Comparison of genetic behaviour of the transposable element Tam3 at two unlinked pigment loci in Antirrhinum majus

Summary In Antirrhinum majus the transposable element Tam3 has been described at two unlinked loci pallida and nivea, both of which are required for the production of anthocyanin pigment in flowers. In each case the element is inserted in the promoter region and gives a variegated phenotype. We show that the rate of Tam3 excision at both loci is greatly affected by temperature, being approximately 1000-fold higher at 15°C compared with 25°C. Tam3 is also controlled by an unlinked gene Stabiliser, which considerably reduces excision rate. We show that the high degree of sensitivity to temperature and Stabiliser is an intrinsic property of Tam3 which is not shared by an unrelated element, Tam1. The Tam3 insertion at nivea gives rise to a series of alleles which confer reduced pigmentation, novel spatial patterns and changed instability. These are probably a result of imprecise excision and rearrangements of the Tam3 element.     

High chromosomal sensitivity of Chinese hamster xrs 5 cells to restriction endonuclease induced DNA double-strand breaks

The cytogenetic effects of restriction endonucleases (RE) and X-rays were examined in the radiosensitive mutant Chinese hamster cell line xrs 5 and its normal parental line CHO K1. Cells were permeabilized with Sendai virus and exposed to Pvu II and Eco RV which induce blunt-ended double-strand breaks (dsb) in the DNA of cells, or Bam H1 and Eco R1 which induce cohesive-ended dsb with a four-base overlap. Treated cells were then assayed for the presence of metaphase chromosomal aberrations by sampling at multiple fixation times and in experiments where cells were exposed to graded series of RE concentrations. Exposure to X-rays or RE causing blunt-ended dsb was found to be between two and three times more effective in xrs 5 than in CHO K1 cells. We interpret this higher chromosomal sensitivity of xrs 5 cells as reflecting the reported defect in dsb repair in xrs 5. Both xrs 5 and CHO K1 cells yielded less aberrations after exposure to Bam H1 or Eco R1 than after exposure to Pvu II or Eco RV, confirming our previous results and demonstrating that cohesive-ended dsb are less damaging than blunt-ended dsb. Multiple fixation time experiments showed that the higher sensitivity of xrs 5 was evident at several different sampling times after treatment. Similarly the low yield of aberrations after exposure of cells to Bam H1 was evident at all sampling times. Overdispersion of chromosomal aberrations was observed in samples exposed to RE. This is thought to be due to a non-uniform permeabilization of the cell population to RE. Our results indicate that RE-induced dsb are handled by cells in a similar way to those arising during X-ray exposure.     

Survey of general practitioners' attitudes to AIDS in the North West Thames and East Anglian regions

As the numbers of people suffering from human immunodeficiency virus infection and the acquired immune deficiency syndrome (AIDS) increase, so will the contribution to care required from general practice. A postal questionnaire survey was therefore carried out among general practitioners in the North West Thames and East Anglian regions to determine their attitudes to AIDS and the issues it raises for them. One hundred and thirty seven questionnaires were returned (response rate 57%) and four factors underlying the doctors'' attitudes identified; these concerned disease control, general practitioner care, patient support, and perception of seriousness. There were wide divergencies of attitude among the general practitioners, younger doctors being more in line with specialist thinking on AIDS than older colleagues, and evidence of important gaps between policies advocated by AIDS specialists and bodies of opinion in general practice.Attitudes to AIDS in general practice may partly be a function of personal experience; further study is required.     

Isotopic differences in the lithium transport rate in human erythrocytes during simultaneous incubations with the stable isotopes 6Li and 7Li.

The membrane transport of the two stable lithium isotopes, 6Li and 7Li, by erythrocytes has been studied using a dual channel atomic absorption spectroscopic technique. 6Li appears to be taken up preferentially to 7Li, in the ratio of 10 to 40%, depending on the concentration of total lithium and on the lithium isotopic ratio in the external medium.     

