The p53 isoforms are differentially modified by Mdm2

The discovery that the single p53 gene encodes several different p53 protein isoforms has initiated a flurry of research into the function and regulation of these novel p53 proteins. Full-length p53 protein level is primarily regulated by the E3-ligase Mdm2, which promotes p53 ubiquitination and degradation. Here, we report that all of the novel p53 isoforms are ubiquitinated and degraded to varying degrees in an Mdm2-dependent and -independent manner, and that high-risk human papillomavirus can degrade some but not all of the novel isoforms, demonstrating that full-length p53 and the p53 isoforms are differentially regulated. In addition, we provide the first evidence that Mdm2 promotes the NEDDylation of p53β. Altogether, our data indicates that Mdm2 can distinguish between the p53 isoforms and modify them differently.     

Teratogenic effect of D-amphetamine sulphate: histodifferentiation and electrocardiogram pattern of mouse embryonic heart

Pregnant albino mice (ICR random-bred strain) received daily injections of 50 or 100 mg/kg body weight of D-amphetamine sulphate between days 9 and 11 of gestation. Parallel control animals were injected with saline solution. Treated mice were sacrificed on day 15 or 19 of gestation. The embryos were examined for gross malformations and direct embryonic ECG recordings were made; they were weighed, and their hearts were carefully dissected. Microscopic sections of the heart were stained with hematoxylin and eosin. It was found that high doses of D-amphetamine raised the incidence of mortality in the treated pregnant mice up to 40%. The resorption rate in the survivors was high (up to 58%) following the high dose of the drug. Up to 15% of the embryos from the treated groups showed gross malformations, including skeletal and eye malformations and exencephaly. The electrocardiogram (ECG) recordings in most 19-day-old embryos from both treated groups showed a pattern with prolonged Q-T interval (PQT), similar to that of control embryos in the intermediate developmental stages (days 14-16 of gestation). The ECG of control embryos (from day 17 on) resembled that of prenatal fetuses. Microscopically, the hearts of treated embryos showed a large number of undifferentiated cardiac myoblasts. It can be inferred that high doses of D-amphetamine affect embryonic development generally and delay the histodifferentiation of the myocardium, resulting in incomplete maturation of the cardiac muscles, thus leading to the immature ECG pattern, with PQT intervals.     

Comparisons of eight commercial on-farm milk progesterone tests

To evaluate eight commercial on-farm milk progesterone kits, milk samples (50 ml each of foremilk and postmilk strippings) were collected during the estrous cycle from 10 cycling Holstein cows for 24 consecutive days. Relative concentrations of progesterone were classified as low or high by comparison with standard progesterone samples supplied with each kit. The concentration of progesterone in each milk sample was determined by radioimmunoassay (RIA). Accuracy of classification into low or high levels by commercial tests was determined by the percentage of similarity with RIA values using discriminant analysis. Accuracy of the eight tests ranged from 89.0 to 98.9% for low progesterone, 74.8 to 85.6% for high progesterone, and 80.3 to 87.3% for all samples (n = 238). The percentage of fat in milk or an interaction of the percentage of milkfat by day of estrous cycle influenced commercial test results for all tests except Accufirm and Calfcheck. Progesterone levels, estimated by the test-kits, were low from 1.5 +/- 0.5 to 2.8 +/- 0.9 days before estrus (X +/- SEM) and until 4.0 +/- 0.6 to 5.9 +/- 1.3 days after estrus. These data support the principle that a single low progesterone sample cannot be used to determine proper timing of insemination. All eight commercial kits can be used to determine accurately the relative concentrations of progesterone in milk samples.     

IL9 maps to mouse chromosome 13 and human chromosome 5

Mouse and human cDNA clones encoding the T-cell and mast cell growth factor P40, now designated IL-9, were used to identify DNA restriction fragment length polymorphisms (RFLPs) in sets of somatic cell hybrids and between inbred strains of mice and interspecific backcross progeny. Segregation of mouse and human chromosomes among somatic cell hybrids indicated a location on mouse chromosome 13 and human chromosome 5. RFLPs were identified among inbred strains of mice. Analysis of chromosome 13 alleles for Tcrg, Dhfr, and Il-9 in an interspecific cross between Mus musculus and NFS/N or C58/J mice indicates that IL-9 is distal to Tcrg and Proximal to Dhfr.     

The accuracy of enzyme-linked immunosorbent assay and latex agglutination progesterone test for the validation of estrus and early pregnancy diagnosis in dairy cattle

The accuracy of the enzyme-linked immunosorbent assay (ELISA) and the latex agglutination (LA) on-farm progesterone kit for detecting estrus and diagnosing early pregnancy was investigated in this study. Italian Friesian dairy cows (n=82) from 6 dairy herds were used for the collection of foremilk samples at the time of breeding and at 19, 21, and 23 days post insemination. Pregnancy status was ascertained by uterine palpation per rectum 40 to 60 days post insemination. Progesterone levels were affected by herd, percentage of milk fat, and the day of testing x diagnosis interaction. Validation of estrus by qualitative on-farm tests was 74.6% (LA) and 100.0% (ELISA) accurate using 0.5 ng/ml of progesterone as the RIA estimate for estrus. The accuracy rate for early pregnancy diagnosis by RIA was 68.4 to 83.8% for day 19 and day 21, respectively, while the detection rate for nonpregnancy was 84.6 to 100% on day 19 and day 21, respectively, as compared with uterine palpation per rectum. The average accuracy rate for early pregnancy diagnosis ranged from 84.7 to 92.3% for the LA and ELISA tests, respectively; the nonpregnancy rate was correctly predicted 93.9% to 68.2% for the LA and ELISA tests, respectively.     

