Interaction of cross-sectional area, driving pressure, and airflow of passive velopharynx

Isono, Shiroh, Thom R. Feroah, Eric A. Hajduk, Rollin Brant,William A. Whitelaw, and John E. Remmers. Interaction ofcross-sectional area, driving pressure, and airflow of passive velopharynx. J. Appl. Physiol. 83(3):851-859, 1997.Previous studies have shown that, when thepharyngeal muscles are relaxed, the velopharynx is a highly compliantsegment of the pharynx. Thus, under these circumstances,cross-sectional area of the velopharynx (A_VP), drivingpressure across the velopharynx (P), and inspiratory airflow(I) willbe mutually interdependent variables. The purpose of the presentinvestigation was to describe the interrelation among these threevariables during inspiration. We studied 15 sleeping patients withobstructive sleep apnea/hypopnea when the pharyngeal muscles wererendered hypotonic by applying continuous positive airway pressure tothe nasal airway.A_VP, determined by endoscopic imaging, was significantly greater at onset ofI limitationthan at minimum oropharyngeal pressure(P < 0.01). Snoring was neverobserved duringIlimitation. In a subgroup of six patients, values for P,I, andA_VP were obtainedat 0.1-s intervals at various levels of mask pressure. For these sixpatients, the mathematical expressionI = 0.657(A_VP/A_max) · P^0.332,where A_max ismaximal A_VP,described the relationship among the three variables(R² = 0.962) forflow-limited and non-flow-limited inspirations. The impedance of thepassive velopharynx, defined asP^0.33/,was inversely related toA_VP and increaseddramatically when A_VP was <0.3cm². In summary, we observed aprogressive decrease inA_VP during flow-limited inspiration in patients with obstructive sleep apnea. Thisconstriction of the velopharynx contributes to an increase invelopharyngeal impedance that, in turn, counterbalances the increase inP during flow limitation.

     

Procedure for the identification of Escherichia coli mutants affected in components containing glycerol derived from phospholipid turnover: Isolation of mutants lacking glycerol in membrane-derived oligosaccharides (MDO)

Abstract A mutant screening procedure is described which allows the identification of mutants carrying lesions in lipoprotein, membrane-derived oligosac-charides (MDO), and other compounds of the E. coli cell envelope containing glycerol derived from phospholipid metabolism. Two mutants lacking glycerol in MDO and one mutant devoid of lipoprotein demonstrate the usefulness of the procedure.     

Murein hydrolase (N-acetyl-muramyl-l-alanine amidase) in human serum

An enzyme was identified in human serum which unlike lysozyme cleaved the amide bond between N-acetyl-muramic acid and l-alanine of the peptide side chain of the rigid layer (murein) of Escherichia coli. The N-acetylmuramyl-l-alanine amidase released all of the peptide side chains including those to which the lipoprotein is bound. A portion of the peptide side chains of the Micrococcus lysodeikticus murein was also hydrolysed from the polysaccharide chains. E. coli, M. lysodeikticus, Bacillus subtilis and Staphylococcus aureus were not killed by the amidase. Treatment of E. coli with EDTA or osmotic shock rendered the cells sensitive to the amidase and they were killed. Possible biological functions of the amidase are discussed.The enzyme was separated from lysozyme in human serum. Gel permeation chromatography indicated a molecular weight of the active enzyme of 82,000 while gel electrophoresis in the presence of sodium dodecyl sulfate revealed a molecular weight of 75,000. Thus, the enzyme probably consists of a single polypeptide chain. Incubation with neuraminidase rendered the amidase more basic suggesting the release of sialic acid residues. The modified glycoprotein disclosed an increased activity to murein. Enzyme activity was inhibited by p-chloromercuribenzene sulfonate and ethyleneglycol-bis(2-aminomethyl) tetraacetate (EGTA) at 1 and 0.2 mM concentration, respectively, whereas EDTA up to 5 mM was without effect. The amidase was also inactivated by agents that reduce disulfide bridges.     

Rapid isolation of plasma membranes in high yield from cultured fibroblasts.

1. A method was developed which allows the rapid preparation of pure plasma membranes in high yield from cultured fibroblasts. 2. Cells are lysed in hypo-osmotic borate/EDTA and, after differential centrifugation, the membranes collected by centrifugation on a sucrose barrier. 3. Electron microscopy of the isolated material shows large membrane vesicles essentially free from contaminating organelles. 4. There is no detectable activity of the endoplasmic-reticulum enzyme marker, NADH2--lipoamide oxidoreductase (EC 1.6.4.3), and that of succinate dehydrogenase (EC 1.3.99.1), a marker for mitochondria, is substantially decreased. Chemical compositions are in good agreement with previous observations. 5. This study confirms the usefulness of applied isotopic markers for isolating plasma membranes.     

