Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in linking number and the apparent winding angle of pBR322 DNA have been evaluated in mixed ethanol-water solvents containing either Na or Mg as the major counterion contributing to the electrostatic shielding of the duplex. The average number of superhelical turns (tau) produced in the standard electrophoresis buffer (Tris-borate-EDTA, pH 8.0) by the transfer of DNA, relaxed in 200 mM NaCl, 10 mM NaH2PO4/Na2HPO4, and 2 mM EDTA, pH 7, by calf thymus topoisomerase or ligated in 6.6 mM MgCl2, 1 mM KCl, 1 mM ATP, 1 mM dithiothreitol, and 66 mM Tris, pH 7.6, by T4 ligase, was determined as a function of the EtOH concentration. At low enzyme concentrations, the tau values became increasingly more positive in the presence of both cations as the ethanol concentration increased, indicating that the duplex structure was overwound in the ethanol solvents. Winding angle changes between 0 and 20% ethanol, calculated from these values of tau, exhibited the same correlations with CD spectral properties as had been previously observed for 100% aqueous systems containing monovalent cations [Kilkuskie, R., Wood, N., Shinn, R., Ringquist, S., & Hanlon, S. (1988) Biochemistry 27, 4377-4386]. The results at higher concentrations of ethanol (25-30%), however, were anomalous for the Mg-ligase system. The anomalies increased with higher ethanol, ligase, or Mg concentration. Gel run under these conditions showed enhanced concentrations of slow-moving components, indicative of ligation of intermolecular associated DNA species. At a 10-fold higher level of ligase, ethanol appeared to unwind the duplex, confirming the results of Lee, Mizusawa, and Kakefuda [(1981) Proc. Natl. Acad. Sci. U.S.A. 78, 2838-2842]. All of these anomalies occur under solvent conditions which are close to conditions which produce a heterogeneous dispersion of sedimenting species in ultracentrifugal experiments and compact rodlike structures, visualized by electron microscopy. The circular dichroism spectra at the onset of the formation of these structures show the characteristics of a chirally packed array of DNA duplexes. The reversal of the trend of the ethanol effect on linking number at higher enzyme and Mg(II) concentrations can be most easily explained by the promotion of the condensation phenomenon by either the ligase or a contaminating factor in the preparation. We suggest that the anomalies in the linking number and winding angle values are due to either ligation of chirally bent DNA species or a change in the helical period as the linear DNA adapts to the conformation required for collapse.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Linking number anomalies in DNA under conditions close to condensation. 265 31

A new suprapubic device that regulates the intravesical pressure automatically during TUR is introduced. This flow controller ensures a constantly low intravesical pressure during TUR. The irrigation fluid constantly flows over into a small open glass jar adjusted to the trocar immediately above the abdominal wall. In this way the pressure is determined by the height of the jar above the bladder, which makes it independent of the irrigation flow. Having constant low pressure conditions between 14 and 18 cm H2O, the bladder wall does not collapse. Thus, the anatomical situation does not change throughout the entire operation, which leads to markedly better overall vision.
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PMID:[Pressure constant, transurethral resection with the new suprapubic "overflow regulator"]. 271 96

It was previously shown that multiple structural variants of the V-1 antigen (variable antigen 1) of Mycoplasma pulmonis could be found within a single strain. This antigen is unusual in that it produces a ladder pattern after sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The present study showed that some variants of V-1 could be extracted into the aqueous phase of a phenol-H2O system. Analysis with anti-V-1 monoclonal antibodies showed that the phenol-H2O-extracted V-1 had a regular spacing of 3.1 kilodaltons (kDa) between bands and trypsinization of this extracted V-1 resulted in the gradual symmetrical collapse (2.9-kDa increments) of the ladder into a single band, suggesting the presence of multiple identical subunits within the V-1 structure. The upper band from the phenol-H2O-extracted V-1 was isolated and analyzed by SDS-polyacrylamide gel electrophoresis immunoblotting, resulting in the regeneration of the original ladder pattern with 3.1-kDa spacing between bands. When V-1 was boiled for increasing times in the presence of SDS, the staining intensity of the upper band decreased with the concurrent appearance of additional lower-molecular-weight bands. Finally, by using whole cells, it was found that the lower-molecular-weight species of the ladder pattern selectively partitioned into the hydrophobic phase of a Triton X-114 phase partitioning system, and the higher-molecular-weight bands were found in the aqueous phase. These data indicate that the V-1 bands are composed of subunits which may aggregate via hydrophobic interactions and that these aggregates at least partially dissociate when exposed to harsh denaturing conditions, resulting in the characteristic ladder pattern of V-1.
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PMID:Subunit structure of the variable V-1 antigen of Mycoplasma pulmonis. 272 35

