A non-destructive method of evaluating the elastic properties of anterior restorative materials.

An ultrasonic pulse transit-time method was used to determine the Young's modulus, shear modulus, and Poisson's ratio of seven anterior-restorative materials. Small rectangular specimens were immersed in a water bath and ultrasonic pulses propagated through them. Two types of ultrasonic wave could be generated inside the specimen by altering the angle of incidence.

Ventricular premature contractions. Which should be treated?

The treatment of ventricular premature contractions (VPCs) is based on two factors: bothersome symptoms from which the patient desires relief and the association of ectopic ventricular beats with sudden cardiac death. The sudden death risk related to ventricular ectopic beats is real, but appears to be a function of the frequency or pattern in which they occur plus the presence of underlying heart disease. A serious risk exists when frequent, multifocal, successive, or R-on-T-type VPCs occur in a patient monitored late after a fresh myocardial infarction, particularly if left ventricular failure is also present.

Toxic synergism of disopyramide and hyperkalemia.

A patient is presented whose electrocardiogram became remarkably abnormal and who developed hypotension while receiving disopyramide and potassium. This report documents a potassium-disopyramide synergism leading to life-threatening toxicity. These abnormalities were corrected by glucose, insulin and bicarbonate therapy, suggesting that serious disopyramide toxicity may be enhanced by hyperkalemia and reversed by lowering the serum potassium.

Unscheduled DNA synthesis and chromosome aberrations induced by inorganic and organic selenium compounds in the presence of glutathione.

Glutathione strongly enhanced the induction of unscheduled DNA synthesis (UDS) in cultured human cells by inorganic selenium compounds: sodium selenate, sodium selenite and sodium selenide. In the presence of 10(-3) M glutathione, high levels of UDS (74-114 grains per nucleus) were observed in cells treated with (i) selenate at 10(-3) M, (ii) selenite at 10(-5)-3 X 10(-4) 7, and (iii) selenide at 10(-5)-10(-3) M. Glutathione at 10(-3) M also enhanced the clastogenic and cytotoxic effects of selenite and selenate in Chinese hamster ovary (CHO) cells.

Dynamic mechanical properties of resin-based filling materials.

The elastic moduli and mechanical damping of a range of polymeric restorative materials have been determined using a torsion pendulum. Composite materials have high moduli and low damping compared with unfilled resin. These materials have stable mechanical properties, but variation occurred as a result of different specimen conditioning methods.

Enhancement by transition metals of unscheduled DNA synthesis induced by isoniazid and related hydrazines in cultured normal and xeroderma pigmentosum human cells.

In combination with transition metals (Mn(II), Cu(II), and Fe(III)), isoniazid and related hydrazine compounds induced unscheduled DNA synthesis (DNA repair) in cultured human fibroblasts. Manganese at 10(-5) and 10(-4) M strongly enhanced DNA repair induced by isoniazid, iproniazid, nialamide and hydrazine. Peak levels of DNA repair occurred at 5 x 10(-4)--10(-3) M of the 4 hydrazine compounds.

Enhancement of the chromosome-damaging action of ascorbate by transition metals.

Freshly prepared ascorbate inhibited mitosis and induced chromosome aberrations in cultured Chinese hamster ovary cells. Cu(II) and Mn(II) (10(-4) or 10(-5) M) enhanced both actions. Fe(II) and Fe(III) (10(-4) or 10(-5) M) reduced or abolished the mitosis-inhibiting action of ascorbate.

Sister chromatid exchanges induced in cultured mammalian cells by chromate.

Chromate compounds induced sister chromatoid exchanges (SCEs) and chromosome aberrations in cultured mammalian cells. Similar increases in SCE frequency were observed in human fibroblasts exposed to the compounds K2Cr2O7 and K2CrO4. Marked increases in SCE frequency in cells exposed to chromate for a 48-h period were detected at concentrations between 10(-7) and 10(-6) M.

DNA damage and DNA repair in cultured human cells exposed to chromate.

DNA damage and DNA repair have been observed in cultured human skin fibroblasts exposed to potassium chromate but not to a chromic glycine complex. DNA repair synthesis (unscheduled incorporation of [3H]thymidine (TdR)) was measured in cells during or following exposure to chromate and was significant for chromate concentrations above 10(-6) M. Maximal DNA repair was observed at about 10(-4) M chromate.

The impact of a required preceptorship on senior medical students.

The impact of a required preceptorship program was measured by comparing the perceptions of senior medical students who would have elected the preceptorship rotation had it not been required (the elective group) and those who participated only to fulfill the requirement (the required group). The main difference between the two groups before the preceptorship was the elective group's career preference for family medicine and the required group's preference for an internal medicine subspecialty. The preceptorship had no impact for either group on inclinations toward other specialties, preferred practice setting, or assessment of practice location determinants.

Enzyme immunoassay and gas--liquid chromatography compared for determination of lidocaine in serum.

Lidocaine, an anti-arrhythmic drug, was quantitated in serum by a commercially supplied enzyme immunoassay procedure. Replicate analyses of serum controls resulted in a within-assay coefficient of variation of less than 5.0 and a between-assay coefficient of variation of less than 6.

Composition of the milk of the common marmoset (Callithrix jacchus) and milk substitutes used in hand-rearing programmes, with special reference to fatty acids.

Analyses of marmoset (Callithrix jacchus) milk were carried out to determine values for crude protein, lactose, total lipids, major minerals, and osmotic pressure. Mean values were (g/100 ml): protein, 3.6; lactose, 7.

BRL 13776: a novel antihypertensive agent with interesting monoamine depleting properties.

1. Oral doses of 10-100 mg/kg of BRL 13776 lowered the blood pressure of both deoxycorticosterone acetate (DOCA)/NaCl-treated hypertensive rats and untreated normotensive rats. 2.

Use of salt bridge in rhythm analysis.

Filling a catheter with electrolyte solution converts it to a conductor and allows the safe recording of an electrogram from near or within the right atrium. This technic is very useful in localizing the internal position of a cardiac catheter and particularly in rhythm analysis. Four cases are presented to review the value of this salt bridge technic.