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H Reiber

Publications and source records attributed to H Reiber.

63 records · Page 4Linked to original sources
PubMed1978

Cholesterol-lipid interactions in membranes. The saturation concentration of cholesterol in bilayers of various lipids.

1. The integration of cholesterol in a lipid bilayer can be visualized by changes in the fluorescence properties of the probe N-phenyl-1-naphthylamine (NPN). An increasing cholesterol content in the lipid phase corresponds to decreasing fluorescence intensity of NPN and a short wave shift of the emission spectrum. 2. Equilibrium constants for the partition of NPN between water and the various lipid phases are reported. An increasing cholesterol content in a bilayer decreases the solubility of NPN in the bilayer. 3. The saturation concentration of cholesterol in bilayers of various lipids prepared by ultrasonication is determined using the flourescence probe NPN. The maximal molar ratio of cholesterol : lipid is 2 : 1 for sphingomyelin or egg phosphatidylcholine and 1 : 1 for cerebroside, dipalmitoyl phosphatidylcholine, or dipalmitoyl phosphatidylethanolamine. 4. The comparison of the maximal molar ratio of cholesterol : lipid with the number of proton donor and proton acceptor sites in the lipid moiety is used for a discussion of the polar interactions of cholesterol within a lipid bilayer.

1-Naphthylamine↗
PubMed1976

Vitamin B-6-catalyzed beta-elimination of serine and O-phosphoserine. Qualitative and quantitative aspects of catalytic influences at the rate-limiting step, a comparison with the rate of enzymatic beta-elimination.

The overall reaction rates for the beta-elimination of serine and O-phosphoserine, catalyzed by various vitamin B-6 analogs (pyridoxal 5'-phosphate, 5'-deoxypyridoxal and N-methylpyridoxal 5'-phosphate) in the presence or absence of Cu2+ ions, are determined. The comparison of the pH-dependence of the molar activities of the three vitamin B-6 aldehydes in beta-elimination of serine enables the characterization of the different active Schiff base species and the single catalytic events. The Schiff base which has a positive charge on the pyridine ring nitrogen and a fully ionized phosphate group shows the highest molar activity. The phosphate group acts as an intramolecular general base catalyst, most probably at the alpha-carbon proton of the amino acid. Furthermore general acid catalysis by buffer species occurs at the beta-hydroxy group serine. These facts together provide a kinetically unambiguous description of the mechanism of the reaction: the removal of the proton at the alpha-carbon atom of serine is the rate-limiting step and is followed by the more rapid elimination of the b-hydroxy group of serine. The forward rate constant of the rate-limiting step is calculated for each of the reactions mentioned. The rate constants are compared with respect to the effectiveness of the individual catalytic components in the vitamin B-6-dependent beta-elimination. For optimal conditions the reaction of O-phosphoserine is faster by a factor of 10(4) in the velocity of the beta-elimination than the corresponding acid-catalyzed beta-elimination of serine. For the eliminations at the alpha- and beta-carbon atoms of O-phosphoserine in vitamin B-6-catalysed reactions a common transition state is discussed. From a comparison of the fastest vitamin beta-6-dependent model reaction with the rate of an enzymatic beta-elimination it is suggested that for those beta-elininating enzymes where the rate-limiting step is the same as in the model, the catalytic components mentioned could suffice to explain the velocity of the rate-limiting step.

Binding Sites↗
PubMedDate not supplied

[Patterns of immunoglobulin synthesis in pediatric patients with Coxsackie A9 meningoencephalitis during the neuropathy epidemic in Cuba].

INTRODUCTION: Simultaneously with the origin and development of the Cuban epidemic neuropathy, cases of viral meningoencephalitis with particular characteristics due to Coxsackie were found. This virus and Inoue-Melnick virus were found too in patients suffering from Cuban epidemic neuropathy. PATIENTS AND METHODS: 31 pediatric patients suffering from viral meningoencephalitis were studied. Albumin, IgA, IgM and IgG were quantified in serum and cerebrospinal fluid by nephelometry. Cytochemical studies and reibergrams were performed. RESULTS: There was a lymphocyte predominance in cerebrospinal fluid. A dysfunction of blood-cerebrospinal fluid barrier was shown in 10 patients. Twenty patients have no immunoglobulins intrathecal synthesis. The synthesis patterns were: five patients with local IgM synthesis, two patients with local IgG synthesis and IgA + IgM. IgA + IgG and IgA + IgM pattern was synthesized in one patient respectively. Two patients with low IgG synthesis percentage or IgG intrathecal fractions were reported. CONCLUSIONS: The absence of immunoglobulins intrathecal synthesis and the immunoglobulins synthesis patterns differ from other pediatric patients with enterovirus meningoencephalitis. These patterns may have relationship with modified antigenic characteristics of the virus, also found in Cuban epidemic neuropathy.

