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To improve the anti-tumor effect of polyethylene glycol-modified liposome containing doxorubicin (DOX-PEG liposome), the effect of sequential administration of PEG-Span 80 niosome was investigated for Colon-26 cancer cells (C26)-bearing mice. The concept of the current study is as follows: Since both particulates would be accumulated in the tumor tissue due to the enhanced permeability and retention (EPR) effect, PEG-Span 80 niosome, mainly composed of synthetic surfactant (Span 80), would interact with DOX-PEG liposome and be a trigger to induce the release of DOX from the liposome within the tumor tissue, leading to the improvement of anti-tumor effect of DOX-PEG liposome. To find out an adequate liposome for this strategy, several PEG liposomes with different compositions were examined in terms of drug release enhancement and it was found that PEG-Span80 niosome could significantly enhance the release of calcein and DOX from a PEG liposome composed of 90% hydrogenated soybean phosphatidylcholine (HSPC) and 10% cholesterol. The sequential administration of PEG-Span 80 niosome at 24 or 48 h after dosing of DOX-PEG liposome provided a higher anti-tumor effect than the single dose of DOX-PEG liposome in the C26-bearing mice. Particularly, the 24 h-later dosing of PEG-Span 80 niosome has been found to be more effective than the 48 h-later dosing. It was also confirmed that the coexistence of PEG-Span 80 niosome with DOX-PEG liposome in 50% serum or in 50% supernatant of tumor tissue homogenate significantly increased DOX release from PEG liposome, suggesting that DOX release from DOX-PEG liposome within tumor tissue would be enhanced via the interaction with PEG-Span 80 niosome. This strategy would lead to the safer and more inexpensive chemotherapy, since it could make it possible to provide the better anti-tumor effect by utilizing the lower dose of DOX., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We investigated new development in photodynamic therapy (PDT), aiming at enhanced tumor selectivity and biocompatibility, which included application of a third-generation photosensitizing agent, i.e. xanthene-origin Rose Bengal (RB) co-encapsulated with up-converting NaYF 4 nanoparticles (NPs) co-doped with lanthanide ions: Er 3+ (2%) and Yb 3+ (20%). The hybrid fluorophores were applied as components of double core nanocarriers (NCs) obtained by double (multiple) emulsion solvent evaporation process. Next, to improve the biocompatibility and photodynamic activity, biodegradable polymer: poly(lactide-co-glycolide) - PLGA and non-ionic surfactants with different hydrophobicity: Span 80 and Cremophor A25, were used. After the engineering process, controlled by dynamic light scattering (DLS) measurements, ζ-potential evaluation, transmission electron and atomic force microscopy (TEM and AFM) imaging, as well as optical analysis provided by measurements of the up-conversion emission spectra and luminescence kinetics for encapsulated only NaYF 4 :Er 3+ ,Yb 3+ NPs and co-encapsulated RB + NaYF 4 :Er 3+ ,Yb 3+ molecules, spherical polyester NCs with average size <200 nm, were tested on human melanoma (Me-45 and MeWo) cells and a control human keratinocyte (HaCaT) cell line. The photodynamic action of the investigated NCs was assessed by oxidoreductive potential measurements with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, that corresponds to percentage of the viable cells. Immunofluorescence and the NCs internalization studies were visualized by confocal laser scanning microscopy (CLSM studies). Our results indicated effective photosensitizer delivery into the cancer cells and significant photodynamic efficiency enhanced by the near infrared (NIR)-activation of the encapsulated hybrid cargo in the skin melanoma cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The aim of present study was to develop an oxybutynin (OXY) transdermal patch with good permeation behavior and mechanical property. Special attention was paid to the effect of chemical enhancer on the molecular mobility of pressure sensitive adhesive (PSA) at molecular level. PSAs and permeation enhancers were investigated through in vitro experiment using rat skin. The optimized formulation was evaluated through pharmacokinetic study using rat. In addition, the molecular mechanism of sorbitan monooleate (Span® 80) in the improvement of PSA molecular mobility was investigated using FT-IR, molecular dynamics simulation, DSC and rheological study. As a result, the optimized formulation using amide PSA demonstrated good adhesion property. And the AUC 0-t and C max of optimized patch were 6435.8 ± 747.8 h ∗ ng/mL and 127.8 ± 18.0 ng/mL, respectively, which had no significant difference with commercial product. Furthermore, the improvement of the PSA mobility by Span® 80 rather than the decrease of interaction between drug and PSA was the main factor that enhanced the release of OXY from patch. In conclusion, a drug-in-adhesive OXY patch was developed, and the effect of PSA molecular mobility increase on the enhancement of drug skin permeation was proposed at molecular level., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Dermal drug delivery system which localizes methotrexate (MTX) in the skin is advantageous in topical treatment of psoriasis. The aim of the current study was to understand dilution effects and formulation variability for the potential formation of niosomes from proniosome gels of MTX. Box-Behnken's design was employed to prepare a series of MTX proniosome gels of Span 40, cholesterol (Chol-X 1 ) and Tween 20 (T20-X 2 ). Short chain alcohols (X 3 ), namely ethanol (Et), propylene glycol (Pg) and glycerol (G) were evaluated for their dilution effects on proniosomes. The responses investigated were niosomal vesicles size (Y 1 ), MTX entrapment efficiency percent (EE%-Y 2 ) and zeta potential (Y 3 ). MTX loaded niosomes were formed immediately upon hydration of the proniosome gels with the employed solvents. Addition of Pg resulted in a decrease of vesicular size from 534 nm to 420 nm as Chol percentage increased from 10% to 30%, respectively. In addition, increasing the hydrophilicity of the employed solvents was enhancing the resultant zeta potential. On the other hand, using Et in proniosomal gels would abolish Chol action to increase the zeta potential value and hence less stable niosomal dispersion was formed. The optimized formula of MTX loaded niosomes showed vesicle size of 480 nm, high EE% (55%) and zeta potential of -25.5 mV, at Chol and T20 concentrations of 30% and 23.6%, respectively, when G was employed as the solvent. Hence, G was the solvent of choice to prepare MTX proniosomal gels with a maintained stability and highest entrapment.

