Biomedical subjects

W J Williams

Publications and source records attributed to W J Williams.

At least 19 recordsLinked to original sources

PubMed2003

The frequency range of TMJ sounds.

There are conflicting opinions about the frequency range of temporomandibular joint (TMJ) sounds. Some authors claim that the upper limit is about 650 Hz. The aim was to test the hypothesis that TMJ sounds may contain frequencies well above 650 Hz but that significant amounts of their energy are lost if the vibrations are recorded using contact sensors and/or travel far through the head tissues. Time-frequency distributions of 172 TMJ clickings (three subjects) were compared between recordings with one microphone in the ear canal and a skin contact transducer above the clicking joint and between recordings from two microphones, one in each ear canal. The energy peaks of the clickings recorded with a microphone in the ear canal on the clicking side were often well above 650 Hz and always in a significantly higher area (range 117-1922 Hz, P < 0.05 or lower) than in recordings obtained with contact sensors (range 47-375 Hz) or in microphone recordings from the opposite ear canal (range 141-703 Hz). Future studies are required to establish normative frequency range values of TMJ sounds but need methods also capable of recording the high frequency vibrations.

Auscultation↗

PubMed2002

Localization of TMJ sounds to side.

Differential diagnosis depends in cases with disk displacement on accurate identification of sound source. Mistakes may occur when clicking from one temporomandibular joint (TMJ) is heard on both sides of the head at auscultation and neither examiner nor patient, is sure about side. The hypothesis was that the head tissues affect spectral characteristics of TMJ sounds and that differences due to different positioning of sensors can be used in localization of source. The aim was to compare bilateral electronic recordings of unilateral TMJ sounds to obtain and compare attenuation, phase shift and time delay. Recordings were made from 12 subjects with unilateral clicking. Small electret condenser microphones, bandwidth 40-20 000 Hz, were placed at the openings of the auditory canals and the sounds were recorded at a sampling rate of 48 000 Hz. The head tissues acted as a filter causing a frequency dependent attenuation and phase shift. There was a time difference between the ipsi- and the contra lateral recordings, the latter always having a longer delay time (range 0.2-1.2 ms, group mean 0.68 ms, s.d. 0.292 ms). In conclusion, spectral analysis of bilateral electronic TMJ sound recordings is of diagnostic value when bilateral clicking is heard at auscultation and can help to avoid diagnosing a silent joint as clicking.

Adult↗

PubMed2001

Simulated shuttle egress: role of helmet visor position during approach and landing.

BACKGROUND: We previously reported that carbon dioxide (CO2) rapidly accumulates in the helmet of the NASA Launch and Entry Suit (LES) during a simulated egress from the Space Shuttle following 6 min of visor-closed seated rest to simulate approach and landing. The purpose of this study was to determine if CO2 accumulation and walking time in the LES would be improved by helmet visor-open rather than visor-closed seated rest prior to the performance of the simulated egress. METHODS: Wearing the LES, 12 male subjects performed 4 laboratory egress simulations consisting of 6-min seated rest, 2-min stand, and 5-min walk at 1.56 m x s(-1) (3.5 mph). During seated rest, subjects sat either with the visor open, breathing room air until the visor was closed on standing, or with the visor closed for the duration of the simulation. For all visor-closed operations 100%, O2 was supplied. The G-suit was either deflated (0.0 psi) or inflated to 1.5 psi. Inspired CO2 and walking time were measured. Data were analyzed at the end of seated rest, standing, and after 5 min of walking at 0.0 psi or after 2 min of walking at 1.5 psi (>90% of data available). RESULTS: Walk time was not different following visor-open (0.0 psi: 5.0 +/- 0.0; 1.5 psi: 3.4 +/- 0.3 min) or visor-closed (0.0 psi: 4.8 +/- 0.2; 1.5 psi: 3.5 +/- 0.4 min) seated rest at either G-suit pressure. Inspired CO2 levels were not different between the two conditions during walking at 5 min at 0.0 psi (p = 0.50; Open: 4.39 +/- 0.14; Closed: 4.48 +/- 0.18%) or at 2 min at 1.5 psi (p = 0.53; Open: 3.59 +/- 0.12; Closed: 3.65 + 0.21%). CONCLUSIONS: Visor position during seated rest immediately preceding the egress walk had no effect on inspired CO2 or walking time.

Adult↗

PubMed2000

Computerized classification of temporomandibular joint sounds.

