Light- and electron-microscopic immunocytochemistry of peptidergic neurons innervating thoracico-abdominal neurohaemal areas in the blowfly

Summary Ventral thoracic neurosecretory cells (VTNCs) of the blowflies, Calliphora erythrocephala and C. vomitoria, innervating thoracic neuropil and the dorsal neural sheath of the thoracico-abdominal ganglion have been shown to be immunoreactive to a variety of mammalian peptide antisera. In the neural sheath the VTNC terminals form an extensive neurohaemal network that is especially dense over the abdominal ganglia. The same areas are invaded by separate, ut overlapping serotonin-immunoreactive (5-HT-IR) projections derived from neuronal cell bodies in the suboesophageal ganglion. Immunocytochemical studies with different antisera, applied to adjacent sections at the lightmicroscopic level, combined with extensive cross-absorption tests, suggest that the perikarya of the VTNCs contain co-localized peptides related to gastrin/cholecystokinin (CCK), bovine pancreatic polypeptide (PP), Met- and Leuenkephalin and Met-enk-Arg⁶-Phe⁷ (Met-enk-RF). Electron-microscopic immunogold-labeling shows that some of the terminals in the dorsal sheath react with several of the individual peptide antisera, whilst others with similar cytology are non-immunoreactive. In the same region, separate terminals with different cytological characteristics contain 5-HT-IR. Both 5-HT-IR and peptidergic terminals are localized outside the cellular perineurium beneath the acellular permeable sheath adjacent to the haemocoel. Hence, we propose that various bioactive substances may be released from thoracic neurosecretory neurons into the circulating haemolymph to act on peripheral targets. The same neurons may also interact by synaptic or modulatory action in the CNS in different neuropil regions of the thoracic ganglion.     

Regeneration of the cell wall in protoplasts of Candida albicans

To assess the dynamics of synthesis of the wall by regenerating Candida albicans protoplasts deposition of chitin and mannoproteins were investigated ultrastructurally using wheat germ agglutinin conjugated with either horseradish peroxidase or colloidal gold, and Concanavalin A coupled to ferritin respectively.Freshly prepared protoplasts lacked wheat germ agglutinin receptor sites but after 1–2 h of regeneration, they were detected. After 4–5 h of regeneration, the cell wall showed a discrete structure which was only labelled with wheat germ agglutinin in thin sections. At this stage of regeneration the outermost layer of the wall was labelled with clusters of Concanavalin A-ferritin particles.After 8 h regeneration, the cell wall appeared compact, and homogenously marked with wheat germ agglutinin whereas only the surface layers appeared consistently labelled with Concanavalin A-ferritin.From these observations we conclude that C. albicans protoplasts are able to regenerate in liquid medium a cell wall consisting of a network of chitin fibrils and mannoproteins at least (glucan polymers were not determined in the present cytological study). The former are the fundamental component of the inner layers at early stages of regeneration, whereas the latter molecules are predominant in the outer layers of the wall.Abbreviations WGA-HRP wheat germ agglutinin conjugated with horseradish peroxidase - WGA-Au wheat germ agglutinin conjugated with colloidal gold - Con A-ferritin Concanavalin A coupled to ferritin     

Taxonomy ofCarminatia (Asteraceae,Eupatorieae)

A taxonomic study of the largely Mexican genusCarminatia is rendered. It is comprised of three closely related species:C. tenuiflora, C. recondita andC. anomala spec. nova. Illustrations, dot maps, keys to species and complete synonymy are presented.     

A new name and a new species in MexicanRuellia (Acanthaceae)

Based on pollen and floral morphology,Blechum grandiflorum is transferred toRuellia, and the nameR. mirandana is proposed for this species. A new species,Ruellia tuxtlensis, is described which is distinguishable fromR. mirandana by its longer spike and elliptic bracts. It is presently known only from the lowlands of Veracruz, Mexico.     

On human speech,syntax, and language

The evolution of human speech and syntax, which appear to be the defining characteristics of modern human beings, is discussed. Speech depends on the morphology of the mouth, tongue, and larynx which yield the human «vocal tract», and neural mechanisms that facilitate the perception of speech and make possible the control of the articulatory gestures that underly speech. The neural mechanisms that underly human syntax may have derived by means of the Darwinian process of preadaption from the structures of the brain that first evolved to facilitate speech motor control. Recent data consistent with this theory are presented; deficits in the comprehension of syntax of normal aged people are correlated with a slowdown in speech rate.     

Diversity and evolution of chloroplast DNA in Triticum and Aegilops as revealed by restriction fragment analysis

Summary Restriction fragment analysis of chloroplast (cp) DNAs from 35 wheat (Triticum) and Aegilops species, including their 42 accessions, was carried out with the use of 13 restriction enzymes to clarify variation in their cpDNAs. Fourteen fragment size mutations (deletions/insertions) and 33 recognition site changes were detected among 209 restriction sites sampled. Based on these results, the 42 accessions of wheat-Aegilops could be classified into 16 chloroplast genome types. Most polyploids and their related diploids showed identical restriction fragment patterns, indicating the conservatism of the chloroplast genome during speciation, and maternal lineages of most polyploids were disclosed. This classification of cpDNAs was principally in agreement with that of the plasma types assigned according to phenotypes arising from nucleus-cytoplasm interactions. These mutations detected by restriction fragment analysis were mapped on the physical map of common wheat cpDNA, which was constructed with 13 restriction endonucleases. Length mutations were more frequently observed in some regions than in others: in a 16.0 kilo base pairs (kbp) of DNA region, including rbcL and petA genes, 6 of 14 length mutations were concentrated. This indicates that hot spot regions exist for deletions/insertions in chloroplast genome. On the other hand, 33 recognition site mutations seemed to be distributed equally throughout the genome, except in the inverted repeat region where only one recognition site change was observed. Base substitution rate (p) of cpDNA was similar to that of other plants, such as Brassica, pea and Lycopersicon, showing constant base substitution rates among related taxa and slow evolution of cpDNA compared with animal mitochondrial DNA. Phylogenetic relationships among Triticum and Aegilops species were discussed, based on the present data.Contributions no. 45 and no. 490 from the Kihara Institute for Biological Research, Yokohama City University and the Laboratory of Genetics, Faculty of Agriculture, Kyoto University, respectively.     

