Proceedings of the National Science Council, Republic of China. Part B, Life sciences最新文献

Cardiac after-load, neurohumoral reaction and the secondary cardiac hypertrophy were studied in six groups of Sprague-Dawley (SD) rats with abdominal aortic constriction. We found that abdominal aortic constriction above the renal arteries decreased the heart rate and cardiac output, and increased the pulse pressure. These abnormalities would return to normal after constriction ended. Captopril, propranolol and prazosin could reduce the increase of pulse pressure but still had decreased in cardiac output of rats with abdominal constriction. Aortic constriction also increased the aortic impedance and cardiac load but decreased aortic compliance. These changes could also be lessened by captopril, propranolol and prazosin. We have confirmed that aortic constriction can induce secondary cardiac hypertrophy, but the pathogenesis might be due to multiple factors.

Intracranial saccular aneurysms have been a well known cerebrovascular disease for over fourty years in the Taiwan area and over two centuries around the world. Up to now, information pertinent to the genesis, progression, and thrombosis or rupture of saccular aneurysms has been mainly acquired from autopsies and various in vivo studies. The present review provides relevant hemodynamic information gathered from in vitro studies. The parallel results between in vitro and in vivo or between in vitro and autopsy investigations are also addressed. Emphases are placed on the terminal and lateral saccular aneurysms. The effects of the branches's flow-rate ratio, bifurcation angle, aneurysmal size, parent vessel curvature, and Wormersley number on the intra-aneurysmal flow characteristics are examined in detail, and possible risky factors are identified.

N-methylation at the arginine residues in RNA binding proteins with the arginine and glycine rich RGG box has been identified. We show that a synthetic peptide R9 (GGRGRGGGF) with the RGG sequence present in human fibrillarin and fragile X mental retardation protein (FMRP) can be specifically methylated by rat brain extract. A control peptide K9 with all arginines replaced by lysines could not be methylated under the same conditions, indicating that the arginines in the peptide were the methylation sites. A novel missense mutation, which changes an arginine to a histidine in the RGG box region of FMRP in a typical fragile X patient, has been identified. A synthetic peptide with this Arg-->His (GGRGHGGGF) substitution was methylated by our in vitro methylation system to a much less extent. Amino acid analysis of the methylated R9 peptide identified the methylated amino acid as monomethylarginine. The R9 peptide may be useful for further studies on arginine methylation in RGG proteins.

A national survey of patient doses for diagnostic radiology was planned in the Republic of China. We performed a pilot study for this survey to develop a protocol of the dose assessments. Entrance skin doses and organ (including ovary, testicle and uterus) doses were measured by thermoluminescent dosimeters and calculated by means of Monte Carlo simulations for several diagnostic procedures. We derived a formula and used the RadComp software for the computation of entrance skin doses. This formula involves several factors, such as kVp, mAs, the focus-to-skin-distance and aluminum filtration. RadComp software was applied to obtain free-air entrance exposures which were converted to entrance skin doses by considering the backscattering radiation from the body. Organ doses were measured using a RANDO phantom and calculated using a mathematical phantom for several diagnostic examinations. Genetically significant doses were calculated from ovary and testicle doses for the evaluation of hereditary effects. Embryo/fetal doses were determined from the uterine doses by considering the increase in uterus size with gestational age. We found that the patient doses studied in this work were all below the reference doses recommended by the National Radiological Protection Board of the U.K.

