Increased Collagen Solubility Research Articles

Procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 promotes collagen cross-linking and ECM stiffening to induce liver fibrosis

Procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (Plod2) is a key collagen lysyl hydroxylase mediating the formation of collagen fiber and stabilized collagen cross-links, and has been identified in several forms of fibrosis. However, the potential role and regulatory mechanism of Plod2 in liver fibrosis remain unclear yet. Mouse liver fibrosis models were induced by injecting carbon tetrachloride (CCl4) intraperitoneally. The morphology and alignment of collagen was observed under transmission and scanning electron microscopy, and extracellular matrix (ECM) stiffness was measured by atomic force microscopy. Large amounts of densely packed fibrillar collagen fibers produced by myofibroblasts (MFs) were deposited in fibrotic liver of mice reaching very large diameters in the cross section, accompanied with ECM stiffening, which was positively correlated with collagen-crosslinking. The expression of Plod2 was dynamically up-regulated in fibrotic liver of mouse and human. In MFs transfection of Plod2 siRNA made collagen fibers more orderly and linear aligned which can be easily degraded and protected from ECM stiffness. Administration of Plod2 siRNA preventatively or therapeutically in CCl4 mice reduced the average size of collagen bundles in transverse section, increased collagen solubility, decreases the levels of crosslinking products hydroxylysylpyridinoline and lysylpyridinoline, prevented ECM stiffening and alleviated liver fibrosis. Altogether, Plod2 mediates the formation of stabilized profibrotic collagen cross-links in MFs, leading to the alteration of collagen solubility and ECM stiffness, and eventually aggravates liver fibrosis, which provide potential target for the treatment of liver disease.

Effects of thermal processing on the texture and collagen characteristics of ready-to-eat chicken claw.

The effects of thermal processing on the texture and collagen properties of ready-to-eat chicken claws were investigated and the relationship between the texture of chicken claws and the collagen properties of connective tissue was further discussed. The texture, sensory and collagen characteristics (content, solubility, and structure), and the degradation of insoluble collagen of chicken claws underwent thermal processing at 90°C/30 min, 100°C/30 min, 115°C/15 min, and 121°C/10 min were measured. The results showed that thermal processing significantly reduced the textural parameters (hardness, springiness, cohesiveness, chewiness, and resilience) of chicken claws, and the textural deterioration intensified with the increase in temperature. Thermal processing aggravated the degradation of collagen fibers in cooked chicken claws, resulting in decreased insoluble collagen content and increased collagen solubility. Moreover, higher thermal processing temperature produced more soluble collagen components composed of low-molecular weight peptides. The textural deterioration of chicken claws caused by thermal processing was related to the decrease of insoluble collagen content and the increase of content of soluble collagen composed of low-molecular weight peptides. On the one hand, the decreased of insoluble collagen content led to the weakening of connective tissue. On the other hand, low-molecular weight peptides hindered the cooling renaturation of soluble collagen, leading to the formation of gels with poor mechanical properties.

Effect of sous vide cooking and ageing on tenderness and water-holding capacity of low-value beef muscles from young and older animals

This study investigated the effect of the age of the animal, sous vide cooking and ageing on tenderness and water-holding capacity of bovine biceps femoris (BF) and semitendinosus (ST). Samples of each muscle from young (<18 months) and older (30–42 months) animals, at 0 and 13 days ageing, were cooked at 55 °C, 65 °C, and 75 °C for 1 h, 8 h and 18 h and tested for Warner-Bratzler shear force (WBSF), cooking loss, total water content and collagen solubility. WBSF reduced with ageing (P < 0.05) and sous vide cooking (P < 0.001) in both muscles. Our results demonstrated that meat from older animals required a higher temperature (75 °C) and prolonged cooking (18 h) to achieve equal tenderness in both BF and ST relative to young animals. Cooking time, temperature and their interaction altered cooking loss (P < 0.001) for both muscles. The higher cooking temperature increased collagen solubility (P < 0.001) in both muscles and solubilisation of collagen may have contributed to improved tenderness of BF and ST in sous vide cooking.