The phosphotransferase system (PTS) plays a pivotal role in the uptake of multiple sugars in Escherichia coli and many other bacteria. In the cell, individual sugar-specific PTS branches are interconnected through a series of phosphotransfer reactions, thus creating a global network that not only phosphorylates incoming sugars but also regulates a number of cellular processes. Despite the apparent importance of the PTS network in bacterial physiology, the holistic function of the network in the cell remains unclear. Here we used Förster resonance energy transfer (FRET) to investigate the PTS network in E. coli, including the dynamics of protein interactions and the processing of different stimuli and their transmission to the chemotaxis pathway. Our results demonstrate that despite the seeming complexity of the cellular PTS network, its core part operates in a strikingly simple way, sensing the overall influx of PTS sugars irrespective of the sugar identity and distributing this information equally through all studied branches of the network. Moreover, it also integrates several other specific metabolic inputs. The integrated output of the PTS network is then transmitted linearly to the chemotaxis pathway, in stark contrast to the amplification of conventional chemotactic stimuli. Finally, we observe that default uptake through the uninduced PTS network correlates well with the quality of the carbon source, apparently representing an optimal regulatory strategy., Competing Interests: The authors have declared that no competing interests exist.

Importance of the Field: Tagatose is a naturally occurring simple sugar that is a more palatable bulk low-calorie (1.5 kcal/g) sweetener. It was approved as a food additive by the FDA in 2003. Tagatose has been studied as a potential antidiabetic and antiobesity medication. In preliminary studies in humans, tagatose has shown a low postprandial blood glucose and insulin response. Its proposed mechanism of action may involve interference in the absorption of carbohydrates by inhibiting intestinal disaccharidases and glucose transport. It may also act through hepatic inhibition of glycogenolysis., Areas Covered in This Review: This article summarizes tagatose Phase I and II diabetes trials. It describes the pharmacodynamics and possible mechanism of action of this agent. Literature from 1974 to 2009 is reviewed., What the Reader Will Gain: Better understanding of the implications of postprandial hyperglycemia. An appreciation of the liver as a target of glucose control. Increased awareness of tagatose, a sweetener, as a potential new medication that operates through improvement of postprandial hyperglycemia., Take Home Message: Tagatose is currently being studied as a postprandial antihyperglycemic agent that may be safer with regard to hypoglycemia. Ongoing Phase III clinical trials will provide more definitive answers.

Spherix Inc (formerly Biospherics) is developing tagatose, an orally active lactose derivative for the potential treatment of obesity and type 2 diabetes. The compound is also under investigation for the potential treatment of anemia, hemophilia and medical problems related to infertility, birth weight and excessive maternal food intake. Phase I and II clinical trials have been completed.

A proniosomal gel for transdermal drug delivery of chlorpheniramine maleate (CPM) was developed based on Span 40 and extensively characterized in vitro. The system was evaluated for the effect of composition of formulation, type of surfactants and alcohols on the drug loading, rate of hydration, vesicle size, polydispersity, entrapment efficiency, and drug release across cellulose nitrate dialysis membrane. The stability studies were performed at 4 degrees C and at room temperature. The results showed that lecithin produced more stable and larger vesicles with higher loading efficiency but lower dissolution efficiency than cholesterol (chol) and dicethyl phosphate (DCP). The type of alcohol had no significant effect on the stability of vesicles, but ethanol produced larger vesicles (approximately equal to 44 microm) and entrapped a greater amount of drug. Drug release from vesicles of lecithin followed a first-order kinetics whereas those with DCP or without lecithin fit better with a Higuchi model. The proniosomes that contained Span 40/lecithin/chol prepared by ethanol showed optimum stability, loading efficiency, and particle size and release kinetic suitable for transdermal delivery of CPM.

An O-3-hexose derivative, shown previously to inhibit a malaria parasite hexose transporter expressed in Xenopus oocytes as well as to suppress the multiplication of parasites, both in vitro and in vivo, was shown here to block the uptake of hexose sugars into isolated blood-stage parasites. This led to a decline in ATP levels and the loss of intracellular pH control. The results are consistent with those obtained with the cloned transporter. They support the notion that the transporter mediates uptake of glucose into the intraerythrocytic parasite and provide further support for the view that it is a suitable antimalarial drug target.

Tagatose, a low-calorie, full-bulk natural sugar, has just attained GRAS (Generally Recognized As Safe) status under U.S. Food and Drug Administration (FDA) regulations, thereby permitting its use as a sweetener in foods and beverages. This paper presents all current aspects of tagatose with respect to demonstrated food and beverage applications and the potential health and medical benefits of this unique substance. Summarized studies are referenced to detailed peer-reviewed papers. The safety studies followed the recommendations in the FDA "Red Book." Results were submitted to an Expert Panel for determination of GRAS status under FDA regulation. Small phase 2 clinical trials showed tagatose to be effective in treating type 2 diabetes. The results, buttressed by the references cited, support the efficacy of the various applications disclosed for tagatose. Tagatose has been found to be safe and efficacious for use as a low-calorie, full-bulk sweetener in a wide variety of foods, beverages, health foods, and dietary supplements. It fills broad, heretofore unmet needs for a low-calorie sweetener in products in which the bulk of sugar is important, such as chocolates, chewing gum, cakes, ice cream, and frosted cereals. Its synergism with high-intensity sweeteners also makes it useful in sodas. Various health and medical benefits are indicated, including the treatment of type 2 diabetes, hyperglycemia, anemia, and hemophilia and the improvement of fetal development.

