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Biomedical subjects

W T Johnson

Publications and source records attributed to W T Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1989

Altered cytoskeletal organization and secretory response of thrombin-activated platelets from copper-deficient rats.

The cytoskeletal organization that occurs following thrombin-induced activation of platelets was investigated in rats consuming either a copper-deficient diet containing less than 1 microgram Cu/g or a copper-adequate diet containing 5.5 micrograms Cu/g. Within 30 s following thrombin activation, the amount of polymerized actin in Triton X-100 extracts of whole platelets from copper-deficient rats was greater than the amount in platelets from copper-adequate rats. Electrophoretic analysis of the cytoskeletal proteins obtained from low speed centrifugation of the Triton X-100 extracts indicated that the myosin content of the cytoskeleton increased with time and reached higher levels following activation in platelets from copper-deficient rats. Actin content of the cytoskeleton also increased with time following activation. However, the difference in cytoskeletal actin content of platelets from copper-deficient and copper-adequate rats was not as great as that observed for myosin. The rate of ATP secretion from thrombin-activated platelets was also increased by copper deficiency. Myosin association with the platelet cytoskeleton may be involved in platelet secretion following thrombin activation. Thus, the increased association of myosin with the cytoskeleton and concomitant increase in ATP secretion suggest that the normal mechanism for stimulus-response coupling is altered in thrombin-activated platelets from copper-deficient rats.

Actins↗
PubMed1988

Management of dental patients with bleeding disorders: review and update.

Management of the dental patient who has a bleeding disorder requires an understanding of the normal hemostatic system and the patient's specific coagulation defect. This patient group can receive quality comprehensive dental care, provided appropriate preoperative planning and evaluation with the patient's physician or hematologist is accomplished. Emphasis should be placed on providing appropriate replacement therapy before the dental procedure, selection of conservative treatment approaches, and use of local hemostatic measures to facilitate hemostasis.

Blood Coagulation Disorders↗
PubMed1988

Influence of iron and the sex of rats on hematological, biochemical and immunological changes during copper deficiency.

The influence of dietary iron and the sex of rats on suppressed lymphocyte functions caused by copper deficiency was examined. Male and female weanling Lewis rats were fed two concentrations of copper (0.6 or 5.6 micrograms Cu/g diet) and iron (50 or 300 micrograms Fe/g diet) for 42 d. Regardless of dietary iron concentrations, male and female rats consuming low copper diets had lower serum ceruloplasmin activity and serum and liver copper concentrations than those fed the high copper diet. However, hemoglobin and hematocrit levels were higher in copper-deficient females than in copper-deficient males and were unaffected by copper deficiency in females fed the high iron diet. Copper-deficient females also had higher serum and liver iron concentrations than copper-deficient males. Proliferation of concanavalin A (Con A)-stimulated spleen lymphoid cells (SLC) was suppressed in copper-deficient males and females, but the suppression was less in the females. Thus, the primary cause of suppressed SLC proliferation in copper-deficient rats is poor copper status; poor iron status induced by copper deficiency had little influence on proliferation.

Animals↗
PubMed1988

Limited dermal ossification: a case report.

A case is reported of a 10-year-old girl with ossification of the dermis in a limited distribution. The patient has no underlying disorder of calcium or phosphate metabolism and the ectopic bone has been analyzed and found to be identical to normal membranous bone. The ectopic ossification has bridged several of the joints of the patient's upper and lower extremities. At present, the patient is nonambulatory, but has no respiratory or cardiac abnormalities. Her mental status and IQ are normal.

Child↗
PubMed1987

The effect of inferior alveolar nerve resection on dentin formation.

The purpose of this investigation was to quantitatively evaluate the effects of inferior alveolar nerve resection on dentinal structures of dogs with the use of fluorescent tissue-time markers. After resection of the mandibular right inferior alveolar nerve and an experimental interval of 70 days, dentin formation was determined from serial cross sections through the mandibular canines. Results indicated that denervation did not appear to affect secondary dentin formation in the canine teeth of dogs.

Animals↗
PubMed1987

Effect of copper deficiency on erythrocyte membrane proteins of rats.

