Biomedical subjects

M H Clench

Publications and source records attributed to M H Clench.

26 records · Page 2Linked to original sources

PubMed1988

Gastric emptying in infants with gastroesophageal reflux. Measurement with a technetium-99m-labeled semisolid meal.

It is well established that liquid emptying occurs in the absence of motor activity of the stomach. In contrast, solid-phase emptying is controlled in part by antral peristalsis and is, therefore, a more precise indicator of gastric motility. We developed a semisolid, radionuclide gastric emptying test using rice cereal and technetium-99m-sulfur colloid to assess antral physiology in infants with vomiting. Computer-programmed mathematical models were used to determine the shape of a line that best fit our emptying data points. Linear, simple exponential [f = 2-(t/t1/2)], and power exponential [f = 2(t/t1/2)beta] patterns of emptying were calculated, where f is the fraction of the meal remaining in the stomach at time t, and t1/2 is the time when 50% of the meal has emptied and is a determinant of the shape of the curve. In infants with simple regurgitation (chalasia) and those with vomiting and failure to gain weight, we made statistical comparisons between gastric emptying patterns after analysis of the mean percentage of retained radionuclide at 120 min, calculated t1/2, and area under the curve. The coefficient of determination, R2, was calculated as an index of whether a curve provided goodness of fit to the data. Differences between groups of patients were statistically significant for all parameters of each mathematical model. However, higher coefficients of determination were noted in the power exponential model. The data suggest that the power exponential mathematical model provides the best analysis of the gastric emptying patterns for infants with chalasia and those with vomiting and failure to gain weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗

PubMed1986

Effect of lidamidine hydrochloride and loperamide on gastric emptying and transit of the small intestine. A double-blind study.

We performed a double-blind randomized study in 24 healthy volunteers, to evaluate the effects of two doses of lidamidine hydrochloride, loperamide, and placebo on transit of the small intestine and gastric emptying. Transit time of the small intestine was determined by measuring the rise in breath hydrogen excretion after ingestion of lactulose. Although there was a trend for prolonged intestinal transit time in both lidamidine groups, this difference was not significant compared with that in the placebo group. Loperamide significantly slowed transit when compared with placebo or lidamidine (p less than 0.001). Gastric emptying was assessed by using a solid-phase radiolabeled meal. Three parameters of gastric emptying were analyzed: half-emptying time, area under the gastric emptying curve, and beta. Although there was a trend for a longer half-emptying time in the group that received 12 mg of lidamidine, this difference approached, but did not reach, statistical significance (p = 0.06) compared with placebo. The area under the gastric emptying curve, a potentially more sensitive parameter for measuring gastric emptying, was significantly increased in the group receiving 12 and 18 mg of lidamidine (p less than 0.05) compared with the group receiving loperamide or placebo. In summary, lidamidine significantly delayed gastric emptying but had no significant effect on small bowel transit. These data suggest that the antidiarrheal properties of lidamidine are the result of enhanced absorption or inhibition of secretion of fluid and electrolytes.

Adolescent↗

PubMed1985

Development of an improved multi-pressure-sensor probe for recording muscle contraction in human intestine.

We have developed an improved semiconductor recording probe for monitoring motility of the upper small intestine in humans. The probe consists of six ultraminiature silicon pressure sensors spaced 10 cm apart and encased in a flexible polyurethane sheath. The probe is small [2.67 mm (8F) diameter], is easily passed transnasally, and is tolerated by patients for prolonged recording periods (24-36 hr) with a minimum of discomfort. The initial semiconductor and catheter material were those designed for use in the cardiovascular system, but they proved to be easily damaged by gastric acid and enzymes. After improvement of this probe, we now have recordings from more than 100 patients for an approximate total of 6000 hr of recording time. The improved probe is a durable recording device that facilitates the investigation of motility of the small intestine in humans in health and disease.

Humans↗

PubMed1985

Nausea, vomiting, and abdominal pain after Roux-en-Y anastomosis: motility of the jejunal limb.

The Roux-en-Y anastomosis is a surgical procedure performed to divert the pancreaticobiliary juices from the gastric pouch in patients who have alkaline reflux gastritis or esophagitis, or both, that develop after vagotomy and Billroth I or II operations. After the Roux-en-Y procedure the inflammation subsides but is often replaced by a characteristic group of symptoms--chronic abdominal pain, nausea, and vomiting worsened by eating. Using a semiconductor recording probe, we investigated the Roux limb in 7 subjects who were fasted and then fed (liquid and solid meals). In the fasted state the migrating motor complex was either completely absent or grossly disrupted. Only 1 subject converted to a fed-state motility pattern in the Roux limb after a liquid meal (Osmolite), and all 7 subjects failed to convert to a fed state after a solid meal. These studies suggest that the Roux-en-Y syndrome of pain, nausea, and vomiting is secondary to a defect in motor function and that the Roux limb is acting as an area of functional obstruction.