Aventis Pharma AG is investigating a series of novel coumarin DNA gyrase B inhibitors, including RU-79115, as potential treatments for bacterial infections. These inhibitors have displayed potent inhibitory activity in vitro against DNA supercoiling by DNA gyrase B and have antibacterial activity. Good antibacterial activity against vancomycin- and teicoplanin-resistant enterococci was observed with most analogs (where the 3-acylamino residue was replaced with reversed isosteres). Amide derivatives were also active against novobiocin-resistant strains [335149]. RU-79115 has shown activity against Gram-positive bacteria, particularly staphylococci and enterococci, and its activity compares favorably to vancomycin. Against oxacillin- and ofloxacin-resistant staphylococci, RU-79115 had MIC50 values 7.5-fold lower than eperezolid and significantly lower than vancomycin. In vivo data suggest that the compound is safe and carries a satisfactory pharmacokinetic profile [216256], [340969], [376199]. The compound is the most potent in the series which also includes RU-78535 and RU-64135 [340969], [341039].

Background: The ketohexose D-tagatose is a new sweetener with a low energy content. This low energy content may be due to either low absorption of the D-tagatose or decreased absorption of other nutrients., Objective: The aims of this study were to measure the excretion of D-tagatose from the human small bowel, to calculate the apparent absorption of D-tagatose, and to study the effects of D-tagatose on the small-bowel excretion of other carbohydrates., Design: A controlled diet was served for 2 periods of 2 d during 3 consecutive weeks to 6 ileostomy subjects. In one of the periods, 15 g D-tagatose was added to the diet daily. Duplicate portions of the diet and ileostomy effluents were freeze-dried and analyzed to calculate the apparent net absorption of D-tagatose and carbohydrates., Results: Median D-tagatose excretion was 19% (range: 12-31%), which corresponded to a calculated apparent absorption of 81% (69-88%). Of the total amount of D-tagatose excreted [2.8 g (1.7-4.4 g)], 60% (8-88%) was excreted within 3 h. Between 3 and 5 h, 32% (11-82%) was excreted. Excretion of wet matter increased by 41% (24-52%) with D-tagatose ingestion. Sucrose and D-glucose excretion increased to a small extent, whereas no significant changes were found in the excretion of dry matter, energy, starch, or D-fructose., Conclusions: The apparent absorption of 15 g D-tagatose/d was 81%. D-Tagatose had only a minor influence on the apparent absorption of other nutrients.

D-Fructose has been found to increase uric acid production by accelerating the degradation of purine nucleotides, probably due to hepatocellular depletion of inorganic phosphate (Pi) by an accumulation of ketohexose-1-phosphate. The hyperuricemic effect of D-tagatose, a stereoisomer of D-fructose, may be greater than that of D-fructose, as the subsequent degradation of D-tagatose-1-phosphate is slower than the degradation of D-fructose-1-phosphate. We tested the effect of 30 g oral D-tagatose versus D-fructose on plasma uric acid and other metabolic parameters in 8 male subjects by a double-blind crossover design. Both the peak concentration and 4-hour area under the curve (AUC) of serum uric acid were significantly higher after D-tagatose compared with either 30 g D-fructose or plain water. The decline in serum Pi concentration was greater at 50 minutes after D-tagatose versus D-fructose. The thermogenic and lactacidemic responses to D-tagatose were blunted compared with D-fructose. D-Tagatose attenuated the glycemic and insulinemic responses to a meal that was consumed 255 minutes after its administration. Moreover, both fructose and D-tagatose increased plasma concentrations of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1). The metabolic effects of D-tagatose occurred despite its putative poor absorption.

Novel multicomponent organogels containing an aqueous phase are described, and some properties which influence their potential as delivery devices for hydrophilic drugs and vaccines are discussed. The gel is produced by preparing a hot water-in-oil (w/o) emulsion using sorbitan monostearate, a nonionic surfactant which is also the organogelator, as the principal emulsifying agent. On cooling at room temperature, the w/o emulsion sets to an opaque, semisolid, thermoreversible organic gel. Cooling the emulsion results in a reduced solubility of the sorbitan monostearate in the oil, with a corresponding decrease in solvent-surfactant affinities, causing surfactant self-assembly into aggregates. The microstructure of the w/o gel is seen by light microscopy to consist of a network of tubules and fibrils (containing the aqueous phase) dispersed in the organic medium. X-ray diffraction and freeze-fracture studies suggest that the tubular aggregates in the w/o gel are made up of surfactant molecules arranged in inverted bilayers and that the aqueous phase is accommodated within these inverted bilayers, bound by the polar headgroups of the surfactant molecules. The presence of water in the tubular skeleton of the organic gels results in the establishment of percolating electroconductive aqueous channels in the organogel. Increasing the water content of a w/o gel causes the surfactant tubules to swell with a corresponding increase in conductivity until the tubules are saturated. Further increase in the water content results in the excess water accumulating in droplets within the organic medium and a decrease in conductivity as the gel integrity is compromised. The w/o gels (containing a model antigen, radiolabeled bovine serum albumin, in the aqueous phase) have demonstrated depot properties after intramuscular administration to mice, entrapped antigen being released over a period of days.

