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Biomedical subjects

M Mayer

Publications and source records attributed to M Mayer.

At least 181 records · Page 10Linked to original sources
PubMed1990

Inhibition of plasmin by fibrinogen.

The kinetics of inhibition of the amidolytic activity of plasmin on D-Val-L-Leu-L-Lys p-nitroanilide hydrochloride (S-2251) by fibrinogen and fibrin were determined. Reciprocal (1/v versus 1/[S]) plots of plasmin inhibition by 0.50 microM-fibrinogen showed a non-linear downward curve. The Hill coefficient (h) was 0.68, suggesting negative co-operativity. By contrast, fibrin produced a simple competitive inhibition of plasmin (Ki = 12 micrograms/ml). Addition of 0.1 mM-6-aminohexanoic acid shifted the non-linear curve obtained in the presence of fibrinogen to a straight line as for controls, indicating that 6-aminohexanoic acid abolishes the fibrinogen-induced inhibition. Transient exposure of the enzyme to pH 1.0 abrogates the ability of fibrinogen to inhibit plasmin activity. Acidification had no effect on the Vmax but increased the Km of plasmin. The present evidence for modulation of plasmin reveals a novel mechanism for control of fibrinolysis by fibrinogen, a component of the coagulation system and the precursor of the physiological substrate of plasmin.

Amino Acid Sequence↗
PubMed1990

[The effect of thrombocytes on the inhibition of granulocyte adherence induced by the ionophore A 23187 in multiple sclerosis].

In patients with disseminated sclerosis and in a control group inhibition of granulocyte adherence was investigated after stimulation with the ionophore A23187 and the effect of autologous thrombocytes on this reactivity was investigated. The granulocyte adherence was not markedly influenced in the described experimental set-up by the ionophore alone not by incubation with thrombocytes alone. The ionophoretic stimulation of granulocytes incubated with thrombocytes caused marked inhibition of leucocyte adherence in healthy controls and to a significantly smaller extent in patients with multiple sclerosis without corticosteroid treatment. In patients treated with corticosteroids this response was not observed. The results suggest a change of membrane properties, dependent on thrombocytes, in the early stage of non-specific granulocyte activation in patients with multiple sclerosis.

Blood Platelets↗
PubMed1990

Two types of neuronal synchrony in monkey striate cortex.

Peaks in more than 5000 spike train correlograms, obtained from monkey striate cortex, were measured. Earlier work had shown qualitatively that there are frequent prominent peaks having widths in a range around 50 ms, and narrower peaks less than about 7 ms wide. Here we demonstrate that the distribution of peak widths shows a dichotomy.

Animals↗
PubMed1990

Biochemical and biological aspects of the plasminogen activation system.

Plasminogen activators (PAs) are specific proteolytic enzymes which convert the inactive proenzyme plasminogen to plasmin. The plasmin formed is a potent and nonspecific protease which cleaves blood fibrin clots and several other extracellular proteins. In addition to their primary role in the initiation of fibrinolysis, PAs are implicated in a variety of basic biological processes, such as, degradation of the extracellular matrix, tumor invasiveness, tissue remodelling, and cellular differentiation. This review describes recent observations on the biochemical and biophysical characteristics of the different components of the plasminogen activation system. This complex system includes: the proenzymes of tissue type PA (tPA) and urokinase type PA (uPA); the active enzymes tPA, uPA and plasmin; the substrate plasminogen; several natural inhibitors of PA and plasmin activity; and the cellular receptors that bind the proenzymes, enzymes, and inhibitor-enzyme complexes. Through the coordinated interactions of these components, the location, timing, and extent of potent proteolytic activity is controlled. Recent findings on the structure, properties, biological functions, and regulation of the different components of the plasminogen activation cascade are reviewed. Current methods for assay of the amount and activity of the enzymes, inhibitors, and receptors are described. Observations implying specific functions of the system in health and disease, and its potential utilization for diagnosis are examined. Specifically, the potential application of PAs as laboratory markers of neoplasia, as diagnostic tools in diseases of the blood clotting system, their use for monitoring of thrombolytic therapy, and their possible relevance in certain disease states are described.

