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M Wiese

Publications and source records attributed to M Wiese.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structure-activity relationships of multidrug resistance reversers.

Multidrug resistance, MDR, is a major obstacle in the chemotherapeutic treatment of cancer. MDR can be reversed by drugs that vary widely in their chemical structure and main biological action. Many efforts are directed to find out the relationships between the structure and MDR reversal effect of these drugs. In this review we try to summarize the results of a variety of studies on identification of structure-activity relationships, SARs, and quantitative SARs, QSARs, of different MDR reversing drugs. As any reasonable (Q)SAR study relies on a real or putative presentation about the mechanism of action of the studied compounds, the most significant MDR mechanisms revealed till now are shortly discussed. Special attention is paid to P-glycoprotein, P-gp, related MDR as the most experimentally and clinically tested form of drug resistance. The currently proposed models of P-gp functioning and mechanisms of MDR modulation are presented. Problems that can arise in (Q)SARs studies are discussed in advance to allow the reader to judge on possible pitfalls. The physicochemical and structural properties of MDR modulators as found by different research groups are commented and summarized. From the discussed studies it can be concluded that the careful selection of relevant structural and biological data processed with appropriate QSAR and especially 3D-QSAR methods, is a promising approach to structure-activity studies of MDR reversers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Extraction and amplification of authentic DNA from ancient human remains.

A total of 36 ancient human remains from 12 individuals (three tooth/bone samples each) and one sample each of three individuals from the newest time was typed in a blind study using the amelogenin sex test. Prior to this molecular sex determination the sex of the individual was determined morphologically. The success rate of the amelogenin amplifications was >90%. For every individual an unambiguous molecular sex typing result was obtained. Furthermore, the morphological and molecular sex determinations were in accordance with each other, giving evidence for the authenticity and ancient origin of the polymerase chain reaction (PCR) amplifications.

Amelogenin↗
PubMed2000

Decreased immunogenicity of recombinant hepatitis B vaccine in chronic hepatitis C.

The immunogenicity of hepatitis B vaccine is unknown for patients with chronic hepatitis C, although hepatitis B vaccination is highly recommended in these patients. We therefore studied in a prospective open trial of 59 patients with chronic hepatitis C (mean age 42 years, hepatitis C for >10 years, Child-Pugh score < or = 5) and 58 healthy hospital staff persons the rate of nonresponse (anti-HBs <10 mIU/mL at 9 months) to recombinant hepatitis B vaccine (Gen H-B-Vax(R),10 microg intradeltoidal at month 0, 1, and 6). Nonresponse was observed in 18/59 (31%) patients with chronic hepatitis C and 5/58 (9%) healthy staff persons (P <.005) (vs. 7% in historical controls; P <.005), low response (anti-HBs 10-99 mIU/mL) in 19% of patients with chronic hepatitis C and 17% of staff persons. High-dose booster vaccination led to seroconversion in 12/15 (80%) of primary nonresponders. Primary nonresponse to HB vaccine was related neither to presence of early-stage liver cirrhosis nor magnitude of serum hepatitis C virus (HCV) RNA concentration, nor explained by the presence of human leukocyte antigen (HLA) types (B8 DR3, B44, DR7, DQ2) predisposing to low antibody response to hepatitis B surface antigen. The rate of primary nonresponse to the standard regimen of recombinant hepatitis B vaccine is surprisingly high in patients with longstanding chronic hepatitis C. Therefore, the antibody to HBV surface antigen (anti-HBs) titer response should be determined in these patients. Depending on the response titer, higher booster doses may be required to achieve and maintain seroprotection in these patients.

Adult↗
PubMed2000

Deletion of the gene for the membrane-bound acid phosphatase of Leishmania mexicana.

The membrane-bound acid phosphatase of Leishmania mexicana (LmxMBAP) has been shown to be a heterogeneously N-glycosylated type I transmembrane protein, which is localized predominantly in vesicular structures close to the flagellar pocket in promastigotes and amastigotes. Its expression in both life stages prompted us to analyse its function by performing deletion analysis. Both alleles of the single copy gene were sequentially replaced by resistance marker genes and the resulting deletion mutant was tested for its potential to infect Balb/c mice and peritoneal macrophages. There was no obvious difference detectable between the mutant and the wild-type. Therefore, we conclude that LmxMBAP is neither involved in the infection process nor required for amastigote survival in the infected host cell. LmxMBAP null mutant promastigotes were used to establish a system for homogeneous overexpression of LmxMBAP which will be useful to investigate protein sorting in L. mexicana.

