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Biomedical subjects

M Lang

Publications and source records attributed to M Lang.

At least 91 records · Page 5Linked to original sources
PubMed1997

Linear synthetic aperture modes for ultrasonic pulse-echo imaging.

A unified approach is developed to characterize and compare the most widely used two-dimensional ultrasound pulse-echo imaging procedures. The methods of monostatic, bistatic and multistatic time-domain holography are theoretically investigated with regard to line spread functions, resolution capabilities, and the effects of multiple scattering and object inhomogeneities. Analytical derivations and computer simulations show the superiority of monostatic holography in applications such as nondestructive testing, where in most cases the assumptions generally made in the calculation of the inverse scattering formulae are justified. However, if higher order scattering and/or the spatial variations of the sound speed play a significant role, then multistatic imaging is more advantageous. A modification of this latter mode, with fixed focus on transmission, is commonly used in medical imaging B-scan systems, but implementation of the full algorithm would offer improved resolving power and reduced side lobe levels throughout the image plane.

Artifacts↗
PubMed1997

State-level clustering of safety measures and its relationship to injury mortality.

This article proposes a social model of investigating injury mortality. The authors hypothesize that (1) state-level laws and regulations on safety cluster together in one or more groupings; (2) groupings of safety measures play a significant role in injury mortality; and (3) injury mortality is very highly associated with social structural variables. There is a clustering of safety policies, with five factors explaining 67 percent of variance, although no "master factor" was discovered. The strongest factor, explaining 21 percent of variance, includes three gun laws and low speed limits before the 1973 federal law. One factor is the most global in that it taps three distinct areas, including helmet laws, minor blood alcohol levels, and smoke detectors, though it only explains 7.5 percent of variance. The only factor that remains in a regression for injury mortality is one that includes strong seat belt laws and strong enforcement of those laws, though in the direction opposite to that hypothesized. This factor, along with percentage rural and environmental spending per capita, is significant for both motor vehicle and non-motor vehicle mortality. For motor vehicle mortality alone, deaths are higher in states with higher percentages of Hispanics and fewer people receiving food stamps and AFDC. Many factors that usually predict individual injury mortality do not hold at the state level, suggesting the usefulness of looking at social factors for new insights into injury mortality and prevention.

Adolescent↗
PubMed1996

Profile of CGP 61755: a novel and potent HIV-1 protease inhibitor that shows enhanced anti-HIV activity when combined with other antiretroviral agents in vitro.

CGP 61755 is a novel hydroxyethylene derivative produced by a high yield 10 step chemical synthesis. It is highly specific for HIV-1 protease with an IC50 of 1 nM. The ED90 in MT-2, PBLs and macrophages is infected with laboratory strains of HIV-1 or clinical isolates is 30-100 nM. In chronically infected macrophages the ED90 is 1000 nM (1000 nM for saquinavir and 10 microM for indinavir). When the antiviral activity of CGP 61755 on HIV-1 infected lymphocytes was examined using serum free medium an ED99 of 60 nM was determined, while in the presence of 10% human serum the same activity was achieved with 120 nM. When examined in combination with RT inhibitors or protease inhibitors, either in a co-culture of CEM-SS and chronically infected H9IIIB cells or in a free virus lymphocyte infection, cooperativity of the antiviral activities was observed. Dog pharmacokinetic studies comparing p.o. and i.v. data indicate that CGP 61755 has a bioavailability between 50 and 80%. Following oral administration the area under the concentration curve (AUC) values increased in a dose proportional manner. The plasma levels of the drug at 6 hours after oral administration were above the ED90. Based on these properties we believe that CGP 61755 has an attractive profile that justifies further preclinical evaluation of the drug.

Animals↗
PubMed1996

Aza-peptide analogs as potent human immunodeficiency virus type-1 protease inhibitors with oral bioavailability.

