A reproducible swine model of proximal descending thoracic aortic aneurysm created with intra-adventitial application of elastase

OBJECTIVE

Animal models are required to explore the mechanisms of and therapy for proximal descending thoracic aortic aneurysm (TAA). This study aimed to establish a reproducible swine model of proximal descending TAA that can further explain the occurrence and progression of proximal descending TAA.

METHODS

Eighteen Chinese Wuzhishan miniature pigs (30.32 ± 1.34 kg) were randomized into the elastase group (n = 12) and the control group (n = 6). The elastase group received intra-adventitial injections of elastase (5 mL, 20 mg/mL), and the control group received injections of physiologic saline solution. A 4-cm descending thoracic aortic segment proximal to the left subclavian artery was isolated. The distance between the left subclavian artery and the injection starting point of the descending thoracic aorta was 0.5 cm. Elastic protease was circumferentially injected intra-adventitially into the isolated segment of the aortic wall in the elastase group by a handmade bent syringe. The length of the elastic protease injection was 2 cm. An average of 12 injection points were distributed in this 2-cm aortic segment. Each injection point used about 0.4 mL of elastic protease. The distance between two injection points was about 1.5 cm. All animals underwent digital subtraction angiography preoperatively and 3 weeks after operation. Three weeks after TAA induction, aortas were harvested for biochemical and histologic measurements.

RESULTS

All animals in the elastase group developed TAAs. No aneurysms were observed in the control group. The distance between the left subclavian artery and the TAA was 8.00 ± 4.19 mm. Preoperative and postoperative aortic diameters of the elastase group were 15.42 ± 0.43 mm and 24.53 ± 1.41 mm, respectively (P < .0001). Preoperative and postoperative aortic diameters of the control group were 15.31 ± 0.33 mm and 15.57 ± 0.40 mm, respectively (P = .5211). The changes of aortic structure and composition included reduction of smooth muscle cells and degradation of elastic fibers. Levels of matrix metalloproteinases 2 and 9 were increased in TAA tissue.

CONCLUSIONS

This study established a reproducible large animal model of proximal descending TAA. This model has the same biochemical characteristics as human aneurysms in the aspects of aortic expansion, aortic middle-level degeneration, and changes in the levels of matrix metalloproteinases and provides a platform for further study.

Histological and anatomical structure of the nasal cavity of Bama minipigs

Objective

The nasal mucosa is equipped with abundant lymphatic tissues, serving as the first line of defense against invasion by microorganisms. In this study, we characterized the features of the nasal mucosa of Bama minipigs (Sus scrofa domestica) via histological analysis.

Methods

Five cross sections (I, II, III, IV, and V) were obtained from the distal end of the nasal cavity toward the pharynx (along the cavity axis) and examined. Specifically, CD3⁺ T cells, immunoglobulin A (IgA)⁺ cells, and M cells were detected by immunohistochemistry, while dendritic cells (DCs) were detected by immunofluorescence. The distribution of goblet cells was determined by periodic acid-Schiff (PAS) staining.

Results

The nasal cavity of Bama minipigs can be divided into three parts: the regio vestibularis (I, II), regio respiratoria (III, IV), and regio olfactoria (V). Lymphoid tissue was present at random locations in the nasal cavity. Abundant lymphoid tissue was located in the roof of the nasopharyngeal meatus and was continuous with the lymphoid tissue of the pharynx. The distribution of CD3⁺ T cells, IgA⁺ cells, M cells, and DCs increased distally in the nasal cavity.

Conclusions

The present work comprises a histological study of the nasal cavity of Bama minipigs, and will be beneficial for understanding the mechanisms of immunity in these animals after nasal vaccination.

Anatomy and Disorders of the Oral Cavity of Miscellaneous Exotic Companion Mammals

Unusual mammalian species such as the hedgehog, sugar glider, and miniature pig are encountered with increasing frequency in exotic companion medicine. Disease of the oral cavity can occur in any species; although occasionally encountered in exotic mammalian species, it is rarely described in the literature. Anatomy and dentition vary significantly; diagnosis and treatment are often extrapolated from that known in other species. The best-documented disease of the oral cavity in this group of species is oral neoplasia in the hedgehog.

Dynamic MR imaging of a minipig's knee using a high-density multi-channel receive array and a movement device

OBJECT

To construct an optimised, high-density receive array and a movement device to achieve dynamic imaging of the knee in orthopedic large animal models (e.g., minipigs) at 1.5 T.

MATERIALS AND METHODS

A 13-channel RF receive array was constructed, and the crucial choice of the array element size (based on considerations like region of interest, geometry of the minipig's knee, achievable signal-to-noise ratio, applicability of parallel imaging, etc.) was determined using the Q factors of loops with different sizes. A special movement device was constructed to guide and produce a reproducible motion of the minipig's knee during acquisition.

RESULTS

The constructed array was electrically characterised and the reproducibility of the cyclic motion was validated. Snapshots of dynamic in vivo images taken at a temporal resolution (308 ms) are presented. Some of the fine internal structures within the minipig's knee, like cruciate ligaments, are traced in the snapshots.

CONCLUSION

This study is a step towards making dynamic imaging which can give additional information about joint injuries when static MRI is not able to give sufficient information, a routine clinical application. There, the combination of a high-density receive array and a movement device will be highly helpful in the diagnosis and therapy monitoring of knee injuries in the future.

Light microscopic, electron microscopic, and immunohistochemical comparison of Bama minipig (Sus scrofa domestica) and human skin

Here we sought to evaluate the possibility of using Chinese Bama miniature pig skin as a suitable animal model for human skin. Morphologic features of the skin of Bama miniature pigs resemble those of human skin, including skin layer thickness, development of a superficial vascular system, structure of the dermal-epidermal interface, and extracellular matrix. The characteristics and densities of Langerhans cells, fibroblasts, vascular endothelial cells, and mast cells were similar between Bama pig and human skin. Immunohistochemistry showed that miniature pigs and humans have the same antigenic determinants of human laminin, fibronectin, filaggrin, collagen I, collagen III, collagen IV, and keratin but not CD34, ICAM1, or S100. In addition, collagen type I from Bama miniature pig skin exhibited physicochemical characteristics resembling those of human skin, in regard to HPLC chromatography, UV spectroscopy, amino-acid composition, and SDS-PAGE analysis. Given these results, we concluded that Bama miniature pigs have great potential as a human skin model and for developing dermal substitute materials in wound repair. However, we also observed some disparities between the skin of Bama miniature pigs and humans, including pigment cell distribution, sweat gland types, and others. Therefore, further studies are needed to completely evaluate the effects of these interspecies differences on the actual application of the model.

