SCA8 CTG repeat: en masse contractions in sperm and intergenerational sequence changes may play a role in reduced penetrance

We recently described an untranslated CTG expansion that causes a previously undescribed form of spinocerebellar ataxia (SCA8). The SCA8 CTG repeat is preceded by a polymorphic but stable CTA tract, with the configuration (CTA)(1-21)(CTG)(n). The CTG portion of the repeat is elongated on pathogenic alleles, which nearly always change in size when transmitted from generation to generation. To better understand the reduced penetrance and maternal penetrance bias associated with SCA8 we analyzed the sequence configurations and instability patterns of the CTG repeat in affected and unaffected family members. In contrast to other triplet repeat diseases, expanded alleles found in affected SCA8 individuals can have either a pure uninterrupted CTG repeat tract or an allele with one or more CCG, CTA, CTC, CCA or CTT interruptions. Surprisingly, we found six different sequence configurations of the CTG repeat on expanded alleles in a seven generation family. In two instances duplication of CCG interruptions occurred over a single generation and in other instances duplications that had occurred in different branches of the family could be inferred. We also evaluated SCA8 instability in sperm samples from individuals with expansions ranging in size from 80 to 800 repeats in blood. Surprisingly the SCA8 repeat tract in sperm underwent contractions, with nearly all of the resulting expanded alleles having repeat lengths of <100 CTGs, a size that is not often associated with disease. These en masse repeat contractions in sperm likely underlie the reduced penetrance associated with paternal transmission.     

Null mutation in human ciliary neurotrophic factor gene confers higher body mass index in males

Ciliary neurotrophic factor (CNTF) administration reduces weight in leptin-resistant mice via the signalling pathway normally activated by leptin. A G>A null mutation in the CNTF gene results in complete absence of protein. We hypothesised that absence of CNTF could lead to diminished initiation of anorectic pathways, with consequent increase in body mass. In 575 Caucasian men aged 59-73 years, the A/A genotype (frequency 1.9%) was associated with a 10 kg increase in weight (P=0.03, 2 df) and 3 kg/m(2) greater BMI (P=0.02, 2 df). There was no effect in women. The CNTF G>A null mutation therefore confers a moderate effect on obesity in males of A/A genotype, who represent 1% of the general population.     

Surgical sperm retrieval and intracytoplasmic sperm injection as treatment of obstructive azoospermia

Male genital tract obstructions may result from infections, previous inguinal and scrotal surgery (vasectomy) and congenital bilateral absence of the vas deferens (CBAVD). Microsurgery can sometimes be successful in treating the obstruction. In other cases and in cases of failed surgical intervention, the patient can be treated by microsurgical or percutaneous epididymal sperm aspiration (MESA, PESA) or testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). We present the results of 39 ICSI procedures for obstructive azoospermia in 24 couples. The aetiology of the obstruction was failed microsurgery in 11 patients, CBAVD in nine and genital infections in four. Sperm retrieval was accomplished via MESA in four cases, PESA in 18 cases and via TESE in 11 cases. TESE was only applied when PESA failed to produce enough spermatozoa for simultaneous ICSI. In six patients, the ICSI procedure was performed with cryopreserved spermatozoa after an initial PESA procedure. Fertilization occurred in 47% of the metaphase II oocytes; embryo transfer was performed in 92% of procedures and resulted in a clinical pregnancy in 13/39 procedures. Ongoing pregnancy was achieved in 10/39 procedures. One pregnancy was terminated early after prenatal investigation showed a cytogenetic abnormality (47,XX+18, Edwards syndrome). The other nine pregnancies resulted in the live birth of 10 children, without any congenital abnormalities. Epididymal and testicular retrieved spermatozoa were successfully used for ICSI to treat obstructive azoospermia, and resulted in an ongoing pregnancy in 10 of 24 couples (41.6%) after 39 ICSI procedures, a success rate of 25.6% per treatment cycle and of 27.7% per embryo transfer.      

