Conformational studies of nucleic acids: IV. The conformational energetics of oligonucleotides: d(ApApApA) and ApApApA

Utilizing a new method for modeling furanose pseudorotation (D. A. Pearlman and S.-H. Kim, J. Biomol. Struct. Dyn. 3, 85 (1985)) and the empirical multiple correlations between nucleic acid torsion angles we derived in the previous report (D. A. Pearlman and S.-H. Kim, previous paper in this issue), we have made an energetic examination of the entire conformational spaces available to two nucleic acid oligonucleotides: d(ApApApA) and ApApApA. The energies are calculated using a semi-empirical potential function. From the resulting body of data, energy contour map pairs (one for the DNA molecule, one for the RNA structure) have been created for each of the 21 possible torsion angle pairs in a nucleotide repeating unit. Of the 21 pairs, 15 have not been reported previously. The contour plots are different from those made earlier in that for each point in a particular angle-angle plot, the remaining five variable torsion angles are rotated to the values which give a minimum energy at this point. The contour maps are overall quite consistent with the experimental distribution of oligonucleotide data. A number of these maps are of particular interest: delta (C5'-C4'-C3'-O3')-chi (O4'-C1'-N9-C4), where the energetic basis for an approximately linear delta-chi correlation can be seen: zeta (C3'-O3'-P-O5')-delta, in which the experimentally observed linear correlation between zeta and delta in DNA(220 degrees less than zeta less than 280 degrees) is clearly predicted; zeta-epsilon (C4'-C3'-O3'-P), which shows that epsilon increases with decreasing zeta less than 260 degrees; alpha (O3'-P-O5'-C5')-gamma (O5'-C5'-C4'-C3') where a clear linear correlation between these angles is also apparent, consistent with experiment; and several others. For the DNA molecule studied here, the sugar torsion delta is predicted to be the most flexible, while for the RNA molecule, the greatest amount of flexibility is expected to reside in alpha and gamma. Both the DNA and RNA molecules are predicted to be highly polymorphic. Complete energy minimization has been performed on each of the minima found in the energy searches and the results further support this prediction. Possible pathways for B-form to A-form DNA interconversion suggested by the results of this study are discussed. The results of these calculations support use of the new sugar modeling technique and torsion angle correlations in future conformational studies of nucleic acids.

Changes of renin isoelectric heterogeneity after acute and chronic stimulation of renin secretion

Changes in the multiple forms of renin secreted or stored in vitro by renal cortical slices were studied in rats made hypertensive with deoxycorticosterone, adrenalectomized rats, and rats fed a high or low salt diet. Renal slices from normal rats were also incubated with angiotensin II, vasopressin, and verapamil. Aliquots of incubation media were subjected to isoelectric focusing, and the six forms of renin were quantified and expressed as a percentage of the total renin activity recovered from the gel. The results showed that chronic and acute stimulation of renin secretion produced a similar modification of the isoelectric focusing profile, consisting of an increased proportion of renin forms with the more acidic isoelectric points. The change in the proportions of the more acidic renin forms was greater with chronic stimulation than that after stimulation with verapamil. However, chronic and acute inhibition or reductions of the rate of renin secretion did not modify the renin profile. We suggest that the progression in the shift of secreted renin forms to those with the more acidic isoelectric points correlates with the intensity or duration of stimulation of renin secretion. These data support the hypothesis that different pools of renin exist and are altered differently by chronic and acute stimulation of renin secretion.

The organization of the human HPRT gene

The organization of the X-linked gene for human hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8.) has been determined by a combination of restriction endonuclease mapping, heteroduplex analysis and DNA sequence analysis of overlapping genomic clones. The entire gene is 42 kilobases in length and split into 9 exons. The sizes of the 7 internal exons and the exon-intron boundaries are identical to those of mouse HPRT gene. The 5' end of the gene lacks the prototypical 5' transcriptional regulatory sequence elements but contains extremely GC-rich sequences and five GC hexanucleotide motifs (5'-GGCGGG-3'). These structural features are very similar to those found in the mouse HPRT gene and to some of the regulatory signals common to a class of constitutively expressed "housekeeping" genes. Several transcriptional start sites have been identified by nuclease protection studies. Extensive sequence homology between the mouse and human genes is found in the 3' non-coding portion of the gene.

