[Increase in amount and affinity of adenosine receptor in rat hippocampal cellular membranes induced by cerebral ischemic preconditioning and its protective effects on the neurons]

To determine the role of adenosine (ADO) receptor in the induction of brain ischemic tolerance, changes in amount and affinity of ADO receptor in rat hippocampal cellular membranes after transient ischemia were investigated using radioligand binding method. Ischemia for 6 min resulted in an apparent delayed neuron death (DND) in the hippocampus, while ischemia for 3 min did not cause DND. Preconditioning ischemia for 3 min could apparently decrease DND caused by ischemia for 6 min after the preconditioning at an interval of 1 d reperfusion. In correspondence with the histological changes, ischemia for 3 min caused an increase in amount and affinity of ADO receptor at 1 or 3 days after reperfusion (P<0.05 vs sham), while ischemia for 6 min caused a decrease in the amount and an increase in the affinity (P<0.05 vs sham). Compared with the rats suffering from ischemia for 6 min followed by reperfusion for 4 h and 1 or 3 d, the amount and affinity of ADO receptor increased in rats with preconditioning ischemia (3 min) 1 d before the ischemia for 6 min. The above results showed that cerebral ischemic preconditioning increased the amount and affinity of ADO receptor in hippocampal cellular membranes, and resisted the down-regulating of ADO receptor caused by severe ischemia, suggesting an important role of the increase in amount and affinity of ADO receptor in the induction of brain ischemic tolerance.

Adipocyte insensitivity to insulin in growth hormone-transgenic mice

Growth hormone (GH) has an inhibitory effect on adipogenesis, and its effect is associated with insulin action in obesity. In this study, the relationship between GH effect on insulin sensitivity and adipocyte differentiation in vivo was investigated. Transgenic (TG) female mice expressing porcine GH had reduced body weights and weights of retroperitoneal and parametrial fat depots. Insulin treatment increased PPARgamma and GLUT4 expression in adipose tissue of WT mice but had no effect in TG mice. Content of transcription factors, PPARgamma and C/EBPalpha and beta, was higher in adipose tissue of WT mice, and for C/EBPalpha and PPARgamma, the difference occurred primarily in 24-, compared to 12-week-old, mice. Expression of preadipocyte factor-1 was higher in adipose tissue of TG mice, and expression of TNF-alpha and leptin was reduced in adipose tissue of 24-week-old TG mice. Our results suggest that increased expression of GH reduces adipogenesis by inducing adipocyte resistance to the adipogenic effect of insulin.

Overexpression of rat neuronal calcium sensor-1 in rodent NG108-15 cells enhances synapse formation and transmission

The role of rat neuronal calcium sensor-1 (NCS-1), a Ca2+-binding protein, in synapse formation and transmitter release was examined in mouse neuroblastoma x rat glioma hybrid NG108-15 cells in culture. Wild-type NG108-15 cells expressed rodent NCS-1. Endogenous NCS-1 was partially co-localized with the synaptic protein SNAP-25 at the plasma membrane in both cell bodies and processes, but not with the Golgi marker [beta]-COP, an individual coat subunit of the coatomer complex present on Golgi-derived vesicles. In NG108-15 cells co-cultured with rat myotubes, partial co-localization of SNAP-25 and NCS-1 was observed at the plasma membrane of neurites and growth cones, some of which had synaptic contacts to muscle cells. Transient co-transfection of the rat NCS-1 cDNA and green fluorescent protein (GFP) resulted in NCS-1 overexpression in about 30 % of the cells as determined by fluorescence microscopy. The rate of functional synapse formation with co-cultured rat myotubes increased 2-fold as determined by the presence of miniature endplate potentials (MEPPs) in NCS-1-overexpressing NG108-15 cells compared to non- and mock-transfected cells. The number of neurites per cell, branches per neurite and length of neurites was slightly less in cells that were either transiently transfected (GFP-NCS-1-fluorescence positive) or stably transformed with NCS-1 compared to GFP-NCS-1-negative, non-transfected or mock-transfected NG108-15 cells. The number of action potentials that elicited endplate potentials increased in NG108-15 cells stably transformed with rat NCS-1. The mean number of quanta per impulse (m) increased 5-fold. These results show that NCS-1 functions to facilitate synapse formation, probably because of the increased quantal content of evoked acetylcholine release.

Cyclic ADP-ribose as a second messenger revisited from a new aspect of signal transduction from receptors to ADP-ribosyl cyclase

Cyclic ADP-ribose (cADPR), an endogenous modulator of ryanodine receptor Ca(2+)-releasing channels, is found in various tissues. Cytosolic injection of cADPR induces an elevation of intracellular Ca(2+) concentrations or potentiates Ca(2+) increases. cADPR facilitates neurotransmitter or insulin release and modifies ionic currents. cADPR is synthesized by ADP-ribosyl cyclase and is metabolized by cADPR hydrolase. ADP-ribosyl cyclase activity is up-regulated by nitric oxide/cyclic GMP-dependent phosphorylation or receptor stimulation via G-proteins within membranes. These findings suggest that cADPR is a second messenger in cellular Ca(2+) signaling. However, many intriguing issues remain to be addressed before this identity is confirmed.

Determination of nucleic acids based on shifting the association equilibrium between tetrasulfonated aluminium phthalocyanine and acridine orange

Based on the ability of nucleic acids to shift the association equilibrium of the ion-association complex of Acridine Orange and tetrasulfonated aluminium phthalocyanine, thus leading to an increase in the phthalocyanine fluorescence, a method is suggested for the fluorimetric determination of nucleic acids. Investigations were carried out on the spectral characteristics, order of addition of reagents, selection of the buffer system, effect of pH, influence of reaction time, effect of salt, the usage of reagents, interference of foreign substances and the effect of different acridine derivatives. Under the optimum conditions, the calibration graphs for the determination of calf thymus DNA (CT DNA), salmon DNA (SM DNA) and yeast RNA were linear over the ranges 0.04-1.2, 0.04-1.2 and 0.1-1.2 micrograms cm-1, respectively. The detection limits for CT DNA, SM DNA and RNA were 17, 24 and 98 micrograms cm-3, respectively. The relative standard deviation (n = 6) was within 4.6% for the detection of samples. The method was applied to the determination of Staphylococcus aureus DNA and the result was in agreement with that achieved by a UV method.

A new red-region substrate, tetra-substituted amino aluminium phthalocyanine, for the fluorimetric determination of H2O2 catalyzed by mimetic peroxidases

A new red-region fluorogenic substrate, tetra-substituted amino aluminium pthalocyanine, was developed for the selective determination of H2O2 based on the catalytic effect of mimetic peroxidases, viz., hemin or iron tetrasulfonatophthalocyanine (FeTSPc). Under the optimum conditions, the linearity of the calibration graph for the determination of H2O2 with hemin (or FeTSPc) as the catalyst was in the range from 0.0 to 3.0 x 10(-7) mol L-1 (or from 0.0 to 2.0 x 10(-6) mol L-1). The detection limits were 3.7 x 10(-9) and 4.9 x 10(-9) mol L-1 H2O2, respectively. The relative standard deviation (n = 7) was within 1.5% in the middle of the linear range. The peroxidase activity of the mimetic enzymes hemin and FeTSPc, the effects of some experimental conditions and the influence of foreign substances were investigated. With this substrate, 0.0-7.5 x 10(-8) mol L-1 hemin and 0.0-2.0 x 10(-6) mol L-1 FeTSPc can be determined with an accuracy and precision of about 1.3%. The potential application of the reagent was tested by the determination of H2O2 in rainwater.

Involvement of pressure-related mechanism in activation of inducible nitric oxide synthase

The goal of this study was to clarify the relationship between blood pressure and inducible nitric oxide synthase (iNOS) activity. Different levels of blood pressure were obtained by long-term (six days) intravenous infusion of different concentrations (0.3%-8%) of NaCl solution to normal SD rats. iNOS activity assay and measurement of urinary nitrate/nitrite (UNOx), an index of NO production of the whole body, were carried out by isotope-labeled L-arginine conversion rate measurement and Greiss Reaction respectively. Groups of normotensive and hypertensive rats including normal Wistar rats, normal Sprague-Dawley (SD) rats, high NaCl-induced hypertensive rats (NaHR) and spontaneously hypertensive rats (SHR) were used to detect the changes in iNOS protein under normotension and hypertension by Western blotting. iNOS activity of aorta and kidney tissues and UNOx increased more significantly in hypertensive animals than in the normotensive control ones. Accordingly, iNOS protein in the aortas of NaHR and SHR increased by 149% and 261% respectively. It is suggested that in addition to cytokine and bacterial products etc, blood pressure is also an effective regulatory factor involved in iNOS activation and expression.

[MK-801 attenuates NOS expression and NO content in the spinal cord of rats with inflammatory pain]

Using NADPH-d histochemistry, the effect of NMDA receptor antagonist MK-801 on the expression of nitric oxide synthase (NOS) in the dorsal horn of the spinal cord was investigated during inflammatory pain and hyperalgesia induced by injection of formalin into the right hind paw. The course of the change in the nitric oxide (NO) content of the lumbar intumescence was observed by measuring the ratio of nitrate/nitrite (NO3T/NO2T) and also the end product of NO. The results showed that the NOS expression and NO contents significantly increased 24 h after formalin injection, which were substantially inhibited when MK-801 was intrathecally injected 15 min prior to formalin injection or 12 h after formalin injection. The results suggest that the increases in the expression of NOS and NO contents in the dorsal horn of the spinal cord are mediated by activation of NMDA receptors during pain and hyperalgesia after formalin injection.

Signal transduction from bradykinin, angiotensin, adrenergic and muscarinic receptors to effector enzymes, including ADP-ribosyl cyclase

Muscarinic acetylcholine receptors in NG108-15 neuroblastoma x glioma cells, and beta-adrenergic or angiotensin II receptors in cortical astrocytes and/or ventricular myocytes, utilize the direct signaling pathway to ADP-ribosyl cyclase within cell membranes to produce cyclic ADP-ribose (cADPR) from beta-NAD+. This signal cascade is analogous to the previously established transduction pathways from bradykinin receptors to phospholipase Cbeta and beta-adrenoceptors to adenylyl cyclase via G proteins. Upon receptor stimulation, the newly-formed cADPR may coordinately function to upregulate the release of Ca2+ from the type II ryanodine receptors as well as to facilitate Ca2+ influx through voltage-dependent Ca2+ channels. cADPR interacts with FK506, an immunosuppressant, at FKBP12.6, FK506-binding-protein, and calcineurin, or ryanodine receptors. cADPR also functions through activating calcineurin released from A-kinase anchoring protein (AKAP79). Thus, some G(q/11)-coupled receptors can control cADPR-dependent modulation in Ca2+ signaling.

Interactions of a series of fluoroquinolone antibacterial drugs with the human cardiac K+ channel HERG

Administration of certain fluoroquinolone antibacterials has been associated with prolongation of the QT interval on the electrocardiogram and, on rare occasions, ventricular arrhythmia. Blockade of the human cardiac K+ channel HERG often underlies such clinical findings. Therefore, we examined a series of seven fluoroquinolones for their ability to interact with this channel. Using patch-clamp electrophysiology, we found that all of the drugs tested inhibited HERG channel currents, but with widely differing potencies. Sparfloxacin was the most potent compound, displaying an IC50 value of 18 microM, whereas ofloxacin was the least potent compound, with an IC50 value of 1420 microM. Other IC50 values were as follows: grepafloxacin, 50 microM; moxifloxacin, 129 microM; gatifloxacin, 130 microM; levofloxacin, 915 microM; and ciprofloxacin, 966 microM. Block of HERG by sparfloxacin displayed a positive voltage dependence. In contrast to HERG, the KvLQT1/minK K+ channel was not a target for block by the fluoroquinolones. These results provide a mechanism for the QT prolongation observed clinically with administration of sparfloxacin and certain other fluoroquinolones because free plasma levels of these drugs after therapeutic doses approximate those concentrations that inhibit HERG channel current. In the cases of levofloxacin, ciprofloxacin, and ofloxacin, inhibition of HERG occurs at concentrations much greater than those observed clinically. The data indicate that clinically relevant HERG channel inhibition is not a class effect of the fluoroquinolone antibacterials but is highly dependent upon specific substitutions within this series of compounds. HERG channel affinity should be an important criterion for the development of newer fluoroquinolones.

[The clinical value of laryngeal image analysis with two methods]

OBJECTIVE

To analyze normal and pathological glottal image quantitatively with computed image technique, and try to calculate the absolute value of the laryngeal parameter.

METHOD

The glottal image parameters of 60 normal adults, 60 cases of vocal polyps and 40 unilateral vocal fold paralysis(UVFP) patients were measured and analyzed, including the relative and absolute maximum or minimum glottal area, that is Amax(r), Amin(r), Amax(a) and Amin(a) respectively.

RESULT

Amin(r) of females was larger than that of males; and both were larger than zero. He and she were equal in Amin(a) and Amax(r), while Amax(a) of males was larger than that of females. Compared with normal adults, Amin(r) of the patients with vocal polyp increased, and Amax(r) of UVFP patients diminished, while their Amin(r) increased.

CONCLUSION

Laryngeal image could be analyzed quantitatively with computer assisted fibrolaryngoscopy. Normal adults have incomplete glottal closure to certain degree, and the level is different between sexes. The patients with vocal polyp and UVFP have relevant pathological glottal image.

A novel method for the determination of total protein in human serum by near infrared fluorescence recovery

A novel fluorometric method has been developed for the determination of total protein in human serum with a new near-IR reagent as a fluorescence probe, based on the fluorescence recovery of the cyanine-CTAB system in the presence of protein. Maximum fluorescence is produced with maximum excitation and emission wave-lengths at 765 and 812 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.4-12.0 microg/mL for protein. The detection limit is 70 ng/mL, and the relative standard deviation of six replicate measurements is 1.14% for 6.0 microg/mL protein. The results are satisfactory.

Effects of cancer chemotherapy on the blood fibrinogen concentrations of cancer patients

Blood fibrinogen concentrations and glutamic-pyruvic transaminase activities of 66 adult cancer inpatients (aged 22 - 70 years) were determined both before and after one or two chemotherapy regimens. The percentage of hepatoma patients with abnormal blood fibrinogen levels (< 1.5 or > 6.0 g/l) was higher (64.3% of 14 patients) than that in other cancer categories (19.2% of 52 patients). The mean blood fibrinogen concentrations of male (3.5 g/l) and female (4.5 g/l) cancer patients were higher than those previously reported for healthy humans (2.8 and 2.9 g/l, respectively). After chemotherapy, blood fibrinogen concentrations decreased in patients whose primary tumours were surgically removed (from 4.8 to 3.2 g/l) but increased (from 3.0 to 4.8 g/l) in those who did not undergo surgery. Glutamic-pyruvic transaminase activities did not appear to be related to blood fibrinogen levels. We conclude that the increase in mean blood fibrinogen levels of cancer patients is probably related to tumour growth. Different mechanisms may operate in patients with hepatoma.

NF- kappa B independent suppression of endothelial vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 gene expression by inhibition of flavin binding proteins and superoxide production

Oxidation-reduction (redox) coupled mechanisms play an important role in the regulation of cell surface adhesion molecule expression. In endothelial cells membrane-bound NADH/NADPH oxidase is a significant source of intracellular superoxide (O(2)(-)) production. We explored the role of flavin containing proteins such as NADH/NADPH oxidase in the induction of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) gene expression in human aortic endothelial cells (HAECs) and human dermal microvascular endothelial cells (HMECs). Treatment of HAECs by tumor necrosis factor- alpha (TNF- alpha, 100 U/ml) for 1 h induced a 31% increase in O(2)(-)production within 5 min as determined by lucigenin chemiluminescence analysis of whole cells (n=4, P<0.05). Pretreatment with the NADH/NADPH oxidase inhibitor diphenylene iodonium (DPI, 40 microm) for 1 h inhibited O(2)(-)production. DPI also inhibited TNF and LPS-induced VCAM-1 and ICAM-1 cell surface expression and TNF- alpha, LPS, or IL-1 beta induced VCAM-1 and ICAM-1 mRNA accumulation. However, DPI did not inhibit TNF- alpha -induced activation of nuclear NF- kappa B-like binding activity in HAECs and HMECs. Furthermore, DPI did not inhibit TNF- alpha induced transactivation of NF- kappa B-driven VCAM-1 and HIV-LTR promoter gene constructs in transiently transfected HMECs. These data suggest that flavin binding proteins such as NADH/NADPH oxidase can regulate VCAM-1 gene expression independent of NF- kappa B. Furthermore, intracellular O(2)(-)generation is not necessary for NF- kappa B activation or for transactivation of NF- kappa B driven promoters.

