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Biomedical subjects

R M Stern

Publications and source records attributed to R M Stern.

At least 91 records · Page 5Linked to original sources
PubMed1984

Nickel in welding fumes--a cancer hazard to welders? A review of epidemiological studies on cancer in welders.

Although the high exposures to metallic aerosols that were formerly encountered in the primary nickel industry are no longer prevalent, large occupational groups, such as welders, are currently exposed to moderate levels and may therefore be at some degree of health risk. Examination of the world literature reveals a number of epidemiological studies which demonstrate a slight excess risk of respiratory tract cancer incidence among the general welding population. Several of these studies are suggestive of the possibility that there may be a larger excess risk exclusively limited to those welding cohorts who are exposed to nickel and chromium in the fumes from the welding of stainless and high alloy steels. Such a hypothesis, although supported in part by in vitro and in vivo genotoxicity tests, can only be verified by international collaboration in specifically designed epidemiological studies using a uniform protocol.

Adult↗
PubMed1984

Toxicity and transformation potency of nickel compounds in BHK cells in vitro.

An in vitro bioassay utilizing BHK-21 cells in culture was used to determine the relative transformation potency of nickel metal and a number of nickel compounds. These included as relatively insoluble particulates a known carcinogen, nickel subsulfide (Ni3S2) and several oxides either of commercial interest or found in the working environment in the metal industry [e.g., nickel oxide (NiO)], and a soluble salt, nickel acetate [Ni(CH3COO)2]. Although a wide range of transformation potency was found as a function of the dose of nickel per area of culture, all substances produced the same number of transformed colonies at the same degree of toxicity (e.g., 50% survival). Toxicity may arise from nickel originating in membrane-bound or phagocytized particles, or nickel available from solution. If toxicity is a direct measure of net available nickel, then apparently nickel or nickel ion per se is the ultimate transforming agent, independent of source or uptake mechanism.

Acetates↗
PubMed1983

Fibrogenic potential of welding fumes.

A search of 3600 indexed pathology cases has disclosed pulmonary fibrosis in 29 welders. Scanning electron microscopy of biopsy material revealed macrophages laden with inorganic particulates which have characteristics compatible with welding aerosols. In order to establish a possible relationship between fibrotic reaction and welding-fume exposure, the fibrogenic potential fo some 11 different welding fumes and metallic aerosols, considered to be reference standard surrogates for the commonly used welding technologies and applications responsible for 70% of welders exposure, were screened using the Rat Peritoneal Macrophage in vitro bioassay. Only one class of fumes, that from the manual metal arc welding of stainless steel, showed distinct fibrogenic potential. This fume is, however, not common to more than four or five of the heretofore 90 cases of pulmonary fibrosis reported among welders. Thus, although insoluble Cr(VI) is probably the active fibrogen in stainless steel fumes, an etiological factor common to all fibrogenic welding exposures must be sought. It is tentatively proposed to be NO2, a potential experimental in vivo fibrogen copiously produced by certain welding processes and ubiquitous at low concentrations in the welding environment.

Adult↗
PubMed1983

Interaural time and amplitude discrimination in noise.

Just-noticeable differences (jnds) of both interaural time delay (ITD) and interaural intensity difference (IID) were measured for binaural tones in the presence of broadband maskers. The tones were presented at 50 dB SPL, the target frequency was 500 Hz, and the masker frequency was 100-1000 Hz, with various combinations of ITD and IID. The time and amplitude jnds exhibit similar dependencies on target-to-masker ratio and masker type. At a given target-to-masker ratio, discrimination was generally best in the presence of diotic maskers and worst in the presence of the interaurally out-of-phase maskers. Results for the other masker types examined tended to fall in between these two extremes. Many of these data trends are consistent with predictions of the lateralization model and the position-variable model based on auditory-nerve activity.

Auditory Threshold↗
PubMed1983

In vitro assessment of equivalence of occupational health risk: welders.

The possibility of using in vitro testing to determine the equivalence of risk for various occupational groups is discussed. In the absence of epidemiological evidence or relevant animal in vivo bioassays on which to determine the health effects of specific occupational exposures, it is proposed to use similarities in the in vitro response to substances with known (or strongly suspected) and unknown risk to demonstrate their risk equivalence. Identification and evaluation of a high risk "hot spot" due to exposure to Cr(VI) for stainless steel welders is discussed in terms of recent developments in collection, analysis and bioassay of welding fumes.

Chromium↗
PubMed1983

In vitro toxicity and transformation potency of nickel compounds.

An in vitro bioassay utilizing BHK-21 cells in culture is used to determine the relative transformation potential of a number of nickel compounds including, as relatively insoluble particulates a known carcinogen (Ni3S2) and several oxides either of commercial interest or found in the working environment in the metal industry (e.g., NiO), and a soluble salt [Ni(CH3COO)2]. Although a wide range of transformation potency is found as a function of the dose of Ni per area of culture, all substances produce the same number of transformed colonies at the same degree of toxicity (e.g., 50% survival). If toxicity is a direct measure of intracellular concentration, then apparently nickel per se is the ultimate transforming agent independent of source or uptake mechanism.

Animals↗
PubMed1983

Detection by replica plating of false revertant colonies induced in the Salmonella-mammalian microsome assay by hexavalent chromium.

The replica plating method as developed by Lederberg has been used to differentiate between "true" and "false" histidine-requiring revertant bacterial colonies which develop on minimal agar plates in the Ames test. Strains of S. typhimurium LT2, TA 100, when exposed to either sodium dichromate or the fumes from the welding of stainless steel, develop colonies whose apparent numbers are directly in proportion to the Cr(VI) content per plate in both cases, over a wide dose range. Replica impressions of the resulting colonies were transferred to Vogel Bonner minimal agar plates and incubated for 48 hr at 37 degrees C. It was then observed that considerable numbers of "false" revertant colonies were obtained at those Cr(VI) doses which resulted in a pronounced toxic effect, albeit with an acceptable level of the bacterial background lawn. No morphological distinction between "true" and "false" revertant colonies could be made. Although it would appear that at low doses (i.e., low toxicity) the true mutagenicity of stainless steel welding fumes can be completely accounted for by the presence of Cr(VI), the dose range over which the mutagenicity assay is reliable cannot be estimated from examination of the background lawn or from an estimate of the degree of survival of the treated cultures. Thus there is raised a serious question concerning the reliability of quantitative data published in bacterial mutagenicity testing where replica testing of the histidine requirement of the resulting "revertant" colonies is not routinely made. It is suggested that the replica technique can easily be developed as a simple and useful tool for the control of histidine requirement and ampicillin resistance in routine mutagenicity testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

In vitro RPM fibrogenic potential assay of welding fumes.

The fibrogenic potential of 11 different welding fumes and metallic aerosols, considered to be reference standard surrogates for the commonly used welding technologies and applications responsible for 70% of welders exposure, is screened by using the rat peritoneal macrophage (RPM) in vitro bioassay. Only one class of fumes, that from the manual metal are welding of stainless steel, shows distinct fibrogenic potential. This fume, however, is not common to more than four or five of the heretofore 90 cases of pulmonary fibrosis reported among welders. Thus, although insoluble Cr(VI) is probably the active fibrogen in stainless steel fumes, an etiological factor common to all fibrogenic welding exposures must be sought; it is tentatively proposed to be NO chi, a potent experimental in vivo fibrogen copiously produced by certain welding processes and ubiquitous at low concentrations in the welding environment.

Animals↗
PubMed1982

The phase angle of addition in temporal masking for diotic and dichotic listening conditions.

The phase angle, alpha, between a tonal signal and a tonal masker was varied from 0 degrees to 135 degrees in simultaneous masking, forward masking, and pulsation-threshold paradigms. In all conditions the frequency of the signal and masker was 500 Hz. For forward masking both diotic (MOSO) and dichotic (MOS pi) listening conditions were investigated. Only the dichotic case was studied using the pulsation threshold method. In simultaneous masking, thresholds varied as a function of alpha in both diotic and dichotic conditions. Thresholds in the diotic conditions were consistently different from those in the dichotic conditions -- i.e., there were masking-level differences (MLDs) at most values of alpha tested. In forward masking and pulsation-threshold, however, thresholds were independent of alpha in the dichotic conditions; and thresholds were independent of alpha in the diotic, forward masking conditions. Nevertheless, for forward masking the dichotic thresholds remained below the diotic thresholds, yielding MLDs of 3-6 dB. Thus, in nonsimultaneous masking, there is a clear effect of the interaural signal phase, but not of the masker-signal phase relationship, on signal detectability. These results imply that masker-signal phase information is either not preserved or not used by subjects in nonsimultaneous tone-on-tone masking experiments.

Auditory Perception↗
PubMed1981

Process-dependent risk of delayed health effects for welders.

In most industrialized countries large numbers of workers are exposed to welding fumes. Although the general pattern of welders' health may not significantly differ from that of workers in other dusty industrial occupations which demonstrate elevated incidence of respiratory tract diseases with long latency periods, the extremely wide range of substances at potentially high concentrations produced by various welding technologies may give rise to undetected process-specific high-risk working conditions: ("hot spots"). The origin, prevalence and range of magnitude of such hot spots, especially for cancer of the respiratory tract, is discussed, with emphasis placed on the assessment of risk resulting from exposure to Cr(VI) and Ni accompanying the use of various technologies for the welding of stainless and high alloy steels. The wide variation of health effects found within the industry, however, indicates the need for a standard protocol for future epidemiological studies, as well as for the development of suitable methodologies for experimental risk assessment.

Air Pollutants↗
PubMed1979

Discrimination of symmetric time-intensity traded binaural stimuli.

Experiments were conducted to determine the extent to which listeners can discriminate between different combinations of interaural time and intensity for binaural stimulus configurations which eliminate loudness, lateralization, and image-diffuseness cues. A two-interval forced choice paradigm was used, and the task of the subject was to determine the order of two stimuli, each of which was a slowly gated 500-Hz tone with a combination of interaural time and intensity differences that resulted in a centered primary spatial image. The two stimuli to be discriminated were symmetric in that they differed only in the polarity of their interaural differences. Also, in order to reduce artifacts introduced by variations in the coupling of the earphones to the head, acoustic monitoring and compensation was performed both before and after each experimental run. The performance of the two most highly trained subjects is consistent with previous experimental results that indicate an incomplete trading of interaural time and intensity information. The subjective perceptions of these observers are not consistent with previous studies that describe a "time image" and a "time-intensity traded" spatial image.

Acoustic Stimulation↗
PubMed1979

A simple analytical technique for the determination of hexavalent chromium in welding fumes and other complex matrices.

A systematic study of analytical methods for the determination of hexavalent chromium showed that currently existing techniques are unsatisfactory when used with welding fumes, the s-diphenylcarbazide method proposed by the U.S. National Institute for Occupational Safety and Health permitting less than 1% recovery of hexavalent chromium from synthetic welding fumes of known composition. A new (carbonate leaching) technique is proposed which permits better than 80% recovery of both soluble and insoluble chromium (VI). This technique is then used as part of a general method for the determination of total chemical composition as distributed among sample fractions of different solubility. The method is specifically designed for use in the analysis of small samples and is especially suitable for the routine evaluation of health risks as found in the work environment.

Air Pollutants↗
PubMed1978

Theory of binaural interaction based in auditory-nerve data. IV. A model for subjective lateral position.

A model for the subjective lateral position of 500-Hz tones is presented and compared with experimental lateralization data. Previous papers in this series have explicitly described the auditory-nerve response to these stimuli and proposed a binaural displayer that interaurally compares the auditory-nerve firing times. The outputs of the displayer are postulated to represent the only information about detailed firing times that is available to the brain. In the present paper, lateral-position predictions are obtained by a central nonoptimal weighting of these outputs that depends on the interaural intensity difference of the tone. These predictions describe the results of lateralization-matching experiments more accurately and over a wider range of stimulus conditions than previous theories, except for those results which suggest that low-frequency binaural tones can generate multiple perceptual images. The predictions of our model are also consistent with the results of centering and laterality-comparison experiments. It is argued that the data discussed in this paper are generally incompatible with theories that propose a peripheral interaction of interaural timing and intensity information such as the latency hypothesis.

Action Potentials↗
PubMed1977

Mutagenicity of fume particles from stainless steel welding.

Welding fume particles collected from different welding procedures were tested for mutagenicity in Escherichia coli, with the inhibition zone in pol A- as compared to pol A+, and in Salmonella typhimurium, TA 100 strain. While no mutagenicity was found with mild steel welding, a mutagenic effect was established with samples from stainless steel welding. This mutagenicity was particularly associated with manual metal arc (MMA) welding, and less so with metal inert-gas welding. A decrease in or an elimination of the effect occurred with a liver microsomal metabolizing system (S-9 mix). The MMA samples produced the strongest mutagenic effect. More-detailed investigations on these samples showed that the mutagenic agent(s) is water soluble. An increased mutagenicity, which also revealed the induction of frame shift mutations, was found with TA 98. The same welding fume sample was used for a mutagenicity test (resistance to 6-thioguanine) with V 79 hamster cells. Because of the high toxicity of these welding fume particles on the cells, only very low concentrations could be tested, but the increase of mutations, when compared to the negative control, was significant. It is suggested that hexavalent chromium may be involved in the mutagenic effect of the welding fumes.

Air Pollutants↗