Bioconservation of iron and enhancement of antioxidant and antibacterial properties of chicken gizzard protein hydrolysate fermented by Pediococcus acidilactici ATTC 8042

BACKGROUND

The poultry industry is one of the fastest growing sectors, and it generates considerable quantities of chicken gizzards (CG) every day. However, due to their hard texture and high microbial load, and due to cultural beliefs, they are not preferred by consumers. Chicken gizzards are a substantial source of proteins, iron, and other nutrients, which can be used effectively to produce nutraceuticals, rich in peptides (antioxidants and antibacterial), bio-iron, essential free amino acids, and fatty acids vital for human health.

RESULTS

Lactic acid fermentation of CG by Pediococcus acidilactici ATTC 8042 increased the antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), azino-bis (3-ethylbenzothiaziline-6-sulphonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) by up to 26 times compared with unfermented CG (P < 0.05). The amount of hydrolysis and solvents (ethanol and water) used for extracting protein hydrolysates significantly affected the antioxidant properties. Moreover, fermented CG showed a negligible reduction in bio-iron (2-3%) compared with heat-processed CG (85 °C for 15 min), in which bio-iron was reduced by up to 20.3% (P < 0.05). The presence of unsaturated fatty acids such as C20:4 and C22:4 n-6 indicated a low level of lipid oxidation.

CONCLUSION

Fermented CG, with its reasonably high antioxidant and antibacterial activity, together with a substantial amount of bio-iron and other nutritional components can serve as a functional food or feed additive to reduce oxidative stress and to treat iron deficiency. © 2020 Society of Chemical Industry.

Elemental imbalance elicited by arsenic and copper exposures leads to oxidative stress and immunotoxicity in chicken gizzard, activating the protective effects of heat shock proteins

Arsenic (As) and copper (Cu) are ubiquitous pollutants that pose a threat to the environment. Our aim is to study the underlying mechanisms by which As and Cu act on the chicken gizzard. In order to detect ionic disorders in chicken gizzard under chronic treatment with As³⁺ and/or Cu²⁺ and whether they can induce oxidative damage as well as immune disorders, 30 mg/kg arsenic trioxide (As₂O₃) and/or 300 mg/kg copper sulfate (CuSO₄) were added to the chicken's basal diet. After 12 weeks of exposure, trace elements were found to have significant interference, accompanied by damage to the antioxidant system. In addition, As³⁺ and/or Cu²⁺ activated the nuclear factor kappa B (NF-κB), inducing severe inflammation. At the same time, damaged structural integrity which might be caused by inflammation was discovered after hematoxylin and eosin (H&E) staining. Moreover, symbolic Th1/Th2 (Th, helper T cell) drift was also observed in treatment groups, meaning that immune function is left to be affected, and the increment in heat shock proteins may be a self-protective mechanism of gizzard. Interestingly, we found that the damage to the gizzard of chicken was aggravated in a time-dependent manner, and the combined exposure was more pathogenic than the single exposure, of which the mechanism needs further exploration. Together, this work helps move us toward a better understanding of the molecular mechanisms that mediate the interactions between Cu excess and As³⁺ exposures and possible health consequences in susceptible species.

The disturbance of autophagy and apoptosis in the gizzard caused by copper and/or arsenic are related to mitochondrial kinetics

As toxic elements when excessive, arsenic (As) and copper (Cu) are two naturally occurring elements that may be ingested by the organism at the same time. However, the precise damaged mechanism and the pathways that are activated by As and/or Cu is rarely researched in gizzard, a unique organ of birds. In this study, ultrastructural observations, TdT-mediated dUTP Nick-End Labeling, real-time quantitative PCR and Western blotting were performed to evaluate the toxic effects of chronic exposure to Cu²⁺ and/or arsenite on chicken gizzard. The results revealed that increased apoptosis and autophagy levels induced by Cu²⁺ and arsenite appeared to be independent of oxidative stress, which didn't have significant changes in different treatment groups at the same time point. Nevertheless, the redox balance gradually deviated with the extension of time. And increased mitochondrial division and decreased fusion were also caused by Cu²⁺ and arsenite. In conclusion, apoptosis and autophagy in gizzard induced by Cu²⁺ and/or arsenite, at least, strongly linked with the disruption of mitochondrial homeostasis. Our study showed that the combination of Cu²⁺ and arsenite produces stronger toxicity. The results of this study can serve as a reference for agicultural feeding and environmental protection, that is, to avoid the combined exposure of Cu²⁺ and arsenite to prevent greater economic losses and health risks.

Selenium Deficiency Induced Injury in Chicken Muscular Stomach by Downregulating Selenoproteins

The aim of the present study was to examine the effect of selenium (Se) deficiency on the expression of selenoproteins in chicken muscular stomach and to detect the correlation of selenoproteins with muscular stomach injuries. One-day-old broiler chickens were maintained for 55 days on a normal diet (0.2 mg/kg) or a Se-deficient diet (0.033 mg Se/kg). The expression levels of 25 selenoproteins, heat shock proteins (HSPs), and inflammatory factors were then examined by real-time PCR. Following this, the correlation between selenoproteins, HSPs, and inflammatory factors was analyzed by principal component analysis (PCA). The results showed that Se deficiency decreased the expression of 25 selenoproteins (P < 0.05), but increased the expression of HSP27, HSP40, HSP60, HSP70, and HSP90, and NF-κB, iNOS, TNF-α, COX-2, and HO-1 (P < 0.05). Selenoproteins showed a high negative correlation with HSPs and inflammatory factors. Thus, the results suggested that Se deficiency induced muscular stomach injuries by decreasing the expression of selenoproteins. In addition, selenoproteins play an important role in regulating HSPs and inflammatory response. The muscular stomach is a key target of Se deficiency and may play a special role in response to Se deficiency.

Lead concentrations in sediments and blue-winged teals (Anas discors) from El Palmar State Reserve, Yucatan, Mexico

Reserve regulations at El Palmar State Reserve, Yucatan, Mexico, prohibit the use of lead (Pb) shot, but hunters continue to use it, and no enforcement is implemented. Pb was quantified in sediments and in blue-winged teal Anas discors. No shot pellets were found in the sediment samples, nor were differences in sediment Pb concentrations observed within the reserve between popular hunting sites and those no longer used for hunting. However, there were differences between the hunting sites and sediments from an adjacent area where hunting is prohibited. Average Pb concentrations were highest at hunting entrances (15.69 ± 18.69 mg/kg) and lowest at decoy locations (5.24 ± 4.84 mg/kg). These averages are lower than the lowest effects level (31 mg/kg), although 10 samples exceeded this level. Pb-shot prevalence in gizzards was 4.88% (n = 41). Pb levels exceeded 5.0 mg/kg dry weight in one or more of the tested tissues (liver, gizzard, and bone) in 14 (34.14%; 7 female, 7 male; 11 adult, 3 juvenile) of the total birds. Bird weight, sex, and age had no effect on Pb concentration. Hunting using Pb shot in the reserve clearly affects Pb levels in sediments and in A. discors that winter there.

Molluscan smooth catch muscle contains calponin but not caldesmon

We isolated Ca(2+)-regulated thin filaments from the smooth muscle of the mussel Crenomytilus grayanus and studied the protein composition of different preparations from this muscle: whole muscle, heat-stable extract, fractions from heat-stable extract, thin filaments and intermediate stages of thin filaments purification. Among the protein components of the above-listed preparations, we did not find caldesmon (CaD), although two isoforms of a calponin-like (CaP-like) protein, which along with CaD is characteristic of vertebrate smooth muscle, were present in thin filaments. Thus, CaD is not Ca(2+)-regulator of thin filaments of this muscle. On the other hand, the mussel CaP-like protein is also not such Ca(2+)-regulator since we have shown that this protein can be selectively removed from isolated mussel thin filaments without loss of their Ca(2+)-sensitivity. We suggest that thin filaments in the smooth catch muscle possess other type of Ca(2+)-regulation, different from that in vertebrate smooth muscles.

