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Biomedical subjects

J Okuda

Publications and source records attributed to J Okuda.

At least 19 recordsLinked to original sources

Stimulatory effect of fatty acid treatment on glucose utilization in human erythrocytes.

We previously reported that treatment of human erythrocytes with bee venom phospholipase A2 increased the rate of lactate production from glucose. This increase was suggested to be mediated through liberation of free fatty acids from membrane phospholipids. So, in the present study we examined the mechanism of stimulation of glycolysis by fatty acids. Treatment of intact erythrocytes with most of the 15 fatty acids tested resulted in stimulation of lactate production from glucose. Among the fatty acids tested, myristoleic acid showed the highest stimulatory activity. The ratio of moles of lactate produced to those of glucose utilized was about 1.9 in both myristoleic acid-treated and untreated cells. Treatment of erythrocytes with myristoleic acid did not affect the amount of 2,3-bisphosphoglycerate. Lactate production from D-glyceraldehyde, which is thought to be phosphorylated to D-glyceraldehyde 3-phosphate and then metabolized in the glycolytic pathway, was not at all affected by treatment of cells with myristoleic acid. The cross-over plot of glycolytic intermediates suggested that the enhancement of glycolysis was induced by activation of the 6-phosphofructokinase (PFK) step. Fatty acids incorporated into erythrocytes were found to be present predominantly in the cytoplasm rather than in the plasma membrane. The PFK activity, but not the hexokinase activity, in hemolysates was clearly increased by a set of fatty acids, and myristoleic acid was again the most potent. However, partially purified human erythrocyte PFK was not activated by the acid. We conclude that fatty acids stimulate glycolysis through activation of PFK in cooperation with some other component(s) in erythrocytes.

Enzyme Activation

Examination of diarrheagenicity of cytolethal distending toxin: suckling mouse response to the products of the cdtABC genes of Shigella dysenteriae.

Some strains of Escherichia coli, Shigella spp., and Campylobacter spp. that have been implicated in diarrheal disease produce cytolethal distending toxin (CDT). CDT induces unique morphological changes in Chinese hamster ovary cells, but its association with diarrheal disease is unclear. We studied the diarrheagenicity of CDT using the cdt genes that we originally cloned from Shigella dysenteriae. The cdt genes were subcloned into a high-copy-number plasmid in E. coli JM109 to achieve high-level CDT production into the culture supernatant. An isogenic CDT- derivative was constructed by deletion of the 0.9-kb sequence internal to the cdt genes. A suckling mouse model was established, in which the intragastrically administered culture supernatant of the CDT+ E. coli strain induced excretion of loose and/or watery feces more often than did that of the CDT- strain in 24 h. The partially purified CDT preparation induced profuse watery diarrhea by 12 h in this model. High-level intestinal fluid accumulation in 4 h appeared to be related to the watery diarrhea. The results indicate that CDT is diarrheagenic to suckling mice and suggest that diarrheagenicity is dependent on CDT level. The preparations containing wild-type CDT induced tissue damage (necrosis and reparative hyperplasia) in the descending colon, whereas the tissues of the small intestines remained apparently intact. Association between the colonic damage and diarrhea is unclear and needs further investigation.

Animals

Molecular analysis of stimulatory anti-thyrotropin receptor antibodies (TSAbs) involved in Graves' disease. Isolation and reconstruction of antibody genes, and production of monoclonal TSAbs.

Anti-thyrotropin (TSH) receptor autoantibodies (TRAbs) have been known to be involved in Graves' disease. To understand the molecular mechanism for pathogenesis of TSAbs in Graves' disease, we isolated and reconstituted the Ig genes of EBV-transformed B cell clones producing monoclonal thyroid stimulating Ab (TSAb) obtained from patients with Graves' disease. The V region genes of Ig heavy (H) and light (L) chains of two TSAb clones, IgG clone B6B7 and IgM clone 101-2, were isolated by the PCR. Nucleotide sequencing analysis revealed that germ-line VH and VK segments widely used for autoantibodies including the previously isolated TRAbs were utilized in the two clones. A significant number of somatic mutations were found in V regions of both clones, indicating the involvement of somatic mutations for the TSAb specificity. Reconstituted Ig H and L chain genes of the two clones were stably introduced into myeloma cells for IgG1 production. IgGs purified from cultured supernatants of both transfectants exhibited significant TSAb activities, while they did not inhibit TSH binding to the receptor. The successful expression of recombinant TSAbs in eukaryotic cells will provide opportunities to apply them to various pathophysiologic, diagnostic and therapeutic investigations in autoimmune thyroid diseases.