Cationic cyanine as a near-infrared fluorescent probe for the determination of nucleic acids

A new method with a cationic near-IR cyanine as fluorescent probe was developed for the determination of nucleic acids. The near-IR cyanine shows maximum excitation and emission wavelengths at 765 and 790 nm, respectively, in aqueous solution. The method is based on the fluorescence decrease of near-IR cyanine in the presence of nucleic acids. Under optimal conditions, the ratio of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.10-1.2 microg/mL for CT (calf thymus) DNA or SM (salmon sperm) DNA, and 0.10-1.6 microg/mL for yeast RNA. The detection limits were 30 ng/mL for CT DNA, 25 ng/mL for SM DNA and 70 ng/mL for yeast RNA. The relative standard deviation (n = 6) was 2.1% for 500 ng/mL CT DNA, 2.4% for 500 ng/mL SM DNA and 2.7% for 500 ng/mL yeast RNA, respectively.

[RP-HPLC determination of MBAMT and its decomposition product]

This paper presents a method of reversed-phase high performance liquid chromatography to determine N,N-methylene-bi-(2-amino-5-mercapto-1,3,4-thiodiazole) (MBAMT) and its decomposition product 2-amino-5-mercapto-1,3,4-thiodiazole (AMT). Recoveries of MBAMT and AMT were 91% and 94% respectively. The detectable limits of them in water samples were 7.19 nmol/L for MBAMT and 2.87 nmol/L for AMT. The resolution between the peaks of MBAMT and AMT was 2.5. The column efficiency and the sensitivity of this method were significantly better in comparison with normal phase chromatography.

Expression of leptin mRNA and CCAAT-enhancer binding proteins in response to insulin deprivation during preadipocyte differentiation in primary cultures of porcine stromal-vascular cells

The aim of this study was to examine the correlation between CCAAT-enhancer binding proteins (C/EBPs) and leptin gene expression in response to insulin deprivation in preadipocytes and adipocytes. Adipose tissue from 7 d-old pigs was digested enzymatically and stromal-vascular (S-V) cells were seeded and plated for 3 d in fetal bovine serum (FBS) with dexamethasone (DEX) followed by 6 d (Days 3-9) in serum-free medium with insulin (850 nM or 10 nM), transferrin, and selenium. During FBS+DEX treatment (Days 0-3) a large number of preadipocytes develop with no lipid accretion. In contrast, preadipocyte number does not change with lipid accretion during insulin treatment (Days 3-9). Total RNA and cells were harvested from S-V cultures after periods with and without insulin after FBS+DEX. Northern-blotting and Western blot analysis were used to study leptin mRNA and C/EBP protein expression in cultures, respectively. Insulin deprivation from Days 3-4 reduced leptin mRNA and C/EBP-alpha protein expression. Treatment with 850 nM or 10 nM insulin from Days 3-9 induced leptin mRNA and C/EBP-alpha expression at a similar level. In cultures treated with 10 nM insulin from Days 3-7, leptin and C/EBP-alpha expression were reduced markedly by insulin deprivation from Days 7-9, but were restored by insulin treatment for 6 hr before harvesting. The restoration of leptin expression by insulin was blocked by cycloheximide treatment. However, C/EBP-beta protein levels did not change regardless of insulin deprivation. Insulin deprivation from Days 7-9 in cultures treatedwith 850 nM insulin from Days 3-7 did not influence C/EBP-alpha or leptin mRNA expression, whereas C/EBP-alpha and leptin expression were reduced after treating these cultures with 1.5 uM okadaic acid for 45 min before harvesting on Day 9. However, cycloheximide treatment for 6 hr before harvesting did not reduce leptin mRNA expression. These results suggest that 1) leptin expression is positively correlated with C/EBP-alpha expression, and 2) the maintenance of leptin expression after insulin deprivation in 850 nM insulin-treated cultures on Day 9 may be associated with the presence of C/EBP-alpha expression and/or activation.

Angiotensin II induces vascular cell adhesion molecule-1 expression in rat vasculature: A potential link between the renin-angiotensin system and atherosclerosis

BACKGROUND

Cardiovascular ischemic events may occur more frequently in hypertensive patients with activated renin-angiotensin systems. We tested the hypothesis that angiotensin II (Ang II) may contribute to atherosclerosis by increasing expression of vascular inflammatory genes such as vascular cell adhesion molecule-1 (VCAM-1).

METHODS AND RESULTS

Rats infused with norepinephrine or Ang II for 6 days developed similar hypertensive responses, but only Ang II-treated rats exhibited significant increases in aortic VCAM-1 protein and mRNA expression. Oral losartan treatment (50 mg. kg(-1). d(-1)) inhibited Ang II-induced hypertension and aortic VCAM-1 mRNA expression. Ang II treatment significantly increased VCAM-1 mRNA expression in cultured rat aortic smooth muscle cells (RASMCs). Ang II also induced nuclear NF-kappaB-like binding activity and transactivated an NF-kappaB-driven VCAM-1 promoter. Losartan and proteasome inhibitors blocked Ang II-induced NF-kappaB activation and VCAM-1 mRNA accumulation. IkappaB-alpha overexpression in RASMCs inhibited Ang II-induced VCAM-1 promoter transactivation.

CONCLUSIONS

Ang II may contribute to atherogenesis by activation of VCAM-1 through proteasome dependent, NF-kappaB-like transcriptional mechanisms.

Analysis of a 762-bp proximal leptin promoter to drive and control regulation of transgene expression of growth hormone receptor in mice

Transgenic (TG) mice expressing porcine GH receptor (pGHR) directed by a 762-bp proximal leptin promoter were used to analyze the capability of the promoter to drive and regulate pGHR expression in vivo. Transgene expression occurred in inguinal, retroperitoneal, and epididymal/parametrial fat depots in both male and female TG mice, but not in wild type (WT) mice. pGHR transgene was also expressed in liver, heart, kidney, muscle, lung, and brain. Levels of pGHR transgene mRNA were higher in tissues other than adipose tissue. Fasting reduced leptin mRNA levels in adipose; however, pGHR transgene expression was not affected in either adipose or muscle. These results suggest (1) the region between +3 and -759 bp of the leptin promoter is able to drive gene expression in vivo, (2) this region may not be responsible for adipose tissue specificity of leptin expression, and (3) this region may not be responsible for negative regulation of leptin gene expression during fasting.

A role for T-type Ca2+ channels in the synergistic control of aldosterone production by ANG II and K+

Independently, plasma K+ and ANG II stimulate aldosterone secretion from adrenal glomerulosa (AG) cells, but together they synergistically control production. We studied mechanisms to mediate this synergy using bovine AG cells studied under physiological conditions (in 1.25 mM Ca2+ at 37 degrees C). Increasing K+ from 2 to 5 mM caused a potentiation of ANG II-induced aldosterone secretion and a substantial membrane depolarization ( approximately 21 mV). ANG II inhibited a K+-selective conductance in both 2 and 5 mM K+ but caused only a slight depolarization because, under both conditions, membrane potential was close to the reversal potential of the ANG II-induced current. ANG II activated calcium/calmodulin-dependent protein kinase II (CaMKII) equivalently in 2 and 5 mM K+. However, CaMKII activation caused a hyperpolarizing shift in the activation of T-type Ca2+ channels, such that substantially more current was elicited at membrane potentials established by 5 mM K+. We propose that synergy in aldosterone secretion results from K+-induced depolarization and ANG II-induced modulation of T-type channel activation, such that together they promote enhanced steady-state Ca2+ flux.

Self-assembly of ordered microporous materials from rod-coil block copolymers

Rod-coil diblock copolymers in a selective solvent for the coil-like polymer self-organize into hollow spherical micelles having diameters of a few micrometers. Long-range, close-packed self-ordering of the micelles produced highly iridescent periodic microporous materials. Solution-cast micellar films consisted of multilayers of hexagonally ordered arrays of spherical holes whose diameter, periodicity, and wall thickness depended on copolymer molecular weight and composition. Addition of fullerenes into the copolymer solutions also regulated the microstructure and optical properties of the microporous films. These results demonstrate the potential of hierarchical self-assembly of macromolecular components for engineering complex two- and three-dimensional periodic and functional mesostructures.

