3D-RISM-KH molecular theory of solvation and density functional theory investigation of the role of water in the aggregation of model asphaltenes.

We applied a multiscale modeling approach that involves the statistical-mechanical three-dimensional reference interaction site model with the Kovalenko-Hirata closure approximation (3D-RISM-KH molecular theory of solvation) as well as density functional theory (DFT) of electronic structure to study the role of water in aggregation of the asphaltene model compound 4,4'-bis(2-pyren-1-yl-ethyl)-2,2'-bipyridine (PBP) [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2008, 22, 715]. The solvation free energy and potential of mean force predicted by 3D-RISM-KH reveal favorable pathways for disaggregation of PBP dimers in pure versus water-saturated chloroform solvent. The water density distribution functions elucidate hydrogen bonding preferences and water bridge formation between PBP monomers. The ΔG(298) values of -5 to -7 kcal mol(-1) for transfer of water molecules in chloroform to a state interacting with PBP molecules are in agreement with experimental results. Geometry optimization and thermochemistry analysis of PBP dimers with and without water bridges using WB97Xd/6-31G(d,p) predict that both PBP dimerization and dimer stabilization by water bridges are spontaneous (ΔG(298) < 0). The (1)H NMR chemical shifts of PBP monomers and dimers predicted using the gauge-independent atomic orbital method and polarizable continuum model for solvation in chloroform are in an excellent agreement with the experimental results for dilute and concentrated PBP solutions in chloroform, respectively [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2009, 23, 3687]. The DFT calculations of PBP dimers with explicit water show that bridges containing 1-3 water molecules lead to stabilization of PBP dimers. Additional water molecules form hydrogen bonds with these bridges and de-shield the PBP protons, negating the effect of water on the (1)H(C3) NMR chemical shift of PBP, in agreement with experiment. The ΔG(298) results show that hydrogen bonding to water and water-promoted polynuclear assembly bridging is as important as π-π interactions for asphaltene aggregation.

Using the Climate Assessment Tool (CAT) in U.S. EPA BASINS integrated modeling system to assess watershed vulnerability to climate change.

During the last century, much of the United States experienced warming temperatures and changes in amount and intensity of precipitation. Changes in future climate conditions present additional risk to water and watershed managers. The most recent release of U.S. EPA's BASINS watershed modeling system includes a Climate Assessment Tool (CAT) that provides new capabilities for assessing impacts of climate change on water resources. The BASINS CAT provides users with the ability to modify historical climate and conduct systematic sensitivity analyses of specific hydrologic and water quality endpoints to changes in climate using the BASINS models (Hydrologic Simulation Program - FORTRAN (HSPF)). These capabilities are well suited for addressing questions about the potential impacts of climate change on key hydrologic and water quality goals using the watershed scale at which most important planning decisions are made. This paper discusses the concepts that motivated the CAT development effort; the resulting capabilities incorporated into BASINS CAT; and the opportunities that result from integrating climate assessment capabilities into a comprehensive watershed water quality modeling system.

Substrate inactivation of enzymes in vitro and in vivo.

Some enzymes are inactivated by their natural substrates during catalytic turnover, limiting the ultimate extent of reaction. These enzymes can be separated into three broad classes, depending on the mechanism of the inactivation process. The first type is enzymes which use molecular oxygen as a substrate. The second type is inactivated by hydrogen peroxide, which is present either as a substrate or a product, and are stabilized by high catalase activity. The oxidation of both types of enzymes shares common features with oxidation of other enzymes and proteins. The third type of enzyme is inactivated by non-oxidative processes, mainly reversible loss of cofactors or attached groups. Sub classes are defined within each broad classification based on kinetics and stoichiometry. Reaction-inactivation is in part a regulatory mechanism in vivo, because specific proteolytic systems give rapid turnover of such labelled enzymes. The methods for enhancing the stability of these enzymes under reaction conditions depends on the enzyme type. The kinetics of these inactivation reactions can be used to optimize bioreactor design and operation.

