Thytropin increases the iodine content of rat circulating thyroglobulin as measured by equilibrium density gradient centrifugation

In previous work we demonstrated that circulating thyroglobulin contains very little or no iodine. We have now characterized circulating thyroglobulin following administration of thyrotropin (TSH) to determine whether its iodine content remains low or increases after stimulation. The iodine content of circulating thyroglobulin was estimated from its density determined by equilibrium density gradient (isopycnic) centrifugation. TSH stimulated thyroglobulin from 182 ± 28 ng/ml to 571 ± 83 ng/ml at 8–14 h. Circulating thyroglobulin in the basal state had a density consistent with very little or no iodine. Its density increased following TSH to a maximum at 8–14 h which was nearly the same as the density of thyroglobulin extracted directly from the thyroid. To determine whether selective peripheral metabolism, based on the degree of iodination, could account for the density shift, purified rat thyroid thyroglobulin was injected into thyroidectomized rats. The density of thyroglobulin remained unchanged for 25 h during which time it was metabolized by more than 97%. Therefore, selective metabolism of thyroglobulin based on iodine content did not occur. We conclude that TSH causes a marked increase in the iodine content of circulating thyroglobulin. It is most likely that in the basal state circulating thyroglobulin comes from selective release of poorly iodinated molecules, while after TSH, it comes from release of previously synthesized, iodinated and stored molecules.     

Collagen synthesis and accumulation in long-term rabbit aortic smooth muscle cell cultures

Summary This study describes the ability of aortic smooth muscle cells to synthesize and accumulate collagen with time in culture. Inasmuch as smooth muscle cell cultures multilayer and continue to divide, albeit slowly, and can be maintained in the same vessels where seeded for extended periods of time, a long-term aging study from a single subcultivated population of cells was carried out. This is different from the usual cell-culture aging achieved by an increase in cell population doublings obtained by repeated subcultivations. The latter process, which is trypsin induced, involves a changing cellular environment including the extracellular matrix that is produced by the cells in culture. Second subcultures of weanling rabbit, aortic media, smooth muscle cells maintained for different periods of time up to 14 wk displayed decreasing hydroxyproline formation with time. Proline hydroxylation was determined by pulsing these second-passage cells with [¹⁴C]proline for 24 h at various times during the 14 wk period. The cell layer and medium were evaluated separately for radioactive proline and hydroxyproline and the medium for bacterial collagenase-susceptible protein as well. The percent of hydroxylation in the medium decreased from >31% within 1 wk after plating to 15.2% after 14 wk in culture. The percent of collagenase-susceptible protein in the medium decreased in a comparable manner. The DNA levels increased during the entire period although initially somewhat more rapidly. Accumulation of protein in the extracellular matrix continued during the 14-wk span. The accumulation of hydroxyproline in the extracellular matrix also continued to increase throughout the culture period, but it did slow down significantly. Yet the cells appear not to have lost their ability to accumulate connective tissue and protein in the insoluble cell layer. The data suggest clearly that the percent collagen synthesis relative to total protein synthesis decreases in the older cultures; total protein synthesis also decreases as expected. This study was supported by NIH Program Projects AG00001 and HL 13262.     

Harderian gland ultrastructure of the black sea bottlenose dolphin (Tursiops truncatus ponticus)

Examination of the Harderian gland structure of the Black Sea bottlenose dolphin, Tursiops truncatus ponticus, at macroscopic, microscopic, and electron microscopic levels shows significant sexual dimorphism. The epithelial cells of male and female glands are different cell types, capable of producing chemically different products. Secretory cells in both sexes contain secretion granules that produce a secretion consisting mainly of proteins and carbohydrates, but thought to be sex-specific in composition. The female glands also contain lipid secretion granules. It is suggested that in the bottlenose dolphin the Harderian gland functions to produce sexually distinct pheromones and may have other physiological activities, e.g., participating in local immunological or endocrine-related reactions. © 1994 Wiley-Liss, Inc.     

Fine-scale spatial and temporal distribution patterns of large marine predators in a biodiversity hotspot

Aim

Large marine predators, such as cetaceans and sharks, play a crucial role in maintaining biodiversity patterns and ecosystem function, yet few estimates of their spatial distribution exist. We aimed to determine the species richness of large marine predators and investigate their fine-scale spatiotemporal distribution patterns to inform conservation management.

Location

The Hauraki Gulf/Tīkapa Moana/Te Moananui-ā-Toi, Aotearoa/New Zealand.

Methods

We conducted a replicate systematic aerial survey over 12 months. Flexible machine learning models were used to explore relationships between large marine predator occurrence (Bryde's whales, common and bottlenose dolphins, bronze whaler, pelagic and immature hammerhead sharks) and environmental and biotic variables, and predict their monthly distribution and associated spatially explicit uncertainty.

Results

We revealed that temporally dynamic variables, such as prey distribution and sea surface temperature, were important for predicting the occurrence of the study species and species groups. While there was variation in temporal and spatial distribution, predicted richness peaked in summer and was the highest in coastal habitats during that time, providing insight into changes in distributions over time and between species.

Main Conclusions

Temporal changes in distribution are not routinely accounted for in species distribution studies. Our approach highlights the value of multispecies surveys and the importance of considering temporally variable abiotic and biotic drivers for understanding biodiversity patterns when informing ecosystem-scale conservation planning and dynamic ocean management.     

Erythrocyte membrane proteins: A modified gorter-grendel experiment

Summary The pressure-area isotherm and shear resistance of spectrin-actin monolayers indicate a close-packed structure at about 1.0 m²/mg protein. This surface area is equivalent to a thickness of about two monolayers at the erythrocyte membrane inner face. The maximum elasticity (lowest compressibility) occurs at 0.7 m²/mg protein, indicating the limit of reversible compression. The mechanical properties of the monolayers approximate those of the intact membrane, suggesting that the structures are similar and that these monolayers may account for many of thein vivo properties.