Protein Breakdown Products Research Articles

The urinary excretion of N tau-methyl histidine in sheep: an invalid index of muscle protein breakdown.

1. The validity of the urinary excretion of N tau-methyl histidine (N tau-MH) in sheep as a measure of the breakdown of muscle protein in vivo was assessed from the urinary recovery of radioactivity following the intravenous administration of N tau-[14CH3]methyl histidine. 2. Recoveries of radioactivity in urine from animals of 4 weeks to 7 years of age were incomplete in 7 d but progressively increased with the age of the animal, becoming almost quantitative (90%) in older animals after recovery for 3 weeks. 3. The incomplete urinary recoveries were not due to partial excretion of N tau-MH in faeces or its oxidation and elimination in expired gases but were related to the presence in muscle of a pool of non-protein-bound N tau-MH which was several times larger than the expected daily urinary excretion. 4. This pool in newly accreted muscle tissue was maintained by retention of some of the N tau-MH released by breakdown of muscle protein. Hence, only a proportion of the N tau-MH released from protein breakdown was available for excretion. This proportion increased with the age of the animal and was probably the main determinant of the improved recoveries of radioactivity obtained in urine from older animals. 5. The non-protein-bound N tau-MH in muscle consisted of free N tau-MH and a dipeptide containing N tau-MH, the latter comprising on average approximately 82% of the total non-protein-bound N tau-MH in muscle. This proportion did not change appreciably with the age of the animal. 6. The dipeptide appeared to be synthesized in muscle from free N tau-MH and was not a terminal product of protein breakdown. 7. The results show that urinary excretion of N tau-MH is not a reliable index of muscle protein breakdown in sheep.

Identification and characterization of the cAMP binding proteins of yeast by photoaffinity labeling

Contrary to previous reports, we find the molecular weight of the major cAMP-binding protein in Saccharomyces cerevisiae to be 54,000 daltons. A number of lower molecular weight proteins have also been identified and are believed to be breakdown products of the major protein. The binding protein is soluble and specific for cyclic purine nucleotides with a 3′:5′ configuration.

Transport of large breakdown products of dietary protein through the gut wall.

Ferritin or tritium labelled immunoglobulin G may, by electron microscopy, be demonstrated entering, within, and leaving the epithelial cells. Quantitative studies using various proteins labelled with radioiodine show that large amounts of protein bound radioactivity may be demonstrated in the tissues after feeding the labelled protein to adult rats by stomach tube. The molecular size of this material as determined by sugar gradient ultracentrifugation of tissue extracts ranges when IgG is fed from 50,000-20,000 Daltons. The material retains its ability to react as antigen with antisera specific to the original molecule: precipitation reactions may be obtained in gels and quantitative studies show that cnosiderable amounts of the protein-bound radioactivity are still specifically precipitable. Such studies have been carried out with alpha-gliadin as well as bovine IgG. At 100 days old rats may absorb as much as 40% of a dose of bovine IgG in the form of these large molecular breakdown products.

Radioimmunoassay of human myelin basic protein in tissue extract, cerebrospinal fluid and serum and its clinical application to patients with head injury

The development of a double antibody radioimmunoassay for myelin basic protein in tissue extract, cerebrospinal fluid and unextracted serum is described. Detection limits for the assays were: for tissue extract 3.1 ng, for cerebrospinal fluid 30 ng/ml and for serum 13.6 ng/ml. Specificity for myelin basic protein is suggested by lack of cross reactivity by tissues other than brain and presence of immunoactivity in cerebrospinal fluid and serum only in samples from patients with brain damage due to intracranial surgery or head injury. Immunoactivity in brain extracts and serum from patients with severe brain damage was indistinguishable from authentic myelin basic protein on serial dilution. Cross reacting material in cerebrospinal fluid samples differed from the authentic protein on serial dilution and on Sephadex G-100 chromatography, and may represent breakdown products of myelin basic protein. Mean serum concentrations of myelin basic protein in patients one day after head injury were significantly higher than in control patients with or without other neurological disease. Highest serum myelin basic protein concentrations were found in patients with severe primary intracerebral damage, with peak levels occurring 2–3 days after head injury. In patients with extracerebral haematoma, without intracerebral damage, the peak serum myelin basic protein concentrations occurred 7–10 days after injury. It is suggested that the measurement of serum myelin basic protein concentrations may be valuable in the management of patients after head injury.

