Biomedical subjects

C Gross

Publications and source records attributed to C Gross.

At least 127 records · Page 7Linked to original sources

PubMed1993

[Effects of the stimulation of the subthalamic nucleus in Parkinson disease].

In Parkinson's disease, experimental studies favour a neuronal hyperactivity of the subthalamic nucleus. We carried out a subthalamic nucleus electrical stimulation in a patient aged 51, suffering for 8 years from a severe akineto-rigid form of Parkinson's disease, complicated with an on-off effect. Stereotaxic surgery was done under local anaesthesia on one side. Within the theoretical target, a 130 Hz stimulation induced akinesia alleviation mainly on the contralateral limbs. No abnormal movement was noticed. Then a long-term quadripolar DBS Medtronic electrode was inserted in that area. The study of the effects of chronic stimulation is in progress to determine the best temporal and electrical stimulation variables.

Electric Stimulation Therapy↗

PubMed1993

[Surgical management of coronary heart disease and simultaneous carotid artery stenosis].

Simultaneous carotid endarterectomy and open-heart procedures (bypass, aortic and mitral valve replacement, arterial myxoma) were performed on 89 patients. The indication for carotid endarterectomy were either preoperative neurological symptoms (n = 36) or radiologically verified, hämodynamically relevant stenosis of more than 50-60% (n = 53). The postoperative course was uneventful in 80 patients (90%). Neurological complications occurred in 5 patients; 4 had required surgery for pre-operative neurological symptomatology and 1 of these patients died from postoperative stroke. Cardiac complications occurred in 4 patients, one of whom died because of bypass thrombosis with subsequent myocardial infarction. Many authors have different opinions regarding indication, technical procedures and optimum time of operation. We consider the simultaneous operative procedure of carotid endarterectomy and open heart procedures justified in view of the neurological complication rate of approximately 5% in our group of patients.

Aged↗

PubMed1992

MPTP induced hemiparkinsonism in monkeys: behavioral, mechanographic, electromyographic and immunohistochemical studies.

A single infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP) into the right internal carotid artery of Macaca mulatta monkeys resulted in akinesia and rigidity of the contralateral limb. The immunohistochemical study revealed a dramatic reduction in the number of TH-immunoreactive cells in the substantia nigra of the infused side (70-81%). After unilateral MPTP-treatment movement parameters and EMG activity were altered; the agonist muscle developed increased EMG activity associated with a shift of antagonist muscle activity. These results confirm that hemiparkinsonian monkeys are a valuable model of parkinsonism which can be useful in studies of movement disorder physiology and therapy of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1992

Early results of cryopreserved pulmonary allografts as aortic valve substitute.

Excellent clinical results with pulmonary autografts and experimental evidence that the pulmonary valve can withstand the higher stress in the systemic circulation led us to use the cryopreserved pulmonary allograft for aortic valve replacement. From September 1988 to March 1991, 45 consecutive patients (59.9 +/- 12.0 years, 25 men and 20 women) received a cryopreserved pulmonary allograft in the aortic position from our hospital based valve bank. All allografts were inserted freehand in the subcoronary position. There were 3 in-hospital deaths (7%) and 1 patient had severe valvular incompetence immediately postoperatively requiring reoperation after 4 weeks. Forty-one patients were followed at 3-6 month interval for 14.7 +/- 7.8 months (3-28 months) and valve performance was assessed routinely by means of color flow Doppler echocardiography: 34 patients (83%) had no or trivial aortic valve regurgitation. Valvular incompetence class II was present in 2 patients (5%) whereas 3 (7%) demonstrated class II-III. Severe aortic regurgitation (class III-IV) could be detected in 2 patients (5%). Both had to undergo reoperation 4 months and 15 months, respectively, postoperatively. Macroscopic and histological evaluation of the explanted valves demonstrated absence of significant degeneration. We assume that a mismatch in size between allograft and aortic annulus could have lead to dilatation of the allograft valve ring and consequently to valvular incompetence. Pulmonary cryopreserved allografts achieve acceptable short-term results which can be improved if initial technical problems can be avoided.

Adult↗

PubMed1992

Aortic valve replacement with the pulmonary autograft--experience of 23 cases.

