Biomedical subjects

J S Li

Publications and source records attributed to J S Li.

At least 73 records · Page 4Linked to original sources

PubMed1999

Modulation of the glycine response by Ca2+-permeable AMPA receptors in rat spinal neurones.

1. In acutely isolated rat sacral dorsal commisural nucleus (SDCN) neurones, application of kainate (KA) reversibly potentiated glycine-evoked Cl- currents (IGly) in a concentration-dependent manner. 2. The cellular events underlying the interaction between non-NMDA receptors and glycine receptors were studied by using nystatin-perforated patch and cell-attached single-channel recording modes. 3. The action of KA was not accompanied by a shift in the reversal potential for IGly. In dose-response curves, KA potentiated IGly without significantly changing glycine binding affinity. 4. GYKI 52466 blocked while NS-102 had no effect on the KA-induced potentiation of IGly. 5. The potentiation was reduced when KA was applied in a Ca2+-free extracellular solution or in the presence of BAPTA AM, and was independent of the activation of voltage-dependent Ca2+ channels. 6. Pretreatment with KN-62, a selective Ca2+-calmodulin-dependent protein kinase II (CaMKII) inhibitor, abolished the action of KA. Inhibition of calcineurin converted the KA-induced potentiation to a sustained one. 7. Single-channel recordings revealed that KA decreased the mean closing time of glycine-gated single-channel activity, resulting in an increase in the probability of channel opening. 8. It is proposed that Ca2+ entry through AMPA receptors modulates the glycine receptor function via coactivation of CaMKII and calcineurin in SDCN neurones. This interaction may provide a new postsynaptic mechanism for control of inhibitory synaptic signalling and represent one of the important regulatory mechanisms of spinal nociception.

Animals↗

PubMed1999

Meta-analysis on the association between environmental tobacco smoke (ETS) exposure and the prevalence of lower respiratory tract infection in early childhood.

The aim of this study was to obtain quantitative information from published data on the association between environmental tobacco smoke (ETS) exposure and the prevalence of serious lower respiratory tract infections (LRTI) in infancy and early childhood. We identified 21 relevant publications on the relation between ETS and the prevalence of serious LRTI by reviewing reference lists in relevant reports and by conducting manual and computer searches (Medline database; Dissertation abstracts index of Xerox University Microfilms) of published reports between 1966 and 1995. Thirteen studies were included in a quantitative overview using random effects modeling to derive pooled odds ratios. Sensitivity analyses were conducted to test the decision rules used in extracting odds ratio data. The results of community and hospital studies are broadly consistent and show that the child of a parent who smokes is at approximately twice the risk of having a serious respiratory tract infection in early life that requires hospitalization. This association was pronounced in children younger than age two and diminished after the age of two. The combined odds ratio for hospitalization for lower respiratory tract infections in infancy or early childhood is 1.93 (95% CI 1.66-2.25); the combined odds ratio of prevalence of serious LRTI at age less than 2 years, between 0 and 6 years, and between 3 and 6 years were 1.71 (95% CI 1.33-2.20); 1.57 (1.28-1.91), and 1.25 (0.88-1.78), respectively. There was no evidence of heterogeneity across the studies in these combined odds ratios. We conclude that this meta-analysis provides strong evidence that exposure to ETS causes adverse respiratory health outcomes such as either a serious LRTI or hospitalization for LRTI. New public health campaigns are urgently needed to discourage smoking in the presence of young children.

Age Distribution↗

PubMed1999

Glycyl-glutamine-enriched long-term total parenteral nutrition attenuates bacterial translocation following small bowel transplantation in the pig.

