[The Goettingen miniature swine as an experimental animal. 1. Review of literature, breeding and handling, cardiovascular parameters]

Refining experimental dental implant testing in the Göttingen Minipig using 3D computed tomography-A morphometric study of the mandibular canal

This study reports morphometric and age-related data of the mandibular canal and the alveolar ridge of the Göttingen Minipig to avoid complications during in vivo testing of endosseus dental implants and to compare these data with the human anatomy. Using 3D computed tomography, six parameters of the mandibular canal as well as the alveolar bone height and the alveolar ridge width were measured in Göttingen Minipigs aged 12, 17 and 21 months. Our null hypothesis assumes that the age and the body mass have an influence on the parameters measured. The study found that the volume, length and depth of the mandibular canal all increase with age. The width of the canal does not change significantly with age. The body mass does not have an influence on any of the measured parameters. The increase in canal volume appears to be due to loss of deep spongy bone in the posterior premolar and molar regions. This reduces the available space for dental implantations, negatively affecting implant stability and potentially the integrity of the inferior alveolar neurovascular bundle. Dynamic anatomical changes occur until 21 months. On ethical grounds, using minipigs younger than 21 months in experimental implant dentistry is inadvisable. Paradoxically the measurements of the 12 months old pigs indicate a closer alignment of their mandibular anatomy to that of humans suggesting that they may be better models for implant studies. Given the variability in mandibular canal dimensions in similar age cohorts, the use of imaging techniques is essential for the selection of individual minipigs for dental prosthetic interventions and thus higher success rates.

Accuracy of Bone Measurements in the Vicinity of Titanium Implants in CBCT Data Sets: A Comparison of Radiological and Histological Findings in Minipigs

Purpose

The aim of this animal study was the determination of accuracy of bone measurements in CBCT (cone-beam computed tomography) in close proximity to titanium implants.

Material and Methods

Titanium implants were inserted in eight Göttingen minipigs. 60 implants were evaluated histologically in ground section specimen and radiologically in CBCT in regard to thickness of the buccal bone. With random intercept models, the difference of histologic measurements and CBCT measurements of bone thickness was calculated.

Results

The mean histological thickness of the buccal bone was 5.09 mm (CI 4.11–6.08 mm). The four raters measured slightly less bone in CBCT than it was found in histology. The random effect was not significant (p value 1.000). Therefore, the Intraclass Correlation Coefficient (ICC) was 98.65% (CI 100.00–96.99%).

Conclusion

CBCT is an accurate technique to measure even thin bone structures in the vicinity of titanium implants.

Ion currents of cardiomyocytes in different regions of the Göttingen minipig heart

INTRODUCTION

The Göttingen minipig is a promising model for pharmacological safety assessment and for translational research in cardiology. We have examined the main ion currents in cardiomyocytes of the minipig heart.

METHODS

Cardiac cells were isolated from different cardiac regions (endo-, mid- and epicardial left ventricle and right ventricle) from Göttingen minipigs and examined using the whole cell patch clamp technique combined with pharmacological interventions.

RESULTS

The inward rectifier (I_K1), the delayed rectifier (I_K), with the rapid and slow components, (I_Kr, I_Ks) and the L-type Ca²⁺ channel (I_Ca,L) were identified in the different regions of the heart, whereas the Ca²⁺-independent transient outward current (I_to1) was observed in only a few cells. I_K1 was similar in the cardiac regions with a slightly lower value in the epicardial cells. I_Ks was smaller in epi- and endo-cardial regions.

DISCUSSION

The equivalents of the main human cardiac ion currents are present in the minipig cardiomyocytes with the exception of the Ca²⁺-independent I_to1. The study provides further evidence that the minipig is a valid model for investigating cardiovascular pharmacology.