Acetylcholinesterase and manometry in the diagnosis of the constipated child

We studied 309 constipated infants and children who underwent rectal manometry (n = 261) and/or punch rectal biopsy, in which acetylcholinesterase histochemistry (n = 124) was compared with routine histologic examination (n = 93) for diagnostic accuracy. A 99% diagnostic accuracy was achieved with acetylcholinesterase histochemistry compared with 61% accuracy with routine hematoxylin-eosin staining on punch rectal biopsy. We recommend screening cooperative, quiet patients with rectal manometry. Most patients with abnormal manometric studies or those on whom manometry cannot be performed should have superficial punch biopsy (except those ill infants who require urgent operative intervention). This plan of management provides the least invasive but the most accurate evaluation of the constipated child. Deep rectal biopsy can be avoided except in the very rare child with hypoganglionosis or "skip-area" aganglionosis, which can be detected by manometry.

Potentiation of radiation effects on two murine tumors by lonidamine

Lonidamine is a potent inhibitor of spermatogenesis and a hyperthermic sensitizer. The principal established locus of biochemical action of lonidamine is a selective inhibitory effect of the energy metabolism either in NAD-linked reactions in germ cell mitochondria, as well as the glycolytic metabolism of a variety of tumor cell lines by means of inhibition of mitochondrially bound hexokinase. We carried out in vivo tumor experiments to determine whether lonidamine when combined with radiation could potentiate the cytotoxic effects of radiation on two murine tumors. The combined effects of single acute lonidamine (100 mg/kg) and single dose X-irradiation were evaluated on the transplanted methylcholanthrene-induced fibrosarcoma in BALB/c mice and on the radiation-induced fibrosarcoma in C3H/He mice. The radiosensitizing effect by lonidamine was maximal when lonidamine was administered immediately prior to or after X-irradiation. The dose modifying factor of lonidamine is estimated to be 1.36 for methylcholanthrene-induced fibrosarcoma tumors and 1.25 for radiation-induced fibrosarcoma tumors. There was no disproportionately enhanced skin reaction following the combined treatments. The present results of the potentiating effects of radiation may be attributed, in part, to the findings of cell culture studies that lonidamine is a potent inhibitor of repair of potentially lethal damage.

Local mobility of nucleic acids as determined from crystallographic data. II. Z-form DNA

Directions and magnitudes of the local mobility of the Z-DNA hexamer duplex CpGpCpGpCpG have been determined by crystallographic refinement of anisotropic displacement parameters using the observed X-ray diffraction data. The cytidine and guanosine residues demonstrate different modes of mobility, implying that a dinucleotide is the smallest repeating unit in terms of flexibility as well as structure. Directions of librational and translational mobility of the cytidine and guanosine residues of Z-DNA are similar to those observed for the same nucleotides in B-DNA. This suggests that the local mobility of DNA is primarily determined by the individual nucleotide type and by the constraints of Watson-Crick base-pairing, rather than by helical form. Differences in the magnitudes of mobility may be responsible for some of the different physical properties of B-DNA and Z-DNA. The B to Z transition is discussed in terms of the observed flexibilities of these two helical forms.

Acquired ureteropelvic junction obstruction in childhood

Ureteropelvic junction (UPJ) obstruction is generally considered to be a congenital lesion or occasionally an intermittent phenomena relating to periods of increased urine flow. Acquired ureteropelvic junction obstruction without a recognizable secondary cause is quite unusual. We present a 5.5-year-old boy who, 4 years after repair of a right sided UPJ obstruction, developed a significant left-sided UPJ obstruction in a system which previously had been normal.

