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Biomedical subjects

A Greenfield

Publications and source records attributed to A Greenfield.

At least 19 recordsLinked to original sources
PubMed2006

Normal-phase chiral liquid chromatography-mass spectrometry of non-UV-active compounds: applications for pharmaceutically relevant racemates.

Mixtures of hexane-like ethoxynonafluorobutane with alcohols were used as MS-friendly mobile phases for separation and efficient detection of non-UV-active enantiomers and diastereomers using normal-phase HPLC-APCI-MS. Racemic muscone, camphorsulfonamide, camphorsultam, BOC-protected 1-(3-aminopropyl)-2-pipecoline and diastereomeric 2-methylhexanoyl camphorsultams were resolved on Chiralpak AS and AD and achiral Luna CN columns. The responses of UV and APCI-MS detectors were compared under separation conditions studied, with MS detection achieving lowest detectable quantity in the range of 0.5-2 ng per chromatographic peak. The absolute configuration of crystalline derivatives of racemic 2-methylhexanoic acid with (S)-(-)-2,10-camphorsultam was determined by X-ray analysis after their automatic purification by preparative LC-MS. The technique described can be used to purify and determine the absolute stereochemistry of compounds of unknown structure which contain free carboxy group and lack sufficient UV absorbance.

Butanes↗
PubMed2004

Molecular phenotyping of the mouse ky mutant reveals UCP1 upregulation at the neuromuscular junctions of dystrophic soleus muscle.

The ky mutant mouse displays a muscular dystrophy that affects almost exclusively slow type muscles in which persistent muscle regeneration, neuromuscular junction instability and an absence of the hypertrophic response are prominent features. In order to gain insights into the pathogenesis of this muscular dystrophy we have undertaken RNA profiling of the extensor digitorum longus, a fast unaffected muscle, and the highly pathological soleus slow muscle, followed by further expression studies to validate the results. In dystrophic soleus, there is a coordinated change in the expression level of genes encoding energy transducing mitochondrial proteins and an increase in the expression of stretch response genes. Upregulation of uncoupling proteins 1 and 2 is a unique molecular signature of the ky muscular dystrophy and was further characterised at the protein level. Our results show a spatial and temporal association between disorganisation of acetylcholine receptor clusters and upregulation of uncoupling protein 1. There is also evidence of a breakdown of neuromuscular junction muscle-specific kinase-dependent signalling in adult mutant soleus. Sarcolemma-associated proteins implicated in muscular dystrophies revealed no differences on microarrays and were confirmed as normally distributed by immunofluorescence. Altogether, the data presented suggest that the ky muscular dystrophy develops by a distinctive pathogenic mechanism.

Animals↗
PubMed2001

Expression of a novel mammalian epidermal growth factor-related gene during mouse neural development.

We have recently reported the preliminary characterisation of a novel EGF-related gene, Scube1 (signal peptide-CUB domain-EGF-related, gene 1), that is expressed prominently in the developing gonad, nervous system, somites, surface ectoderm and limb buds of the mouse. Here we describe the expression pattern of a closely related gene, Scube2 (also known as Cegp1), which maps to the distal region of mouse chromosome 7. Scube2 transcription is restricted to the embryonic neurectoderm but is also detectable in the adult heart, lung and testis.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Cloning, mapping, and expression analysis of a gene encoding a novel mammalian EGF-related protein (SCUBE1).

The epidermal growth factor (EGF) superfamily comprises a diverse group of proteins that function as secreted signaling molecules, growth factors, and components of the extracellular matrix, many with a role in vertebrate development. We have isolated a novel mammalian gene encoding an EGF-related protein with a CUB (C1s-like) domain that defines a new mammalian gene family. The Scube1 (signal peptide-CUB domain-EGF-related 1) gene was isolated from a developing mouse urogenital ridge cDNA library and is expressed prominently in the developing gonad, nervous system, somites, surface ectoderm, and limb buds. We have mapped Scube1 to mouse chromosome 15 and show that it is orthologous to a human gene in the syntenic region of chromosome 22q13. We discuss the possible functions of this novel gene and its role in heritable disease in light of these data.

Amino Acid Sequence↗
PubMed2000

Sexually dimorphic expression of protease nexin-1 and vanin-1 in the developing mouse gonad prior to overt differentiation suggests a role in mammalian sexual development.

