The cluster method in conducting epidemiological research

The Expanded Programme on Immunization (EPI) whose goal is to reduce morbidity and mortality by providing children with immunizations against diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis continually faces the problem of documenting immunization coverage rates. Therefore the EPI seeks simple, effective, and inexpensive methods of evaluation which could be implemented in different countries. An example of such a method is a simplified cluster sampling technique of estimation of immunization coverage through the examination of 210 children, selected randomly as 30 groups of 7 children each. In 1978-1984 more than 1000 immunization coverage surveys were performed all over the world, mainly in developing countries. In a modified way this method is also used to collect data on morbidity and mortality of certain EPI target diseases as well as diarrhoeal diseases.     

Antibodies against calcium-regulating hormones in infectious-allergic forms of bronchial asthma

Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal.     

Phase determination of the circadian rhythm of conidiation in heterocaryons between two out-of-phase mycelia in Neurospora crassa

Neurospora grows vegetatively as a syncytium in which multiple nuclei exist within a connected cytoplasm. Because of the ability of separate and distinct mycelia to fuse, the possibility exists of generating heterocaryotic cultures in which the nuclei and cytoplasms of two different strains are comingled into the same syncytium. We have used such heterocaryons, in which the component parts differed with respect to their circadian clock phase, to examine whether or not clock-dominant phases exist in the circadian cycle. To this end, the phase subsequent to the formation of heterocaryons by pairs of mycelial discs that are initially at different circadian phases was examined in Neurospora crassa. The resulting phase was an average of the parent phases in many cases, but was sometimes observed to correspond more closely to just one of the original parental phases. In these cases, we did not observe any dominant phases in the circadian cycle; the phase of a particular parent disc was more dominant in the heterocaryon when the proportion of the nuclei from that parent was greater in the heterocaryon. In some instances, which occurred mostly when the difference in phase of the parental discs was large, the resultant phase could not be related in a simple way to the parental phases. An interpretation based on a limit cycle model of the circadian oscillation is possible.     

Metyrapone - reduced cytochrome P-450 complex: A specific method for the determination of the phenobarbital inducible form of rat hepatic microsomal cytochrome P-450

Using homogeneous cytochrome P-450, we have shown that the well-known metyrapone-dithionite reduced cytochrome P-450 complex is specific for the cytochrome P-450b induced by phenobarbital. A linear relationship was observed between the absorbance of metyrapone-reduced cytochrome P-450 complex and the one of CO-reduced cytochrome P-450 complex, the usual method for the determination of cytochrome P-450. A method has been proposed for the specific determination of the cytochrome P-450b.     

Molecular control of rabbit follicular testosterone production. Role of protein and RNA after stimulation with luteinizing hormone.

The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis.     

The effect of hemoglobin ligands on the kinetics of human hemoglobin A1c formation

HbA1c is the most prevalent of the minor human hemoglobins. It is formed by the nonenzymatic addition of glucose to the alpha-amino group of the beta chain by an initial condensation reaction and a subsequent intermolecular Amadori rearrangement. We have developed a method of analysis which utilizes high performance liquid chromatography to follow the formation of HbA1c and greatly simplifies the determination of the kinetic parameters associated with this reaction. This has allowed us to study the effects of several Hb ligands, including the hydrogen ion, on the kinetics of this glycosylation reaction. Both the initial condensation reaction and the subsequent rearrangement are shown to exhibit acid catalysis, but the rate of the condensation step is limited by the extent of protonation of the alpha-amino group. The variation in kinetic parameters as a function of hydrogen ion concentration has allowed us to determine the probable reaction mechanism of HbA1c formation by comparison to previously reported model systems of Schiff base formation and Amadori rearrangement. The formation of pre-HbA1c from deoxy-Hb shows an increased forward rate when compared to oxy-Hb. The presence of physiologic concentrations of CO2 causes a proportional decrease in both k1 and k-1. 2,3-Diphosphoglycerate causes a significant increase in the keq of the formation reaction. The effects of CO and the substitution of L-glucose for D-glucose are not significant.