Specific paracrystalline structures of rough endoplasmic reticulum in the follicular (stellate) cells of the dog adenohypophysis

Summary The fine structure of follicular cells of the adenohypophysis was examined in fetal, neonatal, and adult beagle dogs. Prior to birth, undifferentiated follicular cells are common. At birth mature cells that form follicles are routinely encountered. The fine structural appearance of follicular cells is unchanged between birth and adulthood. Follicular cells of puppies and adults are, however, distinguished by the presence of unusual complexes within distended cisternae of the rough endoplasmic reticulum. These complexes vary greatly in morphology, some appear as a maze of interconnecting tubules while others show a highly organized paracrystalline configuration. The presence of these paracrystalloid structures in follicular cells supports the view that they represent a distinct pituitary cell type.Supported by NIH Grants AM19743 and NS12969The authors wish to thank John Patrikes and Helen Mantulin for their expert technical assistance     

The effects of different horticultural practices on the chemical flavour composition of some cabbage cultivars

Variations in the chemical flavour composition of three cultivars of cabbage were determined for plants of different horticultural histories. In some i     

A yeast mutant with glucose-resistant formation of mitochondrial enzymes

Summary Yeast mutants with glucose-insensitive formation of mitochondrial enzymes were isolated starting with a strain completely lacking alcohol dehydrogenase activity. The mutations could uniquely be attributed to a single nuclear gene, designated CCR80. They were largely dominant. Glucose-resistant enzyme formation was most prominent with regard to mitochondrial enzymes succinate dehydrogenase and NADH: cytochrome c oxidoreductase. The effect of CCR80 ^r mutations was rather small but significant on the gluconeogenetic enzymes isocitrate lyase, malate synthase and fructose-1,6-bisphosphatase and on invertase synthesis. The repressive effect of maltose in CCR80 ^r mutants was also reduced showing that glucose-resistance is not caused by a mere hexose uptake defect. This regulatory disorders were not accompanied by reduced levels of glycolytic enzymes or drastically altered levels of glycolytic intermediates.Aerobic fermentation of glucose was almost completely inhibited in the mutants; anaerobic glucose degradation was reduced but not completely abolished. Therefore, the mutants appear to be altered in the regulation of glycolysis. A largely glucose-resistant synthesis of respiratory enzymes is obviously a corollary of this alteration.     

The amino acid sequences of plastocyanin from Mercurialis perennis and Capsella bursa-pastoris

The amino acid sequences of the plastocyanins from Mercurialis perennis and Capsella bursa-pastoris have been determined. The amides at positions 64 and 68 in the Mercurialis sequence were positioned by ‘homology’ Both proteins are single polypeptide chains of 99 residues and are closely related to other higher plant plastocyanins.     

Fertile and sterile frond segments of the lyginopterid seed fern Feraxotheca

Fertile and sterile frond segments of the lyginopterid seed fern Feraxotheca culcitaus are described. In both the fertile and sterile specimen three orders of frond axes are borne alternately and in the same plane. Antepenultimate and penultimate frond axes are characterized by a C-shaped vascular bundle and numerous canals containing a golden-colored material in the fossilized condition. Synangia with only four sporangia demonstrate radial symmetry; bilateral symmetry is present in larger synangia. Pinnules possess dichotomous venation, with a single vein entering each lobe of the deeply incised lamina. A single canal occurs below each vein, and vein ends have an amplified vascular bundle. Morphologically Feraxotheca compares most closely with the compression genus Crossotheca. The morphology of the vascular bundle in the largest pinna is similar to a Lower Carboniferous specimen of Rhodea.     

Death on Denali: Fatalities Among Climbers in Mount McKinley National Park From 1903 to 1976—Analysis of Injuries,Illnesses and Rescues in 1976

Between 1903 and 1975 about 1 percent of climbers on Mount McKinley (Denali) and Mount Foraker in Alaska died. In 1976 a total of ten (1.7 percent) of 587 mountaineers died, but this rate of death was not significantly higher than previously.Nineteen percent of climbers in 1976 suffered major or minor injuries, illness or death. Acute mountain sickness (AMS), frostbite and fractures were common. Thirty-three rescues or retrievals of bodies were mounted at a cost of more than $82,000.Inexperience (particularly with arctic mountaineering), poor leadership, faulty equipment and undue reliance on rescue by helicopter contributed to the alarming incidence of accident, illness and death on big peaks in Mount McKinley National Park in 1976.     

The effect of prostaglandin inhibition on the natriuresis of drug-induced renal vasodilatation

It has been suggested that increased prostaglandin release may mediate the natriuresis seen during the administration of renal vasodilators. To further investigate this possibility, either acetylcholine (40 μg/min) or bradykinin (5 μg/min) was infused into the left renal artery of anesthetized dogs previously given an inhibitor of prostaglandin synthesis. During the infusion of either vasodilator drug in the prostaglandin-inhibited dogs, urinary sodium excretion increased to a similar degree as in a group of normal dogs with intact prostaglandin synthesis. These studies therefore do not confirm that prostaglandins play a significant role in the natriuresis of drug-induced vasodilatation.     

Planning an adaptive numerical classification

Summary While numerical methods of classification seek to strictly formalise one part of the classificatory process, a human classifier uses a variety of different approaches to obtain a satisfactory organisation of data. In this paper some means of increasing the flexibility of numerical methods are discussed, in particular the possible uses of the taxonomic hierarchy. It is first necessary to show that higher taxonomic units contain ecologically interesting information. Then, using a two parameter classification method a means of progressing from higher to lower taxonomic units, during analysis and in a data dependent manner, is outlined. A similar procedure is possible with nested samples. However, since the value of a classification resides in its ecological interpretation, an automatic classification requires some means of ascribing meanings to classes. While such a semantic analysis seems theoretically possible, its practical attainment presents considerable difficulties.Contribution to the Symposium on Plant species and plant communities, held at Nijmegen, 11–12 November 1976, on the occasion of the 60th birthday of Professor Victor Westhoff.