Rapid method for the purification of the elastin cross-links, desmosine and isodesmosine

Biochemical and technological characteristics of wooden breast chicken fillets and their consumer acceptance

The wooden breast (WB) has caused great damages to meat producing industries, being its etiology still not fully understood. Thus, the objective of this work was to investigate biochemistry and technological characteristics of WB chicken fillets and their consumer acceptance. WB fillets were evaluated in regards to color, pH, approximate chemical composition, water holding capacity, cooking loss, shear force, total and soluble collagen, and comparison estimated of pyridinoline. The sensorial analysis used real size images of fillets. The WB showed changes in physical parameters such as an increase in luminosity and shear force. In regards to the chemical parameters, showed an increase in pH value, moisture content, lipids, and mineral, and protein content reduction. There were biochemistry changes in the collagen with an increase of 17.32% in total collage content and a reduction by 30.96% in the estimated pyridinoline content. Technological parameters were negatively altered by a reduction in water holding capacity. WB fillets showed a low acceptance rate and intention to purchase. Results show the WB meat presented biochemistry and technological characteristics compromised besides a low acceptance and purchase intention, leading to economic losses for the poultry sector.

Comparison of quality traits among breast meat affected by current muscle abnormalities

Over the past several decades, as a result of the increasing growth rate and body size of modern hybrid birds, poultry industry has been facing up the occurrence of many breast meat abnormalities, such as White Striping (WS), Wooden Breast (WB) and Spaghetti Meat (SM), whose incidence has recently reached alarming levels. Thus, the present study aimed at simultaneously investigating the implications of WS, WB and SM abnormalities on meat colour, pH, proximate composition, fatty acid profile, collagen, thermal properties as well as texture and water mobility, assessed on both superficial and deep section of Pectoralis major muscle. Overall, the occurrence of breast abnormalities is associated with a higher ultimate pH and a significant increase in moisture and fat level, coupled with a decrease in protein and ash content with WB showing the most detrimental effect. However, fatty acid profile resulted to be mildly modified only by WS. Moreover, WB fillets showed significantly higher (P < .001) collagen content and stromal protein denaturation enthalpy associated with an altered water distribution and mobility within the muscle tissue. On the contrary, SM samples displayed a lower (P < .001) collagen cross-linking and a softer texture after the cooking. Overall, these findings reveal that the occurrence of WB abnormality exerts a more profound and prominent effect on meat quality traits rather than the presence not only of WS, but also of SM.

Desmosine-inspired cross-linkers for hyaluronan hydrogels

We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

Quantification of mouse lung elastin during prenatal development

Elastic fibres play a crucial function during the process of lung alveolisation. During the perinatal period, any changes in the elastogenic process during foetal development may result in permanent lifetime defects. In pre-natal life, well-developed pulmonary elastic fibres should favor the pre-natal maturation of the lung and an enhanced alveolisation, which in many species, such as humans begins only after birth. The authors present a quantitative study by image analysis and by high-pressure liquid chromatography (HPLC) of the mouse lungs’ elastic fibre content from the 15th till the 19th gestational day.

Collagen, cross-linking, and advanced glycation end products in aging human skeletal muscle

We examined intramuscular endomysial collagen, cross-linking, and advanced glycation end products, as well as the general and contractile protein concentration of 20 young (25 +/- 3 yr) and 22 old (78 +/- 6 yr, range: 70-93 yr) sedentary men and women to better understand the underlying basis of changes in skeletal muscle mass and function that occur with aging. The old individuals had an impaired ability (increased time) (P < 0.05) to climb stairs (80%), rise from a chair (56%), and walk (44%), as well as lower (P < 0.05) quadriceps muscle volume (-29%), muscle strength (-35%), muscle power (-48%), and strength (-17%) and power (-33%) normalized to muscle size. Vastus lateralis muscle biopsies revealed that intramuscular endomysial collagen (young: 9.6 +/- 1.1, old: 10.2 +/- 1.2 microg/mg muscle wet wt) and collagen cross-linking (hydroxylysylpyridinoline) (young: 395 +/- 65, old: 351 +/- 45 mmol hydroxylysylpyridinoline/mol collagen) were unchanged (P > 0.05) with aging. The advanced glycation end product, pentosidine, was increased (P < 0.05) by approximately 200% (young: 5.2 +/- 1.3, old: 15.9 +/- 4.5 mmol pentosidine/mol collagen) with aging. While myofibrillar protein concentration was lower (-5%, P < 0.05), the concentration of the main contractile proteins myosin and actin were unchanged (P > 0.05) with aging. These data suggest that the synthesis and degradation of proteins responsible for the generation (myosin and actin) and transfer (collagen and pyridinoline cross-links) of muscle force are tightly regulated in aging muscle. Glycation-related cross-linking of intramuscular connective tissue may contribute to altered muscle force transmission and muscle function with healthy aging.

Use of a proteomics approach to identify favourable conditions for production of good quality lambskin leather

It is necessary to understand the changes that occur during the initial processing of lamb skins, because these will affect the final quality of the leather. The types of collagen, their macro and micro structures, the presence of proteins other than collagens, and the quantity and the type of proteoglycans, all have a profound effect on the quality of leather. Proteins isolated from untreated or raw sheep skin and from pickled skin (skins treated with sodium sulfide and lime followed by bating with enzymes, then preserved in sodium chloride and sulfuric acid) were significantly different when analysed by use of 2D gel electrophoresis and mass spectrometry. Agarose gel electrophoresis with a very sensitive sequential staining procedure has been used to identify the glycosaminoglycans present in raw and treated skin and their impact on quality of leather. Results showed that effective removal of proteoglycans acting as inter-fibrillar adhesives of collagen fibrils seemed to improve leather quality. Removal of these molecules not only opens up the fibre structure of the skin but may also be important in wool removal. The presence of elastin, which imparts elastic properties to skin, is of significant importance to tanners. The amino acids desmosine and isodesmosine, found exclusively in elastin, were quantitatively analysed to assess the role of elastin in leather quality.

