Ankle Brachial Pressure Index: identifying cardiovascular risk and improving diagnostic accuracy.
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Ankle↗
Biomedical subjects
N Bhasin
Publications and source records attributed to N Bhasin.
How should a candidate assess varicose veins in the MRCS clinical examination? A vascular viewpoint.
INTRODUCTION: Varicose veins are a common problem and, therefore, regularly feature in the vascular bay of the MRCS clinical examination. Candidates are still being instructed to perform tests in the examination that are considered by many to be obsolete and inaccurate. Using the current cohort of vascular examiners, we aim to clarify which tests a candidate should be performing when assessing varicose veins. We also aim to assess basic surgical trainees' experience in the use of hand-held Doppler (HHD). MATERIALS AND METHODS: Postal questionnaires were sent to all English College Court examiners with a declared vascular interest to gain their opinion on what tests should be used in the vascular bay to assess primary varicose veins. E-mail questionnaires were also sent to basic surgical trainees to assess their experience in the use of hand-held Doppler to assess varicose veins. RESULTS: There was a 100% response rate from the examiners with 93%, 86% and 79% feeling that clinical examination, HHD examination of the SFJ and HHD examination of the SPJ, respectively, should form part of the examination of primary varicose veins in the vascular bay. Only 50% indicated the Trendelenburg test and cough impulse and 57% believed the tap test should form part of the examination of varicose veins. Of the BSTs, 53% believed they could examine varicose veins with HHD. Of the BSTs who could use HHD, 74% had held a vascular SHO post. DISCUSSION: Published data and opinion show many consultant surgeons have totally abandoned the use of the Trendelenberg, cough, tap and Perthes tests and support the opinion that HHD increases the accuracy of the examination of varicose veins. This study shows the opinions of the examiners supports the evidence-based recommendations that, in the light of easily accessible HHD, the older tests are now outdated. The majority of BSTs who were able to use HHD had held a vascular SHO post (74%) but otherwise it was unlikely that the BST would be comfortable with this skill. CONCLUSIONS: The Brodie-Trendelenburg (tourniquet) test, cough impulse and tap test are outdated but candidates should be aware of the principles and failings behind them. In the MRCS clinical examination, candidates should examine varicose veins by means of clinical examination and HHD as this is now accepted standard practice. To aid candidate education, the HHD technique should replace traditional clinical tests which continue to be taught in medical school and remain within the classical surgical text books.
Clinical Competence↗
Opposing regulation of cell proliferation by retinoic acid and the serotonin2B receptor in the mouse frontonasal mass.
Development of the frontonasal mass (FNM), branchial arches, heart, and limbs depends on neural crest-mediated epithelial-mesenchymal (E-M) interactions. Teratogenesis by retinoic acid (RA) or blockade of serotonergic (5-HT) signaling by the pan-5-HT(2) receptor antagonist, ritanserin, perturbs development of these embryonic structures. In both cases, resulting phenotypes include forebrain and olfactory placode anomalies, malformations of the face, eye and lens, as well as posterior neural tube and cardiac defects. Similar sites of malformations, together with the presence of RA response elements in the 5-HT(2B) receptor promoter, have led to the suggestion that a negative regulatory relationship may exist between RA and 5-HT(2)-mediated 5-HT signaling at sites of E-M interaction (Choi et al. 1997); however, another possibility is that RA and 5-HT act independently as opposing signals to regulate development of common embryonic targets. Together with recent evidence for opposite effects on chondrogenic differentiation in hindlimb micromass cultures (Bhasin et al. 2003a), results of the present study raise the possibility that these pathways may act as opposing signals for common targets in the mouse embryo. The RA receptors, co-factors and metabolic enzymes, and 5-HT(2B) receptors were found to be are coordinately expressed at sites of E-M interaction, including the FNM, in the embryonic day (E)10.5 mouse. Cell proliferation experiments using [(3)H]thymidine incorporation demonstrated that RA or activation of 5-HT(2B) receptors caused opposite effects in FNM explants, namely stimulation or inhibition of cell proliferation, respectively, 5-HT(2B) receptor activation did not appreciably alter patterning in FNM explants. While RA has been shown to regulate lateral patterning in the FNM (LaMantia et al. 2000), 5-HT(2B) receptor activation did not alter patterning in FNM explants. Quantification of 5-HT(2B) receptor transcripts by real-time PCR provided no evidence of negative regulation of 5-HT(2B) receptor expression by RA in FNM explants, although preliminary studies using in situ hybridization had suggested that this was a possibility in both explants and RA teratogenized embryos. Future studies using quantitative PCR may still show this to be the case in teratogenized embryos. Together with the finding of coordinate expression of 5-HT(2B )receptors and RA signaling molecules, results of the present study suggest that RA, and 5-HT mediated by 5-HT(2B )receptors, may act as opposing signals to regulate cell proliferation during craniofacial development in the mouse embryo.
