Adolescent Pigs Research Articles

Muscle Belly Repair: Biomechanical Assessment of the Anchor Suture and the Modified Kessler Techniques.

Background: Treatment of muscle belly lacerations remains a problem for surgeons. Inadequate repair of lacerations can cause functional disability. To date, there is no consensus on the method of repair for these injuries. We have previously described a technique of repairing mid-substance muscle belly lacerations. The aim of this study was to determine the ultimate strength of an intact muscle belly and to compare the anchor suture (AS) technique with the modified Kessler (MK) technique. Methods: Fifteen fresh frozen hind-legs from adolescent pigs were divided into three groups and used for the testing. Each group consisted of five specimens. Group one was the intact control group, group two was repaired with the MK technique and group three was repaired with the AS technique. Following repair, the muscles were secured in a custom-made fixation apparatus and underwent linear tensioning at a rate of 25 mm/min, generating a load-displacement curve for each specimen. The data regarding ultimate strength, modes of failure and number of intact suture/anchor constructs (for groups 2 and 3) was calculated. Results: The ultimate strength of the intact muscle group of was found to be 608.1 ± 107.9 N. This was significantly (p < 0.05) higher than the pull-out strength of the MK and AS groups. The pull-out strength of the AS group was 143.1 ± 36.7 N, nearly twice that of the MK group 69.8 ± 16.4 N (p = 0.11). Suture pull-out was the most common mode of failure. Conclusions: The AS technique was found to have both higher strain and nearly twice the ultimate pull-out strength compared to the MK repair group. We suggest the AS technique as a viable technique for mid-substance muscle belly repairs.

Extracellular matrix deformations of the porcine recurrent laryngeal nerve in response to hydrostatic pressure

Damage to the recurrent laryngeal nerve (RLN) caused by supraphysiological compression or tension imposed by adjacent tissue structures, such as the aorta, may contribute to onset of idiopathic unilateral vocal fold paralysis (iUVP) resulting in difficulty speaking, breathing, and swallowing. We previously demonstrated in adolescent pigs that the right RLN epineurium exhibits uniform composition of adipose tissue, with larger quantities along its length within the neck region in contrast to the left RLN that shows greater collagen composition in the thoracic region and greater quantities of adipose tissue in the neck region. In contrast, the epineurium in piglets was primarily composed of collagen tissue that remained uniform along the length of the left and right RLNs. Tensile testing of the left and right RLN in piglets and pigs showed associated differences in strain by RLN side and segment by age. The goal of this study was to investigate how external hydrostatic compression of the RLN affects the nerve's connective tissue and microstructure. RLN segments were harvested from the distal (cervical/neck) regions and proximal (subclavian for the right RLN, thoracic for the left RLN) regions from eight adolescent pigs and nine piglets. RLN segments were isolated and assessed under fluid compression to test hypotheses regarding epineurium composition and response to applied forces. Second harmonic generation (SHG) imaging of epineurial collagen was conducted at 0, 40, and 80 mmHg of compression. The cartesian strain tensor, principal strain (Eps1), and principal direction of the RLN collagen fibers were determined at each pressure step. Significantly larger values of the 1st principal strain occurred in the proximal segments of the pig left RLN when compared to the same segment in piglets (p = 0.001, pig = 0.0287 [IQR = 0.0161 - 0.0428], piglet = 0.0061 [IQR = 0.0033 - 0.0156]). Additionally, the median transverse strain Eyy) for the second pressure increment was larger in the right proximal segment of pigs compared to piglets (p < 0.001, pig = 0.0122 [IQR = 0.0033 - 0.0171], piglet = 0.0013 [IQR = 0.00001 - 0.0028]). Eyy values were significantly larger in the right proximal RLN versus the left proximal RLNs in pigs but not in piglets (p < 0.001). In contrast to piglets, histological analysis of pig RLN demonstrated increased axial alignment of epineurial and endoneurial collagen in response to compressive pressure. These findings support the hypothesis that the biomechanical response of the RLN to compressive pressure changed from being similar to being different between the right and left RLNs during development in the porcine model. Further investigation of these findings associated with age-related onset of idiopathic UVP may illuminate underlying etiologic mechanisms. Statement of significanceDamage to the recurrent laryngeal nerve (RLN) caused by compression imposed by the aorta may contribute to the onset of left-sided idiopathic unilateral vocal fold paralysis resulting in difficulty speaking, breathing, and swallowing. The goal of this study was to investigate how compression affects the connective tissue and microstructure of the RLN. We quantified the pressure induced deformation of the RLN using multiphoton imaging as a function of both location (proximal versus distal) and age (piglets, adolescent pigs). Our results demonstrate that the biomechanical response of the RLN to compression changes in the right versus left RLN throughout development, providing further evidence that the the left RLN is exposed to increasing dynamic loads with age.

