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At least 721 records · Page 40Linked to original sources
PubMed1997

Precipitation methods for high-density lipoprotein cholesterol measurement compared, and final evaluation under routine operating conditions of a method with a low sample-to-reagent ratio.

We evaluated six precipitation methods for high-density lipoprotein cholesterol (HDL-chol) determination: the heparin/Mn2+ precipitation reagent method (Hep), two variants of the phosphotungstic acid/Mg2+ method (Tung-L and Tung-B), the dextran sulfate 50,000/Mg2+ method (Dex), the PEG 6000 method (PEG), and the PEG 6000/dextran sulfate 15,000 (PEG/Dex) method. The Tung-B and PEG/Dex precipitation methods have a low sample/precipitation reagent volume ratio (< 0.4). The Tung-B, Dex, PEG, and PEG/Dex methods gave similar values, averaging within 0.1 mmol/L of each other, showing that the precipitation selectivity of these methods is comparable. The precipitation efficiency of Tung-B and Peg/Dex, however, was superior. Ultrafiltration of the supernatants was needed only at triglyceride concentrations > 16.4 mmol/L (undiluted sample) or > 28.0 mmol/L (sample diluted twofold); however, ultrafiltration without dilution was the most accurate method. Results of Tung-B under routine conditions (33 technicians) agreed well with those of the PEG method for 406 normo- and hyperlipidemic plasma samples. By comparison with the HDL-chol method from the Centers for Disease Control and Prevention, the Tung-B method showed a total error of 10.6% which fulfills the criteria of the National Cholesterol Education Program for HDL-chol analysis. In conclusion, with motivated personnel, Tung-B is a reliable, cost-effective method for routine HDL-chol analysis.

Chemical Precipitation↗
PubMed1996

Acinetobacter radioresistens metabolizing aromatic compounds. 1. Optimization of the operative conditions for phenol degradation.

A strain of Acinetobacter radioresistens was able to utilize phenol as the only carbon and energy source, after an acclimatization period of 3 days in which increasing phenol concentrations from 50 to 200 mg/l were supplied. At 30 degrees C, the complete phenol utilization in batch degradation tests occurred in 2.5-3 h at pH 7 and 8, but it increased strongly at pH 6 (over 40 h). No microbial growth was detected at 40 degrees C, while at 20 degrees C (pH 7-8) the time necessary for complete phenol degradation was about twofold longer than that at 30 degrees C (pH 7-8) revealing a good capability of the strain as a seed-micro-organism for enhancing phenol degradation. The bacterial growth in acclimatized cultures, evaluated with the viable cell count, always displayed a trend consistent with the use of phenol as a substrate with an eventual lag phase and then an exponential phase, while in the non-acclimatized cultures an initial stage of cellular death was observed.

Acinetobacter↗
PubMedDate not supplied

The cerebellum in maintenance of a motor skill: a hierarchy of brain and spinal cord plasticity underlies H-reflex conditioning.

Operant conditioning of the H-reflex, the electrical analog of the spinal stretch reflex, is a simple model of skill acquisition and involves plasticity in the spinal cord. Previous work showed that the cerebellum is essential for down-conditioning the H-reflex. This study asks whether the cerebellum is also essential for maintaining down-conditioning. After rats decreased the soleus H-reflex over 50 d in response to the down-conditioning protocol, the cerebellar output nuclei dentate and interpositus (DIN) were ablated, and down-conditioning continued for 50-100 more days. In naive (i.e., unconditioned) rats, DIN ablation itself has no significant long-term effect on H-reflex size. During down-conditioning prior to DIN ablation, eight Sprague-Dawley rats decreased the H-reflex to 57% (+/-4 SEM) of control. It rose after ablation, stabilizing within 2 d at about 75% and remaining there until approximately 40 d after ablation. It then rose to approximately 130%, where it remained through the end of study 100 d after ablation. Thus, DIN ablation in down-conditioned rats caused an immediate increase and a delayed increase in the H-reflex. The final result was an H-reflex significantly larger than that prior to down-conditioning. Combined with previous work, these remarkable results suggest that the spinal cord plasticity directly responsible for down-conditioning, which survives only 5-10 d on its own, is maintained by supraspinal plasticity that survives approximately 40 d after loss of cerebellar output. Thus, H-reflex conditioning seems to depend on a hierarchy of brain and spinal cord plasticity to which the cerebellum makes an essential contribution.

