Mycoparasitic relationships

The mode of attack and the infection structures of the necrotrophic mycoparasite, Pythium acanthicum, as well as the responses of various fungal hosts to parasitism were studied using both electron and light microscopy. Many taxonomically distinct fungal hosts were used, though Phycomyces blakesleeanus, Pythium aphanidermatum, Rhizoctonia solani and a basidiomycete identified as Corticium sensu lato were studied in greatest detail. Parasitism was by direct penetration of the fungal host without appressorium formation by the parasite. The host's cells responded to contact by P. acanthicum by forming papillae. The morphological features of the papillae varied with the particular host. In P. blakesleeanus they were comprised of vesicles and segments of cytoplasm entrapped in a fibrillo-granular matrix, while in R. solani and the Corticium basidiomycete they contained considerable amounts of electron-opaque and electron-translucent material. Evidence for both mechanical and enzymatic penetration of the host fungi by the parasite are presented. Details of host wall and septum penetration by the parasite are presented using time-lapse light microscopy with in vivo systems. Many of these stages of parasitism were examined ultrastructurally. Some comparisons of these mycoparasitic relationships are discussed in relation to what is known from the literature about phytoparasitic interactions.     

Potential availability of cadaver organs for transplantation.

OBJECTIVE--To determine the potential number of cadaver kidney donors by applying defined donor criteria to people dying in hospital. DESIGN--Prospective study of all deaths occurring in 21 hospitals from 1 September 1988 to 31 August 1989. Questionnaires were administered to medical and nursing staff and families of potential donors aged 1-69. SETTING--Acute care hospitals in Gwent, South Glamorgan, Mid Glamorgan, West Glamorgan, Pembrokeshire, and East Dyfed health authorities, serving a population of 2.2 million. MAIN OUTCOME MEASURES--Cause of death, age, ventilation at time of death, diagnosis of brain death, and consideration of consent. RESULTS--Adequate data were available for 9840 of 10,095 hospital deaths (97.5% coverage). 188 patients aged 0-69 were identified as potential organ donors (widest definition), and of these 108 died without being ventilated at the time of death. Tests of brain stem death were formally completed in 57 cases, and organ donation was considered by the families of 47 of these potential donors. 26 patients became organ donors. Patients aged 50-69 with stroke were less likely to be ventilated than those aged less than or equal to 49 (21/96 v 24/34). Families of potential donors aged 20-39 were least likely to give permission. CONCLUSIONS--The supply of donor organs (specifically kidneys) could be increased by altering the management of patients aged 50-69 dying of severe cerebrovascular disease in general medical wards, in particular by increasing the proportion ventilated. The ethics of elective ventilation for the purposes of organ donation require discussion.     

Oral papillae of adults of the southern hemisphere lamprey Geotria australis

The morphology, cell types, and innervation of the several small papillae (x? = 17) and two larger papillae, which together form a ring just outside the fimbriae surrounding the suctorial disc of adult Geotria australis, have been studied using various histological stains, including silver impregnation, and scanning and transmission electron microscopy. The epithelium of all papillae consists almost entirely of mucigenic cells. The multivillous and oligovillous cells, which are found elsewhere in the lamprey epidermis, were not observed, and Merkel and polyvillous cells are rare. Free nerve endings are common, however, in the basal layers of the epidermis. Unlike the small papillae, the two large papillae contain a core of skeletal muscle and a prominent layer of dermal collagen. In the submucosa of these large papillae, the nerves form a dense, compact layer that contains many large and probably sensory axons. It is suggested that the oral disc papillae of adult G. australis are encapsulated mechanosensory structures that play a role in enabling the animal to locate and attach to a suitable point on host fishes or other surfaces.     

Effectiveness of 1-bromo-3-chloro-5,5-dimethylhydantoin against Legionella pneumophila in a cooling tower.

Cooling towers are considered to be man-made amplifiers of Legionella spp. Thus, the proper maintenance and choice of biocides is important. The only biocidal measure that has thus far been shown to be effective in field tests is the judicious use of chlorination. Perturbation studies with 1-bromo-3-chloro-5, 5-dimethylhydantoin (Bromicide; Great Lakes Chemical Corp., West Lafayette, Ind.) (BCD) were conducted on an industrial cooling tower shown to contain Legionella pneumophila. At the concentrations recommended by the manufacturer, neither the density nor the activity of L. pneumophila was affected. At comcentrations greater than 2.0 ppm (2.0 micorgram/ml) free of residual, BCD was not effective in reducing L. pneumophila to source water concentrations, nor was it effective in reducing the 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride activity of the bacterium in situ. The data indicate that at concentrations up to 2.0 ppm, BCD is not effective in these tower studies.     

The solution structure of human transforming growth factor alpha

The solution structure of transforming growth factor alpha has been determined by a combination of high-resolution 1H-nuclear magnetic resonance and distance geometry and restrained molecular dynamics. The 382 restraints derived from the NMR experiments were used to calculate many distance geometry structures, which were then refined by restrained molecular mechanics. Five of these structures were further refined using a variety of methods. Comparison of independently measured parameters, such as calculated hydrogen bonding patterns and experimental amide exchange rates, have been used to evaluate the accuracy of the structures. Also, possible mechanisms to explain the pH-dependent conformational interconversion observed are suggested. Finally comparisons between this work and others on this topic have been made.