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K Song

Publications and source records attributed to K Song.

At least 109 records · Page 6Linked to original sources
PubMed1994

Quantitative localization of angiotensin II receptor subtypes in spontaneously hypertensive rats.

Angiotensin II (Ang II) receptors were labelled by in vitro autoradiography using 125I-[Sar1,Ile8]Ang II as a ligand in the kidney, adrenal gland, thoracic aorta, and hindbrain of adult spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Ang II receptors were differentiated into subtypes by susceptibility to subtype 1 (AT1) and subtype 2 (AT2) antagonists. In both rat strains, the adrenal cortex contained predominantly AT1 receptors, while AT2 receptors predominated in the adrenal medulla. The kidney contained exclusively AT1 receptors in glomeruli, proximal tubules, and the outer medulla. AT1 receptors were predominant in the thoracic aorta. The nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus (DM10), area postrema, and spinal trigeminal nucleus (Sp5) contained exclusively AT1 receptors, whereas the nucleus of the inferior olive contained AT2 receptors predominantly. Significant differences in receptor density were observed between SHR and WKY. The adrenal cortex, renal outer medulla, NTS, DM10, and Sp5 displayed higher AT1 receptor density in SHR than in WKY. These results indicate that expression of AT1 receptors is regulated differently in important targets of Ang II in SHR, and suggest that altered regulation of AT1 receptor expression may be relevant to the pathogenesis of hypertension in SHR.

Adrenal Glands↗
PubMed1993

Distribution of angiotensin II receptor subtypes in the rabbit brain.

We have determined the distribution of angiotensin II receptor subtypes in rabbit brain using in vitro autoradiography. AT1 receptors were found in very high concentrations in the forebrain circumventricular organs--the subfornical organ, organum vasculosum of the lamina terminalis, and the median eminence as observed in other mammals. However, there was very little labeling in the area postrema. In the paraventricular nucleus, median preoptic nucleus, supraoptic nucleus there were high levels of predominantly AT1 receptors. High densities of AT1 receptors were also found in the nucleus of the solitary tract and the rostral and caudal ventrolateral medulla. All of these regions have putative roles in the regulation of blood pressure and fluid and electrolyte balance. In the rabbit brain there is less AT2 receptor binding than the rat, with most AT2 binding found in the molecular layer of the cerebellum and in the septohypothalamic nucleus. In the subthalamic nucleus, the mediodorsal and ventroposterior nuclei of the thalamus, locus coeruleus and inferior olivary nuclei, areas containing mostly AT2 receptors in the rat, no binding was detected in the rabbit except in the locus coeruleus which contains moderate levels of AT1 receptors. Taken in conjunction with our previous results in the rat and human brains, these results reveal that AT1 receptors predominate in rostral forebrain, hypothalamus and autonomic control centers of the medulla oblongata in all three species. However, the distribution and density of AT2 bearing sites in regions such as the septum, thalamus subthalamic nuclei, locus coeruleus, cerebellum and inferior olivary nuclei show marked species differences.

Amygdala↗
PubMed1993

m-Calpain requires DNA for activity on nuclear proteins at low calcium concentrations.

m-Calpain (calpain II, m-CANP), which normally requires millimolar Ca2+ for activity in vitro, was capable of proteolyzing a number of matrix proteins in isolated rat liver nuclei at Ca2+ concentrations as low as 3 microM (Mellgren, R. L. (1991) J. Biol. Chem. 266, 13920-13924). Treatment of nuclei with deoxyribonuclease I eliminated the activity of m-calpain at low Ca2+ concentrations, while ribonuclease A and phospholipase C had no effect. Addition of DNA to DNase-treated nuclei restored m-calpain activity at low Ca2+. RNA had little if any effect. Eukaryotic and prokaryotic DNA were equally effective, and synthetic polydeoxyribonucleotides were also activators. m-Calpain did not bind to a DNA-cellulose column in the presence of 200 microM Ca2+, and m-calpain preincubated in the presence of DNA and 200 microM Ca2+ was not activated at low Ca2+ concentrations following removal of the DNA. DNA did not alter the Ca2+ requirement for m-calpain-catalyzed cleavage of casein. These results demonstrate that the Ca2+ requirement for proteolysis of nuclear matrix proteins by m-calpain can be dramatically decreased in the presence of DNA. Activation did not seem to be a result of DNA binding directly to calpain but appeared to require interaction of DNA, calpain, and calpain substrates in the nuclear matrix.

