Biochemistry of the uremic syndrome.
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Biological Transport↗
Biomedical subjects
R H Williams
Publications and source records attributed to R H Williams.
A study of xanthopterin in chronic renal failure.
Xanthopterin, a metabolic end product of the nonconjugated pterins dihydrobiopterin and tetrahydrobiopterin, is present in many organs and is known to inhibit the proliferation and growth of conconavalin-stimulated lymphocytes. We have developed a simple fluorometric method to measure xanthopterin in the blood and have validated the method by high pressure liquid chromatography (HPLC). Serum levels were 14 +/- 7 nmol/l in normal subjects and 141 +/- 51 nmol/l in hemodialysis patients (p < 0.02). Intermediate levels from patients with renal insufficiency not on dialysis correlated with serum creatinine levels (p < 0.001). Xanthopterin (MW 179) was cleared by hemodialysis at a slightly lower rate than creatinine. It is bound to protein, but the binding, 90 +/- 5% in normal subjects, is decreased in uremia to 60 +/- 15%, p < 0.01. Red cell levels of xanthopterin were five times higher than those of plasma in normal subjects (69 +/- 15 vs. 14 +/- 7 nmol/l, p < 0.001), but uremic patients had lower levels in red cells than in plasma (101 +/- 24 vs. 141 +/- 51 nmol/l, p < 0.05). Slight or moderate hemolysis induced by mechanical stress increased plasma xanthopterin levels by 35%, the effect being more pronounced when hemolysis was severe. We conclude that xanthopterin is increased and its binding to protein is decreased in chronic renal failure. The altered ratio of red cell/plasma xanthopterin levels may reflect an abnormality of the red cell membrane in uremia. We are conducting further studies to amplify our preliminary findings that xanthopterin inhibits cellular growth in vitro.
Chromatography, High Pressure Liquid↗
Purification and biochemical characterization of xanthopterin from patients with chronic renal failure. I. Isolation, purification and preliminary characterization.
We describe the purification and initial characterization of a hitherto unrecognized fluorescence (excitation/emission maxima at 380/440 nm and 400/460 nm) reported from this laboratory in patients with chronic renal failure (Clin Chem 31: 1988, 1985). Purification was achieved using Sephadex G-10 gel chromatography combined with reverse phase and ion exchange high-performance liquid chromatography (HPLC). Purity of the "blue-green" fluorescent compound was determined to be greater than 99% by HPLC, and two-dimensional thin layer chromatography using an acidic and basic solvent system. The excitation/emission maxima were shown to be 390 nm/456 nm, and ultraviolet scans, at pH 1.0, 7.0, and 13.0, gave absorbance optima at 261 nm/356 nm, 278 nm/390 nm, and 255 nm/394 nm, respectively. The isoelectric point of 4.05 in conjunction with the fluorescent and ultraviolet spectra suggests that the fluorophore belongs to the class of compounds known as pteridines.
Chromatography, High Pressure Liquid↗
Purification and biochemical characterization of xanthopterin from patients with chronic renal failure. II. Biochemical elucidation and structural analysis.
We have identified the primary endogenous fluorescent substance, which has characteristic excitation/emission maxima at 380/440 nm and 400/460 nm, found in the sera of patients with chronic renal failure (Clin Chem 32: 1276, 1988). Preliminary studies, using thin layer chromatography (with cellulose) in conjunction with pteridine standards, indicated that the compound is an unconjugated pteridine. Characterization by gas chromatography-mass spectrometry (electron impact), direct probe-mass spectrometry (electron impact/chemical ionization), and Fourier Transform Infrared analysis showed this compound to be xanthopterin (2-amino 4,6 pteridinedione), an unconjugated pteridine known to be present in man in trace quantities. An authentic sample of this compound had a retention time with high-performance liquid chromatography (HPLC) identical to that of the purified fluorophore. The physiological role of xanthopterin in the pathogenesis of uremia has yet to be elucidated.
Chromatography, Thin Layer↗
Schistosoma mansoni: immuno-localization of the calcium binding protein Sm20.
The 20 kDa calcium binding protein of Schistosoma mansoni, Sm20, is expressed in all stages of the life cycle from the cercaria to the adult worm and in the egg, with equal levels of Sm20 present in adult male and female worms. Localization of Sm20 by immuno-electron microscopy using Sm20-specific antisera and the protein A gold technique demonstrated that the majority of Sm20 is expressed in muscle but that it may also be expressed at low levels in the tegument. These results suggest that Sm20 plays a role in the calcium mediated regulation of muscle contraction. However, it is not clear whether Sm20 acts as a reservoir for calcium in muscle or is directly involved in the regulatory mechanisms of contraction.