Acid Phosphatase↗
PubMed2000

Partial resistance of E. coli mutants against 2, 4-diamino-5-benzylpyrimidines by interactions with bacterial membrane lipopolysaccharides. Derivation of quantitative structure-binding relationships.

A series of previously synthesized 2,4-diamino-5-benzylpyrimidines, inhibitors of bacterial dihydrofolate reductase (DHFR) showed decreased inhibition of E. coli cultures, despite increased inhibitory activity against DHFR. Preliminary studies using E. coli mutants with different degrees of outer membrane deficiencies suggested that the decrease in activity was partly due to inactivation because of binding to outer membrane constituents. In the present study antibacterial activities of the benzylpyrimidines have been systematically determined as a function of cell membrane defects in E. coli using bacterial growth kinetic techniques. It has been shown that the observed differences in activity were not due to different binding affinities to the target enzyme of the mutants. Lipopolysaccharides have been extracted from the mutants and used in binding studies by ultrafiltration, photometric and NMR techniques. The observed differences in binding affinity to the lipopolysaccharides have been related to the differences in the lipophilic properties and molecular weight of the substituents. Quantitative structure-activity relationships have been derived. The results of the study show the importance of drug-membrane interactions for the rational development of antibacterials.

Cell Division↗
PubMed2000

Cellular immune responses persist and humoral responses decrease two decades after recovery from a single-source outbreak of hepatitis C.

As acute hepatitis C virus (HCV) infection is clinically inapparent in most cases, the immunologic correlates of recovery are not well defined. The cellular immune response is thought to contribute to the elimination of HCV-infected cells and a strong HCV-specific T-helper-cell (Th) response is associated with recovery from acute hepatitis C (ref. 2). However, diagnosis of resolved hepatitis C is based at present on the detection of HCV-specific antibodies and the absence of detectable HCV RNA, and detailed comparison of the humoral and cellular immune response has been hampered by the fact that patient cohorts as well as HCV strains are usually heterogeneous and that clinical data from acute-phase and long-term follow-up after infection generally are not available. We studied a cohort of women accidentally exposed to the same HCV strain of known sequence and found that circulating HCV-specific antibodies were undetectable in many patients 18-20 years after recovery, whereas HCV-specific helper and cytotoxic T-cell responses with an interferon (IFN)-gamma-producing (Tc1) phenotype persisted. The data indicate these HCV-specific CD4 + and CD8+ T cells are biomarkers for a prior HCV exposure and recovery. Because of undetectable antibodies against HCV, the incidence of self-limited HCV infections and recovery may be underestimated in the general population.

Antibody Specificity↗
PubMed2000

Low frequency of cirrhosis in a hepatitis C (genotype 1b) single-source outbreak in germany: a 20-year multicenter study.

From August 1978 until March 1979, 14 batches of anti-D immune globulin contaminated with hepatitis C virus (HCV) genotype 1b (20, 000-480,000 copies/dose) from a single erythrocyte donor had been administered for prophylaxis of rhesus isoimmunization throughout East Germany. All 2,867 women involved had been recalled after January 12, 1979 for repeated screening of alanine transaminase (ALT). They were prospectively followed in regional centers. We have reexamined a cohort of 1,018 women (median age 24, range 16-38 years at infection) on follow-up for 20 years in 9 representative centers. Within 6 months after anti-D administration, 10% of these women had no evidence of disease and 90% had acute hepatitis C (n = 917) including 49% with symptomatic and 22% with icteric course. After 20 years, 85% of the 917 affected women still tested positive for HCV antibodies (among them 3% responded to interferon treatment) and 55% were positive for HCV RNA (among them 7% were nonresponders to interferon and 3% were apparent HCV carriers). Only 4 (0.4%) had overt cirrhosis. Two (0.2%) died of superinfected fulminant hepatitis B or alcoholism and cirrhosis, respectively. Histology obtained in 44% of the viremic women showed hepatitis of minimal to moderate grade in 96%, portal fibrosis in 47%, and septal fibrosis in 3% of the cases. In conclusion, formerly healthy young women, without hepatic comorbidity, may clear HCV (1b) infection in half of the cases or develop mild chronic hepatitis C with low risk of progression to cirrhosis within 20 years.

Adolescent↗
PubMed2000

Subunit vaccination of mice against new world cutaneous leishmaniasis: comparison of three proteins expressed in amastigotes and six adjuvants.

