Stability of cisatracurium besylate in vials, syringes, and infusion admixtures

The stability of cisatracurium besylate was studied. Cisatracurium (as besylate) 2 mg/mL in 5- and 10-mL unopened vials and 10 mg/mL in 20-mL unopened vials, as well as 3 mL of solution from additional 2-mg/mL vials, repackaged in 3-mL sealed plastic syringes, was stored at 4 and 23 degrees C in the dark and in normal fluorescent room light. Admixtures of cisatracurium (as besylate) 0.1, 2, or 5 mg/mL in polyvinyl chloride (PVC) minibags of 5% dextrose injection or 0.9% sodium chloride injection were stored at 4 and 23 degrees C in normal fluorescent room light. Triplicate samples for each storage condition were taken initially and at 1, 3, 5, 7, 14, 21, and 30 days; samples from vials were also removed at 45 and 90 days. Solutions were stored in sterile vials at -70 degrees C and then thawed at room temperature before analysis of chemical stability by high-performance liquid chromatography. Physical stability was assessed as well. Cisatracurium besylate was physically stable in all samples throughout the study. Cisatracurium (as besylate) 2 mg/mL exhibited drug losses at 23 degrees C in vials at 45 days and in syringes at 30 days. Cisatracurium (as besylate) 0.1, 2, and 5 mg/mL in 5% dextrose injection and in 0.9% sodium chloride injection was stable for at least 30 days at 4 degrees C, but substantial drug losses occurred at 23 degrees C. Admixtures prepared with cisatracurium (as besylate) 0.1 mg/mL and with 5% dextrose injection exhibited the greatest losses. Cisatracurium besylate was stable in most samples for at least 30 days at 4 and 23 degrees C; admixtures containing cisatracurium (as besylate) 0.1 or 2 mg/mL exhibited substantial drug loss at 23 degrees C.

A small-scale procedure for extracting nucleic acids from woody plants infected with various phytopathogens for PCR assay

The complexity of most nucleic acid extraction procedures limits the number of samples that can be easily processed for analysis by polymerase chain reaction (PCR). A simple, small-scale procedure was developed which can be carried out entirely in 1.5-ml microfuge tubes whereby the container and contents are frozen with liquid nitrogen, tissue is pulverized, and targeted nucleic acids are extracted. DNA of bacterial and phytoplasmal plant pathogens was extracted in hot CTAB buffer followed by chloroform clarification. Following centrifugation, the DNA in the aqueous fraction was precipitated with isopropanol and resuspended in water. RNA originating from viruses and viroids was extracted from triturated tissue using STE buffer and phenol. The nucleic acid fraction was purified using CF-11 cellulose. All purified preparations were used as PCR or RT-PCR templates to detect DNA or RNA, respectively. These procedures were used to detect Xylella fastidiosa, peach yellow leaf roll phytoplasma, sour cherry green ring mottle virus, and peach latent mosaic viroid by agarose gel electrophoresis.

Identification of 'genotoxic' and 'non-genotoxic' alerts for cancer in mice: the carcinogenic potency database

