Murine cytomegalovirus-induced immunosuppression

The mechanism of murine cytomegalovirus-induced immunosuppression was investigated by examining the roles played by lymphocytes and adherent cells derived from spleens of infected SWR/J mice. As few as 100 infected cells per spleen were correlated with complete abrogation of mitogen responses at 4 and 5 days after infection. In a series of cell mixing experiments it was shown that the deficiency in infected spleens was due partly to the adherent cells, which apparently secreted an immunosuppressive factor, and partly to the infected lymphocytes, which upon exposure to this factor could no longer respond to concanavalin A presented to them by normal adherent cells.

Murine cytomegalovirus infection in the spleen and its relationship to immunosuppression

An attempt was made to correlate murine cytomegalovirus-induced immuno-suppression with the presence of virus-infected cells in the spleen. For this purpose, SWR/J mice were infected with murine cytomegalovirus, and spleens were removed periodically and assayed for the presence of infectious centers in different cell populations and for their capacity to respond to mitogens. The maximal degree of immunosuppression correlated with the peak in adherent cell infectious centers. This was followed by a rapid rise in the number of cells per spleen (splenomegaly), a more gradual return to normal responsiveness to mitogens, and a rapid disappearance of infectious centers. These results add more support to the hypothesis that murine cytomegalovirus-induced immunosuppression is caused indirectly by infection of adherent spleen cells.

Pain due to lesions of central nervous system removed by sympathetic block

Eight patients were studied in whom a lesion within the central nervous system caused constant pain and hyperpathia. Blockade of the sympathetic supply to the periphery was carried out in each patient by stellate ganglion block or intravenous infusion of guanethidine 15 mg in 30 ml saline into a limb on the affected side. On almost every occasion the pain and hypersensitivity were reduced, sometimes completely. Thus chronic pain and hyperpathia arising from a lesion in the central nervous system may be abolished by blocking the sympathetic supply to the periphery; this effect may be achieved when not all the peripheral nerves of the affected region have had their sympathetic nerve supply blocked. Such blockade may be worth repeating in the hope of achieving lasting relief of the intractable pain.

Regional lung function in bilateral diaphragmatic paralysis

1. The distribution of regional function in the lungs of six patient with bilateral diaphragmatic paralysis was investigated by continuous inhalation and infusion of the radioactive gases 81mKr and 85mKr during tidal breathing. 2. In the supine and right lateral decubitus postures the vertical distribution of ventilation per unit alveolar volume was less in the dependent zones, the reverse of that found in normal subjects. In the upright posture ventilation was slightly decreased at the lung base. Perfusion per unit alveolar volume was more uniformly distributed than normally in the upright posture, and decreased from superior to inferior in the supine posture. In the lateral decubitus posture, perfusion of the lower lung was greater than that of the upper. Ventilation/perfusion ratios were more uniformly distributed in the patients than in normal subjects, except in the right lateral decubitus posture. 3. Alterations in the distribution of ventilation may be explained in terms of the altered mechanical interaction of chest wall, mediastinal and abdominal contents, with selective use of intercostal and accessory muscles. The effects on the distribution of blood flow are probably related to the low end-expiratory lung volume.

Effects of regional guanethidine infusion in certain painful states

Guanethidine was infused by the regional intravenous technique into upper and lower limbs of patients with painful hyperpathic states, due to peripheral or central lesions. The relief of pain and hyperpathia occurred within 20 minutes of infusion and lasted between three and 128 hours; in a few patients, the relief has lasted for months. Great reduction in skin conductance and vasodilatation occurred, there being marked variation in the time of onset and duration of these effects. In some cases there was marked pilo-erection. Guanethidine given in this way did not completely block the sympathetic control of digital blood-vessels. There were no effects on sensibility of normally innervated regions.

Immunosuppressive effect of murine cytomegalovirus

Murine cytomegalovirus suppressed the ability of spleen cells to respond to mitogens in vitro. The degree of suppression was proportional to the multiplicity of infection. This effect could not be explained by cytolysis of lymphocytes, an alteration in the kinetics of the response to mitogen, or a direct competition between virions and mitogen molecules for cell-surface receptors. Nor was it due to simple contact between cell and virus, since ultraviolet-inactivated murine cytomegalovirus failed to suppress the response to mitogens. Reconstitution experiments were performed which involved mixing various combinations of infected and uninfected macrophages and lymphocytes. Under these conditions, it was found that the infected macrophages and lymphocytes. Under these conditions, it was found that the infected macrophages had an impaired capacity to mediate the response ot T lymphocytes to concanavalin A. This suggests that murine cytomegalovirus may cause immunosuppression indirectly by interfering with macrophage function.