Animals↗
Underestimation of cardiac output by thermodilution in patients with tricuspid regurgitation.
INTRODUCTION: This study was done to assess the accuracy and reliability of the thermodilution technique in measuring cardiac output in patients with tricuspid regurgitation. PATIENTS AND METHODS: In 30 subjects (17 men, 13 women, aged 50 +/- 14 [mean +/- SD] years), cardiac output was measured in close temporal proximity by thermodilution as well as Fick or indocyanine green dye, after which the presence and severity of tricuspid regurgitation were assessed by contrast right ventriculography or pulsed Doppler echocardiography. RESULTS: In the 13 patients without tricuspid regurgitation, there was excellent agreement between the results of thermodilution and Fick or indocyanine green dye cardiac output determinations (4.95 +/- 1.19 liters/minute by thermodilution, 4.90 +/- 1.11 liters/minute by Fick or indocyanine green dye; NS). In contrast, in the 17 patients with tricuspid regurgitation, the results of thermodilution were consistently lower than those of Fick or indocyanine green dye (4.22 +/- 1.45 liters/minute by thermodilution, 4.99 +/- 1.67 liters/minute by Fick or indocyanine green dye; p less than 0.001). CONCLUSION: Thus, the thermodilution technique of measuring cardiac output is inaccurate in patients with tricuspid regurgitation, yielding results that are consistently lower than the actual outputs.
Adult↗
Dosing of contrast material to prevent contrast nephropathy in patients with renal disease.
PURPOSE: Contrast-induced renal dysfunction has been reported to occur in 15% to 42% of patients with underlying azotemia, but there is disagreement as to whether its incidence is reduced by limiting the amount of contrast material. To adjust the amount of contrast material to the severity of azotemia, we have utilized the following formula to calculate a contrast material "limit" in patients with renal disease: Contrast material limit = (formula; see text) PATIENTS AND METHODS: Over a 10-year period, 115 patients (53 men, 62 women, aged 61 +/- 11 [mean +/- SD] years) with renal dysfunction (baseline serum creatinine level greater than or equal to 1.8 mg/dL) underwent cardiac catheterization and angiography, after which the level of serum creatinine was measured daily for five days. The amount of contrast material that was given adhered to the limit in 86 patients (Group I) and exceeded it in 29 (Group II). RESULTS: Contrast-induced renal dysfunction (an increase in serum creatinine greater than or equal to 1.0 mg/dL) occurred in two (2%) patients in Group I and in six (21%) patients in Group II (p less than 0.001). Of the 48 patients with concomitant diabetes mellitus, the contrast limit was surpassed in 16, six (38%) of whom had contrast nephropathy. Only two of the 32 (6%) diabetic patients in whom the contrast limit was not exceeded had contrast nephropathy (p less than 0.001). CONCLUSIONS: Thus, contrast-induced renal dysfunction occurs infrequently if the amount of contrast material is limited in accordance with the degree of azotemia. Diabetic patients have a high incidence of contrast nephropathy, particularly when they receive an excessive amount of contrast. In patients with diabetes and renal impairment, it may be preferable to perform angiography as a staged procedure or to utilize alternative (non-contrast) techniques to obtain the desired information rather than to exceed the prescribed contrast limit.
Acute Kidney Injury↗
Amino acid composition of uremic middle and low molecular weight retention products.
In order to characterize the spectrum of small peptides retained in chronic renal failure, we carried out high pressure liquid chromatography (HPLC) of serum ultrafiltrates from patients with chronic renal failure (CRF), acute renal failure (ARF), and normal subjects. HPLC patterns in CRF resolved into more than twenty peaks; those in ARF contained fewer peaks and resembled that of normals. We carried out amino acid analysis of HPLC fractions after hydrolysis with 6N HC1 of four patients with CRF, one patient with ARF, and one normal subject. Following hydrolysis each HPLC fraction yielded several amino acids. Glycine, leucine, serine, phosphoserine, glutamic acid, and phenylalanine were found in greatest frequency in the four CRF patients.
Amino Acids↗
Biochemical elucidation and HPLC fractionation of fluorescent peptides in patients with chronic renal failure.