The purpose of this research was to document the biochemical response of rat osteosarcoma cells (ROS 17/2.8) to mechanical stress in vitro. The influence of mechanical stress on ROS 17/2.8 cells was studied using a stress application device. Briefly, the device was fabricated by bonding an orthodontic expansion screw outside the bottom of a plastic culture dish with self-curing acrylic resin. Irreversible deformation of the culture dish was produced by activating an expansion screw. The resulting mechanical stress was transferred to the cells which attached to the culture dish. The response in terms of cyclic adenosine monophosphate (cAMP) of ROS 17/2.8 cells to mechanical stress was measured using a competitive protein-binding method. The effect of mechanical stress on cellular growth was assessed through the incorporation of 3H-thymidine after different periods of mechanical stress application. The results revealed that mechanical stress could increase the production of cAMP in ROS 17/2.8 cells at an early phase after stress stimulation. This change in the cAMP level was dependent on the duration of stress application, and the maximal response occurred when the mechanical stress was applied for one hour. Although the cellular incorporation of 3H-thymidine decreased 40-60% in ROS 17/2.8 cells subjected to mechanical stress for 1 hour, this reaction recovered from the inhibition effect to 80-85% of the baseline when the mechanical stress lasted for 24 hours. The observations in this study indicate that mechanical stress stimulates the production of cAMP and inhibits the 3H-thymidine incorporation of ROS 17/2.8 cells at an early phase of stress application.

Characterization of adrenergic stimuli on luteinizing hormone (LH) release induced by ovarian steroids in short-term ovariectomized (OVX) rats was studied. Female Sprague-Dawley rats were OVX about 1000 h on the diestrous day 1. After ovariectomy, rats were immediately inserted estradiol-containing Silastic capsules s.c. and implanted atrial Silastic tubing for frequent blood samplings. All the rats received 2 mg of progesterone s.c. at 0930 h the next morning. At 1200 h, the rats received additional treatments: a saline vehicle, prazosin HC1 (an alpha 1-adrenergic antagonist), yohimbine HC1 (an alpha 2-adrenergic antagonist), or propranolol HC1 (a beta-adrenergic antagonist) s.c., respectively. Two different doses of individual adrenergic antagonists were used on an equimolar basis in order to show their effectiveness on steroids-induced LH secretion. Blood samples were collected before and 1, 3, and 5 hours after the treatments through indwelt tubings. LH surge induced by ovarian steroids was suppressed/delayed by prazosin and yohimbine, but potentiated by propranolol in a dose-dependent manner. Results suggested that the hypothalamic alpha 1-, alpha 2-, and beta-adrenoreceptors were involved in the control of LH surge in the short-term OVX-steroids-primed rats. Principally, the alpha 1- and alpha 2-adrenoreceptors played a facilitatory role, and the beta-adrenoreceptors played an inhibitory role in the regulation of LH surge induced by ovarian steroids.

Resveratrol (trans-3,4',5-trihydroxystibene) is a phytopolyphenol isolated from the seeds and skins of grapes. Recent studies indicate that resveratrol can block the process of multistep carcinogenesis, namely, tumor initiation, promotion and progression. Resveratrol can also reduce the risk of cardiovascular disease in man. The molecular mechanisms of resveratrol in chemoprevention of cancer and cardiovascular disease are interesting and under intensive investigation. Resveratrol was found to strongly inhibit nitric oxide (NO) generation in activated macrophages, as measured by the amount of nitrite released into the culture medium, and resveratrol strongly reduced the amount of cytosolic inducible nitric oxide synthase (iNOS) protein. The activation of nuclear factor kappa B (NF kappa B) induced by lipopolysaccharide (LPS) was inhibited by resveratrol. The phosphorylation and degradation of nuclear factor inhibitor kappa B alpha (I kappa B alpha) were inhibited by resveratrol simultaneously. Reactive oxygen species (ROS) are regarded as having carcinogenic potential and have been associated with tumor promotion. Resveratrol may act as a reactive oxygen species scavenger to suppress tumor development. In addition, resveratrol may block multistep carcinogenesis through mitotic signal transduction blockade. Reactive oxygen species are pivotal factors in the genesis of heart disease. Meanwhile, efficient endogenous antioxidants, including superoxide dismutase (SOD), glutathione peroxidase (GSHPx), and catalase, are present in tissues. A fine balance between reactive oxygen species and endogenous antioxidants is believed to exist. Any disturbance of this balance in favor of reactive oxygen species causes an increase in oxidative stress and initiates subcellular changes, leading to cardiomyopathy and heart failure. The experimental results indicate that exogenous antioxidant resveratrol is of value in chemopreventing the development of heart disease. It is urgent that more efforts be made to investigate newer therapies employing antioxidants for the chemoprevention of cardiovascular disease and cancer.

