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Biomedical subjects

M L North

Publications and source records attributed to M L North.

At least 55 records · Page 3Linked to original sources
PubMed1984

[Assay of glycosylated hemoglobin by agar gel electrophoresis in an acid pH. Value of the determination of the stable fraction in clinical biology].

Total glycosylated haemoglobin (Hbg) has been determined by electrophoresis on agar gel, using commercially available materials. This method is simple and unaffected by changes of temperature or buffers pH. With a performing densitometer, its coefficient of variation is less than 4% within batch, less than 6% between batch. There is a significant correlation with the small column separation technique (r = 0,93; p less than 0,001). The labile glycosylated haemoglobin is removed by 5 methods: 18 hrs dialysis of haemolysate at 4 degrees C; 30 mn incubation of whole-blood with semi-carbazide and aniline at pH 5 and 37 degrees C; 6 hrs saline incubation of erythrocytes at 37 degrees C; 18 hrs saline incubation of erythrocytes at 25 degrees C; 7 days storage at 4 degrees C. The two first methods appear to be the best. In our study we can conclude that: 1) In basal conditions the size of the labile fraction of Hb g was close to the limits of variability of the methods (less than or equal to 10%). 2) Therefore, except for brittle diabetics, it is not necessary to determine the labile fraction routinely.

Chemical Fractionation↗
PubMed1983

[Hemoglobin A1c and its variations in pregnancy].

Variations in haemoglobin A1c were studied at different stages of pregnancy in 306 non-diabetic women, using a specific method. It was found that HbA1c levels progressively decreased during the first 25 weeks of pregnancy, then remained stable. No correlation was noted between carbohydrate metabolis and Hb A1c levels. The new assay provides additional information on glucose tolerance in pregnant women and could be used to detect gestational diabetes.

Adult↗
PubMed1983

[Assay of plasma fibronectin in clinical biology: comparison of nephelometric and turbidimetric technics].

The aim of this study was to determine the optimal conditions for the assay of plasma Fn by laser nephelometry, to compare the nephelometric and turbidimetric techniques and to confirm the influence of various parameters on the Fn concentration. The results reveal that both techniques are sensitive (threshold of sensitivity: 20 mg/l with laser nephelometry, 125 mg/l with turbidimetry), reproducible (coefficient of variation of less than 10 p. cent), specific, simple and rapid. The interpretation of the results must take into account the influence of various factors on the Fn concentration. Fn is present in lower concentrations in the serum and the percentage of serum Fn to the plasma concentration varies from one sample to another in the same patient. The optimal conditions for the assay include collection of the plasma on EDTA, storage of the samples at - 20 degrees C and incubation of the sample at 37 degrees C prior to the assay. There is a relationship between the concentration of Fn and the sex and age of the subject. There is a significant difference between the sexes between the ages of 18 and 40, which is no longer seen after the age of 50. The ability to assay plasma Fn by rapid, specific and sensitive techniques enables us to evaluate the capacity of response of the reticulo-endothelial system in conditions of severe sepsis.

Adult↗
PubMed1982

Effect of diabetic control on the level of circulating thyroid hormones.

Basal plasma levels of thyroxine (T4), triiodothyronine (T3) and reverse T3 were determined by radioimmunoassay in 44 control subjects, 44 Type 1 (insulin-dependent) and 39 Type 2 (non insulin-dependent) diabetic patients aged from 15 to 75 years. All were clinically euthyroid. The quality of diabetic control was assessed by the percentage of glycosylated haemoglobin. In both the diabetic groups there was a significant decrease in T3 and a rise in reverse T3 whereas T4 was normal. We found no significant differences between plasma thyroid hormone levels in Type 1 and Type 2 diabetic patients. In the poorly controlled diabetics (glycosylated haemoglobin greater than or equal to 12%), T3 was 90 +/- 5 ng/dl, which differed significantly from the level found in the better controlled patients (106 +/- 5 ng/dl, p less than 0.01). In the diabetic patients without associated illness, a negative linear correlation was found between T3 and glycosylated haemoglobin and a positive correlation between reverse T3/T3 and glycosylated haemoglobin. No correlation between T3 or reverse T3 and fasting blood glucose could be established. In conclusion, many diabetics showed a low T3 syndrome suggesting that there may be an impairment in the extrathyroidal conversion of T4 to T3. This may well be enhanced by a poor diabetic control (glycosylated haemoglobin greater than or equal to 12%).

Adolescent↗
PubMed1981

Effect of some physical features and of amino acid substitutions on the mechanical precipitation of hemoglobin.

