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J Ringo

Publications and source records attributed to J Ringo.

18 recordsLinked to original sources
PubMed2002

Modulation of the cardiac pacemaker of Drosophila: cellular mechanisms.

The myogenic cardiac pacemaker of Drosophila melanogaster responds to a range of neurotransmitters and hormones by adjusting heart rate. These cardioactive substances ultimately affect the activity of ion channels comprising the pacemaker. We report here work utilizing genetic variants and pharmacological tools to explore a subset of possible mechanisms for this cellular signaling, specifically: receptors, cAMP, cGMP, G proteins, and calcium. We found that alpha(1) adrenergic and 5-hydroxytryptamine(2) (5-HT(2)) receptors are critical components of mediating modulation of heart rate. There was no evidence that the cAMP system is part of the modulatory mechanism. cGMP is likely to be integral to one active pathway, as non-hydrolyzable forms of this cyclic nucleotide increase heart rate, and flies bearing the mutation sitter, a recessive allele of the foraging gene, which encodes a cGMP-dependent kinase, have tachycardia. Heart rhythm is affected by pertussis toxin and by agonists and antagonists of both alpha(1) adrenergic and 5-HT(2) receptors; this suggests involvement of two different types of G proteins. The l(4)16/ciD line, containing a mutation in CaM kinase II, eliminates pacemaker responsiveness to serotonin but is without effect on norepinephrine sensitivity. This result is the same as that for the CaM kinase II enzyme inhibitor KN-93. This work establishes a framework for further investigations into the control of the cardiac pacemaker, and expands the applicability of the Drosophila heart model.

Adrenergic alpha-Agonists↗
PubMed2001

Dynamin, encoded by shibire, is central to cardiac function.

Employing the Drosophila heart, a model system for genetic and molecular investigation of cardiac physiology, we demonstrate here an essential role for the protein dynamin, encoded by the Drosophila gene shibire(ts) (shi(ts)), in maintaining normal heart function. In flies bearing two temperature-sensitive alleles of shi, shi(ts1) and shi(ts2), heartbeat is both slower and less rhythmic than in wild-type animals. Serotonin and norepinephrine, normally cardioacceleratory in wild type, are without effect in flies bearing the shi mutation. Electrocardiogram (EKG) analysis reveals a bigeminal beat in mutant hearts, unlike the single electrical pulse in wild-type. The gene no action potential (temperature sensitive), with previously-described cardiac aberrations similar to those of shi, interacts with shi: shi/shi;nap/nap mutants have almost wild-type heart function. J. Exp. Zool. 289:81-89, 2001.

Animals↗
PubMed2000

Native and heterologous neuropeptides are cardioactive in Drosophila melanogaster.

Nine neuropeptides isolated from Drosophila melanogaster and five neuropeptides, previously isolated from the CNS of Limulus with antisera to FMRFamide-related peptides, were tested for their effects on the myogenic heart of Drosophila melanogaster. Of the native peptides, TDVDHVFLRF-NH(2) (Dromyosuppressin), DPKQDFMRFamide, and PDNFMRFamide significantly slowed the heart. Of the Limulus peptides, DEGHKMLYFamide (LP1) increased heart rate significantly, GHSLLHFamide (LP2) and PDHHMMYFamide (LP3) decreased the heart's rate, while DHGNMLYFamide (LP4) and GGRSPSLRLRFamide (LP5) had no effect at the concentrations we employed. Dromyosuppressin, DPKQDFMRFamide, and PDNFMRFamide from Drosophila, and LP2 and LP3 from Limulus, which belong to a novel group of peptides structurally unrelated to FMRFamide, are among only a very few substances from within the general group of neuropeptides and neurohormones known to slow the heart of Drosophila, and as such offer an important tool for investigating the molecular mechanisms underlying the control of the pacemaker.

Journal Article↗
PubMed1998

The period gene controls courtship song cycles in Drosophila melanogaster.

We developed a technique that assists in objective identification of pulse and sine components in the Drosophila melanogaster courtship song. The song was recorded digitally and subjected to wavelet analysis, which decomposed the signal into a series of bands of decreasing frequency in which acoustic power appeared as a function of time. This time-frequency analysis expresses characteristic 'fingerprints' of the pulses, which appear in all frequency bands, and characteristic 'fingerprints' of the sine song, which appear only in the band containing its frequency. Means of the interpulse intervals (IPIs) for each second of 10-min recordings of song in which pulse singing occurred constituted an irregularly sampled time series, intractable to common spectral analysis techniques. Therefore, we took the discrete Fourier transform of this series, which retained all the spectral information in the Fourier coefficients, and used the inverse Fourier transform of these coefficients to yield a new series that was regularly spaced, with an estimate of IPI for each second in the interval. We observed an IPI period of 67.9 s in wild type, 31.1 s in per0, 45.9 s in pers, and 72.0 s in perL. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Genetic and pharmacological identification of ion channels central to the Drosophila cardiac pacemaker.

