Normal fetal cardiac anatomy–a basis for the echocardiographic detection of abnormalities

Real-time examination of the fetal heart in 350 pregnancies has allowed a composite picture of normal fetal cardiac anatomy to be established and echocardiographic interpretation has been confirmed by anatomical studies. Two echocardiographic sections are readily obtainable and are suggested as applicable to routine scanning but the specialist nature of interpreting abnormalities is stressed. Six abnormalities have been suspected during the study and five confirmed anatomically or at cardiac catheterization. In view of the low incidence of congenital heart disease in a normal obstetric population, high risk groups should perhaps be selected for cardiac scanning at the present time. These include mothers of previously affected babies, diabetic mothers and certain abnormalities of pregnancy. Fetal ascites is particularly important, being present in three of the four proven cases of cardiac abnormality.     

First-trimester amniotic fluid and extraembryonic coelomic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on samples of amniotic fluid and extraembryonic coelomic fluid obtained by high resolution transvaginal ultrasound-guided amniocentesis from 38 women between 8 and 12 weeks of pregnancy. AChE was positive in 33 per cent (12/36) of the amniotic fluid samples; the percentage of positive results decreased as gestation advanced. AChE was positive in 32 per cent (9/28) of the extraembryonic coelomic fluid samples. In 81 per cent (21/26) of matched samples, the AChE results were identical in the two fluids. Amniotic fluid and extraembryonic coelomic fluid AChE electrophoresis cannot be used to diagnose neural tube defects prior to 12 weeks of gestation.     

Early sonographic diagnosis of body stalk anomaly

Ultrasonographic features of a fetus at 18 weeks of gestation suggesting a body stalk anomaly are presented. These included a large abdominal anterior wall defect in apparent continuity with the placenta, severe kyphoscoliosis of the lower spine, the absence of one kidney, and a very short umbilical cord with only one umbilical artery. The amniotic fluid was reduced and the fetus was almost immobile at short-interval ultrasound examinations. The pregnancy was terminated and autopsy of the fetus showed abnormalities compatible with maldevelopment of both cephalic and caudal embryonic folds.     

Measurement of the fetal mandible—feasibility and construction of a centile chart

The prenatal diagnosis of micrognathia is usually based on a subjective impression of the size of the jaw when examining the fetal profile. We have constructed a centile chart for mandibular length between 12 and 27 post-menstrual weeks in a cross-sectional study of 184 fetuses. The application of this chart in clinical practice may permit a more objective diagnosis of micrognathia in the prenatal period.     

Seasonal cycles in the carotenoid content in Mytilus edulis

The carotenoid content of Mytilus edulis was studied over a period of 3 years from 1965 to 1967; a seasonal cycle was observed which appeared to be controlled by the spring bloom of phytoplankton, and the sexual cycle of the mussel. Infestation by the copepod Mytilicola intestinalis and hours of exposure in the tidal cycle were found to contribute to variations in carotenoid content. Maturation of the gonads and spawning occurred in the late spring and early summer of the period studied. In addition, a second sexual phase was recorded in October 1967. The possible effect of exposure on the time of spawning is discussed. Lack of food affects both carotenoid content and the maturation of the gonads. M. edulis kept at 10 °C with little food showed no seasonal variation in the carotenoid content when compared with animals fresh from the shore. Lack of food resulted in regression in gonadal tissue after a period of time, and an absence of mature and spawning individuals.     

Lethal levels of hypoxia for gulf coast estuarine animals

There is increasing concern about eutrophication and subsequent hypoxia problems in estuaries. The US Environmental Protection Agency has developed Water Quality Criteria (WQC) for dissolved oxygen (DO) in saltwater for Cape Cod, MA to Cape Hatteras, NC but inadequate data exists for development of such criteria for other coastal geographic areas. We performed acute tests with two species of crustaceans and seven species of estuarine fishes native to the Gulf of Mexico to complement the data base for northeastern species. Flow-through tests were conducted for either 24- or 48-h at test temperatures from 24 to 28°C and at salinities from 20 to 31.5‰. Estimated 24-h LC50 values obtained for crustaceans ranged from 1.36 mg/l for adult pink shrimp to 1.56 mg/l for 10-day-old mysids. Similarly, estimated LC50 values for fish ranged from 1.34 mg/l in one of the three tests with pinfish to 2.22 mg/l in one of the two tests with scaled sardines. The majority of mortality attributable to low DO concentrations in our experiments usually occurred within the first 4 h of exposure. LC50 values for the species tested are below the WQC recommended protective limit of 2.3 mg/l for juvenile and adult animals.     

