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Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 991 records · Page 55Linked to original sources
PubMed1991

[Effects of blast wave on methionine-enkephalin-like substance (MES) in guinea pig cochleas].

Methionine-enkephalin-like substance in the Corti's organs of guinea pigs with blast trauma-induced deafness was found to be lowered. The most serious changes occurred in the second turn 7 days after the exposure, MEE was then obviously elevated and almost totally recovered at the 23rd day. The transient changes of MEE suggest a reversible decrease of methionine-enkephalin (ME) which might be a neural transmitter within the olivocochlear bundle. The decrease of ME would possibly injure the resistance of hearing organ to further acoustic stimulation.

Animals↗
PubMed1990

Outer membrane permeability and beta-lactamase stability of dipolar ionic cephalosporins containing methoxyimino substituents.

Some enteric bacteria, such as Enterobacter cloacae, can develop high-level resistance to broad-spectrum cephalosporins by overproducing their chromosomally encoded type I beta-lactamases. This is because these agents are hydrolyzed rapidly at pharmacologically relevant, low (0.1 to 1 microM), concentrations, owing to their high affinity for type I enzymes. In contrast, the more recently developed cephalosporins, with quaternary-nitrogen-containing substituents at the 3 position, show increased efficacy against beta-lactamase-overproducing strains and, indeed, have a much lower affinity for type I enzymes. However, the possible contribution of an improved outer membrane permeability in their increased efficacy has not been studied. We found by proteoliposome swelling assays that cefepime, cefpirome, and E-1040 all penetrated the porin channels of Escherichia coli and E. cloacae much more rapidly than did ceftazidime and at least as rapidly as did cefotaxime. Considering that the influx of anionic compounds such as cefotaxime and ceftazidime will be further retarded in intact cells, owing to the Donnan potential, we expect that the newer compounds will penetrate intact cells 2 to 10 times more rapidly than will cefotaxime and ceftazidime. The kinetic parameters of hydrolysis of these agents by E. cloacae beta-lactamase showed that at 0.1 microM, they were hydrolyzed much more slowly than was cefotaxime and at about the same rate as or a lower rate than was ceftazidime. The combination of these two effects explains nearly quantitatively why these newer agents are more effective against some of the beta-lactamase-overproducing gram-negative bacteria.

Bacteria↗
PubMed1990

Some chemical and physical properties of nisin, a small-protein antibiotic produced by Lactococcus lactis.

Nisin is a small gene-encoded antimicrobial protein produced by Lactococcus lactis that contains unusual dehydroalanine and dehydrobutyrine residues. The reactivity of these residues toward nucleophiles was explored by reacting nisin with a variety of mercaptans. The kinetics of reaction with 2-mercaptoethane-sulfonate and thioglycolate indicated that the reaction pathway includes a binding step. Reaction of nisin at high pH resulted in the formation of multimeric products, apparently as a result of intramolecular and intermolecular reactions between nucleophilic groups and the dehydro residues. One of the nucleophiles had a pKa of about 9.8. The unique vinyl protons of the dehydro residues that give readily identifiable proton nuclear magnetic resonances were used to observe the addition of nucleophiles to the dehydro moiety. After reaction with nucleophiles, nisin lost its antibiotic activity and no longer showed the dehydro resonances, indicating that the dehydro groups had been modified. The effect of pH on the solubility of nisin was determined; the solubility was quite high at low pH (57 mg/ml at pH 2) and was much lower at high pH (0.25 mg/ml at pH 8 to 12), as measured before significant pH-induced chemical modification had occurred. High-performance liquid chromatography on a C18 column was an effective technique for separating unmodified nisin from its reaction products. The cyanogen bromide cleavage products of nisin were about 90% less active toward inhibition of bacterial spore outgrowth than was native nisin. These results are consistent with earlier observations, which suggested that the dehydro residues of nisin have a role in the mechanism of antibiotic action, in which they act as electrophilic Michael acceptors toward nucleophiles in the cellular target.

Amino Acid Sequence↗
PubMed1990

Human leukocyte antigens -A, -B, -C, and -DR and nasopharyngeal carcinoma in northern China.

