A novel site of synaptic relay for climbing fibre pathways relaying signals from the motor cortex to the cerebellar cortical C1 zone

The climbing fibre projection from the motor cortex to the cerebellar cortical C1 zone in the posterior lobe of the rat cerebellum was investigated using a combination of physiological, anatomical and neuropharmacological techniques. Electrical stimulation of the ipsilateral fore- or hindimbs or somatotopically corresponding parts of the contralateral motor cortex evoked climbing fibre field potentials at the same cerebellar recording sites. Forelimb-related responses were located in the C1 zone in the paramedian lobule or lobulus simplex and hindlimb-related responses were located in the C1 zone in the copula pyramidis. Microinjections of anterograde axonal tracer (Fluoro-Ruby or Fluoro-Emerald) were made into the fore- or hindlimb parts of the motor cortex where stimulation evoked the largest cerebellar responses. After a survival period of 7–10 days, the neuraxis was examined for anterograde labelling. No terminal labelling was ever found in the inferior olive, but labelled terminals were consistently found in a well-localized site in the dorso-medial medulla, ventral to the gracile nucleus, termed the matrix region. Pharmacological inactivation of the matrix region (2 mm caudal to the obex) selectively reduced transmission in descending (cerebro-olivocerebellar) but not ascending (spino-olivocerebellar) paths targeting fore- or hindlimb-receiving parts of the C1 zone. Transmission in spino-olivocerebellar paths was either unaffected, or in some cases increased. The identification of a novel pre-olivary relay in cerebro-olivocerebellar paths originating from fore- and hindlimb motor cortex has implications for the regulation of transmission in climbing fibre pathways during voluntary movements and motor learning.     

Inhibition of GABA-gated chloride channel function by arachidonic acid

The effects of arachidonic acid and its metabolites on gamma-aminobutyric acid (GABAA) receptor function were determined in rat cerebral cortical synaptoneurosomes. Incubation of synaptoneurosomes with phospholipase A2 decreased muscimol-induced 36Cl- uptake. Arachidonic acid, the major unsaturated fatty acid released by phospholipase A2, also inhibited muscimol-induced 36Cl uptake. Similar inhibition was obtained with other unsaturated fatty acids (docosahexaenoic, oleic) but not with saturated fatty acids (stearic, palmitic). The effect of arachidonic acid on muscimol responses was inhibited by bovine serum albumin (BSA), and BSA enhanced muscimol responses directly, indicating the generation of endogenous arachidonic acid in the synaptoneurosome preparation. The generation of endogenous arachidonic acid was also indicated by the ability of 2 inhibitors of arachidonic acid metabolism, indomethacin and nordihydroguaiaretic acid (NDGA), to inhibit muscimol-induced 36Cl uptake. We conclude that arachidonic acid probably has both direct and indirect actions on muscimol responses since both enzyme inhibitors inhibited muscimol responses but did not prevent the effect of exogenously added arachidonic acid. In additional experiments, arachidonic acid metabolites generated by cyclooxygenase, prostaglandins D2, E2 and F2 alpha, each decreased muscimol responses; prostaglandins F2 alpha was the most potent inhibitor. Since the unsaturated fatty acids and their metabolites are most susceptible to peroxidation, a generating system of superoxide radicals was tested on muscimol responses. A combination of xanthine and xanthine oxidase inhibited muscimol-induced 36Cl uptake in a concentration-dependent manner. We propose that the inhibition of GABAA neurotransmission by arachidonic acid and its metabolites can lead to increased neuronal excitability. This mechanism may play an important role in the development of neuronal damage following seizures or cerebral ischemia.     

Alcohol and drug use following traumatic brain injury: A prospective study

Primary objectives: To establish pre-morbid alcohol and drug use in persons with TBI, relative to controls, investigate how patterns of substance use change over time following TBI and identify factors associated with heavy post-injury substance use.

Methods and procedures: The Alcohol Use Disorders Identification test (AUDIT) and Drug Abuse Screening Test (DAST) was completed by 121 hospital inpatients with TBI, documenting pre-injury alcohol and drug use, and 133 demographically similar controls. Participants with TBI completed these measures and the Hospital Anxiety and Depression Scale (HADS) again 1 and 2 years post-injury and 76 also completed them at 3 years.

Results: Participants with TBI showed similar levels of drug and alcohol use to controls pre-injury, with 31.4% of the TBI group and 29.3% of controls drinking at hazardous levels. Alcohol and drug use declined in the first year post-injury, but increased by 2 years post-injury, with only 21.4% of participants with TBI reporting abstinence from alcohol and 25.4% drinking at hazardous levels. Only 9% showed a drug problem, but 24% had returned to some drug use. Those showing heavy alcohol use post-injury were young, male and heavy drinkers pre-injury. Drug and alcohol use was similar at 3 years post-injury.

Conclusions: More active intervention is needed to reduce alcohol and drug use following TBI.     

Role of endothelin in the exercise intolerance of chronic heart failure

In conclusion, plasma levels of the endothelialderived vasoconstrictor endothelin-1 (but not those of other neurohormonal vasoconstrictor factors), measured during exercise correlated closely with objective variables of exercise capacity in patients with heart failure. These findings suggest that endothelin-1 may contribute to exercise intolerance in patients with heart failure, perhaps by limiting the ability of the peripheral vasculature to dilate during exercise.     

