Divergent regulation of vascular endothelial growth factor and of erythropoietin gene expression in vivo

There is accumulating evidence from in vitro experiments that the gene expression of the vascular endothelial growth factor (VEGF) is, like that of the erythropoietin (EPO) gene, regulated by the oxygen tension and by divalent cations such as cobalt. Since the information about the regulation of VEGF gene expression in vivo is rather scarce, this study aimed to examine the influence of hypoxia and of cobalt on VEGF gene expression in different rat organs and to compare it with that on EPO gene expression. To this end male Sprague-Dawley rats were exposed to carbon monoxide (0.1% CO), hypoxia (8% O₂ ) or to cobalt chloride (12 and 60 mg/kg s.c.) for 6 h. mRNA levels for VEGF- 188, -164, and -120 amino acid isoforms in lungs, hearts, kidneys and livers were semiquantitated by RNase protection. For these organs we found a rank order of VEGF mRNA abundance of lung >> heart > kidney = liver. EPO mRNA levels were semiquantitated in kidneys and livers. Hypoxia, CO and cobalt increased EPO mRNA levels 60-fold, 140-fold and 5-fold, respectively, in the kidneys, and 11-fold, 11-fold and 3-fold, respectively, in the livers. None of these manoeuvres caused significant changes of VEGF mRNA in lung, heart or kidneys. Only in the livers did hypoxia lead to a significant (50%) increase of VEGF mRNA. These findings suggest that, in contrast to the in vitro situation, the expression of the VEGF gene in normal rat tissues is rather insensitive to hypoxia. In consequence, the in vivo regulation of the VEGF and the EPO genes appear to differ substantially, suggesting that the regulation of the VEGF and EPO genes may not follow the same essential mechanisms in vivo. Received: 31 July 1995/Received after revision: 20 November 1995/Accepted: 27 November 1995     

CO对局灶性缺血脑组织血脑屏障通透性的影响

目的:研究一氧化碳及其限速酶(血红素氧合酶-1)对局灶性缺血脑组织血脑屏障通透性的影响。方法:将SD大鼠随机分为3组(n=6),使用血红素氧合酶诱导剂及抑制剂腹腔注射,用等量生理盐水腹腔注射作为对照组,12h后复制MCAO模型。梗塞后24h后检测血液中一氧化碳浓度、血脑屏障通透性。结果:诱导剂组一氧化碳浓度明显高于对照组(P＜0.01),血脑屏障通透性明显低于对照组(P＜0.05),而抑制剂组一氧化碳浓度明显低于对照组(P＜0.01),血脑屏障通透性明显高于对照组(P＜0.05)。血红素氧合酶诱导剂、抑制剂对非梗塞侧的血脑屏障通透性没有影响(P＞0.05)。结论:一氧化碳作为一种信使分子,脑缺血时浓度升高具有保护血脑屏障的作用。     

Reproducibility of the parameters of the on-transient cardiopulmonary responses during moderate exercise in patients with chronic obstructive pulmonary disease

To be clinically useful as indices reflective of altered physiological function consequent to interventions in patients with chronic obstructive pulmonary disease (COPD), the time constant (τ) and steady-state amplitude of the kinetic responses for oxygen uptake ( ) carbon dioxide output ( ) ventilation ( ) and heart rate (HR) have to be appropriately differentiable and reproducible. We therefore assessed the reproducibility of τ and steady state amplitude values in 41 patients with severe COPD [mean (SD)] [forced expiratory volume in 1 s=41 (7)% predicted], aged 64 (5) years. Of the total, 6 of the patients (15%) did not produce breath-by-breath data of sufficient quality to warrant kinetic analysis. The remaining 35 patients completed two moderate-intensity 10 min square-wave exercise tests separated by 2 h, both before and after an endurance training programme. Tests were conducted on an electromagnetically-braked cycle ergometer at an exercise intensity corresponding to 80% of the estimated lactate threshold (θ_La) or 50% of peak oxygen uptake if θ_La was insufficiently differentiable. Breath-by-breath measurements of , , and HR were averaged into 10 s bins and the on-transient response kinetics were estimated using a mono-exponential model. Analysing the pre-training and the post-training test 1 and test 2 comparisons together, the test 1 –test 2 differences were not significantly different from 0 for either τ or A. The standard deviation of the test 1 –test 2 differences allowed us to define the magnitude of change that would reach statistical significance. For τ, this averaged some 8, 10, 11 and 8 s, for , , and HR, respectively, for a one-tailed paired-comparisons test (i.e. appropriate for assessing hypothesised improvements resulting from an intervention); for a two-tailed comparison, the differences were approximately 2 s greater. The corresponding one-tailed values for A were 100 ml·min^–1, 95 ml·min^–1, 2.5 1·min^–1 and 4 beats·min^–1, respectively; the two-tailed values were 10%–15% greater. We therefore conclude that both τ and A for moderate-intensity exercise can be reproducibly estimated in patients with COPD when the data set provides a sufficiently large amplitude of response and sufficiently low sample variability to allow appropriate parameter estimation. Electronic Publication     

