Biomedical subjects

A Bult

Publications and source records attributed to A Bult.

At least 73 records · Page 4Linked to original sources

PubMed1996

Purity determinations in the bulk drug of the novel indoloquinone antitumor agent EO9.

The pharmaceutical development of the investigational cytotoxic drug EO9 included the structural characterization of the bulk drug by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and infrared (IR) spectroscopy, and analytical characterization by high-performance liquid chromatography and ultraviolet/visible spectrophotometry. The presence of impurities in the bulk drug was investigated. The intermediates in the synthesis of EO9 were structurally characterized by NMR spectroscopy and MS, and analytically characterized by HPLC analysis with photodiode array (PDA) detection. All of the intermediates were below their limits of detection in EO9 bulk drug. The amounts of residual organic solvents were determined by gas chromatography. Methanol and ethanol were detected, but the amounts present did not exceed the limits as set in the United States Pharmacopeia XXII.

Antineoplastic Agents↗

PubMed1996

Multiple selection responses in house mice bidirectionally selected for thermoregulatory nest-building behavior: crosses of replicate lines.

Replicate high-selected, control, and low-selected lines were crossed at generation 46 of bidirectional selection for thermoregulatory nest-building behavior. Previous analysis of the lines at their limits had revealed multiple responses to uniform selection, where each of the four selected lines responded differently to reverse selection (Laffan, 1989). The reciprocal F1 crosses showed significant heterosis for nest-building behavior compared to the contemporaneous generations of the parental lines. This pattern of heterosis in all three crosses is consistent with the finding that nest-building behavior in each of the four replicate lines had a different genetic basis, in spite of the phenotypic similarity between the two replicate lines in the high and low direction of nesting. This heterosis effect and the larger number of young weaned in all three crosses compared to their respective contemporaneous generation of the parental lines also support earlier findings that larger nests are closely related to fitness.

Animals↗

PubMed1996

Systematic study on the chemical stability of the prodrug antitumor agent carzelesin (U-80,244)

The chemical stability of the novel anticancer agent carzelesin in aqueous buffer/acetonitrile (1:1, v/v) mixtures has been investigated utilizing a stability-indicating reversed-phase high-performance liquid chromatographic assay. The degradation kinetics of carzelesin has been studied as a function of pH, buffer composition, ionic strength, and temperature. Degradation of carzelesin follows (pseudo-) first-order kinetics. A pH-rate profile, using rate constants extrapolated to zero buffer concentration, was constructed demonstrating that carzelesin is most stable in the pH region 1-4. The degradation rate of carzelesin was not significantly affected by buffer components and by the ionic strength. In addition to the formation of the degradation products U-76,073, U-76,074, and aniline in alkaline medium and in acetate buffer solution, another degradation product was formed in acetate buffer solution. In perchloric acid buffer solution (pH* < 3), U-76,073 and U-76,074 could not be detected as degradation products.

Antineoplastic Agents↗

PubMed1996

Degradation kinetics of gonadorelin in aqueous solution.

The degradation kinetics of gonadorelin were investigated systematically with reversed-phase high-performance liquid chromatography. The stability-indicating properties of this system were checked with photodiode array detection and by comparison with capillary zone electrophoretic analysis. Influences of gonadorelin concentration, pH, temperature, buffer ions, and ionic strength on the degradation kinetics were studied. The pH-log Kobs profile can be divided into three parts, a proton, a solvent, and a hydroxyl-catalyzed section, with different degradation products. These degradation products were characterized by mass using LC-MS. Gonadorelin is most stable at pH 5-5.5 with a half-life of 70 days at 70 degrees C. The overall degradation rate constant as a function of the temperature under acidic and alkaline conditions obeys the Arrhenius equation. The gonadorelin concentration and the concentrations of acetate, phosphate, borate, and carbonate buffer have no influence on the decomposition rate of the analyte. Increasing ionic strength led to higher Kobs at pH 2 and lower Kobs at pH 9, but influences were relatively small.

Buffers↗

PubMed1996

A putative poststreptococcal case of OCD with chronic tic disorder, not otherwise specified.

