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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Noninvasive measurement of myocardial blood flow in absolute terms (i.e., milliliters per gram per min) has been difficult to accomplish despite the intrinsically quantitative power of positron emission tomography because of the nonphysiologic nature of tracers that have been employed conventionally as well as the limited spatial resolution of currently available instruments. It was previously demonstrated that myocardial blood flow in animals can be quantitated accurately with the diffusible tracer oxygen-15-labeled water (H2(15)O) when the arterial input function and myocardial radiotracer concentration were measured directly. To extend the approach for completely noninvasive measurement of blood flow, a parameter estimation procedure was developed whereby effects of limited tomographic spatial resolution and cardiac motion were compensated for within the operational flow model. In validation studies in 18 dogs, myocardial blood flow measured with positron emission tomography after intravenously administered H2(15)O correlated closely with flow measured with concomitantly administered radiolabeled microspheres over the range of 0.29 to 5.04 ml/g per min (r = 0.95). Although regional ischemia was clearly identifiable tomographically, absolute flow could not be determined accurately in ischemic regions in four dogs because of poor count statistics related to wall thinning. Subsequently, myocardial blood flow was measured in 11 normal human subjects. Flow was homogeneous throughout the myocardium, averaged 0.90 +/- 0.22 ml/g per min at rest and increased to 3.55 +/- 1.15 ml/g per min after intravenous administration of dipyridamole. Therefore, positron emission tomography with H2 15O and the approach developed permits noninvasive measurement of myocardial blood flow in absolute terms in humans and should facilitate objective assessment of interventions designed to enhance nutritive perfusion.
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PMID:Noninvasive quantitation of myocardial blood flow in human subjects with oxygen-15-labeled water and positron emission tomography. 278 69

Preservation solutions for short-term storage of isolated donor corneas for use in penetrating keratoplasty have all been based on tissue culture medium, on the assumption that media designed to maintain the viability of cells at physiological temperatures will also provide suitable conditions for preservation at reduced temperatures. But for hypothermic preservation of some other tissues and organs, when ionic pumps are inhibited, it is unnecessary to support metabolism, and beneficial control of ion and water distribution between intra- and extracellular compartments is achieved by storage in appropriately formulated 'intracellular-type' solutions. We have therefore designed a solution that will restrict ionic imbalances and minimise endothelial cell swelling in corneas during exposure at reduced temperatures. This potassium-rich solution contains the biological pH buffer TES as an impermeant anion and is designated CPTES (corneal-potassium-TES). The structural and functional integrity of rabbit corneas stored at 0 degrees C in CPTES, without the addition of colloid osmotic agents, is compared with that of corneas stored in glutathione bicarbonate Ringers' solution (GBR), an 'extracellular-type' medium formulated for the maintenance of endothelial integrity during in-vitro perfusion at 34 degrees C. Corneas swelled significantly less during storage in CPTES than in GBR and could be stored for five days before reaching the same degree of hydration as corneas stored for only three days in GBR. Gross structural integrity and endothelial ultrastructure were maintained during storage for three and five days in CPTES. The rate of thinning of corneas stored in CPTES was significantly greater than in comparable groups of corneas stored in GBR. However, the efficient dehydration of corneas stored in CPTES was always preceded during perfusion by a brief period of additional swelling which was shown to be an osmotic response during the elution of the buffer compound TES that had permeated the stroma during storage. The omission of calcium or the addition of adenosine and glutathione to the CPTES preservation medium had no detectable effect on the integrity of the endothelium, but the omission of bicarbonate was beneficial, producing significantly higher rates of stromal thinning during normothermic perfusion. Additional benefits for extending storage by including colloid osmotic agents are described in a companion paper.
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PMID:Hypothermic preservation of corneas in a hyperkalaemic solution (CPTES): I. Short-term storage in the absence of colloid osmotic agents. 281 86

