Chemical studies of the tertiary structure of transfer RNA. Iodination of exposed cytosine residues with 125I.
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Binding Sites↗
Biomedical subjects
D M Brown
Publications and source records attributed to D M Brown.
Physico-chemical and immunological properties of allophycocyanins.
Allophycocyanins were purified from diverse cyanobacteria and one rhodophytan alga (Cyanidium caldarium). The native proteins are trimeric molecules with the structure (alpha beta)3. Representative native allophycocyanins and their alpha and beta subunits were characterized with respect to molecular weight, amino acid composition, isoelectric point, absorption and fluorescence spectra and immunological properties. All of the allophycocyanins studied were strikingly similar with respect to each of these properties. Renatured alpha and beta subunits of allophycocyanin were distinct immunologically from each other, and both cross-reacted with the antiserum to the native protein. Trimeric allophycocyanin was readily reconstituted from the purified alpha and beta subunits. Formation of hybrid allophycocyanins was demonstrated by direct isolation and characterization of the hybrid proteins and by immunological techniques. The results support the view that allophycocyanins are a highly conserved group of proteins.
Amino Acids↗
Multiple hypothalamic-pituitary abnormalities in an adolescent girl with galactorrhea.
A patient with multiple hypothalamic abnormalities is presented who had galactorrhea at seven years of age followed ten years later by secretory deficiencies of growth hormone, TSH, and gonadotropins. There was no clinical evidence of a mid-brain tumor. Patients presenting with galactorrhea and amenorrhea associated with hyperprolactinemia may develop additional hypothalamic malfunctions over a period of several years and should be observed carefully for appearance of them as well as for evidence of brain tumors.
Adolescent↗
Objective determinations of sensibility in the upper extremity. Part I. Median nerve sensory conduction velocities.
Distal sensory conduction velocities were determined in 109 normal median nerves. A significant decrease in sensory conduction velocity was noted with increasing age. Latencies increased with age but this relationship was not significant in men. Variables which contribute to the wide range of normal conduction velocities are discussed, and the need for each clinician to establish his own testing procedure is stressed. An additional method for assessing sensory function is suggested.
Adult↗
Objective determinations of sensibility in the upper extremity. Part II. Application of cutaneous stimuli in control subjects.
Sensitization statements were read to two groups of normal subjects to determine whether quantifiable thresholds for pressure, electrical, or tactile stimuli could be altered. Significant reductions in perception thresholds were observed for pressure and digital pulsed stimulation, but not for stimulation to the discomfort threshold, or two point discrimination. These data seem to suggest that increased sensitization is related to the ease of stimulus applications and the comparative simplicity of sensory processing.
Adult↗
Objective determinations of sensibility in the upper extremity. Part III. Application of cutaneous stimuli in patients with peripheral nerve lesions.
Quantitative values for pressure, electrical, and two-point touch stimulation were examined in five patients with peripheral nerve injuries of the ulnar or median nerves. Analyses of profiles generated for each stimulus application in each patient participating in this preliminary study suggest that, following the reading of a sensitization statement, pressure and electrical shock threshold values are clearly reduced compared to similar measurements in the unaffected limb. Values obtained prior to the statement indicated progressively reduced thresholds, however. Changes in sensation appear to precede significant improvements in sensory nerve conduction velocity. Limitations in the sensory testing techniques as well as suggestions for improving its validity are discussed.
Adult↗
Purification, characteristics and sequence of a peptide containing an essential lysine residue.
Glutamate dehydrogenase (EC 1.4.1.2-4) has been purified and crystallized from the acetone powder of tuna liver. The enzyme has a molecular weight of 333 000 +/- 15 000 as evaluated by sedimentation equilibrium and constists of six identical subunits. Unlike the bovine enzyme the molecular weight does not increase with increasing protein concentration indicating that the tuna enzyme has no tendency to polymerize. The amino acid composition and peptide maps of the tuna and bovine liver enzyme are similar, suggesting considerable homology between the two enzymes. Furthermore, from the tryptic digest a hexadecapeptide containing a lysine residue reactive to pyridoxal 5'-phosphate exhibits the same composition and sequence as the peptide containing the reactive lysine-126 in the sequence of the bovine enzyme. The molecular activity is 25 and 510 mol of substrate per mol enzyme per s, respectively, for the glutamate oxidation and the alpha-ketoglutarate reduction with NAD or NADP as coenzymes. The enzyme is regulated by pyridine nucleotides like other vertebrate enzymes, but it also exhibits some coenzyme specificity, the activity being about fifteen times higher with NAD than with NADP.
Amino Acids↗
Glycosaminoglycans of EDTA soluble and insoluble dentin in dentinogenesis imperfecta type I.