[Comparative ultrastructural study of parotid gland, lacrimal gland and pituitary gland between miniature pig and mouse]

OBJECTIVE

To study the ultrastructure of parotid glands, lacrimal glands and pituitary glands between miniature pig and mouse.

METHODS

Five adult miniature pigs and 5 mice were studied. Ultrastructure of their parotid glands, lacrimal glands, and pituitary glands was observed.

RESULTS

The secretary granules in acinar cell of miniature pig parotid glands showed higher density and more aequalis than those of mice. The cell apparatus in acinar cell of mouse parotid glands were more plentiful than those of miniature pigs. The secretary granules on blood vessel wall were richer in parotid gland of miniature pigs compared with mouse parotid gland. Lacrimal gland had the similar ultrastructure to parotid gland in these two animals. Many blood vessel antrum were found in pituitary glands of these two animals.

CONCLUSIONS

Compared with mouse parotid glands, there are more secretary granules in acinar cells and vascular endothelial cells in miniature pig parotid glands, which might enter blood stream and have function of endocrine secretion.

Radiographic techniques for medical–dental research with minipigs

Techniques were developed to obtain standardised intra- and extra-oral radiographs in minipigs for use in medical-dental research. Twelve male minipigs (BR-1 Minipigs) were chosen at random. Two animals each at 3, 5, 7, 9, 12 and 15 months of age were anaesthetised and subjected to radiographic examinations to assess six techniques. Three intra-oral and three extra-oral techniques, standardised for humans, were used with variations of the angle of incidence of the X-ray beams, focus-film distance and exposure time. Two film positioners were developed for the intra-oral techniques. Two examiners then chose the radiographs with the least image distortion, greatest clarity and least superimposition of images. For each technique, the suitable angle of incidence of the X-ray beams, the focus-film distance and exposure time that produced the highest quality radiographs were standardised.

Visualization of the visual cortex in minipigs using fMRI

Minipigs are widely used to examine physiologic mechanisms under experimental settings. The purpose of our study was to localize the visual cortex of minipigs using visual stimulation in functional magnetic resonance imaging (fMRI). Five male Göttinger minipigs were studied with fMRI during visual stimulation with series of light impulses conducted into the MR cabin via fibre optical wave guides (EPI sequences, block design, 1.5 T clinical routine MR-scanner). Statistics were performed using SPM'99. All minipigs showed activation of the visual cortex due to light stimulation. The activation could be superimposed to T2-weighted structural images with good spatial resolution revealing the exact location of the visual cortex. We were able to localize the visual cortex in minipigs for the first time utilizing fMRI on a routine scanner. However, this may be useful for precise positioning of electrodes or implants or be used as a further uncomplicated non-invasive method in physiologic experiments.

The postnatal development of cerebellar Purkinje cells in the Göttingen minipig estimated with a new stereological sampling technique--the vertical bar fractionator

The postnatal development of total number and perikaryon volume of cerebellar Purkinje cells was estimated in the Göttingen minipig cerebellar cortex using a new stereological approach, the vertical bar fractionator. Data were obtained from the brains of five neonate and five adult female Göttingen minipigs. The total number of Purkinje cells ranged from 1.83 x 10(6) in the neonate to 2.82 x 10(6) in the adult Göttingen minipig. The number-weighted mean perikaryon volume of Purkinje cells increased concurrently from around 6,800 microm(3) in the neonate to 17,600 microm(3) in the adult. The study demonstrates that a pronounced postnatal neurogenesis in Purkinje cell number and perikaryon volume is part of the growth and development of the cerebellum in the Göttingen minipig. The Purkinje cells of the Göttingen minipig were found to be substantially large compared with human and represents the largest cells described hitherto from mammalian cerebella. The vertical fractionator is a new sampling technique, which allows the combination of a fractionator design on vertical bar sections excluding exhaustive sampling and bias from artificial edges. By design, the sections are perfect stereological vertical sections and provide the basis for unbiased estimates of total number of structural entities in the brain, including surface area, fibre length and particle volume.

Localization of Hyaluronic Acid in the Seminal Vesicles of the Miniature Pig

We studied the detailed localization of hyaluronic acid in the seminal vesicles of the miniature pig, using hyaluronic acid-binding protein as a specific histochemical probe at the ultrastructural level. According to the results, the basolateral surface of the plasma membrane of the glandular epithelial cells, was found to contain hyaluronan. However, abundantly present was hyaluronan in the subepithelial connective tissue, in particular, in the extracellular matrix surrounding the fibroblasts, smooth muscle cells, small blood vessels and capillaries. The substance was also observed in the surface coat of the plasma membrane of the fibroblasts, but not in that of the smooth muscle cells. The findings suggest that hyaluronan in the seminal vesicles of the miniature pig is synthesized onto the surface coat of the plasma membrane of the fibroblasts, is contributed to the extracellular matrix, and consequently concentrates in the subepithelial connective tissue. The substance may particularly be involved in a variety of cellular functions to maintain morphological organization as well as to regulate physiological homeostasis in the reproductive organ of this species, rather than participate in sperm functions.

Tongue deformation, jaw movement and muscle activity during mastication in pigs

This study was undertaken to address the lack of information about tongue functional deformation in relation to jaw movement and muscle activity. Dimensional changes in tongue anterior and base widths, body length and base thickness were measured using six ultrasonic crystals implanted into the tongue in eight Yucatan minipigs. Jaw movements were captured on videotape and digitized, and electromyography (EMG) of tongue intrinsic (verticalis/transversus [V/T], superior and inferior longitudinalis [SL, IL]), extrinsic (genioglossus and styloglossus [GG, SG) and jaw (masseter and digastricus [MA, DI]) muscles were recorded. Signals from these three sources were synchronized. Tongue dimensions showed stereotyped and rhythmic changes during chewing cycles, with the largest changes in the body length and base thickness of the contralateral (non-working) side. The anterior tongue widened during jaw opening while the tongue base widened and thickened during jaw closing. The body lengthening accompanied base widening and ended at early power stroke, while base thickening lasted through most of the power stroke. Significant associations were found between changes of anterior width, body length and base thickness and integrated EMGs of VT, SL, SG, GG, MA and DI, but not IL. Thus, majority of tongue dimensional expansions occur during jaw closing. Intrinsic tongue muscle activities are not correlated more with tongue dimensional changes than are extrinsic tongue and jaw muscle activities.

