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Biomedical subjects

F Chen

Publications and source records attributed to F Chen.

At least 487 records · Page 27Linked to original sources
PubMed1995

Distribution of the Na+/Ca2+ exchange protein in developing rabbit myocytes.

The Na+/Ca2+ exchanger is a major pathway for transmembrane flux of Ca2+ in cardiac cells. Immunolabeling in adult rabbit myocytes showed localization of the Na+/Ca2+ exchanger to the peripheral sarcolemma and especially in the T tubules. Previous studies have also demonstrated higher Na+/Ca2+ exchanger activity in fetal and newborn rabbit hearts in which the T tubular system is not completely developed. Indirect immunofluorescent studies were performed to localize the Na+/Ca2+ exchanger in isolated myocytes from immature (5, 11, 17, and 30 days) and adult rabbits. Cells were incubated with a monoclonal antibody to the exchanger followed by fluorescein-labeled goat anti-mouse antibody. It is found that at 5 days of age the immunofluorescent labeling was very intense and confined to the peripheral sarcolemma. After 11 days of age, localization of labeling followed the development of the T tubules. The exchanger appeared in the T tubules as soon as they were formed. The Na+/Ca2+ exchange protein is abundantly localized to the peripheral sarcolemma before and during the development of T tubule system.

Aging↗
PubMed1995

Na+/Ca2+ exchange and cell contraction in isolated neonatal and adult rabbit cardiac myocytes.

Recent studies have demonstrated a relative deficiency in voltage-gated Ca2+ currents (ICa) in immature myocardium. We hypothesized that contraction in developing heart results in part from Ca2+ influx via "reverse" Na+/Ca2+ exchange current (INa/Ca). Accordingly, INa/Ca and cell contraction amplitude were measured in single neonatal and adult rabbit ventricular myocytes. INa/Ca was dependent on Ca2+ concentration, Na+ concentration, and membrane potential and was blocked by 5 mM Ni2+ but not by the Ca(2+)-channel blocker nifedipine. In neonatal cells, contraction amplitude reached a plateau for depolarizations positive to 0 mV. In adult myocytes, contraction amplitude was maximal at 0 mV and decreased at positive membrane potentials. Inhibition of ICa with nifedipine did not affect maximal contraction amplitude in neonatal myocytes but almost completely suppressed contraction of adult cells. These data suggest that Ca2+ influx via ICa is not required for contraction of neonatal rabbit cardiac myocytes. Moreover, Ca2+ influx via reversal of the Na+/Ca2+ exchange mechanism may provide a significant portion of the Ca2+ regulating cell contraction, especially during depolarization to positive membrane potentials.

Aging↗
PubMed1995

Effects of triiodothyronine on retention of beta-adrenergic responsiveness of voltage-gated transmembrane calcium current during culture of ventricular myocytes from neonatal rabbits.

To study the effects of triiodothyronine (T3) on responsiveness of L-type calcium currents to beta-adrenergic stimulation in neonatal hearts, ventricular myocytes were isolated from neonatal rabbits and cultured in medium containing 10% fetal bovine serum to which T3 had been added to achieve either hypothyroid, euthyroid, or hyperthyroid conditions, as assessed by measurement of free T3 concentrations. During a 24-h culture period, the striated rod-shaped myocardial cells progressively assumed a stellate shape with reduced surface area; however, the rate constants for diffusion of Na+ from a microelectrode pipette into the cells remained unchanged. Voltage-dependent characteristics of L-type calcium currents as assessed by whole-cell voltage clamp studies were also unchanged after culture with various concentrations of free T3. By contrast, the stimulation of voltage-gated transmembrane calcium current from baseline by isoproterenol was reduced (p < 0.05) in hypothyroid cells (15 +/- 8%; n = 14) compared with either euthyroid (86 +/- 15%; n = 18), hyperthyroid (54 +/- 16%; n = 12) or freshly isolated (50 +/- 12%; n = 10) myocytes. The differences in beta-adrenergic responsiveness of voltage-gated transmembrane calcium current to isoproterenol between euthyroid, hyperthyroid, and freshly isolated cells were not significant (p > 0.05). These results indicate that retention of beta-adrenergic responsiveness of voltage-gated transmembrane calcium current in neonatal cardiac myocytes depends on physiologic amounts of active thyroid hormone. Our culture method for neonatal cardiac myocytes will be useful for studying physiologic modulation of beta-adrenergic responsiveness.