Biomedical applications of tunable diode laser spectrometry: Correlation between breath carbon monoxide and low level blood carboxyhemoglobin saturation

Tunable diode laser spectrometry was used to measure breath carbon monoxide (CO) concentrations in nonsmoking subjects. Corresponding blood carboxyhemoglobin (COHb) saturations between physiological levels and levels after 1 and 8 hours exposure to 9 ppm CO, the maximum permissible concentration in the air under federal regulations, were also determined. A good linear correlation between breath CO and blood COHb saturation for low levels representing ambient conditions was established, with a correlation coefficient better than 0.999 for the means and 0.945 for the individual data points. Similar studies on the other compounds of concern are also possible using tunable diode laser spectrometry, requiring only a breath sample and with no sample preparation. This technique will facilitate fast, noninvasive environmental health effect and biomedical studies.     

Diffusion of oxygen and carbon dioxide through blood flowing in a channel

The numerical solutions of diffusion equations have been obtained for the cases of oxygen and carbon dioxide diffusing through blood flowing between two porous parallel planes. It is assumed that at the entrance to the channel the concentration profiles are uniform and the velocity profile is fully developed. The rheological characteristics of blood are described by the Casson equation. The computations have been made employing the explicit finite-difference forward-marching procedure. The results have been obtained for a wide range of yield numbers, inlet partial pressures, pH, membrane resistances and haemoglobin concentrations.     

Chylomicron Retention Disease: The Role of Ultrastructural Examination in Differential Diagnosis

Three children with malabsorption presumably caused by celiac disease had undergone jejunal biopsy. While a histological examination revealed microvacuolization of enterocytes in the absence of celiac lesions, an ultrastructural investigation disclosed numerous chylomicrons and larger lipid vacuoles inside the cytoplasm of enterocytes, mostly in the supranuclear region. No chylomicrons were evident in the interstitium between adjacent enterocytes, as observed in normal subjects. These ultrastructural findings allowed for the diagnosis of "Chylomicron retention disease" (CRD). CRD was described for the first time by Anderson in 1961, and it is included in the group of disorders of biosynthesis and secretion of B apolipoproteins (apoB). This disease, in particular, appears to result from a specific defect involving the secretion of lipoproteins containing apoB-48 from the gut, with the complete absence of post prandial chylomicrons in the sera. CRD needs to be recognized early because of its adverse effects on growth and its potential for neurological and ocular complications, and the ultrastructural identification of chylomicron-size lipid droplets clustered in the enterocytes, with the absence of fat outside the cells, represents the gold standard to identify CRD. together with clinical aspects and laboratory measurements. In this study, we describe the histological and ultrastructural aspects observed in three pediatric cases of CRD.     

Ventral medulla pHi measured in vivo by 31P NMR is not regulated during hypercapnia in anesthetized rat

Chemoreceptors in the ventral medulla contribute to the respiratory response to hypercapnia. Do they ‘sense’ intracellular pH (pH_i)? We measured pH_i in the ventral medulla or cortex (control) using ³¹P-NMR obtained via a novel 3×5 mm² surface coil in anesthetized rats breathing air or 7% CO₂. During air breathing over 240 min, pH_i decreased slightly from 7.13±0.02 to 7.05±0.02 (SEM; n=5; 2 cortex, 3 ventral medulla). During 180 min of hypercapnia, cortical pH_i (n=4) decreased from 7.17±0.02 to 6.87±0.01 by 90 min and recovered by 150 min. Ventral medulla pH_i showed no such regulation. It decreased from 7.11±0.02 to 6.88±0.02 at 90 min and recovered only after cessation of hypercapnia (n=5), results consistent with pH_i being the chemoreceptor stimulus. However, non-chemoreceptor neurons that contribute to our medullary NMR signal also do not appear to regulate pH_i in vitro. Regional differences in pH_i regulation between cortex and ventral medulla may be due to both chemosensitive and non-chemosensitive neurons.     

