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Biomedical subjects

R B Low

Publications and source records attributed to R B Low.

At least 109 records · Page 6Linked to original sources
PubMed1977

Defense mechanisms of the respiratory membrane.

The success or failure of pulmonary defense mechanisms largely determines the appearance of clinical lung disease. The lung is protected by interlucking systems of nonspecific and specific defenses. Inhaled substrances can be isolated by mechanical barriers or can be physically removed from the lung either by transport up the bronchial mucociliary escalator or by transport through interstitial and lymphatic channels leading to lymph nodes. Substances can be locally detoxified within the lung by interaction with secretory proteins, such as antibodies, or by neutralization and dissolution within phagocytic cells. The pulmonary alveolar macrophage is the central figure in the protection of the respiratory membrane, operating in all 3 of the nonspecific modes of defense and augmented by specific immunologic mechanisms as well. Alterations in macrophage function and physiology may be crucial in determining the effectiveness of pulmonary defense. Recent advances in the cell biology of the alveolar macrophage have led to a greater understanding of its complex funcition. The multiple origins of macrophages from local and circulating cell pools and the variability in their fate and lifespan reflect the multi-faceted role of this cell type. The importance of the interactions between macrophages, orther lung cells, and other defense mechanisms has become increasingly clear. As well as functioning as resident defender of the alveolus, the macrophage is an important effector of the pulmonary immune response and plays a key role in the pathogenesis of a wide variety of inflammatory, destructive, and fibrotic lung diseases. Humoral and cell-mediated immune responses amplify and direct lung defenses against infection and may also participate in protection against other agents. Immunoglobulin A and G, microbial neutralizing and opsonizing anti-bodies, and macrophage-stimulating T lymphocytes are the major immunospecific forms of lung defense. Infectious agents, cigarette smoke, air pollutants, industrial dusts, and a spectrum of coexistent disease states may impair pulmonary defense mechanisms and increase susceptibility to asute and chronic respiratory diseases. A thorough understanding of the ways in which the lung protects itself against the daily assault of infectious, toxic, and immunogenic materials should lead to a beter understanding of pathogenesis and consequences of lung disease and to better clinical care of the patient with respiratory disease.

Animals↗
PubMed1977

Correlated effects of cigarette smoke components on alveolar macrophage adenosine triphosphatase activity and phagocytosis.

An initial examination was made of the hypothesis that one action of cigarette smoke components on pulmonary alveolar macrophage function involves the inhibition of contractile protein adenosine triphosphatase activity. Pulmonary alveolar macrophage calcium-dependent adenosine triphosphatase activity, magnesium-dependent adenosine triphosphatase activity, sodium-potassium-dependent adenosine triphosphatase activity, phagocytosis, and cell adhesiveness were measured in the presence of cigarette smoke, acrolein, ouabain, and ethacrynic acid. Calcium-dependent adenosine triphosphatase activity, magnesium-dependent adenosine triphosphatase activity, phagocytosis, and adhesiveness were inhibited by smoke and ethacrynic acid, but not by ouabain. Acrolein, a component of smoke, inhibited phagocytosis, adhesiveness, and calcium-dependent adenosine triphosphatase activity, indicating that another component of smoke must be effective at inhibiting magnesium-dependent adenosine triphosphatase activity. Sodium-potassium-dependent adenosine triphosphatase activity was inhibited by ouabain and ethacrynic acid, but not by smoke or acrolein. Finally, sulfhydryl reagents at least partially protected the macrophages against the inhibitory actions of each of the agents. The results are in accord with recently obtained experimental evidence that calcium-dependent adenosine triphosphatase and, perhaps, magnesium-dependent adenosine triphosphatase play a role in phagocytosis. The data also suggest that smoke components affect a number of macrophage activities, including adhesion and phagocytosis, by altering the cell's contractile apparatus.

Acrolein↗
PubMed1975

Protein biosynthesis by the pulmonary alveolar macrophage. Comparison of synthetic activity of suspended cells and cells on surfaces.

