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Biomedical subjects

A L Robertson

Publications and source records attributed to A L Robertson.

At least 37 records · Page 2Linked to original sources
PubMed1985

The effect of extreme acid and alkali changes upon the echogenicity of blood.

The degree of red cell aggregation is dependent upon multiple conditions. The purpose of these experiments was to ultrasonically determine the threshold and reversibility of human red cell aggregation to extreme pH changes at varying shear rates. Real-time B- and A-mode ultrasonography were used to measure echogenicity. Measurements were recorded at original, acidic, and alkaline pH and following return of both acidic and alkaline pH to neutral pH levels. The results showed that 1) neutral red cell suspensions did not become echogenic at any shear rate; 2) acidification produced a shear-related, partly reversible echogenicity; and 3) alkalinization caused a less intense but more shear-resistant and less reversible echogenicity. Alkalinization produced a microscopically discernible greater persistence of intense red cell aggregation. Cell membrane protein loss was detected by electrophoresis.

Adult↗
PubMed1985

Growth potential of human uterine leiomyomas: some in vitro observations and their implications.

Tissue culture techniques commonly applied to the study of human vascular smooth muscle were used to evaluate in vitro survival and proliferation of normal and neoplastic human myometrial cells. Despite their growth advantage in vivo, leiomyoma cells displayed a growth disadvantage in vitro compared with normal myometrium from the same patient. Hormonal supplementation with alpha-estradiol, progesterone, and insulin-stimulated myometrial proliferation, whereas beta-estradiol appeared ineffective at the doses tested. Hormonal supplementation also stimulated leiomyoma proliferation in vitro, but there appeared to be heterogeneity in hormonal responsiveness. Heterogeneity in the host hormonal milieu and in the ability of uterine leiomyomas to respond to various hormones may be important factors contributing to the wide variation in growth potential observed in leiomyomas.

Adult↗
PubMed1984

Role of red cells in preventing the growth of platelet aggregation.

Using high-resolution real-time two-dimensional ultrasound, we have investigated the role of red cells in the growth of already established platelet aggregates under controlled flow conditions. Platelet rich plasma (PRP) was circulated in vitro in horizontally and vertically arranged tubing at mean shear rate ranging from 60 to 0 sec-1, and adenosine diphosphate (ADP) was used to induce platelet aggregation. ADP-induced platelet aggregates grew in size and tended to sediment as shear rate decreased, in particular, below 10 sec-1. At 0 sec-1 (stasis), large clusters of platelet aggregates formed. The addition of washed red cells to produce a hematocrit of only 2% significantly interfered with the growth and sedimentation of platelet aggregates as shear rate was reduced. Formaldehyde-hardened erythrocytes had a similar effect in preventing the growth of platelet aggregates, suggesting that mechanical collision of red cells with platelet aggregates may be the cause of growth inhibition. Therefore, the thrombotic process may be enhanced in red cell poor zones in circulation resulting from flow disturbances associated with vascular stenosis or within artificial organs and extracorporeal systems. The present study also suggested that red cell free PRP should be carefully administered therapeutically.

Adenosine Diphosphate↗
PubMed1984

Ultrasonic detection of platelet aggregation at variable shear rates.

We have observed that high-resolution ultrasonic imaging can be used to detect and measure the size and sedimentation of large human platelet aggregates formed in vitro. At progressively lower shear rates, individual platelet aggregates grew in cross-sectional area from the limit of ultrasonic detectability of less than 1 mm2 at moderate shear rates to an approximate mean area of 25 mm2 at zero shear. Platelet aggregates tended to sediment at mean shear rates higher than zero shear. At a shear rate of 5.5 s-1, 70% of platelet aggregates had settled, and at 1.6 s-1, 90% had settled to the dependent half of horizontal tubes in less than 15 s. Ultrasonic aggregometry of platelets may be a valuable technique for investigation of platelet dynamics under controlled flow conditions in vitro.

Adult↗
PubMed1984

Bovine aortic endothelial cells elaborate an inhibitor of the generation of lipopolysaccharide-stimulated human blood monocyte procoagulant activity.

