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Biomedical subjects

M Kong

Publications and source records attributed to M Kong.

30 records · Page 2Linked to original sources
PubMed1998

[Solid-phase extraction coupled with high-field proton nuclear magnetic resonance spectroscopy: application to the analysis of brodimoprim metabolites in rat urine].

The use of coupled solid-phase extraction and high-field proton nuclear magnetic resonance spectroscopy (SPE-1HNMR) for the detection and identification of the urinary metabolites of brodimoprim is described. Urine was obtained from Wistar rats following a dose of 200 mg.kg-1 of brodimoprim. Analysis was performed on partially purified extracts obtained by solid-phase extraction onto C-18 bonded silica gel. As each spectrum was often given by a mixture of more than two kinds of metabolites, stepwise identification of the individual metabolites was achieved by sorting out signal sets having invariant proportionality. Five kinds of metabolites of the drug were found by the analysis.

Animals↗
PubMed1998

[Study on Trichosanthin induced apoptosis of leukemia K562 cells].

Trichosanthin (TCS), an eukaryotic ribosome-inactivating protein isolated from the root tuber of Trichosanthes plant, has various biological activities including abortion induction, antitumor, and anti-HIV. In this study, cultured human leukemia K562 cells treated with trichosanthin were examined. Analysis of the cells by single laser flow cytometry showed the sub-G1 peak. DNA extracted from these cells formed a characteristic "ladder" on agarose gel electrophoresis. Under electromicroscope, typical morphological changes of apoptosis were also observed. From all of these findings, we concluded that trichosanthin was able to induce apoptosis in K562 cells.

Antineoplastic Agents, Phytogenic↗
PubMed1997

[Chemical constituents of Isodon pharicus (Prain) Murata].

Two compounds were isolated from Isodon pharicus. Their structures were elucidated as 11 beta, 13 alpha, 15 alpha-trihydroxy-entkaur-16-en-3 alpha-(beta-D-glucoside) (named isodopharicin F) and eugenyl-beta-D-glucopyranoside by spectral data and chemical evidence.

Drugs, Chinese Herbal↗
PubMed1996

A1 adenosine receptor antagonists block ischemia-reperfusion injury of the heart.

BACKGROUND: It has been reported that A1 adenosine receptor antagonists are highly effective for the prevention and early treatment of ischemia-reperfusion injury of isolated perfused cat lung, which suggests that activation of A1 adenosine receptors is important in ischemia-reperfusion injury of the lung. In addition, preconditioning ischemia reduces ischemia-reperfusion injury of the lung and heart. Moreover, activation of A1 adenosine receptors by adenosine and selective A1 adenosine receptor agonists mimics the protective effects of preconditioning ischemia in the heart. It has been reported that prior treatment with selective A1 adenosine receptor agonists results in a rapid uncoupling of A1 adenosine receptors from signal transduction mechanisms. In the heart, these effects of A1 adenosine receptor agonists have not been reported. However, if prior treatment of ischemia of the heart with adenosine or A1 adenosine receptor agonists results in uncoupling of A1 adenosine receptors from signal transduction mechanisms that produce injury after prolonged ischemia and reperfusion, A1 adenosine receptor antagonists should provide a protective effect similar to these treatments for ischemia-reperfusion injury of the heart. Therefore, it was the purpose of these experiments to investigate the effect of selective A1 adenosine receptor antagonists on ischemia-reperfusion injury of the heart. METHODS AND RESULTS: With the use of a regional infarct model in open-chest cats, the left anterior descending artery or first diagonal branch was occluded for 1 hour followed by 2 hours of reperfusion. Infarct size (area of necrosis/area at risk; AN/AR) was estimated with the use of nitroblue tetrazolium staining. The selective A1 adenosine receptor antagonists xanthine amine congener (XAC; 0.1 mg.kg-1.h-1), bamifylline (BAM; 10 mg.kg-1.h-1), 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 10 micrograms.kg-1.min-1) administered as continous intravenous infusions for 1 hour before ischemia [DPCPX (I)], or DPCPX 30 micrograms.kg-1.min-1 administered intravenously during 30 minutes of ischemia and 30 minutes of reperfusion [DPCPX (I/R)] significantly (P < .05) reduced AN/AR from 52.2 +/- 3.8% (control, n = 5) to 23.4 +/- 6.6% (XAC, n = 5), 34.9 +/- 3.6% (BAM, n = 5), 15.9 +/- 2.9% [DPCPX(I), n = 5], or 13 +/- 3.2% [DPCPX (I/R), n = 5]. CONCLUSIONS: A1 adenosine receptor antagonists significantly reduce ischemia-reperfusion injury of the heart. A1 adenosine receptor antagonists may be useful for the prevention or early treatment of ischemia-reperfusion injury of the heart after coronary artery bypass graft surgery or cardiac transplant surgery and during or after angioplasty or thrombolytic therapy of the heart.

