Quantitative Ultrastructural Investigations of Mitochondrial Development in Leishmania donovani During Transformation*

SYNOPSIS. The ultrastructure of the mitochondrion during transformation of Leishmania donovani from amastigote to promastigote stages was studied by morphometric analysis. There was a slight but significant decrease in relative mitochondrial volume (Vvli) during transformation. This decrease was linear with time for at least 27 hr. No change in relative lipid inclusion volume (Vvli) was observed during transformation. The ratio of inner to outer mitochondrial surface membrane densities (Svmii:Svmio) also remained unchanged. Although the relative number of cristae remains unchanged after transformation, there is an increase in cristae number in the portion of the kinetoplast opposite the flagellum.     

Cytochromes,Lactic Dehydrogenase and Transformation in Leishmania*

SYNOPSIS. A major difference in heme content was found between leishmanias and leptomonads of Leishmania donovani. When tested with a fluorescence method for heme, leishmanias gave a negative response whereas leptomonads fluoresced brightly. Studies on the terminal respiration of L. tarentolae leptomonads by absorption spectra assay and respiratory inhibitors indicated the presence of cytochromes. Lactic dehydrogenase could not be detected in the leptomonad stage nor could it be found in any other hemoflagellate culture form tested.     

Influence of Complexation on the Uptake by Plants of Iron, Manganese, Copper and Zinc: II. EFFECT OF DTPA IN A MULTI-METAL AND COMPUTER SIMULATION STUDY

Barley (Hordeum vulgare L.) plants were grown in nutrient solutionscontaining the chelating agent, DTPA. The experiments replicatedthose reported in the preceding paper in which EDTA was thechelating agent used. The concentrations of all the chemicalspecies of metals were stimulated using the program NUTRIENT.The concentrations of DTPA used were chosen to give a similarrange of complexation as used in the EDTA experiments. The effectof complexation by DTPA on the uptakes of the metal ions Fe³⁺,Mn²⁺, Cu²⁺, and Zn²⁺ and on plant growth were sufficiently differentfrom those with EDTA to indicate some dependence on the natureof the chelating agent used. The biggest difference betweenthe EDTA and DTPA experiments occurred in the solutions containingthe largest concentrations of these reagents. With DTPA, chlorosiswas seen only in the early stages; otherwise the plants showednormal growth. A simple chemical model for metal uptake is discussed. Key words: DTPA, EDTA, micronutrients, trace metals, computer simulation, plants, absorption, iron, manganese, copper, zinc     

Chemical Patterns, Compartments and a Binary Epigenetic Code in Drosophila

I propose a model which accounts for the geometries and sequencein which compartmental boundary lines arise on the differentimaginal discs, and on the blastoderm of Drosophila melanogaster;and propose that successive lines are recorded by differentbinary switches, to create a binary epigenetic code word specifyingeach disc, and disc compartment. I suppose a biochemical systemundergoing reaction and diffusion acts throughout development.As an imaginal disc grows, a succession of differently shapedchemical concentration patterns form at a discrete set of discsizes. I suppose a specific concentration of one chemical isa threshold. Concentrations above or below threshold switchcells to one or another of two commitments. Then the line acrossthe imaginal disc with the threshold concentration is a predictedcompartmental boundary. The sequence and geometries of suchlines predict the compartmental boundaries seen on the wingdisc, the other discs, and on the blastoderm stage egg. Thecompartmental lines on the wing disc suggest that a terminalcompartment is specified by a combination of binary names recordinga sequence of binary commitments: anterior, not posterior; dorsal,not ventral; wing, not thorax; proximal, not distal. Each combinationcomprises a binary epigenetic code word. Recently I constructedan independent model for transdetermination in Drosophila whichproposed a similar binary epigenetic code for the differentdiscs. The clone restriction lines predicted on the blastodermby my transdetermination model, the chemical pattern model,and analogy with the wing disc, are nearly identical. Severalare already confirmed. The resultant binary code scheme correctlypredicts many relative transdetermination frequencies and accountssimply for the action of most homeotic mutants as genes whichalter a single switch state in one or more discs.     

“Trace Metabolites”–Effect of High Concentrations on Leishmania tarentolae Promastigotes*

SYNOPSIS. Relatively high concentrations (10–100 μM) of chromate, selenate, and vanadate ions accelerated growth of Leishmania tarentolae in a chemically defined medium containing taurine as the sole sulfur source. These ions also enhanced the incorporation of [³⁵S]taurine label in whole cell, 10% trichloroacetic acid insoluble, and 10% trichloroacetic acid soluble cell fractions.     

Territorial Sea Baselines along Ice-Covered Coasts: International Practice and Limits of the Law of the Sea

This article considers the relevant international law pertaining to territorial sea baselines and reviews the application of that law to ice-covered coasts. The international literature concerning the status of ice in international law is examined and state practice for both the Arctic and Antarctic is reviewed. The Law of the Sea Convention contains virtually no provisions pertaining to ice, as during its negotiation, in an effort to reach a consensus, all discussion of Antarctica was avoided. International lawyers appear to favour the notion that where ice persists for many years and is fixed to land or at least is connected to ice that is connected to land, it may be able to generate territorial sea baselines. Neither the International Court of Justice nor any other international tribunal has had the opportunity to consider the status of ice, except in the most general terms. This article considers some alternatives and difficulties in their application. The impact of the Antarctic Treaty on any system is also considered, as Articles IV and VI of the Treaty may be affected by any international action by claimants in proclaiming baselines.-