An association of multiple well differentiated liposarcomas, lipomatous tissue and hereditary retinoblastoma

Well differentiated liposarcoma (atypical lipomatous tumour) is a low grade tumour, with no metastatic potential unless dedifferentiation supervenes. When superficial, it recurs locally only occasionally after marginal excision. We present a patient in whom bilateral childhood retinoblastoma was followed by later development of massive confluent areas of low grade liposarcoma and lipomatous tissue affecting the upper extremities and trunk. We discuss the role of mutations in the retinoblastoma gene (RB1) in linking these conditions and demonstrate the surgical management of an extremely unusual and challenging case.

Computer-aided surgical planning in the treatment of soft-tissue sarcoma

INTRODUCTION

Soft-tissue sarcoma resections are often highly complex procedures that demand meticulous pre-operative planning in order to maximise the potential for complete excision with clear margins, while preserving vital neurovascular structures and muscle groups.

SUBJECTS AND METHODS

We present a computer-aided model for surgical planning using Microsoft Powerpoint as a tool for cross referencing magnetic resonance images and normal anatomical diagrams.

RESULTS

Using this system the operator follows a sequence of pre-planned steps, minimising intra-operative decision making and unexpected adverse events. Four case studies are discussed.

CONCLUSIONS

The visual plan optimises the potential to meet surgical and oncological goals, and serves as an excellent adjunct to the operation note for documentation of the procedure.

Extranodal lymphomas presenting as soft tissue sarcomas to a sarcoma service over a two-year period

Non-Hodgkin's lymphoma usually presents with lymphadenopathy at multiple sites but can also involve any part of the musculoskeletal system. Occasionally the presentation is with a soft tissue mass. The presentation of large, superficial lymphomatous masses is similar both clinically and radiologically to that of soft tissue sarcomas. The six cases of lymphoma presenting to the Exeter Sarcoma Service as suspected soft tissue sarcomas, over a two-year period (2002-2004), are presented. We describe the clinical and imaging characteristics of these tumours and their subsequent management. Our cases showed variability in presentation. Only one of the six cases presented with pain and one with tenderness. Four of the cases had no lymphadenopathy and the other two had lymphadenopathy restricted to one nodal basin. Overlying soft tissue swelling occurred in four cases and in distal limb swelling beyond the mass in one case. Radiologically, lymphomas are known to be likely to exhibit confluent lymphadenopathy that is rare in patients with soft tissue sarcoma. Confluent lymphadenopathy was demonstrated in only one case of this series of patients. It is thought that lymphomas infiltrate across anatomical fascial planes more readily than sarcomas and in four of our six cases this feature was present. Clinical history, examination and MRI are insufficient to differentiate between soft tissue sarcoma and lymphoma and the importance of obtaining a pathological diagnosis prior to surgery is clear. It is crucial to differentiate lymphoma from sarcoma in order to avoid unnecessary excisional procedures in lymphoma patients.

Biphasic solitary fibrous tumour: a report of two cases with epithelioid features

We present two cases of solitary fibrous tumour (SFT) showing biphasic morphology with a spectrum of malignant epithelioid components. Slides prepared from formalin-fixed and paraffin-embedded tissue from both cases were stained with haematoxylin and eosin and by immunohistochemistry. Interphase fluorescent in situ hybridisation studies were performed in both cases using paraffin-embedded tissue to look for the t(X;18) translocation, thereby to exclude synovial sarcoma. Both cases showed biphasic morphology with some areas having typical benign spindled SFT morphology (including CD34 expression) and other areas having a malignant epithelioid appearance. In one of the cases, the epithelioid area, which was well circumscribed and showed packeting of cell groups, demonstrated expression of cytokeratin and epithelial cadherin but not of CD34. In the second case, the immunophenotype of the epithelioid component was similar to that of the benign SFT component. These findings suggest that epithelioid change in SFT shows a range of differentiation at one end, similar to that of a standard SFT, and at the other end, possibly acquiring epithelial characteristics.

Screening for lung cancer: a systematic review and meta-analysis of controlled trials

BACKGROUND

Lung cancer is a substantial public health problem in western countries. Previous studies have examined different screening strategies for lung cancer but there have been no published systematic reviews.

METHODS

A systematic review of controlled trials was conducted to determine whether screening for lung cancer using regular sputum examinations or chest radiography or computed tomography (CT) reduces lung cancer mortality. The primary outcome was lung cancer mortality; secondary outcomes were lung cancer survival and all cause mortality.

