The role of glutamine in skeletal muscle ischemia/reperfusion injury in the rat hind limb model

OBJECTIVES

Ischemia/reperfusion injury is a commonly occurring event with severe pathologic consequences. Reperfusion initiates both the local and systematic damage in part through rapid oxygen generation. The glutathione system is a major mechanism of reducing this oxidative stress. If this system can be maintained or augmented during this stress then less damage may occur. Glutamine provides the source of glutamate to this system and has been shown to preserve total glutathione levels after injury/ischemia to both hepatic and gut models. To test this effect, we looked at glutamine and its role in ischemia/reperfusion injury in a rat hind limb model.

METHODS

Fifty male HSD/Holtzman rats weighing 350-400 g were randomized to receive glutamine (3% sol) or normal saline via intraperitoneal injections. The groups were then subjected to 2 hours of ischemia to their hind limbs using the Tourni-Cot method. Animals were then randomized to reperfusion groups of 30 minutes, 2 hours, and 4 hours. Muscle tissue assays were performed for lipid peroxidation (LPO), total glutathione (GSH), and myeloperoxidase (MPO). Peripheral blood was analyzed for creatinephosphokinase levels (CPK).

RESULTS

Animals that received glutamine showed a general trend of less lipid peroxidation products than the normal saline groups. In animals that received glutamine and underwent 2 hours of ischemia and reperfusion times of 0 minutes, 30 minutes, and 2 hours, there were significantly less percent changes in lipid peroxidation products from controls (4.6% vs 48.2%, P <0.05), (18.9% vs 123%, P <0.05), (12.6% vs 115%, P <0.05). A general trend upward was noted in CPK levels in both groups. In animals receiving 2 hours of ischemia and 30 minutes of reperfusion, there was a significantly greater level of creatinephosphokinase (CPK) calculated as percent change from control in the normal saline group as compared with the glutamine group (209.2% vs 92.7%). Myeloperoxidase assay of muscle tissue revealed a progressive increase as the reperfusion times grew. In animals receiving 2 hours of ischemia and 30 minutes of reperfusion, the normal saline group had a significantly larger percent increase from controls than the group that received glutamine (1126.4% vs 108%, P <0.05). Also, in those animals receiving 4 hours of reperfusion, the normal saline group had a significantly higher percent increase in MPO content than the glutamine group (6245% vs 108%, P <0.05). Total glutathione levels decreased rapidly as reperfusion occurred in both the normal saline and glutamine groups. No significant difference between the groups was noted.

CONCLUSIONS

Total glutathione levels during reperfusion were not significantly different in the groups receiving glutamine versus normal saline. Glutamine may provide an initial protective effect on reperfusion injury after moderate reperfusion times in the hind limb model as defined by CPK and LPO levels. Glutamine may blunt neutrophil recruitment after longer reperfusion times (4 hours) in the ischemic hind limb. Total glutathione levels decreased significantly after moderate levels of ischemia (2 hours) and reperfusion (30 minutes, 2 hours).

Low-power high-efficiency wavelength conversion based on modulational instability in high-nonlinearity fiber

Bandwidth and peak efficiency are enhanced for wavelength conversion based on induced modulation instability by use of dispersion-shifted fiber in which the nonlinearity (n(2)/A(eff)) is enhanced by a factor of ~4.5 over that of conventional dispersion-shifted fiber. We experimentally obtain a peak conversion efficiency as high as 28 dB over a 40-nm bandwidth with 600 mW of peak pump power. Considerations for further enhancement of fiber-based wavelength conversion are also discussed.

Long-term effects of continuous combined HRT on bone turnover and lipid metabolism in postmenopausal women

This study was undertaken to investigate the effect of 10 years of hormone replacement therapy (HRT) on bone turnover and lipid metabolism in postmenopausal women. The single-centre trial was initiated as a 1-year, double-masked, randomized, parallel-group study of continuous combined HRT with 2 mg 17 beta-estradiol and 1 mg norethisterone acetate administered once daily with or without 1 mg estriol. Following preliminary results which showed no difference between the addition and omission of estriol, patients continued on an open-label extension phase of continuous combined HRT without estriol for a further 9 years. Of the 52 women who entered the original double-masked study, 32 entered the open-label extension phase. The 10-year analysis was based on 27 patients. Major increases in bone mineral density (BMD) of the lumbar spine were seen during the first 3 years of treatment, remaining statistically significant compared with baseline at all visits throughout the 10-year follow-up (p < or = 0.025). Statistical modelling confirmed that there were no decreases in BMD after these initial increases. BMD remained 5.5% higher than baseline values after 10 years of continuous combined HRT. Mean total cholesterol levels were significantly reduced after 10 years of therapy (p = 0.012), with no significant changes in serum triglyceride and low-density lipoprotein (LDL)-cholesterol levels from baseline values at this time. High-density lipoprotein (HDL)-cholesterol levels, however, were reduced by 15.4% (p < 0.001). In conclusion, 10 years of continuous combined HRT resulted in a significant and sustained increase in BMD. This treatment regimen therefore appears to be well suited for the long-term prevention of osteoporosis in postmenopausal women.

