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Biomedical subjects

R Kannan

Publications and source records attributed to R Kannan.

At least 55 records · Page 3Linked to original sources
PubMed1996

Transforming growth factor-alpha overexpression in proliferative verrucous leukoplakia and oral squamous cell carcinoma: an immunohistochemical study.

Proliferative verrucous leukoplakia is a unique type of oral leukoplakia that has a high risk of malignant transformation. The aim of this study was to examine the expression of transforming growth factor-alpha in proliferative verrucous leukoplakia, oral squamous cell carcinoma, and normal mucosa. Transforming growth factor-alpha, a potent mitogen, is known to play an important role in various neoplasms including oral squamous cell carcinoma. Immunohistochemical localization of transforming growth factor-alpha in archival paraffin-embedded sections was performed with commercially available monoclonal antibodies. Ten cases each of normal mucosa, proliferative verrucous leukoplakia, and oral squamous cell carcinoma were stained. Quantification of the staining intensity, expressed as the cytoplasmic optical density, was done with the Roche Image Analysis System. The data were statistically analyzed with the one-way analysis of variance and Tukey tests. Notably, the mean cytoplasmic optical density of proliferative verrucous leukoplakia was significantly higher than the mean cytoplasmic optical density of normal mucosa (p < 0.01). The mean cytoplasmic optical density of proliferative verrucous leukoplakia was slightly higher than that of oral squamous cell carcinoma, however, this difference was not significant (p > 0.05). The mean cytoplasmic optical density values demonstrate that increased transforming growth factor-alpha immunoreactivity occurs in proliferative verrucous leukoplakia and oral squamous cell carcinoma relative to normal mucosa.

Adult↗
PubMed1996

GSH transporters: molecular characterization and role in GSH homeostasis.

Considerable progress has been made in the last few years in the molecular identification and characterization of hepatic GSH transporter-associated polypeptides. We are now poised to determine their precise mechanisms of action and regulation at the transcriptional and post-translational level. It is also anticipated that molecular characterization of the mitochondrial GSH transporter and sodium GSH co-transporters will be accomplished in the near future. With this information, a more complete understanding of GSH/cysteine homeostasis can be achieved which can be applied to furthering the prevention and treatment of the diseases of oxidative stress, such as aging, HIV, cataract, atherosclerosis, cancer and alcoholic liver disease.

Animals↗
PubMed1996

Identification of a novel, sodium-dependent, reduced glutathione transporter in the rat lens epithelium.

PURPOSE: To determine whether glutathione (GSH) transporter(s) other than the previously identified rat canalicular GSH transporter (RcGshT) is present in the lens. METHODS: Poly (A) +RNA isolated from rat and guinea pig lens cortex and epithelium was injected into Xenopus laevis oocytes. The effect of sodium removal was determined by measuring cell-associated radioactivity in lenticular epithelium or cortex mRNA injected oocytes (pretreated with acivicin to inhibit gamma glutamyltranspeptidase) after 1 hour of incubation in NaCl medium or choline chloride (Na(+)-free) medium containing tracer GSH (plus unlabeled GSH). The effect of 2 mM bromosulfophthalein-GSH (BSP-GSH) on GSH uptake in the lens epithelium and cortex in NaCl medium at two GSH concentrations also was determined. The molecular form of uptake of GSH in lens epithelial mRNA-injected oocytes was examined by high-performance liquid chromatography. Western blot analysis was performed to study the presence of RcGshT in the cortex and epithelium. RESULTS: Oocytes injected with mRNA from rat and guinea pig lens epithelium and cortex compartments expressed GSH transport. High-performance liquid chromatography confirmed that epithelial uptake was as intact GSH under conditions of inhibition of GSH synthesis with dl-buthionine sulfoximine. The mean GSH uptake (nmol/oocyte per hour) in epithelial mRNA-injected oocytes was significantly reduced (P < 0.01, n = 4 oocyte preparations) under Na(+)-free conditions compared to NaCl medium at 0.05 mM and 2 mM GSH in the medium. Uptake in cortical mRNA-injected oocytes was unaffected by Na+ removal. Lens epithelial uptake exhibited a strong inhibition by BSP-GSH at 0.05 mM (55%) and 2 mM (64%), whereas cortical uptake was unaffected by BSP-GSH. Western blot analysis identified RcGshT in the cortical and epithelial regions. CONCLUSIONS: Results from the current study provide strong evidence for the presence of a hitherto unreported Na(+)-dependent, BSP-GSH inhibitable GSH transporter in the lens epithelium, which may mediate concentrative, basolateral uptake of aqueous GSH consistent with in situ eye perfusion studies. The Na(+)-independent, BSP-GSH insensitive RcGshT may function as an apical GSH effluxer in lens epithelium and in mediating concentration gradient driven inward GSH movement by uptake-efflux in the lens cortex.

