PubMed Health⌕ Search

Biomedical subjects

D Mathias

Publications and source records attributed to D Mathias.

At least 19 recordsLinked to original sources
PubMed2006

Circadian rhythmicity and photoperiodism in the pitcher-plant mosquito: can the seasonal timer evolve independently of the circadian clock?

The two major rhythms of the biosphere are daily and seasonal; the two major adaptations to these rhythms are the circadian clock, mediating daily activities, and the photoperiodic timer, mediating seasonal activities. The mechanistic connection between the circadian clock and the photoperiodic timer remains unresolved. Herein, we show that the rhythmic developmental response to exotic light:dark cycles, usually used to infer a causal connection between the circadian clock and the photoperiodic timer, has evolved independently of the photoperiodic timer in the pitcher-plant mosquito Wyeomyia smithii across the climatic gradient of eastern North America from Florida to Canada and from the coastal plain to the mountains. We conclude that the photoperiodic timing of seasonal events can evolve independently of the daily circadian clock.

Animals↗
PubMed2005

Geographic and developmental variation in expression of the circadian rhythm gene, timeless, in the pitcher-plant mosquito, Wyeomyia smithii.

Expression of the circadian rhythm gene timeless was investigated in the pitcher-plant mosquito, Wyeomyia smithii (Coq.), and was found to vary with time of day, instar of diapause, and latitude of origin. The temporal pattern of timeless expression differed between the two diapausing instars and was significantly higher in southern (38-40 degrees N) than in northern (50 degrees N) populations, when diapausing instar was held constant. Expression of timeless is therefore both developmentally and evolutionarily variable. This result provides the first example of a latitudinal difference in the expression of timeless, suggesting that, along with evidence from other insects, timeless has the potential to affect photoperiodic response and its adaptive evolution in temperate seasonal environments.

Animals↗
PubMed2000

Percutaneous (Portex) tracheostomy: an audit of the Newcastle experience.

The purpose of this study was to audit the results of percutaneous tracheostomies performed by ENT surgeons in Newcastle. During a 3-year period, 298 tracheostomies: 196 percutaneous and 102 open were studied. A complication rate for percutaneous tracheostomy was found to be 10% compared to 8% for open, this difference was not statistically significant chi 2 = 0.279, P = 0.598 (DF = 1). The indications for percutaneous tracheostomy were mainly limited to respiratory support for intensive care unit patients, whereas the majority of open tracheostomies were performed in the operating theatre. The results of this audit suggest that percutaneous tracheostomy is the method of choice for respiratory support in the intensive care unit and is as safe as the open technique.

England↗
PubMed1998

Mutations in btk in patients with presumed X-linked agammaglobulinemia.

In 1993, two groups showed that X-linked agammaglobulinemia (XLA) was due to mutations in a tyrosine kinase now called Btk. Most laboratories have been able to detect mutations in Btk in 80%-90% of males with presumed XLA. The remaining patients may have mutations in Btk that are difficult to identify, or they may have defects that are phenotypically similar to XLA but genotypically different. We analyzed 101 families in which affected males were diagnosed as having XLA. Mutations in Btk were identified in 38 of 40 families with more than one affected family member and in 56 of 61 families with sporadic disease. Excluding the patients in whom the marked decrease in B cell numbers characteristic of XLA could not be confirmed by immunofluorescence studies, mutations in Btk were identified in 43 of 46 patients with presumed sporadic XLA. Two of the three remaining patients had defects in other genes required for normal B cell development, and the third patient was unlikely to have XLA, on the basis of results of extensive Btk analysis. Our techniques were unable to identify a mutation in Btk in one male with both a family history and laboratory findings suggestive of XLA. DNA samples from 41 of 49 of the mothers of males with sporadic disease and proven mutations in Btk were positive for the mutation found in their son. In the other 8 families, the mutation appeared to arise in the maternal germ line. In 20 families, haplotype analysis showed that the new mutation originated in the maternal grandfather or great-grandfather. These studies indicate that 90%-95% of males with presumed XLA have mutations in Btk. The other patients are likely to have defects in other genes.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1997

The wind of change.

Explore the source record for details and available documents.

Education, Medical, Graduate↗
PubMed1997

Serum neuron-specific enolase as early predictor of outcome after cardiac arrest.