The effects of copper deficiency on the proteins of rat erythrocyte membranes were assessed by electrophoretic analysis. For 42 d, rats were fed diets containing less than 1 ppm Cu with 35 or 250 ppm Fe or 5 ppm Cu with 35 or 250 ppm Fe. Electrophoresis of erythrocyte membrane proteins indicated a significant increase in the amount of a 170,000-dalton protein in rats fed copper-deficient diets. High dietary iron reduced the amount of the 170,000-dalton protein in erythrocyte membranes from rats in both the copper-deficient and copper-adequate groups. However, feeding high dietary iron to copper-deficient rats did not reduce the amount of the protein to the level found in rats fed the copper-adequate diet containing 35 ppm Fe. Triton X-100 extraction of erythrocyte membranes demonstrated that the 170,000-dalton protein was associated with the membrane cytoskeleton. Thus, copper deficiency possibly alters the cell's mechanical properties and consequently decreases erythrocyte survivability by modifying the membrane cytoskeleton.

Animals↗
PubMed1987

Blood flow and epithelial thickness in different regions of feline oral mucosa and skin.

The relationship between epithelial thickness and blood flow was examined in 6 mucosal and 3 skin regions of the cat. Blood flow to these tissues was determined using the radiolabelled microsphere method. From histologic sections the proportion of the tissue biopsy occupied by epithelium and the average epithelial thickness were calculated. The oral tissues had a significantly higher blood flow than the skin regions (p less than 0.05). In terms of epithelial thickness, the tissues could be divided into 4 groups (p less than 0.05). These were: a) palate; b) gingival regions and dorsum of the tongue; c) lip and buccal mucosa; d) all skin regions. When epithelial thickness was related to blood flow there was a significant positive correlation (p less than 0.005) indicating that a thicker epithelium is associated with a higher blood flow. This finding may reflect the greater metabolic demands of the thicker epithelia.

Animals↗
PubMed1986

Arterial intimal embrittlement. A possible factor in atherogenesis.

Sections of aorta, coronary artery, basilar artery and vena cava were collected at autopsy. Macroscopically normal intimal specimens were removed by stripping. Intimal collagen was measured as hydroxyproline. Intimal film embrittlement was measured in vitro by a bursting volume distensibility test developed in our laboratory. There was an average increase of over 100% in the collagen content of apparently lesion-free human arterial intima on aging over a fifty-year period. This includes an increase of 113% for aortic intima, 49% increase for coronary artery intima, and an increase of 158% in collagen in basilar artery intima. In contrast the collagen level in the vena caval intima decreases on aging, by 42% in fifty years. The large increase in collagen in arterial intima is accompanied by a large increase in intimal embrittlement. The decreasing collagen content of the venous intima on aging results in increased distensibility. Increased aortic intimal film embrittlement (lower distensibility) correlates with age (R = 0.699), but even better with intimal collagen (R = 0.911), suggesting that aortic intimal collagen level is a more important determinant of intimal embrittlement than age. Men, older than 55, have significantly higher aortic intimal collagen levels than women. Embrittlement of arterial intima should make it more susceptible to injury under the pulsatile pressure of the blood. Decreased venous intimal collagen and greater distensibility on aging could be factors in the development of venous valvular insufficiency and varicose veins. However, our study of veins was performed primarily as a control in this instance. Fundamental elements in the atherogenic process are increased intimal collagen, increased intimal brittleness, endothelial injury, followed by intimal cell proliferation. In the vena caval intima on aging there is decreased collagen, increased intimal distensibility, no injury due to increased pulse or blood pressure, and, therefore, no cell proliferation and no intimal lesion.

Adolescent↗
PubMed1986

Mandibular paresthesia secondary to cerebrovascular changes.

An unusual case of mandibular paresthesia as the only presenting symptom of a cerebrovascular accident is presented. The differential diagnosis of inferior alveolar nerve paresthesia is discussed. Obtaining a definitive diagnosis depends on a thorough medical and dental history complemented by a complete clinical and radiographic examination. The etiology of cerebral vascular accidents is reviewed, as well as risk factors that may increase the possibility of a cerebrovascular accident.

Adult↗
PubMed1985

Evaluation of treatment provided patients hospitalized with orofacial odontogenic infections: a retrospective study.

The purpose of this study was to evaluate the treatment that patients receive when they are hospitalized for orofacial infections. Results indicated that dental consultations were not always obtained by medical personnel prior to the diagnosis and treatment of patients and that the antibiotic therapy employed did not always involve the recognized drug of choice.

Adolescent↗
PubMed1985

Replantation of avulsed teeth with immature root development.

