Hypertrophy of intestinal smooth muscle in cats

Meta-Assessment of Metformin Absorption and Disposition Pharmacokinetics in Nine Species

The objective of this study was to systematically assess literature datasets and quantitatively analyze metformin PK in plasma and some tissues of nine species. The pharmacokinetic (PK) parameters and profiles of metformin in nine species were collected from the literature. Based on a simple allometric scaling, the systemic clearances (CL) of metformin in these species highly correlate with body weight (BW) (R2 = 0.85) and are comparable to renal plasma flow in most species except for rabbit and cat. Reported volumes of distribution (VSS) varied appreciably (0.32 to 10.1 L/kg) among species. Using the physiological and anatomical variables for each species, a minimal physiologically based pharmacokinetic (mPBPK) model consisting of blood and two tissue compartments (Tissues 1 and 2) was used for modeling metformin PK in the nine species. Permeability-limited distribution (low fd1 and fd2) and a single tissue-to-plasma partition coefficient (Kp) value for Tissues 1 and 2 were applied in the joint mPBPK fitting. Nonlinear regression analysis for common tissue distribution parameters along with species-specific CL values reasonably captured the plasma PK profiles of metformin across most species, except for rat and horse with later time deviations. In separate fittings of the mPBPK model to each species, Tissue 2 was considered as slowly-equilibrating compartment consisting of muscle and skin based on in silico calculations of the mean transit times through tissues. The well-fitted mPBPK model parameters for absorption and disposition PK of metformin for each species were compared with in vitro/in vivo results found in the literature with regard to the physiological details and physicochemical properties of metformin. Bioavailability and absorption rates decreased with the increased BW among the species. Tissues such as muscle dominate metformin distribution with low permeability and partitioning while actual tissue concentrations found in rats and mice show likely transporter-mediated uptake in liver, kidney, and gastrointestinal tissues. Metformin has diverse pharmacologic actions, and this assessment revealed allometric relationships in its absorption and renal clearance but considerable variability in actual and modeled tissue distribution probably caused by transporter differences.

Ultrasonographic and histopathological features in 8 cats with fibrotic small intestinal stricture

Benign stricture is an uncommon cause of chronic small intestinal obstruction in the cat. The purpose of this retrospective case series was to describe the ultrasonographic features, histopathological findings, and clinical presentation in a group of cats with benign small intestinal stricture. Inclusion criteria were cats presenting during the period 2010-2017, and that had ultrasonography and small intestinal stricture confirmed at surgery. For each cat, clinical data and ultrasonographic findings were retrieved from the medical record, and histopathology, where available, was reviewed. Eight cats met the inclusion criteria. The location of strictures was duodenum (1/8), mid- to distal jejunum (4/8), and ileum (3/8). Ultrasonographic findings included gastric distension (8/8) and generalized (3/8) or segmental (5/8) intestinal dilation consistent with mechanical obstruction. Ingesta did not propagate beyond the strictured segment. Wall thickening was mild to moderate (3-6 mm). Normal wall layering was disrupted in all cats. Strictures were predominantly hypoechoic (7/8) and associated with hyperechoic peri-intestinal mesentery (6/8). Annular strictures (5/8) were less than 15 mm in length whereas long-segment strictures (3/8) were greater than 15 mm in length. Histopathology showed transmural disease with fibrosis and inflammation (8/8), often (6/8) extending into the bordering mesentery. The mucosa was the most severely affected layer and epithelial injury accompanied the mucosal fibrosis/inflammation. Clinical presentation reflected delayed diagnosis of chronic bowel obstruction with debilitation (8/8), marked weight loss (8/8), and prerenal azotemia (5/8). Benign fibrostenotic stricture should be considered a differential diagnosis in debilitated young cats presenting with chronic bowel disease and ultrasonographic features of intestinal obstruction.

