Histochemistry and histoenzymology of the hydatid cyst (Echinococcus granulosus Batsch, 1786). I. The germinal membrane.

Healthy germinal membranes of hydatid cysts from lungs of human and bovine sources were dissected and isolated for histochemical and histoenzymatic research. These techniques were performed in frozen sections and pieces of the whole membrane. Enzymatic research showed that the germinal membrane presents highly differentiated metabolic areas. These areas were topographically related with the origin and insertion of brood capsules, having differentiated structures for metabolic interchange with scolices. Taking our data into account it may be suggested that this functional differentiation could be transitory and variable for all the membrane surface. The accumulation of lipids and enzymes such as simple estarase, lipase, beta-HDH, alpha-GDH and NADPH-reductase in those areas, suggests that lipids are not a simple excretory product. This distribution probably implies that lipid metabolism or its resultant products are important in development and growth of scolices. In that sense other authors' findings and hypothesis about the possible existence of an endocrine system of the parasite, are considered. This idea being demonstrated in further researches, the lipid metabolic pathways shall bring a good pharmacological approach to the interference with parasite development.     

In situ rheology of yeast biofilms

The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G’₀ values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5–5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.     

Partial characterization of IR-alpha-MSH peptides found in melanoma tumors.

Our previous work indicated that IR-alpha-MSH (immunoreactive alpha-melanocyte-stimulating hormone) plasma levels are three times as high in melanoma patients with progressing disease than in disease-free patients, and that the melanoma tumor itself may be the source of IR-alpha-MSH. Further identification of the material in tumor extracts has been carried out in this study, and the results presented here show that the immunoreactivity is associated with a major fraction of about 16 kDa and another of 5-9 kDa. Significant amounts of the immunoreactive material were also found in human melanoma cells but not in culture supernatants. The presence of this material may be related to the melanogenic status of the tumor cells. We have estimated the intracellular IR-alpha-MSH to be within a 0.4 to 2.3 nM range in melanoma tumor cells. We have investigated the melanogenic effect of the IR-alpha-MSH material and its relationship to alpha-MSH. Purified extracts both from metastases and cultured cells were found to promote frog skin darkening as well as tyrosinase activity in Cloudman S91 melanoma cells. The IR material could also displace labeled alpha-MSH from its binding sites in human melanoma cells. Our data clearly indicate that melanoma cells engage in an autocrine production of alpha-MSH-like bioactive peptides by melanoma cells, of larger mol.wt., which are able to bind to MSH receptors. These peptides may be involved in the regulation of melanogenesis and possibly in the growth and proliferation of melanoma cells by an autocrine/paracrine mechanism.