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Biomedical subjects

R M Stern

Publications and source records attributed to R M Stern.

At least 73 records · Page 4Linked to original sources
PubMed1988

Lateralization of complex binaural stimuli: a weighted-image model.

This article describes a new model that predicts the subjective lateral position of bandpass stimuli. It is assumed, as in other models, that stimuli are bandpass filtered and rectified, and that the rectified outputs of filters with matching center frequencies undergo interaural cross correlation. The model specifies and utilizes the shape and location of assumed patterns of neural activity that describe the cross-correlation function. Individual modes of this function receive greater weighting if they are straighter (describing consistent interaural delay over frequency) and/or more central (describing interaural delays of smaller magnitude). This weighting of straightness and centrality is used by the model to predict the perceived laterality of several types of low-frequency bandpass stimuli with interaural time delays and/or phase shifts, including bandpass noise, amplitude-modulated stimuli with time-delayed envelopes, and bandpass-filtered clicks. This model is compared to other theories that describe lateralization in terms of the relative contributions of information in the envelopes and fine structures of binaural stimuli.

Acoustic Stimulation↗
PubMed1987

Effect of barium meals on gastric electromechanical activity in man. A fluoroscopic-electrogastrographic study.

UNLABELLED: The relationship between the cutaneously recorded electrogastrogram (EGG) and gastric contractions in man is unclear. We investigated: (1) the relationship between the electrogastrogram (EGG) signals and gastric contractions elicited by barium meals and (2) the effects of barium meals on frequency and amplitude of EGG signals. As documented by fluoroscopy in four healthy subjects, barium meals stimulated three per minute gastric peristalsis which corresponded with simultaneously recorded three cycle per minute (cpm) EGG waves. Eighteen other healthy volunteers ingested 45% (w/v) or 60% barium suspensions. As determined by Fourier analysis, the dominant EGG frequency before barium was 3 cpm in 16 subjects; two subjects had no distinct frequency peaks. After barium ingestion, the mean amplitude or power at 3 cpm and 1 cpm increased, but the increase was significant only after 45% barium. IN CONCLUSION: (1) individual EGG waves after barium reflect gastric peristaltic sequences, which are reflected in increases in amplitude or power of 3 cpm EGG activity; (2) density or viscosity of the barium meal affects the gastric myoelectric response; and (3) mechanical correlates of 1 cpm EEG activity are unknown.

Adolescent↗
PubMed1987

Spectral analysis of tachygastria recorded during motion sickness.

The purpose of the present experiment was to study frequency changes in gastric myoelectric activity of healthy human subjects and the development of symptoms of motion sickness as brought about by vection or illusory self-motion. Fifteen fasted healthy human subjects were seated inside a circular vection drum, the rotation of which produces visual signals of self-motion that are in conflict with vestibular signals (i.e., mismatched sensory input). An electrogastrogram was obtained for three 15-min. periods: baseline, rotation, and after drum rotation stopped. Respiration, symptoms volunteered by subjects, and a continuous measure of intensity of symptoms were recorded. Five subjects showed a continuation of normal 3-cycles/min. activity during drum rotation and reported no symptoms of motion sickness. Ten subjects showed a shift of their dominant gastric frequency from 3 cycles/min. to 4-9 cycles/min. during drum rotation and reported symptoms of motion sickness. Running spectral analysis revealed a close correspondence over time between tachygastria and reports of symptoms of motion sickness.

Adult↗
PubMed1987

Synthesis, absolute configuration, and antibacterial activity of 6,7-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H- benzo[ij]quinolizine-2-carboxylic acid.

The tricyclic quinolone antibacterial agent 6,7-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H-benzo[ij]quinolizine -2-carboxylic acid has an asymmetric center at position 5 of the molecule. The R and S isomers of the compound have been prepared from the corresponding (R)- and (S)-2,5-dimethyl-6-fluoro-1,2,3,4-tetrahydroquinolines, which were separated via their diastereomeric amides of N-tosyl-(S)-proline. The absolute configuration was established by X-ray analysis of one of the diastereomeric amides. The 5-desmethyl analogue was prepared for antibacterial comparison with the isomers and the racemic mixture. It has now been established that the S isomer is much more active than the R isomer. The 5-desmethyl analogue was found to be more active than the R isomer but not as active as the S isomer or the racemic mixture. The importance of stereochemistry at position 5 in this system has been established.

Bacteria↗
PubMed1987

Cancer incidence among welders: possible effects of exposure to extremely low frequency electromagnetic radiation (ELF) and to welding fumes.

Epidemiological studies of cancer incidence among welders disclose a pooled total of 146 cases of leukemia observed versus 159.46 expected, a risk ratio of 0.92, and 40 cases of acute leukemia observed versus 43.39 expected, a risk ratio of 0.92. For respiratory tract cancer, the pooled total is 1789 cases observed versus 1290.7 expected, a risk ratio of 1.39. Most electric welders are exposed to extremely low frequency electromagnetic radiation (ELF) (magnetic flux densities of up to 100,000 microT), a suspected leukemogen, and to concentrated metallic aerosols (up to 200 mg/m3), which can contain the putative respiratory tract carcinogens Cr(VI) and Ni. The two exposures are usually coincident, since welding with an electric current produces welding fumes. The observation of an excess risk for respiratory tract cancer strongly suggests significant exposure both to fumes and to ELF. The absence of increased risk for all leukemia or for acute leukemia among ELF-exposed welders does not support the hypothesis that the observed excess risk for leukemia or acute leukemia among workers in the electrical trades is due to their ELF exposure, which on the average is lower than that of welders.

Air Pollutants, Occupational↗
PubMed1986

Analysis of the decision making process in chemical safety.

Risk management, for the control of toxic chemicals in particular, and risky human activity in general, begins with the perception of risk and the identification of hazards. The machinery of quantification and evaluation of risk proceeds in a climate of risk perception, and is affected by the state of such perception among all participants in the process. The management of risk, either through legislation or corporate decision making, although ideally objective, is frequently governed by subjective considerations, especially when those individuals or bodies responsible for management decisions develop a 'local' perception of risk. The details of decision making and the sensitivity of the process to various sources of information is reviewed with emphasis on the control of toxic chemicals.

Accidents, Occupational↗
PubMed1986

Ocular findings in juvenile nasopharyngeal angiofibroma.

Juvenile nasopharyngeal angiofibroma (JNA) is the most common benign neoplasm of the nasopharynx. While histologically benign, it has the propensity for aggressive local growth. This highly vascular tumor predominantly occurs in adolescent males. The literature fails to provide a thorough description of ocular complications and their incidence in JNA. This report summarizes the data from those clinical series detailing ocular findings in a total of 218 JNA cases. Exophthalmos was found in 14% of all cases. Decreased visual acuity and partial ophthalmoplegia occurred in 5% and 2% respectively. Recognition of ocular involvement in JNA is of the utmost importance, for it is often a manifestation of orbital or intracranial extension or both. We describe the diagnosis and management of a case of JNA in a five-year-old white male. The patient developed ocular findings of marked exophthalmos and optic atrophy. Early multidisciplinary diagnostic evaluation (otolaryngological, neurosurgical, and ophthalmological) followed by a team surgical approach to excision is most likely to yield efficacious results.

Child, Preschool↗
PubMed1985

Multiple recurrent serosanguineous retinal pigment epithelial detachments in black women.

Three middle-aged black women suffered recurrent, multiple, bilateral, asymmetric, serosanguineous retinal pigment epithelial detachments. These involved the posterior fundus with resolution and recurrences producing subretinal hemorrhages, vitreous hemorrhages, retinal pigment epithelial pigmentary mottling, and chorioretinal scars. Fluorescein angiography showed evidence of choroidal neovascular membranes, choroidal serosanguineous leaks, or both. Ocular inflammation was not evident. Systemic laboratory tests were noncontributory. The clinical pattern was not characteristic of any other entity producing serosanguineous retinal pigment epithelial detachments. The origin remains to be defined.

Black People↗
PubMed1985

Welding fumes and chromium compounds in cell transformation assays.

Fumes generated from mild steel and stainless steel welding were collected on paper filters and tested in the BHK and SHE cell transformation assays. Fumes from the manual metal arc welding of stainless steel (MMA/SS) had a toxic and transforming effect attributable to their Cr(VI) content. The fumes from metal inert gas stainless steel (MIG/SS) welding also had a toxic effect but this was 2-3 times greater than that expected from their soluble Cr(VI) content based on the activity of soluble Cr(VI) from pure chromium compounds. When collected in an impinger, the fumes from MIG/SS were found to contain approximately 10 times the soluble Cr(VI) content of samples collected on filters. This additional Cr(VI), when collected in a water impinger, also exhibited a greater toxicity compared with that found for the additional Cr(VI) collected in an impinger filled with growth medium. This comparison implies the presence of a short-lived biologically active Cr(VI) species usually lost in conventional sampling techniques. It also implies that there is a detoxification step associated with the formation of Cr(VI) organic complexes. Relatively insoluble Cr(VI) compounds showed a higher toxic and transforming effect in the BHK assay than could be ascribed to the soluble Cr(VI) content of the medium, indicating the importance of phagocytosis as a pathway for the uptake of Cr(VI) and other toxic substances from particulates.

Animals↗
PubMed1985

Differentiation of fluorinated quinolone antibacterials with Neisseria gonorrhoeae isolates.

Clinical isolates of Neisseria gonorrhoeae were tested for growth inhibition by various quinolones. One acrosoxacin-resistant isolate was also resistant to several fluorinated quinolones with 7-heterocyclic substitution, but, inhibitory concentrations were not elevated for quinolones substituted with a methyl group in the corresponding position (nalidixic acid:position 7, S-25930:position 8) or unsubstituted (flumequine:position 8). Isolates resistant to flumequine demonstrated elevated inhibitory concentrations for all quinolones examined.

Anti-Bacterial Agents↗
PubMed1985

The management of risk: application to the welding industry.

The management of health risk in the welding industry is considered based on a discussion of the major sources of harm to welders arising from their employment (e.g., accidents and inhalation of fumes and gases). It is shown that present methods neither enable the assessment of the societal and human costs involved, nor permit the specific association of delayed health effects to occupational fume exposures. Reported accidents usually occur early in the working experience and contribute to a large number of working days lost, while fume exposures may contribute to a reduction in life quality which is poorly defined. It is concluded that risk management can only be attempted after much more information is made available concerning the origin, nature, and duration of health effects, especially as related to individual welding technologies and applications.

Accidents, Occupational↗
PubMed1985

Lateral-position-based models of interaural discrimination.

This letter investigates the hypothesis that lateral position is the only cue available for interaural discrimination experiments using 500-Hz stimuli. The discussion of this hypothesis is in the context of comparisons of the experimental data to predictions of the "position-variable" model of binaural interaction. The model predicts the mean and variance of the subjective lateral position of stimuli used in the discrimination experiments, assuming that discrimination performance is based on optimal processing of this subjective position. To the extent that the laterality predictions of the model are accurate, data that are inconsistent with its predictions would also be problematical for any model based on the subjective laterality of a single binaural image. The predictions (at least qualitatively) describe much of the observed experimental data, including a number of results that have not been addressed by any previous theory. Nevertheless, the observed performance is significantly better than the corresponding predictions for three types of experiments in which the utility of the position cue has been eliminated by experimental design. We believe that our results indicate that changes in lateral position are the primary cue in most interaural discrimination experiments, but that secondary attributes of the perceptual images can be useful when performance based on position alone would be poor.

Auditory Perception↗
PubMed1985

Tachygastria and motion sickness.

Cutaneously-recorded electrogastrograms (EGGs) were obtained from 21 healthy volunteers who were seated within a drum, the rotation of which produced vection or illusory self-motion. Fourteen subjects developed symptoms of motion sickness during vection and in each the EGG frequency shifted from the normal 3 cpm to 5-8 cpm, tachygastria, an abnormal pattern. In 6 of 7 asymptomatic subjects, the 3 cpm EGG pattern was unchanged during vection. It was concluded that illusory self-motion produces tachygastria and motion sickness in susceptible subjects.

Adolescent↗
PubMed1984

Excretion of propoxyphene and norpropoxyphene in breast milk.

Propoxyphene (P) and norpropoxyphene (NP) excretion in breast milk was studied in six healthy nursing mothers. Concentrations of P and NP in breast milk and plasma were quantitated by an HPLC method. Plasma P t 1/2 s in mothers averaged 4.40 hr. P and NP breast milk concentrations generally followed plasma levels. NP/P averaged 2.69 in plasma and 2.73 in breast milk. While there was substantial inter- and intrasubject variability, the ratio of drug in the milk and plasma averaged 0.417 and 0.382 for P and NP. These similarities in distribution in breast milk were also reflected in elimination. Clearances of P and NP in milk were of the same order (3.97 ml/hr) as were elimination t 1/2 s in milk in most subjects (mean = 3.68 hr for P and 5.49 hr for NP). Approximately twice as much NP was excreted in the milk, primarily because of the higher NP levels in plasma. Clearance of P and NP in breast milk also correlated strongly with breast milk volume. While little information is available concerning P and NP disposition in neonates, dosage estimates based on kinetic and pharmacologic assumptions suggest that the estimated amounts consumed by the neonate after the mother is given the recommended dose of the drug are not likely to result in toxic plasma levels.

Adult↗