Use of Fmoc-N-(2-hydroxy-4-methoxybenzyl) amino acids in peptide synthesis

The use of N, O-bisFmoc-N-(2-hydroxy-4-methoxybenzyl) amino acid derivatives in the synthesis of peptides with difficult sequences has already been described. With these amino acid derivatives the reversible protecting group 2-hydroxy-4-methoxybenzyl (Hmb) for the backbone amide bonds of peptide chains is introduced, and thus the aggregation due to hydrogen-bond interchain association is inhibited. This paper describes the synthesis and use of Fmoc-N-(2-hydroxy-4-methoxybenzyl)amino acid derivatives as an alternative means of introducing Hmb backbone protection. These new monoFmoc derivatives were obtained in higher yield than the bisFmoc derivatives. Coupling yields to the amino peptide resin were the same as those obtained with bisFmoc derivatives, under the TBTU/HOBt/DIEA conditions. We also compared different syntheses of a difficult peptide with the Fmoc approach [triple coupling, capping, use of chaotropic agents, backbone protection using monoFmoc (Hmb)Ala] and with optimized Boc chemistry. Both the backbone protection and optimized Boc chemistry approaches gave the desired product in excellent yield and purity. © Munksgaard 1997.     

LIVER BIOPSY VERSUS ULTRASOUND IN METHOTREXATE-TREATED PSORIASIS: A DECISION ANALYSIS

Before starting methotrexate therapy for cases of recalcitrant psoriasis, a liver biopsy has been usual in order to exclude cirrhosis and moderate or severe fibrosis, which are contraindications for methotrexate treatment. As mortality and morbidity of liver biopsy are not negligible, and as this invasive procedure is unpleasant for the patient and urges clinical admission, we evaluated the possibility of ruling out severe liver pathology by means of ultrasonography, which we compared to liver biopsy. We made this comparison by means of a decision tree. The advantages of this analysis are the clear definition of the decision problem and its alternatives, and the possibility of calculating the risk of each alternative, thus being able to choose the best diagnostic method. In this study, the results of various research groups are discussed, in which liver biopsy and liver ultrasound were compared. In our decision tree we used some of these results and other assumptions, based on comparable studies. We varied the biopsy mortality and the sensitivity of ultrasound to show the change in the risk of each alternative. Our analysis shows that the differences of expected values between the liver biopsy branch and the ultrasonography branch are relatively small. Therefore, we advise each center, which has at its disposal a specialist in liver ultrasonography, to re-evaluate its guidelines with regard to the detection of severe liver pathology before starting methotrexate for the treatment of psoriasis.     

Ostial PV Isolation:

Pulmonary vein (PV) isolation by elimination of spike potentials has been reported to cure drug refractory atrial fibrillation. Because of the heterogenous morphology of the PVs, sequential electroanatomic reconstruction of the PVs was performed in 39 patients (group A), who underwent subsequent PV isolation by interruption of all conductive myocardial fibers by distinct RF current applications using a "lasso" approach. In group B (157 patients), only biplane two-dimensional fluoroscopy was performed to guide the diagnostic and the ablation catheters. After reprocedures (in 7% of patients in group A and 22% of group B), which depicted a recurrence of a spike potential inside or at the ostium of  >1 previously isolated PV in all restudied patients, stable sinus rhythm was documented in 69% of patients in group A and 60% of patients in group B. Reasons for the relapse of the previously eliminated spike potentials include a temporary ablation effect and a too distal interruption of the conducting myocardial fiber. Detailed knowledge of the individual three-dimensional morphology enhanced the clinical success rate of PV isolation but is time-consuming using CARTO   (8.0 ± 1.7 vs 5.0 ± 1.6, P < 0.001)   . Further technical improvement to fuse the individual three-dimensional anatomy and the electrophysiological markers to a composed "electroanatomic" map may overcome this limitation in the future. (PACE 2003; 26[Pt. II]:1624–1630)     

Perinatal epidemiology in Belgium

Data on the civil registration of all births and deaths recordedin 1987 in Belgium were analysed following WHO rules. The followingstatistics with significant regional variations were recorded:2.5% of teenage pregnancies, 7% of late pregnancies (35 years),6.1% of low birth weights and 5.3% of preterm deliveries. Pretermbirth rates did not improve during the last decade and are higherthan in neighbouring countries. Infant mortality rate is 9.74per 1000. This rate has remained unchanged since the early 1980sbut the relative importance of post-neonatal mortality is increasing.Congenital anomalies account for 26% of all infant deaths followedby the sudden infant death syndrome (17%). Maternal conditionssuch as eclampsia are related to 29% of the infants' deaths.     

Pulmonary Response to Toner upon Chronic Inhalation Exposure in Rats

Pulmonary Response to Toner upon Chronic Inhalation Exposurein Rats. MUHLE, H., BELLMANN, B., CREUTZENBERG, O., DASENBROCK,C., ERNST, H., KILPPER, R., MACKENZIE, J. C., MORROW, P., MOHR,U., TAKENAKA, S., AND MERMELSTEIN, R., Fundam. Appl. Toxicol.17, 280–299. A chronic inhalation study of a test tonerwas conducted by exposure of groups of F-344 rats for 6 hr/day,5 days/week for 24 months The test toner was a special Xerox9000 type xerographic toner, enriched in respirable-sized particlescompared to commercial toner, such that it was about 35% respirableaccording to the ACGlH criteria. The target test aerosol exposureconcentrations were 0, 1.0 (low), 4.0 (medium), and 16.0 (high)mg/m³. Titamum dioxide (5 mg/m³) and crystalline silicon dioxide(1 mg/m³), used as negative and pasitive controls for fibrogenicity,were also evaluated. Inhalation of the test toner or the controlmaterials showed no signs of overt toxicity. Body weight, clinicalchemistry values, food consumption, and organ weights were normalin the toner- and TiO₂-exposed groups, except for a 40% increasein lung weight in the toner highexposure group. All of the changesin the toner-exposed groups were restricted to the lungs orassociated lymph nodes. A chronic inflammatory response wasevident from the bronchoalveolar lavage parameters for the tonerhigh-exposure group. The incidence of primary lung tumors wascomparable among the three toner-exposed groups and the TiO²-exposed,and air-only controls, as well as consistent with historicalbackground levels A mild to moderate degree of lung fibrosiswas observed in 92% of the rats in the toner high-exposure group,and a minimal to mild degree of fibrosis was noted in 22% ofthe animals in the toner high-exposure group. The pulmonarychanges in the toner high-exposure group were smaller in magnitudethan those found in the crystalline silica-exposed group. Thecomparative fibrogenic potency of TiO², toner, and SiO² wasestimated to be 1:5:418 using a dasimetric model and assuminga common mechanistic basis. There were no pulmonary changesof any type at the toncr low-exposure level, which is most relevantin regard to potential human exposures The lung alterationsin the toner high-exposure group are interpreted in terms of"lung overloading," a generic response of the respiratory systemto saturation of its detoxification capacity. The maximum tolerateddose (MTD) criterion was met at the toner high (16 mg/m³)-exposurelevel.     

The Reduction of Methemoglobin in Erythrocytes of a Patient with Congenital Methemoglobinemia, Subjects with Erythrocyte Glucose-6-Phosphate Dehydrogenase Deficiency, and Normal Individuals

The pathways for the reduction of methemoglobin to hemoglobin that aredependent upon the generation of reduced pyridine nucleotides were studiedin normal human erythrocytes, in erythrocytes deficient in G-6-PD activityand in erythrocytes of a subject with congenital methemoglobinemia. Reduction of methemoglobin, produced by treatment with nitrite, occurred atequivalent rates in normal and G-6-PD deficient erythrocytes, but failed tooccur in the erythrocytes of the patient with congenital methemoglobinemiaupon incubation with glucose or inosine. The DPNH-utilizing diaphorase-likesystem was normal in hemolysates of G-6-PD deficient erythrocytes, but wasmarkedly deficient in hemolysates of erythrocytes of the subject with congenital methemoglobinemia. The marked acceleration of methemoglobinreduction that occurred upon the addition of methylene blue to normal erythrocytes and to the erythrocytes of the woman with congenital methemoglobinemia did not occur with G-6-PD deficient erythrocytes. The TPNH-utilizing methemoglobin reductase system was normal in hemolysates oferythrocytes of the patient with congenital methemoglobinemia, but was reduced to about 50 per cent of normal activity in hemolysates of G-6-PD deficient erythrocytes.

The reduction of methemoglobin to hemoglobin in intact normal and G-6-PD deficient human erythrocytes probably proceeds by way of a DPNH-utilizing, diaphorase-like system that is deficient in the erythrocytes of onetype of congenital methemoglobinemia. The TPNH-utilizing methemoglobinreductase appears to be a reserve system that requires an artificial electroncarrier, such as methylene blue, to become fully effective in reducing methemoglobin to hemoglobin. The TPNH-methemoglobin reductase system isimpaired in G-6-PD deficient erythrocytes not only because of a deficientsource of TPNH, but, perhaps, also because of a defect in this methemoglobinreductase system itself.

Accepted on December 11, 1962     

THE SEMI-PROPORTIONAL HAZARDS MODEL REVISITED: PRACTICAL REPARAMETRIZATIONS

Reformulations of the semi-proportional hazards model are outlined making estimation and testing of stratum-covariate interaction effects easily accessible within the framework of the stratified Cox proportional hazards model. The method is illustrated by a practical analysis of variables influencing bronchial responsiveness with data from the Hordaland study of obstructive lung disease.     

Cutaneous immunofluorescence studies in bowel bypass syndrome

Five patients that developed a multisystem disease after bowel bypass surgery for the treatment of obesity were studied. Patients developed a non-pruritic papular eruption following bypass surgery. Immunofluorescence studies were done on (1) an early skin lesion, (2) from uninvolved sun-exposed skin from the dorsum of left wrist, and (3) uninvolved non-sun-exposed skin from the buttock. Deposition of immunoglobulin (Ig) and/or complement (C) was seen along the dermoepidermal (DE) junction in the skin from the early lesions and uninvolved sun-exposed skin in all five patients. No deposition of Ig and/or C was seen along the DE junction in uninvolved non-sun-exposed skin or in the blood vessels of any of the sections studied. Later, in all five patients, the bowel was restored to normal continuity. In repeat biopsies of the same sites the earlier observations were no longer present. This study indicates that DE junction deposition of Ig and/or C is a dynamic process, and supports the hypothesis that immune mechanisms may play an important role in the pathogenesis of bowel bypass syndrome.     

Hereditary Hemolytic Anemia Associated With Abnormal Membrane Lipids: Mechanism of Accumulation of Phosphatidyl Choline

In order to study the mechanism of theaccumulation of phosphatidyl choline(PC) in erythrocytes with abnormal erythrocyte phospholipids from patientswith a hereditary hemolytic anemia, thephospholipids of the erythrocytes werelabeled radioactively. Labeling of phosphatides was achieved by both passiveequilibration with preformed phosphatides, and active "acylase"-mediated incorporation of fatty acid (FA) in thepresence of glucose, ATP and coenzymeA. The labeled cells were then reincubated in fresh compatible sera and thecatabolism of the labeled erythrocytephospholipids was followed. In addition,total acylase capacity of erythrocytestroma was determined under optimalconditions in a system with excesslysophosphatide, FA, ATP, CoA, andMg⁺⁺. No differences in passive uptakeor release of phosphatides were found between the patients’ erythrocytes andcomparable reticulocyte-rich controls. Onthe other hand, overall active incorporation of FA into PC was abnormally increased in the patients’ erythrocytes,whereas incorporation of FA intophosphatidyl-ethanolamine (PE) was decreased. However, acylase capacity forboth lysophosphatidylcholine (LPC) andlysophosphatidylethanolamine (LPE) wasnormal in the patients’ cells. This apparent paradox could be explained by thesubsequent turnover of actively incorporated PC-FA which was found to bereduced. A brief labeling experiment designed to approximate pulse-chase conditions and to label primarily PC showed aconsiderable inhibition of the subsequenttransfer of PC-FA to PE upon reincubation in fresh serum. This transfer haspreviously been shown to be responsiblefor a significant portion of PC-FA catabolism. Reincubation in hyperlipemicsera obtained from patients with liverdisease or artificially enriched with PCdid not influence the abnormal outflow ofphosphatide-FA in actively labeled cells.The findings were consistent with theconcept that PC accumulated in thesecells because of a defect in the catabolismof actively incorporated PC-FA. This defect appeared to be in the transfer ofPC-FA to PE prior to final release fromthe cell. Passive exchange pathways andthe active anabolic acylase pathway werenot abnormal in these patients’ erythrocytes.

Submitted on March 4, 1971 Revised on May 4, 1971 Accepted on May 10, 1971