The volume and area of the capillaries in the endocrine and exocrine pancreas of the rat

The Effect of Oat Hay, Alfalfa Hay, and Their Combined Diets on the Morphology and Function of the Pancreas in Preweaning Yak Calves

In this study, we used a combination of animal nutrition and nontargeted metabolomics to investigate the effects of feeding different sources forages rations on the morphology and function of the pancreas in preweaning yak calves, providing theoretical guidance and important references for the healthy and high-quality rearing of yak calves. At 45 days old, 21 yak calf males were divided into OP, AP, and AOP groups, with seven animals in each group, which were fed with oat hay, alfalfa hay, and mixed oat and alfalfa hay, respectively. Five calves from each group were selected randomly to slaughter after a pretest period of 21 days and the official period of 120 days, when the average daily feed intake reached 1 kg. During the test, the growth and pancreas weight of yak calves were recorded, and the morphology and function of the pancreas tissues were determined using tissue sectioning methods, enzyme-linked immunosorbent assay (ELISA) tests, and nontargeted metabolomics strategies. The results showed that the body weight and pancreatic organ index of yak calves in the AOP group were significantly higher than those of the AP and OP groups. Compared to the AP and OP groups, the AOP group had considerably lower ratios of the area of the pancreatic endocrine component and overall percentage of that section of the organ, and the AOP group increased pancreatic amylase activity and a higher concentration of growth inhibitor. The AP group had significantly higher levels of the differential metabolites L-ascorbic acid, spermidine, spermine, and dopaquinone in the glutathione, β-alanine, and tyrosine metabolic pathways than the OP group. The AOP group had significantly lower levels of the differential metabolites spermine and phenylacetylglycine in the glutathione and phenylalanine metabolic pathways than the AP group. In summary, compared to feeding oat or alfalfa hay alone, combined feeding oat hay and alfalfa hay is more beneficial to promote the morphological and functional development of the pancreas in preweaning yak calves, so as to enhance the digestion and absorption of nutrients in the diet and maintain the positive regulation of blood glucose levels. This provides an important basis for the optimized forage supply of healthy and high-quality rearing in preweaning yak calves.

The Effect of Supplemental Concentrate Feeding on the Morphological and Functional Development of the Pancreas in Early Weaned Yak Calves

Simple Summary

This study aimed to investigate the nutritional intake deficiency on rearing yak calves. We investigated supplemental concentrate feeding effects on the morphological and functional development of the pancreas in early weaned yak calves. In the study, we determined the apparent digestibility of nutrients by digestion trail, the morphological development of the pancreas in yak calves by tissue sectioning, the activity of main digestive enzymes and hormone levels by ELISA kits, and the content of major small molecule metabolites in the pancreas by non-targeted metabolomics techniques. The morphological and functional development of the pancreas and its small molecule metabolites are mainly presented in graphical form, which had positive regulatory effects on the development of the pancreas in early weaned yak calves. In summary, we found that supplemental concentrate feeding was crucial for the high-quality growth and development of early weaned yak calves and had a positive influence on the intrinsic relationship between the overall development level and physiological functions of the pancreas, which could provide an important reference for scientific rearing of early weaned yak calves.