Computational fluid dynamics modeling of impeller designs for the HeartQuest left ventricular assist device

To finalize the design of the next generation of the HeartQuest left ventricular assist device, a suitable impeller had to be designed and tested. The new prototype was based on calculations and test results of previous designs, but required several changes to decrease the size. For most pump designs, this is a simple matter of altering impeller geometry and rotational speed to achieve the desired pressure rise and flow rate. However, this particular pump was limited by housing geometry and the magnetic bearings that support the impeller. Without much freedom in the overall impeller size, the only parameters open to the designers were the blade profiles and the rotating speed. Rather than build several candidates and test them in a rig at enormous cost, computational models of several designs were tested and analyzed. This not only saved money, but also sped up the development time for the project. The computer models were developed in TASCflow, a computational fluid dynamics software package from AEA Technologies. This paper analyzes the data from several of the selected models, paying close attention to pumping performance and general trends from specific design changes.     

Associations of IGF2 ApaI RFLP and INS VNTR class I allele size with obesity

Body mass index (BMI) is an established epidemiological predictor of coronary disease, diabetes and hypertension. In a previous study of 2560 healthy British Caucasoid males aged 50-61 years (Northwick Park Heart Study II; NPHSII), we showed that IGF2 ApaI AA homozygotes display a mean body weight 3.3 kg lower than GG homozygotes (P = 0.0002) independent of height. Two RFLPs in the insulin (INS) gene, +1127/PstI shown previously and -23/HphI in this study, both of which are in strong linkage disequilibrium with class I/III alleles of the INS 5' variable number tandem repeat (VNTR), are not associated with weight or BMI. The IGF2 ApaI polymorphism therefore appears to mark an effect independent of INS VNTR class I vs class III. We now show by regression that there is a positive correlation of BMI with INS VNTR class I allele size, with an average 0.33% (95% CI = 0.13%, 0.50%) increase in BMI per extra tandem repeat (P < 0.0001) representing variation of 4.8% over the allele size range. However, an alternative interpretation is of 'step' rather than 'slope', the small class I subclass allele group (mode 669 bp) being lighter than the large subclass group (mode 814 bp). This small effect would not be evident as an association between INS VNTR class I/I1 genotype and BMI. The IGF2 ApaI association and INS VNTR class I subclass regression association account for at least 1.1% of population BMI variance. Neither, both, or a third site may be aetiological.     

HLA Antigens in 16 Families with Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disease. HLA-A and -B typing was performed on peripheral blood lymphocytes and platelets. Sixteen Tunisian families were typed with 37 patients and 108 relatives. Genetic transmission of the disease and of the HLA system seemed to be independent in this study. Comparison of HLA gene frequencies between (unrelated) parents of patients and a control population showed no difference, proving that there is no clear association in populations between deleterious XP genes and a particular HLA gene. However, an excess of identical HLA among pairs of diseased siblings would suggest that the disease is polymorphic and a form of the XP could be linked to HLA.     

Oxytocin localization and function in the A1 noradrenergic cell group: ultrastructural and electrophysiological studies

Antibodies to oxytocin and noradrenalin were utilized in an immunocytochemical study of the caudal ventrolateral medulla of the rat brainstem. Noradrenalin was visualized by using antibodies to noradrenalin and by means of a silver-gold intensification of diaminobenzidine, whereas oxytocin could be demonstrated in the same section by using the diaminobenzidine precipitate as a marker. At the light microscopic level, oxytocin fibers were densely distributed around the A1 cell bodies. At the ultrastructural level, oxytocin-containing fibers were seen to terminate synaptically onto noradrenalin-containing neurons. Previous studies have shown that electrical stimulation of A1 neurons selectively activates vasopressin-secreting neurons in the supraoptic nucleus. Therefore, separate electrophysiological studies were set up, in which we observed that oxytocin infusions (100-200 pg) into the A1 area enhanced the activity of 16 out of 19 putative vasopressin-secreting neurons and elicited no response from any of 10 oxytocin-secreting neurons. This finding suggests that some of the parvicellular neurons in the paraventricular nucleus of the hypothalamus, from which the A1 neurons derive their oxytocin innervation, can activate the A1 cell group via this peptidergic neurotransmitter. One of the consequences of A1 neuronal activation is enhanced firing of hypothalamic supraoptic (and paraventricular) vasopressin-secreting neurons, and a consequent rise in plasma vasopressin.