Cloning of a cDNA for a second retinol dehydrogenase type II. Expression of its mRNA relative to type I

A retinol dehydrogenase, RoDH(1), which recognizes holo-cellular retinol-binding protein (CRBP) as substrate, has been cloned, expressed, and identified as a short-chain dehydrogenase/reductase (Chai, X., Boerman, M. H. E. M., Zhai, Y., and Napoli, J. L. (1995) J. Biol. Chem. 270, 3900-3904). This work reports the cloning and expression of a cDNA encoding a RoDH isozyme, RoDH(II). The predicted amino acid sequence verifies RoDH(II) as a short-chain dehydrogenase/reductase, 82% identical with RoDH(I). RoDH(II) recognized the physiological form of retinol as substrate, CRBP, with a Km of 2 mM. Similar to microsomal RoDH and RoDH(I), RoDH(II) had higher activity with NADP rather than NAD, was stimulated by ethanol and phosphatidyl choline, was not inhibited by the medium-chain alcohol dehydrogenase inhibitor 4-methylpyrazole, but was inhibited by phenylarsine oxide and the short-chain dehydrogenase/reductase inhibitor carbenoxolone. Northern blot analysis detected RoDH(I) and RoDH(II) mRNA only in rat liver, but RNase protection assays revealed RoDH(I) and RoHD(II) mRNA in kidney, lung, testis, and brain. These data indicate that short-chain dehydrogenases/reductase isozymes expressed tissue-distinctively catalyze the first step of retinoic acid biogenesis from the physiologically most abundant substrate, CRBP.

Kinetochore microtubule dynamics and the metaphase-anaphase transition

We have quantitatively studied the dynamic behavior of kinetochore fiber microtubules (kMTs); both turnover and poleward transport (flux) in metaphase and anaphase mammalian cells by fluorescence photoactivation. Tubulin derivatized with photoactivatable fluorescein was microinjected into prometaphase LLC-PK and PtK1 cells and allowed to incorporate to steady-state. A fluorescent bar was generated across the MTs in a half-spindle of the mitotic cells using laser irradiation and the kinetics of fluorescence redistribution were determined in terms of a double exponential decay process. The movement of the activated zone was also measured along with chromosome movement and spindle elongation. To investigate the possible regulation of MT transport at the metaphase-anaphase transition, we performed double photoactivation analyses on the same spindles as the cell advanced from metaphase to anaphase. We determined values for the turnover of kMTs (t1/2 = 7.1 +/- 2.4 min at 30 degrees C) and demonstrated that the turnover of kMTs in metaphase is approximately an order of magnitude slower than that for non-kMTs. In anaphase, kMTs become dramatically more stable as evidenced by a fivefold increase in the fluorescence redistribution half-time (t1/2 = 37.5 +/- 8.5 min at 30 degrees C). Our results also indicate that MT transport slows abruptly at anaphase onset to one-half the metaphase value. In early anaphase, MT depolymerization at the kinetochore accounted, on average, for 84% of the rate of chromosome movement toward the pole whereas the relative contribution of MT transport and depolymerization at the pole contributed 16%. These properties reflect a dramatic shift in the dynamic behavior of kMTs at the metaphase-anaphase transition. A release-capture model is presented in which the stability of kMTs is increased at the onset of anaphase through a reduction in the probability of MT release from the kinetochore. The reduction in MT transport at the metaphase-anaphase transition suggests that motor activity and/or subunit dynamics at the centrosome are subject to modulation at this key cell cycle point.

LAR-PTPase cDNA transfection suppression of tumor growth of neu oncogene-transformed human breast carcinoma cells

The incidence of amplification of neu oncogene-encoded protein tyrosine kinase in human breast cancer strongly supports the concept that protein tyrosine phosphorylation and dephosphorylation are key regulatory mechanisms in the proliferation, differentiation, and neoplastic transformation of breast epithelial cells. We examined the potential regulatory role of protein tyrosine phosphatases (PTPases) in the maintenance of cellular tyrosine phosphorylation by the introduction of leukocyte common-antigen-related PTPase (LAR-PTPase) cDNA into a tumorigenic human breast carcinoma cell line that overexpressed p185neu protein tyrosine kinase. The transfected human breast carcinoma cells expressed elevated levels of LAR-PTPase as assessed by reverse transcription-polymerase chain reaction and by analysis of LAR-PTPase protein. The LAR-PTPase-transfected human breast carcinoma cells had a significantly (P < 0.01) slower proliferation rate in vitro than control-transfected cells. When LAR-PTPase-transfected cells were inoculated into athymic nude mice, a consistent and significant (P < 0.05) suppression of tumor growth was observed. These results provide evidence that a specific PTPase, LAR-PTPase, can play a suppressive regulatory role in the tumor growth of human breast carcinoma cells that overexpress p185neu protein tyrosine kinase.

