New concepts in air abrasion

There is no doubt that air abrasion is going to be part of the millennial shift in dentistry away from traditional treatment modalities. With the change in incidence and morphology of caries as a result of the hardening effect of fluoride on enamel, this ability to remove only decayed areas and permanently seal the less susceptible areas becomes increasingly desirable.     

Poly(3-hydroxybutyrate) is associated with specific proteins in the cytoplasm and membranes of Escherichia coli

Poly(3-hydroxybutyrate) (PHB) is well-known as a high molecular weight homopolymer of R-3-hydroxybutyrate which accumulates in storage granules within the cytosols of certain bacteria. Escherichia coli does not amass these granules; however, small amounts of low molecular weight PHB (<0.02% of dry weight) have been found in the plasma membranes in complexes with calcium polyphosphate; the complexes serve as voltage-activated calcium channels. Here we report that polyphosphate-complexed PHB is only a minor fraction of the polyester in E. coli. PHB comprises 0.36 to 0. 55% of the dry weight of log-phase cells, depending on culture medium, and this amount increases by 15 to 20% when the cells are made genetically competent. The PHB is widely distributed throughout the cell, wherein it is primarily associated with proteins. The identity of protein-associated PHB was established by antibody reaction, chemical assay, and 1H NMR spectroscopy. As expected, the physical and chemical properties of protein-associated PHB were found to be considerably different from those of the bulk polymer or granule PHB, e.g. protein-PHB complexes are normally insoluble in chloroform, soluble in water and alkaline hypochlorite, and are converted to crotonic acid more slowly on heating in concentrated sulfuric acid. Our studies indicate that the majority of cellular PHB (over 80%) is located in cytoplasmic proteins, especially proteins of the ribosomal fraction. Western immunoblots, probed with polyclonal anti-PHB IgG, revealed a number of PHB-polypeptides having a wide range of molecular weights in all cell fractions. These results suggest that PHB is a fundamental constituent of cells that may have physiological functions in addition to facilitating ion transmembrane transport or serving as a carbon reserve.     

An electrophysiological study of the postnatal development of the corticospinal system in the macaque monkey

We characterized toxin-insensitive calcium currents expressed by acutely dissociated embryonic dorsal root ganglion neurons. In the presence of 3 microM omega-conotoxin-GVIA, 3 microM nitrendipine and either 500 nM omega-agatoxin-IVA or 500 nM omega-conotoxin-MVIIC to inhibit N-, L- and P/Q-type currents, respectively, all neurons expressed two residual currents: a T-type and another which we referred to as toxin-resistant current. The toxin-resistant current (i) consisted of an inactivating and a sustained components, (ii) had a threshold of activation and a steady-state inactivation comprised between that of the T-type current and that of the other high-voltage-activated currents, (iii) had the same permeability for barium and calcium used as charge carriers, (iv) was highly sensitive to both cadmium and nickel; and (v) was insensitive to 500 microM amiloride which abolished the T-type at this concentration. The properties of the toxin-resistant current are very similar to those of the currents expressed in oocytes following injection of alpha(1E) subunits which we demonstrated to be present in these neurons. Therefore a component of the toxin-resistant current calcium channels in sensory neurons may be closely related to those calcium channels formed by alpha(1E) subunits.     

Changing trends in melanoma incidence and mortality

OBJECTIVES: This article analyzes trends in melanoma incidence and mortality rates. Information on sun exposure supplements these statistics. DATA SOURCES: Melanoma incidence data were obtained from the National Cancer Incidence Reporting System and from the Canadian Cancer Registry. Cancer mortality data were extracted from the Canadian Vital Statistics Data Base. Information on sun exposure is from the 1996 Sun Exposure Survey. ANALYTICAL TECHNIQUES: Incidence and mortality rates were age-standardized to the 1991 Canadian population to account for changes in the age structure of the population over time. The average annual percentage changes in age-specific rates were calculated for selected time periods. MAIN RESULTS: After years of steady increases, melanoma incidence and mortality rates have levelled off as a result of declining rates in younger age groups, and for melanoma of the trunk among men and of the leg among women. Incidence rates for men are now higher than those for women; mortality rates for men are twice as high as for women.     

Important immunoregulatory role of interleukin-11 in the inflammatory process in rheumatoid arthritis

OBJECTIVE: To investigate the possible immunoregulatory role of interleukin-11 (IL-11) in rheumatoid arthritis (RA). METHODS: IL-11 protein was assayed in RA tissue, and the effect of exogenous IL-11 on neutralization of endogenous IL-11 was investigated with respect to tumor necrosis factor alpha (TNFalpha), matrix metalloproteinase (MMP), and tissue inhibitor of metalloproteinases (TIMP) production. RESULTS: IL-11 was found in RA synovial membranes, synovial fluids, and blood sera. Blockade of endogenous IL-11 resulted in a 2-fold increase in TNFalpha levels, which increased to 22-fold if endogenous IL-10 was also blocked. Addition of exogenous IL-11 inhibited spontaneous TNFalpha production in RA synovium only in the presence of soluble IL-11 receptor. However, exogenous IL-11 directly inhibited spontaneous MMP-1 and MMP-3 production, and up-regulated TIMP-1 in RA synovial tissue. CONCLUSION: IL-11 has important endogenous immunoregulatory effects in RA synovium, which suggests that exogenous IL-11 may have therapeutic activity in RA.     

Investigation of a Monte Carlo model for chemical reactions

Many new technologies are being developed to improve the efficiency and productivity of nursing staff. A key to the success of these technologies is acceptance by nurses. Davis' constructs of perceived ease of use and perceived usefulness were developed to measure the acceptance of computer systems. This article presents a discussion on nursing acceptance of computer systems, reviews the development of the perceived ease of use and perceived usefulness measures, and reports findings of a study based on these constructs along with attitude of bedside-computer systems. Results of the study showed that nurses in general are accepting of bedside-computer technology.