Biomedical subjects

M Reitz

Publications and source records attributed to M Reitz.

At least 37 records · Page 2Linked to original sources

PubMed2000

Expression and characterization of a single-chain polypeptide analogue of the human immunodeficiency virus type 1 gp120-CD4 receptor complex.

The infection of CD4(+) host cells by human immunodeficiency virus type 1 (HIV-1) is initiated by a temporal progression of interactions between specific cell surface receptors and the viral envelope protein, gp120. These interactions produce a number of intermediate structures with distinct conformational, functional, and antigenic features that may provide important targets for therapeutic and vaccination strategies against HIV infection. One such intermediate, the gp120-CD4 complex, arises from the interaction of gp120 with the CD4 receptor and enables interactions with specific coreceptors needed for viral entry. gp120-CD4 complexes are thus promising targets for anti-HIV vaccines and therapies. The development of such strategies would be greatly facilitated by a means to produce the gp120-CD4 complexes in a wide variety of contexts. Accordingly, we have developed single-chain polypeptide analogues that accurately replicate structural, functional, and antigenic features of the gp120-CD4 complex. One analogue (FLSC) consists of full-length HIV-1BaL gp120 and the D1D2 domains of CD4 joined by a 20-amino-acid linker. The second analogue (TcSC) contains a truncated form of the gp120 lacking portions of the C1, C5, V1, and V2 domains. Both molecules exhibited increased exposure of epitopes in the gp120 coreceptor-binding site but did not present epitopes of either gp120 or CD4 responsible for complex formation. Further, the FLSC and TcSC analogues bound specifically to CCR5 (R5) and blocked R5 virus infection. Thus, these single-chain chimeric molecules represent the first generation of soluble recombinant proteins that mimic the gp120-CD4 complex intermediate that arises during HIV replication.

AIDS Vaccines↗

PubMed1999

Seroprevalence of human herpesvirus-8 (HHV-8) in countries of Southeast Asia compared to the USA, the Caribbean and Africa.

Seroprevalence of HHV-8 has been studied in Malaysia, India, Sri Lanka, Thailand, Trinidad, Jamaica and the USA, in both healthy individuals and those infected with HIV. Seroprevalence was found to be low in these countries in both the healthy and the HIV-infected populations. This correlates with the fact that hardly any AIDS-related Kaposi's sarcoma has been reported in these countries. In contrast, the African countries of Ghana, Uganda and Zambia showed high seroprevalences in both healthy and HIV-infected populations. This suggests that human herpes virus-8 (HHV-8) may be either a recently introduced virus or one that has extremely low infectivity. Nasopharyngeal and oral carcinoma patients from Malaysia, Hong Kong and Sri Lanka who have very high EBV titres show that only 3/82 (3.7%) have antibody to HHV-8, demonstrating that there is little, if any, cross-reactivity between antibodies to these two gamma viruses.

Adolescent↗

PubMed1999

Effects of propofol (intravenous propofol emulsion) on cell membranes measured by electrofusion and electroporation.

The influence of propofol (CAS 2078-54-8 (intravenous propofol emulsion) on cell membrane properties was investigated in vitro with techniques of cell electrofusion and cell electroporation. Human lymphoma cells and plant protoplasts were chosen as a model system. Propofol (intravenous propofol emulsion) decreased the electrofusion yield of the cells and their membrane permeability. A 50% decrease in relative electrofusion was observed in human lymphoma cells in the presence of about 0.05 mmol/l propofol (intravenous propofol emulsion) and in plant protoplasts in the presence of about 0.1 mmol/l. The fusion of human lymphoma cells was inhibited to 100% at concentrations higher than 0.2 mmol/l propofol and 0.4 mmol/l intravenous propofol emulsion. The membrane permeability of human lymphoma cells decreased by the factor of two with increasing propofol concentrations up to about 0.1 mmol/l. The effects of electroporation were highly reversible. Propofol (intravenous propofol emulsion) was more effective than tetracaine. These sensitive techniques are suitable for the investigation of interactions between anesthetic drugs and the cell membrane.

