Search PubMed⌕ Search

Biomedical subjects

D Samson

Publications and source records attributed to D Samson.

At least 109 records · Page 6Linked to original sources
PubMed1985

Antithrombin III "Northwick Park": a variant antithrombin with normal affinity for heparin but reduced heparin cofactor activity.

Further studies have been carried out in a previously reported family with congenital antithrombin III (AT III) deficiency due to an abnormal variant of AT III (AT III Northwick Park). The variant has been identified in five members of the family, three of whom had a history of venous thrombosis. Inheritance followed an autosomal dominant pattern. The affected family members have reduced levels of antithrombin heparin cofactor (41-67%) and progressive antithrombin activity (44-62%) but normal levels of immunoreactive AT III (91-162%). Two dimensional immunoelectrophoresis (2 DIE) of AT III in the absence of heparin revealed an abnormal fast-moving peak in addition to the normal peak but 2 DIE in the presence of heparin appeared normal. Further studies confirmed that the abnormal AT III binds completely to heparin but has no heparin cofactor or progressive antithrombin activity. These results would be consistent with a mutation affecting the binding site for thrombin.

Adolescent↗
PubMed1985

The effects of ethanol and anticonvulsants on erythroid delta-aminolaevulinic acid synthase.

The activity of delta-aminolaevulinic acid (ALA) synthase was measured in bone marrow from 13 control subjects, 12 chronic alcoholic patients and 9 patients on long term anticonvulsant therapy. The majority of patients in both groups had macrocytic red cells in the absence of megaloblastic changes in the marrow. There was a significant increase in ALA synthase activity in the alcoholic patients but no significant increase in enzyme activity in the patients on anticonvulsants and overall there was no correlation of activity with MCV. The macrocytosis associated with these drugs does not therefore appear to result from accelerated erythroid haem synthesis.

5-Aminolevulinate Synthetase↗
PubMed1985

Arteriovenous malformations of the cerebellar vermis.

Fifteen cerebellar vermian arteriovenous malformations were surgically treated over a 7-year period. Intracranial hemorrhage was the presenting symptom in 73% of the cases and recurrent bleeding episodes occurred in 60%. Computed tomographic scans demonstrated the site of the malformation in 80% and documented the presence of intracerebral bleeding in all posthemorrhage patients. Angiography revealed two consistent patterns of arterial supply depending on the involvement by the malformation of the superior inferior cerebellar vermis. All lesions were surgically removed via a midline suboccipital posterior fossa microsurgical approach. Intraventricular extension of arteriovenous malformation was common, often in association with the choroid plexus of the 4th ventricle. Immediate postoperative angiography was used to document arteriovenous malformation removal. Three instances of unsuspected residual malformation were documented and required reexploration. The total operative mortality was 7%, and the neurological morbidity was 21%.

Cerebellum↗
PubMed1984

Management of planned pregnancy in a patient with congenital antithrombin III deficiency.

Long-term warfarin therapy was changed to subcutaneous heparin to cover a planned pregnancy in a patient with congenital antithrombin III (AT III) deficiency. Satisfactory anticoagulation was easily maintained in spite of low levels of biologically active AT III. Delivery and the puerperium were covered by a reduced dose of heparin and alternate day infusions of AT III concentrate. A mean dose of 0.77 U/kg of AT III concentrate produced a rise of 1% in AT III and the half-life was of the order of 24 h, with no evidence of increased consumption during labour and delivery. Pregnancy and labour were uncomplicated and resulted in delivery of a healthy female infant. The importance of early and adequate anticoagulation during pregnancy is emphasized.

Adult↗
PubMed1983

A fluorimetric method for the measurement of pyridoxal and pyridoxal phosphate in human plasma and leucocytes, and its application to patients with sideroblastic marrows.

A highly sensitive fluorimetric assay for the measurement of pyridoxal and pyridoxal phosphate in biological tissues is described. The method involves the enzymic hydrolysis of pyridoxal phosphate to pyridoxal. The pyridoxal (free or total) is separated on an anion-exchange column, concentrated by cation-exchange chromatography and reacted with potassium cyanide under slightly alkaline conditions to form 4-pyridoxolactone, a highly fluorescent compound. The method is applied to the measurement of pyridoxal, pyridoxal phosphate and total pyridoxal in plasma and neutrophils from control subjects and patients with sideroblastic marrow and identified the patient with pyridoxine-responsive sideroblastic anaemia.

Anemia, Sideroblastic↗
PubMed1983

Fractionation of whole body irradiation before bone marrow transplantation for patients with leukaemia.

Thirty patients in various stages of acute leukaemia or chronic granulocytic leukaemia (CGL) were treated with cytotoxic drugs followed by whole body irradiation (TBI) administered in 200 cGy fractions twice daily to a total of 1000 or 1200 cGy. The immediate toxicity of fractionated TBI administered in this way was negligible and patients required only minor premedication and little treatment subsequently for complications attributable to TBI. Fourteen (47%) patients have died, ten of the 12 transplanted with active disease, and four of the 18 subjected to transplantation in remission of acute leukaemia or in chronic phase of CGL. Though the duration of follow-up is still short, no patient in the latter group (follow-up of survivors ranging from six to 146 weeks) has yet relapsed with any evidence of recurrent leukaemia. We conclude that this method of fractionating TBI reduced toxicity for the patient without necessarily reducing its antileukaemic effect.

