bluuebunny/crossref_metadata_2025 huggingface dataset:
Bilateral Macrostomia as an Isolated Pathology
Authors: Gleizal Arnaud , Wan Derrick C. , Picard Arnaud , Lavis Jean-François , Vazquez Marie-Paule , Beziat Jean-Luc
Published: March 2006

Objective:

Congenital macrostomia is a lateral orofacial cleft between the maxillary and mandibular components of the first branchial arch. Bilateral macrostomia is a poorly characterized malformation, with only 14 cases reported in the literature. The purpose of this study was to compare our experience with the world literature.

Method:

A retrospective analysis of 20 cases of bilateral congenital macrostomia was conducted; 6 cases were drawn from 2 maxillofacial surgery units and 14 cases from the world literature. Cases of bilateral congenital macrostomia were compared with cases of unilateral forms using a review of the literature post-1954. Among the six cases identified from the two maxillofacial surgery units, three were treated with linear sutures and three with Z-plasty. Subsequent aesthetic and functional results were analyzed.

Results:

Compared to unilateral forms, bilateral macrostomia is more often isolated without ear or skin deformities. Moreover, there are a greater proportion of larger defects among cases with bilateral macrostomia when compared to unilateral macrostomia. Alimentation, phonation, and mouth opening were always normal. The two sides were always symmetric. Only one case presented with the complication of skin contractions during lip movement.

Conclusion:

The etiopathogenesis of bilateral macrostomia is unclear. Although over 50% of the reported cases of bilateral macrostomia are isolated, this condition presents a therapeutic challenge. In the case of bilateral forms, the surgeon must define the commissure position without a normal side. Repair thus requires extraoral landmarks and normal measurements.
Tessier 3 Cleft with Clinical Anophthalmia: Two Case Reports and a Review of the Literature
Authors: Wenbin Zhang , Hanjiang Wu , Xiaoli Chen , Zhonglin Li
Published: March 2006

Objective:

Tessier 3 cleft with clinical anophthalmia is one of the rarest craniofacial clefts, and hence little has been published about its management and treatment. This article presents two cases of Tessier 3 cleft with clinical anophthalmia. A review of the literature helps to diagnose these complex facial deformities. The treatment and etiopathogenesis are discussed.
Contribution of ammonium ions to the lethality and antimetamorphic effects of ammonium perchlorate
Authors: Goleman Wanda L. , Carr James A.
Published: March 2006

Ammonium perchlorate (AP) is a widespread military waste product in the United States and is a potent thyroid function disruptor in all vertebrates tested thus far. To determine the relative contribution of ammonium ions to the toxicity of AP, we exposed embryonic and larval Xenopus laevis to various concentrations of sodium perchlorate (SP) or ammonium chloride (AC). Ammonium perchlorate was significantly more lethal than SP; 5-d LC50s were 83 and 2,780 mg/L, respectively. To determine whether ammonium ions contribute to the antithyroid effects of AP, we exposed embryonic and larval X. laevis to two sublethal, environmentally relevant concentrations of AP or identical concentrations of AC or SP. At the smaller concentration, only AP delayed metamorphosis and reduced hindlimb growth. Sodium perchlorate and AP, but not AC, prevented metamorphosis and reduced hindlimb growth at the greater concentration. Although AP was slightly more effective in reducing outward manifestations of thyroid disruption, both perchlorate salts, unlike AC, caused profound histopathologic changes in the thyroid. Exposure to the higher concentration of either perchlorate salt produced a feminizing effect, resulting in a skewed sex ratio. We conclude that ammonium ions contribute significantly to the toxicity of AP but not to the direct antithyroid effects of perchlorate.
Biochemical and histopathological effects in pearl dace (Margariscus margarita) chronically exposed to a synthetic estrogen in a whole lake experiment
Authors: Palace Vince P. , Wautier Kerry G. , Evans Robert E. , Blanchfield Paul J. , Mills Kenneth H. , Chalanchuk Sandra M. , Godard Danielle , McMaster Mark E. , Tetreault Gerald R. , Peters Lisa E. , Vandenbyllaardt Lenore , Kidd Karen A.
Published: March 2006

Potential effects of exposure to the synthetic estrogen 17α-ethynylestradiol (EE2) were examined in several species of fish from a lake experimentally treated with environmentally relevant concentrations of the contaminant. Ethynylestradiol was added to Lake 260, a small Precambrian shield lake at the Experimental Lakes Area in northwestern Ontario, Canada, from May to October of 2001, 2002, and 2003. Mean concentrations of EE2 in epilimnetic waters ranged between 4.5 and 8.1 ng/L during the three years, with overall means of 6.1 (±2.8), 5.0 (±1.8), and 4.8 (±1.0) ng/L for the three years, respectively. Male and female pearl dace (Margariscus margarita) captured after EE2 additions began contained up to 4,000-fold higher concentrations of the egg yolk precursor vitellogenin than fish captured from the same lake before the EE2 additions or when compared to fish from reference lakes. Edema in the ovaries, inhibited development of testicular tissue, intersex, and histopathological kidney lesions were all evident in fish exposed to EE2. Some indications that EE2 exposure affected in vitro steroidogenic capacity of the ovaries and the testes existed, although results were not always consistent between years. Pearl dace abundance was similar in the lake treated with EE2 and the reference lake. A trend exists toward a reduced overall population of pearl dace from the treated and reference lakes, as do indications that young-of-the-year size classes are less abundant in the EE2-treated lake. Biochemical and histopathological impacts observed in fish exposed to EE2 in this study have not yet been linked to clear population level impacts in pearl dace. Monitoring of these populations is ongoing.
Reproductive effects of the endocrine disruptor fenarimol on a Baltic amphipod Monoporeia affinis
Authors: Jacobson Therese , Sundelin Brita
Published: March 2006

