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Biomedical subjects

Y Song

Publications and source records attributed to Y Song.

At least 415 records · Page 23Linked to original sources
PubMed1993

Putative melatonin receptors in the male guinea pig kidney.

The direct action of pineal melatonin on the renal system is supported by our demonstration of 2-[125I]iodomelatonin binding sites in the male guinea pig kidney. Scatchard analyses and Hill coefficients revealed a single type of binding site with an equilibrium dissociation constant (Kd) of 22.3 +/- 1.6 pmol/l and a maximum binding density (Bmax) of 0.99 +/- 0.03 fmol/mg protein (n = 7) at mid-light. There was no significant difference in the Kd and Bmax values between kidney tissues collected at the middle of light and dark periods. The pharmacological profile of these 2-[125I]iodomelatonin binding sites indicated high specificity for melatonin, 2-iodomelatonin and 6-chloromelatonin while kinetic studies generated a Kd value of 28.4 +/- 7.3 pmol/l (n = 5) which was comparable to that determined from Scatchard transformations. Our results suggest that these binding sites are stable, reversible, saturable, specific, and of high affinity. Regional distribution study showed that specific binding of 2-[125I]iodomelatonin was 8-fold higher in the cortical region than that in the medullary region. Studies of subcellular distribution showed that 59.3% of binding sites were localized in crude nuclear fractions followed by crude mitochondrial fractions (22.3%) and crude microsomal fractions (18.3%) with no detectable binding in cytosolic fractions. Our present findings suggest the presence of putative melatonin receptors in the guinea pig kidney, which support the hypotheses of melatonin-regulated renin secretion together with renal excretory functions via melatonin receptors.

Animals↗
PubMed1993

In vitro transcription of a Drosophila U1 small nuclear RNA gene requires TATA box-binding protein and two proximal cis-acting elements with stringent spacing requirements.

Transcription of a Drosophila U1 small nuclear RNA gene was functionally analyzed in cell extracts derived from 0- to 12-h embryos. Two promoter elements essential for efficient initiation of transcription in vitro by RNA polymerase II were identified. The first, termed PSEA, is located between positions -41 and -61 relative to the transcription start site, is crucial for promoter activity, and is the dominant element for specifying the transcription initiation site. PSEA thus appears to be functionally homologous to the proximal sequence element of vertebrate small nuclear RNA genes. The second element, termed PSEB, is located at positions -25 to -32 and is required for an efficient level of transcription initiation because mutation of PSEB, or alteration of the spacing between PSEA and PSEB, severely reduced transcriptional activity relative to that of the wild-type promoter. Although the PSEB sequence does not have any obvious sequence similarity to a TATA box, conversion of PSEB to the canonical TATA sequence dramatically increased the efficiency of the U1 promoter and simultaneously relieved the requirement for the upstream PSEA. Despite these effects, introduction of the TATA sequence into the U1 promoter had no effect on the choice of start site or on the RNA polymerase II specificity of the promoter. Finally, evidence is presented that the TATA box-binding protein is required for transcription from the wild-type U1 promoter as well as from the TATA-containing U1 promoter.

Animals↗
PubMed1993

Selective A2-adenosine receptor agonists do not alter action potential duration, twitch shortening, or cAMP accumulation in guinea pig, rat, or rabbit isolated ventricular myocytes.

In this study, the hypothesis that mammalian ventricular myocytes possess A2-adenosine receptors was tested. Electrophysiological, contractile, and cAMP responses to the selective A2-adenosine receptor agonists 2-[2-(4-methylphenyl)ethoxy]adenosine (WRC-0090) and 2-(2-cyclohexylethoxy)adenosine (WRC-0013) and the nonselective adenosine receptor agonist 5'-(N-ethylcarboxamido)adenosine (NECA) were measured using ventricular myocytes isolated from guinea pig, rabbit, and rat hearts. Pertussis toxin pretreatment and/or the selective A1-adenosine receptor antagonists 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and (+/-)N6-endonorbornan-2-yl-9-methyladenine (N-0861) were used to prevent activation of A1-adenosine receptors in these cells. Action potential duration at 50% repolarization was not altered by WRC-0090, NECA, or WRC-0013 with or without 0.1 microM DPCPX or pertussis toxin pretreatment, and WRC-0090 and NECA failed to prolong the action potential duration of myocytes exposed to 0.1 or 1 microM forskolin. WRC-0090 alone or with 0.1 microM DPCPX did not increase the amplitude of shortening of pertussis toxin-treated or untreated myocytes, and WRC-0090 or NECA did not significantly increase cAMP accumulation. In contrast to these results with myocytes, in the smooth muscle cell line DDT1MF-2 the effect of both selective A2-agonists on cAMP accumulation was biphasic: low concentrations (< or = 0.3 microM) increased but higher concentrations decreased accumulation of cAMP. The decreased cAMP accumulation seen at higher agonist concentrations was completely abolished by either 0.1 microM DPCPX or pretreatment of cells with pertussis toxin. In summary, the results of the present study do not provide evidence for A2-adenosine receptors on mammalian ventricular cardiomyocytes but confirm reports of the coexistence of both A1 and A2 subtypes of adenosine receptors on DDT1MF-2 cells.

