Fate of inoculated Escherichia coli in hay

AIMS

To monitor the fate of inoculated Escherichia coli in dry and moist hay of various types, under laboratory conditions.

METHODS AND RESULTS

Wheat, vetch and clover hay were used as received or wetted to 250-300 g kg(-1) moisture. The hay was inoculated at about 10(6) CFU g(-1) with a kanamycin-resistant E. coli strain that expresses the green fluorescence protein, and was stored in small open glass jars that were covered with aluminium foil. Three jars per treatment were sampled on days 1 and 3, or 4 and 7, or 8, 20 and 50, respectively, after the initiation of the experiments, and the numbers of E. coli in the hay were determined. The results indicated that E. coli disappeared from both dry and moist hay by 7-8 days after inoculation. However, in a few cases colonies that were presumed to be E. coli developed after incubation in Luria broth medium.

CONCLUSIONS

The tagged E. coli strain usually disappeared rapidly from both the dry and the moist hay, in spite of the high level of inocula used. However, in some cases a few, possibly injured E. coli might have persisted, and could be detected after incubation in a rich growth medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is part of a risk assessment associated with sewage irrigation of forage crops in Israel. The results indicate that E. coli added to the hay is not likely to pose a health risk to cattle or to humans. Nevertheless, more research with natural strains of E. coli and other enteric pathogens that might be more adapted to forage conditions is warranted in order to ensure the safety of sewage-irrigated crops.

Effects of Diethyldithiocarbamate (DETC) on Liver Injury Induced by Ischemia-Reperfusion in Rats

PURPOSE

In organ transplantation, ischemia-reperfusion injury (I/R) is a constant occurrence. Dithiocarbamates, a class of antioxidants, have been reported to inhibit nuclear factor-kappaB (NF-kappaB), a critical transcription factor in the intracellular inflammatory cascade. We studied the effects of diethyldithiocarbamate (DETC) on liver injury induced by I/R.

MATERIALS AND METHODS

Male Wistar rats were pretreated with DETC (100 mg/kg IV) 10 minutes before hepatic ischemia, which was followed by 2 hours reperfusion, or 10 minutes prior to the reperfusion. Blood samples were obtained at the end of the reperfusion period to determine the biochemical markers of liver injury. Results were compared using the one-way analysis of variance (ANOVA), followed by the Bonferroni posttest, and presented as mean values +/- SEM.

RESULTS

I/R produced significant increases in aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and gamma-glutamyl transferase (gamma-GT) serum levels compared with sham-operated rats. Administration of DETC prior to the onset of reperfusion significantly reduced the liver injury. However, DETC administered before the ischemic period failed to protect the liver from an I/R injury.

CONCLUSION

DETC, administered just before the reperfusion period, resulted in a significant decrease in the I/R injury to the liver, an observation that may have therapeutic implications.

Anaphylactic reactions during cesarean section

Sensitization to latex seems to occur more frequently in women than in men. Obstetric and gynecological surgical procedures have recently been shown to be a common setting for latex anaphylaxis. We analyzed all the cases of anaphylactic reactions during 1240 cesarean sections in 2004; the patients were questioned for risk factors and underwent allergy testing for drugs and latex. Four patients had anaphylaxis under spinal anesthesia and in all cases it was due to latex allergy. Reported symptoms included facial edema, profuse sweating, itching, generalized erythematous rash and hypotension. Only one patient manifested a severe reaction which included bronchospasm, dyspnea, tachypnea and anaphylactic shock, requiring orotracheal intubation and epinephrine. Our data showed a high incidence (1:310) of intraoperative latex anaphylactic reactions in the one-year study period. This may be related to the very specific population (all women) in a very specific setting (obstetrics). To prevent anaphylactic reactions during obstetric surgery it is important to identify potential risk factors to include, for example atopy, adverse reactions to foods and latex items. If latex allergy is confirmed or strongly suspected, patients should be managed in a latex-safe environment. Premedication with antihistamines and steroids might be useful to further reduce the risk. After the delivery, specific desensitization may represent a good therapeutic option.