Antibodies, Monoclonal

Amelioration of insulin resistance in genetically obese rodents by M16209, a new antidiabetic agent.

Improvement of metabolic disorders by M16209 (1-(3-bromobenzofuran-2-ylsulfonyl)hydantoin), an antidiabetic agent, was studied in genetically obese Zucker fa/fa rats and C57BL/6J ob/ob mice. In fa/fa rats oral administration of M16209 (30 and 100 mg/kg/day) for 7 days dose dependently improved hyperinsulinemia without affecting body weight. Oral glucose loading (2 g glucose/kg body weight) after 10 days of administration to fa/fa rats revealed that M16209 significantly improved glucose tolerance both 30 and 60 min after glucose loading, but did not affect preload serum glucose levels. At one day after 13 days of administration of M16209, the serum levels of triglyceride, total cholesterol and free fatty acid were clearly lower in treated fa/fa rats than those in untreated rats. In C57BL/6J ob/ob mice, M16209 given for 28 days at doses of 30 and 100 mg/kg/day improved hyperinsulinemia, hyperglycemia and hypercholesterolemia without affecting body weight. In a hyperinsulinemic euglycemic clamp study in fa/fa rats, administration of M16209 for 7 days at a dose of 100 mg/kg/day significantly normalized the decreased metabolic clearance rate but did not show any effect on the augmented hepatic glucose output. These findings demonstrate that improvement of metabolic disorders in genetically obese rodents by M16209 is due to amelioration of insulin resistance in peripheral tissues.

Administration, Oral

Effects of M16209, a new antihyperglycemic agent, on insulin sensitivity in vivo: euglycemic clamp studies in rats.

The effects of M16209 (1-(3-bromobenzo[b]furan-2-ylsulfonyl)hydantoin) on the in vivo insulin sensitivity of rats were studied by euglycemic clamp methods after 1 week of administration (10 or 100 mg/kg/d). M16209 increased both the glucose infusion rate (GIR) and metabolic clearance rate (MCR) of 3-[3H]-glucose, but did not suppress hepatic glucose output. M16209 also increased the [3H]-2-deoxyglucose utilization rate, rate of incorporation of [14C]-glucose into glycogen, and glycolytic flux in the soleus and red gastrocnemius muscles, but not in the extensor digitorum lungus and white gastrocnemius muscles. M16209 affected neither the [3H]-2-deoxyglucose utilization rate nor the rate of incorporation of [14C]-glucose into lipids in epididymal adipose tissue. In the soleus muscle, M16209 decreased glucose-6-phosphate (G6P) and fructose-6-phosphate (F6P) content, but did not affect fructose-1,6-bisphosphate (F-1,6-BP) content. Moreover, M16209 increased glycogen synthase-I activity and fructose-2,6-bisphosphate (F-2,6-BP) content in the soleus muscle. These results suggest that M16209 increases insulin-stimulated glucose uptake in peripheral tissues, particularly oxidative muscles, through potentiation of insulin action on glycogen synthesis and glycolysis. Glycogen synthase and phosphofructokinase (PFK) appear to be major targets of the action of M16209.

Adult

Acceleration of glycolysis in erythrocytes by the antidiabetic agent M16209.

The effects of M16209 (1-(3-bromobenzofuran-2-ylsulfonyl)hydantoin), an antidiabetic agent and aldose reductase inhibitor, on glycolysis were studied in rat and human erythrocytes in vitro. M16209 increased lactate production from glucose when incubated with rat and human erythrocytes, and also increased glucose consumption in rat erythrocytes. The rates of production of lactate in rat erythrocytes treated with M16209 at 10, 25 and 50 microM were 113, 118 and 123%, respectively, of those in vehicle treated cells. Sorbinil (aldose reductase inhibitor), tolbutamide (sulfonylurea), and buformine (biguanide) did not increase lactate production in rat erythrocytes when tested at 50 microM. On the other hand, M16209 did not affect lactate production from D-glyceraldehyde in rat erythrocytes. At 100 microM the agent decreased both glucose-6-phosphate and fructose-6-phosphate in rat erythrocytes, and increased fructose-1,6-bisphosphate; at 10 microM it also increased 6-phosphofructokinase activity in rat hemolysates. These findings suggest that M16209 accelerates glycolysis in erythrocytes via activation of 6-phosphofructokinase.

