Perinatal changes in bombesin-stimulated muscle contraction in rabbit stomach and colon

Bombesin and its mammalian homologue, gastrin-releasing peptide, stimulate smooth muscle contraction and may promote the growth of gastrointestinal tissues. Isometric contraction of strips from circular muscle of the gastric fundus and longitudinal muscle of the distal colon were used to compare changes in the response to bombesin in newborn and weanling rabbits. There was an age-related qualitative change in gastric muscle from biphasic contractions including phasic and tonic components in the newborn to phasic contractions alone in the weanling. The colon contractions were tonic at both ages. In both tissues there was an age-related fivefold increase in stress in response to maximally effective concentrations of bethanechol (P less than 0.05). In contrast, in the stomach age-related decreases in the response to maximally effective concentrations of bombesin were observed, from 2930 +/- 179 mN/cm2 (98% of the maximal response to bethanechol) in the newborn to 565 +/- 81 mN/cm2 (4% of the maximal response to bethanechol) in the weanling (P less than 0.005). In the colon, a twofold increase in response to bombesin was observed, from 446 +/- 59 mN/cm2 (82% of the response to bethanechol) in the newborn to 862 +/- 11 mN/cm2 (29% of the response to bethanechol) in the weanling (P less than 0.05). No age-related changes were observed in the potency of bombesin in either tissue. Neither atropine nor tetrodotoxin altered the contractions in either tissue, suggesting that bombesin interacted directly with myocytes. There was three times as much bombesinlike immunoreactivity in the stomach compared with the colon, but no age-related changes in either tissue. In summary, by the age of weanling the stomach lost the tonic component of contraction and 80% of the efficacy of bombesin-stimulated phasic contraction that had been present in the newborn. The loss of efficacy, absolute in the stomach and relative to bethanechol in the colon, suggest that bombesin may be most important in stimulating motility in the neonatal period.     

Histological and angiographic effects of a pulsed holmium:YAG laser in normal and atherosclerotic human coronary arteries and aorta.

OBJECTIVE: The aims were (1) To determine the histological and angiographic effects of holmium:YAG laser energy delivered through clinical multifibre laser catheters on fresh cadaveric coronary arteries; and (2) to relate the placement of optical fibres in the catheter to patterns of tissue ablation in cadaveric aorta. METHODS: Eight fresh cadaveric hearts and segments of aorta were used. Hearts were mounted on a new pressure perfusion device. The laser catheter was delivered over a guidewire in the lumen until it met an area of resistance. The coronary artery lumen was perfused at approximately 100 mm Hg mean pressure. These arterial areas were identified on angiography, marked, and then exposed to laser energy in the range 600-3000 mJ.mm-2. Normal and atherosclerotic areas of fresh cadaveric aortic strips were exposed to increasing laser energies using either constant or increasing fluence. Coronary arteries were pressure perfused with formalin for 18-24 h at 100 mm Hg mean pressure, and aortic strips were immersed in 5% formalin. Light and scanning electron microscopy studies were carried out. RESULTS: There were no perforations or dissections by angiography in the fresh coronary arteries. One of 15 normal coronary artery segments and 10 of 16 of the pressure perfused, fixed, atherosclerotic coronary artery segments showed thermal changes associated with atherosclerotic plaque ablation. In aortic tissue, thermal effects extended 0 to 0.6 mm lateral to the ablated crater. Acoustic effects were seen only in the aortic strips after ablation at fluences > 1000 mJ.mm-2. The "dead spaces" around the optical fibres in the catheter resulted in significant amounts of coagulated tissue fragments remaining in the crater. CONCLUSIONS: Holmium:YAG laser energy delivered through multifibre catheters ablated atherosclerotic tissue in coronary arteries with minimal damage to the normal walls. The cadaveric coronary artery perfusion apparatus is useful for assessing catheter delivery and mobility and the effects of laser energy on the coaxially orientated normal and atherosclerotic coronary arterial wall.     

Selective vascular coagulation of rabbit colon using a flashlamp-excited dye laser operating at 577 nanometers

Previous studies have demonstrated that brief pulses of selectively absorbed optical radiation can be used to confine thermal injury to pigmented targets within tissues. We performed studies in rabbits to assess the usefulness of this technique for selectively coagulating the colonic vasculature. By measuring the optical absorbance of rabbit colon with a spectrophotometer, it was determined that hemoglobin exhibits strong absorption relative to the rabbit colon at a wavelength of 577 nm. Because light must be absorbed to affect tissue, it was hypothesized that laser pulses of this wavelength would selectively damage blood vessels. This hypothesis was tested by examining the effect of 300-microseconds-long 577-nm laser pulses on rabbit colon in vivo. For delivered radiant exposures between 4 and 8 J/cm2, selective coagulation of the colonic vasculature could be produced without damage to the surrounding colon. At greater radiant exposures, vessel hemorrhage was occasionally noted but no transmural thermal injury was produced with delivered radiant exposures as high as 22 J/cm2. This technique may form the basis of a safe and simple treatment of vascular lesions of the colon such as angiodysplasia.     

