NAD(P)H:quinone reductase activity in human epidermal keratinocytes and reconstructed epidermal models

Reconstructed epidermal models may provide a suitable and relevant model for screening compounds such as quinones, which affect the activities of phase I and II enzymes involved in epidermal detoxification. Reconstructed epidermis may also allow the study of the metabolism of topically applied compounds by the phase I and II enzymes. We demonstrate that NAD(P)H:quinone reductase (NQR) activity is present in three different types of reconstructed epidermal models and that levels vary depending on the type of model. We also determined the inter- and intrabatch variability and demonstrate that NQR activity can be significantly inhibited by dicumarol treatment. The NQR activity in reconstructed epidermis is similar to that in human epidermis and lower than in cultured keratinocytes. Therefore reconstructed epidermis is a more suitable model for testing the effects of topically applied compounds on NQR activity or the metabolism of the compound by NQR.     

Serotonin uptake into dopamine neurons via dopamine transporters: a compensatory alternative

Monoamine neurons are believed to use neuronal-specific transporters to remove their own transmitters from the extracellular space and thus terminate transmission to postsynaptic neurons. We report here, for the first time, conclusive evidence that a cross clearance of serotonin into dopamine neurons exists. Such alternative uptake by different neurons is adopted under circumstances when their own transporter function is no longer adequate. When the serotonin transporter (5-HTT) is disrupted in 5-HTT knockout mice, serotonin (5-HT) is found in dopamine (DA) neurons of homozygous (-/-) but not of heterozygous (+/-) mutant mice or their normal littermates. DA neurons containing 5-HT are seen in the substantia nigra and ventral tegmental area (VTA), but not in other brain areas of 5-HTT -/- mice. Normal rats treated with a 5-HT uptake blocker paroxetine also showed similar result. To verify the role of the DA transporter in such ectopic uptake, 5-HTT -/- mice were treated with DA uptake blocker GBR-12935, ectopic 5-HT in DA neurons was disappeared. These data indicate that: (a) 5-HT can be taken into DA neurons in rats and mice when the 5-HTT is not functionally adequate to remove extracellular 5-HT; (b) the 5-HT uptake into DA neurons is not affected by the 5-HT uptake blocker paroxetine; and (c) the DA transporter is responsible for the 5-HT uptake into DA neurons. This study thus demonstrates that cross neuronal type uptake exists and serves as a compensatory backup when a specific transporter is dysfunctional. This study also demonstrates that DA neurons can store 5-HT for possible "false neurotransmitter" or other usage.     

Susceptibility for schizophrenia is not influenced by a functional insertion/deletion variant in the promoter of the serotonin transporter gene

A possible dysregulation of serotonergic neurotransmission has been implicated in the aetiology of schizophrenic psychoses. In the present study we analysed allelic and genotypic variations of a recently described functional polymorphic region in the promoter of the human serotonin transporter gene (5-HTTLPR) and a variable tandem repeat (VNTR) in intron 2 of the 5-HTT gene. We investigated 413 unrelated individuals, 180 schizophrenic patients and 233 blood donors as controls. With regard to the 5-HTTLPR, both the schizophrenic and the control group did not significantly differ between genotype frequencies (χ², p = 0.920) and allele frequencies (χ², p = 0.836). The odds ratio for subjects with schizophrenia who were homozygous for the short allele was 1.04 (95% CI 0.59–1.84). No evidence of allelic association to specific schizophrenia subtypes was found. The 5-HTT associated VNTR also showed no significant differences between either the allelic or the genotypic distributions. Haplotype analysis revealed a significant overall linkage disequilibrium at a level of p = 0.00004. Our findings indicate that both polymorphisms are unlikely to play a substantial role in the genetic predisposition to schizophrenic disorders. Received: 14 April 1997 / Accepted: 16 October 1997     

High prevalence of antibodies to acquired immune deficiency syndrome (AIDS)-associated retrovirus (ARV) in AIDS and related conditions but not in other disease states.

