PubMed Health⌕ Search

Biomedical subjects

M Weisse

Publications and source records attributed to M Weisse.

10 recordsLinked to original sources
PubMed2001

Induction of alpha-synuclein aggregation by intracellular nitrative insult.

Brain lesions containing filamentous and aggregated alpha-synuclein are hallmarks of neurodegenerative synucleinopathies. Oxidative stress has been implicated in the formation of these lesions. Using HEK 293 cells stably transfected with wild-type and mutant alpha-synuclein, we demonstrated that intracellular generation of nitrating agents results in the formation of alpha-synuclein aggregates. Cells were exposed simultaneously to nitric oxide- and superoxide-generating compounds, and the intracellular formation of peroxynitrite was demonstrated by monitoring the oxidation of dihydrorhodamine 123 and the nitration of alpha-synuclein. Light microscopy using antibodies against alpha-synuclein and electron microscopy revealed the presence of perinuclear aggregates under conditions in which peroxynitrite was generated but not when cells were exposed to nitric oxide- or superoxide-generating compounds separately. alpha-Synuclein aggregates were observed in 20-30% of cells expressing wild-type or A53T mutant alpha-synuclein and in 5% of cells expressing A30P mutant alpha-synuclein. No evidence of synuclein aggregation was observed in untransfected cells or cells expressing beta-synuclein. In contrast, selective inhibition of the proteasome resulted in the formation of aggregates detected with antibodies to ubiquitin in the majority of the untransfected cells and cells expressing alpha-synuclein. However, alpha-synuclein did not colocalize with these aggregates, indicating that inhibition of the proteasome does not promote alpha-synuclein aggregation. In addition, proteasome inhibition did not alter the steady-state levels of alpha-synuclein, but addition of the lysosomotropic agent ammonium chloride significantly increased the amount of alpha-synuclein, indicating that lysosomes are involved in degradation of alpha-synuclein. Our data indicate that nitrative and oxidative insult may initiate pathogenesis of alpha-synuclein aggregates.

Ammonium Chloride↗
PubMed2001

Dynamic regulation of metabolism and respiration by endogenously produced nitric oxide protects against oxidative stress.

One of the many biological functions of nitric oxide is the ability to protect cells from oxidative stress. To investigate the potential contribution of low steady state levels of nitric oxide generated by endothelial nitric oxide synthase (eNOS) and the mechanisms of protection against H(2)O(2), spontaneously transformed human ECV304 cells, which normally do not express eNOS, were stably transfected with a green fluorescent-tagged eNOS cDNA. The eNOS-transfected cells were found to be resistant to injury and delayed death following a 2-h exposure to H(2)O(2) (50-150 microM). Inhibition of nitric oxide synthesis abolished the protective effect against H(2)O(2) exposure. The ability of nitric oxide to protect cells depended on the presence of respiring mitochondria as ECV304+eNOS cells with diminished mitochondria respiration (rho(-)) are injured to the same extent as nontransfected ECV304 cells and recovery of mitochondrial respiration restores the ability of nitric oxide to protect against H(2)O(2)-induced death. Nitric oxide also found to have a profound effect in cell metabolism, because ECV304+eNOS cells had lower steady state levels of ATP and higher utilization of glucose via the glycolytic pathway than ECV304 cells. However, the protective effect of nitric oxide against H(2)O(2) exposure is not reproduced in ECV304 cells after treatment with azide and oligomycin suggesting that the dynamic regulation of respiration by nitric oxide represent a critical and unrecognized primary line of defense against oxidative stress.

Adenosine Triphosphate↗
PubMed2000

Proteolytic degradation of tyrosine nitrated proteins.

Tyrosine nitration is a covalent posttranslational protein modification that has been detected under several pathological conditions. This study reports that nitrated proteins are degraded by chymotrypsin and that protein nitration enhances susceptibility to degradation by the proteasome. Chymotrypsin cleaved the peptide bond between nitrated-tyrosine 108 and serine 109 in bovine Cu,Zn superoxide dismutase. However, the rate of chymotryptic cleavage of nitrated peptides was considerably slower than control. In contrast, nitrated bovine Cu,Zn superoxide dismutase was degraded at a rate 1. 8-fold faster than that of control by a gradient-purified 20S/26S proteasome fraction from bovine retina. Exposure of PC12 cells to a nitrating agent resulted in the nitration of tyrosine hydroxylase and a 58 +/- 12.5% decline in the steady-state levels of the protein 4 h after nitration. The steady-state levels of tyrosine hydroxylase were restored by selective inhibition of the proteasome activity with lactacystin. These data indicate that nitration of tyrosine residue(s) in proteins is sufficient to induce an accelerated degradation of the modified proteins by the proteasome and that the proteasome may be critical for the removal of nitrated proteins in vivo.

Animals↗
PubMed1999

Gene expression from the ORF50/K8 region of Kaposi's sarcoma-associated herpesvirus.

The ORF50 gene of Kaposi's sarcoma (KS)-associated herpesvirus, or human herpesvirus 8 (KSHV), activates viral replication and is weakly homologous to the herpesvirus family of R transactivators; therefore, the transcription and translation events from this region of KSHV are key events in viral reactivation. We demonstrate that ORF50 is expressed in a bicistronic message after induction of the viral lytic cycle. ORF50 migrated as a series of polypeptides: the major ones as 119 and 101 kDa, respectively. Using 3' rapid amplification of cDNA ends, RT-PCR, and cDNA library screening, we demonstrate that the major ORF50 transcript also encodes K8. The ORF50/K8 transcript was resistant to cyclohexamide, whereas the K8 transcript was only partially resistant to cyclohexamide at early timepoints. Both transcripts showed partial resistance after 12 h of phorbol ester induction. Using a GAL4-ORF50 fusion protein expression vector, we demonstrate that the transactivation domain of ORF50 resides within a 160-amino-acid region of the carboxyl portion of the ORF. Upstream regions of both ORF50 and K8 have basal promoter activity in KSHV-infected cells. K8, which had sequence homology to Bzip proteins, did not activate either promoter. However, both promoters were activated after cotransfection of ORF50 in BCBL-1 cells.

