Biomedical subjects

H Lin

Publications and source records attributed to H Lin.

At least 253 records · Page 14Linked to original sources

PubMed1998

High-Resolution Spectroscopic Study of the (310) Local Mode Combination Band System of AsH3

The high-resolution spectra of AsH3 in the 8130-8340 cm-1 region, which were assigned to the (310;A1), and (310;E1), and the (310;E2) local mode combination bands, have been recorded at a resolution of 0.01 cm-1 and rotationally analyzed. The spectroscopic parameters were obtained by least-squares fitting. The rotational energy levels were fitted for the (310;A1) state (21 levels in all) up to J = 5, for the (310;E2) state (43 levels in all) up to J = 7, and for the (310;E1) state (43 levels in all) up to J = 5. The complication of the rotational structure indicates rotational perturbation. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗

PubMed1998

Franck-Condon Factors and Analysis of Several Electronic Systems of C2

The D1Sigma+u-X1Sigma+g (Mulliken) and E1Sigma+g-A1Piu (Freymark) systems of C2 have been analyzed. Molecular constants have been determined for the D1Sigma+u and E1Sigma+g states. Using these molecular constants, Franck-Condon factors (FCFs) have been calculated for the previously observed Mulliken and D1Sigma+u-B'1Sigma+g band systems. FCFs for two new electronic transitions, D1Sigma+u-C1Pig and E1Sigma+g-D1Sigma+u, have also been calculated. Knowledge of FCFs will help spectroscopists in the search for and identification of these bands. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

Absorption Intensity of Stretching Overtone States of Silane and Germane.

The band absorbance and line absorbance of R branch transitions are obtained from high-resolution Fourier transform measurement of silane and germane local mode overtones (n000), n = 1-5, under proper sample pressures and absorption lengths. The absorption coefficients of these overtones are derived by linear least-squares fitting. The relative intensities of overtones can be satisfactorily reproduced with the bond dipole model containing two adjustable parameters. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

Differential effects of bone mineral content and bone area on vertebral strength in a swine model.

Since the biomechanical competence of a vertebral body may be closely related to the content and distribution of the bone mineral, we have evaluated the effects of projected vertebral bone area (BA) and bone mineral parameters [bone mineral content (BMC) or bone mineral density (BMD)] on their biomechanical competence. We used dual-energy X-ray absorptiometry (DXA) to assess the bone mineral parameters of 36 swine thoracic vertebrae (T1-T12) and 15 lumbar vertebrae (L1-L5) after removal of the posterior elements. The failure load, compressive stress, and the stored strain energy of these vertebral bodies were assessed by a uniaxial compressive test using an MTS 810 testing system. Multiple regression analysis showed a significantly negative effect of BA and significantly positive effect of BMC on the biomechanical competence (compressive stress, r2 = 0.67, P < 0.0001; failure load, r2 = 0.75, P < 0.0001). However, the stored strain energy was only related to the BMC (r2 = 0.35, P < 0.0001). The contributory effects of BMC and BA on the biomechanical competence were not equal. The effects of BMC was larger than BA in determining the failure load and stored strain energy, whereas the reverse was found for the compressive stress. Using the log-transformed parameters as the regressors resulted in similar results. These results suggested the differential effects of BA and BMC in determining the biomechanical competence of vertebral bodies. We recommend the use of both parameters instead of BMD alone for evaluation of the vertebral biomechanical competence.

Absorptiometry, Photon↗

PubMed1998

Effects of methanol extract of Chansu on hypothalamic-pituitary-testis function in rats.

