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Biomedical subjects

G J Walker

Publications and source records attributed to G J Walker.

At least 19 recordsLinked to original sources
PubMed1992

Influence of the culture medium on the synthesis of alpha-D-glucans by Streptococcus cricetus AHT.

Three different alpha-D-glucosyltransferases (GTFs) were separated from culture filtrates of Streptococcus cricetus strain AHT grown in a complex, standard medium in batch culture or under defined conditions of growth in the chemostat. Two of the enzymes (GTF-S1 and GTF-S2) converted sucrose into branched, soluble dextrans, and the third (GTF-I) produced a relatively linear, water-insoluble, predominantly (1----3)-linked alpha-D-glucan. When the organism was grown in complex medium modified by the removal of the fraction of high molecular weight, only GTF-S1 and GTF-S2 were released, and no GTF-I was detected. The water-insoluble glucan fraction obtained by incubating the cell-free filtrate with sucrose contained from 17 to 25% of (1----3)-glucosidic linkages, and accounted for up to 78 and 4% of the total glucans derived from growth in standard and modified medium, respectively. The soluble glucans produced in the same reaction were fractionated with ethanol to give, from both media, two distinct dextrans comprising (1) a highly branched dextran similar to the S1-dextran product of GTF-S1 and (2) a dextran containing fewer branch linkages and up to 86% of (1----6)-alpha-D-glucosidic linkages. A GTF responsible for the synthesis of the latter dextran was not separated. The structures of the glucan fractions and the products of the separated GTF were examined by enzymic degradation and methylation analysis.

Bacteriological Techniques↗
PubMed1992

Linkage mapping of melanoma (MLM) using 172 microsatellite markers.

The incidence of malignant melanoma is currently increasing faster than any other cancer and in 5-12% of cases occurs in a familial context in which the disease cosegregates as an autosomal dominant trait. To identify the location of genes that predipose individuals to familial melanoma (MLM), we have carried out linkage analysis in three large Australian melanoma pedigrees using 172 microsatellite markers spread across all autosomes. Three additional smaller families were typed for 70 of the same markers. In five of the six families we found lod scores between 1.0 and 2.3, which may provide evidence for the location of melanoma genes in proximity to some of these markers. If this turns out to be the case, these data potentially demonstrate that MLM is genetically heterogeneous since there was no marker for which all families gave significantly high LODs. These data provide the foundation for an exclusion map for melanoma and, more importantly, high-light areas of the genome for others to substantiate the potential positions of some of the genes that may be responsible for susceptibility to MLM.

Chromosome Mapping↗
PubMed1991

Loss of somatic heterozygosity in hepatocellular carcinoma.

Loss of tumor suppressor genes is involved in the mechanism of tumorigenesis of many solid tumors. We tested 9 hepatitis B virus (HBV)-positive and 10 HBV-negative hepatocellular carcinomas for loss of somatic heterozygosity using 14 polymorphic probes mapping to chromosomes 4, 11, 13, and 17. Losses were found on all chromosome arms tested. The highest frequency of loss was observed at the D13S1 locus (67%) at band 13q12. Losses were also observed at three other loci on 13q. Twenty-one % of informative cases showed loss on 17p using the probe pYNZ22 which maps near the p53 locus. Losses on 4q were infrequent with 17% found at one locus and no loss at two others. The retinoblastoma gene and the locus on 17p were only inactivated in our HBV-negative tumors, although the numbers were too small for statistical significance. For all loci tested, we found no significant differences in the frequency of losses with HBV status, ethnic background, cirrhosis, grade of tumor, or presence of hemochromatosis.

Adult↗
PubMed1991

Early neonatal mortality and cesarean delivery in Mexico City.

The relationship between cesarean delivery and neonatal mortality is presented with information from 292 early neonatal deaths (cases) and 3098 survivors (controls) born in 25 hospitals in Mexico City during the summer of 1984. The overall rate of cesarean delivery was 27%. Variations between health agencies and different social groups were not related to obstetric risk, suggesting that a sizable proportion of the operations were probably unjustified. Babies of normal birth weight (greater than or equal to 2500 gm) delivered by cesarean section were 2.5 times more likely to die in the early neonatal period compared with vaginally delivered babies of the same weight. The excess of mortality could not be explained by the effect of maternal characteristics or complications or by differences in birth weight or gestational age. It is suggested that the conditions under which the operation was performed probably explain the increased risk of early neonatal death. It is likely that poor quality of resuscitation and respiratory care are implicated in the link between "unnecessary" cesarean section and early neonatal mortality.