Successful treatment of the avulsed tooth with immature root development is dependent on both pulpal and periodontal responses. The pulpal reaction is often one of revascularization with subsequent replacement of the necrotic pulp tissue. Continued root development and further calcification of the existing root structure are often seen with revitalization. The periodontal response to avulsion is dependent on the vitality of the periodontal ligament cells on the root surface. Normal healing occurs when the vitality is maintained, while replacement resorption results when the vitality is lost. Replantation after a short extra-alveolar period appears to provide the best prognosis for long-term retention of the avulsed tooth.

Child↗
PubMed1985

Intestinal absorption and excretion of zinc in streptozotocin-diabetic rats as affected by dietary zinc and protein.

65Zn was used to examine the effects of dietary zinc and protein on true zinc absorption and intestinal excretion of endogenous zinc by an isotope dilution technique in streptozotocin-diabetic and control rats. Four groups each of diabetic and control rats were fed diets containing 20 ppm Zn, 20% egg white protein (HMHP); 20 ppm Zn, 10% egg white protein (HMLP); 10 ppm Zn, 20% egg white protein (LMHP); and 10 ppm Zn, 10% egg white protein (LMLP). Measurement of zinc balance was begun 9 d after an i.m. injection of 65Zn. True zinc absorption and the contribution of endogenous zinc to fecal zinc excretion were calculated from the isotopically labeled and unlabeled zinc in the feces, duodenum and kidney. Results from the isotope dilution study indicated that diabetic rats, but not control rats, absorbed more zinc from 20 ppm zinc diets than from 10ppm zinc diets and that all rats absorbed more zinc from 20% protein diets than from 10% protein diets. Furthermore, all rats excreted more endogenous zinc from their intestines when dietary zinc and protein levels resulted in greater zinc absorption. In diabetic and control rats, consuming equivalent amounts of zinc, the amount of zinc absorbed was not significantly different, but the amount of zinc excreted by the intestine was less in the diabetic rats. Decreased intestinal excretion of endogenous zinc may be a homeostatic response to the increased urinary excretion of endogenous zinc in the diabetic rats and may also lead to the elevated zinc concentrations observed in some organs of the diabetic rats.

Analysis of Variance↗
PubMed1984

Effects of the interrelationship between dietary protein and minerals on tissue content of trace metals in streptozotocin-diabetic rats.

Zinc, iron and copper concentrations were measured in several organs from streptozotocin-diabetic and normal male, Long-Evans rats that were maintained for 21 days on a dietary regimen designed to study the combined or singular effects of insulin-dependent diabetes, dietary protein and dietary minerals on the tissue content of trace metals. The diets contained either 20 ppm zinc and iron, 5 ppm copper and 20% protein (HMHP); 8 ppm zinc and iron, 2 ppm copper and 8.3% protein (LMLP); 20 ppm zinc and iron, 5 ppm copper and 8.3% protein (HMLP) or 8 ppm zinc and iron, 2 ppm copper and 20% protein (LMHP). The concentrations of zinc, iron and copper in liver, zinc and iron in kidney and iron in femur were elevated in the diabetic rats and were not influenced by dietary protein and mineral interaction. However, dietary protein, mineral or protein X mineral interaction significantly affected trace metal concentrations of several organs in diabetic rats but had no significant effect in normal rats. Specifically, copper concentration in kidney and duodenum of diabetic rats were influenced by protein X mineral interaction, duodenal zinc concentrations were higher in diabetic rats fed high mineral diets (HMHP and HMLP) compared to diabetic rats fed low mineral diets (LMHP and LMLP) and femur zinc concentration was higher in diabetic rats fed high protein diets (HMHP and LMLP) compared to diabetic rats fed low protein diets (HMLP and LMLP). While hepatic picolinic carboxylase was elevated severalfold in diabetic rats, it was highest in the diabetic rats fed high protein diets (HPHM and HPLM) suggesting that picolinic acid may, at least in part, mediate the effects of dietary protein and minerals on tissue trace metal concentrations in diabetic rats.

Animals↗
PubMed1984

Managing odontogenic infections.

Odontogenic infections are caused by a complex ecosystem of anaerobic and aerobic organisms that arise from the indigenous oral flora. No specific organism or combination of organisms appears to be essential to the disease process. Evacuation of pus and removal of necrotic tissue are the essential steps in treating such infections. Antibiotics are adjuncts to definitive therapy; penicillin is the empiric drug of choice.

Anti-Bacterial Agents↗