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Biomedical subjects

Z Tong

Publications and source records attributed to Z Tong.

At least 55 records · Page 3Linked to original sources
PubMed1997

Transcriptional and post-transcriptional regulation of prolactin during the turkey reproductive cycle.

The present study examined turkey prolactin (PRL) transcription and PRL mRNA stability during different reproductive stages. Nuclear run-on transcription assays were performed using isolated nuclei from pituitaries of turkeys at different reproductive stages. Meanwhile, cytoplasmic PRL mRNA and plasma PRL were measured by slot blot and RIA respectively. The PRL transcription, pituitary cytoplasmic PRL mRNA abundance and plasma PRL levels increased after photostimulation and peaked at the incubating stage (P < 0.05). A decrease in PRL transcription, pituitary cytoplasmic PRL mRNA and plasma PRL (P < 0.05) was observed during the transition from incubation to photorefractoriness. Nest-deprivation reduced circulating PRL (P < 0.05), whereas pituitary cytoplasmic PRL mRNA and PRL transcription were not significantly altered from those in incubating birds (P > 0.05). The half-life of PRL mRNA was determined in pituitaries of non-photostimulated, laying, incubating and photorefractory hens. Primary pituitary cell cultures were treated with the transcription inhibitor actinomycin-D and the decay of the pre-existing PRL mRNA was quantified using Northern blot analysis. The PRL mRNA half-life was 1.5- and 1.4-fold greater in incubating and laying birds respectively than in non-photostimulated turkeys (P < 0.05). The half-life of PRL mRNA in photorefractory and incubating hens was similar in spite of great differences in pituitary PRL mRNA steady-state levels and PRL transcription. Our data suggest that photoinduced changes in pituitary PRL mRNA and plasma PRL are due to changes in both PRL transcription and PRL mRNA stability. Nest-deprivation inhibits the PRL releasing mechanism(s) independently of PRL transcription in turkeys.

Animals↗
PubMed1997

[Changes of K+ channel behaviors in airway smooth muscle from asthmatic guinea-pigs].

OBJECTIVE: To observe asthma-induced changes of single K+ channel behaviors in acutely dissociated airway smooth muscle of guinea-pig. METHODS: The resting membrane potential (MP) was measured in whole-cell recording configuration. The elementary currents flowing through single K+ channel were recorded in cell-attached patches. RESULTS: The properties in asthmatic group were as follows: (1) MP was decreased from -70.3 +/- 3.5 mV to -62.8 +/- 5.6 mV. (2) In the same depolarization conditions, the amplitudes of currents decayed and conductant values were decreased with significantly difference (about 51%) from the values obtained from the control group. (3) Open time constants of fast- and slow-open states shortened markedly to 25% and 7% of controls respectively. Shut time constants were prolonged. (4) Open probability showed voltage-dependence and was decreased in the same voltage range. CONCLUSIONS: Asthmic airway hyperreactivity-related kinetic properties of K+ channel deficits, which may result a reduced threshold of excitation.

Animals↗
PubMed1997

[Effects of K+ channel openers on voltage-dependent K+ channel behavior in airway smooth muscle of guineapig].

In order to determine whether the K+ channel openers (PCOs), which are suggested to open K+ channels and to relax bronchial smooth muscle, would directly activate voltage-dependent K+ channels, single channel currents were studied on cell-attached and inside-out patches of smooth muscle acutely dissociated from bronchi of guinea-pig. The resting membrane potentials measured in whole-cell recording configuration showed no difference with control when cromakalim and lemakalim were applied extracellularly, which, however increased the conductance values of K+ channels with depolarization from 75.2 +/- 5.1 pS to 85.9 +/- 11.8 pS and 82.1 +/- 5.5 pS, respectively. The channels kinetics were also affected by PCOs. Mean open time (tau o) and open probability increased, in which the effects of lemakalim was stronger than that of cromakalim. Both PCOs elicited the multichannel activities in some patches. It is suggested that PCOs could evoke K+ channels with depolarization and stimulate K+ efflux, which may affect the excitability of muscle cells.

Animals↗
PubMed1997

Dietary modulation of phase 1 and phase 2 activities with benzo(a)pyrene and related compounds in the intestine but not the liver of the channel catfish, Ictalurus punctatus.

