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AbstractThe benefits attributed to field trips by science educators are: social development; observation and perception skills; giving meaning to learning; providing first-hand experience and stimulating interest and motivation. Arguably, the “real value” of field work is attributed by students. In this study, 100 first-year students took part in an analysis of the value of a residential field trip. The field trip was a purposeful combination of personal development and academic activities. Pairwise comparison showed that the attributed value score for “Personal and Social Development” was significantly higher than scores for “Provide First-hand Experience” and “Observation and Perception Skills”. The attributed value for “Stimulate Interest and Motivation in the Subject” also scored more highly than “Provide First-hand Experience”, and “Observation and Perception Skills”; “Give meaning to Learning” was significantly higher than that for “Observation and Perception Skills”. In addition, the “educator” was also able to significantly improve students’ scores for “Stimulate Interest and Motivation”. This insight into students’ perceptions of field work recasts our thinking as educators; social capital is a key factor in student persistence and subsequence academic success. Field trips should be considered a valuable addition to retention strategies in a way that is tangible for students themselves.

The efficacy of immunizing with a combination of simian immunodeficiency virus (SIV) Nef vaccines was evaluated. Four vaccinates received three intradermal immunizations with recombinant vaccinia virus that expressed SIV Nef, followed by three intramuscular immunizations with rDNA also expressing SIV Nef. Finally, the four vaccinates received two subcutaneous boosts with recombinant SIV Nef protein. This immunization protocol elicited anti-Nef antibodies in all of the vaccinates as well as specific proliferative responses. However, specific cytotoxic T cell responses were not detected before virus challenge. All vaccinates were challenged intravenously with 10 MID50 of SIVmacJ5 along with four controls. All eight subjects became infected after SIV challenge and there were no group-specific differences in virus load as measured by virus titration and vRNA analysis. The results of this study support indirectly the report from Gallimore and colleagues (Nat Med 1995;1:1667) suggesting that CD8+ T lymphocyte responses are required for Nef-based vaccines to restrict SIV infection. If Nef-based vaccines are to be beneficial in controlling infection with immunodeficiency viruses, then it will be necessary to develop more effective immunization protocols that elicit potent CD8+ cell responses reproducibly.

Eleven monoclonal antibodies (MAbs) to SIV Nef were produced and characterized. Five antibody-binding sites on SIV Nef were identified on the basis of the reactivity of the antibodies with recombinant proteins. Two of the five epitopes were defined using overlapping peptides. A further three epitopes could not be defined with peptides but all antibodies reacted in Western blot, suggesting that the epitopes were at least partially conformation dependent. Antibodies in two of the five epitope groups were further differentiated by competition analysis. The panel of MAbs described is able to distinguish between a number of recombinant Nef proteins currently under investigation in vivo in macaques. Two of the MAbs described are able to distinguish between the Nef protein from pathogenic (J5) and attenuated (C8) strains of SIV, thus providing useful tools for studying the relevance of the Nef protein in the pathogenesis of SIV infection. In FACScan analysis two of the MAbs, KK70 and KK75, were used to identify an in vitro-induced mutation in J5 Nef grown in C8166 cells. Sequence analysis of the phenotypic variants identified a mutation of the tryptophan (TGG) at amino acid 214 to a stop codon (TGA), thus truncating the Nef protein. The functional significance of this observation remains unclear but highlights the need to interpret data with caution if virus has been cultured in vitro even for a short period of time.

Intradermal injections of normal saline and different concentrations of bradykinin were made into the forearms of healthy volunteers. Cutaneous blood flow was recorded just outside and over the centre of the weals by laser Doppler flowmetry (LDF), and flare area and weal volume were measured. There were concentration-related changes in the mean LDF output adjacent to the weal, flare area and weal volume. LDF recordings performed over the centre of the weals, however, failed to show any dose-response relationship. When similar concentrations of bradykinin were injected intradermally and the skin response measured by the above parameters, there was less variation in the mean LDF output adjacent to the weal than flare or weal measurements. The non-invasive technique of LDF is a useful, objective and sensitive technique of quantifying the skin blood flow changes induced by intradermal bradykinin and provides an alternative method of quantifying skin response to intradermal bradykinin to measurement of flare or weal sizes.

The effect of human papillomavirus (HPV) and activated oncogenes on the growth and morphology of primary baby mouse kidney (BMK) cells has been studied. Early region DNA from HPV types 16, 18, 31, and 33, but not type 6, under the transcriptional control of a heterologous, retroviral promoter cooperated with EJ-ras to produce cell lines that gave rise to carcinomas in syngeneic immunocompetent animals. The same HPV constructs, when cotransfected with a plasmid containing sequences from the Finkel-Biskis-Jinkins murine sarcoma virus provirus (v-fos), produced cell lines that were tumorigenic in nude mice. None of the other activated oncogenes tested, including activated c-myc, displayed any activity with HPV in this cotransfection assay. When the heterologous promoter was replaced by the homologous HPV16 promoter, the transforming effect of HPV16 with either EJ-ras or v-fos required the presence of either glucocorticoid or progestogen. Cell lines derived from transfection of HPV16 with either EJ-ras or v-fos required the continued presence of hormones for proliferation.

