Abstract When strips of human skeletal muscle from biopsies of normal children and donors with Duchenne muscular dystrophy (DMD) are explanted in organotypic coculture with fetal mouse spinal cord, many regenerating muscle fibers develop, become innervated, and maintain a remarkable degree of mature structure and function for more than 3–6 months in vitro. Sequential light microscopy in correlation with electron‐microscopic and electrophysiologic analyses showed that despite cross‐species innervation, these human muscle fibers develop stable cross‐striations, peripherally positioned myonuclei, and mature, functional motor endplates. Of special interest is the onset of significant progressive abnormalities, e.g., unusual focal myofibrillar lesions, in substantial numbers of innervated mature DMD muscle fibers after 2–4 months in culture. The focal myofibrillar lesions were not detected in normal muscle fibers maintained as long as 6 months in coculture, nor are they comparable to the generalized loss of cross‐striations observed in muscle atrophy following in vitro denervation of mature DMD fibers.
Long-term organotypic cultures of rat dorsal root ganglia were exposed to a single 40 kR dose of 184 kvp X-rays and studied in the living and fixed states by light or electron microscopy at 1-14 day intervals thereafter. Within the first 4 days following irradiation, over 30% of the neurons display chromatolytic reactions (eccentric nuclei, peripheral dispersal of Nissl substance, central granular zone) as well as abnormal nucleolar changes and dissociation of ribosomes from endoplasmic reticulum cisternae. Some satellite cells undergo retraction or acute degeneration, leaving only basement membrane to cover the neuron in these areas. 8 days after irradiation, neurons also exhibit (a) areas in which ribosomes are substantially reduced, (b) regions of cytoplasmic sequestration, (c) extensive vacuolization of granular endoplasmic reticulum and Golgi complex, and (d) diversely altered mitochondria (including the presence of ribosome-like particles or association with abnormal glycogen and lipid deposits). Nucleolar components become altered or reoriented and may form abnormal projections and ringlike configurations. Sizeable areas of the neuronal soma are now denuded of satellite cells; underlying these areas, nerve processes are found abnormally invaginated into the neuronal cytoplasm. By the 14th day following irradiation, most neurons display marked degenerative changes including extensive regions of ribosome depletion, sequestration, vacuolization, autolysis, and, in some areas, swirls of filaments, myelin figures, and heterogeneous dense bodies. These observations demonstrate that X-irradiation produces profound cytopathological changes in nervous tissue isolated from the host and that many of these changes resemble the effects of radiation on nervous tissue in vivo.
Methods for obtaining maximum aerobic and anaerobic bacterial counts on fresh and irradiated (750,000 rad) shucked, soft-shelled clams and haddock fillets were investigated. This involved an evaluation of the composition and temperature of the dilution water, the composition of various culture media, the culture incubation temperature, and the culture incubation time. On the basis of the results of tests to determine the most suitable methods of counting, procedures and materials were selected for obtaining maximum aerobic bacterial counts and maximum counts for Clostridia in fresh and irradiated shucked, soft- shelled clams and haddock fillets. The bacterial content of shucked, soft- shelled clams from three plants, and of haddock fillets from three plants, was determined over a period of approximately one month. This survey involved the examination of three samples daily from each plant. While bacterial counts indicated that the product produced in some clamshucking and fish-filleting plants is superior in sanitary quality to that produced in others, no evaluation of different plants will be made until the survey has been completed and all data are available. (auth)
