Molecular beacons: probes that fluoresce upon hybridization

We have developed novel nucleic acid probes that recognize and report the presence of specific nucleic acids in homogeneous solutions. These probes undergo a spontaneous fluorogenic conformational change when they hybridize to their targets. Only perfectly complementary targets elicit this response, as hybridization does not occur when the target contains a mismatched nucleotide or a deletion. The probes are particularly suited for monitoring the synthesis of specific nucleic acids in real time. When used in nucleic acid amplification assays, gene detection is homogeneous and sensitive, and can be carried out in a sealed tube. When introduced into living cells, these probes should enable the origin, movement, and fate of specific mRNAs to be traced.

Multicolor molecular beacons for allele discrimination

Molecular beacons are hairpin-shaped oligonucleotide probes that report the presence of specific nucleic acids in homogenous solutions. When they bind to their targets they undergo a conformational reorganization that restores the fluorescence of an internally quenched fluorophore. We found that their hairpin conformation enables the use of a wide variety of differently colored fluorophores. Using several molecular beacons, each designed to recognize a different target and each labeled with a different fluorophore, we demonstrate that multiple targets can be distinguished in the same solution, even if they differ from one another by as little as a single nucleotide. A comparison of "hairpin probes" with corresponding "linear probes" confirms that the presence of the hairpin stem in molecular beacons significantly enhances their specificity.

Thermodynamic basis of the enhanced specificity of structured DNA probes

Molecular beacons are DNA probes that form a stem-and-loop structure and possess an internally quenched fluorophore. When they bind to complementary nucleic acids, they undergo a conformational transition that switches on their fluorescence. These probes recognize their targets with higher specificity than probes that cannot form a hairpin stem, and they easily discriminate targets that differ from one another by only a single nucleotide. Our results show that molecular beacons can exist in three different states: bound to a target, free in the form of a hairpin structure, and free in the form of a random coil. Thermodynamic analysis of the transitions between these states reveals that enhanced specificity is a general feature of conformationally constrained probes.

Molecular beacon sequence analysis for detecting drug resistance in Mycobacterium tuberculosis

We developed a new approach to DNA sequence analysis that uses fluorogenic reporter molecules--molecular beacons--and demonstrated their ability to discriminate alleles in real-time PCR assays of genomic DNA. A set of overlapping molecular beacons was used to analyze an 81-bp region of the Mycobacterium tuberculosis rpoB gene for mutations that confer resistance to the antibiotic rifampin. In a blinded study of 52 rifampin-resistant and 23 rifampin-susceptible clinical isolates, this method correctly detected mutations in all of the resistant strains and in none of the susceptible strains. The assay was carried out entirely in sealed PCR tubes and was simple to perform and interpret. This approach can be used to analyze any DNA sequence of moderate length with single base pair accuracy.

Differential expression of 10 sigma factor genes in Mycobacterium tuberculosis

The ability of Mycobacterium tuberculosis to adapt to different environments in the infected host is essential for its pathogenicity. Consequently, this organism must be able to modulate gene expression to respond to the changing conditions it encounters during infection. In this paper we begin a comprehensive study of M. tuberculosis gene regulation, characterizing the transcript levels of 10 of its 13 putative sigma factor genes. We developed a real-time RT-PCR assay using a family of novel fluorescent probes called molecular beacons to quantitatively measure the different mRNAs. Three sigma factor genes were identified that have increased mRNA levels after heat shock, two of which also responded to detergent stress. In addition, we also identified a sigma factor gene whose mRNA increased after mild cold shock and a second that responded to conditions of low aeration.