Enzymes and binding proteins affecting retinoic acid concentrations

Free retinoids suffer promiscuous metabolism in vitro. Diverse enzymes are expressed in several subcellular fractions that are capable of converting free retinol (retinol not sequestered with specific binding proteins) into retinal or retinoic acid. If this were to occur in vivo, regulating the temporal-spatial concentrations of functionally-active retinoids, such as RA (retinoic acid), would be enigmatic. In vivo, however, retinoids occur bound to high-affinity, high-specificity binding proteins, including cellular retinol-binding protein, type I (CRBP) and cellular retinoic acid-binding protein, type I (CRABP). These binding proteins, members of the superfamily of lipid binding proteins, are expressed in concentrations that exceed those of their ligands. Considerable data favor a model pathway of RA biosynthesis and metabolism consisting of enzymes that recognize CRBP (apo and holo) and holo-CRABP as substrates and/or affecters of activity. This would restrict retinoid access to enzymes that recognize the appropriate binding protein, imparting specificity to RA homeostasis; preventing, e.g. opportunistic RA synthesis by alcohol dehydrogenases with broad substrate tolerances. An NADP-dependent microsomal retinol dehydrogenase (RDH) catalyzes the first reaction in this pathway. RDH recognizes CRBP as substrate by the dual criteria of enzyme kinetics and chemical crosslinking. A cDNA of RDH has been cloned, expressed and characterized as a short-chain alcohol dehydrogenase. Retinal generated in microsomes from holo-CRBP by RDH supports cytosolic RA synthesis by an NAD-dependent retinal dehydrogenase (RalDH). RalDH has been purified, characterized with respect to substrate specificity, and its cDNA has been cloned. CRABP is also important to modulating the steady-state concentrations of RA, through sequestering RA and facilitating its metabolism, because the complex CRABP/RA acts as a low Km substrate.

Cloning of a cDNA for liver microsomal retinol dehydrogenase. A tissue-specific, short-chain alcohol dehydrogenase

Retinoic acid, a hormone biosynthesized from retinol, controls numerous biological systems by regulating eukaryotic gene expression from conception through death. This work reports the cloning and expression of a liver cDNA encoding a microsomal retinol dehydrogenase (RoDH), which catalyzes the primary and rate-limiting step in retinoic acid synthesis. The predicted amino acid sequence and biochemical data obtained from the recombinant enzyme verify it as a short-chain alcohol dehydrogenase. Like microsomal RoDH, the recombinant enzyme recognized as substrate retinol bound to cellular retinol-binding protein, had higher activity with NADP rather than NAD, was stimulated by ethanol or phosphatidylcholine, was not inhibited by 4-methylpyrazole, was inhibited by phenylarsine oxide and carbenoxolone and localized to microsomes. RoDH recognized the physiological form of retinol, holocellular retinol-binding protein, with a Km of 0.9 microM, a value lower than the approximately 5 microM concentration of holocellular retinol binding protein in liver. Northern and Western blot analyses revealed RoDH expression only in rat liver, despite enzymatic activity in liver, brain, kidney, lung, and testes. These data suggest that tissue-specific isozyme(s) of short chain alcohol dehydrogenases catalyze the first step in retinoic acid biogenesis and further strengthen the evidence that the "cassette" of retinol bound to cellular retinol-binding protein serves as a physiological substrate.

Long-term genome stability and minimal genotypic and phenotypic alterations in HPV16 E7-, but not E6-, immortalized human uroepithelial cells

Parameters of genome instability and morphological alterations associated with cell transformation were studied in an isogeneic set of clonal human uroepithelial cell (HUC) lines immortalized by the human papilloma virus 16 (HPV16) E6 and/or E7 gene(s). HPV16 E6 binds p53, leading to rapid degradation of p53, whereas E7 binds and alters pRb and other proteins. We report that two independent E7-immortalized HUC lines showed minimal phenotypic or genotypic alterations, except that both lines contained amplification of 20q DNA sequences and a greater polyploidization at an early passage. The E7-immortalized HUC line resembled normal HUC lines, except that they failed to senesce. In contrast, the E6-immortalized HUC lines were morphologically altered, contained numerous random chromosome aberrations, and showed unstable evolving karyotypes with passage in culture. No amplified DNA sequences were detected in E6-immortalized HUC lines. Instead, clonal losses of chromosome regions (i.e., -3p, -6q, -9p), putatively containing tumor suppressor or senescence genes, accompanied the E6-HUC immortalization event. E6-immortalized HUC lines showed transformed phenotypes similar to E6/E7-HUC lines. The difference in genome stability between E6- and E7-immortalized HUC was highly significant statistically (p-value < 10(-6). Thus, the HPV16 E7 gene led to HUC immortalization by a pathway that blocked cellular senescence, but did not disrupt genome stability. These results implicate p53 loss, but not pRb alteration, in genome destabilization.