High-resolution magnetic resonance imaging-based atlases for the young and adolescent domesticated pig (Sus scrofa)

BackgroundNeurodevelopmental studies utilize the pig as a translational animal model due to anatomical and morphological similarities between the pig and human brain. However, neuroimaging resources are not as well developed for the pig as they are for humans and other animal models. We established a magnetic resonance imaging-based brain atlas at two different ages for biomedical studies utilizing the pig as a preclinical model. New MethodTwenty artificially-reared domesticated male pigs (Sus scrofa) and thirteen sow-reared adolescent domesticated male pigs (Sus scrofa) underwent a series of scans measuring brain macrostructure, microstructure, and arterial cerebral blood volume. ResultsAn atlas for the 4-week-old and 12-week-old pig were created along with twenty-six regions of interest. Normative data for brain measures were obtained and detailed descriptions of the data processing pipelines were provided. Comparison with Existing MethodAtlases at the two different ages were created for the pig utilizing newer imaging technology and software. This facilitates the performance of longitudinal studies and enables more precise volume measurements in pigs of various ages by appropriately representing the neuroanatomical features of younger and older pigs and accommodating the proportion differences of the brain over time. ConclusionTwo high-resolution MRI brain atlases specific to the domesticated young and adolescent pig were created using defined image acquisition and data processing methods to facilitate the generation of high-quality normative data for neurodevelopmental research.

Impact of Capnoperitoneum on Renal Perfusion and Urine Production in Infant and Adolescent Pigs: Crystalloid versus Colloid Fluid Resuscitation.

Infants are likely to develop anuria during laparoscopy which is uncommon in older patients. The reason for this susceptibility remains unknown. We compared the impact of CO2 pneumoperitoneum on renal perfusion and urine production in piglets compared with adolescent pigs. We furthermore investigated the effects of different resuscitation strategies. Male piglets (n = 21) were divided into four groups: (a) infant controls (n = 5), (b) infants with crystalloid restitution (n = 6), (c) infants with colloidal restitution (n = 5), and (d) adolescents with crystalloid restitution (n = 5). Animals were ventilated, the central vessels and ureters were cannulated, and the animals were subjected to a 3-hour, 10 mm Hg CO2 pneumoperitoneum followed by 2-hour resuscitation. Renal perfusion was assessed by fluorescent microspheres and the rate of urine flow was measured. Urine production significantly decreased after insufflation only in the infant crystalloid and adolescent group, but not in controls or infants treated with colloids. In the infant crystalloid group, urine production remained at levels below 20% of baseline throughout the experiment. In this group, the renal perfusion dropped significantly after the beginning of the capnoperitoneum and remained significantly reduced throughout the experiment. Our data indicates that capnoperitoneum impairs renal perfusion and urine production in infants. In moderate-pressure capnoperitoneum, this effect cannot be compensated by application of crystalloids but with colloids.

