Search PubMed⌕ Search

Biomedical subjects

T Marshall

Publications and source records attributed to T Marshall.

At least 145 records · Page 8Linked to original sources
PubMed1993

Effect of environmental stress and surface treatment on resin-to-metal bonding.

This study compares the bond strength and durability of three metal surface treatments subjected to two types of environmental stress for both short- and long-term exposures. The luting resins Panavia and Comspan were applied to alumina-blasted, non-beryllium, nickel-chromium alloy coupons. Metal surface treatments consisted of either microscopic roughening by electrochemical etching, or one of two types of adhesives: a silanated silica coating (Silicoating) or a phosphate ester monomer (a component in the Panavia liquid). Shear bond strength was determined following short- or long-term exposure to either thermocycling in 6-60 degrees C water (2,672 cycles/7 days or 10,584 cycles/42 days) or storage in 37 degrees C water (7 or 42 days). Three-way ANOVA showed that both the type of environmental stress and the exposure time affected the bond strength of electroetched surfaces, but that only exposure time affected the two chemical adhesives (P < 0.05), regardless of the environmental stress used. In the short-term, the silica/silane coated surfaces produced and maintained the higher shear bond strengths (15.9 +/- 2.3 MPa). However, after 42 days the silica/silane bonds decreased 30% (to 11.3 +/- 2.2 MPa), while the phosphate ester bonds were essentially unchanged (11.4 +/- 3.0 at 4 days, 10.4 +/- 2.2 MPa at 42 days). Electroetched bonds were the weakest and decreased by 18% between 7 and 42 days in water (8.8 +/- 1.2 to 7.2 +/- 3.0 MPa) and 27% after 42 days of thermocycling (7.2 +/- 2.8 to 5.3 +/- 1.8 MPa).

Analysis of Variance↗
PubMed1992

Residential care for the long term mentally ill in Canterbury: options, costs and funding sources.

AIMS: To obtain estimates of the costs of the main options of care for the long term mentally ill and to compare different approaches to costing. METHOD: Resources used by samples of residents in extended hospital care (EC, n = 43), community staffed houses (SH, n = 30), boarding houses (BH, n = 43) and group homes (GH, n = 100) were identified and costed using both the expenditure and total resource concepts of cost estimation. RESULTS: Using the expenditure concept of cost SH was the most expensive at $773 per person per week, compared to $700 for EC, $189 for BH and $155 for GH. Using the resource cost approach, valuing all resources used, SH and EC were similar at $790, compared to $184 and $169 for BH and GH care. Nursing was the most costly input with striking differences between nursing costs in the four modes of care. CONCLUSIONS: The results indicate a gap in the spectrum of residential care options, between high and low cost care. Future funding arrangements will require improved linkage between needs assessment and resource provision.

Capital Financing↗
PubMed1992

Recovery of protein by coomassie brilliant blue precipitation prior to electrophoresis.

The interaction of protein with Coomassie Brilliant Blue G-250 results in formation of an insoluble protein-dye complex which can be recovered by centrifugation and redissolved for electrophoretic analysis. The precipitated protein can be washed in acetone to remove excess dye in order to enhance resolution. The residual dye becomes dissociated from the proteins on electrophoresis and can be exploited as a "dye front". The method allows simultaneous protein assay and recovery of microgram amounts of protein from dilute solution and could be widely applied for conserving, concentrating and desalting minute amounts of valuable sample prior to electrophoretic analysis.

Chemical Precipitation↗
PubMed1992

Modulation of matrix vesicle enzyme activity and phosphatidylserine content by ceramic implant materials during endosteal bone healing.

This study examined effects of bone bonding and nonbonding implants on parameters associated with matrix vesicle-mediated primary bone formation, matrix vesicle alkaline phosphatase and phospholipase A2 specific activities, and phosphatidylserine content. Tibia marrow ablation followed by implantation of KG-Cera, Mina 13 (bonding), KGy-213, or M 8/1 (nonbonding) was used as the experimental model. Postsurgery, matrix vesicle-enriched microsomes (MVEM) were isolated from implanted and contralateral limbs. MVEM alkaline phosphatase and phospholipase A2 were stimulated adjacent to bonding implants with similar, though reduced, effects contralaterally. Alkaline phosphatase exhibited slight stimulation in nonbonding tissue; phospholipase A2 was inhibited or unchanged in treated and contralateral limbs. Phosphatidylserine content of MVEM was differentially affected by the implant materials. Thus, MVEM are modulated by implant materials locally and systemically. The data demonstrate that the model is a biologically relevant diagnostic for assessing the tissue/implant interface, primary calcification is affected by implant materials, and implant-specific effects are detected in the contralateral unimplanted limb.

Alkaline Phosphatase↗
PubMed1992

Coomassie blue protein dye-binding assays measure formation of an insoluble protein-dye complex.

The solubility of the protein-Coomassie brilliant blue (CBB) complex formed upon Bradford (Anal. Biochem. 72, 248-254, 1976) or Sedmak and Grossberg (Anal. Biochem. 79, 544-552, 1977) protein assay has been investigated by centrifugation or filtration of the assay mix within 10 min of adding dye reagent. The results show complete loss of color yield in the respective supernates and filtrates. This indicates that the protein-CBB complexes are insoluble at the time of absorbance measurement. Protein solubility in the dye reagent may dictate the relative response of the assay to an individual protein and the requirement for macromolecular structure.

Animals↗
PubMed1992

Determinants of child mortality in south-west Uganda.