Animals↗
PubMed1995

Overexpression of extracellular sucrase (SacC) of Zymomonas mobilis in Escherichia coli.

The extracellular sucrase (SacC) gene of Zymomonas mobilis was overexpressed in Escherichia coli BL21 using the T7 polymerase expression system. A low cell density induction method was designed to have maximum expression, and the conditions (IPTG concentration, ampicillin addition) were optimised to overexpress to the level of more than 60% of the total cellular protein representing SacC protein.

Bacteriological Techniques↗
PubMed1995

Stimulation of "prohormone thiol protease" (PTP) and [Met]enkephalin by forskolin. Blockade of elevated [Met]enkephalin by a cysteine protease inhibitor of PTP.

Proenkephalin and other prohormones require proteolytic processing at paired basic and monobasic residues for the biosynthesis of active neuropeptides. The novel "prohormone thiol protease" (PTP) has been proposed as a candidate proenkephalin processing enzyme for the production of [Met]enkephalin in chromaffin granules (Krieger, T. J., and Hook, V. Y. H. (1991) J. Biol. Chem. 266, 88376-8383). In this study, PTP was examined during elevation of cellular [Met]enkephalin by forskolin, a direct activator of adenylate cyclase that produces cAMP. Treatment of chromaffin cells with forskolin for 72 h increased enkephalin precursor cleaving activity (measured by following the conversion of the model substrate [35S-Met]preproenkephalin to trichloroacetic acid-soluble radioactivity) in isolated chromaffin granules by 170-180% over controls (100%). The increased activity was associated with the membrane fraction, rather than the soluble fraction, of chromaffin granules. The elevated activity was inhibited by E-64c, which is a potent inhibitor of PTP and cysteine proteases; however, the activity was not inhibited by serine or aspartic protease inhibitors. The elevated activity was identified as PTP based on immunoprecipitation by anti-PTP immunoglobulins. Stimulation of PTP synthesis was involved in the forskolin-induced increase in PTP activity, as demonstrated by a 10-fold increase in [35S]PTP pulse labeling in forskolin-treated chromaffin cells. Forskolin elevation of PTP protein levels within chromaffin granules was also detected in Western blots. Importantly, the forskolin-mediated rise in cellular [Met]enkephalin levels was completely blocked when cells were preincubated with the cysteine protease inhibitor Ep453, which is known to be converted by intracellular esterases to the more effective inhibitor E-64c (Buttle, D. J., Saklatvala, J., Tamai, M., and Barrett, A. J. (1992) Biochem. J. 281, 175-177). Both E-64c and Ep453 inhibit PTP, with E-64c being more potent (Azaryan, A. V., and Hook, V. Y. H. (1994b) Arch. Biochem. Biophys. 314, 171-177). These results demonstrate a role for PTP in proenkephalin processing in chromaffin cells and indicate that [Met] enkephalin formation and PTP are both regulated by cAMP.

Adrenal Glands↗
PubMed1995

Molecular cloning and characterization of the extracellular sucrase gene (sacC) of Zymomonas mobilis.

The Zymomonas mobilis gene sacC that encodes the extracellular sucrase (protein B46) was cloned and expressed in Escherichia coli. The gene was found to be present downstream to the already described levansucrase gene sacB in the cloned chromosomal fragment of Z. mobilis. The expression product was different from SacB and exhibited sucrase but not levansucrase activity; therefore, SacC behaves like a true sucrase. Expression of sacC in E. coli JM109 and XL1 was very low; overexpression was observed in E. coli BL21 after induction of the T7 polymerase expression system with IPTG. Subcellular fractionation of the E. coli clone carrying plasmid pLSS2811 showed that more than 70% of the sucrase activity could be detected in the cytoplasmic fraction, suggesting that the enzyme was soluble and not secreted in E. coli. The nucleotide sequence analysis of sacC revealed an open reading frame 1239bp long coding for a 413 amino acid protein with a molecular mass of 46 kDa. The first 30 deduced amino acids from this ORF were identical with those from the N-terminal sequence of the extracellular sucrase (protein B46) purified from Z. mobilis ZM4. No leader peptide sequence could be identified in the sacC gene. The amino acid sequence of SacC showed very little similarity to those of other known sucrases, but was very similar to the levansucrases of Z. mobilis (61.5%), Erwinia amylovora (40.2%) and Bacillus subtilis (25.6%).