Effects of sodium bromate on cochlear potentials and electrolyte composition of the cochlear fluids in guinea pigs were investigated following administration of sodium bromate into the cochlea, using perilymphatic perfusion. Cochlear microphonics and the whole nerve action potential of the auditory nerve were markedly suppressed. The K+ and Cl- activities in the endolymph as well as the endocochlear dc potential (EP) decreased significantly and irreversibly, in proportion to the concentration of sodium bromate. A negative EP never developed during the monitoring of 120 min. Microsamples of the endolymph showed substantial decreases of K+ and Cl- concentrations and an increase in the concentration of Na+. Osmolality of the endolymph was much lower than that of the perilymph. The severe edema of the stria vascularis and collapse of Reissner's membrane were histologically evident. These events suggest a breakdown of the endolymph-perilymph barrier, coincident with an inhibition of the strial active transport, as a result of the ototoxic action of sodium bromate. The possible ion and water movement across the endolymph-perilymph barrier in the presence of sodium bromate is discussed.
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PMID:Effects of sodium bromate on ionic concentrations and osmolalities of the cochlear fluids in guinea pigs. 275 29

Edematous reactions surrounding brain lesions are less extensive in old patients. There also is a general tendency of the aging brain to be vulnerable to osmotic stress, to yield space, and to collapse. In order to elucidate these clinical phenomena, brain sodium, potassium and water, brain osmolarity, and Na+-K+-ATPase activity were studied in old and young rats following three experimental aggressions: cold induced vasogenic edema, osmotically induced edema, and osmotically induced dehydration. This study supports the hypothesis that: (a) extracellular edema is slightly smaller in the aged brain, but cellular swelling is relatively greater and (b) that protective adaptation of brain volume to acute osmotic changes is less efficient and slower in the aged brain.
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PMID:Brain water and aging. 282 97

The rate of collapse of a proton gradient across the apical membrane of rat kidney proximal tubule increases upon treatment with calcium, mercuric chloride and mellitin, substances which activate phospholipase A2. Treatment with phospholipase A2 or oleic acid also enhances the rate of proton gradient dissipation. Membrane water permeability is not affected. This phenomenon may have implications in pathological states arising from ischemia or toxic exposure.
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PMID:Phospholipase activation, free fatty acids and the proton permeability of a biological membrane. 283 61

Pituitary function and short-term clinical effects after transsphenoidal hypophysectomy were investigated in clinically normal dogs. In study I, 8 dogs were given polyionic fluids IV during the first 12 hours after surgery. In study II, 4 dogs were given polyionic fluids IV and glucocorticoid supplementation for 7 days. Pituitary function was assessed by evaluating basal ACTH concentrations and results of a growth hormone stimulation test before and 1 and 12 weeks after hypophysectomy, an ACTH stimulation test, a thyrotropin-releasing hormone-stimulation test, and a modified water deprivation/vasopressin response test before and 1, 4, 8, and 12 weeks after hypophysectomy. Gross and histologic evaluations of the surgery site, thyroid and adrenal glands, and skin were done at 12 weeks after surgery. Four dogs from study I died within 27 hours after hypophysectomy. Postmortem examinations of these dogs revealed liver and lung congestion compatible with circulatory collapse. None of the dogs in study II died. For the surviving dogs in both studies, diabetes insipidus developed immediately after hypophysectomy and resolved within 2 weeks. Hypernatremia also developed immediately after hypophysectomy and resolved by 1 week. Production of ACTH was evident at 1 and 12 weeks after hypophysectomy in all dogs, and results of ACTH stimulation tests after surgery were not notably different from results obtained before surgery. Results of thyrotropin-releasing hormone stimulation and growth hormone-stimulation tests supported the diagnosis of hypothyroidism and hyposomatotropism attributable to hypophysectomy. Histologic examination revealed thyroid atrophy, epidermal and dermal atrophy, and normal adrenal glands in all dogs and remnants of the hypophysis in 2 dogs from study I.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transsphenoidal hypophysectomy in the clinically normal dog. 284 9

