Maturation-related changes in mass and elemental contents of secretory granules as measured by electron-microprobe

Summary The relationship between granule density, protein content, and Ca and S contents were studied in two secretory granule fractions, from parotid glands of the rat, previously shown to constitute different stages in granule maturation. The density of the lighter fraction was between 1.133 and 1.142 g/ml, while that of the heavier fraction was greater than 1.142 g/ml. The mean protein content of the denser granules was 12% greater than that of the lighter granules (P<0.03), while the dry-mass elemental concentrations in the two granule fractions were unchanged. These results indicate that protein is added to granules during the maturation process (presumably by vesicular traffic), and that the resulting increase in granule density is not driven simply by decrease in water content and/or increased concentrations of inorganic Ca or S in the granules. The elemental concentration values also indicate that the diffusible elements permeate the granule membrane during the fractionation procedures.     

Ultrastructural visualization of exocytosis in the pig pineal gland

Summary The pinealocytes of the pig contain conspicuous dense bodies, the nature and role of which are not yet fully elucidated. The aim of this study was to demonstrate whether or not these structures are involved in the secretion process. The tannic acid-Ringer incubation (TARI)-method, which allows a clear-cut ultrastructural study of secretory discharge by exocytosis, has been used. The results indicate that pig pinealocytes release the content of the dense bodies with an amorphous inner structure into the extracellular space via exocytosis and that this secretion is quantitatively important. The secreted material is proteinaceous in nature; this indicates that polypeptides are released by the pineal.     

Experimental effects of elevated salinity on three benthic invertebrates in Pyramid Lake,Nevada

Salinity of Pyramid Lake increased from 3.7 to 5.5 between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m³) mesocosms.Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0 compared with 5.6 controls in year one, but not in 8.5 salinity mesocosms in year two. The 96-h LC₅₀ for H. azteca was high at 19.5. Short-term mortalities of C. utahensis were 100% at salinities of 13.3 and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5 salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0 and higher compared with controls. Mortality of Heterocypris sp. was 50% at a salinity of 18.6 in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0 than in controls.Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.     

Spanish salt lakes: Their chemistry and biota

A large number of small saline lakes are distributed throughout Spain. Four main lake districts occur from sea level to 1000 m.a.s.l. Most lakes are temporary because of the arid conditions in the Spanish endorheic areas. Many lakes are situated in Tertiary depressions in NE. and S. Spain. Lake basins were formed in karstic areas by hydrologic and aeolian erosion. Saline lakes in NE. Spain occupy areas isolated between river basins. The major ions encountered in these lakes are usually sodium-chloride and magnesium-sulphate; sodium carbonate or sodium-sulphate rich waters also occur.The biota of Spanish salt lakes is related to that of a larger biogeographical region which includes the Mediterranean countries. The main types of salt lakes in Spain include: (1) temporarily mineralized but not highly saline lakes, salinity is less than 7 g l^-1. Chara canescens, C. aspera, Zanichellia palustris, Daphnia atkinsoni, Mixodiaptomus incrassatus and Arctodiaptomus wierzejskii are the most characteristic organisms. (2) Temporary salt lakes, salinity fluctuates between 7 and 300 g l^-1. Chara galioides, Lamprothamnion papulosum, Daphnia mediterranea, Arctodiaptomus salinus and Cletocamptus retrogressus are the most common species. (3) Permanent salt lakes, Ruppia maritima, Najas marina and Artemia salina are the characteristic organisms.     

Ultrastructure of the frontal organ in Convoluta and Macrostomum spp.: significance for models of the turbellarian archetype

Present models of turbellarian evolution depict the organism with a frontal organ — a complex of glands whose necks emerge at the anterior tip of the body — and therefore imply that this organ is homologous throughout the Turbellaria. However, comparisons of representatives of the Acoela and Macrostomida, two putatively primitive orders of the Turbellaria, show that frontal organs in these two are not similar in ultrastructure or histochemistry. The acoel Convoluta pulchra had a prominent cluster of frontal mucous glands whose necks emerged together in a frontal pore at the exact apical pole of the organism, and an array of smaller glands of at least five other types opened at the anterior end, separately from and ventral to this pore. The frontal organs (Stirndrüsen) of two species of Macrostomum on the other hand, comprised an array of discretely emerging necks of at least two gland types including one with rhabdiform (rhammite) and one with globular mucous secretion granules neither of which emerge at the apical pole. In neither species did the organ appear to be sensory. Our findings indicate a low probability of homology between the frontal glands of the Acoela and Macrostomida.     