Structural changes in a ternary gel prepared using the mixed emulsifier system of cetrimide and cetostearyl alcohol after prolonged low temperature (4 degrees C) storage have been studied using freeze-etch transmission electron microscopy and other techniques. The system changed from an opaque smooth gel of high viscosity, low conductivity and low free water, to a pearlescent milky lotion of low viscosity, high conductivity and high free water. Subsequent equilibration of the thinned system to room temperature (25 degrees C) over 48 h produced an opaque granular gel of similar consistency, but slightly higher conductivity and higher free water than the initial sample. Microscopical examination by both differential interference contrast and freeze-etch electron microscopy showed the system changed from one consisting of a liquid crystalline network localized around cetostearyl alcohol particles, to a system consisting of large waxy plates coexisting with some residual liquid crystalline network. A supportive mechanism for the thinning of the ternary gel at prolonged low temperature storage has been inferred by comparing data with that produced by other workers studying the fusion of phospholipid membranes considered to be morphologically similar to the liquid crystalline network observed in this ternary gel.
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PMID:An investigation of the structural changes occurring in a cetostearyl alcohol/cetrimide/water gel after prolonged low temperature (4 degrees C) storage. 286 99

Water vapour conductance (GH2O) was determined for 25 grey heron Ardea cinerea eggs in the laboratory, and in nests during natural incubation at two Scottish colonies. The mean GH2O of eggs measured in the nest which successfully hatched was 9.0 mgH2O/mmHg/day and the mean water vapour pressure gradient between egg and nest (delta PH2O), measured using "calibrated" duck eggs, averaged at 31 mmHg (4.13 kPa). Based on eggshell porosity results, from the eggs which hatched, such a gradient would result in a loss of water from the eggs during incubation equivalent to 11% of their fresh weight. Shell thickness, the number of pores/cm2 of eggshell and DDE content were also determined for the 25 eggs measured in the laboratory. Eggs containing high levels of DDE had thinner shells, more pores in the eggshell and a higher overall eggshell porosity. The main problem posed by a high level of DDE would appear, however, not to be an excessive water loss from the egg during incubation, but rather eggshell thinning leading to a loss of the egg due to breakage in the nest.
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PMID:A note on eggshell porosity, nest humidity and the effects of DDE in the grey heron (Ardea cinerea). 287

The influence of soft contact lenses (SCL) with low (37%, L) and high (65%, H) water content on rabbit corneas was investigated. The lenses were worn continuously for 1, 2, 4, 7, 10, 14, 21 or 28 days. The changes in corneal transparency, hydration and enzyme activities were studied. A slight change in corneal transparency due to higher hydration caused by a decreased activity of Na+-K+-dependent adenosine triphosphatase (Na+-K+-ATPase) in the corneal endothelium is followed by a decrease in the activity of gamma-glutamyl transferase (GGT). Slight morphological disturbances appear within 4 days in animals wearing SCL (L). SCL (H) produce similar changes one week later. Subsequently, the corneal epithelium becomes thinner and changes in the size of corneal endothelial cells are obvious. Disturbances of enzyme activities in cells of all corneal layers are present. In the epithelium highly increased activities of acid glycosidases, acid phosphatase, and dipeptidyl peptidase I and II, in keratocytes decreased activities of alkaline phosphatase and GGT, and in the endothelium decreased activity of Na+-K+-ATPase and GGT were found. These changes are more severe after SCL (L). In this case, inflammatory cells displaying high activities of lysosomal hydrolases appear in the anterior part of the stroma during the 3rd and 4th weeks and local degradation of glycosaminoglycans and proteins takes place. In contrast, after SCL (H) a remarkable thinning of the corneas was observed during extended wear, accompanied by decreased stainability of stromal glycosaminoglycans and highly decreased enzyme activities in keratocytes. The histochemical methods proved very useful in the assessment of lesions caused by a continuous wear of SCL.
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PMID:Disturbances in the rabbit cornea after short-term and long-term wear of hydrogel contact lenses. Usefulness of histochemical methods. 289 48

The basic magnetic resonance (MR) imaging pattern of normal and degenerated hyaline articular cartilage was studied in vitro in 40 fresh bovine patellae. With the use of an ample spectrum of strongly T1- to T2-weighted sequences, two zones of cartilage with different signal intensities were observed in all specimens. A superficial cartilaginous layer in the MR image with higher water content and longer T1 and T2 correlated with the tangential and transitional zones of normal articular cartilage, whereas a second MR imaging zone with shorter T1 and T2 was identified in the depth of the articular cartilage. Different functional properties in pressure resistance were observed in the two layers. In early cartilage degeneration without thinning, there was increased hydration of the superficial cartilage layer. This study suggests that strongly T1- and T2-weighted images are indispensable for evaluating details in articular cartilage degeneration.
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PMID:Structure, function, and degeneration of bovine hyaline cartilage: assessment with MR imaging in vitro. 291 74