The buffer barrier hypothesis, [Ca2+]i homogeneity, and sarcoplasmic reticulum function in swine carotid artery

1. The goal of this study was to evaluate the buffer barrier hypothesis in an intact arterial smooth muscle. Specifically, we investigated the interrelationships between intracellular [Ca2+] ([Ca2+]i) homogeneity and sarcoplasmic reticulum function in swine carotid artery. 2. We measured focal changes in [Ca2+]i by exploiting the different characteristics of several [Ca2+]i indicators: (1) aequorin, which can detect focal increases in [Ca2+]i such as those that occur in the subplasmalemmal region ([Ca2+]pm); (2) fura-2, which is primarily a measure of mean cytoplasmic [Ca2+] ([Ca2+]c); and (3) force, which reflects increases in [Ca2+] near the contractile apparatus. We then estimated the relative degree of [Ca2+]i homogeneity with the aequorin/fura-2 ratio. Finally, we inhibited sarcoplasmic reticulum Ca2+ pumping with cyclopiazonic acid (CPA), an inhibitor of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). 3. We found that, after Ca2+ depletion, the sarcoplasmic reticulum could be partially reloaded with Ca2+ by manipulations that increased the aequorin signal relatively more than the fura-2 signal. Complete reloading required large increases in the fura-2 signal. These data suggest that increases in [Ca2+]pm (as measured with aequorin) can partially reload the sarcoplasmic reticulum, but complete reloading required increases in [Ca2+]c (as measured with fura-2). Reloading could be partially inhibited by 10 microM CPA, indicating that SERCA function was important for reloading. 4. In unstimulated arteries, 10 microM CPA increased the fura-2 signal without altering the aequorin signal, thereby decreasing the aequorin/fura-2 ratio. Removal of extracellular Ca2+ without CPA also reduced the aequorin/fura-2 ratio. These data suggest that resting cells have a [Ca2+] gradient with [Ca2+]pm > [Ca2+]c; this gradient is maintained by SERCA function. 5. CPA slowed the decline in the fura-2 signal observed when histamine stimulation was removed. This result is consistent with the concept of vectorial Ca2+ efflux in which Ca2+ pumping by SERCA reduces [Ca2+]c after stimulation. 6. Ca2+ depletion by prior treatment with 100 microM histamine and CPA transiently attenuated subsequent histamine-induced aequorin and fura-2 transients. The effect on contraction was smaller: a delay in contraction of approximately 10 s. These data suggest that histamine-induced Ca2+ release has at least a small role in the initial phase of contraction; however, other contractile mechanisms appear to be able to compensate for loss of Ca2+ release with only modest changes in contraction kinetics. 7. These data suggest that there is a complex interrelationship between smooth muscle sarcoplasmic reticulum function and [Ca2+] in at least two cytoplasmic compartments. [Ca2+]pm and [Ca2+]c can differentially regulate sarcoplasmic reticulum Ca2+ filling; and sarcoplasmic reticulum function regulates [Ca2+]pm and [Ca2+]c.

Angiotensin II induces monocyte chemoattractant protein-1 gene expression in rat vascular smooth muscle cells

Monocyte infiltration into the vessel wall, a key initial step in the process of atherosclerosis, is mediated in part by monocyte chemoattractant protein-1 (MCP-1). Hypertension, particularly in the presence of an activated renin-angiotensin system, is a major risk factor for the development of atherosclerosis. To investigate a potential molecular basis for a link between hypertension and atherosclerosis, we studied the effects of angiotensin II (Ang II) on MCP-1 gene expression in rat aortic smooth muscle cells. Rat smooth muscle cells treated with Ang II exhibited a dose-dependent increase in MCP-1 mRNA accumulation that was prevented by the AT1 receptor antagonist losartan. Ang II also activated MCP-1 gene transcription. Inhibition of NADH/NADPH oxidase, which generates superoxide and H2O2, with diphenylene iodonium or apocynin decreased Ang II-induced MCP-1 mRNA accumulation. Induction of MCP-1 gene expression by Ang II was inhibited by catalase, suggesting a second messenger role for H2O2. The tyrosine kinase inhibitor genistein and the mitogen-activated protein kinase kinase inhibitor PD098059 inhibited Ang II-induced MCP-1 gene expression, consistent with a mitogen-activated protein kinase-dependent signaling mechanism. Ang II may thus promote atherogenesis by direct activation of MCP-1 gene expression in vascular smooth muscle cells.

Self-assembled aggregates of rod-coil block copolymers and their solubilization and encapsulation of fullerenes

Amphiphilic poly(phenylquinoline)-block-polystyrene rod-coil diblock copolymers were observed to self-organize into robust, micrometer-scale, spherical, vesicular, cylindrical, and lamellar aggregates from solution. These diverse aggregate morphologies were seen at each composition, but their size scale decreased with a decreasing fraction of the rigid-rod block. Compared to coil-coil block copolymer micelles, the present aggregates are larger by about two orders of magnitude and have aggregation numbers of over 10(8). The spherical and cylindrical aggregates have large hollow cavities. Only spherical aggregates with aggregation numbers in excess of 10(9) were formed in the presence of fullerenes (C60, C70) in solution, resulting in the solubilization and encapsulation of over 10(10) fullerene molecules per aggregate.

Hormonal regulation of leptin mRNA expression and preadipocyte recruitment and differentiation in porcine primary cultures of S-V cells

The hormonal regulation of leptin mRNA expression and the association between leptin expression and adipocyte differentiation were examined in primary cultures of porcine S-V cells with Northern blot and immunocytochemical analysis. Seeding for 3 days with fetal bovine serum (FBS) with varying levels of dexamethasone (Dex) increased levels of leptin mRNA in a dose-dependent manner in parallel with increases in the proportion of preadipocytes (AD-3 positive cells; AD-3, a preadipocyte marker). Six-day treatment with 10 or 850 nM insulin after FBS+Dex treatment resulted in a similar increase in leptin mRNA expression and morphological differentiation. However, significantly lower levels of leptin mRNA and smaller fat cells were observed in cultures treated with 1 nM insulin or 10 nM insulin-like growth factor-I (IGF-I). Dex-induced increases in leptin mRNA levels and AD-3 cell numbers were blocked completely by the addition of transforming growth factor-beta (TGF-beta) to FBS+Dex-treated cultures. However TGF-beta significantly increased fat cell size and leptin mRNA expression when added to ITS (insulin, 850 nM; transferrin, 5 microg/ml; and selenium, 5 microg/mL) treated cultures during the lipid-filling stage. When added with FBS+DEX for the first 3 days, growth hormone (GH) did not influence the Dex-induced increase in AD-3 cells and leptin mRNA expression, but GH reduced leptin mRNA levels when added with insulin for 6 days after FBS+Dex. These results demonstrated that regulation of leptin mRNA expression by Dex, insulin, IGF-I, TGF-beta, and GH may be associated with changes in preadipocyte number and fat cell size.

Mechanisms responsible for forskolin-induced relaxation of rat tail artery

The goal of the present study was to determine the physiologically relevant mechanisms for forskolin-induced relaxation of intact rat tail artery. We stimulated deendothelialized rat tail artery with phenylephrine and then relaxed the tissue with the addition of forskolin, a specific activator of adenylyl cyclase. We measured membrane potential with the use of microelectrodes, estimated intracellular Ca2+ concentration ([Ca2+]i) with the use of fura 2, and measured isometric force with a strain-gauge transducer. We found that 0.3 to 1.0 micromol/L forskolin relaxed 0.3 to 1.0 micromol/L phenylephrine-stimulated rat tail artery by decreasing the [Ca2+]i sensitivity of force as well as through repolarization. There was no evidence for forskolin-induced inhibition of Ca2+ influx beyond that associated with repolarization. There also was no evidence for forskolin-induced enhancement of Ca2+ efflux or sequestration. Inhibition of ATP-activated K+ channels with 10 micromol/L glibenclamide, Ca2+-activated K+ channels with 50 nmol/L iberiotoxin, Ca2+-activated K+ channels with 3 or 10 mmol/L tetraethylammonium ion, inwardly rectified K+ channels with 20 micromol/L Ba2+, and voltage-activated K+ channels with 0.5 mmol/L 4-aminopyridine did not significantly attenuate forskolin-induced reductions in [Ca2+]i or force. Forskolin-induced repolarization was not altered by 10 micromol/L glibenclamide or 0.5 mmol/L 4-aminopyridine. These data suggest that these K+ channels were not individually involved in forskolin-induced relaxation and that other channels and/or multiple channels are involved in forskolin-induced repolarization of intact rat tail artery. Our data also suggest that forskolin-induced relaxation of intact rat tail artery occurred primarily through repolarization and reductions in the [Ca2+]i sensitivity of force.