Effect ofD-penicillamine on rat lung elastin cross-linking during the perinatal period

This study was designed to clarify the effects of D-penicillamine (DPA), a drug used for treatment of various pathological events, on lung elastin formation and maturation of the newborn in the perinatal period. The investigation was conducted on 20 newborn rats bred from 40 female and six male rats. DPA doses 400 mg kg(-1) day(-1) and physiological saline were given intraperitoneally (i.p) to experimental and control groups. To assess newborn maturation, their body and lung weights were determined. Serum Cu levels were measured by atomic absorption spectroscopy and ceruloplasmin (Cp) activities were measured spectrophotometrically. Newborn lung tissue elastin, desmosine (DES) and isodesmosine (IDES) levels were measured by HPLC. The results showed that DPA treatment caused loss of skin elasticity and reduction in body and lung weight in newborns of the experimental group. The serum Cu levels and Cp activity were found to be significantly lower in both maternal and newborn of the experimental groups compared with the control group. The lung DES, IDES and elastin values of newborns in the experimental group were decreased compared with the control group. In conclusion, our results indicate that 400 mg kg(-1) day(-1) DPA, a dose that is used in the treatment of Wilson's disease, rheumatoid arthritis and cystinuria, caused the retardation of newborn maturation, a decrease in DES-IDES cross-links and levels of lung elastin of offspring in the perinatal period. Another conclusion to be drawn from this study is that even low levels of Cu depletion due to DPA administration induces a change in cross-linking in lung elastin during the perinatal period.

Glycated collagen cross-linking alters cardiac mechanics in volume-overload hypertrophy

Alteration of hemodynamic loading induces remodeling that includes changes in myocardial properties and extracellular matrix structure. We investigated the hypothesis that cardiac hypertrophy due to volume overload produces changes in myocardial diastolic mechanics and stiffness that are in part due to alterations in advanced glycation end-product (AGE) collagen cross-linking. Rats developed volume overload induced by arteriovenous fistula (AVF). To assess the dependence of AGE cross-linking on mechanics, we prevented AGE formation by administering the drug aminoguanidine (AG) to one group of AVF rats (AG+AVF). Volume overload did not modify collagen concentration. Right ventricular AGE cross-links were modestly elevated in AVF hearts but were significantly reduced by AG. AVF rats exhibited significantly increased septal AGE cross-links that were inhibited in the AG+AVF group. AVF-induced increases in left ventricular longitudinal stiffness and septal circumferential stiffness were prevented in AG+AVF hearts. Volume overload appears to regionally modify AGE collagen cross-linking and stiffness, and AG treatment prevented these increases, demonstrating that AGE cross-linking plays a role in mediating diastolic compliance in volume-overload hypertrophy.

Extracellular matrix maturation in the left ventricle of normal and diabetic swine

The main objective of this study is to determine the transmural distribution of extracellular matrix (ECM) collagen and maturation in non-diabetic and diabetic hearts. The Yucatan miniature swine heart ECM was analyzed in eight streptozotocin (STZ) induced diabetic pigs (Diabetic-Swine) and age matched normal control pigs (Nondiabetic-Swine). After 12 weeks of STZ induced diabetes, transmural biopsies were obtained from the left ventricular free wall divided into subendocardial, mid- and subepicardial layers. Collagen concentration and maturation were measured by RP-HPLC determination of hydroxyproline (Hyp) and content of hydroxylysylpyridinoline (HP) cross-links, respectively. Results showed a significant elevation in arterial glucose (P<0.05) and reduction in arterial plasma insulin levels in the Diabetic-Swine. Hyp concentration was significantly greater (P<0.05) in the subendocardial layers in both the Diabetic and Nondiabetic animals. The HP cross-link content was significantly greater (17%) in the Diabetic-swine subendocardial layer compared to Nondiabetic-Swine (P<0.05), but not in other layers. In summary, the accumulation and/or increase in HP cross-link content in the Diabetic-Swine subendocardial layer suggests that myocardial fibrosis may be greater in this specific region.

Collagen characteristics and organization during the progression of cholesterol-induced atherosclerosis in Japanese quail

This study reports the concentration of collagen and its hydroxypyridinoline crosslinks, collagen fibril organization in the dorsal aortas, and systolic blood pressure during the progression of atherosclerosis in Japanese quail selected for cholesterol-induced atherosclerosis. The quail were placed on either a control or 0.5% cholesterol-added diet at approximately 16 weeks of age. The concentration of total collagen did not change in the control arteries during the course of the study, whereas at 5 and 10 weeks of cholesterol feeding, collagen levels decreased in the cholesterol-fed birds. Hydroxypyridinoline concentration increased during the duration of the study in the cholesterol-fed birds and by 15 and 20 weeks of cholesterol feeding, levels were significantly increased over those observed in the control arteries. Transmission electron microscopy showed changes in the organization of collagen fibrils. Increased systolic blood pressure was noted beginning at 10 weeks of cholesterol feeding, which is suggestive of other systemic changes induced by hypercholesterolemia. These results demonstrated remodeling of the collagen component of the dorsal aorta extracellular matrix during the progression of atherosclerosis and are suggestive of other systemic cardiovascular system changes.

Effects of depletion of neutrophils or macrophages on development of cigarette smoke-induced emphysema

The aim of this study was to ascertain the putative roles of neutrophils or macrophages in the pathogenesis of cigarette smoking-induced emphysema on the basis of effects of anti-neutrophil (anti-PMN) antibody or anti-monocyte/macrophage (anti-MoMac) antibody on the development of emphysema in cigarette smoke-exposed rats. Rats were treated with rabbit anti-PMN or anti-MoMac antibody and exposed 7 days/wk for 2 mo to cigarette smoke inhalation; rats treated with nonimmunized rabbit IgG (control antibody) and exposed to cigarette smoke or normal room air served as controls. Antibody treatments began 24 h before the start of smoke or air exposure and was continued with 1 treatment/wk. Total and differential cell counts in bronchoalveolar lavage fluid and collagenase-dissociated lung and determinations of the elastinolytic activity of lung neutrophils or macrophages in [(3)H]elastin-coated wells indicated specific suppression of neutrophil accumulation and neutrophil-related elastinolytic burden in the lungs of the anti-PMN antibody-treated smoke-exposed rats, in contrast to specific suppression of macrophage accumulation and macrophage-related elastinolytic burden in the lungs of the anti-MoMac antibody-treated smoke-exposed rats. Cigarette smoke exposure-induced lung elastin breakdown (quantitated by immunologic assay of levels of elastin-derived peptides and desmosine in lavage fluid) and emphysema in the lungs (based on morphometric analysis of alveolar mean linear intercepts and alveolar tissue density in fixed lungs) were not prevented in the lungs of anti-PMN antibody-treated smoke-exposed rats but was clearly prevented in lungs of the anti-MoMac antibody-treated smoke-exposed rats. These findings implicate macrophages rather than neutrophils as the critical pathogenic factor in cigarette smoke-induced emphysema.