The Use of Syrian Sumac (Rhus coriaria) as a Meat Tenderizer: Effect on Fat, Protein and Collagen Profiles on Pectoralis superficialis Cut

The Syrian Sumac (Rhus coriaria) is a widely used spice in the Arab world of attractive economic importance in food, cosmetic and pharmaceutical industries. Meat tenderness is one of the very most important factors for customers‘ acceptability. The global objective of this study was to add an additional value to Sumac by evaluating its meat tenderizing effect. Crude sumac fruits were used to create three different extracts (aqueous, ethanolic and purified enzymatic extract). Pectoralis superficialis cuts were treated with the extracts and studied for their shear stress, pH, protein and fat contents and collagen. The hypothesis that Sumac could have a meat tenderizing effect was supported by our results showing a significant decrease in shear stress and protein content with increase in collagen solubility. Moreover, an effect on decreasing meat fat was detected, where the aqueous sumac extract decreased significantly the fat percentage in meat. The active enzymes in Sumac were shown to be variate in nature, lipase and protease, with a significant effect on collagen, thus proving Sumac‘s possibility to be potentially used as a meat tenderizer.

An analysis of the influence of various tenderising treatments on the tenderness of meat from Polish Holstein-Friesian bulls and the course of changes in collagen

The aim of the study was to analyse the influence of tenderising treatments applied to the carcasses of Polish Holstein-Friesian (PHF) bulls of Black-and-White variety on the process of meat tenderisation and to assess the role of collagen in this process. The research was carried out on m. longissimus thoracis et lumborum. The carcasses were subjected to high-voltage electrical stimulation (ES), conditioning (CD), and both treatments together (ES + CD). The carcasses which were only refrigerated were the control group. The content of collagen in meat, its solubility, the share of the polypeptide subunits α1(I)CB7 and α1(I)CB8 of type I collagen and α1(III)CB5 of type III collagen were also analysed. ES with and without CD significantly accelerated the meat tenderisation and increased collagen solubility. CD always caused the degradation of type I collagen subunits, especially the α1(I)CB7 subunit. However, CD had significantly lesser influence on the rate of meat tenderisation than ES.

Tenderization Efficiency of Cucumis Extract (Cucumis Trigonus Rox-b) Compared with Papain enzyme on the Aged Bull Meat by Injection Method

This study was carried out to develop a method for enhancing tenderness and overall qualities of Karadi tough aged bull meat (more than 5 years old) by using a proteolytic extract from cucumis fruit (Cucumis trigonus Rox-b) compared to papain enzyme. After slaughter bull and dressing carcass, the three main muscle, longissimus dorsi (LD), semimembranosus (SM) and supraspinatus (SS) were evaluated by injecting brine supplied with extract solutions in different concentrations. (0.1, 0.2 and 0.3 % of cold cucumis extract solution and 0.02 % of Papain extract solution and distilled water as a group) at an average of injection of 10 % muscle weight. Overall, there were significant (p˂0.05) reduction of muscle pH, water holding capacity and cooking loss and significant (p˂0.05) increase in collagen solubility, nitrogen solubility in LD, SM and SS muscle samples treated with cucumis extract compared with control and Papain enzyme. The increased concentration of cucumis extract resulted in a significant increase (p˂0.05) in total and myofibrillar protein solubility with a slight increase of sarcoplasmic solubility in muscle samples that treated with cucumis extract compared to control and Papain enzyme. The electrophoresis pattern of muscle treated samples also revealed extensive proteolysis occurring in each muscle type. The results of the sensory evaluation indicated that the tenderness, juiciness and overall acceptability of all treated muscle samples significantly (p&lt;0.05) improved compared with control. In our experiment, generally, cucumis extract tended to be more effective than papain extract for most of the studied traits. Therefor it can be summarized that cucumis extract is one of the best alternative source of proteolytic enzymes for the effective tenderizing of meat.

