The effect of matrix phase morphology on the structure of Ag-Cu-Pd dispersed phase dental amalgam

The effect of an Ag-Cu-Pd dispersant alloy on the structure of amalgams fabricated with two different particle types of low-copper amalgam matrices was investigated. In amalgams L and L (0), a low-copper lathe-cut amalgam Aristalloy was used as the matrix. In amalgams S and S(0), the matrix used was Spheralloy, a low-copper spherical amalgam. X-ray diffraction was used to analyse the relative content of the phases in the amalgams. The presence of Pd in the dispersant of amalgams L and S resulted in a decrease in the amount of eta' (Cu6Sn5) and an increase in the amount of unreacted particles when compared to the controls L(0) and S(0). Amalgams fabricated with a spherical alloy matrix (S and S(0)) showed a greater effect than amalgams fabricated with a lathe-cut matrix alloy (L and L(0)).

Rehydration in palliative and terminal care: if not--why not?

Patients who are in the last few days of life are often too frail to take oral fluids and nutrition. This may be due entirely to the natural history of their disease, although the use of sedative drugs for symptom relief may contribute to a reduced level of consciousness and thus a reduced oral intake. Rehydration with intravenous (i.v.) fluids is the usual response in acute care settings, whereas the hospice movement has often argued against this approach. The issues are complex and involve not only physical, psychological and social concerns, but also ethical dilemmas. A review of the literature gives conflicting reports of the physical discomfort that may be attributed to dehydration in dying patients. There are many confounding variables, including the concomitant use of antisecretory drugs, mouth breathing and oral infection. It remains unproven whether i.v. fluids offer symptomatic relief in this situation. Hospice doctors are concerned that the use of i.v. fluids gives confusing messages to relatives about the role of medical intervention at this stage in a patient's illness. A drip may cause a physical barrier between a patient and their loved one at this important time. The use of other methods of fluid replacement are discussed. In the absence of definitive research in this area, the balance of the burdens and benefits of such treatment remains subjective. The prime goal of any treatment in terminal care should be the comfort of the patient. Decisions should be made on an individual basis, involving both patients and their carers wherever possible. Prolonging life in such circumstances is of secondary concern and i.v. fluids given in this context may be futile. The ethical dilemmas of withholding and withdrawing medical treatment in addition to those of conducting research in this area are discussed.

Modulation of skeletal muscle sodium channels by human myotonin protein kinase

In myotonic muscular dystrophy, abnormal muscle Na currents underlie myotonic discharges. Since the myotonic muscular dystrophy gene encodes a product, human myotonin protein kinase, with structural similarity to protein kinases, we tested the idea that human myotonin protein kinase modulates skeletal muscle Na channels. Coexpression of human myotonin protein kinase with rat skeletal muscle Na channels in Xenopus oocytes reduced the amplitude of Na currents and accelerated current decay. The effect required the presence of a potential phosphorylation site in the inactivation mechanism of the channel. The mutation responsible for human disease, trinucleotide repeats in the 3' untranslated region, did not prevent the effect. The consequence of an abnormal amount of the kinase would be altered muscle cell excitability, consistent with the clinical finding of myotonia in myotonic dystrophy.

Analysis of a novel cDNA encoding a C219-reactive peptide isolated from methotrexate-selected multidrug-resistant human leukemic cells

We have isolated and sequenced a novel cDNA clone (D320), from methotrexate-selected multidrug-resistant (MDR) human leukemic CCRF-CEM cells, which encodes a peptide reactive with monoclonal antibody (mAb) C219. Despite having been cloned using this ostensibly P-glycoprotein-specific mAb, clone D320 has no significant homology with either the MDR-encoding gene or, at the amino acid (aa) level, with its product, P-glycoprotein. A putative C219-binding site has been identified in D320, which differs at two positions from the 6-aa C219 epitope previously described in P-glycoprotein.

Analysis of mycotoxins in food and feed: certification of DON in wheat and maize

Worldwide there are either statutory limits or in some instances advisory guidelines for the maximum levels of mycotoxins in foods and feeds. These limits which have been agreed for the protection of human health and as standards for trade are often set at surprisingly low levels in view of both the problems of sampling and the abundant evidence of the difficulties of mycotoxin analysis, particularly so when approaching the limits of detection. Improved methodology for mycotoxins and improvements in performance even of expert laboratories have, however, been achieved through intercomparison exercises organised by the EC Measurement and Testing programme (formerly BCR). On a wider scale, participation in proficiency testing through schemes such as the UK Food Analysis Performance Assessment Scheme (FAPAS) have indicated that between 10 and 40% of laboratories experience difficulties in obtaining satisfactory results in monitoring mycotoxins. Reference materials provide an important means of checking method performance. BCR has made a unique contribution in the production and certification of maize and wheat reference materials naturally contaminated with the Fusarium mycotoxin 4-deoxynivalenol (DON), which has now been available for purchase for some 2 years.

The mechanical properties of milled and cast titanium for ceramic veneering

This study compared the mechanical properties of machine-milled pure titanium and cast titanium. The metals were cast or milled to the dimensions of a standard tensile bar pattern. Each group was treated under three different conditions: as-cast (or as-milled), standard heat, and extended heat. Tensile testing found no difference in the mechanical properties of as-cast and as-milled titanium. Heat treatment significantly increased the ultimate tensile strength and the yield strength of cast titanium but had no such effects on milled titanium. There was no significant difference between the two metals in the modulus of elasticity or the percentage of elongation under the three treatment conditions.