Animals↗
PubMed1993

Marked species-difference in the vascular angiotensin II-forming pathways: humans versus rodents.

Using isolated arteries, we demonstrated a marked difference in the angiotensin II-forming systems between human and rodent vessels. In human arteries, only 30-40% of the conversion of angiotensin I to angiotensin II depended on the angiotensin-converting enzyme (ACE), and the rest of the angiotensin II formation was ascribed to chymostatin-sensitive angiotensin II-generating enzyme (CAGE). On the contrary, angiotensin II formation in rodent arteries totally depended upon ACE, without any sign of CAGE involvement. Such a marked species-difference can be relevant to the reported difference between humans and rodents in the ACE inhibitor effects on the myointimal hyperplasia after intimal balloon injury.

Adult↗
PubMed1993

In vitro pharmacology of a novel non-peptide angiotensin II-receptor antagonist, E4177.

E4177, 3-[(2'-carboxybiphenyl-4-yl)methyl]-2-cyclopropyl-7-methyl-3H- imidazo[4,5-b]pyridine, was characterized by in vitro autoradiography and by examining functional antagonism upon angiotensin II (Ang II)-induced contraction of isolated vessels. In rat adrenal cortex and liver, E4177 competitively inhibited the specific binding of 125I-[Sar1,Ile8]Ang II, with IC50 being (5.2 +/- 1.0) x 10(-8) M for the adrenal cortex and (1.2 +/- 0.3) x 10(-7) M for the liver. These IC50 values were similar to those for losartan, which showed an IC50 of (6.0 +/- 0.9) x 10(-8) M for the adrenal cortex and (1.3 +/- 0.5) x 10(-7) M for the liver. In contrast, E4177 and losartan had little effect on the binding to rat adrenal medulla where AT2-receptors predominate. These results indicate that E4177 is AT1-specific as is losartan. E4177 and losartan competitively antagonized the Ang II-induced contraction of human and rabbit arterial strips without any agonistic action. The obtained IC50 values indicated that E4177 was twice as potent as losartan in human arteries and three times more so in rabbit aortic strips. Responses to norepinephrine, serotonin, histamine or KCl were not affected by E4177. In addition, E4177 (10(-5) M) had no effect on angiotensin-converting enzyme activity. These data indicate that E4177 is a potent AT1 Ang II-receptor antagonist that may be clinically useful for the treatment of cardiovascular diseases such as hypertension.

Adrenal Cortex↗
PubMed1992

Expression of Hox-7.1 in myoblasts inhibits terminal differentiation and induces cell transformation.

The terminal differentiation of myogenic cells initiates in the proximal portion of the limb bud whereas the distal region remains undifferentiated and proliferative. The apical ectodermal ridge maintains the progress zone in an undifferentiated state and induces proliferation of limb mesenchymal cells. Hox-7.1, a homeobox-containing gene, is expressed throughout the limb bud when limb outgrowth begins, whereas transcripts are later restricted to distal limb mesenchyme which is the proposed site of positional specification. Transplantation of proximal limb bud tissue into the distal portion of the limb results in a re-expression of Hox-7.1 in the transplanted mesenchyme. Similar grafts result in a positional reassignment to distal structures as well as de-differentiation of the grafted proximal tissue. Because of the association of Hox-7.1 expression with proliferative and undifferentiated cells, we tested whether Hox-7.1 regulates differentiation by transfection of Hox-7.1 complementary DNA into determined myogenic cells which represent one mesenchymal lineage in the limb. Here we report that forced expression of Hox-7.1 blocks terminal differentiation and results in a corresponding decrease in steady-state levels of MyoD1. Consistent with the association of Hox-7.1 with proliferation, Hox-7.1-expressing cells also acquire a transformed phenotype. Forced expression of Hox-8.1, a related Hox-gene, does not affect terminal differentiation indicating that the effects of Hox-7.1 are specific.

