Harnessing Big Data in Amyotrophic Lateral Sclerosis: Machine Learning Applications for Clinical Practice and Pharmaceutical Trials

The arrival of genotype-specific therapies in amyotrophic lateral sclerosis (ALS) signals the dawn of precision medicine in motor neuron diseases (MNDs). After decades of academic studies in ALS, we are now witnessing tangible clinical advances. An ever increasing number of well-designed descriptive studies have been published in recent years, characterizing typical disease-burden patterns in vivo and post mortem. Phenotype- and genotype-associated traits and "typical" propagation patterns have been described based on longitudinal clinical and biomarker data. The practical caveat of these studies is that they report "group-level", stereotyped trajectories representative of ALS as a whole. In the clinical setting, however, "group-level" biomarker signatures have limited practical relevance and what matters is the meaningful interpretation of data from a single individual. The increasing availability of large normative data sets, national registries, extant academic data, consortium repositories, and emerging data platforms now permit the meaningful interpretation of individual biomarker profiles and allow the categorization of single patients into relevant diagnostic, phenotypic, and prognostic categories. A variety of machine learning (ML) strategies have been recently explored in MND to demonstrate the feasibility of interpreting data from a single patient. Despite the considerable clinical prospects of classification models, a number of pragmatic challenges need to be overcome to unleash the full potential of ML in ALS. Cohort size limitations, administrative hurdles, data harmonization challenges, regulatory differences, methodological obstacles, and financial implications and are just some of the barriers to readily implement ML in routine clinical practice. Despite these challenges, machine-learning strategies are likely to be firmly integrated in clinical decision-making and pharmacological trials in the near future.

Supra- and infra-tentorial degeneration patterns in primary lateral sclerosis: a multimodal longitudinal neuroradiology study

BACKGROUND

Primary lateral sclerosis (PLS) is traditionally solely associated with progressive upper motor neuron dysfunction manifesting in limb spasticity, gait impairment, bulbar symptoms and pseudobulbar affect. Recent studies have described frontotemporal dysfunction in some patients resulting in cognitive manifestations. Cerebellar pathology is much less well characterised despite sporadic reports of cerebellar disease.

METHODS

A multi-timepoint, longitudinal neuroimaging study was conducted to characterise the evolution of both intra-cerebellar disease burden and cerebro-cerebellar connectivity. The volumes of deep cerebellar nuclei, cerebellar cortical volumes, cerebro-cerebellar structural and functional connectivity were assessed longitudinally in a cohort of 43 individuals with PLS.

RESULTS

Cerebello-frontal, -temporal, -parietal, -occipital and cerebello-thalamic structural disconnection was detected at baseline based on radial diffusivity (RD) and cerebello-frontal decoupling was also evident based on fractional anisotropy (FA) alterations. Functional connectivity changes were also detected in cerebello-frontal, parietal and occipital projections. Volume reductions were identified in the vermis, anterior lobe, posterior lobe, and crura. Among the deep cerebellar nuclei, the dorsal dentate was atrophic. Longitudinal follow-up did not capture statistically significant progressive changes. Significant primary motor cortex atrophy and inter-hemispheric transcallosal degeneration were also captured.

CONCLUSIONS

PLS is not only associated with upper motor neuron dysfunction, but cerebellar cortical volume loss and deep cerebellar nuclear atrophy can also be readily detected. In addition to intra-cerebellar disease burden, cerebro-cerebellar connectivity alterations also take place. Our data add to the evolving evidence of widespread neurodegeneration in PLS beyond the primary motor regions. Cerebellar dysfunction in PLS is likely to exacerbate bulbar, gait and dexterity impairment and contribute to pseudobulbar affect.

Language deficits in primary lateral sclerosis: cortical atrophy, white matter degeneration and functional disconnection between cerebral regions

BACKGROUND

Primary lateral sclerosis (PLS) is traditionally regarded as a pure upper motor neuron disorder, but recent cases series have highlighted cognitive deficits in executive and language domains.

METHODS

A single-centre, prospective neuroimaging study was conducted with comprehensive clinical and genetic profiling. The structural and functional integrity of language-associated brain regions and networks were systematically evaluated in 40 patients with PLS in comparison to 111 healthy controls. The structural integrity of the arcuate fascicle, frontal aslant tract, inferior occipito-frontal fascicle, inferior longitudinal fascicle, superior longitudinal fascicle and uncinate fascicle was evaluated. Functional connectivity between the supplementary motor region and the inferior frontal gyrus and connectivity between Wernicke's and Broca's areas was also assessed.

RESULTS

Cortical thickness reductions were observed in both Wernicke's and Broca's areas. Fractional anisotropy reduction was noted in the aslant tract and increased radical diffusivity (RD) identified in the aslant tract, arcuate fascicle and superior longitudinal fascicle in the left hemisphere. Functional connectivity was reduced along the aslant track, i.e. between the supplementary motor region and the inferior frontal gyrus, but unaffected between Wernicke's and Broca's areas. Cortical thickness alterations, structural and functional connectivity changes were also noted in the right hemisphere.

CONCLUSIONS

Disease-burden in PLS is not confined to motor regions, but there is also a marked involvement of language-associated tracts, networks and cortical regions. Given the considerably longer survival in PLS compared to ALS, the impact of language impairment on the management of PLS needs to be carefully considered.

The involvement of language-associated networks, tracts, and cortical regions in frontotemporal dementia and amyotrophic lateral sclerosis: Structural and functional alterations

BACKGROUND

Language deficits are cardinal manifestations of some frontotemporal dementia (FTD) phenotypes and also increasingly recognized in sporadic and familial amyotrophic lateral sclerosis (ALS). They have considerable social and quality-of-life implications, and adaptive strategies are challenging to implement. While the neuropsychological profiles of ALS-FTD phenotypes are well characterized, the neuronal underpinnings of language deficits are less well studied.

METHODS

A multiparametric, quantitative neuroimaging study was conducted to characterize the involvement of language-associated networks, tracts, and cortical regions with a panel of structural, diffusivity, and functional magnetic resonance imaging (MRI) metrics. Seven study groups were evaluated along the ALS-FTD spectrum: healthy controls (HC), individuals with ALS without cognitive impairment (ALSnci), C9orf72-negative ALS-FTD, C9orf72-positive ALS-FTD, behavioral-variant FTD (bvFTD), nonfluent variant primary progressive aphasia (nfvPPA), and semantic variant PPA (svPPA). The integrity of the Broca's area, Wernicke's area, frontal aslant tract (FAT), arcuate fascicle (AF), inferior occipitofrontal fascicle (IFO), inferior longitudinal fascicle (ILF), superior longitudinal fascicle (SLF), and uncinate fascicle (UF) was quantitatively evaluated. The functional connectivity (FC) between Broca's and Wernicke' areas and FC along the FAT was also specifically assessed.

