The role of the gut in the development of sepsis in acute pancreatitis

The pathogenesis of sepsis in acute pancreatitis is unknown. Since the intestinal tract has recently been identified as a possible source for sepsis in other conditions, we explored whether the gut may serve as a reservoir for bacteria causing systemic and pancreatic infection in acute pancreatitis. Bacterial translocation, alterations of intestinal microflora, and intestinal motility, as reflected by gut propulsion, were studied in a rat pancreatitis model. Acute pancreatitis was induced by biliopancreatic obstruction (AP); sham manipulated animals served as controls (sham). Bacteriologic cultures were obtained from various segments of the intestinal tract and from blood, liver, spleen, pancreas, and mesenteric lymph nodes 48 and 96 hr after induction of AP or sham. Bacteria were recovered from mesenteric lymph nodes of all 12 animals with AP, but only from 3/14 sham animals (P less than 0.05). Spread to distant organ sites occurred in 4 of 12 animals with AP compared to none of the sham animals (P less than 0.05). A disruption of the intestinal microflora was found in the cecum, where the gram-negative bacterial count (log/g) was significantly higher during AP when compared with sham controls: 10.62 +/- 1.04 vs 8.05 +/- 1.45 at 48 hr and 7.92 +/- 0.62 vs 6.79 +/- 0.87 at 96 hr, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

N-acetyl-cysteine: protective agent or promoter of gastric damage?

N-acetyl-cysteine (NAC), when given orally, has been shown to prevent gastric damage induced by ethanol, but when administered intraperitoneally, it appears to potentiate such damage. In an effort to resolve these seemingly discordant findings, fasted rats (six per group) received 1 ml of saline or 20% NAC orally or intraperitoneally (ip). Two hours or 15 min later, they received 1 ml of 100% ethanol orally. At sacrifice 5 min later, rats receiving oral pretreatment with 20% NAC at both 15 and 120 min prior to ethanol exposure demonstrated a significant reduction in the magnitude of gastric injury when compared with saline controls. In contrast, actual promotion of ethanol damage was noted when NAC was given intraperitoneally, but was more pronounced when NAC was administered 15 min prior to exposing the mucosa to 100% ethanol. In all animals receiving intraperitoneal NAC, large amounts of peritoneal fluid (4-6 ml/rat) were recovered at the time of sacrifice, most of which occurred within 15 min of NAC administration; these more pronounced peritoneal effects at 15 min after NAC correlated with the more severe injury from ethanol at this time period compared to 120 min after intraperitoneal NAC. Saline controls had no peritoneal fluid. Mucosal glutathione (GSH) levels generally paralleled these results in that a significant decrease in tissue GSH occurred at 15 min following intraperitoneal NAC when compared with controls; at 120 min after intraperitoneal NAC, GSH levels were similar to control values. Additional experiments demonstrated that within 15 min following NAC administration, systemic blood pressure dropped by approximately 20% and basically remained unchanged over the next 2 hr; intraperitoneal saline had no sustained adverse effects on blood pressure. It was concluded that the inability of NAC to prevent ethanol injury when given intraperitoneally in contrast to orally is related to the drop in blood pressure secondary to NAC's peritoneal irritant effects, which presumably altered gastric mucosal blood flow, thus obivating its ability to prevent ethanol damage under these conditions. Furthermore, the decreased levels in mucosal GSH following the hypotension induced by intraperitoneal NAC suggest that perturbations in GSH metabolism may also have contributed to the decreased resistance to ethanol injury.

Stress erosive gastritis

Bleeding from stress erosive gastritis continues to be a potential problem in critically ill and injured patients, but fortunately its incidence has decreased dramatically over the last decade. The explanation for this circumstance is probably multifactorial, but clearly relates to our increased knowledge of its pathophysiology. This understanding has led to the routine use of measures to reduce intragastric acidity (luminal acid being a prerequisite for stress ulcer to occur), coupled with improved techniques for the treatment of shock and the accompanying gastric mucosal hypoperfusion (another prerequisite for the formation of stress ulcers). A number of measures have been used to lower intragastric acidity with H2 receptor blockers emerging as the agents of choice to accomplish this goal. In the unlikely event that bleeding occurs despite these prophylactic measures, aggressive medical management will result in cessation of hemorrhage in over 80% of patients. In those few individuals requiring surgery to control bleeding, no operation has emerged as the recognized procedure of choice. Thus, we believe that a conservative operative approach is indicated in this setting and recommend vagotomy and pyloroplasty with oversewing of the bleeding erosions as appropriate therapy for most patients requiring surgical intervention.