A set of chemicals tested for carcinogenicity in mice that have been analyzed by Gold et al. [L.S. Gold, C.B. Sawyer, R. Magaw, G.M. Backman, M. deVeciana, R. Levinson, N.K. Hooper, W.R. Havender, L. Bernstein, R. Peto, M.C. Pike, B.N. Ames, Environ. Health Perspect. 58 (1984) 9-319; L.S. Gold, M. deVeciana, G.M. Backman, M. Lopipero, M. Smith, R. Blumenthal, R. Levinson, L. Bernstein, B.N. Ames, Environ. Health Perspect. 67 (1986) 161-200; L.S. Gold, T.H. Slone, G.M. Backman, R. Magaw, M. DaCosta, P. Lopipero, M. Blumenthal, B.N. Ames, Environ. Health Perspect. 74 (1987) 237-329; L.S. Gold, T.H. Slone, G.M. Backman, S. Eisenberg, M. DaCosta, M. Wong, N.B. Manley, L. Rohrbach, B.N. Ames, Environ. Health Perspect. 84 (1990) 215-286; L.S. Gold, N.B. Manley, T.H. Slone, T.H. Garfinkle, L. Rohrbach, B.N. Ames, Environ. Health Perspect. 100 (1993) 65-135] in the first five plots of the carcinogenic potency database (CPDB) was subjected to CASE/MULTICASE analyses. Briefly, CASE/MULTICASE is a computer-automated structure evaluation system that is capable of identifying structural features of chemicals associated with a specified biological activity (e.g., carcinogenicity or mutagenicity). These features are then incorporated into a structure-activity relationship (SAR) model for the analyzed database. The mouse CPDB used in this study consists of 627 chemicals, 289 of which are carcinogens, 11 marginal or weak carcinogens (i.e., chemicals requiring high doses to induce cancer) and 327 non-carcinogens. In an internal prediction analysis where the CASE/MULTICASE SAR model was used to predict the carcinogenicity of chemicals used to create the model, a concordance between experimental and predicted results of 96% was obtained. This indicates that the model is able to satisfactorily explain the chemicals in the learning set. In a drop-one cross-validation study where chemicals were removed one at a time and the remaining n - 1 chemicals were used in an iterative method to create a model to predict the removed chemical, CASE/MULTICASE was able to achieve a concordance between experimental and predicted results of 70%. Using a modified validation process designed to investigate the predictivity of a more focused SAR model, the system achieved a 78% concordance between experimental and predicted results. Among the major biophores identified by CASE/MULTICASE associated with cancer causation in mice several are derived from electrophilic or potentially electrophilic compounds (e.g., hydrazines, N-mustards, N-nitrosamines, aromatic amines, reactive halogens, and quinones). Other biophores however are derived from chemicals seemingly devoid of actual or potential DNA-reactivity and as such may represent structural feature of non-genotoxic carcinogens.

Assignment of three Chinese xeroderma pigmentosum patients to complementation group C and one to group E

Four Chinese patients with xeroderma pigmentosum (XP), who had different degrees of skin symptoms, were tested for their genetic complementation groups. Skin fibroblasts obtained from the patients were used for complementation analysis done by a cell-fusion technique. Three of the patients belonged to group C and one, who had the mildest cutaneous manifestations, to group E. This is the first report of a group E XP patient in China. Our present findings together with previous reports suggest that group C XP is more common in China, similar to the distribution among Caucasian XP patients but markedly different from the Japanese distribution.

In vivo detection of calcium from dicalcium phosphate dihydrate dentifrices in demineralized human enamel and plaque

A series of studies was conducted to clarify the role of DCPD in improving the effects of fluoride in the mouth. We performed plaque fluid studies to see if the use of DCPD dentifrices increases the levels of free Ca2+ ions and the DSenamel in plaque fluid. The results of these studies showed that plaque fluid was undersaturated with respect to DCPD; therefore, DCPD would dissolve in the mouth. The Ca2+ activity in plaque fluid measured 12 hours post-treatment was significantly elevated with the use of DCPD dentifrices in comparison with silica dentifrices. The use of DCPD dentifrices also increased the DSenamel of plaque fluid in comparison with a NaF/silica dentifrice. To determine whether Ca from DCPD could be detected in demineralized enamel and whole plaque after in vivo usage of a DCPD/ fluoride dentifrice, we conducted a 44Ca labeling study. Secondary Ion Mass Spectrometry (SIMS) was used to detect and measure changes in 44Ca levels in enamel before and after 6 days of in vivo treatment with a 44DCPD/fluoride dentifrice. The results showed that 44Ca from DCPD was incorporated into enamel and detected in plaque 18 hours post-treatment. The findings from these studies show that brushing with a DCPD dentifrice introduces additional, exogenous Ca into the oral environment, which fosters improved remineralization of teeth in combination with fluoride.

Structural determinants associated with risk of human developmental toxicity

OBJECTIVES

Identifying drugs or chemicals that represent hazards to human development is a continuous challenge. Of the approximately 60,000 chemicals in commercial use only 5% have been evaluated for developmental toxicity. Identification of inexpensive, rapid, validated techniques to demonstrate chemical hazards for the human embryo or fetus is the objective of this research.

