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Biomedical subjects

N Watson

Publications and source records attributed to N Watson.

At least 19 recordsLinked to original sources
PubMed2000

17p- syndrome arising from a novel dicentric translocation in a patient with acute myeloid leukemia.

The cytogenetic contribution to the poor prognosis when myelodysplastic syndrome (MDS) progresses to acute myeloid leukemia (AML) is not well understood. We present a 66-year-old male who had thrombocytopenia with dysplastic features in peripheral blood neutrophils (hypogranular, hyposegmented neutrophils) comprising the Pelger-Huet anomaly, increased blasts in the marrow, and markers consistent with AML. Diagnostic marrow cytogenetics showed a complex karyotype including del(5q), a novel unbalanced dicentric translocation, t(17;20), resulting in both del(20q) and del(17p). Fluorescence in situ hybridization (with probe TP53) showed deletion of 17p13 on the dicentric chromosome, completing the criteria for the 17p- syndrome. Fluorescence in situ hybridization with probes for two tumor suppressor genes on chromosome 5q also showed deletion (CSF1R [at 5(q33.2-q33.4) and EGR-1 [5(q31-q32)]). Remission was difficult to achieve and cytogenetic relapse occurred 6 months postdiagnosis, and clinical relapse approximately one month later. Our case provides a novel mechanism for the 17p- syndrome, and highlights the difficulty of attributing prognostic significance to a particular cytogenetic abnormality in AML.

Aged↗
PubMed2000

The effect of mammographic screening on invasive breast cancer in Western Australia.

OBJECTIVE: To determine whether mammographic screening has affected the presentation of invasive breast cancer in Western Australia. DESIGN: Population-based reviews of the presentation of all invasive breast cancers diagnosed in Western Australia in 1989 and 1994. SETTING: Western Australia (population 1.8 million). Active recruitment of women aged 50-69 years for mammographic screening began in 1989. MAIN OUTCOME MEASURES: Size and stage of invasive breast cancers at diagnosis. RESULTS: From 1989 to 1994, the age-standardised incidence rose from 109 to 123 per 100,000 woman-years, based on 584 and 750 cases, respectively. The proportion of all invasive breast cancers detected as a result of a mammogram increased from 9.2% in 1989 to 34.5% in 1994. Among the cases where relevant information was recorded, the proportion of "impalpable" tumours increased from 7.7% in 1989 to 27.6% in 1994, and the average size of palpable tumours fell. There was an unexpected increase in the proportion of tumors that were negative on assays for oestrogen and progesterone receptors. CONCLUSIONS: A relatively simple and inexpensive clinical review has boosted confidence that the outlay of public monies required to establish and conduct screening in Australia appears likely to yield the reductions in mortality from breast cancer that would be predicted on the basis of the earlier controlled trials of mammography.

Age Distribution↗
PubMed2000

Sequencing and four-state minisatellite variant repeat mapping of the D1S7 locus (MS1) by fluorescence detection.

Minisatellite variant repeat mapping by polymerase chain reaction (MVR-PCR) reveals an enormous degree of variation in the human minisatellite regions. The original approach involved the use of 32P-labelled probes to detect the MVR-PCR products generated. To date, the loci mapped include D1S8, D7S21 and D16S309. However, the most polymorphic locus, D1S7 (MS1), which has been used in forensic analysis, has presented technical difficulties, initially due to its short 9 bp repeats that are much shorter than any conventional primer sequences. This was overcome by using the method of "wrapping around" primers employing inosine at the redundancy position. The difficulty of cloning highly repetitive DNA was overcome by utilising specialised competent SURE cells. We report the cloning and sequencing of selected short MS1 alleles to determine the variety of repeat types. This survey revealed nine types, four of which represented greater than 80% of the sequenced repeats. The reported MVR-PCR system maps the MS1 locus for these four common repeat types by fluorescence detection.

Base Sequence↗
PubMed2000

Comparison of the pharmacokinetics of crinone 8% administered vaginally versus Prometrium administered orally in postmenopausal women(3).

