Effects of repeated morphine treatment on metabolism of cerebral dopamine and serotonin in alcohol-preferring AA and alcohol-avoiding ANA rats

The alcohol-preferring AA (Alko Alcohol) rats are more rapidly sensitized to the locomotor activity-stimulating effects of small doses of morphine than the alcohol-avoiding ANA (Alko Non-Alcohol) rats. To study the involvement of dopaminergic and serotonergic transmission in this behaviour, the effects of acute morphine (1 mg/kg) challenge on the concentrations of dopamine (DA), 5-hydroxytryptamine (5-HT, serotonin) and their metabolites were estimated in three dopaminergic areas in AA and ANA rats on the fourth day after a 3-day morphine or saline treatment. Acute administration of morphine enhanced DA metabolism in the caudate-putamen in the AA, but not in the ANA, rats; in the nucleus accumbens and in the olfactory tubercle the acute effect of morphine was similar in rats of both lines. Morphine pretreatment did not significantly enhance acute morphine's effects on DA metabolites in any of the brain areas studied in rats of either line. Acute administration of morphine enhanced brain 5-HT metabolism in the AA rats but not in the ANA rats, but after repeated treatment it induced no enhancement of 5-HT metabolism. With the methods used, no significant differences were found between the AA and ANA rats in the effects of repeated morphine on cerebral dopaminergic or serotonergic mechanisms which could account for the different behavioural sensitization found previously in rats of these lines. However, both monoamines studied might be involved in the acute locomotor stimulatory effects of morphine.     

Polyamines regulate serine/threonine protein phosphatases in insulin-secreting cells

Reversible protein phosphorylation is an important mechanism by which cells transduce external signals into biologic responses. Levels of protein phosphorylation are determined by the balanced actions of both protein kinases and protein phosphatases (PPases). However, compared with protein kinases, regulation of PPases has been relatively neglected. The insulin secretagogue L-arginine, an immediate metabolic precursor to polyamines, causes a rapid and transient decrease in PPase-1 activity in insulin-secreting RINm5F cells. We here show that polyamines dose-dependently suppress PPase-1-like activity when added to RINm5F cell homogenates at physiologic concentrations (spermine > spermidine > putrescine), while having minor and inconsistent effects on PPase-2A-like activity. The IC50 value for spermine on PPase-1-like activity was approximately 4 mM. The inhibitory effect was reproduced and of comparable magnitude on purified PPases types 1 and 2A. On the other hand, when endogenous polyamine pools were exhausted by 4 days of exposure to the specific L-ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine, there was an increase in PPase-2A-like activity. Quantitative Western analysis revealed that the amount of PPase-2A protein did not change after this treatment. It is concluded that polyamines cause time-and concentration-dependent inhibitory effects on RINm5F cell PPase activities, which may contribute to the increase in phosphorylation state that occurs after secretory stimulation.     

Enhanced locomotor stimulation by NMDA receptor antagonists in alcohol-sensitive ANT rats

The ability of the antagonists for the N-methyl-D-aspartate (NMDA) type of glutamate receptor to modulate locomotor activity were compared in alcohol-sensitive (or alcohol-nontolerant, ANT) and alcohol-insensitive (or alcohol-tolerant, AT) rat lines. Both rat lines showed altered locomotor activity after acute injections of a competitive antagonist (LY235959), a glycine-site antagonist (L-701,324), or noncompetitive antagonists [MK-801, phencyclidine (PCP), and ketamine] of the NMDA receptor. MK-801 at 0.5 mg/kg caused a strong increase in horizontal activity in both rat lines, the effect being significantly greater in the ANT rats. There was a subpopulation among AT rats that was almost completely unresponsive to MK-801. This insensitivity to MK-801 correlated with the lack of c-fos induction in the retrosplenial and cingulate cortices. Fos immunoreactive cells in these brain regions after MK-801 treatment were more numerous in ANT than AT rats, although c-fos induction in the inferior olivary nucleus was similar in all animals after MK-801. The ANT rats showed greater locomotor stimulation also after ketamine and LY235959, while stimulation induced by PCP and depression induced by L-701,324 did not differ between the rat lines. The data suggest that altered NMDA receptor-mediated processes may correlate with differences in innate alcohol sensitivity in the ANT/AT rat model.     

