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Biomedical subjects

H Lees

Publications and source records attributed to H Lees.

At least 19 recordsLinked to original sources
PubMed1992

ME: is it a genuine disease?

Myalgic encephalomyelitis (ME) is a postviral syndrome whose dominant clinical features are exercise-induced muscle fatigue, disturbances in cognitive functioning and symptoms of overactivity of the autonomic nervous system. The syndrome tends to affect previously fit young adults between the ages of 20 and 40 but no age group is excluded. One recent epidemiological survey suggested a prevalence rate of 1.3 per 1000 adults, with females outnumbering males by 1.8:1. ME is currently the subject of intense medical (and media) debate, especially over its pathophysiology and management. It has also become known as the postviral/chronic fatigue syndrome (PVFS/CFS).

Adult↗
PubMed1988

Avoidable hazard to New Zealand children: case reports of haemorrhagic disease of the newborn.

Haemorrhagic disease of the newborn is preventable by the routine administration of vitamin K to newborn babies. Despite this, prophylactic administration of Vitamin K1 remains controversial and haemorrhagic disease of the newborn continues to cause significant morbidity and mortality. We present two cases of this disease occurring recently in this region of New Zealand; one resulting in an infant's death, the other baby suffering from an intraventricular haemorrhage and secondary hydrocephalus. These cases prompted us to survey major New Zealand hospitals to assess their policy as regards routine vitamin K administration to newborn infants. The results of this survey suggest that there is now a uniform policy in New Zealand hospitals of giving intramuscular vitamin K. However, intramuscular vitamin K administration may still be objected to by some parents and lead to further cases of this preventable disease. Evidence now available shows that vitamin K1 given orally in a dose of 1 mg is effective in preventing haemorrhagic disease of the newborn.

Cerebral Hemorrhage↗
PubMed1988

Effect of nitroblue tetrazolium concentration on the fructosamine assay for quantifying glycated protein.

Experiments with nitroblue tetrazolium (NBT) at 0.25, 0.50, and 0.75 mmol/L confirmed that reactivity of 1-deoxy-1-morpholino-D-fructose, the standard, was more sensitive to reagent concentration than was protein ketoamine and demonstrated why an increase in NBT or a decrease in sample volume yields lower values for serum fructosamine. Analyses of clinical samples from diabetic and nondiabetic patients and from healthy subjects indicated that, with NBT at 0.25 mmol/L, discrimination between diabetics and other subjects was improved by changing the sample:reagent volume ratio from the usual 1:10 to 1:25 (9- to 12-min reading time). Discrimination improved further with NBT at 0.75 mmol/L and a 1:25 ratio but a later reading time (18-21 min); these conditions may minimize the effects of some but not all interferents.

Adult↗
PubMed1986

The emergence of Serratia marcescens as a pathogen in a newborn unit.

During a 12 month period, the Waikato Hospital Newborn Intensive Care Unit experienced an epidemic of Serratia marcescens infection. Seventeen serious infections occurred, resulting in three deaths. A further 15 cases of minor infection were also noted. Although no point source of introduction was found, gut colonization proved to be the most important reservoir for nosocomial spread of the organism. At the peak of the outbreak, a 95% incidence of rectal colonization with S. marcescens was observed. Eradication was achieved within a 4 month period using cohort isolation of affected infants.

Bacterial Infections↗
PubMed1980

Glomerulonephritis associated with an infected ventriculo-atrial shunt.

We present the case of a seven year old girl with a ventriculo-arterial shunt who developed haematuria and the nephrotic syndrome. Renal biopsy showed a diffuse proliferative glomerulonephritis of mesangiocapillary type. Cultures of blood, cerebrospinal fluid and later, the removed shunt, grew Staphylococcus epidermidis. Her renal function subsequently improved following antibiotic therapy and revision of the shunt.

Cerebrospinal Fluid Shunts↗
PubMed1980

Superoxide dismutase from nitrogen-fixing Azotobacter chroococcum: purification, characterization, and intracellular location.

Superoxide dismutase (SOD, EC 1.15.1.1) from nitrogen-fixing Azotobacter chroococcum was purified and identified as being similar to the manganese SOD of other procaryotes. The enzyme was relatively thermostable and insensitive to cyanide. A molecular weight of approximately 33 000 was estimated. Superoxide dismutase was found to be cytoplasmic (not bound to cell membranes) in A. chroococcum, but some enzyme was released by sonication of membrane vesicles.

