Transbilayer movement of NBD-labeled phospholipids in red blood cell membranes: outward-directed transport by the multidrug resistance protein 1 (MRP1)

The outward movement (flop) of fluorescently labeled analogues of phosphatidylserine (PS) and phosphatidylcholine (PC) in human and murine red blood cells (RBC) was examined. 1-Oleoyl-2-[6(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]caproyl (C6-NBD) analogues of PS and PC were incorporated in the inner leaflet of the plasma membrane through the action of aminophospholipid translocase or through equilibration upon prolonged incubation, respectively. After removal of noninternalized probe, externalization of C6-NBD-PS or C6-NBD-PC from the inner to outer leaflet was monitored by continuous incubation of the cells in the presence of bovine serum albumin. Flop rates for both probes in intact human RBC were virtually identical (t1/2 approximately 1.5 h), confirming earlier findings by Bitbol et al. [Bitbol, M., et al. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 6783-6787] and Connor et al. [Connor, J., et al. (1992) J. Biol. Chem. 267, 19412-19417]. Flop activity in resealed RBC ghosts could only be found upon coinclusion of both ATP and oxidized glutathione (GSSG). Furthermore, flop in intact cells was sensitive to verapamil (IC50 = 5-7 microM), vincristine (IC50 = 20 microM), and indomethacin (IC50 = 50 microM), suggesting the involvement of proteins conferring multidrug resistance (MDR). Experiments with RBC from knock-out mice for multidrug resistance P-glycoproteins (Mdr1a/1b-/- and Mdr2-/-) and multidrug resistance protein 1 (Mrp1-/-) revealed that Mrp1 is responsible for the observed flop of the fluorescent lipid analogues. We found no indications for outward transport of endogenous PS by any of these drug-transporting proteins as measured by a sensitive prothrombinase assay. Neither aminophospholipid translocase nor Ca2+-induced lipid scramblase activities were affected in RBC of these knock-out mice. We conclude that lipid floppase activity, as detected with lipid probes, reflects the activity of MRP1 recognizing the modified lipid analogues as xenobiotics to be expelled from the cell.     

Annelid cytochrome P-450

Both classes of Annelida--Polychaeta and Clitellata--have been shown to contain cytochrome P-450. The metabolism of a number of aromatic hydrocarbons, drugs and pesticides by annelids required oxygen and NADPH, and was inhibited by a variety of cytochrome P-450 inhibitors. A number of types I and II substrates bound to the cytochrome P-450 in polychaete microsomes to give typical types I and II binding spectra. These results suggest that xenobiotics in annelids are metabolized by a typical cytochrome P-450 mixed function oxygenase. In addition to xenobiotics, annelid cytochrome P-450 systems are likely to function in the biosynthesis and metabolism of sterols and hormones found in annelids, such as cholesterol, ecdysteroids and eicosanoids. The primary source of cytochrome P-450 isolated to date from annelids has been intestinal microsomes. Cytochrome P-450 concentrations in these microsomes varied from 8 to 580 pmol mg-1 of protein. The only cytochrome P-450s purified from annelids were the three isomers isolated from microsomes of the oligochaete, Lumbricus terrestris, whose molecular masses were 48,000, 51,000 and 53,000 Da. Work on the induction of cytochrome P-450 in polychaetes by exposure to polycyclic aromatic hydrocarbons or polychlorinated biphenyls has given conflicting results, since some groups found induction after such exposure, but others found no induction. One possible explanation may be exposure to natural soil and sediments inducers, e.g. plant alkaloids, during feeding. Since gene and protein sequences have yet to be carried out on the cytochrome P-450 of any annelid, the relationship of annelid cytochrome P-450s to the 74 families of P-450 so far found, remains to be carried out.     

Variability in the interpretation of dimercaptosuccinic acid scintigraphy after urinary tract infection in children

Technetium-99m-dimercaptosuccinic acid (DMSA) scintigraphy is a frequently used diagnostic test in pediatric practice to assess the presence and severity of renal damage. Most commonly it is performed after urinary tract infection. The aim of this study was to investigate the variability in the interpretation of DMSA scans by pediatric nuclear medicine physicians in this clinical setting. METHODS: We selected all 441 scans from children with first-time urinary tract infection who presented between 1993 and 1995 to a pediatric casualty department and who are participants in a prospective cohort study. Two hundred and ninety-four scans were performed at a median time of 7 days after diagnosis, and 147 scans were from children who were free from further infection over a 1-yr follow-up period. Two experienced nuclear medicine physicians independently interpreted the 441 scans according to whether renal damage was present or absent and using the modified 4-level grading system for DMSA abnormality of Goldraich. Apart from being informed that urinary tract infection was the indication for DMSA scintigraphy, no other clinical information was given to the nuclear medicine physicians. The indices of variability used were the percentage of agreement and the kappa statistic. For the grading scale used, both measures were weighted with integers representing the number of categories from perfect agreement. Disagreement was analyzed for children, kidneys and kidney zones. RESULTS: There was agreement in 86% (kappa = 69%) for the normal-abnormal DMSA scan dichotomy, and the weighted agreement was 94% (weighted kappa = 82%) for the grading of abnormality. Disagreement of DMSA scan interpretation of > or =2 grades was present in three cases (0.7%). The same high level of agreement was present for patient, kidney and kidney zone comparisons. Agreement was not influenced by age or timing of scintigraphy after urinary tract infection. CONCLUSION: Two experienced nuclear medicine physicians showed good agreement in the interpretation of DMSA scintigraphy in children after urinary tract infection and using the grading system of Goldraich.     