Drosophila provides an excellent model for delineating the role of ion channels in the origin and transmission of heartbeat. We report here tests in Drosophila on a wide range of mutations and pharmacological agents known to interfere with K+, Ca2+, Na+, and Cl- ion channels in well-characterized ways. We find K+ channels are central to heart function. Tetraethylammonium, which blocks all four K+ currents, slowed the heart. We were able to distinguish among these currents. The mutation slowpoke and the agent charybdotoxin, both of which affect a fast Ca(2+)-gated K+ channel, virtually eliminate heartbeat. Shaker and ether-a-go-go, which encode subunits of K+ channels, have moderate, possibly regulatory effects. "OPQ-type" Ca2+ channels are critical. omega-Conotoxin MVIIC, which blocks these channels, virtually stops the heart. Amiloride, which may affect T-type Ca2+ channels, has no effect, nor do the L-type Ca2+ blockers verapamil and diltiazem. temperature induced paralysis E, involved in the function of Na+ channels, the Na+ channel blockers tetrodotoxin and amiloride, and the Cl- blockers mefanamic and niflumic acids have no effect. Na+ and Cl- channels thus appear unnecessary for cardiac function.

Animals↗
PubMed1997

Modulation of Drosophila heartbeat by neurotransmitters.

The heart of Drosophila melanogaster is a simple muscular tube with a posterior pulsatile portion and a thoracic-cranial vessel. The pacemaker, located caudally, is myogenic. Its rate of firing is modulated by neurotransmitters. Serotonin, octopamine, norepinephrine, dopamine, and acetylcholine accelerate the heart, in that order of potency. Dihydroxyphenylalanine, gamma-aminobutyric acid, glutamate, and glycine have no effect. Generally, the regularity of the heartbeat is not adversely affected by treatment with any of these neurotransmitters. We show here that amnesiac, a neurological mutation, and Dihydroxyphenylalanine decarboxylasetemperature sensitive, a mutation that interferes with synthesis of dopamine, norepinephrine, and serotonin, result in slower heart rate and reduced regularity across a normal range of temperatures for these flies. Dopamine-N-acetyltransferase, which is on the catabolic route to dopamine, serotonin, and octopamine, has no effect. hypoactiveC reduces the rate of the heart, but its mechanism of action is unknown.

Acetylcholine↗
PubMed1997

Icebox, a recessive X-linked mutation in Drosophila causing low sexual receptivity.

The X-linked recessive mutation icebox (ibx; 1-23, 7F1) of Drosophila melanogaster lowers the sexual receptivity of females. The probability of mating with mature wild-type males is reduced in ibx homozygotes, and the frequency of rejection behavior (rate per minute) towards courting males is increased. ibx fails to complement In(1)RA35, which is a lethal allele of Neuroglian (Nrg, which encodes a transmembrane protein found in embryonic tissues including the nervous system) due to a breakpoint in that gene; however, both l(1)B4 and l(1)VA142, other lethal mutations of Nrg, do complement ibx. 12-h ibx embryos exhibit a normal pattern of staining for the Neuroglian-specific antibody, Mab BP104. Males and females mutant for ibx have normal egg-to-adult survival and appear normal in several "general" behavioral traits including olfaction, phototaxis, locomotor activity, and heartbeat. ibx males court normally, and are successful in mating. These characteristics suggest that ibx does not cause sensory or motor defects. Ovarian growth and sperm storage are wild-type in ibx/ibx females. Treatment with the JH analog methoprene increases the receptivity of ibx/ibx females.

Animals↗
PubMed1996

Sexual receptivity in insects.

Sexual receptivity is female behavior that allows or helps a male to fertilize her eggs; through this behavior, females play an active role in reproduction. Multiple signals may be used for receptivity or unreceptivity. Insect species exhibit three ontogenetic patterns of receptivity: cyclic, in which females alternately become receptive and unreceptive; brief, in which females mate during on short developmental period; and continuous. Primary (initial) receptivity may be stimulated or inhibited by diet, ovarian development, or juvenile hormone. In species with cyclic receptivity, remating may be inhibited by copulation itself, the presence of eggs, sperm stored in spermathecae, or seminal factors--usually peptides--secreted by the male accessory glands. In many species, there is substantial genetic variation for both primary receptivity and speed of remating. Several single-gene mutations reduce female receptivity; most of these mutations also impair sensory functioning.