RESULTS

Patients with nfvPPA and svPPA exhibit distinctive patterns of gray and white matter degeneration in language-associated brain regions. Individuals with bvFTD exhibit Broca's area, right FAT, right IFO, and UF degeneration. The ALSnci group exhibits Broca's area atrophy and decreased FC along the FAT. Both ALS-FTD cohorts, irrespective of C9orf72 status, show bilateral FAT, AF, and IFO pathology. Interestingly, only C9orf72-negative ALS-FTD patients exhibit bilateral uncinate and right ILF involvement, while C9orf72-positive ALS-FTD patients do not.

CONCLUSIONS

Language-associated tracts and networks are not only affected in language-variant FTD phenotypes but also in ALS and bvFTD. Language domains should be routinely assessed in ALS irrespective of the genotype.

Presymptomatic grey matter alterations in ALS kindreds: a computational neuroimaging study of asymptomatic C9orf72 and SOD1 mutation carriers

BACKGROUND

The characterisation of presymptomatic disease-burden patterns in asymptomatic mutation carriers has a dual academic and clinical relevance. The understanding of disease propagation mechanisms is of considerable conceptual interests, and defining the optimal time of pharmacological intervention is essential for improved clinical trial outcomes.

METHODS

In a prospective, multimodal neuroimaging study, 22 asymptomatic C9orf72 GGGGCC hexanucleotide repeat carriers, 13 asymptomatic subjects with SOD1, and 54 "gene-negative" ALS kindreds were enrolled. Cortical and subcortical grey matter alterations were systematically appraised using volumetric, morphometric, vertex, and cortical thickness analyses. Using a Bayesian approach, the thalamus and amygdala were further parcellated into specific nuclei and the hippocampus was segmented into anatomically defined subfields.

RESULTS

Asymptomatic GGGGCC hexanucleotide repeat carriers in C9orf72 exhibited early subcortical changes with the preferential involvement of the pulvinar and mediodorsal regions of the thalamus, as well as the lateral aspect of the hippocampus. Volumetric approaches, morphometric methods, and vertex analyses were anatomically consistent in capturing focal subcortical changes in asymptomatic C9orf72 hexanucleotide repeat expansion carriers. SOD1 mutation carriers did not exhibit significant subcortical grey matter alterations. In our study, none of the two asymptomatic cohorts exhibited cortical grey matter alterations on either cortical thickness or morphometric analyses.

DISCUSSION

The presymptomatic radiological signature of C9orf72 is associated with selective thalamic and focal hippocampal degeneration which may be readily detectable before cortical grey matter changes ensue. Our findings confirm selective subcortical grey matter involvement early in the course of C9orf72-associated neurodegeneration.

Radiological correlates of pseudobulbar affect: Corticobulbar and cerebellar components in primary lateral sclerosis

INTRODUCTION

Pseudobulbar affect (PBA) is a distressing symptom of a multitude of neurological conditions affecting patients with a rage of neuroinflammatory, neurovascular and neurodegenerative conditions. It manifests in disproportionate emotional responses to minimal or no contextual stimulus. It has considerable quality of life implications and treatment can be challenging.

METHODS

A prospective multimodal neuroimaging study was conducted to explore the neuroanatomical underpinnings of PBA in patients with primary lateral sclerosis (PLS). All participants underwent whole genome sequencing and screening for C9orf72 hexanucleotide repeat expansions, a comprehensive neurological assessment, neuropsychological screening (ECAS, HADS, FrSBe) and PBA was evaluated by the emotional lability questionnaire. Structural, diffusivity and functional MRI data were systematically evaluated in whole-brain (WB) data-driven and region of interest (ROI) hypothesis-driven analyses. In ROI analyses, functional and structural corticobulbar connectivity and cerebello-medullary connectivity alterations were evaluated separately.

RESULTS

Our data-driven whole-brain analyses revealed associations between PBA and white matter degeneration in descending corticobulbar as well as in commissural tracts. In our hypothesis-driven analyses, PBA was associated with increased right corticobulbar tract RD (p = 0.006) and decreased FA (p = 0.026). The left-hemispheric corticobulbar tract, as well as functional connectivity, showed similar tendencies. While uncorrected p-maps revealed both voxelwise and ROI trends for associations between PBA and cerebellar measures, these did not reach significance to unequivocally support the "cerebellar hypothesis".

CONCLUSIONS

Our data confirm associations between cortex-brainstem disconnection and the clinical severity of PBA. While our findings may be disease-specific, they are consistent with the classical cortico-medullary model of pseudobulbar affect.

Promises and pitfalls of imaging-based biomarkers in motor neuron diseases

PURPOSE OF REVIEW

Although neuroimaging in motor neuron diseases (MNDs) continues to generate important novel academic insights, the translation of novel radiological protocols into viable biomarkers remains challenging.

RECENT FINDINGS

A multitude of technological advances contribute to the success of academic imaging in MND such as the availability of high-field MRI platforms, novel imaging techniques, quantitative spinal cord protocols to whole-brain spectroscopy. International collaborations, protocol harmonization efforts, open-source image analysis suites also fuel developments in the field. Despite the success of academic neuroimaging in MND, the meaningful interpretation of radiological data from single patients and accurate classification into relevant diagnostic, phenotypic and prognostic categories remain challenging. Appraising accruing disease burden over the short follow-up intervals typically used in pharmacological trials is also notoriously difficult.

SUMMARY

Although we acknowledge the academic achievements of large descriptive studies, an unmet priority of neuroimaging in MND is the development of robust diagnostic, prognostic and monitoring applications to meet the practical demands of clinical decision-making and pharmacological trials. A paradigm shift from group-level analyses to individual-level data interpretation, accurate single-subject classification and disease-burden tracking is therefore urgently needed to distil raw spatially coded imaging data into practical biomarkers.

Brainstem-cortex disconnection in amyotrophic lateral sclerosis: bulbar impairment, genotype associations, asymptomatic changes and biomarker opportunities

BACKGROUND

Bulbar dysfunction is a cardinal feature of ALS with important quality of life and management implications. The objective of this study is the longitudinal evaluation of a large panel imaging metrics pertaining to bulbar dysfunction, encompassing cortical measures, structural and functional cortico-medullary connectivity indices and brainstem metrics.

METHODS

A standardised, multimodal imaging protocol was implemented with clinical and genetic profiling to systematically appraise the biomarker potential of specific metrics. A total of 198 patients with ALS and 108 healthy controls were included.

RESULTS

Longitudinal analyses revealed progressive structural and functional disconnection between the motor cortex and the brainstem over time. Cortical thickness reduction was an early feature on cross-sectional analyses with limited further progression on longitudinal follow-up. Receiver operating characteristic analyses of the panel of MR metrics confirmed the discriminatory potential of bulbar imaging measures between patients and controls and area-under-the-curve values increased significantly on longitudinal follow-up. C9orf72 carriers exhibited lower brainstem volumes, lower cortico-medullary structural connectivity and faster cortical thinning. Sporadic patients without bulbar symptoms, already exhibit significant brainstem and cortico-medullary connectivity alterations.

