Comparative Response of Nodulated and Nitrogen-Supplied Cowpea (Vigna unguiculata (L.) Walp. var. Tuy) Plants to Infection by Cowpea Mosaic Virus

The effect of infection by the Cowpea Mosaic Virus (CpMV) onseveral parameters relevant to symbiotic nitrogen fixation wasdetermined in cowpea (Vigna unguiculata (L.) Walp. var. Tuy)plants nodulated with two strains of Rhizobium cowpea: IVIC–124and IVIC–38. Plants were virus-infected at the seedlingstage before Rhizobium inoculation. The effect of CpMV infectionon plant growth was analysed in nodulated and nitrogen-suppliedplants at 18, 25 and 35 d after germination. At all developmentalstages of nodulated plants CpMV infection caused a reductionof leaf chlorophyll content, leaf area, dry weight of shootsand roots, total nodule weight and nodule number. Most of thenodules from 18- and 25-d-old CpMV-infected plants did not exhibitleghaemoglobin pigmentation. CpMV infection delayed the onsetof nitrogenase activity in nodules of the rhizobial strain IVIC–124and the enzyme activity measured on a per plant basis was reducedin both strains at the first and second harvests. Significantnitrogenase activity was detected in 35-d-old infected plants.Some of the nodules of the rhizobial strain IVIC-124 and mostof the nodules from plants nodulated with the strain IVIC-38developed leghaemoglobin; however, the nodule-specific nitrogenaseactivity, estimated on a milligram nodule dry weight basis,was always higher in virus-infected plants, particularly in18-d-old CpMV-infected plants harbouring the IVIC–124strain. CpMV-infected nodules had a larger peribacteroidal space,a reduced number of peribacteroid units, a greater number ofbacteroids per unit, a lower number of vesicles and 88% lowertotal reducing sugar content. Starch accumulation was detectedin infected leaves of nodulated plants during the first harvest,while high levels of leaf reducing sugars and protein were presentat the second harvest. In healthy nodulated plants the rhizobialstrain IVIC–124 was shown to be more efficient than IVIC–38in promoting plant growth. However, the results indicate thatnodulation by rhizobial strain IVIC–124 and growth ofplants harbouring this strain were affected to a greater extentby virus infection. The effect of CpMV infection on leaf chlorophyllcontent, leaf area, carbohydrate level, leaf proteins and growthof nitrogen-supplied plants, as well as the symptoms inducedin the leaves, were less conspicuous than in nodulated plants. Key words: Cowpea, Rhizobium, virus infection, nodule untrastructure     

Biochemical Requirements for Intracellular Invasion by Trypanosoma cruzi: Protein Synthesis1

The effects of irreversible inhibition of protein synthesis by pactamycin in either infective forms of Trypanosoma cruzi or mammalian host cells on cellular invasion by this human pathogen were investigated. Treatment of bloodstream forms of T. cruzi with pactamycin markedly reduced their ability to bind either fibroblast-like cells of monkey origin or myoblasts of rat origin. The number of amastigote forms that could be established intracellularly was also significantly decreased with respect to control values obtained when mock-treated (medium alone) trypomastigotes were incubated with the cells. Pactamycin treatment also reduced the infectivity of T. cruzi trypomastigotes for mice as evidenced by both significantly reduced parasitemia levels and mortality rates when compared with those of control mice infected with mock-treated parasites. Inhibition of protein synthesis in the host cells neither prevented cell infection by untreated trypomastigotes nor altered the percentages of infected cells or the magnitude of the infection in vitro. These results indicate that protein synthesis is a requirement for cell invasion by T. cruzi and that the parasite can establish itself and replicate within cells relying on its own protein synthesis ability.     

A review of the genus Semele (Ruscaceae) systematics in Madeira

The present study attempts to review the systematics of Semele (Ruscaceae) in Madeira, based on phenotypic diversity. The variation in some vegetative (climbing shoot, second-order branches or 'phylloclades') and sexual (inflorescence and flowers) characters was analysed in 115 plant specimens from 30 field populations, herbaria of the Costa collection and Madeira Botanical Garden (MADJ) and certain gardens. Thirty-one quantitative and qualitative characters have been utilized in the analysis. Kaiser–Meyer–Olkin (KMO) analysis indicates adequate sampling. Principal component analysis (PCA) reveals that the spatial distribution of individuals has a discontinuous behaviour. Principal coordinate analysis (PCO) utilizing the Gower coefficient on standardized data revealed a significantly discontinuous distribution of individuals, such that two different clusters can be defined. The Student's t -test and Tukey test on separate characters, when individuals were classified according to the Costa classification, confirms the significant differences between grouping accessions. This leads to the recognition of two species within the genus in Madeira. Literature and herbarium studies show that these two taxa are conspecific with Semele androgyna (L.) Kunth sensu stricto (s.s.) and Semele menezesi Costa sensu lato (s.l.) . A separated statistical analysis of the S. androgyna cluster shows the possible existence of additional subgroups. Based on field population distribution, ecological behaviour and variation in features, we propose the recognition of two species, S. androgyna (L.) Kunth and S. menezesi (Costa) Pinheiro de Carvalho, and two subspecies S. androgyna (L.) Kunth androgyna Pinheiro de Carvalho and S. androgyna (L.) Kunth pterygophora Pinheiro de Carvalho.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 483–497.     

