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Biomedical subjects

H Hughes

Publications and source records attributed to H Hughes.

At least 37 records · Page 2Linked to original sources
PubMed1995

The effect of lipid peroxides on isolated human umbilical artery contraction.

OBJECTIVE: Our purpose was to determine the effect of oxidized lipids on the contractile activity of isolated human umbilical arteries. STUDY DESIGN: Umbilical artery rings were prepared for isometric tension recording and exposed to cumulative concentrations of oxidized and nonoxidized lipid and control solutions. Rings were also incubated with the lipid or control solutions and then contracted with cumulative concentrations of U46619. A final set of rings in Ca(++)-free depolarized solution was incubated with the agents above, and then the Ca++ concentration was increased cumulatively. RESULTS: The lipids had no direct contractile effect. Both lipids inhibited the response to U46619 and Ca++, with the oxidized lipids having the most significant effect. CONCLUSION: Oxidized lipids lack a direct contractile effect on isolated human umbilical arteries and inhibit the contractile response to thromboxane and calcium.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

Toxicity of oxidized low density lipoproteins for vascular smooth muscle cells and partial protection by antioxidants.

Oxidized low density lipoprotein (oxLDL) is known to be toxic to a variety of cell types, but relatively little is known about the toxic effects of oxLDL on vascular smooth muscle cells (SMC). We found that LDL oxidized by incubation with 5 microM cupric ions was toxic to cultured porcine SMC when administered at concentrations of 25 micrograms protein/ml and higher. The toxicity was demonstrated whether cells were proliferating or not, and was more evident in the presence of 0.4% lipoprotein-deficient serum than in 10%. Because of recent evidence that 7-ketocholesterol and 7-hydroxycholesterol are toxic species in copper-oxidized LDL, inhibition of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase was hypothesized as a mechanism of toxicity. However, mevalonic acid, the product of this enzyme, failed to protect against the toxicity of either oxLDL or the pure oxysterols. Alpha-tocopherol, alpha-tocopherol acetate, probucol, butylated hydroxytoluene, and deferoxamine provided partial protection to SMC exposed to oxLDL. These results suggested a toxic role for newly initiated lipid peroxidation, either in cells or in media oxLDL. Cellular lipid peroxidation appeared more likely, since no further oxidation of media oxLDL was demonstrated in the presence or absence of antioxidants. Overall, the results suggest that toxicity of copper-oxidized LDL for SMC is multifactorial and differs from the previously described toxicity of iron-oxidized LDL for fibroblasts.

Animals↗
PubMed1995

NMR study of whole rat bile: the biliary excretion of cefoperazone and benzyl chloride by an isolated perfused rat liver.

1H NMR spectroscopy at 400 MHz has been applied to the analysis of whole bile samples produced by the isolated perfused rat liver. Using relatively simple NMR experiments biliary excretory products of cefoperazone and benzyl chloride were identified as cefoperazone itself and a benzyl-glutathione conjugate, respectively. Our use of 13C isotopic labelling demonstrates how 1H/13C heteronuclear NMR techniques can be used to produce uncrowded and informative spectra from whole bile. From the use of a HMQC-COSY experiment the structure of a benzyl-glutathione conjugate contained in whole bile was confirmed.

Animals↗
PubMed1995

NMR study of whole rat bile: the biliary excretion of 4-cyano-N,N-dimethyl aniline by an isolated perfused rat liver and a liver in situ.

The structure of two biliary metabolites of 4-cyano-N,N-dimethyl aniline (CDA) contained in whole rat bile have been studied in detail by NMR at 400 MHz. A 4-cyano-N-methyl glutathione-N-aniline conjugate was identified as a biliary metabolite of CDA using relatively simple 1H NMR techniques. Isotopically 13C labelled CDA was used to generate 13C labelled xenobiotic conjugates. Our use of 1H/13C heteronuclear NMR techniques, in particular a 13C-selective HMQC-TOCSY experiment, allowed a N-beta-glucuronide conjugate, a previously unknown biliary metabolite of CDA, to be identified. Bile samples obtained from both the isolated perfused rat liver and the rat liver in situ were analysed.

Aniline Compounds↗
PubMed1995

Potentiation of the hyporeactivity induced by in vivo endothelial injury in the rat carotid artery by chronic treatment with fish oil.

1. The present study investigates whether or not chronic feeding of rats with a diet enriched in fish oil affects the reactivity of balloon-injured carotid arteries. The left carotid arteries were injured in vivo by the repeated passage of a balloon catheter. Both the right (control artery) and the left carotid arteries were excised 24 h after the injury, and suspended in organ chambers for the measurement of changes in isometric tension in the presence of indomethacin. 2. Phenylephrine evoked similar concentration-contraction curves in the right (control) carotid arteries without endothelium from control and fish oil-fed rats. Balloon injury decreased the contractility of carotid arteries to phenylephrine in both types of rats and the pEC50 for phenylephrine was significantly decreased in balloon-injured arteries from control rats compared to those obtained in arteries from fish oil-fed rats (pEC50 7.59 +/- 0.1 and 7.28 +/- 0.06, respectively) while maximal contractions were similar (1.93 +/- 0.15 g and 1.79 +/- 0.12 g, respectively). 3. The treatment of control right carotid arteries without endothelium with either NG-nitro-L-arginine (an inhibitor of nitric oxide synthase) or superoxide dismutase (which protects nitric oxide from degradation) did not affect significantly the contractions to phenylephrine in either group. In these preparations, methylene blue (an inhibitor of soluble guanylate cyclase) decreased slightly but significantly maximal contractions to phenylephrine in both groups. The treatment of balloon-injured carotid arteries with NG-nitro-L-arginine or methylene blue partly restored contractions to phenylephrine in arteries from both types of rat. Superoxide dismutase further depressed the contractility to the alpha l-adrenoceptor agonist in balloon-injured arteries from control diet-fed rats but had no effect in balloon-injured preparations from fish oil-fed rats.4. 3-Morpholino-sydnonimine (SIN-1, a donor of nitric oxide) evoked similar concentration-dependent relaxations in control and balloon-injured carotid arteries from both types of rat.5. Balloon injury caused an increase in the tissue content of cyclic GMP in carotid arteries from control diet-fed rats. This production of cyclic GMP was abolished by N0-nitro-L-arginine. Superoxide dismutase potentiated significantly the production of cyclic GMP caused by balloon injury in control but not in fish oil-fed rats.6 These observations confirm that in vivo balloon injury causes the production of nitric oxide in the injured blood vessel wall. This production of nitric oxide from L-arginine accounts for the decreased contractility to phenylephrine and the accumulation of cyclic GMP in balloon-injured arteries. They further indicate that chronic feeding of rats with fish oil potentiates the L-arginine-nitric oxide pathway in the injured vessel leading to an enhanced hyporeactivity to phenylephrine.

Analysis of Variance↗
PubMed1995

Endothelium-dependent contractions are associated with both augmented expression of prostaglandin H synthase-1 and hypersensitivity to prostaglandin H2 in the SHR aorta.

Prostaglandin H2 (PGH2 [endoperoxide]) is an immediate product of prostaglandin H (PGH) synthase activity (cyclooxygenase) and a likely candidate to mediate endothelium-dependent contractions evoked by acetylcholine in the aorta of the spontaneously hypertensive rat (SHR). Experiments were designed to investigate whether or not endothelium-dependent contractions were associated with an increased expression of PGH synthase, an augmented acetylcholine-induced release of PGH2, and/or a hypersensitivity of the smooth muscle to endoperoxides in SHR aorta compared with normotensive Wistar-Kyoto (WKY) aorta. In SHR aorta, endothelium-dependent contractions to acetylcholine were abolished by tenidap (10(-8) mol/L), a preferential PGH synthase-1 inhibitor, but slightly impaired by NS-398 (10(-6) mol/L), a preferential PGH synthase-2 inhibitor. PGH synthase-1 expression, which was evaluated by both reverse transcriptase-polymerase chain reaction and Western blotting, was about twofold greater in preparations with endothelium from SHR than from WKY rats. There was no difference in PGH synthase-1 expression between preparations with and those without endothelium in both strains. In SHR but not WKY aortas, acetylcholine (10(-5) mol/L, 5 minutes) caused a significant endothelium-dependent release of PGH2 as measured by gas chromatography/mass spectrometry. PGH2 evoked more potent contractions in rings without endothelium from SHR than from WKY rats, whereas the thromboxane analogue U46619 and prostaglandin F2 alpha caused a comparable response in both preparations. These results show that endothelium-dependent contractions to acetylcholine in SHR aorta are associated with a greater expression of PGH synthase-1, a significant release of PGH2, and a hypersensitivity of the smooth muscle to the endoperoxide.

