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Biomedical subjects

J G Li

Publications and source records attributed to J G Li.

At least 55 records · Page 3Linked to original sources
PubMed1995

The relationship of Oxalobacter formigenes and calcium oxalate calculi.

The intestinal Oxalobacter Formigenes were isolated in 30 cases of urolithaiasis and in 45 controls. The biologic characters and morphology of the bacteria were also observed. The results showed that the colony counts in urolith group 9 (mean 10(3)/g. faeces) were significantly less than that of controls (mean 10(8)/g. faeces) (P < 0.001). It is believed that the lesser amount of oxalobacter formigenes in urolith was the important factor of the calcium oxalate calculi formation.

Adult↗
PubMed1994

[Primary implantation of posterior chamber intraocular lenses in eyes with defective posterior capsule].

Primary implantation of posterior chamber intraocular lens (PC IOL) was performed in 70 eyes with defective posterior capsule following extracapsular cataract extraction. The visual acuity was 0.5 or better at 3 months and 12 months postoperative in 97.1% and 88.6% of the cases respectively. Complications were rare. The authors put forth the following principles for such cases: (1) injection of air or Healon to maintain a deep anterior chamber: (2) the insertion or rotation of the IOL should be away from the area of capsular rupture; (3) the long axis of the IOL should cross the meridian of the posterior capsule rupture: (4) the residual anterior capsule may be utilized to support the IOL; (5) complete clearance of any vitreous in the anterior chamber; and (6) performance of at least 2 peripheral iridectomies to guard against pupillary block. This technique is applicable in eyes with peripheral posterior or capsule defect of less than 120 degrees or with central rupture of less than 4mm.

Adolescent↗
PubMed1993

Influence of thymosin on the level of cyclic nucleotides in rats with experimental varicocele.

Experimental varicocele was induced by partial ligation of the left renal vein in rats, and the effect of thymosin (fraction 5), a hormone secreted by the thymus, on the level of cyclic nucleotides was investigated. The levels of cAMP and cGMP in plasma and testicular tissue were estimated using radioimmunoassay techniques. The results showed that the level of cAMP in bilateral testicular tissues in rats with experimental varicocele decreased considerably, especially in the left testicular tissue as compared with that in the control group (P < 0.05). 4 weeks after thymosin administration (0.5 mg/rat, twice a week), the level of cAMP in bilateral testicular tissues rose significantly, as compared with that in the experimental varicocele group (P < 0.01). These findings indicate that there exists imbalance in the metabolism of cyclic nucleotides in rats with experimental varicocele. This suggests that the abnormal level of cyclic nucleotides is one of the causes of infertility with varicocele. Since thymosin participates in the metabolism and regulation of cyclic nucleotides, it may have a direct or an indirect effect on the growth and function of reproductive cells.

Animals↗
PubMed1992

[Synthesis and pharmacological activities of the 1-substituted 4-methoxycarbonyl fentanyl derivatives].

Five derivatives of 4-methoxycarbonyl fentanyl were synthesized, four of them carry in the molecules some radicals that may alkylate opiate receptors. Their analgesic activities were measured and the irreversible inhibitory effects of all compounds on the electrically elicited contraction of MVD were investigated. The analgesic test showed that the compounds in this series possess analgesic activity with typical morphine--like action. The isolated tissue experiment indicated that these new compounds were all capable of binding with opiate receptors, and that compounds 2, 4 and 5 were determined to be a new irreversible ligand of opiate receptors.

Analgesics, Opioid↗
PubMed1991

[Comparative studies on the affinities of K-II and U-50488H for kappa opiate receptor].

3,4-Dichloro-N-methyl-N-[trans-2-(1-delta 3-pyrrolinyl)-cyclohexyl] benzenacetamide hydrochloride (K-II) is a novel analogue of U-50488H. Previous studies have demonstrated that K-II is more potent than U-50488H in analgesic activity in mice and in inhibitory effect on electrically induced contractions of the isolated rabbit vas deferens. In this paper, we determined the affinities of K-II and U-50488H for kappa opiate receptor in guinea pig cerebellum and frontal cortex using radioreceptor binding assay (saturation studies and competition studies), and calculated Ki values of K-II and U-50488H by the Cheng-Prusoff equation. The results indicate that the affinity of K-II for kappa opiate receptor is 6-42 times greater than that of U-50488H. The selectivity of K-II for opiate receptor subtypes is being studied.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1991

[Comparison of pharmacological profile of selective kappa-opioid agonist K-II and U-50488].

