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Biomedical subjects

A Vincent

Publications and source records attributed to A Vincent.

At least 361 records · Page 20Linked to original sources
PubMed1987

[Pulmonary lymphangiomyomatosis and renal angiomyolipoma. Apropos of 2 cases].

Pulmonary lymphangiomyomatosis (LAM) is a rare and serious disease in women of reproductive age, in which hamartomatous smooth muscle proliferation occurs in lymphatics. The most frequent presenting symptoms or complications are dyspnea, chylothorax and pneumothorax. Chest X-ray reveals a diffuse interstitial infiltrate associated, curiously, with airflow obstruction, air trapping and even hyperinflation. In more than a third of cases, pulmonary LAM coexists with a rare renal tumor, angiomyolipoma. Two new cases additional to the hundred published are reported. The first patient died undiagnosed after a typical seven years' evolution including removal of a renal angiomyolipoma late in the disease. In the second case a renal angiomyolipoma was excised several years before the first respiratory symptoms; at the time of diagnosis there was already severe airflow obstruction now stable under treatment with progesterone. Early hormonal therapy with medroxyprogesterone seems to be the only treatment likely to improve this disease, whose prognosis is usually fatal. Previous attempts to treat LAM are also discussed.

Adult↗
PubMed1987

Lambert-Eaton myasthenic syndrome: II. Immunoelectron microscopy localization of IgG at the mouse motor end-plate.

The autoimmune origin of the Lambert-Eaton myasthenic syndrome (LEMS) was documented by passive transfer of its electrophysiological features from humans to mice with IgG. Freeze-fracture electron microscopy has demonstrated a loss of active-zone particles in human LEMS and in its mouse passive transfer model. These data imply that the active zones are targets of the pathogenic LEMS autoantibodies. Immunolocalization of the antibodies has been hindered, however, by a paucity of active-zone particles (about 50/micron2 normally and still lower in LEMS) and by diffusion artifacts in the immunoperoxidase method. To obviate these problems, we employed sensitive avidin-biotin detection systems, both peroxidase and ferritin labels, and quantitative immunoelectron microscopy and end-plate morphometry. We compared mice treated with LEMS IgG, control IgG, and no IgG. In all mice, nonspecific background staining was found in the basal lamina covering the muscle fibers and Schwann cells. When a single 10-mg dose of IgG was injected intravenously, IgG samples from 12 patients produced significant immunostaining of the mouse active zones; from 7 patients they did not. Higher doses of intraperitoneally injected IgG (20 mg, three times a day for 2 days, or 10 mg/day for 15 days) from each of 4 patients (3 of whose IgG previously transferred LEMS to mice) caused significant immunostaining of mouse active zones: (1) the mean density (no./micron presynaptic membrane length) of positive active zones was 0.91 in the immunoferritin study and 0.72 in the immunoperoxidase study (control values, 0.12 and 0.02); and (2) 43% of the ferritin particles in the primary cleft were concentrated at the active zones and the rest were scattered randomly (control value, 5.3%). The findings indicate that LEMS IgG binds to the active zones of the presynaptic membrane.

Animals↗
PubMed1987

Acetylcholine receptors in human thymic myoid cells in situ: an immunohistological study.

Myoid cells were studied by double immunofluorescence in sections of thymus from 47 patients with myasthenia gravis and 15 control subjects, using polyclonal sheep anti-troponin T and monoclonal antibodies to troponin I, striated muscle myosin, and acetylcholine receptor (AChR). The myoid cells were rare and located mainly in the medulla, and most were clearly positive for AChR; labeling was similar with four individual monoclonal antibodies specific for extrajunctional AChR and five that also recognize endplate AChR. They were mostly keratin-positive and consistently HLA-DR-negative. In the myasthenia gravis samples, the myoid cells were similar but largely confined to medullary epithelial areas; AChR labeling was slightly weaker, but otherwise they did not differ noticeably from those of control subjects. A preliminary finding was of even rarer AChR-positive/HLA-DR-positive antigen-presenting (possibly) cells seen in 9 of 9 myasthenia gravis samples and in none of 9 control samples. Although myoid-cell AChR appears antigenically similar to extrajunctional muscle AChR, and must therefore express the epitopes that myasthenics' antibodies recognize, these cells do not appear to be foci of immunological stimulation in myasthenia gravis.

Binding Sites↗
PubMed1987

The slow channel syndrome. Two new cases.

