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Biomedical subjects

M McGill

Publications and source records attributed to M McGill.

At least 55 records · Page 3Linked to original sources
PubMed1982

Biochemical and ultrastructural alterations in platelets, reticulocytes, and lymphocytes from rats fed vitamin E-deficient diets.

Effects of vitamin E-deficiency, dietary fat (corn oil versus lard), and incubation on ultrastructure of platelets, red and white cells, and on selected biochemical parameters of platelets and plasma were studied. Platelets from vitamin E-deficient rats had no obvious morphological defects, but reticulocytes and lymphocytes had swollen and deformed mitochondria. Fatty acid and glycogen levels of platelets were not affected by the deficiency but total lipid levels in plasma were decreased of increased depending upon the type and level of dietary fat. In comparison with supplemented controls, the proportion of stearate increased in the phospholipid fraction of plasma from vitamin E-deficient, lard-fed but not corn oil-fed rats. In platelets, total fatty acids per mg protein were 8-12% lower with lard than with corn oil as fat source. Oleate and linoleate were higher and lower, respectively, although not to the same degree, and arachidonate was not affected. With incubation of platelet-rich plasma at 37 degrees C for 6 hr, there were no obvious morphological changes in platelets from control or from deficient, lard-fed rats, but platelets from deficient, corn oil-fed rats contained mitochondria that were swollen and deformed. Incubation did not affect fatty acid, glycogen, or tocopherol levels of platelets or tocopherol levels of plasma, regardless of type or amount of dietary fat.

Animals↗
PubMed1982

The use of a perfusion model for studying aggregation and attachment of platelets and tumor cells at subendothelial surfaces.

The Baumgartner perfusion apparatus has been applied to the study of the interaction of platelets and tumor cells and their attachment to subendothelial structures. Cells derived from an anaplastic murine tumor (Hut 20 line) induced platelet aggregation and were included in platelet thrombi that deposited on vascular subendothelium in perfusion experiments with heparinized human blood. In contrast, perfusion of blood samples containing cells from a line derived from a human epithelial carcinoma of the lung (A549 line), which did not interact with platelets, resulted in the deposition of platelets alone, with no tumor cells or blood cells other than platelets being observed in the thrombus. Extremely large platelet-tumor cell thrombi were found at the vascular surface in Hut 20 perfusions using vessel segments which had been treated with alpha-chymotrypsin. These large heterogeneous thrombi perturbed blood flow through the system and entrapped both erythrocytes and white cells. In order to quantitate the deposition of tumor cells, Hut 20 cells were labeled with 125I-deoxyuridine and perfused in whole blood at a concentration of 3.7x10(5)/ml. Tumor cell incorporation into platelet-tumor cell thrombi on chymotrypsinized segments yielded about 30,000 cpm/mg of vascular tissue but this value was reduced some 2 orders of magnitude by the inclusion of PGE1 (1 ng/ml of perfusing blood; 2.8 microM) in parallel samples. Aspirin at 100 microM reduced tumor cell-dependent platelet aggregation but did not decrease the platelet-dependent deposition of radiolabeled Hut 20 cells on vascular subendothelium, suggesting the release reaction may not be of major significance in this interaction. Tumor cell-induced platelet aggregation was not observed in a perfusion experiment using blood from a patient with severe von Willebrand's disease. However addition of 0.1 vol of ABO-compatible, heterologous plasma as a source of factor VIII to the von Willebrand blood sample restored the platelet-dependent deposition of radiolabeled tumor cells to control values.

Animals↗
PubMed1981

Functional and morphological studies of platelet reactivity with vessel wall subendothelium in chronic myeloproliferative disease.

Mechanisms of thrombus formation in myeloproliferative disease were studied using a technique which visualized platelet-vessel wall interactions under physiological conditions of blood flow. Whole blood from four patients with chronic myelogenous leukaemia and three with thrombocythaemia were pumped through perfusion chambers containing de-endothelialized artery segments. Platelet reactivity with vessel walls (thrombus formation) was measured in sections of vessels by light microscopy and quantitative morphometric analysis. Five patients produced platelet reactivity values of 130--258% of controls while two gave decreased values. The two highest platelet reactivity values occurred in samples with elevated platelet counts and normal haematocrits. In contrast, when anti-platelet drugs were administered to three patients with high platelet counts, reactivity values decreased to 11--34% of controls. Clinical correlations revealed that patients with highest platelet reactivity values (165--258%) were those subjects who also exhibited thrombotic or haemorrhagic complications. Thus absolute platelet count and haematocrit may be major determinants in predicting these complications. Qualitative evaluations of thrombus formations by light and electron microscopy provide further evidence that platelets in myeloproliferative disease also possess qualitative abnormalities.

