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Biomedical subjects

H Zahner

Publications and source records attributed to H Zahner.

At least 55 records · Page 3Linked to original sources
PubMed1994

Litomosoides carinii: macrofilariae-derived glycolipids--chromatography, serology and potential in the evaluation of anthelminthic efficacy.

A preliminary characterization of the glycolipids of Litomosoides carinii macrofilariae, resolved according to their chromatographic, chemical and serological properties, has been performed. Emphasis has been placed on the neutral fraction glycolipids. These are separable on thinlayer chromatography into two groups of fast and slow migrating band components, that differ in their migration, differential chemical staining and serological traits, respectively. Serological analyses have been accomplished by thin-layer chromatography immunostaining and ELISA. Only components of the slow migrating band group react with infection serum from Litomosoides carinii-infected Mastomys coucha. Cross-reactivity experiments with homologous and heterologous infection sera of various helminthiases indicate that, epitopes bound to the neutral glycolipid fraction show structural similarity within the Nematoda, but not to the Cestoda or Trematoda. The dynamic development of specific Ig-, IgG- and IgM-anti-neutral glycolipid fraction antibody levels were correlated with the different progression of L. carinii and Brugia malayi infections in the multimammate rat, Mastomys coucha. The reduction in the dynamics of IgG- and IgM-antibody levels on chemotherapeutic treatment with the filaricides flubendazole and CGP 20376 has been related to their macrofilaricide-activity.

Animals↗
PubMed1994

Ivermectin-induced cell-dependent lethal effects on litomosoides carinii microfilariae in vitro.

Ivermectin affected the motility of Litomosoides carinii microfilariae in vitro in a dose dependent manner but did not completely immobilize the larvae and had no lethal effects when tested up to a concentration of 1000 ng/ml. However, killing of microfilariae was induced by ivermectin in vitro in the presence of spleen cells of Mastomys coucha or rats within 14 h. Optimum effects occurred at drug levels of 10-100 ng ivermectin/ml. Addition of infection serum led to increased cytotoxicity when compared with normal serum. Pretreatment in vitro of L. carinii microfilariae with ivermectin in cell-free medium and subsequent exposure to spleen cells caused also cytotoxic effects which appeared to be accelerated in comparison with simultaneous exposure of microfilariae to ivermectin and cells. Pretreated microfilariae, injected intravenously into naive M. coucha were rapidly eliminated from the blood of the recipients. These results suggest that the microfilariae become altered by the drug and thus susceptible to cell-mediated cytotoxic effects. Cytotoxicity did not depend on the attachment of cells to L. carinii microfilariae and was also induced when targets and effector cells were separated by membranes impermeable for cells. Thus ivermectin-induced cellular cytotoxicity to L. carinii microfilariae is at least partly mediated by soluble factors released by effective cells.

Animals↗
PubMed1994

Antifilarial activity of macrocyclic lactones: comparative studies with ivermectin, doramectin, milbemycin A4 oxime, and moxidectin in Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi, and B. pahangi infection of Mastomys coucha.

The avermectins ivermectin and doramectin and the milbemycins milbemycin A4 oxime and moxidectin were tested for filaricidal activity in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi, and B. pahangi. Single subcutaneous doses of 0.005-5 mg/kg (L. carinii), 0.0005-0.5 mg/kg (A. viteae), 0.5 and 5 mg/kg (B. malayi), and 5 mg/kg (B. pahangi) were injected. Necropsies were performed 42 days after treatment. The avermectins caused a strong and rapid reduction of microfilaraemia in L. carinii and A. viteae infections within a few hours after treatment but showed only moderate efficacies on microfilariae of Brugia spp. The effects of the milbemycin derivatives on L. carinii and A. viteae microfilariae were generally weaker than those of the avermectins. However, moxidectin was comparatively active against microfilariae of Brugia spp. Subsequently the parasitaemia levels of L. carinii and A. viteae infected animals remained either almost completely depressed or tended to reincrease in a dose dependent manner whereas there was generally a continuous decrease of microfilaraemia levels in Brugia spp. infected animals. Adulticidal effects were limited to A. viteae although with neither dose of neither drug > 95% reductions of adult worm counts were reached. However, pathogenic influences of the drugs were observed on intrauterine embryonic stages of the parasites.

Animals↗
PubMed1994

IgG subclasses of the multimammate rat, Mastomys coucha: isolation and characterization of IgG1 and IgG2.