Amino Acid Sequence↗
PubMed1995

Bidirectional glutathione transport by cultured human retinal pigment epithelial cells.

PURPOSE: To characterize glutathione (GSH) transport by cultured human retinal pigment epithelial (HRPE) cells. METHODS: Cultured HRPE cells were pretreated with acivicin for GSH efflux and with buthionine sulfoximine for GSH uptake to prevent the breakdown and resynthesis of GSH. Efflux was measured by the linear rate of accumulation of GSH in the supernatant; uptake was measured using [35S] GSH plus varying concentrations of GSH. Molecular forms were verified by high-performance liquid chromatography. HRPE cell mRNA was probed for the presence of the two recently cloned rat sinusoidal and canalicular GSH transporters, (RsGshT and RcGshT), by Northern blot analysis. RESULTS: Glutathione efflux was temperature dependent (undetectable at 4 degrees C), and its averaged 23 +/- 3.3 pmol/10(6) cells/minute or 10% of the total GSH effluxed per hour (total cell GSH = 13.6 +/- 1.5 nmol/10(6) cells). Efflux was not influenced by dithiothreitol or sulfobromophthalein-reduced GSH adduct, agents known to affect liver sinusoidal GSH transport. Glutathione uptake was linear up to 45 minutes and was temperature dependent. The difference between 37 degrees C and 4 degrees C uptake values represented true uptake. Glutathione uptake (2 microCi/ml + 1 mM mass) was Na independent and was inhibited significantly by phenol-3,6-dibromphthalein disulfonate. The kinetics of GSH uptake was assessed by measuring uptake with 35S-GSH and 0.05 to 40 mM extracellular GSH for 30 minutes. Uptake was saturable with Vmax = 18.7 +/- 1.7 nmol/10(6) cells/30 minutes, Km = 12.1 +/- 1.9 mM, n (binding site) = 1. On Northern blot analysis, HRPE cells express mRNA for RcGshT but not for RsGshT. CONCLUSIONS: The similarities in functional characteristics of GSH transport and the presence of RcGshT-like mRNA suggest GSH transport in HRPE cells is mediated by a RcGshT homolog. Although the transporter can operate bidirectionally, it is expected to be a net efflux pump under normal physiologic conditions because the intracellular GSH concentration is much higher.

Biological Transport↗
PubMed1995

Molecular characterization of a reduced glutathione transporter in the lens.

PURPOSE: To characterize glutathione (GSH) transporter in the lens. METHODS: Poly (A) +RNA isolated from bovine lens was injected into Xenopus laevis oocytes. Oocytes were incubated for 1 hour in either NaCl or sucrose medium containing tracer GSH, and cell-associated radioactivity was determined. Glutathione efflux was determined in lens mRNA injected oocytes preloaded with GSH. Relationship of lens GSH transporter to the two recently cloned sodium-independent hepatic membrane GSH transporters was studied by Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses. Bovine lens mRNA also was probed for gamma glutamyl transpeptidase (GGT) by RT-PCR. RESULTS: Uptake of tracer 35S-GSH could be demonstrated in X. laevis oocytes injected with poly (A) +RNA from bovine lens. Glutathione transport was carrier mediated (Km approximately 1.3 mM) and was sodium independent. High-performance liquid chromatography confirmed that the molecular form of uptake was predominantly (> 98%) as it was for GSH. Poly (A) +RNA-injected oocytes preloaded with 16.5 nmol GSH-oocyte showed GSH efflux at a rate of 2.6 nmol/oocyte per hour. When bovine lens poly (A) +RNA was hybridized with the cDNA probe for the sodium-independent rat canalicular GSH transporter (RcGshT), the transcript for RcGshT was observed. RT-PCR confirmed the presence of RcGshT and showed the absence of rat sinusoidal GSH transporter (RsGshT) and GGT mRNA in rat lens. CONCLUSIONS: The authors have demonstrated for the first time that lens contains mRNA for RcGshT and expresses a low-affinity GSH transporter in oocytes. Glutathione efflux from the apical side of the anterior epithelium and progressive uptake, and inward efflux into cortical fibers, might be explained by expression of RcGshT alone or in combination with as yet unidentified GSH transporters.

