Shailendra Saxena

Stimulation of neomucosal growth by systemic urogastrone

Patching small intestinal defects with colon serosa results in the growth of functional neomucosa. However, the rate of neomucosal growth is slow and the defect contracts markedly. The aim of this study was to determine if systemic urogastrone would enhance neomucosal growth. Twenty-two New Zealand white rabbits had two 2 X 5-cm ileal defects patched with colon serosa and osmotic pumps placed subcutaneously. Eleven animals had saline infused at a rate of 5 microliter/hr. The other eleven rabbits had urogastrone (1 mg/ml saline) infused at the same rate. One animal died in this group. There was a modest increase in neomucosal growth after 2 weeks of urogastrone infusion. Three weeks after patching, defect coverage was significantly greater in the urogastrone group (99.8 +/- 0.1 vs 96.0 +/- 1.2%, P less than 0.005) and more defects were completely covered by neomucosa (6/10 vs 1/12, P less than 0.05). Less contraction occurred in the urogastrone group (46 +/- 2 vs 35 +/- 3% initial defect, P less than 0.005) and resultant neomucosal surface area was greater (361 +/- 12 vs 266 +/- 20 mm2, P less than 0.0005). In vitro glucose uptake was significantly greater in the urogastrone group but disaccharidase and diamine oxidase activity were similar. Crypt cell production rate was significantly greater 2 weeks after operation compared to 3 weeks in both groups and was greater in the urogastrone group compared to the saline group at 2 weeks (24.9 +/- 1.1 vs 20.1 +/- 1.1, P less than 0.02). Systemic urogastrone enhances neomucosal growth by increasing the rate of growth and diminishing contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of intestinal regeneration: New insights

Intestinal regeneration is the process by which intestinal injury penetrating deep to the lamina propria heals. The regenerative process involves epithelial cell migration and proliferation, changes in cellular function, adaptation of subepithelial tissues, and contraction of the injured area. This requires interaction of multiple cell types. While many observations have been made about the process of regeneration, its regulation is not well understood. Previous studies, performed primarily in a serosal patch model, have identified many potential regulatory factors. These include location and size of the injury, other associated injury, e.g., resection, and a variety of agents that influence one or more of the primary processes involved. Epidermal growth factor (EGF), in particular, appears to play a role in many aspects of regeneration. Recent advances in the understanding of intestinal growth regulation have provided new insights into the regulation of intestinal regeneration. Developmental studies in genetically manipulated mice suggest a role for gene products not previously implicated in regeneration. The importance of apoptosis in growth regulation has recently been emphasized. Mesenchymal‐epithelial interactions have gained greater appreciation. Finally, it has become clear that immune cells and cytokines are important factors in this process. Transforming growth factor‐beta (TGFβ) has been implicated as another important regulator of several of the processes involved in intestinal regulation. Improved understanding of the regulation of intestinal regeneration will lead to new therapeutic approaches to stimulate intestinal healing in the clinical setting. Microsc. Res. Tech. 51:129–137, 2000.

Intestinal glucose uptake is increased in aged mice

Carbohydrate metabolism is impaired in the aged. Whether this is related to impaired glucose uptake or to other factors remains unclear. We measured changes in proliferative activity, glucose uptake, and disaccharidase activity in the intestinal mucosa of mice aged 2, 12, 24, and 30+ months to evaluate glucose absorption and its relationship to intestinal structure and proliferative activity. In vitro glucose uptake was increased significantly in the 30+ month-old mice compared to the younger animals. Similarly, crypt cell production rate and thymidine uptake were also increased. However, there were no significant changes in intestinal weight and length and villus height and crypt depth. These findings suggest that altered carbohydrate absorption in the aged is related to factors other than diminished mucosal glucose uptake. Whether this increased function is related to structural changes in the gut remains unclear.

Warfarin and bosentan interaction in a patient with pulmonary hypertension secondary to bilateral pulmonary emboli.

