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J W Blankenship

Publications and source records attributed to J W Blankenship.

18 recordsLinked to original sources
PubMed2000

A mechanism of vasodilatory action of polyamines and acetylpolyamines: possible involvement of their Ca2+ antagonistic properties.

Polyamines, a class of low-molecular weight organic polycations, have been shown to produce relaxing effects in vascular smooth muscles, although the mechanism has not been carefully examined. In this study, the mechanism of vascular action of polyamines and their metabolites, acetylpolyamines, was pharmacologically examined in the rabbit isolated thoracic aorta focusing on an endothelium-dependent component of vasodilatation and Ca2+ influx through plasma membrane channels. Both polyamines and acetylpolyamines (except N1-acetylputrescine, which produced no response or very slight contraction) caused concentration-dependent relaxation in preconstricted aortic rings containing an intact endothelium. Aortic rings denuded of endothelium were also responsive to both polyamines and acetylpolyamines. Inhibitors of nitric oxide (reduced haemoglobin and Nomega-nitro-L-arginine methyl ester), vasodilator prostaglandins (indomethacin) and guanylyl cyclase (methylene blue) did not affect the relaxation induced by both polyamines and acetylpolyamines in either endothelium-intact or -denuded aortic rings. Both polyamines and acetylpolyamines inhibited the concentration-dependent contraction for phenylephrine and K+. The Ca2+ agonist Bay K 8644 induced concentration-dependent contraction in segments of rabbit aorta partially depolarized with 15 mM KCl, and both polyamines and acetylpolyamines relaxed the Bay K 8644-induced contraction in a concentration-dependent manner. Interestingly, both polyamines and acetylpolyamines also decreased contractions evoked by the Ca2+ ionophore A23187. The concentration-response curve to exogenous Ca2+ in K+-depolarization medium (K+ = 120 mM) was shifted to the right by both polyamines and acetylpolyamines. The response elicited by Ca2+ was increased by Bay K 8644 (10(-6) M), and this potentiation was also inhibited by both polyamines and acetylpolyamines. The results indicate that both polyamines and acetylpolyamines can induce vasorelaxation of rabbit thoracic aorta by an endothelium-independent mechanism in-vitro and relax vascular smooth muscle by acting at the plasma membrane level, decreasing the influx of Ca2+. Therefore, polyamines and acetylpolyamines may have Ca2+ antagonistic properties which may, in part, be involved in the mechanism of rabbit aortic vascular smooth muscle relaxation.

Acetylation↗
PubMed1993

Quantitation of lung elastin and collagen in protein and essential fatty acid malnourished rats.

Thirty-nine 40-day old male Sprague-Dawley rats (average wt. 115g) were divided into 4 groups and fed diets A, control; B, essential fatty acid (EFA) deficient; C, protein deficient; D, combined protein and EFA deficient. At the end of 5 weeks, lungs were removed from the animals for collagen and elastin quantitation and for morphometric measurements. The collagen content of the lungs which ranged from 95-100 micrograms/mg dried fat-free (D.F.F.) tissue, was not altered by protein or EFA deficiencies. The elastin content of lungs was markedly increased in diets C and D while the cross-linking (Isodesmosine-desmosine content) expressed as residues per 1,000 (R/1000) was not different in the four groups. The elastin content of lungs from group D animals was greater than group C suggesting an additive effect from the EFA deficiency in diet D. The morphometric measurements indicated no change in alveolar linear diameter (Lm) while the total alveolar surface area (ISAA1V) was decreased by the deficient diets C and D. The protein deficiency and the combined protein and EFA deficiencies produced an increased elastin content in lung. Elastin cross-linking and collagen quantity was not affected by the dietary treatments. The morphometric measurements indicated that protein deficiency in these animals did not produce structural changes in the lungs as indicated by alveolar dimensions.

Animals↗
PubMed1992

Inhibition of N8-acetylspermidine deacetylase by active-site-directed metal coordinating inhibitors.

