Oestrogen relaxes human epicardial coronary arteries through non-endothelium-dependent mechanisms

BACKGROUND

Oestrogen-replacement therapy is associated with a reduced incidence of cardiovascular disease. The acute administration of oestrogen improves myocardial ischemia in women with coronary heart disease. In this study we investigated the relaxing effect of oestradiol-17 beta on human coronary arteries in vitro and determined the role of endothelial modulation in this relaxation by using isolated human coronary arteries.

METHODS

Atherosclerosis-free epicardial arteries from men and women were removed from patients undergoing heart or combined heart and lung transplantation. The arteries were cut into ring segments and placed into organ baths containing Tyrode's solution. Changes in isometric tension were measured. The relaxing response to oestradiol-17 beta (10(-10) - 10(-5) mol/l) was investigated and the effects of endothelium, NGmonomethyl-L-arginine and indomethacin on the response of oestradiol-17 beta were assessed.

RESULTS

Oestradiol-17 beta (10(-10) - 10(-5) mol/l) induced significant relaxation in coronary arteries pre-contracted with the thromboxane A2 analog (U46619; 3 x 10(-8) mol/l). Relaxation was significantly greater in coronary arteries from female patients. No significant differences were observed between arteries with or without endothelium nor after nitric oxide synthase or cyclo-oxygenase inhibition. These results indicate that oestradiol-17 beta induces human coronary artery relaxation via an endothelium-independent mechanism in vitro. The sex of the patients significantly affects sensitivity of the coronary arterial rings to oestrogen.

CONCLUSION

Oestradiol-17 beta-induced coronary relaxation may play an important role in regulation of coronary tone, and may partly explain why oestrogen improves myocardial ischemia in women and why it protects postmenopausal women from the risk of developing coronary heart disease.

[Comparative study on baicalin contents in 4 traditional Chinese medicinal preparations of ying huang]

The contents of baicalin in four different traditional Chinese medicinal preparations of Ying Huang were determined by HPLC. The contents of baicalin in Ying Huang tablets, Ying Huang oral liquid, Ying Huang injection and Ying Huang granules are respectively: 124.18 mg/g, 21.12 mg/ml, 12.39 mg/ml and 6.79 mg/g. The HPLC method suggested in this paper can be used for quality control in the production of Ying Huang preparations.

A mechanistic link between an inherited and an acquired cardiac arrhythmia: HERG encodes the IKr potassium channel

Mutations in HERG cause an inherited cardiac arrhythmia, long QT syndrome (LQT). To define the function of HERG, we expressed the protein in Xenopus oocytes. The biophysical properties of expressed HERG are nearly identical to the rapidly activating delayed rectifier K+ current (IKr) in cardiac myocytes. HERG current is K+ selective, declines with depolarizations above 0 mV, is activated by extracellular K+, and is blocked by lanthanum. Interestingly, HERG current is not blocked by drugs that specifically block IKr in cardiac myocytes. These data indicate that HERG proteins form IKr channels, but that an additional subunit may be required for drug sensitivity. Since block of IKr is a known mechanism for drug-induced cardiac arrhythmias, the finding that HERG encodes IKr channels provides a mechanistic link between certain forms of inherited and acquired LQT.

Counting total cell numbers microscopically on stained films

Two main sources of error in the conventional stained film cell count method, i.e. errors from imperfect spreading of the suspension and uneven distribution of cells in the film, have been eliminated by counting all the cells in the film. Staining solution and sodium alginate were added to the suspension before spreading over the slide. With a microsyringe, 20-microliters suspension was spread in two bands of ca 1.7 mm x 60 mm each. Then total cells could be counted easily in the x 100 magnification field by moving the slide in one direction. Results were satisfactory. Coefficients of variation were 2.6 and 1.1% in two separate yeast determinations each with five replicates. For counting higher magnifications, a suitable image analyser for automating the method is believed worthy of study.

Cellular and metabolic effects of triphenylselenonium chloride in a mammary cell culture model

Triphenylselenonium chloride, a novel synthetic organic selenium compound in which selenium is bonded to three unsubstituted benzene rings, possesses significant chemopreventive activity against chemically-induced mammary carcinogenesis. The effects of triphenylselenonium chloride on a mammary tumor cell line (MOD) were compared to selenite, a reference compound in selenium chemoprevention research. It was observed that triphenylselenonium chloride treatment exerted a cytostatic effect in the absence of membrane damage or DNA strand breaks. The observed cytostasis was associated with a selenium concentration-dependent inhibition of cell proliferation, measured by [3H]thymidine incorporation into DNA, and delayed cell cycle progression. In contrast, selenite treatment rapidly induced DNA damage and cell death. These marked differences were observed across the same levels of cellular selenium. In addition, triphenylselenonium chloride treatment increased glucose consumption and lactate production, indicating an effect of the compound on cellular energy metabolism. Collectively these observations demonstrate that the toxic activities associated with selenite treatment do not occur when cells are treated with triphenylselenonium chloride. This compound represents a new type of selenium compound that exerts significant cellular effects through mechanisms distinct from those induced by selenite.

[The investigation on actinomycete population and resources in some areas in Yunnan. IX. The actinomycetes in the west and the northeast of Yunnan]

Two hundred of soil samples of primeval forest, secondary forest, wasteland, nonirrigated farmland, vegetable farmland and paddy farmland were collected from both the west and the northeast of Yunnan in February, 1989. The actinomycetes in the samples were isolated and identified by various methods. This paper discussed the actinomycete population and its difference in the both areas of Yunnan.

