Cell proliferation and cellular activity of primary cell cultures of the oral cavity after cell seeding on the surface of a degradable, thermoplastic block copolymer]

Using standard cell biological and biochemical methods we were able to test the ability of a degradable, thermoplastic block copolymer to support the adhesion, proliferation, and the cellular activity of primary cell cultures of the oral cavity in vitro. The delicate balance between a group of endogenous enzymes, Matrix Metalloproteinases (MMPs), and their inhibitors (Tissue Inhibitor of MMPs, TIMPs) have a decisive function in the remodeling of the extracellular matrix during processes like wound healing or the integration of biomaterials in surrounding tissues after implantation. Recently developed, biodegradable thermoplastic elastomers with shape-memory properties may be the key to develop new therapeutical options in head and neck surgery. Primary cell cultures of the oral cavity of Sprague-Dawley rats were seeded on the surface of a thermoplastic block copolymer and on a polystyrene surface as control. Conditioned media of the primary cells were analyzed for MMPs and TIMPs after different periods of cell growth. The MMP and TIMP expression was analysed by zymography and a radiometric enzyme assay. No statistically significant differences in the appearance and the kinetic of MMP-1, MMP-2, MMP-9 and TIMPs were detected between cells grown on the polymer surface compared to the control. An appropriate understanding of the molecular processes that regulate cellular growth and integration of a biomaterial in surrounding tissue is the requirement for an optimal adaptation of biodegradable, polymeric biomaterials to the physiological, anatomical, and surgical conditions in vivo to develop new therapeutic options in otolaryngology and head and neck surgery.     

Models of gastric hyperalgesia in the rat

Despite the prevalence of dyspepsia, nonhuman models for study of gastric hyperalgesia are limited. We thus characterized responses to gastric distension (GD) in the absence of and after two different gastric insults. A balloon was surgically placed into the stomach, and electromyographic responses to GD were recorded from the acromiotrapezius muscle at various times after balloon placement. Rats received either 20% acetic acid (HAc) or saline injections into the stomach wall or 0.1% iodoacetamide (IA) in drinking water. Responses to GD were monotonic with increasing distending pressure (10-80 mmHg) and were reproducible from days 3-14 after balloon implantation. Both HAc injection and IA ingestion led to increased responses to GD (i.e., gastric hyperalgesia), which, in the case of HAc, persisted for 60 days after HAc treatment. HAc injection produced ulcers in all treated animals; IA ingestion produced no lesions. Myeloperoxidase activity significantly increased after HAc but not saline injection or IA ingestion. In the awake, unrestrained rat, visceromotor responses to GD are quantifiable, reliable, and reproducible. Significantly enhanced responses to GD were apparent in two models of gastric insult, both of which may be useful for the study of the mechanisms of gastric hyperalgesia.     

Active water selective channels in the stomach: investigation of aquaporins after ethanol and capsaicin treatment in rats

Recent studies discovered the existence of aquaporins (AQP), suggesting their roles in the active, ATP dependent water secretion or absorption. Our recent development of the monoclonal antibody family against aquaporins (Type 1 and 4) allowed us a good opportunity to investigate the mechanism of the gastric mucosal edema in a rat model. THE AIM OF OUR STUDY was to evaluate the changes in the tissue level of aquaporins (AQP1 and AQP4) after ethanol and capsaicin treatment in rat stomach. MATERIALS AND METHODS: the experiments were carried out on Sprague-Dawley rats weighing 150-200 g. The animals were fasted for 24 h, after the 1 ml of ethanol (50% v/v) or capsaicin (2 mg/ml) was given intragastrically. Rats were sacrificed after 5, 30, 60, 120 and 240 min, the tissue level of AQP1 and AQP4 was investigated immunoserologically by ELISA and dot-blot methods using our monoclonal antibodies. The location of these aquaporins in the gastric tissue was demonstrated by immunohistochemistry. RESULTS: (1) in ethanol-treated stomach, both AQP1 and AQP4 increased after 5 min simultaneously with gastritis, then decreased dramatically depending on time. (2) In the capsaicin-treated group there were no changes in the tissue level of aquaporins in the first hour. After 60 min both AQP1 and AQP4 increased in the stomach without any macroscopically detectable changes, then decreased depending on time. (3) The immunohistochemical investigations using our monoclonal antibodies seem to support our present quantitative results. CONCLUSION: chemically induced gastric mucosal lesions are started by an extended edema. In the induction of the edema and the subsequent gastric injury, aquaporins (both AQP1 and AQP4) play an important role in the maintenance of mucosal integrity.     