Time course of neutrophil and macrophage elastinolytic activities in cigarette smoke-induced emphysema

The aim of this study was to compare the time course of neutrophil and macrophage elastinolytic potentials in the lungs of rats exposed daily to cigarette smoke inhalation for 1-6 mo in relation to the onset and progression of cigarette smoke-induced emphysema. Normal room air-exposed rats served as controls. Morphometric data of lung histological sections showed evidence of emphysema lesions in the lungs of smoke-exposed rats at month 2 and continuing to month 6. Data of total and differential cell counts in bronchoalveolar lavage fluid and collagenase-dissociated lung showed an increased number of lung neutrophils at month 1 of smoke exposure, but this was reduced to control levels at months 2-6. In contrast, an increased number of lung macrophages was evident in the smoke-exposed rats at month 2 of exposure and continued to month 6. Data of the elastinolytic activities of the neutrophils and macrophages, determined in [3H]elastin-coated culture wells, showed that the elastinolytic activity of lung neutrophils in the smoke-exposed rats was similar to that of the control air-exposed rats at months 1-6 of exposure. In contrast, the elastinolytic activity of lung macrophages in the smoke-exposed rats was increased at month 2 of exposure and remained increased at month 6. Excessive in vivo lung elastin breakdown (judged by increased levels of elastin-derived peptides and desmosine in lavage fluid, determined immunologically) was observed in the smoke-exposed rats at months 2-6 of exposure. These data indicate that the time course of increased macrophage-directed elastinolytic activity in the lung, not that of neutrophils, is more closely associated with the evolution of cigarette smoke-induced emphysema.

Effect of exercise training on passive stiffness in locomotor skeletal muscle: role of extracellular matrix

The purpose of this study was to evaluate the effect of endurance exercise training on both locomotor skeletal muscle collagen characteristics and passive stiffness properties in the young adult and old rat. Young (3-mo-old) and senescent (23-mo-old) male Fischer 344 rats were randomly assigned to either a control or exercise training group [young control (YC), old control (OC), young trained (YT), old trained (OT)]. Exercise training consisted of treadmill running at approximately 70% of maximal oxygen consumption (45 min/day, 5 days/wk, for 10 wk). Passive stiffness (stress/strain) of the soleus (Sol) muscle from all four groups was subsequently measured in vitro at 26 degreesC. Stiffness was significantly greater for Sol muscles in OC rats compared with YC rats, but in OT rats exercise training resulted in muscles with stiffness characteristics not different from those in YC rats. Sol muscle collagen concentration and the level of the nonreducible collagen cross-link hydroxylysylpyridinoline (HP) significantly increased from young adulthood to senescence. Although training had no effect on Sol muscle collagen concentration in either age group, it resulted in a significant reduction in the level of Sol muscle HP in OT rats. In contrast, exercise had no effect on HP in the YT animals. These findings indicate that 10 wk of endurance exercise significantly alter the passive viscoelastic properties of Sol muscle in old but not in young adult rats. The coincidental reduction in the principal collagen cross-link HP also observed in response to training in OT muscle highlights the potential role of collagen in influencing passive muscle viscoelastic properties.

Rapid method for the isolation of hydroxylysylpyridinoline and lysylpyridinoline from concentrated bone hydrolysates by liquid chromatographic techniques

A rapid method for the isolation of hydroxylysylpyridinoline and lysylyridinoline from bone by liquid chromatographic methods is described. Decalcified bone is hydrolysed in 7 M hydrochloric acid. After evaporation of the acid, the high molecular mass and dark coloured degradation products are removed by adsorption on non-polar adsorbents. The pyridinolines are separated from the majority of the amino acids by adsorption on cellulose. Separation of HP and LP is performed either by cation-exchange chromatography or by reversed-phase ion-pair chromatography. The pyridinoline containing fractions are desalted by size-exclusion chromatography. The progress of the hydrolytic cleavage of collagen and the optimal parameters for purification and separation were examined. As a result the existing method allows the isolation of high amounts of pyridinolines with low amounts of adsorbents and chemicals within a short time.

Partial characterization of ovine skeletal muscle proteoglycans and collagen

Ovine longissimus dorsi and biceps femoris muscles were analyzed for proteoglycan content, collagen and lysine aldehyde-derived collagen crosslinking concentrations at 2-4 days, six-month-old, and six-year-old stages of development. Tissue extracted proteoglycan molecular sieve distribution on a Sephacryl S-200HR column revealed two proteoglycan populations with estimated relative molecular weight ranges of 200,000 to 250,000 daltons and 23,000 to 70,000 daltons. The molecular sieve distribution was similar between the two muscles within a developmental age, but changed as a function of developmental age. Primary culture from both the longissimus dorsi and biceps femoris muscle liberated proteoglycans into the culture medium. In contrast to the tissue extracted proteoglycans, at the six-year-old stage of development, culture medium liberated proteoglycan Sephacryl S-200HR molecular sieve distribution differed between the two muscles. In both the tissue extracted and medium liberated proteoglycans at all developmental stages, nitrous acid deamination demonstrated the presence of heparan sulfate. Immunoblot analysis of the tissue extracted proteoglycans indicated the presence of decorin at each developmental stage. Longissimus dorsi and biceps femoris collagen concentrations (5.13 +/- 0.9 vs. 5.53 +/- 1.5%, respectively) and crosslink concentrations (0.07 +/- 0.01 moles HP/mole collagen) were initially similar between the two muscles; however, by six-months the muscles differed in both collagen concentration (1.72 +/- 0.5 and 2.53 +/- 0.7%, respectively) and crosslinking (0.24 +/- 0.02 and 0.27 +/- 0.03 moles HP/mole collagen, respectively). At six years of age, both the longissimus dorsi and biceps femoris exhibited slightly elevated collagen concentrations (2.49 and 3.05%, respectively) while crosslinking values were decreased relative to values at six-months of age (0.11 +/- 0.01 and 0.18 +/- 0.01 moles HP/mole of collagen, respectively). The results from this study indicate that skeletal muscle proteoglycans and collagen show developmental changes, which suggests that they are subject to developmental regulation.