[Monosynaptic transmission between mesodiencephalic neurons and motoneurons innervating extraocular inferior oblique muscle in cats]

The present study was performed to define the synaptic connection of neurons located within the dorsal mesodiencephalic junction with motoneurons innervating extraocular inferior oblique muscle (IOMN) using electrophysiologic, especially spike-triggered averaging technique in cats. In response to electric shocks applied to the medial part of Forel's field H (FFH) located in the mesodiencephalic junction, excitatory monosynaptic field potentials were observed in the IOMN pool. Moreover, while the spontaneous discharges of FFH neurons were used to trigger the activity of IOMN pool from which the induced potential changes were averaged, an excitatory monosynaptic field potential was also obtained. These results indicate that the mesodiencephalic neurons connect with and activate the IOMNs monosynaptically, and drive vertical eye movements via such a way.

E-selectin gene expression in vascular smooth muscle cells. Evidence for a tissue-specific repressor protein

E-Selectin is an inducible, endothelium-specific, cell surface adhesion molecule that mediates inflammatory responses in the vasculature. Nonendothelial cell types such as cultured human aortic smooth muscle cells (HASMCs) lack the ability to express E-selectin. We tested the hypothesis that HASMCs express a negative regulatory factor that inhibits E-selectin gene expression. E-Selectin mRNA and gene transcription were not detected in HASMCs after treatment with tumor necrosis factor-alpha (TNF-alpha) by Northern and nuclear runoff analyses, respectively. However, both E-selectin mRNA and gene transcription were dramatically induced by TNF-alpha in the same cells pretreated with the protein synthesis inhibitor cycloheximide. Lipopolysaccharide demonstrated similar effects. Furthermore, E-selectin was detected on the cell surface of HASMCs after washing out of cycloheximide. Cycloheximide pretreatment enabled immortalized human dermal microvascular endothelial cells that have lost the ability to express E-selectin to induce both E-selectin mRNA and gene transcription in response to TNF-alpha. Induction of E-selectin mRNA by lipopolysaccharide or TNF-alpha in cycloheximide-treated HASMCs was inhibited by the antioxidant pyrrolidinedithiocarbamate and the serine protease inhibitor N alpha-L-tosyl-L-phenylalanine chloromethyl ketone, suggesting that a nuclear factor-kappa B-like mechanism may play an important role in E-selectin gene expression in HASMCs. These data strongly suggest that a labile repressor protein(s) plays an important role in inhibiting E-selectin gene expression in HASMCs likely at the level of gene transcription. Except for this repressor, HASMCs and endothelial cells may share similar regulatory mechanisms for controlling E-selectin expression.

Metformin relaxes rat tail artery by repolarization and resultant decreases in Ca2+ influx and intracellular [Ca2+]

BACKGROUND

Metformin treatment of type II diabetes is frequently associated with decreases in blood pressure, an effect that could result from a direct action of metformin on arterial smooth muscle.

OBJECTIVE

To determine the mechanisms responsible for arterial smooth muscle relaxation induced by acute application of metformin and to evaluate the effect of insulin pretreatment on intracellular [Ca2+] ([Ca2+]i) and contraction in an intact artery.

METHODS

We stimulated intact deendothelialized rat tail artery with phenylephrine, relaxed the tissue by adding increasing concentrations of metformin, and measured the membrane potential (Em), Mn2+ influx, Fura 2-estimated [Ca2+]i, and isometric force. We also evaluated the effect of insulin pretreatment on aequorin-estimated [Ca2+]i in deendothelialized swine carotid artery.

RESULTS

In rat tail artery we found that a high concentration of metformin-induced repolarization associated with proportional decreases in Mn2+ influx, Fura 2-estimated [Ca2+]i, and isometric force. Incubation of swine carotid artery in 100 mU/ml insulin for 30 min or overnight (16-22 h) did not significantly alter histamine or high-K+-induced increases in [Ca2+]i or contraction.

CONCLUSION

These data suggest that acute administration of high concentrations of metformin induces rat tail artery relaxation primarily by repolarization. Additionally, we found that insulin was not vasoactive in the swine carotid artery. It is possible that insulin may alter [Ca2+]i handling in other arteries, in other species, or only in cultured smooth muscle.

Nitroglycerin relaxes rat tail artery primarily by lowering Ca2+ sensitivity and partially by repolarization

At least five mechanisms are hypothesized to account for guanosine 3',5'-cyclic monophosphate (cGMP)-induced relaxation of arterial smooth muscle: 1) repolarization, 2) inhibition of Ca2+ release, 3) inactivation of L-type Ca2+ channels, 4) enhancement of Ca2+ efflux/sequestration, and 5) decreasing the intracellular Ca2+ concentration ([Ca2+]i) sensitivity of force. The goal of this study was to investigate the physiological relevance of these five mechanisms in the intact rat tail artery. We stimulated deendothelialized rat tail artery with phenylephrine or high extracellular K+ concentration ([K+]o) and then relaxed the tissue by adding nitroglycerin to increase guanosine 3',5'-cyclic monophosphate concentration. We measured membrane potential (Em) with microelectrodes, [Ca2+]i with fura 2, and isometric force with a strain-gauge transducer. We found that decreases in the [Ca2+]i sensitivity of force accounted for most of the nitroglycerin-induced relaxation of tissues prestimulated with maximal (1 microM) phenylephrine or 30 mM [K+]o. In submaximally (0.1-0.3 microM) phenylephrine-prestimulated tissues, nitroglycerin-induced relaxation was caused primarily by a decrease in the [Ca2+]i sensitivity of force and partially by repolarization and the resultant decrease in [Ca2+]i. Nitroglycerin also partially attenuated transient increases in [Ca2+]i and force induced by 100 microM phenylephrine in the absence of extracellular Ca2+, indicating that nitroglycerin also inhibited intracellular Ca2+ release. Nitroglycerin-induced relaxation was not associated with inactivation of Ca2+ channels or enhancement of Ca2+ efflux/sequestration. These data suggest that nitroglycerin relaxes precontracted rat tail artery primarily by decreasing the [Ca2+]i sensitivity of force.

Focal increases in [Ca2+]i may account for apparent low Ca2+ sensitivity in swine carotid artery

Estimates of [Ca2+]i sensitivity in intact smooth muscle are frequently obtained by measuring [Ca2+]i with indicators such as aequorin or Fura-2. We investigated whether focal increases in [Ca2+]i could impair such measures of [Ca2+]i sensitivity. Stimulation of swine carotid artery with 10 microM histamine increased aequorin estimated [Ca2+]i, Fura-2 estimated [Ca2+]i and Ca2+ sensitivity without significantly altering the aequorin/Fura-2 ratio (an estimate of [Ca2+]i homogeneity). Subsequent inhibition of Na+/Ca2+ exchange by replacement of Na+ in the PSS with choline+ significantly increased aequorin-estimated [Ca2+]i but only minimally increased Fura-2 estimated [Ca2+]i, myosin light chain (MLC) phosphorylation and force. This resulted in a large increase in the aequorin/Fura-2 ratio, suggesting an increase in [Ca2+] inhomogeneity. Addition of 100 microM histamine to tissues in the choline+ buffer initially increased both aequorin and Fura-2 estimated [Ca2+]i, but after 10 min exposure both of the [Ca2+]i estimates declined to pre-histamine levels. Histamine addition significantly increased MLC phosphorylation and force, indicating increased Ca2+ sensitivity, but the aequorin/Fura-2 ratio remained elevated and unchanged from pre-histamine values. These data show that under certain conditions, aequorin and Fura-2 can yield widely differing estimates of [Ca2+]i and thus can cause misleading assessments of Ca2+ sensitization mechanisms. These discrepancies may arise from inhomogeneous or focal increases in [Ca2+]i which can be evaluated with the aequorin/Fura-2 ratio.

