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Biomedical subjects

M Block

Publications and source records attributed to M Block.

At least 127 records · Page 7Linked to original sources
PubMed1990

Falling among the sensorially impaired elderly.

Recent studies of the healthy elderly indicate that accidental falls account for many lengthy hospital stays and permanent disabilities. An ongoing investigation by our group is examining the contribution of neuromuscular feedback and the possible substitution of visual-perceptual feedback as a major contributor to falling in this population. This combination of decreased weighting of neuromuscular factors and increased weighting of the visual-perceptual factors led to the following hypothesis: Those persons who cannot see should show less change in frequency of falling as they age than sighted cohorts. The deaf, who rely more than others on visual perceptual stimuli, are less likely to fall as they age than the general elderly population, who first begin to rely more heavily on visual stimuli when they age. Thus, the deaf and blind constitute a population whose change in frequency of falls with increased age should differ markedly from change in the frequency of falls among the nonblind and nondeaf segments of the population. Our results support the hypothesis. The blind demonstrated a higher rate of falls than the deaf or nonimpaired population. However, the more elderly blind failed to show the increase in falling demonstrated by the deaf and nonimpaired. If these findings are confirmed in subsequent studies, the nonimpaired and deaf elderly could be trained to focus on visual feedback. The blind may be able to reduce the frequency of falls by enhancing musculoskeletal feedback and strength via exercise.

Accidental Falls↗
PubMed1989

[The reliability of angiographic volume determination of the left ventricle using digital image subtraction--significance in stress tests].

Using the technique of digital subtraction angiography (DSA), left ventricular volumes can be determined after intravenous injection of contrast medium at rest and during exercise. The significance of the well known errors of angiographic determination of left ventricular volumes was investigated in 22 patients before and during a bicycle exercise test. Before and after exercise 40 ml of contrast medium were injected (18 ml/s) intravenously to calculate left ventricular volumes. Enddiastolic and endsystolic contours of the left ventricle were traced by two investigators (A and B) on five different days. Using these contours, volumes were calculated by a computer system. The first calculation of both investigators (single measurement) and the mean value of all five calculations (repetitive measurements) were compared. In the same procedure left ventricular contours of six patients were calculated after conventional contrast ventriculography (40 ml of contrast medium). No systematic deviations were found in comparing the results of both investigators using the single or repetitive method by means of DSA: (VolB = 0.86 VolA + 12.2, r = 0.97 versus VolB = 0.96 VolA + 9.1, r = 0.99). Compared to single method the residuals (Syx) of the repetitive method were significantly smaller: Syx = +/- 16.3 ml vs +/- 8.9 ml (p less than 0.01). Similar results were found in conventional ventriculography: single method Syx = +/- 18.7 ml and repetitive method Syx = +/- 8.8 ml (p less than 0.01). Comparing the volumes determined by DSA and by conventional ventriculography, respectively, no significant differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1989

The effect of different dosages of a transdermal nicotine substitution system on the success rate of smoking cessation therapy.

The effectiveness of different nicotine dosages on abstinence rates was investigated in a smoking cessation study. One hundred smokers underwent nine weeks of self-controlled treatment based on behavioral principles. The overall group was divided into two subgroups randomized according to sex, cigarette consumption and age. The first group (n = 51) was given a nicotine dose adapted to daily cigarette consumption. The second group (n = 49) was given a standardized dose. There was, unexpectedly, no difference between the two groups in respect to short-term abstinence rates. These results suggest that standardized dosage is preferred to individually adapted dosage.

Administration, Cutaneous↗
PubMed1989

Contact allergies induced by TTS-treatment.

The efficiency of a nicotine-containing transdermal therapeutic system (TTS) was investigated in a clinical study, the purpose of which was to help 183 heavy smokers give up their addiction by systematic and continuous nicotine application and simultaneous behavioral therapy. During the treatment period, 53% of the patients complained of pruritus and 39% developed erythemas that were almost exclusively confined to those areas where the patches had been applied. However, most symptoms appeared only in slight or moderate forms. In contrast to irritative cutireactions, 6 patients developed a genuine contact allergy (type IV, delayed type reaction) which proved in 5 cases to be induced by the nicotine contained in the patches. Presumably TTS-treatment may induce contact allergies to pharmaceutic agents, as has already been described in other observations on allergies to haptens.

