Effects of bile acid and salicylate on isolated surface and glandular cells of rabbit stomach

Little is known about the response of surface cells and glandular cells of the gastric mucosa to various injurious agents. This study examines the effects of bile acid and salicylate on oxygen consumption and membraneolysis of isolated gastric mucosal surface cells and compares these responses to those of cells constituting the gastric glands. The effects of salicylate and bile acid on oxygen consumption by surface cells are similar to previous observations for intact gastric glands and isolated mitochondria, indicating alterations of oxidative phosphorylation. Salicylate does not appreciably alter lipid release from either surface or glandular cells. However, bile acid causes a profound increase in lipid release from both surface and glandular cells. Salicylate does not alter the number of visibly intact surface or glandular cells, but 1 mM of taurocholic acid decreases the number of surface cells by 45% without altering the glandular cells. In contrast, 5 mM of taurocholic acid completely destroys the surface cells and reduces the number of gastric glandular cells by 51%. These data suggest that surface cells are more susceptible to membraneolytic effects of bile acid than are gastric glandular cells. This may account for the superficial nature of bile acid-induced injury to the gastric mucosa. Although both bile acid and salicylate interfere with oxidative metabolism, this effect alone does not appear to account for cellular destruction.     

The relationship between renal metabolism and proximal tubule transport during ontogeny

The proximal tubules of newborn and adult animals reabsorb a similar fraction of the filtered load of Na⁺ and H₂O (65%–70%). In tubules from adult animals, transcellular, active Na⁺ reabsorption accounts for one-third of the total, while two-thirds occur passively through the paracellular pathway, driven by hydrostatic and oncotic forces (one-third) and by cell-generated effective osmotic and ionic gradients (one-third). Since two-thirds of the Na⁺ is reabsorbed passively and does not require energy, the mature proximal tubule has a high Na⁺/O₂ molar ratio (48 Eq of Na⁺/mol of O₂). Measurements of ouabain-sensitive oxygen consumption in suspensions of proximal tubules indicate that in newborn, aerobic metabolism can support about 50% of the net Na⁺ transport rate compared with the 33% in tubules from adult animals. Independent confirmation of the direct and proportional relationship between active Na⁺ transport and ouabain-sensitive O₂ consumption exists for the adult but not for the newborn. However, measurements of epithelial conductances and of transepithelial hydrostatic and oncotic pressure differences indicate that passive paracellular fluxes can account for the remaining 50% of the proximal Na⁺ reabsorption in newborn. The high permeability of the proximal tubules of newborn animals to small molecular weight solutes suggests that cell-generated osmotic and ionic transepithelial gradients are minimal in the tubules of newborn animals. Yet in the newborn, the osmolality of the end proximal tubule fluid was found to exceed that in plasma. This indicates that osmotic gradients due to differences in reflection coefficients for preferentially reabsorbed solutes and Cl^– do exist across the proximal tubules of the newborn and suggests that these gradients may contribute to Na⁺ and H₂O reabsorption. If this is indeed the case, then the contribution of active and of hydrostatic and oncotic pressure-driven flows to the overall reabsorption of Na⁺ and fluid has been overestimated. Resolution of this discrepancy requires measurements of the reflection coefficients for HCO ₃ ^– and Cl^– in the proximal tubule of the newborn. The metabolic processes by which energy is supplied to renal proximal cells during development are also incompletely characterized. There is evidence that maturation of aerobic metabolism, Krebs cycle enzymes activity, and of the mitochondrial membrane surface area precede the development of net reabsorptive transport (Na⁺, H₂O, HCO₃, glucose). By contrast, maturation of Na⁺–K⁺-ATPase activity at the basolateral cell membrane follows that in reabsorptive transport and does not limit its development. The extent to which age-related changes in reabsorptive fluxes are due to the development of luminal membrane transport systems, to the decrease in paracellular permeability, or both remains to be determined. The high activity of enzymes in the hexosemonophosphate pathway and the high NADH/NAD ratio present during the first few weeks of extrauterine life poise the proximal tubules for high rates of biosynthesis of membrane lipids, glycoproteins, nucleic acids, and transporter proteins necessary for final differentiation.     

