Changes in the activities of NADP+‐linked dehydrogenases during ontogenesis in the chicken

1. Changes in the activities of glucose‐6‐phosphate dehydrogenase [EC 1.1.1.49], 6‐phosphogluconate dehydrogenase [EC 1.1.1.44] and cytoplasmic and mitochondrial “malic” enzyme [EC 1.1.1.40] and NADP⁺‐linked isocitrate dehydrogenase [EC 1.1.1.42] were measured in the liver, heart, lung and brain during ontogenesis in the chicken.

2. In the liver the cytoplasmic malic enzyme was constant during embryonal development, increasing suddenly and markedly thereafter and isocitrate dehydrogenase increased in the embryo and decreased after hatching while their mitochondrial isoenzymes showed parallel but less marked changes. Activities of the other dehydrogenases were essentially unchanged.

3. In the heart only cytoplasmic isocitrate dehydrogenase showed important changes, increasing three‐fold during growth after hatching.

4. In the lung, glucose‐6‐phosphate dehydrogenase and cytoplasmic malic enzyme attained their maximum activities respectively at 16 to 18 d and 14 d of development. Mitochondrial malic enzyme did not change, while isocitrate dehydrogenase reached its maximum between 14 and 18 d.

5. In the brain cytoplasmic malic enzyme was activated only after hatching, while its mitochondrial isoenzyme and isocitrate dehydrogenase showed discontinuous variations of an insignificant magnitude. Other activities were unchanged.

     

Cell surface immunoglobulin regulated checkpoints in chicken B cell development

The bursa of Fabricius is critical for the normal development of B lymphocytes in avian species. Productive colonization of bursal follicles by B cell precursors requires surface immunoglobulin expression. We have shown using retroviral gene transfer that expression of chimeric receptors containing the extracellular and transmembrane domains of murine CD8alpha and CD8beta fused to the cytoplasmic domains of chicken Igalpha and Igbeta can support productive bursal colonization in the chicken embryo in bursal cells lacking the expression of endogenous sIgM. We show here that chimeric receptor expression does not support continued bursal cell development after hatch. However intrabursal administration of anti-CD8 antibodies that ligate the CD8alpha:Igalpha chimeric receptor results in maintained numbers of bursal cells that express the chimeric receptor in the absence of endogenous sIgM. These results support a model in which sIgM receptor expression is required for productive bursal colonization in the chick embryo but sIgM receptor ligation is required to support later B cell development after hatch.     

Microstructure,texture and colour development during crust formation on whole muscle chicken fillets

1. The development of crust during a 22-min period was evaluated in an oven, and in previously cooked-in-bag products (no crust) placed in an oven for 10 min. The oven-roasted products started to develop a thin (2–4 μm) crust layer after 4 min. At that point, the colour of the fillets turned white but no browning was observed. As roasting time increased, crust thickness and shear force increased, the product turned brown and eventually black at certain spots.

2. Light microscopy revealed the shrinking of muscle fibres close to the surface, as they also lost water. At a certain point, tears between the different layers started to appear. The inner muscle fibres also progressively shrank and the spaces between them increased. Microscopy of cook-in-bag products revealed no crust formation during heating. Upon moving to the oven, crust started to form but was much faster compared with the other products.

3. Cook-in-the-bag samples showed a higher rate of cook loss during the first 12 min (to internal 70°C) compared with oven heating. This could have been due to the fast heating rate in water and/or no crust formation.

4. White colour was fully formed on water-cooked fillets within 2 min (L* = 83), while it was gradually forming on oven-roasted samples (max L* of 79 after 12 min).

5. Shear force measurements showed an increase in both treatments up to 18 min, with a decrease thereafter (when dry crust started to crack).     

Volatile components of raw chicken breast muscle

The volatile components of raw chicken breast muscle have been analysed. Twenty‐two components have been separated and twenty have been tentatively identified. Circumstantial evidence is presented to support the hypothesis that these volatile components may be divided into two classes according to their origin: namely those that are endemic, mainly carbonyls, and those that are adventitious, mainly thiols, sulphides and alcohols. From analyses of the caeca of both living and dead birds it is further proposed that the substantial micro‐flora present in this organ may be a major metabolic source of adventitious muscle components.     