In an attempt to explain the rather short half-life of molecules at the injection site after their intra-muscular administration in a sorbitan monostearate organogel, in vitro studies were carried out to study the effects of an aqueous medium (simulating interstitial fluid at injection site) on the physical form of the organogel. When the gel mass comes in contact with an aqueous phase, the latter penetrates into the organic gel via the sorbitan monostearate tubular network, resulting in gel breakdown into smaller fragments. The surfactant tubular network act as a conduit for water penetration into the gel. Meanwhile, emulsification, aided by the surfactants present in the gel, also occurs at the gel surface between the organogel and the aqueous phase. This leads to a gradual erosion of the gel as oil droplets bud off from the gel mass. From these in vitro observations, we speculate that after gel administration in vivo, dynamic interactions occur between the local interstitial fluid and the gel mass: fluid penetration into the gel and emulsification at the gel surface is thus responsible for gel breakdown and so a relatively short duration of drug at the injection site., (Copyright.)

The purpose of this experiment was to determine the disposition of D-tagatose, under development as a low-calorie sweetener, in conventional and germ-free male rats. One group of conventional rats was fed a diet containing D-tagatose (100 g/kg) mixed with the nonpurified diet (900 g/kg) for 28 days. Then, [U-14C]-labeled D-tagatose was administered as a single dose (approximately 220-380 kBq) to 4 of these adapted rats, as well as to 15 conventional and germ-free rats with no prior exposure (i.e., unadapted) to D-tagatose. Eleven of the 19 dosed animals (4 adapted conventional, 3 unadapted conventional and 2 unadapted germ-free, all dosed orally, plus 2 unadapted conventional dosed intravenously) were placed in metabolism chambers and samples of CO2, urine, and feces taken at regular intervals. At termination, a complete material balance was obtained based on the recovery of 14C. Over the 6-h digestive period, D-tagatose was metabolized to release 39.9 and 13.9% of the oral dose as CO2 in the adapted conventional rats and in the unadapted germ-free rats, respectively. Total releases approximated 68 and 22%, respectively. The difference in CO2 evolution is ascribed to microbial fermentation of D-tagatose in the gut of the conventional rats. The role of adaptation was confirmed by finding 93% less D-tagatose in the feces of the adapted conventional rat than in the feces of the unadapted conventional rat. The intestinal absorption of D-tagatose in the rat is estimated to be 20%. The results demonstrate that D-tagatose is metabolized primarily by microorganisms in the gut of the rat, with an upper limit between 15 and 20% of oral dose metabolized by the host., (Copyright 1999 Academic Press.)

The dual lumenaly and vascularly perfused small intestine was used to determine the mechanism by which cholecystokinin octapeptide (CCK-8) decreases the rate of glucose absorption. With CCK-8 in the vascular perfusate the rate of 3-O-methyl-D-glucose absorption decreased, whereas the rate of D-fructose absorption was unaffected. The substrate pool size within the tissue during steady-state transport, in the presence and absence of CCK-8, was estimated by compartmental analysis of the 3-O-methyl-D-glucose washout into the vascular bed. When CCK-8 was included in the vascular perfusate, the absorptive cell pool size decreased when compared with untreated tissue. Both the steady-state hexose absorption data and the washout studies indicated that the locus of action of CCK-8 was the SGLT1 transporter located in the brush-border membrane. The SGLT1 protein abundance in isolated brush-border membranes, as quantified by Western blotting, showed a decrease that paralleled the decrease in the steady-state transport rate induced by CCK-8. These results indicate that CCK-8 diminishes the rate of intestinal hexose absorption by decreasing SGLT1 protein abundance in the brush-border membrane of the rat jejunum and therefore provides evidence for acute enteric hormonal regulation of the rate of glucose absorption across the small intestine.

Glucagon-like peptide-1 (7-36 amide) (GLP-1) is known to increase insulin release when given as a bolus in the fasted and fed state. GLP-1 also increases glucose uptake and lipid synthesis in cultured adipocytes. In this study we investigated the effects of GLP-1 on glucose uptake and on the levels of expression of the facilitative glucose transporters, GLUT1 and GLUT4, in fully differentiated 3T3-L1 adipocytes. Cells were incubated with GLP-1 (10 nM) with or without insulin (10 and 100 nM) for 24 h. Under these conditions, GLP-1 alone caused an increase in basal and acute insulin-stimulated glucose uptake along with an increase in GLUT1 and GLUT4 protein levels. However, there was no change in the expression of GLUT1 and GLUT4 mRNAs. In the absence of GLP-1, prolonged exposure to insulin caused a marked reduction in the levels of GLUT4 mRNA and protein, and an inhibition of glucose uptake after an acute exposure to insulin. This insulin-induced down-regulation of GLUT4 was prevented when GLP-1 was present during the 24-h treatment. In contrast, the acute insulin-stimulated glucose uptake could not be restored by GLP-1. GLP-1 is therefore the first gut hormone shown to be capable of modulating glucose transporter levels in cultured adipocytes.

The synthesis and biological evaluation of sixteen-membered macrolides possessing a 4-O-alkyl-alpha-L-cladinosyl moiety as a neutral sugar are described. These potent novel derivatives have been efficiently synthesized avoiding glycosylations. Two hydroxyl groups in mycarose of the tri-(tert-butyldimethylsilyl) ether intermediate were successively alkylated. Sequential deprotections of silyl groups afforded 4-O-alkyl-L-cladinose analogues and 3,4-di-O-alkyl-L-mycarose analogues of leucomycin V. Some 4-O-alkyl-L-cladinose analogues exhibited potent antibacterial activities. The most active derivative, 3"-O-methyl-4"-O-(3-methylbutyl)leucomycin V, showed improved metabolic stability in rat plasma in vitro and extremely high concentrations in serum after oral administrations in mice and in hamsters.