BACKGROUND: Improvements in immunosuppression, operative procedure, and posttransplant management have made clinical small bowel transplantation (SBT) feasible. Ischemia and reperfusion injury, total parenteral nutrition (TPN), and devoidment of enteral feeding lead to graft atrophy, gut barrier dysfunction, and bacterial translocation. Glutamine (Gln) is the principal fuel for the enterocyte. The influence of Gln dipeptide-supplemented TPN, especially long-term TPN, on intestinal graft permeability and bacterial translocation is not clear following SBT in the large animal model. Therefore, we studied the effect of glutamine dipeptide, glycyl-glutamine (Gly-Gln), on bacterial translocation following SBT in the pig, which has a physiology similar to humans. MATERIALS AND METHODS: The outbred pigs underwent segmental small bowel autotransplantation and were divided into two groups. In the STPN group (n = 5), the animal received standard TPN devoid of Gly-Gln for 28 days. In the GTPN group (n = 5), the animal received isonitrogenous (0.3 g/kg.day) and isocaloric (33 kcal/kg.day) TPN solution with 2% Gly-Gln for 28 days. RESULTS: At the end of the experiment, Gly-Gln-enriched TPN could maintain the plasma Gln level, graft mucosal Gln and protein concentrations, and skeletal muscle Gln and protein concentrations. Gly-Gln-enriched TPN significantly decreased the bacterial number of mesenteric lymph nodes in the liver and spleen and intestinal permeability to 99mTc-DTPA. There were no significant differences in body weight gain. CONCLUSIONS: The Gly-Gln-enriched long-term TPN may maintain the plasma Gln level, mucosal and muscle Gln, and protein concentrations and attenuate the intestinal permeability to 99mTc-DTPA and bacterial translocation following small bowel transplantation in the pig.

Animals↗

PubMed1999

Enhanced learning by posttrial injection of H1-but not H2-histaminergic antagonists into the nucleus basalis magnocellularis region.

The aim of this study was to examine the effects of histaminergic antagonists on memory upon injection into the region of the nucleus basalis magnocellularis (NBM). In experiment 1, rats with chronically implanted cannulae were trained on the uphill avoidance task, which involves a punishment of a high-probability turning response on a tilted platform (negative geotaxis). Immediately after the training trial, that is, after a tail shock was administered upon performing the response, rats received one microinjection (0.5 microliter) of H1-receptor blocker chlorpheniramine (dose range 0.1 to 20 microgram) or the H2-receptor blocker ranitidine (same dose range) or saline into the NBM region. When tested 24 h later, rats treated with chlorpheniramine (20 micrograms) had significantly longer uphill latencies than vehicle controls and ranitidine-treated animals, indicative of superior learning of the avoidance response. In experiment 2, a test for possible proactive effects of posttrial chlorpheniramine on performance during the retention trial was performed. Animals were injected with either 20 micrograms chlorpheniramine or saline immediately after the training trial of the uphill task. One chlorpheniramine control group was treated with a delay of 5 h. Additional groups which received chlorpheniramine or vehicle after the training trial but no trail shock were included. When tested 24 h later, rats injected with 20 micrograms chlorpheniramine again exhibited significantly longer uphill latencies than did vehicle-injected rats. Retention latencies for the rats of the chlorpheniramine 5-h delayed group did not differ from those of the vehicle-injected rats, ruling out proactive effects of chlorpheniramine on performance. In summary, the histaminergic H1-blocker chlorpheniramine can enhance mnemonic functioning in addition to its reinforcing effects upon NBM injection as reported previously.

Animals↗

PubMed1999

Deterministic properties of apnoeas in an abdominal breathing signal.

The paper describes a general set of properties that represent most apnoeas as found in an abdominal breathing signal. An apnoea is a pause in breathing during sleep, and only central apnoeas in infants are considered. Human experts are consulted to determine what properties of the signal they use to recognise apnoeas. A set of deterministic, or shape, properties is developed to represent expert opinion. An apnoea is modelled as a flat region with four properties: flatness, duration, thinness and smoothness. Mathematical descriptions of each property are formulated that discriminate between apnoea and non-apnoea events, and each description is tested for discrimination and independence. The average power of discrimination is 24% +/- 16% and the average correlation coefficient is 0.28 +/- 0.16. Applications include scoring apnoeas for sleep studies and developing standard definitions of apnoeas.

