Effect of inhibition of prostaglandin synthesis on epinephrine-induced gastroduodenal electromechanical changes in humans.

We conducted a double-blind randomized study to investigate the role of endogenous prostaglandins in epinephrine-induced changes in human gastric electromechanical activity. Intravenous administration of a pharmacologic dosage of epinephrine (222 ng/kg per min) caused gastric dysrhythmia in 8 of 12 healthy subjects. After indomethacin treatment, the incidence of epinephrine-induced gastric dysrhythmia was reduced to 4 of 12 healthy subjects, which is similar to the incidence of gastric dysrhythmia noted in the placebo group. The difference, however, was not statistically significant (P = 0.2). Epinephrine also substantially inhibited both the amplitude and the frequency of antral contractions. Indomethacin treatment partially reversed the reduction in the amplitude but not the frequency of antral contractions. These results suggest that endogenous prostaglandins may, in part, regulate the amplitude of human antral contractions; however, the role of prostaglandins in epinephrine-induced gastric dysrhythmia in humans remains uncertain.

Colonic tone and motility in patients with irritable bowel syndrome.

In this study, our aim was to test the hypothesis that colonic tone is abnormal in patients with irritable bowel syndrome (IBS). We studied eight patients with IBS and eight age-matched asymptomatic control subjects, in whom tone and motility were measured by an electronic barostat and by pneumohydraulic perfusion manometry, respectively. Tone and motility were recorded from the descending colon for a 14-hour period--3 hours awake, 7 hours asleep, 2 hours fasting after awakening, and 2 hours postprandially. In patients with IBS and in healthy subjects, colonic tone decreased by up to 50% during sleep and increased promptly on awakening. Fasting colonic tone (as quantified by the volume in the barostat balloon) in the awake state was not significantly higher in patients with IBS than it was in healthy subjects (125 +/- 13 versus 152 +/- 15 ml; P = 0.19). Tone increased postprandially in both study groups, and the increase was greater in healthy subjects than it was in patients with IBS (P < 0.05). The motility index during fasting was greater in patients with IBS than it was in healthy control subjects (3.2 +/- 0.6 versus 1.6 +/- 0.4; P = 0.05), and the postprandial increase in motility index was greater in the healthy subjects. Preprandially and postprandially, we noted a trend for high-amplitude prolonged contractions to be more frequent in patients with IBS than in healthy subjects. We conclude that colonic tone in patients with IBS showed the same nocturnal and postprandial variations as it did in healthy subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Restoration of myoelectrical propagation across a jejunal transection using microsurgical anastomosis.

The aim of this study was to determine whether microsurgical anastomosis can restore propagation of jejunal pacesetter potentials (PPs) across a site of canine jejunal transection and preserve motility and transit in bowel distal to the transection. A complete jejunal transection with exact microsurgical anastomosis was performed in five dogs, while five dogs with intact jejunum and five dogs with complete transection and end-to-end conventional macrosurgical anastomosis were used as controls. Long-term recording electrodes and intraluminal, open-tipped pressure catheters were implanted in all dogs. The mean frequency of PPs decreased distal to the transection in both groups of transected dogs. However, aborad propagation of PPs across the anastomosis occurred episodically by 3 months in each dog that had a microsurgical anastomosis, but never occurred in any dog with a conventional macroanastomosis. Moreover, the motility and transit in bowel distal to the transection were unaltered in the dogs with a microsurgical anastomosis, whereas they decreased in the dogs with a macroanastomosis. The conclusion was that microsurgical anastomosis of transected canine jejunum restored episodic propagation of PPs across the anastomosis, and preserved motility and maintained transit in bowel distal to the anastomosis. The conventional macroanastomosis did none of these.

The jejunal pouch as a rectal substitute after proctocolectomy.

Our hypothesis was that a jejunal pouch used as a rectal substitute after proctocolectomy would slow enteric transit, delay defecation, and decrease stool frequency compared to an ileal pouch so used. Twelve dogs underwent proctocolectomy; six had a jejunal pouch-distal rectal anastomosis and six had an ileal pouch-distal rectal anastomosis. After recovery, postprandial mouth-to-anus transit was slower in jejunal pouch dogs (253 +/- 18 minutes [mean +/- SEM]) than in ileal pouch dogs (112 +/- 7.9 minutes; P <0.05). Moreover, jejunal pouch dogs passed only 4.1 +/- 0.3 stools during the 12 hours after eating, whereas ileal pouch dogs passed 6.3 +/- 0. 9 stools (P <0.05). The mean frequency of proximal ileal pacesetter potentials after feeding was less in jejunal pouch dogs (12 +/- 0.4 cycles/min) than in ileal pouch dogs (16 +/- 0.3 counts/min; P = 0. 01), and jejunal pouches had more action potentials (jejunal = 82% +/- 4.3% of pacesetter potentials had action potentials, ileal = 61% +/- 3.0%; P <0.05). In contrast, gastric emptying and pouch motility, emptying, mucosal integrity, and bacteriologic and histologic properties were similar in the two groups of dogs. We concluded that the jejunal pouch operation slowed enteric transit, delayed defecation, and decreased postprandial stooling compared to the ileal pouch operation.

