Effects of hyperventilation and hypocapnic/normocapnic hypoxemia on renal function and lithium clearance in humans

BACKGROUND: Using the renal clearance of lithium as an index of proximal tubular outflow, this study tested the hypothesis that acute hypocapnic hypoxemia decreases proximal tubular reabsorption to the same extent as hypocapnic normoxemia (hyperventilation) and that this response is blunted during normocapnic hypoxemia. METHODS: Eight persons were studied on five occasions: (1) during inhalation of 10% oxygen (hypocapnic hypoxemia), (2) during hyperventilation of room air leading to carbon dioxide values similar to those with hypocapnic hypoxemia, (3) during inhalation of 10% oxygen with the addition of carbon dioxide to produce normocapnia, (4) during normal breathing of room air through the same tight-fitting face mask as used on the other study days, and (5) during breathing of room air without the face mask. RESULTS: Hypocapnic and normocapnic hypoxemia and hyperventilation increased cardiac output, respiratory minute volume, and effective renal plasma flow. Glomerular filtration rate remained unchanged on all study days. Calculated proximal tubular reabsorption decreased during hypocapnic hypoxemia and hyperventilation but remained unchanged with normocapnic hypoxemia. Sodium clearance increased slightly during hypocapnic and normocapnic hypoxemia, hyperventilation, and normocapnic normoxemia with but not without the face mask. CONCLUSIONS: The results indicate that (1) respiratory alkalosis with or without hypoxemia decreases proximal tubular reabsorption and that this effect, but not renal vasodilation or natriuresis, can be abolished by adding carbon dioxide to the hypoxic gas; (2) the increases in the effective renal plasma flow were caused by increased ventilation rather than by changes in arterial oxygen and carbon dioxide levels; and (3) the natriuresis may be secondary to increased renal perfusion, but application of a face mask also may increase sodium excretion.     

Production of inflammatory mediators by human macrophages obtained from ascites

Ascites is a readily available source of human macrophages (M phi), which can be used to study M phi functions in vitro. We characterized the mediators of inflammation produced by human peritoneal M phi (hp-M phi) obtained from patients with portal hypertension and ascites. The production of the cytokines interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) was found to be lipopolysaccharide (LPS) concentration dependent (0-10 micrograms/ml) with a maximal production at 10 micrograms/ml and also dependent on the time of exposure to the stimulus (0-36 h). IL-1 beta, IL-6 and TNF-alpha production after LPS administration reached a plateau at 24 h. In vitro stimulation for 24 h with LPS does not influence the eicosanoid production from endogenous arachidonate. 13 min of exposure of the cells to the calcium ionophore A23187 gives a significant increase in eicosanoid production from both exogenous and endogenous arachidonate. The main eicosanoids produced are the 5-lipoxgenase products LTB4 and 5-hydroxyeicosatetraenoic acid (HETE). The increase in production of the other eicosanoids is not significant. The eicosanoid production depends on the stimulus concentration. The optimal A23187 concentration is 1 microM. Oxygen radical production was measured in the M phi by a flowcytometric method. The fluorescence intensity of phorbol 12-myristate 13-acetate stimulated and dihydro-rhodamine 123 loaded hp-M phi increases significantly after 15 min. We conclude that LPS stimulation of hp-M phi from liver disease results in similar production of IL-1 beta, IL-6 and TNF-alpha, but that the profile of the eicosanoid production of these M phi stimulated with LPS and A23187 differs from M phi of other origin and species.     

Biological activities of some Argyranthemum species

Seven species of the genus Argyranthemum were studied for antimicrobial and cytotoxic activities. Argyranthemum adauctum, A. foeniculaceum and A. frutescens showed antimicrobial activity against Gram-positive and Gram-negative and cytotoxic activity against HeLa and Hep-2 cell lines. Two new acetylenic compounds, frutescinol isovalerate and 3'-demethyl frutescinol isovalerate, were isolated from A. frutescens and their structures elucidated by spectroscopic studies.     

Neoplastic fixation to the prevertebral compartment by squamous cell carcinoma of the head and neck

OBJECTIVE: The purpose of this study was to determine the accuracy of MR imaging in determining fixation of squamous cell carcinomas to the prevertebral space. MATERIALS AND METHODS: MR images of 15 patients with large pharyngeal carcinoma (n = 13) or laryngeal carcinomas with pharyngeal extension (n = 2) were retrospectively reviewed independently by two head and neck radiologists who were unaware of the surgical findings. MR images were evaluated for four criteria in the prevertebral longus muscle complex: muscle concavity, irregular tumor-muscle interface, T2 hyperintensity, and enhancement. All patients underwent panendoscopy where fixation or mobility of the tumor relative to the prevertebral fascia was assessed by manual manipulation. Tumors in six patients were fixed to the prevertebral space and inoperable. In nine patients whose tumors were not fixed, open neck explorations were performed and tumors were resected in seven patients. MR findings were compared with panendoscopy in all patients and with intraoperative assessment in nine patients. RESULTS: Eleven of 15 patients had at least two of the MR imaging criteria present. None of the MR findings were both sensitive and specific for tumor fixation. Although muscle concavity and enhancement each had a sensitivity of 88%, both criteria suffered from low specificity (14% and 29%, respectively). An irregular tumor-muscle interface and muscle T2 hyperintensity were criteria that suffered from both low sensitivity and specificity. Accuracy of the imaging criteria independently ranged from 53% to 60%. CONCLUSION: Although abnormal muscle contour, T2 hyperintensity, and enhancement are frequently present in neck carcinomas that are fixed to the prevertebral space, these findings may also be present in patients in whom the tumor is mobile and resectable. MR imaging may not be able to differentiate between neoplastic fixation and nonneoplastic changes in the prevertebral space.     

