Are seals frequently infected with avian influenza viruses?

Influenza A virus isolates of the H4N5 subtype (which has previously been detected only in birds) were recovered from harbor seals dying of viral pneumonia on the New England coast from June 1982 through March 1983. When these isolates were compared with other mammalian and avian viruses in serological assays and RNA-RNA competitive hybridization, it was found that the seal viruses were most closely related antigenically and genetically to recent avian virus strains and were readily distinguishable from mammalian viruses, including H7N7 isolates recovered from seals in 1980. Unlike any previous isolates from mammals, these recent seal viruses replicate in the intestinal tracts of ducks, a characteristic of avian viruses. The association of avian viruses with influenza outbreaks in seals suggests that transmission of avian viruses to seals is occurring in nature. Potentially, this may be an example of the adaptation of avian viruses to mammals, which would represent an intermediate step in the evolution of new mammalian strains.     

Differentiation properties of pure populations of human dystrophic muscle cells

The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation.     

Climatic adaptation in recently shorn merino sheep

Heart rates, respiratory rates, body temperatures, ad libitum ‘day’ and ‘night’ food consumption and body weight changes have been examined in 15 mature Merino wethers shorn in moderate environmental conditions. All sheep showed a depression in food consumption for two days after shearing. Sheep that gained weight during the next three weeks then increased their food consumption at night by approximately 30% although the average daily consumption was only increased by 5%. Sheep that lost weight showed a depressed food consumption throughout the three week period after shearing. Marked increases in the temperature difference between ear skin and air as well as thermal tachypnoea during the warmest period of the day were recorded in all sheep 14–16 days after shearing. This indicated that the critical temperature for all sheep had decreased by about 10°C. These signs of acclimatisation appeared at similar times in all sheep, suggesting that increased resistance to body cooling developed at similar rates in weight gain and weight loss sheep and independent of the origin of body heat production. The results of the investigations are discussed in relation to the concept that the initial response to cold stress includes a depression in food intake and that the duration of this depression is a function of the cold stimulus and the strain it induces in the sheep.     

Some properties of influenza virus nucleocapsids

Nucleocapsids released from influenza virions by sodium deoxycholate sedimented heterogeneously in sucrose gradients. Highly infectious virus (complete) preparations yielded nucleocapsids with peak distributions at 64 and 56S; von Magnus type virus (incomplete) lacked 64S nucleocapsids. Treatment of influenza virus nucleocapsids with pancreatic ribonuclease rendered the associated viral ribonucleic acid (RNA) molecules acid-soluble, indicating that capsid proteins do not completely surround the viral RNA's. However, the capsid proteins remained associated after enzymatic hydrolysis of the RNA, as judged by persistently high sedimentation rates. Sedimentation rates of viral nucleocapsids reflected the sedimentation rates of the associated RNA's: 64S nucleocapsids contained 18S RNA, whereas 56S nucleocapsids contained 15S RNA, although in both cases RNA's sedimenting at 4 to 13S were also recovered. Furthermore, just as incomplete virions lacked 64S nucleocapsids, they also lacked 18S RNA. These findings support the hypothesis that the influenza virus genome is divided among several distinct pieces of RNA.     

Procedure for Evaluating the Effects of 2,450- Megahertz Microwaves upon Streptococcus faecalis and Saccharomyces cerevisiae

Modifications of a commercial 2,450-megahertz microwave oven were made so that 6 ml of microbial suspension could be exposed to the microwave field for various periods of time. The microorganisms were contained in the central tube of a modified Liebig condenser positioned in the approximate geometric center of the oven cavity. Kerosene at -25 C was circulated through the jacket of the condenser during microwave exposure permitting microwaves to reach the microbial suspension. Flow rates of the kerosene were varied to permit the temperature of the suspension to range from 25 to 55 C during microwave exposure. Conductive heating experiments using similar temperatures were also conducted. A thermocouple-relay system was employed to measure the suspension temperature immediately after the magnetron shutoff. Continuous application of microwaves to suspensions of 10(8) to 10(9)Streptococcus faecalis or Saccharomyces cerevisiae per ml appeared to produce no lethal effects other than those produced by heat. Respiration rates of microwave-exposed Scerevisiae were directly related to decreases in viable count produced by increased microwave exposure times.     

On the site of action of phosphatide acyl-hydrolase activity of rat brain homogenates on lecithin

The hydrolysis of 2- [14C]acyl-labelled and [Me-3H]choline-labelled lecithins by rat brain homogenates has been studied. The acyl-labelled substrate was hydrolysed with the production of both radioactive lysolecithin and radioactive free fatty acid in the proportions of 60 per cent and 40 per cent; traces of labelled mono- and diglyceride were also formed. In addition to radioactive lysolecithin the [3H]choline-labelled lecithin also gave rise to much smaller amounts of radioactive water soluble derivatives, consisting almost entirely of free choline and phosphorylcholine with only traces of glycerylphosphorylcholine. The results provide evidence for the production of a mixture of 1- and 2-acyl isomers of lysolecithin by phospholipase action in brain homogenates at pH 7.4, the latter predominating slightly.     

Intensity of photosynthesis and chlorophyll content as related to leaf age inNicotiana Sanderae hort

U r?zně starých list? v listové r??ici 90 a? 110 denních rostlin Nicotiana sanderae hort. byly sledovány rozdály v intensitě ?isté fotosynthesy a v obsahu chlorofylu (a + b). Ke stanovení intensity fotosynthesy bylo pou?ito dvou odli?ných metod, a to váhového stanovení p?ír?stku su?iny podle Barto?e, KubÍna a ?et-lÍka (1960) a gazometrického stanovení infra?erveným analyzátorem CO₂. Nejvy??í intensitu fotosynthesy i nejvy??í obsah chlorofylu (vzhledem k plo?e listové) mají mladé, ale ji? dob?e rozvinuté listy, tj. t?etí a? ?tvrté od vrcholu (prvním listem se rozumí list o plo?e asi 20 cm²). Tyto listy nazýváme ?fotosyntheticky dospělými“. Listy nejmlad?í a zejména pak listy star?í mají intensitu fotosynthesy i obsah chlorofylu ni??í; u nejstar?ích list? je intensita fotosynthesy prakticky nulová. Intensita fotosynthesy i obsah chlorofylu se během vývoje mění: jejich momentální rozdíly u list? v genetické spirále jsou z?ejmě shodné s jejich změnami v ontogenesi listu. Pokles intensity fotosynthesy p?i stárnutí list? je rychlej?í ne? pokles obsahu chlorofylu. P?i ur?itém obsahu chlorofylu (tj. asi 2,25 a? 2,45 mg/dm²) klesá intensita ?isté fotosynthesy k nule. Intensita fotosynthesy je v lineárním vztahu k mno?ství chlorofylu (p?i p?epo?tu na plo?nou jednotku), a to nezávisle na poloze listu v genetické spirále. Obě pou?ité metody ke stanovení intensity fotosynthesy poskytly obdobné výsledky.