Is translocation of bacteria and endotoxin from the gastrointestinal tract a source of sepsis in critically ill patients?

Estimation of relatedness among non-pedigreed Yakutian cryo-bank bulls using molecular data: implications for conservation and breed management

BACKGROUND

Yakutian cattle, the last remaining native cattle breed in Siberia, are well adapted to the extreme sub-arctic conditions. Nowadays only ca. 1200 purebred animals are left in Yakutia. The semen of six Yakutian bulls was stored in a cryo-bank without any pedigree documentation because of the traditional free herding style of the population.

METHODS

To clarify the genetic relatedness between these bulls and to provide recommendations to use their semen in future conservation and breed management programs, we have analysed 30 autosomal microsatellites and mitochondrial DNA sequences in 60 individuals including the six for which semen has been stored. Four relatedness estimators were calculated. In addition, we assessed the value of the cryo-bank bulls for the preservation of genetic variation of the contemporary Yakutian cattle by calculating allelic and gene diversity estimates and mean molecular coancestries.

RESULTS

On the basis of microsatellite variability, including the Yakutian cryo-bank bulls increases the allelic variation in the contemporary population by 3% and in the male subpopulation by 13%. In terms of the mean molecular coancestries, they are less related to the contemporary cow population than the breeding bulls and therefore could be used to reduce inbreeding in the living population. Although 30 loci are insufficient to resolve definitely their relatedness categories, the data suggest four pairs of cryo-bank bulls as possible half-sibs.

CONCLUSIONS

Our results show that even relatively limited cryo-bank storage of semen can carry allelic variation through a bottleneck. We propose a breeding scheme based on the rotation of breeding females and the division of cryo-bank bulls into three groups. Thus, if molecular data (e.g. autosomal microsatellite genotypes) for the contemporary population are available and based on relatively small-scale laboratory analyses, it is possible to avoid serious mistakes in their use for breeding applications. The approach suggested here based on the use of Yakutian cryo-bank semen can be easily extended to cryo-bank materials of other animals in future breeding programs.

Endotoxin and Mammalian Host Responses During Experimental Disease

Endotoxin is an integral component of the outer membrane of Gram-negative bacteria and a prime example of unique and highly conserved bacterial surface molecules that engage with the innate immune system of the mammalian host via pattern recognition receptors on a range of host cells. The results of this interaction, which may be beneficial or detrimental to the development and welfare of the host, are reviewed, focusing on the different sensitivities and consequences in a range of hosts of experimental exposure to endotoxin, the disease outcomes and recent developments in our understanding of the mechanisms involved.

Effects of epinephrine, norepinephrine, and phenylephrine on microcirculatory blood flow in the gastrointestinal tract in sepsis*

OBJECTIVE

The use of vasopressors for treatment of hypotension in sepsis may have adverse effects on microcirculatory blood flow in the gastrointestinal tract. The aim of this study was to measure the effects of three vasopressors, commonly used in clinical practice, on microcirculatory blood flow in multiple abdominal organs in sepsis.

DESIGN

Random order, cross-over design.

SETTING

University laboratory.

SUBJECTS

Eight sedated and mechanically ventilated pigs.

INTERVENTIONS

Pigs were exposed to fecal peritonitis-induced septic shock. Mesenteric artery flow was measured using ultrasound transit time flowmetry. Microcirculatory flow was measured in gastric, jejunal, and colon mucosa; jejunal muscularis; and pancreas, liver, and kidney using multiple-channel laser Doppler flowmetry. Each animal received a continuous intravenous infusion of epinephrine, norepinephrine, and phenylephrine in a dose increasing mean arterial pressure by 20%. The animals were allowed to recover for 60 mins after each drug before the next was started.

