inhA, a gene encoding a target for isoniazid and ethionamide in Mycobacterium tuberculosis

Isoniazid (isonicotinic acid hydrazide, INH) is one of the most widely used antituberculosis drugs, yet its precise target of action on Mycobacterium tuberculosis is unknown. A missense mutation within the mycobacterial inhA gene was shown to confer resistance to both INH and ethionamide (ETH) in M. smegmatis and in M. bovis. The wild-type inhA gene also conferred INH and ETH resistance when transferred on a multicopy plasmid vector to M. smegmatis and M. bovis BCG. The InhA protein shows significant sequence conservation with the Escherichia coli enzyme EnvM, and cell-free assays indicate that it may be involved in mycolic acid biosynthesis. These results suggest that InhA is likely a primary target of action for INH and ETH.

Removal of poly(A) and consequent degradation of c-fos mRNA facilitated by 3' AU-rich sequences

The c-fos proto-oncogene provides a good system to study the processes underlying messenger RNA degradation. After growth factor stimulation of susceptible cells, the c-fos transcription rate transiently increases from a low basal level by as much as 50-fold, producing a large amount of exceedingly unstable c-fos mRNA that is rapidly degraded. Here, we investigate the c-fos mRNA degradation process, and find that: (1) ongoing translation of the c-fos mRNA itself is required for its degradation; (2) after synthesis, the mRNA poly(A) tail is rapidly removed, in a translation-dependent manner, leading to accumulation of apparently deadenylated RNA; (3) deletion or replacement of an AU-rich sequence at the mRNA 3' end significantly stabilizes the mRNA; (4) deletion of the 3' AU-rich sequences dramatically slows the poly(A) shortening rate. These results suggest that the 3' AU-rich sequences act to destabilize the mRNA by directing rapid removal of the mRNA poly(A) tract.

Method of obtaining optical sectioning by using structured light in a conventional microscope

We describe a simple method of obtaining optical sectioning in a conventional wide-field microscope by projecting a single-spatial-frequency grid pattern onto the object. Images taken at three spatial positions of the grid are processed in real time to produce optically sectioned images that are substantially similar to those obtained with confocal microscopes.

hMSH2 forms specific mispair-binding complexes with hMSH3 and hMSH6

The genetic and biochemical properties of three human MutS homologues, hMSH2, hMSH3, and hMSH6, have been examined. The full-length hMSH6 cDNA and genomic locus were isolated and characterized, and it was demonstrated that the hMSH6 gene consisted of 10 exons and mapped to chromosome 2p15-16. The hMSH3 cDNA was in some cases found to contain a 27-bp deletion resulting in a loss of nine amino acids, depending on the individual from which the cDNA was isolated. hMSH2, hMSH3, and hMSH6 all showed similar tissue-specific expression patterns. hMSH2 protein formed a complex with both hMSH3 and hMSH6 proteins, similar to protein complexes demonstrated by studies of the Saccharomyces cerevisiae MSH2, MSH3, and MSH6. hMSH2 was also found to form a homomultimer complex, but neither hMSH3 nor hMSH6 appear to interact with themselves or each other. Analysis of the mismatched nucleotide-binding specificity of the hMSH2-hMSH3 and hMSH2-hMSH6 protein complexes showed that they have overlapping but not identical binding specificity. These results help to explain the distribution of mutations in different mismatch-repair genes seen in hereditary nonpolyposis colon cancer.

Bioluminescence

Bioluminescence has evolved independently many times; thus the responsible genes are unrelated in bacteria, unicellular algae, coelenterates, beetles, fishes, and others. Chemically, all involve exergonic reactions of molecular oxygen with different substrates (luciferins) and enzymes (luciferases), resulting in photons of visible light (approximately 50 kcal). In addition to the structure of luciferan, several factors determine the color of the emissions, such as the amino acid sequence of the luciferase (as in beetles, for example) or the presence of accessory proteins, notably GFP, discovered in coelenterates and now used as a reporter of gene expression and a cellular marker. The mechanisms used to control the intensity and kinetics of luminescence, often emitted as flashes, also vary. Bioluminescence is credited with the discovery of how some bacteria, luminous or not, sense their density and regulate specific genes by chemical communication, as in the fascinating example of symbiosis between luminous bacteria and squid.

