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At least 451 records · Page 25Linked to original sources
PubMed1996

Scanning two-photon fluctuation correlation spectroscopy: particle counting measurements for detection of molecular aggregation.

Scanning fluctuation correlation spectroscopy (FCS) is an experimental technique capable of measuring particle number concentrations by monitoring spontaneous equilibrium fluctuations in the local concentration of a fluorescent species in a small (femtoliter) subvolume of a sample. The method can be used to detect molecular aggregation for dilute, submicromolar samples by directly "counting particles". We introduce the application of two-photon excitation to scanning FCS and discuss its important advantages for this technique. We demonstrate the capability of measuring particle number concentrations in solution, first with dilute samples of monodisperse 7-nm and 15-nm radius latex spheres, and then with B phycoerythrin. The detection of multiple species in a single sample is shown, using mixtures containing both sphere sizes. The method is then applied to study protein aggregation in solution. We monitor the concentration-dependent association/ dissociation equilibrium for glycogen phosphorylase A and malate dehydrogenase. The measured dissociation constants, 430 nM and 144 nM respectively, are in good agreement with previously published values. In addition, oligomer dissociation induced by pH titration from pH 8 to pH 5.0 is detectable for the enyme phosphofructokinase. The possibility of measuring dissociation kinetics by scanning two-photon FCS is also demonstrated using phosphofructokinase.

Biophysical Phenomena↗
PubMed1984

A general model for the light and electron microscopic morphometry/stereology (M & S) of precancerous epithelial transformation using clinical biopsies.

A morphometric model is presented which has proved valuable in the analysis of precancerous lesions at the light and electron microscopic level. The material consisted of biopsies of nasal mucosa embedded in plastic and sectioned perpendicular to the luminal surface. Sampling was restricted to the basal layer in order to compare in the different metaplastic and dysplastic stages a common cell type which is easy to identify in all stages and to reduce the workload. The application of digitizers, classical point counting procedures and linear parameters all allow a good separation between the different types of epithelium. The latter method is especially advisable in diagnostic pathology since the workload becomes drastically reduced as a consequence of linear instead of area parameters (e.g. cell width, i.e. contract zone with basement membrane, instead of cell size) and classifying instead of counting points. A 3-class ruler served for the estimation of the transverse diameters of nuclei, cell width and the sum of the longitudinal and transverse nucleolar axes. The use of a weighted index is more sensitive than simple measurements. The reliability of the method was also tested in a prospective study in which the biopsies were first analyzed by morphometry. The agreement between the prior morphometric classification and the subsequent histologic classification was 91%. The results demonstrate that basal cells alone carry the information for grading metaplastic and dysplastic changes in epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Epithelium↗
PubMed2001

Morphometric assessment of testicular changes in drug-related fatalities.

Testicular sections of 50 deceased drug addicts were examined by light microscopy using morphometric methods and determining the extent of spermatogenesis by application of the Johnsen score count. Twenty cases of violent death served as reference sample. The study was aimed at obtaining data about the degree of germinal gland damage following the duration of the individual drug career, which was correlated to the histologic findings. Progressively reduced maturation of germinal cells, decrease of tubular diameter and height of sperm-producing epithelium were found the longer the individual case history has been. The results clearly indicated a substantial impairment of male fertility in the course of a drug career, but etiology seems to be multifactorial, since most of the deceased were polytoxicomanic and more than 40% were under the influence of alcohol at the time of death. Testicular damage is obviously a sequel of long-lasting abuse and a very complex process, presumably progressing with the duration of the adverse habit.

Adult↗
PubMed1997

A generic population model for the African tick Rhipicephalus appendiculatus.

We present a simulation population model for the African tick Rhipicephalus appendiculatus, based on previous analyses of the mortality factors most closely correlated with observed population changes at 11 sites in equatorial and South Africa. The model incorporates temperature-dependent rates of egg production and development, climate-driven density-independent mortality rates, particularly during the adult-larval stage, and density-dependent regulation of both nymphs and adults. Diapause is also included for tick populations in southern Africa. The model successfully describes both the seasonality and annual range of variation in numbers of each tick stage observed at each of 4 test sites in Uganda, Burundi and South Africa. Sensitivity analysis showed that the final version of the model is robust to 4-fold variation in most parameter values (that were per force based on informed guesses), but is more sensitive to the regression coefficients determining density-dependent interstadial mortality (that were derived from analysis of field data). The model is able to predict the seasonality of ticks from a site in Kenya where a full prior population analysis was not possible because only adults and nymphs had been counted. The model is potentially applicable to other species of ticks, both tropical and temperate, to predict tick abundance and seasonality as risk factors for tick-borne diseases.