Interaction of murine cytomegalovirus with separated populations of spleen cells

Mouse spleen cultures were infected with murine cytomegalovirus, either before or after separating the cells into various classes, and the growth of virus and production of infectious centers were measured in each cell class. The separation techniques, which were used in various combinations, comprised: adherence to plastic surfaces; adherence to nylon wool columns; gamma irradiation; and treatment with anti-immunoglobulin serum plus complement. The "macrophage population" took up most of the input virus, as shown by autoradiography of spleen cells infected with radioactive virus. These cells formed infectious centers but replicated the virus only transiently. In contrast, the "B-lymphocyte population" contained a minor cell fraction which was permissive for replication. The "T-lymphocyte population" appeared to be nonpermissive for replication and did not produce infectious centers.

Errors in fuel cell oxygen analysers during NEEP

A fuel cell oxygen analyser was found to underread during the application of negative end-expiratory pressure. Further investigation revealed that air leaks into the analyser head through the plastic housing and causes the analyser to read low. A remedy is suggested.

Preservation of the pulmonary vasoconstrictor response to alveolar hypoxia during the administration of halothane to dogs

The action of halothane on the pulmonary vasoconstrictor response to unilateral alveolar hypoxia was studied in two groups of dogs. In the first group the redistribution of blood flow between the two lungs was studied with a radioactive isotope method, which provided intermittent measurements, whilst in the second group the distribution of blood flow was observed continuously. In both groups there was no significant alteration of the hypoxic vasoconstrictor response with inspired halothane concentrations varying from 0.5 to 1.5%.

Painful peripheral states and sympathetic blocks

In various chronic painful states, the sympathetic nerve supply was blocked either by injecting the sympathetic chain and ganglia with local anaesthesia or by the injection of guanethidine during occlusion of the circulation. There was a striking relation between the presence of hyperpathia and the relief of pain by the blocks. The sympathetic block was unlikely to relieve the pain unless hyperpathia accompanied the pain; when hyperpathia was present, a sympathetic block relieved both the constant pain and the hyperpathia. The effectiveness of the guanethidine blocks shows that the pain and the hyperpathia are maintained by the emission of noradrenaline in the periphery. The facts related to the sympathetic system and sensibility are discussed.

Diagnosis of subdural haematoma by computed axial tomography: use of xenon inhalation for contrast enhancement

A subdural haematoma is described in which a definite computed tomographic (CT) scan diagnosis was made only after contrast enhancement had been achieved by the inhalation of xenon. The different types of enhancement obtained with iodide containing contrast media and with xenon are discussed. The use of xenon to obtain further information in conditions which are inadequately elucidated by conventional CT must be balanced against its anaesthetic effects and relatively high cost.

Multiple interactions between murine cytomegalovirus and lymphoid cells in vitro

Spleen cultures from various strains of mice were infected in vitro with murine cytomegalovirus (MCMV). Infectious centres were established in a small proportion (not greater than 1%) of the cells. Virus could be rescued from these cells by co-cultivation with syngeneic or allogeneic fibroblasts, but the frequency of rescue could not be altered by incubation with cyclic nucleotide analogues, iododeoxyuridine, cortisol, or allogeneic spleen cells. In addition a smaller fraction of the cell population, possibly a sub-population of the infectious centres, replicated virus spontaneously. The presence of mitogens did not affect these interactions qualitatively or quantitatively. A third response to infection was an inhibition in DNA synthesis, which was suffered by unstimulated cultures and by cells transformed by concanavalin A and bacterial lipopolysaccharides, although overall cell viability was maintained. This response was also mediated by u.v.-inactivated virus.

Effects of general anaesthesia on size of cerebrospinal fluid spaces during and after pneumoencephalography

The mode of anaesthesia used during pneumoencephalography has a significant effect on the size of the cerebral ventricles 24 hours after the procedure. Post-encephalographic ventricular enlargement is less marked in patients examined under nitrous oxide anaesthesia. This appears to be related to passage of the gas into the ventricles during the encephalogram, and subsequent diffusion outwards. Variations in arterial carbon dioxide tension during the anaesthesia do not contribute significantly to changes in ventricular size. However, both hyperventilation and inhalation of nitrous oxide may cause apparent increase in size of the cerebral sulci.

Abdominal wall movement in normals and patients with hemidiaphragmatic and bilateral diaphragmatic palsy

Higenbottam, T., Allen, D., Loh, L., and Clark, T. J. H. (1977).Thorax,32, 589-595. Abdominal wall movement in normals and patients with hemidiaphragmatic and bilateral diaphragmatic palsy. The abdomen and ribcage volume contribution to the tidal volume have been determined using magnetometers in three groups of subjects—normal males, patients with hemidiaphragmatic palsy, and patients with bilateral diaphragmatic palsy. In all three groups the main moving parts appear to be the anterior surfaces of the abdomen and ribcage even in the presence of bilateral diaphragmatic palsy.