Adult↗

PubMed1985

Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine.

The bacterial overgrowth syndrome constitutes an intestinal problem involving alterations in motility and injury to the brush border and mucosa. The overgrowth of bacteria also causes secretion, malabsorption, and maldigestion. These alterations result in a clinical syndrome that manifests itself as weight loss, malabsorption of specific nutrients, and (usually) diarrhea. There are known causes of bacterial overgrowth, such as intestinal diverticuli or surgical procedures involving a vagotomy, but in our experience most cases remain idiopathic. This review evaluates the mechanisms of bacterial overgrowth, as currently understood, and specifically addresses the known causes of diarrhea that results from bacterial contamination of the small intestine.

Animals↗

PubMed1985

Migrating action potential complex: unmasked by 6-hydroxydopamine.

We have previously described the myoelectric characteristics of a single moving ring contraction, the migrating action potential complex (MAPC), in rabbit ileal loops exposed to certain bacteria or their enterotoxins. The MAPC is thought to act as a defense mechanism of the host, clearing unwanted substances from the lumen. In the present study, 6-hydroxydopamine, a substance that selectively destroys adrenergic varicosities containing the neurotransmitter norepinephrine, unmasked the MAPC from the activity front of the migrating motor complex in an unanesthetized rat model. The animals developed diarrhea and lost weight. The study suggests that the MAPC may also be a physiological complex and under the modulation of the enteric nervous system. The MAPC may not be seen under normal control conditions because the complex migrates with the activity front and is under inhibitory control. Destroying the inhibitory mechanisms unmasked the MAPC from the activity front of the migrating motor complex and allowed neural transmission of the ring contraction.

Action Potentials↗

PubMed1984

Purified Shigella enterotoxin does not alter intestinal motility.

A purified Shigella enterotoxin (pST) and a cell-free lysate with pST removed (CFL-pST) from the whole-cell lysate of Shigella dysenteriae 60 R were used to study their effect on the myoelectric activity and mucosal integrity of rabbit ileal segments. We have previously defined two myoelectric patterns: the migrating action potential complex and repetitive bursts of action potentials that occur in response to certain bacteria and their enterotoxins. The in vivo model consisted of isolated ileal segments in male New Zealand White rabbits. The segments were infused with sterile saline (1 ml/h), pST (2.4-micrograms injection), or CFL-pST (1 ml/h). Myoelectric activity in the segments exposed to pST was similar to that with the saline infusion, but CFL-pST induced significant alterations in myoelectric activity in the form of repetitive bursts of action potentials. The mucosa of the segments exposed to pST showed only mild inflammatory changes. In contrast, CFL-pST caused moderate to severe inflammatory changes with enterocyte necrosis. These studies show that pST, a known enterotoxin, did not alter myoelectric activity and had no significant effect on the integrity of ileal mucosa, as determined by light microscopy. CFL-pST caused both inflammation and tissue necrosis with significant alterations in motor activity. These studies suggest that S. dysenteriae 60 R produces a substance or substances other than pST that cause florid in vivo cytotoxicity and alter myoelectric activity.

Action Potentials↗

PubMedDate not supplied

Relationship of reproductive hormones and neuromuscular disease of the gastrointestinal tract.

Functional disorders of the gastrointestinal tract comprise a common but ill-defined group of diseases; they primarily afflict women. Although predominantly involving nerve and muscle, the cellular and molecular bases of the pathogenesis of these functional disorders are unknown. Clinical studies indicate that some result from neural dysfunction within the enteric nervous system, others may be due to muscular problems, and the causes of still others remain unknown. Laboratory studies have shown that ovarian products such as progesterone, luteinizing hormone, human chorionic gonadotropin, and relaxin (but not estrogen), are neural antagonists of gastrointestinal motility. The production and secretion of these ovarian substances are controlled by gonadotropin-releasing hormone (GnRH) released from the hypothalamus; they probably act on gamma-aminobutyric acid receptors and alter chloride influx into the cell. GnRH analogs are effective drugs that downmodulate the hypothalamic-pituitary-gonadal axis and inhibit the secretion of gonadal products involved in such hormone-dependent diseases as endometriosis and prostate cancer. Acting on the GnRH receptors (seven transmembrane domain receptors) on myenteric neurons, GnRH analogs are also effective neural modulators in such disorders as functional bowel disease. These analogs are a promising new group of compounds that may be used to treat difficult gastrointestinal problems.

Chorionic Gonadotropin↗