A study of the structure-activity relationship for diazaborine inhibition of Escherichia coli enoyl-ACP reductase.

Enoyl acyl carrier protein (ACP) reductase catalyses the last reductive step of fatty acid biosynthesis, reducing the enoyl group of a growing fatty acid chain attached to ACP to its acyl product using NAD(P)H as the cofactor. This enzyme is the target for the diazaborine class of antibacterial agents, the biocide triclosan, and one of the targets for the front-line anti-tuberculosis drug isoniazid. The structures of complexes of Escherichia coli enoyl-ACP reductase (ENR) from crystals grown in the presence of NAD+ and a family of diazaborine compounds have been determined. Analysis of the structures has revealed that a mobile loop in the structure of the binary complex with NAD+ becomes ordered on binding diazaborine/NAD+ but displays a different conformation in the two subunits of the asymmetric unit. The work presented here reveals how, for one of the ordered conformations adopted by the mobile loop, the mode of diazaborine binding correlates well with the activity profiles of the diazaborine family. Additionally, diazaborine binding provides insights into the pocket on the enzyme surface occupied by the growing fatty acid chain.

Photosynthetic adaptation of Solanum dulcamara L. to sun and shade Environments : IV. A comparison of North American and European genotypes.

Clonal replicates of six genotypes of Solanum dulcamara L. grown in eight different environments were compared for photosynthesis and growth. Four of the genotypes were native to shaded habitats, two to sun habitats. The experimental growth environments differed in light level, daily temperature amplitude and substrate moisture availability. Treatments elicited large differences in lightsaturated photosynthetic rates and growth. Genotypic differences in response to the treatments were identified. However, when genotypes native to sun and shade habitats were compared, there were no consistent differences in photosynthesis or total plant dry weight. It was concluded that previously reported differences in the photosynthetic response of genotypes native to sun and shade habitats to treatment light level may have been the result of the persistent after-effects to changes in leaf water potential and not an adaptive response to growth light level.

Photosynthetic adaptation ofSolanum dulcamara L. to sun and shade environments. III. Characterization of genotypes with differing photosynthetic performance.

Clone mal9, a genotype ofSolanum dulcamara L. having photosynthetic characteristics similar to previously hypothesized shade ecotypes, is compared to five other genotypes having photosynthetic characteristics similar to previously hypothesized sun ecotypes. The primary differences are a 35% reduction in total leaf conductance and a 15% reduction in leaf chlorophyll content in mal9. Both factors contribute to a 44% reduction in lightsaturated photosynthetic rate in mal9. In relation to the 5 other genotypes, mal9 appears to be poorly adapted for growth in the normal range of natural habitats.

Photosynthetic adaptation of Solanum dulcamara L. to sun and shade environments : I. A Comparison of Sun and Shade Populations.

The photosynthetic response properties of individuals of Solanum dulcamara L. collected from sun and shade habitats were compared in controlled environments. Light-saturated photosynthetic rates and seven additional parameters associated with photosynthetic and growth performance were measured over a range of 12 environmental conditions that simulated natural habitat differences in light intensity, moisture availability and daily temperature amplitude. In contrast to previous studies, the results suggest there is no ecotypic differentiation with respect to the sun and shade environments from which the individuals were collected. It appears that all but one of the field-collected individuals are capable of successfully inhabiting the full range of light environments from which the species was collected.

Radioimmunoassay of vinblastine and vincristine.

1 The cytotoxic agent, vinblastine, was conjugated to albumin, using the Mannich reaction. Rabbits immunized with two conjugates, containing differing amounts of hapten, produce antibodies which bound [3H]-vinblastine. 2 Antisera from one rabbit cross-reacted with both vinblastine and vincristine and were used to develop radioimmunoassays for measuring their concentration in plasma. 3 The antisera showed no cross-reactivity with other alkaloids or cytotoxic drugs and provided assays sensitive to a concentration of 2.1 ng vinblastine or 3.8 ng vincristine/ml of plasma added direct to the assay tubes. 4 This is sufficiently sensitive to permit the measurement of plasma vinblastine levels for up to 24 h after the intravenous administration of 15 mg of the drug.

Radioimmunoassay of bleomycin in plasma and urine.

Antibodies to bleomycin were raised by immunization of sheep and rabbits with bleomycin-albumin conjugates. The combination of a high-titre, high-avidity sheep antiserum and iodinated bleomycin produced a radioimmunoassay sensitive to 8 ng of bleomycin per ml of plasma or urine. Untreated specimens (100 microliter) of plasma or urine could be added directly to the assay tubes. The antiseerum was specific for bleomycin and showed no cross-reaction with other anticancer agents used in combination chemotherapy. Over a concentration range of 20-100 ng/ml, recovery of bleomycin from plasma was 110% and from urine, 93%. Repeated assay of plasma samples showed a decrease in bleomycin levels unless the samples were kept at 4 degrees C or below. Assay of bleomycin levels in plasma and urine from patients under treatment with bleomycin showed similarities with results reported using a microbiological assay. The radioimmunoassay offers a more reliable, rapid and sensitive method for the measurement of bleomycin.

