Search PubMed⌕ Search

Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 523 records · Page 29Linked to original sources
PubMed1982

Factors involved in the control of proliferation of bovine corneal endothelial cells maintained in serum-free medium.

Experimental conditions have been defined that allow bovine corneal endothelial (BCE) cells to grow in the complete absence of serum. Low density BCE cell cultures maintained on extracellular matrix (ECM)-coated dishes and plated in the total absence of serum proliferate actively when exposed to a synthetic medium supplemented with high density lipoprotein (HDL 500 micrograms protein/ml), transferrin (10 micrograms/ml), insulin (5 micrograms/ml), and fibroblast (FGF) or epidermal growth factor (EGF) added at concentrations of 100 or 50 ng/ml, respectively. Omission of any of these components results in a lower growth rate and/or final cell density of the cultures. BCE cell cultures plated on plastic dishes and exposed to the same synthetic medium grow very poorly. The longevity of BCE cultures maintained on plastic versus ECM and exposed to serum-free virus serum-containing medium has been studied. The use of ECM-coated dishes extended the life span of BCE cultures maintained in serum-supplemented medium to over 120 generations, as compared to less than 20 generations for cultures maintained on plastic. Likewise, BCE cells maintained on ECM and exposed to a synthetic medium supplemented with optimal concentrations of HDL, transferrin, insulin, and FGF underwent 85 generations, whereas control cultures maintained on plastic could not be passaged. The enhancing effect of ECM on BCE cell growth and culture longevity clearly illustrates the importance of the cell substrate in the control of proliferation of these cells.

Animals↗
PubMed1981

High density lipoproteins and the growth of vascular endothelial cells in serum-free medium.

Low density bovine vascular endothelial cell cultures maintained on dishes coated with an extracellular matrix can be grown in serum-free Dulbecco's modified Eagle's medium supplemented with high density lipoprotein (HDL) and transferrin. Such cultures do not require insulin. Early passage cultures exposed to HDL and transferrin grew as well as cultures exposed to optimal serum concentrations and could be passaged repeatedly in total absence of serum. A requirement for fibroblast growth factor to ensure an optimal growth could be observed only with late-passage cultures. The present results suggest strongly that HDL is involved in supporting the proliferation of vascular endothelial cells in vitro. This may be important for our understanding of the biological role of HDL "in vivo."

Animals↗
PubMed1980

Effect of high and low density lipoproteins on proliferation of cultured bovine vascular endothelial cells.

Bovine vascular endothelial cells maintained on dishes coated with an extracellular matrix and exposedto medium supplemented with lipoprotein-deficient serum (LPDS) require the presence of lipoprotein to proliferate optimally. High density lipoprotein (HDL) seems to be the major factor involved in the proliferation of vascular endothelial cells. This is mostly due to its lack of toxicity when added at high concentration, as well as to its nondependence on LPDS to exhibit its mitogenic properties. Therefore, HDL at physiological concentrations (1,000--1,500 microgram protein/ml) can fully replace serum. Low density lipoprotein, unlike HDL, has a biphasic effect. Although mitogenic for vascular endothelial cells when added at low concentration, once physiological concentrations are reached it becomes toxic for the cells. Moreover, and in contrast with HDL, the mitogenic effect of low density lipoprotein was found to be a function of the LPDS concentration to which cultures were exposed. The substrate upon which cultures are maintained has been found to be an important factor if a mitogenic effect of HDL is to be observed. When maintained on plastic, cells proliferate poorly in response to HDL unless fibroblast growth factor is added to the medium. In contrast, when maintained on extracellular matrix, an optimal growth rate is induced by HDL, even in the absence of fibroblast growth factor. This suggests that, in vivo, the integrity of the basement membrane upon which endothelial cells rest and migrate is an important factor in determining the cells response to lipoproteins present in plasma.

Animals↗
PubMedDate not supplied

The contoured auricular projection graft for nasal tip projection.

In all rhinoplasty surgery, the universal need exists to increase, decrease, or preserve existing tip projection. When proper tip projection is lacking, a variety of techniques are useful for improving projection. We describe a valuable technique for tip projection, particularly useful and indicated in the Asian rhinoplasty, African American rhinoplasty, and in certain revision rhinoplasties. In the past 15 years, the senior author (M.E.T.) has used the contoured auricular projection graft in selected patients for achieving satisfactory tip projection in patients with blunted tips. The aesthetic outcomes have been predictable, pleasing, and reliable for the long term. Precision pocket preparation for auricular conchal cartilage graft placement is key to symmetry and projection of the final outcome. The results yielded a rounded nasal tip that may be more natural-appearing in Asians, African Americans, and selected patients with revision rhinoplasty. The contoured auricular projection graft provides a highly useful graft for the nasal tip.