Administration, Cutaneous↗
PubMed1988

Ascorbate antagonizes the behavioral effects of amphetamine by a central mechanism.

The behavioral response to amphetamine was monitored in rats that received simultaneous intraventricular infusions of saline or ascorbate. Both groups of animals displayed comparable responses, although ascorbate significantly delayed the onset of amphetamine-induced locomotion and rearing. In rats pretreated with a threshold dose of haloperidol (0.025 mg/kg), virtually all aspects of the amphetamine response were attenuated, and this effect was enhanced by ascorbate. In haloperidol-pretreated rats, ascorbate significantly lowered sniffing and forepaw shuffling throughout the amphetamine response. These results suggest that ascorbate antagonizes dopaminergic transmission by a central mechanism.

Amphetamine↗
PubMed1987

Metabolic and ultrastructural abnormalities during ischemia in canine myocardium: noninvasive assessment by positron emission tomography.

Positron emission tomography allows the noninvasive assessment of regional myocardial blood flow and metabolism. The purpose of this study was to correlate N-13 ammonia uptake as a measure of regional blood flow and C-11 palmitate kinetics as a marker for fatty acid metabolism in ischemic canine myocardium using positron emission tomography. Furthermore, the metabolic results were compared with ultrastructural findings obtained in the same animal model. Regional ischemia was induced by balloon occlusion of the left anterior descending artery in a closed chest dog model. The three myocardial sites studied were the center and "border" of the ischemic segment as well as the control myocardium. C-11 palmitate uptake closely correlated with blood flow (r = 0.88). In the center of ischemia uptake of C-11 palmitate was decreased and clearance of C-11 activity significantly prolonged. In the "border" of the ischemic segment with only mild reduction of flow and C-11 palmitate uptake (approximately 20%) clearance halftime and residual activity were significantly different from control. The residual activity normalized for initial uptake of C-11 palmitate was highest in the "border" regions consistent with increased deposition of C-11 palmitate in lipid pools. The electron microscopic studies showed in 8 of 11 dogs lipid droplets as the only abnormality in corresponding segments with only mild reduction in microsphere blood flow. Thus, these data indicate the potential of metabolic imaging to characterize ischemia on a cellular level. Positron emission tomography provides a sensitive means to detect mild ischemia and to define extent and severity. Metabolic imaging may prove clinically useful to identify not only necrosis, but also myocardium at risk.

Ammonia↗
PubMed1987

Recognition of alcoholism and substance abuse in primary care patients.

Alcohol and other substance abuse are frequently seen in primary medical practice but are underdiagnosed. Forty-two (14%) of 294 adult primary care patients suffered from alcohol or other substance abuse, as diagnosed by a structured psychiatric interview. Primary care physicians identified 17 (40%) of these patients, as well as another patient identified during a six-month follow-up period, as having a substance abuse problem at initial clinical evaluation. Clinically identified substance abusers were older, more likely to be married, and more often used multiple drugs. They more frequently had antisocial personality disorders, while patients not clinically recognized were often depressed. Logistic regression analysis indicated that the presence of antisocial personality, the absence of a coexisting depressive disorder, and better social functioning scores were the factors most strongly associated with clinical recognition. The study suggests clinical judgment issues, which may be useful to physicians in training to improve their recognition and treatment of substance abuse disorders.

Alcoholism↗
PubMed1986

Psychiatric decision making in family practice. Future research directions.

Psychiatric illnesses in family practice are significantly underdiagnosed because of factors associated with both the physician and patient. Clinicians too often fail to utilize a biopsychosocial approach in the assessment process, tending to assess symptoms as organic regardless of their etiology. Patients similarly tend to emphasize the physical nature of their complaints when presenting in medical settings. Efforts have been made to improve the physician's diagnostic accuracy through the use of screening scores. The results, however, are inconclusive. It remains unclear whether the physician disregards this information or considers it irrelevant. We suggest that future research investigate not only the accuracy of the clinician's diagnostic formulation but also the processes whereby the family practitioner elicits, analyzes, and synthesizes or discards cues pertinent to mental illness. By combining statistical analyses with the analytic techniques developed in studies of medical decision making and general problem solving, detailed leads should emerge for the design of improved didactic and experiential training programs.

