The effect of cephaloridine on the stability of rat kidney lysosomes.

The administration of cephaloridine to rats caused a decrease in the excretion of acid phosphatase into the urine. The antibiotic itself had no effect on urinary acid phosphatase and inhibitors or proteolytic enzymes were not present in the urine from treated rats. Cephaloridine may therefore be stabilizing the lysosomal membrane in vivo and experiments with isolated lysosomes confirm this hypothesis. The lysosomal integrity was followed by measuring the acid phosphatase activity and the light scattering properties of the particles. A good correlation was obtained between these parameters in the case of thermal disruption and progesterone induced lysis of the lysosomes and low concentrations of cephaloridine (0.1-1.0 mmol/1) protected the lysosomes against this form of damage.     

The interaction of cephaloridine with model membrane systems and rat kidney lysosomes.

The antibiotic cephaloridine has been shown to interact with phospholipid structures, using the techniques of ultraviolet difference spectroscopy, surface pressure measurements and liposome models. The results indicate that this interaction is at least partly hydrophobic in nature and help explain the disruptive effects of high concentrations of cephaloridine on both artificial and natural phospholipid structures (lysosomes). Low concentrations of cephaloridine were shown to inhibit a lysosomal membrane-bound phospholipase 2 and it is suggested that such an inhibition may explain the cephaloridine-induced stabilization of rat-kidney lysosomes.     

The effect of salinity on experimental infections of a Hematodinium sp. in blue crabs, Callinectes sapidus

The parasitic dinoflagellate Hematodinium sp. parasitizes blue crabs along the Atlantic seaboard of the United States. Infections in blue crabs have only been reported from waters where salinity is >11 practical salinity units (psu). Blue crabs maintain a hyperosmotic internal concentration at low salinities (0-5 psu), roughly comparable to 24 psu, and should be capable of maintaining an infection in low-salinity waters even if Hematodinium spp. cells are intolerant of low salinities. We tested this notion by observing the effect of low salinity on the progression of disease in crabs experimentally infected with the parasite. Blue crabs were acclimated to 5 psu or 30 psu salinity treatments. They were inoculated with Hematodinium sp. and necropsied 3, 7, 10, and 15 days post-inoculation. The low-salinity treatment did not have an effect on the proliferation of Hematodinium sp. infections in blue crabs; moreover, a greater proportion of infections in crabs in the low-salinity treatment developed dinospore stages than did those in the high-salinity treatment, indicating that salinity may affect the development of the parasite. However, dinospores from in vitro cultures rapidly became inactive when held in salinities <15 psu. Our experiments indicate that Hematodinium spp. can develop in blue crabs at low salinities, but that the parasite is incapable of transmission in this environment, which explains the lack of natural infections in crabs at low salinities.     

The bystander effect in radiation oncogenesis: II. A quantitative model

There is strong evidence that biological response to ionizing radiation has a contribution from unirradiated "bystander" cells that respond to signals emitted by irradiated cells. We discuss here an approach incorporating a radiobiological bystander response, superimposed on a direct response due to direct energy deposition in cell nuclei. A quantitative model based on this approach is described for alpha-particle-induced in vitro oncogenic transformation. The model postulates that the oncogenic bystander response is a binary "all or nothing" phenomenon in a small sensitive subpopulation of cells, and that cells from this sensitive subpopulation are also very sensitive to direct hits from alpha particles, generally resulting in a directly hit sensitive cell being inactivated. The model is applied to recent data on in vitro oncogenic transformation produced by broad-beam or microbeam alpha-particle irradiation. Two parameters are used in analyzing the data for transformation frequency. The analysis suggests that, at least for alpha-particle-induced oncogenic transformation, bystander effects are important only at small doses-here below about 0.2 Gy. At still lower doses, bystander effects may dominate the overall response, possibly leading to an underestimation of low-dose risks extrapolated from intermediate doses, where direct effects dominate.     

The effect of resveratrol on surgery-induced peritoneal adhesions in an experimental model

Adhesion formation is a common cause of complications following surgery. The aim of this study was to investigate the effect of resveratrol on intra-abdominal adhesion prevention in a rat model. Twenty one Wistar-Albino rats weighing 200-250 g were assigned to three groups, of 7 rats each. After a midline laparotomy was performed, a 1 cm area of the ceacum was abraded in two of the groups. They were then given either resveratrol (Group 1), or saline (Group 2) intraperitoneally. Group 3 rats (sham operation) received no treatment, without the serosal damage. On the 14th day, the rats were killed and the adhesion score was determined according to Mazuji's adhesion grade scale. The tissue levels of malondialdehyde (MDA), nitric oxide (NO), and reduced glutathione (GSH) were measured. The mean Mazuji's adhesion grade in the resveratrol group was 1.0 +/- 0.0, in the saline group 2.57 +/- 1.51, and zero in the sham operated group (p < 0.05 between the resveratrol group and saline group comparison). The levels of MDA and NO in the resveratrol group were significantly lower than those of the saline group (p < 0.001). The level of GSH in the resveratrol group was significantly higher than in the saline and sham operated groups (p < 0.001 and p < 0.001, respectively). Introduction of resveratrol into the peritoneal cavity at the time of surgery reduced adhesion formation effectively in this model. Resveratrol probably acts through reduction of lipid peroxidation products.     

