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J Kang

Publications and source records attributed to J Kang.

At least 199 records · Page 11Linked to original sources
PubMed1995

In vivo responses of single olfactory receptor neurons in the channel catfish, Ictalurus punctatus.

1. We report for the first time in any teleost, a quantitative in vivo study of recordings from single olfactory receptor neurons (ORNs) in the channel catfish, Ictalurus punctatus, with odorant stimuli. 2. Responses of 69 spontaneously active single ORNs were recorded simultaneously with the electroolfactogram (EOG). Recording times ranged from 10 to 72 min per receptor cell with an average of 24 +/- 15 (SD) min/cell. The averaged spontaneous frequency ranged from < 1 to 12 action potentials/s with a mean frequency of 4.7 +/- 2.5 action potentials/s. 3. Catfish ORNs responded to the odorant stimuli (amino acids, bile salts, and ATP) with either an excitation or suppression of the background neural activity. Suppressive responses were encountered more frequently than excitatory responses, suggesting that suppressive responses also play an important role in olfactory coding. 4. Excitatory and suppressive responses to the different odorants were elicited from the same ORN, suggesting that different olfactory receptor molecules and different transduction pathways exist in the same ORN.

Adenosine Triphosphate↗
PubMed1995

Electrophysiological responses of single olfactory bulb neurons to amino acids in the channel catfish, Ictalurus punctatus.

1. Responses of 89 single olfactory bulb neurons from 43 channel catfish, Ictalurus punctatus, to amino acid odorants were recorded in vivo simultaneously with the electro-olfactogram (EOG). Recording time for individual neurons ranged from 16 to 344 min. The averaged spontaneous frequency ranged from < 1 to 16 action potentials/s with a mean frequency of 5.2 +/- 3.6 (SD) action potentials/s. 2. Histological examinations of carbocyanine dye 1,1'diocadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled olfactory bulbs and electrical stimulation of the olfactory tracts in a subset of experiments suggested that the majority of the recorded olfactory bulb neurons in this study were mitral cells. 3. Olfactory bulb neurons responded to amino acids with either an excitation or suppression of the background neural activity. Of the 337 stimulus applications, 28% of the responses were excitatory, and 33% were suppressive. The approximately 1:1 ratio of excitatory to suppressive responses for all stimulus applications suggests that suppressive responses also play important roles in the coding of odorant information in the channel catfish. 4. Responses of single olfactory bulb neurons were highly reproducible over time (up to 5 h). Responses to any amino acid never changed from excitation to suppression, or vice versa over time. 5. Single olfactory bulb neurons responded with excitation or suppression to more than one amino acid previously indicated to bind to independent receptors. 6. Estimated threshold concentrations for activation of an olfactory bulb neuron ranged from 10(-7) to 10(-3) M and were different from neuron to neuron for a particular stimulus and from stimulus to stimulus for a particular neuron. Responses of single olfactory bulb neurons to a given amino acid did not change from excitation to suppression, or vice versa, across different suprathreshold concentrations.

Amino Acids↗
PubMed1995

Electrophysiological responses of single olfactory bulb neurons to binary mixtures of amino acids in the channel catfish, Ictalurus punctatus.

1. For the first time in any vertebrate, responses of single olfactory bulb neurons to odorant mixtures were studied quantitatively in the channel catfish, Ictalurus punctatus. 2. Extracellular electrophysiological responses of 61 single olfactory bulb neurons from 36 channel catfish to binary mixtures of amino acids and to their components were recorded simultaneously with the electro-olfactogram (EOG). Tested were a total of 297 mixture trials consisting of 18 different stimulus pairs formed from 8 amino acids. 3. For 42% (126 of the 297) of the tests, no significant change (N) from spontaneous activity occurred. Responses to the remaining 171 tests of binary mixtures were excitatory (E; 29%) or suppressive (S; 29%). No response type was associated with any specific mixture across the neurons sampled. 4. Mixture interactions that changed response types (E or S) from those observed to the individual components were rare, because 89% of the responses of single olfactory bulb neurons to the tested binary mixtures were classified similarly as the responses to at least one of the components. 5. Responses of single olfactory bulb neurons were generally predictable for binary mixtures whose component responses were classified as both E, both S, and both N. For binary mixtures whose component responses were classified differently (e.g., one component evoked excitatory responses and the other evoked suppressive responses), the predictability of the response was dependent on the specific mixture type.

