Effect of adenine nucleotides on NAD-dependent isocitrate dehydrogenases in rhizobia and bacteroids of legume root nodules.

ATP, ADP, AMP and cyclic AMP inhibit NAD-dependent isocitrate dehydrogenase (L-s-isocitrate : NAD-+ oxidoreductase, EC 1.1.1.41) from rhizobia but have no effect on the enzyme from corresponding bacteroids. This was observed using three rhizobial strains two of which are effective, and one ineffective, with Lotus pedunculatus. Using partially purified enzyme from each of the three rhizobial strains it was found that the adenine nucleotides inhibit the enzyme by competing with NAD-+, not with isocritrate. The rate of reaction catalysed by the enzyme (expressed as activity per mg protein) in cell-free extracts of each of the effective rhizobial strains was about three times that of the reaction in extracts of the corresponding bacteroids. No correlation was found between effectiveness and NAD-dependent isocitrate dehydrogenase activity in the rhizobial cells.

Developmental dyslexia revisited and projected.

There are three parts to this paper. First, I review briefly the signposts from research, theory, and application in developmental dyslexia in the 1960s and the 1970s that have led us from there to here, and show the pitfalls to avoid. Second, I discuss some of the pertinent issues of the 1980s: the role of intelligence in the diagnosis of children with specific reading disabilities, the distribution of reading difficulties and disabilities, and the important place of verbal efficiency. Third, I project to the 1990s to emphasize the challenge of the computer technology as mediated learning and the challenge of "bounded rationality" and "collective rationality" in education. Throughout this survey, the paramount role of knowledgeable and caring teachers is implicit.

Productive knowledge of derivational rules in poor readers.

The present report with two complementary experiments examined the productive knowledge of derivational morphology in 75 grade 4, 5, and 6 "poor" readers further divided into those performing better, or worse, inboth reading and spelling ((R + S +) or R - S -)), or better in the one or the other (mixed) subgroups. Experiment 1 required individual subjects to vocalize rapidly the derived forms of words when primed with 40 target base words in four derivational conditions or levels embedded in sentence frames shown on the computer screen. Experiment 2 required the reverse process of vocalizing the base forms of words when primed with 40, complex derived forms in the same four morphology conditions embedded in sentence frames shown on the computer screen. Results of the analysis of the reaction times show a developmental trend and that the subgroups of poor readers used different mechanisms in producing derived or base forms of words according to the complexity of the orthographic and/or phonological changes needed in the derivational process. The important role of morphemic structure and origin of words in instruction is emphasized.

What does accessing a morphemic script tell us about reading and reading disorders in an alphabetic script?

This paper discusses the commonalities and differences in the processing mechanism of analytic reading in the English orthography and the Chinese orthography. Readers of English generally use the phonological processing route, although the morphological aspect should also be emphasized. Readers of Chinese would need to take advantage of the morphemic nature of the script, although speech recoding is also used. The interplay of the phonological, morphological, syntactic, and semantic processing is emphasized. Reading disorders may implicate certain processing routes, but may spare other components.

A componential approach to understanding reading and its difficulties in preadolescent readers.

The present study is predicated on the logic of interrelated functional information processing components as an approach to understanding reading and its difficulties in preadolescent readers. The structural equation modelling (and its variants) involved these three latent components: (a) orthographic/phonological component, (b) morphological component, and (c) sentence and paragraph comprehension component. These components were subserved by a total of ten measurable tasks, all administered on-line via the microcomputer under laboratory conditions with reaction time measures as indices of mental representation of word knowledge and sentence/paragraph comprehension. The latent dependent component of reading performance was subserved by standardized vocabulary and reading comprehension tests. The total sample consisted of 298 children in grades, 4, 5, and 6. Maximum likelihood analyses using LISREL show that the data in general do not disconfirm the proposed model for grade 4 readers. The three-component model, with some variables set free, provides a reasonable fit for the grade 5 data but less claim could be made about the goodness of fit for grade 6. The results show the mutually reinforcing and mutually facilitating effects of multilevels and multicomponents of reading. Word structure and word knowledge are particularly predictive of reading. The present Phase 1 work would be validated in a follow-up of another cohort of readers and would also lead to the systematic training of some of the components with poor readers.

Confessions of a schoolman-On dyslexia and laterality.

This paper relates the early work of Samuel Orton on cerebral dominance to the current neuropsychological concept of laterality as reciprocal functions of the two cerebral hemispheres. The genetic-cultural perspectives of laterality and functional asymmetry in relation to learning disorders are discussed. A balanced and integrative view of the cognitive contribution of the two hemispheres is needed.

The effect of systematic training in elaboration on word meaning and prose comprehension in poor readers.

This paper reports two interrelated, exploratory training studies to promote word knowledge and textual comprehension through elaboration in poor readers compared with their controls. The results suggest that systematic, sustained in situ training helped these poor readers, although both the training approaches and stimulus materials would need refinement.

Differential cerebral involvement in perceiving Chinese characters: levels of processing approach.

Three experiments were designed to determine the accuracy and latency with which right-handed Chinese university students (12 females and 12 males) recognized Chinese characters in the left and right visual half-fields (VHFs). The experiments varied in the "depth" of processing required. Experiment 1 was a lexical decision task in which the configuration of the stimulus (a real Chinese character or the mirror image of a real character) determined whether the grapheme was an actual character. Experiment 2 required phonological processing; i.e., subjects had to decide whether a character (or a foil) matched the sound of an orally presented Chinese character. Experiment 3 required semantic processing; i.e., subjects had to decide if a character (or a foil) belonged to a particular semantic category. In each experiment, single characters were presented unilaterally for 150 msec. There was a significant right VHF superiority for accuracy scores for Experiments 2 and 3 but not for Experiment 1. None of the experiments yielded significant visual asymmetries in reaction time. The results do not support previous claims of orthography-specific laterality, but instead show that laterality effects for morphemic stimuli vary with the orthographic, phonological, and semantic processing demands of the task.

Phonological and morphological processing in adult students with learning/reading disabilities.

A target group of college students with learning/reading disabilities was compared with reading-level (RA) and chronological-age (CA) contrast groups on several phonological and morphological computerized information-processing tasks. Results confirm the importance of accurate and rapid processing of simple lexical items to the automatic level. The target students were less accurate and took longer reaction time, as compared with their CA controls, though not with the RA contrast group, in deciding if pseudohomophonics sounded like real words and if pairs of words with different rime conditions rhymed. The target students showed both quantitative and qualitative differences in processing morphological words and morphographic letter strings, in contrast to some earlier findings. The integration of phonological and morphological knowledge is emphasized in working with adult college students with learning/reading disabilities.

The locus of so-called IQ test results in reading disabilities.

It would appear the question of relevance of IQ in the assessment and remediation of children with RD is not quite the relevant question to ask, if only traditional intelligence tests are the focus. From the psychoeducational point of view of refining diagnosis, and from the administrative perspective of accountability, it would be helpful to accept a threshold of something like an IQ of 85 as the lower bound in defining learning or reading disabilities. A discrepancy from this threshold as derived from regression analysis or other more refined analyses and taking into account varying reliabilities, intercorrelations, and standard errors of measurement of different measuring instruments may constitute a learning or reading disability. How discrepant the aptitude-achievement should be to constitute a "significant" difference is a function of, among other factors, the material and human resources available to any particular school system. Leong (1987) has made suggestions for essentially a two-stage assessment leading to more refined diagnosis with the use of well-standardized group tests and teachers' estimates for the first stage (assessment) and more refined individual tests to diagnose those showing discrepant aptitude-learning performance in the border-zone. The rationale is that all those children requiring special services are so served and those in the uncertainty region must be carefully diagnosed so as to minimize so-called "misfits" in accordance with signal detection principles. It should be noted that the diagnosis of learning or reading disabilities can never be exact, even with the use of reliable and valid test instruments, and the "fuzzy set" approach should apply to the process (Horvath, Kass, & Ferrell, 1980).(ABSTRACT TRUNCATED AT 250 WORDS)

Dilated common bile duct in opium addicts with and without biliary symptoms --implication for research in AIDS cholangiopathy.

BACKGROUND: Opium addicts (OA) with no biliary symptoms have been shown to have dilated common bile duct (CBD). Endoscopic retrograde cholangio-pancreatography (ERCP) without biliary drainage in such asymptomatic OA is hazardous. Hence it is not indicated unless there are clear clinical and laboratory evidences of biliary stasis. AIMS: To show that even when matched with controls with the same clinical diagnosis of the biliary system, OA still have significantly larger CBD diameters and that OA with biliary symptoms should be treated no differently from non-OA with biliary symptoms. METHOD: Seven OA (all Chinese males), four of whom had undergone ERCP (three for CBD stones and one for ampullary carcinoma), were compared, using t-test, to 7 age, sex, race and diagnosis-matched controls, four of whom had also undergone ERCP (three for CBD stones and one for ampullary carcinoma). When ERCP was not done, ultrasonography was used to assess the biliary system and measure the CBD diameter. RESULTS: The mean (SD) CBD diameters of OA and controls were 15.7 mm (5.65) and 8.3 mm (5.95) respectively (t = 2.399, p = 0.032). The mean (SD) weight of OA and controls were 55.8 kg (9.22) and 57.3 kg (9.21) respectively (t = -0.305, p = 0.763). Only two of the seven OA were born in China, the remaining five in Malaysia. CONCLUSIONS: OA do get CBD pathology like non-OA and if indicated there should be no qualms about performing ERCP in them. When matched for age, sex, race and clinical diagnosis, OA still have a significantly larger CBD despite no difference in body weight.

