Accuracy of noninvasive estimates of respiratory muscle effort during spontaneous breathing in restrictive diseases.

Mean inspiratory pressure (Pi), estimated from the occlusion pressure at the mouth and the inspiratory time, is useful as a noninvasive estimate of respiratory muscle effort during spontaneous breathing in normal subjects and patients with chronic obstructive pulmonary disease. The aim of this study was to compare the Pi with respect to mean esophageal pressure (Pes) in patients with restrictive disorders. Eleven healthy volunteers, 12 patients with chest wall disease, 14 patients with usual interstitial pneumonia, and 17 patients with neuromuscular diseases were studied. Pi, Pes, and mean transdiaphragmatic pressure were simultaneously measured. Tension-time indexes of diaphragm (TTdi) and inspiratory muscles (TTmu) were also determined. In neuromuscular patients, significant correlations were found between Pi and Pes, Pi and transdiaphragmatic pressure, and TTmu and TTdi. A moderate agreement between Pi and Pes and between TTmu and TTdi was found. No significant correlation between these parameters was found in the other patient groups. These findings suggest that Pi is a good surrogate for the invasive measurement of respiratory muscle effort during spontaneous breathing in neuromuscular patients.     

Structure of maritimin,a sesquiterpene lactone from artemisia maritima gallica

1-Keto-6β,7α,11β-H-selin-4(5)-en-6,12-olide, vulgarin and a new eudesmanolide, maritimin, were isolated from Artemisia maritima gallica. The structure and stereochemistry of this lactone have been determined by spectral studies and chemical transformations.     

Factors controlling the metabolic response to glucose in isolated rat lung cells

Glucose decreases the oxygen utilization by isolated rat lung cells. Its effect displays saturation type kinetics with a “Ki” of 2.2. mM. The similarity of this value with the reported “Km” of 2.4 mM described for glucose uptake by these cells, suggests that both processes may be intimately related and both of them are under the control of the same rate limiting step. Several arguments point to glucose transport into these cells as the most important rate limiting step for its utilization: 1) Phloridzin prevented glucose inhibition of oxygen uptake while mannoheptulose did not; 2) The activity of hexokinase which is the least active glycolytic enzyme in these cells far exceeded the observed rates of glucose utilization and a decrease of 45 per cent in its activity in starved animals did not affect the rate of glucose uptake; 3) The “Km” of hexokinase for glucose is two orders of magnitude below the observed “Km” for glucose uptake and the “Ki” for glucose inhibition of respiration.     

Transglutaminase-catalyzed incorporation of [2,5-3H]histamine into a Mr 84000 particulate protein in pancreatic islets

Rat pancreatic islet homogenates catalyze the incorporation of [2,5^–3-H]histamine into endogenous proteins recovered in both the stacking gel and a Mr 84000 protein separated by polyacrylamide electrophoresis. The labelling of these proteins represents a Ca²⁺-dependent process inhibited by glycine methylester, but not sarcosine methylester, and enhanced after preincubation of the islets at a high concentration of D-glucose. Although transglutaminase activity is found in both soluble and particlate subcelluler fractions, the endogenous transglutaminase substrates were located mainly in paarticulate, possibly membrane-associated, material.     

H and B human blood-group antigen expression in cochlear hair cells is modulated by thyroxine

The presence of human blood-group antigens in developing and adult hypothyroid rat cochleas was analyzed using antibodies directed against antigens H and B. During postnatal development, hypothyroid rat cochleas exhibited a highly selective expression of both B and H antigens, mainly at the hair cell level. Labeling for antigen B was found throughout the hair cells, whereas the antibody directed against antigen H selectively labeled the apical part of these cells. These immunostaining patterns were similar to those found in normal (euthyroid) rat cochleas, but antigenic expression periods were clearly prolonged. Thus, whereas in normal rat cochleas, the B and H antigenic expression disappears from postnatal day (PD) 9 on, in cochleas of hypothyroid rats the reactivity was intense until PD15; it decreased from this developmental stage, and was negative or only faintly positive at PD30. Therefore, in congenital hypothyroidism, hair cell immunoreactivity is present at developmental stages that are negative in normal rat cochleas. These results suggest that human blood-group antigen expression on the developing cochlear hair cells of rats is modulated by thyroxine and that thyroxine is necessary for the temporal expression pattern and secretion of normal glycoproteins.     

Characterization of transport-mediated methotrexate resistance in human tumor cells with antibodies to the membrane carrier for methotrexate and tetrahydrofolate cofactors.

An earlier report (Matherly, L. H., Czajkowski, C. A., and Angeles, S. M. (1991) Cancer Res. 51, 3420-3426) described a K562 human erythroleukemia line (K562.4CF), characterized by an elevated uptake capacity for methotrexate (MTX) and 5-formyltetrahydrofolate, and the identification of a highly glycosylated membrane transporter (GP-MTX) by radioaffinity labeling with N-hydroxysuccinimide [3H] methotrexate. In the present study, radioaffinity-labeled GP-MTX from K562.4CF cells was isolated by Ricinus communis agglutinin I-agarose affinity chromatography, coupled with gel filtration and preparative electrophoresis. Antiserum to the purified, radio-labeled protein was raised in a rabbit and screened by immunoblot analysis of K562.4CF plasma membrane proteins or purified GP-MTX. The antiserum detected a broad GP-MTX band centered at 92 kDa on 7.5% gels. On 4-10% gels, the apparent molecular mass for GP-MTX shifted to 99 kDa. Antiserum specificity was established by quantitatively converting the immunoreactive glycoprotein in plasma membrane homogenates to its N- and O-deglycosylated forms with N- and O-glycanases, respectively. Whereas the methotrexate uptake capacity of K562.4CF cells was elevated 6.1-fold over parental cells, the GP-MTX content on immunoblots was increased approximately 3-fold. For two methotrexate-resistant K562 lines (33- and 70-fold), decreased drug uptake (28 and 18% of parental levels) closely correlated with their reduced GP-MTX contents. A GP-MTX isoform was also detected on immunoblots of membrane proteins from CCRF-CEM human lymphoblastic leukemia cells. With a transport-impaired CCRF-CEM line (13% of wild type uptake), an aberrant electrophoretic migration for GP-MTX was observed, establishing the presence of structural modifications in the transport protein. These structural differences were independent of carrier glycosylation since they were detected following the glycosidase treatments. These findings implicate important roles for distinct carrier-specific alterations in the expression of diminished drug transport in methotrexate-resistant human tumor cells.