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Biomedical subjects

B Schuster

Publications and source records attributed to B Schuster.

At least 55 records · Page 3Linked to original sources
PubMed1992

[Scintigraphic imaging of head and neck cancers with 99m technetium (v) dimercaptosuccinic acid. A prospective clinical study].

In patients with cervical metastases conventional examination by ultrasound, CT or MRI imaging often fails to identify an unknown primary tumor. Also the retrieval of a recurrent malignancy may be difficult. Scintigraphy, utilizing technetium-99m (v) dimercaptosuccinic acid was chosen for a prospective study in 17 patients to evaluate its properties for imaging metastasizing squamous cell carcinoma of the head and neck. Scintigraphic findings were correlated with the results of clinical examination and conventional imaging techniques. In all cases the primary tumor revealed good uptake of 99mTc(v)DMSA. Manifest cervical metastases could only be imaged in some cases. In future, therefore, 99mTc(v)DMSA scanning may be used for the detection of unknown primary tumors. However, it does not appear helpful in the evaluation of cervical nodes.

Carcinoma, Squamous Cell↗
PubMed1991

Extended middle cranial fossa approach for acoustic neuroma surgery.

The enlarged middle cranial fossa approach was used for removal of acoustic neuromas in 209 cases. Complete tumor removal was accomplished in 96% of cases. Hearing was preserved in 51% of cases, with better results in smaller tumors. Our experience with the enlarged middle fossa approach has led us to discard the translabyrinthine approach for removal of acoustic neuromas.

Journal Article↗
PubMed1991

Cryptosporidium sp. in stool specimens from diarrhoeic and asymptomatic individuals in the Magdeburg area (East Germany).

Unselected stool specimens from a total of 2,944 individuals with diarrhoea including 1,172 children under 14 years of age were investigated for Cryptosporidium oocysts in the Magdeburg area from 1987 to 1988, 43 (1.46%) were found positive. Three of these were additionally infected with bacterial pathogens (Campylobacter species). In all cases the symptoms of diarrhoea ceased spontaneously after an average of 8 days. The incidence was highest among children and infants under 6 years of age (2.50%). No cryptosporidia were found in stool specimens of 570 healthy individuals of all age groups. Cysts of Giardia sp. were detected more frequently in healthy than in diarrhoeic individuals (3.3% and 2.0%, respectively). The postulation to search for cryptosporidia in all cases of diarrhoea lasting longer than two days is inferred from these results.

Adolescent↗
PubMed1991

Posture and central compensation after acoustic neurinoma surgery.

After acoustic neurinoma surgery via the enlarged middle cranial fossa approach the patients usually benefit from a good prognosis of the vestibular compensation, almost independent of the size of the tumour and of the patient's age, if the central vestibular pathways were not injured. Only 8% of the patients showed a reduced vestibular compensation. The success and gradation of the vestibular compensation in diseases with a permanent labyrinthine loss, even though after acoustic neurinoma surgery, can easily be classified by the so-called vestibular-index.

Adult↗
PubMed1991

[Sinusitis in long-term intubated, intensive care patients: nasal versus oral intubation].