Animals↗
PubMed1982

Deliberate hypotension for spinal fusion: prospective randomized study with evoked potential monitoring.

Twenty-four patients requiring spinal fusion with Harrington rod instrumentation were studied prospectively to determine the effects of moderate hypotension on blood loss, operating conditions, operating time and spinal cord function. Hypotension reduced blood loss and improved operating conditions but did not shorten operating time. Five patients had alterations in somatosensory cortical evoked potentials after straightening of the spine that prompted us to reverse hypotension (when present) and haemodilution, and then to do wake-up tests. All wake-up tests were normal and all evoked potential alterations resolved during operation. Hypotension seems unlikely to increase the risk of neurological damage if spinal cord function is monitored. Our findings suggest that patients subjected to spinal fusion need not be awakened during operation for testing of cord function provided somatosensory evoked potentials are monitored and remain stable.

Adolescent↗
PubMed2004

Factors influencing flux decline during nanofiltration of solutions containing dyes and salts.

In this paper, factors influencing the flux decline of nanofiltration membranes for the treatment of dye bath wastewaters were investigated. Experiments were performed with synthetic wastewaters. Synthetic solutions were prepared in different dye and salt concentrations at laboratory conditions. Operating conditions including cross-flow velocity and pH were changed to observe the effects of interactions between NaCl, dyes and the membrane. Cake formation rate of dye molecules on membrane surface with time was investigated by using linearized forms of cake filtration equations. The results suggest that cake layer formation of dye molecules on membrane surface, especially at low salt concentrations was the principal cause of flux decline. Operating conditions had a strong influence on permeate flux. Effects of cross-flow velocity on permeate flux were more pronounced at low NaCl concentrations. Furthermore, the lowest permeate flux values were obtained at the alkaline conditions due to increased dye hydrophobicity at high pH values.

Coloring Agents↗
PubMed1990

The effects of ibotenic acid lesions of the nucleus basalis and cholinergic-rich neural transplants on win-stay/lose-shift and win-shift/lose-stay performance in the rat.

Rats were trained to criterion performance in 2-lever operant conditional memory tasks that required them to follow either a Win-stay/Lose-shift, or else a Win-shift/Lose-stay response rule. Substantial impairments in performance of both pretrained conditional tasks were seen following ibotenic acid lesions of the nucleus basalis, but not of the globus pallidus. The deficit in both tasks was apparent at all inter-response retention intervals, indicating that nucleus basalis lesions produced a general impairment in the performance of the complex conditional operant tasks, and not a specific deficit in short-term memory. The nucleus basalis lesion rats were then divided into groups matched for equivalent performance. One group was given cell suspension grafts into neocortex of E15 cholinergic-rich forebrain tissue; a second group was given similar grafts of E17 hippocampal tissue; and a third group was given sham transplants. Testing beginning 3 months post-transplant showed that there was no evidence of recovery of performance on these tasks in the cholinergic-rich transplanted groups compared to the controls. However, the rats with cholinergic-rich transplants subsequently showed a significant improvement in retention of a step-through passive avoidance task. The results indicate that either cholinergic deafferentation of the neocortex is not critical for the observed deficits in the operant conditional tasks, or recovery of function following cholinergic-rich transplants is task-specific, in that more complex cognitive tasks may require different levels of graft-host neural integration.

Animals↗
PubMed1976

Neuronal circuits involved in learning: the use of modifiable synapses in the simulation of behavior.

Our present knowledge of brain structure and function requires that any model of neuronal circuitry designed to account for learning must satisfy three conditions. It must (1) meet economy restrictions on the number of cells in the brain, (2) use the same set of cells to account for a number of different behaviors, and (3) not require a detailed embryological specification of its connections. Previously published models have failed to meet one or more of these conditions. In this paper, a model is presented which does satisfy them, and in doing so accounts in detail for classical conditioning, operant conditioning, and other learning tasks. The model employs the types of synapses proposed by Burke and Hebb in simple modular circuits as a means of providing independent storage of information at each modifiable synapse.

