Search PubMed⌕ Search

Biomedical subjects

C Ma

Publications and source records attributed to C Ma.

At least 199 records · Page 11Linked to original sources
PubMed1990

[The influence of P-chlorophenylalanine on the analgesia of electro-acupuncture and the level of SP in CNS of rats].

P-Chlorophenylalanine (PCPA) 250 mg/kg IP, was given to a group of rats. 72 hrs later the electro-acupuncture analgesia was tested and substance P (SP) in the brain stem and the lumbar spinal of the rats was determined by RIA. After PCPA injecting the electro-acupuncture no longer caused analgesia but lowered the pain threshold. Meanwhile the level of SP in the brain stem and lumbar spinal did not increased but much lowered than the group of vehicle injection combined with electro-acupuncture. It suggests that by PCPA depleting the 5-HT in CNS and abating the 5-HT-energic descending inhibition the electro-acupuncture no longer causes analgesia but promotes the SP transmitted release. It further suggests that in lower brain stem and spinal transmission of SP was regulated by descending inhibition. Analgesia of electro-acupuncture activates the 5-HT-energic descending inhibition and decreases the nociceptive transmission of SP partly.

Acupuncture Analgesia↗
PubMed1990

[A study on pathogen antigen and serodiagnosis of Malleus and Melioidosis with McAbs].

A study on pathogen antigen and serodiagnosis of Malleus and Mlioidosis was made with McAbs which are against Ps. mallei or Ps. pseudomallei. The results showed that (1) Ps. mallei and Ps. pseudomallei express different surface antigen types respectively, and there are antigen overlapping in some degree between them; (2) Epitope 2D4 is common to Ps. mallei and Ps. pseudomallei; (3) The antibody which is similar to McAbs 4D4 or 1A9 might be a common serum antibody of Malleus and Melioidosis; and (4) McAb 3A1 is a high specific one which reacts with Ps. pseudomallei only, and with it, it is possible to resolve the immunological problem of distinguishing diagnosis between Malleus and Melioidosis.

Animals↗
PubMed1989

Ortho-iodosobenzoic acid: its acute toxicity and neurobehavioral effects in mice.

o-Iodosobenzoic acid (IBA), in a surfactant micellar medium, is a rapid and efficient catalyst for the hydrolysis of organophosphate (OP) esters. Since little is known about the toxicity of IBA, a primary screen of neurobehavioral toxicity was evaluated in male ICR mice. IBA was administered intraperitoneally in a pH 7.4 phosphate buffer solution containing 8% dimethylformamide. The predominant overt signs of toxicity included an immediate and transient writhing reflex and/or persistent spasmodic myotwitching of the abdomen, and conspicuous suppression of orienting/exploratory behavior and emotional defecation. The dose ranges for ED50 of writhing response, suppression of rearing and spontaneous motor activity overlapped at levels of about one-tenth the acute LD50, 742 (633-856) mumol/kg, being 94.9 (74.5-122.5), 69.8 (47.9-105.4) and 71.1 (49.9-101.3) mumol/kg, respectively; the dose ranges for ED50 of abdominal myotwitching and depression of emotional defecation in a novel environment also overlapped but at levels of about one-fifth the acute LD50, being 138.4 (115.3-167.2) and 146.2 (110.7-196.3) mumol/kg, respectively. Morphine (1.25-10 mg/kg s.c.) antagonized the IBA-induced writhing response and abdominal myotwitching in a dose-dependent manner, with a PD50 of 4.2 and 4.9 mg/kg, respectively. The present report demonstrates that acute intraperitoneal administration of IBA produces an intriguing, non-specific behavioral syndrome, probably resulting from nociceptive stimulation. This implies that IBA might be irritating to the skin and mucosa.

Animals↗
PubMed1988

The dihydrofolate reductase amplicons in different methotrexate-resistant Chinese hamster cell lines share at least a 273-kilobase core sequence, but the amplicons in some cell lines are much larger and are remarkably uniform in structure.

We have previously cloned and characterized two different dihydrofolate reductase amplicon types from a methotrexate-resistant Chinese hamster ovary cell line (CHOC 400). The largest of these (the type I amplicon) is 273 kilobases (kb) in length. In the present study, we utilized clones from the type I amplicon as probes to analyze the size and variability of the amplified DNA sequences in five other independently isolated methotrexate-resistant Chinese hamster cell lines. Our data indicated that the predominant amplicon types in all but one of these cell lines are larger than the 273-kb type I sequence. In-gel renaturation experiments as well as hybridization analysis of large SfiI fragments separated by pulse-field gradient gel electrophoresis showed that two highly resistant cell lines (A3 and MK42) have amplified very homogeneous core sequences that are estimated to be at least 583 and 653 kb in length, respectively. Thus, the sizes of the major amplicon types can be different in different drug-resistant Chinese hamster cell lines. However, there appears to be less heterogeneity in size and sequence arrangement within a given methotrexate-resistant Chinese hamster cell line than has been reported for several other examples of DNA sequence amplification in mammalian systems.