Gross anatomy of the gastrointestinal system of harp seals (Phoca groenlandica)

The gross anatomy of the gastrointestinal system of 12 harp seals ( Phoca groenlandica ) was investigated. Harp seals have a typical carnivore monogastric stomach. The tissue wet weight of the stomach of harp seals represented 27.01 (S.D. 3.99)% ( n = 12) of the total gastrointestinal tract (GI-tract). All animals were killed while resting on the ice, and had empty stomachs, but when expanded with water to a 30cm pressure the stomach contained 0.60 to 1.60 litres, representing 1.00 (S.D. 0.26)% ( n = 12) of the body mass. The small intestine ranged in length from 20.44 to 25.32m, being 14.36 (S.D. 1.58) times the body length, and the tissue wet weight constituted 67.61 (S.D. 4.55)% of the total GI-tract ( n = 12). Both caecum and colon were short, maximally 5 and 78 cm, respectively, being 0.022 (S.D. 0.005) and 0.38 (S.D. 0.06) times the body length ( n = 12). The caecum tissue wet weight was only 0.18 (S.D. 0.04)% of the total GI-tract weight, while the colon tissue wet weight contributed to 5.33 (S.D. 1.19)% ( n = 12). It is concluded that harp seals have relatively long intestines compared to minke whales eating a comparable diet in the North Atlantic Ocean.     

兔VX2肝癌模型制作技术改良

目的探讨制作兔VX2肝癌模型的新技术、新方法。方法将新西兰兔30只随机等分为3组,分别为嵌插组、改良嵌插组和经皮穿剌组。分别按不同方法建立肝癌模型,于建模后第1、2、3周分别进行CT扫描,评估肿瘤大小。3周后处死动物进行解剖,观察肝脏成瘤及转移情况,比较各组转移率,并行常规病理组织学检查。结果 30只动物建模成功28只,成功率93%,经皮穿剌组有2只肝脏未见种植灶,嵌插组和改良嵌插组全部种植成功。改良嵌插组腹壁转移率显著低于嵌插组和经皮接种组。结论改良嵌插法3周内不会形成接种部位腹壁以及远处的转移,是一种理想的移植性肝癌模型建模方法。     

Light,electron microscopical,and immunocytochemical investigation of the stomach wall of the tigerfish Hydrocynus forskahlii

The wall of the stomach of the tigerfish is described and compared with that of other vertebrates. Light microscopic and ultrastructural characteristics of the stomach wall correspond to a large extent to those of other vertebrates, although some differences are found. The mucosa contains (1) surface epithelium characterized by narrow columnar cells with abundant mucous granules; (2) gastric glands consisting of pepsinogenic cells of variable height, containing tubulovesicles and bearing microvilli; (3) five granulated cell types located basally in the epithelium (types 1–5); and (4) lamina propria and muscularis mucosae. Connective tissue separating smooth muscle fibers of the muscularis mucosae constitutes a stratum compactum. The submucosa contains a loose connective tissue, a tunica muscularis of inner circular and outer longitudinal layers, and a serosa of mesothelium and subjacent connective tissue. Immunocytochemical tests with antisera to five polypeptides show gastrin/cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP) immunoreactivities in some cells of the gastric glands, and somatostatin in cells lying among epithelial cells lining the gastric luminal surface or gastric pits.     

