PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Mass concentration”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1979

Human traumatic cataract. A quantitative microradiographic and electron microscopic study.

Six cases representing different stages of cataract formation secondary to eye trauma were subjected to quantitative microradiographic or electron microscopic examination. Anterior and posterior subcapsular cataracts were found to contain extensively swollen lens fibers in the subcapsular cortex. Microradiographic measurements revealed a reduced concentration of dry mass in the subcapsular cortex around the whole circumference of the lens. The inner cortex and the nucleus appeared normal both microradiographically and electron-microscopically. Two of the examined cases had an opaque-cataract membrane and one had a Soemmerring's ring. The opaque membranes consisted of irregular masse of degenerated lens fiber material as well as regenerated lens epithelial cells. A wide range of dry mass concentration was found in the opaque membrane that was studied microradiographically. Alterations in morphology and dry mass concentration are more than sufficient to explain the development of opacification in traumatic cataract.

Adolescent↗
PubMed1979

Notation of physical equations no longer a problem.

Physical quantities and equations are used to define the laws of natural and engineering sciences. Clarity has been brought in equal measure into the the theory of physical quantities and the SI-system of units due to the basic work of Wallot and that of national and international institutions. For practical use in this paper, the most important rules and definitions for the formulation of physical equations are treated in an elementary form and the ease of their use is demonstrated in the following examples: speed of a car, capacitance of a plate capacitor, thermal emission of the cathode of an x-ray tube, oxygen uptake in cardiology, mole concentration and mass concentration of a substance in a solution. In addition, some important quantities and units of cardiology were summarized in a table.

Cardiology↗
PubMed1979

Experimental traumatic cataract. I. A quantitative microradiographic study.

Traumatic cataract was induced in rat and rabbit. The progression of the posterior subcapsular cataract and the wound healing were followed by quantitative microradiography. This method makes it possible to determine the dry mass content and to calculate the refractive indices in the lens. In the injured rat lens a reduced dry mass concentration was determined in both the wound region and the posterior subcapsular region immediately after trauma. During the first week a subcapsular opacity was observed to enlarge. This opacification always corresponded to a reduction in the subcapsular concentration of dry mass. This reduced content of dry material, mainly consisting of protein, is interpreted as a hydration of the subcapsular cortex. In the rabbit lens a much larger injury had to be made in order to cause any posterior cataract. The same reduction in the content of dry material was determined in regions corresponding to opacitices but the reduction was less pronounced than in the rat lens. The border zones between different concentrations of dry mass are suggested to be the main sources of scattered light in the traumatic cataract.

Animals↗
PubMed1978

Male--female variability in the dietary cholesterol-induced hyperlipoproteinemia of cynomolgus monkeys (Macaca fascicularis).

The characteristics of dietary cholesterol-induced hyperlipoproteinemia were studied in adult Macaca fascicularis to determine if significant male--female differences could be identified. The plasma lipoproteins from individual animals were separated by agarose column chromatography and the resulting size populations of lipoproteins were chemically characterized. The distribution of constituents among the lipoprotein classes was determined. The lipoproteins that increased most significantly in response to dietary cholesterol were the low density lipoproteins (LDL) which were those of region III of the column elution profile. The LDL mass concentrations (in mg/dl of plasma) were not different between males and females. However, these lipoproteins showed a characteristic difference between males and females in response to dietary cholesterol. The primary response in the males was an increased LDL molecular weight. In females, the primary response was an increased number of LDL particles (measured as mumolar concentration). Thus, at the same LDL mass concentration, males had significantly larger LDL particles and yet fewer of them. Analysis of the chemical composition data showed that size differences between LDL of males and females was due primarily to the incorporation of more cholesteryl ester into the LDL particles from male animals; the content per LDL particle of free cholesterol, phospholipid, and protein showed the same proportionality to size for both sexes. Another significant difference between lipoproteins of males and females was in the extent to which the plasma HDL (identified in these studies as the lipoproteins of region IV of the elution profile) decreased in response to dietary cholesterol. Chemical composition differences were also noted. The HDL particles of males and of cholesterol-fed animals contained more cholesteryl ester than did HDL of females and control animals, respectively.

Animals↗
PubMed1978

An evaluation of the GCA respirable dust monitor 101-1.

The GCA RDM 101-1 has been evaluated using aerosols of coal, Arizona road dust, silica, potash, and rock (copper ore) particles. The effects of the dust mass concentration, particle size distribution, and dust material on the instrument response were investigated. The instrument was found to measure the mass concentrations of respirable dust aerosols up to about 16 mg/m3 for coal and rock dust and about 20 mg/m3 for silica, potash, and Arizona road dust, providing there is not appreciable mass in the size range below approximateley 0.7 micrometer aerodynamic diameter.