Animals↗
PubMed1995

Sequence and localization of the mouse sperm autoantigenic protein, Sp17.

The present study characterizes the sperm protein Sp17 in the mouse. Sp17 is a mammalian testis- and sperm-specific protein that has been isolated, sequenced, and characterized from rabbit testis and spermatozoa. In this study, a rabbit Sp17 cDNA probe representing the entire protein coding region was used to screen a mouse testis cDNA library to obtain the mouse Sp17 sequence. The mouse mRNa for Sp17 encodes a 149-amino acid protein with a predicted molecular weight of 17,296. The mouse Sp17 (MSp17) cDNA sequence is 82% identical to the rabbit Sp17 cDNA sequence while the MSp17 protein sequence is 74% identical to the rabbit protein sequence. The presence of native Sp17 in mouse spermatozoa and testis was demonstrated by Western blot analysis, immunoprecipitation, and immunolocalization. After SDS-PAGE, the native Sp17 has an apparent molecular mass of 24 kDa. The sequence of the native Sp17 was confirmed by Western blots of mouse testis and spermatozoa probed with two anti-peptide antibodies--one, anti-G22C, made against amino acids 61-82 in the rabbit sequence (61-83 in the mouse), and a second, anti-K18C, made against amino acids 120-136 in the C-terminal region in the human sequence (118-134 in the mouse sequence). In the absence of proteolytic inhibitors, part of the C-terminal of native MSp17 is cleaved, giving rise to an 18-kDa band. Sp17 is present in spermatocytes and spermatids in the testis. In spermatozoa, Sp17 is not available to bind antibody on the surface of live, acrosome-intact spermatozoa, but it is present on the equatorial surface of live, acrosome-reacted spermatozoa. In fixed spermatozoa, staining is observed along the length of the principal piece, weakly along the midpiece, and over the acrosomal region of the head. When the acrosome reaction begins, acrosomal staining is seen throughout the equatorial region of the acrosome. Using mimotope analysis, this study has also demonstrated that native Sp17 is a sperm autoantigen and that recombinant mouse Sp17 is immunogenic in males with a highly restricted linear epitope.

Amino Acid Sequence↗
PubMed1993

Tolbutamide, but not glyburide, affects the excitability and contractility of unfatigued frog sartorius muscle.

The goal of this study was to characterize the effects of tolbutamide and glyburide, two known KATP channel blockers, on intact, unfatigued sartorius muscle fibres of the frog, Rana pipiens. Tetanic contractions were elicited by field stimulation with 200 ms long train of pulses (0.5 ms, 6 V, 140 Hz). Resting and action potentials were measured using conventional microelectrodes. At pHo 7.2 (extracellular pH), the tetanic force was unaffected by 0.5 mM and 1.0 mM tolbutamide, but at 2.0 mM it decreased by 15.5 +/- 1.0%. The effect of tolbutamide on the tetanic force was significantly greater at pHo 6.4: all three tolbutamide concentrations caused a significant decrease in tetanic force, being 62.3 +/- 9.4% at 2 mM. In the presence of tolbutamide a large number of fibres became unexcitable at pHo 6.4, but not at pHo 7.2. Glyburide at 10 microM, on the other hand, caused a 5-7% decrease in tetanic force at both pHo 6.4 and 7.2, but no further decreases in tetanic force were observed when the glyburide concentration was increased up to 100 microM. Unlike tolbutamide, glyburide did not affect the excitability of muscle fibres, but significantly prolonged the repolarization phase of action potentials, especially at pHo 6.4. We suggest that several of the tolbutamide effects reported in this study cannot be accounted for by a direct effect on KATP channels, and that the large decrease in membrane excitability and muscle contractility in the presence of tolbutamide must seriously be taken into consideration when this channel blocker is used to study the physiological role of KATP channels in intact muscle fibres.

Action Potentials↗
PubMed1991

The effects of isotonic contractions on the rate of fatigue development and the resting membrane potential in the sartorius muscle of the frog, Rana pipiens.