Hybrid pig versus Göttingen minipig-derived cartilage and chondrocytes show pig line-dependent differences

Minipigs are widely used as a large animal model for cartilage repair. However, many in vitro studies are based on porcine chondrocytes derived from abundantly available premature hybrid pigs. It remains unclear whether pig line-dependent differences exist which could limit the comparability between in vitro and in vivo results using either hybrid or miniature pig articular chondrocytes. Porcine knee joint femoral cartilage was isolated from 3- to 5-month-old hybrid pigs and Göttingen minipigs. Cartilage from both pig lines was analysed for thickness, zonality, cell content, size and proteoglycan deposition. Cultured articular chondrocytes from both pig lines were investigated for gene and/or protein expression of cartilage-specific proteins such as type II collagen, aggrecan, the chondrogenic transcription factor Sox9, non-specific type I collagen and the cell-matrix receptor β1-integrin. Cartilage was significantly thinner in the miniature pig compared to the hybrid pig, but the differences between the medial and lateral femur condyles did not reach a significant level. Knee joint cartilage zone formation started only in the minipig, whereas cellularity and cell diameters were comparable in both pig lines. Blood vessels could be detected in the hybrid pig but not the minipig cartilage. Sulphated proteoglycan deposition was more pronounced in cartilage zones II–IV of both pig lines. Minipig chondrocytes expressed type II and I collagen, Sox9 and β1-integrin at a higher level than hybrid pig chondrocytes. These distinct line-dependent differences should be considered when using hybrid pig-derived chondrocytes for tissue engineering and Göttingen minipigs as a large animal model.

Accelerated intimal hyperplasia in aortocoronary internal mammary vein grafts in minipigs

Background

More than 50% of aortocoronary saphenous vein grafts are occluded 10 years after surgery. Intimal hyperplasia is the initial critical step in the progression toward occlusion. Internal mammary veins, which are physiologically prone to less hydrostatic pressure, may undergo an accelerated progression to intimal hyperplasia and thus be suitable for investigation of the mechanisms of aortocoronary vein graft disease.

Methods

Six minipigs underwent aortocoronary bypass grafting using standard cardiopulmonary bypass and cardioplegic arrest. Mammary vein were grafted in a reversed manner from ascending aorta to left anterior descending coronary artery (LAD). The proximal LAD was ligated, rendering the anterior left ventricle vein graft-dependent. Minipigs were killed after 4 weeks, and vein grafts were harvested. Histological and immunohistological investigation were performed with respect to morphometric analysis, endothelial damage/dysfunction (v-Willebrand-factor (vWF)), smooth muscle cells (α-smooth actin) and proliferation rate (proliferation marker Ki 67).

Results

Mean intimal area of vein grafts was increased compared to ungrafted mammary veins. Intimal hyperplasia in vein grafts was characterized by massive accumulation of smooth muscle cells with a high proliferation rate and endothelial perturbation. Significant (p = 0.001) intimal hyperplasia of the grafted mammary vein compared to the ungrafted mammary vein was found. These changes were absent in ungrafted mammary veins.

Conclusion

The present study demonstrates a pig model of aortocoronary vein graft intimal hyperplasia which is characterized by an accelerated progression within internal mammary veins. The model is suitable to investigate the pathophysiology of aortocoronary vein graft intimal hyperplasia as well as therapeutic approaches.

Experimental and comparative study of the blood supply to the mandibular cortex in Göttingen minipigs and in man

INTRODUCTION

Since the blood supply to the mandibular cortex is an important factor for bone growth and bone repair, experimental studies on the blood supply in animal models (such as Göttingen minipigs) applicable to man are necessary. Their value depends on the requirement that the patterns of blood supply in the two species are similar.

MATERIAL AND METHODS

Twelve Göttingen minipig mandibles (24 halves) and four human mandibles (eight halves) were investigated for the blood supply to the mandibular cortex.

RESULTS

Only minor differences were found in blood supply to the mandibular cortex between the two species. Common to both was: in the cranial part of the mandible (including the condyle), the endosteal blood supply prevailed, whereas the periosteal blood supply predominated in the caudal part of the mandible (the body). Both patterns of blood supply were in balance in the centre section, i.e. angle and ascending ramus of the mandible.

CONCLUSION

The present study confirms that results obtained from Göttingen minipigs, used as an experimental animal model, are applicable to man: three different types of blood supply are evident in the mandibular cortex in both species.

Blood supply of the mandibular cortex: an experimental study in Göttingen minipigs with special reference to the condyle

INTRODUCTION

Blood supply of the mandible is an important factor that influences bone growth and bone repair.

