Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.

The v‐erbA oncogene confers two prominent properties on transformed erythroblasts: a block of spontaneous differentiation and tolerance to wide variations in the pH or ionic strength of culture medium. V‐erbA acts as a constitutive repressor of erythrocyte‐specific gene transcription, arresting the expression of at least three different erythroid genes: the erythrocyte anion transporter (band 3), carbonic anhydrase II (CAII) and delta‐aminolevulinate synthase (ALA‐S). To test whether or not the v‐erbA induced repression of these genes is causally related to the v‐erbA induced leukaemic phenotype, we have reintroduced the genes for band 3 or CAII into transformed erythroblasts via retrovirus vectors. We show here that such erythroblasts, expressing v‐erbA, require the same narrow range of medium pH and ion concentration for growth as do transformed erythroblasts lacking v‐erbA, i.e. the v‐erbA induced tolerance to pH variation was abrogated. The v‐erbA induced differentiation block, however, remained unaffected by the re‐expression of band 3 and was only slightly affected by the re‐expression of CAII. Our experiments show that the two v‐erbA‐related ‘erythroblast transformation parameters’ are separable: suppression of band 3 and CAII accounts for one parameter (pH/ion tolerance), while the second parameter (differentiation block) must involve v‐erbA regulation of a different set of target genes.

A malignant glioma cell line was infected with the human T-lymphotropic virus type IIIB isolate of the human immunodeficiency virus. Infection appeared to be latent rather than productive. Through contact with monocytic or lymphoid cells, the virus present in the glioma cells could be transmitted and gave rise to a fully productive infection.

Unlike any other known plant transposon, the maize transposable element Bs1 is similar to the retrotransposons previously described in yeast and Drosophila. Bs1 is bounded by 302 bp identical long terminal repeats (LTRs), and it contains open reading frames with apparent amino acid sequence similarity to reverse transcriptase and other retroviral pol gene enzymes. Bs1 is 3203 bp long, very short for a retrotransposon, and the apparent organization of its genetic information is significantly different from any previously described element. Although transcription of Bs1 has not been observed, it is probably an active transposon, since it was observed to transpose in a maize line that contains only two sequences hybridizing to Bs1 probes. Both of these sequences share 35 restriction sites with the cloned Bs1 element, and thus must be very similar or identical with it.