These studies demonstrated that intestinal mucosa of the channel catfish contained activities comparable with liver for several phase 2 xenobiotic-metabolizing enzymes, and showed that CYP1A-dependent monooxygenase activities were inducible in intestine but not liver by dietary exposure to low concentrations of the Ah agonist, beta-naphthoflavone (BNF). The diets administered were laboratory-prepared, semisynthetic pellets of known composition, commercial chow, or chow supplemented with BNF at 10 or 100 mg BNF/kg chow. Very low intestinal benzo(a)pyrene hydroxylase [aryl hydrocarbon hydroxylase (AHH)] and ethoxyresorufin O-deethylase (EROD) activities were found in catfish fed the semisynthetic diet. Intestinal EROD and AHH activities were elevated by the commercial chow diet and further induced by supplementation with 10, but not 100, mg BNF/kg diet. In vitro studies showed that catfish EROD and AHH activities were sensitive to inhibition by BNF, with mean IC50 values of 0.078 and 2.2 microM, respectively. Thus, residues of BNF retained in intestinal mucosa may have masked monooxygenase induction in catfish fed the 100 mg BNF/kg diet. Microsomal UDP-glucuronosyltransferase and cytosolic PAPS-sulfotransferase activities with 3-hydroxybenzo(a)pyrene as substrate were largely unaffected by the diets studied, and intestinal activities were similar to hepatic activities. Glutathione S-transferase activity was slightly induced in intestinal, but not hepatic cytosol of catfish treated with BNF at the 10 mg/kg diet level relative to chow controls. Epoxide hydrolase activity with styrene oxide as substrate was not affected by diet in intestinal microsomes.

Animals↗
PubMed1996

[Relationship between aflatoxin and sclerotia production in aspergillus flavus].

Eighty strains of Aspergillus flavus (AF) isolated from grain produced in Zhejiang Province were studied experimentally on their abilities of sclerotia production, and 51.3% of the strains could produce sclerotia in Czapek solution agar containing 3% sodium nitrate at 30 C incubation for 12 days, with an average diameter of 827 +/- 131 microns, and no toxigenic S strain producing abundant small sclerotia was found. Most of the toxigenic strains producing sclerotia were L strain. There were no significant difference in the rates and amount of sclerotia production between toxigenic and a toxigenic strains. There was difference in diameter of sclerotia produced between them, with a smaller one in the toxigenic strains.

Aflatoxins↗
PubMed1995

A serotypic study of hemorrhagic fever with renal syndrome in rural China.

Apodemus agrarius was trapped in the fields and Rattus norvegicus was trapped within the houses in the villages of Jiande County, a region in the Zhejiang Province of China endemic for hemorrhagic fever with renal syndrome (HFRS). Antibodies to hantaviruses were detected in three (16.7%) of 18 A. agrarius and 12 (13.5%) of 89 R. norvegicus, whereas hantavirus antigens were detected in the lung tissues of four (22.2%) of 18 and nine (10.1%) of 89 of these rodents, respectively. Three hantaviruses, one from A. agrarius and two from R. norvegicus, were isolated and found to be antigenically similar to Hantaan and Seoul serotype viruses, respectively. A serologic study of 437 clinically defined HFRS patients conducted in Jiande County in 1988 revealed that the ratio of Hantaan (72.5%) to Seoul (26.8%) serotype virus infections was 2.7:1. Two epidemic seasons were found, with a major peak in November and a minor peak in June, and both were associated with Hantaan serotype virus infections that coincided with two seasonal peaks of the A. agrarius population and local agricultural activities in the fields. Seoul serotype virus infections occurred with a small peak during the months of December through May, in which in-house activities were dominant. All data suggested that Jiande County was an area endemic for HFRS, predominantly of the Hantaan virus serotype, combined with Seoul serotype virus infections.

Animals↗
PubMed1995

[Effect of electroacupuncture on the discharges of pain-sensitive neurons in the hypothalamic dorsomedial nucleus of rats].

The discharges of pain-sensitive neurons of the hypothalamic dorsomedial nucleus (DMH) in Sprague-Dawley rats were recorded with glass microelectrodes, After electroacupuncture acupoints "Zusanli" and "Sanyinjiao", the rate of spontaneous discharges and the rate and duration of the pain-evoked discharges of pain-excitatory units of DMH were profoundly decreased, and the spontaneous firing rate of pain-inhibitory units was increased while their inhibitory response to nociceptive stimulation was released by the electroacupuncture. The results mentioned above suggest that DMH participates in the activity of acupuncture analgesia.

Acupuncture Analgesia↗
PubMed1994

Retrospective and prospective studies of hemorrhagic fever with renal syndrome in rural China.

Residents of two villages in Zhejiang Province, China, were interviewed and serum samples were collected to assess prevalence of hantavirus infection. Antibody prevalence was 12% (219/1811), with a ratio of illness to infection of 1.0:5.4. Seroprevalence increased with age, but no association was found with sex. There was also no evidence of vertical transmission. One year later, 2.3% (30/1325) of seronegative subjects had seroconverted including 2 who had hemorrhagic fever with renal syndrome. Peak incidence of infection occurred in those 15-39 years old. Hantaan was the dominant serotype; Seoul serotype was less common (5:1). Host reservoirs were Apodemus agrarius in agricultural fields and Rattus norvegicus in houses. Risk factors for infection were traces of rat-contaminated food, travel to other areas for farm work, direct rodent contact, camping in grain fields, living in a house on the periphery of a village, stacking straw stacks outside houses, and keeping cats. All may provide exposure to infectious rodent reservoirs.

