Localization in highly anisotropic systems.
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Journal Article↗
Biomedical subjects
Q Li
Publications and source records attributed to Q Li.
Specific thermal responsiveness of ventromedial hypothalamic neurons to localized scrotal heating and cooling in rats.
1. The specificity of thermoresponsive ventromedial hypothalamic (VMH) neurons to localized, incremental scrotal thermal cooling and heating of urethane-anaesthetized male Sprague-Dawley rats (maintained at 37 degrees C colonically) was investigated. 2. Ventromedial hypothalamic extracellular neuronal activity and surface (scalp) electroencephalogram (EEG) activity from the parietal region were recorded. Intrascapular brown adipose tissue (TIBAT), surface tail (Tt) and scrotal (Tsc) temperatures, where thermal stimulation was evoked, were also monitored. 3. One hundred and twenty-five VMH neurons were recorded, with forty (32%) VMH neurons classified as warm-responsive neurons (WRNs), twenty-three (18%) as coldresponsive neurons (CRNs) and sixty-two (50%) as thermal non-responsive neurons (TNRNs) based on their thermal coefficients. Of VMH WRNs, 60% (i.e. 24) were classified as having biphasic neuronal activity responses, as were 60% (i.e. 14 of 23) of the CRNs. Forty per cent of WRNs and CRNs were classified as having monophasic changes in neuronal activity. 4. Scrotal heating or cooling from 5 to 40 degrees C resulted in specific firing rate changes of VMH WRNs and CRNs without any associated change in EEG activity (i.e. no significant change in EEG frequency or amplitude from initial baseline EEG activity when Tsc was 20 degrees C). EEG desynchronization (increased EEG frequency, decreased amplitude) was only observed when scrotal temperatures were at 45 degrees C or after each tail pinch (noxious stimulation) but not with scrotal brushing (mechanical stimulation). 5. With core temperature maintained at 37 degrees C, localized, scrotal heating and cooling of rats did not induce IBAT temperature changes indicative of brown adipose tissue activation, but delayed changes in tail temperature, indicative of vasoactive effector responses, did occur.
Adipose Tissue, Brown↗
A functional medial preoptic nucleus (MPO) is required for scrotal thermal stimuli to alter the neuronal activity of thermoresponsive ventromedial hypothalamic (VMH) neurons.
Thermoresponsiveness of ventromedial hypothalamic (VMH) neurons to scrotal thermal stimulation was determined before and after microinjection of lidocaine into the medial preoptic nucleus (MPO). Male, urethane anesthetized Sprague-Dawley rats, maintained colonically at 37 degrees C had VMH extracellular neuronal activity recorded following 3 cycles of scrotal thermal stimulation (localized, incremental heating and cooling, between 10 and 40 degrees C). Based on their thermal coefficients (TC), warm (WRN), cold (CRN) thermoresponsive and temperature non-responsive (TNRN) VMH neurons had their neuronal activity recorded following each cycle of scrotal thermal stimulation before and after MPO injections of sterile saline (300 nl volume) or 2% buffered lidocaine (200 ng). Thermoresponsiveness of all warm and cold VMH neurons to scrotal thermal stimulation was blocked by prior lidocaine administration into the MPO, effects that were reversed approximately 60 min after. However, MPO lidocaine administration caused no significant change in the thermal coefficients of VMH TNRNs to scrotal thermal stimulation. Results infer that a functional MPO is required for thermal afferent signals arising from the scrotum to reach thermoresponsive VMH neurons.
Anesthetics, Local↗
Isolation of a novel gene down-regulated by v-src.
We have isolated a novel gene which was expressed in normal rat cells, but completely suppressed in cells transformed by v-src. The molecularly cloned cDNA was about 1.8 kb in size, containing an open reading frame composed of 464 amino acid residues. DNA sequence analysis showed that there was no corresponding gene in the data bases. Besides the suppression of gene expression in the v-src transformed cells, its expression was also strongly suppressed in cells transformed by other oncogenes such as v-abl, v-fps, v-mos, v-sis, v-K-ras, and polyomavirus middle T, but not affected in cells transformed by human papillomavirus type 16 E6E7 and polyomavirus large T. We named the gene drs for a gene down-regulated by v-src.
