Transabdominal chorionic villus biopsy in second and third trimesters of pregnancy to determine fetal karyotype.

Transabdominal chorionic villus biopsy is an established method of obtaining material for analysing fetal chromosomes in the first trimester of pregnancy but has not been widely used for karyotyping in the second and third trimesters, when rapid results are required. The technique was evaluated in two groups of patients, comprising 106 at risk of having a fetus with chromosomal anomalies (105) or X linked disease (one) studied between 13 and 22 weeks (median 15 weeks) of gestation (group 1) and 21 with abnormal fetal findings on ultrasonography studied between 13 and 38 weeks (median 27 weeks) (group 2). Chorionic tissue was collected at the first attempt in 109 patients and at the second attempt in a further 17 independent of the position of the placenta. In one case from group 1 sufficient material for analysis could not be obtained. Seven abnormal karyotypes (six in group 1 and one in group 2) were diagnosed. Karyotyping was unsuccessful in two cases in group 1 (at 17 and 18 weeks'' gestation) and in two in group 2 (at 29 and 38 weeks'' gestation). Follow up of group 1 four weeks after sampling showed no signs of adverse fetal development apart from one unexplained intrauterine fetal death. The findings suggest that chorionic sampling is a safe and valuable additional technique for the late detection of chromosomal defects.     

Pineal 'synaptic' ribbons in sympathectomized rats

The melatonin metabolism in the mammalian pineal gland is under the clear influence of sympathetic fibers originating in the superior cervical ganglia (SCG). Previous studies suggested that also pineal 'synaptic' ribbons (SR) are regulated by the gland's sympathetic innervation. To gain more insight into the mechanisms involved, SR numbers were determined in adult rats which were chemically sympathectomized as newborns by injection of 6-hydroxydopamine (6-OHDA). In control animals (saline injections), a clear day/night difference in the number of SR is present. In sympathectomized animals, SR are higher in number throughout the 24-hour cycle but are not significantly elevated at night. The present results further strengthen the hypothesis that SR are involved in intercellular communication in the mammalian pineal gland.     

Measurement of the effective thickness of the mucosal unstirred layer in Necturus gallbladder epithelium

The effective thickness of the unstirred fluid layer (USL) adjacent to an epithelial barrier can be estimated from the time course for the accumulation or depletion of a solute at the membrane surface. In 1985 we reported an unstirred layer thickness of approximately 70 microns for Necturus gallbladder epithelium. In our earlier studies the delay caused by noninstantaneous bulk solution mixing was not taken into account and thus the USL thickness was systematically overestimated. In the present studies we describe an analysis of the time course of solute arrival at the membrane surface that takes into account noninstantaneous bulk solution mixing. We also describe a simple technique to monitor the accumulation or depletion of a solute at the membrane surface. The time course for the change in the concentration of either tetramethylammonium (TMA+) or tetrabutylammonium (TBA+) upon elevation of bulk solution concentration is sensed at the membrane surface with an ion-sensitive microelectrode. Because of the high selectivity of the ion-sensitive resin for TMA+ or TBA+ over other monovalent cations in the solution (Na+ and K+), a low concentration (1-2 mM) of the probe can be used. By measuring the time course of the arrival of first one probe and then the other, under identical superfusion conditions, sufficient information is obtained to eliminate multiple fits to the data, obtained when only one probe is used. Neglecting bulk solution mixing caused an error greater than 50% in estimated apparent USL thickness. The effective thickness of the USL depends critically upon chamber geometry, flow rate, and the position of superfusion and suction pipettes. Under our experimental conditions the effective USL at the mucosal surface of Necturus gallbladder epithelium was approximately 40 microns.     

Genetics of intracisternal-A-particle-related envelope-encoding proviral elements in mice.