OBJECTIVE: Compare the pharmacokinetics of vaginal progesterone gel (Crinone 8%, 90 mg) with that of oral progesterone (Prometrium, 100 mg). DESIGN: Open-label, randomized, parallel-group protocol. SETTING: Outpatient clinic. PATIENT(S): Twelve healthy postmenopausal women. INTERVENTION(S): Six subjects each were randomized to receive progesterone, which was administered either as 90 mg of progesterone gel (Crinone 8%) given vaginally or 100 mg progesterone in a capsule (Prometrium) given orally. MAIN OUTCOME MEASUREMENT(S): Serum progesterone levels were measured by both radioimmunoassay (RIA) and liquid chromatography-mass spectrometry (LC-MS). RESULT(S): Progesterone given vaginally resulted in greater bioavailability with less relative variability in absorption than oral progesterone (mean AUC(0-24) = 1.48 +/- 0.16 ng. h/mL per milligram vs. 0.035 +/- 0.0052 ng. h/mL per milligram). Mean C(max) for oral progesterone was much lower than that of vaginal progesterone (i.e., 2.20 +/- 3. 06 ng/mL vs. 10.51 +/- 0.46 ng/mL). Mean T(max) occurred earlier for oral progesterone than for Crinone (1.00 +/- 0.41 hours vs. 7.67 +/- 3.67 hours). Radioimmunoassay is inappropriate for determining serum progesterone levels after oral administration, because it provided erroneously high values that were approximately eightfold higher than those obtained with LC-MS. CONCLUSION(S): Crinone (progesterone gel) given vaginally results in greater bioavailability with less relative variability than oral progesterone, thus providing more reliable delivery of progesterone, compared with oral progesterone. Measuring circulating progesterone with use of direct RIA is not appropriate after oral progesterone administration.

Administration, Intravaginal↗
PubMed2000

Routine HLA-B genotyping with PCR-sequence-specific oligonucleotides (PCR-SSO) detects eight new alleles: B*0807, B*0809, B*1551, B*3529, B*3532, B*4025, B*5304 and B*5508.

This paper describes eight new alleles (B*0807, B*0809, B*1551, B*3529, B*3532, B*4025, B*5304 and B*5508) that have been found by routine HLA-B genotyping with sequence-specific oligonucleotides (SSOs). All of the new alleles have variations which cause changes in residues that occur within antigen binding pockets and T-cell recognition sites of the antigen. The new polymorphisms within these new alleles may affect the nature and specificity of peptide binding and cause differential T-cell activation, which may have an affect in transplantation.

Alleles↗
PubMed2000

Serum immunoglobulin E levels predict human airway reactivity in vitro.

BACKGROUND: Airway hyperresponsiveness to non-specific stimuli is one characteristic feature of airway diseases such as bronchial asthma and chronic bronchitis. Until now, studies aiming to demonstrate a relationship between in vivo conditions associated with airway hyperreactivity and in vitro airway responsiveness have been inconclusive. OBJECTIVE: Since serum immunoglobulin (Ig) E is believed to be one determinant of airway reactivity in vivo, we studied whether in vitro airway reactivity in lung resection material from patients with elevated levels of serum IgE was increased as compared with patients with undetectable IgE. By this approach, we aimed to elucidate the role of circulating IgE for bronchial smooth muscle reactivity in vitro. METHODS: Bronchial rings from nine patients with total serum IgE levels above 200 U/mL and 10 patients with total serum IgE levels below 10 U/mL were passively sensitized, i.e. incubated overnight with buffer or sensitizing serum containing high levels of total IgE (> 250 U/mL). Afterwards, contractile responses to histamine were assessed in the organ bath. RESULTS: Histamine responsiveness was significantly increased in airways obtained from patients with IgE levels above 200 U/mL as compared with airways from patients with IgE levels below 10 U/mL (P < 0.05). Passive sensitization of bronchi from patients with low IgE significantly increased histamine responsiveness, as compared with non-sensitized controls from the same patients (P < 0.05). In contrast, passive sensitization of airways from patients with elevated IgE did not further increase responsiveness. There was no difference in histamine reactivity between non-passively sensitized and passively sensitized tissue preparations from patients with IgE above 200 U/mL and passively sensitized tissues from patients with IgE below 10 U/mL. CONCLUSION: Our findings reveal that elevated levels of serum IgE predict airway hyperresponsiveness to histamine in vitro. At the same time, they indicate that the in vitro model of passive sensitization, in addition to its ability to induce allergen responses, also mimics conditions of non-specific airway hyperreactivity, which are relevant under in vivo conditions.

Aged↗
PubMed1999

Frequency of trisomy 15 and loss of the Y chromosome in adult leukemia.