Early steps of insulin receptor signaling in chicken and rat: apparent refractoriness in chicken muscle

The early steps of insulin receptor (IR) signaling (tyrosine phosphorylation of IR beta-subunit, IRS-1 and Shc and PI 3'-kinase activity) have been characterized in two target tissues in the chicken: liver and muscle. The signaling cascade appeared to depend on nutritional status in the liver, but not in muscle (with a possible exception for a minor tyrosine phosphorylation of the 52 kDa Shc isoform). In this study, we compared the responses of the liver and muscle to exogenous insulin (10 or 1000 mU/kg) in chickens and rats. In the liver, IRS-1 and Shc proteins were present in smaller amounts and the regulatory subunit p85 of PI 3'-kinase was present in larger amounts in chickens than in rats. In the basal state (saline injection), the level of tyrosine phosphorylation of IR was lower, and that of Shc higher, in chickens than in rats. PI 3'-kinase activity in chickens was half that in rats. Insulin activated all components of the cascade in a dose-dependent manner in both species. A different pattern was observed in the muscle. In the basal state, the levels of tyrosine phosphorylation of IR and of PI 3'-kinase activity were much higher in chickens than in rats (by factors of 2 and 30, respectively). Insulin strongly activated all components of the cascade in rats (but with no significant increase in the phosphorylation of Shc). No activation was observed in chickens (with only a slight but significant increase in the tyrosine phosphorylation of Shc). The insulin cascade therefore appears to respond normally in chicken liver but to be refractory in chicken muscle. The large amount of p85 and high levels of PI 3'-kinase activity in muscle may contribute to this situation, making chicken muscle an interesting model of insulin resistance.     

The muscular dystrophic chicken is hypernatremic

1. The E3 ubiquitin protein ligase 1 (WWP1) gene, the mutation of which causes muscular dystrophy in chickens, is expressed not only in the pectoral muscle, but also in a number of tissues such as the kidney. Therefore, this study examined some parameters related to kidney function in muscular dystrophic (MD) chickens.

2. Plasma osmolality, Na⁺ and K⁺ concentrations, aldosterone levels, and the expression of aquaporin (AQP) 2, AQP3, and α subunits of the amiloride-sensitive epithelial sodium channel (αENaC) were analysed in the kidneys of 5-week-old MD chickens and White Leghorn (WL) chickens under physiological conditions or after one day of water deprivation.

3. Plasma osmolality, Na⁺ concentrations, and plasma aldosterone levels were significantly higher in MD chickens than in WL chickens. αENaC mRNA expression levels were lower in MD chickens than in WL chickens. AQP2 and AQP3 mRNA expression levels were similar in the two strains of chickens.

4. Plasma osmolality correlated with aldosterone levels and AQP2 and αENaC mRNA levels in WL chickens. In MD chickens, plasma osmolality correlated with AQP2 mRNA levels, but not with plasma aldosterone or αENaC mRNA levels.

5. These results suggest that neither water reabsorption nor the expression of AQP2 and AQP3 is impaired in MD chickens and that a WWP1 gene mutation may or may not directly induce an abnormality in Na⁺-reabsorption in the kidneys of MD chickens, potentially through αENaC.     

Protein metabolism in chicken muscle cell cultures treated with cimaterol

Primary muscle cell cultures were prepared from the leg muscle of 12-d broiler chicken embryos. The partitioning agent cimaterol (10(-6) to 10(-10) M) was added on d 1 and each day thereafter, and cells were studied after 7 d in culture. Cimaterol had no effect at any level either on the percentage of nuclei within multinucleated myotubes or on the total number of nuclei within myotubes. At 10(-7) M cimaterol, the quantity of the myofibrillar protein fraction was increased by 25.1 +/- 8.0% (P less than .05) and the quantity of myosin heavy chain was increased by 30.9 +/- 4.5% (P less than .05). To understand the basis for the increase in myofibrillar protein, the incorporation rate of [3H]Leu was measured in pulse labeling experiments. The apparent synthesis rate of the soluble protein fraction and the crude myofibrillar fraction was not significantly increased by cimaterol; however, cimaterol levels greater than 10(-8) M caused a 10 to 12% increase (P less than .05) in the incorporation rate of [3H]Leu into myosin heavy chain. The effect of cimaterol on release of [3H]Leu from prelabeled protein also was assessed in pulse-chase experiments; the apparent rate of protein degradation was inhibited by 10 to 15% (P less than .05) at the higher levels of cimaterol. Dot blot analysis indicated that the quantity of myosin heavy chain mRNA was elevated in cimaterol-treated cultures. Thus, the increased quantity of myofibrillar proteins in embryonic broiler muscle cell cultures is the combined result of a stimulation in the rate of protein synthesis and an inhibition in the rate of protein degradation.     