A comparison of the hardness of different types of titanium and conventional metal ceramics

This study compared the surface hardness of machine milled titanium and cast titanium, and the surface hardness profile of a gold-palladium alloy, a nickel chromium alloy, milled and cast titanium. For each group, 15 discoid specimens, 10 mm in diameter and 5 mm thick, were fabricated by either casting or milling. Five specimens of each group underwent one of three treatments: (1) no heat treatment, (2) a standard heat treatment, or (3) an extended heat treatment. Knoop hardness values were determined. Results indicated that the Knoop hardness of cast titanium was less than that of the cast titanium standard treatment group, which was less than the Knoop hardness of the cast titanium extended treatment group. Knoop hardness of milled titanium was less than that of the milled titanium standard treatment and milled titanium extended treatment groups. For the surface hardness profile, cast titanium showed a decreasing surface hardness as the distance from the surface of the specimen increased. No such trend was identified for the other groups tested.

Marginal fit of machine-milled titanium and cast titanium single crowns

Eighteen type IV dental stone dies were fabricated from a metal master die that replicated a tooth prepared to receive a metal ceramic crown. They were divided into three groups according to the type of crowns to be made: (a) machine-milled, spark-eroded titanium crowns (Procera); (b) cast titanium crowns; and (c) noble alloy crowns (as the control). The control specimens showed the smallest mean marginal openings at 25 microns and were significantly different from both the machine-milled crowns (54 microns) and the cast titanium crowns (60 microns). The two types of titanium crowns were not significantly different from each other.

Investigation of stiffness and microstructure of joints soldered with gas-oxygen torch and infrared methods

The stiffness of soldered connectors fabricated with the gas-oxygen torch technique was compared with those fabricated with the infrared technique. Untreated solder materials were used as controls. Untreated solder materials of gold-palladium, palladium-silver, and chromium-cobalt alloys exhibited significantly higher stiffness than the soldered specimens fabricated with either method. There was no significant difference between the gas-oxygen torch and the infrared groups of the gold-palladium and palladium-silver alloys. Photomicrographs revealed that the soldered specimens displayed porosities. For the chromium-cobalt alloy, the infrared group demonstrated significantly higher stiffness than the gas-oxygen torch group. Photomicrographs also disclosed that the chromium-cobalt alloy soldered with the gas-oxygen torch technique had a significant heat-affected zone.

A review of the research requirements for Europe to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision making process involved in determining future European Community legislation in the area of food contact materials and articles. The generation of this science base should be undertaken on a Europe-wide basis and needs to be coordinated to avoid duplication of effort and to secure agreement on the underlying science being used to determine future strategy. This review considers possible work that might be required in the future to support legislation on food contact materials and classifies it in terms of short-term problem-solving and longer-term strategic research.

1H magnetic resonance imaging of freezing and thawing in freeze-tolerant frogs

Proton magnetic resonance imaging (MRI) of the processes of freezing and thawing in the wood frog Rana sylvatica provided noninvasive and real-time analysis of the mode of ice propagation through the body of a freeze-tolerant vertebrate. MRI revealed a directional movement of ice from the exterior inward that required several hours to reach completion. Freezing in core organs such as liver, which produces and exports cryoprotectant, and heart, which circulates it, was delayed and occurred well after the organs were surrounded by extraorgan ice. Natural thawing was a very different process; thawing began uniformly throughout the body, but core organs melted more rapidly than peripheral ones, an adaptation that may be key to the early restoration of heartbeat and breathing. The images presented demonstrate the sensitivity and power of MRI and its potential to become a critical monitoring technology in the development of cryopreservation techniques for mammalian organ explants.

Measles immunization of 2-year-olds in a rural southern state

OBJECTIVE

To assess the measles vaccine coverage of 2-year-old children living in Mississippi during the national measles epidemic of 1989 and 1990.

DESIGN

Survey of 2-year-olds randomly selected from the 1987 birth cohort. The status of measles-mumps-rubella (MMR) vaccination was determined by medical record reviews and family contacts.

SETTING

A predominantly rural state in the southeastern United States with a large black minority population (35%) and a low per capital income ($9827 to $12,899). Approximately 80% of MMR immunizations are given by public health service nurses working in nine health districts.

SUBJECTS

A total of 2450 preschool-aged children representing 6% of the 1987 birth cohort (n = 41,279). Three hundred forty-one children were considered ineligible, leaving 2109 in the final sample.

MAIN OUTCOME MEASURES

Confirmed vaccination by the age of 2 years. Rates of immunization were calculated for the entire state, its health districts, and subgroups based on population density, per capita income, type of clinic visited, and race.

RESULTS

The statewide immunization rate was 87% (95% confidence interval, 86% to 88%). Among the nine health districts, rates varied from 79% to 97% (median, 88%). They were similar for white and black children in each health district and within the state as a whole. The level of vaccine coverage was significantly higher in districts with lower population densities (89% vs 85%, P = .02) and in those with higher per capita incomes (89% vs 86%, P = .03). There were four minor outbreaks of measles during 1989 and 1990; half of the cases occurred in unimmunized children too young to receive the MMR vaccine.

CONCLUSION

A high rate of measles immunization is attainable among 2-year-olds living in a rural state with a large black minority population and limited economic resources.