Present Study1 Research Articles

Letter: Early Diffusion Magnetic Resonance Imaging Changes in Normal-Appearing Brain in Pediatric Moyamoya Disease.

To the Editor: Recently, we read with great interest the article by Quon et al1 regarding the early diffusion magnetic resonance imaging (MRI) changes in normal-appearing brain in pediatric moyamoya disease (MMD). The authors found the significantly elevated apparent diffusion coefficient (ADC) values for MMD children in the representative brain regions could reflect microstructural changes stemming from exhaustion of cerebrovascular reserve (CVR). We really appreciate the interesting observation for their conclusion. Meanwhile, we would like to highlight 3 important questions that it raises. First, in recent years, the researchers of MMD have gradually formed a consensus: prior to the obvious ischemic changes on MRI, the microstructural impairments caused by reduced blood supply had appeared in the brain of MMD patients.2,3 Hypoperfusion and cytotoxic edema have been considered as the major cause of microstructural impairments.4,5 There are 2 different types of cerebral ischemic edema: the early cytotoxic type and the later vasogenic type. When the stimulation of anaerobic metabolism leads to the increase of osmotic pressure of brain tissue, which leads to the swelling of permeable cells, cytotoxic edema occurrs.6 With the development of tissue necrosis and the degradation of basement membrane, the blood-brain barrier is destroyed, and serum protein begins to leak into the brain from the blood, thus further improving the water content of the tissue and a later vasogenic type occurrs.7 However, due to the insensitivity of conventional MRI to the cytotoxic edema, most MMD patients had already suffered serious brain parenchymal damage by the time they receive treatment. In the present study,1 via the high sensitivity of diffusion-weighted imaging in distinguishing cytotoxic and vasogenic edema,8 the authors found the ADC value could precisely differentiate pediatric MMD patients from normal controls in the absence of imaging evidence of ischemic stroke. This observation indicated that it is possible to detect the serious imbalance of energy supplies and demands via the ADC value before the occurrence of irreversible lesions in brain parenchyma in MMD patients, so as to timely implement the intervention measures to obtain the maximum clinical effect. Second, revascularization surgery is considered to be the most effective way to treat MMD. Previous studies have confirmed that the preoperative clinical and hemodynamic changes could indicate the outcomes and complications from revascularization surgery for MMD patients.9,10 However, which severity of the preoperative changes in MMD patients can maximize the benefits from bypass surgery has always puzzled neurosurgeons. Recently, many non-invasive examination methods and indicators, such as CVR,11 ivy sign,12 and cortical hyperintensity belt sign,13 were proposed to reflect the clinical severity of MMD before obvious (usually means serious) changes appear on conventional MRI. The same is true for the ADC value in present study. Third, the authors in present study1 tried to explain a possible relation between the elevated ADC value and the impaired CVR. Although previous studies have observed simultaneous appearance of reduced CVR and elevated ADC in MMD patients, the mechanism remains to be clarified.14 In our opinion, CVR reflects the compensatory ability of cerebral arteries to compensate for the hypoperfusion, and its mechanism may partially due to the vasodilatory stimulation of metabolites like lactate to arteries. Meanwhile, the early cytotoxic edema in MMD patients may also due to the change of metabolism in brain cells during hypoperfusion.6 Therefore, there may not be a direct causal relationship between impaired CVR and elevated ADC, they may be 2 simultaneous results of the same change (hypoperfusion). Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

Prophylactic use of hydroxychloroquine among healthcare workers in a case-control study

