Maximum entropy approach to statistical inference for an ocean acoustic waveguide.

A conditional probability distribution suitable for estimating the statistical properties of ocean seabed parameter values inferred from acoustic measurements is derived from a maximum entropy principle. The specification of the expectation value for an error function constrains the maximization of an entropy functional. This constraint determines the sensitivity factor (ß) to the error function of the resulting probability distribution, which is a canonical form that provides a conservative estimate of the uncertainty of the parameter values. From the conditional distribution, marginal distributions for individual parameters can be determined from integration over the other parameters. The approach is an alternative to obtaining the posterior probability distribution without an intermediary determination of the likelihood function followed by an application of Bayes' rule. In this paper the expectation value that specifies the constraint is determined from the values of the error function for the model solutions obtained from a sparse number of data samples. The method is applied to ocean acoustic measurements taken on the New Jersey continental shelf. The marginal probability distribution for the values of the sound speed ratio at the surface of the seabed and the source levels of a towed source are examined for different geoacoustic model representations.

New species of Entolomataceae from Cameroon.

Six species of Entoloma (Entolomataceae, Agaricales, Basidiomycota) are described from recent Cameroonian collections: E. bisterigmatum, E. brunneoloaurantiacum, E. djaense, E. intricatum, E. versiforme, and E. parvistellatum.These species occur in tropical rainforests dominated by ectomycorrhizal trees in the genera Gilbertiodendron and Uapaca. Data on macromorphology, micromorphology, DNA sequences, habitat and comparisons with similar taxa are provided for each. This is the first contemporary taxonomic work on the Entolomataceae from Cameroon.

New species of Amanita subgen. Lepidella from Guyana.

New species of Amanita subgen. Lepidella are described from Guyana. Amanita cyanochlorinosma sp. nov., Amanita fulvoalba sp. nov., and Amanita guyanensis sp. nov. represent the latest additions to the growing body of newly described ectomycorrhizal fungi native to Dicymbe-dominated tropical rainforests. Macro- and micromorphological characters, habitat, and DNA sequence data for the ITS, nrLSU, rpb2, and ef1-α are provided for each taxon, and ß-tubulin for most. Distinctive morphological features warrant the recognition of the three new species and a molecular phylogenetic analysis of taxa across Amanita subgen. Lepidella corroborates their infrageneric placements.

Liposomes fuse with sperm cells and induce activation by delivery of impermeant agents.

Sperm cell activation is a critical step in fertilization. To directly investigate the cell signaling events leading to sperm activation it is necessary to deliver membrane impermeant agents into the cytoplasm. In this study, the use of liposomes as possible agent-loading vectors was examined using (1) the octadecylrhodamine B (R18) and NBD phosphatidylethanolamine (NBD DHPE)/rhodamine phosphatidylethanolamine (rhod DHPE) fusion assays in bulk samples, (2) membrane transfer of fluorescence from liposome membranes labeled with R18 and rhodamine-tagged phosphatidylethanolamine (TRITC DHPE), and (3) lumenal transfer of impermeant calcium ions from liposomes to sperm cells, a process that stimulated sperm cell activation. Intermediate-sized unilamellar liposomes (98.17+/-15.34 nm) were prepared by the detergent-removal technique using sodium cholate as the detergent and a phosphatidylcholine/phosphatidylethanolamine/cholesterol (2:1:1 mole ratio) lipid composition. In the R18 fusion assays, self-quenching increased logarithmically with increasing concentrations of R18 in the liposome membranes; addition of unlabeled sperm to R18-labeled liposomes lead to a rapid release of self-quenching. In the NBD DHPE/rhod DHPE resonance energy transfer (RET) fusion assay, RET was rapidly reduced under similar conditions. In addition, individual sperm became fluorescent when TRITC DHPE-labeled liposomes were incubated with unlabeled sperm cells. Incubation of sperm cells with empty liposomes did not significantly affect sperm cell activation and did not alter cell morphology. However, incubation with Ca (10 mM)-loaded liposomes resulted in a time-dependent increase in sperm cell activation (7.5-fold over controls after 15 min). We conclude that liposomes can be used for direct loading of membrane-impermeant agents into sea squirt sperm cell cytoplasm, and that delivery occurs via fusion and content intermixing.

Myoelectric assessment of bowel viability.