Intraperitoneal 5-fluoro-2'-deoxyuridine (FUDR) and (S)-leucovorin for disease predominantly confined to the peritoneal cavity: a pharmacokinetic and toxicity study

Intraperitoneal (IP) administration of fluorinated pyrimidines has been evaluated for ovarian and gastrointestinal malignancies in phase I, II, and III trials. The tolerance and pharmacokinetic profile of IP 5-fluoro-2'-deoxyuridine(FUDR) alone and with (R,S)-leucovorin ((R,S)-LV) have each been evaluated in previous phase I studies. FUDR doses of 3 g per day with and without (R,S)-LV doses up to 640 mg per day given IP are well tolerated. The current phase I study was designed to determine the pharmacokinetic profiles and clinical tolerance of escalating doses of the pure biologically active S-isomer of leucovorin ((S)-LV) given IP with the same dosing schedule of FUDR. A group of 16 patients with disease confined to the abdominal cavity were treated in this study. Pharmacokinetic studies of blood and peritoneal fluid, toxicity profiles, and clinical response for the first three cycles are reported here. The toxicity profile did not significantly differ from the prior two studies. All non-hematologic toxicities, such as fatigue, nausea, vomiting, diarrhea, and abdominal discomfort were less than grade 4, and most were less than grade 3. Neutropenia and thrombocytopenia were uncommon and observed only in patients with compromised bone marrow reserve. The pharmacokinetic profiles were also congruent with the previous studies and indicate a three-log advantage for FUDR. The (S)-LV profiles in the peritoneal cavity paralleled those of FUDR. Antitumor effects or absence of progression until after cessation of therapy were documented in 11 patients. At a median follow-up of 18 months 44% of patients were alive. IP administration of 3-g of FUDR and up to 640 mg (S)-LV daily for three days was well tolerated. The tolerance and antitumor effects observed during IP FUDR and LV in these studies encourage further exploration of this regimen against ovarian and gastrointestinal malignancies. The actual role and optimal dose of LV as an enhancer of the antitumor actions of FUDR administered by this route remain unknown.

ras may mediate mammary cancer promotion by high fat

High fat consumption has been implicated as a risk factor for breast cancer. Experimental mammary carcinogenesis studies have demonstrated that the effect of high fat consumption is mainly exerted on the postinitiation stage of the disease process. We report data that have recalled in the formulation of a new hypothesis about the effect of dietary fat on mammary carcinogenesis, namely, that it promotes the development of a subpopulation of cells lacking a specific pathogenetic characteristic. In comparison with animals fed a low-fat diet, female Sprague-Dawley rats fed high-fat diets during the promotional stage developed significantly more (number and proportion) 1-methyl-1-nitrosourea-induced mammary adenocarcinomas that did not contain a codon 12 GGA-->GAA mutation in the c-Ha-ras protooncogene. The effect was independent of the types of fat fed, i.e., corn oil vs. fish oil. A model is presented to account for the preferential promotional effect of high fat consumption on 1-methyl-1-nitrosourea-initiated mammary epithelial cells. The hypothesis that the level of dietary fat consumed affects the proportion of mammary carcinomas that occur with a particular pathogenetic characteristic, in this case, the presence or absence of a Ha-ras point mutation, has important implications on the direction of future investigations concerning fat and cancer risk.

Use of recombinant pp38 antigen of Marek's disease virus to identify serotype 1-specific antibodies in chicken sera by western blotting

A fowlpox recombinant expressing the pp38 antigen of Marek's disease virus has been constructed. Production of pp38 in chick embryo fibroblasts (CEF) infected at a m.o.i. of 1 pfu/cell occurred over a period of 5 days and reached a peak at 72 h after infection. The pp38 antigen could be released from infected cells by freezing and thawing. Western blot analysis showed that denatured pp38 antigen reacted with antisera from chickens inoculated with serotype 1 MDV but failed to react with antisera from chickens inoculated with MDV serotype 2 or HVT. The results suggest that MDV pp38 contains a serotype 1-specific epitope which becomes available upon denaturation of the antigen and that this could be exploited to identify MDV-specific antibodies in epidemiological studies. The relationship between pp38 and the related polypeptides pp24 and pp41 in MDV-infected cells was also examined. The results suggest that pp24 and pp38 are synthesised independently and that MDV coded proteins (probably a protein kinase) might be required to convert pp38 to pp41.

Oxygen deprivation inhibits a K+ channel independently of cytosolic factors in rat central neurons

1. K+ channel modulation has been shown to be an integral and important cellular response to O2 deprivation. Although part of this modulation occurs as a result of changes in concentrations of several cytosolic factors such as ATP and Ca2+, it is unknown whether there are mechanisms other than those originating from the cytosol. To test the hypothesis that membrane-delimited mechanisms participate in the O2-sensing process and are involved in the modulation of K+ channel activity in central neurons, we performed experiments using patch-clamp techniques and dissociated cells from the rat neocortex and substantia nigra. 2. Whole-cell outward currents were studied in voltage-clamp mode using Na(+)-free or low-Na+ (5 mM, with 1 microM tetrodotoxin) extracellular medium plus 0.5 mM Co2+. O2 deprivation produced a biphasic response in current amplitude, i.e. an initial transient increase followed by a pronounced decrease in outward currents. The reduction in outward currents was a reversible process since perfusion with a medium of PO2 > 100 mmHg (1 mmHg = 133 Pa) led to a complete recovery. 3. In cell-free excised membrane patches, we found that a specific K+ current (large conductance, inhibited by micromolar concentrations of ATP and activated by Ca2+) was reversibly inhibited by lack of O2. This was characterized by a marked decrease in channel open-state probability and a slight reduction in unitary conductance. The magnitude of channel inhibition by O2 deprivation was closely dependent on O2 tension. The PO2 level for 50% channel inhibition was about 10 mmHg with little or no inhibition at PO2 > or = 20 mmHg. 4. Single-channel kinetic analysis showed that channel open times consisted of two components and closed times were composed of three. The hypoxia-induced inhibition of K+ channel activity was mediated by selective suppression of the longer time constant channel openings without significantly affecting closed time constants. This led to an increase in frequency of opening and closing and rapid channel flickerings. 5. Our data showed that O2 deprivation had no effect on another K+ current characterized by a much smaller conductance and Ca2+ independence. This provides evidence for the selective nature of the hypoxia-induced inhibition of some species of K+ channels. 6. These results therefore provide the first evidence for regulation of K+ channel activity by O2 deprivation in cell-free excised patches from central neurons.