Effects of soy sauce on physicochemical and textural properties of tumbled chicken breast

The objective of this study was to evaluate the effects of soy sauce on the physicochemical and textural properties of tumbled chicken breasts. Chicken breasts marinated with distilled water (Con), 4% NaCl solution, 4% NaCl and lactic acid solution (pH 4.9), and soy sauce solution (4% salt concentration and pH 4.9) were vacuum tumbled at 3°C for 60 min. The chicken breast marinated with soy sauce solution showed lower lightness and higher redness and yellowness due to the color of the soy sauce. The acidic marinades led to a decrease in pH value of tumbled chicken breast. The acidic marinades increased collagen solubility of sample compared with 4% NaCl solution, resulting in decreased shear force. Water-holding capacity, marination and cooking yields, and solubility of myofibrillar proteins were mainly affected by the presence of salt in the marinade, rather than by pH alternation. Our results suggested that soy sauce marination can improve the tenderness of tumbled chicken breast.

Tenderization effect of soy sauce on beef M. biceps femoris

This study was conducted to evaluate the tenderization effect of soy sauce on beef M. biceps femoris (BF). Five marinades were prepared with 4% (w/v) sodium chloride and 25% (w/v) soy sauce solutions (4% salt concentration) and mixed with the ratios of 100:0 (S0, pH 6.52), 75:25 (S25, 5.40) 50:50 (S50, 5.24), 25:75 (S75, 5.05), and 0:100 (S100, 4.85), respectively. The BF samples which were obtained from Hanwoo cows at 48h postmortem (n=24) were marinated with five marinades for 72h at 4°C (1:4 w/w), and the effects of soy sauce on tenderness were evaluated. Soy sauce marination resulted in a decrease in the pH value of the BF sample. However, there were no significant differences in the water holding capacity (P<0.05). The S100 treatment showed the significant (P<0.05) increase in collagen solubility and myofibrillar fragmentation index, contributing to decreased shear force compared to S0 (control). Reduction in intensity of few myofibrillar protein bands were observed for S100 treatment compared to control using SDS–PAGE. Scanning electron microscopy revealed breakdown of connective tissue surrounding muscle fibers of the S100 treatment. The tenderization effect of soy sauce may attribute various mechanisms such as increased collagen solubility or proteolysis which depend on soy sauce level in marinade.

Biochemical and microstructural characteristics of meat samples treated with different plant proteases

This study was conducted to compare the efficiency of different plant proteases for changing biochemical and microstructural characteristics in muscle foods. The meat samples from chicken, giant catfish, pork and beef were treated with four types of proteolytic enzymes: Calotropis procera latex proteases, papaya latex proteases, commercial papain and bromelain at the concentrations of 2 × 10 3 to 6 × 10 3 activity units/100 g of muscle. The pH, collagen solubility, trichloroacetic acid (TCA) soluble peptides, protein patterns and muscle microstructures of the treated samples were evaluated after 24 h at 4°C. A decrease of muscle pH in chicken, giant catfish and pork was observed when the enzymes were added (p < 0.05). A significant increase in collagen solubility was also found in all of the muscle samples (chicken increased from 37.64 to 83.59%; giant catfish increased from 52.82 to 84.14%; pork increased from 14.34 to 86.78; and beef increased from 26.02 to 86.18%; p < 0.05). An increase in TCA-soluble peptides (from 0.90 to18.53 μmole/g sample), and myofibrillar protein degradation was observed in all of the enzyme treated samples as compared to the control (p < 0.05). The electrophoretic pattern of the muscle proteins also revealed extensive proteolysis and reduction of protein bands in all of the treated samples. At the microstructural level, tissue fibers were broken, and the connections between the sarcolemma and the myofibrils were loosened when each enzyme was applied. When comparing all proteolytic enzymes used, papaya latex proteases showed the highest hydrolysis activity in all muscle types, which was followed by C. procera latex proteases, commercial papain, and then bromelain. The results show that these proteolytic enzymes could be used as an effective meat tenderizer. Key words: Proteases, muscle foods, collagen, tenderization, toughness.