Intraorganic venous bed of the stomach cardia in children during the first 3 years of life

The intraorganic venous bed of the gastric cardial part has been studied in 27 organs, obtained from children corpses of both sex beginning from birth up to three years of life. They died from causes that were not connected with gastric or vascular system pathology. The results of the investigation prove the presence of mucous, submucous, muscular and serous-subserous venous plexuses in the wall of the gastric cardial part in children of the first three years of life. Every membrane of the stomach wall has its specific structure of the venous link in the microcirculatory bed. In the stomach mucous membrane already in a newborn there are complexly built microcirculatory pathways. Age changes are mostly expressed in the venous link of the gastric mucous membrane; this is probably connected with functional activity of the given layer of the organ. The largest venous vessels are situated in the gastric submucous base. By the end of the newborn period and, especially fully, during the successive age periods immune protection of the gastric wall is formed as an accumulation of lymphoid tissue to an antigenic effect of food. In these age groups certain structural mechanisms of blood outflow from the gastric wall appear.     

Disorganization of stroma alters epithelial differentiation of the glandular stomach in adult mice

Summary The response of adult epithelium in contact with heterologous mesenchymes/stromas was studied in three digestive organs (forestomach, glandular stomach, and duodenum). After various tissues were implanted beneath the epithelial layer of adult mice, the epithelial differentiation was examined after sacrifice of animals at intervals up to 24 weeks. In the forestomach and duodenum, the epithelial differentiation was not affected at all by the tissue implantation. In the glandular stomach, in contrast, epithelial cells exhibited altered differentiation in which chief and parietal cells disappeared and were replaced by columnar epithelial cells with PAS-positive granules. These epithelial cells often formed immature villi. Such differentiation-altered columnar epithelium (DACE) was induced by implanting any type of tissue and even by sham operation, indicating that it was induced by disorganization of the tissue-implanted stroma. The size of DACE was significantly influenced by the stage of implanted tissue; 14.5-day fetal mesenchyme induced the largest DACE, and was followed by 16.5-day fetal mesenchyme, adult stroma, and sham operation. These results suggest the importance of stromal organization in maintaining epithelial differentiation in the glandular stomach.     

Gastric Infection with Kazachstania heterogenica Influences the Outcome of a Helicobacter suis Infection in Mongolian Gerbils

Background:  The Mongolian gerbil model is often used to investigate the interactions between different gastric Helicobacter species and the gastric tissue. A preliminary screening of a gerbil population intended for use in Helicobacter suis infection studies revealed a natural yeast infection in the stomach of these animals. After identification, we have investigated the effect of the gastric yeast infection on the outcome of an experimental H. suis infection in Mongolian gerbils.
Materials and methods:  Yeast cells were isolated from the stomachs of Mongolian gerbils. Identification was done by Internally Transcribed rRNA Spacer 2 Region PCR fragment length analysis. To investigate a possible pathologic role of this yeast, Mongolian gerbils were infected experimentally with this yeast. Co-infection with the newly isolated H. suis was performed to investigate possible interactions between both micro-organisms.
Results:  Kazachstania heterogenica was found colonizing the stomach of Mongolian gerbils, mainly in the antrum. Few pathologic changes were seen in the stomachs of infected animals. Experimental co-infection of gerbils with this yeast and the newly isolated H. suis showed a significant increase in inflammation in animals infected with both micro-organisms compared to animals infected only with H. suis .
Conclusions:  K. heterogenica colonizes the stomach of Mongolian gerbils in exactly the same regions as gastric Helicobacter species. The uncontrolled presence of this yeast in the gerbil stomach can lead to an overestimation of the inflammation caused by Helicobacter in this animal model.     