Carbon balance during CAM: an assessment of respiratory CO2 recycling in the epiphytic bromeliads Aechmea nudicaulis and Aechmea fendleri

Abstract The regulation of crassulacean acid metabolism (CAM) under controlled environmental conditions has been investigated for two tropical epiphytes, relating plant water and carbon balance to growth form and habitat preference under natural conditions. Aechmea fendleri is restricted to wet, upper montane regions of Trinidad, while A. nudicaulis has a wider distribution extending into more arid regions of the island. Morphological characteristics of these plants are related to habitat preference in terms of leaf succulence (0.44 and 0.94 kg m^?2 for the two species respectively) and a distinct layer of water storage parenchyma in A. nudicaulis In contrast, the thinner leaves of A. fendleri contain little water-storage parenchyma and less chlorenchyma per unit area, but the plants have a more open leaf rosette. The two species differ in expression of CAM, since the proportion of respiratory CO₂ recycled as part of CAM had been found to be much lower in A. fendleri This study compared the efficiency of water use and role of respiratory CO₂ recycling under two PAR regimes (300 and 120 μnol m^?2 s^?1) and three night temperatures (12, 18 and 25 °C). Dark CO₂ uptake rates for both species were comparable to plants in the field (maximum of 2.3 ± 0.2 μmol m^?2s^?1± SD, n= 3). Total net CO₂ uptake at night increased on leaf area basis with temperature for both species under higher PAR, although under the low PAR regime CO₂ uptake was maximal at 18 °C. Water-use efficiency (WUE) increased at 18 °C and 25 °C during dark CO₂ uptake (Phase I) and also during late afternoon photosynthesis (Phase IV) in both species. For A. fendleri, dawn to dusk changes in titrable acidity (ΔH ⁺) were similar under high and low PAR, although ΔH⁺ was correlated to night temperature and PAR in A. nudicaulis. The proportion of ΔH⁺ derived from respiratory CO₂ also varied with experimental conditions. Thus percentage recycling was lower in A. fendleri under high PAR (0–10%), but was only reduced at 18 °C under low PAR. Recycling by A. nudicaulis ranged from 32–42% under high PAR, but was also reduced to 6% under low PAR at 18 °C; at 12 °C and 25 °C, recycling was 37% and 52% respectively. Previous studies have suggested a relationship between the proportion of recycling and degree of water stress. This study indicated that CAM as a CO₂ concentrating mechanism regulates both water-use efficiency and plant carbon balance in these epiphytes, in response to PAR and night temperature. However, the precise relationship between respiratory processes and the balance between external and internal sources of CO₂ is as yet unresolved.     

Molecular biology of wound-inducible proteinase inhibitors in plants

Abstract. The techniques of molecular biology are being employed to investigate at the gene level the systemically mediated, wound-induced accumulation of two defensive proteinase inhibitor proteins in plant leaves. These techniques have added a new dimension to biochemical and physiological studies already underway to understand the mechanism of induction by wounding. The acquisition of cDNAs from the RNAs coding for the two inhibitors facilitated studies of mRNA synthesis in leaves in response to wounding, and provided probes to obtain wound-inducible proteinase inhibitor genes from tomato ( Lycopersicon esculentum ) and potato (Solarium tuberosum) genomes. Successful transformations of tobacco plants with fused genes, containing the 5' and 3' regions of the inhibitor genes with the open reading frame of the chloramphenicol acelyltransferase ( cat ) gene, have provided a wound-inducible chloramphenicol acetyltransferase (CATase) activity with which to seek cis- and transacting elements that regulate wound-inducibility to help to understand the interaction of cytoplasmic and nuclear components of the intracellular communication systems that activate the proteinase inhibitor genes in response to wounding by insect pests.     

Chromium in plants

Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance. For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared to 0.5–1.5 μg/g).     

Assembly of the barley light-harvesting chlorophyll a/b proteins in barley etiochloroplasts involves processing of the precursor on thylakoids

A barley gene encoding the major light-harvesting chlorophyll a/b-binding protein (LHCP) has been sequenced and then expressed in vitro to produce a labelled LHCP precursor (pLHCP). When barley etiochloroplasts are incubated with this pLHCP, both labelled pLHCP and LHCP are found as integral thylakoid membrane proteins, incorporated into the major pigment-protein complex of the thylakoids. The presence of pLHCP in thylakoids and its proportion with respect to labelled LHCP depends on the developmental stage of the plastids used to study the import of pLHCP. The reduced amounts of chlorophyll in a chlorophyll b-less mutant of barley does not affect the proportion of pLHCP to LHCP found in the thylakoids when import of pLHCP into plastids isolated from the mutant plants is examined. Therefore, insufficient chlorophyll during early stages of plastid development does not seem to be responsible for their relative inefficiency in assembling pLHCP. A chase of labelled pLHCP that has been incorporated into the thylakoids of intact plastids, by further incubation of the plastids with unlabelled pLHCP, reveals that the pLHCP incorporated into the thylakoids can be processed to its mature size. Our observations strongly support the hypothesis that after import into plastids, pLHCP is inserted into thylakoids and then processed to its mature size under in vivo conditions.