Animals↗
PubMedDate not supplied

Version of zones and zigzag structure in icosahedral fullerenes and icosadeltahedra.

A circuit of faces in a polyhedron is called a zone if each face is attached to its two neighbors by opposite edges. (For odd-sized faces, each edge has a left and a right opposite partner.) Zones are called alternating if, when odd faces (if any) are encountered, left and right opposite edges are chosen alternately. Zigzag (Petrie) circuits in cubic (= trivalent) polyhedra correspond to alternating zones in their deltahedral duals. With these definitions, a full analysis of the zone and zigzag structure is made for icosahedral centrosymmetric fullerenes and their duals. The zone structure provides hypercube embeddings of these classes of polyhedra which preserve all graph distances (subject to a scale factor of 2) up to a limit that depends on the vertex count. These embeddings may have applications in nomenclature, atom/vertex numbering schemes, and in calculation of distance invariants for this subclass of highly symmetric fullerenes and their deltahedral duals.

Journal Article↗
PubMed2004

Observations on the clinical examination of the camel (Camelus dromedarius) in the field.

Camels usually inhabit remote areas, where diagnostic facilities and laboratories are very scarce. The species differences between the camel and other domestic animals necessitate some specific examination techniques. The objective of this study was to describe the clinical examination methods and sources of common errors that require special consideration in the camel. Young camels are examined in the standing position, while adults require restraint. Restraining procedures, both standing and in sternal recumbency, are described. New equipment and a crush were designed. The body temperature of the camels examined fluctuated from 35.7 to 38.9 degrees C, being lowest in the morning and highest in the afternoon; high temperature in the morning is indicative of fever, while high afternoon temperatures could be hyperthermia. It was difficult to take the pulse rate for routine procedures. The heart rate ranged from 35 to 50 per min; there was no difference between the heart rate in the morning and in the afternoon. The mean respiratory rate was 11 per min and respiration was of thoracol-lumbar type. The mucous membranes of the eye were an important site for appreciating signs of discoloration, while those of the mouth, rectum and vagina were unsuitable. The left flank was the best site for determining the rate of rumen contractions, which was 3+/-1.2 every 5 min, as determined by auscultation; counting the contractions by the application of the fist was difficult. The palpable external lymph nodes were the parotid, maxillary, prescapular, inferior cervical, thoracic, cubital, ilial and popiteal; they are large and can be seen on inspection in healthy animals, so that was not indicative of disease. A list of diagnostic indicators for the rapid diagnosis of ten endemic camel diseases was generated from the empirical signs.

Animal Diseases↗
PubMedDate not supplied

A thresholding for radionuclide angiocardiography.

A thresholding algorithm for nuclear angiocardiographic studies is presented. The algorithm is free of operator intervention. The threshold is defined on the basis of the distribution of picture elements with decreasing count rates during systole. The application is valid for first-pass and equilibrium ECG gated studies. Reproducibility by different operators with various degrees of experience is high; concordance of the results with those of contrast studies is within the published ranges. The method provides a reliable step in full automation and standardization of scintigraphic angiocardiographies.

Heart↗
PubMed1990

[Studies on the health standard for room temperature in cold regions].

The microclimate of 205 rooms of single storey houses in four new rural residential districts in coastal and inland Shandong was monitored and studied the blood circulation of the finger, skin temperature, sweating function and other physiological indexes among 2,401 peasants. We interrogated their personal sensation to cold and warmth. The count was done by the application of thermal equilibrium index (TEI), predicted 4-hour Sweat Rate (P4SR) and the uncomfortable index. The standard room temperature is recommended as follows. In rural area in winter the appropriate room temperature is 14-16 degrees C, the comfortable room temperature is 16-20 degrees C, the lowest room temperature must not be below 14 degrees C. In summer the appropriate room temperature is 25-28 degrees C, the comfortable room temperature is 26-27 degrees C, the highest temperature must not be above 28 degrees C.

Fingers↗
PubMed1967

Use of repellents and attractants in filariasis control.

The ways in which repellents and attractants could be used to interrupt the transmission of bancroftian filariasis, especially by Culex pipiens fatigans, are assessed. Dimethyl phthalate (DMP) is an effective repellent against C. p. fatigans. It is also very toxic to all larval stages of Wuchereria bancrofti. The median lethal time to microfilariae of a solution of about 0.2% in normal saline is about 10 minutes. Other stages are similarly sensitive. Contact with DMP in very thin films is almost immediately lethal. It is highly unlikely that infection could take place under ordinary conditions through skin treated with DMP for at least many hours afterwards. This toxicity made it impossible to evaluate repellency in vitro. An in vivo test of the effect of skin applications of DMP on microfilaria counts gave anomalous results. A schedule for filariasis control, involving education, garbage disposal, rodent control, sewage disposal, and mosquito control, is proposed, and the research needed to allow repellents and attractants to play a full role in such a schedule is delineated.

