Managing Increased Cognitive Load in a Guided Search

In the Sternberg item recognition task and its variants, an individual’s mean reaction time increases with the number of items to be retained in the memory set. An increase in reaction time has also been seen when a secondary task was added. The usual interpretation for this increased reaction time is that adding cognitive load makes tasks more difficult. In a series of three experiments, we manipulated cognitive load through increases in the memory set or through a second task. In each experiment, high cognitive load was associated with higher mean response times but a reduced slope, based on the target position in a series of probes. Thus, in a Sternberg task with multiple word targets and multiple word probes, participants searched more efficiently per probe under high load than under low load. This pattern was replicated with the addition of a working memory task requiring participants to calculate a cumulative price based on the price per target word item. By considering both initial response times and reaction time slopes in large memory sets, this study provides a challenge to the traditional interpretation of cognitive load effects on search performance.

Interference, aging, and visuospatial working memory: the role of similarity

OBJECTIVE

Older adults' performance on working memory (WM) span tasks is known to be negatively affected by the buildup of proactive interference (PI) across trials. PI has been reduced in verbal tasks and performance increased by presenting distinctive items across trials. In addition, reversing the order of trial presentation (i.e., starting with the longest sets first) has been shown to reduce PI in both verbal and visuospatial WM span tasks. We considered whether making each trial visually distinct would improve older adults' visuospatial WM performance, and whether combining the 2 PI-reducing manipulations, distinct trials and reversed order of presentation, would prove additive, thus providing even greater benefit.

METHOD

Forty-eight healthy older adults (age range = 60-77 years) completed 1 of 3 versions of a computerized Corsi block test. For 2 versions of the task, trials were either all visually similar or all visually distinct, and were presented in the standard ascending format (shortest set size first). In the third version, visually distinct trials were presented in a reverse order of presentation (longest set size first).

RESULTS

Span scores were reliably higher in the ascending version for visually distinct compared with visually similar trials, F(1, 30) = 4.96, p = .03, η² = .14. However, combining distinct trials and a descending format proved no more beneficial than administering the descending format alone.

CONCLUSIONS

Our findings suggest that a more accurate measurement of the visuospatial WM span scores of older adults (and possibly neuropsychological patients) might be obtained by reducing within-test interference.

Short article: Age and synchrony effects in visuospatial working memory

Younger and older adults were administered a computerized version of the Corsi Block visuospatial working memory (VSWM) span task at either their peak or off-peak time of day and in either a high-interference (ascending order of administration, starting with short lists first) or low-interference (descending order, starting with longest lists first) format. Young adults’ span scores were highest in the ascending format. By contrast, older adults performed better in the low-interference format, replicating findings with verbal memory span studies. Although both age groups benefited from being tested at their peak time, the advantage was far greater for older adults, but only in the low-interference format; their scores on the high-interference format were not helped by peak-time testing. These findings are consistent with the suggestion that young adults’ performance on span tasks is influenced by practice and strategies, but the performance of older adults is heavily influenced by interference—which is best controlled at peak times of day. Our findings suggest that both time of testing and interference play critical roles in determining age differences in VSWM span, and both a reduction in interference and peak-time testing may be necessary to optimize older adults’ performance and to maximize the reduction in age differences.

Age differences in visuospatial working memory

In two visuospatial working memory (VSWM) span experiments, older and young participants were tested under conditions of either high or low interference, using two different displays: computerized versions of a 3 x 3 matrix or the standard (randomly arrayed) Corsi block task (P. M. Corsi, 1972). Older adults' VSWM estimates were increased in the low-interference, compared with the high-interference, condition, replicating findings with verbal memory span studies. Young adults showed the opposite pattern, and together the findings suggest that typical VSWM span tasks include opposing components (interference and practice) that differentially affect young and older adults.

The TNF-alpha-238G > a single-nucleotide polymorphism protects against memory decline in older adults with type 2 diabetes

Inflammatory markers predict memory dysfunction in elderly patients, but their contribution to memory deficits in adults with Type 2 diabetes mellitus (T2DM) is less well understood. The present study determined whether specific single-nucleotide polymorphisms in the promoter region of tumor necrosis factor-alpha (TNF-alpha) predict verbal memory in older patients with T2DM. Immediate and delayed verbal memory were assessed using word list and paragraph recall tests in a cohort of subjects with T2DM during 2 sessions, separated by 48 weeks. The presence of the TNF-alpha-238A allele, which has been shown to decrease gene expression, consistently predicted better baseline performance and protected against memory decline over a period of 48 weeks. Therefore, inflammatory mediators may be important modulators of memory function in individuals with T2DM.

Effects of organ motion on IMRT treatments with segments of few monitor units

Interplay between organ (breathing) motion and leaf motion has been shown in the literature to have a small dosimetric impact for clinical conditions (over a 30 fraction treatment). However, previous studies did not consider the case of treatment beams made up of many few-monitor-unit (MU) segments, where the segment delivery time (1-2 s) is of the order of the breathing period (3-5 s). In this study we assess if breathing compromises the radiotherapy treatment with IMRT segments of low number of MUs. We assess (i) how delivered dose varies, from patient to patient, with the number of MU per segment, (ii) if this delivered dose is identical to the average dose calculated without motion over the path of the motion, and (iii) the impact of the daily variation of the delivered dose as a function of MU per segment. The organ motion was studied along two orthogonal directions, representing the left-right and cranial-caudal directions of organ movement for a patient setup in the supine position. Breathing motion was modeled as sin(x), sin4(x), and sin6(x), based on functions used in the literature to represent organ motion. Measurements were performed with an ionization chamber and films. For a systematic study of motion effects, a MATLAB simulation was written to model organ movement and dose delivery. In the case of a single beam made up of one single segment, the dose delivered to point in a moving target over 30 fractions can vary up to 20% and 10% for segments of 10 MU and 20 MU, respectively. This dose error occurs because the tumor spends most of the time near the edges of the radiation beam. In the case of a single beam made of multiple segments with low MU, we observed 2.4%, 3.3%, and 4.3% differences, respectively, for sin(x), sin4(x), and sin6(x) motion, between delivered dose and motion-averaged dose for points in the penumbra region of the beam and over 30 fractions. In approximately 5-10% of the cases, differences between the motion-averaged dose and the delivered 30-fraction dose could reach 6%, 8% and 10-12%, respectively for sin(x), sin4(x), and sin6(x) motion. To analyze a clinical IMRT beam, two patient plans were randomly selected. For one of the patients, the beams showed a likelihood of up to 25.6% that the delivered dose would deviate from the motion-averaged dose by more than 1%. For the second patient, there was a likelihood of up to 62.8% of delivering a dose that differs by more than 1% from the motion-averaged dose and a likelihood of up to approximately 30% for a 2% dose error. For the entire five-beam IMRT plan, statistical averaging over the beams reduces the overall dose error between the delivered dose and the motion-averaged dose. For both patients there was a likelihood of up to 7.0% and 33.9% that the dose error was greater than 1%, respectively. For one of the patients, there was a 12.6% likelihood of a 2% dose error. Daily intrafraction variation of the delivered dose of more than 10% is non-negligible and can potentially lead to biological effects. We observed [for sin(x), sin4(x), and sin6(x)] that below 10-15 MU leads to large daily variations of the order of 15-35%. Therefore, for small MU segments, non-negligible biological effects can be incurred. We conclude that for most clinical cases the effects may be small because of the use of many beams, it is desirable to avoid low-MU segments when treating moving targets. In addition, dose averaging may not work well for hypo-fractionation, where fewer fractions are used. For hypo-fractionation, PDF modeling of the tumor motion in IMRT optimization may not be adequate.

The effect of old age on the learning of supraspan sequences

Two experiments examined age-related differences in sequence learning using computerized versions of the D. O. Hebb (1961) paradigm. In this learning task, the participant executes immediate serial recall of 24 supraspan sequences. Without the participants' knowledge, 1 sequence is presented several times. Repetition leads to improved recall of this repeated sequence relative to random sequences. Results showed a dissociation in age-related learning deficits depending on the nature of the to-be-remembered material. The effect of repetition is similar for younger and older adults with familiar and unfamiliar verbal material (words and pseudowords) but is significantly reduced in older adults when learning is assessed with a visuospatial version of Hebb's supraspan learning task (P. M. Corsi, 1972).

