Collagen Fraction Research Articles

Ouabain induces cardiac remodeling in rats independent of blood pressure

To investigate the ouabain's effects on cardiac remodeling in rats. Male Sprague-Dawley rats were treated with ouabain. Systolic blood pressure (SBP) was recorded weekly. After 4 and 6 weeks, echocardiography were performed, hemodynamic parameters were measured by invasive cardiac catheterization, changes in cardiac ultrastructure were analyzed using transmission electron microscopy, the collagen fraction of the left ventricle was assessed with Picrosirius red stain, and RT-PCR was applied to evaluate the mRNA level of myosin heavy chain-alpha and -beta in the left ventricle. Having been treated with ouabain for 4 weeks, there was no significant difference in the mean SBP of the two groups. However, left ventricular hypertrophy, myocardial ultrastructure deterioration, and extracellular matrix remodeling were induced by ouabain treatment; meanwhile, cardiac systolic and diastolic performance were both worsened. Moreover, the cardiac MHC-beta mRNA was upregulated by ouabain treatment, whereas MHC-alpha mRNA was downregulated. After 4 weeks, the mean SBP in the ouabain group began to increase and was significantly higher than that in control group after 6 weeks (P<0.01); the rats'cardiac structure and function were worsened. These results suggested that ouabain induces alterations in cardiac structure and function, and the effects happened before the increase of blood pressure. The results indicated that ouabain induced cardiac remodeling in rats independent of blood pressure.

Acute cerebral vascular injury after subarachnoid hemorrhage and its prevention by administration of a nitric oxide donor

Structural changes in brain parenchymal vessels occur within minutes after subarachnoid hemorrhage (SAH). These changes include platelet aggregation, activation of vascular collagenases, and destruction of perivascular collagen IV. Because collagen IV is an important component of the basal lamina, the authors attempted to further define changes in vascular structure (length and luminal diameter) and their relationship to vascular permeability immediately after SAH. In addition, the authors explored whether such alterations were attenuated by administration of a nitric oxide (NO) donor. Endovascular perforation was used to induce SAH in rats. Two sets of experiments were performed. The first established changes in vascular structure and permeability (collagen IV and endothelial barrier antigen [EBA] dual immunofluorescence) during the first 24 hours after SAH. In the second, the investigators examined the effects of an NO donor on vascular structure, permeability, and collagenase activity (in situ zymography). In this second study, animals received intravenous infusion of the NO donor S-nitrosoglutathione (GSNO, 1 microM/8 microl/min) 15 minutes after induction of SAH and were killed 3 hours after SAH onset. Controls were naive unoperated animals for the first study and saline-infused SAH animals for the second. The authors found a time-dependent decrease in area fraction, length, and luminal diameter of collagen IV- and EBA-immunofluorescent vessels after SAH. The greatest change occurred at 3 hours after onset of SAH. Administration of GSNO was associated with striking preservation of collagen IV and EBA immunofluorescence compared with saline treatment. Zymography indicated decreased collagenase activity in GSNO-treated SAH animals compared with saline-treated SAH animals. These results demonstrate changes in the structure and permeability of brain parenchymal microvessels after SAH and their reversal by treatment with an NO donor.

How Clean is Ultrafiltration Cleaning of Bone Collagen?

As part of our bone dating development, we have tested the ultrafiltration of bone gelatin using 2 different filters—Vivaspin 20™ (VS20), a polyethersulfone, and Vivaspin 15R™ (VS15R), a cellulose, both with a 30,000 molecular weight cutoff—and bone collagen from dated samples ranging in age from 1.5 to &gt;50 kyr BP. A direct accelerator mass spectrometry (AMS) measurement yielded radiocarbon concentrations of ∼0.5 pMC (∼42 kyr) for the polyethersulfone, ∼14.4–17.5 pMC (∼15.6–14 kyr) for the cellulose, and ∼107.4 pMC for the glycerin. The filters were cleaned before use similar to the Oxford protocol (Bronk Ramsey et al. 2004), and a series of freeze-dried archaeological bone gelatin samples and a modern pig-skin gelatin were passed through VS20 and VS15R filters (Vivascience™). We recovered both the eluent (&lt;30-kD fraction) and the liquid that stayed above the filter (&gt;30 kD) in order to obtain a carbon mass and isotope balance. While the &gt;30-kD collagen fraction that is usually selected for AMS analysis does not appear to be significantly contaminated, measurements show significant age differences between the eluent &lt;30 kD and the unfiltered bone collagen, indicating that, despite cleaning, both glycerin and filter still give off contaminants in the eluent. Ultrafiltration with young collagen from pig skin generally confirms these results for the &lt;30-kD fraction but also shows the possibility of small contaminations in the &gt;30-kD fraction. Until a contamination with filter carbon of the &gt;30-kD collagen fraction can be excluded, we would recommend caution in the use of ultrafiltration for cleaning bone collagen with VS20 or VS15R ultrafilters.