Wavelength-shifting molecular beacons

We describe wavelength-shifting molecular beacons, which are nucleic acid hybridization probes that fluoresce in a variety of different colors, yet are excited by a common monochromatic light source. The twin functions of absorption of energy from the excitation light and emission of that energy in the form of fluorescent light are assigned to two separate fluorophores in the same probe. These probes contain a harvester fluorophore that absorbs strongly in the wavelength range of the monochromatic light source, an emitter fluorophore of the desired emission color, and a nonfluorescent quencher. In the absence of complementary nucleic acid targets, the probes are dark, whereas in the presence of targets, they fluoresce-not in the emission range of the harvester fluorophore that absorbs the light, but rather in the emission range of the emitter fluorophore. This shift in emission spectrum is due to the transfer of the absorbed energy from the harvester fluorophore to the emitter fluorophore by fluorescence resonance energy transfer, and it only takes place in probes that are bound to targets. Wavelength-shifting molecular beacons are substantially brighter than conventional molecular beacons that contain a fluorophore that cannot efficiently absorb energy from the available monochromatic light source. We describe the spectral characteristics of wavelength-shifting molecular beacons, and we demonstrate how their use improves and simplifies multiplex genetic analyses.

Multiplex detection of four pathogenic retroviruses using molecular beacons

We describe a multiplex nucleic acid assay that identifies and determines the abundance of four different pathogenic retroviruses (HIV-1, HIV-2, and human T-lymphotrophic virus types I and II). Retroviral DNA sequences are amplified in a single, sealed tube by simultaneous PCR assays, and the resulting amplicons are detected in real time by the hybridization of four differently colored, amplicon-specific molecular beacons. The color of the fluorescence generated in the course of amplification identifies which retroviruses are present, and the number of thermal cycles required for the intensity of each color to rise significantly above background provides an accurate measure of the number of copies of each retroviral sequence that were present originally in the sample. Fewer than 10 retroviral genomes can be detected. Moreover, 10 copies of a rare retrovirus can be detected in the presence of 100, 000 copies of an abundant retrovirus. Ninety-six samples can be analyzed in 3 hr on a single plate, and the use of a closed-tube format eliminates crossover contamination. Utilizing previously well characterized clinical samples, we demonstrate that each of the pathogenic retroviruses can be identified correctly and no false positives occur. This assay enables the rapid and reliable screening of donated blood and transplantable tissues.

Multiplex detection of single-nucleotide variations using molecular beacons

We demonstrate that single-nucleotide differences in a DNA sequence can be detected in homogeneous assays using molecular beacons. In this method, the region surrounding the site of a sequence variation is amplified in a polymerase chain reaction and the identity of the variant nucleotide is determined by observing which of four differently colored molecular beacons binds to the amplification product. Each of the molecular beacons is perfectly complementary to one variant of the target sequence and each is labeled with a different fluorophore. To demonstrate the specificity of these assays, we prepared four template DNAs that only differed from one another by the identity of the nucleotide at one position. Four amplification reactions were prepared, each containing all four molecular beacons, but each initiated with only one of the four template DNAs. The results show that in each reaction a fluorogenic response was elicited from the molecular beacon that was perfectly complementary to the amplified DNA, but not from the three molecular beacons whose probe sequence mismatched the target sequence. The color of the fluorescence that appeared in each tube during the course of the amplification indicated which nucleotide was present at the site of variation. These results demonstrate the extraordinary specificity of molecular beacons. Furthermore, the results illustrate how the ability to label molecular beacons with differently colored fluorophores enables simple multiplex assays to be carried out for genetic analysis.

Race-specific HIV-1 disease-modifying effects associated with CCR5 haplotypes

Genetic variation in CC chemokine receptor 5 (CCR5), the major HIV-1 coreceptor, has been shown to influence HIV-1 transmission and disease progression. However, it is generally assumed that the same CCR5 genotype (or haplotype) has similar phenotypic effects in different populations. To test this assumption, we used an evolutionary-based classification of CCR5 haplotypes to determine their associated HIV-1 disease-modifying effects in a large well-characterized racially mixed cohort of HIV-1-seropositive individuals. We demonstrate that the spectrum of CCR5 haplotypes associated with disease acceleration or retardation differs between African Americans and Caucasians. Also, we show that there is a strong interactive effect between CCR5 haplotypes with different evolutionary histories. The striking population-specific phenotypic effects associated with CCR5 haplotypes emphasize the importance of understanding the evolutionary context in which disease susceptibility genes are expressed.

