Showing papers on "Low protein published in 1982"

Mortality risk factors in patients treated by chronic hemodialysis. Report of the Diaphane collaborative study.

Abstract: A survival analysis was applied to 1,453 patients treated between 1972 and 1978 in 33 French dialysis centers and prospectively followed up in the computerized Diaphane Dialysis Registry. 198 deaths (overall mortality = OM) were registered, of which 87 (43%) were secondary to cardiovascular complications (cardiovascular mortality = CVM). Risk factors for OM and CVM (p values less than 0.05) were age, male sex, nephroangiosclerosis or diabetic nephropathy as the primary renal disease, elevated systolic and diastolic blood pressure and two weekly dialysis rather then three. In contrast with the results observed for the general population, a high body mass index and elevated cholesterol, triglycerides and uric acid were not found to be associated with significantly increased CVM or OM. On the contrary, low body mass index (less than 20 kg/m2), low cholesterol (less than 4.5 mmol/l) and low mean predialysis blood urea (less than 4.6 mmol/l) were associated with increased OM and CVM, and more especially with high stroke mortality. Results for urea but not for cholesterol remain significant after adjustment for age, sex, weekly dialysis schedule and body mass index. They suggest that, in addition to elevated blood pressure, a poor nutritional state and/or low protein intake may be important factors for explaining the high cardiovascular mortality, particularly for strokes, observed in dialyzed patients.

Quantitation of changes in lymph protein concentration during lymph node transit

Abstract: Many investigators assume the protein concentration and colloid osmotic pressure of interstitial fluid and lymph to be identical even after the lymph has passed through a lymph node. We quantitated the degree of modification of lymph by the dog popliteal lymph node by perfusing isolated lymph nodes in situ at physiological flow rates with homologous plasma or plasma diluted to low protein concentration. This enabled us to compare directly prenodal and postnodal lymph flows and protein concentrations. When undiluted plasma was infused into the node, fluid filtered from the blood into the lymph, diluting the lymph. When diluted plasma was infused, fluid was absorbed from the lymph, concentrating the lymph. Nearly all (98%) of the change in lymph protein concentration could be explained by transfer of protein-free fluid either into or out of the lymph. However, when the nodes were perfused with lymph having a colloid osmotic pressure that exactly balanced the hydrostatic and osmotic forces acting across the lymph node blood-lymph barrier, the lymph was not modified during nodal transit. This "equilibrium colloid osmotic pressure" averaged 60% of that of plasma. The concentrating-diluting mechanism became more significant as the perfusion rate decreased and/or as the colloid osmotic pressure of the afferent lymph was made progressively greater than or less than the equilibrium colloid osmotic pressure. We conclude that lymph nodes modify lymph protein concentration and colloid osmotic pressure except when these are already at equilibrium values for given lymph node conditions. Therefore, the assumption that postnodal lymph is representative of interstitial fluid, especially at low but still physiological lymph flows, is likely to be incorrect.

Antifungal Action of Amphotericin B in Combination with Other Polyene or Imidazole Antibiotics

Abstract: We compared the in vitro antifungal action of amphotericin B (AmB) used alone or in combination with a second polyene antibiotic or with miconazole or ketoconazole. When AmB was used in combination with either filipin or Etruscomycin (Farmitalia, Milan, Italy), antagonism or potentiation of the antifungal effect against Candida albicans resulted. Addition of AmB to Etruscomycin- or filipin-treated cultures resulted in antagonism. In contrast, potentiation occurred when Etruscomycin or filipin was added to cultures treated with AmB. The outcome of incubating C. albicans with combinations of AmB and either miconazole or ketoconazole depended on the duration of exposure of the cells to the drugs. Short-term incubations resulted in antagonism, whereas potentiation of antifungal effects occurred after prolonged exposure of cells to the antibiotics. In addition, supplementation of cultures with serum protein-potentiated AmB induced k+ leakage at low protein concentrations and inhibited K+ leakage at high protein concentrations.