Biomechanical and histomorphometric esophageal remodeling in type 2 diabetic GK rats

Diabetes mellitus induces remodeling of the morphology and mechanical properties in the gastrointestinal tract. This study aimed to investigate the histomorphometric and biomechanical remodeling of esophagus in the diabetic type 2 model Goto-Kakizaki (GK) rats. Five male diabetic GK rats and five male nondiabetic Wistar rats were used in this study. The mechanical test was performed in vitro where the whole esophagus was stretched to its in situ length and distended with pressures up to 10 cm H 2O using a ramp distension protocol. The pressure and outer diameter were recorded. Circumferential stress (force per area) and strain (deformation) were computed from the diameter and pressure data using the zero-stress state as reference. The zero-stress state was obtained by cutting esophageal rings radially. This caused the rings to open up into a sector. The thickness, area, and the opening angle were measured from the digitized images. The layer circumference, thickness, and area were measured from histological slides. The collagen fraction was determined from histological slides with Van Gieson stain. Diabetes induced pronounced morphometric changes, e.g., the wall thickness and wall cross-sectional area significantly increased in the GK rats ( P<.01). Histologically, the circumference, thickness, and area of the muscle layer and the collagen fraction of mucosa–submucosa layer were significantly increased in the GK rats ( P<.01). The opening angle, outer residual strain, and residual strain difference to wall thickness ratio decreased significantly in the GK rats ( P<.05 and P<.01). Furthermore, the circumferential stiffness of the esophagus is significantly higher in the GK rats than in the normal rats ( P<.01). In conclusion, histomorphometric and biomechanical remodeling is a feature of the esophageal wall in GK rats.

A theoretical approach of the relationships between collagen content, collagen cross-links and meat tenderness

This work concerns the relationship between meat tenderness and the rubber-like properties, i.e. pressure and elastic modulus, that endomysium and perimysium connective tissues develop when meat has been heated to a temperature above which collagen contracts. For rest length meats with similar intramuscular connective tissue morphology, and which are at the same ageing state and pH, the elastic modulus of the collagenous fraction of connective tissues is approximately proportional to the total number of collagen cross-links present per volume of meat. Calculations from various published experiments concerned with the effect on tenderness of muscle type, animal age, type, and sex from different species show that this modulus follows most of the variations of meat toughness. Moreover, the proportionality between the increase in this elastic modulus and the increase in meat toughness approaches unity in situations where toughness mainly depends on connective tissues. This work demonstrates the decisive role of rubber-like properties of connective tissues in meat tenderness variations.

Radiocarbon chronology of the mammoth site at Niederweningen, Switzerland: Results from dating bones, teeth, wood, and peat

The peat section at Niederweningen is a site of spectacular excavations of numerous bones of mammoth and other animals that was first recognized in the late 19th century. In 1987/1990, new excavations provided more peat material, which was radiocarbon dated to 33,000 14C years BP and 42,000 14C years BP. The first AMS radiocarbon ages of mammoth bones from 1890/1891 excavations placed the age between 33,000 14C years BP and 35,000 14C years BP. In this study, new results were obtained on bones, teeth, wood and peat from the layer that buried the mammoths. The ages confirm that the mammoths as well as the peat section, in which they were found, are older than 40,000 14C years BP. In order to explain the discrepancy between the previous chronology and the new results, two preparation techniques were applied for the dating of bones. An organic fraction called “collagen” used to obtain the first radiocarbon ages was dated as well as gelatine prepared using the modified Longin method. The differences of up to 7000 years between ages obtained on collagen and gelatine fractions show contamination of the collagen fraction with modern carbon. The oldest age of 45,870±1080 14C years BP was obtained on base cleaned gelatine from mammoth bone. This age is close to an age of 45,430±1020 14C years BP obtained for the peat layer that buried the mammoths.