DISCUSSION

Our results indicate that ALS is associated with multi-level integrity change from cortex to brainstem. The demonstration of significant corticobulbar alterations in patients without bulbar symptoms confirms considerable presymptomatic disease burden in sporadic ALS. The systematic assessment of radiological measures in a single-centre academic study helps to appraise the diagnostic and monitoring utility of specific measures for future clinical and clinical trial applications.

Not a benign motor neuron disease: longitudinal imaging captures relentless motor connectome disintegration in primary lateral sclerosis

BACKGROUND AND PURPOSE

Primary lateral sclerosis (PLS) is a progressive upper motor neuron disorder associated with considerable clinical disability. Symptoms are typically exclusively linked to primary motor cortex degeneration and the contribution of pre-motor, supplementary motor, cortico-medullary and inter-hemispheric connectivity alterations are less well characterized.

METHODS

In a single-centre, prospective, longitudinal neuroimaging study 41 patients with PLS were investigated. Patients underwent standardized neuroimaging, genetic profiling with whole exome sequencing, and comprehensive clinical assessments including upper motor neuron scores, tapping rates, mirror movements, spasticity assessment, cognitive screening and evaluation for pseudobulbar affect. Longitudinal neuroimaging data from 108 healthy controls were used for image interpretation. A standardized imaging protocol was implemented including 3D T1-weighted structural, diffusion tensor imaging and resting-state functional magnetic resonance imaging. Following somatotopic segmentation, cortical thickness analyses, probabilistic tractography, blood oxygenation level dependent signal analyses and brainstem volumetry were conducted to evaluate cortical, brainstem, cortico-medullary and inter-hemispheric connectivity alterations both cross-sectionally and longitudinally.

RESULTS

Our data confirm progressive primary motor cortex degeneration, considerable supplementary motor and pre-motor area involvement, progressive brainstem atrophy, cortico-medullary and inter-hemispheric disconnection, and close associations between clinical upper motor neuron scores and somatotopic connectivity indices in PLS.

DISCUSSION

Primary lateral sclerosis is associated with relentlessly progressive motor connectome degeneration. Clinical disability in PLS is likely to stem from a combination of intra- and inter-hemispheric connectivity decline and primary, pre- and supplementary motor cortex degeneration. Simple 'bedside' clinical tools, such as tapping rates, are excellent proxies of the integrity of the relevant fibres of the contralateral corticospinal tract.

Thalamic pathology in frontotemporal dementia: Predilection for specific nuclei, phenotype-specific signatures, clinical correlates, and practical relevance

BACKGROUND

Frontotemporal dementia (FTD) phenotypes are classically associated with distinctive cortical atrophy patterns and regional hypometabolism. However, the spectrum of cognitive and behavioral manifestations in FTD arises from multisynaptic network dysfunction. The thalamus is a key hub of several corticobasal and corticocortical circuits. The main circuits relayed via the thalamic nuclei include the dorsolateral prefrontal circuit, the anterior cingulate circuit, and the orbitofrontal circuit.

METHODS

In this paper, we have reviewed evidence for thalamic pathology in FTD based on radiological and postmortem studies. Original research papers were systematically reviewed for preferential involvement of specific thalamic regions, for phenotype-associated thalamic disease burden patterns, characteristic longitudinal changes, and genotype-associated thalamic signatures. Moreover, evidence for presymptomatic thalamic pathology was also reviewed. Identified papers were systematically scrutinized for imaging methods, cohort sizes, clinical profiles, clinicoradiological associations, and main anatomical findings. The findings of individual research papers were amalgamated for consensus observations and their study designs further evaluated for stereotyped shortcomings. Based on the limitations of existing studies and conflicting reports in low-incidence FTD variants, we sought to outline future research directions and pressing research priorities.

RESULTS

FTD is associated with focal thalamic degeneration. Phenotype-specific thalamic traits mirror established cortical vulnerability patterns. Thalamic nuclei mediating behavioral and language functions are preferentially involved. Given the compelling evidence for considerable thalamic disease burden early in the course of most FTD subtypes, we also reflect on the practical relevance, diagnostic role, prognostic significance, and monitoring potential of thalamic metrics in FTD.

CONCLUSIONS

Cardinal manifestations of FTD phenotypes are likely to stem from thalamocortical circuitry dysfunction and are not exclusively driven by focal cortical changes.

Neuroimaging in hereditary spastic paraplegias: from qualitative cues to precision biomarkers

INTRODUCTION

: Hereditary spastic paraplegias (HSP) include a clinically and genetically heterogeneous group of conditions. Novel imaging modalities have been increasingly applied to HSP cohorts which helps to quantitatively evaluate the integrity of specific anatomical structures and develop monitoring markers for both clinical care and future clinical trials.

AREAS COVERED

: Advances in HSP imaging are systematically reviewed with a focus on cohort sizes, imaging modalities, study design, clinical correlates, methodological approaches, and key findings.

EXPERT OPINION

: A wide range of imaging techniques have been recently applied to HSP cohorts. Common shortcomings of existing studies include the evaluation of genetically unconfirmed or admixed cohorts, limited sample sizes, unimodal imaging approaches, lack of postmortem validation, and a limited clinical battery, often exclusively focusing on motor aspects of the condition. A number of innovative methodological approaches have also be identified, such as robust longitudinal study designs, the implementation of multimodal imaging protocols, complementary cognitive assessments, and the comparison of HSP cohorts to MND cohorts. Collaborative multicentre initiatives may overcome sample limitations, and comprehensive clinical profiling with motor, extrapyramidal, cerebellar, and neuropsychological assessments would permit systematic clinico-radiological correlations. Academic achievements in HSP imaging have the potential to be developed into viable clinical applications to expedite the diagnosis and monitor disease progression.

Pre-symptomatic radiological changes in frontotemporal dementia: propagation characteristics, predictive value and implications for clinical trials

Computational imaging and quantitative biomarkers offer invaluable insights in the pre-symptomatic phase of neurodegenerative conditions several years before clinical manifestation. In recent years, there has been a focused effort to characterize pre-symptomatic cerebral changes in familial frontotemporal dementias using computational imaging. Accordingly, a systematic literature review was conducted of original articles investigating pre-symptomatic imaging changes in frontotemporal dementia focusing on study design, imaging modalities, data interpretation, control cohorts and key findings. The review is limited to the most common genotypes: chromosome 9 open reading frame 72 (C9orf72), progranulin (GRN), or microtubule-associated protein tau (MAPT) genotypes. Sixty-eight studies were identified with a median sample size of 15 (3-141) per genotype. Only a minority of studies were longitudinal (28%; 19/68) with a median follow-up of 2 (1-8) years. MRI (97%; 66/68) was the most common imaging modality, and primarily grey matter analyses were conducted (75%; 19/68). Some studies used multimodal analyses 44% (30/68). Genotype-associated imaging signatures are presented, innovative study designs are highlighted, common methodological shortcomings are discussed and lessons for future studies are outlined. Emerging academic observations have potential clinical implications for expediting the diagnosis, tracking disease progression and optimising the timing of pharmaceutical trials.

