Distribution and characterization of enzymes causing starch degradation in rice (Oryza sativa cv. koshihikari)

The thermal dependency and stability of enzymes producing reducing sugar (RS) were examined in bran, the exterior 13% part (outer endosperm), and the remaining inner endosperm of rice grains. RS-producing enzymes in the inner endosperm showed a higher optimum temperature than those in other parts of the rice grain. Diethylaminoethyl-Sephacel chromatography of crude extracts revealed two peaks of RS-producing activity with different optimum temperatures (60 and 37 degrees C) in all three parts. alpha-Glucosidase (EC 3.2.1.20) and alpha-amylase (EC 3.2.1.1) isoform G were thought to be major components of the RS-producing activities with high and low optimum temperatures, respectively. The peak with a high optimum temperature was a more abundant component in the inner endosperm, compared with other parts of the rice grain. Thus, different parts of rice were found to have distinct enzyme sets having different thermal dependency and to be involved in starch degradation to various sugars.

Therapist competence ratings in relation to clinical outcome in cognitive therapy of depression

This study reports on the relationship of therapist competence to the outcome of cognitive-behavioral treatment in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. Outpatients suffering from major depressive disorder were treated by cognitive-behavioral therapists at each of 3 U.S. sites using a format of 20 sessions in 16 weeks. Findings provide some support for the relationship of therapist competence (as measured by the Cognitive Therapy Scale) to reduction of depressive symptomatology when controlling for therapist adherence and facilitative conditions. The results are, however, not as strong or consistent as expected. The component of competence that was most highly related to outcome is a factor that reflects the therapist's ability to structure the treatment.

Lifestyle factors affecting bone ultrasonometry of the calcaneus in Japanese women

Ultrasonometry is increasingly used to assess bone characteristics. A group of 1412 women with a mean age of 57 years attended a screening examination in a Japanese city. Seventy-four percent of participants were postmenopausal. Broadband ultrasound attenuation (BUA), speed of sound (SOS), and Stiffness index (SI) of the calcaneus were measured; subjects also completed a questionnaire examining lifestyle factors; anthropometric data were recorded. Analysis showed that the strongest predictors of decreased BUA, SOS, and SI were increased age and menopausal status. Higher body mass index and current participation in exercise or sports were significant predictors of increased BUA, SOS, and SI in a multivariate model. Higher calcium intake predicted increased BUA (P = 0.004) and missing meals predicted a lower SOS (P = 0.019). This study suggests that dietary factors as well as physical activity influence bone characteristics assessed by QUS. QUS may be a suitable technique to assess the effect of lifestyle changes on bone.

Characterization of isoforms of hexose kinases in rice embryo

Hexose kinases in rice embryos have been characterized. Six isoforms were detected: i.e. three glucokinases (GK1-3), two hexokinases (HK1 and HK2) and one fructokinase (FK1). Out of these, GK3, HK1 and HK2 were inhibited by mannoheptulose and glucosamine, known inhibitors of hexokinase activity. These inhibitors are also known to be modulators of sugar sensing processes. The results suggest that GK3, HK1 and HK2 may play a role in sensing the cellular sugar status in the rice embryo.

Electron microscopic and immunohistochemical studies of gastrointestinal stromal tumors

Sixteen gastrointestinal stromal tumors (GISTs) were studied by immunohistochemical analysis and an ultrastructural procedure. The tumor locations were as follows: esophagus (2), stomach (7), small intestine (3), and large intestine (4). Four of the lesions were classified as malignant, 2 as borderline, and 10 as benign. On the basis of the immunohistochemical analysis, the tumors were classified as follows: 1 as myogenic type, 2 as Schwann cell type, 8 as Cajal cell type (including 2 gastrointestinal autonomic nerve tumors, GANTs), and 5 as mixed-cell type. In each subtype the phenotype was compared to the ultrastructural findings. Myogenic and Schwann cell type revealed ultrastructurally smooth muscle differentiation and schwannian tumor. All 8 tumors of the Cajal cell type revealed interdigitating cytoplasmic processes with occasional clusters of filopodia. Two tumors were subdivided as GANT. Five tumors of mixed-cell type were composed of a mixture of cells with variable myogenic features or variable neural differentiation. We confirmed in this study that immunohistochemical analysis reflected electron microscopic findings.

