Differences in the retinal GABA system among control, spastic mutant and retinal degeneration mutant mice

Immunocytochemical methods were used to compare the GABA system in control mice and two mutant strains: spastic which has reduced glycine receptors and retinal degeneration mutant in which the photoreceptors degenerate and reportedly have increased GABA and GAD levels. We found that the spastic mutant retina had reduced GABA-immunoreactivity (IR) in the proximal retina, reduced staining for GAD-1440 in the OPL, and reduced GABAA receptor staining in the OPL, compared to control. The retinal degeneration mutant retinas had enhanced GABA-IR throughout the retina, particularly in Müller cells, bipolar cells and IPL, and enhancement of GABAA receptor staining in the OPL, compared to control. The distributions of GABA-IR, GAD-1440-IR and GABAA receptor-IR in retinas of spastic mutant mice that also expressed the retinal degeneration phenotype resembled those found in retinas of mice that expressed only the retinal degeneration phenotype rather than those that expressed only the spastic mutation. No differences were observed among the conditions for GAD-65, GAD-67 or GABA-T. Our results with the spastic and retinal degeneration mutant mice demonstrate that attenuation in the glycinergic system and photoreceptor degeneration, respectively, is accompanied by alterations in different aspects of the GABA system, giving impetus for caution in the interpretation of experiments involving genetic manipulation of complex phenotypes.     

DNA mismatch repair in plants. An Arabidopsis thaliana gene that predicts a protein belonging to the MSH2 subfamily of eukaryotic MutS homologs

PURPOSE: To determine the impact of high-dose cytarabine (ARA-C) (HDAC) dose modification, based on renal function, on the incidence of neurotoxicity (NT). PATIENTS AND METHODS: We retrospectively analyzed the records of 256 patients treated with HDAC (> or = 2.0 g/m2 per dose) for acute myelogenous leukemia (AML) at the University of California, San Francisco (UCSF). From 1985 to 1994, a total of 358 cycles of HDAC were administered, using either a twice-daily schedule (n = 208) or a once-daily regimen (n = 48). In 1989, a dose-modification algorithm was initiated at our institution, which reduced ARA-C doses in the setting of renal insufficiency (RI). For patients with a serum creatinine (Cr) level of 1.5 to 1.9 mg/dL during treatment, or an increase in Cr during treatment (deltaCr) of 0.5 to 1.2 mg/dL, ARA-C was decreased to 1 g/m2 per dose. For patients with a Cr > or = 2.0 mg/dL or a deltaCr greater 1.2 mg/dL, the dose was reduced to 0.1 g/m2/d. RESULTS: Overall, the incidence of NT was 16% (34 of 208) for patients treated with twice-daily HDAC and 0% (none of 48) for patients treated with daily HDAC (P = .003). NT occurred more often in patients treated on a twice-daily schedule with 3 g/m2 per dose compared with 2 g/m2 per dose (25% v 8%; P = .009). NT occurred in 55% of the twice-daily-treated patients with RI, compared with 7% of those with normal renal function (P = .00001). In patients with RI, NT occurred in none of 11 dose-modified cycles versus five of 11 (45%) total unmodified cycles (P = .01). None of 14 patients treated with once-daily HDAC given during RI developed NT, compared to 55% of patients (23 of 42) receiving twice-daily HDAC during RI (P = .009). By univariate analysis, NT was not associated with patient age or serum alkaline phosphatase, but NT was significantly increased in patients treated with twice-daily HDAC when the serum bilirubin was > or = 2.0 mg/dL compared with twice-daily HDAC given when the total bilirubin was less than 2.0 mg/dL (33% v 14%; P = .017). Multivariate analysis confirmed that RI was the most significant risk factor associated with the development of NT. CONCLUSION: HDAC NT is strongly associated with RI. The risk of HDAC NT can be reduced by the following: (1) routinely reducing the ARA-C dose from 3 to 2 g/m2 per dose; (2) modifying the ARA-C dose based on daily Cr values; and (3) administering HDAC on a once-daily rather than twice-daily schedule.     

Determination of the nucleotide conformation in the productive enzyme-substrate complexes of RNA-depolymerases

Docking of ER-derived vesicles to the cis-Golgi compartment in yeast requires vesicle and target membrane receptors (v-SNAREs and t-SNAREs) and the GTPase Ypt1p. The t-SNARE Sed5p is complexed with Sly1p in vivo. The mutant form Sly1-20p rescues Ypt1p-lacking cells from lethality, suggesting an inhibitory function of Sly1p in v-SNARE/t-SNARE interaction. Using surface plasmon resonance spectroscopy, we found that Sed5p binds Sly1p and Sly1-20p with equally high affinity (K(D) = 5.13 x 10(-9) M and 4.74 x 10(-9) M, respectively). Deletion studies show that the N-terminal half of Sly1p rather than the C-terminus (harbouring the E532K substitution in Sly1-20p) is most critical for its binding to Sed5p. These data appear to argue for an active rather than an inhibitory role of Sly1p in vesicle docking.     

