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Biomedical subjects

S Adams

Publications and source records attributed to S Adams.

At least 55 records · Page 3Linked to original sources
PubMed2000

The RPM1 plant disease resistance gene facilitates a rapid and sustained increase in cytosolic calcium that is necessary for the oxidative burst and hypersensitive cell death.

Early events occurring during the hypersensitive resistance response (HR) were examined using the avrRpm1/RPM1 gene-for-gene interaction in Arabidopsis challenged by Pseudomonas syringae pv. tomato. Increases in cytosolic Ca2+ were measured in whole leaves using aequorin-mediated bioluminescence. During the HR a sustained increase in Ca2+ was observed which was dependent on the presence of both a functional RPM1 gene product and delivery of the cognate avirulence gene product AvrRpm1. The sequence-unrelated avirulence gene avrB, which also interacts with RPM1, generated a significantly later but similarly prolonged increase in cytosolic Ca2+. Accumulation of H2O2 at reaction sites, as revealed by electron microscopy, occurred within the same time frame as the changes in cytosolic Ca2+. The NADPH oxidase inhibitor diphenylene iodonium chloride did not affect the calcium signature, but did block H2O2 accumulation and the HR. By contrast, the calcium-channel blocker LaCl3 suppressed the increase in cytosolic Ca2+ as well as H2O2 accumulation and the HR, placing calcium elevation upstream of the oxidative burst.

Aequorin↗
PubMed2000

True hermaphroditism.

OBJECTIVE: True hermaphroditism is a rare cause of atypical genitalia which presents significant diagnostic and management challenges. We present the clinical and laboratory findings and management of four patients with true hermaphroditism. METHODOLOGY: Case studies from a teaching hospital and literature review. RESULTS: All four patients had atypical genitalia identified at birth. All had a palpable gonad, only one of which was palpable at birth. Three patients were 46XX (SRY -ve) and one 46XY (SRY +ve). Three patients were raised as females (two 46XX and one 46XY) and one as a male. All four patients were found to have an ovotestis present. CONCLUSIONS: The management of true hermaphroditism is controversial and requires a multidisciplinary approach. It has many implications for both the parent and child. We discuss the issues involved for the patients and their parents.

Disorders of Sex Development↗
PubMed2000

Molecular detection of thyroglobulin mRNA transcripts in peripheral blood of patients with thyroid disease by RT-PCR.

The sensitive detection of circulating tumour cells in patients with differentiated thyroid cancer may precede the detection of relapse by other diagnostic studies--such as serum thyroglobulin-and thus may have important therapeutic and prognostic implications. We performed reverse transcription-polymerase chain reaction (RT-PCR) on blood samples from patients diagnosed with thyroid disease using two different RT-PCR sensitivities. Additionally, tissue specificity of TG mRNA-expression was determined using RNA extracts from 27 different human tissues. The lower limit of detection was 50-100 TG mRNA producing cells/ml blood using a 'normal' RT-PCR sensitivity and 10-20 cells/ml blood using a 'high' sensitivity. With the normal sensitivity TG mRNA was detected in 9/13 patients with thyroid cancer and metastasis, 63/137 patients with a history of thyroid cancer and no metastasis, 21/85 with non-malignant thyroid disease and 9/50 controls. With the high sensitivity TG mRNA was detected in 11/13 patients with thyroid cancer and metastasis, 111/137 patients with a history of thyroid cancer and no metastasis, 61/85 with non-malignant thyroid disease and 41/50 controls. Interestingly, using the normal RT-PCR sensitivity TG mRNA transcripts are specific for thyroid tissue and detectable in the peripheral blood of controls and patients with thyroid disease, which correlates with a diagnosis of metastasized thyroid cancer. However, with a high RT-PCR sensitivity, TG mRNA expression was found not to be specific for thyroid tissue and was not correlated with a diagnosis of thyroid cancer in patients. As a consequence, to date TG mRNA detected by RT-PCR in the peripheral blood cannot be recommended as a tumour marker superior to TG serum-level.

Case-Control Studies↗
PubMed2000

Staging of the neck in patients with oral cavity squamous cell carcinomas: a prospective comparison of PET, ultrasound, CT and MRI.