Development of a Novel Model for the Assessment of Dead-Space Management in Soft Tissue

Following extensive surgical debridement in the treatment of infection, a “dead space” can result following surgical closure that can fill with hematoma, an environment conducive to bacterial growth. The eradication of dead space is essential in order to prevent recurrent infection. This study describes a novel small animal model to investigate dead-space management in muscle tissue. Two absorbable test materials were implanted in each animal; beads of calcium sulfate alone, and beads loaded with vancomycin and tobramycin. In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 1, 7, 21, 42, and 63 days post-operatively (n = 4), and implant sites were analysed by micro-computed tomography, histology and immunohistochemistry. Complete resorption was confirmed radiographically at 3 weeks post-implantation. Histologically, the host tissue response to both materials was identical, and subsequent healing at the implant sites was observed with no dead space remaining. Vancomycin was not detected in blood serum. However, peak tobramycin levels were detected in all animals at 6 hours post-implantation with no detectable levels in any animals at 72 hours post implantation. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials or surgical procedure. The model was found to be convenient and effective for the assessment of implant materials for management of dead space in muscle tissue. The two materials tested were effective in resolving the surgically created dead space, and did not elicit any unexpected adverse host response.     

Transmural gradient of leukocyte-endothelial interaction in the rat gastrointestinal tract

Gastrointestinal injury usually starts in the superficial mucosa. We investigated whether leukocyte-endothelial interactions were greater in the gastrointestinal mucosa than the submucosa and muscularis in control tissue and after upregulation of adhesion molecules with endotoxin and after chemical insult with nonsteroidal anti-inflammatory drugs. Inactin-anesthetized rats were given either endotoxin, flurbiprofen, or nitric oxide (NO)-flurbiprofen, after which ICAM-1 and P-selectin expression was measured with the dual-label antibody technique. Leukocyte-endothelial interactions in the different gastric layers were assessed after endotoxin using intravital microscopy. Endotoxin caused a two- to threefold increase in ICAM-1 expression in the stomach and duodenum. There was, however, a gradient in expression across the gut wall with the level of expression in the superficial mucosa (per g) being only 10-25% of that in the deeper layers in both control and endotoxin-treated animals. Constituitive expression of P-selectin in control animals was barely detectable. Endotoxin caused a modest increase in mucosal P-selectin but a very significant increase in the deeper layers. Flurbiprofen caused a slight upregulation of ICAM-1 in the gastric mucosa and duodenum, whereas NO-flurbiprofen had no affect on expression. Intravital microscopy revealed no adhesion and virtually no leukocyte rolling in the vessels of the gastric mucosa despite endotoxin treatment. There was, however, some adhesion and significant leukocyte rolling in the submucosa and muscularis. Thus the superficial gastric and duodenal mucosal microcirculations have a much lower density of ICAM-1 and P-selectin and less leukocyte-endothelial interactions than occurs in the deeper layers of the gut wall even during stimulated upregulation with endotoxin.     

Refinement of the charcoal meal study by reduction of the fasting period

The aim of this investigation was to determine whether a shorter fasting period than the one historically employed for the charcoal meal test, could be used when measuring gastric emptying and intestinal transit within the same animal, and to ascertain whether the scientific outcome would be affected by this benefit to animal welfare. Rats and mice were fasted for 0, 3, 6 or 18 hours before the oral administration of vehicle or atropine. One hour later, the animals were orally administered a charcoal meal, then 20 minutes later, they were killed and the stomach and small intestine were removed. Intestinal transit time (the position of the charcoal front as a percentage of the total length of the small intestine) and relative gastric emptying (weight of stomach contents) were measured. Rats and mice fasted for six hours showed results for gastric emptying and intestinal transit which were similar to those obtained in animals fasted for 18 hours. Reducing the fasting period reduced the body weight loss in both species, and mice on shorter fasts could be group-housed, as hunger-induced fighting was lessened. Therefore, a fasting period of six hours was subsequently adopted for charcoal meal studies at our institution.     