Aldehyde Reductase

Laboratory tests necessary at the first examination of patients with suspected thyroid disorders.

In order to determine what and how many test items are necessary for the initial tests when examining patients with thyroid disorders, a questionnaire was sent to the council members of the Japan Thyroid Association. Thyroid disorders were divided into 4 categories; hyperthyroidism, hypothyroidism, diffuse goiter, and nodular goiter. The questionnaire was designed to assess: 1) tests routinely ordered at the initial examination; 2) minimum test battery necessary; 3) the 5 most important tests in order; and 4) selection of only 2 tests at most. The data on 112 completed questionnaires were collected and analyzed. When the choice was limited to only 2 tests, TSH and fT4 were commonly selected for hyperthyroidism hypothyroidism and diffuse goiter, but these 2 tests would be insufficient for the differentiation of disorders. In the case of nodular goiter, ultrasonogram and fine needle aspiration biopsy (FNA) were selected. The mean number of routinely ordered tests was 6.62 +/- 2.00 (S.D.) for hypothyroidism and 8.06 +/- 2.48 for nodular goiter, but many fewer tests were cited as absolutely necessary. In hyperthyroidism, 4.56 +/- 1.92 tests were required, in hypothyroidism 4.39 +/- 1.92, in diffuse goiter 4.93 +/- 1.75, and in nodular goiter 5.15 +/- 2.13. Most of the function-related tests, ultrasonogram and autoantibodies were commonly selected, while TBII and thyroid 123I or 99mTcO4 uptake in hyperthyroidism, and FNA, Tg and scintigram in nodular goiter were considered to be for specific purposes. Summarizing all these, the authors propose 5 or 6 tests to be necessary as the initial tests when examining patients with 4 individual thyroid disorders.

Autoantibodies

Antihyperglycemic effects of M16209, a novel aldose reductase inhibitor, in normal and diabetic rats.

The effect of a single oral administration of M16209 (1-(3-bromobenzo[b]furan-2-yl-sulfonyl)hydantoin), a novel aldose reductase inhibitor, on serum glucose was investigated. In normal rats, M16209 (100 mg/kg) had a weak hypoglycemic effect but markedly stimulated the disappearance of serum glucose in intravenous glucose tolerance tests. In diabetic rats, M16209 (100 mg/kg) significantly suppressed the hyperglycemia of streptozotocin-induced, mildly diabetic rats and stimulated serum glucose disappearance in neonatally streptozotocin-induced, non-insulin-dependent diabetes mellitus (NIDDM) rats in glucose tolerance tests. Additionally, M16209 augmented insulin secretion in glucose-loaded, normal and NIDDM rats and restored the reduced serum insulin in streptozotocin-induced, mildly diabetic rats. M16209, however, showed no hypoglycemic effect in severely diabetic rats. In contrast, gliclazide, a sulfonylurea, showed a much more potent hypoglycemic effect in normal rats than in mildly diabetic rats. These results suggest that M16209 suppresses hypoglycemia through augmentation of glucose-stimulated insulin secretion. The antihyperglycemic activity of M16209, combined with its potent aldose reductase inhibiting activity, is expected to be beneficial in the treatment of diabetic complications.

Aldehyde Reductase

Effects of M16209 on insulin secretion in isolated, perfused pancreases of normal and diabetic rats.

