DNA-Directed alkylating agents. 7. Synthesis, DNA interaction, and antitumor activity of bis(hydroxymethyl)- and bis(carbamate)-substituted pyrrolizines and imidazoles

A series of bis(hydroxymethyl)-substituted imidazoles, thioimidazoles, and pyrrolizines and related bis(carbamates), linked to either 9-anilinoacridine (intercalating) or 4-(4-quinolinylamino)benzamide (minor groove binding) carriers, were synthesized and evaluated for sequence-specific DNA alkylation and cytotoxicity. The imidazole and thioimidazole analogues were prepared by initial synthesis of [(4-aminophenyl)alkyl]imidazole-, thioimidazole-, or pyrrolizine dicarboxylates, coupling of these with the desired carrier, and reduction to give the required bis(hydroxymethyl) alkylating moiety. The pyrrolizines were the most reactive alkylators, followed by the thioimidazoles, while the imidazoles were unreactive. The pyrrolizines and some of the thioimidazoles cross-linked DNA, as measured by agarose gel electrophoresis. Strand cleavage assays showed that none of the compounds reacted at purine N7 or N3 sites in the gpt region of the plasmid gpt2Eco, but the polymerase stop assay showed patterns of G-alkylation in C-rich regions. The corresponding thioimidazole bis(carbamates) were more selective than the bis(hydroxymethyl) pyrrolizines, with high-intensity bands at 5'-NCCN, 5'-NGCN and 5'-NCGN sequences in the PCR stopping assay ( indicates block sites). The data suggest that these targeted compounds, like the known thioimidazole bis(carbamate) carmethizole, alkylate exclusively at guanine residues via the 2-amino group, with little or no alkylation at N3 and N7 guanine or adenine sites. The cytotoxicities of the compounds correlated broadly with their reactivities, with the bis(hydroxymethyl)imidazoles being the least cytotoxic (IC50s >1 microM; P388 leukemia) and with the intercalator-linked analogues being more cytotoxic than the corresponding minor-groove-targeted ones. This was true also for the more reactive thioimidazole bis(carbamates) (IC50s 0.8 and 11 microM, respectively), but both were more active than the analogous "untargeted" carmethizole (IC50 20 microM). The bis(hydroxymethyl)pyrrolizine analogues were the most cytotoxic, with IC50s as low as 0.03 microM.     

Crystal growth in dental enamel: the role of amelogenins and albumin

Amelogenin-mineral interactions were investigated using an in vitro binding approach. Rat incisor enamel matrix proteins (mainly amelogenins) were dissolved in synthetic enamel fluid and allowed to equilibrate with deproteinised developing enamel crystals. The results showed that amlogenin proteins of 21, 23, 24, 26 and 27-kDa (corresponding to nascent and partially degraded amelogenins) were associated with the crystals whilst the lower Mr amelogenins (< 21 KDa) remained free in the synthetic enamel fluid. These data suggest the nascent and partially degraded amelogenins may interact with developing enamel crystals and could influence their growth. Albumin-mineral interactions were investigated by extracting developing rat incisor enamel with synthetic enamel fluid. Insoluble material (including the enamel crystals) was then further extracted with 0.1 M phosphate buffer (pH 7.4) to desorb any mineral bound proteins. Western blotting using anti-albumin antibodies showed that almost all of the albumin from the secretory stage enamel and a significant proportion of the albumin present in early transition stage was extractable in the synthetic enamel fluid. However, synthetic enamel fluid did not extract albumin from late transition or maturation stage tissue, which could only be removed following further extraction with phosphate buffer. Albumin degradation was apparent during the transition and maturation stages, where it is degraded and ultimately removed. This binding pattern may be related to amelogenin degradation and removal during the transition stage, permitting albumin access to the previously obscured crystal surfaces. That the secretory stage matrix appears to "protect" secretory stage crystals from albumin may be an important consideration in the aetiology of enamel hypoplasias (i.e. incomplete crystal growth) and when using dissociative extraction procedures for the identification of mineral bound proteins.     

Signal transduction in vertebrate growth cones navigating in vivo

Navigating growth cones need signal transduction machinery to amplify and transmit the effects of extracellular signals throughout the growth cone. In culture, many drugs that affect second messengers are known to modulate neurite extension (with different effects on different neurons), and gradients of calcium influx and cyclic nucleotide analogs can cause growth cones to turn. However, it is not clear which of these responses are physiologically relevant, as axons grow through much more complex environments in vivo. The "exposed brain" preparation in Xenopus embryos provides an experimentally tractable system in which it is possible to study growth, pathfinding, and target recognition of retinal growth cones in vivo, while pharmacologically manipulating their signal transduction systems. These growth cones can also be easily studied in explant culture. We describe preliminary results of parallel in vivo and in vitro experiments using an array of drugs that perturb transduction molecules. Surprisingly, calcium ionophores and cyclic nucleotide analogs have no significant effect on retinal axon growth or pathfinding. Several agents including herbimycin A, ML-7, mastoparan, and RHC80267 inhibit retinal axon growth, both in vivo and in vitro, suggesting that tyrosine kinases, myosin, heterotrimeric G-proteins, and diacylglycerol lipase are important for retinal growth cones navigating in the optic pathway.     