Animals↗
Differential regulation of chondrogenic differentiation by the serotonin2B receptor and retinoic acid in the embryonic mouse hindlimb.
Retinoic acid (RA) synthesizing and metabolizing enzymes are coordinately expressed with serotonin 2B (5-HT2B) receptors at sites of epithelial-mesenchymal (E-M) interaction in the mouse embryo (Bhasin et al., 1999). The promoter of the 5-HT2B receptor contains potential RA response element (RAREs) as well as an AP-2 site. Because both retinoid and serotonergic signaling have been implicated in the regulation of chondrogenic differentiation, the present study investigated whether these signals may work together to regulate this morphogenetic process in hindlimb bud micromass cultures. Results indicate that 5-HT promotes [35S]sulfate incorporation (chondrogenic differentiation) by activation of 5-HT2B receptors, which use the mitogen activated protein kinase (p42 MAPK) signal transduction pathway, whereas RA dose-dependently inhibits sulfate incorporation and promotes expression of RARbeta, which could lead to inhibition of p38 MAPK. No evidence was found to support the possibility that RA negatively regulates expression of 5-HT2B receptors. Taken together, these results suggest that 5-HT and RA may act as opposing signals to regulate chondrogenic differentiation in the developing hindlimb, possibly mediated by different MAPK signal transduction pathways.
Animals↗
Penile ulcer: an unusual presentation of cholesterol emboli.
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Aged↗
Endovascular treatment of a MRSA infected left external iliac artery pseudoaneurysm.
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Adult↗
Internal iliac artery aneurysm--a cause of leg swelling and cellulitis.
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Aged↗
Mesenchymal/epithelial regulation of retinoic acid signaling in the olfactory placode.
We asked whether mesenchymal/epithelial (M/E) interactions regulate retinoic acid (RA) signaling in the olfactory placode and whether this regulation is similar to that at other sites of induction, including the limbs, branchial arches, and heart. RA is produced by the mesenchyme at all sites, and subsets of mesenchymal cells express the RA synthetic enzyme RALDH2, independent of M/E interactions. In the placode, RA-producing mesenchyme is further distinguished by its coincidence with a molecularly distinct population of neural crest-associated cells. At all sites, expression of additional RA signaling molecules (RARalpha, RARbeta, RXR, CRABP1) depends on M/E interactions. Of these molecules, RA regulates only RARbeta, and this regulation depends on M/E interaction. Expression of Fgf8, shh, and Bmp4, all of which are thought to influence RA signaling, is also regulated by M/E interactions independent of RA at all sites. Despite these common features, RALDH3 expression is distinct in the placode, as is regulation of RARbeta and RALDH2 by Fgf8. Thus, M/E interactions regulate expression of RA receptors and cofactors in the olfactory placode and other inductive sites. Some aspects of regulation in the placode are distinct, perhaps reflecting unique roles for additional local signals in neuronal differentiation in the developing olfactory pathway.
Aldehyde Oxidoreductases↗
Staphylococcus aureus Cap5O has UDP-ManNAc dehydrogenase activity and is essential for capsule expression.
The Staphylococcus aureus serotype 5 capsular polysaccharide (CP5) has a repeating unit composed of (-->4)-3-O-acetyl-beta-D-ManNAcA-(1-->4)-alpha-L-FucNAc (1-->3)-beta-D-FucNAc-(1-->)(n). Sixteen chromosomal genes (cap5A through cap5P) are involved in the synthesis of CP5. We recently demonstrated that Cap5P, a 2-epimerase, catalyzes the conversion of UDP-N-acetyl glucosamine (UDP-GlcNAc) to UDP-N-acetylmannosamine (UDP-ManNAc). In this study, we show that UDP-ManNAc is oxidized to UDP-N-acetylmannosaminuronic acid (UDP-ManNAcA) by a UDP-ManNAc dehydrogenase encoded by S. aureus cap5O. We expressed Cap5O in Escherichia coli and purified the recombinant protein. The UDP-ManNAc dehydrogenase activity of purified Cap5O was assessed by incubating Cap5P and UDP-GlcNAc (to produce UDP-ManNAc), together with Cap5O, NAD(+), and a reducing agent. Enzymatic activity was quantitated indirectly by measuring the increase in absorbance at 340 nm resulting from NADH formation. The product of the reaction was confirmed as UDP-ManNAcA by gas chromatography-mass spectroscopy. A cap5O mutation, created by deletion of 727 bp in the 5' end of the gene, was introduced by allelic replacement into S. aureus Reynolds, rendering it CP5 negative. Mice inoculated intravenously or subcutaneously with the wild-type strain Reynolds had greater numbers of S. aureus recovered from their kidneys (P = 0.019) or their subcutaneous abscesses (P = 0.0018), respectively, than did animals inoculated with the cap5O mutant. The results of this study indicate that S. aureus cap5O is essential for capsule production and that capsule promotes staphylococcal virulence in mouse models of abscess formation.