STUDY DESIGN

This research explored identification of structure activity predictors associated with human developmental toxicity by means of MULTICASE (multiple computer-automated structure evaluation), an algorithm that evaluates associations between chemicals and their constituent fragments and a biologic response. This algorithm allows identification of chemicals (and specific substructures) that may be human developmental toxicants. Developmental toxicity data were compiled from two sources (the Teratogen Information System and Food and Drug Administration guidelines) and analyzed to identify structural determinants (biophores) associated with human developmental toxicity.

RESULTS

This analysis identified 17 biophores associated with human developmental toxicity. Testing the biophores against the learning set demonstrated 99% concordance, 100% sensitivity, and 98% specificity. Cross-validation studies were conducted, in which the original database was randomly separated into five learning and test sets; these demonstrated a mean concordance of 73%, with a mean sensitivity of 63% and a mean specificity of 79%.

CONCLUSIONS

The MULTICASE structure-activity model is useful for identifying potential human developmental toxicants, as well as serving as a starting point for mechanistic investigations.

Stability of aminocaproic Acid injection admixtures in 5% dextrose injection and 0.9% sodium chloride injection

The purpose of this study was to determine that stability of aminocaproic acid 10 and 100mg/mL admixed in 5% dextrose injection and 0.9% sodiium cholride injection in polyvinyl chloride bags over periods up to seven days at 4 deg and 23 deg C. The aminocaproic acid 250-mg/mL injection was filtered and admixed in filtered 5% dextrose injection and 0.9% sodium chloride injection to yield nominal aminocaproic acid concentrations of 10 and 100 mg/mL. Evaluations were performed initially and after one, three, and seven days of storage for physical and chemical stability. The admixtures were evaluated for physical stability using visual observation in normal fluorescent room light and a high-intensity monodirectional light beam, as well as electronic measurement of turbidity and particcle content. The chemical stability was evaluated by using a stability-indicating high performance liquid chromatography (HPLC) analytical technique. Aminocaproic acid admixtures were clear and colorless. However, the admixtures in 5% dextrose injection developed a slight yellowish discoloration after 24 hours at 23 deg C. This discoloration did not indicate substantial loss of aminocaproic acid. The HPLC evalurations found that an aminocaporic acid otency of at least 98% was retained throughout seven days in all solutions at both 4 deg and 23 deg C.

Calorimetric and spectroscopic studies of the thermotropic phase behavior of the n-saturated 1,2-diacylphosphatidylglycerols

The polymorphic phase behavior of a homologous series of n-saturated 1,2-diacyl phosphatidylglycerols (PGs) was studied by differential scanning calorimetry and Fourier transform infrared and 31P-nuclear magnetic resonance spectroscopy. When dispersed in aqueous media under physiologically relevant conditions, these compounds exhibit two thermotropic phase transitions that are structurally equivalent to the well-characterized pretransitons and gel/liquid-crystalline phase transitions exhibited by bilayers of the corresponding 1,2-diacyl phosphatidylcholines. Furthermore, when incubated at low temperatures, their gel phases spontaneously transform into one or more solid-like phases that appear to be highly ordered, quasicrystalline bilayers that are probably partially dehydrated. The quasicrystalline structures, which form upon short-term, low-temperature annealing of these lipids, are meta-stable with respect to more stable structures, to which they eventually transform upon prolonged low-temperature incubation. The rates of formation of the quasicrystalline phases of the PGs generally tend to decrease as hydrocarbon chain length increases, and PGs whose hydrocarbon chains contain an odd number of carbon atoms tend to be slower than those of neighboring even-numbered homologs. The calorimetric data also indicate that the quasicrystalline phases of these compounds become progressively less stable relative to both their gel and liquid-crystalline phases as the length of the hydrocarbon chain increases and that they decompose either to the liquid-crystalline phase (short- and medium-chain compounds) or to the normal gel phase (long-chain compounds) upon heating. The spectroscopic data indicate that although there is odd-even alternation in the structures of the quasicrystalline phases formed upon short-term low-temperature incubation of these compounds, the structural features of the stable quasicrystalline phases eventually formed are all similar. Furthermore, the degree of hydration and the nature of hydrogen bonding interactions in the headgroup and interfacial regions of these PG bilayers differ significantly from that observed in all other phospholipid bilayers studied so far. We suggest that many of the properties of PG bilayers can be rationalized by postulating that the glycerol moiety of the polar headgroup is directly involved in shielding the negative charges at the surface of the bilayer by means of hydration-like hydrogen bonding interactions with the phosphate moiety.