Preservation of continence after ileoanal anastomosis by the coordination of ileal pouch and anal canal motor activity.

Nocturnal incontinence may occur after ileoanal anastomosis and may be related to loss of an effective anal canal pressure barrier during sleep; how pressure and contractions in the proximal bowel influence this barrier is unknown. Our aim was to evaluate the relationship between anal canal pressure and contractions and contractile activity of the pouch in continent subjects after ileal pouch-anal anastomosis (IPAA) and of the rectum in normal controls. A fully ambulatory system for 24-hour pressure recording was used. A flexible transducer catheter was introduced endoscopically so that sensors were at 2, 3, 8, 12, 16, and 24 cm from the anal orifice in 12 healthy controls (7 men, 5 women, mean age: 35 years) and 7 fully continent IPAA patients (4 men, 3 women, mean age: 34 years) more than 12 months postoperatively. Twenty-four hour spontaneous motor activity was stored in a 2.5 megabyte (MB) digital portable recorder. Mean anal canal pressure was calculated, and rectal motor complexes and ileal pouch large pressure waves were characterized. During sleep, resting anal canal pressures were similar in the two groups (72 +/- 12 mm Hg in controls versus 66 +/- 9 mm Hg in IPAA patients [mean +/- standard deviation (SD)], p = NS), but anal canal pressure showed cyclic relaxations (periodicity: 95 +/- 11 min in controls, 54 +/- 18 min in IPAA patients, p less than 0.05), during which the mean pressure trough was 15 +/- 4 mm Hg in controls and 14 +/- 5 mm Hg in IPAA patients (p = NS). In the control patients, during sleep, a mean of six rectal motor complexes were identified (range: 3 to 9). In patients with IPAA, during sleep, a mean of eight large pressure waves per hour were identified (range: 2 to 20). Importantly, in both controls and patients, rectal motor complexes or large pressure waves were always accompanied by rapid return of anal canal pressure from trough to basal values and increased contractile activity. We concluded that, in healthy patients and in continent patients after IPAA, motor activity of the rectum and of the ileal pouch was associated with changes in pressure and contractile activity of the anal canal so that rectal- and neorectal-anal canal pressure gradient, and, in turn, fecal continence were preserved.

Prolonged ambulatory recording of anorectal motility in patients with slow-transit constipation.

Our aim was to determine phasic contractile activity of the distal bowel and anus in patients with slow-transit constipation; if readily identifiable patterns were present, prolonged recordings could confirm a diagnosis of slow-transit constipation. In 12 healthy control subjects and 11 women patients with slow-transit constipation (mean colonic transit time: 120 +/- 11 hours) and normal pelvic floor function, a flexible catheter was positioned endoscopically with sensors in the sigmoid colon, rectum, and anal canal in order to perform ambulatory recordings. A motility index (MI = mm Hg/h/100) was calculated during fasting and after feeding. Overall, the rectal MI and the frequency of anal canal contractions were less in the patients with constipation compared with those in the control group (rectum: 22 +/- 5 mm Hg/h/100 in the control group versus 13 +/- 10 mm Hg/h/100 in the constipation group; anal contractions/h: 23 +/- 7 in the control group versus 3 +/- 2 in the constipation group, p < 0.05). Moreover, in response to feeding, only control subjects had a significantly increased MI and frequency of anal canal contractions. Compared with control subjects, patients with slow-transit constipation had significantly reduced motor activity in the distal bowel and anal canal. Phasic contractile activity recorded during fasting and in response to a meal may be a means of confirming the diagnosis of slow-transit constipation in patients with borderline marker transit times.

Immature mouse uterine tissue in organ culture: estrogen-induced growth, morphology and biochemical parameters.

