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Biomedical subjects

B Becker

Publications and source records attributed to B Becker.

At least 91 records · Page 5Linked to original sources
PubMed1994

In situ screening assay for cell viability using a dimeric cyanine nucleic acid stain.

A rapid and sensitive assay is described for the determination of cell viability of adherent and nonadherent cells that can be performed in situ in 96-well microtiter plates using fluorescence plate scanners. The assay, based on dye exclusion, utilizes a plasma membrane-impermeable, dimeric cyanine dye (YOYO-1). YOYO-1 fluoresces brightly only when bound to nucleic acids. Cells are incubated with YOYO-1, and fluorescence is measured before and after the addition of detergent, which allows the dye to enter the cells. The fluorescence before detergent treatment originates from nonviable cells that have membrane damage and take up YOYO-1. The fluorescence after detergent treatment originates from all cells in the sample. The ratio of the two fluorescence values is used as an indicator of cell viability. The cell viability results of this microplate assay closely resemble those of dye exclusion studies by flow cytometry and are similar but not identical to those of the thiazolyl blue assay, which uses a metabolic indicator of cell death. Because the assay can be performed in situ, without removing the medium, disintegrated cells, cell aggregates, and cells that stick to culture vessel walls are all included in the measurement.

Benzoxazoles↗
PubMed1994

Melanocytic nevi in Turner syndrome.

One morphologic feature of Turner syndrome is increased numbers of melanocytic nevi; however, little attention has been given to their characterization. The development of a melanoma in one of our patients with Turner syndrome prompted this study. We prospectively examined 10 patients with the disease, confirmed by karyotype. All patients underwent full body skin examination noting the number, size, distribution, and degree of clinical atypia of melanocytic nevi. Representative and unusual lesions were photographed. An average of 115 nevi were seen, with the majority measuring 1 to 5 mm. Most were located on the back and extremities. Clinical atypia was uncommon. Our patients had larger numbers of benign-appearing nevi than the general population. Large numbers of melanocytic nevi is a risk factor for melanoma, suggesting that these patients have an increase in one risk factor. Longitudinal studies are indicated to clarify this issue; nevertheless, we recommend periodic skin examinations and the regular use of sunscreens for individuals with Turner syndrome.

Adolescent↗
PubMed1994

Hypertrophic lichen planus in three HIV-positive patients: a histologic and immunological study.

It is well known that several dermatoses, such as psoriasis vulgaris and seborrheic dermatitis, present with more extensive and severe disease in patients infected with the human immunodeficiency virus (HIV-1). Except for one report, however, lichen planus (LP) has not been described in patients with HIV infection. In this report we describe the clinical and morphological features of 3 HIV-positive patients who presented with extensive hypertrophic LP. To determine if alteration in the immune status in HIV-positive hosts is reflected in the nature of the infiltrate in LP, we determined the proportion of T-helper and T-suppressor cells in the infiltrate in 1 case. The majority of the infiltrating lymphocytes in the dermis were of the T-helper phenotype. Epidermal lymphocytes, however, were predominantly of the T-suppressor phenotype. We conclude that LP in HIV-positive hosts may present with more extensive disease than in immunocompetent hosts. Based on our immunohistochemical studies, we conclude that, similar to immunocompetent hosts, T-helper cells are the predominant cells in the dermal infiltrate of LP in HIV-positive patients. However, in contrast with reports in the literature on LP in immunocompetent hosts, we found that, in the case studied, the epidermal lymphocytes were predominantly of the T-suppressor phenotype.

Adult↗
PubMed1994

Effects of R80122, a new phosphodiesterase inhibitor, on liver and global haemodynamics in patients undergoing coronary artery bypass surgery.

R80122 (0.3 mg/kg body weight), a new phosphodiesterase inhibitor, was tested in ten patients undergoing coronary artery bypass surgery. Haemodynamic measurements were made and hepatic blood flow assessed by the indocyanine green infusion method using liver vein catheterization. Cardiac index increased by 63% and systemic vascular resistance decreased by 47%. Hepatic blood flow and intestinal vascular resistance were not significantly affected; nor was hepatic oxygen consumption. It is concluded that R80122 is a highly cardioselective phosphodiesterase inhibitor and that the reduction in systemic vascular resistance by this drug is not an effect of extensive intestinal vasodilatation.

