Diagnostic accuracy of functional imaging modalities for chondrosarcoma: A systematic review and meta-analysis

•

Functional imaging modalities may have an important role in diagnosing chondrosarcomas.

•

PET is a sensitive and specific test for differentiating chondrosarcomas and benign chondroid tumours.

•

Thallium-201 scintigraphy has a high positive predictive value for chondrosarcomas.

•

DMSA (V) has a 100% negative predictive value and can be used to rule out chondrosarcomas.

Introduction

The distinction between low-grade (grade 1) chondrosarcoma and its benign counterparts can be challenging. This systematic review aims to quantify the diagnostic accuracies of all functional imaging modalities used in the diagnosis of chondrosarcoma.

Methods

Medline and Embase were searched in February 2019. We included studies of either retrospective or prospective design if the results of functional scans were compared with pre-determined reference standards. Studies had to be primary diagnostic reports on patients with chondral tumours at first diagnosis. Two review authors independently performed study selection, extracted data and assessed the methodological quality. We calculated diagnostic accuracy measures for each included study.

Results

Four functional imaging modalities were identified across thirteen studies that met the inclusion criteria. 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) was a sensitive and specific test. Technetium-99 m with methylene diphosphonate (Tc-99 m MDP) had an overall low specificity of 4%. Thallium-201 scintigraphy demonstrated high positive predictive values across the studies. The negative predictive values of Technetium-99 m pentavalent dimercaptosuccinic acid (Tc-99 m DMSA (V)) were consistently 100%.

Conclusions

Low-grade chondrosarcomas continue to pose a diagnostic dilemma. FDG-PET demonstrated superior diagnostic accuracy compared to Tc-99 m MDP, Thallium-201 and Tc-99 m DMSA (V). Characteristic uptake patterns of Thallium-201 and Tc-99 m DMSA (V) may provide additional metabolic information to guide the diagnosis in this challenging group of tumours.

Realization of a Valley Superlattice

In a number of widely studied materials, such as Si, AlAs, Bi, graphene, MoS_{2}, and many transition metal dichalcogenide monolayers, electrons acquire an additional, spinlike degree of freedom at the degenerate conduction band minima, also known as "valleys." External symmetry-breaking fields such as mechanical strain, or electric or magnetic fields, can tune the valley polarization of these materials, making them suitable candidates for "valleytronics." Here we study a quantum well of AlAs, where the two-dimensional electrons reside in two energetically degenerate valleys. By fabricating a strain-inducing grating on the sample surface, we engineer a spatial modulation of the electron population in different valleys, i.e., a "valley superlattice" in the quantum well plane. Our results establish a novel manipulation technique of the valley degree of freedom, paving the way to realizing a valley-selective layered structure in multivalley materials, with potential application in valleytronics.

Commensurability Oscillations of Composite Fermions Induced by the Periodic Potential of a Wigner Crystal

When the kinetic energy of a collection of interacting two-dimensional (2D) electrons is quenched at very high magnetic fields so that the Coulomb repulsion dominates, the electrons are expected to condense into an ordered array, forming a quantum Wigner crystal (WC). Although this exotic state has long been suspected in high-mobility 2D electron systems at very low Landau level fillings (ν≪1), its direct observation has been elusive. Here we present a new technique and experimental results directly probing the magnetic-field-induced WC. We measure the magnetoresistance of a bilayer electron system where one layer has a very low density and is in the WC regime (ν≪1), while the other ("probe") layer is near ν=1/2 and hosts a sea of composite fermions (CFs). The data exhibit commensurability oscillations in the magnetoresistance of the CF layer, induced by the periodic potential of WC electrons in the other layer, and provide a unique, direct glimpse at the symmetry of the WC, its lattice constant, and melting. They also demonstrate a striking example of how one can probe an exotic many-body state of 2D electrons using equally exotic quasiparticles of another many-body state.

Correlation of Primary Tumor FDG Uptake with Clinicopathologic Prognostic Factors in Invasive Ductal Carcinoma of the Breast

PURPOSE

The purpose of this study was to investigate the correlation of primary tumor FDG uptake to clinicopathological prognostic factors in invasive ductal carcinoma of the breast.