Attitude of Health Personnel↗
PubMed1985

Factor XIII catalyzed formation of fibrinogen-fibronectin oligomers--a thiol enhanced process.

Fibrinogen and plasma fibronectin were shown to interact in the presence of factor XIIIa. The reaction was enhanced by dithiothreitol and was accompanied by an increase in the turbidity of the solution and the formation of particulate matter and gel structures. At a constant concentration of fibrinogen the turbidity increase was dependent on the fibronectin concentration and at a constant concentration of fibronectin, on the fibrinogen concentration. Kinetic experiments showed that an initial step in the reaction between fibrinogen and fibronectin was the formation of a transient intermediate containing 1 mole of fibrinogen and 1 mole of fibronectin. Transient intermediates of larger molecular weight and containing both fibrinogen and fibronectin were also formed. These heterooligomers eventually reached huge molecular sizes and at early times formed particulate matter that sedimented on centrifugation. The predominant molecular species formed in an equimolar mixture of fibrinogen and fibronectin were heteropolymers. Small amounts of homopolymers composed of fibrinogen and possibly also homopolymers of fibronectin were detected. The results are discussed in terms of reaction mechanism and potential importance of this novel oligomerization pathway in haemostasis, thrombosis and tissue repair.

Dithiothreitol↗
PubMed1985

Anatomy and function of the heart and intrathoracic vessels in congenital heart disease: evaluation with the Dynamic Spatial Reconstructor.

The Dynamic Spatial Reconstructor is a unique high speed volume imaging X-ray scanner based on computed tomographic principles. It has several potential advantages over conventional angiographic methods, including reduced invasion, reduced rate of false negative results and increased accuracy of measurements of structure and function. To evaluate the utility of the Dynamic Spatial Reconstructor in the investigation of congenital heart disease, scanning was performed in several pediatric patients with pulmonary valve atresia. Early results show that three-dimensional images of the cardiac chambers and intrathoracic vessels can be acquired and displayed with the system. All the information necessary for quantitative analysis of the pulmonary arteries can be obtained with a single scan involving injection of 0.6 to 2.0 cc/kg of contrast agent and radiation exposure of 0.54 to 0.95 rad/s over 5 to 8 seconds.

Angiography↗
PubMed1985

Megestrol acetate used as primary hormonal therapy in stage D prostatic cancer.

The majority of patients with advanced prostatic cancer respond either to castration or estrogen therapy. In an attempt to identify an alternative hormonal therapy, 25 symptomatic stage D prostate cancer patients were treated with megestrol acetate as initial hormonal therapy. Thirty-three patients were evaluable for response as defined by the National Prostatic Cancer Project criteria. Partial remission was observed in 11 patients and stable disease in 5, with an overall response rate of 70%. The projected median duration of response and survival were 10 and 20 months, respectively. Weight gain was common, but only two patients showed evidence of fluid retention. Gynecomastia, thromboembolic episodes, and gastrointestinal side effects were not observed in this group of patients, though two patients had increased pain shortly after therapy was initiated. Thus, in advanced prostatic cancer, megestrol acetate is effective primary therapy with minimal side effects.

Aged↗
PubMed1985

Ethics of clinical trials in family medicine.

In this paper several issues are examined that arise from conducting randomized clinical trials in a family practice setting. The distinctive research tradition in family practice involves a patient's primary care physician performing an experimental investigation that usually, though not invariably, is focused on common health problems. Representative clinical trials are presented as examples that illustrate two ethical difficulties evoked by such research: a potential violation of the primary care physician's therapeutic imperative to provide the best possible treatment for his or her patient, and the likelihood that the type of physician-patient relationship fostered in family practice significantly diminishes the capacity of the patient to give true informed consent. In an attempt to resolve these ethical difficulties, a model of moral reasoning is presented that is based on easily understood ethical principles and is applicable to actual clinical decision making. Using that model, a tentative set of rules or guidelines is offered for implementing clinical trials in family medicine.

Clinical Trials as Topic↗
PubMed1984

Metastatic neuroblastoma arising in an ovarian teratoma with long-term survival. Case report and review of the literature.

