Evidence that Meishan and Large-White hybrid preovulatory follicles may differentially affect oocyte in vitro maturation and fertilization

Two experiments were carried out to test the hypothesis that follicles recovered from Meishan animals may provide a more favourable environment for oocyte maturation in vitro than follicles recovered from Large-White hybrid animals. In Experiment 1, all follicles ≥4 mm were recovered from six Meishan and seven Large-White hybrid gilts in the late follicular phase and healthy oocyte cumulus complexes recovered. Cumulus oocyte complexes were randomly divided into two groups, and each group cultured for 27 or 34 h (62 and 64; 56 and 56 for Meishan and Large-White hybrid, respectively) in defined medium in the presence of either of the two largest follicle shells per animal. Subsequent examination of oocyte nuclear maturation showed that although maturation did not differ significantly between the breeds after 27 h, more (P<0.01) Meishan oocytes co-cultured with Meishan follicles developed to metaphase II stage than Large-White hybrid oocytes co-cultured with Large-White hybrid follicles after 34 h. The next eight largest follicles per animal were cultured for 34 h to produce conditioned media. In Experiment 2, oocytes recovered from the slaughterhouse were matured for 46 h in the presence of conditioned media from Meishan (612 oocytes) or Large-White hybrid (731 oocytes) follicles, or in fresh medium in the presence of a follicle shell from slaughterhouse ovaries. Oocytes were then inseminated and 12 h later examined for penetration and male pronuclear formation. A higher (P<0.05) percentage of oocytes cultured in Meishan follicle conditioned medium underwent sperm penetration and male pronuclear formation than oocytes cultured in conditioned media from Large-White hybrid animals. Concentrations of oestradiol and progesterone in the conditioned media did not differ between the breeds (P>0.1). In conclusion, these results suggest that (1) Meishan oocytes have advanced maturational capacity when cultured with Meishan preovulatory follicle shells and (2) differences in follicle maturation in the Meishan compared to the Large-White hybrid pig may result in an improved ability of the follicles, via conditioned media, to support oocyte maturation and fertilization in vitro.     

Age at puberty, ovulation rate, uterine length, prenatal survival and litter size in Chinese Meishan and Yorkshire females

Studies on the ovulation rate, prenatal survival and litter size of Chinese Meishan pigs have given widely divergent results depending on the extent of inbreeding of the animals, their original genetic diversity, the age and parity, and the conditions of management. To obtain meaningful results, it is necessary to characterize the population under study. The following report characterizes populations of Meishan and Yorkshire of a widely diverse background. First farrowing data were collected on 21 Meishan and 20 Yorkshire gilts. Meishan gilts had 12.4 fully formed piglets and Yorkshire gilts had 7.4 fully formed piglets (P < 0.01). Meishan gilts averaged 1.86 mummified fetuses per litter vs 0.05 per Yorkshire litter (P < 0.01). Yorkshire piglets averaged 1.3 kg body weight at birth vs 0.9 kg for Meishan piglets (P < 0.01). At 47 days of second gestation, 19 Meishan and 12 Yorkshire sows averaged 22.7 and 16.3 corpora lutea (CL), respectively (P < 0.01). Uterine length and number of fetuses were not different (P > 0.40) in the two breeds. Daily estrous detection of 50 Meishan and 34 Yorkshire gilts began at 60 and 120 days of age, respectively. Meishan gilts reached sexual maturity at 95 days of age, which was 105 days earlier than Yorkshire gilts (P < 0.01). Meishan gilts were in estrus nearly 1 day longer than Yorkshire gilts at first, second and third estrus (P < 0.05). No differences in cycle length between breeds were detected for the first or second estrous cycle (P > 0.60). Nineteen Meishan gilts were slaughtered at 51 days of gestation and their reproductive tracts were recovered. The mean number of dissected CL (17.0), number of fetuses (13.1), total uterine length (396 cm), spacing per fetus (29.9 cm), allantoic (124.9 ml) and amniotic (32.2 ml) volumes, crown-rump length (82.8 mm), weight (35.4 g), sex, and direction of each fetus were determined. Chinese Meishan gilts reached puberty much earlier and were in estrus longer than Yorkshire gilts and Meishan sows had more CL than Yorkshire sows.     