Colloidal gold localization of type IV collagen in the extracellular matrix of rat gastric mucosa: influence of alcohol and prostaglandin

The effect of acute alcohol exposure on the gastric mucosal basal lamina, and its major structural protein type IV collagen, was assessed by transmission electron microscopy (TEM) and immunogold (IG) labeling of this collagenous material. Fasted rats orally received either 50% or 100% ethanol. Five or 60 minutes later animals were sacrificed and mucosal samples were obtained from the glandular epithelium for TEM or IG localization of type IV collagen. For IG studies, the number of gold particles/area lamina densa was quantified in interfoveolar, pit, and gland regions as an index of the molecular integrity of type IV collagen. Both ethanol concentrations induced epithelial exfoliation with pleating of the denuded lamina densa. Absolute ethanol, and to a lesser extent 50% ethanol, caused frequent rupture of a thickened, precipitated lamina densa. Immunolabeling of type IV collagen varied with the experimental protocol. In control tissues exposed to oral saline, binding was greatest in the interfoveolar zone. Low binding occurred with 100% ethanol in all regions when compared with controls, but 50% ethanol evoked significantly higher binding in interfoveolar regions, in a similar fashion to controls. In additional studies in which 16,16 dimethyl prostaglandin E2 (PGE2) (10 micrograms/kg) was injected subcutaneously prior to oral ethanol exposure, PGE2 pretreatment prevented the large decrease in IG binding induced by absolute ethanol, but the level still remained significantly less than with corresponding controls. In contrast, pretreatment with PGE2 prior to 50% ethanol exposure restored type IV collagen immunolabeling to control levels. These results indicate that ethanol induces a concentration-dependent lowering of IG binding to type IV collagen which also effects its reversibility by PGE2.

A functional c-myb gene is required for normal murine fetal hepatic hematopoiesis

The c-myb proto-oncogene encodes a sequence-specific DNA-binding protein. To better understand its normal biological function, we have altered the c-myb gene by homologous recombination in mouse embryonic stem cells. Resulting homozygous c-myb mutant mice displayed an interesting phenotype. At day 13 of gestation these mice appeared normal, suggesting that c-myb is not essential for early development. By day 15, however, the mutant mice were severely anemic. Analysis indicated that embryonic erythropoiesis, which occurs in the yolk sac, was not impaired by the c-myb alteration. Adult-type erythropoiesis, which first takes place in the fetal liver, was greatly diminished in c-myb mutants, however. Additional hematopoietic lineages were similarly affected. These results are compatible with a role for c-myb in maintaining the proliferative state of hematopoietic progenitor cells.

Adaptive cytoprotection against alcohol injury in the rat stomach is not due to increased prostanoid synthesis