METHODS

We retrospectively reviewed 136 of 215 female patients with pathologically proven invasive ductal breast cancer from January 2008 to December 2011 who underwent F-18 FDG PET/CT for initial staging and follow-up after curative treatment with analysis of estrogen receptor (ER), progesterone receptor (PR) and human epithelial growth factor receptor 2 (HER2). The maximum standardized uptake value (SUVmax) of the primary breast tumor was measured and compared with hormonal receptor and HER2 overexpression status.

RESULTS

The high SUVmax of primary breast tumors is significantly correlated with the clinicopathological factors: tumor size, histologic grade, TNM stage, negativity of ER, negativity of PR, HER2 overexpression and triple negativity. The recurrent group with non-triple negative cancer had a higher SUVmax compared with the non-recurrent group, though no significant difference in FDG uptake was noted between the recurrence and non-recurrent groups in subjects with triple-negative cancer. Lymph node involvement was the independent risk factor for cancer recurrence in the multivariate analysis.

CONCLUSIONS

In conclusion, high FDG uptake in primary breast tumors is significantly correlated with clinicopathological factors, such as tumor size, histologic grade, TNM stage, negativity of the hormonal receptor, HER2 overexpression and triple negativity. Therefore, FDG PET/CT is a helpful prognostic tool to direct the further management of patients with breast cancer.

Mini-Mental Status Examination as predictors of mortality in the elderly

OBJECTIVE

Because the number of elderly is increasing worldwide, cognitive dysfunction becomes important health care issue. This study investigated the association between cognitive dysfunction and mortality in the elderly.

METHOD

Data were analyzed from a longitudinal mortality follow-up study of 2712 Korean elderly aged 60 and over, examined in 2002 with complete data followed an average 6.03 years. Measurements included socio-demographic and clinical factors and Mini-Mental State Examination (MMSE). MMSE was categorized into groups with no, mild, or moderate cognitive dysfunction, and the subscores of MMSE domains were categorized into no dysfunction or dysfunction. The Cox proportional hazards models were conducted to examine the association between MMSE score and mortality, after adjusting for age, gender, education and other socio-demographic factors.

RESULTS

Death during follow-up occurred in 318 subjects. The mortality risk was significantly associated with the elderly with mild cognitive dysfunction [hazard ratio (HR) = 1.93] and with moderate cognitive dysfunction (HR = 2.66). 'Orientation-to-time' (HR = 1.39) and 'Attention' (HR = 1.48) domains of MMSE were independently associated with mortality.

CONCLUSION

This study showed that cognitive dysfunction independently predicted mortality in the elderly. Cognitive dysfunction should be considered part of identifying the elderly at high risk for mortality.

Age-dependent association between sleep duration and hypertension in the adult Korean population

BACKGROUND

In Western countries, sleep deprivation has been reported to elevate blood pressure. Here, we examined whether this association is true also for an Asian population.

METHODS

The study sample comprised 5,393 Korean adults aged 19-99 years who had participated in the 2005 Korean National Health and Nutrition Examination Survey. Hypertension was defined as a systolic blood pressure (SBP) ≥140 mm Hg or a diastolic blood pressure (DBP) ≥90 mm Hg, or regular use of antihypertensive medication.

RESULTS

Among the participants, 1,345 subjects (24.9%) displayed hypertension. The median sleep duration was 7 h/day. In the young and middle-aged adults aged <65 years, the unadjusted odds ratio (OR) for hypertension was 1.5-fold greater in those with a sleep duration of ≤5 h (OR 1.52; 95% confidence interval (CI) 1.19, 1.94) as compared to those who slept 7 h. This trend did not significantly change after adjustments for putative risk factors for hypertension such as gender, obesity, smoking status, alcohol consumption, physical activity, depressive symptom, diabetes mellitus, and stroke (OR 1.31; 95% CI 1.01, 1.71). However, in the older adults aged ≥65 years, no association was found between sleep duration and the risk of hypertension. Long sleep duration (≥8 h) was not associated with hypertension in either the younger or older adults in this study.

CONCLUSION

Short sleep duration (≤5 h) is independently associated with hypertension in young and middle-aged Korean adults.

High glucose dialysis solutions increase synthesis of vascular endothelial growth factors by peritoneal vascular endothelial cells

OBJECTIVE

Increased peritoneal vasculature has been reported in long-term peritoneal dialysis (PD), and vascular endothelial growth factors (VEGFs) have been found in dialysate. High concentrations of glucose or lactate, glucose degradation products (GDPs), and low pH of dialysis solutions are all possible factors in increased peritoneal VEGF synthesis. In this study, we investigated the effects of high glucose dialysis solutions on VEGF synthesis by peritoneal vascular endothelial cells (PVECs).