Genetic diversity and divergence in Chinese yak (Bos grunniens) populations inferred from blood protein electrophoresis

In 6 Chinese yak (Bos. grunniens) populations including 177 yaks, 34 blood protein loci were studied by horizontal starch gel electrophoresis, four of these loci (AKP, ALB, LDH-1, TF) were found to be polymorphic. The percentage of polymorphic loci(P) is 0.118, the mean individual heterozygosity(H) is 0.015, which means a low level of genetic diversity in the whole Chinese yak population. The coefficient of gene differentiation (Gst) is 0.0625, which indicated an almost-indistinguishable divergence among different populations at the level of blood protein electrophoresis.

Self-assembling DNA-lipid particles for gene transfer

PURPOSE

We have demonstrated that a heteromolecular complex consisting of cationic lipids and DNA can be prepared and isolated (1). Cationic lipids bind DNA through electrostatic interactions. However, when sufficient lipids are bound to DNA the physical and chemical properties of the complex are governed by hydrophobic effects. Here we describe an approach where this hydrophobic complex is used as an intermediate in the preparation of lipid-DNA particles (LDPs).

METHODS

The approach relies on the generation of mixed micelles containing the detergent, n-octyl beta-D-glucopyranoside (OGP), the cationic lipid, N-N-dioleoyl-N, N-dimethylammonium chloride (DODAC), and selected zwitterionic lipids, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) or egg sphingomyelin (SM).

RESULTS

When these micelles were prepared at low detergent concentrations (20 mM OGP) and combined with pCMV beta DNA, LDPs spontaneously formed. The mean diameter of these particles as measured by quasielastic light scattering was 55-70 nm, a result that was confirmed by negative stain electron microscopy. Further characterization of these LDPs showed that DNA within the particles was inaccessible to the small fluorochrome TO-PRO-1 and protected against DNase I degradation. LDPs could also be prepared in high concentrations of OGP (100 mM), however particles formed only after removal of OGP by dialysis. Particles formed in this manner were large (> 2000 nm) and mediated efficient transfection of Chinese hamster ovary cells. Transfection activity was greater when the lipid composition used consisted of SM/ DODAC. Small particles (< 100 nm) prepared of SM/DODAC were, however, inefficient transfecting agents.

CONCLUSIONS

We believe that LDP formation is a consequence of the molecular forces that promote optimal hydrocarbon-hydrocarbon interactions and elimination of the hydrocarbon-water interface.

Prediction of the carcinogenicity of a second group of organic chemicals undergoing carcinogenicity testing

Twenty-four organic compounds currently undergoing testing within cancer bioassays under the aegis of the U.S. National Toxicology Program (NTP) were submitted to the computer automated structure evaluation (CASE) and multiple computer automated structure evaluation (MULTICASE) system for predictions of activity. Individual predictions resulting from the NTP combined rodent, NTP mouse, Carcinogenic Potency Database (CPDB) combined rodent, and CPDB mouse databases were combined using Bayes' theorem to yield an overall probability of rodent carcinogenicity. Based upon an arbitrary probability cut-off of 0.50, nine compounds were predicted to be rodent carcinogens. The predicted carcinogens are chloroprene, 1-chloro-2-propanol, codeine, emodin, furfuryl alcohol, isobutyraldehyde, primaclone, sodium xylenesulfonate, and t-butylhydroquinone.

