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PubMed1998

Modified double burst stimulation of varying stimulating currents.

BACKGROUND: Using modified double burst stimulation (modified DBS), sufficient level of recovery from neuromuscular blockade (train-of-four (TOF) ratio > 0.7) can properly be diagnosed. Modified DBS may often be applied in awake patients in the postanesthetic care unit. As the stimulating current decreases, the neurostimulation-induced discomfort becomes less for awake subjects. It is relevant to investigate the usefulness of the modified DBS delivered at low currents. METHODS: One hundred and twenty-one adult patients undergoing nitrous oxide-oxygen-isoflurane anesthesia were randomly divided into one of four groups: group 50 (n = 40), group 30 (n = 40), group 20 (n = 40), and supramaximality group (n = 1). After administration of vecuronium, in one hand and forearm (fixed arm), the degree of neuromuscular blockade was quantified mechanically. In the contralateral arm (free arm), modified DBS stimuli were delivered at 50, 30, and 20 mA in groups 50, 30, and 20, respectively. An observer determined tactilely on the free arm the presence or absence of fade in response to the modified DBS applied at 50, 30, and 20 mA. In one patient (the supramaximality group), modified DBS ratios (D2/D1) were examined at 50, 40, 30, 20, and 10 mA before administration of vecuronium. Moreover, discomfort associated with modified DBS applied at 50, 30, and 20 mA was evaluated using a 10-cm visual analog scale (VAS) in 15 awake volunteers. RESULTS: Probabilities of detection of fade in response to modified DBS in groups 50, 30, and 20 were 90, 86, and 96% (TOF ratios of 0.61-0.70), 62, 73, 94*#% (0.71-0.80), 26, 39, and 79*#% (0.81-0.90), and 4, 33*, and 51*#% (0.91-1.00), respectively. *P < 0.05 as compared to group 50. #P < 0.05 as compared to group 30. Supramaximal responses to D1 and D2 could be elicited at a current > or = 30 mA. The mean VAS scores were 8.7, 6.5*, and 4.1* when stimulated at 50, 30, and 20 mA, respectively. *P < 0.05 as compared to 50 mA. #P < 0.05 as compared to 30 mA. CONCLUSION: Modified DBS-induced discomfort becomes less as the stimulating current decreases. However, when stimulated at 30 or 20 mA, fade in response to modified DBS is felt in too many cases, even after neuromuscular blockage subsides to an adequate level.

Adult↗
PubMed1987

Gastric acid and pancreatic polypeptide responses to modified sham feeding. Effects of truncal and parietal cell vagotomy.

The effects of truncal vagotomy and parietal cell vagotomy on gastric acid secretion and plasma gastrin and pancreatic polypeptide release were studied in 28 duodenal ulcer patients under basal conditions and after modified sham feeding and infusion of pentagastrin (2 micrograms/kg/h). Before vagotomy gastric acid output in response to modified sham feeding was significantly higher than basal acid secretion in all subjects tested and reached about 45% of the pentagastrin maximum. No difference in the increase in acid response, or in the pancreatic polypeptide response to modified sham feeding was found between patients with high and low basal secretion. Plasma gastrin concentration was unaltered by modified sham feeding before and after truncal vagotomy or parietal cell vagotomy, although after vagotomy it tended to reach higher values than before this procedure. After truncal vagotomy, basal pancreatic polypeptide concentration was decreased and modified sham feeding-induced pancreatic polypeptide increment was completely eliminated. Four weeks after parietal cell vagotomy, the modified sham feeding-induced increment in plasma pancreatic polypeptide was significantly decreased and observed only in seven of 12 patients. Four to five years after parietal cell vagotomy all subjects responded to modified sham feeding with pancreatic polypeptide increment similar to that before vagotomy and in three of 12 patients acid response to modified sham feeding was seen. This study indicates that truncal vagotomy eliminates gastric acid and plasma pancreatic polypeptide responses to vagal excitation while parietal cell vagotomy abolishes gastric acid response and reduces temporarily the pancreatic polypeptide response to modified sham feeding (possibly because of transient impairment of the vagal innervation of the pancreas). (2) A high ratio of basal to maximal acid output in non-operated duodenal ulcer patients is not associated with a low acid response to modified sham feeding, nor with a high pancreatic polypeptide concentration, and (3) Restitution of the pancreatic polypeptide response to modified sham feeding five years after parietal cell vagotomy does not indication ineffective denervation of the parietal cells.