Nitrate reductase for nitrate analysis in water

Nitrate analysis in water is one of the most frequently applied methods in environmental chemistry. Current methods for nitrate are generally based on toxic substances. Here, we show that a viable alternative method is to use the enzyme nitrate reductase. The key to applying this Green Chemistry solution for nitrate analysis is plentiful, inexpensive, analytical grade enzyme. We demonstrate that recombinant Arabidopsis nitrate reductase, expressed in the methylotrophic yeast Pichia pastoris, is a highly effective catalyst for nitrate analysis at 37°C. Recombinant production of enzyme ensures consistent quality and provides means to meet the needs of environmental chemistry.     

Sub-cellular partitioning of Cd, Cu and Zn in tissues of indigenous unionid bivalves living along a metal exposure gradient and links to metal-induced effects

We studied organ and sub-cellular distributions of several trace metals in a freshwater bivalve that has been proposed for use as a metal biomonitor. Specimens of Pyganodon grandis were collected from nine lakes located along a Cd, Cu and Zn concentration gradient (Rouyn-Noranda area, Quebec). Gills and digestive gland were isolated, homogenized and six sub-cellular fractions were separated by differential centrifugation and analysed for their Cd, Cu and Zn content. Metallothionein was quantified independently. Gill tissues contained abundant calcium concretions that accounted for over 60% of the total gill burden of each metal. Cadmium and Zn concentrations in this granule fraction reflected ambient metal concentrations. Metal concentrations in the digestive gland also responded to the metal contamination gradient, but to a lesser extent than the gills, reflecting the lower abundance of granules in the digestive gland. Metals (Cd, Cu) in this organ were present largely in the "heat-stable proteins" fraction, and metal concentrations in this fraction were strongly correlated with those of both metallothionein and, to a lesser extent, the "lysosomes+microsomes" and "mitochondria" fractions. In both organs, Cd concentrations in the "heat-denaturable protein" fraction remained low and constant, suggesting reasonably effective metal detoxification. Some evidence for oxidative stress was noted in the gills but not in the digestive gland. Overall, we conclude that in nature metals in P. grandis are bound differently in the gills and in the digestive gland and that metal detoxification in the former organ may be less effective than in the latter.     

Persistence of carbofuran in marine sand and water

Marine sand and seawater samples were collected in March 2002 from Laysan Island in the Hawaiian Islands National Wildlife Refuge, where a small area was contaminated by the carbamate insecticide carbofuran. Carbofuran was still detected at microg g(-1) levels in the Laysan sand after its identification in 1998 and initial observation of the toxicity in 1988. The persistence of carbofuran in the marine sand was investigated in the dark in a 30 degrees C oven, and in distilled deionized water and seawater samples exposed to artificial 300 nm light and to direct sunlight. The laboratory study showed a half-life (t1/2) of approximately 40 days for carbofuran in the native sand and in Ottawa sand. The photolysis of carbofuran was faster in seawater than in distilled deionized water when it was exposed to 300 nm light (t1/2, 0.1 vs. 3.1 h) and to direct sunlight (t1/2, 7.5 vs. 41.6 h). The large difference between the laboratory results and the field observation of carbofuran dissipation suggests that carbofuran degradation at the remote, undisturbed marine site may be governed by its unique environmental factors.     

Relating cadmium concentrations in three macrophyte-associated freshwater invertebrates to those in macrophytes,water and sediments

We found that Cd concentrations in three species of macrophyte-associated invertebrates (the gastropods Bithynia tentaculata and Physa gyrina, and the amphipod Gammarus fasciatus) collected at twenty sites along the St. Lawrence River were correlated with Cd concentrations in their main food source, i.e. macrophytes and associated periphyton. Cd in these invertebrates was not significantly correlated with Cd concentrations in the sediments (even when corrections for iron oxide or organic carbon content were applied) or to calculated free-cadmium concentrations in the water. Cd levels in juveniles of B. tentaculata were very tightly linked to Cd concentrations in macrophytes, which is consistent with the close relationship that these organisms have developed with macrophytes. Linear models predicting Cd levels in juveniles of B. tentaculata from Cd levels in different macrophyte species were strong (R2 = 0.69-0.90). Analysis of covariance on these models showed no statistical difference of slope or intercept for any of the macrophyte species, except Vallisneria americana. We suggest that the macrophyte-periphyton complex is a key link in the transfer of cadmium to some aquatic invertebrates in the littoral zone of the St. Lawrence River and that macrophytes and their associated epiphytes should also be used as biomonitors.