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Aims: The aims of this study were to compare the differences in forearm muscle activities between two types of thumb orthoses and the optimal handle diameter when the orthosis is worn during a power grasp for individuals with chronic de Quervain's Tenosynovitis. Methods: A 2 × 3 (Group × orthosis) and a 2 × 2 × 3 (Group × orthosis × diameter) repeated factorial design were used. Grip strength and muscle load were measured. A 2 × 3 mixed repeated measures ANOVA was conducted, and the Least Significant Difference (LSD) test was used for post hoc analysis. Cohen's d was used to calculate the effect size between groups and handle diameters. Results: Grip strength was significantly lower (in long/short/no-orthosis conditions) and muscle load was higher in 12 participants with chronic de Quervain's Tenosynovitis than in 16 healthy participants ( p  < 0.001). No differences in muscle activities were found when the two different orthoses were worn. The muscle activities were higher during grasping of the 33 mm handle diameter. Conclusion: Individuals with chronic de Quervain's Tenosynovitis require greater muscle loads than healthy controls to produce the same power grasp, and when one of the two orthoses is worn, the optimal handle diameters for performing a power grasp are relatively larger (45 and 55 mm).Implications for RehabilitationBoth the long and short thumb orthoses can be worn by individuals with de Quervain's Tenosynovitis during daily activities because wearing both orthoses requires the same exertion of muscle load.When performing a power grasp, individuals with de Quervain's Tenosynovitis tend to exert greater muscle loads than healthy controls to produce the same power grasp.We suggest that patients with de Quervain's Tenosynovitis use utensils with larger handle diameters, such as 45 mm and 55 mm.

Objectives: The objectives of this study were to investigate whether people with rheumatoid arthritis (RA) require greater muscle loads to equal the grip strength of healthy adults and to find the optimal grip distance for people with RA using carpometacarpal and metacarpophalangeal immobilization orthoses as measured by electromyography of the forearm muscles., Method: A 2 × 2 (Group × Orthosis) experiment and a 2 × 3 (Orthosis × Grasp Distance) factorial were conducted. Grip strength and muscle load were measured., Results: Grip strength was significantly lower, and muscle load was greater, in 18 participants with RA than in 18 healthy adults. No effect of orthosis use on grip strength and muscle load was found. Muscle load was lower for the 42.25-mm diameter dynamometer handle than for handles with larger diameters., Conclusion: People with RA require more muscle load than healthy adults to produce the same exertion, and 42.25 mm is recommended for people with RA as the optimal grasp distance., (Copyright © 2017 by the American Occupational Therapy Association, Inc.)

Changes in the CD-1 mouse uterine transcriptome during proestrus and estrus were investigated to help elucidate mechanisms of uterine tissue remodeling during the estrus cycle and their regulation by estrogen and progesterone in preparation of the uterus for pregnancy. Mice were staged beginning at 6 weeks of age, and uterine horns were harvested after monitoring two estrus cycles. Microarray analysis of whole uterine horn RNA identified 2428 genes differentially expressed in estrus compared to proestrus, indicating there is extensive remodeling of mouse uterus during the estrus cycle, affecting ~10% of all protein-encoding genes. Many (~50%) of these genes showed the same differential expression in independent analyses of isolated uterine lumenal epithelial cells. Changes in gene expression associated with structural alterations of the uterus included remodeling of the extracellular matrix, changes in cell keratins and adhesion molecules, activation of mitosis and changes in major histocompatibility complex class II (MHCII) presentation, complement and coagulation cascades, and cytochrome P450 expression. Signaling pathways regulated during the estrus cycle, involving ligand-gated channels, Wnt and hedgehog signaling, and transcription factors with poorly understood roles in reproductive tissues, included several genes and gene networks that have been implicated in pathological states. Many of the molecular pathways and biological functions represented by the genes differentially expressed from proestrus to estrus are also altered during the human menstrual cycle, although not necessarily at the corresponding phases of the cycle. These findings establish a baseline for further studies in the mouse model to dissect mechanisms involved in uterine tissue response to endocrine disruptors and the development of reproductive tract diseases.