We evaluated the biochemical characteristics of endogenous fluorescent substances, Ex 380 nm/Em 440 nm and Ex 400 nm/Em 460 nm, present in sera of patients with chronic renal failure (Clin. Chem. 31:1988, 1985). Sera from 23 patients with chronic renal failure (CRF) and from 10 normal subjects were filtered through ultrafiltration membranes (cutoff limit of 500 Da). Fluorescence intensity of the aforementioned substances was significantly elevated as compared to normals (p less than 0.001). Fluorescence characteristics of these substances remained unaltered after ultrafiltration and treatment with beta-glucuronidase. Extraction of these fluorescent compounds with organic solvents (dichloromethane, ethyl acetate, chloroform:methanol) could not be achieved after ultrafiltrates were subjected to 6N hydrochloric acid (HC1) hydrolysis. In addition, treatment with 6N HC1 enhanced fluorescence intensity without altering fluorescence excitation/emission maxima. Removal of fluorescence could be accomplished in toto by adsorption onto activated charcoal with subsequent recovery from charcoal by treatment with sodium hydroxide, pH 12 (Ex 380 nm: 51.1%, Ex 400 nm: 91.8%). Analysis of alkali-treated specimens by high performance liquid chromatography demonstrated that peptides associated with these fluorescent substances were denatured, although fluorescence at these previously described excitation/emission maxima persisted. Our studies indicate that the unique fluorescence observed in the sera of patients with CRF is not an intrinsic characteristic of a specific peptide or its amino acids, but rather an inherent property of fluorescent molecules which may bind to these peptides.
Chromatography, High Pressure Liquid↗
Pharmacologic role of rubidium in psychiatric research.
Rubidium appears to exert several biologic and pharmacologic effects that are similar if not identical to those of many of the classic antidepressant drugs. This mineral element, if given orally as rubidium chloride, appears to be nontoxic and therapeutically effective in several types of depressive disorders. Currently, however, it is unclear whether or not rubidium will serve as an invaluable pharmacologic agent of a direct clinical nature. Further pharmacometric studies and clinical evaluations are needed to elucidate its mechanism of action and to ascertain its future therapeutic role as an antidepressant drug in clinical psychiatry.
Antidepressive Agents↗
The potential of using recombinant DNA species-specific probes for the identification of tropical Leishmania.
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Animals↗
Evidence for the existence of 5-hydroxytryptamine receptors, which are not of the 5-HT2 type, mediating contraction of rabbit isolated basilar artery.
In the rabbit isolated basilar artery the contractile action of 5-hydroxytryptamine (5-HT) was little affected by high concentrations of ketanserin (1.0 X 10(-6) M) indicating that 5-HT-receptors other than those of the 5-HT2-type were involved. The contractile action of 5-HT was mimicked by methysergide and 5-carboxamidotryptamine (5-CT) with equipotent concentration ratios (5-HT = 1) of about 22 and 0.6 respectively. This profile is characteristic of that in the dog saphenous vein which contains a 5-HT receptor type that may be described as '5-HT1-like'.
Animals↗
Nucleotide sequence of cucumber mosaic virus RNA. 1. Presence of a sequence complementary to part of the viral satellite RNA and homologies with other viral RNAs.
The nucleotide sequence of the 3389 residues of RNA 1 (Mr 1.15 X 10(6) of the Q strain of cucumber mosaic virus (CMV) was determined, completing the primary structure of the CMV genome (8617 nucleotides). CMV RNA 1 was sequenced by the dideoxy-chain-termination method using M13 clones carrying RNA 1 sequences as well as synthetic oligonucleotide primers on RNA 1 as a template. At the 5' end of the RNA there are 97 noncoding residues between the cap structure and the first AUG (98-100), which is the start of a single long open-reading frame. This reading frame encodes a translation product of 991 amino acid residues (Mr 110791) and stops 319 nucleotide residues from the 3' end of RNA 1. In addition to the conserved 3' region present in all CMV RNAs (307 residues in RNA 1), RNAs 1 and 2 have highly homologous 5' leader sequences, a 12-nucleotide segment of which is also conserved in the corresponding RNAs of brome mosaic virus (BMV). CMV satellite RNA can form stable base pairs with a region of CMV RNAs 1 and 2 including this 12-nucleotide sequence, implying a regulatory function. This conserved sequence is part of a hairpin structure in RNAs 1 and 2 of CMV and BMV and in CMV satellite RNA. The entire translation products of RNA 1 of CMV and BMV could be aligned with significant homology. Less prominent homologies were found with alfalfa mosaic virus RNA 1 translation product and with tobacco mosaic virus Mr-126000 protein.
Amino Acid Sequence↗
Tryptamine-induced vasoconstrictor responses in rat caudal arteries are mediated predominantly via 5-hydroxytryptamine receptors.