Defects in Mitochondrial Efficiency and H2O2 Emissions in Obese Women Are Restored to a Lean Phenotype With Aerobic Exercise Training

The notion that mitochondria contribute to obesity-induced insulin resistance is highly debated. Therefore, we determined whether obese (BMI 33 kg/m²), insulin-resistant women with polycystic ovary syndrome had aberrant skeletal muscle mitochondrial physiology compared with lean, insulin-sensitive women (BMI 23 kg/m²). Maximal whole-body and mitochondrial oxygen consumption were not different between obese and lean women. However, obese women exhibited lower mitochondrial coupling and phosphorylation efficiency and elevated mitochondrial H₂O₂ (mtH₂O₂) emissions compared with lean women. We further evaluated the impact of 12 weeks of aerobic exercise on obesity-related impairments in insulin sensitivity and mitochondrial energetics in the fasted state and after a high-fat mixed meal. Exercise training reversed obesity-related mitochondrial derangements as evidenced by enhanced mitochondrial bioenergetics efficiency and decreased mtH₂O₂ production. A concomitant increase in catalase antioxidant activity and decreased DNA oxidative damage indicate improved cellular redox status and a potential mechanism contributing to improved insulin sensitivity. mtH₂O₂ emissions were refractory to a high-fat meal at baseline, but after exercise, mtH₂O₂ emissions increased after the meal, which resembles previous findings in lean individuals. We demonstrate that obese women exhibit impaired mitochondrial bioenergetics in the form of decreased efficiency and impaired mtH₂O₂ emissions, while exercise effectively restores mitochondrial physiology toward that of lean, insulin-sensitive individuals.     

The role of gastric mucosal blood flow and H+ back-diffusion in the pathogenesis of acute gastric erosions.

To evaluate the relationship between ischemia and disruption of the gastric permeability barrier in the pathogenesis of acute gastric erosions, we studied the effect of (1) hemorrhagic shock, (2) topical application of p-chloromercuribenzene sulfonate (PCMBS), and (3) shock plus PCMBS on total and mucosal blood flow, H⁺ back-diffusion, and mucosal injury in 14 dogs. The fractional distribution of blood flow through the layers of gastric tissue remained unchanged during control, shock, and reinfusion periods. Exposure of the mucosa to PCMBS resulted in a significant increase in H⁺ back-diffusion, which was accompanied by a rise in mucosal blood flow. Hemorrhagic shock alone caused a marked mucosal ischemia without disruption of the permeability barrier. The severest mucosal injury occurs only under experimental conditions where ischemia and increased H⁺ back-diffusion are induced simultaneously. These results suggest that: (1) A cause-effect relationship does not exist between ischemia and barrier disruption in the pathogenesis of acute ulcerations. (2) Mucosal blood flow may play an important role in the disposal of H⁺ permeating the mucosa. (3) The ratio of mucosal blood flow to back-diffusion of H⁺ may determine the degree of mucosal injury.     

Mitochondrial‐derived reactive oxygen species (ROS) play a causal role in aging‐related intervertebral disc degeneration

Oxidative damage is a well‐established driver of aging. Evidence of oxidative stress exists in aged and degenerated discs, but it is unclear how it affects disc metabolism. In this study, we first determined whether oxidative stress negatively impacts disc matrix metabolism using disc organotypic and cell cultures. Mouse disc organotypic culture grown at atmospheric oxygen (20% O₂) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O₂). Human disc cells grown at 20% O₂ showed increased levels of mitochondrial‐derived superoxide anions and perturbed matrix homeostasis. Treatment of disc cells with the mitochondria‐targeted reactive oxygen species (ROS) scavenger XJB‐5‐131 blunted the adverse effects caused by 20% O₂. Importantly, we demonstrated that treatment of accelerated aging Ercc1^?/Δ mice, previously established to be a useful in vivo model to study age‐related intervertebral disc degeneration (IDD), also resulted in improved disc total glycosaminoglycan content and proteoglycan synthesis. This demonstrates that mitochondrial‐derived ROS contributes to age‐associated IDD in Ercc1^?/Δ mice. Collectively, these data provide strong experimental evidence that mitochondrial‐derived ROS play a causal role in driving changes linked to aging‐related IDD and a potentially important role for radical scavengers in preventing IDD. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1150–1157, 2013

     

Overtime expression of plasma membrane and mitochondrial function markers associated with cell death in human spermatozoa exposed to nonphysiological levels of reactive oxygen species