Cyclodextrin glucanotransferase (CGTase, EC 2. 4. 1. 19) converts starch and related alpha-1,4-glucans to cyclodextrin (CD). Our previous studies of the enzyme have suggested that E344 on the polypeptide is crucial to the enzyme activity. Mutational analysis of CGTase was performed to confirm this idea. Three mutant CGTases containing either E344D, E344K or E344L substitution were overexpressed in Escherichia coli. However, only the wild-type and E344D CGTases became soluble when expressed at 20 degrees C. These two enzymes were purified to homogeniety from E. coli cells after beta-CD and Ni-NTA affinity chromatographies. The Km values of the authentic Bacillus macerans CGTase (2.10 mM), and of the wild-type (0.58 mM) and E344D (1.05 mM) CGTases purified from E. coli were different. The kcat values of the three CGTases were 99.8, 26.5 and 90.7 s-1, respectively. The percentage of alpha-CD production was 18.4% for the authentic CGTase, 24.9% for the wild-type and 14.5% for the E344D CGTases purified from E. coli. The changes of both the coupling and cyclization activities of CGTase caused by E344D suggest that E344 is important to the catalytic function of CGTase.

A UDP-glucose pyrophosphorylase encoding gene was identified through functional complementation screening by using an Escherichia coli galU mutant. Sequence analysis of the gene indicated that it is most likely derived from a Pseud monas sp. The gene is located immediately upstream and transcribed in the same direction of the gor (glutathione reductase) gene and is capable of encoding a protein 30,943 daltons in size. The gene product synthesized in Escherichia coli was purified and its biochemical properties characterized. The recombinant UDP-glucose pyrophosphorylase exhibited a molecular weight of 130 kDa, suggesting a tetrameric organization of the gene product. Two mutant forms of the enzyme were identified. The activity of the mutant enzyme with a tyrosine to histidine (Y26 1H) substitution was found to be greatly reduced. On the other hand, the tyrosine to cysteine (Y84C) substitution resulted in an enzyme that functions normally at 37 degrees C but rather poorly at temperatures lower than 30 degrees C.

A variegated leaf mutant in soybean [Glycine max (L.) Merr.] has been identified and characterized. E25-10 was derived by exposure of seeds of the "Williams' 82" cultivar to gamma-radiation. In this mutant, yellow leaf sectors contain defective chloroplasts, in which the thylakoid membranes are presented as long, parallel structures with little or no overlap. No starch grains have been detected in the mutant chloroplasts. Small vesicles and plastoglobuli can be found within the defective chloroplasts. Genetic studies revealed that a single nuclear-encoded gene is responsible for the mutation in E25-10. The total chlorophyll content is reduced in yellow leaf tissue by 70-80%. However, the chlorophyll a/b ratio is not altered. The absorbance spectrum of pigments in the mutant leaf tissue differed from that of the green extracts in the range of 400-500 nm. This reduction in total chlorophyll and the change in the absorbance spectrum pattern in the yellow tissue is related to a loss of certain photosynthetic complexes. Green gel analysis revealed that four major pigment-protein complexes (CP1, LHCP1, LHCP2, and CPa) of the thylakoid membranes were absent in the E25-10 mutant. Lithium dodecyl sulphate polyacrylamide gel analysis showed that at least 5-6 polypeptides (51, 44, 25, 15, 13, and 12 kDa) were missing in the thylakoid membranes of chloroplasts from the yellow tissue. Changes in chloroplast- and nuclear-encoded gene message levels were detected. The psaA transcripts which code for the P700 apoprotein in PSI were reduced in chloroplasts from the E25-10 mutant yellow tissue. The levels of the large subunit of ribulose bisphosphate carboxylase (rbcL) and light harvest complex protein (LHCP) of PSII mRNA appeared to be reduced slightly in the mutant plants. However, a much more significant reduction in the 16S rRNA and the small subunit of ribulose bisphosphate carboxylase (rbcS) expression was detected in the yellow leaf sectors. Our results suggest that the possible lesion in E25-10 is located in the photosystem I even though fewer grana were observed in the defective chloroplasts.