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Biomedical subjects

J Herkovits

Publications and source records attributed to J Herkovits.

At least 37 records · Page 2Linked to original sources
PubMed1988

T and B lymphocyte populations in uterus draining lymph nodes at estrus and diestrus in Wistar rats.

In this paper, data are presented on the characterization of uterus draining lymph nodes (UDLN) B and T lymphocytes of virgin rats at estrus (E) and diestrus (D). We established that the T/B lymphocyte relationship in the UDLN is less than one at estrus and more than one at diestrus. This is due to a decrease in the percentage and in the total number of mature T cell population in association with a decrease in the percentage of the OX8 subset in the UDLN at estrus. This situation may be related to an increase in estrogens known to produce thymic involution. These changes were not observed when we studied peripheral (popliteal) lymph nodes. The changes observed in the UDLN T cell population at estrus could be under hormonal control and we think that this condition may be important to prepare the immune system for an eventual pregnancy.

Animals↗
PubMed1987

Ontogenic screening of aldosterone in the South American toad Bufo arenarum (Hensel).

The content of aldosterone in the South American toad Bufo arenarum embryos developed in Holtfreter's 10% solutions and in distilled water was measured. The screening was carried out on embryos from the following periods of their development: 15 min after fertilization; gray crescent-32 cells; mid cleavage-late gastrula; neural plate-neural tube; tail bud-heart beat; gill circulation-tail fin circulation and operculum fold-complete operculum. The aldosterone content of embryos incubated both in Holtfreter and in distilled water decreased gradually up to gill circulation-tail fin circulation stages. The steroid content of both groups of embryos rose sharply at the end of their development (operculum fold-complete operculum); the observed increase was significantly higher in distilled water animals.

Aging↗
PubMed1986

Teratogenic effects of cadmium on Bufo arenarum during gastrulation.

Developing Bufo arenarum embryos were treated during gastrulation with cadmium chloride in concentrations ranging from 6x10(-7) to 1.5x10(-5)M Cd++ at 20 and 30 degrees C. Initial failures at gastrulation result mainly in axial incurvations, microcephaly, hydropsy and abnormal tail formation. The higher temperature has a dual effect: at high concentrations of Cd early malformations are significantly increased; whereas, at low concentrations the higher temperature prevents alterations.

Animals↗
PubMed1986

Adenylic nucleotides and energy charge during the embryonic development of Bufo arenarum.

The contents of ATP, ADP and AMP were determined by HPLC and adenylic energy charge (AEC) was estimated during different stages of the embryonic development of Bufo arenarum up to the tailbud stage. All the developmental stages studied showed a high ATP content (about 1.04-1.48 nmol/emb.). The concentration of ADP was low (0.025-0.041 nmol/emb.) but rose slightly at the neural tube stage. AMP was undetectable before the tailbud stage. AEC values were almost constant (about 0.987-0.992) throughout the period studied. Only a fall at the tailbud stage could be detected which can be related to this more advanced cellular differentiation stage.

Adenine Nucleotides↗
PubMed1985

Effects of low concentrations of ethanol on the embryonic development of Bufo arenarum.

The effects of low concentrations of ethanol on embryos of Bufo arenarum were studied. Embryos maintained continuously (from stage 3 on) in 0.84-3.34 microM ethanol showed concentration dependent effects: delay in the development rate and on eclosion, loss of equilibrium, arrhythmic contractions, swimming in atypical positions and high death rate. At lower concentrations the anomalies were concentration independent. Embryos treated continuously with 0.002 and 0.21 microM ethanol until stages 19, 20 and 21 showed an important and selective increase in their Na content. When the embryos were incubated discontinuously in 0.002 and 0.21 microM ethanol, from stage 3 to stages 12-13 and then transferred to Holtfreter solution, only a few of the above mentioned anomalies were observed; they were transient and the embryos recovered rapidly. Treated embryos did not exhibit ultrastructural changes in their ectodermal cells.

