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Biomedical subjects

J Ren

Publications and source records attributed to J Ren.

337 records · Page 19Linked to original sources
PubMed1990

[Pest control and yield increase of areca by root-zone application of carbofuran in admixture with fertilizers].

The result of our experiment has shown that by root-zone application of carbofuran in admixture with fertilizers to Areca in spring the serious pest Tirathaba rufivena can be controlled for 4 months during flowering and young fruiting stage and the yield can increase by 50%. The final residual amount of carbofuran in fruits is below 0.1-0.01 ppm or too low to be examined, and there is no decrease in total alkaloid content in fruits.

Alkaloids↗
PubMed1989

Modulation of esophageal contractions by distension in vitro.

Stimulation of the intrinsic nerves of the esophageal body leads to a twitch of the circular muscle after the end of the stimulation (the esophageal off-response), and the twitch spreads in the distal direction because of a latency gradient in the onset of the off-response between the proximal and the distal esophagus. We investigated the possibility that local input can modulate the basic off-response through intrinsic mechanisms and make it resemble more closely the sequential ring contractions that move boluses in the esophagus of intact animals (esophageal peristalsis). The esophagus up to the aortic arch and down to the gastroesophageal junction was removed from opossums and suspended in an organ bath containing 2 liters of Krebs solution at 36 degrees C. The mechanical activity of the esophagus was recorded by force transducers on the serosal surface of the esophagus 2, 4, and 6 cm above the LES. The intramural nerves of the proximal esophagus were stimulated by electrical pulses with and without distension of the esophagus by inflation of a luminal balloon. Balloon distension increased the latency of the off-response in the distal esophagus, thereby reducing the velocity at which the circular muscle contraction spread through the esophagus. In addition, balloon distension increased the amplitude and the duration of the esophageal circular muscle contraction (both off- and on-responses), and decreased the amplitude of the longitudinal muscle contraction (duration response) and LES response (relaxation response). Similar changes in the esophageal contraction responses were produced by radial stretch of an open preparation of the esophagus from which the mucosa had been removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Motility changes in opossum esophagus from experimental esophagitis.

We assessed how acute inflammation affects the contractile activity of the esophageal body. Two models of esophagitis were used: nine opossums had an esophageal perfusion of 100 meq hydrochloric acid for 2 hr and were studied at 24 hr. Ten had the perfusion for 4 h and their esophagitis were studied in vitro after 72 hr. Comparisons were made in all instances to animals who had esophageal saline perfusion for identical periods. All acid-perfused animals developed gross and histologic evidence of mucosal inflammation; in three animals, inflammatory changes extended into the submucosa and the muscularis propria. Manometric recordings in the acid-perfused animals revealed esophageal shortening, frequent failure of primary peristalsis and frequent occurrence of spontaneous contractions. Recordings of isometric tension of muscle in vitro revealed spontaneous contractions in strips from the mucosa and from the circular and from the longitudinal muscle. The amplitude of contractions in response to electrical stimulation was decreased, but the duration of contractions was increased largely because of a prolonged recovery phase. These changes in mechanical response occurred with stimulus parameters directed at both the muscle and the intrinsic nerves. We conclude that esophageal inflammation can lead to an increased irritability and decreased stimulus response of the smooth muscle of the esophagus even where it is not directly involved in an inflammatory response. These changes correspond to the functional abnormalities of the esophagus seen in patients with reflux esophagitis.

Animals↗
PubMed1989

Evidence for inhibition of opossum LES through intrinsic gastric nerves.

We have studied the mechanical responses of the isolated opossum gastroesophageal junction to a variety of stimuli. Lower esophageal sphincter (LES) relaxations were readily produced by gastric stretch and by electrical stimulation of the intramural gastric nerves. Gastric stimulation also led in 60% of stimuli to a contraction of circular muscle (the off response) in the distal esophagus, but in less than 15% of stimuli to a contraction of longitudinal esophageal muscle (the duration response). Mechanical or electrical stimulation of the esophagus led to a mechanical response of the stomach (relaxation, contraction, or both) in 76% of stimuli. The LES relaxation produced by esophageal stimulation was not as long as that produced by gastric stimulation. Direct electrical stimulation of the esophageal or gastric muscle produced a ring contraction that spread readily across the gastroesophageal junction but did not produce a relaxation of the LES or a contraction of the longitudinal esophageal muscle. Thus intramural nervous pathways can coordinate the mechanical activity of the esophagus, LES, and stomach. LES relaxations may occur as part of intrinsic reflexes that mediate gastric accommodation to volume.

