Effect of DNA fragment size on transformation frequencies in tobacco (Nicotiana tabacum) and maize (Zea mays)

During eukaryotic cell transformation, the transforming DNA must enter the host cell, traverse the cytoplasm and enter the nucleus before becoming stably integrated into the genome. The limiting step for plant protoplast transformation may lie at the cell membrane, the nuclear membrane, or at the integration step. We show here that the size of the DNA fragment containing the selectable marker used to monitor transformation can directly affect the efficiency of stable transformation. In both tobacco and maize protoplasts, the smallest DNA fragments gave the highest stable transformation frequencies.     

Isolation of cyanobacterial auxotrophs by direct selection of regulatory-mutant phenotypes

We have isolated a chorismate mutase bradytroph (leaky auxotroph) ofAnabaena sp. PCC 7119 (ATCC 29151) as a spontaneous 6-fluorotryptophan-resistant mutant. The decreased chorismate mutase activity resulted in the production of quantities of the phenylalanine and tyrosine that limited rate of growth. 3-Deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase activity in the mutant was elevated more than twofold over the wild-type activity, suggesting derepression of this enzyme. The physiological deregulation of DAHP synthase and the genetic-based deficiency of chorismate mutase promoted an elevated level of intracellular chorismate, which then overwhelmed the competitive inhibition of anthranilate synthase by tryptophan, resulting in the overproduction of tryptophan and indoleglycerolphosphate. The presence of exogenous serine increased the production of tryptophan at the expense of indoleglycerolphosphate. This indicated that the endogenous potential for increasing the amount of serine available for increased tryptophan production is limited.     

The use of scat samples in primate diet analysis

The need for increased dietary studies on nonhuman primates is discussed. A method combining both direct observation and fecal analysis is proposed as the most satisfactory for such studies. The procedure for fecal analysis is outlined and the application of the results discussed. A field investigation concerning the diet of four primates—baboon, vervet, Sykes', and colobus—was greatly aided by the investigator's use of scat analysis. The information proved invaluable for gathering data on the insect portion of the diet as well as for determining the period over which items were eaten. Analysis also indicated the presence in the diet of some items which were not observed being eaten and counteracted differences in morphology and behavior that affected feeding behavior data.     

Age-related motor and catecholomine alterations in mice on levodopa supplemented diet

Old mice reared on regular diet show reduced motor activity, decreased basal adenylate cyclase, and increased MAO activities compared to adults. Brain DDC and COMT activities, DA, NE levels and DA-stimulated adenylate cyclase remained unchanged. By contrast, mice fed levodopa for life did not develop decreased motor activity with aging, lived about 50% longer, had slightly elevated whole brain DA and NE levels and failed to develop the expected rise in MAO activity with aging. Levodopa did not alter the number of dopaminergic and muscarinic cholinergic receptors or the adenylate cyclase activity in the striatum during aging. On levodopa, hepatic and renal DA, dopa, and HVA increased but the latter two returned to basal levels by mid life. In liver, DDC was unchanged but MAO tended to be higher in levodopa-fed mice. Thus, motor impairment is an age-related phenomenon in mice associated with selective alterations in brain dopaminergic systems, which may be prevented by dietary levodopa. Extracerebral tissues, through possibly adaptive metabolic mechanisms, play a significant role in regulating brain catecholamines during chronic administration of large doses of levodopa.     

Fluorometric assay for 1-deoxyfructose

A sensitive fluorometric assay has been developed for the measurement of 1-deoxyfructose in biological fluids. Samples containing 1-deoxyfructose are incubated with an equal volume of 0.01 m 3,5-diaminobenzoic acid in 5.0 m phosphoric acid in a boiling-water bath for 15 min. The fluorescent product has an emission maximum at 502 nm and an excitation maximum at 396 nm. Fluorescence is proportional to 1-deoxyfructose concentrations over a range from 0.002 to 1.0 mm. The method can be used to detect as little as 0.03 μmol of 1-deoxyfructose in deproteinized blood and in urine and no interference is observed with glucose, fructose, pyruvate, or ketone bodies. The method will also detect 1-deoxytagatose, 2-deoxyaldohexoses, and -pentoses, 2,5-anhydromannose, and a number of 2-, 3-, 4-, and 5-mono- or bis(hydroxymethyl)furans. The fluorescence properties of the products formed from all of the above compounds are similar suggesting structural similarities of the adducts formed and possible mechanistic similarities of the reactions involved.     