Adrenergic beta-Agonists↗
PubMed1995

Potentiating effects on pilocarpine-induced saliva secretion, by extracts and N-containing sugars derived from mulberry leaves, in streptozocin-diabetic mice.

The effects of hot water extracts and six compounds of N-containing sugars, 1-deoxynojirimycin (DNJ), N-methyl-DNJ (N-Me-DNJ), 2-O-alpha-D-galactopyranosyl-DNJ (GAL-DNJ), fagomine, 1,4-dideoxy-1,4-imino-D-arabinitol (DAB), and 1,2 alpha,3 beta,4 alpha-tetrahydroxynortropane (calystegin B2), derived from mulberry leaves (Morus alba L.), were investigated on pilocarpine-induced saliva secretion in streptozocin (STZ)-induced diabetic mice. The extracts (100 and 200 mg/kg, i.p.) significantly potentiated the pilocarpine-induced salivary flow but not the protein content. The component compounds (37.5-300 mumol/kg) potentiated the saliva secretion, and the potency order was DAB > fagomine > GAL-DNJ. Only fagomine significantly increased the protein content in the saliva. The potentiation of pilocarpine-induced salivary flow was correlated with anti-hyperglycemic effects by the extract and GAL-DNJ from mulberry leaves in the same dose ranges.

Amino Sugars↗
PubMed1995

[Hypoglycemic activity and mechanisms of extracts from mulberry leaves (folium mori) and cortex mori radicis in streptozotocin-induced diabetic mice].

Averaged blood glucose levels were 400 mg/dl in nonfasted mice, and 250 mg/dl in fasted mice in 4 weeks after injection with streptozotocin (STZ, 150 mg/kg, i.v.). These mice were used for experiments. Hypoglycemic effects of hot water extracts (W) from Folium Mori (Mulberry leaves, Morus alba L., China and Japan) or Cortex Mori Radicis (Morus alba L., China) were observed in fasted and nonfasted STZ-induced diabetic mice at a single dose of 200 mg/kg (i.p.). The W from Folium Mori exhibited most potent hypoglycemic effects. The most potent fractions of Folium Mori and Cortex Mori Radicis were ethanol-insoluble extracts (A2). These A2 fractions demonstrated a fall in blood glucose levels of 24.6 +/- 6.0% and 60.5 +/- 9.1% at nonfasted STZ-mice, and 81.4 +/- 7.9% and 77.3 +/- 5.8% at fasted STZ-mice, respectively. The increase in glucose uptake was a mechanism of hypoglycemic actions by W and A2 of Folium Mori.

Animals↗
PubMed1995

[Rapid detection of platelet glycoprotein IIb, IIIA gene variety by single strand conformation polymorphism analysis].

Glanzmann thrombasthenia (GT) is the most common inherited disorder of platelet defective function. Most of the molecular defects of GT identified in recent years have been caused by point mutation in the platelet glycoprotein (GP) IIb, IIIa genes. Trying to rapidly detect point mutation (or subtle variety) in GPIIb, IIIa genes, we have used single strand conformation polymorphism analysis (SSCPA) and studied the gene structure of platelet GPIIb. IIIa from normal controls and patients with Glanzmann thrombasthenia. After DNA preparation from peripheral blood, all the exons of GPI-Ib, IIIa were amplified by PCR. Denaturated PCR products were separated on mini polyacrylamide gel and stained by silver staining method in the Phast System. Only the PCR products with different migration on the gel were sequenced. 2 GT patients with point mutations and 1 GT patient with 16 bp deletion were found in our study. At the same time, we determined 3 polymorphisms in GPIIb gene. We conclude that SSCPA is a rapid, sensitive and effective method for detecting platelet IIb, IIIa gene variety.