Arthritis, Rheumatoid↗
PubMed1990

The effect of HCG supplementation after combined GnRH agonist/HMG treatment in an IVF programme.

The necessity of luteal-phase supplementation in an IVF programme is of continuing interest. After ovarian stimulation with clomiphene and human menopausal gonadotrophin (HMG), the beneficial effect of supporting the luteal phase has never been scientifically demonstrated. After ovarian stimulation with GnRH agonist/HMG, the luteal phase seems to be inadequate, but in a previous study we did not find evidence to support the need for oral progesterone supplementation. To evaluate the beneficial effect of human chorionic gonadotrophin (HCG) supplementation, we performed a multicentre, double-blind, randomized study with HCG (193 transfers) against placebo (194 transfers). The ongoing pregnancy rate per transfer cycle was significantly better with HCG (18.7 versus 9.3). This is the first truly objective (randomized) study demonstrating the beneficial effect of supporting the luteal phase in an IVF programme.

Adult↗
PubMed1990

Protease and plasminogen activator activity in human bladder carcinoma.

The ability of human bladder tissue extracts to cleave 14C-labelled globin in the absence and in the presence of plasminogen was assayed to quantify non-specific protease and plasminogen activator (PA) activity, respectively. In normal human bladder tissue the non-specific protease activity was approximately 2-fold higher than in tissue samples obtained from transitional cell carcinoma of the bladder (TCC). In contrast, PA activity was almost 4-fold higher in TCC than in normal transition cell epithelium. Acid-treated urine from 19 patients with TCC of the bladder exhibited significantly higher levels of plasminogen activator activity than similarly treated urine from controls. These results indicate that malignant transformation of the bladder epithelial tissue results in elevated levels of PA in the tissue and in urine. Further studies are needed to assess the potential of PA determination in the management of bladder cancer patients.

Carcinoma, Transitional Cell↗
PubMed1990

Interferons, interleukins, virus-host interaction: relation to leukotrienes and other lipoxygenase derivatives of the arachidonic acid.

The leukotrienes and other lipoxygenase-derived metabolites of the arachidonic acid were proved to possess various biological activities and to participate in a number of pathological states and diseases, especially those associated with inflammatory processes and with altered immune response. The present paper reviews the role of these eicosanoids in the regulation of natural-killer cell activity and in production and action of some cytokines including interferons. Furthermore, the participation of the arachidonic acid lipoxygenase metabolism in the virus-host interaction and the relation of these findings to some experimental and human diseases is discussed.

Arachidonic Acids↗
PubMed1990

[The effect of propofol-ketamine anesthesia on hemodynamics and analgesia in comparison with propofol-fentanyl].

