A step-down procedure for multiple tests of treatment versus control in each of several groups

Cheung and Holland extended Dunnett's treatment versus control multiple comparison procedure to the case of several groups. Dunnett and Tamhane provided a step-down procedure more powerful than that of Dunnett for situations where the researcher's interest is in testing and not in simultaneous confidence interval estimation. In this paper we show how one can use the approach of Dunnett and Tamhane to devise a testing procedure for the multi-group problem with power greater than that of Cheung and Holland. We illustrate the new procedure with reanalyses of published data from a clinical experiment.

Pertussis immunisation in children with a family or personal history of convulsions: a review of children referred for specialist advice

Recent guidelines recommend that children with a family or personal history of convulsions should receive all vaccinations. To determine vaccination status and adverse events following vaccination, questionnaires were sent to the general practitioners of 83 children referred for specialist advice between January 1988 and June 1991 in Redbridge Health Authority. Details of consultations within seven days of vaccination, and of any subsequent neurological or developmental problems were collected. Follow-up data were obtained for 77 of the 83 children (93%); 66 of whom had a family history, and 11 a personal history, of convulsions. Of the 66 children with a family history of convulsions, 57 received pertussis-containing vaccines, of whom one child was reviewed for a possible neurological event. Of the nine remaining children who received diphtheria-tetanus (DT) only vaccine, two children were reviewed for possible neurological events. Of the 11 children with a personal history of convulsions, nine received pertussis-containing vaccines and two received DT vaccines; none had any further neurological event. At late follow-up, none of the 77 children vaccinated had developed recurrent convulsions or any other neurological or developmental problems. Children with a family or personal history of convulsions who are given pertussis-containing vaccines seem unlikely to suffer adverse events or long-term neurological sequelae, and should be considered for all routine vaccinations in line with current recommendations.

Enzyme immunoassay for detection of human immunodeficiency virus-specific immunoglobulin A antibodies

Early diagnosis of human immunodeficiency virus (HIV) infection may be difficult in adults with acute or recent HIV infection and in infants with perinatally acquired HIV. Detection of HIV-specific immunoglobulin A (IgA) antibodies in infant serum by Western blot (immunoblot) has been suggested as a reliable method to identify HIV-infected infants, especially those over the age of 6 months, and as an adjunct to diagnosis of acute HIV infection in adults. We developed a simple enzyme immunoassay for detection of HIV-specific IgA, using standard commercially available reagents. Enzyme immunoassay was comparable to Western blot for detection of HIV-specific IgA in sera from adults (n = 216), older children (n = 49), and infants born to HIV-infected mothers (n = 65). Specificity was 100% and sensitivity ranged from 80 to 92%. IgA-enzyme immunoassay is a simple, highly sensitive method for detection of HIV-specific IgA antibodies and is easily adapted to the standard clinical laboratory.

Nontuberculous mycobacteria in children with acquired immunodeficiency syndrome

Among 139 children with acquired immunodeficiency syndrome at Children's Hospital of New Jersey, 20 had positive cultures for non-tuberculous mycobacteria. Eighty-five percent had Mycobacterium avium complex isolated and 70% had definite evidence of disseminated disease. Ninety-three percent had CD4 lymphocyte counts less than 100 cells/mm3 and 95% had met acquired immunodeficiency syndrome criteria before the time of first positive culture. Clinical findings included failure to gain weight, anorexia, fever, abdominal pain/tenderness and anemia. The median age at onset of symptoms was 46 months and the median time between onset of symptoms and positive culture was 9 months. Outcome for patients with positive cultures for nontuberculous mycobacteria was poor, with 75% of the children surviving for less than or equal to 10 months. Nontuberculous mycobacteria are increasingly important causes of morbidity and indirect mortality in human immunodeficiency-infected children. Children with severe immunodeficiency are at particular risk. In addition to M. avium complex, other species of nontuberculous mycobacteria may be involved.

Clinical and laboratory correlates of Pneumocystis carinii pneumonia in children infected with HIV

The case histories of 27 children with Pneumocystis carinii pneumonia (PCP) who were followed up in the AIDS Program at the Children's Hospital of New Jersey, Newark, are reviewed. The mean and median age at PCP diagnosis were 10.8 and 7.7 months, respectively. All of the children had other clinical evidence of infection with the human immunodeficiency virus that was documented prior to the diagnosis of PCP or found at the time of PCP diagnosis. Most patients who presented to the hospital were acutely ill, and complications of treatment occurred in 70%. Overall, 89% of the patients died and 70% survived for less than 6 months after diagnosis of PCP. Median survival after the diagnosis of PCP was only 2.0 months and the median life span of children with PCP was only 14.4 months. Only 40% of children with PCP had CD4 lymphocyte counts at or below the threshold for institution of PCP prophylaxis in adults of 200 x 10(6) cells/L (200 cells/mm3).