BACKGROUND: The choice of treatment in patients with oral malignancies depends on accurate pretreatment staging and particularly the detection of lymph node involvement. Therefore staging of the neck should be as accurate as possible. PATIENTS: One hundred and six patients with histologically proven squamous cell carcinoma of the oral cavity. STUDY DESIGN: In a prospective study, PET using fluoro-desoxy-glucose (18F-FDG), ultrasound, CT and MRI of head and neck were compared with the postoperative histologic tissue evaluation. Two thousand one hundred and ninety-six neck lymph nodes of 106 patients were investigated. In all patients the tumour was resected and a lymph node dissection was performed. RESULTS: The diagnostic procedures showed the following results when compared with the histological findings: PET: sensitivity 70%, specificity 82%, accuracy 75%; Ultrasound: 84%, 68%, 76%; CT: 66%, 74%, 70%; MRI: 64%, 69% 66%. Thus PET showed the highest specificity while ultrasound had the highest sensitivity compared with the other staging procedures. A nonsignificant correlation was found between the size of a lymph node metastasis and the ability to detect it. In 10 patients, second primary tumours or distant metastases were detected by PET only. CONCLUSION: Due to the high number of small lymph node metastases from oral cavity carcinoma, the non-invasive neck staging methods are limited to a maximum accuracy of 76%. Elective neck treatment should be mandatory for all patients with squamous cell carcinoma of the oral cavity.

Adult↗
PubMed2000

Hypomethylation promotes autonomous endosperm development and rescues postfertilization lethality in fie mutants.

In most flowering plants, fertilization is necessary for development of the central cell into endosperm, but in the fie-1 mutant of Arabidopsis, the central cell can proliferate autonomously. However, autonomous fie-1 endosperms do not develop completely: They have fewer nuclei than sexually produced endosperms, cellularization does not take place, and no clear distinction is seen between the different endosperm compartments. Here, we show that autonomous endosperm develop much further in hypomethylated than normally methylated fie-1 mutants, undergoing cellularization and regional specification to resemble endosperm in sexually produced wild-type seeds. Therefore, the combination of maternal hypomethylation and loss of FIE function enables formation of differentiated endosperm without fertilization. A maternal fie-1 mutation is also lethal to sexual seeds, even if the pollen donor is wild type. We report that sexual mutant fie-1 endosperms fail to cellularize and overproliferate, consistent with the hypothesis that embryo abortion may be due, at least in part, to a defect in endosperm development. Finally, we show that pollen from hypomethylated plants rescues fie-1 mutant seeds provided that it also donates a wild-type paternal FIE allele. These results are discussed in light of models for parent-of-origin effects on seed development.

Arabidopsis↗
PubMed2000

Antral-type mucosa in the gastric incisura, body, and fundus (antralization): a link between Helicobacter pylori infection and intestinal metaplasia?

OBJECTIVES: Helicobacter pylori is a carcinogen; gastric carcinoma involves a multistep process from chronic gastritis to atrophy, intestinal metaplasia, and dysplasia. The aims of this study were to determine the types of mucosa at different gastric sites in H. pylori-infected and uninfected patients, and whether the presence of antral-type mucosa in the incisura, body, and fundus is associated with gastric atrophy and intestinal metaplasia. METHODS: Two hundred and sixty-eight patients with dyspepsia were enrolled. Eight biopsies (i.e., antrum x3, body x2, fundus x2, and incisura x1) were obtained. One antral biopsy was used for the CLO-test. Three (each from the antrum, body, and fundus) were cultured. The remaining biopsies were examined histologically according to the updated Sydney System after staining with hematoxylin and eosin and Giemsa. A validated serological test was also applied. RESULTS: Overall, 113 (42%) patients were infected with H. pylori. At the incisura, antral-type mucosa was more prevalent in infected than in uninfected patients (84% vs. 18%; odds ratio [OR] = 23.9, 95% confidence interval [CI] 12.5-45.8; p<0.001). Atrophic gastritis and intestinal metaplasia at the incisura was present in 19.5% and 13.3%, respectively, of infected, and 4.5% and 3.2%, respectively, of uninfected patients (both p<0.01). Moreover, atrophic gastritis at the incisura was associated with the presence of antral-type mucosa at the site (termed antralization); the prevalence of atrophic gastritis was 19.5% (24/123) in the presence of antralization, whereas the rate was 2.1% (3/145) without antralization (OR = 11.4, 95% CI 3.4-39.2; p<0.001). Similarly, at the incisura, 16.3% (20/123) of "antralized" cases and 1.4% (2/145) of "unantralized" cases had intestinal metaplasia (OR = 13.8, 95% CI, 3.2-60.7; p<0.001). The association between antralization at gastric body and fundus also appeared to be associated with atrophic gastritis and intestinal metaplasia at these sites. CONCLUSIONS: Atrophic gastritis and intestinal metaplasia occurs predominantly at the gastric antrum and incisura with H. pylori infection. Antralization of the gastric incisura is a common event in H. pylori-infected patients, and appears to be associated with an increased risk of atrophic gastritis and intestinal metaplasia.