In the interpretation of the varied and complex cytogenetic counts obtained in analysis of bone marrow (BM) samples for leukemia, loss or gain of certain chromosomes may or may not be significant for prognosis. Loss of the Y chromosome in elderly males is a benign finding. Trisomy 15 is rare and may represent another age-related abnormality, particularly in males, together with -Y. We reviewed 3,242 routine referrals sent to our laboratory for BM cytogenetics, over a period of 34 months. We detected 5 cases with uncomplicated trisomy 15, 3 in males and 2 in females. Three of these patients had the diagnosis of myelodysplastic syndrome (MDS). All 3 males showed a -Y cell line, although the 2 females did not have an X chromosome loss. All 5 patients were alive and well at times varying from 12 months to 4 years post-diagnosis. In the further analysis of our referral cohort, there were 62 males with loss of the Y chromosome as the sole abnormality, and of these 47 (76%), were referred with myeloid disease. The frequency of trisomy 15 in our laboratory was 1/475 referrals, but 1/292 in successful cultures from new patients. This is the first report providing frequency data for trisomy 15. Further data with longer term follow-up is required to establish the significance of trisomy 15 in elderly leukemic patients.

Adult↗
PubMed1999

Two children with acute lymphoblastic leukemia and "jumping" translocations: both involve 1q23 as the donor breakpoint.

"Jumping" translocations (JT) are relatively rare and are associated with poor prognosis. We report two male patients with childhood acute lymphoblastic leukemia (ALL) and abnormal cell lines detected on bone marrow cytogenetics. Diagnostic marrow cytogenetics were not available for either patient. In patient 1, approximately 11 years after diagnosis, cytogenetics revealed a single translocation, t(1;2)(q23;q32), which was followed by translocations t(1;22)(q23;p11) and t(1;1)(q23;q21.3). In patient 2, two translocations were present together, t(1;6)(q23;p21.3) and t(1;11)(q23;q21), 12 years after diagnosis. The unbalanced JTs in both patients resulted in partial trisomy for (1)(q23-->qter). Both died within 1-2 years after the appearance of the JT. Our patients provide additional support for chromosome 1q preferential involvement in JTs, and that their appearance is associated with a poor prognosis.

Child, Preschool↗
PubMed1999

Novel chromosome 16 abnormality--der(16)del(16) (q13)t(16;21)(p11.2;q22)--associated with acute myeloid leukemia.

Inversion of chromosome 16 is a common feature of acute myeloid leukemia (AML) M4, while t(16;21), although also associated with AML, appears to be a separate entity. We present a patient with myelodysplastic syndrome (MDS) who transformed to AML-M1. The karyotype was normal at diagnosis; at 15 months, hematological evidence of transformation was present, and repeat cytogenetics showed a novel rearrangement of one chromosome 16. Two breaks had occurred; one in the short arm at 16p11, with translocation of the segment distal to this onto chromosome 21q, and the other in the long arm at 16q22 with subsequent deletion of the segment from 16q22-->qter. Fluorescence in situ hybridization (FISH) confirmed the abnormalities detected by cytogenetics and excluded involvement of the AML1 gene on 21q22. While the 16q22 breakpoint was at the usual site for the inv(16), the 16p11 was not. The patient is more characteristic of t(16;21) than inv(16), and adds to the spectrum of chromosome 16 abnormalities in AML.

Aged↗
PubMed1999

Identification of the major intestinal fatty acid transport protein.

While intestinal transport systems for metabolites such as carbohydrates have been well characterized, the molecular mechanisms of fatty acid (FA) transport across the apical plasmalemma of enterocytes have remained largely unclear. Here, we show that FATP4, a member of a large family of FA transport proteins (FATPs), is expressed at high levels on the apical side of mature enterocytes in the small intestine. Further, overexpression of FATP4 in 293 cells facilitates uptake of long chain FAs with the same specificity as enterocytes, while reduction of FATP4 expression in primary enterocytes by antisense oligonucleotides inhibits FA uptake by 50%. This suggests that FATP4 is the principal fatty acid transporter in enterocytes and may constitute a novel target for antiobesity therapy.

Binding, Competitive↗
PubMed1999

Comparative pharmacology of recombinant human M3 and M5 muscarinic receptors expressed in CHO-K1 cells.

