Biomedical subjects

J R Zhang

Publications and source records attributed to J R Zhang.

At least 55 records · Page 3Linked to original sources

PubMed1990

Improved technique for a one-stage repair of significant defects of the ear.

An improved technique for repair of severe acquired partial defects of the auricle in one stage is described. The common postauricular flap with its base on the margin of the auricular defect is usually unable to repair a severe partial auricular defect in one stage because of the limited length of the flap. The authors developed this technique by means of lengthening the flap with a piece of subcutaneous tissue of the scalp, so that the ear framework can be covered completely in one stage. All flaps in this group survived totally. Seven patients with severe acquired partial defects of the auricle underwent this procedure, and good results were obtained.

Adult↗

PubMed1990

Effects of galanin on electrical activity of pancreatic islet cells.

Intracellular microelectrode technique was used to investigate the effect of galanin on the electrical activity of beta cells of Langerhans islets of mice. Galanin 0.15 and 0.3 mumol/L in the perfusion medium inhibited the basic electrical activity induced by glucose 5.5, 11.1 and 20 mmol/L in decreasing the frequency and amplitude of the spikes. In some cells, during galanin inhibition there was a hyperpolarization after the spike. Verapamil (30, 60 and 90 mumol/L), a blocker of voltage-dependent Ca channels, blocked dose-dependently the electrical activity induced by glucose and attenuated the depolarization induced by KCl 50 mmol/L. Galanin 0.3 mumol/L also attenuated the depolarization induced by KCl 50 mmol/L, similar to the effect of verapamil. The results suggest that the effect of galanin on inhibition of the electrical activity of beta cell might be due to blocking of voltage-dependent Ca2+ channels.

Animals↗

PubMed1990

[Determination of two major metabolites of A-OT-Fu in mice serum by 4th order derivative UV spectrophotometry].

A 4th order derivative UV spectrophotometric method was developed for the determination of two major metabolites (TFu and 5-Fu) of A-OT-Fu in mice serum following per os of 290 mg/kg of the drug. TFu and 5-Fu were extracted from mice serum by ethyl acetate. The amplitudes of 252 and 289 nm for axle are linear with concentration of TFu and 5-Fu within the range of 5-50 micrograms/ml. Under the given experimental condition the recovery of TFu and 5-Fu were over 95%. The maximum concentration of TFu and 5-Fu appeared at 1 h and 2 h respectively after administration.

Animals↗

PubMed1990

[Endogenous creatinine clearance rate and normal values in healthy young subjects].

Serum creatinine (Scr) and creatinine clearance rate (Ccr) were measured for their normal values in young and youngster. The subjects included 251 health individuals between the age of 15 and 29.251 of them were tested actually. The datum had been treated by a computer. The Scr normal values are 72.49 and 50.39 mumol/L respectively in the males and females. Their means showed significance differences between the males and females. The upper limit of 95% of normal values were 94.59 and 66.3 mumol/L respectively. The Ccr means of the males and females were 136.89 and 132.13 ml/min/1.73 m2 respectively. Their means showed no significance difference between them. A common lower limit of 95% of normal values was 75.03 ml/min/1.73 m2. It is expected that the information above provide a scientific base and important reference in the future.

Adolescent↗

PubMed1989

Analysis of the upstream region of the Escherichia coli rnd gene encoding RNase D. Evidence for translational regulation of a putative tRNA processing enzyme.

The upstream region of the Escherichia coli rnd gene has been analyzed. A single promoter and transcription start site were identified in the 170-nucleotide upstream region of the clone based on deletion analysis, nuclease S1 mapping, primer extension, and quantitative dot-blots. The start site of transcription is 70 nucleotides upstream of the UUG initiation codon of the RNase D coding region. Between the RNA initiation site and the coding region is a GC-rich hairpin structure followed by 8 T residues that looks like a rho-independent transcription terminator. Surprisingly, deletion of the hairpin structure elevates rnd mRNA levels only slightly (less than 2-fold), but it dramatically decreases RNase D expression (greater than 95%), measured both by activity and immunoblotting. No evidence for an effect on mRNA stability or processing was observed. The uncommon UUG translation initiation codon was converted to AUG by site-directed mutagenesis. This alteration led to an 11-fold elevation of RNase D expression in single-copy plasmids. These data indicate that RNase D expression is negatively regulated at the translational level by the initiation codon, and that an upstream structure (or sequence) also influences translation of this gene.

