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G Liang

Publications and source records attributed to G Liang.

83 records · Page 5Linked to original sources
PubMed1989

Sodium channel binding and anticonvulsant activities for the enantiomers of a bicyclic 2,4-oxazolidinedione and monocyclic models.

Racemic 7-phenyl-9,10-dioxo-1-aza-8-oxabicyclo[5.2.1]decane (1), a bicyclic 2,4-oxazolidinedione that we previously reported was a possible sodium channel anticonvulsant, was resolved into its enantiomeric forms, the absolute configurations were determined, and the stereoisomers were evaluated for relative sodium channel binding and whole animal anticonvulsant activities. Similar studies were carried out with two monocyclic models, 5-ethyl-5-phenyl-2,4-oxazolidinedione (2) and 5-ethyl-3-methyl-5-phenyl-2,4-oxazolidinedione (3). None of these isomers exhibited stereoselective effects in the sodium channel assay, and only modest enantioselectivities were observed for 2 and 3 in the anticonvulsant assays. (R)-(-)-1 was, however, 4 times more toxic than (S)-(+)-1 in the rotorod test, and due to its larger protective index, (S)-(+)-1 exhibited greater therapeutic potential than either (R)-(-)-1 or racemic 1.

Animals↗
PubMed1983

Neovascular glaucoma and vitreous hemorrhage following cataract surgery in patients with diabetes mellitus.

The potential complications of cataract surgery in the general population are well known. In addition, cataract extraction in the patient with diabetes mellitus is associated with other potential complications common to this disease: neovascular glaucoma and acceleration of proliferative diabetic retinopathy with or without vitreous hemorrhage. We analyzed the records of 154 patients with diabetes mellitus who had undergone standard intracapsular cataract extraction in one eye only with the other eye serving as the unoperated control eye. We were able to determine the status of the diabetic retinopathy before the operation and to note the development of vitreous hemorrhage and rubeosis iridis/neovascular glaucoma after the operation. If either event occurred within six weeks of the surgery, it was considered to be a complication of the cataract extraction. Intracapsular cataract extraction in this diabetic population, without regard of the preoperative status of the retinopathy, was associated with a statistically significant incidence of postoperative rubeosis iridis/neovascular glaucoma (7.8% vs 0%). In patients with preoperative active proliferative diabetic retinopathy, the risk of developing postoperative rubeosis iridis/neovascular glaucoma was even higher (40% vs 0%). There was also a statistically significant incidence of vitreous hemorrhage after surgery in eyes with no diabetic retinopathy or background diabetic retinopathy (6.5% vs 0%). In patients with active proliferative diabetic retinopathy, there was an increased incidence of vitreous hemorrhage after surgery (20% vs 6.5%), but this was not statistically significant due to the small number of patients studied. Possible explanations for these findings are explored and therapeutic and prophylactic measures recommended.

Cataract↗
PubMed1977

C nuclear magnetic resonance study of five- and six-coordinated carbon in nonclassical organometallic compounds: Dimeric trialkyl-, tricyclopropyl-, and triarylaluminums and some nido and closo carboranes.

A (13)C nuclear magnetic resonance spectroscopic study of dimeric trimethyl-, triethyl-, tricyclopropyl-, and triarylaluminums is reported. The five-coordinated bridging carbons are found consistently more shielded than the terminal carbons, in accordance with the increased p-character of the former. The nature of bridging two-electron three-centered Al-C-Al bonds is discussed. (13)C nuclear magnetic resonance shifts of several nido and closo carboranes containing five and six coordinated carbons and their (13)C-(1)H spin-spin coupling constants were also obtained. The relationship between the carbon chemical shifts and coordination number of the carbon atom is discussed. There is approximately a 20- to 40-ppm shielding of the (13)C chemical shifts of five- and six-coordinated carbons, compared with those of four valent carbons, with a simultaneous general increase of J(C-H) coupling constants.

Journal Article↗
PubMed1976

The unusual Favorskii-Nazarov reaction of dicyclopropyl ketone.

Dicyclopropyl ketone under Favorskii-Nazarov reaction conditions neither gave tetracyclopropylethylene glycol nor 1,1,4,4-tetracyclopropyl-1,4-butanediol by ether incorporation as expected. The hitherto unknown 1,1,5-tricyclopropyl-1-hydroxypentan-5-one is obtained, presumably through the intermediacy of a dianion which nucleophilically attacks the neutral ketone through the cleavage of the cyclopropyl bond.

Journal Article↗
PubMedDate not supplied

Reaction of N-(2-chloroethyl)-N-nitrosoureas with DNA: effect of buffers on DNA adduction, cross-linking, and cytotoxicity.

N-(2-Chloroethyl)nitrosoureas (CNU) are clinically used anticancer drugs whose cytotoxicity is associated with the generation of DNA interstrand cross-links. While studying the sequence selectivity for a series of CNU, a dramatic increase in the formation of N7-alkyldeoxyguanosine was observed when Tris buffer was used rather than phosphate or cacodylate buffers. Moreover, the formation of N7-alkyldeoxyguanosine lesions continues in Tris long after all of the CNU has hydrolyzed. These effects are not seen with the monofunctional alkylating analogues, e.g., N-methyl- and N-(2-hydroxyethyl)-N-nitrosourea. In order to determine if the nature of the CNU-mediated DNA damage was altered by Tris, studies were initiated on the following: (1) alkylation of N7-G in end-labeled DNA restriction fragments; (2) covalent modification of DNA with [ethyl-3H]-N-(2-chloroethyl)-N-nitrosourea; and (3) cytotoxicity in L1210 cells. The data presented demonstrate that Tris increases the yield of the "normal" CNU monofunctional cross-linked adducts, i.e., N7-(2-hydroxyethyl)deoxyguanosine, N7-(2-chloroethyl)deoxyguanosine, O6-(2-chloroethyl)deoxyguanosine, and bifunctional adducts, i.e., 1-(deoxycytid-3-yl)-2-(deoxyguanosin-1-yl)ethane and 1,2-bis(deoxyguanosin-7-yl)ethane. In addition, CNU appears to react with Tris to give a long-lived alkylating intermediate that affords large amounts of DNA adducts not seen with CNU in the absence of Tris. However, in vivo toxicity of CNU in L1210 cells is not affected by the presence of Tris, indicating that the reaction pathway(s) responsible for cross-linking is not significantly sensitive to the nature of the buffer.

Alkylation↗
PubMedDate not supplied

Amyloid arthropathy: possible association with chondrocalcinosis.

Three patients with symptomatic articular or periarticular amyloidosis associated with chondrocalcinosis are reported. None of these patients had evidence of dysproteinemia which has been considered the primary predisposing factor in amyloid arthropathy. The clinical features of these patients are described and possible pathogenesis discussed.

Aged↗