PubMed Health⌕ Search

Biomedical subjects

J Renn

Publications and source records attributed to J Renn.

7 recordsLinked to original sources
PubMed2006

Zebrafish and medaka as models for bone research including implications regarding space-related issues.

Teleost fish develop bones directly from mesenchymal condensations and from cartilage precursors. At the cellular level, the involved cell populations share many features with their mammalian counterparts. In addition, several genes are already described in fish showing high homology in amino acid sequence and expression with the corresponding genes of tetrapods that are involved in bone metabolism. Therefore, analysis of the underlying molecular mechanism in fish, in particular zebrafish and medaka, will increase the knowledge in teleosts. Furthermore, it will help to identify novel genes and regulatory pathways of bone homeostasis and skeletal disorders also in higher vertebrates, including disorders caused by altered gravity.

Adaptation, Physiological↗
PubMed2003

The teleost fish medaka (Oryzias latipes) as genetic model to study gravity dependent bone homeostasis in vivo.

Long-term space flight and microgravity result in bone loss that can be explained by reduced activity of bone-forming cells (osteoblasts) and/or an increase in activity of bone resorbing cells (osteoclasts). Osteoprotegerin (OPG) has been shown to regulate the balance between osteoblast and osteoclast cell numbers and is involved in maintaining constant bone mass under normal gravitational conditions. The small bony fish medaka (Oryzias latipes) has attracted increasing attention as a genetic model system to study normal embryonic developmental and pathological processes. To analyze the molecular mechanisms of bone formation in this small vertebrate, we have isolated two opg genes, opgl and opg2, from medaka. Our phylogenetic analysis reveals that both genes originated from a common ancestor by fish-specific gene duplication and represent the orthologs of the mammalian opg gene. Both opg genes are differentially expressed during embryonic and larval development, in adult tissues and in cultured primary osteoblast-like cells. Furthermore, we have characterized the opg2 promoter region and identified consensus binding sites for the transcription factor core-binding-factor-1A (CBFA1). In mammals, CBFA1 has been shown to be a regulator of opg expression and to be essential for several steps during osteoblast differentiation. Here we show that sequence and expression domains of opg, cbfal and a member of the dlx gene family are highly conserved between medaka and higher vertebrates. This suggests that not only single genes but entire genetic networks for bone formation are conserved between teleosts and mammals. These findings will open medaka fish as a genetic model to monitor bone formation under different gravity conditions in a living whole animal allowing the identification of novel factors involved in bone homeostasis.

Animals↗
PubMed1998

Reliability and validity of depressive personality disorder.

OBJECTIVE: Depressive personality disorder was introduced into DSM-IV's appendix amid controversy. While that disorder appears to be a reliable and valid one, the authors offer new data about its relationship to major depression, dysthymic disorder, and other personality disorders. METHOD: The authors assessed 54 subjects with early-onset, long-standing mild depressive features for depressive personality disorder, axis I and axis II disorders, family history, and treatment history; they conducted follow-up interviews 1 year after the baseline assessment. Subjects with (N=30) and without (N=24) depressive personality disorder were characterized and compared in terms of those variables. RESULTS: Although depressive personality disorder and dysthymia co-occurred in some subjects, 63% of subjects with depressive personality disorder did not have dysthymia, and 60% did not have current major depression. Although subjects with depressive personality disorder were more likely than the mood disorder comparison group to have another personality disorder, 40% had no such disorder. Contrary to study hypotheses, mood disorder was not more common in first-degree relatives of subjects with depressive personality disorder than in relatives of the comparison group. Subjects with and without depressive personality disorder had similar rates of past treatment with medication and psychotherapy; however, the duration of psychotherapy was significantly longer for subjects with than for those without depressive personality. The depressive personality diagnosis was relatively stable over the 1-year follow-up period. CONCLUSIONS: Depressive personality disorder appears to be a relatively stable condition with incomplete overlap with axis I mood disorders and personality disorders. Further studies are needed to better characterize its treatment response and relationship to axis I mood disorders.

Adult↗
PubMed1997

The Origin of Gravitational Lensing: A Postscript to Einstein's 1936 Science Paper

Gravitational lensing, now taken as an important astrophysical consequence of the general theory of relativity, was found even before this theory was formulated but was discarded as a speculative idea without any chance of empirical confirmation. Reconstruction of some of Einstein's research notes dating back to 1912 reveals that he explored the possibility of gravitational lensing 3 years before completing his general theory of relativity. On the basis of preliminary insights into this theory, Einstein had already derived the basic features of the lensing effect. When he finally published the very same results 24 years later, it was only in response to prodding by an amateur scientist.

Journal Article↗