Respiratory manifestations of carbamazepine. Apropos of a case

A 14-year-old girl developed skin rash, fever and dyspnea. The chest roentgenogram showed diffuse reticulonodular infiltration. Pulmonary function tests revealed mild restrictive defect and blood oxygen pressure at 71 mm Hg. BAL showed increased cell counts with lymphocytosis at 15% and neutrophilia at 3%. Outcome was good after carbamazepine withdrawal and without corticosteroid therapy. Relapse was observed after patient-induced rechallenge.     

Post-translational processing in the Golgi plays a critical role in the trafficking of the luteinizing hormone/human chorionic gonadotropin receptor to the cell surface

Point mutations in the luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor have been shown to cause constitutive activation which results in precocious puberty in affected males. We introduced one of these mutations, Asp-556 --> Gly, into the rat LH/hCG receptor and demonstrated that the mutant receptor constitutively activated adenylate cyclase in transfected 293 T cells. The cell surface expression of the mutant receptor was lower than that of the wild type receptor. Pulse-chase studies showed that the 73-kDa precursor of both the mutant and wild type receptors was synthesized at comparable efficiencies. However, post-translational processing of the mutant receptor to the mature 92-kDa form, which has N-linked complex type oligosaccharide chains, was impaired. Sensitivity of the mutant receptor to peptide-N-glycanase F and endoglycosidase H, and insensitivity to sialidase indicated that the 73-kDa species represents the high mannose form that has not yet been trafficked through the medial and trans Golgi. Additionally, although the wild type receptor was palmitoylated, the mutant receptor was not. Although the high mannose 73-kDa species is capable of binding LH/hCG, our results show that post-translational processing in the Golgi is required for the mature 92-kDa receptor to reach the cell surface.     

Gastric polypoid lesions--illustrative cases and literature review

Currently, upper gastrointestinal endoscopies are frequently performed for patients with various gastrointestinal symptoms. From time to time, lumps and bumps in the stomach are encountered on endoscopy. Four cases of gastric polypoid lesions are presented. The classification, differentiation, and management approach to these lesions are discussed. Although there is consensus that all gastric adenomatous polyps should be removed, as should gastric hyperplastic polyps that are symptomatic and/or bear dysplastic foci on forceps biopsy, controversy still exists over the management of asymptomatic gastric hyperplastic polyps that do not bear any dysplastic focus on forceps biopsies. Endoscopic ultrasonography (EUS) has a promising role in the evaluation of gastric submucosal polypoid lesions.     

Predictive signs of discogenic lumbar pain on magnetic resonance imaging with discography correlation

STUDY DESIGN: The correlation between discogenic lumbar pain and disc morphology was investigated by using magnetic resonance imaging and discography. OBJECTIVES: To assess the various pathologic parameters seen on magnetic resonance imaging in patients with discogenic lumbar pain and to correlate them with observations on discography. SUMMARY OF BACKGROUND DATA: Although numerous previous studies on the subject have been performed, the correlations between various pathologic findings on magnetic resonance imaging and pain reproduction by provoked discography have not been explained fully. METHODS: One hundred and one lumbar discs in 39 patients were studied with magnetic resonance imaging and pain provocation discography. When pain reproduction under discography was concordant, various pathologic parameters on magnetic resonance imaging were analyzed by three statistical parameters to determine the associated magnetic resonance imaging findings. RESULTS: Radial tears commonly are demonstrated on magnetic resonance imaging in discs with concordant pain on discography. The presence of these tears is not a reliable predictor of a painful disc on discography. Although a high-intensity zone on T2-weighted images is a relatively reliable predictor of pain, the statistical values were lower than those in previous studies. Massive degeneration and severe disc height loss were rare in this population. These findings were good predictors of pain on disc injection. CONCLUSIONS: Although the lumbar intervertebral discs with posterior combined anular tears are likely to produce pain, the validity of these signs for predicting discogenic lumbar pain is limited.     

The von Hippel-Lindau tumor suppressor protein is required for proper assembly of an extracellular fibronectin matrix

Fibronectin coimmunoprecipitated with wild-type von Hippel-Lindau protein (pVHL) but not tumor-derived pVHL mutants. Immunofluorescence and biochemical fractionation experiments showed that fibronectin colocalized with a fraction of pVHL associated with the endoplasmic reticulum, and cold competition experiments suggested that complexes between fibronectin and pVHL exist in intact cells. Assembly of an extracellular fibronectin matrix by VHL-/- renal carcinoma cells, as determined by immunofluorescence and ELISA assays, was grossly defective compared with VHL+/+ renal carcinoma cells. Reintroduction of wildtype, but not mutant, pVHL into VHL-/- renal carcinoma cells partially corrected this defect. Finally, extracellular fibronectin matrix assembly by VHL-/- mouse embryos and mouse embryo fibroblasts (MEFs), unlike their VHL+/+ counterparts, was grossly impaired. These data support a direct role of pVHL in fibronectin matrix assembly.