Nitric oxide accounts for dose-dependent estrogen-mediated coronary relaxation after acute estrogen withdrawal

BACKGROUND

Estrogen replacement therapy reduces the risk of coronary heart disease in postmenopausal women, and estrogen treatment modulates endothelium-dependent vasodilation in ovariectomized, atherosclerotic monkeys. Estradiol-17 beta also induces relaxation in isolated rabbit coronary arteries as well as cerebral basilar arteries. The estrogen concentrations required to induce such relaxation are in the pharmacological range (10(-6) to 10(-5) mol/L).

METHODS AND RESULTS

The present study was designed to test whether the sensitivity and specificity of the relaxing response of coronary vascular smooth muscle to exogenous estradiol-17 beta is dependent on the sex hormone status of the animal. In coronary artery rings contracted with PGF2 alpha (3 x 10(-5) mol/L), estradiol-17 beta caused significant relaxation at a physiological estrogen concentration (10(-9) mol/L), in coronary artery rings from oophorectomized, estrogen-treated and acutely estrogen-withdrawn rabbits only. Relaxation induced by estradiol-17 beta at lower concentrations (10(-9) to 10(-6) mol/L) in these rings was 20 +/- 6%, 42 +/- 8%, 54 +/- 9%, and 75 +/- 8%, respectively, compared with 4 +/- 2%, 12 +/- 5%, 16 +/- 7%, and 25 +/- 12% and 5 +/- 2%, 12 +/- 5%, 18 +/- 8%, and 23 +/- 10% in rings from estrogen-maintained and oophorectomized rabbits, respectively (P < .01). The relaxation in coronary artery rings from estrogen-treated and acutely estrogen-withdrawn rabbits was endothelium and nitric oxide dependent since it was abolished by endothelium removal and the nitric oxide synthase inhibitor N omega-nitro-L-arginine.

CONCLUSIONS

This study demonstrates that estrogen-induced, endothelium-dependent relaxation of coronary arteries may, in some species, depend on the sex hormone status of the animal. These findings may help to better understand the effects of ovarian steroids in the coronary circulation of females.

Two long QT syndrome loci map to chromosomes 3 and 7 with evidence for further heterogeneity

Cardiac arrhythmias cause sudden death in 300,000 United States citizens every year. In this study, we describe two new loci for an inherited cardiac arrhythmia, long QT syndrome (LQT). In 1991 we reported linkage of LQT to chromosome 11p15.5. In this study we demonstrate further linkage to D7S483 in nine families with a combined lod score of 19.41 and to D3S1100 in three families with a combined score of 6.72. These findings localize major LQT genes to chromosomes 7q35-36 and 3p21-24, respectively. Linkage to any known locus was excluded in three families indicating that additional heterogeneity exists. Proteins encoded by different LQT genes may interact to modulate cardiac repolarization and arrhythmia risk.

Oxygen deprivation activates an ATP-inhibitable K+ channel in substantia nigra neurons

Depending on its severity and duration, O2 deprivation activates mechanisms that can lead to profound deleterious changes in neuronal structure and function. Hypoxia also evokes inherent adaptive mechanisms that can possibly delay injury and increase neuronal survival. One of these neuronal adaptive mechanisms is believed to be the activation of K+ channels, but direct evidence for their activation is lacking. We performed experiments to test the hypothesis that hypoxia induces activation of K+ channels via changes in cytosolic and membrane factors such as ATP, Ca2+, and membrane potential. The effect of hypoxia on single-channel currents was studied in rat substantia nigra neurons, since these have a high density of glibenclamide binding sites. In cell-attached patches, hypoxia or cyanide reversibly activated an outward current. This hypoxia-activated current in excised inside-out patches was K+ selective and voltage dependent, and had a high sensitivity to internal ATP, ADP, and AMP-PNP, a nonhydrolyzable ATP analog. Activation of this channel required the presence of free Ca2+ on the cytosolic side, but charybdotoxin or apamin did not have any effect on this channel. The effect of ATP on channel activity was not a result of Ca2+ chelation because Mg.ATP in high Mg2+ background and K2.ATP in high Ca2+ environment inhibited the channel. These results suggest that although this hypoxia-activated K+ channel shares properties with ATP-sensitive K+ (KATP) channels in other tissues, substantia nigra neurons seem to have a different subtype or isoform of KATP channels. Gating this channel by multiple factors simultaneously would allow this channel to be particularly suitable for activation during metabolic stress.

Membrane ionic currents and properties of freshly dissociated rat brainstem neurons

It is well known that neuronal firing properties are determined by synaptic inputs and inherent membrane functions such as specific ionic currents. To characterize the ionic currents of brainstem cardio-respiratory neurons, cells from the hypoglossal (XII) nucleus and the dorsal motor nucleus of the vagus (DMX) were freshly dissociated and membrane ionic currents were studied under whole-cell voltage and current clamp. Both of these neurons showed a TTX-sensitive Na+ current with a much larger current density in XII than DMX neurons. This Na+ current had two (fast and slow) distinct inactivation decay components. The ratio of the magnitudes of the fast to slow component was roughly two-fold greater in DMX than in XII cells. Both DMX and XII neurons also showed a high voltage-activated Ca2+ current, but this current density was significantly greater (three-fold) in DMX than XII neurons. A relatively small amount of low-voltage activated Ca2+ current was also observed in DMX neurons, but not in the majority of XII cells. A transient and a sustained outward current components were observed in DMX cells, but only sustained currents were present in XII neurons. These outward currents had a reversal potential of about -70 mV with 3 mM external K+ and -30 mV with 25 mM K+, and substitution of K+ with cesium and tetraethylammonium suppressed more than 90% the outward currents, indicating that most outward currents were carried by K+. The transient outward current consisted of two components with one sensitive to 4-aminopyridine and the other to intracellular Ca2+. In XII neurons, BRL 38227 (lemakalim), an ATP-sensitive K+ (KATP) channel activator, increased the sustained K+ currents by 10% of control, and glibenclamide, a KATP channel blocker, decreased the sustained K+ currents by 20%. Evidence for the presence of an inward rectifier K+ current was also obtained from both XII and DMX neurons. These results on XII and DMX neurons indicate that (1) the methods used to dissociate neurons provide a useful means to overcome voltage clamp technical difficulties; (2) ion channel characteristics such as density and biophysical properties of DMX neurons are very different from those of XII neurons; and (3) several newly discovered membrane ionic currents are present in these cells.

