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Biomedical subjects

M Richardson

Publications and source records attributed to M Richardson.

At least 307 records · Page 17Linked to original sources
PubMed1990

Survival of rabbit platelets exposed to immune complexes.

Rabbits injected with human serum albumin (HSA) formed detectable immune complexes after 5 days; complex formation was maximal between 11 and 14 days after which the complexes were cleared from the circulation. Platelets from control rabbits or HSA-injected rabbits had a reduced survival upon injection into rabbits in which complexes were forming. Platelets from HSA-animals tended to survive for a longer period upon injection into control rabbits than when they were injected into HSA-rabbits, raising the possibility that some of the immune complexes may have eluted from their surface. Platelets prepared from either control animals or from HSA-treated animals at the time when complexes were being cleared from the circulation (14-21 days) did not have a shortened life span in HSA- or control rabbits. When platelet survival was reduced, it could not be attributed to platelet accumulation at sites of vessel wall injury or to accumulation in kidneys damaged by immune complexes, since the tissues (aorta and kidney) appeared to be morphologically normal and free of thrombi. The reduction in platelet survival likely results from the interactions of immune complexes with the surface of platelets leading to the platelets being recognized as "foreign" and cleared from the circulation by the reticuloendothelial system.

Animals↗
PubMed1990

The use of postoperative irradiation for the prevention of heterotopic bone after total hip replacement with biologic fixation (porous coated) prosthesis: an animal model.

Radiation has been shown to be effective in the prevention of heterotopic bone. The exact etiology of heterotopic bone is unknown. Total Hip prosthetic devices that do not depend upon bone cement for fixation have become increasingly popular. The mechanism by which the bone forms around the prosthesis is similar to the process by which fractures heal which has been shown to be sensitive to irradiation. Using a rabbit model we have undertaken a study to investigate the effect of irradiation on the bony ingrowth on porous coated implants. Forty-five rabbits had porous coated implants surgically placed in the tibiae bilaterally. Each rabbit had one tibae randomly irradiated with 1,000 cGy in 5 fractions starting on the first post-operative day. Animals were sacrificed weekly starting 2 weeks post-operatively and the tibae were sent for pullout studies. The amount of force necessary to pullout the treated tibae was statistically less than the amount of force necessary to remove the untreated tibae at 2 weeks. From 3 weeks on there was no difference in the force necessary to remove the prosthesis from the untreated or treated tibae. Histologically, the untreated tibae showed bone formation while the treated tibae did not. Because of these results, it is suggested that the treatment of patients at risk for development of heterotopic bone be modified to only include the area between the femur and pelvis avoiding treatment of the prosthetic device.

Animals↗
PubMed1990

Late lower arch crowding: the effect of second molar extraction.

Mesial drift and change in crowding over a 5-year period were compared in 30 subjects whose lower second molars were extracted between ages 11 and 17 years and 30 subjects whose lower second molars were not extracted. Significant differences were found. The nonextraction subjects showed an average forward movement of first molars and an increase in crowding. The extraction group showed slight distal movement of first molars and a decrease in crowding. It is concluded that lower second molar extraction reduces the tendency to forward movement of buccal segments and increased crowding by relieving eruptive pressure from third molars and that the presence of a developing lower third molar with insufficient space can be one cause of late lower arch crowding.

Adolescent↗
PubMed1990

Enhanced binding of fibrinogen by the subendothelium after treatment of the rabbit aorta with thrombin.