Chemical liver function tests and epidemiologic studies of HBsAg positive blood donors

The HBsAg positivity in age, sex, occupation, blood type, past history and chemical liver function tests were analyzed in 869 cases without symptoms of liver disease and positive testing for HBsAg by RPHA method, who were selected among 11, 197 blood donors of the Red-Cross Blood Bank in Pusan, Korea from August 1, to September 30, 1982. The following results were obtained: 1. The overall HBsAg positivity in random blood donors was 7.76%. 2. The HBsAg positivity of males was 8.36% and females 6.0%; males had a slightly higher positivity than females. 3. The HBsAg positivity of the 16–20 year old age group had the highest frequency (9.05%), 21–25 year old age group 8.23%, 26–30 year old age group 5.72%, 31–35 year old age group 5.76%, 36–40 year old group 5.85%, 41–45 years old age group 4.76%, and 46–50 year old age group 3.7%. HBsAg positivity had decreasing tendency of frequency by increasing age. 4. The HBsAg positivity of the merchant group had the highest frequency (10.26%), and next, the unemployed, salary man, student, soldier, in order of frequency. 5. The HBsAg positivity in cases with blood type A had the highest frequency (8.07%), and next, cases with B type, O type, and AB type in order of frequency. 6. The HBsAg positivity in cases with no past history in liver disease had the highest frequency (75.37%), and next, cases with history of liver diseases among family 12.54%, hepatitis with jaundice 5.06%, admission due to other diseases except liver diseases 3.57%, transfusion 2.42%, hepatitis without jaundice 1.04%. 7. In chemical liver function tests of HBsAg positive blood donors, elevation of SGPT level showed highest frequency (10.70%), SGOT 7.7%, total serum bilirubin 5.29% and elevation of one or more than of SGPT, SGOT, total serum bilirubin 18.99%.

Gossypol, a hyperthermic sensitizer of HeLa cells

Gossypol, a polyphenolic aldehyde extracted from cotton plants, is a potent antifertility agent in humans. Since we have previously reported that several male antifertility agents including 5-thio-D-glucose and lonidamine demonstrate hyperthermic sensitizing effects in HeLa cells, we wished to determine whether gossypol also exhibits the hyperthermic sensitization. Gossypol was not cytotoxic up to 4 h at 37 degrees C (10 micrograms/ml). When HeLa cells were exposed to gossypol at 41 degrees and 42 degrees C, significant potentiation of hyperthermia induced cytotoxicity was observed. The magnitude of the potentiation was dependent on the drug concentration, pH of the culture medium, glucose concentration, temperature, and duration of treatment. The hyperthermic sensitizing effect of gossypol was increased by an acidic pH and glucose deprivation. These data suggest that the sensitizing effect of the drug may be mediated through the lowering of cellular energy level by the inhibition of both glycolysis and oxidative phosphorylation.

Frozen section technique to evaluate early burn wound biopsy: a comparison with the rapid section technique

The importance of early diagnosis and treatment of burn wound infection has prompted many efforts to use frozen section technique for processing burn wound biopsies, most of which have been unsuccessful. A frozen section technique which facilitates quick, reliable evaluation of biopsies was developed, and has been used in the evaluation of 169 biopsies over a period of 18 months. The frozen section technique takes 30 minutes compared with 4 hours for the rapid section method. Comparison of diagnoses made using both methods for each of the 169 biopsies produced a 96% coincidence. Each discrepant diagnosis was corrected by the rapid technique approximately 3 1/2 hours after the frozen section diagnosis. The frozen section technique is a generally accurate and rapid means of assessing the microbial status of a burn wound and diagnosing invasive infection. Permanent sections produced by rapid section technique should always be examined to confirm the frozen section diagnosis.

Enhancement of pyrimidine nucleoside uptake into K562 and YAC-1 cells by cadeguomycin

Cadeguomycin markedly stimulated the uptake of thymidine, deoxycytidine and uridine into the acid-insoluble fraction of K562 human leukemic cells, but did not significantly affect adenosine incorporation. The enhancement of pyrimidine nucleoside uptake was 6 approximately 17 fold over the control. Aspartate incorporation into nucleic acid was not significantly blocked by the antibiotic, suggesting that the stimulation of pyrimidine nucleoside incorporation is not due to the inhibition of de novo pyrimidine nucleotide synthesis. Net DNA and RNA syntheses, observed by [32P]phosphate uptake, were not significantly affected by cadeguomycin. The enzymatic activity of thymidine, deoxycytidine and uridine kinases was higher in cadeguomycin-treated cells than in untreated cells, suggesting that the enhancement of pyrimidine nucleoside uptake occurs in the phosphorylation process. The stimulatory activity of cadeguomycin of thymidine uptake was reversed by guanosine and deoxyguanosine, but not by adenosine and deoxyadenosine, suggesting that intracellular metabolism and/or action of cadeguomycin is related to that of guanosine and deoxyguanosine. The stimulation of pyrimidine nucleoside incorporation by cadeguomycin was also found with YAC-1 cells, but not with the other cell lines. The enhancement effect of the antibiotic seems to be not directly related to its cytotoxicity.