Detection of telomerase activity in exfoliated cancer cells in colonic luminal washings and its related clinical implications

Telomerase is a ribonucleoprotein capable of replacing telomeric DNA sequences that are lost at each cell division. Under normal circumstances, it is active in rapidly dividing embryonic cells and in stem cell populations but not in terminally differentiated somatic cells. Much attention has recently focused on the hypothesis that activity of this enzyme is necessary for cells to become immortal. This predicts that telomerase activity should be detectable in malignant cells and tissues but not in their normal counterparts, which slowly senesce and die. In accordance with this notion, telomerase activity has been reported in a wide range of malignancies, including those of the gastrointestinal tract, breast and lung. In the present study, we used a polymerase chain reaction (PCR)-based assay for telomerase activity, designated the "telomeric repeat amplification protocol (TRAP)', to examine initially 35 colonic carcinomas, their corresponding normal tissues and 12 inflammatory bowel disease (IBD) lesions. We detected strong enzyme activity in 32 (92%) of the 35 colon carcinomas while there was no activity in 30 (86%) of 35 matched normal colonic tissue specimens and only very weak activity in the remainder. Four of seven specimens of ulcerative colitis and two of five Crohn's disease lesions were negative, and the rest were only weakly positive. These results led us to examine whether telomerase could be detected in carcinoma cells exfoliated into the colonic lumen. We assayed lysates of exfoliated cells in luminal washings from colectomy specimens of 15 patients with colon carcinoma and nine with IBD. Telomerase activity was detected in washings from 9 (60%) of the 15 colon carcinoma cases but not in any from cases with IBD, suggesting that it can be a good marker for the detection of colon carcinoma, possibly even in non-invasively obtained samples.

Wound coverage: is there a difference?

Many different wound-covering materials, making various claims regarding wound healing effectiveness, are currently available. However, no controlled, comparison trials have been performed to document these claims. This prospective, randomized study was undertaken to compare wound healing among several synthetic burn dressings. Micrografts were placed on 20 New Zealand white rabbits, then randomly covered with four commonly used synthetic burn dressings, to evaluate the impact on wound healing. No statistically significant difference in wound healing was observed among the dressings. With equal wound healing, the choice of wound coverage should be based on other factors such as availability, cost, and handling properties of the dressing.

Simultaneous but independent activation of adenylate cyclase and glycosylphosphatidylinositol-phospholipase C under stress conditions in Trypanosoma brucei

Previous observations suggested a concomitant relationship between the release of the variant surface glycoprotein (VSG) and the activation of adenylate cyclase in the bloodstream form of the parasitic protozoan Trypanosoma brucei. In order to evaluate this hypothesis, adenylate cyclase activity was measured in live trypanosomes subjected to different treatments known to induce the shedding of the VSG coat, namely low pH and trypsin digestion. In both cases adenylate cyclase activation occurred in parallel with the release of the VSG. The latter was found to be mediated by the glycosylphosphatidylinositol-specific phospholipase C that cleaves the glycosylphosphatidylinositol anchor of the protein (VSG lipase). Furthermore, both adenylate cyclase and VSG release were activated by the incubation of trypanosomes with specific inhibitors of protein kinase C, suggesting a repressive role for protein kinase C on both VSG lipase and adenylate cyclase activities. Significantly, in mutant trypanosomes lacking VSG lipase, adenylate cyclase was activated under conditions where VSG release did not occur. Moreover,VSG release was also found to occur in the absence of activation of the cyclase, as observed in the presence of low concentration of the thiol modifying reagent p-chloromercuriphenylsulfonic acid. These observations provide the first demonstration that release of the VSG in response to cellular stress is mediated by the VSG lipase and that while both release of the VSG and activation of adenylate cyclase occur in response to the same stimuli they are not obligatorily coupled.