Control of the bacterial cell cycle

New insights into the control of DNA replication through growth, hemimethylated DNA and DnaA protein have been described. Fundamental shifts in thinking have resulted in the identification of new cell cycle genes with potential roles in initiation of DNA replication, chromosomal segregation and division. Excitingly, this trend may also narrow the apparent differences between the prokaryotic and eukaryotic cell cycles.

Development of sugar-induced blood pressure elevation after uninephrectomy in a resistant rat strain

Certain rat strains acutely increase blood pressure (BP) when given diets high in NaCl. Prior results showed that "salt-sensitive" rat strains, at least the ones studied, also increase BP in response to sugar loading. To examine this relationship further and learn more about the pathogenesis of sucrose-induced BP elevations, we examined the effects of unilateral nephrectomy (uninephrectomy) on sucrose-induced BP changes. The rationale is based upon the findings that renal mass removal sensitizes BP response to salt loading. Over 15 weeks, augmented sugar (sucrose) consumption by Long-Evans (LE) rats did not increase BP markedly compared to rats consuming a diet relatively low in sugar unless uninephrectomy was performed. The differences in BP caused by the high sugar diet in a uninephrectomized rat could not be explained adequately by alterations in catecholamine excretion, plasma renin activity, excesses in blood volume, or the other parameters examined. However, salt-induced hypertension has been attributed to the presence of circulating substances affecting ion transport. Among the dietary groups, there was a significant correlation between the ability of plasma to depress PAH and TEA renal slice uptake and the difference in BP. This is consistent with the presence of a circulating factor affecting cell transport that has its greatest activity in the high sugar-uninephrectomy group of LE rats. We conclude that reducing renal mass potentiates sugar-induced BP elevation similar to salt-induced BP elevation in a normally resistant rat strain, and the rise of BP may be caused by a circulating factor.

Red cell volume and cardiac output in anaemic preterm infants

To test the hypothesis that haemoglobin concentration is a poor predictor of benefit from transfusion in preterm infants, and that red cell volume is the most important indicator of anaemia, 24 preterm infants receiving red cell transfusions had red cell volume, haemoglobin concentration, and cardiac output measured before and after transfusion. Red cell volume was measured either using dilution of autologous fetal haemoglobin with donor adult haemoglobin, or with a new technique using biotin as a red cell label. The two techniques give similar results. Mean (SD) values before transfusion were 27.4 (13.3), and after transfusion 45.0 (13.7) ml/kg. Cardiac output was measured using imaging and Doppler ultrasonography, and fell with transfusion from mean 286 (121) to 251 (95.6) ml/kg/min. The red cell volume before transfusion correlated well with changes in cardiac output following transfusion, infants with a red cell volume before transfusion of less than 25 ml/kg showing a fall in cardiac output, and those with a red cell volume of greater than 25 ml/kg not showing a significant fall. There was no correlation between haemoglobin concentration, packed cell volume, or change in packed cell volume with changes in cardiac output after transfusion. A red cell volume of 25 ml/kg seems to be critical in preterm infants with anaemia, and infants with values below this are those most likely to benefit from transfusion.

Excess sucrose and glucose ingestion acutely elevate blood pressure in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) were fed 6 different diets. The baseline diet (I) derived equal calories from sucrose, proteins, and fats. Three other diets (II, III, VI) derived the majority of calories from refined CHO, sucrose or glucose, with decreases in calories from proteins or fats. The last two diets (IV, V) were relatively low in sucrose with a higher percentage of the total calories from proteins and fats, respectively. From 3 to 15 weeks on the diets, the highest average BP was in rats consuming high concentrations of sucrose or glucose (II, III, VI). Urinary excretory rates of norepinephrine (NE) at 5, 10 and 15 weeks and epinephrine at 5 and 10 weeks were significantly elevated in rats ingesting diets high in refined CHO, and NE positively correlated with blood pressure (BP) at 5 and 10 weeks of the study. At the end of the study, serum insulin levels were not different, but plasma renin and serum glucagon levels were lower in SHR consuming the diets with high CHO concentrations. We conclude that equally elevated BP are seen with relatively high intakes of either sucrose or glucose, whether the balance of calories is derived from lessening fat or protein. This is secondary, at least in part, to alterations in NE metabolism.