In many cell types, the potential of reactive oxygen species to induce death processes has been largely demonstrated. Studies in spermatozoa have associated the imbalance of reactive oxygen species and phosphatidylserine externalisation as an apoptosis marker. However, the lack of consensus about time effect in the joint expression of these and other death markers has made it difficult to understand the set of mechanisms influenced beyond the concentration effect of reactive oxygen species to stimulate cell death. Here, the plasma membrane permeability and integrity, phosphatidylserine externalisation and mitochondrial membrane potential were jointly evaluated as death markers in human spermatozoa stimulated with H₂O₂. The results showed a profound and sustained effect of dissipation in the mitochondrial membrane potential and an increased phosphatidylserine externalisation in human spermatozoa exposed to 3 mmol⁻¹ of H₂O₂ at 30 min. This was followed by an increased membrane permeability after 45 min. The last observed event was the loss of cell membrane integrity at 60 min. In conclusion, mitochondria are rapidly affected in human spermatozoa exposed to reactive oxygen species, with the barely detectable mitochondrial membrane potential coexisting with the high phosphatidylserine externalisation in cells with normal membrane permeability.     

Cimetidine-induced bicarbonate production in canine gastric pouches

Secretion of HCO₃^? into a mucus-gel “unstirred layer” has been proposed as part of the gastric mucosal defense system. Cimetidine has a cytoprotective effect on salicylate-challenged gastric mucosa independent of its acid-inhibiting property. This study was done to (1) evaluate whether cimetidine increases gastric mucosal HCO₃ and to (2) ascertain if ionic shifts accompany the HCO₃^? to explain the mechanism of its production. Six dogs with Heidenhain gastric pouches were fasted 24 hr prior to testing. Pouch access was provided by a cannula fitted with an airtight apparatus for test solution instillation and removal and transmucosal potential difference (PD) measurement. A test solution composed of 175 mM mannitol, 25 mM NaCl, and 50 mM EPPS buffer was used, its pH adjusted to above 8.0; ¹⁴C-labeled polyethylene glycol was added for volumetric determinations. Nine 15-min periods comprised each test: four control periods of iv saline infusion; a fifth period when an iv cimetidine bolus was given; and four test periods when doses of 2.5, 5, or 10 mg/kg/hr cimetidine were infused iv. Test solution (50 ml) was placed in the pouch and an initial sample taken; 15 min later a final sample was taken, the pouch rinsed, and the next period begun. Concentrations of HCO₃^?, Na⁺, K⁺, and Cl^? were determined for each sample as well as changes in osmolality, pH, volume, and PD. Mean net HCO₃^? increased from 79 μmol/15 min during saline infusions to 109, 124, and 123 μmol/15 min with 2.5, 5, and 10 mg/kg/hr cimetidine iv; all are significantly increased compared to saline controls (P < 0.01). None of the other measured parameters changed significantly after cimetidine infusion. Cimetidine causes modest but significant increases in gastric mucosal HCO₃^?. The clinical role, if any, of these increases in HCO₃^? in gastric mucosal defense remains to be determined.     

Progenitor cells are responsible for formation primary epithelial cultures in the prostate epithelial model

The adult stem cells (ASC) are supposed to regenerate epithelium. We hypothesized prostate epithelial CD133-positive ASC to be responsible for establishing the primary cell culture. The prostate epithelial stem cells were isolated using anti-CD133 microbeads in order to form different cell populations. The morphology of cultures developed from CD133⁺ and CD133⁻ prostate epithelial cells were compared with prostate epithelium cell culture obtained after simple isolation procedure. Four 8-week-old Wistar rats were used in the experiment and six cultures were obtained. Double CD133⁺ and CD133⁻ cultures from two rats were established after enzymatic digestion and positive selection by SuperMACS device, and two non-selected CD133⁺/CD133⁻ cultures were developed by simple prostate epithelial cell isolation from two other rats. The epithelial nature was confirmed by anti-cytokeratine antibodies. It was observed that growth of the CD133⁺/CD133⁻ and CD133⁺culture resembled epithelial-like prostate cell culture. It was not possible to establish epithelial-like culture from CD133⁻ cell population. The primary epithelial cell culture collapsed in a few days after the CD133-positive ASC were removed. We concluded that the epithelial progenitor cells are responsible for establishing primary prostate epithelial cultures in vitro.     