Cardiac procholecystokinin expression during haemodynamic changes in the mammalian heart

Cardiac myocytes express the cholecystokinin gene (CCK) at propeptide level. We recently reported that cardiac CCK expression is acutely regulated by isoprenaline in a porcine model.The regulation of CCK expression after myocardial infarction, in exercise, and in severe heart failure is, however, unknown. Cardiac tissue was obtained from healthy new-born and adolescent farm pigs. Myocardial infarction was induced by coronary artery occlusion in adult minipigs. Healthy male subjects performed a 3-hour exercise test, and patients with severe heart failure referred for right heart catheterization were included. Extracts of porcine cardiac tissue and human plasma were analysed with specific proCCK radioimmunoassays. Cardiac proCCK expression shifted from the right atrium in new-born piglets to include the left atrium in adolescent pigs. Regional proCCK expression in the adolescent pig heart was mainly confined to the atria without different expression in sinus node tissue. In adult minipigs with myocardial infarction, no changes in overall left ventricular function or proCCK expression were observed after 8 weeks. In healthy adults, proCCK in circulation increased markedly during exercise in parallel with pro-B-type natriuretic peptide. Finally, patients with severe heart failure displayed markedly increased proCCK – but not CCK – concentrations in plasma. Taken together, our data shows that regional proCCK expression reflects haemodynamic changes in the mammalian heart. The data supports the notion that cardiac CCK expression resembles that of cardiac natriuretic peptides in atria. The ventricular content of proCCK, however, differs from natriuretic peptides and suggests a distinct secretory pathway in ventricular cardiomyocytes.

Miniature pig magnetic resonance spectroscopy model of normal adolescent brain development

BackgroundWe are developing the miniature pig (Sus scrofa domestica), an in-vivo translational, gyrencephalic model for brain development, as an alternative to laboratory rodents/non-human primates. We analyzed longitudinal changes in adolescent pigs using proton magnetic resonance spectroscopy (1H-MRS) and examined the relationship with white matter (WM) integrity derived from diffusion weighted imaging (DWI). New methodTwelve female Sinclair™ pigs underwent three imaging/spectroscopy sessions every 23.95 ± 3.73 days beginning at three months of age using a clinical 3 T scanner. 1H-MRS data were collected using 1.2 × 1.0 × 3.0 cm voxels placed in left and right hemisphere WM using a Point Resolved Spectroscopy sequence (TR = 2000 ms, TE = 30 ms). Concentrations of N-acetylaspartate, myo-inositol (MI), glutamate + glutamine, choline, creatine, and macromolecules (MM) 09 and 14 were averaged from both hemispheres. DWI data were collected using 15 shells of b-values (b = 0–3500 s/mm2) with 32 directions/shell and fit using the WM Tract Integrity model to calculate fractional anisotropy (FA), kurtosis anisotropy (KA) and permeability-diffusivity index. ResultsMI and MM09 significantly declined with age. Increased FA and KA significantly correlated with decline in MI and MM09. Correlations lost significance once corrected for age. Comparison with existing methodsMRI scanners/protocols can be used to collect 1H-MRS and DWI data in pigs. Pigs have a larger, more complex, gyrencephalic brain than laboratory rodents but are less complex than non-human primates, thus satisfying the “replacement” principle of animal research. ConclusionsLongitudinal effects in MRS measurements were similar to those reported in adolescent humans. MRS changes correlated with diffusion measurements indicating ongoing WM myelination/maturation.

Establishing a model for childhood obesity in adolescent pigs.

SummaryObjectiveRising worldwide prevalence of obesity and metabolic diseases in children has accentuated the importance of developing prevention and management strategies. The objective of this study was to establish a model for childhood obesity using high‐fat feeding of adolescent pigs, as pigs have a longer developmental period and are physiologically more similar to humans than rodents.MethodsCrossbred pigs were fed a high‐fat diet (HFD) or low‐fat diet (n = 6/treatment) from postnatal day 49 to 84. On postnatal day 84, an oral glucose tolerance test was performed, jugular blood sampled to determine lipopolysaccharide levels and plasma lipids, intestinal digesta collected to characterize microbial and metabolite composition and back fat and intestinal tissue assayed for gene expression.ResultsFive‐week HFD increased weight gain and back fat thickness, caused dyslipidaemia and impaired glucose tolerance and increased expression of genes in back fat suggesting inflammation. HFD pigs had distinct proximal colon microbiota with 48% reduction (P < 0.05) in Bacteroidetes and increased expression of pro‐inflammatory genes interleukin‐18 and tumour necrosis factor in ileum (P < 0.05).ConclusionsThese findings indicate that adolescent pigs should be considered a suitable model for childhood obesity, because short‐term HFD feeding is sufficient to induce obesity and glucose intolerance, recapitulating disease characteristics in adolescent pigs.