Animals↗
PubMed2005

Organization of frontohippocampal neuronal networks in cats in different types of directed behavior.

Food-related operant conditioned reflexes to light were developed in four cats on the basis of the "active choice" of reinforcement quality: short-latency pedal presses were reinforced with a mixture of meat and bread, while long-latency presses were reinforced with meat. Animals showed differences in their behavioral strategies: two preferred long-latency pedal presses (animals with "self-control"), while the other two preferred short-latency pedal presses ("impulsive" animals). At the second stage of the study, animals of both groups were retrained to a short-delay (1 sec) conditioned operant food-related reflex in response to light with meat reinforcement. Chronically implanted Nichrome semimicroelectrodes were used to record multicellular activity in the frontal cortex and hippocampus (field CA3). The interaction of neighboring neurons within the frontal cortex and hippocampus (local neural networks) and neurons of the frontal cortex and hippocampus (distributed frontohippocampal and hippocampofrontal neural networks) were assessed by statistical cross-correlation analysis of spike trains with an analysis epoch of 100 msec. The frontal and frontohippocampal neural networks had different modes of functional organization in the simplified task for the animals of the two groups. However, intergroup differences in local networks of the hippocampus persisted in conditions of the simplified task lacking the requirement for the animals to select the quality of the reinforcement, indicating the likely genetic determinacy of these networks.

Action Potentials↗
PubMed2006

Monkey sound localization: head-restrained versus head-unrestrained orienting.

The sound localization abilities of three rhesus monkeys were tested under head-restrained and head-unrestrained conditions. Operant conditioning and the magnetic search coil technique were used to measure eye and head movements to sound sources. Whereas the results support previous findings that monkeys localize sounds very poorly with their heads restrained, the data also reveal for the first time that monkeys localize sounds much more accurately and with less variability when their heads are allowed to move. Control experiments using acoustic stimuli known to produce spatial auditory illusions such as summing localization confirmed that the monkeys based their orienting on localizing the sound sources and not on remembering spatial locations that resulted in rewards. Overall, the importance of using ecologically valid behaviors for studies of sensory processes is confirmed, and the potential of the rhesus monkey, the model closest to human, for studies of spatial auditory function, is established.

Acoustic Stimulation↗
PubMed2002

Correlation of pre-operative nutritional condition with post-operative complications in surgical treatment for oesophageal carcinoma.

AIMS: The relationship between the pre-operative nutritional condition and the outcome of the surgical treatment in patients with oesophageal carcinoma has been discussed diversely. The aim of the current study was to demonstrate the relationship between pre-operative nutritional condition and post-operative complications and prognosis following surgical treatment for oesophageal carcinoma. METHODS: Two hundred and fifty-eight patients with oesophageal carcinoma treated with oesophageal resection and reconstruction were selected. The correlation of pre-operative values of prognostic nutritional index (PNI) with the incidence of post-operative complications and prognosis of the patients was investigated. RESULTS: The mean pre-operative value of PNI in patients with post-operative complications (41.8+/-5.4) was significantly lower than that in patients without post-operative complications (46.5+/-5.3; P<0.0001). The survival in patients with higher PNI value was significantly more favourable than that in patients with lower PNI value (P=0.0001). CONCLUSIONS: Pre-operative assessment of the nutritional condition could provide predictive information for post-operative complications in patients with oesophageal carcinoma.

Aged↗
PubMedDate not supplied

Psychological principles of burn wound pain in children. I: theoretical framework.

Burn injuries and the care of burn injuries are punishing experiences for hospitalized children. Pain, novelty, and altered reinforcement schedules elicit instinctive escape and avoidance behaviors that complicate wound care. An understanding of the psychological principles that underlie these complex, complicating behaviors paves the way for effective cognitive and behavioral interventions. In this first article of a two-part series, we use the principles of classical conditioning, operant conditioning, and control coping to describe the developmentally normal emergence of avoidance behaviors that are incompatible with burn wound care. Then, using brief case examples, we outline how classical conditioning transforms neutral stimuli into anxiety-producing, fearful stimuli, how operant behaviors are intentionally or unintentionally reinforced, and how the umbrella of reduced control in the novel hospital environment makes coping difficult for children. We conclude by discussing obstacles to effective application of cognitive and behavioral strategies for the enhancement of control and of compliance with wound care.

