Reducing everyday memory and planning problems by means of a paging system: a randomised control crossover study

OBJECTIVES

To evaluate a paging system designed to improve independence in people with memory problems and executive deficits.

METHODS

After a successful pilot study, a randomised control trial was conducted involving a crossover design with 143 people aged between 8 and 83 years. All had one or more of the following: memory, planning, attention, or organisation problems. Most had sustained a traumatic head injury or a stroke although a few had developmental learning difficulties or other conditions. The crossover design ensured that some people received a pager after a 2 week baseline whereas others were required to wait for 7 weeks after the baseline before receiving the pager. Participants were assessed at three time periods-namely, at baseline, 7 weeks, and at 14 weeks postbaseline.

RESULTS

More than 80% of those who completed the 16 week trial were significantly more successful in carrying out everyday activities (such as self care, self medication, and keeping appointments) when using the pager in comparison with the baseline period. For most of these, significant improvement was maintained when they were monitored 7 weeks after returning the pager.

CONCLUSIONS

This particular paging system significantly reduces everyday failures of memory and planning in people with brain injury.

Compensating for cognitive deficits following brain injury

Two of the most important goals of rehabilitation are to (a) reduce everyday consequences of impaired cognitive functioning (disabilities) and (b) reduce the level of handicap (the extent to which these problems prevent successful return to society). One of the ways by which we can achieve these goals is to enable people to compensate for their cognitive deficits. This paper (i) describes a theoretical framework for understanding compensatory behavior, (ii) discusses different forms of compensation, (iii) considers compensation for several cognitive disorders, and (iv) presents suggestions for predicting which patients will find it easy to compensate and which require more intensive and focused rehabilitation.

Adapting the Rivermead Behavioural Memory Test Extended Version (RBMT-E) for people with restricted mobility

OBJECTIVES

The study aimed to facilitate use of the RBMT-E with people who have impaired mobility by devising substitute tasks for the route and message subtests that do not require the individual to move around, and by presenting normative data for these substitute tasks.

DESIGN

A within-subjects design was used to assess a standardization sample. Participants completed two parallel versions of the tasks in counter-balanced order in two test sessions approximately 1 week apart.

METHODS

Substitute versions of the route and message subtests not requiring the individual to move around the test room were devised using commercially available materials. These were administered to participants along with other RBMT-E subtests. Scores for each version were compared for the group as a whole and for subgroups divided according to age, gender and IQ. Based on the results, profile scores were derived for each task using box plot analysis. The participants (N = 111) were part of the standardization sample for the RBMT-E and comprised consecutive series of recruits in two centres, Cambridge (UK) and Sydney (Australia).

RESULTS

Normative data are presented in the form of mean scores for the group as a whole, for men and women, for people aged under 30, 30 to 50, and over 50 years, and for people with an IQ of either 90-110 or over 110. Profile score transformations for the substitute tasks are provided.

CONCLUSIONS

Where mobility problems preclude the use of the route and message subtests of the RBMT-E, the 'model' tasks described here can be substituted and profile scores calculated. This allows clinicians to obtain a full spectrum of subtest scores for the RBMT-E with mobility-impaired patients, thus allowing the calculation of a total profile score.

Lithium and protein kinase C modulators regulate swelling-activated K-Cl cotransport and reveal a complete phosphatidylinositol cycle in low K sheep erythrocytes