The rates of formation and dissociation of actin-myosin complexes. Effects of solvent, temperature, nucleotide binding and head-head interactions

Abstract: The rates of formation and dissociation of actin-subfragment 1 and actin-heavy mero-myosin complexes were measured by using light-scatter and the change in fluorescence of N-iodoacetyl-N'-(5-sulpho-1-naphthyl)ethylenediamine (IAEDANS)-labelled acting as probes. Association rate measurements were made at low protein concentration, where the transients approximated to single exponentials with rate constants proportional to the concentration of reactant in excess. Dissociation rate measurements were made by displacing IAEDANS-actin from myosin with excess native actin and by a salt jump. The second-order rate constant of association for actin-subfragment 1 was 3 x 10(6) M-1 . s-1 in 60 mM-KCl at 13 degree C. It was decreased 10-fold in 500 mM-KCl and in 50% (v/v) glycol. It was decreased 6-fold when MgADP or Mg[beta gamma-imido]ATP bound to myosin. The dissociation rate constant was 0.012 s-1 in 60 mM-KCl at 13 degree C. It was increased 4-fold by 500 mM-KCl, 25-fold by 50% glycol, 8-fold by MgADP binding and 170-fold by Mg[beta gamma-imido]ATP binding. Ea for association was 70 kJ . mol-1 and for dissociation 35 kJ . mol-1. Heavy meromyosin associated at twice the rate observed for subfragment 1 and dissociated at less than one-twentieth of the rate for subfragment 1 (60 mM-KCl, 25 degree C), but when Mg[beta gamma-imido]ATP bound actin-heavy meromyosin dissociated at one-half the rate for subfragment 1. There were significant correlations between increase in the dissociation rate constant, decrease in binding constant and increase in magnitude of conformational change. The association rate constant did not correlate with any property of the actin-myosin complex.

Purification, composition, and physical properties of a thermal hysteresis "antifreeze" protein from larvae of the beetle, Tenebrio molitor.

Abstract: Proteins which produce a thermal hysteresis (difference between the freezing and melting points) in aqueous solution are well-known for their antifreeze activity in polar marine fishes. Much less is known about the biology and biochemistry of similar antifreeze proteins found in certain insects. A thermal hysteresis protein was purified from cold acclimated larvae of the beetle, Tenebrio molitor, by using ethanol fractionation, DEAE ion-exchange chromatography, gel filtration, and high-pressure liquid chromatography. The purified protein had a molecular mass of 17 000 daltons and its N terminus was lysine. The amino acid composition of the antifreeze protein contained more hydrophilic amino acids than the fish antifreezes. This is consistent with the compositions of previously purified insect thermal hysteresis proteins. However, the percentage of hydrophilic amino acids in this Tenebrio antifreeze protein was considerably less than that of other insect thermal hysteresis proteins. The freezing point depressing activity of the Tenebrio antifreeze was less than that of fish proteins and glycoproteins at low protein concentrations but was greater at high protein concentrations.

Energy, Protein, and Seasonal Influences on White-Tailed Deer Fawn Nutritional Indices

Abstract: Shortand long-term influences of dietary energy and protein on physiological indices of nutritional status were determined in a factorial experiment with 12 male and 12 female captive whitetailed deer (Odocoileus virginianus) fawns. Blood and urine samples were collected after 1, 2, 4, 8, 16, and 32 weeks on experimental diets. Body weights throughout the experiment were greater (P < 0.001) for male than for female fawns. Concentrations of blood urea nitrogen (BUN) and urinary urea/creatinine (U/C) ratios throughout the experiment were greater (P < 0.001) in fawns on high protein diets than in fawns on low protein diets. Blood urea nitrogen concentrations and urinary U/C ratios also were greater (P < 0.01) in fawns on low energy diets than in fawns on high energy diets over the duration of the experiment. A substantial reduction in BUN concentrations was observed after 8 months in those fawns which initially exhibited elevated BUN concentrations. Significant differences were observed among sample periods during the 8-month experiment for hemoglobin, packed cell volume, mean corpuscular hemoglobin content, albumin, BUN, cholesterol, nonesterified fatty acids, total ketone bodies, and urinary U/C ratios. J. WILDL. MANAGE. 46(2):302-312 Physiological indices for assessing nutritional status of populations of wild animals, most notably cervids, have long been the subject of research in wildlife science. Biochemical analyses of blood and urine hold promise as being reliable nutritional indices. However, assessing nutritional status with these methods must necessarily depend on controlled experiments to evaluate their efficiency and accuracy. Several investigators have examined nutritional indices of whitetailed deer under controlled conditions (Kirkpatrick et al. 1975, Seal et al. 1978a, Bahnak et al. 1979). No reports have been found in which differences in nutritional indices according to energy, protein, sex, and duration of dietary exposure were examined in a single experiment. The objective of the present study was to determine the shortand long-term effects of dietary energy and protein on nutritional indices of male and female white-

