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Biomedical subjects

G Sun

Publications and source records attributed to G Sun.

245 records · Page 14Linked to original sources
PubMed1988

Effect of magnesium sulfate on fetal heart rate variability in preeclamptic patients during labor.

Forty-two preeclamptic patients between 36 and 41 weeks gestation were investigated for baseline fetal heart rate (FHR) variability 1 hour after the initiation of magnesium therapy, at midlabor, and at the time of delivery. With a standard regimen of intravenous magnesium sulfate therapy, the mean maternal serum magnesium levels at the three different sampling times were statistically different (f = 6.94, p less than 0.01 by one-way analysis of variance), documenting the cumulative effect of continuous intravenous magnesium administration. The majority of the fetuses (86%) that exhibited a decrease in long-term FHR variability were associated with a maternal serum magnesium level above the lower limit of the therapeutic range (4.8 mg/dl). Of all fetuses whose maternal serum magnesium levels were 4.8 mg/dl or greater at delivery, only 40% exhibited a decrease in FHR variability. A higher mean maternal magnesium level, a higher mean cord blood magnesium level, and a higher total dose of magnesium sulfate were observed in the group of fetuses showing a decrease in FHR variability than in the group showing no change in FHR variability. The good fetal outcome seen in both study populations suggests that the effect of magnesium sulfate on FHR variability is a transient, reversible phenomenon that should not be considered as a sign of fetal distress.

Adult↗
PubMed1979

Uptake of radioactive calcium by hard tissue cells.

45Ca was injected into prenatal mice to study the calcium uptake by tooth germ cells. Both dental papillae, containing the odontoblasts, and the enamel organs were found to actively metabolized the labeled calcium. The maximum specific radioactivity occurred at 15 minutes after injection. The subcellular organelles (e.g. mitochondria) of the papillae were more active in metabolizing the labeled calcium whereas a large portion of the radioactivity of the enamel organ was found in a fraction containing the precalcified material. In fetal tooth germs, the rate of incorporation of labeled calcium into the precalcified material was slower than in the postnatal tooth germs since a large portion of the radioactivity remained in the soluble fraction.

Animals↗
PubMedDate not supplied

Coexistence of amyloid beta-protein precursor and basic fibroblast growth factor in single cells of the rat parietal cortex, hippocampus and basal magnocellular nucleus.

The coexistence of amyloid beta-protein precursor (APP) and basic fibroblast growth factor (basic FGF) in single cells of the parietal cortex, hippocampus and basal magnocellular nucleus was investigated immunohistochemically in adult rats. A monoclonal antibody directed against human recombinant APP and a polyclonal antibody against a synthetic fragment of basic FGF (the N-terminal 12 residues) were used. APP and basic FGF were frequently colocalized in the pyramidal cells of layers III and V of the parietal cortex, in the pyramidal and extrapyramidal cells of the hippocampus, and in large cells of the medial septal nucleus and the horizontal limb of the diagonal band of Broca. Such a frequent colocalization suggests a close functional relationship between APP and basic FGF in the neuronal cells.

Amyloid beta-Protein Precursor↗
PubMedDate not supplied

Tumor necrosis factor-alpha and interleukin-1 induce activation of MAP kinase and SAP kinase in human neuroma fibroblasts.

Two cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1), which are released by macrophages during the early inflammatory phase of nerve injury, are known to induce activation of mitogen-activated protein kinase (MAPK) and stress-activated protein kinase (SAPK), which locate at different signal transduction pathways and are involved in cell cycle G0/G1 transition and cellular proliferation in human fibroblasts. Activation of these two protein kinases by the cytokines may stimulate fibroblast proliferation in damaged nerves and thereby play a role in the formation of a neuroma, a disorganized mass of tissue that interferes with neural regeneration and repair. To investigate the possibility that this mechanism is operative in neuroma formation, we used cultured, serum-starved fibroblasts from surgically removed human neuromas stimulated with TNF-alpha and/or IL-1 alpha and IL-1 beta, and measured the activation of MAPK and SAPK using myelin basic protein (MBP) and human c-Jun (1-169) glutathione S-agarose transferase (GST) fusion protein as substrates. For comparison, neuroma fibroblast cultures were also stimulated with phorbol 12-myristate 13-acetate (PMA) and platelet-derived growth factor-AB (PDGF-AB), a potent activator for MAPK. TNF-alpha and both forms of IL-1 produced a rapid activation of MAPK, with a peak at 15 min for TNF-alpha stimulation, and a peak at 30 min for IL-1 stimulation. TNF-alpha combined with either IL-1 alpha or IL-1 beta produced a synergistic effect on the activation of MAPK. The increases in MAPK induced by TNF-alpha and IL-1 were similar to the increases induced by PMA and PDGF-AB. To confirm the presence of MAPK, immunoprecipitation and immunoblotting were carried out on experimental and control lysates. TNF-alpha and IL-1 also increased activation of SAPK, but to a lesser extent than MAPK. PMA and PDGF-AB were also much less effective in stimulating activation of SAPK. Our findings indicate that TNF-alpha and IL-1 activate parallel signal transduction pathways in human neuroma fibroblasts, and that they are relatively stronger activators of MAPK than of SAPK. Previous studies have convincingly demonstrated that MAPK and SAPK are involved in human fibroblast proliferation. The results of our study suggest that TNF-alpha and IL-1 may play a role in frustrating functional nerve regeneration after injury by stimulating these two kinases, which, in turn, leads to fibroblast proliferation and formation of neuromas.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMedDate not supplied

Mechanical properties of melamine-formaldehyde microcapsules.

The mechanical properties of melamine-formaldehyde (M-F) microcapsules were studied using a micromanipulation technique. Single microcapsules with diameters of 1-12 microm were compressed and held between two parallel planes, compressed and released, and compressed to burst at different speeds, whilst the force being imposed on the microcapsules and their deformation were measured simultaneously. This force increased as single microcapsules were compressed and then relaxed slightly as they were held. When the microcapsules were repeatedly compressed and released, a pseudo yield point was found for each microcapsule. Before the microcapsules were compressed to this point, the deformed microcapsules recovered to their original shape once the force was removed. However, when the deformation was beyond the 'yield point' there was profound hysteresis and the microcapsules showed plastic behaviour. As the microcapsules were compressed to burst at different speeds, ranging from 0.5-6.0 microm/s, it was found that their mean bursting forces did not change significantly. The deformations at the pseudo yield point and at bursting were also independent of the compression speed. On average, these melamine-formaldehyde microcapsules reached their 'yield point' at a deformation of about 19 +/- 1%, and burst at a deformation of 70 +/- 1%.

Biomechanical Phenomena↗
PubMedDate not supplied

A case-control study of the relationship between dietary factors and risk of lung cancer in women of Shenyang, China.

A 1:1 case-control study of lung cancer incidence among women in Shenyang was conducted to explore the relationship between diet and the risk of lung cancer, with emphasis on the potential effects of a list of specific dietary constituents on modifying lung cancer risks. Dietary information on 290 cases and population-matched controls was obtained by personal interviews. Multiple logistic regression models were used for the statistical analysis and summarization of the data. A significant difference was found between cases and controls with respect to intake of beta-carotene, vitamin C and fibers, all of which reduced the risk for lung cancer in a dose-dependent manner; yielding calculated odds ratio (OR) of 0.84, 0.75, and 0.46, respectively. The apparent effects of these nutrients persisted after adjusting for cigarette smoking;suggesting that they may function as protective factors to reduce the risk for lung cancer in Chinese women.

Adult↗