Pseudodiverticula of the Small Intestine Associated With Idiopathic Smooth Muscle Hypertrophy in Domestic Rabbits (Oryctolagus cuniculus)

Acquired outpouches of the intestinal tract are referred to as pseudodiverticula or false pulsion diverticula. In contrast to true diverticula, in which the wall contains all layers of the intestinal tract, the wall of pseudodiverticula lacks the tunica muscularis. Smooth muscle hypertrophy of the small intestine is commonly considered a cause of pseudodiverticulosis in animals due to increased intraluminal pressure. This study reports pseudodiverticula associated with idiopathic smooth muscle hypertrophy of the small intestine in lagomorphs. Four domestic rabbits had single or multiple (up to 200) pseudodiverticula of various size in the small intestine. In all cases the tunica muscularis was diffusely thickened, significantly exceeding reference thickness of 14 rabbits (mean, 112.3 µm; range, 26.3–389.0 µm). Clinical signs were considered to be caused by severe necrosis and inflammation of the wall of large pseudodiverticula, leading to perforation with subsequent peritonitis and mesenteric and omental abscess formation in 2 cases.

A Mouse Model of Intestinal Partial Obstruction

Intestinal obstructions, that impede or block peristaltic movement, can be caused by abdominal adhesions and most gastrointestinal (GI) diseases including tumorous growths. However, the cellular remodeling mechanisms involved in, and caused by, intestinal obstructions are poorly understood. Several animal models of intestinal obstructions have been developed, but the mouse model is the most cost/time effective. The mouse model uses the surgical implantation of an intestinal partial obstruction (PO) that has a high mortality rate if it is not performed correctly. In addition, mice receiving PO surgery fail to develop hypertrophy if an appropriate blockade is not used or not properly placed. Here, we describe a detailed protocol for PO surgery which produces reliable and reproducible intestinal obstructions with a very low mortality rate. This protocol utilizes a surgically placed silicone ring that surrounds the ileum which partially blocks digestive movement in the small intestine. The partial blockage makes the intestine become dilated due to the halt of digestive movement. The dilation of the intestine induces smooth muscle hypertrophy on the oral side of the ring that progressively develops over 2 weeks until it causes death. The surgical PO mouse model offers an in vivo model of hypertrophic intestinal tissue useful for studying pathological changes of intestinal cells including smooth muscle cells (SMC), interstitial cells of Cajal (ICC), PDGFRα⁺, and neuronal cells during the development of intestinal obstruction.

Clinicopathological and ultrasonographic features of cats with eosinophilic enteritis

Eosinophilic enteritis (EE) in cats is poorly characterized. The aim of the current study was to retrospectively evaluate the clinical and ultrasonographic findings in cats with histologic evidence of eosinophilic inflammation on gastrointestinal biopsy. Twenty-five cats with tissue eosinophilia on surgical (10) or endoscopic (15) biopsy of the gastrointestinal tract, having an abdominal ultrasound performed within 48 h of biopsy acquisition, were enrolled. History, clinical presentation, clinical pathology and abdominal ultrasound findings were reviewed. Intestinal biopsies were evaluated by a single pathologist and separated into two groups based on the degree of eosinophilic infiltrate: mild (<10 eosinophils/high-power field [HPF], 11/25 cats), or moderate/marked (>10 eosinophils/HPF, 14/25 cats). The former were considered primary lymphoplasmacytic or lymphocytic inflammatory bowel disease (LPE) with subtle eosinophilic infiltrates, and the latter to have EE. Signalment, history and clinical signs were similar in all cats. Only cats with EE (6/14) had palpably thickened intestines. The only distinguishing clinicopathological feature of cats with EE was the presence of peripheral eosinophilia (6/14). On ultrasound, when compared with cats with LPE, cats with EE had a greater mean jejunal wall thickness (3.34 mm ± 0.72 mm vs 4.07 mm ± 0.58 mm, respectively) and an increased incidence of thickening of the muscularis layer (1/11 and 11/14, respectively). In conclusion, ultrasonographic evidence of a prominent intestinal muscularis layer, palpably thickened intestines and peripheral eosinophilia can serve as biomarkers for the presence of EE in cats with chronic intestinal signs.

In vitro smooth muscle contractility before and after relief of experimental obstruction in the rat: application to the surgical management of ileal dilatation

PURPOSE

Bowel dilatation occurs proximal to an obstruction and predisposes to intestinal dysmotility. The present study sought to determine whether or not changes in smooth muscle contractility and the thickness of the proximal, dilated bowel wall can be reversed following relief of the obstruction.