The effect of old age on supra-span learning of visuo-spatial sequences under incidental and intentional encoding instructions

Recent findings [Turcotte, Gagnon, & Poirier, 2005. The effect of old age on the learning of supra-span sequences. Psychology and Aging, 20, 251-260.] indicate that incidental learning of visuo-spatial supra-span sequences through immediate serial recall declines with old age (Hebb's paradigm). In this study, we examined whether strategies induced by awareness of the repeated sequence might explain age differences. Young (18-35 years old) and older (65-80 years old) participants underwent either incidental or intentional learning instructions. Results indicated that older adults demonstrated reduced learning of the repeated sequence under both incidental and intentional instructions. In comparison, young adults showed superior learning of the repeated sequence in both conditions but intentional instructions triggered faster and greater learning in this age group. The results strongly indicated that knowledge of the repeated sequence enhanced learning only in the group of young adults. Older adults were unable to translate the knowledge of the repetition into elaborate strategies that would increase recall of the repeated sequence. Other findings suggest that incidental learning in young adults was mediated by both non-conscious and conscious recollection processes.

Word length effects are not due to proactive interference

In immediate serial recall short words are better recalled than long words. The word length effect has become pivotal in the development of short-term memory models. The current research tests one explanation of the word length effect; that it is related to proactive interference (PI). We report two experiments in which the relationship is directly tested. In the first experiment we show that word length effects can be observed over the first few trials in an experiment and that the effect shows itself primarily in the number of omissions made. In the second experiment we simultaneously test for PI and word length effects. Strong word length effects were present but there was little evidence for PI influencing either overall levels of recall or the word length effect. In short, no empirical support was found for PI as an explanation of the word length effect.

A population-based, randomized clinical trial on back pain management

STUDY DESIGN

Population-based randomized clinical trial.

OBJECTIVES

To develop and test a model of management of subacute back pain, to prevent prolonged disability.

SUMMARY OF BACKGROUND DATA

The present management of back pain seems inadequate, and development of innovative models has been urged.

METHODS

A model for the treatment of subacute work-related back pain has been developed and evaluated in a population-based randomized clinical trial. Workers (n = 130) from eligible workplaces in the Sherbrooke area (N = 31), who had been absent from work for more than 4 weeks for back pain, were randomized, based on their workplace, in one of four treatment groups: usual care, clinical intervention, occupational intervention, and full intervention (a combination of the last two). The duration of absence from regular work and from any work was evaluated using survival analysis. Functional status and pain were compared at study entry and after 1 year of follow-up.

RESULTS

The full intervention group returned to regular work 2.41 times faster than the usual care intervention group (95% confidence interval 1.19-4.89; P < 0.01). The specific effect of the occupational intervention accounted for the most important part of this result, with a rate ratio of return to regular work of 1.91 (95% confidence interval = 1.18-3.10; P < 0.01). Pain and disability scales demonstrated either a statistically significant reduction or a trend toward reduction in the three intervention groups, compared with the trend in the usual care intervention group.

CONCLUSIONS

Close association of occupational intervention with clinical care is of primary importance in impeding progression toward chronicity of low back pain.

A role for ultraviolet A in solar mutagenesis

It is well established that exposure to solar UVB (290-320 nm) gives rise to mutations in oncogenes and tumor suppressor genes that initiate the molecular cascade toward skin cancer. Although UVA (320-400 nm) has also been implicated in multistage photocarcinogenesis, its potential contribution to sunlight mutagenesis remains poorly characterized. We have determined the DNA sequence specificity of mutations induced by UVB (lambda > 290 nm), and by UVA (lambda > 350 nm), at the adenine phosphoribosyltransferase locus of Chinese hamster ovary cells. This has been compared to results previously obtained for stimulated sunlight (lambda > or = 310 nm) and 254-nm UVC in the same gene. We demonstrate that T-->G transversions, a generally rare class of mutation, are induced at high frequency (up to 50%) in UVA-exposed cells. Furthermore, this event comprises a substantial proportion of the simulated sunlight-induced mutant collection (25%) but is significantly less frequent (P < 0.05) in cells irradiated with either UVB (9%) or UVC (5%). We conclude that the mutagenic specificity of broad-spectrum solar light in rodent cells is not determined entirely by the UVB component and that UVA also plays an important role.

