Biomedical subjects
Publications and source records attributed to N J Russell.
When moderately halophilic bacteria adapt phenotypically to altered salinity, they modify the composition of their cell envelopes. These alterations are discussed in the context of how external salt concentration could be sensed and the adaptive changes triggered. A general model for salt sensing and signal transduction is suggested.
A rapid ion-exchange method has been used to purify the alginate from the extracellular material of mucoid strains of Pseudomonas aeruginosa isolated from the lungs of cystic fibrosis patients. The structure has been investigated by chemical analysis, infrared spectroscopy, paper chromatography, and gas-liquid chromatography. The alginates contain mainly random or poly(D-mannuronic acid) block structures, and are highly acetylated. The relative viscosity is not correlated with the ratio of D-mannuronic acid to L-guluronic acid residues, or the degree of acetylation. The chemical/physical properties of the alginate from P. aeruginosa are considered in the context of the growth of the organism in the lung.
The response characteristics of non-myelinated vagal lung receptors have been studied in the anaesthetized rabbit. The results indicate that the behaviour of these endings strongly resembles those found in cats and dogs and that they can be classified into 'pulmonary' 'bronchial' and 'pulmonary-bronchial' groups depending on their accessibility from either circulation. Experiments involving pericardial block with local anaesthetic to exclude responses from cardiac receptors and the use of sodium dithionite as a novel stimulus to 'pulmonary' endings alone, have shown that the predominant effect of these endings in the anaesthetized rabbit is to increase respiratory frequency. Reflex responses from 'bronchial' endings similar provided sufficient amount of the activating chemical was given.
Conventional chest tomography and fibreoptic bronchoscopy were performed in 100 patients with a localised chest abnormality on their chest radiographs who had been referred with a possible diagnosis of bronchial carcinoma. Carcinoma was eventually confirmed in 74 cases and in 26 the lesion proved to be benign. The accuracy of tomography in the overall series was 83%, with a sensitivity of 92% and a specificity of 58%. These figures compare favourably with the results of other imaging techniques used in the diagnosis of bronchial carcinoma. In 50 patients bronchoscopy did not suggest carcinoma and in this group of patients 24 had a carcinoma and 26 a benign lesion. The accuracy of tomography in the bronchoscopy negative patients was 74%, the major source of error being the false positive category. The lesion eventually proved to be benign in 33% of the cases where tomography suggested malignancy, but when the tomograms suggested that the lesion was benign a tumour was found to be present in only 12% of cases.
The respiratory response to hypercapnia has been investigated in 10 anesthetized rabbits by use of a rebreathing technique. The responses were obtained in three situations: with one intact vagus nerve (control), during differential block of conduction, and after vagotomy. Differential block was achieved using anodal hyperpolarization by application of a direct current to the cervical vagus nerve. Great care was taken during the differential block to establish that all impulse conduction in myelinated fibers of the cervical vagus nerve was abolished but that the nonmyelinated fibers conducted normally. Additionally, in five more rabbits the nature of the differential block was confirmed from single-fiber recordings of activity in both myelinated and nonmyelinated fibers. The same increase in tidal volume in response to hypercapnia was present in all three experimental situations, indicating that it was not vagally mediated. The increase in frequency in response to hypercapnia in the control state was abolished by vagotomy but preserved when only the nonmyelinated fibers were functioning during the differential block. This increased frequency response, attributable to decreases in both inspiratory and expiratory durations, was usually enhanced during the differential block, despite the slower deeper pattern of breathing attributed to loss of activity in myelinated fibers. The implications of this reflex increase in frequency in response to hypercapnia, mediated by nonmyelinated vagal endings in the lung, are discussed.
The radiologic position of tumors in 100 patients with bronchial carcinoma was compared with the diagnostic yield from fiberoptic bronchoscopy. A new method for dividing the chest x-ray film into three areas (hilar, perihilar, and peripheral) was based upon the expected range of vision of the fiberoptic bronchoscope. At bronchoscopy without fluoroscopy, only eight (36 percent) of 22 radiologically peripheral tumors were diagnosed, compared with 31 (94 percent) out of 33 hilar tumors (p less than 0.001) and 34 (76 percent) out of 45 perihilar tumors (p less than 0.01). The results show that in hilar and perihilar tumors, fiberoptic bronchoscopy gives a high diagnostic yield, whereas in peripheral tumors the yield is poor. This method allows the clinician to judge from the chest x-ray film whether a tumor is likely to be visible bronchoscopically. Thus, in radiologically peripheral tumors, as defined by our method, fluoroscopy at the time of fiberoptic bronchoscopy should be available to the clinician, or alternative diagnostic methods should be considered.
The formation of the selenite-induced cataract was investigated by examining the ultrastructure of the cataract with transmission electron microscopy (TEM). A lacy, or honeycomb, appearance of the nuclear cataract seen by light microscopy was resolved by TEM to be due to the aggregation or precipitation of cytoplasmic material. Despite severe intracellular changes the fibers retained their close apposition to one another. These results are consistent with the hypothesis that a major lesion in selenite-induced nuclear cataracts is the formation of insoluble cytoplasmic aggregates.