Adult↗
PubMed1980

Inhibition of mitochondrial-specific protein symthesis in human lymphocytes and platelets is dependent upon the stage of cellular differentiation.

Small lymphocytes differentiate into functionally active blast cells in vitro upon stimulation with such mitogens as phytohemagglutinin and sodium periodate. If stimulated lymphocytes are subsequently treated with the nucleic acid intercalating dye ethidium bromide, electron-dense complexes containing nucleic acid are formed in mitochondria, protein synthesis in mitochondria is inhibited, and lymphoblast division ceases. Formation of complexes and the development of morphologically abnormal mitochondria provide ultrastructural evidence of mitochondrial protein inhibition and serve as markers for mitogen-responsive lymphocytes. The formation of these abnormalities in all mitochondria of treated megakaryocytes and 22% of mitochondria in platelets indicates that platelets contain functional nucleic acid and that the induced structural changes may be occurring in a less-differentiated (i.e., younger) subpopulation of circulating platelets.

Blood Platelets↗
PubMed1979

Effects of storage on platelet reactivity to arterial subendothelium during blood flow.

The usual in vitro methods for studies of platelets after storage do not measure physiological parameters such as capability for interaction with vessel wall subendothelium during blood flow conditions. For studies reported here we adapted a technique described by Baumgartner (Microvasc Res 5:167, 1973) to quantitate platelet interactions with subendothelium during blood flow and before and after storage at 4 degrees and 22 degrees and by a modified 4 degrees procedure called temperature cycling. The results indicated that platelets kept at 22 degrees for 72 hr interacted with subendothelium in quantities which were less than 10% that of fresh controls. However, storage at 4 degrees and by temperature cycling produced interactions equal to 71% and 42% of controls, respectively. The data also indicated that utilization of Baumgartner's technigue as described here will (1) provide an in vitro technique for identification of qualitative defects responsible for the delayed hemostatic effectiveness of 22 degrees-stored platelets and (2) permit an objective and quantitative analysis of prospective improvements in storage before in vivo function testing is necessary.

Animals↗
PubMed1978

Platelet storage by temperature cycling.

The following summarizes our observations on in vitro viability and function and ultrastructure of platelets stored at 4 degrees, 22 degrees, and by temperature cycling: 1) Continuous 4 degrees storage for 24 hours resulted in irreversible loss of discoid shape and eliminated platelet capability for microtubule reassembly. 2) Abnormal in vitro platelet function (aggregation) and significant decreases in viability (recovery from hypotonic shock) occurred concomitantly with losses in microtubule reassembly capabilities. 3) Platelets demonstrating a capability for microtubule reassembly during 4 degrees storage (temperature cycled) produced normal aggregation responses and gave enhanced viability scores. 4) Platelets stored by temperature cycling for 96 hours produced viability scores equal to those produced after storage at 4 degrees for 24 hours or those kept at 22 degrees for 72 hours.

Blood Platelets↗
PubMed1978

Temperature cycling preserves platelet shape and enhances in vitro test scores during storage at 4 degrees.

Platelets stored at 4 degrees develop morphological changes which precede decreases in in vitro aggregation and recovery from hypotonic shock. Platelets maintained at 4 degrees for 60 min lack microtubules and lose their discoid shape as a result of the formation of pseudopodia. Exposure to continuous cold for 24 hr causes irreversible platelet shape changes and induces spontaneous aggregation. Quantitative electron microscopic analysis of platelet microtubules showed that platelets lost their ability to reassemble microtubules after 24 hr of continuous storage at 4 degrees. However, interruption of continuous cold storage with short, repeated pulses of 37 degrees (temperature cycling) extended microtubule reassembly capabilities for 72 hr and maintained platelet shape change capabilities. A comparison of platelets stored continuously at 4 degrees with those stored by temperature cycling showed that temperature-cycled platelets possessed improved aggregation responses and significantly improved recoveries from hypotonic shock. These data indicate that 37 degrees reactivation pulses during cold storage provide platelets with markedly improved morphology and in vitro test scores and suggest that temperature cycling may be used to extend blood bank storage of platelets.