Structural analysis of Sindbis virus capsid mutants involving assembly and catalysis

Sindbis virus core protein (SCP) has been isolated from virus and crystallized. The X-ray crystallographic structure showed that the amino-terminal 113 residues appeared to be either disordered or truncated during crystallization and that the carboxy-terminal residues 114 to 264 had a chymotrypsin-like structure. The carboxy-terminal residues 106 to 264 and 106 to 266 of SCP have now been expressed in Escherichia coli. Most crystal forms of the truncated proteins were isomorphous with those of the virally extracted protein. There are only small structural differences between the truncated recombinant protein and the ordered part of the wild-type virus-extracted protein. Hence, E. coli-expressed SCP can be used to study proteolytic properties and the contribution of SCP to nucleocapsid assembly, interaction with the E2 glycoprotein and interaction with RNA. The same dimer that was found in two different crystal forms of the virus-extracted SCP was present also in some of the crystals of the truncated recombinant protein. The monomer-monomer interface is maintained by two pairs of hydrogen bonds and by hydrophobic interactions. Removal of the hydrogen bonds by single substitutions did not prevent dimer formation. However, a mutation that reduced the hydrophobic contacts did inhibit dimer formation. The wild-type truncated SCP is active in E. coli, as evidenced by proteolytic processing of a series of progressively longer precursors that extend beyond residue 264. Unlike the virus-extracted capsid protein, the E. coli-expressed SCP described here is terminated following the carboxy-terminal residue and, therefore, does not require autocatalysis. Nevertheless, the E. coli-expressed protein folds with the carboxy-terminal tryptophan residue in the specificity pocket. Two crystallographically independent molecules of SCP(106 to 266), which had two additional downstream residues and had the essential S215 mutated to alanine, showed two distinct modes of binding the uncleaved carboxy-terminal residues. These may represent successive steps of binding substrate prior to catalytic cleavage. Refinement of the various crystal structures of SCP showed that the amino-terminal arm from residues 107 to 113 was not disordered, but is associated with neighboring molecules. Residues 108 to 111 bind into a hydrophobic pocket composed primarily of Y180, W247 and F166. It had been shown that the double mutant (Y180S; E183G), with the Y180S substitution in this pocket, produced a large number of non-infectious virions, possibly because of modification in the interaction of the glycoprotein spikes with core proteins. The crystal structure of this double mutant showed that there was a large positional change in the side-chain of W247, which moved into the space created by the replacement of Y180 with serine. These conformational changes may alter the stability of the virion and, thus, regulate its functional requirements during cell entry.

Doxorubicin cellular pharmacokinetics plays no role in chemosensitizing effect of verapamil on Swiss-3T3 cells

AIM

To find whether or not the doxorubicin (Dox) cellular pharmacokinetics plays a role in chemosensitizing effect of verapamil (Ver) on drug sensitive cells.

METHODS

Cytotoxicity and cellular Dox contents (during accumulation and retention periods) were measured in the absence and presence of verapamil in Swiss-3T3 cells and compared with those in multidrug resistant (MDR) MCF-7Adr cells and drug sensitive MCF-7WT cells. mdr-1 mRNA expression in Swiss-3T3 cells was analyzed.

RESULT

Dox cytotoxicity was enhanced 2.0-fold in Swiss-3T3 cells by Ver (3 mumol.L-1) and 3.6-fold in MCF-7Adr cells by Ver (6 mumol.L-1), but not in MCF-7WT cells (Ver 6 mumol.L-1). Cellular accumulation of equi-effective concentrations of Dox increased at 6-h incubation in the presence of Ver in Swiss-3T3 (1.5-fold)i and MCF-7WT cells (2.1-fold) but decreased rapidly in MCF-7Adr cells by 20% to 50% compared to that in the absence of Ver. Cellular retention of Dox decreased after 10-min increase in the presence of Ver in Swiss-3T3 cells compared to that in the absence of Ver, that was similar to that in MCF-7WT cells, while the retention was augmented by Ver in MCF-7Adr cells. Slot blot analysis of RNA revealed no mdr-1 gene expression in Swiss-3T3 cells.

CONCLUSION

Changes in cellular accumulation and retention of Dox did not account for the chemosensitizing effect of Ver on Swiss-3T3 cells.

The effects of nonsteroidal anti-inflammatory drugs on posterior spinal fusions in the rat

STUDY DESIGN

This was a prospective study to determine the potential effects of indomethacin on spinal fusions in the rat.

OBJECTIVES

To determine if indomethacin exerts a deleterious effect on spinal fusions in the rat model.