Lactobacillus plantarum 299v Supplementation Improves Vascular Endothelial Function and Reduces Inflammatory Biomarkers in Men With Stable Coronary Artery Disease

RATIONALE

A strong association has emerged between the gut microbiome and atherosclerotic disease. Our recent data suggest Lactobacillus plantarum 299v (Lp299v) supplementation reduces infarct size in male rats. Limited human data are available on the impact of Lp299v on the vasculature.

OBJECTIVE

To determine whether oral Lp299v supplementation improves vascular endothelial function and reduces systemic inflammation in humans with stable coronary artery disease (CAD).

METHODS AND RESULTS

Twenty men with stable CAD consumed a drink containing Lp299v (20 billion CFU) once daily for 6 weeks. After a 4-week washout, subjects were given an option of additionally participating in a 10-day study of oral liquid vancomycin (250 mg QID). Vascular endothelial function was measured by brachial artery flow-mediated dilation. Before and after Lp299v, plasma short-chain fatty acids, trimethylamine oxide, and adipokine levels were measured. Additional plasma samples underwent unbiased metabolomic analyses using liquid chromatography/mass spectroscopy. 16S rRNA sequencing was used to determine changes of the stool microbiome. Arterioles from patients with CAD were obtained, and endothelium-dependent vasodilation was measured by video microscopy after intraluminal incubation with plasma from Lp299v study subjects. Lp299v supplementation improved brachial flow-mediated dilation ( P=0.008) without significant changes in plasma cholesterol profiles, fasting glucose, or body mass index. Vancomycin did not impact flow-mediated dilation. Lp299v supplementation decreased circulating levels of IL (interleukin)-8 ( P=0.01), IL-12 ( P=0.02), and leptin ( P=0.0007) but did not significantly change plasma trimethylamine oxide concentrations ( P=0.27). Plasma propionate ( P=0.004) increased, whereas acetate levels decreased ( P=0.03). Post-Lp299v plasma improved endothelium-dependent vasodilation in resistance arteries from patients with CAD ( P=0.02).16S rRNA analysis showed the Lactobacillus genus was enriched in postprobiotic stool samples without other changes.

CONCLUSIONS

Lp299v improved vascular endothelial function and decreased systemic inflammation in men with CAD, independent of changes in traditional risk factors and trimethylamine oxide. Circulating gut-derived metabolites likely account for these improvements and merit further study.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01952834.

Detection of rifampin resistance in Mycobacterium tuberculosis in a single tube with molecular beacons

Current clinical assays for determining antibiotic susceptibility in Mycobacterium tuberculosis require many weeks to complete due to the slow growth of the bacilli. Here we demonstrate an extremely sensitive single-tube PCR assay that takes less than 3 h and reliably identifies rifampin-resistant M. tuberculosis in DNA extracted directly from sputum. Ninety-five percent of mutations associated with rifampin resistance occur in an 81-bp core region of the bacterial RNA polymerase gene, rpoB. All mutations that occur within this region result in rifampin resistance. The assay uses novel nucleic acid hybridization probes called molecular beacons. Five different probes are used in the same reaction, each perfectly complementary to a different target sequence within the rpoB gene of rifampin-susceptible bacilli and each labeled with a differently colored fluorophore. Together, their target sequences encompass the entire core region. The generation of all five fluorescent colors during PCR amplification indicates that rifampin-susceptible M. tuberculosis is present. The presence of any mutation in the core region prevents the binding of one of the molecular beacons, resulting in the absence of one of the five fluorescent colors. When 148 M. tuberculosis clinical isolates of known susceptibility to rifampin were tested, mutations associated with rifampin resistance were detected in 63 of the 65 rifampin-resistant isolates, and no mutations were found in any of the 83 rifampin-susceptible isolates. When DNA extracted directly from the sputum of 11 patients infected with rifampin-resistant tuberculosis was tested, mutations were detected in all of the samples. The use of this rapid assay should enable early detection and treatment of drug-resistant tuberculosis in clinical settings.

