A comparison of topoisomerase I activity in normal and transformed cells

Many viral oncogenes encode protein~yrosine kinase activities. However, importantin vivo substrates of these enzymes have yet to be identified. Recently, type I topoisomerases were shown to bein vitro substrates for two tyrosine kinases. Following tyrosine phosphorylation, topoisomerase I activity was reduced 10-fold (Tse-Dinhet al. Nature 312:785–786, 1984). To determine whether topoisomerase I activity was modulated by tyrosine phosphorylationin vivo, we have measured topoisomerase I activity in nuclear lysates prepared from both normal fibroblasts and cells transformed by two different viral oncogenes (v-abl, v-src). Under a variety of experimental conditions, we have found no evidence to support the notion that type I topoisomerase activity is modulated by tyrosine phosphorylationin vivo.     

Use of progesterone 11-glucuronide-alkaline phosphatase conjugate in a sensitive microtitre-plate enzymeimmunoassay of progesterone in milk and its application to pregnancy testing in dairy cattle

A simple direct-addition microtitre plate enzymeimmunoassay (EIA) for progesterone in whole milk is described. The assay used antiserum raised against 11 alpha-hydroxyprogesterone 11-hemisuccinate (progesterone 11-hemisuccinate) and a heterologous label prepared by conjugation of 11 alpha-hydroxyprogesterone 11-glucuronide (progesterone 11-glucuronide) with alkaline phosphatase using an active ester procedure. The sensitivity, analytical recovery, linearity of response and precision of the assay compared favourably with radioimmunoassay (RIA). Results from EIA of milk samples were compared with determinations made after isolation of progesterone by HPLC (r = 0.910). Milk samples (200) were assayed by RIA at both the Milk Marketing Board and the Cattle Breeding Centre and the results were correlated with EIA performed at the Cattle Breeding Centre (r = 0.890 and r = 0.833 respectively). Calving data were obtained from a further 110 cows for which the milk progesterone EIA had provided a pregnancy test 24 days after AI; 46 cows were correctly identified as non-pregnant and 58 as pregnant and there were 4 false positive and 2 inconclusive results.     

TRANSPORT OF 14C INCORPORATED PROTEIN IN THE CORTICOSPINAL TRACT OF THE RAT BRAIN

Abstract— The origin of fibres of a corticospinal pathway in rat brain was located by cortical ablation and Marchi staining and also by electrical stimulation of the motor cortex.
Enzyme changes investigated histochemically over 0–14 days post-injection of 5 μ10.15 m NaCl into the neocortex indicated that very little apparent disturbance of nerve cell metabolism beyond a narrow band adjacent to the path of the microneedle within the cortex had occurred. [¹⁴ C]Leucine as a precursor of protein synthesis was used to study incorporation of the amino acid into protein. At the site of injection the maximum level of labelled protein was recorded at 30 min post-injection, the level decreasing to less than 2 per cent of this at 6 hr.
The subsequent axonal flow of labelled protein along the corticospinal pathway was investigated during the period 15 min to 21 days post-injection. Within 24 hr increasing amounts of labelled proteins were measured caudally, but not more than 6 per cent had migrated beyond 5 mm from the site of injection. At 3 days this percentage had increased to 14.6 per cent, the labelled proteins being distributed in progressively decreasing amounts to a further 13 mm caudal. Very little change from this position was seen during the following 18 days.     

Familial nontoxic multinodular thyroid goiter locus maps to chromosome 14q but does not account for familial nonmedullary thyroid cancer.

Thyroid goiter is a common condition that is often associated with iodine deficiency. Familial forms of goiter in areas not known to feature iodine deficiency are much less common. We have performed a genomic search on a single large Canadian family with 18 cases of nontoxic multinodular goiter in which 2 individuals also had papillary lesions highly suggestive of papillary carcinoma. A locus on chromosome 14q (MNG1 [multinodular goiter 1]) has been identified, with a maximal two-point LOD score of 3.8 at D14S1030 and a multipoint LOD score of 4.88 at the same marker, defined by D14S1062 (upper boundary) and D14S267 (lower boundary). The gene encoding thyroid-stimulating hormone receptor (TSHR), which is located on chromosome 14q, is outside the linked region. To determine the role of this gene in familial nonmedullary thyroid cancer (NMTC), we studied 37 smaller pedigrees each containing at least two cases of NMTC. Analysis by both parametric and nonparametric methods indicates that only a very small proportion of familial NMTC (point estimate 0.001, support intervals 0-.6 under a dominant model) is attributable to MNG1.     