In the group of patients with bilateral diaphragmatic paralysis the anterior abdominal wall moved inward paradoxically on inspiration. This `negative' movement increased with larger tidal breaths and was best seen in recumbent patients. The normal subjects and those with hemidiaphragmatic palsy showed an outward movement of the anterior abdominal wall on inspiration which increased with larger tidal breaths. It is believed that the paradoxical movement of the abdomen in bilateral diaphragmatic palsy is a valuable clinical sign of this condition.

The contribution of the abdominal volume displacement to the tidal volume in the normal subjects and the hemidiaphragmatic palsy patients varied considerably between subjects and with different postures, but no difference could be discerned between the two groups. This supports the suggestion that the diaphragm is concerned more with maintaining a pressure difference between the abdomen and ribcage than displacing abdominal volume.

Reduction of hypoxic pulmonary vasoconstriction by nitrous oxide administration in the isolated perfused cat lung

Local pulmonary vasconstriction in response to alveolar hypoxia is a protective mechanism reducing blood flow to poorly oxygenated areas of lung. Pulmonary blood flow is thereby directed to better oxygenated lung units and venous admixture and the resulting arterial hypoxaemia is reduced. The effect of nitrous oxide on the pulmonary pressor response to alveolar hypoxia was assessed in the isolated perfused cat lung preparation under conditions of constant flow and constant left atrial and airway pressures. Nitrous oxide, in concentrations of 50 per cent and 75 per cent, was found to produce a reversible depression of the hypoxic pulmonary pressor response. The importance of hypoxia pulmonary vasconstriction and the possible implications of its reduction by anaesthetic agents are discussed.

The effects of halothane and ether on the pulmonary circulation in the innervated perfused cat lung

The effects of halothane and diethyl ether on pulmonary vascular resistance and the pulmonary vasoconstrictor response to alveolar hypoxia were studied in the innervated perfused cat lung. A left and right heart bypass technique was used to allow perfusion of the lungs at constant flow. Neither anaesthetic agent caused a significant change in pulmonary vascular resistance but both agents caused a depression of the pulmonary vasoconstrictor response to hypoxia.

Evaluation of a new method for the continuous measurement of the distribution of the blood flow between the two lungs

The magnitude of the pulmonary vasoconstrictor response to alveolar hypoxia may be studied by measuring the reduction in blood flow when one lung is ventilated with nitrogen. A radioisotope technique has been developed which permits the distribution of blood flow between the two lungs to be measured continuously. This technique was evaluated in dogs and found to be satisfactory.

The assessment of diaphragm function

Paralysis or severe weakness of the diaphragm (the principal muscle of inspiration) is commonly associated with hypoventilation which may be profound during sleep, but the disorder is often unrecognized. The clinical sign of paradoxical (inward) movement of the abdominal wall during spontaneous inspiration in the supine posture may be overlooked, or the appearances at fluoroscopy may mislead, for it is not generally appreciated that descent of the diaphragm in early inspiration in these patients may be an entirely passive event. Measurement of transdiaphragmatic pressure is a simple, reliable and quantitative means of assessing diaphragm function, and will aid in the diagnosis of diaphragm paralysis which has important implications for clinical management.

The effect of methoxyflurane on pulmonary vascular resistance and hypoxic pulmonary vasoconstriction in the isolated perfused cat lung

The effects of methoxyflurane on pulmonary vascular resistance and the pulmonary vasoconstrictor response to alveolar hypoxia were studied in isolated cat lungs perfused at a constant flow. Methoxyflurane decreased pulmonary vascular resistance and depressed the pulmonary vasoconstrictor response to hypoxia.

Chlormethiazole in treatment of status epilepticus

Chlormethiazole (Heminevrin) was successful in controlling fits in seven out of nine episodes of intractable status epilepticus. It was administered as a constant intravenous injection at rates of up to 0.7g/h. No serious side effects were encountered, and the drug deserves wider recognition as a useful therapeutic agent in the management of status epilepticus.

Closing volume and pregnancy

Measurements of closing volume have been made in 20 women between the 36th and 40th weeks of pregnancy. The patients were studied in the erect and supine positions and the point of airway closure was related to functional residual capacity. The results show that airway closure occurred during tidal ventilation in 10 patients in the erect position and in six patients in the supine position. These results may explain the variation found in maternal arterial oxygen tension during pregnancy.

Cardiorespiratory effects of intravenous isoprenaline and salbutamol in dogs

1. The cardiorespiratory effects of intravenous infusions of isoprenaline and salbutamol (1 and 5 mug/min) have been compared in twelve dogs.2. Both drugs produced a rise in pulse rate, a fall in systemic arterial pressure and a rise in pulmonary arterial pressure. Salbutamol produced a greater increase in cardiac output than isoprenaline.3. Both drugs produced an increase in venous admixture, but a significant fall in arterial oxygen tension occurred only with isoprenaline at the higher dose.