Goran Radenkovic

Development of c-kit immunopositive interstitial cells of Cajal in the human stomach.

Interstitial cells of Cajal (ICC) include several types of specialized cells within the musculature of the gastrointestinal tract (GIT). Some types of ICC act as pacemakers in the GIT musculature, whereas others are implicated in the modulation of enteric neurotransmission. Kit immunohistochemistry reliably identifies the location of these cells and provides information on changes in ICC distribution and density. Human stomach specimens were obtained from 7 embryos and 28 foetuses without gastrointestinal disorders. The specimens were 7–27 weeks of gestational age, and both sexes are represented in the sample. The specimens were exposed to anti‐c‐kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined by using anti‐neuron specific enolase and the differentiation of smooth muscle cells (SMC) was studied with anti‐α smooth muscle actin and anti‐desmin antibodies. By week 7, c‐kit‐immunopositive precursors formed a layer in the outer stomach wall around myenteric plexus elements. Between 9 and 11 weeks some of these precursors differentiated into ICC. ICC at the myenteric plexus level differentiated first, followed by those within the muscle layer: between SMC, at the circular and longitudinal layers, and within connective tissue septa enveloping muscle bundles. In the fourth month, all subtypes of c‐kit‐immunoreactivity ICC which are necessary for the generation of slow waves and their transfer to SMC have been developed. These results may help elucidate the origin of ICC and the aetiology and pathogenesis of stomach motility disorders in neonates and young children that are associated with absence or decreased number of these cells.

Morphological and biomechanical features of the temporomandibular joint disc: an overview of recent findings.

The temporomandibular joint is a type of synovial joint with unique structure and function. Between the mandibular condyle and the mandibular fossa there is a dense fibrocartilaginous oval articular disc, temporomandibular joint disc. This disc serves as a nonossified bone, thus permitting the complex movements of the joint, and plays a major role in jaw function by providing stress distribution and lubrication in the temporomandibular joint. Pathological mechanical loads are one of the principal causes of temporomandibular joint disc displacement. There is a high frequency of temporomandibular joint disc disorders and treatment options are very limited. For this reason, it is necessary to examine possible alternatives to current treatment options like physiotherapy, drugs, splints or surgical techniques. Recent discoveries in the field of structure and functions of temporomandibular joint disc have created the need for their particular systematization, all in order to create an implant that would be used to replace the damaged disc and be more similar to the natural one. There is a need to more fully meet the morphology and biomechanical properties of the temporomandibular joint disc, and using tissue engineering, make a substitute for it, as faithful as possible, in a case where the natural TMJ disc is damaged so much that the normal function of the joint can be preserved only through implanted disc. Therefore, the aim of this paper was to describe morphology and structure, as well as biomechanical properties of the TMJ disc, in light of the possible applications of this knowledge for the purposes of tissue engineering.

Two patterns of development of interstitial cells of Cajal in the human duodenum

At the end of the embryonic period of human development, c‐kit immunoreactive (c‐kit IR) cells identifiable as interstitial cells of Cajal (ICC) are present in the oesophagus and stomach wall. In the small and large bowel, c‐kit‐IR cells appear later (in the small bowel at 9 weeks, and in the colon at 10–12 weeks), also in the MP region. The object of this study was to determine the timing of appearance and distribution of c‐kit IR cells in the human embryonic and foetal duodenum. I used immunohistochemistry to examine the embryonic and foetal duodenum for cells expressing CD117 (Kit), expressed by mature ICC and ICC progenitor cells and CD34 to identify presumed ICC progenitors. Enteric plexuses were examined by way of antineuron‐specific enolase and the differentiation of smooth muscle cells was studied using antidesmin antibodies. At the end of the embryonic period of development, c‐kit IR cells were solely present in the proximal duodenum in the form of a wide belt of densely packed cells around the inception of the myenteric plexus (MP) ganglia. In the distal duodenum, c‐kit IR cells emerged at the beginning of the foetal period in the form of thin rows of pleomorphic cells at the level of the MP. From the beginning of the fourth month, the differences in the distribution of ICC in the different portions of the duodenum were established, and this relationship was still present in later developmental stages. In fact, in the proximal duodenum, ICC of the MP (ICC‐MP), ICC of the circular muscle (ICC‐CM) and ICC of the septa (ICC‐SEP) were present, and in the distal duodenum ICC‐MP and ICC‐SEP only. In conclusion, in the humans there is a difference in the timing and patterns of development of ICC in the proximal duodenum compared to the distal duodenum.

Differentiation of Interstitial Cells of Cajal in the Human Distal Colon

At the end of the embryonic period of human development, interstitial cells of Cajal (ICC) are present in the esophagus, stomach, and proximal duodenum, around the inception of the myenteric plexus (MP) ganglia. In the small and large bowel, ICC appear later. The object of the present study was to determine the timing of appearance and pattern of distribution of ICC in the human embryonic and fetal distal colon. Human distal colon specimens were obtained from 8 embryos and 14 fetuses without gastrointestinal disorders. The specimens were 7–16 weeks of gestational age. The specimens were exposed to anti-c-kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined using anti-neuron-specific enolase, and the differentiation of smooth muscle cells was studied with anti-desmin antibodies. In the distal colon, ICC emerged at weeks 10–11 of the fetal period in the form of two parallel belts of densely packed cells extending at the submucous plexus (SMP) and the MP level. These cells correspond to ICC of the SMP (ICC-SMP) and ICC of the MP (ICC-MP). The simultaneous appearance of ICC at the SMP and MP level in the distal colon can be explained by the fact that there are differences in the migration of neural crest cells in particular portions of the digestive tube. In conclusion, in humans, there was a difference in the patterns of development of ICC in the distal colon compared to the rest of the gut.