Since 1988 an intensive homograft-program has existed at the Linz General Hospital. We have installed an own hospital-based homograft bank, where the allografts, after a 24-hour sterilization-period in an antibiotic solution and a controlled freezing procedure, are stored in liquid nitrogen at -196 degrees C. In 1991 for the first time aortic valve replacement was performed by pulmonary autograft in 23, mainly younger, patients. Essentially our technique conforms with that of D. N. Ross, in the course of which 18 autografts were implanted in subcoronary position and 5 aortic-root replacements were performed. 3 patients died perioperatively, 2 times a severe post-operative bleeding with following hypoxemic brain damage being the cause; 3 more patients had to be rethoracotomized because of postoperative bleedings. All these were attributed to a technical difficulty, which was overcome. In one patient a left-ventricular assist device had to be installed due to a left-ventricular failure, a successful heart transplantation followed on the 8th postoperative day. A follow-up was conducted in all patients every 3 months. In 2 patients a substantial valve incompetence of grade II-III and grade III was detected, all other patients showed no regurgitation of clinical relevance. Despite our initial difficulties it is our opinion that the many advantages-no anticoagulation necessary, no valve sound, less incidence of bacterial endocarditis, and longer durability-do justify this operative procedure.

Adolescent↗

PubMed1992

Severe tubulopathy and kidney graft rupture after coadministration of mannitol and ciclosporin.

Spontaneous allograft rupture after kidney transplantation is a rare complication usually due to an acute rejection of the interstitial type. In a 32-year-old man kidney transplantation was performed under immunosuppression with prednisolone and ciclosporin (CS). The dose of CS was 5 mg/kg body weight intravenously for the first 24 h, on the 2nd day 10 mg/kg/day orally, with gradually decreasing doses thereafter. The patient remained oliguric in the postoperative period and received additionally 600 ml mannitol solution intravenously for osmodiuresis within a period of 6 days. On the 8th postoperative day, 48 h after the last intravenous infusion of mannitol, spontaneous renal rupture occurred. The CS concentrations in the blood during the days before the rupture were within the upper normal range for effective immunosuppression (300-600 ng/ml). Intraoperatively the kidney appeared enlarged due to edematous swelling of the graft, but it showed no signs of rejection. The histological finding was a toxic tubulopathy with extensive isometric vacuolization and peritubular congestion, a known side effect of both of CS and of mannitol. The rupture was successfully repaired. Thirty-four days after the transplantation diuresis increased and hemodialysis therapy could be discontinued. In a second biopsy of the kidney the signs of toxic tubulopathy with isometric vacuolization were reduced. On the following days the serum creatinine dropped below 160 mumol/l. It can be assumed that the combination of CS therapy and administration of massive and continued doses of mannitol in an oliguric patient with allograft kidney may potentiate severe tubulopathy with concomitant edematous swelling of the graft. This can result in an increasing danger of spontaneous renal rupture.

Adult↗

PubMed1992

[Development of arterial revascularization of the myocardium at the Linz general hospital. Personal experiences with 1000 patients].

Arterial revascularization of the myocardium, particularly the use of the internal mammary artery (IMA) as a bypass graft in coronary artery surgery has become an established procedure over the past decade. From March 1986 to June 1991, of 2070 patients who underwent coronary heart surgery at our department, revascularization of the myocardium was performed with an IMA graft in 1000 cases, whereby the percentage increased from 10.4% in 1986 to 75.0% in 1991 (p less than 0.01). The range of indications gradually widened throughout the period, age no longer being a contradiction today. One reason for this development is the substantial improvement in IMA preparation technique. No increase was found in rethoracotomy rate or in the rate of perioperative infarctions. The mean age of patients receiving an IMA graft increased from 55.2 years (1986) to 64.7 years (1991) and therefore reflects the change in ranges of indication. 54 IMA jump grafts were anastomosed, in 30 cases bilateral IMAs were used and the IMA was implanted as a free graft twice. In the future these successful results with the implementation of IMA grafts will lead to a further displacement of the saphenous vein as main bypass material.

Austria↗

PubMed1991

A quantitative study of neuronal discharge in areas 5, 2, and 4 of the monkey during fast arm movements.

1. The properties of parietal neurons were studied in four adult rhesus monkeys during fast arm movements. The animals were trained to perform flexion or extension of the forearm about the elbow in response to specific auditory cues. Single neuron activity was recorded in 272 area 5 neurons, 81 neurons of the somatosensory cortex, and 92 neurons of the motor cortex. 2. In area 5, 42% of neuronal changes occurred before movement onset (early changes) and 58% after (late changes), with 21% before the earliest electromyogram. The range of modification in activity took place between 260 ms before movement onset and 180 ms after. Complex receptive fields were found in area 5 with a greater proportion among the late neurons (72%) than among the early neurons (32%). 3. Different patterns of activity were observed in neurons recorded in both movement directions. Reciprocal neurons represented 52% of the motor cortex neurons and 41% of the neurons in the somatosensory cortex but only 14% of the area 5 neurons. Of the remainder area 5 neurons, 46% were direction-sensitive neurons and 39% coactivated neurons. This suggests a more complex encoding of movement direction in area 5 than in area 2 or 4. 4. Temporal characteristics of the neuronal bursts were quantitatively analyzed in areas 5, 2, and 4. Neuronal burst duration was longer in area 5 than in the other areas. Above all, a variability of burst parameters, which did not depend on variable movement execution, was noticed in area 5. Therefore neuronal activity in this cortical area cannot be simply explained by a convergence of sensory and motor inputs but may depend on the behavioral context in which the movement is performed. 5. A correlation between neuronal burst duration and movement duration was found in 41% of area 2 neurons. In area 5, this correlation was observed in 20% of the late neurons and in 14% of the early neurons. A correlation between neuronal discharge frequency and movement velocity was found in 34% of area 2 neurons and 24% of area 4 neurons. About 16% of both late and early neurons in area 5 showed such a correlation. These neurons received polyarticular input, and it is suggested that they may be involved in the kinematic encoding of polyarticular movements. 6. A topographic and functional organization of area 5 was noticed. In anterior area, 5, 83% of the neurons had receptive fields and most of the reciprocal neurons and those exhibiting a correlation with movement parameters were found there.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1991

Effects of high-dose aprotinin on blood loss, platelet function, fibrinolysis, complement, and renal function after cardiopulmonary bypass.

The use of aprotinin to reduce blood loss after cardiopulmonary bypass is under debate. Concern has been raised about the renal effects of aprotinin. We administered a mean aprotinin dose of 4.2 x 10(6) kallikrein-inhibiting units to 13 patients with coronary disease undergoing cardiopulmonary bypass for 74 +/- 5 minutes (mean +/- standard error of the mean); 13 comparable patients having cardiopulmonary bypass served as control subjects, and all were studied postoperatively for 24 hours. Aprotinin reduced postoperative blood loss by 50% (p = 0.0082). Two of the 13 patients who received aprotinin needed one red cell unit each versus a total of 18 units in eight of 13 control patients (p = 0.0096). Blood pressure, hemoglobin value and serum protein concentration were higher after operation in the aprotinin group (p less than 0.05 to p less than 0.01). Platelet counts did not differ, but plasma thromboxane was lower in aprotinin recipients (p less than 0.001). In control patients fibrinogen degradation products (D dimer) doubled, and alpha 2-antiplasmin activity was halved during and after cardiopulmonary bypass (p less than 0.01 to p less than 0.001), whereas aprotinin patients showed no changes. The complement breakdown products C4a, C3a, and C3dg as well as C9 neoantigen increased from prebypass baseline in both groups (p less than 0.001); the increment of C3a and C3dg was greater in the aprotinin than in the control patients (p less than 0.001). Serum electrolytes, osmolality, and creatinine remained normal in both groups of patients. Creatinine clearance was normal or above normal and virtually identical in both groups. Osmolar clearance and fractional sodium excretion were higher in the aprotinin group than in the control group shortly after cardiopulmonary bypass (p less than 0.05 to p less than 0.01); renal function was unremarkable the next morning. No adverse clinical effects attributable to aprotinin were seen. In summary, aprotinin offers advantages for cardiopulmonary bypass.

Antithrombin III↗

PubMed1990

Expression of cloned human reticulocyte 15-lipoxygenase and immunological evidence that 15-lipoxygenases of different cell types are related.