1. Affinity estimates were obtained for several muscarinic antagonists against carbachol-stimulated [3H]-inositol phosphates accumulation in Chinese hamster ovary (CHO-KI) cells stably expressing either human muscarinic M3 or M5 receptor subtypes. The rationale for these studies was to generate a functional antagonist affinity profile for the M5 receptor subtype and compare this with that of the M3 receptor, in order to identify compounds which discriminate between these two subtypes. 2. The rank order of antagonist apparent affinities (pK(B)) at the muscarinic M5 receptor was atropine (8.7) > or =tolterodine (8.6) = 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, 8.6)> darifenacin (7.7) > or =zamifenacin (7.6)>oxybutynin (6.6)= para-fluorohexahydrosiladifenidol (p-F-HHSiD, 6.6)>pirenzepine (6.4) > or = methoctramine (6.3)=himbacine (6.3)>AQ-RA 741 (6.1). 3. Antagonist apparent affinities for both receptor subtypes compare well with published binding affinity estimates. No antagonist displayed greater selectivity for the muscarinic M5 subtype over the M3 subtype, but himbacine, AQ-RA 741, p-F-HHSiD, darifenacin and oxybutynin displayed between 9- and 60 fold greater selectivity for the muscarinic M3 over the M5 subtype. 4. This study highlights the similarity in pharmacological profiles of M3 and M5 receptor subtypes and identifies five antagonists that may represent useful tools for discriminating between these two subtypes. Collectively, these data show that in the absence of a high affinity M5 selective antagonist, affinity data for a large range of antagonists is critical to define operationally the M5 receptor subtype.

Animals↗
PubMed1999

Characterization of the muscarinic receptor in isolated uterus of sham operated and ovariectomized rats.

1. The pharmacological characteristics of muscarinic receptors in rat isolated uterus were studied in ovariectomized (ov.) and sham operated (sh.) animals. 2. Competition radioligand binding studies, using uterine membranes and [3H]-NMS, were undertaken with several muscarinic receptor antagonists. Most of the antagonists indicated a one-site fit with apparent affinity estimates (pKi) unchanged by ovariectomy. The selective M2 antagonist, tripitramine revealed high (representing 33+/-8 and 38+/-2%) and low (67+/-8 and 62+/-2%) affinity binding sites in both sh. and ov. rat uterus, respectively. These sites likely represented muscarinic M2 and M3 receptors and the proportions were not significantly different in the two conditions. 3. Carbachol induced concentration-dependent contractions which were surmountably antagonized by several muscarinic receptor antagonists (pKB, sh.; ov.): zamifenacin (9.19; 9.18), p-F-HHSiD (8. 50; 9.06), tripitramine (7.23; 7.54), himbacine (7.21; 7.41), methoctramine (6.79; 7.49), pirenzepine (6.48; 7.21), AF DX 116 (6. 26; 6.61), MTx 3 (<7.00; <7.00) and PD 102807 (<7.00; <7.00). 4. The apparent affinity values obtained in functional studies using the uteri from both sh. and ov. animals correlated most closely with values reported at human recombinant muscarinic M3 receptors. This suggests that the muscarinic M3 receptor mediates contraction under both conditions. 5. Radioligand binding experiments indicate the presence of M2 receptors, in addition to M3 receptors, which probably explains the discrepancies between functional and binding affinities. These data further suggest that the pharmacological profile and proportions of the two populations of muscarinic receptors are unaffected by ovariectomy.

Animals↗
PubMed1999

Media reviews

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Journal Article↗
PubMed1999

Regression of melanoma, but not keratoacanthoma, is associated with increased HLA-B22 and decreased HLA-B27 and HLA-DR1.

Sixty three Caucasian patients with either melanoma, keratoacanthoma or squamous cell carcinoma were human leucocyte antigen (HLA) typed. The regressing tumour groups were compared with their non-regressing counterparts, and the patient groups were compared with a control Caucasian population. Melanoma patients showing histological regression were more likely to be HLA-B22 positive, and HLA-B27 and -DR1 negative, than those without features of regression. When compared with a control population, the group of melanoma patients were more likely to be HLA-B22 positive. Comparison of the group of keratoacanthomas, a self-regressing tumour, and the group of squamous cell carcinomas, a non-regressing tumour, did not show any significant differences in HLA typing.

Carcinoma, Squamous Cell↗
PubMed1998

Expression of GTPase-deficient Gialpha2 results in translocation of cytoplasmic RGS4 to the plasma membrane.