Intracisternal-A-particle-related envelope-encoding (IAPE) proviral elements in the mouse genome encode and express an envelope-like protein that may allow transmission of IAPEs as infectious agents. To test IAPE mobility and potential transmission in mice, we have analyzed the distribution of IAPE elements in the genomes of Mus spretus and Mus musculus inbred strains and wild-caught animals. Potential full-length (IAPE-A) proviral elements are present as repetitive copies in DNA from male but not female animals of M. musculus inbred strains and Mus musculus castaneus. Analysis of IAPE-cellular junction fragments indicates that fixation of most IAPEs in the germ line occurred in M. musculus and M. spretus after speciation but before M. musculus inbred strains were derived.     

Investigation of Local Ethylene Emission from Intact Cherry Tomatoes by Means of Photothermal Deflection and Photoacoustic Detection

The function of the coronet region of the cherry tomato (Lycopersicon esculentum Cherry) as the main emission channel for ethylene was investigated. Ethylene was measured employing two laser-based detection systems, the photothermal deflection instrument and the photoacoustic detection setup. It is possible to detect minimum ethylene concentrations of 1 nL L-1 locally and rapidly with the first instrument and concentrations of 6 pL L-1 in a continuous flow system with the second setup. The continuous flow system makes it possible to change the air composition and to monitor its influence on the ethylene production of the tomato. The response times of the two instruments are 30 s and 4 min, respectively. The local character of the measurements makes it possible to determine the emission sites of the gaseous plant hormone ethylene and their relative importance. Transient anoxic conditions stop production of ethylene; return to aerobic conditions shows the evolution of the accumulated ethylene precursor 1-aminocyclopropane-1-carboxylic acid and its renewed production on the measured ethylene emission, with a time resolution of several minutes. Temporarily sealing the main emission channel yields results comparable to anoxia.     

Demonstration of retinal afferents in the RCS rat,with reference to the retinohypothalamic projection and suprachiasmatic nucleus

In the Royal College of Surgeons (RCS) rat, characterized by inherited retinal dystrophy, retinal projections to the brain were studied using anterograde neuronal transport of cholera toxin B subunit upon injection into one eye. The respective immunoreactivity was found predominantly contralateral to the injection site in the lateral geniculate nucleus, superior colliculus, nucleus of the optic tract, medial terminal nucleus of the accessory optic tract, and bilateral hypothalamic suprachiasmatic nuclei. Although terminal density was somewhat reduced in dystrophic rats, the projection patterns in these animals appeared similar to those seen in their congenic controls and were comparable to the visual pathways described for the rat previously. In dystrophic rats, the number of cell bodies exhibiting immunoreactivity to vasoactive intestinal polypeptide, viz. a population of suprachiasmatic neurons receiving major retinohypothalamic input, was reduced by one-third, and some differences were observed in the termination pattern of the geniculohypothalamic tract, as revealed by immunoreactivity to neuropeptide Y in the suprachiasmatic nucleus.This study was supported by grants from the DFG (Re 644/2-1) and the NMFZ, Mainz (to S.R.).     

Mechanisms of voltage transients during current clamp inNecturus gallbladder

Summary Microelectrode techniques were employed to study the mechanisms of the transepithelial voltage transients (V _ms ) observed during transmural current clamps in the isolatedNecturus gallbladder. The results indicate that: a) part of V _ms is due to a transepithelial resistance change (R _t ), and part to a tissue emf change. b) R _t is entirely caused by changes of the resistance of the paracellular pathway. At all current densities employed, the measured changes are probably due to changes in both fluid conductivity and width of the lateral intercellular spaces. At high currents, in addition to the effects on the lateral spaces, the resistance of other elements of the pathway (probably the limiting junction) drops, regardless of the direction of the current. c) The magnitude and polarity of the R _t -independent transepithelial and cell membrane potential transients indicate that the largest emf change takes place at the basolateral membrane (E _b ), with smaller changes at the luminal membrane (E _a ) and the paracellular (shunt) pathway (E _s ). It is shown that two-thirds of the transient are caused by E _s , and one-third by (E _b –E _a ). E _s can be explained by a diffusion potential generated by a current-dependent NaCl concentration gradient across the tissue. E _a and E _b are caused by [K] changes, mainly at the unstirred layer in contact with the basolateral membrane.