Quality collaboratives: lessons from research

Quality improvement collaboratives are increasingly being used in many countries to achieve rapid improvements in health care. However, there is little independent evidence that they are more cost effective than other methods, and little knowledge about how they could be made more effective. A number of systematic evaluations are being performed by researchers in North America, the UK, and Sweden. This paper presents the shared ideas from two meetings of these researchers. The evidence to date is that some collaboratives have stimulated improvements in patient care and organisational performance, but there are significant differences between collaboratives and teams. The researchers agreed on the possible reasons why some were less successful than others, and identified 10 challenges which organisers and teams need to address to achieve improvement. In the absence of more conclusive evidence, these guidelines are likely to be useful for collaborative organisers, teams and their managers and may also contribute to further research into collaboratives and the spread of innovations in health care.

Highly prolific Booroola sheep have a mutation in the intracellular kinase domain of bone morphogenetic protein IB receptor (ALK-6) that is expressed in both oocytes and granulosa cells

The Booroola fecundity gene (FecB) increases ovulation rate and litter size in sheep and is inherited as a single autosomal locus. The effect of FecB is additive for ovulation rate (increasing by about 1.6 corpora lutea per cycle for each copy) and has been mapped to sheep chromosome 6q23-31, which is syntenic to human chromosome 4q21-25. Bone morphogenetic protein IB (BMP-IB) receptor (also known as ALK-6), which binds members of the transforming growth factor-beta (TGF-beta) superfamily, is located in the region containing the FecB locus. Booroola sheep have a mutation (Q249R) in the highly conserved intracellular kinase signaling domain of the BMP-IB receptor. The mutation segregated with the FecB phenotype in the Booroola backcross and half-sib flocks of sheep with no recombinants. The mutation was not found in individuals from a number of sheep breeds not derived from the Booroola strain. BMPR-IB was expressed in the ovary and in situ hybridization revealed its specific location to the oocyte and the granulosa cell. Expression of mRNA encoding the BMP type II receptor was widespread throughout the ovary. The mutation in BMPR-IB found in Booroola sheep is the second reported defect in a gene from the TGF-beta pathway affecting fertility in sheep following the recent discovery of mutations in the growth factor, GDF9b/BMP15.

hMSH2-hMSH6 forms a hydrolysis-independent sliding clamp on mismatched DNA

Mismatch recognition by the human MutS homologs hMSH2-hMSH6 is regulated by adenosine nucleotide binding, supporting the hypothesis that it functions as a molecular switch. Here we show that ATP-induced release of hMSH2-hMSH6 from mismatched DNA is prevented if the ends are blocked or if the DNA is circular. We demonstrate that mismmatched DNA provokes ADP-->ATP exchange, resulting in a discernible conformational transition that converts hMSH2-hMSH6 into a sliding clamp capable of hydrolysis-independent diffusion along the DNA backbone. Our results support a model for bidirectional mismatch repair in which stochastic loading of multiple ATP-bound hMSH2-hMSH6 sliding clamps onto mismatch-containing DNA leads to activation of the repair machinery and/or other signaling effectors similar to G protein switches.

Magnetic resonance imaging and mood disorders. Localization of white matter and other subcortical abnormalities

BACKGROUND

Recent reports in the literature document an association between focal white matter abnormalities in bipolar as well as unipolar mood disorder. The importance of this finding and other associated anatomic differences is uncertain.

