Human erythrocyte membrane proteins of zone 4.5 exist as families of related proteins

Role of inflammation in mouse lung tumorigenesis: a review

Peritumoral and intratumoral macrophages are associated with human and mouse lung cancer The mouse model allows manipulation of the macrophage population to experimentally evaluate its contribution to tumor growth. Genetic and pharmacologic strategies also permit testing the invol vement of specific inflammatory mediators in tumor progression. Among those endogenous mediators thus identified are interleukin (IL)-10, glucocorticoids, prostacyclin, nitric oxide, and surfactant apoprotein D (SP-D); serum SP-D levels are a useful biomarker to monitor tumor growth rate. The importance of understanding the mutually antagonistic roles of individual prostaglandins downstream from cycloxygenase (COX) and how this affects the efficacy of COX-inhibitory drugs is discussed. Promising drug candidates include synthetic glucocorticoids such as budesonide and the sulfone derivative of sulindac, apotosyn.

Effects of streptozotocin-induced diabetes on postpneumonectomy lung growth and connective tissue levels

Diabetes is generally accompanied by abnormal levels of growth hormone and adrenal steroids, hormones known to modulate postpneumonectomy (post-PNX) compensatory lung growth. Thus, we examined the possibility that diabetes may affect post-PNX lung growth processes. Left PNX was performed in young diabetic rats (streptozotocin-induced; 75 mg/kg body weight) (DM-PNX) and in control rats (C-PNX), for comparison with sham-operated control rats (C-SHAM). The rats were permitted free access to food and water. Examination at day 7 after surgery showed that right lung absolute dry weight and absolute DNA, collagen and elastin contents were increased in C-PNX and DM-PNX rats (but only C-PNX values reached those of both lungs in C-SHAM rats). Body weights (BW) of DM-PNX rats were lower than those of C-PNX and C-SHAM rats. Lung DNA/BW in C-PNX and DM-PNX rats were comparable, and matched values for both lungs in C-SHAM rats. Lung dry weight/BW, collagen/BW, and elastin/BW in DM-PNX rats exceeded values in C-PNX rats and even more for values of both lungs in C-SHAM rats. Data of another experiment, comparing DM-PNX rats with body weight-matched (by food limitation) PNX and control rats (WMC-PNX and WMC-SHAM rats, respectively) indicated comparable lung absolute DNA contents in DM-PNX and WMC-PNX rats (which matched values for both lungs in WMC-SHAM rats), however, lung absolute collagen and elastic contents were greater in the DM-PNX rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and function of multiple anion transporter proteins in brain tumor cell lines in relation to glucose transport

The anion transport, "band 3," family of proteins in mammalian brain performs the same functions as that of erythroid band 3. These functions are anion transport, ankyrin binding, and generation of senescent cell antigen, an aging antigen that terminates the life of cells. The presence of 5-7 band 3 related proteins in brain tissue was suggested by the reaction of antibodies to synthetic peptides of erythroid band 3 with a number of bands in immunoblots. Since there are a number of different cell types in brain, tissue cultures of neural cell types were examined to determine whether multiple band 3 related proteins are present in each cell type or whether several band 3 related proteins are present in each cell type. The tumor cell lines exhibit anion transport and are inhibited by the anion transport inhibitors 4,4'-diisothiocyano-2,2' disulfonic acid (DIDS), phenylglyoxal, and furosemide. Glucose transport is inhibited by cytochalasin B and the anion transport inhibitor, phenylglyoxal, in these cell lines, but not by 4,4'-diisothiocyano-2,2' disulfonic acid. Furosemide gave partial inhibition of most, but not all, cell lines. Since phenylglyoxal inhibits anion transport by binding to an arginine near the transport site, inhibition of glucose transport by phenylglyoxal suggests that an arginine lies in the substrate binding site. The number of cytochalasin B and DIDS binding sites was quantitated on cell lines as an approximation of the number of glucose transporter and anion transporter sites, respectively.