Vitamins E and C May Increase Collagen Turnover by Intramuscular Fibroblasts. Potential for Improved Meat Quality

Vitamins influence collagen metabolism in animals grown for meat. This study investigated whether vitamins E and C regulate collagen turnover in muscle by the balance of effects on the synthesis of collagen and its degradation by secretion of matrix metalloproteinases (MMPs) by bovine intramuscular fibroblasts. Fibroblasts isolated from longissimus dorsi (LD) and semitendinosus (ST) muscle were treated with different concentrations of vitamins. Pro-MMP-2, MMP-2, and total soluble collagen (TSC) synthesis were determined. Vitamins E and C each preferentially increased (P < 0.05) MMP-2 in cells derived from LD relative to those derived from ST. Higher TSC values (P < 0.05) were found for ST cells than for LD cells. Both vitamins may increase collagen turnover exerted by intramuscular connective tissue fibroblasts. These results may have implications in vivo on animal production, as a high rate of collagen turnover may lead to increased collagen solubility in muscles, which can affect meat tenderness.

I024 Comparison of the effects of semicarbazide and beta-aminopropionitrile on arteries in the brown norway rat

Semicarbazide-sensitive amine oxidase (SSAO) is highly expressed by the smooth muscle cells of the aorta but its function within the arterial wall is unknown. This contrasts with another lifeessential amine oxidase expressed in the aortic wall, lysyl oxidase (LO), responsible for post-translational cross-linking of tropoelastin and collagen molecules to produce insoluble, highly mechanically resistant fibres. It has been hypothesized that SSAO may participate in extracellular matrix cross-linking, but proof is lacking. To investigate whether SSAO may play such a role physiologically, we compared effects of semicarbazide (SCZ) and β-aminopropionitrile (BAPN), two amine oxidase inhibitors with different properties and relative specificities for SSAO and LO, on arteries in growing Brown Norway rats, which present a rare phenotype of spontaneous rupture of the internal elastic lamina (IEL) that is aggravated by LO inhibition. We measured aortic LO and SSAO activities during and at the end of 8-9 weeks of treatment, started at weaning, and quantified aortic insoluble elastin and total collagen contents, IEL ruptures in several arteries, ex vivo carotid artery wall rupture pressure and solubility of tail tendon collagen. After a pilot study using equivalent doses by weight, and combining the two compounds to test for additivity, we performed a study using low and high equimolar doses of SCZ and BAPN. Both compounds similarly inhibited LO, whereas SCZ was far more effective than BAPN in inhibiting SSAO. Both compounds decreased carotid rupture pressure, increased collagen solubility, decreased aortic insoluble elastin (% dry weight) and also increased IEL ruptures in abdominal aorta, iliac, renal and caudal arteries in a dose-dependent manner. The high dose of SCZ increased aortic collagen and extracellular proteins other than insoluble elastin markedly more than did equimolar BAPN, possibly revealing a specific effect of SSAO inhibition. We conclude that the majority of SCZ effects are mediated by LO inhibition, SCZ being more effective than BAPN in our in vivo experimental conditions, and to demonstrate unequivocally a specific effect of SSAO inhibition on extracellular matrix formation or organization, we must await availability of more specific inhibitors.

Cervical remodeling during pregnancy and parturition: molecular characterization of the softening phase in mice

Cervical remodeling during pregnancy and parturition is a single progressive process that can be loosely divided into four overlapping phases termed softening, ripening, dilation/labor, and post partum repair. Elucidating the molecular mechanisms that facilitate all phases of cervical remodeling is critical for an understanding of parturition and for identifying processes that are misregulated in preterm labor, a significant cause of perinatal morbidity. In the present study, biomechanical measurements indicate that softening was initiated between gestation days 10 and 12 of mouse pregnancy, and in contrast to cervical ripening on day 18, the softened cervix maintains tissue strength. Although preceded by increased collagen solubility, cervical softening is not characterized by significant increases in cell proliferation, tissue hydration or changes in the distribution of inflammatory cells. Gene expression studies reveal a potentially important role of cervical epithelia during softening and ripening in maintenance of an immunomucosal barrier that protects the stromal compartment during matrix remodeling. Expression of two genes involved in repair and protection of the epithelial permeability barrier in the gut (trefoil factor 1) and skin (serine protease inhibitor Kazal type 5) were increased during softening and/or ripening. Another gene whose function remains to be elucidated, purkinje cell protein 4, declines in expression as remodeling progressed. Collectively, these results indicate that cervical softening during pregnancy is a unique phase of the tissue remodeling process characterized by increased collagen solubility, maintenance of tissue strength, and upregulation of genes involved in mucosal protection.