Amino Acids↗
PubMed1995

Metabolic and perceptual responses during arm and leg ergometry in water and air.

This investigation determined metabolic (i.e., kcal.min-1) responses and ratings of perceived exertion (RPE) for varying pedal-crank rates (PCR) and power outputs (PO) during arm and leg exercise in thermoneutral air (TA) and water (TW). Nine males (age 28.2 yr; leg cycle VO2peak 3.4 l.min-1) undertook the 24 exercise trials. During the TW trials kcal.min-1 were less (P < 0.05): at 50 W for 40 (X +/- SE; 10.9 +/- 0.8) than 50 (8.2 +/- 0.2), 60 (8.2 +/- 0.6), or 70 (7.4 +/- 0.3) rev.min-1 and at 100 W for 40 (15.2 +/- 0.7), 50 (14.0 +/- 1.1), and 60 (13.8 +/- 0.7) than 70 (12.1 +/- 0.5) rev.min-1. All other comparisons of kcal.min-1 between PCR at the three PO were not significant. During the TA trials kcal.min-1 were less (P < 0.05): at 50 W for 40 (11.4 +/- 0.3) than 60 (9.7 +/- 0.4) and 70 (9.1 +/- 0.4) rev.min-1 and for 50 (11.0 +/- 0.5) than 70 rev.min-1. During the TW trials: RPE-Arms and RPE-Overall at 50 W were lower (P < 0.05) for 40 (8.1 +/- 0.5; 8.3 +/- 0.4) than 60 (9.6 +/- 0.5; 9.8 +/- 0.6) and 70 (9.3 +/- 0.5; 9.9 +/- 0.7) rev.min-1, RPE-Legs at 50 W was lower (P < 0.05) for 40 (8.3 +/- 0.4) than 70 (9.9 +/- 0.7) rev.min-1. All other comparisons of RPE between PCR at the three PO were not significant.

Adult↗
PubMed1995

[Determination of tuberculostearic acid for diagnosis of tuberculous meningitis with negative culture of tubercle bacillus].

Tuberculostearic acid, a structural component of Mycobacterium tuberculosis, was identified by gas chromatography in cerebrospinal fluid from 44 out of 59 patients with tuberculous meningitis. Tuberculostearic acid was found in the cerebrospinal fluid of 5 patients out of 112 with non-tuberculous meningitis or non-infectious disorders. The results showed the test had a sensitivity of 74.6% and a specificity of 95.9%. Detection of tuberculostearic acid in cerebrospinal fluid is a rapid, sensitive and specific test for tuberculous meningitis.

Adolescent↗
PubMed1994

Conserved amino acid residues in the complementarity-determining region 1 of the TCR beta-chain are involved in the recognition of conventional Ag and Mls-1 superantigen.

Superantigens activate T cells by interacting primarily with the V beta region of the TCR. This report describes a series of studies performed to elucidate the role of the conserved amino acid motif (Asp-His-Asn) in the complementarity-determining region 1 (CDR1) of the TCR V beta chains that recognize murine endogenous superantigen Mls-1. By using site-directed mutagenesis of the Mls-1-reactive TCR V beta 6 gene, it is shown that the alterations of the conserved CDR1 motif disrupt Mls-1 superantigen and conventional Ag recognition in vitro. The loss of V beta 6 (mutant)+ TCR reactivity to Mls-1 superantigen is apparently dependent on the partner alpha-chain in the V beta 6/V alpha 3 TCR pairing shows some reactivity to Mls-1, whereas other TCR pairings do not. The examination of the developmental fate of the mutated form of the V beta 6 chain in Mls-1+ mice by using retroviral vector-mediated gene transfer confirms the critical role played by the CDR1 residues in Mls-1 recognition in vivo. Collectively, the results indicate that the CDR1 of the TCR V beta 6 chain is involved in interacting with peptide/MHC as well as in Mls-1 recognition. The observation that the conserved residues in selective TCR V beta chains are imparting a significant contribution to Ag recognition suggests a molecular basis for the intrinsic bias of some V beta chains for MHC molecules.