Photosynthetic Adaptation of Solanum dulcamara L. to Sun and Shade Environments: II. Physiological Characterization of Phenotypic Response to Environment.

Photosynthetic and growth properties of Solanum dulcamara L. were studied under controlled environments. The 200 experimentally tested plants were clonal replicates of five field-collected individuals, three from fully exposed habitats and two from deeply shaded habitats. After 4 weeks of growth in one of eight environmental treatments, each plant was measured for leaf adaxial and abaxial conductance to water vapor, specific leaf weight, chlorophyll per square decimeter of leaf, photosynthetic unit size, light-saturated photosynthetic rate, total leaf area, and total leaf, stem, and root dry weights. Changes in light level influenced photosynthesis and growth of each plant more than changes in water availability or temperature. It is strongly suggested that the primary adaptive response of the tested individuals to changes in levels of light involves the regulation of leaf thickness.

Effects of High Atmospheric CO(2) and Sink Size on Rates of Photosynthesis of a Soybean Cultivar.

The effect of sink strength on photosynthetic rates under conditions of long-term exposure to high CO(2) has been investigated in soybean. Soybean plants (Merr. cv. Fiskeby V) were grown in growth chambers containing 350 microliters CO(2) per liter air until pod set. At that time, plants were trimmed to three trifoliolate leaves and either 21 pods (high sink treatment) or 6 pods (low sink treatment). Trimmed plants were either left in 350 microliters CO(2) per liter of air or placed in 1000 microliters CO(2) per liter of air (high CO(2) treatment) until pod maturity. Whole plant net photosynthetic rates of all plants were measured twice weekly, both at 350 microliters CO(2) per liter of air and 1000 microliters CO(2) per liter of air. Plants were also harvested at this time for dry weight measurements. Photosynthetic rates of high sink plants at both measurement CO(2) concentrations were consistently higher than those of low sink plants, and those of plants given the 350 microliter CO(2) per liter of air treatment were higher at both measurement CO(2) concentrations than those of plants given the 1000 microliters CO(2) per liter of air treatment. When plants were measured under treatment CO(2) levels, however, rates were higher in 1,000 microliter plants than 350 microliter CO(2) plants. Dry weights of all plant parts were higher in the 1,000 microliters CO(2) per liter air treatment than in the 350 microliters CO(2) per liter air treatment, and were higher in the low sink than in the high sink treatments.

Comparative study of pinning in situ and open epiphysiodesis in 105 patients with slipped capital femoral epiphyses.

One hundred five patients were treated for slipped capital femoral epiphyses during the period from 1964 to 1976. Attempts were made to evaluate the differences in results of multiple pinning and open epiphysiodesis performed to treat this problem. Pinning in situ was performed in 61 hips, and open epiphysiodesis was performed in 33 hips. The average follow-up period was seven years four months for pinning in situ and six years seven months for open epiphysiodesis. The average slippage was 22 degrees for patients treated by pinning in situ and 30 degrees for patients treated by open epiphysiodesis. At follow-up evaluation 91.7% of the patients treated by pinning in situ had good or excellent results, as compared with 71.6% of the patients treated by epiphysiodesis. For the patients treated by pinning in situ, 5% had poor results, and 3.3% were considered failures. For the patients treated by epiphysiodesis, 3.4% had poor results, while 25% were considered failures. Pinning in situ is the treatment of choice. It is more predictable, has less complications, and provides better long-term results.

Plasma cannabinoids measured by radioimmunoassay in rabbits after intravenous injection of tetrahydrocannibinol, 11-hydroxy-tetrahydrocannabinol, cannabinol and cannabidiol.

An antiserum raised in sheep against a conjugate of tetrahydrocannabinol with bovine serum albumin has been used as the basis of a radioimmunoassay for cannabinoids in the blood of rabbits given tetrahydrocannabinol, 11-hydroxy-tetrahydrocannabinol, cannabinol or cannabidiol by rapid intravenous injection. In the case of both 11-hydroxy-tetrahydrocannabinol and cannabinol plasma cannabinoid concentrations fell exponentially from an initial peak plasma level attained immediately after the completion of intravascular distribution of the injected bolus. In the case of tetrahydrocannabinol itself, however, there was a progressive rise in plasma cannabinoid concentration between five and fifteen minutes after the rapid intravenous injection. The reasons for this rise in plasma cannabinoid concentration are discussed.