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Biomedical subjects

C Mitchell

Publications and source records attributed to C Mitchell.

At least 181 records · Page 10Linked to original sources
PubMed1976

Interaction between bronchoconstrictor stimuli on human airway smooth muscle.

In healthy human subjects, the simultaneous aerosol administration of histamine and methacholine results in a pronounced decrease in maximum flow rates on partial expiratory flow-volume (PEFV) curves. When given alone in the same concentrations, these drugs produced no or minimal decreases in flow rates. The results suggest an interaction of histamine and cholinergic stimuli on airway smooth muscle (ASM). This mechanism might explain many experiments where vagal blockade diminished or abolished ASM response to histamine and other stimuli, simply by interfering with histamine-cholinergic interaction at the ASM level. These findings confirm similar findings of animal in vitro experiments. The experiments clearly confirm the sensitivity and value of assessing drug effects prior to a deep breath. Flow-rate changes after a full inspiration, taken from the maximum expiratory flow-volume (MEFV) curve, show either no relationship to the concentration of inhaled methacholine or significantly less effect than that seen on the PEFV curve.

Adult↗
PubMed1975

Continuous negative chest-wall pressure as therapy for severe respiratory distress in older children.

Continuous negative chest-wall pressure (CNP) was used to treat five children, 4 to 11 years of age, who had progressively severe respiratory distress caused by Pneumocystis carinii penumonitis. After initial improvement, two patients developed progressive increases in respiratory rate, alveolar-arterial oxygen gradient, intrapulmonary right-to-left shunt, and hypoxia. The disease ended fatally in both. The remaining three patients continued to improve and recovered from their pulmonary disease. These results show that CNP therapy provides an effective means of improving arterial oxygenation in spontaneously breathing older children, just as in neonates, without the need for endotracheal intubation, prolonged sedation, and muscle relaxants.

Acid-Base Equilibrium↗
PubMed1973

Transfection of Escherichia coli spheroplasts. II. Relative infectivity of native, denatured, and renatured lambda, T7, T5, T4, and P22 bacteriophage DNAs.

The change of infectivity of phage DNAs after heat and alkali denaturation (and renaturation) was measured. T7 phage DNA infectivity increased 4- to 20-fold after denaturation and decreased to the native level after renaturation. Both the heavy and the light single strand of T7 phage DNA were about five times as infective as native T7 DNA. T4 and P22 phage DNA infectivity increased 4- to 20-fold after denaturation and increased another 10- to 20-fold after renaturation. These data, combined with other authors' results on the relative infectivity of various forms of phiX174 and lambda DNAs give the following consistent pattern of relative infectivity. Covalently closed circular double-stranded DNA, nicked circular double-stranded DNA, and double-stranded DNA with cohesive ends are all equally infective and also most highly infectious for Escherichia coli lysozyme-EDTA spheroplasts; linear or circular single-stranded DNAs are about 1/5 to 1/20 as infective; double-stranded DNAs are only 1/100 as infective. Two exceptions to this pattern were noted: lambda phage DNA lost more than 99% of its infectivity after alkaline denaturation; this infectivity could be fully recovered after renaturation. This behavior can be explained by the special role of the cohesive ends of the phage DNA. T5 phage DNA sometimes showed a transient increase in infectivity at temperatures below the completion of the hyperchròmic shift; at higher temperatures, the infectivity was completely destroyed. T5 DNA denatured in alkali lost more than 99.9% of its infectivity; upon renaturation, infectivity was sometimes recovered. This behavior is interpreted in terms of the model of T5 phage DNA structure proposed by Bujard (1969). The results of the denaturation and renaturation experiments show higher efficiencies of transfection for the following phage DNAs (free of single-strand breaks): T4 renatured DNA at 10(-3) instead of 10(-5) for native DNA; renatured P22 DNA at 3 x 10(-7) instead of 3 x 10(-9) for native DNA; and denatured T7 DNA at 3 x 10(-6) instead of 3 x 10(-7) for native DNA.

Coliphages↗