Biomedical subjects

H G Kang

Publications and source records attributed to H G Kang.

29 records · Page 2Linked to original sources

PubMed1999

Cloning and molecular analyses of a gibberellin 20-oxidase gene expressed specifically in developing seeds of watermelon.

To understand the biosynthesis and functional role of gibberellins (GAs) in developing seeds, we isolated Cv20ox, a cDNA clone from watermelon (Citrullus lanatus) that shows significant amino acid homology with GA 20-oxidases. The complementary DNA clone was expressed in Escherichia coli as a fusion protein, which oxidized GA(12) at C-20 to the C(19) compound GA(9), a precursor of bioactive GAs. RNA-blot analysis showed that the Cv20ox gene was expressed specifically in developing seeds. The gene was strongly expressed in the integument tissues, and it was also expressed weakly in inner seed tissues. In parthenocarpic fruits induced by 1-(2-chloro-4-pyridyl)-3-phenylurea treatment, the expression pattern of Cv20ox did not change, indicating that the GA 20-oxidase gene is expressed primarily in the maternal cells of developing seeds. The promoter of Cv20ox was isolated and fused to the beta-glucuronidase (GUS) gene. In a transient expression system, beta-glucuronidase staining was detectable only in the integument tissues of developing watermelon seeds.

5' Untranslated Regions↗

PubMed1998

Identification of class B and class C floral organ identity genes from rice plants.

The functions of two rice MADS-box genes were studied by the loss-of-function approach. The first gene, OsMADS4, shows a significant homology to members in the PISTILLATA (PI) family, which is required to specify petal and stamen identity. The second gene, OsMADS3, is highly homologous to the members in the AGAMOUS (AG) family that is essential for the normal development of the internal two whorls, the stamen and carpel, of the flower. These two rice MADS box cDNA clones were connected to the maize ubiquitin promoter in an antisense orientation and the fusion molecules were introduced to rice plants by the Agrobacterium-mediated transformation method. Transgenic plants expressing antisense OsMADS4 displayed alterations of the second and third whorls. The second-whorl lodicules, which are equivalent to the petals of dicot plants in grasses, were altered into palea/lemma-like organs, and the third whorl stamens were changed to carpel-like organs. Loss-of-function analysis of OsMADS3 showed alterations in the third and fourth whorls. In the third whorl, the filaments of the transgenic plants were changed into thick and fleshy bodies, similar to lodicules. Rather than making a carpel, the fourth whorl produced several abnormal flowers. These phenotypes are similar to those of the agamous and plena mutants in Arabidopsis and Antirrhinum, respectively. These results suggest that OsMADS4 belongs to the class B gene family and OsMADS3 belongs to the class C gene family of floral organ identity determination.

Cloning, Molecular↗

PubMed1997

Characterization of two rice MADS box genes that control flowering time.

Plants contain a variety of the MADS box genes that encode regulatory proteins and play important roles in both the formation of flower meristem and the determination of floral organ identity. We have characterized two flower-specific cDNAs from rice, designated OsMADS7 and OsMADS8. The cDNAs displayed the structure of a typical plant MADS box gene, which consists of the MADS domain, I region, K domain, and C-terminal region. These genes were classified as members of the AGL2 gene family based on sequence homology. The OsMADS7 and 8 proteins were most homologous to OM1 and FBP2, respectively. The OsMADS7 and 8 transcripts were detectable primarily in carpels and also weakly in anthers. During flower development, the OsMADS genes started to express at the young flower stage and the expression continued to the late stage of flower development. The OsMADS7 and 8 genes were mapped on the long arms of the chromosome 8 and 9, respectively. To study the functions of the genes, the cDNA clones were expressed ectopically using the CaMV 35S promoter in a heterologous tobacco plant system. Transgenic plants expressing the OsMADS genes exhibited the phenotype of early flowering and dwarfism. The strength of the phenotypes was proportional to the levels of transgene expression and the phenotypes were co-inherited with the kanamycin resistant gene to the next generation. These results indicate that OsMADS7 and 8 are structurally related to the AGL2 family and are involved in controlling flowering time.