Amino Acid Sequence↗
Identification of a second transmembrane protein tyrosine phosphatase, IA-2beta, as an autoantigen in insulin-dependent diabetes mellitus: precursor of the 37-kDa tryptic fragment.
A novel cDNA, IA-2beta, was isolated from a mouse neonatal brain library. The predicted protein sequence revealed an extracellular domain, a transmembrane region, and an intracellular domain. The intracellular domain is 376 amino acids long and 74% identical to the intracellular domain of IA-2, a major autoantigen in insulin-dependent diabetes mellitus (IDDM). A partial sequence of the extracellular domain of IA-2beta indicates that it differs substantially (only 26% identical) from that of IA-2. Both molecules are expressed in islets and brain tissue. Forty-six percent (23 of 50) of the IDDM sera but none of the sera from normal controls (0 of 50) immunoprecipitated the intracellular domain of IA-2beta. Competitive inhibition experiments showed that IDDM sera have autoantibodies that recognize both common and distinct determinants on IA-2 and IA-2beta. Many IDDM sera are known to immunoprecipitate 37-kDa and 40-kDa tryptic fragments from islet cells, but the identity of the precursor protein(s) has remained elusive. The current study shows that treatment of recombinant IA-2beta and IA-2 with trypsin yields a 37-kDa fragment and a 40-kDa fragment, respectively, and that these fragments can be immunoprecipitated with diabetic sera. Absorption of diabetic sera with unlabeled recombinant IA-2 or IA-2beta, prior to incubation with radiolabeled 37-kDa and 40-kDa tryptic fragments derived from insulinoma or glucagonoma cells, blocks the immunoprecipitation of both of these radiolabeled tryptic fragments. We conclude that IA-2beta and IA-2 are the precursors of the 37-kDa and 40-kDa islet cell autoantigens, respectively, and that both IA-2 and IA-2beta are major autoantigens in IDDM.
Amino Acid Sequence↗
Reply to "Charge transfer in high-Tc (Y/Pr)Ba2Cu3O7 superlattices"
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Journal Article↗
Diphtheria toxin-mediated ablation of parietal cells in the stomach of transgenic mice.
The self-renewing epithelial populations present in the gastric units of the mouse stomach are descended from a multipotent stem cell and undergo an orderly migration-associated differentiation followed by apoptosis. The steady state census of the three principal cell types (acid-producing parietal cells, mucus-producing pit cells, and pepsinogen and intrinsic factor-producing zymogenic cells) is accurately controlled, despite marked differences in the rates of migration of each lineage. A transgenic mouse model has been created to define functional interrelationships between the proliferation, differentiation, and death programs of these lineages. Nucleotides -1035 to +24 of the noncatalytic beta subunit gene of mouse H+/K+-ATPase were used to direct expression of an attenuated diphtheria toxin A subunit in the parietal cell lineage. These transcriptional regulatory elements are not active in members of the pit and zymogenic lineages. Stomachs, prepared from postnatal day 28-80 transgenic mice and their normal littermates, were subjected to single- and multilabel immunohistochemical studies as well as qualitative and quantitative light and electron microscopic morphologic analyses. The toxin produced complete ablation of differentiated parietal cells. Loss of parietal cells was accompanied by a 5-fold increase in the number of undifferentiated granule-free cells located in the proliferative compartment of gastric units. This amplified population of granule-free cells included the multipotent stem cell as well as committed precursors of the pit and zymogenic lineages. Loss of mature parietal cells was also associated with (i) a block in the differentiation program of the zymogenic lineage with an accumulation of pre-neck cells and a depletion of their neck and mature zymogenic cell descendants, and (ii) an approximately 2-fold amplification of pit cells. These findings are consistent with the notion that epithelial homeostasis within gastric units is maintained by instructive interactions between their different cell lineages. Unlike pit and zymogenic cells, parietal cells complete their differentiation in the gastric unit's proliferative compartment before undergoing a bipolar migration along the unit. Thus, the mature parietal cell is in a strategic position to influence decision-making among gastric epithelial cell precursors and to modulate the migration-associated terminal differentiation programs of the pit and zymogenic lineages.
Aging↗
Differences between outward currents of human atrial and subepicardial ventricular myocytes.