Adult↗
PubMed1993

Effect of oxymetazoline on aqueous humor dynamics and ocular blood flow in monkeys and rabbits.

OBJECTIVE: To evaluate the ocular effects of oxymetazoline hydrochloride, an alpha 2 agonist, in cynomolgus monkeys and albino rabbits. METHODS: Intraocular pressure was measured before and for 6 hours after application to glaucomatous monkey eyes. Outflow facility and aqueous flow rates were measured in normal monkey eyes. Uveoscleral outflow was measured in rabbit eyes. Ocular peak pulse volume was determined with the ocular blood flow system in normal and glaucomatous monkey eyes. RESULTS: Single applications of ozymetazoline reduced (P < .001) intraocular pressure up to 6.0 +/- 1.0 mm Hg (mean +/- SEM). Enhancement of the ocular hypotensive effect was observed with 5-day twice-daily administration. Outflow facility was unaltered; aqueous flow rate was decreased (P < .001) by 39% in the treated eyes compared with baseline values; and uveoscleral outflow was increased (P < .005) by 56% in the treated eye. Peak pulse volume was unchanged. CONCLUSION: Oxymetazoline reduces intraocular pressure by decreasing aqueous humor flow rates and increasing uveoscleral outflow. Oxymetazoline may have clinical potential as an ocular hypotensive drug.

Animals↗
PubMed1993

Ultrastructural studies on a chlorella virus from Germany.

This is the first report on the morphology and fine structure of chlorella virus Göttingen-1 (CVG-1), an European member of the newly approved family Phycodnaviridae, which infects certain unicellular, eukaryotic, exsymbiotic, green algae. CVG-1 are polyhedral particles 145-160 nm in diameter. The capsid consists of two shells, apparently composed of ca. 7 nm subunits. Whereas the outer shell of the capsid appears to be icosahedral, the inner shell appears to be irregular underneath one vertex of the virion. In this vertex the inner shell is separated from the outer shell leaving a distinct space ("empty vertex") of unknown function.

Capsid↗
PubMed1993

The role of early versus late removal of GTAM membranes on bone formation at oral implants placed into immediate extraction sockets. An experimental study in dogs.

The purpose of this study was to compare the effect of early versus late removal of expanded polytetrafluoroethylene (e-PTFE) membranes on bone formation at oral implants. Thirty Brånemark fixtures were placed into immediate extraction sockets with buccal bone dehiscences augmented by e-PTFE membranes. At 4 weeks, the membranes and underlying soft tissues were removed from 5 implants, but at 16 sites only the membranes were extirpated. In 9 sites, the membranes remained in place during the healing period. Sixteen weeks after fixture insertion, the sites in which the membrane was retained (MRET) showed an average of 5.2 mm of clinical bone height increase (100% of bone fill). For sites where the membrane together with underlying soft tissues were removed (MRB), the corresponding value was 2.0 mm (42% of bone fill). Implants at which only the membrane was removed (MR) showed the least clinical bone height increase (1.0 mm), resulting in 21% coverage of original threads. Histometric measurements verified that the MRET sites had the least distance from the top of the fixture to the newly formed bone level (0.4 mm). However, in contrast with the clinical findings, the histometric analyses showed that the MRB group had the greatest remaining bone defect (3.3 mm). The clinical and histometric results of the MRET group were statistically better, though, compared with those of the other two groups. Biopsies, removed from beneath the membranes, revealed slightly inflamed connective tissue, containing spicules of newly formed bone, indicating that more bone might have been created if the membranes had been retained longer.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗
PubMed1993

Isolation and characterization of the Golgi apparatus of a flagellate scaly green alga.