Influence of oat bran on sucrose-induced blood pressure elevations in SHR

To determine whether oat fiber influences BP, we gave spontaneously hypertensive rats (SHR) a diet high in sucrose and low in protein (calories: sucrose 52%, protein 15%, fat 33%) or a diet low in sucrose and high in protein (calories: sucrose 13%, protein 52%, fat 35%). The amount of fat in these particular diets has not been shown to influence BP, so we modified the 2 diets by replacing fat with oat bran (10% w/w). Accordingly, we examined 4 groups of 5 rats consuming different diets: high sucrose, high sucrose + oat bran, low sucrose, and low sucrose + oat bran. Not unexpectedly, SHR consuming the diet high in sucrose had a significantly higher BP after 2 weeks than those consuming the diet low in sucrose. The significant difference in BP continued over the next 3 weeks. At the end of 6 week duration of study, we found the following BP: SHR ingesting the high sucrose diet, 217 mm Hg +/- 5 (SEM) vs SHR consuming the low sucrose diet, 187 mm Hg +/- 4 (SEM) p less than .0001]. SHR eating the low sucrose diet and consuming supplemental bran showed no significant change in BP after 6 weeks compared to SHR eating the basic diet alone, 188 mm Hg +/- 6 (SEM); however, 5 SHR consuming the high sucrose diet with added oat bran showed a significantly lower BP 200 mm Hg +/- 2 (SEM) than SHR ingesting the basic high sucrose diet devoid of oat bran [p less than .01]. We conclude that addition of oat bran to the diet can ameliorate sucrose-induced BP elevations in SHR.

[The rare phenomenon of intraosseous gas collections (the so-called pneumatoceles]

We present two unusual cases of gas-filled cavities, the first in a 5th lumbar vertebra, the second in the subcortical area of the iliac bone close to the iliosacral joint. These accumulations of gas are evidently connected to vacuum phenomena in anatomically adjacent joints. They are characterised as pneumatoceles. Different mechanisms of these rare intraosseous gas accumulations are discussed.

Reproducibility of measurements of cardiac output in newborn infants by Doppler ultrasound

Interobserver reproducibility in deriving cardiac output by measuring aortic blood flow velocity and diameter with imaging and Doppler ultrasound was investigated in 20 healthy infants born at full term. Aortic diameter was measured in three ways. Mean blood flow velocity was measured at three sites with both continuous wave and pulsed Doppler. Two observers carried out each study independently. Intraobserver reproducibility was investigated in 12 infants using the suprasternal site for measuring blood flow velocity. The most reproducible determination of cardiac output was found when the suprasternal site with continuous wave Doppler was used for measurement of blood flow velocity and M mode trailing edge to leading edge echocardiography was used for diameter. Normal mean (2 SD) cardiac output is 231 (77) ml/kg/min. Technical difficulties in measuring aortic diameter accurately limit direct comparison between infants.

Genotype-by-environment and epistatic interactions in Drosophila melanogaster: the effects of Gpdh allozymes, genetic background and rearing temperature on larval developmental time and viability

The possible role of temperature as a component of natural selection generating the latitudinal clines in Gpdh allele frequencies in natural populations of Drosophila melanogaster was examined. Effects of rearing temperature (16 degrees, 22 degrees and 29 degrees) and of Gpdh allozymes (S and F) on larval developmental time and viability were measured. Eight genetic backgrounds from each of three populations (continents) were used to assess the generality of any effects. Analyses of variance indicated significant temperature effects and allozyme-by-genetic background interaction effects for both characters. Viability showed significant genetic background effects, as well as significant temperature-by-allozyme and temperature-by-allozyme-by-population interactions. In general, the S/S genotype was significantly lower in viability than the F/F and F/S genotypes at extreme temperatures (16 degrees and 29 degrees), with no significant differences at 22 degrees. However, each population had a slightly different pattern of viability associated with temperature, and only the Australian population showed a pattern that could contribute to the observed cline formation. Although the same two interactions were not significant for developmental time, examination of the means showed that the S/S genotype had a slightly faster rate of development at 16 degrees than the F/F genotype in all populations (by an average of 0.25 day or 1.1%). The low temperature effect on developmental time is consistent with the clines observed in nature, with the S allele increasing in frequency with higher latitudes. The results for both viability and developmental time are consistent with the interpretation of Gpdh as a minor polygene affecting physiological phenotypes, as indicated by previous work with adult flight metabolism. Finally, it is proposed that the temperature-dependent antagonistic effects of the allozymes on viability vs. developmental time and flight metabolism may be the underlying force giving rise to the worldwide polymorphism.