K-Cl cotransport (COT), a ouabain-insensitive, Cl-dependent bidirectional K flux, is ubiquitously present in all cells, plays a major role in ion and volume homeostasis, and is activated by cell swelling and a variety of chemical interventions. Lithium modulates several cation transport pathways and inhibits phospholipid turnover in red blood cells (RBCs). Lithium also inhibits K-Cl COT by an unknown mechanism. To test the hypothesis whereby Li inhibits swelling-activated K-Cl COT by altering either its osmotic response, its regulation, or by competing with K for binding sites, low K (LK) sheep (S) RBCs were loaded with Li by Na/Li exchange or the cation ionophore nystatin. K-Cl COT was measured as the Cl-dependent, ouabain-insensitive K efflux or Rb influx. The results show that Li altered the cell morphology, and increased both cell volume and diameter. Internal (Li(i)) but not external (Li(o)) Li inhibited swelling-activated K-Cl COT by 85% with an apparent K(i) of approximately 7 mm. In Cl, Li(i) decreased K efflux at relative cell volumes between 0.9 and 1.2, and at external pHs between 7.2 and 7.4. Li(i) reduced the V(max) and increased the K(m) for K efflux in Cl. Furthermore, Li(i) increased the production of diacylglycerol in a bimodal fashion, without significant effects on the phosphatidylinositol concentration, and revealed the presence of a complete PI cycle in LK SRBCs. Finally, phorbol ester treatment and PD89059, an inhibitor of mitogen-activated protein kinase (ERK2) kinase, caused a time-dependent inhibition of K-Cl COT. Hence, Li(i) appears to inhibit K-Cl COT by acting at an allosteric site on the transporter or its putative regulators, and by modulation of the cellular phospholipid metabolism and a PKC-dependent regulatory pathway, causes an altered response of K-Cl COT to pH and volume.

Differential modulation and subsequent blockade of mitogenic signaling and cell cycle progression by Pasteurella multocida toxin

The intracellularly acting protein toxin of Pasteurella multocida (PMT) causes numerous effects in cells, including activation of inositol 1,4,5-trisphosphate (IP(3)) signaling, Ca(2+) mobilization, protein phosphorylation, morphological changes, and DNA synthesis. The direct intracellular target of PMT responsible for activation of the IP(3) pathway is the G(q/11)alpha-protein, which stimulates phospholipase C (PLC) beta1. The relationship between PMT-mediated activation of the G(q/11)-PLC-IP(3) pathway and its ability to promote mitogenesis and cellular proliferation is not clear. PMT stimulation of p42/p44 mitogen-activated protein kinase occurs upstream via G(q/11)-dependent transactivation of the epidermal growth factor receptor. We have further characterized the effects of PMT on the downstream mitogenic response and cell cycle progression in Swiss 3T3 and Vero cells. PMT treatment caused dramatic morphological changes in both cell lines. In Vero cells, limited multinucleation, nuclear fragmentation, and disruption of cytokinesis were also observed; however, a strong mitogenic response occurred only with Swiss 3T3 cells. Significantly, this mitogenic response was not sustained. Cell cycle analysis revealed that after the initial mitogenic response to PMT, both cell types subsequently arrested primarily in G(1) and became unresponsive to further PMT treatment. In Swiss 3T3 cells, PMT induced up-regulation of c-Myc; cyclins D1, D2, D3, and E; p21; PCNA; and the Rb proteins, p107 and p130. In Vero cells, PMT failed to up-regulate PCNA and cyclins D3 and E. We also found that the initial PMT-mediated up-regulation of several of these signaling proteins was not sustained, supporting the subsequent cell cycle arrest. The consequences of PMT entry thus depend on the differential regulation of signaling pathways within different cell types.

Assessing subtle memory impairments in the everyday memory performance of brain injured people: exploring the potential of the extended Rivermead Behavioural Memory Test

A substantial number of brain injured patients complain of memory deficits, despite achieving scores within the normal range on tests of memory functioning. The Rivermead Behavioural Memory Test is an ecologically valid test used to assess everyday memory problems. This test is effective at detecting moderate to-severe impairments, yet subtle memory deficits may go undetected for some patients who achieve a score within the normal range. The initial development of an extended version of this test (RBMT-E), designed to detect subtle decrements in memory performance, has recently been described. The performance of 16 brain injured patients was assessed on both the RBMT and the KBMT-E. The performance of these patients on the RBMT-E was compared with that of matched controls. Overall, the patients performed significantly worse than the controls, and showed particular difficulty in two subtests involving recalling a route and remembering to deliver a message. Those patients who scored in the 'normal' range on the RBMT could be further differentiated on the basis of their RBMT-E scores into 'good', 'average' and 'poor' performance categories. The patients' performance was not significantly associated with general intellectual ability. These results suggest that the RBMT-E may be a useful clinical tool to aid therapists in the assessment of subtle impairments of everyday memory performance following brain injury.