Cloned 15-lipoxygenase has been expressed for the first time in eukaryotic and prokaryotic cells. Transfection of osteosarcoma cells with a mammalian expression plasmid containing the cDNA for human reticulocyte 15-lipoxygenase resulted in cell lines that were capable of oxidizing body arachidonic acid and linoleic acid. The lipoxygenase metabolites were identified by reverse-phase and straight-phase high pressure liquid chromatography, ultraviolet spectroscopy, and direct mass spectrometry, verifying that the cDNA for 15-lipoxygenase encodes an enzyme with authentic 15-lipoxygenase activity. Incubation of the transformed cells with arachidonic acid generated 15-hydroxyeicosatetraenoic acid (HETE) and 12-HETE in a ratio of 8.6 to 1, demonstrating that 15-lipoxygenase can also perform 12-lipoxygenation. Lesser amounts of 15-keto-ETE, four isomers of 8,15-diHETE, and one isomer of 14,15-diHETE were observed. Incubation with linoleic acid generated predominantly 13-hydroxy linoleic acid. The reaction was inhibited by eicosatetraynoic acid but not by indomethacin. Antibodies to a peptide corresponding to a unique region of the predicted amino acid sequence were generated and shown to react with one major band of 70 kDa on immunoblots of human leukocyte 15-lipoxygenase. To obtain antibodies to the full length enzyme, the cDNA was subcloned into a bacterial expression vector and was expressed as a fusion with the CheY protein. The overexpressed protein was readily purified from bacteria and was shown to be immunoreactive to the peptide-derived antibody. Antibodies raised to this recombinant enzyme did not cross-react with human leukocyte 5-lipoxygenase but did identify 15-lipoxygenase in rabbit reticulocytes, human leukocytes, and tracheal epithelial cells, suggesting that the 15-lipoxygenases from these different cell types are structurally related.

Amino Acid Sequence↗

PubMed1990

[Ventricular septum rupture following acute myocardial infarct].

Between 1980 and 1989 15 patients underwent 16 operations for repair of a postinfarction ventricular septal defect. Cardiogenic shock developed in 11 patients, in 9 cases an intraaortic balloon-pump was implanted. 7 patients died, the 8 survivors are in clinical stadium II after a mean follow up of 49 months. We think, that septal rupture after myocardial infarction should be referred to urgent assessment. The results in long term survivors are very satisfying.

Aged↗

PubMed1990

[Aneurysm of the ascending aorta].

Between January 1983 and March 1988 25 patients with aneurysms of the ascending aorta were operated, out of these only 15 (56%) electively. Acute incompetence (10) were the main indications for operation. Poststenotic aneurysms (2), mycotic (2) and saccular sclerotic (1) aneurysms have also been observed. A rare case of a ruptured ascending aorta due to histologically and serologically proven Brucellosis is presented. Valved conduits were used in 16 patients to reconstruct the aortic root, whereas the remaining patients had different types of supra-coronary reconstruction, i.e. resection with or without graft insertion (6 and 3 respectively). We lost 6 patients out of 25 during or immediately after operation. All of them were operated in an acute state of rupture or dissection with left heart failure, some of them already presenting neurologic deficits preoperatively. Operative and hospital mortality in 14 patients operated electively was 0%. Bentall's operation using valved conduits is a safe operation in elective patients with a reasonable mortality rate worldwide. Clinical follow up should include ultrasound studies of the operative site the remaining aorta, i.v. DSA and CT of NMR scanning in 6-12 month intervals in order to detect late complications as false or dissecting aneurysms.

Aged↗

PubMed1990

Modifications of precentral cortex discharge and EMG activity in monkeys with MPTP-induced lesions of DA nigral neurons.