Therapist competence ratings in relation to clinical outcome in cognitive therapy of depression

This study reports on the relationship of therapist competence to the outcome of cognitive-behavioral treatment in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. Outpatients suffering from major depressive disorder were treated by cognitive-behavioral therapists at each of 3 U.S. sites using a format of 20 sessions in 16 weeks. Findings provide some support for the relationship of therapist competence (as measured by the Cognitive Therapy Scale) to reduction of depressive symptomatology when controlling for therapist adherence and facilitative conditions. The results are, however, not as strong or consistent as expected. The component of competence that was most highly related to outcome is a factor that reflects the therapist's ability to structure the treatment.

Utility of postcolumn addition of 2-(2-methoxyethoxy)ethanol, a signal-enhancing modifier, for metabolite screening with liquid chromatography and negative ion electrospray ionization mass spectrometry

A strategy for highly sensitive metabolite screening by liquid chromatography-electrospray ionization (ESI) mass spectrometry with the negative-ion mode that involves the use of a reversed-phase column in gradient-elution mode and postcolumn addition of 2-(2-methoxyethoxy)ethanol (2-MEE), a novel signal-enhancing modifier, has been described. When a mobile phase of 50 mM ammonium acetate/acetic acid buffer (pH 4.4) at a flow rate of 100 microL/min was employed, poor ESI response of ibuprofen as a model drug, probably due to both the high surface tension of the mobile phase and the ion-suppression effect of acetate anion in the mobile phase, was observed. On the other hand, the postcolumn addition of 2-MEE (50 microL/min) into the mobile phase counteracted the ion suppression as well as the surface tension problem, resulting in approximately 100-fold signal enhancement of the analyte. The metabolite screening of ibuprofen in human urine was subsequently carried out comparing the results with and without postcolumn addition of 2-MEE. The results indicated that the postcolumn addition of 2-MEE dramatically improved the ESI responses of all urinary metabolites detected without affecting the chromatographic separation.

[Delineation of calf arteries using 2D-TOF MR angiography without contrast medium: efficacy of cardiac gating and leg warming]

We evaluated the image quality of non-contrast enhanced 2D-TOF MRA of the calf and the efficacy of cardiac gating and leg warming. In 10 healthy volunteers, MRA was carried out under the following four conditions: (a) usual MRA, (b) MRA with cardiac gating, (c) MRA after leg warming and (d) MRA with cardiac gating after leg warming. Although MRA with cardiac gating was not suitable, MRA after leg warming was well suited to the imaging of calf arteries. The image quality of MRA with cardiac gating after leg warming was the same as that of MRA after leg warming.

Gnarley1 is a dominant mutation in the knox4 homeobox gene affecting cell shape and identity

Maize leaves have a stereotypical pattern of cell types organized into discrete domains. These domains are altered by mutations in knotted1 (kn1) and knox (for kn1-like homeobox) genes. Gnarley (Gn1) is a dominant maize mutant that exhibits many of the phenotypic characteristics of the kn1 family of mutants. Gn1 is unique because it changes parameters of cell growth in the basal-most region of the leaf, the sheath, resulting in dramatically altered sheath morphology. The strongly expressive allele Gn1-R also gives rise to a floral phenotype in which ectopic carpels form. Introgression studies showed that the severity of the Gn1-conferred phenotype is strongly influenced by genetic background. Gn1 maps to knox4, and knox4 is ectopically expressed in plants with the Gn1-conferred phenotype. Immunolocalization experiments showed that the KNOX protein accumulates at the base of Gn1 leaves in a pattern that is spatially and temporally correlated with appearance of the mutant phenotype. We further demonstrate that Gn1 is knox4 by correlating loss of the mutant phenotype with insertion of a Mutator transposon into knox4.

Gnarley1 is a dominant mutation in the knox4 homeobox gene affecting cell shape and identity

Maize leaves have a stereotypical pattern of cell types organized into discrete domains. These domains are altered by mutations in knotted1 (kn1) and knox (for kn1-like homeobox) genes. Gnarley (Gn1) is a dominant maize mutant that exhibits many of the phenotypic characteristics of the kn1 family of mutants. Gn1 is unique because it changes parameters of cell growth in the basal-most region of the leaf, the sheath, resulting in dramatically altered sheath morphology. The strongly expressive allele Gn1-R also gives rise to a floral phenotype in which ectopic carpels form. Introgression studies showed that the severity of the Gn1-conferred phenotype is strongly influenced by genetic background. Gn1 maps to knox4, and knox4 is ectopically expressed in plants with the Gn1-conferred phenotype. Immunolocalization experiments showed that the KNOX protein accumulates at the base of Gn1 leaves in a pattern that is spatially and temporally correlated with appearance of the mutant phenotype. We further demonstrate that Gn1 is knox4 by correlating loss of the mutant phenotype with insertion of a Mutator transposon into knox4.

