Involvement of the protein kinase Cgamma isoform in development of tolerance to nitrous oxide-induced antinociception in mice

Prolonged exposure to nitrous oxide (N2O) results in development of acute tolerance to its antinociceptive effect. Cross-tolerance to N2O-induced antinociception is also observed in morphine-tolerant animals. Despite increasing evidence of tolerance development to N2O-induced antinociception, the details of the mechanisms that underlie this tolerance remain unknown. The present study was conducted to investigate the involvement of brain protein kinase C (PKC) isoform in these two types of tolerance to N2O-induced antinociception in mice. Prolonged exposure (41 min in total, including 30 min pre-exposure and 11 min of antinociceptive testing) to 70% N2O produced a reduction in N2O-induced antinociception, indicating development of acute tolerance. The prolonged exposure to 70% N2O caused an activation of PKCgamma isoform in the brain, but not the PKCepsilon isoform. Pretreatment with a PKCgamma-antisense oligonucleotide but not the corresponding mismatch oligonucleotide (i.c.v.) prevented the development of acute tolerance to N2O-induced antinociception. Chronic morphine treatment (10 mg/kg, s.c., b.i.d. for 5 days) resulted in development of tolerance to morphine-induced antinociception and cross-tolerance to N2O-induced antinociception. The development of tolerance to morphine and cross-tolerance to N2O were both inhibited by pretreatment with PKC inhibitor, chelerythrine (1 nmol, i.c.v.). Morphine-tolerant mice showed an activation of PKC within the brain, which was suppressed by pretreatment with chelerythrine (1 nmol, i.c.v.). Thus, activation of brain PKC, in particular, the PKCgamma isoform, appears to play an important role in the development of both acute tolerance and cross-tolerance to N2O-induced antinociception in mice.     

Serum phospholipase — Regulatory and pathophysiological aspects

Summary The development of a photometric procedure to measure phospholipase A activity has extended previous observations that this enzyme activity increases in several pathological states including pancreatic and inflammatory diseases. Serum phospholipase A in pancreatitis was characterized as a mixture of the pancreatic enzyme and a different phospholipase with a pH optimum at 8.0. The latter enzyme was also observed in nonpancreatic diseases like septicemia and acute lung failure which are characterized by an increase in tissue phagocyte activity. The possible pathogenic role of phospholipase(s) A, their intracellular regulation and the proposed mechanisms of release into the blood stream are discussed with respect to the present pathobiochemical knowledge. This includes the mechanism of activation of phagocytosis and the possible role of lipocortins known to be stimulated by glucocorticoid treatment.Abbreviation PLA Phospholipase A     

Silk fibroin porous scaffolds by N2O foaming

Silk fibroin has acquired increasing interest for biomedical applications, and namely for the fabrication of scaffolds for tissue engineering, because of its highly positive biological interaction and the possibility to adapt the material to several application requirements by adopting different fabrication methods, in order to make films, sponges, fibers, nets or gels with predictable degradation times. For tissue engineering, in most cases porous scaffolds are required, in some cases possibly in situ forming and therefore fabricated in mild body-compatible conditions. In this work, we present a novel one-step method for the preparation of silk fibroin foams starting from water solutions and using low-pressure nitrous oxide gas as foaming agent. This foaming technique allows preparing fibroin porous scaffolds with easily tunable porosity, in mild processing conditions with the use of a relatively inert foaming agent saturating a fibroin water solution, that could be occasionally injected through a thin needle in the implantation site where expansion and foaming would occur. Optimal foaming processing conditions have been investigated, and the prepared foams have been characterized with Fourier Transform Infrared Spectroscopy (FTIR) compressive mechanical and rheological properties measurements, and by scanning electron microscopy and microCT.     