An endocrine disruptor, the fungicide fenarimol, was investigated regarding its effects on reproduction and hormone (ecdysteroid) levels in the deposit-feeding amphipod Monoporeia affinis. In addition, the influence of food shortage, both by itself and in combination with fenarimol, on reproduction was examined. Field-collected amphipods were exposed in flow-through microcosms during the period of sexual maturation and mating in four treatment series: Control with low food, fenarimol with low food, control with high food, and fenarimol with high food. Fenarimol was added at a concentration of 0.3 mg/L in two pulses/week. Results show that fenarimol has a negative effect on fertilization rate and male mating ability. Results were supported by a tendency toward delayed male sexual development. Food shortage decreased weight in both sexes and retarded female oocyte development. Higher ecdysteroid levels were recorded in males than in females, and food shortage increased male ecdysteroid levels. No effect of fenarimol exposure on ecdysteroid levels was observed. No synergistic effects of fenarimol and food shortage could be distinguished in any variable examined. Thus, M. affinis was vulnerable to reproductive impairment by fenarimol, with effects on the next generation (i.e., a disturbed sexual development and fertilization ability). Food shortage has negative effects on M. affinis, but it does not enhance the effects of fenarimol.
Elevated fluctuating asymmetry in eastern mosquitofish (Gambusia holbrooki) from a river receiving paper mill effluent
Authors: Estes Eleanor C. J. , Katholi Charles R. , Angus Robert A.
Published: March 2006

The present study investigated whether fluctuating asymmetry can serve as a useful biomarker of environmental stress in the eastern mosquitofish (Gambusia holbrooki). Fluctuating asymmetry was measured in sexually mature females sampled from two Florida, USA, coastal streams: The Fenholloway River, which is dominated by effluent from a paper mill, and Spring Creek, a tributary to the Fenholloway River (Taylor County, FL, USA) that does not receive paper mill effluent. Nine morphometric (lengths of the A and B scales, fifth pectoral fin ray, supraorbital canal, and preorbital canal and the sixth gill raker on the first brachial arch; orbit diameter; distance from the dorsal-ventral midpoint of the eye socket to the base of the pectoral fin; and distance from the postorbital canal to the operculum) and five meristic traits (numbers of scales in the lateral line, radii on the A and B scales, pectoral fin rays, and gill rakers on the first brachial arch) were included. For each of the three indexes of fluctuating asymmetry that were used, the majority of the traits showed a higher level of fluctuating asymmetry in fish from the Fenholloway River than in fish from Spring Creek. For two of the indexes, the difference was significant. Comparisons of mean values for fluctuating asymmetry (over all traits) for each fish and the means of a composite index of asymmetry both indicated that fish from the Fenholloway River had significantly greater overall fluctuating asymmetry than those from Spring Creek. Results of the present study are consistent with the hypothesis that environmental stress increased the level of fluctuating asymmetry in fish from the Fenholloway River. Thus, fluctuating asymmetry appears to be a useful biomarker for stress-induced developmental instability in the eastern mosquitofish.
Toxicity of weathered Exxon Valdez crude oil to pink salmon embryos
Authors: Brannon Ernest L. , Collins Keya M. , Brown John S. , Neff Jerry M. , Parker Keith R. , Stubblefield William A.
Published: March 2006

Research was conducted at the University of Idaho (Moscow, ID, USA) on the toxicity of weathered Exxon Valdez crude oil to embryos of pink salmon from 2001 to 2003 for the purpose of comparing these data with those from the National Oceanic and Atmospheric Administration Fisheries Laboratory at Auke Bay (AK, USA). Mortality reported at Auke Bay for embryos chronically exposed to very low concentrations of aqueous solutions of weathered oil, measured as dissolved polycyclic aromatic hydrocarbons (PAHs), was inconsistent with that in other published research. Using the Auke Bay experimental design, we found that toxicity is not evident in pink salmon embryos until chronic exposure to laboratory weathered and naturally weathered oil concentrations exceeding 1,500 and 2,250 ppm, respectively, representing a total PAH tissue burden in excess of 7,100 ppb. Effluent hydrocarbons also drop well below concentrations sufficient to cause harm over the time frame of a few weeks, regardless of oiling level. Resolution of differences with Auke Bay involved the source of contributing hydrocarbons. The experimental design did not exclude dispersed oil droplets from the aqueous solution; thus, toxicity was not limited to the dissolved hydrocarbon fraction. The implications of the present results are discussed regarding the toxic risk of weathered oil to pink salmon embryos in streams of Prince William Sound (AK, USA).
Source apportionment modeling of volatile organic compounds in streams
Authors: Pankow James F. , Asher William E. , Zogorski John S.
Published: March 2006

It often is of interest to understand the relative importance of the different sources contributing to the concentration cw of a contaminant in a stream; the portions related to sources 1, 2, 3, etc. are denoted cw1, cw2, cw3, etc. Like cw, the fractions α1 = cw,1/cw, α2 = cw,2/cw, α3 = cw,3/cw, etc. depend on location and time. Volatile organic compounds (VOCs) can undergo absorption from the atmosphere into stream water or loss from stream water to the atmosphere, causing complexities affecting the source apportionment (SA) of VOCs in streams. Two SA rules are elaborated. Rule 1: VOC entering a stream across the air/water interface exclusively is assigned to the atmospheric portion of cw. Rule 2: VOC loss by volatilization, flow loss to groundwater, in-stream degradation, etc. is distributed over cw,1, cw,2, cw,3, etc. in proportion to their corresponding a values. How the two SA rules are applied, as well as the nature of the SA output for a given case, will depend on whether transport across the air/water interface is handled using the net flux F convention or using the individual fluxes J convention. Four hypothetical stream cases involving acetone, methyl-tert-butyl ether (MTBE), benzene, chloroform, and perchloroethylene (PCE) are considered. Acetone and MTBE are sufficiently water soluble from air for a domestic atmospheric source to be capable of yielding cw values approaching the common water quality guideline range of 1 to 10 μg/L. For most other VOCs, such levels cause net outgassing (F > 0). When F > 0 in a given section of stream, in the net flux convention, all of the αj for the compound remain unchanged over that section while cw decreases. A characteristic time τd can be calculated to predict when there will be differences between SA results obtained by the net flux convention versus the individual fluxes convention. Source apportionment modeling provides the framework necessary for comparing different strategies for mitigating contamination at points of interest along a stream.
An algal probe for copper speciation in marine waters: Laboratory method development
Authors: Karner Dawn A. , Shafer Martin M. , Overdier Joel T. , Hemming Jocelyn D. C. , Sonzogni William C.
Published: March 2006

Laboratory-based algal assays were developed to explore the bioavailability of copper to the marine alga Thalassiosira weissflogii. A calibration strategy was developed that avoided use of the synthetic ligand ethylenediaminetetraacetic acid (EDTA) in the Aquil growth medium, thereby allowing ambient metal speciation. In a comparison of T. weissflogii cells grown in Aquil medium with EDTA to medium containing no added copper, zinc, and less than 0.003 nM of EDTA, no significant growth differences were observed after 8 d, indicating adequate stored nutrients. A 30-h assay was selected as the optimal time frame after examination of data from concentration-response experiments. Using 65Cu stable isotope additions, parameters examined included growth, chlorophyll a, copper uptake, phytochelatin production, and dissolved organic carbon excretion. The T. weissflogii specific growth rates decreased from 1.36 d−1 at pCu (i.e., the negative logarithmic concentration of free Cu) = 8.8 to 0.56 d−1 at pCu = 7.8, whereas intercellular copper concentrations increased from 13.6 to 70.1 fg/cell, respectively. Calculated values of the copper concentration that caused a 50% reduction in algal growth of pCu = 7.7 and copper per algal mass of 625 μg/g were established. Using an algal assay based on EDTA-free culture medium, along with trace-metal clean techniques, the effect of copper on T. weissflogii and the speciation of copper in marine waters can be studied.
Estimation of soil sorption coefficients of veterinary pharmaceuticals from soil properties
Authors: ter Laak Thomas L. , Gebbink Wouter A. , Tolls† Johannes
Published: March 2006

Environmental exposure assessment of veterinary pharmaceuticals requires estimating the sorption to soil. Soil sorption coefficients of three common, ionizable, antimicrobial agents (oxytetracycline [OTC], tylosin [TYL], and sulfachloropyridazine [SCP]) were studied in relation to the soil properties of 11 different soils. The soil sorption coefficient at natural pH varied from 950 to 7,200, 10 to 370, and 0.4 to 35 L/kg for OTC, TYL, and SCP, respectively. The variation increased by almost two orders of magnitude for OTC and TYL when pH was artificially adjusted. Separate soil properties (pH, organic carbon content, clay content, cation-exchange capacity, aluminum oxyhydroxide content, and iron oxyhydroxide content) were not able to explain more than half the variation observed in soil sorption coefficients. This reflects the complexity of the sorbent-sorbate interactions. Partial-least-squares (PLS) models, integrating all the soil properties listed above, were able to explain as much as 78% of the variation in sorption coefficients. The PLS model was able to predict the sorption coefficient with an accuracy of a factor of six. Considering the pH-dependent speciation, species-specific PLS models were developed. These models were able to predict species-specific sorption coefficients with an accuracy of a factor of three to four. However, the species-specific sorption models did not improve the estimation of sorption coefficients of species mixtures, because these models were developed with a reduced data set at standardized aqueous concentrations. In conclusion, pragmatic approaches like PLS modeling might be suitable to estimate soil sorption for risk assessment purposes.
The effect of pH and ionic strength on the sorption of sulfachloropyridazine, tylosin, and oxytetracycline to soil
Authors: ter Laak Thomas L. , Gebbink Wouter A. , Tolls Johannes
Published: March 2006