Effect of traditional Chinese medicine Qin-Dan-Jiang-Ya-Tang on remodeled vascular phenotype and osteopontin in spontaneous hypertensive rats

Qin-Dan-Jiang-Ya-Tang (QDJYT) is a traditional Chinese herbal medicine for the treatment of hypertension. The effect of QDJYT on blood pressure and on vascular remodeling in hypertension was investigated in the model of spontaneous hypertensive rats (SHR). Sixteen SHRs were divided into two groups, the SHR group and the SHR + QDJYT group. Eight WKY rats were a normal control group. QDJYT (750 mg/kg) was orally administered daily for 12 weeks in SHR + QDJYT group. After 12 weeks, thoracic aortas were segregated. Media thickness (MT), lumen diameter (LD), the ratio of MT to LD, the volume fraction of collagen (VFC) in media, the ultrastructure of vascular smooth muscle cells (VSMCs) and the expression of osteopontin (OPN) mRNA were examined by histological staining, transmission electron microscope (TEM), and real-time PCR, respectively. It was observed in our study that MT, MT/LD, VFC and the expression of OPN mRNA were higher in the SHRs than in the WKY rats, volume and numeral density of mitochondria in vascular smooth muscle cells (VSMCs) in media increased obviously. However, in the SHRs treated with QDJYT, we found MT, MT/LD, VFC and the expression of OPN gene were lower than in the SHRs, and the phenotype of VSMCs were close to normal. These results suggest that QDJYT could reverse the vascular remodeling in SHR, and the mechanisms may be related to the suppressive effect of QDJYT on the expression of OPN mRNA in arterial wall.

Remodeling of renal interstitial and tubular lesions in pancreas transplant recipients

Tubular atrophy and interstitial fibrosis, important in progression of renal diseases, including diabetic (D) and cyclosporine-induced (CSA) nephropathy, have been considered irreversible. Normoglycemia for 10 years following pancreas transplantation alone (PTA) reversed D glomerulopathy lesions. This study quantified tubular, interstitial, and arteriolar parameters in PTA recipients. Kidney function studies and biopsies were performed in eight non-uremic type I D patients (pts) at 5 and 10 years after PTA. Renal biopsies were analyzed by morphometric analysis. All pts were normoglycemic and insulin independent and received CSA during the study. Cortical interstitial volume fraction was increased at 5 years (0.31+/-0.07 vs normal 0.15+/-0.02, P<0.01) and decreased at 10 years post-PTA (0.23+/-0.03, P<0.02 vs 5 years). There was a reduction in the volume fraction of interstitial collagen and cells per cortical tissue, measured using electron microscopy, from 5 (0.126+/-0.061 and 0.103+/-0.026, respectively) to 10 years (0.079+/-0.031, P<0.05, and 0.074+/-0.018, P<0.05, respectively). The volume fraction of tubules which were atrophic (AT) was abnormal at 5 years (0.160+/-0.090) and decreased from 5 to 10 years (0.044+/-0.034, P<0.02), apparently due to AT reabsorption. The index of arteriolar hyalinosis did not change during the study (1.30+/-0.22 and 1.34+/-0.33 at 5 and 10 years, respectively, nonsignificant). This study demonstrates, for the first time in humans, that interstitial expansion is reversible and that atrophic tubules can be reabsorbed. In contrast, there was no improvement in the arteriolar lesions. Whether this is due to long-term normoglycemia, reduction of CSA dose or other mechanisms is unclear.