Detection, accumulation, distribution, and depletion of furaltadone and nifursol residues in poultry muscle, liver, and gizzard

Nitrofurans were broadly used as an extremely effective veterinary antibiotic especially in pig and poultry production farms. Because of fears of the carcinogenic effects on humans, the nitrofurans were banned from use in livestock production in many countries, including the European Union. The present study examines the accumulation, distribution, and depletion of furaltadone and nifursol and of their tissue-bound metabolites [3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) and 3,5-dinitro-salicylic acid hydrazine (DNSAH), respectively, in poultry edible tissues (muscle, liver, and gizzards) following administration to chickens of therapeutic and subtherapeutic concentrations of both compounds. Nitrofurans determination was performed by high-performance liquid chromatography-diode array detection and liquid chromatography-tandem mass spectrometry, respectively, for feeds and for poultry tissues. Furaltadone and nifursol, in very low concentrations, were found in samples of muscle, liver, and chicken's gizzard collected from slaughtered animals after 5 weeks of treatment and no withdrawal time period. When a withdrawal time period of 3 weeks was respected, no detectable nitrofuran parent compounds was observed in all of the studied matrices. For AMOZ, concentrations of 270 μg/kg in meat, 80 μg/kg in liver, and 331 μg/kg in gizzard were determined after administration of a medicated feed with furaltadone (132 mg/kg), 3 weeks after withdrawal of treatment. For DNSAH, the concentration values obtained are much lower than those observed for AMOZ. For meat, liver, and gizzard, DNSAH concentrations of 2.5, 6.4, and 10.3 μg/kg, respectively, were determined, after administration of a medicated feed with nifursol (98 mg/kg), 3 weeks after withdrawal of treatment. The gizzard could be considered a selected matrix for nitrofuran residues evaluation in poultry, due to its capacity of retaining either nitrofuran parent compounds or metabolites in higher concentrations, regardless of the administered dose or of the respected withdrawal time period.

Trace metal depositional patterns from an open pit mining activity as revealed by archived avian gizzard contents

Archived samples of blue grouse (Dendragapus obscurus) gizzard contents, inclusive of grit, collected yearly between 1959 and 1970 were analyzed for cadmium, lead, zinc, and copper content. Approximately halfway through the 12-year sampling period, an open-pit copper mine began activities, then ceased operations 2 years later. Thus the archived samples provided a unique opportunity to determine if avian gizzard contents, inclusive of grit, could reveal patterns in the anthropogenic deposition of trace metals associated with mining activities. Gizzard concentrations of cadmium and copper strongly coincided with the onset of opening and the closing of the pit mining activity. Gizzard zinc and lead demonstrated significant among year variation; however, maximum concentrations did not correlate to mining activity. The archived gizzard contents did provide a useful tool for documenting trends in metal depositional patterns related to an anthropogenic activity. Further, blue grouse ingesting grit particles during the time of active mining activity would have been exposed to toxicologically significant levels of cadmium. Gizzard lead concentrations were also of toxicological significance but not related to mining activity. This type of "pulse" toxic metal exposure as a consequence of open-pit mining activity would not necessarily have been revealed through a "snap-shot" of soil, plant or avian tissue trace metal analysis post-mining activity.

The differences between the localizations of MUC1, MUC5AC, MUC6 and osteopontin in quail proventriculus and gizzard may be a reflection of functional differences of stomach parts

Mucins are high molecular weight glycoproteins which constitute the major component of the mucus layer and are produce by many epithelial tissues in vertebrates. Osteopontin (OPN) is an adhesive phosphorylated glycoprotein that is expressed by a broad range of tissues and cells. Although gastric mucins MUC1, MUC5AC, MUC6 and OPN have been widely used in histological studies and in diagnostic pathology in order to diagnose gastric carcinomas, their localizations in the stomach of quail have not yet been studied. In this study, the localizations of MUC1, MUC5AC, MUC6 and OPN in the proventriculus and gizzard of Japanese quail during the post-hatching period were compared at light microscope levels by applying immunohistochemical methods. In all ages studied, the immunoreactivity of MUC5AC was present in the lining epithelium of both folds and superficial proventricular glands in the proventriculus, whereas MUC1, MUC6 and OPN reactivity was found in the oxynticopeptic cells of profound proventricular glands. In addition, some cells in the fold epithelium of the proventriculus showed a positive reaction to OPN. The immunoreactivity of MUC1 in gizzard was different from that of MUC5AC. Although MUC5AC was expressed in the cells of both the surface epithelium and profound glands of the gizzard, MUC1 was only localized in the profound glands of the gizzard. However, MUC6 and OPN immunoreactivity was absent in the gizzard. The results indicated that the differences between the localizations of MUC1, MUC5AC, MUC6 and OPN in quail proventriculus and gizzard may be a reflection of functional differences of stomach parts. Although the biological significances of the expressions of MUC1, MUC5AC, MUC6 and OPN in the quail stomach remains unknown, these notable glycoproteins may be associated with barrier function, host defence, and/or secretion.

Ontogeny of ghrelin mRNA expression and identification of ghrelin-immunopositive cells in the gastrointestinal tract of the Peking duck, Anas platyrhynchos

Ghrelin is an acylated peptide and an endogenous ligand for the growth hormone secretagogue receptor (GHS-R), and stimulates growth hormone release and food intake in mammals. Peking duck is a very fast growing species of poultry. Although the sequence and structure of ghrelin have recently been determined, the expression of ghrelin in Peking duck has not been studied. Here, we investigated the tissue expression and distribution of ghrelin by RT-PCR and immunohistochemistry, respectively, in Peking duck at different stages of development. Ghrelin mRNA expression was mainly detected in the proventriculus and proventriculus-gizzard junction. It was first expressed, but weakly, on embryonic day 14 (E14); the expression increased by embryonic day 21 (E21), and was maintained at high levels between post-hatching-day 1 (P1) and post-hatching-day 60 (P60). Weak expression of ghrelin mRNA was also found in the gizzard and duodenum. In the gastrointestinal tract of growing Peking duck in P60, the largest number of ghrelin-ip cells was detected in the epithelium of the compound tubular glands in the proventriculus and the next largest number was in the proventriculus-gizzard junction. Very few ghrelin-ip cells were located in the epithelium of the simple tubular glands adjacent to the gizzard. No ghrelin-ip cells were observed elsewhere in the gastrointestinal tract. Ghrelin-ip cells were found in embryos as early as day E21; at the same time, the compound tubular glands in the proventriculus had formed. The numbers of ghrelin-ip cells on P1 were similar to those of E21 embryos. However, on P60, high numbers of strongly stained ghrelin-ip cells were found to be scattered in the epithelium of the compound tubular glands in the proventriculus. The density of ghrelin-ip cells (cells/mm(2)) in the proventriculus on P60 was significantly greater than those of P1 and E21 embryos. These results demonstrate that ghrelin is expressed in the Peking duck gastrointestinal tract, especially in the proventriculus, from mid-late-stage embryos to growing period and suggested an involvement of ghrelin in the development and biology of the gastrointestinal tract of the Peking duck.

Avian digestive tract simulation to study the effect of grit geochemistry and food on Pb shot bioaccessibility

Lead shot dissolution was investigated in a dynamic in vitro simulated avian gizzard-intestine system. The method allows simulated digestive fluid to pass (at intervals) from a gizzardlike environment to an intestine-based one, and then considers the dissolution of Pb shot (0-3 pellets) in the presence of differing grit geochemistries (siliceous and calcareous) and variable amounts of food (0-4 g of partially milled wheat seed). Dissolved Pb levels in simulated gizzards were consistently higher in the presence of siliceous, than with calcareous, grit. This was also seen in simulated intestines, except when less food was used (0-1 g), when Pb levels in solution were higher in calcareous systems. The Pb concentrations in gizzard and intestine solutions increased directly with the number of Pb shot used. In all treatments Pb levels in intestine liquids were lower than in gizzard liquids. Calcareous grit simulations maintained 2.5-34 times more Ca in solution than those that used siliceous grit. Dietary supplementation with calcareous grit may reduce Pb bioaccessibility of ingested Pb shot in birds by reducing gizzard acidity, by enhancing Pb precipitation (as Pb-carbonate), and by promoting higher dissolved Ca levels in the intestine, which may then compete with Pb for intestinal absorption.

Biochemical properties of gastrokine-1 purified from chicken gizzard smooth muscle

The potential role and function of gastrokine-1 (GNK1) in smooth muscle cells is investigated in this work by first establishing a preparative protocol to obtain this native protein from freshly dissected chicken gizzard. Some unexpected biochemical properties of gastrokine-1 were deduced by producing specific polyclonal antibody against the purified protein. We focused on the F-actin interaction with gastrokine-1 and the potential role and function in smooth muscle contractile properties.

