Interferon inhibits DNA Synthesis induced in Mouse Lymphocyte Suspensions by Phytohaemagglutinin or by Allogeneic Cells

IN addition to its well known antiviral activity, interferon has recently been shown to inhibit the multiplication of tumour and mammalian cells in cell culture^1–6. We report here the inhibition by interferon of DNA synthesis induced in mouse spleen lymphocytes by the non-viral stimuli phytohaemagglutinin (PHA) and allogeneic lymphocytes. These findings are in accord with our contention that interferon affects cell function and, furthermore, they suggest that by acting on lymphocytes, interferon plays a role in the immunological response of the host.     

Effect of Conditioned Media from Several Cell Types on Invasion by Eimeria adenoeides Sporozoites1

ABSTRACT. The effect of conditioned media (media aspirated from a variety of cell cultures after 4 d of growth) on cellular invasion by sporozoites of the turkey coccidium, Eimeria adenoeides, was examined. Conditioned medium from turkey kidney cells and baby hamster kidney cells failed to alter invasion. However, conditioned medium from turkey cecal cell cultures produced a significant (P ≤ 0.05), two-fold increase in invasion over control medium in a variety of cell types. Retentates of conditioned medium from the turkey cecal cells that were passed through microconcentrators having molecular mass cutoffs of 50, 100, and 300 kDa similarly enhanced invasion over retentates from control medium. However, retentates from microconcentrators with a cutoff of 1,000 kDa failed to enhance invasion. Pretreatment in conditioned medium, followed by washing of sporozoites prior to inoculation into cultures, did not result in enhanced invasion. Moreover, when the interval between inoculation of sporozoites into cells and fixation of cultures was reduced to less than 3 h, no enhancement of invasion occurred. Conditioned medium from turkey cecal cells that were grown in the presence of ³⁵S-translabel had at least two labeled bands at 150 kDa and > 200 kDa that were absent in conditioned media from turkey kidney and baby hamster kidney cells.     

Immunoparasitology in Avian Species

There has been no work on the immunological response of birdsto helminth infections since the late 1960s, an area of investigationthat has been too long ignored. Similarly, studies of arthropod-mediatedresponses in birds are lacking except for a few scattered investigations.Recently, a serum antibody response has been seen against onearthropod, the northern fowl mite. The appearance of antibodiesrecognizing an 8–10 kilodalton mite antigen seems to correlatewith a reduction in the mite population on infested chickens.Most of the studies on parasite immunity in avian species havecentered on the economically important Eimeria species, protozoanparasites that infect the intestine of chickens and turkeys.These investigations encompass wide areas of interest includingthe effect of immunity on parasite invasion, development ofT-cell proliferation assays and T-cell clones, inhibition ofparasite penetration and development by hybridoma antibody treatment,production of genetically engineered Eimeria antigens used inbird immunization studies, and studies using inbred or congeniclines of birds to determine what effect the major histocompatibilitycomplex has on parasite immunity. From these efforts it hasbeen learned that not only is the immunity species-specific,but also depending on where in the intestine the parasite invades,penetration is either not affected or inhibited by as much as50%. The T-cell proliferation assays suggest that this specificitymay be due to a species-specific T-cell response. Immunizationstudies using a genetically engineered antigen have indicatedthat at least partial protection against one species of Eimeriais possible. Studies done with the inbred congenic lines ofbirds have shown that the genetic makeup of the bird is importantin how it responds to either a natural infection or to immunizationwith a genetically engineered antigen. Clearly, these resultsshow not only the complexity of the bird response to parasiteinfection, but also the amount of work still undone.     

The Effects of Priming and Accelerated Ageing upon the Nucleic Acid Content of Leek Seeds and their Embryos

Using seed priming and accelerated ageing techniques, a singlelot of leek (Allium porrum) seeds was manipulated to producefour lots of seeds with different germination performance. Changesin content of the major nucleic acid species in whole seedsand embryos of two of these lots (primed and unprimed), weredetermined over the early stages of germination. The major effectof priming was an increased level of RNA species in the seedsand embryos, and this difference was maintained during germination.Comparison of nucleic acid levels in the dry seeds of thesetwo lots and two others (aged and aged then primed) indicatedthat there was no correlation with germination performance.Similar comparisons of the nucleic acid levels in the embryosof seeds imbibed for 1 d showed only a limited correlation betweenrRNA levels and germination performance. Analysis of these datasuggests that accelerated ageing has an adverse effect uponendosperm cells, which results in the degradation of their nucleicacids during priming. Furthermore, the viability of these agedseeds also falls during priming. The data also indicate thatratios of rRNA to DNA correlate with germination performanceof the four lots of seeds studied. It is proposed that sucha relationship is indicative of the efficiency of a primingtreatment, and may be useful in comparisons of naturally varyingseed lots. Key words: Leek, seed, germination, priming, nucleic acids     

Cyclic Changes in Chloroplast Structure in Synchronized Euglena gracilis*

SYNOPSIS. In populations of Euglena gracilis strain Z synchronized by cultivation on a repetitive light-dark cycle, chloroplasts undergo cyclic changes in structure. During most of the light period chloroplasts are relatively compact with closely appressed lamellae; during the dark (division) period the chloroplasts become quite distended. This change persists for at least one cycle even when the cells are left in continuous light, suggesting that the periodicity may be related more to the age of the cell than to a direct effect of light. In addition, the pyrenoid in synchronized cells has a transient existence, being present only in the first half of the light period.     

The Growth of Apple Fruitlets, and the Effect of Early Thinning on Fruit Development: With fourteen Figures in the Text

The development of fruitlets of the apple varieties Cox's OrangePippin and Miller's Seedling was investigated with particularreference to rate and duration of cortical cell division andexpansion. The fruitlet weight increases slowly for the first few daysafter pollination, then exponentially at a rapid rate for about3 weeks, and then at a declining rate until harvest. The rate of cell division is very rapid during the exponentialphase of fruitlet growth, and then the rate declines, but divisioncontinues until about 12 weeks after full bloom in Miller'sSeedling and for at least 6 or 7 weeks after pollination inCox's Orange Pippin. The cells expand exponentially until about 7 weeks after pollination,then continue to expand at a diminishing rate until harvest. Heavy pre-blossom thinning increased fruit size and weight,affecting the rate of both cell division and cell expansion;the differences in fruit weight showed by the 4th week and incortical cell number and cell diameter by the 5th week afterfull bloom.     

Lysosomal Compartmentation: Ultrastructural Aspects of the Origin, Development, and Function of Vacuoles in Root Cells of Lepidium sativum

The origin and development of vacuoles in root and root capcells of Lepidium sativum was investigated at the ultrastructurallevel. The vacuoles originated as vesiculations of the ER, andacid phosphatase activity was found associated with the membranesbounding developing vacuoles. As development proceeded activityof acid phosphatase became associated with the accumulated vacuolarcontent, but was confined within these bodies in all cells exceptsome of those in the outermost layer of the cap, which werein various stages of senescence. In these cells activity ofthis enzyme appeared in the cytoplasm, associated with apparenttonoplast dissolution. These findings are discussed in the context of current hypothesesconcerning the origin and relationship of vacuoles and lysosomalcompartmentation in plant cells.