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Biomedical subjects

M A Austin

Publications and source records attributed to M A Austin.

103 records · Page 6Linked to original sources
PubMed1984

Simple and precise method for liquid chromatographic determination of chloramphenicol in serum using a phase separation extraction.

A high-performance liquid chromatographic method for the determination of chloramphenicol using an alkaline salt-induced phase separation extraction is described. The extraction procedure is as simple as miscible organic solvent deproteinization methods, yet produces extracts that have negligible protein and minimal interference from acidic compounds. The use of 2,4-dinitroacetanilide as an internal standard and of microprocessor-stored standard relative response factors results in a more precise assay without need for daily routine standardization. Serum is mixed with an equal volume of acetonitrile containing the internal standard, and then solid sodium chloride containing 20% of sodium phosphate by weight is added and mixed. The resulting upper phase is chromatographed on a C-18 reversed-phase column and monitored at 278 nm. Between-day precision is excellent. Comparison with an alternate method and with drug-monitoring proficiency samples showed the method to have excellent accuracy. The possible use of this phase separation extraction in other assays in which miscible solvent extraction is used is discussed.

Cephalosporins↗
PubMed1982

Impact of a heart disease risk factor screening survey on an upper-middle class community.

The impact of a community-based heart disease risk factor screening program was evaluated after three years. The study population was predominantly white, older, and upper-middle class. Rescreening of the 211 study subjects showed improvements in both health-related behaviors and in risk factor distributions to a degree which would be expected to reduce the risk of heart disease. Although some changes were attributable to secular trends and regression to the mean, direct impact of the survey itself was also demonstrated.

Adult↗
PubMed1981

Direct intravascular fetal blood transfusion by fetoscopy in severe Rhesus isoimmunisation.

Two fetuses with severe anaemia due to rhesus incompatibility each received two early blood transfusions (between 23 and 25 weeks) by fetoscopy. The blood was given directly into an umbilical vessel, either at the umbilicus or at the placental cord insertion. Fetal blood samples were taken before and after transfusion to assess the haematological status of the fetus. One grossly hydropic fetus survived.

Adult↗
PubMed1981

The effect of response bias on the odds ratio.

The effect of response bias on odds ratio results was determined based on data from a population-based cardiovascular disease survey. The study subjects consisted of 5000 adult residents of a predominantly white, upper-middle class community. Information from 60% of the 1100 non-respondents was obtained by telephone. Consistent patterns of participation associated with risk factors and diseases under study were found. A simple error term was developed to convert the odds ratio for respondents to the odds ratio for the target population using individual cell response rates. This error term demonstrates that the response patterns found tended to minimize the error in odds ratio calculations for respondents. Only by obtaining relevant information on non-respondents can investigators accurately estimate response bias and its effects on the odds ratio.

Adult↗
PubMed1979

Methods for determining long-term survival in a population based study.

A 98.8% response rate was achieved in a follow-up study of a community based health survey. The follow-up methodology used in contacting the residents of 1700 households in a suburban upper-middle class community is presented. Study subjects, who were predominantly white, older adults, participated in the original health survey during 1972 and 1973. When the follow-up study was conducted three years later to determine the vital status of study participants, 30% of the households had moved. Follow-up response of two sets of mailings totaled 76.1%. An additional 12.1% response was obtained by calling residents at their last known address. The final 10.5% of the contacted households were located by intensive telephone tracing. A wide variety of sources of information, both local and non-local, were used to locate these "hard to trace" households. They were different from all other contacted households with respect to mobility rate, household size, and death rate. A 15.5% underestimate of the three-year death rate would have occurred if the hard to trace group had not been contacted. These results emphasize the importance of complete follow-up in prospective studies.

Adolescent↗
PubMed1978

Growth characteristics of influenza virus type C in avian hosts. Brief report.

Influenza virus type C could be propagated to high yield in primary chick embryo kidney cell culture (PCEK) provided that trypsin (2 microgram/ml) was used as a medium supplement. The virus could also be titrated by plaque assay using PCEK host cells and influenza C virus that had been plaque-purified in PCEK cells could then be serially passaged to high titer using the allantoic route of 10--11-day-old embryonated eggs.

Cells, Cultured↗
PubMedDate not supplied

Inheritance of low density lipoprotein subclass patterns in familial combined hyperlipidemia.