Propofol (Diprivan), a modern intravenous hypnotic, produces a reduction in both cardiac index (CI) and mean arterial pressure (MAP). Ketamine (Ketanest), a potent analgesic, in contrast, causes an increase in MAP and CI. The aim of the present study was to investigate whether the combination of propofol and ketamine can give better hemodynamic stability during the induction and maintenance of general anesthesia than propofol used with fentanyl, whose cardiodepressant actions may cumulate. METHODS. For induction of general anesthesia 10 patients (ASA I and II) each received 3-5 boluses of propofol (0.5 mg.kg-1 during 35 s until predetermined level of anesthesia was reached (stage D2/E0 according to [20]) followed by a continuous propofol infusion (0.120 mg.kg-1.min). Fentanyl 0.1 mg was administered to each patient in group A for induction of anesthesia and again if evident pain was present. In group B ketamine was given following a pharmacokinetic model based on computer-simulated calculation. After an initial bolus of 38 mg injected within 2 min further doses of 42 mg, 35 mg, 32 mg and 28 mg ketamine were administered over 30 min at a time. Signs of evident pain were treated by means of supplementary doses of 0.5 mg.kg-1. RESULTS. In both groups a moderate drop of MAP was observed after the induction of general anesthesia. Two patients in each group showed a distinct decrease in MAP (-32%). The heart rate dropped slightly (-9%) in group A, but did not change in group B. Following intubation the MAP rose by less in group A (+8%) than in group B (+21%). After the beginning of the operation the group treated with propofol/fentanyl showed major hemodynamic changes; in particular, bradycardia with less than 40 bpm was observed in more patients than in the propofol/ketamine group. Postoperatively, fewer patients in group B required rescue doses of analgesics (1 of 10) than these in group A (7 of 10), though vigilance was better in group B. DISCUSSION. The dose of ketamine administered during the induction of general anesthesia may have been not high enough to neutralize the cardiodepressant effect of propofol. But during the maintenance of anesthesia there was in fact better hemodynamic stability in group B than in group A as a result of the neutralization of opposing actions. Fentanyl even intensified the fall in MAP after propofol. Patients in group B showed better vigilance as well as better pain relief postoperatively. The population of the fentanyl group was obviously more deeply sedated and analgesia was still inadequate. In our study general intravenous anesthesia with propofol and ketamine offered the advantages of better analgesia, a higher state of vigilance and the absence of respiratory depression during the postoperative phase compared with the combination of propofol and fentanyl.

Analgesia↗
PubMed1990

Mononuclear leucocytes, granulocytes and thrombocytes in the calcium ionophore-induced leucocyte adherence inhibition in multiple sclerosis patients and controls.

The calcium ionophore A23187-induced adherence inhibition of mononuclear leucocytes and granulocytes in multiple sclerosis patients and in controls was investigated. Furthermore, the role of thrombocytes in the ionophore-induced adherence inhibition of both the mononuclears and the granulocytes was evaluated. In the control group and in patients treated with corticosteroids the ionophore consistently induced the adherence inhibition of mononuclear leucocytes. In multiple sclerosis patients without corticosteroid treatment rather heterogenous results were obtained, which appears to reflect the fluctuation of the disease activity. Addition of thrombocytes to the mononuclear leucocyte suspension led to a decrease of leucocyte adherence in both multiple sclerosis groups regardless of the presence of the ionophore. The ionophore stimulation of granulocytes preincubated with the thrombocyte suspension resulted in an increase of the granulocyte nonadherence in healthy controls. An analogous response in multiple sclerosis patients without corticosteroid treatment was significantly less expressed and was not found in patients treated with corticosteroids. These results suggest a thrombocyte-dependent alteration of the membrane properties in the early phase of nonspecific granulocyte activation in patients with multiple sclerosis.

Adrenal Cortex Hormones↗
PubMed1990

[Response in patients with melanoma to immunization using melanoma oncolysates of vaccine virus].

Thirty-two patients with high risk melanoma (either primary melanoma of the limbs or trunk, or recurrent melanoma) and clinically disease-free following appropriate surgical treatment were immunized with a vaccinia virus oncolysate made from a pool of 4 human melanoma cell lines. Injections were given id weekly for 3 months, and then bi-monthly for a further 21 months or until relapse. Treated patients have been under study for 11-72 months, and 15 of them for more than 36 months. Twelve patients received a full 24-month treatment: 3 relapsed and 10 are alive (9 of them disease-free) with a survival of 34-72 months. One patient is still under treatment. Nineteen patients relapsed during treatment: among the 13 patients that relapsed early during the course of treatment, 9 patients died after a survival of 5-30 months and 4 are alive with a survival of 30-59 months; among the 6 patients that later relapsed, 2 patients died after a survival of 21 and 29 months and 4 are alive with a survival of 16-69 months. An analysis of the patients' disease-free survival and overall survival was made using the actuarial method, and limited to 5 years: the disease-free survival curve shows a 35% plateau reached after 40 months, and the survival curve shows a 60% plateau reached after 30 months. The patients' responses to the immunization antigens expressed by the oncolysate were studied. Lymphocytes from immunized patients do respond in vitro to the stimulation by oncolysate in the presence of low amounts of IL-2, and this response is greater than that of normal individuals. IgG antibody production to gangliosides with N-glycolyl neuraminic acid is of prognostic significance, the increase in IgG anti-ganglioside antibody in patients after 3 and 6 months of treatment being linked to the absence of relapse in these patients. Finally, preliminary results show, in several patients under treatment, the appearance of antibodies directed against a 31 kD protein of the oncolysate not detectable in the vaccinia virus or in melanoma cell lysates. Such results are in accordance with previously reported ones from similar studies conducted by other investigators and tend to indicate the efficacy of vaccinia virus oncolysate immunization in the treatment of high risk melanoma.