Antimicrobial agents are the most heavily used pharmaceuticals in intensive husbandry. Their usual discharge pathway is application to agricultural land as constituents of animal manure, which is used as fertilizer. Many of these compounds undergo pH-dependent speciation and, therefore, might occur as charged species in the soil environment. Hence, pH and ionic strength of the soil suspension can affect the sorption behavior of these compounds to soil. Consequently, the soil sorption of three antimicrobial agents—sulfachloropyridazine (SCP), tylosin (TYL), and oxytetracycline (OTC)—was investigated. Their respective sorption coefficients in two agricultural soils ranged from 1.5 to 1,800 L/kg. Sorption coefficients were greater under acidic conditions. Addition of an electrolyte to the solution led to decreased sorption of TYL and OTC by a factor of 3 to 20, but it did not influence the sorption of SCP. This behavior was analyzed by accounting for the pH-dependent speciation of TYL and OTC and considering the presence of OTC-calcium complexes. It appears that the decreased sorption of TYL and OTC with increasing ionic strength results from competition of the electrolyte cations with the positively charged TYL species and the positively charged OTC complexes. A model linking sorbate speciation with species-specific sorption coefficients can describe the pH dependence of the apparent sorption coefficients. This modeling approach is proposed for implementation in the assessment of sorption of ionizable compounds.
Daphnia magna mortality when exposed to titanium dioxide and fullerene (C60) nanoparticles
Authors: Lovern Sarah B. , Klaper Rebecca
Published: March 2006

Nanoparticles (1–100 nm) comprise the latest technological advances designed to do everything from absorb environmental toxins to deliver drugs to a target organ. Recently, however, they have come under scrutiny for the potential to cause environmental damage. Because compounds in this miniature size range have chemical properties that differ from those of their larger counterparts, nanoparticles deserve special attention. Our main objective was to assess the potential impact that nanoparticles may have on release into aquatic environments. We prepared titanium dioxide (TiO2) and fullerene (C60) nanoparticles by filtration in tetrahydrofuran or by sonication. Daphnia magna were exposed to the four solutions using U.S. Environmental Protection Agency 48-h acute toxicity tests. Images of the particle solutions were recorded using transmission-electron microscopy, and the median lethal concentration, lowest-observable-effect concentration, and no-observable-effect concentration were determined. Exposure to filtered C60 and filtered TiO2 caused an increase in mortality with an increase in concentration, whereas fullerenes show higher levels of toxicity at lower concentrations. Exposure to the sonicated solutions caused varied mortality. Understanding the potential impacts of nanoparticles will help to identify the most appropriate nanotechnology to preserve the aquatic environment while advancing medical and environmental technology.
Mercury fractionation, bioavailability, and ecotoxicity in highly contaminated soils from chlor-alkali plants
Authors: Zagury Gerald J. , Neculita Carmen-Mihaela , Bastien Christian , Deschênes Louise
Published: March 2006

Mercury (Hg) fractionation, speciation, bioavailability, and ecotoxicity wereinvestigated in three highly contaminated soils from chlor-alkali plants. Single extractions and a validated four-step sequential extraction scheme were used. Total, volatile, and methyl-Hg concentrations were determined. Mercury was then separated in fractions defined as water-soluble (F1), exchangeable (F2), organic (F3), and residual (F4). Germination and growth inhibition of barley (Hordeum vulgare) and mortality of earthworms (Eisenia andrei) were assessed, and tissue-Hg concentrations of exposed organisms were determined. Results revealed highly (295 ± 18–11,500 ± 500 μg Hg/g) contaminated soils, but extracted fractions indicated relatively low mobility of Hg. Nevertheless, the water-soluble and the CaCl2-extractable fractions represented significant Hg concentrations (299 ±18 μg/g in soil 3, 67.4 ± 2.3 μg/g in soil 1, and 9.5 ± 0.3 μg/g in soil 2), and volatile Hg ranged between 14 and 98% of total Hg. Overall, Hg concentrations reached 6,560 ± 240 μg/g in roots, 4,200 ± 1,070 μg/g in aerial plants, and 1,410 ± 120 μg/g in E. andrei. Earthworm mortality was 100% after exposure to the soil with the highest concentration of mobile Hg. In the latter soil, earthworm fragmentation and chlorotic plants were observed. Bioconcentration factors (BCFs) were higher in barley compared to earthworms, but BCFs yielded misleading values after exposure to the extremely contaminated soil. This study shows that Hg accumulated primarily in the roots, but results also indicate uptake of gaseous Hg by the aerial plants of barley. Tissue-Hg concentrations of both exposed organisms were correlated with water-soluble and CaCl2-extractable Hg, and growth inhibition was in agreement with Hg fractionation.
Virtual screening for environmental pollutants: Structure—activity relationships applied to a database of industrial chemicals
Authors: Öberg Tomas
Published: March 2006

The current risk paradigm calls for individual consideration and evaluation of each separate environmental pollutant, but this does not reflect accurately the cumulative impact of anthropogenic chemicals. In the present study, previously validated structure-activity relationships were used to estimate simultaneously the baseline toxicity and atmospheric persistence of approximately 50,000 compounds. The results from this virtual screening indicate fairly stable statistical distributions among small anthropogenic compounds. The baseline toxicity was not changed much by halogen substitution, but a distinct increase seemed to occur in the environmental persistence with increased halogenation. The ratio of the atmospheric half-lives to the median lethal concentrations provides a continuous scale with which to rank and summarize the incremental environmental impacts in a mixture-exposure situation. Halogenated compounds as a group obtained a high ranking in this data set, with well-known pollutants at the very top: DDT metabolites and derivatives, polychlorinated biphenyls, diphenyl ethers and dibenzofurans, chlorinated paraffins, chlorinated benzenes and derivatives, hydrochlorofluorocarbons, and dichlorononylphenol. Environmentally friendly chemicals that obtained the lowest rank are nearly all hydroxylated and water-soluble. Virtual screening can assist with “green chemistry” in designing safe and degradable products and enable assessment of the efficiency in chemicals risk management.
Thyroid function and reproductive success in rodents exposed to perchlorate via food and water
Authors: Smith Philip N. , Severt Scott A. , Jackson W. Andrew , Anderson Todd A.
Published: March 2006

The purpose of the present study was to determine if exposure to perchlorate via food items would have effects on mammals similar to those caused by exposure through drinking water at approximately equivalent doses. Prairie voles (Microtus ochrogaster) and deer mice (Peromyscus maniculatus) were used to assess the potential toxicity of perchlorate-contaminated food items. Voles and mice were divided randomly into three treatment groups—perchlorate-contaminated food (PCF), perchlorate-contaminated water (PCW), and control groups—such that each treatment group contained equal numbers of males and females. Rodents in PCF treatment groups were fed chow formulated with soybean plant matter that had been grown with perchlorate-contaminated irrigation water. Individuals in the control and PCF groups were provided distilled/deionized drinking water, whereas the PCW group received drinking water containing sodium perchlorate. Only slight differences among treatment groups were observed in a variety of endpoints, including reproductive success, tissue perchlorate concentrations, thyroid hormone concentrations, and thyroid histology. However, trends observed in the present study suggest that perchlorate exposure via water may result in slightly greater effects than exposure to perchlorate via food. These data and recent reports of perchlorate in a wide variety of food items indicate that exposure via food intake is an important consideration when examining cumulative risk among humans, livestock, and wildlife.
Relationships between T-cell-mediated immune response and Pb, Zn, Cu, Cd, and As concentrations in blood of nestling white storks (Ciconia ciconia) and black kites (Milvus migrans) from Doñana (southwestern Spain) after the Aznalcóllar toxic spill
Authors: Baos Raquel , Jovani Roger , Forero Manuela G. , Tella Jose L. , Gómez Gemma , Jiménez Begoña , González María J. , Hiraldo Fernando
Published: March 2006

In the Aznalcóllar mining accident (April 1998), nearly six million cubic meters of toxic wastes were spilled in the surroundings of the Doñana National Park (southwestern Spain). The present study focused on the likely effects of metal pollution on the immune system of nestling white storks (Ciconia ciconia) and black kites (Milvus migrans) sampled in the nearby area. Using the phytohaemagglutinin skin test, we examined cell-mediated immune response (CMI) in relation to Pb, Zn, Cu, Cd, and As concentrations in blood of 281 nestling white storks and of 89 black kites. The former species was monitored along a four-year period (1999, 2001–2003), while black kites were sampled in 1999. Overall, average levels of heavy metals and As were relatively low when compared to those reported for birds in metal-polluted areas. Copper showed a negative effect on CMI in both species, although the relationship was significant only for white storks in 2002. We found no evidence that environmental exposure to Pb, Zn, As, and Cd had any effect on nestlings' CMI. Interannual consistency is revealed as an important factor, supporting the need of long-term studies when assessing the immunotoxic effects of metal exposure in the wild.
ON THE FORM OF LEARNING CURVES
Authors: Stevens Joseph C. , Savin Harris B.
Published: March 2006

In a wide variety of learning experiments, cumulated measures of performance turn out to be a power function of practice time or number trials, typically with an exponent between 1 and 2. The effects of various conditions on the course of learning can frequently be described in terms of the two constants of the function.
BEHAVIOR IN A NOVEL SITUATION AS INFLUENCED BY THE IMMEDIATELY PRECEDING ENVIRONMENT1
Authors: Woods Paul J.
Published: March 2006

Behavior in a novel situation, which basically represented an increase in complexity for some Ss and a decrease in complexity for others, was sampled by the use of an exhaustive list of response categories at 5‐sec intervals for 24 min. Wide behavioral differences are described. In addition, the feasibility of the time‐sampling technique for the study of animal behavior is further demonstrated, and its more general use is advocated.
CONCURRENT GENERALIZATION GRADIENTS FOR FOOD‐CONTROLLED AND SHOCK‐CONTROLLED BEHAVIOR
Authors: Hearst Eliot
Published: March 2006

In the presence of a bright light, monkeys were trained to press a lever to avoid shock and to pull a chain for food reward. After gradients of generalization to other light intensities had been determined for each response, gradients were subsequently secured after training in a brightness discrimination and under several free‐shock conditions. The following results were obtained: (1) Generalization gradients prior to discrimination training were much steeper for the food‐controlled response than for the shock‐controlled response. This finding was confirmed in another study in which rats served as subjects. (2) After discrimination training, both gradients became much steeper, but the avoidance gradient still showed more generalized responding than that of reward. (3) After a period of continuous testing with all the different test intensities, the two gradients became even steeper. In addition, differences between the two gradients virtually disappeared. (4) The intermittent delivery of free shocks during a previously non‐shocked light intensity radically affected the shape of the avoidance gradient, just as the addition of an avoidance contingency did during the same, previously non‐shocked, light intensity.
INTERLOCKING SCHEDULES OF REINFORCEMENT1
Authors: Berryman R. , Nevin J. A.
Published: March 2006