Alternative Splicing↗
PubMed1999

Centennial year of Ronald Ross' epic discovery of malaria transmission: an essay and tribute.

Malaria has been in existence since ancient times and for millennia thought to be carried by vapors. Alphonse Laveran made the discovery of the malarial parasite in 1880. The next most important milestone in the history of malaria was the unraveling of the mystery of malaria transmission. Ronald Ross, born in British India and educated as a doctor in England, was working in the Indian Medical Service when he discovered the transmission of malarial parasites by mosquitoes in 1897. The next year, he completed the life cycle of malarial parasites in birds. In celebration of the centennial year of that epic discovery, we reminisce on that event, focusing on the discoverer.

England↗
PubMed1999

Comparative study of clinical evaluation of heart murmurs by general pediatricians and pediatric cardiologists.

In a study to compare the clinical diagnostic skills of academic general pediatricians and academic pediatric cardiologists in the evaluation of heart murmurs, a total of 128 patients (aged 1 month to 18 years) newly referred to a university pediatric cardiology clinic were evaluated by one of three general pediatricians and one of four pediatric cardiologists. The murmurs were clinically classified as innocent, pathologic, or possibly pathologic. The classification was revised after the review of electrocardiogram (EKG) and chest radiograph (CXR), if indicated. The definitive diagnosis was ascertained by echocardiography (94 normal, 34 abnormal). The general pediatricians identified as many pathologic heart murmurs as the pediatric cardiologists (27/34 vs. 29/34), with no difference in sensitivity, 79% vs. 85% (p = 0.53). The similarity in sensitivity could be because the general pediatricians were more cautious in the classification of heart murmurs and had classified more innocent heart murmurs as pathologic than the pediatric cardiologists (13/39 vs. 3/23), 41% vs. 13% (p = 0.02). The pediatric cardiologists correctly identified more innocent murmurs than general pediatricians (52/94 vs. 72/94), with a better specificity, 55% vs. 76% (p = 0.001); however, the accuracy of prediction of innocence was similar for both groups (52/59 vs. 72/77), 88% vs. 93% (p = 0.36). The revision of diagnosis with review of EKG and CXR was more often misleading than helpful for either group. Academic general pediatricians would identify most of the pathologic murmurs and are no more likely than an academic pediatric cardiologist to misclassify a pathologic heart murmur as innocent.

Adolescent↗
PubMed1993

False-negative urine latex particle agglutination testing in neonates with group B streptococcal bacteremia. A function of improper test implementation?

Although blood cultures remain the most specific indicator of Group B streptococcus (GBS) sepsis, a potentially life-threatening infection in neonates, test results may not be available for 24 to 48 hours. Detection of GBS antigen in the urine by latex particle agglutination (LPA) may speed diagnosis. This study analyzed the sensitivity of the GBS urine LPA assay under clinical conditions. The urine of neonates with early-onset GBS bacteremia was analyzed for GBS antigen over a three-year period at six military medical centers. Overall, 53.5% (38/71) of infants with positive blood cultures had a positive urine LPA test. Only one medical center routinely followed manufacturer's recommendations to concentrate urine specimens before testing. These data suggest that the sensitivity for the urine LPA assay, when performed on unconcentrated urine, is lower than previously reported. Clinicians should insist that the laboratory maximize sensitivity by concentrating urine prior to GBS LPA testing.

Antigens, Bacterial↗
PubMedDate not supplied

Failure of intrapartum antibiotics to prevent culture-proved neonatal group B streptococcal sepsis.

Early-onset group B streptococci (GBS-EOS) sepsis may be prevented by intrapartum antibiotics administered for GBS maternal colonization, premature labor, or prolonged rupture of membranes. We sought to identify cases of neonatal GBS sepsis after apparent failure of intrapartum chemotherapy and to determine the factors associated with failure of intrapartum antibiotics in these cases. We identified 96 GBS blood culture-positive infants at five military medical centers from 1987 to 1990. Eighteen (18.7%) of these infants had mothers who had received intrapartum antibiotics; 16 of 18 cases were early-onset disease, 15 of which initially had symptoms at less than 1 hour of age. Two infants had late-onset disease develop at 3 weeks of age. At least one perinatal risk factor (prematurity, prolonged rupture of membranes > 12 hours, maternal fever) was present in each of the 16 cases. Indications for intrapartum antibiotics were suspected chorioamnionitis (13 cases), GBS colonization and prolonged rupture of membranes or prematurity (3), and GBS colonization alone (2). Maternal antibiotics included ampicillin (14 cases), cephadyl (1), vancomycin (1), clindamycin (1), and gentamicin alone (1). The median number of doses of ampicillin before delivery was 1 (range, 1 to 21), which was administered at a median of 4 hours (range, 1 to 84) before birth. The mean dose of ampicillin was 1.8 gm/dose (range, 1 to 2 gm/dose). Two of 16 (12.5%) infants with GBS-EOS died as a result of GBS sepsis. In our population of neonates with GBS-EOS, 18.4% (16 of 87) of the infants had positive blood cultures despite intrapartum antibiotics. Intrapartum antibiotics may fail to prevent GBS sepsis in a number of infants born to mothers colonized with GBS or to those with acute chorioamnionitis.

Ampicillin↗