Wall motion in expiratory flow limitation: choke and flutter

Limitation of expiratory airflow from mammalian airways is currently understood to be due to choking at wave speed (S. V. Dawson and E. A. Elliott. J. Appl. Physiol. 43: 498-515, 1977). A critical weakness of the theory is the lack of a mechanism for the dissipation of energy when effort exceeds that needed for maximal flow. We have observed substantial wall motion with flow limitation in a physical model of a trachea. Therefore we have examined a simple two-dimensional mathematical model, designed to approximate the behavior of the physical model of the trachea, to try to identify a relationship between flow limitation and wall oscillation. The model matches wave-speed predictions when only long waves are considered. The model predicts that aerodynamic flutter will occur in the zone of supercritical flow described in wave-speed theory. Aerodynamic flutter in the zone of supercritical flow provides a potential mechanism for the energy dissipation necessary for transition from supercritical to subcritical flow and explains the high-frequency pure tone heard with flow limitation.

Effects of converting enzyme inhibition on blood pressure, plasma renin activity (PRA) and plasma aldosterone in hypertensive diabetics compared to patients with essential hypertension

Hypertension with diabetes mellitus has been associated with suppression of the renin-angiotensin-aldosterone system. We have studied the effects of the converting enzyme inhibitor, captopril, on blood pressure, plasma renin activity (PRA) and plasma aldosterone in 10 stable hypertensive diabetic subjects and 10 age-matched patients with essential hypertension. There was no clinical evidence of complication in the diabetic subjects and their diabetic treatment remained unchanged throughout the study. Mean captopril doses used were similar in both groups. In the diabetics and the essential hypertensives, treatment resulted in a significant and similar decrease in blood pressure. Pre-treatment basal and stimulated PRA and the change of PRA with captopril were also similar. Pre-treatment stimulated plasma aldosterone and the response of aldosterone to postural stress was significantly lower in the diabetic group, suggesting an impaired adrenal responsiveness to stress. Despite this, our findings indicate that the hypotensive action of captopril is at least as effective in hypertension associated with otherwise uncomplicated diabetes mellitus as in essential hypertension.

Morphological studies of N-acetylglucosamine induced germ tube formation by Candida albicans

In N-acetylglucosamine induced germ tube formation by Candida albicans, multiple (up to five) protuberances appeared within 90 min at 37 degrees C on each yeast cell. The protuberances were extensions of the cytosol and contained vesiclelike structures. Usually only one protuberance subsequently developed into a germ tube. The germ tubes emanated from all aspects of the cell surface but seldom from the budding (long axis) poles. Pseudohyphae, which originated from the budding pole, exhibited a marked constriction at the site of emergence and were 0.6-2.5 microns in diameter compared with a diameter of 0.6-0.8 micron for germ tubes. The presence of septa confirmed that germ tubes are precursors of septate mycelia. Ultrathin-section transmission electron microscopy of aldehyde plus osmium fixed cells revealed electron-lucent walls with a thin electron-dense outer layer. A fibrillar border was also routinely associated with germ tubes. Poststaining with potassium permanganate revealed, in addition, a previously invisible fuzzy layer on the outer region of the cell wall which extended over bud scars and germ tubes and which coalesced at sites of contact between cells.

The kinetics and divalent cation inhibition of plasma membrane ATPase in the yeast Candida albicans

The kinetics of ATP hydrolysis and cation effects on ATPase activity in plasma membrane from Candida albicans ATCC 10261 yeast cells were investigated. The ATPase showed classical Michaelis-Menten kinetics for the hydrolysis of Mg X ATP, with Km = 4.8 mM Mg X ATP. Na+ and K+ stimulated the ATPase slightly (9% at 20 mM). Divalent cations in combination with ATP gave lower ATPase activity than Mg X ATP (Mg greater than Mn greater than Co greater than Zn greater than Ni greater than Ca). Divalent cations inhibited the Mg X ATPase (Zn greater than Ni greater than Co greater than Ca greater than Mn). Free Mg2+ inhibited Mg X ATPase weakly (20% inhibition at 10 mM). Computed analyses of substrate concentrations showed that free Zn2+ inhibited Zn X ATPase, mixed (Zn2+ + Mg2+) X ATPase, and Mg X ATPase activities. Zn X ATP showed high affinity for ATPase (Km = 1.0 mM Zn X ATP) but lower turnover (52%) relative to Mg X ATP. Inhibition of Mg X ATPase by (free) Zn2+ was noncompetitive, Ki = 90 microM Zn2+. The existence of a divalent cation inhibitory site on the plasma membrane Mg X ATPase is proposed.

