Sur le mode de croissance de Nuia,algue incertae sedis

The authors recall some data concerning the distribution, the ecology and the taxonomy of Nuia and describe in detail its mode of growth, distinguished by 6 different growth-forms.     

Drosophila X virus RNA polymerase: tentative model for in vitro replication of the double-stranded virion RNA.

An RNA polymerase activity was found to be associated with the infectious drosophila X virus particles extracted from infected flies. The rate of synthesis was at first linear as a function of time, and then a plateau was reached. During the linear phase of the synthesis, the template and product were associated as replicative intermediates which were larger than the double-stranded RNA of the drosophila X virus genome, but the final product of the reaction was indistinguishable from the RNA genome with respect to its density, sedimentation coefficient, electrophoretic mobility, and RNase resistance. The results indicated that both strands of the genomic RNA were copied. The implications of these findings with regard to other virion polymerases are discussed.     

Chromosome breakage and xenotropic C-type virus in embryonic cultures from New Zealand black mice.

A considerable increase in chromatid and chromosome breaks, as well as excessive fragmentation and "pulverization" of whole metaphase plates was observed in embryonic fibroblast cultures from New Zealand black mice. A C-type RNA virus with a xenotropic host range was isolated from the supernatant fluid of co-cultures of NZB cells and heterologous permissive cells (SIRC cell line). One of the NZB cultures produced this virus without amplification by co-cultivation after spontaneous transformation of the cells. NZB cells are supposed to lack normal restriction of complete xenotropic virus expression and to release this endogenous virus spontaneously at a high level. It is hypothesized that the excessive chromosome damage observed in these cell cultures is related to the permanent production of virus, thus indicating a chromosome breaking effect of endogenous viruses.     

Spectral sensitivities of retinular cells measured in intact,living flies by an optical method

Summary The spectral sensitivity of the peripheral retinular cells R1–6 in nine species of intact flies was determined using non-invasive, optical measurements of the increase in reflectance that accompanies the pupillary response. Our technique is to chronically illuminate a localized region of the eye with a long wavelength beam, adjusted to bring pupillary scattering above threshold, then, after stabilization, to stimulate with monochromatic flashes. A criterion increase in scattering is achieved at each wavelength by adjusting flash intensity. Univariance of the pupillary response is demonstrated by Fig. 3.Action spectra measured with this optical method are essentially the same as the published spectral sensitivity functions measured with intracellular electrophysiological methods (Fig. 4 forCalliphora, Fig. 5 forDrosophila, Fig. 7 forEristalis, and Fig. 8 forMusca). This holds for both the long wavelength peak and the high sensitivity in the UV as was consistently found in all investigated fly species.Spectral sensitivity functions for R1–6 of hover flies (family Syrphidae) are quite different in different regions of the same eye. There can also be substantial differences between the two sexes of the same species. The ventral pole of the eye of femaleAllograpta (Fig. 10) contains receptors with a major peak at 450 nm, similar to those ofEristalis. However, the dorsal pole of the same eye contains receptors with a major peak at 495 nm, similar to those ofCalliphom. Both dorsal and ventral regions of the maleToxomerus eye, and the ventral region of the female eye, contain only the 450 nm type of R1-6 (see Fig. 12). However, the dorsal region of the female eye also contains another spectral type of receptor that is maximally sensitive at long wavelength. Eyes of both sexes ofAllograpta (Figs. 10 and 11) contain a mixture of spectral types of receptors R1-6.We thank Dr. Chris Maier of the Connecticut Agricultural Experiment Station, for determination of the Syrphidae. This work was supported by grants EY01140 and EY00785 from the National Eye Institute, U.S.P.H.S., (to GDB), by the Connecticut Lions Eye Research Foundation (to GDB), and by the Netherlands Organization for the Advancement of Pure Research (Z.W.O.), (to DGS).     

Septic superficial thrombophlebitis: a major threat from a minor lesion

Sites of insertion of peripheral intravenous catheters remain an important but often overlooked source of hospital-acquired septicemia and the most important source of staphylococcal septicemia. Septic superficial thrombophlebitis is characterized by severe local pain and is readily evident clinically. Care of the intravenous line can prevent this complication. To be diagnosed, it must be suspected. Treatment consists of removal of the intravenous line and administration of heparin and antibiotics effective against penicillinase-producing organisms. Occasionally the vein must be ligated or, preferably, removed.     

Causes and consequences of Robertsonian exchange

At least two types of Robertsonian exchange are now known in the acrocentric chromosomes of man. Both types involve breakage in the arms adjacent to the centromere. Evidence is presented for a third type of exchange, one involving breakage within the centromere itself, in the grasshopper Percassa rugifrons. In this species, which is regularly homozygous for a single fusion metacentric, the eighteen rod autosomes have small but pronounced granules at the centric end of the chromosome. When C-banded these granules show differential Giemsa staining and appear to represent centromeric chromomeres; these chromomeres are lacking in the metacentric fusion product. Equivalent fusions may have occurred in some mammal species too and possible examples of this are discussed in sheep and mice. The Percassa fusion has led to a modification in both the frequency and the distribution of chiasmata as judged by a comparison of these properties in the metacentric relative to the two next smallest rod equivalents. Comparable modifications are known to occur in other naturally occurring fusions but these changes are certainly not automatic consequences of fusion since they are not shown in at least some newly produced fusion mutants.