We examined the effect of bovine aortic endothelial cell culture supernatants upon the generation of procoagulant activity by human blood monocytes. Confluent endothelial monolayers were cultured for up to 96 h. At timed intervals, culture supernatants were collected and incubated for 5 h with lipopolysaccharide-stimulated human peripheral blood mononuclear cells. The procoagulant activity of mononuclear cell lysates was determined in a one-stage clotting assay. In five experiments, procoagulant activity with culture supernatant (time 0) was 2,294 +/- 761 U/ml (mean +/- SEM). Culture supernatants from endothelial cells incubated for 24-96 h strongly inhibited mononuclear cell generation of procoagulant activity. Indomethacin (10 microM) added to endothelial cells delayed the appearance of procoagulant inhibitor for 72 h. Bovine aortic smooth muscle cell culture supernatants did not inhibit procoagulant activity. The inhibitor was heat stable, effective at 1:50 dilution, soluble, and acid sensitive, with a molecular weight of less than 1,500. Further studies on subpopulations of mononuclear cells demonstrated that endothelial inhibitor selectively decreased the generation of monocyte procoagulant activity and interfered with T lymphocyte amplification of monocyte production of procoagulant activity. Thus, we have demonstrated that endothelial cells elaborate a potent inhibitor of monocyte procoagulant activity.

Animals↗
PubMed1981

Platelet adherence to collagen: role of plasma, ADP, and divalent cations.

The effect of varying methods of platelet preparation and the role of ADP and divalent cations in supporting platelet adherence to collagen and the release of 14C-serotonin were assessed by affinity chromatography on collagen/Sepharose to define physiological conditions for this interaction. Platelets were separated by centrifugation or gel filtration from blood anticoagulated with EDTA or citrate and suspended in native plasma or buffer. After labelling with 51Cr or 14C-serotonin, they were passed though columns of collagen covalently linked to cyanogen bromide-activated Sepharose. Adherence to collagen was less in plasma as compared to buffer, was increased by centrifuging the platelets before testing, and was unaltered by addition of ADP. Removal of ADP with CP/CPK decreased the adherence of gel-filtered citrated and EDTA platelets and washed EDTA platelets (P less than 0.001) but not EDTA platelets in plasma. Adherence and release of citrated platelets in plasma or buffer containing CP/CPK were greater than that of EDTA platelets (P less than 0.01); no difference existed with gel-filtered platelets. The addition of 1 mM Mg++ to citrate or EDTA-anticoagulated washed platelets increased adherence and release (P less than 0.01). The results indicate that the choice of experimental conditions affect the assessment of factors which influence or promote platelet interaction with collagen. Platelet-collagen adherence is enhanced by laboratory manipulations and partially inhibited by normal plasma. Maximal adherence and release occur when divalent cations, particularly Mg++, and ADP are available. Their absence reduces but does not inhibit these reactions.

Adenosine Diphosphate↗
PubMed1979

LDL-induced cytotoxicity and its inhibition by HDL in human vascular smooth muscle and endothelial cells in culture.

Human aortic medial smooth muscle cells (SMC) and umbilical vein endothelial cells (EC) in culture were exposed to various concentrations of plasma low density (LDL) and high density (HDL) lipoproteins prepared from normolipemic donors in order to assess their effects on cell growth. So that the effects of each lipoprotein could be evaluated separately and in combination, lipoproteins were added to culture medium containing lipoprotein deficient serum (LPDS, d greater than 1.25 g/ml at a protein concentration of 4.5 mg/ml of medium). The addition of LDL at cholesterol concentrations of 160 microgram/ml of culture medium, resulted in significant reductions in both the number of SMC and EC cells per dish within 3 days of exposure (P less than 0.001, SMC; P less than 0.01, EC), when compared with LPDS controls and the starting cell numbers. This cytotoxic phenomenon was dose-related, and only at LDL cholesterol concentrations equal to or below 50 microgram/ml were no marked changes observed. In contrast, HDL at all concentrations tested produced no such deleterious effects. Autoradiographic assessment of DNA synthesis confirmed these findings. After 48 h of continuous exposure to tritiated thymidine, labeling indexes reached much lower plateaus in the LDL-treated groups.

Aorta, Thoracic↗
PubMed1979

Migration of human vascular endothelial and smooth muscle cells.

Migration of endothelial and smooth muscle cells was studied in vitro by measuring the increase in surface area at specific time intervals of confluent cell colonies advancing under agarose gels that contained both Morgan's medium 199 and variuos types of sera. First passage cultures of endothelial cells or 3 to 6 passage smooth muscle cells were plated into wells punched in agarose gels, at a seeding density of 50,000 cells per well. At zero time the size of the cell colonies was 35.4 sq. mm. +/- standard error 0.1. Irradiation (1500 rads) did not affect the expansion of the cell colonies although 3H-thymidine uptake was inhibited. Endothelial cells migrated under the agarose gels concentrically as contiguous sheets. When exposed to either 20 per cent platelet-poor plasma serum, platelet-rich plasma serum, or whole blood serum, the average increase in surface area was approximately 9 sq. mm. per day. In contrast, arterial smooth muscle cell colonies expanded with an increment of approximately 9 sq. mm. per day when exposed to 10 per cent platelet-poor plasma serum but 12 sq. mm. per day when exposed to 10 per cent platelet-rich plasma serum (p less than 0.001). Platelet factors also had stimulatory effects on the migration of venous smooth muscle cells. Cytochalasin B, dibutyryl cyclic AMP, and theophylline inhibited the migration of both endothelial and smooth muscle cells, but the latter responded more to the inhibitory effects of all three agents. It is concluded that in contrast to vascular smooth muscle, endothelial cells do not require platelet factors for migration and are less responsive to specific inhibitors affecting cell movement.