Actins↗
PubMed1992

The p70 tumor necrosis factor receptor mediates cytotoxicity.

Tumor necrosis factor alpha (TNF) selectively kills tumor cells, but this specificity is not clearly understood. Two distinctly different cell surface receptors (TNFRs), proteins of 55 kd (p55) and 70-80 kd (p70), mediate TNF action. Mouse TA1 cells are not killed by human (h) TNF, but are killed by mouse (m) TNF alone. Since the mouse p70 TNFR is recognized only by mTNF, these results implicate p70 receptor action in TA1 cell killing. Human HeLa cells have mainly the p55 receptor and are not killed by hTNF alone. When transfected with the human p70 TNFR, HeLa p70 die within 24 hr. HeLa p70 cells also show reduced c-fos and manganous superoxide dismutase induction by TNF. NIH 3T3 mouse fibroblasts are sensitive to only mTNF, but overexpression of the human p70 receptor causes cell death by hTNF and increased sensitivity to mTNF. These results provide a direct function for the p70 TNFR in TNF-induced cytotoxicity.

3T3 Cells↗
PubMed1992

Mapping of angiotensin II receptor subtype heterogeneity in rat brain.

Angiotensin II (Ang II) exerts a number of central actions on fluid and electrolyte homeostasis, autonomic activity, and neuroendocrine regulation. In order to evaluate likely sites where these actions are mediated, Ang II receptor binding was localized in rat brain by in vitro autoradiography with the aid of the antagonist analogue 125I-[Sar1, Ile8]Ang II. Two subtypes of Ang II receptor have been identified using recently developed peptide and nonpeptide antagonists. In the periphery, the receptor subtypes differ in distribution, second messenger coupling, and function. Brain Ang II receptor subtypes were therefore differentiated into AT-1 (type I) and AT-2 (type II) subtypes by using unlabelled nonpeptide antagonists specific for the two Ang II subtypes. AT-1 binding was determined to be that inhibited by Dup 753 (10 microM) and AT-2 binding to be that inhibited by PD 123177 (10 microM). The reducing agent dithiothreitol (DTT) decreased binding to AT-1 receptors and enhanced binding to AT-2 receptors. Many brain structures, such as the vascular organ of the lamina terminalis, subfornical organ, median preoptic nucleus, area postrema, nucleus of the solitary tract, and dorsal motor nucleus of the vagus, which are known to be related to the central actions of Ang II, contain exclusively AT-1 Ang II receptors. By contrast, the locus coeruleus, ventral and dorsal parts of lateral septum, superior colliculus and subthalamic nucleus, many nuclei of the thalamus, and nuclei of the inferior olive contain predominantly AT-2 Ang II receptors. The detailed binding characteristics of each subtype were determined by competition studies with a series of analogues of angiotensin and antagonists. The pharmacological specificity obtained in rat superior colliculus and the nucleus of the solitary tract agreed well with published data on AT-1 and AT-2 receptors, respectively. There was a high degree of correlation between the distribution of Ang II binding sites with published data on Ang II-immunoreactive fields and on the sites of Ang II-responsive neurons. The present study also reveals pharmacological heterogeneity of brain Ang II receptors. The subtype-specific receptor mapping described here is relevant to understanding the role of angiotensin peptides in the central nervous system and newly discovered central actions of nonpeptide Ang II receptor antagonists.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1992

Nephrectomy and a newly identified binding site for angiotensin II in the rat adrenal cortex.