Previous studies have proposed that the inner retina is affected in myopes. This study aimed to investigate the changes in adaptive circuitry of the inner retina in myopia, using the global flash multifocal electroretinogram (global flash mfERG) with different levels of contrast (luminance modulation). Fifty-four myopes had global flash mfERG recorded with different contrasts. The direct component (DC) and the induced component (IC) of the mfERG response were pooled into six regions for analysis. The response amplitudes and implicit times at different contrasts were also analysed. Results showed that myopes had significant reduction in the paracentral DC amplitude for the 29% and 49% contrasts and in the paracentral IC amplitude at all contrasts measured. The peripheral IC amplitude for the 49% contrast was also reduced. No significant change was found in implicit time for either DC or IC response. Refractive error explained about 14% of the variance in DC and 16% of the variance in IC amplitude respectively; axial length could not account for additional variance in either paracentral DC or IC amplitudes in the hierarchical regression models used. We concluded that the paracentral retinal region in myopes showed signs of impaired retinal adaptation, suggesting a functional loss at the inner retinal layer. In addition, functions attributed to the outer retinal layer showed only small changes due to myopia., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

A prospective multicenter study was conducted to assess the epidemiology of antimicrobial resistance among uropathogens causing uncomplicated cystitis. Adult women with clinical diagnosis of uncomplicated cystitis were enrolled from 54 participating centers distributed all over Hong Kong during 2006 to 2008. A positive urine culture was found in 59.5% (352/592) patients. The patients had mean age of 44.9 years, and most (89.2%) were otherwise healthy. The most prevalent causative organism was Escherichia coli (77%), followed by other Enterobacteriaceae (14.2%), staphylococci (5.1%), and other Gram-positive bacteria (3.7%). The resistance rates of E. coli to co-trimoxazole and ciprofloxacin were 29.5% and 12.9%, respectively, and 14 isolates (5.2%) were confirmed as extended-spectrum beta-lactamase (ESBL) producers. Of the ESBL producers, molecular studies showed CTX-M-14, CTX-M-24, or CTX-M-9. Nitrofurantoin and fosfomycin were active against >90% of the isolates, regardless of resistance phenotypes for other drugs. Pulsed-field gel electrophoresis of representative isolates showed that the antibiotic-resistant strains were genetically diverse. Patients with history of recent antibiotic use were significantly more likely to have infection by E. coli with co-trimoxazole resistance (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.4-5.7; P = 0.003) and ciprofloxacin resistance (OR, 2.5; 95% CI, 1.1-5.8; P = 0.03). Knowledge of the resistance data and risk factors could inform better use of antibiotics for empiric therapy for acute uncomplicated cystitis.

This study evaluated the antimicrobial resistance profile of outpatient urinary Escherichia coli isolated from women obtained throughout Hong Kong during 2004-2005. Of 1067 single patient isolates analyzed, 60.1% were resistant to ampicillin, 34% were resistant to co-trimoxazole, and 22.1% were resistant to ciprofloxacin. Thirty-four (6.6%) of 519 isolates in 2004 and 55 (10%) of 548 isolates in 2005 were extended-spectrum beta-lactamase (ESBL) producers with a CTX-M phenotype. Rates of non-beta-lactam resistance and ESBL production were strongly influenced by patient age. The age-stratified rates for dual co-trimoxazole and ciprofloxacin resistance and for ESBL production were 10.9% and 7.6% in women aged 18-35 years, 13% and 6.9% in women aged 36-50 years, 20.4% and 8.8% in women aged 51-64 years, and 23.7% and 11.8% in women aged > or =65 years, respectively. Nitrofurantoin and fosfomycin remain active against >90% of the isolates, irrespective of the resistance phenotypes for other drugs. Our results documented the emergence of problematic resistance phenotypes among community urinary E. coli and highlight the need to explore strategies for their containment.

