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At least 73 records · Page 4Linked to original sources
PubMed1995

Calcium channel blocker decreases pentagastrin-stimulated alkaline-tide: a role for extracellular calcium in gastric acid secretion.

We previously showed that repeated stimulation of the gastrin receptor may lead to down-regulation. We hypothesized that entry of extracellular Ca2+ may replenish cytosolic Ca2+ and enable continuation of the acid-secretion process. Pentagastrin-stimulated alkaline-tide study was performed in seven duodenal ulcer patients on 2 separate days--with and without pretreatment with verapamil (Ca2+ channel blocker). The alkaline-tide test may substitute the conventional gastric acid collection as previously described. A significant rise in base excess after pentagastrin injection was found on the first day of the study, from 0.400 +/- 1.233 to 2.230 +/- 1.330 (mean +/- SD, P = 0.02). On the second day the rise was not statistically significant, from -0.200 +/- 0.838 to 0.440 +/- 1.200 (mean +/- SD, P = 0.27). In 6 of the 7 patients the alkaline-tide decreased from 45.29 +/- 21.75 mEq/45 min on the first day to 21.56 +/- 17.48 mEq/45 min on the second day of the study (mean +/- SD, P = 0.029), a decrease of 63.6 +/- 36.2%. Our findings may support a dual source for Ca2+, the second messenger in gastrin-dependent gastric acid secretion. The first increase of intracellular Ca2+ comes from cellular stores, and the second from extracellular source by Ca2+ channels, which can be blocked by verapamil.

Acid-Base Equilibrium↗
PubMed1994

Magnetic resonance imaging of the brain during alcohol absorption and elimination--a study of the "rising tide phenomenon".

The absorption phase of alcohol is typically accompanied by more marked behavioral effects than the elimination phase. The mechanism behind this so-called "rising tide phenomenon" has not been fully elucidated. We hypothesized that the rising tide of alcohol during the absorption phase increases the permeability of the blood-brain barrier (BBB), thus elevating the free water content with consequent edema. The resulting increase in intracranial pressure, combined with alcohol's direct toxic effects, results in a synergetic reinforcement of the symptoms of intoxication. To test this hypothesis we performed proton magnetic resonance imaging (MRI) on the human brain during the alcohol absorption and elimination phases. Our results indicate that the alcohol-induced transient opening of the BBB is a possible factor behind the rising tide phenomenon.

Adult↗
PubMed2000

The clocks controlling the tide-associated rhythms of intertidal animals.

The living clock that governs tide-associated organismic rhythms has previously been assumed to have a fundamental period of approximately 12.4 h, an interval that reflects the average period of the ebb and flow of the tide. But, in 1986, marine chronobiologists began to accumulate laboratory results that could not be explained by the action of such a clock. Prime among these findings was the discovery that, occasionally, one of the two daily peaks in an organism's rhythm assumed a different period from its partner. Similar results have since been observed in a host of different organisms. These data led to the circalunidian-clock hypothesis that envisions two basic 24.8 h clocks, coupled together in antiphase, as the driving force for these rhythms. There is, however, only a slight difference (50 minutes) in running times between a solar-day clock with a period of approximately 24 h and a lunar-day clock with a period of approximately 24.8 h, both of which display "circa" periods that overlap. Here, I postulate that the two clocks are fundamentally one and the same. BioEssays 22:32-37, 2000.

Adaptation, Physiological↗
PubMed1986

Abolition of postprandial alkaline tide after vagotomy and its use as a screening test in the assessment of vagotomy.

Assessment of completeness of vagotomy has always been an irksome and time-consuming affair. The commonly employed test of insulin-induced hypoglycaemia (Hollander) is tedious, risky and associated with practical limitations and theoretical objections, which have resulted in its being replaced by the modified sham feed technique in some centres. The postprandial alkaline tide is attributed to HCO3- release consequent to H+ secretion. Any procedure which reduces acid secretion is expected to affect the postprandial urinary pH. This study was performed to evaluate the effect of vagotomy on the postprandial alkaline tide by measuring prevagotomy and postvagotomy fasting and postprandial urinary pH. The results show that postprandial urinary pH falls after vagotomy and this method may be used to assess the completeness of vagotomy. The proposed test is convenient and may be used as a screening method in the assessment of vagotomy and other acid reducing operative procedures, if further validated, by comparison with already established tests.