The objective of the study was to characterize the IgG-system of Mastomys coucha and to provide antibodies specific for IgG subclasses of this animal species. Serum proteins binding to protein A at pH 8.0 could be eluted in two distinct peaks at pH 7.5 - 6.2 and pH 5.0 - 3.9. The fractions were analysed by SDS-PAGE and immunoelectrophoresis. Both tests suggested an IgG character of the fractions. Based on their migration behavior in the electric field they were classified as IgG1 (anodic position) and IgG2 (cathodic position). After cleavage of IgG1 and IgG2 with papain, the Fc fragments were isolated by their binding to protein A and used to raise antisera in rabbits. The specificity of these antisera to IgG1 and IgG2 was improved by mutual affinity purification. Subsequently these specific reagents were used for further characterization of IgG1 and IgG2. Thus, affinity chromatography of IgG to protein G allowed a differentiation of IgG1 into two subtypes which either bound to protein G at pH 8.0 or not. In combination with isoelectric focussing and 2-dimensional immunoelectrophoresis the results suggest the occurrence of two and three subtypes of IgG1 (IgG 1a-b) and IgG2 (IgG 2a-c) respectively. A synoptical table of available information on the immunoglobulins of M. coucha including IgM, IgA, IgE and a homocytotropic IgG3 is presented. In addition, serum levels of IgG1 and IgG2 are determined in male and female M. coucha of different ages.

Animals↗
PubMed1993

Experimental chemotherapy of filariasis: comparative evaluation of the efficacy of filaricidal compounds in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi and B. pahangi.

Eleven types/classes of compound with antifilarial activity were comparatively evaluated in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi or B. pahangi. The paper deals with the efficacy of (i) predominantly microfilaricidal compounds [diethylcarbamazine, levamisole, avermectins (ivermectin, milbemycin), nitrofurans (nitrofurantoin, hydroxymethylnitrofurantoin, nifurtimox, furazolidone, furapyrimidone), organophosphorals (metrifonate, haloxon), and aminophenyl-amidines], (ii) predominantly macrofilaricidal compounds [suramin, benzimidazoles (flubendazole, mebendazole, oxfendazole, ciclobendazole, albendazole, cambendazole, fenbendazole), and arsenicals (thiacetarsamide, Mel PH, R7/45)], and (iii) micro- and macrofilaricidal compounds [benzazole derivatives (CGP 20376 and other benzothiazoles) and nitrophenylamines (amoscanate, CGP 6140)]. Minimum effective doses against microfilariae and minimum curative doses against adult filariae as well as detailed data on dose-efficacy relationships are reported for the various drugs. The results obtained in M. coucha are compared with those published for other experimental in vivo filarial systems, thus attempting to describe a general status of in vivo antifilarial activity of the compounds.

Animals↗
PubMed1993

The gene coding for the major sheath protein of Litomosoides carinii microfilariae, gp22, is transcribed in oocytes and embryonic cells.

The transcription and translation of the gene encoding gp22, a major constituent of the microfilarial sheath of the filarial parasite Litomosoides carinii were studied by in situ hybridisation and immunohistology. Transcription of the gp22 gene is confined to oocytes and embryos in the reproductive organs of adult female worms. It starts in oocytes in the rhachis zone, is maximal in multicellular embryos and decreases slowly as the microfilariae develop. Blood microfilariae lack the gp22 transcript. The gp22 gene product is first detectable in parasites recovered on day 32 post infection. Expression of gp22 begins in multicellular embryos in the uteri of mature female worms and can be detected in all further developed intrauterine stages. The gp22 gene product appears to be exported by the embryonic cells and becomes integrated into the sheath where it may contribute to the flexibility of the latter structure.

Amino Acid Sequence↗
PubMed1992

Trans-splicing of an early embryo mRNA in Litomosoides carinii, coding for the major microfilarial sheath protein gp22.

Both genomic and cDNA clones have been isolated encoding the major sheath glycoprotein, gp22, of Litomosoides carinii microfilariae. The mature gp22 mRNA is shown to result from both trans-splicing of a 22-nucleotide 5'-leader sequence to an acceptor site at position 313 of the pre-mRNA, immediately upstream from the start codon, and from cis-splicing of a 117-nt intron located within the coding sequence. Cis-splicing precedes the trans-splicing reaction. The gp22 reading frame of 148 codons has the inferred structure of a prepro-protein and includes a leader peptide and a pro-segment ahead of the known N terminus of the mature, extracellular protein of 105 amino acids. The N-terminal part of that protein contains five repeats of an elastin-related pentapeptide sequence, which, together with a proline-threonine segment between two Cys clusters in the center and at its C terminus, may cause an elongated conformation with an apparent molecular size of 22 kDa in contrast to the calculated M(r) of 11,200.

Amino Acid Sequence↗
PubMed1992

Litomosoides carinii: extraction of the microfilarial sheath components and antigenicity of the sheath fractions.

