On vitamin B1 metabolism in avitaminosis and its correction with thiamine and taurine

The levels of phosphate esters and the activities of thiamine biotransformation enzymes in the blood and tissues of albino rats were studied during oxythiamine-induced B1 deficiency and after metabolic correction with thiamine and taurine. Among thiamine phosphates, the most informative indicators of thiamine deficiency were shown to be triphosphate esters and free thiamine diphosphate. The biosynthetic enzymes thiamine kinase and thiamine diphosphate kinase played a decisive role in maintaining the initial rate and in recovering the physiologically active forms of vitamin B1. The activation of hydrolytic enzymes of thiamine phosphate esters occurred by producing abundant free thiamine diphosphate and thiamine triphosphate. Within the first hours, taurine favoured the acceleration of phosphoester biosynthesis and, accumulating in the tissues, inhibited vitamin phosphorylation reactions.     

Characterization of the mutant visual pigment responsible for congenital night blindness: a biochemical and Fourier-transform infrared spectroscopy study

A mutation in the gene for the rod photoreceptor molecule rhodopsin causes congenital night blindness. The mutation results in a replacement of Gly90 by an aspartic acid residue. Two molecular mechanisms have been proposed to explain the physiology of affected rod cells. One involves constitutive activity of the G90D mutant opsin [Rao, V. R., Cohen, G. B., & Oprian, D. D. (1994) Nature 367, 639-642]. A second involves increased photoreceptor noise caused by thermal isomerization of the G90D pigment chromophore [Sieving, P. A., Richards, J. E., Naarendorp F., Bingham, E. L., Scott, K., & Alpern, M. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 880-884]. Based on existing models of rhodopsin and in vitro biochemical studies of site-directed mutants, it appears likely that Gly90 is in the immediate proximity of the Schiff base chromophore linkage. We have studied in detail the mutant pigments G90D and G90D/E113A using biochemical and Fourier-transform infrared (FTIR) spectroscopic methods. The photoproduct of mutant pigment G90D, which absorbs maximally at 468 nm and contains a protonated Schiff base linkage, can activate transducin. However, the active photoproduct decays rapidly to opsin and free all-trans-retinal. FTIR studies of mutant G90D show that the dark state of the pigment has several structural features of metarhodopsin II, the active form of rhodopsin. These include a protonated carboxylic acid group at position Glu113 and increased hydrogen-bond strength of Asp83. Additional results, which relate to the structure of the active G90D photoproduct, are also reported. Taken together, these results may be relevant to understanding the molecular mechanism of congenital night blindness caused by the G90D mutation in human rhodopsin.     

Functional analysis of the placenta-specific enhancer of the human glycoprotein hormone alpha subunit gene. Emergence of a new element

Placental expression of the alpha subunit gene of the human glycoprotein hormones requires a multicomponent enhancer composed of tandem cAMP-response elements and an adjacent upstream regulatory element. Based on recent studies indicating that the upstream regulatory element includes binding sites for more than one protein, we investigated how functional activity correlated with these binding sites. Through extensive replacement mutagenesis of the native promoter regulatory region, we provide the first functional map of the upstream regulatory element. Within this region, we find that distinct proteins interact with three overlapping binding sites. While each site is functionally significant, no single site is essential or displays clear dominance. This is surprising since one of the sites binds a placenta-specific protein that heretofore has been regarded as essential for activity of the human alpha subunit placenta-specific enhancer. Consequently, our refined functional map of the upstream regulatory element reveals a complex combinatorial code that directs expression of the human alpha subunit gene to placenta.     

Acquisition of CD24 expression by Lin-CD43+B220(low)ckit(hi) cells coincides with commitment to the B cell lineage

The present study describes three subsets of bone marrow-derived Lin CD43+B220(low) (B220(low)) progenitor cells which represent distinct stages in hematopoietic development. These populations differ in their expression of CD24 and ckit and the occurrence of IgH gene rearrangement. B220(low) CD24-ckit(hi) progenitors have their IgH loci in germ-line configuration and are multipotent since they can give rise to B cells, T cells and myeloid cells. B220lowckit(hi) cells which have acquired CD24 expression have retained IgH loci in germ-line configuration and the ability to generate B cells, however, they have lost the ability to generate T cells and myeloid cells. Thus acquisition of CD24 by B220(low) cells occurs concurrently with the transition from a multipotent to a lineage-restricted progenitor population. B220(low)CD24+ cells expressing low levels of ckit are also lineage restricted, giving rise to only B cells and have begun D-J(H) rearrangement, implying that initiation of IgH rearrangement coincides with the down-regulation of ckit expression.     