Acetylcholine↗
PubMed1994

PAF formation by H2O2-stimulated perfused canine carotid arteries.

Perfusion of noncytotoxic concentrations of hydrogen peroxide (H2O2) through canine carotid arteries potentiates neutrophil adhesion to vessel endothelium. Platelet-activating factor (PAF) receptor antagonists block neutrophil adhesion to vessels pretreated with low millimolar concentrations of H2O2. We have used a specific gas chromatographic-mass spectrometric (GC-MS) assay for PAF and applied this to studies of canine carotid arteries perfused with H2O2. Vessels perfused with 1 and 10 mM H2O2 for 20 min produced PAF in a dose-dependent manner, 331 +/- 67 pg/g tissue with 1 mM H2O2 and 1160 +/- 194 pg/g with 10 mM. Vessels that had been denuded of endothelium with a balloon catheter prior to H2O2 perfusion produced similar quantities of PAF in response to H2O2 (220 +/- 72 pg/g and 960 +/- 210 pg/g with 1 and 10 mM, respectively). Cultured canine jugular venous endothelial cells produced PAF in response to 10 mM H2O2 (809 +/- 117 pg/10(7) cells) but carotid arterial smooth muscle cells did not. These results suggest that vascular cells other than endothelial cells may produce PAF following H2O2 perfusion of canine carotid arteries.

Animals↗
PubMed1994

Cytotoxicity of oxidized LDL to porcine aortic smooth muscle cells is associated with the oxysterols 7-ketocholesterol and 7-hydroxycholesterol.

The cytotoxicity of oxidized low-density lipoprotein (Ox-LDL) to arterial smooth muscle cells (SMCs) may contribute to atherogenesis by causing cell death in core regions of plaques. The aim of the present study was to identify the components of copper-oxidized LDL responsible for its toxicity to porcine aortic SMCs. Toxicity to SMCs was assessed as the decrease in viable cell counts after 3-day cell incubation. Extracts of LDL were tested for toxicity at concentrations equivalent to that derived from 100 micrograms LDL protein per milliliter. Lipid extracts of Ox-LDL but not native-LDL were toxic to SMCs. When separated into neutral and polar lipid classes, only the neutral lipids were toxic (89.7 +/- 0.7% cell loss). The neutral lipids were fractionated further by use of solid-phase extraction and high-performance liquid chromatography (HPLC). Two toxic fractions, causing 93.3% and 60.3% cell loss, were isolated from HPLC and analyzed by gas chromatography/mass spectrometry. The most toxic of these fractions contained 7-ketocholesterol, and the other contained 7 alpha- and 7 beta-hydroxycholesterol. Quantification of these unesterified oxysterols in LDL extracts and comparison with the toxicity of authentic standards indicate that 7-ketocholesterol and 7-hydroxycholesterol are present in Ox-LDL at levels sufficient to account for its toxicity to SMCs.

Animals↗
PubMed1994

Chemical assay of glutaraldehyde incorporation into pericardial tissue.

This paper describes the development of a chemical assay to determine the incorporation of glutaraldehyde into pericardial tissue. The procedure is based upon the hydrolysis of the Schiff's bases formed between the glutaraldehyde and the E-amino groups of lysine, the liberated glutaraldehyde being determined as its 2,4-dinitrophenyl-hydrazone by high performance liquid chromatography (HPLC). The HPLC system uses a reverse phase column eluted with a gradient of aqueous acetonitrile (from 60%-70% over 30 minutes). The glutaraldehyde 2,4-dinitrophenylhydrazone is detected at 356 nm. The results show that the assay has sufficient sensitivity (minimum detectable limit 20 pmol of glutaraldehyde 2,4-dinitrophenyl-hydrazone) and reproducibility (+/- 9% at 100 pmol +/- 4% at 1 nmol) to estimate glutaraldehyde incorporation into pericardial tissue. A series of subsequent experiments have documented that temperature and buffer pH are the main determinants affecting glutaraldehyde incorporation into pericardial tissue. Immersion of pericardial tissue in glutaraldehyde solution of pH 9 and 37 degrees C yields an approximately six times greater incorporation than can be achieved if the reaction is performed at 0 degrees C. Further study is underway to relate the amount of Schiff's base bound to that of total incorporated glutaraldehyde.