METHODS

We examined the volume of abnormal white matter and other brain volumes using quantitative magnetic resonance imaging analysis. We explored the relationship of these variables with diagnosis, cognitive function, and clinical variables in 36 patients with bipolar disorder, 30 patients with unipolar disorder, and 26 control subjects who were free from significant medical and neurologic illness.

RESULTS

Younger patients with bipolar disorder (but not similarly aged patients with unipolar disorder or controls) have an increased volume of abnormal white matter. Data also indicate that the total volume of abnormal white matter may be associated with increased cognitive impairment, increased rate of psychiatric illness in the family, and onset after adolescence.

CONCLUSION

Patients with bipolar disorder demonstrate a pattern of subcortical brain morphologic abnormalities and cognitive impairment.

Multicentre post-infarction trial of propranolol in 49 hospitals in the United Kingdom, Italy, and Yugoslavia

A multicentre study of survivors of an anterior myocardial infarction is reported. The trial consisted of 720 patients and was a double-blind, placebo-controlled study with propranolol 40 mg three times a day. Trial entry was at two to 14 days (mean 8.5 days) and follow-up at one, three, and in most centres, six and nine months. The trial was designed to detect a 50 per cent reduction in mortality and this was not shown. The non-fatal reinfarction rate was similar in both groups. Subgroup analysis identified several prognostic risk factors for death, none of which interacted with treatment.

Adamts-1 Is Essential for the Development and Function of the Urogenital System1

Successful ovulation and implantation processes play a crucial role in female fertility. Adamts-1, a matrix metalloproteinase with disintegrin and thrombospondin motifs, has been suggested to be regulated by the progesterone receptor in the hormonal pathway leading to ovulation. With the primary aim of investigating the role of Adamts-1 in female fertility, we generated Adamts-1 null mice. Forty-five percent of the newborn Adamts-1 null mice die, with death most likely caused by a kidney malformation that becomes apparent at birth. Surviving female null mice were subfertile, whereas males reproduced normally. Ovulation in null females was impaired because of mature oocytes remaining trapped in ovarian follicles. No uterine phenotype was apparent in Adamts-1 null animals. Embryo implantation occurred normally, the uteri were capable of undergoing decidualization, and no morphological changes were observed. These results demonstrate that a functional Adamts-1 is required for normal ovulation to occur, and hence the Adamts-1 gene plays an important role in female fertility, primarily during the tissue remodeling process of ovulation.

Inactivation of the transcription factor Elf3 in mice results in dysmorphogenesis and altered differentiation of intestinal epithelium

BACKGROUND & AIMS

The mammalian small intestine is lined by a highly specialized epithelium that functions in the digestion and absorption of nutrients. The molecular mechanisms that direct intestinal epithelial cell morphogenesis and terminal differentiation are poorly understood. We have previously identified Elf3 (E74-like factor-3) as a member of the ETS transcription factor family strongly expressed in small intestinal epithelium. The aim of this study is to investigate the biological roles of Elf3 in vivo.

METHODS

Mice with a null mutation of Elf3 were generated through targeted gene disruption. Characterization of intestinal development was performed by histologic and immunohistochemical techniques.

RESULTS

Targeted disruption of Elf3 resulted in fetal lethality of about 30% at around embryonic day 11.5. Seventy percent of the Elf3-deficent progeny were born and displayed severe alterations of tissue architecture in the small intestine, manifested by poor villus formation and abnormal morphogenesis and terminal differentiation of absorptive enterocytes and mucus-secreting goblet cells. Crypt cell proliferation, however, appeared intact in Elf3-deficient mice.Elf3-deficient enterocytes express markedly reduced levels of the transforming growth factor beta type II receptor (TGF-beta RII), an inducer of intestinal epithelial differentiation.

CONCLUSIONS

Elf3 is an important regulator of morphogenesis and terminal differentiation of epithelial cell lineages in the small intestine.

Reactive oxygen species as cellular messengers

Reactive oxygen species (ROSs) have recently been found to be important signaling molecules in several cellular responses. Individual species have characteristic reactive properties, yet are easily interconverted, making it difficult to identify the ROSs involved in each response.

