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The inflammatory response of the liver to hemorrhagic shock includes the production of acute phase proteins and a variety of mediators, such as the cytokine interleukin (IL)-6. The transcription of acute phase protein genes in hepatocytes has been shown to be activated by Stat3, one of six distinct signal transducers and activators of transcription (STAT) proteins. IL-6 signals through activation of Stat3. In this study, we examined whether or not Stat3 was activated and IL-6 mRNA produced in the liver of rats subjected to hemorrhagic shock and whether or not both phases of shock, the ischemic and the resuscitation phases, were required. We report here that Stat3 activation and increased IL-6 expression required resuscitation and displayed identical kinetics following resuscitation, suggesting that liver production of IL-6 was responsible for liver Stat3 activation in hemorrhagic shock.

Objective: To investigate the pathophysiologic mechanisms that lead to ileus after abdominal surgery., Summary Background Data: The common supposition is that more invasive operations are associated with a more extensive ileus. The cellular mechanisms of postsurgical ileus remain elusive, and few studies have addressed the mechanisms., Methods: Rats were subjected to incremental degrees of surgical manipulation: laparotomy, eventration, "running," and compression of the bowel. On postsurgical days 1 and 7, muscularis infiltrates were characterized immunohistochemically. Circular muscle activity was assessed using mechanical and intracellular recording techniques in vitro., Results: Surgical manipulation caused an increase in resident phagocytes that stained for the activation marker lymphocyte function-associated antigen (LFA-1). Incremental degrees of manipulation also caused a progressive increase in neutrophil infiltration and a decrease in bethanechol-stimulated contractions. Compression also caused an increase in other leukocytes: macrophages, monocytes, dendritic cells, T cells, natural killer cells, and mast cells., Conclusion: The data support the hypothesis that the degree of gut paralysis to cholinergic stimulation is directly proportional to the degree of trauma, the activation of resident gut muscularis phagocytes, and the extent of cellular infiltration. Therefore, postsurgical ileus may be a result of an inflammatory response to minimal trauma in which the resident macrophages, activated by physical forces, set an inflammatory response into motion, leading to muscle dysfunction.

Hemorrhagic shock (HS) initiates an inflammatory cascade that includes the production of cytokines and recruitment of neutrophils (PMN) and may progress to organ failure, inducing acute respiratory distress syndrome (ARDS). To examine the hypothesis that interleukin-6 (IL-6) contributes to PMN infiltration and lung damage in HS, we examined the lungs of rats subjected to unresuscitated and resuscitated HS for the production of IL-6 and activation of Stat3. Using semiquantitative RT-PCR, we found a striking increase in IL-6 mRNA levels only in resuscitated HS, with peak levels observed 1 h after initiation of resuscitation. Increased IL-6 protein expression was localized to bronchial and alveolar cells. Electrophoretic mobility shift assay of protein extracts from shock lungs exhibited an increase in Stat3 activation with kinetics similar to IL-6 mRNA. In situ DNA binding assay determined Stat3 activation predominantly within alveoli. Intratracheal instillation of IL-6 alone into normal rats resulted in PMN infiltration into lung interstitium and alveoli, marked elevation of bronchoalveolar lavage cellularity, and increased wet-to-dry ratio. These findings indicate that IL-6 production and Stat3 activation occur early in HS and may contribute to PMN-mediated lung injury, including ARDS after HS.

The basal presence of immunologically potent cells within the intestinal muscularis externa and their functional significance is unclear. Our aim was to investigate the basal distribution of various leukocyte populations within the rat jejunal muscularis. In addition, we sought to immunohistochemically phenotype the muscularis macrophage in jejunal whole-mounts, isolate these cells in primary culture, and investigate their ontogenesis. Macrophages form a regularly distributed network that expresses major histocompatibility complex class II, CD14 receptors, and a low level of CD11/CD18. The macrophages are activated by dissection and are present in fetal animals. Enriched macrophage cultures show a normal resident phenotype and remain present for weeks in dissociated muscularis cultures. The results also demonstrate the presence of neutrophils, monocytes, mast cells, and lymphocytes within the muscularis and suggest that the dense network of muscularis macrophages may be a potent resident trigger for inflammation in response to tissue injury or bacterial translocation.