Effects of freezing, thawing and storage on some quality factors for portion-size beef cuts

Portion-size beef cuts packaged in oxygen impermeable plastic bags were used to study the effects of rates of freezing and thawing, and storage time and temperature on drip and cooking losses, shear force, destruction of glutathione and accumulation of protein-breakdown products in meat. Portions weighing 150 g or over and frozen in an air-blast at −30°C gave lower losses of drip and lower amounts of nitrogenous constituents in drip than samples weighing less than 150 g or samples frozen in cardboard boxes in still air at −18°C. Freezing and thawing or frozen storage had no significant effect on shear force of meat frozen after ageing. During frozen storage, the destruction of glutathione and accumulation of protein-breakdown products increased, depending directly on storage temperature and time. The results show that a test based on these two biochemical changes would be suitable for assessing the quality of frozen beef.

Klinotaxis and rheotaxis in orientation of sharks toward chemical stimuli

1. 1. EEG and behavioral experiments on lemon sharks ( Negaprion brevirostris) and nurse sharks ( Ginglymostoma cirratum) demonstrate a marked sensitivity of these species to protein breakdown products, especially amino acids and amines. 2. 2. Initial responses of both species during chemical stimulation are stereotyped and similar. 3. 3. Subsequent orientation mechanisms differ. Those of Negaprion involve rheotaxis, while Ginglymostoma utilizes klinotaxis to a greater degree. 4. 4. Recognition of these differing orientation mechanisms appears to resolve some conflicting interpretations in the published observations on shark behavior.

The share of pancreatic lymph and blood circulation in pancreatic self-digestion.

The concentration of 10 ml of131J-tagged albumin infused into the pancreas under pressure of 30 to 50 cm water through the duct of Santorini was found to be significantly higher in the lymph from the thoracic duct than in the plasma from the pancreatic vein, both in normal dogs and in dogs with bile-induced pancreatitis. In both groups, during the first 2 h after infusion more tagged albumin left the gland by way of the blood than the lymph circulation. In the 3. h, the amounts removed were roughly the same. It is an important point that the lymph circulation carries the enzymes and protein break-down products into the circulation circumventing the liver.

Effects of Anabolic Steroids in Chronic Renal Failure

PROTEIN anabolic steroids have been advocated in the treatment of uremia for at least a decade.¹The rationale for their use is to minimize net protein catabolism and thereby decrease the formation of intoxicating protein breakdown products. Despite this rationale and despite their widespread use, it has been difficult for clinicians to evaluate the effects of these steroids in azotemic patients. In the patient with acute renal failure the problem has been to differentiate the steroid effects from other variables which could also influence the level of azotemia. Such variables include infection, gastrointestinal hemorrhage, changing renal function, and numerous stress responses. In contrast, the patients with chronic renal failure are less subject to such changes in protein catabolism and renal function and hence are more amenable to controlled studies. Freedman and Spencer²studied the anabolic effects of testosterone propionate in chronic renal failure patients and noted a fall in blood

Serum osmolality in the coelacanth, Latimeria chalumnae: urea retention and ion regulation.

Samples of blood (hemolyzed) were obtained from the renal vein, the hepatic portal vein, and the heart of a freshly thawed specimen of Latimeria chalumnae. The coelacanth uses high concentrations of urea to maintain its serum osmolality at approximately that of sea water. The mean value for the total osmolality was 1181 milliosmoles per liter. The mean values (milliequivalents per liter) were: for sodium, 181; for potassium, 51.3; for calcium, 6.9; for magnesium, 28.7; for chloride, 199; and for bicarbonate, 4.7. The mean urea concentration was 355 millimoles per liter, and the mean nonprotein nitrogen was 1343 milligrams percent. Heart blood showed significantly lower values for osmolality (921 milliosmoles per liter) and nonprotein nitrogen (1030 mg percent) and was probably less severely contaminated with products of protein breakdown. Fluid from the anterior chamber of the eye showed values of 952 milliosmole/liter; the urea value for this fluid was 303 mmole/liter, and the magnesium was 7.3 meq/liter. The magnesium value for the aqueous humor was used to correct the abnormally high concentrations in the hemolyzed serum. The high level of serum potassium also was attributed to hemolysis.