The effect of prior in vitro exposure of donor cells to trophic factors in neurotransplantation

The ability of PC12 cells to regenerate processes is substantially enhanced in vitro if they have been previously exposed to nerve growth factor (NGF-primed), compared to cells that have not been exposed (NGF-naive). These studies were carried out to determine if the enhanced neuritogenic ability of NGF-primed cells is retained following transplantation. NGF-naive or NGF-primed PC12 cells were transplanted into the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice and allowed to survive for 2 weeks. Mice were given daily injections of cyclosporin A (CyA) to prevent anti-species graft rejection. The transplanted PC12 cells were visualized by tyrosine hydroxylase immunoreactivity. The NGF-naive transplanted cells formed dense clusters and large tumor masses in more than half the animals. Only a few of the naive PC12 cells had short processes. In contrast, many of the transplanted NGF-primed PC12 cells had processes. Furthermore, fewer of the animals transplanted with primed cells produced tumor masses in the striatum compared to animals that received NGF-naive cells. Transplantation of NGF-naive PC12 cells leads to a significant increase in the number of dopaminergic neurons in the host substantia nigra (SN) compared to MPTP-treated animals. The increase of host dopaminergic neurons was not statistically significant when NGF-primed PC12 cells were used. Following MPTP treatment and PC12 cell transplantation, injection of CyA did not affect the dopaminergic neurons in the host SN. These data suggest that exposure of cells to trophic factors, prior to transplantation, can enhance their level of differentiation and integration into the host brain.

[The effect of early chest physiotherapy on blood gas and circulatory function in old patients after thoracotomy]

In this study, 15 old patients undergoing thoracotomy were selected for observing the influence of effective chest physiotherapy started early in postoperation on blood gas and circulatory function. Following ultrasonic aerosol inholation for 20 minutes, turning the body, and chest percussion in head-up were started at 6th hour after operation. The result showed that PaO2, SaO2 were significantly increased and PaCO2 were decreased at 30 minutes after treatment comparied with it before treatment. In other side, although the hemodynamics could maintain stabilization, cardiac arrhythmias were occured during treatment in three cases, whose ECG were abnormal in preopration. It concluded that effectively chest physiotherapy, started early in postoperation, could prevent postoperative hypoxemia in old thoracotomy patients, But, ECG monitoring is necessary during treatment in patients whose ECG was abnormal before operation.

Focal [Ca2+]i increases detected by aequorin but not by fura-2 in histamine- and caffeine-stimulated swine carotid artery

1. We hypothesized that the homogeneity of intracellular [Ca2+] ([Ca2+]i) varies and is regulated in arterial smooth muscle. 2. We evaluated this hypothesis by exploiting the different characteristics of several [Ca2+]i indicators: (1) aequorin, which theoretically can measure focal increases in [Ca2+]i, (2) fura-2, which is predominantly a measure of mean cytoplasmic [Ca2+], and (3) myosin light chain phosphorylation and force, which reflect increases in [Ca2+] near the contractile apparatus. 3. From the differences in the observed aequorin and fura-2 signals, we developed an index of the relative degree of [Ca2+]i homogeneity as the ratio of the aequorin signal and fura-2 signal. 4. Stimulation with intermediate concentrations of histamine (1 and 10 microM) or high [K+]o (25 and 40 mM) increased [Ca2+]i and contractile stress. Relative [Ca2+]i homogeneity, estimated from the aequorin/fura-2 ratio, remained similar to levels observed in unstimulated tissues. 5. Higher concentrations of histamine (100 microM) also increased [Ca2+]i and stress, but the aequorin/fura 2 ratio declined , indicating increased [Ca2+]i homogeneity. Similarly, the aequorin/fura-2 ratio decreased when extracellular Ca2+ was removed. 6. Stimulation with histamine in low extracellular [Ca2+] transiently increased [Ca2+]i and the aequorin/fura-2 ratio. Similarly, in tissues treated with low extracellular [Ca2+], restoration of extracellular Ca2+ transiently increased both [Ca2+]i and the aequorin/fura-2 ratio. Although both of these experiments demonstrated a transient decrease in [Ca2+]i homogeneity, only histamine stimulation led to increased myosin light chain phosphorylation and force. These results indicate that the focal increases in [Ca2+]i observed with histamine stimulation and Ca2+ restoration occurred in different cellular regions. 7. Addition of caffeine (20 mM) increased [Ca2+]i and [cAMP], but this was not accompanied by sustained increased myosin light chain phosphorylation or contraction. Phosphorylation of myosin light chain kinase did not appear to underlie the lack of increase in myosin light chain phosphorylation. Rather, caffeine induced a sustained increase in the aequorin/fura-2 ratio, suggesting that caffeine inhibits smooth muscle contraction by localizing increases in [Ca2+]i to a region distant from the contractile apparatus. 8. These data suggest that there can be transient and sustained focal increases in [Ca2+]i. Aequorin detected increased [Ca2+]i in small regions of the cytoplasm during release from and refilling of the intracellular Ca2+ store and with caffeine stimulation. Dual use of aequorin and fura-2 permits determination of relative [Ca2+]i homogeneity in smooth muscle.

Influences of phenylephrine on delayed afterdepolarization and triggered activity in sheep Purkinje fibers

AIM

To compare the effects of phenylephrine (Phe) on DAD and TA in the absence or presence of propranolol (Pro).

METHODS

Using intracellular microelectrode methods to record transmembrane potentials in sheep Purkinje fibers.

RESULTS

Perfused Phe 1 mumol.L(-1) for 60 min, in the absence of Pro, Phe increased the amplitude of DAD from 7.5 +/- 1.2 to 9.0 +/- 2.0 mV (n = 8, P < 0.05), nonsignificantly changed the duration of DAD and induced TA in 3/11 preparations; but in the presence of Pro 0.5 mumol.L(-1) blocking beta-adrenoceptors, the amplitude of DAD increased from 7.2 +/- 1.8 to 8.3 +/- 2.1 mV at the first 20 min (n = 8, P < 0.01), and then decreased to 6.3 +/- 1.6 mV, the duration of DAD prolonged from 192 +/- 17 to 280 +/- 27 ms (n = 8, P < 0.01 vs control), meanwhile Phe could suppress the TA induced by acetylstrophanthidin and this effect was blocked by prazosin.

CONCLUSION

When Pro is efficiently used in abolishing arrhythmias evoked by catecholmines, apart from directly blocking beta-adrenoceptors, relatively aggravating excitation of alpha-adrenoceptors to suppress DAD and TA is one of the important reasons.

pHi, [Ca2+]i, and myosin phosphorylation in histamine- and NH4(+)-induced swine carotid artery contraction

We examined the interaction among changes in pHi, [Ca2+]i, myosin light-chain phosphorylation, and contraction in arterial smooth muscle stimulated by histamine, NH4+, Tris+, and/or changes in extracellular pH (pHo). We loaded swine carotid medial tissues with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein to measure pHi or aequorin to measure [Ca2+]i. Incubation of tissues in NH4+ increased pHi, [Ca2+]i, myosin phosphorylation, and force. Washout of NH4+ decreased pHi and transiently further increased in [Ca2+]i and force. Incubation of tissues in a similar concentration of Tris+ or increasing pHo also increased pHi; however, there were only modest changes in [Ca2+]i and force. Increasing extracellular pH coincidentally with washout of NH4+ prevented the decrease in pHi but did not affect the NH4+ washout-induced contraction. These data suggest that NH4+ altered [Ca2+]i and contraction by mechanisms other than its effects on pHi. The type of pH buffer did not affect the [Ca2+]i, myosin phosphorylation, or stress response to histamine stimulation. The time course of changes in pHi was much slower than the time course of histamine-induced changes in [Ca2+]i, myosin phosphorylation, and stress. Addition of 10 mmol/L NH4+ concurrently with histamine aborted the histamine-induced decrease in pHi and significantly slowed the histamine-induced increase in [Ca2+]i, myosin phosphorylation, and stress. There was little effect on histamine-induced increases in [Ca2+]i, myosin phosphorylation, or contraction when three other protocols aborted the histamine-induced decrease in pHi. These data show that incubation in NH4+ can alter [Ca2+]i and contraction in both unstimulated and histamine-stimulated smooth muscle. However, these effects were not caused by NH4(+)-dependent changes in pHi.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenylephrine contracts rat tail artery by one electromechanical and three pharmacomechanical mechanisms

There are at least four mechanisms hypothesized to account for excitation-contraction coupling in arterial smooth muscle. 1) Contractile agonists and changes in extracellular [K+] ([K+]o) induce contraction by depolarization, which increases Ca2+ influx; this is the only mechanism involving a change in membrane potential (Em). 2) Contractile agonists release Ca2+ from the intracellular Ca2+ store. 3) Contractile agonists increase Ca2+ influx without changing Em either by activating voltage-dependent L-type Ca2+ channels or by opening other Ca(2+)-permeable channels. 4) Contractile agonists increase intracellular Ca2+ ([Ca2+]i) sensitivity of force; this is the only mechanism that does not involve changes in [Ca2+]i. Each of these mechanisms has been demonstrated in intact, skinned, or dissociated smooth muscle preparations. However, these four mechanisms have not been compared in the same preparation. The goal of this study was to determine which of these four contractile mechanisms are physiologically relevant in the intact rat tail artery. We stimulated deendothelialized rat tail artery with phenylephrine and high [K+]o. We then measured Em with microelectrodes, [Ca2+]i with fura 2, and isometric force with a strain gauge transducer. We find that all four mechanisms contributed to phenylephrine-induced rat tail artery contraction. The majority of phenylephrine-induced contraction was caused by depolarization and by increases in the [Ca2+]i sensitivity of force. Low concentrations of phenylephrine also increased [Ca2+] independent of changes in Em, potentially by increases in Ca2+ influx. Release of Ca2+ from intracellular stores was only observed with high concentrations of phenylephrine. Smooth muscle appears to invoke multiple mechanisms for excitation-contraction coupling.