Adolescent↗
PubMed2003

Novel phosphoramidite building blocks in synthesis and applications toward modified oligonucleotides.

In recent years modified oligonucleotides (oligos) have become an area of increased research activity. These synthetic biopolymers have long been used as molecular probes to understand better the interaction between proteins and nucleic acids at molecular level, which in fact is responsible for all aspects of cellular or viral gene expression. Modified oligos have also been used as therapeutic and diagnostic agents. For example, the antisense oligos are used to block gene expression by binding especially with complimentary sequences of target mRNA. Also, over the past decade efforts are made to modify the native phosphodiester linkages to improve nuclease resistance and membrane permeation of naturally occurring oligonucleotide for therapeutic applications. Therefore, design and synthesis of modified oligonucleotides for a wide range of applications are of interest for bioorganic chemists and biologists. The advent of the phosphoramidite chemistry has accelerated the development of oligos with modified nucleobases, phosphate-protecting groups and modified sugars. In this review, we have presented the recently reported nucleoside based phosphoramidites with modified base, sugar or backbone units and their subsequent conversion into modified DNA and RNA analogs. The effect of such modification on structural, thermodynamic, and hybridization properties of the modified oligos and their duplex with natural complementary oligos have also been discussed for some cases. Similarly, we have highlighted the role of modified nucleoside phosphoramidite building blocks in synthesis of oligos modified with optically or electrochemically active molecules. Nucleoside phosphoramidites or small oligos immobilized over solid supports through different linkages or groups and their biological applications has also been mentioned.

Amides↗
PubMed2004

A modified CT severity index for evaluating acute pancreatitis: improved correlation with patient outcome.

OBJECTIVE: This study was conducted to assess the correlation with patient outcome and interobserver variability of a modified CT severity index in the evaluation of patients with acute pancreatitis compared with the currently accepted CT severity index. MATERIALS AND METHODS: Of 266 consecutive patients diagnosed with acute pancreatitis during a 1-year period, 66 underwent contrast-enhanced MDCT within 1 week of the onset of symptoms. Three radiologists who were blinded to patient outcome independently scored the severity of the pancreatitis using both the currently accepted and modified CT severity indexes. The modified index included a simplified assessment of pancreatic inflammation and necrosis as well as an assessment of extrapancreatic complications. Outcome parameters included the length of hospital stay; the need for surgery or percutaneous intervention; and the occurrences of infection, organ failure, and death. For both the current and modified indexes, correlation between the severity of the pancreatitis and patient outcome was estimated using the Wilcoxon's rank sum test and Fisher's exact test. Interobserver agreement for both indexes was calculated using the kappa statistic. RESULTS: When applying the modified index, the severity of pancreatitis and the following parameters correlated more closely than when the currently accepted index was applied: the length of the hospital stay (0-34 days) (modified index [p = 0.0054-0.0714] vs current index [p = 0.0052-0.3008]); the need for surgical or percutaneous procedures (10/66 patients) (modified index [p = 0.0112] vs current index [p = 0.0324]); and the occurrence of infection (21/66 patients) (modified index [p < 1e(-10)] vs current index [p < 1e(-04)]). Significant correlation between the severity of pancreatitis and the development of organ failure (9/66 patients) was seen only using the modified index (p = 0.0024), not the current index (p = 0.0513). The interobserver agreement was similar with the modified (kappa range, 0.71-0.85) and the current (kappa range, 0.63-0.86) indexes. CONCLUSION: The modified CT severity index correlates more closely with patient outcome measures than the currently accepted CT severity index, with similar interobserver variability.