Damage to the endothelial surface of an artery invokes a hemostatic response that causes platelet deposition and activation of the coagulation and fibrinolytic pathways on the exposed subendothelial surface. Plasma fibrinogen is rapidly adsorbed at the site of injury. To gain insight into fibrinogen uptake, undamaged and de-endothelialized rabbit thoracic aortas were pretreated with various concentrations of thrombin and then incubated with fibrinogen labeled with iodine 125 in vitro. Uptake of fibrinogen by the subendothelium was not affected by low thrombin concentrations (less than 10 nmol/L), probably because of the antithrombin capacity of the vessel wall to inactivate any thrombin adsorbed. Over the thrombin concentration range of 10 to 90 nmol/L. fibrinogen binding increased linearly as binding of thrombin labeled with iodine 131 increased. In contrast, treatment of the subendothelium with enzymatically inactive thrombin did not enhance fibrinogen binding. Fibrinogen binding was inhibited by exposing the thrombin-treated subendothelium to hirudin or phenylalanyl-prolyl-arginyl-chloromethyl ketone. High thrombin concentrations (greater than 100 nmol/L) caused either a steadily decreasing uptake of fibrinogen with low fibrinogen concentrations or fibrin coagulation on the subendothelial surface from a high fibrinogen concentration. Glycyl-prolyl-arginyl-proline (0.1 mg/ml), a selective inhibitor of fibrin polymerization, inhibited 72% to 78% of fibrinogen uptake by the thrombin-treated subendothelium. Fibrinogen uptake was Ca2(+)-dependent, but ethylenediaminetetraacetic acid (10 mmol/L) did not displace subendothelium-bound fibrinogen. Plasmin effectively removed at least 75% of bound fibrinogen, indicating an extracellular location for the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Herpes simplex virus interstitial nephritis in a renal allograft.

We report a 35-year-old woman who developed herpes simplex virus (HSV) type 1 interstitial nephritis following a cadaveric renal transplant. Transplant function was poor and a transplant nephrectomy was performed 23 days post-transplant. Histological changes characteristic of herpes virus infection were seen on the renal biopsy with positive immunoperoxidase staining for HSV. HSV 1 was cultured from the transplant nephrectomy specimen.

Adult↗
PubMed1990

Wound healing in the media of the normolipemic rabbit carotid artery injured by air drying or by balloon catheter de-endothelialization.

The response to air-dry injury to the carotid artery of the normolipemic rabbit was compared with the response to de-endothelialization with a balloon catheter. Air drying induced an inflammatory response that resembled arteritis rather than atherosclerosis. There was medial damage, neutrophil but not macrophage infiltration, and fibrin formation, limited smooth muscle proliferation, which regressed after 3 months, and no lipid deposition. Within 1 week the smooth muscle cells were mainly of the secretory phenotype, and a neointima had formed. At 4 weeks the neointimal proliferation continued, but most cells showed a contractile phenotype. By 3 months, the lesion consisted of fibromuscular thickening with few small smooth muscle cells. Balloon injury induced minimal medial damage and continuing intimal proliferation with no evidence of regression by 3 months. It is concluded that air drying the carotid artery induces smooth muscle damage as well as endothelial cell loss, and this stimulates a wound-healing mechanism that is different from the response to selective intimal injury.

Air↗
PubMed1989

Purification and characterization of an insect alpha-amylase inhibitor/endochitinase from seeds of Job's Tears (Coix lachryma-jobi).

A protein inhibitor of locust gut alpha-amylase was purified from seeds of Job's Tears (Coix lachryma-jobi) using ammonium sulphate precipitation, affinity chromatography on Red Sepharose and reversed-phase HPLC. It consisted of two major isomers, each a dimer of two closely similar or identical subunits of Mr about 26,400, and associated by inter-chain disulphide bonds. These isomers also had closely similar amino acid compositions. The major isomer showed no inhibitory activity against amylases from other sources: human saliva, porcine pancreas, Bacillus subtilis, Aspergillus oryzae and barley malt. The manual DABITC/PITC method was used to determine about half of the amino acid sequence of the major isoform. This showed a high degree of homology with previously reported sequences of endochitinase enzymes from several species (tobacco, potato, barley, bean), and endochitinase activity was demonstrated by following the release of radioactivity from [3H]chitin. This novel combination of functions may be relevant to protection of the grain from insect feeding and fungal infection.

Amino Acid Sequence↗
PubMed1989

The amino acid sequence of Erythrina corallodendron lectin and its homology with other legume lectins.