Animals↗
PubMed1994

Glutaraldehyde, gamma-carboxyglutamic acid and calcium in explanted bioprosthetic heart valves.

This paper describes the determination of glutaraldehyde, gamma-carboxylglutamic acid (gamma-CGA) and calcium concentrations in nine bioprosthetic heart valves after explantation. The glutaraldehyde and gamma-CGA were determined by high performance liquid chromatography (HPLC) procedures and the calcium by atomic absorption spectrometry. Glutaraldehyde was detectable in only two of these valves at levels of 17% and 2% of that present in an unimplanted valve. The results indicate that there is no correlation between gamma-CGA and calcium deposition, indicating that the gamma-CGA is probably absorbed onto the forming calcium deposit from the circulation and does not contribute to the calcification process, and that the acid hydrolysable glutaraldehyde decreases with time during implantation. There is, however, no correlation between the duration of implantation and the decrease in glutaraldehyde concentration.

1-Carboxyglutamic Acid↗
PubMed1993

Lack of variation in the nucleotide sequence corresponding to the transmembrane domain of the beta-amyloid precursor protein in Alzheimer's disease.

The nucleotide sequence corresponding to the APP transmembrane domain and flanking regions of charged amino acids was determined for 91 patients with histologically confirmed Alzheimer's disease, 9 patients with dementias of other etiologies, and 14 controls who had no identifiable brain disease. Twenty-eight of the AD patients had a first-degree relative with dementia. No mutations were detected among the 100 demented patients. However, one of the 14 controls exhibited a change in the 3' base of codon 716 which would not be expected to result in an amino acid substitution at this position.

Alzheimer Disease↗
PubMed1993

Effects of S9977 on adrenergic neurotransmission.

1. Experiments were designed to determine whether or not the putative promnesic drug S9977 (1,3,7-trimethyl 8-[3-(4-diethylaminocarbonyl-1-piperazinyl) 1-propyl]-3,7-dihydro (1H)2,6-purinedione hydrochloride) affects peripheral adrenergic neurotransmission. 2. Rings of canine saphenous veins (without endothelium) were suspended for isometric tension recording in conventional organ chambers filled with modified Krebs-Ringer bicarbonate solution. The adrenergic nerve endings were activated with electrical impulses (9 V, 2 msec, 0.25-8 Hz). 3. At 10(-5) M, S9977 significantly reduced the contraction to 0.25, 0.5 and 1 Hz. The compound did not affect the response to higher stimulation frequencies or to exogenous noradrenaline. The inhibitory effect of S9977 was prevented by methiothepin, and not affected by atropine or 8-phenyltheophylline. 4. Helical strips of canine saphenous veins were incubated with [3H]noradrenaline and suspended for superfusion and isometric tension recording. Under basal conditions, S9977 (10(-4) M) augmented, the total 3H-overflow which was due mainly to an augmented overflow of [3H]deoxyphenylglycol (DOPEG); the extraneuronal metabolites 3,4-dihydromandelic acid (DOMA) and 3-methoxy-4-hydroxymandelic acid (VMA) were reduced. 5. During electrical stimulation of the adrenergic nerves, S9977 (10(-4) M) augmented the total 3H-overflow but reduced the contractile response; the evoked overflow of [3H]noradrenaline was not significantly affected. 6. These experiments suggest that S9977 causes the displacement of noradrenaline from the adrenergic varicosities; most of the displaced transmitter is metabolized by intraneuronal monoamine oxidase before reaching the junctional cleft. In addition, S9977 exerts an inhibitory effect on the extraneuronal metabolism of catecholamines. S9977 does not inhibit the exocytotic release of the adrenergic neurotransmitter.

Analgesics↗
PubMed1993

Two cases of coloboma associated with unbalanced translocations.

Two cases of coloboma are recorded, both secondary to previously unreported unbalanced translocations. These cases underline the association of chromosomal abnormalities and coloboma, particularly when accompanied by systemic abnormalities. They also highlight the importance of a full systemic assessment of coloboma patients and adequate genetic counselling for both patients and their families.

Chromosome Aberrations↗
PubMed1993

The role of biological response modifiers in disease control.