The two mitochondrial Na+/H+ antiporters differ in several important respects, and the most physiologically significant of these may be their differences in regulation. The Mg2+-dependent Na+/H+ antiporter controls mitochondrial volume in a dangerous, high-K+ environment. To play this vital role, this porter must always lie poised far from K+/H+ equilibrium; i.e., it must be under dynamic regulation, as proposed in the Mg2+ carrier-brake hypothesis (7). Being regulated, it is not necessary for this antiporter to be cation-selective, since all electroneutral cation movements will be followed by redistributions of anions and water. On the other hand, there is no indication at present that the Mg2+-independent Na+/H+ antiporter is regulated. This transporter is therefore required to exhibit high discrimination against K+ in order to prevent the collapse of matrix volume dueto uncontrolled loss of K+ salts and water (4). Do the properties of the mitochondrial Na+/H+ antiporters help us in any way to understand the plasmalemmal Na+/H+ antiporters? I believe they do, if we allow that there are a limited number of ways in which nature constructs such porters. The difference in cation selectivities very likely reflects a fundamental structural difference between the two mitochondrial antiporters, and this difference appears to be mirrored in two types of plasmalemmal Na+/H+ antiporters. Thus, the Mg2+-independent Na+/H+ antiporter resembles the renal tubular Na+/H+ antiporter in its discrimination against K+ and its competitive inhibition by Li+. On the other hand, the Mg2+-dependent Na+/H+ antiporter resembles a cardiac sarcolemmal Na+/H+ antiporter which transports all alkali cations, including Na+ and K+, and which is inhibited by DCCD and amphiphilic amines (S. Kakar, A. Askari and K. Garlid, in preparation). The existence of the latter class of antiporter in plasmalemma may seem unlikely at first glance, since it would tend to catalyze Na+/K+ exchange and dissipate the effects of the Na+,K+-ATPase. Nevertheless, a sound design principle would be followed if the cell, like mitochondria, were to regulate volume by governing a passive back-flow process rather than an active transport process. In conclusion, it seems premature to conclude that plasma membranes contain only one type of Na+/H+ antiporter. Nor does it seem likely that there is an unlimited variety of such transporters. I propose as a working hypothesis that antiporters from both mitochondria and plasmalemma may be separated into two classes: Na+-selective and non-Na+-selective.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Sodium/proton antiporters in the mitochondrial inner membrane. 285 Jul 31

Surface pressure-area isotherms (pi-A) of poly(isobutylcyanoacrylate) monolayers with or without glucose and dextran as polymerization adjuvants used in the preparation of nanoparticles have been derived from measurements made at the air-water interface with the subphase pH at 2.7, 5.5 or 8.8. The isotherms were characteristic of the expanded type of polymer monolayer curves, yielding unusually low limiting area values compared with those of other known poly(acrylate) derivatives. This behaviour may be explained by the folding of polar moieties of the polymer groups in the water subphase. Ampicillin incorporated during preparation of nanoparticles had a negligible effect on the general behaviour of adjuvant-free monolayers, but a significant one on the adjuvant-loaded polymer monolayer system which showed an increase in surface area throughout the compression cycle, as compared with the surface area of the adjuvant-free polymer system although the collapse pressure was practically the same at 67 mN m-1.
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PMID:Monolayer studies on poly(isobutylcyanoacrylate)-ampicillin association. 289 44

Previous studies have shown that upper airway muscle activity is augmented in response to increased respiratory drive, thereby improving upper airway patency. In the present study we evaluated the effect of salicylate, a well-known respiratory stimulant, on upper airway stability and pressure-flow relationship. Multiple levels of airflow were used to assess pressure-flow relationship in the isolated airways of anesthetized dogs and to calculate the coefficients of Rohrer's equation P = K1V + K2V2. In addition, we measured the negative intraluminal pressure needed to collapse the upper airway. These measurements were repeated after intravenous administration of sodium salicylate, 250 mg/kg. Salicylate-induced hyperventilation was associated with increased alae nasi electrical activity. Resistance to airflow and K2 decreased significantly (p less than 0.01), suggesting dilation of the upper airway lumen. The intraluminal pressure under which upper airway collapse occurred became more negative in all dogs (from -5.0 +/- 0.8 to -8.5 +/- 1.3 cm H2O, p less than 0.01), indicating improved stability of the upper airway walls. These findings suggest that salicylate, and presumably other pharmacologic agents that stimulate ventilation, can improve both upper airway patency and upper airway stability.
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PMID:Effect of salicylate on upper airway stability and pressure flow: relationship in anesthetized dogs. 290 55


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