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.     

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.     

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.     

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.     

Bovine toxoplasmosis: experimental infections.

Three calves dosed per os with 0.75 × 10⁶, 0.75 × 10⁶ and 1.5 × 10⁶Toxoplasma oocysts developed high titres of Toxoplasma antibodies as measured by the indirect fluorescent antibody test and the dye test. Toxoplasma gondii was reisolated from 2 of these animals. Two calves given 1 × 10³ tissue cysts and 2 × 10⁶ tachyzoites intramuscularly did not develop such high fitres, but T. gondii was reisolated from the calf injected with tachyzoites.Of 4 pregnant cows given 7 × 10⁴, 7 × 10⁴ and 1.6 × 10⁵ oocysts and 1.5 × 10² tissue cysts only 2 developed significant levels of Toxoplasma antibodies. There was no evidence of Toxoplasma infection in the calves born by these cows.It was concluded that cattle do not readily acquire persistent T. gondii infections, and this may be due, in part at least, to early elimination of Toxoplasma from their tissues.     

The structure of cephaloridine hydrochloride monohydrate

The crystal and molecular structure of cephaloridine hydrochloride monohydrate (Fig. 1), an antibiotic inhibiting the synthesis of bacterial

cell walls in a fashion similar to that of the penicillins, has been determined by three-dimensional, single crystal X-ray diffraction methods. The central part of the molecule is found to be similar to that of cephalosporin C.