The inactivation of ornithine transcarbamoylase by N delta-(N'-sulpho-diaminophosphinyl)-L-ornithine

Phaseolotoxin, a tripeptide inhibitor of ornithine transcarbamoylase, is a phytotoxin produced by Pseudomonas syringae pv. phaseolicola, the causal agent of halo-blight in beans. In vivo the toxin is cleaved to release N delta-(N'-sulpho-diaminophosphinyl)-L-ornithine, the major toxic chemical species present in diseased leaf tissue. This paper reports on the interaction between N delta-(N'-sulpho-diaminophosphinyl)-L-ornithine and ornithine transcarbamoylase. N delta-(N'-Sulpho-diaminophosphinyl)-L-ornithine was found to be a potent inactivator of the enzyme, in contrast with phaseolotoxin, which previously has been reported to inhibit the enzyme reversibly. Inactivation by N delta-(N'-[35S]sulpho-diaminophosphinyl)-L-ornithine resulted in the incorporation of 35S into ethanol-precipitated protein. The stoicheiometry of 35S incorporation was approximately 1 mol/mol of active sites. Inactivation was second-order and a rate constant of 10(6) M-1 X s-1 at 0 degree C in 50 mM-Tris/HCl, pH 9.0, was obtained. Carbamoyl phosphate, a substrate of ornithine transcarbamoylase, protected the enzyme from inactivation. A dissociation constant of 3 microM for the enzyme-carbamoyl phosphate complex was calculated. L-Ornithine, the second substrate for ornithine transcarbamoylase, protected the enzyme only at high concentrations. The results are consistent with N delta-(N'-sulpho-diaminophosphinyl)-L-ornithine being a potent affinity label that binds via the carbamoyl phosphate-binding site of ornithine transcarbamoylase. Cleavage of phaseolotoxin to N delta-(N'-sulpho-diaminophosphinyl)-L-ornithine in vivo appears to be an important function in the physiology of the disease.

Characterization of a tetraploid derivative of Candida albicans ATCC 10261

A morphometric analysis of Candida albicans yeast cells utilizing scanning electron microscopy showed that the cell volume and the DNA content of a tetraploid strain (derived by cell fusion) were 2.4 to 3.0 and 2.0 times, respectively, those of the progenitor diploid strain, ATCC 10261. The pathogenicities of both strains were similar.

N-acetyl-D-glucosamine-induced morphogenesis in Candida albicans

N-acetylglucosamine is a morphogenic effector in the human pathogenic yeast Candida albicans. Depending on temperature, N-acetylglucosamine induces yeast-mycelial conversion or chlamydospore formation. N-acetylglucosamine is also a carbon source for growth in the yeast form. Germ-tube formation, i.e. the intermediary of yeast-mycelial conversion, is induced at temperatures in excess of 33 degrees C; at lower temperatures the yeast or the pseudomycelial form of the organism predominates. 2-Deoxyglucose, at concentrations which do not affect yeast growth, is a potent inhibitor of N-acetylglucosamine-induced germ-tube formation. N-acetylglucosamine suffices as both the inducer and the carbon sources for morphogenesis and both transcription and translation are required for the yeast to mycelial transition. The metabolism of N-acetylglucosamine is essentially the same for yeast phase cells (28 degrees C) and germ-tube forming cells (37 degrees C): enzymes for N-acetylglucosamine uptake and catabolism are equally well induced by gene expression at 28 degrees C and 37 degrees C. During germ-tube formation, the chitin content and the activity of the regulatory enzyme chitin synthase increase. Germ-tube formation in C. albicans can also be induced gratuitously by a number of N-acetylhexosamine derivatives (N-acetylglucosamine covalently linked to agarose, N-acetylmannosamine, hyaluronic acid, colloidal chitin, and mucin). These compounds are not taken up by the yeast cells and do not support growth which suggests that germ-tube formation is triggered by a cell-surface receptor mechanism. It is proposed that, after binding to the receptor, N-acetylglucosamine produces an intracellular message which primes the cell for morphogenesis. This message would ultimately be responsible for the choice of the mode of growth, spherical versus apical, that is characteristic of yeast or mycelial form.