Algorithms↗

PubMed1999

Distribution of double-negative (CD4- CD8-, DN) T subsets in blood and synovial fluid from patients with rheumatoid arthritis.

Double-negative (CD4- CD8-) T (DNT) cells have been postulated to be potentially autoreactive. However, the role of DNT cells in rheumatoid arthritis (RA) has received limited attention. We investigated the distribution of DNT subsets in peripheral blood (PB) and synovial fluid (SF) from patients with active RA to determine whether these cells have relevance to RA. Two-colour flow cytometric analysis was performed to detect DNT cells in PB from 35 RA patients, 26 healthy controls and in SF aspirated from 19 inflamed rheumatoid joints. The subsets of DNT cells, i.e those expressing T cell receptor alphabeta (alphabeta DNT) or gammadelta (gammadelta DNT) were simultaneously examined. Our results showed that DNT cells constituted a very minor subset of PB lymphocytes. When expressed as a percentage of total lymphocytes, alphabeta DNT levels in normal individuals ranged from 0.27 to 2.08% (average 0.76%), while those of gammadelta DNT ranged from 1.02 to 11.42% (average 3.23%). Compared with normal individuals, RA patients had a similar distribution of alphabeta DNT cells in both PB and SF. However, RA patients had significantly lower levels of gammadelta DNT cells in PB than control subjects (1.38 +/- 1.08% vs 3.23 +/- 2.12%, p<0.05), while the levels of gammadelta DNT cells in SF of RA patients were higher than those in PB from RA patients and normal controls. The difference between PB and SF in RA was statistically significant (3.90 +/- 1.88% vs 1.38 +/- 1.08%, p<0.05). A higher level of gammadelta DNT in SF than their paired PB was consistently noted from nine available paired samples. Our findings suggest that gammadelta NT cells, but not alphabeta DNT cells, are probably relevant to RA. The lower percentage of circulating gammadelta DNT cells might have resulted from migration from the circulation into the synovium, suggesting a role for gammadelta DNT cells in the pathogenesis of rheumatoid synovitis.

Adult↗

PubMed1999

Functional properties of ionotropic glutamate receptor channels in rat sacral dorsal commissural neurons.

Nystatin perforated patch and conventional whole-cell recording configurations were used to characterize the properties of ionotropic glutamate receptor (GluR) channels in neurons freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN). L-Glutamate (Glu), N-methyl-D-aspartate (NMDA), quisqualate (QA), alpha-amino-3-hydroxy-5-methyl-4-isoxazoleprop ionate (AMPA) and kainate (KA) applied via a Y-tube produced inward currents at -44 mV which increased in a concentration-dependent manner; they desensitized when induced at higher concentrations except for the KA-induced current (IKA). (1S-3R)1-amino-cyclopentane-1,3-dicarboxylate (1S-3R-ACPD) evoked no response. The EC50 and Hill coefficient (nH) values of the GluR responses were 3.3 x 10(-5) M, 0.74 for Glu; 9.0 x 10(-5) M, 0.83 for NMDA; 6.4 x 10(-7) M, 1.30 for QA; 1.3 x 10(-4) M, 1.10 for AMPA and 9.6 x 10(-5) M, 1.30 for KA, respectively. The reversal potentials of the GluR responses were all near 0 mV. The 6-Cyano-7-nitroquinoxaline-2-3-dione (CNQX) and D-2-amino-5-phosphonovalerate (D-APV) suppressed the non-NMDA and NMDA responses in a concentration-dependent manner, respectively. Cyclothiazide strongly potentiated both KA- and AMPA-induced responses while concanavalin A potentiated both the responses to a much lesser degree. NS-102 produced no significant effect on either KA- or AMPA-activated currents, while GYKI 52466 reversibly blocked both the currents. The Ca2+ permeabilities (PCa/PCs) of the NMDA and AMPA receptor channels were 8.33 and 1.23, respectively. In addition, the current-voltage (I-V) relationship of IKA showed little rectification. There was a poor correlation between the Ca2+ permeability and the shape of the I-V curves of IKA. These results suggest that rat SDCN neurons possess NMDA and non-NMDA receptor channels, and express AMPA type receptors with unique properties (slow desensitization to AMPA, high Ca2+ permeability but lack of inward rectification). These ionotropic receptor channels may play important roles in mediating and regulating pelvic visceral information including nociception.