Objectives: To conduct a territory-wide study of extended-spectrum beta-lactamases (ESBLs) among community isolates of urinary Escherichia coli from women in Hong Kong., Methods: Up to 50 consecutive single-patient E. coli isolates, collected from 13 laboratories in 2004, were studied. The ESBLs were characterized by PCR sequencing using specific primers. The epidemiological relationship of the isolates was studied by PFGE and phylogenetic group PCRs., Results: Forty-two ESBL producers were found among 600 consecutive isolates tested. The ESBL prevalence was 7.3% (15/205) for women aged 18-35 years, 5% (11/219) for women aged 36-50 years, 6.3% (4/63) for women aged 51-64 years and 10.6% (12/113) for women aged >or=65 years (P=0.3). The ESBL-producing isolates were often multidrug-resistant and CTX-M-14 was found in 37 isolates, CTX-M-15 in 3 isolates and CTX-M-3 in 2 isolates. PFGE revealed no significant clusters among the ESBL producers. Overall, CTX-M-14 producers were significantly more likely to belong to group D than non-ESBL producers [18/37 (48.6%) versus 13/57 (22.8%), P=0.009]. However, 7 of 13 (53.8%) CTX-M-14 producers from women aged 18-35 years represented phylogenetic group B2, compared with 7 of 24 (29.2%) for women of all other ages (P=0.1)., Conclusions: The study documented the community emergence of CTX-M as the predominant ESBL type among urinary isolates from women. The spread of CTX-M enzymes among isolates from young women is concerning and deserves close monitoring.

This paper is an attempt to describe the vocational rehabilitation services of persons with mental illness in China. It includes work therapy station, mental health services in factories, occupational activities in hospitals, welfare factories, and enterprise based sheltered workshops. Its dilemmas and implications to future development are also mentioned.

Community mental health has long been the crucial modality in service delivery of mental health services. This paper is an attempt to evaluate community mental health services in the People's Republic of China. The writer critically argues that community mental health services in the People's Republic of China still have faced a lot of difficulties such as huge demand but scarce resources, withdrawal of governmental funding in related services, inaccessibility of services to deprived and remote rural areas, political control, high mental health illiteracy and problems in formation of multidisciplinary team. An articulation of community mental health in the China context is also discussed.

Background: This paper is an attempt to describe the historical development of the mental health services in the PRC., Research Methods: An archive of related literature., Findings: The development of the mental health services in the PRC could be divided into several stages: the introduction of mental asylums by western missionaries before 1949; indigenization of the treatment model after the establishment of the PRC (1949-1963). Strong political control governed diagnosis and treatment as well as detention and discharge of mental patients during the Cultural Revolution (1964-1976). Later, because of modernization and reform advocated by Deng Xiao-ping, western models of treatment and rehabilitation were gradually introduced by psychiatrists in the PRC. Nevertheless, dilemmas such as human rights versus political control, community integration versus community control, diversity versus centrality, huge demand but inadequate services seemed to challenge the further development of the mental health service in the PRC.

Adolescent self-cutting behaviours has a long been a problem in modern society. In this paper, the writer tries review six perspectives in interpreting adolescent self-cutting behaviours. Based on these six perspectives, the writer tries to re-conceptualise a multidimensional model on adolescent self-cutting behaviours. This model tries to include the family system, peer system and socio-cultural context in perceiving the antecedents, process and aftermath in adolescents' self cutting behaviours. The implications of this perspective to intervention with adolescents are also discussed.

Depression has long been a problem in our society. In this paper, the writer tries to contrast a disease orientation and a strengths perspective in helping an adolescent with depression. The strengths perspective advocates identifying needs and ability behind client's symptoms and deficits; nurturing individuals' positive mood and hope to recovery; establishing enlightening encounter between worker and client; and developing positive coping in working with individuals with depression.

Family caregiving is very important in psychiatric rehabilitation for people with mental illnesses. By reviewing related studies, the writer describes the situation of family caregivers for people with mental illnesses. Studies showed that only 16.8% of them received psychiatric rehabilitation services. The other 83.2% relied on their family caregivers as the only support in their rehabilitation process. Forty percent of people with mental illnesses were cared for by their mothers. However, most of these family caregivers were fatigued and at risk of mental breakdown.