Sounds, such as clicking and/or crepitation, evoked in the temporomandibular (jaw) joint during function may indicate pathology. Analysis of the reduced interference time-frequency distribution of these sounds is of diagnostic value. However, visual evaluation is expensive and error prone, and there is, thus, a need for automated analysis. The aim of this study was to find the optimal signal representation and pattern recognition method for computerized classification of temporomandibular joint sounds. Concepts of time-shift invariance with and without scale invariance were employed and mutually compared. The automated analysis methods provided classification results that were similar to previous visual classification of the sounds. It was found that the classifier performance was significantly improved when scale invariance was omitted. This behavior occurred because scale invariance interfered with the frequency content of the signal. Therefore, scale invariance should not be pursued in the classification scheme employed in this study.

Biomedical Engineering↗

PubMed2000

Core temperature measurement during supine exercise: esophageal, rectal, and intestinal temperatures.

BACKGROUND: The purpose of this study was to characterize intestinal temperature (T(in)) in comparison to esophageal (T(es)) and rectal temperature (T(re)) during supine exercise. METHODS: Seven subjects completed a continuous supine protocol of 20 min of rest, 20 min of cycle exercise at 40% peak oxygen consumption (V(O2peak)), 20 min of cycle exercise at 65G% V(O2peak), and 20 min of recovery. T(es), T(re), and T(in) were recorded each min. RESULTS: Temperatures were not different after 20 min of rest, but T(es) and T(in) were greater than T(re) at the end of the 40% (T(es): 37.38 +/- 0.11; T(in): 37.35 +/- 0.06; T(re): 37.20 +/- 0.10 degrees C) and 65% V(O2peak) stages (T(es): 37.83 +/- 0.10; T(in): 37.75 +/- 0.05; T(re): 37.63 +/- 0.08 degrees C). After 20 min of recovery, T(es) (37.24 +/- 0.011 degrees C) was less than either T(re) or T(in), which were not different from each other (T(in): 37.39 +/- 0.09; T(re): 37.44 +/- 0.09 degrees C). Time to threshold for increased temperature from rest (+0.10 degrees C) for T(es) (10.0 +/- 1.1 min) was not different from T(in) (14.0 +/- 1.2 min) but less than T(re) (15.7 +/- 1.6 min). Time to reach peak temperature was less for T(es) (36.6 +/- 1.8 min) than T(in) (40.6 +/- 0.9 min) and T(re) (41.4 +/- 0.5 min). Similarly, time to a decrease in temperature (-0.10 degrees C) after exercise was less for T(es) (3.7 +/- 0.4 min) than T(in) (7.1 +/- 1.5 min) and T(re) (10.6 +/- 1.9). CONCLUSIONS: Measurement of T(in) may be an alternative to T(es) to measure T(core) specific time points during exercise with an understanding of the slower response of Tin compared with T(es).

Adult↗

PubMed1999

Molecular cloning and characterization of two novel human renal organic anion transporters (hOAT1 and hOAT3).

The cloned organic anion transporters from rat, mouse, and winter flounder (rOAT1, mOAT1, fROAT) mediate the coupled exchange of alpha-ketoglutarate with multiple organic anions, including p-aminohippurate (PAH). We have isolated two novel gene products from human kidney which bear significant homology to the known OATs and belong to the amphiphilic solute facilitator (ASF) family. The cDNAs, hOAT1 and hOAT3, encode for 550- and 568-amino-acid residue proteins, respectively. hOAT1 and hOAT3 mRNAs are expressed strongly in kidney and weakly in brain. Both genes map to chromosome 11 region q11.7. PAH uptake by Xenopus laevis oocytes injected with hOAT1 mRNA is increased 100-fold compared to water-injected oocytes. PAH uptake is chloride dependent and is not further increased by preincubation of oocytes in 5 mM glutarate. Uptake of PAH is inhibited by probenicid, alpha-ketoglutarate, bumetanide, furosemide, and losartan, but not by salicylate, urate, choline, amilioride, and hydrochlorothiazide.

Amino Acid Sequence↗

PubMed1999

Measuring the coherence of intracranial electroencephalograms.

OBJECTIVE: Previous coherence studies of human intracranial electroencephalograms (EEGs) can be faulted on two methodological issues: (1) coherence estimates in a majority were formed from a very small number of independent sample spectra, and (2) the statistical significance of coherence estimates was either not reported or was poorly evaluated. Coherence estimator performance may be poor when a small number of independent sample spectra are employed, and the coupling of poor estimation and statistical testing can result in inaccuracy in the measurement of coherence. The performance characteristics of the coherence estimator and statistical testing of coherence estimates are described in this manuscript. METHODS: The bias, variance, probability density functions, and confidence intervals of the estimate of magnitude squared coherence (MSC); and power analysis for the test of zero MSC were developed from the exact analytic form of the probability density function of the estimate of MSC for Gaussian random processes. The coherence of a single epoch of background EEG, recorded from a patient with intractable seizures, was evaluated with different parameter values to aid in the exposition of the concepts developed here. RESULTS: The statistical characteristics of WOSA coherence estimates are a function of a single estimator parameter, the number of independent sample spectra employed in the estimation. Bias and variance are high, confidence intervals may be large, and the probability of Type II errors is high if a small number of independent sample spectra are employed. A considerable improvement in measurement accuracy is possible with careful selection of estimator parameter values. CONCLUSIONS: Coherence measurement accuracy can be improved over previous applications by attention to estimator performance and accurate statistical testing of coherence estimates.

Adult↗

PubMed1999

False localization of TMJ sounds to side is an important source of error in TMD diagnosis.

The results of the study indicate that the head tissues act as a band pass filter that is far from flat. Instead there seems to be strong frequency variations in attenuation of transmitted sounds. The sounds are subject to phase shift and time delay, which can be used to decide from which TMJ the sound comes. Bilateral electronic recording with high sampling rate (>> 44 kHz) is needed to accurately and consistently identify the origin of a TMJ sound. Further studies on autopsy specimens and large subject groups are motivated.

Acoustics↗

PubMed1999

Conjunctive effects of fibroblast growth factor and glycosaminoglycan on bone metabolism in neonatal bartter syndrome.

The calciotropic activity of urine from a subject with neonatal Bartter syndrome (NBS) has been partially purified using ion-exchange and gel chromatographic techniques. A bioassay using bone disks from rat calvaria was used to estimate calciotropic activity, which in the urine of the subject with NBS appears to be due to basic fibroblast growth factor (bFGF) bound to a glycosaminoglycan susceptible to heparitinase digestion. The calciotropic activity is eluted from DEAE-Sephacel and Sepharose CL-6B in a narrow band in association with metachromatic material and is destroyed by heparitinase and blocked by an antibody to bFGF. After treatment of purified preparations with heparitinase, a component that is inactive alone but develops calciotropic activity in association with heparin can be isolated by affinity chromatography on heparin-Sepharose columns. This component is recovered from the column at NaCl concentrations expected to elute bFGF and is inactivated by antibodies to bFGF. No calciotropic activity can be shown in glycosaminoglycan-containing fractions from urine from a normal boy or a normal man, but such fractions exhibit calciotropic activity if bFGF is added to the assay system. When bFGF is added to urine from either normal subject followed by ion-exchange chromatography on DEAE-Sephacel, calciotropic activity is eluted at NaCl concentrations closely similar to those found to elute calciotropic activity from the urine of the NBS subject. It appears that the abnormal findings in NBS urine are due to excess bFGF, although they could be due to some abnormality of the glycosaminoglycan component.

Aged↗

PubMed1999

Carbon dioxide accumulation, walking performance, and metabolic cost in the NASA launch and entry suit.

BACKGROUND: In the event of an emergency on landing, Space Shuttle crewmembers while wearing the Launch and Entry Suit (LES) must stand, move to the hatch, exit the spacecraft with the helmet visor closed breathing 100% O2, and walk or run unassisted to a distance of 380 m upwind from the vehicle. The purpose of this study was to characterize the inspired CO2 and metabolic requirements during a simulated unaided egress from the Space Shuttle in healthy subjects wearing the LES. METHODS: As a simulation of a Shuttle landing with an unaided egress, 12 male subjects completed a 6-min seated pre-breathe with 100% O2 followed by a 2-min stand and 5-min walking at 1.56 m x s(-1) (5.6 km x h(-1), 3.5 mph) with the helmet visor closed. During walks with four different G-suit pressures (0.0, 0.5, 1.0, 1.5 psi; 3.4, 6.9, 10.3 kPa), inspired CO2 and walking time were measured. After a 10-min seated recovery, subjects repeated the 5-min walk with the same G-suit pressure and the helmet visor open for the measurement of metabolic rate (VO2). RESULTS: When G-suit inflation levels were 1.0 or 1.5 psi, only one-third of our subjects were able to complete the 5-min visor-closed walk after a 6-min pre-breathe. Inspired CO2 levels measured at the mouth were routinely greater than 4% (30 mmHg) during walking. The metabolic cost at the 1.5 psi G-suit inflation was over 135% of the metabolic cost at 0.0 psi inflation. CONCLUSION: During unaided egress, G-suit inflation pressures of 1.0 and 1.5 psi resulted in elevated CO2 in the LES helmet and increased metabolic cost of walking, both of which may impact unaided egress performance. Neither the LES, the LES helmet, nor the G-suit were designed for ambulation. Data from this investigation suggests that adapting flight equipment for uses other than those for which it was originally designed can result in unforeseen problems.

Adult↗

PubMed1999

Bilateral sound propagation characteristics in electronic TMJ sound recording.

Temporomandibular Joint (TMJ) sounds, clicking and crepitation, are important signs of possible TM disorder or dysfunction (TMD). The sound are usually recorded and observed by stethoscope auscultation or palpation. Sound from one TMJ may propagate through head tissues and be recorded on the contra lateral side misleading the examiner to classify both joints as non-silent. Errors in localization of sound source may lead to an erroneous diagnosis. Widmalm et al. (1997) suggested a mathematical model for estimation of the sound propagation characteristics through the head tissues. A modified model applying the auto-spectral density and cross-spectral density of the signal was used to estimate the bilateral sound propagation characteristics of temporomandibular joint sounds from two subjects. The result indicates that the head tissues act as a bandpass filter causing strong attenuation in some frequency areas with little attenuation in others. The phase response of the transfer function provides a good mean to estimate the latency in time between sounds.

Humans↗

PubMed1999

Automatic recognition of the source of temporomandibular joint sounds.

Sounds evoked in the temporomandibular joint (TMJ) during jaw movements may indicate pathology. They are in dental clinics usually recorded by auscultation and noted in protocols by verbal, subjective descriptions. Time-frequency analysis of electronically recorded TMJ sounds makes possible a more objective and sophisticated analysis. Such sounds were recorded from four subjects and grouped into two sets. One was used for training a classifier, while the other was used for testing its ability to relate a given sound to the subject from which it was recorded. Both scale and time-shift invariant representations, as well as only time-shift invariant representations of the Reduced Interference Distributions of the TMJ sounds were used for pattern recognition. The nearest neighbor, zero-subspace and nearest constrained linear combination classification methods were employed. It was observed that TMJ sound patterns could be very typical for a given person. This indicates that our classification approach can be developed into a useful diagnostic tool by obtaining training sets from patients where a definitive diagnosis of TMJ pathology has been obtained.

Humans↗

PubMed1998

Molecular characterization of two novel transporters from human and mouse kidney and from LLC-PK1 cells reveals a novel conserved family that is homologous to bacterial and Aspergillus nucleobase transporters.

Nucleobase transport is important for the metabolism of nucleic acids and antiviral and antineoplastic drugs. This transport has been functionally described in several mammalian cells but has not been well characterized molecularly. We report the cloning of two novel transporters. YSPL2 encodes a 650-residue protein and has an ubiquitous 8 kb transcript. The human and pig homologs are 95% similar. YSPL3 encodes a 598-residue protein with a 3 kb transcript that is expressed only in kidney and liver. Human YSPL2 and YSPL3 are 60% similar at the amino acid level and both show 31% similarity to the first nucleobase permease gene described in vertebrates, YSPL1. These proteins appear to be members of a new family of possible nucleobase transporters with significant sequence similarities with bacterial and Aspergillus nucleobase transporters. Further functional studies will be needed to unveil the role of these transporters in nucleic acid metabolism in normal and in disease states.

Amino Acid Sequence↗

PubMed1997

Mutual information analysis and detection of interictal morphological differences in interictal epileptiform discharges of patients with partial epilepsies.

The purpose of this paper is to compare the morphological features of interictal epileptiform discharges (IED) in patients with benign epilepsy of childhood with centrotemporal spikes to IED of those with symptomatic localization related epilepsies using information theory. Three patients from each clinical group were selected. Two-second epochs centered at the peak negativity of the sharp waves were analyzed from a referential montage during stage I sleep. The epochs from the two groups were compared using parametric and information theory analysis. Information analysis determined the likelihood of correctly identifying the clinical group based on the IED. Standard parametric, morphological and spectral analyses were also performed. We found no significant difference in the morphology of the sharp wave between the two groups. The after-going slow wave contained the greatest information that separated the two groups. This result was supported by morphological and spectral differences in the after-going slow wave. Greater distinguishing information is held in the after-going slow wave than the sharp wave for the identification of clinical groups. Information analysis may assist in differentiating clinical syndromes from EEG signals.

Adult↗

PubMed1996

Classification of temporomandibular joint sounds based upon their reduced interference distribution.