Smoking in the Singapore Armed Forces.

The Singapore Armed Forces has, since 1986, established a comprehensive smoking control programme which combines health education, counselling and administrative measures aimed at discouraging non-smokers from smoking, and encouraging smokers to quit the habit. The prevalence of regular smoking decreased from 28.6% in 1987 to 20.7% in 1993. The latest, 1993 survey as in past surveys covered 3,545 respondents, made up of regulars (32.0%), NSF (62.2%) and NUSAF (5.6%). The 1993 survey revealed that the majority of smokers (88.9%) in the SAF who consist primarily of 18 to 20-year-olds, had started smoking before enlistment. Most acquired the habit on their own (49.8%) or through influences outside the SAF (40.3%). Very few smokers became smokers through the influence of fellow soldiers (4.9%). The majority (87.7%) of smokers readily agreed that smoking is harmful, but this is not translated into practice. Health education efforts need to focus more on bringing about positive attitudinal and behavioural changes, rather than merely give information and advice. The young age of smoking onset (mean age of 14.3 years) In the SAF population surveyed points to the need to focus preventive efforts further upstream than hitherto emphasised.

A case report of heparin resistance due to acquired antithrombin III deficiency.

A case of heparin resistance and its management during cardiopulmonary bypass is reported. A patient with a history of post-infarct angina and arrhythmias was treated with intravenous heparin infusion for five days prior to myocardial revascularisation surgery. He required 13,500 IU/kg of heparin to increase his activated clotting time to a therapeutic level for safe institution of cardiopulmonary bypass. This phenomenon of heparin resistance was postulated to be due to consumption of circulating antithrombin III as a result of prior heparinisation. Treatment with fresh frozen plasma restored heparin effectiveness.

Caudal morphine in paediatric patients: a comparison of two different doses in children after major urogenital surgery.

We compared the duration of postoperative analgesia and the occurrence of side-effects of two different doses of caudal morphine in children undergoing major urogenital surgery. Fifty-two children aged between 1 and 12 years were randomly selected to receive caudal morphine, either 25 micrograms.kg-1 (Group A) or 50 micrograms.kg-1 (Group B) with 0.5 ml kg-1 of 0.25% plain bupivacaine immediately before surgery. They were monitored for 24 hours in a high dependency area for known complications of epidural morphine. There was no significant difference in postoperative analgesia between the two doses of caudal morphine. Clinically significant respiratory depression or sedation was not detected in either group. The occurrence of vomiting and pruritus was similar in both groups. Urinary retention was not recorded as all children had an indwelling catheter as required by the surgical procedure. We concluded that 25 micrograms.kg-1 of caudal morphine is as effective as 50 micrograms.kg-1 for providing postoperative analgesia in children undergoing urogenital surgery.

Changing the institutional practice of prolonged mechanical ventilation after coronary artery bypass graft surgery to early extubation.

Since 1997 some of our cardiac anaesthetists have, whenever possible, extubated the patients early after cardiac surgery to improve their level of comfort, to allow an early return of the cardiopulmonary physiological function, and to help reduce health care costs. After a few months of implementing this practice, an audit was carried out to evaluate the success of early extubation after coronary artery bypass graft (CABG) surgery. Over a 6-month period starting from May 1997, the perioperative data of 110 consecutive patients with good or moderate left ventricular function scheduled for elective CABG were prospectively collected and analysed. The anaesthetic regime was according to the preference of the anaesthetists. Initially consent was obtained from the surgeons when the extubation criteria were fulfilled, but subsequently as the practice became more accepted by the surgeons, extubation was initiated by the anaesthetists. Within 4 hours of admission into the intensive care unit (ICU), 50 (45.5%) of the 110 patients satisfied the early extubation criteria and were extubated. The extubation criteria are described in the article. For the remaining patients, the median duration of mechanical ventilation was 14.3 hours. The profiles of the two groups of patients and the possible reasons for not extubating early are discussed. Forty-five per cent of the patients with moderate to good ventricular function were extubated safely within 4 hours of admission into the ICU after CABG surgery. With gradual acceptance of the practice and a change in mindset amongst all the care givers, more patients can benefit from this practice. This article highlights the challenges associated with changing institutional practices with respect to the postoperative care of cardiac patients.

Simultaneous-successive syntheses and planning in chinese readers.

The present study investigated simultaneous-successive syntheses and planning as cognitive processing constructs in 66 grade 4 and 63 grade 6 Chinese children. Principal factor and promax analyses provided evidence of the realities of these independent factors. Simultaneous and successive components contributed to composite reading with varying degrees of variance for each grade. The Luria paradigm provides a useful framework for research into patterns of readers.