Role for anti-Müllerian hormone in congenital absence of the uterus and vagina.

Molecular genetic techniques were used to determine if mutations in the genes encoding anti-Müllerian hormone (AMH) (also known as Müllerian inhibiting substance (MIS)) and its receptor (AMHR) are commonly present in patients with congenital absence of the uterus and vagina (CAUV). Twenty-two CAUV patients and 96 control subjects from diverse ethnic groups were studied after obtaining informed consent. Genomic DNA samples prepared from leukocytes were digested separately with several different restriction enzymes, and the resultant fragments were analyzed for restriction fragment melting polymorphisms (RFMPs) by denaturing gradient gel electrophoresis (DGGE). Electrophoretic mobility of DNA fragments which were 200-700 base pairs in length was compared using polyacrylamide gels that included linear gradients of denaturing solvents designed to separate DNA fragments according to sequence-dependent variation in thermal stability. Two RFMPs were found in the AMH gene in both patients and normal control subjects. One RFMP in the AMHR gene was present at low frequencies in both patients and normal control subjects. No RFMPs specific to CAUV patients were found in either gene. Because no mutations or rare DNA sequence polymorphisms were detected in the AMH and the AMHR genes in this group of CAUV patients, it is unlikely that either gene commonly has an etiologic role in CAUV.

Rapid serodiagnosis of leptospirosis using the IgM-specific Dot-ELISA: comparison with the microscopic agglutination test.

The dot enzyme-linked immunosorbent assay (Dot-ELISA) was compared to the microscopic agglutination test (MA test) for the diagnosis of human leptospirosis. Of 177 sera from 68 soldiers who trained in the Republic of Panama, 102 sera were positive in the MA test and 93 of these sera were positive in the IgM-specific Dot-ELISA. Incidence of infection was 50 of 68 patients with the MA test and 48 of 68 in the IgM Dot-ELISA. Five MA test-positive sera were reactive only in the IgG-specific Dot-ELISA, suggesting previous exposure. All 21 infecting serovars of Leptospira interrogans, as determined by positive reactions in the MA test or culture of blood and urine specimens, were reactive in the Dot-ELISA. Of 75 sera negative in the MA test, 61 were nonreactive in the Dot-ELISA. However, 9 of these 14 Dot-ELISA-positive/MA test-negative sera were acute samples from patients whose later sera were MA test-positive. Positive reactions in the IgM Dot-ELISA occurred in 2 of 30 control, 4 of 10 Lyme disease, 1 of 11 relapsing fever, and 1 of 8 yaws sera; 10 syphilis patient sera were nonreactive. The IgM-specific Dot-ELISA appears to be sensitive and specific for the serodiagnosis of acute leptospirosis. In addition, this rapid test is inexpensive, simple to perform, utilizes minute volumes of killed leptospiral antigen and is easily adaptable to field use.

A prospective study of 750 definite spider bites, with expert spider identification.

BACKGROUND: Spider bite is a subject of much medical mythology with prevalent fears that spiders cause severe envenoming, with neurotoxic effects or necrotic ulcers. Clinical experience and small studies suggest otherwise, but this has not been confirmed by prospective studies of bites by identified spiders. AIM: To describe the clinical effects of bites by accurately identified spiders, and determine whether early clinical features and circumstances can predict spider type. DESIGN: Prospective follow-up study. METHODS: Patients were recruited from admissions to two emergency departments (n=48) and referrals from three state poison information centres (n=1426), over 27 months. Overall, there were 750 people with definite spider bites where the spiders were immediately collected and expertly identified. RESULTS: Significant effects occurred in 44 bites (6%), including 37 (of 56) redback spider bites (Latrodectus hasselti) with significant pain lasting >24 h. Of these, only 6 (11%) received antivenom. One severe neurotoxic envenoming by an Australian funnelweb spider required antivenom. No definite spider bites resulted in necrotic ulcers (0%, 99%CI 0-0.7%). There were no early allergic reactions and secondary infection occurred in seven cases (0.9%, 95%CI 0.4-1.9%). Circumstances and early clinical effects were strongly associated with taxonomic spider identification, with positive predictive values >0.95 for common groups of spiders. CONCLUSIONS: Australian spider bite caused minor effects in most cases and is unlikely to cause necrotic ulcers, allergic reactions or infection. Redback spider bite (widow spider) caused prolonged pain, and antivenom could have been used more frequently. The circumstances and early clinical features of spider bites may allow early appropriate advice and treatment of spider bite without taxonomic identification.

Dominant transmission of imperforate hymen.

OBJECTIVE: Imperforate hymen is an uncommon anomaly of the reproductive tract, occurring in approximately 0.1% of newborn females. The familial occurrence of imperforate hymen in a child, her mother, and her mother's monozygotic twin is reported. DESIGN: Case report. SETTING: Academic medical center. PATIENT(S): Three affected family members. MAIN OUTCOME MEASURE(S): Karyotype and pedigree analysis. RESULT(S): The proband, presenting with peritonitis, was evaluated at age 12 for imperforate hymen because this condition was diagnosed in her mother at age 14. At age 14, the mother's monozygotic twin was asymptomatic except for primary amenorrhea and was also demonstrated to have imperforate hymen. No other reproductive system abnormalities were known to be present in the remaining family members. Chromosomal structural analysis confirmed that the mother of the proband had no chromosomal abnormalities. CONCLUSION(S): The occurrence of imperforate hymen in two consecutive generations of a family is consistent with a dominant mode of transmission, either sex-linked or autosomal. Previously reported examples of siblings with imperforate hymen suggested a recessive mode of inheritance. Taken together, these cases suggest that imperforate hymen can be caused by mutations in several genes. This case highlights the importance of evaluating all family members of affected patients. Familial examples of other developmental anomalies of the female reproductive tract also suggest a multifactorial genetic etiology.

Congenital absence of the uterus and vagina is not commonly transmitted as a dominant genetic trait: outcomes of surrogate pregnancies.

OBJECTIVE: To determine the inheritance pattern of congenital absence of the uterus and vagina in affected women undergoing surrogacy IVF with this disorder. DESIGN: Retrospective study. SETTING: A hospital-based reproductive endocrinology and infertility center. PATIENT(S): Women diagnosed with congenital absence of the uterus and vagina undergoing IVF with subsequent transfer of embryos to a surrogate uterus. INTERVENTION(S): Questionnaires were sent to all infertility treatment centers performing surrogate procedures. MAIN OUTCOME MEASURE(S): Number, gender, and frequency of congenital anomalies in progeny. RESULT(S): Thirty-two of 53 surveyed programs responded (60%). One hundred sixty-two IVF cycles were performed, and 34 liveborn children were delivered (half female). No congenital anomalies were found, except for one male child with a middle ear defect and hearing loss. CONCLUSION(S): These results strongly suggest that congenital absence of the uterus and vagina, if genetically transmitted, is not inherited commonly in a dominant fashion.

Gonadotropin-releasing hormone-associated peptide gene sequences in women with hyperprolactinemia.