A study of glycoasminoglycans (GAGs) in dentinogenesis imperfecta Type I (DI I) revealed increased GAG in DI I EDTA soluble dentin as compared to controls. EDTA insoluble GAG contained less GAG than age-matched controls. The role of GAG in dentin pathosis is discussed.
Dentin↗
Glycosaminoglycans of predentin, peritubular dentin, and dentin: a biochemical and electron microscopic study.
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Child↗
The acro-osteolysis syndrome: Morphologic and biochemical studies.
The acro-osteolysis syndrome consists of dissolution of terminal phalanges of the hands and feet, dolichocephaly with multiple wormian bones, delayed closure of cranial sutures, absence of frontal sinuses, a prominent occipital ridge, skeletal demineralization, vertebral and extremity fractures, joint laxity, and coarse hair. Studies of bone morphology reveal diminished bone density and bone formation. Osteoblasts have widely dilated smooth endoplasmic reticulum. It is postulated that an abnormality of a structural protein is the pathogenic basis of this disease.
Abnormalities, Multiple↗
Biliproteins of cyanobacteria and Rhodophyta: Homologous family of photosynthetic accessory pigments.
Amino-terminal sequence determinations are reported of the subunits of biliproteins of prokaryotic unicellular and filamentous cyanobacteria and of eukaryotic unicellular red algae. The biliproteins examined, allophycocyanin, C-phycocyanin, R-phycocyanin, b-phycoerythrin, and phycoerythrocyanin, vary with respect to the chemical nature and the number and distribution of the bilin chromophores between the two dissimilar subunits. The amino-terminal sequences fall into two classes, "alpha-type" and "beta-type", with a high degree of homology within each class.In those biliproteins where the number of bilin chromophores on the two subunits is unequal, the subunit with the greater number of chromophores has the beta-type amino-acid sequence.Extensive homology also exists between alpha- and beta-type sequences, strongly supporting the view that these arose by gene duplication to give rise to the ancestral alpha- and beta-type genes early in the evolution of the biliproteins. The subsequent generation of the various classes of biliproteins appears to be the result of further gene duplication of the alpha- and beta-type genes, ultimately to give rise to families of polypeptide chains of similar sequence, but varying in the number of chromophore attachment sites and the structure of the chromophores.
Journal Article↗
Clearance of gentamicin during hemodialysis: comparison of four artificial kidneys.
The effects of four types of artificial kidney on dialyzer clearance rates and serum pharmacokinetics of gentamicin were compared. In 19 patients undergoing chronic hemodialysis, the mean (+/-SE) interdialysis half-life of gentamicin in serum was 49.3 +/- 3.5 hr, whereas during dialysis this value was reduced to 10.0 +/- 0.7 hr. The mean half-life of gentamicin in serum at conventional flow rates for the Hollow Fiber Kidney, Kiil, Gambro, and Coil dialyzers was 11.3, 10.9, 8.2, and 7.4 hr, respectively, and the mean values for clearance of gentamicin were 26,28,42, and 48 ml per min, respectively. For all dialyzers, rates of clearance of gentamicin increased linearly with plasma flow rate over the flow range studied. The Gambro and Coil dialyzers had significantly higher rates of clearance of gentamicin from serum (P less than 0.05) than the Hollow Fiber Kidney and Kiil dialyzers over a wide range of clinically useful plasma flow rates (119-300 ml per min), whereas the Kiil dialyzer cleared gentamicin more effectively (P less than 0.05) than the Hollow Fiber Kidney dialyzer over a more limited interval (117-177 ml per min). Therapeutic recommendations for patients undergoing hemodialysis were made in light of current findings.
Anti-Bacterial Agents↗
Normal development and experimental models of cystic renal disease.
From a review of renal development and experimental cystic disease, the following observations can be made: 1. The previous theories developed to explain cystic renal disease (nonunion, failure of regression, and obstruction to urine flow) do not adequately fit with the numerous recent observations made in studies of most experimental models or in human renal cystic disease. 2. The most acceptable theory to date for most types of renal cystic abnormalities (except those due to known obstruction of urine flow) is that abnormalities of the tubular supporting wall occur, probably as a result of toxic or metabolic injury to the tubular cells of the wall and the related interstitial tissues, which are exposed to the highest concentrations of these compounds. This theory would also help explain the etiology of cystic renal diseases in man and should lead to attempts to isolate toxic factors or enzyme abnormalities in susceptible families and in early cases. 3. Induction of cystic abnormalities through a variety of experimental manipulations and drugs reveals impressive strain, sex, and species variability, and these differences should be more carefully examined. 4. The same chemical that induces a cystic change in the mature, fully developed kidney may cause changes which are quite different (location, severity, etc.) in both the fetal and newborn kidney, in which continual nephrogenesis is occurring. 5. Many of the previous explanations of cystic changes require careful reinterpretation of the findings (to reconcile certain differences), and confirmatory studies should be performed to help piece together some of the puzzling observations noted, such as the cystic changes seen with adrenocorticosteroids, and their relationship to potassium depletion.