Animals↗
PubMedDate not supplied

Basal and ethanol-induced cardiac contractile response in lean and obese Zucker rat hearts.

Obesity plays a pivotal role in metabolic and cardiovascular diseases. Certain types of obesity may be related to alcohol ingestion, which itself leads to impaired cardiac function. This study analyzed basal and ethanol-induced cardiac contractile response using left-ventricular papillary muscles and myocytes from lean and obese Zucker rats. Contractile properties analyzed include: peak tension development (PTD), peak shortening amplitude (PS), time to PTD/PS (TPT/TPS), time to 90% relaxation/relengthening (RT(90)/TR(90)) and maximal velocities of contraction/shortening and relaxation/relengthening (+/-VT and +/-dL/dt). Intracellular Ca(2+) transients were measured as fura-2 fluorescence intensity (DeltaFFI) changes and fluorescence decay time (FDT). In papillary muscles from obese rats, the baseline TPT and RT(90) were significantly prolonged accompanied with low to normal PTD and +/-VT compared to those in lean rats. Muscles from obese hearts also exhibited reduced responsiveness to postrest potentiation, increase in extracellular Ca(2+) concentration, and norepinephrine. By contrast, in isolated myocytes, obesity reduced PS associated with a significant prolonged TR(90), normal TPS and +/-dL/dt. Intracellular Ca(2+) recording revealed decreased resting Ca(2+) levels and prolonged FDT. Acute ethanol exposure (80-640 mg/dl) caused comparable concentration-dependent inhibitions of PTD/PS and DeltaFFI, associated with reduced +/-VT in both groups. Collectively, these results suggest altered cardiac contractile function and unchanged ethanol-induced depression in obesity.

Animals↗
PubMedDate not supplied

Influence of ovariectomy on ventricular myocyte contraction in simulated diabetes.

We studied the effect of ovariectomy (OVX) on cardiac contraction in myocytes maintained under a 'diabetes-simulated high-glucose' environment. Female rats were ovariectomized or sham operated (SHAM) and kept for 6 weeks. Isolated myocytes were maintained in a diabetes-simulated high [glucose] medium (HG; 25.5 mM) for 24 h before mechanical properties were measured. Contractile indices analyzed included peak shortening (PS), time to PS (TPS), time to 90% relengthening (TR90), maximal velocity of shortening and relengthening (+/- dL/dt), intracellular Ca2+ fura-2 fluorescence intensity and decay rate (tau). Nitric oxide synthase (NOS) activity was also evaluated. OVX myocytes displayed a longer TR(90), slower +/- dL/dt, lower fluorescence intensity and higher tau (slower decay rate) when compared to SHAM myocytes. In the SHAM group, HG exerted diabetes-like contractile dysfunctions, including depressed PS, prolonged TR90, reduced fluorescence intensity, higher tau and enhanced NOS activity when compared to myocytes maintained in low [glucose] medium (5.5 mM). Interestingly, the HG- induced mechanical alterations were significantly exaggerated (TPS, TR90 and tau), reversed (PS and NOS) or lost (+/- dL/dt and fluorescence intensity) in the OVX group. These data suggest that ovarian hormones play a role in the regulation of cardiac contractile function, and may have potentially protective effects against diabetes-associated cardiac dysfunction.

Animals↗
PubMedDate not supplied

Intra- and inter-individual variability in measurements of biomarkers for oxidative damage in vivo: Nutrition and Breast Health Study.

