INTERLEUKIN 10 PROTECTS ACTIVATED HUMAN T LYMPHOCYTES AGAINST GROWTH FACTOR WITHDRAWAL-INDUCED CELL DEATH BUT ONLY ANTI-FAS ANTIBODY CAN PREVENT ACTIVATION-INDUCED CELL DEATH

Interleukin 10 (IL-10) is a pleiotropic T cell-derived cytokine best known for its negative regulatory effects on T cell immunity. It inhibits responses indirectly by downregulating expression of major histocompatibility complex (MHC) molecules and co-stimulatory molecules such as CD80 on antigen presenting cells as well as directly via its effects on responding cells. On the other hand, IL-10 has been shown to protect activated T cells against apoptosis caused by withdrawal of the major growth factor, IL-2, and allow proliferation of T cells in the absence of IL-2. However, we show here that this IL-10-dependent, IL-2 independent proliferative response is short-lived, and that IL-10-responsive T cells cannot multiply in its presence. Moreover, inclusion of exogenous IL-10 in clonal cultures propagated with IL-2 results in suppression of their growth. These findings, together with the observation that IL-10 fails to protect T cells against activation-induced cell death (a fas/fas-ligand-dependent phenomenon blocked only by certain antagonistic anti-fas reagents), suggest that the negative regulatory effects of IL-10 outweigh the upregulated proliferation observed on some T cell clones (TCC) in the absence of IL-2.     

Noncancer Risk Assessment: A Probabilistic Alternative to Current Practice

Based on imperfect data and theory, agencies such as the United States Environmental Protection Agency (USEPA) currently derive “reference doses” (RfDs) to guide risk managers charged with ensuring that human exposures to chemicals are below population thresholds. The RfD for a chemical is typically reported as a single number, even though it is widely acknowledged that there are significant uncertainties inherent in the derivation of this number.

In this article, the authors propose a probabilistic alternative to the EPA's method that expresses the human population threshold as a probability distribution of values (rather than a single RfD value), taking into account the major sources of scientific uncertainty in such estimates. The approach is illustrated using much of the same data that USEPA uses to justify their current RfD procedure.

Like the EPA's approach, our approach recognizes the four key extrapolations that are necessary to define the human population threshold based on animal data: animal to human, human heterogeneity, LOAEL to NOAEL, and subchronic to chronic. Rather than using available data to define point estimates of “uncertainty factors” for these extrapolations, the proposed approach uses available data to define a probability distribution of adjustment factors. These initial characterizations of uncertainty can then be refined when more robust or specific data become available for a particular chemical or class of chemicals.

Quantitative characterization of uncertainty in noncancer risk assessment will be useful to risk managers who face complex trade-offs between control costs and protection of public health. The new approach can help decision-makers understand how much extra control cost must be expended to achieve a specified increase in confidence that the human population threshold is not being exceeded.     

Use of two freezing extenders to cool stallion spermatozoa to 5 degrees C with and without seminal plasma