Serum levels of chicken mannan-binding lectin (MBL) during virus infections; indication that chicken MBL is an acute phase reactant

Mannan-binding lectin (MBL) is a serum collectin which is believed to be an opsonin of the innate immune defence against various microorganisms. MBL is a minor acute phase reactant in man. We investigated the concentration of serum MBL in chickens infected with infectious bronchitis virus (IBV) and infectious laryngotracheitis virus (ILTV). The concentration of serum MBL increased about twofold (from approximately 6 to 12 μg/ml) due to these viral infections. The concentration peaked 3–7 days after infection with IBV, and 3–5 days after ILTV infection, depending on the ILTV strain used. The increased levels returned to normal values 6–10 days after infection. The results indicated that MBL is a minor acute phase reactant in chickens.     

H-FABP基因在芦花鸡等3种优质肉鸡胸肌中的差异表达

利用实时荧光定量PCR技术对110日龄芦花鸡、黄鸡和麻鸡胸肌中H-FABP基因mRNA表达水平的差异进行了检测。结果表明,H-FABP基因在3种优质肉鸡胸肌中的表达水平呈现出显著的品种差异,其中麻鸡胸肌中H-FABP基因的表达水平显著比芦花鸡和黄鸡小174.8%,170.07%（P〈0.05）,而芦花鸡与黄鸡差异不显著（P〉0.05）。这为进一步研究3种肉鸡的肌肉品质和脂肪性状提供了依据。     

离子对反相高效液相色谱法测定盐酸氨丙啉在鸡肉中残留方法的建立

目的:建立检测鸡肉中盐酸氨丙啉的离子对反相高效液相色谱法。方法:乙腈处理鸡肉组织,正己烷液-液分配除去脂肪等杂质,W atersOasisHLB固相萃取柱进行净化处理。色谱柱为SunfireTMC18(250 mm×4.6 mm,5μm)柱,以甲醇-5 mmol/L庚烷磺酸钠水溶液(40∶60)(其中每100 mL 5 mmol/L庚烷磺酸钠水溶液含冰醋酸2.4 mL,三乙胺0.6 mL)为流动相,流速1.0 mL/m in,检测波长为270 nm,柱温:30℃。结果:盐酸氨丙啉在0.05μg/mL~1.5μg/mL范围内线性关系良好,相关系数R=0.999 907,平均回收率为(82.30±3.20)%,最低检测限为0.04μg/g。该方法符合兽药残留检测要求。     

酶联免疫法测定鸡肉中尼卡巴嗪残留

为了建立鸡肉中尼卡巴嗪残留标志物4,4’-二硝基均二苯脲（DNC）残留酶联免疫（ELISA）检测方法。将N-琥珀酰-L-丙氨酰-L-丙氨酰-L-丙氨酸4-硝基苯胺（SAN）与载体蛋白偶联作为抗原免疫动物,获得抗DNC抗体,在此基础上建立了鸡肉中尼卡巴嗪残留的检测方法。人工抗原中SAN与载体蛋白的结合比约为12：1,血清效价1：2000倍,鸡肉中检测限为9．2μg／kg,添加回收率在49．4％～118％之间,批内、批间变异系数均小于20％。该方法在灵敏度、精密度和准确度方面均能满足兽药残留筛选检测要求。     

微生物法测定鸡肉组织中的氨苄西林残留

采用藤黄八叠球菌作为测试菌,用标准曲线进行定量测定,建立了鸡肉组织中氨苄西林残留的微生物学检测方法.在8.89～67.50 ng/mL浓度范围内抑菌圈直径与药物浓度的线性关系良好,相关系数达0.997以上,回收率为77%～96%,批内变异系数≤10%,批间变异系数≤11%.该方法具有样品前处理简单、操作简便、具备一定灵敏度和特异性等优点,可作为一种筛选方法对大批样品同时检测.     

