Mono- and dysfunctional nitrogen mustard analogues of the DNA minor groove binder pibenzimol. Synthesis, cytotoxicity and interaction with DNA

Two series of mono- and dysfunctional aniline mustards linked to a bisbenzimidazole minor groove binder have been prepared using a new method (polyphosphate ester-mediated direct coupling of appropriate mustard acids with a preformed advanced phenylenediamine intermediate). As the linker chain attaching the mustard was lengthened the binding site size of the compounds to calf thymus DNA remained essentially constant at 2.6 nucleotides, but reversible binding strength declined by a factor of 2. Analogues with longer linker chains alkylated DNA much more rapidly than those with shorter chains, consistent with the electronic factors. The short chain analogues also failed to alkylate a 120 bp HindIII to Bg/II fragment of the gpt gene, as measured by gel electrophoresis cleavage assays. The longer chain analogues (both mono- and dysfunctional mustards) showed patterns of DNA alkylation that varied with chain length. In particular, while most compounds showed substantial N7 alkylation at many guanine residues, the analogue with a (CH2)3 linker chain showed strong alkylation at adenine sites in poly-AT regions. For the longer chain analogues, the bifunctional mustards were substantially (10- to 20-fold) more cytotoxic than the corresponding monofunctional analogues.     

Frontofacial osteotomies, advancement, and remodeling by distraction: an extended application of the technique

The purpose of this clinical report is to present the distraction technique for advancement of the frontofacial skeleton as a unit. Our 14-year-old patient was diagnosed with Carpenter's syndrome and kleblattsch?del deformity at birth. At other centers the patient underwent corrective surgeries, including repeated fronto-orbital advancement in an attempt to correct the residual deformity. This has resulted in bony malunion and recurrent deformity, and it has left the patient with no available donor sites for harvesting of bone graft. The patient had class III malocclusion, severe midfacial and frontal deficiency, and relative turricephaly. We performed frontofacial osteotomies and placement of the distraction devices. Distraction of 20 mm was accomplished, correcting the exophthalmos and midface retrusion and producing class I dental occlusion. We conclude that distraction is an optional surgical method that can be applied in selected cases for advancement of the entire frontofacial skeleton.     

Minor groove binding of a bis-quaternary ammonium compound: the crystal structure of SN 7167 bound to d(CGCGAATTCGCG)2

The X-ray crystal structure of the complex between the synthetic antitumour and antiviral DNA binding ligand SN 7167 and the DNA oligonucleotide d(CGCGAATTCGCG)2 has been determined to an R factor of 18.3% at 2.6 A resolution. The ligand is located within the minor groove and covers almost 6 bp with the 1-methylpyridinium ring extending as far as the C9-G16 base pair and the 1-methylquinolinium ring lying between the G4-C21 and A5-T20 base pairs. The ligand interacts only weakly with the DNA, as evidenced by long range contacts and shallow penetration into the groove. This structure is compared with that of the complex between the parent compound SN 6999 and the alkylated DNA sequence d(CGC[e6G]AATTCGCG)2. There are significant differences between the two structures in the extent of DNA bending, ligand conformation and groove binding.     

Method of creating local semi-insulating regions on silicon wafersfor device isolation and realization of high-Q inductors

Penetrating proton beams from a compact ion cyclotron (diameter: 1.5 m, height: 2 m) were employed to create local semi-insulating regions within silicon substrates to facilitate device isolation in mixed-mode (analog-digital) integrated circuits (IC's) and realization of RF IC's with high-Q inductors. Experiments revealed that resistivity values of I MΩ-cm could be reached by practical proton fluences on silicon wafers of original resistivity of more than about 1 Ω-cm. Significant improvement was evidenced on Q values of irradiated inductors. Effect of reduced inductor metal conductivity from bombardment was over-shadowed by the more enhanced Q behavior, if the proton fluence is sufficiently large     

Exploiting tumor hypoxia through bioreductive release of diffusible cytotoxins: the cobalt(III)-nitrogen mustard complex SN 24771

