Search for intracranial aneurysm susceptibility gene(s) using Finnish families

Background

Cerebrovascular disease is the third leading cause of death in the United States, and about one-fourth of cerebrovascular deaths are attributed to ruptured intracranial aneurysms (IA). Epidemiological evidence suggests that IAs cluster in families, and are therefore probably genetic. Identification of individuals at risk for developing IAs by genetic tests will allow concentration of diagnostic imaging on high-risk individuals. We used model-free linkage analysis based on allele sharing with a two-stage design for a genome-wide scan to identify chromosomal regions that may harbor IA loci.

Methods

We previously estimated sibling relative risk in the Finnish population at between 9 and 16, and proceeded with a genome-wide scan for loci predisposing to IA. In 85 Finnish families with two or more affected members, 48 affected sibling pairs (ASPs) were available for our genetic study. Power calculations indicated that 48 ASPs were adequate to identify chromosomal regions likely to harbor predisposing genes and that a liberal stage I lod score threshold of 0.8 provided a reasonable balance between detection of false positive regions and failure to detect real loci with moderate effect.

Results

Seven chromosomal regions exceeded the stage I lod score threshold of 0.8 and five exceeded 1.0. The most significant region, on chromosome 19q, had a maximum multipoint lod score (MLS) of 2.6.

Conclusions

Our study provides evidence for the locations of genes predisposing to IA. Further studies are necessary to elucidate the genes and their role in the pathophysiology of IA, and to design genetic tests.     

Low plasma glutamine in combination with high glutamate levels indicate risk for loss of body cell mass in healthy individuals: the effect of N-acetyl-cysteine

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an anaerobic physical exercise program causes similar changes in plasma amino acid levels, and (b) whether low plasma glutamine or high glutamate levels are risk factors for loss of body cell mass (BCM) in healthy human subjects, i.e., in the absence of a tumor or virus infection. Longitudinal measurements from healthy subjects over longer periods suggest that the age-related loss of BCM occur mainly during episodes with high venous glutamate levels, indicative of decreased muscular transport activity for glutamate. A significant increase in venous glutamate levels from 25 to about 40 M was seen after a program of anaerobic physical exercise. This was associated with changes in T lymphocyte numbers. Under these conditions persons with low baseline levels of plasma glutamine, arginine, and cystine levels also showed a loss of BCM. This loss of BCM was correlated not only with the amino acid levels at baseline examination, but also with an increase in plasma glutamine, arginine, and cystine levels during the observation period, suggesting that a loss of BCM in healthy individuals terminates itself by adjusting these amino acids to higher levels that stabilize BCM. To test a possible regulatory role of cysteine in this context we determined the effect of N-acetyl-cysteine on BCM in a group of subjects with relatively low glutamine levels. The placebo group of this study showed a loss of BCM and an increase in body fat, suggesting that body protein had been converted into other forms of chemical energy. The decrease in mean BCM/body fat ratios was prevented by N-acetyl-cysteine, indicating that cysteine indeed plays a regulatory role in the physiological control of BCM.Abbreviations BCM Body cell mass - HIV Human immunodeficiency virus type 1 - NAC N-Acetyl-cysteine     

Development of a rapid PCR method for identification ofHelicobacter pylori in dental plaque and gastric biopsy specimens

A rapid and simple polymerase chain reaction (PCR) method was developed to detectHelicobacter pylori in gastric biopsy specimens and dental plaque samples. The primers were targeted to the 16S rRNA sequence ofHelicobacter pylori strain ATCC 43504. The system was found to have a theoretical detection level of 0.5 to 5Helicobacter pylori cells in a 5 l sample of dental plaque. In the absence of plaque, the detection level was even better: theoretically, 0.05 to 0.5Helicobacter pylori cells were detected in water suspension. However, this appeared to be due to the presence of free bacterial DNA in the culture used for the sensitivity determination. Thus, the actual sensitivity of the system was found to be fewer than fiveHelicobacter pylori cells, irrespective of the type of sample used. The method was then used to analyse 29 dental plaque and gastric biopsy specimens collected from patients with a history of recurrent peptic ulcer disease. Fourteen stomach specimens were positive forHelicobacter pylori when tested with the PCR method, while the respective figures with culture, histological examination and the urease test were 11, 12 and 9. No positive dental plaque samples were observed.     