Arterioportal shunting, splanchnic capillary perfusion, and the effects of colloids during capnoperitoneum in neonatal and adolescent pigs

Clinical and experimental data indicate that neonates are sensitive to the CO2 pneumoperitoneum. An impaired splanchnic perfusion during laparoscopy in adults has been reported. We recently confirmed that intravenous colloids improve macrocirculatory function in neonates. We aimed to determine the impact of CO2 pneumoperitoneum on the perfusion of splanchnic organs in the young including effects of colloid application. Male piglets (n = 25) were divided into four groups: (1) neonatal controls, (2) neonates with crystalloid restitution, (3) neonates with colloidal restitution, and (4) adolescents with crystalloid restitution. Animals were ventilated and subjected to a 3-h, 10mmHg CO2 pneumoperitoneum followed by 2h resuscitation. Hepatic, splanchnic, and arteriovenous shunt perfusion was assessed via central and portal venous catheters. Capillary organ flow was detected by fluorescent microspheres. The rate of bile flow was measured. The neonatal crystalloid group showed a significant decrease in the intestinal capillary perfusion at the end of the recovery period. This was not detectable in the adolescent and colloid group. There was a significant increase in microcirculatory arterioportal shunt flow during the CO2 pneumoperitoneum in both neonatal groups but not in the sham and adolescent groups (p < 0.05). Hepatic arterial perfusion increased after insufflation in all groups and dropped during capnoperitoneum to levels of about 70% baseline. There was no significant impairment of splanchnic perfusion or bile flow as a result of the pneumoperitoneum in all groups. Capillary perfusion of the abdominal organs was stable during capnoperitoneum and recovery in adolescents and neonates with colloid restitution, but not with crystalloid restitution. Significant arterioportal shunting during capnoperitoneum could affect hepatic microcirculation in neonates. Our data confirm that moderate pressure capnoperitoneum has no major effect on the perfusion of abdominal organs in neonates with adequate substitution.

Sulphur-isotope compositions of pig tissues from a controlled feeding study

ABSTRACTSulphur-isotope determinations are becoming increasingly useful for palaeodietary reconstruction, but knowledge of isotopic discrimination between diet and various tissues remains inadequate. In this study, we explore the sensitivity of δ34Stissue values to changes in δ34Sdiet values, sulphur isotopic discrimination between diet and consumer, and the potential impact of terrestrial vs. marine protein consumption on these discrimination offsets. We present new δ34S values of bone collagen, muscle, liver, hair, milk and faeces from ten mature sows, ten piglets and fifteen adolescent pigs from a controlled feeding study. The δ34Stissue values were found to co-vary with the δ34Sdiet values, the δ34Stissue – δ34Sdiet isotopic offsets (Δ34Stissue-diet) are small but consistent, and dietary protein source does not systematically alter the Δ34Stissue-diet isotopic discrimination. The outcomes of this study are of particular relevance to questions that are difficult to resolve using carbon and nitrogen stable isotopes alone, and will also be useful in regions where terrestrial, freshwater, and marine resources could have all potentially contributed to human diet.

Latent porcine circovirus type 2-infected domestic pigs: A potential infection model for the effective development of vaccines against latent or chronic virus induced diseases

