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Biomedical subjects

C J Brown

Publications and source records attributed to C J Brown.

At least 127 records · Page 7Linked to original sources
PubMed1991

Electrically evoked auditory brainstem response: growth of response with current level.

The electrically evoked brainstem response (EABR) was measured in cochlear implant users who had received either the Ineraid multichannel implant or the Nucleus multichannel implant. Although both implants use a multi-electrode array, they are different in a number of ways. In the Ineraid system the electrodes can be accessed directly through a percutaneous plug and stimulation is generally on four different intracochlear electrodes relative to a common ground outside the cochlea. In the Nucleus implant stimulation is accomplished via an internal coil and stimulation is bipolar between pairs along the 22 electrode array. The ABR waveforms were similar for both groups of subjects, consisting of a series of 3 or 4 positive peaks at the highest levels of stimulation. Using the normal stimulation mode (bipolar for Nucleus and monopolar for Ineraid), users of both devices demonstrated an increase in response amplitude and a decrease in response latency with increases in current level. The threshold of response tended to be higher and growth of the response with level tended to be more gradual for Nucleus users than for Ineraid users. However, with bipolar stimulation for both implant types, when the stimulating electrodes were closely spaced the threshold of response was higher and the growth of amplitude with level was more gradual than the case where the electrodes were separated further. When bipolar stimulation and similar electrode spacing was used, the response growth and threshold were similar for both implant types. Results from neither device showed a strong correlation with performance on word recognition tests.

Adult↗
PubMed1991

Electrically evoked auditory brainstem response: refractory properties and strength-duration functions.

The electrically evoked auditory brainstem potential (EABR) was recorded in users of both the Nucleus cochlear implant and the Ineraid cochlear implant. The refractory properties of the EABR were evaluated by measuring the response amplitude to a two-pulse stimulus where the interpulse interval was varied. The threshold of response for a single pulse stimulus was also measured as a function of the duration of the biphasic pulse. These strength-duration functions were then used to calculate an EABR chronaxie measure. Both of these measures showed a similar range for the monopolar stimulation used with the Ineraid implant and the bipolar stimulation used with the Nucleus implant. Neither of these two measures of the temporal response properties showed any clear relationship to the ability of individual subjects to perform on a speech perception task.

Adult↗
PubMed1991

Physical mapping of 60 DNA markers in the p21.1----q21.3 region of the human X chromosome.

Using a panel of human/rodent somatic cell hybrids and human lymphoblast lines segregating 18 different human X-chromosome rearrangements and deletions, we have assigned 60 DNA markers to the physical map of the X chromosome from Xp21.1 to Xq21.3. Data from Southern blot hybridization and polymerase chain reaction (PCR) amplification assign these markers to 15 primary map intervals. This provides a basis for further long-range cloning and mapping of the pericentromeric region of the X chromosome.

Base Sequence↗
PubMed1991

Variance and covariance estimates for weaning weight of Senepol cattle.

Variance and covariance components were estimated for weaning weight from Senepol field data for use in the reduced animal model for a maternally influenced trait. The 4,634 weaning records were used to evaluate 113 sires and 1,406 dams on the island of St. Croix. Estimates of direct additive genetic variance (sigma 2A), maternal additive genetic variance (sigma 2M), covariance between direct and maternal additive genetic effects (sigma AM), permanent maternal environmental variance (sigma 2PE), and residual variance (sigma 2 epsilon) were calculated by equating variances estimated from a sire-dam model and a sire-maternal grandsire model, with and without the inverse of the numerator relationship matrix (A-1), to their expectations. Estimates were sigma 2A, 139.05 and 138.14 kg2; sigma 2M, 307.04 and 288.90 kg2; sigma AM, -117.57 and -103.76 kg2; sigma 2PE, -258.35 and -243.40 kg2; and sigma 2 epsilon, 588.18 and 577.72 kg2 with and without A-1, respectively. Heritability estimates for direct additive (h2A) were .211 and .210 with and without A-1, respectively. Heritability estimates for maternal additive (h2M) were .47 and .44 with and without A-1, respectively. Correlations between direct and maternal (IAM) effects were -.57 and -.52 with and without A-1, respectively.

Analysis of Variance↗
PubMed1991

Effects of 84-, 112- and 140-day postweaning feedlot performance tests for beef bulls.

Changes in performance traits in beef cattle over the last 30 yr necessitate the re-evaluation of central testing procedures to ensure that they are cost effective and appropriate for current test objectives. The objective of this study was to evaluate the potential for reducing the length of evaluation from 140 d to either 112 or 84 d. Data evaluated were postweaning feedlot performance test records (collected from 1977 to 1986) on 1,830 individually fed bulls. Bulls representing 13 breeds (n greater than 25 per breed) were evaluated in the University of Arkansas Cooperative Bull Tests at Fayetteville, Hope, and Monticello, Arkansas. Models were fit for ADG, daily feed intake (FI) and feed conversion (FCONV) from d 1 to d 140 (ADG1-140, FI1-140 and FCONV1-140, respectively) and from d 1 to d 112 (ADG1-112, F11-112 and FCONV1-112, respectively). Models fit for ADG1-140, FI1-140, and FCONV1-140 using information up to d 112 had R2 of .90, .99, .88, and .94, respectively, and using information up to d 84 had R2 of .82, .94, and .80, respectively. Spearman rank correlation coefficients (all P less than .0001) were .93 for ADG1-140 and ADG1-112, .93 for ADG1-112 and ADG1-84, .99 for FI1-140 and FI1-112, .91 for FCONV1-140 and FCONV1-112, and .90 for FCONV1-112 and FCONV1-84. These coefficients indicate that bulls ranked similarly for performance traits at 84, 112, and 140 d. If the primary objective of central station testing is to evaluate ADG during the linear phase of growth, and if testing procedures are those currently recommended by the Beef Improvement Federation, then feeding bulls beyond 112 d has no advantage because the information upon which selection decisions are made is similar at both 112 and 140 d.

Analysis of Variance↗
PubMed1991

Initial findings with a wearable multichannel vibrotactile aid.

Data are presented on the speech perception performance of two profoundly hearing-impaired subjects while using a two-channel vibrotactile aid (Tactaid II) or a new, seven-channel instrument. Both subjects, one a profoundly hearing-impaired teenager and one a postlingually deaf adult, are experienced users of tactile aids. The data suggest better recognition of speech features, words, environmental sounds, and enhancement of lipreading skills with the new multichannel instrument than with the two-channel device.

Adolescent↗
PubMed1990

X chromosome inactivation of the human TIMP gene.

X chromosome inactivation results in the cis-limited inactivation of most, but not all, genes on one of the two X chromosomes in mammalian females. The molecular basis for inactivation is unknown. In order to examine the transcriptional activity of human X-linked genes, a series of mouse-human somatic cell hybrids under positive selection for the active or inactive human X chromosome has been created. Northern blot analysis of RNA from these hybrids showed that the human MIC2 gene, which is known to escape X inactivation, was transcribed in hybrids with either the active or inactive X chromosome. In contrast, the human TIMP gene was only transcribed in hybrids with an active human X chromosome. Further analysis using the polymerase chain reaction showed that there was at least one-hundred fold less transcription of the TIMP gene from the inactive X than from the active X chromosome. These findings demonstrate that the human TIMP gene is subject to X inactivation at the level of transcription, and illustrate the usefulness of the polymerase chain reaction to study the extent of X-linked gene repression by the process of X inactivation.

Animals↗
PubMed1990

Variations in self-paced behaviors in stutterers and nonstutterers.

Ten stuttering and 10 nonstuttering subjects performed self-paced rhythmic tasks with the finger and jaw and were asked to repeat "ah." The tasks were performed at three rates: "comfortable" rate; and "slightly higher" and "slightly lower" than comfortable, but still in the comfortable range. The stutterers performed each of the three tasks more slowly than the nonstutterers and were less variable than nonstutterers. The reduced rates and more constrained variability of the stutterers were interpreted as manifestations of less flexible systems, which may be more susceptible to breakdown.

Adult↗
PubMed1990

DNA sequence evolution of the amylase multigene family in Drosophila pseudoobscura.

The alpha-Amylase locus in Drosophila pseudoobscura is a multigene family of one, two or three copies on the third chromosome. The nucleotide sequences of the three Amylase genes from a single chromosome of D. pseudoobscura are presented. The three Amylase genes differ at about 0.5% of their nucleotides. Each gene has a putative intron of 71 (Amy1) or 81 (Amy2 and Amy3) bp. In contrast, Drosophila melanogaster Amylase genes do not have an intron. The functional Amy1 gene of D. pseudoobscura differs from the Amy-p1 gene of D. melanogaster at an estimated 13.3% of the 1482 nucleotides in the coding region. The estimated rate of synonymous substitutions is 0.398 +/- 0.043, and the estimated rate of nonsynonymous substitutions is 0.068 +/- 0.008. From the sequence data we infer that Amy2 and Amy3 are more closely related to each other than either is to Amy1. From the pattern of nucleotide substitutions we reason that there is selection against synonymous substitutions within the Amy1 sequence; that there is selection against nonsynonymous substitutions within the Amy2 sequence, or that Amy2 has recently undergone a gene conversion with Amy1; and that Amy3 is nonfunctional and subject to random genetic drift.

Amylases↗
PubMed1990

Heterogeneity of HLA-DR4 in Greeks including a unique DR4-DQw2 association.

It has been shown that Greek RA patients do not show an increased frequency of HLA-DR4 compared with Greek controls. As only the Dw4 and Dw14 subtypes of DR4 are implicated in RA, we have characterised DR4-positive Greek RA patients and controls using serology, MLC typing and RFLP analysis to see whether the distribution of DR4 subtypes or other HLA antigens associated with DR4 could account for these findings. In the 10 patients and 12 controls studied, Dw10 was common, being present in almost half the controls. Dw4 was not detected in the controls, but was present in three of the RA patients, indicating that there may be some relationship between Dw4 and RA in this population; Dw13 and Dw14 were also found, Dw15 was not detected. Eight of the subjects did not type as any of the HLA-D antigens mentioned. Three controls had unusual DR4-DQ associations, two having DR4-DQw2 and one possessing DR4-DQw4. Analysis of the TaqI DRB RFLP of the subjects showed that one control did not have the 6.1 kb band characteristic of DR4s. All these results indicate that DR4 is a heterogeneous antigen in this population and that several as yet undescribed variants of DR4 may be present.

Arthritis, Rheumatoid↗
PubMed1990

Electrically evoked whole-nerve action potentials: data from human cochlear implant users.

This study describes a method for recording the electrically evoked, whole-nerve action potential (EAP) in users of the Ineraid cochlear implant. The method is an adaptation of one originally used by Charlet de Sauvage et al. [J. Acoust. Soc. Am. 73, 615-627 (1983)] in guinea pigs. The response, recorded from 11 subjects, consists of a single negative peak that occurs with a latency of approximately 0.4 ms. EAP input/output functions are steeply sloping and monotonic. Response amplitudes ranging up to 160 micro V have been recorded. Slope of the EAP input/output function correlates modestly (approximately 0.6-0.69) with results of tests measuring word recognition skills. The refractory properties of the auditory nerve were also assessed. Differences across subjects were found in the rate of recovery from the refractory state. These findings imply that there may be difference across subjects in the accuracy with which rapid temporal cues can be coded at the level of the auditory nerve. Reasonably strong correlations (approximately 0.74-0.85) have been found between the magnitude of the slope of these recovery curves and performance on tests of word recognition.

Cochlear Implants↗
PubMed1990

Electrically evoked whole-nerve action potentials: parametric data from the cat.

In a companion paper [Brown et al., J. Acoust. Soc. Am. 88, 1385-1391 (1990)], a method for recording the electrically evoked whole-nerve action potential in human cochlear implant users was reported. The procedure for recording the response requires that two biphasic current pulses, a "masker" and a "probe," be presented at a rate and level sufficient to drive the auditory nerve into a refractory state. The present study was designed to assess the sensitivity of that recording technique to variations in stimulation parameters. The experiments described in this paper demonstrate that: (1) the EAP as recorded in the cat is triphasic and is defined by two negative peaks occurring at latencies of approximately 0.26 and 0.82 ms; (2) EAP amplitude is independent of the level of the masker stimulus for current levels equal to or greater than the current level of the probe stimulus; and (3) the time course of recovery of the EAP from the refractory state is stable over a range of both probe and masker current levels.

Animals↗
PubMed1990

Amylase gene expression in intraspecific and interspecific somatic transformants of Drosophila.

The Amylase locus in Drosophila melanogaster normally contains two copies of the structural gene for alpha-amylase, a centromere-proximal copy, Amy-p, and a distal copy, Amy-d. Products of the two genes may display discrete electrophoretic mobilities, but many strains known to carry the Amy duplication are characterized by a single amylase electromorph, e.g., Oregon-R, which produces the mobility variant AMY-1. A transient expression assay was used in somatic transformation experiments to test the functional status of the Amy genes from an Oregon-R strain. Plasmid constructs containing either the proximal or distal copy were tested in amylase-null hosts. Both genes produced a functional AMY-1 isozyme. Constructs were tested against an AMY-3 reference activity produced by a coinjected plasmid that contains the Amy-d3 allele from a Canton-S strain. With reference to the internal control, the Amy-p and Amy-d genes from Oregon-R expressed different relative activity levels for AMY-1 in transient assays. The transient expression assay was successfully used to test the functional status of Amy-homologous sequences from strains of other species of Drosophila characterized by a single amylase elctromorph, namely, Drosophila pseudoobscura ST and Drosophila miranda S 204. The amylase-null strain of D. melanogaster provided the hosts for these interspecific somatic transformation experiments.