Oxidative stress has been implicated in the pathogenesis of various chronic diseases, such as cancer, cardiovascular disease and inflammatory conditions, as well as in ageing. Although a number of markers are now available, little is known about the reliability of single measurements of such markers in healthy individuals. The study examined the distribution of variance for three oxidative stress markers, 8-oxo-2'-deoxyguanosine (8-oxodG), 5-hydroxymethyl-2'-deoxyuridine (5-OHmdU) and total 8-isoprostane-F2alpha, which were measured every 3-6 months over 1 year in blood and breast nipple aspirate fluid (NAF) for 103 premenopausal women. For both plasma and NAF, the between-subject variances of 8-isoprostane-F2alpha were consistently greater than the within-subject variances. Consequently, their reliability coefficients were close to the level of those for cholesterol. On the other hand, the within-subject variances were much greater than the between-subjects variances for blood 5-OHmdU, resulting in low reliability coefficients, i.e. <0.3. Overall, the reliability coefficients for blood 8-oxodG were between those of 8-isoprostane-F2alpha and 5-OHmdU, but closer to those of 8-isoprostane-F2alpha. The results suggest that the reliability of oxidative stress markers may vary considerably depending on the type of marker. Caution should be exercised in selecting markers as well as in determining the number of study subjects or the number of samples per subject in a study. There also may be ample room to optimize laboratory techniques to quantify markers of oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMedDate not supplied

Influence of chronic alcohol ingestion on acetaldehyde-induced depression of rat cardiac contractile function.

Long-standing ethanol consumption acts as a chronic cardiac stress and often leads to alcoholic cardiomyopathy. We have recently shown that the acute ethanol-induced depression in myocardial contraction was substantiated by chronic ethanol ingestion. Acetaldehyde (ACA), the main ethanol metabolite, has been considered to play a role in ethanol-induced cardiac dysfunction. To evaluate the ACA-induced cardiac contractile response following chronic ethanol ingestion, mechanical properties were examined using left ventricular papillary muscles and myocytes from rats fed with control or ethanol-enriched diet. Muscles and myocytes were electrically stimulated at 0.5 Hz and contractile properties analysed included peak tension development (PTD) and peak shortening (PS). Intracellular Ca(2+) transients were measured as fura-2 fluorescence intensity changes (DeltaFFI). Papillary muscles from ethanol-consuming animals exhibited reduced baseline PTD and attenuated responsiveness to increase of extracellular Ca(2+). Acute ACA (0.3-10 mM) addition elicited a dose-dependent depression of PTD. However, the inhibition magnitude was significantly reduced in ethanol-treated rats. Myocytes from both control and ethanol-treated rats exhibited comparable ACA-induced depression in both PS and DeltaFFI. Collectively, these data suggest that the ACA-induced depression of myocardial contraction is reduced at the multicellular level, but unchanged at the single cell level, following chronic ethanol ingestion.

Acetaldehyde↗
PubMedDate not supplied

DNA binding properties of the indolocarbazole antitumor drug NB-506.

Indolocarbazoles derived from the antibiotic rebeccamycin represent an important group of antitumor agents. Several indolocarbazoles are currently undergoing clinical trials. These compounds inhibit topoisomerase 1 to produce DNA breaks that are responsible for cell death. Unlike classical topoisomerase I poisons like camptothecin, glycosyl indolocarbazoles can form stable complexes with DNA even in the absence of topoisomerase I. At least in part, their mode of action is reminiscent of that of the anthracyclines, which also bind to nucleic acids and interfere with topoisomerase II. The lead synthetic compound in the series is the uncharged drug NB-506, which bears a glucose residue attached to the indolocarbazole chromophore substituted with two hydroxyl groups at positions 1 and 11. Here we report a detailed biophysical study aimed at characterizing the DNA binding properties of NB-506. Molecular modeling was used to compare the conformation and electronic properties of NB-506 and its analogue ED-571 bearing the two hydroxyl groups at positions 2 and 10. Surface plasmon resonance experiments, performed with DNA hairpin oligomers, indicate that NB-506 binds almost equally well to both AT and GC base pairs, and the binding affinity (K = 10(5) M(-1)) is similar to that of certain classical intercalators such as amsacrine and bisantrene. Isothermal titration calorimetry experiments show that the binding of NB-506 is enthalpy-driven (deltaH = -7.2 kcal/mol). The binding enthalpy measured for NB-506 is similar to that obtained with doxorubicin but the DNA interaction processes for the two drugs differ markedly in terms of entropy and deltaG. The free energy of NB-506 binding to DNA is considerably less favorable than that of doxorubicin. These biophysical data help us to understand further how rebeccamycin-type anticancer drugs interact with DNA.

Algorithms↗