Until recently, knowledge of the pathogenicity of Circoviridae and Anelloviridae family members was limited. Our previous discoveries provided clues toward resolving this issue based on studies of the latent nature of porcine circovirus type 2 (PCV2) genotype group members. We developed a conventional pig infection model that indicated that weaners already harbored latent PCV2 infection in the thymus, which enabled the viruses to specifically modulate the maturation of T-helper cells. This finding raised the possibility that the thymi of normal fetuses were already infected with PCV2. The present findings further substantiate our hypothesis that PCV2 masquerades as the host by infecting fetuses before they acquire immune-competence. We provide the first demonstration that all domestic pig fetuses preferentially harbor latent PCV2-infected cells in their thymi. These PCV2-infected cells are different from thymocytes and are located in the medulla of the fetal thymus. These latent PCV2-infected cells in fetuses are found at the same location and share characteristics with the infected cells observed in adolescent pigs. Moreover, fetuses also harbor these infected cells in other lymph system organs. We provide the first demonstration that the fetal thymus virus pools are minimally affected by sow vaccination, highlighting the immune-privileged character of this organ. Furthermore, we found a striking reduction in virus-infected cells in the fetal spleen and an increase in PCV2-infected cells in the fetal intestine of anti-PCV2-vaccinated mothers. These data indicate that specific immune response interactions occur between mothers and their progeny that are not dependent on the humoral immunity of the mother and cannot be attributed to the rudimentary humoral responses of the fetuses because these pig fetuses do not have any PCV2-specific antibodies. These shifts in our understanding of the PCV2-infected cell pool will lead to different avenues in the search for effective vaccination strategies against latent and chronic pathogens.

Age effects and the influence of varying proportions of terrestrial and marine dietary protein on the stable nitrogen-isotope compositions of pig bone collagen and soft tissues from a controlled feeding experiment

In this study, femoral collagen, rib collagen, femoral muscle, loin muscle and liver samples from sows, piglets and pigs raised in a controlled feeding study are analysed for their nitrogen-isotope compositions. The objectives of this research are to investigate the relationship between tissue and dietary δ15N values across age categories under controlled feeding and housing conditions, and to assess tissue 15N-enrichment relative to diet when pigs of different ages are consuming terrestrial, marine, or mixed terrestrial-marine dietary protein. There is a strong linear relationship between all tissue δ15N values and the amount of marine protein consumed, but the δ15N values do not become consistently elevated for all individuals consuming the same diet until at least 25% of the dietary protein source is marine-derived. Adolescent pigs also had consistently lower δ15N values than either piglets or sows consuming the same diet for collagen and muscle, which is most likely caused by the differences in growth rate among the age categories. Further, for some tissues and animals, a linear relationship between the amount of marine protein consumed and the Δ15NTissue – Whole Diet offset was also observed. We suggest that this variability results from both age-associated growth rates and differential incorporation of amino acids from terrestrial and marine dietary protein into rapidly growing tissue.

Renal glucose release during hypoglycemia is partly controlled by sympathetic nerves - a study in pigs with unilateral surgically denervated kidneys.

Catecholamines are known to increase renal glucose release during hypoglycemia. The specific extent of the contribution of different sources of catecholamines, endocrine delivery via circulation or release from autonomous sympathetic renal nerves, though, is unknown. We tested the hypothesis that sympathetic renal innervation plays a major role in the regulation of renal gluconeogenesis. For this purpose, instrumented adolescent pigs had one kidney surgically denervated while the other kidney served as a control. A hypoglycemic clamp with arterial blood glucose below 2 mmol/L was maintained for 75 min. Arteriovenous blood glucose difference, inulin clearance, p-aminohippurate clearance, and sodium excretion were measured in intervals of 15 min separately for both kidneys. Blood glucose was lowered to 0.84 ± 0.33 mmol/L for 75 min. The side-dependent renal net glucose release (SGN) decreased significantly after the unilateral ablation of renal nerves. In the linear mixed model, renal denervation had a significant inhibitory effect on renal net glucose release (P = 0.036). The SGN of the ablated kidney decreased by 0.02 mmol/min and was equivalent to 43.3 ± 23.2% of the control (nonablated) kidney in the pigs. This allows the conclusion that renal glucose release is partly controlled by sympathetic nerves. This may be relevant in humans as well, and could explain the increased risk of severe hypoglycemia of patients with diabetes mellitus and autonomous neuropathy. The effects of denervation on renal glucose metabolism should be critically taken into account when considering renal denervation as a therapy in diabetic patients.