Intestinal cadmium permeability in mature and immature rats

To compare the intrinsic permeability properties of the small intestine in adult (average body wt 300 g) and 25- to 27-day-old (average body wt 50 g) male rats, the uptake rates of cycloleucine and of cadmium were measured in intestinal segments isolated in situ with their blood supply intact. Uptake rates were expressed on the basis of that of ethanol, a solute whose absorption depends primarily on the size, rather than the composition, of the available surface area and on the presence of unstirred layers. These layers may be concluded to affect movement of cycloleucine, cadmium, and ethanol to the same extent. The ratio of uptake rates, therefore, provides in arbitrary units a measure of the intrinsic permeability of the luminal surface area to cadmium and to cycloleucine. On this basis, no developmental change in cycloleucine permeability could be detected. In contrast, the rate of cadmium uptake relative to that for ethanol decreased with age by about 50%. Possible mechanisms are discussed for this significant change in the intrinsic cadmium permeability of the jejunum in post-"closure" animals.     

The CDKN2A (p16) gene and human cancer.

CDKN2A, the gene encoding the cell-cycle inhibitor p16CDKN2A, was first identified in 1994. Since then, somatic mutations have been observed in many cancers and germline alterations have been found in kindreds with familial atypical multiple mole/melanoma (FAMMM), also known as atypical mole syndrome. In this review we tabulate the known mutations in this gene and discuss specific aspects, particularly with respect to germline mutations and cancer predisposition.     

Modelling cereal root systems for water and nitrogen capture: towards an economic optimum

A quantitative model of wheat root systems is developed that links the size and distribution of the root system to the capture of water and nitrogen (which are assumed to be evenly distributed with depth) during grain filling, and allows estimates of the economic consequences of this capture to be assessed. A particular feature of the model is its use of summarizing concepts, and reliance on only the minimum number of parameters (each with a clear biological meaning). The model is then used to provide an economic sensitivity analysis of possible target characteristics for manipulating root systems. These characteristics were: root distribution with depth, proportional dry matter partitioning to roots, resource capture coefficients, shoot dry weight at anthesis, specific root weight and water use efficiency. From the current estimates of parameters it is concluded that a larger investment by the crop in fine roots at depth in the soil, and less proliferation of roots in surface layers, would improve yields by accessing extra resources. The economic return on investment in roots for water capture was twice that of the same amount invested for nitrogen capture.     

Haplotype analysis of BRCA2 8765delAG mutation carriers in French Canadian and Yemenite Jewish hereditary breast cancer families

The BRCA2 8765delAG mutation was previously reported in hereditary breast cancer families of French Canadian and Yemenite Jewish descent. Haplotype analysis, using six microsatellite markers that span BRCA2 and two intragenic polymorphisms, was performed on 8765delAG mutation carriers to determine if there was evidence that the mutations were identical by descent. The alleles of the microsatellite markers most closely flanking BRCA2 (D13S1697 and D13S1701) were found to be identical in state in all the mutation carriers. However, the disease-associated allele of one of the intragenic markers differed between the Yemenite Jews and French Canadian families, indicating that the 8765delAG mutation has independent origins in these two geographically and ethnically distinct populations.     

Identifying wheat genomic regions for improving grain protein concentration independently of grain yield using multiple inter-related populations

Grain yield (GY) and grain protein concentration (GPC) are two major traits contributing to the economic value of the wheat crop. These are, consequently, major targets in wheat breeding programs, but their simultaneous improvement is hampered by the negative correlation between GPC and GY. Identifying the genetic determinants of GPC and GY through quantitative trait loci (QTL) analysis would be one way to identify chromosomal regions, allowing improvement of GPC without reducing GY using marker-assisted selection. Therefore, QTL detection was carried out for GY and GPC using three inter-connected doubled haploid populations grown in a large multi-environment trial network. Chromosomes 2A, 2D, 3B, 7B and 7D showed co-location of QTL for GPC and GY with antagonistic effects, thus contributing to the negative GPC–GY relationship. Nonetheless, genomic regions determining GPC independently of GY across experiments were found on chromosomes 3A and 5D and could help breeders to move the GPC–GY relationship in a desirable direction.