Biomedical subjects

C M Moore

Publications and source records attributed to C M Moore.

At least 37 records · Page 2Linked to original sources

PubMed2000

Responses of inferior colliculus neurons to amplitude-modulated intracochlear electrical pulses in deaf cats.

Current cochlear prostheses use amplitude-modulated pulse trains to encode acoustic signals. In this study we examined the responses of inferior colliculus (IC) neurons to sinusoidal amplitude-modulated pulses and compared the maximum unmodulated pulse rate (Fmax) to which they responded with the maximum modulation frequency (maxFm) that they followed. Consistent with previous results, responses to unmodulated pulses were all low-pass functions of pulse rate. Mean Fmax to unmodulated pulses was 104 pulses per second (pps) and modal Fmax was 60 pps. Above Fmax IC neurons ceased responding except for an onset burst at the beginning of the stimulus. However, IC neurons responded to much higher pulse rates when these pulses were amplitude modulated; 74% were relatively insensitive to carrier rate and responded to all modulated carriers including those exceeding 600 pps. In contrast, the responses of these neurons (70%) were low-pass functions of modulation frequency, and the remaining (30%) had band-pass functions with a maxFm of 42 and 34 Hz, respectively. Thus temporal resolution of IC neurons for modulated frequencies is significantly lower than that for unmodulated pulses. These two measures of temporal resolution (Fmax and maxFm) were uncorrelated (r(2) = 0.101). Several parameters influenced the amplitude and temporal structure of modulation responses including modulation depth, overall intensity and modulation-to-carrier rate ratio. We observed distortions in unit responses to amplitude-modulated signals when this ratio was 1/4 to 1/6. Since most current cochlear implant speech processors permit ratios that are significantly greater than this, severe distortion and signal degradation may occur frequently in these devices.

Animals↗

PubMed2000

Brain kinetics of paroxetine and fluoxetine on the third day of placebo substitution: a fluorine MRS study.

OBJECTIVE: This study tested whether a relationship exists between concentration and response following discontinuation of selective serotonin reuptake inhibitors. METHOD: Eight patients with remitted major depression who were taking 20 mg/day of either fluoxetine or paroxetine underwent placebo substitution for 3 days. Serum drug and brain fluorine levels were obtained before and after placebo substitution. RESULTS: With placebo substitution, a mean of 88% (SD=13%) of brain fluorine signal from fluoxetine (plus fluorinated metabolites) remained, compared with a mean of 38% (SD=17%) of the brain fluorine signal from paroxetine (plus fluorinated metabolites). Among patients taking paroxetine, adverse events during placebo substitution correlated highly with steady-state brain drug levels. CONCLUSIONS: The correlation of clinical effects with brain drug levels in the paroxetine group suggests that relationships between drug response and brain drug concentrations merit further investigation.

Adult↗

PubMed2000

Role of perceptual organization while attending in depth.

Seven experiments were conducted in order to explore the conditions under which visual attention can be allocated in depth. In each experiment, observers were cued to the most likely target location in stereoscopic depth displays, and targets could appear in either the cued location or in another location. In Experiments 1 and 2, we show that previous failures to observe effects of cuing in depth may have depended on the specific timing characteristics of the displays. In Experiments 3, 4, and 5, we eliminated the hypothesis, suggested by Experiments 1 and 2, that in order to allocate attention in depth, attention must be allocated to a specific object token. Experiment 6 provides evidence that, in the absence of other organizing information (e.g., color), attention can be allocated in depth on the basis of the surface information available in the display. Finally, in Experiment 7, we demonstrate that, although sufficient, surface information is not necessary for the allocation of attention; color supported the allocation of attention across multiple items that failed to fall on a single coherent surface in depth. Together, these findings suggest that attention in depth, like attention in two-dimensional displays, is determined by the perceptual organization of the display.

Attention↗

PubMed2000

m-hydroxy benzoylecgonine recovery in fetal guinea pigs.

Recently, meta-hydroxybenzoylecgonine (m-OH BE) was identified by gas chromatography-mass spectroscopy during quantitative analysis for cocaine. Identification of m-OH BE in addition to the routinely identified benzoylecgonine by gas chromatography-mass spectroscopy confirmatory assays may increase detection of cocaine-exposed infants and decrease false negative results. However, it is not known whether m-OH BE is derived directly from benzoylecgonine or from hydroxylated cocaine, or whether this metabolite is produced in the fetus or transferred across the placenta from the maternal circulation. We quantitated the recovery of cocaine, benzoylecgonine, and m-OH BE from amniotic fluid, fetal meconium, fetal intestine, and maternal urine for up to 4 days after single dose administration of either cocaine or benzoylecgonine to pregnant time-bred guinea pigs. m-OH BE was recovered from meconium after maternal injections of cocaine and benzoylecgonine. There was no significant detection of m-OH BE from amniotic fluid or intestine and minimal recovery from maternal urine after either cocaine or benzoylecgonine administration. Detection of m-OH BE in meconium increased the identification of in utero exposed guinea pigs, and the greatest yield of m-OH BE from meconium occurred later than that observed for cocaine or benzoylecgonine.

Amniotic Fluid↗

PubMed2000

Elimination of 7-aminoflunitrazepam and flunitrazepam in urine after a single dose of Rohypnol.

The hypnotic benzodiazepine flunitrazepam (Rohypnol) has been identified as the drug of choice for the purposes of "drugging" unsuspecting victims and raping them while they are under the influence of this substance. The objective of this paper was to study elimination of flunitrazepam and 7-aminoflunitrazepam in urine collected from ten healthy volunteers who received a single 2 mg oral dose of Rohypnol, to determine how long after drug administration 7-aminoflunitrazepam can be detected. A highly sensitive NCI-GC-MS method for the simultaneous quantitation of flunitrazepam (LOQ 100 pg/mL) and 7-aminoflunitrazepam (LOQ 10 pg/mL) in urine was developed. All samples were screened for benzodiazepines using optimized micro-plate enzyme immunoassay. The highest concentrations of 7-aminoflunitrazepam (70-518 ng/mL) and flunitrazepam (0.7-2.8 ng/mL) in urine were observed 6 h after drug administration in nine subjects and after 24 h in one subject. In six subjects 7-aminoflunitrazepam was detected up to 14 days after flunitrazepam administration, in one subject up to 21 days and in three subjects up to 28 days. In urine samples collected from six volunteers, flunitrazepam was detected three days after Rohypnol intake, in three subjects 24 h, and in one subject 5 days later. Benzodiazepine micro-plate enzyme immunoassay kit allowed the detection of flunitrazepam and metabolities 5 to 21 days after drug administration.

Adult↗

PubMed1999

Effects of myo-inositol ingestion on human brain myo-inositol levels: a proton magnetic resonance spectroscopic imaging study.

BACKGROUND: Cerebrospinal fluid levels of myo-Inositol (m-Ino) are reported to be decreased in patients with affective disorder, and dietary supplements of m-Ino have been shown to reduce the symptoms of major depression. Myo-Inositol transport across the blood-brain barrier is mediated by a low capacity, saturable system. This study tests whether dietary m-Ino increases brain m-Ino or changes brain metabolism of m-Ino, possibly explaining the ability of this compound to alter mood. METHODS: Using proton magnetic resonance spectroscopic imaging, we measured m-Ino levels in occipital gray and parietal white matter of seventeen healthy subjects. Magnetic resonance spectroscopic imaging was performed twice at baseline as well as at day 4 and day 8 while subjects ingested 6 g of m-Ino twice a day. RESULTS: Following 4 days of m-Ino, m-Ino/Cr was 20% higher than baseline levels in occipital gray matter (p < 0.04) and 8% higher in parietal white matter (p = ns). By day 8, m-Ino/Cr ratios had returned to baseline values. CONCLUSIONS: Brain m-Ino levels initially increase during m-Ino administration and subsequently return to baseline levels. The time-limited increases observed for brain m-Ino may reflect homeostatic mechanisms, possibly associated with the role of m-Ino as a cerebral osmolyte, or with changes in brain phosphoinositide metabolism.

Adult↗

PubMed1999

Cytogenetic and fertility studies of a rheboon, rhesus macaque (Macaca mulatta) x baboon (Papio hamadryas) cross: further support for a single karyotype nomenclature.

Historically, two different numbering systems have been used to describe the baboon and macaque karyotypes. However, G-banding studies and, more recently, fluorescence in situ hybridization results have shown that the two karyotypes are virtually identical. To confirm this hypothesis, cytogenetic analysis of an unusual animal, a rheboon, was undertaken. The rheboon reported here, an 18-year-old male, is the only long-term survivor of 26 pregnancies resulting from matings between female baboons (Papio hamadryas) and male rhesus macaques (Macaca mulatta). A G-banded karyotype was prepared from the rheboon and compared with the karyotypes of the two parental species. Spectral karyotyping (SKY) was carried out on the rheboon chromosomes, and the results were compared with SKY studies reported for the baboon and with CISS (chromosome in situ suppression) studies in the rhesus macaque. No differences were detected in any of the rheboon's pairs of autosomes, reinforcing the apparent identity of the two parental karyotypes. Based on these results, we argue that a single karyotyping system should be adopted for the two species. Fertility studies were initiated to determine if the rheboon is sterile, as are most hybrid animals. Two semen ejaculates were devoid of sperm. A testicular biopsy revealed hypoplasia of the seminiferous tubules with few Leydig cells and large lumena. Meiotic arrest occurred during meiosis I, resulting in absence of mature spermatozoa. Thus, the testicular and meiotic findings in the rheboon were similar to those observed in other hybrids, even though the parental karyotypes appear identical.

Animals↗

PubMed1999

Temporal properties of chronic cochlear electrical stimulation determine temporal resolution of neurons in cat inferior colliculus.

As cochlear implants have become increasingly successful in the rehabilitation of adults with profound hearing impairment, the number of pediatric implant subjects has increased. We have developed an animal model of congenital deafness and investigated the effect of electrical stimulus frequency on the temporal resolution of central neurons in the developing auditory system of deaf cats. Maximum following frequencies (Fmax) and response latencies of isolated single neurons to intracochlear electrical pulse trains (charge balanced, constant current biphasic pulses) were recorded in the contralateral inferior colliculus (IC) of two groups of neonatally deafened, barbiturate-anesthetized cats: animals chronically stimulated with low-frequency signals (< or = 80 Hz) and animals receiving chronic high-frequency stimulation (> or = 300 pps). The results were compared with data from unstimulated, acutely deafened and implanted adult cats with previously normal hearing (controls). Characteristic differences were seen between the temporal response properties of neurons in the external nucleus (ICX; approximately 16% of the recordings) and neurons in the central nucleus (ICC; approximately 81% of all recordings) of the IC: 1) in all three experimental groups, neurons in the ICX had significantly lower Fmax and longer response latencies than those in the ICC. 2) Chronic electrical stimulation in neonatally deafened cats altered the temporal resolution of neurons exclusively in the ICC but not in the ICX. The magnitude of this effect was dependent on the frequency of the chronic stimulation. Specifically, low-frequency signals (30 pps, 80 pps) maintained the temporal resolution of ICC neurons, whereas higher-frequency stimuli significantly improved temporal resolution of ICC neurons (i.e., higher Fmax and shorter response latencies) compared with neurons in control cats. Furthermore, Fmax and latencies to electrical stimuli were not correlated with the tonotopic gradient of the ICC, and changes in temporal resolution following chronic electrical stimulation occurred uniformly throughout the entire ICC. In all three experimental groups, increasing Fmax was correlated with shorter response latencies. The results indicate that the temporal features of the chronically applied electrical signals critically influence temporal processing of neurons in the cochleotopically organized ICC. We suggest that such plastic changes in temporal processing of central auditory neurons may contribute to the intersubject variability and gradual improvements in speech recognition performance observed in clinical studies of deaf children using cochlear implants.

Acoustic Stimulation↗

PubMed1999

Compounds containing cytosolic choline in the basal ganglia: a potential biological marker of true drug response to fluoxetine.

OBJECTIVE: Studies have identified two types of antidepressant response: true drug response and placebo pattern response. This study examined the relationship between true drug response and choline-creatine ratios in the basal ganglia of depressed patients treated with fluoxetine. METHOD: The authors evaluated drug-free outpatients with major depression before (N = 41) and after (N = 15) 8 weeks of fluoxetine treatment, 20 mg/day, by using proton magnetic resonance spectroscopy. RESULTS: There was a significant difference in the degree of change from baseline to week 8 in choline-creatine ratios between the true drug response group (N = 8) and the placebo pattern response/nonresponse group (N = 7); the true drug response patients had a 20% increase in choline-creatine ratios, and the placebo pattern response/nonresponse patients had a 12% decrease in choline-creatine ratios. CONCLUSIONS: These data suggest that true drug response to fluoxetine treatment in depression may be associated with an increase in choline-creatine ratios in the basal ganglia.

Adult↗

PubMed1999

Brain biochemistry using magnetic resonance spectroscopy: relevance to psychiatric illness in the elderly.

Magnetic resonance spectroscopy (MRS) allows for the noninvasive study of cerebral biochemistry. It has been used to investigate cerebral metabolic changes associated with mental illness in vivo and in vitro. In this review, we will discuss the application of MRS to psychiatric illness in the elderly. Following a brief description of the basic principles of MRS, the use of phosphorus (31P) and proton (1H) MRS to enable a better understanding of normal brain aging, dementia (Alzheimer's disease, multiple subcortical infarct dementia, Down syndrome, frontotemporal dementia, vascular dementia, age-associated memory impairment, and other dementias), major depression, and electroconvulsive therapy is detailed.

Aged↗

PubMed1998

Determination of phenethylamine, a phenethyl isothiocyanate marker, in dog plasma using solid-phase extraction and gas chromatography-mass spectrometry with chemical ionization.

Phenethyl isothiocyanate is unstable in aqueous media and at low pH, and rapidly degrades to phenethylamine. Concentrations of phenethylamine, a phenethyl isothiocyanate marker, in dog plasma, were determined utilizing solid-phase extraction and gas chromatography-mass spectrometry with chemical ionization using acetone as the reagent gas. Deuterated d5-amphetamine was used as an internal standard. After extraction, phenethylamine and d5-amphetamine were derivatized using MBHFBA. Ions monitored for d5-amphetamine were m/z 337 and 338; and for phenethylamine were m/z 318 and 319. Precision and accuracy were studied using control solutions prepared in naive dog plasma (80 and 300 ng/ml). Intra-day variability was determined using six replicates of each control solution analyzed on a single day. The relative standard deviation for the 80 ng/ml control was 12.9% and for the 300 ng/ml it was 12.1%. Relative accuracy was 10.9% for the low control and -4.1% for the high control. Inter-day variability was determined over a 6-day period. For the 80 and 300 ng/ml control solutions, the relative standard deviations were 15.8 and 9.1%, respectively, and relative accuracy values were 10.1 and -5.2%, respectively. Standard curves were prepared in naive dog plasma and were linear over the range of phenethylamine assayed (10-500 ng/ml). The results of this study indicate that the proposed method is simple, precise, accurate and sensitive enough for analysis of large numbers of plasma samples.

Animals↗

PubMed1998

Second 46,XX male with MLS syndrome.

We report on a second 46,XX male with microphthalmia with linear skin defects (MLS) syndrome. In addition to microphthalmia and linear skin streaks, he had a secundum ASD, hypospadias with chordee, anal fistula, and agenesis of corpus callosum with colpocephaly. Biopsy of a linear streak showed smooth muscle hamartomata rather than the presumed dermal aplasia. Detailed ophthalmologic examination did not show retinal lacunae typical of Aicardi syndrome. DNA studies with distal Xp specific probes indicated a deletion in one X chromosome and fluorescence in situ hybridization (FISH) studies with X- and Y-specific probes demonstrated the presence of a derivative X chromosome from an X;Y translocation.

Agenesis of Corpus Callosum↗

PubMed1998

Technical note: chromosomal and mtDNA analysis of Oliver.

Oliver is an African ape whose species identity has been debated in the popular media and by various scientists since the early 1970s. Although decisive morphological data has never been adduced on Oliver, many reports indicated that Oliver was morphologically unusual for a chimpanzee, particularly in his habitual bipedal posture. In addition, his diploid chromosome number was reported to be inconsistent with either human or chimpanzee, but instead intermediate between those species. We performed standard chromosomal studies which demonstrated that Oliver had the diploid number expected for a chimpanzee (2N = 48) and that the banding patterns of his chromosomes were typical for a chimpanzee and different from both humans and bonobos. We also sequenced a 312 bp region of his mitochondrial DNA D-loop region. Results indicated a high sequence homology to the Central African variety of chimpanzee, Pan troglodytes troglodytes. The highest percent homology was observed with a previously characterized specimen from Gabon, strongly suggesting that Oliver originated from this region.

Animals↗

PubMed1998

Teratoma with trisomy 16 in a baboon (Papio hamadryas).

A teratoma was found during a planned cesarean section in a 10-year-old primigravida baboon. This teratoma had a female sex chromosome complement and trisomy for chromosome 16. This is the first report of a teratoma in a baboon and the first report of a chromosomal abnormality in a nonhuman primate teratoma. It is also the first case in a nonhuman primate to address the mechanism of origin. Through the use of genetic markers from human chromosomes 5, 8 and 17, the origin of the teratoma was shown to be most consistent with failure of meiosis II or endoreduplication in a mature ovum, while the trisomy for chromosome 16 originated after the formation of the tumor.

