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At least 19 recordsLinked to original sources
PubMed1977

[Factors influencing particle measurement of aerosols and their retention in the lung].

The dimensional characteristics of the particles of an aerosol depend on the means used for producing them. Mechanical spray and ultrasonic dispersion give polydispersed particles. On the other hand, centrifugal atomization produces a monodispersed aerosol. Particle retention in the lung system depends on the particle diameter. In addition, retention varies according to the respiratory characteristics: it is minimal for about 15 inspirations per minute. Using iron-59 labeled particles, it was shown that the degree of retention varies considerably from one individual to the other and accessibility to the depths of the lungs is decreased under the effect of certain lesions. Bronchial retention appears to be increased in smokers.

Aerosols↗
PubMed1976

Mean velocity of optically detected intraaxonal particles measured by a cross-correlation method.

A method which uses by the cross correlation of optical signals is described for the determination of the mean velocity of somatopetally moving particles within nerve fibers. The method was validated by simulation experiments and by comparing the results with those obtained by averaging collections of velocities of individual particles. The significant contribution of the method is that it allows objective and rapid serial evaluation of mean particle velocity within individual nerve fibers with good accuracy and precision. A series of results from normal myelinated nerve fibers from Xenopus laevis is presented. Considerable variation (up to 50%) in mean velocity was found between individual nerve fibers. The mean of all determinations indicates that the mean velocity of somatopetally moving particles in axons with diameters greater than 10mum is in the region of 1.14 mum/s at a temperature of 22-24 degrees C. The findings are compared with small collection of such determinations which have been reported in the literature.

Animals↗
PubMed1975

Measurement of particle sizes by elastic and quasi-elastic light scattering.

A method of measuring an average particle radius in a highly polydisperse dispersion using the wavelength dependence of turbidity is described. For particles which are no larger than 0.3 of the wavelength of light used, a polynomial representation of the scattering cross-section can be used. For larger particles, more extensive numerical calculations are required. The use of the method is illustrated by determining the average particle radius of casein micelles by both elastic and quasi-elastic light scattering techniques. A polydisperse homogeneous sphere model is found to be a reasonably accurate representation of casein micelles. Several modifications of the model which would improve the agreement between the two techniques are mentioned briefly.

Animals↗
PubMed1975

Electronic particle size measurements of platelet aggregates formed in vitro.

The aggregation of human platelets induced by adenosine diphosphate (ADP) was used to evaluate electronic particle size analyzer measurements of platelet aggregates in plasma. As platelets began to clump in plasma, the total volume and the diameter of individual aggregates increased; after a time dependent on experimental conditions, the diameter increased but the total volume remained unchanged. Similar but opposite changes in size distribution occurred during platelet deaggregation. The total volume of aggregates formed in plasma varied (linear correlation coefficient = 0.99) with the total volume of platelets which were available to clump and with simultaneous changes in optical density. The diameter of the aggregates varied with the concentration of, and time of exposure to, ADP and with the total volume of platelets and aggregates in plasma was not different from that of control platelets in untreated plasma, the individual platelets aggregated without an accompanying increase in size. This study demonstrates that platelet aggregation can be characterized by electronic measurements of the size distribution of platelet aggregates.

Adenosine Diphosphate↗
PubMed1979

Ultrastructural changes in small intestinal epithelium of neonatal pigs infected with pig rotavirus.

The small intestine of piglets orally infected with rotavirus was examined by electron microscopy 18, 24, 48 and 60 hours after infection. At 18 and 24 hours after infection columnar epithelial cells covered the villi. Infected epithelial cells tended to be less electron-dense than uninfected cells and were more numerous at 24 hours after infection. Two types of rotavirus particle were seen, usually within dilated cisternae of the RER: non-enveloped particles measuring 50 to 60 nm and enveloped particles measuring 65 to 75 nm. Non-membrane bound viroplasm containing electron-dense cores was encountered outside the cisternae 18 and 24 hours after infection. Tubular structures measuring 44 to 56 nm were often found in nuclei of infected cells. Single-membraned (44 to 55 nm) and double-membraned tubules (70 to 80 nm) associated with viral manufacture were found in the cytoplasm of infected cells. At 48 and 60 hours after infection a proportion of villous epithelial cells were cuboidal. Virus particles were detected in only a few epithelial cells and nuclear and cytoplasmic tubules were not seen. At all times after infection some infected cells showed a reduction in the number and size of the microvilli comprising the brush border.

Animals↗
PubMed1977

Human factor VIII: morphometric analysis of purified material in solution.