A series of aza-peptide analogs with a (hydroxyethyl)hydrazine isostere has been synthesized as HIV-1 protease inhibitors using a simple synthetic scheme. Structure-activity studies based on the X-ray of a previously described inhibitor-enzyme complex led to potent inhibitors with antiviral activity in the low-nanomolar range. The S-configuration of the transition-state hydroxyl group was preferred in this series. Small modifications of the P2P3 and P2'P3' substituents had little effect on enzyme inhibition but greatly influenced the pharmacokinetic profile. As a result of these studies, the symmetrically acylated compound 8a and its close analog 24a bearing a methyl carbamate in P3 and an ethyl carbamate in P3' position were identified as potent inhibitors with plasma concentrations exceeding antiviral ED50 values 150-fold following oral application in mice.

Administration, Oral↗
PubMed1996

Synthesis of potent and orally active HIV-protease inhibitors.

A series of potent HIV-protease inhibitors has been prepared. Several of the newly synthesized compounds showed high plasma even after oral administration to animals. Based on the overall biological profile, CGP 61755 was chosen for further preclinical evaluation. For this compound, a 10 step synthesis potentially suitable for large scale production was developed.

Administration, Oral↗
PubMed1996

The last 3 months of life of cancer patients: medical aspects and role of home-care services in southern Switzerland.

The clinical data on terminal cancer patients who have died since the establishment of a program of collaboration between community services and the cancer center of Canton of Ticino, southern Switzerland, were retrospectively analyzed to describe the characteristics of patients seen and the effect on them of a home-care program coordinated by the cancer center. The home-care program is based on five geographically grouped community-based domiciliary services, with the addition of one nurse responsible for coordination and one physician from the oncology center. Selection criteria for participation in the home-care program are defined. The main outcome measures were: number of hospitalizations and median hospital stay during the last 3 months of life; reasons for and median length of last hospitalization; place of death of patients who had home care and those who did not. In the group of 993 patients analyzed, the median contact time with the cancer center was 9.5 months (10th percentile: 1 month, 90th percentile: 71 months); the most frequent neoplasm was lung cancer (22%) with the briefest contact time (7.5 months; 10th percentile: 1 month; 90th percentile: 21 months); 13.5% of patients were never hospitalized; half of the patients had a total hospital stay of 24 days or longer and 23% died at home. The sociodemographic and medical characteristics of home-care users were similar to those of the home-care non-users and to those of the overall group. In the group of home-care users (32% of the total) 22% were never hospitalized, half of the patients had a total hospital stay of 17 days or longer, and 43.5% of them died at home. These values were significantly different (P > 0.001) from those reported in the group of home-care non-users. Palliative care, provided at home through community-based domiciliary services, is associated with less frequent and shorter hospitalizations in the last 3 months of life. Medical oncology and palliative treatments should be mutually complementary to improve patients care. Cancer centers should be involved in the planning and coordination of supportive-care domiciliary services.

Aged↗
PubMed1996

[T3 hyperthyroidism with metastatic follicular thyroid carcinoma in substitution therapy].

This case report shows the anamnesis of a female patient with follicular Thyroidglandular-Ca. in an advanced stage with multiple metastases in the skeletal system, lungs and hilar lymph nodes. In addition, the patient showed a T3 hyperthyroidism with clinical symptoms but normal to low level of T4. After exclusion of hormone producing metastases as a reason for the hyperthyroidism, the most likely explanation would be an increased 5'-deiodination from T4 to T3.

Adenocarcinoma, Follicular↗
PubMed1995

Introduction of laparoscopic cholecystectomy in a large teaching hospital: independent audit of the first 3 years.

Commencing with the introduction of laparoscopic cholecystectomy, a detailed independent prospective audit of all cholecystectomies attributable to 12 general consultant surgeons has been carried out over a period of 3 years. Of 650 operations 502 were intended laparoscopic cholecystectomies. In the first year 58 per cent were intended laparoscopic cholecystectomies; this rose to 80 per cent in the second year and to 90 per cent in the third. The conversion rate was 21 per cent in the first year, 21 per cent in the second and 15 per cent in the third. The mean operating time for laparoscopic cholecystectomy was 133 min for year 1, 123 min for year 2 and 115 min for year 3, compared with 92, 101 and 95 min respectively for open cholecystectomy. The overall complication rate was 10 per cent for laparoscopic and 21 per cent for open cholecystectomy. This included six bile duct injuries (1.2 per cent) in the patients undergoing the laparoscopic procedure and one (0.7 per cent) in those having open cholecystectomy. This unselected audit of a group of general surgeons introducing laparoscopic cholecystectomy into their practice has revealed complication and conversion rates that are higher than those reported in most of the published literature, but may be representative of practice throughout the UK.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1995

Unimanual motor learning impaired by frontomedial and insular lesions in man.