Seasonality of births: stability and change in a developing country

A marked seasonality of births for the two main ethnic groups of peninsular Malaysia, far exceeding the cyclic fluctuations in births in the United States and Canada, was reported for the 1960s. A 36% excess of births over the average monthly number was observed among Malays each January. Among the ethnic Chinese in Malaysia a regular periodicity in the numbers of births was also found, but it was far less marked and the peak occurred in October or November. The peaks in both groups were due in large measure to conceptions that correlate with religious observances or holidays. Here I report on cyclic birth patterns in peninsular Malaysia for the period 1970-1985. Rapid economic development has occurred during this time and has brought with it demographic changes, such as a massive rise in contraceptive use and a decline in birth rates. These demographic changes have been accompanied by the loss of the pronounced seasonal pattern of births among the Malays. The seasonality of Malay births is now of roughly the same magnitude as the seasonality in the United States and Canada, whereas seasonality of births among the Chinese in Malaysia remains essentially unchanged.

Peptide YY antagonizes beta-adrenergic-stimulated release of insulin in dogs

Peptide YY (PYY) and neuropeptide Y (NPY) are peptides of 36 amino acids that share structural homologies with pancreatic polypeptide (PP). PP is predominantly found in the endocrine pancreas. PPY is primarily found in mucosal endocrine cells of the distal ileum, colon, and rectum, whereas NPY is found in both the peripheral and central nervous systems. Previous studies indicate that these peptides can interact with the autonomic nervous system. The objective of the present experiments was to study the effect of PYY on neurally stimulated insulin release [i.e., in response to 2-deoxy-D-glucose (2-DG), a nonmetabolizable glucose analogue] in conscious dogs. Intravenous administration of PYY (100, 200, and 400 pmol.kg-1.h-1) reduced 2-DG-stimulated insulin release in a dose-dependent manner (P less than 0.05) without affecting plasma glucose levels. Administration of NPY (800 pmol.kg-1.h-1), but not PP (400 pmol.kg-1.h-1), reduced 2-DG-stimulated release of insulin (P less than 0.05). The inhibitory action of PYY on 2-DG-stimulated insulin release persisted in the presence of atropine or phentolamine treatment; however, hexamethonium alone or phentolamine plus propranolol treatment blocked the inhibitory action of PYY. Release of insulin stimulated by the beta-agonist isoproterenol was also inhibited by PYY (P less than 0.05). These results indicate that PYY can inhibit autonomic neurotransmission by a mechanism that may involve ganglionic or postganglionic inhibition of beta-adrenergic stimulation. Our findings suggest a role for PYY and NPY in the autonomic regulation of insulin release.

Expression of human immunodeficiency virus in cerebrospinal fluid of children with progressive encephalopathy

The retrovirus that causes acquired immune deficiency syndrome (AIDS) is now designated the human immunodeficiency virus (HIV). The cerebrospinal fluid (CSF) of 27 children with HIV infection was assayed for intra-blood-brain barrier (IBBB) synthesis of HIV-specific antibodies and for the presence of HIV antigen. In this cohort, 11 children had a progressive encephalopathy (PE), 9 had a static encephalopathy (SE), and 7 had normal neurological findings (N). IBBB synthesis of HIV-specific antibodies was identified (using matched serum and CSF specimens) in 7 of 11 children with PE, 4 of 9 children with SE, and 2 of 7 children with N. HIV antigen was found (using a highly sensitive solid-phase enzyme immunoassay) in the CSF of 8 of 11 children with PE, none of the children with SE, and none of the 7 children with N. On the basis of these data, we conclude that: IBBB synthesis of HIV antibodies indicates invasion of the central nervous system but may reflect prior or current infection; and HIV antigen in CSF indicates viral expression and correlates with the occurrence of PE. These findings strongly implicate HIV as the causative agent of PE in these children. The assay for HIV antigen in the CSF may be of value in determining the prognosis of children with HIV infection and for evaluating the efficacy of therapeutic agents against this retrovirus.