Fluid production by in vitro lungs from fetal guinea pigs

Lungs from fetal guinea pigs (54-67 days of gestation) were supported in vitro, and lung liquid secretion rates were measured by a dye-dilution technique. The average secretion rate in the first hour was 2.14 +/- 0.08 (SE) mL x kg-1 body weight.h-1 (0.21 +/- 0.01 mL/h) (n = 450); this was comparable to intact preparations. In an independent study of 30 lungs, secretion continued unchanged for 3 h, with no significant change in fluid composition. Between 54 days and term, production appeared to fall in terms of millilitres per kilogram per hour. The following agents were placed in the supporting saline during the middle hour of incubation. (i) Sodium iodoacetate: at 10(-4) M this produced a fall in secretion (fall, succeeding hours; 55.4 +/- 23.0 and 64.9 +/- 17.5%; n = 6); at 10(-3) M it stopped secretion (fall, succeeding hours; 87.2 +/- 10.3 and 100%, n = 6). (ii) Ouabain: at 10(-5) M there was no change in production (n = 6); at 10(-4) M, four preparations were unaffected, two reduced production. (iii) Epinephrine (10(-7) M) produced a significant fall in production in all cases (n = 6); in four preparations secretion reduced (average fall, 64.4 +/- 10.8%); in two preparations there was reabsorption (average rate, -1.03 mL.kg-1.h-1). This extends the effect of epinephrine to the guinea pig, and suggests that the in vitro preparation is a useful model for studies of the fetal lung.     

Vacuoles from Sugarcane Suspension Cultures : I. ISOLATION AND PARTIAL CHARACTERIZATION

Vacuoles were isolated from suspension cultures of sugarcane (Saccharum sp.) cells by centrifugation of protoplasts at high g force against a 12% (w/v) Ficoll solution. Distribution of marker enzymes and Concanavalin A binding showed an 11% contamination of the vacuole preparation by cytoplasmic components, mitochondria, and endoplasmic reticulum, and 18% contamination by plasma membrane. Acid phosphatase, carboxypeptidase, protease, peroxidase, and ribonuclease activities were enriched in isolated vacuoles. Carboxypeptidase was tonoplast-bound, whereas the other enzymes were soluble. Sucrose, reducing sugars, and free amino acids were measured in protoplasts and vacuoles during growth of cells in suspension culture. Sucrose and reducing sugar content of vacuoles increased as the culture aged, while free amino acids decreased sharply.     

Relation between plasma hormone profiles,symptoms, and response to oestrogen treatment in women approaching the menopause.

Out of a consecutive series of 300 patients seen at a menopause clinic, 82 complained of symptoms generally associated with the climacteric, although they were still menstruating. Vasomotor disturbances were absent in 42 of these patients (group 1) and present in 40 (group 2). Headaches, insomnia, and dyspareunia were the most common complaints among the women with vasomotor symptoms, whereas loss of libido and depression predominated in those without. Conjugated equine oestrogens (Premarin) 1.25 mg daily given for three weeks out of four relieved nearly all symptoms in group 2, but in group 1 the response was disappointing. The mean plasma oestradiol concentration in women with vasomotor symptoms was significantly lower than that observed during days 1-10 of the menstrual cycle, but plasma testosterone values were not significantly different from those observed in younger women. Plasma follicle-stimulating hormone (FSH) and luteinising hormone (LH) concentrations were similar to those seen after the menopause. Concentrations of these hormones in the women without vasomotor symptoms were similar to those in the younger, regularly menstruating women. After six months of oestrogen treatment patients in group 2 had a 2.1-fold increase in mean plasma oestradiol concentration, and plasma FSH and LH concentrations were reduced to 39% and 66% of their pretreatment values respectively; in group 1, however, no such pronounced changes occurred. High concentrations of FSH were present in patients with oestrogen-responsive symptoms, 15 U/1 being the diagnostic cut-off point. This measurement in the presence of characteristic symptoms therefore constitutes the best method of selecting patients for oestrogen-replacement therapy.     

An improved method based on the Porter-Silber reaction for determining 17-hydroxycorticosteroids in urine

This paper describes a highly specific method for determining urinary 17-hydroxycorticosteroids, which has been developed by (i) changing the composition of the Porter-Silber reagent and (ii) removing contaminants interfering with the color reaction by addition of sodium bisulfite to β-glucuronidase-hydrolyzed urine before extraction with solvent. For a reference method the Norymberski-Riondel (J. K. Norymberski and A. Riondel 1970, Biochem. J. 120, 493–498) gas chromatography (glc) was used: Correlation coefficient between the present method and GLC = 0.988, deviation from the theoretical regression LINE = 6.8%, and coefficient of SIMILARITY = 0.56. These results are much better than those obtained by I. Ernest, B. Håkansson, J. Lehmann, and B. Sjögren (1964, Acta Endocrinol. 46, 552–562) for the original Porter-Silber method in comparison with the chromatographic measurement of grouped and individual steroids.