Search PubMed⌕ Search

Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 1,369 records · Page 76Linked to original sources
PubMed1993

High binding affinity chimeric anti-colorectal carcinoma antibody correlated to enhanced tumor binding and effector function.

The genetically engineered mouse/human chimeric cB72.3m4 and cB72.3m12 antibodies all recognized the tumor-associated TAG72 antigen. The high affinity cB72.3m4 antibody had an approximately 18-fold higher affinity constant for the TAG72 antigen than the low affinity cB72.3m12 antibody. The relationship amongst antibody binding affinity, tumor binding and effector functions was studied by using these two antibodies. The data showed that the high affinity cB72.3m4 antibody was reactive with, on average, 15% more colon adenocarcinoma cells on tissue sections than the low affinity cB72.3m12 antibody, and it did not produce any cross-reactivities with various normal tissues. The high affinity cB72.3m4 antibody was able to mediate more effective ADCC and CDC to the human ovarian cancer cells in vitro than the low affinity cB72.3m12 antibody. This study provides evidence that this high affinity chimeric cB72.3m4 antibody may be useful in both immunodetection and immunotherapy of cancer.

Adenocarcinoma↗
PubMed1993

The tyrosine residue at position 97 in the VH CDR3 region of a mouse/human chimeric anti-colorectal carcinoma antibody contributes hydrogen bonding to the TAG72 antigen.

One amino acid, tyrosine at position 96 and 97 in the VH CDR3 region of a mouse/human chimeric anti-TAG72 antibody cB72.3m4 was substituted by the phenylalanine residue and by a number of amino acids from different amino acid groups by the site-directed mutagenesis technique. The expression vector mpSV2neo-EP1-Vm11-16C1 containing mutant VH region fragments (Vm11-16) as well as the immunoglobulin enhances (E), promoter (P1) and the human genomic C1 region fragments, were transfected into a heavy-chain-loss mutant cell line B72.3Mut(K), respectively. Mutant chimeric cB72.3m11-16 antibodies were purified from the transfectant supernates and compared based upon their binding affinity for the TAG72 antigen relative to that of the original cB72.3m4 antibody. The data showed that a single amino acid substitution of tyrosine by phenylalanine and a number of amino acids including serine, asparagine, histidine and arginine at position 97 in the VH CDR3 region all resulted in approximate 18-fold lower binding affinity, whereas the substitution of tyrosine by phenylalanine at position 96 in the VH CDR3 region did not affect the binding affinity of the cB72.3m4 antibody. This suggests that the tyrosine residue at position 97 in the VH CDR3 region is in a contact position in the B72.3/TAG72 antibody/antigen interaction, and that the terminal hydroxyl group of the position 97 tyrosine side-chain contributes hydrogen bonding to the TAG72 antigen, whereas the position 96 tyrosine side-chain does not.

Animals↗
PubMed1993

Construction of multiple copy of alpha-domain gene fragment of human liver metallothionein IA in tandem arrays and its expression in transgenic tobacco plants.

Metallothioneins (MT) are low molecular weight, cysteine-rich, metal-binding proteins. An MT molecule contains two domains which appear to act independently--an alpha-domain, which is characterized by cadmium-binding, and a beta-domain, which binds preferentially to copper. Based on this conception, DNA duplex encoding the alpha-domain (106 bp) of human MT-IA was constructed from a chemically-synthesized oligomer by repair synthesis and enzymatic ligation and cloned into pUC19. The genes cloned were sequenced and found to be in the correct order as designed. Synthetic directional adapters were attached to the terminals of the alpha-domain gene fragment of human MT-IA to establish complete control over fragment orientation during ligation. The use of these directional adapters thereby ensured the production of multiple copies of the alpha-domain in tandem arrays. The successive alpha-domains were linked by a peptide linker consisting of 10 residues. A chimeric gene containing 12 cloned tandemly repeated copies of the 106 bp alpha-domain DNA was introduced into tobacco cells on a disarmed Ti-plasmid of Agrobacterium tumefaciens. A total of 10 different transgenic tobacco plants were generated, of which two showed root and shoot growth unaffected by up to 200 mg/l kanamycin and 100 microM cadmium, whereas root growth of control plants was severely inhibited and leaf chlorosis developed on media containing only 10 microM cadmium.

