Functional characterization of three novel tissue-specific anion exchangers SLC26A7, -A8, and -A9

A second distinct family of anion exchangers, SLC26, in addition to the classical SLC4 (or anion exchanger) family, has recently been delineated. Particular interest in this gene family is stimulated by the fact that the SLC26A2, SLC26A3, and SLC26A4 genes have been recognized as the disease genes mutated in diastrophic dysplasia, congenital chloride diarrhea, and Pendred syndrome, respectively. We report the expansion of the SLC26 gene family by characterizing three novel tissue-specific members, named SLC26A7, SLC26A8, and SLC26A9, on chromosomes 8, 6, and 1, respectively. The SLC26A7-A9 proteins are structurally very similar at the amino acid level to the previous family members and show tissue-specific expression in kidney, testis, and lung, respectively. More detailed characterization by immunohistochemistry and/or in situ hybridization localized SLC26A7 to distal segments of nephrons, SLC26A8 to developing spermatocytes, and SLC26A9 to the lumenal side of the bronchiolar and alveolar epithelium of lung. Expression of SLC26A7-A9 proteins in Xenopus oocytes demonstrated chloride, sulfate, and oxalate transport activity, suggesting that they encode functional anion exchangers. The functional characterization of the novel tissue-specific members may provide new insights to anion transport physiology in different parts of body.     

Urinary excretion of epsilondA is not predictive of cancer development: a prospective nested case-control study

Human biomonitoring of the lipid peroxidation DNA modification 1,N⁶-ethenodeoxyadenosine (εdA) excreted into urine is thought to be a potential marker for oxidative stress-related DNA damage and human cancer. We have tested this hypothesis in a prospective, nested case-control study. During the years 1984-1989, 24-h urines were collected from 1956 men in the Kuopio Ischaemic Heart Disease (KIHD) Risk Factor Study. εdA concentrations were measured by LC-MS/MS in 24-h urine samples from 47 men with cancer diagnosed at follow up until 2001 and from 31 cancer free smoking-matched control subjects. Odds ratio for having higher than control median εdA excretion rate and cancer, estimated by binary logistic regression, was 0.73 (95% CI 0.29-1.80, p=0.49). In this study, the urinary excretion of εdA provides no additional prediction of cancer development in males after controlling for smoking.     

Is mood chemistry?

The chemical hypothesis of depression suggests that mood disorders are caused by a chemical imbalance in the brain, which can be corrected by antidepressant drugs. However, recent evidence indicates that problems in information processing within neural networks, rather than changes in chemical balance, might underlie depression, and that antidepressant drugs induce plastic changes in neuronal connectivity, which gradually lead to improvements in neuronal information processing and recovery of mood.     

Behavioral alterations induced by repeated testing in C57BL/6J and 129S2/Sv mice: implications for phenotyping screens

The C57BL/6JOlaHsd and 129S2/SvHsd mice were tested in a battery designed for behavioral phenotyping of genetically modified mice. The study was performed in order to reveal the effect of training history on the behavior by comparison with the experimentally naïve mice in the same tests. Significant strain differences were obtained in all experiments. Previous handling and testing reduced exploratory activity and emotionality significantly in the mice. The coordination ability was better and nociceptive sensitivity was increased in the trained mice. The contextual fear was reduced whereas the cued fear was enhanced in the experienced mice. The training history did not alter initial learning in the water maze. However, after reversal learning the naïve mice displayed significant preference for both old and new platform locations, whereas the battery animals did not exhibit preference to the old location. The experienced mice appeared to be less active in the forced swimming test and exhibited decreased conditioned taste aversion. The influence of test history was strain-dependent in certain cases. Therefore, the experience has substantial consequences on the behavior, mainly by reducing exploratory activity, and the previous experience of the animals has always to be considered in the analysis of genetically modified mice.     

Analysis of the human TrkB gene genomic organization reveals novel TrkB isoforms, unusual gene length, and splicing mechanism.

