Sympathetic and parasympathetic nervous control of airway resistance in dog lungs

We studied autonomic nervous control of central (Rc), peripheral (Rp), and extremely peripheral (Rep) airway resistances using a combination of a retrograde catheter method and a pleural capsule method. Airflow through the pleural capsule enabled us to measure Rep, which mainly reflected the resistance of local bronchioles less than 0.6 mm in diameter. Rp of the airways less than about 2 mm in diameter was not negligibly small at any lung volume (VL). With vagi intact, Rc increased at high as well as low VL, whereas Rp and Rep increased sharply as VL decreased. Vagal stimulation increased Rp more markedly than Rc, and Rep least of all. Propranolol augmented total airway resistance (Rtot) two to four times as much as vagal stimulation, mainly because of increased Rp. Stimulation of stellate ganglia inhibited up to half the increase of Rtot elicited by vagal stimulation; most of the inhibition occurred in Rp, but little in Rc and Rep. Our data suggest that both sympathetic and parasympathetic control is more extensive for Rp than for Rc or Rep.     

Effect of alveolar liquid on distribution of blood flow in dog lungs.

Previous studies have shown that a shift in blood flow away from edematous regions does not occur until the alveoli contain liquid. The present experiments were designed to examine the separate effect of air space liquid, air space plus interstitial liquid, and reduced lung volume on blood flow. We found that reduced lung volume was not associated with significant changes in blood flow and that no systematic change in blood flow occurred when alveoli were filled with isosmotic liquid (autologous plasma). However, when hyposmotic liquid (dilute plasma) was instilled so that both the air space and the alveolar wall interstitial space were filled, blood flow was systematically reduced. This suggested that interstitial liquid was responsible raising vascular resistance in these experiments and that it might also be important in raising local vascular resistance in pulmonary edema. This latter hypothesis was tested in isolated perfused lobes where rapid freezing and quantitative histology showed that the number of open capillaries was significantly reduced in the liquid-filled alveoli (P less than 0.001). These observations suggest that interstitial pressure rises in pulmonary edema with the result that the transmural pressure of the alveolar vessels falls and vascular resistance is increased.     

Iodide-induced inhibition of adenylate cyclase activity in horse and dog thyroid

The characteristics of the iodide-induced inhibition of cyclic AMP accumulation in dog thyroid slices have been previously described [Van Sande, J., Cochaux, P. and Dumont, J. E. (1985) Mol. Cell. Endocrinol. 40, 181-192]. In the present study we investigated the characteristics of the iodide-induced inhibition of adenylate cyclase activity in dog and horse thyroid. The inhibition of cyclic AMP accumulation by iodide in stimulated horse thyroid slices was similar to that observed in dog thyroid slices. The inhibition was observed in slices stimulated by thyroid-stimulating hormone, cholera toxin and forskolin. Increasing the concentration of the stimulators did not overcome the iodide-induced inhibition. Adenylate cyclase activity, assayed in crude homogenates or in plasma-membrane-containing particulates (100,000 x g pellets), was lower in homogenates or in particulates prepared from iodide-treated slices than from control slices. This inhibition was observed on the cyclase activity stimulated by forskolin, fluoride or guanosine 5'-[beta, gamma-imino]triphosphate, but also on the basal activity. It was relieved when the homogenate was prepared from slices incubated with iodide and methimazole. Similar results were obtained with dog thyroid. The inhibition persisted when the particulate fraction was washed three times during 1 h at 100,000 x g, in the presence of bovine serum albumin or increasing concentration of KCl. It was similar whatever the duration of the cyclase assay, in a large range of protein concentration. These results indicate that a stable modification of adenylate cyclase activity, closely related to the plasma membrane, was induced when slices were incubated with iodide. Iodide inhibition did not modify the affinity of adenylate cyclase for its substrate (MgATP), but induced a decrease of the maximal velocity of the enzyme. The percentage inhibition was slightly decreased when Mg2+ concentration increased, and markedly decreased when Mn2+ concentration increased. A detectable adenylate cyclase activity was demonstrated when intact slices were incubated in the presence of [alpha-32P]ATP, probably because of the presence of broken cells produced during the slicing. Iodide had no direct effect on this cyclase system, which confirms that iodide needs the integrity of the cell to induce the inhibition and suggests that the inhibition is not transmitted between cells.     