Hemocyanins in spiders .15. the role of the individual subunits in the assembly of eurypelma hemocyanin

Abstract: The role of the seven different subunits in the quaternary structure of the 24-meric (37 S) hemocyanin of the tarantula, Eurypelma californicum, was studied by reassembly experiments. Individual subunits and combinations of 2, 3, 4, etc. different subunits were incubated in a total concentration of 1-2 mg/ml overnight in Tris buffer, pH 7.5, omitting divalent cations. The reassembly mixtures were then analyzed by thinlayer gel filtration, electron microscopy, analytical ultracentrifugation, and polyacrylamide gel electrophoresis. At least at the low protein concentration employed, none of the isolated monomeric subunits (a, d, e, f, g) is capable of hexamer are likewise ineffective. The minimal number of monomers required for hexamer formation is three, but only about half of the 10 possible combinations was effective. The best results were obtained with a + f + g. Four and five monomers always yielded hexamers, although the composition of the latter is not known. The heterodimer bc is a prerequisite to go beyond the hexameric state. bc alone forms tetramers and large, strand-like aggregates. a shows a high affinity towards bc, trimers and tetramers being formed. Out of all combinations of bc and two monomers, only one (bc + a + g) produced hexamers or heptamers. With three monomers plus bc, dodecamers and larger structures (but no 24-mers) were obtained, but only if also a was present (bc + a + f + g being the best combination). If all subunits minus one monomer were combined, the hexamer/heptamer level was not exceeded if a was omitted. 24-mers were formed in appreciable yield only in one case, namely if e was absent. However, this reassembly product turned out to be unstable. To obtain stable 24-meric hemocyanin, the complete set of subunits had to be present. The roles of the different subunits are defined as follows: bc is a "core" subunit which forms the inter-hexamer link within each dodecameric half. It serves also in inter-dodecamer bonding. The artificial homodimers bb and cc are ineffective in this respect. bc must be supplemented by a which is needed for dodecamer stabilization. f is also required to link two dodecamers, while g serves to stabilize this bridge. d and e are required to finish off and to stabilize the 24-mer. A model is proposed showing some neighbourhood relationships of the subunits within the hemocyanin 24-mer, and a pathway of reassembly is discussed.

Reversal of hyperparathyroidism in severe uremics following very low-protein and low-phosphorus diet.

Abstract: Serum iPTH levels decreased markedly in 16 severe chronic uremic patients who changed from a standard low-protein diet to a very low-nitrogen and very low-phosphorus diet supplemented with essential a

Investigations into the etiology of elevated serum T3 levels in protein-malnourished rats

Abstract: Thyroid function studies and the peripheral metabolism of thyroid hormone were examined in rats fed a low protein diet (9% casein) for 4–8 wk. Compared to animals fed a normal protein diet ad libitum, both the low protein rats and a pair-fed control group weighed less at the end of the study. However, serum total T3 levels were significantly higher only in the protein deficient rats. The elevated serum T3 was not explainable by enhanced peripheral T4 to T3 conversion, as there was no evidence of any change in hepatic or renal 5′-deiodinase activity when homogenates were examined for conversion of T4 to T3, reverse T3 to 3,3′-diiodothyronine, or 3′,5′-diiodothyronine to 3′-monoiodothyronine. Neither was there an effect on hepatic T3 receptor maximal binding capacity (204 ± 24 versus 168 ± 15 fmol/mg DNA control) or binding affinity (2.07 ± 0.38 versus 2.49 ± 0.24 × 10−10 M control). In two separate experiments the dialyzable fraction of T3 was significantly lower in the low protein group while free T3 concentrations were unchanged or reduced. In contrast, serum total and free T4 were either normal or reduced and dialyzable T4 was unaffected by protein deficiency. We conclude that while serum total T3 is elevated in rats chronically fed a low protein diet, this elevation is not due to enhanced T4 to T3 conversion. Rather, the increased T3 levels can be accounted for by a striking alteration in protein binding to T3. Moreover, the failure to demonstrate similar changes in serum total and dialyzable T4 suggests that in the rat, protein deficiency has different effects on binding to the two major thyroid hormones. Dietary induced changes in serum thyroid hormone binding must be kept in mind in nutrition studies in the rat.