Amino Acid Sequence↗
PubMed1994

Exogenous Mtv-7 superantigen transgene expression in major histocompatibility complex class II I-E- mice reconstituted with embryonic stem cell-derived hematopoietic stem cells.

Direct genetic manipulation of hematopoietic cells is limited by the lack of an established hematopoietic stem cell line. It has been demonstrated that embryonic stem (ES) cell<-->tetraploid embryos are completely ES cell-derived and that fetal liver (FL) cells from these embryos support hematopoiesis in lethally irradiated recipients. In this report, we demonstrate that FL cells from ES cell<-->tetraploid embryos support normal lymphopoiesis and T-cell repertoire development. Moreover, the introduction of the Mtv-7 superantigen transgene coding for minor lymphocyte stimulatory antigen 1 into murine hematopoietic cells via reconstitution with ES cell<-->tetraploid FL cells demonstrates that this method can effectively confer stable genetic changes into the hematopoietic tissues without going through the germ line. Long-term and secondary reconstitution with ES cell<-->tetraploid FL cells expressing the Mtv-7 superantigen transgene clonally deleted minor lymphocyte stimulatory antigen 1-reactive T-cell receptor V beta 6+, -8.1+, and -9+ T cells, but not V beta 7+ T cells, in H-2b (I-E-) mice. This model system will be extremely important for analyzing structure-function relationships of molecules involved in proliferation, differentiation, and selection of hematopoietic cells in vivo and for examining hematopoiesis-specific effects of mutations that are lethal during embryogenesis.

Animals↗
PubMed1994

Expression of Mtv-7 sag gene in vivo using a retroviral vector results in selective inactivation of superantigen reactive T cells.

T cells expressing specific TCR V beta chains are intrathymically eliminated in mice expressing the murine Mls (minor lymphocyte stimulating) superantigens. Recently, in vitro studies have shown that the endogenous mouse mammary tumor virus (MMTV)-7 sag gene encodes Mls-1 Ag. The demonstrated ability of MMTV superantigen proteins to react with TCRs has led to the postulate that other infectious retroviruses may use superantigen-like molecules to modify the host's immune system. In this report, successful retrovirus-mediated Mtv-7 sag gene transfer into pluripotent hematopoietic stem cells is described. In two different strains of Mls-1- host mice (CBA/Ca and BALB/c) reconstituted with Mtv-7 sag gene expressing bone marrow cells, low levels of ectopic Mtv-7 sag gene expression on syngeneic donor hematopoietic stem cell-derived population alone can induce partial clonal deletion of Mls-1 reactive V beta 6+ and V beta 8.1+ T cells, and complete clonal inactivation of V beta 8.1+ T cells.

Animals↗
PubMed1994

Receptor-mediated effects of angiotensin II on neurons.

Aside from its well-known and numerous actions at peripheral tissues, the octapeptide angiotensin II (ANG II) elicits specific receptor-mediated effects within the central nervous system. In this review we focus on the receptor-mediated actions of ANG II on neurons. The distribution of ANG II receptors in the brain and physiological, electrophysiological, and cellular effects mediated by these receptors are discussed. This is extended to a review of the characteristics of ANG II receptor subtypes on cultured neurons and the cellular and genomic actions mediated by these receptors. Finally, we develop this information into speculative models for the cellular effects mediated by each ANG II receptor subtype in neurons.

