Biologically active bisbenzylisoquinoline alkaloids from the root bark of Epinetrum villosum.

Methanol and water extracts of the root of Epinetrum villosum (Exell) Troupin (Menispermaceae) were found to exhibit antimicrobial and antiplasmodial activities. Investigation of the active methanol fraction led to the isolation of four bisbenzylisoquinoline alkaloids, i.e.

Antiviral activity of simalikalactone D, a quassinoid from Quassia africana.

After removing lipophilic material, the ground root bark of Quassia africana Baill. (Simaroubaceae) was extracted with ethanol 95 %. Partitioning between chloroform, ethyl acetate and water yielded three crude extracts.

Pyruvate-induced long-term maintenance of glutathione s-transferase in rat hepatocyte cultures.

The addition of pyruvate to the culture medium has been reported to improve the maintenance of P450-dependent enzyme expression in primary rat hepatocyte cultures. In this study, the effects of 30mM pyruvate on cell morphology, albumin secretion and glutathione S-transferase (GST) expression were investigated as a function of the time in culture. The effect of triiodothyronine (T3) exposure on GST expression was also measured in pyruvate-treated cultures.

Antidiarrhoeal activity of root extracts from Roureopsis obliquifoliolata and Epinetrum villosum.

The methanol extracts of Roureopsis obliquifoliolata and Epinetrum villosum root significantly reduced castor oil-induced diarrhoea in mice. This effect supports the use of these plants in Congolese folk medicine as antidiarrhoeal remedies.

Contribution to the ethnobotanical, phytochemical and pharmacological studies of traditionally used medicinal plants in the treatment of dysentery and diarrhoea in Lomela area, Democratic Republic of Congo (DRC).

In order to collect ethnobotanical information about antidiarrhoeal plants, we performed inquiries among traditional healers, community leaders, and native people of Lomela villages in Congo. Six medicinal plants widely used in this region were designated as having antidysenteric and antidiarrhoeal properties. These six medicinal plants were screened for groups of phytochemical compounds with antibacterial and antiamoebic activities.

Hormonal regulation of glutathione S-transferase expression in co-cultured adult rat hepatocytes.

Glutathione S-transferases (GSTs) are subject to regulation by thyroid and sex hormones and by GH. We have used an in vitro experimental system comprising adult rat hepatocytes co-cultured with rat liver epithelial cells of primitive biliary origin, to distinguish between direct and indirect effects of various hormones on GSTs; to identify the GST subunits affected by individual hormones; and to investigate the level at which the hormones act. Tri-iodothyronine (T3), thyroxine (T4) and 17beta-oestradiol (OE2) reduced GST activities, whereas testosterone, dihydrotestosterone, and human growth hormone (hGH) had little effect on total GST activity.

In vitro antimicrobial activity of six medicinal plants traditionally used for the treatment of dysentery and diarrhoea in Democratic Republic of Congo (DRC).

Twenty-four crude extracts derived from six medicinal plants highly valued as antidiarrhoeal agents in Congolese folk medicine were screened for antimicrobial activity against several enteric pathogens. The results of this study indicated that the methanolic and aqueous extracts derived from three of them (Roureopsis obliquifoliolata, Epinetrum villosum and Cissus rubiginosa) possessed prominent antibacterial activity, therefore supporting the ethnomedical uses of these species. In addition, phytochemical analysis of these medicinal plants showed that 1/6 plant sample contained alkaloids, 6/6 triterpenes and/or sterols, 4/6 flavonoids, 3/6 tannins and 5/6 saponins.

Prolonged exposure of pancreatic beta cells to raised glucose concentrations results in increased cellular content of islet amyloid polypeptide precursors.

Most non-insulin dependent diabetic patients have amyloid deposits in their pancreatic islets. It is not known whether chronic hyperglycaemia contributes to the formation of amyloid fibrils from the islet amyloid polypeptide that is produced by the pancreatic beta cells. Since islet amyloid exhibits islet amyloid polypeptide precursors immunoreactivity, we examined whether sustained in vitro exposure to raised glucose increases the abundance of these precursors in human beta cells.

Separation of a triterpenoid saponin mixture from Maesa lanceolata: semipreparative reversed-phase wide pore high performance liquid chromatography with temperature control.

