Prenatal diagnosis and carrier detection of a cryptic translocation by using DNA markers from the short arm of chromosome 5.

DNA markers from the short arm of chromosome 5 were used to examine a large family in which a microscopically undetectable translocation was segregating. In addition to confirming that three retarded children were hemizygous for loci distal to 5p14, these analyses identified five individuals as being carriers of the balanced translocation. The use of molecular probes provided informed genetic counseling to the family for the first time. With the DNA markers from 5p, prenatal diagnosis was performed on two fetal chorionic villus samples, both of which were found to have unbalanced karyotypes. The identification of translocation carriers was complicated by recombination between the small translocated segment of 5p and the corresponding region on the normal homologue, which changed the haplotype of the translocated 5p segment.     

Occupational hydrocarbon exposure among fathers of Prader-Willi syndrome patients with and without deletions of 15q.

Prader-Willi syndrome (PWS) is a multiple-anomaly disorder in which 50%-70% of cases are associated with a de novo interstitial deletion [del 15(q11-13)] on prometaphase cytogenetic analysis, the remainder having apparently normal chromosomes. In most instances, the paternally derived chromosome has become deleted in the affected child, suggesting the possibility of a predisposing environmental factor. Strakowski and Butler found an increased incidence of paternal periconceptional employment in hydrocarbon-exposing occupations in this population. This observation may suggest a causal relationship to PWS. To determine whether this association may distinguish the cytogenetically different groups, we identified 81 patients with the disorder who were physically and cytogenetically examined in three centers, and we compared the frequency of possible periconceptional occupational hydrocarbon exposure between fathers of patients who demonstrate a 15q deletion and those who do not. There was no statistically significant difference between the cytogenetically different groups. In both groups, approximately half of the fathers had been employed in hydrocarbon-exposing jobs. These findings suggest lack of etiologic heterogeneity between the cytogenetically different groups for PWS and affirm the need to seek submicroscopic deletions through molecular genetic studies. These data also provide additional evidence that hydrocarbon exposure among fathers of children with PWS may be causally related to the disorder, and they also suggest the need for more accurate assessment of exposure via a large, controlled study.     

Antidepressant Treatments, Including Sibutramine Hydrochloride and Electroconvulsive Shock, Decrease β1 but Not β2-Adrenoceptors in Rat Cortex

The beta 1- and beta 2-adrenoceptor populations in rat cortex were individually quantified by labelling all of the receptors with [3H]dihydroalprenolol and displacing with isoprenaline (200 microM) or CGP 20712A (1-(2-[(3-carbamoyl-4-hydroxy)phenoxy]ethylamino)-3-[4-(1-methyl-4- trifluoromethyl-2-imidazolyl)phenoxy]-2-propanol methanesulphonate; 100 nM) to define total beta-adrenoceptors and beta 1-adrenoceptors, respectively. Binding parameters for beta 2-adrenoceptors were calculated by the difference. Oral administration of the monoamine reuptake inhibitors sibutramine HCl (3 mg/kg), amitriptyline (10 mg/kg), desipramine (10 mg/kg), or zimeldine (10 mg/kg) for 10 days decreased the total number of beta-adrenoceptors present in rat cortex. This effect was entirely due to a reduction in the number of beta 1-adrenoceptors. Similarly, 10 days of treatment with the monoamine oxidase inhibitor tranylcypromine (10 mg/kg p.o.) or five electroconvulsive shocks (ECSs; 200 V, 2 s) spread over this period also down-regulated beta-adrenoceptors by reducing the content of the beta 1-subtype. By contrast, treatment with clenbuterol (5 mg/kg p.o.) for 10 days reduced the number of cortical beta-adrenoceptors by an effect on the beta 2-adrenoceptor population. The effects of short-term treatment with these drugs were also investigated, and, using the doses shown above, the results of 3 days of administration or a single ECS were determined. Sibutramine HCl and desipramine were alone in producing a reduction in number of beta-adrenoceptors after 3 days. Once again, this was exclusively due to a loss of beta 1-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mobile domains in ribosomes revealed by proton nuclear magnetic resonance

Ribosomes and subunits from eukaryotic and prokaryotic sources were studied by high-resolution proton magnetic-resonance spectroscopy. If all ribosomal components are firmly bound within the particle, then only broad spectra would be expected. However, relatively sharp resonances were found both in ribosomal subunits and in 70 or 80 S ribosomes. The regions of these mobile protein domains have been partially assigned in Escherichia coli ribosomes. Large and small ribosomal subunits were treated to remove selectively proteins L7/12 and S1, respectively. Sharp proton magnetic resonance spectra were not observed for the stripped large subunit showing that proteins L7/12 comprise the flexible protein region and that there is little other flexibility in the stripped subunit. Complete removal of S1 from the small subunit greatly reduced but did not abolish the sharp protein resonance peaks, indicating that protein S1 contains a substantial flexible component but that other flexible components remain in the stripped small subunit. Evidence for generality of these features of ribosome organization is provided by similar studies on ribosomes from eukaryotic sources.     

Tentacle contraction inDiscophrya collini: The effects of ionophore A23187 and ruthenium red on Ca2+-induced contraction and uptake of extracellular calcium

Summary The tentacles of the suctorian protozoonDiscophrya collini are stimulated to contract by externally applied Ca²⁺. The role of extracellular Ca²⁺ in tentacle contraction was studied by monitoring⁴⁵Ca²⁺ uptake, using ionophore A23187 to facilitate membrane transport of calcium and ruthenium red (RR) as an inhibitor of transport. The degree of tentacle retraction was dependent upon external Ca²⁺ concentration and studies with⁴⁵Ca²⁺ using scintillation counting indicated a linear relationship between external Ca²⁺ concentration and Ca²⁺ uptake. Uptake of Ca²⁺ was enhanced in the presence of the ionophore while RR caused little inhibition.⁴⁵Ca²⁺ uptake was only partially inhibited by RR when cells were subjected to a Ca²⁺, ionophore and RR mixture. Grain counts from light microscope autoradiographs after treatment of cells with⁴⁵Ca²⁺/ionophore,⁴⁵Ca²⁺/RR or⁴⁵Ca²⁺ alone showed heavy, light and intermediate labelling respectively. In all instances the grains were evenly distributed within the cell.These observations are interpreted as supporting the suggestion that the ionophore enhances both the uptake of extracellular Ca²⁺ and release of Ca²⁺from an internal source, while the RR could only partially prevent movement of Ca²⁺ through the plasma mebrane. A model is presented suggesting that tentacle retraction is mediated by cytosolic Ca²⁺ levels which are determined by the fluxing of Ca²⁺ across the plasma membrane and the membrane of elongate dense bodies which act as internal Ca²⁺ reservoirs.     

Optimization of a whole‐cell cadmium sensor with a toggle gene circuit

This work demonstrates improvement of a whole‐cell cadmium detection sensor through construction of a gene circuit. A cadmium (II) specific regulatory promoter, P_cadR, from Psuedomonas putida 06909, is used in the assembly of a toggle circuit. The circuit contains the cadR promoter fused to lacIq and gfp, and a divergently transcribed tac promoter and cadR. The toggle sensor exhibits lower background fluorescence, and a 20‐fold lower detection limit in comparison to a nontoggle gene circuit. The detection limit of the toggle sensor is 0.01 μM (1.12 ppb) cadmium chloride, and tunable with the addition of isopropyl‐b‐D ‐thiogalactopyranoside (IPTG). The toggle sensor is highly specific to cadmium (II), and no response is elicited from zinc, lead, manganese, nickel, copper, and mercury. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009