The use of multiple sites for the diagnosis of osteoporosis

Introduction It has been suggested that bone mineral density (BMD) measurements should be made at multiple sites, and that the lowest T–score should be taken for the purpose of diagnosing osteoporosis. Purpose The aim of this study was to examine the use of BMD measurements at the femoral neck and lumbar spine alone and in combination for fracture prediction. Methods We studied 19,071 individuals (68% women) from six prospective population-based cohorts in whom BMD was measured at both sites and fracture outcomes documented over 73,499 patient years. BMD values were converted to Z-scores, and the gradient of risk for any osteoporotic fracture and for hip fracture was examined by using a Poisson model in each cohort and each gender separately. Results of the different studies were merged using weighted β-coefficients. Results The gradients of risk for osteoporotic fracture and for hip fracture were similar in men and women. In men and women combined, the risk of any osteoporotic fracture increased by 1.51 [95% confidence interval (CI)=1.42–1.61] per standard deviation (SD) decrease in femoral-neck BMD. For measurements made at the lumbar spine, the gradient of risk was 1.47 (95% CI=1.38–1.56). Where the minimum of the two values was used, the gradient of risk was similar (1.55; 95% CI=1.45–1.64). Higher gradients of risk were observed for hip fracture outcomes: with BMD at the femoral neck, the gradient of risk was 2.45 (95% CI=2.10–2.87), with lumbar BMD was 1.57 (95% CI=1.36–1.82), and with the minimum value of either femoral neck and lumbar spine was 2.11 (95% CI=1.81–2.45). Thus, selecting the lowest value for BMD at either the femoral neck or lumbar spine did not increase the predictive ability of BMD tests. By contrast, the sensitivity increased so that more individuals were identified but at the expense of specificity. Thus, the same effect could be achieved by using a less stringent T–score for the diagnosis of osteoporosis. Conclusions Since taking the minimum value of the two measurements does not improve predictive ability, its clinical utility for the diagnosis of osteoporosis is low.     

Design, spectrum measurements and simulations for a 238Pu alpha-particle irradiator for bystander effect and genomic instability experiments.

Design, spectrum measurements and simulations for an alpha-particle irradiator for bystander effect and genomic instability experiments are presented. Measured alpha-particle energy spectra were used to confirm the characteristics of the source of the irradiator specified by the manufacturer of the source. The spectra were measured in vacuum with a high-resolution spectrometer and simulated with an AASI Monte Carlo code. As a next step, we simulated alpha-particle energy spectra at the target plane of the irradiator for three different source-to-target distances. In these simulations, helium was used as the medium between the source and the exit window of the irradiator; its pressure and temperature corresponded to those of the ambient air. Mean energies and full-widths at half-maximum (FWHM) were calculated for the three different helium gas tracks.     

Risk Factors for Perimenopausal Fractures: A Prospective Study

This prospective study was aimed at determining the risk factors for the development of fractures in perimenopausal women. The study group (n= 3068) was comprised of a stratified population sample of women aged between 47 and 56 years. During the follow-up period of 3.6 years, 257 (8.4%) of the women sustained a total of 295 fractures. After adjustment for covariates, the relative risk (RR) of sustaining a fracture was found to be 1.4 [95% confidence interval (CI) 1.2–1.6] for a 1 standard deviation (SD) decrease in the spinal and femoral neck bone mineral density (BMD). Women with a previous fracture history were found to have an increased risk of fracture [RR 1.7 (95% CI 1.3–2.2)] and those reporting three or more chronic illnesses exhibited a RR of 1.4 (95% CI 1.0–1.9). Women not using hormone replacement therapy (HRT) had a RR of 1.5 (95% CI 1.1–2.2) for all fracture types. When osteoporotic fractures (vertebral, hip, proximal humerus and wrist fractures; n= 98) were used as an endpoint, the independent risk factors were found to be a low BMD (RR for a 1 SD decrease in both spinal and femoral neck BMD was 1.6, 95% CI 1.3–2.0), a previous fracture history (RR 1.9, 95% CI 1.3–2.9) and nonuse of HRT (RR 2.2, 95% CI 1.3–4.0). The independent risk factors for all other fractures (n = 158) were a low BMD (RR for a 1 SD decrease in the spinal BMD was 1.4, 95% CI 1.2–1.6 and in the femoral neck BMD was 1.3, 95% CI 1.1–1.5), a previous fracture history (RR 1.6, 95% CI 1.1–2.2), smoking (RR 1.8, 95% CI 1.1–2.7) and having had three or more chronic illnesses (RR 1.6, 95% CI 1.1–2.2). Weight, height, age, menopausal status, maternal hip fracture, use of alcohol, coffee consumption or dietary calcium intake were not independently associated with the development of any particular type of fracture. We conclude that the independent risk factors for perimenopausal fractures are a low bone density, previous fracture history, nonuse of HRT, having had three or more chronic illnesses and smoking, the gradient of risk being similar for spinal and femoral neck BMD measurements in the perimenopausal population. The risk factors are slightly different for perimenopausal osteoporotic than for other types of fractures. Received: 6 April 1999 / Accepted: 18 August 1999     

Association of 18 Confirmed Susceptibility Loci for Type 2 Diabetes With Indices of Insulin Release, Proinsulin Conversion, and Insulin Sensitivity in 5,327 Nondiabetic Finnish Men

OBJECTIVE

We investigated the effects of 18 confirmed type 2 diabetes risk single nucleotide polymorphisms (SNPs) on insulin sensitivity, insulin secretion, and conversion of proinsulin to insulin.

RESEARCH DESIGN AND METHODS

A total of 5,327 nondiabetic men (age 58 ± 7 years, BMI 27.0 ± 3.8 kg/m²) from a large population-based cohort were included. Oral glucose tolerance tests and genotyping of SNPs in or near PPARG, KCNJ11, TCF7L2, SLC30A8, HHEX, LOC387761, CDKN2B, IGF2BP2, CDKAL1, HNF1B, WFS1, JAZF1, CDC123, TSPAN8, THADA, ADAMTS9, NOTCH2, KCNQ1, and MTNR1B were performed. HNF1B rs757210 was excluded because of failure to achieve Hardy-Weinberg equilibrium.