Adolescent↗
PubMed1994

A Selective Medium for the Isolation and Quantification of Bradyrhizobium japonicum and Bradyrhizobium elkanii Strains from Soils and Inoculants.

The ecological examination of members of the family Rhizobiaceae has been hampered by the lack of a selective medium for isolation of root nodule bacteria from soil. A novel non-antibiotic-containing medium has been developed which allows selective isolation of Bradyrhizobium japonicum and B. elkanii strains from soil and inoculants. The medium, BJSM, is based on the resistance of B.japonicum and B. elkanii strains to more than 40 mug of the metals ions Zn and Co per ml. BJSM does not allow growth of Rhizobium sp. strains. We used BJSM to isolate bacteria from a Hubbard soil and from several commercially prepared soybean inoculants. Ninety-eight percent of the isolates obtained from Hubbard soil nodulated Glycine max cv. Kasota, and between 55 and 95% of the isolates from the commercial inoculants had the ability to nodulate soybeans. Numbers of bradyrhizobia obtained by using BJSM, strain-specific fluorescent antibodies, and the most-probable-number plant infection assay indicated that the three techniques were comparable in quantifying B. japonicum strains in soils and inoculants, although most-probable-number counts were generally 0.5 order of magnitude greater than those obtained by using BJSM. Results of our studies indicate that BJSM is useful for direct isolation and quantification of B. japonicum and B. elkanii from natural soils and inoculants. This medium may prove to be an important tool for autecological and enumeration studies of diverse populations of bradyrhizobia and as a quality control method for soybean inoculants.

Journal Article↗
PubMed1994

[A study on the pectinase-producing abilities of Aspergillus flavus in grain of Zhejiang Province].

Eighty strains of Aspergillus flavus were isolated from 110 specimens of rice, wheat flour and malt, and their pectinase-producing abilities were studied in toxigenic and non-toxigenic strains. Levels of pectinase-production by A. flavus were determined with measuring the diameter of the colourless and transparent zone formed around the colonies stained with ruthenium red. Toxigenic strains with high levels of pectinase-production (with a diameter of transparent zone more than 5 mm) accounted for 82.6% and non-toxigenic strains for 42.1% of the total, respectively, and their difference reached a significant level. The level of pectinase-production in toxigenic strains was higher than that in non-toxigenic ones.

Aspergillus flavus↗
PubMed1993

Human toxicosis caused by moldy rice contaminated with fusarium and T-2 toxin.

This is the first report on human toxicosis in China caused by moldy rice contaminated with Fusarium and T-2 toxin due to heavy rainfall during rice harvest season. One hundred and sixty-five persons ate the moldy rice and ninety-seven persons fall ill of food poisoning. The incidence was 58.8% and latent period was 10-30 min. The chief symptoms were nausea, dizziness, vomiting, chills, abdominal distension, abdominal pain, thoracic stuffiness and diarrhea. The fungi isolated from the moldy rice were predominantly Fusarium heterosporum (F. heterosporum) and F. graminearum. T-2 toxin was found in these moldy rice and the highest level was 420 ppb. The chief causative agent of intoxication was T-2 toxin.

China↗
PubMed1992

[Effect of electro-acupuncture on cortical and hippocampal EEG in adjuvant arthritis rats].

Adjuvant arthritis (AA) rats were used as the chronic pain model. The cortical and hippocampal (HPC) EEG were recorded. The behaviour and local inflammatory reaction were observed. The results showed an arousal response of desynchronization of the ECoG and HPC EEG in the AA rats, the delta waves were decreased and beta waves increased significantly. However, the inhibited effect to the desynchronization were showed could be inhibited by the electro-acupuncture (EA) on bilateral Zusanli points and morphine in the AA rats. The results suggested that the cortex and hippocampus participate in the modulating action of chronic pain, and the EA has an analgesic action.

Acupuncture Analgesia↗
PubMed1992

[A study of the regularity of pain threshold changes after trauma and the effect of electroacupuncture].

Pain threshold of rats was measured by the latent period of tail flick and limb withdrawal elicited by radiant heat. 52 male SD rats were used and trauma was produced by aseptic amputation just beneath the right ankle joint. The effect of nerve block and electroacupuncture (EA) was studied and non-traumatic groups were arranged as control. The pain threshold was reduced right after trauma and the lowest level appeared on the 3rd day and then recovered gradually up to the 7th day after trauma. Nerve block and EA markedly raised the pain threshold. Particularly, EA elevated pain threshold of traumatic rats more marked and long-lasted than the effect of nerve block. This may be resulted by mobilizing the functions of the endogenous analgesic systems.