Eating↗
PubMed2006

Use of quantitative real-time PCR to investigate the dynamics of the red tide dinoflagellate Lingulodinium polyedrum.

A new method based on quantitative real-time polymerase chain reaction (qPCR) was developed and applied to quantify the red tide dinoflagellate Lingulodinium polyedrum in natural seawater samples and in laboratory cultures. The method uses a Molecular Beacontrade mark approach to target a species-specific region of the small subunit ribosomal RNA gene. The accuracy of the method was verified by microscopical counts using cultures of the dinoflagellate isolated from coastal waters near Los Angeles, CA, and with natural water samples spiked with cultured L. polyedrum. The method was applied to document the pattern and timing of vertical migration by the dinoflagellate in a 2-m water column on an 11:13 h light/dark photoperiod established in the laboratory. Positive phototaxis of L. polyedrum resulted in dense aggregations of the dinoflagellate within the top few centimeters of the water column during the light period. This pattern of distribution was readily established by both methods, although abundances of L. polyedrum determined using qPCR were higher than abundances determined by microscopy in the morning and lower in the afternoon and evening. These differences may have been a consequence of variability in the DNA content per cell because of synchrony of cell division. Counts using both methods to analyze natural samples collected from coastal waters in the Long Beach-Los Angeles area and adjacent San Pedro Channel were in close agreement. However, the qPCR method exhibited greater sensitivity than the microscopical method when L. polyedrum was present at low abundances, and qPCR had a much higher rate of sample throughput than microscopy. The development of this new approach for enumerating L. polyedrum provides a useful tool for studying the ecology of this important red tide species.

Animals↗
PubMed2004

Trophic cascades in rocky shore tide pools: distinguishing lethal and nonlethal effects.

The effects of predators on the density of their prey can have positive indirect effects on the abundance of the prey's resource via a trophic cascade. This concept has strongly influenced contemporary views of how communities are structured. However, predators also can transmit indirect effects by inducing changes in prey traits. We show that the mere presence of predator risk cues can initiate a trophic cascade in rocky shore tide pools. In large (mean surface area =9 m2), natural tide pools, we manipulated crab density and their foraging ability to examine the relative importance of lethal (density-mediated) and non-lethal (trait-mediated) predator effects to algal community development. We found that perceived predation risk reduced snail density as much as the direct predation treatment, showing that green crab predation was not an important factor regulating local snail density. Instead, snail emigration away from resident crabs appears to be the most important factor regulating local snail density. As a result, the abundance of ephemeral green algae was similar in the predation risk and direct predation treatments, suggesting that the consumption of snails by crabs plays a minimal role in mediating the trophic cascade. Increased attention to trait-mediated effects that are transmitted by predator-induced changes in prey behavior may change our view of how predators exert their strong influence on community structure.

Analysis of Variance↗
PubMed2000

Molecular cloning and antiserum development of cyclin box in the brown tide alga Aureococcus anophagefferens.

Cyclins can be useful cell cycle markers for growth rate studies on harmful algal blooms. In this study, a gene fragment corresponding to cyclin box was cloned for the brown tide alga Aureococcus anophagefferens. This algal gene fragment, designated as Btcycl1, was most similar to cyclin B. Oligopeptides based on the deduced amino acid sequence were synthesized and used to raise an antiserum that reacted on Western blots with a protein of about 63 kDa, the same size as cyclin B in other organisms. The cyclin B-like protein recognized by this antiserum, and the messenger RNA amplified using the primers, were more abundant in exponential cultures and decreased markedly in stationary cultures. This protein also appeared to be cell cycle dependent. Immunofluorescence labeling showed that this antiserum specifically stained a protein in Aureococcus cells and had no cross-reaction with bacteria that were present in the algal culture. The Btcycl1 sequence and the antiserum will provide a useful tool for studies on regulation of in situ growth rate for this brown tide alga.

Journal Article↗
PubMed1982

Effects of toxin of red tide, Ptychodiscus brevis, on canine tracheal smooth muscle: a possible new asthma-triggering mechanism.