RESULTS

One non-randomised controlled trial and six randomised controlled trials with a total of 245 610 subjects were included in the review. In all studies the control group received some type of screening. More frequent screening with chest radiography was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, 95% CI 1.00 to 1.23). A non-statistically significant trend to reduced mortality from lung cancer was observed when screening with chest radiography and sputum cytological examination was compared with chest radiography alone (RR 0.88, 95% CI 0.74 to 1.03). Several of the included studies had potential methodological weaknesses. Controlled studies of spiral CT scanning have not been reported.

CONCLUSIONS

The current evidence does not support screening for lung cancer with chest radiography or sputum cytological examination. Frequent chest radiography might be harmful. Further methodologically rigorous trials are required before any new screening methods are introduced into clinical practice.

Use of colour duplex Doppler imaging in the postoperative assessment of buried free flaps

The postoperative assessment of free flaps is essential to identify and act on signs of incipient flap failure. Where the flap is completely buried, this becomes almost impossible unless part of the flap is exteriorised or an overlying skin window is used. Alternatively, complicated and often impractical monitoring devices have been advocated, but these have failed to gain widespread acceptance. A simpler solution to this problem has been evaluated in a series of patients using colour duplex Doppler imaging. This re-appraisal of a previously reported technique has been facilitated by updated technology in diagnostic radiology. Duplex Doppler imaging was confirmed as an accurate, non-invasive, and inexpensive tool for the postoperative measurement of blood flow within the pedicles of five buried free flaps in four patients undergoing surgery in our unit.

Validity evidence for using a general critical thinking test to measure nursing students' critical thinking

This study examined validity evidence for using a general test of critical-thinking skills and dispositions to measure nursing students' critical-thinking abilities. Content evidence indicated strong support for the theoretical framework underlying the test but less support for the way in which the critical-thinking constructs were specifically measured. Scores related to critical-thinking skills demonstrated significant but low correlations with grade point averages, were moderately correlated with SAT scores, and were uncorrelated with scores related to critical-thinking dispositions. The evidence suggests that nursing programs may need to reconsider how critical thinking should be measured and evaluated.

Neural tube defects in Victoria, Australia: potential contributing factors and public health implications

OBJECTIVES

To measure population prevalence and determine potential predictors of neural tube defects.

METHOD

Analysis of all births reported to a mandated collection of perinatal data, and terminations prior to 20 weeks' gestation that have been reported to a data collection of birth defects in Victoria from 1983 to 1997. Prevalence at birth and risk ratios of infant and maternal characteristics associated with neural tube defects were calculated.

RESULTS

Prevalence of spina bifida has remained steady for 15 years and was 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After exclusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are identified in 1 in 1600 fetuses, the risk being significantly higher for epileptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% CI 2.25-6.07), multiple births (AOR = 4.56, 95% CI 3.46-6.02), teenage mothers (AOR = 1.47, 95% CI 1.09-2.00) compared with those aged 25-29, and women with three or more previous pregnancies (AOR = 1.40, 95% CI 1.10-1.78). The risk was lower for women of East Asian (AOR = 0.70, 95% CI 0.49-1.00) and Middle Eastern origin (AOR = 0.60, 95% CI 0.35-1.02) and these differences were approaching statistical significance.

CONCLUSION

Total prevalence of neural tube defects did not decline up to 1997.

IMPLICATIONS

It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. However, consideration could be given to identifying larger 'at risk' groups such as those with homocysteine metabolism defects.

Healing at skin graft donor sites dressed with chitosan

Chitosan is a derivative of chitin, extracted from the exoskeleton of lobsters, crabs and shrimps. As a semi-permeable biological dressing, it maintains a sterile wound exudate beneath a dry scab, preventing dehydration and contamination of the wound to optimise conditions for healing. In this study, evaluation of healing at split skin graft donor sites, dressed half with chitosan and half with a conventional dressing, showed that chitosan facilitated rapid wound re-epithelialisation and the regeneration of nerves within a vascular dermis. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas.