UNLABELLED: Discussion of paranasal sinusitis as a nosocomial infection in the mechanically ventilated intensive care (ICU) patient has recently been intensified. Some authors have emphasized nasotracheal intubation as a possible pathogenetic pathway. The aim of this study was to investigate the impact of nasotracheal or orotracheal intubation on the development of sinusitis in ICU patients. METHODS: In a prospective study, we followed 44 patients who required mechanical ventilation (greater than 24 h) in the ICU because of prolonged recovery from abdominal, thoracic, or posttraumatic surgery. Twenty patients were intubated nasotracheally and 24 orotracheally. Assignment to the groups was random. All were provided with a nasogastric tube and initially treated with systemic antibiotics. They received local antimicrobial prophylaxis of the nose, oropharynx, and stomach. Daily a-scan examinations of the maxillary sinuses were performed from the day of admission to the ICU until extubation, tracheotomy, death, or transfer. The average observation period was 6.9 days in the oral group and 7.1 days in the nasal group. In the case of a pathologic finding, aspiration of the antral sinus was carried out. In this study sinusitis indicated a sonographic finding; it did not necessarily imply a bacterial infection. RESULTS: At the beginning of the observation period, 6 patients in the oral group and 4 in the nasal group already had a pathologic maxillary sinus finding. At the end, in 15 of 24 in the oral group and 19 of 20 in the nasal group unilateral or bilateral sinusitis could be demonstrated. Development of bilateral sinusitis (13/20 in the nasotracheal group, 8/24 in the orotracheal group) was mainly observed after the appearance of unilateral sinusitis. The site corresponded to the site of the nasal tube in 65%. Unilateral paranasal infection was observed in nasotracheally and orotracheally intubated patients after an average of 2.8 and 2.6 days, respectively, whereas bilateral sinusitis had an average time delay of 4.5 and 5.7 days. Aspiration of the maxillary sinus was performed in 22 of 34 cases with sinusitis. Pathogenic organisms could be demonstrated in 7 of 13 nasotracheally intubated patients but only 2 of 9 with orotracheal tubes. CONCLUSION: We found that patients intubated orotracheally developed significantly less sinusitis than those intubated nasotracheally. Edema, local infection of the nasal mucosa, or mechanical obstruction of sinus drainage pathways by the tube are possible explanations. The fact that 63% of orally intubated patients had a pathologic maxillary sinus finding as well suggests that in addition to other reasons, an increased central venous pressure, positive pressure ventilation, and the supine position must be regarded as predisposing factors that increase the incidence of sinusitis. We conclude that the conditions of critically ill patients predispose to the development of sinusitis. Nasotracheal intubation is to be regarded as an additional risk, and therefore oral intubation should be preferred.

Adult↗
PubMed1989

The neural structures involved in cross-modal recognition and tactile discrimination performance: an investigation using 2-DG.

Given the failure of the ablation method to identify the neural structures/systems that are crucial for cross-modal recognition (CMR) and for tactile discrimination performance (TDP), we injected radioactive 2-deoxy-[14C]glucose (2-DG) into monkeys trained to a high level of CMR or TDP. Nine monkeys were trained to recognize in one sense-modality, to a level greater than 80% correct, the objects experienced in the alternate modality on only a single prior trial. After injection, CMR was continued (Expt. 1a) exactly as before, except that all CMR problems were now in only one direction; or (Expt. 1b) the second--the CMR--trial of each problem was not realized (i.e. no objects were available in the second modality) so that the monkey merely 'expected' the cross-modal trial. Nine other monkeys were trained on a graded roughness discrimination task with conventional 'titration' procedures to a stable level of performance, either (Expt. 2a) without having undergone any cortical removal, or (Expt. 2b) after unilateral removal--contralateral or ipsilateral to the preferred hand--of the posterior insula or of the second somatosensory projection cortex (SII). Exactly the same training procedures were continued in Expt. 2 after injection of 2-DG. Coronal radiographs were made at 490 microns for all 18 monkeys (and also for a 19th, which served as a control in Expt. 1b). The optical densities of the autoradiographs were measured quantitatively in respect of 50 structures or part-structures (e.g. sulci, thalamic nuclei, subcortical structures); they were rated either with the aid of 'pseudo-colours' produced by the computer, or directly by judging the black/white optical densities, in respect of 29 other structures. These 79 structures were then the dependent variables in MANOVAs or ANOVAs, to determine differences between groups; or within groups with respect to the left/right and ipsilateral/contralateral hemispheres; or interaction effects. It was found that certain structures (e.g. the ventral portion of the claustrum, the insula with its extension ventrally into the fundus, nucleus Medialis dorsalis and nucleus Pulvinar oralis) repeatedly, whereas others (e.g. the amygdala) never gave rise to significant outcomes. Structures in the left cerebral hemisphere were frequently found to be more strongly labelled than those in the right hemisphere.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Clinical relevance of the substitution of different brands of sustained-release theophylline.

