The results demonstrate that autoregulation is primarily dependent on the arteriovenous pressure difference and that it is diminished or abolished when this pressure is lower than approximately 90 mm. Hg. It is suggested that in the kidney the arteriovenous pressure gradient is probably close to the true distending pressure (i.e., the transmural pressure) of the intraparenchymal renal arteries and arterioles. It is concluded that renal autoregulation is due to an active response of the muscular coats of the renal arteries and arterioles to changes in transmural pressure.

The exact relationships of carbon dioxide tension (PC02) and hydrogenion activity (pH) to the chemical control of respiration are still not clearly understood. Attempts to correlate ventilation quantitatively with the pH or PCO2 of blood under all circumstances have not been successful.

A total of 166 consecutive clinical episodes of pneumonitis in patients with acquired immune deficiency syndrome (AIDS) or antibody positive for human immune deficiency virus (HIV) were investigated for evidence of cytomegalovirus (CMV) infection in their lungs and at peripheral sites to determine the pathogenicity of this virus in the lung and its relationship to peripheral CMV shedding. Evidence of CMV infection was sought in bronchoalveolar lavage (BAL) fluid, blood, saliva, and urine using a specific monoclonal antibody to antigens produced by CMV-infected cells within 24 h. Although CMV was detected in 31 (19%) of BAL fluid specimens, in only six episodes was this the sole pathologic finding. In the remaining episodes either another infectious agent, Kaposi's sarcoma, or lymphoid interstitial pneumonitis was found or no pathogen was detected. None of the patients were given specific anti-CMV treatment, and all but two recovered, including those patients in whom CMV was the sole finding at BAL. The presence of peripheral shedding of CMV did not have any significance in mortality or morbidity. Our findings are in direct contrast to those in recipients of allogeneic bone marrow transplants, in whom CMV pneumonitis is associated with a high mortality. We postulate that this difference is because AIDS patients cannot mount the destructive immune response to CMV in the lung, which we believe to be the basis of the pathology seen in the former group. We conclude that CMV is not a pathogen in the lungs of patients with HIV infection, and we suggest that its presence at this site does not warrant specific therapy in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

SUMMARY1. The ventilatory response to electrically induced exercise was studied in thirteen patients with traumatic spinal cord transaction at or about the level of T6. The steady-state and on-transient responses to this exercise were compared with those obtained in eighteen normal subjects (Adams, Garlick, Guz, Murphy & Semple, 1984).2. Exercise was produced by surface electrode stimulation of the quadriceps and hamstring muscles so as to produce a pushing movement at 1 Hz against a spring load.3. At rest there was no significant difference between normals and patients, except that the patients had a lower CO2 elimination (Pco2) and end-tidal Pco, (PET,Co2) and a higher heart rate. 5. In the steady state there was a mean rise in PETCO, of 0-9 mmHg (S.D. 1-4) in the normals, and 3-2 mmHg (S.D. 2 7) in the patients, but there was overlap between the two groups. In many experimental runs in both groups, PET,Co2 did not rise, and sometimes fell. Where PCO2 did rise, the ventilatory response to exercise could not be accounted for on the basis of the ventilatory sensitivity to CO2 inhalation. From arterial sampling in three of the patients it was found that when PETC02 rose, the corresponding change in Paco2 was less.6

SUMMARY1. An in vivo pH monitoring technique was used to assess changes in pH, and by inference changes in PCO., in the carotid artery of anaesthetized cats. The changes in carotid artery pH and respiration following abrupt injections of various acids into the carotid artery or aorta were investigated.2. Injections of saline equilibrated with 100% C02, timed to produce changes at the carotid body chemoreceptors during early inspiration caused an increase in the tidal volume of that breath. The amplitude and rate of change of the pH changes so produced were comparable with those of the oscillations in pH produced by respiration itself.3. The respiratory responses to injection of saline equilibrated with 100 % C02 occurred whether the animal was breathing air or 100 % 02.4. Injections of lactic or hydrochloric acid were without an effect on respiration, except when pH changes larger than 0.1 pH unit were produced. A NaHCO3 solution equilibrated with 30 % C02 stimulated respiration, even though the solution was alkaline to the cat's arterial blood and induced an alkaline change in arterial pH.5. Infiltration of the carotid sinus nerve area with procaine temporarily abolished the respiratory response to injections of saline equilibrated with 100 % C02.