Cell lineage of zebrafish blastomeres. I. Cleavage pattern and cytoplasmic bridges between cells.

Patterns of cleavage and cytoplasmic connections between blastomeres in the embryo of the zebrafish, Brachydanio rerio have been described. The cell division pattern is often very regular; in many embryos a blastomere's lineage may be ascertained from its position in the cluster through the 64-cell stage. At the 5th cleavage, however, significant variability in pattern is observed, and alternative patterns of the 5th cleavage are described.

Postnatal toxicity following prenatal reserpine exposure in rats: effects of dose and dosing schedule.

Pregnant CD rats were treated subcutaneously with 0, 0.1, 0.33, or 1.

Blood flow changes and conceptal development in pregnant rats in response to caffeine.

Alterations in blood flow to the uterus and its contents during pregnancy have been suggested to account for the teratogenicity and/or embryotoxicity of several agents, including caffeine. Using a radioactive microsphere technique, blood flow to several maternal organs, including ovary, uterus, decidua, and chorioallantoic placenta (CAP), was measured following a single dose of 0 or 120 mg/kg caffeine by gavage to pregnant CD rats on Day 12 of gestation. At 1 or 4 hr after treatment, animals were anesthetized and strontium 85-labeled microspheres (25 micrometers diam) were infused into the left ventricle.

The role of maternal diet in the developmental toxicology of ethanol.

A commonly observed result of ethanol administration to experimental animals is a reduction in voluntary dietary intake. The purpose of this investigation was to examine the role of this reduction in the developmental/reproductive toxicity of ethanol. To achieve this objective, female C3H mice were administered one of the following diets from Day 0 to Day 17 of pregnancy: (1) liquid diet, (2) liquid diet plus 4.

Developmental uncoupling between blastoderm and yolk cell in the embryo of the teleost Fundulus.

During cleavage and blastula stages of embryos of the teleost Fundulus heteroclitus all of the cells are both electotonically coupled and dye coupled to one another, as determined by microelectrode impalements and spread of Lucifer Yellow. At about the time that gastrulation begins we observed a specific loss of junctional coupling between the yolk cell and cells of the blastoderm. Passage of Lucifer Yellow between the yolk cell and blastoderm was reduced at stage 12 (late blastula), and not detected at stage 13 and thereafter, although cells of the blastoderm remain dye coupled to one another through gastrula stages.

Sex and strain differences in the developmental activity profile of rats prenatally exposed to sodium salicylate.

Pregnant Sprague-Dawley (CD) and Long-Evans (LE) rats were treated by gavage on days 8-10 of gestation with either 0, 125 or 175 mg/kg/day sodium salicylate. Locomotor activity was monitored repeatedly for 30 min in the offspring on postnatal days 12, 16, 20, 24, 30, 60, 90 and 120 in the presence or absence of olfactory cues from home cage bedding. Prenatal exposure during organogenesis to the doses of sodium salicylate used here resulted in subtle alterations in developmental locomotor activity, the pattern of which was dependent on sex, strain and bedding condition during testing.

Sex and strain differences in the developmental activity profile of the rat tested over clean vs home cage bedding.

In the first of two experiments, CD rat litters were used to characterize activity patterns obtained in a size-adjustable, single photodetector chamber. Beginning on postnatal Day 10 or 12, pups were tested repeatedly over clean bedding (C) or over bedding removed from each pup's home cage (HC). In C rats of both sexes and in HC females, short-term activity levels peaked on Day 16.

Correlating pharmacokinetics and teratogenic endpoints.

The use of pharmacokinetics can improve the extrapolation of animal teratology data for human risk evaluation. Before one can extrapolate between species, however, the pharmacokinetic model must be predictable within the species for which it was developed. This article summarizes an approach being used for correlating pharmacokinetics and teratology endpoints in the same animal and predicting the teratogenic outcome for other animals of the same species.

The embryotoxic effects of ultrasound exposure in pregnant ICR mice.

The embryotoxicity of ultrasound exposure during pregnancy was investigated in DUB:(ICR) mice. On day 0 of gestation (day of plug), pregnant mice were assigned to one of five groups: cage control, sham exposed (0 W/cm2), 0.05 W/cm2, 0.

Noninvasive recording of the Mauthner neurone action potential in larval zebrafish.

We describe the identification of Mauthner (M-) cell action potentials in an intact zebrafish larva, utilizing recording electrodes located outside the fish: 1. The externally recorded spike occurs at approximately the same time, and its waveform changes with recording site in the same way, as the extracellular M-spike recorded within the central nervous system. 2.

Brain neurons which project to the spinal cord in young larvae of the zebrafish.

A small number of brain neurons project to caudal levels of the spinal cord in the larva of the teleost Brachydanio rerio. These cells were identified in animals 6 days after fertilization by backfilling with horseradish peroxidase following transection of the cord at the level of the cloaca. In preparations with the most labeled cells a total of 30-40 were present on each side of the midline.

Synaptogenesis and its relation to growth of the postsynaptic cell: a quantitative study of the developing Mauthner neuron of the axolotl.

We describe the relation between growth and branching of an identified dendrite and the formation of synapses on its surface during a 3 1/2-day period early in development. We studied the lateral dendrite and the adjacent lateral perikaryon of the Mauthner cell (M-cell) during embryonic stages 39-43 in the axolotl Ambystoma mexicanum. Reconstructions from light micrographs of serial sections through the cell revealed that during this interval the dendrite elongates rapidly, and large numbers of ventrally directed branches are formed.

A rapid procedure for routine double staining of cartilage and bone in fetal and adult animals.

A simple, rapid procedure for dual staining of cartilage and bone in rodents, particularly in late gestation, has been developed for routine use. The procedure involves rapid, complete skinning of fresh eviscerated specimens following a 30 sec immersion in a 70 C water bath. The unfixed specimen is stained in a mixture of 0.

Morphogenesis and synaptogenesis of the zebrafish Mauthner neuron.

The shape of the Mauthner neuron (M-neuron) and the distribution of its afferent synapses were studied between days 2 and 6 after fertilization in the zebrafish Brachydanio rerio. This interval is just after the outgrowth of M-dendrites begins, and during this time the M-cell acquires its definitive shape. The M-cell has two large invariant dendrites: The lateral dendrite terminates in the sensory neuropil of the acoustico-lateral area, and th ventral dendrite terminates in the neuropil of the motor tegmentum.

Target recognition in neurogenesis: formation of the Mauthner axon cap.

To learn whether presence of a specific neuron, the Mauthner (M) cell, is required for the organization, during embryogenesis, of an associated synaptic neuropil, the M-axon cap, M-cell precursors were experimentally deleted in embryos of the zebra fish (Brachydanio rerio) and the axolotl (Ambystoma mexicanum). Examination of early larvae revealed that in about half of the cases M-axon caps were present in the absence of the corresponding M-cells. The locations and structures of such caps were approximately normal.