Mineral nutrition of cacao (Theobroma cacao L.)

Summary Two experiments on cacao seedlings grown in sand culture are described, the first of which was concerned with variations in the levels of nitrogen, phosphorus, potassium, calcium, magnesium and sulfur (the macronutrient experiment) and the second dealing with variations in the levels of iron, copper, zinc, boron, manganese, and molybdenum (the micronutrient experiment).Many of the deficiency symptoms obtained were similar to those reported in the literature and they have not been described again. However, additional information is provided for symptoms of phosphorus, potassium, calcium, iron, manganese, copper, boron, and molybdenum deficiencies.The effects of all treatments on the dry weights of leaves, stems, and roots are presented. The effects of the macronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, and magnesium in the leaves of eight month old plants and the effects of micronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese, copper, zinc, boron, molybdenum, sodium, and aluminium in the leaves of eleven-month-old plants are presented and discussed.     

Proposal for adoption of the base of the Undulograptus austrodentatus Biozone as a global Ordovician stage and series boundary level

The base of the Undulograptus austrodentatus Biozone appears to be a synchronous event that is widely recognizable within graptolitic facies around the world. It occurs within an interval in which graptolite species ranges are now well known and in which there is a rapid turnover in the composition of graptolite faunas. This turnover reflects the rapid evolutionary radiation of the Diplograptacea simultaneously with the appearance of several distinctive pseudisograptid and glossograptid species. These events provide the basis for the recognition of two thin but widely applicable subzones; a lower Arienigraptus zhejiangensis Subzone and an upper U. sinicus Subzone. The occurrence of the lower boundary of the U. austrodentatus Biozone within a succession of first appearances also permits accurate and reliable identification of the boundary as well as assessment of stratigraphic completeness across the boundary interval in correlated sections. Diverse graptolite faunas of late Yapeenian and early Darriwilian age occur in association with the Histiodella altifrons Biozone of the North American midcontinent conodont zonation and the Paroistodus originalis and Microzarkodina parva biozones of the North Atlantic conodont zonation. They also occur in association with the shelly-fossil zonations developed for several different continents. These features of the base of the U. austrodentatus Biozone make it a suitable level for use as the boundary level for a global stage. Its stratigraphic position within the Ordovician System relative to other likely global stages as well as its coincidence with one of the major events in graptolite evolutionary history suggest that this level also may be a suitable level for the base of a global Middle Ordovician Series.Ordovician System, Ordovician stages, graptolite zonation, chronostratigraphy, international correlation. Charles E. Mitchell and Jörg Maletz, Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260-1550, USA; 13th July, 1994; revised 22nd May, 1995.     

Ultrastructural changes in Blastomyces dermatitidis after in vitro exposure to lidocaine

Electron microscopic examination of yeasts of Blastomyces dermatitidis, exposed in vitro to concentrations of lidocaine that occur when the drug is used for topical anesthesia, showed that lidocaine rapidly damaged intracellular structures. The extent of damage was dependent on the concentration of drug and length of exposure. The observed ultrastructural changes were very similar to those reported for other drugs that directly damage membranes. This relationship suggests that the antifungal effect of lidocaine is the result of direct membrane damage.     

Mapping of psoralen cross-linked nucleotides in RNA

A method is described for using the cross-linking reagent 4'-(hydroxy-methyl)-4,5',8-trimethylpsoralen (HMT) to map base paired regions and higher-order structure within RNA molecules. Applying this method to yeast tRNAPhe, we have specifically identified cross-links within the acceptor stem between U6 X U68, in the D-stem between C11 X C25, and in the T psi-stem between U50 X C63 and U52 X C63. We have also identified a unique cross-link between U8 X C48 which are trans pyrimidines in the core region due to tertiary interactions between U8:A14 and C48:G15. The precise point of cross-linking was deduced in every case by using purine-specific U2 ribonuclease along with cytidine-specific CL3 ribonuclease which will anomalously cleave after photoreversed pyrimidines. The ability to map the precise point of cross-linking should prove invaluable in identifying nucleotides in close proximity within the tertiary structure of other RNA molecules.     