OBJECTIVE: To examine the prognostic value of serum neuron-specific enolase for early prediction of outcome in patients at risk for anoxic encephalopathy after cardiac arrest. DESIGN: Prospective study. SETTING: Coronary intensive care unit of the University of Heidelberg. PATIENTS: Forty-three patients (66.8 +/- 12.7 [SD] yrs, range 33 to 85) who had had either primary or secondary cardiac arrest, followed by cardiopulmonary resuscitation (CPR). INTERVENTIONS: Serial blood samples and clinical examinations. MEASUREMENTS AND MAIN RESULTS: Serum neuron-specific enolase concentrations were determined after CPR on 7 consecutive days. Twenty-five patients remained comatose and subsequently died; 18 patients survived the first 3 months and had no relevant functional deficit at 3-month follow-up. Neuron-specific enolase concentrations were correlated with neurologic outcome. Concentrations of >33 ng/mL predicted persistent coma with a high specificity (100%) and a positive predictive value of 100%. Overall sensitivity was 80%, with a negative predictive value of 78%. Serum concentrations of neuron-specific enolase exceeded this cutoff value no more than 3 days after cardiac arrest in 95% of patients in whom these concentrations had exceeded 33 ng/mL. CONCLUSIONS: In patients who have been resuscitated after cardiac arrest, serum neuron-specific enolase concentrations of >33 ng/mL predict persistent coma with a high specificity. Values below this cutoff level do not necessarily indicate complete recovery, because this method has a sensitivity of 80%.

Adult↗
PubMed1994

Factors determining the long-term outcome of surgery for acromegaly.

Seventy-nine patients with acromegaly were investigated before and after transsphenoidal adenomectomy, to determine the immediate and late outcome, the pre-operative features associated with a good result, and the accuracy of post-operative testing in predicting outcome. Pre-operative evaluation included basal growth hormone (GH), GH response to oral glucose tolerance test (OGTT), GH response to thyrotrophin-releasing hormone (TRH), tests of pituitary reserve, and pituitary scanning to assess tumour size. A few weeks after surgery, these tests were repeated. The patients were recalled for late assessment 1-13 years (median 86 months) after the operation. At the immediate postoperative testing, minimum GH after oral glucose was < or = 2 mU/l in 48.7%, < 5 mU/l in 76.3% and < 10 mU/l in 84.2%. Only 12 patients had GH > 10 mU/l. Basal GH was < or = 2 mU/l in 21%, < 5 in 59.2%, < 10 in 73.6% and < 20 in 90.8%. A minimum GH of < or = 2 mU/l during an OGTT was achieved in 67.4% of patients with intrasellar tumours, compared with 27.3% with extrasellar tumours. Basal GH and post-glucose GH correlated with the late outcome. GH response to TRH showed no correlation with outcome. IGF-1, which could not be assessed in detail, correlated with GH but was not a reliable indicator of outcome. Transsphenoidal adenomectomy is thus a very satisfactory treatment for acromegaly. Postoperative levels of basal growth hormone < 5 mU/l and post-glucose GH < or = 2 mU/l can be regarded as a biochemical cure. Postoperative radiotherapy is not required in patients who achieve a good result. The preoperative factors which significantly influenced the final outcome were basal GH, post-glucose minimum GH, tumour size and impaired pituitary reserve.

Acromegaly↗
PubMed1992

[Autologous transfusion--organization and results of preoperative blood donation by heart surgery patients].

This study presents our preoperative autologous blood donation programme that is in use since 1987. 246 patients of cardiothoracic surgery participated in this program. 77% of all patients had preoperative concentrations of haemoglobin above 12g/dl despite frequent donations. 36.5% of patients were transfused exclusively with their own blood products. Reduction of homologous blood transfusion has been achieved with second preoperative plasmaphereses and more restricted indication for blood transfusion. More blood donation could be performed with application of erythropoietin resulting in more frequent preoperative blood donations.

Adult↗
PubMed1992

[Comparative study of antibody identification in the gel centrifugation test (ID Microtyping System), solid phase antiglobulin test (Solidscreen Capture R, Ready ID) and tube test].

The gel centrifugation test (ID Microtyping System)--a new method for antibody screening--was compared with solid phase systems (Solidscreen, Capture R, Ready ID) and the conventional tube test. 141 different antibodies were tested and the results were compared. The ID Microtyping System identified 138 (98%) of all antibodies, the tube test 110 (78%), Capture R 86 (61%), Ready ID 79 (56%) and Solidscreen 75 (53%). The results in identification of all antibodies except cold agglutinins (n = 107) were: in the ID Microtyping System 98% (105), tube test 76% (82), Capture R 70% (75), Ready ID 68% (73) and Solidscreen 61% (65).

