Thallium-induced achondroplasia in chicken embryos and the concept of critical periods during development

Exposure to metal mixtures and young children's growth and development: A biomonitoring-based study in Eastern China

Exposure to metal mixtures may affect children's health but the conclusions are controversial. We aimed to investigate the associations of metal mixture exposure with children's physical and behavioral development. 15 metals were detected in the urine samples of 278 preschoolers aged 3-6 years from eastern China. Multiple linear models and restricted cubic splines were used to evaluate dose-response relationships between single metal and children's physical and behavioral development. The Bayesian Kernel Machine Regression (BKMR) models, the weighted quantile sum (WQS) models and Quantile G-Computation were applied to evaluate the joint effects of metal mixtures. The results showed that arsenic (As) was negatively associated with z score of height for age (HAZ) in individual-metal models [β (95%CI): - 0.22 (-0.38, -0.06), P = 0.006]. Concerning children's behavioral development, multiple-metal models demonstrated a negative association with strontium (Sr) [β (95%CI): - 0.82 (-1.38, -0.26), P = 0.004], and a positive association with tin (Sn) [β (95%CI): 0.69 (0.16, 1.21), P = 0.010]. Notably, these associations remained significant or suggestive even after adjustments for multiple tests, sensitivity analyses, and application of different statistical models, including BKMR, WQS, and Quantile G-Computation. Furthermore, the study identified a negative joint effect of the metal mixture on HAZ, as demonstrated by BKMR and Quantile G-Computation models, with As playing an irreplaceable role in this observed impact. In summary, exposure to As appears to have adverse effects on HAZ, while exposure to Sn may hinder children's behavioral development. Conversely, exposure to Sr may have a protective effect on children's behavioral development. Additionally, the combined impact of metal mixtures is implicated in potentially impairing children's physical development, particularly in terms of HAZ.

Effect on the offspring of pregnant females CD-1 mice treated with a single thallium(I) application

Thallium (Tl) is a highly toxic metal for human beings; higher amounts found in diverse fluids of pregnant women are associated with low birth weight and preterm birth. However, experimental data concerning their effects on the embryonic development of mammalian organisms are limited. Hence, in the present work, TI(I) acetate of 0, 4.6, 9.2, or 18.5 mg/kg body weight were administered by intraperitoneal injection to groups of 10 pregnant CD-1 mice on the 7th gestational day, and animals were sacrificed on day 18 of gestation. The fetuses obtained showed some variations, such as trunk bent over (18.5 mg/kg), tail variations (all doses), forelimbs malrotation and hind limbs (all doses). Skeletal examination of the fetuses showed a delay in the ossification of skull bones, ribs, and limbs (all doses). In conclusion, the Intraperitoneal injection of Tl(I) acetate to pregnant mice induced morphological variations and a delay of the fetus ossification.

Prenatal thallium exposure and poor growth in early childhood: A prospective birth cohort study

BACKGROUND

Thallium (Tl) exposure remains a public health problem with potential impacts on humans. Studies have suggested that prenatal exposure to thallium may be associated with fetal growth, but no studies are known have explored its association with early childhood anthropometry.

OBJECTIVE

To investigate the effects of prenatal Tl exposures on early child growth and development aged 0-2 years in a prospective birth cohort study.

METHODS

3080 pregnant women and their children participated in the study, which were recruited from a birth cohort in China. Serum samples collected in the first and second trimester of pregnant subjects and umbilical cord blood of infants were analyzed for Tl exposure assessment. Infant length or standing height and weight were obtained from medical records and 2 years planned visits. We used length/height and weight to calculate z-scores for weight-for-age (WAZ), height-for-age (HAZ), weight-for-height (WHZ), and body mass index-for-age (zBMI) based on World Health Organization standards. Linear mixed model was used to investigate the association between serum concentrations of Tl and the children's anthropometric characteristics (WAZ, HAZ, WHZ, and zBMI), and stratification analysis by sex was also examined.

