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Biomedical subjects

S S Shirazi

Publications and source records attributed to S S Shirazi.

At least 19 recordsLinked to original sources
PubMed1998

Contractions move contents by changing the configuration of the isolated cat stomach.

To understand how contractions move gastric contents, we measured, in isolated cat stomachs, the effects of contractions on gastric length, diameters, pressures, and emptying. Movements of the stomach and of gastric contents were monitored by video camera and ultrasound and were related to mechanical events. Based on pressures, we defined the following four phases of contractions: 1) Po, a steady pressure associated with tonic contraction of proximal stomach; 2) P', a pressure wave during which the contraction indents the gastric body; 3) a pressure nadir while the contraction lifts the gastric sinus toward the incisura; and 4) a second pressure wave, P", as the contraction advances through the antrum. In open preparations, liquid output and shortening of the greater curvature are large during Po, stop during P', and resume with P". Contractions generate higher pressures when gastric volume is held steady. Contractions increase wall thickness and decrease gastric diameters at sites they involve and have opposite effects at remote sites. Contractions move the incisura and hence redraw the borders between gastric segments and shift volumes back and forth within the gastric lumen. Contractions furthermore stir up, compress, and disperse particulate beans without moving them to the pylorus. We conclude that gastric contractions 1) reverse changes in gastric length that occur during gastric filling, 2) move gastric contents directly through local contact and indirectly by changing the configuration of the stomach, and 3) interact with structures such as the incisura in retaining and breaking up solid gastric contents.

Animals↗
PubMed1997

Gastric contractions, secretions and injury in cold restraint.

The clinical syndrome of stress ulceration has been studied for years using rodent cold restraint stress models, although the pathogenesis of the characteristic focal gastric mucosal lesions produced in these models has been controversial. We used gastric strain gauges to characterize fully the gastric motility effects of a 4-h cold restraint protocol, and we determined the relationship of variations in gastric contents and in gastric contractions to the amount of gastric mucosal injury. Additionally, we examined rat stomachs histologically, and determined the location of focal haemorrhagic mucosal lesions on the mucosal rugae. We found a consistent relationship between force of gastric contractions and gastric mucosal injury, and also a relationship between the initial duration of contractions during restraint and ultimate mucosal injury. Volume, acidity and mucus in the gastric contents were unrelated to mucosal injury. The majority (91%) of the mucosal lesions had some relationship to a rugal fold, with 59% of all lesions at the base of a rugal fold. Thus, the mechanical forces of gastric hypercontractility may contribute to the gastric mucosal injury of rodent cold restraint models.

Animals↗
PubMed1995

Haustral septations increase axial and radial distribution of luminal contents in glass models of the colon.

We used two glass models of the colon to test the hypothesis that luminal septations increase efficiency of flow. Each was a straight glass tube 4 cm in diameter and filled with water. One had four septations narrowing the lumen to 2 cm; the other had no septations. For each run, liquid dye and one solid test particle were placed at one end of the model. A single pressure pulse was applied to the dye and particle. The distance each traveled was compared using analysis of variance. The nonseptated model had poor mixing of dye, and the particle moved only short distances. In the septated model, there was thorough mixing of dye and the particle moved rapidly along what appeared as a central core of high-velocity liquid flow from one septal opening to another. Compared with the nonseptated model, this produced statistically significant increases in the distances traveled by means of 32 (dye) and 90% (particle). Our studies suggest that septations in a tubular organ facilitate intraluminal mixing and flow of liquids and solids.

Colon↗
PubMed1989

Evidence for inhibition of opossum LES through intrinsic gastric nerves.

We have studied the mechanical responses of the isolated opossum gastroesophageal junction to a variety of stimuli. Lower esophageal sphincter (LES) relaxations were readily produced by gastric stretch and by electrical stimulation of the intramural gastric nerves. Gastric stimulation also led in 60% of stimuli to a contraction of circular muscle (the off response) in the distal esophagus, but in less than 15% of stimuli to a contraction of longitudinal esophageal muscle (the duration response). Mechanical or electrical stimulation of the esophagus led to a mechanical response of the stomach (relaxation, contraction, or both) in 76% of stimuli. The LES relaxation produced by esophageal stimulation was not as long as that produced by gastric stimulation. Direct electrical stimulation of the esophageal or gastric muscle produced a ring contraction that spread readily across the gastroesophageal junction but did not produce a relaxation of the LES or a contraction of the longitudinal esophageal muscle. Thus intramural nervous pathways can coordinate the mechanical activity of the esophagus, LES, and stomach. LES relaxations may occur as part of intrinsic reflexes that mediate gastric accommodation to volume.