Comparative maternal and neonatal effects of halothane and enflurane for cesarean section

The effects of placental transfer of enflurane and halothane were studied in 81 women undergoing cesarean sections. All patients had rapid sequence induction using thiopental, succinylcholine, and endotracheal intubation. They were then randomly assigned to one of five groups: Group I (n = 16) received N2O and oxygen, Group II (n = 16) N2O, oxygen, and 0.25% halothane, Group III (n = 18) N2O, oxygen, and 0.5% halothane, Group IV (n = 18) N2O, oxygen, and 0.5% enflurane, Group V (n = 13) N2O, oxygen, and 1% enflurane. At delivery, blood was drawn from the maternal artery, umbilical vein and artery for measurement of the halogenated agents using gas chromatography. The neonates were evaluated by Apgar scores, umbilical artery and vein acid base status and the Early Neonatal Neurobehavioral Scores (ENNS) at 2 and 24 h of age. Blood loss and the incidence of maternal awareness were also determined. The umbilical vein to maternal vein ratio was approximately 0.5 and 0.6 for enflurane and halothane, respectively. The umbilical artery to umbilical vein ratio was 0.5 with both agents; higher inspired anesthetic concentrations produced higher blood levels. All neonates had Apgar scores of 8 or more at 5 min with the exception of one neonate in the N2O group. Maternal and neonatal acid base status, blood loss, and ENNS were not affected by the addition of the halogenated agents. Of the patients who had N2O alone, 12% had awareness versus none in the other groups. These data demonstrate that low dose halothane or enflurane decreases the incidence of maternal awareness and does not adversely affect the neonate.

Brain tissue acidosis and changes of energy metabolism in mild incomplete ischemia--topographical study

Regional changes of brain tissue pH and its correlation to energy metabolism were studied in various degrees of incomplete ischemia for 5 and 60 min in the unilateral common carotid occlusion of normally fed mongolian gerbils. The degree of ischemia was evaluated by the severity of neurological deficits following 60 min of occlusion, and animals were divided into three groups: symptomatic, borderline, and asymptomatic. Changes of NADH and ATP distribution corresponded well to the degree of ischemia. On the other hand, acidosis developed more clearly and extended in wider areas than the changes of NADH and ATP distribution. These changes were already seen at 5 min of occlusion. From the results of this experiment, it was suspected that acidosis in mild incomplete ischemia was due to stimulated anaerobic glycolysis that might supplement NADH oxidation and ATP yields. Further, acidosis without energy failure was considered not to be detrimental to neuronal cells.

Effects of vitamin E on the distribution and metabolism of nitrofurantoin in rats

Previous studies have shown a significant increase in the pulmonary toxicity of nitrofurantoin (NF) in animals fed a diet lacking vitamin E. The authors have therefore examined the pharmacokinetics of NF in control and vitamin E-deficient male Sprague-Dawley rats. NF was rapidly absorbed following subcutaneous injection and was cleared from all tissues examined (blood, lung, liver and kidney) in a biphasic manner. Substantial metabolism of the drug was observed, and the disposition of NF metabolites was qualitatively similar to that of the parent compound. The most apparent difference between control and vitamin E-deficient animals was a significant increase in tissue metabolite levels 4-16 hr after treatment. Unchanged NF was also elevated in all tissues examined 16 hr after treatment in the vitamin E-deficient animals. Urinary excretion of NF and metabolites accounted for 68% of the total dose in control rats and 35% in vitamin E-deficient rats. This study illustrates a marked alteration in NF disposition in animals fed a diet lacking vitamin E when compared with controls. The observed alterations appear to be related to a decreased renal clearance of both NF and metabolites.