It has been suggested that tryptamine can stimulate specific receptors distinct from those for 5-hydroxytryptamine (5-HT). We have examined this possibility in the rat isolated caudal artery, paying particular attention to the involvement of monoamine oxidase metabolism and alpha-adrenoceptors, two factors that can complicate the quantification of antagonist potencies at 5-HT receptors. 5-HT and tryptamine were agonists over the concentration-ranges 3.0 X 10(-8) - 3.0 X 10(-5) mol l-1 and 1.0 X 10(-6) - 3.0 X 10(-4) mol l-1 respectively. The sensitivity of the caudal artery to tryptamine was increased by about 44 fold in the presence of iproniazid (5.0 X 10(-5) mol l-1) and about 17 fold in the presence of pargyline (1.0 X 10(-5) mol l-1), while responses to 5-HT and methoxamine were unaffected. In the absence of iproniazid, ketanserin and methysergide were potent antagonists of responses to 5-HT with pA2 values of 9.08 and 9.11 and slopes of the Schild regressions of 1.15 and 1.00 respectively. However, against tryptamine the antagonists were weaker such that pA2 values were similar to those against 5-HT but the slopes of the Schild regressions were 0.47 and 0.47. In the presence of iproniazid (or pargyline), the 5-HT antagonists were more potent against tryptamine such that the pA2 values and the slopes of the Schild regressions were not significantly different from those against 5-HT. Phentolamine was a weak antagonist of responses to both 5-HT and tryptamine in the presence of iproniazid. 5 The findings in this study suggest that the contractile action of tryptamine in rat caudal artery is mediated predominantly by the same receptor as 5-HT and that the differential inactivation of tryptamine by monoamine oxidase enzymes largely accounts for the different susceptibilities of 5-HT and tryptamine to the antagonists examined.
Animals↗
Nucleotide sequence of cucumber-mosaic-virus RNA 2 reveals a translation product significantly homologous to corresponding proteins of other viruses.
The nucleotide sequence of the 3035 residues of RNA 2 (Mr 1.03 X 10(6) ) of the Q strain of cucumber mosaic virus (CMV) was determined by sequencing M13 clones of the RNA 2 cDNA and by dideoxy sequencing using primers prepared either from M13 clones or by chemical synthesis. A single long open reading frame starts at the second AUG from the 5' end of RNA 2 and encodes 839 amino acids (Mr 94333). This frame has flanking regions of 92 nucleotides at the 5' terminus and 423 nucleotides at the 3' terminus. Computer analysis of the nucleotide sequence showed that CMV RNA 2 has a significant homology with RNA 2 of brome mosaic virus (BMV) and alfalfa mosaic virus (AMV) and also with a region for tobacco mosaic virus (TMV) RNA encoding the read-through part of the 183-kDa protein. About 400 amino acids in the central region of the CMV RNA 2 translation product have a striking homology with the corresponding proteins encoded by BMV and AMV and with the read-through part of the TMV 183-kDa protein. Hydrophobicity plots of CMV and BMV RNA translation products also had apparent similarities. It is concluded that CMV is related to BMV, AMV and TMV in order of increasing evolutionary divergence.
Amino Acid Sequence↗
Reye's syndrome associated with long-term aspirin therapy.
Reye's syndrome has been infrequently described in children receiving long-term salicylate therapy. We report the clinical and laboratory findings of two children in whom Reye's syndrome developed while taking salicylates for systemic inflammatory disorders. Monitoring of hepatocellular function should be considered in children who are receiving long-term salicylate therapy.
Adolescent↗
Abrogation of calcium exclusion by erythrocytes under hypotonic stress.
Normal human erythrocytes in isotonic suspension maintain a high gradient of calcium ion concentration across the membrane, with the cytosol [Ca2+] several orders of magnitude below plasma concentration. Despite the high degree of exclusion maintained against the entry of Ca2+, the osmotic resistance of red cells in hypotonic saline is significantly augmented by the presence in the medium of Ca2+ in concentrations greater than 0.07 mmol/l. Resistive particle spectroscopy showed this to occur without alteration of the mean critical haemolytic volume; furthermore, in the presence of Ca2+ there was a reduction in cell volume at prolytic osmolalities when compared with cells in calcium-free sodium chloride solutions. This is shown to be due to augmentation of the prolytic loss of K+ in the presence of Ca2+ through calcium-sensitive channels, and indicates that the pathway for passive K+ efflux uncovered in the prolytic state is indistinguishable from that of normal passive K+ diffusion. It is also demonstrated that the prolytic red cell membrane is permeable to Ca2+ and admits the divalent cation to the inner aspect of the plasma membrane. These changes are comparable to those of cells prior to haemolysis in vivo, as in the irreversibly sickled cell, and are therefore not specific to the latter condition.
Calcium↗
Farewell with a full heart.
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Family Practice↗