Ontogeny of bone strain: the zygomatic arch in pigs

At the time of weaning, infant animals have little experience with hard food, and thus their skulls are not likely to be epigenetically adapted for the loads imposed by mastication. We examined bone strain in the zygomatic arch of 4-week-old weanling piglets. Functional strains in piglets differed from those previously reported for older pigs in that the squamosal bone was not bent in the horizontal plane and the principal tensile strain on the zygomatic bone did not correspond to the direction of masseter muscle pull. Strain patterns were more variable in piglets than in older pigs. In older pigs, masticatory strains can be reproduced by stimulating the masseter muscles. When the piglet masseter was stimulated, strain patterns were more similar to those of older pigs, but shear strain magnitudes were the largest yet recorded from mammalian skull bones, up to 4000 muepsilon. To put these findings in the context of skeletal adaptation, 45 dry skulls, including some animals from the strain study, were measured. Reduced major axis regressions indicated that the infant arch was rounder in cross section and straighter than that of older animals. With growth, the arch became dorsoventrally higher, while mediolateral thickness decreased in the squamosal bone. Overall, these changes should make strain more predictable, explaining the lower variability in older animals. Other factors likely to be important in causing unique strain regimes in piglets include (1) unfamiliarity with hard food, (2) greater importance of muscles other than the same-side masseter and (3) greater proximity of molariform teeth to the arch. Collectively, these data indicate that the skeleton is not pre-adapted for specific functional loads.

The prefrontal cortex in the Göttingen minipig brain defined by neural projection criteria and cytoarchitecture

In an attempt to delineate the prefrontal cortex (PFC) in the Göttingen minipig brain the distribution of reciprocal thalamocortical projections was investigated using anterograde and retrograde tracing techniques and evaluated in relation to the specific cytoarchitectonic organization. Tracers were visualized using standard immunohistochemistry or evaluated in vivo using manganese (Mn2+) as an MRI paramagnetic tracer. The in vivo tract tracing turned out to be very sensitive with a high correspondence to the histological labelling. Tracers injected into the mediodorsal thalamus labelled the medial and rostral pole of the frontal lobe as well as the anterior cingulate, anterior insular and dorsomedial frontal cortices. Subsequently, the reciprocity and specificity of these connections were tested from injections into the traced frontal cortices indicating that the PFC has cortical connections to different parts of the MD nucleus. Although the granular layer IV, characteristic of primate PFC could not be identified, both cytoarchitectonic and connectional data suggests that the Göttingen minipig has a structurally divided prefrontal cortex. Stereological estimates of PFC volume showed that the Göttingen minipig PFC constitutes about 24% of the total neocortex volume and 10% of the total brain volume.

Dental and skeletal characterization of the BR-1 minipig

This study was designed to characterize the development of oral structures in the BR-1 minipig and to compare these data with literature reports on domestic swine and other minipig lineages. Twelve male minipigs were anesthetized and given physical and radiographic examinations. The presence and chronology of tooth eruption from 3 to 15 months of age were assessed, and the radiographic results were interpreted by two certified researchers, who obtained a high index of agreement (kappa>0.81). The eruption chronology was similar to that reported for domestic swine and other minipig lineages. The results indicate that it is possible to use the BR-1 minipig in dental research.

Morphological characteristics of submandibular glands of miniature pig

BACKGROUND

Miniature pig (minipig) is increasingly used as a large animal model for a variety of biomedical studies. Little information is available in the literature on anatomy, histology and sialograghy of the submandibular gland of the minipig. The purpose of this study was to characterize the morphology of a miniature pig's (minipig) submandibular gland as a large animal model for further biomedical studies.

METHODS

Five minipigs were subjected to sialographic, anatomic, histologic, histochemical and ultrastructural evaluations for submandibular glands.

RESULTS

Sialograms showed a long, horizontal main excretory duct and a pear-shaped gland located inferoposterior to the angle of the mandible. The submandibular glands lied superficial to the suprahyoid, and infrahyoid muscle groups, and were covered by the inferior portion of the parotid gland. The submandibular glands were characterized by a mixed parenchyma of mucous and serous secretory acini. Alcian blue (AB) staining and periodic acid-Schiff (PAS) reactions demonstrated that minipig submandibular glands synthesized and secreted acid mucous substances by serous cells and polysaccharide, and neutral mucous substances, by mucous cells.

CONCLUSION

The submandibular gland of the minipig is considered a useful large salivary gland animal model for biomedical studies.

Immunolocalization of Steroidogenic Enzymes P450scc, 3.BETA.HSD, P450c17, and P450arom in Goettingen Miniature Pig Testes

The objective of this study was to investigate immunolocalization of steroidogenic enzymes in Göttingen miniature (GM) pig testes. Testes of 6 adult GM pigs were obtained in September 1996 (n=2), February (n=2) and June (n=2), 1997. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3beta-hydroxysteroid dehydrogenase (3betaHSD), porcine testicular 17alpha-hydroxylase cytochrome P450 (P450c17), and human placental aromatase cytochrome P450 (P450arom). Histologically, all types of spermatogenic cells including mature-phase spermatozoa in seminiferous tubules were observed in all testes throughout the year. Moreover, P450scc, 3betaHSD, P450c17and P450arom were identified in Leydig cells but not in Sertoli cells of all testes. These results suggested that adult GM pig testes have the ability to produce germ cells throughout the year, and the synthesis of progestin, androgen and estrogen occurs in the Leydig cells of GM pig testes.

Development of the palatine tonsil in conventional and germ-free piglets

Palatine tonsils, like the Peyer's patches, are considered to be major inductive sites for the mucosa-associated lymphoid tissue (MALT), providing sampling and effector functions for the upper respiratory tract. Consistent with this, they have the architecture required of a classic inductive site (B-cell follicles, immunoglobulin class switching and the presence of naïve and memory T-cells). Here we show that much of this architecture develops after birth in the neonatal piglet, the numbers of T-cells, B-cells and accessory cells increasing with age. Conventional piglets also had higher levels of activated and memory T-cell subsets than germ-free piglets, consistent with development occurring as a result of microbial stimulus. The results suggest that the microbial environment influences the development of the tonsil immunological architecture. Given the role of the tonsil in induction of mucosal responses, this raises questions as to the effectiveness of the tonsil in dealing with colonising organisms in the neonate.