In order to assess whether clinically important changes in serum theophylline concentrations occur when patients switch their brand of slow-release (SR) theophylline, 10 subjects with asthma were administered the same dose of four different SR theophylline formulations for 2-week periods in a random, double-blinded, crossover manner. Analysis of the data revealed significant differences in mean peak-to-trough fluctuations of serum theophylline concentrations between the formulations of SR theophylline, which varied from 60% to 106% of trough concentration (p less than 0.0001, analysis of variance). On at least one occasion in every subject, switching between brands of SR theophylline was responsible for raising the serum theophylline concentrations outside the accepted therapeutic range, and this was associated with symptoms of toxicity in five of the subjects. Worsening pulmonary functions were observed in two of the subjects whose switching resulted in lowered theophylline concentrations. Many of the formulation-related changes in theophylline concentrations appeared to be idiosyncratic and could not be predicted by the overall bioavailability differences between the drugs. These results argue against the open substitution of these formulations and suggest that if patients are switched between different brands of SR theophylline, their serum theophylline concentrations need to be closely monitored.

Adult↗
PubMed1987

Pharmacokinetics of vancomycin in serum and tissue of patients undergoing open-heart surgery.

Penetration of vancomycin into serum, heart valves, subcutaneous tissue and muscle was determined in 33 adult patients undergoing open-heart surgery. Each patient received 15 mg/kg vancomycin as a 30-min intravenous infusion preoperatively. Within 6 h vancomycin plasma concentrations declined from 28.9 to 4.2 mg/l. Vancomycin concentrations decreased in subcutaneous tissue slowly and varied in muscle between 1.2 and 3.2 mg/kg, in subcutaneous tissue between 1.3 and 4.4 mg/kg and in heart valves between 2.3 and 4.2 mg/kg. Vancomycin concentrations in heart valves are high enough to inhibit most oxacillin-resistant Staphylococcus aureus, and coagulase-negative staphylococci causing postoperative wound infections and endocarditis.

Adipose Tissue↗
PubMed1986

Phenylpropanolamine OROS (Acutrim) vs. placebo in combination with caloric restriction and physician-managed behavior modification.

We added phenylpropanolamine OROS (Acutrim; Ciba-Geigy Corp.) or placebo to a physician-managed behavior modification, mild caloric restriction, and exercise weight control program. One hundred six healthy, overweight (115% to 130% ideal body weight) women participated in this 14-week double-blind clinical trial. On average, the participants who took Acutrim lost significantly more weight (X +/- SE; 6.1 +/- 0.6 kg; 8.0% +/- 0.8%) than did those taking placebo (4.3 +/- 0.7 kg; 5.5% +/- 0.8%; P less than 0.05). Those taking Actrim continued to lose weight over the Christmas holiday, while the placebo group gained weight. Fifteen participants taking placebo withdrew, three because of adverse drug reactions (ADRs). Thirteen of 53 participants in the Acutrim group left the study, two because of ADRs. Dry mouth was the most frequent complaint from participants taking Acutrim. No serious cardiovascular effects occurred. Both complaints and the number of participants reporting ADRs decreased with continued dosing. We conclude that Acutrim is a safe, modestly effective adjunct to a physician-managed, integrated weight control program.

Adolescent↗
PubMed1985

C1-Tetrahydrofolate synthase from rabbit liver. Structural and kinetic properties of the enzyme and its two domains.