Estimation of rate constants for reactions of pulmonary microvascular angiotensin converting enzyme with an inhibitor and a substrate in vivo

We developed a method of measuring the mole quantity of pulmonary angiotensin-converting enzyme (ACE) bound by a partially saturating dose of an ACE inhibitor injected i.v. For each test animal (11 guinea pigs), tracer (nonsaturating) doses of the ACE substrate [14C]benzoyl-Ala-Gly-Pro (14C-BAGP) and the ACE inhibitor 3H-RAC-X-65 were coinjected at timed intervals for a total of four studies per animal. The injectate used for the second study contained, in addition, a partially saturating dose of unlabeled RAC-X-65. With indicator-dilution techniques supplemented with measurements of fractional hydrolysis of 14CBAGP and uptake of 3H-RAC-X-65 during a single transit through the pulmonary vascular bed, the following parameters were computed: plasma flow (Qp), (kcat/Km)[E] vector c, k1[E] vector c and Eb, where [E] is the concentration of active ACE, Eb is the mole quantity of ACE bound by inhibitor, kcat/Km is the second-order rate constant for substrate hydrolysis, k1 is the inhibitor-ACE association rate constant and vector c is capillary mean transit time. As shown elsewhere (Catravas et al., 1990; Catravas and White, 1984), the product of Qp (in liters per second) multiplied by (kcat/Km)[E] vector c is (kcat/Km)E, and the product of Qp multiplied by k1[E] vector c is k1E, where E is the mole quantity of ACE. Values of (kcat/Km)Eb and k1Eb were computed and divided by Eb to obtain kcat/Km and k1. The fractional degree of inhibition conferred by a partially saturating dose of an ACE inhibitor can be understood to be the ratio Eb/ET, where ET is total ACE. With Eb in moles and the ratio Eb/ET, we computed the mole quantity of ET. By measuring the rate of recovery of ACE activity following partial inhibition of ACE, an apparent dissociation rate constant, k(dissoc), was computed. With k(dissoc) and K1, an apparent Ki was computed. The following computations were obtaine: ET of 0.90 +/- 0.20 (S.E.M.) nmol; kcat/Km, 5.16 +/- 0.89E + 06 M-1.sec-1; k1, 1.26 +/- 0.21E + 06 M-1.sec-1; k(dissoc), 6.47 +/- 0.63E - 04 sec-1 and Ki, 5.13E - 10 M. Although we focused on the characterization of ACE, the methods developed are general and may be applicable to studies of other vascular surface proteins, including other enzymes and hormone receptors.

[Correlationship between cellular DNA and AgNOR protein content in the developing course of colorectal adenocarcinoma]

Cellular DNA and AgNOR protein content were evaluated by automatic image analysis in tissue sections stained by combined Feulgen-AgNOR method of 9 normal colonic mucosae, 45 colorectal adenomas and 27 colorectal correlation between AgNOR protein and DNA contents. In adenocarcinomas, the DNA and AgNOR protein contents were higher than those in adenomas, which were in turn higher than those in normal colonic mucosa. However, there was considerable overlapping in the DNA or AgNOR protein content between adenoma and adenocarcinoma groups and between adenoma and normal colonic mucosa groups. By assessing the correlationship between the DNA and AgNOR protein contents, the number of the overlapping cases was reduced significantly. Therefore it is much more reliable to distinguish colorectal adenomas from adenocarcinomas by using the correlationship between the cellular DNA and the AgNOR protein contents in the same specimens.

Radiation-induced early pulmonary endothelial ectoenzyme dysfunction in vivo: effect of indomethacin

We investigated the early effects of radiation on pulmonary endothelial function in vivo 7-8 hr after exposure of rabbits to a single dose of 30 Gy to the chest. Utilizing multiple indicator-dilution techniques, we measured rates and kinetics of hydrolysis of the synthetic substrates [3H]benzoyl-Phe-Ala-Pro (BPAP) and [14C]benzoyl-Ala-Gly-Pro (BAGP) by endothelial-bound angiotensin-converting enzyme (ACE) and of 5'[14C]-AMP by endothelial-bound 5'-nucleotidase (NCT) and binding of the synthetic ACE inhibitor [3H]RAC-X-65 during a single transpulmonary passage in anesthetized, artificially ventilated, open-chest rabbits in which both systemic and pulmonary circulations were fully supported by an extracorporeal pump. We have shown that these techniques and the use of the aforementioned probes provide reliable information on pulmonary endothelial function in vivo. Radiation to the chest produced endothelial ectoenzyme dysfunction, as reflected in altered available perfused capillary surface area and altered enzyme kinetics of all probes (decreases in substrate hydrolysis, inhibitor binding, first- and second-order kinetic constants) over a wide range of pulmonary blood flow values (reflecting approximately 60-200% of normal cardiac output). Indomethacin prevented most of these alterations in partially as well as fully recruited lungs. We conclude that impairment of endothelial ectoenzyme activity is an early event in the pathogenesis of radiation-induced lung damage, which occurs independently of hemodynamic influences and may involve synthesis of arachidonic acid metabolites.

Assay of pulmonary microvascular endothelial angiotensin-converting enzyme in vivo: comparison of three probes

We monitored the activity of pulmonary microvascular endothelial-bound angiotensin-converting enzyme (ACE) in vivo by means of multiple indicator-dilution-type techniques, utilizing three different probes: the hydrolysis of two substrates, [3H]-benzoyl-Phe-Ala-Pro (BPAP) and [14C]benzoyl-Ala-Gly-Pro (BAGP), and the binding of the inhibitor [3H]RAC-X-65 (RAC), all measured during a single transpulmonary passage in anesthetized rabbits, placed on total heart bypass, so that both systemic and pulmonary circulations were fully supported by means of a two-channel extracorporeal pump. Experiments were performed at pulmonary blood flows (Qb) of 250, 400, 560, and 800 ml/min in control or indomethacin-pretreated rabbits. ACE activity was also compared to that of pulmonary microvascular endothelial-bound 5'-nucleotidase, by measuring the dephosphorylation of its natural substrate 5'-[14C]AMP. We calculated substrate utilization, mean lung transit time (t), and volume of distribution (i.e., central blood volume) of all substrates, as well as inhibitor binding. We also calculated Amax/Km and Bmax products of enzyme mass and kinetic constants for substrates and inhibitor, respectively. As Qb increased, Amax/Km values for all three substrates and Bmax increased linearly, indicating microvascular recruitment. In experiments in which either BPAP and 5'-AMP metabolism or BAGP metabolism and RAC binding were studied concomitantly, a linear relationship was observed between Qb-induced changes in Amax/Km values of BPAP vs 5'-AMP as well as in Amax/Km of BAGP vs Bmax of RAC. Similarly, increasing Qb increased central blood volume and decreased t. Indomethacin had no effect on most of the hemodynamic or enzyme parameters measured. We conclude that in vivo assays of ACE proceed as predicted by Michaelis-Menten kinetics and offer insights into pulmonary endothelial pathophysiology.

