Mass-spectrometric disequilibrium analysis was applied to investigate CO2 uptake and HCO3 2 transport in cells and chloroplasts of the microalgae Dunaliella tertiolecta and Chlamydomonas reinhardtii, which were grown in air enriched with 5% (v/v) CO2 (high-Ci cells) or in ambient air (low-Ci cells). Highand low-Ci cells of both species had the capacity to transport CO2 and HCO3 , with maximum r...

1. Salt-water crocodiles, Crocodylus porosus Schneider, were catheterized and Po2, Pco2, pH and lactate concentration ([lactate]) were measured in arterial blood during rest and after forced exhaustive activity at 30°C. 2. Gas exchange ratio (R), calculated from blood Po2 and Pco2, decreased from about 1-0 to 03 during resting voluntary breath-holding and indicated CO2 sequestration in the body...

Luminal acidification provides the strongest physiological stimulus for duodenal HCO3- secretion. Various neurohumoral mechanisms are believed to play a role in acid-stimulated HCO3- secretion. Previous studies in the rat and human duodenum have shown that guanylin and Escherichia coli heat-stable toxin, both ligands of the transmembrane guanylyl cyclase receptor [guanylate cyclase C (GC-C)], a...

BACKGROUND The aim of the study was to test the hypothesis that in the fasting state, proximal intestinal HCO3- absorption, which depends on villus Na+/H+ exchanger activity, is tonically inhibited by a cholinergic atropine sensitive mechanism. SUBJECTS The experiments were performed in 34 healthy volunteers and in eight patients with intestinal villus atrophy. METHODS HCO3- absorption was ...

Submerged lobsters at 15°C were normoxaemic (CaO2 = 0-52 mmol 1~ 1 at a PaO2 of 6-53 kPa) and normocapnic (Paco2 = 0-44kPa; [HCO3~] = 9-3mequivl~ 1 and pHa = 7-78). After 3h in air the haemolymph was markedly hypoxic and hypercapnic (Paoj= 1-6 kPa; C a o ^ 0-2 mmol I"; Paco2 = 0-7kPa and pHa = 7-64). Disturbance after 3h in air caused a greater increase in PacO2 to 1-28 kPa and a fourfold incre...

In vivo experiments were conducted to determine how the physiological response to exhaustive exercise in rainbow trout (Oncorhynchus mykiss) is affected by environmental temperature. The white muscle acid­base status (e.g. pH, PCO2, HCO3- and deltaH+m) and metabolite (e.g. lactate, phosphocreatine, ATP and glycogen) content, and the acid­base status and lactate concentrations in the blo...

INDIAN PEDIATRICS 1051 VOLUME 42OCTOBER 17, 2005 and hepatosplenomegaly. She was started on ART due to clinical deterioration and immunological suppression. Her serial CD4 and virological parameters with ART regimes are depicted in Table I. At 91⁄2 years of age, she had positive Mantoux test (20 × 15 mm) with weight loss and normal X-ray chest. She was started on antituberculous therapy (ATT) c...

We have developed a technique to measure the fluorescence of a pH-sensitive dye (2,7-biscarboxyethyl-5(6)-carboxyfluorescein) in single glomerular mesangial cells in culture. The intracellular fluorescence excitation ratio of the dye was calibrated using the nigericin-high-K+ approach. In the absence of CO2-HCO3-, mesangial cells that are acid loaded by an NH+4 prepulse exhibit a spontaneous in...

The pancreatic duct secretes alkaline fluid that is rich in HCO3- and poor in Cl-. The molecular mechanisms that mediate ductal secretion and are responsible for the axial gradients of Cl- and HCO3- along the ductal tree are not well understood because H+ and HCO3- transport by duct cells have not been characterized or localized. To address these questions, we microdissected the intralobular, m...

The medullary collecting duct (MCD) from renal outer medulla possesses significant HCO3 absorptive capacity. In vitro microperfusion studies have shown that HCO3 absorption in this segment is carbonic anhydrase dependent, affected by peritubular and luminal chloride concentrations, is independent of the presence of Na or the presence of Na transport, and is stimulated by mineralocorticoid hormo...