Survival of Cryptosporidium parvum oocysts under various environmental pressures.

The survival of various isolates of Cryptosporidium parvum oocysts under a range of environmental pressures including freezing, desiccation, and water treatment processes and in physical environments commonly associated with oocysts such as feces and various water types was monitored. Oocyst viability was assessed by in vitro excystation and by a viability assay based on the exclusion or inclusion of two fluorogenic vital dyes. Although desiccation was found to be lethal, a small proportion of oocysts were able to withstand exposure to temperatures as low as -22 degrees C. The water treatment processes investigated did not affect the survival of oocysts when pH was corrected. However, contact with lime, ferric sulfate, or alum had a significant impact on oocyst survival if the pH was not corrected. Oocysts demonstrated longevity in all water types investigated, including seawater, and when in contact with feces were considered to develop an enhanced impermeability to small molecules which might increase the robustness of the oocysts when exposed to environmental pressures.     

Conidiogenesis in Petriellidium boydii (Pseudallescheria boydii)

Slide cultures of the type strain of P. boydii Shear, showed percurrent production of conidia by light microscopy over a period of several hours. Scanning and transmission electron microscopy were used to examine the conidiogenesis. The conidiogenous cells developed annular ridges rather than typical annellophoric scars. Evidence that these ridges represented sequential spore production was shown by T.E.M. in the form of a discontinuity of the outer conidiophore wall at the widest point of each ridge.Since submission of this paper the taxonomy of the organism has been changed to Pseudallescheria boydii. (Mycotaxon 14: 94 1982).     

ZINC ADSORPTION AND TRANSPORT BY CHLAMYDOMONAS VARUIABILIS AND SCENEDESMUS SUBSPICATUS (CHLOROPHYCEAE) GROWN IN SEMICONTINUOUS CULTURE1

The amount of zinc adsorbed onto the cell surface of the unicellular green algae Scenedesmus subspicatus Hodat and Chlamydomonas variabilis Dangeard was operationally defined by extraction with EDTA; it was a function of the concentration of free ionic zinc remaining in the growth medium, rather than that of the total (free plus complexed) zinc concentration, and could be described by Langmuir isotherms. Conditional adsorption equilibrium constants for zinc were 0.123 and 0.039 L ·μmol^?1 for S. subspicatus and C. variabilis, respectively. A portion of the zinc adsorbed onto C. variabilis was released into solution after 1 h of contact with the metal, providing a possible tolerance mechanism for this alga; the division rate of C. variabilis was not altered by up to 12 μmol Zn²⁺· L^?1, although the cell yield obtained during the stationary phase was significantly decreased. The amount of transported or cellular zinc, for both algal species, was operationally defined as the zinc remaining with the cell after EDTA-extraction; it was a linear function of the free ionic zinc concentration remaining in solution, suggesting that the zinc transported into the cell was not derived from the total adsorbed fraction, although the latter may contain some zinc originating from specific sites leading to zinc transport.     

Colonoscopic polypectomy in children.

Five children presenting with chronic and intermittent rectal bleeding were diagnosed as having colorectal polyps by fibreoptic colonoscopy performed under sedation. Three of the children had had barium-enema films reported on as normal. Eight polyps were seen, of which six were proximal to the sigmoid colon. All were removed endoscopically (one by proctoscopy, one by snare-intussusception) without complication. Colonoscopic polypectomy is a safe and efficient procedure in children, and colonoscopy may be regarded as first-line management in those with rectal bleeding.     

Prophylaxis of infection after appendicectomy: a survey of current surgical practice.

Two hundred and eighty questionnaires were sent to junior surgical staff throughout England inquiring about their use of systemic antibiotic prophylaxis, topical antibacterial agents, and surgical drainage in appendicectomy. One hundred and seventy-five (63%) replies were received from 81 of the 87 hospitals included in the survey. Prophylactic systemic antibiotics were used by 78 surgeons (46%) when operating on a normal appendix but by 168 (99%) when the organ had perforated. Most surgeons started antibiotics before operation, but proportionately fewer did so when the appendix was gangrenous or perforated. Patients with severe contamination tended to receive longer courses of antibiotics, although the duration of administration varied considerably. Metronidazole was included in over 95% of all the prophylactic regimens and was often combined with other drugs when the appendix was gangrenous and perforated. Topical antibacterial agents were applied to the wound routinely by only 45 surgeons (26%), although 106 (61%) used them sometimes. Povidone-iodine was the agent most commonly used. Only 98 surgeons (56%) ever drained appendicectomy wounds, while 135 (77%) sometimes drained the peritoneal cavity. Evidence suggests that present methods of giving systemic antibiotic prophylaxis should continue, but that topical agents and surgical drainage are perhaps unnecessary when surgeons are confident of the efficacy of the systemic treatment used.     

Nutritional factors controlling exocellular protease production by Pseudomonas aeruginosa.

A defined medium capable of supporting growth and exocellular protease production by clinical isolates of Pseudomonas aeruginosa has been developed. Control of protease production is effected by a mixture of three amino acids and glucose.     

Red blood cell lysis induced by the venom of the brown recluse spider: the role of sphingomyelinase D.

Red blood cell lysis induced by the venom of Loxosceles reclusa, the brown recluse spider, may be related to the hemolytic anemia observed in several cases of spider envenomation. These investigations demonstrate that the venom of the brown recluse spider contains a calcium-dependent, heat-labile hemolysin of molecular weight approximately 19,000. The pH optimum for the hemolytic reaction was 7.1, and the optimum calcium concentration for venom-induced lysis was observed within the range of 6 to 10 mm. Sheep red blood cells were more susceptible to the spider hemolysin than human red blood cells, although both types exhibited appreciable lysis. Digestion of sheep red blood cell membranes with partially purified venom lysin resulted in degradation of the sphingomyelin component. However, reaction of the membranes with the venom lysin produced no release of water-soluble phosphate, and no free fatty acids were generated. These results indicate that the sphingomyelin-degrading activity of the venom is not a phospholipase C- or a phospholipase A₂-type activity. Sphingomyelin was employed as substrate for the venom hemolysin, and the organic and aqueous fractions of the reaction mixtures were analyzed by thin-layer chromatography. Analysis of the organic fraction revealed a phosphate-containing product with the solubility and chromatographic characteristics of N-acylsphingosine phosphate (ceramide phosphate), and analysis of the aqueous fraction demonstrated the presence of choline. The isolation and identification of these products indicate that the sphingomyelin of the red cell membrane is hydrolyzed by a sphingomyelinase D-type activity expressed by the partially purified venom hemolysin. A close correspondence between the hemolytic and sphingomyelinase D activities was observed when the partially purified hemolysin was further characterized in polyacrylamide gel electrophoresis at pH 8.3 and pH 4.9. The hemolytic and sphingomyelinase activities were coincident within the electrophoretic pattern at both pHs. The results presented demonstrate conclusively a direct lytic action of brown recluse venom upon red blood cells and report for the first time the presence of sphingomyelinase D in spider venom.