plasma concentration of testosterone, 17beta-estradiol, or prolactin. These findings are consistent with a previously-reported spironolactone-induced destruction of the microsomal enzyme cytochrome P-450, an enzyme necessary for 17-hydroxylase and desmolase activity. The results do not explain the decrease of libido, the impotence, and the gynecomastia frequently associated with spironolactone therapy in males.

Volumetric magnetic resonance imaging in men with dementia of the Alzheimer type: correlations with disease severity.

Using magnetic resonance imaging (MRI), we measured the volumes of various brain structures and cerebrospinal fluid (CSF) in 19 men with dementia of the Alzheimer type (DAT) and 18 healthy age-matched control men. The mean (+/- S.D) Mini-Mental State exam score (MMSE) of the DAT men was 16 +/- 7; 9 were mildly (MMSE > 20), 5 moderately (MMSE 10-20), and 5 severely (MMSE < 10) demented. Brain and CSF volumes were normalized as a percent of the traced intracranial volume to control for the relation of volumes of cerebral structures to head size, and analyzed statistically. The whole group of DAT subjects had significantly smaller mean cerebral brain matter and temporal lobe volumes (p < 0.05), and significantly larger mean ventricular and temporal lobe peripheral CSF volumes than did controls. Mean volumes of the subcortical nuclei did not differ significantly between groups, and mean volume of temporal lobe brain matter decreased significantly more than whole brain, suggesting regional loss of brain matter in DAT. Mildly demented DAT patients had significantly smaller mean cerebral brain matter and temporal lobe volumes and significantly larger volumes of lateral ventricles, and of temporal lobe peripheral CSF, than did controls. Neuropsychological measures of disease severity in DAT patients were significantly (p < 0.05) and appropriately correlated to volumes of cerebral brain matter and right lateral ventricle. These results suggest that in DAT: (i) significant brain atrophy is present early in the disease process, (ii) brain atrophy correlates with severity of cognitive impairment, and (iii) there is greater involvement of the telencephalic association system than whole brain, and there is relative sparing of the caudate, lenticular and thalamic nuclei.

Activation of cerebral blood flow during a visuoperceptual task in patients with Alzheimer-type dementia.

Changes in regional cerebral blood flow (rCBF) associated with a face-matching task were examined using positron emission tomography (PET) and H2(15)O in 7 patients with mild-moderate dementia of the Alzheimer type (DAT) and in 8 healthy age-matched controls. rCBF was normalized to whole brain flow and pixel-by-pixel difference images were computed by contrasting flow during a control task to flow during face matching. Both patients and controls showed bilateral rCBF increases in occipitotemporal extrastriate cortex during face matching. The magnitude of these increases was not significantly different between the groups. In addition, the patients showed greater rCBF activation in regions of occipital and frontal cortex. These results show that early in the course of DAT, patients utilize extrastriate cortex to perform a visuoperceptual task, as do control subjects but also show rCBF increases in additional cortical areas. Activation of these additional areas of cortex in the patients may reflect an increased attentional load during face matching due to their reduced cognitive capacity.

Interindividual differences in amitriptyline demethylation.

Amitriptyline (AT) and its demethyl metabolite nortriptyline (NT) were given orally and intramuscularly to 6 normal subjects, and the areas under the blood concentration--time curves (AUC) were calculated. The mean unbound fraction of AT and NT in plasma was 5.4% and 8.3%, respectively. The blood-plasma ratio of NT was nearly double that of AT, which was close to unity. The mean systemic availability of oral relative to intramuscular AT and NT was 43% and 61%. The calculated mean oral blood clearance of AT as measured by dose (oral)/AUC was 1.6 1/min. The demethylation of orally administered AT varied considerably between the 6 individuals (from 25% to 89%) and correlated with oral drug clearance. Demethylation was estimated from the AUC applied to the NT metabolite. The estimated oral clearance of AT from demethylation ranged from 0.21 to 1.80 1/min.

Longitudinal changes in lateral ventricular volume in patients with dementia of the Alzheimer type.

We determined the rates of lateral ventricular enlargement and decline in cognitive performance for 11 men and nine women with dementia of the Alzheimer type (DAT), and compared these rates with the same measures obtained for age-matched healthy controls (nine men and eight women). DAT patients, as a group, had only mild cognitive impairment at initial evaluation, and each patient was followed from 9 months to over 7 years with yearly evaluations. Six DAT patients had isolated memory impairment as their only cognitive deficit early in the course of the disease. The rate of total lateral ventricle enlargement (cm3/yr) was significantly different between DAT and healthy controls, and was more specific and sensitive to the diagnosis of DAT than comparison of cross-sectional volumes at final evaluation. The rate of total lateral ventricular enlargement did not differ significantly by patient sex, ventricular size at initial evaluation, age, or degree of cognitive impairment as measured by Mini Mental State Examination scores. However, in the six DAT patients initially found to have isolated memory impairment, the rate of ventricular enlargement during the period of isolated memory impairment was significantly less than the rate of ventricular enlargement after the onset of nonmemory cognitive impairment. The diagnostic power of total lateral ventricular measures made from two CTs separated by 1 year and obtained early in the course of the illness, however, was only 0.33. We conclude that the total lateral ventricular enlargement accompanying DAT is due to continuous, pathologic cell loss, significantly greater than cell loss due to the healthy aging process.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of white matter hyperintensity volume on brain structure, cognitive performance, and cerebral metabolism of glucose in 51 healthy adults.