Effects of the glucagon-like peptide-1 receptor agonist liraglutide in juvenile transgenic pigs modeling a pre-diabetic condition.

BackgroundThe glucagon-like peptide-1 receptor (GLP1R) agonist liraglutide improves glycemic control and reduces body weight of adult type 2 diabetic patients. However, efficacy and safety of liraglutide in adolescents has not been systematically investigated. Furthermore, possible pro-proliferative effects of GLP1R agonists on the endocrine and exocrine pancreas need to be further evaluated. We studied effects of liraglutide in adolescent pigs expressing a dominant-negative glucose-dependent insulinotropic polypeptide receptor (GIPRdn) in the beta-cells, leading to a pre-diabetic condition including disturbed glucose tolerance, reduced insulin secretion and progressive reduction of functional beta-cell mass.MethodsTwo-month-old GIPRdn transgenic pigs were treated daily with liraglutide (0.6-1.2 mg per day) or placebo for 90 days. Glucose homeostasis was evaluated prior to and at the end of the treatment period by performing mixed meal and intravenous glucose tolerance tests (MMGTT and IVGTT). Finally animals were subjected to necropsy and quantitative-stereological analyses were performed for evaluation of alpha- and beta-cell mass, beta-cell proliferation as well as acinus-cell proliferation.ResultsMMGTT at the end of the study revealed 23% smaller area under the curve (AUC) for glucose, a 36% smaller AUC insulin, and improved insulin sensitivity, while IVGTT showed a 15% smaller AUC glucose but unchanged AUC insulin in liraglutide- vs. placebo-treated animals. Liraglutide led to marked reductions in body weight gain (-31%) and food intake (-30%) compared to placebo treatment, associated with reduced phosphorylation of insulin receptor beta (INSRB)/insulin-like growth factor-1 receptor beta (IGF1RB) and protein kinase B (AKT) in skeletal muscle. Absolute alpha- and beta-cell mass was reduced in liraglutide-treated animals, but alpha- and beta-cell mass-to-body weight ratios were unchanged. Liraglutide neither stimulated beta-cell proliferation in the endocrine pancreas nor acinus-cell proliferation in the exocrine pancreas, excluding both beneficial and detrimental effects on the pig pancreas.ConclusionsAlthough plasma liraglutide levels of adolescent transgenic pigs treated in our study were higher compared to human trials, pro-proliferative effects on the endocrine or exocrine pancreas or other liraglutide-related side-effects were not observed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0431-2) contains supplementary material, which is available to authorized users.

Metabolic footprint of the GLP-1 receptor agonist liraglutide in adolescent transgenic pigs with impaired incretin function

Metabolic footprint of the GLP-1 receptor agonist liraglutide in adolescent transgenic pigs with impaired incretin function

Effects of mammalian in utero heat stress on adolescent body temperature

In utero hyperthermia can cause a variety of developmental issues, but how it alters mammalian body temperature during adolescence is not well-understood. Study objectives were to determine the extent to which in utero hyperthermia affects future phenotypic responses to a heat load. Pregnant first parity pigs were exposed to thermal neutral (TN) or heat stress (HS) conditions during the entire gestation. Of the resultant offspring, 12 were housed in TN conditions, and 12 were maintained in HS conditions for 15 days. Adolescent pigs in HS conditions had increased rectal temperature and respiration rate (RR) compared to TN pigs, regardless of gestational treatment. Within the HS environment, no gestational difference in RR was detected; however, GHS pigs had increased rectal temperature compared to GTN pigs. As rectal temperature increased, GTN pigs had a more rapid increase in RR compared to the GHS pigs. Adolescent HS decreased nutrient intake, and body weight gain, but neither variable was statistically influenced by gestational treatments. In summary, in utero HS compromises the future thermoregulatory response to a thermal insult.