We investigated the stimulatory effect of M16209 (1-(3-bromobenzo[b]furan-2-yl-sulfonyl)hydantoin), a novel aldose reductase inhibitor, on insulin secretion using isolated, perfused pancreases of rats. In the pancreases from normal rats, M16209 (100 microM) greatly augmented glucose-stimulated insulin secretion, but showed no effect on unstimulated insulin secretion at 2.8 mM glucose. In contrast, gliclazide (10 microM), a sulfonylurea, strongly enhanced both glucose-stimulated and unstimulated insulin secretion. Sorbinil and epalrestat, potent aldose reductase inhibitors, had no stimulatory effect on insulin secretion. M16209 (100 microM) improved appreciably the decreased insulin response to 22.2 mM glucose and enhanced slightly unstimulated insulin secretion in the pancreases of rats with neonatally streptozotocin-induced, non-insulin-dependent diabetes mellitus (NIDDM). Gliclazide (10 microM), however, failed to affect the pancreases of NIDDM rats. Furthermore, M16209 showed no appreciable effect on ATP-sensitive K(+)-channels in pancreatic beta-cells. These results suggest that M16209, unlike sulfonylureas, selectively enhances glucose-stimulated insulin secretion in both normal and NIDDM rats through a direct action on the pancreas. The site of action remains unknown, but the inhibition of aldose reductase or the ATP-sensitive K+ channels is unlikely to be involved.

Aldehyde Reductase

Isolation of Epstein-Barr-virus-transformed lymphocytes producing IgG class monoclonal antibodies using a magnetic cell separator (MACS): preparation of thyroid-stimulating IgG antibodies from patients with Graves' disease.

In autoimmune diseases, IgG class autoantibodies are generally considered to be more pathognomonic than IgM class ones. Although Epstein-Barr virus (EBV)-transformation of lymphocytes is a useful method to obtain human monoclonal autoantibodies, it tends to result predominantly in IgM-producing cells. We depleted IgM+ cells before EBV-transformation with a Magnetic Cell Separator (MACS) in order to increase the chance of acquisition of cells producing IgG class anti-thyrotropin (TSH) receptor antibodies (TRAb). As a result, we obtained four independent B cell clones producing IgG class monoclonal thyroid-stimulating antibodies (TSAb) from three patients with Graves' disease. None of these clones showed any TSH binding inhibitor immunoglobulin (TBII) activity, suggesting independence of TSAb-producing lymphocytes from those producing TBII.

Antibodies, Monoclonal

Changes in subcellular and zonal distribution of glucokinase in rat liver during postnatal development.

Subcellular and zonal distribution of glucokinase in rat liver during postnatal development was examined immunohistochemically. Before day 11 after birth, only some hepatocytes were immunostained, and a positive immunostaining was found in the cytoplasm but not in the nucleus. No zonal distribution of glucokinase was observed in livers of such pups. From day 15, at which time a dietary change from milk to laboratory chow begins to take place, glucokinase immunoreactivity increased; this increase was associated with increases in glucokinase activity and in glucokinase protein, and also the immunostaining was observed mainly in the nuclei. At day 21, the glucokinase immunoreactivity was found almost exclusively in the perivenous zone. At day 30, an intense immunostaining was seen both in the perivenous zone and in the periportal zone, being slightly predominant in the former. The present results indicate that dramatic changes in the distribution of glucokinase in developing rat liver may be related to dietary change.

Aging

Tissue and subcellular distribution of glucokinase in rat liver and their changes during fasting-refeeding.

The distribution of glucokinase in rat liver under both normal feeding and fasting-refeeding conditions was investigated immunohistochemically. Under normal feeding conditions, glucokinase immunoreactivity was observed in both nuclei and cytoplasm of parenchymal cells. The nuclei were stained intensely and evenly, whereas the cytoplasm showed weak immunoreactivity of different degrees of staining intensity depending on the location of the cells. The cytoplasm of perivenous hepatocytes was stained more intensely, though not so much more, than that of periportal hepatocytes. The cytoplasm of hepatocytes surrounding the terminal hepatic venule (THV), of hepatocytes surrounding the portal triad, and of some other hepatocytes showed a stronger immunoreactivity than that of residual hepatocytes. The nuclear immunoreactivity in hepatocytes surrounding the portal triad and in some other hepatocytes was weak or absent, and positive immunoreactivity was detected at the plasma membrane of some of these cells. After 72 h of fasting, glucokinase immunoreactivity was markedly decreased in all hepatocytes. After the start of refeeding, the cytoplasmic immunoreactivity began to increase first in the parenchymal cells surrounding the THV and extended to those in the intermediate zone followed by those in the periportal zone. In contrast, the increase in nuclear immunoreactivity started in hepatocytes situated in the intermediate zone adjacent to the perivenous zone and then extended to those in the perivenous zone followed by those in the periportal zone. Hepatocytes surrounding either THV or portal triad showed a distinctive change in immunoreactivity during the refeeding period. After 10 h of refeeding, strong immunoreactivity was observed in both the cytoplasm and the nuclei of all hepatocytes, and appreciable glucokinase immunoreactivity was detected at the plasma membrane of some hepatocytes. These findings are discussed from the standpoint of a functional role of glucokinase in hepatic glucose metabolism.