Adolescent↗
PubMed2000

Genotypic heterogeneity of Streptococcus oralis and distinct aciduric subpopulations in human dental plaque.

The genotypic heterogeneity of Streptococcus oralis isolated from the oral cavity was investigated using repetitive extragenic palindromic PCR. Unrelated subjects harbored unique genotypes, with numerous genotypes being isolated from an individual. S. oralis is the predominant aciduric bacterium isolated from noncarious tooth sites. Genotypic comparison of the aciduric populations isolated at pH 5.2 with those isolated from mitis-salivarius agar (MSA) (pH 7.0) indicated that the aciduric populations were genotypically distinct in the majority of subjects (chi(2) = 13.09; P = 0.0031). Neither the aciduric nor the MSA-isolated strains were stable, with no strains isolated at baseline being isolated 4 or 12 weeks later in the majority of subjects. The basis of this instability is unknown but is similar to that reported for Streptococcus mitis. Examination of S. oralis strains isolated from cohabiting couples demonstrated that in three of five couples, genotypically identical strains were isolated from both partners and this was confirmed by using Salmonella enteritidis repetitive element PCR and enterobacterial PCR typing. These data provide further evidence of the physiological and genotypic heterogeneity of non-mutans streptococci. The demonstration of distinct aciduric populations of S. oralis implies that the role of these and other non-mutans streptococci in the caries process requires reevaluation.

Dental Plaque↗
PubMed2000

Differential binding of clonal variants of Plasmodium falciparum to allelic forms of intracellular adhesion molecule 1 determined by flow adhesion assay.

Adhesion of Plasmodium falciparum-infected erythrocytes to the endothelial ligand intercellular adhesion molecule 1 (ICAM-1) has been implicated in the pathogenesis of cerebral malaria. Recently, a high-frequency coding polymorphism in the N-terminal domain of ICAM-1 (ICAM-1(Kilifi)) that is associated with susceptibility to cerebral disease in Kenya has been described. Preliminary static adhesion assays suggested that two different selected P. falciparum lines, ITO4-A4 (A4) and ItG-ICAM (ItG), have different properties of binding to the natural variant proteins ICAM-1 and ICAM-1(Kilifi). Using a flow adhesion assay system, we have confirmed differences between the two lines in binding of parasitized erythrocytes to the variant ICAM-1 proteins. Total adhesion of ItG-infected erythrocytes to ICAM-1 and ICAM-1(Kilifi) is greater than that of A4-infected erythrocytes, and erythrocytes infected by both parasite strains show reduced binding to ICAM-1(Kilifi). However, under these physiologically relevant flow conditions, we have shown differences between A4 and ItG strains in dynamic rolling behavior on ICAM-1(Kilifi). The percentage of erythrocytes infected with A4 that roll on both ICAM-1 and ICAM-1(Kilifi) is greater than that of those infected with ItG. Also, the rolling velocity of A4-infected erythrocytes on ICAM-1(Kilifi) is markedly increased compared to that on ICAM-1, in contrast to the rolling velocity of ItG-infected erythrocytes, which is similar on both proteins. These findings suggest that different parasite lines can vary in their avidity for the same host ligand, which may have important consequences for the pathophysiology of P. falciparum malaria.

Alleles↗
PubMed2000

Parent-of-origin effects on seed development in Arabidopsis thaliana require DNA methylation.