High-performance liquid chromatographic determination of pyridinium crosslinks in serum, urine and dialysate of patients in chronic renal failure

This study describes an isocratic reversed phase high-performance liquid chromatographic method for the analysis of pyridinium crosslinks in serum, urine and dialysates obtained from patients with chronic renal failure on haemodialysis. The mean (SD) urine pyridinoline (PYD) and deoxypyridinoline (DPD) to creatinine (Cr) ratio in 19 healthy volunteers was 28.9 (6.3) and 9.1 (3.6) mumol/mol, respectively. In the 22 patients the PYD/Cr and DPD/Cr ratio was 244.6 (436.5) and 66.5 (116.8) mumol/mol, respectively. The mean serum PYD concentration in 29 patients of 268.5 (334.4) nmol/L was significantly higher than that of 5.9 (1.5) nmol/L found in normal volunteers: the mean DPD concentration was 82.9 (93.7) nmol/L in the patients but was undetectable in the serum from the normal volunteers. The concentration of crosslinks in pre-dialysis serum samples was higher than those found post-dialysis reflecting a significant removal of the crosslinks during dialysis. The assay of pyridinium crosslinks in serum, urine and dialyses fluid could potentially provide evidence of bone collagen turnover in patients in renal failure. Their measurement in serum and dialysate could be particularly useful in anuric patients.

The avian low score normal muscle weakness alters decorin expression and collagen crosslinking

Extracellular matrix development of chicken pectoral muscle was examined in the Low Score Normal (LSN) genetic muscle weakness and compared to both normal and avian muscular dystrophy (MD). At 20 days of embryonic development significant elevations were noted in LSN total glycosaminoglycan concentration and decorin, while at 14 days, LSN glycosaminoglycan and decorin levels were indistinguishable from the controls. Levels of a large skeletal muscle chondroitin sulfate proteoglycan (M-CSPG) appear to be unaffected. Morphologically, at 20 days, the extracellular matrix space between muscle fibers increased to a level characteristic to that observed in avian muscular dystrophy. At six weeks posthatch a marked increase in LSN collagen crosslinking relative to MD or control tissues was observed, while collagen concentration was not altered. By one year posthatch LSN collagen crosslink levels did not significantly differ from normal tissue. These data support the concept that the LSN muscle weakness is associated with changes in both proteoglycan and collagen characteristics.

Enrichment and analysis of desmosine and isodesmosine in biological fluids

A method has been developed for the enrichment and analysis of the elastin crosslinks, desmosine and isodesmosine, in biological fluids and tissues. It is adapted from published methods, offering improved recovery, sensitivity, resolution, and speed of analysis. Samples were hydrolyzed in 6 M HCl, after which the desmosines were enriched by CF1 cellulose chromatography and analyzed by HPLC with a C18 column. Isodesmosine and desmosine were quantitated based on absorbance at 275 nm, with a limit of detection of approximately 30 pmol and recovery of approximately 66% in urine. Their tR values on our HPLC system were approximately 9 and 12 min, respectively. This method was used to evaluate the daily and weekly variation in the concentrations of desmosine and isodesmosine in human urine. The results suggest that this method can be used to process large numbers of biological samples for analysis of desmosine and isodesmosine.

Effects of streptozotocin-induced diabetes on postpneumonectomy lung growth and connective tissue levels

Diabetes is generally accompanied by abnormal levels of growth hormone and adrenal steroids, hormones known to modulate postpneumonectomy (post-PNX) compensatory lung growth. Thus, we examined the possibility that diabetes may affect post-PNX lung growth processes. Left PNX was performed in young diabetic rats (streptozotocin-induced; 75 mg/kg body weight) (DM-PNX) and in control rats (C-PNX), for comparison with sham-operated control rats (C-SHAM). The rats were permitted free access to food and water. Examination at day 7 after surgery showed that right lung absolute dry weight and absolute DNA, collagen and elastin contents were increased in C-PNX and DM-PNX rats (but only C-PNX values reached those of both lungs in C-SHAM rats). Body weights (BW) of DM-PNX rats were lower than those of C-PNX and C-SHAM rats. Lung DNA/BW in C-PNX and DM-PNX rats were comparable, and matched values for both lungs in C-SHAM rats. Lung dry weight/BW, collagen/BW, and elastin/BW in DM-PNX rats exceeded values in C-PNX rats and even more for values of both lungs in C-SHAM rats. Data of another experiment, comparing DM-PNX rats with body weight-matched (by food limitation) PNX and control rats (WMC-PNX and WMC-SHAM rats, respectively) indicated comparable lung absolute DNA contents in DM-PNX and WMC-PNX rats (which matched values for both lungs in WMC-SHAM rats), however, lung absolute collagen and elastic contents were greater in the DM-PNX rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclical treatment of osteopenic ovariectomized adult rats with PTH(1-34) and pamidronate

Administration of PTH(1-34) at low intermittent doses stimulates bone formation in vivo. However, the new bone is quickly resorbed after drug withdrawal. Following the concept of lose, restore, and maintain, we studied the possibility of maintaining the PTH(1-34)-mediated new bone by APD post-treatment and the effect of a second PTH(1-34)-APD cycle in osteopenic ovariectomized (OVX) adult rats. Eighty OVX rats (6-months-old, 3 months after OVX) and 10 sham-operated rats were divided into nine groups. One OVX group was killed as baseline (BL). Five OVX groups were injected with PTH(1-34) (20 micrograms/kg/day, subcutaneously) for 3 weeks (5 days/week). The remaining two OVX groups and the sham group (S) were injected with saline as controls. One PTH(1-34) group (A) and one control group (B) were then killed. Three PTH(1-34) groups were post-treated with APD injections (250 micrograms/kg/day, subcutaneously) for 5 days; the remaining PTH(1-34) group, the other control group, and group S were injected with saline; and all these groups were left untreated for 3 weeks. At the end, one PTH-APD group (C), the PTH-saline group (D), and the saline-saline group (E) were killed. Another PTH-APD cycle was applied to the remaining two PTH-APD groups, with group F killed after the second PTH treatment and group G killed after two complete cycles. We found a 90% increase in cancellous bone volume (Cn.BV/TV) and a 28% increase in trabecular thickness (Tr.Th) in group A over group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Elastin production and degradation in cutis laxa acquisita