A device capable of quantitative measurement of intestinal ischemic damage has been designed. The device is called the electrical contractility meter and employs a clip-on strain gauge transducer that delivers a precisely controlled electrical stimulus to the bowel. Threshold stimulus level (TSL) is the stimulus current in milliamperes (mA) that is necessary to produce a clearly defined smooth-muscle contraction. In 30 dogs, TSL was used to establish viability boundaries in 40 cm ischemic bowel segments. Bowel viability was assessed with the use of TSL in comparison with gross features (color, peristalsis) and blood flow measured by means of Doppler ultrasound at 2 cm intervals in the ischemic small-bowel segments. The TSL scale ranges to 100 mA and varied from a low of 22 +/- 2 mA in normal bowel outside the ischemic segment to 97 +/- 4 mA in grossly gangrenous bowel. There was a consistent correlation between rising TSL and worsening bowel color, disappearance of visible peristalsis, and progressive disappearance of audible Doppler signals. Resection and anastomosis were performed in three groups of 10 dogs at TSL measurements of 30 mA, 40 mA, and 50 mA, respectively. Dogs were killed and anastomoses were inspected on the tenth postoperative day. There were no leaks at TSL = 30 mA, one leak at TSL = 40 mA, and four leaks at TSL = 50 mA. The number of leaks at TSL = 50 mA was significantly greater than at TSL = 30 mA (p less than 0.04, Fisher's exact test). These results show that the quantitative myoelectric parameters established by this device provide a reliable in vivo assessment of bowel viability. The electrical contractility meter is easy to use and may have clinical applicability.

The halo vest: an evaluation of motion and forces across the neck.

Flexion-extension motion and compression-distraction forces across the cervical spine were evaluated in 6 patients in halo vests and in 1 patient in a halo cast. Motion in the vest was evaluated in supine and upright positions and averaged 31% of normal motion at the levels tested. Compression-distraction forces showed great individual variation and frequent compression. The average distraction force varied in different positions by nearly 20 pounds in the vest and over 30 pounds in the cast. Methods of improving cervical spine stability in halo orthoses are discussed.

Broadband modeling of downslope propagation in a penetrable wedge.

Sound propagation in a wedge-shaped environment with a penetrable bottom is simulated with broadband adiabatic mode, coupled mode, and parabolic equation model computations. Simulated results are compared to measured data taken in a tank experiment by Tindle et al. The coupled mode formalism is shown to predict, in agreement with that experiment, that modal wave fronts in penetrable wedges are approximately circular arcs centered at the apex of the wedge for a source near the apex. It is also shown that for wedge angles up to 6 degrees, the received waveforms are well approximated by the adiabatic waveforms time-shifted by a depth-dependent interval to account for the curvature of the modal wave fronts. A small deviation from circularity in the modal wave fronts is possibly observed in the 6 degrees case.

Perturbation of intracellular calcium and hydrogen ion regulation in cultured mouse hippocampal neurons by reduction of the sodium ion concentration gradient.

Na(+)-Ca2+ exchange has been identified as a mechanism for regulation of intracellular Ca ion concentration ([Ca2+]i) in neurons of invertebrates and vertebrates, but for mammalian central neurons its role in restoration of resting [Ca2+]i after transient increases induced by stimulation has been less clear. We have examined the recovery of [Ca2+]i following K+ depolarization and glutamate receptor activation of cultured mouse hippocampal neurons using the Ca(2+)-sensitive dye Fura-2. Reduction of the transmembrane Na+ gradient by removal of external Na+ slowed the recovery of neurons from imposed Ca2+ loads. We observed that [Ca2+]i regulation was disrupted more severely when N-methyl-D-glucamine (N-MG), Tris, or choline rather than Li+ replaced external Na+. Additional disruption of intracellular pH regulation by substitutes other than Li+ may account for this difference. Measurement of [Ca2+]i and [H+]i (using the H(+)-sensitive dye BCECF) during glutamate receptor activation indicated that Ca2+ influx resulted in production of intracellular H+, and that Li+ but not N-MG could prevent cytoplasmic acidification on removal of external Na+. We also observed that intracellular acidification alone was sufficient to slow recovery from Ca2+ load. We conclude, therefore, that Na(+)-Ca2+ exchange contributes to recovery of [Ca2+]i after stimulation leading to Ca2+ entry into hippocampal neurons, and that Na(+)-H+ exchange limits the acidification (and secondary increase in [Ca2+]i) that accompanies Ca2+ influx. We suggest that because both Na(+)-Ca2+ and Na(+)-H+ exchangers will be compromised during ischemia and hypoglycemia, increased intracellular H+ may synergize with cytoplasmic Ca2+ to potentiate excitotoxic neuronal death.

Ultrastructure of sperm, spermiogenesis, and sperm-egg interactions in selected invertebrates and lower vertebrates which use external fertilization.