Animals

Statistical analysis of functional region(s) of the TSH receptor.

In this study, we apply recently developed methods to evaluate the thyrotropin receptor (TSH-R). These methods are called deviation (DEV) model, deviation decrease (DD) and DEV/DD analyses, and are based on deviation of amino acid sequences. A 3-dimensional structure model of TSH-R was graphically constructed, and found to possess a large central cavity (donut-like structure). The N-terminus was found to be in the center of the whole extracellular structure and to form a part of the bottom of the cavity. High DEV values indicate deviated amino acid compositions in the protein and were seen in 7 regions, 6 of which were found to be in regions with hydrophilic and acrophilic character. On the basis of the analysis of intra-molecular cis-acting relationships, 7 pairs of regions were presumed to be closely related. Further, when 3 exoplasmic loop lesions were analyzed similarly, 3 other regions were shown to have a close relationship with the cell surface. DEV/DD values were applied to predict the interface of TSH-R with trans-acting molecules such as TSH-R antibody or TSH. The regions in association with trans-acting molecules were seen in 14 regions, 11 of which included the high DEV regions. Both of the TSH-R specific regions in the N- and C-terminal side, especially the latter, were found to be the major components.

Amino Acid Sequence

Distribution of the cytolethal distending toxin A gene (cdtA) among species of Shigella and Vibrio, and cloning and sequencing of the cdt gene from Shigella dysenteriae.

We investigated the distribution of the cytolethal distending toxin A gene (cdtA) among S. dysenteriae, Vibrio cholerae 01 and Vibrio parahaemolyticus by polymerase chain reaction (PCR) using primers constructed from the nucleotide sequences of Escherichia coli cdtA gene reported independently by Scott and Kaper (Infect Immun 1994; 62: 244-51) and by Pickett et al. (Infect Immun 1994; 62: 1046-51). The cdtA gene reported by Scott and Kaper was found to occur among eight of the 35 strains of S. dysenteriae but was not found among V. cholerae O1 and V. parahaemolyticus. The cdtA gene reported by Pickett et al. was not found among S. dysenteriae, V. cholerae O1 and V. parahaemolyticus. To further investigate the distribution of the cdtA gene among a large number of Shigella spp. (S. dysenteriae, S. flexneri, S. boydii and S. sonnei), and among Vibrio spp. (Vibrio cholerae O1, V. cholerae O139 and V. parahaemolyticus) by colony hybridization test, we constructed a cdtA gene specific DNA probe by amplifying the cdtA gene by PCR with primers designed from the nucleotide sequence of the cdtA gene reported by Scott and Kaper. The cdtA gene reported by Scott and Kaper was found to occur among eight of the 35 strains of S. dysenteriae and one of the 100 strains of S. sonnei, but was not found among other species of Shigella or among the Vibrio species examined. From one cdtA gene-positive S. dysenteriae strain that showed cytolethal distending toxin (CDT) activity on Chinese hamster ovary cells, we cloned and sequenced the entire cdt gene comprising cdtA, cdtB and cdtC genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence

Establishment and characterization of an antihuman thyrotropin (TSH) receptor-specific CD4+ T cell line from a patient with Graves' disease: evidence for multiple T cell epitopes on the TSH receptor including the transmembrane domain.

From the peripheral lymphocytes of a patient with Graves' disease, we established a T cell line using its reaction to a pool of 49 synthetic peptides corresponding to the entire human thyrotropin receptor (TSHR) sequence. This T cell line showed a specific response to the pool of peptides in a microproliferation assay (stimulation index: 4.8). Flow cytometry analysis revealed that the cell surface markers were CD4+ CD8-, T cell receptor (TcR) alpha beta+, and Tcr gamma delta-. To investigate T cell epitopes on TSHR, the T cell line reacted well against three groups: the N-terminal (amino acids 31-169) and C-terminal (338-420) regions of the extracellular domain and the N-terminal half (441-661) of the transmembrane domain of the receptor. This suggests a multiplicity of T cell epitopes on the TSHR, and was further supported by analysis of TcR gene expression in the cell line that showed the expression of 5 V alpha genes; V alpha-1, 2, 10, 20, and w25. In conclusion, the results of the present study indicated multiple T cell epitopes on the TSHR molecule including the transmembrane domain.