Chansu, a galenical preparation of the dried white venom of Chinese Bufo bufo gargarizans, is one of the major components of Kyushin, a traditional Chinese medicine. Kyushin is reported to have a cardiotonic effect that has been suggested to be due to the action of bufadienolides such as bufalin and cinobufagin. Recently, we found that administration of bufalin in male rats diminished the luteinizing hormone (LH) response to gonadotropin-releasing hormone (GnRH) and the secretion of testosterone both in vivo and in vitro. These observations suggest that Chansu may possess hypogonadal effects in male rats. In the present study, the effects of the methanol extract of Chansu on hypothalamic-pituitary-testicular function in male rats were examined. Crude Chansu was extracted by methanol and purified by a Sep-Pak C18 column. No activity of bufalin, cinobufagin, estradiol, or digoxin in purified methanol extract was detected; all Chansu used in this study was the purified methanol extract. A single intravenous injection of Chansu resulted in a decrease of the basal (20% to 55%) and human chorionic gonadotropin (hCG)-induced (35% to 40%) levels of plasma testosterone and the GnRH-induced level of plasma LH (25% to 30%). Administration of Chansu in vitro decreased basal and hCG-stimulated testosterone production by 60% to 70% and 40% to 60%, respectively, as well as spontaneous and forskolin- or 3-isobutyl-1-methylxanthine (IBMX)-induced accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) by 30% to 45% in rat testicular interstitial cells. Although LH release by rat anterior pituitary glands was diminished, GnRH release by the rat mediobasal hypothalamus was enhanced by administration of Chansu in vitro. These results suggest that the bufalin-free extracts of Chansu inhibit testosterone secretion in rats, in part, due to (1) a decreased production of testicular cAMP, (2) a decreased response of testosterone to gonadotropin, and (3) a reduction of the LH response to GnRH.

Animals↗

PubMed1998

Dinuclear palladium(II) complexes containing two monofunctional [Pd(en)(pyridine)Cl]+ units bridged by Se or S. Synthesis, characterization, cytotoxicity and kinetic studies of DNA-binding.

Two novel dinuclear palladium(II) complexes, ¿[Pd(en)Cl]2(bpse)¿(NO3)2 (1) and ¿[Pd(en)Cl]2 (bpsu)¿(NO3)2 (2), (where en is ethylenediamine; bpse is bis(3-methyl-4-pyridyl) selenide; bpsu is bis(3-methyl-4-pyridyl) sulfide) have been synthesized. The complexes have been characterized by elemental analysis, IR, 1H NMR, and 13C NMR. They have been assayed for antitumor activity in vitro against the mice leukemia L1210 and the human coloadenocarcinoma HCT8 cell lines. The results show that compound 1 has a lower I.D.50 value against the two cancer cell lines as compared to compound 2; the compounds also shows a lower I.D.50 value than cisplatin against the HCT8 cell line, but a higher I.D.50 value than cisplatin against the L1210 cell line. Binding studies indicate that compound 1 possibly interacts with DNA by a nonintercalative mode. Kinetics of binding of the two compounds to DNA are firstly studied using ethidium bromide as a fluorescence probe with stopped-flow spectrophotometer under pseudo-first-order condition. The stronger binding of two steps in the process of the compounds interacting with DNA are observed, and the Kobs and Ea of binding of the two steps (where Kobs is the observed pseudo-first-order rate constant, Ea is the observed energy of activation) are obtained.

Animals↗

PubMed1998

Palladium(II) complexes with N,N'-dialkyl-1,10-phenanthroline-2,9-dimathanamine: synthesis, characterization and cytotoxic activity.

Five new tetradentate ligands and their corresponding palladium complexes, [Pd(L)]Cl2 (L = N,N'-dimethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-diethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dipropyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-ditert-butyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dicyclohexyl-1,10-phenanthroline-2,9-dimathanamine) have been synthesized. The ligands and their complexes have been characterized by elemental analysis, IR, and 1H NMR. The complexes have been assayed for antitumor activity in vitro against the mouse leukemia L1210 and the mouse liver carcinoma Bel7402 cell lines. The results showed that the activities of these complexes are significantly dependent on the nature of the alkyl groups on the coordinated amine moieties, and three of these palladium complexes showed lower ID50 values against the two cell lines than cisplatin.