Birth Weight↗
PubMed1991

Some properties of an endodextranase inhibitor from continuous cultures of Streptococcus sobrinus.

Cell-free filtrates of Streptococcus sobrinus, cultured at low growth rate in the chemostat, contain a dextranase inhibitor that can completely inhibit the activity of S. sobrinus endodextranase. The range of conditions under which inhibition occurs, and the situations in which enzyme activity can reappear, have been examined in continuous cultures of strain 6715-13WT and the dextranase-deficient mutant 6715-13-201. A purified preparation of the inhibitor was specific for S. sobrinus dextranase, having no action on dextranases from other oral streptococci. The percentage inhibition of S. sobrinus dextranase varied with the enzyme concentration, and the complete inhibition of low amounts of enzyme indicated a very tight bond between the inhibitor and the enzyme.

Chromatography↗
PubMed1991

Effect of variation in growth conditions on the activity of dextranase inhibitor in continuous cultures of Streptococcus sobrinus.

The activity of free extracellular dextranase inhibitor was determined in strains of Streptococcus sobrinus which were grown in a chemostat under a variety of defined conditions. Maximum release of dextranase inhibitor occurred at low growth rate in glucose-limited medium at pH 6.5. Free inhibitor could not be detected when the strains were grown at high growth rate or in batch culture.

Culture Media↗
PubMed1990

Evaluation of rational drug prescribing in Democratic Yemen.

The government of Democratic Yemen started an essential drugs programme in 1984. Every month quantities of 30 drugs are delivered in prepacked kits to health units and standard treatment schedules have been agreed. The quantities of each drug were estimated by applying the standard treatment schedules to the typical morbidity patterns seen at these facilities. Most health workers attended a training course on the correct use of the standard treatment schedules. Hospital and health centres have been included in the programme to a more limited extent. In March 1988 an evaluation of the programme was carried out. Comparisons were made between random samples of health units included in the programme and those where it had not yet been implemented. The adequacy of knowledge necessary for reasonable use of drugs was assessed by interviewing health workers. Actual drug prescription was studied by means of quantitative indicators. A more qualitative insight was obtained by reviewing drug prescriptions for four tracer diseases at a sample of health centre and hospital out-patient departments. Health workers at units included in the programme had significantly (P less than 0.05) higher levels of rational drug knowledge and 'better' actual drug prescription in terms of proportions of patients receiving injections (25% vs 58%), antibiotics (45% vs 67%) and the average number of drugs per patient (1.5 vs 2.4)--all P less than 0.001. Many patients treated at health centres and hospitals were receiving irrational drug treatment for the tracer conditions. It is suggested that the methods used in this evaluation to measure rational drug prescription could be appropriate in the assessment of other essential drugs programmes.

Drug Prescriptions↗
PubMed1990

Identifying maternal deaths in developing countries: experience in Jamaica.

Multiple sources were used to identify maternal deaths and their causes in a study carried out in Jamaica. These sources of information included a review of all deaths of women aged 12 to 49 years and included those occurring in hospitals (on maternity, surgical and medical wards and in casualty departments); reported to coroners' offices and the police; on whom post-mortems were carried out at hospitals, public morgues and for the Ministry of National Security; obtained from interviews with public health staff in all parishes and which were registered with the Registrar General's Department. Some 193 maternal deaths were identified giving a maternal mortality rate of 10 per 10,000 live births. No one source independently identified all maternal deaths. Hospital in-patient records yielded 133 deaths (69%), death certificates 74 (38%). Deaths due to certain causes were far more likely to be identified from particular sources eg those due to clinical mismanagement (complications of anaesthesia and blood transfusion) from hospital in-patient records; while deaths from ruptured ectopic pregnancy were more likely to come from coroners', police and morgue records. It is concluded that using multiple sources to identify maternal deaths in developing countries is an effective method to identify all maternal deaths.