Highly purified Golgi membranes were isolated from the scaly green flagellate Scherffelia dubia using osmotic shock for controlled cell rupture, differential centrifugations and a discontinuous sucrose density gradient centrifugation. Three Golgi membrane fractions (based on the distribution of IDPase activity in the gradient) at densities 1.14 g/ml, 1.17 g/ml and 1.20 g/ml were obtained. The specific IDPase activity in these fractions was enriched about 78-fold compared to the crude cell homogenate. The Golgi membrane fractions were further characterized by electron microscopy, SDS-PAGE and lectin blotting. The low density fraction (1.14 g/ml) contained two distinct vesicle populations and scale precursors associated with the outer surface of the larger-size vesicles. The medium density fraction (1.17 g/ml) contained in addition to the larger vesicles, multilamellate vesicles and semicircular cisternae. Finally, in the high density fraction (1.20 g/ml) in addition to small and large vesicles, a tubular membrane reticulum was observed. The three Golgi membrane fractions revealed the same complex overall polypeptide composition when analyzed by SDS-PAGE, but gradual quantitative differences in the polypeptide profile between fractions were observed. The lectins GNA, DSA, and AAA bound to several glycoproteins in all Golgi membrane fractions. Deglycosylation with N-glycosidase F showed that all carbohydrate structures recognized by GNA and DSA, and one recognized by AAA were of the N-glycosidic type indicating the presence of both "high mannose" and "processed" N-glycans in the Golgi apparatus of S. dubia.

Centrifugation, Density Gradient↗
PubMed1992

Prediction of immediate ventricular arrhythmias after coronary artery ligation.

OBJECTIVES: Our aim was to test the hypothesis that increased beat to beat morphologic variations in the body surface electrocardiogram (ECG) are associated with fragmented diastolic electrical activity that appears after coronary artery ligation and to correlate the appearance of spontaneous ventricular fibrillation after coronary ligation with the magnitude of the ECG beat to beat variability. BACKGROUND: Unstable and variably delayed electrical activation precedes the development of ventricular fibrillation in dogs with acute ischemia. Detection of these highly variable low amplitude signals from the body surface is currently impossible. We have developed a system designed to measure the degree of beat to beat variability of the ECG. METHODS: With high fidelity electrocardiography, subtle beat to beat ECG morphologic variations were detected in epicardial and body surface electrograms and quantified as the variance of the ECG voltage at specific points of the cardiac cycle. The ratio of the variance at the QRS offset to that of the QRS onset (beat to beat variability index) was then calculated. RESULTS: Ventricular fibrillation developed in 12 of 27 dogs after left anterior descending coronary artery ligation. In 7 of the 12 dogs it occurred immediately (< 15 min) after ligation; in the other 5 it developed late (> 15 min) after ligation. Dogs with subsequently immediate ventricular fibrillation had a significantly higher beat to beat variability index than that of dogs with late or no ventricular fibrillation both before coronary ligation (4.7 +/- 1.4 vs. 1.1 +/- 0.2 and 0.8 +/- 0.1, respectively, p < 0.001) and after ligation (6.4 +/- 2.6, 1.0 +/- 0.6 and 1.2 +/- 0.6, respectively, p < 0.001). In dogs that developed ventricular fibrillation immediately after coronary ligation, the arrhythmia was preceded by fragmented diastolic electrical activity on the epicardial electrogram and a simultaneous increase in the beat to beat morphologic variability of the terminal portion of the body surface ECG QRS complex. CONCLUSIONS: Beat to beat QRS offset morphologic variations appear to be increased before and further increased after coronary artery ligation in dogs that develop ventricular fibrillation immediately after ligation. Increased beat to beat variability index may be associated with the presence of electrophysiologic instability and can predict early ventricular fibrillation.

Analysis of Variance↗
PubMed1992

Transient ST segment depression during Holter monitoring: how to avoid false positive findings.

To increase the specificity of 24-hour Holter monitoring in detecting transient myocardial ischemia, we separated genuine ST deviations from those dependent on artifacts by adding a detailed shape analysis of real-time printouts to the usual criteria of significant ST segment depression. We screened 116 apparently healthy subjects; 31 had to be excluded, because of pathologic findings in preliminary examinations. The remaining 85 (49 women and 36 men; mean age, 43.1 years) underwent Holter monitoring for assessment of the extent, frequency, and duration of episodes of horizontal and descending ST segment depression of at least 0.1 mV that persisted for at least 60 msec after the J point and that were at least 1 minute apart. On the basis of these criteria, six subjects (7.1%) showed 24 episodes of horizontal or descending ST segment depression with a mean of 0.2 mV (range, 0.15 to 0.25 mV), a frequency of four episodes per 24 hours (one to nine), and a duration of 12.2 minutes (range 3-range 41 minutes). Supplementary criteria--e.g., sudden onset of ST segment depression, identical orientation of PQ and ST segments, or simultaneous increase in R and P wave amplitude--made it possible to identify ST changes caused by artifacts in four volunteers. In only two subjects (2.4%) could true silent ischemia not be differentiated from false positive results. Thus consideration of only the extent, frequency, and duration of episodes does not permit a differentiation between true silent ischemia and false positive results. A supplementary shape analysis increases the specificity of ST segment analysis in detecting transient myocardial ischemia during 24-hour Holter monitoring.