Adrenal Cortex Hormones↗
Human glomerular smooth muscle (mesangial) cells in culture.
Glomerular smooth muscle cells were grown and subcultured from human glomeruli in vitro. These cells, stained with antiserum to smooth muscle actomyosin and examined by immunofluorescence, had brightly stained intracellular fibrils similar to those seen in smooth muscle cells. Actomyosin fibrils were altered by conditions affecting actomyosin in vitro. Glomerular smooth muscle cells lacked the antihemophilic factor and blood group antigens present in endothelial cells, and are, therefore, most likely derived from the smooth muscle cells of the glomerular mesangium. By radio-labeled amino acid analysis, they synthesize a collagen differing from that of fibroblasts, and which probably differs from basement membrane collagen. Other cell types could be grown and subcultured using a different glomerular isolation technique, culture medium and method of subculture.
Actomyosin↗
Studies of diabetic nephropathy in animals and man.
Animal models of diabetes mellitus allow for the manipulation of the metabolic state and the performance of experiments that may shed light on the pathogenesis of diabetic nephropathy. Rats with long-standing chemically induced diabetes develop glomerular mesangial thickening and immunoglobulin and complement deposition. These glomerular changes are reversible on the transplantation of a kidney from a diabetic rat into a normal host and on cure of the diabetic state by pancreatic islet transplantation. Conversely, diabetic renal changes develop in normal kidneys transplanted into diabetic rats (within tow to four months) and humans (within two years). These studies suggest that nephropathy results from the diabetic state. The mesangium is thickened in diabetic rats, mice, and humans. In rats, mesangial function is the processing of macromolecules localized therein is disturbed in areas of mesangial pathology. The finding that glomerulopathy is accelerated in uninephrectomized diabetic rats and is retarded in rat kidneys "protected" by narrowing of the renal artery suggests that alterations in glomerular blood flow are related to the pathogenesis of diabetic glomerular damage. Marked hyperglycemia in animals and man leads to "glycogen nephrosis," which affects the distal tubule at the level of the macula densa of the juxtaglomerular apparatus (JGA). This could lead to disturbance of JGA blood pressure regulation. Disturned mesangial function may result from failure of macula densa cells to process macromolecules that have reached that site from the mesangium.
Animals↗
The selective iodination of yeast phenylalanine transfer RNA with 125-I.
Yeast tRNA-Phe has been labelled with 125-I under conditions which conserve the tertiary structure. Significant labelling was only found to occur on specific cytidines in single stranded regions, while other cytidines in single stranded regions and all those in the double stranded region underwent iodination to a very small extent. The pattern obtained from iodine labelling satisfies the conformation of a model recently proposed for this tRNA.
Binding Sites↗
Clinician bias: the effects of pretesting information on the evaluations of speech clinicians.
The purpose of this investigation was to determine if pretesting information has a biasing effect on the speech evaluations of student speech clinicians. A total of three groups of clinicians evaluated 10 speech characteristics of each of 17 recorded speech samples. The clinicians participated in two listening sessions. In the first (control) session, they evaluated the speech samples using a 4-point scale of defectiveness and were given no background information on the speakers. In the second (experimental) session, they were given fabricated case history information prior to their evaluations. Results of their ratings indicate that the pretesting information had a biasing effect on the clinicians' evaluations of the speech samples. Implications of these findings and suggestions for future inquiry are discussed.
Adolescent↗
The combined effect of halothane-induced hypotension and hypocapnia on canine myocardial blood-flow and oxygen consumption.
In eleven intact mechanically ventilated dogs anaesthetized with pentobarbitone, mean arterial pressure was reduced to 55% of the control value by ventilating with 1-1.5% halothane. At normocapnia this resulted in decreases in myocardial blood-flow and oxygen consumption to 47% and 55% of their respective control values and an increase in myocardial vascular resistance to 123% of control value. When hypocapnia (mean PaCO2=26 mm Hg) was superimposed on hypotension, myocardial blood-flow was further decreased to 38% of control value whereas oxygen consumption did not alter significantly. When halothane was discontinued, allowing recovery from hypotension, the rate of recovery of myocardial blood-flow and cardiac output was much slower than that of arterial pressure.
Animals↗