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N Young

Publications and source records attributed to N Young.

At least 55 records · Page 3Linked to original sources
PubMed1997

Use of spiral and non-spiral computed tomography arterial portography in the detection of potentially malignant liver masses.

The present study assesses the usefulness of computed tomography (CT) arterial portography (CTAP) in detecting and defining the number and anatomy of potentially malignant liver lesions. One hundred and one adults studied in 1993 and 1994 were retrospectively reviewed, including patients with primary or secondary tumours for possible resection and patients with non-hepatic malignancies in whom the detection of liver metastases would preclude surgery. Twenty-three patients underwent non-spiral CT studies and 78 had studies on a spiral unit, with 22 of these having single phase and 56 having dual phase studies to overcome artefact problems. The relationship between lesion size and detection sensitivity is critical. On non-spiral studies, the overall lesion detection sensitivity and positive predictive value was 69 and 90%, respectively. Detection sensitivity was 100 and 20% for lesions > 1 cm and < 1 cm, respectively. On single phase spiral CTAP the overall detection sensitivity and positive predictive value was 80 and 66%, respectively. Detection sensitivity for lesions > 1 cm and < 1 cm was 100 and 0%, respectively. On dual phase spiral CTAP the overall detection sensitivity and positive predictive value was 76 and 71%, respectively. For lesions > 1 cm and < 1 cm the sensitivity was 81 and 55%, respectively. Eighteen patients with non-hepatic malignancies with unsuspected metastatic spread did not proceed to major surgery because of liver metastases detected on CTAP. Perfusion artefacts occurred in 30 and 64% of non-spiral and of initial portal venous spiral CTAP studies, respectively. By using the double-phase technique, these artefacts were substantially diminished. In conclusion, CTAP is a valuable tool for assessing the presence, site and size of possible liver tumours and confers a benefit even when previous ultrasound and conventional CT have already been used. In addition, CTAP has a lower limit of useful resolution of approximately 1 cm. Perfusion artefacts can be reduced by a dual phase protocol.

Adult↗
PubMed1997

Detection of genetically diverse human immunodeficiency virus type 1 group M and O isolates by PCR.

A panel of 136 genetically diverse group M and 5 group O adult isolates from outside the United States and Europe were evaluated by PCR with the Roche AMPLICOR HIV-1 test, a modified version of the AMPLICOR HIV-1 test, and a new primer pair/probe system. Detection of some of these isolates was less efficient with the AMPLICOR HIV-1 test; however, the assay was significantly improved by reducing the sample input and lowering the annealing temperature. The new primer pair/probe set detected 140 of 141 isolates, including the 5 group O isolates that were not detected with either of the AMPLICOR HIV-1 test formats.

Adult↗
PubMed1996

Does weight-bearing exercise protect against the effects of exercise-induced oligomenorrhea on bone density?

