A Mycobacterial Systems Resource for the Research Community

Functional characterization of bacterial proteins lags far behind the identification of new protein families. This is especially true for bacterial species that are more difficult to grow and genetically manipulate than model systems such as Escherichia coli and Bacillus subtilis To facilitate functional characterization of mycobacterial proteins, we have established a Mycobacterial Systems Resource (MSR) using the model organism Mycobacterium smegmatis This resource focuses specifically on 1,153 highly conserved core genes that are common to many mycobacterial species, including Mycobacterium tuberculosis, in order to provide the most relevant information and resources for the mycobacterial research community. The MSR includes both biological and bioinformatic resources. The biological resource includes (i) an expression plasmid library of 1,116 genes fused to a fluorescent protein for determining protein localization; (ii) a library of 569 precise deletions of nonessential genes; and (iii) a set of 843 CRISPR-interference (CRISPRi) plasmids specifically targeted to silence expression of essential core genes and genes for which a precise deletion was not obtained. The bioinformatic resource includes information about individual genes and a detailed assessment of protein localization. We anticipate that integration of these initial functional analyses and the availability of the biological resource will facilitate studies of these core proteins in many Mycobacterium species, including the less experimentally tractable pathogens M. abscessus, M. avium, M. kansasii, M. leprae, M. marinum, M. tuberculosis, and M. ulceransIMPORTANCE Diseases caused by mycobacterial species result in millions of deaths per year globally, and present a substantial health and economic burden, especially in immunocompromised patients. Difficulties inherent in working with mycobacterial pathogens have hampered the development and application of high-throughput genetics that can inform genome annotations and subsequent functional assays. To facilitate mycobacterial research, we have created a biological and bioinformatic resource (https://msrdb.org/) using Mycobacterium smegmatis as a model organism. The resource focuses specifically on 1,153 proteins that are highly conserved across the mycobacterial genus and, therefore, likely perform conserved mycobacterial core functions. Thus, functional insights from the MSR will apply to all mycobacterial species. We believe that the availability of this mycobacterial systems resource will accelerate research throughout the mycobacterial research community.

Early-onset type 2 diabetes: higher burden of atherogenic apolipoprotein particles during statin treatment

AIMS

To determine the burden of atherogenic apolipoprotein particles in early-onset type 2 diabetes (T2D) compared to those with later-onset disease during statin treatment.

METHODS

Early and later-onset T2D was defined as current age below and above 40 years respectively. Conventional lipid profile, LDL, non-HDL cholesterol, apolipoprotein B and A1 were determined in those without cardiovascular disease treated with simvastatin to achieve LDL cholesterol <2 mmol/l.

RESULTS

Fifty subjects were recruited (early-onset n=24 and later-onset n=26). The mean age was 34.5 and 59.6 years and mean age of diagnosis was 29.1 and 49.1 years for early and later-onset T2D respectively. Obesity, dyslipidaemia, microalbuminuria, glycaemic control and diabetes complication burden were similar in both cohorts. Early-onset subjects received non-significantly higher simvastatin dose (37.5 vs. 31.9 mg daily, p=NS). On-treatment LDL cholesterol was similar in both cohorts (early vs. later-onset; 2.12 vs. 1.97 mmol/l, p=NS). Fasting triglyceride, non-HDL, apo B and B/A1 ratio were significantly higher in early-onset cohort. There was no difference in apo A1, HDL and total cholesterol/HDL ratio. Apo B level remained significantly higher among early-onset subjects after adjustment for insulin treatment. Lower current age and age of diagnosis were significant predictors of higher apo B level.

CONCLUSION

The burden of atherogenic apolipoprotein particles was greater in early-onset T2D despite adequate statin treatment indicating an adverse phenotype for vascular disease.

A survey of laboratory practice in the clinical authorization and reporting of results

BACKGROUND

The aim of this survey was to determine the practice of authorization and reporting of results in clinical biochemistry laboratories in the UK.

METHOD

Questionnaires were distributed to the heads of clinical biochemistry departments through the National Audit Committee of the Association of Clinical Biochemists. The standards surveyed were based on guidelines for the reporting of results produced by the Royal College of Pathologists and the relevant Clinical Pathology Accreditation standards.

RESULTS

Completed questionnaires were received from 137 laboratories. Workload ranged from 15,000 to 750,000 requests per annum (median 276,883). Most laboratories (98%) release results electronically to at least some wards in real-time. Areas where difficulties were identified included identifying requests that had posed specific questions and access to clinical information at the authorization stage, recording clinical advice given, and ensuring comments remained attached to printed reports or were on the same screen on computer reports. All but six laboratories had consultant advice available, including out of hours, but only 17% had an arrangement for clinical authorization to occur out of hours.

CONCLUSION

Only 45 laboratories (33%) were able to achieve 100% compliance with the standards that currently exist, but many others showed evidence of good practice. The practical obstacles still to be overcome include limitations in the capabilities of laboratory computer systems, the lack of accessible electronic clinical records, the difficulties of covering work out of hours and insufficient appropriately trained staff.

Quarts out of pint pots -- expanding the pint. Clinical budgeting in practice

Clinical budgeting is the process whereby clinical users are charged for the resources they use. A system for recharging users for the costs of tests was introduced at the Northern General Hospital, Sheffield, in 1995, and has been in operation since. The system has allowed pathology to maintain budgetary balance, has automatically compensated for workload increases, has allowed the introduction of new tests, and has encouraged clinical users to include pathology costs in their bids for funding for clinical developments. The system works according to rules agreed between pathology and its users at the outset, but once set up takes a minimal amount of work to operate and maintain.

