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PubMed2006

A "silent" polymorphism in the MDR1 gene changes substrate specificity.

Synonymous single-nucleotide polymorphisms (SNPs) do not produce altered coding sequences, and therefore they are not expected to change the function of the protein in which they occur. We report that a synonymous SNP in the Multidrug Resistance 1 (MDR1) gene, part of a haplotype previously linked to altered function of the MDR1 gene product P-glycoprotein (P-gp), nonetheless results in P-gp with altered drug and inhibitor interactions. Similar mRNA and protein levels, but altered conformations, were found for wild-type and polymorphic P-gp. We hypothesize that the presence of a rare codon, marked by the synonymous polymorphism, affects the timing of cotranslational folding and insertion of P-gp into the membrane, thereby altering the structure of substrate and inhibitor interaction sites.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1977

Evolutionary conservation of chloroplast genes coding for the large subunits of fraction 1 protein.

Crystalline fraction 1 protein, obtained from four species of Nicotiana, have identical polypeptide compositions and isoelectric points. However, the tryptic peptide map of the large subunit of this protein from N. knightiana and N. paniculata differs from that of N. tomentosa and N. tomentosiformis. Since the large subunits of fraction 1 protein are coded by chloroplast DNA, the difference in their primary structure reflects the structural changes of the chloroplast genes containing the coding information. This indicates that the rate of mutation of chloroplast DNA seems to be higher than predicated from the analysis of isoelectric points of this protein.

Journal Article↗
PubMed1985

Leucine tRNA family of Escherichia coli: nucleotide sequence of the supP(Am) suppressor gene.

We describe the cloning and the DNA sequence of an amber suppressor allele of the Escherichia coli leuX (supP) gene. The suppressor allele codes for a tRNA with anticodon CUA, presumably derived by a single base change from a CAA anticodon. The mature coding sequence of the leuX gene is preceded by a putative Pribnow box sequence (TATAAT) and followed by a termination signal. The sequence of the leuX-coded tRNA is compared with the sequences of the four remaining tRNALeu isoacceptors of E. coli and with two tRNALeu species from bacteriophage T4 and T5. The conserved nucleotides in these seven tRNAs recognized by E. coli leucyl-tRNA synthetase are located mainly in the aminoacyl stem and in the D-stem/loop region.

Anticodon↗
PubMed1993

5'-flanking region responsible for endosperm-specific expression of rice prolamine chimeric gene in transgenic tobacco.

The 5' upstream region (-680-(+)40) containing the complete signal peptide coding sequence of the rice seed storage prolamine gene was amplified in vitro with polymerase chain reaction from the genome of Chinese super rice cultivar Zhonghua 8. Physical map and DNA sequence analysis showed strong homology with the 5'-flanking region of rice prolamine gene reported by Kim in 1988. No changes in the signal peptide coding sequence and a long leader sequence with several small ORFs were found. Chimeric gene containing 5'-flanking region of the prolamine gene has been transcriptionally fused with the beta-glucuronidase reporter gene. The fusion junction was confirmed by both physical map and DNA sequence analysis. The resultant chimeric gene was used to transform the tobacco explants by Ti binary system of Agrobacterium tumefaciens LBA4404. With dot and Southern blotting hybridization, three transgenic tobacco plants with the copies of chimeric GUS genes as many as 20 were obtained. Histochemical analysis revealed that the GUS activity in the endosperm tissues of tobacco seeds at the developmental stage was about 20 DAP. No GUS activity was found in leaves, stems, roots and flowers of the transgenic tobacco plants. Therefore, we concluded that the 5'-upstream cis-elements from -680 to -18 were enough to confer the endosperm-specific and temporal expression of rice prolamine gene.

Base Sequence↗
PubMed1998

Measuring human ventilation for apnoea detection using an optical encoder.

We have designed, built and tested a proof-of-concept system based on optical encoder technology for measuring adult or infant ventilation. It uses change in chest circumference to provide an indirect measure of ventilation. The Hewlett-Packard HEDS-9720 optical encoder senses displacement of its matching codestrip. It yields a resolution of 0.17 mm and is accurate to 0.008 mm over a 10 mm test distance. The encoder is mounted on a nylon web belt wrapped around the torso and responds to changes in circumference. Motion of the code strip during respiration is converted to direction of movement (inhalation or exhalation) as well as magnitude of circumference change. Use of two sensor bands, one on the chest and one on the abdomen, may allow detection of obstructive apnoea in which there is no air flow out of or into the subject despite respiratory movement. Applications of this technology include infant apnoea monitoring as well as long-term adult monitoring.