A direct mechanism for sensing low oxygen levels by central neurons

The cascade of cellular events that is triggered by low O2 levels in the central nervous system depends on initial sensing mechanisms that can be crucial in determining the overall cell response, adaptation, or injury. In this report, we demonstrate that the activity of an identified K+ channel is regulated directly by environmental O2. Membrane ionic currents were recorded from neurons of the neocortex and the substantia nigra and studied by using whole-cell or excised membrane patches. O2 deprivation reversibly induced an initial transient increase in whole-cell outward currents, and this was followed by a pronounced decrease in these currents. In cell-free excised membrane patches, lack of O2 reversibly inhibited a class of K+ channels that are inhibited by ATP and activated by Ca2+. K+ channel inhibition depended on pO2 level, with a 50% inhibition at approximately 11 torr (1 torr = 6.9 kPa). By the use of specific agents that chelate metal in metal-containing O2-sensing centers, including heme, nonheme iron, copper, and flavin, we also demonstrated that iron-center but not copper-center blockers inhibited the channel in excised patches in a similar fashion as low pO2. These results strongly suggest that K+ channel activity is modulated during O2 deprivation by nonheme iron-containing proteins that are associated with channel molecules, thus providing evidence for a direct O2-sensing mechanism in neuronal membranes.

[Application of the thoraco-umbilical flap in emergent repair of large defect of limbs]

We have repaired larger detect of limbs after emergent debridement using the thoraco-umbilical flap on 13 cases, 6 of which were vascular island flaps, 7 were free flaps. The size of the flaps was 10 cm x 26 cm to 12 cm x 42 cm. All the flaps survived completely. The advantages of the flap are: (1) the pedicle of the flap is long and has a large diameter, (2) the flap can be made quite long so as to cover the whole ulna or tibia, (3) the flap can be used to repair bony defect by carrying a rib as an osteocutaneous flap.

Effect of lemakalim on action potentials, intracellular calcium, and contraction in guinea pig and human cardiac myocytes

OBJECTIVE

The aim was to investigate the effects of lemakalim on action potential duration, intracellular free calcium ([free Ca2+]i), and cell contraction in human and guinea pig cardiac myocytes. In addition, the possible modulation by pH of lemakalim induced activation of ATP sensitive potassium (KATP) channels was assessed.

METHODS

Single ventricular myocytes were enzymatically dissociated from adult male guinea pigs (300-600 g). Single myocytes were isolated from human ventricular tissues. Cells were loaded with the acetoxymethyl ester form of fura-2 to monitor changes in [free Ca2+]i and subjected to conventional electrophysiological techniques.

RESULTS

In guinea pig cells, lemakalim (3, 10, 30 microM) reduced action potential duration in a concentration dependent manner. This decrease was accompanied by hyperpolarisation of the resting membrane potential. Lemakalim (3, 10, 30 microM) reduced the systolic fura-2 fluorescence ratio without having a significant effect on diastolic fluorescence and also reduced the cell contraction in concentration dependent manner. Glibenclamide (1 microM), a specific inhibitor of KATP channels, did not affect action potential duration, fura-2 fluorescence ratio, or cell contraction in the absence of lemakalim. However, the same dose of glibenclamide markedly inhibited the lemakalim induced decrease in action potential duration, fura-2 fluorescence ratio, and cell contraction. Reducing extracellular pH enhanced the decrease in action potential duration induced by lemakalim. In human ventricular myocytes, lemakalim (3, 10 and 30 microM) caused a decrease in action potential duration and systolic fura-2 fluorescence ratio. The reduction in action potential duration and fura-2 fluorescence ratio was also reversed by glibenclamide (1 microM).

CONCLUSIONS

These results suggest that lemakalim reduces systolic [free Ca2+]i by activating ATP sensitive potassium channels which results in a decrease of action potential duration in guinea pig and human ventricular myocytes. The reduction in [free Ca2+]i mediates the negative inotropic effect induced by lemakalim. In addition, pH may modulate the KATP channel activation by the channel opener.

Studies on atrophic change of soleus muscle and its countermeasures in suspended rat

In the environment of microgravity, the disused atrophy of skeletal muscle, especially leg's muscle, would occur. The three purposes of this study were: 1. To observe the dynamic changes of disused atrophy of skeletal muscle under simulated weightlessness; 2. To approach the mechanism of disused atrophy of muscle; 3. To approach the countermeasures for reducing the degree of atrophy of muscle.

Selenite induction of DNA strand breaks and apoptosis in mouse leukemic L1210 cells

The effects of selenite on DNA integrity, cell viability, and long-term proliferative potential of mouse leukemic L1210 cells were examined in this study. Selenite treatment resulted in concentration-dependent increases in DNA single-strand breaks and double-strand breaks, as detected by a modified filter elution assay. A time-course experiment showed that DNA single-strand breaks preceded DNA double-strand breaks. Agarose gel electrophoresis of DNA extracted from selenite-treated cells displayed a nucleosomal fragmentation pattern that is characteristic of apoptotic cell death. The involvement of a Ca2+,Mg(2+)-dependent endonuclease responsible for DNA double-strand fragmentation was implied by the observation that two inhibitors of endonuclease activity, i.e. aurintricarboxylic acid and zinc, blocked selenite-induced DNA double-strand breaks. These inhibitors also prevented selenite-induced cell death as defined by loss of ability to exclude trypan blue dye. Selenite treatment severely impaired the colony-forming ability of cells capable of trypan blue exclusion. The induction of DNA strand breaks and commitment to apoptosis may explain the selenite-mediated growth inhibition and loss of long-term proliferative potential.