Animals↗

PubMed1998

The self-renewing mechanism of stem cells in the germline.

Germline stem cells (GSCs) are a self-renewing population of germ cells that serve as the source of gametes in diverse organisms. Current research suggests that the self-renewing division of GSCs is controlled both by somatic signaling and by intracellular mechanisms such as differential gene expression, asymmetric cytoskeletal organization, and the cell cycle machinery. These findings provide a framework for the further study of GSCs and stem cell renewal in general.

Animals↗

PubMed1998

Pretreatment for cellulose hydrolysis by carbon dioxide explosion

Cellulosic materials were treated with supercritical carbon dioxide to increase the reactivity of cellulose, thereby to enhance the rate and the extent of cellulose hydrolysis. In this pretreatment process, the cellulosic materials such as Avicel, recycled paper mix, sugarcane bagasse and the repulping waste of recycled paper are placed in a reactor under pressurized carbon dioxide at 35 degreesC for a controlled time period. Upon an explosive release of the carbon dioxide pressure, the disruption of the cellulosic structure increases the accessible surface area of the cellulosic substrate to enzymatic hydrolysis. Results indicate that supercritical carbon dioxide is effective for pretreatment of cellulose. An increase in pressure facilitates the faster penetration of carbon dioxide molecules into the crystalline structures, thus more glucose is produced from cellulosic materials after the explosion as compared to those without the pretreatment. This explosion pretreatment enhances the rate of cellulosic material hydrolysis as well as increases glucose yield by as much as 50%. Results from the simultaneous saccharification and fermentation tests also show the increase in the available carbon source from the cellulosic materials for fermentation to produce ethanol. As an alternative method, this supercritical carbon dioxide explosion has a possibility to reduce expense compared with ammonia explosion, and since it is operated at the low temperature, it will not cause degradation of sugars such as those treated with steam explosion due to the high-temperature involved.

Journal Article↗

PubMed1998

The role of the hedgehog/patched signaling pathway in epithelial stem cell proliferation: from fly to human.

The hedgehog-patched (hh-ptc) intercellular signaling pathway has recently been shown to control the proliferation of epithelial stem cells in both Drosophila and vertebrates. Mutant and ectopic expression analyses in Drosophila suggest that the HH protein diffuses from the signaling cells to promote the proliferation of nearby ovarian somatic stem cells by antagonizing the suppression of its receptor PTC towards the CI transcription factor in the stem cells. Consequently, the transcription of CI-dependent genes leads to stem cell proliferation. This regulatory pathway appears to function also in vertebrates, where defects in ptc cause basal cell carcinoma, tumors of epidermal stem cell origin. Basal cell carcinoma can also be induced by ectopic expression of Sonic hedgehog (shh) or Gli1, the vertebrate homolog of ci. These studies suggest the conservation of the hh signaling pathway in controlling epithelial stem cell divisions among different organisms.

Animals↗

PubMed1998

Inhibition of gastric emptying and intestinal transit by amphetamine through a mechanism involving an increased secretion of CCK in male rats.

1. The effect of amphetamine on gastrointestinal (GI) transit and the plasma levels of cholecystokinin (CCK) were studied in male rats. 2. Gastric emptying was inhibited both acutely and chronically by the administration of amphetamine. GI transit was decreased by the acute administration of amphetamine but not affected by the chronic administration of amphetamine. 3. Plasma CCK levels were increased dose-dependently by amphetamine. 4. Proglumide, a CCK receptor antagonist, prevented amphetamine-induced inhibition of gastric emptying and the decrease in GI transit in male rats. 5. The selective CCK(A) receptor antagonist, lorglumide, dose-dependently attenuated the amphetamine-induced inhibition of gastric emptying in male rats. In contrast, the selective CCK(B) receptor antagonist, PD 135,158, did not reverse the effect of amphetamine on gastric emptying. 6. Both lorglumide and PD 135,158 reversed the inhibitory effect of amphetamine on GI transit in male rats. 7. These results suggest that amphetamine-induced inhibition of gastric emptying and intestinal transit is due in part to a mechanism associated with the hypersecretion of endogenous CCK.