MATERIAL AND METHODS

An experimental study was carried out in 24 mandibles of 12 Göttingen minipigs to study the blood supply of the mandibular cortex.

RESULTS

Endosteal blood supply prevails in the cranial part of the mandible including the condyle, whilst periosteal blood supply predominates in the caudal part of the mandible, the body. The two forms of blood supply are in balance in the ascending ramus and the angle of the mandible.

CONCLUSION

The mandibular cortex can be divided into three parts, each having different sources of blood supply. The results of this study may be of significance for man and could help to understand some pathological disorders of the mandible.

Do mature pulmonary lobes grow after transplantation into an immature recipient?

BACKGROUND

The use of reduced-size adult lung transplants could help solve the profound pediatric donor lung shortage. However, adequate long-term function of the mature grafts requires growth in proportion to the recipient's development.

METHODS

Mature left lower lobes from adult mini-pigs (age: 7 months; mean body weight: 30 kg) were transplanted into 14-week-old piglets (mean body weight: 15 kg). By the end of the 14-week holding period, lungs of the recipients (n = 4) were harvested. After volumetric measurements, the lung morphology was studied using light microscopy, scanning, and transmission electron microscopy. Changes of alveolar airspace volume were determined using a computer aided image analysis system. Comparisons were made to age- and weight-matched controls.

RESULTS

Volumetric studies showed no significant differences (p = 0.49) between the specific volume (mL/kg body weight) of lobar grafts and left lower lobes of adult controls. Morphologic studies showed marked structural differences between the grafts and the right native lungs of the recipients, with increased average alveolar diameter of the grafts. On light microscopy and scanning electron microscopy, alveoli appeared dilated and rounded compared to the normal polygonal shape in the controls. The computer generated semi-quantitative data of relative alveolar airspace volume tended to be higher in transplanted lobes.

CONCLUSIONS

The mature pulmonary lobar grafts have filled the growing left hemithorax of the developing recipient. Emphysema-like alterations of the grafts were observed without evidence of alveolar growth in the mature lobar transplants. Thus, it can be questioned whether mature pulmonary grafts can guarantee sufficient long-term gas exchange in growing recipients.

Anaesthetics for general anaesthesia in growing pigs

A comparison was made between different anaesthetics for general anaesthesia in growing pigs, with focus on minor surgery under field conditions and for experiments in clinical research. Healthy cross-breed pigs (Hampshire x Yorkshire x Swedish Landrace) weighing 20-45 kg were used. The anaesthetics combinations compared were 1) azaperone plus metomidate (AM), 2) Zoletil (zolazepam + tiletamine) plus xylazine (ZX), and 3) Zoletil plus xylazine plus ketamine (ZXK). Parameters measured were: heart rate, respiratory rate, blood pressure, body temperature, and depth of analgesia (pin-prick). Minor surgery was performed to test the reliability of the "pin-prick" tests. It was clearly shown that AM produces anaesthesia with good cardiovascular stability and is a drug combination that is suitable for minor surgery. ZX also produces a good anaesthesia characterized by reliable and rapid induction. Good cardiovascular function is maintained, and the laryngeal relaxation makes intubation possible. These characteristics are very useful in a laboratory environment, as easy handling to avoid stress is necessary for research. Although it is difficult to evaluate the quality of analgesia from this study, it is concluded that ZX did not provide a superior anaesthesia and analgesia compared to AM in crossbreed pigs. However, these drugs are too expensive for regular use in ambulatory practice. The effects of ZXK resemble those of ZX, but the ZXK-drug combination has no anaesthetic advantages and is more laborious to work with.