Color image generation of a three-dimensional object with rainbow holography and a one-wavelength laser

Based on conventional one-step true-color rainbow holography, a new true-color rainbow holography of a three-dimensional diffused object is presented. By means of conjugate reconstruction with a onewavelength laser of a master hologram recorded with three laser wavelengths, the hologram can be transferred to a single type of recording material with a single exposure to achieve true-color holographic display. Therefore a photoresist master can be produced for embossing copy.

Inhibition of hypoxia-induced relaxation of rabbit isolated coronary arteries by NG-monomethyl-L-arginine but not glibenclamide

1. The effects of NG-monomethyl-L-arginine, tetrodotoxin and glibenclamide on hypoxia-induced coronary artery relaxation, induced by bubbling Krebs solution with 95% N2 and 5% CO2 instead of 95% O2 and 5% CO2, were assessed by measuring the changes in isometric tension in isolated epicardial coronary artery rings of the rabbit. In addition, the effects of glibenclamide on the relaxation induced by adenosine were investigated. 2. Hypoxia caused a transient relaxation of 38 +/- 3% (P < 0.01) and 17 +/- 2% (P < 0.01) in endothelium-intact or -denuded arteries respectively. NG-monomethyl-L-arginine (30 and 100 microM) inhibited the relaxation in endothelium-intact rings to 31 +/- 2% (P < 0.05) and 16 +/- 2% (P < 0.01) respectively and slightly but significantly attenuated the relaxation in endothelium-denuded rings to 15 +/- 1% and 13 +/- 1% (P < 0.05) respectively. 3. Glibenclamide, a potassium channel inhibitor, did not significantly after the hypoxia-induced relaxation. 4. Incubation with tetrodotoxin (3 and 10 microM) for 30 min reduced the relaxation to 31 +/- 3% (P < 0.05) and 14 +/- 2% (P < 0.01), and 14 +/- 2% (P < 0.05) and 11 +/- 1% (P < 0.05) in endothelium-intact and -denuded rings respectively. However, indomethacin (10 microM), atropine (1 microM), propranolol (10 microM) and phentolamine (10 microM) did not significantly affect the relaxation. 5. Adenosine (1, 10 and 100 MicroM) caused relaxation of 6 +/- 1%, 52 +/-3% and 97 +/-2% respectively in endothelium-denuded rings precontracted with prostaglandin F2alpha (PGF2 alpha, 3 MicroM) and the relaxation was markedly inhibited by 8-phenyltheophylline. Furthermore, glibenclamide (1 and 10 MicroM) reduced the relaxation induced by adenosine (1, 10 and 100 MicroM) to 2 +/-1% (P<0.05), 38 =/-3% (P<0.05) and 85 +/-2%(P<0.05), and 0.6 +/- 0.4% (P<0.05), 27 +/- 4% (P<0.05) and 72 +/- 4% (P<0.01) respectively, in these endothelium-denuded preparations.6. These data suggest that hypoxia-induced relaxation is mediated by the release of nitric oxide rather than by the activation of glibenclamide-sensitive potassium channels in rabbit isolated coronary arteries. A neurogenic mechanism partially modulates the relaxation, possibly by activating non-adrenergic and noncholinergic nerve endings. The inhibition by glibenclamide on adenosine-induced relaxation in isolated coronary arteries may help to explain the fact that glibenclamide inhibits hypoxic coronary relaxation in perfused hearts but not in isolated coronary preparations.

[Morphological observations of effects on mouse brain exposed to subteratogenic--dose of methylmercury]

Short-term and long-term changes in mouse brain caused by in utero exposure to subteratogenic-dose of methylmercury were studied with electronic computer digitalized graphic system, electron microscopy and other methods. Results revealed degeneration and loss of mouse brain cells occurred both in short-term and long-term groups, but the lesions were more severe in the latter than in the former groups. The fact that exposed young mice exhibited no obvious abnormality in their outward appearance and behavior indicated subteratogenic-dose of methylmercury had a long-term and latent toxic effects on mouse brain.

Start site selection by Sp1 in the TATA-less human Ha-ras promoter

The promoter of the human Ha-ras gene is very GC-rich, has four Sp1-binding sites and no TATA element. Transcription initiates at multiple start sites spread over a 90-base pair region, with a major cluster between +1 and +11. We detected the binding of a HeLa nuclear protein to the region from +6 to +20, a region which overlaps the major cluster and includes nine start sites within its boundaries. When part of this region was mutated, the nine start sites were abolished, so the region may be an initiator. The regulatory elements of the promoter have no differential effect on start site usage. But Sp1 bound to GCIV located at -38 acts as a start site selector, increasing the activity of the start sites from +1 downstream but not the upstream sites at -31, -21, and -10. When spacers of increasing length were inserted 3' to GCIV, the major cluster dwindled, and the upstream sites became strong sites, first the one at -10 and then the one at -21. Thus start sites were strongest when put into an Sp1-selected locus 36 to 53 base pairs downstream from GCIV and weak when outside this locus. The start sites with these properties may be due to initiators.

Comparison of the effects of an organic and an inorganic form of selenium on a mammary carcinoma cell line

The development of new compounds with greater cancer inhibitory activity and that are well tolerated continues to be a priority in chemoprevention research involving selenium. One compound, 1,-4-phenylene-bis(methylene)selenocyanate (p-XSC), is representative of a series of organoselenium compounds with these characteristics. In this study, the effects of p-XSC on a mouse mammary carcinoma cell line were compared to those of sodium selenite, which has been shown to be growth inhibitory. Treatment with p-XSC caused a 3- to 6-fold greater accumulation of selenium within cells than did treatment with equivalent amounts of selenite and cells were able to better tolerate higher cellular levels of selenium derived from p-XSC. Both compounds resulted in a dose-dependent reduction in cell number after 24 h of exposure. Selenite and p-XSC also caused a dose-dependent increase in cell death by apoptosis. This effect was observed within 5 h of treatment. The effect of p-XSC on apoptosis was more pronounced than that of selenite, especially at the 20 microM level of exposure. The induction of apoptosis by selenium compounds may partially account for their chemopreventive activity.