A rapid, sensitive indirect immunofluorescence assay has been developed for detection of antibodies to the acquired immune deficiency syndrome (AIDS)-associated retrovirus (ARV). The human T-cell line HUT-78 was chronically infected with ARV-2 and used to detect antibodies to virus-specific cytoplasmic antigens. Because the helper T-cell marker Leu-3 is substantially reduced in this cell line after ARV infection, it appears to be an important receptor for virus infection. Nearly all patients with AIDS and most cases with related conditions showed antibodies against ARV. Some healthy individuals in risk groups for developing AIDS also had antibodies to the agent. In contrast, no antibodies to the virus were found in any individuals outside the risk groups for developing AIDS or with diseases other than those associated with AIDS. The titers of antibodies to ARV and to Epstein-Barr virus varied independently from each other. The level of anti-ARV antibodies in a patient's serum was found to reflect the severity of the disease; it was lower in individuals with more severe manifestations. Taken together, these data support the role of ARV in AIDS and its related disorders.     

Bird orientation and the geomagnetic field: A review

The possibility that birds use the geomagnetic field to guide their orientation has been repeatedly suggested over the last century. Early attempts to experimentally verify this hypothesis were largely unsuccessful. Recently, however, this issue has been more thoroughly examined, from a variety of approaches, with positive results. Magnetic fields have been shown to have a biological effect on a variety of animals ranging from unicellular organisms to mammals. Many of these organisms, including birds, show changes in orientation behavior as a result of changes in the ambient magnetic field. Specific data supporting the existence of a “magnetic-compass” in birds include demonstrations that (a) changes in the intensity of the ambient magnetic field disrupt various kinds of orientation behavior and (b) that systematic changes in the direction of the ambient magnetic field are accompanied by systematic changes in the direction of orientation. The biggest obstacle in further study of the “magnetic-compass” is the almost complete ignorance of the biophysical mechanism(s) involved in the biological detection of the geomagnetic field. Some theoretical speculations about possible biomagnetic mechanisms are discussed and suggestions for the direction of future research on the “magnetic-compass” and its relation to other orientation behaviors are provided.     

Epstein-Barr virus genome studies in Burkitt's and non-Burkitt's lymphomas in Uganda.

Burkitt's lymphoma (BL) has been widely investigated and has attracted attention because of the possible etiologic role of the Epstein-Barr virus (EBV). To further determine the role of EBV in the causation of this tumor, we measured EBV-specific nuclear antigen (EBNA) and EBV DNA using immunofluorescence and nucleic acid hybridization techniques, respectively. Of 34 BL biopsies, 27 tissues (79%) were EBNA-positive, whereas none of the 25 non-BL biopsy tissues were EBNA-positive. Of 15 BL tumors tested, 14 (93%) were EBV DNA-positive with a mean of 39 (range, 8-86) EBV genome equivalents per cell. Each of the 15 non-BL biopsy specimens subjected to nucleic acid hybridization had less than two virus genome equivalents per cell, although all had serologic evidence of past EBV infection. The findings further supported the possible etiologic role of EBV in African BL and negated the passenger hypothesis. The EBV genome could, therefore, be used as a separating marker between African BL and non-BL lymphomas.     

Demonstration of Epstein-Barr virus-associated nuclear antigen in nasopharyngeal carcinoma cells from fresh biopsies

Fresh nasopharyngeal carcinoma (NPC) biopsies were treated in several ways to yield satisfactory cell preparations for detection of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA) by anti-complement immunofluorescence tests. If the cells were well dispersed (trypsinization or extensive mechanical dispersal) few or none of them were EBNA-positive. In contrast, if the biopsy preparations contained small to moderately sized tissue fragments (touch preparations or limited mechanical dispersal), nuclear staining was detected in nearly every cell at the margin of the fragments or in cell sheets protruding from them. The stained cells corresponded to the carcinoma cells when compared to histologically stained replicate cell preparations. Nuclear staining was obtaining with anti-EBNA positive sera [healthy donors, NPC patients, convalescents from infectious mononucleosis (IM)], shown to be free of antibodies to other nuclear antigens, but not with anti-EBNA negative sera (healthy donors or patients in the early acute phase of IM). These results confirm and extend previous reports that the carcinoma cells harbor EBV genomes. The implications of these findings are discussed.