This review discusses the ultrastructure of sperm with reference to their development, the surface morphology of the egg, and the processes of sperm binding and penetration during fertilization. These topics are treated for selected invertebrates and lower vertebrates which live in aquatic environments and fertilize their eggs externally. Specifically, sperm eggs from cnidarians, echinoderms, decapod crustaceans, ascidians, lampreys, bony fishes, and amphibians are discussed. Sperm from the majority of these groups exhibit the classical head-midregion-tail configuration characteristic of primitive sperm. Specific variations within this general morphology have been described. The notable exceptions to the primitive-sperm paradigm are the sperm of decapod crustaceans and amphibians. Eggs from all of the animals considered are covered by complex vitelline envelopes except those of cnidarians. In general, the ultrastructural analysis of these egg envelopes shows that they are composed of fibrous subunits. Sperm bind to the vitelline envelope and then penetrate through it to fertilize the egg in all groups reviewed except fishes. In sperm ultrastructure which occur during penetration of the egg envelopes in both flagellated and non-flagellated sperm. These changes, which involve membrane fusion and reorganization as well as movement of membranous organelles, aid the sperm in reaching the actual site of gamete fusion.

Low frequency coupled mode sound propagation over a continental shelf.

A two-way integral equation coupled mode method is applied to a continental shelf ocean waveguide proposed for a special session devoted to range-dependent acoustic modeling at the 141st meeting of the Acoustical Society of America. The coupled mode solution includes both sediment trapped and continuum modes. The continuum is approximated by a finite number of leaky modes but neglects the branch cut contribution. Mode coupling matrix elements and the range evolution of the modal amplitudes show the nature of the mode coupling. Transmission loss versus range at 100 Hz predicted by the integral equation approach is compared to the transmission loss predicted by a wide angle parabolic equation method. While there is very good agreement, one observes small differences that can be interpreted as backscattering predicted by the integral equation solution.

Immunohistochemical localization and radioenzymatic measurements of serotonin (5-hydroxytryptamine) in hearts of Aplysia and several bivalve mollusks.

Serotonin immunoreactivity was localized in hearts of the opisthobranch gastropod, Aplysia californica (sea hare) and several species of bivalve mollusks, the heterodonts, Mercenaria mercenaria (quahog or cherry stone clam), Protothaca staminea (little neck clam), and the pteriomorphs, Hinnites multirugosus (rock scallop), Crassostrea virginica (eastern oyster), Mytilus edulis (eastern mussel), and Geukensia demissa (ribbed mussel). In addition, serotonin was assayed in the ventricles, auricles and heart-associated tissues in A. californica, M. mercenaria, H. multirugosus, and G. demissa with a sensitive radioenzymatic assay. Serotonin concentrations and the density of innervation were significantly higher in members of the subclass Heterodonta compared to the subclass Pteriomorpha. Serotonin immunoreactivity was observed in all species surveyed except G. demissa, which also contained relatively low concentrations of serotonin. Varicose fibers presumably corresponding to release sites were localized in the ventricles, auricles, and the auricular-ventricular valves. We hypothesize that in the species where serotonin-immunoreactive fibers are present, serotonin serves to modulate cardiac myogenic activity. The significance of the observed distribution and concentration of serotonin to the physiological effects of serotonin on cardiac function in these species is discussed.

Sperm-surface chymotrypsin-like protease activity required for fertilization in ascidians.

During fertilization, species-specific gamete binding must be followed by sperm penetration of egg vestments before gamete fusion can occur. Sperm proteases, called lysins, aid this process. Sperm from Ascidia ceratodes, Ascidia callosa, and Ascidia paratropa were found to have a surface-mounted chymotrypsin-like protease when studied by enzymology, biotinylated, immunolabeling, and histochemistry. Chymotrypsin substrates and inhibitors blocked fertilization in a concentration-dependent manner in A. ceratodes and decreased the number of sperm heads which penetrated the egg's vitelline coat, but had no effect on sperm binding to follicle cells. Sperm bound to agarose beads coated with the chymotrypsin inhibitor alpha 2-macroglobulin. Chymotrypsin-like enzyme activity, assayed fluorimetrically using N-succinyl-leucinyl-leucinyl-valinyl-tyrosinyl-7 -amido-4-methyl-coumarin as the substrate, was associated with head fractions prepared by differential centrifugation. Biotinylation of live sperm followed by detergent extraction showed that chymotrypsin-like activity could be removed from the detergent extract using avidin-agarose beads. Indirect immunofluorescence of unreacted and reacted sperm heavily labeled membrane domains overlying the mitochondrion and at the base of the head with occasional labeling of the sperm tip. Histochemical studies, which used N-succinyl-alanyl-alanyl-prolyl-phenylalanyl-beta-naphthylamide as the substrate, colocalized enzyme activity in head regions of unreacted and near the mitochondrion of reacted sperm. Thus, we conclude that in ascidian sperm a chymotrypsin-like protease is exposed on the external surface of the plasma membrane of the head, is required for fertilization, and plays a role in sperm penetration but not binding.