A 12-year-old girl presented with an atypical, recurrent, increasingly treatment-resistant case of obsessive-compulsive disorder and chronic tic disorder associated with profound separation anxiety, learning difficulty, and intermittent upper respiratory symptoms. In addition to detailed reviews of history and findings from many clinical caretakers from the prior 7 years, current pediatric, psychiatric, neuropsychological, neuroimaging, and clinical laboratory data were also available. Treatment options were considered from multiple perspectives: psychoanalytically oriented psychotherapy, conventional pharmacotherapy, family interventions, cognitive-behavioral therapy, and learning-supportive strategies. Psychological, neuropsychiatric, and neuroimmunological formulations of etiology were considered. Subsequent treatments included supportive psychotherapy, neuroleptic augmentation of selective serotonin reuptake inhibitors, prophylactic penicillin, and a course of six sessions of plasmapheresis over a 2-week period. The case raises questions for ongoing consideration that juxtapose dynamic, neuropsychiatric, and neuroimmunological perspectives.

Antibiotic Prophylaxis↗

PubMed1996

Pharmacokinetics of fluconazole in saliva and plasma after administration of an oral suspension and capsules.

The concentrations of fluconazole were determined at steady state in the saliva and plasma of 10 healthy volunteers after ingestion of fluconazole as capsules and after flushing the mouth for 2 min with the same dose formulated as an oral suspension and swallowing of the drug. Saliva and plasma samples were analyzed by a validated high-performance liquid chromatographic assay. Flushing and swallowing of the oral suspension resulted in a significantly (P = 0.005) higher mean area under the concentration-versus-time curve (AUC) from 0 to 24 h in saliva (89.13 +/- 23.42 mg.h/liter) than that obtained after ingestion of the same dose as capsules (69.27 +/- 12.89 mg . h/liter). The calculated mean maximum concentration in saliva just after swallowing of the suspension was 97.99 +/- 6.12 mg/liter. The peak fluconazole concentration in saliva after the ingestion of the capsules was 3.55 +/- 0.40 mg/liter. The fluconazole oral suspension and capsules resulted in comparable concentrations and AUCs in plasma. Thus, because of a higher local level of drug exposure in terms of both higher peak concentrations in saliva and a higher salivary AUC, the fluconazole oral suspension has theoretical advantages over the capsule formulation in the treatment of oropharyngeal candidiases.

Administration, Oral↗

PubMed1995

Distribution of AVP and Ca(2+)-dependent PKC-isozymes in the suprachiasmatic nucleus of the mouse and rabbit.

The suprachiasmatic nucleus (SCN) is the circadian pacemaker in mammals and contains a network of arginine-vasopressin-immunoreactive (AVP-ir) neurons. AVP-recipient cells contain the V1a class of receptors linked to phosphoinositol turnover and protein kinase C (PKC). The present study describes the localization of AVP and the four Ca(2+)-dependent PKC-isoforms in the mouse and rabbit SCN. An estimate of the numerical density of AVP-ir neurons at the rostral, medial, and caudal level of the SCN revealed that the mouse SCN contains more than twice the number of AVP-ir neurons than the rabbit SCN. Neurons immunostained for AVP or PKC dominated in the dorsomedial and ventrolateral aspects of the mouse SCN, while the central area of the SCN revealed only weakly stained neurons. The rabbit SCN was characterized by a more homogeneous distribution of AVP-ir and PKC-ir neurons. PKC alpha was the most abundantly expressed isozyme in both species, whereas the presence of the other isoforms differed (mouse: PKC alpha > PKC beta I >> PKC beta II > PKC gamma; rabbit: PKC alpha > PKC beta II > or = PKC gamma > PKC beta I). Clear PKC gamma-positive neurons were only observed in the rabbit SCN, while the mouse SCN predominantly contained immunolabeled fiber tracts for this PKC isozyme. Astrocytes immunoreactive for each PKC isoform were frequently encountered in the rabbit SCN, but were absent in mice. Immunofluorescence double labeling showed that numerous AVP-recipient cells in the mouse SCN were immunopositive for PKC alpha, and that nearly all AVP-ir neurons express PKC alpha abundantly. These results substantiate the putative role for PKC alpha in vasopressinergic signal transduction in the SCN. The differential expression in degree and cell type of the Ca(2+)-dependent PKC-isoforms in the mouse and rabbit SCN may be related to the differences observed in circadian timekeeping between the two species.