Postpneumonectomy lung growth following thyroparathyroidectomy

Hormonal regulation of compensatory lung growth is not well understood, but it may be similar to that during compensatory growth of other organs. Liver regeneration is blocked by hypocalcemia in thyroparathyroidectomized (TPX) animals. Although calcium status is an important regulator of growth in many biological systems, the effect of TPX on compensatory lung growth is unknown. In male Sprague-Dawley rats, TPX lowered blood ionized calcium by 42% (p < .01) within two days; it remained depressed for at least one additional week. Thyroid-intact and TPX animals were therefore subjected either to sham thoracotomy or to left pneumonectomy on post-TPX day 2. Growth of the right lung was assessed on day 9 when, in pneumonectomized animals, lung mass had increased 23% (p < .01). TPX had no effect on right lung mass in sham animals. Similarly, TPX had no effect on the postpneumonectomy increase in right lung mass, which reached 118% (p < .01) of that in TPX controls. Analysis of right lung DNA, RNA, and protein concentrations on day 9 revealed that tissue macromolecule content increased postoperatively in both PNX and TPX/PNX rats in proportion to lung growth. These results demonstrate that postpneumonectomy compensatory growth of the lung is not blocked in the thyroparathyroprivic hypocalcemic rat.

Molecular aspects of water transport

Due to its fundamental importance, the movement of water across cell membranes has been an active area of research for more than 100 years. This subject is central to consideration of normal water metabolism by terrestrial animals, as well as derangements in overall water balance that are frequently encountered by nephrologists in the care of their patients. The objective of this review is to discuss the most basic aspects of cell membrane water permeability and provide a framework for these data in the context of the care of pediatric patients with renal disease. While the water permeability of most cell membranes can be accounted for by the diffusion of water across the lipid bilayer, other cells, including the red blood cell and certain epithelial cells that line the proximal and collecting tubules of the kidney and the urinary bladder of amphibians, possess specialized water channels. Water channels are composed of specialized proteins that create aqueous pores across cell membrane. Currently, there are active research efforts to isolate and characterize water channel proteins from these cell types. Data concerning the distribution, permeability and function of these various water channels will greatly enhance our knowledge of how water is transported across cell membranes.

Autoradiographic assessment of the sequence of cellular proliferation in postpneumonectomy lung growth

To determine the extent and sequence of proliferation of the various types of cells in postpneumonectomy lung growth, 4-wk-old male Sprague-Dawley rats were injected with tritiated thymidine prior to sacrifice on days 2, 4, 7, and 10 after left pneumonectomy. Autoradiography of sections from each lobe of the remaining lung was performed and compared to controls. All of the cell types studied, both parenchymal and nonparenchymal, participated in postpneumonectomy lung growth. Mesothelial cell labeling peaked on day 2 and declined thereafter. Labeling of alveolar endothelial cells, alveolar interstitial cells, types I and II pneumonocytes, bronchial epithelium, and nonparenchymal endothelium occurred in parallel, peaking on day 4. The different lobes had equal percentages of dividing cells, suggesting that a global stimulus such as an endocrine factor has a dominant role in postpneumonectomy lung growth.

Erythrocyte membrane skeleton phosphoproteins: identification of two unrelated phosphoproteins in band 4.9

Human erythrocyte membrane band 4.9 is phosphorylated by several erythrocyte protein kinases. Chromatography of erythrocyte membrane skeleton proteins on DEAE-Sephacel produces two proteins with relative mobilities, on gel electrophoresis, similar to that of band 4.9. The first, with a molecular mass of 49 kDa, is quite basic (pI greater than 8) while the second, 50.5 kDa, is slightly acidic (pI = 6.2). Comparative two-dimensional peptide mapping reveals that both proteins are present in band 4.9 on one-dimensional gels of total erythrocyte membrane proteins and membrane skeleton proteins. The 49 kDa protein, but not the 50.5 kDa protein, binds to actin filaments in a sedimentation assay. In intact erythrocytes metabolically labeled with [32P]orthophosphate, the 49 kDa protein is phosphorylated by protein kinase C, cAMP-dependent protein kinase, and protein kinases which are active in the absence of exogenous kinase activators. In contrast, the 50.5 kDa protein is phosphorylated by protein kinase C but not by the other protein kinases examined. Finally, two-dimensional peptide mapping was employed to compare the 49 kDa protein and a 57 kDa protein which copurifies with, and has many characteristics of, the 49 kDa protein. Significant similarities were found in both 125I-labeled chymotryptic peptide maps and 32P-labeled tryptic peptide maps, suggesting that the 49 kDa and 57 kDa proteins are closely related.

