Implication of Papio anubis in the transmission of intestinal schistosomiasis in three new foci in Kime area, Ethiopia.

Epidemiological studies were conducted in the Lake Langano area in the Rift Valley of Ethiopia to determine the occurrence of schistosomiasis and assess factors involved in its transmission. Microscopic examination of faecal specimens from free ranging Papio anubis (anubis baboon) troops from Bishan Gari and Burka Dita forest reserves revealed Schistosoma mansoni eggs with a prevalence of 12.1% (11/91) and 26.2%(34/130), respectively. The eggs were viable as confirmed by miracidial hatching and infectivity tests. Out of the total 12 communities (three schools, five villages and one herdsmen community) surveyed for schistosomiasis around Lake Langano, individuals excreting S. mansoni eggs were found in nine communities with prevalence of infection ranging from 1.4 to 43%. The intensity of infection ranged from 24 EPG (eggs per gram of faeces) to 243 EPG. Excretion of viable eggs by the baboons indicate that they play a role in maintenance of S. mansoni infection in the locality. The detection of S. mansoni eggs in young children, collection of cercarial-infected Biomphalaria pfeifferi in water bodies, and establishment of S. mansoni infection in lab-bred mice have confirmed establishment of transmission foci in Kime area, south-east of Lake Langano. However, the lake itself does not seem to support transmission of schistosomiasis since no snails were found along the shore of the Lake. Further investigations are indicated to fully elucidate the role baboons play in the epidemiology of schistosomiasis in the Rift Valley of Ethiopia. The risk of introduction of water-based development projects in these new endemic foci in relation to S. mansoni infection in the baboons is discussed.     

Substitution of top predators: effects of pike invasion in a subarctic lake

1. Invasions of top predators may have strong cascading effects in ecosystems affecting both prey species abundance and lower trophic levels. A recently discussed factor that may enhance species invasion is climate change and in this context, we studied the effects of an invasion of northern pike into a subarctic lake ecosystem formerly inhabited by the native top predator Arctic char and its prey fish, ninespined stickleback. 2. Our study demonstrated a strong change in fish community composition from a system with Arctic char as top predator and high densities of sticklebacks to a system with northern pike as top predator and very low densities of sticklebacks. A combination of both predation and competition from pike is the likely cause of the extinction of char. 3. The change in top predator species also cascaded down to primary consumers as both zooplankton and predator‐sensitive macroinvertebrates increased in abundance. 4. Although the pike invasion coincided with increasing summer temperatures in the study area we have no conclusive evidence that the temperature increase is the causal mechanism behind the pike invasion. But still, our study provides possible effects of future pike invasions in mountain lakes related to climate change. We suggest that future pike invasions will have strong effects in lake ecosystems, both by replacing native top consumers and through cascading effects on lower trophic levels.     

The reduction of endplate responses by botulinum toxin

Endplate responses were recorded in frog muscle fibres during an advanced stage of botulinum (BoTX) paralysis, when transmitter release had fallen to a very low level. By simultaneous recording from two points, it was found that, even when the quantal responses had been reduced to less than 0.01 per impulse (that is, four to five orders of magnitude below normal), the release continued to be spatially dispersed along the terminal arborization. These observations make it very unlikely that whole "active zones' could be eliminated, as has been suggested, in all-or-none fashion by local action of BoTX molecules, and they suggest a more graded, indirect mechanism by which the toxin molecules interfere with the sites of transmitter release.     

Antagonism of botulinum toxin by theophylline

Theophylline increased the time required for botulinum toxin to cause neuromuscular blockade in an isolated phrenic nerve-diaphragm preparation. Theophylline also offered some protection against botulinum toxin in mice, $\text{in}\text{vivo}$.     

The Effect of DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) on Photosynthesis, Glycolate Excretion ('Photorespiration') and Amino Acid Metabolism in the Blue-Green Alga Anacystis

When photosynthesis of the blue-green alga Anacystis nidulans was measured as ¹⁴CO₂-fixation, the inhibitory effect of DCMU at low concentrations was greatest when mainly Photosystem 1 (PS 1) (excitation at 446 or 687 nm) was operative. At concentrations above 10-⁶M the inhibition on ¹⁴CO₂-fixation was greatest when mainly Photosystem 2 (PS 2) was operative (excitation at 619). During excitation of PS 1, the excretion of glycolate was stimulated at low concentrations of DCMU (5 × 10^-8M and lower), while higher concentrations inhibited excretion. All concentrations of DCMU inhibited glycolate excretion when mainly PS 2 was excited. The curves showing the relative effect of DCMU on the two photosystems, measured as PS 1/PS 2, had opposite shapes for ¹⁴CO₂-fixation and glycolate excretion. An increase in ¹⁴CO₂-fixation coincided with a decrease in glycolate excretion and vice versa. It appears that the increased rate of photosynthesis when mainly PS 1 was operative relative to that when mainly PS 2 was excited, increases the consumption of glycolate in an oxidation process associated with the excitation of PS 1, resulting in less excretion of glycolate to the medium. The influence of DCMU inhibition on labelled amino acid pools connected to the glycolate pathway (glycine-serine) is quite similar to that for ¹⁴CO₂-fixation. At concentrations below 10^-6M DCMU, inhibition of ¹⁴CO₂- incorporation into the amino acids was greatest when PS 1 was excited, while at the higher concentrations tested, inhibition was greater when PS 2 was excited. We conclude that the metabolism of glycine and serine is closely connected to the rate of photosynthesis.     

Multiphasic uptake of potassium by barley roots of low and high potassium content: Separate sites for uptake and transitions

In the range 10^?6M - 5 × 10^?2M uptake of K⁺ in excised roots of barley (Hordeum vulgare L. cv. Herta) with low and high K content could in both cases be represented by an isotherm with four phases. Uptake, especially in the range of the lower phases, was reduced in high K roots through decreases in V_max and increases in K_m. Similar data for other plants are also shown to be consistent with multiphasic kinetics. The concentrations at which transitions occurred were not affected by the K status, indicating the existence of separate uptake and transition sites. Uptake was markedly reduced in the presence of 10^?5M 2,4-dinitrophenol, especially at low K⁺ concentrations, but the isotherms remained multiphasic. This contraindicates major contributions from a non-carrier-mediated, passive flux. A tentative hypothesis for multiphasic ion uptake envisions a structure which changes conformation as a result of all-or-none changes in a separate transition site. The structure is “tight” at low external ion concentrations (low V_max. low K_m. active uptake, allosteric regulation) and “loose” at high concentrations (high V_max- high K_m- facilitated diffusion, no regulation).     

Glomerular epithelial foot processes in normal man and rats

Summary The width of individual glomerular epithelial foot processes appears very different on electron micrographs.A method for obtaining distributions of the true width of foot processes from that of their apparent width on electron micrographs has been developed based on geometric probability theory pertaining to a specific geometric model. Analyses of foot process width in humans and rats show a remarkable interindividual invariance implying rigid control and therefore great biological significance of foot process width or a derivative thereof.The very low inter-individual variation of the true width, shown in the present paper, makes it possible to demonstrate slight changes in rather small groups of patients or experimental animals.In part presented at the International Symposium on Correlation of Renal Ultrastructure and Function, August 1978, Aarhus, Denmark