Does weight-bearing exercise offset bone loss associated with oligomenorrhea? If so, bone mineral density (BMD) will be stable at weight bearing sites but decrease at non-weight-bearing sites with increasing duration of oligomenorrhea. To test this hypothesis, BMD (g/cm2), was measured by dual-energy X-ray absorptiometry in 41 oligomenorrheic ballet dancers aged 17.7 +/- 0.2 years (mean +/- SEM) and 46 age-matched controls with normal menstrual function. BMD correlated negatively with the duration of oligomenorrhea at weight-bearing and non-weight-bearing sites (femoral neck, r = -0.33, p < 0.05; Ward's triangle, r = -0.29, p = 0.06; trochanter, r = -0.33, p < 0.05; lumber spine, r = -0.25, p = 0.1; skull, r = -0.29, p = 0.06; arms, r = -0.32, p < 0.05; ribs, r = -0.30, p = 0.06). The slopes of the regression of BMD on duration of oligomenorrhea were greater at the proximal femur (trochanter, -0.28 +/- 0.13, femoral neck, -0.24 +/- 0.11; Ward's triangle, -0.29 +/- 0.15) than the skull (-0.15 +/- 0.08, p < 0.05, p < 0.1, p < 0.1 respectively). The slopes at the trochanter and femoral neck were also greater than at the ribs (-0.10 +/- 0.05; both p < 0.1). In the dancers with oligomenorrhea of less than 40 months duration, BMD was higher than the age-predicted mean at weight-bearing sites (except the lumber spine), but not at non-weight-bearing sites (femoral neck, 9.1 +/- 3.4%; Ward's triangle, 10.0 +/- 1.7%; trochanter, 9.4 +/- 4.1%, all p < 0.05; lumbar spine, -2.1 +/- 2.7%, NS; skull, -2.5 +/- 2.1%, NS; ribs, -3.0 +/- 1.6% NS; arms, -3.9 +/- 1.6%; p < 0.05). In the dancers with greater than 40 months oligomenorrhea, BMD was no higher than the age predicted mean, at the weight bearing sites, and was lower at non-weight bearing sites (femoral neck, 4.3 +/- 2.3%, NS; Ward's triangle, 3.5 +/- 3.2%, NS; trochanter, 2.1 +/- 2.7%, NS; lumbar spine, -3.8 +/- 2.1%, NS; arms, -7.5 +/- 0.8%, p < 0.05; skull, -6.2 +/- 1.8%, p < 0.01; ribs, -5.4 +/- 1.1%, p < 0.0001). In conclusion, weight-bearing exercise is unlikely to offset the deleterious effects of oligomenorrhea. Bone loss appears to occur at all sites but may begin from a higher level at weight-bearing sites and may proceed more rapidly.

Absorptiometry, Photon↗
PubMed1996

Genome duplication in soybean (Glycine subgenus soja).

Restriction fragment length polymorphism mapping data from nine populations (Glycine max x G. soja and G. max x G. max) of the Glycine subgenus soja genome led to the identification of many duplicated segments of the genome. Linkage groups contained up to 33 markers that were duplicated on other linkage groups. The size of homoeologous regions ranged from 1.5 to 106.4 cM, with an average size of 45.3 cM. We observed segments in the soybean genome that were present in as many as six copies with an average of 2.55 duplications per segment. The presence of nested duplications suggests that at least one of the original genomes may have undergone an additional round of tetraploidization. Tetraploidization, along with large internal duplications, accounts for the highly duplicated nature of the genome of the subgenus. Quantitative trait loci for seed protein and oil showed correspondence across homoeologous regions, suggesting that the genes or gene families contributing to seed composition have retained similar functions throughout the evolution of the chromosomes.

Chromosome Mapping↗
PubMed1996

Imaging of orbital floor fractures.

The aim of this study was to compare the efficacy of plain films and computed tomography (CT) in defining inferior orbital fractures and any muscle involvement. Forty-four patients with final diagnosis of orbital floor fractures in the period 1990-94 were retrospectively studied. Computed tomography was performed in 28 patients, 20 being direct coronal acquisitions and eight being fine axial acquisitions with coronal reconstructions. Water's view radiographs were performed in 34 patients. Fourteen fractures on plain films were associated with soft tissue opacities to suggest inferior rectus (IR) muscle involvement, but only two required surgical elevation of the orbital floor. The remaining patients were successfully treated conservatively. Three patients had IR entrapment on direct coronal CT, all requiring surgical elevation of the orbital floor. Seven patients had IR muscle displacement on direct coronal CT and all had conservative management. In four patients with axial acquisition and coronal reconstructions, the CT images were of inadequate quality to determine the presence or absence of a fracture. One patient who had no IR muscle involvement identified on reconstructed coronal CT required surgical elevation of the orbital floor on clinical grounds. We conclude that: (i) soft tissue opacities on plain films are not an accurate indicator of clinically significant IR involvement; (ii) axial CT is not efficacious in detection of fractures or IR involvement; and (iii) direct coronal CT is the most efficacious imaging modality.

Adolescent↗
PubMed1996

A review of the radiological features of intracranial meningiomas.