Comparison of the muscarinic receptors in the coronary artery, cerebral artery and atrium of the pig

The affinity of various muscarinic antagonists for the muscarinic receptors mediating contraction (induced by acetyl-beta-methylcholine) of the isolated pig coronary and basilar artery was determined in order to compare the muscarinic receptor subtype involved in the contractile response of these arteries. In order to identify the muscarinic receptor subtype(s) involved, the affinity of the antagonists for the M2 receptor present in the pig atria was also investigated. The following muscarinic antagonists were used: atropine, pirenzepine, AF-DX 116 (11-2[[2-[(diethylamino)methyl]-1- piperidinyl]acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepin-6-one),4-DAMP(4-diphenylacetoxy-N- methylpiperidine methiodide), HHSiD (hexahydrosiladifenidol), methoctramine (N,N'-bis[6-[(2- methoxybenzyl)amino]hexyl]-1,8-octane-diamine tetrahydrochloride) and ipratropium. The order of affinity of the antagonists with respect to the muscarinic receptor in the coronary artery was clearly different from that for the muscarinic receptor in the basilar artery. The order of affinity established on the basilar artery closely resembled that for the M2 receptor in the atria. It is concluded that the muscarinic receptors on smooth muscle of the coronary and basilar arteries are not identical. The muscarinic receptor involved in the contraction of the basilar artery adheres to the M2 receptor subtype. A comparison of the selectivity of the antagonists suggests that the muscarinic receptor involved in the contraction of the coronary artery belongs to the M3 (like in exocrine glands) or M4 (as found in ileal smooth muscle) receptor subtype.

Chromogranin A (CGA) in the gastro-entero-pancreatic (GEP) endocrine system. I. CGA in the mammalian endocrine pancreas

Chromogranin A (CGA), a protein at first detected in the adrenal medulla, has recently been found also in other organs, e.g. the endocrine pancreas. However, immunohistochemical findings concerning the cellular source of pancreatic CGA were controversial. Therefore, the endocrine pancreas of 10 mammalian species (man, tupaia, mole, cat, dog, pig, guinea pig, rabbit, rat) was investigated immunohistochemically for CGA-like immunoreactivities on serial semithin plastic sections using a high-titer polyclonal antiserum against bovine CGA. The results show that basically all pancreatic endocrine cell types are CGA-immunoreactive; however, every species has its own pattern of CGA-immunoreactive cell types. Other findings of the present studies indicate that the physiological function of CGA in pancreatic endocrine cells is related to the storage mechanisms of peptide hormones. Finally, a methodological approach is given to obtain not only qualitative but also semi-quantitative data during immunohistochemical investigations.

Reference values of various blood constituents in young minipigs

In the Göttinger minipig, the reference values of 18 parameters in whole blood or plasma were determined. The results are expressed both as the mean value and +/- 2 SD presuming a symmetrical normal distribution and as the median value with the corresponding range. For most blood constituents, the results of the two modes of calculation were similar. Comparison of the values from young minipigs with those from children shows that these animals are well suited in this respect for experimental work related to human medicine.

Norepinephrine and acetylcholine transmitter mechanisms in large cerebral arteries of the pig

This study examines, using an in vitro tissue bath technique, the nature of the transmitter mechanism(s) in the pig cerebral artery. Of the arteries with intact endothelium, about 25% relaxed on application of acetylcholine (ACh) at low concentration (3 × 10−7 to 3 × 10−6 M) and constricted at concentrations exceeding 10−5 M. The remaining arterial preparations either constricted (61%) or exhibited no response (14%) at any concentration of ACh tested (3 × 10−7 to 3 × 10−3 M). On the other hand, none of the arteries without endothelium relaxed at any concentration of ACh tested (3 × 10−7 to 3 × 10−3 M); of these, 90% constricted and 10% exhibited no response. These results show that ACh-induced cerebral vasodilation is dependent on endothelial cells and the direct action of ACh on the vascular smooth muscle cells is constriction. Contrary to findings in the large cerebral arteries of the cat and several other species, about 90% of the pig cerebral arteries, with or without endothelium, dilated upon application of norepinephrine (NE) at low concentration (10−7 to 3 × 10−5 M) and constricted at concentrations exceeding 3 × 10−5 M. The NE dose–response relationships were not different in arteries with and without endothelial cells, indicating that the NE-induced vasodilation was independent of the endothelial cells. The relaxation and constriction were blocked by the respective β- and α-receptor antagonists, suggesting that both responses resulted from direct stimulation by NE of β and α receptors on the smooth muscle cells. Transmural nerve stimulation (TNS) consistently induced vasodilation of the arteries whether or not the endothelial cells were present. The vasodilation was abolished by tetrodotoxin (TTX) and cold storage denervation. The TNS-induced vasodilation was not smaller in arteries without endothelium than in those with endothelium. This suggests that TNS-induced vasodilation was independent of the endothelial cells. When examined histochemically, the pig cerebral artery exhibited rich catecholamine fluorescence. Biochemical assays indicate that NE is the primary catecholamine. However, the TNS-induced vasodilation was not affected by atropine, guanethidine, or propranolol, nor prevented by reserpine. It is suggested that an as yet unidentified transmitter is responsible for the TNS-induced vasodilation. Results of this study suggest that the nerve-released ACh is a potential vasoconstrictor transmitter and that NE is a potential vasodilator transmitter in the large cerebral artery of the pig. The neurogenic control of the pig cerebral circulation may be different from that of other species, including humans.