Knowledge and attitudes of health-care providers toward cancer pain management: a comparison of physicians, nurses, and pharmacists in the state of New Hampshire

The knowledge and attitudes toward cancer pain management of physicians, nurses, and pharmacists in the state of New Hampshire were examined through the use of a statewide survey. Many of the providers who completed the survey, and thus indicated that they treated patients with cancer pain on a regular basis, were not pain or oncology specialists. Most of these providers were quite well informed about the fundamentals of cancer pain management. Approximately 90% of providers in all three groups were not concerned about addiction among cancer patients. Yet, there was a small percentage of providers who responded in less than optimal ways to items dealing with opioid pharmacology, pain assessment, and the importance of pain relief. Comparison of responses among provider groups indicated that nurses were the most knowledgeable and pharmacists the least knowledgeable about pain assessment. Physicians were the most knowledgeable regarding opioid pharmacology but seemed the least committed to providing optimal pain relief. Further analysis identified a small group of physicians that included a disproportionately high percentage of family practitioners and surgeons who consistently responded in less than optimal ways to items dealing with the importance of pain relief. The results of this study indicate a continuing need for broad-based educational programs in cancer pain management and for new initiatives focused on practitioners who see relatively few cancer patients and may have difficulty accessing traditional educational programs.     

Upregulation of aquaporin 2 water channel expression in pregnant rats

Water retention is characteristic of pregnancy but the mechanism(s) of the altered water metabolism has yet to be elucidated. The collecting duct water channel, aquaporin 2 (AQP2), plays a pivotal role in the renal water regulation, and we hypothesized that AQP2 expression could be modified during pregnancy. Sprague-Dawley female rats were studied on days 7 (P7), 14 (P14), and 20 (P20) of pregnancy, and expression of AQP2 in papillae was examined. Nonpregnant (NP) littermates were used as controls. Plasma osmolalities were significantly lower in pregnant rats by day 7 of gestation (P7 283.8+/-1.82, P14 284.3+/-1.64, P < 0.001, P20 282. 4+/-1.32, P < 0.0001, vs. NP 291.8+/-1.06 mosmol/kgH2O). However, plasma vasopressin concentrations in pregnant rats were not significantly different than in nonpregnant rats (NP 1.03+/-0.14, P7 1.11+/-0.21, P14 1.15+/-0.21, P20 1.36+/-0.24 pg/ml, NS). The mRNA of AQP2 was increased early during pregnancy: AQP2/beta actin: P7 196+/-17.9, P14 200+/-6.8, and P20 208+/-15.5%, P < 0.005 vs. NP (100+/-11.1%). AQP2 protein was also increased during pregnancy: AQP2 protein: P7 269+/-10.0, P14 251+/-12.0, P < 0.0001, and P20 250+/-13.6%, P < 0.001 vs. NP (100+/-12.5%). The effect of V2 vasopressin receptor antagonist, OPC-31260, was then investigated. AQP2 mRNA was suppressed significantly by OPC-31260 administration to P14 rats (AQP2/beta actin: P14 with OPC-31260 39.6+/-1.7%, P < 0.001 vs. P14 with vehicle) and was decreased to the same level of expression as NP rats receiving OPC-31260. Similar findings were found with the analysis of AQP2 protein. The decreased plasma osmolality of P14 rats was not modified by OPC-31260. The results of the study indicate that upregulation of AQP2 contributes to the water retention in pregnancy through a V2 receptor-mediated effect. In addition to vasopressin, other factors may be involved in this upregulation.     

Synthesis and in vitro antimalarial activity of sulfone endoperoxides

A series of 4,8-dimethyl-4-phenylsulfonylmethyl-2,3-dioxabicyclo[3.3.1]+ ++nonanes, carrying a variety of substituents at position-8 (4) were prepared by a short and efficient method from R-(+)-limonene. Key reactions include thiol oxygen cooxidation, and alkylation and acylation of a sterically hindered tertiary alcohol compatible with the endoperoxy functionality. Some of compounds 4, which are structurally related to yingzhaosu A (2), were found to exhibit in vitro antimalarial activity comparable to that of artemisinin (1) and superior to that of arteflene (3).     

Effects of low radiation doses on Chinese hamster cells

The induction of cytogenetic damages after irradiation with single dose of gamma-rays (0.1-2 Gy) have been studied. It is shown non-linear curve for the induction of chromosome aberrations, detected by anaphase method. After irradiation in S-stage of the cell cycle at dose below 0.2 Gy the cells were more radiosensitive than after irradiation with doses 0.3-2 Gy. Between the phases of high radiosensitivity and radioresistance the reversal dose-effect relation was observed. This phenomenon was not marked for the cells after irradiation in G2-stage of the cell cycle. It is possible, this results could reflect an induced radioresistance at low dose of irradiation.