Some aspects of determination of the cardiac output by the rebreathing method

It is shown that the rebreathing method can be used to study the cardiac output even when the ventilation does not correlate with the pulmonary blood flow. pCO₂ was measured in mixed venous blood by equilibrating it with pCO₂ in the alveolar air by the rebreathing method. A gas mixture with a CO₂ concentration close to that in venous blood was produced by the subject himself during rebreathing into a bag with a capacity of 2–3 liters, filled with oxygen. Irregularity of distribution of ventilation relative to blood flow was judged from the shape of the CO₂ concentration versus time curve. If signs of irregularity are present, it is impossible to make p_etCO₂ equal to p_ACO₂ and for that reason pCO₂ of arterialized blood was determined. By means of this correction it is possible to determine the cardiac output of patients with cardiac and pulmonary diseases. The possibility of using standard nomograms for calculating the CO₂ concentration in the arterial and venous blood in the presence of appreciable disturbances of the acid-base balance is discussed.Department of Experimental and Clinical Physiology, A. V. Vishnevskii Institute of Surgery, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician V. N. Chernigovskii). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 2, pp. 245–247, February, 1977.     

Gas mixing in lung model ventilated by high frequency oscillation: Effect of tidal volume,frequency and molecular diffusivity

The efficiency of gas mixing during sinusoidal oscillatory flow in a model of human lung cast was assessed by using a multibreath carbon dioxide washout manoeuvre. The experiments were performed at high frequencies (5, 10, 15 and 20 Hz) and low tidal volumes (50, 90 and 120 cm³). A particular effort was made to analyse the influence of flow oscillation conditions (f and V_r) as well as the effect of resident alveolar gas density (molecular diffusion) on the effective diffusion coefficient (D_eff). This longitudinal mixing parameter was found to be strongly dependent on the tidal volume (approximately proportional to V _r ^1·4 ) and weakly dependent on the frequency (approximately proportional to f^0·5). However, molecular diffusion was not, in general, a limiting factor in the gas transport process during high-frequency oscillation (HFO).     

Perfluorochemicals as a treatment of decompression sickness in rats

Perfluorodecalin and perfluorotripropylamine which have N₂ solubility coefficients of 28.4 and 35.7 ml/dl, respectively, were used for treatment of decompression sickness in this study. Rats with chronically implanted venous catheters were held for 30 min at 800 kPa (7 bar, 8 ATA) by introducing compressed air into a chamber in which they were kept; a relatively short period of decompression followed (200 kPa/min). Immediately thereafter injections of the perfluorochemicals (PFCs) in a dose of 10 g/kg were given, controls received saline in the same volume or remained without treatment. An observation period of 2 h followed; after this time the incidence of death amongst the experimental animals (as compared with controls tested by theX ²-test) showed that PFC treatment increased the likelihood of survival. Probit-log time relationship for the incidence of death also revealed a significant decrease in lethality in treated rats 30 min after the end of decompression. The mean lethal timesLt ₅₀ differed significantly, too.A still greater effect might be expected if the PFC emulsion were deprived of its normal nitrogen content by oxygenation before administration. Under the conditions of the present experiments PFCs produced an improvement in N₂ exhalation at least in terms of the survival rate after compression followed by a very short decompression time.Supported by the Deutsche Forschungsgemeinschaft (Lu 162/7)     

The effects of titania nanotubes with embedded silver oxide nanoparticles on bacteria and osteoblasts

A versatile strategy to endow biomaterials with long-term antibacterial ability without compromising the cytocompatibility is highly desirable to combat biomaterial related infection. TiO₂ nanotube (NT) arrays can significantly enhance the functions of many cell types including osteoblasts thus having promising applications in orthopedics, orthodontics, as well as other biomedical fields. In this study, TiO₂ NT arrays with Ag₂O nanoparticle embedded in the nanotube wall (NT-Ag₂O arrays) are prepared on titanium (Ti) by TiAg magnetron sputtering and anodization. Well-defined NT arrays containing Ag concentrations in a wide range from 0 to 15 at % are formed. Ag incorporation has little influence on the NT diameter, but significantly decreases the tube length. Crystallized Ag₂O nanoparticles with diameters ranging from 5 nm to 20 nm are embedded in the amorphous TiO₂ nanotube wall and this unique structure leads to controlled release of Ag⁺ that generates adequate antibacterial activity without showing cytotoxicity. The NT-Ag₂O arrays can effectively kill Escherichia coli and Staphylococcus aureus even after immersion for 28 days, demonstrating the long lasting antibacterial ability. Furthermore, the NT-Ag₂O arrays have no appreciable influence on the osteoblast viability, proliferation, and differentiation compared to the Ag free TiO₂ NT arrays. Ag incorporation even shows some favorable effects on promoting cell spreading. The technique reported here is a versatile approach to develop biomedical coatings with different functions.     