Adjuvants, Immunologic↗
PubMed1990

[Prognostic factors in the response of a first line chemotherapy in advanced breast cancer].

Anthracyclines containing regimen are widely used in advanced breast cancer. The response to first line chemotherapy varies according to many individual factors and the theoretical response to a given protocol cannot predict the response of a patient. A randomized clinical trial (ERASME) was initiated in order to evaluate the more appropriate first line chemotherapy scheme in advanced breast cancer. Prognostic factors were included in a multiple logistic regression to explain the response after the first 3 chemotherapy courses (monthly FEC). Three factors were found to be statistically significant: adjuvant hormonotherapy, loco-regional metastases, adjuvant adriamycin containing regimen (pejorative prognostic factor). By combining these factors, this statistical model enables us to predict a response rate to a first line chemotherapy from 27 to 87%. Such a model can be taken into account in a decision-making procedure of first line chemotherapy in advanced breast cancer.

Aged↗
PubMed1990

[Is liver biopsy in gallbladder operations still indicated?].

Biopsy of the liver with the Tru-cut needle was done as a routine diagnostic procedure during gallbladder surgery in 166 cases. The data of history, ultrasonography and laboratory were compared with the microscopic liver findings. Preoperatively in 89% of the cases there was an indication for liver biopsy. In 11% of the cases, where there was no indication for preoperative biopsy, we found severe changes in liver histology. Therefore we recommend liver biopsy during gallbladder surgery as a routine procedure.

Adult↗
PubMed1990

[The diagnosis of pleural effusion using thoracoscopy].

By analysis the results of thoracoscopy in 57 patients suffering from pleural effusion of unknown cause in the Surgical Department of Marienhospital Herne, it is clear that we can reach the exact diagnosis in 98% of these patients by this examination, which can be done in local anaesthesia with little complications. In the same time the histological examination of the tissue and the cytological examination of the effusion make the diagnosis sure and in the same time improved the complaints of the patients by removing of effusion.

Adolescent↗
PubMed1990

Acute non-calculous cholecystitis.

Shock gall-bladder is a complication that can arise following trauma or after an operation. The sex distribution, disease frequency and mortality rate associated with this condition are presented and possible pathophysiology is discussed. Post-traumatic cholecystitis seems to occur most often in the second to fourth decade of life. The aetiology remains unknown and may be multifactorial. An awareness of this complication and a resort to early surgery can largely protect the patient from severe consequences.

Acute Disease↗
PubMed1990

[Prognosis and treatment of advanced breast cancer from the surgical viewpoint].

Twenty-four patients with advanced mammary carcinoma (stage T4) were treated between 1983-1986 at the Department of Surgery of the University of Bochum, Marienhospital Herne 1. The primary surgical treatment was supported in 18 cases by an ablatio modified from Patey, the ablatio simplex were performed on 4 patients; while a thoracical-epigastric flap was applied to one patient. Because of the high percentage (16.6%) of advanced breast cancer on all our breast cancer patients, we feel obliged to show the survival time of different under-groups by an interdisciplinary making follow up examination. So we believe to give a better and more different statement on the prognosis of the advanced breast cancer.

Adult↗