Angiotensin II↗
PubMed1994

Coagulation profile as a predictor for post-tonsillectomy and adenoidectomy (T + A) hemorrhage.

The risk of hemorrhage after tonsillectomy and adenoidectomy (T + A) was studied in 1061 children. Twenty-seven (2.5%) had at least one abnormality on a preoperative coagulation profile consisting of a prothrombin time (PT), partial thromboplastin time (PTT), bleeding time (BT) and platelet count (PC). Of these 27 who had an initially abnormal test (PTT or bleeding times only), 8 had diagnosed coagulopathies by hematology evaluation (Group A), and 17 had repeat tests which returned to normal (Group B). Two borderline tests (PTT) were not repeated (Group C). Sixty-four patients (6.0%) bled after T + A. Six of these (9.3%) had an initially abnormal coagulation profile--one in Group A (12.5%), four in Group B (23.5%) and 1 in Group C (50%). This is in contrast to the bleed rate of 5.7% for the 1034 children with normal coagulation profiles. Although it is not surprising that 6 (22.2%) children with an initially abnormal coagulation profile bled, of note is that 4 of them had an initially abnormal coagulation profile which upon repeat testing returned to normal. However, none of these four bleeders required active intervention for control. Coagulopathies were newly diagnosed in 7 (0.57% of total group; 25.9% of 27 with abnormal laboratory values). One additional child had a known intrinsic platelet dysfunction prior to surgery. Only one child was newly identified by a positive family history for abnormal bleeding. These results suggest that new hematologic disorders were diagnosed infrequently. An initially abnormal coagulation profile may identify those more likely to bleed after surgery (22.6% vs. 5.5%). A coagulation profile which includes a PTT and BT may be a valuable screening tool for children undergoing T + A.

Adenoidectomy↗
PubMed1994

Angiotensin II type 2 receptor stimulation of neuronal K+ currents involves an inhibitory GTP binding protein.

Angiotensin II (ANG II) elicits an ANG II type 2 (AT2) receptor-mediated increase in outward K+ current (IK; delayed rectifier K+ current) in neurons cocultured from rat hypothalamus and brain stem. Here we have shown that the AT2-receptor-mediated stimulation of neuronal IK by ANG II (100 nM) was abolished by pretreatment of cultures with pertussis toxin (PTX; 200 ng/ml) and by intracellular application of an antibody against the inhibitory guanine nucleotide (GTP) binding protein (anti-Gi alpha, 1:200). Antibodies against other GTP binding proteins (anti-Go alpha, 1:50 and 1:200; anti-Gq/11 alpha, 1:200) did not alter the AT2-receptor-mediated stimulation of neuronal IK by ANG II (100 nM). Furthermore, this effect of ANG II (100 nM) was inhibited by the serine/threonine phosphatase inhibitor okadaic acid (1-10 nM) and by anti-type 2A protein phosphatase (PP2A) antibodies but not by the tyrosine phosphatase inhibitor sodium orthovanadate (1 mM). Thus we have identified key components (Gi and PP2A) of the signal transduction pathway that is responsible for the AT2-receptor-mediated stimulation of neuronal K+ currents.

Animals↗
PubMed1994

Calcium-modulated inward rectification of a calcium-activated potassium channel in neurons.

1. Inward rectification of a calcium-activated K+ channel in neurons cultured from the hypothalamus and brain stem of 1-day-old rats was studied by using patch-clamp techniques. A big conductance calcium-activated K+ channel with a slow gating rate was observed in inside-out patches. With symmetrical K+ across patches, inward conductance of this calcium-activated K+ channel was 216 +/- 14 (SE) pS (n = 4 patches), which changed little as different [Ca2+] was included in the bath solution. Outward conductance of this calcium-activated K+ channel was regulated by [Ca2+] in the bath solution and was 74 +/- 15 pS with 500 microM Ca2+. The higher level of Ca2+ on the intracellular side of the membrane caused the larger degree of rectification. Mg2+ only had a minor effect on rectification of this calcium-activated K+ channel.

Animals↗