Antibody Specificity↗
PubMed1990

[Transfusion-induced Yersinia infection].

After a primary operation for renal artery stenosis a 48-year-old woman had to be re-operated twice for renewed arterial stenosis and retroperitoneal bleeding. The patient's respiratory and cardiovascular functions were stable two days after the second operation and renal function was recovering. But because of suspected renewed bleeding a transfusion with erythrocyte concentrate was begun. Fifteen minutes later the patient started to shiver and this was followed by signs of cardiocirculatory decompensation under the picture of a septic-toxic shock. Laboratory tests did not indicate a haemolytic transfusion reaction. Controlled mechanical ventilation and circulatory drug support were required over the next two days, renewed anuria persisting for longer than a week. Microbiological tests of the erythrocyte concentrate demonstrated Yersinia enterocolitica, serotype 03. Questioning of the blood donor revealed a mild gastroenteritis at the time of donation. This case underlines the need of excluding donors, if only temporarily, when there is even slight suspicion of a Yersinia infection.

Blood Donors↗
PubMed1990

LH and FSH secretion and responses to GnRH and TRH in patients with clinically functionless pituitary adenomas.

Serum concentrations of LH and FSH and their response to the separate administration of GnRH (100 micrograms i.v.) and TRH (200 micrograms i.v.) have been studied preoperatively in 12 patients with a clinically functionless pituitary adenoma, of whom nine (3F: 6M) were found to secrete gonadotrophins in vitro. In three patients with a gonadotrophin-secreting adenoma (GSA) the pulsatile release of LH and FSH was also assessed preoperatively. An elevated serum FSH was recorded in six of nine patients with a GSA, and was subnormal in one, whilst an elevated LH was recorded in only two and was subnormal in six. A doubling of LH occurred in only four of the nine patients after GnRH and in three of six after TRH. None of the three patients with a non-GSA was shown to have an aberrant response to GnRH or TRH. In patients with a GSA, pulsatile release of LH and FSH was usually asynchronous and neither hormone demonstrated any regular harmonic pattern. These data show that in patients with a GSA the serum FSH level is usually elevated but this is not invariable, and the LH may well be low. Pathological responses of LH are frequently found following the administration of either GnRH or TRH and these stimulation tests should be performed separately in patients presenting with a clinically 'non-functioning' pituitary tumour to assist in the preoperative diagnosis. The absence of normal LH and FSH pulsing also appears to be a feature of GS adenomas, and suggests that tumorous gonadotrophin secretion is not under physiological control by hypothalamic GnRH.

Adenoma↗
PubMed1990

[Preoperative autologous blood donation].

This presentation shows our experiences with the preoperative autologous blood donation existing since 1987, 246 patients of the cardiothoracic surgery participated in this program. The preoperative concentration of hemoglobin was above 12g/dl 76.8% of the patients despite the frequent donations, 36.5% of the participants could be transfused with their own blood products. Further reduction of homologous blood transfusion could be achieved with a second preoperative plasmapheresis and the donation of erythropoietin.

Blood Transfusion, Autologous↗
PubMed1990

[The gel centrifugation test in serologic compatibility testing].

The gel centrifugation test is described in compatibility testing. The conventional method was modified resulting in easy handling for technical assistant. 2560 of compatibility testings were performed. 5% of more relevant antibodies could be detected compared with conventional tube test.

ABO Blood-Group System↗
PubMed1989

Immunoradiometric assay of carcinoembryonic antigen with use of avidin-biotin labeling.

In evaluating an enzyme-linked immunoassay of carcinoembryonic antigen (CEA) we found that the IgG fraction of polyclonal anti-CEA antibodies (DAKO) bound very well to the walls of polypropylene test tubes. We therefore developed an immunoradiometric CEA assay based on this binding of polyclonal anti-CEA antibody. We biotinylated a commercially available monoclonal antibody (Hybritech) and bound this to the CEA-anti-CEA bound to the tube wall. For detection we used 125I-labeled streptavidin. In comparison with several immunoassays for CEA this system offered several advantages such as greater linearity of the standard curve (from 0 to 74 micrograms/L), a steeper dose-response curve, and smaller coefficients of variation in the clinically useful range. This assay system may be used for other large molecules, so that only one tracer, the 125I-labeled streptavidin, has to be labeled; thus the technique seems suited for several different assays.

Antibodies, Monoclonal↗