BACKGROUND Bosentan is an endothelin-receptor antagonist that reportedly induces both cytochrome P450 (CYP) 3A4 and CYP2C9 enzymes, which are also involved in warfarin metabolism. We present a case report describing a probable drug interaction between warfarin and bosentan in a patient with pulmonary hypertension. CASE SUMMARY A 52-year-old black female (weight, 77 kg) diagnosed with pulmonary hypertension secondary to bilateral pulmonary emboli had a stable international normalized ratio (INR; target range, 2-3) with a weekly warfarin dose of 52.5 mg for 2 months before the initiation of bosentan therapy. Other concurrent medications included telmisartan/ hydrochlorothiazide 40/12.5 mg once daily and a daily multivitamin (which contained no vitamin K). Three weeks after starting bosentan 62.5 mg BID, a therapeutic INR concentration was reached with a weekly warfarin dose 14% higher (an increase of 7.5 mg/wk) than her weekly warfarin dose before initiation of bosentan. After a brief discontinuation (7 days) and retitration of bosentan and warfarin, the final weekly warfarin dose (75 mg/wk) was 43% greater (an increase of 22.5 mg/wk) than the previously stable dose, which enabled the patient to reach her therapeutic INR goal range of 2 to 3. CONCLUSIONS Bosentan has CYP3A4- and CYP2C9-inducing properties and is therefore likely to cause decreased concentrations of warfarin. We describe here a probable drug interaction between bosentan and warfarin that resulted in a 43% increase in warfarin dose to maintain the patients therapeutic INR.

Role of Organized Intestinal Lymphoid Aggregates in Intestinal Regeneration

Intestinal lymphoid tissue has a complex interrelationship with the epithelium. The epithelia of intestinal crypts associated with lymphoid aggregates have an increased proliferation rate. In the present study, the authors tested the hypothesis that organized intestinal lymphoid tissue (Peyers patches) enhances intestinal regeneration by studying this process with and without an adjacent Peyers patch. Forty adult male Sprague-Dawley rats had full-thickness ileal defects patched with cecal serosa to allow regeneration of ileal mucosa. Control animals (group I) had the patch constructed adjacent to a Peyers patch, whereas this Peyers patch was excised in group II. Intestinal regeneration in both groups was evaluated on the third, fifth, seventh, and ninth days after operation. During the early phase of regeneration, both epithelial cell proliferation and migration were decreased in the patched defect after excision of the Peyers patch. Crypt cell production rate in the adjacent normal mucosa also was decreased after excision of the Peyers patch. Excision of the Peyers patch resulted in less well-developed crypts and villi. Wound contraction, however, was greater in the intestinal defect adjacent to the Peyers patch until day 7. In conclusion, Peyers patches have a facilitative effect on the healing of intestinal wounds by promoting both epithelial cell migration on the defect and epithelial cell proliferation in the crypts adjacent to the wound and by decreasing the rate of wound contraction. These findings support a role for intestinal lymphoid tissue in the regulation of epithelial cell maintenance.

Effect of the duration of infusion of urogastrone on intestinal regeneration in rabbits

Abstract Urogastrone (UG) increases the rate of mucosal regeneration on patched intestinal defects. Our aim was to determine the effect of the duration of UG administration on regeneration of serosa patched ileal defects in rabbits. Group I (n= 18) were controls. Group II (n= 15), Group III (n= 10) and Group IV (n= 5) received UG 1.5 μ/kg/h subcutaneously for 7 days, 14 days or 21 days respectively. Animals were sacrificed at 7 day intervals up to 21 days after patching. Neomucosal growth was significantly greater in the animals receiving UG and was greatest in Group IV. Group II and III animals had less contraction of the patched defect and greater neomucosal surface area than Group I animals at each interval but had a lesser effect than animals receiving UG continuously. Crypt cell production rate was significantly greater in UG treated animals at 7 and 14 days but fell to control levels at 21 days. Prolonging the duration of UG infusion increased the quantity of neomucosa produced by intestinal regeneration. However, UG stimulation of mucosal cell migration and proliferation occurred transiently within 14 days after patching.

Epithelial Cell Proliferation and Uptake of Radiolabeled Urogastrone in the Intestinal Tissues Following Abdominal Irradiation in the Mouse

We have evaluated the rate of crypt cell production and uptake of radiolabeled recombinant human urogastrone (125I-rhUG) in the intestinal tissues of the mouse at 3, 5, 7, 9, and 12 days following irradiation of the abdomen with 9 Gy. At autopsy, the animals were injected intraperitoneally with 1 microgram/g body weight of the metaphase arrest agent, vincristine sulfate, and 25 muCi of 125I-rhUG (specific activity 1.7 muCi/micrograms) to quantify the rate of crypt cell production and uptake of radiolabeled urogastrone, respectively. The results indicated that the rate of crypt cell production was increased significantly in the irradiated animals compared to the unirradiated animals and showed a peak on the 3rd and 5th postirradiation days in small intestine and colon, respectively. The uptake of 125I-rhUG was increased significantly on the 3rd postirradiation day in the intestinal tissues but showed a bimodal pattern with peaks on the 3rd and 9th postirradiation days. These results suggest that there may be a close association between epithelial cell proliferation and uptake of 125I-rhUG, particularly in the early part of recovery of intestinal mucosa following irradiation. However, these data do not discriminate whether the increased uptake of 125I-rhUG is the cause or the effect of proliferation induced by an irradiation stimulus. Further analysis also revealed that there was no relationship between crypt depth and 125I-rhUG uptake. However, crypt depth was inversely correlated with villus height in the proximal small intestine but not in the ileum. Villus height was correlated inversely with 125I-rhUG uptake in the ileum and jejunum but not the duodenum. The rate of crypt cell production was strongly correlated with crypt depth throughout the intestine and inversely correlated with villus height. This suggests that villus-to-crypt inhibitory feedback may be a primary regulator of cellular proliferation in the crypts and the association of 125I-rhUG uptake with proliferation indirectly reflects this interaction.