SUMMARY OF BACKGROUND DATA

Nonsteroidal anti-inflammatory drugs are a class of compound that affect bone osteogenesis during fracture healing and heterotopic ossification. Spinal fusion is a process that occurs via osteogenesis and, therefore, may be similarly affected.

METHODS

Thirty-nine adult, Sprague-Dawley rats underwent a three-level posterior spinal fusion. Fusion was performed using morselized autogenous vertebral bone graft obtained via caudectomy and stabilized using a cerclage wiring technique. The 39 rats were divided into two groups consisting of 17 study animals and 22 control animals. The control group was injected with 1.5 cc of 0.9 normal saline subcutaneously for 12 weeks, whereas the test animals were injected on an identical schedule using 3 mg/kg of indomethacin sodium salt. Two control animals died, and three animals in the treatment group died of drug-related complications. Twelve weeks after surgery, all animals were killed, and the involved spinal segments were evaluated by direct manual examination. A fusion was probable if the spinal segments exhibited decreased scaled micromotion.

RESULTS

Sixty segmental levels in 20 control animals were assessed. Overall, 27 of 60 levels (45%) achieved fusion. In the indomethacin-treated group, 42 levels in 14 animals were evaluated. Overall, four of 42 levels (10%) achieved a fusion. Chi-square analysis demonstrated a significant difference (P < 0.001) between the control and indomethacin-treated groups.

CONCLUSIONS

This study raises serious questions about the inhibitory effects of nonsteroidal anti-inflammatory drugs on spinal fusion. Clinically, the widespread use of nonsteroidal anti-inflammatory drugs in the postoperative period after spinal fusion may need to be avoided.

[Effects of injectio reduqing on plasma IL-8 and nitric oxide levels in rabbits with endotoxin induced disseminated intravascular coagulation]

Experiments were performed for investigating the effects of Injectio Reduqing (RDQ) on plasma interleukin-8 (IL-8), NO2-/NO3-, complement 5a(C5a) and polymorphonuclear neutrophilic leukocyte (PMN) Chemotaxis Index (CI) in rabbits with endotoxin-induced disseminated intravascular coagulation (DIC). The results showed that plasma IL-8, NO2-/NO3-, C5a and CI levels of PMN increased markedly in model group, which were confirmed pathologically with obvious damage of tissues or organs. While in RDQ group the abov-mentioned parameters and damage of tissues or organs were reduced significantly (P < 0.01). The results suggested that the IL-8 and NO might be involved in pathogenesis of endotoxin-induced DIC, and RDQ could be used in preventing or treating DIC through mechanism of regulation of cytokines network.

[A new way for inbred strain mice genetic monitoring and the discovery of sex-linkaging RAPD markers]

We used 21 10 bp random primers to amplify DNA for four colonies of BALB/ c mice, four individuals of C 57 BL mice, and four individuals of Kunming stock mice. The amplified band patterns were different between BALB/c and C 57 BL mice in the products of 13 primers, and 8 primer products showed difference between BALB/c and Kunming stock mice. These results indicated that we can easily distinguish different strains of mice by RAPD method. For the four colonies of BALB/c mice, the genetic background of Chengdu colony. Shanghai colony and Beijing colony were homogeneous at all RAPD markers, however, in Kunming colony, there were two BALB/c individuals were disclosed different amplified patterns by 4 primers, showing that these two Kunming BALB/c mice maybe suffer genetic contamination or mutation some time. An unexpected phenomenon discovered in this study is that sex specific amplification bands were amplified by primer OPG 2, OPE 4, OPE 9 in all male mice. Although an 1.2 kb band were disclosed by both OPG 2 and OPE 4 in male mice, cross RAPD and not hybridization showed that the two bands were not homologous.

Chemosensitizing effect of verapamil on Swiss-3T3 cells transfected with human MDR1 gene

To further understand the characteristics of drug resistance reversal of verapamil, the relationship between the level of doxorubicin resistance and the magnitude of modulation by verapamil was examined in multidrug resistant Swiss-3T3 cells transfected with human MDR1 gene. In independently isolated transfectants doxorubicin cytotoxicity decreased markedly compared with parent cells. Potentiation of doxorubicin toxicity by a noncytotoxic concentration of 3 mumol.L-1 of verapamil was much greater in transfectants than in parent cells, while the magnitude of reversal was inversely dependent on the level of resistance. Southern blot hybridization indicated the MDR1 cDNA integration in genomics of each transfectant. Defect in cellular accumulation of doxorubicin was restored by verapamil in transfected cells. The saturation of active drug transport that may involve the magnitude changes of potentiation by verapamil, and the mode of interaction between P-glycoprotein and drugs, were discussed.