OBJECTIVE: To assess the association of MRI white matter hyperintensities (WMHI) with cognitive performance, cerebral structure, and cerebral metabolism in 51 healthy individuals aged 19 to 91 years without cerebrovascular risk factors. BACKGROUND: Abnormal white matter signals have been associated with brain atrophy, reduced cerebral blood flow, focal neurologic signs, gait disorder, and poorer neuropsychological test performance. Most studies of WMHI, however, include subjects with hypertension or other identifiable causes of cerebrovascular disease that may have an independent effect on brain structure and function. To assess brain changes associated with WMHI independent of cerebrovascular risk factors, we determined WMHI volume, brain volume, cerebral metabolism, and cognitive performance for a group of subjects free of medical illness. Regional cerebral metabolism and cognitive domains were also assessed to evaluate the possible role of frontal lobe dysfunction in subjects with WMHI. DESIGN: Cross-sectional study of 51 very healthy subjects aged 19 to 91 years. METHODS: WMHI, brain, and CSF volumes were determined by MRI segmentation. Neuropsychological tests were employed to assess multiple cognitive domains. Brain metabolism was determined from 18-fluoro-2-deoxy-D-glucose PET. Multivariate relations were tested with stepwise linear regression. Models included the potential confounders of age and education where appropriate. RESULTS: The distribution of WMHI volume was bimodal, with five subjects having WMHI volumes beyond three SDs from the normally distributed population. A WMHI volume of greater than 0.5% of intracranial volume was considered abnormal. Within the multivariate models, WMHI volumes were significantly predictive of increased ventricular volume, reduced brain volume, and reduced cognitive scores. Subjects with greater than 0.5% WMHI volume also had significantly lower frontal lobe metabolism, significantly higher systolic blood pressure, significantly larger ventricular volume, and significantly lower scores on frontal lobe-mediated neuropsychological tests than age-matched controls. CONCLUSION: WMHI volume is associated with structural and functional brain changes even within a group of very healthy individuals. WMHI is associated with poorer frontal lobe cognitive function and, when severe, is accompanied by significantly reduced frontal lobe metabolism. Subjects with large WMHI volumes have significantly higher systolic blood pressure, brain atrophy, reduced cerebral metabolism, and lower scores on tests of frontal lobe function than age-matched controls. Large amounts of WMHI are, therefore, pathologic and may be related to elevated systolic blood pressure even when it is within the normal age-related range.

Elevation of serum cholesterol levels in mice by the antioxidant butylated hydroxyanisole.

The food antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are structurally related to the hypocholesterolemic drug probucol. The purpose of this study was to determine if BHA can lower serum cholesterol levels as is observed with probucol. Treatment of mice with 0.75% BHA in their feed for 10 days resulted in a significant (P < or = 0.01) elevation of serum cholesterol levels. This effect contrasts with the cholesterol-lowering effect of probucol. Further, the degree of cholesterol elevation was comparable to that observed in mice administered 3% cholesterol in their feed for 7 days. The enzyme acyl CoA:cholesterol acyltransferase (ACAT) was decreased significantly (P < or = 0.01) in liver microsomes from BHA-treated mice. In contrast, hepatic microsomal ACAT activity was increased significantly (P < or = 0.01) in cholesterol-fed mice. These results suggested that the increased serum cholesterol observed in BHA-treated mice was not accompanied by an increase in hepatic cholesterol levels. Indeed, hepatic microsomal cholesterol levels were reduced in BHA-treated mice, but were increased significantly (P < or = 0.01) in cholesterol-fed mice. These results demonstrate that the common food additive BHA elevates serum cholesterol levels by a mechanism that apparently involves the decreased uptake of cholesterol by the liver.

The role of biotransformation in chemical-induced liver injury.

The role of drug metabolism in chemical-induced liver injury is reviewed. Parameters for studying the formation of chemically reactive metabolites are discussed and the factors that alter the formation and covalent binding of reactive metabolites are selectively emphasized. Some of the experimental work that led to these concepts is discussed, especially the chemical toxicology of the hepatic injury produced by acetaminophen, bromobenzene, furosemide, isoniazid and iproniazid.

Human simulations of vocabulary learning.