Background

GNK1 is thought to provide mucosal protection in the superficial gastric epithelium. However, the actual role of gastrokine-1 with regards to its known decreased expression in gastric cancer is still unknown. Recently, trefoil factors (TFF) were reported to have important roles in gastric epithelial regeneration and cell turnover, and could be involved in GNK1 interactions. The aim of this study was to evaluate the role and function of GNK1 in smooth muscle cells.

Methodology/Principal Findings

From fresh chicken gizzard smooth muscle, an original purification procedure was used to purify a heat soluble 20 kDa protein that was sequenced and found to correspond to the gastrokine-1 protein sequence containing one BRICHOS domain and at least two or possibly three transmembrane regions. The purified protein was used to produce polyclonal antibody and highlighted the smooth muscle cell distribution and F-actin association of GNK1 through a few different methods.

Conclusion/Significance

Altogether our data illustrate a broader distribution of gastrokine-1 in smooth muscle than only in the gastrointestinal epithelium, and the specific interaction with F-actin highlights and suggests a new role and function of GNK1 within smooth muscle cells. A potential role via TFF interaction in cell-cell adhesion and assembly of actin stress fibres is discussed.

Lead pellet ingestion and liver-lead concentrations in upland game birds from southern Ontario, Canada

One-hundred twenty-three gizzards from upland game birds (chukar, Alectoris chukar; and common pheasant, Phasianus colchicus) harvested by hunters in southern Ontario, Canada, were examined for lead pellet ingestion by manual examination of gizzard contents and by radiography. Lead pellets were found to be ingested by chukars (6/76; 8%) and the common pheasant (16/47; 34%). Further, 13% (17/129) of the bird (wild turkey, Meleagris gallopavo; Hungarian partridge, Perdix perdix; chukar; and common pheasant) livers analyzed had elevated lead concentrations (> or =6 microg/g wet weight [ww]). Liver-lead concentrations above Health Canada's guideline for human consumption of fish protein (<0.5 microg/g ww) were found in 40% (51/129) of livers analyzed. Data indicate that the ingestion of lead pellets in upland game birds and the potential consumption of lead-contaminated meat by humans are concerns related to the continued use of lead shotshell for hunting.

MYPT1 mutants demonstrate the importance of aa 888–928 for the interaction with PKGIα

During nitric oxide signaling, type Iα cGMP-dependent protein kinase (PKGIα) activates myosin light chain (MLC) phosphatase through an interaction with the 130-kDa myosin targeting subunit (MYPT1), leading to dephosphorylation of 20-kDa MLC and vasodilatation. It has been suggested that the MYPT1-PKGIα interaction is mediated by the COOH-terminal leucine zipper (LZ) of MYPT1 and the NH2-terminal LZ of PKGIα (HK Surks and ME Mendelsohn. Cell Signal 15: 937–944, 2003; HK Surks et al. Science 286: 1583–1587, 1999), but we previously showed that PKGIα interacts with LZ-positive (LZ+) and LZ-negative (LZ−) MYPT1 isoforms ( 13 ). Interestingly, PKGIα is known to preferentially bind to RR and RK motifs (WR Dostmann et al. Proc Natl Acad Sci USA 97: 14772–14777, 2000), and there is an RK motif within the aa 888–928 sequence of MYPT1 in LZ+ and LZ− isoforms. Thus, to localize the domain of MYPT1 important for the MYPT1-PKGIα interaction, we designed four MYPT1 fragments that contained both the aa 888–928 sequence and the downstream LZ domain (MYPT1FL), lacked both the aa 888–928 sequence and the LZ domain (MYPT1TR), lacked only the aa 888–928 sequence (MYPT1SO), or lacked only the LZ domain (MYPT1TR2). Using coimmunoprecipitation, we found that only the fragments containing the aa 888–928 sequence (MYPT1FL and MYPT1TR2) were able to form a complex with PKGIα in avian smooth muscle tissue lysates. Furthermore, mutations of the RK motif at aa 916–917 (R916K917) to AA decreased binding of MYPT1 to PKGIα in chicken gizzard lysates; these mutations had no effect on binding in chicken aorta lysates. However, mutation of R916K917to E916E917eliminated binding, suggesting that one factor important for the PKGIα-MYPT1 interaction is the charge at aa 916–917. These results suggest that, during cGMP-mediated signaling, aa 888–928 of MYPT1 mediate the PKGIα-MYPT1 interaction.

AFCF and clinoptilolite use in reduction of (137)Cs deposition in several days' contaminated broiler chicks

The objective of this study was to investigate the binding efficiency of AFCF and clinoptilolite, mixed to the feed and administered orally using gastric tube to chronically (137)Cs alimentary contaminated broiler chicks. Seventy-five male Hybro broiler chicks, between 35 and 47 days of age were divided into five groups (15 birds per group) reared in cages (five birds in a cage) and fed a standard diet. Every day during 13 days of the experimental period all chicks received orally 1 ml CsCl water solution with activity of 1310 Bq ml(-1)(137)Cs (gastric tube). Group 1 was the control group and received no binders. The experimental groups received the binders. Group 2 received 0.2 g of AFCF in the form of water solution (gastric tube); group 3 received 0.2% AFCF in the feed; group 4 received 2g clinoptilolite in the form of water suspension (gastric tube) and group 5 received 2% clinoptilolite in the feed. Five chicks from each group were sacrificed on days 4, 10 and 13 of the experimental period. Using gamma spectrometric methods specific activity of (137)Cs was determined in the samples of breast meat, liver and gizzard. The results obtained showed that administering binders to the chronically contaminated broiler chicks significantly (p<0.01) reduced (137)Cs transfer and deposition in breast meat, liver and gizzard. Decreasing deposition of (137)Cs in breast meat and internal organs increased with time of contamination and binders' administration. With AFCF as a cesium binder, on day 13 of measuring the (137)Cs activity in breast meat was 80-83% lower than that in the control group, 89% in liver and 83-84% in gizzard. Natural clinoptilolite demonstrated lower binding efficiency. On day 13 of measuring the (137)Cs activity in breast meat was 53-69% lower than that in the control group, 67-60% in liver and 59-71% in gizzard.

Effect of Arsanilic Acid on Performance and Residual of Arsenic in Tissue of Japanese Laying Quail

Three hundred seventy-five 63-d-old laying Japanese quail were randomly distributed into 3 experimental groups (125 birds per group) and fed the following diets for 40 d, with 30 d on the experimental diets, followed by a 10-d withdrawal period: 1) control; 2) 50 mg of 4-arsanilic acid/kg of feed; and 3) 100 mg of 4-arsanilic acid/kg of feed. Each treatment consisted of 5 replicates of 25 birds. During the first 30 d of the experiment, all eggs were recorded, collected, individually weighed daily, and feed consumption was determined every 10 d. Five quail from each replicate in the experiment were euthanized by cervical dislocation at 0, 30, 35, and 40 d. Tissue samples from the liver, kidney, heart, gizzard, and the muscle on the breast and leg were collected for determination of As residue. The feces and eggs at 0, 30, 35, and 40 d of the experiment were selected for determination of As. Results showed that dietary inclusion of 50 and 100 mg/kg of 4-arsanilic acid significantly improved feed utilization and egg production, but the concentration of As in the tissues and feces in groups fed 4-arsanilic acid was higher than in control group. The results of the present study demonstrate that the use of organic As compounds as feed additives in diet is a matter for argument.

