Atypical Manifestations of Hyperthyroidism

Patients with hyperthyroidism usually present with symptoms of hypermetabolism with or without goitre and/or eye signs. Occasionally, however, the chief complaints are not immediately suggestive of hyperthyroidism. Patients with hyperthyroidism are described who presented with such atypical manifestations as periodic muscular paralysis, myasthenia, myopathy, encephalopathy, psychosis, angina pectoris, atrial fibrillation, heart failure without underlying heart disease, skeletal demineralization, pretibial myxedema, unilateral eye signs, and pitting edema of the ankles.     

Ventricular septal defect with bidirectional shunting: Mathematical considerations

Previously proposed formulae for the quantitative estimation of bidirectional shunts across ventricular septal defects require determination of the oxygen contents of mixed venous, pulmonary artery, pulmonary venous, and aortic blood. Because these formulae do not take into account the mixing of oxygenated with unoxygenated blood within the ventricles, their use must result in underestimation of shunt flows in each direction. A mathematical model for a ventricular defect is examined, in which it is assumed that mixing of blood occurs in each of six sites in the venae cavae or right atrium, right ventricle, pulmonary artery, left atrium, left ventricle, and aorta. A total of fourteen streams of blood can flow from one to another of these mixing sites. As long as complete mixing occurs in the six specified mixing sites, any degree of mixing or non-mixing of the various streams is permitted. From the equations characterizing the model, formulae are derived in which the shunt flow in each direction is expressed in terms of the oxygen contents in the six mixing sites and the fractions of blood which enter the shunt from either side without prior mixing in a ventricular mixing site. The previously reported formulae, which apply when no ventricular mixing is allowed to occur, lead to theoretical minimum values for the shunt flows in each direction. At the opposite extreme where all the shunting blood is required to mix in a ventricle before entering the shunt, formulae for maximum possible shunt flows are also obtained. The absolute values for the left-to-right and right-to-left shunt flows, which must lie somewhere between the theoretical maximum and minimum values, cannot be computed from blood gas data alone. This work was supported in part by grant HE-07563 from the National Heart Institute of the National Institutes of Health and grants-in-aid from the American and North Carolina Heart Associations and the Life Insurance Medical Research Fund. Work completed during tenure as U.S.P.H.S. post-doctoral fellow.     

Vegetation Changes Following Large-scale Fence Removal Across a Protected Area Network Within the Kruger to Canyons Biosphere Reserve,South Africa

Ecosystems - In the early 1990’s, reserves adjacent to Kruger National Park (KNP) removed their fences to create a continuous landscape within the Kruger to Canyons Biosphere Reserve....     

Fine-scale mapping of physicochemical and microbial landscapes of the coral skeleton

The coral skeleton harbours a diverse community of bacteria and microeukaryotes exposed to light, O₂ and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O₂ and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef-building corals Porites lutea and Paragoniastrea benhami. The physicochemical environment was more stable in the deep skeleton, and the diversity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O₂ habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O₂ and pH of the coral skeleton explained the β-diversity of the bacterial communities, and skeletal layers that showed O₂ peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism.     

Coordinate regulation by iron of the synthesis of phenolate compounds and three outer membrane proteins in Escherichia coli.

The biosynthesis of the low-molecular-weight iron carrier enterochelin and of three outer membrane polypeptides appears to be coordinately regulated by the amount of cell-associated iron in Escherichia coli K-12. Measurements of iron acquisition made throughout the growth cycle in iron-deficient media indicate that a very rapid accumulation of iron occurs in the first 2 h of growth; there is comparatively little iron uptake during exponential growth, which results in a gradual decrease in the cellular iron content with each generation. When this level falls below 400 ng of iron per mg (dry weight) of cells, there is a simultaneous onset of synthesis of the three outer membrane polypeptides and of enterochelin. This coordinate regulation was also observed in cells able to transport iron actively using only citrate as an iron-carrier.     

Effects of condensed phosphates on plant growth and phosphorus uptake

Summary Four condensed phosphates with large and small molecules, including ring and chain structures, were equivalent to orthophosphate in terms of phosphorus uptake and the dry matter yield of ryegrass grown in two soils in pots. This equivalence was maintained at each of 6 cuts during two seasons.Increasing N rate greatly increased uptake of applied phosphorus but there was no differential effect with different sources of phosphorus, nor was there any interaction between source and application rate.Phosphorus was not leached at any time, indicating that the phosphates were rapidly adsorbed by the soils.Fairly rapid hydrolysis of all the condensed phosphates occurred in a soil of neutral pH but a slower hydrolysis seemed to occur in an acid soil.There was a good correlation between the phosphorus uptake by ryegrass and the additional orthophosphate released by an acid hydrolysis of soil extracts.     

Studies on the mechanism of action of isopropyl N-phenyl carbamate

The binding of [¹⁴C]isopropyl N-phenyl carbamate (IPC) to microtubular protein isolated from chick brains, and the effect of isopropyl N-phenyl carbamate (IPC) on the in vitro reassembly of microtubules was investigated. While [¹⁴C]colchicine binds to microtubular protein, [¹⁴C]IPC does not. Concentrations from 1 × 10⁻⁴ M to 1 × 10⁻³ M IPC do not prevent in vitro repolymerization of microtubular protein. IPC (1 × 10⁻⁴ M) does not affect the rate of reassembly of microtubules. We conclude that IPC does not exert its effect through an interaction with microtubular protein; we suggest that IPC probably interacts with microtubule organizing centers.     

Powdery mildew resistance and Lr34/Yr18 genes for durable resistance to leaf and stripe rust cosegregate at a locus on the short arm of chromosome 7D of wheat

The incorporation of effective and durable disease resistance is an important breeding objective for wheat improvement. The leaf rust resistance gene Lr34 and stripe rust resistance gene Yr18 are effective at the adult plant stage and have provided moderate levels of durable resistance to leaf rust caused by Puccinia triticina Eriks. and to stripe rust caused by Puccinia striiformis Westend. f. sp. tritici. These genes have not been separated by recombination and map to chromosome 7DS in wheat. In a population of 110 F₇ lines derived from a Thatcher × Thatcher isogenic line with Lr34/Yr18, field resistance to leaf rust conferred by Lr34 and to stripe rust resistance conferred by Yr18 cosegregated with adult plant resistance to powdery mildew caused by Blumeria graminis (DC) EO Speer f. sp. tritici. Lr34 and Yr18 were previously shown to be associated with enhanced stem rust resistance and tolerance to barley yellow dwarf virus infection. This chromosomal region in wheat has now been linked with resistance to five different pathogens. The Lr34/Yr18 phenotypes and associated powdery mildew resistance were mapped to a single locus flanked by microsatellite loci Xgwm1220 and Xgwm295 on chromosome 7DS.