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[Effect of carbostimulin and its mixture with vitamin D3 on the mineralization process of the bone callus in rabbits].

Mineralization of rabbit bone callus was studied within 15 days after resection of the upper part of radius bone inder conditions of treatment with carbostimuline and its mixture with vitamin D3. Content of calcium in the bone regenerate was increased by 40.8% after administration of carbostimuline and--by 70.5% after treatment with mixture containing vitamin D3. These preparations caused only slight effects on the phosphorus content. Dry residue in the regenerate os f animals, treated with the preparations, was increased approximately 2-fold (43% and 23%, respectively, p less than or equal to 0.001) as compared with control group. Content of citric acid was distinctly higher in the bone tissue of the treated animals. Within 15 days after the operation content of sialic acids wanormalized in blood serum of the animals. The data obtained were corroborated by X-ray and histologic examinations.

Animals↗
PubMed1976

Mung bean nuclease I. Physical, chemical, and catalytic properties.

A simplified purification procedure for mung bean nuclease has been developed yielding a stable enzyme that is homogeneous in regards to shape and size. The nuclease is a glycoprotein consisting of 29% carbohydrate by weight. It has a molecular weight of 39 000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme contains 1 sulfhydryl group and 3 disulfide bonds per molecule. It has a high content (12.6 mol %) of aromatic residues. Approximately 70% of the enzyme molecules contain a peptide bond cleavage at a single region in the protein. The two polypeptides, 25 000 and 15 000 daltons, are covalently linked by a disulfide bond(s). Both the cleaved and intact forms of the enzyme are equally active in the hydrolysis of the phosphate ester linkages in either DNA, RNA, or adenosine 3'-monophophate. The enzymatic activity of mung bean nuclease can be stabilized at pH 5 in the presence of 0.1 mM zinc acetate, 1.0 mM cysteine, and 0.001% Triton X-100. The enzyme can be inactivated and reactivated by the removal and readdition of Zn2+ or sulfhydryl compounds.

Amino Acids↗
PubMed1979

The role of zinc with special reference to the essential thiol groups in delta-aminolevulinic acid dehydratase of bovine liver.

delta-Aminolevulinic acid dehydratase (5-aminolevulinic acid hydro-lyase (adding 5-aminolevulinic acid and cyclizing), EC 4.2.1.24 purified from bovine liver in the presence of both SH-reducing reagent and zinc during the purification contained one zinc atom and eight SH groups/subunit. This preparation showed the full enzymatic activity even in the absence of thiol activator. It was found that two cysteine residues, one zinc atom and two histidine residues were involved in the active site. The enzyme was fullly active as long as two SH groups in the active site remained in the reduced form even in the absence of zinc. However, the enzymatic activity was completely lost, with a concomitant loss of bound zinc, upon oxidation of the SH groups to a disulfide bond, modification of SH groups with chemical reagents, or mercaptide formation by heavy metals. Thus, it is apparent that the activity depends on the essential SH groups. The zinc is not absolutely essential for the activity but may be required to prevent the essential SH groups from autooxidation by coordination. Binding experiments indicated that there was one binding site of zinc/subunit. Photooxidation of histidine residues diminished both enzymatic activity and bound zinc, suggesting that the histidine residues not only constituted the active site but also served as a possible ligand to zinc.

Animals↗
PubMed1977

The relationship of zinc to protein utilization in the preadolescent child.

The effects of zinc intake on nitrogen utilization was investigated during a 20-day balance study with 23 preadolescent girls. The children were fed a diet which provided 4.17 g of nitrogen and 5.5 mg of zinc daily; the diet was supplemented with a combination of 5 mg of zinc and/or nitrogen supplied from either amino acids or nonspecific nitrogen. Complete collections of excreta were made throughout the study. Neither the supplementation of amino acids nor zinc improved the retention of nitrogen. Urinary excretion of urea nitrogen, uric acid, and creatinine were not different as a result of zinc supplementation. Subjects consuming the lower level of zinc were in negative zinc balance, but the subjects consuming 10.5 mg of zinc were in positive balance. The supplementation of this low protein diet with amino acids did not improve nitrogen retention.