Exposure setup to study potential adverse effects at GSM 1800 and UMTS frequencies on the auditory systems of rats

To investigate possible biological effects of exposure to electromagnetic (EM) fields at the frequencies of global system for mobile communication (GSM) 1800 system and universal mobile telecommunication system (UMTS) on the auditory system of rats, an exposure setup for in vivo experiments is presented. The study was carried out in the framework of two European research projects. The target of the investigation was the cochlea. A dosimetric study was performed, both numerically and through direct measurements, to assess the interaction of the radiated fields and the dose distribution in the biological target. For the local exposure of rats, a loop antenna operating at the frequency bands of interest was designed, realised and characterised through numerical and experimental dosimetric procedures. Moreover, an exposure apparatus was set up, consisting of three arrays of four loop antennas, placed on three levels, thus allowing simultaneous exposure of 12 rats to give statistical power to the experiments. To isolate the exposure arrays, the setup was assembled by a wooden rack with EM field absorbing panels, inserted among the levels and at the four sides of the rack. Isolation was verified by direct measurements. Two exposure arrays were simultaneously supplied, whereas the third one was used for sham exposure. Blind exposure was achieved through a black box, hiding physical connections to the microwave power supply. During exposure sessions, rats were restrained in special plastic jigs for repeatable positioning, thus assuring the fixed level of dose in the target.

Effect of phthiocerol dimycocerosate deficiency on the transcriptional response of human macrophages to Mycobacterium tuberculosis

The control of mycobacterial infections is dependent on the finely tuned synergism between the innate and adaptive immune responses. The macrophage is the major host cell for Mycobacterium tuberculosis and the degree of virulence of mycobacteria may influence the initial macrophage response to infection. The cell wall molecule, phthiocerol dimycocerosate (DIM), is an important virulence factor that influences the early growth of M. tuberculosis in the lungs. To explore the basis for this effect we have compared the early gene response of human THP-1 macrophages to infection with virulent M. tuberculosis and the DIM-deficient DeltafadD26 M. tuberculosis strain using microarrays. Detailed analysis revealed a common core of macrophage genes, which were rapidly induced following infection with both strains, and deficiency of DIM had no significant effect on this initial macrophage transcriptional responses. In addition to chemokines and pro-inflammatory cytokines, the early response genes included components of the Toll-like receptor signalling, antigen presentation and apoptotic pathways, interferon response genes, cell surface receptors and their ligands, including TNF-related apoptosis inducing ligand (TRAIL) and CD40, and other novel genes. Therefore, although fadD26 deficiency is responsible for the early attenuation of the growth of M. tuberculosis in vivo, this effect is not associated with differences in the initial macrophage transcriptional response.

Proliferation and apoptosis in a neuroblastoma cell line exposed to 900 MHz modulated radiofrequency field

The aim of this study was to examine whether a modulated radiofrequency of the type used in cellular phone communications at a specific absorption rate (SAR) higher than International Commission on Non-ionizing Radiation Protection (ICNIRP) reference level for occupational exposure, could elicit alterations on proliferation, differentiation, and apoptosis processes in a neuroblastoma cell line. The cell line was exposed for 24, 48, and 72 h to 900 MHz radiofrequency and proliferation and differentiation were tested by WST-I assay and by a molecular analysis of specific markers, two oncogenes and a cytoskeleton protein, in exponential growth phase and in synchronized cell cultures. Apoptosis was evaluated by caspase activation analysis and by molecular detection of Poly (ADP-ribose) polimerase (PARP) cleavage. Combined exposures to radiofrequency and to the differentiative agent retinoic acid or to the apoptotic inducer camptothecin were carried out to test possible interference between electromagnetic field and chemical agents. Overall our data suggest that 900 MHz radiofrequency exposure up to 72 h does not induce significant alterations in the three principal cell activities in a neuroblastoma cell line.

Fate of Escherichia coli during ensiling of wheat and corn

A recombinant Escherichia coli strain carrying a plasmid with an antibiotic resistance marker and expressing the green fluorescent protein was inoculated at a concentration of 3.8 x 10(8) CFU/g into direct-cut wheat (348 g of dry matter kg(-1)), wilted wheat (450 g of dry matter kg(-1)), and corn (375 g of dry matter kg(-1)). The forages were ensiled in mini-silos. The treatments included control (no E. coli added), application of tagged E. coli, and delayed sealing of the inoculated wheat. Three silos per treatment were sampled on predetermined dates, and the numbers of E. coli were determined on Chromocult TBX medium with or without kanamycin. Colonies presumptively identified as E. coli were also tested for fluorescence activity. Addition of E. coli at the time of ensiling resulted in a more rapid decrease in the pH but had almost no effect on the chemical composition of the final silages or their aerobic stability. E. coli disappeared from the silages when the pH decreased below 5.0. It persisted longer in silages of wilted wheat, in which the pH declined more slowly. Control silages of all crops also contained bacteria, presumptively identified as E. coli, that were resistant to the antibiotic, which suggests that some epiphytic strains are naturally resistant to antibiotics.