A case of neuroblastoma arising in an immature teratoma of the ovary in a 22-year-old woman is reported. Differentiation was grade 3 in the primary and metastases. Metastases to retroperitoneal, mediastinal, and supraclavicular lymph nodes and to bone were diagnosed 2 years after presentation of the primary tumor. Electron microscopic study demonstrated dense-core granules of the neurosecretory elements. Treatment with combination chemotherapy followed by radiotherapy resulted in complete remission which continues to the time of this report, more than 4 years after diagnosis of the primary tumor. Prolonged survival of metastasizing grade 3 immature teratoma is distinctly uncommon. The literature pertaining to this unusual tumor and to neuroblastoma of adults is reviewed.

Adult↗
PubMed1984

Quantitative analysis of a vascular tree model with the dynamic spatial reconstructor.

The accuracy in determining the three-dimensional anatomy of a vessel network by computed tomography (CT) is evaluated using a glass model of a pulmonary artery. The dynamic spatial reconstructor (DSR), a high temporal resolution, volumetric, roentgenographic, CT scanner, was used to scan the model. The glass of the model had a roentgen attenuation coefficient mu = 0.55 cm-1, which is approximately equivalent to the 20% dilution of contrast medium to be expected in the pulmonary arterial tree following a contrast agent bolus injection of 2 ml/kg in the right atrium. The model was scanned inside a 20 cm diameter Plexiglas cylinder with a 1 cm thick wall (mu congruent to 0.2 cm-1) to simulate the chest wall of a 20 kg dog, and it was filled with potato flakes to simulate lung parenchyma (mu congruent to 0.06 cm-1). In one 0.011 s scan, information for reconstruction of a stack of images of transaxial sections was recorded. Sequential scans were performed to obtain data for either maximum transaxial resolution (14 angles of view every 0.0167 s, 120 parallel slices each 1.8 mm thick) or maximum axial resolution (eight angles of view every 0.0167 s, 240 parallel slices each 0.9 mm thick) reconstructions. Estimated detectable "vessel" size, cross-sectional area, branching angle, and interbranch segment length were determined as a function of imaged slice thickness, orientation of section image, and number of angles of view (i.e., scan duration) used to make images. Retrospective selection of 0.05 s duration scan apertures at sequential 0.5 s intervals was used to simulate a typical, retrospectively gated reconstruction from a DSR scan. Using these reconstructed images, 2 mm diameter "vessels" could be readily detected and their structure quantitated. Comparing direct measurements and DSR estimates, cross-sectional area (SEE = 3 mm2), branching angles (SEE = 2 degrees), and segment length (SEE = 1 mm) all had a correlation coefficient greater than 0.99, and the regression lines showed no significant differences from the lines of identity (p greater than 0.05).

Animals↗
PubMed1984

Coronary angiographic examination with the dynamic spatial reconstructor.

The dynamic spatial reconstructor (DSR), a high temporal resolution, three-dimensional roentgenographic, computed tomography scanner, was used to scan the coronary arteries of five dogs. After one injection of contrast medium into the left main coronary artery or into the aortic root of each dog, all major epicardial coronary arteries and the septal artery could be imaged. After selective removal of all nonangiographically enhanced anatomical structures within the three-dimensional images, pseudo three-dimensional displays were generated to show the arteries from all possible views--even the strictly cranial view--so that superposition of arteries could be avoided. The geometric accuracy of the images was evaluated by comparing coronary arterial segment length measured by the DSR with postmortem measurements (r = .99, SEE = 3.12 mm, n = 35) and by measuring the stenosis produced by nine hollow plastic cylinders lodged in coronary arterial lumina via percutaneous catheterization. Three of the plugs had irregular noncircular lumina drilled into them so that the percentage of stenosis seen in some projection images underestimated the severity of stenosis. The DSR overestimated the length of a 3 mm long stenosis by 0.4 +/- 0.5 mm. The percent area reduction caused by the hollow cylinders varied between 53% and 92% and was underestimated by the DSR on the average by 7%. The correlation between DSR measurements and the direct measurements was r = .85 (SEE = 5%, n = 9). The volume of plastic in each plug (average 13.2 mm3), calculated from the length, cross-sectional area, and degree of the stenosis, showed a better correlation (r = .90, SEE = 2 mm3) with the actual plastic volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