METHODS

The PVECs were isolated from rat omentum and were incubated for 4 hours in three different culture media [M199 media (control), conventional dialysis solutions containing 4.25% glucose diluted with an equal volume of M199 media (HGD), and M199 media containing 118 mmol/L mannitol as an osmolar control (mannitol)]. Levels of VEGF protein in the culture supernatant were measured by ELISA, and mRNA expression was determined by Northern blot analysis. Data are presented as percent of control.

RESULTS

After incubation for 4 hours, the number of cells did not differ between the 3 groups. Levels of VEGF in culture supernatant were significantly higher in the HGD group (124% +/- 19%, p = 0.006) as compared with the control and mannitol (85% +/- 10%) groups. The mRNA expression of VEGF appeared to be higher in the HGD group (128% +/- 49%) than in the control and mannitol (94% +/- 18%) groups.

CONCLUSION

High glucose dialysis solutions increased VEGF synthesis by PVECs. The relationship between VEGF synthesis by PVECs and neovascularization of the peritoneum observed in long-term peritoneal dialysis patients has to be studied further.

AQP2 is a substrate for endogenous PP2B activity within an inner medullary AKAP-signaling complex

We have demonstrated that inner medullary collecting duct (IMCD) heavy endosomes purified from rat kidney IMCD contain the type II protein kinase A (PKA) regulatory subunit (RII), protein phosphatase (PP)2B, PKCzeta, and an RII-binding protein (relative molecular mass ~90 kDa) representing a putative A kinase anchoring protein (AKAP). Affinity chromatography of detergent-solubilized endosomes on cAMP-agarose permits recovery of a protein complex consisting of the 90-kDa AKAP, RII, PP2B, and PKCzeta. With the use of small-particle flow cytometry, RII and PKCzeta were localized to an identical population of endosomes, suggesting that these proteins are components of an endosomal multiprotein complex. (32)P-labeled aquaporin-2 (AQP2) present in these PKA-phosphorylated endosomes was dephosphorylated in vitro by either addition of exogenous PP2B or by an endogenous endosomal phosphatase that was inhibited by the PP2B inhibitors EDTA and the cyclophilin-cyclosporin A complex. We conclude that IMCD heavy endosomes possess an AKAP multiprotein-signaling complex similar to that described previously in hippocampal neurons. This signaling complex potentially mediates the phosphorylation of AQP2 to regulate its trafficking into the IMCD apical membrane. In addition, the PP2B component of the AKAP-signaling complex could also dephosphorylate AQP2 in vivo.

Prevalence, awareness, treatment, control and risk factors of hypertension in Korea: the Ansan study

OBJECTIVES

To determine prevalence, awareness, treatment, and control of hypertension, and its risk factors in an urban Korean population.

DESIGN AND SETTING

A cross-sectional survey in Ansan-city, Korea.

SUBJECTS AND METHODS

Population-based samples of people aged 18-92 years in Ansan-city, Korea, were selected, yielding 2278 men and 1948 women, and their blood pressures were measured using a highly standardized protocol. Hypertension was defined as a systolic BP > or = 140 mmHg or diastolic BP > or = 90 mmHg or reported treatment with antihypertensive medications, and subclassified according to 1999 WHO-ISH guidelines. Isolated systolic hypertension (ISH) defined as a systolic BP > or = 140 mmHg and diastolic BP < 90 mmHg was also examined. Data were stratified by age and sex.

RESULTS

The overall prevalence of hypertension in this study was 33.7%. Among these, 64.9% had Grade 1 hypertension, 22.5% Grade 2, and 12.5% Grade 3. Age-specific prevalence of hypertension increased progressively with age, from 14.19% in 18 to 24 year-olds to 71.39% in those 75 years or older. Hypertension prevalence was significantly higher in men (41.5%) than in women (24.5%) (P < 0.001). Isolated systolic hypertension had significantly lower prevalence (4.33%) within the population, although in the elderly aged 55 years or more it rose by 11.13%. Overall, 24.6% of hypertensive individuals were aware that they had high blood pressure, as much as 78.6% were being treated with antihypertensive medications, and 24.3% were under control. Hypertension awareness as well as treatment and control rates varied by sex, with women higher in all three rates. Multivariate analysis revealed that age, body mass index and abdomen circumference were significantly associated with prevalence of hypertension both in men and women.

