Fibulin is localized at sites of epithelial-mesenchymal transitions in the early avian embryo.

Fibulin is a 100-kDa calcium-binding, extracellular matrix (ECM), and plasma glycoprotein (Argraves et al., Cell 58, pp. 623-629, 1989; Argraves et al., J. Cell Biol. 111, 3155-3164). Immunoprecipitation analysis showed that antibodies against human fibulin react with an avian isoform (M(r) 100,000). The spatial and temporal distribution of fibulin was examined in the early avian embryo using immunofluorescence microscopy. In stage 15-22 quail embryos fibulin is a constituent of most basement membranes. Areas undergoing epithelial-mesenchymal transitions such as the endocardial cushions, developing myotomes, and neural crest display especially prominent immunostaining. In the early heart fibulin expression was most pronounced in the cardiac jelly at sites where endocardial cushion cells begin the migrations that lead to the formation of valvular and septal primordia. Laser scanning confocal microscopy showed extensive extracellular accumulations of fibulin on the surface of endocardial mesenchyme cells that were motile at the time of fixation (stage 19). These data suggest that enhanced deposition of fibulin at sites of epithelial-mesenchymal transitions may influence cell behavior.     

Funnel web spider venom produces spontaneous action potentials in nerve

Venom from the lethal Australian spider, $\text{Atrax robustus}$, causes fasciculation of muscles $\text{in vivo}$ and in isolated diaphragms in mice. Spontaneous end-plate potentials were recorded in muscle fibres exposed to the venom and associated spontaneous electrical activity could also be recorded from the phrenic nerve. It was proposed that the venom produces muscle fasciculation by causing abnormal, spontaneous, repetitive firing of motor nerves. The mechanism of this action was investigated in aplysia neurones. The venom produced abnormal, spontaneous, repetitive inward currents in voltage clamped neurones and changed the current-voltage characteristics of the surface membrane. It is suggested that the basic mode of action of Funnel-web venom is to change the electrical field in nerve membrane.     

Infection of CV1 cells expressing the polyoma virus middle T antigen or the SV40 agnogene product with simian virus 40 host-range mutants

Summary SV40 viruses bearing mutations at the carboxy-terminus of large T antigen exhibit a host-range phenotype: such viruses are able to grow in BSC monkey kidney cells at 37° C, but give at least 10 000-fold lower yields than wild type virus in BSC cells at 32° C or in CV1 monkey kidney cells at either temperature. The block to infection in the nonpermissive cell type occurs after the onset of viral DNA replication. Infectious progeny virions are produced at very low efficiency. Although capsid proteins are synthesized at decreased levels, this does not account for the magnitude of the defect. Presumably some step of virion assembly or maturation is affected in these mutants. We have previously reported that the viral agnogene product, a protein throught to be involved in viral assembly or release, fails to accumulate in CV1 cells infected with host-range mutants. In polyoma virus the middle T antigen plays a role in virion maturation by influencing the phosphorylation of capsid proteins. In this communication we show that host-range mutants fail to undergo productive infection of CV1 cells expressing middle T antigen. These mutants do form plaques on an agnoprotein-expressing cell line. However, the agnoprotein does not seem to act by correcting the mutational block but rather increases the efficiency of plaque formation. This work was supported by grants CA40586 and BRSG 2S07RR07084-23 to J. M. P. and grant CA33079 to L. T., from the National Institutes of Health, Bethesda, MD.     

Characterizing biological aerosol in a chamber: an approach to estimation of viable organisms in a single biological particle

There are practical and valid reasons topresent biological field trial referenceresults as agent containing particles per literof air (ACPLA). However, workers in biologicalaerosol research have a need to know how manyviable individual organisms are contained in asingle particle of a given diameter. Anecdotalevidence may exist suggesting that the task hasbeen accomplished but without a way toreplicate the measurements, it is difficult toaccept unsubstantiated claims. It is verydifficult to declare a finite number thatsatisfies all the experimental requirements, asthe problem is a statistical probability issue. This paper describes a method for estimatingthe number with practical instructions forreplicating the work in other laboratories.The test aerosol was contained in a 90 m³chamber at concentrations as low as 5 ACPLA. Amodified version of slit sampler collectedviable particles. A statistical method was usedto demonstrate sampling predictability at 95%confidence level. By using glass fiber filtersmounted in a dichotomous sampler, samplingefficiencies were estimated for a variety ofcommon aerosol collectors. The accumulated datapermitted the estimation of the number ofviable spores per particle. For a 2.5 to4 µm particle, arguments have beenpresented for considering 4.5 as the mostprobable ACPLA value.     

Use of antisera against bovine (NCDV) and simian (SA11) rotaviruses in ELISA to detect different types of human rotavirus.

Two ELISA systems for the detection of human rotaviruses were developed. In the first system antibodies to Nebraska calf diarrhea virus (NCDV) were used for coating the solid matrix and for the preparation of the enzyme conjugate. In the second system antibodies to human rotavirus and antibodies to simian rotavirus (SA11) were used for coating the solid matrix and for the preparation of the enzyme conjugate respectively. The second ELISA system proved to have a broader spectrum for the detection of human rotaviruses. By using the two ELISA systems, the different types of human rotavirus could be distinguished. The ELISA tests developed were 8 to 64 times as sensitive as electron microscopy (EM) and (or) counterimmunoelectrophoresis (CIEP). The antigen detected by ELISA was shown to be different from that detected by the hemagglutination test.     

Osmoregulation inThiobacillus ferrooxidans: Stimulation of iron oxidation by proline and betaine under salt stress

The osmoregulatory mechanisms of chemolithotrophs have not previously been investigated. We tested glutamic acid, proline, and betaine as potential osmorprotectants for the acidic chemolithotrophThiobacillus ferrooxidans. Salt stresses were imposed by NaCl, KCl, Na₂SO₄, and K₂SO₄ in separate experiments. Proline enhanced rates of iron oxidation in all saltstressed cultures, whereas betaine acted as an osmoprotectant only in sulfate-salt-stressed cultures and in cultures severely stressed by NaCl (0.3–0.4M). Glutamic acid inhibited iron oxidation in all cases.