Total and respirable dust in swine confinement buildings: the benefit of respiratory protective masks and effect of recirculated air

Caretakers and pigs in dusty environments inhale particles and toxic gases which can cause subclinical illness. We determined the reduction in sampled dust elicited by respiratory masks mounted on glass funnels. Open-faced filters or British cyclones were sampled to measure quantities of dust which the masks had trapped. Respiratory masks reduced the sampled total suspended particulates (open-faced filters) by > or = 75% with NIOSH/MSHA certified protectant (2-tie) masks and > or = 50% with NIOSH/MSHA non-certified comfort (1-tie) masks. Respirable particulates (British cyclones) were reduced by > or = 45% with NIOSH/MSHA certified protectant (2-tie) masks. These data suggest properly worn respiratory protective masks afford significant protection against both total suspended and respirable particulates in swine confinement facilities. Penetration of 3-25% of total aerosol mass through masks allowing only 1% penetration of a silica aerosol with an aerodynamic diameter of 0.6-1.0 microns suggested that measurable portions of the aerosol mass in these confinement houses behaved as if they were less than 1 micron in diameter. Because of the small size of the aerosol, NIOSH/MSHA certified respiratory protective masks should be worn when working in those facilities. We also studied concentrations of ammonia, endotoxin and total and respirable dust particles to determine effects of a recirculation fan which increased the nominal air flow capacity of the building by 10%. Recirculated air had minimal effects on ammonia, total airborne endotoxin or total particulate mass.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of a zinc based bioceramic as an osteoconductive agent in the rat model

The many complications and risks of autograft and allograft bone have resulted in the search for an effective synthetic bone graft substitute [1,2]. The purpose of this study is to determine the effectiveness of ZCAP (zinc calcium phosphate) ceramic organic acid composite as an osteoconductive agent, including its possible benefits or risks for patients requiring bone grafting. A solid control model has been developed with an isolated mid-diaphyseal femur fracture immobilized by intramedullary threaded K-wire fixation. Two trials were performed in which two formulations of ZCAP composite ceramic were tested. The first, used in eighteen rats will be referred to as ZCAP1, the second, used in six rats will be referred to as ZCAP2. In the first trial rat femurs were augmented with 0.1 g ZCAP1 composite ceramic which varied in pore size. One pore size performed better than the others, so that pore size along with some minor changes in the composite design to increase resistance to the stresses inherent in our weight bearing model resulted in ZCAP2, which was tested in the second trial. The rats were sacrificed at ten weeks, during which time all rats remained viable. Blood work was done prior to sacrifice and radiography was done on all femurs. After sacrifice, gross morphological exam showed filling of the defect. Sections of the femurs from each group were analyzed by decalcified histological examination, electron microscopy, and tensile strength testing. The ZCAP composite ceramic had no significant effect on blood chemistry or body weight. Initial histological studies were consistent with endochondral ossification which was confirmed by electron microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel heterodimeric transferrin receptor encoded by a pair of VSG expression site-associated genes in T. brucei

In T. brucei, a transferrin-binding protein has been found to share sequence homology with pESAG-7 and -6, the products of two related genes present in the VSG gene polycistronic transcription unit. When expressed in Xenopus oocytes, they appear as N-glycosylated proteins secreted in the medium (pESAG-7) and GPI anchored to the membrane (pESAG-6). These proteins are able to homo- or heterodimerize, probably through association in the same orientation. Only heterodimers can bind Tf, possibly two molecules per dimer. A comparison of Tf binding to pESAG-7/6-expressing oocytes and trypanosomes suggests that pESAG-7/6 is the Tf receptor of the parasite. In trypanosomes, the majority of pESAG-7/6 is released from the membrane and associates, together with Tf, with a glycosylated matrix present in the lumen of the flagellar pocket. Both pESAG-7/6 and Tf are internalized via coated pits and vesicles. These observations suggest a novel mode of Tf binding and uptake in trypanosomes.

Characterization of particles, ammonia and endotoxin in swine confinement operations

To define the atmospheres swine confinement operations, we measured concentrations of total and respirable dust particles, ammonia and endotoxin in the nursery and grower areas of 4 swine confinement houses. Increased ventilation in spring-summer relative to that in winter reduced concentrations of large dust particles more rapidly than it did smaller particles or ammonia. The greater decrease in large particles correlating to increased room air velocity may reflect larger particles' momentum causing impaction on surfaces. There was significant spatial variation in the concentration of airborne endotoxin within individual swine rooms and pens reflecting different mixing of large feed and smaller manure particles. Smaller particles had 4-fold higher concentrations of endotoxin than did larger particles, suggesting they had higher fecal material concentrations. Total airborne endotoxin and total suspended particulates correlated to the fraction of functional endotoxin contained in large particles, suggesting that small particles (0.5-2.0 micrometers) collide with large particles (50 micrometers). These data suggest that large non-respirable particles remove smaller respirable particles from indoor atmospheres due to kinematic coagulation.

