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Biomedical subjects

J Fu

Publications and source records attributed to J Fu.

At least 235 records · Page 13Linked to original sources
PubMed1992

[Experimental study of use of shuttle vector to develop a system of detecting mutagenesis in mammalian cells].

UNLABELLED: The paper presents a series of experimental studies of the use of shuttle vector to develop a short-time mutagenesis system of detecting gene mutation in the mammalian cell at DNA level. The system is based on the finding that in the EB virus the shuttle vector pMCi5 carries LacI gene. The LacI is used as a target of induced mutagenesis in mouse cells. Use pMCi5 plasmid to transform the 3T3 mouse cell, expose it to a chemical mutagen, ethyl methanesulfonate (EMS); transfer the treated plasmid DNA to E. coli strain MC1061F' 150Kan; and then plate the transformation on a special culture medium containing X-gal for rapid detection and analysis of LacI mutation. RESULTS: The spontaneous mutant frequency of the system is less than 1.21 x 10(-4). After the treatment with 300 micrograms/ml EMS, the induced mutant frequency increases to 3.8 x 10(-3). No gross alteration has been discovered in seven LacI mutants at DNA level. No point mutation has occurred in the EcoRI site by analysis with restriction enzyme EcoRI.

3T3 Cells↗
PubMed1991

A histopathologic study of retinal lesions inflicted by transscleral iontophoresis.

In the present study, retinal lesions were induced by transscleral iontophoresis (1.5 mA) in rabbits. The size and severity of the lesions increased with the duration of application (2-25 min). No lesion was noted after less than 1 min application. Immediately after 5 min iontophoresis, the edematous retina exhibited necrotic retinal pigment epithelium (RPE), loss of outer segments, and thinning of the inner and outer nuclear layers. At 5 days after iontophoresis, there was a proliferation of RPE cells and macrophages in the subretinal space, with thinning of the inner and outer retinal layers continuing. By day 14, the retina had been reduced to a glial membrane. Immediately after 15 min iontophoresis, the damaged retina appeared in a mummified form containing no cellular elements. By day 5 thereafter, macrophages and actively proliferating RPE cells had been noted in the necrotic retina. By day 14, a glial membrane had formed.

Animals↗
PubMed1991

Pressure-induced retinal ischemia in rats: an experimental model for quantitative study.

The advent of treatment modalities with the potential to ameliorate retinal ischemic injury calls for methods allowing their quantitative assessment. We thus established a model of pressure-induced retinal ischemia/reperfusion injury in rats. The intraocular pressure (IOP) was raised to 110 mm Hg by cannulation of the anterior chamber for a duration of 0, 90 or 120 min. The eyes were reperfused for 3 or 7 days. Morphologically, retinal injury occurred in a pattern consistent with retinal and choroidal vascular occlusion. Damage increased in severity with prolonged durations of ischemia. Morphometric determination of the mean thickness of inner retinal layers (MTIRL) revealed significant differences between controls and the 90- or 120-min ischemia groups (p less than 0.05 and p less than 0.01, respectively). The difference in MTIRL between 3 and 7 days of reperfusion was not significant. Replacement of normal saline by a solution of 5% dextrose in the hydrostatic device used to increase the IOP led to a decrease in retinal injury after 120 min of ischemia (p less than 0.01). This model combines a relatively simple methodology, cost-effective execution and a fast, semicomputerized method of quantitation. Depletion of carbohydrates during ischemia may contribute to retinal injury in this model.

Animals↗
PubMed1991

Use of an intra-oral model to evaluate 0.05% sodium fluoride mouthrinse in radiation-induced hyposalivation.

The present study was undertaken to evaluate the effect of a twice-daily topical application of a 0.05% NaF mouthrinse on de- and remineralization in the oral cavities of subjects suffering from radiation-induced hyposalivation. Six subjects each wore a bonded intra-oral appliance containing a sound and a demineralized human enamel slab for four weeks. During that period, the subjects used 0.05% NaF rinses, twice daily, instead of the 1.1% NaF gel that had previously been a part of their preventive regimen. Salivary flow rates, plaque pH profiles following a 10% sucrose rinse, S. mutans and lactobacillus counts, fluoride clearance, and enamel microhardness were determined during the study. Sound enamel samples displayed no evidence of demineralization, and the previously demineralized enamel showed remineralization in the outer 50 microns in three of the six subjects. The results suggest that a twice-daily oral rinse with 0.05% NaF can prevent demineralization and enhance remineralization in subjects with radiation-induced hyposalivation.