The work reported here experimentally investigates a striking generalization about vocabulary acquisition: Noun learning is superior to verb learning in the earliest moments of child language development. The dominant explanation of this phenomenon in the literature invokes differing conceptual requirements for items in these lexical categories: Verbs are cognitively more complex than nouns and so their acquisition must await certain mental developments in the infant. In the present work, we investigate an alternative hypothesis; namely, that it is the information requirements of verb learning, not the conceptual requirements, that crucially determine the acquisition order. Efficient verb learning requires access to structural features of the exposure language and thus cannot take place until a scaffolding of noun knowledge enables the acquisition of clause-level syntax. More generally, we experimentally investigate the hypothesis that vocabulary acquisition takes place via an incremental constraint-satisfaction procedure that bootstraps itself into successively more sophisticated linguistic representations which, in turn, enable new kinds of vocabulary learning. If the experimental subjects were young children, it would be difficult to distinguish between this information-centered hypothesis and the conceptual change hypothesis. Therefore the experimental "learners" are adults. The items to be "acquired" in the experiments were the 24 most frequent nouns and 24 most frequent verbs from a sample of maternal speech to 18-24-month-old infants. The various experiments ask about the kinds of information that will support identification of these words as they occur in mother-to-child discourse. Both the proportion correctly identified and the type of word that is identifiable changes significantly as a function of information type. We discuss these results as consistent with the incremental construction of a highly lexicalized grammar by cognitively and pragmatically sophisticated human infants, but inconsistent with a procedure in which lexical acquisition is independent of and antecedent to syntax acquisition.

Lack of age-related differences in temporal lobe volume of very healthy adults.

PURPOSE: To evaluate age-related differences in temporal and supratemporal brain regions in carefully selected, very healthy men 19 to 92 years of age. METHODS: MR quantification of brain regions used image segmentation into cerebrospinal fluid and brain matter based on nonlinear modeling of pixel intensity distributions. RESULTS: There was a significant age-related decrease (approximately 1% per decade) of posterior frontal lobe volume, but not of temporal lobe volume. The mean volume of the right temporal lobe was significantly greater than the left, and this relation did not change with age. CONCLUSION: In very healthy aging, the volume of the temporal lobes remains constant over the age range of human life.

Ornithine decarboxylase: a biochemical marker of repair in damaged tissue.

The purpose of this study was to: (a) determine the temporal pattern of expression of ornithine decarboxylase (ODC), an established marker of cells engaged in proliferation and differentiation, during repair of traumatized skeletal muscle, and (b) evaluate ODC as a biochemical marker for indexing the extent and rate of repair of traumatized skeletal muscle in response to therapeutic agents. Adult female Wistar rats weighing 240 to 280 grams were anesthetized and injected with 100 ul of 2% lidocaine into the right or left anterior tibialis muscle to induce a localized injury. The animals were treated 1 hour post-injection and every 12 hours for five minutes up to the time of sacrifice using ultrasonic irradiation at 1.5 watts/cm2, sham-irradiation, or no treatment. An analysis of variance for repeated measures and a Tukey's post hoc test were used to determine the significance of treatment effects. Animals irradiated with ultrasound demonstrated an accelerated pattern of change in ODC activity at 24 hours (P less than 0.001), 30 hours (P less than 0.003), and at 48 hours (P less than 0.002) compared to control and sham-irradiated animals at these time intervals. Irradiated animals also demonstrated less edema at 48 hours compared to sham-irradiated and control animals (P less than 0.003). These findings suggest that ODC is a useful biochemical marker for determining the extent and rate of tissue repair in traumatized skeletal muscle, and it provides a temporal and quantifiable parameter for evaluating the efficacy of therapeutic agents used to treat damaged skeletal muscle.

Bromobenzene and p-bromophenol toxicity and covalent binding in vivo.

A hepatotoxic dose of bromobenzene (3 mmoles/kg) decreases hepatic glutathione concentration in rats by approximately 80% within 5 hr following ip injection. A major bromobenzene metabolite, p-bromophenol at a similar dose did not significantly alter hepatic glutathione levels compared to controls. Twenty four hr after administration, serum glutamate pyruvate transaminase (SGPT) levels were significantly increased by bromobenzene but not by p-bromophenol. After 14C-bromobenzene administration, a significant amount of covalently bound radiolabel was detected in liver, kidney and small intestine. A small amount of covalently bound radiolabel was also detected in the lung. After a similar dose of 14C-bromophenol, covalently bound radiolabel was found in liver (62% of the amount detected with 14C-bromobenzene) and smaller amounts were detected in kidney, small intestine and lung. These data are consistent with the view that the hepatotoxicity and glutathione depleting ability of bromobenzene are mediated mainly by bromobenzene-3,4-oxide rather than by chemically reactive metabolites of p-bromobenzene. Covalently bound radiolabel from 14C-bromobenzene, however, may be derived from both bromobenzene-3,4-oxide and the nontoxic reactive metabolites of p-bromophenol.