Construction and expression of retroviruses encoding dual drug resistance genes in human umbilical cord blood CD34+ cells

A series of retroviral vectors encoding human mdr1 gene alone as well as in combination with either human mgmt gene or human mutant Ser31-dhfr gene are engineered. The resultant retroviruses are used to transduce human umbilical cord blood CD34+ cells. It has been shown that expression of dual drug resistance genes in transduced cells confers a broad range of resistance to both kinds of corresponding drugs. These data suggest a rationale for the use of such double chemoresistance gene constructs in an in vivo model in which transduced hematopoietic cells will acquire multiple protection against the cytotoxic side effects of combination chemotherapy and may have future application in chemoprotection of normal tissues, thus killing tumor cells more effectively.     

An initial exploration of the relevance of complexity theory to group research and practice

The purpose of this paper is to describe some findings from an ongoing investigation of naturally occurring groups and to discuss them utilizing concepts from complexity theory. The paper proposes that groups meet the criteria outlined by complexity theorists for designation as complex adaptive systems. Research evidence from an ongoing investigation of group dynamics and development is provided to support this conclusion. The paper concludes that integrating concepts from complexity theory and group development theory provides a different way of thinking about groups, group research, and group consultation and intervention.     

Lysozyme is a component of human vascular elastic fibers

Lysozyme has been demonstrated in the elastic fibers of normal human arteries and veins by the peroxidase-antiperoxidase technique. Preliminary trypsinization of paraffin sections is necessary to unmask the immunoreactive lysozyme.     

Respiration characteristics differ among cheatgrass ( Bromus tectorum L.) populations

Cheatgrass ( Bromus tectorum L.) is a dominant weed that has increased the frequency of wildfire in the Great Basin since its introduction about 100 yr ago. This study examines characteristics of respiratory metabolism in several different populations. Seeds from 6 populations were germinated and metabolic heat rates (q) and dark respiration rates (R co2 ) of all seedlings were measured calorimetrically at 15° and 25° C or (for 3 populations) at 5° intervals from 5° to 35° C. Growth rates, substrate carbon conversion efficiencies, and Arrhenius temperature coefficients were calculated from the data. Results show that cheatgrass metabolism is most efficient at temperatures near 0° C; at temperatures above 20-25° C, efficiency goes to zero. Cheatgrass populations differ in their temperature dependencies of substrate carbon conversion efficiency and predicted growth rate. Measurements of respiratory heat and CO 2 rates as functions of temperature can be made relatively quickly and used to aid understanding of metabolic adaptation by invasive and native species to the environment.     

Freshwater sponges (Porifera: Spongillidae) of western Montana

Between May 1992 and April 1996, freshwater sponges (Porifera: Spongillidae) were collected at 24 sites, distributed among 6 sub-major drainage basins in western Montana, to determine the species present. Water samples also were analyzed from 16 of these sites and from 9 sites at which no sponges were detected to characterized sponge habitats chemically. Three species of sponges were identified: Ephydatia muelleri (Em), Eunapius fragilis (Ef), and Spongilla lacustris (Sl). A 4th type of specimen was present at 2 sites but could not be identified because of the absence of gemmules and gemmoscleres. At 46% of the sites containing sponges, more than 1 specimen type was present. Sponges were most commonly found near outlets of lakes, attached to sides or undersides of submerged rocks and logs. They appeared as encrusting (Em, Ef, Sl), lobate (Em), and fingerlike (Sl) growths, varying in color from light tan to green. Dimensions of the spicules varied greatly within each species and expanded previously recorded ranges. No factors limiting sponge distribution were identified, but ranges of conductivity (Em) and of silica (Em, Sl), calcium (Em), and magnesium (Em) concentrations were expanded beyond those reported previously.