Animals↗

PubMed1995

Structural identification of the degradation products of the antitumor peptide antagonist [Arg6,D-Trp7,9,MePhe8]substance P (6-11).

The basic hexapeptide antagonist [Arg6,D-Trp7,9,MePhe8]-substance P (6-11) was degraded in acid and alkaline media. In acid solution, only one degradation product is found whereas in alkaline solution at least six products are formed. These compounds were analytically characterized and structurally identified by reversed-phase high-performance liquid chromatography, capillary electrophoresis, liquid chromatography/mass spectrometry, fast atom bombardment tandem mass spectrometry, optical rotation analysis, and chiral gas chromatography. The product formed in acidic solution is the terminally deamidated antagonist [Arg6,D-Trp7,9,MePhe8]substance P (6-11); this product was also found in alkaline degradation mixtures. Other important degradation products originate from racemization of the amino acid residue L-Met, formation of ornithine from Arg, and the oxidation of Met to its sulfoxide form.

Amino Acid Sequence↗

PubMed1995

Substitution of didanosine sachets by chewable tablets: a pharmacokinetic study in patients with AIDS.

We have conducted a pharmacokinetic study of didanosine (ddI), formulated in sachets and in tablets, in patients with acquired immune deficiency syndrome (AIDS). Fifteen subjects received 250 or 167 mg of ddI twice daily as the sachet formulation and used this for at least 1 month. Subsequently, the patients were converted to receive ddI chewable/dispersible tablets (250-mg sachets to 200-mg tablets; 167-mg sachets to 125-mg tablets). Four subjects withdrew because of clinical deterioration or adverse effects. Serial blood samples were collected for pharmacokinetic monitoring during the use of the sachets and after 1 month of use of the tablets. No statistically significant differences were found in the maximum plasma concentration (Cmax), the time to reach Cmax (tmax), the area under the plasma concentration-time curve (AUC), or the terminal elimination half-life (t1/2) between the two formulations. Patients who received low-dose ddI (sachets, 167 mg; tablets, 125 mg) displayed lower plasma concentrations than did the patients receiving high-dose ddI (sachets, 250 mg; tablets, 200 mg), despite an equal weight-normalized dose of ddI in these two groups.

Absorption↗

PubMed1995

Degradation kinetics of antagonist [Arg6, D-Trp7,9, MePhe8]-substance P [6-11] in aqueous solutions.

Antagonist [Arg6, D-Trp7,9, MePhe8]-substance P {6-11} was subjected to a systematic stability study in which kinetic parameters were obtained for the degradation of this hexapeptide under several well-defined conditions. The influences of pH, temperature, ionic strength, buffer concentration, and initial concentration of the peptide on the reaction rate constant, kobs, were investigated with a stability-indicating reversed-phase high-performance liquid chromatographic system. From the pH-log kobs degradation profile, obtained at 63 degrees C, it appears that antagonist [Arg6, D-Trp7,9, MePhe8]-substance P {6-11} shows its maximum stability around pH 4.2. The half-life at this pH and temperature is 150 days. In both the hydroxyl- and proton-catalyzed parts of the pH-log kobs degradation profile, the influence of temperature was investigated and Arrhenius plots were constructed. The activation energies in both parts were comparable; however, the frequency factor in the hydroxyl-catalyzed part was 3.3 x 10(4) times higher than in the proton-catalyzed part. Eyring analysis of the data reveals that in both acidic and alkaline media the overall degradation was endotherm (delta H++ as well as delta G++ positive between 273 and 373 degrees K) and the entropy was negative. Increasing ionic strengths in acidic media causes an increase in kobs, while in alkaline media the kobs decreases with increasing ionic strength. Increasing buffer concentrations of acetate, phosphate, and carbonate led to an increase of kobs values. Drug concentrations up to 1 mg/ml at pH 10.8 and constant temperature and ionic strength have no influence on the overall degradation rate. At higher concentrations, above 1 mg/ml, kobs decreases.(ABSTRACT TRUNCATED AT 250 WORDS)

Buffers↗

PubMed1995

High-performance liquid chromatographic determination of the antifungal drug fluconazole in plasma and saliva of human immunodeficiency virus-infected patients.