Microfilarial sheaths of Litomosoides carinii were isolated and extracted with 2% sodium dodecyl sulfate (SDS) and 5% 2-mercaptoethanol (2ME). Extraction with SDS alone did not alter the ultrastructure of the sheaths and yielded five polypeptides (27-67 kDa) that were not recognized by antibodies of infected hosts but reacted with antibodies to host-serum proteins. 2ME treatment caused partial solubilization of the sheaths (45% as determined by amino acid analysis), which could be further improved by combining 2ME with SDS. The remainder showed filamentous/threadlike structures on electron microscopic examination. As compared with whole sheaths, the insoluble proportion was markedly enriched in alanine and cysteine but contained less galactosamine, serine, and threonine. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of 2ME/SDS-extractable components showed 12-16 bands of 14- greater than 120 kDa. A predominant component had an apparent molecular mass of 22 kDa. Two bands (42 and 120 kDa) could be stained with Coomassie blue but showed "negative" staining when gels were stained with silver. Several components (but not the 22-kDa polypeptide) bore phosphocholine epitopes. Apart from the negatively staining bands, most of the 2ME-soluble sheath components were recognized by antibodies of L. carinii-infected Mastomys coucha. Except for several polypeptides that had been unspecifically recognized by IgM, the antibody response to sheath components started at the end of the prepatent period.

Amino Acids↗
PubMed1992

Eimeria bovis in cattle: colostral transfer of antibodies and immune response to experimental infections.

IgM, IgG1, and IgG2 antibodies to Eimeria bovis first-generation merozoite antigens were determined by enzyme-linked immunosorbent assay and Western blotting in naturally infected cows and in their offspring before and after the uptake of colostrum. In addition, calves were examined following experimental primary and challenge infections. Neonate calves received maternal antibodies via colostrum. All isotypes determined were transmitted, but only IgG1 was concentrated in the colostrum and it occurred at significantly increased levels in sera from the calves as compared with those from the respective dams. Recognition patterns (Western blotting) displayed by related maternal serum and colostrum and those shown by calves that had ingested colostrum were very similar, but marked variations occurred between individual pairs. Experimental infection of 15-week-old calves with 0.7 x 10(5) oocysts caused strong protective immunity against a challenge with 1 x 10(5) oocysts. In contrast, animals that had undergone a weak intercurrent infection were not protected. Experimental infections induced a considerable increase in IgG1 and IgG2 antibody levels, whereas IgM values increased only slightly. The spectrum of merozoite antigens recognized by the sera increased markedly after experimental infection, although high individual variations were found in the calves. However, there was no correlation between the levels of any specific antibody or the recognition patterns and the status of immunity to a severe challenge.

Animals↗
PubMed1992

Activity, mechanism of action and pharmacokinetics of 2-tert-butylbenzothiazole and CGP 6140 (amocarzine) antifilarial drugs.

A variety of recently developed drugs, designed to be used in antifilarial chemotherapy, contain a thiocarbonylamide group as a common structural element. One group of these compounds is based on a 2-tert-butylbenzothiazole ring in which the carbonylamide linkage is present as an isothiocyanate, dithiocarbamic acid ester or thiourea derivative. The single representative of another series is an N-methylpiperazine adduct of amoscanate (CGP 6140 or amocarzine). CGP 6140 is currently undergoing clinical trials in patients suffering from onchocercosis. All of the drugs with antifilarial activity affect the motility of filarial worms in vitro. The primary site of action of most of these compounds is the mitochondrion. The drugs result in the swelling of this organelle and also the inhibition of respiration and other associated metabolic functions. The dithiocarbamic acid esters (e.g., CGP 20376) are devoid of intrinsic antifilarial activity. Activity of these compounds requires conversion to the corresponding isothiocyanates. This occurs spontaneously in aqueous solution at physiological pH. The thiourea compounds were found to inhibit acetylcholinesterase activity by competing with its substrate. There is also evidence that the latter drugs are metabolized by a host-derived enzyme to their isothiocyanate analogs. CGP 6140 affects both mitochondrial function and acetylcholinesterase activity. The biochemical effects of the antifilarial compounds were not found to be significantly different between mammalian and parasite test systems. Biochemical and pharmacokinetic studies suggest that the selective toxicity of the new series of drugs towards filarial parasites is most likely preferential drug uptake by the pathogen. The lack of a unique target for these compounds in the parasite may explain the side-effects seen upon their administration to humans.

Animals↗
PubMed1992

Chemical composition of Litomosoides carinii microfilarial sheaths.