The Escherichia coli rpsU-dnaG-rpoD operon contains an internal transcription terminator T1 located in the intergenic region between the rpsU and dnaG genes (Smiley et al. 1982). By cloning T1 as a small 127 bp fragment into the terminator probe plasmid pDR720 between the trp operator promoter and the assayable galK gene, it was shown that T1 acts as a strong transcription terminator, comparable in strength to the 3' operon terminator T2. However, an operon sequence that occurs 5' to T1 within the coding region of the rpsU gene and which has homology with the lambda nut site, (Lupski et al. 1983) when placed 5' to T1 in the pDR720 plasmid construct, modifies transcription through T1 allowing expression of the galK gene. This sequence, called the dnaG nut site also modifies the termination activity of the external operon terminator T2. It is proposed that the dnaG nut site is a cis-acting element of an antitermination system in E. coli.

We have cloned a simian immunodeficiency virus (SIV) proteinase gene directly from proviral DNA of the infectious viral stock SIV_mac251-32H (11/88 pool). The deduced amino acid sequence from this proteinase gene 15 similar to that for the published SIV_mac239 molecular clone. SIV_mac251-32H proteinase (SIV PR) and its flanking pol sequences were expressed in Escherichia coli as a fusion protein with most of the T7 bacteriophage gene 10 protein. The expressed protein formed cytoplasmic inclusion bodies which were solubilized in 8 M urea, and the recombinant SIV PR was refolded, yielding active, self-processed enzyme. The SIV PR was purified to homogeneity using a single pepstatin A affinity chromatography step, and had a specific peptidolytic activity of 20 µmol/min/mg. Enzymatic characteristics similar to those previously documented for other immunodeficiency virus proteinases (EC 3.4.23) were observed. These include an acidic pH optimum (pH 5.3), sensitivity to sodium chloride concentration, and complete inhibition by pepstatin A. In addition to these properties we have observed quantitative crystallization from low protein concentrations. We describe the first crystal habit for the proteinase from the HIV-2/SIV class of immunodeficiency virus, which is distinctly different from that for HIV- 1 proteinase crystals.Copyright 1994, 1999 Academic Press

The effect of captopril on skin response to intradermal injection of bradykinin was investigated by laser Doppler flowmetry (LDF) and weal and flare measurements in this randomised, double-blind, placebo-controlled, cross-over balanced study. Intradermal injections of 1 and 2.5 µg of bradykinin and normal saline were made into the forearm skin of six healthy volunteers between 1 and 2 h (t1) and between 3 and 4 h (t2) after either 25 mg captopril or placebo. Skin blood flow outside the induced weal was monitored continuously by LDF for 15 min and the mean LDF values over the last 15 s were used for analysis. Weal and flare sizes were measured at 15 min.

Abstract:Attenuated simian immunodeficiency virus (SIV) induces potent protection against infection with wild‐type virus, but the mechanism of this immunity remains obscure. Allogeneic antibodies, which arise within animals as a result of SIV infection, might protect against challenge with exogenous SIV grown in allogeneic cells. To test this hypothesis, eight macaques were infected with attenuated SIV and subsequently challenged with wild‐type SIV grown in autologous cells or heterologous cells.

The effect of constitutive expression of the c-myc oncogene on the biological properties of cells transformed or immortalized by human papilloma virus type 16 (HPV16) was studied. Whereas transfection of HPV16 alone into primary baby mouse kidney (BMK) cells failed to generate any immortalized cell lines unless the tumor promoter phorbol 12-myristate 13-acetate was present, cotransfection of HPV16 with a plasmid that constitutively expresses murine c-myc (pSVc-myc-1) generated numerous rapidly growing colonies of cells. Cell lines transformed by HPV16 and pSVc-myc-1 did not require phorbol ester or steroid hormones for growth and were tumorigenic in syngeneic immunocompetent mice. Transfection of pSVc-myc-1 into established cell lines transformed by HPV16 and the v-fos oncogene increased the growth rate and saturation density of these lines severalfold, allowed growth in low-serum medium, and abolished the requirement of these cell lines for glucocorticoids or progestogens. Transfection of the EJ-ras oncogene into these lines did not significantly affect any of these properties.

The reflection anisotropy spectra (RAS) of a Au(110)surface in an HClO4electrolyte have been measured as the potential is cycled into the oxidation region. RAS spectral signatures are obtained for the adsorption of OH−and the oxidation of the surface. RA spectra indicate that both processes destroy surface states associated with the Au(110)(1×2)surface, that the oxidation of the Au(110)surface is reversible, and that there are no significant kinetic barriers to any of the surface processes that occur as the potential is cycled.