Animals↗
Neisseria meningitidis lipopolysaccharide modulates the specific humoral immune response to neisserial porins but has no effect on porin-induced upregulation of costimulatory ligand B7-2.
The role of lipopolysaccharide (LPS) in the specific humoral response to meningococcal porins was investigated by measuring anti-PorA or -PorB antibody levels in mice immunized with wild-type meningococcal strain H44/76 or with its recently described LPS-negative mutant. Two murine strains were used for these immunizations: C3H/HeJ, which is LPS hyporesponsive, or C3H/HeOuJ, which is LPS responsive. A high level of anti-PorB immunoglobulin G (IgG) response was induced in both strains of mice immunized with either organism. The response induced by the wild-type strain was greater in C3H/HeOuJ mice than in C3H/HeJ mice, while the response induced by the LPS-negative mutant was similar in the two murine strains. Additionally, the anti-PorB response was similar in C3H/HeJ mice immunized with either bacterial strain. In general, the anti-PorA IgG response was lower than the anti-PorB response. These findings indicate that the presence of LPS is not essential for the induction of an antineisserial porin humoral response but can augment such a response. To determine whether LPS has any effect on the B-cell-stimulatory effect of neisserial porins (essential for the adjuvant activity of neisserial porins), B cells from both murine strains were incubated with outer membrane complexes (OMCs) prepared from strain H44/76 and its LPS-negative mutant. OMCs from either meningococcal strain were able to increase the surface expression of the costimulatory ligand B7-2 on B cells from either murine strain. Consistent with previously reported findings, LPS does not significantly affect the ability of neisserial porins to induce the costimulatory ligand B7-2.
Animals↗
Mesenchymal/epithelial induction mediates olfactory pathway formation.
In the olfactory pathway, as in the limbs, branchial arches, and heart, mesenchymal/epithelial induction, mediated by retinoic acid (RA), FGF8, sonic hedgehog (shh), and the BMPs, defines patterning, morphogenesis, and differentiation. Neuronal differentiation in the olfactory epithelium and directed growth of axons in the nascent olfactory nerve depend critically upon this inductive interaction. When RA, FGF8, shh, or BMP signaling is disrupted, distinct aspects of olfactory pathway patterning and differentiation are compromised. Thus, a cellular and molecular mechanism that facilitates musculoskeletal and vascular development elsewhere in the embryo has been adapted to guide the differentiation of the olfactory pathway in the developing forebrain.
Animals↗
Staphylococcus aureus cap5P encodes a UDP-N-acetylglucosamine 2-epimerase with functional redundancy.
The serotype 5 capsule gene cluster of Staphylococcus aureus comprises 16 genes (cap5A through cap5P), but little is known about how the putative gene products function in capsule biosynthesis. We propose that the N-acetylmannosaminuronic acid (ManNAcA) component of the S. aureus serotype 5 capsular polysaccharide (CP5) is synthesized from a UDP-N-acetylglucosamine (UDP-GlcNAc) precursor that is epimerized to UDP-N-acetylmannosamine (UDP-ManNAc) and then oxidized to UDP-ManNAcA. We report the purification and biochemical characterization of a recombinant UDP-GlcNAc 2-epimerase encoded by S. aureus cap5P. Purified Cap5P converted approximately 10% of UDP-GlcNAc to UDP-ManNAc as detected by gas chromatography-mass spectrometry. The epimerization of UDP-GlcNAc to UDP-ManNAc occurred over a wide pH range and was unaffected by divalent cations. Surprisingly, CP5 expression in S. aureus was unaffected by insertional inactivation of cap5P. Sequence homology searches of the public S. aureus genomic databases revealed the presence of another putative UDP-GlcNAc 2-epimerase on the S. aureus chromosome that showed 61% identity to Cap5P. Redundancy of UDP-GlcNAc 2-epimerase function in S. aureus was demonstrated by cloning the cap5P homologue from strain Newman and complementing an Escherichia coli rffE mutant defective in UDP-GlcNAc 2-epimerase activity. Our results confirm the putative function of the S. aureus cap5P gene product and demonstrate the presence of a second gene on the staphylococcal chromosome with a similar function.
Bacterial Proteins↗
Identification of a gene essential for O-acetylation of the Staphylococcus aureus type 5 capsular polysaccharide.