A MRI-compatible stereotaxic localizer box enables high-precision stereotaxic procedures in pigs

We present a nonmagnetic Plexiglas stereotaxic localizer box that can be fitted directly to the pig skull by aluminum screws, allowing stereotaxic MRI or ventriculography and subsequent high-precision stereotaxic procedures. The localizer box was used to target the subthalamic nucleus (STN) bilaterally in five female Göttingen minipigs. Stereotaxic markers were inserted in the pig skull, the head fixated in the localizer box by aluminum screws inserted bilaterally in the zygoma bone with the hard palate locked on a horizontal palate holder. MRI was obtained on a 3T-MR-imager revealing the relation between the inserted markers and the estimated STN-position, and thus the target coordinates. After the MRI, a stereotaxic frame with attached micromanipulator was locked on to the localizer box converting it into a stereotaxic device. The stereotaxic markers were exposed and used as starting point for the stereotaxic procedure, whereby a microelectrode for electrolytic lesioning was inserted in the STN. Postmortem histological analysis revealed 70% correct STN-targeting. The average distance from the lesion center to the STN center was 1.2 mm with a S.D. of 1.1 mm. The most displaced lesion being 3.6 mm from the STN center. We conclude that the described localizer box secure firm head fixation, allowing stereotaxic MRI and subsequent conversion into a stereotaxic device for high-precision stereotaxic procedures.

CLONING CYP2D21 AND CYP3A22 CDNAS FROM LIVER OF MINIATURE PIGS

To compare the identity of the primary structure of drug-metabolizing cytochrome P450 between miniature pigs and humans, two cDNA clones, coding for miniature pig CYP2D21 and CYP3A22, were isolated. The deduced amino acid sequences of CYP2D21 and CYP3A22 were 78.3 and 75.0% identical to human CYP2D6 and CYP3A4, respectively. These values were nearly the same as those of bovine, dog, and some rodent isoforms, and 12.2 to 18.4% lower than those of nonhuman primates such as cynomolgus monkeys, Japanese monkey, and marmosets. These data indicate that miniature pig P450s are genetically not so close as monkey P450s to human P450s as previously expected. The recombinant CYP2D21 enzyme, however, showed bufuralol 1'-hydroxylase activity, suggesting that miniature pig CYP2D21 is capable of metabolizing some of the same substrates associated with human CYP2D6 despite its low identity to human counterparts.

Biomechanics of the rostrum and the role of facial sutures

The rostrum is a large diameter, thin-walled tubular structure that receives loads from the teeth. The rostrum can be conceptualized both as a rigid structure and as an assemblage of several bones that interface at sutures. Using miniature pigs, we measured in vivo strains in rostral bones and sutures to gain a better understanding of how the rostrum behaves biomechanically. Strains in the premaxillary and nasal bones were low but the adjacent maxillary-premaxillary, internasal, and intermaxillary suture strains were larger by an order of magnitude. While this finding emphasizes the composite nature of the rostrum, we also found evidence in the maxillary and nasal bones for rigid structural behavior. Namely, maxillary strain is consistent with a short beam model under shear deformation from molar loading. Strain in the nasal bones is only partially supported by a long beam model; rather, a complex pattern of dorsal bending of the rostrum from incisor contact and lateral compression is suggested. Torsion of the maxilla is ruled out due to the bilateral occlusion of pigs and the similar working and balancing side strains, although it may be important in mammals with a unilateral bite. Torsional loading does appear important in the premaxillae, which demonstrate working and balancing side changes in strain orientation. These differences are attributed to asymmetrical incisor contact occurring at the end of the power stroke.

[Anatomy of heart in banna mini-pig inbred-lines]

OBJECTIVE

To observe the heart anatomic and histological structure of the Banna mini-pig inbred-lined and to provide the morphological data for heart xenotransplantation and breeding transgens pig.

METHODS

Ten Banna mini-pigs (12-18 months old) were affused and fixed by common coratid artery. The heart were observed and measured by gross anatomy and histology.

RESULTS

There were many similarities between the Banna pig heart and the human heart in anatomy and histology. However, the following differences were observed in the Banna pig heart: 1. Azygos vein directly drew into right atrium cordis. 2. The intercalated disk of cardiac muscle was less than that of human. 3. The Purkinje's fibre was bigger than that of human.

CONCLUSION

On the morphology and histology, the structure of Banna pig heart is similar to the heart of human being. It is possible that Banna minipig heart becomes organ donors for xenotransplantation.

[Experimental study on kidney anatomic structure of banna minipig inbred-lines for xenotransplantation]

OBJECTIVE

To explore the kidney anatomic structure of banna minipig inbred-lines, and to provide data for kidney xenotransplantation.

METHODS

The fresh and infused kidneys of banna minipig (including the vessel and the ureter) were checked by anatomic microscope and vernier caliper in original location and away body. The tissue structure was observed by HE stain.

RESULTS

The structure of kidney of banna minipig inbred-lines (including the vessel and the ureter) are similar to that of human being. The fascia propria of kidney is divided into three layers including capsula fibrosa, capsula adipose and fascia renalis. The thickness of cortex renalis is (20.0 +/- 2.4) mm. The average diameter of renal artery is 5.1 mm and is similar to that of human being. All the kidneys of banna minipig inbred-lines have a single branch renal artery. The diameters of left and right ureters are 5.1 mm and 4.7 mm, respectively.

CONCLUSION

The kidney of banna minipig inbred-lines is an ideal replacement of human kidney for xenotransplantation.

Use of CD9 expression to enrich for porcine hematopoietic progenitors

OBJECTIVE

The aim of this study was to develop novel markers for enrichment of hematopoietic progenitors from bone marrow of swine.

MATERIALS AND METHODS

We previously showed that pig bone marrow contains a "side population" (SP) of Hoechst dye-effluxing cells that resembles the hematopoietic stem cell (HSC)-containing murine SP and therefore represents a putative pig stem cell population. We screened a panel of monoclonal antibodies for those that allowed positive or negative enrichment of porcine SP cells and tested one of these for enrichment of hematopoietic progenitors in short-term and long-term in vitro assays. We then screened an expression library to clone the gene whose product is recognized by this antibody.

RESULTS

Among a panel of 35 monoclonal lines screened, we found three that were useful for positive enrichment of SP cells and seven for negative enrichment. The 4-6 monoclonal line, allowing around 10-fold negative enrichment of SP cells, recognized the product of the porcine CD9 gene. Hematopoietic progenitors measured by short-term colony-forming unit and long-term cobblestone area-forming cell assays were around 10-fold enriched in the CD9(negative/low) fraction and were significantly depleted in the CD9(high) fraction.

CONCLUSIONS

The antibody against the porcine CD9 gene product may be of use for enrichment of porcine hematopoietic stem cells. This approach to identify novel markers for enrichment of hematopoietic progenitors may be applicable to other mammalian species.

Mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs. II. Dynamics

We described the dynamic mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs and the effects of caudal tracheal displacement. During general anesthesia and neuromuscular blockade, airflow through the upper airway (V) and pharyngeal cross-sectional area were measured during ramp decreases in pressure downstream from the pharynx (Pdown). Measurements were made with 0, 1, and 2 cm of caudal tracheal displacement. Airflow limitation and/or negative pressure dependence (NPD) were observed in all animals. Tracheal displacement (2 cm) increased maximal V (V(max)) by 205.1 +/- 105.1% (P < 0.05) relative to the value with no displacement and increased the magnitude of NPD, expressed as percent decrease in V from V(max), from 22.9 +/- 27.4 to 56.6 +/- 37.5% (P < 0.05). Initial decreases in Pdown narrowed all levels of the pharynx, but, once V(max) was reached, further decreases in Pdown narrowed the hypopharynx but not the nasopharynx and oropharynx. We conclude that the hypopharynx is the flow-limiting site in the pig pharynx. Tracheal displacement not only improved airflow dynamics as V(max) increased but also resulted in pronounced NPD.

Mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs. I. Statics

The static mechanical properties of the passive pharynx were investigated in Vietnamese pot-bellied pigs by using an isolated upper airway preparation. During general anesthesia and neuromuscular blockade, cross-sectional area (A) of the pharynx was measured while airway pressure (Paw) was held at various pressures in the absence of airflow. The static A-Paw relationship was measured during application of 0, 1, and 2 cm of caudal tracheal displacement. Relative to humans, closing pressures (Pclose) of the pig pharynx were very low (-15 to -35 cmH(2)O). Tracheal displacement significantly decreased compliance of the hypopharynx (from 0.074 +/- 0.02 cm(2)/cmH(2)O with no displacement to 0.052 +/- 0.01 cm(2)/cmH(2)O with 2 cm of displacement) and decreased Pclose of the oropharynx (from -18.2 +/- 9.9 cmH(2)O to -24.1 +/- 10.5 and -28.7 +/- 12.3 cmH(2)O with 1 and 2 cm of displacement, respectively). Tracheal displacement did not affect A of the pharyngeal segments. In conclusion, tracheal displacement decreased collapsibility of the passive pharynx. The pharynx of the pot-bellied pig is structurally more resistant to collapse than the human pharynx.

Temporomandibular joint in miniature pigs: anatomy, cell replication, and relation to loading

The mechanical environment is a regulator of growth and adaptation of the musculoskeletal system, including joints. Although pigs (Sus scrofa) are used frequently as models for temporomandibular joint (TMJ) dysfunction, no systematic description of microanatomy exists for this species. We injected the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) into 10- to 11-month-old miniature pigs that were undergoing measurements of TMJ bone strain. Ten hr later, the animals were sacrificed and their heads were perfused. Histological sections were used to map the distribution of replicating cells. Additional observations were made on gross dissections of jaw joints obtained from an abattoir. The pig TMJ is better supported than that of humans laterally and medially, but more vulnerable posteriorly. The posterior attachment area of the intra-articular disc is fibro-fatty rather than vascular, as in humans. Cartilage lines the articular eminence as well as the condylar surface. At the posterosuperior region of the condyle, the cartilage ends abruptly and is replaced by an invaginating, actively replicating periosteum. Almost all of the BrdU-labeled cells resided in the prechondroblastic zones. The condyle had more replicating cells than did the eminence (P < 0.02), but lateral and medial locations did not differ in either element. In sagittal sections, the condyle had more replicating cells posteriorly (P < 0.001), but no A-P differences were seen in the eminence. Comparisons of these data with data on bone strain indicate that increased loading is negatively associated with cell replication.

MR-based statistical atlas of the Göttingen minipig brain

Thedomestic pig is increasingly being used as an experimental model for brain imaging studies with positron emission tomography (PET). The recording of radiotracer uptake by PET gives functional and physiological information, but with poor spatial resolution. To date, anatomical regions of interest in pig brain have been defined in MR images obtained for each individual animal, because of the lack of a standard stereotaxic coordinate system for the pig brain. In order to define a stereotaxic coordinate system, we coregistered T1-weighted MR images from 22 male Göttingen minipigs and obtained a statistically defined surface rendering of the average minipig brain in which stereotaxic zero is defined by the position of the pineal gland. The average brain is now used as a target for registration of dynamic PET data, so that time-activity curves can be extracted from standard volumes of interest. In order to define these volumes, MR images from each individual pig were manually segmented into a total of 34 brain structures, including cortical regions, white matter, caudate and putamen, ventricular system, and cerebellum. The mean volumes of these structures had variances in the range of 10-20%. The 34 brain volumes were transformed into the common coordinate system and then used to generate surface renderings with probabilistic threshold greater than 50%. This probabilistic threshold gave nearly quantitative recovery of the mean volumes in native space. The probabilistic volumes in stereotaxic space are now being used to extract time-radioactivity curves from dynamic PET recordings.

Parameters of glucose and lipid metabolism in the male Göttingen minipig: influence of age, body weight, and breeding family

The pig is useful as a model for human physiology and pathophysiology and could be an important supplement to the many available rodent models of diabetes mellitus. Due to their small size, Göttingen minipigs are especially suitable for long-term studies. The aim of the study reported here was to establish reference values for a range of glucose and lipid homeostasis parameters of interest that could be used to identify possible diabetes-prone male Göttingen minipig individuals, families, or age groups. Plasma samples from nonfed animals were analyzed for glucose, leptin, fructosamine, insulin, C-peptide, triglyceride, free fatty acids, and total cholesterol values. Breeding family had significant effects only on plasma triglyceride concentrations (P < 0.001). Plasma concentrations of glucose (P = 0.012), fructosamine (P < 0.001) and triglycerides (P < 0.001) increased significantly with age, whereas total cholesterol concentration decreased significantly (P = 0.001) with age. Age did not influence other parameters. In conclusion, glycemia and insulinemia increased with age and body weight, possibly indicating a small deterioration in insulin sensitivity with age. It is, therefore, hypothesized that older, compared to younger animals may be more useful in the development of a model of type-2 diabetes mellitus. Furthermore, on the basis of decrease in cholesterol concentration with age, animals fed ad libitum with possibly a high calorie diet might be even more useful in the development of a type-2 diabetes mellitus model.

Growth pattern of the maxillary sinus in the miniature pig (Sus scrofa)

The biological role of the paranasal sinuses is obscure, can be elucidated through a cross-sectional growth study of the maxillary sinus in miniature pigs. The maxillary sinus area was obtained from lateral cephalograms of left skull halves of 103 female miniature pigs of known ages, from newborn to 24 months. Out of several nonlinear models, the growth of the maxillary sinus was best described with the Gompertz model. The first derivative of the Gompertz curve revealed an increase in the growth rates of the maxillary sinus until 4 months, after which sinus growth slowed down. The eruption of the permanent molars did not seem to have a significant influence on this growth pattern. Furthermore, growth in maxillary sinus size in the miniature pig does not follow growth in skull size closely, which showed the highest growth rates in newborn animals. In addition, a correlation analysis revealed that the relationship between maxillary sinus area and different characteristics of the masticatory apparatus (including linear cranial dimensions, and the dry weight of the masseter and zygomatico-mandibularis muscles) were influenced greatly by skull size. These results suggest that the existence of pneumatic cavities within the mammalian skull is not satisfactorily explained solely by an architectural theory. Epigenetic factors are likely to influence the final shape of the maxillary sinus.