A case of cutis laxa acquisita was studied with the aim of defining the molecular defects involved and comparing them with those of an inherited form of cutis laxa. In the acquisita form of cutis laxa ultrastructural and biochemical observations confirmed a dramatic reduction of dermal elastin, whereas collagen content was normal. Elastin mRNA expression as well as tropoelastin production by dermal fibroblasts, in vitro, were normal compared with control cells, as revealed by in situ hybridization and enzyme-linked immunosorbent assay, respectively. Lysyl oxidase activity, measured on cultured fibroblasts, was reduced to 60% compared with age-matched control subjects. Unlike control skin fibroblasts or fibroblasts from inherited cutis laxa, the affected skin cells from cutis laxa acquisita predominantly expressed an elastolytic activity identified as cathepsin G. Patient serum also has reduced elastase inhibitory capacity and reduced levels of alpha 1-antiproteinase inhibitor (alpha 1-antitrypsin). Although cutis laxa acquisita is a heterogeneous group of disorders, findings in this patient were consistent with excessive loss of cutaneous elastin due to the combined effects of several factors, such as low lysyl oxidase activity together with high levels of cathepsin G and reduction of circulating proteinase inhibitor(s).

Determination of pyridinium crosslinks in plasma and serum by high-performance liquid chromatography

A chromatographic method for the determination of pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in serum and plasma is described. The analytical procedure involved plasma or serum purification by ultrafiltration (20,000 relative molecular mass cut-off) under centrifugation at 2500 g for 4 h, as an innovative step. Analysis was done by isocratic high-performance liquid chromatography with fluorescence detection. The linearity of the method was tested from 0.6 to 15 pmol/ml and 0.12 to 3 pmol/ml for Pyr and Dpyr, respectively. The detection limit was 60 fmol/ml for both crosslinks. Except for Dpyr in plasma (coefficient of variation 19.9%), intra-assay variation was always below 10% in serum and plasma. The method has been applied to the quantification of crosslinks in serum and plasma of healthy volunteers and also in mouse and rat plasma. Serum proved to be the most suitable biological fluid for the systemic measurement of these compounds in humans and under the experimental conditions used, contained an average of 3.62 +/- 0.65 and 0.7 +/- 0.18 pmol/ml Pyr and Dpyr, respectively.

Urinary excretion of pyridinium cross-links in healthy women; the long-term effects of menopause and oestrogen/progesterone therapy

OBJECTIVES

We investigated the effect of the menopause when followed longitudinally for a decade to evaluate whether women with an increased bone loss continue to have elevated urinary excretion of pyridinium cross-links later in menopause. Furthermore, we investigated the effect of oestrogen/progesterone therapy on the urinary excretion of pyridinium cross-links.

PARTICIPANTS

In the cross-sectional study: 18 healthy premenopausal, 142 healthy post-menopausal women and 41 osteopenic post-menopausal women. In the longitudinal study: 45 healthy post-menopausal women followed up for 7-10 years after the menopause; these women were further divided into two equal groups, according to their loss of forearm bone mineral content over 2 years. In the oestradiol/progesterone double-blind, placebo-controlled 2-year trial: early post-menopausal women were given either hormone replacement therapy (n = 38) or placebo (n = 16).

MEASUREMENTS

The urinary excretion of pyridinoline/creatinine (Pyr/Cr) and urinary deoxypyridinoline/creatinine (D-Pyr/Cr), two new markers of bone resorption.

RESULTS

Pyr/Cr and D-Pyr/Cr increased significantly after the menopause (Pyr/Cr, 77%; D-Pyr/Cr, 98%, P < 0.001). Hormone replacement therapy reversed this increase towards premenopausal levels. Both pyridinium cross-links remained fairly constant during the first decade of the menopause, when measured in the longitudinal study. When the women were divided according to loss in forearm BMC, those with a loss greater than 3.5%/2 years had significantly higher levels of pyridinium cross-links (P < 0.05-0.01). Furthermore, both Pyr/Cr and D-Pyr/Cr were significantly higher in elderly osteopenic women (aged 68-72 years) than in age-matched non-osteopenic women (P < 0.01-0.001).

CONCLUSIONS

Both Pyr/Cr and D-Pyr/Cr, two new markers of bone resorption, increased significantly at the time of the menopause, thereafter remaining fairly constant during the first post-menopausal decade. Women with increased bone loss continue to have elevated urinary excretion of pyridinium cross-links during the first decade of the menopause. This post-menopausal change is reversed by hormone replacement therapy to the premenopausal level.

Enhancement of aortic cholesterol deposition by dietary linoleic acid in cholesterol-fed mice: an animal model for primary screening of antiatherosclerotic agents

We tried to develop an experimental model using mice for the primary screening of antiatherosclerotic agents. Male ICR strain mice were given a high-cholesterol diet supplemented with 10% linoleic acid for 14 weeks. Throughout the experimental period, weight gain of these mice was significantly inhibited as compared to that of control mice given a basal diet, but displayed a steady increase comparable to that of the high-cholesterol diet without linoleic acid. The cholesterol and linoleic acid-fed mice showed increased serum cholesterol and phospholipid levels, and decreased serum triglyceride and high-density lipoprotein-(HDL) cholesterol levels and lecithin/cholesterol acyltransferase (LCAT) activity, as well as a markedly increased lipid peroxide level which was a characteristic appearance in the serum of this mouse model. At the end of the experiment, uniform and significant increases in cholesterol, notably cholesteryl ester, were observed in the aorta. Also found were marked decreases in the aorta contents of desmosine and isodesmosine, which are cross-linking amino acids present only in the elastin. Histological observations showed accumulations of fatty droplets in the intima. These changes were much less in mice receiving a high-cholesterol diet without linoleic acid. In this mouse model, probucol prevented elevation of serum cholesterol, phospholipid, and cholesterol accumulation in the aorta. Increases in lipid peroxide level and decreases in LCAT activity were also prevented. These findings indicate that this mouse model is useful for primary screening of antiatherosclerotic agents with antioxidative activity.

Quantitative studies of human lung airspace wall in relation to collagen and elastin content

Biochemical determinations of the collagen and elastin content in 50 mm3 samples of human lung are presented in relation to morphometric measurements of lung structure, as the amount of alveolar wall surface area per unit volume (AWUV), on adjacent slices. There were no differences in AWUV values, collagen content (determined as hydroxyproline) or elastin content (determined as isodesmosine) between upper and lower lobes within a single lung. In a study of 102 samples from 9 smokers lungs with no evidence of macro- or microscopic emphysema (as estimated by AWUV measurement), there was a negative correlation between AWUV and the amounts of collagen or elastin per unit volume of inflated lung. The correlation was stronger when collagen and elastin content were expressed per unit area of alveolar wall. The negative correlation is interpreted as representing either the anatomical variation within the complex hierarchy of normal lung structure or possibly low levels of fibrosis in response to cigarette smoking.