Adult↗
PubMed1992

Hypothyroidism in adults with sickle cell anemia.

Persons with sickle cell anemia have several indications for transfusion of red blood cells. One of the complications of transfusion of red blood cells is iron overload. Iron overload has been associated with multiple endocrine abnormalities. We report herein three cases of hypothyroidism in adult individuals with sickle cell disease. All three patients were over the age of 45 years at the time of the diagnosis and had received multiple units of transfused red blood cells and had serum ferritin levels of greater than 6,000 ng/mL. All patients were diagnosed during times when they were critically ill. Replacement therapy was instituted in all cases; however, all three patients died shortly after the diagnosis of hypothyroidism was made. Congestive heart failure appeared to be a primary cause of death in all three patients. In the one patient in whom a postmortem examination was done, there was evident extensive fibrosis of the thyroid gland as well as extensive deposition of iron in the cells lining the thyroid follicles. We believe that this represents the first report of clinical hypothyroidism in patients with sickle cell anemia who have received multiple transfusions. Awareness of this condition is especially important given that congestive heart failure is common in sickle cell disease.

Anemia, Sickle Cell↗
PubMed1992

Psoriasis and human immunodeficiency virus infection.

BACKGROUND: Psoriasis associated with human immunodeficiency virus (HIV) infection has been reported to be severe and perhaps associated with decreased survival. OBJECTIVE: Our purpose was to document the natural history, response to therapy, and effect of psoriasis and its treatment on survival in HIV-infected patients with psoriasis. METHODS: This was an observational cohort study of 50 persons with psoriasis and HIV infection followed up during a 2-year period. RESULTS: In one third of the patients the psoriasis appeared before 1978, the year when HIV seroconversion began in San Francisco (group I). In two thirds psoriasis developed after 1978 (group II). Group I had a lower mean age of onset (19 vs 36 years) and more commonly had a family history of psoriasis. Palmoplantar and inverse psoriasis were more common in group II. Severe psoriasis occurred in one fourth of this group (12 of 50 patients). The median survival in this group after diagnosis of acquired immunodeficiency syndrome (AIDS) was 19 months, which is comparable to the median survival for all AIDS patients diagnosed in San Francisco between 1984 and 1990. CONCLUSION: Psoriasis in the setting of HIV disease may be mild, moderate, or severe. Standard therapies and zidovudine are effective in management. Survival does not seem to be adversely affected by the presence of psoriasis or its therapy.

Adolescent↗
PubMed1991

Beat-to-beat electrocardiographic morphology variation in healed myocardial infarction.

Using high-fidelity electrocardiographic (ECG) amplifiers, we measured subtle beat-to-beat ECG morphologic variations at different phases of the ECG complex. The electrocardiograms were recorded from 49 men with a documented Q-wave myocardial infarction and from 30 age-matched normal men. Forty consecutive beats were averaged to achieve an average ECG signal from which variance could be calculated. The relative variance, defined as the ratio between the integrated variance of the examined window and the integrated variance of the ECG signal that was close to full cycle length, was calculated at QRS onset and at offset in 2 frequency bands (4 to 40 and 60 to 120 Hz). Patients with healed infarction had a relative variance of 2.1 +/- 0.5 (mean +/- standard deviation [SD]) at QRS offset (a window of 40 ms), which was significantly lower than that of the healthy volunteers: 2.5 +/- 0.33 (mean +/- SD; p less than 0.02) at the low-frequency band. At the high-frequency band, patients with healed infarction had a significantly higher relative variance than the control subjects at QRS onset: 1.95 +/- 0.58 vs 1.55 +/- 0.35 (mean +/- SD; p less than 0.005). A model based on the numerous minor conduction abnormalities that exist in the chronically ischemic myocardium is presented to explain the changes in variance at the onset and offset of the QRS. The variance changes described can eventually serve as quantitative indexes of myocardial injury and electrical stability in patients with ischemic heart disease.