Adolescent↗
PubMed1990

Designing a state-of-the-art operating room complex.

1. When designing a new operating room complex, it is important to remember that, with a life expectancy of 15 years or more, you must take into account not only your current needs, but also anticipate those of the future. 2. The OR facility needs to be designed both for patients and providers: provide private, comfortable surroundings for your patients that are efficient and conducive to developing an enjoyable work environment for your staff. 3. Be sure to solicit input from various department managers as well as physicians during the initial design phases so that all needs may be met. In addition, ensure that state guidelines are satisfied.

Hospital Design and Construction↗
PubMed1989

Impact of an essential drugs programme on availability and rational use of drugs.

Availability and rational use of drugs was assessed in a random sample of 19 peripheral health units in two governorates in Democratic Yemen in which an essential drugs programme has been operational for the past few years. Findings were compared with those from seven health units in one governorate in which no such programme had been started. On average, 27 essential drugs were available in the programme area, compared with 17 in the control area. Programme areas carried on average 1 non-essential drug, compared with 17 in control areas. Average stock was adequate for 4 weeks in programme areas and for 1 week in control areas. Health workers in the programme area scored slightly, but not significantly, better in a test on theoretical knowledge on rational drug use. However, programme areas differed considerably from control areas in patterns of drug use, with fewer injections (24.8% vs 57.8% of prescriptions) and fewer antibiotics (46.3% vs 66.8%) being prescribed in programme areas, which also had fewer drugs per prescription (1.5 vs 2.4). The programme has significantly improved the availability and rational use of essential drugs in peripheral health units.

Community Health Centers↗
PubMed1988

The quality of care is related to death rates: hospital inpatient management of infants with acute gastroenteritis in Jamaica.

The quality of care of random samples of about 40 infants admitted with acute gastroenteritis to each of five hospitals in Jamaica was assessed. Low levels of adherence to consensus care criteria appeared to be correlated with high levels of hospital-specific severity standardized mortality ratios X100 (SSMRs); poor adherence, SSMR 127-230; intermediate adherence, SSMR 95; good adherence, SSMR 14. The main deficiencies in care at certain hospitals were: non-weighing of infants, incomplete physical examination, inadequate estimation of fluid requirements, and irregular recording of fluid intake. To improve the effective care of infants with gastroenteritis, a quality assurance program is required.

Acute Disease↗
PubMed1988

Estimating vaccination coverage: routine information or sample survey?

The manager of a district immunization programme needs to regularly assess vaccination coverage. This case study from Zimbabwe describes how routine information can be used for this purpose. The number of children and their location in the district was estimated from several sources using a variety of methods. This suggested that under-enumeration at the 1982 census was probably as high as a third and was a particular problem among children aged under 1 year. Routinely collected figures of the number of vaccinations were then used to calculate coverage levels for different health unit catchment areas within the district. These levels varied considerably and were lowest in areas with significant numbers of Apostolics, a group who often reject immunization on religious grounds. Comparisons between estimates of coverage obtained from routine information and a sample cluster survey raised several issues. These included accuracy of routine information, precision of sample surveys, estimating differential coverage in the district, management uses of estimates and the cost of data collection.

Adolescent↗
PubMed1986

Maternal mortality in Jamaica.

A confidential inquiry into all maternal deaths in Jamaica during 3 years (1981 to 1983) was carried out. 192 maternal deaths were identified by a variety of means. The maternal mortality rate of 10.8 per 10 000 live births was considerably higher than the official rate of 4.8. The most common causes of death were hypertensive diseases of pregnancy (26%), haemorrhage (20%), ectopic pregnancy (10%), pulmonary embolus (8%), and sepsis (8%). Maternal mortality was closely related to both age and parity. The lowest rates were for women of para 2-4 aged 20-24 years and para 3-4 aged 25-29 years. The largest groups of avoidable factors were: non-use of and deficiencies in antenatal care; inadequacy in ensuring the delivery in hospital of women at high risk; and delays in taking action when signs of complications developed before, during, and after delivery.

Adolescent↗