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H T Chen

Publications and source records attributed to H T Chen.

At least 73 records · Page 4Linked to original sources
PubMed1987

Nucleotide and translated amino acid sequences of cDNA coding for the variable regions of the light and heavy chains of mouse hybridoma antibodies to blood group A and B substances.

This is the first report of nucleotide and translated amino acid sequences of the variable region light (VL) and heavy (VH) chains of mouse monoclonal hybridoma anti-blood group A and B substances, the combining sites of which have been mapped. Monoclonal hybridoma anti-A and anti-B produced in BALB/c mice by immunization with A or B blood group substances, with A1 erythrocytes, and water-soluble blood group A substance or with synthetic B determinants coupled to bovine serum albumin or to O erythrocytes have been characterized immunochemically. To relate the immunochemical properties of the monoclonals to their primary structures, we have cloned and sequenced cDNAs of variable regions of light and heavy chains of two anti-A and two anti-B. The anti-A hybridomas have very similar combining site specificities and have almost identical VH sequences belonging to the J558 germ-line family, but their VL are from different germ-line VK gene families. The two anti-B hybridomas have different combining site specificities and use the same VL which differs completely from the anti-A VL; their VH are derived from different VH germ-line genes belonging to the J606 family. The results suggest that the heavy chains play a major role in determining the specificities of the antibody combining sites, with only minor contribution of VL. Additional sequence data on monoclonal antibodies of defined specificity for blood group substances are needed for further insights into the genetic and structural basis for their specificities.

ABO Blood-Group System↗
PubMed1987

Immunochemical studies on monoclonal antibodies to stearyl-isomaltotetraose from C58/J and a C57BL/10 nude mouse.

Six hybridomas, five from C58/J and one from C57BL/10 nu/nu, immunized with stearyl-isomaltotetraose (S-IM4) were established. One produced IgG3, one IgM and four IgA. The specificities and sizes of the antibody combining sites were determined by quantitative precipitin and ELISA quantitative inhibition assays. All cross-react with alpha(1----6)dextran B512. Their combining sites were complementary to five to seven glucose residues. Association constants of hybridoma antibodies for dextran B512 ranged from 10(3) to 10(5) ml/g, and for isomaltoheptaose (IM7) from 10(3) to 10(4)M-1. Two hybridoma antibodies, one IgA and another IgM derived from different fusions have identical inhibition curves and combining sites, and very close association constants. It will be important to establish whether they have very similar or identical nucleotide sequences in their variable regions. These studies provide further insight into the specificity and repertoire of antidextran combining sites.

Amines↗
PubMed1987

Postnatal development of pituitary lactotropes in the rat measured by reverse hemolytic plaque assay.

Developmental changes and sexual differences in the lactotrope population were studied with a reverse hemolytic plaque assay for detection and measurement of PRL secretion from individual cells in conjunction with PRL immunocytochemistry (ICC). Pituitary glands from both sexes at different ages were monodispersed with 0.1% trypsin. Freshly dispersed cells were incubated in Cunningham chambers for measurement of the fraction of plaque-forming cells and the size of plaques formed, or attached to glass slides for measurement of the fraction of cells staining for PRL by ICC. The percentage of plaque-forming cells in both sexes gradually increased with age from about 5% of the total anterior pituitary cell population at 5 days of age to the adult levels of about 54% in the females at proestrus and about 37% in the males. Sexual differences in the percentage of plaque-forming cells were consistently seen at 40 days of age and thereafter. The mean size of plaques in both sexes also increased with age from about 1,100 microns 2 at 5 days of age to a peak level of about 15,600 microns 2 in the females at proestrus and about 6,700 microns 2 in the males at 60 days of age; then fell to the adult levels of about 5,500 microns 2 in the females at proestrus and about 3,200 microns 2 in males. Sexual differences first appeared at 40 days of age and were estrogen-dependent. The results from ICC closely matched those from the plaque assay, except at 5 days of age and in the adult males. At 5 days, the fraction of cells staining for PRL was twice that of cells forming plaques. In adult male rats there were about 47% immunostained PRL cells but only about 39% plaque-forming cells. This difference, however, disappeared after estrogen treatment. These results demonstrate that sexual differences in the lactotrope population develop around puberty in rats and appear to be estrogen dependent.