Motion characteristics of cooled stallion spermatozoa in 2 freezing extenders were studied. Ejaculates from 8 stallions were split into treatments and cooled in thermoelectric cooling units at each of 2 rates. Cooling started at 37 degrees C for Experiments 1 and 3 and at 23 degrees C for Experiments 2 and 4, at a rate of -0.7 degrees C/min to 20 degrees C and from 20 to 5 degrees C, at either -0.05 degrees C/min (Rate I) or -0.5 degrees C/min (Rate II). Percentages of motile (MOT) and progressively motile spermatozoa (PMOT) were determined at 6, 24 and 48 h. Treatments in Experiment 1 were modified skim milk extender (SM); SM + 4% egg yolk (EY); SM + 4% glycerol (GL); and SM + 4% egg yolk + 4% glycerol (EY + GL). At 24 and 48 h, MOT and PMOT were lowest (P < 0.05) for spermatozoa extended in SM + EY; spermatozoa in SM + GL had the highest MOT and PMOT. Thus, glycerol partially protected spermatozoa against the effects of cooling after long-term storage. Treatments in Experiment 2 were SM, semen centrifuged and pellet resuspended in SM (SMc), SM + EY, and semen centrifuged and pellet resuspended in SM + EY (EYc). Spermatozoa in SM + EYc had the highest (P < 0.05) PMOT at 24 h and MOT and PMOT at 48 hours. Spermatozoa in SM + EY (not centrifuged) had the lowest MOT and PMOT at 24 and 48 h, respectively. There was a detrimental interaction between egg yolk and seminal plasma. Extenders in Experiment 3 were Colorado extender (CO3), CO3 + 4% egg yolk (EY), CO3 + 4% glycerol (GL), and CO3 + 4% egg yolk + 4% glycerol (EY + GL). Spermatozoa in CO3 + EY had the lowest (P < 0.05) PMOT at 24 and 48 h. CO3 did not protect spermatozoa cooled in the presence of seminal plasma. Therefore, in Experiment 4 we tested CO3 with seminal plasma present (control) and semen centrifuged and pellet resuspended in CO3 (CO3c), CO3 + EY (EYc), CO3 + GL (GLc) and CO3 + EY + GL (EY + GLc). Spermatozoa in CO3 had the lowest (P < 0.05) MOT and PMOT at all time periods, which suggested a detrimental interaction of this extender with seminal plasma.     

Geographic and between-generation variation in the parasitoid communities associated with an invading gallwasp,Andricus quercuscalicis (Hymenoptera: Cynipidae)

The knopper gallwasp Andricus quercuscalicis Burgsdorf 1783 (Hymenoptera: Cynipidae) has invaded western and northern Europe from southern and eastern Europe over the last 400 years. A. quercuscalicis has two alternating generations, which differ in phenology, structure, and host oak species. This study describes geographic variation in the community in the tiny catkin galls of the sexual generation on Turkey oak, Quercus cerris, and compares the patterns obtained with those in the community attacking the alternate agamic generation. As predicted from considerations of parasitoid recruitment to the communities of invading phytophagous insects (Cornell and Hawkins 1993), in its native range the sexual generation shows (1) higher parasitoid community species richness, (2) higher total mortality due to parasitoid attack and (3) a higher ratio of specialist to generalist parasitoid species than is evident in the invaded range. Counter to predictions, there is no indication that parasitoid community richness in the invaded range has increased with time since the arrival of the new host. Higher host mortality in the native range is due principally to a single specialist, Aulogymnus obscuripes Mayr 1877 (Hymenoptera: Eulophidae), and is not distributed evenly among parasitoid species which attack the gall-former only in this area. This contrasts with the community in Britain, where three principal generalist parasitoids cause approximately equal mortalities. The agamic gall contains a taxonomically and structurally diverse guild of parasitoid and inquiline species, associated with the changing resource provided by a large, long-lived, complex gall. In contrast, the sexual community includes a taxonomically and structurally narrow guild, associated with a resource which is structurally simple, small in size and short-lived. No parasitoid species attacks the gall-former in both generations. Surprisingly, in spite of these differences in the nature of the gall resource in the two generations, over their entire range (native and invaded) the parasitoid guilds of the two are equally species rich.     

Importance of seed Zn content for wheat growth on Zn-deficient soil

Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3 to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO₃ (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source. Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand not buffered with CaCO₃. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the nutrient solutions. In quartz sand buffered with CaCO₃ ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased. These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched shoots. The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor     

Inositol lipid-mediated signalling in response to endothelin and ATP in the mammalian testis

Molecular and Cellular Biochemistry - The testis is a complex organ in which local control is achieved by signalling between its constituent cells. Herein we describe the responses of cultured rat...     