Aerosols↗
PubMed1978

Histophysical and histochemical investigations on muscle arterioles in hypertensive arteriolosclerosis; an interference microscopical, polarization optical and histophotometrical study.

In 50 formol fixed biopsies from the m. quadriceps femoris normal and hypertensive arteriolosclerotic arterioles were characterized by quantitative histophysical and histochemical methods. The interference microscopical measurements showed a real increase of dry mass concentration in the pathologically changed vessels. Additional histophotometrical results are interpreted as an increase of proteins with higher isoelectric point (globulins, actomyosin). An augmentation of actomyosin is compatible with the medial hyperplasia demonstrated histologically. Likewise a positive correlation was found between the fibrin incorporation proved histochemically and the quantitatively evaluated protein reaction with Fast green; Glycosaminglycans do not carry weight quantitatively. The polarization optical measurements yielded an alteration of the submicroscopical structure in arteriolosclerosis. It consists in a diminution of the submicroscopical volum of gaps and in a diminished orientated dye binding of Congo red. Thereby the pathogenesis of hypertensive arteriolosclerosis of skeleton muscle is above all characterized by an increase of heterogeneous proteins (blood plasma proteins, actomyosin) in the arteriolar wall, leading to a diminution of the submicroscopical volume of gaps and to an elevation of the dry mass concentration.

Arteries↗
PubMed1979

The kinetics of ATP-dependent exonuclease V from Micrococcus lysodeikticus. A Michaelian dependence on DNA concentration.

The ATP-dependent exonuclease V from Micrococcus lysodekticus shows a Michaelian relation between steady-state velocity and the concentration of T7 DNA substrate. The Km (expressed as a mass concentration) does not change when the T7 DNA is broken into smaller fragments by a restriction enzyme. This is interpreted to mean that the predominant process by which the exonuclease-V--DNA complex breaks down is digestion of the entire DNA molecule rather than physical dissociation, in accord with the already known processive nature of degradation by this enzyme. The way that the V and Km towards DNA vary with ATP and ADP concentration suggests that enzyme-DNA complex is predominantly formed by reaction of DNA with an enzyme-ATP complex rather than with bare enzyme.

Adenosine Diphosphate↗
PubMedDate not supplied

Effect of chronic inhalation of sulfuric acid mist upon mucociliary clearance from the lungs of donkeys.

The effect of chronic inhalation exposures to sulfuric acid mist upon mucociliary clearance from the lungs was studied, using the donkey as an analogue for man. Four animals were exposed 1 hr/day, 5 days/week, for 6 months. The mean mass concentration of acid mist was 102 microgram/m3 for two animals, and 106 microgram/m3 for the other two. The mass median aerodynamic diameter was approximately 0.5 micrometer. Clearance was monitored by serial, external in vivo measurements of the retention of an insoluble, radioactively tagged ferric oxide aerosol which was inhaled following exposure to the acid mist. Bronchial clearance became erratic within the first week of exposure; rates were significantly different, usually slower than control on many test days, although the degree of response varied among the four animals. Two animals exhibited a sustained impairment of clearance towards the end of the 6-month exposure period and continued to have erratic clearance during a 3-month follow-up period. No changes in the regional deposition of the ferric oxide occurred during the course of the study in any of the animals. It is proposed that alterations in bronchial mucociliary clearance may be an early, if not the first, physiologic effect resulting from the inhalation of sulfuric acid mist, and this may be a factor in the pathogenesis of chronic bronchitis in populations exposed to the sulfur oxide-particulate-complex in the ambient air, which often includes sulfuric acid.

Aerosols↗
PubMed1979

Human and experimental data on translocation of asbestos fibers through the respiratory system.

The translocation of fibrous dusts through the respiratory system is discussed on the basis of human and experimental data obtained with the transmission electron microscope. Comparison of the characteristics (numerical and mass concentrations, sizes, types) of asbestos fibers retained in different locations of the respiratory system in humans exposed to asbestos has shown that there is no relationship between the numerical concentrations in lung parenchyma and those in parietal pleura. Moreover, almost al fibers encountered in the pleura were ultimate, short fibrils of chrysotile. The animal data are from rats injected intrapleurally with different types of fibers (chrysotile, crocidolite and glass fibers) and sacrificed at different times. There was a progressive increase in the number and mass of fibers translocated into lung parenchyma from the pleural cavity that was particularly obvious after 90 days. After this time, the mean length of fibers, especially chrysotile, increased, indicating that more long fibers are retained in alveolar tissue than short fibers.

Animals↗
PubMed2025

Effects of aerosol aging on composition and light-absorbance of nitrogen-containing organic compounds: Evidences from ultra-high-resolution mass spectrometry analysis.