Although estrogens have been shown to stimulate a variety of morphologic and biochemical changes in the uterus in vivo, no clear consistent demonstration of similar responses in vitro have been made; thus, a defined organ culture system using the immature mouse uterus was established to study the possibility of demonstrating estrogenic responses in vitro. Uterine tissue from immature outbred mice (17 to 24 days of age) were cut crosswise in 1-mm3 coins and cultured in a defined medium in the absence of serum, phenol red, or growth factor supplements. Diethylstilbestrol (DES), a synthetic estrogen, was added to the media at doses ranging from 1 to 100 ng/ml. The effect of DES on uterine cell proliferation was assessed by morphologic changes in uterine epithelial and stromal cells, increase in number of epithelial cells per unit basement membrane, increase in height of luminal epithelial cells, and [3H]thymidine incorporation. Functional changes were determined by measuring the amounts of the estrogen-inducible uterine protein, lactoferrin, that was localized in the epithelial cells and secreted into the media, and the localization of the estrogen receptor in the cultured tissues. Results indicate that under the described conditions of culture, estrogens like DES can induce morphologic and biochemical responses in the uterus that are similar to those seen in vivo. This organ culture system will aid in the investigation of various mechanisms involved in the hormonal regulation of growth and differentiation of estrogen target tissues.

Immature mouse uterine tissue in organ culture: Estrogen-induced growth, morphology and biochemical parameters.

Although estrogens have been shown to stimulate a variety of morphologic and biochemical changes in the uterus in vivo, no clear consistent demonstration of similar responses in vitro have been made; thus, a defined organ culture system using the immature mouse uterus was established to study the possibility of demonstrating estrogenic responses in vitro. Uterine tissue from immature outbred mice (17 to 24 days of age) were cut crosswise in 1-mm(3) coins and cultured in a defined medium in the absence of serum, phenol red, or growth factor supplements. Diethylstilbestrol (DES), a synthetic estrogen, was added to the media at doses ranging from 1 to 100 ng/ml. The effect of DES on uterine cell proliferation was assessed by morphologic changes in uterine epithelial and stromal cells, increase in number of epithelial cells per unit basement membrane, increase in height of luminal epithelial cells, and [(3)H]thymidine incorporation. Functional changes were determined by measuring the amounts of the estrogen-inducible uterine protein, lactoferrin, that was localized in the epithelial cells and secreted into the media, and the localization of the estrogen receptor in the cultured tissues. Results indicate that under the described conditions of culture, estrogens like DES can induce morphologic and biochemical responses in the uterus that are similar to those seen in vivo. This organ culture system will aid in the investigation of various mechanisms involved in the hormonal regulation of growth and differentiation of estrogen target tissues.

Comparison of Nitrogen Fixation Activity in Tall and Short Spartina alterniflora Salt Marsh Soils.

A comparison of the N(2) fixers in the tall Spartina alterniflora and short S. alterniflora marsh soils was investigated. Zero-order kinetics and first-order kinetics of acetylene reduction were used to describe the activity of the N(2) fixers in marsh soil slurries. It was found that the V(max) values were approximately 10 times greater for the N(2) fixers in the tall Spartina than in the short Spartina marsh when raffinose was used as the energy source. In addition, the (K(s) + S(n)) values were approximately 4 to 15 times lower for the N(2) fixers in the tall Spartina than in short Spartina marsh. First-order kinetics of nitrogen fixation for several substrates indicate that the N(2) fixers in the tall Spartina marsh were two to seven times more active than those in the short Spartina marsh. Ammonium chloride (25 mug/ml) did not inhibit nitrogen fixation in the tall Spartina marsh, but there was a 50% inhibition in nitrogen fixation in the short Spartina marsh. On the other hand, sodium nitrate inhibited nitrogen fixation almost 100% at 25 mug/ml in both soil environments. Amino nitrogen (25 to 100 mug/ml) had little or no effect on nitrogen fixation. The results indicate that the N(2) fixers in the tall Spartina marsh were physiologically more responsive to nutrient addition than those in the short Spartina marsh. This difference in the two populations may be related to the difference in daily tidal influence in the respective areas and thus provide another explanation for the enhanced S. alterniflora production in the creek bank soil system.

Nitrogen fixation (acetylene reduction) in a salt marsh amended with sewage sludge and organic carbon and nitrogen compounds.

Seasonal distribution of nitrogen fixation by Spartina alterniflora epiphytes and in surface and soil samples was investigated in a Georgia salt marsh which was amended with sewage sludge or with glucose and/or ammonium nitrate. There was no significant difference between the rates of fixation in the unamended and sewage sludge plots. Additional perturbation experiments suggested that nitrogen addition indirectly stimulates nitrogen fixation by enhancing Spartina production and root exudation. Glucose additions, on the other hand, suppressed nitrogen fixation on a long-term basis. It is suggested that the microbial population in the soil out-competed the plants for the available nitrogen and in turn suppressed plant production and possibly root exudation. A comparison of nitrogen fixation in clipped and unclipped Spartina plots substantiated the suggestion that root exudation probably supports nitrogen fixation. Fixation in the clipped plots was significantly lower (P < 0.05) than the rates in the unclipped plots.