Phylogenetic conservation of the makorin-2 gene, encoding a multiple zinc-finger protein, antisense to the RAF1 proto-oncogene

Natural endogenous antisense RNAs have been reported in multiple loci, with evidence in some cases supporting a regulatory role for the antisense transcript. Here, we describe a novel gene, makorin RING zinc finger-2 (MKRN2), that overlaps and is antisense to the gene RAF1 in mammals. Phylogenetic analysis of the 3' untranslated region of RAF1 orthologues suggests that this relationship may have existed for up to 450 million years. We have also identified MKRN2 orthologues in two species of fish. This places the gene duplication event that created this locus from an ancestral MKRN1 gene early in vertebrate evolution, over 450 million years ago. Northern blot analyses show that human MKRN2 and RAF1 are co-expressed in tissues and cell lines, raising the possibility of mRNA duplex formation. The encoded makorin-2 protein is likely a ribonucleoprotein of unknown function, but its conservation suggests an important cellular role. The data presented here describe a conserved vertebrate MKRN2 gene that is closely associated with the RAF1 locus.

Diverse splicing mechanisms fuse the evolutionarily conserved bicistronic MOCS1A and MOCS1B open reading frames

Molybdenum is an essential cofactor in many enzymes, but must first be complexed by molybdopterin, whose synthesis requires four enzymatic activities. The first two enzymes of this pathway are encoded by the MOCS1 locus in humans. We describe here a remarkably well-conserved novel mRNA splicing phenomenon that produces both an apparently bicistronic MOCS1AM-OCS1B transcript, as well as a distinct class of monocistronic transcript. The latter are created by a variety of splicing mechanisms (alternative splice donors, alternative splice acceptors, and exon-skipping) to bypass the normal termination nonsense codon of MOCS1A resulting in fusion of the MOCS1A and MOCS1B open reading frames. Therefore, these "no-nonsense" transcripts encode a single bifunctional protein embodying both MOCS1A and MOCS1B activities. This coexpression profile was observed in vertebrates (human, mouse, cow, rabbit, opossum, and chicken) and invertebrates (fruit fly and nematode) spanning at least 700 million years of evolution. Our phylogenetic data also provide evidence that the bicistronic form of MOCS1 mRNA is likely to only produce MOCS1A protein and, combined with Northern analyses, suggests that MOCS1B is translated only as a fusion with MOCS1A. Taken together, the data presented here demonstrate a very highly conserved and physiologically relevant dynamic splicing scheme that profoundly influences the protein-coding potential of the MOCS1 locus.

The ancient source of a distinct gene family encoding proteins featuring RING and C(3)H zinc-finger motifs with abundant expression in developing brain and nervous system

Intronless genes can arise by germline retrotransposition of a cDNA originating as mRNA from an intron-containing source gene. Previously, we described several members of a family of intronless mammalian genes encoding a novel class of zinc-finger proteins, including one that shows imprinted expression and one that escapes X-inactivation. We report here the identification and characterization of the Makorin ring finger protein 1 gene (MKRN1), a highly transcribed, intron-containing source for this family of genes. Phylogenetic analyses clearly indicate that the MKRN1 gene is the ancestral founder of this gene family. We have identified MKRN1 orthologs from human, mouse, wallaby, chicken, fruitfly, and nematode, underscoring the age and conservation of this gene. The MKRN gene family encodes putative ribonucleoproteins with a distinctive array of zinc-finger motifs, including two to four C(3)H zinc-fingers, an unusual Cys/His arrangement that may represent a novel zinc-finger structure, and a highly conserved RING zinc-finger. To date, we have identified nine MKRN family loci distributed throughout the human genome. The human and mouse MKRN1 loci map to a conserved syntenic group near the T-cell receptor beta cluster (TCRB) in chromosome 7q34-q35 and chromosome 6A, respectively. MKRN1 is widely transcribed in mammals, with high levels in murine embryonic nervous system and adult testis. The ancient origin of MKRN1, high degree of conservation, and expression pattern suggest important developmental and functional roles for this gene and its expressed family members.

Conserved characteristics of heterochromatin-forming DNA at the 15q11-q13 imprinting center

Nuclear matrix binding assays (NMBAs) define certain DNA sequences as matrix attachment regions (MARs), which often have cis-acting epigenetic regulatory functions. We used NMBAs to analyze the functionally important 15q11-q13 imprinting center (IC). We find that the IC is composed of an unusually high density of MARs, located in close proximity to the germ line elements that are proposed to direct imprint switching in this region. Moreover, we find that the organization of MARs is the same at the homologous mouse locus, despite extensive divergence of DNA sequence. MARs of this size are not usually associated with genes but rather with heterochromatin-forming areas of the genome. In contrast, the 15q11-q13 region contains multiple transcribed genes and is unusual for being subject to genomic imprinting, causing the maternal chromosome to be more transcriptionally silent, methylated, and late replicating than the paternal chromosome. We suggest that the extensive MAR sequences at the IC are organized as heterochromatin during oogenesis, an organization disrupted during spermatogenesis. Consistent with this model, multicolor fluorescence in situ hybridization to halo nuclei demonstrates a strong matrix association of the maternal IC, whereas the paternal IC is more decondensed, extending into the nuclear halo. This model also provides a mechanism for spreading of the imprinting signal, because heterochromatin at the IC on the maternal chromosome may exert a suppressive position effect in cis. We propose that the germ line elements at the 15q11-q13 IC mediate their effects through the candidate heterochromatin-forming DNA identified in this study.

