Oligosaccharide composition of an influenza virus hemagglutinin with host-determined binding properties

We have previously reported that the binding properties of the hemagglutinin (HA) of the WSN-F strain of influenza A are affected by the cells in which the virus is grown (Crecelius, D. M., Deom, C. M., and Schulze, I.T. (1984) Virology 139, 164-177); at 37 degrees C chick embryo fibroblast-grown F virus has a greater affinity for host cells than does the same virus grown in Madin-Darby bovine kidney (MDBK) cells. In an attempt to explain this host-determined property, we have characterized the carbohydrate put onto the viral HA by these two cells. Experiments using tunicamycin indicate that the HA made by MDBK cells contains about 4000 daltons of carbohydrate in excess of that on the HA from chick embryo fibroblast. Serial lectin affinity chromatography of the asparagine-linked oligosaccharides on the HA subunits, HA1 and HA2, detected a number of host-dependent differences in the complex oligosaccharides. Both HA1 and HA2 from MDBK cells contained more highly branched (i.e. tri- and tetraantennary) complex oligosaccharides than did the subunits from chick embryo fibroblasts. In addition, the HA subunits from the two sources differed in the amount of galactose-containing "bisected" complex oligosaccharides and in the presence of certain fucosylated triantennary oligosaccharides. Profiles of the asparagine-linked oligosaccharides from the host cells did not show these differences, indicating that the HA subunit profiles were not necessarily representative of the structures found on the cellular glycoproteins. The data support the conclusion that bulky oligosaccharides on the MDBK-HA subunits of WSN-F reduce the affinity of the virus for cellular receptors.     

The murine homeo box gene product, Hox 1.1 protein, is growth-controlled and associated with chromatin

In order to gain insight into the function of the Hox 1.1 gene, we studied the expression of the murine homeo box gene product, the Hox 1.1 protein. Monoclonal antibodies were raised against synthetic peptides of the Hox 1.1 protein to study the localization and expression pattern of this protein under various culture conditions. By means of indirect immunofluorescence we localized the Hox 1.1 protein to the nucleus in differentiated F9 and NIH 3T3 cells. During mitosis the protein was found to be associated with chromatin. Confluent NIH 3T3 cells harbored little if any Hox 1.1 protein. After "wounding" the cells in this confluent monolayer, we observed an induction of the expression of the Hox 1.1 protein. However, addition of insulin to F9 and contact-inhibited NIH 3T3 cells led to an increase of the Hox 1.1 RNA and protein expression. Thus, the induction of the Hox 1.1 protein is associated not only with the differentiation of embryonal carcinoma (EC) cells, but may also correlate with stages of cell growth.     

Microtubule dynamics in interphase cells

The sites of microtubule growth and the kinetics of elongation have been studied in vivo by microinjection of biotin-labeled tubulin and subsequent visualization with immunocytochemical probes. Immunofluorescence and immunoelectron microscopy demonstrate that injected biotin-labeled subunits are incorporated into new segments of growth which are contiguous with unlabeled microtubules. Rapid incorporation occurs by elongation of existing microtubules and new nucleation off the centrosome. The growth rate is 3.6 micron/min and is independent of the concentration of injected labeled tubulin. This rate of incorporation together with turnover of existing microtubules leads to approximately 80% exchange in 15 min. The observed kinetics and pattern of microtubule turnover allow for an evaluation of the relevance of several in vitro models for steady-state dynamics to the in vivo situation. We have also observed a substantial population of quasi-stable microtubules that does not exchange subunits as rapidly as the majority of microtubules and may have specialized functions in the cell.     

Identification of the Cloned Gene for the Murine Transplantation Antigen H-2Kb by Hybridization with Synthetic Oligonucleotides

The H-2K^b gene is a member of the large major histocompatibility complex class I gene family. Since many members of this family cross-hybridize with class I cDNA probes, the cloned H-2K^b gene was identified by hybridization with specific oligonucleotide probes. This clone was definitively shown to encode the H-2K^b polypeptide by partial DNA sequencing and by serological and tryptic peptide analyses of the expressed product.     

Electron Microscopy of Tissue Culture Cells Infected with Brucella abortus

Thin sections of hamster kidney tissue cultures were examined by electron microscopy over a 7-day period after infection with Brucella abortus 3183. Numerous bacteria and structures resembling L-forms were present both intracellularly and extracellularly after the first 24 hr of infection. Most intracellular microorganisms were enclosed by a cytoplasmic membrane, but in a few instances no limiting membrane was detected. After 4 to 7 days, fewer microorganisms were present, and most normal-appearing bacteria were intracellular, particularly in antibiotic-treated cultures. Structures typical of Brucella L-forms were extracellular at the latter time intervals. Several structures were observed in cells from infected cultures whose relationship to the infecting organisms is not known. These consisted of various membranous structures within cytoplasmic vacuoles, myelin-like structures surrounding occasional intracellular organisms, and small bodies present within vacuoles and extracellularly. The latter structures observed throughout the experimental period appeared to occur more frequently as the duration of the infection increased.     

Concentrations of Indole-3-acetic Acid and Its Esters in Avena and Zea

An isotope-dilution method has been developed for the assay of free indole-3-acetic acid and ester indole-3-acetic acid as measured by indole-3-acetic acid liberated by mild alkaline hydrolysis. Application of this method to seedlings of Avena sativa and Zea mays indicates the upper limit of free indole-3-acetic acid in Avena to be about 16 μg per kg and in Zea, about 24 μg. The amount of 1 n alkali-labile indole-3-acetic acid in Zea is about 330 μg per kg and there is very little 1 n alkali-labile IAA in Avena. A chemical characterization of the indole-3-acetic acid of Avena and a confirmation of the chemical characterization of the indole-3-acetic acid of Zea is presented.     

An empirical model of net photosynthesis for the desert plant Hammada scoparia (Pomel) Iljin

Summary An empirical model for describing daily courses of net photosynthesis in Hammada scoparia is being developed. The model is based on the functional relationships, by which various environmental factors affect the photosynthetic activity and which can be measured by experiment in the field. In a sequence of steady-states daily courses of net photosynthesis are predicted during a growing season considering the variability of the physiological states and the capacity for regulative adaptations. The rate of net photosynthesis at a certain date is calculated from the maximal rate of CO₂ uptake being expected at that season and from the effects of light, temperature, and air humidity which are scaled from 0 to 1. All factors are connected multiplicatively. The light function accounts for the seasonal changes in the light curve, the temperature function is based on the seasonal shift of the temperature optimum, and the humidity function considers the increasing sensitivity of the stomatal humidity response at increasing water stress. The model is built to be a submodel of a general ecosystem model, where various other submodels (i.e. water stress model, phenology model) are supplied. The present model is tested by predicting daily courses at extreme climatic conditions during the year and by comparing the predicted values of gas exchange with values being measured in an independent experimental procedure. The result shows that the model is able to simulate the natural behaviour of Hammada scoparia during the growing and dry season of a desert habitat. The problems of incorporating the influence of water stress, the interaction of the various factors, and the phenological aspect of the photosynthetic activity is being discussed.