The goal of this study was to characterize how isotonic contractions affect the rate of fatigue development. Muscle bundles dissected from frog sartorius muscles were stimulated with 100-ms long train of pulses (0.5 ms, 6 V, 140 Hz). To measure the effect of the isotonic contractions, isometric tetanus were elicited at regular time intervals during the stimulation to fatigue. In general, isotonic contractions caused a faster decrease in tetanic force than isometric contractions. The difference in tetanic force between an isotonic and isometric fatigue increased gradually over a 20-min period to 7.9 and 13.5% at 0.04 and 0.1 trains/s (TPS), respectively. At 0.2, 0.5, and 1.0 TPS, the decrease in tetanic force was also faster during an isotonic fatigue, which resulted in an initial difference in tetanic force between the two types of fatigue. The difference did not exceed 18.5% and did not persist throughout the stimulation period; i.e., the difference disappeared before the end of the fatigue stimulation. The half-relaxation time was prolonged during fatigue development, and the prolongation was greater during an isotonic fatigue, except at 0.04 TPS. The increases in the half-relaxation time at 0.2, 0.5, and 1.0 TPS were followed by a decrease, and the decreases were especially pronounced during an isotonic fatigue at 0.5 and 1.0 TPS. The results showed for the first time that isotonic contractions cause a faster rate of fatigue development in frog sartorius muscles, and this effect depends on the frequency of stimulation.

Animals↗
PubMed1978

25-hydroxy-vitamin D, diet and sunlight exposure in patients admitted to a geriatric unit.

Dietary intake, sunlight exposure and 25-hydroxy-vitamin D levels were estimated in 62 patients admitted to a geriatric assessment unit. There was a significant correlation between vitamin D intake and 25-hydroxy-vitamin D levels but none between sunlight exposure and these. This suggests that in old age dietary deficiency may be a more important cause of metabolic bone disease than limited sunlight exposure.

Adolescent↗
PubMedDate not supplied

Unmasking large and persistent reductions in proliferation rate of aging cells.

We have reported that nontransformed sublines of NIH 3T3 cells that are incubated under the growth constraint of confluence for 10 d or longer exhibit heritable reductions of growth rate upon serial subculture at low density, which simulate the effects of aging in vivo on cell growth. There is also a marked increase in the likelihood of neoplastic transformation. After switching to a new batch of calf serum (CS), we found the reduced growth rate was no longer produced within the previously established timeframe. However, substitution of fetal bovine serum (FBS) for CS during the period of recovery from confluence or the following tests of growth rate resulted in profound inhibition of growth in cells serially subcultured from confluent cultures. In some cases, fewer than one in a thousand cells from subcultures of confluent cultures formed colonies in FBS although they cloned at relatively high efficiency in CS. The reduced growth in FBS was retained in the postconfluent subcultures after many generations of multiplication at low density in CS. Generally, similar results with individual variations were obtained with three other batches of FBS. The numbers of cells per 3-d colony initiated from subcultures of confluent cultures were lower than those of control cultures that had never been confluent. Supplementation of FBS-containing medium with CS fully restored the growth of the postconfluent subcultures to the rate in CS medium, indicating that there is a deficiency of growth factor(s) in FBS rather than the presence of an inhibitor. The results show that prolonged incubation at confluence induces a populationwide heritable increase in requirement for growth factor(s) in short supply in FBS. Because clonal studies have shown that the reduction in growth rate is irreversible and varies in degree from clone to clone, we propose it arises from damage to DNA at any of many different genetic loci or from chromosome aberrations. Such genetic damage is also consistent with the increased tendency for neoplastic transformation in subcultures from the long-term confluent cultures.

3T3 Cells↗
PubMedDate not supplied

Recovery time and safe discharge of endoscopy patients after conscious sedation.

The aim of this study was to identify the best method for determining when to safely discharge the endoscopy patient; specifically, it was designed to determine whether the patient's risk factors, intraoperative occurrences, and/or medications used during endoscopy should be used to determine the minimum length of stay postconscious sedation or whether a general policy can be used, as is currently practiced at many institutions. Preoperative, intraoperative, and postoperative data were collected on a convenience sample of 405 adult ambulatory outpatients undergoing upper endoscopy and/or colonoscopy. Subjects were also interviewed by phone within 48 hours of discharge to assess postdischarge complications and their duration. Age predicted length of time in recovery, but only 2% of the variation in recovery time was predicted by the study variables. Intraprocedure occurrences predicted postprocedure occurrence. The implications of these and other findings are discussed in relation to nursing practice and future research.

Adult↗