A high-performance liquid chromatographic (HPLC) assay has been developed for the determination of the antifungal drug fluconazole in saliva and plasma of patients infected with the human immunodeficiency virus (HIV). Samples can be heated at 60 degrees C for 30 min to inactivate the virus without loss of the analyte. The sample pretreatment involves a liquid-liquid extraction with chloroform-1-propanol (4:1, v/v). The chromatographic analysis is performed on a Lichrosorb RP-18 (5 microns) column by isocratic elution with a mobile phase of 0.01 M acetate buffer (pH 5.0)-methanol (70:30, v/v) and ultraviolet (UV) detection at 261 nm. The lower limit of is 100 ng/ml in plasma (using 500-microliters samples) and 1 microgram/ml in saliva (using 250-microliters samples) and the method is linear up to 100 micrograms/ml in plasma and saliva. At a concentration of 5 micrograms/ml the within-day and between-day precision in plasma are 7.1 and 5.7%, respectively. In saliva the within-day and between-day precision is 10.8% (at 5 micrograms/ml). The methodology is now being used in pharmacokinetic studies in HIV-infected patients in our hospital.

Calibration↗

PubMed1995

A comparison between house mouse lines selected for attack latency or nest-building: evidence for a genetic basis of alternative behavioral strategies.

House mouse lines bidirectionally selected for either nest-building behavior or attack latency were tested for both attack latency and nest-building behavior under identical conditions. Male mice selected for high nest-building behavior had shorter attack latencies, i.e., were more aggressive, than those selected for low nest-building behavior and their randomly bred control lines. Conversely, male wild house mice selected for short attack latency showed more nest-building behavior than those selected for long attack latency when tested at 110 days of age. These findings imply a common genetic basis for control of aggression and nesting and support earlier proposals as to how animals may exhibit fundamentally different responses to environmental challenges, either reacting actively to aversive situations (aggressive and high-nesting animals: active copers) or adopting a passive strategy (nonaggressive and low-nesting animals: passive copers).

Aggression↗

PubMed1995

Identification of two alternatively spliced transcripts of STEP: a subfamily of brain-enriched protein tyrosine phosphatases.

A brain-enriched protein tyrosine phosphatase termed STEP46 (striatal enriched phosphatase) was previously isolated and characterized. Immunological studies with a STEP monoclonal antibody recognized several STEP-immunoreactive proteins, and suggested that additional STEP-related polypeptides existed. This study reports the isolation of two alternatively spliced transcripts of the STEP gene. One of these, STEP20 (with a predicted molecular mass of 20 kDa) was further characterized and found to lack the conserved tyrosine phosphatase domain. Northern analysis detected a 2.8 kb STEP20 message in mouse brain. The second alternatively spliced transcript, STEP61, has a 5'-extended open reading frame that encodes a protein with a predicted molecular mass of 61 kDa and contains a single tyrosine phosphatase domain. The exon-intron organization responsible for the novel STEP20 and STEP61 sequences was determined in the mouse STEP genomic DNA. We propose that the original STEP46, along with STEP20 and STEP61, are members of a brain-enriched subfamily of protein tyrosine phosphatases, and that STEP isoforms may have distinct functions within the central nervous system.

Alternative Splicing↗

PubMed1994

Reversed-phase high-performance liquid chromatography and capillary electrophoresis in the stability study of the neuropeptide growth factor antagonist [Arg6,D-Trp7,9,MePhe8]-substance P (6-11): a comparative study.

Reversed-phase high-performance liquid chromatography and capillary zone electrophoresis are widely used in protein and peptide analysis. Degradation of the basic peptide [Arg6,D-Trp7,9,MePhe8]-substance P (6-11) (antagonist G) was monitored with reversed-phase high-performance liquid chromatography, free capillary zone electrophoresis, and capillary zone electrophoresis with a capillary cationic coating. Capillary zone electrophoresis with a dynamically coated capillary provided better separation between antagonist G and its degradation products (formed at pH/Hv 13) than high-performance liquid chromatography and free zone capillary electrophoresis. Rate constants of the alkaline degradation of antagonist G measured with reversed-phase high-performance liquid chromatography and capillary zone electrophoresis with a dynamic coated capillary wall are similar whereas the values measured with free zone capillary electrophoresis are lower. Rate constants for the degradation of antagonist G in acidic media are comparable for the three techniques. It is concluded that capillary zone electrophoresis using a dynamic coating with Fluorad is the most suited of the above-mentioned techniques in analyzing antagonist G and its degradation products.