Prenatal stress and ketamine affect the behavioral and physiological responsiveness of early adolescent pigs to a novel arena and social confrontation test

Elevated maternal glucocorticoid concentrations during gestation can affect how the offspring respond, both behaviorally and physiologically, to a challenge later in life. The objectives of this study were to first, determine if elevated maternal glucocorticoid concentrations during late gestation affect the behavioral and physiological response of the female offspring to a challenge during early adolescence, and secondly, determine if giving ketamine (an anxiolytic drug) effects these behavioral and physiological responses. During late gestation (d 76 until 115) sows were either repeatedly injected with ACTH (n=7) or control handled (n=7). Three female offspring from each sow were used in the study. A back test was performed on all experimental pigs during the first week of life. Pigs were tested in a novel arena (n=21/treatment) and social confrontation test (n=10/treatment) at 25 and 28 wk of age respectively, to assess anxiety-like behaviors. Two h prior to testing in the novel arena and social confrontation tests, pigs were given either ketamine (KET) or saline (SAL). The same pigs were then re-tested 7 d later and given the alternative drug treatment. Hypothalamic-pituitary adrenal function in response to an ACTH challenge and a social confrontation test was assessed. ACTH sows tended to have fewer (P=0.057) stillborn pigs than controls (0.4 and 0.0±0.14 pigs, respectively). In response to the novel arena test, ACTH pigs tended (P=0.056) to cross fewer squares than controls (77.2±6.71 and 93.5±93.5 squares, respectively), and pigs given ketamine spent less (P<0.05) time performing escape behaviors compared to pigs given saline (log-transformed, 0.0 and 0.3±0.11, respectively). In a social confrontation test, ACTH pigs spent more (P<0.05) time performing mounting behaviors than control pigs (log-transformed, 1.3 and 0.5±0.41, respectively). Furthermore, ACTH pigs given ketamine spent more (P<0.05) time nudging their pen-mate than ACTH pigs given saline (log-transformed, 3.9±0.29 and 2.9±0.27, respectively). Plasma cortisol concentrations in response to the social confrontation test were lower (P<0.05) in ACTH pigs given ketamine than ACTH pigs given saline (log-transformed, 1.9±0.37 and 2.7±0.23, respectively). These results suggest that exposure to elevated maternal glucocorticoids and ketamine can affect the behavioral and physiological reactivity of pigs in response to a challenge during early adolescence, and ketamine effects behavioral reactivity of control and prenatally stressed pig's differentially.

Alveolar ridge reduction after tooth extraction in adolescents: An animal study

ObjectiveThe mechanism for tooth extraction induced residual alveolar ridge reduction (RRR) during adolescence is poorly understood. This study investigated the alveolar bone morphology, growth, resorption and functional loading at normal and extraction sites using an adolescent pig model. DesignSixteen 3-month-old pigs were divided into two groups – immediate post-extraction (IE) and 6-week post-extraction (SE). The IE group received an extraction of one deciduous mandibular molar, immediately followed by a final experiment to record masseter muscle EMGs and strains from the buccal surface of the extraction and contralateral non-extraction sites during function (mastication). The SE group was given the same tooth extraction, then kept for 6 weeks before the same final functional recording as the IE group. Both groups also received baseline (pre-extraction) EMGs and fluorescent vital stains 10 and 3 days before the final functional recording. Immediately after the final functional recording, animals were euthanized and alveolar bone specimens from extraction and contralateral non-extraction sites were collected and used to analyse alveolar bone morphology, apposition and resorption based on fluorescent and hematoxylin and eosin stained histological sections. ResultsAt control sites (IE-extraction, IE-non-extraction and SE-non-extraction), the alveolar ridges grew gingivally and buccally. Bone formation characterized the buccal surface and lingual bundle bone, whereas resorption characterized the lingual surface and buccal bundle bone. The SE-extraction sites showed three major alterations: convergence of the buccal and lingual gingival crests, loss of apposition on the lingual bundle bone, and decelerated growth at the entire buccal surface. These alterations likely resulted from redirected crestal growth as part of the socket healing process, loss of tongue pressure to the lingual side of the teeth which normally provides mechanical stimulation for dental arch expansion, and masticatory underloading during the initial post-extraction period, respectively. ConclusionsThese data indicate that the initial phase of RRR in adolescents is a product of modified growth, not resorption, possibly because of decreased mechanical stimulation at the extraction site.