[Study on clinical application of expanded skin tubes]

Skin transplantation is an operative method generally used in reparative and reconstructive surgery. How to minimize the cicatrices of the donor site, how to repair larger recipient site, and how to reconstruct organs with restoration of their functions and shapes are important problems in plastic surgery. Since September 1990, we have designed a technique of expanding skin tubes for the repair of wounds and for the reconstruction of organs when larger area of skin is required while the skin of the donor site is deficient, or when the cicatrices of the donor site are to be minimized. This technique had been applied clinically in 10 cases. Clinical practice has proved that this new operative method is superior to skin grafts, transplantation of skin flaps, and the conventional technique of expanding skin and soft tissue. This paper describes the five characteristics and the theoretical basis of the technique of expansion of skin tubes.

The use of mixture models to detect effects of major genes on quantitative characters in a plant breeding experiment

An analysis based on Elston's model of mixed major locus and polygenic inheritance is extended to include populations of progeny testing such as F3, B1s and B2s families derived from F2 and backcrosses in a cross between two inbred lines. Genetic hypotheses that can be validly tested by the likelihood ratio method in the analysis of a breeding experiment include homogeneity of variances due to environment and/or polygenes with transformable scale effect by Box-Cox power function, random and independent segregation of major genes, invariance of the effects of major genes with population types and additive and dominant models for polygenes. Testing hypotheses in the order suggested here can lead to a gradual simplification of the models and increases the feasibility of the subsequent analysis, but caution must be paid to the possible bias in parameter estimation and hypotheses tests. The procedure is applied to a set of data on plant height of rice with the effects of dwarf genes in crosses among three varieties. Two recessive dwarf genes are shown to be nonallelic and unlinked. One dwarf gene is shown to reduce plant height about 36-56 cm, and another 52-61 cm. The effect of polygenes, estimated as the standard deviation among possible inbred lines derived from these crosses, is about 11.7 cm. Interactions between the dwarf genes and the polygenic background are found, especially for one of the two genes. Both the polygenic effects and the interactions are much smaller than the effects of the major dwarf genes.

Mechanisms of neuronal survival during hypoxia: ATP-sensitive K+ channels

There has been an explosion in our understanding of how nerve cells in mammals respond to O2 deprivation and what are the mechanisms involved in nerve cell injury or survival. This is due to the development of new approaches, techniques and the clinical importance of brain ischemia and hypoxia. Recently, we have focussed on some issues pertaining to brain hypoxia in the newborn and adult. We have demonstrated that during anoxia intracellular K+ decreases significantly in nerve cells and that this K+ efflux is mediated by K+ channels that are sensitive to ATP. We have preliminary evidence that the activation of these channels attenuates the anoxia-induced depolarization in medullary neurons and can play a role in cell survival during anoxia. Further, we have characterized the distribution of these receptors/channels complexes in the CNS of the rat and in an anoxia-resistant animal: the turtle. These channels are present mainly in the cortex, substantia nigra and the cerebellum. Whole cell recordings (dissociated cells) established that these channels are postsynaptic in nature in medullary neurons. Single-channel recordings from our laboratory and those of others have started to reveal the intricacies of the regulation of these channels in excitable cells in general and in nerve cells in particular.

Mechanisms of anoxia-induced depolarization in brainstem neurons: in vitro current and voltage clamp studies in the adult rat

To determine the mechanisms underlying the depolarization induced by anoxia in brainstem neurons, we studied single neurons in brainstem slices using conventional micro-electrodes and freshly dissociated hypoglossal and vagal cells using patch clamp techniques (whole-cell configuration). Since glutamate concentration increases in the extracellular space during O2 deprivation, we first tested whether N-methyl-D-aspartate (NMDA) and non-NMDA receptors are involved in this anoxia-induced depolarization. APV, MK-801, CNQX and KYN (NMDA and non-NMDA blockers), which bathed slices after control anoxia runs, did not affect the depolarization trajectory. Decreasing extracellular Na+ (Nao+) from 150 mM to 5 mM attenuated markedly and significantly the depolarization observed during anoxia (15-20% of control). The relation between intracellular adenosine triphosphate (ATP) and the anoxia-induced depolarization was also investigated in the slice and in dissociated single brainstem neurons. In the slice, iontophoresis of ATP did not give consistent results. Since we could not ascertain that ATP was actually iontophoresed through high resistance (50-80 M omega) microelectrodes, we patched single neurons and studied the effect of clamping intracellular ATP levels on the hyperpolarizing holding current (IH) in the voltage clamp mode. The increase in IH with anoxia (or cyanide) was markedly attenuated in cells patched with pipettes containing ATP. We conclude that in brainstem neurons, the anoxia-induced depolarization: (a) is not a function of an increase in extracellular glutamate concentration; and (b) depends on Na+ and ATP-mediated processes.

Inhibition kinetics of chloramphenicol acetyltransferase by selected detergents

Kinetic analyses indicate that the inhibitory effects of the nonionic detergents Triton X-100 and Nonidet P-40 on chloramphenicol acetyltransferase are exerted by a competitive and a non-competitive mechanism with respect to the substrates chloramphenicol and acetyl-CoA, respectively. Comparison with nonionic detergents without an aromatic moiety like that present in Triton X-100 and Nonidet P-40 suggests that the aromatic groups in these two detergents may compete with chloramphenicol for binding to the hydrophobic, active site in the chloramphenicol acetyltransferase.

