IsK and KvLQT1: mutation in either of the two subunits of the slow component of the delayed rectifier potassium channel can cause Jervell and Lange-Nielsen syndrome

The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules.     

Lateral rectus whole muscle and motor unit contractile measures with the extraocular muscles intact

Both extracellular and intracellular stimulation of single motoneurons were shown to be similarly effective and consistent in eliciting contractile responses in single lateral rectus muscle motor units. The whole muscle was activated by stimulating the sixth nerve in the brain stem. Both whole muscle and motor unit contractile characteristics, under isometric conditions, were found to remain consistent regardless of whether this extraocular muscle was detached or left attached to the globe. In addition, whole muscle twitch and maximum tetanic tension evoked by sixth nerve stimulation was significantly less than would be predicted by the linear summation of individual motor unit twitch and maximum tetanic tensions.     

Cryopreservation of all prezygotes in patients at risk of severe hyperstimulation does not eliminate the syndrome, but the chances of pregnancy are excellent with subsequent frozen-thaw transfers

In-vitro fertilization patients (n = 15) at risk of ovarian hyperstimulation syndrome (OHSS) (oestradiol > or =4500 pg/ml on the day of human chorionic gonadotrophin administration and 25 or more follicles of intermediate or large size) underwent aspiration of all follicles and cryopreservation of all fertilized oocytes at the pronuclear stage. Patients were monitored for up to 2 weeks post-retrieval. Subsequent transfer of cryopreserved-thawed embryos was performed in programmed cycles using exogenous oestrogen and progesterone for endometrial preparation. Two patients (13%) developed OHSS necessitating hospitalization and vaginal aspiration of ascitic fluid. Two other patients (13%) developed moderate OHSS requiring ascitic fluid vaginal aspiration in the office setting, with dramatic improvement of the condition. Subsequent transfer of cryopreserved-thawed embryos yielded a clinical pregnancy rate of 58% per transfer and ongoing or delivery rates of 42 and 67% per transfer and per patient respectively. By eliminating pregnancy potential with cryopreservation of all prezygotes and examining the pregnancy potential with subsequent cryopreserved-thawed transfers, it is concluded that OHSS is reduced, but not eliminated for patients at risk. Subsequent transfer of cryopreserved-thawed prezygotes in a programmed cycle with exogenous steroids yields an excellent pregnancy rate.     

Spontaneous bacterial peritonitis in patients with ventriculoperitoneal shunts

A questionnaire to evaluate the needs of dialytic patients and the burden that these have on the health service and staff, was formulated by the nurses. The results showed how the patient's case history indicate, significantly, not only personal and subjective aspects (e.g. interpersonal relationships), but also how they construct their relationships with the hospital and its service (including the hospital staff). This opens up certain reflections on what role communication and information play within the hospital structure.     

Identification of the blood-borne somatotroph-differentiating factor during chicken embryonic development

Somatotrophs become a significant population by day 16 of chicken embryonic development. We have previously demonstrated that an earlier induction of GH cell differentiation is possible with the addition of day 16 embryonic serum to cultures of day 12 pituitary cells, an age when somatotrophs are rare. The present study was designed to identify the blood-borne signal(s) responsible for the serum activity, using reverse hemolytic plaque assays to identify individual GH-secreting cells. The activity was found to be a heat-stable, ether-soluble compound(s) that is bound or inhibited by a trypsin-sensitive protein. The extent of GH cell differentiation was greater (P < 0.05; n = 3) in response to the ether phases of heated day 16 (14.1 +/- 0.4% of all cells) and day 12 sera (9.3 +/- 0.4%) than with untreated serum from days 16 and 12 (6.1 +/- 0.4% and 0.82 +/- 0.4%, respectively). Furthermore, ether-extracted day 16 serum was more effective than ether-extracted day 12 serum, which was also different from basal (0.85 +/- 0.4%; P < 0.05). Based on this biochemical profile, the abilities of various steroids to stimulate differentiation were tested. Three steroids were found to stimulate somatotroph differentiation in vitro: 17beta-estradiol, corticosterone, and progesterone. However, the estradiol receptor antagonist, tamoxifen, while abolishing the effect of estradiol, had no effect on the induction of differentiation by day 16 serum. In contrast, RU486, a specific glucocorticoid receptor antagonist in chickens, blocked the stimulatory effects of corticosterone, progesterone, and day 16 serum on somatotroph differentiation. We next tested whether the active compound in day 16 embryonic serum was corticosterone, the predominant glucocorticoid in chickens. Incubation of day 16 serum with corticosterone antiserum, but not control antiserum, suppressed day 16 serum-induced GH cell differentiation. Therefore, we conclude that corticosterone is the blood-borne signal capable of stimulating somatotroph differentiation in vitro. The present findings together with previous reports indicate that somatotroph differentiation during embryonic development may result from an increase in circulating glucocorticoid concentrations.     