Study of purified human factor VIII in buffer by freeze-etch electron microscopy reveals rounded, rod-shaped particles measuring 22 by 42 nanometers. When thrombin was added to purified normal factor VIII, there was a rapid loss of rod-shaped particles during the first 15 minutes of incubation at 37 degrees C. Purified plasma from two patients with severe hemophilia contained spherical particles measuring 10 to 50 nanometers in diameter, with no evidence of significant numbers of rod-shaped forms. Negatively stained and unstained air-dried samples of factor VIII corroborate the relative shape and size differences between normal and hemophiliac material.

Blood Coagulation Factors↗
PubMed1978

Dust levels and particle-size distributions in high-capacity cotton gins.

Dust samples were collected inside high-capacity cotton gins with the personal, stationary personal, and the vertical elutriator cotton dust samplers. Dust particles collected on the filters were sized with a particle measurement computer system. Particle-distribution data revealed that gin dust contains a high percentage of dust particles larger than 20 micrometers in diameter.

Air Pollutants↗
PubMed1977

Freeze fracture studies on the annelid septate junction.

Freeze-fractured preparations of septate junctions between epidermal cells of annelids (Lumbricus terrestris and Tubifex spec.) have been investigated. In Lumbricus the protoplasmic face (PF) of the plasma membrane is characterized by variously arranged rows of particles. Apically the rows take an undulating course and often are separated by wide distances. In the basal part of the junction the rows run closely together and more or less in parallel. The diameter of the particles measures 80--120 A, the distance between two particles (centre to centre) is 150--250 A. Additionally striking rows of large particles (long diameter 150--200 A). Are to be observed mainly near the basal part of the junction. In Tubifex both faces of the plasma membrane could be studied in detail. The protoplasmic face (PF) contains rows of distinct individual particles (mean diameter 100--150 A, centre to centre distance approx. 250 A) whereas the particles of the extracellular face (EF, mean diameter 200-250 A) usually form continuous strands in which the individual particles seem to fuse. The density of arrangement of the strands varies considerably. Additionally ladder-shaped membrane structures have been observed in plasma membranes of this species.

Animals↗
PubMed1977

Fine structural study of annulate lamellae complexes in human tumors.

Specific intracytoplasmic organelles, annulate lamellae and radial cisternae, have been studied in several human tumours. Annulate lamellae are observed in all cases of leiomyoma, leiomyosarcoma, rhabdomyosarcoma and malignant melanoma, whereas radial cisternae are only found in a case of leiomyosarcoma. Annulate lamellae are characterized by stacks of parallel arrayed long cisternae showing alternative arrangement of annuli and sacs. Some of these cisternae are connected directly with rough-surfaced endoplasmic reticulum and there is continuity with the lumen and membrane. Radial cisternae are mainly composed of two structures: numerous short cisternae, which are a variant of annulate lamellae, and numerous spherical particles derived from the cisternae. The cisternae are arranged parallel or radially around particles measuring up to 1100 A in diameter. These particles consisting of an amorphous high electron dense material without distinct limiting membrane are organized in groups and vary in number. There is no evidence of a direct relationship between these structures and viral infection.

Aged↗
PubMed1978

[Morphology of nasopharyngeal fibroma (author's transl)].

Light and electron microscopic investigations of four cases with juvenile nasopharyngeal fibroma revealed the characteristic structures like a fibrous stroma, and inclination to hyalinisation and formation of scar like tissue, a lacunar thin walled vascular component, a high amount of mast cells, and of fibroblasts with different nuclear bodies and particles. The well known electron dense nuclear inclusions were subdivided into three groups of size. The tumor cell nuclei also contained five different types of more or less complex bodies with spherical shape. In addition to the earlier described ultrastructural properties of the tumor the nuclei of the tumorous fibroblasts were found to contain virus like particles measuring 40 to 55 nm in diameter. These particles were aggregated to groups; they were different from chromatin condensations and from perichromatin granules. The structure and size of the smaller particles was not comparable to that of the electron dense nuclear inclusions regarded as pathognomonic in the nasopharynegal fibroma.

Adolescent↗
PubMed1977

Some experimental results on W values for heavy particles.

The total ionization produced by ions stopped in argon and tissue-equivalent (TE) gas has been measured in the energy range 25-500 keV. A large ionization chamber was used for this study. The chamber was alternately operated as a proportional counter and as a ionization chamber to measure particle rate and the total ionization produced by them, respectively. The average energy loss per ion pair (W value) was found to be dependent on both the energy and mass of the incident ions. For argon gas the accelerated ions were H+, He+, Ar+; the W value ranges from 23.72eV for 25 keV H+ to 63.12 eV for 50 keV Ar+; Irregularities in the W value were found for He+ in the region 70-130 keV. For TE gas the accelerated ions were H+, He+, C+, N+, O+; the W value ranges from 29.13 eV for 25 keV H+ to 51.45 eV for 50 keV O+. Comparisions with existing data show a good agreement in the absolute values for TE gas and in the relative variations in argon gas. Differences between absolute values in argon might be due to impurities in composition.

Argon↗