Agrobacterium tumefaciens↗
PubMed1993

Sequences of 3' end of genome and of 5' end of open reading frame 1a of lactate dehydrogenase-elevating virus and common junction motifs between 5' leader and bodies of seven subgenomic mRNAs.

The sequences of the 3'-terminal 3.7 kb of the genome and of a 1.7 kb 5' end cDNA clone of one isolate of lactate dehydrogenase-elevating virus (LDV) are reported. The 3' end sequence encodes six major independent open reading frames (ORFs 2 to 7), which are overlapping by between one and 130 nucleotides. Each ORF is expressed at the 5' end of one of six 3'-coterminal subgenomic mRNAs (mRNAs 2 to 7, respectively; 3.5 to 0.8 kb). The smallest mRNA, mRNA 7, encodes the nucleocapsid protein, VP1; mRNA 6 probably encodes the non-glycosylated envelope protein, VP2; and mRNAs 2 to 5 encode proteins of 26.0K, 21.5K, 19.2K and 22.4K, respectively, each possessing several potential N-glycosylation sites and membrane-spanning segments. About 72% of the LDV genome segment carrying ORFs 2 to 7 exhibits about 50% or higher nucleotide identity with the corresponding genome segment of swine infertility and respiratory syndrome (Lelystad) virus (LV), whereas only limited similarity is observed in discontinuous regions of the same corresponding genome segments of LDV and equine arteritis virus (EAV). EAV and LV belong to the same new group of positive-strand RNA viruses as LDV. One additional subgenomic mRNA of about 4 kb is produced in LDV- but not in EAV- or LV-infected cells. The 5' end of this mRNA (1-1) carries a continuous coding sequence. The N-terminal 80 amino acids of the predicted product exhibit about 50% identity with segments in the ORF 1b proteins of both EAV and LV. These segments are located 117 to 150 amino acids upstream of the C termini of the ORF 1b proteins of these viruses. The 5' end cDNA clone contains part of a 5' leader associated with all seven subgenomic mRNAs and the 5' end of ORF 1a. The junctions between the 5' leader and the bodies of all seven subgenomic mRNAs have been determined. Only a single junction sequence was detected for each mRNA. Linkage occurs between a 5' UAUAACC 3' sequence at the 3' end of the leader and only partially identical segments specified downstream in the genome preceding ORFs 2 to 7. The generated junctions differ for different subgenomic mRNAs but possess the consensus sequence 5' U(A/G)(U/A)AACC 3'. In mRNA 7, the UA in positions 1 and 2 are derived from the leader, but a G in position 2 in mRNAs 1-1, 3 and 4 and an A in position 3 in mRNA 6 seem to be specified by the 3' genomic sequences.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1993

Prodigiosin 25C: effect in in vitro models for T cell activation and T cell cycling and in vivo for rat heart allografts.

Prodigiosin 25C inhibited both lymphocyte activation (concanavalin-A-activated mouse spleen cells) and constitutive cell cycling of T cells and fibroblasts. This suggests that prodigiosin 25C is not selective for activation of T lymphocytes as has been previously reported. Use of prodigiosin 25C to suppress allograft rejection of rat hearts (DA to PVG) showed that 1 mg/kg/day i.p. had no effect whilst 10 mg/kg/day i.p. was toxic as manifest by weight loss and diarrhoea at 3 days. Although this toxicity was reversible upon reversion to 1 mg/kg/day, no major prolongation in allograft survival was seen. Our data suggests that prodigiosin 25C has a low therapeutic index and may not be selective for T cell activation.

Animals↗
PubMed1993

Rearrangements of the retinoic acid receptor alpha and promyelocytic leukemia zinc finger genes resulting from t(11;17)(q23;q21) in a patient with acute promyelocytic leukemia.

Cytogenetic study of a patient with acute promyelocytic leukemia (APL) showed an unusual karyotype 46,xy,t(11;17) (q23;21) without apparent rearrangement of chromosome 15. Molecular studies showed rearrangements of the retinoic acid receptor alpha (RAR alpha) gene but no rearrangement of the promyelocytic leukemia gene consistent with the cytogenetic data. Similar to t(15;17) APL, all-trans retinoic acid treatment in this patient produced an early leukocytosis which was followed by a myeloid maturation, but the patient died too early to achieve remission. Further molecular analysis of this patient showed a rearrangement between the RAR alpha gene and a newly discovered zinc finger gene named PLZF (promyelocytic leukemia zinc finger). The fusion PLZF-RAR alpha gene found in this case, was not found in DNA obtained from the bone marrow of normals, APL with t(15;17) and in one patient with AML-M2 with a t(11;17). Fluorescence in situ hybridization using a PLZF specific probe localized the PLZF gene to chromosomal band 11q23.1. Partial exon/intron structure of the PLZF gene flanking the break point on chromosome 11 was also established and the breakpoint within the RAR alpha gene was mapped approximately 2 kb downstream of the exon encoding the 5' untranslated region and the unique A2 domain of the RAR alpha 2 isoform.