Muscle and flesh quality traits in wild and farmed Atlantic salmon

Muscle characteristics that are important for flesh quality traits were assessed in populations of wild and farmed Atlantic salmon ( Salmo salar L.). The wild fish were obtained from a commercial fishery on the North Esk, Scotland in 2001 and 2003. The farmed fish comprised 7 families from the Stofnfiskur breeding programme (Stofnfiskur A/S, Iceland) grown in 5 m × 5 m × 5 m net pen sea cages in a dedicated trial unit on South Uist, Scotland. Total carotenoid pigment (mg kg − 1 wet mass flesh) concentrations were higher in farmed (7.68 and 8.43 for grilse and salmon, respectively) than wild fish (5.53 and 6.44 for grilse and salmon, respectively). In contrast, the average flesh colour, measured with a SalmonFan™, was similar for all groups (27.4 to 28.0), indicating a superior colour visualisation per unit pigment concentration in wild fish. The flesh lipid content was 46%-higher (grilse) and 84%-higher (salmon) in farmed than wild fish. Vitamin E concentrations per unit wet mass lipid were similar in wild and farmed salmon and in the range (208–259 mg kg − 1 ). Fillet firmness was measured using a shear test and instrumental texture analyser. The work done (WD) to shear standardised post-rigor muscle samples was higher in grilse than salmon and was significantly greater for the wild (710 and 811 mJ, respectively) than farmed (415 and 602 mJ, respectively) fish, indicating a firmer texture in the wild fish. The grilse and salmon sampled had stopped recruiting fast muscle fibres and both wild and farmed fish had around 650,000 fibres per trunk cross-section. Thus differences in fillet texture and colour between these populations could not be explained by the muscle cellularity which was similar between groups. Hydroxyproline (HYP) was used to estimate collagen concentration. Alkaline-insoluble HYP was 72.5% higher in wild than farmed salmon (14.0 vs. 8.1 μmol g − 1 dry mass, respectively) whereas alkaline-soluble HYP was 5.2-fold higher in farmed than wild salmon (31.0 vs. 6.0 μmol g − 1 dry mass, respectively). The alkaline-insoluble collagen fraction is thought to be enriched with reducible and non-reducible cross-linked collagen. There was a significant positive correlation between pyridinoline (PYD) crosslink concentration and WD, explaining 25% of the within population variation in firmness. However, PYD concentration (pmol g − 1 dry mass) was similar between wild (476) and farmed (445) salmon and cannot explain the differences in flesh firmness observed between populations. It was hypothesised that the higher average values of firmness in the wild than farmed salmon flesh can in part be attributed to higher concentrations of reducible immature collagen crosslinks.

Dose‐dependent separation of the hypertrophic and myotoxic effects of the β2‐adrenergic receptor agonist clenbuterol in rat striated muscles

Muscle growth in response to large doses (milligrams per kilogram) of beta(2)-adrenergic receptor agonists has been reported consistently. However, such doses may also induce myocyte death in the heart and skeletal muscles and hence may not be safe doses for humans. We report the hypertrophic and myotoxic effects of different doses of clenbuterol. Rats were infused with clenbuterol (range, 1 microg to 1 mg.kg(-1)) for 14 days. Muscle protein content, myofiber cross-sectional area, and myocyte death were then investigated. Infusions of >or=10 microg.kg(-1).d(-1) of clenbuterol significantly (P<0.05) increased the protein content of the heart (12%-15%), soleus (12%), plantaris (18%-29%), and tibialis anterior (11%-22%) muscles, with concomitant myofiber hypertrophy. Larger doses (100 microg or 1 mg) induced significant (P<0.05) myocyte death in the soleus (peak 0.2+/-0.1% apoptosis), diaphragm (peak 0.15+/-0.1% apoptosis), and plantaris (peak 0.3+/-0.05% necrosis), and significantly increased the area fraction of collagen in the myocardium. These data show that the low dose of 10 microg.kg(-1).d(-1) can be used in rats to investigate the anabolic effects of clenbuterol in the absence of myocyte death.

