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Biomedical subjects

J Jin

Publications and source records attributed to J Jin.

At least 145 records · Page 8Linked to original sources
PubMed1996

Stabilization of a HemA-LacZ hybrid protein against proteolysis during carbon starvation in atp mutants of Salmonella typhimurium.

Transposon insertions that stabilize the beta-galactosidase activity of a HemA-LacZ hybrid protein following carbon starvation were mapped to the atp operon of Salmonella typhimurium. This effect is similar to that seen with nuo mutants defective in the energy-conserving type I NADH dehydrogenase. Insertions in several other genes, including such highly pleiotropic mutants as rpoS, polA, and hfq, were isolated with the same phenotypic screen, but they do not affect the beta-galactosidase activity of HemA-LacZ. All of these mutants act indirectly to alter the colony color of many different fusion strains on indicator plates.

Aldehyde Oxidoreductases↗
PubMed1996

Role of tyrosine phosphorylation in radiation-induced cell cycle-arrest of leukemic B-cell precursors at the G2-M transition checkpoint.

Here we provide experimental evidence that ionizing radiation induces inhibitory tyrosine phosphorylation of the p34cdc2 kinase in human leukemic B-cell precursors. Herbimycin A markedly reduced tyrosine phosphorylation of p34cdc2 in irradiated leukemic B-cell precursors, thereby preventing radiation-induced cell cycle arrest at the G2-M transition checkpoint. Thus, tyrosine phosphorylation is directly responsible for the inactivation of p34cdc2 in irradiated human leukemic B-cell precursors and activation of protein tyrosine kinases is a proximal and mandatory step in radiation-induced G2-arrest arrest at the G2-M checkpoint. Human WEE1 kinase isolated from unirradiated or irradiated leukemic B-cell precursors had minimal tyrosine kinase activity towards p34cdc2. We detected no increase of human WEE1 kinase activity after radiation of leukemic B-cell precursors, as measured by (a) autophosphorylation, (b) tyrosine phosphorylation of a synthetic peptide derived from the p34cdc2 amino-terminal region or (c) recombinant human p34cdc2-cyclin B complex. Thus the signaling pathway leading to inhibitory tyrosine phosphorylation of p34cdc2 and G2-arrest in irradiated human leukemic B-cell precursors functions independent of p49 WEE1 HU and enzymes which augment the tyrosine kinase activity of p49 WEE 1HU.

B-Lymphocytes↗
PubMed1996

Role of hydroxyl radicals in radiation-induced activation of lyn tyrosine kinase in human B-cell precursors.

Here we show that exposure of human B-cell precursors to gamma-rays stimulates the enzymatic activity of the Src protooncogene family protein tyrosine kinase LYN. LYN activation in irradiated cells is not triggered by DNA damage or a nuclear signal since gamma-rays effectively stimulated LYN kinase in enucleated B-cell precursors as well. LYN activation in irradiated cells was abrogated by presence of the OH* radical scavenger dimethylsulfoxide and exposure of intact or enucleated B-cell precursors to chemically generated OH* radicals instead of gamma-rays also triggered LYN kinase activation and enhanced tyrosine phosphorylation of multiple electrophoretically distinct protein substrates. Thus, OH* radicals appear to be both mandatory and sufficient for radiation-induced LYN kinase activation in irradiated B-cell precursors. We further present evidence which indicates that OH* radicals activate LYN by a novel mechanism which involves disruption of inactive LYN-LYN homodimers and monomerization of the LYN kinase after proteolytic degradation of a putative LYN-associated adapter protein through a cytoplasmic TPCK-sensitive chymotrypsin-like protease following its oxidation. LYN kinase plays a pivotal role in initiation of signal cascades that affect the proliferation, differentiation, and survival of B-cell precursors. Our results prompt the hypothesis that a growth regulatory balance might be altered in human B-cell precursors by radiation-induced stimulation of LYN kinase.

B-Lymphocytes↗
PubMed1996

[The pulmonary function in scoliotic patient].

This paper investigated preoperative pulmonary functions in 134 scoliotic patients, of whom 32 cases was followed up for their postoperative pulmonary functions. The results show that the bigger the Cobb of the scoliosis, the greater the damages of the pulmonary functions. Congenital scoliosis is more severely affected by pulmonary functions than idiopathic scoliosis. There was no significant difference among the different sections of scoliosis with regard to their effect on the pulmonary functions. The authors concluded that the Harrington Instrumentation improved pulmonary functions in scoliosis.