Demonstration of discrete secreted and membrane-bound ocular mucins in the dog

Our aims were to separate and characterize secreted canine ocular mucins, and to provide definitive evidence of membrane-bound mucins at the canine ocular surface. Mucus was collected by suction from the ocular surface of normal dogs and dispersed in guanidine hydrochloride and a cocktail of protease inhibitors. Caesium chloride density gradient centrifugation separated secreted mucins from membranes, which were collected from the top of the gradients. Membranes were extracted with octyl glucoside and screened using lectins and anti-mucin antibodies. Gradient fractions containing secreted mucins were constituted into pools on the basis of differential lectin and antibody staining. High molecular weight material from each pool was purified by gel filtration. This material, and the membrane extract, were reduced and alkylated. Vacuum blotting of separated materials after agarose gel electrophoresis was used to compare subunit structure. Density gradient profiles indicated three principal secreted glycoprotein peaks: one staining strongly with anti-mucin antibodies. Gel filtration demonstrated that each contained high molecular weight material. Vacuum blots demonstrated the presence of two secreted glycoproteins with differently sized subunits. On the basis of buoyant density, one of these may be lipid complexed. Membrane extracted material stained with anti-mucin antibodies, and vacuum blotting of this material provided evidence for two membrane-bound components. In conclusion, we have shown that normal canine ocular mucus contains two secreted mucins, each exhibiting different subunit structure; one of these mucins may undergo lipid complexation. Normal canine ocular mucus also contains two membrane-bound mucins: one of which is unique among membrane mucins in showing subunit structure.     

Characterization of Rev function using subgenomic and genomic constructs in T and COS cells

The effects of extracellular Ca2+ on cytotoxicity induced by cardiotoxin (CTX), isolated from Chinese cobra venom, were investigated in cultured rabbit aortic endothelial cells (RAECs). In Hank's buffered saline solution (HBSS) containing 1.2 mM Ca2+, CTX (1-30 microM) caused cell necrosis and cell death in a concentration-dependent manner, as determined by trypan blue exclusion test performed after a 20-min CTX treatment. The concentration of CTX that caused 50% cell death was about 6.5 microM. CTX (10 microM)-induced RAEC damage was also evident but less prominent in Ca2+-free medium and almost completely prevented in medium containing 7-10 mM Ca2+. Therefore, Ca2+ appears to provoke CTX-induced injury at physiological concentrations, but protects against it at high concentrations. The protection of RAECs from CTX-induced injury could also be achieved by high concentrations of Ni2+ and Mg2+. Using the fura-2 fluorescence technique to measure the cytosolic free Ca2+ concentration ([Ca2+]i) of single RAEC, it was shown that in 1.2 mM Ca2+-containing HBSS, treatment of RAECs with 10 microM CTX for 7-35 min resulted in a tremendous and irreversible [Ca2+]i elevation, suggestive of cell membrane damage and extracellular Ca2+ entry. Ni2+ could also enter the cytosol of these damaged RAECs. However, there was no [Ca2+]i elevation or Ni2+ entry in RAECs that were preincubated in HBSS containing 7 mM Ca2+ or Ni2+ before CTX exposure. In RAECs protected with 7 mM Ca2+, the intracellular Ca2+ signals triggered by 100 microM extracellular ATP or 10 microM bradykinin in CTX-treated groups were similar to those in the untreated control groups. Taken together, the results indicate that high extracellular Ca2+ concentrations protected RAECs from CTX-induced injury, and preserved the ability of CTX-treated RAECs to generate Ca2+ signals in response to physiological stimuli.     

Homogeneity of fruits and vegetables comminuted in a vertical cutter mixer

The homogeneity of comminuted composites of 20 lb samples of apples, cabbage, and green beans containing field-incurred residues of p, p'-methoxychlor was studied to determine whether a 5 min comminution in a 40 qt vertical cutter mixer produces a homogeneous composite and whether the size of test portions used accurately represents the composite. Duplicate test portions of 100, 50, 25, 10, 5, and 2 g taken from each of 6 separate sections of the mixer were analyzed by standard pesticide residue methodology for p, p'-methoxychlor. Results of this study confirmed that comminution of fresh produce in a 40 qt vertical cutter mixer, according to instructions described in the U.S. Food and Drug Administration's Pesticide Analytical Manual, Volume I, Section 203B, produces a homogeneous composite. No significant differences were found in the data for the 3 crops taken from the 6 sections of the mixer. Test portion weights of 100, 50, and 25 g produced equivalent results for all 3 crops. Statistically significant differences were observed for cabbage at 2, 5, and 10 g and for green beans at 2 g.