1. Individual neurons were recorded extracellularly in the precentral forelimb area of two monkeys trained to perform rapid, large amplitude flexion and extension movements of the contralateral forearm in response to auditory signals. Electromyographic (EMG) activity in the biceps/triceps muscles was recorded separately under the same conditions. The dopaminergic (DA) neurons of the substantia nigra (SN) were destroyed selectively by repeated series of intravenous injections of MPTP. The lesion was verified on serial slices using both tyrosine hydroxylase immunocytochemistry and classical staining methods. 2. In normal monkeys, the frequency of firing of precentral neurons shows rapid changes shortly before the onset of displacement. In our sample (n = 102), most of the neurons (49%) tested during movement in both directions (flexion, extension) showed a reciprocal pattern of activity for the two directions of movement, a small percentage (19%) exhibited a change for only one direction (unidirectional neurons), and the remaining 32% displayed a similar change for both directions of movement (bidirectional neurons). 3. In MPTP-treated monkeys, movement-related modification of neuronal activity was more gradual, beginning earlier and lasting longer relative to the onset of movement. The cellular reaction time (the time between the auditory cue and a significant change in neuronal activity) was not significantly altered. Spontaneous firing of precentral neurons (n = 124) did not increase significantly, and the dynamic discharge rate was unchanged after the nigral lesion. However, only 18% of cortical neurons still presented a reciprocal pattern of discharge for the two directions of movement, while the percentage of unidirectional neurons increased (50%), and the percentage of bidirectional neurons remained the same (32%). 4. After MPTP treatment, alterations in movement parameters and EMG activity were observed. Mean reaction time and movement duration increased by 20-25% and 25-30% respectively. The movements were slower and were associated with a generalized depression in the shape and the amplitude of EMG activity in the agonist muscle. 5. The neuronal basis for the observed central and peripheral disturbance in the MPTP-treated monkeys is discussed. We conclude that SN lesion leads to two main disturbances of cortical activity: i) the loss of the reciprocal pattern of response of movement-related cortical cells, and ii) an inability of the motor cortex to modify its activity in response to peripheral input.

Animals↗

PubMed1990

Cell growth and enzyme synthesis of a mutant of Arthrobacter sp. (DSM 3747) used for the production of L-amino acids from D,L-5-monosubstituted hydantoins.

A microorganism with the ability to form L-tryptophan from D,L-5-(3-indolyl-methyl)hydantoin (D,L-5-IMH) was isolated and identified as Arthrobacter sp. (DSM 3747). After isolation of a mutant with high tryptophan production activity but low tryptophan degradation, cultural conditions were optimized to achieve high amounts of biomass with good specific activities concerning the enzymatic hydantoin-cleaving reactions. The ability of the microorganism to perform these bioconversions was found to be inducible by D,L-5-IMH as well as to be dependent on the presence of Mn2+. The highest specific D,L-5-IMH-cleaving activity of the cells was observed in the exponential phase of growth. The addition of yeast extract to the mineral salts medium was found to be essential for obtaining biomass concentrations of about 25 g l-1 cell dry mass by bioreactor cultivations. In order to obtain a constantly high growth rate, feeding of the C-source was pO2-controlled. The inducer D,L-5-IMH had to be continuously fed to prevent a decline of the L-tryptophan-forming enzyme activities, because it was subjected to degradation with the enzymes induced and higher concentrations of D,L-5-IMH aggravated the growth significantly. The synthesis of the enzymes was also inducible, when inducer and Mn2+ were not added until the late growth phase. Using this process, the consumption of D,L-5-IMH was reduced remarkably. So, under these conditions biomass concentrations of 25 g l-1 cell dry weight with a specific enzymatic activity of 0.20 mmol g-1 h-1 (tryptophan per dry mass per time) could be obtained within 13 h. Using 1 g l-1 of the chemically modified inducer D,L-5-(3-indolylmethyl)-3-N-methylhydantoin, which was not degradable by the microorganisms, a biomass concentration of 28 g l-1 cell dry weight with a specific activity of 0.34 mmol g-1 h-1 (tryptophan per dry mass per time) could be obtained within 28 h.

Amidohydrolases↗

PubMed1990

Production of L-tryptophan from D,L-5-indolylmethylhydantoin by resting cells of a mutant of Arthrobacter species (DSM 3747).