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Pharmaceutical Research -     

Quantitative autoradiography of nicotinic [H]acetylcholine binding sites in rat brain

Quantitative autoradiography was used to localize nicotinic [³H]acetylcholine (ACh) binding sites in rat brain. High concentrations of nicotinic [³H]ACh binding sites were observed in the anterior and medial nuclei of the thalamus, the medial habenula and the superficial layer of the superior colliculus. Moderate levels of binding sites were observed in a variety of brain regions such as the frontoparietal cortex and the hippocampus. Low levels of nicotinic ACh sites occurred throughout the hypothalamus and the primary olfactory cortex.     

A comprehensive haplotype analysis of CYP19 and breast cancer risk: the Multiethnic Cohort

The CYP19 gene encodes for aromatase (P450arom), a key steroidogenic enzyme that catalyzes the final step of estrogen biosynthesis. Apart from rare mutations in CYP19 which result in severe phenotypes associated with estrogen insufficiency, little is known about whether common variation in CYP19 is associated with risk of hormone-related diseases. In this study, we employed a haplotype-based approach to search for common disease-associated variants in this candidate breast cancer susceptibility gene among African-American, Hawaiian, Japanese, Latina and White women in the Multiethnic Cohort Study (MEC). We utilized 74 densely spaced single-nucleotide polymorphisms (SNPs) (one every approximately 2.6 kb) spanning 189.4 kb of the CYP19 locus to characterize linkage disequilibrium (LD) and haplotype patterns among 69-70 individuals from each ethnic population. We detected four regions of strong LD (blocks 1-4) that were quite closely conserved across populations. Within each block there was a limited diversity of common haplotypes (5 to 10 with a frequency >/=5%) and most haplotypes were observed to be shared across populations. Twenty-five haplotype-tagging SNPs (htSNPs) were selected to predict the common haplotypes with high probability (average Rh2=0.92) and genotyped in a breast cancer case-control study in the MEC (cases, n=1355; controls, n=2580). We first performed global tests for differences in risk according to the common haplotypes and observed significant haplotype-effects in block 2 [P=0.01; haplotypes 2b (OR=1.23; 95% CI, 1.07-1.40), 2d (OR=1.28; 95% CI, 1.01-1.62)]. We also found a common long-range haplotype comprised of block-specific haplotypes 2b and 3c to be associated with increased risk of breast cancer (haplotype 2b-3c: OR=1.31; 95% CI, 1.11-1.54). Our findings suggest the hypothesis that women with the long-range CYP19 haplotype 2b-3c may be carriers of a predisposing breast cancer susceptibility allele.     

Number of C-bands of human isochromosome Xqi and relation to 45,X mosaicism

With combination of C and G banding techniques, three morphologically different types of isochromosome for the long arm of X (Xqi) have been identified, i.e. those with one C-band and symmetrical banding patterns of both arms, those with two C-bands and symmetrical banding patterns of two arms, and those with two C-bands but with asymmetrical banding patterns of two arms. The last type is a heterogeneous group with various different asymmetrical patterns. We have studied 6 cases of Xqi with C, G, and Q banding: 3 showed one C-band and symmetrical arms and all these were without 45,X mosaicism; the other 3 cases showed two C-bands, 2 of the cases having symmetrical arms and being mosaic for 45X/46,XXqi/47,XXqiXqi (those 2 were a pair of identical twins). One other had asymmetrical arms and was mosaic for 45,X/46,XXqi. Including our 6 cases, there have been a total of 30 reported cases of Xqi with C and G banding studies. Two-thirds of Xqi's were found to have 2 C-bands and one-third to have 1 C-band. Mosaicism was found in 85% of Xqi's with 2 C-bands and in only 44% of Xqi's with 1 C-band. Apparently, Xqi's with 2 C-bands have a greater tendency for anaphase lag and mitotic nondisjunction. Several possible mechanisms for the formation of the different types of Xqi's are discussed.     

Inhibition of Migration of Mouse Macrophages by Tuberculin-Sensitive Mouse Lymphocytes and by Mouse Migration Inhibitory Factor

The guinea pig migration inhibition technique, an accepted in vitro correlate of delayed hypersensitivity, has been adapted to a murine system. Peritoneal exudate cells from CF-1 mice vaccinated with viable cells of the H37Ra strain of Mycobacterium tuberculosis were inhibited in vitro by purified protein derivative (PPD) or whole H37Ra microorganisms. Peritoneal exudate cells from the inbred C57Bl/6 mice immunized with H37Ra cells also were inhibited in vitro by PPD or whole H37Ra microorganisms. Migration inhibitory factor (MIF) was produced by splenic lymphocytes from the H37Ra-immunized C57Bl/6 mice when incubated with either antigen. Intravenous injection of PPD or viable H37Ra organisms into H37Ra mice resulted in MIF production in vitro by splenic lymphocytes without further antigenic stimulation. Peritoneal exudate cells from nonimmunized C57Bl/6 mice and supernatant fluids from cultures of lymphocytes from nonimmunized C57Bl/6 mice were not inhibited in the presence of antigen. The production of MIF by splenic lymphocytes from immunized C57Bl/6 mice depended upon the conditions under which the lymphocytes were cultured, the time of exposure to antigen (3 days), the use of a higher concentration of PPD for stimulation of lymphocytes than that required for guinea pig cells, and also the use of cells from a highly inbred mouse strain.     

The syndrome of ectrodactyly, ectodermal dysplasia and cleft lip and palate: report of a family demonstrating a dominant inheritance pattern

The syndrome of ectrodactyly, ectodermal dysplasia and cleft lip and palate (EEC syndrome) is described in a mother and 3 of her 4 children. Autosomal dominant inheritance was suggested in this family. However, genetic heterogeneity may exist in this syndrome. The significance of associated finClings, incluCling carcinoma of the cervix uteri, lacrimal duct stenosis and urinary tract strictures in patients with ectodermal dysplasia is considered.