We correlated impaired unimanual motor learning with the lesion site in 53 patients with chronic lesions predominantly of the frontal lobe. The lesions were assessed using computed tomography (CT), then transferred to standard templates of nine slices parallel to the canthomeatal plane and digitized with a raster matrix of 3 mm by 3 mm width. The learning task was to track a moving target on a computer screen with a dot guided by the preferred hand, while the horizontal coupling between hand movement and screen was inverted. The mean tracking error was recorded over eight successive trials of 80s duration. If the mean error of the last three trials was not lower than that of the first three trials, impaired motor learning was assumed. We correlated performance and lesion with a contingency table analysis for each raster element. Impaired motor learning was associated with a lesion within the supplementary motor area and adjacent anterior cingulate, and within the anterior insular region. Our results indicate that these regions are critical for motor learning and functional plasticity in man. Our data support activation patterns obtained with positron emission tomography.

Adolescent↗
PubMed1995

Improving the applicability of myocardial densitometry and parametric imaging by extended automated densogram analysis.

In clinical applications the analysis of X-ray contrast densograms acquired in regions of interest (ROI's) over the myocardium is disturbed by many complex factors. For this reason we acquire redundant densogram information for quality control before extracting densitometric parameters. In our approach, initially some stable measures of quality for densograms are used to lower the influence of poor quality densograms by a quality weighted averaging. For example a shape quality measure, Q1, is calculated using regions of optimal and minimal acceptable quality defined with respect to a prototype densogram. Not a few myocardial ROI's yield densograms that differ from single-source densograms (SSD's) due to e.g. superposition of different perfusion beds or the position of the ROI relative to the coronary sinus or stenoses. This might result in a densogram shape with oscillating or plateau behavior. For densograms of a such general shape many parameters defined in the usual way do not depend smoothly on the densogram values. The conventional definitions of some parameters (appearance time, rise time) are therefore extended for application to multi-maxima densograms as well as to SSD's. These new methods are evaluated using digitized clinical angiocardiograms and are applied to parametric imaging (pixeldensograms) in a slightly modified way. Taking into account the densogram quality, its shape and its origin results in a considerable improvement both for densitometry and parametric imaging of myocardial perfusion.

Absorptiometry, Photon↗
PubMed1995

[Loss of brain stem auditory evoked potential waves I and II during controlled hypotension].

For surgical removal of a malignant choroid melanoma, it is necessary to reduce systolic blood pressure to around 50-60 mmHg in order to prevent choroidal haemorrhages. However, blood pressure reduction is associated with the risk of cerebral ischaemia. We report a patient with a malignant choroid melanoma in whom waves I and II of the brainstem auditory evoked potentials (BAEP) disappeared during surgery under controlled arterial hypotension and hypothermia (31.1 degrees C). The waves could be recorded again immediately after the mean arterial pressure was increased from 48 to 77 mmHg. The oesophageal temperature had dropped by 0.3 degrees C at this time. The 2-channel electroencephalogram (EEG) showed no irregularities during this time period. A bilateral, reversible, apparently blood-pressure-dependent loss of waves I and II during arterial hypotension despite a normal EEG has to our knowledge not been previously described in the literature. The isolated loss of waves I and II with maintenance of waves III, IV, and V is unusual. The literature contains reports of acoustic neurinoma patients in whom only wave V could be recorded. This is regarded as an indication of continued impulse conduction despite the loss of waves I to IV. Others have observed a patient with temporary and reversible loss of BAEP wave I due to vasospasm of the internal auditory artery that apparently occurred during or shortly after manipulation of the internal auditory meatus. Assuming anatomic peculiarities in the blood supply to the generators of the BAEP waves, a stenosis of the basilar artery could be considered as the cause of the bilateral reversible loss of waves I and II. Another potential source could be induced hypothermia, but this does not seem very likely because the patient's temperature was 0.3 degrees C lower at the return of the waves than at their loss.