Abnormalities, Drug-Induced↗
PubMed1985

[Effects of cadmium on the development of an amphibian].

The effects of continuous treatment with cadmium on Bufo arenarum embryos from the 2-cell stage onwards, were evaluated by light and scanning electron microscopy. Damages were concentration-dependent (between 0.03 and 4.00 mg Cd++/L in 10% Holtfreter's solution) and ranged between teratogenic effects and lethality. In the 0.50-4.00 mg Cd++/L range high mortality, delayed development and significant alterations in the gastrulation and neurulation processes were observed. In embryos maintained at concentrations between 0.03 and 0.25 mg Cd++/L, lethality was considerably lower and development proceeded to more advanced stages. In this group of embryos the toxicity signs were: retarded growth rate, reduced body size, behavioral disorders and a variety of malformations such as microcephaly, underdevelopment of gills and abnormal fins. The ectodermal tissue exhibited predominance of ciliated cells and/or atypical distribution of them. These findings were compared with the effect of cadmium and other heavy metals on embryos, larvae and adults of several amphibian, fish and mammalian species. The findings were interpreted on the basis of known biochemical effects of cadmium.

Animals↗
PubMed1979

The ultrastructure of the dorsal yolk-free cytoplasm and the immediately surrounding cytoplasm in the symmetrized egg of Xenopus laevis.

Cytoplasmic segregation and subsequent dorsad displacement of the segregated cytoplasm lead to symmetrization of the egg of Xenopus laevis. At 60 min post-fertilization (p.f.) the 'dorsal yolk-free cytoplasm' (DYFC) is located in the dorso-animal part of the egg. Its ultrastructure and that of the immediately surrounding cytoplasm have been studied with transmission electron microscopy (TEM). The endoplasmic reticulum (ER) within the DYFC consists of single or paired cisternae and many small vesicles, both with moderately dense contents. Numerous particles, presumably ribosomes and glycogen, are present together with many mitochondria and some Golgi structures. The fraction of total yolk-free area occupied by mitochondria in the DYFC is about three times that in the adjacent cytoplasm. The number of cytoplasmic vesicles per unit area of cytoplasm is far larger in the DYFC than in the surrounding area. The morphological characteristics of the DYFC at 60 min p.f. suggest that it represents a region of high metabolic activity. Since it is located in the dorso-animal quadrant of the uncleaved egg, it may be partly responsible for a difference in metabolism between the dorsal and the ventral side of the egg, and hence may play an essential role in the determination of dorso-ventrality.

Animals↗
PubMed1978

Shape: its development and regulation capacity during embryogenesis.

Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation together with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development.

Animals↗
PubMed1978

Shape regulation capacity during development: recovering capacity of embryos developing notwithstanding dramatic deformations.

1. The development was studied of embryos in which dramatic deformations were produced by physical means during the period in which they are highly susceptible to teratogenesis. 2. In spite of the deformations histogenesis as a whole as well as cytodifferentiation seems to be normal. 3. With only few exceptions the embryos showing dramatic deformations ultimately recover a normal morphology. 4. The shape recovering capacity raises the question whether morphogenesis and shape are not in fact more or less independent phenomena.

Animals↗
PubMed1977

Are shape and morphogenesis independent phenomena?

Amphibian embryos can develop inspite of dramatic deformations produced by constraints in the surrounding medium, and can even ultimately recover a normal morphology. Consequently, no sequential change of shape is necessary for normal morphogenesis and the form of the embryo appears to be determined by cell activities intrinsic to each stage.

Animals↗
PubMedDate not supplied

Potential developmental toxicity of anatoxin-a, a cyanobacterial toxin.

