Biological glass coating on ceramic materials: in vitro evaluation using primary osteoblast cultures from healthy and osteopenic rat bone

ZrO2 and Al2O3 substrates were successfully coated by a double layer of a silica-based glass named RKKP, using a low-cost firing technique. RKKP is a glass well known for its bioactivity; therefore, a RKKP coating on Al2O3 or ZrO2, allows to combine the excellent mechanical properties of these strong ceramic substrates with its bioactivity. ZrO2 samples were easily coated using a double layer of RKKP by a simple enamelling technique. To accommodate the thermal expansion coefficient mismatch between Al2O3 and RK K P, this substrate was coated using a multilayered composite approach. All of the coatings were characterised from a morphological and compositional point of view, and an extensive biological evaluation was performed using fresh rat osteoblasts. Osteoblast primary cultures were derived from the trabecular bone of femoral condyles harvested from intact (NB) and osteopenic (OB) rats. After characterisation of their phenotype, osteoblasts were seeded on material samples of ZrO2 or Al2O3 coated with RKKP, and cultured for 7 days. Cell proliferation (MTT test) and cell differentiation (alkaline phosphatase activity) were evaluated at the end of the experiment, to assess osteoblast behaviour in the presence of biomaterials and determine if the results were related to the host bone quality. Results of both materials showed a good level of biocompatibility. In particular, MTT significant higher values were detected in NB cultures on ZrO2-RKKP samples; ALP activity significantly increased in NB cultures on Al2O3-RKKP and in OB cultures on both coated samples.     

Fast measurement of the CO2 partial pressure in gases and fluids

A CO₂-electrode system consisting of a membrane covered pH electrode, an electronic antilog modul and a special electronic analog circuit is described. Since the electrode output signal is a logarithmic function of the CO₂ partial pressure the output signal of the antilog module is proportional to the CO₂ partial pressure. The time course of the electrode signal has been analyzed after a step change of . This step response may be approximated by a sum of three exponential functions. Knowing the dynamic behaviour, the transfer function is formulated mathematically and a special analog circuit is constructed with a frequency response inverse to the frequency response of the electrode. Using this device the response time (T ₉₅) of the electrode system is diminished from 11,5 s to 750 ms after a step change of in gas (Luttmann, et al., 1974). If the time for the hydration of CO₂ is decreased by the addition of carbonic anhydrase the response time of the electrode is diminished to 6.5 s. Using the analog circuit yields a response time of 200 ms.Further studies were made to analyze the transient response in fluids at various flow velocities and various mountings. In order to analyze the influence of the fluid boundary layer on the surface of the electrode a photometric method has been developed (Luttmann and Mückenhoff, 1975), which allows to estimate the time course of the CO₂ partial pressure independently of and simultaneously with the electrode measurement.The experimental data are compared with a theory based on theoretical considerations of Schuler and Kreuzer (1967) and Crank (1956).List of Symbols A _i gain factor of thei-th compartment - A _i gain factor of the simulation network - C _i capacity - D diffusion coefficient - d electrode diameter - fraction of CO₂ - F _c (j) frequency response of the linearizing network - F _g (j) frequency response of the boundary layer - F _M (j) frequency response of the measuring system - F _M frequency response of the simulation network - I _i impedance transformer - j Gauss number (j ²=–1) - (j) frequency function of the CO₂ partial pressure - (t) time function of the CO₂ partial pressure - R _i electrical resistance - T _i time constant of the electrode - T _i time constant of the simulation network - T ₉₅ time for reaching 95% of the total difference - V voltage gain factor - v velocity of the streaming fluid - x coordinate - x(t) time function - X(j) corresponding frequency function - dilution factor - inverse time constant - thickness of boundary layer - ^* kinematic viscosity - thickness of diffusion layer - radian frequency Supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 114 (Bionach)     

Quantitative continuous measurement of partial oxygen pressure on the skin of adults and new-born babies

Summary It is possible to perform continuous quantitativeP _{O 2} measurements on vasodilated skin by means of surface Pt electrodes according to Clark when the electrode is fixed to the skin with a synthetic plastic material and in situ calibration is performed. A new in situ calibration of theP _{O 2} electrode is described. At first the skinP _{O 2} increases with O₂ inspiration. After perfusion stop the skinP _{O 2} shows a linear decrease because of the skin respiration, down to aP _{O 2} at which hemoglobin liberates chemically bound O₂. As thisP _{O 2} value of hemoglobin is known it is possible to use it for calibrating the electrode. TheP _{O 2} of normal skin is about 0–7 Torr. After vasodilation obtained by rubbing with a nicotinic acid derivate (Finalgon^®, Anasco, Wiesbaden),P _{O 2} increases to a mean value of 38.1 (±8.1) Torr (n=77). Under these conditions, skinP _{O 2} reaches arterial values never in adults and rarely in new-born babies.Part of the results have been reported during the Workshop on Oxygen Transport in Tissue, 19–22 July, 1971, in Dortmund and at the 4. Deutsche Kongress für Perinatale Medizin, 4–6 Nov. 1971, in Berlin. The study was carried out with partial support from the German Research Council (DFG).     

