Lethal and sublethal effects of phthalate diesters in Silurana tropicalis larvae

Degenerative Osteoarthropathy in Laboratory Housed Xenopus (Silurana) tropicalis

In this case study, 15 adult laboratory Xenopus (Silurana) tropicalis (7 adult males and 8 adult females) were examined for nodular enlargements of the clawed digits (digits 0, I, II, and III) on the hind feet. Radiographs showed smoothly margined, rounded, peripherally mineralized lesions arising from the distal phalanges of digits 0-III with osteoproductive and osteolytic components in all frogs. Micro computed tomography (microCT) scans further revealed interphalangeal (IP), metacarpophalangeal (MCP), and metatarsophalangeal (MTP) joint osteoarthritis characterized by periarticular new bone formation, rounded mineral foci both peripherally and centrally within the joints, and more rarely, linear mineralization palmar/plantar to the joints in the flexor tendons. In the nonclawed digits, the shape of the distal phalanx was variably distorted and both subluxation and malangulation of IP joints were identified. Histologically, nodules corresponded to a peripheral rim of mature cortical bone surrounding central adipose tissue, scattered hematopoietic elements, and residual bone of the distal phalanx. Occasionally, the peripheral rim of cortical bone extended proximally to encompass the distal aspect of adjacent phalanx. MCP, MTP and IP joint spaces of most digits exhibited widespread osteoarthritis characterized by periarticular cartilaginous or osseous metaplasia, bony remodeling, and less frequently, granulomatous osteomyelitis. Nutritional analyses of the feed did not indicate imbalances nor were the lesions consistent with metabolic bone disease. The exact etiopathogenesis of these lesions is unknown; however, we hypothesize that the osteoarthritic changes are due to a combination of the frogs' mature age, the unique structure of the Xenopus spp. claw, genetics and biomechanical forces on the digits and distal phalanges of the hind feet.

Effects of Dimethyl Phthalate (DMP) on Serum Sex Hormone Levels and Apoptosis in C57 Female Mice

BACKGROUND

The effects of dimethyl phthalate (DMP) on the reproductive system of mammal females are unclear because no studies have been conducted on this topic.

METHODS

In this study, 40 C57 female mice were used as experimental subjects and evenly divided into 8 groups, which were fed with mixed DMP (0, 0.5, 1, and 2 g/kg bw/day) and corn oil. After 20 days and 40 days of gavage, the mice were weighed and their individual ovary organ coefficients measured.

RESULTS

Changes were discovered on progesterone, estradiol, follicle-stimulating hormone and luteinizing hormone in mouse serum, and on the apoptosis rate of ovarian granulosa cells.

CONCLUSIONS

Prolonged exposure to DMP led to decreased secretion of FSH hormones and increased secretion of E2 and LH hormones. Furthermore, DMP interfered with the pituitary-ovary axis and increased the apoptosis rate of ovarian granulosa cells. Therefore, prolonged exposure to DMP is likely to have negative effects on reproduction and development.

Phthalates modulate steroid 5-reductase transcripts in the Western clawed frog embryo

Phthalates are used worldwide in the manufacturing of plastics, added to cosmetic products, personal care products, pharmaceuticals, medical devices, and paints; and are widely detected in soil, surface water, and organism tissues. Phthalate esters have been previously shown to interfere with the endocrine system in vertebrates. However, few studies have investigated the effects of phthalates on testosterone-converting enzymes that affect hormone levels and reproduction. In the present study, we exposed the Western clawed frog (Silurana tropicalis) to 0.1, 1, and 10 μM diethylhexyl phthalate (DEHP), dibutyl phthalate (DBP), and diethyl phthalate (DEP) during early amphibian embryonic development. Additional DBP exposures were conducted ex vivo using mature frog testes. Malformations and mRNA levels of genes associated to reproduction and oxidative stress were evaluated. 0.1 μM DEHP, DBP, and DEP induced an array of malformations, including incomplete gut coiling, edemas, and eye malformations. Moreover, all three phthalates increased the expression of androgen-related genes, such as steroid-5α-reductase 1, 2, 3, steroid-5β-reductase, and androgen receptor at concentrations ranging from 0.1 to 10 μM depending on the phthalate and gene. Data suggest that the phthalate esters tested are teratogens to the amphibian embryo and that these phthalates exhibit an androgenic activity in amphibians.

Influence of Lipophilicity on the Toxicity of Bisphenol A and Phthalates to Aquatic Organisms

Bisphenol A (BPA) and phthalates are among the most popular plasticizers used today and have been reported ubiquitously in surface water, ground water, and sediment. For aquatic organisms, BPA was the most toxic (96 h LC50s) to aquatic invertebrates (0.96-2.70 mg/L) and less toxic to fish (6.8-17.9 mg/L). The toxicity of BPA to amphibians differed among developmental stages, with embryos having an LC50 of 4.6-6.8 mg/L and juveniles 0.50-1.4 mg/L. The toxicity of phthalates is affected by aromatic ring substitution, alkyl chain length, and metabolism. The toxicity (96 h LC50s) of phthalates was similar to aquatic invertebrates (0.46-377 mg/L) and fish (0.48-121 mg/L). In general, the toxicity of phthalates appears to be highest around a log KOW of 6, which corresponds to the highest potential for bioconcentration and bioaccumulation. In conclusion, the lipophilicity of BPA and phthalates influence their toxicity to aquatic species.