Abrupt RNA changes precede the first cell division during the differentiation of Trypanosoma brucei bloodstream forms into procyclic forms in vitro

We have monitored the timing of DNA and RNA synthesis during the synchronous differentiation of Trypanosoma brucei bloodstream forms into procyclic forms in vitro. Both are triggered after a lag period of 4 h and reach a first peak after 9 h. The division of the kinetoplast precedes that of the nucleus by about 4 h. The first cell divisions are observed after 10 h, and the cell number is doubled after 20 h. The total RNA content per cell increases sharply between 4 and 10 h, then progressively decreases as cell division progresses. The increase in RNA content cannot be due solely to accumulation of rRNA since it is also observed for mRNAs such as actin. The VSG mRNA has almost disappeared within 2 h, while the procyclin mRNA accumulates soon after the triggering of differentiation, with a strong peak between 4 and 6 h. At this moment, the amount of procyclin mRNA per cell is at least 20-fold higher than in established procyclic culture forms. The loss of the VSG and the appearance of procyclic-specific proteins essentially occur before the first cell division. These observations contrast with the progressive transition observed when monomorphic slender forms are induced to transform under the same conditions.

The effect of sufentanil on the cardiovascular responses to tracheal intubation

The effects of sufentanil 0.5 or 1 microgram/kg, given intravenously after induction of anaesthesia, on the cardiovascular responses to tracheal intubation were examined in a controlled, randomised, double-blind investigation. The control group of patients exhibited significant rises in arterial blood pressure and heart rate for 4 minutes after tracheal intubation. Heart rate exceeded 100 beats/minute and systolic pressure increased by over 20% in every patient. All patients moved or breathed within 10 minutes of the administration of suxamethonium. Sufentanil 0.5 microgram/kg prevented increases in the mean values of heart rate and arterial blood pressure, although increases were observed in five patients. Significant falls in the mean values of heart rate and arterial pressure occurred from 4 minutes after intubation until observations ended 15 minutes after induction of anaesthesia. Two patients moved or breathed during this time, although movement in response to nerve stimulation occurred in all patients 10 minutes after administration of suxamethonium. Sufentanil 1 microgram/kg was effective in suppressing a rise in heart rate or arterial pressure in every patient. Significant falls in these variables occurred from 2 minutes after tracheal intubation onwards. No patient moved or breathed for 15 minutes after induction of anaesthesia, although neuromuscular transmission was present 10 minutes after giving suxamethonium in each case.

Enzyme Immunoassay for Detection of Salmonella in Foods: Collaborative Study

A collaborative study was performed in 25 laboratories to validate an enzyme immunoassay (EIA) procedure utilizing 2 specific monoclonal antibodies for rapid detection of Salmonella in foods. The EIA was compared with the standard culture procedure for detection of Salmonella in 6 food types: ground black pepper, soy isolate, dried whole eggs, milk chocolate, nonfat dry milk, and raw deboned turkey, Uninoculated and inoculated samples were included in each food group analyzed, with the exception of poultry which was naturally contaminated. There was no significant difference in the productivity of the EIA and culture procedures at the 5% level for any of the 6 foods. The enzyme immunoassay screening method has been adopted official first action.

Altered lymphocyte markers and blastogenic responses associated with 24 hour delay in processing of blood samples

Lymphocytes separated from fresh heparinized blood or from blood stored 24 h at room temperature were tested for E rosettes, EAC Rosettes, and blastogenic response to phytohemagglutinin. Compared to lymphocytes from fresh blood, lymphocytes from 24 h stored blood contained a lower percentage of E rosette-positive cells, a higher percentage of E rosette-negative EAC rosette-negative null cells, and manifested a decreased blastogenic response to phytohemagglutinin. Fewer viable mononuclear cells were recovered by Ficoll-Hypaque separation from stored blood than from fresh blood. These findings suggest that storage-related changes may occur in T cells which cause a selective loss of such cells during Ficoll-Hypaque separation. A delay in processing of blood samples may therefore yield results of lymphocyte marker and functional assays which give the false impression of a decrease in T cells and an increase in null cells.