Acute Disease↗
PubMed1982

In-vitro studies of ineffective erythropoiesis in rheumatoid arthritis.

Ineffective erythropoiesis was assessed in a series of 32 patients with rheumatoid arthritis by means of a new in-vitro method which measures the release of haem from a labelled cohort of erythroblasts in culture. Haem release was significantly increased in patients with the anaemia of chronic disorders but was normal in those who were not anaemic or who had an iron-deficiency anaemia. In 2 patients with anaemia of chronic disorders haem release returned to normal after successful antirheumatic therapy. The increased ineffective erythropoiesis in patients with rheumatoid arthritis and anaemia of chronic disorders appeared to be unrelated to functional iron deficiency and was not attributable to a serum factor.

Adolescent↗
PubMed1982

Furosemide in the intraoperative reduction of intracranial pressure in the patient with subarachnoid hemorrhage.

The effect of furosemide in the intraoperative reduction of intracranial pressure was measured in 25 patients undergoing the operative repair of a ruptured intracranial aneurysm. Seven patients with similar intracranial lesions served as controls. A single bolus of 80 mg of furosemide was administered intravenously after the induction of anesthesia, and sequential measurements were made of intracranial pressure, mean arterial pressure, and arterial blood gases. A mean decrease of intracranial pressure of 56% was measured in the furosemide-treated patients, whereas the control patients demonstrated a mean decline of subarachnoid pressures of 18%. These changes are significant at the P less than 0.005 confidence level, whereas changes in mean arterial pressure, mean arterial pCO2, and base line arterial pCO2 were statistically insignificant. This study suggests that intravenous furosemide is a quick, dependable, and effective mechanism for the intraoperative reduction of intracranial pressure in the postsubarachnoid hemorrhage aneurysm patient.

Adult↗
PubMed1982

[Current methods of vascular exploration: Doppler, thermography, capillaroscopy].

According to a national study, the currently available vascular investigations give fragmentary information. Ultrasound velocimetry is usually normal, but sometimes, it reveals, early in the course of the disease, an original finding, diastolic flow. Thermography demonstrates thermic gradients in phase I, hyper- or iso-thermia in phase II and hypothermia in phase III. Capillaroscopy can demonstrate pericapillary edema, venulo-capillary stasis and tortuosities which are non-specific criteria, only significant by their associations. This study needs to be pursued in order to define the course of these vasomotor changes.

Angiography↗
PubMed1981

Determination of delta-aminolaevulinic acid synthase activity in human bone marrow using high performance liquid chromatography.

A high performance liquid chromatographic (HPLC) method is described for the rapid and specific determination of the activity of the enzyme delta-aminolaevulinic acid synthase (ALA-S) in mitochondria prepared by sonication of human bone marrow cells. After incubation with 14C-alpha-ketoglutarate the 14C-delta-aminolaevulinic acid (ALA) formed is converted to a pyrrole derivative, 2-methyl-3-carbethoxy-4-(3-propionic acid) pyrrole. This is isolated by reversed-phase ion-pair chromatography on a Hypersil-SAS column with methanol-water (45:155, v/v) in the presence of 0.005 mol/l 1-heptanesulphonic acid (PIC B-7) as the mobile phase. The radioactivity of the isolated pyrrole is determined by scintillation counting. The optimal substrate concentration and pH were 0.17 mmol/l alpha-ketoglutarate and pH 7.4, with an optimal period of sonication of 18s. Under these conditions ALA production was proportional to the concentrations of erythroblasts in the initial sample and was linear with time up to 60 min. The addition of pyridoxal phosphate (PLP) did not affect ALA-S activity in normal subjects. The mean ALA-S activity in 10 haematologically normal control subjects was found to be 318.8 pmol.10-6 erythroblasts.h-1 (S.D. 125.8, range 193-444.6).

5-Aminolevulinate Synthetase↗
PubMed1981

Neurosurgical applications of the cyanoacrylate adhesives.

The cyanoacrylate adhesives are a biologically heterogenous group, some of which are potentially valuable additions to the neurosurgical armamentarium. The commercially available cyanoacrylates usually contain the more toxic methyl and ethyl monomers. The safe butyl monomer, isobutyl 2-cyanoacrylate, is approved in the United States by the Food and Drug Administration for investigational use only. Isobutyl 2-cyanoacrylate may prove to be useful for the extravascular reinforcement of intracranial aneurysms and for the intravascular occlusion of carotid-cavernous fistulae. Safe and effective alternatives exist for the management of these two problems. The sealing of certain cerebrospinal fluid fistulae and the intravascular occlusion of certain arteriovenous malformations may be more effectively accomplished with isobutyl 2-cyanoacrylate than with other currently available techniques. The ultimate role of this and of other as yet untested cyanoacrylates in neurosurgery remains to be determined.

Animals↗