Journal Article↗
PubMed1995

Genetic variation for resistance to chlorpyrifos in Drosophila melanogaster (Diptera: Drosophilidae) infesting grapes in Israel.

Five species of drosophilid flies were observed breeding in grapes growing in Israel; of these, 2 species, Drosophila melanogaster (Meigen) and D. simulans Sturtevant, are major pests. Natural populations of both species were sampled and tested for resistance to chlorpyrifos; the 2 more intensively sampled populations were D. melanogaster in commercial vineyards. One vineyard had been treated repeatedly with chlorpyrifos to control this secondary pest species; the other had never been treated with an organophosphorus compound. The LC50 to chlorpyrifos of a genetically heterogeneous line of D. melanogaster from the exposed population (Be'er Tuvia) was 99 ng/cm2, and the LC50 of a corresponding line from the unexposed population (Sde Eliahu) was 52 ng/cm2; the wild-caught lines were much more resistant than a laboratory strain, Canton-S, whose LC50 was 0.25 ng/cm2. Genetic variance for resistance existed in both natural populations but realized heritability did not differ significantly between the populations. In crosses between a highly resistant strain and several sensitive laboratory strains of D. melanogaster, resistance was dominant. A resistance factor was mapped to a locus on chromosome 2 (approximately 2-72).

Animals↗
PubMed1995

A congenital heart defect in Drosophila caused by an action-potential mutation.

The mutation no action potential (nap) induces arrhythmia in the heartbeat of Drosophila melanogaster larvae at temperatures above 20 degrees C; heartbeat becomes normally rhythmic again after a shift back to 20 degrees C. For this phenotype, napa is almost completely recessive to the wild type, napa also reduces the temperature-sensitivity of heart rate over a wide range of temperature, for this phenotype, napa is dominant over the wild type, napa causes reversible paralysis in adults by epistatic effects on the expression of paralyrica, a gene encoding a voltage-dependent sodium channel. However, the paramutation, which induces paralysis in adults at 29 degrees C, has no effect on larval heartbeat at temperatures between 20 degrees and 37.5 degrees C. The period gene, contra earlier reports, has no effect on heartbeat.

Action Potentials↗
PubMed1995

The role of light in the initiation of circadian activity rhythms of adult Drosophila melanogaster.

Rearing Drosophila melanogaster in constant darkness (DD) for multiple generations disrupts the circadian activity rhythm of adults. In order to determine under what conditions normal rhythms can be initiated, DD-reared Drosophila (either the wild type or the periodshort [pers] mutant) were exposed to light either as embryos, third-instar larvae, or adults. Exposing DD-reared flies to light as embryos or larvae had no effect, while exposing them as adults fully restored normal rhythms in pers and partially restored normal rhythms in the wild type. The percentage of adults with normal rhythms was not significantly different between animals given a 1-h pulse of light as adults and animals given two LD cycles as adults. LD-reared and DD-reared animals given 2 LD cycles were synchronous. In the latter, offset of activity followed the LD transition (CT 12) by 2-6 subjective hours in pers and 2-3 subjective hours in per+. Circadian rhythms did not exhibit phase coherence in the other treatments.

Activity Cycles↗
PubMed1992

Male sexual signaling is defective in mutants of the apterous gene of Drosophila melanogaster.

The apterous (ap) gene of Drosophila melanogaster exhibits extreme pleiotrophy: its functioning is essential for life, normal wing structure, juvenile hormone production, female fertility, and normal development of female sexual receptivity. Four mutant ap alleles (ap4, ap56f, apc, and apblt) were characterized for three additional phenotypes: male mating success, courtship behavior, and immature male sex appeal (the ability of males to stimulate homosexual courtship). Mating success with mature wild-type virgin females is reduced in males mutant for the ap gene, the extreme case being ap4/ap4 males, which are behaviorally sterile. In ap mutants, nonwing courtship elements are qualitatively like those of ap+/ap+ males. However, the mean rate of nonwing courtship directed toward virgin wild-type females (i.e., the mean temporal frequency of these displays) is reduced in males homozygous for ap4, ap56f, or apc alleles. In contrast, the apblt allele makes for wild-type rates of nonwing courtship. Immature male sex appeal persists for at least 3 days in males homozygous for apc and, to a lesser extent, in ap56f or ap4 homozygotes; apblt/apblt and wild-type males lose immature male sex appeal after 1 day. All three male phenotypes map to the ap locus, which is therefore essential for the development of normal levels of male courtship and male mating success and for the timely loss of immature male sex appeal. For each phenotype, ap+ is dominant to ap alleles making for behavioral abnormalities, with a single exception (for rate of nonwing courtship, ap+/apc was low). For mating success and frequency of nonwing courtship, each allele pair exhibits at least partial complementation, except for ap4 and ap56f, which fail to complement. For immature male sex appeal, apc, ap4, and ap56f fall into the same complementation group. Juvenile hormone production is not correlated with effects on male reproductive behavior.