Age Factors↗
PubMed1985

Immunochemical studies on blood groups. The combining site specificities of mouse monoclonal hybridoma anti-A and anti-B.

Mouse monoclonal hybridomas, five anti-blood group A, three anti-B, and one anti-AB, produced by various methods of immunization, have been characterized by quantitative precipitin tests and the fine structures of their combining sites have been mapped by oligosaccharide inhibition assays. The combining sites of antibodies of each specificity differed among themselves. Three of the five monoclonals were specific for difucosyl and two for monofucosyl A determinants. All but the anti-AB were strictly specific for blood group A or blood group B erythrocytes; all of the anti-A monoclonals gave essentially equivalent titers in hemagglutination tests with A1 and A2 erythrocytes except for a monoclonal anti-A prepared by immunization with a human gastric cancer cell line. The data provide additional evidence for the heterogeneity of the antibody response to the different antigenic determinants present on blood A and B substances and emphasize the importance of difucosyl determinants which comprise most of the determinants on the water-soluble blood group substances.

ABO Blood-Group System↗
PubMed1984

Effect of adrenalectomy and 5-hydroxytryptophan on phasic release of luteinizing hormone.

The effect of 5-hydroxytryptophan (5-HTP) on serum progesterone and the possible role of adrenal progesterone in mediating stimulation by 5-HTP of phasic release of luteinizing. hormone (LH) were investigated in estradiol benzoate (EB)-treated ovariectomized rats. LH surges were induced in long-term (at least two weeks) ovariectomized rats by two injections of EB (20 micrograms/rat, s.c.) with an interval of 72 hrs. Administration of 5-HTP (50 mg/kg, i.p.) at 1000 hr in EB-treated ovariectomized rats resulted in a four-fold increase in serum progesterone within 30 mins, and significantly stimulated the LH surge at 1600 hr. This facilitative effect of 5-HTP on serum LH, but not progesterone, was further potentiated in rats pretreated with P-chlorophenylalanine (PCPA) 72 hrs earlier. Adrenalectomy shortly before 5-HTP administration attenuated the LH surge in saline treated controls, and completely blocked the facilitative effect of 5-HTP on the afternoon surge of LH in rats pretreated with PCPA 72 hrs earlier. On the other hand, chronic adrenalectomy (for 6 days) followed by hydrocortisone (0.2 mg/rat/day) replacement not only had no effect on the LH surge in saline treated controls, but also failed to prevent 5-HTP from facilitating the LH surge in PCPA pretreated rats. On the first day of bleeding, the basal LH value at 1000 hr in sham operated controls was significantly suppressed by PCPA pretreatment 48 hrs earlier. The second dose of 5-HTP administered on the next day failed to potentiate LH surges in either sham operated or adrenalectomized rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1984

Identification of alpha-adrenergic receptor subtypes in the steer stalk-median eminence.

The presence of alpha 1- and alpha 2-receptor subtypes were studied in steer stalk-median eminence (SME) using a selective alpha 1-ligand, [3H]-prazosin, and a selective alpha 2-ligand, [3H]-clonidine. Scatchard analysis of the equilibrium isotherms of specific [3H]-prazosin binding indicated a single class of high affinity (Kd = 0.36 +/- 0.05 nM) and low capacity (Bmax = 111 +/- 19 fmol/mg protein) binding sites, which accounted for approximately 26% of the total sites identified by the non-subtype-selective-alpha-antagonist, dihydroergocryptine ([3H]-DHE). Similarly, computer modeling of the biphasic competition curve of prazosin displacing [3H]-DHE also revealed that there are approximately 26% high affinity sites, presumably alpha 1-, and approximately 74% low affinity sites, presumably alpha 2-receptors in the steer SME. A scatchard plot of specific [3H]-clonidine binding was biphasic and was resolved into a high (Kd = 1.60 +/- 0.34 nM) and low (Kd = 34.5 +/- 7.85 nM) affinity site with the binding capacities of 43 +/- 5 and 200 +/- 37 fmol/mg protein, respectively. The total number of alpha 2-sites identified by [3H]-clonidine accounted for approximately 58% of the total sites labeled by [3H]-DHE, which was in good agreement with that calculated from the competition of clonidine for [3H]-DHE binding (approximately 65% alpha 2 and approximately 35% alpha 1). The rank orders of potency of alpha-adrenergic agents to compete for sites labeled by [3H]-prazosin and [3H]-clonidine were consistent with their labeling alpha 1- and alpha 2-subtypes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Estimates of absorbed energy in trabecular bone due to beta-particles or electrons.