Quantitative determination of the proportion of microtubule polymer present during the mitosis-interphase transition

We have developed a new method for determining levels of tubulin polymer, based on quantitative fluorescence detection of x-rhodamine tubulin microinjected into living cells and we have applied this method to analysis of the mitosis-interphase transition. LLC-PK cells in interphase and mitosis were microinjected, then cooled and rewarmed to drive tubulin incorporation. Total tubulin fluorescence in individual, living cells was quantified using a cooled, scientific grade CCD image sensor. Cells were then washed and lysed into a microtubule-stabilizing buffer to extract the soluble pool. Total tubulin polymer fluorescence was determined for the extracted cells in the same way as for living cells. Fluorescence images were corrected by flat-fielding and background subtraction. The ratio of extracted cell fluorescence/living cell fluorescence for individual cells, was taken as the proportion of tubulin as polymer. Cells in M-phase, G1 and random interphase were analyzed. G1 cells had almost the same proportion as random interphase cells. Mitotic cells gave a value of 90 +/- 5% of G1 cells at 37 degrees C. Within M-phase, levels of tubulin as polymer in metaphase and early anaphase were not significantly different. In contrast to the general expectation of microtubule depolymerization at anaphase onset, these results indicate that as cells exit mitosis, the overall proportion of tubulin as polymer does not change dramatically even though the mitotic spindle disassembles. We conclude that the mitosis-interphase transition is accompanied by a redistribution of tubulin at an essentially constant polymer level. Therefore, a global shift to depolymerization conditions is not the driving force for anaphase chromosome movement.

Lamin B distribution and association with peripheral chromatin revealed by optical sectioning and electron microscopy tomography

We have used a combination of immunogold staining, optical sectioning light microscopy, intermediate voltage electron microscopy, and EM tomography to examine the distribution of lamin B over the nuclear envelope of CHO cells. Apparent inconsistencies between previously published light and electron microscopy studies of nuclear lamin staining were resolved. At light microscopy resolution, an apparent open fibrillar network is visualized. Colocalization of lamin B and nuclear pores demonstrates that these apparent fibrils, separated by roughly 0.5 micron, are anti-correlated with the surface distribution of nuclear pores; pore clusters lie between or adjacent to regions of heavy lamin B staining. Examination at higher, EM resolution reveals that this apparent lamin B network does not correspond to an actual network of widely spaced, discrete bundles of lamin filaments. Rather it reflects a quantitative variation in lamin staining over a roughly 0.5-micron size scale, superimposed on a more continuous but still complex distribution of lamin filaments, spatially heterogeneous on a 0.1-0.2-micron size scale. Interestingly, lamin B staining at this higher resolution is highly correlated to the underlying chromatin distribution. Heavy concentrations of lamin B directly "cap" the surface of envelope associated, large-scale chromatin domains.

TCM treatment of male infertility due to seminal abnormality--a clinical observation of 82 cases

82 male patients of infertility due to seminal abnormality were treated by Ju Jing Powder with a total effective rate of 85.4%. The sperm density in seminal fluid, the total sperm number in a single ejaculation and the activity rate of sperms markedly improved as compared with those before treatment (P less than 0.01), especially the grading of sperm motility.

Observations on the treatment of coronary heart disease by kuo guan qu yu ling

Based on the therory of promoting flow of qi and dispersing blood stasis, the KUO GUAN QU YU LING coronary--dilating and stagnation--dispersing) powder in capsules were prepared for the treatment of 60 cases of coronary heart disease. After a 30 day course of treatment, cardiac ischemia was improved in 64.7% and the symptom of angina pectoris was relieved in 61.7% of the patients. This drug also acted to reduce blood lipids and to improve left cardiac function. Pharmacological study indicated that this preparation improved the tolerance of cardiac muscle against anoxia and prevented ventricular fibrillation and cardiac damage from ischemia.