The CD3-gamma and CD3-delta subunits of the T cell antigen receptor can be expressed within distinct functional TCR/CD3 complexes.

The T cell receptor for antigen (TCR) consists of two glycoproteins containing variable regions (TCR-alpha/beta or TCR-gamma/delta) which are expressed on the cell surface in association with at least four invariant proteins (CD3-gamma, -delta, -epsilon and -zeta). CD3-gamma and CD3-delta chains are highly homologous, especially in the cytoplasmic domain. The similarity observed in their genomic organization and their proximity in the chromosome indicate that both genes arose from duplication of a single gene. Here, we provide several lines of evidence which indicate that in human and murine T cells which expressed both the CD3-gamma and CD3-delta chains on their surface, the TCR/CD3 complex consisted of a mixture of alpha beta gamma epsilon zeta and alpha beta delta epsilon zeta complexes rather than a single alpha beta gamma delta epsilon zeta complex. First, a CD3-gamma specific antibody failed to co-immunoprecipitate CD3-delta and conversely, several CD3-delta specific antibodies did not coprecipitate CD3-gamma. Secondly, analysis of a panel of human and murine T cell lines demonstrated that CD3-gamma and CD3-delta were expressed at highly variable ratios on their surface. This suggested that these chains were not expressed as a single complex. Thirdly, CD3-gamma and CD3-delta competed for binding to CD3-epsilon in transfected COS cells, suggesting that CD3-gamma and CD3-delta formed mutually exclusive complexes. The existence of these two forms of TCR/CD3 complexes could have important implications in the understanding of T cell receptor function and its role in T cell development.     

Enhancement of susceptibility of HSV-1-infected cells to natural killer lysis by interferon

The effect of interferon (IFN) on the natural killer (NK) activity of human PBL against HSV-1-infected HeLa cells was studied. Human PBL from several individuals did not consistently show a preferential lysis of HSV-1-, vaccinia-, or adenovirus type 5-infected cells with respect to uninfected HeLa cells. Treatment with IFN of effector PBL increased their lytic activity but did not alter the degree of preference on the lysis of the target cells shown by untreated PBL. Pretreatment with IFN of HSV-1-infected HeLa cells increased their susceptibility to lysis 5- to 10-fold. In contrast, identical pretreatment of the uninfected, adenovirus type 5- or vaccinia virus-infected HeLa cells before the assay decreased their susceptibility to NK lysis. This effect was not likely to be due to a block of the viral replication because other inhibitors like mitomycin C did not have the same effect. All target cells induced IFN synthesis in effector PBL cells. A similar level of IFN was induced by HSV-1-infected or uninfected HeLa cells. Pretreatment with IFN of HSV-1-infected, but not uninfected, HeLa cells induced 5 to 10 times more IFN by PBL, in good correlation with the increase in lytic activity. PBL treated with IFN, however, in conditions to give maximal stimulation of NK activity, presented the same preferential lysis of HSV-1-infected HeLa cells and synthesized similar levels of IFN as untreated PBL. In addition, HSV-1-infected HeLa cells were killed through different target structures than uninfected cells. Taken together, our results indicate an effect of IFN at the level of the NK target structures in HSV-1-infected HeLa cells by increasing either their number or, more likely, their affinity for NK cells independent of the effect of IFN in the effector cells or as an antiviral agent.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

Proteins synthesized by inducer T cells: evidence for a mitogenic peptide shared by inducer molecules that stimulate different cell types

Inducer T lymphocytes synthesize and secrete peptides that stimulate growth and differentiation of many cell types, including lymphocytes and monocytes that kill foreign organisms, B lymphocytes, mast cells and hematopoietic precursor cells. To define these inducer molecules more precisely, we have generated clones of these T cells as a source of homogeneous material for biochemical analysis. These clones synthesize peptides that stimulate T and B cells to divide and that also induce the latter cells to secrete immunoglobulin. Inducer cells synthesize a 14 kilodalton growth polypeptide that stimulates T and B lymphocytes, as well as other cell types, to divide. This 14 kilodalton peptide is normally associated with different, larger peptides that appear to focus its mitogenic activity to one or another target cell.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.     

Evidence of a landlocked reproducing population of the marine pejerrey Odontesthes argentinensis (Actinopterygii; Atherinopsidae)

In South America, the order Atheriniformes includes the monophyletic genus Odontesthes with 20 species that inhabit freshwater, estuarine and coastal environments. Pejerrey Odontesthes argentinensis is widely distributed in coastal and estuarine areas of the Atlantic Ocean and is known to foray into estuaries of river systems, particularly in conditions of elevated salinity. However, to our knowledge, a landlocked self-sustaining population has never been recorded. In this study, we examined the pejerrey population of Salada de Pedro Luro Lake (south-east of Buenos Aires Province, Argentina) to clarify its taxonomic identity. An integrative taxonomic analysis based on traditional meristic, landmark-based morphometrics and genetic techniques suggests that the Salada de Pedro Luro pejerrey population represents a novel case of physiological and morphological adaptation of a marine pejerrey species to a landlocked environment and emphasises the environmental plasticity of this group of fishes.     

Economic evaluation of water loss saving due to the biological control of water hyacinth at New Year’s Dam,Eastern Cape province,South Africa

Water hyacinth Eichhornia crassipes is considered the most damaging aquatic weed in the world. However, few studies have quantified the impact of this weed economically and ecologically, and even fewer studies have quantified the benefits of its control. This paper focuses on water loss saving as the benefit derived from biological control of this plant between 1990 and 2013 at New Year’s Dam, Alicedale, Eastern Cape, South Africa. Estimates of water loss due to evapotranspiration from water hyacinth vary significantly; therefore, the study used three different rates, high, medium and low. A conservative raw agriculture value of R 0.26 per m³ was used to calculate the benefits derived by the water saved. The present benefit and cost values were determined using 10% and 5% discount rates. The benefit/cost ratio at the low evapotranspiration rate was less than one, implying that biological control was not economically viable but, at the higher evapotranspiration rates, the return justified the costs of biological control. However, at the marginal value product of water, the inclusion of the costs of damage to infrastructure, or the adverse effects of water hyacinth on biodiversity, would justify the use of biological control, even at the low transpiration rate.