The mammalian sex-determining pathway is controlled by the presence or absence of SRY expression in the embryonic gonad. Expression of SRY in males is believed to initiate a pathway of gene expression resulting in testis development. In the absence of SRY, ovary development ensues. Several genes have now been placed in this pathway but our understanding of it is far from complete and several functional classes of protein appear to be absent. Sex-determining genes frequently exhibit sexually dimorphic patterns of expression in the developing gonad both before and after overt differentiation of the testis or ovary. In order to identify additional sex-determining or gonadal differentiation genes we have examined gene expression in the developing gonads of the mouse using cDNA microarrays constructed from a normalized urogenital ridge library. We screened for genes exhibiting sexually dimorphic patterns of expression in the gonad at 12.5 and 13.5 days post-coitum, after overt gonad differentiation, by comparing complex cDNA probes derived from male and female gonadal tissue at these stages on micro-arrays. Using in situ hybridization analysis we show here that two genes identified by this screen, protease nexin-1 (Pn-1) and vanin-1 (Vnn1), exhibit male-specific expression prior to overt gonadal differentiation and are detected in the somatic portion of the developing gonad, suggesting a possible direct link to the testis-determining pathway for both genes.

Amidohydrolases↗
PubMed1999

Groucho/transducin-like enhancer of split (TLE) family members interact with the yeast transcriptional co-repressor SSN6 and mammalian SSN6-related proteins: implications for evolutionary conservation of transcription repression mechanisms.

The yeast proteins TUP1 and SSN6 form a transcription repressor complex that is recruited to different promoters via pathway-specific DNA-binding proteins and regulates the expression of a variety of genes. TUP1 is functionally related to invertebrate and vertebrate transcriptional repressors of the Groucho/transducin-like Enhancer of split (TLE) family. The aim was to examine whether similar mechanisms underlie the transcription repression functions of TUP1 and Groucho/TLEs by determining whether TLE family members can interact with yeast SSN6 and mammalian SSN6-like proteins. It is shown in the present work that SSN6 binds to TLE1 and mediates transcriptional repression when expressed in mammalian cells. Moreover, TLE1 and TLE2 interact with two mammalian proteins related to SSN6, designated as the products of the ubiquitously transcribed tetratricopeptide-repeat genes on the Y (or X) chromosomes (UTY/X). These findings suggest that mammalian TLE and UTY/X proteins may mediate repression mechanisms similar to those performed by TUP1-SSN6 in yeast.

Basic Helix-Loop-Helix Proteins↗
PubMed1998

The mouse Y chromosome interval necessary for spermatogonial proliferation is gene dense with syntenic homology to the human AZFa region.

The Delta Sxrb deletion interval of the mouse Y chromosome contains Spy, a spermatogenesis factor gene(s) whose expression is essential for the postnatal development of the mitotic germ cells, spermatogonia. The boundaries of Delta Sxrb are defined by the duplicated genes Zfy1 and Zfy2 and four further genes have previously been mapped within the interval: Ube1y and Smcy, linked with Zfy1 on a contig of 250 kb, and Dffry and Uty, which were unanchored. The interval was estimated to be >450 kb. In order to identify any further gene(s) that may underlie Spy, systematic exon trapping was performed on an extended contig, anchored on Zfy1, which covers 750 kb of the Delta Sxrb interval. Exons from two novel genes were isolated and placed together with Dffry and Uty on the contig in the order Dffry-Dby-Uty-Tspy-Eif2gammay-Smcy- Ube1y-Zfy1. All the genes, with the double exception of Tspy, are X-Y homologous and produce putatively functional, spliced transcripts. The tight linkage and order of Dffry, Dby and Uty was shown to be conserved in deletion intervals 5C/5D of the human Y chromosome by the construction of a contig of human PAC and YAC clones; this represents the first example of syntenic homology between Y chromosomes from two distinct mammalian orders. Interval 5C/5D contains the distal boundary of the AZFa interval, which, like Delta Sxrb, is believed to be necessary for spermatogonial development in the prepubertal testis. Our results therefore show that AZFa and Spy may be encoded by homologous genes.

Animals↗
PubMed1998

The UTX gene escapes X inactivation in mice and humans.

We recently have identified a ubiquitously transcribed mouse Y chromosome gene, Uty , which encodes a tetratricopeptide repeat (TPR) protein. A peptide derived from the UTY protein confers H-Y antigenicity on male cells. Here we report the characterization of a widely transcribed X-linked homologue of Uty , called Utx , which maps to the proximal region of the mouse X chromosome and which detects a human X-linked homologue at Xp11.2. Given that Uty is ubiquitously transcribed, we assayed for Utx expression from the inactive X chromosome (Xi) in mice and found that Utx escapes X chromosome inactivation. Only Smcx and the pseudoautosomal Sts gene on the mouse X chromosome have been reported previously to escape inactivation. The human UTX gene was also found to be expressed from Xi. We discuss the significance of these data for our understanding of dosage compensation of X-Y homologous genes in humans and mice.