A number of substrate analogues of N8-acetylspermidine (N8-AcSpd) (16) and chemical modifying agents containing metal coordinating ligands were assayed as inhibitors of the cytoplasmic enzyme N8-AcSpd deacetylase from rat liver. The enzyme is inhibited by metal chelators, several omega-amino-substituted carboxylic acids, and some thiol reagents. Inhibition by diisopropyl fluorophosphate was observed only at high concentrations. These results suggest that the catalytic mechanism of the enzyme requires a transition state metal and free sulfhydryl groups for activity. The most potent inhibitor synthesized 6-[(3-aminopropyl)amino]-N-hydroxyhexanamide (15), has an apparent Ki of 0.001 microM. It binds to the target enzyme 11,000 times tighter than the substrate (apparent Km = 11 microM). These compounds and a previously reported series of compounds (Dredar, S. A.; Blankenship, J. W.; Marchant, P. E.; Manneh, V. A.; Fries, D. S. J. Med. Chem. 1989, 32, 984-989) are useful in mapping the active site and determining the physiological function of N8-AcSpd deacetylase.

Amidohydrolases↗
PubMed1991

Oxysterol incorporation into rat aorta resulting in elastin compositional changes.

The incorporation of dietary cholestan-3 beta,5 alpha,6 beta-triol (triol) into rat thoracic aortic tissue and changes in amino acid composition of the elastin were investigated to identify the cytotoxic properties of the triol. Weanling male Sprague-Dawley rats were fed the following diets for three months: (i) normal chow, (ii) normal chow with 1% (w/w) cholesterol added, or (iii) normal chow with 0.9% (w/w) cholesterol and 0.1% (w/w) triol added. Triol levels in the blood and in the thoracic aortic tissue were measured. Compositional changes of elastin were also determined. After three months on the triol-containing diet, triol was found in the thoracic aorta but was not detected in the blood. Amino acid analyses of the aortic tissue elastin revealed that the proline levels in the triol-fed animals were significantly greater than in the other two diet groups, while the elastin levels of leucine, aspartate, arginine, and phenylalanine decreased significantly. The mechanism for these observed changes induced by triol may reflect alternate splicing of elastin messenger ribonucleic acid (mRNA) resulting in structual changes in the elastin molecule. Dietary triol does contribute to tissue triol content and is associated with aortic elastin compositional changes. How these changes may contribute to the development of cardiovascular disease is not known.

Amino Acid Sequence↗
PubMed1991

Modification of the pulmonary connective tissue developmental response in the neonatal rat by ciclosporin.

Neonatal rat pups were treated either with ciclosporin at 10 mg/kg/day dissolved in olive oil (experimental) or with pure olive oil (control). Lung protein biosynthesis was evaluated in a protocol which involved the measurement of total accumulated protein, collagen and elastin. Four time points were studied in the first 21 days of life, 12 animals contributing to each point (6 control and 6 ciclosporin). Ciclosporin levels in the treated group ranged widely (2,000-4,000 ng/ml). There were significant differences in total body weight and lung weight in treated vs. controls during and after the first week. DNA contents per unit wet weight varied significantly during the second week of life, indicating increased cellularity of the ciclosporin-treated animals. Associated with this was an increase in the lung protein/DNA ratio as well as the elastin/DNA ratio in the control animals, but not in the treated ones. The lung collagen/DNA ratio was not as dramatically affected by the ciclosporin treatment. However, the collagen content per unit wet weight of lung tissue was increased in the ciclosporin-treated animals at 15 days of life. We conclude that ciclosporin has a marked effect on lung connective tissue metabolism in early life, the long-term effects of which are unappreciated and undocumented but may well be of vital importance in the lungs of long-surviving organ transplant patients.

Animals↗
PubMed1990

Quantitation of elastin in tissues and culture: problems related to the accurate measurement of small amounts of elastin with special emphasis on the rat.

