Identification of a male-specific (H-Y) antigen on the flagellar plasma membrane of ram epididymal spermatozoa

Summary H-Y (male-specific) antigen has been detected on the plasma membranes of both caput and caudal ram spermatozoa using both immunoperoxidase and immunofluorescence labelling techniques. In these spermatozoa the distribution of H-Y antigen appears to be confined to both the posterior region of the head and the mid-piece region of the flagellum. In addition, caput spermatozoa also exhibit intense immunoperoxidase staining of the cytoplasmic droplet which is situated on the flagellum at the base of the head. Western blot analyses of purified plasma membranes from the flagella of caudal spermatozoa have revealed the presence of a malespecific protein with an estimated molecular weight of 25,000–27,000.     

Epithelium Expressing the E7 Oncoprotein of HPV16 Attracts Immune-Modulatory Dendritic Cells to the Skin and Suppresses Their Antigen-Processing Capacity

Antigen presenting cells (APCs) in skin can promote either antigen-specific effector functions or antigen tolerance, and thus determine clearance or persistence of cutaneous viral infections. Human papillomavirus (HPV) infections can persist in squamous epithelium in immunocompetent individuals, and some persisting HPV infections, particularly with HPV16, promote malignant epithelial transformation. Here, we investigate whether local expression of the HPV16 protein most associated with malignant transformation, HPV16-E7, affects the phenotype and function of APC subsets in the skin. We demonstrate an expanded population of Langerhans cells in HPV16-E7 transgenic skin with distinct cell surface markers which express immune-modulatory enzymes and cytokines not expressed by cells from non transgenic skin. Furthermore, HPV16-E7 transgene expression in keratinocytes attracts new APC subsets to the epidermis. In vivo migration and transport of antigen to the draining lymph node by these APCs is markedly enhanced in HPV16-E7 expressing skin, whereas antigen-processing, as measured by proteolytic cleavage of DQ-OVA and activation of T cells in vivo by APCs, is significantly impaired. These data suggest that local expression of HPV16-E7 in keratinocytes can contribute to persisting infection with this oncogenic virus, by altering the phenotype and function of local APCs.     

Magnetic circular dichroism and electron paramagnetic resonance studies of hydrogenases I and II from Clostridium pasteurianum

The two iron-only hydrogenases (I and II) from Clostridium pasteurianum have been investigated by variable temperature magnetic circular dichroism (MCD) and electron paramagnetic resonance (EPR) spectroscopies. Samples were studied both reduced with dithionite under an atmosphere of H2 and after oxidation with thionine. The results are consistent with four and two [4Fe-4S]1+,2+ (F)-clusters in hydrogenases I and II, respectively. All four F-clusters are reduced and paramagnetic in reduced hydrogenase I, with up to one exhibiting an S = 3/2 ground state and the remainder having conventional S = 1/2 ground states. Both F-clusters have S = 1/2 ground states in reduced hydrogenase II; however, one appears to be only partially reduced under the conditions used for reduction. MCD studies of the oxidized enzymes show no temperature-dependent features in the visible region which can be attributed to the EPR-active S = 1/2 hydrogen-activating cluster, suggesting predominantly oxygen and nitrogen coordination for the iron atoms of this center. However, temperature-dependent MCD transitions arising from a hitherto undetected S greater than 1/2 Fe-S clusters are apparent in both oxidized hydrogenases. Detailed EPR studies of oxidized hydrogenase I revealed resonances from an S = 3/2 species, however, spin quantitation reveals this to be a trace component that is unlikely to be responsible for the observed low temperature MCD spectrum. The nature and origin of these S greater than 1/2 Fe-S clusters are discussed in light of the available spectroscopic data for these and other iron-only hydrogenases.     

Long‐term population dynamics of a coral reef gastropod and responses to disturbance

The age‐specific density of the red‐lipped stromb Strombus luhuanus (Mollusca: Gastropoda) was monitored over 13 years (1981–1993) at four locations on the intertidal reef flat at Heron Island, Great Barrier Reef. Densities were highly variable, but there were persistent, location‐specific differences in population density, age structure and adult body size, the latter indicating that the populations were not extensively linked by adult movement. There was relatively high recruitment at most locations in 1984, 1989 and 1993, each occurring approximately 2 years after El Niño/Southern Oscillation events, although recruit density during these years varied in both space and time. The studied strombs experienced three disturbance events: (i) experimental harvesting at two locations (1984–1985); (ii) siltation from a harbour dredging operation (1987–1988); and (iii) a severe cyclone (1992). Resilience to harvesting at a local scale (0.5–2 ha) was high: density had recovered within a year, due to immigration of adults and older juveniles. Strombus luhuanus responded much more strongly to broad‐scale changes to its environment than to localized harvesting. After dredging, there was a progressive density decline coupled with low recruitment at two locations, and a later decline at a third location, followed by a recruitment‐driven rebound after the cyclone. Generalized environmental effects of siltation and the cyclone were also reflected in substantial changes in algal cover. Long‐term variations in environmental conditions probably cause high temporal variation over large spatial scales through effects on the survival of larvae or recruits. Localized short‐term field monitoring of such species would give a misleading picture of key factors affecting population dynamics.     

The influence of age and sex on phagocyte chemiluminescence

The process of ageing is associated with increased susceptibility to infection. Phagocytes form the primary defence mechanism against infecting microorganisms, but the influence of ageing on phagocyte function remains controversial. In this study we have applied a microtitre plate phagocyte chemiluminescence (CL) assay suitable for clinical use to compare phagocyte oxidative metabolism in younger healthy subjects (age 20–60 years) and healthy older (60–70 years) subjects. Polymorphonuclear leukocytes (PMNL) and monocytes were stimulated using phorbol myristate acetate (PMA), serum opsonized zymosan (SOZ), and non-opsonized zymosan (ZYM) in the presence of both lucigenin and luminol. Monocytes showed a higher luminolenhanced CL response to PMA in males compared with females in the younger age group. No PMNL differences were observed between the sexes. Although no difference were found in relation to age when cells were stimulated with PMA and SOZ, significantly lower background (unstimulated) CL was obtained from PMNL with luminol. PMNL luminol-enhanced CL responses were also lower in response to ZYM. The findings suggest a reduced response of PMNL from older subjects to minimal stimulation. This could be related to abnormalities in the triggering of the respiratory burst or myeloperoxidase release due to ageing. The influence of age and sex should be taken into account in clinical studies of phagocyte CL.