Genetic characterization of the murine Ym1 gene and identification of a cluster of highly homologous genes

The induction of Fos protein was examined within LHRH neurons of guinea pigs; the aim was to delineate relationships between subgroups of LHRH neurons during an LH surge in a laboratory rodent in which the distribution of LHRH neurons and the presence of a true luteal phase in the reproductive cycle resemble those in primates. Approximately one third of the forebrain population of LHRH neurons was examined in ovariectomized steroid-treated guinea pigs killed either before or during a steroid-induced LH surge. LHRH/Fos double-labeled neurons were more abundant in surging compared to presurge guinea pigs (p = 0.008) and were most abundant within the preoptic area and anterior hypothalamus. Nonetheless, double-labeled LHRH/Fos neurons were observed throughout the remainder of the population of LHRH neurons in surging guinea pigs. A relative loss of LHRH reaction product was detected by image analysis in the LHRH terminals in the median eminence of surging guinea pigs, consistent with augmented LHRH release. Thus, there appears to be a coordinated increase in Fos expression in subgroups of LHRH neurons, more pronounced in rostral, as compared to caudal, regions in guinea pigs killed after the peak of the steroid-induced LH surge.     

Identification of a phosphate regulatory site and a low affinity binding site for glucose 6-phosphate in the N-terminal half of human brain hexokinase

Crystal structures of human hexokinase I reveal identical binding sites for phosphate and the 6-phosphoryl group of glucose 6-phosphate in proximity to Gly87, Ser88, Thr232, and Ser415, a binding site for the pyranose moiety of glucose 6-phosphate in proximity to Asp84, Asp413, and Ser449, and a single salt link involving Arg801 between the N- and C-terminal halves. Purified wild-type and mutant enzymes (Asp84 --> Ala, Gly87 --> Tyr, Ser88 --> Ala, Thr232 --> Ala, Asp413 --> Ala, Ser415 --> Ala, Ser449 --> Ala, and Arg801 --> Ala) were studied by kinetics and circular dichroism spectroscopy. All eight mutant hexokinases have kcat and Km values for substrates similar to those of wild-type hexokinase I. Inhibition of wild-type enzyme by 1,5-anhydroglucitol 6-phosphate is consistent with a high affinity binding site (Ki = 50 microM) and a second, low affinity binding site (Kii = 0.7 mM). The mutations of Asp84, Gly87, and Thr232 listed above eliminate inhibition because of the low affinity site, but none of the eight mutations influence Ki of the high affinity site. Relief of 1,5-anhydroglucitol 6-phosphate inhibition by phosphate for Asp84 --> Ala, Ser88 --> Ala, Ser415 --> Ala, Ser449 --> Ala and Arg801 --> Ala mutant enzymes is substantially less than that of wild-type hexokinase and completely absent in the Gly87 --> Tyr and Thr232 --> Ala mutants. The results support several conclusions. (i) The phosphate regulatory site is at the N-terminal domain as identified in crystal structures. (ii) The glucose 6-phosphate binding site at the N-terminal domain is a low affinity site and not the high affinity site associated with potent product inhibition. (iii) Arg801 participates in the regulatory mechanism of hexokinase I.     

Current zinc intake and risk of diabetes and coronary artery disease and factors associated with insulin resistance in rural and urban populations of North India

OBJECTIVE: To determine the association between current zinc intake and prevalence of coronary artery disease (CAD) and diabetes as well as factors associated with insulin resistance. DESIGN, SUBJECTS AND METHODS: In this cross sectional survey, 3575 subjects, aged 25 to 64 years, including 1769 rural (894 men. 875 women) and 1806 urban (904 men, 902 women) subjects were studied. The survey methods included questionnaires for 7-day food intake record, physical examination, and electrocardiography using World Health Organization criteria. RESULTS: The prevalence of CAD, diabetes and glucose intolerance was significantly higher among subjects consuming lower intakes of dietary zinc. There was a higher prevalence of hypertension, hypertriglyceridemia and low high-density lipoprotein cholesterol levels which showed significant upward trend with lower zinc intakes. Serum lipoprotein (a) and 2-hour plasma insulin levels also were associated with low zinc intake. Multivariate logistic regression analysis after adjustment for age showed that zinc intake and CAD were inversely associated. Serum zinc (odds ratio:men 0.77, women 0.57), serum triglycerides (men 0.86, women 0.81), blood pressure (0.83 men, women 0.76), diabetes mellitus (men 0.90, women 0.85), central obesity (men 0.88, women 0.87), glucose intolerance (men 0.66, women 0.57) and low high-density lipoprotein cholesterol (men 0.72, women 0.70) were significant risk factors for CAD (explained by tertiles of zinc status) in urban subjects. These associations were not observed in rural subjects. CONCLUSION: Lower consumption of dietary zinc and low serum zinc levels were associated with an increased prevalence of CAD and diabetes and several of their associated risk factors including hypertension, hypertriglyceridemia and other factors suggestive of mild insulin resistance in urban subjects.     

