指示肺通气不均匀性的熵变及其同其他指标的理论比较

熵代表无序的水平，作者使用通气的熵变（ＥＣＶ）指示肺通气的不均匀性，ＥＣＶ定义为当前泡潮气量趋近于零时每摩尔被吸入气体从不均匀通气到均匀通气的熵变的极限。本文从熵的基本公式民地出ＥＣＶ的计算方程。用几个数学模型肺将ＥＣＶ同其他７个洗出指标进行了比较。８个指标中，只有ＥＣＶ仅取决于通气分布，其他７个指标不仅取决于通气分布，还同潮气量和死腔的大小有关。这影响了它们评价肺通气不均匀性的效果，ＥＣＶ的另一     

Altered expression of TGFB receptors and mitogenic effects of TGFB in pancreatic carcinomas.

Alteration of the transforming growth factor beta (TGFB) signalling pathway is important in pancreatic carcinogenesis, as shown by the frequent inactivation of the downstream target SMAD4. We recently analysed a series of pancreatic carcinoma cell lines with respect to alterations of five SMAD genes involved in TGFB signalling, and showed that SMAD4 was structurally rearranged in 42% of these. This pathway may, however, also be affected by alterations of genes whose products regulate the activation of TGFB as well as of TGFB receptor genes. We therefore studied the expression of UPA, UPAR, IGF2R, ALK5 (TGFBR1), TGFBR2, TGFBR3, ENG, ALK1, TGFB1, TGFB2, and TGFB3 in a series of 14 pancreatic carcinoma cell lines. We also analysed ALK5 and TGFBR2 for mutations, cell surface localisation of TGFBR2 and ENG, and TGFB1 response. No mutations of ALK5 or TGFBR2 were found. However, 4 cell lines were methylated within the ALK5 promoter region. ALK5 expression was strongly reduced in 9 cases, whereas TGFBR2 expression was increased in 12 of the cell lines. The TGFB signalling associated receptors ENG and ALK1 were co-expressed in 4 of the cell lines. There was no evidence for disruption of the UPAR-IGF2R TGFB activating pathway. The response to TGFB1 was analysed in 12 cell lines, and 6 of these (50%) showed increased proliferation. The cell lines stimulated by TGFB showed frequent mutations of SMAD4, KRAS2, and TP53, as well as frequent absence of CDKN2B expression. These results suggest that the ALK5-SMAD4 part of the TGFB signalling pathway is a major target for inactivation in pancreatic carcinomas, that the expression of TGFBR2, TGFBR3, and receptors involved in TGFB activation are maintained, and that alterations of components of the TGFB signalling pathway may be accompanied by a positive effect of TGFB on cell growth.     

EANM guidelines for ventilation/perfusion scintigraphy Part 1. Pulmonary imaging with ventilation/perfusion single photon emission tomography

Pulmonary embolism (PE) can only be diagnosed with imaging techniques, which in practice is performed using ventilation/perfusion scintigraphy (V/P_SCAN) or multidetector computed tomography of the pulmonary arteries (MDCT). The epidemiology, natural history, pathophysiology and clinical presentation of PE are briefly reviewed. The primary objective of Part 1 of the Task Group’s report was to develop a methodological approach to and interpretation criteria for PE. The basic principle for the diagnosis of PE based upon V/P_SCAN is to recognize lung segments or subsegments without perfusion but preserved ventilation, i.e. mismatch. Ventilation studies are in general performed after inhalation of Krypton or technetium-labelled aerosol of diethylene triamine pentaacetic acid (DTPA) or Technegas. Perfusion studies are performed after intravenous injection of macroaggregated human albumin. Radiation exposure using documented isotope doses is 1.2–2 mSv. Planar and tomographic techniques (V/P_PLANAR and V/P_SPECT) are analysed. V/P_SPECT has higher sensitivity and specificity than V/P_PLANAR. The interpretation of either V/P_PLANAR or V/P_SPECT should follow holistic principles rather than obsolete probabilistic rules. PE should be reported when mismatch of more than one subsegment is found. For the diagnosis of chronic PE, V/P_SCAN is of value. The additional diagnostic yield from V/P_SCAN includes chronic obstructive lung disease (COPD), heart failure and pneumonia. Pitfalls in V/P_SCAN interpretation are considered. V/P_SPECT is strongly preferred to V/P_PLANAR as the former permits the accurate diagnosis of PE even in the presence of comorbid diseases such as COPD and pneumonia. Technegas is preferred to DTPA in patients with COPD.     

Binding of bacteria to carbohydrates immobilized on beads to demonstrate the presence of cell-associated hemagglutinins in Vibrio cholerae

We describe a phase contrast microscopy method for direct observation of classical and El Tor vibrios to agarose beads containing covalently attached L-fucose or D-mannose. Binding of the vibrios to L-fucose beads was found to correlate with fucose-sensitive agglutination of human O erythrocytes, while binding of bacteria to beads with D-mannose was consistent with mannose-sensitive agglutination of chicken erythrocytes. Furthermore, vibrios expressing both fucose and mannose-sensitive hemagglutinins adhered equally to L-fucose and D-mannose-containing beads. Because this procedure is neither subject to biological variations in different populations of erythrocytes nor affected by other factors known to interfere with hemagglutination tests, it offers a suitable, more robust and specific alternative to detect functional adhesins in Vibrio cholerae and other bacteria.     