Amino Acids↗
PubMed1978

Induction by alpha-mercapto-beta-arylacrylic acids of low-molecular-weight zinc-binding protein in rat liver.

Intraperitoneal injections of alpha-mercapto-beta-(2-furyl)acrylic acid (MFA) induced incorporation of zinc into a low-molecular-weight metalloprotein fraction in rat-liver cytosol. Cytosol of control rats contained little or none of this material. alpha-Mercapto-beta-(2-thienyl)acrylic acid induced less incorporation of zinc in this fraction than did MFA. Twenty-two hours after administration of 65ZnSO4 (50 mumol/kg) and MFA (200 mumol/kg), serum concentrations of both total and radioisotopic zinc were markedly elevated, compared to serum concentrations in rats administered only 65ZnSO4. Further, in livers of MFA-treated rats, radioisotopic zinc concentration was significantly greater in all cytosol zinc-containing proteins resolved by gel chromatography, but total zinc was elevated only in the metallothionein fraction and not in proteins of higher molecular weight. This appears to be the first example of induction of a metallothionein-like protein by a procedure not involving food restriction or administration of metal salts.

Acrylates↗
PubMed1976

Bovine lens leucine aminopeptidase. A study of possible roles for the thiol groups in holo- and apoenzyme.

The apoenzyme of leucine aminopeptidase has to be prepared either under inert conditions or in the presence of 2-thioethanol. Due to the removal of essential zinc ions, buried -SH groups are exposed. These -SH groups show a higher reactivity than the six -SH groups accessible in the native zinc enzyme. During the incubation of the zinc enzyme with guanidine hydrochloride, up to 36 -SH groups are titratble in dependence on the concentration of guanidine hydrochloride. The -SH groups can be distinguished by their reactivity towards Ellman's reagent and can be differentiated into four classes with respect to their function.

Animals↗
PubMed1977

An improved method for measuring blood mercaptans.

An improved method for measuring MT in the blood is described which uses zinc as a reducing agent and utilizes a more sensitive gas chromatograph. The method measures covalently bound MT that was not previously detected and permits determinations in patients for the first time. The average normal whole blood MT in rat blood was 200 +/- 42 pmol/ml and in human blood 229 +/- 29 pmol/ml. Eleven rats in experimental hepatic coma following acute massive hepatic necrosis had blood levels four to 18 times the average normal, and seven cirrhotic patients with hepatic encephalopathy or coma had blood levels four to five times the average normal.

Animals↗
PubMed1977

[Biochemical evaluation of damage due to lead: importance and significance of erythrocyte zinc-protoporhyrin IX and urinary amino acid determination].

The early detection of lead intoxitation needs practical, simple, reproducible and diagnostically valid screening test. The determination of ALA-D (delta-amino-levulinic acid-dehydratase) in erythrocytes is one of the most reliable test for the evaluation of the occupational exposure to lead. However this test is difficult to standardize, sensible to lead contamination of laboratory glassware and the activity of enzyme decreases rapidly if stored. The determination of erythrocytes ZPP (zinco-protoporphyrin IX) was proposed as useful, alternative test. The protoporphyrin IX is a metabolic intermediate in heme biosynthesis; in erythrocytes is present as free form and zinc-boundend compound. The ZPP give high values only in lead intoxication and sideropenic anemia. The ALA-D and ZPP in erythrocytes were measured and compared in a group of workers exposed to lead. We have shown a good correlation between these two biochemical parameters. Aminoacid excretion in urine from workers exposed to lead was measured and compared with other biochemical parameters of intoxication. All lead workers examined had excessive urinary CP (coproporphyrin) and ALA (delta-amino-levulinic acid) excretion. An abnormal excretion of glycine was present in eight workers (32%), whereas in other four (15%) the glycinuria was at limit of normal values. An abnormal excretion of lysine was present in six workers (21%). The last data appear very interesting because the action of lead in lysine metabolism was not known.