Animals↗
PubMed1987

Long-term follow-up for treatment of complicated chronic reflux esophagitis.

In the past 18 years the Nissen fundoplication has undergone a few modifications and changes in our institution and all over the world. The aim of this study is to review the long-term (up to 20 years) results of Nissen fundoplication in 350 patients and to evaluate the effect of major modifications in the technique of fundoplication in these patients. Three hundred fifty patients with symptomatic chronic reflux esophagitis have been treated with Nissen fundoplication in our institution since 1966. They were divided into four groups: patients who had a long, tight fundoplication; patients who had a short, floppy fundoplication; patients with crural approximation; and patients without crural approximation. The preoperative and postoperative findings of these patients were evaluated in each group. Group 1 had more immediate and long-term dysphagia compared with group 2. Also, "gas bloat" syndrome was more prevalent in group 1 than group 2. The location of Nissen fundoplication (chest or abdomen) or the addition of hiatal hernia repair did not change the outcome. In patients with intact Nissen fundoplications, their esophagitis healed, and their symptoms disappeared. The rate of recurrence of symptoms was 5%. Recurrence of symptoms was associated with disruption of the fundoplication, which usually happened within the first two years after operation.

Adolescent↗
PubMed1987

Pressure and length adaptations in isolated cat stomach.

Correlations were made between the adaptation of gastric pressure and longitudinal muscle tension. Isolated cat stomachs were filled with physiological solution and longitudinal strips marked in five segments over the lesser and the greater curvature (LC and GC). Strip length changed the most in the proximal segments of GC. Volume changes led to triphasic changes in gastric pressure. On filling, there was a pressure peak and pressure accommodation to a new base-line pressure. On emptying there was an initial pressure nadir that was followed by a pressure recovery. When isolated longitudinal strips were stretched and released to their lengths at specific gastric volumes, they generated triphasic tension adaption and recovery. Strips from the proximal greater curvature generated the highest base-line tension, highest peak tension, and largest amplitude of tension adaptations. Addition of KCl, carbachol, or physostigmine increased base-line tension and tension adaptations in parallel, whereas atropine reduced them. Tetrodotoxin had no effect. The base-line tension of the isolated cat stomach is maintained by a tonic cholinergic neurosecretion but its tension adaptations do not require neural control.

Animals↗
PubMed1986

Use of an absorbable mesh to repair contaminated abdominal-wall defects.

When polypropylene mesh (Marlex) is used to repair contaminated abdominal-wall hernias, a high incidence of mesh-related chronic infection, drainage, erosion, and bleeding is noted. As an alternative to placing polypropylene mesh in a contaminated field, in the past 18 months we have used an absorbable polyglycolic acid mesh (Dexon) to repair contaminated abdominal-wall defects in eight patients--three with necrotizing abdominal-wall infections, one with an extensive electrical burn of the abdominal wall, three with infected polypropylene mesh from a previous repair, and one whose hernia was covered by a chronically infected scar. In seven of the eight cases, a single sheet of polyglycolic acid mesh was sewn to the fascial margins. In four cases, skin was closed over the mesh; wound packing and subsequent skin grafting were required in the other four. In follow-up studies that ranged from three to 18 months, six of the eight patients developed abdominal-wall hernias at the site of absorbable mesh placement. None of the patients required an abdominal binder. Postoperative hernia development is probable in patients whose defects are repaired with absorbable mesh. However, this complication is balanced against the more serious complications of fistula, bleeding, skin erosion, drainage, and chronic infection, which require removal of the more rigid nonabsorbable meshes in 50% to 90% of cases when the latter are placed under contaminated conditions. Placement of absorbable mesh for temporary abdominal-wall support until wound contamination resolves enhances the likelihood of subsequent successful placement of a permanent mesh.

Abdominal Muscles↗
PubMed1985

Corset liver.

We describe four patients with a benign hepatic malformation most consistent with the rarely described anomaly known as corset liver. Three of these patients were extensively evaluated to rule out a malignancy because of an abdominal mass. These patients illustrate several features which may help in making the diagnosis and avoiding unnecessary surgery.

Age Factors↗
PubMed1985

Carcinoid tumors of the gastrointestinal tract.