We determined the gene structure of the human TrkB gene. The gene is unusually large and spans at least 590 kbp. It contains 24 exons. Using alternative promoters, splicing, and polyadenylation sites, the gene can create at least 100 isoforms, that can encode 10 proteins. RT-PCR and Northern blot analysis reveals that only three major protein isoforms are generated by the gene: the full length receptor, an isoform lacking the tyrosine kinase domain, and a novel isoform lacking the tyrosine kinase domain but containing a Shc binding site. This novel isoform, TrkB-T-Shc is generated by the use of a new alternative exon 19. It is expressed only in brain. TrkB-T-Shc protein is located in the plasma membrane. Coimmunoprecipitation experiments show that TrkB-T-Shc is not phosphorylated by the full length receptor, indicating that it could be a negative regulator of TrkB signaling in the brain.     

Laminin α1-Chain Shows a Restricted Distribution in Epithelial Basement Membranes of Fetal and Adult Human Tissues

Two novel monoclonal antibodies were raised and used to study the expression of laminin (Ln) α1-chain in developing and adult human tissues. In both fetal and adult kidney, a distinct immunoreactivity was seen in basement membranes (BM) of most proximal tubules but not in the distal tubular or glomerular BM or in the basal laminae of blood vessels. Immunoprecipitation of metabolically labeled cultured human renal proximal tubular cells showed an abundant production and deposition of Ln α1-chain to the extracellular matrix, suggestive of an epithelial origin of kidney Ln-1. Quantitative cell adhesion experiments with JAR choriocarcinoma cells showed that purified human Ln-1 is a good substrate for cell adhesion that it is differently recognized by integrin receptors when compared to mouse Ln-1. In fetal and adult testes immunoreactivity was solely confined to BM of the seminiferous epithelium. In the airways BM-confined reaction was only seen in fetal budding bronchial tubules (16–19 weeks) at the pseudoglandular stage of development. In the skin a distinct immunoreactivity was confined to BM of developing hair buds but not in epithelial BMs of adult epidermis or of epidermal appendages. In other adult tissues, immunoreactivity was found in BMs of thyroid, salivary, and mammary glands as well as in BMs of endometrium and endocervix, but not of ectocervix or vagina. No immunoreactivity was found in BMs of most of the digestive tract, including the liver and pancreas, except for BMs of esophageal submucosal glands and duodenal Brunner's glands. In fetal specimens, BMs of the bottoms of the intestinal and gastric glands were positive. Basal laminae of blood vessels were generally negative for Ln α1 chain with the exception of specimens of both fetal and adult central nervous system in which immunoreactivity for Ln α1 chain was prominently confined to capillary walls. The results suggest that outside the central nervous system, Ln α1 chain shows a restricted and developmentally regulated expression in BMs of distinct epithelial tissues.     

Predator control and the density and reproductive success of grouse populations in Finland

The impact of predator removal or protection on the reproductive success and density of grouse populations was studied experimentally in southern and northern Finland. In predator removal areas small and medium-sized carnivores wore efficiently hunted, while in predator protection areas hunting was prohibited. Both predator (red fox, raccoon dog, pine marten and stoat) and grouse populations were monitored. The breeding success of grouse, indicated by the young/adults ratio, decreased in the predator protection area in northern Finland during a vole low. Despite a decline in the vole population, the breeding success of grouse did not decline in the predator removal area. The mean brood size during the experiment was significantly higher in the removal areas than in the protection areas both in southern and northern Finland. Predator removal/protection thus affected the reproductive success of grouse, but the impact of control on adult grouse populations was not as evident.     

Nonuniform effect of prolonged haloperidol administration on the GABA(A) and benzodiazepine receptors in different parts of the brain

The experiments on male mice and rats have revealed reversed behavioral effects of muscimol and Ro 15-1788 after 15 days of haloperidol (0.25 mg/kg, twice daily) treatment. Muscimol (0.75 mg/kg), which depressed motor activity in saline-pretreated mice, stimulated it after discontinuation of long-term haloperidol administration. Ro 15-1788 stimulating effect in saline-pretreated rats gave way to sedative effect following haloperidol withdrawal. Simultaneously, the number of 3H-muscimol and 3H-flunitrazepam binding sites was decreased in forebrain, but increased in hindbrain. It was suggested that GABAA and benzodiazepine receptors in forebrain and hindbrain play opposite (inhibiting and stimulating, respectively) functional roles in the regulation of behaviour.