Angiotensin II (Ang II) binding sites in adrenal glands of nephrectomized rats were investigated by in vitro autoradiography using 125I-[Sar1,Ile8]Ang II as ligands. Ang II binding site was increased to 161% in the cortex and decreased to 67% in the medulla 48 h after nephrectomy. In the medulla, the AT2 antagonist (PD123177, 5 microM) inhibited specific binding by 90% whereas the AT1 antagonist (DuP753, 5 microM) inhibited by only 10%. In contrast, in the cortex, neither DuP753 (5 microM) nor PD123177 (5 microM) substantially inhibited the binding. Binding in the presence of either the AT1 or AT2 antagonist was abolished by the simultaneous presence of both antagonists. These results suggest the presence of a new Ang II binding site with unique pharmacological properties and differing from currently known subtypes of Ang II receptors, in the adrenal cortex after nephrectomy.

Adrenal Cortex↗
PubMed1992

Partial protection of 1 alpha-hydroxyvitamin D3 against the development of diabetes induced by multiple low-dose streptozotocin injection in CD-1 mice.

1 alpha-Hydroxyvitamin D3 (1 alpha-OH-D3), a precursor of active vitamin D3, 1 alpha,25-dihydroxyvitamin D3, was tested in CD-1 mice for its in vivo effect against the development of diabetes induced by administering multiple low doses of streptozotocin (STZ). Daily intraperitoneal (IP) injections of 35 mg/kg body weight of STZ administered for 5 consecutive days to mice from 7 weeks of age induced a delayed-onset hyperglycemia, insulitis, and beta-cell degranulation in 26 of 28 mice. Only 12 of 29 mice developed diabetes when treated with simultaneous daily IP injections of 1 alpha-OH-D3 for 14 consecutive days, with diabetes defined as a plasma glucose level greater than 200 mg/dL. A daily dose of 0.3 micrograms/kg 1 alpha-OH-D3 also protected against the development of hyperglycemia in five of 13 mice, whereas 0.2 micrograms/kg 1 alpha-OH-D3 was ineffective, indicating a dose-related effect. Histological study showed that, among the 1 alpha-OH-D3-treated mice, the pancreatic islets of euglycemic mice showed neither massive islet infiltration nor beta-cell degranulation, whereas those of the hyperglycemic mice showed insulitis. However, when diabetes was chemically induced with a single high dose of STZ, the simultaneous administration of 1 alpha-OH-D3 to mice failed to protect against the development of hyperglycemia; all five mice so treated developed hyperglycemia. Their pancreatic islets did not show insulitis. Therefore, it is suggested that 1 alpha-OH-D3 may protect against the development of diabetes following administration of multiple low doses of STZ, probably via an immune mechanism.

Animals↗
PubMed1992

A new method to localize active renin in tissues by autoradiography: application to dog kidney.

A method was developed to localize active renin in dog kidney sections using autoradiography to detect in vitro binding of the radiolabeled renin inhibitor, 125I-H77. Light fixation by prior perfusion of the kidney with paraformaldehyde was used to immobilize renin without denaturing its binding activity. Snap frozen sections were cut on a cryostat and incubated with 125I-H77. Dry film autoradiography revealed discrete binding of 125I-H77 to the vascular pole of glomerulus as well as diffuse binding to the outer medulla and to the cortex. Binding of 125I-H77 to other aspartyl proteases in the latter two regions was then suppressed by addition of the aspartyl protease inhibitor, N-acetyl-pepstatin (1 microM). This revealed only the juxtaglomerular binding and successfully suppressed binding of the radioligand to other sites. Light microscopic emulsion autoradiography revealed highly selective discrete labelling of the juxtaglomerular apparatus. Competition for this 125I-H77 binding by a series of structurally different renin inhibitors showed a close correspondence between their reported inhibitory potency for renin and potency in the binding system. This strongly suggests that the radioligand binds to the active site of renin immobilized in the kidney. These results demonstrate a new method to localize active renin in tissues using in vitro autoradiography and radioinhibitor binding. The method shows promise for localization and quantitation of tissue renin in extra renal tissues.

Animals↗
PubMed1992

Rapid screening of libraries with radiolabeled DNA sequences generated by PCR using highly degenerate oligonucleotide mixtures.