CONCLUSIONS

Hypertension is highly prevalent in Korea. Despite the high rate of treatment, the rates of awareness and control are relatively low, suggesting the nationwide demand for preventing and controlling high blood pressure in Korea in order to avert an epidemic of cardiovascular disease.

Nongenomic stimulation of nitric oxide release by estrogen is mediated by estrogen receptor alpha localized in caveolae

Acute administration of 17beta-estradiol (E(2)) exerts antiatherosclerotic effects in healthy postmenopausal women. The vasoprotective action of E(2) may be partly accounted for by a rapid increase in nitric oxide (NO) levels in endothelial cells (ECs). However, the signaling mechanisms producing this rise are unknown. In an attempt to address the short-term effect of E(2) on endothelial NO production, confluent bovine aortic endothelial cells (BAECs) were incubated in the absence or presence of E(2), and NO production was measured. Significant increases in NO levels were detected after only 5 min of E(2) exposure without a change in the protein levels of endothelial NO synthase (eNOS). This short-term effect of estrogen was significantly blunted by various ligands which decrease intracellular Ca(2+) concentration. Furthermore, plasma membrane-impermeable BSA-conjugated E(2) (E(2)BSA) stimulated endothelial NO release, indicating that in the current system the site of action of E(2) is on the plasma membrane rather than the classical nuclear receptor. The partial antagonist tamoxifen did not block E(2)-induced NO production; however, a pure estrogen receptor alpha (ERalpha) antagonist ICI 182,780 completely inhibited E(2)-stimulated NO release. The binding of E(2) to the membrane was confirmed using FITC-labeled E(2)BSA (E(2)BSA-FITC). Western blot analysis showed that plasmalemmal caveolae possess ERalpha in addition to well-known caveolae-associated proteins eNOS and caveolin. This study demonstrates that the nongenomic and short-term effect of E(2) on endothelial NO release is Ca(2+)-dependent and occurs via ERalpha localized in plasmalemmal caveolae.

Apical extracellular calcium/polyvalent cation-sensing receptor regulates vasopressin-elicited water permeability in rat kidney inner medullary collecting duct

During antidiuresis, increases in vasopressin (AVP)-elicited osmotic water permeability in the terminal inner medullary collecting duct (tIMCD) raise luminal calcium concentrations to levels (> or = 5 mM) above those associated with the formation of calcium-containing precipitates in the urine. Calcium/polycation receptor proteins (CaRs) enable cells in the parathyroid gland and kidney thick ascending limb of Henle to sense and respond to alterations in serum calcium. We now report the presence of an apical CaR in rat kidney tIMCD that specifically reduces AVP-elicited osmotic water permeability when luminal calcium rises. Purified tIMCD apical membrane endosomes contain both the AVP-elicited water channel, aquaporin 2, and a CaR. In addition, aquaporin 2-containing endosomes also possess stimulatory (G(alpha q)/G(alpha 11) and inhibitory (G(alpha i1, 2, and 3)) GTP binding proteins reported previously to interact with CaRs as well as two specific isoforms (delta and zeta) of protein kinase C. Immunocytochemistry using anti-CaR antiserum reveals the presence of CaR protein in both rat and human collecting ducts. Together, these data provide support for a unique tIMCD apical membrane signaling mechanism linking calcium and water metabolism. Abnormalities in this mechanism could potentially play a role in the pathogenesis of renal stone formation.

The 17 kDa band identified by multiple anti-aquaporin 2 antisera in rat kidney medulla is a histone

The osmotic water permeability of epithelial cells of the inner medullary collecting duct of the kidney is regulated by antidiuretic hormone (ADH). ADH causes the insertion and removal of cytoplasmic vesicles containing the aquaporin (AQP-2) water channel protein which is recognized by multiple rabbit antipeptide antisera raised against amino acid sequences comprising its cytoplasmic carboxyl terminal. Immunoblots of rat kidney membrane fractions as well as human urine have all shown that AQP-2 is expressed exclusively by collecting duct cells and have identified a 29 kDa band (corresponding to the nonglycosylated AQP-2 protein), a broad 35-45 kDa band (corresponding to the mature glycosylated form of AQP-2 protein) and an additional immunoreactive 17 kDa band of unknown origin. We now report that the 17 kDa band identified by these anti-AQP-2 antisera is not an AQP-2 component but rather a denatured histone protein type H2A1. This binding of anti-AQP-2 antisera to denatured H2A1 present in protein samples derived from both kidney inner medulla and human urine is blocked specifically by preincubation of immunoblots with solutions containing the acidic protein gelatin.