Adult↗
PubMed1999

Haemodynamic brain responses to acute pain in humans: sensory and attentional networks.

Turning attention towards or away from a painful heat stimulus is known to modify both the subjective intensity of pain and the cortical evoked potentials to noxious stimuli. Using PET, we investigated in 12 volunteers whether pain-related regional cerebral blood flow (rCBF) changes were also modulated by attention. High (mean 46.6 degrees C) or low (mean 39 degrees C) intensity thermal stimuli were applied to the hand under three attentional conditions: (i) attention directed towards the stimuli, (ii) attention diverted from the stimuli, and (iii) no task. Only the insular/second somatosensory cortices were found to respond whatever the attentional context and might, therefore, subserve the sensory-discriminative dimension of pain (intensity coding). In parallel, other rCBF changes previously described as 'pain-related' appeared to depend essentially on the attentional context. Attention to the thermal stimulus involved a large network which was primarily right-sided, including prefrontal, posterior parietal, anterior cingulate cortices and thalamus. Anterior cingulate activity was not found to pertain to the intensity coding network but rather to the attentional neural activity triggered by pain. The attentional network disclosed in this study could be further subdivided into a non-specific arousal component, involving thalamic and upper brainstem regions, and a selective attention and orientating component including prefrontal, posterior parietal and cingulate cortices. A further effect observed in response to high intensity stimuli was a rCBF decrease within the somatosensory cortex ipsilateral to stimulation, which was considered to reflect contrast enhancing and/or anticipation processes. Attentional processes could possibly explain part of the variability observed in previous PET reports and should therefore be considered in further studies on pain in both normal subjects and patients with chronic pain.

Acoustic Stimulation↗
PubMed1996

Medical savings accounts. American College of Physicians.

This position paper examines medical savings accounts (MSAs) as a supplemental mechanism for financing health care services. Although federal legislation to encourage MSAs did not pass in 1995 and is not likely to pass in 1996, MSAs will continue to be seriously considered by public policymakers. Individual retirement accounts accumulate funds for retirement; MSAs could be used to accumulate funds for health care expenditures. Changes in the federal tax code would be required to permit tax-deductible contributions and tax-free earnings to individual MSAs. To be withdrawn without penalty, funds from an MSA could only be used to pay for approved medical or health insurance expenses. Each person would own and control his or her account, regardless of changes in employment. Coupled with high-deductible health insurance, MSAs could empower cost-conscious patients in health care decision making, increasing competitive pressure to reduce health care costs. Administrative costs and paperwork associated with health insurance might also be reduced, and some people who currently do not have health insurance might be able to obtain some financial protection. Medical savings accounts may not help unemployed persons or low- and middle-income persons who cannot afford to contribute to such accounts. These accounts may result in reduced health insurance protection and greater out-of-pocket expenses for those most in need of health care. Problems of adverse risk selection could arise if healthy persons choose insurance options involving MSAs; this choice would cause premiums to increase for persons who desire traditional health insurance.

Deductibles and Coinsurance↗
PubMed1996

Heterogeneity in the haemagglutinin gene and emergence of the highly pathogenic phenotype among recent H5N2 avian influenza viruses from Mexico.

Molecular changes in the haemagglutinin (HA)-coding regions and proteolytic cleavage sites from multiple H5N2 subtype viruses isolated during a recent outbreak of avian influenza (AI) in central Mexico have been characterized. Eighteen isolates, collected during a 15 month period (October 1993 to January 1995) from six central states, were sequenced. None of the 18 predicted HA1 amino acid sequences were identical and changes were not restricted to a specific region of the sequence. Phylogenetic analyses of the HA1 sequences demonstrated two virus lineages, designated Puebla and Jalisco, with sequence variation as high as 10.5 percent for amino acid and 6.2 percent for nucleotide sequences. During the latter months of the surveillance period, highly pathogenic (HP) strains of AI emerged causing lethal disease in commercial poultry flocks. In each of the HP strains isolated, the HA protein was cleaved in chicken embryo fibroblast cells in the absence of trypsin, and two alterations not found in earlier non-HP isolates were detected. In the HA protein, HP strains all had a glutamic acid --> lysine substitution at amino acid position 324 and an insertion of arginine and lysine as new residues 325 and 326. The insertion appears to be due to a duplication of the nucleotide sequence AAAGAA at nucleotide positions 965-970 of the HA1-coding region. Computer-assisted secondary structure analyses place the target for the insertion in a predicted RNA stem-loop structure. A mechanism is suggested by which the polymerase duplicates the sequence.