The PCR technique can use protein-derived oligonucleotide sequences as primers to develop probes for screening recombinant libraries. Here we report a method with highly degenerate mixtures of oligonucleotides as primers for the PCR that eliminates the need to identify or isolate the DNA sequences derived by PCR. The method uses the pool of PCR-generated DNA sequences radiolabeled during the extension reaction as a probe, combined with highly stringent hybridization and wash conditions that permit only homologous sequences to hybridize and therefore target desired clones. This technique was used successfully to clone the receptor for tumor necrosis factor.

Amino Acid Sequence↗
PubMed1991

Overamplification of macronuclear linear DNA molecules during prolonged vegetative growth of Oxytricha nova.

During prolonged vegetative growth of a clonal line of Oxytricha nova, several macronuclear linear DNA molecules increased greatly in copy number over the rest of the approx. 24,000 kinds of molecules comprising the macronuclear genome. One of the amplified sequences was the linear DNA molecule encoding rRNA (rDNA). We have cloned and sequenced the other, smaller, amplified molecules and found that they comprise a gene family, with different allelic versions of one of the family members being amplified. Thus, increased replication is a general property of the molecules comprising this gene family. To date, no function has been assigned to these genes; thus, whether the amplification of these sequences has functional significance is unknown. The rDNA molecule and the two small amplified sequences increased 11-, 24- and 107-fold, respectively, during clonal growth of this line, eventually comprising up to 15% of the macronuclear DNA molecules. Seven other macronuclear DNA molecules did not vary substantially in copy number at different times during the clonal growth of this strain. Analysis of cell-to-cell differences in copy numbers in this clonally aged strain indicated more extensive variation than is evident when large populations from different times are compared.

Amino Acid Sequence↗
PubMed1991

Tumor necrosis factor receptor genes, TNFR1 and TNFR2, on human chromosomes 12 and 1.

Tumor necrosis factor, TNF, is a 17-kDa protein secreted by macrophages and classified as a cytokine. TNF binds to high-affinity receptors on the cell surface and is involved in a wide variety of biological responses. There are at least two types of receptors, tumor necrosis factor receptors 1 and 2 (TNFR1 and TNFR2). The genes for TNFR1 a 55-kDa protein, and TNFR2, a 70-kDa protein, have been mapped to human chromosomes 1 12 (12pter-cen) and (1pter-p32), respectively, by Southern blot analysis of human x Chinese hamster somatic cell hybrid panels. Recently, the corresponding genes in the mouse have been mapped to chromosomes 4 and 6 in regions that are conserved on human chromosomes 1 and 12.

Animals↗
PubMed1991

Angiotensin II receptor subtypes in rat brain.

1. Angiotensin II (AII) receptor binding was localized in the rat brain by in vitro autoradiography using the antagonist analogue, 125I-[Sar1, Ile8] AII. AII receptor binding was then differentiated into type I and type II subtypes by displacement with unlabelled non-peptide antagonists specific for AII subtypes. 2. Type I binding was determined as that inhibited by Dup753 (10 mumol/L) and type II binding as that inhibited by XD329-1 (10 mumol/L). The reducing agent dithiothreitol (DTT) decreased the binding to type I receptors and enhanced the binding to type II receptors. 3. Structures such as the vascular organ of the lamina terminalis, subfornical organ, median preoptic nucleus, area postrema, nucleus of the solitary tract, which are known to be related to some central actions of AII, contain exclusively type I AII receptors. 4. In contrast, the locus coeruleus, ventral and dorsal parts of lateral septum, superior colliculus, subthalamic nucleus, some nuclei of the thalamus, and the nuclei of the inferior olive contain predominantly type II AII receptors. 5. These results reveal important pharmacological heterogeneity of brain AII receptors which suggest different regional functions and are relevant to the central actions of emerging classes of new non-peptide AII receptor antagonists.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1991

Angiotensin II receptor subtypes in rat brain and peripheral tissues.