PURPOSE: To assess the oxygen dependence of a novel cobalt-nitrogen mustard complex, SN 24771, designed to release a diffusible cytotoxic metabolite in hypoxic tumor microenvironments. METHODS AND MATERIALS: Oxygen dependence of cell killing was assessing in well-stirred single cell suspensions obtained by enzymatic dissociation of EMT6 spheroids, using a sensitive oxygen electrode to measure oxygen concentrations in solution. Cell killing in intact EMT6 spheroids was also compared with that in single cell suspensions. RESULTS: Cytotoxicity of SN 24771 in single cell suspensions was inhibited by very low concentrations of oxygen. The C50 value (O2 required for 50% inhibition of log cell kill) was ca. 0.02% O2 at 1 h, and the K value (O2 required to give a cytotoxic potency equal to the average of that at zero and infinite O2) was of a similar order. However, intact spheroids were much more sensitive to SN 24771 than could be accounted for by the K curve for single cell suspensions, this estimate being based on published data for the oxygen concentration profile in these spheroids. CONCLUSION: The cytotoxicity of SN 24771 is inhibited appreciably at oxygen concentrations which are too low to provide radiosensitization. In this respect, SN 24771 resembles organic bioreductive drugs such as quinones and nitroaromatic compounds. However, the extensive killing observed in multicellular spheroids is consistent with release of a diffusible nitrogen mustard on reduction. Bioreductive drugs with a low K value for activation, but which release a diffusible cytotoxin, may have desirable properties as tumor radiosensitizers.     

Child care history and kindergarten adjustment.

Parents gave histories of 589 children just before kindergarten. Children were later assessed with teacher, peer, and observer measures of social adjustment in school. Children with higher day-care amounts in each of 3 eras (0–4, and 4–5 yrs) scored higher on the composite negative adjustment and lower on positive adjustment (however, they also scored lower on teacher-rated internalizing problems). Day care predicted even after statistical control for measures representing alternative explanations, such as family stress and socioeconomic status, accounting for 2.7% of variance in negative adjustment and 2.9% of positive adjustment. Interactions between day care and other variables did not add to predictions of the molar adjustment composites. Extensive infancy care did not in itself predict adjustment, according to planned contrasts that controlled for total amount of day care received across the 3 eras of the child's life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure-activity relationships for 1-phenylbenzimidazoles as selective ATP site inhibitors of the platelet-derived growth factor receptor

1-Phenylbenzimidazoles are shown to be a new class of ATP-site inhibitors of the platelet-derived growth factor receptor (PDGFR). Structure-activity relationships (SARs) are narrow, with closely related heterocycles being inactive. A systematic study of substituted 1-phenylbenzimidazoles showed clear SARs. Substituents at the 4'- and 3'-positions of the phenyl ring are tolerated but do not significantly improve activity, while substituents at the 2'-position abolish it. Substituents in the 2-, 4-, and 7-positions of the benzimidazole ring (with the exception of 4-OH) also abolish activity. Most substituents at the 5- and 6-positions maintain or increase activity, with the 5-OH, 5-OMe, 5-COMe, and 5-CO2Me analogues being >10-fold more potent than the parent 1-phenylbenzimidazole. The 5-OMe analogue was both the most potent inhibitor, and showed the highest selectivity (50-fold) between PDGFR and FGFR isolated enzymes, and also a moderately effective inhibitor (IC50 = 1.9 microM) of PDGF-stimulated PDGFR autophosphorylation in rat aorta smooth muscle cells.     