The direct effect of carbon monoxide on KCa channels in vascular smooth muscle cells

 The vasorelaxation induced by carbon monoxide (CO) has been demonstrated previously. Both a guanosine cyclic monophosphate (cGMP) signalling pathway and cGMP-independent mechanisms have been proposed to be responsible for the vascular action of CO. A direct effect of CO on the activity of calcium-activated K (K_Ca) channels in vascular smooth muscle cells (SMCs) and the underlying mechanisms were investigated in the present study. It was found that CO hyperpolarized single SMCs isolated from rat tail arteries. The whole-cell outward K⁺ channel currents in vascular SMCs, but not in neuroblastoma cells, were enhanced by CO. Extracellularly or intracellularly applied CO increased the open probability of single high-conductance K_Ca channels concentration-dependently without affecting the single channel conductance. Although it did not increase the resting level of intracellular free calcium concentration, CO significantly enhanced the calcium sensitivity of single K_Ca channels in SMCs. Furthermore, the effect of CO on K_Ca channels was not mediated by cGMP or guanine nucleotide-binding proteins (G proteins, G_i/G_o or G_s) in excised membrane patches. Our results suggest that the direct modulation of high-conductance K_Ca channels in vascular SMCs by CO may constitute a novel mechanism for the vascular effect of CO. Received: 9 January 1997 / Received after revision: 21 February 1997 / Accepted: 10 March 1997     

The diffusion of carbon dioxide in erythrocytes and hemoglobin solutions

Summary The CO₂ diffusion constant (Krogh's diffusion constant) has been estimated from the CO₂ flux across layers with defined thickness under steady state conditions.At 22°C and in hemoglobin solutions with a concentration of 33 g% the diffusion constant for CO₂ was found to be 3.3×10^–4 cm² min^–1 atm^–1. This value is about 40% of the diffusion constant for CO₂ in water. The relationship between the diffusion constant and the hemoglobin concentration was approximately linear in a concentration range of 10–40 g%. The temperature coefficient of the diffusion constant was –0.5%/°C both in water and hemoglobin solutions. At 38°C and in a hemoglobin solution with a concentration of 33 g%, the diffusion constant for CO₂ was therefore 3.0×10^–4 cm² min^–1 atm^–1, the diffusion coefficient 11×10^–6 cm² s^–1.A general theory for the diffusion of CO₂ in hemoglobin solutions has been derived. According to this theory the diminution of the CO₂ diffusion in hemoglobin solutions in comparison to water can be explained quantitatively by a reduction of the water space by the hemoglobin molecules.The diffusion constant for CO₂ in layers of erythrocytes was insignificantly (0–3%) smaller than in hemoglobin solutions with the same hemoglobin concentration. It is concluded that the erythrocyte membrane does not offer a considerable resistance for the CO₂ diffusion.     

HO-1/CO径路在肺缺血-再灌注损伤中的作用

目的：探讨血红素氧合酶-1（HO-1）/一氧化碳（CO）径路在肺缺血-再灌注损伤中的作用。 方法： 采用在体兔单肺原位缺血-再灌注模型。实验兔40只，随机均分为假手术对照（C）组、肺缺血-再灌注（I-R）组、肺缺血-再灌注加氯铁血红素(H)组和肺缺血-再灌注加锌原卟啉(Z)组。分别在缺血前、缺血后、再灌注1 h、2 h、3 h抽血，检测一氧化碳血红蛋白(COHb)浓度。实验结束时取肺组织检测湿干重比（W/D）、肺泡损伤率（IAR），观察肺组织超微结构的改变、HO-1的活力、表达部位及强度。 结果： 血浆COHb浓度，I-R组、H组明显高于C组，以H组为著（P<0.01）；H组、Z组显著高于、低于I-R组（P<0.01）。肺组织HO-1活力H组最高，其次是I-R组，Z组和C组最低（P<0.05和P<0.01）。I-R组、H组、Z组HO-1在肺血管内皮、部分血管平滑肌、外膜层及部分气道上皮均有阳性表达，明显高于C组，尤以H组最为明显（P<0.01）。W/D、IAR值，I-R组和Z组均明显高于C组，尤以Z组为著，H组虽较C组为高，但显著低于IR组和Z组（P<0.05和P<0.01）。肺组织形态学异常改变，以Z组为著，H组较轻。 结论： HO-1/CO径路对缺血-再灌注肺发挥积极的保护作用。