Nitrogen-containing organic compounds (NOCs) are key components of particulate matter (PM), but their compositional evolution and light-absorbing properties during atmospheric aging remain poorly understood. In this study, ultra-high-performance liquid chromatography coupled with Orbitrap mass spectrometry was used to semi-quantitatively analyze 59 PM1 samples collected in Shanghai. NOCs accounted for 31 % and 64 % of the detected species in negative (ESI-) and positive (ESI+) ionization modes, respectively. Atmospheric aging significantly reduced the molecular diversity of polar organics, with both the number and mass concentration percentages of CHON- compounds showing significant negative correlations with aging degree. Van Krevelen analysis demonstrated a decrease in the number of carboxylic-rich alicyclic molecules and their CHON- contributions during the aging process (from 37.7 % in fresh samples to 21.2 % in aged samples). CHN+ compounds, a major NOCs group in ESI+ mode, also decreased with aging. Correlation analyses involving the Bep/(Bep+Bap) ratio, relative humidity, and mass absorption efficiency at 365 nm revealed a decline in light absorption capacity with aging, suggesting aqueous-phase oxidation as a dominant aging mechanism. CHON- and CHN+ compounds were identified as the principal light-absorbing constituents in PM1. This work provides new insights into the aging-induced transformations of NOCs in urban PM1, and their changing role in light absorption, highlighting the need for further investigation of the aging mechanisms of NOCs.

Aerosols↗
PubMed2026

Oxidative potential of fresh vs. O₃-aged PM2.5 across urban and rural sources in China.

Fine particulate matter (PM2.5) is a major health risk, yet its impacts are still largely assessed using mass concentration, which does not capture toxicity. Recently, oxidative potential (OP) has emerged as a more relevant metric, reflecting the ability of particles to generate reactive oxygen species. A current challenge, especially in China, is understanding how emission sources and ozone (O3) aging affect PM2.5 toxicity, given that O3 is an increasingly important pollutant there. A work by Ma and co-workers published in J. Environ. Sci. (doi.org/10.1016/j.jes.2024.04.023) addressed this by evaluating the OP of fresh and O3-aged PM2.5 from multiple sources in China using the dithiothreitol (DTT) assay. Biomass burning particles exhibited the highest OP, up to 35 times greater than suburban PM2.5, driven by water-soluble organics and transition metals. While O3 aging generally reduced OP, it also induced complex chemical transformations. These findings highlight that PM2.5 toxicity is dynamic and source-dependent, underscoring the need to move beyond mass-based air quality metrics.

Particulate Matter↗
PubMed1978

Silica flour exposures in Ontario.

A total of 16 cases of silicosis are reported in Ontario plants where there was exposure to silica flour. Dust counts expressed as mppcf are shown for four of these plants taken over a period of 37 years. A relationship has been obtained experimentally to permit conversion of the counts to respirable mass concentrations. Based on the information obtained, a TLV of 0.05 mg/m3 for silica flour is proposed.

Air Pollutants↗
PubMed1979

The relationship between coal rank and the prevalence of pneumoconiosis.

As part of the Periodic X-ray Scheme of the National Coal Board (NCB), a comparison is made between the previous and new films of all miners who were face-workers on the former occasion, five years earlier. This assessment is made by distributing the films randomly to all the NCB readers. This paper compares the rank of coal mined in each colliery with each colliery's percentage prevalence of pneumoconiosis of at least ILO category 1 in the films of previous face-workers obtained during the third survey round (1969-73). Of the NCB's 291 collieries in Britain, information enabling a rank classification to be made was available for 250, employing 62 362 face-workers. In these 250 mines a progressive and five-fold increase in prevalence was observed from collieries mining low-rank (bituminous) coal to those mining coal of high ranks (anthracite and high-grade steam and coking coal). A possible reason for this is that, in the past, high-rank collieries may have had the highest mass-concentrations of respirable dust.

Carbon↗
PubMed1979

Lysosomal enzyme activities in pulmonary macrophages from rabbits breathing iron oxide.