Anterior bulbus perforation and vitrectomy in the 'minipig'

Wound healing after experimental anterior eye perforation, including lens, ciliary, body and vitreous, was studied in 12 miniature pigs (minipigs). In half of the eyes, perforation was followed by removal of the damaged lens and suturing of the wound. In the other half, a primary subtotal vitrectomy was performed after removal of the lens. The behaviour of the connective tissue in the wound-healing process was not fundamentally changed by subtotal vitrectomy. In both groups very little fibrous ingrowth into he vitreous structure was observed, suggesting that the pig vitreous has marked antifibroplastic properties. The anatomical and technical features of vitrectomy in the minipig, and the advantages and disadvantages of this animal model are discussed. It appears that the eye of the minipig is ideal for the study of biochemical factors preventing fibrous ingrowth into the vitreous.

Vascular effects of vasopressin an oxytocin in the pig mesenteric bed

The influence of intraarterial infusions of lysine-vasopressin and oxytocin on mesenteric vascular resistance has been studied in anaesthetized young pigs. Vasopressin provokes a pronounced vasoconstrictor effect, whereas oxytocin induces a biphasic response: a transient vasodilation, followed by a more pronounced and sustained vasoconstriction. The comparison of the plasma concentrations of these hormones during parturition and hemorrhage in the pig with the minimal effective doses infused, suggests a possible mesenteric vasoconstrictor effect of oxytocin during parturition and of lysine-vasopressin during hemorrhage.

Species differences in the disposition and metabolism of sulfinpyrazone

1. The disposition and metabolism of sulfinpyrazone have been studied in rats, guinea-pigs, rabbits, dogs, rhesus monkeys and miniature swine after intravenous administration of 100 mg/kg of 14C-labelled drug. 2. In all species, the integrated plasma concentration (AUC, 0-24 h) of total radioactivity was almost completely covered by the sum of the AUC-values of unchanged sulfinpyrazone and six metabolites, i.e. the sulphide, the sulphone, p-hydroxy-sulfinpyrazone, the p-hydroxy-sulphide, the p-hydroxy-sulphone and 4-hydroxy-sulfinpyrazone. 3. Comparison of the plasma level profiles of unchanged sulfinpyrazone and the metabolites revealed pronounced differences between the species. Unchanged sulfinpyrazone was the most prominent compound in plasma of rats, dogs, monkeys and swine, whereas the sulphide metabolite predominated in guinea-pigs. In plasma of rabbits, these two compounds were found in similar amounts. 4. Species with predominant renal excretion of the 14C dose, i.e. rabbits, dogs and monkeys, eliminated sulfinpyrazone to a high extent unchanged. The renal excretion of the sulphide metabolite was low in all species. 5. Species differences in the biotransformation of sulfinpyrazone explain previously observed differences in inhibitory effect on platelet aggregation. This effect is intensive and long-lasting in species showing high plasma concentrations of the sulphide metabolite.

Substance P: a powerful intestinal vasodilator in the pig

In anaesthetized young pigs the influence of intra-arterial infusions of Substance P (SP) on mesenteric vascular resistance is studied, both before and after serotoninergic and nervous conductivity blockade by dihydroergotamine (DHE) and tetrodotoxin (TTX). SP has a strong dilator effect on pig mesenterial vessels, which is not significantly modified by DHE or TTX; presumably SP acts directly on the vascular smooth muscle. By comparing the threshold level of SP with that of other intestinal vasdodilators, it may be concluded that SP is the most powerful intestinal vasodilator so far extperimented in the pig.