Base Sequence↗

PubMed1989

[Detection of gastric cancer associated antigens in ascitic and pleural fluid for ascertaining the nature of the exudate].

A new group of gastric cancer associated antigens (MG-Ag) in ascitic fluid and pleural effusion was detected. First of all, the monoclonal antibodies (MG series) were purified and coupled to the miniglobules. The samples to be examined were then mixed with the MG-miniglobules to react. After being blocked by serum of normal mouse, the MG-miniglobules were mixed and made to react with the monoclonal antibodies labeled with HRP. With ELISA method, the MG-Ag levels in ascitic and pleural fluid were determined in 171 patients. The mean value of 87 non-malignant patients plus 3 standard deviations was arbitrarily set as the highest normal limit. Values above this limit were found in 39 (75%) of 52 patients with lung cancer and 20 (83%) of 24 patients with gastric cancer. The MG-Ag level was elevated in 4 (4.6%) of 87 patients with benign diseases. It is not elevated in 8 patients with ovarian cancer. It is suggested that determination of MG-Ag in ascitic and pleural fluid can be used for ascertaining the nature of ascites and pleural effusion.

Antigens, Tumor-Associated, Carbohydrate↗

PubMed1989

[Effects of microiontophoretically applied flurazepam on the respiratory units in the region of the nucleus parabrachialis of the rabbit].

Experiments were carried out on 36 urethane-chloralose aneasthesized, paralyzed, vagotomized and artificially ventilated rabbits. Five-barrel glass micropipettes were used to record unit discharges and to apply flurazepam iontophoretically in the region of the nucleus parabrachialis. Inspiratory units (IUs), expiratory units (EUs), phase-spanning units (I-EUs and E-IUs) and non-respiratory units (NRUs) were observed. 26 (55.3%) out of 47 IUs, 17 (94.4%) out of 18 EUs, 11 (91.7%) out of 12 I-EUs, 2 (18.1%) out of 11 E-IUs and 43 (60.6%) out of 71 NRUs were depressed by flurazepam. The depressant ratio of EUs and I-EUs was statistically different from that of IUs and E-IUs respectively. In flurazepam sensitive 5 IUs and 2 EUs, the depressant effect could not be antagonized by GABA-A receptor antagonist bicuculline. In 10 flurazepam sensitive NRUs, there were 6 (60%) units whose depressant effect of flurazepam could be antagonized by bicuculline. In addition, the effects of acetylcholine (ACh) on the respiratory units and NRUs were examined, 15 (75%) out of 20 IUs were excited and the remaining units were not influenced. The effects of ACh on the EUs, I-EUs and E-IUs were variable, but the effects of ACh on the NRUs were mainly excitatory. In 5 IUs and 1 phase-spanning respiratory units, the depressant effect of flurazepam could not be antagonized by ACh. The results showed that flurazepam mainly depressed the EUs and I-EUs in the region of nucleus parabrachialis, thus interfering with the normal phase transition between the inspiratory and expiratory phase and reducing the respiratory rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Transfer RNA is a substrate for RNase D in vivo.

RNase D is a 3'-exonuclease whose in vitro specificity has suggested a role in tRNA processing. However, since mutant Escherichia coli strains devoid of RNase D display a normal phenotype, it has not been possible to ascertain the enzyme's function or even to determine which RNA is its substrate in vivo. Here we show that transformation of strains devoid of tRNA nucleotidyltransferase with a multicopy plasmid carrying the rnd+ gene leads to extremely slow growth due to elevated levels of RNase D activity. Analysis of such a slow-growing strain revealed that less tRNA is present in the cell and that the tRNA that could be recovered is substantially damaged. These studies demonstrate that RNase D can act at the 3' terminus of tRNA in vivo, and they support the conclusion that RNase D participates in tRNA metabolism.