A mixture of triterpenoid saponins derived from the dried leaves of Maesa lanceolata was separated, without structure deterioration, in its components. Seven fractions (I-VII) of high molecular weight (1234-1358) saponins were obtained on a semipreparative scale using wide pore reversed-phase high performance liquid chromatography with an acetonitrile trifluoroacetic acid (500:0.3 w/w)-water-trifluoroacetic acid (391:0.

Effect of glucose on production and release of proinsulin conversion products by cultured human islets.

Isolated human islets were examined for the rates of conversion and release of newly formed (pro)insulin-like peptides. The rate of proinsulin (PI) conversion was 2-fold slower in human beta-cells (t(1/2) = 50 min) than in rat beta-cells (t(1/2) = 25 min). During the first hour following labeling of newly synthesized proteins, PI represented the main newly formed hormonal peptide in the medium; its release was stimulated 2-fold over the basal level by 20 mmol/L glucose.

Differential expression of rat insulin I and II messenger ribonucleic acid after prolonged exposure of islet beta-cells to elevated glucose levels.

Prolonged exposure of rat islet beta-cells to 10 mmol/liter glucose has been previously shown to activate more cells into a glucose-responsive state (>90%) than has exposure to 6 mmol/liter glucose (50%). The present study demonstrates that this recruitment of more activated cells results in 4- to 6-fold higher levels of proinsulin I and proinsulin II messenger RNA (mRNA). However, only the rate of proinsulin I synthesis is increased.

Proinsulin and its conversion intermediates in human pancreas and isolated islet tissue: kinetics and steady-state analysis.

In non-insulin-dependent diabetes, circulating insulin-related immunoreactivity (IRI) is often composed of a higher fraction of the incompletely converted forms proinsulin and des-31,32 proinsulin. The present study describes an immunoadsorption method for measuring the proportions of proinsulin, its two split products, and insulin in human pancreatic tissue and for determining their rates of formation in human isolated islets. The method uses two junction-specific monoclonal proinsulin antibodies in a protein G fractionation; it is validated by > or = 90% specificity and recovery.

Abnormal circulating pancreatic enzyme activities in more than twenty-five percent of recent-onset insulin-dependent diabetic patients: association of hyperlipasemia with high-titer islet cell antibodies. Belgian Diabetes Registry.

Pancreatic amylase and lipase activities were measured in sera of 307 Caucasian insulin-dependent diabetes mellitus patients (IDDM) at clinical onset, 303 nondiabetic siblings of registered patients, and 207 control subjects under age 40 years. In all subject groups lipasemia and pancreatic (but not salivary) amylasemia increased with age and were significantly correlated. Using age-dependent reference ranges, reduced pancreatic enzyme levels were measured in 18% of patients, 6% of siblings, and only 2% of control subjects (p < 0.

Effect of ethanol on glutathione S-transferase expression in co-cultured rat hepatocytes.

To examine the effects of ethanol (EtOH) on rat liver glutathione S-transferase (GST, E.C. 2.

Formation of poliomyelitis subviral particles in the yeast Saccharomyces cerevisiae.

The sequence of the poliovirus genome encoding 3CD (a protease) was transferred to the yeast Saccharomyces cerevisiae on expression vectors with either a constitutive or an inducible promoter. Transformants could only be obtained with vectors carrying the inducible transcription unit. Extracts of induced cells were able to cleave cell-free synthesized P1, the precursor of the poliovirus capsid proteins, into VP0, VP3 and VP1.

Comparison of capillary zone electrophoresis with high-performance liquid chromatography for the determination of additives in foodstuffs.

A capillary zone electrophoretic (CZE) method was developed to determine caffeine, aspartame and benzoic acid in diet cola soft drinks and in artificial sweetening powders. The effects of pH, ionic strength, organic solvents and different buffers were investigated to select the optimum conditions. These consisted of a sodium phosphate buffer at pH 11 and ionic strength 0.

Detection of autoantibodies against islet amyloid polypeptide in human serum. Lack of association with type 1 (insulin-dependent) diabetes mellitus, or with conditions favouring amyloid deposition in islets. The Belgian Diabetes Registry.