Acute Disease↗
PubMed2001

Short term surgical outcomes of modified deep sclerectomy with catgut implant.

We compared the effectiveness of and complications resulting from modified deep sclerectomy with catgut implant (modified-DSCI) with those of standard deep sclerectomy with collagen implant (DSCI) in the short term following surgery. In this retrospective study, standard-DSCI was performed on thirteen patients (17 eyes), and modified-DSCI was performed on seven patients (11 eyes). After dissection of a 5x5 mm sized superficial scleral flap, a 3x4 mm sized rectangular deep scleral flap was constructed in DSCI and a 2x3 mm sized triangular deep scleral flap in modified DSCI. A collagen implant was placed on the scleral bed in DSCI and # 0 CHROMIC Catgut Absorbable Suture was used in modified DSCI. The mean follow up was 11.0+/-6.1 months in DSCI and 9.3+/-4.7 months in modified DSCI. The mean preoperative intraocular pressure (IOP) was 38.6+/-10.9 mmHg in DSCI and 34.8+/-8.6 mmHg in modified DSCI. In the DSCI group, the IOP was 13.4+/-3.0 mmHg at final follow up, and was 11.4+/-3.2 mmHg in the modified DSCI group. The number of Nd:YAG goniopuncture was 3 cases (25%) in the modified DSCI group, and 3 cases (21.4%) in the DSCI group. The number of intraoperative microperforations was 3 in the DSCI group and 2 in the modified DSCI group. Temporary hypotony was encountered in 8 eyes (57.1%) of the DSCI group and 4 eyes (50%) of the modified DSCI group. There was no significant difference observed between the two groups in regards to the effectiveness or rate of complications seen during short term follow up.

Adult↗
PubMed1982

Active subunits in hybrid-modified malate dehydrogenase.

Inactivation of porcine heart mitochondrial malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37) by selective modification of an active center histidine residue with the reagent iodoacetamide has been further investigated to examine the existence of and the enzymatic activity of a hybrid (half)-modified dimer. The loss of enzymatic activity during iodo(1-14C) acetamide modification is linear with 14C incorporation. Enzyme was modified to various extents and the reaction was quenched. Microzonal electrophoresis was performed to separate native dimeric enzyme, hybrid-modified enzyme, and doubly modified enzyme. The distribution of each species was quantitated by scanning densitometry. The distribution generated throughout the time course of inactivation indicates that both subunits are modified independently and at the same rate. It is apparent that the hybrid-modified dimer contributes one-half of the enzymatic activity of a native dimer in the standard assay. Kinetic studies were performed and the results indicate that there is no apparent change in kinetic parameters between a subunit of the native dimer and the active subunit in the hybrid-modified dimer. Dissociation and reassociation of a mixture of native enzyme and doubly-iodoacetamide-modified enzyme indicates that there is no preferential association of a modified subunit with another modified subunit, or of a native subunit with another native subunit, but rather, association is random with respect to native and iodoacetamide-modified subunits.

Animals↗
PubMed1999

Malondialdehyde-modified LDL as a marker of acute coronary syndromes.