Retinoic Acid Supplementation Attenuates Ventricular Remodeling after Myocardial Infarction in Rats1–3

The objective of this study was to evaluate the role of retinoic acid in experimental postinfarction myocardial remodeling. Wistar rats were subjected to myocardial infarction (MI) and treated with retinoic acid (RA), 0.3 mg/(kg x d) (MI-RA, n = 29), or fed a control diet (MI, n = 34). After 6 mo, the surviving rats (MI-RA = 18 and MI = 22) underwent echocardiograms, and isolated hearts were tested for function in vitro. The cross-sectional area of the myocyte (CSA) and interstitial collagen fraction (IC) were measured in a cross section of the heart stained by hematoxylin-eosin and picrosirius red, respectively. The CSA was smaller in the MI-RA group [229 (220,234) microm2] [medians (lower quartile, upper quartile)] than in the MI group [238 (232,241) microm2] (P = 0.01) and IC was smaller in the MI-RA group [2.4 (1.7, 3.1)%] than in the MI group [3.5 (2.6, 3.9)%] (P = 0.05). The infarct size did not differ between the groups [MI = 44.6 (40.8, 48.4)%, MI-RA = 45 (38.6, 47.2)%]. Maximum rate of rise of left ventricular pressure (+dp/dt) was greater in the MI-RA group (2645 +/- 886 mm Hg/s) than in the MI group (2081 +/- 617 mm Hg/s) (P = 0.05). The other variables tested did not differ between groups. Retinoic acid supplementation of rats for 6 mo attenuates the ventricular remodeling process after MI.

Estrogen enhances vasoconstrictive remodeling after injury in male rabbits

The complete spectrum of estrogen vascular effects remains unclear. In particular, estrogen effects in the vascular response to profound injury in males have not been explored in detail. Therefore, we submitted 44 male New Zealand rabbits weighing 3.4 +/- 0.6 kg to overdistention balloon injury of the right iliac artery. Rabbits were given 17beta-estradiol (5.45 micromol/day, sc) or vehicle for 7 days before and 14 days after injury, when the arteries were examined by post-mortem histomorphometry. Arteriographic caliber was assessed in vivo at baseline and before sacrifice. On day 14 after injury, in vivo arteriographic caliber (baseline = 2.44 +/- 0.43 mm) was decreased by 23.1 +/- 0.1% in controls and by 44.5 +/- 0.1% in estrogen-treated rabbits (P < 0.001). Neither the neointimal area nor the neointima/media area ratio changed after estrogen treatment. Collagen fraction was increased in the media and neointima of estrogen-treated rabbits vs control (1.38 +/- 1.30 vs 0.35 +/- 0.67, respectively, P = 0.01). Taken together, these findings suggest that estrogen increased negative vascular remodeling. Transcription of endothelial and inducible nitric oxide synthases (eNOS and iNOS) was analyzed by RT-PCR. eNOS mRNA expression was marginally increased after estrogen (P = 0.07) and injury. iNOS mRNA was increased 2- to 3-fold on day 14 after injury. With estrogen treatment, iNOS mRNA increased in uninjured arteries and exhibited a further 5.5-fold increase after injury. We concluded that estrogen increased lumen loss after balloon injury in male rabbits, likely by increased negative remodeling, which may be related to increased iNOS transcriptional rates.

Carbon and nitrogen isotopic fractionation in bone collagen during chemical treatment

In measuring radiocarbon ages of fossil bone samples, it is necessary to extract pure bone protein from the samples by chemical treatment. To evaluate the effect of the chemical treatment including XAD-2 chromatography on carbon and nitrogen isotopic values, we measured C / N ratio, δ 13C and δ 15N in decalcified fraction, gelatin, hydrolysate, and XAD-treated hydrolysate extracted from fossil bones together with modern samples. The C / N ratios of the collagen fractions progressively decreased as chemical treatment proceeded. The δ 13C values of the fractions became more positive as purification proceeded. There was an overall + 0.5∼+ 2.0‰ difference in δ 13C and a slight trend of decrease in δ 15N during chemical processing and around + 0.3‰ difference in δ 13C and + 0.2‰ in δ 15N during XAD-2 treatment only. The large change in C / N ratio and δ 13C of the hydrolysates following XAD-2 chromatography in the Bovine Achilles tendon collagen standard could be explained by the removal of lipids unextracted before the XAD-2 treatment. There was no difference in δ 13C between hydrolysates and XAD-treated hydrolysates in fossil bones because the latter contains negligible preserved lipids. Fossil bones and lipid-extracted collagen standard showed the similar C / N change and isotopic fractionation during sequential chemical treatment. Individual amino acid standards showed little to no increase in δ 13C and δ 15N values during XAD-2 treatment, except for aspartic acid and glutamic acid, which showed pronounced increase in δ 15N values. Furthermore, regarding amino acid compositions separated by XAD-2 treatment, alanine and glycine tend to be enriched, while valine, threonine, isoleucine, leucine, and serine compositions tend to be depleted. The carbon and nitrogen isotopic fractionation during sequential chemical treatment might reflect variation in the amino acid composition of the extracted fractions due to degradation, such as decarboxylation, rather than removal of contaminants. The variation during XAD-2 treatment is due to both degradation by HCl and isotopic fractionation related to the XAD-2 resin.