Some genes in mammals and flowering plants are subject to parental imprinting, a process by which differential epigenetic marks are imposed on male and female gametes so that one set of alleles is silenced on chromosomes contributed by the mother while another is silenced on paternal chromosomes. Therefore, each genome contributes a different set of active alleles to the offspring, which develop abnormally if the parental genome balance is disturbed. In Arabidopsis, seeds inheriting extra maternal genomes show distinctive phenotypes such as low weight and inhibition of mitosis in the endosperm, while extra paternal genomes result in reciprocal phenotypes such as high weight and endosperm overproliferation. DNA methylation is known to be an essential component of the parental imprinting mechanism in mammals, but there is less evidence for this in plants. For the present study, seed development was examined in crosses using a transgenic Arabidopsis line with reduced DNA methylation. Crosses between hypomethylated and wild-type diploid plants produced similar seed phenotypes to crosses between plants with normal methylation but different ploidies. This is consistent with a model in which hypomethylation of one parental genome prevents silencing of alleles that would normally be active only when inherited from the other parent - thus phenocopying the effects of extra genomes. These results suggest an important role for methylation in parent-of-origin effects, and by inference parental imprinting, in plants. The phenotype of biparentally hypomethylated seeds is less extreme than the reciprocal phenotypes of uniparentally hypomethylated seeds. The observation that development is less severely affected if gametes of both sexes (rather than just one) are 'neutralized' with respect to parent-of-origin effects supports the hypothesis that parental imprinting is not necessary to regulate development.

Arabidopsis↗
PubMed2000

Intraoperative use of gamma-detecting probes to localize neuroendocrine tumors.

Neuroendocrine tumors are characterized by the expression of different peptides and biogenic amines. These rare tumors tend to grow slowly and are notoriously difficult to localize, at least in the early stages. Surgical removal is the only definitive therapeutic option for neuroendocrine tumors and relief from hyperfunctional status. The effectiveness of surgical treatment is invariably dependent upon the complete surgical excision of all tumor tissue, because microscopic and occult disease not readily seen by the surgeon may remain in situ, leading to shortened survival. Therefore, pre- and intraoperative localization of the primary as well as of metastatic tumors is of utmost importance. Radioguided surgery (RGS) is an intraoperative technique that enables the surgeon to localize radiolabelled tissue based on the characteristics of the various tissues. Concerning gastroenteropancreatic tumors (GEP), intraoperative gamma probe examination is able to reveal small tumor sites accumulating (111In-DTPA-D-Phe1)-pentetreotide more efficiently (> 90%) than somatostatin receptor scintigraphy (68%-77%), because lesions with a size smaller than 5 mm in greatest dimension could be identified. Furthermore, RGS identified 57% more lesions when compared to the "palpating finger" of the surgeon. In medullary thyroid cancer (MTC), surgical removal of the tumor is the first and most efficient treatment of the disease. Persistent or increasing serum calcitonin and carcinoembryonic antigen (CEA) levels imply tumor recurrence after thyroid ablation. For imaging recurrent MTC many radiopharmaceuticals have been used to visualize tumor sites, but none of them has shown excellent sensitivity. Preoperative somatostatin receptor scintigraphy and intraoperative RGS in patients with recurrent MTC demonstrate only part of the tumor sites and cannot visualize small tumor sites (less than 10 mm). In comparison, RGS using 99mTc(V)-DMSA detects metastases with a size of 5 mm in diameter, whereas the "palpating finger" of the surgeon localized metastases with a size of more than 1 cm in diameter. In patients with recurrent MTC, intraoperative gamma probe examination is able to localize over 30% more tumor lesions when compared with conventional preoperative imaging modalities and surgical findings. MIBG scintigraphy is the most sensitive technique for the detection and staging of neuroblastoma (sensitivity 92%; specificity nearly 100%). Intraoperative RGS with iodine labelled MIBG has been developed to improve the definition of tumor limits or to localize small, nonpalpable tumors. Comparison of 123I- and 125I-labelled MIBG revealed a sensitivity of 91% and 92%, respectively; the specificity of 125I (85%) was significantly higher than that of 123I (55%). In addition to scintigraphy of the adrenal glands by precusors of adrenal hormones, imaging with a radiolabelled somatostatin analogue is possible; however, (111In-DTPA-D-Phe1)-pentetreotide is not specific for any adrenal disease or function and the relatively high radioligand accumulation in the kidneys limited the use for detection of tumors in the area of the adrenal glands.