Abstract

This experiment was conducted to investigate the effect of supplemental concentrate feeding on the pancreatic development of yak calves. Twenty one-month-old yak calves with healthy body condition and similar body weight were selected as experimental animals and randomly divided into two groups, five replicates in each group. The control group yak calves were fed milk replacer and alfalfa hay, the experimental group yak calves were fed milk replacer, alfalfa hay and concentrate. The pre-feeding period of this experiment was thirty days, the trial period was one hundred days. At the end of feeding trail, five yak calves from each group were selected and slaughtered and the pancreas tissues of yak calves were collected and determined. The results showed that: (1) Dry matter and body weight of yak calves in the test group were significantly higher than those of the control group. (2) The apparent nutrient digestibility of crude protein, crude fat, calcium and phosphorus in the test group of yak calves was significantly higher than that of the control group, while the apparent nutrient digestibility of neutral detergent fiber and acid detergent fiber in the test group was significantly lower than that of the control group. (3) Pancreatic weight, organ index, total ratio of exocrine part area and total ratio of endocrine area of yak calves in the test group were significantly higher than those in the control group, while the ratio of exocrine area was significantly lower in the test group than that of the control group. (4) The activities of the main pancreatic digestive enzymes: pancreatic amylase, pancreatic lipase, pancreatic protease and chymotrypsin were significantly higher in the test group than those of the control group, as were the hormonal contents of glucagon, insulin and pancreatic polypeptide. (5) The main differential metabolites of the pancreas in the test group were significantly higher than those of the control group, such as D-proline, hypoxanthine, acetylcysteine, gamma-glutamylcysteine, thiazolidine-4-carboxylic acid, piperidinic acid, ellagic acid, nicotinamide, tropolone, D-serine, ribulose-5-phosphate, (+/-)5(6)-epoxyeicosatrienoic acid(EET), 2-hydroxycinnamic acid, L-phenylalanine, creatinine, tetrahydrocorticosterone, pyridoxamine, xanthine, 5-oxoproline, asparagine, DL-tryptophan, in-dole-3-acrylic acid, thymine, trehalose, docosapentaenoic acid, docosahexaenoic acid, fatty acid esters of hydroxy fatty acids(FAHFA) (18:1/20:3), fatty acid esters of hydroxy fatty acids(FAHFA) (18:2/20:4), adrenic acid and xanthosine. In conclusion, supplemental concentrate feeding promoted the good development of morphological and functional properties of the pancreas in early weaned yak calves to improve the digestion and absorption of feed nutrients, so as to enhance the growth and development quality of early weaned yak calves.

Pancreatic Blood Flow with Special Emphasis on Blood Perfusion of the Islets of Langerhans

The pancreatic islets are more richly vascularized than the exocrine pancreas, and possess a 5- to 10-fold higher basal and stimulated blood flow, which is separately regulated. This is reflected in the vascular anatomy of the pancreas where islets have separate arterioles. There is also an insulo-acinar portal system, where numerous venules connect each islet to the acinar capillaries. Both islets and acini possess strong metabolic regulation of their blood perfusion. Of particular importance, especially in the islets, is adenosine and ATP/ADP. Basal and stimulated blood flow is modified by local endothelial mediators, the nervous system as well as gastrointestinal hormones. Normally the responses to the nervous system, especially the parasympathetic and sympathetic nerves, are fairly similar in endocrine and exocrine parts. The islets seem to be more sensitive to the effects of endothelial mediators, especially nitric oxide, which is a permissive factor to maintain the high basal islet blood flow. The gastrointestinal hormones with pancreatic effects mainly influence the exocrine pancreatic blood flow, whereas islets are less affected. A notable exception is incretin hormones and adipokines, which preferentially affect islet vasculature. Islet hormones can influence both exocrine and endocrine blood vessels, and these complex effects are discussed. Secondary changes in pancreatic and islet blood flow occur during several conditions. To what extent changes in blood perfusion may affect the pathogenesis of pancreatic diseases is discussed. Both type 2 diabetes mellitus and acute pancreatitis are conditions where we think there is evidence that blood flow may contribute to disease manifestations. © 2019 American Physiological Society. Compr Physiol 9:799-837, 2019.

In vitro biodegradability and mechanical properties of bioabsorbable bacterial cellulose incorporating cellulases

Bacterially produced cellulose is being actively studied as a novel scaffold material for wound care and tissue engineering applications. Bioabsorbability of the scaffold material is desired to enable improved restoration of targeted tissue. Recently, a bioabsorbable bacterial cellulose (BBC) incorporating cellulase enzymes has been demonstrated. It was revealed that some cellulases may lose up to 90% of their activity if present in a suboptimal pH environment. Therefore, a key challenge in the practical implementation of this approach rests in compensating for the variation in the wound or tissue pH, which may significantly reduce the activity of some enzymes. In this work, buffer ingredients were incorporated into the bacterial cellulose in order to create a more optimal pH microenvironment for the preferred acid cellulases, which are significantly less active at the biological pH 7.4. The results demonstrated that incorporation of buffer ingredients helped to retain the activity of the cellulases. The glucose released from degraded materials was also increased from 30% without incorporation of buffer ingredients to 97% in the presence of incorporated buffer ingredients at the suboptimal pH environment of 7.4. The use of simulated body fluid and simulated tissue padding, both mimicking the real wound environment, also demonstrated some improvements in terms of material degradation. Measurements of mechanical properties of materials revealed that BBC materials have tensile strength and extensibility similar to human skin, especially when hydrated with saline water prior to use.