Animals↗
PubMed1992

A circadian clock of Drosophila: effects of deuterium oxide and mutations at the period locus.

Mutations at the period (per) locus (1:1.3; 3B1-2) in Drosophila melanogaster lengthen (perL), shorten (pers), or abolish (per0) overt circadian rhythmicity. Deuterium oxide lengthens the free-running circadian period. We tested the effects of deuterium on three mutants of the per gene (pers, perL, and per0) and wild-type Drosophila melanogaster (per+) to assess interactions. With increasing concentrations of deuterium, the free-running circadian period of locomotor activity rhythms increased. The dose-response was linear in all genotypes tested. With increasing dosages of deuterium, circadian rhythms became weaker as evidenced by the signal-to-noise ratio (SNR). Genotype and deuterium changed circadian period length independently and additively, showing no interaction. SNRs for all genotypes converged on a low level as deuterium concentration increased. Deuterium increased life span, except at high concentrations (40 and 50%).

Analysis of Variance↗
PubMed1991

Female sexual receptivity is defective in juvenile hormone-deficient mutants of the apterous gene of Drosophila melanogaster.

During reproductive maturation of female insects, the acquisition of sexual receptivity is coordinated with ovarian development. Juvenile hormone regulates vitellogenesis in the ovaries, but the action of this hormone in the development of sexual behavior is less well-understood. A strain of Drosophila melanogaster carrying a mutation in the apterous gene (ap4) was known to exhibit arrested vitellogenesis (rescuable by applying exogenous juvenile hormone), sterility of both sexes, and a deficiency of juvenile hormone. In this study, we examined the effects of mutations of ap on female receptivity and its relationship to juvenile hormone. We observed abnormally low female receptivity in homozygous ap strains, and heteroallelic combinations of ap mutations exhibited low receptivity. For female receptivity, ap showed no dominance (i.e., ap/ap+ was intermediate between ap/ap and ap+/ap+). Low receptivity mapped genetically to the ap locus. The reduction in female receptivity in these mutants is positively correlated with levels of juvenile hormone synthesized by their corpora allata.

Animals↗
PubMed1984

Pattern ERG of the cat.

Recent reports on pattern ERGs reopened the discussion of pattern or luminance origin of the ERG to pattern reversal stimulation. In this report cat ERGs to checkerboard stimuli were recorded. The stimulus parameters were manipulated in order to vary the strength of local luminance and contrast stimulation independently. Special care was taken to eliminate stray light effects. The results clearly show that pattern specific components in the cat ERG, if present at all, are no greater than the variance of the responses from local luminance nonlinearities. Thus a "Pattern ERG" can be recorded by luminance modulation.

Action Potentials↗
PubMed1980

Cone contributions to cat retinal ganglion cell receptive fields.

Extracellular microelectrode recordings were made from ganglion cells of the intact, in situ eyes of adult common domestic cats. Three different photopic systems, with peak spectral sensitivities at 450, 500, and 556 nm, were observed. All ganglion cells received input from a cone system with a peak spectral sensitivity of 556 nm. The blue-sensitive cone system was observed in about one-half of the ganglion cells studied. In each case the 450-nm cone system contributed to only one functional type of response, either ON or OFF, in the same cell. The other two photopic systems most often contributed to both the ON and OFF responses of an individual ganglion cell. In four cases the 450-nm cone system mediated responses that were opponent to those of the other two photopic systems. The third photopic mechanism has a peak spectral sensitivity at 500 nm and contributed to most receptive field surrounds and many receptive field centers. It is distinguished from the rod system by the occurrence of a break in both dark-adaptation curves and increment-sensitivity curves. No apparent differences in receptive field cone contributions between brisk-sustained and brisk-transient cells were seen.

Animals↗
PubMed1977

Trichromatic vision in the cat.

Many cat retinal ganglion cells (types X, Y, and W) have inputs from three separate cone systems. Those with peak sensitivities at 450 and 555 nanometers have been previously shown. A gamma max cone with a peak sensitivity of 500 nanometers can be differentiated from other cones by spectral sensitivity and from rods by receptive field differences, functioning above rod saturation levels, and by cone-rod breaks in the dark-adaptation curves. The similarity of the three-cone cat retina to the extramacular retina of the rhesus monkeys suggests that the cat may have photopic trichromatic vision.

Action Potentials↗