The inheritance of low density lipoprotein (LDL) subclass patterns was investigated in 234 members of seven large kindreds with familial combined hyperlipidemia (FCHL), a disorder characterized by elevated LDL cholesterol and/or triglyceride and increased coronary disease risk in families. Analysis of LDL subclasses by nondenaturing gradient gel electrophoresis showed a predominance of large, buoyant LDL particles (pattern A) in 71% of the family members and a predominance of small, dense LDL particles (pattern B) in 29% of family members. Based on complex segregation analysis, pattern B appeared to be inherited as an autosomal trait with either a dominant or an additive mode of inheritance and a small, but significant, multifactorial inheritance component. The proposed allele for pattern B was common (frequency = 0.3), and reduced penetrance was observed among men under age 20 and among women under age 50. These results in these FCHL families are consistent with those from a previously reported population-based sample of families, in which pattern B showed an apparent dominant mode of inheritance. In that study, reduced penetrance was observed for men under age 20 and for premenopausal women, but a somewhat lower allele frequency was found for pattern B (0.25). In the FCHL family members, LDL subclass pattern B was associated with significantly increased plasma levels of apolipoprotein B and triglyceride and decreased high density lipoprotein cholesterol. In comparison with a group of controls, the FCHL family members with pattern A had similar mean triglyceride levels, but higher mean apolipoprotein B. Thus, in families with FCHL, a predominance of small, dense LDL particles appears to be inherited as a common, single-gene trait, which is closely associated with the higher plasma triglyceride levels found in these families. The increased plasma apolipoprotein B levels found in FCHL cannot, however, be accounted for by this proposed locus.

Adult↗
PubMedDate not supplied

Plasma triglyceride and coronary heart disease.

Although the literature on epidemiological associations between plasma triglyceride and CHD is not completely consistent, trends do emerge from the studies described here. First, the majority of observational studies demonstrate a significant univariate relation, although the results of case-control and cross-sectional studies are more uniform than those from prospective study designs. In many but not all studies, triglyceride remains a significant predictor of CHD in multivariate statistical analyses after controlling for TC or LDL-C. Perhaps the least consistent result is that the triglyceride association does not persist in some analyses controlling for HDL-C, while in other studies, the association remains significant. Although most studies have been conducted in men, the studies providing data on women, normocholesterolemic subjects, and diabetic subjects have generally found triglyceride to be, at the very least, a univariate risk factor. The results of intervention trials differ considerably, but no such study to date has been specifically designed to evaluate triglyceride-lowering effects on primary prevention of CHD. Important statistical properties must be taken into consideration in evaluating triglyceride as a risk factor for CHD. The large variability of triglyceride measurements and the correlation of triglyceride values with other lipid measures appears to result in the underestimation of the association between triglyceride and disease in multivariate analyses. Finally, individual genetic susceptibility may play an important role in the relation between plasma triglyceride levels and CHD. For example, risk of CHD clearly varies among the well-established familial forms of hypertriglyceridemia. A predominance of small, dense, LDL particles (LDL subclass pattern B) also appears to be a genetic trait associated with both increased risk of MI and increases in plasma triglyceride levels.

Coronary Disease↗
PubMedDate not supplied

Effect of total parenteral nutrition with intravenous fat on lipids and high density lipoprotein heterogeneity in neonates.

Plasma lipid concentrations and high density lipoprotein (HDL) subclass distributions were evaluated in 22 newborn infants nourished with intravenous (iv)-fat. The majority of infants were premature with respiratory distress syndrome. Based on baseline (prior to iv-fat) HDL subclass profiles determined by gradient gel electrophoresis (GGE), infants fell into two classes, one with two or more pronounced peaks within the normal HDL spectrum (group I, 17 subjects) and the other with highly unusual HDL distribution (group II, five subjects). Total plasma cholesterol increased in both groups during low and high fat intravenous feeding. HDL-cholesterol, however, did not change with iv-fat where mean values for groups I and II at baseline, iv-low fat and -high fat were: group I, 31.2 +/- 7.1, 30.0 +/- 8.8, and 36.6 +/- 16.7 mg/dl, respectively; and group II, 20.0 +/- 7.8, 20.2 +/- 7.4, and 19.8 +/- 8.8 mg/dl, respectively. Unlike HDL-cholesterol levels that remained constant with iv-fat, apolipoprotein (apo) AI concentrations increased significantly: group I, 73.0 +/- 11.0, 88.3 +/- 15.9, and 93.1 +/- 21.9 mg/dl, respectively; and group II, 31.8 +/- 10.5, 41.0 +/- 12.8, and 59.3 +/- 18.5 mg/dl, respectively. In group I infants, iv-fat is associated with an increase in larger-sized particles, particularly in the (HDL2b)gge range; in group II there is an increase in (HDL3b)gge and (HDL3c)gge components and a disappearance of particles that fall outside of the size range of normal HDL. In both groups, enteral feeding is associated with a further normalization of HDL subclass distribution. The aberrant GGE profiles and very low apoAI levels of group II infants at baseline were associated with unusual HDL morphology determined by electron microscopy where discoidal structures were prominent. With iv-fat, discoidal particles decline in number while normal spherical structures increase. Prevalence of discoidal HDL at baseline was associated with low concentrations of lecithin:cholesterol acyltransferase (LCAT) (1.12 +/- 0.5 micrograms/ml); with iv-fat this enzyme rose to 1.61 +/- 0.18 micrograms/ml. Increased LCAT is associated with the normalization of HDL morphology. It is likely that iv-fat improves the nutritional status of premature infants, thereby stimulating increased liver synthesis of important proteins, including apoAI and LCAT, associated with HDL metabolism.

Apolipoprotein A-I↗