Size of the detector in confocal imaging systems

We consider the role of the detector size in the imaging of confocal systems. We introduce a criterion for detector size to give true confocal operation and show that the lateral resolution is considerably more sensitive to detector size than is the depth-discrimination or optical-sectioning property.

MutS homologs in mammalian cells

Alterations of the human mismatch repair genes have been linked to hereditary non-polyposis colon cancer (HNPCC) as well as to sporadic cancers that exhibit microsatellite instability. The human mismatch repair genes are highly conserved homologs of the Escherichia coli MutHLS system. Six MutS homologs have been identified in Saccharomyces cerevisiae and four MutS homologs have been identified in human cells. At least three of these eukaryotic MutS homologs are involved in the recognition/binding of mispaired nucleotides and nucleotide lesions. MSH2 plays a fundamental role in mispair recognition whereas MSH3 and MSH6 appear to modify the specificity of this recognition. The redundant functions of MSH3 and MSH6 explain the greater prevalence of hmsh2 mutations in HNPCC families.

Linkage disequilibrium in domestic sheep

The last decade has seen a dramatic increase in the number of livestock QTL mapping studies. The next challenge awaiting livestock geneticists is to determine the actual genes responsible for variation of economically important traits. With the advent of high density single nucleotide polymorphism (SNP) maps, it may be possible to fine map genes by exploiting linkage disequilibrium between genes of interest and adjacent markers. However, the extent of linkage disequilibrium (LD) is generally unknown for livestock populations. In this article microsatellite genotype data are used to assess the extent of LD in two populations of domestic sheep. High levels of LD were found to extend for tens of centimorgans and declined as a function of marker distance. However, LD was also frequently observed between unlinked markers. The prospects for LD mapping in livestock appear encouraging provided that type I error can be minimized. Properties of the multiallelic LD coefficient D' were also explored. D' was found to be significantly related to marker heterozygosity, although the relationship did not appear to unduly influence the overall conclusions. Of potentially greater concern was the observation that D' may be skewed when rare alleles are present. It is recommended that the statistical significance of LD is used in conjunction with coefficients such as D' to determine the true extent of LD.

Subtyping binge eating-disordered women along dieting and negative affect dimensions

OBJECTIVE

Because etiologic and maintenance models of binge eating center around dieting and affect regulation, this study tested whether binge eating-disordered (BED) individuals could be subtyped along dieting and negative affect dimensions and whether subtypes differed in eating pathology, social functioning, psychiatric comorbidity, and response to treatment.

METHOD

Three independent samples of interviewer-diagnosed BED women (N = 218) were subtyped along dieting and negative affect dimensions using cluster analysis and compared on the outcomes of interest.

RESULTS

Cluster analyses replicated across the three independent samples and revealed a dietary subtype (63%) and a dietary-depressive subtype (37%). The latter subtype reported greater eating and weight obsessions, social maladjustment, higher lifetime rates of mood, anxiety, and personality disorders, and poorer response to treatment than did the dietary subtype.

DISCUSSION

Results suggest that moderate dieting is a central feature of BED and that affective disturbances occur in only a subset of cases. However, the confluence of dieting and negative affect signals a more severe variant of the disorder marked by elevated psychopathology, impaired social functioning, and a poorer treatment response.

A proposed function for spermine and spermidine: protection of replicating DNA against damage by singlet oxygen

Like all aliphatic amines, the polyamines spermine and spermidine are physical quenchers of singlet molecular oxygen (1O2*). The rate constants of these processes were determined in vitro with photochemically generated 1O2* and the hydrocarbon rubrene as substrate, in pyridine. At millimolar concentration, spermine and spermidine should quench 1O2* in vivo and prevent it from damaging DNA. It is proposed that a biological function of polyamines is the protection of replicating DNA against oxidative damage.