Long-term results and comparison of the Green-Anderson and multiplier growth prediction methods after permanent epiphysiodesis using Canale's technique

PURPOSE

The aim of the study was to evaluate the accuracy and radiographic outcomes of Canale's method in patients with idiopathic leg-length discrepancy (LLD) following percutaneous epiphysiodesis. The accuracy of two common growth prediction methods was assessed.

METHODS

A total of 18 patients with 26 affected bones (eight distal femur, two proximal tibia, five combined) were clinically and radiologically analyzed after reaching skeletal maturity. We compared the final effect of epiphysiodesis at maturity with the expected effect of epiphysiodesis before surgery; these measures were calculated using the Green-Anderson and multiplier methods, respectively. We furthermore compared pre- and postoperative frontal and lateral plane radiographs.

RESULTS

The average LLD was 21.2 mm before surgery and 7.9 mm after epiphysiodesis. The final effect of both methods was not significantly different compared with the expected effect of epiphysiodesis before surgery. However, the prediction by the Green-Anderson method was closer to the definitive epiphysiodesis effect. The frontal plane radiographic deformity parameters did not change significantly after epiphysiodesis. The postoperative sagittal plane radiographic deformity parameters were in the normal range.

CONCLUSION

The Canale technique is a reliable method to reduce LLD in children. With regards to growth prediction, the Green-Anderson method using bone age seems to be more accurate than the multiplier method using chronological age. However, a relative over-estimation was observed with both methods in several cases, which might result in an insufficient correction.

LEVEL OF EVIDENCE

IV, Therapeutic study.

Peromelia - congenital transverse deficiency of the upper limb: a literature review and current prosthetic treatment

Peromelia or congenital transverse deficiency describes a truncation of the upper limb below various limb levels. Recommendations regarding treatment vary and are mainly based on expert opinions. This paper summarizes the current literature regarding the aetiology, pathogenesis and specifically treatment algorithms for children with peromelia. We performed a non-systematic review of the current literature from MEDLINE/PubMed to obtain comprehensive up-to-date information about peromelia, focusing on current recommendations for the treatment of peromelia (e.g. prosthetic fitting, external stump lengthening). The current literature lacks clear evidence as to whether prosthetic treatment is superior to prosthetic non-usage. However, based on the available studies, children with transradial or transhumeral peromelia should preferably be fitted with passive/cosmetic prostheses at the age between six and 24 months, followed by active/myoelectric devices at the age of 2.5 to four years. It remains controversial whether early myoelectric prosthetic fitting can reduce prosthesis rejection times; however, cognitive readiness and the ability to absolve a guided training programme are seen as important prerequisites for myoelectric fitting. Children with very short stumps may benefit from stump lengthening using external fixators and prosthetic modification. The treatment of children with peromelia generally requires a guided, multidisciplinary team approach. A training programme is essential to optimize individuals' performance in the execution of activities of daily living and decrease rejection risks whenever a myoelectric device is prescribed. Myoelectric fitting should preferably be commenced at no later than four years of age. However, long-term reports on the benefits of prosthetic treatment are still pending.

[Congenital tibial hemimelia]

BACKGROUND

The congenital tibia hemimelia, also called tibial deficiency, is a rare disorder with unknown cause, showing many associated abnormalities or varying syndromes.

METHODS

The correct diagnosis can be easily established using radiographs and/or magnetic resonance imaging in the postpartum setting. However, treatment may be difficult and needs to take into consideration the given anatomic situation in the knee and ankle joint.

CONCLUSION

Prosthetic fitting may be possible in mild cases. Nevertheless, the majority of patients need to undergo surgical reconstruction in order to restore a functional, mobile, and stable knee and ankle joint.

Open surgery versus nonoperative treatments for paediatric trigger thumb: a systematic review

The purpose of this systematic review was to determine the outcome of interphalangeal (IP) joint motion in children undergoing open surgical release, splinting, and passive exercising therapy for the treatment of paediatric trigger thumb. We conducted an online literature search of seven major databases. Only studies with a mean follow-up of at least 12 months were considered for inclusion. Seventeen retrospective studies and one prospective study met all the inclusion criteria. They reported on the results of surgery (634 children, 759 thumbs), splinting (115 children, 138 thumbs), and passive exercising (89 children, 108 thumbs). The mean follow-up periods were 59 (surgery), 23 (splinting), and 76 months (exercising), respectively. Full IP joint motion without residual triggering was achieved in 95% of all children undergoing surgery, in 67% of children treated with continuous splinting, and 55% after passive exercising. Based on the low level of evidence available, it seems that open surgery resulted in more reliable and rapid outcomes compared with nonoperative treatment.

