Utilization of 5-fluorouracil byMyobacterium avium

Myobacterium avium LM1 was exposed to concentrations of 5-fluorouracil (5FU) that ranged from 0 to 100 g/ml. Growth inhibition was inversely proportional to the concentration of the drug. DNA was extracted from cells grown in medium that contained [¹⁴C]5FU, but no carrier. The [¹⁴C]DNA was enzymatically hydrolyzed to deoxyribonucleotides, which were separated and fractionated by high-performance liquid chromatography (HPLC). The isotope was located in 2-deoxycytidine 5-monophosphate (dCMP) and 2-deoxythymidine 5-monophosphate (dTMP), with dCMP containing the majority. There was no radioactivity at the elution times for 5-fluoro-2-deoxyuridine 5-monophosphate or 2-deoxyuridine 5-monophosphate. These results suggested that 5FU was dehalogenated and the uracil moiety ultimately converted into cytosine and thymine deoxyribonucleotides. Cells were grown in [³H]uracil, and [³H]DNA was extracted and analyzed by HPLC. The isotope was found only in the pyrimidine deoxyribonucleotides, with dCMP containing 4.1 times that in dTMP. Thus, it was demonstrated that uracil and dehalogenated 5FU were not directly incorporated into DNA, but rather converted to cytosine and thymine and then incorporated into DNA by a salvage pathway.     

Biochemical pathways in prokaryotes can be traced backward through evolutionary time

For the first time, a credible prokaryotic phylogenetic tree is being assembled by Woese and others using quantitative sequence analysis of oligonucleotides in the highly conservative rRNA. This provides an evolutionary scale against which the evolutionary steps that led to the arrangement and regulation of contemporary biochemical pathways can be measured. This paper presents an emerging evolutionary picture of aromatic amino acid biosynthesis within a large superfamily assemblage of prokaryotes that is sufficiently developed to illustrate a new perspective that will be applicable to many other biochemical pathways.      

Three-dimensional structure of clathrin cages in ice.

We have collected tilt series of electron micrographs from unstained clathrin cages embedded in vitreous ice. From these micrographs we have generated three-dimensional reconstructions of individual hexagonal barrels, which show details of the internal structure. Four types of preparation have been examined: (i) coated vesicles; (ii) cages reassembled from clathrin heavy and light chains; (iii) reassembled cages treated with elastase to remove the light chains; and (iv) reassembled cages treated with trypsin to remove the light chains and the terminal domains of the clathrin heavy chains. In the intact and elastase-treated cages, the clathrin extends from the vertices into the interior of the polyhedron and forms an inner shell of material. Limited digestion with trypsin removes the inner shell, which indicates that this material corresponds to the terminal domains of the clathrin heavy chains.     

Location of the 100 kd-50 kd accessory proteins in clathrin coats.

We present a three-dimensional map of the clathrin coat of coated vesicles, generated from tilt series of electron micrographs of unstained specimens embedded in vitreous ice. We have examined native placental coated vesicles and coats reassembled from their purified constituents, namely clathrin triskelions and accessory proteins of approximate mol. wts 100 kd and 50 kd. Our results show that the accessory proteins contribute a further shell of density within the double shell of the clathrin cage, extending from the terminal domains of the clathrin to the membrane of the vesicle. The thickness of the complete coat is approximately 22 nm.     

Combination Chemotherapy using L-Asparaginase,Daunorubicin, and Cytosine Arabinoside in Adults with Acute Myelogenous Leukaemia

Cytosine arabinoside and daunorubicin used in an intensive intermittent regimen have been shown to be an effective combination for the induction of complete remissions in 14 out of 23 adult patients with acute myelogenous leukaemia. This gives an overall complete remission rate of 60%. A further patient had a good partial remission. The addition of L-asparaginase to the regimen has not increased the incidence of remission and there were more side effects in the L-asparaginasetreated group. Of the 10 patients treated with L-asparaginase in addition to cytosine arabinoside and daunorubicin, five achieved a complete remission. Of the 13 patients treated with cytosine arabinoside and daunorubicin without L-asparaginase, nine achieved a complete remission and one a good partial remission.     