Potassium,sodium, and the intracellular fluid space of cells from bone

Summary Cells enzymatically dispersed from fetal rat calvaria were analyzed for sodium and potassium content and intracellular fluid space (ICF). Even when obtained in comparatively high yield, the cells are damaged by the isolation procedure as evidenced by high sodium and low potassium content immediately after isolation. During a post-incubation period potassium is accumulated and sodium extruded to steady-state levels. Although electrolyte content of cells after recovery did not vary as a function of cell yield, ICF was increased in cells obtained in lower yield, suggesting cell swelling as a result of membrane damage. The weighted mean values obtained for the best cell preparations were 117 mM K⁺ and 27 mM Na⁺. Based on DNA assay of isolated cells and the whole tissue, 20- to 21-day calvaria were found to have an average of 8.1 × 10⁶ cells/calvarium. Combining cell data with analysis of total tissue sodium, potassium, and water, it was concluded that the tissue extracellular sodium is in equilibrium with blood but that the potassium concentration is approximately 5-fold higher than blood levels.     

Electrophysiological properties of osteoblastlike cells from the cortical endosteal surface of rabbit long bones

Summary The mean transmembrane potential of cultured osteoblastlike cells isolated from the cortical endosteal surface of rabbit long bones was −16.9±0.64 mV (n=335). Elevation of potassium concentration in medium caused a decrease in potential. As the external concentration of potassium reached 15 mmol/liter and above, there was a linear relationship between the potassium concentration in log scale and the membrane potential with a slope of −13 mV per 10-fold change in external potassium concentration. Dibutyryladenosine 3′,5′-cyclic monophosphate, parathyroid extract, hydrocortisone, and sodium fluoride all depolarized the membrane of osteoblast-like cells after both short (1–2 h) and long (24 h) exposures at suitable doses, whereas calcitonin and prostaglandin E₂ hyperpolarized the membrane after long exposures. The Na⁺, K⁺ and Cl⁻ concentrations of cultured osteoblastlike cells were 0.538, 0.984, and 0.358 mmol/g protein or 52.6, 96.3, and 35.0 mmol/liter cell water, respectively. The protein content of these cells was 8.18±0.6 g/100 g cells and the water content was 83.7 g/100 g cells. The above-mentioned chemical and hormonal preparations in doses that produced significant changes in the membrane potential of these cultured cells did not alter their electrolyte or protein contents 24 h after exposure. Intracellular pH of cultured osteoblastlike cells as determined by [¹⁴C]-dimethyloxazolidine-2,4-dione and³H₂O averaged 7.03 ± 0.11 when the pH of culture medium was maintained at 7.4. Calculations based on the values for the membrane potential and the electrolyte concentrations observed in this study indicate that Na⁺, and H⁺, and Cl⁻ are actively transported out of the cells and K⁺ into the cells.     

Dynamics of cholesterol gallstone dissolution in canine bile

The effects of comparable grades of gastric ischemia induced either by intraarterial infusion of vasopressin or by tourniquet occlusion of the arterial supply were assessed in 12 anesthetized dogs. An ultramicro-electrode technique was used to determine intracellular oxygen tension and transmembrane potential difference in mucosal epithelial cells; total gastric oxygen consumption was calculated as the product of total gastric blood flow and arteriovenous oxygen content difference. At equivalent grades of gastric ischemia, the tourniquet method reduced oxygen tension and potential difference significantly more than did the vasopressin method. Conversely, total gastric oxygen consumption was significantly inhibited by vasopressin ischemia, but not by tourniquet ischemia, at 50 and 25% of baseline gastric blood flow. Our results suggest that, during tourniquet ischemia, blood flow in the stomach is redistributed away from the mucosal epithelium. Vasopressin, on the other hand, maintains mucosal oxygenation and metabolism relatively well, possibly at the expense of total gastric oxygen consumption. We conclude that the two methods of producing gastric ischemia should not be used interchangeably to study gastric mucosal ulceration during severe stress states.     