Animals↗
PubMed1994

Evidence for transcapillary transport of reduced glutathione in vascular perfused guinea-pig brain.

Using a vascular brain perfusion model in the guinea-pig, the net uptake of [35S]-GSH by the brain was found to be linear and similar in various regions during 10 min perfusion. Dual labeled [35S and 3H] GSH taken up by the brain had the same isotope ratio as the injected stock whether or not gamma- glutamyl transferase was inhibited. Greater than 96% of brain uptake of [35S]-cysteine-labeled GSH and [3H]-glycine-labeled GSH were in intact form. Transcytosis of [35S]-GSH from lumen into brain parenchyma was demonstrated using a capillary depletion technique. Both GSH and GSH-monoethyl ester inhibited [35S]-GSH transport. Thus, we have demonstrated blood-brain barrier extraction of circulating GSH in a brain perfusion model, and the transcytosis of intact GSH into the brain parenchyma without breakdown.

Animals↗
PubMed1994

Blood-to-lens transport of reduced glutathione in an in situ perfused guinea-pig eye.

Transport mechanisms of reduced glutathione (GSH) in intact eye are poorly understood. In this study, an in situ vascular eye perfusion (VEP) model was used to characterize the transport kinetics of circulating GSH into the aqueous humor and lens in guinea pigs. Radiolabeled [35S]GSH or [3H]GSH and [14C]sucrose (an extracellular space marker) were exposed to the blood-aqueous barrier up to 10 min, and uptake of tracers by the aqueous humor and lens was determined in the presence of different concentrations of unlabeled peptide as GSH, a gamma-glutamyl compound as a derivative of GSH (GSH monoethyl ester), and an inhibitor of gamma-glutamyl transpeptidase (GGT) activity. Plasma-aqueous and aqueous-lens compartmental unidirectional transport constant, K(in), and the initial rapid volume of distribution, Vi, were estimated by multiple-time-point graphic analysis. Our results indicated that both labeled GSH and sucrose entered the aqueous humor slowly at comparable rates with respective blood-aqueous K(in) values of 1.34 +/- 0.12 and 1.25 +/- 0.08 min-1 x 10(3). In contrast to blood-aqueous transport, GSH uptake by the lens was rapid, and the respective aqueous-lens K(in) values for labeled GSH and sucrose were 79.3 +/- 4.1 and 3.5 +/- 0.7 min-1 x 10(3). Over 94% of plasma-derived GSH remained in its original molecular form of GSH in the lens, during the 10 min perfusion both with and without the GGT inhibitor, serine borate. The amount of [35S]GSH in lens anterior epithelium (dpm mg-1) was more than three times that of aqueous humor (dpm microliter-1) within only 10 min of VEP. There was also significant accumulation of [35S]GSH in the interior cortex, as indicated by 10-min cortex/aqueous ratio of 0.65. A specific GGT independent GSH transport system was demonstrated in the lens in situ, with a Km of 26 +/- 3 microM, and Vmax of 34 +/- 3 pmol min-1 g-1 of whole lens tissue water. The lenticular influx of GSH was inhibited by GSH monoethyl ester with an affinity that was half that for GSH. It is concluded that: (a) uptake of plasma-derived GSH into the aqueous humor is by simple diffusion, and (b) cellular uptake of GSH by the lens is carrier-mediated via mechanism that is separate from the transpeptidation metabolic pathway.

Animals↗
PubMed1994

Galactose-induced cataract formation in guinea pigs: morphologic changes and accumulation of galactitol.