Inferring landscape resistance to gene flow when genetic drift is spatially heterogeneous

In connectivity models, land cover types are assigned cost values characterizing their resistance to species movements. Landscape genetic methods infer these values from the relationship between genetic differentiation and cost distances. The spatial heterogeneity of population sizes, and consequently genetic drift, is rarely included in this inference although it influences genetic differentiation. Similarly, migration rates and population spatial distributions potentially influence this inference. Here, we assessed the reliability of cost value inference under several migration rates, population spatial patterns and degrees of population size heterogeneity. Additionally, we assessed whether considering intra-population variables, here using gravity models, improved the inference when drift is spatially heterogeneous. We simulated several gene flow intensities between populations with varying local sizes and spatial distributions. We then fit gravity models of genetic distances as a function of (i) the ‘true’ cost distances driving simulations or alternative cost distances, and (ii) intra-population variables (population sizes, patch areas). We determined the conditions making the identification of the ‘true’ costs possible and assessed the contribution of intra-population variables to this objective. Overall, the inference ranked cost scenarios reliably in terms of similarity with the ‘true’ scenario (cost distance Mantel correlations), but this ‘true’ scenario rarely provided the best model goodness of fit. Ranking inaccuracies and failures to identify the ‘true’ scenario were more pronounced when migration was very restricted (<4 dispersal events/generation), population sizes were most heterogeneous and some populations were spatially aggregated. In these situations, considering intra-population variables helps identify cost scenarios reliably, thereby improving cost value inference from genetic data.     

Response of citrus trees to modified radiation regime in semi-arid conditions

Citrus trees are characterized by a large canopy and low hydraulicconductivity. In Israel's semi-arid summer climate this couldcause transpiration to exceed water uptake and cause temporaryexcessive water deficits. It was hypothesized that reductionof radiative load would reduce transpiration and thus reducedeficits. Net radiation of lemon trees in the hottest season was reducedby shading hedgerows with reflective nets for approximatelyone month in both 1994 and 1995. Stem sap flow and climate variableswere measured continuously. Daily courses of leaf conductanceand leaf water potentials were measured on selected days. Midday net radiation below the dense and sparse shade net treatmentswas 47% and 73% of that above the control trees. Midday ‘sunlit’leaf temperatures below the nets were reduced by 2.7 and 1.6C,respectively. The reduction in net radiation caused large changes in leafconductance. Average midday sunlit leaf conductance measuredin 1995 under the dense and sparse treatments and control were4.1, 2.9 and 1.8mm s^–1, respectively (significantly differentat P <0.01). Similar differences in sunlit leaf conductancewere found in 1994. Shade leaf conductance was not affectedby the treatments. Daily total and midday sap flow under the dense net were reducedby 6–7% and 10–11%, respectively. Sap flow underthe sparse net did not change significantly in 1994, but in1995 daily and midday sap flows were reduced by 6% and 7%, respectively.Midday leaf water potentials increased by 0.2 and 0.1 MPa underdense shade in 1994 and 1995, respectively. Under sparse shademidday leaf water potentials increased by 0.1 MPa in 1994, butdid not change significantly in 1995. A modified Penman-Monteith model evaluated transpiration ifleaf conductance were constant in the different radiation environments.At leaf conductance levels found in the unshaded trees, denseshade was estimated to cause a 25% reduction in transpiration,while leaf conductance values found in trees under the denseshade would lead to an increase in transpiration of more than35% in unshaded trees. The ability of the tree to maintain almost constant transpirationin different radiation environments and thus avoid water deficitby adjusting the conductance of sunlit leaves is discussed interms of environmental influences and significance to the plant'swater balance. Key words: Tree transpiration, stomatal closure, climate modification, citrus     

Evaluation of an on-farm blood progesterone test for predicting the day of parturition in cattle

An on-farm blood progesterone enzymeimmunoassay (EIA) was evaluated as a diagnostic test to predict the time of calving within a 24-hour period in near-term dairy cows. Blood samples were taken daily from 45 cows beginning 5 days prior to their expected due dates until calving, and plasma was stored at -20 degrees C until all cows had calved. The EIA test was performed on frozen-thawed plasma samples, and progesterone concentrations were determined to be low (positive test for calving within 24 hours) or high (negative test for calving within 24 hours). Sensitivity, specificity and predictive value of the EIA to accurately determine parturition within 24 hours were 86.7, 90.8 and 75.0%, respectively. The EIA correctly predicted the day of parturition in 168 of 187 (89.8%) plasma samples. Ten additional cows were similarly monitored except the EIA was performed on whole blood immediately after collection, and the sensitivity, specificity and predictive value of the test were 80.0, 97.6 and 88.9%, respectively. The day of parturition was correctly predicted in 49 of 52 (94.2%) whole blood samples. More than 95% of the cows calved within 24 hours when their plasma progesterone reached < 1.3 ng/ml. When results of the EIA were compared with those of a radioimmunoassay (RIA), the EIA findings were used to correctly classify 190 of 232 (81.9%) plasma samples as having low (< 2.0 ng/ml) or high (>/= 2.0 ng/ml) concentrations of progesterone. The EIA test was found to be a quick, practical means of estimating progesterone concentrations in bovine plasma or whole blood and was a useful test for predicting the day of parturition in cows.