Dependence of changes in beta-adrenoceptor signal transduction on type and stage of cardiac hypertrophy.

To examine whether cardiac hypertrophy is associated with changes in beta-adrenoceptor signal transduction mechanisms, pressure overload (PO) was induced by occlusion of the abdominal aorta and volume overload (VO) by creation of an aortocaval shunt for 4 and 24 wk in rats. After hemodynamic assessment of the animals, the left ventricular (LV) particulate fraction was isolated for measurement of beta(1)-adrenoceptors and adenylyl cyclase activity, and cardiomyocytes were isolated for monitoring of the intracellular Ca(2+) concentration. Although PO and VO produced cardiac hypertrophy and increased LV end-diastolic pressure at 4 wk, cardiac function was increased in animals subjected to PO but remained unaltered in animals subjected to VO. Cardiac hypertrophy and increased LV end-diastolic pressure were associated with depressed cardiac function at 24 wk of PO or VO, but clinical signs of congestive heart failure were evident only in animals subjected to VO. Isoproterenol-induced increases in cardiac function, activation of adenylyl cyclase activity, and increase in intracellular Ca(2+) concentration, as well as beta(1)-adrenoceptor density, were unaltered by PO at 4 wk, augmented by VO at 4 wk, and attenuated by PO and VO at 24 wk. These results suggest that alterations in beta(1)-adrenoceptor signal transduction are dependent on the type and stage of cardiac hypertrophy.     

Phosphorylation of phospholamban at threonine-17 reduces cardiac adrenergic contractile responsiveness in chronic pressure overload-induced hypertrophy

Physiological hemodynamic stress, such as aerobic exercise, is intermittent and requires an increase in Ca2+ -dependent contractility through sympathetic nervous system activation. Pathological hemodynamic stress, such as hypertension, is persistent and requires sustained increases in cardiac function. Over time, this causes left ventricular hypertrophy (LVH)-reduced responsiveness to sympathetic stimulation. In this study, we examined the hypothesis that blunted in vivo adrenergic contractile responsiveness in pressure overload (PO)-induced cardiac hypertrophy is caused by abnormalities in the abundance and/or basal phosphorylation state of Ca2+ regulatory proteins. PO, induced by aortic constriction, caused concentric LVH or dilated LVH. Only animals with dilation exhibited a decrease in baseline left ventricle function [fractional area change (FAC); measured with echocardiography]. All PO animals had a reduced contractile response to adrenergic agonists (increase in FAC with 40 microg.kg(-1).min(-1) dobutamine, control 0.30 +/- 0.04, n = 5 vs. banded 0.10 +/- 0.03, n = 10; P < 0.01). PO animals had reduced phospholamban (PLB) protein abundance (P = 0.07, not significant) and increased PLB phosphorylation at the calmodulin-dependent kinase II (CaMKII)-specific site (PLB-Thr17, P < 0.05) but not at the protein kinase A-specific site (PLB-Ser16). PLB-Thr17 phosphorylation was inversely correlated with dobutamine-induced increases in contractility in PO animals (r2 = 0.81, P < 0.05). Continuous induction of Ca2+ transients in isolated ventricular myocytes for 24 h increased phosphorylation at PLB-Thr17 and diminished inotropic responsiveness and PLB-Ser16 phosphorylation after exposure to isoproterenol (P < 0.05). These data show that reduced adrenergic responsiveness in feline PO hypertrophy and failure involves increases in basal PLB-Thr17 phosphorylation, suggesting that activation of CaMKII in PO hypertrophy contributes to defective adrenergic reserve in compensated LVH and early heart failure.     