Soils in warmer and less developed countries have less micronutrients globally

Soil micronutrients are capital for the delivery of ecosystem functioning and food provision worldwide. Yet, despite their importance, the global biogeography and ecological drivers of soil micronutrients remain virtually unknown, limiting our capacity to anticipate abrupt unexpected changes in soil micronutrients in the face of climate change. Here, we analyzed >1300 topsoil samples to examine the global distribution of six metallic micronutrients (Cu, Fe, Mn, Zn, Co and Ni) across all continents, climates and vegetation types. We found that warmer arid and tropical ecosystems, present in the least developed countries, sustain the lowest contents of multiple soil micronutrients. We further provide evidence that temperature increases may potentially result in abrupt and simultaneous reductions in the content of multiple soil micronutrients when a temperature threshold of 12–14°C is crossed, which may be occurring on 3% of the planet over the next century. Altogether, our findings provide fundamental understanding of the global distribution of soil micronutrients, with direct implications for the maintenance of ecosystem functioning, rangeland management and food production in the warmest and poorest regions of the planet.     

Using ecological networks to answer questions in global biogeography and ecology

Ecological networks have classically been studied at site and landscape scales, yet recent efforts have been made to collate these data into global repositories. This offers an opportunity to integrate and upscale knowledge about ecological interactions from local to global scales to gain enhanced insights from the mechanistic information provided by these data. By drawing on existing research investigating patterns in ecological interactions at continental to global scales, we show how data on ecological networks, collected at appropriate scales, can be used to generate an improved understanding of many aspects of ecology and biogeography—for example, species distribution modelling, restoration ecology and conservation. We argue that by understanding the patterns in the structure and function of ecological networks across scales, it is possible to enhance our understanding of the natural world.     

Commentary: assessing the effects of environmental pollution when people know that they have been exposed.

OBJECTIVE: To examine the effectiveness of routine clinic review in detecting relapse after treatment for Hodgkin''s disease. DESIGN: Review of hospital records. SETTING: Regional centre for cancer treatment and research. SUBJECTS: 210 patients with Hodgkin''s disease recruited to a chemotherapy trial protocol between 1984 and the end of 1990 who had achieved a complete or partial remission after treatment. MAIN OUTCOME MEASURES: The number of clinic visits made by patients over the period of observation, the number of relapses occurring during that time, and the route by which relapse was detected. RESULTS: The 210 patients generated 2512 outpatient reviews, and 37 relapses were detected. Thirty relapses (81%) were diagnosed in patients who described symptoms, which in 15 cases had resulted in an earlier appointment being arranged. In only four cases (11%; 95% confidence interval 4% to 25%) was relapse detected as a result of routine physical examination on investigation of a patient who did not have symptoms. CONCLUSIONS: Relapse of Hodgkin''s disease after treatment is usually detected as a result of the investigation of symptoms rather than by routine screening of asymptomatic patients. It is therefore proposed that the frequency of routine follow up visits should be reduced and greater emphasis placed on patient education. This should underline the importance of symptoms and encourage patients to arrange an earlier appointment if these develop.     

MVPP chemotherapy regimen for advanced Hodgkin's disease

During January 1968 to December 1972, 133 patients with advanced Hodgkin''s disease (HD) were admitted to hospital for combination chemotherapy with mustine, vinblastine, procarbazine, and prednisolone (MVPP regimen). Remission rates were 76% among 49 untreated patients and 90% among 42 patients who had relapsed after radiotherapy. The corresponding five-year survival rates were 65% and 86% respectively. Provided the observed yearly mortality (6%) remains unchanged 75% of patients who had previously received no treatment or irradiation and achieved remission are expected to continue in first remission after five years. Forty-two patients had received prior chemotherapy. They had lower remission and five-year survival rates (40% and 33% respectively), and fewer than half of those achieving remission were still in first remission after five years. There were several reasons for the poor prognosis in this group, including advanced-stage disease (stage IVB), age over 40, and achievement of remission.Chemotherapy was administered on an outpatient basis. Haematological toxicity and immediate drug-related side effects were similar to those of other regimens but there was no appreciable neurotoxicity. Most deaths were due to either HD itself or complications of advanced disease. Five malignancies other than HD occurred in patients who had received both single-agent chemotherapy and radiotherapy before MVPP chemotherapy. Two patients developed osteonecrosis of the femoral heads.Combination chemotherapy has a profound effect on the prognosis of advanced HD. The MVPP regimen yields results comparable to those of other regimens but with perhaps less toxicity.