One Molecule of Guanosine Triphosphate is Present in Each 30S Initiation Complex

FOR some time guanosine triphosphate (GTP) has been known to be involved in the initiation of bacterial protein synthesis^1–4, although its exact function remains obscure. Although GTP stimulates the binding of fMet-tRNA to 30S ribosomes^5,6, it does not seem to be hydrolysed in the process⁷. Hydrolysis is thought to occur later, either during or immediately after the junction of the 30S initiation complex (composed of a 30S ribosome, fMet-tRNA, mRNA, initiation factor F₁ and probably other components as we shall show; and hereafter referred to as 30S i-complex) with a 50S ribosome to form a 70S initiation complex^7–9. The use to which the energy released in this hydrolysis step is put is not yet known for certain.     

Towards an understanding of the Sarcostemma viminale (Asclepiadaceae) complex

LIEDE, S. & MEVE, U., 1993. Towards an understanding of the Sarcostemma viminale (Asclepiadaceae) complex. All names in Sarcostemma sensu Bullock (Asclepiadaceae, Asclepiadeae, Cynanchinae) are listed and their current status evaluated. Chromosome numbers are given for most taxa. The typification of S. viminale is clarified. A new subspecies of S. viminale is described from the Orange Free State, South Africa, and relationships of the Namaqualand/Namibia populations are discussed.     

State‐dependent attacks in a mosquito

Mosquito biting frequency and meal size are considered to be important parameters in the epidemiology of insect‐vectored diseases such as malaria. Because both parameters are likely to depend on the size and energetic state of adult mosquitoes, the present study investigates the effects of body size and energy state on attack behaviours in the malaria mosquito, Anopheles gambiae. Attack rates are measured as well as total time spent before giving up for individual females when provided with an unobtainable human hand (i.e. mosquitoes are dislodged every time that they land). The factorial design considers two body sizes, small and large, as well as three sugar deprivation states, 0, 1 and 2 days. The results reveal a positive effect of size on attack rate and a nonlinear effect of energy state, where mosquitoes of intermediate energy state show lower attack rates than either 2‐day food‐deprived or nondeprived mosquitoes. Moreover, attack rate is negatively associated with persistence time in nondeprived and 2‐day food‐deprived Anopheles but is unrelated to persistence time in 1‐day food‐deprived mosquitoes, Interestingly, although persistence times are generally inversely related to attack rates, they are not significantly influenced by either energetic or size states.     

Two new species of Mussaenda (Rubiaceae) from Panay Island,Philippines

Two new species of Mussaenda (Rubiaceae) from Aklan, Panay, Philippines are described and illustrated. Mussaenda ustii sp. nov. is distinct by its long pedicel (up to 7 mm), yellow with white margins corolla lobes forming a star and recurved stigma lobes which are always semi‐ or distinctly exserted in long‐styled morphs. Mussaenda viridiflora sp. nov. is characterized by its white, sweet‐scented corolla lobes, which are green tinged on the median ridges and bases, and strongly reflexed calyx lobes. A discussion of the relationships of the new taxa to closely related Philippine Mussaenda is provided. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 87–92.     

On the function of sex pheromone components in Periplaneta americana: improved odour source localization with periplanone-A

ABSTRACT. The female American cockroach, Periplaneta americana L., produces two sex pheromone components: periplanone-A (PA) and periplanone-B (PB). PB induces male locomotion and upwind orientation. PA, when presented alone, has the same effect but with a higher threshold concentration. When added to PB in the natural ratio, however, PA reduces rather than increases locomotory activity. To examine whether PA affects male orientation in the natural blend, a pheromone source was suspended above the centre of a circular arena. Efforts were made to exclude air movements so that pheromone concentration declined centrifugally. Males walking in a PB gradient spent more time near the source than in the peripheral areas when low doses were presented. At emission rates approximately equivalent to those of a female, however, they were not able to locate the pheromone source as precisely as at lower rates. In contrast, males walking in a PA gradient spent more time in the centre of the arena when the pheromone dosage was increased. When PA was added to natural levels of PB, males walked more slowly and stopped more frequently near the source than with PB alone. Thus PA improves chemo-orientation of males when presented in a natural ratio with PB. A reduction of linear velocity near the pheromone source (an orthokinetic effect) is involved in this process.     

Seed coat morphology of Aizoaceae–Sesuvioideae, Gisekiaceae and Molluginaceae and its systematic significance

Macro- and micromorphological characters of the seeds of 32 species belonging to Aizoaceae (26 species), Gisekiaceae (one species) and Molluginaceae (five species) were analysed for their taxonomic value. Seed morphology is found to be of considerable taxonomic value within the taxa investigated, although additional criteria are usually necessary for distinguishing the species. However, a subgroup of Trianthema , consisting of T. cussackiana , T. megasperma , T. pilosa , T. rhynchocalyptra and T. oxycalyptra var. oxycalyptra (Aizoaceae) shares the synapomorphy of seeds with scattered idioblast cells (papillae). There is little infrageneric variation within Sesuvium and Zaleya in contrast to Trianthema , whose seeds are considerably polymorphic. The fairly different seed structures found in Aizoaceae s.s . and Molluginaceae support their treatment as two distinct families. However, the position of Lineum (Molluginaceae) remains uncertain. Moreover, seed characters support the independence of Gisekia (Gisekiaceae) in a family of its own.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 189–206.     

The genus Sarcostemma R.Br. (Asclepiadaceae) in Madagascar

The Madagascar! representatives of the genus Sarcostemma are investigated. All Malagasy material studied can be assigned to four taxa. S. viminale ssp. viminale occurs in Madagascar as well as on other islands along the African coast and on the African mainland: the other three species are endemic to Madagascar. All four species occur in the southern, arid part of the island, to which S. decorsei is endemic. S. membranaceum and S. elachistemmoides are new. All species are described and illustrated and a key and distribution maps are presented.     

Myth and reality of the subtribe Astephaninae (Decne.) Schumann (Asclepiadaceae)

The subtribe Astephaninae (tribe Asclepiadeae, Asclepiadaceae) is recircumscribed to contain 11 genera: Astephanus, Blyttia, Diplostigma, Goydera, Aiicroloma, Oncinema, Pentatropis, Pteurosteima, Rhyncharrhena, Schizostephanus, and Tylophoropsis. Following a character analysis, phylogeny was analysed by means of a computerized parsimony program (HENNIG86). Astephanus /Microloma is identified as the most stable clade, followed by Tylophopropsis/Pentatropis/Rhyncharrhena, Blyttia/Diplostigma and Schizostephanus/Goydera. A key to the genera is presented, as well as notes on distribution, important characters, and present state of knowledge for each genus. The genus Schizostephanus is resurrected and four new combinations are proposed.