Amphetamines↗

PubMed1998

Inhibitory effect of digoxin on testosterone secretion through mechanisms involving decreases of cyclic AMP production and cytochrome P450scc activity in rat testicular interstitial cells.

1. In vivo and in vitro experiments were performed to examine inhibitory effects of digoxin on testosterone secretion and to determine possible underlying mechanisms. 2. A single intravenous injection of digoxin (1 microg kg(-1)) decreased the basal and human chorionic gonadotropin (hCG)-stimulated plasma testosterone concentrations in adult male rats. 3. Digoxin (10(-7) - 10(-4) M) decreased the basal and hCG-stimulated release of testosterone from rat testicular interstitial cells in vitro. 4. Digoxin (10(-7) - 10(-4) M) also diminished the basal and hCG-stimulated production of cyclic 3':5'-adenosine monophosphate (AMP) and attenuated the stimulatory effects of forskolin and 8-Br-cyclic AMP on testosterone production by rat testicular interstitial cells. 5. Digoxin (10(-4) M) inhibited cytochrome P450 side chain cleavage enzyme (cytochrome P450sec) activity (conversion of 25-hydroxy cholesterol to pregnenolone) in the testicular interstitial cells but did not influence the activity of other steroidogenic enzymes. 6. These results suggest that digoxin inhibits the production of testosterone in rat testicular interstitial cells, at least in part, via attenuation of the activities of adenylyl cyclase and cytochrome P450sec.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1998

Review and evaluation of MRI nonuniformity corrections for brain tumor response measurements.

Current MRI nonuniformity correction techniques are reviewed and investigated. Many approaches are used to remedy this artifact, but it is not clear which method is the most appropriate in a given situation, as the applications have been with different MRI coils and different clinical applications. In this work four widely used nonuniformity correction techniques are investigated in order to assess the effect on tumor response measurements (change in tumor volume over time): a phantom correction method, an image smoothing technique, homomorphic filtering, and surface fitting approach. Six brain tumor cases with baseline and follow-up MRIs after treatment with varying degrees of difficulty of segmentation were analyzed without and with each of the nonuniformity corrections. Different methods give significantly different correction images, indicating that rf nonuniformity correction is not yet well understood. No improvement in tumor segmentation or in tumor growth/shrinkage assessment was achieved using any of the evaluated corrections.

Biophysical Phenomena↗

PubMed1998

Treatment of carcinoma of the hard palate with gamma knife radiosurgery.

The Gamma Knife radiosurgical treatment of two patients suffering from carcinomas of the hard palate is reported. A 67-year-old woman was treated with partial resection of an adenocarcinoma of the hard palate two years previously. Computerized tomographic imaging showed the tumor had grown (T4N1M0). The second patient, a 58-year-old woman, had a cauliflower-like tumor of the hard palate (T2N0M0). Pathological diagnosis obtained by needle biopsy was squamous cell carcinoma. These two patients underwent radiosurgical treatment with the Gamma Knife. A surface dose of 20 Gy was administered at the 35% isodose curve. These two patients were followed up for 18 and 15 months, respectively. Encouraging results were obtained. Further research is needed in order to validate this new treatment of carcinomas of the hard palate.

Adenocarcinoma↗

PubMed1998

Antioxidative activities of several marine polysaccharides evaluated in a phosphatidylcholine-liposomal suspension and organic solvents.