Stomach stress and strain depend on location, direction and the layered structure

The stomach is as other parts of the gastrointestinal tract functionally subjected to dimensional change. Hence, the biomechanical properties are of functional importance. Our group has previously demonstrated that the stress–strain properties of the rat and rabbit stomach wall were species-, location- and direction-dependent. We further wanted to study the anisotropic biomechanical properties of the stomach wall in pigs. Furthermore, we made an in-depth biomechanical test on the layered wall of the stomach in different regions. Two stomach strips were cut both in longitudinal direction (parallel with the greater curvature) and circumferential direction (perpendicular to the greater curvature) from the gastric fundus, corpus and antrum. One strip was used for the non-separated (intact) wall test and the other one was separated for the test on the mucosa–submucosa and muscle layers individually. The length, thickness and width of each strip were measured from digital images. The uni-axial stress and strain were computed from the force generation and the tissue strip deformation during stretching. The muscle layer was the thickest in the antrum whereas the mucosal–submucosal layer was the thickest in the corpus of the stomach (P<0.01). The strips from the corpus were stiffest among the three regions in both longitudinal and circumferential directions (P<0.001). The longitudinal strips was stiffer than the circumferential strips in all three regions (P<0.001) and the mucosa–submucosa strips was stiffer than the intact wall and the muscle layer in both directions for the fundus and the corpus (P<0.001). The constant a of the intact wall and mucosa–submucosa layer was in both directions linearly associated with the mucosa–submucosa thickness. In conclusion, the uni-axial stress–strain curves of pig stomach were location-, direction- and layer-dependent. The stiffer wall in the corpus is likely due to its thicker mucosa, i.e., the stiffness of the mucosa–submucosa layer seems can explain the intact wall stiffness. Since the structure and function of the pig stomach are similar to the human stomach, we believe that the data obtained from this study can be extended to humans. Detailed biomechanical mapping of the stomach will likely help us to understand physiological functions of the different parts of the human stomach, such as gastric accommodation and mechanosensation.     

Gastric Electrical‐Stimulation Effects on Canine Gastric Emptying,Food Intake,and Body Weight

Objective: It has been reported that electrical stimulation at the distal stomach can disrupt intrinsic gastric electrical activity and delay gastric emptying. Gastric dysrhythmia and impaired gastric emptying are associated with upper gastrointestinal symptoms and weight loss. The purpose of this study was to evaluate the effect of low‐frequency/long‐pulse gastric electrical stimulation (GES), at proximal and distal stomach, on canine gastric emptying, food intake, and body weight. Research Methods and Procedures: Eight dogs were surgically implanted with four pairs of electrodes along the greater curvature and a gastric tube at the dependent part of the stomach. Liquid gastric emptying at baseline, during proximal and distal GES at 6 cycles per minute, was assessed first by a dye dilution technique. Proximal and distal GES were then randomly delivered during feeding for 10 consecutive days, and food intake and body weight were recorded daily. Results: There was no significant difference in gastric emptying parameters among the various sessions. The mean daily food consumption was significantly reduced during both sessions of GES, resulting in significant immediate weight loss. Percentage weight loss was comparable between both sessions of GES. Discussion: Short‐term GES significantly reduced canine food intake and weight. This effect may not be related to changes in gastric emptying. GES may have a potential role in the treatment of obesity.     

豆渣活性成分的提取、改性及应用研究进展

豆渣是以纤维等天然高分子为主的食品加工行业废弃物,是一种具有广阔应用前景和潜力的原材料。本文综述了豆渣的活性成分和药用价值与保健功能,以及豆渣中可溶性膳食纤维的结构、提取方法、改性及应用。豆渣作为可降解生物材料的研究与利用倍受关注,将为废弃天然高分子的再利用提供新途径。     

In vivo degradation and tissue response to poly(5-ethylene ketal ε-caprolactone-co-D,L-lactide)

