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Biomedical subjects

C Brenner

Publications and source records attributed to C Brenner.

At least 73 records · Page 4Linked to original sources
PubMed1998

A revolution in apoptosis: from a nucleocentric to a mitochondriocentric perspective.

In contrast to previous belief, it is now generally assumed that nuclear alterations constitute a sign rather than a mechanism of apoptosis. Until recently, research on apoptosis has been marked by three additional incorrect premises, namely that (1) mitochondria are not important for the regulation of cell death; (2) apoptosis is a linear sequence of molecular events in which clearly different effectors participate in pro-apoptotic signal transduction and apoptosis execution; and (3) apoptosis is fundamentally different from necrosis. Recent experimental data shed doubts on these notions, and rather suggest that (1) mitochondria exert a decisive role in cell death control; (2) apoptosis is likely to involve self-amplifying feedback loops in which the same molecule or process can participate at several levels; and (3) apoptosis and necrosis share a common pathway. These notions are changing the perception of the apoptotic process and will affect the exploration of age-associated alterations in cell death control.

Animals↗
PubMed1998

The central role of the mitochondrial megachannel in apoptosis: evidence obtained with intact cells, isolated mitochondria, and purified protein complexes.

The mitochondrial megachannel (also called permeability transition pore) is a polyprotein complex formed in the contact site between the inner and the outer mitochondrial membranes and participates in the regulation of mitochondrial membrane permeability. We have obtained three independent lines of evidence suggesting the implication of the mitochondrial megachannel in apoptosis. First, in intact cells, apoptosis is accompanied by an early dissipation of the mitochondrial transmembrane potential (delta psi m). In several models of apoptosis, specific agents inhibiting the mitochondrial megachannels prevent this delta psi m dissipation and simultaneously abolish the manifestations of caspase- and endonuclease activation, indicating that megachannel opening is a critical event of the apoptotic process. Second, mitochondria are rate-limiting for caspase and nuclease activation in several cell-free systems of apoptosis. Isolated mitochondria release apoptogenic factors capable of activating pro-caspases or endonucleases upon opening of the mitochondrial megachannel in vitro. Third, opening of the purified megachannel reconstituted into liposomes is inhibited by recombinant Bcl-2 or Bcl-XL, two apoptosis-inhibitory proteins which also prevent megachannel opening in cells and isolated mitochondria. This indicates that the megachannel is under the direct regulatory control of anti-apoptotic members of the Bcl-2 family. Altogether, our results suggest that megachannel opening is sufficient and (mostly) necessary for triggering apoptosis.

Animals↗
PubMed1998

Ooplasmic transfer in mature human oocytes.

Ooplasmic transplantation aimed at restoring normal growth in developmentally compromised oocytes and embryos was evaluated in seven couples (eight cycles) with multiple implantation failures. Two approaches were investigated to transfer ooplasm from donor eggs at metaphase II (MII) stage into patient MII eggs: (i) electrofusion of a ooplasmic donor fragment into each patient egg (three cycles), and (ii) direct injection of a small amount of ooplasm from a donor egg into each patient egg (five cycles). Some donor eggs were used multiple times. Donor eggs were divided into two groups, one being used for ooplasmic extraction and the other one for egg donation. Cleaved embryos resulting from the latter were cryopreserved, where numbers and satisfactory development permitted. A second control group consisted of embryos derived from patient eggs after intracytoplasmic sperm injection without ooplasmic transfer. This was performed when sufficient number of eggs were available (n = 5). Donor eggs (n = 40) were evaluated cytogenetically after micromanipulation in order to confirm the presence of chromosomes. One egg was anuclear and the recipient embryos were not transferred. Normal fertilization was significantly higher after injection of ooplasm (63%) in comparison with fusion (23%). Pronuclear anomalies appeared enhanced after fusion with ooplasts. Embryo morphology was not improved in the three cycles with electrofusion and patients did not become pregnant. An improvement in embryo morphology was noted in two patients after injection of ooplasm and both became pregnant, but one miscarried. A third pregnancy was established in the repeat patient, without obvious embryo improvement. One baby was born and the third pregnancy is ongoing with a normal karyotype. Two other patients with male factor infertility had poor embryos after ooplasmic injection, but the donor embryo controls were also poor. The patients did not become pregnant and had no donor embryos frozen. Ooplasmic transfer at the MII stage may be promising in patients with compromised embryos; however, evaluation of ooplasmic anomalies and optimization of techniques will require further investigation prior to widescale application.

