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Biomedical subjects

H M Müller

Publications and source records attributed to H M Müller.

At least 73 records · Page 4Linked to original sources
PubMed1993

Peripheral blood leukocytes serve as a possible extrahepatic site for hepatitis C virus replication.

To study possible extrahepatic sites for the replication of hepatitis C virus (HCV), we examined fresh and cultured peripheral blood mononuclear leukocytes (PBML), as well as different subpopulations of PBML of HCV-infected patients, for the presence of viral genomic and antigenomic RNA. Sense and antisense oligonucleotide primers derived from HCV sequences were used for reverse transcription (RT) followed by an amplification with the polymerase chain reaction assay (PCR). Using antisense primers for RT, genomic viral RNA could be detected in serum, liver, total PBML and B lymphocytes of chronically infected patients. However, only liver tissue and PBML specimens were positive when a sense primer was used. To demonstrate further the specificity of these findings, total PBML were stimulated using pokeweed mitogen and synthesis of HCV RNA was determined by incorporation of [3H]uridine into nascent viral RNA molecules using a hybrid release assay. Additionally, total PBML from an uninfected person could be infected in vitro using an HCV RNA-positive serum. The PCR products obtained from serum, liver and PBML specimens of an HCV-positive individual were found to have nearly identical sequences. Our findings suggest that PBML could be a site for viral replication of HCV during the natural course of infection and may represent a reservoir for hepatitis C virions.

B-Lymphocytes↗
PubMed1993

Characterization and immunolocalization of a Cryptosporidium protein containing repeated amino acid motifs.

The oocyst wall is one of the components that permits cryptosporidia both to survive in the environment and to retain infectivity. With the aim of identifying Cryptosporidium proteins specifically expressed at the oocyst stage, we screened lambda gt11 genomic libraries of Cryptosporidium parvum with both an oocyst antiserum and a specific genetic probe. We isolated, from distinct libraries, two overlapping clones containing an open reading frame encoding a 1,252-amino-acid polypeptide. The analysis of the deduced amino acid sequence revealed unusually high contents of cysteine, proline, and histidine. The sequence was also characterized by two distinct amino acid motifs, each repeated several times. The DNA sequences coding for the amino acid repeats showed a high frequency of synonymous mutations, a result suggesting that the repeated motifs may be functionally and/or structurally important to the parasite. Antisera and monoclonal antibodies developed against a recombinant polypeptide encompassing the first 786 amino acids revealed that the corresponding protein in C. parvum had an apparent molecular weight of 190,000. Moreover, confocal microscopy analysis with immunofluorescence indicated that the protein was localized on the oocyst wall as a uniform stain and within the oocyst itself as bright granules in close association with the residual body.

Amino Acid Sequence↗
PubMed1993

Analysis of the human antibody response to thrombospondin-related anonymous protein of Plasmodium falciparum.

Thrombospondin-related anonymous protein (TRAP) of the malaria parasite Plasmodium falciparum shares two sequence motifs with other proteins which possess adhesive properties. Recently, findings indicate that TRAP is an antigen which contributes to antisporozoite immunity. We have cloned and expressed the TRAP coding sequences in Escherichia coli to investigate the human humoral immune response against this protein in a region of malaria endemicity of West Africa characterized by a seasonal transmission. Our results show that antibodies against TRAP are present in infected individuals. The anti-TRAP antibodies were analyzed in both a longitudinal and a prospective study. The longitudinal analysis shows seasonal fluctuations of the levels of specific antibodies as well as age-dependent quantitative differences. The immune response is long-lived in most of the adults and some of the older children but short-lived in young children. More importantly, the prospective analysis suggests that the presence of anti-TRAP antibodies in older children before the beginning of malaria transmission correlates with the subsequent control of parasite densities.

Adolescent↗
PubMed1993

Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum in parasite-host cell interactions.

Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum is characterized by the presence of an amino acid motif based on the sequence Trp-Ser-Pro-Cys-Ser-Val-Thr-Cys-Gly (WSPCSVTCG) that is found in a growing family of proteins. The sequence WSPCSVTCG is considered to confer sulpho-galactosyl-cerebroside (sulphatide) binding properties to antistasin, TSP, CS protein and properdin. The observation that TRAP is localized both on the micronemes and on the surface of P. falciparum sporozoites would suggest a role played by TRAP, and its putative sulphated glycoconjugates binding motif, in the recognition and/or entry of hepatocytes by the sporozoite. Our results indicated that TRAP constructs, expressed in E. coli, bind to sulpho-galactosyl-cerebrosides (sulphatides) and to the surface of HepG2 cells using the conserved amino acid motif WSPCSVTCG. Antisera raised against TRAP constructs inhibited sporozoite invasion of HepG2 cells thus suggesting, thus, that TRAP may be one of the parasite-encoded molecules implicated in the sporozoite invasion of hepatocytes. Moreover, the possibility that TRAP antibodies may be relevant in malaria immunity is supported by the results obtained in a prospective study conducted in a malaria endemic area. In adolescents, the presence of TRAP antibodies, before malaria transmission, correlated positively with the control of parasite density.

Adolescent↗
PubMed1993

Temporal and spatial expression of serine protease genes in Anopheles gambiae.

Serine proteases play a crucial role during the digestion of the blood meal in the mosquito gut. The isolation and the analysis of the genomic organisation of the corresponding genes may lead to the characterization of gut-specific, inducible promoters, suitable for the expression of anti-parasitic agents in the gut of transgenic mosquitoes. We report here on the identification of a trypsin and a chymotrypsin gene family of Anopheles gambiae. Following a blood meal, the transcription of all members of the two identified gene clusters, seven trypsin genes (Antryp1-7) and two chymotrypsin genes (Anchym1-2), is induced. Recombinant Antryp1 and Antryp2, expressed in E. coli, were both active in vitro against blood proteins. Moreover, mouse sera raised against Antryp1, Anchym1 and Anchym2 recognized the corresponding proteases among the proteins of a lysate prepared from dissected guts of An. gambiae mosquitoes.

Animals↗
PubMed1993

Studies on the refrigerated storage of wheat (Triticum aestivum). 2. Ergosterol, xanthomegnin, viomellein and brevianamide A after inoculation with Penicillium viridicatum.

Wheat seed was adjusted to 18, 20, 22, 24 and 26% moisture content (m.c.), and stored for 240 days at 4 or 10 degrees C following inoculation with a strain of Penicillium viridicatum producing the toxins, xanthomegnin (XA), viomellein (VIO), and brevianamide A (BA). Wheat kernels were not sterilized before inoculation. The concentration of ergosterol (ERG), a chemical indicator of fungal biomass, remained constant at 18% m.c./4 degrees C, but increased under the other conditions. The time before a detectable increase of ERG concentration was higher and the rate of ERG production lower with decreasing moisture content and temperature. XA and BA were produced at both temperatures at 20-26% m.c., VIO was produced at 22-26% m.c./4 degrees C and 20-26% m.c./10 degrees C. The results suggest or indicate that the onset of XA, VIO and BA production (detection limits: 10, 15, and 0.1 micrograms/kg, respectively) coincided with the onset of ERG production. Maximum toxin contents were lower with decreasing moisture content at both temperatures, but were similar at 4 and 10 degrees C at 22-26% m.c. It is concluded that wheat contaminated with P. viridicatum should not be stored beyond the onset of ergosterol production; maximum storage periods are recommended.

Alkaloids↗
PubMed1992

Determination of alpha- and beta-zearalenol and zearalenone in cereals by gas chromatography with ion-trap detection.

A method for determination of estrogenic mycotoxins, alpha- and beta-zearalenol and zearalenone, in cereals (wheat, barley, oats, corn) is described. After extraction with ethylacetate, clean-up involved a base treatment and partition with water; derivatization was by trimethylsilylation. For quantitation and confirmation a capillary gas chromatograph combined with a selective mass detector (ion trap), working in the electron impact-mode was used. The detection limit for the complete method is 1 microgram/kg for each of the three mycotoxins in full scan. Recoveries from spiked cereals were 82-86%.

Chromatography, Gas↗
PubMed1992

[Cold storage of wheat. 1. Ergosterol, ochratoxin A and citrinin after inoculation with Penicillium verrucosum].

Seed wheat was inoculated without having been sterilized with an ochratoxin A and citrinin forming strain of Penicillium verrucosum and stored at moisture contents of 18, 20, 22, 24, and 26% at 10 and 4 degrees C. The production of ergosterol, a chemical indicator of fungal biomass, started within the storage time investigated (240 days). Only at 18% H2O/4 degrees C an increase of the ergosterol content was not observed. Ochratoxin A and Citrinin were not detected at 18% H2O/4 degrees C and 20% H2O/4 degrees C within 240 days (detection limit: 10 and 25 micrograms/kg, respectively). At the other combinations of moisture content and temperature the first detection of the two toxins approximately coincided with the onset of ergosterol production. With increasing moisture content and temperature the time up to the start of ergosterol production decreased, whereas the production rates of ergosterol, ochratoxin A and citrinin increased. Both toxins were produced with about the same rate during a first phase of accumulation. At 20-26% H2O there was no influence of moisture content and temperature on the relation between toxin content and the simultaneously reached ergosterol content. It is recommended that wheat highly contaminated with Penicillium verrucosum should not be stored beyond the start of ergosterol production.