Clinical, genetic, and cellular analysis of 49 osteopetrotic patients: implications for diagnosis and treatment

BACKGROUND

Osteopetrosis, a genetic disease characterised by osteoclast failure, is classified into three forms: infantile malignant autosomal recessive osteopetrosis (ARO), intermediate autosomal recessive osteopetrosis (IRO), and autosomal dominant osteopetrosis (ADO).

METHODS

We studied 49 patients, 21 with ARO, one with IRO, and 27 with type II ADO (ADO II).

RESULTS

Most ARO patients bore known or novel (one case) ATP6i (TCIRG1) gene mutations. Six ADO II patients had no mutations in ClCN7, the only so far recognised gene implicated, suggesting involvement of yet unknown genes. Identical ClCN7 mutations produced differing phenotypes with variable degrees of severity. In ADO II, serum tartrate resistant acid phosphatase was always elevated. Bone alkaline phosphatase (BALP) was generally low, but osteocalcin was high, suggesting perturbed osteoblast differentiation or function. In contrast, BALP was high in ARO patients. Elevated osteoclast surface/bone surface was noted in biopsies from most ARO patients. Cases with high osteoclasts also showed increased osteoblast surface/bone surface. ARO osteoclasts were morphologically normal, with unaltered formation rates, intracellular pH handling, and response to acidification. Their resorption activity was greatly reduced, but not abolished. In control osteoclasts, all resorption activity was abolished by combined inhibition of proton pumping and sodium/proton antiport.

CONCLUSIONS

These findings provide a rationale for novel therapies targeting pH handling mechanisms in osteoclasts and their microenvironment.

Which patients with primary biliary cirrhosis or primary sclerosing cholangitis should undergo endoscopic screening for oesophageal varices detection?

BACKGROUND

Recent guidelines from an AASLD Single Topic Symposium suggest that patients with cirrhosis, including those with primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC), should be screened for oesophageal varices when the platelet count is <140,000/mm3.

AIM

To determine the validity of these guidelines in clinical practice in patients with PBC or PSC.

METHODS

Retrospective review of individuals undergoing screening upper endoscopy for oesophageal varices at a single centre. Oesophageal varices were reported as being present or absent.

RESULTS

A total of 235 patients with chronic liver disease, including 86 patients with PBC (n=79) or PSC (n=7), 104 patients with chronic viral hepatitis, and 45 with non-alcoholic cirrhosis of differing aetiologies, underwent a single screening endoscopy between 1996 and 2001. Oesophageal varices were detected in 26 (30%) of the PBC/PSC group, 38 (37%) of the viral hepatitis group, and 21 (47%) of the "other" group. Applying multiple logistic regression analysis to the data in the group with PBC/PSC, platelets <200,000/mm3 (odds ratio (OR) 5.85 (95% confidence interval (CI) 1.79-19.23)), albumin <40 g/l (OR 6.02 (95% CI 1.78-20.41)), and serum bilirubin >20 micromol/l (OR 3.66 (95% CI 1.07-12.47)) were shown to be independent risk factors for oesophageal varices. Prothrombin time was unhelpful. The values at these cut offs were not useful in predicting oesophageal varices in the other groups.

CONCLUSION

We conclude that current guidelines recommended by the AASLD Single Topic symposium are invalid in our cohort of patients with PBC and PSC. Patients with a platelet count <200,000/mm3, an albumin level <40 g/l, and a bilirubin level >20 micromol/l should be screened for oesophageal varices.

Epithelioid hemangioendothelioma and multiple thoraco-lumbar lateral meningoceles: two rare pathological entities in a patient with NF-1

Epithelioid hemangioendothelioma (EHE) is a rare vascular soft-tissue tumour of intermediate malignancy. Neurofibromatosis type I (NF-1) is a genetic syndrome associated with soft tissue sarcoma and higher risk of developing neoplasia. Lateral meningoceles are uncommon entities, being mostly associated with NF-1. We report a case of a 31-year-old woman, with NF-1 and past history of right thalamic/peduncular astrocytoma WHO grade II, admitted to the Neurosurgery Department in December 2003 due to severe low back pain, irradiating to the left leg without a radicular pattern. Thoraco-lumbar magnetic resonance imaging (MRI) showed a large left posterior paravertebral expansive lesion, bilateral and multiple thoraco-lumbar lateral meningoceles and dural ectasias with scalloping of the vertebral bodies. Biopsy of the paravertebral mass lesion disclosed EHE. We present this case because of the novel association between NF-1 and EHE, and the unusual aggressiveness of the neoplasia. Additionally, we highlight the co-existence of bilateral and multiple lateral meningoceles.