Erosive Effect of Different Soft Drinks on Enamel Surface in vitro: Application of Stylus Profilometry

Objective: To assess the erosive potential of various soft drinks by measuring initial pH and titratable acidity (TA) and to evaluate enamel surface roughness using different exposure times. Materials and Methods: The initial pH of the soft drinks (group 1: Coca-Cola; group 2: orange juice; group 3: Cedevita; group 4: Guarana, and group 5: strawberry yoghurt) was measured using a pH meter, and TA was measured by titration with NaOH. Enamel samples (n = 96), cut from unerupted human third molars, were randomly assigned to 6 groups: experimental (groups 1-5) and control (filtered saliva). The samples were exposed to 50 ml of soft drinks for 15, 30 and 60 min, 3 times daily, during 10 days. Between immersions, the samples were kept in filtered saliva. Enamel surface roughness was measured by diamond stylus profilometer using the following roughness parameters: Ra, Rq, Rz, and Ry. Data were analyzed by one-way ANOVA, Tukeys post hoc and Student-Newman-Keuls post hoc tests. Results: The pH values of the soft drinks ranged from 2.52 (Guarana) to 4.21 (strawberry yoghurt). Orange juice had the highest TA, requiring 5.70 ml of NaOH to reach pH 7.0, whereas Coca-Cola required only 1.87 ml. Roughness parameters indicated that Coca-Cola had the strongest erosion potential during the 15 min of exposure, while Coca-Cola and orange juice were similar during 30- and 60-min exposures. There were no significant differences related to all exposure times between Guarana and Cedevita. Strawberry yoghurt did not erode the enamel surface regardless of the exposure time. Conclusion: All of the tested soft drinks except yoghurt were erosive. Erosion of the enamel surfaces exposed to Coca-Cola, orange juice, Cedevita, and Guarana was directly proportional to the exposure time.

The effect of bilberries on diabetes-related alterations of interstitial cells of Cajal in the lower oesophageal sphincter in rats.

Diabetic gastroenteropathy involves not only the parasympathetic and sympathetic autonomic nerves, but also enteric neurons, smooth muscle cells and interstitial cells of Cajal (ICC). ICC are the cells of mesenchymal origin that occur within and around the muscle layers in the gastrointestinal tract. The objective of the present study was to investigate the alterations of ICC in the lower oesophageal sphincter (LOS) of streptozotocin-nicotinamide non-insulin-dependent diabetes rats. Moreover, we investigated possible ICC in rats with the same type of diabetes, treated with bilberry fruit extract, bearing in mind that its hypoglycemic effect had been already proven. Male Wistar rats (10 weeks old) were used, and diabetes was induced by an intraperitoneal injection of streptozotocin, immediately after intraperitoneal application of nicotinamide. The specimens were exposed to anti-c-kit antibodies to investigate the distribution of ICC, and the smooth muscle cells were immunohistochemically labelled using anti-desmin antibodies. Intramuscular ICC were very abundant in the LOS of rats. They were spindle-shaped, with two long processes connecting them into long linear sequences. In the LOS of diabetic rats, intramuscular ICC were rarely present and linear cell-cell connections between these cells were completely missing. In groups treated with bilberry, the number and distribution of ICC were exactly the same as in the above described rats with induced diabetes. In summary, a decrease of intramuscular ICC, discontinuities and breakdown of contacts between ICC were observed in streptozotocin-nicotinamide induced diabetes rats and in groups treated with bilberry. Bilberry fruit extract was shown to have hypoglycemic activity, but without any protective effects on ICC in the LOS of diabetic rats.

Development of interstitial cells of Cajal in the human digestive tract as the result of reciprocal induction of mesenchymal and neural crest cells

Neural crest cells (NCC) can migrate into different parts of the body and express their strong inductive potential. In addition, they are multipotent and are able to differentiate into various cell types with diverse functions. In the primitive gut, NCC induce differentiation of muscular structures and interstitial cells of Cajal (ICC), and they themselves differentiate into the elements of the enteric nervous system (ENS), neurons and glial cells. ICC develop by way of mesenchymal cell differentiation in the outer parts of the primitive gut wall around the myenteric plexus (MP) ganglia, with the exception of colon, where they appear simultaneously also at the submucosal border of the circular muscular layer around the submucosal plexus (SMP) ganglia. However, in a complex process of reciprocal induction of NCC and local mesenchyma, c‐kit positive precursors are the first to differentiate, representing probably the common precursors of ICC and smooth muscle cells (SMC). C‐kit positive precursors could represent a key impact factor regarding the final differentiation of NCC into neurons and glial cells with neurons subsequently excreting stem cell factor (SCF) and other signalling molecules. Under the impact of SCF, a portion of c‐kit positive precursors lying immediately around the ganglia differentiate into ICC, while the rest differentiate into SMC.

The effects of passivation parameters on pitting potential of biomedical stainless steel

Passivation is a chemical process where electrochemical condition of passivity is gained on the surface of metal alloys. Biomedical AISI 316LVM stainless steel (SS) can be passivized by means of nitric acid immersion in order to improve a protective oxide layer on the surface and consequently increase corrosion resistance of the SS in the physiological solutions. In this study, multiple regression analysis and artificial neural network (ANN) were employed for mathematical modeling of the AISI 316LVM SS passivation process after immersion in the nitric acid solution. Pitting potential, which represents the measure of pitting corrosion resistance, was chosen as the response while passivation parameters were nitric acid concentration, temperature and passivation time. The comparison between experimental results and models predictions showed that only the ANN model provided statistically accurate predictions with a high coefficient of determination and a low mean relative error. Finally, based on the derived ANN equation, the effects of the passivation parameters on pitting potential were examined. [Projekat Ministarstva nauke Republike Srbije, br. ON174004 i br. TR35034]