Adolescent↗
PubMed1996

Three-dimensional modeling for modern diagnosis and planning in maxillofacial surgery.

The existing methods of recording the face in three dimensions are reviewed, and a new method for three-dimensional facial modeling is introduced. The technique utilizes two stereo pairs of videocameras, a stereo pair at each side of the patient's face. The system allows rapid capture of the face in three dimensions and precise measurement of anatomic landmarks. The system can be used to capture the facial image and a cephalogram almost simultaneously, allowing more accurate superimposition of soft and hard tissues. This precision will facilitate development of the surgical treatment plan. A computer program in the early stages of development will use the data generated by this biostereometric measurement system to predict soft tissue changes following orthognathic surgery.

Cephalometry↗
PubMed1995

Studies on mu and delta opioid receptor selectivity utilizing chimeric and site-mutagenized receptors.

Opioid receptors are members of the guanine nucleotide binding protein (G protein)-coupled receptor family. Three types of opioid receptors have been cloned and characterized and are referred to as the delta, kappa and mu types. Analysis of receptor chimeras and site-directed mutant receptors has provided a great deal of information about functionally important amino acid side chains that constitute the ligand-binding domains and G-protein-coupling domains of G-protein-coupled receptors. We have constructed delta/mu opioid receptor chimeras that were express in human embryonic kidney 293 cells in order to define receptor domains that are responsible for receptor type selectivity. All chimeric receptors and wild-type delta and mu opioid receptors displayed high-affinity binding of etorphine (an agonist), naloxone (an antagonist), and bremazocine (a mixed agonist/antagonist). In contrast, chimeras that lacked the putative first extracellular loop of the mu receptor did not bind the mu-selective peptide [D-Ala2,MePhe4,Gly5-ol]enkephalin (DAMGO). Chimeras that lacked the putative third extracellular loop of the delta receptor did not bind the delta-selective peptide, [D-Ser2,D-Leu5]enkephalin-Thr (DSLET). Point mutations in the putative third extracellular loop of the wild-type delta receptor that converted vicinal arginine residues to glutamine abolished DSLET binding while not affecting bremazocine, etorphine, and naltrindole binding. We conclude that amino acids in the putative first extracellular loop of the mu receptor are critical for high-affinity DAMGO binding and that arginine residues in the putative third extracellular loop of the delta receptor are important for high-affinity DSLET binding.

Amino Acid Sequence↗
PubMed1995

Nerve-mast cell interaction in normal guinea pig urinary bladder.

Urinary bladders of normal adult female guinea pigs were analyzed for anatomical evidence of nerve-mast cell interaction using light microscopy and electron microscopy. Nerves, ganglia, and individual nerve fibers were visualized on paraffin sections using immunohistochemistry with antisera against the neural antigens neurofilament protein and protein gene product 9.5, and sections were also immunoreacted with antisera against the neuropeptides substance P and calcitonin gene-related peptide. Separate mast cell populations were identified by counterstaining with toluidine blue and alcian blue. Mast cells of both types were found within nerves and intramural ganglia and were in close contact with individual nerve fibers displaying substance P- and calcitonin gene-related peptide-like immunoreactivity. Moreover, serotonin-immunoreactive mast cells were innervated with nerve fibers that reacted with antiserum against vasoactive intestinal polypeptide. At the ultrastructural level, these fibers were almost exclusively identified as unmyelinated primary sensory afferents. Mast cells contacted these fibers with lamellipodia that wrapped around and enclosed the fibers deeply within the cell. Close association between mast cells, nerves, and vessels was common. Ultrastructural evidence suggests that bidirectional communication occurs between nerve fibers and mast cells. These structures may participate in axon reflexes that regulate normal vascular and detrusor smooth muscle function and cause vasodilation, edema, inflammation, and bladder hyperreactivity. In summary, a close relationship exists between mast cells and peptidergic nerve fibers, including primary sensory afferents. Results suggest that bidirectional interaction could occur between nerves and mast cells.

Animals↗
PubMed1995

Exposure of B-lineage lymphoid cells to low energy electromagnetic fields stimulates Lyn kinase.