Aminolevulinic Acid↗
PubMed1975

Inhibitory effect of benzethonium and zinc chloride mouthrinses on human dental plaque and gingivitis.

In a double-blind study the plaque- and gingivitis-inhibiting capacities of three aqueous mouthrinse solutions of benzethonium chloride, zinc chloride, and benzethonium chloride combined with zinc chloride were compared to those of a placebo mouthrinse. Forth-three adults with clean teeth and healthy gingiva were randomly assigned to the treatment and control groups. All participants received an initial prophylaxis. Assessments of plaque and gingivitis were made before and after a 10-day test period. During this time the subjects suspended oral hygiene procedures and rinsed daily with 20 ml of their respective rinse solutions. According to the measurements made before and after the test period, the mouthrinse containing benzethonium chloride produced 42 to 42.9% less plaque than any of the other three formulations. The differences were statistically significant ( P smaller than 0.05). Gingivitis scores of the four groups did not differ significantly. These findings indicate that benzethonium chloride is a moderately effective antiplaque agent.

Adult↗
PubMed2026

A Review on Heat Stress in Broiler Chickens: Mechanisms, Effects and Mitigation Strategies.

BACKGROUND: Heat stress (HS) is a major environmental challenge for broilers, particularly under rising global temperatures and high humidity. Broiler chickens are highly susceptible because of their rapid growth rate, high metabolic heat production, limited thermoregulatory capacity and genetic selection for fast growth. OBJECTIVE: This review aims to synthesise current evidence, evaluate the effectiveness of existing mitigation strategies, identify key knowledge gaps and provide future research directions to improve broiler resilience, welfare and productivity under increasingly HS conditions. METHODS: This review synthesised evidence published between 2010 and 2025 on the physiological, metabolic, intestinal, immunological and productive consequences of HS and evaluated mitigation strategies. RESULTS: The reviewed studies demonstrate that HS reduces feed intake by approximately 10%-30%, suppresses body weight gain and feed efficiency and increases mortality, with severity depending on temperature, humidity and broiler genotype. HS disrupts carbohydrate, protein and lipid metabolism; induces acid-base imbalance and oxidative stress; compromises intestinal barrier integrity; alters gut microbiota; suppresses immune function; and reduces meat quality. Nutritional interventions, including dietary electrolyte balance, antioxidants, vitamins, selenium, zinc, phytogenic compounds, probiotics, betaine and optimised feeding strategies, environmental management and genetic approaches, including naked-neck and frizzle genes, can partially alleviate these adverse effects. However, inconsistencies among studies persist because of differences in broiler strains, environmental conditions, dietary formulations and experimental protocols. CONCLUSION: HS substantially compromises broiler health, welfare, productivity and meat quality. Nutritional, environmental and genetic approaches can partially mitigate its adverse effects; however, further research is needed to improve broiler resilience under increasingly HS conditions.

Animals↗
PubMed1977

Thiolation and disulphide cross-linking of insulin to form macromolecules of potential therapeutic value.

Macromolecules have been prepared containing native insulin carried by a modified insulin skeleton made by partially thiolating the insulin hexamer and forming intermolecular cross-links through disulphide bridges. Oxidation of partially thiolated insulin (0.5-0.7 SH group/mole), formed by reacting insulin with AHTL, with, (a) potassium ferricyanide, (b) Cu++-oxygen gave water soluble macromolecules containing 20-26 and 410-708 monomer units respectively which had rod-random coil shape (light scattering). The larger molecules formed by (b) contained 8g-atom CU++/hexamer unit and insulin. The insulin was firmly bound within the marcomolecules and was probably bound within an insulin-modified insulin hexamer through coordination to copper.

Chemical Phenomena↗