Bacteria↗
PubMed1991

Establishment of human myeloma cell line KM-2R and its preliminary application to human-human hybridoma research.

The authors report the establishment of a human myeloma cell line--KM-2R--and its preliminary use in human-human hybridoma research. KM-2R cells are resistant to both 6-TG and ouabain. Their doubling time is about 30 h. They have a modal chromosome number of 81-85. Using ELISA and immunodiffusion techniques, gamma-heavy and kappa-light chains were detected in the concentrated cell culture supernatant. KM-2R cells are sensitive to HAT medium. When fusing with normal human spleen cells, tonsil cells, and B lymphoblasts transformed by EB virus, fusion frequencies of 20-60% resulted.

Cell Division↗
PubMed1991

[Experimental and clinical study of activated platelet in allergic asthma].

Twenty-five asthmatic Guinea pigs and fourteen asthmatic patients were included in this study. The results showed that the plasma concentration of lyso platelet activating-factor (lyso-PAF), B-thromboglobulin (B-TG), platelet factor 4 (PF4), TXB2, the ratio of TXB2/6-keto-PGF1a and the platelet aggregation rate (PAgT) were significantly increased (P less than 0.01) during acute attack, but the platelet count and plasma level of 6-keto-PGF1a were markedly decreased (P less than 0.01). During remission, the function of platelet gradually returned to normal. BN 52021 inhibited platelet aggregation and secretion and relieved the symptoms in seven asthmatic guinea pigs. We suggest that platelet may play an important role in allergic asthma and antiplatelet drugs may be used for prophylaxis and treatment.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Collagen, proteoglycan and hyaluronidase activity in cultures from normal and scoliotic chicken fibroblasts.

Connective tissue matrix components were investigated using skin fibroblasts from normal or inbred scoliotic lines of chickens. Specifically, the fibroblasts were obtained from either an isogenic line or a backcross, derived by crossing the isogenic line with a pure line of scoliotic birds. From the backcross, both affected (35-45%) and non-affected (55-65%) progeny were produced. The affected birds had spinal curves greater than 20 degrees. Several abnormalities of connective tissue were observed when cells from scoliotic chicks were grown in culture: increased collagen extractability, decreased aggregatability of proteoglycans under associative conditions and lower than normal levels of hyaluronic acid. There was also less collagen deposited in the cell layer with proportionately increased amounts of collagen secreted into the culture media by cells from scoliotic versus normal chick fibroblasts. Values for collagen matrix stability, as estimated by extractability and net deposition, were intermediate for cells from the backcrossed, but non-affected, birds. Moreover, hyaluronidase, an enzyme that degrades hyaluronic acid, was abnormally elevated in the fibroblast cultures from scoliotic chicks. It is proposed that the increase in hyaluronidase contributes to the abnormalities observed in extracellular matrix components and may be a factor in the expression of scoliosis in susceptible birds.

Animals↗
PubMed1990

Strains from both Theiler's virus subgroups encode a determinant for demyelination.

The GDVII strain and other members of the GDVII subgroup of Theiler's murine encephalomyelitis viruses (TMEV) cause an acute lethal neuronal infection in mice, whereas the DA strain and other members of the TO subgroup of TMEV cause a chronic demyelinating disease associated with a persistent virus infection. We used GDVII/DA chimeric infectious cDNAs to produce intratypic recombinant viruses in order to clarify reasons for the TMEV subgroup-specific difference in demyelinating activity. We found that both the GDVII and DA strains contain a genetic determinant(s) for demyelinating activity. No demyelination occurs following GDVII strain inoculation because this strain produces an early neuronal disease that kills mice before white matter disease and persistent infection can occur.

Animals↗
PubMed1990

Comparison of the iodide permeability test, the surface microhardness test, and mineral dissolution of bovine enamel following acid challenge.

The relationship among the iodide permeability (Ip) test, the surface microhardness (SMH) test, and enamel demineralization chemically analyzed as mineral loss was investigated using bovine enamel blocks. Demineralization periods of 0 (control) and 5, 15, 30, and 45 min using 0.05 mol/l lactate (pH 4.75) were chosen to approximate the acid challenge occurring during the intraoral enamel demineralization test. Mineral loss (Ca and PO4) was found to be directly proportional to dissolution time (r = 0.95). Changes (delta) in Ip and SMH each increased linearly over time (r = 0.58 and 0.64, respectively) and were similarly related to mineral loss (r = 0.60 and 0.65, respectively). The correlation between delta Ip and delta SMH was 0.55. When longer demineralization periods (60, 120, and 240 min) were included, the correlation between delta Ip and delta SMH was 0.68. We conclude that both the Ip test and the SMH test can be used as measures of the early stages of enamel dissolution.