Echocardiography, color-coded Doppler imaging, and abdominal sonography, a non-invasive method for investigation of heart and aortic morphology and function in female gottingen minipigs: method and reference values for M-mode, B-mode, and flow parameters

OBJECTIVE

The aim of the study reported here was to set up a method for echocardiography (EC) and abdominal sonography and to obtain EC reference values for left ventricular (LV) morphology and function and sonographic abdominal aortic morphology, function, and flow values in conscious, unsedated Gottingen minipigs.

METHODS

Applying a standardized investigation procedure, the following parameters were measured by use of M-mode EC, color-coded Doppler imaging, and B-mode sonography, or were calculated, in 58 female minipigs: LV end-diastolic and end-systolic diameter, interventricular septum thickness, LV caudal wall thickness, LV end-diastolic volume and end-systolic volume, fractional shortening, ejection fraction, and percentage of thickening of interventricular septum and LV caudal wall. In addition, morphology, pulsatility, flow values, and flow patterns in the abdominal aorta were recorded or calculated during abdominal sonography and color-coded Doppler imaging.

RESULTS

Variable EC values were obtained due to individual variations of motor activity. Variation could be reduced by accustoming the animals to a standardized investigation procedure. Reference values could be obtained for EC, partially indicating clear correlation with body weight. Color-coded Doppler and Doppler spectra did not indicate flow disturbances in large arterial abdominal vessels.

CONCLUSIONS

Results indicate that handling during EC and sonography can cause discomfort in unsedated minipigs that may interfere with recording of valid reference values for functional cardiac parameters in young animals. Accustoming the animals to a standardized investigation procedure reduces stress to a satisfactory level and enables data recording. Thus the minipig is considered suitable for assessment of cardiovascular parameters in experimental or toxicologic studies.

An anatomical study of the arteries feeding the triceps brachii muscle of swine

The arterial vascular network of the porcine triceps brachii muscle (TBM) (an extensor muscle to the forearm) was studied and compared to another extensor muscle (the soleus muscle) of small rodents. The left axillary arteries (LAA) of nine Yucatan miniature swine were perfused with latex material to reveal the organization of the arterial blood supply to the TBM. Blood is supplied to the TBM by the main branches of the LAA. Some of the branches end in one of the four heads of the TBM. Other branches continue to bifurcate further and to supply blood to adjacent muscles. The feed arteries (FAs) arise as side-branches at regular distances from the branches of the LAA. The mean number of FAs per TBM was 109.7 and the mean diameter was 388 microns. The distribution of FAs to the muscle area is heterogenous. Most FAs penetrate the epimysium of the TBM on its medial aspect. It appears that more FAs come out of the branches of LAA that end in the TBM as compared to arteries which continue to bifurcate away from TBM. FA diameters were in the range of 300 microns. This study is the first necessary step towards understanding the distribution of oxygen and nutrients to the porcine skeletal muscle. It reveals the presence of a more complicated vascular network than that observed previously in small laboratory animals.

[The pulmonary arteries and veins of miniature swine, together with a common view of their supportive and stabilizing functions in the lung]

With respect to distribution and flow, the Vasa pulmonalia resemble those of the normal grown domestic pig to a great extent. The present article investigates whether, like the human lung (Hayek, 1970), the arrangement of the blood vessels has a function over and above that of directing blood; that is to say, a mechanical function. The arteries through which the blood streams act as flexible supporting structures, and the veins as elastic holding structures, for the quadrupede animal also.

Emergency care for potbellied pigs

Because of the limited number of veterinarians treating potbellied pigs, many pet pigs do not receive proper preventative health care. The potbellied pig's continued popularity among urban dwellers ensures that veterinarians who treat small and exotic animals will be contacted by owners of pet pigs with real or perceived emergencies. Regardless of their knowledge of swine, the information contained in this article should enable any veterinarian to provide basic emergency care for pet pigs.

A comparative immunohistochemical study of pancreatic islets in laboratory animals (rats, dogs, minipigs, nonhuman primates)

The aim of the present study was to distinguish and describe the patterns of distribution of pancreatic islets within the pancreas of four species of laboratory animals, including rats, dogs, minipigs and monkeys, and furthermore, to identify immunohistochemically various islet cell types and characterize their content. Histopathological examinations were performed on sections stained with hematoxylin and eosin (H&E) and immunostained using rabbit polyclonal antibodies (pAb) against insulin, glucagon, pancreatic polypeptide (PP), somatostatin, chromogranin A, keratin, bombesin and gastrin, or mouse monoclonal antibodies (mAb) against synaptophysin, Leu-7 and proliferating cell nuclear antigen (PCNA) in three-step rabbit immunoperoxidase (PAP) and streptavidin/peroxidase (StreptABC/HRP) reactions. Positive immunohistochemical reactions were observed in the pancreatic islets of all animal species with all antibodies, except with anti-bombesin and anti-gastrin antibodies. Our results revealed that: 1) there is species specific regional arrangement of islets in the pancreas, 2) each species presents a characteristic distribution of cells producing different hormones. 3) immunoreactivity with immunohistochemical markers varies between species and/or age. The present comparative immunohistochemical study could be helpful for answering questions which are important for understanding some of the intricate mechanisms that govern the integrated function of the endocrine pancreas.

The course of the mandibular canal in the growing miniature pig

Miniature pigs are extensively used as laboratory animals in studies concerning craniofacial growth and adaptation. However, in contrast to the vast amount of literature regarding the overall growth pattern of the pig's mandible, little is known about the internal structures of the mandible such as the mandibular canal. In order to investigate the position of the mandibular canal (MC) and the thickness of its buccal and lingual walls, a cross-sectional study was performed on female miniature pigs MINI-LEWE covering the period from newborn to adult. The position of the MC was analyzed at bony segments that were obtained by cutting the drys mandibles interdentally. At each segment a central point of the MC was defined and its relation to the buccal and lingual margin of the mandible was measured. Located at the lower part of the mandibular corpus, the MC runs in the form of an arch within the sagittal plane in anterior direction, getting enlarged into the form of an ampulla in the molar and premolar region. Whereas during the primary dentition the biggest size of the MC was found behind the third deciduous molar, during the secondary dentition the biggest size of the MC was seen in the region of the first and second permanent molar. With regard the buccolingual aspect, the central point of the MC was found mainly in the center of the mandibular corpus. Between the 2nd and 5th month as well as at the beginning of the 18th month the thickest canal wall existed on the buccal side. In the period of the eruption of the succedaneous teeth, however, the lingual wall was thicker than the buccal wall. Results suggest that the definite course of the MC achieves relatively early in the miniature pig with the completion of the primary dentition. There were no major changes of the position of the MC in the postnatal period suggesting that the age factor has only a minor effect on the location of the MC.