The evolution of bacterial resistance against bacteriophages in the horse chestnut phyllosphere is general across both space and time

Insight to the spatial and temporal scales of coevolution is key to predicting the outcome of host–parasite interactions and spread of disease. For bacteria infecting long-lived hosts, selection to overcome host defences is just one factor shaping the course of evolution; populations will also be competing with other microbial species and will themselves be facing infection by bacteriophage viruses. Here, we examine the temporal and spatial patterns of bacterial adaptation against natural phage populations from within leaves of horse chestnut trees. Using a time-shift experiment with both sympatric and allopatric phages from either contemporary or earlier points in the season, we demonstrate that bacterial resistance is higher against phages from the past, regardless of spatial sympatry or how much earlier in the season phages were collected. Similarly, we show that future bacterial hosts are more resistant to both sympatric and allopatric phages than contemporary bacterial hosts. Together, our results suggest the evolution of relatively general bacterial resistance against phages in nature and are contrasting to previously observed patterns of phage adaptation to bacteria from the same tree hosts over the same time frame, indicating a potential asymmetry in coevolutionary dynamics.     

Comparison of isogravimetric and venous occlusion capillary pressures in isolated dog lungs

Venous occlusion capillary pressures (Pcv) were simultaneously compared with isogravimetric capillary pressures (PcI) in the same isolated perfused dog lung preparations. For 26 determinations, PcI averaged 1.23 +/- 0.22 (SE) mmHg higher than Pcv. However, the two measurements of capillary pressure were highly correlated (r = 0.99), and the following regression equation was obtained: Pcv = 1.12 PcI - 2.1. Pcv could be easily measured several times in the same preparation, either by total venous occlusion or regional venous occlusion using a Swan-Ganz balloon catheter. In addition, Pcv did not require an isogravimetric state for its determination. These data suggest that the major sites of filtration and vascular capacitance in the pulmonary circulation reside in the microvessels and that the more easily determined Pcv is an adequate measure of the average capillary filtration pressure in the lungs.     

An ultrastructural study of the carotid body of horse and dog

Summary Carotid body tissue from horse and dog has been investigated ultrastructurally. Several cell types are recognized: glomus cells which are regarded as chemoreceptors, sustentacular cells which enclose the glomus cells, and nerve fibers.The glomus cells contain electron dense granules which are interpreted as packages of biogenic monoamines. There are both dark and light glomus cells, the former containing more granules and ribosomes. Invaginations of the plasma membranes as well as free coated vesicles are often seen in the cytoplasm of glomus cells. Nerves within the glomus lobules are generally wrapped by sustentacular cells, but nerve endings are also seen in close contact with the glomus cells. Some endings contain synaptic vesicles as well as a great concentration of mitochondria. The corresponding fibers are thought to be efferent. Another type of contact is interpreted as en passant synapses of afferent fibers.The author wishes to express his gratitude to Professor L. Nicander who initiated this project and took most of the micrographs and to Professor Nils Obel and associate Professor Gustav Björk at the Royal Veterinary College for their valuable help with the surgical procedure and to Dr. Martin Ritzén of the Royal Medical College for making the tests for biogenic monoamines.     

Gas mixing in the airways of dog lungs during high-frequency ventilation

Washout of insoluble inert test gases of different diffusivity (He and SF6 or He and Ar) from dog lungs was studied during high-frequency ventilation (HFV). Test gas equilibrium and subsequent washout were performed with HFV, succeeding measurements being performed at different stroke volumes (1.5-2.5 ml/kg body wt), oscillation frequencies (10-30 Hz), and with different lung volumes (32-74 ml X kg-1). Test gas concentrations were continuously measured by a mass spectrometer. The time course of washout could be described as the sum of two exponentials. There were no consistent differences in the time courses of washout between He and SF6 or between He and Ar. It is concluded that gas mixing in the airways during HFV is not significantly limited by diffusion, and this is suggested to apply during HFV to steady-state transport of respiratory gases (e.g., O2 and CO2) as well as to the transient state of inert gas washout.