Ultrastructure and some other properties of inverted thyroid follicles in suspension culture

Separated thyroid follicles in suspension culture invert in 5% serum. In some, the inversion is not complete in that a small normal follicle persists completely in the interior of an inverted follicle. In inverted follicles the lumens are distended and electron lucent. The bounding epithelial cells are stretched, have relatively few microvilli on the surface toward the medium but they have bundles of oriented microfilaments usually located near the lumen. The cells are connected together by tight junctions. When inverted follicles are punctured, the lumen shrinks, the cells retract and become cuboidal and microvilli reappear. Microfilaments persist at the luminal surface but no longer in oriented bundles. No appreciable extracellular matrix is present at the basal cell surface in contact with the lumen, but matrix is occasionally observed between cells. Since bundles of microfilaments like stress fibers are observed in the cells in suspension culture, the presence of stress fibers in cells in monolayer culture is probably not dependent on attachment but might be a reflection of the spreading of the attached cells.     

Subspecies differences in hormonal and behavioral responses after group formation in squirrel monkeys

The behavioral and hormonal responses of squirrel monkeys of the Bolivian and Guyanese subspecies were compared after a group formation procedure. Two groups of each subspecies, consisting of five females and three males (later reduced to two) were observed daily during the week of group formation and for nine weeks following removal of a single male from each group. Measures of plasma cortisol were examined in the females after the initial group formation and after the groups were reduced by one male. The levels of plasma testosterone were assessed in all the males during the initial week of group formation. Linear dominance hierarchies were determined both within and across the sexes in both subspecies. The frequency and directionality of low-level aggressive interactions indicated that females of the Bolivian subspecies were dominant to the males, while the males of the Guyanese subspecies ranked over all the females. Additionally, the Bolivian squirrel monkey females showed an elevation of plasma cortisol on the day of group formation, which declined 48 hr later, then reelevated after the groups were reduced by one male and declined gradually over a nine-week period. Guyanese females showed little change in cortisol levels during both periods. This suggests fundamental hormonal, as well as behavioral, differences between the two subspecies. The change in plasma testosterone levels in the males during the initial week of group formation was positively correlated with social status. Furthermore, differences in the dynamics within individual groups for each subspecies were reflected by the levels of plasma cortisol of the female members.     

Gas exchange through the jelly capsule of the terrestrial eggs of the frog,Pseudophryne bibroni

Summary The terrestrial eggs of the Australian frog,Pseudophryne bibroni, increase in diameter during development by absorbing water from the substrate into the perivitelline space. This decreases the thickness of the jelly capsule and increases its effective surface area, both effects joining to increase the O₂ conductance of the capsule in parallel with the rate of O₂ consumption. PerivitellineP _{O 2}, calculated from capsule morphology and metabolic rate, and confirmed with micro-O₂-electrodes, remains high and constant (17–19 kPa) throughout the 39 day incubation period at 12°C. The increase in conductance is essential for adequate oxygenation of late embryos. Eggs incubated on substrates of 0 and –25 kPa matric tension (bracketing field conditions) take up disparate amounts of water but show similar conductance.     

Respiration and heat production by the inflorescence of Philodendron selloum Koch

During a 2-d sequence of anthesis, the spadices of the thermogenic arum lily, Philodendron selloum, regulated maximum temperature within a small range (37–44°C) by reversible thermal inhibition of respiratory heat production. This response protects the inflorescence and the attracted insects from thermal damage. Heat production by whole spadices, measured by O₂ respirometry, equalled heat loss, measured by gradient layer calorimetry, which confirmed the heat equivalence of O₂ consumption (20.4 J ml^-1). This also indicated that there was no net phosphorylation during thermogenesis, heat production being the primary function of high rates of respiration. The sterile male florets consumed about 30 ml g^-1 h^-1 and the average 124-g spadix produced about 7 W to maintain a 30°C difference between spadix and ambient temperature. Most of the energy for thermogenesis is present in the florets before anthesis. Despite high respiratory rates, thermogenesis is an energetically inexpensive component of the reproductive process.     

Protein carboxyl-methylation: Role in exocytosis and chemotaxis

The enzyme, protein carboxyl-methylase adds methyl groups to the free carboxyl groups of proteins resulting in the neutralization of their negative charges. This reaction may affect both the structure and the function of these proteins. Protein carboxyl-methylation has been implicated in exocytosis and in chemotaxis. The enzymes involved in the turnover of carboxyl-methylated proteins are described and criteria to evaluate the role of these enzymes in exocytosis and chemotaxis are discussed.     

Enhanced release of striatal dopamine following medial hypothalamic damage in rats

Rats given bilateral lesions of the medial hypothalamus, using either direct or radio frequency current, and killed 2 hours later showed a significant elevation in striatal concentration of homovanillic acid (HVA), while striatal dopamine (DA) was unaltered. After unilateral damage the elevated HVA was seen only in the hemisphere ipsilateral to the lesion. In rats killed 2 days after such damage, the striatal HVA did not differ from controls. The elevation of HVA, suggesting an enhanced release of striatal DA, is associated with a resistance to the cataleptic action of the DA receptor blocking agent droperidol. The present findings suggest that medial hypothalamic lesions can increase neurotransmission within brain DA neurons, and that this neurochemical event may account for at least some of the short-term behavioral effects of these lesions. The relationship of these brain events to the long-term behavioral effects of the lesion remains an important issue for future research.     

Effect of Gravity on the Colonial Morphology of Staphylococci in Soft Agar

After horizontal rotation on a clinostat at 1 rev/min, subsurface colonies of staphylococci in soft agar were compact and spherical; nonrotated colonies were diffuse and elongated.     

The influence of Phaeocystis globosa on microscale spatial patterns of chlorophyll a and bulk-phase seawater viscosity

A two-dimensional microscale (5 cm resolution) sampler was used over the course of a phytoplankton spring bloom dominated by Phaeocystis globosa to investigate the structural properties of chlorophyll a and seawater excess viscosity distributions. The microscale distribution patterns of chlorophyll a and excess viscosity were never uniform nor random. Instead they exhibited different types and levels of aggregated spatial patterns that were related to the dynamics of the bloom. The chlorophyll a and seawater viscosity correlation patterns were also controlled by the dynamics of the bloom with positive and negative correlations before and after the formation of foam in the turbulent surf zone. The ecological relevance and implications of the observed patchiness and biologically induced increase in seawater viscosity are discussed and the combination of the enlarged colonial form and mucus secretion is suggested as a competitive advantage of P. globosa in highly turbulent environments where this species flourishes.