Endocrine Gland Neoplasms↗
PubMed1999

Comparison of the depression of H-reflexes following previous activation in upper and lower limb muscles in human subjects.

When conditioning-testing (C-T) stimuli are applied to Ia afferents to elicit H-reflexes, the test reflex is abolished immediately following the conditioning reflex. As the C-T interval is increased, the test response slowly begins to recover, taking several hundred milliseconds to attain control values. The time course of this recovery is known as the H-reflex recovery curve. H-reflex recovery curves were compared using surface EMG and single motor unit activities in lower limb soleus and upper limb flexor carpi radialis (FCR) muscles in seven healthy human subjects. Under rest conditions, the recovery of H-reflexes and single motor unit activity was slow for soleus; the recovery was not complete even in 1 s. In comparison, the recovery was very fast for FCR motor units, occurring in 200-300 ms. The effects of rate of stimulation (0.1-10.0 imp/s) were also examined on the magnitude of H-reflex responses. The reflex response declined with increasing rate of stimulation, the decline being slightly greater in soleus than in FCR. When these phenomena were examined with voluntary facilitation of the spinal cord, the time of recovery shortened and the effect of stimulus rate also diminished. Changes with background facilitation were greater in FCR than in soleus. The differences between the two muscles are attributed mainly to differences in presynaptic inhibition in the two spinal segments, and/or to the differences in dynamics of the transmitter release in terminals of Ia afferents synapsing with slow soleus motoneurons and those synapsing with the fast FCR motoneurons.

Adult↗
PubMed1999

A comparison of anaesthetic tensions in arterial blood and oxygenator exhaust gas during cardiopulmonary bypass.

This study evaluates the usefulness of the analysis of gas sampled from the exhaust port of a membrane oxygenator in the estimation of anaesthetic tension in arterial blood. Sixty-seven arterial blood samples were drawn from patients undergoing hypothermic cardiopulmonary bypass with anaesthesia maintained by either isoflurane or desflurane. Anaesthetic tensions in the oxygenator exhaust gas were measured using an infrared analyser and in arterial blood using a two-stage headspace technique with a gas chromatograph. Both measurement systems were calibrated with the same standard gas mixtures. There was no difference in anaesthetic tension measured in arterial blood and gas leaving the oxygenator exhaust (isoflurane: n = 29, range: 0.3-0.8%, 95% limits of agreement: -0.08% to 0.09%; desflurane: n = 38, range: 1.5-5.4%; 95% limits of agreement -0.65% to 0.58%). We conclude that anaesthetic tensions in arterial blood can be accurately monitored by analysis of the gas emerging from the exhaust port of a membrane oxygenator.

Anesthetics, Inhalation↗
PubMed1999

Autoimmune ovarian inflammation triggered by proinflammatory (Th1) T cells is compatible with normal ovarian function in mice.

The detection of noninfectious ovarian inflammation (oophoritis) and serum ovarian autoantibodies in a patient with premature ovarian failure is indicative of an autoimmune etiology. The mechanisms of autoimmune ovarian injury leading to loss of function are currently unknown. In this study we investigated the impact of oophoritis on ovarian function based on two murine autoimmune ovarian disease (AOD) models. AOD can be induced by thymectomy at Day 3 after birth (d3tx). D3tx mice develop ovarian inflammation and atrophy with loss of oocytes. In these mice, ovarian atrophy and not oophoritis correlated with abnormal estrous cyclicity. The second AOD model is induced by active immunization of adult mice with a murine ZP3 peptide (pZP3) in adjuvant. After active immunization, the zona pellucida antibody titer, not oophoritis, correlated with reduced fertility. To investigate the effect of oophoritis in the absence of antibody response or ovarian atrophy, pZP3-specific T cells were passively transferred into naive syngeneic mice. This recruited cytokine-producing cells into the ovaries so that elevated cytokine production and its effect on ovarian function could be examined. Recipients of pZP3-specific T cells developed severe granulomatous oophoritis, and the diseased ovaries had elevated ovarian mRNA levels of interferon-gamma, interleukin-1beta, and tumor necrosis factor alpha. Despite these changes, fertility rates and gonadotropin-induced follicular development remained essentially normal. Therefore, normal ovarian function is compatible with severe ovarian inflammation mediated by autoreactive T cells.

Animals↗