The reaction parameters and the stereospecificity of the enzymatic cleavage of D,L-5-indolylmethylhydantoin in producing L-tryptophan with resting cells of Arthrobacter sp. DSM 3747 were studied. When intact cells were tested, the optimal pH was between 8.5 and 9.0 and the optimal temperature was 50 degrees C. Both, L-N-carbamoylase and hydantoinase could be stabilized over 24 h at 30 and 40 degrees C by the addition of D,L-5-indolylmethylhydantoin. Furthermore, the hydantoinase was stable over 24 h at 50 degrees C by the addition of 0.5 mM Mn2+ ions. The treatment with sodium desoxycholate turned out to be successful in overcoming the poor availability of D,L-5-indolylmethylhydantoin for the cells. The optimal temperature with permeabilized cells decreased to 30 degrees C and therefore ensured a good enzyme stability. While the L-N-carbamoylase proved to be absolutely L-specific, the hydantoinase led to a mixture of enantiomers of N-carbamoyltryptophan. The produced D-N-carbamoyl-tryptophan caused an inhibition of the L-N-carbamoylase. The transformation yield from D,L-5-indolylmethylhydantoin always reached 100%.

Amidohydrolases↗

PubMed1990

Thoracic aneurysm in association with an aberrant right subclavian artery.

A case of a 45-year-old man is presented with clinical signs of a dissecting aortic aneurysm. Angiography and CT demonstrated a dissecting thoracic aneurysm (deBakey type III a) and an aberrant right subclavian artery arising from this aneurysm at the fourth branch of the aortic arch. In the first step, the aberrant artery was implanted into the right common carotid artery. In a second operation, the aneurysm was replaced by a Dacron tube. The advantage of our procedure is the perfusion of at least one vertebral artery during aortic cross-clamping and easier access to the aneurysm through a left thoracotomy. As far as we know, this is the fourth presentation of such a case in the literature in which the other cases concern angiographic or post-mortem findings.

Anastomosis, Surgical↗

PubMed1990

Neurotoxicity of iohexol vs iopamidol in lumbar myelography. Clinical, electrophysiological and brain CT scan correlations.

The potential neurotoxicity of iohexol and iopamidol in lumbar myelography was investigated in 20 patients using three criteria: clinical symptoms, EEG recordings with spectral analysis and CT scans of the brain. There was no significant difference in clinical side-effects between the two groups (Iopaminol, Iohexol). In 10 patients (iopaminol 4, iohexol 6) CT scans revealed an important penetration of the contrast media into the subarachnoid spaces at 3 hours and into the cerebral cortex at 24 hours. This cerebral contamination was unrelated to the headaches experienced by the patients or to the electrophysiological disturbances observed. Spectral analysis in brain-contaminated subjects showed a reduction of delta, beta 1 and beta 2 bands with iohexol. This reduction suggests that EEG activation is less pronounced with this agent than with iopaminol.

Brain↗

PubMed1989

Expression of HLA-A, -B, -C, -DR, -DP, -DQ, and of HLA-D-associated invariant chain (Ii) in non-neoplastic mammary epithelium, fibroadenoma, adenoma, and carcinoma of the breast.

Non-neoplastic mammary gland, 20 benign tumors and 206 carcinomas of the breast were immunohistochemically examined for expression of HLA-A, -B, -C, HLA-DR, -DP, and -DQ molecules and the HLA-D associated invariant chain (Ii). In contrast to cells from benign lesions, tumor cells of 51.2% of carcinomas had an abnormally low content of HLA-A, -B, and -C determinants ranging from reduction of antigenic density per cell (28.8%) over an incomplete (15.6%) to complete loss of antigens (6.8%). Associated with lymphohistiocytic stromal infiltrates, HLA-D/Ii determinants were found to be induced in benign duct and acinar epithelium after the order Ii greater than or equal to HLA-DR greater than or equal to HLA-DP greater than or equal to HLA-DQ. These antigens were also expressed, mostly noncoordinately, in 55.5% of carcinomas, and in 98 cases according to the above order. In 28.6%, Ii expression clearly exceeded HLA-D antigen expression; conversely, 6.2% contained HLA-DR+/Ii- tumor cell subsets. In breast carcinoma, the association of reduced HLA-A, -B, and -C expression and a noninduction of HLA-DR was highly significant (P less than 0.0009), suggesting an abnormal signal acting down-regulating on the expression of both classes of antigens. Because the modality of HLA-A, -B, and -C and HLA-D/Ii expression correlated with neither tumor type nor grade, it might be an independent parameter.

Adenofibroma↗