Management of occupational back pain: the Sherbrooke model. Results of a pilot and feasibility study

OBJECTIVES

The aim was to combat occurrence of chronic occupational back pain.

METHODS

A multidisciplinary model to manage back pain that includes both clinical and ergonomic approaches has been developed. Early detection, early clinical and ergonomic evaluations, and early active treatment make up the cornerstone of management. Detection of cases starts after four weeks of absence from work. An ergonomic intervention is implemented at six weeks. A medical specialist is involved at eight weeks. If return to work is not possible after 12 weeks, a functional recovery therapy followed by a therapeutic return to work is implemented. A multidisciplinary team decides if return to original or modified work is possible or if vocational rehabilitation is necessary. This model has been implemented by the investigators in the Sherbrooke (Quebec, Canada) area, and is presently being evaluated through a randomised trial in 31 industrial settlements (about 20,000 workers). A cluster randomisation of industries and workers will allow separate testing of ergonomic and clinical interventions.

RESULTS

One year after implementation, 31 of 35 of the eligible industrial sites participated in the study and 79 of 88 of the eligible workers affected by recent back pain had agreed to participate. Ergonomic and clinical interventions have been implemented as planned. Only three workers dropped out. Hence this global clinical and ergonomic management programme has been shown to be feasible in a general population.

CONCLUSION

A global management programme of back pain joining ergonomic and clinical intervention with a multidisciplinary approach has not been tested yet. Linking these two strategies in a same multidisciplinary team represents a systemic approach to this multifactorial ailment. During the first year of this trial we did not find any conflict between these two interventions from the employer's or worker's point of view.

Immunocytochemical localization of estrogen-induced progestin receptors in guinea pig brain

By using a combination of monoclonal antibodies to progestin receptors and a double-bridge peroxidase-antiperoxidase technique, a sensitive immunocytochemical method was developed for visualizing progestin receptor immunoreactivity (PR-IR) in brains of estrogen-primed guinea pigs. PR-IR neurons were observed throughout the hypothalamus and preoptic area. They were seen in largest numbers in the arcuate nucleus, periventricular preoptic regions, medial preoptic nucleus, medial preoptic area and in the ventrolateral area of the hypothalamus. Lower numbers of PR-IR positive cells were detected in the bed nucleus of stria terminalis, paraventricular nucleus and lateral hypothalamus with scattered cells seen throughout the hypothalamus and preoptic area. The PR-IR was mostly intranuclear with lighter staining in neuronal processes. Electron microscopy confirmed the predominantly intranuclear localization and further demonstrated that the reaction product was dispersed throughout the nucleus, but not associated with the nucleolus. Few PR-IR cells were observed in the absence of estradiol priming, and the reaction product was much lighter than in the presence of estradiol. Progesterone injection was without apparent effect on intensity of the PR-IR.

Further evidence of noradrenergic regulation of rat hypothalamic estrogen receptor concentration: possible non-functional increase and functional decrease

The regulation of estrogen receptors by the alpha 2-noradrenergic system was studied. A single injection of the alpha 2-noradrenergic antagonist, yohimbine, caused a biphasic effect on the concentration of cytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland. A short-latency increase was seen at 1.5-3 h, followed by a longer-lasting decrease at 8-16 h. Scatchard analysis revealed that the apparent, short-latency increase is in the concentration of binding sites, not in the affinity of the receptor for [3H]estradiol. The increase in the concentration of cytosol estrogen receptors is not blocked by pretreatment with the alpha 2-noradrenergic agonist, clonidine. In addition, no increase is detected in the concentration of cell nuclear estrogen receptors accumulating in response to a saturating dose of estradiol. Therefore, the apparent increase in the concentration of cytosol estrogen receptors may not represent a functional increase in receptors. The decrease in the concentration of estrogen receptors, which occurs 8-16 h after yohimbine treatment, is also seen after injection of the alpha 2-adrenergic antagonist, idazoxan, and is not due to a change in the in vitro rate of association of the receptors with [3H]estradiol. Furthermore, the decrease seems to be a functional decrease in the concentration of receptors capable of cell nuclear accumulation in response to estradiol injection, as indicated by the results of experiments in which the concentration of cell nuclear estrogen receptors was assayed after estradiol injection. These experiments provide further support for the hypothesis that the alpha-noradrenergic system, and perhaps specifically the alpha 2-subtype, is involved in decreasing the concentration of estrogen receptors in parts of the brain and pituitary gland. This interaction provides a mechanism by which the environment could regulate the sensitivity of certain neurons to estradiol. However, the finding that the initial increase in the concentration of cytosol estrogen receptors after yohimbine treatment is not followed by the predicted increase in cell nuclear estrogen receptors after estradiol injection raises questions about the physiological relevance of the apparent increase under some conditions.

Small apomorphine-induced increase in the concentration of cytosol estrogen receptors in female rat hypothalamus and pituitary

A series of experiments was performed to investigate the previously-reported modulation of estradiol binding in female rat brain and pituitary gland by drugs that influence the dopaminergic system. Injection of the dopamine agonist, apomorphine, at minimum doses of 1-2 mg/kg body weight caused slight increases (in most cases, less than 10%) in the concentration of cytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland without influencing the concentration in the preoptic area. However, after subsequent injection of a saturating dose of estradiol, the level of nuclear estrogen receptors accumulating did not differ significantly between apomorphine-treated animals and vehicle-injected controls. These results extend, in part, previous reports that have shown an apomorphine-induced increase in the concentration of [3H]estradiol in brain and pituitary cell nuclei after an injection of [3H]estradiol. However, we failed to observe differences in the concentration of cytosol estrogen receptors as large as would be expected by previous work, and we failed to observe differences in the concentration of nuclear estrogen receptors after estradiol injection.

Surgical reconstruction of the proximal vertebral artery

The authors have reviewed their experience in the management of 55 patients admitted to Henry Ford Hospital with symptoms of vertebrobasilar insufficiency and associated proximal vertebral artery stenosis or occlusion. In 48 patients, the symptoms occurred as multiple repeated events, five of which resulted in permanent deficits. The remaining seven patients had single events, four of which caused permanent deficit. These patients had been treated unsuccessfully with antiplatelet agents (37 cases) and with anticoagulant drugs (15 cases) before surgery. Most patients had multiple angiographic abnormalities, including bilateral vertebral stenosis in 19 cases, unilateral vertebral stenosis and contralateral occlusion in 18, unilateral vertebral hypoplasia and contralateral stenosis in 10, subclavian artery stenosis with steal in seven, and bilateral vertebral artery occlusion in one case. Posterior communicating arteries could not be demonstrated angiographically in 18 patients. Thirty-four patients had associated stenotic or occlusive lesions of the internal carotid artery. Forty-eight underwent a vertebral-to-carotid artery transposition. Of these, 18 had an associated carotid endarterectomy and seven had a vertebral artery endarterectomy immediately before the transposition. Two patients had saphenous vein grafts, one from the subclavian and one from the common carotid artery to the vertebral artery. Other surgical procedures included vertebral artery ligation in one case, transposition of the vertebral artery to the thyrocervical trunk in two cases and to the subclavian artery in one case, and endarterectomy of the origin of the vertebral artery in one case. All but two patients had complete resolution of their symptoms: one had persistent dizziness and the other had syncopal episodes. Complications included transient Horner's syndrome (30 cases) which became permanent in four cases, vocal cord paralysis (three cases), elevated hemidiaphragm without respiratory difficulty (two cases), and superficial would infection (one case). There were no deaths. Although the presentation of patients with vertebrobasilar insufficiency is generally characteristic, we believe that a specific diagnosis can be established only by angiographic means. Anticoagulants have been used to alleviate symptoms in some cases but are ineffective in solving the primary hemodynamic problem. Surgical reconstruction of the affected area deserves further evaluation in the management of these patients.

Analysis of Gamma Radionuclides in Selected Farm Produce of Oka, Quebec - A Niobium Mining Community

An investigation of the gamma emitting radionuclides present in selected farm produce of Oka, Quebec, was conducted. In the three categories of foodstuffs, such as cheese, apple and maple sugar, obtained from the immediate vicinity of niobium mill tailings piles, distinguishable radioactivity from natural sources and worldwide fallout was evident. Except for lead-214 and radium-226, the tailings spectrum showed a typical pattern of natural background value. With the exception of lead-212, uranium-235, thallium-208 and actinium- 228, all radionuclides in farm produce were near or below levels of detection. There was no significant difference in the radiation level of food samples grown in control areas.

Differing effects of ursodeoxycholic or chenodeoxycholic acid on biliary cholesterol saturation and bile acid metabolism in man. A dose-response study

A dose-response study comparing ursodeoxycholic and chenodeoxycholic acid was carried out in six men with asymptomatic radiolucent gallstones present in well-visualizing gallbladders. The study tested the effects of a low (averaging 6 mg/kg/day) or medium dose (averaging 11 mg/kg/day) of each bile acid on the cholesterol saturation of bile as well as on bile acid metabolism, as inferred from biliary and fecal bile acid composition. Ursodeoxycholic acid, at low or medium doses, induced bile desaturation in most patients, whereas chenodeoxycholic acid did not. Despite the greater desaturation efficacy of ursodeoxycholic acid, biliary bile acids became less enriched with the administered bile acid during ursodeoxycholic acid treatment than during chenodeoxycholic acid treatment. Both bile acids were nearly completely 7-dehydroxylated to lithocholic acid by colonic bacteria, but biliary lithocholic increased only slightly (and similarly) with each bile acid. Fecal bile acid composition suggested that administered ursodeoxycholic acid suppressed endogenous bile acid synthesis much less than chenodeoxycholic acid. The results indicate that ursodeoxycholic acid and chenodeoxycholic acid have similar but not identical effects on bile acid metabolism, but that for a given dose, ursodeoxycholic acid is a more potent desaturating agent than chenodeoxycholic acid. The results suggest that cholesterol gallstone dissolution with ursodeoxycholic acid should occur with a dose of 8-10 mg/kg in most nonobese patients.

Peritransplant fluid collections. Ultrasound evaluation and clinical significance

Gray-scale ultrasonography was used to detect, localize, and guide percutaneous aspirations of peritransplant fluid collections. Fifty-one (51%) transplant recipients had abnormal fluid collections; 18 of these patients required surgery. Analysis of the 23 proved fluid collections (10 lymphocytes, 7 abscesses, 4 urinomas, and 2 hematomas) revealed certain sonographic and temporal patterns. Lymphoceles were the most common cause of an obstructed transplant and were usually septated. Most of the undiagnosed fluid collections were small and crescentic and were located in the abdominal wall. They usually did not enlarge or resolve on serial ultrasound examinations. A role for ultrasound in the management of peritransplant fluid collections is proposed.

Extended treatment with antithymocyte globulin (ATGAM) in renal allograft recipients

Twenty renal allograft recipients were treated with antithymocyte globulin (ATGAM; ATG) for up to 16 weeks in addition to azathioprine and prednisone, while 20 controls received no ATG. The ATG group showed a lower incidence of first rejection episodes during the first month after transplantation, and also a better functional graft survival rate up to 2 years after transplantation. The results in this early ATG trial were better than those in subsequent trials which used 14-day treatment regimens. Longer treatment deserves another look.

Radioimmunoassay of unsulfated lithocholates

A simple, rapid, precise radioimmunoassay for total unsulfate species of lithocholate (lithocholyglycine, lithocholyltaurine, and lithocholate) in serum is described. Antiserum was raised in rabbits by injection of lithocholylglycine coupled to bovine serum albumin (prepared by a carbodiimide method) and emulsified in complete Freund's adjuvant; antisera capable of measuring 40-120 pmol at 1:400 dilution were obtained. The tracer was [11, 12-3[H]lithocholyglycine. The radioimmunoassay featured a 2-hr binding step at 42 decrease C and a 1-hr separation step using polyethylene glycol. The antibody had the following relative specificities: lithocholyglycine and lithocholytaurine, 1; lithocholate, 1.5; chenodeoxycholyglycine, 20; and deoxycholylglycine, 55. There was no binding of various other free or conjugated sulfated and unsulfated bile acids. The mean fasting-state level in 50 healthy subjects was 0.3 mu mol/l (0.14 microgram/ml), but 11 of the 50 subjects had level too low to measure by this technique.

Radioimmunoassay of sulfated lithocholates

A sensitive, rapid radioimmunoassay for sulfated species of lithocholic acid (sulfolithocholyglycine, sulfolithocholyltaurine, and sulfolithocholic acid) was developed and used to measure the total concentration of sulfated lithocholates in serum from healthy human subjects. Sulfolithocholylglycine was conjugated to bovine serum albumin by a carbodiimide procedure, and the reaction product, emulsified in Freund's adjuvant, was injected into rabbits. The antiserum obtained was capable to binding 40% of [3H]sulfolithocholylglycine at 1:1000 dilution. The assay featured a 2-hr binding step at 42 degrees C followed by precipitation of bound tracer with polyethylene glycol at 4 degrees C. The assay can be used with 0.1 ml of serum and was reproducible. The antibody had little affinity for the 3-sulfate of cholic or chenodeoxycholic acid, a number of steroid sulfates, or unsulfated bile acids. In 50 healthy subjects, mean (+/-SE) fasting-state serum levels of immunoreactive sulfated lithocholyl conjugates (+sulfated lithocholate) was 1.6 +/- 0.1 micrometer; based on results with a separate radioimmunoassay for unsulfated lithocholyl conjugates, most of the lithocholate in serum in healthy man is present in sulfated form.

Radioimmunoassay of bile acids: development, validation, and preliminary application of an assay for conjugates of chenodeoxycholic acid

A rapid, sensitive, precise radioimmunoassay for conjugates of chenodeoxycholic (chenic) acid has been developed and validated. Immunogen was prepared with chenylglycine couples to bovine serum albumin, emulsified in Freund's complete adjuvant, and injected intracutaneously in rabbits. Antibodies of moderate titer (used at 1:7500 final dilution) were obtained. Tracer of high specific activity was prepared by reductive tritiation of delta11-chenylglycine. The binding step required 1 hr at room temperature; separation of bound tracer was achieved by addition of ammonium sulfate. The limit of sensitivity of the assay was about 20 nmoles per liter, and the lower limit of the working range was 0.4 mumole per liter. The assay was validated by measuring levels in samples of fasting state serum to which known amounts of chenylglycine had been added; the assay was also validated by means of gas-liquid chromatography on sera from jaundiced patients. The median fasting state serum level in 56 Caucasians and blacks was 0.9 mumole per liter (upper limit of normal (95% confidence) being 2.3), which is in the same range as that reported by others using gas-liquid chromatography. A 5- to 10-fold increase in levels of chenyl conjugates was observed 1 hr after the ingestion of a liquid meal in healthy persons.

Factors affecting the frequency infection in renal transplant recipients

A retrospective review of 149 patients receiving 162 renal transplants showed that 83% of these patients developed one or more infections during a follow-up period averaging one year. In 32 (73%) of 44 deaths, infection was an important contributing cause. In only four (9%) of the deaths were the patients free of infection at the time of death. The Klebsiella-Enterobacter group was the most common agent causing pneumonitis and sepsis. Cryptococcus neoformans caused seven of 11 cases of meningitis. Pseudomonas was the most frequent agent associated with infections documented during postmortem examinations. In a short-term controlled study comparing daily and alternate daily therapy with prednisone, the alternate daily group had significantly (P less than .05) more infections per patient, especially in patients who had no evidence of rejection (P less than .025).

Release phenomena and iterative activities in psychiatric geriatric patients

This survey was undertaken to assess the frequency of some of the so-called release phenomena and iterative activities in an aged psychiatric population. Three groups of geriatric psychiatric patients with diagnoses of (I) organic brain syndrome, including senile dementia (56), (II) functional psychoses, predominantly schizophrenia (51) and (III) chronic schizophrenia never treated by neuroleptics or other biologic agents (16), were compared with (IV) a control group of 32 elderly people in good physical and mental health.In general, for the manifestations studied, the geriatric psychiatric patients suffering from an organic brain syndrome and treated with neuroleptics differed notably from the control group. This latter group, although older, had few neurological signs of senescence and the spontaneous oral movements usually associated with the use of neuroleptics were absent. Release phenomena such as the grasp and pouting reflexes, as well as the stereotyped activities, were encountered significantly more frequently in patients with an organic brain syndrome than in the two other groups of patients. Our survey has yielded limited results with regard to the possible influence of type of illness and neuroleptic treatment on the incidence of release phenomena and iterative activities.

σ- and π-Bonding capabilities of , , and in molybdenum hexacarbonyl derivatives

cis- and trans-[Formula: see text] and cis- and trans-[Formula: see text] have been prepared. The dipole moments of Mo(CO)5L, cis-Mo(CO)4L2, and cis-Mo(CO)3L3[Formula: see text] as well as those of cis- and trans-[Formula: see text] have been measured.As the infrared data for stretching as well as deformation vibrations do not clearly explain the differences in stability, ease of substitution, or dipole moments with the different ligands, we have used the model of variable donor–acceptor ability of ligands combined with the model of non-retention of charges on the metal to show the importance of steric hindrance in substituted metal carbonyls. It is also possible to differentiate the σ and π bonding capabilities of the ligands [Formula: see text], [Formula: see text], [Formula: see text]. It is shown that [Formula: see text] is a better donor or acceptor than [Formula: see text] or [Formula: see text].

Appareil pour la mesure de moments dipolaires

A system is described which enables the determination of dipole moments of magnitude 1.0 D from as little as 10−4 mole of substance. The dielectric constant can be measured with a precision of ± 0.000008 unit. Only one weighing is necessary. A modified Guggenheim method, in which only the values of the dielectric constant are required, is used to calculate the dipole moments.

Use of ionic bombardment to increase the conductivity of metallized thin plastic films for making source mounts

A study was made of the conductivity of thin flexible collodion films metallized either with gold (99.95%) or with gold – 18% palladium alloy and the results obtained were compared with the conductivity of VYNS (a polyvinylchloride–acetate copolymer) films coated with the same metals. For both types of films the conductivity is better with the alloy, especially for VYNS. VYNS films coated with gold or the alloy show better conductivity than collodion coated with either metal. However, ionic bombardment of the collodion films prior to metal coating considerably improves their conductivity, especially with the Au – 8% Pd alloy. For this' alloy the conductivity goes up by a factor of 100 to 1 000 000, and then becomes better than that obtained with VYNS. Although ionic bombardment had a less pronounced effect on the VYNS, an improvement in conductivity was still observed.On a fait une étude comparative de la conductivité de films minces de collodion et de VYNS métallisés soit avec de l'or, soit avec un alliage or – 18% palladium, en couches variant de 2 à 30 μg/cm2. Pour les deux types de films, la conductivité s'est révélée meilleure avec l'alliage; de plus le VYNS devient plus facilement conducteur que le collodion. Toutefois, les films de collodion soumis à un bombardement ionique avant leur métallisation sont beaucoup plus faciles à rendre conducteurs et leur conductivité devient même supérieure à celle obtenue avec les films de VYNS métallisés par l'alliage. Quoique le bombardement ionique ait un effet moins prononcé sur la conductivité subséquente des films de VYNS, elle est tout de même améliorée de façon appréciable. On décrit également des méthodes simples et rapides pour déterminer l'épaisseur des films de collodion et des couches métalliques déposées sur les films.