Low molecular weight poly(5-ethylene ketal ε-caprolactone-co-D,L-lactide) (PEKCDLLA) is being considered as a viscous liquid, injectable depot for localized drug delivery. This polymer degrades in vitro via surface erosion, which is potentially advantageous for the proposed application. However, the in vivo degradation rate and mechanism, and tissue response, to polymers based on 5-ethylene ketal ε-caprolactone have not yet been reported. The purpose of this study was to measure the in vivo weight loss and change in polymer properties and assess the tissue response to PEKCDLLA after subcutaneous injection in rats. The tissue response was assessed histologically using Masson's trichrome staining and immunohistochemically by staining for CD68 positive cells. The polymer lost weight with time in a nearly linear fashion but did not exhibit significant changes in number average molecular weight, polydispersity index, and glass transition temperature or monomer ratio, consistent with a surface erosion process. The tissue response to the polymer was moderate and comparable to that reported in the literature for other degradable polymers used in clinical applications. These findings indicate that PEKCDLLA is a promising candidate for injectable drug delivery.     

Incidence and development of rhythmic episodic activity in the electroencephalogram of a large rat population under chronic conditions

689 long-term electroencephalographic recordings from 88 rats with chronically implanted electrodes were evaluated with reference to the onset and development of rhythmic spike episodes of 8-9 Hz frequency characteristic of quiet wakefulness. Episodes occurred in the recordings of 88% of the test animals. Recordings completely devoid of episodes came from selected rats highly sensitive to an acoustic epileptogenic stimulus and from 50% of rats of a Wistar-Velaz barrier breed. These two groups differed from the other animals in respect of their greater aggressiveness and restlessness in the chronic experiment. The episodes were not evoked by the surgical procedure--implantation of a cobalt-gelatin pin in the brain--or to the actual implantation of chronic electrodes in the brain. The shortest recorded latent period for the appearance of episodes was one week after the implantation of electrodes and the longest was 6 months. The animals' mean age at the time of the onset of episodes was 3.8 months and the lowest age was 2.5 months (i.e. immediately after implantation of the electrodes). The electrodes were not implanted before the age of 2.5 months. In repeated chronic recordings during the animals' life, both the number and the duration of the episodes increased. In most of the rats, the spike frequency in the episode was 8-9 Hz and was maintained at a stable value characteristic for each rat. Episodic rhythmic activity can thus occur in a state of quiet wakefulness in the electroencephalogram of all the given groups of rats (except highly sensitive animals) from early adulthood up to the age regarded in the rat as senility. The results to date indicate that the main condition for its appearance is the attainment of an optimum state of vigilance--quiet immobile wakefulness. The mechanisms leading to this stage of vigilance display both individual and group differences and are evidently related to the ability to become habituated to the experimental environment.     

Vagus nerves and the gastric tissue histamine concentration in pylorus ligated albino rats.

Gastric tissue histamine concentration was determined, 6 and 16 hours after pylorus ligation in vagus intact and vagotomized albino rats and the results were compared with those of respective control animals, sacrificed, 6 and 16 hours after ether anaesthesia alone. The gastric tissue histamine concentration of rats subjected to none of the experimental situations was also determined and taken into comparison. The results show that the stress of pylorus ligation reduced the gastric tissue histamine concentration, the reduction being more with increased duration of stress. On the other hand, subdiaphragmatic vagtomy preserved the histamine concentration of gastric tissue irrespective of the duration to which the animals were exposed following pylorus ligation. It appears that increase in vagal discharges during stress leads to increased liberation of histamine from the gastric wall, thereby, reducing the gastric tissue histamine concentration; the reduction being proportional to the duration of stress and increase in vagal discharges, whereas, in the absence of vagal impulses following subdiaphragmatic vagotomy, the gastric tissue histamine concentration is preserved in spite of the stress to which the animals were exposed.     