Carcinoid tumors continue to be of specific clinical interest because of their diverse presentation, hormonal secretion, and malignant potential. One hundred ninety-two patients with carcinoid tumors were treated at the University of Iowa Hospitals and Clinics between 1938 and 1982. The most common location of these tumors was the appendix (30%), followed by the ileum (23%) and rectum (9%). Metastatic disease occurred in 29 per cent of all patients, with colonic and ileal tumors being the most likely to metastasize (40% and 35%, respectively). Surgical excision continues to be the treatment of choice in resectable tumors. Appendectomy alone proved effective in the treatment of appendiceal tumors less than 2 cm in diameter and without lymph node metastases. Local excision was also sufficient for the treatment of rectal tumors less than 2 cm in diameter and without invasion of the muscularis propria. Ileal, colonic, and locally advanced appendiceal and rectal tumors should be treated with radical excision including resection of the regional lymph nodes. The overall 5-year survival rate was 47%. Patients with metastatic disease had a lower survival rate (25%) compared with patients without metastases (64%).

Adolescent↗
PubMed1984

Hepatic artery ligation and chemotherapeutic infusion in the treatment of hepatic malignancy.

This report reviews the results of treatment of hepatic malignancies by intra-arterial infusional chemotherapy and hepatic artery ligation. Seventy-nine patients with liver metastases or primary hepatomas were treated by this technique between the years 1970 and 1982. The majority of patients had metastatic disease from colon and rectal cancers. The median and mean survivals in the total group was 10 and 14 months, respectively (including operative deaths). Patients with metastatic disease from colon and rectal cancers had better survival than those with metastases from other primaries. Patients with synchronous liver malignancy had better survival than those with metachronous disease. Length of survival correlated positively with the duration of chemotherapeutic infusions, the latter being frequently (in 42% of patients) interrupted because of catheter complications. A new technique utilizing implantable pumps can be expected to further improve the results by reducing catheter malfunction and prolonging treatment courses.

Antineoplastic Agents↗
PubMed1984

Colonic pseudoobstruction.

Isolated colonic pseudoobstruction can occur in two forms, acute and chronic. Acute colonic pseudoobstruction is a transient problem that is usually associated with systemic illnesses. Chronic colonic pseudoobstruction usually recurs or persists. It may occur with or without underlying systemic diseases. Clinical manifestation and treatment of each form is different. Therefore, these two syndromes should be dealt with differently.

Cathartics↗
PubMed1984

Selectivity of histamine for the proximal muscle loop of the cat pylorus.

Most drugs stimulate tonic and phasic muscular activity of the gastroduodenal junction to similar degrees except for histamine which enhances purely phasic contractions. The present study examined whether this selective histamine effect is due to a preferential action of histamine on the proximal muscle loop of the pylorus (PPL) which, unlike the distal loop (DPL), generates mostly phasic contractions. Strips were cut so as to represent the mechanical activity of muscle from the antrum, the PPL and the DPL of the cat stomach. All strips responded to acetylcholine with a combination of tonic and phasic activity. Histamine increased the frequency and the amplitude of phasic contractions in most strips from the antrum and the PPL; it increased the tonic contraction of a few DPL strips. In all types of strips, maximal histamine effects were only a fraction of the effects occurring with acetylcholine. Exposure to histamine produced no mechanical response in one fifth of the antral strips and in more than one third of the strips from both the PPL and the DPL. Histamine tachyphylaxis was marked, and sometimes irreversible. Histamine also led to phasic interruptions of flow across the isolated gastroduodenal junction without altering baseline flow. The present study demonstrates that histamine acts preferentially on those parts of the gastroduodenal junction that generate phasic rather than tonic muscular activity.

Acetylcholine↗
PubMed1984

Natural history of adult Hirschsprung's disease.

The natural history of adult Hirschsprung's disease was reviewed in 22 patients (four from our hospital and 18 from the literature). The diagnosis in nearly half the patients was made before age 30, and the oldest patients were 69 years of age. Male to female ratio was 4:1. Almost all patients had severe constipation since birth. Barium enema showed rectal narrowing in 77%, and colonic dilation in 100%. Anorectal manometry was performed in only four patients; three showed no relaxation with rectal distention. In all patients, rectal biopsy showed no ganglion cells. Appropriate operation for Hirschsprung's disease improved symptoms in over 80% of patients. Hirschsprung's disease should be considered in all adult patients who have had severe constipation since birth, especially if they are male.

Adult↗
PubMed1983

Neuromuscular differentiation of the human pylorus.