Action Potentials↗
PubMed1993

Pharmacokinetic characteristics and antitumor activity of the N-succinyl-chitosan-mitomycin C conjugate and the carboxymethyl-chitin-mitomycin C conjugate.

The conjugate between N-succinyl-chitosan (Suc-chitosan) and mitomycin C (MMC), named Suc-chitosan-MMC, and that between carboxymethyl-chitin (CM-chitin) and MMC, named CM-chitin-MMC, were investigated in vivo. As for the intraperitoneal drug administration using rats, the order of the maximum blood concentration of MMC was unconjugated MMC > CM-chitin-MMC > Suc-chitosan-MMC. The plasma concentration of MMC for Suc-chitosan-MMC was maintained at an almost constant level over 24 h. Pharmacokinetic analysis of each plasma concentration indicated that for each conjugate, the in vitro drug release reported previously was useful for the approximate estimation of the in vivo regeneration of MMC. The chemotherapeutic effect of MMC and the conjugates was investigated using mice bearing L1210 leukemia or B16 melanoma. Concerning antitumor activity against L1210 leukemia, the conjugates exhibited a marked effect at higher doses, and their effect increased even in the dose range where the effect of MMC decreased. MMC and the conjugates exhibited a good growth-inhibitory effect against B16 melanoma. Complete inhibition of growth of B16 melanoma was observed at the dose of 10 mg eq MMC/kg for CM-chitin-MMC.

Animals↗
PubMed1993

Involvement of cytokines and vascular adhesion receptors in the pathology of fronto-ethmoidal mucocoeles.

Fronto-ethmoidal mucocoeles have the capacity to destroy bone. Sinus lining tissue has been obtained at surgery from patients with mucocoeles, from those with chronic sinusitis undergoing endoscopic sinus surgery and from patients undergoing craniofacial resection. Tissues have been frozen, sectioned, and subjected to immunohistochemical examination with monospecific antibodies for the presence of the potent osteolytic cytokines interleukins-1 and -6 and tumour necrosis factor alpha. In addition, the chemotactic intercrine--interleukin-8 was investigated. The presence of the cytokine-inducible vascular endothelial adhesion receptors--Inter-Cellular Adhesion Molecule (ICAM)-1 and E-Selectin (also known as Endothelial Leukocyte Adhesion Molecule--ELAM) was also determined. Normal sinus tissue showed no immunoreactivity with the antibodies to these various moieties. Surprisingly, only a small proportion of tissues from patients with chronic sinusitis showed the presence of cytokines or vascular adhesion receptors. In contrast, all specimens of fronto-ethmoidal mucocoeles showed positive staining for IL-1 alpha and beta and for ICAM-1 and E-selectin. IL-1 immunostaining was restricted to the epithelial cell population not being found in infiltrating leukocytes. In 40% of mucocoeles infiltrating macrophage-like cells showed the presence of tumour necrosis factor alpha. The presence of the potent osteolytic cytokine--IL-1 in all specimens of fronto-ethmoidal mucocoeles coupled to the finding of the IL-1-inducible adhesion molecules ICAM-1 and E-Selectin argues strongly that IL-1 is released from the epithelial cells and that this cytokine may be the factor causing the erosion of bone overlying the expanding mucocoele. The nature of the signals inducing cytokine synthesis remain, however, unidentified.

Adult↗
PubMed1993

Cement particles inhibit bone growth into titanium chambers implanted in the rabbit.