Aged↗
PubMed1991

Scale formation in algae.

Scale biogenesis in algae represents a unique model system to study the transport of secretory macromolecules through the Golgi apparatus (GA) and their exocytosis. The larger scales can be visualized in the light microscope, and thus the kinetics of scale assembly, transport, and secretion can be studied in vivo. In addition, scales are osmiophilic and readily visible in conventional transmission electron microscopy; thus, details of scale assembly and sorting can be studied without invoking immunolabeling techniques. The following are distinctive features of scale biogenesis in algae: 1) transport of scales through the GA-stack occurs by cisternal progression; 2) scale secretion may be very rapid (in some cases a single GA-cisterna leaves the stack every 15-20 s); 3) sorting of different scale types does not occur in the GA, but in a post-GA-compartment. Recent progress in the analysis of scale formation in the green flagellates Tetraselmis and Scherffelia is reviewed.

Animals↗
PubMed1991

Centers of rotation with transverse forces: an experimental study.

A new noninvasive method for simultaneously applying a known force system and measuring tooth movement was developed and tested. The instruments proved to be highly accurate and reliable. Using a model of an upper canine with a simulated periodontal ligament, we located the center of rotation and the center of resistance and found that the product of two distances--a, from the center of resistance to the line of application of force (F) and, b, from the center of resistance to the center of rotation (Co)--yields a constant that represents the parallel transverse forces in the same plane. Knowing this constant enables the clinician to determine the appropriate force position for a given center of rotation. We also found that the occlusoapical position of the center of resistance varies somewhat, depending on the transverse direction of loading around the long axis. Differences in values of the constant were found also to depend on the direction of loading in a given plane. Thus a transverse force exerted in a mesiodistal direction at the level of an orthodontic bracket through the long axis produces different effects from those produced when an identical force is applied in a labiolingual direction.

Computer Simulation↗
PubMed1991

Cloning and sequencing of rat plectin indicates a 466-kD polypeptide chain with a three-domain structure based on a central alpha-helical coiled coil.

We have determined the complete cDNA sequence of rat plectin from a number of well-characterized overlapping lambda gt11 clones. The 4,140-residue predicted amino acid sequence (466,481 D) is consistent with a three-domain structural model in which a long central rod domain, having mainly an alpha-helical coiled coil conformation, is flanked by globular NH2- and COOH-terminal domains. The plectin sequence has a number of repeating motifs. The rod domain has five subregions approximately 200-residues long in which there is a strong repeat in the charged amino acids at 10.4 residues that may be involved in association between plectin molecules. The globular COOH-terminal domain has a prominent six-fold tandem repeat, with each repeat having a strongly conserved central region based on nine tandem repeats of a 19-residue motif. The plectin sequence has several marked similarities to that of desmoplakin (Green, K. J., D. A. D. Parry, P. M. Steinert, M. L. A. Virata, R. M. Wagner, B. D. Angst, and L.A. Nilles. 1990. J. Biol. Chem. 265:2,603-2,612), which has a shorter coiled-coil rod domain with a similar 10.4 residue charge periodicity and a COOH-terminal globular domain with three tandem repeats homologous to the six found in plectin. The plectin sequence also has homologies to that of the bullous pemphigoid antigen. Northern blot analysis indicated that there is a significant degree of conservation of plectin genes between rat, human, and chicken and that, as shown previously at the protein level, plectin has a wide tissue distribution. There appeared to be a single rat plectin gene that gave rise to a 15-kb message. Expression of polypeptides encoded by defined fragments of plectin cDNA in E. coli has also been used to localize the epitopes of a range of monoclonal and serum antibodies. This enabled us to tentatively map a sequence involved in plectin-vimentin and plectin-lamin B interactions to a restricted region of the rod domain.

Amino Acid Sequence↗