Sir, It is with great interest that we read the article by Chatterjee et al1 and appreciate the work done by the authors in the trying times of COVID-19. The attempt to bring out both risk and protective factors for the disease, including hydroxychloroquine (HCQ), among healthcare workers (HCWs), is indeed pertinent in the times of the ongoing discussion on the subject in scientific community. The study has also brought forth certain other issues which deter evidence generation from the national-level data. The case-control design to identify new risk factors if any, was most suitable to carry out the study in the shortest possible time based on the real data. The information being from across the country and the range of HCWs also added to the strength of the study. The positivity of confirmed SARS-CoV-2 of five per cent among the symptomatic HCWs was certainly reassuring. Further, it proves beyond doubt that personal protective equipment (PPE) is protective and the results substantiate the guideline insistence on appropriate PPE for all HCWs. The study provided the first published literature on the benefits of HCQ prophylaxis and could generate evidence that intake of four or more maintenance doses of HCQ was protective against COVID-19 infection1. In vitro studies on HCQ have already found it to have antiviral properties as well as immunomodulatory effects2. The fact that the number of HCWs in the study who experienced side effects was low, further strengthens the case for using HCQ chemoprophylaxis. The evidence regarding usefulness of HCQ in COVID-19 so far had been derived only from anecdotal reports and studies without a control group3. Hence, the present study does put forth some evidence of its usefulness, and with the postulated mechanism of action at a molecular level, it may have some role in the prevention of COVID-19 in the early stage of the disease. However, in spite of existing guidelines from the government, it is not a happy situation to note that barely, 50 per cent of HCWs seemed to be taking HCQ as evident from the available data1. In the study, regardless of having records of nearly 23,000 symptomatic HCWs with more than 1000 positive patients, the estimated sample size for cases and controls could not be met which does not augur well for our data quality. A high proportion of non-response in both cases and controls also indicates towards a low motivation among HCWs to participate in the research studies, which may generate important data for the benefit of others. The study could have been more robust if the minimum required sample size could have been achieved and non-response minimized. The initial increased odds observed in cases with lesser number of doses of HCQ taken by the HCWs also posed some questions which could not be explained fully. Notwithstanding the same and some other minor analytical issues, we are of the opinion that it may be a case for starting the HCQ prophylaxis early, i.e. 2-4 wk before being put on duty in the COVID facilities, keeping in mind the fewer side effects in these data. We also feel that it would be of interest to compare the severity of symptoms among the positive patients between those with and without HCQ. Although the use of various non-pharmacological measures, such as hygiene measures, social distancing, and PPE, is being actively promulgated as the preventive measure against COVID-19, these have not proved to be sufficient for protecting the HCWs, and therefore, some form of pharmacological intervention is essentially required. The present study1 generated some evidence of HCQ effectiveness. However, the convincing evidence of HCQ utility in prophylaxis against COVID-19 will still require some well-planned large-scale clinical trial. At present, a large number of clinical trials (some of which are multicentric) have been registered with ClinicalTrials.gov that focus on prophylaxis effect of HCQ4, and it is hoped that, in the near future, these will be able to generate definitive evidence of HCQ utility in the containment of COVID-19 pandemic.

The Role of Ecotourism Potentials in Ecological and Environmental Sustainable Development of Miankaleh Protected Region

Protected areas are considered as suitable environments for tourism development where the performance of tourism, consumer, and economic activities consistent with each region based on total management plan provides the context for sustainable tourism development. Therefore, the aim of the present study1 was to explore the role of ecotourism potentials in the environmental development of Miankaleh Protected Region using a descriptive, analytical, survey method. It also aimed to examine factors affecting sustainable tourism development in the region under study. The data were collected using documentation and library techniques, field methods, questionnaires, note taking, observation, and conducting interviews with people, tourists, and authorities in charge of ecotourism development. The research population included people living in Noushahr, of whom 384 families, 30 experts, and 100 tourists were selected as the respondents in the research sample using Cochrane formula. The collected data were analyzed using descriptive and inferential statistics, and Spearman test through SPSS. The results of the study showed that there was a significant relationship between ecotourism potentials, environmental, economic and sociocultural development in the region under study.

Circadian rhythms and mood disorders: a guide for the perplexed.

Circadian rhythms and mood disorders: a guide for the perplexed.

Editorial Comment

There has been a rise in the frequency of infectious complications from prostate biopsy, leading many investigators to explore alternative strategies for prophylaxis. The present study1 retrospectively compared 535 men who had a transrectal prostate biopsy from 2011 to 2012 with single-dose ciprofloxacin 500 mg plus aminoglycoside vs 654 men undergoing biopsy from 2012 to 2013 with single-dose levofloxacin 750 mg plus aminoglycoside. Although there was no significant difference in the overall infection rate between the 2 regimens (3.18% vs 2.14%; P = .26), there was a significant reduction in severe infections after the switch to levofloxacin (2.43% vs 0.92%; P = .04).