Secondary structure of mouse and rabbit α- and β-globin mRNAs: Differential accessibility of α and β initiator AUG codons towards nucleases

The nucleotide sequence from the 5′ terminus inward of one third of mouse α- and β^maj-globin messenger RNAs has been established. In addition, using 5′ ³²P end-labeled mRNAs as substrates and S1 and T1 nucleases as probes for single-stranded regions, the secondary structures of mouse and rabbit α- and β-globin mRNAs have been analyzed. Our results indicate that the AUG initiator codon in both mouse and rabbit β-globin mRNA is quite susceptible to cleavage with S1 and T1 nucleases, suggesting that it resides in a single-stranded exposed region. In contrast, the initiator AUG in the α-globin mRNA of both species is inaccessible to cleavage, indicating that it is either buried by tertiary structure or is base-paired. Since the rate of initiation of protein synthesis with β-globin mRNA in rabbit reticulocyte is 30–40% faster than for α-globin mRNA, these results imply a possible correlation between the differential rates of initiation with these two mRNAs and the accessibility of the respective AUG initiator codons.     

Heterogeneity of Intermediate Filament Expression in Vascular Smooth Muscle: A Gradient in Desmin Positive Cells from the Rat Aortic Arch to the Level of the Arteria Iliaca Communis

The display of the two distinct intermediate filament proteins, desmin and vimentin, in rat vascular smooth muscle tissue was studied by immunofluorescence microscopy on frozen sections of aorta and other blood vessels. Vascular smooth muscle cells present in these vessels always appeared rich in vimentin. However, staining of sections covering six distinct but contiguous parts of the aorta showed that the number of desmin containing cells was low distal to the truncus brachiocephalicus, but increases until in distal parts of the aorta and in the arteria iliaca communis almost all cells appear positive for desmin. Thus blood vessels show heterogeneity of intermediate filament expression not only in cross-section but can also display heterogeneity along their length. Muscular arteries such as the renal artery and the arteria femoralis, as well as arterioles and veins including the vena jugularis and the vena cava also contain desmin. Thus it may be that low numbers of desmin-positive cells are typical of elastic arteries, while muscular arteries and other blood vessels are characterized by large numbers of desmin-positive cells. We discuss whether desmin-positive and desmin-negative vascular smooth muscle cells may perform different functions and raise the possibility that desmin expression may coincide with the turn on of a specially regulated contractility program.     

Babysitting behavior by age/sex classification in squirrel monkeys (Saimiri sciureus)

The aunting behavior in a captive group of 22 squirrel monkeys containing three infants was done in terms of the age/sex classification of those animals involved. The time course of the aunting phenomena and the type and intensity of the interactions between the mothers and the aunts were recorded. Males as well as females were observed to ascertain if the babysitters were sex specific. Observations were gathered before, during, and after a particular threat to any monkey who was carrying an infant. Three categories of protective behavior (protect, retreat, and nothing) were tabulated. The results indicated that most aunting and protection occurred between infant ages 2-1/2-5 weeks when the infants were growing rapidly but not as yet socially self-sufficient. Mothers protected infants the most against juveniles, then subadult males, and least against other adult females. Subadult males were occasionally observed to carry and protect older infants. Aunting behavior was discussed in terms of the selective pressures by which it may have evolved.     

The blood-brain barrier: an alternative hypothesis

Brain blood vessels, unlike most vessels elsewhere in the body, exhibit a blood-brain barrier (BBB) to certain substances, e.g. trypan blue. Under some circumstances this barrier is no longer effective and the permeability of the vessels increases. Although capillarization is much less in the brain than in many other organs, e.g. heart muscle, total cerebral blood flow per minute is enormous. Consequently, to accommodate a large blood volume with a limited capillary bed, the velocity of blood through brain vessels must be extremely fast. The hypothesis presented in this paper is that this rapid flow results in a low or negative pressure on the endothelium, and plasma and trypan blue are prevented from passing through the wall. The tight junctions of cerebral endothelial cells may be able to withstand only a limited amount of pressure on their luminal surface. If the velocity of blood in brain capillaries decreases, pressure on the endothelium should increase, and brain vessels, like blood vessels elsewhere in the body, become permeable to vital dyes. Other conditions also increase capillary permeability, e.g. acute arterial hypertension or venous congestion. Although brain vessels can adapt to a moderate, gradual change in systemic pressure, when a significant rise in cerebral arterial pressure is abrupt, the compensatory changes in the postcapillary venous bed may be inadequate and consequently intracapillary pressure and vascular permeability are increased. Venous congestion increases intracapillary pressure by restricting capillary outflow as well as by reducing velocity through capillary beds. Under such conditions increased capillary permeability may be indicated by cerebral edema, and even, on occasion, by petechial hemorrhages. In short, if the flow is fast and unimpeded the BBB will be effective; if the velocity decreases, or intracapillary pressure increases for whatever reason, the permeability of the brain endothelium will be abnormally increased.