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Biomedical subjects

M Richardson

Publications and source records attributed to M Richardson.

At least 325 records · Page 18Linked to original sources
PubMed1989

Deendothelialization in vivo initiates a thrombogenic reaction at the rabbit aorta surface. Correlation of uptake of fibrinogen and antithrombin III with thrombin generation by the exposed subendothelium.

Purified radiolabeled fibrinogen and antithrombin III (ATIII) were injected intravenously into rabbits before a deendothelializing injury to the aorta, and allowed to circulate for 0.1 to 6 hours before exsanguination, excision of the aorta, and quantification of each protein/unit area of subendothelium (intima-media). Uptake of fibrinogen was rapid (saturation 10 minutes after injury was approximately 13.0 pmol/cm2) compared with that of ATIII (45 to 60 minutes; 3.5 to 4.3 pmol/cm2). Both proteins associated primarily (greater than 90%) with the subendothelium rather than the platelet monolayer. The avidity of the deendothelialized vessel of these proteins was measured after a 20-minute circulation time at various intervals after injury. Whereas turnover of fibrinogen was fairly constant (approximately 100% per hour), that of ATIII was maximal (approximately 200% per hour) at 1 hour, decreasing to approximately 105% per hour at 5 hours after injury. The profile of ATIII turnover mirrored that of thrombin released in vitro from the deendothelialized aorta up to 10 days after injury, whereas the uninjured aorta and the aorta deendothelialized ex vivo adsorbed fibrinogen poorly and released negligible thrombin. Pretreatment of the aorta, deendothelialized ex vivo with thrombin in vitro increased fibrinogen uptake significantly. It is possible that, after deendothelialization in vivo, fibrinogen adsorption is determined largely by thrombin generation at the vessel wall. ATIII binding is limited by the availability of binding sites in the subendothelium, although the rate of thrombin generation influences ATIII turnover.

Animals↗
PubMed1989

The in vitro interactions between serum lipoproteins and proteoglycans of the neointima of rabbit aorta after a single balloon catheter injury.

The effect of injury-induced alterations in the aortic neointimal proteoglycans on their binding with homologous serum lipoproteins was examined. Proteoglycans of the aortic intimal-medial tissues of rabbits that had undergone denudation with a balloon catheter 12 weeks earlier were isolated after homogenization of the tissues in 0.33 M sucrose, ultracentrifugation and subsequently by gel-exclusion chromatography. Lipoproteins from the plasma of healthy donors were prepared by sequential, ultracentrifugal floatation after density adjustment with KBr. To study the interactions, aliquots of electrophoretically pure very low-density lipoproteins (VLDL, d less than 1.006 g/ml), low-density lipoproteins (LDL, d = 1.019-1.063 g/ml), or high-density lipoproteins (HDL, d = 1.210 g/ml) were incubated with proteoglycans in the presence of Ca++ and Mg++ at 4 C. The amount of cholesterol found in the resulting pellet was measured as a marker of the binding capacity of the proteoglycans. Among lipoprotein fractions both VLDL and LDL showed strong binding with proteoglycans, whereas no appreciable binding was observed when incubation experiments were done with HDL. There were significant differences in the lipoprotein binding capacity of proteoglycan of control and injured animals, indicating that injury induced changes in proteoglycan composition exert profound influences on their ionic interactions.

Animals↗
PubMed1988

Conditions influencing the interaction of asialo von Willebrand factor with human platelets--the effects of external ionized calcium concentration and the role of arachidonate pathway.

