Biomedical subjects

P K Choi

Publications and source records attributed to P K Choi.

6 recordsLinked to original sources

PubMed2001

IGF-I and bFGF improve dopamine neuron survival and behavioral outcome in parkinsonian rats receiving cultured human fetal tissue strands.

To promote dopamine cell survival in human fetal tissue strands transplanted into immunosuppressed 6-OHDA-lesioned rats, we have preincubated tissue in insulin-like growth factor-I (IGF-I, 150 ng/ml) and basic fibroblast growth factor (bFGF, 15 ng/ml) in vitro for 2 weeks. Growth factor treatment did not affect the rate of homovanillic acid production in vitro but increased overall dopamine neuron survival in animals after transplant from 1240 +/- 250 to 2380 +/- 440 neurons (P < 0.05). Animals in the growth factor-treated group had a significantly greater reduction in methamphetamine-induced rotation (66%) compared to control transplants (30%, P < 0.05). We conclude that in vitro preincubation of human fetal tissue strands with IGF-I and bFGF improves dopamine cell survival and the behavioral outcome of transplants.

Abortion, Induced↗

PubMed2000

Co-grafts of muscle cells and mesencephalic tissue into hemiparkinsonian rats: behavioral and histochemical effects.

Extracts from skeletal muscle cell cultures have been shown to increase levels of the enzyme tyrosine hydroxylase (TH) and promote survival of different types of developing neurons in vitro. To determine the effect of muscle cell co-grafts on the survival of dopamine neurons in a rat model of Parkinson's disease, we transplanted an embryonic day (ED)-15 rat mesencephalic cell suspension alone or with neonatal muscle cells into 6-hydroxydopamine (6-OHDA) denervated rat striatum. In parallel experiments conducted in vitro, we cultured ED-15 rat mesencephalon or rat striatum in conditioned medium from neonatal rat muscle cultures (MC-CM). Our results showed that: (A) in vitro, MC-CM increased the number of TH-immunoreactive (TH-IR) neurons in embryonic mesencephalic cultures but did not induce expression of TH in embryonic striatal cultures; (B) in vivo, animals with co-grafts of muscle cells and ED-15 mesencephalon had more TH-IR in the grafted striatum compared to animals that received mesencephalic cells grafts alone, although the graft-induced reversal of circling behavior in response to methamphetamine was the same in both transplanted groups; and (C) grafts of muscle cells alone did not induce TH-IR in the denervated striatum and did not reduce methamphetamine-induced circling. These findings suggest that in vivo, neonatal muscle cells secrete factors that promote survival and/or outgrowth of fetal midbrain dopamine cells and improve the levels of TH-IR in grafted striatum.

Animals↗

PubMed1998

Somatic cell cloned transgenic bovine neurons for transplantation in parkinsonian rats.

Parkinson's disease symptoms can be improved by transplanting fetal dopamine cells into the putamen of parkinsonian patients. Because the supply of human donor tissue is limited and variable, an alternative and genetically modifiable non-human source of tissue would be valuable. We have generated cloned transgenic bovine embryos, 42% of which developed beyond 40 days. Dopamine cells collected from the ventral mesencephalon of the cloned fetuses 42 to 50 days post-conception survived transplantation into immunosuppressed parkinsonian rats and cells from cloned and wild-type embryos improved motor performance. Somatic cell cloning can efficiently produce transgenic animal tissue for treating parkinsonism.

Animals↗

PubMed1996

Sexual harassment of Chinese college students.

Sexual harassment of Chinese college students with a focus on their awareness, experiences, responses, and expectations of institutional intervention to the problem was examined. 358 male and 491 female Chinese college students in Hong Kong participated. There were no gender differences in students' awareness of the phenomenon. Students' own experiences were less frequent than what they had heard about sexual harassment. Peer harassment occurred twice as frequently as faculty harassment. Compared to men, twice as many women said they had been sexually harassed. About one in four women students experienced various forms of sexual harassment and 1% were coerced into sexual activities during their college years by either teachers or peers. Students typically avoided and ignored the harassers and felt that the university should take up active roles in combating the problem. Comparisons with U.S. studies suggested that Chinese college students had a lower awareness and experience level in sexual harassment than U.S. students.

Adult↗

PubMed1990

Ultrasonic spectroscopy in bovine serum albumin solutions.

Ultrasonic absorption and velocity spectra in bovine serum albumin (BSA) aqueous solutions have been measured at 20 degrees C over the broad frequency range 0.1-1600 MHz in the pH range 1.5-13.2. Five different techniques were used: the plano-concave resonator, plano-plano resonator, pulse-echo overlap, Bragg reflection, and high-resolution Bragg reflection methods. The absorption spectrum at neutral pH was well fitted to the relaxation curve assuming a distribution of relaxation frequency with a high-frequency cutoff and long low-frequency tail. The relaxation behavior was interpreted in terms of various degrees of hydration of BSA molecules. At acid pH's, excess absorption over that at pH 7 was explained by double relaxation. The pH dependences of the relaxation frequency and maximum absorption per wavelength showed that the relaxation at about 200 kHz was related to the expansion of molecules and that at 2 MHz resulted from the proton transfer reaction of carboxyl group. At alkaline pH's, the excess absorption was explained by triple relaxation. The relaxation at about 200 kHz was associated with a helix-coil transition, and the two relaxations at 2 and 15 MHz were attributed to the proton transfer reactions of phenolic and amino groups, respectively. The rate constants and volume changes associated with these processes were estimated.

Animals↗

PubMed1984

Luxatio erecta.

Luxatio erecta or inferior dislocation of the shoulder joint is rare and is caused by a hyperabduction injury. The clinical appearance is characteristic, with the arm locked in an elevated position. Radiographically, the shaft of the humerus is directed upwards and the humeral head lies inferior to the glenoid fossa, although not in contact with it. Attention should be given to possible complication, particularly concurrent fractures, as well as injury to the brachial plexus or the axillary artery.

Adolescent↗