The effects of propofol on rat transcranial magnetic motor evoked potentials

INTRAOPERATIVE MONITORING OF motor evoked potentials (MEPs) may become a valuable test of spinal cord function during surgery. Unfortunately, MEP responses are affected by most common anesthetics. We studied the effect of intravenous propofol on transcranial magnetic MEPs (tcMMEPs) in the rat. Baseline tcMMEPs were recorded before administration of the drug. Each rat then received three induction doses of propofol, 10, 5, and 5 mg/kg (totaling 10, 15, and 20 mg/kg) and three successive 20-minute infusion doses at rates of 10, 20, and 40 mg/kg/h, respectively. An MEP intensity series was performed after each induction dose, during each infusion, and during a 20-minute recovery period. tcMMEPs recorded during the induction period demonstrated a significant, dose-dependent increase in onset latency and a marked decrease in amplitude. Infusion tcMMEPs displayed increased onset latencies but demonstrated a significant change in amplitudes only after the largest infusion dose. The MEPs approached baseline levels after discontinuation of the propofol. This study demonstrates that tcMMEPs can be successfully recorded from the rat during propofol anesthesia.

Risk identification using structural concepts: the potential carcinogenicity of praziquantel

The potential of praziquantel (PZ) to induce cancers in rodents was evaluated using a structure-activity relational expert system (CASE/MULTICASE). The analyses indicated that based upon structural features PZ had the potential for being a "nongenotoxic" carcinogen. The potential risk to humans of nongenotoxic carcinogens is considered to be much less than that posed by "genotoxic" ones. Moreover, PZ has demonstrated therapeutic effectiveness against parasitic diseases that affect millions of individuals. Additionally, PZ was developed to replace antiparasitic agents which were genotoxic rodent carcinogens. Thus, on balance, the beneficial effects of PZ appear to outweigh its potential for causing harm to humans.

Transcranial magnetic motor-evoked potentials in scoliosis surgery

Spinal cord monitoring using SSEPs is an accepted adjunct in the surgical correction of spinal deformities, but does not directly assess motor function. Motor-evoked potentials have been introduced in an effort to meet this important need. In this series of 18 patients, the feasibility of intraoperative monitoring using transcranial magnetic motor-evoked potentials is documented. The potential value of this neurophysiologic monitoring technique, as well as the pitfalls in interpretation, are reviewed.

Transfer and expression of human O6-methylguanine-DNA methyltransferase cDNA confers resistance of Mer- HeLa MR cells to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosoure a

Previous studies have demonstrated that O6-methylguanine-DNA methyltransferase (MGMT) is a major contributor to tumor cellular resistance toward chloroethylnitrosoureas. To further clarify the effect of MGMT gene expression on cellular chemosensitivity to 1-(4-amino-2-methyl-5-pyrimidinyl)-3-(2-chloroethyl)-3-nitrosourea (ACNU) in human cells, a repair-deficient human tumor cell line (HeLa MR) was transfected with a human MGMT expression vector (pSV2MGMT-neo). Multiple unique transfectants were isolated which exhibited variable levels of MGMT mRNA by Northern hybridization analysis. Vector-transfected controls were generated simultaneously. Transfectants expressing high levels of MGMT activity showed an increased resistance to ACNU-induced cytotoxicity. Furthermore, the levels of the protective effect against ACNU correlated generally with the levels of introduced MGMT expression. This study further provided direct evidence of MGMT contribution to ACNU resistance in human tumor cells. Based on the results presented here, we also discussed the perspective of the clinical utility of MGMT cDNA transfer and expression.

An evaluation of motor-evoked potentials for detection of neurologic injury with correction of an experimental scoliosis

STUDY DESIGN

Controlled correction of scoliosis in a rat model was used to assess the accuracy of intraoperative motor-evoked potential monitoring.