Animals↗
PubMed1989

Generation of monoclonal antibodies to prostatic acid phosphatase isoenzyme 2 and application in solid-phase enzyme immunoassay.

Monoclonal antibodies specific to prostatic acid phosphatase (PAP) isoenzyme 2 were generated by using an improved hybridoma technique. After three subcutaneous immunizations and three intravenous boosters, cell fusion experiments were performed. The hybrid cells were first cultured in a semisolid medium containing methylcellulose and later transferred to a liquid medium for further subculture. Out of a total of 600 colonies recovered after two cell fusion experiments, 13 were shown to exhibit affinity to PAP isoenzyme 2 by radioimmunoassay. Nine hybrid cell lines which showed high affinity and specificity were established for further evaluation. Their immunoglobulin subclass was determined to be immunoglobulin G. The association constants between PAP isoenzyme 2 and each monoclonal antibody were determined by titration curve in radioimmunoassay (RIA). Three of them (PAP 1, PAP 03, and PAP 019) were shown to be over 1 X 10(9) M-1. From the results of a matrix cross-matching procedure, a pair of antibodies (PAP 03 and PAP 1) reacting with discrete antigenic determinants were identified for preparing a solid phase sandwich enzyme immunoassay (EIA) kit. The designed EIA procedure could be performed within 40 min in a one-stage incubation protocol. The assay time was shorter than that of other commercial RIA or EIA kits, and the sensitivity was 0.4 ng/ml which was comparable to that of RIA kits. The EIA kit was shown not to cross-react with human thyroid stimulating hormone, alpha-fetoprotein, carcinoembryonic antigen, and acid phosphatases derived from tissues other than prostate. Therefore, this design was a simple and rapid method with high sensitivity and specificity for determining PAP isoenzyme 2 in human serum.

Acid Phosphatase↗
PubMed1989

Generation of monoclonal antibodies to alpha-fetoprotein and application in solid-phase enzyme immunoassay.

By using an improved hybridoma technique, monoclonal antibodies specific to alpha-fetoprotein (AFP) were generated. After three subcutaneous immunizations and three intravenous boosters, cell fusion experiments were performed. The hybrid cells were initially cultured in a semisolid medium containing methylcellulose and later transferred to a liquid medium for subculture. Out of 800 colonies recovered after two cell fusion experiments, 16 were shown to exhibit affinity to AFP by radioimmunoassay. Six hybrid cell lines which showed high affinity and specificity were selected for further evaluation. From the results of a cross-matching procedure, two pairs of antibodies (AFP 3 and AFP 05; AFP 3 and AFP 013) reacting with discrete antigenic determinants were identified for preparing solid-phase sandwich enzyme immunoassay (EIA) kits. The association constants between AFP and these three antibodies (AFP 3, AFP 05, and AFP 013) were 2.0, 3.7, and 3.8 X 10(9) M-1, respectively. The immunoglobulin subclass of them was determined to be IgG1. The EIA procedure designed could be performed within 40 min in a one-stage incubation and 70 min in a two-stage incubation. The incubation time was shown to be equal to or shorter than that of any other known commercial kits and the sensitivity was less than 1 IU/ml. In order to avoid the high-dose hook effect which occurred in the one-stage incubation procedure, a two-stage incubation protocol was advised.

Animals↗
PubMed1989

[Embryonic development and structure of human Bruch's membrane].

A morphological study of Bruch's membrane was performed on 61 human embryonic and fetal eyes by transmission and scanning electron microscopy. The basement membrane of retinal pigment epithelium could be identified in the 5 week embryo. At the 11th week, the five components of Bruch's membrane were all discernible. The features of the five components were topographically examined by scanning electron microscopy.

Basement Membrane↗
PubMed1989

Prolonged hemopoiesis of murine bone marrow derived epithelioid cells in vitro.