Ultrasensitive determination of NE-100, a novel sigma ligand, in human plasma by liquid chromatography and electrospray ionization tandem mass spectrometry combined with a column-switching technique

For the highly sensitive and selective determination of NE-100, a novel sigma ligand, at levels of low picogram per milliliter of human plasma, a method with excellent reliability employing liquid chromatography (LC)-electrospray ionization (ESI) tandem mass spectrometry (MS-MS) combined with a column-switching technique has been developed. The method involves the use of a stable isotope labeled compound as the internal standard (I.S.), liquid-solid extraction of a plasma specimen with a C8 cartridge, automated on-line clean-up on a short trapping column, subsequent separation on a micro-bore C18 column and detection with ESI-MS-MS using m/z 356 ([M+H]+) as a precursor ion and m/z 105 as a product ion in a selected reaction monitoring mode. The detection and the quantification limits of NE-100 in plasma were 0.5 pg/ml with a signal-to-noise ratio (S/N) of 3 and 2.3 pg/ml, respectively, with an S/N of 21. The good linearity of the calibration graph was obtained in the range of 2.3 to approximately 907.0 pg/ml with excellent reliability. The developed method was applied to the determination of NE-100 in plasma obtained from the clinical trail.

Utility of technetium-99m-labeled-galactosyl human serum albumin scintigraphy for estimating the hepatic functional reserve

Technetium-99m-diethylenetriaminepentaacetic acid-galactosyl-human serum albumin (Tc-GSA) is a receptor binding agent, specific for asialoglycoprotein receptor, that resides exclusively on the plasma membrane of mammalian hepatocytes. The usefulness of Tc-GSA for estimating the hepatic functional reserve was retrospectively evaluated in patients undergoing a hepatic resection. Tc-GSA scintigraphy was performed in 35 patients before hepatectomy, and the hepatic uptake ratio (LHL15) was calculated. The LHL15 was then compared with the findings of conventional liver function tests, the indocyanine green retention rate in 15 minutes (ICG R15), and histologic activity index (HAI) score. Significant correlations were observed between the LHL15 and values of ICG R15, prothrombin time activity, serum levels of total bilirubin, hyaluronic acid, and values of HAI score. Ratios of LHL15 to preoperative liver volume (LHL-V) correlated well with the regenerative rates of the residual liver after major hepatectomy. In addition, patients with more than 0.76 of LHL-V value had no complications in postoperative course, whereas those with less than 0.73 had several complications due to hepatic dysfunction. Tc-GSA scintigraphy thus appears to be a useful diagnostic tool for evaluating functioning mass of the liver and the values of LHL-V seems to be able to demonstrate regenerative activity in the residual liver after hepatectomy.

Leaf senescence is delayed in tobacco plants expressing the maize homeobox gene knotted1 under the control of a senescence-activated promoter

Leaf senescence is an active process involving remobilization of nutrients from senescing leaves to other parts of the plant. Whereas senescence is accompanied by a decline in leaf cytokinin content, supplemental cytokinin delays senescence. Plants that overexpress isopentenyl transferase (ipt), a cytokinin-producing gene, or knotted1 (kn1), a homeobox gene, have many phenotypes in common. Many of these phenotypes are characteristic of altered cytokinin physiology. The effect of kn1 on leaf senescence was tested by driving its expression using the promoter of the senescence-associated gene SAG12. SAG:kn1 tobacco plants showed a marked delay in leaf senescence but otherwise developed normally. The delay in senescence was revealed by an increase in chlorophyll content in SAG:kn1 leaves relative to leaves of the control plants and by a decrease in the number of dead leaves. Senescence was also delayed in detached leaves of SAG:kn1 plants. Delayed senescence was accompanied by increased leaf cytokinin content in older leaves expressing kn1. These experiments extend the current understanding of kn1 function and suggest that in addition to mediating meristem maintenance, kn1 is capable of regulating the onset of senescence in leaves.