MEASUREMENTS AND MAIN RESULTS

During infusion of epinephrine (0.8 +/- 0.2 mug/kg/hr), mean arterial pressure increased from 66 +/- 5 to 83 +/- 5 mm Hg and cardiac index increased by 43 +/- 9%. Norepinephrine (0.7 +/- 0.3 mug/kg/hr) increased mean arterial pressure from 70 +/- 4 to 87 +/- 5 mm Hg and cardiac index by 41 +/- 8%. Both agents caused a significant reduction in superior mesenteric artery flow (11 +/- 4%, p < .05, and 26 +/- 6%, p < .01, respectively) and in microcirculatory blood flow in the jejunal mucosa (21 +/- 5%, p < .01, and 23 +/- 3%, p < .01, respectively) and in the pancreas (16 +/- 3%, p < .05, and 8 +/- 3%, not significant, respectively). Infusion of phenylephrine (3.1 +/- 1.0 mug/kg/min) increased mean arterial pressure from 69 +/- 5 to 85 +/- 6 mm Hg but had no effects on systemic, regional, or microcirculatory flow except for a 30% increase in jejunal muscularis flow (p < .01).

CONCLUSIONS

Administration of the vasopressors phenylephrine, epinephrine, and norepinephrine failed to increase microcirculatory blood flow in most abdominal organs despite increased perfusion pressure and-in the case of epinephrine and norepinephrine-increased systemic blood flow. In fact, norepinephrine and epinephrine appeared to divert blood flow away from the mesenteric circulation and decrease microcirculatory blood flow in the jejunal mucosa and pancreas. Phenylephrine, on the other hand, appeared to increase blood pressure without affecting quantitative blood flow or distribution of blood flow.

Defective glucose homeostasis during infection

Infection leads to profound alterations in whole-body metabolism, which is characterized by marked acceleration of glucose, fat and protein, and amino acid flux. One of the complications of infection, especially in the nutritionally supported setting, is hyperglycemia. The hyperglycemia is caused by peripheral insulin resistance and alterations in hepatic glucose metabolism. The defects in hepatic glucose metabolism include overproduction of glucose and a failure of the liver to appropriately adapt when nutritional support is administered. Investigators have suggested that multiple factors contribute to the observed defects. In this review, I focus primarily on alterations in carbohydrate metabolism, examining both the metabolic response to infection and inflammatory stress, the role of the accompanying neuroendocrine and inflammatory responses in the metabolic response, and the interaction between the endocrine response to infection and nutritional support.

Variability of bacterial translocation in the absence of intestinal mucosal damage following injury and the influence of interleukin-6

Bacterial translocation and intestinal mucosal damage have been reported as potentially clinically important sequelae of injury. Evidence that endogenous interleukin-6 (IL-6) is able to protect against infection, and that orally administered IL-6 could prevent bacterial translocation and mucosal damage following haemorrhage, led us to evaluate the impact of injury on the intestinal mucosa and the role of endogenous IL-6. Normal and IL-6-deficient (IL-6-/-) mice were subjected to haemorrhage of increasing severity, hind limb ischaemia, or both. Mucosal integrity and bacterial translocation to the liver, spleen and mesenteric lymph nodes (MLN) were examined after 16 h. Bacterial translocation to each of these tissues was observed in unoperated animals. The more severe haemorrhage procedures, and hind limb ischaemia, increased bacterial translocation to the liver significantly in most experiments with normal mice. The IL-6-/- mice survived the most severe haemorrhage procedure less well (p = 0.0015), although increased bacterial translocation was not seen. There was no clear evidence of mucosal damage, or bacterial translocation to spleen and mesenteric lymph nodes, in either normal or IL-6-/- mice. Intestinal IgA concentrations were the same in IL-6-/- mice and controls. These data demonstrate that increased bacterial translocation can be observed following severe injury, but that neither bacterial translocation nor severe injury are inevitably associated with morphological damage to the intestinal mucosa, and endogenous IL-6 is more likely to promote bacterial translocation than protect the gut.