1800 MHz in vitro exposure device for experimental studies on the effects of mobile communication systems

A wire patch cell (WPC) operating at the uplink frequency band of GSM 1800 MHz has been designed for in vitro experiments with the aim of investigating the possible biological effects of electromagnetic radiation associated with cellular phones. The 1800 MHz WPC design is a direct descendant of the original 900 MHz WPC introduced by Laval et al. This system provides a homogeneous specific absorption rate distribution, using four 3.5 cm petri dishes simultaneously. Numerical dosimetry has been performed using a commercial code (CST Microwave Studio), in order to evaluate accurately the efficiency of the structure (in terms of W kg(-1) per 1 W input power) and the distribution in the chosen biological target. The numerical results have been confirmed by experimental measurements performed by measuring thermal increase due to a high power impulse. The efficiency of the structure is 1.25 +/- 25% W kg(-1) per 1 W input power higher than the efficiency of the 900 MHz WPC. A few adjustments have been made in order to use the WPC in a standard incubator and to avoid thermal increases related to the radio frequency exposure. This exposure system has been adopted for the experiments scheduled in the RAMP and GUARD projects (VFPE).

Effects of interferon and ribavirin combination therapy on CD4+ proliferation, lymphocyte activation, and Th1 and Th2 cytokine profiles in chronic hepatitis C

We studied the relationship between immunological markers such as CD4+ proliferation, cytokines profile and lymphocyte activation markers in patients with chronic hepatitis C, having different responses to interferon (IFN) and ribavirin (RBV) treatment. A prospective study of 20 patients was conducted, six had received IFN-alpha-2b alone and 14 IFN in combination with RBV. The proliferative immune responses of peripheral blood mononuclear cells to hepatitis C virus peptides and the lymphocyte activation markers (CD25+, CD38+ and CD69+) were assessed before treatment, at 1 week, and 1, 3 and 6 months of treatment. Cytokines interleukin (IL)-2, IFN-gamma, IL-4 and IL-10 were determined in supernatants before onset of treatment and at 1 and 6 months thereafter. Stimulation indices (SI) were higher in the sustained responders (SR), in comparison with those with no response (NR), before treatment (5.2 +/- 3.7 to 3.3 +/- 1.9, P = 0.028) and also at 6 months (7.8 +/- 1.9 to 4.1 +/- 1.2, P = 0.021). Patients with SR also had high SI to NS3 when compared with those with transitory response or no response (NR) (4.9 +/- 2.5 and 3.3 +/- 1.1, P = 0.033). At 1 month, SR had higher supernatant IL-2 than those with NR (133.8 +/- 119.2 to 56.0 +/- 89.3 pg/mL, P = 0.023) and lower levels of IL-10 (13.8 +/- 10.1 and 167.1 +/- 272.0 pg/mL, P = 0.023) in response to NS3. Combination therapy induced a higher percentage of the lymphocyte activation markers CD69+ and CD38+. In conclusion, we found that SR is associated with higher CD4+ proliferation particularly in response to the NS3 region, promoting a T-helper (Th)1/Th0 profile of cytokines, and that combination therapy induced a higher percentage of lymphocyte activation than therapy with IFN alone.

Tempol, an intracelullar free radical scavenger, reduces liver injury in hepatic ischemia-reperfusion in the rat

Liver ischemia is of clinical interest because of its role in liver failure and also hepatic graft rejection. The generation of reactive oxygen species contributes to the injury that follows ischemia-reperfusion. One therapy utilizes the administration of antioxidants; however, only limited experience suggests a potential benefit of systemic administration of these compounds. To overcome the limitations of these compounds, small molecules with improved cell membrane permeability characteristics and higher potency, such as tempol, are being tested in vivo. Tempol, a membrane-permeable radical scavenger, interferes with the formation or the effects of many radicals, including superoxide anions, hydroxyl radicals, and peroxynitrite. The aim of this study was to investigate the effects of tempol in an in vivo rat model of liver ischemia-reperfusion injury. Male Wistar rats were pretreated with tempol (30 mg/kg, i.v.) 5 minutes prior to liver ischemia (for 30 minutes) and reperfusion (for 2 hours). The liver injury was assessed by measuring serum levels of transaminases, lactate dehydrogenase, and gamma-glutamyl transferase. Tempol significantly mitigated the increase in transaminases, lactate dehydrogenase, and gamma-glutamyl transferase following liver ischemia-reperfusion, suggesting an improvement in liver function and resistance to injury.

