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D Wirth

Publications and source records attributed to D Wirth.

36 records · Page 2Linked to original sources
PubMed1995

Determinants of HIV infection and recent risk behaviour among injecting drug users in Berlin by site of recruitment.

This study investigated differences in prevalence and determinants of HIV infection, and in recent risk behaviour (previous 6 months) among injecting drug users (IDUs) who are in contact with different types of services for IDUs in Berlin. Participants (n = 557) were recruited from drug-free long-term treatment centres, a storefront agency and a syringe exchange bus. HIV seroprevalence was lowest (3.9%) at the treatment centres, and highest among IDUs at the storefront agency (20.7%). In logistic regression, independent risk factors for HIV infection were duration of injecting drug use, borrowing syringes in prison, sex with HIV-positive partners, and prostitution. Syringe sharing in prison was the most important independent determinant of HIV infection among all three subpopulations of IDUs. Participants entering long-term treatment were most likely, and IDUs at the syringe exchange bus were least likely to have borrowed and passed on syringes in the previous 6 months. In logistic regression, site of recruitment was independently associated with recent borrowing of syringes, but not with condom use. Injection of drugs other than heroin only, and injecting in prisons, were also independent predictors of recent borrowing. The results indicate that IDUs entering treatment form an important target group for health education. There is a need for AIDS prevention measures in prisons. The comparatively low levels of recent injection risk behaviour among IDUs at the syringe exchange bus suggest that this type of intervention may be effective in harm reduction.

Adult↗
PubMed1995

Prevalence and determinants of anti-HCV seropositivity and of HCV genotype among intravenous drug users in Berlin.

A cross-sectional study was carried out to identify risk factors for seropositivity for antibodies against hepatitis C virus (HCV) and to assess to the distribution and determinants of HCV genotypes among intravenous drug users (IVDUs). The study population consisted of 405 IVDUs. Serum specimens were tested for seromarkers for HCV, for human immunodeficiency virus (HIV), for hepatitis B virus (HBV) and for syphilis. HCV RNA determination by polymerase chain reaction (PCR) and virus typing were performed in a subsample of anti-HCV-positive specimens (n=135). Of the IVDUs, 83% were anti-HCV-positive, 18% HIV-infected, and 58% HBV (anti-HBc)-positive. Longer duration of intravenous drug use, syringe sharing in prison, and higher number of IDVU sex partners were independent risk factors for anti-HCV positivity. GCV RNA was detected in 76% of anti-HCV-positive IVDUs. HCV genotypes 1 (49%) and 3 (44%) were most commonly found. All the type 3 isolates were identified as subtype 3a, and 95% of the type 1 isolates as subtype 1b. In logistic regression analysis, HCV type 3a viraemia was significantly associated with lack of HIV infection and a higher number of sex partners. The results indicate that preventive measures are needed to reduce syringe sharing among IVDUs in prisons. Sexual contacts with other IVDUs may play a role in the HCV epidemic among IVDUs. In Germany, HCV type 3a infection appears to be much more common among IVDUs than among other HCV risk groups such as transfusion recipients or haemophiliacs.

Adolescent↗
PubMed1995

Imprisonment: a risk factor for HIV infection counteracting education and prevention programmes for intravenous drug users.

OBJECTIVES: To examine changes of risk behaviour and its determinants as well as risk factors for HIV infection in intravenous drug users (IVDU) with particular attention to imprisonment and its risk patterns. SETTING: In 1993 a multisite cross-sectional study was carried out by standardized questionnaires and blood/saliva samples in which 612 IVDU from Berlin were enrolled. RESULTS: Multifactorial analysis revealed that the most important risk factor for HIV infection was needle-sharing in prison. In total, 353 IVDU (58%) reported reduced risk behaviour; changes related more to injection behaviour than sexual practices (91 versus 68%). Important determinants for needle-sharing during the last 6 months were intravenous drug use in prison, duration of drug-taking history, and knowledge of a negative HIV test. The most frequently reported reasons for current needle-sharing were having shared needles with only one regular partner (45%) and imprisonment (26%). CONCLUSION: Information campaigns and other prevention measures appear to have produced risk awareness in IVDU, and as a consequence, a reduction in risk behaviour. The situation in prisons (no sterile injecting equipment, no effective disinfectants), however, is counteractive to prevention measures implemented outside prisons. An important task for future strategies should be to enable IVDU to avoid HIV transmission while in prisons.

Adult↗
PubMed1994

Cloning, genomic organization and transcription of the Entamoeba histolytica alpha-tubulin-encoding gene.