CONTEXT: Release of circulating malondialdehyde (MDA)-modified low-density lipoprotein (LDL) may reflect endothelial injury or plaque instability. OBJECTIVE: To determine the usefulness of MDA-modified LDL for identifying patients with unstable angina and acute myocardial infarction (AMI). DESIGN: Blinded comparison of MDA-modified LDL, C-reactive protein, and troponin I followed by multiple receiver operating curve analysis. SETTING: University hospital. PARTICIPANTS: A total of 104 consecutive patients with acute coronary syndromes (42 with unstable angina and 62 with AMI), and 64 patients with stable coronary artery disease (CAD) without evidence of ischemia. MAIN OUTCOME MEASURES: Ability of MDA-modified LDL, C-reactive protein, and troponin I to discriminate patients with stable CAD, unstable angina, or AMI. RESULTS: Malondialdehyde-modified LDL (chi2 = 10.2; P = .001), but not troponin I or C-reactive protein, discriminated between stable CAD and unstable angina. Troponin I (chi2 = 14.5; P<.001), but not MDA-modified LDL or C-reactive protein, discriminated between unstable angina and AMI. Both MDA-modified LDL and troponin I (chi2 = 14.5; P<.001 and chi2 = 5.3; P = .02, respectively) but not C-reactive protein discriminated between stable CAD and AMI. The sensitivity of MDA-modified LDL was 95% for unstable angina and 95% for AMI, with a specificity of 95%. Values for troponin I were 38% and 90%, respectively, with a specificity of 95%. The combination of MDA-modified LDL and troponin I had a sensitivity of 98% for unstable angina and 100% for AMI, with a specificity of 99%. CONCLUSION: The combination of MDA-modified LDL, which may reflect endothelial injury or plaque instability, and troponin I, which reflects myocardial cell injury, allows better discrimination between stable CAD and acute coronary syndromes than troponin I alone.

Acute Disease↗
PubMed1997

The evolution of genomic imprinting: two modifier-locus models.

We present two autosomal two-locus models in which the primary locus, A, may be imprinted according to the alleles present at the second, modifier locus, M. In the first model, the modifier is cis-acting, which assumes that imprinting occurs late in gametogenesis: whether or not A is imprinted depends only on the M allele in the (unfertilized) egg. We examine three cases in which polymorphism at A is maintained by a mutation-selection balance or heterozygote advantage. We show that a newly arising modifier allele without direct fitness effects can increase at a rate only of the order of the mutation rate at the A locus. This result mirrors that found in two-locus models of the evolution of dominance modifiers. Modifiers that also alter fitnesses, however, may spread quickly. In the second model, a monomorphic primary locus, A, is imprinted according to the mother's genotype at the second, diallelic modifier locus, M. The model is therefore trans-acting, which assumes imprinting occurs early in gametogenesis: whether or not A is imprinted depends on both of the mother's M genes. We show that a newly arising modifier will increase in frequency via selection if either imprinting is advantageous and the modifier increases the proportion of imprinted gametes or imprinting is disadvantageous and the proportion is decreased. Both of these factors-the selective effect of imprinting and the proportion of gametes imprinted-affect the rate of modifier evolution. Selectively maintained polymorphism at the modifier locus is unlikely unless the alleles interact in a nonadditive fashion.

Biological Evolution↗
PubMed1983

Sequence specificity of tRNA-modifying enzymes. An analysis of 258 tRNA sequences.

The specificity and recognition of tRNA-modifying enzymes may be accounted for in part by nucleotide sequences which are localized next to the modifiable nucleoside. In order to determine the sequence specificity of tRNA-modifying enzymes, we have surveyed 55 published tRNA sequences from Escherichia coli, Salmonella typhimurium and T4 phage. For each modified nucleoside, the nucleotide sequence surrounding the modification site was determined for all tRNAs known to contain the modified nucleoside. Subsequently all tRNAs not containing the modified nucleoside were examined for the absence of the putative recognition site. We present the detailed analysis of 12 modified nucleosides for which we found a strong correlation between the modified nucleoside and the local nucleotide sequence. This suggests that these sequences may be recognition sites for tRNA-modifying enzymes. For each of the 12 modified nucleosides we have identified a recognition sequence present in the tRNA set containing the modification and not in the set without it. All 203 other published tRNA sequences were then examined to see if the sequence specificity rules apply to other organisms, including both prokaryotes and eukaryotes. In several cases a good adherence was found, indicating conservation of the putative recognition sequences.

Animals↗
PubMed1983

Aggregation of hemoglobin S modified by bifunctional imidoesters.