C16, a novel advanced glycation endproduct breaker, restores cardiovascular dysfunction in experimental diabetic rats1

Advanced glycation endproducts (AGE) have been implicated in the pathogenesis of diabetic complications, including diabetic cardiovascular dysfunction. 3-[2-(4-Bromo-phenyl)-1-methyl-2-oxo-ethyl]-4,5,6,7-tetrahydro-benzothiazol-3-ium bromide (C16), a novel AGE breaker, was investigated for its effects on the development of cardiovascular disease in diabetic rats. Rats that had streptozotocin-induced diabetes for 12 weeks were divided into groups receiving C16 or vehicle by gavage. In hemodynamic studies of the left ventricle, C16 treatment (25 or 50 mg/kg) for 4 weeks resulted in a significant increase in left ventricular systolic pressure, +dp/dt(max), and -dp/dt(max) as compared with vehicle-treated diabetic rats. Furthermore, in hemodynamic studies of the cardiovascular system, C16 (12.5, 25, or 50 mg/kg) treatment for 4 weeks resulted in a dose-dependent and significant increase in cardiac output, a reduction of total peripheral resistance, and an increase in systemic arterial compliance when compared with vehicle-treated diabetic rats. Biochemical studies showed that C16 treatment also resulted in a significant decrease in immunoglobulin G-red blood cell surface crosslink content and an increase in collagen solubility. Morphological and immunohistochemical examinations indicated that C16 was able to prevent increases of the collagen type III/I ratio in the aorta and decrease the accumulation of AGE in the aorta. C16 has the ability to reduce AGE accumulation in tissues in vivo, and can restore diabetes-associated cardiovascular disorders in rats. This provides a potential therapeutic approach for cardiovascular disease associated with diabetes and aging in humans.

Proteolysis of Cell-Surface Tissue Transglutaminase by Matrix Metalloproteinase-2 Contributes to the Adhesive Defect and Matrix Abnormalities in Thrombospondin-2-Null Fibroblasts and Mice

Thrombospondin (TSP)-2-null dermal fibroblasts display an attachment defect that results from increased matrix metalloproteinase (MMP)-2 levels in their conditioned media. To investigate the molecular mechanisms responsible for this defect, we analyzed the activity of tissue transglutaminase (tTG) in TSP-2-null dermal fibroblasts and in tissues of TSP-2-null mice. tTG functions as a co-receptor for beta1 and beta3 integrins and stabilizes extracellular matrix proteins by introduction of isopeptide cross-links. Cell-surface tTG activity was reduced in TSP-2-null cells (0.50 +/- 0.05 arbitrary units versus 0.84 +/- 0.07 for wild type; P < or = 0.05), and addition of MMP-2 to the culture medium of wild-type cells caused a 35% reduction in cell-surface tTG activity. tTG was susceptible to proteolysis by MMP-2 in vitro, and addition of the MMP inhibitor TIMP-2 to TSP-2-null cells restored tTG activity (0.3 +/- 0.08 for untreated cells; 0.71 +/- 0.09 with TIMP-2). TSP-2-null mice had reduced tTG activity in skin, as measured by incorporation of fluorescein isothiocyanate-labeled cadaverine, and a threefold increase in acetic acid-extracted dermal collagen. Furthermore, isopeptide cross-links were reduced in both uninjured skin and in excisional wounds of TSP-2-null mice, as determined by morphometric immunohistochemical analysis, indicating that isopeptide cross-links are important for the stabilization of the collagenous matrix in dermis. These findings provide a mechanism for the reduced adhesion of TSP-2-null fibroblasts and an explanation for the increased collagen solubility and fragility of TSP-2-null skin.