[The Göttinger minipig as a laboratory animal. 5. Communication: cardiac output, its regional distribution and organ blood flow (author's transl)]

In 16 juvenile minipigs weighing 3.08 kg an average cardiac output of 23 ml/100 g body weight was measured with the dye-dilution method. The microsphere technique was used to assess distribution of cardiac output and organ blood flow. In 12 adult minipigs with a mean body weight of 21.5 kg the cardiac output of 14 ml/100 g body weight was measured with an electromagnetic flowmeter. The values of total systemic and organic blood flow correlated well with those of man and partly with those of other laboratory animals.

Influence of primary prostaglandins, prostacyclin and arachidonic acid on mesenteric hemodynamics in the pig

In anesthetized young pigs the influence of intraarterial infusion of prostaglandin E2, prostacyclin, prostaglandin F2 alpha, and arachidonic acid on mesenteric vascular resistance was studied. Infusion of PGE2 and prostacyclin induced a dose-dependent direct decrease in resistance. Infusion of PGF2 alpha resulted in a dose-dependent difference in response. Infusion of lower doses provoked a decrease in mesenteric vascular resistance, whereas infusion of higher doses resulted in an increase. Lower doses of arachidonic acid induced a gradual decrease in resistance, while higher doses provoked biphasic or triphasic responses. After previous blockade of the PG synthetase and lipoxygenase pathways with indomethacin and ETA, arachidonic acid only provoked a decrease in vascular resistance. The resultssuggest a possible role of prostaglandins and their precursors in autoregulation of mesenteric blood flow in the pig.

[The Göttinger minipig as a laboratory animal. 4. Communication: respiration parameters (author's transl)]

The following parameters were determined: Rate of breathing (f): 31.95 +/- 6.73/min. Minute volume (V): 5.11 +/- 6.73 liter/min. Tidal volume (VT): 0.166 +/- 0.053 liter. Ratio expiratory to inspiratory time Et/It : 1.04 +/- 0.18. Physiological dead space (VD): 0.061 +/- 0.024 liter. Dead space quotient (VD)/VT): 29.92 +/- 1.53%. Dynamic lung compliance (C dyn): 0.06 +/- 0.06 liter/cm H2O. Maximum interpleural negative pressure during inspiration (max. neg. Ppl. Insp.): 12.00 +/- 4.06 cm H2O. Minimum interpleural negative respectively maximum interpleural positive pressure during expiration (min. neg. or pos. Ppl. Exp.): +0.07 +/- 6.53 cm H2O. Maximum change of interpleural pressure (delta Ppl. max): 11.97 +/- 3.18 cm H2O.

[Experiences with the hemorrhagic shock in immature pigs (author's transl)]

In 74 immature pigs a hemorrhagic shock (3 hrs duration: mean arterial pressure 40 mm Hg) was established (NORTON 1972). Following this systemic stress all animals developed stress-lesions of stomach and duodenum. In comparison to other stress-models porcine hemorrhagic shock seems to be qualified to study pathogenesis, prophylaxis and therapy of gastric stress-lesions: Pigs correspond best to humans in their gastro-intestinal physiology, hypotension simulates one of the most important surgical causes of stress complications and stress-lesion produced by this model have a marked similarity to those of humans. In contrast to these advantages there are some problems in using this model: Prompt and dangerous electrolyte imbalance following correction of disturbances in acid base equilibrium; irreversible shock following protracted hypotension (3 hrs). For this reason 19% of all piglets died before (1 animal), during (10 animals) or immediately after shock (3 animals). By careful observation of the mentioned problems, however, this experimental model combines a high incidence of stress-lesions with a low rate of casualities.

[The Göttinger minipig as a laboratory animal (author's transl)]

Blood pictures, serumelectrolytes, acid-base- and bloodgas-values of the arterial blood were determined from two juvenile and one adulte collectives of minipigs (Gottingen strain), which were kept under SPF-conditions. The results were compared with the corresponding values of human blood and should be regarded as base- or orienting values for further investigations.