Animals↗

PubMed1999

Alpha2-adrenoceptor-mediated enhancement of glycine response in rat sacral dorsal commissural neurons.

The effect of noradrenaline on the glycine response was investigated in neurons acutely dissociated from the rat sacral dorsal commissural nucleus using nystatin perforated patch recording configuration under voltage-clamp conditions. Noradrenaline reversibly potentiated the 10(-5)M glycine-induced Cl- current in a concentration-dependent manner. Single channel recordings in a cell-attached mode revealed that noradrenaline decreased the closing time of the glycine-activated channel activity. Noradrenaline neither changed the reversal potential of the glycine response nor affected the affinity of glycine to its receptor. Clonidine mimicked and yohimbine blocked the noradrenaline action on glycine response. N-[2(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride, protein kinase A inhibitor, mimicked the effect of noradrenaline on glycine response. Noradrenaline failed to affect the glycine response in the presence of these intracellular cyclic AMP and protein kinase A modulators. However, noradrenaline further enhanced the glycine response even in the presence of phorbol-12-myristate-13-acetate and chelerythrine, a protein kinase C inhibitor. Pertussis toxin treatment for 6-8 h blocked the noradrenaline facilitatory effect on the glycine response. In addition, noradrenaline potentiated the strychnine-sensitive postsynaptic currents evoked in a slice preparation of sacral dorsal commissural nucleus. These results suggest that the activation of alpha2-adrenoceptor by noradrenaline coupled with pertussis toxin-sensitive G-proteins reduces intracellular cyclic AMP formation through the inhibition of adenyl cyclase. The reduction of cyclic AMP decreases the protein kinase A activity, thus resulting in the potentiation of the glycinergic inputs to the sacral dorsal commissural neurons. It is thus feasible that the noradrenergic input to the sacral dorsal commissural nucleus modulates such nociceptive signals as pain by intracellular enhancing the glycine response.

1-Methyl-3-isobutylxanthine↗

PubMed1999

Altered angiotensin II-induced small artery contraction during the development of hypertension in spontaneously hypertensive rats.

This study assessed whether the angiotensin-II (Ang II)-induced contractile responsiveness of resistance arteries is altered during the development of hypertension in spontaneously hypertensive rats (SHR). Structural parameters and Ang II-stimulated contraction were determined in small mesenteric arteries from 6-week-old (phase of developing hypertension) and 21-week-old SHR (phase of established hypertension), compared with age-matched Wistar-Kyoto rats (WKY). To ascertain whether effects were specific for Ang II, contractile responses to another vasoactive agonist, vasopressin (AVP), were also determined. Systolic blood pressure was measured in conscious rats by the tail-cuff method. Segments of third-order mesenteric arteries (approximately 200 microm in diameter and 2 mm in length) were mounted in a pressurized system with the intraluminal pressure maintained at 45 mm Hg. Blood pressure was significantly increased in SHR (P < .001) and was higher in adult than in young SHR (P < .001). Ang II dose-dependently increased contraction, with responses significantly greater (P < .05) in SHR than in age-matched WKY. SHR, in the early phase of hypertension, exhibited significantly augmented contractile responses (Emax = 70 +/- 5%), compared with SHR with established hypertension (Emax = 33 +/- 5%). These effects were not generalized, as responses to AVP were not significantly different between young and adult SHR. Functional Ang II-elicited alterations were associated with structural modifications: 6-week-old SHR had smaller media to lumen ratio compared with 21-week-old SHR (8.1% +/- 0.17% v 10.6% +/- 0.20%, P < .01). In young SHR vessels the media cross-sectional area was unchanged relative to age-matched WKY rats, suggesting eutrophic remodeling (remodeling index 101.4% v 93.3% young v adult), whereas the cross-sectional area of adult vessels was increased in comparison to WKY rats, suggesting mild hypertrophic remodeling (growth index -1.0% v 15.2%, young v adult). In conclusion, the present study demonstrates that in SHR with early hypertension and slight medial thickening, Ang II-mediated vascular contractile responsiveness is significantly augmented compared with SHR with established hypertension and more severe vascular structural changes. These findings indicate attenuation, as hypertension progresses, of the initially enhanced vascular reactivity to Ang II that is present during the development of hypertension in SHR.