Amino Acid Sequence↗

PubMed1994

Pharmaceutical development of a parenteral lyophilized formulation of the novel indoloquinone antitumor agent EO9.

The aim of this study was to design a stable parenteral dosing form of the investigational cytotoxic drug, encoded EO9. EO9 exhibits poor aqueous solubility and stability characteristics. Freeze-drying was selected as the manufacturing process. Differential scanning calorimetry studies were conducted to determine the freeze-drying cycle parameters. A stable lyophilized formulation of EO9 was developed. The prototype, containing 8.0 mg EO9 and 200 mg lactose/vial, was found to be the optimal formulation in terms of solubility, length of the freeze-drying cycle, stability, and dosing requirements for phase I clinical trials. Quality control of the freeze-dried formulation showed that the manufacturing process does not change the integrity of EO9. Shelf-life studies demonstrated that the formulation remains stable for at least 1 year when stored at +4 degrees C in a dark environment.

Antineoplastic Agents↗

PubMed1994

Plasma pharmacokinetics, tissue disposition, excretion and metabolism of vinleucinol in mice as determined by high-performance liquid chromatography.

We investigated the pharmacokinetics of the experimental semisynthetic vinca alkaloid vinleucinol (VileE; O4-deacetyl-3-de(methoxycarbonyl)-3-[[[1-ethoxycarbonyl-2- methylbutyl]amino]carbonyl]-vincaleukoblastine). The study was performed in male FVB mice receiving 10.5 mg/kg VileE i.v. or p.o. Plasma, urine, faeces and tissue samples were analysed by a selective method based on ion-exchange normal-phase high-performance liquid chromatography (HPLC) with fluorescence detection and liquid-liquid extraction for sample clean-up. Apart from the parent drug, two other metabolic compounds were detected. One of these metabolites is vinleucinol acid (VileA; O4-deacetyl-3-de(methoxycarbonyl)-3-[[[1-carboxyl-2- methylbutyl]amino]carbonyl]-vincaleukoblastine), which possesses no cytotoxic activity. The structure proposed for the second metabolite (VileX) was based on tandem mass spectrometry (MS-MS) and infrared (IR) spectroscopy data. Metabolization of VileE to VileX must occur in the amino acid moiety of the molecule, with a (beta- or gamma-) lactone ring being formed after oxidation of the (beta- or gamma) carbon of the amino acid. VileX is a major metabolite, which is excreted in faeces and urine after i.v. administration and accounting for up to 23% of the administered dose. The activity of VileX against cultured L1210 cells is four times that of the parent drug VileE and comparable with that of vinblastine (VBL). At 48 h after administration of VileE, the concentration of VileX exceeds that of the parent drug in many tissues. These findings indicate that the metabolite VileX may be at least largely responsible for the activity observed against xenografts in mice after administration of the parent drug, VileE.

Animals↗

PubMed1994

Pharmaceutical development of a parenteral formulation of the novel anti-tumor agent carzelesin (U-80,244).

The aim of this study was to design a parenteral dosage form for the investigational cytotoxic drug carzelesin. A stable formulation in PET (Polyethylene glycol 400/absolute ethanol/Tween 80, 6:3:1, v/v/v) was developed. The prototype, containing 0.50 mg carzelesin in 2.0 ml PET formulation, was found to be the optimal formulation in terms of solubility, stability and dosage requirements in phase I clinical trials. Quality control of the formulation showed that the pharmaceutical preparation of carzelesin in PET is not negatively influenced by the manufacturing process. Shelf life studies demonstrated that the formulation is stable for at least 1 year, when stored at -30 degrees C in the dark. In addition, the stability of carzelesin in the PET formulation is discussed as a function of temperature, additives and after dilution in infusion fluids.

Antineoplastic Agents↗

PubMed1994

Chemiluminescence and immunoassays.

The principles of chemiluminescence and the application of chemiluminescent labels and substrates in immunoassays are reviewed. Various immunoassay formats and all known classes of chemiluminescent molecules, including 1,2-dioxetanes, luminol and derivatives, acridinium esters, oxalate esters and firefly luciferins are described as well as the many sensitizers and fluorescent enhancers. Recent promising developments are discussed.

Animals↗