Functional properties of recombinant GABAA receptors composed of single or multiple β subunit subtypes

GABA_A receptor (GABAR) isoforms in the central nervous system are composed of combinations of α(1–6), β(1–4), γ(1–4), δ(1) and (1) subunit subtypes arranged in a pentamer. Many regions of the brain express high levels of mRNA encoding several different subunits and even multiple subunit subtypes. The stoichiometry of GABAR isoforms is unclear, and the number and identity of individual subunit subtypes that are coassembled remain uncertain. To examine the role of β subunit subtypes in the functional properties of GABARS and to determine whether multiple β subtypes can be coassembled in functional GABARs, plasmids containing cDNAs encoding rat β1 and/or β3, α5 and γ2L subtypes were cotransfected into L929 fibroblasts. The properties of the expressed receptor populations were determined using whole-cell and single-channel recording techniques. The α5β1γ2L isoform was less sensitive to GABA than the α5β3γ2L isoform. α5β1γ2L isoform currents were also insensitive to the allosteric modulator loreclezole, while α5β3γ2L isoform currents were strongly potentiated by loreclezole. Fibroblasts transfected with plasmids containing cDNAs for both β1 and β3 subtypes along with α5 and γ2L subtypes produced a receptor population with an intermediate sensitivity to GABA which was insensitive to loreclezole. These results suggest that functional GABARs can be formed that contain two different β subunit subtypes with properties different from receptors that contain only a single β subtype and that the β subunit subtypes influence the response of GABARs to GABA and to the allosteric modulator loreclezole.     

Application of magnetic resonance imaging to evaluation of femoral neck structure in growing girls.

Conventional density measures by dual-energy X-ray absorptiometry (DXA) are confounded by increases in bone size and do not assess bone geometry. We assessed precision of magnetic resonance imaging (MRI) and used MRI, DXA, and hip structure analysis (HSA) to assess 7-mo changes in bone structure at the femoral neck in 18 prepubertal girls. At baseline, girls were 10.4 (0.5) yr, 144.0 (8.2) cm, and 35.2 (7.0) kg, on average. Total bone and cortical cross-sectional area (ToA and CoA) were calculated from high-resolution T1-weighted MRI oblique axial images of the femoral neck. We used proximal femur DXA scans (Hologic QDR-4500) and the HSA program to estimate bone cross-sectional area (CSA), and calculate section modulus. MRI precision was determined by scanning 10 volunteers (13-46 yr old) three times with and without repositioning. Precision (CVrms) was 2% for ToA and 7% for CoA. Significant correlations were observed between FN area and MRI-derived ToA (r = 0.57, p = 0.013) and CoA (r = 0.47, p = 0.050). There were significant positive changes over 7 mo by both methods. In conclusion, MRI provides useful information on femoral neck bone area in children. The reproducibility of cortical dimensions at the femoral neck needs improvement through technical modifications and appropriate analysis software.     

Neonatal rectal colonization with Malassezia furfur

Malassezia furfur and Candida albicans are fungal pathogens which have been recognized with increasing frequency as agents of mortality and serious morbidity in neonatal intensive care unit patients. A longitudinal study of oral, rectal and umbilical colonization by these organisms of newborns admitted to a neonatal intensive care unit within 24 h of birth was undertaken. Of 71 infants followed for a minimum of 10 days, 24 were colonized with M furfur and 12 with C albicans during the first 10 days of life. The lower gastrointestinal tract was found to be the most common colonization site for both organisms. Statistically significant (P<0.05) inverse associations were demonstrated between gestational age and risk of colonization with either organism at any site, and between birthweight or gestational age and risk of rectal colonization with either organism. Antibiotics were associated with a relative risk colonization of 4.06 (P=0.06) with either organism at any site. It is concluded that M furfur and C albicans are common colonizing organisms in a neonatal intensive care unit setting and are most frequently harboured in the lower gastrointestinal tract. M furfur, recently implicated as a systemic pathogen in this population, has not been previously recognized as a gastrointestinal commensal organism. The relationship between colonization and invasive fungal disease, and potential roles for preventive strategies, remain to be elucidated.     

Localization of a gene for otosclerosis to chromosome 15q25-q26

Among white adults otosclerosis is the single most common cause of hearing impairment. Although the genetics of this disease are controversial, the majority of studies indicate autosomal dominant inheritance with reduced penetrance. We studied a large multi- generational family in which otosclerosis has been inherited in an autosomal dominant pattern. Five of16 affected persons have surgically confirmed otosclerosis; the remaining nine have a conductive hearing loss but have not undergone corrective surgery. To locate the disease- causing gene we completed genetic linkage analysis using short tandem repeat polymorphisms (STRPs) distributed over the entire genome. Multipoint linkage analysis showed that only one genomic region, on chromosome 15q, generated a lod score >2.0. Additional STRPs were typed in this area, resulting in a lod score of 3.4. STRPs FES (centromeric) and D15S657 (telomeric) flank the 14. 5 cM region that contains an otosclerosis gene.      