Asian People↗
PubMedDate not supplied

Reduced GABA-mediated chloride flux in entorhinal cortex-kindled rat brains.

Gamma-aminobutyric acid (GABA)-mediated chloride uptake was determined in synaptoneurosomes prepared from the brains of entorhinal cortex-kindled and paired control rats. Subjects were sacrificed either 24 h or 28 days after the experimental animals had exhibited their sixth stage 5 convulsion. In the cortex and cerebellum, no difference was observed between kindled and control animals at either time period. In the brain-stem, however, a significant reduction (approximately 50%) in chloride uptake was observed in kindled subjects both 24 h and 28 days after the last seizure. These findings are consistent with the hypothesis that the 'kindled state' results from a long-lasting decrease in GABA-mediated inhibitory activity.

Animals↗
PubMedDate not supplied

Porcine endogenus retrovirus transmission from pig cell line to mouse tissues but not human cells in nude mice.

The continuous shortage of human donor organs for transplantation has led to new interest in the application of pig organs. However, reports of pig endogenous retroviruses (PERV), which are able to infect human cells in vitro, have raised concerns about the transmission of PERV to the recipients or even to other community members. In this study, PK15 and human 7721 cell lines were implanted into each flank of nude mice and tumors appeared several weeks postimplantation. PERV infection was detected by PCR, using cytochrome oxidase B sequences as the specific marker for pig DNA. The results showed that PERV gag sequence were positive in mice livers, kidneys, hearts, and lungs, but no cytochrome oxidase B sequences detected, which indicates the absence of pig-mouse microchimerism. The results also showed that PERV did not infect human 7721 tumors in mice. This study confirmed the presence of PERV transmission from pig-to-mouse tissue and strengthened the concern of the risk of transmitting PERV through pig cells xenotransplantation.

Animals↗
PubMedDate not supplied

CD80, but not CD86, express on cultured murine keratinocyte stem cells.

Although cultured keratinocyte allografts are initially accepted, grafted donor cells are gradually replaced by recipient elements. The precise mechanisms underlying this process are not clear. Keratinocyte stem cells (KSCs) were isolated and purified from neonatal C57BL/6 (H-2(b)) and BALB/c (H-2(d)) mice. Cultured KSCs were negative for IA/IE, indicating the absence of any contamination with Langerhans cells. Immunostaining showed that over a 7-day culture period, KSCs expressed increasing amounts of CD80, while CD86 could not be detected. RT-PCR results were consistent with these data. Mixed lymphocyte reaction assays showed that KSCs cultured in 10% serum for 7 days stimulated allogeneic rather than syngeneic T-cell proliferation. This study demonstrates that the costimulatory molecule CD80, but not CD86, may be expressed on cultured KSCs. The data indicate KSCs could act as antigen-presenting cells and thus provide an alternative explanation for the ultimate rejection of allogeneic keratinocytes.

Animals↗
PubMedDate not supplied

Extraction of high quality genomic DNA from microsamples of human blood.

A simple and efficient method for extracting human genomic DNA from microsamples of blood has been developed. This method used sodium perchlorate, chloroform, polymerised silica gel and a dumbbell-shape tube, instead of proteinase K and phenol. The entire process took less than two hours, and high molecular weight DNA, in high yield and purity, was obtained from a few microlitres of human blood. DNA prepared in this way can be easily digested with restriction endonucleases and has been employed for DNA profiling and the polymerase chain reaction.

DNA↗
PubMedDate not supplied

An event-related potential study of age-related changes in sensitivity to stimulus deviance.

The mismatch negativity (MMN) of the event-related (brain) potential (ERP) has been shown to reflect the storage of information in sensory memory and is thought to reflect the operation of a mechanism that compares frequently occurring standard with infrequently occurring deviant acoustic events. The MMN was recorded from young (mean = 23 years) and elderly (mean = 72 years) adults to small (50 Hz) and large (300 Hz) frequency deviants and to a variety of novel, environmental sounds. At each level of deviance, MMN amplitude was smaller in the ERPs of older relative to younger adults. Young, but not older adults showed robust MMNs at the smallest level of deviance. Moreover, a P3 component was observed in the ERPs of the young to both large tonal and novel deviants, whereas a robust P3 component was evident only to the novel deviants in the ERPs of the old. The data suggest that older adults demonstrate less sensitivity to stimulus deviance and that only highly deviant events are likely to involuntarily capture their attention.

Adult↗