The ORF3 protein of hepatitis E virus binds to Src homology 3 domains and activates MAPK

The hepatitis E virus (HEV) is the causative agent of hepatitis E, an acute form of viral hepatitis. The biology and pathogenesis of HEV remain poorly understood. We have used in vitro binding assays to show that the HEV ORF3 protein (pORF3) binds to a number of cellular signal transduction pathway proteins. This includes the protein tyrosine kinases Src, Hck, and Fyn, the p85alpha regulatory subunit of phosphatidylinositol 3-kinase, phospholipase Cgamma, and the adaptor protein Grb2. A yeast two-hybrid assay was used to further confirm the pORF3-Grb2 interaction. The binding involves a proline-rich region in pORF3 and the src homology 3 (SH3) domains in the cellular proteins. Competition assays and computer-assisted modeling was used to evaluate the binding surfaces and interaction energies of the pORF3.SH3 complex. In pORF3-expressing cells, pp60(src) was found to associate with an 80-kDa protein, but no activation of the Src kinase was observed in these cells. However, there was increased activity and nuclear localization of ERK in the pORF3-expressing cells. These studies suggest that pORF3 is a viral regulatory protein involved in the modulation of cell signaling. The ORF3 protein of HEV appears to be the first example of a SH3 domain-binding protein encoded by a virus that causes an acute and primarily self-limited infection.

Early and long-term results of subclavian angioplasty in aortoarteritis (Takayasu disease): comparison with atherosclerosis

PURPOSE

To compare the early and long-term outcomes of subclavian artery angioplasty in patients with aortoarteritis and atherosclerosis.

METHODS

Sixty-one subclavian artery angioplasties were performed in 55 consecutive patients with aortoarteritis (n = 32) and atherosclerosis (n = 23) between 1986 and 1995. An arch aortogram followed by a selective subclavian artery angiogram was done to profile the site and extent of the lesion, its relation to the vertebral artery, and the distal circulation. Percutaneous transluminal angioplasty (PTA) was performed via the femoral route for 56 stenotic lesions and 5 total occlusions.

RESULTS

PTA was successful in 52 (92.8%) stenotic lesions and 3 (60%) total occlusions. Three patients (5.4%) had complications, that could be effectively managed nonsurgically. Compared with atherosclerosis, patients with aortoarteritis were younger (27.4 +/- 9.3 years vs 54.5 +/- 10.5 years; p < 0.001), more often female (75% vs 17.4%; p < 0.001), gangrene was uncommon (0% vs 17.4%; p < 0.05), and diffuse involvement was seen more often (43.8% vs 4.4%; p < 0.001). The luminal diameter stenoses were similar before PTA (88.6 +/- 9.7% vs 89.0 +/- 9.1%; p = NS). Higher balloon inflation pressure was required to dilate the lesions of aortoarteritis (9.9 +/- 4.6 ATM vs 5.5 +/- 1.0 ATM; p < 0.001). This group had more residual stenosis (15.5 +/- 12.4% vs 8.3 +/- 9.4%; p < 0.05) after PTA. There were no neurological sequelae, even in PTA of prevertebral lesions. On 3-120 months (mean 43.3 +/- 28.9 months) follow-up of 40 patients, restenosis was more often observed in patients with aortoarteritis, particularly in those with diffuse arterial narrowing. These lesions could be effectively redilated. Clinical symptoms showed marked improvement after successful angioplasty.