Four male pigmented rats were exposed to a procedure designed to investigate the relation between several performance measures and a schedule continuum ranging from FR 36 to FI 2 through four intermediate interlocking schedules. On all schedules, each subject developed a stable performance that was generally break‐and‐run. Analysis of the cumulative records, post‐SR breaks, and running rates showed a continuum of performance related to the schedule continuum.
DELAYED ALTERNATION IN THE PIGEON1
Authors: Hearst Eliot
Published: March 2006

Pigeons were studied in a delayed‐response task requiring alternation of key pecks on two response keys. Blackouts of from 1 to 10 sec intervened between successive choices on the two keys.

The following results were obtained: (1) Birds performed at well above chance accuracy on all the delays tested. Accuracy was generally lowest at 1‐ and 10‐sec delays. (2) Overt postural orientations during the delay interval appeared to mediate accurate key‐pecking behavior. (3) The shape of the delay vs. accuracy function was discussed in terms of the possibly confounding influences of (a) stimulus “trace” variables, and (b) aversive effects of the time outs produced by incorrect responding.
INTERACTIONS BETWEEN THE DISCRIMINATIVE AND AVERSIVE PROPERTIES OF PUNISHMENT1
Authors: Holz William C. , Azrin Nathan H.
Published: March 2006

Punishment acquires a discriminative property when it is selectively paired with either reinforcement or extinction. At the milder punishment intensities, the discriminative control exerted by punishment is similar to the discriminative control exerted by a response‐produced neutral (nonaversive) stimulus. However, the effect of the aversive property is apparent as the intensity of the punishment is increased. The aversive property of the punishment acts to enhance the discriminative control when the punishment is selectively applied during extinction periods, and to attenuate the discriminative control when the punishment is selectively applied during reinforcement periods. One major difference was found between the control exerted by the punishment and the response‐produced neutral simulus: Responding greatly increased after the SΔ punishment but not after the SΔ neutral stimulus; this increase in responding was independent of the punishment intensities studied.
THE QUAIL, Coturnix coturnix, AS A LABORATORY ANIMAL
Authors: Reese Ellen P. , Reese T. W.
Published: March 2006

The quail, Coturnix coturnix, is small, gentle, hardy, adaptable, easy to house, and economical to maintain. Wetherbee and Jacobs (1960) call it the “Drosophila of the avian laboratory,” and yet this charming bird is virtually unknown to the psychological laboratory. Our preliminary investigations show that the pecking operant is readily conditioned and that little or no deprivation is necessary to maintain behavior with food as a reinforcer. Visual and temporal discriminations were very quickly made. Our observations suggest that the social behavior of these birds might be a fruitful area for psychological study. On the basis of our somewhat limited observations, we believe that C. coturnix should prove a useful experimental animal for comparative studies, for basic research in learning, motivation, and perhaps social behavior, and for teaching the analysis of behavior in demonstrations and laboratory courses.
PROGRAMMING STIMULI IN MATCHING TO SAMPLE1
Authors: Hively Wells
Published: March 2006

In these investigations, a “teaching machine” was used to train pre‐school and first‐grade children in a series of progressively difficult discrimination tasks, leading up to matching to sample. Such training was much more efficient than training in the final discrimination alone. The errors the subjects made were found to be a functon both of the differences between consecutive discriminations (the “size of the steps” in the program) and the length of training on each discrimination. Theoretical and practical implications of these findings are discussed.
RESPONSE LATENCY AS A FUNCTION OF REINFORCEMENT SCHEDULE1
Authors: Stebbins William C. , Lanson Robert N.
Published: March 2006

Four Ss were trained to press and hold down a telegraph key in the presence of a light. Subsequent release of the key during a tone was followed by water reinforcement. The schedule of reinforcement for key release was varied, and its effects on the latency (RT) of key release to the tone were studied. Both median RT and variability of RT were found to be inversely related to frequency of reinforcement as determined by the schedule.
RESPONSE LATENCY AS A FUNCTION OF AMOUNT OF REINFORCEMENT
Authors: Stebbins William C.
Published: March 2006

Food‐deprived rats were trained to press and hold down a telegraph key in the presence of a light. Subsequent release of the key during a tone was followed by 0.15 ml of a 20‐percent sucrose solution as reinforcement. The Ss were subsequently shifted to a 0‐percent and to a 5‐percent solution from the 20‐percent base line. The median RT and the variability of RT increased markedly as a result of the shift to the lower sucrose concentrations. For all Ss, the change in median and variability was greater for the shift to the 0‐percent solution than for the shift to the 5‐percent solution. It is probable that median RT and variability of RT are inversely related to amount of reinforcement.
THE CONDITIONING OF TEXTUAL RESPONSES USING “EXTRINSIC” REINFORCERS1
Authors: Staats Arthur W. , Staats Carolyn K. , Schutz Richard E. , Wolf Montrose
Published: March 2006