Concerted regulation and molecular evolution of the duplicated SNRPB'/B and SNRPN loci

The human small nuclear ribonucleoprotein SNRPB ' /B gene is alternatively spliced to produce the SmB or SmB' spliceosomal core proteins. An ancestral duplication gave rise to the closely related SNRPN paralog whose protein product, SmN, replaces SmB'/B in brain. However, the precise evolutionary and functional relationship between these loci has not been clear. Genomic, cDNA and protein analyses presented here in chicken, two marsupials (South American opossum and tammar wallaby), and hedgehog, suggest that the vertebrate ancestral locus produced the SmB' isoform. Interestingly, three eutherians exhibit radically distinct splice choice expression profiles, producing either exclusively SmB in mouse, both SmB and SmB' in human, or exclusively SmB' in hedgehog. The human SNRPB ' /B locus is biallelically unmethylated, unlike the imprinted SNRPN locus which is unmethyl-ated only on the expressed paternal allele. Western analysis demonstrates that a compensatory feedback loop dramatically upregulates SmB'/B levels in response to the loss of SmN in Prader-Willi syndrome brain tissue, potentially reducing the phenotypic severity of this syndrome. These findings imply that these two genes encoding small nuclear ribonucleoprotein components are subject to dosage compensation. Therefore, a more global regulatory network may govern the maintenance of stoichiometric levels of spliceosomal components and may constrain their evolution.

Genetic abnormalities in Prader-Willi syndrome and lessons from mouse models

Prader-Willi syndrome is a multigenic disorder with developmental and neurobehavioural abnormalities. There are multiple genetic causes, although all ultimately involve the loss of paternally derived gene expression of chromosome region 15q11-q13. Multiple imprinted genes expressed only from the paternal allele have been identified in the specific region of human chromosome 15q associated with Prader-Willi syndrome and in the syntenic mouse chromosome 7C region, including a novel polycistronic gene (SNURF-SNRPN) that encodes two independent proteins. The latter genetic locus may play a key role in Prader-Willi syndrome and the evolution of imprinting in this domain, because it is uniquely involved with mutations in the imprinting process and balanced translocations in this syndrome. Indeed, based on the co-localization of SNURF and SNRPN within the imprinting control region critical to Prader-Willi syndrome, evolutionary arguments would suggest that this genetic locus is a prime candidate for mutations producing the failure-to-thrive phenotype of neonates with this syndrome and of corresponding mouse models. Hence, the SNURF-SNRPN gene may encode a paternally derived postnatal growth factor.

Validation of the SpaceLabs 90207 ambulatory blood pressure device for hemodialysis patients

BACKGROUND

Background Ambulatory blood pressure monitoring (ABPM) has been used increasingly in assessing dialysis patients. However, devices have not been validated formally for this population. Formal device validation is important in order to guarantee adequate performance for populations with special characteristics, such as patients undergoing hemodialysis.

OBJECTIVE

To achieve formal validation of the SpaceLabs 90207 ambulatory blood pressure device (SLD) using a modified British Hypertension Society protocol.

METHODS

Eighty-five hemodialysis patients were studied, generating 255 readings. Readings were obtained with patients supine (in a dialysis chair) over 5-10 min during hemodialysis. Simultaneous, same-arm readings were obtained through the use of a T connector to a calibrated mercury manometer. The mean differences between readings obtained by observers and those obtained by the device were calculated. Limits of agreement between observers and SLD were determined and plotted according to the method of Bland and Altman. For grading of performance, we determined the number of readings for which the readings obtained by the device were within 5, 10, and 15mmHg of manometer readings. Final gradings were ascribed according to British Hypertension Society criteria.

RESULTS

The mean blood pressure (+/-SD) was 141/76+/-31/15mmHg (observers) and 141/77+/-27/15mmHg (SLD), and the mean (+/-SD) difference between observers and device (observer-device) was -0.5+/-7.5mmHg for systolic blood pressure (SBP) and -0.2+/-5.2mmHg for diastolic blood pressure (DBP). The device was less accurate in extreme ranges of SBP. In fact, there was a positive correlation between average [(observer+device)/2] and difference (observer-device) for SBP (r =0. 54, P <0.0001), showing that underestimation in higher ranges, and overestimation in lower ranges of blood pressure occurred for SBP. For SBP, 53% of readings were within 5mmHg of those obtained by the observers, 85% were within 10mmHg, and 97% within 15mmHg. For DBP, 78% were within 5mmHg, 96% within 10mmHg, and 98% within 15mmHg. These observations conferred on the device grade C for SBP and grade B for DBP. The type of vascular access and the presence of non-functioning arteriovenous grafts and fistulas in the ipsilateral arm did not alter these results significantly.

CONCLUSIONS

These data validate the use of this device for hemodialysis patients. However, caution should be exercised in the evaluation of upper and lower ranges of SBP.

Chromium homeostasis in patients with type II (NIDDM) diabetes

The purpose of this study was to assess chromium handling in non-insulin dependent diabetic patients (NIDDM) compared to healthy volunteers. Chromium handling was evaluated using fasting blood and second morning void urine samples from 93 NIDDM patients and 33 healthy volunteers. Significant differences in chromium homeostasis were seen between patients and controls. NIDDM patients had mean levels of plasma chromium around 33% lower and urine values almost 100% higher than those found in health. Healthy volunteers showed a significant negative correlation between fasting levels of plasma chromium and insulin. This was not evident in NIDDM patients. In the early years of onset of NIDDM, plasma chromium values were inversely correlated with plasma glucose. This was lost in patients with diabetes of more than 2 years duration. We suggest large losses of chromium over many years may exacerbate an already compromised chromium status in NIDDM patients and might contribute to the developing insulin resistance seen in patients with type 2 diabetes.

An imprinted, mammalian bicistronic transcript encodes two independent proteins

Polycistronic transcripts are common in prokaryotes but rare in eukaryotes. Phylogenetic analysis of the SNRPN (SmN) mRNA in five eutherian mammals reveals a second highly conserved coding sequence, termed SNURF (SNRPN upstream reading frame). The vast majority of nucleotide substitutions in SNURF occur in the wobble codon position, providing strong evolutionary evidence for selection for protein-coding function. Because SNURF-SNRPN maps to human chromosome 15q11-q13 and is paternally expressed, each cistron is a candidate for a role in the imprinted Prader-Willi syndrome (PWS) and PWS mouse models. SNURF encodes a highly basic 71-aa protein that is nuclear-localized (as is SmN). Because SNURF is the only protein-coding sequence within the imprinting regulatory region in 15q11-q13, it may have provided the original selection for imprinting in this domain. Whereas some human tissues express a minor SNURF-only transcript, mouse tissues express only the bicistronic Snurf-Snrpn transcript. We show that both SNURF and SNRPN are translated in normal, but not PWS, human, and mouse tissues and cell lines. These findings identify SNURF as a protein that is produced along with SmN from a bicistronic transcript; polycistronic mRNAs therefore are encoded in mammalian genomes where they may form functional operons.

A novel imprinted gene, encoding a RING zinc-finger protein, and overlapping antisense transcript in the Prader-Willi syndrome critical region

We describe a complex imprinted locus in chromosome 15q11-q13 that encodes two genes, ZNF127 and ZNF127AS. The ZNF127 gene encodes a protein with a RING (C3HC4) zinc-finger and multiple C3H zinc-finger motifs, the former being closely related to a protein from variola major virus, the smallpox etiological agent. These motifs allow prediction of ZNF127 function as a ribonucleoprotein. The intronless ZNF127 gene is expressed ubiquitously, but the entire coding sequence and 5' CpG island overlaps a second gene, ZNF127AS, that is transcribed from the antisense strand with a different transcript size and pattern of expression. Allele-specific analysis shows that ZNF127 is expressed only from the paternal allele. Consistent with this expression pattern, in the brain the ZNF127 5' CpG island is completely unmethylated on the paternal allele but methylated on the maternal allele. Analyses of adult testis, sperm and fetal oocytes demonstrates a gametic methylation imprint with unmethylated paternal germ cells. Recent findings indicate that ZNF127 is part of the coordinately regulated imprinted domain affected in Prader-Willi syndrome patients with imprinting mutations. Therefore, ZNF127 and ZNF127AS are novel imprinted genes that may be associated with some of the clinical features of the polygenic Prader-Willi syndrome.

Imprinting-mutation mechanisms in Prader-Willi syndrome

Microdeletions of a region termed the "imprinting center" (IC) in chromosome 15q11-q13 have been identified in several families with Prader-Willi syndrome (PWS) or Angelman syndrome who show epigenetic inheritance for this region that is consistent with a mutation in the imprinting process. The IC controls resetting of parental imprints in 15q11-q13 during gametogenesis. We have identified a larger series of cases of familial PWS, including one case with a deletion of only 7.5 kb, that narrows the PWS critical region to <4. 3 kb spanning the SNRPN gene CpG island and exon 1. Identification of a strong DNase I hypersensitive site, specific for the paternal allele, and six evolutionarily conserved (human-mouse) sequences that are potential transcription-factor binding sites is consistent with this region defining the SNRPN gene promoter. These findings suggest that promoter elements at SNRPN play a key role in the initiation of imprint switching during spermatogenesis. We also identified three patients with sporadic PWS who have an imprinting mutation (IM) and no detectable mutation in the IC. An inherited 15q11-q13 mutation or a trans-factor gene mutation are unlikely; thus, the disease in these patients may arise from a developmental or stochastic failure to switch the maternal-to-paternal imprint during parental spermatogenesis. These studies allow a better understanding of a novel mechanism of human disease, since the epigenetic effect of an IM in the parental germ line determines the phenotypic effect in the patient.

Structure and function correlations at the imprinted mouse Snrpn locus

The human SNRPN gene maps within Chromosome (Chr) 15q11-q13, the region responsible for Prader-Willi syndrome (PWS) and Angelman syndrome (AS). As one of several 15q11-q13 transcripts expressed from the paternal allele-only, SNRPN is a candidate gene to explain at least some of the PWS phenotype in human and in genetic mouse models. The promoter and first exon of the SNRPN gene also correspond to an imprinting center element responsible for resetting of the maternal to paternal imprints within 15q11-q13 during spermatogenesis. Through characterization of the imprinted murine Snrpn locus in mouse Chr 7C, we have found that the gene structure is very similar to the human, with ten conserved exons spanning 22 kb, the last seven of which are tightly clustered. The promoter of Snrpn is differentially methylated in ES cells and adult tissues, supporting a role for DNA methylation at this site in somatic establishment and/or maintenance of Snrpn imprinting. The first intron of the mouse and human genes contains structurally conserved G-rich clustered repeats which may play a role in establishing DNA methylation patterns associated with imprinting of this gene. On the basis of the conserved structural and imprinted features of the human SNRPN and mouse Snrpn genes, we suggest that imprinting mechanisms are conserved between human and mouse.

Amiodarone and the thyroid: a practical guide to the management of thyroid dysfunction induced by amiodarone therapy

Amiodarone induces predictable changes in thyroid function tests that are largely explicable in terms of the physiological effects of iodide excess and inhibition of deiodinase activity. Clinically relevant thyroid dysfunction is not uncommon during amiodarone therapy, and requires careful diagnosis and treatment. The diagnosis and management of thyrotoxicosis is probably best supervised by a specialist endocrinologist. Control of hypothyroidism can generally be achieved simply by the addition of T4 to the therapeutic regimen, ideally after an initial assessment by an endocrinologist. The frequency with which amiodarone causes thyroid and other complications serves to emphasize the need for rational prescribing and long-term cardiological follow up.

Evidence based practice: clinicians' use and attitudes to near patient testing in hospitals

AIM

To survey the use made of laboratory services for urgent tests and clinicians' attitudes to near patient testing.

METHODS

A questionnaire was sent to clinicians working in acute hospitals within Trent and North West Thames Regions.

RESULTS

197 replies were received. Most demand came from intensive care units. Overall, clinicians requested a median of six urgent tests a day. Blood glucose and dip stick urine testing were the most commonly performed bedside tests, but 41% of clinicians did not use ward testing. The most frequently cited indication for bedside testing was the need for speed. 85% of clinicians trusted results obtained in their central hospital laboratory, but there was an almost equal division between those who did (34%) and those who did not (38%) trust the results from near patient testing. A slightly larger proportion indicated they would accept responsibility (44%) for results obtained on the ward than would not (35%). Most staff indicated that better transport to the laboratory would remove the need for near patient testing.

CONCLUSIONS

Clinicians have demonstrated an apparent need for rapid response testing but there is a strong preference for rapid transport systems and central laboratory analysis rather than bedside testing as a solution to this problem. There is a need to investigate the clinical and cost-effectiveness of near patient testing as a solution to rapid response testing.

Escherichia coli-Salmonella typhimurium hybrid nusA genes: identification of a short motif required for action of the lambda N transcription antitermination protein

The Escherichia coli nusA gene, nusAEc, encodes an essential protein that influences transcription elongation. Derivatives of E. coli in which the Salmonella typhimurium nusA gene, nusASt, has replaced nusAEc are viable. Thus, NusASt can substitute for NusAEc in supporting essential bacterial activities. However, hybrid E. coli strains with the nusASt substitution do not effectively support transcription antitermination mediated by the N gene product of phage lambda. We report the DNA sequence of nusASt, showing that the derived amino acid sequence is 95% identical to the derived amino acid sequence of nusAEc. The alignment of the amino acid sequences reveals scattered single amino acid differences and one region of significant heterogeneity. In this region, called 449, NusAEc has four amino acids and NusASt has nine amino acids. Functional studies of hybrid nusA genes, constructed from nusAEc and nusASt, show that the 449 region of the NusAEc protein is important for lambda N-mediated transcription antitermination. A hybrid that has a substitution of the four E. coli codons for the nine S. typhimurium codons, but is otherwise nusASt, supports the action of the N antitermination protein. The 449 region and, presumably, adjacent sequences appear to compose a functional domain of NusAEc important for the action of the N transcription antitermination protein of phage lambda.

The inter-relationship between insulin and chromium in hyperinsulinaemic euglycaemic clamps in healthy volunteers

Evidence in the literature suggests that the trace element chromium may have a role in glucose homeostasis through the regulation of insulin action. We have previously reported a significant reduction in plasma chromium levels in healthy individuals, following a 75 g oral glucose load, and after meals and glucose-dependent uptake of chromium in insulin-dependent tissues in vitro. However, in vivo it is unclear whether the changes in plasma chromium relate to changes in plasma glucose or insulin. The present study describes a series of euglycaemic hyperinsulinaemic clamps designed to attempt to define the initiator of changes in plasma chromium levels in ten healthy individuals. The data showed a significant (P < 0.01) reduction in fasting plasma chromium levels following glucose infusion and an initial bolus of insulin. Significant (P < 0.02) increases in post-clamp urinary chromium excretion were insufficient to explain the decrease in plasma levels. During the recovery phase of an extended two-phase clamp protocol we found plasma insulin levels decreased by 70% within 10 min, associated with an increase in plasma chromium levels of 30% and no significant change in plasma glucose level. These data indicate that alterations in plasma glucose are unlikely to be directly related to changes in plasma chromium, whilst supporting the hypothesis that plasma insulin may influence plasma levels of this trace element. In contrast, plasma zinc was unaffected throughout these clamp studies.

Glucose-dependent uptake of chromium in human and rat insulin-sensitive tissues

1. This study was designed to investigate the influence of insulin and glucose on the distribution of trivalent chromium in human plasma and blood cells and in human and rat insulin-sensitive and -insensitive tissues. 2. Evidence is provided that, in the rat in vitro, a clear difference exists in chromium binding between insulin-sensitive and -insensitive tissues in that chromium binding is significantly enhanced by glucose in insulin-sensitive tissues. 3. Glucose-dependent association of chromium with human adipose tissue was blocked by inhibitors of glucose transport. 4. Addition of insulin slightly increased the response to glucose in muscle and reduced the response to glucose in adipose tissue; such effects were less marked than those seen in response to glucose alone. 5. The results of this study in vitro support the hypothesis that, in vivo, chromium translocates from the blood compartment to insulin-sensitive tissues.

Phylogenetic footprinting reveals a nuclear protein which binds to silencer sequences in the human gamma and epsilon globin genes

Tissue- and developmental stage-specific expression of the human beta-like globin genes is regulated by a combination of ubiquitous and erythroid-restricted trans factors that bind to cis elements near each of the five active genes. Additional interactions of these cis and trans factors with sequences located in the far 5' end of the cluster occur by as yet obscure mechanisms. Because of the complexity of this regulatory puzzle, precise identification of the determinants that control hemoglobin switching has proven difficult. Phylogenetic footprinting is an evolutionary approach to this problem which is based on the supposition that the basic mechanisms of switching are conserved throughout mammalian phylogeny. Alignment of the 5' flanking regions of the gamma genes of several species allows the identification of footprints of 100% conserved sequence. We have now tested oligomers spanning 13 such phylogenetic footprints and find that 12 are bound by nuclear proteins. One conserved element located at -1086 from the gamma genes exhibits repressor activity in transient transfection studies. The protein that binds this element, CSBP-1 (conserved sequence-binding protein 1), also binds at three sites within a silencer element upstream from the epsilon globin gene. Further analysis reveals that the CSBP-1 binding activity is identical to that of a recently cloned zinc finger protein that has been shown to act as a repressor in other systems. The binding of CSPB-1 to silencer sequences in the epsilon and gamma globin genes may be important in the stage-specific silencing of these genes.

The trace element chromium--a role in glucose homeostasis

To better define the normal metabolism of the trace element chromium, we studied its diurnal variation and its response to an oral glucose challenge in nine healthy volunteers. Plasma and urine chromium concentrations were measured by electrothermal atomic-absorption spectroscopy and plasma insulin by radioimmunoassay. A significant inverse relationship was found between plasma chromium and plasma insulin concentrations both over a 24-h period (P less than 0.001) and after a 75-g glucose load (P less than 0.01). This interesting observation, suggesting the removal of chromium from the plasma compartment after meals (confirmed by glucose tolerance test), is not explained simply by increased urinary loss but might be explained by transient changes in uptake or binding of chromium by insulin-sensitive tissues.

Interaction of Sp1 with the human gamma globin promoter: binding and transactivation of normal and mutant promoters

We have analyzed the binding of Sp1, a ubiquitously expressed transactivator, to the promoter region of the gamma genes. Low-affinity Sp1 sites were found at -50 and -200. A high-affinity site was detected at -140, over the CACCC sequence. To analyze the function of these sites, Drosophila SL-2 cells, which lack Sp1, were cotransfected with an Sp1 expression plasmid and gamma globin promoter-CAT constructs. In these assays, the gamma promoter was significantly stronger in the presence than in the absence of Sp1. Thus, the three Sp1 sites in the gamma promoter allow binding as well as transactivation of the promoter. The majority of this transactivation was due to the strong binding site at -140 because introduction of a point mutation at -144 (CACCC----AACCC) reduced Sp1-dependent promoter strength by 57%. Analysis of the -200 region suggested that in the wild-type promoter, Sp1 binding at this site contributes little to promoter strength. However, a point mutation (-198 T----C) associated with hereditary persistence of fetal hemoglobin (HPFH) dramatically increased the affinity of this site for Sp1 and significantly increased Sp1 dependent promoter strength in SL-2 cells. Three other point mutations associated with HPFH did not significantly affect the interaction of Sp1 with the -200 region.

Haem arginate in acute hereditary coproporphyria

An 11 year old boy presented with severe acute hereditary coproporphyria. Despite supportive measures his condition deteriorated after admission. Haem arginate, started two days after presentation, produced appreciable inhibition of porphyrin precursor overproduction and clinical improvement.

Measurement of prostate-specific antigen and prostatic acid phosphatase concentrations in serum before and 1-42 days after transurethral resection of the prostate and orchidectomy

Preoperative intra-individual variation for determinations of prostate-specific antigen and prostatic acid phosphatase concentrations, 15-30% in 92 patients with benign prostatic hyperplasia, limits the diagnostic usefulness of both tumor markers. In benign prostatic hyperplasia (214 patients), concentrations of these tumor markers increased in the initial postoperative period. Prostatic acid phosphatase concentration then decreased by the third postoperative day. Prostate-specific antigen concentration remained above normal in the first postoperative week but had decreased by 42 days. In prostatic carcinoma (46 patients), the concentrations of these tumor markers did not increase postoperatively. During the first week, the concentrations of prostatic acid phosphatase began to fall, but prostate-specific antigen showed a decrease only at 42 days. After orchidectomy (11 patients), the concentrations of both markers had decreased by five days. Concentrations of prostate-specific antigen but not of prostatic acid phosphatase were significantly increased in patients with metastases at 42 days postoperatively. When the concentration of tumor marker did decrease, the magnitude of change was greater for prostatic acid phosphatase than for prostate-specific antigen. These changes were accentuated after an orchidectomy.

Effect of N-alkyl substituents on the DNA binding properties of meso-tetrakis (4-N-alkylpyridinium-4-yl)porphyrins and their nickel derivatives

Resonance Raman, NMR, and visible spectroscopies, as well as viscosity and equilibrium dialysis studies were used to assess the effect of the N-alkyl substituent of meso-tetrakis(4-N-alkylpyridinium-4-yl)porphyrin cations on DNA binding. The DNAs studied include the native DNA, calf thymus DNA (CT DNA), the synthetic polynucleotides [poly(dGdC)]2 and [poly(dAdT)]2, and the oligonucleotide d(TATACGTATA)2. Both the porphyrins and the metalloporphyrins containing Ni(II) were examined with the N-alkyl = propyl (TPrpyP(4) and NiTPrpyP(4)) and 2-hydroxyethyl (TEtOHpyP(4) and NiTEtOHpyP(4)). The results were compared to those from the parent porphyrins with the N-methyl substituent (TMpyP(4) and NiTMpyP(4)). For almost all the comparisons made, the new porphyrin cations gave results very similar to those for the TMpyP(4) species. The resonance Raman study indicated that for the three DNA polymers all the Ni species were in the four-coordinate form when bound to all three polymers. It is suggested that both TPrpyP(4) and TEtOHpyP(4) bind to GC regions of DNA in the same intercalative manner as TMpyP(4) with the N-alkyl substituent extended into the solvent. For AT regions of DNA, the binding of TPrpyP(4) and TEtOHpyP(4) is nonintercalative, as found previously for TMpyP(4). The NiPrpy(4) and NiTEtOHpyP(4) cations bind to these polymers in a similar manner to the apo-porphyrins. The similar Raman spectral changes for the three Ni porphyrins upon addition of [poly(dAdT)]2 suggest that partial intercalation is not occurring because models indicate that it would be difficult to accommodate the bulkier N-alkyl substituents.