CONCLUSION

Subclavian PTA is safe and can be performed as effectively in aortoarteritis as in atherosclerosis, with good long-term results. Long-term follow-up shows that it provides good symptomatic relief.

Ocular cicatricial pemphigoid antigen: partial sequence and biochemical characterization

Ocular cicatricial pemphigoid (OCP) is an autoimmune disease that affects mainly conjunctiva and other squamous epithelia. OCP is histologically characterized by a separation of the epithelium from underlying tissues within the basement membrane zone. Immunopathological studies demonstrate the deposition of anti-basement membrane zone autoantibodies in vivo. Purified IgG from sera of patients with active OCP identified a cDNA clone from a human keratinocyte cDNA library that had complete homology with the cytoplasmic domain of beta 4-integrin. The sera recognized a 205-kDa protein in human epidermal, human conjunctiva, and tumor cell lysates that was identified as beta 4-integrin by its reaction with polyclonal and monoclonal antibodies to human beta 4-integrin. Sera from patients with bullous pemphigoid, pemphigus vulgaris, and cicatricial pemphigoid-like diseases did not recognize the 205-kDa protein, indicating the specificity of the binding. These data strongly implicate a role for human beta 4-integrin in the pathogenesis of OCP. It should be emphasized that multiple antigens in the basement membrane zone of squamous epithelia may serve as targets for a wide spectrum of autoantibodies observed in vesiculobullous diseases. Molecular definition of these autoantigens will facilitate the classification and characterization of subsets of cicatricial pemphigoid and help distinguishing them from bullous pemphigoid. This study highlights the function and importance of beta 4-integrin in maintaining the attachment of epithelial cells to the basement membrane.

Percutaneous transluminal angioplasty for renovascular hypertension in children: initial and long-term results

OBJECTIVE

To evaluate the efficacy and safety of percutaneous transluminal renal angioplasty (PTRA) in children.

METHODS

We performed aortography and attempted PTRA in 35 consecutive children (age 5 to 14 years, mean 10.8 +/- 2.5 years) with severe hypertension having > or = 75% renal artery stenosis (RAS).

RESULTS

The stenosis was caused by aortoarteritis in 31 (88.6%) cases and by juvenile idiopathic fibromuscular disease (FMD) in four (11.4%) cases. Twenty-seven (77.1%) patients, including three having RAS of solitary functioning kidney with total occlusion of contralateral renal artery, had bilateral RAS and eight (22.9%) had unilateral RAS. PTRA was technically successful in 54 (91.5%) of 59 stenotic lesions in 31 (88.6%) of 35 patients. Both aortoarteritis and FMD patients had significant decrease in RAS after PTRA. One patient had acute reocclusion of one renal artery after bilateral PTRA, which could be successfully opened by reangioplasty. Postangioplasty angiographic restudy performed in 18 patients at 4 to 72 months (mean 23.1 +/- 27.9 months) after successful angioplasty showed restenosis in 8 (25.8%) of 31 lesions initially dilated and de novo lesions of aorta in two patients. All seven restenotic renal artery lesions attempted and both stenosis of aorta were successfully dilated. Twenty-nine of 31 patients with successful PTRA have been followed up from 4 to 108 months (mean 41.0 +/- 29.3 months). Mean systolic blood pressure decreased from 185.1 +/- 27.4 to 120.6 +/- 19.2 mm Hg and mean diastolic blood pressure decreased from 118.4 +/- 13.2 to 84.6 +/- 10.4 mm Hg after PTRA. Twenty seven (93.1%) of these 29 patients had benefical blood pressure response. Seventeen (58.6%) patients improved, 10 (34.5%) were cured, although 2 (6.9%) patients failed to respond to PTRA. Blood pressure response was better in FMD as compared to aortoarteritis group. Patients with unilateral RAS, discrete stenosis, and post-PTRA stenosis < or = 20% also identified good blood pressure response.