The red tide toxin produced by Ptychodiscus brevis becomes airborne by the thrashing action of the surf and wind and induces cough, rhinorrhea, watery eyes, and sneezing in normal humans and wheezing in asthmatic patients. The mechanism of the contractile response induced by P. brevis toxin (PBTX) was investigated with isolated canine tracheal smooth muscle. Tetrodotoxin and atropine blocked the contractile effect of PBTX, and neostigmine potentiated the contraction. Mepyramine, phentolamine, methysergide, and chlorisondamine did not inhibit the effect of PBTX. This is the first description of a naturally occurring airborne substance that causes smooth muscle contraction by stimulating the axon sodium channels, resulting in the release of acetylcholine at postganglionic parasympathetic efferent nerve endings. The in vitro effect of PBTX on canine tracheal smooth muscle indicates that PBTX is capable of causing respiratory irritation and thus may precipitate an asthmatic attack. It is possible, however, that the mechanism is vivo may also include stimulation of a cough receptor reflex and/or stimulation of sodium channels of afferent vagus nerve fibers. In vitro evidence suggests that isoproterenol, atropine, and verapamil may be used to eliminate or prevent the respiratory symptoms that follow exposure to airborne red tide toxin. The use of high-pressure liquid chromatography separated fractions indicates that the neurotoxic component, not the hemolytic component, is responsible for contractions.

Acetylcholine↗
PubMed2003

Studies of the effect of Psi-APONIN from Nannochloris sp. on the Florida red tide organism Karenia brevis.

Studies were conducted on the conditions under which the red tide organism, Karenia brevis (a.k.a., Gymnodinium breve), was treated with Nannochloris sp. The latter organism is known to produce cytolytic agents called Apparent Oceanic Naturally Occurring Cytolin (APONINs). Conventional wisdom might suggest that brevetoxins would be released upon destruction of the single-celled dinoflagellate K. brevis and that efforts to treat red tide outbreaks would lead to release of brevetoxins and enhanced toxicity toward marine species. Earlier studies described conditions by which K. brevis cells were converted to a non-motile form when cultures of K. brevis were treated with an isolate (Psi-APONIN) produced by Nannochloris sp. but when centrifuged only a small amount of the toxin was released. The present study confirms that the toxin is not released when the K. brevis is undisturbed, however, when the culture is stressed (stirred with a magnetic stirring bar for 24, 48, and 72h) toxin was released, and the toxicity could be measured using a Microtox analyzer. In the study, it was found that at as few as eighty cells of K. brevis produced a toxic effect of 20% as measured by the effect on Vibrio fischeri. Nannochloris sp. had no effect on the bacteria used in the Microtox analyzer, nor did interaction of Nannochloris sp. with K. brevis in the short term. This effect is presumed to be due to the production of Psi-APONIN and conversion of K. brevis to a non-motile or resting form.

Animals↗
PubMed2001

A model of oscillatory transport in granular soils, with application to barometric pumping and earth tides.

A simple algebraic model is proposed to estimate the transport of a volatile or soluble chemical caused by oscillatory flow of fluid in a porous medium. The model is applied to the barometric pumping of vapors in the vadose zone, and to the transport of dissolved species by earth tides in an aquifer. In the model, the fluid moves sinusoidally with time in the porosity of the soil. The chemical concentration in the mobile fluid is considered to equilibrate with the concentration in the surrounding matrix according to a characteristic time governed by diffusion, sorption, or other rate processes. The model provides a closed form solution, to which barometric pressure data are applied in an example of pore gas motion in the vadose zone. The model predicts that the additional diffusivity due barometric pumping in an unfractured vadose zone would be comparable to the diffusivity in stagnant pore gas if the equilibration time is 1 day or longer. Water motion due to the M2 lunar tide is examined as an example of oscillatory transport in an aquifer. It is shown that the tidal motion of the water in an aquifer might significantly increase the vertical diffusivity of dissolved species when compared to diffusion in an absolutely stagnant aquifer, but the hydrodynamic dispersivity due to tidal motion or gravitational flow would probably exceed the diffusivity due to oscillatory advection.

Atmospheric Pressure↗
PubMed2004

Production of superoxide anion and hydrogen peroxide by the red tide dinoflagellate Karenia mikimotoi.

We found that the red tide dinoflagellate Karenia mikimotoi (Gymnodinium mikimotoi) generates reactive oxygen species (ROS). In chemiluminescence analysis using an O2- specific probe, a slightly lower but significant level of O2- was detected in a K. mikimotoi cell suspension as compared to one containing Chattonella marina, a well-known ROS-producing red tide phytoplankton. Interestingly, the chemiluminescence response pattern caused by K. mikimotoi was different from that of C. marina, although both responses were almost completely abolished in the presence of superoxide dismutase (SOD). By fluorescence spectrophotometric analysis, H2O2 was also detected in the K. mikimotoi cell suspension, but the level of H2O2 was approximately 10% of that in the C. marina suspension based on the cell number. No significant increase in O2- generation by K. mikimotoi was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus substances prepared from the skin and gills of yellowtail, whereas C. marina generated an increased level of O2- in response to these stimuli. Furthermore, O2- production in C. marina, but not in K. mikimotoi, was inhibited by treatment with proteinase K.