Angiotensin II↗

PubMed1999

Differential expression and modulation of costimulatory molecules CD80 and CD86 on monocytes from patients with systemic lupus erythematosus.

Patients with systemic lupus erythematosus (SLE) were recently shown to be defective in costimulatory molecule CD80 (B7-1) expression on antigen-presenting cells. This study was undertaken to further investigate the expression and cytokine regulation of both CD80 and CD86 (B7-2) on monocytes from patients with SLE. Freshly isolated and in vitro cytokine-stimulated peripheral blood mononuclear cells from 13 patients with SLE and 10 healthy subjects were analysed, cytometrically with dual-fluorescence staining, to detect expression of CD80 and CD86 in the CD14+ monocyte population. The results showed that, as in normal individuals, an overwhelming majority (95.62+/-3.54%) of monocytes from patients with SLE expressed the CD86 molecule, but only a few monocytes (5.54+/-4.36%) had detectable CD80 expression. The effects of interleukin-10 (IL-10) on the expression of CD80 and CD86 on monocytes from patients with SLE and normal controls were similar. IL-10 down-regulated the expression of CD86 while it slightly enhanced that of CD80. Interferon-gamma (IFN-gamma) increased both CD80 and CD86 expression on monocytes from both SLE patients and normal groups, albeit less significantly in the former than in the latter, i.e. CD80: 142.84+/-65.99% versus 226.08+/-78.90%, P<0.05; and CD86: 72.55+/-74.23% versus 153.99+/-94.14%, P<0.05, when expressed as percentage modulation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) showed a capacity for up-regulation of CD80 and CD86 expression on monocytes, of a magnitude that was similar both in patients with SLE and in normal subjects. We concluded that CD80 and CD86 were differentially expressed and modulated on monocytes and the defective IFN-gamma-induced up-regulation of CD80 and CD86 expression on SLE monocytes might be a factor in the pathogenesis of SLE.

Adolescent↗

PubMed1999

Increased expression of down-regulatory CTLA-4 molecule on T lymphocytes from rheumatoid synovial compartment.

Since the CTLA-4 molecule expressed on activated T lymphocytes has recently been suggested to be an important negative regulator in autoimmune diseases, this study was undertaken to investigate the expression and function of CTLA-4 on synovial T cells from patients with rheumatoid arthritis. CTLA-4-expressing T cells were detected using a dual fluorescence flow cytometric method. Only a small percentage of peripheral blood T cells from patients with rheumatoid arthritis had detectable surface CTLA-4 expression (mean +/- SD, 1. 89 +/- 1.92%). However, the levels of CTLA-4-positive T cells was increased significantly in rheumatoid synovial fluids (5.44 +/- 4. 96%) and synovial membranes (28.76 +/- 14.30%). To explore the role of CTLA-4 molecule in the inflammation of rheumatoid joints, CTLA-4 was blocked with anti-CTLA-4 antibody to assess its effects on the production of tumour necrosis factor alpha and interleukin 1beta in synovial fluid mononuclear cell culture. The addition of anti-CTLA-4 antibody enhanced the production of tumour necrosis factor alpha and interleukin 1beta in a dose-dependent manner. The data suggest that the expression of CTLA-4 plays a down-regulatory role in rheumatoid articular inflammation. We thus concluded that CTLA-4 was up-regulated on synovial T cells from patients with RA, and the increased CTLA-4 expression might exert a down-regulation effect on tumour necrosis factor alpha and interleukin 1beta production.