Citrinin↗
PubMed1992

Role of hepatitis C virus infection in German patients with fulminant and subacute hepatic failure.

To investigate the possible role of hepatitis C virus (HCV) in fulminant and subacute liver failure, we tested serum and liver of 13 patients undergoing orthotopic liver transplantation for the presence of HCV RNA. HCV RNA was detected in specimens from two out of eight patients negative for all viral markers with suspected hepatitis non-A, non-B infection and in one out of four patients with hepatitis B virus infection. Only in this patient replication of HCV could be demonstrated. We conclude, that fulminant and subacute hepatic failure is induced by hepatitis C virus only in few patients with hepatitis non-A, non-B.

Adult↗
PubMed1992

Liver transplantation for acute or chronic liver failure by hepatitis non-A, non-B and hepatitis C viral infections: a postoperative follow-up.

Orthotopic liver transplantation (OLT) was performed for liver failure related to hepatitis non-A, non-B (HNANB) or hepatitis C (HCV) infections in 12 patients. Of those, 8 patients had chronic and 4 acute hepatic failure. To determine the incidence of recurrent infection, the clinical course, histological findings and serological HCV markers (HCV-RNA and detection of anti HCV antibodies, respectively) were comparatively studied in these patients. Recurrent infection was apparent in 5 of 6 patients transplanted for liver cirrhosis attributable to chronic HCV infection and with HCV-RNA detectable in serum. The clinical course of infection after OLT varied considerably. Chronic active hepatitis, progressing to liver cirrhosis 13 months postoperatively and an acute hepatitis, resolving spontaneously were seen in one case each. Recurrent infection led to chronic persistent hepatitis in the remainder. None of the patients with acute liver failure experienced recurrent infection. HCV-RNA was detectable in all the patients after OLT, with HCV-RNA present pretransplant, however the presence of HCV-RNA in serum was not necessarily associated with clinical illness.

Budd-Chiari Syndrome↗
PubMed1992

Lipoprotein (a): a risk factor for retinal vascular occlusion.

The protein moiety of lipoprotein (a) consists of apoB-100 and apolipoprotein (a). Lipoprotein (a) is an independent risk factor for premature atherosclerosis. Apolipoprotein (a) and plasminogen are structurally homologous. Through interference with the fibrinolytic system, lipoprotein (a) may act as a thrombogenic factor. In the present study, we determined lipoprotein (a) concentrations in 84 patients (60 men and 24 women) with retinal vascular occlusion (RVO) and in 2 groups of healthy volunteers (n = 40 and 46). In all, 29% of the patients had Lp (a) levels of above 300 mg/l. In the two reference groups, only 10% and 9% of the subjects exceeded this level. According to the chi-square test, the association between Lp (a) levels and RVO was significant. Lp (a) concentrations did not differ between patients with arterial occlusion and those with venous occlusion. No difference in the total cholesterol, triglyceride, or LDL-cholesterol values was observed between patients and controls. We therefore conclude that Lp (a) represents an independent risk factor for RVO.

Adolescent↗
PubMed1991

Epitopes of the human malaria parasite P. falciparum carried on the surface of HBsAg particles elicit an immune response against the parasite.

The development of recombinant subunit vaccines against pathogenic organisms requires not only the identification of epitopes eliciting a protective immune response but also suitable carriers with adjuvant function. B- and T-cell epitopes of the malaria vaccine candidate gp190 were selected on the basis of a systematic search along the gp190 molecule and by computer prediction based on the amino acid sequence. Using some of the epitopes identified, we have redesigned the surface of the hepatitis B surface antigen lipoprotein particles by replacing the major antigenic determinants with malaria-specific sequences of up to 61 amino acids in length. Upon expression via vaccinia virus the hybrid particles elicit an anti-gp190 immune response in animals. Monoclonal antibodies derived from such infections recognize the native parasite.