Journal Article↗
PubMed2004

Facile synthesis of @-tide beta-strand peptidomimetics: improved assembly in solution and on solid phase.

The synthesis of @-tide beta-strand peptidomimetics has been improved such that oligomers now can be obtained from solution- and solid-phase synthesis protocols approaching the efficiency and flexibility of peptide chemistry. These methods enable the synthesis of @-tide oligomers with a variety of amino acids and with lengths up to 13 units. [reaction: see text]

Combinatorial Chemistry Techniques↗
PubMed2004

Palaeoclimate: ocean tides and Heinrich events.

Climate varied enormously over the most recent ice age--for example, large pulses of ice-rafted debris, originating mainly from the Labrador Sea, were deposited into the North Atlantic at roughly 7,000-year intervals, with global climatic implications. Here we show that ocean tides within the Labrador Sea were exceptionally large over the period spanning these huge, abrupt ice movements, which are known as Heinrich events. We propose that tides played a catalytic role in liberating iceberg armadas during that time.

Journal Article↗
PubMed1980

Relative sea levels from tide-gauge records.

Mean annual sea levels at 247 tide-gauge stations of the world exhibit a general rise of relative sea level of about 3 mm/year during the past 40 years. In contrast, general uplift of the land is typical of high northern latitudes, where unloading of the crust by melt of Pleistocene ice sheets is significant. Erratic movements are typical of belts having crustal overthrusting and active volcanism. Short-term (5- and 10-year) records reveal recent changes in rates, but such short time spans may be so influenced by climatic cycles that identification of new trends is difficult, especially with the existing poor distribution and reporting of tide-gauge data.

Journal Article↗
PubMed1975

Land drainage as a factor in "red tide" development.

Although the exact mechanisms and factors of red tides are not fully understood, red tides are essentially a coastal phenomenon. The role of land drainage in the modification of coastal waters is discussed. The role of other factors (salinity, biologically active substances, etc.) that are altered by the process of land drainage is analyzed and correlated to experimental evidence derived from laboratory-grown dinoflagellate cultures.

Animals↗
PubMed1975

Effect of anaerobic conditions in bottom waters on the occurrence of red tides at omura bay.

The field observation that the occurrence of red tides at Omura Bay may have a close connection with the development of anoxic conditions in bottom waters was tested by bioassays of seawater collected during summer 1971. The stimulating effect of anaerobically-decomposed products of bottom mud on the growth of Gymnodinium type-'65 was examined. The results suggest that the development of oxygen deficiency in the bottom waters of Omura Bay makes the environment favourable for the growth of red tide organisms, both by the supply of inorganic nutrients and of some unidentified stimulants.

Anaerobiosis↗
PubMed1975

An analytical study of the role of various factors causing red tide outbreaks of trichodesmium as deduced from field and laboratory observation.

The marine blue green alga Trichodesmium sp is found in red-tide outbreaks in sub-tropical areas in the Pacific and Indian Oceans, the Arabian Seas and the equatorial currents of the Gulf of Mexico. Giberellic acid stimulated the growth of Trichodesmium cultures to a greater extent than in the diatom Melosira sulcata. While increasing either the nitrate or phosphate above the normal levels in the culture medium did not greatly stimulate the growth of this organism, Trichodesmium did thrive in nitrogen impoverished waters by nitrogen fixation. The relevance of these findings to the hydrological factors which favour red-tide outbreaks is discussed.

Cyanobacteria↗
PubMed1975

Report on a biochemical red tide repressive agent.

Organisms were isolated from the November 1973 red tide outbreak in a search for a naturally occurring predator organism. Two organisms were found which look promising as a means of biocontrol: a Tintinnideae spp., ciliate and Gomphosphaeria aponina Kutzing, a blue-green algae. This report characterizes a blue-green algal toxin found to be lethal to the Florida red tide organism Gymnodinium breve Davis.

Cyanobacteria↗