Abatacept↗

PubMed1999

kappa-Opioid receptor-mediated antinociceptive effects of stereoisomers and derivatives of (+)-matrine in mice.

The antinociceptive effects of seven matrine-type lupin alkaloids were examined using the acetic acid-induced abdominal contraction test (the writhing test) and the tail-flick test in mice. (+)-Allomatrine, the C-6 epimer of (+)-matrine, produced the antinociceptive effect at 1/3 potency of (+)-matrine or pentazocine. It was demonstrated that the antinociceptive effects of (+)-allomatrine were mediated through the activation of kappa-opioid receptors, while the antinociceptive effect of (+)-matrine was mediated by both mu- and kappa-opioid receptors. (-)-Sophoridine, the C-6 epimer of (+)-matrine, (+)-sophoranol, (-)-14 beta-hydroxymatrine and (+)-matrine N-oxide, which possess a hydrophilic group, and (-)-sophocarpine and (-)-sophoramine having a double bond(s) did not show significant antinociceptive activity.

Alkaloids↗

PubMed1999

Role of AT2 receptors in angiotensin II-stimulated contraction of small mesenteric arteries in young SHR.

This study assesses the receptor subtype (AT1 and AT2) through which angiotensin II (Ang II) mediates contraction in small arteries of young and adult spontaneously hypertensive rats (SHR). Segments of third-order mesenteric arteries ( approximately 200 microm in lumen diameter) were mounted in a pressurized system. Systolic blood pressure and media:lumen ratio of small arteries were significantly greater (P<0.001) in young SHR and adult SHR than in age-matched Wistar-Kyoto rats (WKY). Ang II-induced contractile effects were significantly increased (P<0.05) in young SHR compared with age-matched WKY. AT1 blockade with losartan, and combined AT1 and AT2 blockade with losartan and PD123319, abolished Ang II-stimulated contraction in young and adult rats. AT2 blockade (PD123319) significantly reduced (P<0.01) Ang II-elicited contraction in young SHR but had no effect in WKY or adult SHR, indicating that AT2 receptors may contribute to Ang II-induced contraction in young SHR. To determine the Ang receptor status in rat mesenteric vessels, AT1 and AT2 receptor mRNA expression was determined by reverse transcription-polymerase chain reaction. AT1 and AT2 receptor protein expression were detected by Western blot analysis. AT1 receptor mRNA was equally expressed in age-matched rats, but expression was significantly lower in young rats compared with adult rats. AT2 receptor mRNA was weakly expressed in WKY and adult SHR. In vessels from young SHR, AT2 receptor mRNA expression was significantly increased compared with the other groups. AT1 receptor protein was equally expressed in adult rats of both strains but was undetectable in young rats. AT2 receptor protein was only detectable in young rats, with the magnitude of expression greater in SHR than WKY. In conclusion, Ang II-stimulated contractile responses are augmented in vessels from young SHR. These effects are reduced by selective AT2 blockade and abolished by AT1 blockade, indicating that both Ang receptor subtypes are involved in contraction in young SHR. In WKY and adult SHR, losartan, but not PD123319, inhibited Ang II-induced contraction, indicating the exclusive involvement of AT1 receptors. Thus, in SHR, in the phase of developing hypertension, enhanced Ang II-stimulated vascular contraction may be associated with changes in Ang II receptor status, as evidenced pharmacologically and by increased vascular AT2 receptor mRNA and protein expression.

Aging↗

PubMed1999

Mechanics and composition of human subcutaneous resistance arteries in essential hypertension.

