Eimeria necatrix: Induced proteolytic sensitivity of infected chick crypt cells

While devising a protocol for the isolation of chick crypt cells infected with Eimeria necatrix, it was observed that infected cells were readily lysed by 0.25% trypsin. Time-course studies at 17 C with 5.5 × 10⁵ cells at 96 hr postinfection revealed that 0.001% trypsin effectively lysed >90% of infected cells within 10 min. Uninfected crypt cells were not lysed under these conditions. To determine the site of action of trypsin, the plasma membrane proteins from trypsin-treated and untreated infected cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. While the major proteins were unaffected by the trypsin treatment, some minor changes were noted: (1) three components (～-60, ～-52, and ～-20 KDa) were trypsin sensitive and (2) a new band (～-42 KDa) appeared in the membrane of trypsin-treated infected cells. Previously, it was found that the plasma membrane of infected cells, in contrast to uninfected cells, accumulated gel-phase lipid (J. E. Thompson, M. A. Fernando, and J. Pasternak, Biochimica et Biophysica Acta555, 472–487, 1979). Here, it was examined whether trypsin would perturb the physical state of the plasma membrane of infected cells. Both X-ray diffraction patterns and transition temperature studies revealed no difference between membranes from untreated and trypsin-treated infected cells. Thus, “trypsin sensitivity” may be a secondary phenomenon that is due primarily to the cellular leakiness that accompanies the accumulation of gel-phase lipid in the plasma membrane of infected cells. The uptake of trypsin may stimulate the release of catabolic enzymes that, consequently, lyse an infected cell.     

Membrane transport and disease

Four situations in which membrane transport is altered by disease are discussed: (a) non-specific leaks induced by poreforming agents; (b) glucose transport and cellular stress; (c) Ca⁺-ATPase and hypertension; (d) Na^– channels and HSV infection.Keynote Lecture delivered at International Symposium onBiomembranes and Disease, on 1 November 1988 at Lucknow, India     

Oxymorphone-naltrexonazine, a mixed opiate agonist-antagonist

Previous studies from our laboratories have reported the synthesis and pharmacological characteristics of a series of symmetrical opiate azines: naloxonazine, oxymorphonazine and naltrexonazine. We have now synthesized and characterized in binding assays and in vivo two asymmetrical azines: oxymorphone-naltrexonazine and oxymorphone-3-methoxynaltrexonazine. Oxymorphone-naltrexonazine, which theoretically could interact with the receptor as either an agonist or antagonist, displayed antagonist properties in vitro and in vivo. Oxymorphone-3-methoxynaltrexonazine, which theoretically could bind only as an agonist, possessed agonist properties in binding studies and was a potent analgesic in vivo.     

Symbiotic bacteria enable olive flies (Bactrocera oleae) to exploit intractable sources of nitrogen

Insects are often associated with symbiotic micro‐organisms, which allow them to utilize nutritionally marginal diets. Adult fruit flies (Diptera: Tephritidae) associate with extracellular bacteria (Enterobacteriaceae) that inhabit their digestive tract. These flies obtain nutrients by foraging for plant exudates, honeydew and bird droppings scattered on leaves and fruit – a nutritional niche which offers ample amounts of carbohydrates, but low quantities of available nitrogen. We identified the bacteria resident in the gut of the olive fly (Bactrocera oleae) – a worldwide pest of olives and examined their contribution to nitrogen metabolism in the adult insect. By suppressing bacteria in the gut and monitoring female fecundity, we demonstrate that bacteria contribute essential amino acids and metabolize urea into an available nitrogen source for the fly, thus significantly elevating egg production. In an ecological context, bacteria were found to be beneficial to females subsisting on bird droppings, but not on honeydew – two natural food sources. We suggest that a main gut bacterium (Candidatus Erwinia dacicola) forms an inseparable, essential part of this fly's nutritional ecology. The evolution of this symbiosis has allowed adult flies to utilize food substrates which are low or imbalanced in assimilable nitrogen and thereby to overcome the nitrogen limitations of their natural diet.     

An algorithm to fit the Gompertz function to growth curves

An algorithm to fit the Gompertz growth Junction is presented.This algorithm is easy to program on a microcomputer. The algorithmis based on employing a searching technique to solve a set ofequations derived from the Gompertz function. Its applicationmay prove valuable when access to a computer mainframe is difficult.Such a method may be useful in construction of a specific growthcurve in biology, or as a managerial tool in livestock enterprise,as well as in the clinical treatment of tumors. Demonstrationof the successful application of this algorithm in experimentallivestock growth data are presented.     

How viruses damage cells: alterations in plasma membrane function

The effect of viruses on plasma membrane function has been studied in two types of situation: (i) during the toxin-like action of paramyxoviruses when fusing with susceptible cells, and (ii) during an infectious cycle initiated by different viruses in various cell types. The nature of the permeability changes induced during the toxin-like action of viruses, and its modulation by extra-cellular Ca²⁺, are described: membrane potential collapses, intracellular ions and metabolites leak out of, and extracellular ions leak into cells, but lysis does not take place. The biological significance of such changes, and their relation to changes induced by other pore-forming agents, are discussed. Changes in membrane permeability such as those mentioned above have not been detected during infection of cultured cells by paramyxo (Sendai, measles, mumps), orthomyxo (influenza), rhabdo (vesicular stomatitis), toga (Semliki Forest) or herpes viruses. On the contrary, sugar uptake is increased when BHK cells are infected with vesicular stomatitis virus, semliki forest virus or herpes virus. Cultured neurones infected with herpes simplex virus show changes in electrical activity. The pathophysiological significance of these alterations in membrane function, which occur in viable cells, is discussed. It is concluded that clinical symptoms may result from cell damage caused by virally induced alterations of plasma membrane function in otherwise intact cells.