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Biomedical subjects

C C Clawson

Publications and source records attributed to C C Clawson.

67 records · Page 4Linked to original sources
PubMed1971

Platelet interaction with bacteria. I. Reaction phases and effects of inhibitors.

Interactions between human platelets and several common species of bacteria have been studied in vitro by the technic of recording nephelometry. Results of this investigation have established the following parameters of platelet-bacterial interaction: (1) Bacteria are potent stimuli of the platelet-aggregating reaction. (2) The platelet-bacterial interaction proceeds through four distinct phases which are separable by varying the platelet-bacterial ratios or adding appropriate chemical inhibitors. (3) The degree and rate of the platelet response is proportional to the ratio of bacteria to platelets. (4) Direct contact between platelets and bacteria, physiologic levels of divalent cations and nucleotide release from platelets are essential for aggregation of platelets by bacteria. (5) By adding equivalent numbers of six species of microorganisms to platelet-rich plasma, their potency as initiators of the platelet reaction was determined, with Staphylococcus being the most powerful.

Adenosine Diphosphate↗
PubMed1971

Platelet interaction with bacteria. II. Fate of the bacteria.

Several common strains of bacteria have been studied to determine their influence on human and rabbit platelets in vitro. Bacteria at a nominal ratio of 1:1 were added to platelets in their native plasma or to platelets in a balanced salt solution. The platelet-bacterial interaction was examined by nephelometry and by sequential light microscopy of fixed specimens taken at key points in the reaction. The results support the following conclusions: (1) Bacteria that were potent stimuli of the platelet aggregation reaction were incorporated in large numbers into the forming platelet aggregates. (2) Bacteria sequestered within platelet aggregates remained in direct contact with the aggregated platelet mass for up to 1 hour in vitro and during this time showed no morphologic changes by light microscopy. (3) Plateletbacterial interaction produced clumping of the bacteria but no demonstrable killing of the microorganisms. (4) Collagen-platelet interaction resulted in release of platelet products that were capable of clumping bacteria but were not lethal to them. (5) Rabbit and human platelets showed no species differences in plateletbacterial interaction. (6) Washed platelets interacted with bacteria without added serum factors but the addition of serum accelerated the aggregation reaction.

Animals↗
PubMed1970

Effect of Bactericidal Substance from Staphylococcus aureus on Group A Streptococci II. Structural Alterations.

Ultrastructural alterations brought about by treatment of a beta-hemolytic streptococcus with a bactericidal substance from Staphylococcus aureus are described and illustrated. The substance causes an early condensation of nucleoid deoxyribonucleic acid (DNA) and a partial loss of ribosomes. These changes are followed by a dissolution of the cell contents resulting in bacterial "ghosts" composed of empty cell wall and capsule. These morphological findings correlate with known biochemical effects of the bactericidal substance on ribonucleic acid degradation and cessation of DNA and protein synthesis.

Journal Article↗
PubMedDate not supplied

Micropipette aspiration of human platelets after exposure to aggregating agents.

The present study examined the influence of activation on platelet deformability. Aspiration of cells after exposure to thrombin, adenosine 5' -diphosphate, or the calcium ionophore A23187 at concentrations producing shape change and stickiness revealed significant changes from control cells. At the lowest negative pressure, 4 X 10(-2) dynes/cm (-1 cm H2O), there were no differences in lengths of membrane segments aspirated from control and activated platelets. Each subsequent increase in negative pressure up to 35 X 10(-2) dynes/cm (-7.5 cm H2O) resulted in significantly longer aspirated segments on activated cells compared to control cells. Greater negative pressures did not cause further increases in lengths of membrane segments drawn into the pipette. Thus, activation, which results in constriction of the circumferential microtubule, makes more membrane available for aspiration as negative pressure is increased. In both control and activated platelets, the microtubule coils served as a barrier to further lengthening of aspirated membrane segments as negative pressure was increased beyond 35 X 10(-2) dynes (-7.5 cm H2O).

Adenosine Triphosphate↗
PubMedDate not supplied

Overview article: biostructure of blood platelets.