Acupuncture Analgesia↗
PubMed1992

Comparison among three screening methods for aflatoxigenic isolates.

Seventy-six isolates of Aspergillus flavus, which were isolated from one hundred food stuffs in Zhejiang Province, were detected with RMC, AMCS and APA methods for aflatoxigenicity. The rates of toxigenic isolates detected by the three methods were 11.8%, 18.4% and 9.2% respectively. There were twenty toxigenic isolates detected by the three methods (26.3%) AMCS method was better than other methods. False negatives appeared in all methods. False positive appeared in both AMCS method and APA method. It was suggested that AMCS method may be a safe, simple and reliable method for screening toxigenic isolated if some aspects were improved.

Aflatoxins↗
PubMed1990

Alteration of the humoral immune response against muscle acetylcholine receptor by timed administration of alpha(1----3)dextran.

Previously, we discovered a profound idiotypic connectivity among antibodies involved in the immune responses to alpha(1----3)dextran (Dex) and the acetylcholine receptor (AChR). The present studies were undertaken to assess whether these connections represent functional pathways for regulation. It was found that immunization of mice with Dex prior to challenge with AChR reduced the subsequent response to receptor. The timing of the Dex administration was crucial for this effect with a 6-day delay between Dex and AChR being optimal whereas 0- or 12-day delays proved ineffective. The suppressive effect was specific for Dex, as treatment with the closely related, but idiotypically distinct, alpha(1----6)dextran did not diminish the anti-AChR response. Consistent with functional connections in the AChR-Dex network, an inverse relationship between anti-AChR and anti-Dex antibodies was observed in these studies. Thus, high levels of anti-AChR antibodies were associated with low levels of anti-Dex antibodies and vice versa. A similar relationship was observed for serum antibodies from patients with myasthenia gravis. To investigate the mechanism for the antigen-induced cross-regulation, hybridomas were constructed from spleen cells of mice treated 6 days earlier with Dex. A variety of idiotypes (Id), anti-Id and anti-anti-Id were obtained from this fusion. In addition, sera from day-6 mice were examined for the expression of key anti-Id which might provide regulation in the anti-AChR response. The main feature of these sera was the presence of EB3-7-reactive antibodies which did not bind Dex, and hence were not identical to J558. A monoclonal antibody with similar properties was obtained from the day-6 fusion (DX6) which had additional binding specificity for anti-AChR antibodies. Antibodies induced by Dex immunization appear to participate in the cross-regulation observed here. Understanding the mechanisms involved in this phenomenon will have important implications for network theory and for prediction of immune responsiveness.

Animals↗
PubMed1990

Monoclonal antibody against alpha(1----3) dextran transfers suppression of the immune response to the acetylcholine receptor.

Previous studies have demonstrated that immunization of BALB/c mice with alpha(1----3) dextran (Dex) is accompanied by a reduction in the subsequent immune response to the acetylcholine receptor (AChR), depending on the timing of the Dex administration relative to AChR challenge. Here, we report that suppression of the anti-AChR response can be transferred by a monoclonal antibody, known as DX2, which is specific for Dex. Serum transfer experiments have also supported the notion that antibody is important for this effect. In addition, two new idiotypic markers have been defined that are expressed mainly by antibodies against Dex, including DX2. The anti-idiotypic reagents (Sh135 and EB5) are derived from the immune response to the AChR. A human monoclonal antibody which binds to Dex (SR 11) resembles the BALB/c antibodies that are involved in the suppression of the anti-AChR response. These findings emphasize the functional relevance of the AChR-Dex network not only for the BALB/c immune response to the AChR, but also for humans with the autoimmune disease, myasthenia gravis.

Animals↗
PubMed1990

Relationship between insulin resistance and insulin receptor deficiency in the elderly.

Insulin receptors on erythrocytes in 59 elderly and 21 youngsters were investigated through a radioreceptor assay. Specific insulin binding to receptors was found to be decreased in the elderly group as compared with the youngsters. The high affinity binding sites averaged 82 +/- 16/RBC in the elderly group, but 109 +/- 22/RBC in the youngsters, and the low affinity binding sites averaged 1497 +/- 371/RBC and 2177 +/- 461/RBC respectively. Affinity constants did not differ significantly between the two groups, and fasting blood glucose and insulin levels were the same statistically. Our results indicate that senility might lead to a decrease in the number of binding sites on cells. A discussion on the relationship between insulin resistance and insulin receptor deficiency in the elderly is presented.

Adult↗