Amylases↗
PubMed1990

Comparison of bite size, biting rate and grazing time of beef heifers from herds distinguished by mature size and rate of maturity.

Sixteen-month-old heifers from herds having known genetic growth patterns were compared for differences in grazing behavior in a 3-yr study. Treatments were heifers from four size-maturity groups defined by the mature size and maturing rate of cow herds in which they originated. Average growth curve parameters indicating mature BW and rate of maturing in these cow herds were 387 kg and .19%/d for treatment Group I; 413 kg and .18%/d for Group II; 468 kg and .15%/d for Group III; and 589 kg and .16%/d for treatment Group IV. Data were from three heifers per treatment group grazing Midland bermudagrass during June and July observation periods. With the exception of the Group II vs Group III comparison, bite size increased with current or mature BW. Biting rate values were similar for all treatment groups but lower than those previously reported on other grass swards. Grazing time increased (P less than .01) in treatment groups defined by larger mature BW. Differences in grazing time for Group IV vs the other treatments and Group I vs Group II and Group III were observed repeatedly; the Group II vs Group III comparison was significant in one period during each of the 3 yr. Diurnal variations in grazing patterns among the treatments were observed. Period of observation affected (P less than .001) bite size and grazing time. These effects were not associated with month but could best be explained by differences in forage height and total mass. Forage availability had a direct influence on bite size, and a compensating effect of longer grazing time with smaller bite size was demonstrated as a regulator of intake. Differences in ingestive behavior were associated with genetic growth patterns in cattle.

Aging↗
PubMed1990

Breed means for average daily gain, feed conversion and intake of beef bulls during postweaning feedlot performance tests.

Comparisons of ADG, feed/gain, daily feed intake and daily feed intake as percentage of body weight may be important to beef cattle producers and researchers in breed selection and computer modeling. Data evaluated were postweaning feedlot performance test records collected from 1967 to 1986 of 3,661 individually fed bulls. Bulls originated from University of Arkansas purebred herds, Fayetteville, and the University of Arkansas Cooperative Bull Tests at Fayetteville, Hope and Monticello. Data were analyzed separately for years 1967 to 1976 (P1) (n = 1,654) and 1977 to 1986 (P2) (n = 2,007). Breeds in P1 were Hereford (HH), Angus (AN), Charolais (CH), Polled Hereford (HP) and Santa Gertrudis (SG). Breeds in P2 were HH, AN, CH, HP, SG, Simmental (SM), Maine-Anjou (MA), Brangus (BN) and Beefmaster (BM). The model fitted included initial age, breed and test number (all P less than .01 except for initial age on ADG in P1). Test number included variation of year, location and season. Breed rankings from highest to lowest for ADG in P1 were CH, SG, HH, HP and AN and in P2 were MA, CH, SM, AN, HP, SG, HH, BN and BM. Breed rankings from highest to lowest for feed/gain in P1 were AN, SG, CH, HP and HH and in P2 were BM, BN, AN, SG, HP, SM, HH, MA and CH. Breeds highest to lowest for daily feed intake (as-fed basis) in P1 were CH, SG, AN, HP and HH and in P2 were SM, MA, CH, AN, BN, HP, SG, HH and BM.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Creating patient satisfaction and loyalty.

Many hospitals are considering enhanced approaches to patient satisfaction measurement and guest relations--or service management. Some are building in-house satisfaction management systems. Others are evaluating the growing number of systems commercially available for purchase. The authors review the successful design, testing, introduction, and nearly 5-year use of an in-house system.

Consumer Behavior↗
PubMed1990

Localization of a gene that escapes inactivation to the X chromosome proximal short arm: implications for X inactivation.

The process of mammalian X chromosome inactivation results in the inactivation of most, but not all, genes along one or the other of the two X chromosomes in females. On the human X chromosome, several genes have been described that "escape" inactivation and continue to be expressed from both homologues. All such previously mapped genes are located in the distal third of the short arm of the X chromosome, giving rise to the hypothesis of a region of the chromosome that remains noninactivated during development. The A1S9T gene, an X-linked locus that complements a mouse temperature-sensitive defect in DNA synthesis, escapes inactivation and has now been localized, in human-mouse somatic cell hybrids, to the proximal short arm, in Xp11.1 to Xp11.3. Thus, A1S9T lies in a region of the chromosome that is separate from the other genes known to escape inactivation and is located between other genes known to be subject to X inactivation. This finding both rules out models based on a single chromosomal region that escapes inactivation and suggests that X inactivation proceeds by a mechanism that allows considerable autonomy between different genes or regions on the chromosome.

Animals↗