The Retina of Crayfish Procambarus clarkii During Development Shows Serotonin and Tryptophan Hydroxylase-like Immunoreactivity Daily Changes

The aim of this work was to investigate possible changes in serotonin (5-HT) and tryptophan hydroxylase (TPH)-like immunoreactivity related to time of day in Procambarus clarkii retina during the first developmental stages. Forty-five animals from postembryonic instars (PO1, PO2) to juvenile stage were kept under LD 12:12 cycles. All animals were anesthetized and decapitated at three times of day, 08:00, 15:00 and 20:00 h. Isolated eyestalks were processed by immunohistochemical methods. The 5-HT-like immunoreactive area of retina was measured using computer-based image analysis. Results indicated 5-HT-like immunoreactive differences among the three crayfish instars studied. In PO1 animals, ANOVA revealed no significant differences in 5-HT-like immunoreactivity in the retina at different times of day. PO2 instars as well as juvenile instars, showed statistically significant retinal 5-HT-like immunoreactivity changes related to time of day. Preliminary results indicated that TPH-like immunoreactivity was located only in the tapetal and retinal cells, and it was related to time of day. These changes suggest a diurnal cyclic regulation in the synthesis of 5-HT in the retina.     

The Retina of Crayfish Procambarus clarkii During Development Shows Serotonin and Tryptophan Hydroxylase-like Immunoreactivity Daily Changes

The aim of this work was to investigate possible changes in serotonin (5-HT) and tryptophan hydroxylase (TPH)-like immunoreactivity related to time of day in Procambarus clarkii retina during the first developmental stages. Forty-five animals from postembryonic instars (PO1, PO2) to juvenile stage were kept under LD 12:12 cycles. All animals were anesthetized and decapitated at three times of day, 08:00, 15:00 and 20:00 h. Isolated eyestalks were processed by immunohistochemical methods. The 5-HT-like immunoreactive area of retina was measured using computer-based image analysis. Results indicated 5-HT-like immunoreactive differences among the three crayfish instars studied. In PO1 animals, ANOVA revealed no significant differences in 5-HT-like immunoreactivity in the retina at different times of day. PO2 instars as well as juvenile instars, showed statistically significant retinal 5-HT-like immunoreactivity changes related to time of day. Preliminary results indicated that TPH-like immunoreactivity was located only in the tapetal and retinal cells, and it was related to time of day. These changes suggest a diurnal cyclic regulation in the synthesis of 5-HT in the retina.     

Evaluation of quantitative trait loci affecting intramuscular fat and reproductive traits in pigs using marker‐assisted introgression

We investigated the effects of previously identified quantitative trait loci (QTL) in an experimental backcross (BC) between Chinese Meishan pigs and commercial Duroc pigs. We performed marker‐assisted introgression of two QTL for intramuscular fat (IMF) content (IMF population) and three QTL for reproductive traits (reproduction population) from a donor Meishan pig into a recipient Duroc pig. At the fourth BC generation of the IMF population and third BC generation of the reproduction population, carrier animals were selected for the production of animals homozygous for the QTL. Our previous studies have shown that the presence of a Meishan allele on the IMF QTL is associated with low IMF values, and the Meishan allele on the reproductive QTL is associated with large litters. In this study, the presence of a Duroc allele at the IMF QTL on SSC9 resulted in a 0.27% increase in IMF (additive effect = 0.27 ± 0.08), whereas the presence of a Meishan allele at the IMF QTL on SSC7 resulted in a 0.34% increase in IMF (additive effect = ?0.34 ± 0.09). The presence of the Meishan allele at the IMF QTL on SSC7 thus had the opposite effect to our previous studies, that is, increased IMF. In the reproduction population, we observed no differences between the genotypes of the three QTL in regard to number of corpora lutea or litter size. Marker‐assisted introgression at these QTL is thus unlikely to result in an associated increase in litter size. These results show that it is possible to introgress alleles from other breeds into a selection population using molecular markers; any unexpected results might be associated with the genetic background.     