Cardiac depression in the isolated rat heart perfused with 4% ethanol was correlated with intracellular phosphate energetics and tissue water distributions. Energy metabolites were assessed using 31P magnetic resonance spectroscopy (MRS) and correlated to the mitochondrial redox state using epicardial surface fluorometry. Changes in myocardial water compartmentation were measured by using 1H NMR spectroscopy with an extracellular chemical-shift reagent (DyTTHA) and correlated to results of 2D echocardiography (2DE). During alcohol perfusion there was a significant decrease in developed pressure and in coronary flow. No change was seen in ATP, PCr, pHi, Pi, or NADH. After withdrawal of alcohol from the perfusate cardiac function reverted to control values without a depletion of energy levels. During alcohol perfusion 1H MRS showed a marked redistribution of water from the intra- to the extracellular space, corresponding to a 35% left ventricular wall thinning confirmed by 2DE. The results indicate that acute alcohol cardiac depression is related to a dehydration of myocardial cells, but is not associated with intracellular acidosis or energy depletion.
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PMID:31P and 1H magnetic resonance spectroscopy of acute alcohol cardiac depression in rats. 317 69

To determine the serial changes in T1 and T2 relaxation times of myocardial infarction, and their relationship to observed changes in water content, regional myocardial blood flow, and histopathology, rabbits were studied at 14 time intervals ranging from 30 min to 6 months after coronary artery ligation. All values were compared to a control group. Hearts were subdivided into infarct and normal segments for measurement of blood flow, water content, and relaxation times (20-MHz spectrometer); other hearts were excised intact for histopathologic studies. T1 relaxation time of infarcted myocardium did not change significantly compared to control over the 6-month study period. T2 relaxation time increased (P less than 0.0001) at 3 days and returned to baseline by 2 months. Consonant with the increase in T2 of infarct, nuclear magnetic resonance (NMR) images at 3 days demonstrated an increase in signal intensity of infarct compared to surrounding normal myocardium. At 6 months, marked myocardial thinning was observed without changes in signal intensity. Changes in T2 of infarcted myocardium were not related to changes in water content or severity of ischemia, but correlated best with infarct healing and scar formation as detected on histopathology. In conclusion, the findings of this study indicate that T2 relaxation time of the infarcted myocardium increases markedly at 3 days and remains elevated for 2 months. These changes correlate best with the onset and progression of infarct healing. These data demonstrate the potential of T2-weighted NMR imaging for assessing healing patterns following ischemic myocardial injury.
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PMID:Serial changes in nuclear magnetic resonance relaxation times after myocardial infarction in the rabbit: relationship to water content, severity of ischemia, and histopathology over a six-month period. 323 Oct 66

The incidence of tracheal tube cuff rupture was noted in 30 polyvinyl chloride tracheal tubes lubricated with three different solutions. All cuffs moistened with water were intact after 2 hours of cuff inflation whereas two of 10 lubricated with 4% lignocaine solution had burst. Both of these had leaked at the site of cuff attachment to the tube. Fifty percent of tubes lubricated with Astra lignocaine spray burst during the study. Four of the five had developed pinholes in the cuffs themselves. The remaining 50% of this group showed marked distortion and thinning of their intact cuff walls. The implications of these findings are discussed in view of the widespread use of PVC tracheal tubes.
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PMID:Cuff failure in polyvinyl chloride tracheal tubes sprayed with lignocaine. 275 69

The authors present a map of malaria transmission intensity in Brazzaville from which they analyse the impact of urbanization on anopheline density and transmission of malaria. Whereas at first each new human settlement promotes the introduction or the proliferation of A. gambiae, the major vector of malaria in Central Africa, urban growth later proves to be unfavourable to this vector. Apart from the canalization of surface water and improvement in sanitation, it is the increase in population density which seems, by its direct or indirect consequences in urban areas, to determine the decrease in malaria transmission intensity. By favouring the absorption of the last remaining open spaces and by the accompanying domestic pollution, urbanization tends to eliminate an increasing number of A. gambiae breeding places; by limiting the dispersion of anopheles from breeding sites, it tends to focus malaria transmission and by thinning out the subsisting anopheline population among a denser human population, it tends to reduce the degree of exposure of each person.
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PMID:Malaria and urbanization in central Africa: the example of Brazzaville. Part III: Relationships between urbanization and the intensity of malaria transmission. 345 64


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