The Staphylococcus aureus serotype 5 capsular polysaccharide (CP5) has a trisaccharide repeating unit of (-->4)-3-O-Ac-beta-D-ManNAcAp-(1-->4)-alpha-L-FucNAcp-(1-->3 )-beta-D-FucNAcp-(1-->). Tn918 mutagenesis of strain Reynolds yielded a mutant that produced wild-type levels of O-deacetylated CP5. The site and orientation of the single transposon insertion in mutant JL232 were determined by analysis of Southern blots and amplification of DNA flanking the transposon. DNA sequencing revealed that Tn918 was inserted within an open reading frame of 627 bp. The predicted amino acid sequence encodes a protein of approximately 26 kDa with homology to members of the NodL-LacA-CysE family of bacterial acetyltransferases. Southern blot analysis showed that genes similar to cap5H were present only in strains of S. aureus belonging to capsular serotypes 2, 4 and 5. In an in vitro assay, the parental strain was more resistant to opsonophagocytic killing than the mutant strain. In a mouse model of staphylococcal infection, the parental strain was able to seed the bloodstream from the peritoneal cavity and colonize the kidneys more efficiently than the O-deacetylated mutant. When cap5H was provided to the mutant in trans, it fully restored CP5 O-acetylation. The virulence of the complemented mutant strain closely approximated that of the parental strain.
Abscess↗
Apolipoprotein E gene expression in various tissues of mouse and regulation by estrogen.
Apolipoprotein (apo) E is associated with several classes of lipoproteins and serves as a ligand for the receptor mediated uptake of cholesterol-rich particles by hepatocytes and peripheral tissues. Variant forms of apo E is also associated with dyslipidemia and late-onset of Alzheimer's Disease (AD). We report here expression of apoE in various mouse tissues, and regulation of apoE in liver, kidney, brain and testes by supraphysiological doses of estrogen. ApoE mRNA was quantified by RNase protection assay and translatable apoE mRNA by in vitro translation. As an internal control the levels of beta-actin mRNA were also quantified. Highest levels of apoE were expressed in liver (220-280 pg/mu g RNA) with negligible levels in small intestine. Brain expressed highest levels of total (35-40 pg/mu g RNA) and translatable apoE mRNA next only to liver. Other tissues that expressed relatively higher levels of apoE were adrenals, testes and ovary. ApoE was also found to be expressed in heart, lung, kidney and spleen. Regulation of apoE gene expression by estrogen (3 mu g 17beta-estradiol/ g body weight/ day for 5 consecutive days) was studied in liver, kidney, brain and testes of 4 mouse strains. Hepatic apoE mRNA did not change significantly in any of the mouse strains following estradiol administration. Of note was significant increases in the levels of brain apoE mRNA in the strain C3H. These studies demonstrate that estrogen regulates apoE gene expression in a tissue-specific manner in mice, and increases in apoE mRNA in the brain by estrogen may have implications in late-onset of Alzheimer's Disease.
Animals↗
Evidence for a weak adaptive response to alkylation damage in Vibrio cholerae.
Wild-type Vibrio cholerae cells, when adapted by a stepwise treatment with sub-lethal concentrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), acquired resistance to killing and mutagenesis by subsequent challenges with higher concentrations of MNNG. This was also seen in the rec isogenic strain indicating that the observed phenomenon was not due to the induction of SOS functions. Further, the adapted cells of both the wild-type and rec strains could reactivate lethally alkylated phages with equal efficiency. Increased resistance of adapted cells correlated with the induction of a 17-kDa DNA methyltransferase, capable of repairing O6-methylguanine lesions in DNA. This induced methyltransferase was found to be antigenically unrelated to the Escherichia coli methyltransferase (Ada protein) as determined by Western blotting with polyclonal antiserum raised against the E. coli protein. Even though no counterpart of the constitutively expressed methyltransferase (Ogt) of E. coli could be detected in V. cholerae, several lines of evidence pointed towards the presence of an E. coli alk A-like gene in the organism.
Adaptation, Physiological↗
Studies on the genesis of Vibrio cholerae O139: identification of probable progenitor strains.
Four lines of evidence suggest that the recent outbreak strains of Vibrio cholerae O139 could have emerged from serogroup O1 strains typified by isolates M01 and M0477 described in this paper, which are neither truly classical nor truly E1 Tor in their biotype attributes. Firstly, like all O139 isolates, these O1 strains, isolated in Madras during and before the O139 outbreak, were resistant not only to polymyxin B but also to all biotype-specific choleraphages, i.e. classical phage phi 149 and E1 Tor phages e4 and e5. Secondly, the restriction fragment pattern (RFP) polymorphism displayed by these strains for the cholera toxin (ctx) gene, were identical with those produced by O139 isolates but were different from those of O1 type strains, namely V. cholerae 569B (classical) and V. cholerae MAK757 (E1 Tor). Thirdly, all the O139 isolates and the two O1 isolates carried an identical large number of copies of cholera toxin gene in their chromosomes. Finally, the outer-membrane protein profiles of strains M01 and M0477 were identical to those of O139 isolates but were different from those displayed by strains 569B and MAK757.
Bacterial Outer Membrane Proteins↗