Blood Platelets↗
PubMed1976

In vivo and in vitro phosphoarylation of nuclear proteins in rat liver.

The incorporation of 32P into nuclear nonhistone proteins was compared in rat liver in vivo, in liver slices incubated in vitro, and in isolated nuclei incubated with gamma-[32P]ATP. The highest specific activities of nuclear phosphorproteins were obtained by incubating isolated nuclei. However, the Radioactivity profiles of polyacrylamide gel electrophoretograms of these proteins differed from those obtained in vivo or in liver slice experiments. A group of low molecular weight nonhistone proteins exhibited a very high incporation of labelled phosphate. These proteins could be obtained from the interface when the phosphoproteins were isolated by the buffered phenol extraction procedure. Phosphorylated proteins were also obtained from three cytoplasmic fractions (mitochondria, microsomes, and cytosol). The specific activities of these proteins were much lower than of the nuclear phosphoproteins.

Animals↗
PubMed1976

Abnormal ultrastructural changes in sodium periodate-stimulated lymphocytes from patients with chronic lymphocytic leukemia.

Lymphocytoid and plasmacytoid blasts have been identified in both normal and chronic lymphocytic leukemia lymphocyte cultures exposed to NaIO4. However, the appearance of ultrastructurally abnormal blasts in chronic lymphocytic leukemia cultures suggests that NaIO4 also stimulates the transformation of an abnormal subpopulation of lymphocytes. Development of invaginated nuclei produced morphological features similar to nuclear blebs, a cellular abnormally described in blood cells from other cancers. Furthermore, the consistent localization of nuclear invagination only to portions of nuclei adjacent to developing cytoplasmic microtublar complexes suggests a role for microtubules in the transformation process. The absence of these unusual blasts in cultures stimulated with other mitogens may indicate that these NaIO4-sensitive cells are not responsive to the more commonly used plant lectins.

Cell Nucleus↗
PubMed1975

Actinomycin D effects on mitosis and chromosomes: sticky chromatids and localized lesions.

When Indian muntjac and Chinese hamster cells in culture were treated with Actinomycin D (1 micron/ml) for 1-2 hours, the sister chromatids, especially the distal segments, appeared to have difficulty separating in anaphase. The separated proximal segments progressively became stretched. The nucleolus organizer regions seemed to be most susceptible to stretching, and breaks in these regions were frequently observed. Electron microscopic observations showed that the sticky chromatids (and less frequently sticky chromosomes) contain connecting submicroscopic chromosome strands. When the treated cells were allowed to grow in a drug-free medium for several days, a high frequency of endoreduplicated mitotic figures was found. Chromosome and chromatid breaks and other aberrations were common, mainly localized at G band negative areas particularly nucleolus organizer regions.

Adhesiveness↗
PubMed1975

Human chromosomes and centrioles as nucleating sites for the in vitro assembly of microtubules from bovine brain tubulin.

Treatment of HeLa cells with Colcemid at concentrations of 0.06-0.10 mug/ml leads to irreversible arrest in mitosis. Colcemid-arrested cells contained few microtubules, and many kinetochores and centrioles were free of microtubule association. When these cells were exposed to microtubule reassembly buffer containing Triton X-100 and bovine brain tubulin at 37 degrees C, numerous microtubules were reassembled at all kinetochores of metaphase chromosomes and in association with centriole pairs. When bovine brain tubulin was eliminated from the reassembly system, microtubules failed to assemble at these sites. Similarly, when EGTA was eliminated from the reassembly system, microtubules failed to polymerize. These results are consistent with other investigations of in vitro microtubule assembly and indicate that HeLa chromosomes and centrioles can serve as nucleating sites for the assembly of microtubules from brain tubulin. Both chromosomes and centrioles became displaced from their C-metaphase configurations during tubulin reassembly, indicating that their movements were a direct result of microtubule formation. Although both kinetochore- and centriole-associated microtubules were assembled and movement occurred, we did not observe direct extension of microtubules from kinetochores to centrioles. This system should prove useful for experimental studies of spindle microtubule formation and chromosome movement in mammalian cells.

Animals↗