K-II is an analogue of U-50488, a selective kappa-opioid agonist. Comparison of pharmacological profile of K-II and U-50488 was studied using in vitro and in vivo methods. The results showed that the IC50 values of K-II and U-50488 on electrically induced contraction of the rabbit vas deferens were 0.42 nmol/L and 26.5 nmol/L, respectively. ED50 values of K-II and U-50488 in impairing motor function of mouse in the horizontal screen test were 1.7 and 15.3 mg/kg, respectively. The effect of K-II in reducing spontaneous activity of mouse was 6 times as potent as U-50488. These results suggest that K-II is a more potent kappa agonist in pharmacological effects than U-50488.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1990

Analysis of Azotobacter vinelandii strains containing defined deletions in the nifD and nifK genes.

Strains of Azotobacter vinelandii which contain defined deletions within the nifD and nifK genes which encode, respectively, the alpha and beta subunits of the MoFe protein of nitrogenase were analyzed. When synthesized without its partner, the beta subunit accumulated as a soluble beta 4 tetramer. In contrast, when the alpha subunit was present without its partner, it accumulated primarily as an insoluble aggregate. The solubility of this protein was increased by the presence of a form of the beta subunit which contained a large internal deletion, such that the alpha subunit could participate in the assembly of small amounts of an alpha 2 beta 2 holoprotein. When synthesized alone, the beta subunit was remarkably stable, even when the protein contained a large internal deletion. The alpha subunit, however, was much more rapidly degraded than the beta subunit, both when it was synthesized alone in its native background and when it was synthesized with its beta subunit partner in a foreign background. Antibodies raised against purified alpha 2 beta 2 MoFe protein recognized epitopes only on the nondenatured beta subunit and not on the nondenatured alpha subunit. Our findings that all epitopes for the alpha2beta2 tetramer appeared to be on the beta subunit, that the beta subunit assembled into beta4 tetramers, and that the alpha subunit alone was very insoluble, combined with the previous finding that the Fe protein binds to the beta subunit (A. H. Willing, M. M. Georgiadis, D. C. Rees, and J. B. Howard, J. Biol. Chem. 264:8499-8503, 1989) all suggest that the beta subunit has a more surface location than the alpha subunit in the alpha2beta2 tetramer.

Antibodies↗
PubMed1990

Effects of PGE1 on platelet deformability.

Prostaglandin E1 (PGE1) is frequently used as a stabilizing agent while isolating platelets. The platelet-stabilizing effect of PGE1 is mediate through the PGE1 receptor and the consequent increase of intracellular cAMP. The discoid shape of platelet is thus maintained. Recently, we have studied the effect of PGE1 on platelet deformability with micropipette aspiration technics, using pipettes with radii (Rp) of 0.26-0.36 micron. Platelets, obtained from platelet-rich plasma, and suspended in Hank's buffer containing BSA, glucose, adenosine and theophylline, were subjected for micropipette aspiration test within 2 hr after sampling. In general, PGE1 treated platelets (greater than 75%) remained as non-activated form as revealed under video microscopy and maintained their discoid shape for as long as 6 hr. The time course of the extension length (Dp, in micron) of the platelets in response to aspiration with a negative pressure of 5 cm H2O (tension = 0.15 dynes/cm) was analyzed by using a digital image analyzer system (IRIS 3120 with IP-512, with a resolution of 0.076 microns). A computer program based on the algorithm of real-time reading of image intensity was developed to facilitate real-time data acquisition. The data of Dp/Rp vs time (sec) were fitted by using a second-order equation. The deformability of PGE1 (0.1 microM) treated platelet was decreased significantly as compared with control. These results indicate that the platelet stabilization by PGE1 is accompanied by a decrease in platelet deformability.

Alprostadil↗
PubMed1989

Iron-molybdenum cofactor insertion into the Apo-MoFe protein of nitrogenase involves the iron protein-MgATP complex.