1. Outward currents were studied in myocytes isolated from human atrial and subepicardial ventricular myocardium using the whole-cell voltage clamp technique at 22 degrees C. The Na+ current was inactivated with prepulses to -40 mV and the Ca2+ current was eliminated by both reducing extracellular [Ca2+] to 0.5 mM and addition of 100 microM CdCl2 to the bath solution. 2. In human myocytes, three different outward currents were observed. A slowly inactivating sustained outward current, I(so), was found in atrial but not ventricular myocytes. A rapidly inactivating outward current, I(to), of similar current density was observed in cells from the two tissues. An additional uncharacterized non-inactivating background current of similar size was observed in atrial and in ventricular myocytes. 3. I(to) and I(so) could be differentiated in atrial myocytes by their different kinetics and potential dependence of inactivation, and their different sensitivities to block by 4-amino-pyridine, suggesting that two individual channel types were involved. 4. In atrial cells, inactivation of I(to) was more rapid and steady-state inactivation occurred at more negative membrane potentials than in ventricular cells. Furthermore, the recovery of I(to) from inactivation was slower and without overshoot in atrial myocytes. In addition, 4-aminopyridine-induced block of I(to) was more efficient in atrial than in ventricular cells. These observations suggest that the channels responsible for atrial and ventricular I(to) were not identical. 5. We conclude that the differences in outward currents substantially contribute to the particular shapes of human atrial and ventricular action potentials. The existence of I(so) in atrial cells only provides a clinically interesting target for anti-arrhythmic drug action, since blockers of I(so) would selectively prolong the atrial refractory period, leaving ventricular refractoriness unaltered.
Action Potentials↗
Comparison of the nucleic acid- and NTP-binding properties of the movement protein of cucumber mosaic cucumovirus and tobacco mosaic tobamovirus.
The cucumber mosaic virus (CMV) 3a movement protein (MP) was compared directly to the well-characterized tobacco mosaic virus (TMV) 30K MP by cloning the genes encoding these proteins into Escherichia coli, isolating the E. coli-expressed MPs, and characterizing them with regard to RNA- and NTP-binding activities. The two MPs were shown to bind single-stranded RNA and DNA cooperatively, but with no sequence specificity. However, discrete lengths of CMV RNA 3 could be protected against RNase digestion by the CMV 3a protein, indicating that the RNA was not uniformly covered by the MP after cooperative binding. The TMV 30K:RNA complex was more stable in NaCl than the CMV 3a:RNA complex; about 50% of the corresponding complexes were stable in 0.6 and 0.4 M NaCl, respectively. Both MPs could bind GTP strongly and UTP weakly, but not ATP or CTP. The CMV 3a protein expressed either in E. coli or in planta from RNA 3 of CMV was tagged at its C-terminus with six histidine residues, which facilitated its purification by affinity chromatography on a matrix containing Ni(2+)-nitrilotriacetate. The soluble, His-tagged 3a proteins, affinity-purified from E. coli and zucchini squash, both were able bind CMV RNA 3 in vitro.
Base Sequence↗
Normal state ac Hall effect in YBa2Cu3O7 thin films.
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Journal Article↗
The affinity of nuclear factor 1 for its DNA site is drastically reduced by nucleosome organization irrespective of its rotational or translational position.
A DNA-bending sequence has been used for in vitro reconstitution of nucleosomes in order to direct a nuclear factor 1 (NF-1) binding site into different nucleosome positions. By this strategy nucleosomes were obtained that had one of two rotational positions of the NF-1 binding site, one oriented toward the periphery and the other toward the histone octamer, translationally positioned 50 and 45 base pairs, respectively, from the nucleosome dyad. The affinity of partially purified NF-1 for these nucleosomal targets was compared with its affinity for free DNA by dimethylsulfate methylation protection and DNase I footprinting assays. The binding affinity of NF-1 to all nucleosomal targets was reduced 100-300-fold compared with its affinity for free DNA. The two rotational settings of the NF-1 site showed the same binding affinity for NF-1 as did other nucleosome constructs in which the NF-1 binding site was translationally positioned from 10 to 40 base pairs from the nucleosome dyad. We conclude that the nucleosomal inhibition of NF-1 binding is an inherent characteristic of NF-1 since another transcription factor, the glucocorticoid receptor, is able to bind to its DNA site in a nucleosome.
Base Sequence↗
Grain-boundary-induced magneto-far-infrared resonances in superconducting YBa2Cu3O7- delta thin films.
