Sarcopenia: etiology, clinical consequences, intervention, and assessment

The aging process is associated with loss of muscle mass and strength and decline in physical functioning. The term sarcopenia is primarily defined as low level of muscle mass resulting from age-related muscle loss, but its definition is often broadened to include the underlying cellular processes involved in skeletal muscle loss as well as their clinical manifestations. The underlying cellular changes involve weakening of factors promoting muscle anabolism and increased expression of inflammatory factors and other agents which contribute to skeletal muscle catabolism. At the cellular level, these molecular processes are manifested in a loss of muscle fiber cross-sectional area, loss of innervation, and adaptive changes in the proportions of slow and fast motor units in muscle tissue. Ultimately, these alterations translate to bulk changes in muscle mass, strength, and function which lead to reduced physical performance, disability, increased risk of fall-related injury, and, often, frailty. In this review, we summarize current understanding of the mechanisms underlying sarcopenia and age-related changes in muscle tissue morphology and function. We also discuss the resulting long-term outcomes in terms of loss of function, which causes increased risk of musculoskeletal injuries and other morbidities, leading to frailty and loss of independence

Formation and Survival of Oospores of Phytophthora-Infestans Under Natural Conditions

Phytophthora infestans is able to produce oospores in leaves of potato and tomato plants after inoculation with a mixture of A1 and A2 mating-type isolates. Various conditions for oospore formation were analysed. Under controlled conditions, oospores were produced in potato leaves at temperatures ranging from 5 to 25 degrees C. In leaves of potato cultivar Bintje incubated at 15 degrees C, oogonia and antheridia were observed 6 days after inoculation and thick-walled oospores appeared 3-4 days later. In field experiments oospores were found in leaves and stems of potato cultivars Bintje, Irene and Pimpernel and in leaves, stems and fruits of tomato cultivar Moneymaker within 2 weeks after inoculation. A bioassay was developed to test the survival of oospores in soil under various conditions. To determine whether late-blight infections derived from infectious soil were caused by oospores, DNA fingerprinting was performed. DNA fingerprint probe RG-57 was suitable for distinguishing asexual progeny from recombinant progeny arising from soil-borne oospores. We demonstrated survival of viable, infectious oospores of P. infestans in soil during the winter of 1992-93. Oospores were not infectious from soil exposed to temperatures of 40 degrees C or higher but in the range 35 degrees C to as low as -80 degrees C for 48 h, oospores survived

Dna-Fingerprinting Uncovers a New Sexually Reproducing Population of Phytophthora-Infestans in the Netherlands

The oomycetous fungus Phytophthora infestans (Mont.) de Bary, which causes late blight disease in potatoes, is heterothallic with two known mating types, A1 and A2. From 1845 until 1980 only A1 mating type isolates were found in Europe. In 1980, the A2 mating type appeared permitting sexual reproduction. Here we show that virulence properties and DNA fingerprint patterns of isolates collected in the Netherlands before and after the appearance of A2 mating type isolates are different. Before 1980, eight different races were found in which virulence factors 1, 2, 3, 4 and 10 were most common. After 1980, new virulence factors (i.e. 5, 6, 7, 8 and 11) showed up and the diversity for virulence increased tremendously: 73 different races were detected among 253 isolates analyzed. DNA fingerprint analyses of isolates collected before 1980 revealed that, for at least two decades, only one RG-57 fingerprint genotype was present in Europe. Among 179 isolates collected after 1980 134 distinct RG-57 fingerprint genotypes were identified. The dramatic increase in genetic diversity strongly suggests that the P. infestans population in the Netherlands is now propagating sexually. The change from asexual to sexual reproduction, and the resulting increased adaptability and ability to survive outside the host, may interfere drastically with the regular disease control methods