Quantitative continuous measurement of pO2 and pCO2 in artery and vein

A technique using a quadrupole mass spectrometer has been developed for the continuous measurement of partial pressures of physiological blood gases. The depletion phenomenon is eliminated with a new sampling cannula equiped with a polyethylene membrane for velocities greater than 1 cm per second. The importance of this development resides in the fact that this phenomenon, which is due to a sampling rate around the cannula in excess of the remplacement by the medium of the molecules withdrawn, leads to an under-estimation of the real partial pressure which increases as the blood velocity falls. Thanks to the new cannula, accurate measurements can now be made in both arteries and veins; moreover, continuous observation of physiological phenomena can be carried out with a time constant of under 1 minute resulting from the thinness of the membrane.     

脑组织氧分压监测技术的研究与应用进展

脑组织氧分压 (brain tissue oxygen partial pressure,Pbti O2 )技术是进入 90年代后逐渐成熟起来的脑氧代谢监测方法 ,与传统的脑氧监测方法相比具有微创、安全、准确的特点。应用这一技术可以对病人进行术中及术后的长期、动态监测 ,有助于正确判断脑血流量、颅内压、脑灌注压之间的关系 ,早期判断预后。但脑组织氧分压监测所获得的信息尚需结合其他监测手段获得的数据加以综合分析 ,才能得出准确结论     

Blood oxygen partial pressure affects plasma prolactin concentration in humans

Responses of plasma prolactin (PRL) concentration to acute and repeated changes in blood oxygen partial pressure (PO2a) at rest were investigated in two studies (A; B), with special reference to possible effects mediated via serotonin (5-HT) synthesis. In A, nine male subjects inhaled for 105 min gas containing different oxygen fractions for 6 days. Gas concentrations consisted of 14% (A14), 21 % (A21), 40% (A40), 60% (A60) and 80% (A80) O2 mixed with N2 as well as 100% O2 (A100). Venous and capillary blood samples were drawn before and every 15 min during gas inhalation for analysis of plasma PRL and PO2a. In B, two groups of subjects (B I; B II) were exposed to 30 min day(-1) of gas inhalation over 14 consecutive days. Gas concentration consisted for B I of 14% O2/86% N2 and for B II of 100% O2. During pre- and post-examination a baseline blood sample was drawn, followed by a neuroendocrine test of serotonergic function using a partial 5-HT1A receptor agonist (60 mg of buspirone hydrochloride). In A, each increase of inhaled oxygen fraction also resulted in higher blood POb2a. In A14, A21 and A40, plasma PRL concentrations did not change from basal level. Increases in plasma PRL concentration were found in A60 after 30 min as well as in A80 and A100 after 15 min. A higher blood PO2a induced a higher plasma PRL secretion but also an earlier decline from peak plasma PRL value despite continued inhalation of the respective oxygen concentration. During post-examination in B, basal plasma PRL concentrations were increased in B I and decreased in B II. Plasma PRL response to stimulation challenge was not affected by treatments. Thus, chronic adaptations of basal plasma PRL concentrations to decreased/increased blood PO2a were not related to up/down-regulation, respectively, of central serotonergic receptor function.     

Continuous mass spectrographic measurement of halothane partial pressure in blood

A method has been devised for the continuous measurement of halothane partial pressure in blood. The technique which was used in 10 dogs employs a silastic covered stainless-steel intra-arterial cannula through which blood gases pass into the analysing portion of a mass spectrometer where they are identified. Halothane produces a spectrographic peak at mass 31 which is proportional to its partial pressure. The peak at 31 results from the splitting of the halothane molecule into an ion composed of an atom of carbon and one of fluorine. The initial response time for the system is 0·4 min. The time from an initial changes to 63% of the final reading (1/e time) is 6·3 min. The calibration of the spectrometer remained stable for up to 7h, the longest test period.     

Tissue oxygen pressure (ptO2) in extracellular volume expansion and hypervolemic polyglobulia.

Muscle tissue oxygen pressure (ptO2) was measured in rats employing the microwire platin electrode according to Kessler and Lübbers. In extracellular volume expansion up to 50% above the normal volume the ptO2 histograms are situated within the normal range. Increase of the interstitial space for oxygen diffusion seems to be effectively counterbalanced by increased cardiac output. In hypervolemic polyglobulia, hematocrit about 60%, four rats presented normal ptO2 levels. In one animal only the ptO2 histogram was shifted to the left (lower values); in this rat also cardiac output was considerably reduced.     

Improved performance of intravascular pO2 sensor incorporating poly(MPC-co-BMA) membrane

The first in vivo evaluation of a pO₂ sensor constructed with a novel copolymer is described. The performance of the sensor is assessed under dynamic conditions in vitro and in vivo. This sensor is more stable and reliable than the control sensor with a heparintreated polyethylene membrane.     

Error reduction in polarographic determination of oxygen partial pressure on blood samples

Biomedical Engineering -