鸡心肌细胞培养及免疫组化鉴定

心肌细胞是研究心脏肥大、心脏衰竭、心肌缺血再灌注损伤及自由基损伤等病理过程发生发展的主要环节。心肌细胞的培养有助于深入研究心脏疾病的病理机制。在人类医学中培养心肌细胞进行研究已成为心血管系统疾病研究的主要手段[1,5～ 7] 。随着对禽类心血管系统疾病研究的不断深入 ,以培养的心肌细胞为材料进行研究将占重要地位[2 ,3,8] 。鸡胚心肌细胞培养方法已经成熟 ,但有些禽类疾病如肉鸡腹水综合征 ,利用疾病高发日龄 ( 2 7～ 45天 )鸡的心肌细胞进行研究应该更能够准确地反映该病发生发展过程中心肌细胞的病理机制。因此 ,需要探索出…     

Partial autolysis of μ/m‐calpain during post mortem aging of chicken muscle

The objective of this study was to investigate changes occurring in μ/m‐calpain in post mortem chicken muscles and to determine the origin of the unknown bands found in calpain casein zymography. The unknown bands were reported with slightly greater mobility compared to conventional μ/m‐calpain bands in casein zymography. Identification of these bands was accomplished using native polyacrylamide gel electrophoresis, liquid chromatography tandem mass spectrometry and with protein phosphatase treatment. Results showed that the unknown bands were corresponding to μ/m‐calpain, and dephosphorylation by protein phosphatase did not change their appearance. The calpain samples were then incubated with various concentrations of Ca²⁺ to determine the relationship between changes in μ/m‐calpain and the appearance of the unknown bands. The products of μ/m‐calpain partial autolysis were found to be consistent with the appearance of the unknown bands. Therefore, the appearance of these bands did not result from phosphorylation of μ/m‐calpain as previously hypothesized, but from partial autolysis of μ/m‐calpain. Also their presence suggests that μ/m‐calpain undergoes partial autolysis during aging which may play certain roles in meat quality improvement.     

Tumor suppressor PTEN is mutated in canine osteosarcoma cell lines and tumors

Canine osteosarcoma (OS) cell lines contain mutations that directly or indirectly inactivate the tumor suppressor genes p53 and retinoblastoma. Another important tumor suppressor, PTEN, is mutated in many human cancers. To determine whether inactivation of PTEN plays a role in the pathogenesis of canine OS, we studied its expression in canine OS cell lines and tumors. Four of five canine OS cell lines (CO2, C03, CO5, and CO7) constitutively express high levels of the phosphorylated form of Akt, an indirect indicator of aberrant PTEN expression. PTEN protein is essentially absent from three of these cell lines (CO2, CO5, and CO7), whereas C03 contains a potentially inactivating amino acid substitution in PTEN at codon 340. Genomic hybridization experiments indicate that CO2, CO5, and CO7 contain large deletions within the PTEN gene. Ten of 15 OS tumors exhibit variable or negative PTEN staining. Evaluation of a PTEN-negative staining tumor by Southern blotting indicates that the PTEN gene is deleted in this tumor. These results indicate that PTEN is mutated or downregulated in a high percentage of canine OS cell lines and tumors and likely plays an important role in the pathogenesis of the disease.     

Development of the glandular epithelium of the bovine parotid gland during ontogenesis

The development of the parotid gland was examined in 36 bovine embryos and foetuses with a crown-rump-length (CRL) from 28 up to 1000 mm by light, transmission electron microscopical and actin-immunohistochemical methods. The anlage of the parotid gland in an embryo with 28 mm CRL can be found at the lateral angle of the primitive oral cavity as a local thickening of the epithelium. During the second month, the differentiation of primary ducts and endbuds starts and a lumen develops in the primary ducts. At the end of the second month a lumen appears in the terminal endbuds. In the immature endpiece cells first secretory granules can be seen from a CRL of 240 mm. In the third month differentiation between intra- and inter-lobular ducts is possible. Immature myoepithelial cells present as a basal layer of flattened cells between the epithelial cells and the basement membrane at the end of the second month. During further development they increase in number, become more flattened and form long cellular processes. At the end of the fourth month isolated actin filament bundles are formed, which were also detected by an antibody against smooth muscle actin. The actin filaments condense continuously until they fill the cell processes completely at the end of foetal development.     

Some aspects of carbohydrate metabolism in the lungs of the domestic fowl during ontogenesis

1. Changes in carbohydrate metabolism of the lung during embryonic and subsequent development of the chicken were examined.

2. Glycogen and glucose concentrations were highest and fructose‐1, 6‐diphosphate and triose phosphate concentrations lowest in embryonic lungs.

3. Activities of glycogen synthase [EC 2.4.1.11], hexokinase [EG 2.7.1.1], 6‐phosphofructokinase [EC 2.7.1.11], fructose biphosphate aldo‐lase [EC 4.1.2.13], and glyceraldehyde‐phosphate dehydrogenase [EC 1.2.1.12] were highest in embryonic tissue.