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Journal Article↗
Suppressive effect of transforming growth factor beta1 on the recurrence of experimental melanin protein-induced uveitis: upregulation of ocular interleukin-10.
Uveitis is induced in Lewis rats by immunization with bovine melanin protein (BMP) derived from the uvea and retinal pigment epithelium. Recurrence of this experimental melanin protein-induced uveitis (EMIU) develops after footpad injection of a minimal amount of Salmonella typhimurium endotoxin (LPS) following the remission of EMIU. To investigate the effect of transforming growth factor beta1 (TGFbeta1) on the recurrence of EMIU, 5 micrograms LPS booster was given to Lewis rats by footpad injection on Day 45 after BMP immunization. Daily TGFbeta1 or phosphate-buffered saline was administered either from Day 0 to 7 (group 1) or from Day 7 to 13 (group 2) after LPS booster. Delayed-type hypersensitivity (DTH) ear test was conducted on Day 12 after LPS booster and eye and blood were collected on Day 14. The incidence and severity of recurrent uveitis markedly decreased in both groups of TGFbeta1-treated rats. A lower level of serum BMP antibody was also observed by agglutination in these groups. There was no statistical difference in DTH responses between the treated and control groups. Ocular cytokine mRNA of group 1 and controls was analyzed by RT-PCR. Interleukin (IL)-2 and interferon-gamma were not detectable. IL-4 was identified at a similar level in both groups. A higher level of IL-10 was observed in group 1 rats. We conclude that TGFbeta1 suppresses recurrent EMIU, probably through upregulation of IL-10.
Animals↗
Epithelial injury induces keratocyte apoptosis: hypothesized role for the interleukin-1 system in the modulation of corneal tissue organization and wound healing.
The purpose of this study was to determine the role of programmed cell death (apoptosis) in the disappearance of keratocytes beneath an epithelial debridement wound in the cornea and to investigate a potential role of interleukin-1 (IL-1) in induction of apoptosis in stromal fibroblasts in vitro and keratocytes in vivo. Keratocyte and stromal fibroblast cell morphology was examined in wounded and unwounded mouse corneas using transmission electron microscopy. Nuclear DNA fragmentation was detected with the TUNEL assay for 3'-hydroxyl DNA ends. The effect of IL-1 on keratocytes in vivo was determined by microinjection of IL-1 alpha into the central corneal stroma via a limbal entry site. The in vitro effects of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) were determined with primary cultures of human corneal stromal and dermal fibroblasts. Cell shrinkage, blebbing with formation of membrane bound bodies, condensation and fragmentation of the chromatin, and DNA fragmentation, consistent with apoptosis were detected in anterior stromal keratocytes after epithelial scrape wounds. Thus, disappearance of keratocytes from the underlying stroma following epithelial debridement is mediated by apoptosis. Microinjection of IL-1 alpha into the central stroma of the mouse cornea caused a redistribution of keratocytes in the stroma via apoptosis and, possibly, negative chemotaxis. IL-1 alpha and IL-1 beta induced apoptosis in corneal stromal and dermal fibroblasts in vitro. The epithelial/endothelial-stromal IL-1 system may mediate corneal tissue organization and responses to mechanical- and pathogen-induced injury through induction of keratocyte apoptosis. Keratocyte apoptosis is likely an initiating event in wound healing following corneal surgery. We hypothesize that derangement's in this system may have a role in the pathogenesis of keratoconus and other diseases of the cornea.
Animals↗
IA-2 and IA-2 beta are major autoantigens in IDDM and the precursors of the 40 kDa and 37 kDa tryptic fragments.
By subtraction strategy and polymerase chain reaction amplification, two novel cDNAs, designated IA-2 and IA-2 beta, were cloned, sequenced and expressed. Both are transmembrane proteins belonging to the protein tyrosine phosphatase family and are expressed in pancreatic islets. Serological studies revealed that a high percentage of patients with IDDM have autoantibodies to IA-2/IA-2 beta and that the presence of these autoantibodies in otherwise normal individuals is highly predictive in identifying those at risk of ultimately developing clinical diabetes. Moreover, many patients who are ICA positive, but who do not have Abs to GAD65, have Abs to IA-2/IA-2 beta. Enzymatic cleavage of IA-2/IA-2 beta and serological analysis showed that IA-2 is the precursor of the 40 kDa tryptic fragment and IA-2 beta is the precursor of the 37 kDa tryptic fragment, both previously shown to be autoantigens. It is concluded that IA-2/IA-2 beta are major autoantigens in IDDM and together with GAD65 are responsible for much of the reactivity of ICA with pancreatic islets. Tests for the detection of autoantibodies to recombinant IA-2/IA-2 beta and recombinant GAD65 are likely to replace the ICA immunofluorescence test for population screening.
