Genetic linkage of the tricho-dento-osseous syndrome to chromosome 17q21

Tricho-dento-osseous syndrome (TDO), MIM# 190320, is transmitted as a highly penetrant autosomal dominant trait that is characterized by variable clinical expression. The principal clinical features include kinky/curly hair in infancy, enamel hypoplasia, taurodontism, as well as increased thickness and density of cranial bones. Possible genetic linkage has been reported for TDO with the ABO blood group locus, but the gene defect remains unknown. We have identified four multiplex families (n = 63, 39 affected, 24 unaffected) from North Carolina segregating TDO. We previously have excluded a major locus for TDO in the ABO region for these families. Utilizing a genome-wide search strategy, we obtained conclusive evidence for linkage of the TDO syndrome locus to markers on chromosome 17q21 (D17S791, Z max = 10.54, Theta = 0.00) with no indication of genetic heterogeneity. Multipoint analysis suggests the TDO locus is located in a 7 cM chromosomal segment flanked by D17S932 and D17S941. This finding represents the first step towards isolation and cloning of the TDO gene. Identification of this gene has important implications for understanding normal and abnormal craniofacial development of hair, teeth and bone.      

Essential role for caspase 8 in T-cell homeostasis and T-cell-mediated immunity

Defects in death receptor-mediated apoptosis have been linked to cancer and autoimmune disease in humans. The in vivo role of caspase 8, a component of this pathway, has eluded analysis in postnatal tissues because of the lack of an appropriate animal model. Targeted disruption of caspase 8 is lethal in utero. We generated mice with a targeted caspase 8 mutation that is restricted to the T-cell lineage. Despite normal thymocyte development in the absence of caspase 8, we observed a marked decrease in the number of peripheral T-cells and impaired T-cell response ex vivo to activation stimuli. caspase 8 ablation protected thymocytes and activated T-cells from CD95 ligand but not anti-CD3-induced apoptosis, or apoptosis activated by agents that are known to act through the mitochondria. caspase 8 mutant mice were unable to mount an immune response to viral infection, indicating that caspase 8 deletion in T-cells leads to immunodeficiency. These findings identify an essential, cell-stage-specific role for caspase 8 in T-cell homeostasis and T-cell-mediated immunity. This is consistent with the recent identification of caspase 8 mutations in human immunodeficiency.     

Missense mutation in a von Willebrand factor type A domain of the alpha 3(VI) collagen gene (COL6A3) in a family with Bethlem myopathy

The Bethlem myopathy is a rare autosomal dominant proximal myopathy characterized by early childhood onset and joint contractures. Evidence for linkage and genetic heterogeneity has been established, with the majority of families linked to 21q22.3 and one large family linked to 2q37, implicating the three type VI collagen subunit genes, COL6A1 (chromosome 21), COL6A2 (chromosome 21) and COL6A3 (chromosome 2) as candidate genes. Mutations of the invariant glycine residues in the triple-helical domain-coding region of COL6A1 and COL6A2 have been reported previously in the chromosome 21-linked families. We report here the identification of a G-->A mutation in the N-terminal globular domain-coding region of COL6A3 in a large American pedigree (19 affected, 12 unaffected), leading to the substitution of glycine by glutamic acid in the N2 motif, which is homologous to the type A domains of the von Willebrand factor. This mutation segregated to all affected family members, to no unaffected family members, and was not identified in 338 unrelated Caucasian control chromosomes. Thus mutations in either the triple-helical domain or the globular domain of type VI collagen appear to cause Bethlem myopathy.      

Lack of increase in time to blood culture positivity in a patient with persistent methicillin-resistant Staphylococcus aureus bacteremia predicts failure of antimicrobial therapy

Time to positivity is an available parameter in automated blood culture systems. We report a patient with persistent methicillin-resistant Staphylococcus aureus bacteremia who received various regimens for treatment of methicillin-resistant S. aureus, and demonstrate that monitoring of the time to positive blood culture might be helpful in the early recognition of treatment failure.     

Remodelling of action potential and intracellular calcium cycling dynamics during subacute myocardial infarction promotes ventricular arrhythmias in Langendorff-perfused rabbit hearts

We hypothesize that remodelling of action potential and intracellular calcium (Ca_i) dynamics in the peri-infarct zone contributes to ventricular arrhythmogenesis in the postmyocardial infarction setting. To test this hypothesis, we performed simultaneous optical mapping of Ca_i and membrane potential ( V _m) in the left ventricle in 15 rabbit hearts with myocardial infarction for 1 week. Ventricular premature beats frequently originated from the peri-infarct zone, and 37% showed elevation of Ca_i prior to V _m depolarization, suggesting reverse excitation–contraction coupling as their aetiology. During electrically induced ventricular fibrillation, the highest dominant frequency was in the peri-infarct zone in 61 of 70 episodes. The site of highest dominant frequency had steeper action potential duration restitution and was more susceptible to pacing-induced Ca_i alternans than sites remote from infarct. Wavebreaks during ventricular fibrillation tended to occur at sites of persistently elevated Ca_i. Infusion of propranolol flattened action potential duration restitution, reduced wavebreaks and converted ventricular fibrillation to ventricular tachycardia. We conclude that in the subacute phase of myocardial infarction, the peri-infarct zone exhibits regions with steep action potential duration restitution slope and unstable Ca_i dynamics. These changes may promote ventricular extrasystoles and increase the incidence of wavebreaks during ventricular fibrillation. Whereas increased tissue heterogeneity after subacute myocardial infarction creates a highly arrhythmogenic substrate, dynamic action potential and Ca_i cycling remodelling also contribute to the initiation and maintenance of ventricular fibrillation in this setting.     

Formoterol provides long-lasting protection against exercise-induced bronchospasm.

BACKGROUND: Patients with exercise-induced bronchospasm (EIB) may benefit from a prophylactic beta2-adrenergic agonist that combines rapid onset with long duration of action. OBJECTIVE: To compare the protective effect against EIB of a single inhaled dose of formoterol powder delivered via the Aerolizer inhaler (Novartis Pharmaceuticals, East Hanover, NJ) with the effect of placebo and albuterol. METHODS: Eighteen patients with EIB were randomized to treatment in a double-blind, placebo-controlled, four-way, crossover study. Seventeen patients completed all four crossover periods. Each patient received in random sequence a single dose of formoterol (12 or 24 microg), albuterol (180 microg), or placebo at intervals of 5 +/- 2 days. Pulmonary function measurements were taken before and after exercise challenge tests (ECTs) at 15 minutes postdosing and at 4, 8, and 12 hours postdosing. RESULTS: Both doses of formoterol produced significantly greater protection against EIB, compared with placebo, at all timepoints (P < or = 0.016). The two doses of formoterol were not significantly different from one another at any time. Protection against EIB with albuterol was clinically significant only for the 15-minute ECT and was statistically superior to placebo for the 15-minute and 4-hour ECTs. Although formoterol and albuterol exhibited a rapid onset of action, formoterol provided longer-lasting protection over the 12-hour observation period. Rescue medication was used substantially less with either dose of formoterol, compared with albuterol or placebo. All treatments were well tolerated. Two-hour postdosing electrocardiograms and vital signs were unremarkable for all study treatments. CONCLUSION: A single dose of formoterol (12 or 24 microg) provides protection against EIB within 15 minutes of dosing and persists for up to 12 hours. Formoterol is safe and well tolerated.     

American Associatin of Anatomists. Eighty Sixth Annual Session,Cornell University Medical College,New York,New York,April 9, 10, 11, 12, 1973. Officers,abstracts, demonstrations

A method for producing flexible silicone rubber casts of the airways of the lungs in-situ is described. Casts are made to correspond to lung volumes occurring during normal breathing. The lung is prepared for casting by replacing the air within with CO₂ followed by filling with degassed physiological saline. The saline dissolves the CO₂ gas within the airways allowing for a bubble-free finished cast. Casting compound is then slowly injected through the trachea. The saline diffuses out of the lung and passes out of the thorax through several small slits in the thoracic wall. After the injection is completed, the cast lung is allowed to cure in-situ before it is removed and the tissue digested away. Finished casts have an overall shape corresponding closely to the shape of the thorax. Casts produced by this in-situ method appear to have more realistic geometrical relationships than those produced from excised lungs.     

Porous carriers for biomedical applications based on alginate hydrogels

Macroporous scaffolds are typically utilized in tissue engineering applications to allow for the migration of cells throughout the scaffold and integration of the engineered tissue with the surrounding host tissue. A method to form macroporous beads with an interconnected pore structure from alginate has been developed by incorporating gas pockets within alginate beads, stabilizing the gas bubbles with surfactants, and subsequently removing the gas. Macroporous scaffolds could be formed from alginate with different average molecular weights (5-200 kDa) and various surfactants. The gross morphology, amount of interconnected pores, and total void volume was investigated both qualitatively and quantitatively. Importantly, macroporous alginate beads supported cell invasion in vitro and in vivo.