Granular-cell myoblastoma of stomach and colon

Summary 1. Two cases of granular-cell lesions (myoblastoma) involving stomach and colon, respectively, are reported.2. The biologic nature of the lesion with reference to histogenesis is reviewed.3. In our opinion, granular-cell myoblastoma, rather than developing as a neoplasm of muscle origin, is a tumor of neural origin arising from Schwann cells, and the term granular-cell neuroma is appropriate.Supported in part by National Cancer Institute Grants C-2090 (C6) and C-4486 (C1) , and The American Cancer Society, Inc., including the Massachusetts Division.     

Management of obstructing pulmonary broncholithiasis with three-dimensional imaging and holmium laser lithotripsy

Major airway obstruction due to broncholithiasis produces significant morbidity, and management is difficult. Many of the patients are elderly and are not good candidates for surgical removal. Bronchoscopic removal may be limited due to anatomic considerations, skill of the bronchoscopist, and exposure of the patient to additional procedural risks. Preprocedural planning with three-dimensional (3D) multidetector CT (MDCT) imaging enhances the bronchoscopist's knowledge of the relationships of the target lesions with critical structures, and improves the efficiency of the application of specific endobronchial therapies. Here we report our experience treating obstructing broncholithiasis in two patients utilizing pretreatment planning with 3D MDCT imaging, followed by bronchoscopically delivered holmium laser fragmentation of the stones.     

Arthroscopic synovectomy for rheumatoid arthritis using a holmium:YAG laser

OBJECTIVE: To determine the usefulness of the holmium:YAG laser system in arthroscopic synovectomy (ASSX) for treating rheumatoid arthritis (RA). METHODS: ASSX was performed on 15 knees (one Larsen Grade 1, 7 Grade 2, 7 Grade 3) and 8 ankles (6 Grade 2, 2 Grade 3) of 17 female patients with RA. The average age at ASSX was 50.6 years (25-70). The average followup period was 24.4 months (10-47). RESULTS: Seven out of 8 knees with grade 1 or 2 had reduced pain and swelling, as well as decreased average serum levels of C-reactive protein (CRP) (from 3.6+/-1.1 to 1.4+/-0.3 mg/dl). However, 4 out of 7 knees with grade 3 showed recurrence of pain and swelling along with persistent average serum level of CRP (from 4.3+/-1.0 to 3.8+/-1.0 mg/dl). All 8 ankles with Grade 2 or Grade 3 experienced reduced pain and swelling, while the average serum CRP levels did not change (from 3.2+/-0.9 to 2.9+/-1.0 mg/dl). CONCLUSION: The Holmium:YAG laser was useful in ASSX for treating RA knees and ankles.     

Percutaneous transmyocardial revascularization with holmium laser in patients with refractory angina: a pilot feasibility study.

BACKGROUND: Percutaneous transluminal myocardial revascularization (PTMR) is a new procedure to improve perfusion of the ventricular wall for patients with intractable angina that is untreatable by surgery or conventional catheter-based intervention. PTMR allows the creation of myocardial channels through the controlled delivery of holmium laser energy from the ventricular chamber. Preliminary studies in animals and human subject have yielded promising results. We now report the feasibility study of PTMR using a laser delivered through a novel Eclipse system, and we present the results of this sole therapy in patients with severe coronary disease and angina refractory to maximal medical treatment angina (III-IV CCS). METHODS: Percutaneous vascular access for PTMR treatment was obtained via the femoral artery. A 9F directional catheter carrying flexible fiber optics was used with a holmium laser (Eclipse system) and was placed across the aortic valve into the left ventricle cavity to create channels with a depth of 5 mm from the endocardial surface into the myocardial tissue. From April to November 1998, 15 patients underwent PTMR with Eclipse system. Two patients were female; the mean age was 66 +/- 8 (range 59-74). Five patients had a severe LV dysfunction (FE < 30%). Preoperative angina class was III in 10 patients and IV in 5 and previous myocardial procedures had been performed in all patients. RESULTS: The procedure was well tolerated and procedural success was obtained in 14 of 15 patients. There was one myocardial perforation because of guiding-catheter manipulation (pericardial drainage in fourth day). We performed a mean of 13 +/- 4 channels in a mean fluoro time of 23 +/- 11 min. Upon release and during follow-up (5.3 months +/- 4.2, range 2-10), angina class had significantly improved in 14 of 14 patients with complete PTMR treatment, with 4 asymptomatic patients, 6 patients in CCS I, 3 in CCS II, 2 in CCS III and only one patient hospitalized due to angina. CONCLUSION: This pilot study confirmed the safety and technical feasibility of PTMR. Immediate and short-term results confirm that a clinical improvement is obtained in most patients. Although these are early clinical benefits, the true efficacy of this approach will necessarily be defined by a randomized trials with prospectively-defined endpoints and with PTMR compared with medical therapy.     