To evaluate the role of radiological imaging of meningiomas in confirming the diagnosis and as a neuroanatomical aid to surgical planning, 115 patients with surgically excised meningiomas between 1990 and 1993 were studied. Computed tomography (CT), magnetic resonance imaging (MRI) (on a 0.5 T unit) and angiography were reviewed, and compared with histopathology (when available). Seventy-eight CT, 89 MRI and 85 angiographic studies were reviewed, and correlated with histopathology in 67 cases. In 48 cases, the surgical specimens could not be pathologically classified. The most common lesion sites were the cerebral convexities, falx and sphenoidal ridges. True demarcation of cleavage planes was seen on 73% of MRI and 10% of CT studies. Computed tomography showed hyperostosis in 27% and MRI in 7% of studies. Tumours enhanced strongly with contrast in 98% of CT scans. On MRI there were variable signal intensities on different sequences, and no correlation between signal intensities and histological subtype was found. Oedema was present in 59% of CT and 66% of MRI studies, and was most pronounced in lesions > 3 cm in diameter. Tumour calcification was seen in 62% of CT and 8% of MRI studies. Vascular abnormalities were seen on 65% of MRI, 21% of CT and 84% of angiogram studies. Angiographic tumour vascularity did not correlate with histologic subtype. All three imaging modalities have management roles: CT for bony changes and calcification, MRI for multiplanar and vessel anatomy imaging, and angiography for vessel delineation and embolization if required.

Aged↗
PubMed1996

Requirement for genes with homology to ABC transport systems for attachment and virulence of Agrobacterium tumefaciens.

Transposon mutants of Agrobacterium tumefaciens which were avirulent and unable to attach to plant cells were isolated and described previously. A clone from a library of Agrobacterium tumefaciens DNA which was able to complement these chromosomal att mutants was identified. Tn3HoHo1 insertions in this clone were made and used to replace the wild-type genes in the bacterial chromosome by marker exchange. The resulting mutants were avirulent and showed either no or very much reduced attachment to carrot suspension culture cells. We sequenced a 10-kb region of this clone and found a putative operon containing nine open reading frames (ORFs) (attA1A2BCDEFGH). The second and third ORFs (attA2 and attB) showed homology to genes encoding the membrane-spanning proteins (potB and potH; potC and potI) of periplasmic binding protein-dependent (ABC) transport systems from gram-negative bacteria. The homology was strongest to proteins involved in the transport of spermidine and putrescine. The first and fifth ORFs (attA1 and attE) showed homology to the genes encoding ATP-binding proteins of these systems including potA, potG, and cysT from Escherichia coli; occP from A. tumefaciens; cysA from Synechococcus spp.; and ORF-C from an operon involved in the attachment of Campylobacte jejuni. The ability of mutants in these att genes to bind to host cells was restored by addition of conditioned medium during incubation of the bacteria with host cells.

ATP-Binding Cassette Transporters↗
PubMed1996

Chemodectoma of the trachea.

The case history is described of a patient with lower tracheal chemodectoma who presented with haemoptysis. After conservative management for eight years she represented with airways obstruction. Preoperative tumour embolisation was followed by laser ablation, stenting, and radiotherapy.

Aged↗
PubMed1996

The control of trichome spacing and number in Arabidopsis.

Arabidopsis trichomes are single-celled epidermal hairs that serve as a useful model for the study of plant cell differentiation. An examination of the distribution of trichomes early in their development revealed that developing trichomes occur adjacent to another trichome much less frequently than would be expected by chance. Clonal analysis of epidermal cell lineages ruled out a role for cell lineage in generating the observed minimum-distance spacing pattern. Taken together, these results are consistent with a role for lateral inhibition in the control of trichome development. We also report the identification of a new locus, Reduced Trichome Number (RTN), which affects the initiation of trichomes. This locus was initially detected by the reduced number of leaf trichomes on Landsberg erecta plants compared to that on Columbia plants. Quantitative Trait Locus mapping revealed that more than 73% of the variation in trichome number was due to a major locus near erecta on chromosome 2. The reduced number of trichomes conditioned by the Landsberg erecta allele of this locus appeared to be due to an early cessation of trichome initiation. The implications of these observations are discussed with regard to previously published models of trichome development.