Animals↗
PubMed1981

The effect of Damvar on the formation of hemopoietic splenic colonies in mice, and on the peripheral blood picture in rats and dogs.

The present paper deals with the effect of Damvar on hemopoiesis. The test of formation of hemopoietic splenic colonies (CFU-S) was used in mice, the peripheral blood picture and bone marrow differential after long-term administration of Damvar was tested in rats and dogs. The bone marrow cells from mice after a single dose of Damvar or cells incubated with Damvar in vitro showed no reduction of colony-forming activity. A single dose or repeated variable doses of Damvar, or combined administration of Damvar and Cyclophosphamide in some cases influenced the number of CFU-S in irradiated mice following transplantation of normal murine bone marrow cells. A number of CFU-S lower than 75% of the control count was never found. The application of Damvar to rats and dogs caused no significant changes in their blood pictures and bone marrows.

Animals↗
PubMed1981

[Methods for the control of disinfection in meat-packing plants].

Forty-eight series of experiments were carried out to establish the effect of disinfections with 2% septin, 1% tagonin, 2.5% chloramine and 2% chlorinated lime, all applied in the meat processing shops. Determined were the total count of bacteria and that of coliforms alone, employing the methods of washings and taking impression (contact) samples (Schothorst et al., 1966). It was found that these disinfection agents did not produce a complete disinfection effect. The contact method of determining the total count of bacteria proved readily applicable and suitable to investigate subjects having smooth surfaces. The combined use of the two methods to record the effect of disinfections is, however, suggested because of the diversity of the various subjects in the meat processing shops.

Bulgaria↗
PubMed1995

[Modifying the stapes footplate with various laser systems. II. The pulsed laser].

The object of the present study was to examine the tissue ablation capacity of various pulsed lasers at the stapes footplate. Isolated human stapes and bovine compact-bone platelets (thickness 90 microns) were used to determine effective laser parameters for achieving a perforation measuring 500 microns to 600 microns in diameter. Apart from achieving the perforation diameters, particular attention was given to the form and quality of the perforations, reproducibility of the perforation effect and the thermally altered border zones occurring at the footplate. Four pulsed laser systems were used: excimer, Ho:YAG, Er:YSGG and CO2 lasers. An adequately large perforation generally could only be achieved by several repeated shots at the same application site, since only a small amount of tissue was ablated per application. The mechanism of the photoablation caused the extent of the thermal side effects to be markedly lower than with the continuous wave (cw) and superpulse systems. For this reason and because of their highly reproducible perforation effect, they were basically better suited for stapedotomy than the cw systems. It was possible, however, that as a result of the longer application time and the need to repeatedly irradiate the same application site, the higher pulse counts could prove to be disadvantageous in clinical practice. Among the pulsed laser systems, the Er:YSGG laser had the highest ablation rate at the stapes and was thus the most effective laser for interventions at the footplate. Although somewhat less effective than the Er:YSGG laser in our studies, the Ho:YAG and pulsed CO2 lasers also appear to be suitable for stapes surgery. On the other hand, we did not consider the excimer laser (308 nm) to be particularly effective at the footplate because of its low ablation rates.

Animals↗
PubMed1996

[ETE (External Tissue Expansion): a new method for external tissue extension].

The authors describes a new device for external tissue extension (ETE) which will be able to replace or complement tissue expanders. The device consists of many ETE units, each unit consisting of a needle and two friction stoppers counted on a silicone string. Application, optimal tension and final surgical procedure are described. The indications are the same as for tissue expanders, e.g. scars, naevi and previous skin grafts, and also concern the closure of acute fasciotomies. The advantages are numerous: very simple technique, application under local anaesthetics, faster cutaneous profits (5-6 days), inexpensive total treatment, low complication rate.

Humans↗
PubMed1976

[On the hazards of nosocomial infections in dental treatment areas (author's transl)].

Using a standardized method of obtaining bacterial counts of surfaces by superficial application and subsequent incubation of agar lamina, density and kind of bacteria present were examined in treatment areas of both individual dentists praxis and of dental poli-clinics. The results obtained showed, that 1. typical bacteria of hospital infections (Micrococcus aureus, Klebsiella) were present in only small numbers in both individual dental praxis or in clinical dental treatment areas. 2. the medium level of contamination was higher in the average individual dental praxis than in comparable clinical dental areas. 3. the increase in bacterial contamination in the course of the daily treatmentperiod was considerably more pronounced in the individual praxis as compared to clinics. 4. the following must be considered as especially liable to contaminated by bacteria: towels used by several persons, the head of the dental turbine, the support of the suction device, the patient head rest, the height control bar of the dental chair, the instrument tray, the operating lamp and working garments.