The effects of an in vivo exposure to a nontoxic particle, iron oxide, on lysosomal hydrolases in pulmonary macrophages were examined. Rabbits breathed a submicron-sized aerosol of iron oxide for 3 h (mass concentration, 186 to 222 mg/m3). Macrophages were recovered by lung lavage 0, 12, 18, and 24 h later. The number of cells lavaged after iron oxide was significantly greater than the control number, whereas the amount of protein recovered per 10(8) cells decreased, suggesting the influx of smaller cells. Macrophages from animals exposed to iron oxide reacted histochemically for acid phosphatase showed increased stain intensity and redistribution of enzyme within the cytoplasm. Considerable cell-to-cell variability in enzyme activity was evident in these macrophages. Homogenates of cells exposed to iron oxide assayed for 6 lysosomal acid hydrolases showed little change in specific activity or in total enzyme per 10(8) cells when compared to homogenates of cells from control animals. Sucrose density gradient centrifugation demonstrated that exposure to iron oxide caused an increase in lysosome heterogeneity over that seen in control preparations and the appearance of a population of lysosomes of increased density. An aerosol of iron oxide did not greatly alter the average concentrations of lysosomal enzymes in pulmonary macrophages, but did stimulate recruitment of new cells and thus increases the total amount of some enzymes in the lung.

Acid Phosphatase↗
PubMed1976

Dust exposure in Finnish foundries.

Dust measurements were made in 51 iron, 9 steel, and 8 nonferrous foundries, at which 4,316 foundrymen were working. The sampling lasted at least two entire shifts or work days continuously during various operations in each foundry. The dust samples were collected at fixed sites or in the breathing zones of the workers. The mass concentration was determined by weighing and the respirable dust fraction was separated by liquid sedimentation. The free silica content was determined by X-ray diffraction. In the study a total of 3,188 samples were collected in the foundries and 6,505 determinations were made in the laboratory. The results indicated a definite difference in the dust exposure during various operations. The highest dust exposures were found during furnace, cupola, and pouring ladle repair. During cleaning work, sand mixing, and shake-out operations excessive silica dust concentrations were also measured. The lowest dust concentrations were measured during melting and pouring operations. Moderate dust concentrations were measured during coremaking and molding operations. The results obtained during the same operations of iron and steel foundries were similar. The distribution of the workers into various exposure categories, the content of respirable dust and quartz, the correlation between respirable dust and total dust, and the correlation between respirable silica and total dust concentrations are discussed. Observations concerning dust suppression and control methods are briefly considered.

Air Pollutants↗
PubMed1979

[26 years of research in pneumoconiosis in the field of British coal mines. Contribution of that research to the epidemiology of pulmonary disorders in miners].

Events leading to the start of the Pneumoconiosis Field Research in 1953 are reviewed. Research methods are outlined, progress is described, and the main results are summarised. Three medical surveys were conducted at approximately five-year intervals in 24 coal mines. A further two quinquennial surveys took place at 10 of them, thus completing 20 years' observations. Individual miners' exposures to dust have been measured throughout the periods of study and earlier exposures have been estimated. The dust exposure have been expressed as cumulative timeweighted mass concentrations of dust in the respirable range. Correlations have been demonstrated between this index of exposure and (a) risks of developing various degrees of simple pneumoconiosis, (b) the occurrence of chronic bronchitis symptoms, (c) level of breathing capacity, and (d) among miners with no pneumoconiosis, mortality attributed to respiratory diseases generally, chronic bronchitis and emphysema in particular, and to cancers of the digestive organs. Exposures to quartz amounting to less than about 10 per cent of mixed coal mine dust do not generally affect the probability of developing simple pneumoconiosis. But there is evidence that some miners may show unusual radiological changes over ten years when exposed to dust with a relatively high quartz content. Current work includes continuation of mortality studies and follow-up surveys of miners no longer working at the research collieries. The inter-disciplinary nature of the research team is emphasized and there are suggestions for further work on unresolved problems.

Coal Mining↗
PubMed1977

Lecithin: cholesterol acyl transfer rate in plasma and its relation to lipid and lipoprotein concentrations in primary hyperlipidemia.

Plasma lecithin: cholesterol acyl transfer (LCAT) rate and concentrations of lipids in plasma and lipoproteins were studied in 107 hyperlipidemic subjects. In all types of hyperlipoproteinemia LCAT rates were higher than in a normolipidemic reference group. LCAT rates were highest in type IV and V. There was a considerable overlap of LCAT rates between type IIa, IIb and reference subjects. The LCAT rate correlated positively with very low density lipoprotein concentration, body mass and excess body mass. Low density lipoprotein concentration correlated positively with the LCAT rate only in the reference group. The high density lipoprotein concentration correlated negatively with the LCAT rate. It was suggested that the LCAT rate in vitro reflects the in vivo turnover of cholesteryl esters as a part of the turnover of apoprotein-B containing lipoprotein complexes in plasma. The results might then indicate an inflow rate of lipoproteins in plasma that is increased in most type IV cases but normal or only moderately increased in type IIa and IIb subjects. Analysing the relations between the LCAT rate and the concentrations of lipids in plasma by multiple regression indicated hypothetically deficiencies of lipoprotein removal from plasma in half of type IIa and one third of type IIb subjects.

Acyltransferases↗