Advances in biochemistry, physiology, immunology, and cytochemistry, combined with a variety of new approaches for the evaluation of fine structure, have yielded new insights into the structural physiology and pathology of blood platelets. Subpopulations of platelet granules have been clearly defined; they include the catalase containing organelles referred to as peroxisomes; lysosomes enclosing hydrolytic enzymes; and the alpha-granules in which platelet factor 4, mitogenic factor, beta thromboglobulin, thrombin sensitive protein, fibrinogen, and coagulation factor V are localized. Features of platelet membrane systems have been particularly well-delineated, and recent evidence suggests that membrane complexes serve as the sarcoplasmic reticulum of platelets and the site of prostaglandin synthesis. Improved understanding of platelet biostructure resulting from these observations has made it possible to develop specific relationships between defects in structure and pathological behavior of the cells in vitro and in vivo.

Blood Platelets↗
PubMedDate not supplied

Chediak-Higashi syndrome: variable cytochemical reactivity of giant inclusions in polymorphonuclear leukocytes.

Neutrophils from the peripheral blood of patients with the Chediak-Higashi syndrome (CHS) contain large numbers of giant granules. Previous studies have demonstrated that the huge neutrophil organelles contain hydrolytic enzymes and are, therefore, massive lysosomes. The basis for the inability of giant granules to react with phagocytic vacuoles containing foreign particulates taken up by CHS neutrophils has not been determined. In the present investigation we have examined the ultrastructural cytochemistry of the huge inclusions in neutrophils from 3 patients. Electron-dense reaction product of the acid phosphatase reaction stained the giant inclusions and a few normal-sized azurophilic granules in the process of fusion with them. The amount of reaction product deposited in the huge organelles and its distribution, however, were extremely variable, even in the same cell. Myeloperoxidase staining revealed a similar variability in the intensity and distribution of its electron-dense reaction product. The findings suggest that giant primary granules in circulating CHS neutrophils retain characteristics similar to newly formed azurophilic lysosomes in promyelocytes and myelocytes. Dilution of enzyme reaction products and variability in their localization indicate that most of the giant primary granules undergo transformation or incorporation into huge secondary lysosomes, which are virtually unable to participate in the degranulation reaction after uptake of foreign particulates by CHS neutrophils.

Acid Phosphatase↗
PubMedDate not supplied

Effects of large latex particle uptake of the surface connected canalicular system of blood platelets: a freeze-fracture and cytochemical study.

The complex structural organization of the platelet's surface-connected or open canalicular system (OCS) and close physical relationships to the dense tubular system have been described in previous cytochemical and freeze-fracture ultrastructural studies. Despite observations that suggest that channels of the OCS are seldom, if ever, single, tubelike invaginations of the surface, others have indicated that the OCS is a readily available source of membrane for evagination onto the exposed surface of the platelet after activation or during phagocytosis. In the presence investigation we have utilized freeze-fracture for the first time to evaluate the uptake of large (0.312 micron, SD +/- 0.0022) latex particles by platelets. Results of the study leave no doubt that channels of the OCS serve as the major route for latex ingestion in te unstirred system employed. Prolonged exposure to latex and uptake of many spherules cause marked changes in platelet surface contour and internal organization. The OSC is transformed from a spiderweb of intercommunicating channels into one or two large vacuoles filled with latex. Conversion of the OCS into large sacs is associated with disk-to-sphere transformation and a decrease in the number of openings of the OCS on the platelet surface. Thus, the OCS appears to be effectively interiorized by the process of phagocytosis, rather than evaginated as others have suggested.

Blood Platelets↗
PubMedDate not supplied

Effects of small latex particle uptake on the surface connected canalicular system of blood platelets: a freeze-fracture and cytochemical study.

Recent investigations have suggested that channels of the surface connected open canalicular system are the major source of membrane contributing to increased surface area of platelets following activation or uptake of particulates. However, study of large latex particle phagocytosis suggested that channels filled with spherules become dilated and lose connections with the outer surface, but do not become extruded onto the platelet membrane. The present study has employed electron dense tracers, freeze-fracture and transmission electron microscopy to follow the uptake of small latex spherules by blood platelets. Small particles were rapidly incorporated into the numerous channels without causing significant changes in surface or internal morphology. Intramembranous particles on both E and P faces in replicas of freeze-fractured platelets were unaffected by ingestion of latex spherules. Prolonged exposure to small latex particles caused platelets to lose their discoid form. The irregular spheres contained two or three dilated vacuoles filled with latex and a reduced number of single channels. Results of this and previous studies suggest that channels of the open canalicular system are internalized in platelets after phagocytosis, and are not extruded onto the platelet surface.

Blood Platelets↗