Amino Acid Sequence↗
PubMed1998

A novel psychophysical illusion resulting from interaction between horizontal vestibular and vertical pursuit stimulation.

HYPOTHESIS: The hypothesis was tested that the perception of an object's motion is made in relation to an internal reference center (IRC), which is under the influence of vestibular receptors. Experiments were designed to evaluate whether induced vestibular self-motion will interact linearly with the perception of a visual target (VT). BACKGROUND: The major complaint of vestibular patients is vertigo, an illusion of motion. However, there is as yet no objective method to measure this illusion, which is produced by vestibular stimulation. METHODS: Six subjects were instructed to track a vertically moving VT while sinusoidally rotating (0.2 Hz) in the yaw plane at 14, 28, and 42 degrees/s. Eye movements were monitored by electro-oculographic electrodes. RESULTS: During visual-vestibular interaction, all subjects perceived a VT moving obliquely while the eyes moved in the vertical plane. The subject then tilted the VT trajectory until vertical was perceived. At this time, the eye had an oblique vectorial trajectory. Interactive horizontal eye velocities, both vertical and horizontal components, were compared with those from rotation in the dark, showing a strong positive linear relationship (slope = 0.96, r = 0.84, n = 18). CONCLUSIONS: Results support the hypothesis of an egocentric sense of orientation whereby velocity of external objects is evaluated in relation to an IRC that is dependent on the status of the vestibular system. These methods may lead to new techniques for clinical evaluation of vestibular patients.

Adult↗
PubMed1997

Adverse events with radiographic contrast agents: results of the SCVIR Contrast Agent Registry.

PURPOSE: To determine prospectively the incidence of adverse events in angiography related to contrast agents, and the relative incidence of events with use of high-osmolality contrast agents (HOCAs) and low-osmolality contrast agents (LOCAs) and to ascertain if risk factors can help identify increased risk of an adverse event and patients likely to benefit from use of LOCAs. MATERIALS AND METHODS: From 26 high-volume institutions, data were collected on every patient who underwent angiography from July 1, 1990, to June 30, 1992. Information included demographic and risk factors, general medical status, previous administration of contrast media, procedural information, occurrence and characteristics of all adverse events up to 12 hours after procedures, and relation to contrast agents, treatment, and outcome. RESULTS: In 60,891 patients, there were 75,616 studies, 56% with nonionic LOCAs, 8% with the ionic LOCA, and 36% with HOCAs. Most major risk factors correlated with an increased incidence of adverse events related to contrast media. Incidence of these adverse events varied with type of procedure, with a higher incidence associated with cardiac and interventional procedures. Overall adverse events related to contrast media and those for which treatment was necessary were significantly increased (P < .001) with use of HOCAs for all but arterial interventional procedures. Serious adverse events were not different between the two classes of agents except for cardiac procedures. Previous reaction to contrast medium was the most important risk factor in prediction of an adverse event. CONCLUSION: The safety benefit of use of LOCAs is limited. Patients most likely to benefit are those with a previous reaction or more than one other major risk factor. Selective use of LOCAs is an appropriate strategy.

Adverse Drug Reaction Reporting Systems↗
PubMed1996

An H-YDb epitope is encoded by a novel mouse Y chromosome gene.

Rejection of male tissue grafts by genotypically identical female mice has been explained by the existence of a male-specific transplantation antigen, H-Y (ref. 1), but the molecular nature of H-Y antigen has remained obscure. Hya, the murine locus controlling H-Y expression, has been localized to delta Sxrb, a deletion interval of the short arm of the Y chromosome. In mice, H-Y antigen comprises at least four distinct epitopes, each recognized by a specific T lymphocyte clone. It has recently been shown that one of these epitopes, H-YKk, is a peptide encoded by the Y-linked Smcy gene, presented at the cell surface with the H-2Kk major histocompatibility complex (MHC) molecule. However, deletion mapping and the analysis of variable inactivation of H-Y epitopes has suggested that the Hya locus may be genetically complex. Here we describe a novel mouse Y chromosome gene which we call Uty (ubiquitously transcribed tetratricopeptide repeat gene on the Y chromosome). We identify the peptide WMHHNMDLI derived from the UTY protein as an H-Y epitope, H-YDb. Our data formally demonstrate that H-Y antigen is the product of more than one gene on the Y chromosome.

Amino Acid Sequence↗