A computer code, DAB-BE, has been written which can be used to calculate the absorbed energies of beta particles or electrons deposited inside human trabecular bone. The radiation source geometry can be either uniformly distributed in the whole bone or located at a fixed point inside the bone. Bremsstrahlung effects are not considered in these calculations. Results are presented and discussed for six monoenergetic sources of electrons distributed uniformly in a mathematical representation of the arm. In addition, a fixed point source configuration of 1.0 MeV monoenergetic electrons was studied.

Bone and Bones↗
PubMed1981

Binding of [3H]dihydroergocryptine to an alpha-adrenergic site in the stalk median eminence of the steer.

Dihydroergocryptine (DHE), a potent dopamine agonist and alpha-adrenergic antagonist, has been used as a radioligand to characterize both dopamine and alpha-adrenergic receptors. In the present study, the binding of [3H]DHE to particulate fractions of the steer stalk median eminence was characterized using a filtration assay. Specific binding was defined by the presence of 10 microM phentolamine or by an iterative nonlinear hyperbolic curve-fitting program. Scatchard analysis of equilibrium isotherms of specific binding defined a single high affinity (Kd = 1.78 +/- 0.22 nM), saturable (maximum binding, 481 +/- 39 fmol/mg protein), stereoselective binding site. The Kd, calculated from the ratio of the rate constants k2 and k1, was 2.8 +/- 0.14 nM. The rank order of potency of agonists to compete for [3H]DHE binding (l-epinephrine greater than l-norepinephrine greater than dopamine greater than l-isoproterenol) was consistent with interactions at an alpha-adrenergic site. The rank order of potency of alpha-antagonists (phentolamine greater than yohimbine greater than prazosin) suggested that this was an alpha 2-adrenergic receptor. The affinity of dopamine agonists for the [3H]DHE-binding site was 10-fold lower relative to their potency at known dopamine receptors, while the affinity of dopaminergic antagonists was 100-fold lower. Furthermore, Scatchard analysis of specific [3H]DHE binding in the presence of a concentration of spiperone which should saturate dopamine receptors, only decreased the number of binding sites by 9%. These data demonstrate the presence of large numbers of alpha-adrenergic receptors in the stalk median eminence of the steer. Only a small number of dopaminergic binding sites for [3H]DHE appeared to be present.

Animals↗
PubMed1980

Effects of naloxone and morphine on the proestrous surge of prolactin and gonadotropins in the rat.

The effects of naloxone hydrochloride and morphine sulfate on the proestrous surge of PRL and gonadotropins (LH and FSH) were investigated in normal cycling Sprague-Dawley rats. Blood samples (0.45-0.50 ml) were withdrawn without anesthesia every 20 min from 1400-2000 h through an atrial cannula implanted the same morning. RIA revealed that a single iv injection of naloxone (0.2 mg/kg) at 1400 h completely suppressed the surge of PRL, and this was reversed by a concomitant injection of morphine (10 mg/kg). Morphine itself did not alter the peak of the PRL surge. Morphine suppressed only the early phase of the LH surge, and this was reversed by naloxone. Naloxone alone did not change the peak of the LH surge but maintained higher levels than controls during the declining phase. The FSH surge was not altered by either morphine or naloxone. These results suggest that endogenous opioid peptides may have a role in regulating the PRL and LH surges during proestrus in the rat.

Animals↗
PubMed1980

Interim follow-up studies of innominate osteotomy for congenital dislocation of the hip.

Innominate osteotomy alone without any adjunctive procedures was performed for congenital dislocation of the hip in 30 children. A complete follow-up study of an average of four years and nine months was obtained for 20 hips in patients. These interim results were quite gratifying. Clinical and radiologic assessments by a score system of Trevor and associates revealed that 85% of the hips that had been operated upon were functionally satisfactory. There were three cases of redislocation which were classified as resulting from technical failures.

Casts, Surgical↗