Dissociation and characterization of pilin isolated from Pseudomonas aeruginosa strains PAK and PAO.

Abstract: Pili isolated from Pseudomonas aeruginosa strains PAK and PAO have been dissociated into subunits using the detergent octyl glucoside. Circular dichroism studies indicated that no change in protein conformation occurs as a result of this treatment. Ultracentrifugation measurements showed that both pilins have a Stokes radius of 21 A (1 A = 0.1 nm) corresponding to an axial ratio of between 3:1 and 5:1, when approximated as prolate or oblate ellipsoids. Sedimentation equilibrium measurements show that even at low protein concentrations the pilin–detergent complex exists as a mixture of monomers and dimers.

On the Analysis of Metabolic Networks

Abstract: In the past quarter of a century, it has become evident that the major pathways of intermediary metabolism are regulated by a remarkable variety of interlocking control mechanisms. These include covalent modification of enzymes: acetylation, methylation, adenylylation, phosphorylation by cAMP-sensitive and -insensitive protein kinases, changes in SH and S-S redox states, among others. Regulation by noncovalent modification is virtually ubiquitous, and includes sensitivity to various ions, especially Ca2+, to substrates and to end products, to ratios of modifier concentrations such as [ATP]/[ADP] · [Pi], [NADH]/ [NAD+], [acyl CoA]/[CoA], etc. While elucidation of regulatory mechanisms is clearly prerequisite to an understanding of the controls acting in vivo, it is not in itself sufficient to allow prediction of the flux of metabolite through any particular metabolic step, even if one were to perform a “complete” analysis of all the known regulatory effectors in the cell. This lack of certainty comes about not only because of the ever-present possibility that compounds which were not measured are important regulatory substances, but also because frequently the enzymes and/or putative regulatory metabolites are in different subcellular environments, whether these be readily indentifiable organelles (such as mitochondria, peroxisomes, glycogen particles) or microenvironments formed by multienzyme complexes (Srere and Mosbach, 1974). The situation is further complicated by much evidence suggesting that proteins interact with one another in the relatively concentrated intracellular or intraorganellar environments where they function, while most of the in vitro studies are performed on partially purified enzymes and at unphysiologically low protein concentrations. The development of techniques for rapid separation of mitochondria from the rest of the cytosol (Siess et al.,1977; Tischler et al.,1977) considerably reduces the ambiguity inherent in measurements of cell metabolite content, but even if it were possible to separate the peroxisomes and other organelles at the same time, it would remain very difficult to assess all the factors determining the metabolite flux through any particular step in vivo. Metabolic network analysis addresses a much simpler question than those we have just discussed—namely, what is the flux of metabolite through the steps of a metabolic pathway in the living cell? Even assuming that the question may be answered by the methods to be described below, it is clear that such information by itself contributes very little to an understanding of how metabolism is regulated. Flux values obtained by network analysis may be compared with the enzyme activity for each step measured in vitro under “optimal” conditions. Frequently the in vitro activity exceeds the in vivo flux, and this information may reinforce accepted views on regulated steps or may indicate new steps where control may be sought. In some cases, however, the apparent in vivo flux exceeds the enzyme activity assayed under “optimal” conditions. This reemphasizes the difficulty of extrapolating from in vitro measurements of enzyme activity to in vivo behavior. When flux values from network analysis are interpreted in the light of information on the in vitro behavior of the enzymes involved and on the concentrations of ligands in the relevant subcellular compartments, one may expect to acquire a deeper understanding of the regulation of metabolism in the living cell.

