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Biomedical subjects

M C Down

Publications and source records attributed to M C Down.

9 recordsLinked to original sources
PubMed1979

Distribution of endogenous cobalamin between the transcobalamins in various mammals.

1. Plasma samples from ten mammals were chromatographed on Sephadex G-200 columns and the total cobalamin content of each fraction was determined. 2. Unlike the situation in man, the bulk of the endogenous plasma cobalamin was found attached to a transcobalamin II-like protein in all ten animals. Transcobalamin 0 carried between 3 and 20% and this proportion appeared to be inversely related to the plasma total cobalamin. No endogenous cobalamin peak corresponding to transcobalamin I was detected in any species, though in the rabbit 5.3% of the plasma total cobalamin was attached to a protein of apparent molecular weight 176 000.

Animals↗
PubMed1979

A comparison of methods for analysing red cell and platelet volume-distribution curves.

Cell volume-distribution curves may be analysed using log-probability paper or by considering volumes corresponding to frequencies of 50 or 60% of that at the mode. All methods give similar results; the log-probability paper method is better because it allows the researcher to check that the underlying distribution is lognormal; methods based on 50 or 60% modal frequency are slightly less reliable but are simpler for routine use. For platelets it may be convenient to estimate the curve from the modal volume and the volume above the mode at which the frequency is reduced to 60% of the modal frequency.

Animals↗
PubMed1976

The transport of endogenous vitamin B12 in normal human serum.

1. Serum from normal subjects has been chromatographed on Sephadex G-200 columns and the fractions containing transcobalamins 0, I and II have been identified. 2. The fractions corresponding to transcobalamin I contained, on average, 90% of the endogenous vitamin B12. Only 3% was attached to transcobalamin 0, and 7% was bound to transcobalamin II.

Adult↗
PubMed1976

Measurement of the mean cell volume using electronic particle counters.

Under carefully controlled conditions electronic cell counters, for example the Coulter Counter, Model FN, and Channelyzer, may be calibrated to give MCV values down to as small as 20 fl which agree with those derived from the centrifugation PCV (corrected for plasma trapping) and the red cell count. The MCV values will be too high if the instrument uses a high cell concentration, has a fixed lower threshold, no effective upper threshold and no edit facility. This may partly explain why the Coulter Counter, Model S, when standardized with 4C cell control gives higher MCV values than the Model FN linked to the Channelyzer. The difference is, on average, 2 fl with normal blood samples and 5 fl in cases of microcytic anaemia. It is suggested that standards of low MCV should be used together with those of normal MCV when calibrating the Model S.

Animals↗
PubMed1976

Microcytosis, anisocytosis and the red cell indices in iron deficiency.

Red cell volume distribution curves have been used to measure microcytosis and anisocytosis in normal subjects, blood donors and patients with iron deficiency anaemia. These measurements were more sensitive than the conventional red cell indices for detecting blood donors with a low transferrin saturation. Three stages are suggested as iron deficiency progressively interferes with haemopoietic function. Anisocytosis and an increased percentage of microcytic cells are the first haematological abnormalities to occur and at this stage haemoglobin concentration is usually normal and trasferrin saturation less than 32%. At the second stage the MCV and MCH decline, haemoglobin concentration is generally sub-normal, though not below 9 g/dl, and transferrin saturation is usually below 16%. The final stage of iron deficiency is associated with a low MCHC, a haemoglobin concentration below 9 g/dl and a transferrin saturation of less than 16%.

Anemia, Hypochromic↗
PubMed1975

Simple method for automating the differential leucocyte-count.

A simple method is described for analysing leucocyte-volume distribution curves to obtain a differential leucocyte-count. The results derived by this method agree well with the differential counts obtained by microscopical examination of the stained blood-film.

Automation↗
PubMed1975

Determination of the packed cell volume using 131I-human serum albumin.

When trace quantities of labelled albumin have been added to blood, the packed cell volume (PCV) may be determined by isotope counting using the relationship: (plasma counts-blood counts)/(plasma counts). This method for measuring the PCV is not affected by plasma trapping between the red cells and the results do not depend upon the centrifugation conditions. The PCV determination with labelled albumin has a high precision (coefficient of variation = 0.9%) and there is very good agreement with the centrifugation PCV using Wintrobe tubes after this measurement has been corrected for plasma trapped between the red cells. No significant compression of the red cells occurred when the blood samples were centrifugated in Wintrobe PCV tubes.

Centrifugation↗
PubMed1975

Role of transcobalamins I, II, and III in the transfer of vitamin B12 to human bone marrow cells in vitro.

A study of the uptake of transcobalamin-bound 57Co-cyanocobalamin by suspensions of human bone marrow cells has indicated that these cells can take up vitamin B12 from all 3 transcobalamins (I, II, and III). Similar transport processes were involved in the uptake from the 3 transcobalamins; uptake was dependent on the presence of calcium ions, cellular respiration and free sulphydryl groups. These results suggest that contrary to current belief, all 3 transcobalamins play a role in the transfer of vitamin B12 to tissue cells.

Biological Transport↗