OBJECTIVE: To determine if mutations in the structural gene for gonadotropin-releasing hormone (GnRH)-associated peptide are present in women with hyperprolactinemia. DESIGN: Patients with hyperprolactinemia and controls were studied retrospectively for GnRH-associated peptide gene mutations. SETTINGS: Patients seen in a clinical setting were studied at a medical school laboratory setting. PATIENTS: Fifteen women with hyperprolactinemia and two fertile controls with normal prolactin levels were studied. INTERVENTIONS: Genomic deoxyribonucleic acid (DNA) was extracted from each patient and subjected to Southern blot analysis and polymerase chain reaction (PCR). For Southern blot analysis, DNA was digested with EcoRI, XbaI, BglII, PstI, and BamHI and hybridized to two DNA probes for GnRH-associated peptide. Exons II to IV, which encode for the structural gene, were amplified by PCR. MAIN OUTCOME MEASURES: Fragment sizes from autoradiographs were compared among patients and controls. Amplified PCR products of exons II to IV of the GnRH-associated peptide were also compared. RESULTS: No large deletions, insertions, or polymorphisms were identified in women with hyperprolactinemia or controls by Southern blotting. Each of the exons was present and of normal size by PCR in the study patients and controls. CONCLUSIONS: No large deletions of the GnRH-associated peptide gene appear to be present in our patients with hyperprolactinemia. Small deletions, insertions, or point mutations are not excluded by this analysis.

Mutation analysis of the gonadotropin-releasing hormone receptor gene in idiopathic hypogonadotropic hypogonadism.

OBJECTIVE: To determine if GnRH receptor mutations occur in patients with idiopathic hypogonadotropic hypogonadism. DESIGN: Patients and controls were studied by molecular genetic analysis. SETTING: A tertiary medical center setting. PATIENT(S): Twenty-four patients with idiopathic hypogonadotropic hypogonadism and 20 controls. INTERVENTION(S): Deoxyribonucleic acid from all individuals was analyzed by Southern blot analysis and denaturing gradient gel electrophoresis. Genomic DNA was digested with restriction enzymes, and Southern blots and denaturing gradient gel blots were constructed. Blots were hybridized with the GnRH receptor complementary DNA probe. The DNA sequencing was performed on samples from two representative patients. MAIN OUTCOME MEASURE(S): Gonadotropin-releasing hormone receptor gene structure was ascertained by comparing fragments from autoradiographs in patients and controls. Individual nucleotides were ascertained from DNA sequencing gels. RESULT(S): No GnRH receptor gene deletions or polymorphisms were identified by Southern blot analysis. New restriction-fragment melting polymorphisms using the enzymes DpnII, RsaI, and HaeIII were identified by denaturing gradient gel blots in patients and controls. CONCLUSION(S): Gonadotropin-releasing hormone receptor gene deletions or rearrangements were not observed in our idiopathic hypogonadotropic hypogonadism patients. Denaturing gradient gel electrophoresis failed to identify single-base differences unique to patients with idiopathic hypogonadotropic hypogonadism, dramatically reducing the likelihood that point mutations of the GnRH receptor gene are present in idiopathic hypogonadotropic hypogonadism.

Effect of dissolved oxygen control on growth and antibiotic production in Streptomyces clavuligerus fermentations.

A proportional-integral control system was used to control dissolved oxygen in a fermentor at constant shear and mass transfer conditions. Growth and antibiotic production in Streptomyces clavuligerus were studied at different dissolved oxygen levels during the fermentation. Three protocols were employed: no-oxygen control to provide a base case, oxygen controlled to a preset saturation level throughout the fermentation, and oxygen controlled at a high level only during the growth phase. The last protocol was aimed at optimizing the consumption of oxygen. Lower specific growth rates and cephamycin C yields were obtained when dissolved oxygen was controlled at 50% throughout the fermentation, compared to the base case. A 2.4-fold increase in the final cephamycin yield was observed when dissolved oxygen was controlled at saturation levels during the growth phase, compared to the experiments without dissolved oxygen control. This enhancement in yield was independent of the dissolved oxygen (DO) level after exponential growth, in the range of 50-100% saturation. The most effective control strategy, therefore, was to control DO only during active growth when the biosynthetic enzymes were probably synthesized.

Pharmacokinetics of drugs that inactivate metabolic enzymes.