Separation of cathepsins A and D of skeletal muscle

Cathepsins A and D were separated and partially purified from extracts of chicken breast muscle. The properties of muscle cathepsin D are similar to those of cathepsin D from other sources: optimal activity with hemoglobin substrate at pH 2.8, lack of requirement for cysteine or ferrous ions, and failure to hydrolyze the synthetic peptides acted upon by cathepsins A, B, or C. Muscle cathepsin A showed a greater affinity for CBZ-α- l-glutamyl- l-phenylalanine than for CBZ-α- l-glutamyl- l-tyrosine, was optimally active at pH 5–5.4, and did not require cysteine activation. Cathepsin A alone showed little or no activity on hemoglobin unless cathepsin D also was present. This demonstrates that cathepsin A is restricted in its activity to breakdown products of proteins resulting from the prior action of cathepsin D or, presumably, other proteinases. When isolated from breast muscle of genetically dystrophic chickens, both cathepsins A and D showed the same enzymic properties as those of normal muscle and differed from the latter only in quantity.

Cryochemistry of animal tissue: Biochemical changes in poultry muscle during freezing and storage

Summary The nature of biochemical changes occurring in chicken muscle tissue as a result of freezing and frozen storage was studied to aid in understanding the mechanism of freezing damage and quality deterioration. Comparative studies on freshly frozen muscle showed that slow freezing caused a larger loss of drip on thawing and a larger loss of nitrogenous constituents and nucleic acid derivatives in the drip as well as a larger loss of waterholding capacity than fast freezing. Quantitative examination of muscle proteins showed that protein extractability decreased during frozen storage because of loss of solubility of the actomyosin fraction. This decrease accompanied a loss of adenosine triphosphatase activity and a decrease in the sulfhydryl group content of muscle proteins. The stroma protein fraction remained unaffected, and the sarcoplasmic protein fraction decreased only after long storage. In the nonprotein nitrogen fraction, protein breakdown products increased as a result of proteolysis. The extent of these changes depended directly on storage temperature and time. The results indicate that slow freezing causes greater damage and greater release of proteolytic enzymes to the muscle tissue than fast freezing, and that during frozen storage muscle proteins undergo denaturation and limited proteolysis. The significance of these changes in freezing damage and quality deterioration was discussed.

Determination of Protein in Dairy Products by Dye-Binding

Procedures are given showing the convenience of dye-binding methods applied to such products as fortified milks, evaporated and dried milks, ice cream, and sherbet. For cheese products the dye-binding capacity is lowered by the aging process, because protein breakdown products bind less dye.Parallel results were found using either Orange G or Acid Orange-12 (Udy's dye). The latter dye has some advantage in added sensitivity. Both dyes are bound less as the ratio of protein to dye in the reaction mixture increases. The factor for converting milligrams of dye bound to protein is related to the concentration of free dye remaining.The content of nonfat milk solids in many dairy products may be estimated from the protein content by assuming a constant per cent protein in the mixed milk used in the product.

Studies on the pathogenesis of uremia comparatie determinaions of glucuronic acid, indican, free and bound phenols in the serum, cerebrospinal fluid, and urine of renal diseases with and without uremia

In 50 healthy adults, 56 renal patients with uremic coma, and 24 renal patients without uremic coma, comparative determinations of glucuronic acid, indican, free and bound phenols were carried out in the serum, CSF and urine. In renal insufficiency without uremic coma, a significant increase of all the investigated substances was found in both serum and CSF. In uremic coma, the increase of aromatic protein metabolites, also controlled by paper chromatography, was still correspondingly higher. From observations of the course of the renal insufficiency, it is suggested that the increase of toxic protein breakdown products and the clinical symptoms of uremia are related.

Objective evaluation of quality in poultry meat.

RECENT work in this laboratory1–5 has indicated a relation between biochemical and quality changes occurring in chicken muscle during storage. During frozen storage the buffer-extractable nitrogen of chicken muscle decreased and the products of protein breakdown increased1. The decrease in buffer-extractable nitrogen occurred as a result of loss of solubility of the actomyosin fraction and was accompanied by a loss of sulphydryl groups (−SH) of muscle tissue. During storage at above freezing temperatures, extensive proteolysis occurred, but the changes in the protein extractability and −SH group content of muscle tissue were small2. In meat in which the proteolytic activity had been destroyed by cooking, the −SH groups of muscle tissue decreased progressively during frozen storage without any increase in the protein-breakdown products3. The loss of −SH groups and solubility of muscle protein was accompanied by a loss of tenderness and development of dryness in frozen stored meat, while the amount of protein-breakdown products increased with the development of off-odour in meat stored either frozen or unfrozen.