C1-Tetrahydrofolate synthase is a multifunctional enzyme which catalyzes three reactions in 1-carbon metabolism: 10-formyltetrahydrofolate synthetase; 5,10-methenyltetrahydrofolate cyclohydrolase; 5,10-methylenetetrahydrofolate dehydrogenase. A rapid 1-day purification procedure has been developed which gives 40 mg of pure enzyme from 10 rabbit livers. The 10-formyltetrahydrofolate synthetase activity of this trifunctional enzyme has a specific activity that is 4-fold higher than the enzyme previously purified from rabbit liver. Conditions have been developed for the rapid isolation of a tryptic fragment of the enzyme which contains the methylenetetrahydrofolate dehydrogenase and methenyltetrahydrofolate cyclohydrolase activities. This fragment is a monomer exhibiting a subunit and native molecular weight of 36,000 in most buffers. However, in phosphate buffers the native molecular weight suggests that the fragment is a dimer. Conditions are also given whereby chymotryptic digestion allows the simultaneous isolation from the native enzyme of a large fragment containing the 10-formyltetrahydrofolate synthetase activity and a smaller fragment containing the dehydrogenase and cyclohydrolase activities. The large fragment is a dimer with a subunit molecular weight of 66,000. The small fragment retains all of the dehydrogenase and cyclohydrolase activities of the native enzyme. The large fragment is unstable but retains most of the 10-formyltetrahydrofolate synthetase activity. Km values of substrates for the two fragments are the same as the values for the native enzyme. The 10-formyltetrahydrofolate synthetase activity of the native enzyme requires ammonium or potassium ions for expression of full catalytic activity. The effect of these two ions on the catalytic activity of the large chymotryptic fragment is the same as with the native enzyme. We have shown by differential scanning calorimetry that the native enzyme contains two protein domains which show thermal transitions at 47 and 60 degrees C. Evidence is presented that the two domains are related to the two protein fragments generated by proteolysis of the native enzyme. The larger of the two domains contains the active site for the 10-formyltetrahydrofolate synthetase activity while the smaller domain contains the active site which catalyzes the dehydrogenase and cyclohydrolase reactions. Replacement of sodium ion buffers with either ammonium or potassium ions results in an increase in stability of the large domain of the native enzyme. This change in stability is not accompanied by a change in the quaternary structure of the enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)

Aminohydrolases↗
PubMed1984

Five-year clinical experience with the Omniscience cardiac valve.

Clinical data on the Omniscience cardiac valve prosthesis (sizes 19 to 31 mm) were obtained from 326 patients (155, aortic valve replacement [AVR]; 125, mitral valve replacement [MVR]; and 46, double-valve replacement) during a five-year period (650 patient-years) with 96% accountability. Mean age was 56 +/- 12 years, and 40% (130) of the patients were 61 years old or older. Thirty-one percent (101) had prior or concomitant coronary artery bypass grafting procedures, 9% (28) had a previous malfunctioning prosthesis, and 17% (57) had other cardiac surgical procedures. Eighty percent were in New York Heart Association (NYHA) Functional Class III or IV preoperatively. Early mortality was 10% (34). Five-year actuarial thrombus-free rate is 96% for patients who underwent AVR and 95% for patients having MVR. Postoperatively, 89% (172/193) were in NYHA Class I or II, and 84% (163/193) improved by at least one Functional Class. A significantly high proportion of the postoperative hematological values fall within normal ranges: red blood cell count, 94% (176/187); hematocrit, 88% (166/188); and hemoglobin, 93% (176/190). Ninety-eight percent (287/292) are free from clinical anemia. Four of the 5 patients with clinical anemia had a preoperative history of this condition. Levels of lactic dehydrogenase in 3 patients suggested the probable presence of clinically significant hemolysis, although all 3 have normal hematological values. Actuarial five-year survival for patients who underwent AVR or MVR are similar (82% and 80%, respectively), indicating satisfactory and comparable levels of safety and performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Factors influencing thromboembolic complications in Omniscience cardiac valve patients.