The primary sequence of Erythrina corallodendron lectin was deduced from analysis of the peptides derived from the lectin by digestion with trypsin, chymotrypsin, Staphylococcus aureus V8 protease, elastase and lysylendopeptidase-C, and of fragments generated by cleavage of the lectin with dilute formic acid in 6 M guanidine hydrochloride. Purification of the individual peptides was achieved by gel filtration, followed by reverse phase HPLC. The glycosylation site (Asn17-Leu18-Thr19) was deduced from analysis of the glycopeptide isolated from a pronase digest of the lectin before and after deglycosylation of the glycopeptide with endoglycosidase F. Comparison of the sequence of 244 residues thus obtained with those of 9 other legume lectins revealed extensive homologies, including 39 invariant positions and 60 partial identities. These data provide further evidence for the conservation of the lectin gene in leguminous plants.

Amino Acid Sequence↗
PubMed1989

Platelet function and survival in rats with genetically determined hypercholesterolaemia.

Platelets from rats with genetically determined hypercholesterolaemia are hypersensitive to aggregation induced by thrombin compared with platelets from their genetic controls without hypercholesterolaemia. Aggregation or release induced by thrombin of platelets from hypercholesterolaemic and control rats correlated significantly with plasma cholesterol concentrations. Platelet responses to ADP or collagen were not different between the groups. The hypersensitivity to thrombin-induced aggregation was independent of released ADP or products of arachidonic acid metabolism. The changes in platelet sensitivity occurred with only moderate increases in plasma cholesterol concentration and with no detectable changes in total platelet cholesterol. The hypersensitivity of platelets from hypercholesterolaemic rats was not associated with a reduction in platelet survival or any significant injury to the aortic endothelium in these animals. Platelets from hypercholesterolaemic rats were smaller than platelets from controls. Thus, platelets from rats with genetically determined hypercholesterolaemia have alterations in function similar to those found with platelets from rats with diet-induced hypercholesterolaemia indicating that this strain can be used to study the mechanisms by which cholesterol can change platelet function without the possible complicating effects of dietary factors. Since platelet hypersensitivity occurred in rats with genetically determined hypercholesterolaemia without a reduction in platelet survival, these studies are also consistent with the reduced platelet survival found in animals with diet-induced hypercholesterolaemia being independent of platelet changes.

Animals↗
PubMed1989

Wide-angle memories of close-up scenes.

We report a picture-memory phenomenon in which subjects' recall and recognition of photographed scenes reveal a pronounced extension of the pictures' boundaries. After viewing 20 pictures for 15 s each, 37 undergraduates exhibited this striking distortion; 95% of their drawings included information that had not been physically present but that would have been likely to have existed just outside the camera's field of view (Experiment 1). To determine if boundary extension is limited to recall and drawing ability, Experiment 2 tested recognition memory for boundaries. Eighty-five undergraduates rated targets and distractors on a boundary-placement scale. Subjects rated target pictures as being closer up than before and frequently mistook extended-boundary distractors as targets. Results are discussed in terms of picture comprehension and memory. In addition to its theoretical value, discovery of the phenomenon demonstrates the importance of more widespread use of open-ended tests in picture-memory methodology.

Adult↗
PubMed1989

Vascular changes associated with deoxycorticosterone-NaCl-induced hypertension.