Both rat and sheep elastin can be quantified by measurement of discrete peptides released from the insoluble protein by thermolysin digestion. These peptides are easily visualized and measured by HPLC. With the sheep the tallest peak on the chromatogram represents the VGVPG pentapeptide derived from a repeating sequence seen in elastin from many species. This repeating sequence allows for amplification of the signal significantly above background so that accurate quantitation can be carried out. The measurement is reproducible over a wide range of protein concentrations. With the rat however the pentapeptide is not present but appears to be replaced by other repeating sequences. We quantitated and determined amino acid sequence on 8 peaks present in the early portion of the chromatogram for purposes of quantifying rat elastin. That signal most reliably present over a range of concentrations was tyrosyl-glycine (YG) which eluted at 8.5 minutes. We have used YG as a basis for quantitation of rat elastin both from tissues and tissue culture. We have also shown that the desmosine crosslinks are not constant in elastin produced in a neonatal rat smooth muscle culture system but vary with the age of the culture. We thus propose that an index of maturation be considered for a given elastin in the form of mumoles of crosslink per gram of elastin so as to better define its quality.

Amino Acid Sequence↗
PubMed1989

Uniqueness of dietary olive oil in stimulating aortic prostacyclin production in post-weanling rats.

Groups of weanling Sprague-Dawley rats developed from conception through gestation, and weanling periods on a formulated diet fed to the dams were continued on the same diet until sacrificed at 30 days of age. The diet groups consisted of control (5% corn oil, w/w) and experimental (15%, w/w) olive, safflower (hi-oleic and hi-linoleic), soy oil, and lard. The object of the study was to identify the effect of high and low fat content and differing proportions of polyunsaturated:saturated (P:S) and mono:polyunsaturated (M:P) fatty acids on arachidonate stimulated aortic prostacyclin (PGI2) production (measured as 6-keto-PGF1 alpha). Neither the amounts of dietary fat or wide ranging P:S or M:P fatty acid ratio levels (P:S or M:P) affected PGI2 production. PGI2 production was, however, markedly enhanced (2x) in aortic segments from rats raised on diets containing olive oil. The unique stimulation of aortic PGI2 production by the olive oil diet suggests an effect of the extraordinarily high M:P fatty acid ratio or, alternatively, of a still-to-be identified substance(s) in this ancient food.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Design and synthesis of inhibitors of N8-acetylspermidine deacetylase.

Analogues of N8-acetylspermidine (1) were synthesized as potential inhibitors of the cytoplasmic enzyme N8-acetylspermidine deacetylase. The compounds were assayed for their ability to inhibit the deacetylation of 1 in a cytosolic fraction from rat liver. The apparent Ki values were determined by Dixon plots. The apparent Km of 1 for this enzyme is 11.0 microM. It was found that compounds which lacked the N1 or the N4 of spermidine were less effective at competing for the enzyme than the substrate. All compounds with acyl substituents larger than acetyl were less potent inhibitors than the corresponding acetylated derivatives. Thus, the enzyme's selectivity as a deacetylase seems to be attributable to steric hindrance which occurs with larger acyl groups. The N8 of the substrate is not essential for its binding to the enzyme. Replacement of N8 with a CH2 group gives the ketone 14, which has an apparent Ki of 0.18 microM, 60-fold lower than the apparent Km of 1. The inhibitory potency of 14 is retained in compounds substituted at the N1 position. The N1,N1-dimethyl and the N1,N1-diethyl analogues (15 and 16) of 14 have apparent Ki values of 0.096 and 0.10 microM, respectively. These agents are the most potent inhibitors of N8-acetylspermidine deacetylase reported, and they are promising tools for use in determining the physiological function of N8-acetylspermidine deacetylation.

Amidohydrolases↗
PubMed1987

Polyamines and acetylpolyamines increase the stability and alter the conformation of nucleosome core particles.

