Sample size considerations when groups are the appropriate unit of analysis.

This article discusses issues to be considered by nurse researchers when groups should be used as the unit of randomization. Advantages and disadvantages are presented, with statistical calculations needed to determine the effective sample size. Examples of these concepts are presented using data from the Black Cosmetologists Promoting Health Program. Different hypothetical scenarios and their impact on sample size are also presented. Given the complexity of calculating the sample size when using groups as the unit of randomization, it is advantageous for researchers to work closely with statisticians when designing and implementing studies that anticipate the use of groups as the unit of randomization.     

Chromosome analysis of 20 breast carcinomas: Cytogenetic multiclonality and karyotypic-pathologic correlations

Short-term cultures from 20 breast carcinomas were analyzed cytogenetically. A normal female chromosome complement was found in 4 cases. Clonal chromosome aberrations were detected in 16 tumors. In 10 tumors, multiple cytogenetic clones were found; in 2 cancers the clones were related, reflecting clonal evolution, but in the remaining 8 tumors the clones were cytogenetically unrelated, indicating clonal heterogeneity in the origin of the tumor parenchyma. Correlation analysis between karyotypic and pathologic parameters indicated that cases with complex karyotypes and/or cytogenetically unrelated clones, when compared with cases with a single simple karyotypic abnormality, were generally of higher histologic malignancy grade, had more mitoses in the histologic sections, and also more often had carcinoma in situ lesions in the same breast. © 1993 Wiley-Liss, Inc.     

Genetic association between the phospholipase A2 gene and unipolar affective disorder: a multicentre case-control study

The co-segregation in one pedigree of bipolar affective disorder with Darier's disease whose gene is on chromosome 12q23-q24.1, and findings from linkage and association studies with the neighbouring gene of phospholipase A2 (PLA2) indicate that PLA2 may be considered as a candidate gene for affective disorders. All relevant genetic association studies, however, were conducted on bipolar patients. In the present study, the possible association between the PLA2 gene and unipolar affective disorder was examined on 321 unipolar patients and 604 controls (all personally interviewed), recruited from six countries (Belgium, Bulgaria, Croatia, Germany, Greece, and Italy) participating in the European Collaborative Project on Affective Disorders. After controlling for population group and gender, one of the eight alleles of the investigated marker (allele 7) was found to be more frequent among unipolar patients with more than three major depressive episodes than among controls (P<0.01); genotypic association was also observed, under the dominant model of genetic transmission (P<0.02). In addition, presence of allele 7 was correlated with a higher frequency of depressive episodes (P<0.02). These findings suggest that structural variations at the PLA2 gene or the chromosomal region around it may confer susceptibility for unipolar affective disorder.     

VEGF-PLCgamma1 pathway controls cardiac contractility in the embryonic heart

The strength of the heart beat can accommodate in seconds to changes in blood pressure or flow. The mechanism for such homeostatic adaptation is unknown. We sought the cause of poor contractility in the heart of the embryonic zebrafish with the mutation dead beat. We find through cloning that this is due to a mutation in the phospholipase C gamma1 (plcgamma1) gene. In mutant embryos, contractile function can be restored by PLCgamma1 expression directed selectively to cardiac myocytes. In other situations, PLCgamma1 is known to transduce the signal from vascular endothelial growth factor (VEGF), and we show here that abrogation of VEGF also interferes with cardiac contractility. Somewhat unexpectedly, FLT-1 is the responsible VEGF receptor. We show that the same system functions in the rat. Blockage of VEGF-PLCgamma1 signaling decreases calcium transients in rat ventricular cardiomyocytes, whereas VEGF imposes a positive inotropic effect on cardiomyocytes by increasing calcium transients. Thus, the muscle of the heart uses the VEGF-PLCgamma1 cascade to control the strength of the heart beat. We speculate that this paracrine system may contribute to normal and pathological regulation of cardiac contractility.     

IDDM2 and the polymorphism of the human tyrosine hydroxylase (hTH) gene in African Americans with type-1 diabetes

In this study, we investigate the polymorphic microsatellite repeat (TCAT)n, in the insulin gene region that has been associated with susceptibility to type-1 diabetes in some Caucasian populations. The microsatellite repeat polymorphism begins at base pair 1,170 in intron 1 of the hTH gene, which is located on the short arm of chromosome 11. This study is the first to investigate the association of this microsatellite repeat polymorphism in African-American type-1 diabetes patients and controls. The predicted amplified sequence was 254 bp. We found five alleles among African Americans in the Washington, DC area. The alleles were labeled K5 (244 bp), K4 (248 bp), K3 (252 bp), K2 (256 bp), and K1 (260 bp), and heterozygosity was greater than 0.75. The most frequent allele of the hTH microsatellite repeats was K5 (248 bp) with a frequency 0.62 in controls and 0.66 in type-1 diabetes patients, which did not differ significantly. Although the largest allele was more frequent in controls, the difference was not statistically significant. The five alleles of the hTH microsatellite generated 15 different genotypes. The most frequent genotype in controls and patients was K5/K4, whose frequencies were 0.19 and 0.17, respectively. No significant differences in genotype frequencies were found between type-1 diabetes patients and controls. This data shifts the focus from hTH to the VNTR at the insulin gene for IDDM2, the second major candidate gene for type-1 diabetes.     