Six 4‐year‐old Ss were presented with a textual program consisting of 26 words arranged so the word stimuli were gradually combined into sentences and then short “stories.” Three Ss were given the No‐Reinforcement condition first, and only social reinforcers were presented. They were switched to the Reinforcement condition as soon as they requested discontinuance of the activity. The other three Ss were given Reinforcement—No Reinforcement—Reinforcement treatments. The No‐Reinforcement treatment in this case lasted until S requested discontinuance of the activity. The reinforcers were mixed edibles and trinkets, as well as tokens backed up by small plastic toys on a 1:24 ratio. The unit of response was the number of new texts acquired as a result of each of the 45‐min experimental sessions. It was demonstrated that the program, procedure, and reinforcement conditions produced curves which are analogous to those produced in common operant‐conditioning procedures. The results indicate that other operant principles may be studied in this significant area of human behavior, with important practical consequences.
QUANTITATIVE RELATIONS BETWEEN AVOIDANCE BEHAVIOR AND PITUITARY‐ADRENAL CORTICAL ACTIVITY1
Authors: Sidman Murray , Mason John W. , Brady Joseph V. , Thach John
Published: March 2006

The rate at which monkeys pressed a lever and avoided shocks was manipulated in several ways. Measurements were also made of their plasma levels of 17‐hydroxycorticosteroids. The rate at which the animals pressed the lever and the frequency with which they received shocks were both implicated as determiners of the steroid levels.
INSTRUCTIONS AND STIMULUS CATEGORIZING IN A MEASURE OF STIMULUS GENERALIZATION1
Authors: Thomas David R. , Mitchell Kevin
Published: March 2006

In Experiment I, three groups of 20 Ss each were exposed to a light of 550 mμ (yellowish‐green) for 60 sec and then viewed a random sequence of wavelengths with instructions to respond only to the original color. The instructions given the three groups were worded differently in an attempt to vary the strength of a set‐to‐discriminate assumed to be created by this procedure. The three groups produced similar gradients, each with a peak of responding at 540 mμ, in agreement with Kalish's (1958) published gradient for the 550 mμ standard stimulus value. It was suggested that the nature of the task is such that a strong discriminatory set is produced regardless of the wording of the instructions.

A temporal analysis of the gradient as it develops during the testing revealed that initially the peak of responding occurs at 550 mμ; but as testing progresses, it shifts gradually in the direction of the shorter wavelengths (purer greens). Experiment II was performed to test the generality of the phenomenon of regression to the primary color. Two groups of 20 Ss each were tested for generalization following exposure to 510 mμ (bluish‐green) and 525 mμ (pure green), respectively. We predicted that the 510 mμ gradient would reveal a progressive shift toward the longer wavelengths (purer greens), whereas the 525 mμ gradient would show no tendency to shift. The results were strikingly in accord with these predictions.

We concluded that although a physiological process could not be ruled out, the verbal labeling of the standard stimulus value may well be responsible for the regression of the gradient toward the primary color.
THE FUNCTIONAL PROPERTIES OF A TIME OUT FROM AN AVOIDANCE SCHEDULE1
Authors: Verhave Thom
Published: March 2006

Investigations are reported of some of the discriminative (cue) and reinforcing properties of stimuli (TOav) correlated with the discontinuation of a free‐operant avoidance schedule. After several unsuccessful initial attempts to demonstrate the positively reinforcing effect of TOav, a special technique was developed. The subjects were trained by means of a free‐operant avoidance procedure to press a lever and postpone electric shock; by pressing a second lever, they could produce a cue correlated with the TOav period. The importance of a distinct cue correlated with TOav was demonstrated in experiments in which this signal was eliminated from the procedure. The reinforcing function of the TOav period was explored by showing its effectiveness under various schedules of reinforcement.

Other observations were made concerning the course of extinction of both TOav‐producing responses and avoidance behavior.

In further experiments in which TOav was used as a reinforcer, the TOav behavior was also brought under separate stimulus control. The development of the various discriminations involved in the resulting performance were described.
EFFECTS OF DEPRIVATION UPON COUNTING AND TIMING IN RATS
Authors: Mechner Francis , Guevrekian Laurence
Published: March 2006

Two procedures were used in an investigation of the effects of deprivation upon counting and timing. Under the first procedure, fixed minimum interval (FMI), the rat received liquid reinforcement every time it pressed bar B after having waited a minimum of 5 sec following a press on bar A. Under the second procedure, fixed consecutive number (FCN), reinforcement was delivered every time the rat pressed bar B following a run of at least four consecutive responses on bar A.

Water deprivation was varied over a set of values ranging from 4 to 56 hr. Deprivation had almost no effect on the waiting time in the FMI procedure, or on the number of responses per run in the FCN procedure. With both procedures, increasing deprivation shortened the pause between reinforcement and the next response. In the FCN procedure, the speed with which the runs were executed increased with increasing deprivation, although the number of responses in these runs was relatively unaffected.
ELECTROENCEPHALOGRAPHIC CORRELATES OF TEMPORALLY SPACED RESPONDING AND AVOIDANCE BEHAVIOR
Authors: Ross Gilbert S. , Hodos William , Brady Joseph V.
Published: March 2006

This study was undertaken to determine whether any EEG changes occurred during a multiple schedule of reinforcement consisting of repeated periods of avoidance behavior, a time‐out (TO) period, and a period of differential reinforcement of low rates (DRL). The two monkeys were permanently implanted with bipolar electrodes in various subcortical areas. The EEG was recorded from these electrodes for several weeks before any behavioral training was undertaken. Training was then begun in the multiple schedule, and EEG recordings were taken frequently throughout the training period. When a stable performance level was achieved, drugs (dl‐amphetamine and sodium pentobarbital) were introduced which disrupted the DRL performance but had little or no effect on avoidance behavior. The EEG recordings continued throughout these drug studies.