A mixture of well-defined recombinant antigens together with an adjuvant that preferentially stimulates specific gamma interferon (IFN-gamma)-secreting helper type 1 CD4(+) T cells (Th1 cells) presents a rational option for a vaccine against leishmaniasis. The potential of this approach was investigated in murine infections with Leishmania mexicana, which are characterized by the absence of a parasite-specific Th1 response and uncontrolled parasite proliferation. A mixture of three antigens (glycoprotein 63, cysteine proteinases, and a membrane-bound acid phosphatase), which are all expressed in amastigotes, the mammalian stage of the parasite, were used for the immunization of C57BL/6 mice in combination with six adjuvants (interleukin 12 [IL-12], Detox, 4'-monophosphoryl lipid A, QS-21, Mycobacterium bovis BCG, and Corynebacterium parvum). All six vaccine formulations containing the mixture of recombinant antigens were protective against challenge infections with promastigotes, the insect stage of the parasite, in that mice controlled and healed infections but developed transient and, in certain cases, accentuated disease. The most effective adjuvants were IL-12 followed by Detox. Further studies using these two adjuvants showed that a similar protective effect was observed with a mixture of the corresponding native proteins, and mice which had controlled the infection showed a preponderance of IFN-gamma-secreting CD4(+) T cells in the lymph nodes draining the lesion. Using the recombinant proteins individually, it is shown that the relatively abundant cysteine proteinases and glycoprotein 63, but not the acid phosphatase, are able to elicit a protective response. The results are discussed in comparison to previous studies with subunit vaccines and with respect to cell biological aspects of antigen presentation in Leishmania-infected macrophages.

Adjuvants, Immunologic↗
PubMed2000

Distribution of GPI-anchored proteins in the protozoan parasite Leishmania, based on an improved ultrastructural description using high-pressure frozen cells.

The cellular distribution of two glycosyl-phosphatidylinositol (GPI)-anchored proteins and a trans-membrane protein and the compartments involved in their trafficking were investigated in the insect stage of Leishmania mexicana, which belongs to the phylogenetically old protozoan family Trypanosomatidae. Electron microscopy of sections from high-pressure frozen and freeze-substituted cells allowed a detailed description of exo- and endocytic structures located in the vesicle-rich, densely packed anterior part of the spindle-shaped cell. A complex of tubular clusters/translucent vesicles is the prominent structure between the trans-side of the single Golgi apparatus and the flagellar pocket, the only site of endo- and exocytosis. A tubulovesicular compartment lined by one or two distinct microtubules and extending along the length of the cell is proposed to be a post-Golgi and probably late endosomal/lysosomal compartment. Using biotinylation experiments, FACS analysis and quantitative immunoelectron microscopy it was found that, at comparable expression levels, 73-75% of the two GPI-anchored proteins but only 13% of the trans-membrane protein are located on the cell surface. The tubulovesicular compartment contains 46%, the ER 5%, the Golgi complex 1.9% and the tubular cluster/translucent vesicle complex 3.6% of the intracellular fraction of the GPI-anchored protease, GP63. The density of GP63 was found to be 23-fold higher on the plasma/flagellar pocket membrane than on the ER and about tenfold higher than on membranes of the Golgi complex or of endo- or exocytic vesicles. These results indicate that there is a considerable concentration gradient of GPI-anchored proteins between the plasma/flagellar pocket membrane and the ER as well as structures involved in exo- or endocytosis. Possible mechanisms how this concentration gradient is established are discussed.

Acid Phosphatase↗
PubMed1999

Synthesis and biological evaluation of the first N-alkyl cage dimeric 4-aryl-1,4-dihydropyridines as novel nonpeptidic HIV-1 protease inhibitors.

A first series of novel NH and N-alkyl-substituted cage dimeric 4-aryl-1,4-dihydropyridines 3a-f has been synthesized and evaluated as HIV-1 protease inhibitors in in vitro assays. While the NH and N-methyl derivatives 3a,b,e,f were almost inactive with IC(50) values of about 200 microM, the N-Benzyl compounds exhibited stronger activity with an IC(50) value of 16.2 microM for the presently best compound 3c. The type of HIV-1 protease inhibition of these novel inhibitors was characterized as competitive. With the increase of observed activity from NH and N-methyl derivatives to N-benzyl compounds, respectively, the binding mode may correspond to that of cyclic and azacyclic ureas showing hydrophobic interactions of the four aromatic residues to the S1/S1' and S2/S2' regions of HIV-1 protease.

Dihydropyridines↗
PubMed1999

Selection of genetic variants of the 5' noncoding region of hepatitis C virus occurs only in patients responding to interferon alpha therapy.