Novel inhibitors of fungal protein synthesis produced by a strain of Graphium putredinis. Isolation, characterisation and biological properties

The isolation and structure determination of 6 analogues of the fungal protein synthesis inhibitor GR135402, from Graphium putredinis, is described. The relative potencies of the compounds as protein synthesis inhibitors and as in vitro antifungal agents provide interesting insights into the structure-activity relationships in this series.     

Cerebellar brain-derived neurotrophic factor-TrkB defect associated with impairment of eyeblink conditioning in Stargazer mutant mice

In the spontaneous ataxic mutant mouse stargazer, there is a selective reduction of brain-derived neurotrophic factor (BDNF) mRNA expression in the cerebellum. BDNF protein levels in the cerebellum are reduced by 70%. Despite normal levels of full-length and truncated TrkB receptor, constitutive and neurotrophin-4/5-induced tyrosine phosphorylation was significantly reduced in several signal transduction molecules, including phospholipase-Cgamma1, erk1, and erk2. Morphological examination revealed an increased number of external granule cells at postnatal day 15 and the presence of abnormal neurons resembling immature granule cells in the adult. These abnormalities are associated with a severe impairment in the acquisition of classical eyeblink conditioning, indicating cerebellar malfunction. Our data suggest that normal BDNF expression and TrkB signal transduction in the cerebellum are necessary for learning and plasticity in this model.     

Mohs micrographic surgery

Gene expression studies with in situ hybridization after focal brain ischemia indicate a variety of distinct anatomical patterns. An important question is to what extent such reactive gene expression correlates with neuronal damage or survival. To study these questions, we focused on two stressed-induced genes, heat shock protein 70 (HSP70) and growth-arrest and DNA damage-inducible gene (GADD) 45 mRNA, and we compared reactive changes in mRNA to loss of the constitutive signal for microtubule-associated protein 2 (MAP2) mRNA. A pixel-based image analysis of mRNA signals was carried out using a highly reproducible model of focal brain ischemia. A poly-l-lysine coated filament was used to occlude the origin of the middle cerebral artery (MCA) for 2 h in ventilated, normothermic rats. Brains were collected after 0, 1, 3 and 6 h, and 1, 3 and 7 days. In situ hybridization analysis was carried out for HSP70 mRNA, GADD45 mRNA and MAP2 mRNA. Autoradiographic data sets were averaged and co-mapped into a common template of the rat brain. These data sets were then compared on a pixel-by-pixel basis with previously acquired image data sets derived from quantitative studies of local cerebral blood flow (LCBF) (obtained at the end of 2-h ischemia) of and infarctive histopathology (obtained at 3 days) in the same focal ischemia model. HSP70 mRNA and GADD45 mRNA were grossly elevated in the hemisphere subjected to ischemia during the first day. Pixel-based analysis showed a strong correlation between HSP70 mRNA signals, the degree of early blood-flow reduction and the probability of histological infarction. GADD45 mRNA was expressed in a more variable fashion. Decreases in MAP2 mRNA signals at 1, 3 and 7 days correlated strongly with histological infarction. These co-mapping procedures allow us to conclude that HSP70 mRNA is a robust indicator of ischemic stress and histological outcome after 2 h of focal brain ischemia. The topographic features of GADD45 expression suggest its possible role in conferring resistance to ischemic injury. Finally, our results indicate that local decreases in constitutive MAP2 expression at 1 day and beyond may be used as a robust marker of tissue regions having a high probability of focal infarction.     

Restrictive dermopathy. Report of 12 cases. Dutch Task Force on Genodermatology

BACKGROUND: This study describes 12 cases of restrictive dermopathy seen during a period of 8 years by the Dutch Task Force on Genodermatology. We present these unique consecutive cases to provide more insight into the clinical picture and pathogenesis of the disease. OBSERVATIONS: Clinical features in more than 85% of these children were prematurity, fixed facial expression, micrognathia, mouth in O position, rigid and tense skin with erosions and denudations, and multiple joint contractures. Ten patients underwent histopathologic skin biopsy. The biopsy results showed flattening of rete ridges in all 10 patients, a thin dermis with collagen aligned parallel to the epidermis in 9 patients, and poorly developed dermal appendages in 9 patients. Additional findings in individual patients included blepharophimosis, inguinal skin tear, skin tear in the frontal neck area that developed during delivery, absent eyelashes, a wide ascendent aorta, and dextrocardia. Fibroblast cultures taken from 5 patients did not show abnormal alpha 2 beta 1 and alpha 1 beta 1 integrin expressions. CONCLUSIONS: The alleged rarity of restrictive dermopathy may be partially caused by medical unfamiliarity with this entity, despite its characteristic clinical and histopathologic picture. The pathogenesis of the disease still needs to be elucidated.