Open surgery versus nonoperative treatments for paediatric trigger thumb: a systematic review

The purpose of this systematic review was to determine the outcome of interphalangeal (IP) joint motion in children undergoing open surgical release, splinting, and passive exercising therapy for the treatment of paediatric trigger thumb. We conducted an online literature search of seven major databases. Only studies with a mean follow-up of at least 12 months were considered for inclusion. Seventeen retrospective studies and one prospective study met all the inclusion criteria. They reported on the results of surgery (634 children, 759 thumbs), splinting (115 children, 138 thumbs), and passive exercising (89 children, 108 thumbs). The mean follow-up periods were 59 (surgery), 23 (splinting), and 76 months (exercising), respectively. Full IP joint motion without residual triggering was achieved in 95% of all children undergoing surgery, in 67% of children treated with continuous splinting, and 55% after passive exercising. Based on the low level of evidence available, it seems that open surgery resulted in more reliable and rapid outcomes compared with nonoperative treatment.

[When is the optimal time for hip ultrasound screening?]

The perfect time for hip screening is when every pathologically deformed hip can be diagnosed by sonography and after spontaneous resolution of immature, dysplastic hips. In addition, the beginning of therapy should be early enough to provide the best possible outcome concerning the anatomically correct healing of the patient's hip. Even though every child should be screened by sonography in the first few days of life, a reasonable way could be ultrasound screening in the first week for clinically unstable hips or newborns with risk factors such as breech position combined with ultrasound screening of every newborn between the fourth and sixth week.

Production of solid lipid nanoparticle suspensions using supercritical fluid extraction of emulsions (SFEE) for pulmonary delivery using the AERx system

The aims of the current work included: development of a new production method for nanoparticles of water-insoluble drugs in combination with lipids, characterization of the nanoparticles and development of lipid nanosuspension formulations, and investigation of the feasibility of delivering the nanosuspensions as aerosols for inhalation using Aradigm's AERx Single Dose Platform (SDP) with micron-sized nozzles and the all mechanical AERx Essence with sub-micron-sized nozzles. The continuous SFEE method was used for particle precipitation of solid lipid nanoparticles (SLN). The method allowed for production of stable particulate aqueous suspensions of a narrow size distribution, with a volume mean diameter below 30 nm (D99% cumulative volume below 100 nm). Thus the particle size obtained was significantly smaller than previously has been achieved by other techniques. The residual solvent content in the final suspension was consistently below 20 ppm. Drug loading values between 10-20% w/w drug were obtained for model compounds ketoprofen and indomethacin in formulation with lipids such as tripalmitin, tristearin and Gelucire 50/13. It was observed that the loading capacity achieved was higher than the thermodynamic limit of the solubility of the drugs in molten lipids. Lipid nanosuspension formulations were successfully aerosolized using both of the AERx systems. As measured by both cascade impactor and laser diffraction, the aerosol fine particle fraction (FPF) was comparable to drug solution formulations typically used in these devices; i.e., greater than 90% of the aerosol mass resided in particles less than 3.5 mum aerodynamic diameter.

Effect of metformin on nitric oxide synthase in genetically obese (ob/ob) mice

Genetically obese (ob/ob) mice were employed for the study of the effect of metformin on activity and expression of nitric oxide synthase (NOS ) in vitro and in vivo. For in vitro analysis, mouse liver extracts were used. For the in vivo study, (ob/ob) and their control litter mates (ob/c) mice were injected with specified amounts of metformin and the expression of NOS in the adipose tissue and hypothalamus was measured by Western blotting. Results show that metformin exhibited a biphasic effect on NOS activity in vitro. Expression of metformin was differentially altered in the hypothalamus and adipose tissues of the normal and ob/ob animals that were treated with metformin. Further, a significant decrease in food intake occurred in the (ob/ob) mice that received metformin. This decrease in food intake was not accompanied by changes in serum glucose. At inhibitory concentrations, hypothalamic NOS expression changes differentially in normal and ob/ob mice. In normal mice, metformin stimulated NOS expression, while in ob/ob mice there was an inhibition. NOS expression increased in brown adipose tissue of metformin treated control mice, while no such increase was observed in ob/ob mice. No effect of metformin was observed in white adipose tissue of control or obese mice. Thus, metformin may produce anorectic effects through modulation of NOS.

Toxicogenomics-based discrimination of toxic mechanism in HepG2 human hepatoma cells

The rapid discovery of sequence information from the Human Genome Project has exponentially increased the amount of data that can be retrieved from biomedical experiments. Gene expression profiling, through the use of microarray technology, is rapidly contributing to an improved understanding of global, coordinated cellular events in a variety of paradigms. In the field of toxicology, the potential application of toxicogenomics to indicate the toxicity of unknown compounds has been suggested but remains largely unsubstantiated to date. A major supposition of toxicogenomics is that global changes in the expression of individual mRNAs (i.e., the transcriptional responses of cells to toxicants) will be sufficiently distinct, robust, and reproducible to allow discrimination of toxicants from different classes. Definitive demonstration is still lacking for such specific "genetic fingerprints," as opposed to nonspecific general stress responses that may be indistinguishable between compounds and therefore not suitable as probes of toxic mechanisms. The present studies demonstrate a general application of toxicogenomics that distinguishes two mechanistically unrelated classes of toxicants (cytotoxic anti-inflammatory drugs and DNA-damaging agents) based solely upon a cluster-type analysis of genes differentially induced or repressed in cultured cells during exposure to these compounds. Initial comparisons of the expression patterns for 100 toxic compounds, using all approximately 250 genes on a DNA microarray ( approximately 2.5 million data points), failed to discriminate between toxicant classes. A major obstacle encountered in these studies was the lack of reproducible gene responses, presumably due to biological variability and technological limitations. Thus multiple replicate observations for the prototypical DNA damaging agent, cisplatin, and the non-steroidal anti-inflammatory drugs (NSAIDs) diflunisal and flufenamic acid were made, and a subset of genes yielding reproducible inductions/repressions was selected for comparison. Many of the "fingerprint genes" identified in these studies were consistent with previous observations reported in the literature (e. g., the well-characterized induction by cisplatin of p53-regulated transcripts such as p21(waf1/cip1) and PCNA [proliferating cell nuclear antigen]). These gene subsets not only discriminated among the three compounds in the learning set but also showed predictive value for the rest of the database ( approximately 100 compounds of various toxic mechanisms). Further refinement of the clustering strategy, using a computer-based optimization algorithm, yielded even better results and demonstrated that genes that ultimately best discriminated between DNA damage and NSAIDs were involved in such diverse processes as DNA repair, xenobiotic metabolism, transcriptional activation, structural maintenance, cell cycle control, signal transduction, and apoptosis. The determination of genes whose responses appropriately group and dissociate anti-inflammatory versus DNA-damaging agents provides an initial paradigm upon which to build for future, higher throughput-based identification of toxic compounds using gene expression patterns alone.

Peripheral administration of CRF and urocortin: effects on food intake and the HPA axis in the marsupial Sminthopsis crassicaudata

The hypothalamic peptides corticotrophin releasing factor (CRF) and urocortin (UCN) decrease food intake and increase energy expenditure when administered either centrally or peripherally to rodents. The effects of CRF and UCN on food intake in other mammals (for example marsupials), however, are not known. Peripherally administered CRF induced cortisol release in the marsupial Sminthopsis crassicaudata via the CRF1 receptor, and central CRF administration potently decreased food intake, as in rodents. When peripherally administered, both CRF and UCN decreased food intake in S. crassicaudata, but UCN was considerably more potent ( approximately 50 fold) in this regard. The anorectic effects of CRF and UCN were not blocked by the CRF1 receptor antagonist antalarmin, suggesting that the peripheral effects of CRF and UCN on food intake are mediated primarily by the CRF2 receptor.

Adult ontogeny of rat working memory of social interactions

BACKGROUND

Social memory has features that may make it uniquely appropriate for studying normal aging. We used a cross-section experimental design with an animal model to survey the lifetime adult ontogeny of memory of a brief social interaction.

METHODS

Groups of healthy adult male rats representing young adulthood (5 months), middle age (10 months), or old age (19-27 months) were tested weekly over a month in two paradigms. Basic social memory and social interference memory were quantified by differences between investigation times of a juvenile rat during a 5-min interaction (acquisition trial) and a second exposure (recall testing), with interexposure intervals (IEI) ranging from 15 min to 24 h.

RESULTS

Although basic social memory of all age groups was similar at the brief or longer IEI, there were memory declines at intermediate IEI delays in older males, especially the oldest groups. Decrements to working memory appeared as early as middle-age when an unfamiliar juvenile was inserted between acquisition and recall testing. Nonetheless, our healthy old animals retained a robust ability to recall identity of a conspecific that a minute by minute comparison suggested involves similar behavioral means of gathering social information.

CONCLUSIONS

Normative aging of working social memory in male rats can be characterized as being more fragile, beginning at middle age but without significant further decline until near the end of the life span. Functional impact of these age-dependent changes in social memory, on the other hand, may be minimal for all but the very oldest animals in the social group.

Inhibition of feeding by a nitric oxide synthase inhibitor: effects of aging

Nitric oxide has been demonstrated to play a role in the modulation of food intake. With advancing age, there is a physiological decrease in food intake. The effect of the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) on food intake in C57BL/6Nnia mice aged 3, 12 and 24 months was studied. L-NAME was more effective at decreasing food intake in 12- and 24-month-old mice than in the 3-month-old mice. NO synthase levels in the hypothalamus were increased in 16- and 25-month-old mice compared to 6-month-old mice (P < 0.01). NO synthase mRNA increased in 16- compared to 6-month-old mice, but decreased in 25-month-old mice. Overall, these studies may suggest that nitric oxide may play an increasingly important role in the feeding drive with advancing age.

Motility disorders of the esophagus before and after pneumonectomy for lung carcinoma

It has been noticed that patients undergoing major lung resection may occasionally develop dysphagia. A prospective study was carried out to evaluate if preoperative or postoperative esophageal motility disorders (EMD) occur in patients subjected to pneumonectomy for lung carcinoma. Twenty-five normal volunteers served as control data and 13 patients, who successfully completed manometry before and after pneumonectomy, were included in the final analysis. Studies were performed using a Gaeltec Model 6 ct/sb, 6-channel intraluminal strain gauge transducer probe. Our results demonstrated that EMD occurred in some patients suffering from lung carcinoma. However, motility disorders were most evident following pneumonectomy. These findings may explain the several anecdotal reports of patients developing dysphagia following lung resection after a variable interval of time.

Aging of the brain-testicular axis: reproductive systems of healthy old male rats with or without endocrine stimulation

To test the hypothesis that endocrine declines in males are incidental to disease, 24 gonadally intact old (22-24 months) rats were selected on the basis of good general health and assigned to one of three groups. One group of aged males was left untreated for comparison with an untreated control group of young adult males. Results from multiple measures of sociosexual behavior and reproductive physiology indicated that endocrine declines in males are not simply a by-product of increased disease incidence with aging. The untreated old animals showed clear decrements on all 13 measures of hypothalamic-pituitary- testicular (HPT) activity. The other two groups of old males were used to compare responsiveness of the aging HPT axis in healthy males to supplements with a typical exogenous (ExT) androgen regimen (300 micrograms testosterone/kg body wt/SC/daily/6 weeks) or to social stimulation (brief daily exposure to an inaccessible estrous female) for additional episodes of endogenous (EnT) hormone. Neither treatment restored our disease-free old male rats to levels approximating those of untreated young adults. Nonetheless, both treatments activated the aging HPT axis. EnT males showed increases in sociosexual behaviors, growth of androgen-sensitive bulbospongiosus muscle, and elevation of epididymal sperm reserves. ExT males, on the other hand, experienced a more foreboding hypertrophy of the ventral prostate gland. Our conclusion is that endocrine aging in males is ubiquitous and inevitable. Still, aged androgen-sensitive systems of healthy old rats retain notable capacity, particularly, for endogenous activation. Evidence points to functional responses by healthy aged males to the presence of sexually receptive females that, although not quantitatively the same, are qualitatively similar to the responses of young adult males.

New molecular endpoints and methods for routine toxicity testing

New molecular and instrumental techniques have made available many markers of cellular damage that can be evaluated in multiple tissues in vivo at low cost without compromising the normal conduct of in vivo toxicity evaluations, and without the need for substitution of new species or strains of animals. These techniques include (1) the activation of stress genes that respond to general classes of toxic agents and cellular damage at doses below those that cause frank toxicity; (2) electrophoretic methods for the detection of DNA strand breakage due to DNA degradation resulting from cell death or genotoxic damage; (3) the use of fluorescent chromosome-specific DNA probes that allow evaluation of stable chromosomal rearrangements, chromosomal breaks, and aneuploidy in laboratory animals; and (4) endogenous and exogenous (transgenic) reporter genes for the evaluation of in vivo gene mutation. Additionally, powerful new analytical techniques such as accelerator mass spectrometry make possible ultrasensitive measurements of metabolite binding to specific macromolecular targets and permit pharmacokinetics studies at very low doses. Often, identical or analogous endpoints can be measured in cellular models, in laboratory animals, and in humans, an approach that allows in vitro screening for product development, in vivo hazard identification, and early risk assessments in animal models and direct risk assessment in humans. These new in vivo techniques will greatly enhance our ability to extrapolate laboratory data to human health risk.