We have studied the interaction of ASvWf with human platelets in PRP and in suspensions of washed platelets containing either physiological or low external ionized calcium concentration [Ca2+]o. In hirudin-PRP or in washed platelets in 1.5-2 mM CaCl2, ASvWf up to 50 micrograms/ml does not induce platelet aggregation or the release reaction. When [Ca2+]o is decreased by addition of citrate to hirudin-PRP or when no CaCl2 is added to washed platelet suspensions, ASvWf does induce platelet aggregation and the release reaction. In low [Ca2+]o, ASvWf interacts with platelet GPIb to cause primary aggregation of disc-shaped platelets to each other through GPIIb/IIIa, with or without added fibrinogen. This primary platelet aggregation leads to thromboxane A2 formation and secondary aggregation and the release reaction. With [Ca2+]o in the physiological range, there is less ASvWf interaction with GPIb, no primary platelet aggregation and no thromboxane A2 formation. The ASvWf-platelet interaction at physiological [Ca2+]o, however, enhances the platelet response to collagen or epinephrine.

Arachidonic Acids↗
PubMed1988

The amino acid sequence of a cereal Bowman-Birk type trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi L.).

The major trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi) was purified by heat treatment, fractional precipitation with (NH4)2SO4, ion-exchange chromatography on DEAE-Sepharose, gel-filtration on Sephadex G-75 and preparative reverse-phase HPLC. The complete amino acid sequence was determined by analysis of peptides derived from the reduced and S-carboxymethylated protein by digestion with trypsin, chymotrypsin and the S. aureus V8 protease. The polypeptide contained 64 amino acids with a high content of cysteine. The sequence exhibited strong homology with a number of Bowman-Birk inhibitors from legume seeds and similar proteins recently isolated from wheat and rice.

Amino Acid Sequence↗
PubMed1988

Proteoglycan distribution in the intima and media of the aortas of young and aging rabbits: an ultrastructural study.

Aortas from normal healthy rabbits, approx. 3 months old, were examined by light and transmission electron microscopy. The proteoglycan of the extracellular matrix, which was stained by ruthenium red and appeared as granules by transmission electron microscopy, was quantitated morphometrically in the intima and the superficial media. The intima included areas which were thickened and which contained connective tissue, including proteoglycan, and some smooth muscle cells. In the thickened intima there was a greater proportion of extracellular space which was occupied by proteoglycan, and the proteoglycan was present in higher concentration than in the media. In the aortas of rabbits, approx. 2 years old, the extent of intimal thickening and the concentration of proteoglycan increased in the thickened intima but there was no evidence of extracellular lipid deposition. The endothelial basement membrane contained small proteoglycan granules (heparan sulphate) which decreased in concentration in older animals. It is possible that the accumulation of proteoglycan in the thickened intima increases the susceptibility of the intima to accumulate lipid following an additional stimulus, such as hyperlipaemia, in the initial stages of atherosclerosis.

Aging↗
PubMed1988

Proteoglycan in fast-frozen, freeze-dried, plastic-embedded rabbit arteries.

In contrast to glutaraldehyde-fixed vascular tissue with or without staining with cationic dye, the nonfibrous extracellular matrix of fast-frozen, freeze-dried rabbit aorta and renal artery contained a continuous reticulum of fine filaments, closely associated with collagen, elastin, and smooth muscle cells. Three morphologically distinct types of filament were distinguished; one type was selectively sensitive to chondroitinase ABC degradation, and therefore contains chondroitin and/or dermatan sulfate. The remaining filaments of the reticulum may represent the protein core of the proteoglycan monomer, and the hyaluronic acid backbone of the aggregate. Filaments associated with the surface of smooth muscle cells were usually linked to a continuous filament parallel to the cell surface, which was degraded by heparitinase and therefore contains heparan sulfate. The filaments linked directly to the cell surface were not degraded by either enzyme. The preservation of PG in fast-frozen material provides a significant improvement over that obtained by any presently available technique.

Actin Cytoskeleton↗
PubMed1988

Evidence that rabbit 125I-antithrombin III binds to proteoheparan sulphate at the subendothelium of the rabbit aorta in vitro.