Amino Acid Sequence↗
PubMed1986

Studies on the mechanism of membrane fusion: site-specific mutagenesis of the hemagglutinin of influenza virus.

Oligonucleotide-directed mutagenesis of a cDNA encoding the hemagglutinin of influenza virus has been used to introduce single base changes into the sequence that codes for the conserved apolar "fusion peptide" at the amino-terminus of the HA2 subunit. The mutant sequences replaced the wild-type gene in SV40-HA recombinant virus vectors, and the altered HA proteins were expressed in simian cells. Three mutants have been constructed that introduce single, nonconservative amino acid changes in the fusion peptide, and three fusion phenotypes were observed: substitution of glutamic acid for the glycine residue at the amino-terminus of HA2 abolished all fusion activity; substitution of glutamic acid for the glycine residue at position 4 in HA2 raised the threshold pH and decreased the efficiency of fusion; and, finally, extension of the hydrophobic stretch by replacement of the glutamic acid at position 11 with glycine yielded a mutant protein that induced fusion of erythrocytes with cells with the same efficiency and pH profile as the wild-type protein. However, the ability of this mutant to induce polykaryon formation was greatly impaired. Nevertheless, all the mutant proteins underwent a pH-dependent conformational change and bound to liposomes. These results are discussed in terms of the mechanism of HA-induced membrane fusion.

Animals↗
PubMed2003

The molecular epidemiology of genital Chlamydia trachomatis in the greater Reykjavik area, Iceland.

BACKGROUND: The diversity in MOMP (major outer membrane protein) of Chlamydia trachomatis is thought to be necessary for the bacteria to survive in its environment. The rate of change in the omp1 gene (coding for MOMP) is not known. Iceland offers a good opportunity to study the epidemiology of chlamydial infections because the population is small (280,000) and geographically well defined. GOAL: The goal was to determine the number and distribution of genotypes in a population attending the STD clinic in Reykjavík and to assess changes in omp1 sequences over a period of 2 years. STUDY DESIGN: Three-hundred thirty isolates of C trachomatis collected periodically from January 1999 to January 2001 were omp1 genotyped with nested PCR and sequencing. RESULTS: The serotypes found, in descending order of prevalence, were E, D, J, F, K, G, H, and I. Eighteen distinctive genotypes were found. During the study period no significant changes in frequency of genotypes were noted, and introduction of new or changed genotypes was not observed. CONCLUSION: The results indicate a relatively stable situation of genotypes and suggest an ecological advantage of serotype E.

Chlamydia Infections↗
PubMed1993

The endosperm-specific expression of a rice prolamin chimaeric gene in transgenic tobacco plants.

The 5' upstream region (-680 to +40), containing the potential promoter and complete signal peptide coding sequence of the rice seed storage prolamin gene was amplified in vitro using the polymerase chain reaction from the genome of Chinese rice cultivar Zhonghua 8. The physical map and DNA sequence analysis show strong homology with the 5' flanking region of the rice prolamin gene published by Kim and Okita (1988a). No change in the signal peptide coding sequence and a long leader sequence with several small open reading frames were found. The chimaeric gene containing the 5' flanking region of the prolamin gene (-680 to -18) was transcriptionally fused with the beta-glucuronidase (GUS) reporter gene and the fusion junction was confirmed by both physical mapping and DNA sequence analysis. The resultant chimaeric gene was used to transform tobacco explants, using the Ti binary system of Agrobacterium tumefaciens LBA4404. Three transgenic tobacco plants with as many as 20 copies of the chimaeric GUS gene (confirmed by dot and Southern hybridization) were analysed further. Histochemical analysis revealed GUS activity in the endosperm tissue of tobacco seed at the developmental stage about 20 days after flowering (DAF). No GUS activity was found in leaves, stems, roots and flowers of the transgenic tobacco plants. Therefore, we conclude that the 5' upstream region from -680 to -18 was sufficient to confer the endosperm-specific expression of the rice prolamin gene.

Base Sequence↗
PubMed1980

Medical student selection: a tentative attempt to establish a code of practice.

Each year medical schools in the United Kingdom select about 3800 entrants from about 12 000 applicants. The problem of selection is thus substantial, but the objectives, policies, and practices of different medical schools differ sharply and details of the procedures used are rarely made clear. There is no reliable or up-to-date information available for schools, careers of advisers, and prospective candidates to keep abreast of these practices and policies and of changes made to them. A code of practice for medical student selection might be helpful and would not only facilitate discussion about the appropriateness and fairness of the widely differing practices but make it easier to evaluate the procedures used. Such a code should list the academic and personal requirements for the school, state any quotas for types of entrants, and describe the selection procedures.

Education, Medical, Undergraduate↗
PubMedDate not supplied

Retinoic acid alters hindbrain Hox code and induces transformation of rhombomeres 2/3 into a 4/5 identity.

It has been suggested that Hox genes play an important part in the patterning of limbs, vertebrae and craniofacial structures by providing an ordered molecular system of positional values, termed the Hox code. Little is known about the nature of the signals that govern the establishment and regulation of Hox genes, but retinoic acid can affect the expression of these genes in cell lines and in embryonic tissues. On the basis of experimental and clinical evidence, the hindbrain and branchial region of the head are particularly sensitive to the effects of retinoic acid but the phenotypes are complex and hard to interpret, and how and if they relate to Hox expression has not been clear. Here we follow the changes induced by retinoic acid to hindbrain segmentation and the branchial arches using transgenic mice which contain lacZ reporter genes that reveal the endogenous segment-restricted expression of the Hox-B1 (Hox-2.9), Hox-B2(Hox-2.8) and Krox-20 genes. Our results show that these genes rapidly respond to exposure to retinoic acid at preheadfold stages and undergo a progressive series of changes in segmental expression that are associated with specific phenotypes in hindbrain of first branchial arch. Together the molecular and anatomical alterations indicate that retinoic acid has induced changes in the hindbrain Hox code which result in the homeotic transformation of rhombomeres (r) 2/3 to an r4/5 identity. A main feature of this rhombomeric phenotype is that the trigeminal motor nerve is transformed to a facial identity. Furthermore, in support of this change in rhombomeric identity, neural crest cells derived from r2/3 also express posterior Hox markers suggesting that the retinoic acid-induced transformation extends to multiple components of the first branchial arch.

Animals↗
PubMed2005

Prevention of hyperglycemia in Zucker diabetic fatty rats by exercise training: effects on gene expression in insulin-sensitive tissues determined by high-density oligonucleotide microarray analysis.

Exercise training (ET) causes metabolic improvement in the prediabetic and diabetic states. However, only little information exists on the changes to ET at the transcriptional level in insulin-sensitive tissues. We have investigated the gene expression changes in skeletal muscle, liver, fat, and pancreatic islets after ET in male Zucker diabetic fatty (ZDF) rats. Eighteen ZDF rats (7 weeks old) were divided in a control and ET group. Exercise was performed using a motorized treadmill (20 m/min 1 hour daily for 6 days a week). Blood glucose, weight, and food intake were measured weekly. After 5 weeks, blood samples, soleus muscle, liver, visceral fat (epididymal fat pads), and islet tissue were collected. Gene expression was quantified with Affymetrix RG-U34A array (16 chips). Exercise training ameliorates the development of hyperglycemia and reduces plasma free fatty acid and the level of glucagon-insulin ratio (P < .05). In skeletal muscle, the expression of 302 genes increased, whereas that of 119 genes decreased. These changes involved genes related to skeletal muscle plasticity, Ca(2+) signals, energy metabolism (eg, glucose transporter 1, phosphorylase kinase), and other signaling pathways as well as genes with unknown functions (expressed sequence tags). In the liver, expression of 148 genes increased, whereas that of 199 genes decreased. These were primarily genes involved in lipogenesis and detoxification. Genes coding for transcription factors were changed in parallel in skeletal muscle and liver tissue. Training did not markedly influence the gene expression in islets. In conclusion, ET changes the expression of multiple genes in the soleus muscle and liver tissue and counteracts the development of diabetes, indicating that ET-induced changes in gene transcription may play an important role en the prevention of diabetes.

Adipose Tissue↗
PubMed2005

Randomized controlled trial of homocysteine-lowering vitamin treatment in elderly patients with vascular disease.

BACKGROUND: Homocysteine is an independent risk factor for vascular disease and is associated with dementia in older people. Potential mechanisms include altered endothelial and hemostatic function. OBJECTIVE: We aimed to determine the effects of folic acid plus vitamin B-12, riboflavin, and vitamin B-6 on homocysteine and cognitive function. DESIGN: This was a factorial 2 x 2 x 2, randomized, placebo-controlled, double-blind study with 3 active treatments: folic acid (2.5 mg) plus vitamin B-12 (500 microg), vitamin B-6 (25 mg), and riboflavin (25 mg). We studied 185 patients aged >or=65 y with ischemic vascular disease. Outcome measures included plasma homocysteine, fibrinogen, and von Willebrand factor at 3 mo and cognitive change (determined with the use of the Letter Digit Coding Test and on the basis of the Telephone Interview of Cognitive Status) after 1 y. RESULTS: The mean (+/-SD) baseline plasma homocysteine concentration was 16.5 +/- 6.4 micromol/L. This value was 5.0 (95% CI: 3.8, 6.2) micromol/L lower in patients given folic acid plus vitamin B-12 than in patients not given folic acid plus vitamin B-12 but did not change significantly with vitamin B-6 or riboflavin treatment. Homocysteine lowering with folic acid plus vitamin B-12 had no significant effect, relative to the 2 other treatments, on fibrinogen, von Willebrand factor, or cognitive performance as measured by the Letter Digit Coding Test (mean change: -1; 95% CI: -2.3, 1.4) and the Telephone Interview of Cognitive Status (-0.7; 95% CI: -1.7, 0.4). CONCLUSION: Oral folic acid plus vitamin B-12 decreased homocysteine concentrations in elderly patients with vascular disease but was not associated with statistically significant beneficial effects on cognitive function over the short or medium term.

Aged↗
PubMed2004

Effect of acarbose treatment on the risk of silent myocardial infarctions in patients with impaired glucose tolerance: results of the randomised STOP-NIDDM trial electrocardiography substudy.

BACKGROUND: The moderate increase in postprandial plasma glucose in subjects with impaired glucose tolerance has been shown to be a predictor of cardiovascular disease. In the randomised STOP-NIDDM trial, we could demonstrate that lowering postprandial plasma glucose with acarbose in subjects with impaired oral glucose tolerance could reduce the risk of diabetes. METHODS: The current report focuses on the effect of acarbose on silent ischaemic events evaluated in the electrocardiographic substudy, using the Minnesota code classification. RESULTS: A total of 1181 patients were included in the ECG substudy. From these 72 patients had significant changes between the baseline and end of treatment ECG, 33 in the acarbose and 39 in the placebo group. Higher rates of myocardial infarctions occurred in the placebo group (P=0.07 with Fisher's Exact test and P=0.023 with Chi-square test), while there were no differences between the two groups with ECG changes classified under the other Minnesota codes. CONCLUSIONS: In this prospective intervention study we could show that acarbose, by decreasing postprandial hyperglycaemia, can reduce the incidence of silent myocardial infarctions in subjects with impaired glucose tolerance. This approach should therefore be evaluated in other higher risk populations.

Acarbose↗
PubMed1993

Relationship between G + C in silent sites of codons and amino acid composition of human proteins.

We have investigated the relationship between the G + C content of silent (synonymous) sites in codons and the amino acid composition of encoded proteins for approximately 1,600 human genes. There are positive correlations between silent site G + C and the proportions of codons for Arg, Pro, Ala, Trp, His, Gln, and Leu and negative ones for Tyr, Phe, Asn, Ile, Lys, Asp, Thr, and Glu. The median proteins coded by groups of genes that differ in silent-site G + C content also differ in amino acid composition, as do some proteins coded by homologous genes. The pattern of compositional change can be largely explained by directional mutation pressure, the genetic code, and differences in the frequencies of accepted amino acid substitutions; the shifts in protein composition are likely to be selectively neutral.

Amino Acids↗
PubMedDate not supplied

FDA's new vending code: a review.

The concept of developing and promoting the nationwide adoption of uniform sanitation regulations for food and beverage vending was agreed upon by the U.S. Public Health Service and industry leaders more than 20 years ago. Two revisions of the original Vending Code which was published in 1957 have kept pace with industry changes, the most recent now available in booklet form. Trends in food and beverage vending prompted code revisions resulting in the 1978 Vending Code which has major changes and effects on existing state and local regulations.

Food Dispensers, Automatic↗