A Miniaturized Carbon Dioxide Gas Sensor Based on Sensing of pH-Sensitive Hydrogel Swelling with a Pressure Sensor

A measurement concept has been realized for the detection of carbon dioxide, where the CO₂ induced pressure generation by an enclosed pH-sensitive hydrogel is measured with a micro pressure sensor. The application of the sensor is the quantification of the partial pressure of CO₂ (Pco₂) in the stomach as diagnosis for gastrointestinal ischemia. The principle is put to the proof by examining the sensor response to changes in Pco₂. Furthermore, the response time, temperature-sensitivity and resolution are determined. The sensor responds well to changes in Pco₂ with a maximum pressure generation of 0.29× 10⁵ Pa at 20 kPa CO₂. The 90% response time varies between 1.5 and 4.5 minutes at 37^∘C. The sensor shows a linear temperature-sensitivity which can easily be compensated for, and enables detection of Pco₂ changes as small as 0.5 kPa CO₂.     

A double-blind, randomized controlled trial on the use of a 50:50 mixture of nitrous oxide/oxygen in pain relief during suction evacuation for the first trimester pregnancy termination

BACKGROUND: This prospective study assessed the role of a 50:50 mixture of nitrous oxide (N2O) and oxygen for pain relief during the termination of first trimester pregnancies by suction evacuation under conscious sedation. METHODS: Ninety women undergoing suction evacuation up to 12 weeks of gestation were randomized by a computer-generated randomization list and allocated using sealed envelopes to receive the N2O/O2 mixture or air during the operation. Pain scores during and after suction evacuation, post-operative side effects and satisfaction level were compared. RESULTS: No statistically significant differences in pain scores, post-operative side effects and satisfaction levels were found between the two groups. CONCLUSION: N2O/O2 did not reduce the pain level during suction evacuation for the first trimester pregnancy termination under conscious sedation.     

Distribution of the myocardial tissuePO2 in the rat and the inhomogeneity of the coronary bed

The structural inhomogeneity of the myocardial capillary bed is simulated by microcirculatory units (MCU's) in a diffusion model. This simulation is based on MCU's in which the arrangement of the capillary ends (concurrent structure, partial and total countercurrent structure, helical structure) as well as the structure and supply parameters are varied. The variation of these parameters is based on own measurements of the intracapillary HbO₂ saturation as well as on the following parameters from the literature: frequency distribution of capillary distance and capillary radius, mean capillary length or capillary section length respectively, arterial and mean venousPO₂, mean coronary blood flow, mean O₂ consumption and diffusion conductivity. The analysis of O₂ supply of the normoxic rat heart shows that an O₂ diffusion shunt is obligatory except for MCU's with an extremely large capillary distance or with a concurrent capillary structure. Therefore the minimal tissuePO₂ lies at the level of the capillary venousPO₂ of a MCU. The maximum of the totalPO₂ frequency distribution in the normoxic rat myocardium lies at 25±5 mm Hg, i.e. above the mean venousPO₂ (20 mm Hg). TissuePO₂ values between 0 and 5 mm Hg amount to 0.5%, i.e. they are extremely rare. TissuePO₂ values of 0–1 mm Hg represent less than 0.2%.List of Symbols a arterial capillary end - a branching point of a capillary near the arterial capillary end (branching point of an anastomosis) - A maximal O₂-consumption - A(P) O₂-consumption dependent uponPO₂ - AVDO₂ arterio-venous difference - AVDO₂; AVDO_{2 c} ^(j) arterio-venous difference of a capillary - c _j weighting factor of the capillary distance - c _Hb hemoglobin concentration in the blood - d, d ^j capillary distance - mean capillary distance - i index for the different MCU's (i=1...8) - i.e. PO₂ intracapillaryPO₂ - j index for the parameters of an MCU with the capillary distanced ^(j) (j=1...7) - K diffusion conductivity - l capillary length - l _s capillary section length - MCU microcirculatory unit - P, P(x,y,z), PO₂ O₂ partial pressure - P _a arterialPO₂ - P _a; P_a ^(j) PO₂ at the branching pointa - P _i; P_v ^(j) venousPO₂ - mean venousPO₂ - P ₅₀ PO₂ at half maximal O₂ consumption - P _min,P _min ^(j) minimal tissuePO₂ - r _c, r_c ^(j) capillary radius - mean capillary radius - s(P) relative HbO₂ saturation (HbO₂ dissociation curve) - s ^–1 inverse function of the HbO₂ dissorciation curve - S _v, S_v ^(j) capillary venous HbO₂ saturation - mean venous HbO₂ saturation - v venous capillary end - V volume of the tissue fragment of a MCU - V _c, V_c ^(j) capillary supply volume - W _c, W_c ^(j) blood flow of the supply volume of a capillary (local blood flow) - mean blood flow - x,y,z cartesian coordinates of thePO₂ in a MCU - Bunsen's solubility coefficient - _c . _c ^(J) capilary blood flow - , ^(j) blood flow of an MCU - _i ^(j) (P) relative frequency distribution of thePO₂ in thei-th MCU - (P) relative frequency distribution of thePO₂ of all MCU's, total frequency distribution of the myocardial tissuePO₂ - Laplace operator Supported by the DFG     