A two year trial of low protein, low arginine diets or vitamin B6 for patients with gyrate atrophy.

Abstract: Four patients with gyrate atrophy on low protein (20-35 g/day), low arginine diets and one on vitamin B6 (300 mgm/day) have maintained their plasma ornithine concentrations in the range of 30-60% of pre-therapeutic trial levels for about two years. After two years, three of the five patients have shown no significant change in Snellen visual acuity, visual fields, final dark-adapted thresholds or full-field electroretinograms. All five patients have shown slight enlargement of areas of chorioretinal atrophy in the midperiphery. These patients continue on low protein, low arginine diets or on vitamin B6 to determine whether any reduction in the hyperornithinemia will result in stabilization of retinal function.

Pituitary-testicular function in protein-deficient rats. Follicle-stimulating hormone hyperresponse to castration and supersensitivity of gonadotropin secretion to androgen negative feedback.

Abstract: Previous studies have shown that weanling male rats fed a low protein diet ad libitum develop hypogonadotropic hypogonadism. Two unusual features of this state were 1) subnormal serum FSH in noncastrate rats but not in castrate rats, suggesting that FSH was being suppressed by a testicular factor, and 2) serum FSH increases after castration that were greater in protein-deficient rats than in controls. In the current study, protein-deficient rats showed FSH hyperresponse to castration, compared to either ad libitum or pair-fed controls, after periods of low protein feeding from 1–8 weeks and periods of castration from 1–8 weeks. FSH hyperresponse to castration was rapidly induced after the start of low protein feeding and was present whether castration was performed before or after low protein feeding was begun. In none of these circumstances did proteindeficient rats show LH hyperresponse to castration. Inhibin production by Sertoli cell cultures prepared from protein-deficient rats was less (P < 0.02) th...

Silver stain after isoelectric focusing of unconcentrated cerebrospinal fluid: Visualization of total protein and direct immunofixation of immunoglobulin G

Abstract: A silver stain technique has been developed to study proteins in unconcentrated cerebrospinal fluid (CSF) after isoelectric focusing. This method is highly sensitive, and bands containing 25 to 50 ng protein can be clearly distinguished, so that small volumes (40 μl maximum) of native CSF can be used. Individual proteins (e. g., immunoglobulin G) can be detected easily by specific immunofixation. It is also possible to perform direct precipitation and direct specific immunofixation on a single gel in order to compare side by side the patterns of the whole and of specific proteins from different samples of CSF. The technique is simple and highly reproducible, and results are obtained 6 h after sample deposition (if immunofixation is used, a further 24 h washing is necessary). The sensitivity and versatility of this technique (immunofixation can be applied to the detection of any antigen) should permit its extension to other biological fluids with a low protein content.

The Effect of Stress and Meditation on Salivary Protein and Bacteria: A Review and Pilot Study

Abstract: Dentally-induced stress and relaxation-induced anxiety reduction have been correlated with salivary changes in dental patients in two recent studies. In two subsequent studies, test anxiety-induced stress and relaxation-induced anxiety reduction were correlated with salivary changes in dental students. In another study using the resazurin dye indicator, increased salivary bacterial levels were correlated with an increased dental caries incidence. As a result of these findings, it was decided to reinvestigate the effects of stress and relaxation on salivary changes and in addition to examine the effects of those conditions on salivary bacteria. The hypotheses under consideration were: (1) Salivary changes from stress to relaxation will be from opaque to translucent and from high to low protein levels; and (2) salivary bacteria will increase under the condition of stress and decrease under the condition of relaxation. The subjects were twelve dental students. Stress and relaxation were evaluated be...

Vascular changes in DOCA hypertension. Influence of a low protein diet.