Changes in body temperature and metabolic rate following microinjection of Met-enkephalinamide in the preoptic/anterior hypothalamus of rats

The effects of Met-enkephalinamide (MET-ENKamide) on brain temperature (Tb) and metabolic rate (MR) were assessed following direct administration into the preoptic/anterior hypothalamus (PO/AH) of freely moving rats. Bilateral microinjections of saline or MET-ENKamide (1-25 micrograms/microliter) were delivered through cannula guide tubes previously implanted in nine animals. Thiorphan, an enkephalinase inhibitor, was microinjected into the PO/AH of two of the animals. All injections were made remotely at an ambient temperature of 22 +/- 1 degree C in a volume of 1 microliter. Measurements of Tb (via a brain-dwelling thermistor) and MR were recorded continuously. The ability of naloxone to antagonize the effects of MET-ENKamide was investigated by fashioning a double-barreled injection cannula to fit within each guide tube; 1 microliter of saline or naloxone (1-10 micrograms) was delivered bilaterally into the PO/AH followed by 1 microliter of MET-ENKamide (25 micrograms) 5-10 min later. PO/AH administration of MET-ENKamide (1-25 micrograms) produced dose-dependent increases in Tb preceded by dose-dependent increases in MR, with a characteristic time course of approximately 30 min. Naloxone antagonized the rise in Tb and MR, either partially or completely, depending on dose. When administered alone, naloxone had no effect on Tb or MR. Microinjection of thiorphan (10 micrograms) into the PO/AH evoked increases in Tb and MR that were similar to those responses induced by MET-ENKamide. These results support a role for endogenous Met-enkephalin in the regulation of Tb in the rat.     

Temporal expression of TnI fast and slow isoforms in biceps femoris and masseter muscle during pig growth

Biceps femoris (BF) and masseter muscle (MM) are the mixture of slow oxidative and fast-twitch fibres. Compared with MM, BF had the significantly higher expression of myosin heavy chain (MyHC) fast IIx and IIb isoforms (MyHCIIx and MyHCIIb), but lower expression of MyHC slow isoform (MyHCI) and fast IIa isoform (MyHCIIa). The objective of this study was to investigate the expression pattern of troponin I (TnI) slow-twitch isoform (TNNI1) and fast-twitch isoform (TNNI2) in BF and MM of Yorkshire and Meishan pigs which differed significantly in the growth rate. The expression of the TNNI1 and TNNI2 peaked at the postnatal 35 days in Yorkshire pigs and postnatal 60 days in Meishan pigs. The expression of TNNI1 and TNNI2 in Meishan pigs was significantly higher than that in Yorkshire pigs at the foetal 60 days, while the opposite occurred at postnatal 35 days. The expression ratio of TNNI1 relative to TNNI2 favoured TNNI2 expression in BF and MM regardless of Yorkshire and Meishan pigs. TNNI1 expression in MM was significantly higher than that in BF at 60, 120 and 180 days in Meishan pigs and at 120 and 180 days in Yorkshire pigs. On the contrary, no significant difference of TNNI2 expression in BF and MM was found except for Yorkshire pigs of 180 days. This study provided the foundation for future research on TnI isoforms as the model gene to study mechanisms of muscle fibre-specific gene regulation in pigs.     

Endometriosis is associated with progesterone resistance in the baboon (Papio anubis) oviduct: evidence based on the localization of oviductal glycoprotein 1 (OVGP1)

Endometriosis has been associated with a reduced response to progesterone in both the eutopic and ectopic endometrium. In this study we evaluated OVGP1 and steroid receptor expression in oviducts of baboons with endometriosis during the midsecretory phase and determined whether progesterone resistance associated with endometriosis also occurs in the oviduct. Oviducts obtained during the window of uterine receptivity (Day 10 postovulation [PO]) from animals with induced and spontaneous disease were compared to control animals during the proliferative stage and in the implantation window as well as animals treated with the progesterone receptor (PGR) antagonist ZK 137.299 (ZK). OVGP1 was significantly higher in animals with endometriosis compared with Day 10 PO controls and was similar to that seen in the late proliferative phase and in ZK-treated animals. Baboons with spontaneous endometriosis also showed a similar persistence of OVGP1, which was correlated with the maintenance of estrogen receptor 1 (ESR1) in the epithelial cells of animals with endometriosis. However, epithelial cell height and the percentage of ciliation were not affected by endometriosis. These data imply that the normal antagonism of progesterone on ESR and OVGP1, which results in their downregulation during the window of implantation, is absent in animals with endometriosis. This was confirmed further when the action of PGR was antagonized in animals without disease, which also resulted in the persistence of ESR1 and OVGP1. These studies suggest that an aberrant oviductal environment may be an additive factor that contributes to endometriosis-associated infertility.     