The empowerment model has long dominated social work practice in Western countries. Many social workers in Hong Kong use this model regardless of the social or cultural context. In this article the author shares local social work practice experiences in Hong Kong and suggests that the empowerment model may need adaptation in Chinese communities. An empowerment approach in communities influenced by traditional Chinese culture may result in types of pseudo empowerment: pragmatic empowerment, autocratic empowerment, hidden empowerment, lonely romantic empowerment, and fashionable empowerment. A culturally sensitive empowerment model for Chinese communities may have to be gradual and harmonious and empower both the individual and his or her significant others.

Starting with Jaspers in 1910, subjective psychotic experiences of people with schizophrenia became an important area in treatment and rehabilitation of people with schizophrenia. Nevertheless, this area of study is overshadowed by the statistically and diagnostically oriented DSM movement. In this article, the writer tries to re-visit various approaches in understanding subjective psychotic experiences of people with schizophrenia. It seems that subjective psychotic experiences represent persons' inner feelings; their spontaneous struggle in their process of treatment and rehabilitation. All these experiences are meaningful for the persons with psychiatric disabilities. In this paper, the writer tries to show that empathetic understanding of subjective experience can help individuals to re-establish a meaningful relationship with people with schizophrenia and motivate them to become involved in their own rehabilitation process.

Spirituality and religious coping is an important and rapidly expanding field in recent years. For the Chinese, traditional Taoism may still have a strong impact on the mental health of Chinese people. Taoistic concepts of mental health stress the transcendence from self and secularity, the dynamic revertism of nature, integration with nature and the pursuit of the infinite. Compared with western concepts of mental health, Taoism advocates self-transcendence, integration with the Law of Nature, inaction and infinite frame of reference instead of social attainment, self-development, progressive endeavor and personal interpretation. By means of a case illustration, the writer tries to describe its impacts on help-seeking, stress and coping, and the meaning of life of a Chinese family. Its generalization to different types of Chinese communities is also discussed.

Airway inflammation can be demonstrated by the modem method of sputum induction using ultrasonic nebulizer and hypertonic saline. We studied whether compressed-air nebulizer and isotonic saline which are commonly available and cost less, are as effective in inducing sputum in normal adult subjects as the above mentioned tools. Sixteen subjects underwent weekly sputum induction in the following manner: ultrasonic nebulizer (Medix Sonix 2000, Clement Clarke, UK) using hypertonic saline, ultrasonic nebulizer using isotonic saline, compressed-air nebulizer (BestNeb, Taiwan) using hypertonic saline, and compressed-air nebulizer using isotonic saline. Overall, the use of an ultrasonic nebulizer and hypertonic saline yielded significantly higher total sputum cell counts and a higher percentage of cell viability than compressed-air nebulizers and isotonic saline. With the latter, there was a trend towards squamous cell contaminations. The proportion of various sputum cell types was not significantly different between the groups, and the reproducibility in sputum macrophages and neutrophils was high (Intraclass correlation coefficient, r [95%CI]: 0.65 [0.30-0.91] and 0.58 [0.22-0.89], p < 0.001). Overall changes in median FEV, were small and comparable between all groups. Induction using ultrasonic nebulizers together with hypertonic saline was generally less well tolerated than compressed-air nebulizers and isotonic saline. We conclude that in normal subjects, although both nebulizers and saline types can induce sputum with reproducible cellular profile, ultrasonic nebulizers and hypertonic saline are more effective but less well tolerated.

Religious beliefs and superstitions have an important impact on the psychopathology of psychiatric patients. Traditional Chinese religious beliefs and superstitions, such as fortune telling, Buddhist gods, Taoist gods, historical heroic gods and ancestor worship, have important influence on subjective psychotic experiences, in particular delusions and hallucinations. By means of empirical phenomenological case narration, the writer shows that all these traditional Chinese religious beliefs and superstitions tend to affect the contents, manifestation and meaningfulness of delusion and hallucination. They also serve as a means to replace clients' self-identity. They appear in the form of a supernatural force to resolve all difficulties, cause of troubles and misfortune, stress and coping mechanisms.