Combination biotherapy utilizing interleukin-2 and alpha interferon in patients with advanced cancer: a National Biotherapy Study Group Trial.

The National Biotherapy Study Group (NBSG) conducted a broad phase II trial using interleukin-2 (IL-2) by continuous infusion and alpha interferon (IFN) subcutaneously in 267 patients with a variety of advanced cancers, including 29 with breast cancer, 89 with renal cancer, and 69 with melanoma. IL-2 [18 million international units (MIU)/m2] was given by continuous infusion for 108 hours with 3 mu/m2 subcutaneous IFN every other day during the IL-2 infusion. The patients were treated for 1 week followed by a 2-week rest. After two cycles of treatment, patients were evaluated for response. Of the 237 patients evaluable for response, 20 (8%) had a complete or partial response and 128 (54%) were stable. Therefore, 62% of the evaluable patients were nonprogressive during the first 90 days of IL-2/IFN therapy. The objective response rate was 11% in melanoma, 7% in renal cancer, 14% in breast cancer, and 3% in patients with a variety of malignancies for an overall response rate of 7% in these patients with advanced cancer. The patients were treated on a general medical ward and tolerated treatment well with fatigue and fever being nearly universal. Dyspnea, pruritus, chills, and elevated creatinines were frequent but less common. This combination biotherapy regimen has minimal activity in a variety of advanced cancers and must be compared with the best existing chemotherapy for each cancer type in randomized, prospective trials.     

Genetic Analysis of a Mouse t Complex Locus That Is Homologous to a Kidney Cdna Clone

A mouse kidney cDNA clone, pMK174, identifies restriction fragment length polymorphisms (RFLPs) that map to two unlinked loci. One, designated D17Rp17, has been mapped near quaking, (qk), on chromosome 17 using three sets of recombinant inbred (RI) strains. A study of several t haplotypes resulted in the identification of t-specific alleles of D17Rp17 that map to the proximal half of the t complex. Neither t-specific nor wild-type D17Rp17 alleles are present in chromosomes carrying either the T Orleans (TtOrl) or the T hairpin tail (Thp) deletions. Comparison with other molecular markers indicates that pMK174 identifies a new proximal t complex locus, Rp17. The second locus identified by pMK174, termed D4Rp18, is tentatively assigned to chromosome 4 by mouse-Chinese hamster somatic cell hybrid analysis.     

A preliminary study of aquatic insect communities and leaf decomposition in acid streams near Dorset,Ontario

Some streams near Dorset in south-central Ontario suffer from acid precipitation via run-off and seepage from thin soils with little buffering capacity. A spring-summer survey of eight headwater streams revealed some characteristics of their insect communities which could be correlated with pH. The streams could be divided into three groups according to pH and community structure. In the most acid group (annual pH range 4.3–4.8), Ephemeroptera were absent from two streams although mature Leptophlebia were collected just after spring thaw from the most acid one (pH 4.3–4.5). One of these three streams also lacked Plecoptera but the others had two or three genera, all shredders. The second group of three streams (pH 5.0–6.3), with one exception, did support Ephemeroptera (3–4 genera) and Plecoptera (1–4 genera), most of the latter being shredders. In all six of these acid streams, Trichoptera were more diverse and more dense than Ephemeroptera and Plecoptera; again, shredders were clearly dominant, especially the limnephilid caddisfly, Frenesia difficilis (Walker). These six streams also had similar chironomid communities (densities were an order of magnitude higher than other insects). Dominance by Chironomini and abundant Tanypodinae typified the most acid streams. In contrast, the two streams in the third group (pH 5.3–6.7) had richer and more balanced communities in general with relatively fewer shredders (no Frenesia), more collectors, and fewer Chironomini and Tanypodinae. As a field experiment showed that autumn-shed leaves decomposed more slowly in acid than in non-acid streams, summer-growing shredders may benefit from the pulse of acidity at snowmelt.