Idiopathic Intracranial Hypertension in a Malaysian Preschooler

A four-year-old girl presented with a three-day history of squint and irritability. Examination showed reduced visual acuity in both eyes, the presence of a false localizing sign, and bilateral optic disc swelling. On investigation, her blood laboratory workup was within the normal range. Imaging of the brain showed no evidence of a space-occupying lesion or cerebral venous sinus thrombosis. The lumbar puncture opening pressure was 27cmH₂0 and the cerebrospinal fluid workup was normal. The diagnosis of idiopathic intracranial hypertension (IIH) was made based on the diagnostic criteria for pseudotumor cerebri syndrome. She was successfully treated with acetazolamide with resolved symptoms and signs. This highlights the possibility of IIH presenting with inconspicuous symptoms in preschool children, which needs a high index suspicion by clinicians. Hence, solving the challenges in the workup, especially in children, is very crucial.

A case of successfully managed pregnancy in a patient with complex cyanotic congenital heart disease

Medical advances have increased survival of patients with congenital heart disease. However, cardiac disease in pregnancy carries significant maternal and fetal risks, posing enormous challenges to obstetricians. Cyanotic congenital heart disease is associated with maternal complications such as arrhythmias, thromboembolic events and death. Fetal complications include small for gestational age, miscarriage and prematurity. Cyanotic congenital heart disease patients who continue their pregnancies require holistic multidisciplinary team care with early and coordinated planning for delivery. Management of such patients include early counseling regarding pregnancy-associated risks, close monitoring of their cardiac function and regular scanning for fetal assessment. Choice of anesthesia for these patients requires meticulous planning to achieve a favorable balance between systemic and pulmonary vascular resistance, ensuring minimal change in right-to-left shunting. We report a case of a successfully managed pregnancy in a patient with complex congenital heart disease and a single ventricle of left ventricle morphology.

Repeated failed non-invasive prenatal testing in a woman with immune thrombocytopenia and antiphospholipid syndrome: lessons learnt

We present a case of a 37-year-old Chinese woman (gravida 4 para 0) with a history of immune thrombocytopenia and type IIb antiphospholipid syndrome. She was started on 100 mg of aspirin, 20 mg of prednisolone and 20 mg of subcutaneous low-molecular-weight heparin daily for her fourth pregnancy. She opted for non-invasive prenatal testing for aneuploidy screening but had failed results three times consecutively from insufficient fetal cfDNA initially or high variance in cfDNA counts on redraws. She declined invasive karyotyping. Her pregnancy was complicated by severe pre-eclampsia and fetal growth restriction at 19+6 weeks of gestation and was terminated. Subsequent fetal karyotyping revealed a normal karyotype of 46XY with no apparent abnormalities.

Magnetoelastic vibrational biomaterials for real-time monitoring and modulation of the host response

Magnetoelastic (ME) biomaterials are ferromagnetic materials that physically deform when exposed to a magnetic field. This work describes the real-time control and monitoring capabilities of ME biomaterials in wound healing. Studies were conducted to demonstrate the capacity of the materials to monitor changes in protein adsorption and matrix stiffness. In vitro experiments demonstrated that ME biomaterials can monitor cell adhesion and growth in real-time, and a long-term in vivo study demonstrated their ability to monitor the host response (wound healing) to an implant and control local cell density and collagen matrix production at the soft tissue-implant interface. This approach represents a potentially self-aware and post-deployment activated biomaterial coating as a means to monitor an implant surface and provide an adjuvant therapy for implant fibrosis.

Insights into the molecular mechanism of RGL2-mediated inhibition of seed germination in Arabidopsis thaliana

BACKGROUND

Seed germination is of immense significance for agriculture and has been studied for centuries. Yet, our understanding of the molecular mechanisms underlying regulation of dormancy and germination is still in its infancy. Gibberellins are the key phytohormones that promote germination, and the DELLA protein RGL2 is the main signalling intermediate involved in this response. Germination is completely inhibited if functional RGL2 is overexpressed and/or stabilized; however, the molecular mechanisms of RGL2 function are still largely unknown. We therefore attempted to shed light onto some of the genetic events downstream of RGL2.

RESULTS

Gene ontology of the transcriptome differentially regulated by RGL2, as well as extensive cross-comparison with other available microarray data indicates that RGL2-mediated inhibition of germination causes seeds to enter a state of dormancy. RGL2 also appears to differentially regulate a number of transcription factors, many of which are known to be involved in light- or phytohormone-mediated aspects of germination. A promoter analysis of differentially expressed genes identified an enrichment of several motifs that can be bound by specific transcription factors, for example GAMYB, ARF1, or Dof-type zinc fingers. We show that Dof-binding motifs indeed play a role in RGL2-mediated transcription. Using Chromatin Immunoprecipitation (ChIP), we show that RGL2 directly downregulates at least one cell wall modifying enzyme, which is predicted to constrain cell growth thereby leading to inhibition of seed germination.

CONCLUSIONS

Our results reveal that RGL2 controls various aspects of germination. Through the repression of cell wall modifying enzymes, cell growth is directly constrained to inhibit germination. Furthermore, RGL2 likely interacts with various types of proteins to regulate transcription, and differentially regulates several transcription factors. Collectively, our data indicate that gibberellins, acting via RGL2, control several aspects of seed germination.

Effects of IL-6, IL-10 and TGF-β on the expression of survivin and apoptosis in nasopharyngeal carcinoma TW01 cells

The aim of this study is to investigate whether IL-6, IL-10 and TGF-β are able to confer resistance to apoptosis in nasopharyngeal carcinoma cells by upregulating the expression of survivin.

METHODS

The human nasopharyngeal carcinoma cell line TW01 (WHO NPC Type I) was cultured in DMEM-F12 Ham medium containing 10% FBS in a humidified atmosphere of 5% CO(2) and 37°C and treated with different concentrations of IL-6, IL-10 and TGF-β. Survivin mRNA expression was measured by real-time quantitative PCR and Western blot. Apoptosis was determined based on the assay for caspase-3 activity.

RESULTS

Of all the cytokines tested, only TGF-β (10 pg/mL) induced the over-expression of survivin at a significant level and this correlated with resistance to apoptosis (p ≤ 0.05). To confirm if survivin is responsible for resistance to apoptosis, YM155 which is a survivin inhibitor was used and the results showed that YM155 abrogated the protective effect of TGF-β. Interestingly, IL-10 did not significantly alter the expression of survivin.

CONCLUSIONS

We conclude that TGF-β up-regulates the expression of survivin leading to the resistance to apoptosis in NPC TW01 cells.