We previously reported the isolation of a murine bone marrow derived stromal cell line, TC-1, and two sublines derived from this line. The monolayer of one subline, TC-1-C-3, directly supported the growth of nonadherent marrow cells in Dexter culture system for eight weeks. We report here the mechanism of the stromal cell effect on hemopoiesis in a long-term bone marrow culture system. When the hemopoietic blasts attach to the TC-1-C-3 cells, they are surrounded by the stromal cell cytoplasm within two hours and develop into cell clusters in a week. The developing hemopoietic cells show cell differentiation towards the granulocytic lineage. A key function of the epithelioid stromal cell, then, is to provide a 'niche' or 'envelope' for stem cells which supports long-term hemopoiesis in the Dexter culture system.

Animals↗
PubMed1988

Retention of topical fluoride in the mouths of xerostomic subjects.

The total fluoride concentration in unstimulated whole saliva was measured before and at selected intervals after a self-applied 1.1% neutral NaF topical fluoride gel or use of a 0.05% neutral NaF fluoride mouthrinse in both normal individuals and patients with radiation-induced xerostomia. As expected, the gel resulted in higher peak fluoride values than the rinse and was retained in the mouth for longer periods of time in both groups. The xerostomic group expressed a mean oral fluoride concentration of 575 micrograms fluoride per gram of saliva within 1 min after the gel application and 150 micrograms/g following use of the mouthrinse, whereas the normal group exhibited peak concentrations of 112 and 71 micrograms/g, respectively, within 1 min after the same two treatments. The initial high levels of fluoride observed in normal subjects following the gel application decreased rapidly to less than 1 microgram/g within 2 h, whereas fluoride levels in the xerostomic subjects remained elevated above 12 micrograms/g for longer than 2 h. Similarly, following use of the mouthrinse, normal subjects' saliva fluoride levels decreased to less than 1 microgram/g within 1 h, whereas xerostomic subjects' saliva fluoride levels remained above 4 micrograms/g for longer than 2 h.

Adult↗
PubMed1988

Effect of an anticalculus dentifrice on lesion progression under pH cycling conditions in vitro.

The aim of the present study was to examine a sodium fluoride anticalculus dentifrice product containing soluble pyrophosphate for its ability to promote remineralization and/or inhibit demineralization of dental enamel in a pH cycling model in vitro. Enamel crowns with windows were subjected to 14 days of alternating demineralization and remineralization periods at 37 degrees C. Teeth were immersed 5 min daily in one of the test dentifrice systems (1:3 slurry in deionized water) between the demineralization and remineralization cycles. Test dentifrices included (1) sodium fluoride (NaF; 1,100 ppm F)/silica abrasive (Crest) and (2) NaF (1,100 ppm F) with 3.3% soluble pyrophosphate/silica abrasive (Crest Tartar Control). Controls included a placebo dentifrice (silica abrasive) with no added fluoride and a group which received no treatment at all, i.e., demineralization/remineralization only. Overall, both of the NaF dentifrices were very effective in limiting in vitro caries progression and were not significantly different from each other. Inclusion of pyrophosphate in the NaF dentifrice did not affect the net outcome of the cycling demineralization/remineralization processes which is in agreement with recent clinical and in situ studies of these products.

Dental Calculus↗
PubMed1988

Comparison of fluoride concentrations in unstimulated whole saliva following the use of a fluoride dentifrice and a fluoride rinse.

Recent evidence has suggested that the cariostatic effects of topical fluoride (F) are related to the presence of low concentrations of ionic F in the oral environment. The purpose of this study was to compare the retention of F in the oral environment over 24-hour periods after the use of a F dentifrice or a F rinse. Groups of ten consenting adult subjects (age 18-52 years) brushed and/or rinsed (B/R) in a standardized manner twice per day in the morning (AM) and before bed (PM) with either a placebo dentifrice (8 ppm F), NaF dentifrice (1100 ppm F), or NaF rinse (225 ppm F). Experiments were performed with placebo dentifrice only (PD); F dentifrice only (FD); F dentifrice followed by F rinse (FD/FR); placebo dentifrice followed by F rinse (PD/FR); and F rinse followed by placebo dentifrice (FR/PD). Unstimulated whole saliva samples were collected at baseline and then at 0, 15, 30, and 45 min, 1, 2, and 8 hr after B/R in the AM, after B/R in the PM and upon rising the following morning. Salivary flow rate and F were determined for each sampling interval. The results of this study suggest that: (1) F rinse may be a more effective way of delivering topical F than F dentifrice; (2) based on F retention, the combination of FD/FR was not more effective than FR only (PD/FR); (3) older individuals with gingival recession retained higher F levels; and (4) bedtime F application resulted in longer F retention than did daytime application, which may have important implications for enamel remineralization.

Adolescent↗