Interferon alpha (IFN alpha) can suppress the replication of hepatitis C virus (HCV) in chronically infected patients. However, HCV persists in a significant number of patients despite the normalization of alanine transaminase (ALT) during IFN alpha therapy. In this study, HCV variants in patients under IFN alpha therapy were characterized to examine their role in viral persistence during the therapy. Sixteen patients selected for this study were infected with HCV genotype 1b and remained HCV RNA positive for at least 1 month after onset of therapy. Nine patients responded to the therapy in terms of normalization of ALT (responders), whereas seven patients did not show a significant decrease of ALT level (nonresponders). To examine HCV populations in these patients, the HCV 5' noncoding region (5' NCR) was analyzed by polymerase chain reaction amplification and sequencing. Newly emerging variants of the HCV 5' NCR replaced predominant variants present prior to IFN alpha therapy in six of nine responders. Most predominant HCV variants during IFN alpha therapy carried a nucleotide substitution G to A at nt 231 within the 5' NCR. An analysis of the HCV quasispecies population in one responder revealed that a preexisting variant became predominant under IFN alpha therapy. These results emphasized the importance of the genetic heterogeneity of the HCV genome for viral resistance to IFN alpha. Five of seven HCV isolates from nonresponders were identical to those found in responders with regard to the nucleotide sequence of the 5' NCR. However, no selection of variants of the HCV 5' NCR occurred in nonresponders during the course of therapy. We conclude that IFN alpha treatment leads to the selection of variants of the HCV 5' NCR only in responders and may act differently in nonresponders. Our results suggest that the HCV 5' NCR may be a target of anti-HCV actions of IFN alpha.

5' Untranslated Regions↗
PubMed1999

Ionization constants and distribution coefficients of phenothiazines and calcium channel antagonists determined by a pH-metric method and correlation with calculated partition coefficients.

The pH-metric technique was used to determine the ionization constants and distribution coefficients of 10 phenothiazines and five ionizable calcium channel antagonists. Because the studied compounds were poorly water soluble and quite lipophilic with partition coefficients in the range of 3.5 to 5.5, organic cosolvents had to be added for the determination of the ionization constants to avoid precipitation of the free bases. The effect of the cosolvents dioxane and methanol on the extrapolation to pure water was compared. For both cosolvents a very good agreement with accessible published ionization constants was obtained, however the slope of the regression line was much smaller for dioxane, yielding more reliable estimates according to the standard deviation of the extrapolated values. Thus, dioxane might be preferable to methanol as a cosolvent for the determination of ionization constants of sparingly water soluble bases. Also the n-octanol/water partition coefficients were determined and compared with published data and values calculated with the ClogP, ACD, and HINT programs. Although the obtained values were approximate in conformity with the published data, the calculated partition coefficients differed from the experimental ones considerably for the majority of the investigated compounds. Furthermore, the ion pair partitioning and the distribution coefficients at physiological pH 7.4 were determined. The pH-dependent distribution profiles showed the strong influence of the ionization constants and of the distribution of the ion pairs on the overall distribution. This result strongly suggests that greater use should be made of measured distribution coefficients in quantitative structure-activity relationship studies. The potentiometric method is a convenient way to determine the distribution properties of drug molecules at pH values relevant for the biological system under investigation.

Algorithms↗
PubMed1999

Comparison of azacyclic urea A-98881 as HIV-1 protease inhibitor with cage dimeric N-benzyl 4-(4-methoxyphenyl)-1,4-dihydropyridine as representative of a novel class of HIV-1 protease inhibitors: a molecular modeling study.

The functional groups of cage dimeric N-alkyl substituted 3,5-bis(hydroxymethyl)-4-(4-methoxyphenyl)-1,4-dihydropyridines are similar to those of cyclic and azacyclic ureas that are potent inhibitors of HIV-1 protease of the dihydroxyethylene- and hydroxyethylene type, respectively. In the following study the conformity of common functional groups is investigated concerning their orientation in space as well as in the enzyme HIV-1 protease. Starting from X-ray crystal data of the centrosymmetric cage dimeric N-benzyl derivative with ester groups, the derivative with hydroxymethylene groups was built and a systematic conformational search was performed for the conformationally important torsion angles considering electrostatic and van der Waals interactions. From the huge number of conformations those comprising centrosymmetrical and C2-symmetrical energy minima were selected and minimized. The three remaining conformers were fitted to the azacyclic urea A-98881 selected from the HIV-1 protease enzyme-inhibitor complex using the centroids of the corresponding aromatic residues and additionally by the field fit option of the Advanced CoMFA module of SYBYL. Interestingly, the energetically most favourable one, which, additionally, possesses C2-symmetry like the active site cavity of HIV-1 protease, showed the best fit. Comparing the electrostatic potential (EP) of the latter with the EP of A-98881 the aromatic residues show excellent accordance. Slight differences in the extent of the EP were found in the areas of the hydroxymethylene groups of the cage dimer and the single hydroxy group as well as the urea carbonyl group of A-98881, respectively. In order to compare the binding possibilities to the enzyme HIV-1 protease for the cage dimer and A-98881, their interaction fields with certain probes (CH3 for alkyl, NHamide, and carbonyl, O- of COO-), representing the decisive functional groups of the active site, have been calculated using GRID and projected into the enzyme placing the structures according to the position of A-98881 in the enzyme-inhibitor complex. The strongest calculated fields of the O- probe were found near Asp 25 for both structures. Another respective conformity consists in the overlap of the fields for the NHamide probe near Ile 50 and 50' for the investigated cage dimer and A-98881.