MATERIALS AND METHODS

Three groups of seven male Wistar rats were studied. In 8-week-old animals in a control group and a sham-operated group, a small segment of bowel (designated as R1 for controls and R2 for shams) was resected 5.0 cm from the cecum. In the third (operated) group, a narrow, isoperistaltic intestinal loop was created proximal to an end-to-end anastomosis of the ileum in 4-week-old animals. When these animals were 6 weeks old, the loop was re-anastomosed to the distal small bowel (after resection of the loop's distal portion, referred to as R3). Two weeks later, a small segment of bowel was resected proximal to the anastomosis (R4). We evaluated the thickness of the smooth muscle layers and the in vitro contractile responses of circular smooth muscle ileal strips (R1-R4) to electrical stimulation and pharmacological stimulation (with KCl, acetylcholine (ACh), substance P, N(G)-nitro-l-arginine methyl ester (L-NAME) and histamine).

RESULTS

The amplitudes of contraction in response to electrical and Ach-mediated stimulation were higher for R3 than for R4 (P<0.001), R1 and R2 (both P<0.05). Compared with R1 and R2, the smooth muscle layer was three times as thick in R3 (P<0.001) and 2.5 times as thick in R4 (P<0.01).

CONCLUSION

Our study provides evidence of the possible recovery of intestinal motility (in response to neurotransmitters involved in gut function) after the relief of an obstruction. If ileal motility can conceivably return to normal values, conservative surgical procedures in pediatric patients should be preferred (in order to leave a sufficient length of bowel and avoid short bowel syndrome).

Intestinal Adenocarcinoma in a Herd of Farmed Sika Deer (Cervus nippon)

Intestinal adenocarcinomas were identified in 76 adult deer from a closed herd of 193 breeding animals grazing pasture heavily infested with bracken fern ( Pteridium aquilinum). Tumors were observed postmortem in 32 animals with rapid weight loss, and similar neoplasms were detected in a further 44 clinically normal deer at “cull.” Tumors were located in distal ileum, cecum, and proximal colon and presented as single (26%) or multiple (74%), variably sized, pale-gray, firm, poorly circumscribed neoplasms with associated intestinal strictures. Histopathologically tumors were well-differentiated, locally infiltrative, low-grade adenocarcinomas of tubular (51%), mucinous (33.5%), or mixed (15.5%) types. Extraintestinal metastases were not observed. The high incidence of intestinal adenocarcinoma within this herd suggests a specific and novel syndrome, and genetic and/or environmental factors may be involved in the pathogenesis.

Goblet cell hyperplasia and muscular layer thickening in the small intestine of a cynomolgus monkey

We report here the interesting case of a 5-year-old male cynomolgus monkey with goblet cell hyperplasia and thickening of the muscular layer throughout the small intestine without exhibiting any clinical symptoms. Necropsy examination showed diffuse thickening of the intestinal wall from the jejunum to the ileum, with an appearance likened to a rubber tube. Histopathologically, marked thickening was observed in both the mucosal and muscular layers in the jejunum and ileum, and slight thickening was observed in the duodenum. Goblet cell hyperplasia with extension of the circular folds and villi was prominently observed. The mucosal surface was covered with a thick mucus layer containing desquamated mucosal epithelial cells, and both the inner and outer muscular layers were markedly thickened due to smooth muscle hypertrophy. Neither macroscopic nor histopathological examination identified any causative factors, such as infection, enteritis and intestinal stenosis, or obstruction that may have caused development of this lesion. Given these observations, this case may simply be considered of spontaneous goblet cell hyperplasia and muscular layer thickening in the small intestine of a cynomolgus monkey.

A light and scanning electron microscope study of the albino rat ileum after partial obstruction

PURPOSE

Induction of an obstruction could be resorted to as a definitive line of management in some cases of short bowel syndrome (SBS). The goal of this study has been to elucidate histological and morphometric alterations in the albino rat ileum after surgically induced partial obstruction.

METHODS AND MATERIALS

Thirty adult male albino rats (240-250 g) were used in this investigation. They were divided into two equal groups: control and experimental. Small pieces of the ileum of the control and experimental animals were processed for histological and scanning electron microscope study.