The mechanical activity of muscle strips from the gastroduodenal junction as obtained at operations was studied. Strips were cut so as to present the activity of the circular muscle layer of the antrum, the duodenum, the intermediate, or the distal pyloric sphincter. All strips increased and maintained a tension with increasing length, but distal sphincter strips did more so than the other types of strips. Phasic contractions were rare in distal sphincter strips, while all intermediate sphincter strips contracted at rates similar to antral strips. Electric field stimulation produced pure contractions in all responsive strips of the antrum and the intermediate sphincter. In most strips from the duodenum and distal sphincter the contraction response occurred during the stimulus, and the relaxation response far outlasted the stimulus. Distal sphincter strips had the larger relaxation responses, and duodenal strips had the larger contraction responses. Relaxation in response to electric stimulation, Ca++ withdrawal, or isoproterenol did not completely abolish the baseline tension of the distal sphincter. At least in its distal segment, muscle from the human pylorus differs from muscle of the antrum and the duodenum by its high baseline tension, its prominent neurogenic relaxation response, and its poor spontaneous contractile activity.

Biomechanical Phenomena↗
PubMed1982

Cardiac arrest in two children with nonfamilial chronic intestinal pseudoobstruction on total parenteral nutrition.

Two children with nonfamilial chronic intestinal pseudoobstruction are reported. Both had no family history. They had an exploratory laparotomy to rule out mechanical intestinal obstruction, and required long-term parenteral nutrition to obtain sufficient nutrients. These two children had dilatation of the whole length of the small intestine, which differs from short segmental dilatation (megaduodenum) in patients with familial chronic intestinal pseudoobstruction. There were also differences in the histology of the gastrointestinal tract between these two patients although they had similar clinical manifestations. Both patients died from cardiac arrest, one after 2 years and the other after 4 months on long-term parenteral hyperalimentation. At autopsy, heart examination was normal in one patient, and a small infarction (0.4 mm diameter) was found in the other. Although mild hypokalemia was found in one case, and mild hyperkalemia in the other, the cause of cardiac arrest in these two children is not known.

Adolescent↗
PubMed1982

Discovery of Crohn's disease at celiotomy.

Many patients with Crohn's disease have abdominal operations, but the role of surgical exploration in the recognition of this syndrome has not been assessed. We reviewed the operative records of 78 patients with a presumptive diagnosis of Crohn's disease who had a celiotomy between 1968 and 1979 at The University of Iowa Hospitals and Clinics. The patients were divided into two groups according to the likelihood of having Crohn's disease. Clinical presentation and operative indications were similar to those commonly reported for Crohn's disease. Most findings at celiotomy occurred with similar frequency in the two groups. Fat wrapping and thickening of the intestinal wall were the most common findings. These were closely followed in frequency of occurrence by the presence of adhesions, abdominal masses or serosal changes. Less common changes included strictures, intestinal dilation, skip lesions, fistulas and abscesses. Free peritoneal fluid and mesenteric lymph node enlargement were rare in 63 patients with established Crohn's disease but were comparatively more common in 15 patients deemed unlikely to have the disease. Even though the diagnosis of Crohn's disease was not firmly established preoperatively in more than one-fourth of the patients, the surgeon rarely took steps to make a specific diagnosis. Preoperatively, the diagnosis in four patients was changed from carcinoma of the cecum in two, from appendicitis in two and from ischemic colitis in one patient to a correct diagnosis of Crohn's disease, but never was a diagnosis preoperatively of Crohn's disease changed postoperatively to an alternative. We conclude that presently recognized operative findings are of limited value in the differential diagnosis of the disease because, in our experience, the preoperative diagnosis of Crohn's disease was never altered at operation. The diagnosis should be made with caution in the presence of free peritoneal fluid or mesenteric lymphadenopathy.

Abdomen↗
PubMed1981

Symptomatic ectopic pancreas relieved by surgical excision.

It is clear that hetereotopic pancreatic tissue not associated with pancreatitis, mucosal ulceration or bleeding can produce symptoms, and as such requires removal. Many benign intramural tumors are asymptomatic and are discovered only at autopsy. The majority of the tumors discovered clinically ae symptomatic; therefore, operative removal of the lesion for relief of symptoms rather than for diagnosis or prophylaxis is generally acceptable to the patient, physician and surgeon. It would seem that, in these patients, radical therapy is the nonoperative choice, while operation leads to rapid recovery and a symptom-free postconvalescent life style.

Adolescent↗