Osmotic responses of preimplantation mouse and bovine embryos and their cryobiological implications

Cells subjected to the events occurring before, during, and after freezing and thawing are exposed to major changes in the osmotic pressure of the surrounding medium; i.e., the osmolalities can exceed 30. An important question in understanding the mechanisms of injury is whether cells respond as ideal osmometers to these strongly anisotonic solutions. Mouse and bovine embryos from eight-cell to blastocyst stage were used to investigate the question. They were found to behave as ideal osmometers at room temperature over a wide range of tonicities; i.e., from four times isotonic to almost 1/3 times isotonic, ideality being defined by a Boyle-van't Hoff equation. Embryo volumes increased from 40 to 200% of isotonic over this range and survivals of mouse embryos were unaffected. However, outside this range the membrane apparently becomes leaky and the survival of mouse embryos drops sharply. Osmolalities rise to high values during freezing and the paper develops the thermodynamic equations to show how computed cell volumes as a function of subzero temperature can be translated into the Boyle-van't Hoff format of cell volume as a function of the reciprocal of osmolality.     

Responses of gibbons (Hylobates muelleri) to self,neighbor, and stranger song duets

To determine whether gibbons discriminate among songs given by different groups, I conducted a series of experimental playbacks of recorded Bornean gibbon (Hylobates muelleri)duets. The gibbons did not respond differentially to their own, neighbors’, and strangers’ songs. Failure to show vocal discrimination may be due to factors associated with the experimental procedure or may indicate that there is no selective advantage gained by responding differentially under the playback circumstances.     

Photomovement in Cyanophora paradoxa

Photomovement has been studied in the symbiontic association of the colorless flagellate, Cyanophora paradoxa Korschikoff with the cyanelles, Cyanocyta korschikoffiana. There is no phototactic orientation in this organism, but a photokinetic effect. In addition, the cells show a pronounced step-up photophobic response (however no or only a weak step-down response). The phobic response is mediated by a subset of the photosynthetic pigments located in the symbiontic cyanelles. It is linked to the noncyclic photosynthetic electron transport chain but it is independent of the photosynthetic generation of a proton gradient and the ATP synthesis linked to it.Abbreviations CCCP carbonyl cyanide m-chlorophenyl hydrazone - DBMIB 2,5-dibromo-3-methyl-6-isopropylbenzo quinone - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea     

Transient breakdown in the selective permeability of the plasma membrane ofChlorella emersonii in response to hyperosmotic shock: Implications for cell water relations and osmotic adjustment

Summary In osmotic experiments involving cells of the euryhaline unicellular green algaChlorella emersonii exposed to hyperosmotic stress by immersion in a range of low molecular weight organic and inorganic solutes, a temporary breakdown in the selective permeability of the plasma membrane was observed during the initial phase of transfer to media of high osmotic strength (up to 2000 mosmol kg^–1). Thus, although the cells appeared to obey the Boyle-van't Hoff relationship in all cases, showing approximately linear changes in volume (at high salinity) as a function of the reciprocal of the external osmotic pressure, the extent of change was least for the triitols, propylene glycol and glycerol, intermediate for glucose, sorbitol, NaCl and KCl, with greatest changes in media containing the disaccharides sucrose and maltose. In NaCl-treated cells, uptake of external solute and loss of internal ions was observed in response to hyperosmotic treatment while sucrose-treated cells showed no significant uptake of external solute, although loss of intracellular K⁺ was observed. These observations suggest that the widely used technique of estimating cellular turgor, and osmotic/nonosmotic volume by means of the changes in volume that occur upon transfer to media containing increasing amounts of either a low molecular weight organic solute or an inorganic salt may be subject to error. The assumption that all algal cells behave as ideal osmometers, with outer membranes that are permeable to water but not to solutes, during the course of such experiments is therefore incorrect, and the data need to be adjusted to take account of hyperosmotically induced external solute penetration and/or loss of intracellular osmotica before meaningful estimates of cell turgor and osmotic volume can be obtained.     

Maturing patterns of organ weights in mice selected for rapid postweaning gain

Summary Correlated responses to selection for increased 3–6 week postweaning gain in male mice were estimated for seven internal organs (testes, spleen, liver, kidneys, heart, small intestine (S intest) and stomach) weighed at specific degrees of maturity in body weight (37.5, 50.0, 62.5, 75.0, 87.5 and 100%). Correlated responses in organ weights were generally large, but the magnitude and direction of response depended upon whether 1) comparisons were made at the same age, degree of maturity or body weight and 2) absolute or proportional organ weights were used. The selected line (M16) weighed more and had larger organ weights than controls (ICR) when compared at either the same degree of maturity or the same age, indicating positive genetic correlations between body weight and the respective organ weights. Positive correlated responses were found in spleen weight/body weight at all degrees of maturity and in liver and S intest weights as a proportion of body weight at some degrees of maturity. Testes, kidneys, heart and stomach weights as a proportion of body weight had negative correlated responses, though this was consistent only for kidneys across all degrees of maturity. Correlated responses in organ weights adjusted for body weight by covariance analysis were positive for spleen, S intest and stomach and negative for testes and kidneys. Based on the constrained quadratic model, degree of maturity in organ weight relative to degree of maturity in body weight responded positively for testes, kidneys and S intest and negatively for spleen and liver. Selection for increased growth caused negative correlated responses in allometric growth of testes, kidneys, S intest and stomach.Paper No. 10,545 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned     

Accumulation and subcellular distribution of cations in relation to the growth of potassium-deficient barley

Abstract Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg^?1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg^?1 than in soils with about 90 mg kg^?1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m^?3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations. When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots. X-ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m^?3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m^?3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed.     

Unusual responses of proboscis muscles ofBusycon canaliculatum to some calcium antagonist agents

Summary K- and ACh-induced responses of the radular sac, odontophore retractor, and radular retractor muscles ofBusycon canaliculatum were found to be strongly dependent upon [Ca]₀. Diltiazem had strong positive inotropic and chronotropic actions on fast twitch activity in the odontophore retractor and radular protractor muscles. K-induced tonic force in these muscles was partly inhibited by diltiazem but only at very high concentrations. ACh responses in all muscles were eliminated by diltiazem. Nifedipine enhanced fast twitches and tonic force in response to high K, and induced persistent spontaneous fast twitch discharges. Nifedipine inhibited ACh-induced tonic force, but induced rhythmic bursts of fast twitches persisting long after nifedipine washout. Verapamil strongly inhibited K- and ACh-induced tonic force in all three muscles at high concentration, but stimulated fast twitch responses and converted ACh contractures into fast twitch activity. Sucrose gap studies showed that nifedipine and diltiazem reduced K- and ACh-induced tension and depolarization. Paradoxically, verapamil reduced K- and ACh-induced tension but significantly enhanced their induced depolarizations. Diltiazem, nifedipine and verapamil did not act like slow Ca channel antagonists in these muscles. This may reflect differences in channel structure between molluscs and mammals, or differences in the cellular calcium release pathways operated by such channels in molluscan and mammalian muscle. These Ca-ant-agonists appeared to act as agonists of fast twitch activity in these muscles and antagonists of the ACh-induced calcium release pathway for tonic force development.