Bone marrow stem cells and polymer hydrogels--two strategies for spinal cord injury repair

1. Emerging clinical studies of treating brain and spinal cord injury (SCI) led us to examine the effect of autologous adult stem cell transplantation as well as the use of polymer scaffolds in spinal cord regeneration. We compared an intravenous injection of mesenchymal stem cells (MSCs) or the injection of a freshly prepared mononuclear fraction of bone marrow cells (BMCs) on the treatment of an acute or chronic balloon-induced spinal cord compression lesion in rats. Based on our experimental studies, autologous BMC implantation has been used in a Phase I/II clinical trial in patients (n=20) with a transversal spinal cord lesion. 2. MSCs were isolated from rat bone marrow by their adherence to plastic, labeled with iron-oxide nanoparticles and expanded in vitro. Macroporous hydrogels based on derivatives of 2-hydroxyethyl methacrylate (HEMA) or 2-hydroxypropyl methacrylamide (HPMA) were prepared, then modified by their copolymerization with a hydrolytically degradable crosslinker, N,O-dimethacryloylhydroxylamine, or by different surface electric charges. Hydrogels or hydrogels seeded with MSCs were implanted into rats with hemisected spinal cords. 3. Lesioned animals grafted with MSCs or BMCs had smaller lesions 35 days postgrafting and higher scores in BBB testing than did control animals and also showed a faster recovery of sensitivity in their hind limbs using the plantar test. The functional improvement was more pronounced in MSC-treated rats. In MR images, the lesion populated by grafted cells appeared as a dark hypointense area and was considerably smaller than in control animals. Morphometric measurements showed an increase in the volume of spared white matter in cell-treated animals. In the clinical trial, we compared intraarterial (via a. vertebralis, n=6) versus intravenous administration of BMCs (n=14) in a group of subacute (10-33 days post-SCI, n=8) and chronic patients (2-18 months, n=12). For patient follow-up we used MEP, SEP, MRI, and the ASIA score. Our clinical study revealed that the implantation of BMCs into patients is safe, as there were no complications following cell administration. Partial improvement in the ASIA score and partial recovery of MEP or SEP have been observed in all subacute patients who received cells via a. vertebralis (n=4) and in one out of four subacute patients who received cells intravenously. Improvement was also found in one chronic patient who received cells via a. vertebralis. A much larger population of patients is needed before any conclusions can be drawn. The implantation of hydrogels into hemisected rat spinal cords showed that cellular ingrowth was most pronounced in copolymers of HEMA with a positive surface electric charge. Although most of the cells had the morphological properties of connective tissue elements, we found NF-160-positive axons invading all the implanted hydrogels from both the proximal and distal stumps. The biodegradable hydrogels degraded from the border that was in direct contact with the spinal cord tissue. They were resorbed by macrophages and replaced by newly formed tissue containing connective tissue elements, blood vessels, GFAP-positive astrocytic processes, and NF-160-positive neurofilaments. Additionally, we implanted hydrogels seeded with nanoparticle-labeled MSCs into hemisected rat spinal cords. Hydrogels seeded with MSCs were visible on MR images as hypointense areas, and subsequent Prussian blue histological staining confirmed positively stained cells within the hydrogels. 4. We conclude that treatment with different bone marrow cell populations had a positive effect on behavioral outcome and histopathological assessment after SCI in rats; this positive effect was most pronounced following MSC treatment. Our clinical study suggests a possible positive effect in patients with SCI. Bridging the lesion cavity can be an approach for further improving regeneration. Our preclinical studies showed that macroporous polymer hydrogels based on derivatives of HEMA or HPMA are suitable materials for bridging cavities after SCI; their chemical and physical properties can be modified to a specific use, and 3D implants seeded with different cell types may facilitate the ingrowth of axons.     

Histological and ultrastructural studies of the rabbit pars intermedia in organ culture

Pars intermedia (PI) tissue from fetal, perinatal, neonatal and juvenile rabbits has been maintained in organ culture for up to nine weeks after explantation. Autoradiography showed that DNA synthesis took place for at least 22 days of culturing. PI-glandular cells and interstitial cells remain identifiable throughout this period but ACT-type cells were recognised only up to six weeks. Material from fetal and perinatal animals had a higher proportion of surviving cells than that from adult animals. The degree of differentiation achieved by PI-glandular cells in vitro appears to depend on three factors: i) the stage of development reached before explantation; ii) the original topographic position in the PI tissue before explantation; and iii) the position in the explant in relation to the gas-liquid interphase.