Phosphorylation of aquaporin-2 does not alter the membrane water permeability of rat papillary water channel-containing vesicles

Antidiuretic hormone modulates the water permeability (Pf) of epithelial cells in the rat kidney by vesicle-mediated insertion and removal of the aquaporin-2 (AQP-2) water channel. AQP-2 possesses a single consensus cAMP-dependent protein kinase A (PKA) phosphorylation site (Ser-256) hypothesized to regulate channel Pf(Kuwahara, M., Fushimi, K., Terada, Y., Bai, L., Sasaki, S., and Marumo, F. (1995) J. Biol. Chem. 270, 10384-10387). To test whether PKA phosphorylation of AQP-2 alters channel Pf, we compared the Pf values of purified AQP-2 endosomes after incubation with either PKA or alkaline phosphatase. Studies using [gamma-32P]ATP reveal that AQP-2 endosomes contain endogenous PKA and phosphatase activities that add and remove 32P label from AQP-2. However, the Pf (0.16 +/- 0.06 cm/s) of endosomes containing phosphorylated AQP-2 (0.7 +/- 0. 3 mol of PO4/mol of protein) is not significantly different from the same AQP-2 endosomes where 95 +/- 8% of the phosphate has been removed (Pf 0.14 +/- 0.06 cm/s). These data do not support a role for PKA phosphorylation in alteration of AQP-2's Pf. Instead, AQP-2 phosphorylation by PKA may modulate AQP-2's distribution between plasma membrane and intracellular vesicle compartments.

Rat kidney papilla contains abundant synaptobrevin protein that participates in the fusion of antidiuretic hormone-regulated water channel-containing endosomes in vitro

Antidiuretic hormone (ADH) regulates renal water excretion by altering the permeability of the collecting duct to water. ADH-responsive epithelial cells are the major cell type lining kidney tubules in the inner medulla and papilla. ADH modulates apical membrane water permeability by the insertion and removal of vesicles containing aquaporin collecting duct water channel protein (now termed AQP-2). To identify and characterize proteins responsible for trafficking of AQP-2-containing vesicles, we utilized antibody and cDNA probes to synaptobrevin b (also termed VAMP-2, for vesicle-associated membrane protein 2), a protein that mediates synaptic vesicle exocytosis in the brain and whose structural homologs are now considered to be components of a complex responsible for intracellular vesicle fusion in all cells. We now report that rat kidney inner medulla and papilla contain abundant synaptobrevin protein. Only light endosomes, one of two types of purified papillary AQP-2-containing endosomes, possess synaptobrevin. Light endosomes fuse in vitro by means of an ATP-dependent process that is significantly inhibited when endosomes are preincubated with either anti-synaptobrevin antibody or tetanus toxin. These data define a functional role for a synaptobrevin protein in the fusion of endosomes in vitro. The presence of abundant synaptobrevin proteins in endosomes containing AQP-2 water channels, as well as insulin-sensitive glucose transporters [Cain, C. C., Trimble, W. S. & Lienhard, G. E. (1992) J. Biol. Chem. 267, 11681-11684], and in cells of Malpighian tubules responsible for urine formation in insects [Chin, A. S., Burgess, R. W., Wong, B. R., Schwartz, T. L. & Scheller, R. H. (1993) Gene 131, 175-181] suggests a specialized role for synaptobrevin in vesicle-mediated membrane transport modulated by peptide hormones.