Litomosoides carinii microfilariae were exsheathed by freezing and thawing, and the sheaths were separated by filtration. Samples of pure sheaths thus obtained were hydrolyzed, methanolyzed or oxidized with nitric acid under pressure at 300 degrees C, respectively, and were analyzed for amino acids, sugars, fatty acids or for metal ions and phosphorus. Almost 75% of the sheath dry weight could thus be accounted for. Amino acids (55 weight %) were the major constituents, and amongst these glutamine and proline (approximately 11% each). The detection of 2% cysteine/cystine indicated the possible presence of disulfide crosslinks. Besides amino acids, approximately 8% of sugars--roughly equimolar amounts of (N-acetyl)galactosamine and uronic acids--1.5% of monovalent cations (Na+ and K+) and 9.5% of phosphate were detected. No appreciable amounts of fatty acids, neutral sugars, neuraminic acid, or (N-acetyl)glucosamine (i.e. no chitin) were found.

Amino Acids↗
PubMed1991

The sheaths of Brugia microfilariae: isolation and composition.

Burgia malayi and B. pahangi microfilariae were isolated from the blood of infected Mastomys natalensis, and were exsheathed by freezing, thawing and agitation. Pure sheaths were obtained by a filtration procedure. The sheaths were found to contain about 95 mol% of amino acids, with proline, glutamic acid/glutamine, alanine, cysteine/cystine and glycine being the major components, and 5 mol% of carbohydrates, notably (N-acetyl)galactosamine, but no (N-acetyl)glucosamine.

Amino Acids↗
PubMed1991

On the pathogenesis of anaemia and leukopenia in filarial (Litomosoides carinii) infection of Mastomys natalensis.

Mastomys natalensis infected with the filarial parasite Litomosoides carinii show anaemia and leukopenia. Alterations start with the onset of microfilaraemia. Anaemia is temporally macrocytic (up to 80 days after infection), subsequently normocytic and hypochromic, accompanied by reticulocytosis. Increased intravascular haemolysis (i) and functional disorders of the haemopoetic system (ii) are involved in the pathogenesis. i: Circulating erythrocytes showed increased osmofragility. Hypoglycaemia demonstrated in parasitaemic animals may be one reason. ii: Histological and electron microscopical investigations of the bone marrow revealed markedly enhanced haemopoiesis in infected animals. However, a high proportion of cells was found pathologically altered already beginning in the late prepatency and increasing in the further course of infection. Thus, dyshaemopoiesis may result in the production of morphologically and functionally aberrant cells which are rapidly eliminated by the MPS which is highly activated in L. carinii infected M. natalensis.

Anemia↗
PubMed1991

In vitro effects of 2-tert-butyl-benzothiazole derivatives on microfilariae of Litomosoides carinii, Brugia malayi and Acanthocheilonema viteae.

Six 2-tert-butyl-benzothiazole derivatives (2-tert-butyl-6-iso-thiocyanato-5-methyl-benzothiazole CGP 21306); 3-[(2-tert-butyl-5-methyl-benzothiazole-6-yl) aminothiocarbonylthiol] propionic acid (CGP 21835); 2-tert-butyl-5-methyl-6-(N-methyl-piperazinyl-thiocarbonylamino)-b enzothiazole (CGP 21833); 2-tert-butyl-5-methyl-6-(4-dimethylamino-piperid-1-yl-thiocarbo nylamino)- benzothiazole (CGP 26702); CGP 20376, the 5-methoxy analogue to CGP 21835 and CGP 20309, the 5-methoxy analogue to CGP 21833) with known, high filaricidal activity in vivo were tested for in vitro efficacy against microfilariae of L. carinii (Lc), B. malayi (Bm) and A. viteae (Av) in order to study intrinsic antifilarial activities. All drugs affected the motility of the microfilariae of the three species in a species, dose and time dependent fashion. Lc was the most sensitive, Av the most resistant species. CGP 20376 and 21835 were the most effective compounds followed by CGP 21306. Complete immobilization of microfilariae was observed after 20 h in protein-free medium RPMI 1640 at drug concentrations of 0.1 to 10 nmol/ml. Effects were still marked 2 when graded on a 4 (full motility) to 0 (immobile) scale at concentrations of 0.01-0.1 nmol/ml. In the case of the thiourea derivatives CGP 21833, 26702 and 20309 concentrations had to be increased 10-100 fold to obtain similar effects. When proteins were present in the incubation medium (10% foetal calf serum, 100% normal serum) the efficacy of the compounds was reduced, i.e. drug concentrations had to be increased up to 100 fold to produce similar effects as in protein-free medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Antifilarial efficacy in vitro of 2-tert-butyl-benzothiazole derivatives on adult Litomosoides carinii.