The mechanism of smooth muscle caldesmon-tropomyosin inhibition of the elementary steps of the actomyosin ATPase

Caldesmon is a component of smooth muscle thin filaments that inhibits the actomyosin ATPase via its interaction with actin-tropomyosin. We have performed a comprehensive transient kinetic characterization of the actomyosin ATPase in the presence of smooth muscle caldesmon and tropomyosin. At physiological ratios of caldesmon to actin (1 caldesmon/7 actin monomers) actomyosin ATPase is inhibited by about 75%. Inhibitory caldesmon concentrations had little effect upon the rate of S1 binding to actin, actin-S1 dissociation by ATP, and dissociation of ADP from actin-S1 x ADP; however the rate of phosphate release from the actin-S1 x ADP x P(i) complex was decreased by more than 80%. In addition the transient of phosphate release displayed a lag of up to 200 ms. The presence of a lag phase indicates that a step on the pathway prior to phosphate release has become rate-limiting. Premixing the actin-tropomyosin filaments with myosin heads resulted in the disappearance of the lag phase. We conclude that caldesmon inhibition of the rate of phosphate release is caused by the thin filament being switched by caldesmon to an inactive state. The active and inactive states correspond to the open and closed states observed in skeletal muscle thin filaments with no evidence for the existence of a third, blocked state. Taken together these data suggest that at physiological concentrations, caldesmon controls the isomerization of the weak binding complex to the strong binding complex, and this causes the inhibition of the rate of phosphate release. This inhibition is sufficient to account for the inhibition of the steady state actomyosin ATPase by caldesmon and tropomyosin.

Risk assessment test for lead bioaccessibility to waterfowl in mine-impacted soils

Due to variations in soil physicochemical properties, species physiology, and contaminant speciation, Pb toxicity is difficult to evaluate without conducting in vivo dose-response studies. Such tests, however, are expensive and time consuming, making them impractical to use in assessment and management of contaminated environments. One possible alternative is to develop a physiologically based extraction test (PBET) that can be used to measure relative bioaccessibility. We developed and correlated a PBET designed to measure the bioaccessibility of Pb to waterfowl (W-PBET) in mine-impacted soils located in the Coeur d'Alene River Basin, Idaho. The W-PBET was also used to evaluate the impact of P amendments on Pb bioavailability. The W-PBET results were correlated to waterfowl-tissue Pb levels from a mallard duck [Anas platyrhynchos (L.)] feeding study. The W-PBET Pb concentrations were significantly less in the P-amended soils than in the unamended soils. Results from this study show that the W-PBET can be used to assess relative changes in Pb bioaccessibility to waterfowl in these mine-impacted soils, and therefore will be a valuable test to help manage and remediate contaminated soils.

A caldesmon peptide activates smooth muscle via a mechanism similar to ERK-mediated phosphorylation

Caldesmon (CaD) is thought to regulate smooth muscle contraction, because it binds actin and inhibits actomyosin interactions. A synthetic actin-binding peptide (GS17C) corresponding to Gly666-Ser682 of chicken gizzard CaD has been shown to induce force development in permeabilized smooth muscle cells. The mechanism of GS17C's action remains unclear, although a structural effect was postulated. By photo-crosslinking and fluorescence quenching experiments with a gizzard CaD fragment (H32K; Met563-Pro771) and its mutants, we showed that GS17C indeed dissociated the C-terminal region of H32K from actin, in a manner similar to extracellular signal-regulated kinase-mediated phosphorylation, thereby reversing the CaD-imposed inhibition and enabling the actomyosin interaction.

Competition of PTB with TIA proteins for binding to a U-rich cis-element determines tissue-specific splicing of the myosin phosphatase targeting subunit 1

A considerable amount of smooth muscle phenotypic diversity is generated by tissue-specific and developmentally regulated splicing of alternative exons. The control mechanisms are unknown. We are using a myosin phosphatase targeting subunit-1 (MYPT1) alternative exon as a model to investigate this question. In the present study, we show that the RNA binding proteins TIA and PTB function as antagonistic enhancers and suppressors of splicing of the alternative exon, respectively. Each functions through a single U-rich element, containing two UCUU motifs, just downstream of the alternative exon 5' splice site. Tissue-specific down-regulation of TIA protein in the perinatal period allows PTB to bind to the U-rich element and suppress splicing of the alternative exon as the visceral smooth muscle acquires the fast-phasic smooth muscle contractile phenotype. This provides a novel role for PTB in the tissue-specific regulation of splicing of alternative exons during the generation of smooth muscle phenotypic diversity.

Sox9 and Nkx2.5 determine the pyloric sphincter epithelium under the control of BMP signaling

The organs of the digestive tract are specified by coordinated signaling between the endoderm and mesoderm during development. These epithelial-mesenchymal interactions lead to the organ-specific morphogenesis and differentiation of regions along the gut tube. In this paper, we show that in the chick, the SRY-related transcription factor Sox9 is a marker for the posterior gizzard. Viral misexpression of Sox9 in the gizzard mesoderm is sufficient to specify epithelium characteristic of the pyloric sphincter. Sox9 expression is normally limited to the region of the posterior gizzard under the regulation of BMP signaling from the adjacent midgut. Misexpression of an activated form of BMPR1b in the gizzard upregulates Sox9 expression, while the BMP antagonist noggin down-regulates Sox9 expression in the gizzard mesoderm. Previously, Nkx2.5 was identified as a marker for the mesoderm of the pyloric sphincter. As with Sox9, BMP signaling appears to regulate Nkx2.5 and its ability to determine the pyloric epithelium. Despite these similarities, our evidence suggests that Sox9 and Nkx2.5 are regulated independently by BMP signaling, and act coordinately to specify the pyloric sphincter.

Modes of Caldesmon Binding to Actin

Smooth muscle caldesmon binds actin and inhibits actomyosin ATPase activity. Phosphorylation of caldesmon by extracellular signal-regulated kinase (ERK) reverses this inhibitory effect and weakens actin binding. To better understand this function, we have examined the phosphorylation-dependent contact sites of caldesmon on actin by low dose electron microscopy and three-dimensional reconstruction of actin filaments decorated with a C-terminal fragment, hH32K, of human caldesmon containing the principal actin-binding domains. Helical reconstruction of negatively stained filaments demonstrated that hH32K is located on the inner portion of actin subdomain 1, traversing its upper surface toward the C-terminal segment of actin, and forms a bridge to the neighboring actin monomer of the adjacent long pitch helical strand by connecting to its subdomain 3. Such lateral binding was supported by cross-linking experiments using a mutant isoform, which was capable of cross-linking actin subunits. Upon ERK phosphorylation, however, the mutant no longer cross-linked actin to polymers. Three-dimensional reconstruction of ERK-phosphorylated hH32K indeed indicated loss of the interstrand connectivity. These results, together with fluorescence quenching data, are consistent with a phosphorylation-dependent conformational change that moves the C-terminal end segment of caldesmon near the phosphorylation site but not the upstream region around Cys(595), away from F-actin, thus neutralizing its inhibitory effect on actomyosin interactions. The binding pattern of hH32K suggests a mechanism by which unphosphorylated, but not ERK-phosphorylated, caldesmon could stabilize actin filaments and resist F-actin severing or depolymerization in both smooth muscle and nonmuscle cells.

Fesselin is a target protein for calmodulin in a calcium-dependent manner

Fesselin is a basic protein isolated from smooth muscle which binds G-actin and accelerates its polymerization as well as cross-links assembled filaments [J. Muscle Res. Cell Motil. 20 (1999) 539; Biochemistry 40 (2001) 14252]. In this report experimental evidence is provided for the first time proving that fesselin can interact with calmodulin in a Ca(2+)-dependent manner in vitro. Using ion exchange, followed by calmodulin-affinity chromatography, enabled us to simplify and shorten the fesselin preparation procedure and increase its yield by about three times in comparison to the procedure described by Leinweber et al. [J. Muscle Res. Cell Motil. 20 (1999) 539]. Fesselin interaction with dansyl-labelled calmodulin causes a 2-fold increase in maximum fluorescence intensity of the fluorophore and a 21nm blue shift of the spectrum. The transition of complex formation between fesselin and calmodulin occurs at submicromolar concentration of calcium ions. The dissociation constant of fesselin Ca(2+)/calmodulin complexes amounted to 10(-8)M. The results suggest the existence of a direct link between Ca(2+)/calmodulin and fesselin at the level of actin cytoskeleton dynamics in smooth muscle.