Anesthetics, Intravenous↗

PubMed1998

Differences between 'congenital mirror movements' and 'associated movements' in normal children: a neurophysiological case study.

In this study we analysed how far physiological associated movements in normal children (which may be present up to the age of 10 years) share the same physiological mechanism with clinically apparent mirror movements. Transcranial magnetic stimulation (TMS) and kinematic movement analysis were applied in a 4-year-old child with congenital mirror movements (CMM). The results were compared with a normative data base of clinically normal children. In the child with CMM focal TMS of one motor cortex induced bilaterally symmetrical responses in distal and proximal upper extremities muscles with identical ipsi- and contralateral latencies. Also kinematic analysis showed a precise symmetrical onset of intended and unintended contralateral movements, whereas normal children with associated movements showed a variable movement onset delay between extremities. The data suggest a different physiological mechanism underlying these two varieties of elementary associated motor activity in childhood.

Biomechanical Phenomena↗

PubMed1998

Variations of DNA damage in human lymphocytes after enflurane exposure in vitro.

The rate of DNA single strand-breaks in lymphocytes of 160 human donors were determined after enflurane (CAS 13838-16-9) exposure in vitro. The rate of DNA damage increased in relation to the exposed enflurane concentration. However, not every lymphocyte sample showed an increased rate of DNA damage; some samples showed an increased rate even after exposure to only 0.4 vol% enflurane and other samples showed no increased rate even after exposure to 4.0 vol% enflurane. After exposure to 0.6 vol% enflurane and more the increased rate of DNA damage is statistically significant. The DNA damage in the lymphocytes differs individually. The reasons may be genetic differences in DNA repair. In patients with DNA repair deficiencies anesthesia with enflurane may induce irreversible DNA damage.

Adolescent↗

PubMed1997

Expression of human herpesvirus 8-encoded cyclin D in Kaposi's sarcoma spindle cells.

BACKGROUND: Human herpesvirus 8 (HHV-8) DNA sequences have been detected in Kaposi's sarcoma, in primary effusion lymphoma (an unusual high-grade non-Hodgkin's lymphoma seen primarily in patients with acquired immunodeficiency syndrome [AIDS]), and in Castleman's disease (a rare lymphoproliferative disorder); however, proof that HHV-8 is involved in the pathogenesis of these diseases remains to be established. HHV-8 contains a gene, i.e., v-cyclin D, that is a homologue of the cellular cyclin D2 gene, which encodes a protein that promotes passage through G1 phase of the cell cycle. Previous studies have identified v-cyclin D messenger RNA (mRNA) in biopsy specimens of Kaposi's sarcoma. In this study, we isolated a full-length v-cyclin D complementary DNA and characterized the pattern of v-cyclin D mRNA expression in Kaposi's sarcoma. METHODS: Standard methods were used to construct and to screen HHV-8 genomic and complementary DNA libraries. Reverse transcription-polymerase chain reaction (RT-PCR) methods and in situ hybridization with RNA probes were used to examine v-cyclin D mRNA expression. RESULTS: RT-PCR demonstrated the presence of v-cyclin D mRNA in biopsy specimens of AIDS-related Kaposi's sarcoma, in early-passage spindle cells from classical (i.e., not AIDS-related) Kaposi's sarcoma, and in spindle cells isolated from the peripheral blood of patients with AIDS-related Kaposi's sarcoma. In situ hybridization indicated that mRNAs for v-cyclin D and kaposin, an HHV-8 latency-associated gene, were present in approximately 1% of the spindle cells in early patch lesions and approximately 60% of the spindle cells in late nodular lesions of Kaposi's sarcoma. CONCLUSIONS: Spindle cells of Kaposi's sarcoma, which have been regarded as the tumor cells of this cancer, contain v-cyclin D mRNA. Expression of v-cyclin D protein may be involved in the pathogenesis of Kaposi's sarcoma by promoting cell proliferation.