Amino Acid Sequence↗

PubMed1997

Isolation and characterization of a rice MADS box gene belonging to the AGL2 gene family.

The MADS box genes that encode regulatory proteins play important roles in both the formation of flower meristem and the determination of floral organ identity. We have characterized a flower-specific cDNA that belongs to the AGL2 gene family from rice, designated OsMADS5. The cDNA displays the structure of a typical plant MADS box gene, which consists of a MADS domain, K domain, a short I region between the MADS and K domain, and the C-terminal region downstream of the K domain. The gene was classified as a member of the AGL2 gene family from sequence homology analysis. The OsMADS5 protein is the most similar to OsMADS1 of rice (72% identity). In spatial and temporal RNA blot analyses, the OsMADS5 gene was expressed preferentially in anthers and weakly in carpels. During flower development, the gene was more highly expressed in the early floral stage than in the late. To study the functions of the gene, the cDNA clone was expressed ectopically using the CaMV 35S promoter in a heterologous tobacco plant system. Transgenic plants of OsMADS5 exhibited the phenotype of weak dwarfism and early flowering. These results indicate that OsMADS5 is structurally related to the AGL2 family and may be involved in controlling flowering time.

Amino Acid Sequence↗

PubMed1996

Cholecystokinin octapeptide reverses the kappa-opioid-receptor-mediated depression of calcium current in rat dorsal root ganglion neurons.

Although the cholecystokinin octapeptide (CCK-8) is reported to antagonize the kappa-opioid-receptor-mediated analgesic effect in spinal cord, its mechanism and sites of action remain obscure. In the present study, the whole-cell patch-clamp recording technique was employed to examine the effect of kappa-opioid agonist U50488H on voltage-gated calcium channels and the interaction between the CCK-8 and U50488H in acutely isolated rat dorsal root ganglion neurons. The results indicate that the calcium currents elicited in dorsal root ganglion neurons can be depressed by U50488H, an effect readily reversed by the kappa-opioid receptor antagonist Nor-BNI or by the antiopioid peptide CCK-8. The effect of the CCK-8 can be abolished by the CCK-B receptor antagonist, L365,260. While CCK-8 showed a potent opioid-reversal effect, it by itself exerted a slight inhibitory effect on calcium current. This novel observation in the dorsal root ganglion neurons indicates that CCK-8 can antagonize the kappa-opioid-receptor-mediated depressant effect on voltage-gated calcium current, and this antagonizing effect appears to be mediated via CCK-B receptor.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1996

Effects of 7-bromoethoxybenzene-tetrahydropalmatine on voltage-dependent currents in guinea pig ventricular myocytes.

AIM: To study the anti-arrhythmic mechanism of 7-bromoethoxybenzene-tetrahydropalmatine (EBP). METHODS: Whole-cell current and voltage clamp on isolated guinea pig ventricular cells. RESULTS: EBP 30 mumol.L-1 prolonged APD90 from 430 +/- 47 ms to 514 +/- 61 ms (n = 5, P < 0.05) without effects on the action potential amplitude and resting potential. Delayed outward K+ current and its tail current were blocked by EBP in a concentration-dependent fashion, while EBP did not change the amplitudes of the sodium current, the L type calcium current, and the inwardly rectifying potassium current. CONCLUSION: The mechanism of anti-arrhythmic action of EBP was to prolong the APD through inhibiting the delayed rectified potassium current.

Action Potentials↗

PubMed1995

Phenotypic alterations of petal and sepal by ectopic expression of a rice MADS box gene in tobacco.

Floral organ development is controlled by a group of regulatory factors containing the MADS domain. In this study, we have isolated and characterized a cDNA clone from rice, OsMADS3, which encodes a MADS-domain containing protein. The OsMADS3 amino acid sequence shows over 60% identity to AG of Arabidopsis, PLE of Antirrhinum majus, and AG/PLE homologues of petunia, tobacco, tomato, Brassica napus, and maize. Homology in the MADS box region is most conserved. RNA blot analysis indicated that the rice MADS gene was preferentially expressed in reproductive organs, especially in stamen and carpel. In situ localization studies showed that the transcript was present primarily in stamen and carpel. The function of the rice OsMADS3 was elucidated by ectopic expression of the gene under the control of the CaMV 35S promoter in a heterologous tobacco plant system. Transgenic plants exhibited an altered morphology and coloration of the perianth organs. Sepals were pale green and elongated. Limbs of the corolla were split into sections which in some plants became antheroid structures attached to tubes that resembled filaments. The phenotypes mimic the results of ectopic expression of dicot AG gene or AG homologues. These results indicate that the OsMADS3 gene is possibly an AG homologue and that the AG genes appear to be structurally and functionally conserved between dicot and monocot.