Embryo survival and conceptus growth after reciprocal embryo transfer between Chinese Meishan and Landrace x Large White gilts

Embryos were transferred between Meishan and Landrace x Large White (control) gilts on Day 4 or 5 to establish approximately equal numbers of all four possible combinations of donor breed and recipient breed. The breed of the donor gilt significantly (P less than 0.01) affected embryo survival with 44.5% of transferred Meishan embryos and 69.6% of transferred control embryos surviving to Day 30 +/- 1. There was no influence of the breed of the recipient gilt on the proportion of embryos which survived. These differences in embryo survival between the two breeds could not be explained by differences in (1) the number of embryos transferred, (2) the stage of development of the embryos transferred, (3) the interval between ovulation and transfer or (4) the degree of asynchrony between donor and recipient gilt. On Day 30 +/- 1 embryos from control donors developed into longer fetuses (P less than 0.01) with larger allantoic sacs (P less than 0.05) than did embryos from Meishan donors. Fetuses in control recipients were longer (P less than 0.01), heavier (P less than 0.001) and had larger allantoic sacs (P less than 0.05) than fetuses occupying Meishan uteri. The interaction between breed of donor gilt and breed of recipient gilt did not significantly affect conceptus growth. These results suggest that Meishan pig embryos may be less tolerant to routine embryo transfer procedures than those of control gilts, that the genotype of the dam does not affect the proportion of embryos surviving to Day 30 +/- 1, and that both fetal and maternal factors affect conceptus growth.     

The efficacy of orally dosed ketamine and ketamine/medetomidine compared with intramuscular ketamine in rhesus macaques (Macaca mulatta) and the effects of dosing route on haematological stress markers

BACKGROUND: This study compared the efficacy of two orally-dosed (PO) anaesthetic regimens for chemical immobilization in rhesus macaques (Macaca mulatta), versus the standard protocol of intramuscular (TM) ketamine. In addition, the effects of dosing route on haematological stress markers were evaluated. METHODS: Testing was conducted on 18 chronically housed animals. Animals were trained to accept oral dosing and then randomly assigned to one of three drug regimens: (1) ketamine IM, (2) ketamine PO, (3) Ketamine/medetomidine PO. Sedation levels for each regimen were evaluated. RESULTS: Oral dosing alone was not sufficient to achieve a plane of sedation that allowed for safe handling. Serum cortisol and glucose levels were unchanged across groups, although differences were observed in the leukogram profiles. CONCLUSION: The oral dosages used in this study fell short in providing adequate sedation for safe handling for routine veterinary procedures. Leukogram profiles indicated that orally dosed animals experienced a higher level of stress.     

Associations of GH gene variants with performance traits in F2 generations of European wild boar, Piétrain and Meishan pigs

The role of the porcine GH gene was investigated in 292 F₂ animals of mating Wild Boar × Piétrain and in 310 F₂ animals of mating Meishan × Piétrain. Forty-three traits of fattening, carcass composition, meat quality and stress resistance were recorded. For the analysis of associations between GH gene variants and quantitative traits, two restriction fragment length polymorphisms were examined. In the Meishan × Piétrain family eight traits related to fatness were significantly associated with GH genotypes, while in the Wild Boar × Piétrain family no significant associations were found. In the Meishan × Piétrain cross, the GH locus explained 11·7% to 17·7% of the total phenotypic variance in the F₂ population. The possibility of multiple alleles at the GH locus is discussed. Based on these results, we conclude that the GH locus should be further investigated in commercial breeds to determine its suitability for use in marker-assisted selection programmes.     