CONCLUSION

Aortoarteritis is the most common cause of renovascular hypertension in South Asian children. PTRA is safe and highly effective and therefore should be the treatment of choice in pediatric renovascular hypertension.

Balloon angioplasty for renovascular hypertension in Takayasu's arteritis

Percutaneous transluminal renal angioplasty was performed in 54 consecutive patients with hypertension and renal artery stenosis caused by Takayasu's arteritis. Angioplasty was technically successful in 67 (89.3%) of 75 lesions attempted. In these 67 lesions, the degree of stenosis decreased from 88.3 +/- 4.8% to 23.5% +/- 13.6% (p < 0.001) after angioplasty. Following successful angioplasty there was significant improvement in hypertension (p < 0.001) within 48 hours. Patients with bilateral renal artery stenosis had higher systolic blood pressure both before balloon dilatation (p < 0.05) and after balloon dilatation before discharge (p < 0.001), compared with patients with unilateral renal artery stenosis. Three to 70 months (mean 26.4 +/- 10.3 months) after successful angioplasty, blood pressure was reduced to normal or was improved in 93% of patients. Angiographic restudy an average of 14.2 +/- 7.8 months after angioplasty showed restenosis at the same site in 7 of 52 (13.5%) lesions and fresh stenosis in one artery. All these eight lesions were successfully dilated. Further improvement in the luminal diameter was observed in 11 (21.2%) lesions. Late angiographic restudy in seven patients an average of 56.1 +/- 6.3 months after angioplasty showed no restenosis. Our results suggest that balloon angioplasty is safe and highly effective in relieving renal artery stenosis caused by Takayasu's arteritis and should be the treatment of choice for renovascular hypertension in this disease.

Hydroxyurea in thalassemia intermedia—a promising therapy

Pharmacological agents such as hydroxyurea (HU) have been known to cause induction of fetal hemoglobin and possibly may alleviate the symptoms in thalassemia intermedia patients. Thirty-seven patients with beta-thalassemia intermedia were enrolled to assess response to HU therapy. Major response was defined as transfusion independence or hemoglobin rise of more than 20 g/l and minor response as rise in hemoglobin of 10-20 g/l or reduction in transfusion frequency by 50%. The median age was 10 years (range: 4-50 years) and median follow-up was 12 months (range: 4-36 months). Twenty-six patients (70.2%) showed response to HU therapy. Seventeen patients (45.9%) were major responders, and nine patients (24.3%) showed minor response. There was no correlation of response with beta-thalassemia mutation or XmnI polymorphism; however, the presence of alpha(3.7) deletion was associated with major response in three patients. Mean fetal hemoglobin (HbF) levels rose on HU therapy. Older age, low baseline F cell percent, and low baseline HbF levels (below 10%) were predictors of poor response. Response was evident within 1 month of starting HU therapy in the majority of responders. Thus, a short trial of HU therapy can predict durable response.

miR-29 contributes to normal endothelial function and can restore it in cardiometabolic disorders

We investigated the role of microRNAs (miRNA) in endothelial dysfunction in the setting of cardiometabolic disorders represented by type 2 diabetes mellitus (T2DM). miR‐29 was dysregulated in resistance arterioles obtained by biopsy in T2DM patients. Intraluminal delivery of miR‐29a‐3p or miR‐29b‐3p mimics restored normal endothelium‐dependent vasodilation (EDVD) in T2DM arterioles that otherwise exhibited impaired EDVD. Intraluminal delivery of anti‐miR‐29b‐3p in arterioles from non‐DM human subjects or rats or targeted mutation of Mir29b‐1/a gene in rats led to impaired EDVD and exacerbation of hypertension in the rats. miR‐29b‐3p mimic increased, while anti‐miR‐29b‐3p or Mir29b‐1/a gene mutation decreased, nitric oxide levels in arterioles. The mutation of Mir29b‐1/a gene led to preferential differential expression of genes related to nitric oxide including Lypla1. Lypla1 was a direct target of miR‐29 and could abrogate the effect of miR‐29 in promoting nitric oxide production. Treatment with Lypla1 siRNA improved EDVD in arterioles obtained from T2DM patients or Mir29b‐1/a mutant rats or treated with anti‐miR‐29b‐3p. These findings indicate miR‐29 is required for normal endothelial function in humans and animal models and has therapeutic potential for cardiometabolic disorders.

Rapid identification of Candida dubliniensis using a species-specific molecular beacon

Candida dubliniensis is an opportunistic fungal pathogen that has been linked to oral candidiasis in AIDS patients, although it has recently been isolated from other body sites. DNA sequence analysis of the internal transcribed spacer 2 (ITS2) region of rRNA genes from reference Candida strains was used to develop molecular beacon probes for rapid, high-fidelity identification of C. dubliniensis as well as C. albicans. Molecular beacons are small nucleic acid hairpin probes that brightly fluoresce when they are bound to their targets and have a significant advantage over conventional nucleic acid probes because they exhibit a higher degree of specificity with better signal-to-noise ratios. When applied to an unknown collection of 23 strains that largely contained C. albicans and a smaller amount of C. dubliniensis, the species-specific probes were 100% accurate in identifying both species following PCR amplification of the ITS2 region. The results obtained with the molecular beacons were independently verified by random amplified polymorphic DNA analysis-based genotyping and by restriction enzyme analysis with enzymes BsmAI and NspBII, which cleave recognition sequences within the ITS2 regions of C. dubliniensis and C. albicans, respectively. Molecular beacons are promising new probes for the rapid detection of Candida species.

Mechanism of thiamine uptake by human jejunal brush-border membrane vesicles

Thiamine, a water-soluble vitamin, is essential for normal cellular functions, growth and development. Thiamine deficiency leads to significant clinical problems and occurs under a variety of conditions. To date, however, little is known about the mechanism of thiamine absorption in the native human small intestine. The objective of this study was, therefore, to characterize the mechanism of thiamine transport across the brush-border membrane (BBM) of human small intestine. With the use of purified BBM vesicles (BBMV) isolated from the jejunum of organ donors, thiamine uptake was found to be 1) independent of Na(+) but markedly stimulated by an outwardly directed H(+) gradient (pH 5.5(in)/pH 7.5(out)); 2) competitively inhibited by the cation transport inhibitor amiloride (inhibitor constant of 0.12 mM); 3) sensitive to temperature and osmolarity of the incubation medium; 4) significantly inhibited by thiamine structural analogs (amprolium, oxythiamine, and pyrithiamine), but not by unrelated organic cations (tetraethylammonium, N-methylnicotinamide, or choline); 5) not affected by the addition of ATP to the inside and outside of the BBMV; 6) potential insensitive; and 7) saturable as a function of thiamine concentration with an apparent Michaelis-Menten constant of 0.61 +/- 0.08 microM and a maximal velocity of 1.00 +/- 0.47 pmol. mg protein(-1). 10 s(-1). Carrier-mediated thiamine uptake was also found in BBMV of human ileum. These data demonstrate the existence of a Na(+)-independent, pH-dependent, amiloride-sensitive, electroneutral carrier-mediated mechanism for thiamine absorption in native human small intestinal BBMV.