In 1973 Asakura demonstrated that, following mechanical shaking, oxy-Hb S was much less stable than oxy-Hb A (Nature 244: 437, 1973). We have studied the mechanical stability of Hb Crétil (beta 89 Ser leads to Asn), Hb Hope (beta 136 Gly leads to Asp), Hb Strasbourg (beta 23 Val leads to Asp), and the hybrid Hb S/Stanleyville-II (beta 6 Glu leads to Val: alpha 78 Asn leads to Lys) by the method of Roth et al. (Blood 45:377, 1975). Hb Créteil, Hb Hope, and Hb S/St-II were sensitive to mechanical shaking, while Hb Strasbourg was more stable than Hb A, a hitherto undescribed finding. The precise mechanisms responsible for this precipitation are not known. From comparisons with published results, but excluding thermosensitive Hbs, we conclude that: - standard methods for isolation of hemoglobins modify its mechanical stability, - alpha mutation increases the mechanical stability of Hb S in the hybrid Hb S/St-II, - some mutations produce a more stable hemoglobin than Hb A.

Amino Acids↗
PubMed1981

[Hemoglobin abnormalities diagnosis in the clinical laboratory (author's transl)].

For routine detection of hemoglobin abnormalities, a number of tests are necessary including hemoglobin electrophoresis at alkaline pH, the study of hemoglobin molecular stability, possibly assay for hemoglobin A2 and hemoglobin F, as well as tests for reduced hemoglobin solubility in cases where hemoglobin S is suspected. Among the complementary techniques required for identification of abnormal hemoglobin or electrophoretically "silent" mutants, isoelectrofocalization is the method of choice and is easily set up in the clinical laboratory.

Clinical Laboratory Techniques↗
PubMed1980

[HLA antigens and responsiveness to tetanic toxoid in man].

HLA-A, B, C and Bf antigens were studied in 153 blood donors who developped a titre of greater than or equal to 25 i.u./ml antitetanus antibodies following tetanus anti-toxin vaccination. Antigen frequency was compared with that of 412-464 normal blood donors living in the same area. Few significant differences were demonstrated: absence of Bw21 antigen and slight increase of Bf F antigen were observed in "good responders".

HLA Antigens↗
PubMed1980

[Clinical and biological studies of an hybrid S/Stanleyville II hemoglobin (alpha 2 78 Asn replaced by Lys beta 2 6 Glu replaced by Val) (author's transl)].

A report of a doubly heterozygous case for both haemoglobins: Hb Stanleyville II (alpha 78 replaced by Lys) and Hb S (beta 6 Glu replaced by Val) with Hb hybrid S/St II. A 29-year-old woman from Zaïre was found to have four haemoglobins: Hb A, Hb Stanleyville II, Hb S and Hb hybrid S/St II. The clinical and hematological effects of this combination were similar to those of heterozygous sickle cell anaemia. Substitution of Lysin for Asparagin at residue alpha 78 reduced the tendency to polymerization and increased mechanical stability. These findings demonstrated involvement of this site in intermolecular interactions and explained the moderate severity of the sickle cell anaemia syndrome.

Adult↗
PubMed1979

Lack of linkage between acute intermittent porphyria and the A and B loci of the HLA system.

Forty-six members of a family known to have Porphyria were studied. As the disease is often latent clinically, erythrocyte uroporphyrinogen I synthetase activity was determined to classify the subjects as being healthy or carriers. HLA--A, B, C, Bf, GLO antigens were determined. No linkage between acute intermittent Porphyria and the HLA system was noted in this family.

Acute Disease↗
PubMed1978

G6PD Vientiane: a new glucose-6-phosphate dehydrogenase variant with increased stability.

A new G6PD variant, called G6PD Vientiane, has been discovered in a patient from Laos. The characteristics of this variant are: mild enzyme deficiency (about 50% of the normal activity) in the granulocytes and the red cells, with normal G6PD-related antigen concentration; increased stability; normal Km glucose 6-phosphate and NADP+; increased inhibition constant by NADPH; decreased inhibition by ATP; slightly increased utilization of the substrate analogue; abnormal pH curve, with maximum activity at pH 9.5; slightly reduced starch gel electrophoretic migration. The implications of the molecular stability of a deficient mutant variant are discussed.

Adult↗
PubMed1978

[Incidence of monoclonal gammopathies in blood donors].

A routine screening of monoclonal gammopathies (M.G.) was performed in the serum from 36, 015 blood donors by cellulose acetate electrophoresis. The incidence of M.G. was estimated to 0.14 per cent. About 86 per cent of cases can be classified as asymptomatic M.G. and 14 per cent as malignant M.G. (myeloma or Waldenström macroglobulinemia). In asymptomatic forms, heavy chain classes are only IgG or IgM with a large predominance of IgG (86,4%). It is suggested that donors in whom M.G. have been detected should not be allowed to give blood. A yearly clinical, hematological and an immunoglobulin check-up is recommended to these patients in order to defect the first sign of a malignant process.

Adult↗