Influenza viruses: transmission between species

The only direct evidence for transmission of influenza viruses between species comes from studies on swine influenza viruses. Antigenically and genetically identical Hsw1N1 influenza viruses were isolated from pigs and man on the same farm in Wisconsin, U.S.A. The isolation of H3N2 influenza viruses from a wide range of lower animals and birds suggests that influenza viruses of man can spread to the lower orders. Under some conditions the H3N2 viruses can persist for a number of years in some species. The isolation, from aquatic birds, of a large number of influenza A viruses that possess surface proteins antigenically similar to the viruses isolated from man, pigs and horses provides indirect evidence for inter-species transmission. There is now a considerable body of evidence which suggests that influenza viruses of lower animals and birds may play a role in the origin of some of the pandemic strains of influenza A viruses. There is no direct evidence that the influenza viruses in aquatic birds are transmitted to man, but they may serve as a genetic pool from which some genes may be introduced into humans by recombination. Preliminary evidence suggests that the molecular basis of host range and virulence may be related to the RNA segments coding for one of the polymerase proteins (P3) and for the nucleoprotein (NP).     

Cellular uptake of L-lactate in mouse diaphragm.

Early uptake curves of L-lactate and of mannitol were measured in quartered, incubated mouse diaphragms. Uptake was determined at 15, 30, and 45 s for various concentrations of lactate in the external solution as well as in the presence and absence of the competitive inhibitor of lactate transport, alpha-cyano-4-hydroxycinnimate. In normal preparations, when the external lactate concentration was 10 mM or less, the ratio of lactate-to mannitol space in the tissue was 1.7. This value was nearly independent of time and of external concentration. In normal preparations, when the external lactate concentration was greater than 10 mM, the ratio of lactate-to-mannitol space rose with time. At a fixed time, however, this ratio fell with increasing lactate concentration. In the inhibited preparations, the ratio of lactate-to-mannitol space rose with time at all concentrations. When lactate concentration was greater than 5 mM, this ratio was independent of the external concentration. The results suggest that there are two modes of lactate entry into these muscle cells. Entry can occur by means of a saturable system. When external lactate concentration is low, entry rates for this process are rapid compared with diffusional rates. This system probably saturates at concentrations near 10 mM and can facilitate transport in either direction. In addition, an appreciable passive leak is present. This leak accounts for about one fourth of the membrane transfer when external lactate is low, but is equal to the carrier transfer when lactate concentration is 30 mM. A model was developed to describe the entry of a permeating solute, such as lactate, into an isolated tissue.     

Interaction of mitochondrial malate dehydrogenase monomer with phospholipid vesicles.

The association between bovine and porcine mitochondrial malate dehydrogenase (EC 1.1.1.37) and phospholipid vesicles was investigated. At concentrations at which malate dehydrogenase exists as a dimer, entrapment within the aqueous compartment but not binding of the 14C-labelled enzyme was observed. The dissociated enzyme was labile to moderate heat and to p-chloromercuribenzoate, but in both cases inactivation was decreased by incubation with suspensions of charged phospholipid vesicles. This suggested an interaction between enzyme subunits and phospholipid, and this was confirmed by direct binding measurements and by studies that followed changes in the fluorescein-labelled enzyme. The circular-dichroism spectra of the enzyme indicated a high alpha-helix content, and suggested that a small conformational change occurred when the enzyme dissociated. Fluorescence data also suggested less-rigid molecules after dissociation. A possible mechanism, based on the flexibility of enzyme monomer and its interaction with phospholipids, by which mitochondrial matrix enzymes are specifically localized in cells, is discussed.     

Comparative effects of estradiol-17beta and estriol on uterine RNA polymerases I, II, and III in vivo.

The early and later effects of estradiol-17β and estriol on the RNA polymerase activities of uterine nuclei obtained from ovariectomized rats were compared. At 4 hr of hormone action both estradiol-17β and estriol stimulated the activity of polymerase I, but not the activities of polymerases II and III. At 24 hr, however, the effect of estriol had disappeared, whereas estradiol-17β stimulated all three polymerase activities. These results indicate that estrogen-induced growth of the uterus occurs in two phases, initiation and maintenance. Estriol initiates uterine growth, but does not maintain the process. Estradiol-17β, in contrast, does both. The differences in the effects of the two estrogens may reside in their different binding affinities.     

Effects of the bark beetle nematode, Contortylenchus reversus, on gallery construction,fecundity, and egg viability of the Douglas Fir beetle, Dendroctonus pseudotsugae (Coleoptera: Scolytidae)

Healthy and Contortylenchus reversus infected Douglas Fir beetles were colonized in logs in the laboratory. At 7, 14, and 23 days after introduction of the beetles into the logs, the bark was removed from some of the logs and the length and shape of the primary gallery, the number of eggs laid, and the egg viability were determined for each pair of parent beetles. Parasitism caused a 25, 28, and 27% reduction in the length of the primary egg gallery built by the infected female at 7, 14, and 23 days, respectively, after the start of colonization. In addition, the number of eggs laid by the infected females by 7, 14, and 23 days after the start of colonization were 50, 33, and 45%, respectively, lower than that of healthy female beetles. Despite the differences in gallery length between control and infected females, linear regression analysis showed that the rates of gallery construction were not significantly different. However, infected female beetles showed significantly lower rates of egg-laying than did healthy female beetles. Nematode parasitism did not affect gallery shape and egg viability of female Douglas Fir beetles. Mating of healthy female beetles with infected males affected neither the gallery length nor the fecundity of the uninfected females.     

Fast muscle fibers are preferentially affected in Duchenne muscular dystrophy

We show that Duchenne muscular dystrophy (DMD) selectively affects a subset of skeletal muscle fibers specialized for fast contraction. Muscle fiber types were characterized immunohistochemically with monoclonal antibodies that distinguish isoforms of fetal and adult-fast or adult-slow myosin heavy chain present in the same fiber. Fetal myosin expression increased with patient age and was not due to arrested development but rather to de novo synthesis, which served as a sensitive indicator of muscle regeneration. A subset of fast fibers were the first to degenerate (type IIb). Extensive fast fiber regeneration occurred before slow fibers were affected. These results suggest that the DMD gene product has a specific function in a subpopulation of muscle fibers specialized to respond to the highest frequency of neuronal stimulation with maximal rates of contraction.     

Fruit thinning plums and apricots

The need for crop load reduction to improve fruit size andconsistency of cropping on plum and apricot trees is discussed. Threealternative strategies of achieving this objective are described: byinhibition of flowering, prevention of fruit set or stimulation ofincreased fruitlet abscission. Methods of achieving each of thesestrategies, by manual, mechanical or chemical means are discussed andevaluated.     

Beta- Lactam Antibiotics Stimulate Biofilm Formation in Non-Typeable Haemophilus influenzae by Up-Regulating Carbohydrate Metabolism

Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended.