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Biomedical subjects

J S Weis

Publications and source records attributed to J S Weis.

At least 37 records · Page 2Linked to original sources
PubMed1987

Toxic effects of mercuric chloride on sperm and egg viability of two populations of mummichog, Fundulus heteroclitus.

Exposure of mummichog (Fundulus heteroclitus) sperm from polluted Piles Creek (PC) to 0.01 ppm mercuric chloride (Hg) for 2 min caused a significant reduction in fertilization success. However, comparable exposure of sperm of mummichog from a relatively clean area in Long Island (LI) did not effect the fertilization success. Exposure of PC mummichog sperm to 0.05 ppm Hg for 2 min caused significant reduction in sperm motility. On the other hand, comparable exposure of LI mummichog sperm did not have any effect on motility. These data indicate that Hg is more toxic for PC mummichog sperm than LI mummichog sperm. Exposure of both PC and LI sperm either to 15 ppt sea water or to 0.05 ppm Hg for 15 min did not affect the morphology of the sperm, as seen by scanning electron microscopy. Exposure of PC and LI mummichog eggs to 0.05 ppm Hg up to 25 min had no effect on fertilization success, indicating that eggs are more tolerant to Hg than sperm.

Journal Article↗
PubMed1987

Effect of methylmercury on egg and juvenile viability in two populations of killifish Fundulus heteroclitus.

Killifish (Fundulus heteroclitus) eggs from a polluted creek (Piles Creek (PC)) and a relatively pristine estuary in Long Island (LI) were exposed for 20 min to various concentrations of methylmercuric chloride (MeHg) prior to combination with untreated sperm. PC killifish eggs showed a higher LC50 value (1.7 mg/liter) than LI eggs (0.7 mg/liter). PC eggs that were fertilized by nontreated sperm after exposure to 1.0 or 2.5 mg/liter meHg and then placed in clean sea water (15 parts per thousand) for 1 week showed a 5 and 7% malformations of the embryos, respectively. However, exposure of LI eggs to 1.0 mg/liter prior to fertilization caused 32% malformations of the embryos, and at 2.5 mg/liter almost all the embryos died. The data indicate that LI killifish eggs are less tolerant to meHg than PC eggs. This is in keeping with previous data on embryonic tolerance to meHg in these two populations. However, 96-hr LC50 values of juvenile fish (25-45 mm standard length) did not differ between these two populations.

Abnormalities, Drug-Induced↗
PubMed1987

Pollutants as developmental toxicants in aquatic organisms.

Pollutants, by disrupting metabolic processes, can interfere with development, and, at critical periods of development, can act as teratogens. Such interference with normal development can be used as a bioassay. Some screening tests are based on this phenomenon. As teratogens, pollutants are fairly nonspecific. Many different classes may elicit the same developmental responses. Mechanisms of teratogenicity include disruption of mitosis, interference with transcription and translation, metabolic disturbances in energy utilization, and nutritional deficits. These in turn interfere with cell interactions, migration, and growth. In aquatic organisms, environmental conditions can be critical. Interactions of pollutant effects with salinity and with temperature have been reported. Interactions between toxicants have also been studied; both synergism and antagonism have been reported. Most reports of teratogenesis have been qualitative. Quantitation has usually been in the form of percentages of embryos affected, but when severity of effect is indexed, more critical analysis is allowed. When effects of other developmental processes such as growth are analyzed, quantitation is readily achieved. Regeneration is an especially useful model of both differentiation and growth. These two components of regeneration can be separately analyzed. Dose-response relationships are readily apparent. In comparison to mammalian embryos, the use of embryos of many aquatic species for testing toxicants has certain advantages, including lower cost and maintenance and shorter development times. They respond to many of the same teratogens. A special advantage is availability for continual examination during development so that abnormalities can be observed and recorded as they arise.

Animals↗
PubMed1986

Cadmium acclimation and hormesis in Fundulus heteroclitus during fin regeneration.

We have previously demonstrated that exposure to cadmium at 0.1 and 0.5 mg/liter will retard the rate of fin regeneration in Fundulus heteroclitus. Since there is a body of literature indicating that preexposure to low levels of metals may increase tolerance during subsequent exposure, these experiments were designed to investigate the effects of preexposure to cadmium, using fin regeneration as the parameter of effect. Fish were exposed for 1 week to 0, 0.01, or 0.05 mg/liter Cd. Following this preexposure, the lower third of the caudal fin was amputated, and regrowth of the fins measured by ocular micrometer twice weekly for 2 weeks. During regeneration fish were maintained in either clean water (25% S, 23-25 degrees C) or in water with 0.1 mg/liter Cd. Fish newly placed in Cd (C----0.1 Cd) regenerated at the slowest rate, while the 0.01----0.1 Cd group approached the growth of control fish regenerating in clean water, indicating a protective effect or acclimation brought about by the preexposure. The 0.05----0.1 Cd group regenerated even more rapidly than controls, a phenomenon which has been termed "hormesis" and is believed to be due to an overcompensation by homeostatic regulatory mechanisms. In a second set of experiments in which regeneration took place in 0.5 mg/liter rather than 0.1 mg/liter, a protective effect of preexposure was again seen, but no hormesis was observed. Uptake data indicated that preexposed groups took up less Cd than the groups not preexposed.

Animals↗
PubMed1977

Methylmercury teratogenesis in the killifish, Fundulus heteroclitus.

Exposure of developing eggs of the killifish, Fundulus heteroclitus, to 0.03 or 0.04 mg/l of methylmercuric chloride resulted in a variety of abnormalities. Percentage of axis formation was reduced somewhat, and many embryos developed cyclopia or intermediate conditions leading to cyclopia, reflecting interference with induction of the forebrain. Defects in the cardiovascular system also appeared in the form of failure of the heart to differentiate properly into chambers. The heart was a thin, feebly beating tube, incapable of causing the blood to circulate. Other tissues, however, continued developing fairly normally, and embryos showed spontaneous movement comparable to controls. Embryos with severe cardiovascular or optic defects did not hatch. Upon hatching, some embryos which had previously appeared normal were found to have skeletal malformations in the form of vertebral bends or the inability to uncurl from the position which they had while still inside the chorion. Exposure to the toxicant for shorter periods of time (6, 12, or 24 hours) reduced the incidence of abnormalities. The second day of development was found to be the most sensitive period.

Abnormalities, Drug-Induced↗
PubMed1977

Limb regeneration in fiddler crabs: species differences and effects of methylmercury.

1. When kept under identical conditions, Uca pugnax regenerates limbs and molts more rapidly than U. pugilator from the same location. 2. The tropical species U. rapax and U. speciosa also regenerate faster than U. pugilator from the same location. U. thayeri is the slowest to replace missing limbs, the slowest to harden the carapace after ecdysis, and also requires the greatest injury before autotomy will take place. 3. When kept in groups, U. thayeri stops regeneration after basal growth and will not molt; U. pugilator is only slightly retarded when kept in groups. U. rapax is also affected by grouping, showing a lengthened proecdysial phase and terminal plateau, thus also delaying molting. 4. Newly regenerated limbs of U. rapax, U. thayeri, and U. speciosa, aside from being lighter than old limbs, have a conspicuous banding pattern. This pattern becomes less obvious during the week or two after ecdysis as melanophores move into the interband regions and the limb as a whole darkens due to increased dispersion of pigment in the melanophores. In U. pugilator the newly regenerated limbs are very pale in color and remain that way for several months under laboratory conditions, even when animals are maintained on a dark background. 5. When treated with 0.5 mg/liter methylmercury, growth was inhibited entirely in U. thayeri. Partial inhibition was seen in U. pugilator, and the least inhibition in U. rapax. A few individuals of U. rapax were able to complete regeneration and molt, but there was no melanin in the regenerated limbs. 6. Inhibition of melanogenesis in regenerated limbs was also seen in U. thayeri and to a smaller extent in U. pugilator at 0.1 mg/liter methylmercury. The lack of black pigment may be due to an inhibition of cell migration but more likely of melanin synthesis. Some of these crabs developed melanin when kept in clean water after ecdysis. 7. Seasonal differences were noted in all species, but especially in U. Thayeri. In this species, regenerated occurred much more rapidly in March-April than in January.

Animals↗