Conformational studies of nucleic acids. I. A rapid and direct method for generating furanose coordinates from the pseudorotation angle

The greatest difficulty in modeling a nucleic acid is generating the coordinates of its furanoses. This difficulty arises from constraints imposed by the closed ring geometries of these sugars. We have developed a new method for modeling these furanose rings. Using this method, the coordinates of a sugar can be obtained quickly and unambiguously for any point on the pseudorotational pathway from one parameter: the phase angle of pseudorotation P. The significant difference between this and previous sugar modeling schemes is that here the endocyclic bond lengths of the five-membered sugar ring are allowed to vary a small amount according to simple, explicit, and experimentally reasonable analytic functions of P. The coefficients of these functions follow from the empirical behavior of the endocyclic bond angles and from geometrical constraints due to ring closure. The ability to model the sugars directly from one parameter greatly facilitates carrying out the global conformational studies on nucleic acid constituents which will be attempted in subsequent papers of this series.

Conformational studies of nucleic acids. II. The conformational energetics of commonly occurring nucleosides

We have examined the conformational energetics of the eight most commonly occurring nucleosides--A, U, G, C, dA, dT, dG, dC--as monitored by a semi-empirical energy force field. These are the first reported calculations to completely explore the entire conformational spaces available to all eight major nucleosides using experimentally consistent furanose geometries and an appropriate force field. Central to our approach is the ability to model an experimentally reasonable furanose for each nucleoside directly from only one parameter, the phase angle of pseudorotation P, as described in the previous paper (D.A. Pearlman, and S.-H. Kim, preceeding paper in this issue). This allows us to specify the conformation of a nucleoside by three variables: torsion angle gamma (O5'-C5'-C4'-C3'); torsion angle chi (O4'-C1'-N9/N1-C4/C2); and P. In our study each of these parameters was allowed to vary independently and in small increments over the range 0-360 degrees. The empirically observed preferences for C3'-endo and C2'-endo sugar conformations, for anti and syn values of chi and for staggered (g+, t, g-) values of gamma can be explained on the basis of the energy maps so obtained. Finer details, such as the different conformational preferences of ribonucleosides and deoxyribonucleosides and of purines and pyrimidines, can also be extracted from these maps and are consistent with experiment. The calculations support previous descriptions of pseudorotation as hindered. Statistical Boltzmann population factors for different conformational ranges in gamma, chi, and P, as predicted by the calculations, are consistent with factors obtained from crystallographic data. The excellent results here provide additional support for the suitability of the new sugar modeling technique used.

Comparative study on amino acid sequences of Kunitz-type soybean trypsin inhibitors, Tia, Tib, and Tic

The amino acid sequences of three variants of the Kunitz-type trypsin inhibitors, Tia, Tib, and Tic, obtained from some cultivars of soybean were determined by conventional methods. All three inhibitors consisted of 181 amino acid residues. The differences in the amino acid sequences are as follows: Tia E12 G55 Y62 H71 S74 M114 L120 P137 L176; Tib S F N R V I T V; Tic E. The amino acid sequences of Pro(60)-Ser(61) and Asp(154)-Asp(155)-Gly(156)-His(157) of Tia reported previously (Koide & Ikenaka (1973) Eur. J. Biochem. 32, 417-431) were amended to Ser(60)-Pro(61) and His(154)-Asp-Asp-Gly(157), respectively.

Interaction of hyperthermia and rhodamine 123 in HeLa S-3 cells in culture

It has previously been shown that the capacity to continue energy production by either oxidative or glycolytic metabolism is a pre-requisite for cellular survival at elevated temperatures. Since rhodamine 123 is a specific mitochondrial binding agent that inhibits oxidative phosphorylation, the present experiments were carried out to examine the influence of cell exposure to the drug which reduces the energy production at elevated temperatures. Exposure of HeLa cells to rhodamine 123 (10 micrograms/ml) up to 4 h was not cytotoxic in the presence or absence of glucose in the medium at 37 degrees C. Prolonged exposure of cells to the drug up to 24 h was quite cytotoxic when glucose was removed from the medium. When cells were exposed to rhodamine 123 at elevated temperatures (up to 42 degrees C) for 4 h, there was a pronounced enhancement of cell kill in the glucose-deprived cells. No enhanced effects of heat were seen in the glucose-fed cells. Hyperthermic treatment under the acidic pH did not further enhance the cytotoxic effects of heat in the glucose-deprived cells; instead, the cell kill under the influence of reduced pH was far less than the cytotoxicity observed at pH 7.4. Selective enhancement of hyperthermic cytotoxicity in glucose-deprived cells by rhodamine 123 appears to be in agreement with the concept that cell kill by heat is dependent on the critical level of cellular energy equilibrium.