Radiation-activated prodrugs as hypoxia-selective cytotoxins: model studies with nitroarylmethyl quaternary salts

Bioreductive drugs are designed to be activated by enzymatic reduction in hypoxic regions of tumours, but activation of these drugs is not always fully suppressed by oxygen in normal tissues. A further limitation is that bioreductive drug activation depends on suitable reductases being expressed in the hypoxic zone. This essay proposes an alternative approach in which prodrugs are reduced, and thereby activated, in hypoxic regions by ionizing radiation rather than by enzymes. This strategy is theoretically attractive, but design requirements for such radiation-activated cytotoxins are challenging. In particular, the reducing capacity of radiation at clinically relevant doses is small, which necessitates the development of prodrugs capable of releasing very potent cytotoxins efficiently in hypoxic tissue. It is shown that nitroarylmethyl quaternary (NMQ) salts possess many of the features required of a radiation-activated prodrug. In some heterocyclic NMQ compounds the cytotoxicity of the latent cytotoxic amine effector is suppressed by > 100-fold in the prodrug form, and the effector is released rapidly by fragmentation following reduction by a single electron. Appreciable cytotoxic activation of NMQ prodrugs can be achieved by irradiation at clinically relevant doses in anoxic plasma. Some of the further drug design challenges required to develop a clinical agent based on this approach are outlined.     

Experimental hepatitis E: pathogenesis in cynomolgus macaques (Macaca fascicularis)

Children with acute lymphoblastic leukemia (ALL) who have completed 2.5 to 3 years of initial chemotherapy have an off-therapy relapse rate of approximately 20%. In an attempt to improve the survival of children with a late bone marrow (BM) relapse (ie, occurring greater than 6 months after cessation of primary therapy), the Pediatric Oncology Group designed a randomized study to compare the efficacy of doxorubicin/prednisone and cytarabine/teniposide in a multidrug retreatment chemotherapy program. Treatment consisted of remission reinduction with vincristine, prednisone, and doxorubicin, central nervous system prophylaxis with triple intrathecal chemotherapy, and continuation therapy (for 132 weeks) with alternating cycles of oral 6-mercaptopurine/methotrexate and intravenous vincristine/cyclophosphamide. Patients received intermittent courses of either prednisone/doxorubicin (regimen 1) or teniposide/cytarabine (regimen 2) during continuation therapy and a late intensification phase with either vincristine, prednisone, and doxorubicin (regimen 1) or teniposide and cytarabine (regimen 2). One hundred two of 105 evaluable patients (97%) achieved a second complete remission. Twenty-eight of 50 patients on regimen 1 have failed compared with 28 or 52 patients on regimen 2 (log-rank analysis, P = .68), indicating that this trial was inconclusive as to which treatment regimen was superior. The overall 4-year event-free survival for children with a late BM relapse was 37% +/- 6%. Age less than 10 years at initial diagnosis (P < or = .001), white blood cell count less than 5,000/microL at relapse (P = .036) and duration of first remission greater than 54 months (P = .039) were independently associated with a more favorable outcome. While the randomized trial was inconclusive, prolonged second complete remissions were secured in more than one-third of children with a late BM relapse of ALL. The prognostic factors identified may help select children with a late BM relapse who can be successfully retreated with chemotherapy alone.     

Continuous spinal anaesthesia

CD59 is a cell membrane-bound complement regulatory protein on glomerular cells that inhibits C5b-9 assembly and insertion. This report describes a recently developed model of immune thrombotic microangiopathy (TMA) induced by the renal artery perfusion of anti-glomerular endothelial cell (anti-GEN) antibody. To examine the role of CD59 in protecting the GEN from immune-mediated injury, rats underwent selective renal artery perfusion with F(ab')2 fragments of anti-CD59 monoclonal antibody to block CD59 activity or control mouse IgG followed by anti-GEN antibody or control goat IgG. Neutralization of CD59 in normal rats did not result in any significant functional or histologic changes. Perfusion with anti-CD59 did not change deposition of the pathogenic anti-GEN IgG used to induce the TMA model. However, neutralization of CD59 in the TMA model resulted in more C5b-9 formation in glomeruli, accompanied by increased platelet and fibrin deposition, more severe endothelial injury, and reduced renal function compared with the animals perfused with control F(ab')2 fragments. These results demonstrate directly that CD59 serves a protective role for GEN in this TMA model of rats, and confirm that C5b-9 formation has a critical pathogenic role in the mediation of the disease. CD59 may play an important role in protecting glomerular endothelium from other complement-mediated types of injury.