The members of a recently identified protein family termed regulators of G-protein signaling (RGS) act as GTPase-activating proteins for certain Galpha subunits in vitro, but their physiological effects in cells are uncertain in the face of similar biochemical activity and overlapping patterns of tissue expression. Consistent with its activity in in vitro GTPase-activating protein assays, RGS4 interacts efficiently with endogenous proteins of the Gi and Gq subclasses of Galpha subunits but not with G12alpha or Gsalpha. Unlike other RGS proteins such as RGS9, RGS-GAIP, and Sst2p, which have been reported to be largely membrane-associated, a majority of cellular RGS4 is found as a soluble protein in the cytoplasm. However, the expression of a GTPase-deficient Gialpha subunit (Gialpha2-Q204L) resulted in the translocation of both wild type RGS4 and a non-Gialpha-binding mutant (L159F) to the plasma membrane. These data suggest that RGS4 may be recruited to the plasma membrane indirectly by G-protein activation and that multiple RGS proteins within a given cell might be differentially localized to determine a physiologic response to a G-protein-linked stimulus.

Animals↗
PubMed1998

The hemochromatosis gene product complexes with the transferrin receptor and lowers its affinity for ligand binding.

We recently reported the positional cloning of a candidate gene for hereditary hemochromatosis called HFE. The gene product, a member of the major histocompatibility complex class I-like family, was found to have a mutation, Cys-282 --> Tyr (C282Y), in 85% of patient chromosomes. This mutation eliminates the ability of HFE to associate with beta2-microglobulin (beta2m) and prevents cell-surface expression. A second mutation that has no effect on beta2m association, H63D, was found in eight out of nine patients heterozygous for the C282Y mutant. In this report, we demonstrate in cultured 293 cells overexpressing wild-type or mutant HFE proteins that both the wild-type and H63D HFE proteins form stable complexes with the transferrin receptor (TfR). The C282Y mutation nearly completely prevents the association of the mutant HFE protein with the TfR. Studies on cell-associated transferrin at 37 degrees C suggest that the overexpressed wild-type HFE protein decreases the affinity of the TfR for transferrin. The overexpressed H63D protein does not have this effect, providing the first direct evidence for a functional consequence of the H63D mutation. Addition of soluble wild-type HFE/beta2m heterodimers to cultured cells also decreased the apparent affinity of the TfR for its ligand under steady-state conditions, both in 293 cells and in HeLa cells. Furthermore, at 4 degrees C, the added soluble complex of HFE/beta2m inhibited binding of transferrin to HeLa cell TfR in a concentration-dependent manner. Scatchard plots of these data indicate that the added heterodimer substantially reduced the affinity of TfR for transferrin. These results establish a molecular link between HFE and a key protein involved in iron transport, the TfR, and raise the possibility that alterations in this regulatory mechanism may play a role in the pathogenesis of hereditary hemochromatosis.

Amino Acid Sequence↗
PubMed1998

Mechanism of RGS4, a GTPase-activating protein for G protein alpha subunits.

GTP hydrolysis by guanine nucleotide-binding proteins, an essential step in many biological processes, is stimulated by GTPase-activating proteins (GAPs). The mechanisms whereby GAPs stimulate GTP hydrolysis are unknown. We have used mutational, biochemical, and structural data to investigate how RGS4, a GAP for heterotrimeric G protein alpha subunits, stimulates GTP hydrolysis. Many of the residues of RGS4 that interact with Gi alpha 1 are important for GAP activity. Furthermore, optimal GAP activity appears to require the additive effects of interactions along the RGS4-G alpha interface. GAP-defective RGS4 mutants invariably were defective in binding G alpha subunits in their transition state; furthermore, the apparent strengths of GAP and binding defects were correlated. Thus, none of these residues of RGS4, including asparagine 128, the only residue positioned at the active site of Gi alpha 1, is required exclusively for catalyzing GTP hydrolysis. These results and structural data (Tesmer, J. G. G., Berman, D. M., Gilman, A. G., and Sprang, S. R. (1997) Cell 89, 251-261) indicate that RGS4 stimulates GTP hydrolysis primarily by stabilizing the transition state conformation of the switch regions of the G protein, favoring the transition state of the reactants. Therefore, although monomeric and heterotrimeric G proteins are related, their GAPs have evolved distinct mechanisms of action.

Amino Acid Sequence↗