Azotobacter↗
PubMed1980

Cytochrome oxidase of Nitrobacter agilis: isolation by hydrophobic interaction chromatography.

Cytochrome oxidase has been purified from Nitrobacter agilis using hydrophobic interaction chromatography. The purified preparation contained 3-5% phospholipid and migrated as a single band during polyacrylamide gel electrophoresis under nondissociating conditions, but appeared as three bands in the presence of sodium dodecyl sulfate and 6 M urea. These three bands corresponded to molecular weights of 37 000, 25 000, and 13 000. The absorption spectra of cytochrome oxidase isolated from Nitrobacter were similar to those reported for a-type cytochrome oxidase from other sources and exhibited absorption maxima at 420 and 600 nm when oxidized and 443 and 606 nm when reduced. The purified enzyme reacted both with horse heart and Nitrobacter cytochrome c. The enzymatic activity depended upon the pH of reaction mixture, with the maximum activity at pH 6.5 and 7.5 for Nitrobacter and horse heart cytochrome c, respectively. The activity of the purified enzyme was inhibited by cyanide, azide, and diethyl dithiocarbamate.

Chromatography, Liquid↗
PubMed1980

Mechanism of interference by hemoglobin in the determination of total bilirubin. I. Method of Malloy-Evelyn.

Oxyhemoglobin is the species of hemoglobin in erythrocyte hemolysates that inhibits the diazo reaction. Ferric hemoglobin derivatives and species with relatively low molecular mass do not interfere. Conversion of oxyhemoglobin to acid hematin under assay reaction conditions is associated with rapid destruction of bilirubin, which accounts for the diazo reaction error. The most probable mechanism for this destruction of bilirubin is an oxidative reaction involving H2O2, formed in the oxidation of hemoglobin, and acid hematin acting as a pseudoperoxidase. We could find no evidence for other mechanisms of interference such as spectral error or azobilirubin destruction. Addition of potassium iodide, 4.0 mmol/L final concentration in the reaction mixture, eliminates interference from hemoglobin added to give concentrations as great as 10 g/L. It also eliminated the effects of hemolysis in the method of Ertingshausen et al. (Clin. Chem. 19: 1366, 1973), in which ethylene glycol is used as the accelerator.

Bilirubin↗
PubMed1980

Mechanism of interference by hemoglobin in the determination of total bilirubin. II. Method of Jendrassik-Grof.

Oxyhemoglobin in erythrocyte hemolysates interferes with the Jendrassik-Grof assay. Destruction of azobilirubin occurs when oxyhemoglobin is oxidized to methemoglobin during diazotization or to alkaline hematin with addition of alkaline tartrate. The most probable mechanism is by oxidation with an agent such as hydrogen peroxide or a related species resulting from hemoglobin oxidation. Methemoglobin also appears to cause some destruction of azobilirubin during diazotization. Methemoglobin forms during diazotization because of reactions of oxyhemoglobin with both diazo reagent and nitrite ion. Formation of methemoglobin is, therefore, more rapid in the test than in the blank mixture and, under reaction conditions, its absorbance is less than that of oxyhemoglobin. This results in spectral interference when neutral azobilirubin is assayed. Alkaline tartrate abolishes this spectral error by causing rapid formation of alkaline hematin in both test and blank.

Bilirubin↗
PubMed1977

Determination of total carbon dioxide in serum and plasma using a carbonate ion-selective membrane electrode.

A new manual method for the determination of carbon dioxide content in serum and plasma, based on the potentiometric measurement of carbonate, is proposed and evaluated. The new method offers good precision and accuracy in the physiological concentration range as shown by detailed studies on synthetic samples, reference standards, and actual patient samples. Moreover, the method yields results which correlate very well with analyses carried out using various conventional techniques. It is expected that the proposed method could be used for manual determinations of CO2 content, especially where rapid start-up time, minimal sample treatment, and low cost are of importance.

Carbon Dioxide↗
PubMed1976

The growth of nitrogen-fixing Azotobacter chroococcum in continuous culture under intense aeration.

Azotobacter chroococcum (ATCC 7493) was grown in continuous culture with intense vortex aeration (stirring rate 1750 rpm) with up to 50% O2 in the gas phase. Under these conditions the dissolved O2 generally remained at zero while the cell growth rose to about twice the normally accepted value. The meaning of the term "O2-limitation" in N2-fixing A. chroococcum cultures is critically examined.

Azotobacter↗