Post-receptor signalling molecules that convey the signal from the activated insulin receptor to the actual process of Glut4 translocation and hexose uptake are poorly understood. Various studies have suggested a requirement of the lipid kinase phosphatidylinositol-3 kinase (PI3-kinase) in this process. PI3kinase regulates the activation status of the small GTP-binding protein Rac which, in turn, is able to activate another G-protein Rho. Rac and Rho are known to regulate the structure of the membrane- and cytoplasmic actin-cytoskeleton. We have examined whether Rac and Rho transfer the signals generated by PI3kinase towards insulin-stimulated hexose uptake. For that purpose, we expressed in 3T3-L1 adipocytes the dominant-negative mutant of RacN17 using vaccinia virus-mediated gene transfer. The expression levels of the RacN17 protein were monitored by Western blotting. The abrogation of endogenous Rac signalling by expression of RacN17 was inferred from the observed loss of arachidonic acid release in response to insulin. Basal and insulin-stimulated hexose transport were not affected by expression of the RacN17 mutant. A possible contribution of Rho.GTP to stimulation of hexose uptake was examined by pre-incubation of adipocytes with lysophosphatidic acid (LPA). We observed a profound effect of LPA on the structure of the cytoskeleton and on the phosphorylation of Focal Adhesion Kinase (p125FAK), indicating that 3T3-L1 adipocytes respond to LPA and that Rho was activated by LPA. However, no effect was detected on the basal or on the insulin-stimulated hexose transport. We conclude that Rac and Rho are unlikely to be involved in insulin-stimulated hexose transport, suggesting a possible contribution of other signalling pathways, downstream of PI3kinase to this process.

The kinetic parameters of hexose uptake by the small and large intestine of the chicken have been determined in vitro. Rates of initial influx of alpha-methyl-D-glucoside and L-glucose were measured in everted sleeves of the duodenum, jejunum, ileum, proximal cecum, and rectum. Results show the following. 1) Maximal transport capacity values for alpha-methyl-D-glucoside show that the jejunum is the segment that is best suited for Na(+)-mediated uptake. 2) The calculated apparent Michaelis constant values were (in mmol/l) 11.6 for duodenum, 7.8 for jejunum, 3.5 for ileum, 2.4 for proximal cecum, and 7.1 for rectum. This suggests that, with the exception of the rectum, the affinity of the carrier for alpha-methyl-D-glucoside progressively increases in the distal direction. 3) Diffusion constant values indicate that influx of hexoses by a passive mechanism in the duodenum and proximal cecum is significantly higher than in the other segments. 4) The sum of passive and mediated mechanisms confers to the duodenum and jejunum a high capacity to absorb hexoses. The ileum, proximal cecum, and rectum have a quantitatively minor role, albeit significant, in completing the absorptive function.

The properties of hexose transport across the apical and basolateral membranes of chicken enterocytes have been studied in the small and large intestine. Results show that (a) isolated epithelial cells from all segments except the coprodeum can accumulate 3-O-methylglucose (Glc3Me) against a concentration gradient, by a Na(+)-dependent and phloridizin-sensitive mechanism. (b) The cell cumulative capacity for Glc3Me (control/phloridizin-incubated cells) is lower in the small intestine than in the large intestine (rectum = proximal caecum = ileum > jejunum > duodenum). (c) Theophylline enhances the cell Glc3Me cumulative capacity 2.9-fold in the duodenum and 2.4-fold in the jejunum but has no effect in the other segments studied. (d) Analysis of sugar uptake indicates that net hexose influx rates decrease from proximal to distal regions: jejunum > duodenum > ileum = proximal caecum = rectum for the apical transport system (alpha-methyl glucoside as substrate and phloridizin as inhibitor) and duodenum > jejunum > ileum = proximal caecum = rectum for the basolateral system (2-deoxyglucose; theophylline). (e) The duodenum and the jejunum show high apical and basolateral hexose transport rates, which confer a significant capacity for sugar absorption on the proximal intestine. More distal regions, including the ileum, the proximal caecum and the rectum, have transport systems analogous to those of the proximal intestine that keep a considerable potential capability to recover hexoses from the lumen.

Preconditioning with brief intermittent periods of ischemia has been shown to lessen the detrimental effects of a subsequent sustained (30-60 min) period of ischemia. Because adenosine has been suggested to be the mediator of preconditioning, we were interested in investigating whether adenosine antagonists would block the effect of preconditioning on ionic changes during ischemia. We found that 10 microM of the adenosine antagonist BW-A1433U did not reverse the effect of preconditioning on intracellular pH (pHi). Hearts preconditioned with BW-A1433U had virtually no decrease in pHi during the 30-min sustained period of ischemia; after 30 min of ischemia, the pH in untreated hearts was 5.97 +/- 0.16 compared with 6.52 +/- 0.10 in preconditioned hearts and 6.90 +/- 0.08 in hearts preconditioned plus BW-A1433U. Because anaerobic glycolysis is largely responsible for the fall in pHi during ischemia, we examined the effect of BW-A1433U [and other adenosine antagonists, such as PD-115,199 and 8-cyclopentyl-1,3-dipropylxanthine (CPDPX)] on glucose uptake and phosphorylation during aerobic perfusion using 31P-nuclear magnetic resonance to monitor uptake and phosphorylation of 2-deoxyglucose (2-DG) to 2-deoxyglucose 6-phosphate (2-DG-6-P) when one-half of the glucose in the perfusate was replaced with 2-DG. Uptake of 2-DG-6-P after 15 min was reduced by 66% in the presence of BW-A1433U and 82% in the presence of PD-115,199 as compared with untreated hearts, but was not reduced in the presence of CPDPX. Thus CPDPX was the only adenosine antagonist tested that did not block accumulation of 2-DG-6-P. We also found that CPDPX did not block the beneficial effect of preconditioning on ionic alterations during a sustained 30-min period of ischemia or the improved recovery of function on reflow.