Rats were injected with deoxycorticosterone (DOC) and salt was added to the drinking water (DOC/NaCl) for 3 weeks. Approximately half of the animals became hypertensive (DOC-H), whereas the remainder showed no increase in blood pressure (DOC-N) compared to age-matched, untreated controls. Morphometric analysis of the alterations in the arteries of the mesenteric bed was carried out in vessels fixed at maximum relaxation. Alterations were observed in the arteries, some of which were related to hypertension, but not to treatment, and some were due to treatment alone. The alterations within the arteries of the mesenteric bed depended in part on the type of artery, i.e. elastic, muscular or arteriolar. An increase in lumen area, in intimal area, and in the area of the media was seen in all types of arteries from DOC-H, but not in either group of normotensive animals. The medial hypertrophy was positively correlated with the increase in blood pressure; and was due to an increase in the number of smooth muscle cell layers in the elastic and muscular arteries, and probably to smooth muscle cell hypertrophy in the arterioles. The adventitial area was increased only in the elastic and muscular arteries. Endothelial injury, degeneration of the basement membrane, loss of heparan sulfate proteoglycan and intimal edema was observed in all the DOC/NaCl-treated animals, but was more severe in those which were also hypertensive. Hypertrophy of the heart and kidneys were observed in both normotensive and hypertensive DOC/NaCl-treated animals. These data indicate that changes in the rat cardiovascular system can be induced by DOC/NaCl treatment in the absence of hypertension, but also that hypertension is associated with specific arterial structural alterations, which vary according to the type of artery.

Animals↗
PubMed1989

A device for the intraoperative identification of the recurrent laryngeal nerve in piglets.

The recurrent laryngeal nerve (RLN) is one of the most frequently injured nerves in head and neck surgery. Routine identification of the RLN during thyroid surgery has reduced the injury rate from 10% to less than 4%. Difficulty in identification of the RLN contributes to this surgical morbidity. Devices previously used for intraoperative identification of the RLN have failed to achieve the simplicity and reliability necessary for clinical use. This animal study uses a simple double-ballooned endotracheal tube and pressure transducer system, which assists intraoperative RLN identification through nerve stimulation and graphic documentation of vocal fold (VF) motion. Iatrogenic injury is demonstrated by a dampened stimulation-pressure tracing. The RLNs of three piglets were injured and examined, and the degree of injury was correlated with perioperative nerve stimulation patterns. The piglet proved to be an adequate model for laryngeal research. An FDA-approved multi-institutional prospective human study using this system of identification of the RLN is in progress.

Animals↗
PubMed1989

Natural history of recurrent carotid artery disease.

Controversy exists as to whether early and late recurrent stenosis of the carotid artery represents two distinct types of recurrence or whether it is the same type of lesion detected at different times. Eleven specimens from patients whose carotid arteries were reoperated upon were examined. A temporal sequence was noted: with increasing intervals, the relative presence of areas of myointimal hyperplasia tended to decrease, whereas the relative presence of features of atherosclerosis tended to increase. The clinical data and B-mode ultrasound studies performed from one to 190 months after 210 carotid endarterectomies were reviewed. Twenty-seven carotid arteries (12.9 per cent) exhibited hemodynamically significant restenosis. Three ultrasonographic patterns were described: homogenous soft plaque, homogenous hard plaque and heterogenous plaque. A previous correlation between ultrasonographic and pathologic findings showed the three ultrasound patterns to correlate with myointimal hyperplasia, fibrous atherosclerotic plaque and complex atherosclerotic plaque, respectively. Soft plaques were detected earlier than heterogenous plaques (p less than 0.001). Results from serial studies showed progression of soft plaque to hard or heterogenous plaque, or both. Early and late recurrent lesions are the same type of lesion detected at different intervals. Symptoms of cerebral ischemia are more common at the stage of heterogenous plaque (p = 0.02).

Aged↗
PubMed1989

Walker carcinosarcoma cells damage endothelial cells by the generation of reactive oxygen species.