Angiotensin II (Ang II) receptor binding was localized in rat adrenal gland, kidney, and brain by in vitro autoradiography using the antagonist analogue 125I-[Sar1, Ile8]Ang II and differentiated into type I (AT-1) and type II (AT-2) subtypes using unlabelled non-peptide antagonists specific for Ang II subtypes. AT-1 binding was determined as that remaining in the presence of an excess of the AT-2 antagonist, PD 123177 (10 microM), and AT-2 binding as that remaining in the presence of an excess of the AT-1 antagonist, DUP753 (10 microM). The reducing agent dithiothreitol decreased the binding to AT-1 receptors and enhanced the binding to AT-2 receptors. The rat adrenal gland contains both AT-1 and AT-2 receptors in the ratio of approximately 3:2 in the cortex and 1:9 in the medulla. By contrast, in the kidney only AT-1 receptors were evident in glomeruli, proximal tubule, and inner stripe of the outer medulla. In the brain, the pattern of Ang II receptor subtypes varies greatly from region to region. Many brain structures known to be involved in blood pressure regulation and fluid and electrolyte balance, such as circumventricular organs (including vascular organ of the lamina terminalis, subfornical organ, median eminence, and area postrema), median preoptic nucleus, hypothalamic paraventricular nucleus, and regions in the medulla oblongata involved in autonomic control (nucleus of the solitary tract, dorsal motor nucleus of the vagus, and intermediate reticular nucleus), contain exclusively AT-1 receptors. By contrast, locus coeruleus, lateral septal nuclei, superior colliculus, subthalamic nucleus, many nuclei of the thalamus, and nuclei of the inferior olive contain predominantly AT-2 receptors. The detailed binding characteristics of each subtype were determined by competition studies with a series of antagonists. The pharmacological specificity obtained in kidney, adrenal cortex and adrenal medulla, superior colliculus, and nucleus of the solitary tract produces specificity patterns which confirm the assignments of AT-1 and AT-2 receptors described above. The present study reveals important pharmacological heterogeneity of Ang II receptors in key target organs. The subtype-specific receptor mapping described here is relevant to the understanding of the role of angiotensin peptides in peripheral organs and in the central nervous system and is relevant to the actions of non-peptide Ang II receptor antagonists.

Adrenal Glands↗
PubMed1990

Amplified expression of tumor necrosis factor receptor in cells transfected with Epstein-Barr virus shuttle vector cDNA libraries.

As an approach to isolate the cell-surface receptor for tumor necrosis factor (TNF), we have developed transfectants of human B-lymphoblastoid cells (UC cells) that overexpress the TNF receptor. These transfectants were isolated from UC cells transfected with cDNA libraries of HeLa or NG108 cells constructed in the mammalian expression vector EBO-pcD. This vector contains the Epstein-Barr virus origin of replication (ori-P) plus the EBNA-1 gene conferring replication function to ori-P and, therefore, the ability to replicate autonomously within the transfected cell (Margolskee, R.F., Kavathas, P., and Berg, P. (1988) Mol. Cell. Biol. 8, 2837-2947). Cells overexpressing the TNF receptor were identified and separated by the binding of fluoresceinated TNF and flow cytometric selection. Scatchard analysis of 125I-TNF binding data revealed a single class of high affinity receptors with a dissociation constant (Kd) of 0.2 to 2 nM and a receptor density of about 150,000 per cell, an increase of approximately 150-fold over UC cells. Cross-linking of receptor-ligand with bis-sulfosuccinimidyl suberate followed by polyacrylamide gel electrophoresis gave estimates of 87 and 104 kDa for the size of the complex. Based on its ability to bind TNF, a 68-kDa receptor protein was identified in cell extracts enriched for the receptor by using immobilized wheat germ agglutinin and TNF affinity chromatography. The difference in the estimated size of the receptor and the receptor-ligand complexes demonstrates that TNF binds to the receptor as a monomer or a dimer. Analysis of cDNA sequences conferring receptor amplification in transfectants revealed that plasmid DNA was present at 30 or more copies per cell, most likely integrated into the genomic DNA or organized into high molecular weight catenanes, and autonomously replicating units could not be recovered. Therefore, while this vector was useful in generating stable receptor-amplified cells, it was not maintained as a recoverable episome.

Animals↗