The Effect of Digestion of Collagen and Elastin on Histomorphometry and the Zero-Stress State in Rat Esophagus

To understand the physiology and pathology of the esophagus, it is necessary to know the mechanical properties and their dependence on the structural components. The aim of this study was to investigate the effect of collagenase and elastase on the morphological and biomechanical properties in the no-load and zero-stress states in the rat esophagus. Twenty tissue rings from each esophagus of seven normal rats were sectioned in an organ bath containing calcium-free Krebs solution with dextran and EGTA. After the rings were photographed in the no-load state, 8 of the 20 rings were separated into mucosa-submucosa and muscle rings and the rings were transferred to four different solutions containing collagenase, elastase, or corresponding control solutions. The rings were cut radially to obtain the zero-stress state and photographed again. The thickness, area, and opening angle were measured from the digitized images. The collagen and elastin area fractions were determined from histological slides with Van Gieson and Weigert's elastic stain. The opening angles and residual strain did not differ in the nonseparated enzyme-treated rings and control rings. However, in the separated mucosa-submucosa ring the opening angle was significantly smaller after treatment than that in control rings (P < 0.01). Collagenase and elastase reduced collagen and elastin in the mucosa-submucosa layer about 40% in the nonseparated wall and 54% in the separated mucosa-submucosa layer (P < 0.01). Collagenase and elastase increased the thickness in the separated mucosa-submucosa layer compared to the control (P < 0.05). Disconnection between the epithelia and the lamina propria was histologically observed after elastase digestion. In conclusion, collagenase and elastase caused the opening angle and the residual strain in the separated mucosa-submucosa layer to decrease. The opening angle of the separated mucosa-submucosa layer depended to some extent on the fraction of collagen and elastin.

Androgen Receptor Gene Knockout Male Mice Exhibit Impaired Cardiac Growth and Exacerbation of Angiotensin II-induced Cardiac Fibrosis

Androgen has anabolic effects on cardiac myocytes and has been shown to enhance left ventricular enlargement and function. However, the physiological and patho-physiological roles of androgen in cardiac growth and cardiac stress-induced remodeling remains unclear. We aimed to clarify whether the androgen-nuclear androgen receptor (AR) system contributes to the cardiac growth and angiotensin II (Ang II)-stimulated cardiac remodeling by using systemic AR-null male mice. AR knock-out (ARKO) male mice, at 25 weeks of age, and age-matched wild-type (WT) male mice were treated with or without Ang II stimulation (2.0 mg/kg/day) for 2 weeks. ARKO mice with or without Ang II stimulation showed a significant reduction in the heart-to-body weight ratio compared with those of WT mice. In addition, echocardiographic analysis demonstrated impairments of both the concentric hypertrophic response and left ventricular function in Ang II-stimulated ARKO mice. Western blot analysis of the myocardium revealed that activation of extracellular signal-regulated kinases (ERK) 1/2 and ERK5 by Ang II stimulation were lower in ARKO mice than those of WT mice. Ang II stimulation caused more prominent cardiac fibrosis in ARKO mice than in WT mice with enhanced expression of types I and III collagen and transforming growth factor-beta1 genes and with increased Smad2 activation. These results suggest that, in male mice, the androgen-AR system participates in normal cardiac growth and modulates cardiac adaptive hypertrophy and fibrosis during the process of cardiac remodeling under hypertrophic stress.