Human lymphocyte adhesion to xenogeneic porcine endothelial cells: modulation by human TNF-alpha and involvement of VLA-4 and LFA-1

Considering that in the allogeneic situation the adhesion of recipient lymphocytes to donor endothelial cells initiates the cellular rejection, we questioned the possible occurrence of a similar process in the xenogeneic situation. The adhesion of human peripheral blood lymphocytes (PBL) to porcine aortic endothelial cells (PAEC) was thus studied in an in vitro porcine-to-human xenogeneic model. It was found that 25.9% of human PBL adhered to resting PAEC. Furthermore, this adhesion increased significantly when the PAEC were stimulated by the human cytokine TNF-alpha (tumor necrosis factor-alpha). The effect of human TNF-alpha was concentration- and time-dependent and was maximal (from 25.9% to 35.6%) with 100 U/ml during 6 h. Moreover, blocking experiments with monoclonal antibody (mAb) demonstrated the role of the PBL adhesion molecules LFA-1 and especially VLA-4. Indeed, an anti-CD11a mAb decreased PBL adhesion to resting PAEC by 17.1% and to TNF-alpha stimulated PAEC by 16.9%, whereas an anti-CD49d mAb decreased dramatically PBL adhesion to resting PAEC by 53.1% and to TNF-alpha stimulated PAEC by 41.0%. Finally, phenotypic analysis of the adherent PBL showed that 50.5% of adherent cells to resting PAEC were NK (natural killer) cells, whereas 50.7% of adherent cells to TNF-alpha stimulated PAEC were T lymphocytes, showing the preferential adhesion of NK cells to resting PAEC, and that the stimulation of the PAEC with human TNF-alpha affects predominantly T lymphocyte adhesion. These results indicate that human PBL could bind to xenogeneic PAEC and that this interaction could be a first step of a xenogeneic cellular rejection.

Human NK cell-mediated direct and IgG-dependent cytotoxicity against xenogeneic porcine endothelial cells

Once hyperacute rejection has been prevented, the pig-to-human xenograft might be exposed to vascular cell-mediated rejection directed against vascular structures. In order to evaluate the relative importance of direct and antibody-dependent anti-endothelial cell-mediated cytotoxicity in different individuals, freshly isolated human blood leukocytes were incubated with confluent porcine aortic endothelial cells (PAEC) in a 4 h Cr-release cytotoxicity assay. Peripheral blood mononuclear cells (PBMC) and lymphocytes (PBL) of all subjects tested (but not monocytes or neutrophils) directly killed PAEC, with wide interindividual variations (from 2.8% to 32%). The addition of heat-inactivated autologous serum to PBMC and PBL (but not to myeloid cells) always enhanced cytotoxicity. This antibody-dependent cell-mediated cytotoxicity (ADCC) was also observed in the presence of adult pooled serum and cord blood pooled serum and was eliminated after adsorption of adult pooled serum to insoluble protein A, demonstrating that IgG is the only class of immunoglobulin involved in this phenomenon. Moreover, blocking Fc gamma RIII with an anti-CD16 mAb eliminated ADCC without affecting direct cytotoxicity. When the ADCC exerted by the PBL of all subjects was assessed with the same preparation of purified IgG, wide interindividual variations were again observed. Surprisingly, there was no correlation between direct cytotoxicity and ADCC although, as depletion experiments demonstrated, both were due to CD16+ natural killer (NK) cells. These results argue that CD16+ NK cells could play an important role in early vascular rejection of porcine discordant xenografts, by both a direct and an IgG xenoreactive natural antibody-dependent cell-mediated cytotoxicity.

Patterns of bone strain in the zygomatic arch

BACKGROUND

The transmission of force through the skull is complicated by the irregular form of the bones, the interposed sutures, and the multiplicity of loads from the teeth, muscles, and environment. The in vivo relationship between bone strain and muscle function in the mammalian skull is best investigated empirically.

METHODS

We studied the zygomatic arch of pigs (Sus scrofa) by simultaneous strain gauge recording and electromyography. Seventeen juvenile animals were used, employing multiple strain gauges arranged either in rosettes or strips. Strain was recorded during mastication and muscle stimulations. Bony architecture was examined on sectioned specimens.

RESULTS

Strain patterns were complex even in this beamlike structure. During masseteric contraction, the more anterior zygomatic bone showed in-plane bending such that its lower border became more convex, and the major principal strain axis (tension) was parallel to the masseter muscle. The posterior squamosal bone was slightly bent in the opposite direction, and the major principal strain was rotated 45-60 degrees from the masseteric line of action. Strain magnitudes in the squamosal were larger than those in the zygomatic. Woven bone composing the surface of the arch appeared denser in the zygomatic bone, where its predominant orientation corresponded with compressive strain. In the squamosal bone trabeculae were more regularly arranged, but their orientation did not correspond with strain axes.

CONCLUSIONS

The magnitude differences are probably related to the different architecture of the zygomatic and squamosal bones, whereas the different strain patterns primarily reflect the influence of the sutures in selectively damping or transmitting loads. In particular, the zygomatic bone may be loaded by three-point, distributed-load bending, whereas the squamosal, loaded at only two points, may be sheared. We conclude that each cranial bone functions in a unique strain environment, with the sutures serving to redirect loading.

Movement of the epiglottis in mammals

In contrast to adult humans, the epiglottis of other mammals and infant humans is situated close to the soft palate. It has been argued that this posture is maintained during swallowing, with food passing laterally around an intact airway. To test this supposition, the movement of the epiglottis in two contrasting mammalian species, pigs and ferrets, was studied by placing radiopaque markers on the epiglottis and soft palate. Swallowing was observed with videofluoroscopy while the animals were feeding on hard and soft foods, liquids, and food mixed with barium sulfate. Analysis of the images showed that bolus formation and downward movement of the epiglottis away from the soft palate were unvarying phenomena in both animals for all tested foods. The duration of the epiglottic movement was approximately 0.3 S for liquids and slightly longer for solids. Because swallowing never occurred past an upright epiglottis, the results of this study do not support the hypothesis that adult animals maintain a patent airway during swallowing. Instead, the epiglottis in nonhuman mammals downfolds similarly to that of adult humans during swallowing.