The Wessex Head Injury Matrix (WHIM) main scale: a preliminary report on a scale to assess and monitor patient recovery after severe head injury

OBJECTIVE

To develop a behavioural assessment based on observations of patients recovering after severe head injury whereby data could be collected by observation and by testing everyday tasks.

DESIGN

A prospective observational study of a cohort of 88 consecutive hospital admissions with severe head injury.

SETTING

Two district general hospitals in the UK.

PATIENTS

Eighty-eight consecutive admissions with severe traumatic head injury. Ages ranged from 14 to 67 years, mean coma duration was 14 days and mean duration of post traumatic amnesia (PTA) was 56 days.

RESULTS

Fifty-eight items of behaviour were identified. Paired preference analysis was used to identify a sequence of recovery of these behaviours. The sequence began with arousal and led on to behaviours signalling recovery of social interaction and communication. Subsequent behaviours indicated increasing cognitive organization and return of orientation and memory. The behaviours on the scale are hierarchical and range from coma to emergence from PTA.

CONCLUSIONS

A scale to assess patients and monitor cognitive recovery after severe head injury has been developed. While individual patients will show some departures from the sequence identified, the scale helps to make explicit the earliest stages of natural recovery patterns after head injury.

Coupling function of endogenous alpha(1)- and beta-adrenergic receptors in mouse cardiomyocytes

Genetically altered mouse models constitute unique systems to delineate the role of adrenergic receptor (AR) signaling mechanisms as modulators of cardiomyocyte function. The interpretation of results from these models depends on knowledge of the signaling properties of endogenous ARs in mouse cardiomyocytes. In the present study, we identify for the first time several defects in AR signaling in cardiomyocytes cultured from mouse ventricles. beta(1)-ARs induce robust increases in cAMP accumulation and the amplitude of the calcium and cell motion transients in mouse cardiomyocytes. Selective beta(2)-AR stimulation increases the amplitude of calcium and motion transients, with only a trivial rise in cAMP accumulation in comparison. beta(2)-AR responses are not influenced by pertussis toxin in cultured mouse cardiomyocytes. alpha(1)-ARs fail to activate phospholipase C, the extracellular signal-regulated protein kinase, p38-MAPK, or stimulate hypertrophy in mouse cardiomyocytes. Control experiments establish that this is not due to a lesion in distal elements in the signaling machinery, because these responses are induced by protease-activated receptor-1 agonists and phospholipase C is activated by Pasteurella multocida toxin (a G(q) alpha-subunit agonist). Surprisingly, norepinephrine activates p38-MAPK via beta-ARs in mouse cardiomyocytes, but beta-AR activation of p38-MAPK alone is not sufficient to induce cardiomyocyte hypertrophy. Collectively, these results identify a generalized defect in alpha(1)-AR signaling and a defect in beta(2)-AR linkage to cAMP (although not to an inotropic response) in cultured mouse cardiomyocytes. These naturally occurring vagaries in AR signaling in mouse cardiomyocytes provide informative insights into the requirements for hypertrophic signaling and impact on the value of mouse cardiomyocytes as a reconstitution system to investigate AR signaling in the heart.

Improvement or simply practice? The effects of twenty repeated assessments on people with and without brain injury

Measuring recovery of function may mean testing the same individual many times, a procedure that is inevitably open to improvement due to learning on the specific tests rather than recovery per se. This is particularly likely to be an issue with measures of memory performance. We therefore studied the performance of normal and brain-injured people across 20 successive test sessions on measures of orientation, simple reaction time, forward and backward digit span, visual and verbal recognition, word list learning and forgetting, and on three semantic memory measures, namely, letter and category fluency and speed of semantic processing. Differences in overall performances between the two groups occurred for all tests other than orientation, digit span forward, and simple reaction time, although the tests differed in their degree of sensitivity. The tests varied in the presence or absence of practice effects and in the extent to which these differed between the two groups. Data are presented that should allow investigators to select measures that are likely to optimize sensitivity while minimizing possible confounding due to practice effects.