Adult

Estimation of bloodstain age by rapid determinations of oxyhemoglobin by use of oxygen electrode and total hemoglobin.

Bloodstain age could be estimated from the ratio of oxyhemoglobin/total hemoglobin (fractional oxyhemoglobin) in the bloodstain by this present method, if the temperature at which the bloodstain had been kept was known. The oxyhemoglobin was determined with an oxygen electrode immersed in water in which the oxygen had been depleted, and the total hemoglobin was determined by conventional colorimetry (cyanomethemoglobin method). Ages of prepared bloodstain samples (within 24 h after bleeding) were estimated by this present method, which requires only 20 microliters of bloodstain and only 5 min for the whole analysis.

Adult

A hyperthyroid patient with Graves' disease who was strongly resistant to methimazole: investigation on possible mechanisms of the resistance.

We treated a patient who was hyperthyroid due to Graves' disease and strongly resistant to methimazole (MMI): in spite of good compliance, she needed 150 mg of MMI daily to control her hyperthyroidism. To elucidate the reasons of resistance to MMI, her serum and intrathyroidal MMI concentrations were determined by high pressure liquid chromatography (HPLC). After taking a 30 mg dose of MMI, she had a similar serum MMI concentration-time curve to that of a normal subject: drug malabsorption and rapid drug metabolism were not evident when studied after surgical treatment. After her serum containing MMI was incubated with Protein G, the MMI concentration of the fraction not bound to Protein G did not change significantly from that of untreated serum: the possibility of anti-MMI IgG antibody production was considered unlikely. Furthermore, the intrathyroidal concentration of MMI in a surgically obtained tissue specimen was 3 micrograms/g wet tissue and appeared to be comparable with those of other Graves' tissues reported. Considering that the patient had been taking 150 mg per day of MMI by the time of thyroidectomy, her intrathyroidal MMI concentration was relatively low, suggesting possible impairment of intrathyroidal MMI accumulation. The possibilities of impaired intrathyroidal actions and the severity of hyperthyroidism, especially high T3 levels, also remained as possible causes. In conclusion, here was a severely hyperthyroid patient who was poorly responsive to conventional doses of MMI, and impairment of thyroid uptake of MMI or of pathways after uptake were considered as possible mechanisms.

Adult

Thyroid-stimulating antibodies in sera from patients with Graves' disease are heterogeneous in epitope recognition.

Two synthetic peptides, P354-14 (amino acid nos. 354 to 367) and P338-16 (nos. 338 to 353), corresponding to the partial amino acid sequences of the hTSH receptor structure were studied for their ability to bind specifically serum IgGs from patients with Graves' disease and to inhibit thyroid stimulating TSH receptor antibody (TSH-R SAb) activity. IgG binding was measured by an ELISA using sera from 102 Graves', 20 Hashimoto patients, and 9 normal subjects. Both peptides showed significantly increased IgG binding of Graves' sera compared with those of Hashimoto and normal sera. There was a significant correlation (r = 0.529) between the amount of IgG bound by the two peptides, but neither of these values correlated well with their TSH-R SAb activity nor thyrotropin-binding inhibitor TSH receptor antibody (TSH-R IAb) activity. TSH-R SAb inhibiting effects of these peptides were then analysed by measuring TSH-R SAb activity after incubation with the peptides. Among eight Graves' IgGs tested the TSH-R SAb activity of three was inhibited by both peptides, two were inhibited only by P354-14 and three were not affected by either. These TSH-R SAb inhibiting effects were dose-dependent and reproducible. To confirm these findings, a peptide-sepharose gel affinity absorption study was performed. Eleven Graves' IgGs were applied to both peptide gels and the TSH-R SAb activity of the unabsorbed fraction was measured. The TSH-R SAb activity of five IgGs was strongly absorbed only by P354-14 and five others were absorbed by both peptides to an almost similar extent.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption