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Biomedical subjects

D J Miller

Publications and source records attributed to D J Miller.

At least 19 recordsLinked to original sources
PubMed1992

Quantitative determination of sulfonated aliphatic and aromatic surfactants in sewage sludge by ion-pair/supercritical fluid extraction and derivatization gas chromatography/mass spectrometry.

Secondary alkanesulfonate (SAS) and linear alkylbenzene-sulfonate (LAS) surfactants were quantitatively (> 90%) extracted from sewage sludges as their tetrabutylammonium ion pairs using 400 atm of supercritical CO2 for 5 min of static extraction followed by 10 min of dynamic extraction at 80 degrees C. Ion pairs of SAS and LAS quantitatively formed butyl esters in the injection port of the gas chromatograph and were determined by gas chromatography/mass spectrometry without class fractionation of the sewage sludge extracts. Concentrations of SAS and LAS in sludges from five different sewage treatment plants ranged from 0.27 to 0.80 g/kg of dry sewage sluge and from 3.83 to 7.51 g/kg, respectively. Good reproducibility was achieved with RSDs of typically 5% for replicate extractions and analyses. Homologue and isomer distributions of SAS in sewage sludge indicated an enrichment of the more hydrophobic components in sewage sludge during sewage treatment.

Alkanesulfonates↗
PubMed1992

Solventless determination of caffeine in beverages using solid-phase microextraction with fused-silica fibers.

Caffeine concentrations in beverages were determined using a simple and rapid method based on microextraction of caffeine onto the surface of a fused-silica fiber. The uncoated fiber was dipped into the beverage sample for 5 min after the addition of isotopically labeled (trimethyl 13C)caffeine. The adsorbed caffeine was then thermally desorbed in a conventional split/splitless injection port, and the concentration of caffeine was determined using gas chromatography with mass spectrometric detection. Quantitative reproducibilities were ca. 5% (relative standard deviation) and the entire scheme including sample preparation and gas chromatographic analysis was completed in ca. 15 min per sample. The potential of the microextraction technique for the analysis of flavor and fragrance compounds in non-caffeinated beverages is also demonstrated. Since no solvents or class-fractionation steps are required, the method has good potential for automation.

Beverages↗
PubMed1992

Complementarity between sperm surface beta-1,4-galactosyltransferase and egg-coat ZP3 mediates sperm-egg binding.

Despite its importance, the molecular basis of mammalian gamete recognition has remained unclear. The enzyme beta-1,4-galactosyltransferase (Gal-transferase) has been viewed traditionally as a biosynthetic component of the Golgi complex, but is also found on the surface of many cells where it can bind its specific glycoside substrate on adjacent cell surfaces or in the extracellular matrix. In mouse it has been suggested that Gal-transferase on the sperm head mediates fertilization by binding oligosaccharide residues in the egg coat, or zona pellucida, and that the ability of the zona pellucida to bind sperm is conferred by oligosaccharides of the ZP3 glycoprotein. However, it has not been confirmed that Gal-transferase and ZP3 are in fact complementary gamete receptors whose interaction mediates sperm-egg binding. Here we show that mouse sperm Gal-transferase specifically recognizes those oligosaccharides on ZP3 that have sperm-binding activity, but does not interact with other zona pellucida glycoproteins. In contrast, all zona pellucida glycoproteins are recognized by non-sperm Gal-transferase, demonstrating a more stringent substrate specificity for the sperm enzyme. This interaction is required for sperm-egg binding because blocking or removing the binding site for Gal-transferase on ZP3 inhibits its ability to bind sperm. After the release of the sperm acrosome, the transferase relocalizes to a new membrane domain where it can no longer bind to ZP3, which is consistent with the inability of acrosome-reacted sperm to bind ZP3 or to initiate binding to the zona pellucida. Following fertilization, ZP3 is modified by egg cortical granule secretions so that it loses sperm receptor activity, which can be accounted for by a selective loss of its binding site for sperm Gal-transferase. These results show that sperm surface beta-1,4-galactosyltransferase and the egg-coat glycoprotein ZP3 are complementary adhesion molecules that mediate primary gamete binding in the mouse.

Acrosome↗
PubMed1992

Analysis of novel imidazoles from isolated perfused rabbit heart by two high-performance liquid chromatographic methods.

The paper reports two analytical high-performance liquid chromatographic methods to detect and quantify cardiac-derived histidyl derivatives. Method A relies on relative hydrophobicities as a basis of separation. Method B is an ion-pairing method in which the compounds are eluted in an entirely different order. Fractions collected from method A have been co-eluted in admixture in method B with authentic reference compounds. Thus the existence of the following imidazole ring-containing compounds derived from heart have been confirmed: N-acetylhistidine, N-acetyl-1-methylhistidine, N-acetylcarnosine, N-acetylhomocarnosine, homocarnosine, anserine, carnosine, balenine. Compounds were found in both tissue samples and perfusates.

Animals↗
PubMed1992

Genomes of diploblastic organisms contain homeoboxes: sequence of eveC, an even-skipped homologue from the cnidarian Acropora formosa.

We report the nucleotide sequence of eveC, a cnidarian eve-class homeobox; this is the first homeobox to be identified in any diploblastic organism, and is only the second eve-class in an invertebrate. Similarity between the predicted amino acid sequence of the eveC homeodomain and its insect and vertebrate equivalents was approximately 75-80% but, in the case of eveC, a role in segmentation can be ruled out. Our findings thus support the 'co-option' hypothesis: homeoboxes were an early feature of metazoan genomes, corresponding to the DNA-binding domains of more general transcription factors.

Amino Acid Sequence↗
PubMed1992

A single autosomal gene defect severely limits IgG but not IgM responses in B lymphocyte-deficient A/WySnJ mice.

Antigen-stimulated B lymphocytes either differentiate into IgM-secreting plasma cells or into memory B cells that secrete other immunoglobulin isotypes upon antigen restimulation. The mechanisms that generate and maintain memory B cells are poorly understood. Previously, we described a severe B lymphocyte deficiency in adult strain A/WySnJ mice compared to subline A/J. Here we show that the single, autosomal co-dominant locus responsible for the deficiency also diminishes IgG-secreting B cell formation without interfering with IgM-secreting plasma cell differentiation. A/WySnJ secondary IgG1 responses to the protein antigens hemocyanin, bovine gamma-globulin, ovalbumin, lysozyme and beta-galactosidase were 6- to 50-fold lower than A/J responses. The defect also decreased secondary IgG2a and IgG3 responses, and primary IgG1 and IgG2a responses. The reduced A/WySnJ secondary IgG1 response was not due to differential response kinetics or dose responsiveness, and could not be augmented to A/J levels by repeated immunizations. Serum IgG1, IgG2a and IgG3 levels from nonimmune A/WySnJ mice were similarly reduced. The secondary IgG1 response and splenic B cell percentage showed significant positive correlation (r = 0.72) in F2 mice, suggesting that a single locus controlled both traits. In contrast, A/WySnJ mice made good primary IgM responses to hemocyanin, beta-galactosidase, and the thymus-independent antigen trinitrophenyl-Ficoll. The A/WySnJ splenic adherent cells were competent in antigen-presenting function, and A/WySnJ immune T cells proliferated in response to antigen and provided the requisite B cell stimulatory signals for an IgG1 response. Together, our results suggest that A/WySnJ mice have a genetic lesion that causes a selective IgG immune response dysfunction. The absence of IgG-secreting cell precursors or a defect in precursor activation or differentiation are two possible mechanisms which could precipitate a selective IgG response dysfunction. We propose that the defective A/WySnJ and normal A/J strain pair offer the opportunity to use a natural genetic variation as a tool to investigate B lymphocyte development and function.

Animals↗
PubMed1992

Effects of cAMP and forskolin on caffeine-induced contractures and myofilament Ca-sensitivity in saponin-treated rat ventricular trabeculae.

Trabeculae from the right ventricle of rat were chemically 'skinned' with saponin (50 micrograms ml-1 for 30 min). Caffeine (10 mM) induced a transient contracture as a consequence of Ca(2+)-release from the sarcoplasmic reticulum and subsequent activation of the myofilaments. The amplitude of the caffeine contracture was used as an index of the Ca(2+)-content of the sarcoplasmic reticulum. cAMP (0.1-10 microM) markedly potentiated the caffeine-induced response under standardized conditions. This was interpreted as a cAMP-induced increase in Ca2+ accumulation by the sarcoplasmic reticulum during the Ca2+ loading period before the application of caffeine. After removal of cAMP, the amplitude of the regularly evoked contractures slowly declined towards standard levels. The characteristic effects of cAMP on the caffeine contracture were mimicked by addition of forskolin (10(-6) M), a substance known to stimulate cAMP production by adenylate cyclase. The results suggest that a significant quantity of functional adenylate cyclase persists after saponin treatment. In these preparations cAMP had no effect on the apparent Ca(2+)-sensitivity of the myofilaments. If the preparations were exposed briefly to saponin, cAMP caused a decrease in the apparent Ca2+ sensitivity of the contractile proteins. However, further exposure to saponin, or to Triton X-100, caused a marked increase in maximum Ca(2+)-activated force (Cmax). It was concluded that 'briefly' saponin-treated preparations, exhibiting a reduction in Ca2+ sensitivity in response to cAMP, are not uniformly permeable to the bathing solution.

Actin Cytoskeleton↗
PubMed1992

Nucleotide sequence of a cDNA from Onchocerca gibsoni encoding a novel repetitive antigen.

mRNA from uterine microfilariae of the cattle parasite Onchocerca gibsoni was used for the construction of cDNA libraries. A cDNA clone encoding an antigen recognized by serum from human individuals infected with O. volvulus was found to contain five copies of an 87 bp unit. These 87 bp units were present in the genome in high copy number as long tandem arrays. These are the first cDNA sequence data obtained directly from larvae of any Onchocerca species.

Amino Acid Sequence↗
PubMed1992

Hyperfractionated radiation therapy and concurrent 5-fluorouracil, cisplatin and mitomycin-C in head and neck carcinoma. A pilot study.

Seventeen patients were entered into a Phase I/II trial of concurrent hyperfractionated radiation therapy (7,440 cGy total dose; 120 cGy b.i.d.) combined with constant infusion of 5-fluorouracil (5-FU) (1,000 mg/m2/24 hours for 72 hours) and cisplatin (DDP) (50 mg/m2) for a total of three cycles. Thirteen patients had Stage IV disease; three, Stage III disease; and one, Stage II hypopharyngeal disease. Thirteen of 17 patients had positive cervical lymph nodes, and the mean size of the largest lymph node was 5.5 x 5.1 cm. The patients were not treated with planned adjunctive surgery except for one patient who had a radical neck dissection for massive, rapidly growing cervical adenopathy, which recurred promptly within 1 month before the initiation of protocol therapy. After the initial six patients were entered, mitomycin-C (Mito 8 mg/m2) was added during the second cycle. All the patients completed the planned course of radiotherapy with a median dose of 7,440 cGy and a mean dose of 7,248 cGy except for two patients who died--one from toxicity and the other, suicide. The predominant toxicity was mucositis, which was grade 3/4 in 11 of 15 patients, resulting in an average interruption of radiation therapy of 12 days. Weight loss was significant and was on the average 12% of baseline weight. Hematological toxicity was mild in the 5-FU/DDP group (only one grade 3 toxicity of six) and severe in the 5-FU/DDP/Mito-treated patients (five of eight patients having grade 3/4 toxicity including one leukopenic pneumonitis death). Additional toxicity included one parapharyngeal cellulitis, which responded to antibiotics. Noncompliance with the complex regimen was only seen in three patients. One patient refused b.i.d. radiation therapy, and one patient refused further chemotherapy after the first cycle. Additionally, one patient who had a severe ethanol withdrawal reaction during the first cycle of 5-FU/DDP did not receive further chemotherapy. The complete response rate of both primary site and neck by the protocol regimen alone was 71%. However, two patients, one from each group, did undergo salvage neck dissection, and the locoregional control is currently 73%, with a mean follow-up time of 18.4 months. The feasibility of combining hyperfractionated radiation therapy with aggressive concurrent chemotherapy was demonstrated. The response and local control rate justifies the added toxicity of concurrent chemotherapy and radiation therapy.

Adult↗
PubMed1992

Calcium sensitizing action of carnosine and other endogenous imidazoles in chemically skinned striated muscle.

1. The imidazole-containing compounds carnosine and homocarnosine, endogenous to skeletal and cardiac muscle, have been tested for effect on the contractile behaviour of chemically skinned (saponin or Triton X-100) skeletal and cardiac muscle. 2. Carnosine, at millimolar concentrations which are near physiological for many skeletal fibres, and in a concentration-dependent fashion, shifts the curve relating [Ca2+] to steady-state tension to lower [Ca2+] in both skeletal (frog but not crab) and cardiac (rat) muscle preparations. 3. Of other imidazoles endogenous to heart, homocarnosine is somewhat more effective, while N-acetyl L-histidine is much less so. 4. The maximum level of Ca(2+)-activated force is increased significantly by homocarnosine in cardiac trabeculae. 5. We propose that the cellular imidazoles related to carnosine are natural 'Ca2+ sensitizers' in striated muscle. Alterations in their levels as a result of disease or training, and between different fibre types, may contribute to differences in contractile performance of the intact tissues.

Animals↗
PubMed1992

Depression of peak force without altering calcium sensitivity by the superoxide anion in chemically skinned cardiac muscle of rat.

Among the mechanisms postulated to contribute to myocardial "stunning" is a depression of contractility by oxygen-derived free radicals. It has been suggested that these radicals might depress the calcium sensitivity of the contractile proteins. We have exposed the myofilaments (in chemically "skinned" rat cardiac muscle) to the superoxide anion and measured isometric force at controlled degrees of activation. Superoxide was generated by the xanthine/xanthine oxidase system: the effects to be described were shown to be specifically attributable to superoxide. Maximum calcium-activated force is reduced, or even completely abolished, in a dose-dependent fashion and without any alteration in calcium sensitivity. The myofilaments are highly sensitive to superoxide: significant force reduction has been shown to be caused by enzyme concentrations as low as 2 microunits/ml xanthine oxidase and with exposures of less than 1 minute to the generating system (at higher enzyme concentrations). Once force has been depressed, it cannot be recovered within the duration of the experiments described. When xanthine oxidase is applied during the calcium-induced contracture, tension falls steadily. However, a similar concentration is without immediate effect on the rigor contracture (evoked by applying ATP-free solutions). To account for the depression of maximum calcium-activated force, we conclude that some aspect of crossbridge behavior is particularly vulnerable to superoxide rather than that the radical has a nonspecific "proteolytic" effect. This action on the fundamental units of force production could contribute to myocardial stunning since the effects we report are consistent with many aspects of this phenomenon.

Actin Cytoskeleton↗
PubMed1992

The role of instrumental responses in memory retrieval in a T-maze.

Retrieval of the memory of non-reward on a rewarded trial was investigated here employing rats in a T-maze. A forced choice procedure was used. The daily rewarded (R) and non-rewarded (N) trials always occurred in a fixed order, two R, four N, and finally two R, i.e. the series was R1-R2-N1-N2-N3-N4-R3-R4. In an original acquisition phase. Trial N4 of the series having occurred in a particular spatial alternative, e.g. left, it was followed by R3 either in the same alternative, Groups C and T, or in the opposite alternative, Group R. Group T, unlike Groups C and R, received a relatively long intertrial interval between N4 and R3. In a shift phase, groups were treated as in original acquisition except that the long intertrial interval (Group T) and the change in response (Group R) now occurred between R3 and R4 rather than N4 and R3. The major finding in original acquisition was slower running by Groups T and R than by Group C on Trials N2, N3, and N4. In shift, differences between the groups disappeared. These findings are consistent with the hypothesis that response-produced cues contribute to memory retrieval.

Animals↗
PubMed1991

Physicochemical characterization of dodecylphosphocholine/palmitoyllysophosphatidic acid/myelin basic protein complexes.

The stoichiometry of dodecylphosphocholine/palmitoyllysophosphatidic acid/myelin basic protein complexes and the location of the protein in the micelles have been investigated by electron paramagnetic resonance, ultracentrifugation, small-angle X-ray scattering, 31P, 13C, and 1H nuclear magnetic resonance spectroscopy, and electron microscopy. Ultracentrifugation measurements indicated that well-defined complexes are formed by association of one protein molecule with approximately 133 detergent molecules. The spin-labels 5-, 12-, and 16-doxylstearate have been incorporated into detergent/protein aggregates. Electron paramagnetic resonance spectral parameters and 13C and 1H nuclear magnetic resonance relaxation times showed that the addition of myelin basic protein does not affect the environment and location of the labels or the organization of the micelles. Previous results suggesting that the protein lies primarily near the surface of the micelles have been confirmed by comparing 13C spectra of the detergents with and without protein with spectra of detergent/protein aggregates containing the spin labels. Electron micrographs of the complexes taken by using the freeze-fracture technique revealed the presence of particles with an estimated radius about three times the radius of the micelles measured by small-angle X-ray scattering. The structural integrity of the complexes appears to be based on intramolecular protein interactions as well as protein-detergent interactions.

Animals↗
PubMed1991

Phenotypic and genetic characterization of a unique B lymphocyte deficiency in strain A/WySnJ mice.

The elucidation of B lymphocyte development has been partially achieved through genetic models such as the X-linked immunodeficiency (xid) mutation. We discovered a unique B lymphocyte developmental defect in strain A/WySnJ mice. We used single- and two-color flow cytometry to analyze lymphocytes from A/J and A/WySnJ mice. Adult A/WySnJ mice had a severe B cell deficiency, which was apparent in the spleen, lymph nodes, peritoneum and peripheral blood, compared to adult A/J mice. An ontogeny study revealed that a developmental defect, inhibiting B lymphocyte maturation or differentiation but not B lymphopoiesis, was responsible for the deficiency. This maturational defect blocked the production of B220hi/Iahi/surface IgMlo B cells, and was manifested in the adult bone marrow and neonatal spleen, but not the adult spleen. Neither Ly-1 B cells nor peripheral T cells were apparently affected by the A/WySnJ defect. The B cell immunodeficiency segregated as an autosomal co-dominant trait in F1 and F2 mice. We propose that A/WySnJ mice have a novel genetic defect arresting B cell differentiation in adult bone marrow and neonatal spleen.

Animals↗
PubMed1991

Computer-controlled positive displacement pump for physiological flow simulation.

A computer-controlled pump for use both in the study of vascular haemodynamics and in the calibration of clinical devices which measure blood flow is designed. The novel design of this pump incorporates two rack-mounted pistons, driven into opposing cylinders by a micro-stepping motor. This approach allows the production of nearly uninterrupted steady flow, as well as a variety of pulsatile waveforms, including waveforms with reverse flow. The capabilities of this pump to produce steady flow from 0.1 to 60 ml s-1, as well as sinusoidal flow and physiological flow, such as that found in the common femoral and common carotid arteries are demonstrated. Cycle-to-cycle reproducibility is very good, with an average variation of 0.1 ml s-1 over thousands of cycles.

Arteries↗
PubMed1991

Synergism of histidyl dipeptides as antioxidants.

Histidyl dipeptides such as carnosine (beta-alanyl-L-histidine) and homocarnosine (gamma-amino-butyryl-L-histidine) are reported at millimolar concentrations in several mammalian tissues (O'Dowd et al., 1988; House et al., 1989), but their precise physiological function, or functions, is uncertain. These compounds are known to be potent buffers at physiological pH (Davey, 1960). They are also able to restore functional capacity to fatigued muscle preparations, stimulate some glycolytic enzymes and maintain coupling between mitochondrial oxidation and phosphorylation (Severin, 1964). Histidyl dipeptides may also have antioxidant activity, though this finding is controversial. For example, Aruoma et al. have argued that these compounds, individually, are unable to scavenge superoxide (O2-.), hydrogen peroxide (H2O2) or hypochlorous acid (HOCl) at rates which could offer antioxidant protection in vivo. Since there is a range of these histidyl dipeptides within mammalian tissue we have investigated possible synergism between them in respect of antioxidant activity. Our results show that combining histidine-containing compounds at near physiological concentrations results in synergistic antioxidant activity.

Anserine↗