Effects of halothane and hypoxia on hepatic oxygen metabolism in the dog

Hepatic oxygen delivery and consumption were assessed in mongrel dogs receiving 2MAC of halothane combined with graded hypoxic hypoxemia (21–8% oxygen). Hepatic blood flow was measured using electromagnetic flowmetry; hepatic oxygen delivery and consumption were calculated from measured hepatic blood flow and oxygen content in hepatic arterial, portal venous and hepatic venous blood. In hypoxia-halothane group, total hepatic blood flow decreased at mild hypoxia (15% O₂) from control value, but recovered to control level at moderate hypoxia (10% O₂), then again decreased at 8% O₂. Oxygen supply to the liver was decreased with the augmentation of hypoxia in hypoxia-halothane and hypoxia-alone groups, and it was significantly lower in the hypoxia-halothane group at 15 and 12% O₂. Hepatic oxygen consumption also decreased from air control values with the increment of hypoxia, but there was no significant difference between the groups. Arterial ketone body ratio, which indicates mitochondrial energy charge level, decreased with the development of hypoxia but there was no significant difference in this ratio between the groups. These results show that halothane aggravated oxygen supply to the liver at mild to moderate hypoxia (15–12% O₂), but did not worsen it specifically at more serious hypoxia (10–8% O₂) compared with hypoxia alone. Hepatic hypoxia itself could not thus be a main cause of halothane hepatotoxicity.(Matsumoto N, Hori T, Miyazaki T et al.: Effects of halothane and hypoxia on hepatic oxygen metabolism in the dog. J Anesth 3: 27–34, 1989)     

The effect of cell-free and erythrocyte-containing perfusion in rat livers

The isolated perfused rat liver (IPRL) has been used to evaluate various aspects of hepatic metabolism. However, varying perfusion compositions, specifically differing concentrations of erythrocytes (RBC), make comparisons difficult. We evaluated oxygen and glucose consumption, sodium and potassium release, and hepatic enzyme release in rat livers perfused with either cell-free (CF) or 10% RBC-containing perfusates for 90 min. Perfusate oxygen content and hepatic oxygen consumption were increased in RBC vs CF perfusion (VO₂ = 0.0208 ± 0.002 (RBC) vs 0.0107 ± 0.001 (CF) ml O₂/min/g). Glucose consumption was increased in CF perfusion (0.295 ± 0.048 (CF) vs 0.173 ± 0.065 (RBC) mg/min/g). Sodium, potassium, and alkaline phosphatase release were not increased in either CF or RBC perfusion. SGOT and SGPT release occurred in both perfusion systems, although significantly greater elevations were documented by 75 min in CF perfusion. Bile flow was significantly elevated with RBC perfusion. High-power light microscopy and electron microscopy documented more cellular and subcellular injury in CF perfusion. We conclude that perfusion with 10% RBCs is associated with less cellular injury and enhanced oxygen delivery to the isolated perfused rat liver.     

Gastric Mucosal Energy Metabolism and “Stress Ulceration,”

Acute gastric erosions following hemorrhagic shock (stress ulceration) have been attributed to gastric hyperacidity, altered gastric secretion of mucus and an abnormal permeability of the gastric mucosa to H⁺. This report aims at presenting evidence supporting an alternate hypothesis: the event linking shock-induced gastric mucosal ischemia to mucosal necrosis is a deficit in gastric mucosal energy metabolism. Our experimental procedure consisted of harvesting the stomachs of rats and rabbits by “stop-freeze” (liquid N₂) at different intervals after the induction of hemorrhagic shock. Levels of adenosine-phosphates and of glycolytic intermediates in gastric mucosa were measured. We studied the changes in the levels of these substrates produced by shock as well as by factors capable, when combined with shock, of rendering the gastric mucosa more vulnerable to stress ulceration. The influence of shock and of these modifying factors were evaluated by comparison with data from appropriately designed control experiments. In parallel experiments we examined the frequency of stress ulceration (gross and microscopic) under these same standard conditions. There have emerged from these studies a number of observations all based upon data with the highest statistical significance. The data are consonant with the hypothesis stated above: an energy deficit severe enough to cause cellular necrosis is the event linking shock-induced gastric mucosal ischemia and stress ulceration.     

