Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice

To compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6- and 24-month-old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice.     

Breast screening: a subject for debate.

The National Health Service Breast Screening Programme was instituted in 1988 following the recommendations of the Forrest report in 1986. From the beginning it has been controversial. Is breast cancer screening efficacious? Can the efficacy produced in trials be reproduced nationwide in the UK? Do the benefits of screening outweigh the adverse effects? Answers to all these questions are not yet available but in the light of current evidence, breast screening does appear to offer a realistic opportunity to reduce the mortality from a disease which constitutes a major public health problem in the UK. The role of the general practitioner and the primary care team is considered in the light of the experience gained in the first phase of the screening programme.     

Expression of rabbit Ig allotypes in litters of mothers immunized against a paternal allotype.

Sera of successive littermates of mothers producing anti-allotype antibodies (Ab) were analysed for altered a locus or b locus allotype expression. We measured the allotype concentration in sera of 66 individuals (17 litters) of seven mothers producing anti-a1 Ab, and 63 individuals (15 litters) of seven mothers producing anti-b4 Ab, in an enzyme-linked immunosorbent assay (ELISA). We confirmed that the ability to induce allotype suppression in utero increases with the number of antigen boosts applied to the mother, even though the Ab titre in the maternal serum may be decreased. All individuals of a litter expressed the allotype in about equal concentration. This contrasts the results we obtained when newborn rabbits were injected with anti-allotype antiserum. Injection of the same amount of anti-allotype antiserum into nine offspring of two mothers caused allotype suppression in only five individuals, showing no effect in the others. No suppression was observed when IgG-depleted antiserum was injected into newborn rabbits. As expected, maternal antibodies to a paternal allotype do not affect the Mendelian distribution of the progeny phenotypes.     

Ameloblastoma after surgical removal of an impacted mandibular molar. A case report

A case of an ameloblastoma diagnosed about 3 1/2 years after removal of an impacted mandibular 3rd molar is presented. The pre-operative radiographs, though poor in quality, showed an ill-defined radiolucency in relation to the tooth. This feature was not apparent to the examiners at the time of first presentation. Despite unfavourable working conditions in developing countries, a high level of suspicion should be maintained to avoid serious sequelae at a later stage.     

Clinical Observations of Porcelain Veneers: A Three-Year Report

One hundred and sixty-five Cerinate porcelain veneers were placed by 11 private practice clinicians from diverse locations throughout the USA. The veneers were evaluated over a 3-year service period using Kodachrome photographs and grading of clinical characteristics by evaluators. The following factors were evaluated: (1) esthetics; (2) margin fit; (3) margin discoloration; (4) breakage; (5) gingival irritation; (6) patient acceptance; and (7) caries. Specific characteristics and their evaluations over three years were: (1) Esthetics started out excellent and remained that way; (2) Margin fit was acceptable at the beginning of the study and was actually perceived to improve, perhaps related to cement at the margins wearing and smoothing; (3) Margin discoloration started very low and became slightly worse; (4) Breakage was present during each of the 3 years, and 13 percent of veneers had some breakage after 3 years. Changes in clinical procedures are suggested in this paper to diminish this problem; (5) Gingival irritation was minimal throughout the study; (6) Patient acceptance was excellent at the beginning of the study and improved; and (7) Dental caries involvement was minimal, with only one veneered tooth showing caries involvement. Over the 3-year period, the veneers provided excellent service overall.     

Daptomycin disrupts membrane potential in growing Staphylococcus aureus.

Daptomycin (LY146032) caused a calcium-dependent dissipation of the membrane potential (delta psi) in Staphylococcus aureus without noticeably affecting the chemical gradient (delta pH) across the membrane. The effect of daptomycin on membrane energization may account for many of the inhibitory effects on macromolecular biosyntheses and membrane function reported for this antibiotic. Our evidence indicates that the bactericidal activity of daptomycin is dependent on an available delta psi.     

Radioimmunoassay for amatoxins by use of a rapid, 125I-tracer-based system

In this new radioimmunoassay system for determination of amatoxins in urine and plasma, a novel chemical approach is used for antigen and 125I-tracer production, based on a detoxified alpha-amanitin derivative (aldoamanitin). Total assay time, including data processing, is less than 100 min. The lowest detectable concentration is 1 microgram/L for urine, 0.1 microgram/L for plasma. In the clinically significant range, within-run CVs are less than 8%. This new 125I-based assay is a significant improvement over existing 3H technology in terms of speed, precision, and freedom from interference.