Influence of sewage discharge on nitrogen fixation and nitrogen flux from coral reefs in Kaneohe Bay, Hawaii.

Nitrogen fixation was investigated in Kaneohe Bay, Oahu, Hawaii, a subtropical eutrophic estuary, by using the acetylene reduction technique on algal samples. No active, planktonic, N2-fixing blue-green algae or bacteria were observed. However, Calothrix and Nostoc capable of fixing N2 were cultured from navigational buoys and dead coral heads. Nitrogen fixation associated with these structures was greater in the middle sector than in the south and north sectors of the estuary. Experiments demonstrated that the fixation was photosynthetically dependent. Examination of the data showed that there was no significant correlation between rates of nitrogen fixation and concentration of combined nitrogen compounds in the Bay water. Fixation was significantly correlated to the inorganic N/P (atomic) ratio in the south and middle sectors but not in the north sector. The nutrient data indicate there was a flux of combined nitrogen, but not phosphate, from the reef flats.

Spatial Distribution, Structure, Biomass, and Physiology of Microbial Assemblages across the Southern Ocean Frontal Zones during the Late Austral Winter.

We examined the spatial distributions of picoplankton, nanoplankton, and microplankton biomass and physiological state relative to the hydrography of the Southern Ocean along 90 degrees W longitude and across the Drake Passage in the late austral winter. The eastern South Pacific Ocean showed some large-scale biogeographical differences and size class variability. Microbial ATP biomass was greatest in euphotic surface waters. The horizontal distributions of microbial biomass and physiological state (adenylate energy charge ratio) coincided with internal currents (fronts) of the Antarctic Circumpolar Current. In the Drake Passage, the biological scales in the euphotic and aphotic zones were complex, and ATP, total adenylate, and adenylate energy charge ratio isopleths were compressed due to the extension of the sea ice from Antarctica and constriction of the Circumpolar Current through the narrow passage. The physiological state of microbial assemblages and biomass were much higher in the Drake Passage than in the eastern South Pacific Ocean. The temperature of Antarctic waters, not dissolved organic carbon, was the major variable controlling picoplankton growth. Estimates of picoplankton production based on ATP increments with time suggest that production under reduced predation pressure was 1 to 10 mug of carbon per liter per day. Our results demonstrate the influence of large-scale hydrographic processes on the distribution and structure of microplankton, nanoplankton, and picoplankton across the Southern Ocean.

Ontogeny of lactoferrin in the developing mouse uterus: a marker of early hormone response.

Lactoferrin (LF) was mapped during organogenesis of the murine reproductive tract, starting on fetal Day 12, as a marker of estrogen responsiveness. To induce LF expression, pregnant outbred CD-1 mice were injected s.c. with diethylstilbestrol (DES; 100 microg/kg maternal body weight), and fetal genital tract tissues were removed; neonatal and immature mice received s.c. injections of DES (2 microg/pup per day). Corn oil-treated and untreated mice at corresponding ages provided the controls. Immunocytochemical techniques using a polyclonal antibody showed no detectable LF in control genital tract tissues until late gestation. However, after DES treatment, LF was localized in uterine epithelial cells as early as fetal Day 14; the intensity of LF staining increased with age and number of DES treatments. Control uterine tissues responded to the rise of circulating estrogens at parturition (fetal Day 19) by producing LF, although the magnitude of response was lower than that of DES-treated tissues. Uterine tissue homogenates from control and DES mice were analyzed by SDS-PAGE and Western blots, verifying the protein to be LF. Isolation of mRNA and Northern blot analysis further showed that LF mRNA was present in the developing Mullerian duct and that DES stimulated early induction of the LF gene. The early appearance of LF suggests that it may play an important role in the hormonal regulation of growth and differentiation of developing uterine tissues.

Comparison of methods for measurement of bacterial growth rates in mixed batch cultures.

Eight methods of assessing growth rate constants of bacteria were compared in batch cultures of 3-micrometers-filtered estuarine water from the Skidaway River in Ga. Mixed assemblages of bacteria were grown under four nutrient regimes of added yeast extract ranging from 0 to 100 mg/liter. Linear and exponential growth rate constants were computed from changes in cell densities, biovolumes, and ATP concentrations. Exponential growth rate constants were obtained from the frequency of dividing cells and RNA synthesis as measured by [3H]adenine uptake. Rate constants obtained during lag, exponential, and stationary growth phases depended largely on the method used. Constants calculated from changes in cell densities, frequency of dividing cells, and adenine uptake correlated most closely with each other, whereas constants calculated from changes in ATP concentrations and biovolumes correlated best with each other. Estimates of in situ bacterial productivity and growth vary depending on the method used and the assumptions made regarding the growth state of bacteria.