Some 2000 species of cyanobacteria (blue-green algae) occur globally in aquatic habitats. They are able to survive under a wide range of environmental conditions and some produce potent toxins. Toxin production is correlated with periods of rapid growth (blooms) and 25%-70% of blooms may be toxic. Anatoxin-a is an alkaloid neurotoxin that acts as a potent neuro-muscular blocking agent at the nicotinic receptor. Acute toxicity, following consumption of contaminated water, is characterized by rapid onset of paralysis, tremors, convulsions and death. Human exposures may occur from recreational water activities and dietary supplements, but are primarily through drinking water. The current studies were conducted to examine the effect of in utero exposure on postnatal viability, growth and neurodevelopment, to evaluate the potential of in vitro embryotoxicity, and to explore the synergistic relationship between anatoxin-a and the algal toxin microcystin-LR by the oral route. The results of preliminary studies on amphibian toxicity are also reported. Time-pregnant mice received 125 or 200 microg kg(-1) anatoxin-a by intraperitoneal injection on gestation days (GD) 8-12 or 13-17. Pup viability and weight were monitored over a 6-day period. Maternal toxicity (decreased motor activity) was observed at 200 microg kg(-1) in both treatment periods. There were no significant treatment-related effects on pup viability or weight on postnatal day (PND) 1 or 6. The GD 13-17 pups were evaluated on PND 6, 12 and 20 for standard markers of neurodevelopmental maturation (righting reflex, negative geotaxis and hanging grip time). No significant postnatal neurotoxicity was observed. In vitro developmental toxicity was evaluated in GD 8 mouse embryos exposed to 0.1-25 microm anatoxin-a for 26-28 h. Perturbations in mouse yolk sac vasculature were noted from the 1.0 microm concentration in the absence of significant embryonic dysmorphology. Potential algal toxin synergism was tested in mice receiving either 0, 500 or 1,000 microg kg(-1) microcystin-LR by gavage and approximately 50 min later receiving either 0, 500, 1,000 or 2,500 microg kg(-1) anatoxin-a by the same route. No deaths occurred at any dose and no definitive signs of intoxication were observed. Stages 17 and 25 toad embryos (Bufo arenarum) were exposed to 0.03-30.0 mg l(-1) of anatoxin-a for 10 days. Adverse effects included a dose-dependent transient narcosis, edema and loss of equilibrium. Most notable was the occurrence of 100% mortality at the high dose in both groups 6-13 days post-exposure. The observed delay between initial exposure and death is highly unusual for anatoxin-a.

Animals↗
PubMedDate not supplied

Lack of teratogenicity of microcystin-LR in the mouse and toad.

Microcystin-LR (MC-LR) is a cyanobacterial toxin generated by the organism Microcystis aeruginosa. Although the hepatotoxicity of this chemical has been characterized, the potential developmental toxicity in vertebrates has not been well studied. The purpose of this study was to elucidate the effects of this toxin on the in vivo and in vitro development of mammals and the development of an Anuran (toad). Initial acute toxicity experiments with female CD-1 mice were accomplished with MC-LR administered i.p. in saline. Lethality occurred at 128 and 160 microg kg (-1) and histopathology revealed massive hepatic necrosis with diffuse hemorrhage. Developmental toxicity studies were done with MC-LR administered i.p. for 2-day periods: gestation days 7-8, 9-10 or 11-12. Doses used ranged from 2 to 128 microg kg(-1). On gestation day 17, fetuses were weighed and analyzed for gross morphological and skeletal defects. No treatment-related differences were seen in litter size, viability, weight or the incidence of anomalies. Groups of dams dosed with 32-128 microg kg(-1) on gestation days 7-8, 9-10 or 11-12 were allowed to give birth and the growth and development of their pups were followed postnatally. There were no significant effects noted in the offspring of the treated dams. Neurulation-staged CD-1 mouse conceptuses were exposed to 50-1000 nM MC-LR in whole embryo culture for 24 h. No significant increase in abnormalities or developmental delays was observed. Finally, exposure of the developing toad. Bufo arenarum was done from stage 17 (tail bud) for 10 days at concentrations of 1-20 mg l(-1). No effect on morphological development or survival was noted in any exposed groups. These data indicate that microcystin does not appear to affect development adversely in the mouse (in vivo or in vitro) or the toad at the doses and exposure parameters used.

Animals↗