Pathophysiologic alterations in Biomphalaria glabrata infected with Angiostrongylus costaricensis

Hemolymph glucose, alkaline phosphatase, lactic dehydrogenase, and creatine phosphokinase in Biomphalaria glabrata infected with Angiostrongylus costaricensis were significantly higher on day 27 postinfection (PI) than in uninfected snails. Hemolymph total calcium from infected snails was less on days 6, 12, and 27 PI than that from controls. Total hemolymph protein was similar for controls and infected animals during the entire study. Throughout the study the mean number of amoebocytes/mm³ hemolymph from infected snails was significantly less than that for controls. Mean total wet weights of digestive gland and foot muscle from infected and uninfected snails was similar throughout the study. Mean μg glycogen/mg wet weight of digestive gland from infected snails was significantly greater on days 24, 27, and 28 PI than that from controls. Mean μg glycogen/mg wet weight of foot muscle from infected snails was significantly reduced between days 12 and 28 PI from that of uninfected snails. It is suggested that hemolymph glucose and digestive gland glycogen in infected snails are augmented by glycogen breakdown in the foot muscle of parasitized animals. Elevations in hemolymph enzymes are due to tissue destruction by larvae emerging from the foot muscle of infected snails. Parasite-induced derangements in shell metabolism underlie observed changes in hemolymph calcium in infected snails.     

Effect of micellar lipids on rabbit intestinal brush-border membrane phospholipid bilayer integrity studied by31P NMR

Summary The effect of biliary salts and fatty acids on the bilayer structure of rabbit intestinal brush-border membranes was studied using the nonperturbing probe³¹P NMR. The broad. asymmetric lineshape of the³¹P NMR spectrum of isolated brush-border vesicles demostrates that their component phospholipids are organized in extended bilayers. These membranes are not significantly perturbed by incubation with physiological concentrations of biliary salts (3, 9, 18mm), demonstrating that the vesicles are highly stable, corresponding to their biological function. However, the emergence of a narrow peak superimposed on the broad lineshape indicates that a small proportion of the membrane phospholipids has reached isotropic motion, which may correspond to external or internal micellar structures. Incubation with mixed micelles of fatty acids and taurochlorate show that long-chain fatty acids enhance the membrane-perturbing effect of taurocholate while short-chain, watersoluble fatty acids do not, suggesting a difference in the absorption mechanisms.     

Chlorophyll differences in Mono Lake (California) observable on Landsat imagery

In Mono Lake (California), a large saline lake, chlorophyll concentrations in the euphotic zone increased from 4 to 45 µg l^–1 between July and October 1979. These seasonal changes in chlorophyll are detectable on imagery obtained with the multispectral scanner on Landsat. Computer-compatible tapes of Landsat images were normalized for solar zenith and corrected for atmospheric scatter and absorption to obtain Landsat band 4 emittances (W m^–2 str^–1) of 13.4 ± 0.5 when chlorophyll was 4 µg l^–1 and 4.6 ± 0.3 when chlorophyll was 45 µg l^–1. Lake wide, spatial heterogeneity of chlorophyll of 2 µg l^–1 in July and 8 µg l^–1 in October was not detectable on the Landsat imagery.     

Effect of Acute Hypoxia on Ascorbate Content of Plasma, Cerebral Cortex, and Adrenal Gland

Levels of ascorbic acid (AA) in the plasma, brain, and adrenal gland of rats were determined after 15 min of hypoxia (PaO2 less than 25 mm Hg) and following asphyxia. In rabbits, AA plasma levels were followed up to 75 min of reoxygenation following 15 min of hypoxia of the same severity. A significant increase (approximately 70%) in AA levels was found in plasma of rats and rabbits after hypoxia and asphyxia. This increase was found to be transient, with a return to normal levels within 1 h after resumption of normal oxygenation. Pretreatment with dexamethasone reduced the increase in AA level in both rabbits and rats. Adrenalectomy in rats, performed 24 h before the experiment, abolished the response to hypoxia. Ascorbate levels in the cerebral cortex, hypothalamus, and adrenal gland of awake rats subjected to hypoxia or asphyxia were found to be the same as in normoxic rats. Our results suggest that the observed changes in plasma AA levels are probably mediated through adrenocorticotropic hormone and that the adrenal gland is the major source of ascorbate efflux into the circulation during oxygen deprivation.