Relationship between anal canal tone and rectal motor activity.

The anal sphincters facilitate fecal continence by maintaining a pressure barrier; whether proximal contractile events influence this barrier is unknown. The aim of this study was to determine whether a relationship exists between anal canal pressures and rectal motor activity. A fully ambulatory system for prolonged pressure recording was developed. In 12 healthy subjects (seven males and five females; mean age, 35 years; range, 22-43 years), a flexible transducer catheter (outside diameter, 4.5 mm) was introduced endoscopically such that sensors were 2, 3, 8, 12, 18, and 24 cm from the anal orifice. Twenty-four-hour spontaneous motor activity was stored in a 2.5-megabyte portable recorder for later transfer to a Microvax II for computerized analysis and display. Mean anal canal pressure was calculated, and rectal motor complexes (RMCs) were characterized. Mean and canal resting pressure was 75 +/- 12 mmHg. During sleep, anal pressures displayed cyclic decreases (mean periodicity, 1.6 hours; range, 1-4 hours), during which the mean +/- SD pressure trough was 15 +/- 4 mmHg (range, 8-21 mmHg). RMCs were identified in all subjects: mean frequency, 16 per 24 hours (range, 12-22 per 24 hours); duration, 15.3 minutes (range, 8-35 minutes); contractile frequency, two to three per minute; mean peak amplitudes, 58 +/- 18 mmHg; and periodicity, 78 +/- 24 minutes (range, 35-265 minutes). Importantly, an RMC was invariably accompanied by a rise in mean anal canal pressure and contractile activity such that pressure in the anal canal was always greater than pressure in the rectum. Anal canal relaxations never occurred during an RMC. Motor activities of the rectum and of the anal canal may be related; the onset of rectal contractions was accompanied by increased resting pressure and contractile activity of the anal canal. This temporal relationship represents an important mechanism preserving fecal continence.

Measurement of axial forces during emptying from the human stomach.

Our aim was to measure axial forces in the stomach and to evaluate their relation to circumferential contractions of the gastric walls and the emptying of gastric content. We used a combination of simultaneous radioscintigraphy, gastroduodenal manometry, and an axial force transducer with an inflatable 2-ml balloon fluoroscopically placed in the antrum. In vitro studies demonstrated that the axial force transducer records only antegrade forces along the longitudinal axis of this probe in an intensity-dependent manner. In vivo studies were performed in five healthy subjects for at least 3 h after ingestion of radiolabeled meals. When administered separately, the emptying of liquids or solids from the stomach is associated with generation of antral axial forces and coincident phasic pressure activity; however, almost 20% (average) of gastric axial forces during emptying of liquids or solids are unassociated with proximal or distal antral pressure activity ("isolated" forces). High amplitude antral axial forces and pressures occur during both lag and postlag emptying phases. During emptying of liquids, there is a trend for axial forces to be coincident more often with proximal than with distal antral pressure activity and vice versa for the emptying of solids (P = 0.015). These data suggest that when placed in the antrum, the transducer can semiquantitatively record axial forces during gastric emptying. By combining these observations with the data from in vitro studies, it appears that axial forces predominantly result from traction on the balloon by the longitudinal vector resulting from circumferential gastric contractions. The combination of radioscintigraphy and measurement of antral axial forces is a promising method to evaluate mechanical forces involved in the emptying of the human stomach.

Electric and motor patterns associated with canine jejunal transit of liquids and solids.

Our hypothesis was that the direction of liquid transit through the canine jejunum is determined by the direction that single jejunal pressure waves spread, while the direction of solid transit depends on the direction of spread of both single waves and clustered waves. In six dogs, 80-cm jejunal Vella loops were made and fitted with manometric catheters and serosal electrodes. After recovery, transit of liquids (Ringer lactate) and solids (2.4-mm nylon spheres) placed into the center of the loop was determined in the conscious animals while pacing the loop in a forward direction or in a backward direction. Under fasting and fed conditions, single pressure waves followed the direction of pacing, while the direction of migration of clustered waves was not determined by the direction of pacing. Liquid transit always followed the direction of single pressure waves. In contrast, solids moved distally regardless of the direction of pacing, except when liquids were also present in the lumen, in which case solids moved in the same direction as the single pressure waves.