Sickle hemoglobin (Hb S) was cross-linked by two types of bifunctional imidoesters, dimethyladipimidate (DMA) and dimethyl-3,3'-dithiobispropionimidate (DTBP). These modified hemoglobins were separated into monomer, dimer and polymer fractions by gel filtration. All of these modified hemoglobins showed extremely left-shifted oxygen equilibrium curves with no cooperativity. The stabilities of these hemoglobins were also decreased. The solubilities of these modified hemoglobins in high-phosphate buffers were lower than those of native Hb S. Studies on the kinetics of the aggregation of these modified hemoglobins showed that intracross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified monomeric Hb S) still retained the capability of aggregation with a delay time, while intercross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified oligomeric Hb S) aggregated without a delay time. When the kinetics of aggregation was measured for mixtures of modified and native deoxy-Hb S, DMA-modified monomeric deoxy-Hb S shortened the delay time prior to aggregation of native deoxy-Hb S. The other modified deoxy-Hb S did not affect the delay time, suggesting that these modified oligomeric hemoglobins neither participate in the formation of nuclei nor copolymerize with native deoxy-Hb S.

Cross-Linking Reagents↗
PubMed2006

Comparison of the scanning peripheral anterior chamber depth analyzer and the modified van Herick grading system in the assessment of angle closure.

PURPOSE: To compare the performance of the scanning peripheral anterior chamber depth analyzer (SPAC) and the modified van Herick grading system in the assessment of angle closure, using gonioscopy as the reference standard. DESIGN: Prospective comparative study. PARTICIPANTS: One hundred twenty phakic subjects (53 with primary angle closure and 67 with open angles) with no history of laser or intraocular surgery. METHODS: The modified van Herick grading system was used to grade the peripheral anterior chamber depth (ACD) clinically. The SPAC was used to assess ACD, and this was graded categorically as S (suspect angle closure), P (potential angle closure), or N (normal) and numerically from 1 to 12. One randomly selected eye of each subject underwent examination with the modified van Herick grading, SPAC, Goldmann applanation tonometry, optic disc examination, and gonioscopy. The SPAC measurements, modified van Herick grades (0%, 5%, 15%, 25%, 40%, 75%, and > or =100% of corneal thickness), and gonioscopy (graded as narrow or open) were correlated using the Spearman correlation coefficient. The receiver operating characteristics of the 2 methods to detect angle closure also were compared. MAIN OUTCOME MEASURES: Grading of ACD by the SPAC, the modified van Herick system, and gonioscopic grading of the angle. RESULTS: The SPAC results correlated well with the modified van Herick grading system (categorical grade, r = 0.527; numerical grade, r = 0.542; P<0.0001). For eyes graded as having narrow angles by gonioscopy, the area under the curve (AUC) for SPAC categorical grade S or P was 0.790; sensitivity and specificity were 84.9% and 73.1%, respectively. For the modified van Herick grading system, using a cutoff of peripheral ACD < or = 25% corneal thickness, the AUC was 0.872 and sensitivity and specificity were 84.9% and 89.6%. Compared with gonioscopy that found 53 of 120 cases of narrow angles, the SPAC graded more eyes as having narrow angles (63/120) than the modified van Herick system (52/120). CONCLUSIONS: The SPAC correlated well with the modified van Herick system in grading peripheral ACD. However, the SPAC appeared to overestimate the proportion of eyes with narrow angles relative to gonioscopy and the modified van Herick grading system.

Adult↗
PubMed1999

Effects of organic modifiers on retention mechanism and selectivity in micellar electrokinetic capillary chromatography studied by linear solvation energy relationships.

The effects of six organic modifiers (urea, methanol, dioxane, tetrahydrofuran, acetonitrile and 2-propanol) on the retention mechanism and separation selectivity of the bulk buffer in micellar electrokinetic capillary chromatography (MECC) with sodium dodecyl sulfate (SDS) micelles as pseudo-stationary phase have been investigated through linear solvation energy relationships (LSERs). It is found that the retention value in MECC systems with or without organic modifier is primarily dependent on the solvophobic interaction and the hydrogen bonding interaction with the solute as proton acceptor, while the dipolar interaction and the hydrogen bonding interaction with the solute as proton donor play minor roles. The effects of the organic modifiers on the solvophobic, dipolar and hydrogen bonding interactions are evaluated in terms of the relationship between regression coefficient of the LSER equations and the modifier concentration. The variations of the solvophobic interaction and the dipolar interaction with change of the modifier concentration can be approximately explained using the solubility parameter and the dipolarity/polarizability parameter of the organic modifier, respectively. However, the relationships between the hydrogen bond acidity and basicity of the bulk buffer and the organic modifiers are rather complicated. Those results may be caused from the displacement of organic modifiers to the water adsorbed on the micellar surface as well as changes in the acidity and basicity of the bulk buffer with the addition of organic modifiers. In addition, it is found that the phase ratio is influenced significantly by the use of organic modifier.