A negative association of schizophrenia with an allele of the HLA DQB1 gene among African-Americans

The present study investigated the relationship between the time of nocturnal onset of urinary 6-sulfatoxymelatonin (aMT6s) secretion, and the timing of the steepest increase in nocturnal sleepiness ("sleep gate"), as determined by an ultrashort sleep-wake cycle test (7 min sleep, 13 min wake). Twenty-nine men (mean age 23.8 +/- 2.7 years) participated. The ultrashort sleep-wake paradigm started at 0700 hr after a night of sleep deprivation and continued for 24 hr until 0700 hr the next day. Electrophysiological recordings were carried out during the 7-min sleep trials, which were then scored conventionally for sleep stages. Urinary aMT6s was measured every 2 hr. The results showed that the timing of the sleep gate was significantly correlated with the onset of aMT6s secretion. These results are discussed in light of the possible role of melatonin in sleep-wake regulation.     

1H-NMR resonance assignments, secondary structure, and global fold of the TR1C fragment of turkey skeletal troponin C in the calcium-free state

The TR1C fragment of turkey skeletal muscle TnC (residues 12-87) comprises the two regulatory calcium binding sites of the protein. Complete assignments of the 1H-NMR resonances of the backbone and amino acid side chains of this domain in the absence of metal ions have been obtained using 2D 1H-NMR techniques. Sequential (i,i+1) and short-range (i,i+3) NOE connectivities define two helix-loop-helix calcium binding motifs, and long-range NOE connectivities indicate a short two-stranded beta-sheet formed between the two calcium binding loops. The two calcium binding sites are different in secondary structure. In terms of helix length, site II conforms to a standard "EF-hand" motif with the first helix ending one residue before the first calcium ligand and the second helix starting one residue after the beta-sheet. In site I, the first helix ends three residues before the first calcium ligand, and the second helix starts three residues after the beta-sheet. A number of long-range NOE connectivities between the helices define their relative orientation and indicate formation of a hydrophobic core between helices A, B, and D. The secondary structure and global fold of the TR1C fragment in solution in the calcium-free state are therefore very similar to those of the corresponding region in the crystal structure of turkey skeletal TnC [Herzberg, O., & James, M.N.G. (1988) J. Mol. Biol. 203, 761-779].     

Reliability of seizure classification using a semistructured interview

Methods for standardized classification of epileptic seizures are important for both clinical practice and epidemiologic research. In this study, we developed a strategy for standardized classification using a semistructured telephone interview and operational diagnostic criteria. We interviewed 1,957 adults with epilepsy ascertained from voluntary organizations. To confirm and expand the seizure history, we also interviewed a first-degree relative for 67% of subjects and obtained medical records for 59%. Three lay reviewers used all available information to classify seizures. To assess reliability, each reviewer classified a sample of subjects assigned to the others. In addition, an expert physician classified a sample of subjects assigned to two of the reviewers. Agreement was "moderate-substantial" for generalized-onset seizures, both for the comparisons between pairs of lay reviewers and for the neurologist versus lay reviewers. Agreement was "substantial-almost perfect" for partial-onset seizures, both for pairs of lay reviewers and for the neurologist versus lay reviewers. These results suggest that seizures can be reliably classified by lay reviewers, using operational criteria applied to symptoms ascertained in a semistructured telephone interview.     

Liposome-cell interaction: transfer and intracellular release of a trapped fluorescent marker

When small, unilamellar lipid vesicles containing a high concentration of the fluorescent dye 6-carboxyfluorescein are incubated with either frog retinas or human lymphocytes, fluroescence distributes widely throughout each cell. Since "self-quenching" largely prevents the dye from fluorescing as long as it remains sequestered in vesicles, it is clear that a considerable amount of dye is released from the vesicles and diluted into the much larger volume of the cell.     

Fibrous myopathy. A rheumatic complication of drug abuse

A progressive fibrous myopathy may result from chronic intramuscular drug abuse. This complication may mimic other rheumatic disorders and early recognition may prevent disability. The patient described here presented with fixed flexion and extension contracture of hips and knees, respectively, after abusing meperidine and other agents for 3 years. Soft tissues of thighs and buttocks were "wood hard," EMG showed absence of action potentials in affected muscles, and biopsy revealed extensive replacement of muscle with dense, acellular fibrous tissue. Possible mechanisms are discussed.     

福州市区配电网遭受百年一遇内涝损失的启示

1 台风引起市区配电网受损情况 2005年第19号台风“龙王”于10月2日21:35 在福建登陆,受其影响,10月2日20:00-22:00, 福州市区普降特大暴雨,市区1 h最大降雨量达 118 mm,3 h最大降雨量达276 mm(福州市区年平均降水量为1 393．6 mm),达到超百年一遇,为1937 年有实测纪录以来的最大值。