Cell Culture Techniques↗
PubMed1998

Babbling of an infant with a repaired cleft lip: a case study.

The infant born with a cleft lip is faced with risk factors that threaten the development of speech-language skills. The earlier the age of identification and management of the developmental delay, the better the outcome. The attainment of the mature syllable is considered to be a critical measure of babbling competency. This single case study aimed to determine whether the formedness of the syllable in babbling would be affected by the cleft lip repaired prior to the onset of meaningful speech. Three samples of babbling in a naturalistic environment were video-recorded. Data was analysed following the principles of infraphonology, employing a perceptually-based method. A profile of infraphonological features was obtained. Results showed that the development of the mature syllable was attained. The results support the theories that babbling is a robust phenomenon. Clinical and research implications are discussed.

Child Language↗
PubMed1998

Mitochondria in chemotherapy-induced apoptosis: a prospective novel target of cancer therapy (review).

Resistance to apoptosis is a frequent characteristic of cancer cells and participates both in the initial phase of carcinogenesis and in the development of chemotherapy resistance. Recently, it has become clear that a disruption in mitochondrial membrane function is a decisive event of the apoptotic process leading to the disposal of chemotherapy-treated cells. Opening of the mitochondrial megachannel (also called permeability transition pore) is at least in part responsible for the disruption of mitochondrial membrane integrity in apoptosis. The megachannel is regulated by numerous endogenous effectors including members of the Bcl-2/Bax family, the redox status of the cell, cytosolic Ca2+ levels, ceramide, and amphipathic peptides. Chemotherapeutic agents may induce opening of the megachannel by modulating some of these endogenous effectors. The disruption of mitochondrial membrane integrity involves a loss of metabolic functions and the liberation of intermembrane proteins into the cytosol. Such proteins, which normally are well secluded in mitochondria, include cytochrome c and AIF (apoptosis inducing factor), which both activate caspases and endonucleases upon release into the cytosol. Strategies for the development of chemotherapeutic agents acting on mitochondria are discussed.

Animals↗
PubMed1997

A cytofluorometric assay of nuclear apoptosis induced in a cell-free system: application to ceramide-induced apoptosis.

Purified nuclei exposed to apoptogenic factors in vitro undergo morphological and biochemical changes in chromatin organization. Most cell-free models of nuclear apoptosis are based on the quantitation of endonuclease-mediated DNA fragmentation on agarose gels or on the changes of nuclear morphology revealed by the DNA-intercalating fluorochrome 4'-6-diamidino-2-phenylindole dihydrochloride. In this work we develop a cytofluorometric system for the accurate quantitation of nuclear DNA loss. This system has been used to determine the conditions of nuclear apoptosis induced by apoptosis-inducing factor (AIF) contained in the supernatant of mitochondria induced to undergo permeability transition. AIF can provoke significant nuclear DNA loss in < or = 5 min, acts over a wide pH range (pH 6 to 9), and resists cysteine protease inhibitors such as iodoacetamide and N-ethylmaleimide. Moreover, we applied this system to the question of how the proapoptotic second messenger ceramide would induce apoptosis in vitro: via a direct effect on nuclei, a direct effect on mitochondria, or via indirect mechanisms? Our data indicate that ceramide has to activate yet unknown cytosolic effectors that, in the presence of mitochondria, can induce nuclear apoptosis in vitro.