Editorial Comment

The need or benefit of cold ischemia during renal hilar clamping for partial nephrectomy for renal cell cancer (RCC) remains controversial, and the results from various series are inconsistent. The topic is clouded further by uncontrolled comparisons between minimally invasive surgery with warm ischemia and open surgery with cold ischemia. Among the uncontrolled biases are case selection, surgeon experience, duration of clamping, tumor complexity, and variable renal function at baseline. To the authors' credit, the present study1 presents a prospective, randomized 1:1 comparison of open partial nephrectomy for clinical stage T1 RCC in 60 patients each with either warm ischemia or cold ischemia.

Drug induced diseases (DID): Need for more awareness & research.

Drug induced diseases (DID): Need for more awareness & research.

Letter to the Editor

I read with interest the article entitled: “Cardiac Troponin I in Calves with Congenital Heart Disease” (Suzuki, et al., JVIM, 2012 DOI: 10.1111/j.1939-1676.2012.00953.x).1 This study deals with an understudied area of internal medicine: cardiology in food animals. Adding evidence-based studies is of great importance but can be challenging especially for unfrequent diseases. The authors concluded that the blood levels of cardiac troponin I (cTnI) can be of interest in for diagnosing congenital heart disease (CHD) in calves. They also state that “using a cutoff value of ≥ 0.035 ng/mL, cTnI in plasma may distinguish calves with and without significant CHD with reasonnable sensitivity and specificity.” Designing of diagnostic accuracy studies is challenging not only in veterinary medicine but also in human medicine.2 The case selection of control group to assess the specificity of the cTnI levels needs to be discussed since it may certainly overestimate test accuracy. Using healthy control subjects in case-control studies commonly led to overestimation of diagnostic accuracy compared with cohort study.3 As discussed by the authors, the clinical diagnosis of CHD in calves is challenging without echocardiography since the clinical signs especially cardiac murmur can be found in calves without CHD (anemia, excitement or fever) as well as various signs of respiratory distress. It has been shown that cTnI can be increased in cattle due to various thoracic diseases4, 5 or endotoxemia.6 Such animals may represent a better group to establish the specificity of the diagnostic accuracy of cTnI in calves with heart murmur and CHD to calves with heart murmur due to various cardiorespiratory condition or endotoxemia/sepsis. Another concern that has not been addressed in that study is that the test accuracy has been determined in only 12 cases with various CHD and 19 healthy control animals. With this small sample although the receiver operating characteristic lead to interesting Se/Sp of this test in their sample of calves, the authors did not mention that before doing any inference of their best Se/Sp value of cTnI, they need to calculate the 95% confidence interval (CI) for their values. Such a small sample of animals would lead to a wider imprecision of their Se/Sp estimate to extrapolate to the general population that needs to be known by any clinician attempting to include cTnI determination in their diagnostic workup for suspected calves with CHD. Morerover, determining a threshold (here 0.035 ng/mL) although interesting, needs to be discussed in regard with the method of determination of cTnI. Previous studies in dogs7 have shown that normal ranges should be established for every technique/analyzer used for establishing cTnI levels since difference in the antibodies used in the assays could lead to differences in results obtained with different analyzers. Moving from this point, it is difficult to extrapolate the proposed threshold without comparisons of other point of care cTnI analyzers that could be used in the farm with portative analyzers that may be used for cTnI determination. Finally, despite having a threshold for diagnosing CHD in calves could be interesting, from a practical perspective, it would have been interesting to know if the cTnI values were quite different depending on the exact nature of CHD. The impact of the heart defect on cardiomyocytes oxygen delivery may (or may not) be different in a case of early VSD without any cardiac chamber modification whereas hypoxemia due to intracardiac shunt may lead to increased cTnI due to myocardial hypoxia in cyanotic heart disease (Tetralogy of Fallot or double outlet right ventricle which represent 6 of 12 cases investigated in the present study1). This study raises interesting points concerning potential interest of cTnI in the diagnosis of CHD in calves. However, the authors did not convince me that it could replace transthoracic echocardiography which is more specific in living animals and more sensitive (for experienced user) especially for commonly encountered CHD such as VSD. Having higher number of CHD calves and calves with various conditions that could clinically mimick CHD would be of great interest to investigate more accurately Se/Sp of this cardiac biomarker. Using the proposed threshold to diagnose CHD in calves without other confirmatory test would certainly lead to overdiagnosing CHD in calves with simple infectious respiratory conditions or endotoxemic condition.

Reply

We thank Craig et al. for their interesting letter. Our present study1 expands on our earlier publication,2 in which we first advocated the use of the Sequential Organ Failure Assessment (SOFA) score for acetaminophen-induced acute liver failure. The usefulness of the SOFA score is partly related to its high negative predictive value and discriminative ability, regardless of the time of acetaminophen administration.1, 3 However, we totally agree with Craig et al. that the SOFA score should be evaluated prospectively in larger studies including patients with non–acetaminophen-induced acute liver failure. In addition, we agree that the SOFA score and all other prognostic scores should be evaluated not only at admission but also 48 to 96 hours after admission and/or after therapeutic intervention. In fact, we have shown for the first time that in patients with cirrhosis who are admitted to the intensive care unit, dynamic changes in the SOFA score or other prognostic scores might have superior performance in comparison with the scores at the baseline.4 Nevertheless, we believe that in daily clinical practice, all main prognostic scores should be used as an aid to clinical judgment and should not be considered to provide absolute precision for clinical decision making. Evangelos Cholongitas M.D.* , Andrew K. Burroughs M.D., F.R.C.P., F.Med.Sci. , * 4th Department of Internal Medicine Medical School of Aristotle University Hippokration General Hospital of Thessaloniki Thessaloniki, Greece, Liver Transplantation and Hepatobiliary Unit Royal Free Hospital, London, United Kingdom.

Statins after ischemic stroke of undetermined etiology in young adults

# {#article-title-2} Putaala et al.1 studied a group of young patients with a first stroke of undetermined etiology and found that individuals who used statin poststroke had lower rates of vascular events in long-term follow-up. However, when the whole young population was studied after first-ever ischemic stroke, it was found that dyslipidemia did not predict the occurrence of future arterial thrombotic events.2 The present study1 suggests that higher cholesterol levels actually are protective after ischemic stroke of undetermined etiology. It is well known that baseline total cholesterol levels of statin-treated populations are higher than those of the …

Young children fail to fully generalize a novel argument structure construction when exposed to the same input as older learners

The present study exposed five-year-olds (M=5 ; 2), seven-year-olds (M=7 ; 6) and adults (M=22 ; 4) to instances of a novel phrasal construction, then used a forced choice comprehension task to evaluate their learning of the construction. The abstractness of participants' acquired representations of the novel construction was evaluated by varying the degree of lexical overlap that test items had with exposure items. We found that both child groups were less proficient than adults, but seven-year-olds showed evidence of across-the-board generalization whereas five-year-olds were sensitive to lexical overlap at test. This outcome is consistent with more conservative, item-based learning of syntactic patterns in younger children. Additionally, unlike adults and seven-year-olds, five-year-olds showed no evidence of having mastered the novel construction's linking rules. Thus, younger learners are less likely to generalize abstract argument structure constructions when exposed to the same systematic input as older learners.

Social Experience and Personality Affect Resilience to Sleep Deprivation

Social Experience and Personality Affect Resilience to Sleep Deprivation

Resurrecting Hope for Antioxidant Treatment of Cardiovascular Disease

Oxidative stress has been associated with cardiovascular disease and the development of hypertension in both humans and in animal models. Antioxidant therapy has been successful in ameliorating disease in animals, but the results from human studies have been largely disappointing. Despite these negative results, a wealth of evidence suggests that oxidative stress is involved in the development of cardiovascular disease both in humans and animal models. Because global attenuation of cellular reactive oxygen species (ROS) may not be advantageous, more recent therapeutic strategies target specific subcellular sources of oxidative stress. Most studies implicate plasmalemmal membrane-bound NADPH oxidase as a key mediator of ROS generation in cardiovascular disease. However, in the current issue of Circulation Research , Dikalova et al1 demonstrate that specific attenuation of mitochondrial derived oxidants prevents the development of angiotensin II–induced hypertension in the mouse. Perhaps more interesting is the mechanism: inhibition of a mitochondrial ROS-triggered activation of NADPH oxidase, interrupting a vicious cycle of ROS production. The novel approach of targeting the inciting source of ROS (mitochondria) to prevent accelerated oxidant production may hold more promise for humans by eliminating pathological but not homeostatic sources of ROS. Seminal observations by Harrison et al2 showed evidence of increased oxidative stress within the systemic vasculature in an Angiotensin II–induced rat model of hypertension, piquing interest in a possible etiologic role for ROS in this condition. In animal models, stimulating ROS production can induce hypertension,2,3 whereas treatment with a variety of antioxidants including vitamin C and E, or targeted inhibition of enzymatic oxidant production, can reduce blood pressure.3–6 Hypertensive patients demonstrate increased NAD(P)H oxidase activity7 with elevated levels of hydrogen peroxide in plasma.8 Antioxidant treatment leads to enhanced vasodilation in both forearm and coronary arteries of human hypertensive subjects,9,10 indicating a functional vasomotor …

Correlation of Flow Cytometrically Determined Expression of ZAP-70 Using Two Different Antibodies with IgVH Mutation Status and Cytogenetics in 539 Patients with Chronic Lymphocytic Leukemia.

The clinical course of chronic lymphocytic leukemia (CLL) is largely heterogeneous. It may be estimated based on clinical and laboratory findings the most important ones of which include chromosomal aberrations, the IgVH mutation status, and the expression of ZAP-70. The optimum procedure of ZAP-70 assessment including selection of antibody clone and the method of analysis still needs to be established. The validation of ZAP-70 has been performed using the course of the disease as well as using the IgVH mutation status. To further clarify the role of ZAP-70 expression in CLL we prospectively analyzed ZAP-70 expression, IgVH mutation status, and chromosome aberrations in peripheral blood and bone marrow samples of 539 patients with CLL. For the flow cytometric assessment of ZAP-70 expression the antibody clones 1E7.2 (Caltag, n=523) and SBZAP (Immunotech, n=81) have been used. IgVH mutation status has been analyzed in 407 cases and chromosome aberrations in 416 cases applying FISH with probes for del(6q), del(11q), +12, del(13q), del(17p), and t(11;14). ZAP-70 expression has been calculated as percentage of positive cells using normal T-lymphocytes as positive controls as well as using the ratio of mean fluorescence intensity (MFI) for ZAP-70 between T-lymphocytes and leukemic B-lymphocytes. Significant correlations were found between the percentages of ZAP-70 positive cells and IgVH homology (1E7.2, p<0.001, r=0.239; SBZAP, p=0.003, r=0.426). Accordingly, patients with mutated and unmutated IgVH status (98% homology used as cut-off) significantly differed in the percentages of ZAP-70 positive cells (1E7.2, mean 32% vs. 46%, p<0.001; SBZAP, mean 7% vs. 29%, p<0.001). Applying a cut-off level of 20% for positivity of ZAP-70 expression significant correlations (ZAP-70 positive and IgVH unmutated and vice versa) were found for 1E7.2 (p<0.001, rate of concordant cases 59.0%) and SBZAP (p=0.002, 80.0%). Even stronger correlations have been found, however, comparing the MFI ratios for ZAP-70 with the IgVH mutation status: 1E7.2, p<0.001, r=−0.283; SBZAP, p<0.001, r=−0.494. The respective differences between cases with mutated and unmutated IgVH status were: 1E7.2, mean MFI ratio 3.45 vs. 2.67, p=0.001; SBZAP, mean MFI ratio 6.18 vs. 2.86, p<0.001. The ratio of MFI between leukemic and normal B-lymphocytes did not correlate with the IgVH mutation status. No associations of ZAP-70 expression with chromosomal aberrations have been found. The results of the present study1) confirm the strong correlation between ZAP-70 expression and IgVH mutation status,2) confirm the independence of ZAP-70 expression from chromosome aberrations,3) argue in favor of analyzing ZAP-70 expression as MFI ratio between T-lymphocytes and leukemic B-lymphocytes, and4) suggest that the SBZAP clone has a significant potential in the diagnostic work-up of CLL.Further studies are warranted to validate the role of the MFI ratio approach and of the SBZAP antibody in the clinical setting.

Author reply

We are pleased to respond to the comments of R.S. Jayshree and H. Sridhar who have suggested that use of multiple primers/probes from surface(S), core(C), and X gene of hepatitis B virus genome can improve detection of HBV infection in HCC. On principle, we agree with their suggestion, but in the present study the need to use S and X gene primers in addition to that of a core gene was considered not necessary. As indicated in their comments, the present study1 was directed primarily to analyse the p53 gene mutation in HCC in India. But since p53 mutation was found in only 3 of 21 cases analysed (14.28%, CI: −0.7 to 29.3), the study was extended to examine infection of hepatitis B virus which has been strongly implicated in the development of hepatocellular carcinoma. For our study, we used primer sequences from the core(C) region of the HBV genome, the gene organization of which is well conserved irrespective of subtypes.2, This is true because 19 of 21 HCC cases (90.45%) were positive for the core primers. Although several mutations or alterations of the four major genes of HBV genome have been reported, it is unlikely to find a HCC patient infected by HBV without a core or other open reading frames. It is well established that if there is a mutation or deletion of core or precore region, no hepatitis B e antigen (HBeAg) is produced.4, 5 Because the two HBV–PCR negative cases in question are positive for HBeAg, as well as HbsAg, it is quite unlikely that the infected HBV genome was without the core or S gene. It is possible that following initial infection, HBV DNA remained in an unintegrated state in these patients and later got cleared by strong immunologic response of the host or by some yet unknown mechanism(s), but the viral gene products such as hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) remained in the circulation or in the target issue. But there are several HCC cases that also may test negative for these HBV serologic markers (see Table 2 of reference 1). Therefore, for a reliable estimate of HBV infection in HCC, both PCR and serologic ELISA should be used as screening assays. Bhudev C. Das Ph.D.*, Varsha Thakur M.Sc. , Raj C. Guptan M.D. , Shiv K. Sarin M.D. , * Division of Molecular Oncology, Institute of Cytology and Preventive Oncology (ICMR), Maulana Azad Medical College Campus, New Delhi, India, Department of Gastroenterology, G.B. Pant Hospital, New Delhi, India

Solvent Extraction of Lanthanides from Their Oxides with TBP in Supercritical Carbon Dioxide.

The supercritical fluid extraction (SFE) of heavy metals from acidic aqueous solution has attracted interest lately(1)-(5). In the present study1, supercritical CO2 was directly applied to lanthanide oxide as an extraction solvent. Lanthanide metals were extracted from lanthanide oxides (Nd2O3 and Gd2O3) by using supercritical CO2 including tri-n-butylphosphate (TBP) and HNO3 complex.

Technological Change and Women’s Participation in Crop Production in Bangladesh

There is a dearth of information on the employment effects of modern agricultural technology on rural women in Bangladesh. The present study1 looks at women’s participation in crop production activities, examines their influence in the diffusion of modern technology and their participation in the hired labor market. Data for this study comes from two intensive surveys conducted in the crop years 1989 and 1996 in three agro-ecological regions of Bangladesh.Findings suggest that the prevailing claim-that women are involved only in postharvest processing of crops-underestimates their contribution to agricultural production. Women’s share of total labor is 10-18 percent in foodgrain production and 6-48 percent in non-cereal crop production. Increased demand for labor owing to technological change is almost entirely being met by hiring male labor. The few women who are hired are paid significantly lower wages than men, revealing unequal opportunities and a lack of bargaining power for women in the hired labor market.An analysis of the behavior determining the adoption of modern technology indicates lack of women’s participation in technology adoption decisions. An examination of the determinants of labor demand indicate that an increased labor demand is met with more female family labor, thereby increasing the women’s workload. A decentralized crop diversification policy coupled with a policy of equal minimum wage for men and women could promote women’s gainful employment. Also, gender-sensitive educational programs through collaborations between government and NGOs could work towards a balanced development in the long run.

Resolution of Actinolite Mössbauer Spectra into Three Ferrous Doublets

THE Mossbauer spectra of several amphibole minerals of the actinolite series, ideally Ca2(Mg,Fe2+)5Si8O22(OH)2, have been resolved by computer into three quadrupole-split ferrous doublets representing each of the M(1), M(2) and M(3) positions of the amphibole structure. Such resolution has not been achieved before, so that for the first time it has been possible to evaluate Mossbauer parameters and to estimate Fe2+ site occupancies of all three positions available to iron in the actinolite structure. Ferric doublets were also resolved for the first time in several specimens, enabling the ratios of Fe3+ to total iron to be determined in actinolites. We report here the results obtained for two extreme actinolite compositions available to us in the present study1. The specimens were illustration from glaucophane schist, Berkeley, California1 (No. 14785) and illustration from quartzite, Cumberland, Rhode Island1,2 (No. USNM 44973). Open image in new window Open image in new window

Partial Reinforcement Effects as a Function of Number of Acquisition Trials and Percent Reinforcement

Recent investigations have indicated that resistance to extinction is an inverted U-shaped function of percentage of reinforcement. Grant and Schipper (1952) suggest that two processes are involved in producing this function: discrimination and learning. The greater the percentage of reinforcement during acquisition, the more discriminable is the acquisition phase from the extinction phase, thereby, producing fewer extinction responses. On the other hand with the CR near zero strength, the greater the percent reinforcement, the greater the effect on habit strength and the greater the number of extinction responses. Lewis (1960, p. 3 ) has pointed out that, if Grant and Schipper are correct, the point of inflection of the inverted U-shaped function would need to vary with the degree of learning. The greater the degree of learning, the more the poinc of inflection should move toward the low end of rhe percentage scale. . The present study1 was an attempt to test this hypothesis in a classical aversive-conditioning paradigm measuring resistance to extinction of the GSR. The general design was to test independent groups under one of six treatments utilizing three percentages of reinforcement ( lo%, 30%, 100% ) and two levels of acquisition ( 10, 30 trials). Procedz~re.-Thirty male undergraduate students at the University of Maryland were assigned to six groups with five in each group. Recording and shock electrodes were placed on the palmar surfaces of the hands and the fingers, respectively. S was told to get comfortable and that he would receive some electric shocks during the course of the experiment. He was further told he could terminate the experiment whenever he wished; but none chose to do so. Next, the shock level was obtained by determining when S could just noticeably detect any stimulation and then increasing the number of turns on the inductoriurn by one and one half. The shock was then presented and maintained at this level for the course of the study. The CS was a 5-sec. 1000-cps tone at 40 db that terminated with a .5-sec. electric shock. The 2 )( 3 design yielded six independent groups which received either 10 or 30 presentations of the CS paired with the UCS on lo%, 30%, or 100% of the trials. The extinction series began immediately after

A Study of Rapid Acceleration in the Elementary School

Much has been written in the past decade in regard to the acceleration of pupils in the elementary school. A great deal of the acceleration in the school systems of the smaller communities has been accomplished by the skip-grade or double-promotion method. Even though this method has been used by many, little has been done to determine the actual results of such acceleration. The present study1 is an attempt to supply this need. The data used as a basis were the teachers' marks of 22 pupils of the elementary school of Monticello, Indiana, and the correspond ing marks of all the pupils of all the groups to which these pupils belonged. Each of the pupils had been accelerated by being taken from a grade and placed in the next higher grade, thereby skipping one full grade of school work. Before acceleration these pupils were scattered through ten groups of children and after accelera tion they belonged to ten other groups. The groups ranged in size from 14 to 70 so that a total of 696 pupils was involved in the investigation. By making comparisons of the standings of each of the 22 accelerated pupils in from three to five subjects, before and after skipping a grade, it was necessary to use 3,211 averages of teachers' marks or more than 10,000 monthly grades. In this manner 101 subject standings before double promotion and 101 corresponding subject standings after double promotion were se cured for comparison. In order to compare the standings already referred to, it was desirable to express each in standard units of measure. This was done by expressing each in standard-deviation or sigma (o-) units derived from the arithmetic means of the teachers' marks of each group in each subject. There are 101 such standings before double