Precocious in vitro development of satellite cells from dystrophic chicken muscle

Summary Satellite cells, liberated from pectoral muscle of juvenile dystrophic chickens by sequential treatment with collagenase, hyaluronidase, and trypsin and preplated to remove fibroblasts and cultured on gelatin proliferated rapidly, fused and formed confluent muscle cultures within 6 d in vitro with minimal contamination by fibroblasts. When identical isolation and culturing techniques were applied to muscle from age-mateched normal chickens proliferation and differentiation were slower, contamination with fibroblasts was much greater, and only a small number of myotubes were formed. After injection of the myotoxic anesthetic marcaine into normal pectoral muscle for 5 consecutive days, myotube formation was accelerated in satellite cell cultures, but the rate of differentiation was not as rapid as that occurring in cells from dystrophic muscle. This research was supported by a grant from the Muscular Dystrophy Association of Canada.     

Plankton communities of an acidic,polymictic, brown-water lake

The plankton of an acidic, polymictic, brown-water lake was investigated over a one-year period. The phytoplankton community was dominated by Chlamydomonas sp., Melosira varians and Peridinium pusillum during different times of the year. Densities were abnormally low, with a maximum of only 13,781 individuals per liter during the March bloom. The water column was nearly void of phytoplankton during the fall. These low densities were attributed to several of the physical and chemical characteristics of the water, including low pH, low levels of nutrients and light limitation. The latter factor was important because of low light transmission into the highly colored water, shading from macrophytes and the nearly continuous transport of the phytoplankton into the aphotic zone due to mixing of the water column by sea breezes.The zooplankton was dominated by Diaptomus floridanus, Polyarthra vulgaris, Keratella cochlearis and Daphnia ambigua. The observed densities were typical of southeastern oligotrophic lakes. The zooplankton community did not exhibit a decrease in density that corresponded with the observed low phytoplankton densities, suggesting the possibility that they relied heavily on bacterial and detrital food sources.     

Taxonomy and ecology of the phytoplankton of Lake Fidler and Sulphide Pool,meromictic Tasmanian lakes

A floristic list of 89 freshwater phytoplanktonic algae occurring in two neighbouring, dystrophic, meromictic Tasmanian lakes is given. In both lakes the preponderance of desmids and phytoflagellates, especially chrysophytes, is a characteristic in keeping with their dystrophic nature. All the alga must be adapted to low levels of red light and some habitually inhabit crepuscular depths rather than executing diel vertical migrations such as happens in many dystrophic waters. Floristic differences between the two lakes are related to morphometric differences and the degree of entrainment of tychoplankton. The photosynthetic biomass of both lakes is predominantly monimolimnetic, made up of few species. The floristically-rich mixolimnion contributes little to biomass. The ecology of the dystrophic flora is discussed in relation to the special circumstances of meromixis.     

Serine proteinase activation of latent human skin collagenase

Latent and active collagenase were demonstrated following direct extraction from normal skin homogenates with 0.1M calcium chloride at 60 degrees C. 83% of the collagenase activity was in latent form and could be maximally activated with trypsin. Partial activation of the latent enzyme could also be demonstrated by incubation of the skin extract without added trypsin. This endogenous activation was inhibited by the addition of soya bean trypsin inhibitor, trasylol, di-isopropylphosphofluoridate and phenylmethanesulphonylfluoride, none of which inhibited collagenase directly. This suggests that the skin extracts contain a collagenase activating enzyme with the inhibition profile of a serine proteinase. A chymotryptic proteinase with a similar inhibition profile was extracted from normal human skin and partially purified. This enzyme activated fibroblast procollagenase derived from tissue culture of normal skin. The procollagenase was also partially activated by plasmin and chymotrypsin. This is the first demonstration of a collagenase activating enzyme in human skin and raises the possibility that collagenase activation by this mechanism may be responsible for collagen degradation in some disease processes.     