The antioxidative activities of several water-soluble marine polysaccharides, alginate (ALG), alginate sulfate (SALG), propylene glucolalginate sodium sulfate (PSS), propylene glucol mannuronate sulfate (PGMS), the oligosaccharide of chitosan (OLC), N,O-carboxymethyl chitosan (NOCC) and hydroxypropylated chitosan (HPC), were examined in a phosphatidylcholine (PC)-liposomal suspension containing the water-soluble radical emitter, 2,2'-azobis (2-amidinopropane) dihydrochloride. In the suspensions containing OLC and SALG, the initial rates of PC-OOH accumulation were 2.78 x 10(-8) MS-1 and 2.88 x 10(-8) MS-1, respectively, while all the polysaccharides tested showed antioxidative activity. Liposoluble marine polysaccharides, hexanoyl chitin (HCH) and an N-benzoylhexanoyl chitosan (NBHC) solution, also retarded the hydroperoxide accumulation of methyl linoleate by effectively trapping peroxide radicals in organic solvents when the radical chain reaction had been initiated by 2,2'-azobis (2,4-dimethylvaleronitrile). The kinetic data presented indicate that the alginate and chitin derivatives can be expected to play a role in the antioxidative mechanism of biological systems.

Alginates↗

PubMed1998

Survival advantages and complications of adjuvant therapy in early-stage cervical cancer with pelvic node metastasis.

BACKGROUND: Patients with early-stage cervical cancer who have pelvic node metastasis usually need adjuvant therapy after surgery for improvement of the length of survival. We attempted to determine the survival advantages and complications associated with different adjuvant therapeutic modalities. MATERIALS AND METHODS: Eighty-seven patients with clinical stage Ib and IIa cervical cancer were treated with radical hysterectomy from July 1986 through December 1994 were reviewed retrospectively. All had had lymph node metastasis. The patients were divided into three groups according to the different adjuvant therapeutic approaches utilized: radiation (group I, n = 43), chemotherapy (group II, n = 23), and chemoirradiation (group III, n = 21). RESULTS: There was no significant difference among these three groups in the 5-year relapse-free survival rate (group I: 63%, group II: 62%, group III: 51%, p = 0.785). The recurrence rates among these three groups were found to be similar (group I: 32.6%, group II: 39.1%, group III: 47.6%, p = 0.331). However, most of the recurrence in patients who had received pelvic radiation was at a distant site (group I: 79%, group III: 80%) as compared to the patients who had received chemotherapy only (group II: 33%), and the differences were significant (p = 0.020). The rates of complications, such as severe leukopenia, lymphedema with cellulitis, proctosigmoiditis and ileus, were found to be lower in the chemotherapeutic group. CONCLUSION: Although we failed to demonstrate the survival advantages of different adjuvant therapeutic approaches, we still favor chemotherapy as an adjuvant basis because it is the least toxic of the regimens.

Adult↗

PubMed1998

[Ultrasonic measurements of fetal thigh soft tissue thickness in the estimation of fetal weight].

OBJECTIVE: To study ultrasonic measurement of fetal thigh soft tissue thickness in the estimation of fetal weight. METHODS: Fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL) and fetal thigh soft tissue thickness (FTSTT) were measured by ultrasonography and analyzed with neonatal birth weight in 178 cases. RESULTS: There was significant correlation between FTSTT and neonatal birth weight (r = 0.8601), and it is better to estimate fetal weight with FTSTT than with the other parameters. The sensitivity and specificity for detection of macrosomia was 91% and 94%, respectively. The FTSTT was positively correlated with gestational age (r = 0.7070). CONCLUSION: The ultrasonic measurement of FTSTT is a simple, accurate and valuable index in estimation of fetal weight.

Adult↗

PubMed1998

[Association of apoB levels and nutrition of coronary heart disease patients].

Blood lipids and apo B levels were measured on 101 Coronary Heart Disease patients and 100 controls. The results showed that the apo B levels of patients were higher than that of controls. The average values were (877 +/- 129) mg/L and (800 +/- 95) mg/L respectively. It was found that there was close association among body mass index(BMI), ratio of waist circumference to hip circumference(WHR) and apo B levels. Besides, the results showed that dietary habit of "eating fat meat" might result in the increase of apo B concentration while the VC intake was negatively associated with serum apo B levels.

Adult↗