Arabidopsis↗
PubMed1996

Major histocompatibility complex class II and complement polymorphisms in postpartum thyroiditis.

The objective was to re-evaluate the association between class II HLA-DR and DQ MIIC antigens and postpartum thyroiditis (PPT) and to determine the prevalence of the class III complement allotypes of Properdin factor B (Bf), C4A and C4B in this condition. Two hundred and sixty-five (of 2897) pregnant women screened positive for thyroid autoantibody activity took part. Further blood samples were obtained for HLA class II (185) and complement (193) typing. The severity of the ensuing PPT was assessed by measuring thyroid function during the postpartum year. The HLA-DR and DQ phenotypes were assigned from restriction fragment length polymorphism analysis, and Bf, C4A and C4B allotypes were determined by immunofixation with anti-Bf or anti-C4 antibodies after electrophoresis. A weak association between the HLA class II antigens and PPT, as indicated by a reduced frequency of DR15 and DQ6 together with an increased frequency of-DR5 and DQ7, was confirmed. However, only the change in DR5 frequency remained significant after correction (corrected p < 0.05). Postpartum thyroiditis was also associated with frequency disturbances in BI and C4A allotypes but not C4B allotypes. Whilst this study has not provided evidence of a strong marker gene for PPT, it does not preclude the involvement of the MIIC in this condition. These data show disturbances in complement allotype frequencies, suggesting that the class III region may provide a useful focus for further study of this pathology.

Complement C4a↗
PubMed1995

Cloning and characterization of the mouse PIG-A gene.

Currently there is no experimental animal model for studying paroxysmal nocturnal hemoglobinuria (PNH), an acquired hemolytic anemia linked to mutations of the PIG-A gene. In this study, we cloned and characterized the mouse PIG-A gene. Sequencing of mouse PIG-A cDNA showed that it encodes a 485 amino acid-long protein. Northern hybridizations identified a major mRNA transcript of 3.6 kb and PCR amplifications identified four smaller alternative splice products. Exon:intron junctional analyses of the mouse PIG-A genome showed 6 exons (1(> or = 60 bp), 2(780 bp), 3(133 bp) 4(133 bp), 5(207 bp), and 6(2276 bp)), the latter 5 of which encompass the coding region. Chromosomal mapping using C57BL/6J x M. Spretus backcross DNA localized the mouse PIG-A gene near the telomeric end of the mouse X chromosome. The isolation of the mouse PIG-A gene opens the possibility for the development of a mouse model of PNH.

Amino Acid Sequence↗
PubMed1995

The evolving molecular epidemiology of HIV-1 envelope subtypes in injecting drug users in Bangkok, Thailand: implications for HIV vaccine trials.

OBJECTIVE: To genetically characterize HIV-1 strains in injecting drug users (IDU) in Bangkok, Thailand in 1994, and compare these with strains found earlier in Thai IDU; such information is essential for HIV-1 vaccine development and evaluation. METHODS: Peripheral blood mononuclear cells were collected from 84 IDU attending 14 drug treatment clinics in Bangkok in 1994. DNA was amplified using a nested polymerase chain reaction (PCR) procedure and sequenced directly (without cloning) from the PCR products. The V3 and flanking regions (345 nucleotides) of the env gene were analyzed using a neighbor-joining tree. RESULTS: Only one (1%) strain was a typical subtype B virus, 69 (82%) were genetically distinct subtype B' viruses (Thai B), and 14 (17%) were subtype E strains (Thai A). Persons with recently acquired infection were more likely to have subtype E viruses (P < 0.001) than those in our 1991 survey, who were more likely to have subtype B' viruses. Pairwise intra-subtype differences within subtypes E and B' were 5.3 and 4.3%, respectively, compared with 3.4 and 3.5% among strains collected in 1991 in Thailand. CONCLUSION: The genetic diversity within subtypes B' and E in Thailand and the proportion of new infections due to subtype E viruses among Bangkok IDU are increasing significantly. These data highlight the importance of monitoring the molecular epidemiology of HIV-1 in populations being considered for HIV-1 vaccine trials.