Genomic signatures reveal selection of characteristics within and between Meishan pig populations

The Chinese Meishan pig breed is well known for its high prolificacy. Moreover, this breed can be divided into three types based on their body size: big Meishan, middle Meishan (MMS) and small Meishan (SMS) pigs. Few studies have reported on the genetic signatures of Meishan pigs, particularly on a genome‐wide scale. Exploring for genetic signatures could be quite valuable for revealing the genetic architecture of phenotypic variation. Thus, we performed research in two parts based on the genome reducing and sequencing data of 143 Meishan pigs (74 MMS pigs, 69 SMS pigs). First, we detected the selection signatures among all Meishan pigs studied using the relative extended haplotype homozygosity test. Second, we detected the selection signatures between MMS and SMS pigs using the cross‐population extended haplotype homozygosity and F_ST methods. A total of 111 398 SNPs were identified from the sequenced genomes. In the population analysis, the most significant genes were associated with the mental development (RGMA), reproduction (HDAC4, FOXL2) and lipid metabolism (ACACB). From the cross‐population analysis, we detected genes related to body weight (SPDEF, PACSIN1) in both methods. We suggest that rs341373351, located within the PACSIN1 gene, might be the causal variant. This study may have achieved consistency between selection signatures and characteristics within and between Meishan pig populations. These findings can provide insight into investigating the molecular background of high prolificacy and body size in pig.     

Association analyses of porcine SERPINE1 reveal sex-specific effects on muscling, growth, fat accretion and meat quality

The serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1), member 1 (SERPINE1) gene encodes plasminogen activator inhibitor type 1 (PAI), which is the major physiological inhibitor of tissue‐type and urokinase‐type plasminogen activators and plays a role in obesity and insulin resistance in women but not in men. We detected SNP FN396538:g.566G>A in intron 3 and a non‐synonymous substitution NM_213910:c.612A>G in exon 3 (p.Ile159Val) and mapped the gene to position 8.4 cM on the linkage map of chromosome 3. Association analyses were conducted on the 12th–15th generation of the Meishan × Large White (MLW) cross (n = 565), with records for weight at the end of test, lifetime daily gain, test time daily gain, loin depth and backfat depth, as well as on a European wild boar × Meishan (W × M) F₂ population (n = 333) with 47 traits recorded for carcass composition and meat quality. Analyses performed across the entire MLW population or in the male animals did not show any trait significantly associated with the loci studied. In female animals, both SNPs were associated with loin depth at nominal P < 0.05 with adjusted P values equal to 0.051 (g.566) and 0.057 (c.612). Differences between homozygotes were up to 0.65 SD. In the entire W × M population and female animals, SERPINE1 was significantly associated at adjusted P < 0.05 in descending order with muscling, growth and fat accretion and in male animals with meat quality (R‐value). In the studied populations, allele effects were in opposite directions, which implies that the SNPs are markers that are in linkage disequilibrium with a causative mutation.     

Real-time PCR quantification of the predominant bacterial divisions in the distal gut of Meishan and Landrace pigs

Firmicutes and Bacteroidetes are closely related to body fat in humans and mice, which are the two dominant bacterial divisions of gut microbiota in mammals. Here real-time PCR analysis indicated that Meishan pigs had a 34% reduction in percentage Bacteroidetes (P=0.008) and a significantly lower proportion of Bacteroides (P=0.013) than Landrace pigs. The percentage of Bacteroidetes or Bacteroides had a negative correlation with body fat (R(2) was 0.63 for Bacteroidetes and 0.57 for Bacteroides, P<0.05). There was a trend that the percentage of Firmicutes in Meishan pigs was higher in numerical value than in Landrace pigs, although this difference was not statistically significant (P=0.290) between the two breeds. These suggested that body fat correlated with the percentage of Bacteroidetes division of the gut microbiota in the common pig breeds, and the differences of gut microbial ecology in obese versus lean animals may be analogous.     