Two patients are described with a myasthenic syndrome that presented in early adult life. One patient had 2 asymptomatic first degree relatives with similar electrophysiological findings. Both patients had abnormal fatiguability, arm weakness being prominent; neither of them responded to anticholinesterase medication. An abnormal decrement at 3 Hz stimulation was present, and a single stimulus evoked a repetitive response. Electrophysiological studies on biopsied intercostal muscle showed miniature endplate potentials of normal amplitudes but with prolonged rise and decay times. Anticholinesterase staining (Case 1) was not reduced, and showed elongation of some endplates. Ultrastructural studies (Case 2) showed degeneration of junctional folds and diffusely thickened endplate basal lamina. Calcium deposits were not observed and myopathic changes were slight. The findings are consistent with a prolonged open time of the ACh-induced ion channel.

Acetylcholinesterase↗
PubMed1987

Antibody heterogeneity and specificity in myasthenia gravis.

Anti-AChR is heterogeneous within individuals and between individuals. Anti-AChR idiotypes are not shared to any large extent. Ten monoclonal antibodies raised against human AChR: (a) bind to five partially overlapping regions; (b) are not idiotypically identical even within a region; (c) do not all bind to the main immunogenic region; (d) four distinguish between normal and denervated human AChR; (e) can be used to define the antigenic determinants in MG. Antigenic specificities vary in different clinical groups. Antigenic specificities can change during the course of the disease, but some remain relatively constant. Thymus cultures make antibodies with the same specificity as those present in the serum of the individual. All monoclonal antibodies bind to myoid cells of normal and MG thymus. We find no convincing evidence of naturally occurring antiidiotype antibodies in MG sera.

Antibodies, Monoclonal↗
PubMed1987

Myasthenia gravis: population differences in disease expression and acetylcholine receptor antibody titers between Chinese and Caucasians.

Clinical features and anti-acetylcholine receptor (AChR) titers were compared in Chinese (n = 258) and Caucasian (n = 258) myasthenia gravis populations. The former had more early onset and ocular cases, lacked the Caucasian late onset peak, and had fewer severe cases. The distribution of anti-AChR titers was broadly similar in the two populations, and their sera reacted equally well with AChR in both races. The significantly lower (chi 2 = 14.6; p less than 0.001) median anti-AChR titer in the Chinese population can be accounted for by the higher frequency of ocular cases and lower frequency of moderate or severely affected cases.

Adolescent↗
PubMed1987

Anisoylated plasminogen streptokinase activator complex versus streptokinase in acute myocardial infarction. Preliminary results of a randomised study.

25 patients with acute myocardial infarction pain lasting more than 20 minutes which was not relieved by nitrates, whose ECGs showed ST segment elevations of 1 mm or more in 2 or more ECG leads, and who presented less than 3 hours after onset of their symptoms were randomly assigned to one of 2 thrombolytic treatment groups: a single intravenous bolus of anisoylated plasminogen streptokinase activator complex (APSAC) 30U in 5 minutes or an intravenous infusion of streptokinase 1,500,000U over 60 minutes. 3 to 4 hours after the administration of the thrombolytic agent, all patients received intravenous heparin at full dosage for 24 hours. The patency of the infarct-related coronary vessels was assessed by angiography 1 to 4 hours after administration of the thrombolytic agent. Clinical signs, ECGs, pulse, blood pressure and temperature were monitored regularly for 24 hours after treatment or as clinically appropriate. APSAC seemed to be at least as effective as streptokinase in terms of patency of the infarct-related vessel (92% vs 63%, respectively). The adverse events were similar and none was life-threatening. APSAC and streptokinase caused similar falls in blood fibrinogen levels. APSAC, given as a bolus injection over 5 minutes, was easier to administer than streptokinase, which was given as an infusion during 60 minutes.

Adult↗
PubMed1987

Disorders affecting the acetylcholine receptor: myasthenia gravis and congenital myasthenia.

Myasthenia gravis (MG) is an autoimmune disease in which anti-acetylcholine receptor antibodies (anti-AChR) cause loss of functional endplate AChR by increasing AChR degradation, and by complement-mediated destruction. MG anti-AChR binds to regions on the human AChR which can be defined by monoclonal antibodies (mabs). Several congenital forms of myasthenia have been described, three of which may directly involve abnormalities of the AChR, including one in which the open-time of the ion channel is prolonged.

Antibodies, Monoclonal↗
PubMed1987

Traumatic rupture of the thoracic aorta. A review of 49 cases.