In vitro modulation of naturally occurring flavonoids on cytochrome P450 2A6 (CYP2A6) activity

1. The effect of flavonoids on coumarin 7-hydroxylation, an activity marker of an important human liver cytochrome P450 isoform, cytochrome P450 2A6 (CYP2A6), was investigated in this study. 2. Coumarin 7-hydroxylase activity was measured fluorometrically in reaction mixtures containing cDNA-expressed CYP2A6, nicotinamide adenine dinucleotide phosphate generating system and 10 uM coumarin, at various concentrations of flavonoids. 3. Among the 23 compounds tested, most of the active members were from flavonol group of hydroxylated flavonoids, with myricetin being the most potent inhibitor followed by quercetin, galangin, and kaempferol. 4. Further exploration of the inhibition mechanism of these compounds revealed that myricetin, galangin, and kaempferol exhibited mixed-type of inhibition pattern while quercetin was observed to exhibit competitive mode of inhibition. 5. Structure-function analyses revealed that degree of inhibition was closely related to the number and location of hydroxyl groups, glycosylation of the free hydroxyl groups, degree of saturation of the flavane nucleus as well as the presence of the alkoxylated function.

Over-investigated and under-treated: children with febrile convulsion in a Malaysian district hospital

INTRODUCTION

We conducted a retrospective audit on the inpatient assessment and care of children admitted with febrile convulsion to Hospital Batu Pahat, a district hospital in Malaysia, using the Malaysian national clinical practice guidelines and the American Academy of Paediatrics practice parameters on febrile convulsion as the reference standards.

METHODS

The case notes of 100 consecutive children admitted in 2004 were analysed. The documentation of major clinical features, selection of investigations, the timeliness of antipyresis and frequency of parental education were evaluated.

RESULTS

In general, the major clinical features that were relevant to the presenting problem were adequately documented, although fever was not mentioned as a presenting complaint in one quarter of the cases. On an average, about five investigations were ordered for every patient on admission. There was no major difference in the number of investigations conducted between children who were more severely ill and the rest of the patients. The majority of the investigations did not yield any useful diagnostic information. Only 38 percent of the children received antipyretics and 53 percent were tepid-sponged during fever, with 23 percent having received tepid-sponging without concurrently receiving antipyretics. No parental education on febrile convulsion was recorded in half of the cases.

CONCLUSION

Excessive unjustified investigations, deficient antipyresis when required and inadequate communication with the family of children with febrile convulsion were observed. Awareness of such deficiencies from this audit should lead to regular staff education, monitoring and future audits in order to improve the quality of our clinical care.

Human leukocyte class I antigen alleles A2 and A11 are not associated with nasopharyngeal carcinoma in West Malaysia

INTRODUCTION

Nasopharyngeal carcinoma (NPC) is the second most common cancer among Malaysian Chinese males. We determined the frequencies of 17 human leukocyte antigens (HLA), HLA-A and HLA-B, alleles in 88 Malaysian Chinese with NPC.

METHODS

Using polymerase chain reaction sequence-specific primers, the frequencies of 17 HLA-A and HLA-B alleles were analysed. They were A1, A2, A11, A31, A32, A33, B8, B13, B27, B38, B39, B44, B46, B55, B58, B61 and B71.

RESULTS

Three of the 17 alleles were detected in NPC patients. They were A1 (0.6 percent), A2 (56.3 percent) and A11 (43.2 percent). Three of the 17 alleles were detected in age- and sex-matched healthy individuals. They were A2 (50.0 percent), A11 (50.0 percent) and B27 (4.7 percent). The A2 and A11 alleles were evenly distributed in both groups, while A1 was only found in one NPC patient and B27 exclusively in healthy individuals.

CONCLUSION

We conclude that A1 is very rare, and A2, A11, A31, A32, A33, B8, B13, B38, B39, B44, B46, B55, B58, B61 and B71 alleles have no associations with the occurrence of NPC in Malaysia, while allele B27 is negatively associated.

Information sources used by New South Wales cancer clinicians: a qualitative study

BACKGROUND

This study identified (i) information sources used by cancer clinicians to guide pharmacological treatments, (ii) utilization of, and opinions about, online information sources and (iii) clinicians' ability to access a specific cancer treatment protocol (escalated bleomycin, etiposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, prednisone (BEACOPP) for Hodgkin's Lymphoma). The work was carried out before activation of the Cancer Institute New South Wales Standard Cancer Treatment (CI-SCaT) programme.

METHODS

We conducted semistructured interviews with a purposeful sample of senior and junior doctors, nurses and pharmacists treating adult cancer patients (n = 32) in eight New South Wales public hospitals.

RESULTS

Information seeking processes are context specific and vary from clinician to clinician and ward to ward. Clinicians use human, electronic and printed information sources at, or close to, the point of patient care; however, experienced colleagues are preferred where information is needed quickly or in unfamiliar clinical situations. Barriers to using online cancer information are environmental (hardware, connection speeds, time), personal (poor computer literacy and lack of awareness of appropriate sites) and economic (costs of journal subscriptions). Just over half of participants were able to locate a specific cancer protocol and none of these protocols was fully consistent with CI-SCaT recommendations.

CONCLUSION

There is no standardized approach to the pharmacological treatment of cancer patients in this sample of New South Wales clinicians. CI-SCaT will fill a gap with respect to standardizing oncology treatment. However, to ensure maximal CI-SCaT uptake, implementation plans should harness positive behavioural influences and attempt to modify the negative forces that act on hospital clinicians in their day-to-day work.

Evaluation of plasma Epstein-Barr virus DNA load as a prognostic marker for nasopharyngeal carcinoma

INTRODUCTION

Nasopharyngeal carcinoma (NPC) is an important cancer in Malaysia and is one of the major causes of cancer mortality in this country. This study evaluates the diagnostic and prognostic values in the quantitative relationship between the cell-free Epstein-Barr virus (EBV) deoxyribonucleic acid (DNA) load and the tumour burden.

METHODS

Blood plasma from 18 untreated NPC patients, 20 NPC patients who had been treated with radiotherapy, and 12 healthy individuals were evaluated. EBV copy number was determined following DNA extraction using real-time quantitative polymerase chain reaction.

RESULTS

The cell-free EBV DNA load was shown to be proportionately related to the presence of malignant disease. While the EBV copy number in untreated NPC patients had a median of 2,043 copies/ml, viral load in plasma of healthy controls was significantly lower (median of 0 copy/ml). A significant decrease in EBV load was observed in patients who had undergone radiotherapy while a high viral load indicated in one patient correlated to tumour relapse and presence of distant metastasis upon clinical investigation.

CONCLUSION

The blood plasma EBV DNA load was shown to be proportionately related to the presence of malignant disease. This preliminary study underscores the prognostic value of cell-free EBV DNA quantification.

