Comparative mapping of the DiGeorge syndrome region in mouse shows inconsistent gene order and differential degree of gene conservation

We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial (VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions (distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved; only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a mouse model for the 22q11 deletion with chromosome engineering technologies. Received: 8 July 1997 / Accepted 11 August 1997     

The variations of NPK of cowpea (Vigna unguiculata (L) Walp) leaves with tillage,plant maturity and flooding on a clay soil

Summary The NPK concentrations in cowpea leaves (cv California Blackeye No. 5) with stage of plant development did not vary significantly with tillage treatment but several features of the concentration of these different ions with age, stage of plant development, incidence of flooding and soil water content are significant.In the major rainy season when soil water content was adequate and seldom above field capacity, there was an almost linear increase in the concentration of N and P in the leaves up to 56 days after planting which coincided with fruit development. This suggested that the accumulation of N and P do take place after flowering which occurred 39 days after planting. The pattern of accumulation of N and P in the minor rainy season suggested that flooding and the occurrence of prolonged soil moisture contents above field capacity suppressed the accumulation of these two nutrients. Potassium accumulation was high in the early stages of cowpea growth and declined with age of the crop. Flooding and high soil moisture contents seem to have had little or no effect on potassium accumulation in the leaves. The pattern of accumulation of N and P suggests that the supply of these nutrients to the cowpea plant must remain high up to fruit development and that additional N and P would need to be added to the soil after a flooding event or when the soil moisture content is above field capacity for prolonged periods.     

Oxonol dyes as monitors of membrane potential. Their behavior in photosynthetic bacteria

The responses of oxonol dyes to single and multiple single turnovers of the photosynthetic apparatus of photosynthetic bacteria have been studied, and compared with the responses of the endogenous carotenoid pigments. The absorbance changes of the oxonols can be conveniently measured at 587 nm, because this is an isosbestic point in the ‘light-minus-dark’ difference spectrum of the chromatophores.The oxonols appear to respond to the light-induced ‘energization’ by shifting their absorption maxima. In the presence of K⁺, valinomycin abolished and nigericin enhanced such shifts, suggesting that the dyes respond to the light-induced membrane potential. Since the dyes are anions at neutral pH values, they probably distribute across the membrane in accordance with the potential, which is positive inside the chromatophores. The accumulation of dye, which is indicated by a decrease in the carotenoid bandshift, poises the dye-membrane equilibrium in favor of increased dye binding and this might be the cause of the spectral shift.The dye response has an apparent second-order rate constant of approx. 2 · 10⁶ M^?1 · s^?1 and so is always slower than the carotenoid bandshift. Thus the dyes cannot be used to monitor membrane potential on submillisecond timescales. Nevertheless, on a timescale of seconds the logarithm of the absorbance change at 587 nm is linear with respect to the membrane potential calibrated with the carotenoid bandshift. This suggests that under appropriate conditions the dyes can be used with confidence as indicators of membrane potential in energy-transducing membranes that do not posses intrinsic probes of potential.     

Effects of activated carbon and bacteriostatic filters on microbiological quality of drinking water

Three activated carbon filters for point-of-use water treatment were tested in laboratory and field studies for chemical removal and microbiological effects on water. All removed free available chlorine in municipally treated water to below the limit of detection, but removed only about 50 to 70% of the total available chlorine and 4 to 33% of the total organic carbon. Standard plate count bacteria in the effluent increased steadily with time for 3 weeks and remained elevated over the 8-week period of the study. Total coliform bacteria were found to persist and proliferate on the filters for several days after transient contamination of the influent water. Silver-containing activated carbon filters suppressed total coliform but not total bacterial growth. Pseudomonas aeruginosa was recovered from the effluents of all filters at some time during the tests.     

Determination of the strength of the cell walls of vegetative cells ofBacillus megaterium andBacillus stearothermophilus

The tensile strength of the cell walls ofBacillus megaterium andBacillus stearothermophilus was found to be about 2.4×10⁷ N/m². The internal pressure and water activity of the cells were 14 atm, 0.99 a_w forB. megaterium and 28 atm, 0.98 a_w forB. stearothermophilus. The greater strength ofB. stearothermophilus cells, considered as pressure vessels, restricts absorption of water by the protoplasm so that the water content on a dry weight basis is 3.4 g/g forB. megaterium cells in water but only 1.8 g/g forB. stearothermophilus.     

Social and emotional complications in a clinical trial among adolescents with diabetes mellitus.

Observations are reported on the social and emotional events occurring among children with diabetes mellitus and their families while taking part in a demanding clinical trial. Participants were selected on the basis of: (1) age over 10 years, (2) "informed consent," (3) cooperation with diabetic care, and (4) family stability. Despite endeavours to apply these criteria, it subsequently emerged that one father had doubts about his daughter participating; one family was suffering from severe marital discord; a girl (11 years) and a boy (10 years) were unexpectedly distressed by the venepunctures required; and another girl (13 years) was falsifying the results of her urine tests. All the families wished to complete the trial, and only one did not because of recurrent hypoglycaemia. The psychosocial problems encountered during the trial were unpredictable and occurred despite selection. Documentation of these problems allowed appropriate emotional support to be offered to the children and their families and provided for a fuller and more reliable interpretation of the trial results than would have been possible from the numerical data alone.     

Prevalence and isolation of Toxoplasma gondii from white-tailed deer in Alabama

Nineteen white-tailed deer (Odocoileus virginianus) from 5 counties in Alabama were examined for infection with Toxoplasma gondii. Twenty-gram samples of heart tissue were bioassayed in mice, serum was examined for T. gondii antibodies using the direct agglutination test, and sections of heart muscle were examined histologically for tissue cysts. Toxoplasma gondii was isolated from 4 of 19 (21%) white-tailed deer hearts. Antibody titers of greater than or equal to 1:50 were found in sera from 7 of 16 (44%) white-tailed deer. Histological examinations of tissue sections from white-tailed deer hearts were negative for T. gondii.     

Examination of tissue cyst formation by Toxoplasma gondii in cell cultures using bradyzoites, tachyzoites, and sporozoites

Tissue cyst formation by a goat isolate (GT-1) of Toxoplasma gondii was examined in bovine monocyte, human fetal lung, and Madin-Darby bovine kidney cell cultures. Transmission electron microscopy (TEM) and cat feeding studies indicated that tissue cysts were present in all 3 cell lines examined. Tissue cysts were first seen 3 days postinoculation (PI) using TEM. Standard cell culture procedures were used and no additional condition was needed to induce tissue cyst formation. Cats fed cell cultures excreted T. gondii oocysts in their feces 5-7 days PI. These oocysts caused lethal infections in mice. Tissue cysts were produced in cell cultures regardless if the initiating inoculum consisted of bradyzoites, sporozoites, or a mixture of bradyzoites and tachyzoites. Tissue cyst formation has been followed through 40 subpassages of infected cells. By TEM tissue cysts still were present after 40 passages, but when 40th-passaged cultures were fed to cats, oocytsts were not excreted. This indicates that the parasite had become oocystless after repeated passage in vitro.     

Measuring the microelastic properties of biological material.

We have used the atomic force microscope (AFM) to measure the local rigidity modulus at points on the surface of a section of hydrated cow tibia. These data are obtained either from contrast changes that occur as the contact force is altered, or from force versus distance curves obtained at fixed points. These two methods yield the same values for rigidity modulus (at a given point). At low resolution, the elastic morphology and topography mirror the features seen in optical and electron micrographs. At high resolution we see dramatic variations in elastic properties across distances as small as 50 nm.