Caregiving by relatives to a person with mental illness is demanding and overwhelming. This paper describes how to use guided imagery, role-playing, humor, and paradoxical intervention to help the wife of a man with mental illness in easing her worry, anxiety, and frustration engendered by caregiving. The intervention made the wife feel normal and relaxed in facing the "symptoms" of her husband's mental illness. It also revived the wife's patience, hope, and strength in the process of rehabilitation.

Background: Mutual-aid group and self-directed group are recognized as important interventions for anti-oppression of disadvantaged groups in our society., Method: In this paper, the writer describes a mutual-aid group implemented in a psychiatric half-way house in Hong Kong. Members in this group were free to set their own agenda for discussion and to invite guest speakers. In terms of various stages of this group, the writer discusses how different group activities facilitated the development of mutual-aid and self-directed natures of mental ex-patients., Results: The findings show that this group can have an impact on the wider community and aid in improving the self-image of mental ex-patients and the perception of them as contributing positively to that community, hence lessening negative stereotypes.

Work and employment has long been regarded as crucial for the mental health of human beings. Unemployment may lead to deterioration of physical and mental health. Nevertheless, for adults with psychiatric disabilities, discontinuity of employment is common. They may have various reasons to discontinue their employment. In Hong Kong, only 2.5% of people with psychiatric disabilities discharged from sheltered workshops are able to seek open employment. By means of illustration, the authors will show that traditional Chinese work culture tends to reinforce the discontinuity of employment of adult males with psychiatric disabilities. In Chinese culture, work is a means to occupy time, control misbehavior, show consistency of words and deeds, and to glorify parents and ancestors. All these factors contribute to the fulfillment of an adult male role and identity in traditional Chinese culture. In this case history, instead of finding realistic employment, a male adult with psychiatric disability tried to indulge himself in what he felt was his ideal job to fulfill all requirement as an adult male in Chinese culture. The imaginative ideal job gave him excuses to discontinue open employment. Its implications to vocational rehabilitation with male adults with psychiatric disability are also discussed.

Informal community care is crucial in community integration and rehabilitation of people with mental illness. In this paper, the writer describes the development of informal community care in Hong Kong. A self-help group, a relative group, integrative aftercare network, and the use of volunteers will be described and analyzed. However, these informal community care projects are underdeveloped. Participation is limited. Community integration is greatly hindered by public discrimination. The writer also suggests ways to develop the informal community care projects in Hong Kong.

Glutamate dehydrogenase catalyses the oxidative deamination of glutamate to 2-oxoglutarate with concomitant reduction of NAD(P)(+), and has been shown to be widely distributed in nature across species ranging from psychrophiles to hyperthermophiles. Extensive characterisation of this enzyme isolated from hyperthermophilic organisms has led to its adoption as a model system for analysing the determinants of thermal stability. The crystal structure of the extremely thermostable glutamate dehydrogenase from Thermococcus litoralis has been determined at 2.5 A resolution, and has been compared to that from the hyperthermophile Pyrococcus furiosus. The two enzymes are 87 % identical in sequence, yet differ 16-fold in their half-lives at 104 degrees C. This is the first reported comparative analysis of the structures of a multisubunit enzyme from two closely related yet distinct hyperthermophilies. The less stable T. litoralis enzyme has a decreased number of ion pair interactions; modified patterns of hydrogen bonding resulting from isosteric sequence changes; substitutions that decrease packing efficiency; and substitutions which give rise to subtle but distinct shifts in both main-chain and side-chain elements of the structure. This analysis provides a rational basis to test ideas on the factors that confer thermal stability in proteins through a combination of mutagenesis, calorimetry, and structural studies., (Copyright 1999 Academic Press.)