HYPERBARIC OXYGENATION IN TREATMENT OF GAS GANGRENE.

GAS GANGRENE is the term applied to grave infections produced by a group of anaerobic bacteria of the clostridial group. The clostridial group are ubiquitous and are found in soil, dust, feces, plaster, etc. They require an anaerobic environment to flourish and are easily killed by several antibiotics. Their great tenacity in in vivo infection lies in their ability to dissolve and destroy the surrounding tissues forming a wide enough buffer zone so that no antibiotics can reach them. The characteristic sickly sweet odor and gas of these infections is due to the anaerobic proteolysis with formation of protein breakdown products. Almost all clinicians feel that the usual cause of death in these infections is localized massive electrolyte shifts that are finally unable to be tolerated by the individual. The patient to be presented gave a hint of this during her clinical course. These infections usually make themselves apparent about

Relationship between Concentrations of Ruminal Nucleic Acids and Excretion of Purine Derivatives by Sheep

PURINES can be synthesized in the animal body from glycine, serine, aspartic acid, glutamine, formate and respiratory carbon dioxide, but they are also derived from dietary and cellular nucleoprotein. Recent work with cattle1 and sheep2 has shown that purine derivatives (uric acid and allantoin in urine) are quantitatively important end-products of these ruminants when they are fed on diets with a high-energy, low-protein content and when the animals are in either N equilibrium or slight positive balance. With such diets protein is utilized very efficiently. It is well known that efficiency of protein utilization in the ruminant depends on the catabolic and synthetic activities of the rumen micro-organisms. For high efficiency, the breakdown products of dietary protein and other nitrogenous compounds must be rapidly synthesized into microbial protein in the rumen3. This evidence suggests that most of the allantoin and uric acid excreted by ruminants may be derived from nucleic acids of rumen micro-organisms. Some support for this suggestion has been reported by Blaxter and Martin4, who showed that after ruminal infusion of casein (which is free of purine and pyrimidine bases) slightly more allantoin was excreted than after abomasal infusion of the same quantity of casein.

FRACTURE IN THE RAT. CHRONIC MUSCLE GLYCOGEN AND BONE CHANGE.

T HE PHYSIOLOGICAL and surgical literature of the past 30 years has reflected an intense interest in the metabolic reactions that follow the fracture of a major bone. It is now clear that in the presence of such severe injuries the body enters a phase of extensive tissue catabolism. 3-5 The urinary excretion of large amounts of various products of protein breakdown leads to negative nitrogen balance in the well-nourished individual. Decreased glucose tolerance may develop and body fat is rapidly consumed in the early days after the trauma. 5,8,10 This initial breakdown reaction is followed by a prolonged period in which protein containing tissues and fat deposits are restored to their prefracture state. 7 While a considerable body of data has been accumulated to document widespread metabolic change in the postfracture period, there is very little information available concerning the nature and extent of the biochemical reactions of the

Protein Synthesis and Turn-Over in Cultured Plant Tissue: Sources of Carbon for Synthesis and the Fate of the Protein Breakdown Products

Protein Synthesis and Turn-Over in Cultured Plant Tissue: Sources of Carbon for Synthesis and the Fate of the Protein Breakdown Products

EFFECT OF WHOLE-BODY IRRADIATION ON THE RATE OF INCREASE OF BLOOD UREA NITROGEN FOLLOWING BILATERAL NEPHRECTOMY IN RATS AND RABBITS.

WHOLE-BODY irradiation is one of the procedures used to promote survival of a kidney homograft. Since such irradiation produces extensive cellular damage it might conceivably lead to a rise in the amount of urea and other products of protein breakdown in the blood stream if, as sometimes happens, the graft remains for a time completely anuric or functions poorly. To investigate the matter we have examined the effect of whole-body irradiation, in doses comparable with those used clinically prior to renal transplantation, in rats and rabbits rendered completely anuric by bilateral nephrectomy.

Buffering capacity of sweet sorghum: The effects of nitrogen content, growth stage and ensilage

AbstractThe buffering capacities of sweet sorghum plant material at three stages of growth and at two plant nitrogen levels were compared before and after 5 days of ensilage.Buffering capacity decreased with plant age, but showed no significant relation to total nitrogen content or non‐protein nitrogen content of the plant. The buffering capacity of the fermented forage was, overall, about twice that of the unfermented forage, but this increase was not apparently related to the increase in the products of protein breakdown which occurred during ensilage.