Th1 and Th2 cytokines exert regulatory effects upon islet microvascular areas in the NOD mouse

In this study, we show that intra- and peri-islet microvascular areas undergo different changes during the islet inflammation in the nonobese diabetes-prone female mice. Actually, although the islet vascular area (IVA) considerably decreases while the infiltration progresses, at 15 weeks of age, the peri-islet vascular bed is unexpectedly and significantly increased. On the contrary, the intra-IVA is significantly decreased, due to vessel dilation. Later, by 20-25 weeks of age, a decrease of both IVA occur, due to a significant islet beta cell loss. Moreover, a dramatic fall of natural free radical scavenger values, which, in turn, exert an influence upon vessels, is observed. These effects are completely counteracted by the administration of IL-4, a Th2 protective cytokine; IL-10, another putative Th2 cytokine, exerts direct effects upon endothelial cell (EC) function, as shown by the increase of endothelial nitric oxide synthase (eNOS) mRNA transcripts and by the release of endothelial NO which, in turn, exert vasodilatory effects; moreover, this cytokine significantly upregulates adhesion molecules on endothelia. On the other hand, IL-1beta, a Th1 proinflammatory cytokine, dramatically increases nitrite and nitrate levels, as well as inducible nitric oxide synthase (iNOS) transcripts and also upregulates islet ICAM-1 expression as well as circulating ICAM-1 levels. Taken together, our findings clearly show that cytokines and islet endothelia are directly involved in the pathophysiology of the disease. Their reciprocal influence gives new insight to understand the role of microvasculature during islet beta cell attack.

Engraftment and growth of transplanted pancreatic islets

Transplantation of pancreatic islets may provide a cure for type 1 diabetes. However, this treatment can currently be offered only to very few patients. To improve transplantation success we need to understand better the mechanisms of how the implanted islets survive, grow and/or maintain adequate function. We herein report on our studies to evaluate the factors responsible for the engraftment, i.e. revascularization, reinnervation etc., of transplanted islets and relate these factors to the metabolism and growth of the islets. Graft metabolism can be monitored by microdialysis probes that allow for the measurement of minute amounts of islet metabolites and hormonal products. Growth of the endocrine cells can be stimulated both in vitro before implantation and in vivo post-transplantation. Another problem is rejection of transplanted islets, which may be overcome by the microencapsulation of islets. The knowledge gained by the present studies will enable us to elucidate the optimal treatment of islets to ensure a maximal survival of the transplanted islets, and may be applied also to clinical islet transplantation.

Angioarchitecture of the atrophic pancreas

The pancreas has a complex vasculature which comprises both exocrine and endocrine structures. Copper deficiency induces highly selective acinar cell degeneration and progressive noninflammatory lipomatosis in pancreas while Langerhans islets, ducts, and nerves remain unaffected. Pancreatic vasculature was examined in rats that had dietary copper deficiency to characterize changes in the angioarchitecture of the gland. This model was used to assess the degree to which the vasculature of non-acinar components of the gland are potentially altered under conditions of exocrine atrophy. Ultrastructure of pancreas was examined by histology, enzyme histochemistry and immunohistochemistry, corrosion casting and scanning electron microscopy, in situ vascular staining, microsphere injection, biochemical analysis, and morphometry in copper-deficient rats. Results show that no acute angiopathic changes indicative of vascular disorganization accompany atrophy. Only a reduction in the complexity of the capillary beds, which normally vascularize the dense acinar parenchyma, was found. Microsphere quantitation also showed that blood flow to the lipomatous gland remains intact. Furthermore, analysis of the angioarchitecture of the atrophied pancreas supports a largely autonomous blood supply to islets and ducts. These observations support the hypothesis that while the vasculature of the atrophied gland is modified in vascular regions severely targeted by acinar necrosis, the overall structural features of the angioarchitecture are preserved. The atrophied gland thus provides an experimental model to study the vascular routes supplying islet and ductal blood flow within the complex pancreatic circulation.