We have isolated and characterized an Entamoeba histolytica alpha-tubulin (alpha Tub)-encoding gene (Eh alpha tub). A 700-bp DNA fragment was amplified by PCR using primers derived from consensus alpha- and beta-Tub amino acid (aa) sequences from different organisms and E. histolytica DNA as the template. These PCR fragments were used to screen both genomic DNA and cDNA libraries in order to isolate an Eh alpha tub structural gene. Two overlapping clones containing the complete alpha tub ORF (1392 bp) were isolated from the genome and cDNA libraries. The deduced aa sequence of Eh alpha Tub has 55.5, 50 and 52% identity to Plasmodium falciparum alpha Tub 2, Saccharomyces cerevisiae alpha Tub 2 and human alpha Tub, respectively. Interestingly, the predicted Eh alpha Tub protein lacks a poly-acidic motif at its C terminus which is involved in Tub polymerization and microtubule-associated protein binding in other organisms. This fact may indicate a difference in tubule assembly in this organism and could provide a potential key for the development of therapeutic agents. According to Southern blot experiments and the sequences of several clones, at least two non-adjacent copies of alpha tub are present in the E. histolytica genome. A 1.5-kb transcript corresponding to the alpha tub mRNA was detected in mRNA from asynchronous E. histolytica trophozoites.

Amino Acid Sequence↗
PubMed1994

Hepatitis C virus (HCV) genotype distribution in German isolates: studies on the sequence variability in the E2 and NS5 region.

We report on molecular characterization of hepatitis C virus (HCV) isolates in intravenous drug abusers, as compared to non-drug using patients with posttransfusion hepatitis or sporadic hepatitis of unknown origin. Virus typing was performed by RFLP analysis of PCR products in the 5' NCR. Subtyping was done by hybridization with subtype specific probes or by sequencing in the NS4 and NS5 region, respectively. HCV subtype 1b was found most commonly among all the isolates. However, the subtype 3a had a high prevalence (about 46%) in the group of drug addicts. In these subtype 3a isolates the N-terminal part of the E2 protein was highly variable. This confirms the presence of a hypervariable region (HVR1) in this envelope protein found in all hepatitis C viruses. Each subtype 3a isolate examined had a characteristic unique hypervariable region in the E2 protein. It is noteworthy that there are four amino acids in this region which were highly conserved between all HCV sequences published. It can be assumed that such conserved amino acids are significant for structure and function of this viral protein. In our HCV subtype 3a isolates the NS5 sequences were highly conserved.

Amino Acid Sequence↗
PubMed1993

Transfection of the malaria parasite and expression of firefly luciferase.

The goal of this work is to develop a method for the functional analysis of malaria genes using the method of DNA transfection. We have developed a transient transfection vector by constructing a chimeric gene in which the firefly luciferase gene was inserted in frame into the coding region of the pgs28 gene of Plasmodium gallinaceum. This plasmid DNA was introduced into P. gallinaceum gametes and fertilized zygotes by electroporation, and luciferase expression was assayed after 24 hr. This report of successful introduction and expression of a foreign gene in a malaria parasite demonstrates the feasibility of this approach to developing methods for the functional analysis of parasite genes.

Animals↗
PubMed1993

Application of the polymerase chain reaction to the epidemiology of pathogenic and nonpathogenic Entamoeba histolytica.

We used the polymerase chain reaction (PCR) to study the epidemiology of pathogenic and nonpathogenic Entamoeba histolytica in a rural community in Mexico. Formalin-fixed stool samples were used for extraction of DNA. The PCR amplifications were performed using two sets of primers that discriminate between pathogenic or non-pathogenic E. histolytica. A total of 201 randomly selected individuals were studied. Among them, 25 (12%) were diagnosed to be infected with E. histolytica by microscopy; PCR identified 24 of these as positive (sensitivity = 0.96) and of 176 negative individuals, only three were identified as positive (specificity = 0.98). The PCR analysis defined three populations: 14 cases were positive for both pathogenic and nonpathogenic E. histolytica, nine cases were positive for pathogenic and negative for nonpathogenic E. histolytica, and only one case was negative for pathogenic and positive for nonpathogenic E. histolytica. Infection by E. histolytica was strongly associated to infection with Entamoeba coli (odds ratio [OR] = 9.41, 95% confidence interval [CI] = 3.09, 28.65, P < 0.0004) and Endolimax nana (OR = 6.15, 95% CI = 2.03, 18.17, P < 0.0004). This new technique has high specificity and sensitivity; it is simple, reproducible, fast, avoids the need to culture trophozoites, and can be applied in the field for epidemiologic studies.

Adolescent↗
PubMed1990

Emetine-resistant mutants of Entamoeba histolytica overexpress mRNAs for multidrug resistance.

We report here the identification of multiple 344-bp segments of amoeba DNA similar to the human multidrug resistance (mdr) gene using primers to conserved regions of the P-glycoprotein and the polymerase chain reaction (PCR). The amino acid sequences of amoeba mdr-like PCR products were 46-97% identical to each other, 46-51% identical to human mdr1 sequences, and 30-35% identical with Plasmodium falciparum mdr-like sequences. On Northern blots, the mdr-like PCR products identified amoeba mRNAs 4.5-5 kb long, similar to the 5-kb mRNAs reported for the mammalian mdr gene. These mdr-like mRNAs were increased at least 7 times in emetine-resistant mutant clone C2 amoebae vs. wild-type clone A parasites. Furthermore, the expression of the mdr-like mRNAs was increased 3-4 times when clone C2 mutants were grown under drug pressure vs. the same parasites grown without emetine. In contrast, the number of genomic copies of the mdr-like DNA segments was not increased in the mutant clone C2 vs. the wild-type clone A amoebae, and no rearrangements of the mdr-like DNA segments by the mutant were identified on Southern blots. In conclusion, there appears to be a family of mdr-like genes in Entamoeba histolytica, which may be involved in drug resistance by the parasite because they are overexpressed in drug-resistant mutants.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Entamoeba histolytica: physiology of multidrug resistance.

