Delta-aminolevulinate dehydratase activity in red blood cells of rats infected with Trypanosoma evansi

The aim of this study was to evaluate the activity of delta-aminolevulinate dehydratase (δ-ALA-D) in red blood cells of rats infected with Trypanosoma evansi and establish its association with haematocrit, serum levels of iron and zinc and lipid peroxidation. Thirty-six male rats (Wistar) were divided into 2 groups with 18 animals each. Group A was non-infected while Group B was intraperitoneally infected, receiving 7·5×106 trypomastigotes per animal. Each group was divided into 3 subgroups of 6 rats and blood was collected during different periods post-infection (p.i.) as follows: day 5 (A1 and B1), day 15 (A2 and B2) and day 30 PI (A3 and B3). Blood samples were collected by cardiac puncture to estimate red blood cell parameters (RBC), δ-ALA-D activity and serum levels of iron, zinc and thiobarbituric acid reactive substances (TBARS). Rats in group B showed a significant (P<0·05) reduction of RBC count, haemoglobin concentration and haematocrit at days 5 and 15 p.i. The activity of δ-ALA-D in blood was significantly (P<0·001) increased at days 15 and 30 p.i. δ-ALA-D activity in blood had a significant (P<0·05) negative correlation with haematocrit (r=-0·61) and haemoglobin (r=-0·70) at day 15 p.i. There was a significant (P<0·05) decrease in serum iron and zinc levels and an increase in TBARS levels (P<0·05) during infection. The δ-ALA-D activity in blood was negatively correlated with the levels of iron (r=-0·68) and zinc (r=-0·57) on day 30 p.i. It was concluded that the increased activity of δ-ALA-D in blood might have occurred in response to the anaemia in remission as heme synthesis was enhanced.     

Cultural consonance and psychological distress: examining the associations in multiple cultural domains

Cultural consonance is the degree to which individuals, in their own beliefs and behaviors, approximate widely shared cultural models. In previous research in Brazil and the United States we found that higher cultural consonance in the cultural domains of lifestyle and social support was associated with lower psychological distress. The aim of this paper is to expand on these results in two ways. First, the measurement of cultural consonance has been improved through a closer link of cultural domain analyses and survey research. Second, the number of domains in which cultural consonance has been examined has been expanded to include—along with lifestyle and social support—family life, national identity, and food. We found that cultural consonance in these five domains can be conceptualized as two latent variables of generalized cultural consonance, and that this generalized cultural consonance is associated with lower psychological distress. These results continue to support the usefulness of cultural consonance as a theoretical construct in the explanation of human social suffering.     

A cross-cultural perspective on obesity and health in three groups of women: the Mississippi Choctaw, American Samoans, and African Americans

This study compares obesity as assessed by Body Mass Index (BMI) and the relationship of BMI to hypertension and diabetes in adult females from three populations, the Mississippi Band of Choctaw (N=50), American Samoa (N=155), and an African American community in West Alabama (N=367). These groups were surveyed in the early to mid 1990s. All three groups of women have very high levels of overweight and obesity, with the Samoans being most extreme in this regard. While there are indications that all three groups of women consume a calorically dense diet, low activity appears to be the most likely causal factor in the high rates of obesity. Relaxed negative attitudes toward an overweight/obese body image may also play a role in the high rates. The prevalences of hypertension and diabetes are alarmingly high in all three groups. There are, however, very different associations between BMI, hypertension, and diabetes in the three groups of women. The Samoans are substantially more obese (and older), but they have lower rates of hypertension than the African American women and lower rates of diabetes than the Choctaw women. While the genetic background of the three groups no doubt plays a role, it is also likely that a BMI of 30+, the common cutoff for obesity, means different things in these different populations. These results provide further support for the idea of variation in the relationship of BMI to disease in different populations.     

Variations in cell surfaces of estrogen treated breast cancer cells detected by a combined instrument for far-field and near-field microscopy.