Benzene Derivatives↗
PubMed2003

Modified renal morcellation for renal cell carcinoma: laboratory experience and early clinical application.

OBJECTIVES: To present our modified technique to expedite the entrapment and morcellation process. Standard renal morcellation is typically performed using a 12-mm incision, with the specimen entrapped within a durable LapSac. Because the LapSac does not have a deployment mechanism, its application is technically demanding and time consuming. The recent elimination of the electrical morcellator has also made the morcellation process time consuming and tedious. METHODS: Using an in vitro porcine kidney morcellation model, we compared traditional morcellation (n = 10) with our modified morcellation technique (n = 10). The modified morcellation technique incorporated an EndoCatch entrapment sac and used standard manual morcellation through a 3-cm incision. The 3-cm incision allowed for extracorporeal morcellation, because the specimen could be seen through the abdominal wall defect. Subsequently, we performed 11 laparoscopic radical/total nephrectomies for renal masses using the modified morcellation technique through a 3-cm incision. RESULTS: In this in vitro model, renal specimen morcellation with the standard technique required a mean of 9.4 minutes (16.5 g/min) and modified morcellation required 3.24 minutes (51.24 g/min; P <0.0001). The mean fragment size with standard and modified morcellation was 1.47 and 4.46 g, respectively (P <0.0001). EndoCatch entrapment sack integrity was confirmed in all 10 cases (100%). Clinically, 12 patients underwent modified morcellation of radical nephrectomy specimens. All specimens were renal cell carcinoma, with a mean specimen weight of 724 g. The mean entrapment time was 2 minutes, 40 seconds, and the mean morcellation time was 11 minutes. EndoCatch entrapment sack integrity was confirmed in all cases. At a mean follow-up of 8 months, no trocar site or local recurrences have developed. CONCLUSIONS: Preliminary laboratory and clinical data have demonstrated that the modified morcellation technique is safe and expeditious. The larger fragments that result from the modified technique may facilitate tumor staging. The technique must be performed with great care to prevent sack perforation. Prospective randomized comparison of the modified and standard morcellation techniques and long-term follow-up are required before routine application of this technique.

Animals↗
PubMed2005

Haemodynamic changes during modified ultrafiltration immediately following the first stage of the Norwood reconstruction.