Branching patterns in coronary artery and ischemic areas induced by coronary arterial occlusion in the CLAWN miniature pig

This study of 28 CLAWN miniature pigs (male 17, female 11, mean weight 29 kg) was undertaken to investigate the coronary arterial branching patterns and the ischemic area induced by surgical occlusion of the left anterior descending artery (LAD) and change in the ischemic area over time. These results were compared with those in dogs, which have frequently been used in myocardial ischemic research. Regarding the coronary arterial branching pattern, there were fewer ventricular branches from the right and left coronary arteries than in dogs. The septal branches arose from only the LAD and the posterior descending artery (PD). The largest septal artery branched from the LAD. There were two types of septal artery branching patterns. In approximately 80% of the CLAWN miniature pigs, the PD arose from the right coronary artery (Right dominance). The peculiarity of the coronary arterial branching pattern in the CLAWN miniature pigs was more similar to human beings than to dogs. The ischemic area induced by occlusion at three-fifths distal section of the LAD was 12.1% to 22.6% (mean 17.1%) of the left ventricle. The ischemic area in all animals that died of global left ventricular malfunction and hemodynamic instability after LAD occlusion was more than 25% of the left ventricle.

Developmental-anatomical observations on cleavage line patterns of the skin in Chinese miniature pigs

In twelve Chinese miniature pigs (CMP), of both sexes and ranging from newborn to 5 months of age, the postnatal developmental features of the cleavage lines of the skin of the whole body were examined by the stab-wound method, using a metal probe with a sharp conical point. 1). The CL patterns of the skin in the 5-month-old CMP were largely similar to those of adult Landrace-strain pigs (Wakuri et al., 1993). 2). At each monthly stage, the CL of the skin of the inter-ocular area, medial ocular angle, umbilicus, preputial orifice and anus presented a convergent arrangement. An annular pattern was found in the skin around the eye, the base of the ear, and the vulva. 3). Some alterations in CL patterns were seen during the general and regional growth of CMP, as shown in the skin of the lateral side of the trunk, the prepuce and the scrotum.

Effects of hypothermia on the survival and cryopreservation of minipig ileal cells and Chinese hamster ovary cells

Temperature of culture can be used to modulate cellular metabolism for improving small intestinal cell culture and cryopreservation. An hypothermia pretreatment (2 days at 25 degrees C and 3 hours recovery at 37 degrees C) improved hamster cell survival to freeze-thaw damage (p < 0.01) but decreased the survival of 2 immortal pig ileal cell lines even though epithelioid IPI-2I cells were more tolerant to hypothermia than IPI-1 fibroblasts. Epithelioid cells survived 3 days at 25 degrees C with unaltered expression of cytokeratin-18 whereas colonies of fibroblasts did not survive more than a day at 25 degrees C (p < 0.001). These results suggest that hypothermia-tolerance of pig ileal cell lines might differ according to cell lineage calling for further experiments on small intestinal primary cell culture.

Ophthalmologic observations in the young Yucatan micropig

Complete ocular examinations, including external observations of the eye and its adnexae, pupil responses to light stimuli (direct and consensual), anterior ocular segment examinations with the biomicroscope, and fundic examinations performed with an indirect ophthalmoscope were carried out on 112 7- to 12-month-old Yucatan micropigs to evaluate the incidence of observed ocular abnormalities. Most of the ocular defects seen were classified as remnants of embryologic vascular tissue. Some findings were considered as congenital changes and the others of indeterminate origin in the absence of further pathologic examinations. The principal ocular abnormalities observed were, in decreasing order of incidence: hyaloid remnants (82.1%), pupillary membrane remnants (66.1%), incomplete pigmentation of the fundus with appearance of choroidal vasculature (tigroïd fundus: 50.0%), and posterior cortical pinpoint opacities of the lens (20.5%). Ten older animals (five aged 15 to 18 months and five aged 19 to 33 months) were examined to evaluate any possible evolution of these findings.

The unique ultrastructure of high-endothelial venules in inguinal lymph nodes of the pig

Lymph nodes in pigs are unique in their inverted structure, with the medulla in the periphery and the cortex in central areas. Furthermore, in this species most migrating lymphocytes do not use the classical route via efferent lymphatics to leave the lymph node. High-endothelial venules (HEV) are the entry sites for lymphocytes and in pigs probably also the exit site for recirculating lymphocytes. Therefore, the blood vessels and especially the HEV of the pig superficial inguinal lymph node were investigated as to whether morphological peculiarities could be found in the vascular system, using vascular casting, transmission- and scanning electron microscopy. A thin layer of capillary network surrounded the periphery of the lymph node and HEV branched acutely. The endothelial cells of HEV possessed well developed cytoplasmic organelles, interdigitated with each other, and demonstrated local cell-cell contacts. There were unusual cells bridging the adluminal wall of HEV. These cells were called intravascular bridging cells. They were characterized by an often invaginated nucleus, few pinocytotic vesicles, many microvilli on the surface, wide, flat, cytoplasmic processes like a pseudopod, Weibel-Palade bodies and local cell-cell contacts with endothelial cells. The pseudopod-like processes ramified over the endothelial junctions and covered lymphocytes. Lymphocytes were seen in different phases of migration between endothelial cells and in the intercellular junctions. The previous functional studies on the peculiar route of lymphocyte recirculation in pig lymph nodes are extended by these morphological data, showing a unique structure of HEV in pigs.

Estrus detection by using vaginal cytologic examination in miniature swine

Vaginal smears were obtained from four Yucatan miniature swine daily for 69 days and stained with hematologic stain. Epithelial cells were categorized as superficial, large intermediate, small intermediate, or parabasal. Leukocytes were also quantitated. External signs of estrus were recorded, including swelling, discharge, restlessness, or vocalization. Mean age of three of the swine was 147 days at the beginning of the study. The fourth pig was 317 days old. The three younger swine had their first observed estrus at the age of 178 days (range, 167 to 196 days). Mean cycle length was 17 to 21 days. The moving mean leukocyte count (i.e., each value was averaged with the values for the previous day and the following day) always exceeded the epithelial cell count (regardless of type), except during the 3 to 4 days when the pigs exhibited external signs of estrus. Further, epithelial cells were at their peak during estrus, decreasing markedly during diestrus, and increasing again during proestrus. The combined superficial plus large intermediate cell counts were significantly higher during estrus than during diestrus or proestrus. We conclude that daily vaginal smears can be used to determine the stage of estrus in Yucatan pigs.