Blood Platelets↗
PubMed1978

Platelet factors and the human vascular wall: variations in growth response between endothelial and medial smooth muscle cells.

In the present investigations, the effects of platelet factors on DNA-synthesis by human arterial and venous smooth muscle and venous endothelial cells were compared. Also studied was the role of such factors in restimulating quiescent endothelial cultures and in endothelial reaction to injury. Aortic smooth muscle cells grown in medium containing 10% human serum prepared from plasma poor in platelets (PPPS) reached 9.7%+/-SE 0.65 labelling index when continuously exposed to [3H] thymidine (1 muCi/ml). When lysate from gel-filtered platelets was added, the index was 19.4% +/- SE 1.13 (P less than 0.01) and in the presence of serum derived from platelet rich plasma (PRPS) it reached 24.6% +/- SE 1.22 (P less than 0.01). Similar results were obtained with smooth muscle cells from umbilical veins. In constrast, platelet factors did not significantly affect DNA-synthesis in endothelial cultures. They reached 25.6% +/- SE 1.97 when grown in medium containing PPPS as compared to 21.9% +/- Se 2.53 (P greater than 0.05), when exposed to PRPS. The ability of sera to stimulate DNA-synthesis in endothelial cultures rendered quiescent by 24 h exposure to medium containing 1.4% serum albumin (labelling index 1.83% +/- SE 0.14) was not affected by platelet factors. Platelet lysates alone were not sufficient to restimulate the quiescent cells (labelling index 3.03% +/- SE 1.06) (P greater than 0.05). Platelet factors did not affect the proliferative response following experimental mechanical injury to endothelial monolayers in vitro. We conclude that while platelet factors are essential for human vascular smooth muscle cells to achieve optimal growth, they are not indispensable for endothelial cell proliferation. It is suggested that these cellular differences in growth requirements may play an important role in human atherogenesis.

Aorta↗
PubMed1978

Platelet factors and the human vascular wall. Part 2. Such factors are not required for endothelial cell proliferation and migration.

The effects of platelet factors on human umbilical venous endothelial cell DNA-synthesis at various serum concentrations were studied. While [3H]thymidine uptake of these cells was almost linearly related to the concentration of serum in the culture medium, no significant differences were found at any serum level between cultures treated with sera derived from either platelet-rich or platelet-poor plasma. The role of platelet factors in cellular migration into standardized mechanical "wounds" was also investigated following inhibition of the proliferative response by irradiation of endothelial monolayers. Repopulation of such "wounds" was not affected by platelet factors. We conclude that endothelial cells proliferate and migrate in vitro independently of platelet factors.

Blood Coagulation Factors↗
PubMed1978

Plane xanthoma and multiple myeloma with lipoprotein--paraprotein complexing.

Clinicopathologic findings are reported of a woman with generalized plane xanthoma, multiple myeloma (IgG type K), and hyperlipemia with very high levels of serum cholesterol and triglyceride. Complexing of the serum lipoproteins and immunoglobulins had cryoglobulin properties and was separable by ultracentrifugation. Immunofluorescent studies of skin and bone marrow demonstrated deposits of IgG with low density lipoprotein apoprotein and IgG with beta-lipoprotein, respectively. Although immunosuppressive therapy resulted in return of serum IgG, lipid, and lipoprotein levels to normal, the patient died from the myeloma. Serum lipoprotein-paraprotein complexes have been demonstrated in at least 20 other cases of cutaneous xanthomatosis and myeloma. This interaction may result in an autoimmune hyperlipemia.

Adult↗
PubMed1977

MASSFORM: a computer program for the assignment of elemental compositions to high resolution mass spectral data.

This paper describes a computer program which calculates all possible empirical formulas for each accurately measured mass in a high resolution mass spectrum. The program, MASSFORM, incorporates a novel mechanism for classifying the empirical formulas generated according to their empirical formula. This mechanism makes it possible to use a set of general empirical formulas to aid in the analysis of complex mixtures in much less time than most other such programs. The program is being used as an important aid to environmental studies.

Chemical Phenomena↗