SOX9 specifies the pyloric sphincter epithelium through mesenchymal-epithelial signals

Gastrointestinal (GI) development is highly conserved across vertebrates. Although several transcription factors and morphogenic proteins are involved in the molecular controls of GI development, the interplay between these factors is not fully understood. We report herein the expression pattern of Sox9 during GI development, and provide evidence that it functions, in part, to define the pyloric sphincter epithelium. SOX9 is expressed in the endoderm of the GI tract (with the exclusion of the gizzard) and its derivate organs, the lung and pancreas. Moreover, SOX9 is also expressed at the mesoderm of the pyloric sphincter, a structure that demarcates the gizzard from the duodenum. Using retroviral misexpression technique, we show that Sox9 expression in the pyloric sphincter is under the control of the BMP signaling pathway, known to play a key role in the development of this structure. By misexpressing SOX9 in the mesoderm of the gizzard, we show that SOX9 is able to transdifferentiate the adjacent gizzard epithelium into pyloric sphincter-like epithelium through the control of mesodermal-epithelial signals mediated in part by Gremlin (a modulator of the BMP pathway). Our results suggest that SOX9 is necessary and sufficient to specify the pyloric sphincter epithelial properties.

Adenoviral gizzard erosion in commercial broiler chickens

Pathologic and immunohistochemical changes caused by group I of the fowl adenovirus (FAV) serotype-1 99ZH strain, isolated from broiler chickens exhibiting gizzard erosion, were investigated in commercial broiler chickens. One hundred twenty-two chickens were inoculated with the strain by both oral and ocular routes at 1, 3, or 5 weeks of age and euthanatized for necropsy within 4-18 days of inoculation. Focal gizzard erosions were observed in the inoculated chickens of each age group. A histologically degenerative koilin layer, necrotic mucosa, intranuclear inclusion bodies in the glandular epithelial cells, inflammatory cell infiltrations in the lamina propria, submucosa, and a muscle layer were seen in the gizzards. Immunohistochemical staining showed evidence of FAV antigens in the intranuclear inclusion bodies. These findings were recognized regardless of their maternal antibody levels for FAV serotype-1. Gizzard lesions appeared later in the lower-dose-inoculated chickens than in the higher-dose-inoculated chickens. Numerous CD3-positive cells and IgY-positive plasma cells were seen in the gizzard lesions. In 5-week-old chickens the heterophil infiltrations in the lesions were milder than in younger chickens. Intranuclear inclusion bodies also were observed in the epithelial cells of the ileum or cecal tonsils of some chickens. Thus, this study shows that FAV-99ZH causes adenoviral gizzard erosion in broiler chickens without hepatic or pancreatic lesions and that cell infiltration is more severe than in dietary gizzard erosions.

Effects of oat hulls and wood shavings on digestion in broilers and layers fed diets based on whole or ground wheat

1. An experiment was conducted to study the effects of inclusion of oat hulls in diets based on whole or ground wheat for broilers. Effects of wood shavings on layers were investigated in a further experiment. 2. Inclusion of oat hulls in wheat-based broiler diets did not affect weight gain. Feed conversion efficiency (FCE), corrected for insoluble fibre contents, was improved by oat hull inclusion. 3. Gizzard size increased with inclusion of oat hulls, whole wheat, wood shavings and grit. 4. Starch digestibility was significantly increased by inclusion of oat hulls for broilers, and by wood shavings for layers. 5. Wood shavings and whole wheat did not affect bile acid concentration of gizzard contents. However, the total amount of bile acids in gizzard increased with access to wood shavings due to an increase in the weight of gizzard contents, indicating an increased gastroduodenal reflux. 6. Fibre concentration was considerably higher in the gizzard contents than in the feed. 7. Duodenal particle size decreased with access to grit. No effect of hulls or whole wheat inclusion was found, indicating that all particles are ground to a certain critical size before leaving the gizzard.

Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate

1. The effects of whole grains of wheat on the digestive tract of broiler chickens was studied. A complete pelleted feed was compared with free choice feeding of whole wheat and a pelleted protein concentrate, given from 7 to 29 d of age. 2. Pepsin activity in proventriculus tissue was lower in whole wheat-fed birds than in complete diet-fed birds. The weight (g/kg body weight) of the gizzard was higher in whole wheat-fed birds and its contents had a lower pH. 3. In the intestine, there were no differences in deoxyribonucleic acid (DNA) concentration, protein/DNA, ribonucleic acid (RNA)/DNA, RNA/protein ratios or alkaline phosphatase activity expressed per tissue weight. The weight (g/kg body weight) of the duodenum was lower in whole wheat-fed birds and its contents had a higher pH. Also the activities of alkaline phosphatase and leucine aminopeptidase in the duodenum, and maltase in the ileum, expressed per unit of bird weight, were lower in whole wheat-fed birds. 4. These results suggest that whole grain feeding increases the chemical (pepsin in proventriculus) and physical (gizzard muscle) functionality of the upper part of the digestive tract but decreases the digestive capacity of the intestine. Higher gizzard functionality may play a positive role in the control of bacterial populations. The lower digestive enzyme activities in the intestine may be detrimental in situations of mucosal deterioration caused by intestinal disease.

An actin-dependent conformational change in myosin

Conformational changes within myosin lead to its movement relative to an actin filament. Several crystal structures exist for myosin bound to various nucleotides, but none with bound actin. Therefore, the effect of actin on the structure of myosin is poorly understood. Here we show that the swing of smooth muscle myosin lever arm requires both ADP and actin. This is the first direct observation that a conformation of myosin is dependent on actin. Conformational changes within myosin were monitored using fluorescence resonance energy transfer techniques. A cysteine-reactive probe is site-specifically labeled on a 'cysteine-light' myosin variant, in which the native reactive cysteines were removed and a cysteine engineered at a desired position. Using this construct, we show that the actin-dependent ADP swing causes an 18 A change in distance between a probe on the 25/50 kDa loop on the catalytic domain and a probe on the regulatory light chain, corresponding to a 23 degrees swing of the light-chain domain.

Feeding diets supplemented with zinc and vitamin A in laying hens: effects on histopathological findings and tissue mineral contents

The effects of different dietary levels of zinc and vitamin A on tissue mineral accumulation and histopathological alterations were examined in laying hens. For this purpose, 130 Hisex brown laying hens aged 56 weeks were divided into two main groups. Each group of hens were fed on diets supplemented with two different levels of vitamin A (0-10,000 IU kg(-1)). Then, laying hens in both of the main groups were subdivided into five treatment groups given different levels of zinc (0, 25, 50, 100, and 200 mg kg(-1)) for 12 weeks. Dietary additions of zinc and/or vitamin A did not significantly affect the zinc concentrations of the pancreas, liver, gizzard, thyroid, and copper concentrations of the pancreas, gizzard, and thyroid. The group fed the highest zinc (200 mg kg(-1)) in the diet had twofold iron concentration in their thyroid tissue compared to the concentration of the control group receiving no extra zinc. Histopathologically, there was slight oedema, degranulation, and vacuolation in exocrine cells and some fibrotic areas in the pancreas and reduced follicular size. Follicular cell hypertrophy and hyperplasia occurred in the thyroids, and gizzard erosions were seen in some cases.

Use of actin isoform-specific antibodies to probe the domain structure in three smooth muscles

We investigated the location of actin isoforms in relation to each other and to filament attachment sites by studying the edge-to-edge distribution of both immunofluorescence and immunogold probes in smooth muscle cells from three sources. Antibodies to alpha- or alpha,gamma-actin labeled uniformly across smooth muscle cells from each source. Antibodies to beta-cytoplasmic actin were concentrated on and near dense bodies, especially in gizzard smooth muscle, but were also located throughout the filament compartment. Double immunofluorescent labeling with antibodies to alpha- or alpha/gamma- and to beta-actin shows overlap of label at dense bodies and attachment plaques. Double immunofluorescent labeling with antibodies to alpha-actinin and to beta-actin identified dense bodies and attachment plaques as sites of colocalization. Immunogold labeling with anti-desmin was most prominent near dense bodies in the gizzard and was widely dispersed in vas deferens and arterial smooth muscle cells. Our results indicate that there is extensive overlap between the locations of contractile and cytoskeletal elements and, thus, do not support the two-domain model of smooth muscle structure. Tissue-specific organizational motif differences were seen when gizzard, vas deferens, and artery were compared and suggest that one model may not apply to these three smooth muscles.