Hemorrhagic shock (HS) initiates a series of inflammatory processes, including the production of proinflammatory cytokines at critical sites such as the lung. We have previously shown that granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) mRNA are produced in the lungs of rats subjected to resuscitated HS and that both the ischemic and reperfusion phases of resuscitated HS were required. G-CSF and IL-6 activate STAT (signal transducers and activators of transcription) proteins which may sustain the inflammatory response that follows resuscitation in HS. We tested the hypothesis that STAT proteins are activated in the lungs of rats subjected to resuscitated HS and examined the factors contributing to their activation including duration of shock and duration of resuscitation. Sprague-Dawley rats were subjected to compensated (66.1 +/- 1.1 min) or decompensated (157.3 +/- 2.3 min) HS (mean arterial pressure 40 mmHg) followed by resuscitation and sacrifice at 4 or 8 h. The amount of activated Stat3 was increased 2.3- to 7-fold compared with sham control animals in all four experimental groups of resuscitated HS. Levels of Stat3 activation increased with increase in duration of shock but did not demonstrate differences at the 4 or 8 h time point of killing. These results indicate that resuscitated HS results in the activation of the intracellular signaling cascade that includes that activation of STAT proteins driven by cytokines such as G-CSF and IL-6.

Bacterial lipopolysaccharide (LPS) is a causative agent of sepsis-induced ileus. Although it is known that LPS activates macrophages and initiates inflammation, the consequences of LPS on the macrophage network and a potential inflammatory response within the intestinal muscularis have not been investigated. This study was designed to identify cellular and functional changes in rat intestinal muscularis after intraperitoneal LPS. Histo- and immunohistochemistry were used to phenotype leukocytes. Functional alterations were determined using an organ bath. Compared with controls, LPS caused a 21-fold increase in staining for the lymphocyte activation marker-1 (LFA-1) localized to the ED2+ macrophage network 1 h after injection. This was followed by a significant infiltration of neutrophils, mast cells, and monocytes into the muscularis. LPS also caused a 62% reduction in spontaneous circular muscle activity and a 91% suppression of bethanechol-stimulated contractions 12 h after injection. These results demonstrate that endotoxemia 1) acutely activates the muscularis macrophage network, 2) causes the extravasation of leukocytes, and 3) results in circular muscle impairment.

One hundred patients with infrarenal abdominal aortic aneurysms were treated by surgery. Fifteen deaths occurred postoperatively. Eleven patients died during the follow-up of a medium period of 13 months. Three patients with a ruptured aneurysm died intraoperatively before the graft was implanted. Three patients were lost to follow-up. Sixty-four patients were examined with colour-coded Duplex sonography after surgical repair. Colour-coded Duplex sonography was able to image the aortic prostheses with the adjacent major vessels. Fifty-eight patients showed a normal prosthesis, 3 dilatation proximal of the prosthesis, 1 dilatation distal of the prosthesis, 1 mild stenosis, 1 haematoma. Colour-coded Duplex sonography imaged the intraluminal space of the prosthesis more easily than ultrasound. Colour-coded Duplex sonography was able to differentiate between intraluminal and extraluminal lesions.

We collected benthic bacterial production data measured by (3)H thymidine incorporation (TTI) (25 studies), frequency of dividing cells (FDC) (3 studies), dark-C02 assimilation (1 study) and (3)H-adenine uptake (2 studies) from the literature, which included 18 marine, 6 river, and 2 lake studies. In all of the studies that used the TTI method, (3)H-DNA was isolated and incubations were carried out at in situ temperatures. Most of the researchers also determined (3)H-DNA extraction efficiencies and isotope dilution, thus interpretable estimates of bacterial production were used in the analysis. In marine sediments, bacterial production rates were linked to bacterial biomass, bacterial abundance, sediment organic matter, temperature, and sediment chlorophyll a, with these variables explaining between 40% and 68% of the variation in production rates. Simple relationships between production and bacterial biomass or bacterial abundance, or between production and sediment organic matter, were improved by also including temperature in the analysis of marine sediments. Sediment organic matter explained an appreciable fraction (58%) of the observed production in freshwater sediments. Temperature was the most powerful predictor of the observed variability in specific growth rates (r (2) = 0.48 and r (2) = 0.58) in marine and freshwater sediments, respectively. Thus, bacterial production and specific growth rates are most closely linked to substrate supply and temperature in marine and freshwater sediments.