AGAMOUS-LIKE 24, a dosage-dependent mediator of the flowering signals

The most dramatic phase change in plants is the transition from vegetative to reproductive growth. This flowering process is regulated by several interacting pathways that monitor both the developmental state of the plants and environmental cues such as light and temperature. The flowering-time genes FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), together with the floral meristem identity gene LEAFY (LFY), are three essential regulators integrating floral signals from multiple pathways in Arabidopsis thaliana. Part of the crosstalk among these genes is mediated by a putative transcription factor, AGAMOUS-LIKE 24 (AGL24). This gene is gradually activated in shoot apical meristems during the floral transition and later located in the whole zone of both inflorescence and floral meristems. Loss and reduction of AGL24 activity by double-stranded RNA-mediated interference result in late flowering, whereas constitutive overexpression of AGL24 causes precocious flowering. The correlation between the level of AGL24 accumulation and the alteration of flowering time suggests that AGL24 is a dosage-dependent flowering promoter. Analysis of AGL24 expression in various flowering-time mutants shows that it is regulated in several floral inductive pathways. Further genetic analyses of epistasis indicate that AGL24 may act downstream of SOC1 and upstream of LFY.

Mammography and screening for breast cancer

Mammography has been in general use as a breast imaging procedure for many years. More recently, it has taken on another important role, as a screening procedure for breast cancer. This article reviews its effectiveness in reducing morbidity and mortality resulting from the disease.

Use of magnetic resonance imaging in the evaluation of nasopharyngeal cancer

Computerised tomographic (CT) scanning is an established modality in the diagnosis and evaluation of tumours of the nasopharynx. Magnetic resonance (MR) imaging is a newer tool which has rapidly gained acceptance in the same regard due to its innate ability to better characterise and detail soft tissue structures, and its multiplanar scanning ability. This study reviews our experience, in a series of 30 cases, with the use of MR imaging in lesions of the nasopharynx, in particular nasopharyngeal carcinoma. Most of our patients showed involvement of the pharyngeal mucosal and parapharyngeal spaces, as expected. A large number also had intracranial extension. Our sample was probably biased as patients with neurological involvement are more likely to be assessed by MR than CT. Soft tissue infiltration, particularly intracranial extension, was very clearly delineated, especially when intravenous contrast (gadolinium DTPA) was administered. Bone erosion was not well demonstrated. In current clinical practice where radiotherapy is the most common form of treatment for nasopharyngeal carcinoma however, there does not in general, appear to be any clear advantage of MR over CT in the imaging of this particular disease, although there are some exceptions.

Transforming growth factor-alpha (TGF-alpha) in a semisolid dosage form: preservative and vehicle selection

The selection of an ideal semisolid vehicle for growth factors presents a challenge. Some antimicrobial agents are known to delay wound healing. The objective of this investigation was to identify appropriate preservatives and vehicles for TGF-alpha. Criteria for acceptance are noninterference with the mitogenic activity of TGF-alpha as well as adequate product preservation. Vehicles considered were o/w creams, ointments, and a gel. Combinations of six preservatives were tested. Selection was determined using both microbial preservative challenge and TGF-alpha mitogenic assay. In the former, 10 species of microorganisms were inoculated into formulation samples. At selected time intervals, it was determined whether colonies decreased, increased, or remained constant. In the mitogenic assay, samples of either preservatives or formulation prototypes were introduced to TGF-alpha-stimulated fibroblast cell cultures. Mitogenesis was determined by measuring 3H-dThd uptake into newly synthesized DNA. As preservatives, sorbic acid and quaternium-15 appear to satisfy both selection criteria. A thermosetting gel appears most promising as vehicle.

Mutagenicity of trinitrotoluene and its metabolites formed during composting

TNT was mutagenic for Salmonella typhimurium without the need of a rat liver metabolic activation system (S9). The mutagenic potency of TNT decreased in proportion to the number of nitro groups that were reduced to the amino form. The presence of a nitro group on the 4 position of the diamino congener is necessary for mutagenicity. Among the active congeners, mutagenicity was generally greater for TA100 than TA98, except that for the 4-amino congener the reverse was true. In cases when S9 was included in the assay, there was always a decrease in the number of mutants induced as compared with those without S9. Tetryl behaved like TNT, except that it was approximately three times more potent. RDX and HMX were not mutagenic under the conditions of the assay. When TNT was composed, the major metabolites identified in organic extracts of compost samples were the 2-amino and 4-amino congeners. An acetonitrile extract of compost was tested and found to be more mutagenic for TA98 than TA100, much like the authentic 4-amino congener, but the amount of this congener in the extract did not account for the degree of mutagenicity.

Formaldehyde in drinking water: comparative hazard evaluation and an approach to regulation

Formaldehyde, a widely used industrial chemical to which humans are ubiquitously exposed, presented cause for concern when it was demonstrated to be carcinogenic in laboratory animals. Risk assessment protocols subsequently applied to formaldehyde are of questionable validity in light of the results of recent mechanistic investigations of biological responses to formaldehyde. Further, the hazard of ingested formaldehyde is not addressed in current assessment protocols. This paper addresses the potential human health risks accompanying low-level exposure to formaldehyde as a contaminant in drinking water. In this exposure scenario, noncarcinogenic risk from inhalation of formaldehyde from drinking water is evaluated through knowledge of the metabolism and biological effects of formaldehyde exposure. Noncarcinogenic risk from ingestion of formaldehyde in drinking water is evaluated from the perspective gained by comparison with dietary sources of formaldehyde. Carcinogenic risk to humans is evaluated in light of recent investigations into the mechanisms underlying biological responses to formaldehyde exposure. Finally, based on a comparison of ingestion of formaldehyde in drinking water with ingestion of naturally occurring formaldehyde in foods, a comparative hazard approach to formaldehyde regulation is offered as a supplement to the rigid evaluation protocols currently used.

A simple adherence test for detection of IgM antibodies in typhoid

A simple adherence test to detect IgM antibodies in patients with typhoid is described. The test utilises the IgM-"capture" approach, in which the test serum is applied to microtitration plate wells previously coated with anti-human IgM, followed by application of a stained Salmonella typhi antigen suspension which shows adherence in positive cases. By this test, 58 (95%) of 61 sera from confirmed cases of typhoid possessed IgM antibodies to the H or O or both antigens of S. typhi. In patients for whom a diagnosis of typhoid was based only on a significant Widal-test titre, 31 (41%) of 76 sera had IgM antibodies to the H or O or both antigens of S. typhi. Some cross-reactivity of the IgM antibodies was detected, especially with the O antigens of S. paratyphi A and B. A total of 82 sera from non-typhoidal fevers (leptospirosis, typhus, dengue fever) showed no reactivity in this test. In normal sera there was no detectable IgM to the O antigen of S. typhi and only a small number (3.9%) had low levels of IgM to the H antigen. The significance and potential importance of this simple, sensitive, specific and economical test is discussed.