CD146 as a new marker for an increased chondroprogenitor cell sub‐population in the later stages of osteoarthritis

Cartilage‐derived mesenchymal stem cells (MSCs) have been isolated with different methods. In this study lateral and medial femoral condyles were respectively collected from patients with late‐stage osteoarthritis during the total knee arthroplasty. After digestion of the cartilage tissues with type II collagenase and analysis by fluorescence‐activated cell sorting (FACS) with CD146, a chondroprogenitor cell sub‐population were isolated and purified. The expression of other MSC‐associated markers in the CD146⁺ chondroprogenitors was analyzed by flow cytometry. Multi‐lineage differentiation capacity of CD146⁺ chondroprogenitors was compared with that of unsorted chondrocytes and adipose‐derived MSCs (ADMSCs). Higher percentage of CD146⁺ chondroprogenitors isolated from the medial femoral condyles was observed than that from the lateral. CD146⁺ chondroprogenitors expressed high levels of MSC‐specific surface antigens, and showed higher chondrogenesis capacity than ADMSCs and unsorted chondrocytes in a 3D cell pellet culture model. Thus CD146 might be a new cell surface marker for cartilage progenitor cell population in the late‐stage osteoarthritis. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:84–91, 2015.     

Pig liver perfusion with membrane oxygenator: a study of liver viability by means of the mitochondrial respiration test

The perfusion of isolated pig livers with autologous or heterologous blood using membrane oxygenators was compared with respect to O₂ consumption, CO₂ production, bile secretion, and mitochondrial function.Significantly low values of mitochondrial respiratory control and ADP:O ratios were found in the group perfused with heterologous blood.Our results indicate that the study of mitochondrial functions is a useful parameter for definition of the metabolic integrity of the perfused liver and the validity of the utilization of membrane oxygenators in hepatic perfusion.     

Halothane suppresses the increase in intracellular calcium concentration of isolated rat myocytes during hydrogen peroxide perfusion

Ischemia-reperfusion injury is probably caused by the generation of oxygen free radicals. The final common pathway to cell injury may be mediated by intracellular calcium overloading induced by oxygen free radicals. Volatile anesthetics have been shown to improve myocardial function following reperfusion. To determine whether or not oxygen radicals are involved in the mechanism by which volatile anesthetics improve myocardial function following reperfusion, we investigated the effects of hydrogen peroxide (H₂O₂) on the intracellular calcium concentration ([Ca²⁺]_i) in isolated rat ventricular cells. First, the effects of volatile anesthetics, halothane, isoflurane, or sevoflurane, on [Ca²⁺]_i were studied in the absence of H₂O₂. Next, myocytes were perfused with volatile anesthetics in the presence of H₂O₂. [Ca²⁺]_i was measured using fura-2, a Ca²⁺-sensitive fluorescent dye. None of the volatile anesthetics changed [Ca²⁺]_i in the absence of H₂O₂. In the presence of H₂O₂, [Ca²⁺]_i gradually increased during H₂O₂ perfusion. Halothane delayed the onset of the increase in [Ca²⁺]_i induced by H₂O₂, whereas sevoflurane and isoflurane accelerated the onset. Furthermore, sevoflurane caused more pronounced accumulation of intracellular calcium than did halothane and isoflurane. Therefore, the reduction of excessive intracellular calcium accumulation caused by halothane may have beneficial effects on myocardial function following reperfusion.     

The role of histamine in control of gastric mucosal blood flow in dogs

The role of the histamine receptors in the control of gastric mucosal blood flow was evaluated in dogs utilizing [¹⁴C]aminopyrine ([¹⁴C]AP) clearance techniques. Because of the importance of maintaining a low intragastric pH to prevent dissociation of AP and back diffusion through the gastric mucosa, AP was traped in the stomach lumen by intragastric perfusion of a marker solution with a pH of 1.16. Results obtained utilizing a marker to determine gastric secretory volume and gastric juice [¹⁴C]AP concentration correlated well with those values obtained from direct measurements from fluid collected from a gastric fistula. Histamine base administration increased [¹⁴C]AP clearance. Cimetidine, an H₂ receptor antagonist, did not significantly change basal [¹⁴C]AP clearance and inhibited [¹⁴C]AP clearance at low doses of histamine administration. An H₂ receptor agonist (4-methylhistamine) and an H₁ receptor agonist (2-methylhistamine) each increased mucosal blood flow approximately 30% and 70%, respectively, of the response produced by histamine base. Blood flow stimulated by 2-methylhistamine was inhibited by the H₁ receptor antagonist diphenhydramine. The results suggest that histamine H₁ and H₂ receptors are involved in the control of canine gastric mucosal blood flow.     