Amiodarone and the thyroid

An antiarrhythmic drug, amiodarone, contains 37% iodine by weight and is structurally similar to the thyroid hormones. The drug inhibits hepatic 5'-deiodinase, resulting in increases in serum thyroxin and "reverse" triiodothyronine, whereas the concentration of triiodothyronine in serum is decreased. There is a significant incidence of either hypothyroidism or hyperthyroidism in patients who are being treated with the drug. This is largely the effect of iodine released from the drug during chronic therapy, but in susceptible individuals amiodarone may unmask autoimmune thyroid disease. Some effects of the drug suggest that it may interfere with the action of thyroid hormones at the cellular level, inducing a state of localized hypothyroidism.

Amiodarone and the thyroid

An antiarrhythmic drug, amiodarone, contains 37% iodine by weight and is structurally similar to the thyroid hormones. The drug inhibits hepatic 5'-deiodinase, resulting in increases in serum thyroxin and "reverse" triiodothyronine, whereas the concentration of triiodothyronine in serum is decreased. There is a significant incidence of either hypothyroidism or hyperthyroidism in patients who are being treated with the drug. This is largely the effect of iodine released from the drug during chronic therapy, but in susceptible individuals amiodarone may unmask autoimmune thyroid disease. Some effects of the drug suggest that it may interfere with the action of thyroid hormones at the cellular level, inducing a state of localized hypothyroidism.

Vascular headache: a presenting symptom of multiple sclerosis

Vascular headache of migraine-type may be a presenting symptom of multiple sclerosis (MS), a condition usually not considered in the differential diagnosis of a severe headache accompanied by neurological signs. We reviewed records of 1,113 patients with MS seen from 1967-1987 and found 44 cases whose initial attack or subsequent exacerbations were heralded by a migraine-type headache. Twenty-seven patients had no prior history of migraine, and of these, 12 presented simultaneously with their first headache and MS attack. Twenty-three patients had symptoms of a posterior fossa mass lesion. The significance of these results and possible pathogenesis is discussed.

Nuclear proteins that bind the human gamma-globin gene promoter: alterations in binding produced by point mutations associated with hereditary persistence of fetal hemoglobin

The molecular mechanisms responsible for the human fetal-to-adult hemoglobin switch have not yet been elucidated. Point mutations identified in the promoter regions of gamma-globin genes from individuals with nondeletion hereditary persistence of fetal hemoglobin (HPFH) may mark cis-acting sequences important for this switch, and the trans-acting factors which interact with these sequences may be integral parts in the puzzle of gamma-globin gene regulation. We have used gel retardation and footprinting strategies to define nuclear proteins which bind to the normal gamma-globin promoter and to determine the effect of HPFH mutations on the binding of a subset of these proteins. We have identified five proteins in human erythroleukemia cells (K562 and HEL) which bind to the proximal promoter region of the normal gamma-globin gene. One factor, gamma CAAT, binds the duplicated CCAAT box sequences; the -117 HPFH mutation increases the affinity of interaction between gamma CAAT and its cognate site. Two proteins, gamma CAC1 and gamma CAC2, bind the CACCC sequence. These proteins require divalent cations for binding. The -175 HPFH mutation interferes with the binding of a fourth protein, gamma OBP, which binds an octamer sequence (ATGCAAAT) in the normal gamma-globin promoter. The HPFH phenotype of the -175 mutation indicates that the octamer-binding protein may play a negative regulatory role in this setting. A fifth protein, EF gamma a, binds to sequences which overlap the octamer-binding site. The erythroid-specific distribution of EF gamma a and its close approximation to an apparent repressor-binding site suggest that it may be important in gamma-globin regulation.

Neurosarcoidosis associated with hypersomnolence treated with corticosteroids and brain irradiation

Narcoleptic features developed in a young man with CNS sarcoidosis. This was associated with a structural lesion in the hypothalamus as demonstrated on CT scans of the head. The diagnosis of narcolepsy was established by compatible clinical history and the Multiple Sleep Latency Test. Treatment with high-dose corticosteroids was ineffective, but when the low-dose, whole-brain irradiation was added, complete resolution of the narcoleptic features ensued.