Characterization of Arp2/3 complex in chicken tissues

Arp2/3 protein complex consists of seven subunits (Arp2, Arp3, p41-Arc, p34-Arc, p21-Arc, p20-Arc and p16-Arc) in apparent 1:1 stoichiometry. This complex has been shown to promote the formation of Y-branch structures of F-actin in cultured cells. We generated specific antibodies against chicken Arp2, Arp3, and p34-Arc to analyze the distribution of these subunits in chicken tissues. In whole samples of brain and gizzard, antibodies against each recombinant protein reacted with single bands of predicted molecular mass based on their cDNA sequences of the antigens. Anti-p34-Arc antibody detected at least two neighboring spots in 2D-PAGE, which might suggest the existence of isoforms or modified forms. Arp2/3 complex bound to an F-actin affinity column from gizzard extract. However, Arp2/3 complex did not tightly bind major actin cytoskeleton because the complex was extracted easily when gizzard smooth muscle was homogenized in PBS. Immunoblot analysis of various tissues revealed that the amounts of Arp2/3 subunits were lower in striated muscle than in non-muscle and smooth muscle tissues. Amounts and ratio of the three subunits varied in tissues, as estimated by quantitative immunoblotting. With immunofluorescence microscopy, we also observed localization of Arp3 and p34-Arc in frozen sections of gizzard with different staining patterns around blood vessels. These results suggest that the Arp2/3 complex exists also in places where rapid actin polymerization does not occur, and that a part of the subunits may exist in different forms from the complex containing the seven subunits in some tissues.

Agonist-induced force enhancement: the role of isoforms and phosphorylation of the myosin-targeting subunit of myosin light chain phosphatase

The magnitude of agonist-induced Ca(2+) sensitization of force is tissue-dependent, but an explanation for this diversity is unknown. Ca(2+) sensitization is thought to involve a G-protein-mediated inhibition of myosin light chain phosphatase activity by phosphorylation of the myosin-targeting subunit (MYPT). The MYPT has two isoforms that differ by a central insert, which lies near this phosphorylation site. Expression of MYPT isoforms is both developmentally regulated and tissue-specific. We hypothesized that the presence or absence of the central insert determines the magnitude of agonist-induced Ca(2+) sensitization. Throughout development, the chicken aorta exclusively expresses the splice-in MYPT isoform, and guanosine 5'-O-(thiotriphosphate) (GTPgammaS) produces a significant force enhancement. Early during development, the chicken gizzard expresses the splice-in MYPT isoform, and GTPgammaS produced a Ca(2+) sensitization. In the gizzard coincident with the shift in expression from the splice-in to splice-out MYPT isoform, GTPgammaS no longer produced force enhancement. In addition, adenosine 5'-O-(thiotriphosphate) (ATPgammaS) phosphorylated only adult gizzard tissue, the only tissue that did not demonstrate a Ca(2+) sensitization. These results suggest that the relative expression of splice-in/splice-out MYPT isoforms determines the magnitude of agonist-induced force enhancement and that MYPT phosphorylation is not required for Ca(2+) sensitization.

Insulin-like growth factor binding protein-2 gene expression can be regulated by diet manipulation in several tissues of young chickens

The relationship between nutritional status and insulin-like growth factor binding protein-2 (IGFBP-2) gene expression in chickens was studied. Chickens (6 wk old) were food deprived for 2 d and then refed. IGFBP-2 mRNA in the brain was significantly decreased by food deprivation and levels did not increase when birds were refed for 24 h. Gizzard and hepatic IGFBP-2 mRNA levels were significantly increased by food deprivation and decreased by refeeding. Any nutrients tested decreased hepatic IGFBP-2 gene expression. In kidney, IGFBP-2 mRNA was detected but not influenced by food deprivation and refeeding. In another study, the influence of dietary protein source [isolated soybean protein vs. casein; crude protein (CP) 20%] and the supplementation of essential amino acids on IGFBP-2 gene expression of young chickens (5 wk old) was examined. The influence of feeding a low soybean protein diet (CP 5%) on tissue IGFBP-2 gene expression was also investigated. Hepatic IGFBP-2 mRNA was not detected in any group. Feeding the low protein diet for 7 d decreased brain IGFBP-2 mRNA level and increased gizzard IGFBP-2 level compared with chickens fed 20% protein diets. A significant interaction between protein source and amino acid supplementation was observed in gizzard IGFBP-2 mRNA level. In both casein-fed groups and in chickens fed 20% soybean protein diet without supplemental amino acids, the levels did not differ from one another or from the low protein diet-fed birds. The level was lower in chickens fed the amino acid-supplemented, 20% soybean protein diet. In conclusion, the response of IGFBP-2 gene expression to variations in nutritional status was rapid and different in several tissues of young chickens, which would help modulate the growth-promoting effect of circulating IGF-I by making the IGF-IGFBP complex.

Smitin, a novel smooth muscle titin-like protein, interacts with myosin filaments in vivo and in vitro

Smooth muscle cells use an actin-myosin II-based contractile apparatus to produce force for a variety of physiological functions, including blood pressure regulation and gut peristalsis. The organization of the smooth muscle contractile apparatus resembles that of striated skeletal and cardiac muscle, but remains much more poorly understood. We have found that avian vascular and visceral smooth muscles contain a novel, megadalton protein, smitin, that is similar to striated muscle titin in molecular morphology, localization in a contractile apparatus, and ability to interact with myosin filaments. Smitin, like titin, is a long fibrous molecule with a globular domain on one end. Specific reactivities of an anti-smitin polyclonal antibody and an anti-titin monoclonal antibody suggest that smitin and titin are distinct proteins rather than differentially spliced isoforms encoded by the same gene. Smitin immunofluorescently colocalizes with myosin in chicken gizzard smooth muscle, and interacts with two configurations of smooth muscle myosin filaments in vitro. In physiological ionic strength conditions, smitin and smooth muscle myosin coassemble into irregular aggregates containing large sidepolar myosin filaments. In low ionic strength conditions, smitin and smooth muscle myosin form highly ordered structures containing linear and polygonal end-to-end and side-by-side arrays of small bipolar myosin filaments. We have used immunogold localization and sucrose density gradient cosedimentation analyses to confirm association of smitin with both the sidepolar and bipolar smooth muscle myosin filaments. These findings suggest that the titin-like protein smitin may play a central role in organizing myosin filaments in the contractile apparatus and perhaps in other structures in smooth muscle cells.

Insulin administration suppresses an increase in insulin-like growth factor binding protein-2 gene expression stimulated by fasting in the chicken

1. We examined the changes in plasma IGF-I concentration and tissue IGFBP-2 gene expression of young fasted chickens refed a commercial diet or administered bovine insulin intravenously. 2. Plasma IGF-I concentration was decreased by fasting for 2 d. Although plasma IGF-I concentration was increased by refeeding, it didn't recover to the level of chickens fed a commercial diet ad libitum. 3. Insulin administration lowered plasma IGF-I concentration compared to other groups. 4. Hepatic IGFBP-2 mRNA was increased by fasting for 2 d and decreased by refeeding for 6 h. Insulin administration also decreased hepatic IGFBP-2 gene expression stimulated by fasting to the level of refed chickens. 5. IGFBP-2 mRNA in the gizzard was increased by fasting for 2 d and tended to decrease after refeeding for 6 h. Insulin administration decreased gizzard IGFBP-2 gene expression to less than that in refed chickens. 6. There was no between-treatment difference in IGFBP-2 mRNA in the brain and kidney. 7. These results suggest that the changes in IGFBP-2 gene expression in the liver and gizzard by fasting and refeeding might be partly regulated by the alteration in plasma insulin concentration.

HoxA and HoxB cluster genes subdivide the digestive tract into morphological domains during chick development

The digestive tract exhibits region-specific morphology and cytodifferentiation along the anteroposterior axis. We analyzed the spatial expression patterns of Hox genes belonging to the HoxA and HoxB cluster (Hoxa-4 approximately a-9, Hoxb-5 approximately b-9) in the developing chick digestive tract. The expression domains of these Hox genes correlated with morphological subdivision of the digestive tract along the anteroposterior axis.