Altered fluid transport across airway epithelium in cystic fibrosis

In cystic fibrosis (CF), absence or dysfunction of a phosphorylation-regulated chloride channel [CF transmembrane conductance regulator (CFTR)] leads to the loss or reduction of chloride secretion into the airways. Active sodium absorption is also increased in CF, and both of these ion transport changes could alter fluid transport across the airways. Under baseline conditions, cultured human airway epithelia from normal individuals absorbed fluid, and this absorption was increased in epithelia from patients with CF. In normal and CF epithelial cultures fluid absorption was inhibited by amiloride. Adenosine 3',5'-monophosphate stimulated fluid secretion in normal epithelial cultures but not in cultures from individuals with CF. In contrast, fluid secretion induced by nucleotide triphosphates (uridine triphosphate or adenosine triphosphate) was unaltered in cultures of epithelia from patients with CF, suggesting an approach to the treatment of CF.

Acute anoxia-induced alterations in MAP2 immunoreactivity and neuronal morphology in rat hippocampus

Cerebral ischemia induces major neuronal morphological alterations. It is not clear, however, whether this is directly caused by O2 deprivation. To determine the effect of hypoxia on cytoskeletal structures and neuronal morphology, we performed experiments and examined anoxia-induced changes in microtubule-associated protein 2 (MAP2) and cell morphology in hippocampal slices in vitro. Anoxia (measured PO2 = 0 Torr) induced a marked loss in dendritic MAP2 immunoreactivity and cell swelling of hippocampal neurons by 2 h after O2 reinstitution. These changes were severe in CA1 and CA3 neurons and comparatively mild in dentate gyrus neurons. Quantitative analysis showed that 10 min of anoxia induced a 30% loss of MAP2-positive dendrites but this increased to 70% after 30 min of anoxia. A concurrent major increase in somata area of about 100% and 200% was observed in CA1 and CA3 neurons respectively. Somata area in the lower dentate gyrus, however, increased either insignificantly or by only 30% for the respective periods of anoxia. These results suggest that deprivation of O2 can by itself induce a major loss in dendritic MAP2 immunoreactivity and changes in cell morphology in hippocampal neurons. These alterations occur rapidly after hypoxia, and the severity of these changes is directly related to the duration of anoxia and brain region in the hippocampus.

Spontaneous nucleosomal DNA fragmentation in murine leukemic L1210 cells

Spontaneous nucleosomal DNA fragmentation (SNDF), characteristic of apoptotic cell death was observed in a murine leukemic cell line grown to high density. This effect was eliminated by permitting free diffusional exchange with a large amount of complete medium. Cells seeded at low density did not show SNDF in a conditioned medium that had been used to culture cells with severe SNDF. Cells seeded at high density in the same conditioned medium showed pronounced SNDF, but addition of 10% fetal bovine serum to such a medium significantly reduced SNDF. These observations indicate that neither physical contact among cells in high density culture per se nor secretion of a death factor by the high density culture could account for the induction of SNDF. The results support a model in which the gradual depletion of a serum factor(s) leads to the activation of a cell death program that is manifested as SNDF.

Determination of the specificities of rat liver Gal(beta 1-4)GlcNAc alpha 2,6-sialyltransferase and Gal(beta 1-3/4)GlcNAc alpha 2,3-sialyltransferase using synthetic modified acceptors

Apparent kinetic parameters have been measured for the transfer of N-acetyl-D-neuraminic acid (Neu5Ac) from CMP-Neu5Ac to analogues of the Gal(beta 1-4)GlcNAc (type II) and Gal(beta 1-3)GlcNAc (type I) substrates by the rat liver Gal(beta 1-4)GlcNAc alpha 2,6-sialyltransferase and the Gal(beta 1-3/4)GlcNAc alpha 2,3-sialyltransferase. In these acceptor analogues, the substituents of the pyranose rings were modified, particularly by deoxygenation, to identify (i) the key polar groups required for efficient transfer and (ii) the substituents that can be removed or modified. A topography including the 6-hydroxyl of the beta Gal and the 2-acetamido of the GlcNAc unit is required for transfer to a terminal type II disaccharide by the alpha 2,6-sialyltransferase. The other hydroxyls can be replaced by hydrogen without a substantial decrease in activity. The alpha 2,3-sialyltransferase requires the 3-, 4-, and 6-hydroxyls of the terminal beta Gal and some contribution from the subterminal sugar. This may explain the cross-reactivity of this enzyme for the type I and type II acceptors. For both enzymes, an influence of the hydrophobic nature of the aglycone is noticed. The results allow an evaluation of the efficiency of the transfer of Neu5Ac to modified substrates.

Short periods of hypoxia activate a K+ current in central neurons

The effect of hypoxia on ionic currents was studied in acutely dissociated substantia nigra neurons. Using an external solution containing 0 mM Na+ and 0.5 mM Co2+, we found that overall whole-cell outward currents increased by 15-20% during 3-4 min of hypoxia. This current was voltage sensitive and could be completely blocked by TEA- and Cs+, suggesting that this is a K+ current. In cell-attached patches with 150 mM K+ in the external solution, we recorded a large-conductance outward current which was not observed during baseline and was reversibly activated by hypoxia. These results therefore provide the first direct evidence for the activation of K+ channels during O2 deprivation in central neurons.

Modelling of safety measure effects and risk compensation

A model is proposed for the description of effects of safety measures introduced into a road transport system. The model explains the motives of road users' risk compensation towards the measures, and indicates when behavioural adaptation is likely to take place and its effects on road safety programmes. At its core the model has the notion that when a transport system is changed by engineering safety measures, road users do not respond only in the direction towards safety improvement but respond, in general, with three possible ways of behavioural adaptations, one of them towards more risk taking. Supported by illustrative examples, it also suggests that due to risk compensation, engineering safety measures alone are usually not sufficient, and, hopefully, carefully designed motivational safety measures can give us chances to modify road users' behaviour to make traffic safer.

Cardiovascular protection by oestrogen--a calcium antagonist effect?

During their premenopausal years, women have a lower risk than men of getting cardiovascular disease. This protection continues after the menopause if women receive oestrogen replacement. Based on new experimental evidence we propose that some of the cardiovascular benefits of oestrogen replacement therapy may be due to a long-term calcium antagonist effect of oestrogen.