The endothelium of the rabbit thoracic aorta was removed from the vessel wall by one of two procedures, and the freshly exposed subendothelial surface was used for 125I-antithrombin III binding studies. Pretreatment of the subendothelium with either heparitinase or thrombin diminished the uptake of 125I-antithrombin III by up to 80%, whereas pretreatment with plasmin, hyaluronidase or FPR thrombin had little effect. Morphometric analysis of the subendothelium from enzyme-treated and -untreated tissues showed that, whereas plasmin, thrombin and heparitinase each caused a dramatic reduction of the large proteoglycan granules of the extracellular matrix, only exposure to heparitinase and thrombin caused a reduction in the small proteoglycans which populate the basement membrane of smooth muscle cells. Of the subendothelium-bound 125I-antithrombin III, more than 80% was efficiently removed by excess thrombin or by excess heparin. Evidence was obtained for the formation of high molecular weight thrombin-antithrombin III complexes. We conclude that antithrombin III binds largely to proteoheparan sulphate located in the basement membrane of the intimal smooth muscle cells for the purpose of inactivating certain proteases which arise during haemostatic change.

Animals↗
PubMed1988

The effects of chronic otitis media on motor performance in 5- and 6-year-old children.

Two 16-member groups of 5- and 6-year-old children, one group with a history of chronic otitis media and one without such a history, were tested on three measures of motor performance. These were the Motor Accuracy Test-Revised, the Stott Test of Motor Impairment, and measures of duration of standing balance. These instruments assess, respectively, fine motor coordination, overall motor skills, and balance. On each of these measures, children with a history of chronic otitis media scored lower than children without such a history. However, when these scores were compared statistically, no significant differences were found between the two groups. Because the results of this study were inconclusive, routine motor performance evaluation of children with a history of chronic otitis media is not advocated at this time.

Child↗
PubMed1988

Sodium butyrate and a T lymphocyte cell line-derived differentiation factor induce basophilic differentiation of the human promyelocytic leukemia cell line HL-60.

Sodium butyrate induces basophilic differentiation of HL-60 promyelocytic leukemia cells that have been previously passaged in alkaline medium. A factor present in Mo conditioned medium (Mo-CM) acts synergistically with sodium butyrate to promote basophilic maturation in a dose-dependent fashion. The induced HL-60 cells exhibit nuclei at various stages of maturity and cytoplasmic granules staining azurophilic with May-Grünwald-Giemsa and metachromatically with toluidine blue. The histamine content of induced HL-60 cells is 50 ng/10(6) cells with sodium butyrate alone or 190 ng/10(6) cells with butyrate in combination with Mo-CM. Induced cells release histamine in response to anti-IgE and have receptors for the Fc portion of human IgE. The basophilic cell-differentiating activity present in Mo-CM appears to be distinct from several other cytokines including recombinant human interleukin-1 alpha, interleukin-2, interferon-gamma, interferon-alpha, murine interleukin-3, erythroid-potentiating activity, and purified human granulocyte/macrophage colony-stimulating factor. This is the first demonstration of a cell line that is capable of differentiation along the basophil lineage and could provide a useful model for examining biochemical and molecular events associated with basophil differentiation.

Basophils↗
PubMed1988

Behavior of plasminogen at the luminal surface of the normal and deendothelialized rabbit aorta in vivo and in vitro.

The behavior of purified rabbit plasminogen at the luminal surface of the uninjured and deendothelialized rabbit aorta has been studied in vivo and in vitro. After intravenous injection, 125I-plasminogen associated rapidly with the endothelium (approximately 0.1 pmol/cm2 at saturation) and passed through to accumulate in the subendothelium. At two to 15 hours after injection, 11 to 15 times more radioactivity was associated with the subendothelium than with the endothelium. Removal of the endothelium by balloon catheter led to a rapid adsorption of 125I-plasminogen by the luminal surface of the vessel; saturation (9.1 pmol/cm2) was attained at ten to 20 minutes after deendothelialization. Of the adsorbed plasminogen (radioactivity), only 2% to 4% was associated with the adherent platelet monolayer. Uptake of 125I-plasminogen by the deendothelialized vessel was not significantly inhibited by epsilon-aminohexanoic acid whether injected before or after the 125I-plasminogen. No evidence of plasmin activity at the aorta surface was found from either transmission electron microscopy studies or from amidolytic assays of plasminogen-saturated deendothelialized aorta samples before or after urokinase treatment. Balloon catheter treatment in vivo, however, generated significant antiplasmin activity of the deendothelialized aorta surface. We conclude that plasmin formed in vivo is probably inactivated by the antiplasmin activity that is associated with the subendothelium.