Colony aging affects the reproductive performance of Swiss Webster females used as recipients for embryo transfer

The objective was to evaluate the influence of colony aging in a Swiss Webster (SW) outbred stock used as recipients for embryo transfer. In the first study, a retrospective analysis was performed throughout several generations during a 38-month period in 2,398 embryos transferred to 108 SW recipients. A decrease in the percentage of live pups from transferred embryos was found at the end of the period. Impairment occurred due to the incidence of maternal cannibalism that increased from 0% to 67-100% (P<0.05), while pregnancy rate (pregnant/transferred recipients) and number of pups per delivered female were not affected throughout the period (P=NS). A following study was carried out to compare the reproductive performance of SW stock vs. B6D2F1 hybrid females in a 5-year interval. The study was conducted on a total of 893 embryos transferred to 40 females (20 SW and 20 B6D2F1) in Year #1, and 514 embryos transferred to 30 females (15 SW and 15 B6D2F1) in Year #5. No cases of maternal cannibalism were found on Year #1 in any of the strains (0/10 and 0/10). However, an incidence of 44,4% (4/9) was seen on Year #5 for SW, while for B6D2F1 the incidence was 0% (0/12) (P<0.05). Further examination of the uterus showed endometrial cysts and abnormal implantation sites in SW on Year #5 but not in B6D2F1 females. In conclusion, this study reports an impairment of the reproductive performance of an early aged SW outbred stock colony mainly due to the occurrence of maternal cannibalism. This finding has important implications for embryo transfer programs conducted in mouse facilities.     

Elabela/toddler: New peptide with a promising future in cancer diagnostic and therapy

Elabela/toddler is the second endogenous ligand recently identified after Apelin, that binds to the G protein-coupled receptor APJ. Elabela is a 54-amino acid peptide initially identified in fish and human genomes and classified as noncoding. This precursor can be cleaved to shorter sequences (32, 21, and 11 amino acids), which bind and activate APJ, and can be blocked by APJ antagonists. Contrary to Apelin and APJ, widely distributed in organs and tissues, Elabela expression is more restricted, and different studies have revealed the potential role of Elabela in cancers. This review summarizes the current studies focusing on the role of Elabela in different cancers.     

Synthesis and antiviral activity of aryl phosphoramidate derivatives of β-D- and β-L-C-5-Substituted 2’,3’-didehydro-2’,3’-dideoxy-uridine bearing linker arms

We have previously reported the synthesis and evaluation of potent anti-human immunodeficiency virus compounds based on β-D-d4T analogues bearing a tether attached at the C-5 position and their β-L-counterparts. Initial study revealed a requirement for an alkyl side-chain with an optimal length of 12 carbons for a weak antiviral activity. As a continuation of that work, we have now prepared the corresponding phosphoramidate derivatives as possible membrane-permeable prodrugs. Phosphorochloridate chemistry gave the target phosphoramidates which were tested for anti-human immunodeficiency virus type 1 activity; unfortunately, they were devoid of anti-HIV activity.     

Boron Containing Pyrimidines,Nucleosides, and Oligonucleotides for Neutron Capture Therapy

Abstract

The synthesis and encouraging biological findings with boron-containing nucleosides, such as 5-dihydroxyboryl-2′-deoxyuridine, which could be used for boron neutron capture therapy (BNCT) for the treatment of various malignancies, has provided momentum to synthesize several boron containing nucleosides and oligomers. BNCT is based on the property of the non-radioactive boron-10 isotope to capture low energy neutrons, thereby producing a localized cell-destroying nuclear reaction. Thus, irradiation of tumor cells with neutrons, following incorporation of the boronated nucleoside, would result in the destruction of tumor tissue only. Intracellular phosphorylation by nucleoside kinases, and/or incorporation into the cancer cell DNA as a false nucleotide precursor, followed by irradiation by neutrons, would lead primarily to tumor cell death. The synthetic and biological approaches for boronated pyrimidines, nucleosides, and oligonucleotides for BNCT are reviewed.