Homologous desensitization of the D1A dopamine receptor: efficacy in causing desensitization dissociates from both receptor occupancy and functional potency

The role of drug efficacy in agonist-induced desensitization was studied in C-6 glioma cells transfected with the monkey dopamine D1A (mD1A) receptor. Dopamine pretreatment for 2 hr produced greater than 80% loss of responsiveness in the stimulation of cAMP accumulation that was blocked by the D1 antagonist SCH23390. A series of full and partial D1 agonists from structurally dissimilar classes were then examined. Three full agonists (dihydrexidine, SKF82958, A77636) desensitized the receptor to the same extent as dopamine, whereas two other full agonists (dinapsoline and A68930) and all the partial agonists tested (SKF38393, pergolide and d-lysergic acid diethylamide tartrate) produced only partial desensitization (i.e., 50% that of dopamine). Whereas partial agonists (i.e., SKF38393, pergolide and d-lysergic acid diethylamide tartrate) caused no alteration in ligand-accessible mD1A receptors, four of the full agonists (dopamine, dihydrexidine, dinapsoline, A68930) caused a 30 to 40% reduction in receptor number. One full agonist, A77636, caused nearly an 80% decrease in receptor number, despite the fact that the degree of functional desensitization was similar to the other full agonists. The desensitization of the D1 receptor was homologous, not affecting beta-2 adrenergic receptors endogenous to C-6 cells. Neither incubation with cAMP analogs, nor inhibition of protein kinase A, affected dopamine-induced desensitization, suggesting a cAMP-independent mechanism in this cell line. Together, these data suggest that functional desensitization of the mD1A receptor expressed in C-6 glioma cells is a cAMP-independent mechanism, cannot be predicted reliably from agonist efficacy for stimulating adenylate cyclase and can occur in the absence of changes in receptor number.     

Plasma L-arginine concentration, oxygenation index, and systemic blood pressure in premature infants

OBJECTIVE: To determine the relationships between plasma L-arginine concentrations and the severity of respiratory distress syndrome (RDS) or systemic blood pressure in premature infants. DESIGN: Prospective, observational study. SETTING: Neonatal intensive care, tertiary referral hospital. SUBJECTS: Fifty-three premature infants. INTERVENTIONS: We measured arginine and nutritional intake, plasma arginine concentration, total amino acid concentrations, and blood pressure on days 3, 7, 14, and 21 of life. In 33 infants who received assisted ventilation, oxygenation index could be calculated to reflect the severity of RDS. The relationships between plasma arginine and oxygenation index or blood pressure were analyzed using multiple linear regression. MEASUREMENTS AND MAIN RESULTS: On day 3, plasma arginine concentrations were decreased compared with normal published values. Arginine concentrations increased with the day of life of measurement (p < .001) and with arginine intake (p < .001). After adjusting for arginine intake and day of life, an inverse relationship was found between oxygenation index and plasma arginine concentrations: (p = .025). No similar relationship was found between oxygenation index and the concentration of total amino acids. A weak positive relationship was found between plasma arginine concentration and systemic blood pressure. CONCLUSIONS: Increments in the oxygenation index, reflective of an increased severity of RDS, are associated with a decrease in plasma arginine concentration. This finding may reflect arginine consumption by the nitric oxide synthase pathway in the lungs of premature infants with RDS, or may be explained by increased arginine catabolism. The lack of a similar relationship between total plasma amino acids and oxygenation index supports the first interpretation.     