Amino Acid Sequence↗
PubMed1991

Human antibody response to the major merozoite surface antigen of Plasmodium falciparum is strain specific and short-lived.

The precursor of the major merozoite antigen of Plasmodium falciparum, gp190, is considered a candidate for inclusion in a malaria vaccine. This protein, which consists of conserved, dimorphic, and polymorphic sequences, is very immunogenic in humans. In a longitudinal study carried out with 94 inhabitants of a rural community in Mali, West Africa, we show that in this endemic area naturally acquired gp190-specific antibodies are predominantly directed against the dimorphic parts of one of the main alleles of gp190. The presence of antibodies against these dimorphic regions correlates with the prevalence of the corresponding antigen in the infecting parasite population. Moreover, qualitative as well as quantitative differences were found in the time course of the humoral immune response to the dimorphic regions in adults and children, who differ in their susceptibility to malaria infection.

Adolescent↗
PubMed1991

The human immune response against the major merozoite surface antigen of Plasmodium falciparum.

The major surface antigen of the merozoite (MMSA) is very immunogenic in humans and it is considered a candidate for developing a malaria vaccine. This protein consists of conserved, dimorphic and polymorphic sequences that might differ in their ability to induce immunity. Epidemiological studies were undertaken in two different endemic areas of West Africa with the aim to identify the sequences within the protein that are the target of the humoral and cellular immune responses. Recombinant polypeptides expressed in E. coli, covering the conserved, the dimorphic and polymorphic regions, were used to evaluate the reactivity of sera and of Peripheral Blood Mononuclear Cells (PBMC) from inhabitants of rural communities exposed to P. falciparum transmission. The analysis of the humoral immune response against the MMSA showed that both qualitative and quantitative differences exist among groups of individuals with different susceptibility to P. falciparum infection. Furthermore, an association between intensity of transmission and antibody reactivity against the dimorphic regions was observed in individuals living in a malaria endemic area. The proliferative response of the PBMC was in most cases very low, however, several T cell clones could be established. The dimorphic region of MMSA was shown to contain T cell epitopes together with sequences most frequently recognized by human sera.

Adult↗
PubMed1991

[Effects of autoclaving and surface disinfection of wheat (Triticum aestivum) on the production of ergosterol, ochratoxin A and citrinin by Penicillium verrucosum].

Moist wheat was autoclaved, surface disinfected with NaOCl or left untreated. After inoculation with conidia of a toxigenic strain of Penicillium verrucosum kernels were stored at 10 and 4 degrees C. The production of ergosterol, a chemical indicator of fungal growth, was accelerated at both temperatures by each of the two treatments, compared to untreated wheat. The accumulation of ochratoxin A and citrinin was accelerated by each of the two treatments at 10 degrees C, whereas it was accelerated or retarded at 4 degrees C. It is concluded that the kinetics of growth and toxin production of Penicillium verrucosum during cold storage of wheat under real agricultural conditions cannot be predicted from in vitro studies with autoclaved or surface disinfected wheat.

Citrinin↗
PubMed1990

[Therapy of moderate hypertension with the calcium antagonist nitrendipine in combination with beta receptor blocker or diuretic].

The efficacy of the calcium channel blocker nitrendipine alone and in combination with the beta blocking agent acebutolol or hydrochlorothiazide was tested in 34 patients with moderate essential hypertension. After a wash out period of three to four weeks, all patients received placebo for two weeks, thereafter 20 mg of nitrendipine per day for four weeks. When diastolic blood pressure remained above 95 mmHg with nitrendipine, acebutolol (200 mg/d) or the thiazide (25 mg/d) was added in a randomised double-blind fashion. With nitrendipine alone, blood pressure could be normalized in nine patients with a drop in pressure from 168/108 to 152/89 mmHg. The other patients showed a fall in blood pressure from 164/110 to 152/102 mmHg. In these patients, the addition of acebutolol or thiazide was followed by a further fall in blood pressure which was similar with both drugs. With acebutolol blood pressure decreased from 154/102 to 146/94 mmHg and with the thiazide from 152/102 to 147/95 mmHg, respectively. Minor and mostly transient side effects were predominantly seen during therapy with nitrendipine alone. The fall in diastolic but not systolic blood pressure with nitrendipine was correlated with age. The blood pressure lowering effect of nitrendipine was independent of plasma renin activity and intracellular electrolyte concentrations. In the therapy of moderate hypertension, nitrendipine given in combination with a betablocker or a thiazide diuretic is effective and well tolerated.

Acebutolol↗