Endoribonucleases↗

PubMed1988

Escherichia coli RNase D: sequencing of the rnd structural gene and purification of the overexpressed protein.

We have determined the nucleotide sequence of a 1.4-kb-pair fragment of the E. coli chromosome that carries the complete rnd gene encoding RNase D, a putative tRNA processing enzyme. The coding region of rnd extends for a total of 1128 nucleotides beginning at an initiator UUG codon and terminating at a UAA codon, and encodes a 375-amino acid polypeptide of 42,679 daltons, consistent with the known size of RNase D. A rapid purification procedure was developed for isolation of RNase D from strains overexpressing the enzyme. The N-terminal sequence and the amino acid composition of the homogenous protein were in excellent agreement with those derived from the sequence of the rnd gene.

Amino Acid Sequence↗

PubMed1988

Laser-induced multiphoton fluorescence of hemoglobin.

Hemoglobin (Hb) and other samples were irradiated by the 1064 nm nanosecond pulses of an Nd:YAG laser. At room temperature, we observed two red fluorescence bands, which resulted from the absorption of two 1064 nm photons in Hb, and measured the fluorescence emission spectra in the red spectral region for Hb and hematoporphyrin derivative. A red shift of the wavelength and a mirror image in the intensity of fluorescence emissions by two-photon excitation were observed. It is shown that the fluorescence of Hb originates from the heme group. In addition, we also observed fluorescence emission at 392 nm for Hb, which may be from its tryptophan groups.

Fluorescence↗

PubMed1988

Cloning, characterization, and effects of overexpression of the Escherichia coli rnd gene encoding RNase D.

RNase D is a 3'-exoribonuclease whose in vitro specificity has suggested that it is involved in the processing of tRNA precursors. Its in vivo role has remained unclear, however, because mutant cells devoid of the enzyme display no defect in growth or tRNA processing. To learn more about the structure and function of RNase D, we cloned the Escherichia coli rnd gene, which is thought to code for this enzyme. The rnd gene was isolated from a cosmid library based on elevated RNase D activity and was subcloned as a 1.4-kilobase-pair fragment in pUC18. Maxicell analysis of the cloned fragment revealed that a single protein of approximately 40 kilodaltons, which is the size of RNase D, was synthesized. The rnd gene is present as a single copy on the E. coli chromosome and is totally absent in a deletion mutant. Cells that harbored the cloned rnd gene displayed RNase D activity that was elevated as much as 20-fold over that of the wild type. As growth of the culture progressed, however, RNase D specific activity declined dramatically, together with a similar decrease in plasmid copy number. In contrast, no decrease in copy number was observed with an inactive rnd gene. Placement of the rnd gene downstream from the lac promoter led to inducible RNase D overexpression and concomitantly slowed cell growth. These findings support the idea that rnd is the structural gene for RNase D and indicate that elevated RNase D activity is deleterious to E. coli.

Cloning, Molecular↗

PubMed1987

Fluorescence of proteins induced by two-photon absorption.

At room temperature, the UV fluorescence of trypsin, thyroglobulin, hemoglobin and albumin are observed; these molecules undergo two-photon absorption when they are excited with the radiation of a frequency-duplicated Q-switched Nd:YAG laser. It is shown that the fluorescence of these proteins comes from the tryptophan residues and that it has a red shift of about 20 nm relative to the one-photon fluorescence. We suggest that the weak emission from tyrosine arises from the forbidden two-photon transition. The influence of concentration on the fluorescence of hemoglobin and tryptophan is discussed. The two-photon absorption cross-sections are estimated.

Hemoglobins↗

PubMed1987