Kelvin Picker

IN VITRO ASSESSMENT OF INDIVIDUAL AND INTERACTIVE EFFECTS OF AROMATIC HYDROCARBONS ON EMBRYONIC DEVELOPMENT OF THE RAT

There have been reports of disruption of embryonic development following exposure of pregnant women to aromatic hydrocarbons. In the present study, the embryotoxicity of toluene, xylene, benzene, styrene, and its metabolite, styrene oxide, was evaluated using the in vitro culture of postimplantation rat embryos. Possible interactions between toluene, xylene, and benzene were also studied using mixtures of these solvents. The results of the study showed that toluene, xylene, benzene, and styrene all have a concentration-dependent embryotoxic effect on the developing rat embryo in vitro. Styrene was embryotoxic at a lower concentration (1.00 mumol/mL) than benzene (1.56 mumol/mL), toluene (2.25 mumol/mL), or xylene (1.89 mumol/mL). The metabolite of styrene, styrene oxide, was embryotoxic at a concentration (0.038 mumol/mL). more than 20 times less than the parent compound. There was no evidence of a synergistic interaction between toluene, xylene, and benzene in causing embryotoxicity; the solvents interacted in an additive manner. The embryos were exposed to the solvents for 40 h of the organogenic period. When the levels of solvents found to be embryotoxic in the present study are compared to blood levels in the human following industrial exposure or solvent abuse, it appears unlikely that the threshold blood levels for embryotoxicity would be exceeded in the workplace. However, the possibility that exposure to solvents earlier or later or throughout the entire organogenic period might result in a different conclusion cannot be excluded.

Coastal aminostratigraphy of the last interglaciation in Southern Australia

Abstract Amino acid racemization data for marine molluscs of the last interglaciation from southern Australia provide the basis for a predictive model for relative dating of late Quaternary sequences. Genera analyzed include Anadara sp., Katelysia sp., Glycymeris sp., and Fulvia sp. that exhibit moderate racemization rates. A genus effect on racemization is not evident in these taxa. Coefficients of variation for intershell D L ratio variation for each deposit are generally less than 12%. The extent of racemization in molluscan fossils of the last interglaciation from temperate coastal settings in southern Australia represents an exponential function of temperature and is in general accord with data from Northern Hemisphere sites with similar contemporary mean annual temperature values. These data highlight the potential of amino acid racemization for global correlation programs. The amino acid data from southern Australia suggest, however, that a larger margin of variation may have to be accounted for in stratigraphic correlation, as indicated by the greater scatter of data around the oxygen isotope substage 5e isochron. These data have implications regarding the age-resolving power of amino acid racemization.

In Vitro Assessment of the Effect of Halogenated Hydrocarbons: Chloroform, Dichloromethane, and Dibromoethane on Embryonic Development of the Rat

Halogenated hydrocarbons are widely used in industry, the laboratory, and in the home. In the present study three of these solvents--chloroform, dichloromethane, and dibromoethane--were examined for embryotoxic/teratogenic potential using rat embryo culture. The results showed that each of the solvents had a concentration-dependent embryotoxic effect on the developing rat embryo in vitro. The effect and no-effect concentrations (expressed in mumol/ml culture medium), respectively, for each of the halogenated hydrocarbons tested were: dibromoethane--0.33, < 0.18; chloroform--2.06, 1.05; dichloromethane--6.54, 3.46. The levels of chloroform and dichloromethane found to be embryotoxic in the present study were compared to reported blood levels attained following controlled human exposure. In the industrial situation, if the current exposure levels are adhered to, chloroform and dichloromethane appear to have little potential for reproductive toxicity in the human. Fatal or near fatal solvent levels would be required in the mother for the embryotoxic level to be reached. For dibromoethane, there are no reports following controlled human exposure presumably due to its carcinogenicity. In an attempt to elucidate the mechanism of embryotoxicity, histological studies were performed after exposure of rat embryos to an embryotoxic level of each of the halogenated hydrocarbons studied, for increasing time periods up to the standard 40-hour culture. Marked cell death in the neuroepithelium of the developing neural tube was a prominent feature in all embryos exposed to an embryotoxic level of these solvents for periods of 16 hours of longer.

Triterpenoid glycosides from Schefflera lucantha.

Three new triterpenoid glycosides were isolated from the leaves of Schefflera lucantha Viguier. Based on the spectroscopic data, especially 2D NMR, the structures of glycosides have been established as 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-glucuronopyranosyl] betulinic acid, 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-xylopyranosyl (1-->2)-beta-D-glucuronopyranosyl]betulinic acid and 3-O-[alpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl (1-->2)-beta-D-glucuronopyranosyl]oleanolic acid.

Methoxylated gramine derivatives from Phalaris aquatica

Abstract 7-Methoxygramine and 5,7-dimethoxygramine were isolated from the roots of 12-day-old seedlings of Phalaris aquatica . The structures were elucidated by spectroscopic methods. 5-Methoxygramine also was detected by TLC. All three gramine derivatives are reported for the first time.