The inhibition of ornithine transcarbamoylase from Escherichia coli W by phaseolotoxin

The mechanism of inhibition of ornithine transcarbamoylase by the bacterial toxin phaseolotoxin [N-delta-(phosphosulphamyl)ornithylalanylhomoarginine] was investigated. Ornithine transcarbamoylase was purified by affinity chromatography from Escherichia coli W argR- by using N-delta-(phosphonoacetyl)ornithine as the ligand. Under steady-state conditions phaseolotoxin inhibition was reversible and exhibited mixed kinetics with respect to carbamoyl phosphate. The apparent Ki and apparent K'i were 0.2 microM and 10 microM respectively. Inhibition with respect to ornithine was noncompetitive, with an apparent Ki of 0.9 microM. These data are consistent with competitive binding of phaseolotoxin to the carbamoyl phosphate-binding site of the enzyme. The toxin also appears to be able to bind to the enzyme-carbamoyl phosphate complex, although, since K'i is 50 times greater than Ki, this event is kinetically much less significant. In the presence of phaseolotoxin ornithine transcarbamoylase exhibited a transient phase of activity before a steady state. This is consistent with low rates of association and dissociation for the toxin with enzyme and the enzyme-toxin complex. Rate constants of 2.5 X 10(4)M-1 X s-1 and 5 X 10(-3)s-1 were estimated for the association and dissociation constants respectively.

Analysis of wall glucans from yeast, hyphal and germ-tube forming cells of Candida albicans

Acid-soluble and alkali-insoluble glucan fractions were prepared from yeast, hyphal and germ-tube forming cells of Candida albicans. Alkali-insoluble glucan was also extracted from purified yeast cell walls. Paper chromatography of partial acid hydrolysates confirmed that the glucan preparations contained beta(1----3)- and beta(1----6)-chains but no mixed intra-chain beta(1----3)/(1----6) linkages. Methylation and 13C-NMR analyses showed that the acid-soluble glucan consisted of a highly branched polymer composed mainly (67.0% to 76.6%) of beta(1----6)-linked glucose residues. The alkali-insoluble glucan from yeast and hyphal cells contained from 29.6% to 38.9% beta(1----3) and 43.3% to 53.2% beta(1----6) linkages. Alkali-insoluble glucan from germ-tube forming cells consisted of 67.0% beta(1----3) and 14% beta(1----6) linkages. Branch points accounted for 6.7%, 12.3% and 17.4% of the residues in the alkali-insoluble glucan of yeast, germ-tube forming and hyphal cells, respectively.

Purification and properties of a beta-1,6-glucanase from Penicillium brefeldianum

An inducible endo-beta-1,6-glucanase was purified from Penicillium brefeldianum by DEAE-cellulose, Bio-Gel P-150 and high-pressure liquid chromatography. The final preparation was essentially free from beta-1,3-glucanase and beta-glucosidase activities. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed one protein band with an Mr of 44000. The Vmax. and Km values were calculated to be 624 units (mumol/min)/mg and 2.78 mg/ml respectively. The glucanase had lytic activity against mycelial cells of the yeast Candida albicans. The yield of purified beta-1,6-glucanase from 100 mg dry weight of freeze-dried culture filtrate varied from 60 to 180 units.

The secretion of N-acetylglucosaminidase during germ-tube formation in Candida albicans

N-Acetylglucosaminidase was induced by either N-acetylglucosamine or N-acetylmannosamine in several strains of Candida albicans. Enzyme activity was not induced in a N-acetylglucosamine non-utilizing mutant which is unable to express the first three steps in the N-acetylglucosamine catabolic pathway. The enzyme, purified 500-fold, had a specific activity of 36.8 units (mg protein)-1 and catalysed the hydrolysis of p-nitrophenyl-beta-n-acetylglucosamine, N,N'-diacetylchitobiose and N,N',N"-triacetylchitotriose. No activity was observed toward colloidal chitin, hyaluronic acid or mucin. The cellular distribution of N-acetylglucosaminidase was determined by measuring in situ enzyme activity before and after acid treatment of intact cells. N-Acetylglucosaminidase (80-88% of the total cellular activity) was rapidly secreted to the periplasm when the enzyme was induced either during yeast growth at 28 degrees C or germ-tube formation at 37 degrees C. Export of the enzyme from the periplasm into the medium was fourfold greater during germ-tube formation, and after 6 h incubation the amount of enzyme released into the medium represented 70% of cell-associated enzyme activity.

Magnesium and the regulation of germ-tube formation in Candida albicans

Candida albicans requires Mg2+ for germ-tube formation. Mg-deficient media, metal ion chelators and the ionophore A23187 inhibited germ-tube formation. Cell Mg content during exponential yeast-phase growth remained constant but increased throughout germ-tube formation. The onset of germ-tube formation coincided with a sharp peak in Mg concentration within the cells. Yeast-phase cells of strain CA2, which did not form germ-tubes, had a lower Mg content and failed to accumulate Mg when incubated under conditions for germ-tube formation. Mg also increased the uptake and incorporation of N-acetylglucosamine. These findings point to a central regulatory role for Mg in C. albicans morphogenesis.