Amino Acid Sequence↗

PubMed1995

Cross-specialty linkage and extrapolation of resource-based relative value scales.

This article describes methods used to produce a RBRVS (resource-based relative value scales), a common scale from two specialties (internal medicine and general surgery) and explains the newly developed extrapolation process within each specialty. To produce a common scale, we selected six 'same' services as linking services common to both specialties. Then we used the bi-weighted least squares method to locate all the same services on a single, common scale. By using the same method, we tried to extrapolate all the services within each specialty, not by the method of Kelly et al, dividing all the services within the specialty into families (small homogeneous groups of services) to apply charge-based ratios. To compare both methods, we extrapolated all the services of general surgery according to each method. With the correlation analysis to compare both results to American RVUs, we found that general surgery's RVUs from our own extrapolation method turned out to be more highly correlated with American RVUs than from Kelly's extrapolation method. Consequently, extrapolation with bi-weighted least squares method gave reasonable results.

General Surgery↗

PubMed1995

Cholecystokinin octapeptide reverses mu-opioid-receptor-mediated inhibition of calcium current in rat dorsal root ganglion neurons.

Cholecystokinin octapeptide (CCK-8) is reported to antagonize the analgesic effect produced by mu- and kappa- but not delta-opioid agonist in spinal cord. However, the mechanisms of interaction remain obscure. In the present study, whole-cell patch-clamp recording was performed on acutely isolated rat dorsal root ganglion (DRG) neurons to evaluate the effects of the highly specific mu-opioid agonist ohmefentanyl and the delta-opioid agonist DPDPE on voltage-gated calcium channels and the possible interaction between CCK-8 receptor and mu- or delta-opioid receptor. The results indicated that ohmefentanyl, but not DPDPE, can suppress the voltage-gated calcium currents elicited in DRG neurons, an effect readily reversed by naloxone or by the antiopioid peptide CCK-8. The effect of CCK-8 can in turn be abolished by the CCK-B receptor antagonist L365,260. CCK-8 used by itself has no enhancing effect, but rather a depressant effect, on calcium currents. However, used simultaneously with ohmefentanyl, CCK-8 shows a clear-cut reversal of depression of the mu-opioid. We conclude that the depressant effect produced by mu-opioid on voltage-gated calcium current in DRG neurons can be antagonized by CCK-8 through CCK-B receptor located in the same neuron. The delta-opioid DPDPE has no direct effect on the voltage-gated calcium current in DRG neurons.

Animals↗

PubMed1994

Detection of beta-Glucosidase Activity in Polyacrylamide Gels with Esculin as Substrate.

beta-Glucosidase can be located after nondenaturing polyacrylamide gel electrophoresis by incubating the gel with 0.1% esculin and 0.03% ferric chloride. The esculetin released from esculin by beta-glucosidase action reacts with ferric ion to produce a black band, corresponding to the beta-glucosidase, against the transparent background.

Journal Article↗

PubMed1992

Purification and characterization of two extracellular beta-glucosidases from Aspergillus nidulans.

Two beta-glucosidases, P-I and P-II, were purified from the culture filtrate of Aspergillus nidulans. The M(r) values of P-I and P-II were about 125,000 and 50,000, respectively. The isoelectric point, optimal pH and temperature, Michaelis constants for several substrates and inhibition constants for glucose and glucono-delta-lactone of each enzyme were determined. We conclude that the high affinity toward cellobiose and low inhibition by glucose of these enzymes may offer significant advantages in improving cellulose hydrolysis.

Aspergillus nidulans↗