RESULTS

The median (P₂₅-P₇₅) of Tl levels in the first trimester, second trimester and umbilical cord serum were 61.7 (50.7-77.0), 60.1 (50.9-74.8) and 38.4 (33.6-43.9) ng/L, respectively. Paired Mann-Whitney tests found Tl concentrations in umbilical cord serum were significantly less than that in maternal serum during the first and second trimesters (all p < 0.01). Using adjusted linear mixed model, no significant relationships were observed between maternal Tl exposure and child growth parameters. However, the umbilical cord serum Tl levels may contributed to decreased WAZ (β = -0.382, 95% confidence interval (CI): -0.670, -0.095) and HAZ (β = -0.427, 95% CI: -0.702, -0.152). When stratified by sex, the umbilical cord serum Tl levels were negatively related to WAZ (β = -0.450, 95% CI: -0.853, -0.048) and HAZ (β = -0.775, 95% CI: -1.160, -0.391) for girls. Among boys, overall Tl exposures were not significantly associated with early children anthropometric outcomes.

CONCLUSIONS

In the present study, our results suggested that prenatal Tl exposures may have a sex specific effect on child anthropometric measurements in the first 2 years of life. Umbilical cord serum Tl levels tended to be reduced child's stature and weight in young girls.

Phenotypical expression of reduced mobility during limb ontogeny in frogs: the knee-joint case

Movement is one of the most important epigenetic factors for normal development of the musculoskeletal system, particularly during genesis and joint development. Studies regarding alterations to embryonic mobility, performed on anurans, chickens and mammals, report important phenotypical similarities as a result of the reduction or absence of this stimulus. The precise stage of development at which the stimulus modification generates phenotypic modifications however, is yet to be determined. In this work we explore whether the developmental effects of abnormal mobility can appear at any time during development or whether they begin to express themselves in particular phases of tadpole ontogeny. We conducted five experiments that showed that morphological abnormalities are not visible until Stages 40–42. Morphology in earlier stages remains normal, probably due to the fact that the bones/muscles/tendons have not yet developed and therefore are not affected by immobilization. These results suggest the existence of a specific period of phenotypical expression in which normal limb movement is necessary for the correct development of the joint tissue framework.

Early effects of embryonic movement: 'a shot out of the dark'

It has long been appreciated that studying the embryonic chick in ovo provides a variety of advantages, including the potential to control the embryo's environment and its movement independently of maternal influences. This allowed early workers to identify movement as a pivotal factor in the development of the locomotor apparatus. With an increasing focus on the earliest detectable movements, we have exploited this system by developing novel models and schemes to examine the influence of defined periods of movement during musculoskeletal development. Utilizing drugs with known neuromuscular actions to provoke hyperactivity (4-aminopyridine, AP) and either rigid (decamethonium bromide, DMB) or flaccid (pancuronium bromide, PB) paralysis, we have examined the role of movement in joint, osteochondral and muscle development. Our initial studies focusing on the joint showed that AP-induced hyperactivity had little, if any, effect on the timing or scope of joint cavity elaboration, suggesting that endogenous activity levels provide sufficient stimulus, and additional mobilization is without effect. By contrast, imposition of either rigid or flaccid paralysis prior to cavity formation completely blocked this process and, with time, produced fusion of cartilaginous elements and formation of continuous single cartilaginous rods across locations where joints would ordinarily form. The effect of these distinct forms of paralysis differed, however, when treatment was initiated after formation of an overt cavity; rigid, but not flaccid, paralysis partly conserved precavitated joints. This observation suggests that 'static' loading derived from 'spastic' rigidity can act to preserve joint cavities. Another facet of these studies was the observation that DMB-induced rigid paralysis produces a uniform and specific pattern of limb deformity whereas PB generated a diverse range of fixed positional deformities. Both also reduced limb growth, with different developmental periods preferentially modifying specific osteochondral components. Changes in cartilage and bone growth induced by 3-day periods of flaccid immobilization, imposed at distinct developmental phases, provides support for a diminution in cartilage elaboration at an early phase and for a relatively delayed influence of movement on osteogenesis, invoking critical periods during which the developing skeleton becomes receptive to the impact of movement. Immobilization also exerts differential impact along the proximo-distal axis of the limb. Finally, our preliminary results support the possibility that embryonic hyperactivity influences the potential for postnatal muscle growth.