Hyperlactataemia and metabolic acidosis following paracetamol overdose

Plasma lactate concentrations and acid-base status were determined in 53 patients poisoned with paracetamol. Eleven patients (Group 1) had plasma paracetamol concentrations below the standard treatment decision line; 19 cases (Group 2) presenting within 15 h of overdose had plasma paracetamol concentrations above the treatment line and received N-acetylcysteine. The remaining 23 patients (Group 3) arrived at hospital too late (more than 15 h after overdose) for treatment with N-acetylcysteine to be completely effective. Compensated metabolic acidosis was present on admission in 55 per cent of Group 1 and 42 per cent of Group 2 patients, and a further 21 per cent of cases in Group 2 had an uncompensated metabolic acidosis. Half the patients in Group 3 were acidotic: 22 per cent had a compensated and 26 per cent an uncompensated metabolic acidosis. On admission, the mean plasma lactate concentration was elevated in both Group 2 and Group 3 patients though not in Group 1 cases. Plasma lactate concentration then fell to normal in patients in Group 2 but became mildly elevated again in some cases at a time which coincided closely with the peak in serum aspartate aminotransferase activity. In patients presenting within 15 h of overdose there was a significant correlation between the elevation in plasma concentrations of lactate and paracetamol at admission. In patients presenting late (Group 3), plasma lactate remained elevated for longer than in Group 2 and acidosis and hyperlactataemia were prominent features in the four patients who died. This study demonstrates first that hyperlactataemia, with or without significant acid-base disturbance, is common following paracetamol overdose particularly in those who are severely poisoned. As uncompensated metabolic acidosis is found in 20 per cent of patients who present early and require protective therapy, it should be sought and corrected if it does not remit spontaneously. Second, half the patients presenting too late for effective treatment are acidotic and those with an uncompensated metabolic acidosis resistant to correction have a poor prognosis. Paracetamol poisoning should be considered in the differential diagnosis of metabolic acidosis of unknown aetiology.

Mood disorder and multiple sclerosis

A systematic psychiatric evaluation was performed on 100 consecutive patients attending a multiple sclerosis clinic. Forty-two percent of the patients had lifetime history of depression, and 13% fulfilled criteria for manic-depressive illness. Only 28% of the patients had no psychiatric diagnosis. The relationship of psychiatric disorder to neurologic dysfunction and other aspects of multiple sclerosis are presented. Clinical and theoretical implications of these findings are discussed.

Personal and family history of affective illness in patients with multiple sclerosis

There is a high prevalence of affective illness, both depression and bipolar disorder, in patients with multiple sclerosis. In this study, the family history method was used to assess the prevalence of affective illness in first-degree relatives of patients with multiple sclerosis. There was not an excess of affective illness in the relatives suggesting that affective disorder associated with multiple sclerosis does not have a familial pattern similar to primary affective disorder. Clinical and theoretical implications of these findings are discussed.

Effects of chronic ethanol treatment on neocortex

Neocortical inhibition and neuronal morphology were studied in rats following chronic ethanol treatment (CET). In terminal acute experiments, spontaneous neuronal discharges in pair-fed and naive rats were inhibited by epicortical stimulation, a procedure known to produce postsynaptic inhibition. Few units in CET rats were inhibited by such stimulation. Cortical recurrent inhibition, indicated by a surface-negative potential in response to antidromic stimulation of the cerebral peduncle, was little affected by a challenge dose of ethanol, compared with the response in pair-fed animals. Recurrent inhibition involves inhibitory interneurons. CET apparently made inhibitory interneurons and inhibitory postsynaptic receptors less responsive to ethanol. Apical dendritic spines on some portions of pyramidal neurons increased in number with CET. This could reflect a compensatory growth in neurons not damaged by CET. The overall observations are consistent with ethanol affecting one or more specific systems of cortical motor control as opposed to its presumed general disinhibitory effect.

Plasma ionized calcium monitoring during liver transplantation

Plasma ionized calcium and citrate concentrations were measured in 11 patients undergoing liver transplantation. During the anhepatic phase of the procedure, ionized calcium concentrations fell to as low as 40% of normal, in spite of calcium supplementation. Simultaneously, citrate concentrations rose to between 20 and 100 times preoperative levels. In two patients low plasma ionized calcium concentrations were associated with hypotension that responded to calcium infusion. Intraoperative monitoring of plasma ionized calcium during liver transplantation is helpful in the rational control of the patient's calcium status.

Inflammatory myelopathy presenting as a cystic intramedullary spinal cord lesion

A case of subacute progressive spinal tetraparesis had myelographic evidence of cervical spinal cord swelling and a delayed metrizamide computed tomographic myelogram (MCTM) suggested cavitation within the swollen spinal cord. Surgical exploration of the cervical cord revealed inflammatory changes only. No syrinx or intramedullary tumour was found. The accumulation of metrizamide within the spinal cord, as demonstrated by MCTM, did not represent a syrinx or a cystic tumour, but more likely an area of inflammation. Because inflammatory myelopathy may simulate an intramedullary tumor or syrinx, careful analysis of all clinical and radiological information is necessary to help make a correct diagnosis.

Filamentous axonopathy in disulfiram neuropathy

A 52-year-old female developed a sensorimotor polyneuropathy while on treatment with disulfiram. Electron microscopic examination of a sural nerve biopsy disclosed occasional axons distended by intermediate filaments. Identical changes can be induced in animals by carbon disulfide (CS2), a metabolite of disulfiram. Our findings suggest that disulfiram neurotoxicity is mediated by CS2 and is exerted on the distal axon.

The relationship between stimulation-induced potassium release and amylase secretion in the mouse parotid

1. The output of amylase from superfused mouse parotid segments in response to stimulation with acetylcholine (ACh), phenylephrine and isoprenaline during exposure to solutions with varying potassium concentrations was monitored by an on line automated fluorometric method. 2. During stimulation with ACh or phenylephrine a 10-fold increase in superfusion fluid potassium concentration caused an immediate very marked reduction in amylase output which was fully reversible. A 10-fold reduction in potassium concentration resulted in a prominent rise in amylase output. During stimulation with isoprenaline there was no effect on the amylase output of varying the extracellular potassium concentration. Acetylcholine and phenylephrine caused potassium release from the mouse parotid whereas isoprenaline had no such effect. 3. It appears that under conditions where stimulation-induced potassium release is enhanced there is also an enhanced amylase secretion and vice cersa. There may therefore be a link between passive potassium transport and amylase secretion.