Cross-resistance to unrelated drugs has been previously observed in multidrug-resistant carcinoma cells and the goal of this work was to determine whether a similar mechanism existed in Entamoeba histolytica. An emetine and a colchicine-resistant clone, C2(90) (IC50 = 62 microM, and 1.5 mM, respectively), and the parental clone, A (IC50 = 5 microM and 1 mM, respectively), were analyzed for resistance to other drugs and for the effect of verapamil. Both clones, C2(90) and A, exhibited similar resistance to both daunomycin (IC50 = 50 microM) and actinomycin D (IC50 = 13 nM). In the presence of verapamil, the IC50 for emetine was reduced to 0.5 microM, while the IC50 for colchicine was reduced to 0.3 mM. These results demonstrate that verapamil reverses both emetine and colchicine resistance in the mutant C2(90). In uptake experiments with [3H]emetine, drug accumulation was lower in resistant trophozoites. However, in the presence of verapamil, drug accumulation was increased in clone C2(90) to a level close to that of the parental strain, clone A. These results are consistent with observations made using malaria and multidrug-resistant tumor cells and suggest that a P-glycoprotein-like molecule may play a role in drug resistance in E. histolytica.

Animals↗
PubMed1989

DNA hybridization probe for clinical diagnosis of Entamoeba histolytica.

As an alternative to microscopic identification of Entamoeba histolytica parasites isolated from stool, a sensitive and species-specific DNA hybridization probe was made for rapid diagnosis of E. histolytica parasites in clinical samples directly applied to nylon membranes. The DNA hybridization probe was made by screening a genomic library of a virulent HM-1:IMSS strain of E. histolytica to detect recombinant plasmids containing highly repeated parasite DNA sequences. Four plasmid clones that reacted across Entamoeba species coded for highly repeated rRNA genes of E. histolytica. Four other plasmid clones were E. histolytica specific in that they bound to four axenized and nine xenic strains of E. histolytica but did not recognize closely related E. histolytica-like Laredo, Entamoeba moshkovskii, or Entamoeba invadens parasites. The diagnostic clones detected as few as eight cultured amoebae and did not distinguish between pathogenic and nonpathogenic zymodemes of E. histolytica. The diagnostic clones were sequenced and contained 145-base-pair sequences which appear to be tandemly repeated in the genome. No stable transcript which is homologous to the diagnostic DNA was detected. In a study of stool samples from Mexico City shown by microscopy to contain E. histolytica, Entamoeba coli, Giardia lamblia, Endolimax nana, Trichuris trichiuria, and Chilomastix mesnili parasites, the DNA hybridization probe demonstrated a sensitivity of 1.0 and a specificity of 0.93. We conclude that the DNA hybridization probe can be used for rapid and accurate diagnosis of E. histolytica parasites.

Animals↗
PubMed1984

Target antigens in malaria transmission blocking immunity.

Malaria transmission blocking immunity has been found to operate against two distinct phases of development of malaria parasites in the mosquito midgut: (i) against the extracellular gametes and newly fertilized zygotes shortly after ingestion by a mosquito of parasitized blood and (ii) against the zygotes during their subsequent development into ookinetes. Immunity is antibody-mediated and stage-specific. A set of three proteins, synthesized in the gametocytes, expressed on the surface of the gametes and newly fertilized zygotes and subsequently shed during later transformation of the zygotes, has been identified as the target antigens of anti-gamete fertilization blocking antibodies. A single protein, synthesized and expressed on the zygote surface during its development to ookinetes, has been identified as the target of antibodies which block the development of the fertilized parasites in the mosquito. Immunization of human populations against gamete or zygote antigens, while not directly protecting an immunized individual from inflection, would reduce the transfer of malaria within the population. Such immunity, in addition to reducing the overall rate of malaria transmission, would, if combined with a vaccine against the asexual (disease-causing) stages, reduce the chance of selection of parasites that are resistant to the asexual vaccine by preventing their entry into the mosquito population.

Animals↗
PubMed1977

[Prognostic significance of myoclonias in aerospace altitude studies and others with acute hypoxia-accompanied status].

Motor phenomena - mostly in the form of myoclonus in the widest sense - are not rare in aeromedical studies conducted at flight altitudes and involving severe and acute hypoxia. At the same time medium to severe general changes can be observed in the EEG. When oxygen is supplied the motor phenomena stop after a few seconds, and the EEG results become normal again. These reversible changes are contrasted with clinical findings after anoxic coma conditions and hypoxic accidents which occurred during flights and where the myoclonus survives the coma, which is an extremely grave prognostic indication.

Altitude Sickness↗