RESULTS

Six SNPs (TCF7L2, SLC30A8, HHEX, CDKN2B, CDKAL1, and MTNR1B) were significantly (P < 6.9 × 10⁻⁴) and two SNPs (KCNJ11 and IGF2BP2) were nominally (P < 0.05) associated with early-phase insulin release (InsAUC_0–30/GluAUC_0–30), adjusted for age, BMI, and insulin sensitivity (Matsuda ISI). Combined effects of these eight SNPs reached −32% reduction in InsAUC_0–30/GluAUC_0–30 in carriers of ≥11 vs. ≤3 weighted risk alleles. Four SNPs (SLC30A8, HHEX, CDKAL1, and TCF7L2) were significantly or nominally associated with indexes of proinsulin conversion. Three SNPs (KCNJ11, HHEX, and TSPAN8) were nominally associated with Matsuda ISI (adjusted for age and BMI). The effect of HHEX on Matsuda ISI became significant after additional adjustment for InsAUC_0–30/GluAUC_0–30. Nine SNPs did not show any associations with examined traits.

CONCLUSIONS

Eight type 2 diabetes–related loci were significantly or nominally associated with impaired early-phase insulin release. Effects of SLC30A8, HHEX, CDKAL1, and TCF7L2 on insulin release could be partially explained by impaired proinsulin conversion. HHEX might influence both insulin release and insulin sensitivity.Impaired insulin secretion and insulin resistance, two main pathophysiological mechanisms leading to type 2 diabetes, have a significant genetic component (1). Recent studies have confirmed 20 genetic loci reproducibly associated with type 2 diabetes (2–13). Three were previously known (PPARG, KCNJ11, and TCF7L2), whereas 17 loci were recently discovered either by genome-wide association studies (SLC30A8, HHEX-IDE, LOC387761, CDKN2A/2B, IGF2BP2, CDKAL1, FTO, JAZF1, CDC123/CAMK1D, TSPAN8/LGR5, THADA, ADAMTS9, NOTCH2, KCNQ1, and MTNR1B), or candidate gene approach (WFS1 and HNF1B). The mechanisms by which these genes contribute to the development of type 2 diabetes are not fully understood.PPARG is the only gene from the 20 confirmed loci previously associated with insulin sensitivity (14,15). Association with impaired β-cell function has been reported for 14 loci (KCNJ11, SLC30A8, HHEX-IDE, CDKN2A/2B, IGF2BP2, CDKAL1, TCF7L2, WFS1, HNF1B, JAZF1, CDC123/CAMK1D, TSPAN8/LGR5, KCNQ1, and MTNR1B) (6,12,13,16–38). Although associations of variants in HHEX (16–22), CDKAL1 (6,21–26), TCF7L2 (22,27–30), and MTNR1B (13,31,32) with impaired insulin secretion seem to be consistent across different studies, information concerning other genes is limited (12,18–25,27,33–38). The mechanisms by which variants in these genes affect insulin secretion are unknown. However, a few recent studies suggested that variants in TCF7L2 (22,39–42), SLC30A8 (22), CDKAL1 (22), and MTNR1B (31) might influence insulin secretion by affecting the conversion of proinsulin to insulin. Variants of FTO have been shown to confer risk for type 2 diabetes through their association with obesity (7,16) and therefore were not included in this study.Large population-based studies can help to elucidate the underlying mechanisms by which single nucleotide polymorphisms (SNPs) of different risk genes predispose to type 2 diabetes. Therefore, we investigated confirmed type 2 diabetes–related loci for their associations with insulin sensitivity, insulin secretion, and conversion of proinsulin to insulin in a population-based sample of 5,327 nondiabetic Finnish men.     

A multivariate analysis of risk factors for anterior atlantoaxial subluxation and an evaluation of the effect of glucocorticoid treatment on the upper rheumatoid cervical spine

Summary A cross-sectional, retrospective computerized analysis of risk factors for anterior atlantoaxial subluxation (AAS) was performed. Logistic regression performed on the clinical variables involved in 145 cases of rheumatoid arthritis (RA) disclosed a high joint score index and a low blood haemoglobin level as significant independent risk factors. This means that the development of anterior AAS is connected with widespread RA. Linear multiple regression analysis showed an association between the extent of anterior AAS in millimetres and the spread of erosions of the dens of axis and negative correlation with the severity of vertical atlantoaxial dislocation (VD). This suggests that whereas the presence of anterior AAS is connected with the severity of the systemic disease, its actual extent is associated with signs of local involvement, other than severe VD. The duration or cumulative dosage of glucocorticoids were not associated with the development or extent of anterior AAS, nor with the severity of vertical dislocation. This suggests that low dose glucocorticoid treatment is not involved with the development of rheumatoid changes in the upper cervical spine. It should be borne in mind, of course, that although no correlation was found, a causal relation cannot be excluded.