Choroid Neoplasms↗
PubMed1995

A clinical study of clozapine treatment and predictors of response in a Canadian sample.

OBJECTIVE: To study the clinical response to clozapine in patients with refractory schizophrenia. METHOD: Open trial of clozapine in 61 consecutively-treated patients. RESULTS: Following clozapine, the level of function of patients was improved relative to admission (p = 0.0001) and to the highest level in the previous year (p = 0.0001). Severity of illness was decreased (p = 0.0001). Overall, 31% of the patients were classified as responders to clozapine and the responders were all identified by 32 weeks of treatment. Poor functioning in the previous year was associated with less favourable response. At a mean interval of 26 months following discharge, 72% of the patients were continuing clozapine treatment. CONCLUSIONS: This open trial of patients who were treated consecutively indicates a comparable degree of response to clozapine as observed in controlled clinical trials, and that level of functioning in the previous year was the best predictor of response.

Adolescent↗
PubMed1995

[Practical experiences with home ventilation in childhood].

BACKGROUND: The introduction of portable ventilators independent of compressed air as well as non-invasive devices for assessment of blood gases, helped to facilitate a long-term mechanical ventilation in family environment in the last decade. Home care is of particular interest at the infant age, as the disruption of the mother-child relationship may induce severe developmental disorders, known as syndrome of psychosocial deprivation. PATIENTS AND METHODS: We investigated retrospectively the tendency of the ventilator parameters, the support and the daily practice of 16 families with children of all ages with long-term ventilator assistance. RESULTS: The duration of the ventilation ranged between 5 months and 14 years, on the average at 5.5 years. The average portion of the ventilation at home care was 78%. The respiratory patterns, tidal volume and positive inspiration pressure, exceeded occasionally the physiologic standard of the age group. The common reason is, that the children prefer small sized tubes, having advantages in comfort and speech abilities. Therefore results an increased tube-resistance and air leakage of the tracheostomy tubes. The long-term tendency of the ventilator parameters is stable or improving, excluding the patients with progredient primary diseases. Commonly the motivation of the family members is high, therefore the psychosocial integration of the patients satisfying. Two thirds of the families have no personal support for the domiciliary care of the ventilator assisted child. Mothers tell about an enormous distress. CONCLUSIONS: The long-term mechanical ventilation of children at home care is an adequate therapy for all ages. It combines technical support of the underlying chronic respiratory failure with the chance of an intact psychosocial development of the child. Specialized centres and a national organisation may provide competent information and support for the increasing number of home-ventilated children in Germany.

Adolescent↗
PubMed1995

History lessons.

Interest in nursing history has grown in North America over the past two decades, in part because of the increase in feminist and nurse historians, but also because of the realization that nursing history can contribute much to the study of health and social issues.

Historiography↗
PubMed1994

Concepts and diagnosis of brain death.

The different concepts of brain death are subject to controversial debate. It is outlined that only the whole-brain concept, that is the irreversible loss of all functions of the entire brain, is consistent with the death of man. Cortical death or brain-stem death should not be considered in this respect. The operational procedure for determining brain death is outlined with special regard to those cases in which a definite diagnosis cannot be made clinically. It is shown that apnea testing must be accompanied by blood-gas analysis, as it may take 15 min for the PaCO2 to achieve the desired level of 8 kPa. The problem with CNS-depressing drugs and their metabolites interfering with the clinical diagnosis--e.g. sedatives, barbiturates, opioids--is described, and it is stressed that, in these cases, the cerebral panangiography (digital subtraction angiography with catheter tip in the aortic arch) is the gold standard for the final and definite proof of brain death.

Brain Death↗