Different messenger RNA expression for the antimicrobial peptides β-defensins between Meishan and crossbred pigs

β-defensins are cysteine-rich endogenously produced antimicrobial peptides that play an important role in innate immunity. In this study, the expressions of genes porcine β-defensins-1(pBD-1), pBD-2 and pBD-3 were determined using real-time PCR for Chinese Meishan pigs and Crossbred (Duroc × Yorkshire × Landrace) pigs of 7 days old in various tissues. The results showed that expressions of pBD-1, 2 and 3 of Meishan pigs in most tissues were higher than those of crossbred pigs and main expression sites for pBD-1 and pBD-3 were tongue and oral mucosa in two varieties of pigs, whereas pBD-2 of crossbred pig was mainly expressed in kidney and liver, and pBD-2 of Meishan pigs mainly in tongue and oral mucosa. The higher expression of pBDs might be the reason of Meishan pigs has higher immunity and disease resistance. The mechanisms of this need a further research.     

Oxygen tension distribution in postcapillary venules in resting skeletal muscle

We tested the hypothesis that blood flow is distributed among capillary networks in resting skeletal muscle in such a manner as to maintain uniform end-capillary PO2. Oxygen tension in venules draining two to five capillaries was obtained by using the phosphorescence decay methodology in rat spinotrapezius muscle. For 64 postcapillary venules among 18 networks in 10 animals, the mean PO2 was 30.1 Torr (range, 9.7-43.5 Torr) with a coefficient of variation (CV; standard deviation/mean) of 0.26. Oxygen levels of postcapillary venules within a single network or single animal, however, displayed a much smaller CV (0.064 and 0.094, respectively). By comparison, the CV of blood flow in 57 postcapillary venules of 17 networks in 9 animals was 1.27 with a mean flow of 0.011 +/- 0.014 nl/s and a range of 3.7 x 10(-4) to 6.5 x 10(-2) nl/s. Blood flow of postcapillary venules within single networks displayed a lower CV (mean, 0.51), whereas that in individual animals was 0.78. Results indicate that among venular networks, heterogeneity of oxygen tension is less than that of blood flow and within venular networks the heterogeneity of oxygen tension is much less than that of blood flow. In addition, postcapillary PO2 was independent of flow among venules in which both were measured. Results of this study may be attributable to three factors: 1) O2 diffusion between adjacent capillaries and venules, 2) structural remodeling in regions of lower PO2, and 3) O2-dependent local control mechanisms.     

Temporal and Molecular Analyses of Cardiac Extracellular Matrix Remodeling following Pressure Overload in Adiponectin Deficient Mice

Adiponectin, circulating levels of which are reduced in obesity and diabetes, mediates cardiac extracellular matrix (ECM) remodeling in response to pressure overload (PO). Here, we performed a detailed temporal analysis of progressive cardiac ECM remodelling in adiponectin knockout (AdKO) and wild-type (WT) mice at 3 days and 1, 2, 3 and 4 weeks following the induction of mild PO via minimally invasive transverse aortic banding. We first observed that myocardial adiponectin gene expression was reduced after 4 weeks of PO, whereas increased adiponectin levels were detected in cardiac homogenates at this time despite decreased circulating levels of adiponectin. Scanning electron microscopy and Masson’s trichrome staining showed collagen accumulation increased in response to 2 and 4 weeks of PO in WT mice, while fibrosis in AdKO mice was notably absent after 2 weeks but highly apparent after 4 weeks of PO. Time and intensity of fibroblast appearance after PO was not significantly different between AdKO and WT animals. Gene array analysis indicated that MMP2, TIMP2, collagen 1α1 and collagen 1α3 were induced after 2 weeks of PO in WT but not AdKO mice. After 4 weeks MMP8 was induced in both genotypes, MMP9 only in WT mice and MMP1α only in AdKO mice. Direct stimulation of primary cardiac fibroblasts with adiponectin induced a transient increase in total collagen detected by picrosirius red staining and collagen III levels synthesis, as well as enhanced MMP2 activity detected via gelatin zymography. Adiponectin also enhanced fibroblast migration and attenuated angiotensin-II induced differentiation to a myofibroblast phenotype. In conclusion, these data indicate that increased myocardial bioavailability of adiponectin mediates ECM remodeling following PO and that adiponectin deficiency delays these effects.