A stochastic model of cellular senescence. II. Concordance with experimental data

This report presents the results of computer simulations of a mathematical model for cell proliferation and senescence. The mathematical model is based on the idea that the in vitro proliferative potential of normal cells is determined by the number of a certain class of self-replicating particles it possesses. In the simulation model these particles are lost by both stochastic and deterministic processes. When all self-replicating particles are lost a cell can divide up to seven times before it irreversibly ceases to replicate. The simulated in vitro lifespans of clones and subclones are shown to be in close agreement with experimental data. We also show that other properties of finitely proliferating cultures can be simulated by this model.     

Protective effect of cellular immunity in experimental Flavivirus infections

Experiments were conducted with the tick-borne encephalitis (TE) virus; confirmation of a protective action of cellular immunity in mice was obtained. Administration of sensitized splenocytes to the animals together with the virus was accompanied with an increase of their mean survival or with the reduction of mortality in comparison with control animals given nonimmune or destroyed cells. The protective action of the effector cells was not connected with the intensification of antibody formation in the recipients. A high specificity of cellular immunity was noted in experimental flaviviral infections. The presence of common antigens in the TE and Langat viruses was revealed with the acid of cross splenocyte migration inhibition test (CSMRT). There was also revealed a difference of these viruses from the viruses of yellow fever, Dengue type 2, or Sindbis. The results of studying of the specificity of cellular immunity in the CSMRT found confirmation in experiments with adoptive transfer of splenocytes. Cross protection was caused only by splenocytes sensitized to the TE and Langat viruses.     

The effect of agricultural practices on the development of indigenous arbuscular mycorrhizal fungi. II. Studies in experimental microcosms

Two glasshouse experiments were performed to assess the development and metabolic activity of mycorrhizas formed by isolates of arbuscular mycorrhizal fungi (AMF) from three different genera, Acaulospora, Gigaspora and Glomus on Desmodium ovalifolium L. plants. In the first experiment the effect of disturbance of a pre-established extra-radical mycelium (ERM) was studied. In the second experiment the effect of phosphate addition as either organic matter (OM) or fertiliser was studied. Disturbance of a pre-established ERM reduced the formation of mycorrhizas by Gigaspora rosea (BEG111) and increased that by Glomus manihotis (BEG112) on D. ovalifolium plants. Acaulospora tuberculata (BEG41) failed to form mycorrhizas in the experiment. Either Gi. rosea (BEG111) or G. manihotis (BEG112) appeared to be the major component of the colonisation resulting from treatments with combinations of two or three of the AMF and determined the sensitivity of these treatments to disturbance of a pre-established ERM. The addition of phosphate fertiliser (10 mg P kg^-1) reduced mycorrhiza formation by each species of AMF compared with the addition of OM (10 mg P kg^-1). This work indicates that AMF from different genera respond differently to management by agricultural practices when in association with a tropical legume. Clearly, there is potential to alter the formation of mycorrhizas of AMF from different genera, through the use of agricultural practices. The significance of the development and metabolic activity of mycorrhizas formed by AMF from different genera for plant growth is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of cephalothin prophylaxis on postoperative ventriculoperitoneal shunt infections.

Postoperative infection is an important complication after insertion of a ventriculoperitoneal (VP) shunt in children with hydrocephalus. A randomized double-blind placebo-controlled study was performed to determine the efficacy of cephalothin in preventing postoperative shunt infection. Sixty-three children who presented for elective VP shunt insertion between January 1982 and December 1985 and who did not have a history of shunt infections were randomly assigned to receive four doses of prophylactic cephalothin, 25 mg/kg (32 patients), or of a multivitamin placebo (31 patients). Postoperative infection developed in 6% of the treatment group, compared with 10% of the placebo group, a difference that was not statistically significant, although a clinical significance may have been masked by the small sample size. A large multicentre trial is needed to determine the efficacy of antibiotic prophylaxis in reducing the incidence of postoperative VP shunt infections.