The interactions of spermine (4+ charge at physiological pH), N1-acetylspermine(3+), spermidine(3+), N1- and N8-acetylsperimidine(2+), putrescine(2+), hexaamminecobalt(3+), and magnesium(2+) with nucleosome core particles have been examined by using thermal denaturation and circular dichroism. Tetra- and triamines were 2-3 times more effective than diamines at stabilizing core particles against thermal denaturation. Secondary effects were also observed, with acetylpolyamines slightly less effective than unmodified polyamines of equivalent charge. Hexaamminecobalt(3+) was less effective than the triamines, while magnesium had essentially no effect. This is surprising since magnesium is more effective than diamines at stabilizing naked DNA. All the cations tested altered the circular dichroism spectra of the core particles in the DNA region (284 nm). The peak at 284 nm was suppressed by tetra- and trivalent compounds to approximately twice the extent of divalent compounds. Magnesium appears to suppress the peak by a lesser extent than the diamines. This indicates that the DNA twist and/or folding is changed by these cations. A plateau of both thermal denaturation and circular dichroism effects was observed at cation concentrations where 30-40% of the total DNA negative charges could be neutralized by the added cations. We suggest that polyamine and histone acetylation function in concert to lower the stability and change the conformation of the nucleosome core, thus facilitating replication and transcription in vivo.

Animals↗
PubMed1987

Thermal denaturation of mononucleosomes in the presence of spermine, spermidine, N1-acetylspermidine, N8-acetylspermidine or putrescine: implications for chromosome structure.

Putrescine (a diamine) raises the thermal denaturation temperature of mononucleosomes but produces only minor changes in the overall shape of the thermal denaturation curve. This is similar to the effect of sodium ions and is consistent with nonspecific binding to the DNA of the nucleosome. At very low levels of spermidine or spermine the same simple rise in thermal denaturation temperature is seen but at higher levels (above 1 microM for total spermidine concentration) the thermal denaturation curve becomes substantially sharper and the premelt region of the curve diminishes in area. The acetylspermidines display intermediate effects. The change in shape of the thermal denaturation curve was resolved into components (R1 and R2) due to mononucleosomes in their original conformation plus a component (T) induced by the presence of spermidine or spermine. The proportion of component T was substantially reduced with acetylspermidine, compared to equivalent concentrations of spermidine. Hence, we suggest that spermidine acetylation in vivo has the potential to partially destabilise the nucleosome structure, possibly in coordination with histone acetylation.

Acetylation↗
PubMed1987

Running endurance in 27-h-fasted humans.

Nine male marathon runners were exercised to exhaustion to determine the effects of a 27-h fast on endurance performance. Each subject completed two exercise tests at the same treadmill speed (set at 70% maximal O2 uptake), one following a 27-h fast and one 3 h after a preexercise meal, in random order. Fasting caused a 44.7 +/- 5.8% (SE) decrease in endurance performance (P less than 0.01). Blood, muscle, psychological, and ventilatory data were examined to determine the cause of the decreased performance. Fasting caused significant increases in O2 uptake (9.3 +/- 2.0%), heart rate (8.4 +/- 2.4%), and rating of perceived exertion, ventilation, and psychological fatigue, evident within the first 60 min of exercise. There were no differences in plasma glucose or epinephrine levels. Muscle glycogen degraded at the same rate (0.482 +/- 0.146 vs. 0.470 +/- 0.281 mumol.g-1.min-1 in the nonfasted and fasted tests, respectively) despite lower respiratory exchange ratio and elevated free fatty acid levels, which may partially explain the elevated O2 uptake. Lactate, insulin, and norepinephrine were all increased in the fasted test (P less than 0.05). The increase in norepinephrine (r = 0.79, P less than 0.01), the diameter of type I muscle fibers (r = 0.70, P less than 0.05), and ending insulin levels (r = -0.88, P less than 0.01) were correlated with endurance time in the fasted state. Fatigue in endurance running for 27-h fasted humans appears to be related to a combination of physiological, psychological, metabolic, and hormonal changes.

Adult↗
PubMed1986

Association constants for the interaction of double-stranded and single-stranded DNA with spermine, spermidine, putrescine, diaminopropane, N1- and N8-acetylspermidine, and magnesium: determination from analysis of the broadening of thermal denaturation curves.

The effect of Mg2+, putrescine, diaminopropane, N1-acetylspermidine, N8-acetylspermidine, spermidine, and spermine on the thermal denaturation of calf thymus DNA was investigated. As in a previous study with magnesium [W.F. Dove and N. Davidson, (1962) J. Mol. Biol. 5, 467-478], these ligands were found to raise the thermal denaturation temperature of the DNA and to broaden the thermal denaturation curve dramatically at the point where 10 to 20% of the DNA charge had been neutralized. At higher levels of charge neutralization the curves became sharper again. This behavior was due to differential binding of the ligands to single- and double-stranded DNA. The broadening was used to determine the ratio of the association constants of each ligand to the two forms of DNA using either an independent sites model of binding or an excluded sites model. The results show that the primary mode of binding of the ligands to DNA is electrostatic but that important secondary, nonelectrostatic, effects are also present.