Nonlethal method for forensic evaluation of aldicarb exposure in wildlife

Forensic evaluation of aldicarb exposure is difficult due to the rapid hydrolysis and oxidation of the parent compound. Oxidation products-aldicarb sulfoxide and aldicarb sulfone-are commonly analyzed, but hydrolytic products-aldicarb nitrile, aldicarb nitrile sulfoxide, aldicarb nitrile sulfone-are infrequently analyzed even though they are the primary stable products of aldicarb degradation. Nitrile analyses provide an important avenue to verify aldicarb exposure or aldicarb-induced mortality. Our aproach allows lethal and sublethal exposure assessment. Extraction of samples with acetonitrile:water is followed by chromatographic determination. Sublethal exposure assessment utilizes excreta samples, which is nonlethal and requires holding animals in captivity for 12 h or less. Sublethal exposures of northern bobwhite Colinus virginianus to aldicarb can be identified with greater than 80% confidence for 6 h after dosing. By analyzing GI tracts, lethal exposures of bobwhite to aldicarb can be identified with greater than 90% confidence for 4 days post mortem and with 75% confidence for 8 days post mortem. Sublethal exposures to aldicarb was identified in greater than 80% of Peromyscus maniculatis for 6 h after dosing. Aldicarb and its transformation products were detected for 8 days post mortem in all mice that received aldicarb doses at or above the LD50.

Can gastric endoderm change the regionally specific inducing ability of presumptive small intestinal mesoderm?

This study was designed to establish the source of gut mesoderm's ability to induce regional pattern in the endoderm. The most obvious possibility is induction by the endoderm through epithelial-mesenchymal interaction. To test this experimentally, reciprocal quail/chick combinations were prepared of early proventricular endoderm (that is already known to be regionally determined) and presumptive small intestinal mesoderm. The combinations were cultured for 7 days to allow for 'programming' of the mesoderm by the endoderm. After removal of the proventricular endoderm the mesoderm was combined with young gizzard endoderm. It is known that gizzard endoderm can be provoked to develop in either a proventricular or a small intestinal direction by association with the appropriate mesoderm. Thus, by combining intestinal mesoderm 'programmed' by association with proventricular endoderm with gizzard endoderm, the subsequent differentiation of the gizzard endoderm would indicate whether or not the inducing ability of the intestinal mesenchyme had been altered. In addition to such experimental grafts, three types of control graft were prepared. The results of the experiment, based on the morphology of the grafts and the immunocytochemical analysis of selected endocrine cell types, showed that in the majority of cases the gizzard endoderm developed the features of small intestine, not those of proventriculus. This indicates that at the stages studied, endoderm does not act to program mesoderm with which it is associated. If this does occur, it must take place at an earlier stage, i.e., before the time of explantation of the presumptive small intestinal mesoderm (1.25 days of incubation).

Ontogeny of PACAP immunoreactivity in extrinsic and intrinsic innervation of chicken gut

An immunohistochemical study was conducted on the ontogeny of pituitary adenylate cyclase-activating polypeptide-27 (PACAP) immunoreactive elements within the extrinsic and intrinsic nerve supply of the chicken embryo gut. The first PACAP-immunoreactivity was detected in the extrinsic nerve supply at E 4 within the pharyngeal region and the primary sympathetic chain. At E 5.5 it appeared in the vagus nerve, the spinal cord, the secondary sympathetic chain, some perivascular plexuses and the Remak ganglion. In the intrinsic nerve supply, the first PACAP-immunoreactive elements were shown at E 4.5-E 5 in the mesenchymal bud of the proventriculus/gizzard. Then they gradually appeared also cranially and caudally both in myenteric and submucous plexuses.

A role for serine-175 in modulating the molecular conformation of calponin

Calponin is an actin filament-associated protein found in smooth muscle and non-muscle cells. Calponin inhibits actin-myosin interaction in a manner that is prevented by protein kinase C (PKC)-catalysed phosphorylation of serine-175. To investigate the molecular basis of serine-175-mediated regulation, we examined the effect of phosphorylation on the conformation of calponin using monoclonal antibody (mAb) epitope analysis. Eight mAbs against different epitopes on chicken gizzard calponin were developed to monitor the conformational changes in calponin induced by PKC-mediated phosphorylation or serine-175-->alanine (S175A) substitution. The relative affinities of the mAbs for calponins immobilized on microtitre plates or bound to actin-tropomyosin thin filaments were determined, and epitope competitions between free and immobilized calponins were carried out. The changes in binding affinity between mAb paratopes and calponin epitopes demonstrate several serine-175 modification-induced conformational effects: (a) structures of calponin are reconfigured by serine-175 modification, supporting the regulatory function of serine-175; (b) there are submolecular structures unaffected by modification of serine-175 in both free and thin filament-associated calponins, suggesting that the serine-175-based conformational modulation is a targeted allosteric effect; (c) significant conformational changes are detected between free and thin filament-associated calponins, indicating two functional states of the molecular conformation; and (d) the different epitope characteristics between thin filament-bound and free calponins suggest that calponin is a flexible molecule, and the modifications of serine-175 may also determine the structural flexibility to increase the epitope accessibility. These results provide novel information concerning the structure-function relationships of calponin and its regulation by phosphorylation.

Roles of BMP signaling and Nkx2.5 in patterning at the chick midgut-foregut boundary

Patterning of the gut into morphologically distinct regions results from the appropriate factors being expressed in strict spatial and temporal patterns to assign cells their fates in development. Often, the boundaries of gene expression early in development correspond to delineations between different regions of the adult gut. For example, Bmp4 is expressed throughout the hindgut and midgut, but is not expressed in the early gizzard. Ectopic BMP4 in the gizzard caused a thinning of the muscularis. To understand this phenotype we examined the expression of the receptors transducing BMP signaling during gut development. We find that the BMP receptors are differentially expressed in distinct regions of the chicken embryonic gut. By using constitutively activated versions of the BMP type I receptors, we find that the BMP receptors act similarly to BMP4 in the gizzard when ectopically expressed. We show that the mesodermal thinning seen upon ectopic BMP signaling is due to an increase in apoptosis and a decrease in proliferation within the gizzard mesoderm. The mesodermal thinning is characterized by a disorganization and lack of differentiation of smooth muscle in the gizzard mesoderm. Further, ectopic BMP receptors cause an upregulation of Nkx2.5, the pyloric sphincter marker, similar to that seen with ectopic BMP4. This upregulation of Nkx2.5 is a cell-autonomous event within the mesoderm of the gizzard. We also find that Nkx2.5 is necessary and sufficient for establishing aspects of pyloric sphincter differentiation.

Kinetic determination of focal adhesion protein formation

I examined the binding kinetics between integrin (alpha(IIb)beta(3)) and purified focal adhesion proteins, including alpha-actinin, filamin, vinculin, talin, and F-actin. Using static light-scatter technique, I observed affinities of the order talin > filamin > F-actin > alpha-actinin > (talin when bound to vinculin) which were lower when integrin was complexed with fibronectin. No binding between integrin and vinculin was detected. The calculated dissociation constants (K(d)) ranged between 0.4 microM and 5 microM. These results in part confirm previously published data using different methods. The modest affinity with which the focal adhesion proteins interact in vitro might be indicative of how cells, e.g., thrombocytes, gain a high degree of versatility and velocity.

Phosphorylation of caldesmon by p21-activated kinase. Implications for the Ca(2+) sensitivity of smooth muscle contraction

We have previously shown that p21-activated kinase, PAK, induces Ca(2+)-independent contraction of Triton-skinned smooth muscle with concomitant increase in phosphorylation of caldesmon and desmin but not myosin-regulatory light chain (Van Eyk, J. E., Arrell, D. K., Foster, D. B., Strauss, J. D., Heinonen, T. Y., Furmaniak-Kazmierczak, E., Cote, G. P., and Mak, A. S. (1998) J. Biol. Chem. 273, 23433-23439). In this study, we provide biochemical evidence implicating a role for PAK in Ca(2+)-independent contraction of smooth muscle via phosphorylation of caldesmon. Mass spectroscopy data show that stoichiometric phosphorylation occurs at Ser(657) and Ser(687) abutting the calmodulin-binding sites A and B of chicken gizzard caldesmon, respectively. Phosphorylation of Ser(657) and Ser(687) has an important functional impact on caldesmon. PAK-phosphorylation reduces binding of caldesmon to calmodulin by about 10-fold whereas binding of calmodulin to caldesmon partially inhibits PAK phosphorylation. Phosphorylated caldesmon displays a modest reduction in affinity for actin-tropomyosin but is significantly less effective in inhibiting actin-activated S1 ATPase activity in the presence of tropomyosin. We conclude that PAK-phosphorylation of caldesmon at the calmodulin-binding sites modulates caldesmon inhibition of actin-myosin ATPase activity and may, in concert with the actions of Rho-kinase, contribute to the regulation of Ca(2+) sensitivity of smooth muscle contraction.