Potential Roles for Gonadal Steroids and Insulin-like Growth Factor I During Final Cervical Ripening

Objective: To determine whether gonadal steroids and insulin-like growth factor I influence the final cervical remodeling during parturition.Methods: Cervical biopsies were obtained transvaginally before labor (n = 10) and after spontaneous cervical ripening and vaginal delivery (n = 20). Levels of estrogen and progesterone receptors, their messenger RNAs, insulin-like growth factor I messenger RNA, and serum estradiol and progesterone were measured. Collagen and proteoglycan concentrations and compositions were measured to estimate the degree of cervical ripeness.Results: The concentrations of estrogen and progesterone receptors decreased in comparison with the clinically unripe cervix before labor. The median estrogen receptor concentration (range) decreased from 10 (2–18) to 4.5 (2–14) fmol/mg protein (P < .01), and the progesterone receptor concentration from 105.5 (32–153) to 74 (30–115) fmol/mg protein (P < .05), whereas their messenger RNA levels were unchanged. The insulin-like growth factor I messenger RNA concentration declined from 16.1 (8.4–20.4) at term to 8.9 (1.5–18.5) amol/μg DNA after parturition (P < .01). The collagen solubility by pepsin increased, but not significantly, and the collagen concentration was unchanged. The concentration of small proteoglycans, mainly decorin, decreased from 1.59 (1.20–1.97) to 0.84 (0.24–1.41) μg/mg wet weight (P < .001), and the concentration of versican increased, but not significantly (P = .07).Conclusion: Concentrations of estrogen and progesterone receptors and insulin-like growth factor I messenger RNA were decreased significantly after spontaneous cervical ripening in comparison to levels before labor. These changes coincided with a tendency toward increased collagen solubility and a decline in concentration of small proteoglycans, which probably alters collagen organization, thus allowing for cervical softening and dilation. These observations suggest that gonadal steroids influence the final cervical remodeling during parturition, an influence perhaps mediated by insulin-like growth factor I.

Cervical ripening in humans: Potential roles of estrogen, progesterone, and insulin-like growth factor-I

OBJECTIVE: During pregnancy in humans a gradual connective tissue remodeling takes place in the cervix. The aim of this study was to examine a possible relationship between the action of gonadal steroids and growth factors and the biochemically identifiable changes in connective tissues during cervical ripening. STUDY DESIGN: Cervical biopsy specimens and serum samples were taken from 20 term pregnant and 20 nonpregnant menstruating women. Estrogen receptors and progesterone receptors were measured with enzyme immunoassays. The messenger ribonucleic acid levels for estrogen receptors, progesterone receptors, and insulin-like growth factor-I were determined by solution hybridization with human complementary deoxyribonucleic acid probes. The concentration of collagen and its solubility by pepsin digestion were measured. Statistical evaluations were done with the Student t test. RESULTS: In term pregnancy the estrogen receptor level decreased to 14% and the progesterone receptor level to 24% of nonpregnant levels ( p < 0.001 and p < 0.01). The insulin-like growth factor-I messenger ribonucleic acid level increased 400% ( p < 0.01), whereas the messenger ribonucleic acid levels for estrogen receptors and progesterone receptors were unchanged. The changes coincided with a twofold decrease in collagen concentration (hydroxyproline) and a twofold increase in collagen solubility. CONCLUSION: Estrogen receptors and progesterone receptors are present in human cervix. A significant down-regulation of estrogen receptors and progesterone receptors and a fourfold increase in the insulin-like growth factor-I messenger ribonucleic acid level were registered in term pregnant cervix. These findings coincided with the remodeling of the cervical connective tissue. (AM J OBSTET GYNECOL 1996;174:1065-71.)

A base substitution at the splice acceptor site of intron 5 of the COL1A2 gene activates a cryptic splice site within exon 6 and generates abnormal type I procollagen in a patient with Ehlers-Danlos syndrome type VII.