Modulation of liver-specific transcription by interactions between hepatocyte nuclear factor 3 and nuclear factor 1 binding DNA in close apposition

The liver-specific enhancer of the serum albumin gene contains an essential segment, designated eH, which binds the hepatocyte nuclear factor 3 alpha (HNF3 alpha) and ubiquitous nuclear factor 1/CCAAT transcription factor (NF1/CTF) proteins in tight apposition. We previously showed that activation of transcription by the eH site was correlated with an increase in intracellular HNF3 alpha levels during the in vitro differentiation of the hepatic cell line H2.35. We now show that transfection of an HNF3 alpha cDNA expression vector into dedifferentiated H2.35 cells is sufficient to induce transcription from the eH site. Mutational analysis of the enhancer demonstrates that NF1/CTF cooperates with HNF3 alpha to induce enhancer activity. However, when the eH site is removed from the context of the enhancer, NF1/CTF can inhibit transcriptional activation by HNF3 alpha. We conclude that the ternary complex of HNF3 alpha, NF1/CTF, and the eH site forms a novel, composite regulatory element that is sensitive to the local DNA sequence environment and suggest that the transcriptional stimulatory activity of NF1/CTF depends on its higher-order interactions with other proteins during hepatocyte differentiation.

[The effects of polylysine on the aggregation of surface and on the cleavage furrow of Rana amurensis eggs]

Polylysine synchronously aggregated pigment granules and egg surface stained uniformly with fluorescein isothiocyanate to form patches (Plate I, fig 1 & 2). Patches always appeared and aggregated first in the opposite grey crescent region, then in grey crescent region and next at animal hemisphere. A fluorescent ring formed at the upper side of the equatorial region. The ring and the patches at the animal hemisphere accumulated to the animal pole to make a cap (Plate I, Fig. 3). Finally the vegetal hemisphere broke due to the contraction of egg surface during aggregation. These indicated that four different domains: opposite grey crescent region, grey crescent region, animal and vegetal hemispheres, were present at the fertilized egg surface. Similar domains also occurred at the unfertilized egg surface as revealed by the same treatment suggesting that the opposite grey crescent region of fertilized egg, which corresponding to the sperm entrance region had existed at the mature egg surface. There were three modes in the early stage of patch formation: (1) the features of granular protrusions did not change greatly (Plate I, Fig. 5-7), (2) the granular protrusions elongated (Plate I, Fig 8-11) and (3) folds radiated from patch (Plate I, Fig. 12, 13). Around each patch new surface membrane arose, which was similar to the nascent membrane of cleavage furrow.(ABSTRACT TRUNCATED AT 250 WORDS)

Human neocortical excitability is decreased during anoxia via sodium channel modulation

When the central nervous system in humans is deprived of oxygen, the effects are potentially disastrous. Electroencephalographic activity is lost and higher brain function ceases rapidly. Despite the importance of these effects, the mechanisms underlying the loss of cortical activity are poorly understood. Using intracellular recordings of human neocortical neurons in tissue slices, we show that, whereas anoxia produces a relatively small depolarization and modest alterations in passive properties, it causes a major decrease in excitability. Whole-cell voltage-clamp studies of acutely isolated human neocortical pyramidal neurons demonstrate that anoxia and metabolic inhibition produce a large negative shift in the steady-state inactivation [h infinity (V)] curve for the voltage-dependent sodium current (INa). Inclusion of ATP in the patch pipette decreased the shift of the h infinity (V) curve by two-thirds. Because increased inactivation of INa decreases cellular metabolic demand, we postulate that this promotes neuronal survival during periods of oxygen deprivation. These data show a novel mechanism by which anoxia links metabolism to membrane ionic conductances in human cortical neurons.

Structure-function studies of the C-terminal alpha-helix of human interleukin-2 by site-directed mutagenesis

By using oligonucleotide-mediated site-directed mutagenesis, we obtained three human interleukin-2 analogs with substitution of Pro in the C-terminal amphiphilic alpha-helix, 125Pro-IL-2, 127Pro-IL-2 and 125Pro-127Pro-IL-2. The bioactivities of all these analogs were decreased. The extent of the decrease in bioactivity coincided with the degrees of secondary and tertiary structure destroyed, as evaluated by circular dichroism and intrinsic fluorescence analysis. The results suggested that the integrity of the hydrophobic face in the C terminal alpha-helix is crucial for the structure and function of interleukin-2.

Differential regulation of the nerve growth factor and brain-derived neurotrophic factor genes in L929 mouse fibroblasts

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are structurally related survival and differentiation factors for distinct sets of peripheral and central neurons. The regulation of NGF gene expression has been extensively studied in L929 mouse fibroblasts. L929 cells also express the BDNF gene. Northern blot hybridization analysis revealed 4 discrete BDNF mRNA species in L929 cells and rat hippocampus after induction of seizures with kainic acid. Serum as well as 12-O-tetradecanoyl phorbol-13-acetate (TPA) stimulated NGF and all 4 BDNF mRNAs in L929 cells. Treatment with both agents induced NGF mRNA to a much larger extent than the BDNF mRNAs. The induction of the BDNF mRNAs was rapid, with nearly maximal levels by 1 hr. In contrast, NGF mRNA induction occurred later and peaked at 4-6 hr. Both NGF and BDNF mRNA induction were inhibited by actinomycin D. Cycloheximide, on the other hand, inhibited only NGF but not BDNF mRNA induction. Corticosterone rapidly decreased NGF mRNA but not the BDNF mRNAs, and had no effect on seizure-induced NGF or BDNF mRNAs. Forskolin did not stimulate NGF or BDNF mRNAs. In contrast to NGF mRNA, forskolin did not interfere with the serum induction of BDNF mRNAs. These results demonstrate that 2 genes which encode closely related neurotrophic factors are differentially regulated in L929 cells. The molecular mechanisms which bring about this differential regulation remain to be elucidated.