The uptake and efflux of radioactivity was monitored in rat erythrocytes exposed to or prelabeled with either 3-O-methyl-D[U-14C]glucose or D-[U-14C]glucose. In the case of 3-O-methyl-D-[U-14C]glucose uptake, the half-life for equilibration of hexose concentration between the extracellular medium and the intracellular 3H2O space increased from 12.5 to 32.5 min as the concentration of the D-glucose analog was raised from 8.3 to 33.3 mM. In erythrocytes preincubated for 60 min with 3-O-methyl-D-[U-14C]glucose at the latter two concentrations, the half-life for the fall in cell radioactive content, after correction for the residual radioactivity recovered in the cells after prolonged incubation, amounted to respectively 6.5 and 9.5 min. Thus, whether in terms of uptake or efflux, the equilibration of hexose concentrations across the plasma membrane represented a delayed phenomenon. In this respect, there was no difference between erythrocytes from control or diabetic rats. Comparable conclusions were reached in the study of influent and effluent radioactivity in rat erythrocytes exposed to or prelabeled with D-[U-14C]glucose. In such a case, the measurement of radioactive acidic metabolites and L-lactic acid indicated that, even after 90 min incubation, the concentration of the hexose in the intracellular 3H2O space remained lower than its extracellular concentration. It is proposed that the delayed equilibration of hexose concentrations accounts, in part at least for an artifact of isotopic dilution in the study of radioactive D-glucose metabolism by erythrocytes from control or diabetic rats.

A fluorine-18 labeled analogue of D-talose, 2-deoxy-2-[18F]fluoro-D-talose ([18F]FDT), was synthesized via nucleophilic fluorination with [18F]fluoride ion and its biodistributions in animals were examined. Radiofluorination of benzyl 3,5,6-tri-O-benzyl-2-O-(trifluoromethanesulfonyl)-alpha-D-galac tof uranoside (5) with aminopolyether supported potassium [18F]fluoride (K18F/Kry222) in acetonitrile followed by deprotection of the [18F]fluorinated intermediate (6) with boron tribromide in CH2Cl2 gave [18F]FDT in an average radiochemical yield of 29% with a radiochemical purity greater than 98%. Biodistribution studies of [18F]FDT in mice bearing fibrosarcoma showed the highest uptake of radioactivity in the liver (34.9% dose/g), followed by the kidney (15.9%dose/g), the small intestine (12.9%dose/g) and fibrosarcoma (5.7%dose/g), at 30 min after i.v. administration. Although the radioactivity in the kidney and small intestine decreased with time, the uptake in the liver and the tumor slightly increased until 120 min. The high liver uptake of [18F]FDT was also observed in normal rats and this uptake was strongly inhibited by co-administration of D-galactose. These preliminary results suggest that [18F]FDT might be metabolized through the galactose metabolic pathway as analogously observed with 2-deoxy-2-[18F]fluoro-D-galactose which is an isomer with respect to carbon-2 of [18F]FDT, and that it may be another candidate for studying liver function by positron emission tomography.

We have investigated the effect of various inhibitors of protein synthesis on hexose transport in human skin fibroblasts using 2-deoxy-D-glucose (2-DG) and 3-0-methyl-D-glucose (3-OMG) to measure hexose transport. Exposure of glucose-fed, serum-free cultures to cycloheximide (CHX) (50 micrograms/ml) for 6 h resulted in increased 2-DG transport (3.81 +/- .53 vs. 6.62 +/- .88 nmoles/mg protein/2 min; n = 9) and 3-OMG transport (1.36 +/- .66 vs. 3.18 +/- .83 nmoles/mg protein/30 sec; n = 4) in the CHX exposed group. Under these conditions inhibition of protein synthesis was greater than 90%. This CHX induced transport increase was time dependent (approaching maximum within 1 h of exposure to CHX) and related to an increase in the Vmax of hexose transport in the CHX exposed group (18.4 +/- 2.4 vs. 4.8 +/- 1.1 nmoles 2-DG/mg protein/min) with no difference in the transport Km (1.55 +/- .63 vs. 2.92 +/- .59 mM). Further, the CHX induced increase in hexose transport was reversible. Exposure of human fibroblasts to inhibitors of protein synthesis with different mechanisms of action (e.g., puromycin, pactamycin, or CHX) all generated hexose transport increases in a concentration-dependent fashion correlating with their increasing inhibitory effects on protein synthesis. Nucleotidase enriched (i.e., plasma membrane) fractions of control and CHX-exposed cells showed no differences in D-glucose inhibitable cytochalasin B binding activity. Further, quantitative Western analysis of nucleotidase enriched fractions indicated CHX exposure resulted in no significant increase in glucose transporter mass compared with control plasma membrane fractions. Glucose deprived cells, however, which exhibited increased sugar transport comparable to the CHX-exposed group, did show increased glucose transporter mass in the plasma membrane fraction. The data indicate that inhibitors of protein synthesis can cause a significant elevation in hexose transport and that the hexose transporter mass in the isolated plasma membrane fractions did not reflect the whole cell transport change. It is suggested that a mechanism other than glucose transporter translocation to the plasma membrane may be involved in causing this sugar transport increase.