What is the value of home blood pressure measurement in patients with mild hypertension?

To investigate the value of home blood pressure (BP) measurements, the BP was recorded daily by the patient at home and compared with recordings in the physician's office and with a 24-hour BP recording taken with a noninvasive ambulatory BP recorder in a group of 93 patients with mild untreated hypertension. Office BPs (mean 148/94 mm Hg) were higher than either home (138/89 mm Hg) or average 24-hour BPs (131/89 mm Hg). For systolic BP, home and office measurements gave similar correlations with 24-hour BP (0.67 and 0.55). For diastolic BP, however, home readings were lower and more accurate (0.76 vs 0.36). Thus, our findings indicate that home readings reflect the overall level of BP more reliably than office readings, and if due consideration is given to the fact that they are usually lower than office readings, they may be used as an alternative and cost-effective means of evaluating patients with mild hypertension.

Exo-(1----3)-beta-glucanase, autolysin and trehalase activities during yeast growth and germ-tube formation in Candida albicans

Exo-(1----3)-beta-glucanase, beta-glucosidase, autolysin and trehalase were assayed in situ in Candida albicans during yeast growth, starvation and germ-tube formation. Cell viability, germ-tube formation, intracellular glucose-6-phosphate dehydrogenase and beta-glucosidase were unaffected in cells incubated in 0.1 M-HC1 for 15 min at 4 degrees C. However, in situ trehalase, (1----3)-beta-glucanase and autolysin activities in acid-treated cells decreased by 95, 50 and 35% respectively, indicating that these enzymes are, in part, associated with the cell envelope. Trehalase activity increased throughout yeast growth and remained elevated during the first hour of incubation for germ-tube formation. All of the in situ trehalase activity in starved yeast cells could be measured without the permeabilizing treatment. beta-Glucosidase activity declined throughout yeast growth and did not alter during germ-tube formation. Both the (1----3)-beta-glucanase and autolysin activities were optimal at pH 5 X 6, inhibited by gluconolactone and HgCl2, and maximal at 15-16 h during yeast growth. Although autolysin activity increased by 50-100% when starved yeast cells were incubated for germ-tube formation, the in situ (1----3)-beta-glucanase remained constant. When acid-treated starved yeast cells were similarly induced, in situ (1----3)-beta-glucanase increased 100% over 3 h of germ-tube formation. Yeast cells secreted (1----3)-beta-glucanase into the growth medium. This was highest in early exponential phase cultures (34% of the maximum in situ activity) and declined throughout growth. (1----3)-beta-Glucanase was also secreted into the medium during germ-tube formation and this represented 80-100% of the in situ activity in germ-tube forming cells. Both secretion of (1----3)-beta-glucanase and germ-tube formation were inhibited by 2-deoxyglucose, ethidium bromide, trichodermin and azaserine.

Isolation and structure of glucan from regenerating spheroplasts of Candida albicans

Regenerating spheroplasts of Candida albicans formed organized glucan nets in liquid culture. The nets consisted of interwoven microfibrils about 50 nm wide, but of an undetermined length. Partial acid hydrolysis of the polysaccharide showed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues, but no intrachain beta(1----3) and beta(1----6) linkages. Periodate oxidation and GLC of the methylated glucan indicated a highly branched polymer (9.5% branch points). Sequential enzymic degradation of the isolated nets confirmed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues. Degradation by (1----3)-beta- and (1----6)-beta-glucanase released 23% (w/w) and 30% (w/w) respectively of the carbohydrate as glucose equivalents. The residual material was degraded by chitinase. Equal amounts of N-acetylglucosamine and glucose equivalents were detected in the chitinase hydrolysate, suggesting a possible linkage between glucan and chitin. Our data indicate that the cell wall of C. albicans contains at least two highly branched glucans with predominantly beta(1----3) or beta(1----6) linkages.

The control of morphogenesis in Candida albicans

Morphogenesis (germ-tube formation) in Candida albicans was induced gratuitously by N-acetylhexosamine derivatives (N-acetyl-glucosamine covalently linked to agarose, N-acetylmannosamine, hyaluronic acid, colloidal chitin, and mucin). These compounds were not taken up by the yeast cells and did not support growth. 2-Deoxyglucose was a potent inhibitor of germ-tube formation (50 microM), but did not affect the yeast growth yield at a concentration of 2.5 mM. 2-Deoxyglucose covalently linked to agarose did not affect germ-tube formation, and the inhibition by free 2-deoxyglucose was overcome by the addition of glucose to the germ-tube-forming cells. Glucose competitively inhibited 2-deoxyglucose uptake (Ki = 0.14 mM), and these data indicate that 2-deoxyglucose acted intracellularly.