Broadband sound propagation in shallow water and geoacoustic inversion.

Part of an experiment to test a measurement package in a shallow water region in the Gulf of Mexico was designed to gather broadband acoustic data suitable for inversion to estimate seabed geoacoustic parameters. Continuous wave tow acoustic signals at multiple frequencies and broadband impulsive source signals were recorded on a horizontal line array in a high-noise environment. Simulated annealing with a normal mode forward propagation model is utilized to invert for a geoacoustic representation of the seabed. Several inversions are made from different data samples of two light bulb implosions, the measured sound speed profiles at the HLA and at the positions of the light bulb deployments, and for two different cost functions. The different cost functions, measured sound speed profiles, and measured time series result in different inverted geoacoustic profiles from which transmission loss is generated for comparison with measurements. On the basis of physical consistency and from the comparison of the transmission loss and time series, a best estimate geoacoustic profile is selected and compared to those obtained from previously reported inversions. Uncertainties in the sound speed profile are shown to affect the uncertainties of the estimated seabed parameters.

Release of Ca(2+) from intracellular stores and entry of extracellular Ca(2+) are involved in sea squirt sperm activation.

A rise in intracellular free Ca(2+) concentration ([Ca(2+)](i)) is required to activate sperm of all organisms studied. Such elevation of [Ca(2+)](i) can occur either by influx of extracellular Ca(2+) or by release of Ca(2+) from intracellular stores. We have examined these sources of Ca(2+) in sperm from the sea squirt Ascidia ceratodes using mitochondrial translocation to evaluate activation and the Ca(2+)-sensitive dye fura-2 to monitor [Ca(2+)](i) by bulk spectrofluorometry. Sperm activation artificially evoked by incubation in high-pH seawater was inhibited by reducing seawater [Ca(2+)], as well as by the presence of high [K(+)](o) or the Ca channel blockers pimozide, penfluridol, or Ni(2+), but not nifedipine or Co(2+). The accompanying rise in [Ca(2+)](i) was also blocked by pimozide or penfluridol. These results indicate that activation produced by alkaline incubation involves opening of plasmalemmal voltage-dependent Ca channels and Ca(2+) entry to initiate mitochondrial translocation. Incubation in thimerosal or thapsigargin, but not ryanodine (even if combined with caffeine pretreatment), evoked sperm activation. Activation by thimerosal was insensitive to reduced external calcium and to Ca channel blockers. Sperm [Ca(2+)](i) increased upon incubation in high-pH or thimerosal-containing seawater, but only the high-pH-dependent elevation in [Ca(2+)](i) could be inhibited by pimozide or penfluridol. Treatment with the protonophore CCCP indicated that only a small percentage of sperm could release enough Ca(2+) from mitochondria to cause activation. Inositol 1,4,5-trisphosphate (IP(3)) delivered by liposomes or by permeabilization increased sperm activation. Both of these effects were blocked by heparin. We conclude that high external pH induces intracellular alkalization that directly or indirectly activates plasma membrane voltage-dependent Ca channels allowing entry of external Ca(2+) and that thimerosal stimulates release of Ca(2+) from IP(3)-sensitive intracellular stores.

Comparison of five methods of assessment of intestinal viability.

A strain gauge device called the electronic contractility meter (ECM) was designed to measure quantitatively intestinal ischemic damage by delivering electrical stimuli to the intestine. Threshold stimulus level (TSL) was the minimum stimulus in milliamps necessary to produce a smooth muscle contractile response. TSL scale ranged from zero to 100 milliamps. Resection and anastomosis in ischemic intestinal segments was carried out in 30 dogs to compare TSL, intestinal color, peristalsis, Doppler ultrasound and resection margin histology with survival. There were five fatal anastomotic leaks, all resulting from intestinal necrosis. Doppler pulse in the marginal artery (MA) was absent at four of the five anastomoses that leaked versus eight of the 25 that healed (p less than or equal to 0.01). Mean TSL at the resection site was 38 +/- 7 milliamps in surviving dogs versus 51 +/- 4 milliamps in nonsurvivors (p less than or equal to 0.001). Mean TSL of normal intestine was 22 +/- 2 milliamps. Both TSL and Doppler ultrasound also correlated with resection margin histology (p less than or equal to 0.02 and p less than or equal to 0.005, respectively). Presence of peristalsis did not correlate with histologic grade or survival rate. Intestinal color correlated with resection margin histology (p less than or equal to 0.001) but not survival. The ECM and Doppler ultrasound were both superior to gross visual assessment in predicting intestinal survival. The ECM quantitatively measures tissue damage, a potential advantage over Doppler ultrasound, which provides only an estimate of local arterial blood flow.