An atypical case of cystic echinococcosis of the liver is reported. During a routine examination of a 75-year-old man an asymptomatic hepatic lesion was found. US, CT and MRI showed a solid, avascular, non-invasively growing lesion. Echinococcus serology was negative. Histological samples taken by biopsy and after cyst extirpation confirmed the diagnosis of an old, scarred Echinococcus cyst. Such findings are rare in echinococcosis and cause difficulties with the diagnosis. Be- cause of the increasing age of the population and the presence of tourists and immigrants from endemic areas, this condition is becoming more frequent. It should be considered in the differential diagnosis of focal hepatic lesions.

We analyzed heterotrophic, pelagic bacterial production and specific growth rate data from 57 studies conducted in fresh, marine and estuarine/coastal waters. Strong positive relationships were identified between 1) bacterial production and bacterial abundance and 2) bacterial production and algal biomass. The relationship between bacterial production and bacterial abundance was improved by also considering water temperature. The analysis of covariance model revealed consistent differences between fresh, marine and estuarine/coastal waters, with production consistently high in estuarine/coastal environments. The log-linear regression coefficient of abundance was not significantly different from 1.00, and this linear relationship permitted the use of specific growth rate (SGR in day(-1)) as a dependent variable. A strong relationship was identified between specific growth rate and temperature. This relationship differed slightly across the three habitats. A substantial portion of the residual variation from this relationship was accounted for by algal biomass, including the difference between marine and estuarine/coastal habitats. A small but significant difference between the fresh- and saltwater habitats remained. No significant difference between the chlorophyll effect in different habitats was identified. The model of SGR against temperature and chlorophyll was much weaker for freshwater than for marine environments. For a small subset of the data set, mean cell volume accounted for some of the residual variation in SGR. Pronounced seasonality, fluctuations in nutrient quality, and variation of the grazing environment may contribute to the unexplained variation in specific growth.

A new system for continuous measurement of oxygen uptake was tested (EMC). Delivered tidal volumes of the system, the accuracy of the oxygen sensor cell, measurement of the oxygen uptake related to different inspiratory oxygen concentrations as well as comparative tests of oxygen uptake according to Fick's principle were studied. Furthermore, we looked for possible leakages in the system. Following to our results even thorough maintenance could not entirely prevent leakages. There was a remarkable increase in measured oxygen uptake if inspiratory oxygen concentration was increased. While carbon-dioxide output was measured at constant levels this led to low respiratory quotients, some of these were less than 0.5. This was caused by a construction error of the system which could be corrected in the meantime. In 70 comparative tests of oxygen uptake between EMC and Fick's principle (measurement of cardiac output and arteriovenous oxygen content difference) we found a mean difference of about 10% (p less than or equal to 0.001) with nearly identical standard deviations. The EMC measured the higher oxygen uptake. Based on our experience the EMC is suitable for continuous measurement of oxygen uptake but it needs good knowledge of the system and the underlying measuring procedures. Additional technical improvements seem to be possible.

We examined the effect of grazer size on periphyton biomass, size structure, and species compostion by removing the largest invertebrate grazers on artificial macrophytes planted in the littoral of Lake Memphremagog (Que-Vt). A series of exclosures with increasingly fine mesh prevented colonization by large invertebrates but allowed in smaller grazers. Oligochaetes, chironomids, and cladocerans effectively replaced snails so that total grazer biomass in the various treatments was not significantly different from the controls. With one exception, algal biomass, measured as chlorophyll a, did not differ significantly among the various treatments. However algal size and taxonomy were affected because the dominance of large blue-green colonies was apperantly related to the presence of large grazers. The results of the size manipulations were qualitatively similar to those induced in phytoplankton communities by size selective zooplankton grazing and are consistent with models based on general allometric equations.

We examined the effect of different sediment types on the staining effectiveness of the fluorochrome DAPI (4'-6-diamidino-2-phenylindole dihydrochloride) over a wide range of concentrations and on the masking effect of sediment particles on DAPI-stained bacteria. Sediment type greatly affects the staining efficiency of DAPI, and most published studies seem to have underestimated bacterial abundances by using suboptimal concentrations of the fluorochrome. A DAPI concentration of 5 mug ml is required to effectively stain the bacteria in most sediments that can be sampled with a gravity corer. When the sediments are diluted 687 times (a dilution factor similar to those most often used in the literature), sediment particle masking of stained bacteria is highly variable for different sediment types. By using a measure of turbidity (A(750)) to indicate masking and the quartz-corrected water content as a measure of the initial (in situ) dilution of each sediment type, it becomes possible to show a linear relationship between masking and the integrated (initial x experimental) dilution of various sediments. This relationship allows the development of a correction procedure for masking which makes accurate and unbiased counts possible. Data so obtained show a strong relationship between bacteria (cells per milliliter of fresh sediment) and sediment organic matter (grams [dry weight] per milliliter of fresh sediment), one that is not discernable without the correction. The proposed method of staining and correction for sediment masking provides the basis for a standardized interpretation of sediment bacterial counts.

A new system for continuous measurement of oxygen uptake was tested. The tidal volumes delivered by the system, the accuracy of the oxygen sensor cell, measurement of the oxygen uptake at different inspired oxygen concentrations, and comparative tests of oxygen uptake using the Fick principle were studied. Judging from our results, even thorough maintenance could not entirely prevent leakages. Due to a construction error, there was a large increase in measured oxygen uptake if inspired oxygen concentration was increased. While carbon-dioxide output was constant, this led to respiratory quotients of less than 0.5. By modifying the system with a mixing chamber for the inspiratory gas, new tubing to the oxygen sensor cell and changes in the computer software, these errors have been corrected in the meantime. In comparative tests of oxygen uptake using the Fick principle (cardiac output and arteriovenous oxygen content difference), we found a mean difference between EMC and the Fick principle of about 6.6% (P less than or equal to 0.001, r = 0.91) with nearly identical standard deviations for both values. Our experience indicates that the EMC is suitable for continuous measurements of oxygen uptake. Additional technical improvements seem to be possible.

Crowded stands of submerged plants in Québec lakes have a weight-density with a shallower, but not significantly different, slope and an intercept 10 fold lower than those for terrestial stands. The examination of a larger data set including both freshwater and submerged macrophytes supported these differences. This data set suggested that those differences, as well as those among submerged stands, are largely attributable to the light levels incident upon the stand. The differences in weight-density relationships between submerged and terrestrial stands were paralleled by a smaller biomass per unit volume outgrown of the submerged plants, as predicted from the dimensional examination of the weight-density relationship. The variations in biomass per unit volume associated to differences in the species growth form explained deviations about the weightdensity relationship of stands growing under relatively similar light conditions.

Six common species of lake algae were found to ingest bacteria. The ingestion rates measured were of the same magnitude as those recorded for marine microflagellates totally dependent on external sources of carbon. A large biomass of Dinobryon species removed more bacteria from the water column of a lake than crustaceans, rotifers, and ciliates combined.

Although the bacterioplankton of lakes are usually considered primarily in terms of mineralization processes, recent studies suggest that they may also strongly compete for phosphorus with the phytoplankton. In the present study, we have tested in chemostat culture, and found support for the hypotheses that (1) a freshwater bacterium (Pseudomonas paucimobilis), whose carbon source is excretion from a phosphorus-limited alga (Synedra ulna var.danica), can outcompete that alga for phosphorus (P) under widely varied P supply rates; (2) exogenously-supplied organic carbon positively influences bacterial biomass and negatively influences algal biomass; (3) the ratio of bacterial to algal phosphorus uptake in short-term(32)P orthophosphate uptake experiments is an accurate predictor of their relative long-term phosphorus assimilation (i.e., growth) in mixed culture.

Nine common species of aquatic macrophytes took all their phosphorus from the sediments when grown in situ in both a mesotrophic and a mildly eutrophic bay. Even under hypertrophic conditions, the sediments contributed an average of 72 percent of all the phosphorus taken up during growth. These experiments unambiguously demonstrate for the first time that submergent macrophytes in nature over-whelmingly depend on the sediments for their phosphorus supply and characterize them as potential nutrient pumps to the open water.

The relationship between rates of phytoplankton photosynthesis and nutrient and growth factor deficiencies was investigated by the nutrient enrichment bioassay technique in a small tundra pond at Barrow, Alaska, Phosphate, nitrate, and ammonia deficiencies limited photosynthesis after the onset of a period of high sustained growth. Toward the end of this period, additional deficiencies for one or more trace elements and growth factors, with vitamin B ( 12) being one deficient growth factor, were noted. No nutrient and growth factor deficiencies were found during the subsequent period of low carbon incorporation. Interactions between nutrients as well as between nutrients and light were found to complicate the recognition deficiencies. The utility of the enrichment bioassay in determining nutrient and growth factor deficiencies is briefly discussed., (© 1971 by the Ecological Society of America.)