The response of single breast cancer cells (cell line T-47D) to 17beta-estradiol (E(2)) under different concentrations was studied by using an instrument that allows to combine far-field light microscopy with high resolution scanning near-field (AFM/SNOM) microscopy on the same cell. Different concentrations of E(2) induce clearly different effects as well on cellular shape (in classical bright-field imaging) as on surface topography (atomic force imaging) and absorbance (near-field light transmission imaging). The differences range from a polygonal shape at zero via a roughly spherical shape at physiological up to a spindle-like shape at un-physiologically high concentrations. The surface topography of untreated control cells was found to be regular and smooth with small overall height modulations. At physiological E(2) concentrations the surfaces became increasingly jagged as detected by an increase in membrane height. After application of the un-physiological high E(2) concentration the cell surface structures appeared to be smoother again with an irregular fine structure. The general behaviour of dose dependent differences was also found in the near-field light transmission images. In order to quantify the treatment effects, line scans through the normalised topography images were drawn and a rate of co-localisation between high topography and high transmission areas was calculated. The cell biological aspects of these observations are, so far, not studied in detail but measurements on single cells offer new perspectives to be empirically used in diagnosis and therapy control of breast cancers.     

Differential distribution of oligodeoxynucleotides in developing organs with epithelial-mesenchymal interactions.

The use of antisense oligodeoxynucleotides (ODNs) to inhibit gene expression is a usefull method for determining protein function and has potential therapeutic applications. However, there is still great variability in the successfull application of antisense technology to individual systems. In order to assess the ability of different cell types to take up ODNs, developing embryonic tissues were cultured in vitro in the presence of fluoresceine labelled, phosphorothioate substituted ODNs. The distribution of ODNs in individual cell populations was assayed by fluorescent microscopy and the tissue sections were counterstained for epithelial basement membrane formation. High intracellular levels of ODNs were observed in all mesenchymal cells of the lung, salivary gland, kidney, ovary and testis. However, a significant decrease in ODN levels was observed with the formation of new epithelium in kidney and gonads, whereas mature epithelial cells in all tissues had no detecable levels of ODNs. The ability to inhibit gene expression in mesenchymal cells, but not in epithelial cells, was consistent with the distribution pattern of labeled ODNs. These results may indicate a general resistance of epithelial cells to take up ODNs in culture and bear directly on the ability of ODNs to affect gene expression in complex organs with epithelial components.     

A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages

The aims of the work were (1) to develop statistical tests to identify whether substitution takes place under a covariotide model in sequences used for phylogenetic inference and (2) to determine the influence of covariotide substitution on phylogenetic trees inferred for photosynthetic and other organisms. (Covariotide and covarion models are ones in which sites that are variable in some parts of the underlying tree are invariable in others and vice versa.) Two tests were developed. The first was a contingency test, and the second was an inequality test comparing the expected number of variable sites in two groups with the observed number. Application of these tests to 16S rDNA and tufA sequences from a range of nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and eukaryotes suggests the occurrence of a covariotide mechanism. The degree of support for partitioning of taxa in reconstructed trees involving these organisms was determined in the presence or absence of sites showing particular substitution patterns. This analysis showed that the support for splits between (1) photosynthetic eukaryotes and prokaryotes and (2) photosynthetic and nonphotosynthetic organisms could be accounted for by patterns arising from covariotide substitution. We show that the additional problem of compositional bias in sequence data needs to be considered in the context of patterns of covariotide/covarion substitution. We argue that while covariotide or covarion substitution may give rise to phylogenetically informative patterns in sequence data, this may not always be so.      

Medical Anthropology in Ecological Perspective. Third Edition

Medical Anthropology in Ecological Perspective. Third Edition. Ann McElroy and Patricia K. Townsend. Boulder, CO: Westview Press, 1996. xxiv. 434 pp.     

Ceramide stimulates epidermal growth factor receptor phosphorylation in A431 human epidermoid carcinoma cells. Evidence that ceramide may mediate sphingosine action