Aged↗
PubMed1993

Localization of rat tryptase to a subset of the connective tissue type of mast cell.

We examined the cellular distribution of rat tryptase in rat skin, lung, small intestine, and peritoneal lavage cells by immunohistochemical techniques. Tryptase purified to apparent homogeneity from rat skin was used to generate a goat polyclonal anti-rat tryptase antibody. Tryptase-containing cells were detected in lung, skin, and peritoneal lavage cells. Small intestine mucosa, on the other hand, showed few if any tryptase-positive cells. Sequential staining with Alcian blue and anti-tryptase antibody showed that tryptase is located only in mast cells. Sequential staining with safranin to identify the connective tissue type of mast cell and anti-tryptase antibody showed that tryptase resides only in this mast cell type. However, only a subpopulation of the safranin-stained mast cells contained tryptase. In lung, 53% of the mast cells stained with safranin; 94% contained tryptase. In skin, 80% stained with safranin; only 6% contained tryptase. In peritoneal cells, more than 95% of the mast cells were stained with safranin; 20% contained tryptase. In the bowel mucosa, where few cells are stained by safranin, no cells with tryptase were detected. The percentages of cells with chymase I that also contained tryptase were 80% and 84% for lung, 4% and 7% for skin, and 15% and 13% for peritoneal cells by respective simultaneous and sequential double labeling with anti-tryptase and anti-chymase I antibodies. This study suggests that the rat connective tissue type of mast cell is subdivided into two forms on the basis of the presence or absence of tryptase, whereas rat mucosal mast cells lack this enzyme. These results contrast with those in humans, in which tryptase is present in all mast cells, but are similar to mice, in which tryptase mRNA has been detected only in the connective tissue type.

Animals↗
PubMed1993

Estramustine and estrone analogs rapidly and reversibly inhibit deoxyribonucleic acid synthesis and alter morphology in cultured human glioblastoma cells.

Estramustine is an estradiol-based agent that has been shown to accumulate in human glioma cells, resulting in a concentration-dependent alteration in cell size and shape within minutes and an inhibition of proliferation over 3 to 6 days. We evaluated human glioblastoma cultures with [3H]thymidine incorporation assays to determine estramustine's early effects on deoxyribonucleic acid synthesis in these tumors. Because estramustine shares a common structural motif with other antimicrotubule drugs, we synthesized four A-ring conjugates of estrone that contained a carbamate moiety but lacked nitrogen mustard. These analogs were examined by [3H]thymidine incorporation and compared with vinblastine. Greater than 70% inhibition of [3H]thymidine incorporation occurred within 1 hour of treatment with estramustine at 10(-5) mol/L, which increased to 80% inhibition at 4 hours. Ethyl carbamate JE208 was nearly as effective as estramustine in inhibiting deoxyribonucleic acid synthesis, and both were more effective than vinblastine. The inhibitory effects of estramustine and estrone analogs were reversible; vinblastine was not reversible. Although estramustine and JE208 induced similar antiproliferative and morphological changes in glioblastoma cells that persisted for at least 4 days, there was a modest recovery of morphology and thymidine incorporation with JE208 after prolonged treatment. The common findings with estramustine and JE208 suggest that these agents may have a similar mechanism of action and form the basis for the investigation of new agents that may rapidly and reversibly inhibit glioblastoma.

Brain Neoplasms↗
PubMed1993

Synthesis of phytochelatins by the continuous flow solid phase procedure.

A nona- and an undecapeptide corresponding to phytochelatins with the general structure H-[gamma-Glu-Cys]n-Gly-OH were each synthesized by the continuous flow solid phase method using two different methodologies. Fmoc-amino acid derivatives were used as precursors, and two different H2N-POE-PS supports were employed. Different procedures were used to remove Acm protecting groups from Cys residues. In a second synthesis, Acm groups were removed before cleavage of the peptides from the polymer supports. The partially protected peptides of the first synthesis were purified by preparative HPLC. The purity and identity of all the synthesized peptides were verified by analytical HPLC and IS-MS and in some cases by amino acid analysis.