Retention mechanism of imidazoles in connective tissue. IV. Identification of a nucleophilic imidazolone metabolite in rats

Formation of a nucleophilic 4(5H)(or 5(4H))-imidazolone structure has been postulated from in vitro studies to be one of the causative elements involved in the retention of drugs with imidazole moiety in connective tissue. To confirm this, we searched for the imidazolone-related metabolite in rats after intravenous dosing of 2-methylimidazole (2MI; 14C-labeled and unlabeled form, 3 and 300 micromol/kg body weight) as a model compound. The excreted urine, the major route of elimination of the compound, was collected and analyzed using the HPLC/MS system with a counterion effect for metabolite separation. 2-Methyl-4(5H)(or 5(4H))-imidazolone (2MIone) was identified as a urinary metabolite by chromatographic and mass-spectral inspection with the corresponding authentic standard. Pretreatment of rats with either SKF-525A (50 mg/kg, i.p.) or cimetidine (200 mg/kg, i.p.) significantly increased the excreted amount of 2MIone in urine and the irreversible binding of 2MI equivalents in the aortic tissue, whereas both factors were reduced by pretreatment with triethylenetetramine dihydrochloride (150 mg/kg/d for 5 d, s.c.). These results support the aforementioned deduction, and also raise the possibility that a cytochrome P450-independent, copper-related metabolic reaction might be involved in the imidazolone formation in vivo.

Characterization of the I-E(d)--restricted peptide recognized by an anti-idiotypic CD4+ T cell line

We have previously reported a CD3+ CD4+ CD8- T cell line, J-2R which specifically recognized J558 individual idiotope (IdI) of anti-alpha (1-->3) dextran antibodies in an I-E(d) restricted manner. The J-2R proliferated in response to J558 IdI-derived peptides; however, the ability of the peptides to evoke the proliferation of J-2R was different. In the present study, we investigated the interaction between J558 IdI-derived peptides and I-E(d) molecules in competition experiments using a M104E IdI-derived peptide, M88-105. The M88-105 inhibited the proliferation of J-2R induced by J558 IdI-derived peptides. Furthermore, the proliferation induced by the peptides J92-109 and J96-105 was inhibited by the M88-105 at much lower inhibitor/antigenic peptide ratios, compared to the proliferation induced by the J88-105. Thus, shift of the framework to C-terminus and deletion of N-terminus amino acid residues from the 18-mer peptide J88-105 made the peptides more susceptible to the inhibition by the M88-105. Sequencing of the J-2R T cell receptor (TcR) revealed that J-2R used TcR, V alpha 1, J alpha 44; V beta 15, D beta 1, J beta 1.5. These results suggest that the peptides, J88-105, J92-109 and J96-105, directly bind to I-E(d) molecules, and that the capacity of J558 IdI-derived peptides to activate J-2R depends on the affinity to the I-E(d) molecules.

Retention mechanism of imidazoles in connective tissue. III. Aldehyde adduct formation of a 4(5H)(or5(4H))-imidazolone product in vitro

2-Methylimidazole (2MI), as well as imidazole, has been thought to undergo cupro-ascorbate (Cu-VC)-catalyzed oxidative transformation in vitro to become a reactive species capable of combining with aldehydes intrinsic to connective-tissue proteins. We attempted to seize the essence of the above reaction through obtaining the structural information of an aldehyde-bonding species. As major products from 2MI in the in vitro Cu-VC system, 2-hydroxymethylimidazole (2(OH)MI) and 2-methyl-4(5H)(or 5(4H))-imidazolone (2MIone) were identified by mass-spectral and chromatographic comparison with the corresponding authentic standards synthesized. The in situ addition of acetaldehyde or propionaldehyde as a simple protein-aldehyde model to the system resulted in the deducible formation of an aldol condensate, 2-methyl-4(or 5)-ethylidene-4(5H)(or 5(4H))-imidazolone (2MEIone) or its possible analogue with a propylidene moiety, respectively. The authentic compound of 2MIone directly reacted with acetaldehyde and easily afforded the products assignable to the isomers of 2MEIone through the ethylidene moiety at physiological pH and temperature, whereas neither 2MI or 2(OH)MI reacted at all. These results suggest that a 4(5H)(or 5(4H))-imidazolone product, although simply a monooxygenated form, is sufficiently reactive to give aldol condensation-typed covalent adducts with aldehydes, even under physiological conditions, probably having an activated methylene moiety in the ring structure. Based on the present results, we discussed the mechanism of the retention of imidazole-containing drugs in connective tissue.