Temporomandibular joint (TMJ) sounds were recorded in 98 orthodontic retention patients, mean age 19 +/- 8.6 (s.d.) years, by interview, auscultation and electronic recording. Sounds were found by auscultation in 41% and by interview in 32% of the subjects, more often in females than in males (P < 0.05). A new method for time-frequency analysis, the reduced interference distribution (RID), was used to classify the electronic sound recordings into five subclasses, RID types 1-5, based upon location and number of their energy peaks. RID types 1-3 had a few energy peaks close in time. RID types 4-5, typical of subjects with crepitation, had multiple energy peaks occurring close in time for a period of 20-300 ms. RID type 1, found in 45% of the subjects, typical of patients with clicking, had its dominant energy peak located in a frequency range < 600 Hz and was significantly more common in the female than in the male subjects (P < 0.01). RID type 2, found in 68% of the subjects, with the dominant peak in the range 600-1200 Hz, and RID type 3, found in 38% of the subjects, with the peak in the frequency range > 1200 Hz, were found to have a similar gender distribution. RID type 4, found in 49% of the subjects, had the energy peaks distributed in the frequency range < 600 Hz. RID type 5, found in 43% of the subjects, more often in females than in males (P < 0.05), had the peaks distributed over the whole frequency range from about 30 Hz up to about 3000 Hz. In conclusion, a more detailed classification could be made of the TMJ sounds by displaying the RIDs than by auscultation. This suggests that RID classification methods may provide a means for differentiating sounds indicating different types of pathology.

Adolescent↗

PubMed1996

The wave forms of temporomandibular joint sound clicking and crepitation.

The aim of the present study was to determine the sound wave forms which correspond to auscultatory findings of temporomandibular joint (TMJ) clicking and crepitation. Such knowledge is important when selecting parts of digital recordings for spectral analysis. Electronic digital recordings were made with a sampling rate of 44,100 Hz from 60 subjects, including 51 patients referred for suspected rheumatological disease and nine healthy subjects. Accelerometers with the bandwidth 20-3600 Hz were used for all subjects and complementary recordings were made from a subgroup of nine subjects using a measurement microphone with the bandwidth 20-20,000 Hz. The clicking sounds could be classified into different types according to differences in temporal period duration (T) as measured on the analogue display. One type of clicking, found in 51% of the patients, had a T of 2-20 ms. Another type, found in 70% of the subjects, had a T of less than 1 ms, often as low 0.2 ms. This type of clicking was not seen at all in the analogue display if the sampling rate was below 3,000 Hz. The character of the two types of clicking differed: the short duration sounds had a very high pitch, while the pitch of the longer duration sound was lower. Crepitation was found in 63% of the subjects and was observed to be composed of a series of short duration sounds, occurring with brief (less than 10 ms) intervals. It is concluded that the accelerometer (or microphone) bandwidth should cover the entire audible range (20-20,000 Hz), and that sampling rates must be much higher than 3000 Hz, and preferably greater than 10,000 Hz, before the true significance of electronically recorded joint sounds/vibrations can be determined.

Acceleration↗

PubMed1996

United Kingdom Beryllium Registry: mortality and autopsy study.

This report is based on 30 deaths from chronic beryllium disease (CBD) in the United Kingdom with details of 19 autopsies. The majority were fluorescent lamp workers and machinists who died from respiratory failure. There were no cases of lung cancer. The survival times ranged from less than 1 to 29 years and was longest in machinists. All of the workers showed interstitial pulmonary fibrosis with varying degrees of cystic change. The majority showed hyalinized, and a few active sarcoid-type, granulomas. Extrathoracic granulomas, as in a U.K. sarcoid autopsy series, were rare. A notable difference was the absence of myocardial involvement in CBD compared to an incidence of 20% in the sarcoid autopsies. The detection of beryllium in the criteria for diagnosis is emphasized and the cases classified as definite include 12 of 19 positive analysis, 6 of 19, negative or unavailable analysis. The remaining case was classified as dubious because, despite a positive analysis, granulomas were absent. The main differential diagnosis is sarcoidosis.

Autopsy↗

PubMed1995

Vitamin B12 deficiency: underdiagnosed, overtreated?

Neurologic damage may become permanent when the disorder is mistaken for multiple sclerosis or diabetic neuropathy--hence the need for prompt parenteral B12 in patients with pernicious anemia. The need for B12 injections is questionable for patients with achlorhydria and for those with a marginal or low serum B12 level but no signs or symptoms of deficiency.

Achlorhydria↗