Cyclic nucleotide-dependent regulation of Mn2+ influx, [Ca2+]i, and arterial smooth muscle relaxation

Elevations in cyclic nucleotide levels can decrease myoplasmic [Ca2+] ([Ca2+]i) and thereby induce arterial smooth muscle relaxation. We evaluated whether cyclic nucleotide-induced reductions in [Ca2+]i are caused by 1) decreased Ca2+ influx or 2) increased Ca2+ sequestration or efflux. Swine carotid medial tissues were loaded with fura-2, and Ca2+ influx was estimated from the quenching rate of 360-nm fluorescence after addition of extracellular Mn2+. Histamine stimulation or high KCl depolarization increased Mn2+ influx, [Ca2+]i, and contractile force. The Ca2+ channel blocker diltiazem attenuated histamine- or KCl-induced increases in Mn2+ influx, [Ca2+]i, and force. Addition of forskolin (which increases cAMP) or nitroglycerin (which increases cGMP) attenuated histamine-induced increases in Mn2+ influx, [Ca2+]i, and force. Addition of forskolin or nitroglycerin also relaxed KCl depolarized tissues; however, Mn2+ influx and [Ca2+]i remained high. These results suggest that Mn(2+)-induced quenching of 360-nm fluorescence is an estimate of Ca2+ influx in the intact swine carotid artery. These results also suggest that cyclic nucleotides can relax swine arterial smooth muscle by at least two mechanisms: 1) reduction of [Ca2+]i primarily induced by decreases in Ca2+ influx and 2) uncoupling force from [Ca2+]i without changing Ca2+ influx or [Ca2+]i.

Nitrovasodilators relax arterial smooth muscle by decreasing [Ca2+]i and uncoupling stress from myosin phosphorylation

Elevations in guanosine 3',5'-cyclic monophosphate concentration ([cGMP]) are proposed to induce arterial smooth muscle relaxation by either 1) decreasing myoplasmic [Ca2+] ([Ca2+]i), 2) decreasing the [Ca2+]i sensitivity of phosphorylation, or 3) uncoupling force from myosin phosphorylation. We evaluated the importance of each of these mechanisms by measuring changes in [cGMP], aequorin- and fura-2-estimated [Ca2+]i, myosin light chain phosphorylation, and stress in histamine-stimulated swine carotid arteries. In tissues submaximally stimulated with 3 microM histamine, nitroprusside (NP) induced a proportional decrease in myoplasmic [Ca2+] and myosin phosphorylation, suggesting that the relaxation was at least partially induced by decreases in [Ca2+]i without a change in the [Ca2+]i sensitivity of phosphorylation. In tissues maximally stimulated with 10 microM histamine, NP and nitroglycerin produced significant relaxations that were not associated with significant sustained reductions in [Ca2+]i or myosin phosphorylation. With both submaximal and maximal histamine stimulation, nitrovasodilators produced more substantial relaxation than that expected from the nitrovasodilator-induced reduction in myosin phosphorylation. These results suggest that nitrovasodilators relax histamine-stimulated swine arterial smooth muscle by at least two mechanisms: 1) reducing [Ca2+]i, an effect observed in submaximally stimulated tissues, and 2) uncoupling of stress from myosin phosphorylation.

Na(+)-Ca2+ exchange, myoplasmic Ca2+ concentration, and contraction of arterial smooth muscle

Na(+)-Ca2+ exchange is proposed to be an important regulator of myoplasmic intracellular Ca2+ concentration ([Ca2+]i) and contraction in vascular smooth muscle. We investigated the role of Na(+)-Ca2+ exchange in regulating [Ca2+]i in swine carotid arterial tissues that were loaded with aequorin to allow simultaneous measurement of [Ca2+]i and force. Reversal of Na(+)-Ca2+ exchange, by reduction of extracellular Na+ concentration ([Na+]o) to 1.2 mM, induced a large increase in aequorin-estimated [Ca2+]i and a low [Ca2+]i sensitivity. The contraction induced by 1.2 mM [Na+]o was partially caused by depolarization and opening of L-type Ca2+ channels because 10 microM diltiazem partially attenuated the 1.2 mM [Na+]o-induced increases in [Ca2+]i. High dose ouabain (10 microM), a putative endogenous Na+,K(+)-ATPase inhibitor, increased both [Ca2+]i and force. However, the increases in [Ca2+]i and force were mostly blocked by 10 microM phentolamine, suggesting the predominant effect of ouabain was to increase norepinephrine release from nerve terminals. In the presence of 10 microM phentolamine, 10 microM ouabain slightly accentuated 1 microM histamine-induced increases in [Ca2+]i and force. The ouabain dose necessary to induce contraction in the absence of phentolamine was significantly less than the ouabain dose necessary to accentuate histamine-induced contractions in the presence of phentolamine. These results suggest that Na(+)-Ca2+ exchange exists in swine arterial smooth muscle. These data also suggest that ouabain (which should increase [Na+]i and inhibit Na(+)-Ca2+ exchange) primarily enhances contractile function in the swine carotid artery by releasing catecholamines from nerve terminals; direct action of Na+,K(+)-ATPase inhibitors on smooth muscle appears to occur only with very high doses.

Anticancer gelatin microspheres with multiple functions

Biodegradable, hydrophilic gelatin microspheres (GM) with an average diameter of 70 microns were prepared by cross-linking gelatin with glutaraldehyde for hepatic intra-arterial infusion. An anticancer agent, mitomycin C (MMC), together with a radioisotope, 131I, were bound to the GM for chemotherapy and local internal radiotherapy. The 131I-labelled MMC-GM (131I-MMC-GM) could accumulate in the specific site and embolize the hepatic arteries after the hepatic intra-arterial infusion, while it caused various effects to the liver cells. The 131I-MMC-GM remained within the hepatic arteries for at least one month. In vitro release of drugs from the GM was also quantified using a dynamic dialysis method.

Tumour-associated antigens of mammary carcinomas recognized by human monoclonal antibody 1G12

We have reported the production of human monoclonal antibodies (mAb), by the fusion of lymph node lymphocytes from a primary carcinoma patient with murine myeloma cells. Seven heterohybridomas showed reactivity with class III antigens, and five hybridomas (1G12, 2D4, 4H5, 5D10 and 3B10) were reactive with class II antigens. One of these human mAbs (1G12) was intensively studied and results are presented here. 1G12 reacted strongly and specifically with five mammary carcinoma cell lines and showed no cross-reactivity with seven normal fibroblast cells. It continuously produced human mAbs (IgM) at a rate of 4.5-12.5 micrograms/ml over a period of 2 years. Human mAb 1G12 (IgM) was purified by either a combination of anion-exchange chromatography (ABx) and gel filtration (Superose 6) or affinity chromatography (agarose). Immunohistological analysis of frozen tissue sections was performed with biotinylated 1G12. All mammary carcinomas analysed (n = 26) were positive, while the connective tissue of 36 different patients was completely negative with 1G12. In normal breast, endometrium and intestine only a weak or moderate staining of the epithelial cells was observed. Normal oesophagus, small bowel, cervix, uterus, lung and skin were completely negative. Partly purified tumour antigen recognized by 1G12 had a molecular mass of 1-2 MDa and showed strong binding with Ulex europaeus lectin I and Bauhina purpurea agglutinin, indicative for the glucoprotein nature of antigens. These results show that human mAb 1G12 may be useful for the analysis of tumour-associated antigen of mammary carcinoma patients. In further studies the therapeutic and diagnostic application of 1G12 should be analysed in more detail.

Characterization of the depressor effect of intrathecal endothelin in anesthetized rats

Intrathecal administration of 1-100 pmol endothelin-1 in urethan-anesthetized rats elicited a dose-dependent decrease in arterial pressure and a modest bradycardia. The depressor response was associated with a sustained hindquarters vasodilation and a modest transient mesenteric vasoconstriction, indicating disparate effects on regional vascular resistance. In contrast, renal sympathetic nerve activity was unaffected except at the highest dose of endothelin-1 (100 pmol). The depressor effect of intrathecal endothelin is unlikely to be due to spinal ischemia produced by vasoconstriction, since a much greater dose of endothelin was needed to produce an increase in spinal vascular resistance compared with the dose necessary to produce hindquarters vasodilation and the depressor effect. Unlike intravenous administration, intrathecal endothelin-1 and endothelin-3 produced indistinguishable effects on arterial pressure, heart rate, renal sympathetic nerve activity, spinal blood flow, and spinal vascular resistance, suggesting that the spinal neuronal endothelin receptors may be less selective than those in the blood vessels. The centrally mediated depressor effect and the selective regional hemodynamic actions of intrathecal endothelin suggest a role of spinal endothelin in regulating cardiovascular function.