Animals↗

PubMed1998

How does feature-based attention affect visual processing?

Five experiments are reported from which it is concluded that attending on the basis of a stimulus feature (e.g., red) does not directly affect the sensory quality of stimuli that possess that feature. Feature-based attention was manipulated in a visual search task by providing information about the probability that the target would possess a given feature (e.g., "The target has a 1.0 probability of being red when present.") Feature-based attention failed to aid performance under "data-limited" conditions (i.e., those under which performance was primarily affected by the quality of the stimulus) but did affect performance under conditions that were not data limited (Experiments 1-3). If attending to a feature had affected the sensory quality of stimuli, performance should have been aided under all conditions. Experiments 4 and 5 provided converging support for this conclusion.

Adolescent↗

PubMed1998

Detection of doxepin and its major metabolite desmethyldoxepin in hair following drug therapy.

Doxepin is a tricyclic antidepressant that is widely prescribed for the treatment of mild depression. In this study, hair samples collected from a patient receiving 25 mg of doxepin daily were analyzed. Doxepin was administered to the patient for 4 months (June 15 to October 15, 1996). Five hair samples were collected: 1 and 3 months after doxepin therapy began and 1, 3, and 5 months after drug therapy ended. Solid-phase extraction was employed to isolate doxepin and its major metabolite desmethyldoxepin from the hair matrix, and gas chromatography-mass spectrometry (GC-MS) was used for quantitation of both drugs. Six-point standard curves (0.25-20 ng/mg) were prepared for both compounds with an internal standard (doxepin-d3). The standard curves for doxepin and desmethyldoxepin were linear over the range reported and had correlation coefficients of 0.984 and 0.985, respectively. The limit of quantitation for both analytes was 0.25 ng/mg of hair. In addition, the replicate analysis of control hair preparations was performed at two levels (2 ng/mg and 15 ng/mg) to determine intra- and interday variability. Doxepin and desmethyldoxepin were not detected in the patient's sample collected 1 month after doxepin therapy began. The samples collected 3 months after doxepin therapy began and 5 months after drug therapy was terminated had detectable amounts of doxepin and desmethyldoxepin. The highest concentrations of doxepin (mean, 0.59 ng/mg) and desmethyldoxepin (mean, 0.40 ng/mg) were found 5 months after doxepin therapy began, which was also 1 month after the patient had stopped using the drug. Five months after doxepin therapy was terminated, the drug and its metabolite were still present in the patient's hair. The concentration of doxepin in hair was always significantly higher than the concentration of desmethyldoxepin.

Adult↗

PubMed1998

A baboon (Papio hamadryas) with an isochromosome for the long arm of the X.

A 5.5-yr-old female baboon was evaluated for sexual immaturity. She was small for her age and had normal external female genitalia. However, she lacked cyclical perineal turgescence and displayed atypical coloration of the perineal skin. Laparoscopy revealed a small uterus and absence of both ovaries. Cytogenetic analysis revealed a 42,X,i(X)(q10) karyotype. DNA analysis using loci DXS1683, which maps to Xp22.1, and DXS297, which maps to Xq27.3, was consistent with inheritance of the normal X chromosome from the dam and formation of the isochromosome Xq from the paternal X.

Animals↗

PubMed1998

Baboon/human homologies examined by spectral karyotyping (SKY): a visual comparison.

Baboon (Papio hamadryas) metaphase chromosomes were analyzed using spectral karyotyping (SKY), a technique combining fluorescence microscopy, CCD-imaging, and Fourier spectroscopy. Results from a comparison of SKY analyses using probes derived from human chromosomes on baboon metaphases were consistent with the majority of comparative gene mapping data between the two species. These data were also compatible with earlier studies comparing macaque and human chromosomes. Human (HSA) chromosome 2 was homologous to baboon (PHA) chromosomes 12 (HSA 2q) and 13 (HSA 2p), whereas three baboon chromosomes corresponded to two different human chromosomes: PHA 3 to HSA 7 and HSA 21, PHA 7 to HSA 14 and HSA 15, and PHA 10 to HSA 20 and HSA 22. These results support the retained synteny between the Hominidae and Cercopithecidae genomes.

Animals↗