Amino Acid Sequence↗
Inhibition of human T lymphoblast proliferation by hydroquinone.
Hydroquinone (HQ) is a major metabolite of benzene and is present in large quantities in cigarette tar as a result of the combustion of tobacco leaf pigments. We hypothesize that the immunosuppressive effects of cigarette smoking are due, in part, to the deposition of large quantities of HQ in the lungs. Exposure of primary human T lymphoblasts (HTL) in vitro to 50 microM HQ blocked IL-2-dependent proliferation by > 90% with no loss in viability. Inhibition of DNA synthesis was observed immediately after the addition of HQ to the cells. However, this effect could be reversed up to 6 hr later by simply washing the cells and reculturing them in the absence of HQ. HQ did not significantly alter intracellular glutathione levels up to 24 hr later, and the presence of 50 microM 2-mercaptoethanol or 500 microM dithiothreitol during the treatment did not prevent inhibition of DNA synthesis. HQ did not block binding of 125I-IL-2 to the cells, but inhibited the IL-2-dependent progression of HTL through S phase of the cell cycle. These observations demonstrate that HQ, in concentrations comparable to those found in cigarette tar, is a potent inhibitor of IL-2-dependent T cell proliferation and may therefore help to explain the potent immunosuppressive effects of cigarette smoke on lung T lymphocytes.
Cell Cycle↗
Splase: a new class IIS zinc-finger restriction endonuclease with specificity for Sp1 binding sites.
A new restriction endonuclease, named Splase, was constructed by genetically fusing the DNA-cleavage domain of the restriction endonuclease Fok1 with the zinc-finger DNA-binding domain of the transcription factor Sp1. The resulting protein was expressed in Escherichia coli., partially purified, and shown to selectively digest plasmid DNA harboring consensus Sp1 sites. Splase was also shown to selectively digest the long terminal repeat of the HIV-1 DNA at Sp1 sites. Splase recognizes a 10-bp DNA sequence and hydrolyzes phosphodiester bonds upstream of the binding sequence. The binding specificity of Splase makes this a "rare cutter" restriction enzyme which could be valuable in creating large DNA fragments for genome sequencing projects. The result also presents the opportunity to create other restriction enzymes by altering the binding specificity of the zinc-finger recognition helix.
Base Sequence↗
Evaluation of cross-sensitization among dye-intermediate agents using a modified lymphocyte transformation test.
We evaluated cross-sensitization between p-phenylenediamine (pPDA) and p-aminophenol (pAP) or m-phenylenediamine (mPDA) by a modified lymphocyte transformation test. Guinea pigs were sensitized with pPDA using the maximization test procedure. Lymph node cells from the animals were then cultured with pPDA, pAP or mPDA in the presence or absence of epidermal cells (EC). Transformed lymphocyte counts were evaluated by means of 3H-thymidine uptake. Non-sensitized guinea pigs were used as controls. Blastogenesis in lymphocytes from sensitized guinea pigs was enhanced when cultured with pPDA, pAP or mPDA in the absence or presence of EC than without the sensitizers, and the extent of response depended on the concentration of pPDA, pAP or mPDA added to the cultures. Blastogenesis in lymphocytes from control animals was not significantly enhanced in response to pPDA, pAP or mPDA in the presence or absence of EC. The extent of the response to pPDA was greater than that to pAP, which in turn was greater than that to mPDA. In contrast, because pPDA, pAP and mPDA are color developing agents, cross-sensitization between pPDA and pAP or mPDA could not be evaluated by the results of an in vivo challenge due to pigmentation in the patch application sites. The results suggested that there is cross-sensitization between pPDA and pAP or mPDA, and that the modified lymphocyte transformation test is a useful predictive means of detecting cross-sensitization among chemicals, especially for color developing agents.
Aminophenols↗