Solubilization of type I and V collagens in Japanese flounder muscle during chilled storage

The post-mortem changes of type I and V collagens in Japanese flounder muscle during chilled storage were examined. The muscle softened significantly within 12 h under chilled storage. Both type I and V collagens isolated by ion-exchange chromatographies showed no remarkable changes in band patterns even after 24 h of storage, suggesting that degraded collagen molecules may be removed from the collagen fraction by a conventional preparation method. In contrast, type I and V collagen molecules were detected by Western blotting with each specific antibody in a saline extract and gradually increased during chilled storage. These results suggest that both type I and V collagens may participate in the post-mortem softening of fish muscle.

Effects of Age and Diet on Rat Skin Histology

To document age-related histologic morphometric changes of rat skin and the effects of calorie restriction on such changes. Fischer 344 rats of three age groups (young, 4 mo; adult, 1 year; old, 24+ months) were procured from ad libitum (AL) diet and calorie-restricted (CR) colonies of the National Institute of Aging and were used for histologic study. Each study group consisted of six animals. Skin samples from the dorsum (DS) and footpad (FP) of these animals were excised and processed for histology with staining techniques for general morphology (hematoxylin-eosin-phloxine) and for differentiation of collagen bundles and elastic fibers (Verhoeff-van Gieson technique). Light microscopic morphometric and stereologic point counting procedures were applied manually to tissue sections to obtain quantitative data on the depth of the epidermis, dermis, and stratum corneum, epidermal nuclear number, and percentage fraction of collagen, elastic fibers, capillaries, and pilosebaceous units. Data were analyzed with two-way of analysis of variance (ANOVA) to determine significant effects of age, diet, and age-diet interaction on these parameters in AL rats and their age-matched cohorts. Significant effects of age, diet, or age-diet interaction were observed in respect of the thickness of epidermis, dermis, stratum corneum of FP, epidermal nuclear number, collagen percentage fraction, and area fraction of capillaries. DS epidermis showed increasing thickness in AL group, but this was reduced in CR rats. A similar trend in DS dermal depth was observed. Fewer capillaries were present in aging CR rats. The DS epidermal nuclear profiles and collagen area fraction also showed effects of diet and age-diet interaction. Aging changes, especially the effect of CR, was more evident in the measured parameters of dorsal skin. No alterations were observed in the distribution of pilosebaceous units and elastic fiber profiles of the skin. The Fischer 344 rat shows many age-related changes in the skin, some of which are different from data reported in literature. The pattern of aging changes in skin parameters was different in the two groups, suggesting an in influence of CR. CR appears to modify the aging rate of some skin components, and this may be caused by metabolic changes imposed by diet.

Inhibition of p38 mitogen-activated protein kinase protects the heart against cardiac remodeling in mice with heart failure resulting from myocardial infarction

Background Mitogen-activated protein kinases (MAPKs) have emerged as an important pathophysiologic regulator during the development of heart failure (HF). p38 MAPK activity is elevated in cardiac hypertrophy and HF. We used a mouse model of myocardial infarction (MI) to test the hypotheses that (1) inhibition of p38 MAPK activity may improve cardiac function and remodeling after myocardial infarction (MI) and (2) coadministration of a p38 inhibitor (p38i) and an angiotensin-converting enzyme inhibitor (ACEI) may provide only limited further cardioprotection in this model. Methods and results MI was induced in C57BL/6J mice by ligating the left anterior descending coronary artery and then either left untreated or treated with a p38i (SC-409, 30 mg/kg/day in chow), ACEI (enalapril, 20 mg/kg in drinking water), or p38i plus ACEI for 12 weeks. Echocardiography was performed and systolic blood pressure measured before MI and weekly thereafter. At the end of the study, interstitial collagen fraction (ICF) and myocyte cross-sectional area (MCSA) were examined histologically. We found that p38i significantly increased left ventricular ejection fraction and cardiac output and decreased left ventricular area at diastole, ICF, and MCSA. ACEi and p38i each had similar beneficial effects in this mouse model of HF produced by a large MI. Coadministration of p38i and ACEi did not provide any additional benefit. Conclusion Our data suggest that inhibition of p38 MAPK provides significant cardioprotection in mice with HF post-MI.