Methanol induction optimization for scFv antibody fragment production inPichia pastoris

Fibronectin splice variant ED B (extracellular domain B) is a promising marker for angiogenesis in growing solid tumors. Currently, recombinant antibodies against ED B are being investigated concerning their potential use, for either therapeutic or diagnostic purposes. Single-chain antibody fragments directed against the ED B can be efficiently expressed in Pichia pastoris; thus, a recombinant strain of the methylotropic yeast P. pastoris was used for this work. Three different forms of scFv antibody fragment are found in the supernatant from this fermentation: covalent homodimer, associative homodimer, and monomer. Both homodimeric forms can be converted to the monomeric form (under reducing conditions) and be efficiently radiolabeled, whereas the monomeric form of scFv already present in the supernatant cannot. It was also found that the fraction of protein in the monomeric form is highly dependent on the mode of induction rather than scFv concentration. This suggests that the monomeric form of the scFv present in the supernatant might be a result of events occurring at the expression, secretion, or folding level. A high cell density fermentation protocol was developed by optimizing methanol induction, yielding the highest scFv antibody fragment production rate and product quality; cell concentration at the induction point and specific methanol uptake rate were found to be the most important control variables. A decrease in specific methanol uptake rate led to a higher specific production rate for the scFv antibody fragment (5.4 microg g(cell) h(-1)). Product quality, i.e., percentage of product in a homodimeric form, also increased with the decrease in methanol uptake rate. Furthermore, the volumetric productivity depended on cell concentration at the induction point, increasing with the increase of cell concentration up to 320 g L(-1) wet cell weight (WCW). The reduction of the methanol feeding rate for induction, and consequently of the oxygen uptake rate, have important consequences for optimizing product titers and quality and thus on the scale-up of this production process; hence one of the major limitations upon high cell density cultivation in bioreactors is keeping the high oxygen transfer rate required. From the results obtained, a scale-up strategy was developed based on the available oxygen transfer rates at larger scales, allowing the definition of the optimum biomass concentration for induction and methanol feeding strategy for maximization of product titer and quality.

Functional blocks in caspase activation pathways are common in leukemia and predict patient response to induction chemotherapy

Defects in apoptosis mechanisms contribute to chemoresistance in malignancy. However, correlations of apoptosis-regulating proteins with clinical outcome in cancer patients are variable, presumably reflecting the difficulty of using static tests of gene expression in a scenario influenced by a dynamic interplay of multiple pro- and antiapoptotic molecules. Therefore, we assessed the functional integrity of apoptosis pathways in intact primary leukemia cells and correlated the functional status of these pathways with clinical outcome. Active apoptogenic proteins were introduced into primary leukemia cells by electroporation followed by measurement of active caspases by flow cytometric techniques. Cytochrome c was introduced to activate the intrinsic (mitochondrial) pathway, whereas caspase-8 was introduced to activate the extrinsic (death receptor) pathway. In a series of 24 patients with acute myeloid leukemia, 79% had a block in at least one pathway, indicating that defects in caspase activation mechanisms are common in patients with leukemia. Simultaneous blocks in both pathways correlated with chemoresistant disease (92% of patients with chemoresistant disease versus 33% of patients with chemosensitive disease; P = 0.005) and decreased overall patient survival (35% versus 89% 1-year survival; P = 0.02). Simultaneous blockage of the intrinsic and extrinsic pathways could be explained by a defect located at a point of convergence of the two pathways, probably related to overexpression of endogenous inhibitors of the effector-caspases, rather than decreased levels of these proteases. This study supports the importance of apoptosis pathways in determining response to chemotherapy and suggests that functional defects in caspase activation are prognostic in patients with leukemia.

Congenital chylothorax: a case report

A case of unilateral congenital hydrothorax diagnosed at 21 weeks and treated with a pleuro-amniotic shunt at 23 weeks' gestation is presented. The rapid production of pleural fluid led to the development of polyhydramnios which was treated with a selective Cox inhibitor. Due to worsening of the hydrothorax, a third thoracocentesis was performed at 30 weeks' gestation prior to a Cesarean section. The neonate responded well to mechanical ventilation, a thoracic drainer that was inserted between days 5 and 14, fluid and protein replacement and gradual transition from parenteral to intestinal nutrition. Early diagnosis of chylothorax should be treated by thoraco-amniotic drainage to prevent fetal pulmonary hypoplasia and congestive cardiac failure. Polyhydramnios is a complication of this therapy and may require treatment with a Cox inhibitor.