Some aspects of functional morphology of extracellular matrix in lymph capillary endothelium

Argyrophilic portion of endothelial glycocalyx in lymph capillaries from the central tendon of rabbit diaphragm was examined. It is shown that optical density along the perimeter of endotheliocyte is unequal and depends on the cell shape (scalloped, fusiform, or irregular). Aseptic inflammation is characterized by a marked increase in high-density zones and expansion of argyrophilic glycocalyx. It is proposed to consider argyrophilic glycocalyx as an independent structural and functional unit of the endothelium. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 1, pp. 107–109, January, 1998     

Changes in haemorheology in the racing greyhound as related to oxygen delivery

Summary Arterial blood samples were obtained from six greyhounds during rest, immediately before, and after a 704-m (7/16th mile) race. Measurements were made of various haematological (red cell count, haemoglobin, packed cell volume, white cell count, plasma proteins) and haemorheological variables. Blood and plasma viscosity were determined at high wall shear stresses (67–200 dynes · cm^–2, 670–2000 N · cm^–2) in a 20-m glass capillary device which was designed to take the diameter dependence of blood viscosity (Fahraeus-Lindgvist effect) into account. Compared to values at rest, substantial haemoconcentration occurred before the race, mainly due to splenic discharge of red cells. Additional haemoconcentration was found after the race. The increase of effective blood viscosity caused by elevation of packed cell volume was greater than the increase in O₂ binding capacity resulting from the elevated haemoglobin concentration, suggesting that the haemoconcentration observed in the exercising greyhound does not enhance O₂ delivery to skeletal muscle. The main physiological effect of red cell discharge from the contracting spleen appeared to be a consequence of the volume rather than the composition of the circulating blood.     

GM1 gangliosidosis: review of clinical, molecular, and therapeutic aspects

GM₁ gangliosidosis is a lysosomal storage disorder due to deficiency of the β-galactosidase enzyme. This deficiency results in accumulation of GM₁ gangliosides and related glycoconjugates in the lysosomes leading to lysosomal swelling, cellular damage, and organ dysfunction. The disease is lethal in the infantile and juvenile forms. To date, up to 102 mutations distributed along the β-galactosidase gene (GLB1) have been reported. This review gives an overview of the clinical and molecular findings in patients with GM₁ gangliosidosis. Furthermore, it describes therapeutic approaches which are currently under investigation in animal models of the disease.     