Lipopolysaccharide administration increases acid and alkaline phosphatase reactivity in the cardiac muscle

The effect of lipopolysaccharide (LPS) administration on the in situ distribution of the reaction product of acid phosphatase (AcPase) and alkaline phosphatase (AlPase) activity was examined in the rat cardiac muscle using catalytical cytochemistry. Tissues of the heart were fixed and then incubated in reaction media for detection of AcPase and AlPase reactivity. In normal hearts, reaction product of AcPase activity was observed in lysosomes. AlPase reactivity was detected at the extracellular surface of the capillary endothelilal cells and in their caveolae. Following LPS administration, the number and the size of lysosomes possessing AcPase reactivity as well as their electron density significantly increased. Furthermore, they tended to form groups consisting of three to five lysosomes. Cytochemical reaction 2 and 24 hours after injection was similar. One week later, the reaction returned to its normal pattern. As in the case with AcPase, the first changes of the distribution of the reaction product of AlPase activity were detected 2 hours after injection. The changes included a remarkable increase of the number of enzymatically positive capillaries, intensified cytochemical reaction in endothelial cells, and an increased number of caveolae. Again, no noticeable differences in reactivity were observed 2 and 24 hours after injection and the reaction returned to normal one week later. Collectively, our data indicate that both cardiac AcPase and AlPase are affected early after injection of LPS. Although the pattern of cytochemical reaction of both phosphatases was restored one week later, it is believed that the altered distribution of their reactivity in early periods after LPS administration may be a factor contributing to the development of pathological changes in this organ at a later stage.

Enteral or parenteral nutrition? Pro-enteral

There is a convincing evidence for the superiority of enteral nutrition as compared with parenteral In critically ill and injured patients. The general objectives of providing nutritional support in the critically ill is to persevere body functions that are functioning normally and to facilitate recovery of those that are failing. The specific objective for enteral nutrition is, however, preservation and restoration of the gastrointestinal structure and function. Today, early enteral nutrition is an integral part of the acute management of critically ill patients. It is no longer a therapy which can be started "if" necessary just to prevent malnutrition. Early enteral nutrition can be successfully carried out in virtually all critically ill patients also after major abdominal surgery and in acute pancreatitis. There are very few contraindications for using enteral nutrition and severe complications are rare. Parenteral nutrition, on the other hand, is associated with increased incidence of infectious complications and is rarely indicated in critically ill patients.

Efficacy of different triglycerides in total parenteral nutrition for preventing atrophy of the gut in traumatized rats

BACKGROUND

The efficacy of different fat emulsions as components of a total parenteral nutrition (TPN) regimen on the integrity of the gut was assessed in traumatized rats. With the release of the short-chain fatty acids butyric or propionic acid during the hydrolysis of a structured triglyceride containing butyric acid (C4-L-C4-TG) or the beta-oxidation of nonanoic acid from trinonanoin (C9TG), respectively, the infusion of these two triglycerides was supposed to reveal positive effects against the TPN-induced atrophy of the intestine.

METHODS

After 3 days of fiber-free liquid diet, rats were traumatized (laparotomy) and catheterized. Afterwards they received equicaloric TPN that delivered 1008 kJ (241 kcal)/kg of body weight per day and 30% nonprotein calories as fat emulsion. The four fat emulsions tested in four groups of six animals contained either long-chain triglycerides (LCT), medium-chain triglycerides (MCT)-LCT (1:1), C9TG/LCT (1:1) or C4-L-C4-TG. Animals of a control group were infused with isovolemic 0.9% NaCl solution and were offered oral standard chow.

RESULTS

After 7 days of MCT/LCT administration, the mass-to-length ratio of the total small bowel as well as the masses of mucosa/submucosa and muscularis/serosa in 10-cm segments of the distal half of the small bowel were significantly higher than that found in the other TPN groups or not different from controls. Histometric measurement of the villus height in the ileum revealed no statistically significant differences from controls for the rats of the MCT/LCT and C4-L-C4-TG groups. In the colon, no statistically significant differences between TPN groups were found for either parameter.

CONCLUSIONS

Within the tested fatty substrates the MCT/LCT fat emulsion revealed less structural impairments in the distal half of the small bowel regarding mucosa/submucosa (mass and villus height), but also muscularis/ serosa (mass).