The passage of circulating tumor cells across vessel walls is an important step in cancer metastasis and is promoted by endothelial injury. Because Walker carcinosarcoma 256 (W256) cells generate oxygen-derived free radicals after cellular activation, the authors tested the hypothesis that these cancer cells can damage endothelial monolayers by producing such reactive oxygen species. To confirm that oxygen-derived radicals can damage endothelial cells, 3H-2-deoxyglucose-labeled human endothelial cell monolayers were exposed to xanthine oxidase in the presence of 0.2 mmol/l xanthine. 3H-2-deoxyglucose release was observed after the addition of xanthine oxidase in concentrations ranging from 6.5 x 10(-3) to 52 x 10(-3) units/ml. The extent of damage correlated with xanthine oxidase-dependent chemiluminescence (r = 0.91). Chemiluminescence assays in the presence of 5 x 10(-5) M luminol confirmed activation of the W256 cells by 1 x 10(-6) M chemotactic peptide fMLP. When fMLP-activated activated W256 cells were incubated with endothelial monolayers, concentrations of 2 x 10(6) to 6 x 10(6) W256 cells/ml were found to cause a 27% increase in the specific release of 2-deoxyglucose after a 90-minute incubation. A small but significant increase in 3H-2-deoxyglucose release also was observed in the absence of fMLP. Detection of 3H-2-deoxyglucose release in the presence of activated or unactivated tumor cells was dependent on preincubating the endothelial cell monolayer with 1 mM buthionine sulfoximine, an inhibitor of glutathione synthesis. Under these conditions, the specific release of 3H-2-deoxyglucose was increased from nondetectable levels to 21%, in the presence of 6.5 x 10(-3) units of the oxidase. Cultured W256 cells promoted isotope release from endothelial cell monolayers when activated with phorbol myristate acetate. Catalase (1000 units/ml) inhibited the tumor cell-induced release of 3H-2-deoxyglucose by 84% whereas superoxide dismutase, even at concentrations of 1 mg/ml, had no effect. A requirement for cell contact was shown because addition of cell-free supernatants from fMLP activated tumor cells did not cause 3H-2-deoxyglucose release and because pretreatment of W256 cells with 1 microM cytochalasin B inhibited their ability to promote isotope release even while increasing tumor cell-generated chemiluminescence threefold. Electron microscopy revealed that fewer cytochalasin B-treated W256 cells were attached to the endothelial cell monolayer than in untreated controls. It is concluded that the W256 tumor cells can damage endothelial cells directly via a mechanism involving production of reactive oxygen species.

Animals↗
PubMed1989

Platelet accumulation and turnover on de-endothelialized aortae in rats.

Previous studies indicate that the subendothelium of rabbit aortae de-endothelialized with a balloon catheter rapidly becomes covered with a monolayer of platelets; after 60 min few additional platelets accumulate and although most platelets are lost from the injured surface by 4 days, there is a substantial delay before re-endothelialization. We examined the dynamics of platelet accumulation on rat aortae de-endothelialized with a balloon catheter to determine if the response to this type of injury is similar to rabbit aortae. When 51Cr-platelets were injected prior to aortic de-endothelialization, 25,500 +/- 2,750 platelets/mm2 accumulated on rat subendothelium in the first 15 min. After 60 and 92 h, fewer platelets remained on the surface (13,740 +/- 2,400 and 5,020 +/- 1,330 platelets/mm2, respectively). When 51Cr-platelets were injected into rats 30 min after injury, platelet accumulation in a 30-min period was 8,610 +/- 1,230 platelets/mm2. By 4 days rat aortae did not accumulate newly injected platelets significantly in a 30-min period, but in a 24-h period 20,600 +/- 3,490 platelets/mm2 accumulated. Morphologically, the non-endothelialized areas of rat aortae were almost completely covered with platelets 4 days after injury. Fourteen days after injury, rat aortae did not accumulate newly injected platelets and, morphologically, no platelets were present on the surface which was almost re-endothelialized. Thus, in rats, as with rabbits, platelets rapidly accumulate on de-endothelialized aortae and the ability to attract newly introduced platelets is considerably reduced shortly after injury. In contrast to rabbits, however, de-endothelialized aortae in rats remain attractive to new platelets up to 4 days following injury, but less so than at the time of injury. Also, in contrast to rabbits, 14 days after injury to rat aortae the surface is almost completely re-endothelialized. Thus, there are species differences in platelet interactions with de-endothelialized vessels.

Animals↗