We observed HLA associations in patients with nasopharyngeal carcinoma from northern China. There was an increased risk of nasopharyngeal carcinoma associated with HLA-B35 and a difference in the HLA association between patients with early- and late-onset disease. The frequency of B35 was significantly higher in patients than in control subjects, especially in early-onset patients (less than 30 years old). Late-onset patients had a higher frequency of DR2 as compared with normal subjects.

Adult↗
PubMed1990

[Involvement of oxytocin in spinal cord in acupuncture analgesia].

The influence of intrathecal injection of oxytocin (OT), anti-OT serum (AOTS) and naloxone on pain threshold and electroacupuncture (EA) analgesia in rats was investigated. The tail-flick induced by potassium iontophoresis was used to measure the pain threshold. The increase in pain threshold was observed within 70 min after OT injection (100 ng), and it was much more effective than that of the ACSF injection (P less than 0.001). The OT administration could enhance the EA analgesia. This effect was of dose-related. Although injection of AOTS did not affect the pain threshold, it diminished EA analgesia. Furthermore, injection of naloxone did not influence the action of OT on EA analgesia. Our results showed that OT in spinal cord plays an important role in the EA analgesia, and its effects is independent of endogenous opiate peptides.

Acupuncture Analgesia↗
PubMed1990

Dynamic study on iliac trabeculae of normal Chinese.

We studied 41 iliac bone blocks taken by biopsies from normal Chinese who were divided into several groups by age. On the schedule of 3-11-3-5 days, double tetracycline labellings were administered before bone biopsies. Ten microns undecalcified sections were made with Reichert-Jung microtome and analyzed with Zeizz MOP-Videoplan by light and fluorescent microscopy. The results showed that bone formation had a peak value at adolescence and the mean wall thickness decreased gradually with age. Bone dynamics fluctuated with age because of endocrinological changes in the intrinsic environment. The data we obtained may be used as a reference for clinical investigation of various metabolic bone disorders.

Adult↗
PubMed1990

[The establishment of experiment model of gastric dysrhythmia and the study of its mechanism in rabbits].

In fasting and anaesthetic rabbits, the experimental model of gastric dysrhythmia could be produced by electric stimulation of inferior phrenicus vagus and splanchnic nerve for innervation of corpus and antrum, or by left gastric artery infusion of Adr, Ach and glucagon at a steady velocity. The results were as follows: (1) Electrical stimulation of inferior phrenicus vagus at low frequency and intensity could increase the frequency and amplitude of basic electric rhythmia (BER) or slow wave (P less than 0.01), and might induced tachygastria and tachyarrhythmia. Electrical stimulation of splanchnic nerve could increase the frequency and amplitude of BER (P less than 0.05), and might induced bradygastria. (2) Bradygastria could be elicited by left gastric artery infusion of Adr (400 micrograms/kg/h). The frequency and amplitude of BER induced were decreased. Tachyarrhythmia could be elicited by infusion of Ach (400 micrograms/kg/h). The frequency and amplitude of BER induced were increased. Dysrhythmia of BER could be elicited by infusion of glucagon (400 micrograms/kg/h). (3) Electroacupuncture of "Zusanli" acupoint may exhibit double modulated effects on experimental model of gastric dysrhythmia. Different types of gastric dysrhythmia including tachygastria, bradygastria and tachyarrhythmia could turned to approach the normal gastric myoelectric activity. It is revealed that such effects of electroacupuncture may be mediated via autonomic nerve and peripheric special receptors.

Acupuncture Therapy↗
PubMed1990

[An approach to mechanism of function of auricular point].