The dermal type I collagen of a patient with Ehlers-Danlos type VIIB (EDS-VIIB) contained normal alpha 2(I) chains and mutant pN-alpha 2(I)' chains in which the amino-terminal propeptide (N-propeptide) remained attached to the alpha 2(I) chain. Similar alpha 2(I) chains were produced by cultured dermal fibroblasts. Amino acid sequencing of tryptic peptides, prepared from the mutant amino-terminal pN-alpha 2(I) CB1' peptide, indicated that five amino acids, including the N-proteinase (the specific proteinase that cleaves the procollagen N-propeptide) cleavage site, had been deleted from the junction of the N-propeptide and the N-telopeptide (the nonhelical domain at the amino-terminus of the alpha chains of fully processed type I polypeptide chains) of the mutant pro-alpha 2(I)' chain. The corresponding 15 nucleotides, which were deleted from approximately half of the alpha 2(I) cDNA polymerase chain reaction products, of the alpha 2(I) cDNA polymerase chain reaction products, were encoded by the +1 to +15 nucleotides of exon 6 of the normal alpha 2(I) gene (COL1A2). These 15 nucleotides were deleted in the splicing of alpha 2(I) pre-mRNA to mRNA as a result of inactivation of the 3' splice site of intron 5 by an AG to AC mutation and the activation of a cryptic AG splice acceptor site corresponding to positions +14 and +15 of exon 6. Loss of the N-proteinase cleavage site explained the persistence of the pN-alpha 2(I)' chains in the dermis and in fibroblast cultures. Collagen production by cultured dermal fibroblasts was doubled, possibly due to reduced feedback inhibition by the N-propeptides. In contrast to previously reported cases of EDS-VIIB, Lys5 of the N-telopeptide was not deleted and appeared to take part in the formation of intramolecular cross-linkages. However, increased collagen solubility and abnormal extraction profiles of the mutant type I collagen molecules indicated that collagen cross-linking was abnormal in the dermis. The proband and her son were heterozygous for the mutation. It is likely that the heterozygous loss of the N-proteinase cleavage site, with persistence of a shortened N-propeptide, was the major factor responsible for the EDS-VIIB phenotype.

Organic Acids as Tenderizers of Collagen in Restructured Beef

ABSTRACTAcetic, citric and lactic acid were incorporated into restructured beef steaks to determine their effect on collagen. These steaks were analyzed for collagen solubility, total collagen content, shear force behavior, sarcoplasmic and myofibrillar protein extractability, thermal stability and color. These results were compared to those obtained from control samples containing high collagen and low collagen. Results indicate that these acids increased collagen solubility, total collagen content and shear force values when compared with the control samples. No differences (P &gt; 0.05) were found in sarcoplasmic protein extractability although myofibrillar protein extractability declined. Acid treatment decreased the thermal stability of collagen. The Hunter Color values of the uncooked and cooked acid‐treated steaks differed (P 0.05) from the controls.

Effect of feed energy intake on collagen characteristics and muscle quality of mature cows

Samples from mature cows fed a high-energy and maintenance-energy diet for 84 days prior to slaughter were used to compare collagen solubility and palatability traits. Cows fed a high-energy diet prior to slaughter had increased percentage heat-labile collagen, less sensory panel detectable connective tissue and lower shear force values than cows fed a maintenance-energy diet. Mature cows fed a high-energy diet were fatter and had more marbling than cows fed a maintenance-energy diet. The increased collagen solubility from feeding a high-energy diet to mature cows resulted in palatability and shear force ratings similar to those expected from young animals.

The physiological role of relaxin in the pregnant rat. IV. The influence of relaxin on cervical collagen and glycosaminoglycans.

Changes in the collagen and glycosaminoglycan components of cervical connective tissue were studied in nonpregnant, intact pregnant, and ovariectomized hormone-treated pregnant rats. Collagen concentration and solubility and the concentration of the glycosaminoglycans dermatan sulfate (DS), heparan sulfate, and hyaluronic acid (HA) in cervices taken from day 9 (D9) pregnant rats were similar to those in cervices from nonpregnant rats. In cervical tissue from late pregnant intact control rats on D18 and D22, the collagen concentration decreased, collagen solubility increased, and there was no significant change in total glycosaminoglycan concentration. In cervices from ovariectomized pregnant rats treated with progesterone and estrogen, collagen and glycosaminoglycan parameters resembled those of D9 and nonpregnant cervices on both D18 and D22. However, treatment of ovariectomized pregnant rats with progesterone, estrogen, and porcine relaxin (R) restored cervical collagen concentrations to those of intact controls on both D18 and D22. On D18 of pregnancy, cervical collagen solubility was partially increased by R treatment, and by D22, it was similar to that of intact D22 pregnant controls. R treatment also resulted in a significantly increased cervical concentration of HA. It is concluded that the decrease in collagen concentration, increase in collagen solubility, and increase in HA concentration resulting from R action may contribute in part to the increased extensibility of the cervix that occurs during late pregnancy in the rat.