Predictors of phase III slope of nitrogen single-breath washout in COPD

The nitrogen (N₂) single-breath washout (SBW) test is a measure of ventilation distribution inhomogeneity and also a small airway function that offers complementary information to spirometry; however, the relevance to the forced oscillation technique (FOT) and pulmonary emphysema in COPD is not fully understood. We hypothesized that pulmonary functions, forced oscillatory parameters, and emphysema extent would contribute independently to the results of the SBW test. In this cross-sectional study we assessed the relationship between the phase III slope (delta N₂) derived from N₂ SBW and these parameters. Spirometry, lung volumes, N₂ SBW, and the broadband frequency FOT were performed in 56 patients with COPD. Emphysema extent was measured by high-resolution computed tomography and scored. In multiple regression analyses, the delta N₂ was independently predicted by forced vital capacity, resonant frequency, and emphysema score (R² = 0.57, p < 0.0001). The degree of ventilation inhomogeneity derived from N₂ SBW is independently predicted by spirometry, lung mechanics, and the degree of emphysema.     

Collagenolytic protease preparations from invertebrates: Biochemical aspects of medical and cosmetological applications

Collagenolytic proteases from invertebrates, the active matter of new structure-destroying enzyme preparations (Collagenase from hydrobionts, Polycollagenase-K, Fermenkol), ensure deep hydrolysis of polypeptide substrates (native or partially denatured collagen types, elastin, fibrin, hemoglobin, and casein) that cannot be attained by collagenases and serine proteases. Biochemical properties of collagenolytic proteases from invertebrates, techniques and doses that may be important for elaboration and employment of preparations based on this complex are described. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 7, pp. 70–75, July, 2000     

Effects of two successive maximal exercise tests on pulmonary gas exchange in athletes

Pulmonary extravascular water accumulation may be involved in exercise-induced hypoxaemia in highly aerobically trained athletes. We hypothesized that if such an alteration were present in elite athletes performing a maximal exercise test, the impairment of gas exchange would be worse during a second exercise test following the first one. Eight male athletes performed two incremental exercise tests separated by a 30-min recovery period. Pulmonary gas exchange and ventilatory data were measured during exercise tests performed in normoxia. Arterial blood samples were drawn each minute during rest, exercise, and recovery. Pulmonary diffusing capacity for CO (D _LCO) was measured at rest, after the first (T1) and the second (T2) test. All the subjects underwent a spirometric test at rest and after T2. Maximal and recovery data for 0₂ uptake and minute ventilation were not statistically different between T1 and T2. Partial pressure of arterial 0₂ (P _aO₂) decreased during both tests but was lower during T2 for rest, 60 W, and 120 W (P < 0.02). Alveolar-arterial difference in partial pressure of 0₂ (P _A-a0₂) increased during both the tests but was significantly larger during T2 for rest, 60 W, and 120 W (P < 0.01). The P _aO₂ and P _A-aO₂ data at maximal exercise were not significantly different between T1 and T2. Compared to rest, P _A-aO₂ remained significantly larger during recovery for both T1 and T2 (P < 0.0001). The P _A-aO₂ during T2 recovery was larger than T1 recovery (P < 0.008). Spirometric data did not change. The D _LCO measurements after T1 and T2 were not significantly different from rest. These results showed an alteration of P _aO₂ and P _A-aO₂ during T1, which tended to be worse during and after T2; however, these data do not allow us to make a definitive statement as to the cause of the hypoxaemia. Our study confirmed that exhausting exercise caused hypoxaemia. It also demonstrated that the disturbance in pulmonary gas exchange persisted for at least 30 min following the end of the exercise period and became worse during submaximal intensities of the following incremental exercise test.     

Measurements of the criticalPO2 of renal mitochondria

Summary The criticalPO₂ of isolated mitochondria from the cortex and outer medullary region of the rat kidney was polarographically measured using the O₂-platinum-electrode. With succinate for substrate at 37°C and 25°C mean criticalPO₂-values of 1.54 Torr (SD±0.58) and 1.01 Torr (SD±0.46) were found resp. Using malate for substrate the corresponding mean values were 0.92 Torr (SD±0.28 and 0.65 Torr (SD±0.25). A positive linear relationship between O₂-uptake and criticalPO₂ was observed. The results are compared with data on the O₂-consumption of rat and dog renal cortex in situ and withPO₂-values measured in the same organs. On the basis of the results here presented with regard to the lowestPO₂-values found in the renal cortex of the dog an additional explanation of the flow limitation of the renal O₂-consumption is developed.This work was supported by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg.