Heavy metal ion-nucleic acid interaction

All the heavy atoms that have so far been found to provide good derivative crystals do so by forming direct coordination bonds to either the backbone or the bases of nucleic acids in an environment where the coordination shell can be further stabilized by several hydrogen bonds. A summary of coordination sites is shown in Fig. 5 and listed below: Lanthanide ions such as Sm(III), Lu(III), Pr(III), Eu(III), Tb(III), Dy(III), Gd(III) form coordination bonds to oxygen atoms of two adjacent phosphates or to phosphates from different parts of the chain. The N-7 position of guanine is the most common site for heavy atoms. N-7 can become a ligand to many metal ions such as Os(VI) from OsO3 X (Py)2, Pt(II) from square-planar cis- or trans-dichlorodiammine complexes, Co(II), and Mn(II). The O-4 position of uracil can be a binding site for the Hg atom of hydroxymercuryhydroquinone-O-O-diacetate. The N-7 of adenine and the N-4 of cytosine in the base sequence A-C can be a binding site for an octahedral platinum(IV) from K2PtCl6.

Comparison of local versus central tumor measurements in a multicenter cancer trial

Four hundred nineteen solid tumors from 92 patients were measured by a local team consisting of a physician and nurse oncologist or physician's assistant, and centrally by one radiologist. The central radiologist also remeasured 137 tumors on 30 patients to assess intraexaminer agreement. Tumor measurements at specific points in time as well as changes in tumor measurements over time were evaluated. When signed differences were calculated, there was little overall difference between local and central examiners, although three of the eight centers did show a significant difference. However, when absolute differences were calculated, the relative errors of the width times length products ranged from 35 to 55%. Although local and central examiners agreed 75% of the time on change in disease, there was only 42% agreement on the subset of patients who had a remission. In general, the intraexaminer agreement was slightly better than the interexaminer agreement. This study suggests that solid tumor measurements are not particularly reliable, and that survival time remains the most satisfactory endpoint in a cancer clinical trial.

'Interactive' recognition in EcoRI restriction enzyme-DNA complex

A solution study of interaction between DNA and EcoRI restriction enzyme shows that there is a definite distortion of DNA in the specific recognition complexes but no measurable DNA distortion in the non-specific interaction.

Isolation of gram quantities of EcoRI restriction and modification enzymes from an overproducing strain

Structural genes for EcoRI restriction endonuclease and modification methylase have been inserted into the plasmid vector pKC30 (Shimatake, H., and Rosenberg, M. (1981) Nature (Lond.) 292, 128-132) downstream from the bacteriophage lambda pL promoter. Upon induction of pL expression in strains producing a thermolabile lambda cI857 repressor, synthesis of EcoRI polypeptides is enhanced to the extent that after 4 h they represent several per cent of the total cell protein. Purification of activities overproduced in this manner yields preparations of endonuclease and methylase which appear identical to those obtained from conventional sources, with overall yields corresponding to 0.5 to 0.9 g of each enzyme/kg of cell paste.

Effect of warfarin anticoagulation on survival in carcinoma of the lung, colon, head and neck, and prostate. Final report of VA Cooperative Study #75

VA Cooperative Study #75 was established to test in a controlled, randomized trial the hypothesis that warfarin anticoagulation would favorably affect the course of certain types of malignancy. No differences in survival were observed between warfarin-treated and control groups for advanced non-small cell lung, colorectal, head and neck and prostate cancers. However, warfarin therapy was associated with a significant prolongation in the time to first evidence of disease progression (P = 0.016) and a significant improvement in survival (P = 0.018) for patients with small cell carcinoma of the lung, including the subgroup of patients with disseminated disease at the time of randomization (P = 0.013). A trend toward improved survival with warfarin treatment was observed for the few patients admitted to this study with non-small cell lung cancer who had minimal disease at randomization. These results suggest that warfarin, as a single anticoagulant agent, may favorably modify the course of some, but not all, types of human malignancy, among which is small cell carcinoma of the lung. Further trials of warfarin may be indicated in patients with limited disease who have cell types that failed to respond when advanced disease was present.

Accrual of patients into a multihospital cancer clinical trial and its implications on planning future studies

Little information exists on the population of cancer patients from which individual patients are selected for admission to a clinical trial. In fact, most reports of clinical trials of cancer chemotherapeutic agents begin by describing samples of treated patients but neglect to collect data and describe the population from which the samples were taken. In a multi-institutional VA Cooperative Study in which two different cancer treatments were compared, an attempt was made to screen all lung, colorectal, prostate, and head and neck patients seen at participating hospitals prior to randomization to a therapeutic regimen. Of a total of 2687 patients screened, 437 (16.3%) were randomized and 2250 (83.7%) were excluded for 2981 reasons. Protocol reasons were the basis for 68.6% of all exclusions, 21.3% were physician refusals, and 10.1% were patient refusals. The number of patients randomized did not correlate well with number of patients screened across participating centers. Patients admitted to the study tended to be younger and in better health than excluded patients. Overestimates of randomization rates projected initially from published information point to the need for improved screening data in the planning of future studies. Factors such as screening methods, physician acceptance of the experimental approach, number of competing protocols within each center, and cooperation among medical center departments and personnel all are important ingredients in any screening effort.

Local mobility of nucleic acids as determined from crystallographic data. I. RNA and B form DNA

The local mobility of DNA and RNA can be described well by a segmented rigid body model in which the phosphates, riboses and bases are treated as independent groups. We have developed a computer program for extracting information about the translational and rotational mobility of these groups from X-ray diffraction data of single crystals of DNA and RNA fragments. We plan to extend our studies from the B DNA helix studied here to A and Z form helices for which diffraction data are available. The mobilities described here may be important in allowing the flexibility necessary for interaction of nucleic acids with proteins, ligands or other nucleic acids, and are crucial to our understanding of the factors governing both structural stability and motion of nucleic acids on a larger scale.

Modification of thermosensitivity of HeLa cells by sodium butyrate, dibutyryl cyclic adenosine 3':5'-monophosphate, and retinoic acid

Studies were carried out with HeLa S-3 cells to determine whether exposure of the cells to "differentiating agents" would modify the thermosensitivity of cells under the cellular conditions where there is no significant perturbation of the cell cycle distribution. Sodium butyrate, dibutyryl cyclic adenosine 3':5'-monophosphate (dbcAMP), and retinoic acid all afforded pronounced protective effects on the thermosensitivity of HeLa cells. The kinetics of expression of thermal resistance induced by the agents varied with different agents. Sodium butyrate (1 mM) was only capable of inducing the thermal resistance during the time of heating (42 degrees), while a minimum 8-hr exposure to dbcAMP (1 mM) and 48-hr exposure to retinoic acid (10 microM) prior to heating at 42 degrees were required to demonstrate the thermal resistance. The presence of dbcAMP and retinoic acid was not required during the heating. The thermal resistance acquired by the exposure of cells to dbcAMP and retinoic acid was reversible following the removal of the drugs with a time course varying with the duration of preexposure time. This difference in the kinetics of thermal resistance suggests that these agents may have a different mode of action for the induction of thermal resistance in HeLa cells.

[Regional change of brain energy metabolism and catecholamine in the early stage of experimental cerebral ischemia--histochemical study]

Ischemic change of cerebral energy metabolism and catecholamine have already been discussed largely using biochemical quantitative assay. However, regional change and their correlation are not well understood. In the present study, the ischemic regional change of cerebral energy metabolism and catecholamine were investigated in gerbils and histochemical method. Adult either sex mongolian gerbils, weighing 50-100 g, were anesthetized with ether and the left carotid artery was ligated. After observation of clinical symptoms, the brain was frozen in situ by pouring liquid N2 after 30 min and 60 min of ischemic insult. The frozen brain was sectioned with precooled saw in the coronal plane. The brain section were placed in liquid N2 bath and illuminated with 366 nm light (UV) from a 200 watt mercury lamp and Corning filter 5840. NADH fluorescence was recorded photographically through Corning filter 3387 and 5562. Also UV reflectance was recorded through Corning filter 5840 to observe quenching effect of hemoglobin. Regional change of catecholamine was observed in the same frozen brain processed with Falck-Hillarp method. According to neurological abnormalities following left carotid ligation, animals were divided into three groups; symptomatic, borderline and asymptomatic. The intensity and distribution of tissue NADH fluorescence were closely correlated to the clinical symptoms. In the symptomatic group, both in 30 min and 60 min of ischemia, homogeneously and markedly increased fluorescence was observed in the ipsilateral temporal cortex, caudate nucleus, hypothalamus and dorsolateral thalamus. Columnar mild increase of NADH fluorescence was seen in the ipsilateral parietal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Quercetin, an inhibitor of lactate transport and a hyperthermic sensitizer of HeLa cells

Since cancer cells produce large amounts of lactate via aerobic glycolysis and since an acidic pH has been shown to selectively enhance the cytotoxic effects of hyperthermia, we are examining the influence of cell exposure to drugs which inhibit lactate transport and lower intracellular pH upon cytotoxic effects of hyperthermia. Quercetin, a bioflavonoid that produces lactate transport inhibition, was not cytotoxic up to 4 hr at 37 degrees (0.1 mM). When HeLa cells were exposed to quercetin at 41 and 42 degrees, significant potentiation of hyperthermia-induced cytotoxicity was observed. The magnitude of the potentiation was dependent on the drug concentration, pH of the culture medium, temperature, and duration of treatment. In contrast, treatment of cells with rutin, a structurally related bioflavonoid that lacks the property of lactate transport inhibition, showed no hyperthermic potentiation.

Lonidamine: a hyperthermic sensitizer of HeLa cells in culture and of the Meth-A tumor in vivo

Lonidamine was studied in HeLa cell cultures and BALB/c mice with Meth-A fibrosarcoma. Lonidamine is a hyperthermia sensitizer, both in vivo and in vivo. In vitro the potentiating effects were higher at low pH conditions.

Radiosensitization of Meth-A fibrosarcoma in mice by Lonidamine

Isogenic male BALB/c mice bearing Meth-A tumors in the ascites form were used. The effects of Lonidamine and irradiation both alone and in combination were studied. Lonidamine administered intraperitoneally produced a significant enhancement of irradiation effects.

Epidural pulse waveform as an indicator of intracranial pressure dynamics

With an increase in intracranial pressure during epidural balloon inflation, epidural pulse waveform, which is polyphasic under normal conditions, becomes monotonous at about 30 mmHg. This change in waveform is considered closely related to the apparent increase in arterial driving pressure to the brain and to a disturbance of venous outflow. When cerebral vasodilatation is prominent, the waveform becomes monotonous at a significantly lower intracranial pressure. These findings correlate well with the results of spectral analysis of the pulse wave. The usefulness of change in epidural pulse waveform, which can indicate an alteration of intracranial pressure dynamics in a relatively low pressure range, is discussed with comparison to other techniques used to determine intracranial pressure dynamics.

Complications of pediatric percutaneous renal procedures: incidence and observations

Successful definitive (complete) percutaneous renal procedures in the pediatric age group were performed in 97 per cent of antegrade pyelograms, in 94 per cent of ureteral perfusions (Whitaker test), in 98 per cent of nephrostomies, and 100 per cent of both retroperitoneal fluid drainages and renal aspiration biopsies. Significant complications, or those necessitating specific treatment or prolonged hospitalization, were 1.1 per cent. 0.7 per cent, 15.2 per cent, 0 per cent, and 0 per cent, respectively, for the above procedures. Not surprisingly, certain operators are more adept than others at successfully performing procedures and at avoiding some but not all complications (see Tables 2 and 3). Proper training, experience, and adherence to basic principles are important. However, there were no deaths, no kidneys lost, and no transfusions or operations required as a result of any complication from the pediatric percutaneous renal procedures; correction of any existing blood coagulation disorder is necessary prior to their performance to avoid potentially fatal hemorrhage.

Melting order of successively longer yeast phenylalanine-accepting transfer ribonucleic acid fragments with a common 5' end

Temperature-jump methods were used to study the kinetics of the helix to coil transition in three fragments of yeast tRNAPhe that share a common 5' terminus (the 5' end of the mature tRNA). Correlation of the extrapolated helix dissociation time constants with NMR exchange broadening results allows assignment of the structural basis of the optical melting transition in the fragments. The results confirm nuclear magnetic resonance findings on these fragments: the 5' 1/4 fragment has no helical structure; the 5' 1/2 fragment contains the D stem; and the 5' 3/5 fragment contains the D stem and the anticodon stem. These are the structures expected if sequential folding of the tRNA during biosynthesis were to occur. The D stem is the last helix to melt in the 5' 3/5 fragment. We suggest that structural elements in addition to the four Watson-Crick base pairs of the D-stem helix are responsible for the anomalously high Tm of that hairpin.

Hypoxic cell radiosensitization by moderate hyperthermia and glucose deprivation

Cell culture studies were carried out to determine whether moderate hyperthermia reduces the oxygen enhancement ratio of cells under well-defined cultural conditions. Using asynchronously growing HeLa cells, the OER of cells with and without glucose was determined following exposure of cells to moderate hyperthermia, 40.5 degrees C for 1 hr, immediately after X irradiation. The OER of cells with 5 mM glucose was 3.2, whereas the OER of glucose-deprived cells was reduced to 2.0. The pH of the cell culture medium was kept at 7.4 throughout the experiments. The present finding may provide a clue toward further enhancing the radiosensitization of hypoxic cells by heat.