This study evaluated the effects of 25% ethanol, a mild irritant, on endogenous prostanoid synthesis in the rat stomach before and after exposure to oral 100% ethanol. Rats received water or 25% ethanol orally. After 15 min, a portion of each group was sacrificed and the remaining animals treated with 100% ethanol prior to sacrifice one minute later. Microsomal membrane fractions were prepared from the glandular gastric mucosa in all groups and incubated with 14C arachidonic acid in the presence of cofactors. Endogenous mucosal prostanoid synthesis was analyzed by radiochromatography and results correlated with the presence or absence of gastric injury macroscopically. Prostanoids measured included PGI2, PGF2 alpha, PGE2, PGD2, PGA2, and thromboxane A2. Additional experiments were performed in like manner to those just described with the exception that indomethacin (5 mg/kg intraperitoneally) pretreatment was rendered. Stomachs exposed to water or 25% ethanol alone demonstrated a modest and equivalent level of synthesis of all prostanoids measured. Exposure to 100% ethanol (with and without mild irritant pretreatment) significantly increased prostanoid synthesis (especially PGI2, PGF2 alpha, and PGE2) compared with stomachs exposed to water or 25% ethanol alone; only mild irritant treated mucosa was protected from injury by 100% ethanol. Indomethacin pretreatment reversed the increased prostanoid synthesis in mucosa exposed to 100% ethanol, with or without mild irritant pretreatment, and partially reversed the protective effect of 25% ethanol. Other experiments using tissue slices in which perturbations in mucosal levels of prostanoids were measured by radioimmunoassay under identical experimental conditions exhibited similar results. These data dispute the notion that adaptive cytoprotection is mediated by increased endogenous prostanoid synthesis. The partial reversal of this process by indomethacin was most likely secondary to some other action of this agent, such as a reduction in gastric blood flow, rather than direct effects on prostanoid synthesis.

Lymphedema

The Scientific Board of the California Medical Association presents the following inventory of items of progress in plastic surgery. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, or scholars to stay abreast of these items of progress in plastic surgery that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Plastic Surgery of the California Medical Association, and the summaries were prepared under its direction.

The induction of bone by an osteogenic protein and the conduction of bone by porous hydroxyapatite: a laboratory study in the rabbit

The influence of the addition of an osteoinductive protein, capable of inducing extraskeletal ossification, on bone ingrowth into coralline porous hydroxyapatite was evaluated in the rabbit using a calvarium onlay model. Twenty-three rabbits received hydroxyapatite implants (10 x 10 x 2 mm) prepared with and without osteoinductive protein. These were implanted on the frontal bone and secured by wire fixation after 0.25 mm of the cortical surface was abraded. The implants were harvested at 3 and 4 months and analyzed for percentage of bone ingrowth by histologic examination of decalcified H&E sections and by scanning electron microscope backscatter image analysis. The osteoinductive protein-treated implants demonstrated significantly greater amounts of bone ingrowth at both 3 (52.0 versus 10.3 percent; p less than 0.001) and 4 months (66.1 versus 39.2 percent; p less than 0.005) than the untreated implants. The type of bone found in all osteoinductive protein-treated implants was predominantly lamellar. Untreated implants contained mostly woven bone at 3 months, with increasing amounts of lamellar bone appearing at 4 months. These results suggest that the combination of a bone-inducing protein and a suitable osteoconductive matrix may provide an alternative to bone grafting.

Hypothermia and blood coagulation: dissociation between enzyme activity and clotting factor levels

Previous studies of hypothermia and blood coagulation have focused on alterations in the levels of blood clotting elements using coagulation tests performed under normothermic conditions. However, because of the enzymatic nature of activated clotting factors, hypothermia should also be expected to affect clotting factor activities. Multiple determinations of activated partial thromboplastin times (APTT), prothrombin times (PT), and thrombin times (TT) were performed on commercially available normal human plasma at assay temperatures similar to those encountered clinically (25-37 degrees C). Both the APTT and the PT were significantly prolonged at temperatures below 35 degrees C (P less than 0.05). Clotting time correlated significantly with assay temperature in a negative exponential fashion for all three tests (r = -0.97 for APTT, -0.93 for PT, -0.71 for TT, P less than 0.001 for all regressions). Clotting time prolongation appears proportional to the number of enzymatic steps involved. These data indicate that the coagulopathy observed during hypothermia is, in part, independent of clotting factor levels.

Effects of alcohol on lectin binding affinity in rat gastric mucosa

Fluoresceinated lectins were employed to qualitatively evaluate cell surface carbohydrates, with and without ethanol exposure, in rat stomach mucosae. Rats received 1 ml of saline, or 50% or 100% ethanol orally. After 30 min, tissue samples of the glandular stomach were retrieved, cryosectioned, and incubated with one of a panel of lectins. Another set of sections was preincubated with neuraminidase to remove sialic acid residues. Qualitative evaluation of lectin binding showed that although several different sites stained, concanavalin A was the only lectin to stain the extracellular matrix, and soybean agglutinin the only lectin to stain chief cells. Neuraminidase preincubation enhanced lectin binding to both stained and previously unstained sites. Ethanol, both 50% and 100%, produced changes in both neuraminidase-treated and untreated tissues, increasing the specific binding of concanavalin A, Ulex europaeus agglutinin I, and wheat germ agglutinin, while decreasing Helix pomatia agglutinin and soybean agglutinin. These results suggest that ethanol can, through unknown mechanisms, alter carbohydrate binding affinity.

Prostaglandin prevents aspirin injury in the canine stomach under in vivo but not in vitro conditions

This study compared the ability of topical 16,16-dimethyl prostaglandin E2 in a dose range of 0.3-3.0 micrograms/ml to prevent aspirin-induced injury in the canine stomach under both in vivo and in vitro conditions. For in vitro studies, isolated strips of oxyntic mucosa were exposed to 10 or 20 mM aspirin (ASA) at pH 1-4, with and without treatment with 16,16-dimethyl prostaglandin E2. For in vivo experiments, a portion of the oxyntic stomach was mounted between the rings of a Lucite chamber, with splenic vessels intact, such that the mucosa was divided into halves. Both sides were exposed to 20 mM ASA at pH 1 or 2, and one side also received concomitant treatment with 16,16-dimethyl prostaglandin E2. After ASA exposure, tissue samples were prepared for quantitative microscopic analysis of the degree of injury. Under both experimental conditions, the magnitude of gastric injury by ASA was pH-related, being most pronounced at pH 1; this damage was worse under in vitro conditions, and both concentrations of ASA were equally damaging in this setting. 16,16-Dimethyl prostaglandin E2 failed to prevent ASA injury in vitro at any pH and ASA concentration tested, but markedly reduced the magnitude of injury in vivo. The most effective protective dose of 16,16-dimethyl prostaglandin E2 under in vivo conditions was 1.0 micrograms/ml. The diminished tolerance to ASA damage in vitro when compared with in vivo, and the inability of 16,16-dimethyl prostaglandin E2 to prevent these damaging effects in vitro, underscores the probable crucial role for blood flow, and possibly neural innervation, in mediating the protective effects of prostaglandins.

Prostaglandin-induced gastric mucosal protection against stress injury. Absence of a relationship to tissue glutathione levels

The effects of 16,16 dimethyl prostaglandin E2 (dmPGE2) on the gastric mucosa of rats subjected to 1, 2, and 24 hours of water immersion stress were examined histologically. Results indicated a time-related increase in the total percentage length of glandular mucosa injured in normal saline (NS) pretreated rats that was significantly attenuated by subcutaneous dmPGE2 pretreatment (5 micrograms/kg) after 1 hour (46.0 +/- 12.9 vs. 16.8 +/- 2.3; p less than 0.005), 2 hours (45.4 +/- 1.0 vs. 13.8 +/- 2.2; p less than 0.001), and 24 hours (93.1 +/- 2.6 vs. 65.1 +/- 7.0; p less than 0.005) of water immersion stress. Moreover, dmPGE2 essentially prevented the occurrence of deep, glandular injury that, in NS controls, involved approximately 13% and 26% of the mucosal surface after 2 and 24 hours of immersion stress, respectively. Additionally, tissue levels of glutathione (mumole/g weight of wet tissue) were measured to determine its role under such conditions. After 1 hour of stress, there were no differences in glutathione levels between NS or dmPGE2 pretreated animals and fasted controls. After 2 and 24 hours of stress, there were likewise no differences in glutathione levels between NS and dmPGE2 pretreated groups, although levels in both groups were significantly decreased from fasted controls by approximately 30% at 2 hours and 37-47% after 24 hours. These histologic and biochemical data indicate that dmPGE2 attenuates both the extent and depth of glandular mucosal injury and does so in a manner unrelated to alterations in glutathione levels in gastric epithelium.

Microscopic correlates of adaptive cytoprotection in an ethanol injury model

The present study histologically investigated the efficacy of pretreating rat gastric mucosa with the mild irritants, 10% and 25% ethanol (EtOH), against the known damaging effects of 100% EtOH. Fasted rats received 1 ml of either water, 10% EtOH, or 25% EtOH by orogastric intubation. Fifteen minutes later, a portion of these animals was sacrificed and tissue samples of the oxyntic region of the stomach were excised and processed for quantitative histologic analysis. Remaining animals received a 1 ml oral bolus of the necrotizing agent, 100% EtOH. Five minutes later, these animals were sacrificed and tissues were prepared in a like manner. In a separate series of experiments, the aforementioned protocols were repeated, except that all animals received the prostaglandin synthetase inhibitor, indomethacin (5.0 mg/kg intraperitoneally), 30 min before administration of the mild irritant. Microscopically, the administration of water or 10% EtOH alone caused a small and comparable amount of superficial injury to the gastric mucosa. Moreover, both substances failed to induce protection in stomachs subsequently exposed to 100% EtOH. Indomethacin pretreatment did not significantly alter any of these findings. In marked contrast, 25% EtOH alone elicited a substantial degree of superficial damage to the gastric mucosa. Nevertheless it significantly reduced the depth of injury in animals subsequently challenged by 100% EtOH. Indomethacin failed to aggravate the effects of 25% EtOH alone, but partially inhibited the protective effect of this mild irritant against 100% EtOH induced damage. Our findings indicate that adaptive cytoprotection is a real phenomenon that can be demonstrated microscopically. Such protection is limited primarily to the deep mucosal layers (i.e. gastric glands), appears in part to be prostaglandin mediated and seems to require the generation of moderate surface cell damage (as occurred with 25% EtOH, but not 10% EtOH) to induce its initiation.

Ultrastructural aspects of prostaglandin cytoprotection in an alcohol injury model

The effects of absolute ethanol (EtOH) and 16,16-dimethyl-prostaglandin E2 (PGE2) on the ultrastructure of rat gastric mucosa were assessed using standard electron microscopic techniques. Fasted rats were injected subcutaneously with 10 micrograms/kg body weight of PGE2 or saline. After 30 min, animals received orally 100% EtOH or an equal volume of saline. Gastric mucosa was sampled at 5 min and 1, 2, 8, and 24 h post-EtOH and tissues procured for scanning and transmission electron microscopy. Both mucosal epithelial and connective tissue compartments were assessed. At 5 min after EtOH, in saline-pretreated animals, tissues showed extensive destruction of epithelium and connective tissue; major breaks in the basal laminae were coincident with hemorrhage. Deep-lying epithelial cells and most of the basal lamina were spared in tissues exposed to PGE2 prior to EtOH, permitting nearly complete repair within 24 h. Restitution proceeded over small breaks or pleats of basal lamina but failed in regions of total destruction of this structure. These data indicate that PGE2 protects not only deep-lying epithelial cells from EtOH damage but associated connective tissue as well and that sparing of both compartments leads to orderly and rapid epithelial restitution.

Elevated PGI2 and PGE2 production in the rat ileum following mild hypotension

Ileal prostaglandin (PGs) biosynthesis was compared in female rats in normal mild hemorrhage (exposed to mild hypotension, reperfusion, and maintenance on hyperalimentation for 5 days) and control groups (instrumentation and hyperalimentation without hemorrhage). Tissue PG levels were analyzed by radiochromatographic analysis of microsomal membrane fractions prepared from the ileum in each group. Total cyclooxygenase activity in the normal and control groups was modest, with low levels of 6-keto-PGF1 alpha, PGE2, PGF2 alpha, thromboxane B2, PGA2, and PGD2 being produced. Hemorrhage, reperfusion, and maintenance on hyperalimentation for 5 days markedly induced total cyclooxygenase activity in the female rat ileum. Ileal microsomal membrane fractions obtained from the mild hemorrhage group synthesized levels of individual PGs three- to seven-fold higher than the normal or control groups, with 6-keto- PGF1 alpha (breakdown product of prostacyclin), PGE2, and PGA2 demonstrating the highest levels of biosynthesis. These data suggest that the gastrointestinal tract could serve as a source for the elevated PGs known to occur in various shock models.