Rehabilitation of executive functioning: an experimental-clinical validation of goal management training

Two studies assessed the effects of a training procedure (Goal Management Training, GMT), derived from Duncan's theory of goal neglect, on disorganized behavior following TBI. In Study 1, patients with traumatic brain injury (TBI) were randomly assigned to brief trials of GMT or motor skills training. GMT, but not motor skills training, was associated with significant gains on everyday paper-and-pencil tasks designed to mimic tasks that are problematic for patients with goal neglect. In Study 2, GMT was applied in a postencephalitic patient seeking to improve her meal-preparation abilities. Both naturalistic observation and self-report measures revealed improved meal preparation performance following GMT. These studies provide both experimental and clinical support for the efficacy of GMT toward the treatment of executive functioning deficits that compromise independence in patients with brain damage.

Intervening with everyday memory problems in dementia of Alzheimer type: an errorless learning approach

Dementia of Alzheimer Type (DAT) is increasingly detected at an earlier stage of the disorder, when interventions to assist with everyday memory difficulties might be most valuable. Some learning is possible in DAT and a number of factors have been identified which may facilitate performance, although applications to everyday memory problems have been limited. The concept of errorless learning has not previously been directly examined in relation to DAT, but might provide a useful additional strategy. In the present study, 6 participants with early stage DAT (MMSE scores 21 - 26) received individually tailored interventions, based on errorless learning principles and targeted at a specific everyday memory problem. Five of the participants showed significant improvement on the target measures, and maintained this improvement up to 6 months later. The results suggest that it is feasible to intervene with everyday memory problems in the early stages

Pasteurella multocida toxin stimulates mitogen-activated protein kinase via G(q/11)-dependent transactivation of the epidermal growth factor receptor

The dermatonecrotic toxin produced by Pasteurella multocida is one of the most potent mitogenic substances known for fibroblasts in vitro. Exposure to recombinant P. multocida toxin (rPMT) causes phospholipase C-mediated hydrolysis of inositol phospholipids, calcium mobilization, and activation of protein kinase C via a poorly characterized mechanism involving G(q/11) family heterotrimeric G proteins. To determine whether the regulation of G protein pathways contributes to the mitogenic effects of rPMT, we have examined the mechanism whereby rPMT stimulates the Erk mitogen-activated protein kinase cascade in cultured HEK-293 cells. Treatment with rPMT resulted in a dose and time-dependent increase in Erk 1/2 phosphorylation that paralleled its stimulation of inositol phospholipid hydrolysis. Both rPMT- and alpha-thrombin receptor- stimulated Erk phosphorylation were selectively blocked by cellular expression of two peptide inhibitors of G(q/11) signaling, the dominant negative mutant G protein-coupled receptor kinase, GRK2(K220R), and the Galpha(q) carboxyl-terminal peptide, Galpha(q)-(305-359). Like alpha-thrombin receptor-mediated Erk activation, the effect of rPMT was insensitive to the protein kinase C inhibitor GF109203X, but was blocked by the epidermal growth factor receptor-specific tyrphostin, AG1478 and by dominant negative mutants of mSos1 and Ha-Ras. These data indicate that rPMT employs G(q/11) family heterotrimeric G proteins to induce Ras-dependent Erk activation via protein kinase C-independent "transactivation" of the epidermal growth factor receptor.

Polycythemia decreases fatigue in tetanic contractions of canine skeletal muscle

PURPOSE

The effects of an acute polycythemia on muscle fatigue development were investigated in the self-perfused canine gastrocnemius in situ.

METHODS

Following isolation of the gastrocnemius, dogs (N = 5) were made polycythemic through a bolus injection of packed erythrocytes (hematocrit (Hct) = 90-92%) to raise systemic Hct to 63.5 +/- 0.5%. Subsequently, the gastrocnemius was stimulated, through the sciatic nerve, to perform 20 min of isotonic tetanic contractions (60 x min(-1), 200 ms, 50Hz). Control (normocythemic) animals (N = 5) underwent an identical contraction regimen.