Animals↗
PubMed1988

Organization and genesis of dihydrofolate reductase amplicons in the genome of a methotrexate-resistant Chinese hamster ovary cell line.

We have recently isolated overlapping recombinant cosmids that represent the equivalent of two complete dihydrofolate reductase (dhfr) amplicon types from the methotrexate-resistant Chinese hamster ovary (CHO) cell line CHOC 400. In the work described in this report, we used pulse-field gradient gel electrophoresis to analyze large SfiI restriction fragments arising from the amplified dhfr domains. The junction between the 260-kilobase type I amplicons (which are arranged in head-to-tail configurations in the genome) has been localized, allowing the construction of a linear map of the parental dhfr locus. We also show that the 220-kilobase type II amplicons are arranged as inverted repeat structures in the CHOC 400 genome and arose from the type I sequence relatively early in the amplification process. Our data indicate that there are a number of minor amplicon types in the CHOC 400 cell line that were not detected in previous studies; however, the type II amplicons represent ca. 75% of all the amplicons in the CHOC 400 genome. Both the type I and type II amplicons are shown to be composed entirely of sequences that were present in the parental dhfr locus. Studies of less resistant cell lines show that initial amplicons can be larger than those observed in CHOC 400. Once established, a given amplicon type appears to be relatively stable throughout subsequent amplification steps. We also present a modification of an in-gel renaturation method that gives a relatively complete picture of the size and variability of amplicons in the genome.

Animals↗
PubMed1987

Occlusion of bridging or avulsed retinal vessels by repeated photocoagulation.

A technique is described for occlusion of bridging vessels associated with retinal breaks, and recurring vitreous hemorrhage. Argon laser photocoagulation, applied around and to the vessel in repeated sessions, produces scarring and progressive thinning of the retina until laser energy absorbed in the deep pigmented layers can reach the vessel and occlude it. Seventeen patients presenting with vitreous hemorrhage from bridging vessels were treated. Vitreous hemorrhage recurred in only two patients, one of whom had not returned for completion of treatment. The authors conclude that repeated argon laser photocoagulation is a safe, simple, and effective method for preventing recurrent vitreous hemorrhage from bridging vessels.

Aged↗
PubMed1986

Kinetic studies and structure-activity relationships of bispyridinium oximes as reactivators of acetylcholinesterase inhibited by organophosphorus compounds.

The kinetics of the reactivation of acetylcholinesterase inhibited by isopropyl methylphosphonofluoridate was studied. The reactivators used include nine bispyridinium monooximes and three bispyridinium dioximes. The dissociation constant (Kd) and the rate constant (k2) of dephosphorylation of the complex formed from the organophosphorus acetylcholinesterase (OP-AChE) and the oxime were measured. The reactivation parameters obtained from the in vitro kinetic studies were used to elucidate the structure-activity relationships. The hydrophobic property of a nonoxime substituent at the 3-position on the pyridinium ring can exert a positive effect on their binding affinity to OP-AChE. However, the rate constants (k2) of the nucleophilic displacement of OP-AChE by oximes depend negatively on these physical and structural factors of the oximes. The correlations of the in vivo antidotal efficacy (ED50) of these bispyridinium oximes have been analyzed with their pharmacological properties, e.g., reactivation potency, antimuscarinic activities, and antinicotinic activities. However, no satisfactory correlations were observed. It may be concluded that the detoxication mechanism of poisoning by isopropyl methylphosphonofluoridate is different from those of pinacolyl methylphosphonofluoridate and paraoxon.

Acetylcholinesterase↗
PubMed1986

Restriction fragment length polymorphism of the human beta-globin gene cluster: analysis of a beta-thalassemic family in Taiwan.

We have analysed seven polymorphic restriction sites of the human beta-globin gene cluster of six members of a Chinese family with a beta +-thalassemic sibling. The seven polymorphic sites analysed are the HincII site at the 5'-end of the epsilon-globin gene, the HindIII sites in the two gamma-globin genes, two HincII sites within and at the 3'-end of the psi beta 1 pseudogene, the AvaII site in the beta-globin gene and the BamHI site located at the 3' side of the beta-globin gene. The beta thal chromosome has been identified to have a haplotype of +----++ with respect to these seven polymorphic sites. This is also the most predominant haplotype associated with beta +-thalassemia in Mediterranean and Chinese populations (Chen et al., 1984; Orkin et al., 1982). Of the seven sites analysed in this family, four will be useful in prenatal diagnosis of beta-thalassemia in subsequent pregnancies in the family.

DNA Restriction Enzymes↗