Animals↗
PubMed1997

Antiphospholipid antibodies and pregnancy rates and outcome in in vitro fertilization patients.

OBJECTIVE: To determine the relationship between antiphospholipid antibodies and pregnancy rates (PRs) and outcome among IVF patients. DESIGN: Prospective collection of all serum samples with assays for immunoglobulin G (IgG), IgA, and IgM antibodies for anticardiolipin, antiphosphatidyl serine, antiphosphatidyl ethanolamine, antiphosphatidyl choline, antiphosphatidyl inositol, antiphosphatidyl glycerol, and antiphosphatidic acid being done following completion of all treatment cycles. SETTING: A tertiary care teaching hospital. PATIENT(S): Seven hundred ninety-three patients attempting to conceive through IVF. MAIN OUTCOME MEASURE(S): Pregnancy rates (PRs) and pregnancy loss rates relative to each of the various antiphospholipid antibodies that were measured. RESULT(S): There were 528 pregnancies for an overall PR of 66%. Pregnancy rates were equal among patients with positive and negative antiphospholipid antibodies for each of the 21 measured antibodies. Use of receiver operator characteristic curves and logistic regression further confirmed that there was no relationship between PRs or outcome based on antiphospholipid antibodies for any definable threshold value. CONCLUSION(S): Elevated antiphospholipid antibody levels are not associated with any change in PRs or pregnancy loss rates in patients attempting to conceive through IVF.

Adult↗
PubMed1997

Crystal structures of HINT demonstrate that histidine triad proteins are GalT-related nucleotide-binding proteins.

Histidine triad nucleotide-binding protein (HINT), a dimeric purine nucleotide-binding protein from rabbit heart, is a member of the HIT (histidine triad) superfamily which includes HINT homologues and FHIT (HIT protein encoded at the chromosome 3 fragile site) homologues. Crystal structures of HINT-nucleotide complexes demonstrate that the most conserved residues in the superfamily mediate nucleotide binding and that the HIT motif forms part of the phosphate binding loop. Galactose-1-phosphate uridylyltransferase, whose deficiency causes galactosemia, contains tandem HINT domains with the same fold and mode of nucleotide binding as HINT despite having no overall sequence similarity. Features of FHIT, a diadenosine polyphosphate hydrolase and candidate tumour suppressor, are predicted from HINT-nucleotide structures.

Amino Acid Sequence↗
PubMed1997

Human immunodeficiency virus infection and AIDS in a person with negative serology.

A 38-year-old woman resident of Ivory Coast died of AIDS, while remaining human immunodeficiency virus (HIV)-seronegative. She had been regularly tested because her husband was HIV-seropositive. The subject's lack of specific antibodies was assessed using commercial tests and confirmed by a radioimmunoprecipitation assay of the patient's virus. She was unquestionably HIV-1-infected, with a high plasma virus load, and her virus could be isolated. Molecular analyses indicated this retrovirus was clade A, which is common in Africa, and it was highly homologous to the virus isolated from her husband. The subject's seronegative status was thought to be due to rapid depletion of specific CD4+ helper T cells, resulting from accelerated disease progression, and was host-related rather than due to a specific HIV strain.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Flunitrazepam excretion patterns using the Abuscreen OnTrak and OnLine immunoassays: comparison with GC-MS.