RESULTS

Although blood flow to the gastrocnemius was not different at any time, oxygen delivery was significantly increased during polycythemia (peak = 33.7 +/- 2.2 mL x 100 g(-1) x min-1) over control (peak = 25.1 +/- 2.1 mL x 100 g(-1)x min(-1)) at all times during contraction. Oxygen uptake by the gastrocnemius, although consistently increased, was not significantly different between the normocythemic and polycythemic conditions at any time. The rate of fatigue was significantly decreased over the first 6 min of contraction in polycythemic animals (3.5 +/- 0.6% x min(-1)) when compared with controls (5.8 +/- 0.7% x min(-1)). Subsequent fatigue development was not different between groups. As a result of the early rate differences in fatigue, however, the work production in polycythemic animals was significantly greater than in normocythemic dogs for the duration of the contraction period.

CONCLUSION

We conclude that during high metabolic rate isotonic tetanic contractions, muscle fatigue development is diminished by polycythemia, but the ergogenic effect appears to be transient.

Current management of AIDS and related opportunistic infections

Significant changes in acquired immunodeficiency syndrome (AIDS) epidemiology and AIDS treatment strategies have emerged in the 17 years since the first case of this disease was reported. In the United States, the human immunodeficiency virus (HIV) is now primarily acquired through heterosexual relationships and intravenous drug use. As a result, dramatic increases in the number of AIDS cases in the female, African American, and Hispanic populations are evident. Treatment strategies now focus on maximal viral suppression and preventing drug resistance. Advances in anti-retroviral therapy and chemoprophylaxis of opportunistic infections have increased the long-term survival of AIDS patients by 10 to 20 years. However, despite abundant research and advances in medical care, AIDS continues to be a devastating epidemic worldwide.

Measuring recovery from post traumatic amnesia

Three groups of participants were assessed. Each participant was tested on 20 occasions. The groups comprised people (i) in post traumatic amnesia (PTA) following severe head injury (n=9), (it) with severe head injury but not in PTA (n=10), and (iii) with no history of head injury or other neurological condition (n=13). Subjects were given several tests of memory, attention and learning in order to determine which tests were good at (a) distinguishing people in PTA from those not in PTA, and (b) monitoring recovery over time. The results indicate that people in PTA have a wide range of deficits and their cognitive recovery is a gradual process rather than an all-or-none phenomenon. In terms of measurement, the study suggests that a good test of PTA should include orientation questions, together with a reaction time measure, a visual recognition test and a speed of information processing measure. Most of the tests administered were good at distinguishing between brain-injured and nonbrain-injured people, although only two tests distinguished between the two brain-injured groups, i.e. those in PTA and those out of PTA. Almost all tests were good at monitoring recovery from PTA.

Criterion-based validity of an intracarotid amobarbital recognition-memory protocol

PURPOSE

We tested whether the behavioral components of an Intracarotid Amobarbital Protocol (IAP) had criterion validity. It was hypothesized that a recognition-memory test designed for intracarotid injections and used to predict the risk of global amnesia before an elective temporal lobectomy should also identify persons who are severely amnesic due to other neurologic causes. Divergent validity predicts that speech tasks would be unaffected by amnesia. Test-retest reliability also was measured.

METHODS

Fifteen persons with severe amnesia were administered four alternate forms of a yes/no recognition-memory protocol and a speech protocol. No drug injection occurred. Standardized neuropsychological tests were used to divide the amnesic group into those with Global Amnesia (i.e., retain no ongoing memories), Severe Amnesia (i.e., memory impaired), and Amnesia Plus (severe amnesia plus other neuropsychologic deficits).

RESULTS

Two persons with Global Amnesia obtained scores at or below chance (i.e., failed) on the memory protocol. Unexpectedly, 12 of 13 severely amnesic persons obtained near-perfect memory scores. Amnesia had no impact on the speech protocol. Pass/Fail outcomes were highly correlated across all four sets.

CONCLUSIONS

A four-item IAP memory protocol showed good reliability and criterion validity in identifying the rare condition of Global Amnesia, but it was insensitive to other disabling, severe amnesic disorders. This IAP memory protocol might have validity in predicting a postsurgical Global Amnesic disorder, but it did not identify and therefore could not predict other more common severe amnesic disorders.