Balloon angioplasty of the aorta in Takayasu's arteritis: Initial and long-term results

Percutaneous transluminal balloon angioplasty for stenosis of the aorta was performed in 36 patients with Takayasu's arteritis (age range, 8 to 36 years; mean, 19.1 +/- 7.7 years). Balloon dilatation was successful in 34 patients and resulted in a decrease in the mean peak systolic pressure gradient (PSG) from 75.2 +/- 29.1 mm Hg to 24.8 +/- 19 mm Hg (p less than 0.001) and a mean increase in the diameter of the stenosed segments from 4.5 +/- 2.2 mm to 9.6 +/- 3.8 mm (p less than 0.001). Hemodynamic and angiographic restudy, which was performed in 20 patients at a mean follow-up period of 7.7 +/- 4.1 months (range, 3 to 24 months), showed a further decrease in PSG (greater than or equal to 15 mm Hg) in seven patients (from 40.0 +/- 11.2 mm Hg to 15.7 +/- 10.2 mm Hg; p less than 0.01), no significant change in PSG in 12 patients (17.1 +/- 13.6 mm Hg vs 16.6 +/- 12.7 mm Hg; p = NS), and an increase in PSG from 15 mm Hg to 85 mm Hg in one patient. The patient who showed restenosis underwent successful redilatation. Six patients who underwent late recatheterization and angiography at 36 to 60 months (mean, 43 +/- 9.4 months) show continued relief of stenosis (mean PSG, 8.8 +/- 7.8 mm Hg). Patients with short-segment (less than 4 cm) stenosis experience more relief than patients with long-segment (greater than or equal to 4 cm) stenosis (residual PSG, 18.6 +/- 8.2 mm Hg vs 40 +/- 16 mm Hg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Changing trends in acute poisoning in Chandigarh zone: a 25-year autopsy experience from a tertiary care hospital in northern India

A 25-year autopsy study (1972-1997) of acute poisoning deaths from a tertiary care hospital in northern India (Postgraduate Institute of Medical Education and Research, Chandigarh) revealed a steep increase in the incidence of acute poisoning since 1987. The majority (68%) of subjects were between the ages of 14 and 30 years, and there was a male preponderance (69%). The main victims were students and unemployed youths, followed by agricultural workers and domestic workers. The proportion of urban victims increased from 45% in the period from 1972 to 1977 to 72% in the period from 1992 to 1997. The proportion of suicidal deaths increased from 34% in the period from 1972 to 1977 to 77% in the period from 1992 to 1997, whereas accidental deaths decreased from 63% to 17% in the same period. Barbiturates (37%) and copper sulfate (22%) were the most common poisons causing mortality between 1972 and 1977; organophosphates (46%) became the most common between 1977 and 1982. Since 1982, aluminum phosphide (65%) has been the most common poison.

Balloon angioplasty of native coarctation of the aorta in adolescents and young adults

Balloon angioplasty of native coarctation of the aorta was performed in 35 consecutive adolescents and young adults, aged 14 to 37 years (mean 22.6 +/- 7.1). Twenty-eight (80%) patients had isolated discrete coarctation, six (17.1%) had tubular hypoplasia of the aortic isthmus, and one (2.9%) had hypoplasia of the post-coarctation aorta. The peak systolic pressure gradient decreased from 78.5 +/- 23.9 to 15.7 +/- 11.6 mm Hg (p less than 0.001), and the mean coarctation diameter increased from 4.7 +/- 2.4 to 13.1 +/- 2.7 mm (p less than 0.001) immediately after angioplasty. Patients with discrete-type coarctation had significantly less residual gradient than patients with long-segment tubular coarctation (12.3 +/- 10.7 vs 27.2 +/- 6.6 mm Hg, p less than 0.01). On recatheterization and angiography in 26 patients at 12.6 +/- 1.5 months after dilatation, there was no significant change in gradient (15.5 +/- 13.3 mm Hg) and diameter (13.1 +/- 1.8 mm) from the immediate post-angioplasty results. However, two patients had an increase in gradient and three had small aortic aneurysms with no change in appearance on restudy after 2 years. After 3 to 67 months' (mean 32.7 +/- 19.2) follow-up, all patients showed continued clinical improvement. Hypertension was relieved in 37.5% (12/32) and improved in 59.4% (19/32). Our experience suggests that balloon angioplasty of native aortic coarctation in adolescents and young adults is safe and highly effective with sustained improvement on intermediate-term follow-up.