Gizzard myoglobin contents and feeding habits in avian species

In an attempt to consider physiological function of myoglobin (Mb), we determined Mb contents of gizzard smooth muscles with special reference to feeding habits in 85 avian species of 19 orders. The Mb content in 44 species of herbivorous birds was 7.52+/-3.81 mg/g wet muscle, which was significantly higher than the value of 2.34+/-1.74 mg/g in 41 species of carnivorous ones (P<0.001). Buffering capacity, as determined by in vitro titration method, was 37.3+/-5.5 slykes/g in gizzard smooth muscles of 75 species and 60.7+/-10.5 slykes in breast skeletal muscles of 77 species (P<0.001), which suggests a significantly higher dependence, almost comparable to cardiac muscles, of the gizzard muscular function on aerobic metabolism. Together with the fact that blood circulation in the gizzard is very low at resting, and might be further limited during activity, we conclude that the higher Mb content in gizzards of herbivorous birds is an adaptation, to allow storage and/or facilitated diffusion of oxygen, during process of high mechanical work required to grind down hard and fibrous vegetable food under the conditions of limited circulatory supply.

NH2-terminal fragments of the 130 kDa subunit of myosin phosphatase increase the Ca2+ sensitivity of porcine renal artery

1. The effects of the NH2-terminal fragments of M130, a 130 kDa regulatory subunit of smooth muscle myosin phosphatase, on contraction and myosin light chain phosphorylation were investigated in Triton X-100-permeabilized porcine renal artery. 2. Incubation of the permeabilized fibres with M1301-633 (a fragment containing amino acid residues 1-633) or M13044-633 enhanced the Ca2+-induced contraction and shifted the [Ca2+]i-force relationship to the left (EC50 of Ca2+: 330 nM, control, without fragment; 145 nM, M1301-633; 163 nM, M13044-633). Pre-incubation for 1-3 h was needed for these long constructs. 3. M1301-374, M130304-511 and M130297-374, i.e. relatively short constructs compared with M1301-633 and M13044-633, also induced leftward shifts of the [Ca2+]i-force relationship (EC50 of Ca2+: 65 nM, 72 nM and 180 nM, respectively). However, these required no pre-incubation. 4. Deletion of residues 304-374 from the most potent construct, M1301-374, abolished the Ca2+-sensitizing effect. 5. Wortmannin inhibited the enhancement of contraction induced by M130 fragments when added before contraction was initiated and partially inhibited the effects when added after steady-state contraction. 6. M1301-374 slowed the rate of relaxation in Ca2+-free medium. The time for 50 % relaxation with this fragment was 510 +/- 51 s, compared with 274 +/- 14 s for control. 7. The levels of myosin light chain phosphorylation (22.4 %) and force (34. 5 %) obtained with 300 nM Ca2+ were increased by 3 microM M1301-374 to 35.7 and 92.2 %, respectively. However, M1301-374 had no effect on the phosphorylation-force relationship. 8. In conclusion, the NH2-terminal M130 fragments containing residues 304-374 inhibited myosin phosphatase, increased myosin light chain phosphorylation and increased the Ca2+ sensitivity of the contractile apparatus in permeabilized porcine renal artery.

Phenotype-dependent expression of alpha-smooth muscle actin in visceral smooth muscle cells

Alpha-Smooth muscle actin is one of the molecular markers for a phenotype of vascular smooth muscle cells, because the actin is a major isoform expressed in vascular smooth muscle cells and its expression is upregulated during differentiation. Here, we first demonstrate that the phenotype-dependent expression of this actin in visceral smooth muscles is quite opposite to that in vascular smooth muscles. This actin isoform is not expressed in adult chicken visceral smooth muscles including gizzard, trachea, and intestine except for the inner layer of intestinal muscle layers, whereas its expression is clearly detected in these visceral smooth muscles at early stages of the embryo (10-day-old embryo) and is developmentally downregulated. In cultured gizzard smooth muscle cells maintaining a differentiated phenotype, alpha-smooth muscle actin is not detected while its expression dramatically increases during serum-induced dedifferentiation. Promoter analysis reveals that a sequence (-238 to -219) in the promoter region of this actin gene acts as a novel negative cis-element. In conclusion, the phenotype-dependent expression of alpha-smooth muscle actin would be regulated by the sum of the cooperative contributions of the negative element and well-characterized positive elements, purine-rich motif, and CArG boxes and their respective transacting factors.

Expression of chicken gizzard RLC complements the cytokinesis and developmental defects of Dictyostelium RLC null cells

Dictyostelium RLC null cells have defects in cytokinesis and development that can be rescued by expression of either the wild type Dictyostelium RLC or an RLC mutant that cannot be phosphorylated by MLCK (S13A) (Ostrow et al., 1994). The wild type and S13A mutant LCs rescued the cells equally well, despite the fact that RLC phosphorylation increases purified Dictyostelium myosin's activity 5-fold. In this report, we assess the ability of foreign RLCs to rescue the RLC null phenotype. The RLC from smooth muscle myosin, whose activity is tightly controlled by phosphorylation, rescued the null cell phenotype. The purified hybrid myosin had an activity and motility comparable to phosphorylated Dictyostelium myosin. In contrast, cells expressing skeletal muscle RLC were deficient in cytokinesis and development, despite having an activity and motility similar to that of myosin with the unposphorylatable S13A mutant RLC. Neither foreign LC was phosphorylated when expressed in Dictyostelium. These results suggest that the level of actin-activated ATPase activity and motility is not the sole determinant of proper myosin function in vivo. Other heavy chain/light chain interactions, which occur only with the native RLC and smooth muscle RLC, appear to be necessary for optimal function.

Ontogeny of galanin-immunoreactive elements in the intrinsic nervous system of the chicken gut

Galanin is a brain-gut peptide that is present in the central and peripheral nervous systems. In the gut, it is contained exclusively in intrinsic and extrinsic nerve supplies, and it is involved overall in the regulation of gut motility. To obtain information about the ontogeny of galanin, we undertook an immunohistochemical study of chicken embryos. The time of first appearance and the distribution patterns of galanin were investigated with fluorescence and streptavidin-biotin-peroxidase (ABC) immunohistochemical protocols by using a galanin polyclonal antiserum. The various regions of the gut and the pancreas were obtained from chicken embryos aged from 3 days of incubation to hatching. All specimens were fixed in buffered picric acid-paraformaldehyde, frozen, and cut with a cryostat. Galanin-immunoreactive neuroblasts were first detected at 4 days in the mesenchyme of the proventriculus/gizzard primordium and within the Remak ganglion. They then extended cranially and caudally, reaching all of the other gut regions at 6.5 days. Galanin-immunoreactive nerve elements mainly occupied the sites of myenteric and submucous plexuses. From day 15, galanin-immunoreactive nerve fibers tended to invade the circular muscular layer and part of the lamina propria of the mucosa. In the pancreas, weak galanin-immunoreactive nerve elements were detected at 5.5 days. They tended to be distributed among the glandular lobules according to the organ differentiation. The widespread distribution during the earlier embryonic stages represents evidence indicating that the neuropeptide galanin may have a role as a differentiating or growth factor. From late embryonic life, its predominant presence in sympathetic nerves and in muscular layers fits with the functions demonstrated previously in adults of other vertebrates for galanin as a modulator of intestinal motility.

A phosphorus-31 nuclear magnetic resonance study on the complex of chicken gizzard myosin subfragment 1 with adenosine diphosphate

The complex of Mg-ADP with chicken gizzard myosin subfragment 1 (S1), obtained by the treatment with Staphylococcus aureus V8 proteinase, was observed with 31P NMR at various temperatures between 0 and 25 degrees C. The signal of S1.ADP complex was observed at -2 to -3 ppm as a rather broad peak. As compared with the results for rabbit skeletal muscle S1.ADP complex (Tanokura M, Ebashi S: J Biochem 113: 19-21, 1993), the signal was assigned to beta-phosphate of ADP in the S1.ADP complex. The signal of the complex was so broad and weak that the dependences on temperature and magnetic field strength were not clear. The observation suggests the tight interaction of S1 with the phosphate moieties of ADP in the complex and the extremely anisotropic distribution of electrons around phosphorus nuclei.