The pharmacokinetics of drugs that cause inactivation of metabolic enzymes were derived for the single-compartment model with linear elimination kinetics. A simple mechanism for suicide inactivation of enzyme by its substrate was used to model the relationship between elimination of drug and enzyme activity as a function of time. Three modes of administration were considered: a single bolus dose, repetitive bolus dosing, and continuous administration. Unlike capacity-limited drug elimination, a bolus dose would always give apparent linear kinetics. The apparent terminal half-life after a bolus dose was a simple function of the remaining elimination activity. Repetitive dosing would give a gradual increase in half-life until the steady-state elimination activity was achieved. The time to achieve steady-state drug levels with continuous administration of drug, or repetitive dosing, was prolonged by the enzyme inactivation process, and was dependent on the rates of elimination, enzyme inactivation, and the dosing rate. Interactions between drugs would occur due to a reduction in elimination activity if they share the inactivated enzyme pathway, and the magnitude of the effect would be characterized by the shift in the terminal half-life of elimination.

Evidence for lidocaine-induced enzyme inactivation.

The effects of lidocaine on hepatic enzyme activity were studied using the isolated perfused rat liver. The in vivo liver activity was examined by infusing lidocaine via the jugular vein, followed by organ isolation and drug perfusion 24 h later. The liver was studied in vitro by perfusing the organ with lidocaine until steady state was reached, then allowing the drug and metabolites to wash out of the organ, followed by a second infusion of lidocaine to probe enzyme activity. In both types of experiments, pretreatment with lidocaine caused a reduction in deethylation, and led to a more rapid attainment of steady state. The experimental concentration-time profiles and literature data were successfully described by a mathematical model.

Experimental studies of transient mass transfer and reaction in the liver: interpretation with a heterogeneous compartment model.

The uptake and metabolism of lipophilic compounds by the liver were studied by administering a model compound, lidocaine, to the isolated rat liver. Lidocaine was continuously infused into the liver until steady state was reached. Subsequent step changes in the inlet concentration were used to obtain information on rates of cellular uptake and release and to assess the extent of mixing within the organ. A simple heterogeneous model combining mass transfer and enzyme reactions was required to simulate the effluent levels of lidocaine and two primary metabolites, monoethylglycinexylidide and 3-hydroxylidocaine. The rate constants for uptake and release of lidocaine were 1200 and 46 min-1, respectively. The rate-limiting step was intracellular reaction, with a rate constant of 0.49 min-1. Although the rate of lidocaine uptake was fast, it was 50 times slower than the rate of facilitated uptake of galactose, a fact suggesting passive transport of lidocaine between the tissue and the vasculature. The rates of mass transfer of lidocaine and its metabolites differed, but the ratios of the rate of uptake to the rate of release were the same. The results suggested that all three species had an affinity for the cellular region of the liver; concentrations in tissue were approximately five times greater than concentrations in effluent. Because of the large capacity of the organ for uptake of lidocaine and its metabolites, concentrations from washout experiments were controlled by linear mass transfer from the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intravenous infusion of lidocaine on its pharmacokinetics in conscious instrumented dogs.

In this study, potential alterations in hepatic blood flow, plasma protein binding, hepatic tissue binding, and enzyme activities induced by LD iv infusion of lidocaine (LD) were evaluated using a chronically instrumented dog model. Four conscious female mongrel dogs (19.0-23.5 kg) were each given, on days 1 and 10, a 5-min infusion of a mixture of unlabeled LD at approximately 2 mg/kg and 14C-labeled LD at approximately 25 microCi and, on day 8, a 12-h constant rate iv infusion of LD (approximately 76 microg/kg/min). During LD infusion, there was a 11-79% increase in total hepatic blood flow, mainly due to a 1.6-9.2-fold increase in hepatic arterial flow. Despite similar blood clearance (27.5 +/- 6.0 mL/min/kg vs 27.5 +/- 3.5 mL/min/kg), volume of distribution at steady state (1.38 +/- 0.08 L/kg vs 1.36 +/- 0.17 L/kg), and free fraction values of LD between days 1 and 10 (p > 0.05), intrinsic clearance values were consistently reduced (1224 +/- 859 mL/ min/kg vs 285 +/- 104 mL/min/kg; p = 0.034). Furthermore, hepatic tissue uptake of LD and/or its metabolites was less on day 10 than on day 1 (39.7 +/- 14.5 micromol vs 30.1 +/- 15.1 micromol; p = 0.072). The extent of N-dealkylation of LD to MEGX was unaltered, whereas sequential biotransformation of MEGX was impaired. Hence, these findings suggested that LD infusion led to a reduction of hepatic intrinsic clearance, although the change was not significant enough to alter its conventional kinetic parameters.