BACKGROUND: Modified ultrafiltration has been shown to reverse haemodilution and improve ventricular function following cardiopulmonary bypass. There has been concern, however, about the safety and efficacy of modified ultrafiltration after the first stage of Norwood reconstruction for palliation of neonates with hypoplasia of the left heart and its variants. METHODS: We reviewed the intraoperative course of all patients undergoing the first stage of Norwood reconstruction between September 1, 2000, and August 31, 2002. RESULTS: The first stage of reconstruction was performed in 99 neonates, 78 with classical hypoplasia of the left heart, and 21 with variants. Mean weight at surgery was 3.1 plus or minus 0.7 kilograms. Genetic syndromes, weight less than or equal to 2.5 kilograms, and/or major additional cardiac or non-cardiac anomalies, were present in 44 patients. We deemed these patients to constitute the group at high risk. A modified Blalock-Taussig shunt was utilized in 95 patients, and a conduit from the right ventricle to the pulmonary arteries in 4. Deep hypothermic circulatory arrest was used in all patients for a mean period of 45 minutes, plus or minus 15 minutes. Total support time on cardiopulmonary bypass plus deep hypothermic circulatory arrest was 100 minutes plus or minus 26 minutes. Modified ultrafiltration was performed in all patients. The mean duration of modified ultrafiltration was 10 plus or minus 2 minutes, and the total volume of filtrate removed was 104 plus or minus 29 millilitres per kilogram. There were no complications from modified ultrafiltration, and no patient required discontinuation of modified ultrafiltration for haemodynamic instability. During modified ultrafiltration, the haematocrit increased from 31 percent plus or minus 4 to 46 percent plus or minus 6. Heart rate decreased from 170 plus or minus 17 beats per minute to 158 plus or minus 16 beats per minute. Systolic blood pressure increased from 57 plus or minus 12 to 63 plus or minus 13 millimetres of mercury, and diastolic blood pressure from 30 plus or minus 8 to 35 plus or minus 7 millimetres of mercury. All these values are significant at a p value of less than 0.0001. Hospital morality in the patients at low risk was 3 of 55 (5.5 percent), but was 12 of 44 (27.3 percent) in the patients deemed to be at high-risk. CONCLUSIONS: Modified ultrafiltration is safe procedure following the first stage of Norwood reconstruction, with improvement in all haemodynamic parameters measured. Modified ultrafiltration is an additional incremental strategy, which may contribute to the overall improvement in outcome following surgical palliation of patients with hypoplasia of the left heart or its variants.

Cardiac Surgical Procedures↗
PubMed1975

Interaction of actin with N-ethylmaleimide modified heavy meromyosin in the presence and absence of adenosine triphosphate.

N-Ethylmaleimide modified heavy meromyosin in only 3-fold activated by actin rather than 200-fold as is normal heavy meromyosin (Silverman, R., Eisenberg, E., and Kielley, W. W. (1972), Nature (London) 240, 207). Ultracentrifuge studies demonstrated that in the absence of ATP the N-ethylmaleimide modified heavy meromyosin binds to actin at a ratio of 2 actins to 1 N-ethylmaleimide modified heavy meromyosin. However, it was found that most of the N-ethylmaleimide modified heavy meromyosin was not bound to actin during ATP hydrolysis. Ultracentrifuge studies demonstrated that in the presence of 25 or 50 mM KCl under conditions where the ATPase is maximally activated by actin, less than 5% of the N-ethylmaleimide modified heavy meromyosin was bound to actin. In the absence of KCl there was limited binding but even this binding did not appear to correlate with the N-ethylmaleimide modified heavy meromyosin ATPase rate. Turbidity and viscosity studies also indicated that in the presence of ATP under conditions of maximal actin activation the N-ethylmaleimide modified heavy meromyosin and actin are almost completely dissociated, whereas there is a marked increase in turbidity and viscosity after all of the ATP is hydrolyzed. These results suggest that in the presence of ATP and actin N-ethylmaleimide modified heavy meromyosin exists most of the time in a refractory state unable to bind to actin and only a small part of the time in a nonrefractory state which can interact with actin. It follows that the major rate-limiting step during actin activation is the transition from the refractory to the nonrefractory state. Since the actin activation of N-ethylmaleimide modified heavy meromyosin is lower than that of normal heavy meromyosin this transition may be slower for N-ethylmaleimide modified heavy meromyosin than for normal heavy meromyosin.

Actins↗
PubMed2006

Electrogenerated chemiluminescence of luminol on a gold-nanorod-modified gold electrode.