An effort to optimize conditions for studying protein biosynthesis by the pulmonary alveolar macrophage in vitro has led to a comparative analysis of the activity of suspended and adherent cells. A number of differences were observed. (1) Suspended cells synthesized protein for only a limited period of time, after which they responded only partially to incubation in fresh medium. This was true even under reincubation conditions in which the cells were allowed to adhere to a surface. Adherent cells, however, synthesized protein during a longer period of time and were fully capable of responding to new medium within the time periods examined. (2) Analyses of the radioactive proteins synthesized using a dual-isotope technique suggested that, during a period of 2 hours, suspended cells synthesized relatively smaller quantities of high molecular weight proteins than adherent cells. (3) The administration of a phagocytic load (zymosan; particle to cell ratio, 10:1) inhibited by 20 per cent the incorporation of isotopic amino acid into protein during a period of 3 hours. The same phagocytic load, however, stimulated incorporation by 20 per cent in adherent cells. (4) The rate of particle uptake measured using oil red O-albumin complexes decreased by approximately 50 per cent in suspended cells preincubated for 2 hours, but was maintained in similarly preincubated adherent cells. It was concluded that pulmonary alveolar macrophages incubated adhered to a surface are more appropriate for metabolic studies than are pulmonary alveolar macrophages incubated in suspension.

Animals↗
PubMed1967

Mammalian ribosomal protein: analysis by electrophoresis on polyacrylamide gel.

Ribosomal protein from five mammalian tissues when analyzed by discontinuous electrophoresis on polyacrylamide gel at pH 4.5 yielded 24 bands. Densitometric tracings indicated that the patterns of the basic ribosomal proteins from the several tissues were qualitatively similar. Protein from Escherichia coli ribosomes analyzed at pH 4.5 gave 29 bands, and the pattern was different from that of mammalian ribosomal protein. No distinct band was found when mammalian ribosomal protein was analyzed at pH 8.3 (acidic proteins). Ribosomal protein from Escherichia coli gave eight bands at pH 8.3. Thus, the structure of the genes responsible for synthesis of ribosomal protein in several mammalian tissues is the same, and different genes direct synthesis of ribosomal protein in bacteria.

Acrylic Resins↗
PubMedDate not supplied

Emergency air transport of pregnant patients: the national experience.

There is considerable debate as to the appropriate role of helicopter transfer of sick patients. The debate over helicopter transfer of high-risk obstetric patients is even more intense. There is clear evidence that high-risk neonates are more likely to survive when they are delivered in a perinatal center compared with local delivery followed by transfer. On the other hand, there is concern that in-flight delivery entails "extreme risks, both to mother and child." In spite of this debate, there has been little research into the frequency of delivery during transport to a hospital or into the mortality associated with such a delivery. A study involving a single center suggests that the incidence of in-flight delivery is very low. We contacted all American Society of Hospital-Based Emergency Air Medical Services (ASHBEAMS) member air ambulance programs to determine the national statistics for in-flight delivery and associated perinatal mortality. We found no instances of in-flight delivery in 357 helicopter transports; 315 of these women were in active labor at the time of transport and 72 were in the accelerated phase of labor. There is evidence that these flights were screened for safety. Airplane flights generally took more time than helicopter flights (P less than .05), and there was one in-flight delivery during 88 airplane transfers. Also presented are additional data that suggest in utero transport of high-risk fetuses to a perinatal center by helicopter is cost effective.

Adolescent↗
PubMedDate not supplied

Cigarette smoke components and alveolar macrophage protein synthesis.

A comparison was made of the effects of acrolein and aqueous cigarette smoke extracts on amino acid incorporation into protein by rabbit pulmonary alveolar macrophages. Studies were on cells maintained in vitro as adherent monolayers. Freshly prepared acrolein inhibited amino acid incorporation by significant amounts after approximately 30 min and aqueous smoke extracts after approximately 15 min of incubation. Fifty percent inhibition by acrolein occurred with a dose of 5.5 microgram acrolein/ml, an amount four times that in the amount of aqueous smoke extract required for 50% inhibition according to previously reported findings. Analysis by a dual-isotope technique and sodium dodecyl sulfate polyacrylamide gel electrophoresis showed the inhibitory effect of acrolein to be nonspecific, as had previously been found for aqueous smoke extracts. The presence of the sulfhydryl reagent cysteine, reduced the inhibitory effect of acrolein by 57.5%, but reduced inhibition induced by aqueous smoke extracts by only 12.2%. These results suggest the effects of acrolein are both quantitatively and qualitatively different than those of aqueous smoke extracts.

Acrolein↗