Modulation of Cutaneous Aging With Calorie Restriction in Fischer 344 Rats

To examine whether histological changes in skin owing to intrinsic aging in a laboratory rodent model are modulated by caloric restriction (CR). The abdominal skin from colony-raised ad libitum-fed Fischer 344 rats and age-matched rats subjected to CR was studied in the light microscope using histological morphometric methods. Animals 4, 12, and 24 months or older were used in this study. We studied the skin to obtain (1) quantitative data on the depth of the epidermis, dermis, and fat layer, the epidermal cellular density, the percentage fraction of dermal collagen, elastic fibers, pilosebaceous units, and capillaries, and the fibroblast density; and (2) qualitative assessment of histological staining for dermal glycosaminoglycans. We analyzed data by means of general linear model 2-way analysis of variance to obtain significance for the effects of age, diet, and age-diet interaction. The ad libitum-fed rats showed age-related increase in the depth of the epidermis, dermis, and fat layer. Calorie restriction prevented these changes, but epidermal nuclear density appeared to be stimulated. A trend toward increased values for collagen and elastic fibers, fibroblasts, and capillaries in skin samples from CR rats was observed. Pilosebaceous units were not modified. Moderately reduced staining for the dermal glycosaminoglycans in the skin of CR rats was noticed. Histomorphological changes resulting from intrinsic aging affected some of the studied variables in the rat skin, and these changes were delayed or prevented by CR. Some stimulatory effects, such as increased densities of fibroblasts and capillary profiles and higher values of connective tissue fibers resulting from CR, were also observed. Cutaneous morphological changes due to natural aging in this rat model seem to be modified by physiological or metabolic alterations imposed by CR.

Remodelação miocárdica após infarto agudo do miocárdio experimental em ratos: efeito do bloqueio do sistema renina angiotensina aldosterona

OBJETIVO: Verificar a ação do lisinopril e do losartan sobre a remodelação miocárdica no infarto experimental em ratos. MÉTODOS: Ratos machos Wistar foram submetidos a infarto e tratados com lisinopril 20 mg/kg/dia (LIS, n=13) ou losartan 20 mg/kg/dia (LOS, n=11), ou mantidos sem tratamento (NT, n=11), por três meses e os resultados comparados com grupo controle (CONT, n=11) de ratos sem infarto. Após a eutanásia, o ventrículo esquerdo foi separado e pesado. Foram medidas a área seccional dos miócitos (AC), fração de colágeno intersticial (CVF) e a hidroxiprolina (HOP) miocárdica. As variáveis foram comparadas pela ANOVA de uma via, para nível de significância de p<0,05. RESULTADOS: O infarto agudo promoveu a hipertrofia do ventrículo esquerdo e os tratamentos com lisinopril e losartam preveniram a hipertrofia quantificada pelo peso do ventrículo esquerdo (LOS=1,06± 0,12g, LIS=0,97±0,18g, NT=1,26±0,17g, CONT=1,02± 0,09g; p<0,05), pelo peso de ventrículo esquerdo corrigido pelo peso corporal VE/PC (LOS=2,37±0,21mg/g, LIS=2,41± 0,38mg/g,NT=2,82±0,37mg/g, CONT=2,27± 0,15mg/g) e pela medida da AC do ventrículo esquerdo (LOS=210±39µ², LIS=217±35µ², NT=256±35µ², CONT= 158±06 µ²; p<0,05). O CVF foi significantemente maior no ventrículo esquerdo do grupo infartado e houve prevenção do aumento com os tratamentos (LOS=1,16±0,4%, LIS=1,27± 0,5%, NT=1,8± 0,4%, CONT=0,7±0,5%). A HOP foi maior no grupo infartado (NT=6,91±2,98mg/g vs. CONT=2,81±1,21mg/g) e não alterou com o tratamento. CONCLUSÃO: A remodelação miocárdica pós-infarto é caracterizada por aumento da massa ventricular remanescente e aumento de colágeno intersticial. O bloqueador da enzima conversora da angiotensina e o antagonista seletivo AT1 da angiotensina II previnem a hipertrofia do miócito e a fibrose intersticial.