Clinical data were gathered over five years (650 patient-years) for all 155 aortic valve replacement, 125 mitral valve replacement and 46 double valve replacement patients implanted with the Omniscience cardiac valve prosthesis at three North American medical cent es. Mean age was 56 +/- 12 years, 80% were preoperatively in NYHA class III or IV, and 57% had previous or concomitant cardiac surgery. Data were evaluated for the incidence of thromboembolic complications. During the late postoperative period, transient ischaemic episodes occurred in six patients (0.92% per patient-year). The five-year actuarial thrombus-free rate for serious thromboembolic complications (valve thrombosis or thromboembolism with residual effects) for aortic valve replacement patients is 96% and 95% for mitral valve replacement patients. For patients experiencing any transient or serious thromboembolic complication, 35% had a compromise of coumadin anticoagulation shortly before the thromboembolic event, 60% had a history of atrial fibrillation, and 76% a history of rheumatic heart disease. Statistically, these rates are significantly higher compared with the original valve population. The low incidence of thromboembolic complications over this five-year clinical study demonstrates a commendable degree of safety and performance for the Omniscience valve.

Actuarial Analysis↗
PubMed1982

Left ventricular work and power: circumferential, radial and longitudinal components. Mathematical derivation and characteristic variation with left ventricular dysfunction.

Cardiac work and power, defined as the wall stress-velocity product per unit volume, have been derived with respect to a circumferential, radial and longitudinal component for the human left ventricle during a complete cardiac cycle. Thirty-nine patients, comprising five clinical groups, were evaluated using pressure and volume data acquired from single-plane cineangiography. The results indicate that work and power are divided into approximately 60% circumferential, 23% radial and 17% longitudinal components for normals. Characteristic variations from normal are presented for selected pathological case studies. With a compensated volume overload patient, diastolic work and power are uniformly reduced in all three directions and systolic radial power approximately equals longitudinal power. With a decompensated volume overload patient, systolic radial power is greater than longitudinal power. With a compensated pressure overload patient, systolic radial work and power are greatly elevated as compared to the normals and represent about 30% of the total work and power, while longitudinal work and power represent only about 8% of the total. With a congestive cardiomyopathy patient, systolic work and power are greatly reduced in all three directions as compared to normals.

Adult↗
PubMed1979

Clinical experience with the Lillehei-Kaster valve prosthesis.

The Lillehei-Kaster valve was used in 215 patients over a 7-year period. The aortic valve was replaced in 81 of them. Hospital mortality was 21% (17 patients). Ten patients were lost to follow-up and long-term mortality was 5% (3 patients). The incidence of thromboembolism was 2.6 per 100 patient-years, and actuarial survival was 96% at 5 and 87% at 7 years. Mitral valve replacement was performed in 108 patients. Hospital mortality was 20% (22 patients), 24 patients were lost to follow-up, and long-term mortality was 13% (11 patients). The combined incidence of thromboembolism was 5.0 per 100 patient-years, and actuarial survival was 81% at 5 years and 75% at 7 years. In both groups, the majority of patients improved clinically. Fifteen patients had double-valve replacement, and 11 had coronary revascularization in addition to valve replacement.

Adolescent↗
PubMed1979

Emotional complications of adolescent grand mal epilepsy.

Adolescents who have grand mal epilepsy and their parents were interviewed, and the adolescents were evaluated neurologically. Better seizure control and less neurologic disability were unexpectedly associated with less open communication between the adolescents and their families and friends, and with a poorer self-image and poorer expectations for the future. These findings were unrelated to IQ or school performance. This outcome is consistent with other studies of invisible defects and stigmatization, and suggests that youngsters who have relatively mild defects involving social disability may be more troubled than those with more apparent defects, for which denial may be operative. An incidental finding in the study was that a question more predictive of overall family, social, and academic function than the neurologic findings was simply whether or not the youngster was attending the appropriate grade in school for his or her age.

Adolescent↗