Interaction of radiation and AT 1727 in HeLa S-3 cells in culture

AT 1727, a synthetic analogue of ICRF 159, was reported to have an increased chemotherapeutic index in in vivo leukemic cells. The present cell culture studies were carried out to compare the cytotoxicity of AT 1727 and ICRF 159 in HeLa S-3 cells grown in monolayer and multicellular spheroid systems. The quantitative comparison of cell culture data demonstrated that AT 1727 was more cytotoxic than ICRF 159 at equimolar doses. The increased cytotoxicity at AT 1727 became apparent when the cell survival curves and growth rates of multicellular spheroids were compared at doses above 0.1 mM. When the spheroids were irradiated and exposed to AT 1727 (0.05 mM), there was a pronounced potentiation of radiation effects in the growth rate of spheroids. Similar treatment to ICRF 159 did not show any enhancement of radiation effects. There were also differential effects of AT 1727 and ICRF 159 on the cell cycle progression. AT 1727 causes a G1 block as well as a G2 block in HeLa monolayers, while ICRF 159 only induces G2 block. These cell culture data may be useful for further in vivo tumor studies to determine the therapeutic index of combined radiation and AT 1727.

Management of toxic epidermal necrolysis in a pediatric burn center

Toxic epidermal necrolysis (TEN) is an acute severe exfoliative skin and mucosal membrane disorder with a clinical picture similar to a total-body scald injury. Toxic epidermal necrolysis shares features with severe erythema multiforme seen in Stevens-Johnson syndrome, and is thought by some to be a maximal expression of this syndrome. Drug-related TEN is uncommon in children. Mortalities of 70% have been reported, and death is usually secondary to the bacterial and metabolic consequences of a large open wound. Over the past two years, four children with probable drug-induced TEN were treated successfully. Since the problems of infection, wound care, fluid balance, nutrition, and pain control are similar in TEN and major burn patients, treatment using the principles of burn care may improve survival.

Molecular models for DNA damaged by photoreaction

Structural models of a DNA molecule containing a radiation-induced psoralen cross-link and of a DNA containing a thymine photodimer were constructed by applying energy-minimization techniques and model-building procedures to data from x-ray crystallographic studies. The helical axes of the models show substantial kinking and unwinding at the sites of the damage, which may have long-range as well as local effects arising from the concomitant changes in the supercoiling and overall structure of the DNA. The damaged areas may also serve as recognition sites for repair enzymes. These results should help in understanding the biologic effects of radiation-induced damage on cells.

Three-dimensional structure of thaumatin I, an intensely sweet protein

Thaumatin and monellin are the two sweetest compounds known to man--about 100,000 times sweeter than sugar on a molar basis and 3000 times on a weight basis. These proteins represent a unique class of proteins that are taste-active. We report the three-dimensional structure of thaumatin I at 3.1 A resolution.

Changes in intracranial pressure and epidural pulse waveform following cold injury

Using anaesthetized spontaneously breathing cats, intracranial pressure (ICP) was monitored for twenty hours following the insult of cold injury; simultaneous recordings were also made of cerebral blood flow (CBF), epidural pulse waveform (EDP-WF), and systemic arterial pressure (SAP). Results could be divided into two groups depending on whether or not ICP exceeded 30 mmHg. In group one, in which marked increase in ICP including occasional episodes of pressure waves were observed, an initial increase in CBF and the changes in EDP-WF from polyphasic to monotonous at about 20 mmHg were characteristic. On the other hand, in group two, ICP never exceeded 30 mmHg, CBF slightly and continuously decreased and EDP-WF was polyphasic throughout the course. There were no significant differences in trends in SAP, in the extent of spread of oedema and in water content of the white matter between both groups. Therefore, the amount of cerebral blood volume (CBV) due to cerebral vasodilatation was considered to account for the further increase in ICP. Moreover, changes in EDP-WF were regarded as a useful indicator in predicting the trends in ICP since these changes could be observed in a relatively lower pressure range prior to a marked increase in ICP.