Hypothalamic response to leptin changes during a hormonally induced estrous cycle in rats

The leptin system regulates body fat mass through a feedback loop between adipose tissue and the hypothalamus. To test if leptin responsiveness may be regulated we assayed hypothalamic response to leptin during the estrous cycle; when changes in food intake are known to occur. Immature rats were treated with pregnant mare’s serum gonadotropin (PMSG) to induce synchronized follicular development, ovulation and corpus luteum formation. Leptin response was estimated by measuring the in vitro induction of tis11, a primary response gene activated by STAT3-dependent cytokines in hypothalamic explants after leptin stimulation. In addition, mRNA levels of the suppressor cytokine signaling-3 (SOCS-3), a possible mediator of leptin resistance, were analyzed. Serum leptin levels did not change between days 2 and day 3 (corresponding to proestrus and estrus, respectively) but the response to leptin was higher on day 2 than on day 3 (p=0.05). Food intake displayed a tendency towards downregulation between day 1 and day 2 (p=0.057), and a tendency towards upregulation between day 2 and day 3 (p=0.072), although the body weight increased on day of the study (p<0.0001). There was no significant difference in hypothalamic expression of SOCS-3 between day 2 and day 3. In conclusion, we have shown that leptin responsiveness changes during a hormonally induced estrous cycle in rats. Our data suggest that a change in the hypothalamic response to leptin may cause the cyclic feeding behavior seen in rats.     

The Cutting Balloon--a new technology?

The Cutting Balloon consists of a standard balloon dilatation catheter with four microtome-sharp blades that incise the plaque and minimize arterial wall trauma. It was used in 31 patients; nine had calcified arteries, ten had non-compliant lesions, three had in-stent restenosis and nine had aorto-ostial lesions. Seventeen lesions were predilated, 28 were post-dilated and 18 required stent implantation. The procedure was very effective in aorto-ostial lesions, non-compliant lesions that were not responsive to high-pressure balloon dilatation, and was partially successful in calcified arteries. It has a very specific niche in selected lesions.     

Carrier-state of D allele in ACE gene insertion/deletion polymorphism is associated with coronary artery disease,in contrast to the C677-->T transition in the MTHFR gene

Angiotensin I-converting enzyme (ACE), which plays an important role in blood pressure regulation, and methylenetetrahydrofolate reductase (MTHFR) involved in homocysteine metabolism belong to a large group of polypeptides which may be potential risk factors for atherosclerosis and coronary artery disease (CAD). To assess whether polymorphisms of the genes encoding these peptides are associated with CAD in Silesian we conducted a study among 68 individuals suffering from CAD (including 52 cases after myocardial infarction), 51 subjects with positive family history of CAD and 111 controls. We analysed the distribution of genotypes and allele frequencies of the insertion/deletion (I/D) polymorphism in the ACE gene using PCR amplification, and the C677-->T polymorphism in the MTHFR gene using PCR-RFLP analysis. We found that D allele frequency was significantly higher in CAD patients (61%) than in controls (43%) (P = 0.001, OR = 2.06). The D allele carriers (DD + ID genotypes) were more frequent in the CAD patients (85%) compared to control group (65%) (P = 0.003, OR = 3.14), whereas the familial CAD risk group shows the highest frequency of the ID genotype (57% vs 43% in controls). In contrast, the MTHFR polymorphism does not seem to be associated with the disease. Our data indicate that in Silesian CAD patients the disease is strongly associated with carrier-state of the ACE D allele, but not with the C677-->T transition in the MTHFR gene.     

Confirmation of a gene for multiple sclerosis (MS) to chromosome region 19q13.3

To identify the chromosomal localizations of the multiple sclerosis (MS) genes, we conducted a genomewide linkage analysis using eighteen affected families. A MS gene is linked to markers located in the 19q13.3 region (multipoint lod-score = 2.1). Apolipoprotein E (ApoE) gene, located in this region, is an excellent candidate gene for MS because the ApoEe4 allele is acting as a severity allele in the disease.     

Substitution bias, rapid saturation, and the use of mtDNA for nematode systematics

Only relatively recently have researchers turned to molecular methods for nematode phylogeny reconstruction. Thus, we lack the extensive literature on evolutionary patterns and phylogenetic usefulness of different DNA regions for nematodes that exists for other taxa. Here, we examine the usefulness of mtDNA for nematode phylogeny reconstruction and provide data that can be used for a priori character weighting or for parameter specification in models of sequence evolution. We estimated the substitution pattern for the mitochondrial ND4 gene from intraspecific comparisons in four species of parasitic nematodes from the family Trichostrongylidae (38-50 sequences per species). The resulting pattern suggests a strong mutational bias toward A and T, and a lower transition/transversion ratio than is typically observed in other taxa. We also present information on the relative rates of substitution at first, second, and third codon positions and on relative rates of saturation of different types of substitutions in comparisons ranging from intraspecific to interordinal. Silent sites saturate extremely quickly, presumably owing to the substitution bias and, perhaps, to an accelerated mutation rate. Results emphasize the importance of using only the most closely related sequences in order to infer patterns of substitution accurately for nematodes or for other taxa having strongly composition-biased DNA. ND4 also shows high amino acid polymorphism at both the intra- and interspecific levels, and in higher level comparisons, there is evidence of saturation at variable amino acid sites. In general, we recommend using mtDNA coding genes only for phylogenetics of relatively closely related nematode species and, even then, using only nonsynonymous substitutions and the more conserved mitochondrial genes (e.g., cytochrome oxidases). On the other hand, the high substitution rate in genes such as ND4 should make them excellent for population genetics studies, identifying cryptic species, and resolving relationships among closely related congeners when other markers show insufficient variation.      

Differentiation-associated modulation of heparan sulfate structure and function in CaCo-2 colon carcinoma cells

Heparan sulfate species expressed by different cell and tissue types differ in their structural and functional properties. Limited information is available on differences in regulation of heparan sulfate biosynthesis within a single tissue or cell population under different conditions. We have approached this question by studying the effect of cell differentiation on the biosynthesis and function of heparan sulfate in human colon carcinoma cells (CaCo-2). These cells undergo spontaneous differentiation in culture when grown on semipermeable supports; the differentiated cells show phenotypic similarity to small intestine enterocytes. Metabolically labeled heparan sulfate was isolated from the apical and basolateral media from cultures of differentiated and undifferentiated cells. Compositional analysis of disaccharides, derived from the contiguous N-sulfated regions of heparan sulfate, indicated a greater proportion of 2-O- sulfated iduronic acid units and a smaller amount of 6-O-sulfated glucosamine units in differentiated than in undifferentiated cells. By contrast, the overall degree of sulfation, the chain length and the size distribution of the N-acetylated regions were similar regardless the differentiation status of the cells. The structural changes were found to affect the binding of heparan sulfate to the long isoform of platelet-derived growth factor A chain but not to fibroblast growth factor 2. These findings show that heparan sulfate structures change during cell differentiation and that heparan sulfate-growth factor interactions may be affected by such changes.