The presence of lysylpyridinoline in the hypertrophic cartilage of newly hatched chicks

The presence of lysylpyridinoline (LP) as a nonreducible cross-link in appreciable quantities has primarily been limited to the mineralized tissues, bone and dentin. However, the results reported here show that LP is not only present in the hypertrophic cartilage of the tibiotarsus isolated from newly hatched broiler chicks, but it is approx. 4-fold as concentrated as hydroxylysylpyridinoline (HP). Bone and articular cartilage surrounding the hypertrophic cartilage do not contain measurable quantities of LP. Purified LP has a fluorescent scan similar to purified HP and literature values, confirming that we indeed were measuring LP. Also, the cartilage lesion produced by immature chondrocytes from birds with tibial dyschondroplasia had LP but the HP:LP ratio was > 1. Thus, the low HP:LP ratio could be a marker for hypertrophic cartilage in avians.

Assay of pyridinium crosslinks in serum using narrow-bore ion-paired reversed-phase high-performance liquid chromatography

The pyridinium crosslinks are important biomarkers of mature hard tissue collagen degradation. This paper describes an isocratic ion-paired reversed-phase high-performance chromatographic assay using narrow-bore columns and high-sensitivity fluorescence detection to enable for the first time the determination of pyridinium crosslinks in both serum and synovial fluid samples. Extracted freeze-dried acid hydrolysates were re-suspended in 20 mM pentafluoropropionic acid (PFPA). Separations were carried out using an Exsil 100 5-microns ODS2 column (100 mm x 2.1 mm I.D.) eluted with 10 mM PFPA in water at 0.15 ml/min and detected using a Jasco 821-FP detector (xenon lamp: excitation 290 nm, emission 400 nm). Fluorescent response was linear from 269 to 8620 fmol for pyridinoline (Pyr) and 85 to 2710 fmol for deoxypyridinoline (dPyr). The limits of detection were 28 and 57 fmol, respectively. The coefficient of variation for extraction and analysis of normal serum was 7.96% for Pyr and 6.30% for dPyr (n = 6). The mean +/- S.D. concentration of Pyr in normal serum was 3.26 +/- 0.83 nM.

Automated analysis of the pyridinium crosslinks of collagen in tissue and urine using solid-phase extraction and reversed-phase high-performance liquid chromatography

A fully automated method for assaying the collagen crosslinking amino acids, pyridinoline and deoxypyridinoline, in human urine samples or tissue hydrolysates is described. Samples were processed using a Gilson ASPEC system with solid-phase extraction of the crosslinks on columns containing 100 mg of microgranular cellulose. Introduction of an additional solvent step during sample preparation allowed direct analysis by reversed-phase HPLC and elimination of the drying step used previously in a manual method. Use of a synthetic pyridinoline derivative as internal standard enabled accurate quantification of the crosslinks by correcting for recoveries through the whole assay. Samples were analyzed in sequential mode with a total assay time of 30 min. The automated assay showed close correlation with the manual method for both free and total crosslink determinations in human urine (r > 0.97). Reproducibility was improved, as seen from replicate analyses of human urine (CV < 3% for automated pyridinoline measurement compared with 8-12% previously observed for the manual method). Crosslink excretion is the most useful marker of collagen degradation in metabolic bone diseases and arthritic disorders. The automated assay which has been developed is rapid, convenient, and reliable and will greatly facilitate the monitoring of urinary collagen crosslinks and their tissue levels in clinical investigations.

High-performance liquid chromatographic determination of 3-hydroxypyridinium derivatives as new markers of bone resorption

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are intermolecular cross-linking amino acids of collagen and their urinary excretion reflects bone resorption. An isocratic high-performance liquid chromatographic assay using a reversed-phase column with a prefractionation step and fluorescence detection was developed. The accuracy and reproducibility were assessed by loading experiments and by double analysis of urinary samples. The recoveries after various loads were above 90% for HP and between 87 and 94% for LP, with an intra-assay relative standard deviation (R.S.D.) of 5% for HP and 8% for LP. The inter-assay R.S.D.s were 8% for HP and 12.4% for LP. The fasting and 24-h urinary excretions of HP and LP were measured in 40 healthy subjects (mean age 35 years) of both sexes. There was no difference between males and females. Mean adult normal values were 33.6 +/- 8.1 pmol/mumol creatinine for HP and 7.0 +/- 2.5 pmol/mumol creatinine for LP in morning fasting urine and 2-.9 +/- 7.0 pmol/mumol creatinine for HP and 5.8 +/- 1.9 pmol/mumol creatinine for LP after 24-h urinary collection. HP and LP excretions were significantly higher in morning fasting urine than in 24-h collections, in agreement with the physiological circadian rythm of bone resorption. This simplified and optimized procedure is a good method for the determination of pyridinolines and should be useful for the evaluation of bone resorption.

Fractionation of urine to allow desmosine analysis by radioimmunoassay

The present study was designed to re-evaluate the radioimmunoassay for desmosine in urine, which is currently used as a measure of elastin metabolism. Using ion exchange chromatography, gel filtration and affinity chromatography it was shown that at least five other compounds in hydrolysates of human urine competed for desmosine in the RIA. Fractionating the urine prior to hydrolysis with acetone removed one of the major contaminants. The other contaminants could subsequently be removed by extracting the urine hydrolysate with a mixture of chloroform/ethanol (60:40). Samples from nine normal adult urines showed that an average of 45% of the RIA competing material in unfractionated urine was not desmosine. The final extracted residue retained all of the desmosine and only 16% of the original solids. The average adult urine contains approximately 50 pmol desmosine/mg creatinine, reflecting a daily turnover of between 3 and 4 mg of elastin per day.

High-performance liquid chromatographic determination of desmosine and isodesmosine after phenylisothiocyanate derivatization

A new sensitive and selective high-performance liquid chromatographic method for the analysis of desmosine and isodesmosine in human and rat tissues is described. This method requires a purification step with column chromatography, followed by precolumn derivatization phenylisothiocyanate. The reaction products are then separated by isocratic chromatography on a C18 column and quantitated by ultraviolet detection at 254 nm. The recovery of standards of both compounds added to tissue samples and analysed by this method is usually greater than 90%, and the absolute detection limit is 0.5 ng for both compounds. The method is sensitive enough to measure both substances in tissue fragments of 30 mg of wet mass, which means that it can be used to study elastin in small human biopsies.

