Dedifferentiation-associated changes in morphology and gene expression in primary human articular chondrocytes in cell culture.

OBJECTIVE: The aim of the present study was the investigation of differential gene expression in primary human articular chondrocytes (HACs) and in cultivated cells derived from HACs. DESIGN: Primary human articular chondrocytes (HACs) isolated from non-arthritic human articular cartilage and monolayer cultures of HACs were investigated by immunohistochemistry, Northern analysis, RT-PCR and cDNA arrays. RESULTS: By immunohistochemistry we detected expression of collagen II, protein S-100, chondroitin-4-sulphate and vimentin in freshly isolated HACs. Cultivated HACs, however, showed only collagen I and vimentin expression. These data were corroborated by the results of Northern analysis using specifc cDNA probes for collagens I, II and III and chondromodulin, respectively, demonstrating collagen II and chondromodulin expression in primary HACs but not in cultivated cells. Hybridization of mRNA from primary HACs and cultivated cells to cDNA arrays revealed additional transcriptional changes associated with dedifferentiation during propagation of chondrocytes in vitro. We found a more complex hybridization pattern for primary HACs than for cultivated cells. Of the genes expressed in primary HACs the early growth response (EGR1) transcription factor showed the strongest expression whereas D-type cyclin was expressed in proliferating cells. Other factors associated with differentiated HACs were the adhesion molecules ICAM-1 and VCAM-1, VEGF, TGFbeta2, and the monocyte chemotactic protein receptor. CONCLUSIONS: Our data support the hypothesis that HACs dedifferentiate when grown in monolayer cultures. Moreover, the expression patterns also show that proliferation and differentiation are exclusive features of human chondrocytes.

Comparison of the deduced amino acid sequence of guinea pig adenovirus hexon protein with that of other mastadenoviruses.

PURPOSE: We sought to isolate, clone, and determine the nucleic acid sequence of the guinea pig adenovirus (GPAdV) hexon gene. From this, the amino acid sequence of the cloned portion was deduced and compared with a set of mastadenovirus hexons. METHODS: The DNA isolated from a histologic section of infected guinea pig lung was subjected to high-fidelity amplification, using degenerate primers complementary to a conserved nucleic acid sequence near the 3' end of the hexon gene of mastadenoviruses and a 5' primer from GenBank accession No. X95630 (GPAdV hexon gene partial sequence). The amplified product was cloned, the nucleic acid sequence was determined, and the amino acid sequence was deduced and compared with the hexon amino acid sequences of 25 mastadenoviruses. RESULTS: The cloned fragment comprised 1,603 base pairs (bp) [approximately 50%]) of the hexon. Of the initial 278 nucleic acids of the clone, 276 were identical with GenBank accession No. X95630, and the deduced amino acid sequences of both were identical. The deduced GPAdV hexon amino acid sequence from the clone aligned with structural regions NT, V1, DE1, and FG1 described for human adenovirus types 2 and 5. The GPAdV hexon had < 50% similarity in amino acid sequence, compared with hexons of 25 other mastadenoviruses. Analysis of regional peptide similarities revealed the GPAdV hexon to be more similar to animal mastadenoviruses and human subgroups A, C and F than to other human subgroups. CONCLUSIONS: The cloned portion of the GPAdV hexon contained a sequence nearly identical to that of GenBank accession No. X95630. Compared with the truncated amino acid sequences of human adenovirus types 2 and 5, the deduced GPAdV hexon amino acid sequence was similar in areas structurally conserved, but different in areas associated with type-specific antigenicity.

Transcription factor Sp3 is essential for post-natal survival and late tooth development.

Sp3 is a ubiquitously expressed transcription factor closely related to Sp1 (specificity protein 1). We have disrupted the mouse Sp3 gene by homologous recombination. Sp3-deficient embryos are growth retarded and invariably die at birth of respiratory failure. The cause for the observed breathing defect remains obscure since only minor morphological alterations were observed in the lung, and surfactant protein expression is indistinguishable from that in wild-type mice. Histological examinations of individual organs in Sp3(-/-) mice show a pronounced defect in late tooth formation. In Sp3 null mice, the dentin/enamel layer of the developing teeth is impaired due to the lack of ameloblast-specific gene products. Comparison of the Sp1 and Sp3 knockout phenotype shows that Sp1 and Sp3 have distinct functions in vivo, but also suggests a degree of functional redundancy.

Mechanisms of adverse drug reactions and interactions in veterinary medicine.

Rapid advances in research in basic pharmacology and the productivity of the pharmaceutical industry have resulted in the introduction of many new drugs for the veterinary profession. The availability of such a large number of drugs has stimulated their concomitant use with the hope that maximum therapeutic effectiveness will be achieved. Indeed, modern therapeutics in veterinary medicine often necessitates the simultaneous administration of several drugs. With the increased use of multiple drug therapy has come the problem of drug interactions, which necessitates greater professional awareness and responsibility on the part of the veterinarian. Drug interactions are essentially a problem of modern medicine.