Six 2-tert-butyl-benzothiazole derivatives (2-tert-butyl-6-isothiocyanato-5-methyl-benzothiazole (CGP 21306); 3-[(2-tert-butyl-5-methyl-benzothiazole-6-yl)aminothiocar-bonyl thiol] propionic acid (CGP 21835); 2-tert-butyl-5-methyl-6-(N-methyl-piperazinyl-thiocarbonylamino)- benzothiazole(CGP 21833); 2-tert-butyl-5-methyl-6-(4-dimethylamino-piperid-1-yl-thiocarbo nylamino)- benzothiazole (CGP 26702); CGP 20376, the 5-methoxy analogue to CGP 21835 and CGP 20309, the 5-methoxy analogue to CGP 21833) were tested in vitro against adult Litomosoides carinii. When exposed to the drugs in protein-free medium RPMI 1640 drug concentrations of 1 nmol/ml caused complete immobilization of female worms within 4 h (CGP 21306, 21835, 20376) or 20 h (CGP 21833, 26702, 20309). Short term exposure for 1 h had similar effects with CGP 21306, 21835, 21833 and 20376. However, the levels of CGP 26702 and 20309 (both thiourea derivatives) had to be increased to 10 nmol/ml to obtain complete immobilization after short term exposure. Male parasites were more resistant to the drugs than females under these experimental conditions. When the medium was supplemented with 10% foetal calf serum (FCS) the efficacy of all compounds was reduced. The effect of the compounds during permanent and short term exposure on the release of microfilariae was determined over an incubation period of 7 days (medium RPMI 1640/10% FCS). In general only drug concentrations which affected markedly the motility of the worms within 2 days reduced significantly the number of microfilariae released by treated worms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

In vivo effect of benzothiazole and amoscanate derivatives on the fine structure of adult Brugia spp. and Litomosoides carinii.

Alterations in the fine structures of female Brugia spp. and Litomosoides carinii were investigated after in vivo treatment with curative doses of 4 compounds: CGP 20376 [2-tert-butyl-benzothiazole-5-methoxy-6-dithiocarbamic-S-(2- carboxyethyl)-ester], CGP 21833 (2-tert-butyl-benzothiazole-5-methyl-6- N-methylamino-piperazinylthiocarbonylamide), CGP 6140 [4-Nitro-4'-(N-methyl-piperazinylthiocarbonylamido)-diphenylamine] and amoscanate (4-isothiocyanato-4'-nitrodiphenylamine). All compounds caused early alterations in the somatic muscle cells. These alterations usually appeared within 24 h after treatment; they occurred later only after treatment of L. carinii with amoscanate. In Brugia spp., swelling of the muscle cells occurred in which the glycogen deposits considerably increased in size. The electron density of the cytoplasm surrounding the myofilaments in the fibrillar portion of the muscle cells increased, and light zones appeared between the fibrils. The muscle cell mitochondria swelled, particularly their inner matrix, which became more electron-lucent, with some dense spots. In L. carinii the muscle cells were not increased in size, but their mitochondria were considerably swollen before disintegration; this was followed by disintegration of the myofilaments and vacuolization of the cytoplasm. Vacuolization before mitochondrial swelling was observed only after treatment with CGP 6140. Other tissues of this species were not altered before the 2nd day after treatment. In Brugia spp., electron-lucent appeared in the hypodermis either simultaneously with the alterations in the muscle cells or a few hours later. At 24 h after treatment with amoscanate, blebs were formed on the luminal side of the intestinal membrane.

Aniline Compounds↗
PubMed1990

Fine-structure alterations in female Brugia malayi and Litomosoides carinii after in vivo treatment with flubendazole.

Female filariae of the species Brugia malayi and Litomosoides carinii were investigated by means of electron microscopy after in vivo treatment with flubendazole. The earliest fine-structure alteration in both species was the disappearance of microtubuli from the intestinal cells as soon as 6 h after treatment. There was no further disintegration of intestinal cells for several days. Microtubuli disappeared from the outer zone of the hypodermal cytoplasm 24 h after treatment. At this time, marked alterations were also observed in the oogonia and in the embryonic cells. Many of these were swollen; their nuclear envelope was partly resolved and the chromatin was condensed, but no spindle apparatus was formed. The early fine-structure alterations observed after in vivo treatment with flubendazole consisted of the disappearance of microtubuli from various tissues. This led to the interruption of cell division in oogonia and embryonic cells and, and subsequently, to the disintegration of most other filarial tissues. These morphological alterations differed considerably from those observed after treatment with benzothiazole derivatives, which do not affect the microtubuli of the filariae.

Animals↗