Recent studies suggest the existence of a signal transduction pathway involving sphingomyelin and derivatives (Kolesnick, R. N. (1989) J. Biol. Chem. 264, 7617-7623). The present studies compare effects of ceramide, sphingosine, and N,N-dimethylsphingosine on epidermal growth factor (EGF) receptor phosphorylation in A431 human epidermoid carcinoma cells. To increase ceramide solubility, a ceramide containing octanoic acid at the second position (C8-cer) was synthesized. C8-cer induced time- and concentration-dependent EGF receptor phosphorylation. This event was detectable by 2 min and maximal by 10 min. As little as 0.1 microM C8-cer was effective, and 3 microM C8-cer induced maximal phosphorylation to 1.9-fold of control. EGF (20 nM) increased phosphorylation to 2.1-fold of control. Sphingosine stimulated receptor phosphorylation over the same concentration range (0.03-3 microM) and to the same extent (1.8-fold of control) as ceramide. The effects of C8-cer and sphingosine were similar by three separate criteria, phosphoamino acid analysis, anti-phosphotyrosine antibody immunoblotting, and phosphopeptide mapping by high performance liquid chromatography. Phosphorylation occurred specifically on threonine residues. N,N-Dimethylsphingosine, a potential derivative of sphingosine, was less effective. Since sphingosine and ceramide are interconvertible, the level of each compound was measured under conditions sufficient for EGF receptor phosphorylation. C8-cer (0.1-1 microM) induced dose-responsive elevation of cellular ceramide from 132 to 232 pmol.10(6) cells-1. In contrast, cellular sphingosine levels did not rise. This suggests that C8-cer acts without conversion to sphingosine. Exogenous sphingosine (0.1-1 microM) also increased cellular ceramide levels to 227 pmol.10(6) cells-1, but did not increase its own cellular level of 12 pmol.10(6) cells-1. Higher sphingosine concentrations that induced no further increase in EGF receptor phosphorylation produced very large elevations in cellular sphingosine. Hence, at effective concentrations, both compounds elevated cellular ceramide but not sphingosine levels. Additional studies performed with [3H]sphingosine demonstrated that cells contain substantially less N,N-dimethylsphingosine than free sphingosine and, during short term incubation, convert less than 5% of added sphingosine to N,N-dimethylsphingosine. These studies provide evidence that ceramide may have bioeffector properties and suggest sphingosine may act in part by conversion to ceramide.     

The rolling circle . capsid complex as an intermediate in phi X DNA replication and viral assembly

Late in the life cycle of the single-stranded DNA phage phi X, the synthesis of positive strand DNA is coupled to the maturation of progeny virions. DNA synthesis and packaging take place in a replication-assembly complex, which we have purified to homogeneity and characterized. The following conclusions can be drawn: 1. The DNA component of the replication-assembly complex is a rolling circle with a single-stranded DNA tail which is less than or equal to genome length. 2. The major protein component of the replication-assembly complex is an intact viral capsid, as shown by gel analysis of 35S-labeled complexes. As replication proceeds at the DNA growing point, the positive strand tail of the rolling circle is displaced directly into the capsid. In addition to the capsid, the complex contains at least 1 molecule of the phi X gene A nicking protein, which appears to be covalently linked to the DNA. 3. The rolling circle . capsid complex can be purified to homogeneity by taking advantage of its uniform sedimentation velocity (35 S) and its uniform density upon equilibrium centrifugation in CsCl (1.50 g/cc). 4. The replication-assembly complex can be visualized in the electron microscope. An electron-dense particle, which has the dimensions of a viral capsid, is observed attached to a rolling circle at the DNA growing point. 5. Hybridization of specific phi X restriction fragments to the deproteinized, single-stranded tails of intact rolling circles has allowed the use of these replicating intermediates to determine both the origin/terminus and the direction of phi X positive strand DNA synthesis. The ends of the rolling circle tails map in the Hae III restriction Fragment Z6b, at the position on the phi X genome at which the gene A endonuclease is known to cut. This result indicates that this endonuclease participates in the "termination" of each round of synthesis by cutting off unit-length viral genomes. 6. Rolling circle . capsid complexes were also isolated from two other icosahedral, single-stranded DNA phages: G4 and St-1. The rolling circle . capsid complex seen in the case of the single-stranded DNA phages represents the first example of a structure in which DNA synthesis and viral assembly occur in a coupled manner. This tight coordination explains why double-stranded DNA circles are the net product of synthesis early in the viral life cycle while only single-stranded DNA circles are produced later. The single-stranded tails of the rolling circle intermediates are available for conversion to the duplex state at early times, whereas the concentration of preformed capsids later is high enough to bind to all of the replicating molecules and package the emerging positive strand DNA.