AIDS Vaccines↗
PubMed1995

Clinical follow-up of patients with percutaneously inserted inferior vena caval filters.

This is a retrospective clinical follow-up study of 45 consecutive patients who had percutaneous placement of inferior venal caval (IVC) filters in the period 1987 to 1993 to prevent mortality, or severe morbidity, from pulmonary embolism (PE). Ten patients had Gunther filters (GF) and 35 had bird's nest filters (BNF) from 1989. Clinical indications for filter placement were: 23 patients with anticoagulation contraindications, six with anticoagulation failure and recurrent PE, 10 with anticoagulation complications, two with critical PE and four with leg thrombi and PE. Two patients died from recurrent PE after filter placement, one with a GF migrating after replacement, and one with a BNF. Two patients died from severe PE, occurring prior to filter placement. Fifteen patients died in the study period, none due to recurrent PE. Twenty-five patients remain alive, with a mean follow-up period of 21 months, with none having recurring PE. One patient was lost to clinical follow-up. One patient suffered technical difficulty in BNF placement, and underwent surgical removal of a hook penetrating an iliac vein wall. Inferior vena cava filters are efficacious in preventing potentially fatal pulmonary embolism, in both the acute period and the medium term. There are low rates of morbidity associated with their use.

Adult↗
PubMed1995

Documentation of blood culture results.

AIMS: To evaluate the adequacy of documentation of blood culture results in patients' medical notes. METHODS: A pro-forma was completed following review of medical notes at 24 and 48 hours after a blood culture had been reported as positive. The study was performed on blood cultures received at the Department of Microbiology, Royal Hallamshire Hospital, Sheffield, from two local hospitals. Two periods were studied: (A) May to June 1993 and (B) September to October 1993. RESULTS: There were 43 results studied in period A and 79 in period B, giving a total of 122 results studied. Overall, 72 (59%) of 122 results were recorded in the medical notes at 24 hours. Of those results deemed highly significant, 40 (63%) of 63 were recorded. There was no significant difference in the documentation of results if the result was given personally or via the telephone. Nor was there any difference in documentation between different medical grades. Throughout the study there were six inaccurate records. The cumulative documentation over 48 hours of positive results was 54 (86%) of 63 of highly significant, 27 (69%) of 39 of uncertain significance, and 11 (55%) of 20 probable contaminant results. CONCLUSIONS: Documentation of blood culture results is currently suboptimal.

Blood↗
PubMed1995

Early experience with spiral CT in the diagnosis of intracranial aneurysms.

We report experience with 16 patients undergoing spiral CT Scans for the evaluation of cerebral aneurysms. There were 10 females and six males, aged between 36 and 73 years. The three-dimensional scanning was useful in five situations: (i) Suspicion of aneurysm on conventional scan. An aneurysm was found in one of four patients and later confirmed by angiography, and two showed arterial ectasia with no saccular aneurysm; the fourth again appeared to have an aneurysm, but this was not shown on angiography. (ii) Follow-up of previously detected aneurysms not planned for surgery. This has been done in three patients, the spiral CT findings correlating well with previous angiography. (iii) Follow-up of aneurysm remnants after surgery (three cases); findings correlate well with previous angiography, and clips cause no artefact problems. (iv) Detection of ruptured aneurysms. In two cases, small aneurysms were found that had been missed on angiography, and in a third, with doubtful angiographic findings, spiral CT was useful. (v) Investigation of patients with past treated aneurysms, or of relatives. Three subjects have been screened so far for that purpose; in one a small aneurysm has been found, and confirmed angiographically.

Adult↗