Electrogenerated chemiluminescence (ECL) of luminol on a gold-nanorod-modified gold electrode was studied, and five ECL peaks were obtained under conventional cyclic voltammetry in both neutral and alkaline solutions. Among them, four ECL peaks (ECL-1-4) were also observed on a gold-nanosphere-modified gold electrode, but the intensities of these ECL peaks were enhanced about 2-10-fold on a gold-nanorod-modified gold electrode in neutral solution. One new strong ECL peak (ECL-5) was obtained at -0.28 V (vs SCE) on a gold-nanorod-modified gold electrode in both neutral and alkaline solutions and enhanced with an increase in pH. In strong alkaline solutions, ECL-1 and ECL-2 on a gold-nanosphere-modified electrode were much stronger than those on a gold-nanorod-modified gold electrode, while ECL-3-5 appeared to only happen on a gold-nanorod-modified gold electrode. The emitter of all the ECL peaks was identified as 3-aminophthalate. The ECL peaks were found to depend on the scan direction, the electrolytes, the pH, and the presence of O(2) and N(2). The reaction pathways for ECL-4 have been further elucidated, and the mechanism of the new ECL peak (ECL-5) has been proposed. The results indicate that a gold-nanorod-modified gold electrode has a catalytic effect on luminol ECL different from that of a gold-nanosphere-modified gold electrode, revealing that the shape of the metal nanoparticles has an important effect on the luminol ECL behavior. The strong ECL of luminol in neutral solution obtained on a gold-nanorod-modified electrode may be used for the sensitive detection of biologically important compounds in physiological conditions.

Bromides↗
PubMed1996

Measuring selective effects of modifier gene polymorphisms on the Bare locus of Drosophila subobscura.

An attempt to quantify the effects of modifier gene polymorphisms on the operation of natural selection on a major locus has been carried out. The modifier system we have investigated is constituted by a set of polygenic modifier loci affecting the morphological expression of the Bare (Ba) bristle mutant of Drosophila subobscura. Ba is a dominant mutant that is lethal in homozygous condition and both the polygenic modifiers and Ba are located on the O chromosome of this species. Experimental populations were found with Ba/+ individuals and two different types of populations were started according to their modifier genetic background: populations with wild O chromosomes of either high or low modifier effect (cages H and L, respectively). Fitness estimates (total fitness, viability and fertility) for genotypes of the Ba locus were obtained under the two different modifier backgrounds. In the populations with high modifier background the total fitness of the Ba/+ heterozygote was very similar to that of the +/+ homozygote (fitness equal to 1). However, in cages with low modifier background a strong selection against the Ba/+ heterozygote was detected (average of total fitnesses over generations was 0.66 +/- 0.10), and fertility appears to be the fitness component responsible for this effect (mean fertility was 0.55 +/- 0.08). These findings demonstrate that modifier gene polymorphisms affecting the expression of the Ba mutant may be associated with large selective effects on the major locus.

Animals↗
PubMed1980

Conformation of poly(dG-dC) . poly(dG-dC) modified by the carcinogens N-acetoxy-N-acetyl-2-aminofluorene and N-hydroxy-N-2-aminofluorene.

Poly(dG-dC) . poly(dG-dC) was modified by reaction with N-acetoxy-N-acetyl-2-aminofluorene (N-AcO-AAF). Two samples with 6.6% and 8.5% modified bases were prepared. The modified bases are randomly distributed along the polymer chain, as deduced from competition experiments between antibodies against N-2-(guanosin-8-yl)-acetylaminofluorene, modified poly(dG-dC) . poly(dG-dC), and modified DNAs. Circular dichroism studies show that poly(dG-dC) . poly(dG-dC) modified by N-AcO-AAF is much more sensitive to the addition of alcohol than poly(dG-dC) . poly(dG-dC). In about 50% (vol/vol) alcohol, both polynucleotides have the same conformation, which is the Z form or a Z-like form. Moreover, in low salt and in the absence of alcohol, poly(dG-dC) . poly(dG-dC) modified by N-AcO-AAF is partially in the Z form. Poly(dG-dC) . poly(dG-dC) modified by N-hydroxy-N-2-aminofluorene can also adopt the Z form, but the transition is induced at a higher percentage than that of poly(dG-dC) . poly(dG-dC) modified by N-AcO-AAF. In low salt and in the absence of alcohol, no Z form was detected in poly(dG-dC) . poly(dG-dC) modified by N-hydroxy-N-2-aminofluorene.

2-Acetylaminofluorene↗