1. Rates of absorption of two hexose (D-glucose and D-galactose) and two pentose (D-xylose and D-arabinose) sugars were measured by in vivo perfusion, in jejunum, ileum and (distal) caecum, in immature hens conditioned to either a standard (ST) or "high fibre" (ST + 20% grass) diet. 2. Each bird was tested in one intestinal segment with all four (U-14C-labelled, 10 mM) sugars, with either the hexoses preceding the pentoses or vice versa. 3. With all treatments, absorption rates of the hexoses were alike, as were those of the pentoses. Hexose absorption was twice as fast as pentose absorption in jejunum and ileum with both dietary pretreatments, whereas in caecum hexose and pentose rates were similarly high, except when pentose (and its associated fluid transfer) was apparently inhibited by prior hexose absorption with the ST diet. 4. With the ST diet, hexose absorption (per unit length and dry weight) was faster in caecum than in jejunum and ileum, and pentose absorption was also fastest in caecum when all pentose data from testing after hexose were excluded. 5. With the ST/grass diet, hexose absorption was faster in jejunum than in ileum and caecum when expressed per unit length, and pentose absorption was fastest in caecum on a dry weight basis. 6. Hexose absorption was faster in jejunum and slower in caecum with the ST/grass pretreatment than with ST. However, the dietary comparison was not conclusive because it involved birds form (two) different hatches (of similar age and weight) tested at different times.

Effects of protein kinase C (PKC) inhibitors and "down-regulation" on insulin and PMA-stimulated 2-deoxyglucose transport were determined in isolated rat adipocytes or BC3H-1 myocytes. In both model systems, H-7, sangivamycin, and staurosporine, inhibitors of the catalytic domain of PKC, each effectively blocked insulin and PMA-stimulated hexose uptake at similar concentrations. In the myocytes, staurosporine completely blocked the insulin effect retained post-chronic phorbol myristate acetate (PMA)-induced "down-regulation." These findings indicate (1) that chronic pretreatment with PMA may not lead to a complete loss of PKC activity in the myocyte, and (2) that PKC is involved in insulin-stimulated hexose transport in both isolated rat adipocytes and BC3H-1 myocytes.

Transtrophectodermal 3-0-methyl glucose (3-0MG) transport in the rabbit blastocyst at Days 6 and 7 post coitum was investigated to understand better how the trophectoderm can regulate inner cell mass growth by controlling substrate availability. 3-0MG rapidly traversed the trophectoderm and displayed saturation kinetics (Km = 4.3 +/- 0.5 mM, Vmax = 79 +/- 3.8 nmol.cm-2). The flux of 3-0MG was inhibited nearly 95% by 10(-4) M-phloretin, and only 15% by 10(-4) M-phlorizin. Furthermore, 3-0MG influx was inhibited by cytochalasin B (5 microM) and was unaffected by removal of sodium. The transport system had a high specificity for 2-deoxy-D-glucose and glucose, and a very low specificity for fructose and 4-alpha-methyl glucoside. Western blots probed with a polyclonal antibody to the human erythrocyte glucose transport protein and also with a polyclonal antibody to the C-terminus of the glucose transport protein of the rat brain revealed a broad band with a molecular weight of 55,000. Using immuno-gold labelling techniques, Na(+)-independent glucose transporters were localized to both the apical and basolateral borders of the trophectodermal cell. These results suggest that the mechanism in the trophectoderm responsible for transport of glucose is similar to other sodium-independent glucose transport systems. In addition, 3-0MG influx was unaffected by short-term incubation with progesterone, the progesterone antagonist mifepristone (RU-486), PGF-2 alpha, PGE-2, insulin, or cAMP. Day-7 p.c. embryos also transported hexoses by a similar system because the influx rate and the phlorizin/phloretin sensitivity were the same as in the Day-6 p.c. embryo.

Characteristic features of hydrolysis and carbohydrate absorption in 106 newly-diagnosed pulmonary tuberculosis patients were studied by means of a combined carbohydrate load method. Certain ways of treating the disturbances were tested. It was found that in 60% of the cases with an active pulmonary tuberculosis and with symptoms of gastrointestinal diseases, there were disturbed processes of hydrolysis and carbohydrate absorption. A long-term administration of antituberculous drugs affects hydrolysis and carbohydrate absorption in the small intestine. A chemotherapeutic regimen supplemented with insulin, glucocorticoids, and folic acid, in particular, leads to the improvement of hydrolysis and carbohydrate absorption in pulmonary tuberculosis patients.

The effect of stress (heat shock, arsenite, or Semliki Forest virus [SFV] infection) on the induction of increased hexose transport has been compared with that of insulin. All four treatments increase the Vmax for transport by BHK cells three- to five-fold, with little effect (less than 40% decrease) on Km. Hydrogen peroxide and phenylarsine oxide (PAO) prevent the increase in hexose transport induced by stress treatments as effectively as they do that induced by insulin. Pinocytosis is not affected by any of the four treatments. On the other hand, the induction by insulin is sensitive to amiloride, whereas that by arsenite is not. Rat embryo fibroblasts, which respond poorly to insulin, respond well to arsenite, heat shock, or SFV infection. It is concluded that the stress response is mediated by certain compounds that may be common to those required for the action of insulin, but that those compounds act at a stage subsequent to the function of the insulin receptor.

The rate of hexose transport was approximately 60% lower for both the high- and the low-affinity components of hexose uptake when a glucose-6-phosphate isomerase mutant of Saccharomyces cerevisiae was preincubated with glucose, as compared with preincubation with water. Similarly the Jmax value of the high-affinity system of the mutant was 25-35% of the corresponding Jmax value for normal cells incubated with glucose. Accumulation of glucose 6-phosphate or of some other metabolite, such as fructose 6-phosphate or trehalose, may be responsible for this striking inhibition.