An increase in superoxide dismutase counteracts islet vascular alterations in low-dose streptozocin-treated mice

A decrease in superoxide dismutase (SOD), the first cellular defence against free radicals, occurs at about the same time as the activation of macrophages within the islets of low-dose streptozocin (LDS)-treated mice. Furthermore, a decrease in the total islet capillary area also has been shown to occur by 10 days after the first streptozocin (STZ) injection and this decline in capillary area is concomitant with the activation of macrophages as is the fall in SOD. Intracellular levels of SOD have been shown to increase after administration of acetyl-homocysteine-thiolactone (citiolone); therefore, the aim of the present study was to observe any relationship between the citiolone-induced increase in SOD levels and islet microvasculature area during LDS-induced diabetes. C57BL6/J male mice were pretreated with daily intramuscular injections of 50 mg citiolone/kg body wt. for 30 days and were then rendered diabetic with 45 mg STZ/kg body wt. given for 5 days; citiolone was given until the animals were killed (days 6, 11 and 18 after the first STZ injection). Further animals were used as non-diabetic and diabetic (STZ-only) controls. The results show that LDS-treated animals when given citiolone: (1) were generally normoglycaemic; (2) had SOD levels that were higher than those of STZ-only control animals; (3) had an islet capillary area that was larger than that of LDS-treated mice. Therefore, the administration of a free radical scavenger, namely citiolone, is able partly to counteract and delay the reduction of islet vascular area and oedema formation in LDS-treated mice.

Washout kinetics of blood cells from the perfused pancreas of normoglycemic and diabetic rats

The aim of the present study was to evaluate vascular compartments within the rat pancreas with compartmental analysis of the outflow of blood cells from the perfused gland in situ. The presence of two vascular compartments requiring approximately 15 and 30 min for emptying, was noted in normoglycemic rats. The pancreas from diabetic rats, in which the islet beta-cells had been destroyed by intravenous injection of streptozotocin 1 or 6 weeks earlier, demonstrated the same outflow characteristics. It is therefore likely that these observations reflect the presence of two vascular compartments within the rat pancreas, possibly representing the islet-acinar vasculature and the ductal vasculature.

Microvasculature of the pancreas. Relation to pancreatitis

Local or generalized alteration of microcirculation may be expected in diseases of the pancreas. Changes may range from increased permeability of capillaries to hemorrhage. Tissue necrosis may result from prolonged ischemia owing to intravascular coagulation and severely impaired blood flow. It is possible to observe early microvascular changes by intravital microscopy. Klar and coworkers have demonstrated by this method that isovolemic hemodilution improves blood flow under conditions that would otherwise lead to tissue damage. This paper presents the basic microcirculation of the pancreas and the changes that accompany pancreatic disease. It emphasizes that concentration on the changes in microcirculation that accompany the early manifestations of pancreatic diseases, particularly pancreatitis, may reveal important clues to their pathogenesis.

Alterations of islet microvasculature in mice treated with low-dose streptozocin

Islet capillary area was followed daily in mice after treatment with low-dose streptozocin (LDS), in order to elucidate the exact period during which the insular vascular bed undergoes a significant reduction. Forty C57BL6/J mice were diabetized with 5 x 40 mg streptozocin (STZ)/kg body wt and killed 6, 8, 9, 10, 11, 12, 15 or 18 days after the first STZ injection. Pancreases were sectioned and processed by staining for alkaline phosphatases using a method devised by Gomori. The percentage of the islet parenchymal area occupied by intra-islet capillaries was measured using a Videoplan videoanalyzer. LDS treatment did not significantly alter the islet capillary area up to day 8; the first signs of reduction were seen on days 9 and 10 (islet capillary area at days 9 and 10 respectively was 2.68% and 2.60% of controls). At day 11 a dramatic decrease in islet capillary area was seen (1.38%), which was not accompanied by a similar reduction of the islet parenchymal area. The reduction in islet capillary area continued to progress up to day 15 by which time it had achieved the lowest level (0.72%). On day 18, values remained practically unchanged.

Capillary area in early low-dose streptozocin-treated mice

It has been reported that vasoconstriction of intra-islet capillaries plays an important role in the initiation of the insulitis seen in the islets of Langerhans of diabetic animals. Nevertheless, only a few studies have concentrated on islet vessels. This led us to perform an experiment with the aim to compare the islet capillary area of normal untreated and multiple low-dose streptozocin (LDS) (40 mg/kg b.wt. i.p./5 days)-treated mice. In order to identify endothelial cells a method devised by Gomori, based on the fact that these cells present alkaline phosphatases on their surface, was used. Results revealed that in LDS-treated animals the capillary area per islet is significantly reduced when compared to the vascular area of controls (p less than 0.05). This could be due to a vasoconstriction phenomenon that occurs in the islet capillaries after the streptozocin administration and before the appearance of any inflammation. Our findings could demonstrate that vasoconstriction events are involved in initiation of the diabetic disease.