The effect of growth hormone (GH) therapy on urinary pyridinoline cross-links in GH-deficient adults

OBJECTIVE

The aim was to study the effect of growth hormone (GH) on new markers of bone resorption (fasting urinary excretion of pyridinium cross-links (pyridinoline and deoxypyridinoline)) in GH-deficient adults.

DESIGN

Randomized, double-blind, placebo-controlled cross-over study. The treatment periods (GH 2 IU/m2 subcutaneously, or placebo daily for 4 months) were separated by a 4-month washout period.

PATIENTS

Twenty GH-deficient adults (aged 18-39).

MEASUREMENTS

Blood and fasting urine samples were collected at the end of each 4-month treatment period. Plasma bone Gla protein was measured by radioimmunoassay and urine pyridinoline and deoxypyridinoline were measured by spectrofluorometry after high performance liquid chromatography and corrected for urinary creatinine.

RESULTS

GH increased fasting urinary excretion of pyridinoline (287 +/- 123%, P less than 0.001) and deoxypyridinoline (313 +/- 140%, P less than 0.001). The GH-induced increment in these parameters correlated with the increase seen in plasma bone Gla protein (r = 0.83-0.86, P less than 0.001).

CONCLUSION

Four months of GH substitution in GH-deficient adults increases bone resorption as well as bone formation. The effect on bone mass has yet to be assessed.

Separation of elastin cross-links as phenylisothiocyanate derivatives

A method has been developed for the separation and quantitation of desmosines in tissue samples. The tissue is treated with cold 10% trichloroacetic acid to remove collagen and hydrolysed in HCl vapours in sealed vials. Preseparation of desmosines from tissue acid hydrolysates is performed on a cellulose column, first eluted with n-butanol-acetic acid-water to wash out other amino acids and then with water to recover desmosines. Separated desmosines are then derivatized with phenylisothiocyanate and determined by reversed-phase high-performance liquid chromatography using a gradient system with sodium acetate pH 6.4 and acetonitrile. Desmosines were detected spectrophotometrically at 254 nm. The method was applied to the determination of desmosine in elastin, rat aorta and bovine ligamentum nuchae.

Morphometric and biochemical changes in lungs of growing rats treated with a calmodulin antagonist

To determine the role of calmodulin in postnatal lung growth and development, 4-week-old rats were injected intraperitoneally on consecutive days with trifluoperazine (TFP), a potent and specific calmodulin antagonist, for a period fo 3 weeks and studied in comparison with normal controls and undernourished weight-matched animals. TFP treatment resulted in stunting of lung growth such that observed normal increments in morphometrically determined total number of alveoli and alveolar surface area and in biochemically determined DNA, elastin, and collagen contents of the lungs were diminished in comparison with age-matched normal controls. However, the TFP treatment also resulted in reduced daily food intake and body weight gain. In the TFP group, lung weight and lung volume were also reduced compared with the weight-matched control group. This resulted in reduced alveolar surface area, total number of alveoli, DNA, collagen, and elastin in the TFP group compared with values in the weight-matched controls. Thus the TFP-induced lung changes were not due to inanition and/or reduced somatic growth. The TFP treatment resulted in reduced activities of calmodulin and cyclic adenosine monophosphate (cAMP)-phosphodiesterase in the lungs of the animals, independent of their nutritional status. Based on these findings, we suggest that calmodulin may be an important regulatory component of postnatal lung growth and development.

Atherosclerosis mouse model induced by a high-cholesterol diet supplemented with beta-aminopropionitrile: effects of various anti-atherosclerotic agents on the biochemical parameters

A mouse model of atherosclerosis was produced by feeding a 1.5% cholesterol diet with 0.4% beta-aminopropionitrile (BAPN) fumarate, a chemical lathyrogen, for 10 weeks, and the pharmacological sensitivity and specificity of this model were evaluated biochemically with various hypolipidemic drugs and calcium antagonists. Histological findings on this model showed typical angiolathyrism with foam cells in the media of the thoracic aorta. Uniform and marked accumulation of cholesterol, notably esterified cholesterol, in the aorta was observed, although it was much less in mice receiving a high-cholesterol diet or BAPN alone. The reduction in elastin contents in the aorta was a characteristic feature of this model. Clofibrate, cetaben and elastase tended to prevent the increase of cholesterol contents in the aorta, together with their significant hypocholesterolemic effects. Nifedipine, diltiazem and verapamil showed a slight preventive effect on the cholesterol accumulation and on the reduction of elastin content in the aorta without a cholesterol lowering effect in the serum. MgCl2 was more effective than other calcium antagonists and even had a hypocholesterolemic effect. The results indicate that this mouse atherosclerosis model may be usable for primary drug evaluation.

Changes with age in the urinary excretion of lysyl- and hydroxylysylpyridinoline, two new markers of bone collagen turnover

Two intermolecular cross-linking amino acids, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), are promising markers in urine of collagen resorption because their levels in urine should reflect only collagen resorption and, unlike hydroxyproline, should not be influenced by degradation of either newly synthesized collagen molecules or noncollagenous proteins. Changes with age in the urinary excretion of HP and LP were studied in 24 h collections of urine from a group of 22 male and 27 female healthy subjects aged from 2 to 70 years. The pyridinolines were quantitated, utilizing their natural fluorescence, after resolution by reversed-phase HPLC. Levels of both pyridinolines were higher in children than in adults, but in adults no evidence of age or sex variations were observed except in the 20-30 year age group. Mean values of HP/Cr and LP/Cr in 37 adults (21-70 years) were 27.2 +/- 1.9 and 8.8 +/- 0.8 mumols/mol, respectively; in the 12 children (2-15 years) the mean values were 14.4 and 12.4 times higher than the respective adult values. Making certain assumptions, the mean amount of bone resorbed in normal adults was tentatively estimated at 1.9 g per 24 h. The finding that differences between children and adults in these relatively specific markers were greater than with hydroxyproline suggests that hydroxyproline values may considerably underestimate the actual amount of bone turnover occurring in growing children or overestimate the adult turnover rate.