Interaction of a redox-sensitive DNA-binding factor with the 5'-flanking region of the micF gene in Escherichia coli

The product of the micF gene is an endogenous antisense RNA which down-regulates the expression of a major outer membrane protein, OmpF, in E. coli. We report here that two DNA-binding factors compete for the same site in the promoter region of the micF gene: RSBF, a high-affinity redox-sensitive DNA-binding factor that responds to an active oxygen species other than hydrogen peroxide or superoxide anions; and HRBF a heat-resistant DNA-binding factor. Both RSBF and HRBF bind to the same DNA sequence, 5'-TTAAAATCAATAACTTATTCTTAA3-', located upstream of the transcription start site of the micF gene. We present evidence that RSBF could be the controlling factor of a novel regulon involved in the response to oxidative stress in E. coli.

Steroidal interactions in the ageing endocrine system: absence of suppression and pathology in reproductive systems of old males from a mixed-sex socially stressful rat colony

A paradigm using chronic social stress and multiple measures of the reproductive system were used to assess changes with ageing in the dynamics of endogenous steroid interactions. The 22- to 24-month-old male rats lived for 8 weeks in one of four types of colony, in groups of the same sex or groups of mixed sex including familiar or unfamiliar old males. Measures of endocrinology (circulating steroid levels), behaviour (exploration and sociosexual responses), physiology (body and organ weights and epididymal sperm count) and histology (adrenal and ventral prostate glands) served as markers of activation of the hypothalamic-pituitary-adrenal (HPA) or hypothalamic-pituitary-testicular (HPT) axes. Old males living under stable conditions as familiar same-sex colonies served as the comparison group. Results indicated clear chronic activation of the HPA axis in the unfamiliar all-male colonies and of the HPT axis in the familiar males from mixed-sex colonies, whereas both steroidal axes were stimulated in colonies of unfamiliar males and females. Findings from aged males under chronic stress suggested that reproductive dysfunction may be limited to situations in which activation of the HPA axis occurs without concurrent stimulation of the HPT axis. Data on steroidal interactions from mixed-sex groups suggested that (1) chronic excitation of the HPA failed to suppress function in the reproductive system of the old males, (2) their stress responses were little affected by chronic HPT activation and (3) there was no evidence for stress-induced pathology, even in the vulnerable prostate gland.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of computer and non-computer-assisted technologies in noninvasive cardiac imaging

We compared gated magnetic resonance imaging (MRI) and dynamic computed tomography (DCT) with two-dimensional cardiac ultrasound (ECHO) to assess differences in diagnostic information. Magnetic resonance imaging was performed in 41 patients; ECHO in 36, and DCT in 28 patients with various pathologic conditions. We measured the left and right ventricular (LV, RV) long and short axes (LA, SA), LV free wall and septal thickness (WT, ST) at end systole (ES) and end diastole (ED) on the apical four-chamber view (ECHO) or appropriate transaxial slice (MRI, DCT) on a subset of 14 patients. Paired-sample analysis of these three techniques, in this preliminary data, yields statistically different results as follows: LV SA: MRI versus ECHO at ED and ES (P less than 0.001 and 0.005); WT: MR versus ECHO at ES (P less than 0.002); CT versus ECHO at ED and ES (P less than 0.05 and 0.01); ST: MRI versus ECHO at ED and ES (P less than 0.001), and CT versus ECHO at ES (P less than 0.05). Thus, CT and MRI yield similar quantitative data, but both differ in varying degree from ECHO measurements. Differential accuracies and utilities of these techniques warrant further careful investigation.

Gonadal hormones and conspecific marking in male rats

Urine deposited by a rat on a conspecific was quantified with injections of sodium fluorescein, a substance that changes the color of urine. The hypothesis examined in experiment 1 was that marking the environment and a conspecific would be similarly androgen-sensitive behaviors during each of three stages--before castration, after castration, and with restorative therapy with testosterone propionate. Findings were that castration reduced both forms of marking, and testosterone therapy to castrated males restored environmental marking in a dose-response fashion. However, the findings for social marking were more complex; for example, a physiological 200-micrograms testosterone dosage to castrated males was unable to elevate conspecific marking over the rates of marking by castrates without testosterone replacement. In experiment 2 the ontogeny conspecific marking in juvenile males was examined in relation to the pubertal surge of androgens. Results suggested that juvenile male marking of an adult male decreased despite a pubertal increase of androgens. Conclusions were that testicular hormones influenced both forms of marking but were less important in the social setting. Moreover, conspecific marking is not simply an extension of marking the environment.

Conservation of oxygen supply using a reservoir nasal cannula in hypoxemic patients at rest and during exercise

A reservoir nasal cannula which stores oxygen during exhalation and delivers it as a bolus during inhalation has been reported to conserve oxygen delivery in patients with chronic obstructive pulmonary disease (COPD) at rest. We compared the effects upon arterial oxygen saturation (SaO2) of the reservoir cannula and a standard nasal cannula in hypoxemic obstructed and restricted patients at rest and during exercise. The SaO2 was monitored by ear oximeter. While at rest, 13 obstructed and four restricted patients breathed oxygen from the reservoir cannula at 0.5, 1.0, 1.5, and 2.0 L/min and from a standard cannula at 0.5, 1.0, 2.0, 3.0, and 4.0 L/min. Mean SaO2 was significantly higher with the reservoir cannula compared to the standard cannula at 1.0 and 2.0 L/min (p less than 0.0006) and tended to be higher at 0.5 L/min (p less than 0.1). Seven obstructed patients walked on a level treadmill at 0.75 mph while breathing oxygen at 0.5 and 1.5 L/min from the reservoir cannula and at 1.0 and 3.0 L/min from the standard cannula. The SaO2 during exercise with the reservoir cannula was comparable to that with the standard cannula at approximately half of the oxygen flow rate. The ratio of the oxygen flow rate of the standard to the reservoir cannula to produce 90 percent saturation was estimated and found to be 2.5 +/- 0.8 (mean +/- SD) for patients at rest and 2.9 +/- 1.8 during exercise. We conclude that in hypoxemic patients at rest and during exercise, the reservoir cannula uses less than half the oxygen of a standard cannula to produce similar improvement in SaO2 and thus has advantages of a reduced cost of ambulatory therapy with low-flow oxygen and a longer time permitted away from a stationary source of oxygen.

Abrupt withdrawal of atenolol in patients with severe angina. Comparison with the effects of treatment

The effects of abrupt withdrawal of atenolol, a long acting cardioselective beta blocker, were studied in 20 patients with severe stable angina pectoris admitted to hospital for coronary arteriography. During the 144 hour postwithdrawal period no serious coronary events occurred. Mean and maximal daily heart rates rose steadily for at least 120 hours. No important arrhythmias were noted on ambulatory electrocardiographic monitoring. Treadmill exercise testing at 120 hours showed little reduction in the times to angina, ST depression, and maximal exercise when compared with those recorded at 24 hours. This deterioration was small when contrasted with the improvements in these indices produced by atenolol treatment in a similar group of patients not admitted to hospital. No change in catecholamine concentrations or acceleration of the heart rate response to exercise occurred after atenolol withdrawal, suggesting that rebound adrenergic stimulation or hypersensitivity was absent or insignificant. Catastrophic coronary events after beta blockade withdrawal (the beta blockade withdrawal syndrome) have occurred almost exclusively in patients taking propranolol, many of whom had unstable angina at the time of withdrawal. This study showed that in patients with stable angina, even when severe, the abrupt withdrawal of atenolol can be expected to result in only minor clinical consequences. The risk to any patient of so called rebound events after withdrawal of beta blockade seems to be related to both the clinical setting and the agent being used.

Expectancy and dual-task interference

This research deals with the relationship between expectancy and attention. In two experiments, expectancy concerning the modality of a probe stimulus was manipulated. In Experiment 1, the frequencies of probes in auditory and visual modalities were varied. In Experiment 2, a cue prior to each trial indicated the relative probabilities of the two types of probes. In both experiments, expectancy effects were observed in a single-task condition during which the subject's only task was to respond to the probes and in a dual-task condition in which probes were inserted in the study phase of a pattern recognition task. If maintaining an expectancy requires attention, then diverting attention from the probe task to the pattern recognition task should have attentuated the effects of expectancy. In fact, the pattern recognition task did not alter frequency effects but did significantly reduce cueing effects. We conclude that expectancy as determined by frequency results from automatic activation, whereas expectancy as determined by cueing involves attention.