Sex and strain differences in the developmental activity profile of rats prenatally exposed to sodium salicylate

Pregnant Sprague-Dawley (CD) and Long-Evans (LE) rats were treated by gavage on days 8-10 of gestation with either 0, 125 or 175 mg/kg/day sodium salicylate. Locomotor activity was monitored repeatedly for 30 min in the offspring on postnatal days 12, 16, 20, 24, 30, 60, 90 and 120 in the presence or absence of olfactory cues from home cage bedding. Prenatal exposure during organogenesis to the doses of sodium salicylate used here resulted in subtle alterations in developmental locomotor activity, the pattern of which was dependent on sex, strain and bedding condition during testing. Many more dose-related changes in activity were found in LE rats and, with one exception, these were decreased levels in treated rats. All significant dose-related differences in CD rats were increased activity levels in treated animals relative to controls. Male rats showed more dose-related changes in activity than did females, and activity testing conducted in the absence of home cage bedding cues resulted in a clearer distinction of treatment-related changes than did testing in the presence of home cage bedding. These results suggest a behavioral teratogenic effect of sodium salicylate. In addition, they point out the subtle nature of many behavioral effects in the absence of more overt toxicity and the impact factors such as strain, sex and procedural variables may have on the conclusions drawn from these studies.

Adaptation of EMIT reagents to the Cobas Bio centrifugal analyzer

Our adaptation of EMIT enzyme immunoassay reagents to the Cobas Bio centrifugal analyzer avoids the decrease in precision at the upper end of the therapeutic range reported in other adaptations. Long-term (12-month) CVs for lidocaine, valproic acid, and tobramycin were 5% or less; for quinidine, acetaminophen, and phenytoin, long-term CVs ranged from 7.2% to 8.6%.

Metabolism of [14C]glucose by regenerating spheroplasts of Candida albicans

Spheroplasts of Candida albicans were regenerated in [14C]glucose and buffered magnesium sulphate (0.1 M-Tris/HCl; 0.5 M-MgSO4, pH 7.2) at 35 degrees C. Uptake of glucose by spheroplasts was faster than that by intact yeast cells. After 6 h, 65% of the glucose taken up by the yeast appeared as CO2 and 30% was incorporated into the cellular material. With spheroplasts, 55% of the glucose taken up was expired as CO2, 25% was excreted into the medium as other metabolites and 20% was incorporated into the cells. The regenerating spheroplasts excreted 14C-labelled carbohydrates into the medium which were fractionated on a Sephadex G-15 column. Acid hydrolysis of the low molecular-weight fraction yielded the following sugars: mannose (75.7%), fucose (3.8%), arabinose (3%), galactose (2.1%) and an unidentified monosaccharide (14%). Spheroplasts did not incorporate mannoprotein into the regenerated wall. The wall carbohydrate from regenerated spheroplasts was fractionated on the basis of solubility in sodium hydroxide. The alkali-insoluble fraction was analysed by sequential enzyme hydrolysis; 40% of the incorporated counts were associated with beta (1----3)-linked glucan and 50% with a mixed glucan comprising beta (1----3)- and beta (1----6)-linkages and chitin.

Sex and strain differences in the developmental activity profile of the rat tested over clean vs home cage bedding

In the first of two experiments, CD rat litters were used to characterize activity patterns obtained in a size-adjustable, single photodetector chamber. Beginning on postnatal Day 10 or 12, pups were tested repeatedly over clean bedding (C) or over bedding removed from each pup's home cage (HC). In C rats of both sexes and in HC females, short-term activity levels peaked on Day 16. However, HC males displayed an earlier and even greater elevation in activity from Day 12 to 16. This overall pattern was found in rats tested either every second or fourth day. In the second experiment, Long-Evans pups were assigned to each testing condition (C vs HC) and activity measured beginning on Day 12. Peak levels were seen in all Long-Evans rats on Day 16 and only females showed significant alterations as a function of bedding condition. When overall activity levels of the two strains were compared, significant differences were found on Days 12, 24, 30, and 120 in males, and 12, 24, and 30 in females. Significant differences between strains in activity as a function of bedding condition were found in males on Days 12, 20, 24, and 120 and in females on Days 12, 30, and 60. These data confirm the generality of a developmental hyperactivity phase in isolated juvenile rats. However, different patterns of hyperactivity were found in male vs female rats across strains. CD males were more active in the presence of HC olfactory cues, while in Long-Evans rats, female activity was affected more by bedding condition.