Blotting, Southern↗

PubMed1997

Ontogeny of ipsilateral corticospinal projections: a developmental study with transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) has been used to describe the maturation of the corticospinal tract in children. Ipsilateral corticospinal connections have been demonstrated with TMS in patients with congenital mirror movements, in patients after hemispherectomy, and in children with hemiplegic cerebral palsy. The goal of the study was to find out whether corticospinal ipsilateral projections in children can be demonstrated during the first decade of life as part of normal ontogeny. For this purpose, we examined 50 normal children (age range, 3-11 years) with focal TMS over the left and right hemispheres to target muscles in proximal and distal parts of the upper extremity (first dorsal interosseus, biceps brachii, and brachioradialis). To lower the stimulation threshold, we stimulated under voluntary preinnervation. In two-thirds of the children we elicited ipsilateral motor evoked potentials (MEPs). This occurred more often in proximal than in distal muscles. The latency of the ipsilateral MEPs was about 12 to 14 msec longer than the usual contralateral response. From the age of 10, and in adults, ipsilateral MEPs could not be detected. Also considering lesion data from adult patients, the most likely explanation for the disappearance of ipsilateral corticospinal connections after the age of 10 years is an increasing transcallosal inhibitory influence during development. The presence of ipsilateral corticospinal connections appears to be a normal state in ontogeny.

Adult↗

PubMed1997

Detection of DNA damage in stimulated human lymphocytes after adding cytostatic drugs in vitro. A model to demonstrate individual damage rates.

The DNA damaging effect of different concentrations of methotrexate, 6-mercaptopurine, 6-thioguanine and cisplatin was tested by nucleoid sedimentation in pokeweed mitogen (PWM)-stimulated lymphocytes of 16 healthy persons in vitro. The examined persons show an individual variation of DNA damage demonstrating individual differences in DNA repair. The method can be used to identify persons with a low DNA repair capacity, and possible cytogenetic side effects of cytostatic drugs can be calculated before starting a cancer therapy. In clinical practice the use of cytostatic drugs is limited because of the side effects on normal tissues. The cancer therapist can improve a cytostatic therapy when he obtains information about possible DNA damage of cytostatic drugs in cells of the patient at the beginning of the therapy.

Adult↗

PubMed1996

Reduced neutral DNase activity in the urine of children after cytostatic therapy.

In children with cancer a reduced neutral urine DNase activity was observed at the end of cytostatic therapy. It is presumed that disorders in the kidney functions are the cause. A low neutral DNase activity is found in the blood; the activity is inhibited by inhibitors. The inhibitors of the enzyme are split away in the kidneys so that the neutral DNase activity in urine increases. Many cytostatic drugs can induce damage to the kidneys. This may be the reason that not all inhibitors of neutral DNase are split away in the kidneys and the activity of the neutral urine DNase is reduced at the end of cytostatic therapy. The process of removing the inhibitors is independent of the filtering capacity of the kidneys.

Antineoplastic Agents↗

PubMed1994

DNA single-strand breaks in peripheral lymphocytes of clinical personnel with occupational exposure to volatile inhalational anesthetics.

The rates of DNA single-strand breaks in peripheral lymphocytes of 41 persons administering anesthesia daily and 44 control persons were determined by nucleoid sedimentation. There is a significantly higher rate of DNA single-strand breaks in nonsmoking anesthesia persons than in nonsmoking control persons (P < 0.01). Smoking anesthesia persons and smoking control persons presented increased rates of DNA single-strand breaks. Nonsmoking nurse anesthetists showed an insignificantly higher rate of damage than nonsmoking anesthesiologists. DNA single-strand breaks indicate damage before the start of DNA repair. Therefore, detected DNA single-strand breaks may be reversible. As not every DNA repair is perfect, increased rates of DNA single-strand breaks may possibly lead to irreversible DNA damage.