Particles of bone cement have been shown previously to stimulate the resorption of bone. The purpose of this study was to determine whether particles of bone cement (BC) have an adverse effect on bone ingrowth. The bone harvest chamber was implanted bilaterally in the proximal tibial metaphysis of 6 mature rabbits. Both the fixed outer cylinder and the inner removable core of the chamber have a transverse 1 mm wide pore providing a continuous canal for tissue ingrowth. After an initial 6-week period for osseointegration of the outer cylinder, the contents of the inner core were harvested repeatedly at 3 weekly intervals. In the first series of rabbits, the carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with small fabricated particles of BC (averaging 3.54 mm in diameter) to fill the channel of the core. The contralateral chamber was left empty and served as a control. In the second series of rabbits, implantation was carried out sequentially using the same material bilaterally. The sections from the control harvests, and those with Healon alone contained extensive trabecular bone arranged longitudinally in the canal, in a fibrovascular stroma. The sections containing BC particles were infiltrated by foamy, mononuclear and multinuclear histiocytic cells. Less trabecular bone was seen in the sections containing BC particles compared to the control sections or those containing Healon alone. Previous studies have shown that particles of bone cement stimulate bone resorption. In this study, BC particles have also been shown to diminish the formation of new bone.

Animals↗
PubMed1993

[Clinical observation on short term nutritional support in the treatment of advanced chronic obstructive pulmonary disease].

Twenty five patients with advanced chronic obstructive pulmonary disease (COPD) having malnutrition were randomly assigned to parenteral nutrition (PN) group (12 cases) and control group (13 cases). Patients in the PN group received 10% Intralipid and 5% Nutrisol-S. Body weight, blood lymphocyte, serum albumin, transferrin, prealbumin, fibronectin and serum free fatty acids (FFA) and serum free amino acids (AA) were monitored. The results showed that parenteral nutritional support for 10-20 days improved the nutritional status, significantly increased the body weight and the serum albumin, prealbumin, fibronectin, transferrin (P < 0.05 or P < 0.01) and some kinds of serum free amino acids: PaCO2 also decreased. Serum FFA remained under the normal level whether nutritional support was given (P < 0.01). It is suggested that nutritional support may promote synthesis of protein in COPD patients with malnutrition. Intralipid infusion would preserve nitrogen and diminish the carbohydrate metabolism and might be beneficial to correct the hypercapnea in COPD.

Amino Acids↗
PubMed1993

[Pre-and postoperative indocyanine green retention rate as a marker of liver functional reserve in cirrhotic patients].

Indocyanine green ICG retention rate was determined before and after in portohypertensive cirrhotic patients undergoing paracardial devascularization (PCDV) and side-to-side mesocaval shunt (MCs-ss). The relationship between ICG retention rate with serum albumin level and the incidence of ascites was investigated no significant change the rate was noted before and after. Operation in PCDV patients. Significant increase of the rate was observed after MCs-ss. There was a negative correlation between the rate and serum albumin level. Addition the incidence of ascites increased with the elevation of the rate, there was a significant difference in the rate in patients with or without ascites.

Adult↗
PubMed1993

[The nutritional status and immune function of patients with chronic obstructive pulmonary disease].

The nutritional status and immune function of 14 patients with exacerbation of chronic obstructive pulmonary disease (COPD) were assessed and were studied again one week after the patients had recovered. The results showed that the nutritional status of the patients was poorer on admission, the level of some kinds of serum free amino acid was significantly lower than the normal value, the value of branch-chain amino acid (BCAA) was significantly lower than that in healthy people (P < 0.01), but the level of aromatic amino acid (AAA) was higher than the normal value. Level of serum free fatty acid was significantly lower during admission and in recovery period (P < 0.01). It is suggested that shortage of essential fatty acid in the patients is obvious. The results also showed that the patients identified as malnourished had a lower cellular immune function, but the humoral immune function was not significant between the patients group and control group. Immune function was improved with the recovery nutritional status of the patients. The results suggest that malnutrition and hypoimmunity may play a very important role in the pathogenesis of COPD.

Amino Acids↗
PubMed1992

Sequence and expression of a rat cDNA for LECAM-1.

A rat cDNA clone encoding an adhesion molecule, LECAM-1, has been isolated from the SD rat and the partial nucleotide sequence was determined. It encodes a peptide of 372 amino acids (aa), including a signal peptide of 38 aa. The protein has three tandem domains: a lectin domain, an EGF-like domain and two repeats of complement regulatory proteins (CR domain). The lectin binding domain has 93.2% and 81.4% and the EGF-like domain has 85.3% and 76.5% aa identity with those of mouse and human, respectively. In the CR repeat domain, the amino acid identity was 72.6% between human and rat and 71.8% between mouse and rat. Northern blot analysis detects the main transcript of about 3 kb in peripheral blood mononuclear cells (PBMC), spleen and thymus. The expression was down-regulated by mitogen stimulation of PBMC and spleen T cells. The protein encoded by this cDNA interacted with PPME when it was expressed on gp90MEL-14 negative mouse EL-4 cells.

Amino Acid Sequence↗
PubMed1992

Sequence and organization of 5S ribosomal RNA-encoding genes of Arabidopsis thaliana.