Effects of age and platelet‐rich plasma on ACL cell viability and collagen gene expression

Platelet-rich plasma (PRP) has shown in vivo potential to stimulate anterior cruciate ligament (ACL) healing at early time points in large animal models. However, in animal models, the healing potential of the ACL is dependent on animal age. In this study, we hypothesized that there are age-dependent differences in ACL cell metabolism, collagen gene expression, and the ability of the cells to respond to growth factors in PRP. To test this hypothesis, ACL cells were obtained from skeletally immature, adolescent and adult pigs, and cultured in a collagen type I hydrogel with or without PRP for 14 days. When cultured in collagen-only hydrogel, ACL cells from adult pigs had a 19% lower apoptotic rate as compared to immature pigs (p = 0.001) and a 25% higher cellular metabolic activity as compared to adolescent pigs (p = 0.006). The addition of PRP to the collagen hydrogel resulted in a significantly increased cellular metabolic activity, reduced apoptotic rate, and stimulation of collagen production in the cells from the immature and adolescent animals (p < 0.05 for all comparisons) but had less effect on adult cells. These findings suggest that skeletal maturity may influence ACL cells' metabolic activity, apoptosis, collagen production, and response to PRP.

Trans-apical beating-heart implantation of neo-chordae to mitral valve leaflets: results of an acute animal study

Trans-apical beating-heart implantation of neo-chordae is yet an experimental procedure for mitral valve (MV) repair. We aimed to assess the performance of a new device in an acute animal study. A total of four domestic adolescent pigs were used as an acute model. The MV was assessed on the beating heart through a conventional trans-apical access. The NeoChord DS1000 device was used to implant polytetrafluoroethylene (PTFE) sutures to the MV leaflets. Procedural performance of the device was assessed and completed with surgical workflow analysis. Overall 57 implantations using epicardial echocardiography guidance were performed (mean 14.3 implantations per animal). The MV leaflets were successfully grasped every second attempt (mean 2.3±1.9) with no difference between the anterior and the posterior leaflet. A significant difference between an 'expert' surgeon (n>20 implantations) and beginner surgeon was detected with regard to the duration for successful leaflet grasping (65±73 vs 127±105 s; p=0.02) and the overall duration for implantation (130±86 vs 230±119 s; p=0.002). Gross anatomy did not show major tear of leaflets. There were no device-related technical problems. The NeoChord DS1000 device for trans-apical beating-heart implantation of neo-chordae to the MV valve showed a high procedural success. A significant difference between an expert and beginner surgeon was detected, which emphasizes the importance of training before introduction of this new technique into clinical practice. Surgical workflow analysis proved to be a valuable tool to assess the performance of this new technique.

Experimentally modified Fontan circulation in an adolescent pig model without the use of cardiopulmonary bypass

SummaryBackgroundThe feasibility and the hemodynamic outcome of Fontan circulation, without the use of cardiopulmonary bypass, were studied on a beating heart of an adolescent pig model, using a modified total cavopulmonary connection.Material/MethodsEight open-chest anesthetized pigs underwent a successful total cavopulmonary connection with the use of an appropriate Y-shaped Dacron-type conduit. Through a median sternotomy, the distal part of the superior vena cava was anastomosed end-to-end to one side of the conduit. The other side of the graft was anastomosed end-to-side to the main pulmonary artery. The conduit was tailored to an appropriate length and anastomosed end-to-end to the inferior vena cava. The hemodynamic status of the animals was recorded before and after the establishment of the total cavopulmonary connection.ResultsForty-five minutes after completion of total cavopulmonary connection, and for a total of 1 hour, hemodynamic measurements showed a decrease in mean arterial and mean pulmonary artery pressures, heart rate and cardiac output. The inferior vena caval pressure and total pulmonary vascular resistance were increased.ConclusionsA total cavopulmonary connection, performed on a beating heart, without extracorporeal circulation or other means of temporary bypass, although it is technically demanding, is feasible.