Primary lysosomal dysfunction causes cargo-specific deficits of axonal transport leading to Alzheimer-like neuritic dystrophy

Abnormally swollen regions of axons and dendrites (neurites) filled mainly with autophagy-related organelles represent the highly characteristic and widespread form of “neuritic dystrophy” in Alzheimer disease (AD), which implies dysfunction of autophagy and axonal transport. In this punctum, we discuss our recent findings that autophagic/lysosomal degradation is critical to proper axonal transport of autophagic vacuoles (AVs) and lysosomes. We showed that lysosomal protease inhibition induces defective axonal transport of specific cargoes, causing these cargoes to accumulate in axonal swellings that biochemically and morphologically resemble the dystrophic neurites in AD. Our findings suggest that a cargo-specific failure of axonal transport promotes neuritic dystrophy in AD, which involves a mechanism distinct from the global axonal transport deficits seen in some other neurodegenerative diseases.     

MICROFISSURATA GEN. NOV. (BACILLARIOPHYTA), A NEW DIATOM GENUS FROM DYSTROPHIC AND INTERMITTENTLY WET TERRESTRIAL HABITATS1

A new freshwater benthic diatom genus, Microfissurata gen. nov., was identified from light and scanning electron micrographs. The most characteristic morphological feature (referred to also by the name of the new genus) is the structure of the striae/alveoli, which are simple, mostly uninterrupted, transapical slits. The combination of characteristics of the new genus is unique. It includes two new species: Microfissurata paludosa Cantonati et Lange‐Bert. sp. nov. and M. australis Van de Vijver et Lange‐Bert. sp. nov., distributed in Europe and on an austral island, respectively. The new genus occurs in freshwater dystrophic lakes, pools, seepage springs, mires, and in intermittently wet terrestrial habitats. It is not abundant but widespread wherever these habitat types are well developed, in Nordic‐alpine and sub‐Antarctic areas. Overall, the new genus appears to be mostly epiphytic (bryophilous) and capable of tolerating a wide range of moisture conditions (xerotolerant). The finding of the type species (M. paludosa) in a well‐investigated area like central Europe highlights the diatom species richness of dystrophic habitats and their importance for diatom biodiversity conservation.     

Primary lysosomal dysfunction causes cargo-specific deficits of axonal transport leading to Alzheimer-like neuritic dystrophy

Abnormally swollen regions of axons and dendrites (neurites) filled mainly with autophagy-related organelles represent the highly characteristic and widespread form of "neuritic dystrophy" in Alzheimer disease (AD), which implies dysfunction of autophagy and axonal transport. In this punctum, we discuss our recent findings that autophagic/lysosomal degradation is critical to proper axonal transport of autophagic vacuoles (AVs) and lysosomes. We showed that lysosomal protease inhibition induces defective axonal transport of specific cargoes, causing these cargoes to accumulate in axonal swellings that biochemically and morphologically resemble the dystrophic neurites in AD. Our findings suggest that a cargo-specific failure of axonal transport promotes neuritic dystrophy in AD, which involves a mechanism distinct from the global axonal transport deficits seen in some other neurodegenerative diseases.     

An Evidence for Vertical Migrations of Small Rotifers – a Case of Rotifer Community in a Dystrophic Lake

Diel vertical migrations of zooplankton were studied in a small, dystrophic Kruczy Staw Lake. Two rotifer species (Synchaeta pectinata Ehrenberg, Trichocerca simonei DeSmet) inhabiting the lake occurred near lake bottom (7–8 m depth) in the daytime. At night they were observed in surface waters (0–2 m). Both amplitude and speed of the rotifer migration were markedly higher than those of crustaceans. As invertebrate predators are scarce or altogether lacking in the lake, vertical stratification of rotifer and crustacean communities both seasonally and dielly may be caused by strong competition for very low food resources in the lake. This assumption is supported by the observed reverse changes in densities of zooplankton and their food (i.e. picoplankton) during a diel cycle.     

Influence of excessive fluoride consumption on the severity of dystrophic cardiac calcification in DBA/2 mice

Soft tissue calcifications in inbred laboratory mice are frequently observed and are often associated with dystrophic cardiac calcinosis (DCC). We tested the hypothesis that an excessive intake of fluoride would inhibit pathological calcifications in DCC-susceptible mice. A diet containing either a high (200 mg F/kg added to the diet) or low fluoride content (no F added) was fed to both weanling and retired breeder DBA/2 mice. The high-fluoride diet reduced feed intake and body weight gain when given after weaning. It was found that a high fluoride intake effectively reduces soft tissue calcifications in young mice, but not in retired breeders. Because DCC in mice is a pathological finding that could interfere with certain experimental procedures, it is suggested that the optimum fluoride concentration in the diet for mice of susceptible strains should be established.