The rat visceral yolk sac is shown to possess a sodium-independent, phloretin-sensitive, and phlorizin- and ouabain-insensitive transport system for hexoses. The rate of uptake of (3H)2-deoxy-D-glucose was measured in vitro and shown to be greatest on the 12th day, decreasing progressively with increasing gestational age up to the 20th day. Little uptake of 3-O-methyl-D-glucose, alpha-methylglucoside or L-glucose occurred. On uptake by the visceral yolk sac, 2-deoxy-D-glucose was phosphorylated, leading to considerable accumulation of this sugar. Several sugars inhibited 2-deoxy-D-glucose uptake as follows: D-glucose = mannose greater than fructose greater than galactose greater than xylose greater than fucose.

The chemotherapeutic agent VM-26 is a membrane-interactive drug which we have previously demonstrated to be a potent inhibitor of nucleoside transport. Since the carriers mediating nucleoside and hexose transport are structurally and functionally similar, we have further characterized the membrane related properties of this agent by examining its effect on the transport and phosphorylation of hexoses in Ehrlich ascites cells. Under conditions in which only the transport component of hexose uptake was measured, VM-26 had no effect on the influx of 2-deoxyglucose, 3-0-methylglucose, or D-glucose. Glucose-sensitive cytochalasin B binding was only weakly inhibited by the drug. However, VM-26 was an apparent non-competitive inhibitor of the net uptake of 2-deoxyglucose (transport and phosphorylation). Measurement of hexokinase activity in cell extracts failed to demonstrate any significant effect of VM-26 on enzyme activity. In summary, although VM-26 is a potent inhibitor of the transport of nucleosides, it has no apparent effect on the transmembrane flux of hexoses indicating a differential effect on nucleoside and hexose transporters. The ability of the drug to decrease the net accumulation of hexoses in the absence of any detectable effect on hexokinase activity warrants further investigation.

Papaverin is shown to have a significant inhibitory effect on the intestinal transport systems for glucose, galactose and glycine but not for fructose. In vitro experiments have revealed that the inhibitory effect of papaverin on the glucose transport take place under mucosal application, nevertheless the serosal one is of a stimulatory character. Papaverin inhibits only the active component of the glucose transport.

We report here the effects of growth conditions and myogenic differentiation on rat myoblast hexose transport activities. We have previously shown that in undifferentiated myoblasts the preferred substrates for the high (HAHT)- and low (LAHT)-affinity hexose transport systems are 2-deoxyglucose (2-DG) and 3-O-methyl-D-glucose (3-OMG), respectively. The present study shows that at cell density higher than 4.4 x 10(4) cells/cm2, the activities of both transport processes decrease with increasing cell densities of the undifferentiated myoblasts. Since the transport affinities are not altered, the observed decrease is compatible with the notion that the number of functional hexose transporters may be decreased in the plasma membrane. Myogenic differentiation is found to alter the 2-DG, but not the 3-OMG, transport affinity. The Km values of 2-DG uptake are elevated upon the onset of fusion and are directly proportional to the extent of fusion. This relationship between myogenesis and hexose transport is further explored by using cultures impaired in myogenesis. Treatment of cells with 5-bromo-2'-deoxyuridine abolishes not only myogenesis but also the myogenesis-induced change in 2-DG transport affinity. Similarly, alteration in 2-DG transport affinity cannot be observed in a myogenesis-defective mutant, D1. However, under myogenesis-permissive condition, the myogenesis of this mutant is also accompanied by changes in its 2-DG transport affinity. The myotube 2-DG transport system also differs from its myoblast counterpart in its response to sulfhydryl reagents and in its turnover rate. It may be surmised from the above observations that myogenesis results in the alteration of the turnover rate or in the modification of the 2-DG transport system. Although glucose starvation has no effect on myogenesis, it is found to alter the substrate specificity and transport capacity of HAHT. In conclusion, the present study shows that hexose transport in rat myoblasts is very sensitive to the growth conditions and the stages of differentiation of the cultures. This may explain why different hexose transport properties have been observed with myoblasts grown under different conditions.

Influence of non-ionic tensides on liberation of chlorotetracycline hydrochloride from ointment bases was investigated. Non-ionic tensides were found to enhance liberation of chlorotetracycline hydrochloride from lipophilic ointment bases, while liberation of this antibiotic from hydrophilic ointment bases proved to be depressed.

The sulfhydryl reagent 5, 5'-dithiobis (2-nitrobenzoic acid) (DTNB) was used to study the functional role of an exofacial sulfhydryl group on the human erythrocyte hexose carrier. Above 1 mM DTNB rapidly inhibited erythrocyte 3-O-methylglucose influx, but only to about half of control rates. Efflux was also inhibited, but to a lesser extent. Uptake inhibition was completely reversed by incubation and washing with 10 mM cysteine, whereas it was only partially reduced by washing in buffer alone, suggesting both covalent and noncovalent interactions. The covalent thiol-reversible reaction of DTNB occurred on the exofacial carrier, since (i) penetration of DTNB into cells was minimal, (ii) blockade of potential uptake via the anion transporter did not affect DTNB-induced hexose transport inhibition, and (iii) DTNB protected from transport inhibition by the impermeant sulfhydryl reagent glutathione-maleimide-I. Maltose at 120 mM accelerated the covalent transport inhibition induced by DTNB, whereas 6.5 microM cytochalasin B had the opposite effect, indicating under the one-site carrier model that the reactive sulfhydryl is on the outward-facing carrier but not in the substrate-binding site. In contrast to glutathione-maleimide-I, however, DTNB did not restrict the ability of the carrier to reorient inwardly, since it did not affect equilibrium cytochalasin B binding. Thus, carrier conformation determines exposure of the exofacial carrier sulfhydryl, but reaction of this group may not always "lock" the carrier in an outward-facing conformation.