Effects of NO inhalation on pulmonary leukocyte sequestration and blood volume in porcine endotoxaemia

Objective: Sequestration and migration of activated neutrophils plays a major role in the pulmonary injury typical of septic shock and the adult respiratory distress syndrome. Inhaled NO may counteract alveolar-capillary damage attributed to activated neutrophils. The present study describes a method to directly demonstrate the effects of NO inhalation on endotoxin-induced sequestration of ^{99 m}Tc-labelled leukocytes [A_s(t)] in the lungs of pigs.¶Design: Prospective controlled study.¶Setting: Laboratory for experimental surgery at a university medical centre.¶Subjects: Anaesthetised and ventilated pigs.¶Interventions: To induce inflammatory shock 26 animals received a continuous endotoxin infusion. Thirteen animals inhaled NO from the start of the experiments, while 13 served as controls. In 13 animals from both groups, leukocytes were labelled in vitro and reinjected, while in the 13 others erythrocytes were labelled in vivo to provide corrections for changes in blood volume.¶Measurements and results: The pulmonary distribution of ^{99 m}Tc-labelled leukocytes or erythrocytes was studied dynamically for 180 min. After correction for changes in pulmonary and heart blood volume (PBV, HBV), leukocyte sequestration curves were generated. Endotoxin induced pulmonary vasoconstriction, reduced PBV, impaired oxygenation, and caused a maximum increase in A_s(t) of 30 % in the lungs. NO inhalation attenuated pulmonary vasoconstriction and the reduction in PBV. The maximum increase in A_s(t) was reduced to 15 % of baseline.¶Conclusions: Inhaled NO exerts its main vascular effects in the pulmonary microvasculature, the primary site of physiological neutrophil margination and pathological adhesion of activated leukocytes. Early use of NO inhalation may offer protection against the development of more lasting pulmonary failure in septic shock by reducing leukocyte sequestration in the lungs.     

A new CT method for measuring cup orientation after total hip arthroplasty

Background It is difficult to assess the orientation of the acetabular component on routine radiographs. We present a method for determining the spatial orientation of the acetabular component after total hip arthroplasty (THA) using computed tomography.

Patients and methods Two CT-scans, 10 min apart, were obtained from each of 10 patients after THA. Using locally developed software, two independent examiners measured the orientation of the acetabular component in relation to the pelvis. The measurements were repeated after one week. To be independent of the patient position during scanning, the method involved two steps. Firstly, a 3D volumetric image of the pelvis was brought into a standard pelvic orientation, then the orientation of the acetabular component was measured. The orientation of the acetabular component was expressed as operative anteversion and inclination relative to an internal pelvic reference coordinate system. To evaluate precision, we compared measurements across pairs of CT volumes between observers and trials.

Results Mean absolute interobserver angle error was 2.3° for anteversion (range 0-6.6°), and 1.1° for inclination (range 0-4.6°). For interobserver measurements, the precision, defined as one standard deviation, was 2.9° for anteversion, and 1.5° for inclination. A Student's t-test showed that the overall differences between the examiners, trials, and cases were not significant. Data were normally distributed and were not dependent on examiner or trial.

Interpretation We conclude that the implant angles of the acetabular component in relation to the pelvis could be detected repeatedly using CT, independently of patient positioning.     

Quantitative SPECT by attenuation correction of the projection set using transmission data: evaluation of a method

A method for measuring attenuation coefficients in single-photon emission tomography (SPECT) is described and evaluated, together with a method for attenuation correction using these measured attenuation coefficients. Build-up, caused by scattered photons, is corrected for by a simple substitution in the algorithms. Transmission studies are performed with a 99mTc- or 57Co flood source, and emission phantom studies with 99mTc line sources. The method is evaluated with variable but well-defined phantoms. The result is accurate attenuation coefficients for different densities, dimensions and geometries, and an accuracy of corrected emission activities of better than +/- 10% in most cases. The present limitations of the method for attenuation correction are discussed.     

Anaphylactic bronchoconstriction in immunized guinea pigs provoked by inhalation and intravenous administration of hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride

We established a guinea-pig model of anaphylactic bronchoconstriction provoked in immunized animals by inhalation and intravenous administration of 4,4-methyltetrahydrophthalic anhydride (MTHPA) and hexahydrophthalic anhydride (HHPA). Guinea pigs were immunized intradermally with either MTHPA ( n = 8) or HHPA ( n = 8) suspended in olive oil. Control animals ( n = 8) were injected with olive oil alone. After 4 weeks, the animals were challenged during mechanical ventilation by inhalation or intravenous administration of MTHPA or HHPA conjugated with guinea-pig serum albumin (GPSA). Airway flow, and airway and esophageal pressures were measured. Resistance ( R ) and static compliance (Cst) of the respiratory system (rs), lung (1), and chest wall were studied with the flow-interruption technique. After challenge with MTHPA-GPSA or HHPA-GPSA, R , rs and R , 1 increased dramatically while Cst, rs and Cst,1 decreased, and severe arterial hypoxia developed. The reaction occurred at a well-defined dose of anhydride and lasted about 30 min. When the same dose was repeated after 30 min, the response was much attenuated. MTHPA and HHPA can induce asthma in guinea pigs. The dose-response curve at antigen challenge is steep. Once a threshold dose is reached, a severe reaction occurs. The reactivity is then exhausted. This model may be suitable for assessing occupational asthma caused by acid anhydrides and possibly by other low-molecular-weight chemicals.