Peritoneal fluid concentrations of interleukin-8 in women with endometriosis: relationship to stage of disease

There is increasing evidence that immunological mechanisms play a role in the pathogenesis and pathophysiology of endometriosis. It was therefore of interest to study interleukin-8 (IL-8), a chemokine, in the peritoneal fluid and peripheral blood of women undergoing laparoscopic procedures. The presence and concentrations of IL-8 in relation to endometriosis, infertility and abdominal pain were evaluated. Samples of peritoneal fluid (n = 49) and peripheral blood (n = 50) were obtained from 50 consecutive patients undergoing laparoscopic surgery for various gynaecological indications (abdominal pain, infertility, sterilization). IL-8 was present in the peritoneal fluid of most women (87%). The concentration of IL-8 in the peritoneal fluid was higher in women with endometriosis compared to women without (P = 0.02). This difference was more pronounced in early (stage 1) endometriosis (P = 0.001). IL-8 concentrations in the peritoneal fluid were also higher in women with early endometriosis compared to women with later stages of the disease (P = 0.003). Peripheral blood concentrations did not correlate with peritoneal fluid concentrations of IL-8 and/or the presence of endometriosis. We conclude that IL-8 is an important factor that may contribute to the pathogenesis of endometriosis possibly by promoting neovascularization. This information can be a guide in the development of new therapeutic approaches for the treatment of endometriosis.      

GABRD encoding a protein for extra- or peri-synaptic GABAA receptors is a susceptibility locus for generalized epilepsies

A major challenge in understanding complex idiopathic generalized epilepsies has been the characterization of their underlying molecular genetic basis. Here, we report that genetic variation within the GABRD gene, which encodes the GABAA receptor delta subunit, affects GABA current amplitude consistent with a model of polygenic susceptibility to epilepsy in humans. We have found a GABRD Glu177Ala variant which is heterozygously associated with generalized epilepsy with febrile seizures plus. We also report an Arg220His allele in GABRD which is present in the general population. Compared with wild-type receptors, alpha1beta2Sdelta GABAA receptors containing delta Glu177Ala or Arg220His have decreased GABAA receptor current amplitudes. As GABAA receptors mediate neuronal inhibition, the reduced receptor current associated with both variants is likely to be associated with increased neuronal excitability. Since delta subunit-containing receptors localize to extra- or peri-synaptic membranes and are thought to be involved in tonic inhibition, our results suggest that alteration of this process may contribute to the common generalized epilepsies.     

Upper tibial corticocancellous flap anatomy study (19.2.93)

Summary A cortico-cancellous flap from the anterolateral aspect of the upper third of the tibia was presented. Sixty lower limbs of fresh cadavers were dissected. The vascular bundle includes the anterior tibial artery and its recurrent collateral branches and recurrent and muscllo periostal arteries. The flap is harvested with the interosseous membrane and can be used either free or pedicled. We used this flap for two patients suffering from pseudarthrosis. Long range clinical and radiological results are good.

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Le transfert osseux vascularisé tibial superieur

Résumé Les auteurs décrivent un transfert ostéo-periosté vascularisé, prélevé sur la face antéro-latérale de l'extremité supérieure du tibia. L'étude anatomique porte sur soixante membres inférieurs, conservés au froid. La vascularisation métaphysaire du transfert provient de la branche récurrente tibiale antérieure et de ses rameaux, la vascularisation diaphysaire étant issue des branches musculo-périostiées proximales. Le transfert vascularisé est prélevé avec la membrane interosseuse et peut être pediculé ou libre. L'expérience clinique porte sur deux cas de pseudarthroses multiopérées. Les résultats cliniques et radiologiques sont bons à long terme.

     

Activation of mucosal Vβ3+ T cells and tissue damage in human small intestine by the bacterial superantigen,Staphylococcus aureus enterotoxin B

Staphylococcus aureus enterotoxin B (SEB) was added to explants of fetal human intestine in organ culture or administered into the lumen of fetal small intestine prior to culture. Both routes produced a massive increase in lamina propria T cells expressing Vβ33, and to a lesser extent, those expressing Vβ5 and Vβ12. SEB-activated lamina propria T cells produced interleukin-2 and interferon-Y and T cell activation was accompanied by tissue damage, which was inhibited by FK506.     

Identifying severely atrophic cortical subregions in Alzheimer's disease

The present study analyses the pattern of atrophy in anatomically discrete brain regions in prospectively-studied pathologically-confirmed patients with Alzheimer's disease (AD) and controls. Standard volumetric measurements were made of the entire cortex subdivided into 23 anatomical regions. Analyses determined regions of significant atrophy in AD and differences between the severity and rates of atrophy. Two levels of severity were found. Atrophy concentrated in medial temporal lobe structures as well as in inferior temporal and superior and middle frontal cortices. The degree of atrophy in these regions related to disease duration, consistent with an early and sustained disease process. The rate of atrophy was significantly greater for the fusiform gyrus. The inferior frontal lobes were entirely spared at all AD stages, while atrophy of other cortical regions was less marked and not related to disease duration, suggesting late involvement. Our findings show that the fusiform gyrus is particularly affected by AD, and suggest two levels of atrophy that correspond with published neurofibrillary tangle (most atrophic) and senile plaque (less atrophic) densities.