The data indicate that the marked behavioral differences noted in each component of the schedule were not reflected in the EEG. However, the EEG did correlate with the general level of alertness of the animals during the various components. The drugs which differentially affected the behavior in the components of the schedule did not differentially affect the EEG, but they did change the brain‐wave activity equally in all components. Finally, EEG changes correlated with the complex motor response of lever pressing were not observed.
EXTEROCEPTIVE CONTROL OF FIXED‐INTERVAL RESPONDING
Authors: Segal Evalyn F.
Published: March 2006

Two pigeons were exposed to several fixed‐interval schedules of food reinforcement. In some cases, exteroceptive stimuli associated with the passage of time were present. Such visual “clock” stimuli were found to gain almost complete control over the behavior, although at the longest fixed interval studied, the superposition of a new temporal discrimination upon the visual discrimination was observed. Where clock stimuli were made contingent upon the birds' behavior, a new form of responding was generated. This behavior was discussed in terms of positive and negative response‐tendencies resulting from several stimulus factors: Some of these functioned as SΔ's and secondary negative reinforcers; some functioned as SD's and secondary positive reinforcers; and some were ambiguous with respect to reinforcement conditions. A “pure temporal” discrimination was superimposed upon these factors, but its exact nature was indeterminate from the present data.
A REVIEW OF POSITIVE CONDITIONED REINFORCEMENT1
Authors: Kelleher Roger T. , Gollub Lewis R.
Published: March 2006

This review critically analyzes experimental data relevant to the concept of conditioned reinforcement. The review has five sections. Section I is a discussion of the relationship between primary and conditioned reinforcement in terms of chains of stimuli and responses. Section II is a detailed analysis of the conditions in which the component stimuli in chained schedules of reinforcement will become conditioned rein forcers; this section also analyzes studies of token reinforcement, observing responses, switching responses, implicit chained schedules, and higher‐order conditioning. Section III analyzes experiments in which potential conditioned reinforcers are used either to prolong responding or to generate responding during experimental extinction. This section discusses hypotheses that have been offered as alternatives to the concept of conditioned reinforcement and hypotheses concerning the necessary and sufficient conditions for establishing a conditioned reinforcer. Section IV discusses other variables that act when a conditioned reinforcer is being established or that act when an established conditioned reinforcer is used to develop or maintain behavior. Section V is a general discussion of conditioned reinforcement.

The evidence indicates that the conditioned reinforcing effectiveness of a stimulus is directly related to the frequency of primary reinforcement occurring in its presence, but is independent of the response rate or response pattern occurring in its presence. Results from chained schedules comprised of several components indicate that a stimulus can be established as a conditioned reinforcer by pairing it with an already established conditioned reinforcer rather than a primary reinforcer; however, this type of higher‐order conditioning has not been clearly demonstrated with respondent conditioning procedures.

Although discriminative stimuli are usually conditioned reinforcers, the available evidence indicates that establishing a stimulus as a discriminative stimulus is not necessary or sufficient for establishing it as a conditioned reinforcer. Discriminative stimuli in chained schedules with several components are not always conditioned reinforcers; stimuli that are simply paired with reinforcers can become conditioned reinforcers.

The hypotheses that have been offered as alternatives to the concept of conditioned reinforcement are too limited to integrate the data that exist. The concepts of conditioned reinforcement and chained schedule, however, can be used to integrate the data obtained with diverse techniques. Recent experiments have revealed several techniques for the development of effective conditioned reinforcers. These techniques provide a powerful tool for advancing understanding of conditioned reinforcement and for extending control over behavior.
RATIO REINFORCEMENT OF MATCHING BEHAVIOR1
Authors: Nevin John A. , Cumming William W. , Berryman Robert
Published: March 2006

Three pigeons, previously trained to a high level of accuracy on matching‐to‐sample procedures, were exposed to various schedules of ratio reinforcement for correct matches. Overall accuracy was lower on fixed ratio than on regular reinforcement. There was a high incidence of errors immediately after reinforcement on fixed ratio schedules with accuracy increasing as the ratio progressed. This increase was found to be inversely correlated with the latency of the observing response to the sample. By contrast, accuracy was high throughout the ratio on a variable ratio schedule.
SIZE AND RELIABILITY OF FREQUENCY‐DIFFERENCE THRESHOLDS DETERMINED WITH OPERANT TRACKING PROCEDURE1
Authors: Frazier Larry F. , Elliott Donald N.
Published: March 2006

Auditory frequency discrimination thresholds have been determined by a “tracking procedure” at five frequencies and two intensity levels for a group of four cats. Intra‐animal thresholds were found to be quite stable, and there was good inter‐animal agreement among three of the four cats. Although quite stable, the tracking thresholds were larger than those which had been obtained using an avoidance procedure. However, because of the several differences between the tracking procedure and avoidance conditioning procedure, no conclusions can be drawn concerning the efficacy of the different types of reinforcement in determining the ultimate limit of the animals' discrimination ability.