Animals↗
PubMed1986

Dietary fat and cholesterol modification of rat abdominal aorta prostacyclin and leukotriene production (in vitro).

Groups of weanling male Sprague-Dawley rats fed formulated diets containing 15% by weight of corn oil (CO), linseed oil (LNO), or corn oil plus 1% cholesterol and 0.25% cholic acid (CH-CH) were sacrificed after 8 weeks and the aortas removed. Three mm length cross-sectional rings were cut from the distal abdominal aorta segment and incubated in either Tris buffer (pH 7.4, 37 degrees, 10 min.) for measurements of prostacyclin as 6-Keto-prostaglandin in F1 alpha (6-Keto-PGF1 alpha) or Tris buffer plus 10 microM ionophore A23187 for measurement of leukotriene C4 (LTC4) production using radioimmunoassay (RIA) procedures. 6-Keto-PGF1 alpha production was greater (p less than 0.01) in the CO than in the LNO and CH-CH fed rats by 54% and 40% respectively. LNO diets significantly lowered LTC4 production when compared to tissues from CO-fed rats (p less than 0.05). LTC4 production by tissues from the CH-CH-fed animals was lower than tissues from CO-fed animals, however, the difference failed to reach levels of significance because of data spread and the number of tissues. Tissues from the CH-CH-fed and LNO-fed rats were significantly different than those of the CO since LTC4 formation was high relative to 6-Keto-PGF1 alpha production (LTC4/6-Keto-PGF1 alpha). These results suggest distinctive effects of dietary fat and cholesterol on the syntheses of vasoactive eicosanoids that may be relevant to arterial tissue physiology and pathology.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Prostaglandin synthetase inhibition by alkaloids of Heimia salicifolia.

Two alkaloids from Heimia salicifolia, cryogenine and nesodine, were respectively 2.48 and 2.24 times as potent as aspirin as inhibitors of prostaglandin synthetase prepared from bovine seminal vesicles. Reference compounds, indomethacin and phenylbutazone, were respectively 2800 and 8.75 times as potent while a synthetic analogue of cryogenine, JB-1-0, was 0.656 times the potency of aspirin. This activity may help to explain the traditional medicine use of H. salicifolia in the Americas.

Alkaloids↗
PubMed1985

Short term effect of a low fat diet on plasma retinol and alpha-tocopherol and red cell alpha-tocopherol levels in hyperlipidemic men.

The effect of a low fat, low cholesterol diet on plasma alpha-tocopherol and retinol and erythrocyte alpha-tocopherol levels was studied in fourteen hyperlipidemic men for a period of 28 days. Plasma alpha-tocopherol decreased with decreasing plasma cholesterol levels while the ratio of plasma alpha-tocopherol to cholesterol remained constant. There was a tendency for plasma retinol levels to decrease but the change was not significant. As plasma alpha-tocopherol levels decreased there was a consistent and significant increase in alpha-tocopherol content of red cells (p less than 0.001). These findings indicate that fat soluble vitamin status is maintained with low fat diets during a short time period.

Adult↗
PubMed1981

Effect of microwave heating of soybeans on protein quality.

The purpose of this study was to determine the protein quality of microwave cooked soybeans by the rat growth and protein efficiency ratio method (PER). It was found that properly cooked, dry, hulled, whole soybean seeds had a PER of 2.4 +/- .06 (mean +/- standard error) and a mean weekly weight gain of 21.2 +/- 1.1 which were equivalent to 2.53 +/- .10 and 18.3 +/- 1.0 g for casein, respectively. These data demonstrate the value of microwave cooked soybeans and suggest further research on the possible economical and biological advantages of microwave cooked soybeans.

Animals↗