[Delineation of the white and gray matter of the normal human cervical spinal cord using diffusion-weighted echo planar imaging]

To delineate the white and gray matter of the normal human cervical spinal cord, diffusion-weighted echo planar imaging (DW-EPI) was performed in 11 healthy volunteers. Three axial (X-, Y- and Z-axis) anisotrophic diffusion-weighted images were obtained on a 1.5T superconducting clinical unit using a single-shot DW-EPI sequence. On X- and Y-axis DWIs the white and gray matter could be well differentiated: the former showed high intensity and the latter low intensity. Anterior columns were clearly visible, whereas posterior columns were not. On Z-axis DWI the white and gray matter could not be differentiated at all, because both showed low intensity. In conclusion, DW-EPI can clearly delineate the white and gray matter of the cervical spinal cord, and this technique will be useful to evaluate white matter disorders such as ischemic or demyelinating disease.

Detection of carcinoembryonic antigen mRNA in the mesenteric vein of patients with resectable colorectal cancer

The detection of tumor cells in the drainage venous blood of patients with colorectal cancer was made feasible by demonstrating carcinoembryonic antigen (CEA) mRNA in the mononuclear cell component of the blood, using a nested reverse transcription-polymerase chain reaction. CEA mRNA was detected in the drainage venous blood from 11 (42%) of 26 patients, and the rate of detection increased according to the grade of vessel invasion. CEA mRNA was detected in all patients with synchronous liver metastases, even though there was no significant correlation between the presence of CEA mRNA in the drainage venous blood and the clinicopathological findings. As the presence of CEA mRNA in the drainage venous blood is an indicator of the spread of tumor cells in patients with colorectal cancer, this assay can be used to assess the possible outcome of patients with colorectal cancer, providing one more tool for the physician-oncologist to use in designing appropriate treatments.

Monoclonal origin of an esophageal carcinosarcoma producing granulocyte-colony stimulating factor: a case report

BACKGROUND

Carcinosarcomas are comprised of carcinomatous and sarcomatous elements, and their histogenesis remains unclear. The authors examined the serum concentrations of hematopoietic growth factors and performed immunohistochemical studies on an esophageal carcinosarcoma from a patient with marked granulocytosis to determine its histopathogenesis and clonality.

METHODS

The authors examined the case of a 63-year-old man with a polypoid tumor of the esophagus associated with marked leukocytosis (131 x 10(9) per liter). Immunohistochemical staining of the esophageal tumor was performed using monoclonal antibodies against granulocyte-colony stimulating factor (G-CSF), keratin, epithelial membrane antigen (EMA), and vimentin.

RESULTS

The patient's leukocyte count was increased (124 x 10(9) per liter) on admission. Because mature granulocytes predominantly were increased despite the absence of apparent infection, the patient's serum G-CSF concentration was examined and found to be 286.0 pg/mL and to increase with time. After thoracic esophagectomy was performed, granulocyte count and serum G-CSF concentration rapidly normalized. G-CSF concentration was 50-fold higher in the tumor tissue extract than in the extract from normal esophageal tissue. Microscopic examination of the resected specimens revealed that the tumor was comprised of squamous cell carcinoma (SCC) and spindle-shaped sarcomatous elements, and transitional features were observed within these two components. Immunohistochemical examination disclosed cells that were positive for keratin and EMA in the carcinomatous element and vimentin positive cells in the sarcomatous element. However, both types of tumor cells were positive for G-CSF.

CONCLUSIONS

The presence of G-CSF in both SCC cells and spindle-shaped sarcomatous cells indicated that these two components originated from a single clone.

Monoclonal origin of an esophageal carcinosarcoma producing granulocyte-colony stimulating factor: a case report

BACKGROUND

Carcinosarcomas are comprised of carcinomatous and sarcomatous elements, and their histogenesis remains unclear. The authors examined the serum concentrations of hematopoietic growth factors and performed immunohistochemical studies on an esophageal carcinosarcoma from a patient with marked granulocytosis to determine its histopathogenesis and clonality.

METHODS

The authors examined the case of a 63-year-old man with a polypoid tumor of the esophagus associated with marked leukocytosis (131 x 10(9) per liter). Immunohistochemical staining of the esophageal tumor was performed using monoclonal antibodies against granulocyte-colony stimulating factor (G-CSF), keratin, epithelial membrane antigen (EMA), and vimentin.