Acute Disease↗
PubMedDate not supplied

[Intrathecal oligoclonal and polyspecific immune response in multiple sclerosis].

INTRODUCTION: The intrathecal response of IgG, is the most frequent neuropathological sign in multiple sclerosis (MS) patients beside the detection of oligoclonal IgG bands in cerebrospinal fluid. At the same time the observation of an intrathecal antibody synthesis (antibody index> 1.4) against neurotropic viruses like measles, rubella, varicella zoster or herpes simple shows a higher frequency in MS than any other chronic disease (MRZH reaction). We report the intrathecal, polyspecific and oligoclonal immune response in patients with definitive MS. PATIENTS AND METHODS: CSF and serum were tested for Albumin, IgG, IgM and IgA by standard immunochemical nephelometry assay while virus specific antibodies in CSF and serum samples were evaluated by ELISA and calculated as antibody index. RESULTS: Oligoclonal IgG by, isoelectric focusing was detectable in all patients. A differential pattern of combined antibody index against neurotropic virus was observed. The largest frequency of a single species in the oligoclonal immune response was for measles antibodies, while the antibody response was found as a combination with increased rubella antibody index and VZ antibody index, respectively. CONCLUSION: Our results although preliminary for our country, enrich the criteria about that MRZH reaction provide a major neuroimmunological support to MS diagnosis.

Herpesvirus 3, Human↗
PubMedDate not supplied

[Neuroimmune epidemiological value of reibergram in the first echovirus 16 meningoencephalitis outbreak in Cuba].

INTRODUCTION: During the third quarter of 2000, an outbreak of echovirus 16 meningoencephalitis was firstly occurred in Cuba and produced vomiting, headache, fever and exanthem that differentiate it from other enterovirus epidemies. OBJECTIVE: To describe the intrathecal immunoglobulin synthesis pattern of the epidemie from the reibergram. PATIENTS AND METHODS: Diagnostic serum and cerebrospinal fluid from 18 children during the acute phase by nephelometrie assay, besides cytochemical and virological study. RESULTS: A predominant absence of intrathecal immunoglobulin synthesis and two patients with IgA and IgM synthesis was produced. 66% of cerebrospinal blood barrier dysfunction, 6.26 10 3 mean albumin ratio, lactate below 2.1 mmol/L and glucose concentration in cerebrospinal fluid was 50% over glucose blood content and 168 cells 10 6 L mainly lymphocytes were observed. CONCLUSIONS: The intratecal immunoglobulin synthesis pattern differs from other enterovirus outbreaks that have affected this population and it seems the one found for the diagnostic period in adults. This finding alerts the possibility of genetic changes in echovirus 16 strain, interesting from the neuroimmunoepidemiological point of view.

Cuba↗
PubMedDate not supplied

[Intrathecal synthesis pattern of immunoglobulins in meningoencephalitis epidemic due to echovirus 9].

INTRODUCTION: Epidemics of meningoencephalitis due to echovirus 9 were commonly occurred when a children population become susceptible for the first time in front the virus. OBJECTIVE: To present the intrathecal synthesis pattern of immunoglobulins of the epidemic that affected Cuba in 1999 and to probe the usefulness of reibergram and antibody index in the diagnostic and characterization of the outbreak. PATIENTS AND METHODS: 23 pediatric patients suffering from viral meningoencephalitis due to echovirus 9 were studied in the income moment. Serum and cerebrospinal fluid IgA, IgM, IgG, albumin and glucose were quantified. Cerebrospinal fluid total protein content and lactate were quantified. Titles of antibodies against echo 9 and Coxsackie A9 and differential cell count were performed. RESULTS: A mean of 555 cells/10 6 L mainly lymphocytes were obtained. Glucose in cerebrospinal fluid was over 50%, serum glucose and lactate levels below 2.1 mmol/L. In the reibergram an absence of intrathecal synthesis was predominant (15/23), IgM synthesis (6/23) and IgM+IgA (2/23). Blood cerebrospinal fluid dysfunction was observed in 15 patients. The mean antibody index was 1,8 for echo 9 and 0,9 for Coxsackie A9. CONCLUSIONS: The intrathecal synthesis pattern of immunoglobulins was different from other enterovirus and from echovirus 9 in non epidemic situations before this epidemic, probably with alteration of viral genome.

Antibodies, Viral↗