Differential phenotypic behaviors of human degenerative nucleus pulposus cells under normoxic and hypoxic conditions: influence of oxygen concentration during isolation,expansion, and cultivation

Background contextIntervertebral discs (IVDs) are the largest avascular structures in the body; therefore, cells within these discs might be adapted to low-oxygen conditions. Although it has been demonstrated that a low oxygen concentration could promote synthesis of the extracellular matrix by IVD cells in the in vitro culture, isolation, expansion, and cultivation of IVD cells under classical tissue culture O₂ saturation could still be detrimental.PurposeTo investigate the phenotypic differences between human degenerative nucleus pulposus (NP) cells during isolation and expansion under normoxic (Nx: 21% O₂) or hypoxic (Hx: 3.5% O₂) conditions.Study designWe investigated in vitro isolation, expansion, and cultivation of human NP cells.MethodsHuman NP tissue samples were obtained from patients who underwent lumbar disc surgeries. Nucleus pulposus cells were then isolated, expanded, and cultivated under normoxic or hypoxic conditions. To determine whether the effects of normoxic expansion are reversible, another group of cells was isolated and expanded in normoxic conditions and then cultivated under hypoxic conditions (Nx→Hx group). Cellular proliferation, RNA expression of selected genes, and immunohistochemical staining were performed to evaluate the phenotypic behaviors of human NP cells under different conditions.ResultsExpressions of Type II collagen and aggrecan in the Nx→Hx group were significantly higher than those in the normoxic group but were significantly lower than those in the hypoxic group. The normoxic group showed higher expression of matrix metalloproteinase (MMP)-2 and MMP-13 than did the other groups. Expression levels of hypoxia-inducible factors (HIFs) were significantly higher in the normoxic groups; however, a greater degree of HIF-1α staining was found in the hypoxic group, whereas a greater degree of HIF-2α staining was found in the normoxic group.ConclusionsHuman degenerative NP cells isolated, expanded, and cultivated in hypoxic conditions could better preserve the cells' regenerative potential. Compromised properties that were observed during isolation and expansion under normoxic conditions could only be partially rescued by later hypoxic cultivation. The superior phenotypic behaviors of human NP cells under hypoxia may be related to higher HIF-1α production and lower HIF-2α production. Cells that are isolated, expanded, and cultivated under hypoxic conditions may show better regenerative results when transplanted; therefore, the isolation and expansion processes of human degenerative NP cells should be managed in a hypoxic environment.     

Gastric mucosal pH does not reflect changes in splanchnic blood flow after cardiac surgery

Despite the widespread use of gastric tonometry to assess splanchnicoxygen transport, no human data are available on the relationshipbetween splanchnic blood flow, splanchnic oxygen delivery andgastric mucosal pH. We have studied the effect of splanchnicblood flow and oxygen delivery on gastric mucosal pH after cardiacsurgery. During the first postoperative hours of intensive care,dopexamine was infused to increase cardiac output in eight patients,while six patients served as controls. Gastric mucosal pH (gastrictonometry), splanchnic blood flow and splanchnic oxygen deliveryand consumption (dye dilution) were measured. Dopexamine administrationsignificantly increased splanchnic blood flow (0.72 vs 1 .02litre min^–1 m^–2 (P < 0.05) and oxygen delivery(117 vs 161 ml min^–1 m^–2 (P < 0.05) comparedwith base line values. However, splanchnic oxygen consumptionremained unchanged and gastric mucosal pH levels decreased (7.30vs 7.25) (P < 0.05). The proportion of splanchnic blood flowof cardiac output did not change in response to infusion ofdopexamine, that is dopexamine did not favour blood flow distributionto the splanchnic region. In the control group there were nochanges in splanchnic blood flow and oxygen delivery, whilesplanchnic oxygen consumption increased (36 vs 39 ml min^–1m^–2 (P < 0.05) and gastric mucosal pH tended to decrease(7.33 vs 7.29) (ns). We conclude that after cardiac surgerygastric mucosal pH did not reflect changes in splanchnic bloodflow and oxygen delivery suggesting heterogeneous or inadequateblood flow distribution within the splanchnic region.