Adult↗

PubMed1994

Temporal analysis of the antibody response to HIV envelope protein in HIV-infected laboratory workers.

Three laboratory workers have been infected with the IIIB strain of HIV; their antibody response to HIV has been studied in serial serum specimens. Because the infecting virus is known, the fine specificity of the antibody response was studied on the homologous strain of HIV. Anti-p17, anti-p24, anti-gp160, CD4/gp120 blocking and neutralizing antibodies developed in parallel. Epitope mapping of the anti-gp160 response indicated several regions that consistently induced an antibody response. Serum contained antibody which reacted with V3-specific peptides corresponding to the very tip of the loop and crossreactivity was seen with V3 loop peptides from other sequence divergent strains of HIV. Antibody to the V1 loop was produced at levels comparable with that seen for the V3-loop. Anti-V1 neutralized HIV with a titration curve equivalent to an anti-V3 monoclonal antibody. Because the infecting virus is known and serial reisolates have been obtained, we explored the relationship between production of antibody to a given epitope and mutation in the virus. The data suggest that an association exists, but do not clearly indicate that antibody drives the selection for mutant viruses. The findings presented here provide a fine specificity analysis of the evolution of the antibody response to HIV in greater detail than has previously been performed.

Amino Acid Sequence↗

PubMed1993

Inhibition of human immunodeficiency virus type 1 replication by regulated expression of a polymeric Tat activation response RNA decoy as a strategy for gene therapy in AIDS.

We are investigating a strategy for somatic gene therapy to treat human immunodeficiency virus type 1 (HIV-1) infection by intracellular expression of an RNA decoy and a ribozyme. The RNA decoy, consisting of polymeric Tat activation response elements (TARs), is designed to compete for Tat binding in an equilibrium with viral TAR RNA, thereby inhibiting viral replication. The expression of polymeric TAR is regulated by the HIV long terminal repeat (LTR) and transcriptional activation is dependent on the presence of HIV Tat. Our initial studies indicated that plasmids expressing up to 50 tandem copies of TAR RNA (50TAR) inhibited tat-mediated gene expression by > 90% in a transient transfection assay. A HIV LTR-driven 50TAR construct was subcloned into a replication-defective retroviral vector to ensure high-efficiency gene transfer into T lymphocytes. In addition, a gag RNA-specific ribozyme gene was introduced into the 50TAR containing retroviral vector to enhance the inhibitory effect of the construct (designated TAR-Rib). A human T-cell line (Molt3) was infected (transduced) with the TAR-Rib recombinant retrovirus and challenged with either HIV-1 or simian immunodeficiency virus (SIV). HIV-1 replication was inhibited by 99% in the TAR-Rib-transduced T cells and was maintained over a 14-month period, suggesting that this antiviral strategy represses the formation of escape mutants. Interestingly, the TAR-Rib also inhibited SIV replication in transduced T cells, which suggests that polymeric TAR is a general inhibitor of primate lentiviruses; therefore, the macaque model could be used for further in vivo testing of this antiviral gene therapy strategy.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Increasing rates of DNA single-strand breaks in lymphocytes of clinical personnel handling cytostatic drugs.

A total of 27 persons, working in cancer stations with exposure to cytostatics, and 40 healthy control persons were examined for DNA single-strand breaks in peripheral lymphocytes. Non-smoking personnel from cancer stations were found to have an increased rate of DNA single-strand breaks compared to the non-smoking control subjects. In the case of smokers an increased rate of DNA single-strand breaks could be recorded for those working in cancer stations as well as with the controls. DNA single-strand breaks indicate reversible damage to DNA. As DNA repair is not perfect in every case, an increased number of DNA single-strand breaks leads to irreversible DNA damage.

Adult↗

PubMed1993

Serological, biological, and molecular characterization of New Zealand white rabbits infected by intraperitoneal inoculation with cell-free human immunodeficiency virus.