[Influence of Gilbert's syndrome on serum bilirubin levels and gallstone formation in children with chronic hemolytic disease]

To determine whether Gilbert's syndrome increases the risk of gallstone formation in children with chronic hemolytic disease, we studied 44 children with this diagnosis. Gallstones were detected by abdominal ultrasonography. This took place annually in scheduled examinations or in the context of acute abdominal pain. In all patients, the mean values of hemoglobin, reticulocyte and serum bilirubin in the chronic phase were recorded. In addition, TA insertion in the A(TA)nTATAA motif within the promoter region of the enzyme uridine-diphosphate-glucuronyl transferase (UGT1A1) was screened, since this is typically associated with GS.We found 10 (22.7 %) homozygotes for the mutated allele TA*7/TA*7, 12 (27.3 %) TA*6/TA*6 heterozygotes and 22 (50 %) homozygotes for the wild-type allele TA*6/TA*6. No statistically significant differences were found in the values of hemoglobin (Kruskal-Wallis test 2.496; p > 0.05) or in reticulocyte count (Kruskal-Wallis test 1.696; p > 0,05) between the three groups of patients, suggesting a similar degree of hemolysis. Patients with the UGT1A1 TA*7/TA*7 genotype showed higher mean serum bilirubin levels than did patients who were homozygous for the wild-type allele (Mann-Whitney test 35.5; p < 0.05). None of the patients with the TA*6/TA*6 genotype developed gallstones, whereas this complication was found in 2 of 12 (16.6 %) heterozygotes and 6 of 10 (60 %) homozygotes for the allele with TA insertion. In this latter group, 4 patients presented acute pancreatitis as a consequence of gallstone formation.The association between increased bilirubin load due to chronic hemolytic disease and diminished hepatic conjugation leads to raised serum bilirubin levels and consequently to an increased risk of gallstone formation. Therefore, we recommend screening for Gilbert's syndrome in children in the initial phases of chronic hemolytic diseases.

Viscosity minimum in bimodal concentrated suspensions under shear

We study a model of concentrated suspensions under shear in two dimensions. Interactions between suspended particles are dominated by direct-contact viscoelastic forces and the particles are neutrally bouyant. The bimodal suspensions consist of a variable proportion between large and small droplets, with a fixed global suspended fraction. Going beyond the assumptions of the classical theory of Farris (R.J. Farris, Trans. Soc. Rheol. 12, 281 (1968)), we discuss a shear viscosity minimum, as a function of the small-to-large-particle ratio, in shear geometries imposed by external body forces and boundaries. Within a linear-response scheme, we find the dependence of the viscosity minimum on the imposed shear and the microscopic drop friction parameters. We also discuss the viscosity minimum under dynamically imposed shear applied by boundaries. We find a reduction of macroscopic viscosity with the increase of the microscopic friction parameters that is understood using a simple two-drop model. Our simulation results are qualitatively consistent with recent experiments in concentrated bimodal emulsions with a highly viscous or rigid suspended component.

Cytometric, morphologic and enzymatic characterisation of haemocytes in Anodonta cygnea

The haemocytes in bivalve mussels are involved in many processes such as lesion repair, shell repair, elimination of small particles and toxic substances. In Anodonta cygnea there are two categories of haemolymph cells, the granulocytes and hyalinocytes. Two groups of cells were identified by flow cytometry and morphological studies: one with larger size and granularity representing 75%, and another group of cells (25%) which were approximately half the size. The cytochemical reactions showed peroxidase activity in the larger cells and a weak prophenoloxidase activity in the smaller cells. These characteristics suggest that the most common haemocytes are granulocytes and hyalinocytes are less common. Enzymatic studies showed clear activities of few enzymes in different compartments of the mantle. Both haemocytes presented significant variations for alpha-manosidase and beta-glucurosidase activities depending on the acid or alkaline pH. Almost all were sensitive to the pH changes, mainly the beta-galactosidase in the haemolymph plasma. On the contrary, the same enzymatic analysis in the extrapallial elements showed more stabilised activities. The simulation of acidic and alkaline condition with the observation of significant morphological and enzymatic activity changes, allow us to speculate some functional role, mainly in the haemolymph elements. The granulocytes may be speculated to have intense involvement in the digestion of small residues with the formation of calcareous stores while the hyalinocytes are more responsible for the elimination of soluble cytotoxic compounds.