We have isolated a genomic clone containing Arabidopsis thaliana 5S ribosomal RNA (rRNA)-encoding genes (rDNA) by screening an A. thaliana library with a 5S rDNA probe from flax. The clone isolated contains seven repeat units of 497 bp, plus 11 kb of flanking genomic sequence at one border. Sequencing of individual subcloned repeat units shows that the sequence of the 5S rRNA coding region is very similar to that reported for other flowering plants. Four A. thaliana ecotypes were found to contain approx. 1000 copies of 5S rDNA per haploid genome. Southern-blot analysis of genomic DNA indicates that 5S rDNA occurs in long tandem arrays, and shows the presence of numerous restriction-site polymorphisms among the six ecotypes studied.

Base Sequence↗
PubMed1992

Adenosine-sensitive afterdepolarizations and triggered activity in guinea pig ventricular myocytes.

This study examines the cellular basis and specificity of the effects of adenosine on early afterdepolarizations (EADs), delayed afterdepolarizations (DADs), and triggered activity (TA) induced by various drugs with different mechanisms of action. Membrane potential and currents were measured in isolated guinea pig ventricular myocytes. Adenosine (10-100 microM) significantly (p less than 0.05) reduced the amplitude of DADs and suppressed TA induced by isoproterenol (10-50 nM) and forskolin (1 microM) but not those induced by dibutyryl cAMP (1 microM), ouabain (1-5 microM), and 7.2 mM [Ca2+]o. Adenosine also abolished EADs and TA induced by isoproterenol. In contrast, adenosine failed to abolish EADs and TA induced by quinidine (3 microM) or those that occurred spontaneously (i.e., in the absence of drugs). Transient inward current (ITi) was induced on repolarization after 2-second-long single depolarizing voltage steps or after 12-second-long trains of 300-msec depolarizing pulses. Concomitant with the attenuation of DADs, adenosine suppressed ITi caused by isoproterenol and forskolin but not those induced by ouabain, dibutyryl cAMP, and elevated [Ca2+]o. The amplitude of ITi was dependent on the magnitude of the activating voltage step, but the suppression of ITi by adenosine was not. The selective A1-adenosine receptor antagonist N-0861 (9-methyladenine derivative) antagonized the effects of adenosine on afterdepolarizations, ITi, and TA. In myocytes from guinea pigs treated with pertussis toxin, adenosine failed to attenuate DADs and ITi or abolish TA induced by isoproterenol or forskolin. In parallel experiments, isoproterenol (10 nM) raised cellular cAMP from 5.7 +/- 0.2 to 8.1 +/- 0.1 pmol and the selective A1 receptor agonist cyclopentyladenosine (5 microM) reduced it to 6.5 +/- 0.2 pmol (p less than 0.05). Thus, adenosine specifically attenuates afterdepolarizations and abolishes TA by suppressing ITiS that are associated with stimulation of adenylate cyclase via a pertussis toxin-sensitive A1 receptor-mediated action. In conclusion, the response of TA to adenosine may identify a mechanism of afterdepolarization related to stimulation of adenylate cyclase.

Action Potentials↗
PubMed1992

Synthesis and drug-release characteristics of the conjugates of mitomycin C with N-succinyl-chitosan and carboxymethyl-chitin.

By condensation of mitomycin C (MMC) with N-succinyl-chitosan (Suc-chitosan) and carboxymethyl-chitin (CM-chitin) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, Suc-chitosan-MMC conjugate (Suc-chitosan-MMC) and CM-chitin-MMC conjugate (CM-chitin-MMC) were prepared, respectively. The reaction conditions for 45 min at pH 5 and for 2 h at pH 5 were selected as the most appropriate for the preparations of Suc-chitosan-MMC and CM-chitin-MMC, respectively. Suc-chitosan-MMC was obtained as a water-insoluble product, while CM-chitin-MMC was partially water-soluble. When the ratio of MMC to the polymer supports changed in the conjugation reaction, the conjugates with 33% (w/w) and 23% (w/w) MMC contents were obtained as those most highly drug-loaded for Suc-chitosan-MMC and CM-chitin-MMC, respectively. At pH 7.4 at 37 degrees C, Suc-chitosan-MMC regenerated MMC very slowly, while the release of MMC from CM-chitin-MMC was relatively fast. Each drug release followed very nearly pseudo-first order kinetics, in which the apparent drug release rate constants (k(apps)) of Suc-chitosan-MMC and CM-chitin-MMC were 3.9 x 10(-3) and 1.1 x 10(-1) (h-1), respectively.

Chitin↗