Characterization of purified endosomes containing the antidiuretic hormone-sensitive water channel from rat renal papilla

Antidiuretic hormone (ADH) stimulation of renal epithelial cells elicits a large increase in apical membrane osmotic water permeability (Pf) produced by the fusion of water channel containing vesicles with the apical membrane. Removal of ADH stimulation results in retrieval of apical water channels into a specialized non-acidic endosomal compartment. Previous studies (Sabolic, I., Wuarin, F., and Shi, L. B. (1992) J. Cell Biol. 119, 111-122) have shown that water channel containing papillary endosomes labeled with fluorescein-dextran can be isolated from rat renal papilla. We have utilized small particle flow sorting methodology to both monitor and improve upon the purification of these water channel containing endosomes (WCV). Flow cytometry analysis on a vesicle-by-vesicle basis demonstrates that WCV are homogeneous with respect to entrapped fluorescein-dextran, the apical membrane enzyme marker leucine amino peptidase and ultrastructural morphology. WCV do not acidify their luminal contents after addition of Mg-ATP but contain abundant functional water channels (Pf0.28 cm/s at 23 degrees C) as determined by stopped flow fluorimetry. SDS-polyacrylamide gel electrophoresis analysis shows that purified WCV are composed of 20 major protein bands. To determine the identity of WCV water channels, WCV proteins were probed with affinity purified antisera recognizing two renal water channel proteins. These include Aquaporin-CHIP found in the proximal tubule and thin descending limb of Henle and the candidate ADH water channel protein WCH-1 or Aquaporin- (AQP) CD present in the ADH-responsive epithelial cells of the collecting duct. These data reveal that WCV contained little or no AQP-CHIP protein. In contrast, WCV are highly enriched for AQP-CD protein. Together, these data define the protein composition of the papillary WCV and link directly the presence of functional apical membrane water channels with the presence of the AQP-CD protein.

Demonstration of an insulin-insensitive storage pool of glucose transporters in rat hepatocytes and HepG2 cells

The subcellular distribution of glucose transporters in rat hepatocytes and HepG2 cells was studied in the absence and in the presence of insulin. Glucose transporters were quantitated by measuring glucose-sensitive cytochalasin B binding and by protein immunoblotting using isoform-specific antibodies. Plasma membrane contamination into subcellular fractions was assessed by measuring distribution of 5'-nucleotidase and cell surface carbohydrate label. In hepatocytes, GLUT-2 occurred in a low-density microsomal (LDM) fraction at a significant concentration, and as much as 15% of cellular GLUT-2 was found intracellularly that cannot be accounted for by plasma membrane contamination. In HepG2 cells which express GLUT-1 and GLUT-2, the two isoforms showed distinct subcellular distribution patterns: GLUT-2 was highly concentrated in LDM while very little GLUT-1 was found in this fraction, indicating that a large portion of GLUT-2 occurs in intracellular organelles. Insulin treatment did not change the subcellular distribution patterns of glucose transporters in both cell types. Our results suggest that rat hepatocytes and HepG2 cells possess an intracellular storage pool for GLUT-2, but lack the insulin-responsive glucose transporter translocation mechanism.

Transport function and subcellular distribution of purified human erythrocyte glucose transporter reconstituted into rat adipocytes

In order to delineate the insulin-independent (constitutive) and insulin-dependent regulations of the plasma membrane glucose transporter concentrations in rat adipocytes, we introduced purified human erythrocyte GLUT-1 (HEGT) into rat adipocytes by poly(ethylene glycol)-induced vesicle-cell fusion and its transport function and subcellular distribution in the host cell were measured. HEGT in adipocytes catalysed 3-O-methylglucose equilibrium exchange with a turnover number that is indistinguishable from that of the basal adipocyte transporters. However, insulin did not stimulate significantly the HEGT function in adipocytes where it stimulated the native transporter function by 7-8-fold. The steady state distribution and the transmembrane orientation assays revealed that more than 85% of the HEGT that were inserted in the physiological, cytoplasmic side-in orientation at the adipocytes plasma membrane were moved into low-density microsomes (LDM), while 90% of the HEGT that were inserted in the wrong, cytoplasmic side-out orientation were retained in the plasma membrane. Furthermore, more than 70% of the LDM-associated HEGT were found in a small subset of LDM that also contained 80% of the LDM-associated GLUT-4, the insulin-regulatable, native adipocyte glucose transporter. However, insulin did not cause redistribution of HEGT from LDM to the plasma membrane under the condition where it recruited GLUT-4 from LDM to increase the plasma membrane GLUT-4 content 4-5-fold. These results demonstrate that the erythrocyte GLUT-1 introduced in adipocytes transports glucose with an intrinsic activity similar to that of the adipocyte GLUT-1 and/or GLUT-4, and enters the constitutive GLUT-4 translocation pathway of the host cell provided it is in physiological transmembrane orientation, but fails to enter the insulin-dependent GLUT-4 recruitment pathway. We suggested that the adipocyte plasma membrane glucose transporter concentration is constitutively kept low by a mechanism where a cell-specific constituent interacts with a cytoplasmic domain common to GLUT-1 and GLUT-4, while the insulin-dependent recruitment requires a cytoplasmic domain specific to GLUT-4.