Unravelling the secrets of foetal wound healing: an insight into fracture repair in the mouse foetus and perspectives for clinical application

This study was designed to investigate the nature of mammalian foetal fracture healing in utero. A compound 'pinch' fracture was created in the foetal mouse ulna at the end of the second trimester, prior to mineralisation, and healing observed in whole mount limbs and in histological section. Cartilaginous ends gained initial contact within a perichondrial sleeve by 24 h. Bony union was achieved within 48 h by cartilage remodelling during the phase of primary endochondral ossification in the limb, a process to which adult fracture healing aspires. The molecular response to wounding was investigated using a whole mount in situ hybridisation technique and antisense mRNA probes to three target genes (BMP-2, BMP-4 and GDF-5). These experiments failed to identify altered expression in wounded limbs compared with controls.

Can a picture really paint a thousand words?

Plastic surgeons require a three-dimensional appreciation of form and function in order to meet reconstructive challenges. The popular perception that plastic surgeons must be artistic was tested in an observational study of sketch illustrations in plastic surgery case notes. Only in the trunk and breast category of illustrations could career plastic surgeons demonstrate superior artistic skill to non-career plastic surgeons and there was little correlation between the artistic merit of a diagram and the likelihood of its meaning being understood by an independent observer. Simple but accurate outline sketches are as capable of leading an observer to the correct diagnosis as complex works of art, while illustrations with low diagnostic scores are not only misleading but may also have medico-legal implications.

Evolution of the Emergency Management of Severe Burns (EMSB) course in the UK

The principle of the 'golden hour' is now well established and forms the basis of a growing number of instructional courses teaching a systematic approach to the management of major trauma. In April 1997, the EMSB course, developed by the Australian and New Zealand Burn Association, was adopted by the British Burn Association to meet the needs of health professionals dealing with major burn injuries in this country. The experience of the first 13 courses following the introduction of EMSB is discussed and the course is recommended as a requirement for the training of UK plastic surgeons and plastic surgery nurses.

Reducing non-attendance at outpatient clinics

Outpatient non-attendance is a common source of inefficiency in a health service, wasting time and resources and potentially lengthening waiting lists. A prospective audit of plastic surgery outpatient clinics was conducted during the six months from January to June 1997, to determine the clinical and demographic profile of non-attenders. Of 6095 appointments 16% were not kept. Using the demographic information, we changed our follow-up guidelines to reflect risk factors for multiple non-attendances, and a self-referral clinic was introduced to replace routine follow-up for high risk non-attenders. After these changes, a second audit in the same six months of 1998 revealed a non-attendance rate of 11%--i.e. 30% lower than before. Many follow-up appointments are sent inappropriately to patients who do not want further attention. This study, indicating how risk factor analysis can identify a group of patients who are unlikely to attend again after one missed appointment, may be a useful model for the reduction of outpatient non-attendance in other specialties.

Should we salvage the scaffolding metaphor?

In response to the six commentaries on my analysis of the value of the scaffolding metaphor, I attempt to highlight common themes and revisit arguments for and against the utility of the metaphor.

The metaphor of scaffolding: its utility for the field of learning disabilities

Over the past 20 years, an increasing number of psychologists and educators have used the notion of scaffolding as a metaphor for the process by which adults (and more knowledgeable peers) guide children's learning and development. The purpose of the present article is to provide a critical analysis of the scaffolding metaphor, with particular emphasis on its applications to the case of atypical learners. In the initial sections of the article, the origins and early applications of the metaphor are sketched. With this as background, criticisms of the metaphor raised by others are reviewed, and a proposal for an enriched version of the metaphor is presented. At the heart of the proposed revision is an emphasis on the communicational dynamics and conceptual reorganization involved in adult-child interactions. With an enriched metaphor as a frame, the next section reviews applications of the scaffolding metaphor to the study of parent-child interactions and teacher-student instructional activities involving children with learning disabilities. The strengths and limitations of this work are evaluated, and proposals are made for how to reap further benefits from applications of the scaffolding metaphor to analyses of the development and instruction of children with learning disabilities.

The Hyphecan cap: a biological fingertip dressing

An occlusive biological dressing, the Hyphecan cap, was evaluated in the management of full-thickness pulp defects of fingers and thumb in 20 consecutive patients. The cap was applied directly to the tip of the injured finger and allowed to separate gradually over the course of several weeks as new skin regenerated. This approach proved simple and effective in achieving a good functional and cosmetic result within a relatively short time, and eliminated the pain and discomfort associated with conventional dressing changes. We recommend the use of this dressing material in the Accident and Emergency department for the out-patient management of de-epithelializing fingertip injuries in both children and adults.

Congenital skin loss following Nd:YAG placental photocoagulation

This is the first reported case of congenital skin loss following endoscopic placental laser coagulation, a new technique for the ante-natal treatment of twin-twin transfusion syndrome. The skin defect healed rapidly after birth with dressings alone, mimicking the spontaneous re-epithelialisation of a minor burn wound or aplasia cutis congenita.

A preliminary study of the use of peer support in smoking cessation programs for pregnant adolescents

This article describes preliminary findings of an experimental, randomized, three-group, controlled design examining the effectiveness of a smoking cessation intervention for pregnant teens. The three groups are: Teen FreshStart with a buddy program (TFSB), a Teen FreshStart program (TFS) without peer support, and the Usual Care (UC) control group. Forty-six subjects completed the post-intervention assessment of smoking status. The TFSB group consistently achieved greater smoking cessation across all measures when compared to the subjects in the other two groups. These results indicate that the use of peer support may be an effective adjunct in smoking cessation programs for pregnant adolescents.

Correspondences among parent, teacher, and student perceptions of adolescents' learning disabilities

A group of 26 adolescents with learning disabilities (Grades 9 through 12), their parents, and their special education teachers were asked to rate the students' skills in each of 21 specific areas covering general ability, oral language, reading, written language, math, study skills, motivation, social skills, attention, and nonverbal skills. Correspondences in the absolute and relative ratings of parents, teachers, and students across the 21 skill areas were examined. The parents' ratings were consistent with those of the teachers in 16 areas and significantly lower than the teachers in 5 areas. The students' ratings were generally higher than those of their parents and teachers. The student-teacher differences were significant in 6 areas, whereas the student-parent differences were significant in 11 areas. Although generally lower in absolute terms than the ratings of their children, the parents' relative ratings were strikingly parallel to their children's ratings across skill areas (r = 80). Differences in the reference groups used for the ratings did not seem to account for the discrepant ratings. Possible implications of the differing perceptions of students' learning disabilities for students' self-esteem and academic progress are discussed.

A molecular approach to bone regeneration

Bone morphogenetic proteins (BMPs) are becoming increasingly recognised as valuable molecular tools for regenerating bone and accelerating fracture healing. New bone growth is the result of BMP-induced differentiation of pluripotent mesenchymal cells along osteoblastic pathways. This phenomenon recapitulates in adults specific aspects of skeletal morphogenesis co-ordinated by BMPs during development. An understanding of the basic scientific research which has led to the characterisation and purification of these remarkable molecules is essential if their full therapeutic potential is to be realised.

Vinylpyridine: an unusual cause of a chemical burn

A case of a chemical burn following cutaneous exposure to vinylpyridine is presented. This unusual injury was distinguished by the delay in onset of pain and erythema, followed by gradual resolution leaving patchy skin discolouration. The properties of vinylpyridine are outlined. This case illustrates the dangers of long-term chemical storage and the importance of proper disposal.

Surgical management of regional lymph nodes in primary cutaneous malignant melanoma

The management of regional lymph nodes in the patient with primary cutaneous malignant melanoma remains a contentious issue. Early removal of nodes, which may harbour occult microscopic disease before the development of clinically detectable malignant lymphadenopathy, is thought by some to confer a survival advantage and/or improve locoregional tumour control. While tumour burden at lymphadenectomy has been shown to correlate with prognosis, there are conflicting reports regarding the efficacy of elective lymph node dissection (ELND) compared with a regimen of delayed therapeutic dissection for clinically detectable nodal involvement. Evaluation of arguments for and against ELND, together with consideration of surgical morbidity and the predictability of lymphatic drainage patterns, has allowed a clinical algorithm to emerge which may identify patients who may benefit from prophylactic surgery. A chronological summary of the relevant studies is presented and the overall division of opinion regarding the efficacy of ELND is discussed.

The conceptual basis for morpheme learning problems in children with specific language impairment

Two groups of children were exposed to instances of a nonlinguistic conceptual rule under controlled instructional conditions to determine whether the problems children with specific language impairment (SLI) have learning and accessing language rules extend beyond the language domain into the general cognitive domain. The performance of 20 children with SLI, aged 5:0 to 6:11 (years:months), was compared to that of 20 normally developing children matched for age and nonverbal ability. These children were taught under two instructional conditions that differed only in whether the child was asked to imitate the solution to a conceptual problem after each demonstration (imitation) or merely to observe it (modeling). Contrary to previous findings regarding linguistic rule-learning using auditory or visual symbol systems and similar instructional conditions, no difference was found between the extent of overall learning displayed by the normally developing children and those with SLI. Also, the performance of the children with SLI was not uniquely better under the imitation condition than under modeling, as had been the case with the learning of a novel morpheme in an auditory linguistic task. These results are interpreted as confirming the earlier assumption that the generally lower overall learning rate of the children with SLI on both the auditory and visual tasks reflects a specific linguistic rule-learning difficulty, rather than a general deficiency in rule induction.

Indoor radon maps of the United States

A recently published compilation of average radon levels in 1,729 U.S. counties with standard errors of approximately 20% is used to generate maps exhibiting these results and showing correlations over multicounty areas. Several large areas and numerous smaller areas with high radon levels are identified.

Induction of a visual symbolic rule in children with specific language impairment

In a design modeled after that of Connell and Stone (1992), two alternative instructional conditions (Modeling and Imitation) were used to teach a novel morpheme to a group of 21 children with Specific Language Impairment (SLI) (ages 5:0 to 6:11) and to 25 age- and ability-matched peers and 21 language-matched younger peers. In contrast to the use of the auditory modality in the Connell and Stone study, in the present study, the morphemes were embodied in a visual symbol system. The objects and meanings conveyed by the symbols were identical to those used in the earlier study. The present results indicated that both the children with SLI and their age-matched peers showed a benefit to their morpheme production from the requirement to imitate the use of the morpheme during learning trials. These results were interpreted as indicating that the group-specific benefit from imitation instruction on the part of the children with SLI found by Connell and Stone with their auditory task is unique to morpheme learning in the auditory modality. As in the earlier study, the children with SLI also tended to learn less than their age-matched peers in all conditions, indicating a possible general deficiency with symbolic rule induction.

Leucogyrophana pinastri, a wood decay fungus as a probable cause of an extrinsic allergic alveolitis syndrome

Two patients were suspected of having extrinsic allergic alveolitis due to exposure to an agent in their home environment. On inspection of their houses, fungal decay was evident in the floorboards, and fungal spores were found deposited on many surfaces. The decay fungus was later identified as Leucogyrophana pinastri. Using an extract of the fruiting bodies and mycelium of this fungus, precipitating antibodies were identified in the sera of both patients. Based on the known exposure by the two patients to these small spores, the absence of a likely alternative allergen, the similarity between these two cases, and the positive precipitin test results, L. pinastri was considered to be the most likely cause of extrinsic allergic alveolitis in our cases.

The role of bronchoalveolar lavage in the diagnosis of suspected opportunistic pneumonia

We report 50 immunocompromised patients with pulmonary infiltrates who underwent fibreoptic bronchoscopy, including bronchoalveolar lavage, on 56 occasions. The underlying diseases were mostly lymphoma, leukemia, other malignancies and renal failure. The commonest immunodeficiency factors were chemotherapy, steroids and neutropenia. A positive diagnosis could be made from analysis of the bronchoalveolar lavage on 59% (33/56) occasions. This was a comparable yield to transbronchial lung biopsy 57% (16/27), and superior to proximal airways wash 24% (13/55), or bronchial brushings 29% (10/34). Open lung biopsy added additional diagnostic information in three of the four cases in which it was performed. The most common final diagnoses were bacterial, viral or Pneumocystis carinii pneumonia and recurrent malignancy. We conclude that bronchoalveolar lavage is a safe procedure with a high diagnostic yield in the immunocompromised host with suspected opportunistic pneumonia.

On the pharmacology of L-645,151: a topically effective ocular hypotensive carbonic anhydrase inhibitor

L-645,151 [(2-sulfamoyl-6-benzothiazolyl)-2,2-dimethylpropionate] is the O-pivaloyl ester of L-643,799 (6-hydroxybenzothiazole-2-sulfonamide), topically administered L-645,151 being a substrate for ocular esterases with the resultant liberation of the active moiety, L-643,799, during penetration of the ocular surface. The minimum concentrations of topically administered suspensions (1 drop of 50 microliters into both eyes) of L-645,151, L-643,799, dichlorphenamide and methazolamide significantly lowering the elevated intraocular pressure (IOP) of the alpha-chymotrypsinized rabbit eye were 0.25, 2, 10 and 5%, respectively. IOP was not significantly decreased by 10% suspensions of acetazolamide or ethoxzolamide. The IOP lowering action of L-645,151 was local as the unilateral instillation of L-645,151 (0.25%) into the contralateral eye was devoid of effect in alpha-chymotrypsinized rabbits. L-645,151 (2%) decreased aqueous humor inflow in both the conscious rabbit and the anesthetized dog. Outflow facility in the conscious rabbit was unaltered by a 10% suspension of L-645,151. Low peak levels (0.52 microgram/g) of L-643,799 were present in rabbit renal cortex after the instillation of L-645,151 (2%) into both eyes; this treatment did not induce diuresis in the conscious rabbit. The corresponding maximum concentration in the iris + ciliary body was 4.01 micrograms/g. These preclinical studies reveal that L-645,151 is the most potent, topically effective ocular hypotensive carbonic anhydrase inhibitor described to date.

Studies on L-640,035: a novel antagonist of contractile prostanoids in the lung

The effects of L-640,035 (3-hydroxymethyl-dibenzo [b,f] thiepin-5,5-dioxide) have been studied on pulmonary smooth muscle contraction in vitro and in vivo. When studied in vitro on guinea-pig tracheal chains, L-640,035 produced significant shifts in the dose-response curves to a prostaglandin (PG) endoperoxide analogue (U-44069) (pA2 7.0), PGF2 alpha (pA2 5.9) and PGD2 (pA2 6.5). L-640,035 produced no significant shift in the dose-response curves to leukotriene D4 or histamine and produced a small but statistically significant shift in the dose-response curve to 5-hydroxytryptamine (5-HT) (pA2 5.2). With the exception of PGF2 alpha, Schild analysis did not in general indicate competitive inhibition. The main metabolite of L-640,035, L-636,499, also produced significant parallel shifts in the dose-response curves to U-44069 (pA2 6.0) and PGF2 alpha (pA2 6.0), but with some reduction in the maximal contraction. When L-640,035 was administered intravenously to guinea-pigs, significant inhibition of increases in pulmonary resistance or insufflation pressure induced by U-44069 (ED50 0.16 mg kg-1), leukotriene D4 (ED50 0.25 mg kg-1) and 5-HT (ED50 3.4 mg kg-1) but not histamine (ED50 greater than 10 mg kg-1) was observed. When L-640,035 was administered intravenously to dogs a significant inhibition of increases in pulmonary resistance induced by U-44069 (ED50 0.85 mg kg-1) but not histamine (ED50 greater than 30 mg kg-1) was observed. 5 When L-640,035 was administered by the intraduodenal route to dogs at doses of 3 and 10 mg kg- significant inhibition of increases in pulmonary resistance induced by sodium arachidonate (3 mgkg1 i.v.) was observed with a duration of action of > 255 min. 6 It is concluded that L-640,035 is a novel, relatively selective, and orally active antagonist of the actions of contractile prostanoids on pulmonary smooth muscle.

R-enantiomer of timolol: a potential selective ocular antihypertensive agent

Various studies were conducted to evaluate the effects of timolol, an S-enantiomer, relative to its R-enantiomer upon intraocular pressure and related ocular systems in the rabbit. The R-enantiomer was about one-third as potent as timolol in displacing 3H-dihydroalprenolol binding to iris-ciliary body tissue, reducing aqueous humor formation, and lowering intraocular pressure of alpha-chymotrypsin hypertensive eyes. In contrast, the R-enantiomer was 50 to 90 times less potent than timolol in antagonizing the effects of isoproterenol on pulmonary and atrial beta-adrenergic receptors. The data indicate that the R-enantiomer may lower intraocular pressure in man at concentrations less likely than timolol to block extraocular beta-adrenergic receptors. Finally, to account for the differential effect of the R-enantiomer upon ocular as opposed to extraocular beta-adrenergic receptors, it is tentatively suggested that this agent may also act upon a population of ocular beta-adrenergic receptors showing relatively poor stereoselectively.

A social interactional analysis of learning disabilities remediation

The remediation of learning—disabled children can often be viewed as providing them with strategies which they can use to direct their own behavior. Insight into why such strategic assistance is effective can be obtained from viewing remediation as a social/communicative setting. This perspective is illustrated with an analysis of an annotated transcript of a remediation session. The analysis makes use of Vygotsky's (1978) notions of “other regulation” and “self regulation” and Rommetveit's (1979) notion of communication as the creation of presuppositions in the listener. The implications of the perspective for our understanding of the remediation process and its differential efficacy are discussed.