Adaptation, Psychological↗
PubMed1994

The conditioning of human sexual arousal.

Although most theories of human sexual behavior claim that much normal sexual behavior is learned, and theories of the etiology and modification of paraphilic and dysfunctional sexual behavior also claim that abnormal sexual behavior is learned and can be counterconditioned, there is no systematic review examining the relationship between conditioning and human sexual behavior. We review research addressing whether habituation, sensitization, classical conditioning, and operant conditioning processes are involved in human sexual behavior. We conclude that, due to the methodological problems of extant studies, the basis for asserting the existence of relationships between habituation, sensitization, classical conditioning, operant conditioning, and sexual behavior is tenuous.

Arousal↗
PubMed1984

The psychosomatic component in prosthodontics.

A classification of psychosomatic symptoms proposed by Whitehead et al. has been discussed. It has been suggested that TMJ dysfunction, the gag reflex, and denture intolerance are representative of the etiologic categories of psychosomatic symptoms, which most often arise from environmental stressors, classic conditioning, or operant conditioning. Operant conditioning is broadly based and the hysteric response may be superimposed on classically conditioned responses such as the gag reflex or the stress-induced muscle tension of TMJ dysfunction.

Conditioning, Classical↗
PubMed2001

Spray scrubbing of the nitrogen oxides into NaClO2 solution under acidic conditions.

The operating conditions of this study were closed to the typical operating conditions of flue gas desulfurization system in the coal-fired power plant. The objective of this study was to investigate the absorption performance of lean NO in an aqueous solution of acidic sodium chlorite using a bench-scale spraying column. The NO conversion and NOx removal efficiency were increasing with the increasing NO concentration, retention time, sodium chlorite concentration, operating temperature, and decreasing initial pH of solution. As the sodium chlorite concentration were higher than 0.4 M, the NO conversion and NOx removal efficiency were 100% and 80%, respectively. The NO conversion and NOx removal efficiency under initial pH 4-7 were higher than that of initial pH > 7. It meant that this process might be suitable to combining with traditional wet flue gas desulfurization system. As the NO2/NOx ratio in the effluent gas was closed to 0.5, it might be suitable to be absorbed in the second scrubbing column operated under alkaline condition.

Adsorption↗
PubMed1989

Behavior therapy: a clinical update.

Through refinements from research and judicious combination with other therapies, behavior therapy has become increasingly relevant in the treatment of psychiatric disorders. After outlining the four models that serve as a framework for behavior therapy (classical conditioning, operant conditioning, social learning theory, and cognitive behavior modification), the authors provide an update for clinicians on developments in the behavioral treatment of anxiety disorders, sexual disorders, depression, and schizophrenia. Most advances have been made in the treatment of anxiety disorders, including definition of variables for successful use of exposure to phobic stimuli in the treatment of phobic disorders and the use of flooding for post-traumatic stress disorder. By becoming better acquainted with cognitive and behavioral therapies, clinicians may be able to offer their patients more effective treatment options.

Anxiety Disorders↗
PubMed1976

[Tricuspid prosthetic replacements. Indications and results].

Out of 350 cases of tricuspid regurgitation operated between 1968 and 1975, a serie of 53 prosthetic replacements (3 of them isolated) was analysed, with specification of operative indications, pre-operative condition, operative findings, procedure used and results. Operative death rate was high (28 per cent) and remote results (6 months to 7 years) were not all satisfactory. This is because functional "tricuspid regurgitation", secondary to advanced mitral lesions, expresses in fact considerable myocardial weakening with severe polyvisceral implications. This picture, where tricuspid patency is in fact contingent, is not always improved by mitral correction and reestablishment of a satisfactory tricuspid function, whatever the procedure used. Thus in very advanced mitral lesions, tricuspid repair should be done only if regurgitation is real and severe. Tricuspid prosthetic replacement should be reserved to valvular destruction; semi-circular annulo-plasty, which is efficient and not very traumatising, is applicable to all the other cases. The best treatment of this syndrome is preventive: as aortic lestions, mitral lesions should be operated early to permit a low risk operation and complete functional recuperation.

Adolescent↗