Inhibition of nitric oxide synthase reduces Sephadex-induced oedema formation in the rat lung: Dependence on intact adrenal function

In the present study we have investigated the effect of L-nitro arginine mono methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase on Sephadex induced inflammation in the rat lung. Instillation of Sephadex into the airways induced an inflammatory reaction characterized by a long-lasting interstitial oedema, measured as an increase in lung weight, and an influx of inflammatory cells into the airways. L-NAME given s.c. prevented the increase in lung weight following Sephadex instillation. The inactive enantiomer D-NAME had no effect, nor did aminoguanidine which indicates that this effect of L-NAME was mediated by inhibition of the constitutive form of NOS. Treatment with L-NAME did not reduce an established oedema. In contrast, L-NAME tended to enhance the influx of oesinophils into the airways of Sephadex-instilled animals.L-NAME did not have any effect on the development of oedema in adrenalectomized rats or in animals where formation of glucocorticosteroids (GCS) was inhibited with metyrapone. L-NAME did not however, increase plasma levels of corticosterone. The present results indicate that, in this model, inhibition of NO-synthesis has marked anti-inflammatory effects. The underlying mechanism is complex but seems not to involve prevention of overproduction of NO.     

Electrophysiologic changes in the lateral and basal amygdaloid nuclei in temporal lobe epilepsy: an in vitro study in epileptic rats

The functional consequences of neuronal loss during epileptogenesis in the lateral and basal amygdaloid nuclei are poorly understood. The present study tested the hypothesis that electrical responsiveness varies in different amygdaloid nuclei in the chronically epileptic amygdala. Further, we examined the amygdaloid region most prone to seizure initiation. Epileptogenesis was triggered in 20 rats by inducing status epilepticus (SE) with electrical stimulation of the lateral nucleus of the amygdala. Electrode-implanted non-stimulated rats served as controls. The occurrence and duration of spontaneous seizures were monitored with video-electroencephalography (EEG) at 8-9 weeks after SE. Thereafter, animals were killed and extracellular recordings were made from slices of both amygdalas. In the lateral nucleus of epileptic animals, the frequency of spontaneous responses was reduced compared with controls (P < 0.05). The amplitudes of evoked field responses were reduced (P < 0.01), whereas paired pulse (PP) facilitation was enhanced (P < or = 0.05). In the basal nucleus of the epileptic animals, PP facilitation was enhanced (P < 0.05) and sensitivity to 4-aminopyridine (4-AP)-induced epileptiform activity was increased compared with controls (P < 0.05). In the epileptic animals, the basal nucleus was also more sensitive than the lateral nucleus to 4-AP-induced epileptiform activity (P < 0.05). Correlation analysis indicated that longer SE duration was associated with longer half widths (P = 0.001) and smaller slopes (P < 0.05) of evoked responses as well as with attenuated PP facilitation (P<0.01). Moreover, a higher frequency of spontaneous seizures was associated with longer half widths (P < 0.05) and smaller slopes (P < 0.05) of evoked responses as well as with enhanced PP facilitation (P < 0.05). These data suggest that there is a reduced release of glutamate and reduced inhibition in the lateral and basal amygdaloid nuclei in epileptic animals. Further, the basal nucleus is more prone to epileptic activity than the lateral nucleus. Finally, the severity of SE and spontaneous seizures in vivo is associated with electrophysiologic alterations in vitro.     

Effect of porosity on the osteointegration and bone ingrowth of a weight-bearing nickel-titanium bone graft substitute

Porous nickel-titanium (NiTi) alloy is a promising new material for a bone graft substitute with good strength properties and an elastic modulus closer to that of bone than any other metallic material. The purpose of this study was to evaluate the effect of porosity on the osteointegration of NiTi implants in rat bone. The porosities (average void volume) and the mean pore size (MPS) were 66.1% and 259+/-30 microm (group 1, n=14), 59.2% and 272+/-17 microm (group 2, n=4) and 46.6% and 505+/-136 microm (group 3, n=15), respectively. The implants were implanted in the distal femoral metaphysis of the rats for 30 weeks. The proportional bone-implant contact was best in group 1 (51%) without a significant difference compared to group 3 (39%). Group 2 had lower contact values (29%) than group 1 (p=0.038). Fibrotic tissue within the porous implant was found more often in group 1 than in group 3 (p=0.021), in which 12 samples out of 15 showed no signs of fibrosis. In conclusion, porosity of 66.1% (MPS 259+/-30 microm) showed best bone contact (51%) of the porosities tested here. However, the porosity of 46.6% (MPS 505+/-136 microm) with bone contact of 39% was not significantly inferior in this respect and showed lower incidence of fibrosis within the porous implant.