Animals↗
PubMed1988

The plasma proteases, thrombin and plasmin, degrade the proteoglycan of rabbit aorta segments in vitro: an integrated ultrastructural and biochemical study.

The effects of plasmin and thrombin on the proteoglycan component of uninjured and deendothelialized rabbit thoracic aorta were examined in vitro. Aortas labelled with 35S in vivo, were exposed to each protease and the 35S-products released from the vessel were analysed. Aortas exposed to the same enzymes were examined by transmission electron microscopy of ruthenium red-stained sections, and the proteoglycan content evaluated by morphometric analysis. In uninjured vessels with endothelium intact, there was no evidence of release of proteoglycan by either enzyme unless very high concentrations were used. High concentrations of both plasmin and thrombin induced vacuolation of endothelial cells, and changes in the fine structure of smooth muscle cells. In contrast exposure of de-endothelialized vessels to smaller concentrations of plasmin or thrombin resulted in a significant loss of proteoglycan, and less marked changes in the morphology of the smooth muscle cells. Thrombin treatment released 35S-labelled products containing chondroitin-, dermatan- and heparan-sulphates whereas plasmin released products containing only chondroitin- and dermatan-sulphates together with other, unknown 35S-labelled products. These observations indicate the potential of non-specific, plasma-derived proteases to degrade arterial connective tissue.

Animals↗
PubMed1988

Ultrasonographic features of carotid plaque and the risk of subsequent neurologic deficits.

In a prospective study, 214 consecutive patients considered not to be candidates for surgical intervention were evaluated by means of duplex scanning. Of the patients, 135 had no symptoms and 79 had a history of previous neurologic symptoms. In 139 sides duplex scanning demonstrated nonhemodynamic stenosis (lumen diameter reduction, less than 50%) and in 99 sides, hemodynamic stenosis (lumen diameter reduction, 50% or greater). Of the 238 carotid artery plaques examined, 167 were homogenous and 71 were heterogenous. During a mean follow-up of 34 months, 27 new focal neurologic deficits occurred. Patients with previous symptoms had a higher incidence of new deficits (18/79 vs 9/135) (p less than 0.01). The severity of the stenosis and the presence of a heterogenous plaque were statistically correlated with the occurrence of new deficits (p less than 0.001). Multivariate analysis showed that the ultrasonographic pattern and the severity of the stenosis were independent variables. We conclude that a heterogenous plaque should be considered an unstable plaque with the possibility of causing cerebral ischemia.

Aged↗
PubMed1988

Sequence of cellular responses in rabbit aortas following one and two injuries with a balloon catheter.

In order to further elucidate the pathogenesis of intimal proliferation and increased thrombogenesis following repeated arterial injuries we studied the sequence of the cellular changes following two injuries of rabbit aortas with a balloon catheter. Following the first injury, the de-endothelialized surface was covered by a platelet monolayer. Polymorphonuclear leucocytes adhered to the inner surface of this monolayer and did not appear to penetrate the vessel wall. By 4 to 7 days, areas of neointima had formed. Within seconds after the reinjury at 7 days after the de-endothelialization small platelet aggregates formed on injured neointimal smooth muscle cells. Within I min platelet thrombi and fibrin strands formed. At 30 min most of the platelet thrombi had become fibrin-rich. Polymorphonuclear leucocytes had accumulated and many had begun to penetrate into the neointimal tissue. The number and extent of penetration of leucocytes into the inner parts of the arterial wall increased with time. Four days after the injury the neointimal cushions were restored and thickened. Both following the first and second injury the formation of neointimal cushions was accompanied by a change in the polarity of the inner layers of medial smooth muscle cells, some of which appeared to have migrated into the neointima.