Immune responses to infectious agents involve a complex set of interactions between cells and the factors they produce that culminate with disease resolution or death. Therefore, the manipulation of the immune system may have a great impact on the preservation and restoration of animal health. Biological response modifiers are agents that modify the host's response to pathogens with resultant beneficial prophylactic or therapeutic effects. The best known example of biological response modifiers are vaccines, by which administration of a nonpathogenic form of a microorganism prepares the immune system to produce a more effective response upon subsequent infection with the pathogenic form. Nevertheless, the use of biological response modifiers other than vaccines that enhance the immune response is now the focus of many investigations. In this review, a brief overview of the immune system is presented, and special emphasis is placed on possible areas of intervention with biological response modifiers and a description of the prophylactic and therapeutic potential of biological response modifiers. Specific examples are presented to demonstrate examples of disease modification by biological response modifiers through stimulation of nonspecific and antigen specific immunities.

Animals↗
PubMed1993

Importance of mild hyperoxaluria in the pathogenesis of urolithiasis--new evidence from studies in the Arabian peninsula.

The hypothesis that mild hyperoxaluria is more important than hypercalciuria in the pathogenesis of urolithiasis is re-examined in the light of new evidence. Small increments in urinary oxalate in the normal to high-normal range are much more critical than similar rises in urinary calcium for increasing the relative supersaturation of urine with respect to calcium oxalate, the oxalate/calcium ratio in urine, the total volume of calcium oxalate crystals excreted, the proportion of abnormally large crystals and aggregates of calcium oxalate and the severity of the disorder as defined by the recurrence rate of stone-formation. Data from the Arabian Peninsula, where the prevalence of calcium-containing stones is considerably higher than in the West, have shown that this occurs in spite of the almost complete absence of hypercalciuria. On the other hand, there is a strong association between stone-formation and the occurrence of mild hyperoxaluria. The life-time expectancy of stone-formation in men from various countries is strongly correlated with the average daily excretion of oxalate in the urine of the normal men in these countries. This relationship extends to include patients with enteric and hereditary hyperoxaluria. There is no such relationship, however, between the life-time expectancy of stones and urinary calcium excretion in the same populations. Studies on the regulation of urinary oxalate indicate that it is largely controlled by the quantity of "free" dietary oxalate available for absorption in the lower intestine. This can be calculated from the intakes of calcium and oxalate and the urinary excretion of calcium.

Calcium↗
PubMed1992

Volume of normal prostate, of prostate cancer, and of benign prostatic hyperplasia: are correlations with prostate specific antigen clinically useful?

This retrospective study correlated prostate volume, determined by transrectal ultrasonography, with serum prostate specific antigen (PSA), by Deming regression analysis, in patients with confirmed benign prostatic hyperplasia (BPH) and patients with non-metastatic (M0) or metastatic (M1) prostate cancer. In BPH, a highly significant correlation was found between log10[PSA] and prostate volume. When this PSA/volume regression pattern for BPH was used as a reference standard, all 17 patients with M1 prostate cancer and 83% of the 23 patients with M0 disease were discriminated from BPH.

Aged↗
PubMed1992

Ultrasonographic dating of pregnancy causes significant errors in Down syndrome risk assessment that may be minimized by use of biparietal diameter-based means.

OBJECTIVES: Gestational dates assessed by ultrasonographic measurement of fetal dimensions are usually quoted in terms of complete weeks because the uncertainty of ultrasonographic measurement is approximately +/- 7 days. This study examines the effect of ultrasonographic dating on Down syndrome risk assessment. STUDY DESIGN: The effect of small changes in measured biparietal diameter resulting in a change in estimated gestational week and the benefits of a more precise measure of fetal gestational age (raw biparietal diameter) are examined mathematically. RESULTS: If maternal serum alpha-fetoprotein and human chorionic gonadotropin are used to assess Down syndrome risk, risks assessed with ultrasonographically determined dates may be less than or equal to 45% too high for fetuses with biparietal diameter at the lowest end of the size band and less than or equal to 22% too low with biparietal diameter at the top of the size band. If the results for maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol are used, these figures become less than or equal to 150% and less than or equal to 60%, respectively. CONCLUSION: If ultrasonography is used to assess gestational age, the raw biparietal diameter and not the estimated week of gestation must be used to derive means for calculation of multiples of the mean.

Down Syndrome↗