A radiobinding assay for the detection of autoantibodies against islet amyloid polypeptide was developed, analytically validated, and--in parallel with a similar assay for the detection of autoantibodies against insulin--applied to sera from recent-onset Type 1 (insulin-dependent) diabetic patients and from age- and sex-matched control subjects. There was no difference in islet amyloid polypeptide autoantibody titres between patient groups and matched control subjects, nor within subject groups according to age. At onset of Type 1 diabetes, elevated islet amyloid polypeptide-autoantibody levels (> 97th percentile of control subjects) were only detected in 1 of 30 patients aged 0-19 years and in 2 of 35 patients aged 20-39 years.

Presence of islet amyloid polypeptide in rat islet B and D cells determines parallelism and dissociation between rat pancreatic islet amyloid polypeptide and insulin content.

The islet amyloid polypeptide (IAPP) immunoreactivity of the adult rat pancreas is located in insulin-containing B cells as well as in somatostatin-containing D cells. In both cell types, the IAPP immunoreactivity is identical to rat synthetic IAPP in terms of its elution position after reversed phase HPLC and its binding to IAPP antibodies. The IAPP content per 10(6) B-cells is more than 100 fold lower than the corresponding insulin content, but comparable to the IAPP content of D cells.

In vitro assembly of poliovirus 14 S subunits: identification of the assembly promoting activity of infected cell extracts.

Purified poliovirus 14 S subunits are assembled into empty capsids in vitro only if their concentration exceeds a 1.6 nM threshold. This also holds true for the 14 S subunits in unpurified extracts of infected cells.

Purification of poliovirus 14 S subunits by sucrose gradient ultracentrifugation and high-performance size-exclusion chromatography.

Purification of 14 S subunits from extracts of poliovirus-infected HeLa cells was achieved by a combination of sucrose gradient ultracentrifugation and high-performance size-exclusion chromatography. The particles were free of admixtures of other subviral particles, of nonstructural viral proteins, and of host cell proteins. The purified material retained the physical and antigenic properties of native 14 S subunits fully, as well as their ability to assemble to empty capsids in vitro.

Changes in expression and "de novo" synthesis of glutathione S-transferase subunits in cultured adult rat hepatocytes.

Glutathione S-transferase (GST) isoenzymes of conventionally and co-cultured adult rat hepatocytes were purified and the GST subunits were separated by reversed phase HPLC in order to study the development of the GST subunit composition as a function of culture time and culture conditions. Several media conditions were tested, namely medium with and without fetal calf serum and with nicotinamide or dimethyl sulphoxide. Compared to the GST subunit composition of freshly isolated hepatocytes, changes in culture and media conditions result in a modification of the subunit profile.

Use of high-performance size-exclusion chromatography for the separation of poliovirus and subviral particles.

The size-dependent separation of viral and subviral particles in the range 10(5)-10(7) daltons was undertaken by high-performance liquid chromatography. A combination of Ultrahydrogel 2000 and 1000 size-exclusion columns, equilibrated and developed with Tris buffer (pH 7.4), was used to fractionate extracts of cells infected with radiolabelled poliovirus.

Cell surface antibodies in type 1 (insulin-dependent) diabetic patients. I. Presence of immunoglobulins M which bind to rat pituitary cells.

A standardized method has been developed for the assay of cell surface antibodies in IgM- and IgG-fractions from human serum. Suspensions of adult rat islet B cells, islet non-B cells, and anterior pituitary cells were used as antigen source and a cell sorter as analyser of the immunoglobulin binding to individual cells. Assay conditions were selected wherein no surface antibodies were detected in 33 control subjects younger than 20 years.

Effect of phenobarbital on the expression of glutathione S-transferase isoenzymes in cultured rat hepatocytes.

Cultured adult rat hepatocytes were treated daily with 3.2 mM phenobarbital (PB) in order to study its effect on the expression of cytosolic glutathione S-transferase isoenzymes. Glutathione S-transferase (GST) activities, using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, were increased when PB was present in the culture medium.

Evidence for the presence of type I insulin-like growth factor receptors on rat pancreatic A and B cells.

Purified rat pancreatic islet cells express somatomedin receptors which are identified by their affinity for insulin-like growth factor (IGF)-I, IGF-II, and insulin. Binding of [125I]IGF-I to islet A cells was half-maximally inhibited by 7.10(-10) M IGF-I, while IGF-II, insulin, and proinsulin were respectively 10-, 500-, and 10,000-fold less potent displacers of IGF-I binding.