[Prevention of alcohol-induced gastric mucosal injury by prostaglandin E-1]

Effects of ethanol and prostaglandin on the glycoprotein synthesis in the gastric mucus cells have been evaluated. The rat gastric mucosal cell were subjected to a short-term tissue culture in the presence of ethanol and prostaglandin E2 (Ornoprostil), using [3H]-proline, [3H]-palmitic acid, [3H]-galactosamine. Low concentration of ethanol (0.05-0.01 M) stimulated the glycoprotein synthesis, but higher concentration of ethanol (0.5-1.5 M) caused a marked reduction in the glycoprotein synthesis. Addition of prostaglandin E2, especially addition of prostaglandin prior to ethanol treatment, has improved the glycoprotein synthesis and secretion in the presence of ethanol. It was suggested that addition of prostaglandin resulted in the stabilization of the synthesis and secretion of the mucus glycoprotein in the presence of ethanol.

Sulfonylurea binding to adipocyte membranes and potentiation of insulin-stimulated hexose transport

We have previously shown that the sulfonylureas increase insulin-stimulated glucose transport in adipocytes mainly by enhancing the insulin-induced recruitment of glucose transporter from its intracellular storage pool to the plasma membrane (Jacobs, D. B., and Jung, C. Y. (1985) J. Biol. Chem. 260, 2593-2596). In order to determine if this sulfonylurea effect is mediated by a specific membrane-associated sulfonylurea-binding protein, in the present report we measured exact dose dependence of the transport enhancement activities of different sulfonylureas in adipocytes in primary culture and equilibrium binding affinities of these agents to various adipocyte membrane fractions. Glycuride was found to increase the insulin-stimulated, 3-O-methyl-D-glucose equilibrium exchange in cultured rat adipocytes by up to 60% with little effect in the absence of insulin. The effect developed gradually reaching the maximum level at 24 h of incubation. The effect was concentration dependent showing a simple, one-to-one stoichiometry and an apparent activation constant (Ka) of approximately 1 microM. Glypizide, tolazamide, and tolbutamide also enhanced the insulin-stimulated hexose transport by up to 60%, but with Ka of approximately 2, 11, and 25 microM, respectively. HB-699 and ciglitazone, non-sulfonylureas, were without effect under the same condition. In equilibrium binding experiments, [3H]glyburide was found to bind to adipocyte membranes at two or more protein-specific, saturable sites, with similar apparent dissociation constants (KD) ranging 1-3 microM. These protein-specific glyburide bindings were displaced not only by tolazamide and tolbutamide, but also by ciglitazone and HB-699, with indicated KD of 11-16, 80-85, 20-25, and 85-95 microM, respectively. However, with the plasma membrane fraction, the displacements by ciglitazone and HB-699 were partial and did not exceed 56-61% at maximum. Based on these findings, we propose that there is a sulfonylurea-specific-binding protein in the plasma membrane of adipocytes, and that this sulfonylurea-binding protein may play a key role in the enhancement of insulin-stimulated hexose transport by sulfonylureas, probably via potentiation of the insulin-induced recruitment of glucose transporter.

Anion carrier in the human erythrocyte exists as a dimer

The in situ state of assembly of the human erythrocyte anion carrier (band 3) has been investigated by applying target size analysis on the radiation-induced inactivation of anion flux and degradation of polypeptide band 3. Irradiation with a high energy electron beam resulted in inactivation of carrier-mediated anion flux in intact cells, in inside-out vesicles devoid of cytoskeletal and cytoplasmic proteins, and in inside-out vesicles whose band 3 protein has been partially proteolyzed, with little change in leak pathway. The inactivation showed a single exponential function of radiation dose from which the target size of the anion carrier was estimated to be 210,000, 220,000, and 98,000 daltons in intact cells, in the inside-out vesicles, and in the vesicles after a limited proteolysis, respectively. Irradiation also resulted in degradation of the band 3 of the inside-out vesicles, as detected on sodium dodecyl sulfate-gel electrophoresis, with a dose dependence characteristic of a target size of 220,000 daltons. It is suggested that the human erythrocyte anion carrier exists in situ as a dimer of band 3.