Myotonic dystrophy and progressive cognitive decline: a common condition or two separate problems?

We report the case of NG, a 43-year old woman with myotonic dystrophy (MYD) who has shown a slow decline in both motor and cognitive abilities since her referral to us at age 32. MYD is an autosomal dominant disorder characterised by weakening and wasting of the muscles together with impaired muscle relaxation. Cognitive abilities are usually little affected in the adult onset form, although there is a high risk of cognitive impairment in those with childhood onset. Cognitive decline is also typically associated with maternal inheritance. NG, who was diagnosed with MYD at the age of 18, inherited it from her father. We report the decline in NG's cognitive abilities over 11 years of longitudinal assessment, and consider whether she is an atypical MYD patient or whether the MYD and cognitive decline are attributable to two separate pathological processes.

Localization of the intracellular activity domain of Pasteurella multocida toxin to the N terminus

We have shown that Pasteurella multocida toxin (PMT) directly causes transient activation of Gqalpha protein that is coupled to phosphatidylinositol-specific phospholipase Cbeta1 in Xenopus oocytes (B. A. Wilson, X. Zhu, M. Ho, and L. Lu, J. Biol. Chem. 272:1268-1275, 1997). We found that antibodies directed against an N-terminal peptide of PMT inhibited the toxin-induced response in Xenopus oocytes, but antibodies against a C-terminal peptide did not. To test whether the intracellular activity domain of PMT is localized to the N terminus, we conducted a deletion mutational analysis of the PMT protein, using the Xenopus oocyte system as a means of screening for toxin activity. Using PCR and conventional cloning techniques, we cloned from a toxinogenic strain of P. multocida the entire toxA gene, encoding the 1,285-amino-acid PMT protein, and expressed the recombinant toxin as a His-tagged fusion protein in Escherichia coli. We subsequently generated a series of N-terminal and C-terminal deletion mutants and expressed the His-tagged PMT fragments in E. coli. These proteins were screened for cytotoxic activity on cultured Vero cells and for intracellular activity in the Xenopus oocyte system. Only the full-length protein without the His tag exhibited activity on Vero cells. The full-length PMT and N-terminal fragments containing the first 500 residues elicited responses in oocytes, but the C-terminal 780 amino acid fragment did not. Our results confirm that the intracellular activity domain of PMT is localized to the N-terminal 500 amino acids of the protein and that the C terminus is required for entry into cells.

The ecological validity of tests of executive function

Ninety-two mixed etiology neurological patients and 216 control participants were assessed on a range of neuropsychological tests, including 10 neuropsychological measures of executive function derived from 6 different tests. People who knew the patients well (relatives or carers) completed a questionnaire about the patient's dysexecutive problems in everyday life, and this paper reports the extent to which the tests predicted the patients' everyday life problems. All of the tests were significantly predictive of at least some of the behavioral and cognitive deficits reported by patients' carers. However, factor analysis of the patients' dysexecutive symptoms suggested a fractionation of the dysexecutive syndrome, with neuropsychological tests loading differentially on 3 underlying cognitive factors (Inhibition, Intentionality, and Executive Memory), supporting the conclusions that different tests measure different cognitive processes, and that there may be limits to the fractionation of the executive system.

Assessment after extremely severe head injury in a case of life or death: further support for McMillan

This paper is a sequel to that of McMillan (1997) and describes further assessment of an extremely severely head injured patient. A combination of direct observations, structured interviews with staff, simple cognitive tests and questions with yes/no answers were used to assess communication and cognitive function in an extremely severely head injured patient with minimal ability to respond. Results confirmed the finding of McMillan and showed that the patient could understand and respond consistently to simple commands, could answer simple autobiographical questions consistently and clearly expressed her wish to live. The results of this study and that of McMillan confirm that valid assessment of minimally responsive patients is possible and that a number of different approaches are appropriate.