New insights into the photocycle of Ectothiorhodospira halophila photoactive yellow protein: photorecovery of the long-lived photobleached intermediate in the Met100Ala mutant

There are previously two known intermediates (I1 and I2) in the room-temperature photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila. The three-dimensional structures of ground-state PYP and of I2 have shown that light-induced conformational changes are localized to the active site. Previous site-specific mutagenesis studies of PYP in our laboratories have characterized two active site mutants (Glu46Gln and Arg52Ala). We now report the construction and characterization of a mutant at a third active site position (Met100Ala) in order to establish the role of this residue in the photocycle. Met100Ala PYP has an absorption spectrum which is very similar to wild-type (WT) PYP, but exhibits very different kinetic properties. At pH 7.0, the light-induced bleaching reaction (I2 formation) has a half-life <1 microseconds and the recovery in the dark has a half-life of 5.5 min, as compared with half-lives of 100 microseconds and 140 ms for the same reactions in WT PYP. The slow rate of recovery from I2 for Met100Ala results in the accumulation of the bleached intermediate even under room light illumination. These results are qualitatively similar to what has been observed with the Arg52Ala mutant of PYP, and with WT PYP in the presence of alcohols or urea, and suggest that Met100 acts to stabilize the ground state of the protein. The midpoint for guanidine denaturation confirms this. The slow recovery of I2 in the Met100Ala mutant has allowed us to obtain direct evidence that this intermediate species is also photoactive and can be returned to the ground state by a 365 nm laser flash, with kinetics (half-life = 160 microseconds; k = 6300 s-1) which are 6 orders of magnitude faster than dark recovery. This implies that chromophore reisomerization limits the rate of conversion of I2 to the ground state in PYP. Met100 is in van der Waals contact with the chromophore in the I2 state, and we suggest that the sulfur atom catalyzes cis-trans isomerization in WT PYP.     

Decomposition of monocrotophos in aqueous solution by UV irradiation in the presence of titanium dioxide

The decomposition of monocrotophos in aqueous solution by UV/TiO2 reduction process was studied under various pH values, TiO2 dosages, light intensities, dissolved oxygen levels and other operating conditions. The presence of dissolved oxygen inhibits the recombination of electrons and holes, and enhance the decomposition of monocrotophos by UV/TiO2 process, but excessive dissolved oxygen posed no further effect on the decomposition of monocrotophos. The decomposition rates of monocrotophos were significantly higher for acidic solutions than those for alkaline solutions. Increasing the light intensity would drastically increase the decomposition rate of monocrotophos, but was ultimately influenced by the amount of TiO2 present in solutions. The quasi-global kinetics based on a simplified consecutive reaction scheme was developed to describe the temporal behavior of monocrotophos decomposition in aqueous solution by UV/TiO2 process.     

Structural determinants of the bifunctional corn Hageman factor inhibitor: x-ray crystal structure at 1.95 A resolution

Corn Hageman factor inhibitor (CHFI) is a bifunctional 127 residue, 13.6 kDa protein isolated from corn seeds. It inhibits mammalian trypsin and Factor XIIa (Hageman Factor) of the contact pathway of coagulation as well as alpha-amylases from several insect species. Among the plasma proteinases, CHFI specifically inhibits Factor XIIa without affecting the activity of other coagulation proteinases. We have isolated CHFI from corn and determined the crystallographic structure at 1.95 A resolution. Additionally, we have solved the structure of the recombinant protein produced in Escherichia coli at 2.2 A resolution. The two proteins are essentially identical. The proteinase binding loop is in the canonical conformation for proteinase inhibitors. In an effort to understand alpha-amylase inhibition by members of the family of 25 cereal trypsin/alpha-amylase inhibitors, we have made three-dimensional models of several proteins in the family based on the CHFI coordinates and the coordinates determined for wheat alpha-amylase inhibitor 0.19 [Oda, Y., Matsunaga, T., Fukuyama, K., Miyazaki, T., and Morimoto, T. (1997) Biochemistry 36, 13503-13511]. From an analysis of the models and a structure-based sequence analysis, we propose a testable hypothesis for the regions of these proteins which bind alpha-amylase. In the course of the investigations, we have found that the cereal trypsin/alpha-amylase inhibitor family is evolutionarily related to the family of nonspecific lipid-transfer proteins of plants. This is a new addition to the group which now consists of the trypsin/alpha-amylase inhibitors, 2S seed storage albumins, and the lipid-transfer family. Apparently, the four-helix conformation has been a successful vehicle in plant evolution for providing protection from predators, food for the embryo, and lipid transfer.