Development and validation of a high-performance liquid chromatographic method for the determination of desmosines in tissues

The development and the validation of a general strategy for the simple and accurate analysis of desmosines (isodesmosine and desmosine) in tissues coupled with the determination of collagen (as hydroxyproline) is described. The method is based on simplified sample (i.e., lung) pretreatment which involves, in a PTFE screw-capped Pyrex tube, homogenization, collagen extraction with hot 5% trichloroacetic acid and hydrolysis of the elastin-containing residue with 6 M hydrochloric acid, followed by cellulose minicolumn purification of desmosines from the hydrolysates, dansyl chloride pre-column derivatization of the purified desmosines and reversed-phase high-performance liquid chromatographic (HPLC) analysis of the dansyl derivatives using a Spherisorb ODS-2 column, an on-column enrichment sample device and a linear gradient of organic modifier (acetonitrile) in phosphate buffer. The simple sample pretreatment, the optimized chromatographic conditions and the short HPLC analysis time (less than 15 min) allow the accurate and rapid determination of desmosine and isodesmosine, thus permitting the determination of elastin in several kinds of tissues with a minimum of sample manipulation.

Determination of desmosines in elastin-related skin disorders by isocratic high-performance liquid chromatography

Abnormalities in the amount of skin elastin occur in several cutaneous disorders. The number of elastic fibers is increased in elastotic disorders such as pseudoxanthoma elasticum (PXE) and cutis rhomboidalis nuchae (actinic elastosis, AE) and is decreased in elastolytic disorders such as cutis laxa (CL). We describe a procedure to quantify desmosines and elastin in small amounts of skin using high-performance liquid chromatography (HPLC). Biopsies were obtained from normal, nonsolar exposed skin and from the lesional skin of patients with PXE, cutis rhomboidalis nuchae, and CL. Specimens were subjected to hot alkali treatment and the desmosines were released by acid hydrolysis and quantified by HPLC. The mean value for normal skin was 252 +/- 28 ng desmosines per milligram wet weight (SD, n = 5). The disorders of elastosis (PXE and AE) demonstrated a two- to fivefold increased content of desmosines. In contrast, the elastolytic disorder (CL) had only 20% of the normal content of desmosines. Furthermore, PXE and normal skin elastins had the same amount of desmosines per milligram purified elastin. This method could be used to evaluate the extent of elastosis or elastolysis in a particular lesion.

Urinary excretion of pyridinium crosslinks: a new marker of bone resorption in metabolic bone disease

The pyridinium derivatives hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are intermolecular crosslinking compounds of collagen which are only present in its mature form. Contrasting to the wide distribution of type I and II collagens, HP and LP are absent from skin, ligament and fascia, and their major sources are bone and cartilage. Using a specific HPLC assay, we have determined the 24-h excretion of HP and LP crosslinks in normal adults of both sexes, in patients with primary hyperparathyroidism and in patients with Paget's disease of bone before and after intravenous treatment with amino-propylidene bisphosphonate (APB). Mean adult normal values were 33 +/- 13 pmol/mumol creatinine for HP and 6.3 +/- 3.4 pmol/mumol creatinine for LP. In women, menopause induced a 2-3-fold increase of HP and LP reflecting the well documented postmenopausal increase of bone turnover. In the urine of patients with primary hyperparathyroidism and of patients with active Paget's disease of bone, urinary crosslinks were significantly higher than in age-matched controls, with a mean 3- and 12-fold increase, respectively. Urinary excretion of hydroxyproline is a well recognized but poorly sensitive marker of bone turnover, reflecting resorption. In the same patients, the effect of menopause and disease state on hydroxyproline excretion was much less dramatic than on HP and LP. During intravenous APB treatment of pagetic patients, there was an early decrease of HP and LP, which was significant after 24 h and reached 62% at 4 days, contrasting with a late and milder decrease of urinary hydroxyproline. Because APB is a potent inhibitor of resorption which does not have a direct short-term effect on bone formation, these data also indicate that urinary excretion of HP and LP reflect only collagen degradation occurring during osteoclastic resorption and not the degradation of newly synthesized collagen. We conclude that urinary HP and LP excretion represents the first sensitive and specific marker of bone resorption. Its use should be valuable in the clinical investigation of metabolic bone diseases, especially osteoporosis.

Urinary excretion of connective tissue protein markers in arterial disease

In diseases of major arteries there is an increased turnover of connective tissue components. This implies a greater excretion of fragments of collagen and elastin. The changes for each of these may be useful in further delineating the nature of the disease. In a preliminary study, the urine of 10 Marfan's syndrome patients was analyzed. The hydroxyproline (collagen) concentration was up to eight times higher than that of control subjects. The desmosine (elastin) crosslink concentration was either normal or slightly reduced in these patients. The mean of the ratio of hydroxyproline to desmosine was nearly seven times higher in the patients.

Quantitative assessment of collagen crosslinks in dissected predentin and dentin

Dentinogenesis offers a unique system for the study of changes in collagen structure occurring simultaneously with mineralization. Bovine dentin was found to contain about one reducible crosslink per collagen molecule; rat dentin contained twice this amount. In contrast, bovine dentin contained twice as much pyridinium crosslink as did rat dentin collagen. These results indicate that the collagen in rat teeth is less mature and again emphasize the difference in composition between the organic matrices of rat and bovine dentin. In dissected bovine predentin, the unmineralized precursor of dentin, the content of reducible crosslinks was almost double that of dentin. Only minute amounts of non-reducible crosslinks were found in predentin, whereas both pyridinoline and deoxy-pyridinoline were present in collagen from mineralized dentin. The observed differences in crosslinking between predentin and dentin of the same teeth may indicate some alterations within the area of mineralization.

In vitro assay of extracellular matrix elastin degradation

This report describes a method for determining specifically and sensitively the degradation of the elastin component within complicated extracellular matrices in vitro. Extracellular matrices rich in elastin were metabolically labeled with [3H]lysine during 3 week cultures of smooth muscle cells under ascorbate-free conditions in vitro. Elastin was quantitated on the basis of labeled desmosine/isodesmosine in the matrices as determined by a cation-exchange HPLC program utilizing a Beckman 6300 amino acid analyzer. The net loss of desmosine/isodesmosine during co-culture of human macrophages with the matrices was then used to assay cellular elastin degradation. This method allows for the production of reproducibly labeled matrices and compares favorably with previously described techniques of elastin degradation by live cells in vitro.