External cueing systems in the rehabilitation of executive impairments of action

The use of a mnemonic cueing system (NeuroPage) and a paper and pencil checklist in the rehabilitation of executive problems in a 50-year-old woman are described. Following a CVA 7 years earlier, the patient, despite intact general intellectual and memory functioning, had specific executive impairments of attention, planning, realizing intended actions, and also exhibited behavioral routines similar in form to obsessive-compulsive rituals. In a series of ABAB single-case experimental designs, the efficacy of 2 external cueing systems in prompting appropriately timed action is demonstrated. It is argued that the combination of external control and increased sustained attention to action were critical to the success of NeuroPage with this patient. Furthermore it is hypothesized that the checklist was effective in facilitating the patient's ability to foresee and recognize the consequences of her actions, which in turn had an impact on the probability of her changing those same actions.

Genetic heterogeneity in familial hyperinsulinism

Familial hyperinsulinism (HI) is a disorder characterized by dysregulation of insulin secretion and profound hypoglycemia. Mutations in both the Kir6.2 and sulfonylurea receptor (SUR1) genes have been associated with the autosomal recessive form of this disorder. In this study, the spectrum and frequency of SUR1 mutations in HI and their significance to clinical manifestations of the disease were investigated by screening 45 HI probands of various ethnic origins for mutations in the SUR1 gene. Single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses of genomic DNA revealed a total of 17 novel and three previously described mutations in SUR1 . The novel mutations comprised one nonsense and 10 missense mutations, two deletions, three mutations in consensus splice-site sequences and an in-frame insertion of six nucleotides. One mutation occurred in the first nucleotide binding domain (NBF-1) of the SUR1 molecule and another eight mutations were located in the second nucleotide binding domain (NBF-2), including two at highly conserved amino acid residues within the Walker A sequence motif. The majority of the remaining mutations was distributed throughout the three putative transmembrane domains of the SUR1 protein. With the exception of the 3993-9G-->A mutation, which was detected on 4.5% (4/88) disease chromosomes, allelic frequencies for the identified mutations varied between 1.1 and 2.3% for HI chromosomes, indicating that each mutation was rare within the patient cohort. The clinical manifestations of HI in those patients homozygous for mutations in the SUR1 gene are described. In contrast with the allelic homogeneity of HI previously described in Ashkenazi Jewish patients, these findings suggest that a large degree of allelic heterogeneity at the SUR1 locus exists in non-Ashkenazi HI patients. These data have important implications for genetic counseling and prenatal diagnosis of HI, and also provide a basis to further elucidate the molecular mechanisms underlying the pathophysiology of this disease.

Recovery of cognitive functions following nonprogressive brain injury

It has recently become clear that the adult human brain is capable of more plasticity than previously thought. Investigations into the natural history of change following brain injury demonstrate that partial recovery of function can and does occur. Furthermore, there is increasing evidence that intervention through re-training or provision of compensatory memory aids can result in improved cognitive functioning.

A nonsense mutation in the inward rectifier potassium channel gene, Kir6.2, is associated with familial hyperinsulinism

ATP-sensitive potassium (K[ATP]) channels are an essential component of glucose-dependent insulin secretion in pancreatic islet beta-cells. These channels comprise the sulfonylurea receptor (SUR1) and Kir6.2, a member of the inward rectifier K+ channel family. Mutations in the SUR1 subunit are associated with familial hyperinsulinism (HI) (MIM:256450), an inherited disorder characterized by hyperinsulinism in the neonate. Since the Kir6.2 gene maps to human chromosome 11p15.1 (1,2), which also encompasses a locus for HI, we screened the Kir6.2 gene for the presence of mutations in 78 HI probands by single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses. A nonsense mutation, Tyr-->Stop at codon 12 (designated Y12X) was observed in the homozygous state in a single proband. 86Rb+ efflux measurements and single-channel recordings of COS-1 cells co-expressing SUR1 and either wild-type or Y12X mutant Kir6.2 proteins confirmed that K(ATP) channel activity was abolished by this nonsense mutation. The identification of an HI patient homozygous for the Kir6.2/Y12X allele affords an opportunity to observe clinical features associated with mutations resulting in an absence of Kir6.2. These data provide evidence that mutations in the Kir6.2 subunit of the islet beta-cell K(ATP) channel are associated with the HI phenotype and also suggest that the majority of HI cases are not attributable to mutations in the coding region of the Kir6.2 gene.