A study was conducted to compare the performance of the OnLine and OnTrak immunoassays for benzodiazepines with gas chromatographic-mass spectrometric (GC-MS) analysis in detecting flunitrazepam (FNP) and its metabolites in human urine. Urine was collected over a 72-h period from six individuals (four male and two female) who had taken a single oral dose of either 1 or 4 mg of FNP. The OnTrak assay was run at a 100-ng/mL cutoff of nordiazepam (NDP), and the OnLine assay was run with a standard curve from zero to 200 ng/mL of NDP with and without beta-glucuronidase treatment. Each sample was analyzed by GC-MS using FNP, 7-amino-FNP, 3-hydroxy-FNP, desmethyl-FNP, 7-amino-3-hydroxy-FNP, and desmethyl-3-hydroxy-FNP as standards with beta-glucuronidase treatment. The specimens from the 1-mg dose did not yield a positive result by immunoassay over the 72-h collection period. Specimens from the 4-mg dose did yield positive results in both immunoassays. The time of the first positive result ranged from 4 to 12 h, and the time to the last positive result ranged from 18 to 60 h. Treatment of the samples with beta-glucuronidase increased the OnLine values between 20 and 60%, but it did not appreciably increase the detection time. GC-MS analysis showed no detectable levels of FNP, 3-hydroxy-FNP, desmethyl-FNP, 7-amino-3-hydroxy-FNP, and desmethyl-3-hydroxy-FNP. However, all samples collected past time zero showed detectable levels of 7-amino-FNP (> 2 ng/mL) with peak concentrations at 12-36 h. The peak levels of 7-amino-FNP by GC-MS paralleled the peak levels of the immunoassay response. The amount of 7-amino-FNP metabolite quantitated by GC-MS, however, accounted for only 15-20% of the total immunoassay crossreactive FNP metabolites.

Administration, Oral↗
PubMed1997

Purification and crystallization of complexes modeling the active state of the fragile histidine triad protein.

Fragile histidine triad protein (Fhit) is a diadenosine triphosphate (ApppA) hydrolase encoded at the human chromosome 3 fragile site which is frequently disrupted in tumors. Reintroduction of FHIT coding sequences to cancer cell lines with FHIT deletions suppressed the ability of these cell lines to form tumors in nude mice even when the reintroduced FHIT gene had been mutated to allow ApppA binding but not hydrolysis. Because this suggested that the tumor suppressor activity of Fhit protein depends on substrate-dependent signaling rather than ApppA catabolism, we prepared two crystalline forms of Fhit protein that are expected to model its biologically active, substrate-bound state. Wild-type and the His96Asn forms of Fhit were overexpressed in Escherichia coli, purified to homogeneity and crystallized in the presence and absence of ApppA and an ApppA analog. Single crystals obtained by vapor diffusion against ammonium sulfate diffracted X-rays to beyond 2.75 A resolution. High quality native synchrotron X-ray data were collected for an orthorhombic and a hexagonal crystal form.

Acid Anhydride Hydrolases↗
PubMed1997

Spiralin, a mycoplasmal membrane lipoprotein, induces T-cell-independent B-cell blastogenesis and secretion of proinflammatory cytokines.

Mycoplasmas are bacteria which can cause respiratory, arthritic, and urogenital diseases. During the early phase of infection, mycoplasmas usually induce an inflammatory response and a humoral response preferentially directed against their membrane-bound, surface-exposed lipoproteins. In this report, we describe the effects on immune cells of spiralin, a well-characterized mycoplasmal lipoprotein. Purified spiralin stimulated the in vitro proliferation of human peripheral blood mononuclear cells and murine splenocytes. The stimulation pathway was probably different from that followed by Escherichia coli lipopolysaccharide because the effect of spiralin was not abolished by polymyxin B. Comparison of the effects of whole, native spiralin with those induced by proteinase K-digested spiralin or by the C-terminal half of spiralin (peptide p[13.5]T) revealed that the first half of the protein, which contains the lipoylated N terminus, is responsible for the mitogenic activity. In contrast to whole spiralin, proteinase K-digested spiralin did not trigger murine B-cell differentiation and immunoglobulin G and M secretion. Stimulation of human or murine immune cells led to early secretion of proinflammatory cytokines (human tumor necrosis factor alpha and murine interleukin 1 or 6). Spiralin induced the T-cell-independent blastogenesis of murine B cells but did not stimulate T cells. Altogether, our data demonstrate that spiralin possesses potent immunostimulating activity, similar to that reported for lipoproteins of pathogenic gracilicutes (gram-negative eubacteria; e.g., Borrelia burgdorferi OspA and E. coli Braun lipoprotein), and are consistent with the fact that lipoproteins are major antigens during mycoplasma infections.