Abstract: The goal of this study was to characterize the influence of low protein diet on vascular changes induced by deoxycorticosterone acetate (DOCA) hypertension. DOCA hypertensive and control normotensive rats were placed on a low protein (5%) diet for 4 weeks. This intervention blocked the further increase in systolic blood pressure of rats treated with DOCA; systolic blood pressures of control rats were not influenced by the low protein diet. The sensitivity of isolated mesenteric arteries to norepinephrine was increased in DOCA hypertensive rats compared to that in arteries from control rats; arterial strips from rats maintained on the low protein diet were less sensitive to the catecholamine than arteries from their respective control diet group. Vascular sensitivity to calcium was identical in both normotensive and DOCA hypertensive rats, and the low protein diet had no effect on this measure of calcium activation. Calcium-induced relaxation was depressed in arteries from DOCA hypertensive rats, suggesting a decreased stabilizing influence of the cation on the excitable membrane. Arteries from rats maintained on the low protein diet showed enhanced relaxation to calcium compared to those from their respective control diet group. Membrane stores of calcium available for activation by norepinephrine were increased in arteries from DOCA hypertensive rats; the low protein diet decreased the storage capacity of these membrane sites. The total protein content of the aorta was increased in DOCA hypertensive rats and depressed to control level in DOCA rats maintained on low protein diet. No change was observed in actomyosin content nor in the actin-to-myosin ratio during the DOCA hypertension or the addition of a low protein diet. Since one action of DOCA is to increase cellular protein synthesis, the attenuation of these vascular changes in DOCA rats maintained on a protein-deficient diet is probably due to a decrease in available substrate.

Effect of lysine, tryptophan and(or) carbadox additions to low protein corn-soybean meal diets for young pigs.

Abstract: Addition of L-lysine (Lys), L-tryptophan (Trp) and(or 55 ppm carbadox (C) to low protein corn-soybean meal diets was evaluated in two experiments using 444 crossbred pigs. In Exp. 1, initial and final weights of pigs were 17.7 and 33.3 kg, respectively, for the 28 d experiment. Pigs fed the 13% protein diet containing added Lys (.17%) or Lys + C had average daily gains (ADG) similar to those fed the 16% protein diet (positive control group) and greater (P less than .05) than those of pigs fed the 13% protein diet (negative controls). Pigs fed the 13% protein diets containing C had average daily feed intakes (ADFI) and ADG similar to those of pigs fed the 13% protein diet / Lys. Main effect comparisons among the 13% protein groups indicated that C increased (P less than .05) ADFI and ADG and that Lys increased (P less than .01) ADG and G:F ratio. In Exp. 2, the initial pig weight for the 28 d starter period averaged 7.4 kg. A 28 d grower period followed, in which the protein level was lowered 2% across treatments. The high and low dietary protein level sequences consisted of 18 and 15%, respectively, during the starter period followed by 16 and 13%, respectively, during the grower period. Lys and(or) Trp additions were also lowered from .18 and .05% to .15 and .04%, respectively. The overall 56 d performance indicated that pigs fed the low protein dietary sequence supplemented with either Lys or C had ADFI and ADG similar to those of the high protein dietary sequence positive control group and greater (P less than .05) than those of the low protein negative control group. The combination of Lys + C further increased (P less than .05) the ADG over that of the high protein sequence group. Overall main effect comparisons among the low protein dietary sequence groups indicated that either added Lys or C increased (P less than .01) ADFI and ADG, with added Lys also increasing G:F ratio. However, added Trp did not improve any performance characteristics. These results indicate that C had a Lys sparing effect in low protein corn-soybean meal diets fed to young pigs.

The effect of protein deprivation on the validity of creatinine and urea in evaluation of renal function. An experimental study in the goat

Abstract: Reliability of plasma creatinine and urea concentrations and clearances in evaluation of renal function was studied in four goats on two diets of equal energy content but differing in protein (14% and 2% of dry matter). Glomerular filtration rate (GFR) was measured with [hydroxymethyl-14C] inulin. GFR was 88.6 +/- 8.4 ml/min on the high protein diet and 36.9 +/- 2.9 ml/min on the low protein diet. The endogenous creatinine clearance values agreed with the inulin clearances on both diets. Reduction of protein intake was followed by significant increase in plasma creatinine concentration (from 83.8 +/- 3.6 mumol/l during high protein diet to 124.6 +/- 3.5 mumol/l during low protein diet). Plasma urea concentration, urea clearance and urea excretion fell to a very low level during low protein intake. Endogenous creatinine clearance seems to be suitable for measurement of GFR even during protein deprivation when GFR is decreased.