Critical periods during development as assessed by thallium-induced inhibition of growth of embryonic chick tibiae in vitro

In ovo application of thallium sulfate has been shown to produce a characteristic shortening and angulation of the tibia of the embryonic chick. The critical period for susceptibility to thallium-induced inhibition of tibial growth ends at 8 2/3 days of incubation, a time when the growth rate of the embryo declines by 55%. The aim of the present study was to expose tibiae to thallium in vitro to determine whether this response was intrinsic to the tibia. A 4-hour exposure to 400 micrograms thallium was found to be most effective. Growth of tibiae from 8-day-old embryos was inhibited, growth of tibiae from 9-day-old embryos was not, and the response of tibiae isolated from embryos of 8 2/3 days of incubation was intermediate. Therefore, the response of the tibia to thallium represents an intrinsic property and is not secondary to inhibited nerve growth as has been suggested. The critical period and its termination is also an intrinsic property of the tibia. Tibiae were exposed to thallium for 4 hours at various times after the tibiae had been established in vitro. Susceptibility to growth inhibition was shown to decline as tibiae developed beyond the critical period, a decline that could be correlated with a declining growth rate. Emphasis is placed upon critical events during development as a more useful concept than critical periods for explaining susceptibility to teratogens.

Thallium determinations in fetal tissues and maternal brain and kidney

The transfer of T1+ cations through the placental barrier of pregnant mice and rats was studied by comparing the thallium concentrations in the maternal brain and kidney and those in fetal tissue at times of 10 min to 50 h after dosage of the animals with 10 mg/kg body wt. T1(2)SO4. The quantitative determinations were performed with field desorption mass spectrometry after dilution of the homogenised tissue samples with enriched stable isotopes of thallium. The total sample quantity required for one complete assay is 1-3 micrograms, the analysis time for one determination about 30 min.

Repeated surveillance of exposure to thallium in a population living in the vicinity of a cement plant emitting dust containing thallium

From 1979 to 1981, several medical surveys were carried out among a population living in the vicinity of a cement plant that emitted dust containing thallium until August, 1979. Air, soil, plants, and domestic animals in the area were contaminated by thallium and this led to an increased intake of thallium in the population, mainly due to the consumption of home-grown vegetables and fruit. In order to assess the degree of the individuals' exposure to thallium, thallium levels in 24-h urine samples (TlU) were determined. Three surveys were carried out from September to December, 1979 to assess the degree of thallium exposure of different parts of the general population. Subjects with relatively high exposure, as indicated by the results of the above mentioned population surveys, or those suffering from health disorders that might be related to an increased intake of thallium, were reexamined several times from 1979-1981. Special attention was also given to children attending a kindergarten situated about 0.5 km from the cement plant. As compared to an "unexposed" reference population (mean TlU: 0.3 microgram/l), the majority of the population living in the cement plant area had significantly elevated urinary thallium levels (range: less than 0.1-76.5 micrograms/l) indicating a substantially increased environmental exposure. A reduction of the intake of thallium was mainly achieved by the fact that the population, as advised by the authorities, largely avoided the consumption of home-grown, potentially contaminated foodstuffs. Reports on the teratogenicity of thallium in certain animal species caused great concern that thallium might have exerted teratogenic effects on the newborn of women exposed to thallium during pregnancy. Therefore, an investigation of children born between January, 1978 and August, 1979 (n = 297) was carried out. Although the number of congenital malformations was greater than expected, we conclude, considering carefully all data available, that there is likely no causal relationship between thallium and the occurrence of congenital malformations in the children investigated.