Bacteria↗
PubMed2000

The effect of beam time structure on counting detectors in SRS experiments.

Counting detector systems are increasingly used in X-ray experiments because of their attractive properties as regards linearity, large dynamic range and simple noise properties. In synchrotron radiation source (SRS) applications of X-ray detectors, counting rates are generally high enough to require dead-time correction. The time structure of an SRS beam interacts with the dead-time characteristics of the detector in a way that the simple stochastic dead-time models cannot always handle. This report generates analytical and Monte Carlo mathematical models which describe the rate performance of any given detector system when used with the typical beam structures encountered in an SRS.

Journal Article↗
PubMed2006

Topical diphenylcyclopropenone as a measure of immune competence in HIV-seropositive subjects.

BACKGROUND: CD4 T cell counts are recognized as the standard method for monitoring HIV-seropositive patients and, along with viral load, are clinically important as indicators for initiating highly active antiretrovival therapy (HAART). Skin reaction scores following topical application of diphenylcyclopropenone (DPC) also demonstrate diagnostic utility as a functional measure of immune competence. METHODS: We used low sensitizing doses of DPC in 40 patients applied in a non-volatile, non-irritating topical delivery system to assess immune competence in 40 HIV-seropositive subjects with a range of CD4 T cell counts. Standardized patch test reading scores were used, with 2+ or greater scores (erythema and induration) indicative of a positive response. The patch test scores were then compared with CD4 counts. RESULTS: Application of DPC in concentrations of 0.4% and 0.2% successfully resulted in 90% sensitivity skin reaction scores in subjects with >300 CD4 T cells/microL, following a single 0.1 mL application to the inner aspect of the arm. Lower DPC concentrations of 0.1% and 0.05% were too low for initial sensitization reactions. Three subjects with CD4 counts between 150 and 300 cells/microL showed positive skin reactions indicating that this DPC test gives the clinician information on cellular immunity beyond the CD4 count. CONCLUSION: We conclude that a single topical application of DPC at concentrations between 0.2% and 0.4% can serve as a measure of immune competence in HIV-seropositive patients. As a functional measure of immunocompetence, this DPC test provides information beyond a CD4 count, which is particularly relevant to HIV-positive subjects with CD4 counts between 200 and 350 cells/microL.

Administration, Cutaneous↗
PubMed1990

The effect of sucrose application and implantation of mutans streptococci on the microbial composition of three-week experimental plaque--an in situ study.

This study describes the predominant cultivable microflora of three-week-old plaque samples obtained from human enamel sites, on the basis of microbial identification of over 9000 fresh isolates. Lower removable appliances, on which were mounted enamel sections and slabs, were worn by five young adult subjects under three experimental protocols. These were (1) 'normal' plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each subject's own mutans streptococci onto the enamel test sites and sucrose applications, as described above. With the exception of slightly higher proportions of Gram-negative bacilli associated with slab plaque following sucrose application, no significant differences in percentage or absolute counts of organisms were found between normal and sucrose plaques. The inoculation of mutans streptococci, combined with extra-oral sucrose applications, was associated with significantly higher percentages and absolute mean counts of both mutans streptococci and lactobacilli, and lower proportions of S. sanguis and S. oralis. Although the isolation frequency of mutans streptococci increased in all subjects and the overall mean proportion rose following inoculation, considerable inter-subject variation was seen in mean percentage counts of these organisms isolated from the three-week plaque samples.

Adult↗
PubMed1990

X-ray studies of synthetic radiation-counting diamonds.

Synthetic diamonds with a nitrogen content less than 100 ppm may be used as radiation dosemeters in a conduction counting mode, and are especially useful in medical applications. Crystal imperfections, revealed by x-ray diffraction topography, were found to affect counting performance. The best quality diamond gave the highest photocurrent (500 nA at 50 V mm-1 and 2.75 Gy min-1). Diamonds containing dislocations had lower photocurrents but had the advantage of shorter settling times (seconds rather than minutes). Placing contacts on two opposite cube (100) faces gave a higher photocurrent than on a pair of octahedral (111) faces. Higher photocurrents were also achieved when the majority of dislocations were perpendicular rather than parallel, to the electric field. Some recommendations for selecting synthetic diamonds for dosemeters are given.

Carbon↗