Animals↗
PubMed1997

Evaluation of the dyspeptic patient: a cost-utility study.

BACKGROUND: Traditionally, patients presenting with uncomplicated dyspepsia have been managed using empiric antisecretory therapy, followed by endoscopy in the event of persistent symptoms or complication. Since Helicobacter pylori is now accepted as an important and potentially reversible cause of ulcer disease, it is important to reevaluate the management of dyspepsia. The goal of this study is to evaluate seven outpatient strategies for the management of dyspeptic patients using a cost-utility analysis. METHODS: The study design was that of a cost-utility analysis. The model assumes that an adult patient with signs of dyspepsia but no signs of complication presents to the outpatient office of a primary care physician. Seven strategies are modeled: empiric antisecretory therapy; empiric H pylori eradication using oral omeprazole (20 mg [corrected] twice daily), clarithromycin (500 mg twice daily), and amoxicillin (1000 mg twice daily); use of either upper endoscopy, an upper gastrointestinal barium study (an upper GI), or the serum titer for H pylori as a diagnostic test to identify patients for H pylori eradication; or use of an initial diagnostic test followed by the serum titer for H pylori. The primary outcome was the cost per quality-adjusted life year (QALY) for each strategy for a 1-year period from presentation; secondary outcomes included the probability of symptomatic ulcer recurrence, cost per ulcer cure, and mortality. RESULTS: Three strategies were similarly cost-effective: empiric H pylori eradication ($1198 per QALY), use of a serum H pylori titer as an initial diagnostic test ($1214 per QALY), and empiric antisecretory therapy ($1288 per QALY). Empiric antisecretory therapy, however, was associated with significantly more symptomatic ulcer recurrences and deaths than any other strategy. CONCLUSIONS: This cost-utility analysis suggests that two strategies are reasonable for patients presenting with dyspepsia: (1) empiric H pylori eradication and (2) use of a serum H pylori titer to identify patients who might benefit from H pylori eradication. The latter strategy may be preferable because it is less likely to lead to antibiotic resistance. Strategies utilizing an upper GI or upper endoscopy (either with or without serum H pylori titer) or empiric antisecretory therapy do not improve outcomes and are associated with greater cost, morbidity, and/or mortality.

Adult↗
PubMed1996

Mycoplasmas and HIV infection: from epidemiology to their interaction with immune cells.

Mycoplasmas are possible HIV cofactors, contributing to the evolution of AIDS. Our knowledge about mycoplasma prevalence in HIV-infected subjects has considerably increased due the development of specific detection assays. A new mycoplasma, Mycoplasma penetrans, has been identified and has been shown to be associated with HIV infection, at least among individuals with homosexual practices. We and others investigated the properties of M. fermentans and M. penetrans concerning cell colonization, cell invasion and cytopathogenicity. The molecular components which are involved in the interaction between these bacteria and immune cells are beginning to be identified and characterized. Membrane lipoproteins of these wall-less prokaryotes are key components in their interaction with B cells and surface capsular material may contribute to their defense from the host immune response.

HIV↗
PubMed1996

Comparison of methaqualone excretion patterns using Abuscreen ONLINE and EMIT II immunoassays and GC/MS.