Generation, annotation, evolutionary analysis, and database integration of 20,000 unique sea urchin EST clusters

Together with the hemichordates, sea urchins represent basal groups of nonchordate invertebrate deuterostomes that occupy a key position in bilaterian evolution. Because sea urchin embryos are also amenable to functional studies, the sea urchin system has emerged as one of the leading models for the analysis of the function of genomic regulatory networks that control development. We have analyzed a total of 107,283 cDNA clones of libraries that span the development of the sea urchin Strongylocentrotus purpuratus. Normalization by oligonucleotide fingerprinting, EST sequencing and sequence clustering resulted in an EST catalog comprised of 20,000 unique genes or gene fragments. Around 7000 of the unique EST consensus sequences were associated with molecular and developmental functions. Phylogenetic comparison of the identified genes to the genome of the urochordate Ciona intestinalis indicate that at least one quarter of the genes thought to be chordate specific were already present at the base of deuterostome evolution. Comparison of the number of gene copies in sea urchins to those in chordates and vertebrates indicates that the sea urchin genome has not undergone extensive gene or complete genome duplications. The established unique gene set represents an essential tool for the annotation and assembly of the forthcoming sea urchin genome sequence. All cDNA clones and filters of all analyzed libraries are available from the resource center of the German genome project at http://www.rzpd.de.     

Responses against complex antigens in various models of CD4 T-cell deficiency

The most common models of CD4 T-cell deficiency are mice exogenously injected with anti-CD4 antibody (Ab), CD4 knockout (CD4^−/−) and major histocompatibility complex (MHC) class II knockout (class II^−/−) mice. We recently described the anti-CD4 Ab transgenic mouse (GK) as an improved CD4 cell-deficient model. This review compares this new GK mouse model with the widely available class II^−/− and CD4^−/− mice, when exposed to complex antigens (foreign grafts and during bacterial or viral infection). We highlight here the cytometric and functional differences (including Ab isotype, viral or bacterial clearance, and graft survival) among these CD4 cell-deficient models. For example, whereas grafts are generally rejected in class II^−/− and CD4^−/− mice as quickly as in wild-type mice, they survive longer in GK mice. Also, CD4^−/− mice produce IgG against both simple model and complex antigens, but class II^−/− and GK mice produce small amounts of IgG2a against complex antigens but not simple model antigens. These differences harbinger the caveats in the use of these various mice.     

Surface carbohydrates as recognition determinants in non-opsonic interactions and intracellular viability of group B Streptococcus strains in murine macrophages

Mononuclear cells have been found to play a key role in phagocytosis and eventual killing of group B streptococci (GBS). The rich array of sugars on bacterial surface plus the presence of membrane-associated lectin-receptors on the macrophage suggests that this is a likely means for GBS recognition by these host defense cells. Macrophages have been shown to bind GBS in the absence of serum components. However, participation of carbohydrate moieties in GBS intracellular survival had not been completely elucidated. The aim of this study was to assess the involvement of sugars on adherence and intracellular viability in murine macrophages of GBS serotypes Ia (85147 and 90222 strains), III (80340 and 90356 strains) and V (88641 and 90186 strains) isolated from assymptomatic carriers and patients, respectively. Most isolates showed higher adherence within 2-h incubation. Only 90222-Ia strain exhibited progressive adherence rate until 12-h incubation. All strains showed intracellular viability during first 0.5-h of incubation. Except for 90186-V strain that survived only for 2 h, strains of all serotypes tested were found to survive 24 h into macrophages. Treatments of bacteria by glycosidases inhibited macrophage interaction with GBS strains at varied levels. Neuraminidase inhibited 90-97% adherence and 100% intracellular survival of GBS strains (P<0.0001). Host cell treatments with Rhamnose, N-acetyl-D-glucosaminidase and Fucose (5 mg/ml) inhibited adherence and intracellular viability of GBS strains at varied levels. Removal of GlcNAc residues of invasive GBS isolates enhanced intracellular viability, suggesting that GlcNAc residues may act by intercepting the expression of hidden receptors probably related with invasiveness and survival within macrophages. Lastly, our results demonstrate involvement of sialic acid specific receptors on macrophages and lectinophagocytosis in non-opsonic interaction and survival of GBS invasive isolates.     

Antibodies against the extracellular enveloped virus B5R protein are mainly responsible for the EEV neutralizing capacity of vaccinia immune globulin

In the event of smallpox bioterrorism, widespread vaccination may be required. Vaccinia immune globulin (VIG) has been used to treat complications from the smallpox vaccine. While the potency of VIG was defined by its ability to neutralize intracellular mature virus, a second form of vaccinia called the extracellular enveloped virus (EEV) is critical for virus spread in the host. The B5R-protein is one of many EEV-specific proteins. Immunoprecipitation and ELISA revealed that VIG recognizes the B5R-protein. An EEV plaque-reduction assay using a recombinant vaccinia that lacks the majority of the extracellular domain of B5R showed that the ability of VIG to neutralize EEV is principally directed at B5R. In addition, absorbing out the anti-B5R antibody present in VIG through the addition of recombinant B5R protein abrogated VIG's ability to significantly neutralize wild-type EEV. This work demonstrates the prominent role of B5R as a target of EEV-neutralizing activity of human antibodies.