The availability of a small laboratory animal model suitable for the evaluation of methods for prevention and treatment of human immunodeficiency virus type 1 infection would be a valuable resource for AIDS research. Here we describe the infection of a strain of domestic rabbits by intraperitoneal inoculation with cell-free human immunodeficiency virus type 1. Evidence of infection includes the presence of an immune response that has persisted for almost 3 years and the detection of an reisolation of infectious virus from peripheral blood mononuclear cells (PBMCs) and other tissues during the first 2 years. Typical viral proteins, DNA and RNA patterns, were observed in rabbit PBMCs and in cells infected by cocultivation with rabbit PBMCs. While a number of possible pathological changes were evaluated in infected rabbits, the presence of changes in lymph node structure similar to those reported in infected humans merits further investigation.

Acquired Immunodeficiency Syndrome↗

PubMed1993

DNA single strand breaks in peripheral human lymphocytes after anesthesia with isoflurane-nitrous oxide-oxygen.

DNA single strand breaks were determined in peripheral lymphocytes of neurosurgical patients before and after 180 min of general anesthesia with isoflurane (CAS 26675-46-7)-nitrous oxide-oxygen. Immediately after anesthesia, the frequency of DNA single strand-breaks appeared to be significantly enhanced. In the majority of patients the DNA single strand breaks induced was equivalent to the effect of 0.2-0.5 Gray following x-ray radiation of lymphocytes in vitro. In a part of the examined patients these investigations were repeated on the first postoperative day. Then an increase of the frequency of DNA single strand breaks could not be demonstrated any more. The DNA single strand breaks were repaired by cellular repair systems. As DNA repair is regulated genetically, isoflurane-nitrous oxide-oxygen could induce DNA damage in patients with DNA repair defects.

Adolescent↗

PubMed1993

Increasing DNase I activity after exposure of isolated DNA to halothane.

DNA was exposed to halothane (CAS 151-67-7) in a cell-free system. After exposure the DNA was used as substrate for DNase I from bovine pancreas. The DNase I activity increased after halothane exposure of the substrate depending on time and doses. Drugs are able to influence the DNA conformation. Conformational changes in the DNA can enhance the DNase I cleavage rate. Therefore, it is possible that halothane exposure induces changes in DNA conformation demonstrable by an increased DNase I activity. The results suggest a mechanism by which halothane may contribute to chromosomal defects and disturbances of DNA metabolism in cells.

Animals↗

PubMed1993

DNA strand breaks in cells with DNA repair deficiency after halothane exposure in vitro.

Halothane (CAS 151-67-7) induced DNA strand breaks in isolated lymphocytes of two patients with a deficient DNA repair (xeroderma pigmentosum). In lymphocytes (resting cells) of healthy human donors and in L 5178 Y cells (proliferating cells) of mouse lymphoma, halothane did not induce demonstrable DNA strand breaks. The cells were exposed to 1.0 vol/% halothane for 60 min, and the DNA strand breaks were demonstrated by alkaline elution. The results suggest a possible genotoxic side effect of halothane in patients with deficiency in DNA repair.

Adult↗

PubMed1992

Detection of DNA damage in stimulated human lymphocytes after enflurane exposure in vitro.

DNA damage was detected by nucleoid sedimentation in human lymphocytes stimulated with pokeweed mitogen after exposure to enflurane. Enflurane induces DNA damage at an exposure concentration of 0.2 vol%. Higher enflurane concentrations increase the rate of DNA damage. The DNA damage seen after exposure to enflurane concentrations of 0.2 and 3.0% vol is comparable to damage after X-radiation of 0.1 and 0.7 Gy. DNA single-strand breaks can be demonstrated by nucleoid sedimentation and can indicate damage before DNA repair begins. Therefore, detected DNA single-strand breaks may be reversible. However, DNA repair is not always successful and an increased number of DNA single-strand breaks could lead to irreversible DNA damage. The method of nucleoid sedimentation helps to show DNA damage in proliferating cells after exposure to volatile anesthetics or therapeutic gases.

Cells, Cultured↗