Does the major histocompatibility complex serve as a specific receptor for Semliki Forest virus?

Murine F9 and PCC4 teratoma cells do not express H-2 major transplantation antigens according to virus-specific T-lymphocyte cytotoxic or serological assays. However, such cells can be infected with and readily replicate many types of viruses (coxsackie B 3, mouse hepatitis, Sindbis, Semliki Forest [SFV], lymphocytic choriomeningitis, Pichinde, vesicular stomatitis, herpes simplex type 1) to the same extent as do murine F12 teratoma cells and mouse embryo fibroblasts, all of which express the H-2 determinants. In contrast, F9 and PCC4 cells are not productively infected with murine cytomegalovirus, whereas F12 and mouse embryo fibroblast cells are. In addition to replicating in H-2-negative murine teratoma cells, SFV replicates in H-2-negative murine lymphoblastoid cells. The ability of SFV to infect cells without H-2 antigens and then to effect viral antigenic expression in the cells' cytoplasm and on their surface with similar kinetics and in equivalent amounts as cells with H-2 antigens indicates that the H-2 receptor is not needed for SFV infection. Daudi cells, which lack HLA antigens, block the replication of SFV. This occurs at some point after receptor binding, as demonstrated by diminished viral mRNA. In addition, a possible membrane defect precludes viral exit in Daudi cells transfected with SFV infectious RNA. These results indicate that a cell's possession of H-2 antigens is not a requirement for SFV infection and that major histocompatibility complex antigens are not specific receptors for this virus.     

Proposal for a uniform nomenclature for defective interfering viruses of vesicular stomatitis virus.

Defective interfering particles of vesicular stomatitis virus have been named according to their parental derivation and to their genomic length and physical properties. This suggested uniform nomenclature can be adapted for other virus systems.     

The effects of manganese doping on UVA absorption and free radical generation of micronised titanium dioxide and its consequences for the photostability of UVA absorbing organic sunscreen components.

The effect of manganese doping on the free radical generation rate, free radical scavenging and UVA absorption properties of micronised sunscreen grade titania has been studied with respect to enhancement of the UVA photostability of test sunscreen formulations containing the organic UVA absorber Parsol 1789. Manganese doping has been shown to increase the UVA:UVB absorption ratio of titania, reduce free radical generation rates by over 90%, and provide free radical scavenging behaviour. Adding manganese-doped titania to a test formulation incorporating Parsol 1789 shows that manganese doping increases UVA attenuation stability by up to 3 times the amount achieved by comparable commercial undoped titania materials. HPLC data shows this to be related to an improved stabilisation of the organic sunscreen components. Manganese doped titania shows improved efficacy over undoped titania in sunscreen formulations containing organic UV absorbers.     

PERSPECTIVE: CHASE-AWAY SEXUAL SELECTION: ANTAGONISTIC SEDUCTION VERSUS RESISTANCE

A model of sexual selection that leads to the evolution of exaggerated male display characters that is based on antagonistic coevolution between the sexes is described. The model is motivated by three lines of research: intersexual conflict with respect to mating, sensory exploitation, and the evolution of female resistance, as opposed to preference, for male display traits. The model generates unique predictions that permit its operation to be distinguished from other established models of sexual selection. One striking prediction is that females will frequently win the coevolutionary arms race with males, leaving them encumbered with costly ornaments that have little value except that their absence understimulates females. Examples from the literature suggest that the model may have broad application in nature. The chase-away model is a special case of the more general phenomenon of Interlocus Contest Evolution (ICE).     

A specific sequence with a bulged guanosine residue(s) in a stem-bulge-stem structure of Rev-responsive element RNA is required for trans activation by human immunodeficiency virus type 1 Rev.