Anthropometric and sociodemographic variables were taken from 4320 children in a baseline survey carried out in March-April 1988 in the district of Mbarara, south-west Uganda. After 12 months a follow-up survey assessed the mortality of the children during the preceding year. Lack of ownership of cattle, recent arrival in the village, using candles for lighting, being of birth order higher than 5 and having a father with less than 8 years of schooling were significantly associated with child mortality. The addition of mid-upper arm circumference significantly improved the logistic model of socioeconomic variables and mortality and did not diminish the predictive power of socioeconomic variables in relation to increased mortality. This suggests that nutritional status and specific socioeconomic factors are both, independently, important predictors of child mortality.

Anthropometry↗
PubMed1992

Space time clustering of births in SIDS: do perinatal infections play a role?

The aetiology of sudden infant death syndrome (SIDS) remains uncertain; many causal pathways have been proposed. In this paper we have examined firstly the variation in the risk of SIDS with age, month of death and month of birth; and secondly the space time clustering of SIDS deaths, and, separately, space time clustering of their births. Data were obtained from the Office of Populations, Censuses and Surveys on all certified SIDS deaths in the period; children were assigned grid references for the address of birth and of death. Data on number of births were abstracted from published material. A log-linear modelling technique was used to investigate the separate effects of age, month of death and month of birth on the risk of SIDS. The Knox method was used to investigate space time clustering of deaths and of births of children who died of SIDS. Separate, statistically significant effects were found for age, month of death and month of birth. There was minor space time clustering of SIDS births and deaths at large time and space intervals, and a marked space time clustering of births in short space time intervals in the first quarter of the year. The finding of an effect of month of birth on the risk of SIDS, and of space time clustering of births suggest that a perinatal hazard--possibly of infectious origin--may play a role in the aetiology of SIDS.

Birth Intervals↗
PubMed1992

Validation of virus inactivation by heat treatment in the manufacture of diaspirin crosslinked hemoglobin.

Diaspirin crosslinked hemoglobin (DCLHb), a hemoglobin based oxygen carrying solution prepared from outdated human blood, is subjected to a heat treatment step to inactivate viruses in our manufacturing process. To validate the efficacy of this inactivation, we have simulated the heat treatment procedure at a reduced scale using hemoglobin solution spiked with representative viruses. Human Immuno-deficiency Virus (HIV), Cytomegalovirus (CMV), and Duck Hepatitis B Virus (DHBV) were used in this validation. Inoculation with concentrated virus was performed just prior to the heat treatment to determine the effect of that specific process step. Samples were taken before, during, and after heat treatment and assayed for virus titer in an attempt to assess the rate as well as the extent of virus inactivation. CMV was analyzed in a plaque assay using MRC-5 indicator cells. The titer was reduced from 3.3 x 10(6) plaque forming units (PFU) per mL to less than 5 x 10(1) PFU/mL (detection limit) within 30 minutes. DHBV was analyzed by inoculation of serially diluted samples into Pekin ducklings, followed at intervals by screening sera for DHBV DNA by dot blot hybridization. The titer was reduced from 5.0 x 10(6) duck infectious units (DIU) per mL to less than 5 x 10(0) DIU/mL (detection limit) within 1 hour. HIV titers were determined through an ELISA assay for p24 antigen present in peripheral blood lymphocyte cocultivation supernatants. The titer was reduced from 2.0 x 10(4) infectious units (IU) per mL to less than 2 x 10(0) IU/mL (detection limit) within 1 hour. These data indicate that high titers of these blood borne viruses are rapidly inactivated by this heat treatment process.

Aspirin↗
PubMed1992

Trace element analyses of diaspirin cross-linked hemoglobin solutions.

A sensitive assay using inductively coupled plasma atomic emission spectroscopy (ICP-AES) has been applied to the measurement of trace elements in diaspirin cross-linked hemoglobin (DCLHb) solutions. Calcium, magnesium, zinc and iron were the only elements detected at greater than background levels. Ag, Al, As, B, Ba, Bi, Cd, Co, Cr, Cu, Mn, Mo, Pb, Sb, Se, Si, Sr, Ti, and V were present at concentrations either equal to the acid blanks or were not detected. Detection of non-heme iron (not incorporated into the hemoglobin porphyrin ring) in a 10 g/dL hemoglobin solution required the development of a special protocol. In this protocol a chelator, DTPA, was added to hemoglobin solutions to complex with both free and non-specifically bound non-heme iron. The resulting iron:DTPA complexes were separated from the hemoglobin molecules by ultrafiltration and the ultra-filtrate analyzed by ICP-AES. A modification of this assay in which the DTPA was omitted was used to measure the free non-heme iron in solution. Typical concentrations of chelatable (free and non-specifically bound) and solution (free) non-heme iron in DCLHb production lots at the completion of manufacture were 0.5-1.0 ppm and 0.1-0.3 ppm, respectively.

Aspirin↗
PubMed1992

Electrophoresis and silver staining of rat urinary proteins including alpha 2u-globulin (rat n II).

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining have been used to monitor the fractionation of rat urinary proteins by Amicon Centriprep C30/C10 ultrafiltration and to assess the purification of alpha 2u-globulin, a laboratory animal allergen, precipitated by exhaustive dialysis. Factors influencing the protein composition of rat urine have been identified. Dialysis procedures have been evaluated for precipitation of alpha 2u-globulin and ultrafiltration used for further purification of the allergen.

Alpha-Globulins↗