PURPOSE: To develop and characterize a new model of galactose-induced cataract formation in young, 3- to 4-week-old Hartley guinea pigs. METHODS: Experimental animals were fed 50% galactose in powdered guinea pig chow containing 0.5 g ascorbate/kg diet. Control animals were fed normal powdered guinea pig chow (0.5 g ascorbate/kg diet). Lenses from all animals were subjected to photo-slit-lamp examination, light microscopic analysis, and high-pressure liquid chromatography (HPLC) analysis of polyol content. RESULTS: Photo-slit-lamp examination indicated initial opacities in equatorial subcapsular region between 3 and 5 days in all galactose-fed animals (20/20); opacities progressed toward the anterior pole when diet was extended to 14 days. Histologic analysis of the equatorial changes confirmed progressive cataract formation consisting of small intra-fibrillar vacuoles in the pre-equatorial region (3 days), an increased number of enlarged and coalesced vacuoles (6 days), and progressive tissue swellings with cellular disruption and signs of epithelial multilayering (14 days). The anterior epithelium showed increased cell height and swelling after 3 days of the galactose diet. HPLC analysis of lens tissue indicated progressive accumulation of galactitol, 18 mM after 3 days, which plateaued to about 30 mM between 6 and 14 days. The level of myo-inositol dropped from a control value of 2.8 +/- 0.7 mM to 1.5 +/- 0.7 mM after 3 days, and was nearly undetectable after 14 days of the galactose diet. CONCLUSIONS: The current study suggests that the guinea pig model may serve as a valuable new tool to study sugar-induced cataract formation and to characterize the early morphologic and biochemical events in cataractogenesis.

Animals↗
PubMed1993

A simple technique to determine glutathione (GSH) levels and synthesis in ocular tissues as GSH-bimane adduct: application to normal and galactosemic guinea-pigs.

A fluorimetric technique previously described for other tissues has been applied to determine levels of glutathione and its synthetic rates in ocular tissues of Hartley guinea-pigs. Monochlorobimane forms a stable, fluorescent adduct with glutathione in a reaction catalyzed by glutathione-S-transferase. The fluorescent signal recorded over time is directly proportional to the synthetic rate of glutathione. Lens, cornea and retina were homogenized and cytosolic fractions dialyzed overnight to deplete endogeneous glutathione. Glutathione synthetic rates were determined from a mixture of glutathione precursors and co-factors, viz. cysteine+dithiothreitol, glutamate+glycine, ATP and Mg++ in the presence of monochlorobimane. The mixture was supplemented with glutathione-S-transferase to catalyze the formation of the fluorescent adduct. Glutathione synthetic rates were determined in the absence and presence of buthionine sulfoximine, an inhibitor of gamma-glutamyl cysteine synthetase. The difference in fluorescence change over time in the presence and absence of buthionine sulfoximine was used to estimate glutathione synthesis. Basal levels of glutathione in pre-dialyzed cytosolic fractions of the lens, cornea, and retina were 21.8 +/- 2.2, 36.5 +/- 4.1 and 38.6 +/- 2.8 nmol mg-1 protein, respectively. The maximal glutathione synthetic rates in these tissues were 0.52 +/- 0.04, 2.25 +/- 0.67 and 3.35 +/- 0.65 nmol min-1 mg-1 protein, respectively. When gamma-glutamyl cysteine is used as a precursor instead of cysteine, the glutathione synthetase activities from lenses and retinas were 0.19 +/- 0.08 and 1.54 +/- 0.76 nmol-1 min mg-1 protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Isolation, characterization, and immunoprecipitation studies of immune complexes from membranes of beta-thalassemic erythrocytes.

beta-Thalassemia, a hemoglobinopathy that results in the precipitation of denatured alpha-globin chains on the membrane, is characterized by erythrocytes with significantly reduced lifespans. We have demonstrated previously that hemoglobin denaturation on the membrane can promote clustering of integral membrane proteins, and that this clustering in turn leads to autologous antibody binding, complement fixation, and rapid removal of the cell by macrophages. To evaluate whether this pathway also occurs in beta-thalassemic cells, we have isolated and characterized the immune complexes from the membranes of these cells. We observe that autologous IgG-containing complexes obtained by either immunoprecipitation or simple centrifugation of nondenaturing detergent extracts of beta-thalassemic cell membranes contain globin, band 3, IgG, and complement as major components. Absorption spectra of these complexes demonstrate that the globin is, indeed, mainly in the form of hemichromes. Immunoblotting studies further show that much of the band 3 protein in the aggregates is covalently cross-linked to a dimeric or tetrameric form, consistent with the preference of the autologous IgG for clustered band 3. Although the insoluble aggregates constitute only approximately 1.6% of the total membrane protein, they still contain 27% of the total IgG and 35% of the total complement C3 on the thalassemic cell surface. Because cell surface IgG and complement component C3 are thought to trigger removal of erythrocytes from circulation, the hemichrome-induced clustering of band 3 may contribute to the beta-thalassemic cell's shortened lifespan.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1992

Postoperative adjuvant chemotherapy for operable esophageal cancer: a pilot clinical study.