Amino Acids↗
PubMed1993

[Influence of lesion of motor cortex on second somatosensory area emanating descending modulation on thalamic intralaminar nuclei].

The present study was undertaken to verify further the participation of motor cortex (MCtx) in the somatosensory area II(SII) emanating descending modulation of thalamic intralaminar nuclei (ILN). Neuronal responses in ILN to noxious stimulation of the superficial peroneal nerve were extracellularly recorded in 34 cats. The effects of electrical stimulating SII on nociceptive responses of neurons in ILN before and after lesion of MCtx were observed and compared. It was shown that electrical stimulation of SII obviously inhibited the nociceptive responses in the majority of neurons recorded (11/13) in ILN in the cats with MCtx intact (P < 0.05). After lesion of MCtx the inhibitory effect still remained (n = 10, P < 0.05), but weakened to a certain extent compared with that before lesion. In the animals with the lesion involving MCtx and the underlying subcortical structures electrical stimulating SII facilitated the nociceptive responses of ILN neurons (n = 7, P < 0.05). The results further support the idea that SII emanating descending modulation on ILN is in part fulfilled via MCtx.

Animals↗
PubMed1993

[Effects of stimulation of SmI and electroacupuncture on nociceptive responses of the ventrobasal complex].

In order to confirm the idea that the cerebral cortex is involved in acupuncture analgesia through descending modulation, the effects of stimulation of SmI and electroacupuncture on nociceptive responses of VB neurons were investigated. The experiments were carried out on lightly anesthetized rats. Single unit activities of VB neurons were extracellularly recorded with glass microelectrodes. The results showed that both electrical stimulation of SmI (n = 11) and electroacupuncture at left. "Huantiao" (G30) point (n = 11) could inhibit the nociceptive responses of VB neurons and their effects were similar. These results suggested that SmI may play a role in acupuncture analgesia through corticofugal modulation on VB.

Animals↗
PubMed1993

Problems existing in differentiation therapy of acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA).

A large number of acute promyelocytic leukemia (APL) patients, treated with all-trans retinoic acid (ATRA) and chemotherapy, were studied. The results of the studies are as follows: (1) Among 65 patients investigated for the postremissional therapy, the 5-year survival probabilities were 0.20 +/- 0.13 (mean +/- SE) in the group treated with ATRA alone, 0.47 + 0.10 (mean +/- SE) in the group using chemotherapy alone and 0.42 +/- 0.09 (mean +/- SE) in the group treated with chemotherapy and ATRA. (2) The main severe adverse effects in the ATRA treatment include retinoic acid syndrome, renal failure, and thrombosis. These sequelae were observed more frequently in cases with persistent, marked elevation of white blood cell count without significant maturation of leukemic promyelocytes. (3) APL is not a homogeneous disease in that among 50 patients studied at the molecular level, although a PML-RARA fusion gene was detected in 45 cases, one had a variant translocation t(11;17) bearing fusion gene PLZF-RARA, one presented no obvious structural alteration of the PML gene while the RARA gene was rearranged, and three patients had no rearrangement of either PML or RARA genes. (4) Using RT/PCR to detect minimal residual disease, we found positive rates of 22%, 18.4%, and 11.5%, respectively, 12, 24, and 36 months after CR. This observation justifies the use of chemotherapy for at least 3 years after CR induced by ATRA. (5) It seems likely that the fusion gene PML-RARA plays an important role in APL leukemogenesis and in its response to the ATRA treatment.

Actuarial Analysis↗
PubMed1993

Cloning and structural analysis of calmodulin gene from rice.

Full-length cDNA encoding rice (Oryza sativa, cv. Nongken 58S) calmodulin (CaM) mRNA has been cloned using polymerase chain reaction (PCR) with synthesized primers from the sequence of barley CaM gene. Sequence analysis revealed that the rice gene is 450 bp in length that and its predicted polypeptide consists of 148 amino acids. It differs from those that of barley and alfalfa in only one position, respectively. The nucleotide homology between rice and barley is 90%, between rice and alfalfa is 88%, between rice and rat is 73%.

Amino Acid Sequence↗