Anti-HIV Agents↗
PubMed1999

A new method to evaluate the consolidation behavior of pharmaceutical materials by using the Fraser-Suzuki function.

A new method was developed to evaluate the consolidation behavior of different pharmaceutical materials. A method to evaluate the elastic deformation of the different parts of the tablet machine is described. The used model is based on the Fraser--Suzuki function, which was modified to fit the force-time course. This function has three parameters, which describe the consolidation behaviour of pharmaceutical materials. Parameter A (form of the increasing part of the force-time course) and tr parameter (time of force maximum) give qualitative evaluation of the irreversible deformation during the compression process. Parameter S (form of the decreasing part of the curve) describes the decompression phase and provides information about the elastic behaviour of the compressed material. In this article, the importance of the different parameters is presented. The applicability of this function to different kinds of ethylcellulose is also presented.

Cellulose↗
PubMed1998

Structure of a filamentous phosphoglycoprotein polymer: the secreted acid phosphatase of Leishmania mexicana.

The insect stage of the protozoan parasite Leishmania mexicana secretes a filamentous acid phosphatase (secreted acid phosphatase, SAP), a polymeric phosphoglycoprotein. The wild-type (wt) SAP filament is a copolymer composed of two related gene products SAP1 and SAP2, which are identical in the enzymatically active NH2-terminal domain and the COOH-terminal domain, but differ in the length of a highly glycosylated Ser/Thr-rich repeat region (32 amino acids and 383 amino acids, respectively) which is located between these domains. When expressed separately, full length SAP1, SAP2, or the NH2-terminal domain alone, are able to assemble into filaments. The Ser/Thr-rich region is the exclusive target for a novel type of O-glycosylation via phosphoserines. By using glycerol spraying/low-angle rotary metal shadowing and labelling with monoclonal antibodies it is demonstrated that the repetitive region adopts an extended conformation forming side arms which project radially from the filament core and terminate with the COOH-terminal domain. The length of the side arms of SAP1 and SAP2 (20 nm and 90 nm, respectively) corresponds to the predicted length of the Ser/Thr-rich repeat region of SAP1 and SAP2. Mass determination by scanning electron microscopy (STEM) shows that one morphologically defined globular particle of the filament core is a polypeptide dimer. We propose a model for the filament core, in which the globular NH2-terminal SAP domains form one strand composed of polypeptide dimers or two tightly associated strands of monomers which may twist into a double helix, similar to actin filaments. The highly O-glycosylated side arms project from the filament core conferring an overall bottle-brush-like appearance. The L. mexicana SAP is compared to SAPs secreted by the closely related species L. amazonensis and L. donovani.

Acid Phosphatase↗
PubMed1998

Molecular modeling of phenothiazines and related drugs as multidrug resistance modifiers: a comparative molecular field analysis study.

A set of 40 phenothiazines, thioxanthenes, and structurally related drugs with multidrug resistance modulating activity in tumor cells in vitro were selected from literature data and subjected to three-dimensional quantitative structure-activity relationship study using comparative molecular field analysis (CoMFA). More than 350 CoMFA models were derived and evaluated using steric, electrostatic, and hydrophobic fields alone and in combination. Four alignment strategies based on selected atom pairs or field fit alignment were compared. Several training and test sets were analyzed for both neutral and protonated drug forms separately. Each chemical class was trained and tested individually, and finally the classes were combined together into integrated models. All models obtained were statistically significant and most of them highly predictive. All fields contributed to MDR reversing activity, and hydrophobic fields improved the correlative and predictive power of the models in all cases. The results point to the role of hydrophobicity as a space-directed molecular property to explain differences in anti-MDR activity of the drugs studied.

Antineoplastic Agents↗