Percutaneous transluminal myocardial revascularization with a holmium laser system: procedural results and early clinical outcome.

Surgical transmyocardial laser revascularization has been reported to improve clinical outcome in patients with refractory angina who are not candidates for angioplasty or bypass surgery. We investigated the feasibility and safety of a nonsurgical, percutaneous technique for laser channel creation using energy from a holmium:yttrium-aluminium-garnet (YAG) laser. The laser energy was directed through a fiber enclosed in a catheter to the ventricular myocardium creating channels between the blood pool and the myocardium. Thirty-five patients with angina and coronary anatomy not amenable to revascularization with coronary angioplasty or bypass surgery underwent percutaneous transluminal myocardial revascularization. A total of 15 +/- 5 channels were formed per patient. There was no procedure-related mortality. One patient developed cardiac tamponade requiring thoracotomy and another a minor self-limiting pericardial effusion. There was no worsening of regional wall motion function in any patient. All patients were discharged alive after a postprocedure hospital stay of 2.1 +/- 1.4 days. Mean Canadian Cardiovascular Society (CCS) functional class declined from 3.68 +/- 0.4 before procedure to 0.82 +/- 0.7 at 30 days (P < 0.01). At 3 months, mean angina class was 0.94 +/- 0.65 (n = 35; P < 0.01) and at 6 months, mean angina class was 1.08 +/- 0.58 (n = 26; P < 0.01). One patient required repeat revascularization after 5 months for progression of disease in a degenerated saphenous venous graft supplying different region of myocardium. We conclude that transmyocardial revascularization using holmium:YAG laser by percutaneous technique can be carried out safely with encouraging early results and a very low complication rate. The symptomatic relief seen up to 6 months has been excellent. The long-term effects of this technique on mortality and relief of angina, however, remain to be defined. Cathet. Cardiovasc. Intervent. 47:287-291, 1999.     

Motility of rabbit proximal colon

To better define the physiologic relevance of the cholinergic muscarinic input to the rabbit colon and the role of different muscarinic receptor subtypes, we studied the effects of atropine, telenzepine (M₁ antagonist) and DF594 (M₃ antagonist) on colonic motility in eight conscious rabbits fitted with bipolar electrodes and strain gauges along the proximal colon. In some experiments, the chronotropic and mydriatic effect of the pharmacological agents were also assessed. Two main patterns of spike activity were identified: short spike bursts (SSBs), which were usually stationary, and long spike bursts (LSBs), which were usually propagated. Both myoelectrical patterns were dose-dependently inhibited by atropine (0.06–4 mol/kg). Atropine, at the doses of 2–4 mol/kg, abolished both myoelectrical and mechanical activity. Telenzepine (0.008–0.125 mol/kg) dose-dependently inhibited migrating LSBs without significant effect on SSBs. Higher doses (0.25–0.5 mol/kg) inhibited both LSBs and SSBs. DF594 (0.06–2 mol/kg) dose-dependently inhibited both migrating LSBs and SSBs. The three antimuscarinic agents, at doses that inhibited colonic spike activity by approximately 80% (equiactive doses), behaved as follows on heart rate and pupil diameter: atropine induced tachycardia and mydriasis, telenzepine had no effect, and DF594 induced slight mydriasis with no effect on heart rate. We conclude that spontaneous motility in the rabbit proximal colon depends on a muscarinic excitatory input. M₃ receptors are involved in the control of both LSBs and SSBs, while M₁ receptors play an important role in the regulation of LSBs. The development of selective antimuscarinic drugs, acting on a given motility pattern and with minimal side effects, may offer new perspectives in the treatment of functional bowel motor disorders.This work was supported in part by a grant from the Ministero dell'Università e della Ricerca Scientifica e Tecnologica.A preliminary report of this paper was presented at the Fifth European Symposium on Gastrointestinal Motility held in Augsburg, Germany, June 13–16, 1990, and appears in abstract form inJ Gastrointest Motil 2:156, 1990.