A study was performed to compare the ONLINE and EMIT II immunoassays with gas chromatographic/mass spectrometric (GC/MS) analysis of methaqualone metabolites on urine using samples obtained from a clinical study. Urine was collected over a 72 h period from six healthy adults (4 male, 2 female) after oral dosing with 200 mg methaqualone (MTQ). Each urine sample was analyzed by ONLINE and EMIT II. The samples were then analyzed by GC/MS, hydrolyzed with beta-glucuronidase and again analyzed by GC/MS. Both immunoassays showed greater than 600 ng/ml concentrations of drug in each sample by the second void and remained highly positive for the rest of the 72 h. Unhydrolyzed samples analyzed by GC/MS showed both low concentrations of MTQ as well as its five major hydroxylated metabolites. The hydrolyzed samples analyzed by GC/MS showed high concentrations of the hydroxylated metabolites with the 2'-hydroxy and 3'-hydroxy metabolites being present at the highest concentrations, the 4'-hydroxy metabolite at a lower amount and the 6-hydroxy and 2-hydroxy metabolites at the lowest concentrations. The GC/MS data coupled with the antibody cross-reactivity data indicate that the major species in clinical samples that cross-react in both immunoassays are the conjugated forms of the hydroxylated metabolites of MTQ. Therefore when confirming by GC/MS after an immunoassay screen it would be prudent to confirm for the major hydroxylated metabolites as glucuronides of MTQ instead of the parent drug.

Adult↗
PubMed1996

Protective immunization with plasmid DNA containing the outer surface lipoprotein A gene of Borrelia burgdorferi is independent of an eukaryotic promoter.

Plasmid DNA encoding the outer surface lipoprotein A (OspA) of Borrelia burgdorferi under the control of either strong eukaryotic/viral or its own bacterial promoter was injected intramuscularly (m. tibialis anterior) or intradermally into BALB/c and AKR/N mice. OspA-specific antibodies and OspA-reactive T helper 1 cells (Th1) were induced only with those plasmids containing the ospA structural gene including its own regulatory control region immediately upstream. In the absence of the ospA promoter, no or only marginal immune responses to OspA were obtained, even when strong eukaryotic promoter/enhancer elements were present. Together with the finding that the ospA promoter is active in a mouse B-lymphoma line, the data suggest that spirochetes are able to express at least part of their genes in the mammalian environment. Mice previously vaccinated with the relevant ospA plasmid DNA were protected against subsequent experimental challenge with a virulent strain of B. burgdorferi, as measured by the appearance of antibodies to a prominent protective epitope (LA-2) and the failure to re-isolate spirochetes from ear biopsies. In addition, C.B-17 severe-combined immunodeficient mice could be protected against infection by passive transfer of immune sera from ospA plasmid DNA-inoculated normal mice. Protective LA-2-related antibody titers obtained after repeated immunization persisted for 200 days and longer. This simple procedure of immunization using plasmid DNA consisting of a prokaryotic gene under the control of its own promoter holds great promise for the development of alternative subunit vaccines against bacterial infections, including Lyme disease. In addition, the availability of this novel prokaryotic promoter element now allows the study of the basis for the differential expression of bacterial genes in prokaryotic and eukaryotic environments.

Animals↗
PubMed1996

Purification of Mycoplasma gallisepticum membrane proteins p52, p67 (pMGA), and p77 by high-performance liquid chromatography.

The plasma membrane of the avian pathogen Mycoplasma gallisepticum contains about 200 polypeptides including the major lipoprotein pMGA. We have developed a simple and efficient procedure for the purification of three membrane proteins of this wall-less bacterium. Proteins were selectively extracted from isolated plasma membranes with the mild zwitterionic detergent (N-dodecyl-N,N-dimethylammonio) undecanoate (DDMAU) and subjected to size-exclusion chromatography (FPLC) in the presence of the same detergent. Two of the thus separated protein fractions were subjected to a third step involving an anion-exchange chromatography (HPLC), also in the presence of DDMAU, which led to the purification to homogeneity of p67, the major acyl protein of M. gallisepticum plasma membrane (yield, 40%; purification factor, 11), p52 (yield, 38%; purification factor, 20), and p77 (yield, approximately 45%; purification factor, 500). Analyses performed by Western blotting and crossed immunoelectrophoresis showed that the three purified proteins are distinct antigens. Furthermore, N-terminal sequencing confirmed that p67 is pMGA. The method described in this paper is simple, efficient, and nondenaturing; it provides pure proteins, at the milligram level for p52 and p67, and should prove easy to being scaled-up if necessary.

Antigens, Surface↗