UNLABELLED: This investigation was performed with thirty adult rabbits which divided auricular vagus, great auricular, cervical sympathetic and all auricular denervation. By gastrointestinal electro-physiologic methods, the changes of gastrointestinal electric activity in corpus, antrum, duodenum and colon were observed with car needing to evaluate the mechanism of function of auricular point. RESULTS: In intact car innervation, the changes of gastrointestinal electric activity on ear needling were obvious (P less than 0.05-0.01). While the one with ear nerve selected showed that influence of ear acupuncture still remained, but when the whole auricle was denervated the influence of ear needling on gastrointestinal electric activity obviously deceased or disappeared. pro- and post needing the changes on gastrointestinal electric activity were not statistically different (P greater than 0.05). Recordings at the four parts of digestive tract gave similar results in frequency, amplitude, motility index, action area integral. Exerting stimulation on gastric vagus or sympathetic nerves could bring about double phase modulatory (excitatory or inhibitory). The above revealed that the functions of ear point in diagnosis and therapy is not due to one kind of nerves in periphery. The functions of ear point at innervation may be in its entirety. It was reported that function of ear points has something to do with auricular vagus or great auricular or sympathetic nerves, but, this is only one side of the matter. Moreover, since auricular point are associated with various propagation tracts and with modulation of nerve centers, their mechanism is very complicated and needs to be further studies.

Acupuncture Points↗
PubMed1989

Molecular cloning and sequencing of chicken liver fatty acid synthase cDNA.

The complete amino acid sequence of chicken liver fatty acid synthase [acyl-CoA:malonyl-CoA C-acyltransferase (decarboxylating, oxoacyl- and enoyl-reducing, and thioester-hydrolyzing), EC 2.3.1.85] has been determined from the corresponding cDNA sequence. A 5.3-kilobase-pair (kbp) region of cDNA coding for chicken fatty acid synthase has been cloned and sequenced that is contiguous to the 2.3-kbp region previously sequenced [Yuan, Z., Liu, W. & Hammes, G.G. (1988) Proc. Natl. Acad. Sci. USA 85, 6328-6331]. The cDNA codes for the remaining 1677 amino acids of the previously unsequenced region of the protein. The amino acid sequence contains peptides known to be associated with the NADPH binding site of the enoylreductase active center, the acetyl/malonyltransacylase active site, the "waiting" site containing cysteine, and a pyridoxal 5'-phosphate binding site. Locations of the NADPH binding site of the beta-ketoacylreductase active site and of the dehydratase active site are proposed on the basis of protein sequence homologies to catalytic sites in other enzymes. The molecular weight of the complete polypeptide chain is 267,288. A linear functional map of the chicken fatty acid synthase derived from its primary sequence is presented.

Amino Acid Sequence↗
PubMed1989

Human beta-globin gene expression in transgenic mice is enhanced by a distant DNase I hypersensitive site.

Several lines of evidence suggest that erythroid-specific DNase I hypersensitive sites (HS) located far upstream of the human beta-globin gene are important in regulating beta-globin gene expression. We used the polymerase chain reaction technique to amplify and clone an 882-base-pair DNA fragment spanning one of these HS, designated HSII, which is located 54 kilobases upstream of the beta-globin gene. The cloned HSII fragment was linked to a human beta-globin gene in either the genomic (HSII-beta) or antigenomic (HSII-beta) orientation. These two constructs and a beta-globin gene alone (beta) were injected into fertilized mouse eggs, and expression was analyzed in liver and brain from day-16 transgenic fetuses. Five of 7 beta-transgenic fetuses expressed human beta-globin mRNA, but the level of expression per gene copy was low, ranging from 0.93 to 22.4% of mouse alpha-globin mRNA (average 9.9%). In contrast, 11 of 12 HSII-beta transgenic fetuses expressed beta-globin mRNA at levels per gene copy ranging from 31.3 to 336.6% of mouse alpha-globin mRNA (average 139.5%). Only three fetuses containing intact copies of the HSII-beta construct were produced. Two of three expressed human beta-globin mRNA at levels per gene copy of 179.2 and 387.1%. Expression of human beta-globin mRNA was tissue-specific in all three types of transgenic fetuses. These studies demonstrate that a small DNA fragment containing a single erythroid-specific HS can stimulate high-level human beta-globin gene expression in transgenic mice.

Animals↗
PubMed1989

[Anti-inflammatory and anti-allergic action of aloperine].