Difluoromethylornithine inhibits urogastrone stimulation of neomucosal growth

Urogastrone (UG) stimulates the growth of intestinal neomucosa on patched intestinal defects. This effect may be dependent on increased polyamine biosynthesis. The aim of this study was to determine if difluoromethylornithine (DFMO), a specific inhibitor of polyamine synthesis, would inhibit urogastrone stimulation of neomucosal growth. Twenty-four New Zealand white rabbits (2.1-2.9 kg) had 2 x 5-cm ileal defects patched with adjacent cecal serosal surface. Group I (n = 6) served as controls. Group II (n = 6) received UG 1.5 micrograms/kg/hr subcutaneously. Group III (n = 6) took 2% DFMO orally. Group IV (n = 6) received the same doses of UG and DFMO simultaneously. Animals were sacrificed 7 days after patching to assess neomucosal growth. Urogastrone infusion resulted in significantly greater neomucosal coverage (54 +/- 4%) and neomucosal surface area (236 +/- 18 mm2) in the Group II animals. Neomucosal coverage and contraction of the intestinal defects and neomucosal surface area were similar in the other three groups. Crypt cell production rate (15.5 +/- 2.0 cells/hr) and disaccharidase activity were also significantly greater in Group II than in the other groups. DFMO alone (Group III) resulted in a significantly lower ornithine decarboxylase (ODC) activity, polyamine content, and crypt cell production rate. Group IV animals had lower ODC activity but not lower polyamine content or crypt cell production rate. UG resulted in a significant increase in neomucosal growth. DFMO prevented this stimulatory effect and inhibited ornithine decarboxylase activity. The stimulation of neomucosal growth by UG is dependent, at least in part, on increased polyamine biosynthesis.

Montelukast for Symptom Control of Interstitial Cystitis

Objective: To describe the effects of montelukast, a leukotriene receptor antagonist commonly used in the treatment of allergic rhinitis and asthma, on the symptoms of interstitial cystitis (IC). Case Summary: A 64-year-old male had a history of IC with previous trials of solifenacin, dutasteride, and tamsulosin and little improvement in IC symptom reduction. When montelukast 10 mg was initiated for allergic rhinitis symptoms, a substantial improvement in urinary urgency and pain during therapy was noted. This improvement subsequently disappeared when montelukast was stopped. Discussion: IC, a rare occurrence in the male population, is related to an inflammatory process and has also been associated with inappropriate leukotriene release, which is the target of montelukast therapy. In general, treatment for IC Includes systemic medical therapy, local bladder treatment, surgical and neurosurgical procedures, and intravesical drug installation. Currently, montelukast is Food and Drug Administration approved for use in the treatment and prevention of mild-to-moderate asthma and exercise-induced asthma, as well as treatment of seasonal and perennial allergic rhinitis. While montelukast treatment did not cure the patients IC, it improved his quality of life through substantial symptomatic relief, including less pain and urgency. Conclusions: Montelukast may be an effective treatment option in the management of interstitial cystitis. Further research is needed to substantiate this novel use.

Effect of systematic interleukin-3 administration on epithelial cell proliferation in mouse intestine

The effect of interleukin-3 (IL-3) on the crypt cell production rate (CCPR) in the intestine of mice was studied using a stathmokinetic technique combined with crypt microdissection. Interleukin-3 (0.71 micrograms/injection) was administered subcutaneously (s.c.) as two injections per day for 7 successive days and small mucosal pieces (duodenum, jejunum, ileum and colon) removed at necropsy were organ cultured in the presence of the metaphase arrest agent vincristine sulfate for two hours. The number of metaphases was enumerated in dissected crypts and CCPR calculated. The results demonstrated that the CCPR was significantly increased in all mucosal segments in the IL-3 treated animals compared to saline injected controls. These results suggest that the growth promoting properties of IL-3 are not restricted to hematopoietic cells when used in vivo and may directly or indirectly increase epithelial cell turnover in gut mucosa.