The discovery of hyperthermophilic microorganisms and the analysis of hyperthermostable enzymes has established the fact that multisubunit enzymes can survive for prolonged periods at temperatures above 100 degreesC. We have carried out homology-based modeling and direct structure comparison on the hexameric glutamate dehydrogenases from the hyperthermophiles Pyrococcus furiosus and Thermococcus litoralis whose optimal growth temperatures are 100 degreesC and 88 degreesC, respectively, to determine key stabilizing features. These enzymes, which are 87% homologous, differ 16-fold in thermal stability at 104 degreesC. We observed that an intersubunit ion-pair network was substantially reduced in the less stable enzyme from T. litoralis, and two residues were then altered to restore these interactions. The single mutations both had adverse effects on the thermostability of the protein. However, with both mutations in place, we observed a fourfold improvement of stability at 104 degreesC over the wild-type enzyme. The catalytic properties of the enzymes were unaffected by the mutations. These results suggest that extensive ion-pair networks may provide a general strategy for manipulating enzyme thermostability of multisubunit enzymes. However, this study emphasizes the importance of the exact local environment of a residue in determining its effects on stability.

The recent structure determination of glutamate dehydrogenase from the hyperthermophile Pyrococcus furiosus and the comparison of this structure with its counterparts from the mesophiles Clostridium symbiosum and Escherichia coli has highlighted the formation of extended networks of ion-pairs as a possible explanation for the superior thermal stability of the hyperthermostable enzyme. In the light of this, we have carried out a homology-based modelling study using sequences of a range of glutamate dehydrogenases drawn from species which span a wide spectrum of optimal growth temperatures. We have attempted to analyse the extent of the formation of ion-pair networks in these different enzymes and tried to correlate this with the observed thermal stability. The results of this analysis indicate that the ion-pair networks become more fragmented as the temperature stability of the enzyme decreases and are consistent with a role for the involvement of such networks in the adaptation of enzymes to extreme temperatures.

A homology-based modeling study on the extremely halophilic glutamate dehydrogenase from Halobacterium salinarum has been used to provide insights into the molecular basis of salt tolerance. The modeling reveals two significant differences in the characteristics of the surface of the halophilic enzyme that may contribute to its stability in high salt. The first of these is that the surface is decorated with acidic residues, a feature previously seen in structures of halophilic enzymes. The second is that the surface displays a significant reduction in exposed hydrophobic character. The latter arises not from a loss of surface-exposed hydrophobic residues, as has previously been proposed, but from a reduction in surface-exposed lysine residues. This is the first report of such an observation.

This paper is a historical review of mental health services in Hong Kong. The development of mental health services in Hong Kong can be roughly divided into several stages: the pre-asylum period (1841-1924), the asylum period (1925-1948), the organization period (1 948-1965), the initial rehabilitation period (1966-1973), the centralized rehabilitation period (1974-1981) and the civic control vs community care period (1982-1995). From the development of mental health services in Hong Kong, it is clearly demonstrated that the aims and the trends of mental health services had gradually progressed from a detention model, to a treatment model and finally to a rehabilitation model. Nevertheless, under a shortage of governmental resources and the severe opposition of public stigmatization, community based rehabilitation existed in the form of institution-like service units. In comparison with the international de-institutionalization and community care movement, mental health services in Hong Kong are not affected by any de-institutionalization movement. Instead, the unique political and social context nurtured a parallel development of both institutional care and community care for mental patients.

The NADP(+)-dependent glutamate dehydrogenase from Thermococcus litoralis has been crystallized by the hanging-drop method of vapour diffusion using an ammonium sulfate and PEG mixture as the precipitant. The crystals belong to the monoclinic system and are in space group C2 with unit-cell dimensions a = 142.7, b = 202.0, c = 125.8 A with beta = 113.1 degrees with a hexamer in the asymmetric unit. T. Litoralis, a hyperthermophilic organism, belongs to the family of Archaea and has a maximum growth temperature of about 370 K. The glutamate dehydrogenase isolated from this organism has a half-life of 2 h at 373 K and a comparison of this structure with that of other GluDH's from hyperthermophilic organisms and from mesophiles will contribute to an understanding of the molecular mechanisms which underlie thermostability.