Whole-body autoradiography of 204Tl in embryos, fetuses and placentas of mice

Whole-body autoradiography was used to study thallium uptake and retention in mice during gestation. Fifteen minutes after an intraperitoneal injection of 50 microCi 204Tl2SO4 into a 15-day pregnant mouse, thallium could be seen within the fetuses. Maximum fetal accumulation occurred 2-4 h after injection, and minimum at the last observation 4 days after injection. The fetal concentration of 204Tl was constantly lower than the placental. Uptake of 204Tl in embryos, fetuses and placentas of mice with gestation ages varying from 5 days to 16 days indicated that thallium crosses the placental barriers throughout gestation. Thallium was retained by the visceral yolk sac placenta during early gestation, by the visceral yolk sac, chorioallantoic placenta and amnion during late gestation. Over a period of time placental transfer and embryonic/fetal retention of small amounts of thallium may be hazardous to the offspring due to the high cumulative toxicity of this metal.

Thallium chondrodystrophy in chick embryos: ultrastructural changes in the epiphyseal plate

Using the transmission electron microscope, we sought to describe the morphology of thallium sulfate-induced chondrodystrophy in chick embryos. There was cell death and degeneration in all zones of growth cartilage, but the cells and matrix of the hypertrophic zone were the most severely affected. Ultrastructural changes of the hypertrophic chondrocytes consisted of alteration of the cytoplasmic contents and of the intercellular matrix; the cell membrane was smooth and without cytoplasmic extensions. The cytoplasm was filled with dilated rough endoplasmic reticulum, vacuoles of varying sizes and contents, and lipidlike bodies with electron-dense granules; mineral crystals, collagen, and degenerating mitochondria were present. The matrix showed only spotty calcification and a reduced number of dense bodies, vesicles, and granules. The cells appeared to have failed to exteriorize cell products across the plasmalemma. Failure to exteriorize cell products and to form cytoplasmic processes reduced the number of potential nucleation sites for calcification. The ultrastructure of osteocytes was much less affected.

Adult and embryo responses to organophosphate pesticides: azodrin

Azodrin was applied to adult embryo chickens, Chukar Partridge, and Bobwhite Quail. Chronic exposure of adult birds to Azodrin mixed in their feed indicated that no a priori predictions could be made about one species based on the results of another; each had a different no effect (MACT) level. The chickens were between 25 and 100 ppm, the Chukar Partridge 5 and 25 ppm, and the Bobwhite quail less than 1.25 ppm. The chicken adults were most resistant, and the quail were least resistant to chronic exposure to Azodrin. Yolk-injected Azodrin caused the embryos of all three species to develop abnormally. The chicken and Chukar embryos developed a generalized achondroplasia, the quail were amuscular, only. In general, the 3 day quail embryos were most resistant to injected Azodrin and the chicken embryo least resistant. The relationship between adult and embryo response was negative.

Use of the L-proline analog, L-azetidine-2-carboxylic acid (LACA) to analyse embryonic growth and determination and expression of the chondrogenic phenotype in vivo and in vitro

The L-proline analog, L-azetidine-2-carboxylic acid, (LACA) was injected into embryonated eggs of the common fowl, Gallus domesticus at daily doses of 350 microgram/egg on one or several days betweeh 8 and 12 days of incubation. Treatment at nine-days of incubation preferentially retarded embryonic growth to the twelfth day but recovery of growth rate occurred by 15 days of incubation. Relationships between growth and LACA-inhibited aspects of collagenogenesis are discussed. The earliest aged embryos from which isolated stem cells from membrane bones will form secondary cartilage is ten days of incubation. Secondary chondrogenesis on the quadratojugal, a membrane bone of the skull, was inhibited by treatment of whole embryos with LACA at nine days of incubation but not by treatment at eight days. We concluded that an event involving collagen began at nine days of incubation, was blocked by LACA and was part of the process of chondrogenic determination of these stem cells. Addition of LACA to the medium in which already determined stem cells from the quadratojugal were cultured prevented expression of the chondrogenic phenotype. This proline analog is then a useful probe for events relating both to determination and to expression of the differentiated state, and allows conclusions to be drawn regarding the role of collagenogenesis in these events.