The relationship between the delta 9-desaturase activity of the psychrophilic bacterium Micrococcus cryophilus grown at different temperatures and the physical state of its membrane lipids as measured by ESR spectroscopy has been studied. Arrhenius plots of desaturase activity were biphasic with a discontinuity at a temperature which depended upon the bacterial growth temperature. Changes in the desaturase activation energy, which increased as the growth temperature was lowered, are discussed in the context of membrane lipid fluidity adaptation to changing environmental temperature. The fluidity of membranes and isolated lipids was measured using nitroxide-labeled fatty acids. The spectra of 2-(10-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl in membranes indicated that there were two lipid environments within the membrane whose relative proportions were dependent both on temperature of measurement and on bacterial growth temperature. In contrast, 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinoxyl spectra showed a single lipid environment and plots of log order parameter (S3) vs 1/T were biphasic with inflexion temperatures which were closely related to the bacterial growth temperature. As with membranes, plots of log S3 vs 1/T for total lipids, phosphatidylglycerol and cardiolipin, but not phosphatidylethanolamine, were biphasic and showed inflexions which correlated well with bacterial growth temperature. These results are interpreted as being consistent with a location for the desaturase within the bulk lipid of the membrane rather than in association with specific lipid types.
The addition of an arrhythmogenic concentration of ouabain (1.37 X 10(-6) M) results in a number of physiological, biochemical, and ultrastructural changes in isolated perfused guinea pig (Langendorff) heart preparations. Chronologically the following alterations occurred: first, a transient rise in ventricular cyclic AMP followed by a reduction in ventricular ATP, relatively minor electrocardiograph abnormalities (e.g., occasional missed beats, transient episodes of tachycardia, and occasional premature ventricular contractions), and a significant decline in coronary flow. A short time later, preparations became tachycardic and within 10 min asystole supervened. Simultaneously with the occurrence of tachyarrhythmias, there was a significant increase in the release of creatine kinase and lactate dehydrogenase into the coronary effluent. Ultrastructural analysis of the ventricular endocardium revealed marked alterations in the mitochondria, disappearance of cytosolic glycogen granules, and chromatin clumping in the nuclei. Pretreatment with d,l-propranolol (3.38 X 10(-6) M) 15 min before ouabain abolished alterations caused by ouabain alone. Studies where ouabain-treated hearts were paced or coronary flow maintained suggest that changes in neither heart rate nor coronary flow are responsible for the protective action of propranolol. Results obtained indicate that ouabain-induced toxicity may in part result from an increase in coronary resistance producing myocardial hypoxia, cell damage, and arrhythmias. Preliminary studies suggest that the membrane-stabilizing action of propranolol appears to be the basis of its protective effect.
The delta 9-desaturase of the psychrophilic bacterium Micrococcus cryophilus is shown to be a membrane-bound enzyme that is probably linked to a cyanide- (and azide-) sensitive respiratory chain with oxygen as the final acceptor. It has a pH optimum of 8.7 and contains an essential thiol group, but has no special ion requirements. The desaturase activity of washed membranes could not be increased by adding supernatant or NADH and NADPH, possibly owing to the endogenous generation of reduced cofactors by the membranes. The substrate for the desaturase is not acyl-CoA and is probably not acyl-acyl-carrier protein. Evidence is presented that the substrate in vivo is saturated phospholipid and a scheme for the possible routes of incorporation of exogenous stearic acid into oleoyl-phospholipid is presented.
The phagocytosis of Staphylococcus epidermis by rabbit alveolar macrophages was measured in the absence or presence of a series of sensory irritants. The phagocytic index was determined in the presence of the sensory irritant dibenzoxazepine and 10 of its derivatives. All of the compounds tested inhibited phagocytosis to some extent. Dibenzoxazepine was the most potent inhibitor and the 1-chloro and 2-chloro derivatives were the least potent. With all the compounds tested, the inhibition of phagocytosis was dose dependent. The degree of inhibition of phagocytosis was not correlated with either the nature or the position of the substituent groups on the dibenzoxazepine molecule. There was no discernible relationship between the inhibition of phagocytosis and the irritancy of the compounds tested.
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A rebreathing method for measuring carbon monoxide transfer factor (TLCO) and transfer coefficient (KCO) is evaluated. The test was performed on 42 subjects. Seventeen of these had normal lung function while the remainder suffered from various conditions, most having fibrosing alveolitis. No patients with severe airways obstruction were included in the group. The results were compared with single-breath measurements and close correlations were found between single-breath KCO and rebreathing KCO (r = 0.78, p less than 0.001) and between single-breath TLCO and rebreathing TLCO (r = 0.97, p less than 0.001). The reasons for discrepancies between single-breath and rebreathing values are discussed. It is concluded that measurement of rebreathing gas transfer is a useful supplement to routine tests of lung function, particularly in breathless patients with a small vital capacity.
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Pulmonary function tests have been carried out on eight adults with cystic fibrosis. There were statistically significant correlations between the severity of the patient's clinical state as assessed by the Shwachman score and TLco, TLC and VC. In addition the RV/TLC ratio increased with increasing clinical severity. There were no significant correlations between clinical severity and other measurements of lung function such as FEV1, PEFR, RV or PCO2. Serial studies indicated that the TLCO falls with increasing clinical severity of the disease. It is suggested that the objective measurements of pulmonary function should be included in any future 'scoring' system used to assess the severity of cystic fibrosis and that measurements of the single-breath TLCO might be one of the more discriminant tests.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.