Nitrogenase is composed of two component proteins, the iron protein (Fe protein) and the molybdenum-iron protein (MoFe protein). The Fe protein is a Mr 60,000 dimer of identical subunits with one bridging [4Fe-4S] center. It serves as a one-electron donor to the MoFe protein in a reaction that is coupled to MgATP hydrolysis. The MoFe protein is an alpha 2 beta 2 tetramer of Mr 220,000 which contains four [4Fe-4S] clusters and two iron-molybdenum cofactor (FeMo cofactor) centers. The exact structure of FeMo cofactor is not known, but it is believed to form the active site of the enzyme. Using specifically constructed deletion mutants of Azotobacter vinelandii, we have previously shown that the Fe protein, but not the MoFe protein, is required for FeMo cofactor biosynthesis (Robinson, A. C., Dean, D. R., and Burgess, B. K. (1987) J. Biol. Chem. 262, 14327-14332). During the partial purification of a FeMo cofactor-deficient form of the MoFe protein from one of these mutants (DJ54, delta nifH), we have discovered that, in addition to biosynthesis, the Fe protein-MgATP complex is involved in FeMo cofactor insertion into the MoFe protein. This insertion process is also sensitive to a number of other parameters (e.g. salt, pH, temperature, protein concentration). Based on our experimental data, we present a model for how this insertion reaction might take place, in which the Fe protein-MgATP complex binds the FeMo cofactor-deficient form of the MoFe protein and stabilizes a specific conformation of the MoFe protein that has the FeMo cofactor binding site exposed and available for coordination by preformed FeMo cofactor.

Adenosine Triphosphate↗
PubMed1989

[Irreversible action of the opioid agonist alpha-CAM and its reaction with SH groups at opioid receptor binding sites].

7 alpha-Bis (beta-chloroethyl)amino-methyl-6,14-endoethenotetrahydrooripavine (alpha-CAM) was found to bind to opioid receptors irreversibly and react directly with sulfhydryl (SH) groups in P2 preparations of rat brain. The P2 preparations were pretreated as follows: protection of the SH groups at the opioid receptor binding sites by morphine or etorphine, and inactivation of the SH groups outside the binding sites by N-ethylmaleimide (NEM), followed by removal of the morphine or etorphine by washing. alpha-CAM was still able to bind the pretreated P2 preparations in an irreversible manner. The results indicate that the formation of covalent bonds between alpha-CAM and the SH groups of opioid receptor binding sites is possibly one of the biochemical mechanisms of the irreversible action of alpha-CAM.

Analgesics↗
PubMed1989

[Pharmacological study on a new irreversible agonist of opioid receptors, 7 alpha-bis(beta-chloroethyl) aminomethyl-6, 14-endoetheno-tetrahydrooripavine].

7 alpha-bis (beta-chloroethyl) aminomethyl-6, 14-endoetheno-tetrahydro oripavine (alpha-CAM) is a new irreversible opioid receptor agonist. Its effect on isolated tissues (guinea pig ileum, mouse vas deferens, rat vas deferens and rabbit vas deferens) were studied. It was shown to be bound irreversibly to rat brain P2 membrane preparations. The ED50 of its analgesic effect in mice (icv) was found to be 0.12 nmol/mouse, and the effect may last as long as 2-3 days. It is a compound which produces the longest analgesia known up to date. A single dose (icv) of alpha-CAM was sufficient to produce dependence in mice. Thus, the compound may serve as an agent for studying the mechanism of physical dependence.

Analgesics↗
PubMed1986

[Ultrasound-guided percutaneous fine-needle puncture cytology in the diagnosis of malignant tumors of the liver].

Results of ultrasound guided percutaneous fine-needle puncture cytology in 142 cases of malignant tumors of the liver are reported. The positive cytology was noted in 118 (83.1%) (10 suspicious). The primary liver cancer comprised 99 cases. In 7 lesions, equal to or less than 3 cm in diameters, 6 were positive in cytology. In 20,3-5 cm in size, 18 were positive. In 15 false-negatives, 12 were larger than 5 cm in diameter. Among 43 cases of metastatic liver cancer, 34 showed positive cytology and 9 false-negative. Among 108 cases of benign hepatic diseases, in 49.1%, it was difficult to arrive at definitive diagnosis by ultrasonography only, but in 97.2% malignancy was excluded by ultrasound guided fine-needle puncture cytology. The suspicious false-positive result occurred only in 3 cases. In this series, there were 250 cases of malignant tumors and benign diseases. The overall accurate diagnostic rate was 89.2%. All the patients had been followed for more than 6 months. The differential diagnosis between malignant and benign tumors, causes of misdiagnosis and complications are discussed.

Adolescent↗