Evaluation of a rapid specific ward based assay for creatinine in blood.

We have evaluated a dry reagent stick test for the quantitation of creatinine in plasma employing a whole blood sample. The assay was found to be specific for creatinine and correlated well (r = 0.993) with an established laboratory procedure. The precision found indicated that the method was suitable for use in the diagnosis and monitoring of renal disease.

Use of urine albumin measurement as a replacement for total protein.

We have investigated the replacement of urine total protein estimations for the assessment of glomerular permeability, by the measurement of urine albumin excretion using a latex particle enhanced immunoturbidimetric assay. An initial screen was performed using Albustix to assess the sample pre-dilution necessary for immunoanalysis. A total of 167 24-hour urine samples were analysed and urine albumin concentration correlated well with that of urine total protein (r = 0.93) over the range 0-16,800 mg/l. This protocol provides a more cost effective and analytically valid assessment of glomerular permeability.

The use of capillary electrophoresis as part of a specificity testing strategy for mitoguazone dihydrochloride HPLC methods.

Capillary electrophoresis (CE) has been used as part of a validation experiment designed to prove the specificity of high performance liquid chromatography (HPLC) methods used for analysis of mitoguazone dihydrochloride drug substance. Data regarding accuracy, precision and sensitivity of the CE methods are presented as well as a comparison of results obtained from CE, HPLC and thin-layer chromatography (TLC) analysis of samples stressed under a variety of conditions. It was concluded that, not only were the HPLC methods being investigated specific, but that CE could potentially be used to replace HPLC for the routine assay of mitoguazone dihydrochloride.

Diode array detection of low level co-eluting species in high-performance liquid chromatography.

A simple and sensitive method for detecting low levels (0.5 and 1.0%, w/w) of co-eluting species in HPLC has been developed. This method is based on the subtraction of normalized peak up-slope and down-slope spectra from that of the apex. Visual inspection of the resultant "difference spectra" allows for a qualitative judgement regarding the integrity of the peak under consideration.

Ultrastructural observations of spermatozoa and spermiogenesis in Wandella orana Gray, 1994 (Araneae: Filistatidae) with notes on their phylogenetic implications.

Spermatozoa and spermiogenesis of the prithine filistatid spider Wandella orana are described. The spider produces coenospermia, i.e. sperm aggregations that include several single sperm cells commonly surrounded by a secretion sheath. One sectioned coenospermium in W. orana contains at least five spermatozoa. During copulation many coenospermia are transferred into the female. Coenospermia are regarded as a peculiar transfer form of sperm which occurs in early derivative spiders such as Liphistiomorphae and Mygalomorphae. The only exception which was found in Araneomorphae until now was the filistatine spider Filistata insidiatrix. Our observation is the second case and supports the view that Filistatidae represent an early derivative taxon. Furthermore, the individual sperm cells show characteristics which also may be regarded as being plesiomorphic. There is a cone-shaped acrosomal vacuole, a very long acrosomal filament, a rather stout nucleus and a small implantation fossa. The axoneme shows the 9x2+3 pattern of microtubules which is synapomorphic in Megoperculata (Uropygi, Amblypygi and Araneae). The finding of coenospermia in two distant taxa of Filistatidae may have consequences for phylogenetic and systematic considerations.