Animals↗
PubMed1988

Distribution of cellular responses in rabbit aortae following one and two injuries with a balloon catheter.

To investigate the mechanisms involved in the cellular reactions to arterial injuries, we studied the distribution of the deposits on the injured intima and the pattern of neointimal thickening following single and double injuries of rabbit aortae with a balloon catheter. Thirty minutes after the first injury most, but not all, of the inner surface of the aortae was covered by adherent, spread platelets. Seven days following the first injury areas of neointima, mainly proliferating smooth muscle cells, had formed around and opposite the orifices of branch vessels. The rest of the inner aortic surface consisted of acellular subendothelial matrix. Thirty minutes after the second injury, 7 days after the first, single platelets adhered once more to parts of the reinjured subendothelium, mostly between the orifices. Numerous fibrin-rich, platelet thrombi were present mainly on the surface of the injured neointima. Thirty minutes after both the first and second injury polymorphonuclear leucocytes adhered to the inner surface downstream from the orifices of branch vessels and in longitudinally oriented zones opposite the orifices. Four days following the second injury, the neointima was restored with the same distribution as before the second injury, and few thrombi, adherent platelets, or leucocytes remained.

Animals↗
PubMed1987

The basement membrane underlying the vascular endothelium is not thrombogenic: in vivo and in vitro studies with rabbit and human tissue.

Studies examining the interaction of platelets with exposed subendothelium in vivo have reported conflicting results. To examine possible explanations for the apparently discrepant findings, we measured the platelet reactivity of subendothelium prepared by a number of methods both in vivo and in vitro. In addition, we examined the possibility that 13-hydroxyoctadecadinoic acid (13-HODE), an endothelial cell-derived chemorepellant, modulates the reactivity of the subendothelium to platelets. In vivo, the subendothelium of segments of rabbit carotid arteries was exposed by removing the endothelial cells by air perfusion or by balloon catheter stripping. Platelet accumulation onto the de-endothelialized segments was assessed by 3H-radioactivity uptake, using 3H-adenine-labelled platelets, and by scanning electron microscopy. In vitro, 3H-adenine-labelled platelet adhesion was measured onto plain plastic discs and onto plastic discs coated with the following purified basement membrane components: collagens type I, III, IV, V, laminin, or fibronectin. In addition, 3H-adenine-labelled platelet adhesion was measured onto plastic discs covered with human endothelial cells or onto the basement membrane underlying the endothelial cells. In vivo, there was marked 3H-platelet accumulation onto the balloon catheter carotid arteries one hour after injury. In contrast, there was no platelet accumulation onto the subendothelium of carotid arteries de-endothelialized by air perfusion. These differences were confirmed by scanning electron microscopy. Transmission electron microscopic examination demonstrated that the extracellular matrix was intact following the air perfusion injury whereas the majority of it was removed by the balloon catheter injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Testicular failure in patients with extragonadal germ cell tumors.

Eight patients with mediastinal or retroperitoneal germ cell tumors who had undergone testicular biopsy or orchiectomy were retrospectively analyzed for primary testicular abnormalities, subfertility, and abnormal sex hormone levels. Testicular tissue was abnormal in all patients, revealing peritubular fibrosis (six), decreased spermatogenesis (eight), interstitial edema (five), Sertoli cells only (one), and Leydig cell hyperplasia (two). Detailed hormone analysis in five patients revealed elevations of luteinizing hormone in four, decreased serum testosterone in two, elevations of estradiol in two, and elevation of human chorionic gonadotropin in one patient. A history of infertility was documented 2 months to 13 years before presentation in four patients and suspected in another. Extragonadal germ cell tumors, like their testicular counterparts are associated with primary germ cell defects, some of which seem to be independent of gonadotropin production by the tumor. In addition, the rather high incidence of antecedent infertility suggests that either a congenital or acquired primary germ cell defect contributes to defective spermatogenesis and the development of cancer in incompletely migrated germ cells.

Adolescent↗