Thirty-eight patients with node positive squamous cell carcinoma of the esophagus were entered into a pilot clinical study using postoperative adjuvant chemotherapy (cisplatinum 100 mg/m2 and methotrexate 150 mg/m2 x 4 cycles) with an intent of improving cure rates and overall survival. Patient compliance was excellent and toxicity minimal. At 24 months of follow-up 22 patients (58%) were disease free, while 14 patients (37%) have relapsed and 2 were lost to follow-up. A highly significant correlation was noted between the number of nodes involved, the grade of the tumour, and the response to chemotherapy. Patients with poorly differentiated tumours and those with more than 4 nodes involved were more likely to develop recurrent disease (P less than 0.01 and P less than 0.005). We conclude that postoperative chemotherapy following resection for carcinoma of the esophagus is well tolerated with minimal side effects. It may also have an impact on improving disease free and overall survival.

Adult↗
PubMed1992

Anorexic contribution to increased linoleate mobilization and oxidation in lymphoma-bearing mice.

To test for a regulatory defect in adipose triacylglycerol (essential) fatty acid mobilization in lymphoma-bearing mice, free [1-14C]linoleic acid/mouse serum albumin was injected iv into lymphoma-bearing and control mice, adapted to a reversed light cycle, and studied in three dietary states in the dark period. Mean daily food intake decreased in mice with small and large tumor burdens. Plasma free fatty acid (FFA) oxidation rates, which approximate FFA mobilization rates, were estimated by multicompartmental analysis (CONSAM). Oxidation of linoleate to CO2 was reduced significantly (85%) in ad libitum fed as compared to briefly fasted control mice but not in fed vs. fasted mice with large or small tumor burdens. However, plasma FFA oxidation rates to CO2 did not differ in briefly fasted tumor-bearing and pair-fed control mice. When re-fed a 250-mg test meal, briefly fasted mice with small tumors suppressed plasma free linoleic acid oxidation, as did controls. During simulated night, mildly anorexic, tumor-bearing mice with small tumor burdens mobilized essential fatty acids much faster than controls. This could explain body fat loss. The abnormally rapid rates of FFA (free linoleic acid) mobilization at night probably result from anorexia rather than from inability of food to suppress fat mobilization.

Animals↗
PubMed1992

An in situ perfused guinea-pig eye model for blood-ocular transport studies: application to amino acids.

A technique for in situ vascular eye perfusion (VEP) in the guinea-pig has been developed for measurements of the blood-ocular transport kinetics of substrates under controlled conditions of arterial inflow. The blood-aqueous and blood-vitreous barriers remained intact to the vascular space marker [3H]dextran (MW 70 kDa) with the perfusion pressure maintained between 80 and 100 mmHg. Several 3H-, 14C- or 35S-labeled amino acids, and 3H- or 14C-labeled sucrose (extracellular space marker) were used to validate the VEP model for transport kinetic studies. Multiple time-point graphic analysis was used to estimate the compartmental unidirectional blood-ocular transport constants, K(in), within the 20 min period of the VEP experiment. Blood-to-aqueous humor K(in) values for [3H]serine, [14C]N-methyl-alpha-aminoisobutyric acid (MeAIB) and [3H] or ]14C]sucrose were 3.57 +/- 0.38, 1.21 +/- 0.13 and 1.13 +/- 0.17 microliters min-1 g-1, respectively. The respective blood-to-lens K(in) values for labeled serine, MeAIB and sucrose were 1.71 +/- 0.19, 0.09 +/- 0.03 and 0.03 +/- 0.002 microliters min-1 g-1. The uptake of newly secreted amino acids from the aqueous humor in the lens followed the order: [35S]methionine greater than [3H]serine greater than or equal to [35S]cysteine greater than or equal to [3H]alanine greater than [14C]cycloleucine greater than or equal to [14C]MeAIB greater than or equal to [3H] or [14C]sucrose. The data indicate lack of a rapid blood-to-lens uptake of two model amino acids defining the A and L amino acid carriers.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