We examined retrospectively the chest radiograph of forty nine patients with angiographically proven aortic ruptures. The plain film findings found most consistently were a wide mediastinum (69.5%), partial obliteration of the descending aorta (67.3%), left apical cap (65.3%), downward displacement of the left main bronchus (65.3%), tracheal deviation to the right (63.2%), obscuration of the aortic arch (55.1%), right paratracheal stripe thickening (53%) and nasogastric tube deviation to the right (50%). We also examined 113 sequential aortograms performed after thoracic trauma over 3 years, to determine the positive rate in our series; 14 studies were positive for a rate of 12.4%. No single case of proved ruptured aorta with a normal chest radiograph was detected.

Aorta, Thoracic↗
PubMed1986

Estrogenic activity of phenol red in rat anterior pituitary cells in culture.

The estrogenic activity of phenol red, a pH indicator widely used in cell culture media, was studied in rat anterior pituitary cells. After 72 hours of incubation with 40 microM phenol red, a 40-50% increase in prolactin cell content and a 100% stimulation of luteinizing hormone-releasing hormone induced luteinizing hormone release was observed. Both effects could be completely reversed by simultaneous incubation with the antiestrogen LY156758. In the rat uterine [3H] estradiol binding assay, phenol red showed a significant displacement at concentrations above 10 microM while its concentration in the commonly used culture media is about 40 microM. From the present results, we conclude that phenol red acts as a weak estrogen in normal tissues and that its estrogenic activity should be taken into account in studies using estrogen-sensitive cell or tissue cultures.

Animals↗
PubMed1986

[Relation between respiratory function, bronchial reactivity and symptoms in heavy smokers].

As part of a study of the morphology of hyperreactive airways, 22 heavy smokers (67 +/- 31 pack-years), all male, were challenged with histamine, questioned on symptoms and skin-tested for common allergens before thoracic surgery, mainly for cancer. Histamine was delivered with a hand operated nebulizer in a total dose of 7.8 mumol or a 20% fall from the baseline FEV1. The PD20 (dose of histamine which causes a 20% fall of FEV1) was determined on a semi-log dose-response curve. Symptoms were recorded by physician-administered questionnaire and skin tests were performed with 8 common allergens. Values for FEV1%VC ratio and response to salbutamol were taken from preoperative spirometric studies. Bronchial hyperresponsiveness (BHR) was found in 45% of the patients. The PD20 was in the range of asthma. Past symptoms of airway allergy did not enhance BHR risk. Half of the 13 subjects with airway obstruction (FEV1%VC of less than 2 SD of the predicted value) had normal bronchial responsiveness; however, PD20 correlated well with FEV1 (% predicted) in the hyperresponsive group (r = 0.90, p less than 0.001). The degree of BHR was unrelated to tobacco consumption, number of positive skin tests and response to salbutamol. Symptoms were those of chronic bronchitis and bronchoconstriction (wheezing, morning chest tightness, sudden dyspnea), as well as cough. They were experienced, to some extent, by 82% of patients, only half of whom had BHR. These smokers with BHR differed from asthmatics in that half of them did not report bronchoconstriction symptoms and none experienced chest discomfort during provocation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

TFIIIA and homologous genes. The 'finger' proteins.

Differential regulation of gene expression, in a precise temporal and spatial pattern during development, is thought to be partly mediated by site specific DNA binding proteins which promote a selective activation of gene transcription. From studies on Xenopus TFIIIA, a factor selectively required for transcription of 5 S ribosomal RNA genes, Miller et al. proposed a novel structural model of interaction between DNA and DNA binding protein. The striking homology of TFIIIA with several recently sequenced Drosophila and yeast gene products suggests that multiple regulatory proteins may have evolved from a small ancestral DNA binding protein domain and that the characteristic features of TFIIIA and TFIIIA-5S DNA interactions may be of general significance.

Animals↗
PubMed1986

Isolation and characterization of a Ty element inserted into the ribosomal DNA of the yeast Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae has about 30 to 50 copies of a transposable element Ty. Most of these elements are located at the 5' ends of protein coding sequences and are flanked by a 5 bp duplication. We report below an insertion of a Ty element into one of the repeated ribosomal RNA (rRNA) genes of yeast. The element is located between the 3' ends of the divergentally transcribed 37S and 5S rRNA's and is not flanked by a 5 bp duplication. In addition, one end of the Ty insertion is contiguous with a 306 bp deletion of the sequences of the rRNA gene. We find that this insertion, unlike most Ty insertions, is mitotically unstable.

Base Sequence↗