Mutational analysis of the RecA protein L1 region identifies this area as a probable part of the co-protease substrate binding site

Previous mutational analysis of the L1 region of the RecA protein suggested that Gly-157 and Glu-158 are 'hot-spots' for the occurrence of constitutive LexA co-protease mutants (coprt^c). In the present study, we clearly establish that position 157 is a hot-spot for the occurrence of such mutants, as 12 of 14 and 10 of 14 substitutions result in this phenotype for UmuD and LexA cleavage respectively. The frequency of such mutations at position 158 is somewhat lower, 8 of 13 and 5 of 13 for UmuD and LexA respectively. Comparison of the UmuD vs. LexA co-protease activity for all single mutants with substitutions at positions 154, 155, 156, 157 and 158 (47 in total) reveals that, although there is good agreement among most mutants regarding their ability to cleave both LexA and UmuD, there are two in particular (Glu-154→Asp and Glu-154→Gln) that show a clear preference for cleavage of UmuD. We also show that three second-site mutations that completely suppress coprt^c activity toward LexA have little or no effect on the coprt^c activity of the primary mutant toward UmuD. In addition, we observe a high frequency of second-site suppressor mutations, suggesting a functional interaction among side-chains in this region. Together, these results support the idea that the L1 region of RecA makes up part of the co-protease substrate-binding site.     

The purified myxoma virus gamma interferon receptor homolog M-T7 interacts with the heparin-binding domains of chemokines.

The myxoma virus T7 protein M-T7 is a functional soluble gamma interferon receptor homolog that has previously been shown to bind gamma interferon and inhibit its antiviral activities in a species-specific manner, but gene knockout analysis has suggested a further role for M-T7 in blocking leukocyte influx into infected lesions. We purified M-T7 to apparent homogeneity and showed that M-T7 is an N-linked glycoprotein that appears to be a stable homotrimer with a molecular mass of approximately 113 kDa in solution. M-T7, in addition to forming inhibitory complexes with rabbit gamma interferon, was also shown to bind to human interleukin-8, a prototypic member of the chemokine superfamily. Moreover, M-T7 was able to interact promiscuously with all members of the CXC, CC, and C chemokine subfamilies tested. Binding of human RANTES to M-T7 can be competed by rabbit gamma interferon and also by cold RANTES competitor with a 50% inhibitory concentration of 900 nM. Although M-T7 retains binding to a number of interleukin-8 N-terminal (ELR) deletion mutants, binding to mutants containing deletions in the C-terminal heparin-binding domain of interleukin-8 is abrogated. Furthermore, heparin effectively competes the interaction of M-T7 with the chemokine RANTES but not with rabbit gamma interferon. We propose that this novel M-T7 interaction with members of the chemokine superfamily may be facilitated through the conserved heparin-binding domains found in a wide spectrum of chemokines and that M-T7 may function by modulating chemokine-glycosaminoglycan interactions in virus-infected tissues.     

Clinical and Molecular Characterization of Patients with Distal 11q Deletions

Jacobsen syndrome is caused by segmental aneusomy for the distal end of the long arm of chromosome 11. Typical features include mild to moderate psychomotor retardation, trigonocephaly, facial dysmorphism, cardiac defects, and thrombocytopenia, though none of these features are invariably present. To define the critical regions responsible for these abnormalities, we studied 17 individuals with de novo terminal deletions of 11q. The patients were characterized in a loss-of-heterozygosity analysis using polymorphic dinucleotide repeats. The breakpoints in the complete two-generation families were localized with an average resolution of 3.9 cM. Eight patients with the largest deletions extending from 11q23.3 to 11qter have breakpoints, between D11S924 and D11S1341. This cytogenetic region accounts for the majority of 11q⁻ patients and may be related to the FRA11B fragile site in 11q23.3. One patient with a small terminal deletion distal to D11S1351 had facial dysmorphism, cardiac defects, and thrombocytopenia, suggesting that the genes responsible for these features may lie distal to D11S1351. Twelve of 15 patients with deletion breakpoints as far distal as D11S1345 had trigonocephaly, while patients with deletions distal to D11S912 did not, suggesting that, if hemizygosity for a single gene is responsible for this dysmorphic feature, the gene may lie distal to D11S1345 and proximal to D11S912.