Mechanical properties of arteries are altered in some rat models of hypertension, and this may influence peripheral resistance and blood pressure as well as some of the complications of hypertension. It has usually been assumed that arterial wall stiffness is increased in hypertension, although recent studies suggest that this may not necessarily be the case in large arteries. We determined whether the mechanics of human resistance arteries are altered in hypertension. Subcutaneous resistance arteries (lumen diameter<300 microm) were isolated from hypertensive and normotensive subjects of similar ages (46+/-3 and 43+/-4 years, respectively). Vessels were mounted in a pressurized myograph, deactivated, and exposed to intraluminal pressures ranging from 3 to 140 mm Hg. At each pressure, lumen and media dimensions were measured. Media-to-lumen ratio and media width were greater in hypertensive vessels, reducing wall stress (P<0.01), whereas media cross section was similar in vessels from both groups. Isobaric elastic modulus (which is influenced by vessel geometry and by wall component stiffness) was lower in hypertensive vessels (P<0. 01). Stiffness of wall components (slope of incremental elastic modulus versus stress, which is geometry-independent) was significantly lower in hypertensive vessels (8.2+/-0.7) versus normotensive vessels (11.0+/-1.0, P<0.05), whereas distensibility was unchanged. Electron microscopic analysis of the media of the small arteries showed a greater collagen to elastin ratio (P<0.05) in the media of vessels from hypertensive patients. In conclusion, the stiffness of wall components (slope of elastic modulus versus stress) is not increased but is in fact decreased in subcutaneous resistance arteries from patients with mild essential hypertension. Reduced stiffness of resistance arteries from hypertensive patients does not appear to relate to changes in volume density of extracellular matrix components but may be the result of changes in extracellular matrix architecture or cell-matrix attachment, which remains to be established.

Adult↗

PubMed1999

In vivo study of AT(1) and AT(2) angiotensin receptors in apoptosis in rat blood vessels.

In vitro experiments suggest that angiotensin II (Ang II) may cause growth via angiotensin type 1 (AT(1)) receptors and apoptosis via angiotensin type 2 (AT(2)) receptors. To answer the question of whether AT(1) or AT(2) receptor activation could induce apoptosis in the vasculature in vivo, Wistar rats were infused for 7 days with Ang II (120 ng. kg(-1). min(-1) subcutaneously) and treated with the AT(2) receptor antagonist PD 123319 (30 mg. kg(-1). d(-1) subcutaneously) or the AT(1) receptor antagonist losartan (10 mg. kg(-1). d(-1) orally). Apoptosis in thoracic aorta was quantified by radiolabeled DNA laddering and by terminal deoxynucleotide transferase-mediated dUTP nick end-labeling. The expression of p53, bax, bcl-2, and caspase-3, which play critical roles in apoptotic signaling, was examined by Western blot analysis. The mRNA expression of AT(1) and AT(2) receptors was determined by reverse transcription-polymerase chain reaction. The increase in systolic blood pressure and aortic growth induced by Ang II infusion was completely prevented by losartan alone or losartan given with PD 123319, whereas PD 123319 resulted in a greater increase in systolic blood pressure and aortic growth than Ang II alone. Radiolabeled DNA laddering showed that Ang II infusion+/-losartan or PD 123319 significantly increased apoptosis (147+/-8%, 178+/-20%, and 238+/-41%, respectively, P<0.05 compared with control). Expression of bax and active forms of caspase-3 was increased in the Ang II+PD 123319 group, whereas the expression of p53 and bcl-2 was not significantly different in all groups. The expression of AT(1) and AT(2) receptor mRNA was downregulated by losartan and PD 123319, respectively. Thus, when AT(1) or AT(2) receptors are stimulated in vivo, apoptosis is enhanced in the media of blood vessels. In the case of AT(1) receptor stimulation, this may occur secondary to vascular growth and modulate the latter. Both bax and caspase-3 participate in the pathways of apoptosis triggered by in vivo AT(1) receptor stimulation.

Angiotensin II↗

PubMed1999

R-dl-verapamil downmodulates multidrug resistance of KBv200 cells to vincristine and doxorubicin.

AIM: To study the attenuation of multidrug resistance (MDR) by R-dl-verapamil (R-Ver) and the acute animal toxicity of R-Ver, and to compare these results of R-Ver with the results of dl-verapamil (Ver). METHODS: Cytotoxicity was determined by tetrazolium (MTT) assay. Cellular accumulation of doxorubicin (Dox) was measured by fluorescence spectrophotometry. Acute animal toxicity was tested by i.p. drug administration in BALB/c mice. RESULTS: R-Ver attenuated MDR of KBv200 cells to vincristine (VCR) and Dox. This attenuation ability was dose-related, and was also dependent on drug exposure time. R-Ver 1.25 mumol.L-1 increased the sensitivity of KBv200 cells to VCR (P < 0.01) with a 24-h period of drug exposure. R-Ver downmodulated MDR and increased cellular Dox accumulation of KBv200 cells as effectively as Ver, but possessed lower acute toxicity in BALB/c mice. While LD50 of Ver was 60 (49-73) mg.kg-1, LD50 of R-Ver was 166 (137-202) mg.kg-1. CONCLUSION: R-Ver downmodulated the MDR to VCR and Dox at 1.25 mumol.L-1, and this effect on VCR can be realized with drug exposure duration of 24 h.

Animals↗

PubMed1999

5-HT potentiates GABA- and glycine-activated chloride currents on the same neurons in rat spinal cord.

The electrophysiological and pharmacological properties of GABA- and glycine (Gly)-induced responses were investigated in neurons acutely dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under voltage-clamp conditions. At a holding potential of -40 mV, the currents evoked by GABA and Gly increased in a sigmoidal fashion with increasing agonist concentration. The reversal potentials of I(GABA)and I(Gly) were close to the Cl- equilibrium potential. Bicuculline (BIC) and strychnine (STR) suppressed I(GABA) and I(Gly) in a concentration-dependent manner, although they have different affinities for GABA and Gly. 5-HT potentiated both I(GABA) and I(Gly) via intracellular protein kinase C on the same neurons. The results indicated that the acutely dissociated SDCN neurons responded to both exogenous GABA and Gly, which activated GABA(A) and STR-sensitive Gly receptors, respectively, and 5-HT may produce spinal antinociception through postsynaptic potentiation of I(GABA) and I(Gly) when they are coreleased; GABA and Gly may act as cotransmitters implicated in the control of spinal nociceptive signal processing in the mammalian spinal cord.

Animals↗

PubMed1999

Modulation of glycine-activated chloride currents by substance P in rat sacral dorsal commissural neurons.

The modulatory effect of substance P (SP) on strychnine-sensitive glycine (Gly) response was examined in neurons acutely dissociated from the rat sacral dorsal commissural nucleus (SDCN) using nystatin perforated patch recording configuration under voltage-clamp conditions. Application of SP potentiated 30 mumol/L Gly-activated chloride current (IGly) in a concentration-dependent manner over the range of 1 nmol/L to 1 mumol/L at a holding potential of -40 mV. SP neither changed the reversal potential of Gly response nor affected the affinity of Gly to its receptor. The SP potentiation effect could be blocked by spantide as well as a selective NK1 receptor antagonist, L-668, 169, but not by NK2 receptor antagonist, L-659, 877. The facilitatory action of SP on IGly could also be abolished by pretreatment with chelerythrine or KN-62 in different neurons, a finding suggesting that protein kinase C (PKC) or Ca2+/calmodulin-dependent protein kinase II (CaMK II) possibly contributes to an intracellular pathway of SP in the augmentation of IGly. The results imply that SP may suppress nociception in the spinal cord by potentiating Gly response.

Animals↗