We demonstrate that both the in vitro RNA binding and in vivo trans activation functions of human immunodeficiency virus type 1 Rev regulatory protein Rev require the presence of a 9-nucleotide 5'-CACUAUGGG-3' RNA motif on its cognate target, the Rev-responsive element RNA. For optimal Rev recognition, this sequence must be presented as a stem-bulge-stem structure and must contain at least two G's, one of which must be unpaired, and include some or all of the CACUAU sequence upstream of the three G's. Distal mutations which result in the base pairing of the G's eliminate the Rev response. The first G is crucial, but changes at the other G's are tolerated if at least one G is unpaired. The secondary structure or the three-dimensional orientation of the B1 and B2 stem-loops of the Rev-responsive element are not relevant as long as the 5'-CACUAUGGG-3' sequence is preserved, with at least one bulged G residue.     

A molecular analysis of the phylogenetic affinities of Saccoglossus cambrensis Brambell & Cole (Hemichordata).

Traditional approaches to phylogeny reconstruction have not allowed precise resolution of the evolutionary relationships between the major deuterostome phyla (chordates, hemichordates, echinoderms). Here we report the use of a molecular approach to investigate deuterostome phylogeny. We have used a polymerase chain reaction-based strategy to amplify, clone and sequence parts of the genes coding for 18S ribosomal RNA from Saccoglossus cambrensis (Hemichordata), Arbacia sp. (Echinodermata) and, for comparison, Mytilus edulis (Mollusca). We report the results of phylogenetic reconstructions using these, and homologous sequences from other eukaryotes. The results of our analyses are consistent with the hypothesis that S. cambrensis and vertebrates share a common ancestor not shared by echinoderms.     

Regulation of the L-lactase dehydrogenase from Lactobacillus casei by fructose-1,6-diphosphate and metal ions.

The lactate dehydrogenase of Lactobacillus casei, like that of streptococci, requires fructose-1,6-diphosphate (FDP) for activity. The L. casei enzyme has a much more acidic pH optimum (pH 5.5) than the streptococcal lactate dehydrogenases. This is apparently due to a marked decrease in the affinity of the enzyme for the activator with increasing pH above 5.5; the concentration of FDP required for half-maximal velocity increase nearly 1,000-fold from 0.002 mM at pH 5.5 to 1.65 mM at 6.6. Manganous ions increase the pH range of activity particularly on the alkaline side of the optimum by increasing the affinity for FDP. This pH dependent metal ion activation is not specific for Mn2+. Other divalent metals, Co2+, Cu2+, Cd2+, Ni2+, Fe2+, Fe2+, and Zn2+ but not Mg2+, will effectively substitute for Mn2+, but the pH dependence of the activation differs with the metal ion used. The enzyme is inhibited by a number of commonly used buffering ions, particularly phosphate, citrate, and tris (hydroxymethyl) aminomethane-maleate buffers, even at low buffer concentrations (0.02 M). These buffers inhibit by affecting the binding of FDP.     

The fine structure of epidermal glands of regenerating and mature globiferous pedicellariae of a sea urchin (Lytechinus pictus)

After a globiferous pedicellaria is lost from a sea urchin, a new appendage of the same kind is usually regenerated in the weeks that follow. During the latter part of regeneration, head glands and stalk glands, both of epidermal origin, develop from undifferentiated cells. Head gland cells begin morphological differentiation in the epidermis and then delaminate into the underlying dermis. In the formation of the stalk gland, by contrast, undifferentiated cells delaminate from the epidermis and then begin morphological differentiation in the dermis. During late regeneration, cells in the head and stalk glands are characterized by extensive rough endoplasmic reticulum distended with intracisternal material; moreover, the Golgi complex is closely associated with some of the large cytoplasmic vacuoles. The accumulating secretions of the two glands differ both in fine structure and in site of storage. Head gland secretions are stored intracellularly in the cytoplasmic vacuoles, while stalk gland secretions leave the gland cells in an apocrine fashion and are stored in an extracellular lumen. After regeneration, the mature cells of the head glands and stalk glands contain relatively little distended endoplasmic reticulum, although a Golgi complex is still present. Presumably, mature gland cells, in comparison to regenerating gland cells, produce relatively little secretion; instead, the glandular products elaborated during regeneration are probably stored in the mature glands with little augmentation or turnover.