RESULTS

The patient's leukocyte count was increased (124 x 10(9) per liter) on admission. Because mature granulocytes predominantly were increased despite the absence of apparent infection, the patient's serum G-CSF concentration was examined and found to be 286.0 pg/mL and to increase with time. After thoracic esophagectomy was performed, granulocyte count and serum G-CSF concentration rapidly normalized. G-CSF concentration was 50-fold higher in the tumor tissue extract than in the extract from normal esophageal tissue. Microscopic examination of the resected specimens revealed that the tumor was comprised of squamous cell carcinoma (SCC) and spindle-shaped sarcomatous elements, and transitional features were observed within these two components. Immunohistochemical examination disclosed cells that were positive for keratin and EMA in the carcinomatous element and vimentin positive cells in the sarcomatous element. However, both types of tumor cells were positive for G-CSF.

CONCLUSIONS

The presence of G-CSF in both SCC cells and spindle-shaped sarcomatous cells indicated that these two components originated from a single clone.

Monoclonal origin of an esophageal carcinosarcoma producing granulocyte-colony stimulating factor: a case report

BACKGROUND

Carcinosarcomas are comprised of carcinomatous and sarcomatous elements, and their histogenesis remains unclear. The authors examined the serum concentrations of hematopoietic growth factors and performed immunohistochemical studies on an esophageal carcinosarcoma from a patient with marked granulocytosis to determine its histopathogenesis and clonality.

METHODS

The authors examined the case of a 63-year-old man with a polypoid tumor of the esophagus associated with marked leukocytosis (131 x 10(9) per liter). Immunohistochemical staining of the esophageal tumor was performed using monoclonal antibodies against granulocyte-colony stimulating factor (G-CSF), keratin, epithelial membrane antigen (EMA), and vimentin.

RESULTS

The patient's leukocyte count was increased (124 x 10(9) per liter) on admission. Because mature granulocytes predominantly were increased despite the absence of apparent infection, the patient's serum G-CSF concentration was examined and found to be 286.0 pg/mL and to increase with time. After thoracic esophagectomy was performed, granulocyte count and serum G-CSF concentration rapidly normalized. G-CSF concentration was 50-fold higher in the tumor tissue extract than in the extract from normal esophageal tissue. Microscopic examination of the resected specimens revealed that the tumor was comprised of squamous cell carcinoma (SCC) and spindle-shaped sarcomatous elements, and transitional features were observed within these two components. Immunohistochemical examination disclosed cells that were positive for keratin and EMA in the carcinomatous element and vimentin positive cells in the sarcomatous element. However, both types of tumor cells were positive for G-CSF.

CONCLUSIONS

The presence of G-CSF in both SCC cells and spindle-shaped sarcomatous cells indicated that these two components originated from a single clone.

Promoter elements required for sugar-repression of the RAmy3D gene for alpha-amylase in rice

There is increasing evidence showing that cereal alpha-amylase gene expression is controlled not only by the classical hormonal regulation, but also by feed-back sugar repression. We demonstrated by in situ hybridization that the sugar repression of rice alpha-amylase gene RAmy3D takes place in scutellar epithelium cells of callus-forming rice embryos. We also used a transient expression system to study the cis-acting elements involved in the sugar repression of the RAmy3D promoter activity. Site-directed mutagenesis of the 50-bp nucleotide sequence from -172 to -123 revealed that consensus sequences of G motif (TACGTA) and TATCCA T/C motif (GATA motif as its antisense sequence) are responsible for sugar repression. The promoter sequences required for sugar repression are reported and discussed.

Sugar sensing and alpha-amylase gene repression in rice embryos

We used a transient expression system to study the mechanism by which carbohydrates repress a rice (Oryza sativa L.) alpha-amylase (EC 3.2.1.1) gene. Exogenously fed metabolizable carbohydrates are able to elicit repression of the alpha-amylase gene RAmy3D in the rice embryo, and our results indicate that repression is also triggered efficiently by endogenous carbohydrates. Glucose analogs that are taken up by plant cells but not phosphorylated by hexokinase are unable to repress the alpha-amylase gene studied, while 2-deoxyglucose, which is phosphorylable but not further metabolized, down-regulates RAmy3D promoter activity, indicating a role for hexokinase in the sugar-sensing mechanism triggering repression of the RAmy3D gene. We tested two different hexokinase inhibitors, mannoheptulose and glucosamine, but only the latter was able to relieve RAmy3D promoter activity from repression by endogenous carbohydrates. This correlates with the higher ability of glucosamine to inhibit the activity of rice hexokinases in vitro. The glucosamine-mediated relief of RAmy3D promoter activity from repression by endogenous carbohydrates does not correlate with a reduced rate of carbohydrate utilization.