Insulin in Invertebrates and Cyclostomes

It seems increasingly clear that insulin is a hormone that doesnot occur exclusively in vertebrates. Several independent reportsnow exist giving evidence of insulin production in the digestivetissues of both deuterostomian and protostomian invertebrates.Cells with some light-microscopical and ultrastructural characteristicsof vertebrate B-cells have also been observed. Recently, evidencehas been obtained that insulin can act as a hypoglycemic hormone,promoting glycogen synthesis, also in a protostomian invertebrate,the gastropod mollusc, Strophocheilus oblongus. The endocrine pancreas of the cyclostomes occupies a key positionin the comparative endocrinology of the islet parenchyma andin the evolution of insulin production. It may represent anevolutionary link between the presumably gut-connected dispersedinsulin-producing cells of deuterostomian invertebrates andthe pancreatic islets of gnathostomian vertebrates. This hypothesiswas supported by the fact that cells with light-microscopicaland ultrastructural similarities to the islet B-cells were observedin the bile duct mucosa of the hagfish, Myxine glutinosa. However,immunofluorescent studies with antisera against human insulinand C-peptide did not show any immunoreactive material outsidethe B-cells of the endocrine pancreas. Particular attentionwas paid to elucidate the biological significance of the largecystic cavities that are so typical for the cyclostomian isletparenchyma. The working hypothesis that they may contain storedinsulin, proinsulin (or even "proto-proinsulin") was not supportedby immunofluorescence, autoradiographic, or ultrastructuralinvestigations, nor by proinsulin assays. It is possible thathagfish islet B-cells contain zinc, despite the fact that theamino acid residue in B₁₀-position is aspartic acid insteadof histidine. The biosynthesis of hagfish insulin shows a patternsimilar to that in gnathostomes. Its rate is related to theambient temperature and at 11 C the conversion of proinsulinto insulin lasts several days.     

Ultrastructure of the “Cyst-like Bodies” of Trypanosoma conorhini*

SYNOPSIS. An electron microscope study was made of the “cyst-like bodies” (CLBs) previously described in cultures of Trypanosoma conorhini. It is again suggested that CLBs are a process of reproduction which involves fusion of epimastigotes, repeated divisions of DNA-containing organelles and organization of daughter epimastigotes that, after being completely formed, may be found free within the large central “vacuole” of the CLB. This “vacuole,” it is now evident, results from the fused and muchdilated flagellar reservoirs of parent epimastigotes. Our interpretation of the CLBs and their possible genetic significance are discussed.     

Isolation of C Reactive Protein and its Effect on Human Lymphocytes <Emphasis Type="Italic">in vitro</Emphasis>

C REACTIVE protein (CRP) appears in the serum of human and other animal species during acute inflammation. Its amount is related to the severity of inflammatory response, irrespective of its cause. CRP is probably made by normal cells¹ and then released locally at the time of injury². It is not made de novo by injured cells³. Its reaction with C polysaccharide requires divalent cations and is related to the polyanionic nature of this highly phosphorylated carbohydrate⁴. The kinetics of the reaction are similar to antigen-antibody reactions but CRP is not an immunoglobulin⁵. Its function is unknown.     

Regulation of Ciliary Pattern in Ciliates*

SYNOPSIS. The modes of pattern regulation found in the ciliates Dileptus and Paraurostyla are compared. These forms are systematically distant but both possess very extensive regenerative capacities. They are characterized by 2 types of ciliary patterns: the ciliature of Dileptus has largely a simple pattern composed of single kinetosomes while that of Paraurostyla has a complex pattern composed of aggregates of kinetosomes interconnected by amorphic matter. In both ciliates a change in cell size evokes pattern regulation which differs substantially in the extent of pattern replacement, timing, and localization of morphogenetic activities. It is concluded that these differences result from the pattern constituents.