Serum opsonic activity in rodent malaria: functional and immunochemical characteristics in vitro.

The functional and immunochemical characteristics of serum opsonic activity in rodent malaria were examined in the present study. Schizont- and late trophozoite-enriched populations of Plasmodium berghei-infected red blood cells (IRBC) were isolated on a Ficoll density-gradient and used in an in vitro phagocytosis system composed of serum and monolayer cultures of rat peritoneal macrophages. Hyperimmune serum augmented the phagocytosis of IRBC to a greater degree than did nonimmune serum. When either IRBC or macrophages were pre-incubated with serum, the phagocytosis-promoting factors acted on the IRBC rather than on the macrophages in a manner characteristic of serum opsonins. The opsonic activity was specific for IRBC since noninfected red blood cells were rarely phagocytized and were unable to absorb opsonic activity from serum. The opsonic activity of both hyperimmune and nonimmune sera was heat stable, and unaffected by agents known to inactivate or inhibit complement (cobra venom factor and ethylenediaminetetraacetic acid). Finally, the opsonic activity was identified in preparations of purified IgG isolated from both hyperimmune and nonimmune sera.     

The Effects of Copper Sulfate on Liver Histology and Biochemical Parameters of Term Ross Broiler Chicks

Copper is an essential trace element that is extremely toxic to organisms and organs at high doses. We have investigated the histological and biochemical effects of a toxic dose of copper sulfate on the liver of term Ross broiler chicks. Fertilized eggs were divided into three groups: experimental, injected with 50 mcg/0.1 ml copper sulfate in the air chambers on day 1; sham, injected with 0.1 ml saline; and control, no injection. Term chicks were killed and their livers investigated histologically, with hematoxylin–eosin-stained sections examined under light microscopy, and biochemically, for malondialdehyde and glutathione levels. Histological examinations showed copper-treated samples with granular degeneration and necrosis of hepatocytes and impairment to the cell lining of the remark cords. The samples had a congestive appearance, with blood in the vena centralis and sinusoids, slight connective tissue increase, and lymphocyte infiltration. Control and sham group sections had normal appearances. As oxidative damage parameters, in the copper-treated group, malondialdehyde levels were increased and glutathione levels decreased. In the sham and control groups, there were no significant differences. At this toxic dose, copper sulfate shows oxidative damage according to the histology of term chick liver that are confirmed biochemically by the changes in malondialdehyde and glutathione levels.     

Glycoproteins of trypanosomes: their biosynthesis and biological significance

1. Trypanosomes are unicellular parasites that cause human sleeping sickness in Africa and Chagas' disease in South America. Glycoproteins are important components of their plasma membrane. 2. The bloodstream form of the extracellular salivarian African trypanosome (e.g. Trypanosoma brucei) has the ability to express on its cell surface a repertoire of variant surface glycoproteins (VSGs) and in so doing, evades the immune response of the host (antigenic variation). 3. The VSG is probably synthesized initially in a manner like that of the membrane-bound glycoproteins of mammalian systems, but it also undergoes some novel post-translational modifications. 4. The stercorarian South American trypanosome (Trypanosoma cruzi) is an intracellular parasite which expresses different glycoproteins on its plasma membrane at various stages of its life-cycle, but does not exhibit antigenic variation. 5. The biosynthesis and functions of trypanosomal glycoproteins are compared with those of mammalian glycoproteins, and are discussed with particular reference to potential targets for chemotherapy and immunotherapy of trypanosomiasis.     

Incorporation of biological information in cancer risk assessment: Example — Vinyl chloride

Vinyl chloride (VC) is used as an example to demonstrate how biological information can be incorporated into quantitative risk assessment. The information included is the pharmacokinetics of VC in animals and humans and the data-generated hypothesis that VC primarily affects the initiation stage of the multistage carcinogenesis. The emphasis in this paper is on the improvement of risk assessment methodology rather than the risk assessment of VC per se.Sufficient data are available to construct physiologically-based pharmacokinetic models for both animals and humans. These models are used to calculate the metabolized dose corresponding to exposure scenarios in animals and in humans.On the basis of the data on liver angiosarcomas and carcinomas in rats, the cancer risk per unit of metabolized dose is comparable, irrespective of routes (oral or inhalation) of exposure. The tumor response from an intermittent/partial lifetime exposure is shown to be consistent with that from a lifetime exposure when VC is assumed to affect the first (initiation) stage of the multistage carcinogenic process. Furthermore, the risk estimates calculated on the basis of animal data are shown to be consistent with the human experience.     

Perfusion method for preparing pig brain cortex for Golgi-Cox impregnation

The perfusion procedure described in this paper produces high quality impregnation of pig visual and somatosensory cortical neurons with a Golgi-Cox solution. Starting within 30 min after death, pig heads were perfused with a fixative solution composed of a mixture (v/v) of liquid phenol, 5%; formalin, 14%; ethylene glycol, 25%; methanol, 28%; and water, 28% for two periods of 4 hr each. After perfusion, the heads were chilled for at least 18 hr. The entire brain was removed from the skull and then placed in 10% buffered formalin, where it remained for at least 10 days before taking the blocks that were to be immersed in the Golgi-Cox solution. Three weeks spent in the Golgi-Cox solution typically produced uniform neuron impregnation. The tissue blocks were then embedded in celloidin and sectioned at 120 micron. This procedure avoids the following difficulties: Golgi-Cox methods that produced excellent results with rodent or primate tissue were unsuccessful with pig tissue, placing fresh tissue in Golgi-Cox solution resulted in incomplete neuron impregnation, and immersion fixation in 10% buffered formalin without perfusion resulted in excessive staining of glia.