Interleukin 2 up-regulates its own production

It has been previously reported that a combination pair of anti-CD2 monoclonal antibodies (mAb) T11(2)+T11(3) induces a strong proliferation of T cells, which does not require the involvement of accessory cells and exogenous interleukin 2 (IL-2). More recently, we have shown that the requirement for optimal T cell proliferation depends on the combination pairs of anti-CD2 mAb used. Among them, anti-GT2+T11(1) mAb do not allow optimal proliferation of TA4 helper cloned T cells due, at least in part, to a low level of IL-2 production. This observation offered us the opportunity to study the effect of IL-2 on its own production. We show here that stimulation of cloned TA4 cells with anti-GT2+T11(1) mAb induces only a marginal level of IL-2 production. By contrast, significantly higher levels of IL-2 activity are detected in the culture supernatant of TA4 cells preincubated with recombinant IL-2 (rIL-2) before stimulation with anti-GT2+T11(1) mAb. This effect is dose-dependent over a wide range (5 to 50 IU/ml) of rIL-2 concentrations added during preincubation time. In addition, it is not due to carryover of rIL-2 bound during the preincubation time, or to lesser IL-2 consumption by these cells, or to increasing numbers of IL-2-producing cells induced by exogenous IL-2. Moreover, the observation was confirmed with IL-2 mRNA. Although neither rIL-2 nor anti-GT2+T11(1) mAb alone could induce a significant production of IL-2, rIL-2 appears to up-regulate its own production when the TA4 cells are activated by the anti-CD2 mAb-mediated second signal.     

Population Heterogeneity of Agrobacterium tumefaciens in Galls of Populus L. from a Single Nursery

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the pathogenic subpopulations.     

Biological and biochemical properties of the c-src+ gene product overexpressed in chicken embryo fibroblasts.

The c-src protein isolated from neuronal cells (pp60c-src+) displays a higher level of protein kinase activity than does pp60c-src from nonneural tissues. There are two structural alterations present in the amino-terminal half of pp60c-src+ expressed in neurons which could contribute to the enhanced activity of this form of pp60c-src: (i) a hexapeptide insert located at amino acid 114 of avian pp60c-src+ and (ii) a novel site(s) of serine phosphorylation. We characterized pp60c-src+ expressed in a nonneuronal cell type to identify factors that regulate the activity of the c-src+ protein and the importance of the neuronal environment on this regulation. The c-src+ protein overexpressed in chicken embryo fibroblasts (CEFs) displayed higher kinase activity than did pp60c-src. The major sites of phosphorylation of the c-src+ protein were Ser-17 and Tyr-527. The unique site(s) of serine phosphorylation originally identified in pp60c-src+ expressed in neurons was not detected in the c-src+ protein overexpressed in CEFs. Therefore, the hexapeptide insert is sufficient to cause an elevation in the tyrosine protein kinase activity of pp60c-src+. Our data also indicate that CEFs infected with the Rous sarcoma virus (RSV)c-src+ display phenotypic changes that distinguish them from cultures producing pp60c-src and that pp60c-src+-expressing cells are better able to grow in an anchorage-independent manner. The level of total cellular tyrosine phosphorylation in RSVc-src+-infected cultures was moderately higher than the level observed in cultures infected with RSVc-src. This level was not as pronounced as that observed in cells infected with RSVv-src or oncogenic variants of RSVc-src. Thus, pp60c-src+ could be considered a partially activated c-src variant protein much like other c-src proteins that contain mutations in the amino-terminal domain.     

Pain, paradox, and value

The author argues that "as soon as one begins to study the understanding and management of pain in science, human medicine, and veterinary medicine, one begins to encounter a variety of apparent paradoxes." He contends that these paradoxes, ten of which he identifies and discusses in this essay, are based on flawed philosophical and valuational assumptions underlying science and medicine. Rollins concludes that, as social morality increasingly has an impact on science, a new ideology will evolve that is more receptive to the moral universe and more capable of a "coherent vision of pain, one which acknowledges that the medical notion of adequacy of anaesthesia is as much a moral as a scientific one."     

Detection and partial purification of two lipases fromCandida rugosa

Summary Two distinct lipases produced byCanadida rugosa were identified and separated by a high resolution anion-exchange column (Mono Q) after an ethanol extraction of the crude lipase. From this Mono Q column, lipase I eluted at 0.05 M NaCl whereas lipase II eluted at 0.15 M NaCl. The less anionic nature of lipase I was also confirmed by native polyacrylamide gel electrophoresis as well as isoelectrophoresis. Both proteins have an apparent molecular weight of 58,000 by SDS-PAGE. The isoelectric points of lipase I and II are 5.6 and 5.8 respectively.     

Single-stranded circular DNA generated from broad host range plasmid R1162 and its derivatives

Extraction of R1162 plasmid DNA with the alkaline lysis method yields considerable amounts of single-stranded circular plasmid DNA. Destabilization of plasmid DNA is stimulated by the R1162 mob region in cis. The formation of single-stranded circular DNA is initiated at a specific site on the plasmid, presumably the origin of transfer (oriT).     

Persistently low natural killer cell activity in normal adults: immunological, hormonal and mood correlates

This current study is concerned with the identification of the incidence of persistently low natural killer (NK) cell activity in an essentially healthy population of young adults, and the characterization of the psychological profile associated with this pattern of NK activity. Eighty-eight individuals, between the ages of 18 and 44 years, were accrued to this project. Subjects were tested serially, at baseline induction into the study, and at 2 and 4 weeks follow-up. Baseline assessment included a complete physical examination and laboratory work-up in order to exclude anyone ill at the time of enrollment, and to have complete physical status information on all subjects at the time of accrual. NK activity, urinary catecholamine levels and psychological status were also assessed at baseline, and at the specified follow-up intervals. Individuals with low NK activity were operationally defined as those having NK function either below the group mean, or below the group lowest quartile, at baseline and at two follow-up assessments. Results showed that in both univariate analyses, as well as in logistic regression models, age and the perception of environmental stressors or 'hassles' predicted persistently low NK activity. Younger subjects, who perceived environmental events to which they were exposed as more serious in nature, were more likely to exhibit a persistently low NK profile over time than older individuals who perceived daily events as less important to them.     

Stereospecificity of C4 nicotinamide hydrogen transfer of the NADP-dependent glyceraldehyde-3-phosphate dehydrogenase

The stereospecificity of the reaction catalysed by the spinach chloroplast enzyme NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate: NADP+ oxidoreductase (phosphorylating), EC 1.2.1.13) with respect to the C4 nicotinamide hydrogen transfer was investigated. NADPH deuterated at the C4 HA position was synthesized using aldehyde dehydrogenase. 1H-NMR spectroscopy was used to examine the NADP+ product of the GPDH reaction for the presence or absence of the C4 deuterium atom. Chloroplast NADP-dependent glyceraldehyde-3-phosphate dehydrogenase retains the deuterium at the C4 HA position (removing the hydrogen atom), and is therefore a B (pro-S) specific dehydrogenase.     

Chromatin reorganization during emergence of malignant Friend tumors: early changes in H2A and H2B variants and nucleosome repeat length

Serial examination of five newly derived Friend murine tumors during early subcutaneous passages showed continuing changes in chromatin composition and structure over the first 10 to 20 passages followed by a period of stabilization over the subsequent 20 passages. These changes were reflected in a decrease in two major histone variants, H2A.1 and H2B.2, with a coordinate increase in histone variants, H2A.2 and H2B.1, and a changing nucleosome repeat length (NRL). The absolute values differed among the five tumors, but all five showed the same general direction of change. There was no obvious relationship among the NRL, H2A, and H2B histone variant values. A low H2A.1/H2A.2 ratio was found in Friend tumors of high malignant potential. Cell lines derived in vitro also showed directional changes in the H2A and H2B variants similar to those of their tumor cell parents, but with different kinetics. Our findings suggest that Friend tumor establishment is accompanied by an early period of chromatin reorganization marked by changes in several parameters of chromatin structure.