Here, we present evidence that exposure of B-lineage lymphoid cells to low energy electromagnetic fields (EMF) stimulates the protein tyrosine kinases Lyn and Syk, results in tyrosine phosphorylation of multiple electrophoretically distinct substrates, and leads to downstream activation of protein kinase C (PKC). EMF exposure enhances protein tyrosine phosphorylation in Syk deficient but not in Lyn-deficient B-lineage lymphoid cells and stimulates Lyn kinase activity in wild-type as well as Syk-deficient B-lineage lymphoid cells. These results indicate that activation of Lyn kinase is sufficient and mandatory for EMF-induced tyrosine phosphorylation in B-lineage lymphoid cells. The PKC activity increases later than the Lyn activity and pretreatment with the PTK inhibitors genistein or herbimycin A abrogates the EMF-induced PKC signal. Thus, stimulation of Lyn is a proximal and mandatory step in EMF-induced activation of PKC in B-lineage lymphoid cells. Our observations prompt the hypothesis that a delicate growth regulatory balance might be altered in B-lineage lymphoid cells by EMF-induced activation of Lyn.

Amino Acid Sequence↗
PubMed1995

In vitro and in vivo activity of topotecan against human B-lineage acute lymphoblastic leukemia cells.

Topotecan [(S)-9-dimethylaminomethyl-10-hydroxycamptothecin hydrochloride; SK&F 104864-A, NSC 609699], a water soluble semisynthetic analogue of the alkaloid camptothecin, is a potent topoisomerase I inhibitor. Here we show that topotecan stabilizes topoisomerase I/DNA cleavable complexes in radiation-resistant human B-lineage acute lymphoblastic leukemia (ALL) cells, causes rapid apoptotic cell death despite high-level expression of bcl-2 protein, and inhibits ALL cell in vitro clonogenic growth in a dose-dependent fashion. Furthermore, topotecan elicited potent antileukemic activity in three different severe combined immunodeficiency (SCID) mouse models of human poor prognosis ALL and markedly improved event-free survival of SCID mice challenged with otherwise fatal doses of human leukemia cells at systemic drug exposure levels that can be easily achieved in children with leukemia.

Adolescent↗
PubMed1995

Efficacy and pharmacokinetics of two formulations of cyclosporine A in patients with psoriasis.

The efficacy and pharmacokinetic profiles of two oral formulations of cyclosporine A (Sandimmune and Neoral; Sandoz Pharmaceuticals, East Hanover, NJ) were evaluated in 37 patients with moderate to severe plaque psoriasis in a randomized, double-blind, modified, crossover study. Cyclosporine A (150 mg twice daily), administered in either formulation, reduced the severity of plaque lesions: 94% of all patients reported at least moderate improvement and 70% reported complete clearing. Approximately 2 weeks of therapy were required for drug exposure to stabilize on either formulation. Cyclosporine A exposure from Neoral was significantly greater relative to that from Sandimmune across all study weeks. At the eighth week (before crossover), AUC and Cmax values for Neoral and Sandimmune were 5618 +/- 1705 versus 3202 +/- 596 ng.h/mL and 1283 +/- 337 versus 623 +/- 173 ng/mL, respectively. In crossover analysis at steady state, the relative oral bioavailability of cyclosporine from the Neoral formulation was 54% greater than that from Sandimmune. Some pharmacokinetic parameters showed less variability both between and within groups of patients taking Neoral versus Sandimmune. Both formulations were well tolerated, in that most adverse events were of mild severity.

Chemistry, Pharmaceutical↗
PubMed1995

Tritium labelling of amino sugars at C-2 by alkaline epimerization in tritiated water.

N-Acetyl-D-[2-3H]glucosamine was synthesized from N-acetyl-D-mannosamine by alkaline 2-epimerization in pyridine containing 3H2O and nickelous acetate. The reaction involves reversible formation of an enol intermediate and therefore also resulted in incorporation of tritium into N-acetylmannosamine. After completed reaction, the two N-acetylhexosamines were separated from other radioactive products and Morgan-Elson chromogens by chromatography on a column of Sephadex G-10, which was eluted with 10% ethanol, and were then separated from each other by chromatography on Sephadex G-15 in 0.27 M sodium borate (pH 7.8). The location of the incorporated tritium was established by treatment of the N-acetylhexosamines with borate under the conditions of the Morgan-Elson reaction, which converts the sugars to Kuhn's chromogen I with concomitant loss of the C-2 hydrogen. As expected, this treatment resulted in the formation of 3H2O, indicating that the tritium was located at C-2. [2-3H]Glucosamine was prepared by acid hydrolysis of the labelled N-acetylglucosamine and was converted to [2-3H]glucosamine 6-phosphate by incubation with hexokinase and ATP. The sugar phosphate was used as a substrate for glucosamine 6-phosphate deaminase (isomerase, EC 5.3.1.10) in a simple 3H2O release assay.

Acetylglucosamine↗