Effect of thermal additions on the density and distribution of thermophilic amoebae and pathogenic Naegleria fowleri in a newly created cooling lake

Pathogenic Naegleria fowleri is the causative agent of fatal human amoebic meningoencephalitis. The protozoan is ubiquitous in nature, and its presence is enhanced by thermal additions. In this investigation, water and sediments from a newly created cooling lake were quantitatively analyzed for the presence of thermophilic amoebae, thermophilic Naegleria spp., and the pathogen Naegleria fowleri. During periods of thermal additions, the concentrations of thermophilic amoebae and thermophilic Naegleria spp. increased as much as 5 orders of magnitude, and the concentration of the pathogen N. fowleri increased as much as 2 orders of magnitude. Concentrations of amoebae returned to prior thermal perturbation levels within 30 to 60 days after cessation of thermal additions. Increases in the thermophilic amoeba concentrations were noted in Savannah River oxbows downriver from the Savannah River plant discharge streams as compared with oxbows upriver from the discharges. Concentrations of thermophilic amoebae and thermophilic Naegleria spp. correlated significantly with temperature and conductivity. Air samples taken proximal to the lake during periods of thermal addition showed no evidence of thermophilic Naegleria spp. Isoenzyme patterns of the N. fowleri isolated from the cooling lake were identical to patterns of N. fowleri isolated from other sites in the United States and Belgium.

Cytidine 5'-monophospho-N-acetyl neuraminic acid and a low molecular weight factor from human blood cells induce lipopolysaccharide alteration in gonococci when conferring resistance to killing by human serum

Recently evidence has been obtained that a minute amount of cytidine 5'-monophospho-N-acetyl neuraminic acid (CMP-NANA) or a closely related compound is the low Mr factor in human red blood cells which induces Neisseria gonorrhoeae (BS4(agar] to resistance to killing by fresh human serum. Induction of gonococci to resistance by both CMP-NANA and semi-purified low Mr factor from red blood cells was accompanied by a 35-55% reduction of silver staining of lipopolysaccharide separated in SDS-PAGE gels of proteinase K digests. These alterations in lipopolysaccharide are probably responsible for conferring serum resistance. However, lipopolysaccharide-containing digests from resistant as well as from susceptible gonococci neutralised serum bactericidal activity. These observations may have wider implications since CMP-NANA is a sialylating agent wide-spread in mammalian tissues and LPS is ubiquitous amongst Gram-negative pathogens.

Protein changes associated with induced resistance of Neisseria gonorrhoeae to killing by human serum are relatively minor

Serum-susceptible (SS) Neisseria gonorrhoeae were induced to resistance (SR) to complement-mediated killing by fresh human serum (FHS) by a small-Mr factor(s) from guinea-pig blood in 3 h at 37 degrees C, but not in the presence of bacteriostatic concentrations of chloramphenicol or neomycin, indicating that proteins mediated the acquisition of resistance. SDS-PAGE protein profiles of lysates of equal numbers of gonococci showed only two qualitative differences between SR and SS organisms, both in minor components (a protein A of about 205 kDa in the former and not the latter and vice versa for a protein B of about 16 kDa). Many proteins, however, including the three principal outer-membrane proteins, were present in larger amounts in SR gonococci. The lack of major changes in proteins when resistance is acquired was confirmed by immunoblotting the two protein profiles with the IgG of hyper-immune rabbit anti-SR and anti-SS sera, of rabbit anti-SR serum after absorption by SS organisms and of FHS used alone and after absorption with SS organisms. The IgM of FHS, which is responsible for most of the bactericidal activity, showed only faint reactions with a few proteins common to both SS and SR gonococci and no reactions when the FHS was absorbed with SS gonococci. This is in contrast to the strong and different reactions given with lipopolysaccharide (LPS) components of SS and SR organisms, which, prepared from the former organisms, neutralize the bactericidal activity of FHS. Hence, the relatively small protein changes accompanying induction are less likely to be directly responsible for serum resistance than the more profound LPS changes.

Indication of thioglucosidase activity in extracts of Neisseria gonorrhoeae

The recent demonstration of a host-derived inducer of gonococcal resistance to complement-mediated killing by human serum in purified serum and red blood cell fractions, which contained small glucopeptides with cysteine as one of the constituent amino acids, prompted an investigation of Neisseria gonorrhoeae for thioglucosidase activity. This involved an examination of supernatants of sonicated gonococci for thioglucoside hydrolysis by following, spectroscopically, the hydrolysis of 6-purine beta-D-glucothiopyranoside to 6-mercaptopurine and glucose. Extracts of N. gonorrhoeae were found to hydrolyse this thioglucoside. A substantial activity was present in a fraction with the same order of molecular weight as plant thioglucosidases. This led us to suspect the presence of a thioglucosidase in N. gonorrhoeae.

Gonococci in vivo and in vitro. Further studies on the host and bacterial determinants of gonococcal resistance to killing by human serum, and by phagocytes

A small M, heat and acid labile, host inducer(s) of gonococcal resistance to complement mediated killing by fresh human serum (-FHS), being purified from red blood cell (RBC) extracts, produced changed in lipopolysaccharide (LPS) structure, surface antigens and proteins; and acquirement of resistance related to loss of a target antigen for bactericidal IgM, possibly LPS components. A 20 kDalt. lipoprotein with a high content of glutamic acid isolated from outer membranes of a gonococcal strain selected in vivo is a determinant of gonococcal resistance to killing by human phagocytes. Sonic extracts of gonococci may contain a cytotoxin for human phagocytes. At the 4th International Pathogenic Neisseriae Conference, we reported (Parsons et al. 1985) that conditions in vivo induced phenotypic change leading to gonococcal resistance to complement-mediated killing by human serum; and, also, selected gonococcal types which showed a greater resistance to intracellular killing by human phagocytes than laboratory strains. Furthermore, evidence was presented that not only was resistance to complement mediated killing important in gonococcal pathogenesis, but also resistance to phagocytic defences. This paper describes the continuance of our studies on the determinants of induced serum resistance and of resistance to killing by phagocytes including toxicity to these cells. Each section begins by summarising previous work that was referenced in Parsons et al. (1985).

Lipopolysaccharide alteration is associated with induced resistance of Neisseria gonorrhoeae to killing by human serum

On SDS-PAGE, solubilized and proteinase K treated preparations of Neisseria gonorrhoeae strain BS4 (agar) showed differences in silver stained lipopolysaccharide (LPS) patterns, before and after induction to resistance to serum killing by incubation for 3 h at 37 degrees C with low Mr fractions from lysates of guinea pig red blood cells. Preparations from the original serum susceptible gonococci and LPS purified from such bacteria showed two components, but the preparations from the serum resistant gonococci were deficient in the higher Mr component. Furthermore, on immunoblotting with fresh human serum (FHS), the two LPS components of the susceptible gonococci reacted strongly with IgM. With preparations from the serum resistant gonococci there was no reaction in the area corresponding to the higher Mr component and a weaker reaction with the component of low Mr. Purified LPS from the susceptible gonococci neutralized the bactericidal activity of FHS against N. gonorrhoeae strain BS4 (agar) probably by reacting with the relevant antibody, since heated FHS was no longer bactericidal when mixed with a source of complement (human placental serum) after prior reaction with the LPS. These neutralization tests coupled with the results of immunoblotting strongly suggest that increased serum resistance is due to the lack of the high Mr LPS moiety.