Changes in plasma lipids and lipoproteins in humans during a 2-year period of dietary restriction in Biosphere 2

BACKGROUND: A cohort study was performed of 8 people sealed inside Biosphere 2 to evaluate the effects of dietary restriction in humans on lipid and lipoprotein levels and the relationship of these levels to energy, fat, and protein content of the diet, and body weight, weight change, and energy expenditure. METHODS: Eight healthy people aged 27 to 67 years, 4 women and 4 men, were sealed inside Biosphere 2 from September 26, 1991, to September 26, 1993, the longest sustained period in an "isolated confined environment" on record. They were studied throughout confinement and for more than 2 years after their exit and return to an ad libitum diet. Food available was severely restricted during most of the 2-year period inside Biosphere 2. High work output was maintained and food quality remained high, resulting in prolonged restriction of energy intake without malnutrition. RESULTS: Fasting plasma cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol levels; HDL subfraction distribution; dietary energy, fat, and protein content intake; and height, weight, weight change, and energy expenditure were measured. Total plasma cholesterol and triglyceride levels decreased 30% and 45%, respectively. The HDL and low-density lipoprotein levels also decreased and, in some participants, levels of HDL2 subfractions were increased. Multivariate analysis showed that the major cause of these changes was energy restriction. CONCLUSIONS: Energy restriction was the major factor leading to low lipid and lipoprotein levels. Energy restriction with adequate nutrition of young and middle-aged people may substantially reduce risk for atherosclerosis and consequent coronary artery and cerebrovascular disease.     

Stereotactic pallidotomy and thalamotomy using individual variations of anatomic landmarks for localization

OBJECTIVE: The optimal choice of imaging and localization for stereotactic surgery for movement disorders remains uncertain, with controversy surrounding the use of microelectrode recording and the role of distortion of magnetic resonance imaging (MRI) scans in reducing the accuracy of lesion placement. We review our experience with 67 pallidotomies and 35 thalamotomies performed without microelectrode recording, using instead individual variations in anatomic landmarks. METHODS: Computed tomography is used as the primary modality, with comparison with carefully angled MRI scans and the use of neural structures, such as the mamillary bodies and the vascular anatomy. Pallidal target sites are chosen immediately lateral and superior to the optic tract on a line bisecting the axis of the peduncle, with macrostimulation guiding the final adjustment of target position. Forty-seven patients undergoing unilateral pallidotomies were studied in the "off" state and the "on" state using a modified Unified Rating Scale for Parkinson's disease (URSP) score and a dyskinesia scale, preoperatively and postoperatively at 2 weeks, 2 months, 6 months, and 12 months. In the 31 patients undergoing thalamotomy, tremor was rated preoperatively and postoperatively as near-complete resolution, partial resolution, and failure. RESULTS: The "off" state Unified Rating Scale for Parkinson's disease motor score declined from 42.0 to 32.2 at 2 weeks after surgery (P < 0.0001, n = 42). The Unified Rating Scale for Parkinson's disease motor score was 34.2 at 2 months (P < 0.0001, n = 35), 29.4 at 6 months (P < 0.0001, n = 27), and 24.9 at 12 months (P = 0.005, n = 12), representing an overall improvement in "off" state motor function of approximately 25 to 40%. The "on" state dyskinesia score fell from 5.5 to 2.0 at 2 weeks (P < 0.0001) and persisted in the later visits. The dyskinesia score for the contralateral side fell from 2.5 preoperatively to 0.26 at 2 weeks, 0.28 at 2 months, 0.22 at 6 months, and 0.0 at 12 months. Of the patients undergoing thalamotomies, 65% experienced near-complete or complete tremor resolution, 23% experienced partial tremor relief, and 13% were considered treatment failures. CONCLUSION: Stereotactic procedures for movement disorders requiring high precision can be safely and successfully performed without the use of microelectrode recording techniques. Meticulous alignment of MRI and computed tomographic scans based on visualized anatomy allows precise lesion placement and avoids the distortion inherent in MRI scans.     

APOE in non-Alzheimer amyloidoses: transmissible spongiform encephalopathies

We have identified a member of the VEGF family by computer-based homology searching and have designated it VEGF-D. VEGF-D is most closely related to VEGF-C by virtue of the presence of N- and C-terminal extensions that are not found in other VEGF family members. In adult human tissues, VEGF-D mRNA is most abundant in heart, lung, skeletal muscle, colon, and small intestine. Analyses of VEGF-D receptor specificity revealed that VEGF-D is a ligand for both VEGF receptors (VEGFRs) VEGFR-2 (Flk1) and VEGFR-3 (Flt4) and can activate these receptors. However. VEGF-D does not bind to VEGFR-1. Expression of a truncated derivative of VEGF-D demonstrated that the receptor-binding capacities reside in the portion of the molecule that is most closely related in primary structure to other VEGF family members and that corresponds to the mature form of VEGF-C. In addition, VEGF-D is a mitogen for endothelial cells. The structural and functional similarities between VEGF-D and VEGF-C define a subfamily of the VEGFs.