DNA Mutational Analysis↗
PubMed1995

[Inhibitive effects of spirulina on aberrant crypts in colon induced by dimethylhydrazine].

Precancerous pathological changes of colon was induced by single injection in a short-term and multiple injection in a long-term intraperitoneally with 1,2-dimethylhydrazine (DMH) in NIH mice and Sprague-Dawley rats. And, protective effects of spirulina, germanium-132 and vitamin E on colon aberrant crypts induced by DMH were observed. Results showed either single injection or multiple injection with DMH could induce aberrant crypts in colon. The number of aberrant crypts scattered by short-term single injection was less than that by multiple one, and less of the aberrant crypts foci were formed by short-term single injection. Spirulina powder, germanium-132 and vitamin E all could inhibit the function of aberrant crypts of colon. In the ninth week during multiple injection with DMH, a lot of aberrant crypts of colon had been induced, and a certain amount of aberrant crypts foci had been generated. The number of aberrant crypts and aberrant crypts foci in the animals with tumor increased with the length of DMH injection. In the ninth-, 13th- and 16th-week, respectively, the number of aberrant crypts and aberrant crypts foci was significantly less in animals protected by spirulina than in positive controls (P < 0.01), but there was no significant difference between them during 21st- and 24th-week of injections.

Animals↗
PubMed1995

[A study of autogenous hair transplantation in Chinese].

From Sep. 1988 to Dec. 1992, a total of 980 procedures of autogenous punch grafts were performed in 395 patients with alopecia. This technique has mainly been used for seborrheic alopecia and cicatricial alopecia with sufficient hair in the donor site. Chinese people are unfavorably characterized by one-third less amount of hair than Westerners, lank hair shaft and strong contrast of color between the hair and hair-bearing scalp. The technique of L shape punch grafts was used for patients with insufficient hair in the donor site. Insertion of mini-grafts between the anterior rows of punch grafts made the frontal hairline more natural in appearance and eliminated the necessity of postoperative scalp tattoo. The results were perfect. We concluded that adult alopecic patients are good candidates for punch graft procedure, and for children and juvenile patients, scalp expansion is preferable.

Adolescent↗
PubMed1995

[An evaluation of nonsurgical treatment for severe acute pancreatitis].

In this prospective study, the rationality of non-operative treatment for severe acute pancreatitis was evaluated. Twenty-four patients aged 15-74 years with a mean age of 46.1 +/- 15.5 years were divided randomly into two groups: 12 patients in nonoperative group and 12 in operative group. The patients treated nonoperatively survived, while 5 patients died of operation. It is suggested that patients with severe acute pancreatitis can be cured by nonoperative management.

Acute Disease↗
PubMed1994

Sequence and position requirements for uridylate-rich downstream elements of polyadenylation signals.

We have defined the positional and sequence requirements of U-rich downstream elements using a simian virus 40 late polyadenylation signal containing a substituted downstream region. A UUUUU element will significantly increase the efficiency of 3' end processing when placed between 6 and 25 bases downstream from the cleavage site. Positions in this interval closer than 15 bases from the cleavage site, however, were noticeably less efficient. Placement of the UUUUU element between +20 and +25 caused a partial shift in cleavage site usage to a CA motif at +4. Mutational analysis indicated that the sequence requirements at individual positions of the UUUUU element were somewhat flexible. Changing more than one base of the UUUUU sequence, however, severely diminished the ability of the element to mediate efficient 3' end processing. Finally, although hnRNP C proteins specifically interact with U-rich sequences, this protein--RNA interaction is not required for efficient in vitro polyadenylation.

Base Sequence↗