The structure determination of the glutamate dehydrogenase from the hyperthermophile Pyrococcus furiosus has been completed at 2.2 A resolution. The structure has been compared with the glutamate dehydrogenases from the mesophiles Clostridium symbiosum, Escherichia coli and Neurospora crassa. This comparison has revealed that the hyperthermophilic enzyme contains a striking series of networks of ion-pairs which are formed by regions of the protein which contain a high density of charged residues. Such regions are not found in the mesophilic enzymes and the number and extent of ion-pair formation is much more limited. The ion-pair networks are clustered at both inter domain and inter subunit interfaces and may well represent a major stabilising feature associated with the adaptation of enzymes to extreme temperatures.

Background: The hyperthermophile Pyrococcus furiosus is one of the most thermostable organisms known, with an optimum growth temperature of 100 degrees C. The proteins from this organism display extreme thermostability. We have undertaken the structure determination of glutamate dehydrogenase from P. furiosus in order to gain further insights into the relationship between molecular structure and thermal stability., Results: The structure of P. furiosus glutamate dehydrogenase, a homohexameric enzyme, has been determined at 2.2 A resolution and compared with the structure of glutamate dehydrogenase from the mesophile Clostridium symbiosum., Conclusions: Comparison of the structures of these two enzymes has revealed one major difference: the structure of the hyperthermophilic enzyme contains a striking series of ion-pair networks on the surface of the protein subunits and buried at both interdomain and intersubunit interfaces. We propose that the formation of such extended networks may represent a major stabilizing feature associated with the adaptation of enzymes to extreme temperatures.

The NADP-linked glutamate dehydrogenase from Neurospora crassa has been crystallized by the hanging-drop method of vapour diffusion in the presence of 0.1 M glutamate. The crystals are trigonal and are in space group P3(1)21 with unit-cell dimensions of a = b = 196.6, c = 102.0 A and with a trimer in the asymmetric unit. A full structure determination of this enzyme will lead to an understanding of the molecular basis of inter-allelic complementation observed with hybrid hexamers of naturally occurring mutants.

In the light of the solution of the three-dimensional structure of the NAD(+)-linked glutamate dehydrogenase from the mesophile Clostridium symbiosum, we have undertaken a detailed examination of the alignment of the sequences for the thermophilic glutamate dehydrogenases from Thermococcus litoralis and Pyrococcus furiosus against the sequence and the molecular structure of the glutamate dehydrogenase from C. symbiosum, to provide insights into the molecular basis of their thermostability. This homology-based modelling is simplified by the relatively small number of amino acid substitutions between the two thermophilic glutamate dehydrogenase sequences. The most frequent amino acid exchanges involve substitutions which increase the hydrophobicity and sidechain branching in the more thermostable enzyme; particularly common is the substitution of valine to isoleucine. Examination of the sequence differences suggests that enhanced packing within the buried core of the protein plays an important role in maintaining stability at extreme temperatures. One hot spot for the accumulation of exchanges lies close to a region of the molecule involved in its conformational flexibility and these changes may modulate the dynamics of this enzyme and thereby contribute to increased stability.

The NAD(P)-dependent glutamate dehydrogenase from Pyrococcus furiosus has been crystallized by the hanging-drop method of vapour diffusion using lithium sulfate as the precipitant. The crystals belong to the tetragonal system and are in space group P4(2)2(1)2 with unit-cell dimensions of a = b = 167.2, c = 172.9 A. Consideration of the values of V(m) and possible packing of the molecules within the cell suggest that the asymmetric unit contains a trimer. P. furiosus belongs to the family of Archaea and is one of the most thermostable organisms known, having an optimal growth temperature of 376 K. The glutamate dehydrogenase isolated from this organism has a half-life of 12 h at 373 K and, therefore, the determination of the structure of this enzyme will be important in advancing our understanding of how proteins are adapted to enable them to survive at such extreme temperatures.