Compensatory growth of the lung following partial pneumonectomy

In a variety of species, partial resection of the lung initiates rapid compensatory growth of the remaining tissue adequate to restore normal total lung mass. Increases in tissue content of protein, RNA, and DNA in proportion to dry lung weight suggest hyperplastic growth of the tissue, rather than cellular hypertrophy. A general acceleration of cell division is supported further by the results of quantitative morphometric studies, which indicate that both cellular and functional characteristics of the peripheral lung, including alveolar and capillary volumes and thickness and surface area of the blood-gas barrier, are maintained when compensatory growth is complete. The rate and nature of the growth response are subject to hormonal modulation, particularly by adrenal steroids and growth hormone. Little is known, however, regarding the specific actions of these agents or of additional factors that may be primary regulators of the initiation and cessation of accelerated compensatory growth. Definition of such regulatory mechanisms is of critical importance in understanding normal growth and development of the lung and the response of the lung to injury, as well as in future efforts to manipulate growth and/or repair of the tissue.

Spectrin and related molecules

This review begins with a complete discussion of the erythrocyte spectrin membrane skeleton. Particular attention is given to our current knowledge of the structure of the RBC spectrin molecule, its synthesis, assembly, and turnover, and its interactions with spectrin-binding proteins (ankyrin, protein 4.1, and actin). We then give a historical account of the discovery of nonerythroid spectrin. Since the chicken intestinal form of spectrin (TW260/240) and the brain form of spectrin (fodrin) are the best characterized of the nonerythroid spectrins, we compare these molecules to RBC spectrin. Studies establishing the existence of two brain spectrin isoforms are discussed, including a description of the location of these spectrin isoforms at the light- and electron-microscope level of resolution; a comparison of their structure and interactions with spectrin-binding proteins (ankyrin, actin, synapsin I, amelin, and calmodulin); a description of their expression during brain development; and hypotheses concerning their potential roles in axonal transport and synaptic transmission.

Effect of altered inflation on pulmonary uptake of methylglyoxal bis(guanylhydrazone)

The effects of increased pulmonary ventilation on uptake of an exogenous, nonmetabolized polyamine analog, methylglyoxal bis(guanylhydrazone) [MGBG] were investigated in rat lungs perfused in situ with buffer containing 4.5% bovine serum albumin, 5.6 mM glucose and plasma levels of amino acids. The perfusate was equilibrated and the lungs were ventilated with warmed, humidified O2/N2/CO2 (20:75:5). A 28% increase in lung inflation rapidly accelerated MGBG uptake at low (1.5 microM) but not at high (50 microM) substrate concentration, a change which appeared to reflect a decrease in the apparent Km of the uptake pathway. This effect was not associated with acute alterations in pulmonary vascular permeability or resistance, nor with instability of the preparations. Taken with observations made previously, these results suggest that deformation of the tissue by increased inflation may account for increased MGBG uptake by lungs from rats subjected to partial pneumonectomy.

The topology of the major band 4.5 protein component of the human erythrocyte membrane: characterization of reactive cysteine residues

A preparation of band 4.5 protein of the red cell membrane, containing largely the sugar transporter, was labelled with the sulfhydryl reagent N-ethyl [14C]maleimide. In preparations denatured with sodium dodecyl sulfate (SDS), all five sulfhydryl groups present in the peptide, Mr 45 000 to 60 000, react with the alkylating agent within 20 min at 37 degrees C. If the peptide is reconstituted in lipid vesicles and cleaved with trypsin before extraction and denaturation with SDS, three sulfhydryl groups are found in a 30 kDa fragment and two in a 19 kDa fragment. In 'native' reconstituted protein only three groups react, even after two hours of exposure, two in the 30 kDa fragment and one in the 19 kDa fragment. Thus, one sulfhydryl group is cryptic, inaccessible to N-ethylmaleimide in each fragment. In intact cells, the single reactive group of the 19 kDa fragment can be protected against reaction with N-ethylmaleimide by the impermeant sulfhydryl reagent, p-chloromercuribenzene sulfonate (PCMBS). It is, therefore, considered to be exposed on the outer face of the membrane. The two reactive groups of the 30 kDa fragment are not protected by PCMBS and are, therefore, not considered to be exposed to the outside medium. Cytochalasin B, a competitive inhibitor of sugar transport affords temporary protection of the exofacial group of the 19 kDa against reaction with N-ethylmaleimide, and affords longer term protection of one of the reactive groups of the 30 kDa fragment. These findings allow conclusions about the topology of the sugar transport protein in the bilayer. Both proteolytic fragments must cross the bilayer. One of three reactive sulfhydryl groups is exofacial and two may be cytoplasmic. The two cryptic groups may be located within the bilayer.