The toxicity of sixteen metallic compounds in Chinese hamster ovary cells

The toxicity of 16 metal salts to Chinese hamster ovary (CHO) cells was determined by measuring the cloning efficiency (CE) of CHO cells after exposure to the metals. CHO cells differed by a factor of 10(5) to 10(6) in their toxic response to these metal salts. While Cd(II) was the most toxic ion, Mg(II) exhibited the least toxicity based on either CE50 (concentration required to reduce the CE to 50%) or D0 (concentration increment which reduced the CE by 63%). On the basis of CE50, the toxicity ranking was Ag greater than Tl for monovalent metals, Cd greater than Zn greater than Hg greater than Co greater Cu greater than Mn greater than Ni greater than Be greater than Pd greater than Sr greater than Mg for divalent metals, and In greater than Rh greater than Y for trivalent metals. A similar ranking was found for D0. For the 11 divalent metals, correlations of CE50 and D0 in the CHO cell assay and the Pearson-Mawby softness parameter for metals (sigma p) were reasonably strong. A good correlation exists between the results of this study on the toxic response in CHO cells and published data on toxicity in mice and Drosophila. It appears that the CHO cell cloning assay may be useful in preliminary screening of metallic compounds as an indicator of their predicted toxicity in higher organisms.

Alteration of pyocin-sensitivity pattern of Neisseria gonorrhoeae is associated with induced resistance to killing by human serum

A laboratory-grown strain of Neisseria gonorrhoeae, selected in vivo, BS4 (agar), is susceptible to complement-mediated killing by fresh human serum but is relatively resistant to killing by human phagocytes. It can be induced to serum resistance by incubation with a small molecular weight fraction of guinea pig serum. The serum-susceptible and induced-resistant forms show differences in pyocin sensitivity tests. This indicates either differences in the structure of their lipopolysaccharides or masking of some determinant(s). The pyocin sensitivity pattern of BS4 (agar) is only slightly different from that of a closely related strain, BSSH, which is more susceptible to killing by human phagocytes.

Mutagenicity and cytotoxicity of dimethyl and monomethyl sulfates in the CHO/HGPRT system

It has recently been shown that coal fly ash collected from coal-fired plants contains dimethyl sulfate (DMS) and monomethyl sulfate (MS) at concentrations as high as 830 ppm. Both these compounds were tested in the CHO/HGPRT system, and it was found that only DMS was cytotoxic and mutagenic to CHO cells. On a molar basis, DMS is twice a mutagenic as methyl methanesulfonate (MMS). Under our treatment conditions, maximum mutation induction and cytotoxicity were obtained after approximately 1 h. The Mutagenic potency of DMS was more stable in aqueous solutions at 4 degrees C than at the ambient temperature of 22 degrees C, but was least stable in DMSO solutions at 22 degrees C. Near-ultraviolet (near-UV) light caused an approximately twofold decrease in the mutagenic and cytotoxic effects of DMS. Although DMS produced by coal combustion could be rendered innocuous by environmental agents in a short span of time, this compound could still pose a health risk to workers closely involved in coal-combustion technology.

Effect of metabolic activation on the cytotoxicity and mutagenicity of 1,2-dibromoethane in the CHO/HGPRT system

When ethylene dibromide (EtBr2) was assayed with the Chinese hamster ovary/hypoxanthine-guanine phosphoribosyl transferase (CHO/HGPRT) system coupled with a rat liver metabolic activation system (S9), which contains Ca2+ (Ca, Mg-S9), the cytotoxicity of EtBr2 was greatly increased over that obtained when NADP was omitted from the Ca, Mg-S9 or when EtBr2 was assayed as a direct-acting agent. However, on a molar basis, the mutagenicity of EtBr2 remained unaffected. The omission of Ca2+ from the Ca, Mg-S9 metabolic activation system (Mg-S9), with either the addition or omission of NADP, caused approximately a 2-fold decrease in the mutagenicity of EtBr2 when compared to the results obtained by using the Ca, Mg-S9 system. The cytotoxicity of EtBr2 was further increased when a purified microsomal fraction, prepared from the S9 fraction, was used in the presence of Ca2+. In the absence of this calcium ion, this metabolic activation system was extremely cytotoxic to Chinese hamster ovary cells even without the presence of a mutagen or promutagen. The cytotoxicity of EtBr2 in the following assay systems decreased in this order: Ca, Mg-microsomes greater than Ca, Mg-S9 greater than S9 greater than direct-acting agent greater than or equal to Ca, Mg-S9 without NADP greater than or equal to Mg-S9 without NADP. Cytotoxicity appears to be NADP-dependent on the presence of NADP in the S9 system, the mutant yield (number of mutants that could be induced) was higher in its absence. Addition of reduced glutathione to Mg-S9 without NADP increased the mutagenicity of EtBr2 to values that did not exceed those obtained when EtBr2 was tested as a direct-acting agent. On a molar basis, ethyl methanesulfonate (EMS) is less cytotoxic but equally as mutagenic as EtBr2. However the mutant yield of EMS was higher than that of EtBr. Inclusion of Ca, Mg-S9 in the assay system had no effect on the biological activities of EMS.

Effect of calcium phosphate and alumina C gamma gels on the mutagenicity and cytotoxicity of dimethylnitrosamine as studied in the CHO/HGPRT system

When CaCl2 was added in increasing concentrations to a rat liver metabolic activation system (S9) buffered with sodium phosphate, the mutagenic activity and cytotoxicity of dimethylnitrosamine (DMN) in the Chinese hamster ovary cell/hypoxanthine-guanine phosphoribosyl transferase (CHO/HGPRT) system were greatly increased. This effect was not observed with an S9 mix buffered with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). The calcium phosphate gel precipitate of the S9 mix possessed approximately 1/3 of the total activity of the mix, while the supernatant had only slight activity. However, when the calcium phosphate gel precipitate of a solution of S9 salts (without S9 protein) was added to the supernatant, the remaining 2/3 of the activity was recovered. Commercially obtained calcium phosphate, tricalcium phosphate, and alumina C gamma gels could substitute for CaCl2 in the S9 mix, but diethylaminoethyl cellulose (DEAE cellulose) could not. Alumina C gamma gel can exert its effect in the absence of both CaCl2 and phosphate in the S9 mix. Increasing the time of contact between the S9 protein and the S9 salts increased the efficacy with which the S9 mix activated DMN; this is indicative of an adsorptive process by calcium phosphate gel.