RESULTS

The ileum of the experimental animals proximal to the site of obstruction showed an apparent enlargement in the Peyer's patches and an increase in the thickness of both the mucosa and muscle layers. The villi showed significant elongation and thickening. Both widening and deepening of the crypts were detected. There was an apparent increase in the goblet cell number and lymphocytic infiltration in both the corium and submucosa. In scanning electron microscopic examination, the microvilli showed scattered areas of shortening and irregular orientation. The surface was more frequently interrupted by goblet cell orifices.

CONCLUSIONS

Partial ileal obstruction resulted in hypertrophy of the ileal wall with considerable structural alterations oral to the obstruction site. Thus, the procedure apparently increased the absorptive surface area together with reduction in the speed of intestinal transit. These effects could support taking this technique into consideration as one of the suggested lines of treatment of some cases of SBS to eliminate the patient's need for parenteral nutrition and all of its associated complications.

Eosinophilic fibrosing gastritis and toxoplasmosis in a cat

A 3-year-old, neutered male Tiffany cat was presented to the Animal Health Trust for investigation of pyrexia and a gastric lesion. Radiography and ultrasound showed severe thickening of the gastric wall and regional lymphadenopathy. There was altered gastric wall layering, predominately due to muscularis thickening. Histopathology confirmed eosinophilic fibrosing gastritis. The cat also had evidence of generalised Toxoplasma gondii infection, which may have been responsible for the gastric changes.

Effects of cholesterol on proliferation and functional protein expression in rabbit bile duct fibroblasts

AIM: To investigate the effect of cholesterol (Ch) on the growth and functional protein expression of rabbit bile duct fibroblasts.

METHODS: The cultured bile duct fibroblasts were divided randomly into two groups: the control group and the experiment group (fibroblasts were incubated respectively with 0.6 g/L Ch for 12, 24, 36 and 48 h). The growth and DNA synthesis of bile duct fibroblasts were measured by the means of ³H-TdR incorporation. The total protein content of fibroblast was measured by BSA protein assay reagent kit, then the expression of α-actin was analyzed semi-quantitatively by Western blot.

RESULTS: After treatment with 0.6 g/L Ch for 12, 24, 36 and 48 h, the values of ³H-TdR incorporation of bile duct fibroblasts were respectively 3.1 ± 0.39, 3.8 ± 0.37, 4.6 ± 0.48 and 5.2 ± 0.56 mBq/cell, and the values of the corresponding control groups were 3.0 ± 0.33, 3.2 ± 0.39, 3.7 ± 0.49 and 4.3 ± 0.43 mBq/cell. After comparing the values of experiment groups and their corresponding control groups, it was found that the ³H-TdR incorporation of bile duct fibroblasts after treatment with 0.6 g/L Ch for 24, 36 and 48 h were significantly increased (P < 0.05, P < 0.01, P < 0.01), while the ³H-TdR incorporation of 12-h group was not different statistically from its control group. Ch had no obvious effect on the total protein content of fibroblasts. After incubated with 0.6 g/L Ch for 12, 24, 36 and 48 h, the total protein content of each experiment group was not altered markedly compared with its corresponding control group. The values of experiment groups were 0.246 ± 0.051, 0.280 ± 0.049, 0.263 ± 0.044 and 0.275 ± 0.056 ng/cell, and those of corresponding control groups were 0.253 ± 0.048, 0.270 ± 0.042, 0.258 ± 0.050 and 0.270 ± 0.045 ng/cell. Western blot analysis revealed that the α-actin expression in fibroblasts affected by Ch for 12 and 24 h was not markedly changed compared with their corresponding control groups (P>0.05), the values of total gray scale of 12- and 24-h groups were 1 748 ± 185 and 1 756 ± 173, respectively. But after stimulation with Ch for 36 h, the total gray scale of fibroblasts (1 923 ± 204) was significantly higher than that of control group (1 734 ± 197). When the time of Ch treatment was lengthened to 48 h, the α-actin expression was markedly elevated, the total gray scale was 2 189 ± 231 (P < 0.01 vs control group).

CONCLUSION: Moderately concentrated Ch can promote the proliferation of bile duct fibroblasts at early stage. With the prolongation of Ch treatment, the α-actin expression of fibroblasts was also increased, but the hypertrophy of fibroblasts was not observed.