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At least 235 records · Page 13Linked to original sources
PubMed1986

Permeability changes in the egg-shell of hookworms during development and eclosion.

The development and hatching of Ancylostoma ceylanicum and Ancylostoma tubaeforme eggs in a range of potentially inimical solutions has been examined using time-lapse video micro-recording techniques. In all compounds tested the larvae developed to the active pretzel stage. The inception of activity resulted in an increase in shell permeability to water and small molecules. In anthelmintics of molecular weight (Mr) 400 development continued normally until about the time that control eggs hatched, when there was a marked decrease in larval activity and eclosion did not occur. The addition of a low Mr surface-active agent potentiated the effect of the anthelmintic and caused larval activity to be lost earlier. The calcium inhibitor lanthanum chloride affected larval development rather than eclosion. Large Mr compounds did not affect either development or hatching and the results suggest that the egg-shell may act as a form of sieve, allowing the essential oxygen to reach the developing larva while excluding large potentially dangerous molecules. No appreciable differences were found between the two species of hookworm examined.

Acridine Orange↗
PubMed1984

Physiological profile of caged layers during one production year, molt, and postmolt: egg production, egg shell quality, liver, femur, and blood parameters.

A longitudinal study of a flock of Single Comb White Leghorn pullets was initiated at 19 weeks of age (preproduction) and continued through a production year, a forced molt, and for 4 months of postmolt production. A representative sample of hens was obtained at 12-week intervals during the first year and at subsequent selected times. Liver lipid, femur weight, femur volume, femur density, egg weight, shell weight, percent shell, milligrams shell/square centimeter of shell surface area, serum calcium, serum phosphorus, and serum alkaline phosphatase were determined. Percent hen-day production peaked at 90% and then declined by .6 to .7% each week during the first production year. After molting, percent hen-day egg production peaked at 80% and declined .9% per week over the subsequent 20 weeks. Egg weight increased continually during the first production year. Shell weight was greatest immediately postmolt; thereafter it declined. Shell thickness was greatest at 31 weeks of age and declined throughout the first year. After molting, the shell thickness of 83-week-old hens was similar to values of hens about 37 weeks of age. Serum calcium and phosphorus of laying hens were influenced by age, feed intake and environmental temperature. The lowest values occurred during hot weather. Liver lipid was lowest in nonlaying hens (17 to 20%) and was approximately 42% of dry weight in laying hens. Femur density was greater in laying than nonlaying hens.

Alkaline Phosphatase↗
PubMed1978

The trichurid egg-shell: evidence in support of the Bouligand hypothesis of helicoidal architecture.

Electron microscopy of thin sections and freeze etch replicas of the eggs of the nematodes Trichuris suis and T. muris is used to provide evidence in support of the Bouligand hypothesis of helicoidal architecture. The evidence presented is as follows: 1. The specific objections to the Bouligand model raised by Dennell (1974) and Dalingwater (1975b) are answered by reference to a pyramid of helicoidal tissue in which the corners are blunt. 2. Sections cut normal to the plane of the laminae do not show parabolic patterning. Parabolae appear if the section is tilted--their direction depending upon the direction of tilting. 3. Freeze etching allows the direct visualization of helicoidal architecture. Fibres are parallel within any one lamina but the fibre direction rotates by an angle of 9 degrees in successive laminae. Parabolic arcs are made up of short lengths of straight fibres--curved fibres were not observed. Planes of sectioning producing single and double spiral artifacts are described and the formation of these artifacts discussed. The sense of rotation of the helicoid is shown to be asymmetrical about any mid-plane through the egg.

Animals↗