OBJECTIVES

The purpose of this study was to develop a model in which motor-evoked potential changes could be compared with neurologic function after surgery, such that a threshold for responding to motor-evoked potential changes may be established.

SUMMARY OF BACKGROUND DATA

Intraoperative motor-evoked potential monitoring has become technically feasible. Clinical application now depends on the development of useful interpretation parameters and correlation with neurologic sequelae.

METHODS

Experimental scoliosis was produced in 30 rat pups. After growth, the rats underwent correction of their scoliosis by distraction. Changes in tcMMEP onset latency and amplitude were measured. Distraction was applied either until a 10% delay in tcMMEP onset latency (Group 1), until tcMMEP responses were ablated (Group 2), or for 10 minutes after the loss of transcranial magnetic stimulation response (Group 3).

RESULTS

In Group 1 (n = 10), all animals had tcMMEP with normal onset latency and normal neurologic examinations 24 hours after surgery. In Group 2 (n = 10), tcMMEP were normal in four rats, markedly delayed in three rats, and absent in three rats 24 hours after surgery. neurologic examination was normal in the four rats with normal tcMMEP. Moderate deficit was noted in two of the three rats with prolonged onset latency 24 hours after surgery; the third was intact. Moderate neurologic injury was noted in two of three rats with absent tcMMEP 24 hours after surgery; the third rat was paralyzed. In Group 3 (n = 10), vertebral dislocation was noted on lateral radiographs in eight of 10 animals. Twenty-four hours after surgery, tcMMEP remained absent, and paralysis was noted in the eight rats with dislocation. The two rats without dislocation had delayed tcMMEP but some return of neurologic function.

CONCLUSIONS

Comparison of the three groups shows a significant correlation between tcMMEP and endpoint neurologic outcome. None of the rats in Group 1 had a neurologic deficit after surgery as opposed to five of 10 rats in Group 2 and 10 of 10 rats in Group 3 with significant neurologic injury. These findings suggest that a 10% delay in onset latency would be an appropriate threshold for responsing to changes in tcMMEP.

[Effects of reducing injection on plasma TNF-alpha and IL-6 levels in rabbits with endotoxin-induced DIC]

Plasma TNF-a and IL-6 levels of endotoxin-induced DIC in rabbits were measured by ELISA methods. Simultaneously, the effects of Reduqing (RDQ) on TNF-alpha and IL-6 were also studied. The results showed that TNF-alpha and IL-6 levels increased markedly in model group, which were confirmed with obvious damage of tissue or organ. Co-administration of RDQ could reduce plasma TNF-alpha and IL-6 levels, together with mild tissue or organ damage. These results indicated TNF-alpha and IL-6 might be involved in pathogenesis of endotoxin-induced DIC, RDQ might be used in preventing or treating DIC through mechanism of reducing TNF-alpha and IL-6 levels.

Primary plexogenic pulmonary hypertension shows imperfect formation of the internal elastic lamina of the pulmonary arteries

Lung tissue from subjects dying from primary plexogenic pulmonary hypertension (PPH) has shown defects of elastin formation of the lung arteries. Lung vessels from 5 cases of PPH were compared with those of 9 age-matched normal subjects, and 24 individuals having secondary pulmonary hypertension (2 degrees PH). PPH cases and those with 2 degrees PH due to congenital heart disease with left-to-right shunts (2 degrees PH, LRS), showed active proliferation of medial smooth muscle cells (SMC) through defects of the internal elastic lamina (IEL) into the arterial lumen to form typical plexiform lesions. Larger arteries showed accelerated intimal thickening similar to normal aging. Plexiform lesions were not seen in normal subjects or in those developing high pulmonary pressures later in life. The observations showed that the development of discontinuities of the IEL of the pulmonary arteries and intimal thickening is accelerated in normal subjects by high pulmonary artery pressure, especially when this is established at a very young age. They suggest that such discontinuities occur in PPH due to inherent abnormality of the elastin of the arterial walls, with advanced early proliferation of medial SMC and obstruction of the pulmonary arterial circulation.