Aloperine, an alkaloid isolated from Sophora alopecuroides L, showed a marked suppressive effect on the swelling of the rat's hind paw induced by injecting carrageenin, macostatin, PGE2, histamine, 5-HT, on the rat's scald oedema induced by scalding its hind paw, and on the increased permeability of capillaries caused by histamine and the leukocytic migratory response. The swelling induced by injecting carrageenin into the hind paw of adrenolectomized rats was still significantly inhibited. Noticeably, aloperine reduced the content of PGE and histamine in the exudate formed after injecting carrageenin and dextran into the rat's hind paw, and increased the stability of red cell membranes, the activity of catalase (CAT) in hepatic tissue of mice, and reduced the content of malondialdehyde (MDA) in hepatic tissue of intoxicated mice. It had no apparent effect either on the activity of superoxide dismutase (SOD) in mice serum or on the phagocytosis of the monocyte-macrophage system, or on Forssman cutaneous vasculitis and the content of immune complex in serum of rats with Arthus reaction. But it had certain inhibitory effect on the PCA reaction and significant inhibitory effect upon such allergic reaction as Arthus reaction, reversible passive Arthus reaction, the delayed hypersensitivity reaction induced by tuberculin in rats, and adjuvant arthritis.

Alkaloids↗
PubMed1989

[Dynamic changes of the plasma prekallikrein activity in patients with acute myocardial infarction].

The activity of the plasma prekallikrein was assayed by using dextran sulfate as activator and chromogenic compound substance Na-benzoyl-DL-arginine-4-nitroanilid-hydrochloride (BAPNA) as substrate. The dynamic changes of the plasma prekallikrein activity were observed in 22 patients with acute myocardial infarction (AMI) at different period. The correlation between plasma prekallikrein activity and serum CPK activity were analysed in part of the patients. The results indicate that the plasma prekallikrein activity decreased significantly in AMI, especially on the third day after onset. The decrease of plasma prekallikrein and increase of serum CPK were correlated negatively. The results indicate that the chromogenic compound substance BAPNA can be used to determine the activity of plasma prekallikrein. The kinin system was activated by certain factors in AMI, causing the decrease of plasma prekallikrein and increase of bradykinin.

Adult↗
PubMed1989

[Studies on the chemical constituents of Liriope spicata Lour (Thunb), var. prolifera Y.T. Ma].

From the methanol extract of the roots of Liriope spicata Lour (Thunb) var. prolifera Y.T. Ma (Liliaceae) cultivated in Hubei province (China) four steroidal glycorides, tentatively named glycoside I, II, III and IV, were isolated. On the basis of chemical evidences, IR, EI-MS, FAB-MS, 1HNMR and 13CNMR analysis, structures of these glycosides were elucidated and identified as beta-sitosterol(major) and stigmasterol(minor)-beta-D-glucopyranoside (glycoside I), 25(S)-ruscogenin 1-O-beta-D-fucopyranosido-3-O-alpha-L-rhamnopyranoside (glycoside II), 25(S)-ruscogenin 1-O-alpha-L-rhamnopyranosyl(1----2)-beta-D-xylopyranoside (glycoside III) and 25(S)-ruscogenin 1-O-[alpha-L-rhamnopyranosyl(1----2)] [beta-D-xylopyra-nosyl(1----3)]-beta-D-fucopyranoside (glycoside IV), in which both glycoside III and glycoside IV are new steroidal saponins.

Chemical Phenomena↗
PubMed1989

[Evaluation of various parameters in the differential diagnosis of Cushing's disease and Cushing's syndrome caused by adrenal adenoma].

Evaluation of the clinical and biochemical parameters for differential diagnosis of two types of Cushing's syndrome, pituitary-dependent Cushing's disease and adrenal adenoma, was studied with analysis of the histories of 79 cases of Cushing's disease and 23 cases of adrenal adenoma. The data show that the symptoms, signs and the routine biochemical analyses were not significantly different between two groups. High-dose dexamethasone suppression test had about 90% coincidence rate in the differential diagnosis with 24-hour urine free cortisol (UFC), which was better than 24-hour urine 17-OHCS. Interestingly, low-dose dexamethasone test was highly valuable and the 24-hour urine 17-KS quite helpful in the differential diagnosis of two types of Cushing's syndrome. Serum N-POMC measurement was the most valuable among the parameters, because there was no overlap between the two groups of Cushing's syndrome.

17-Ketosteroids↗