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Biomedical subjects

R A Clark

Publications and source records attributed to R A Clark.

At least 415 records · Page 23Linked to original sources
PubMed1979

Traumatic renal artery occlusion.

Six cases of complete occlusion of the main renal artery and one case of incomplete renal artery occlusion secondary to blunt abdominal trauma are reported, and the literature reviewed. The reported cases are analyzed as to clinical and radiographic findings, and mechanism of injury. Left renal artery occlusion occurs due to intimal fracture secondary to deceleration forces on the abdomen. Right renal artery occlusion results from direct epigastric trauma and compression of the artery against the vertebral column. An intravenous urogram with nonvisualization of the affected kidney should lead to immediate angiography. Arteriography is diagnostic, showing abrupt occlusion of the renal artery several centimeters beyond its origin, or before occlusion, an intimal flap.

Abdominal Injuries↗
PubMed1979

Interactions between human granulocytes and Blastomyces dermatitidis.

We studied interactions in vitro between human granulocytes and the yeast-like form of Blastomyces dermatitidis, because granulocytes are prominent in the host response to systemic blastomycosis. In Boyden chamber assays, broth culture filtrates of B. dermatitidis contained levels of granulocyte chemotactic activity that were significantly higher than those present in similar culture filtrates of Histoplasma capsulatum and Cryptococcus neoformans, two fungi that characteristically do not elicit granulocytes in infected tissues. Microscopic study, including electron microscopy, demonstrated that granulocytes phagocytosed B. dermatitidis promptly and efficiently. Moreover, granulocytes emitted light (chemiluminescence) at a brisk rate during phagocytosis of B. dermatitidis, indicating activation of intracellular metabolic pathways. However, fungicidal assay showed that granulocytes (1:1 cell-yeast ratio, 10% serum) killed only 29% of the B. dermatitidis inoculum during 3 h of incubation. Taken together, these findings suggest that there is disparity between phagocytosis and intracellular killing of B. dermatitidis by human granulocytes, perhaps because of resistance of this fungus to granulocyte microbicidal mechanisms.

Blastomyces↗
PubMed1979

Renal vein thrombosis: an underdiagnosed complication of multiple renal abnormalities.

Thirty-one cases of renal vein thrombosis (RVT) were reviewed retrospectively for clinical laboratory, and radiographic findings. An underlying renal disorder was present in 28 cases, absent in only 3. This supports other evidence that RVT is usually a complication of renal disease rather than a primary event, and that nephrotic syndrome may be due to renal disease rather than RVT. The findings also confirmed the large spectrum of urographic appearances in RVT, and were used as a basis for developing specific and liberal indications for renal venography.

Humans↗
PubMed1979

Myeloperoxidase-mediated platelet release reaction.

The ability of the neutrophil myeloperoxidase-hydrogen peroxide-halide system to induce the release of human platelet constituents was examined. Both lytic and nonlytic effects on platelets were assessed by comparison of the simultaneously measured release of a dense-granule marker, [(3)H]serotonin, and a cytoplasmic marker, [(14)C]adenine. Incubation of platelets with H(2)O(2) alone (20 muM H(2)O(2) for 10 min) resulted in a small, although significant, release of both serotonin and adenine, suggesting some platelet lysis. Substantial release of these markers was observed only with increased H(2)O(2) concentrations (>0.1 mM) or prolonged incubation (1-2 h). Serotonin release by H(2)O(2) was markedly enhanced by the addition of myeloperoxidase and a halide. Under these conditions, there was a predominance of release of serotonin (50%) vs. adenine (13%), suggesting, in part, a nonlytic mechanism. Serotonin release by the complete peroxidase system was rapid, reaching maximal levels in 2-5 min, and was active at H(2)O(2) concentrations as low as 10 muM. It was blocked by agents which inhibit peroxidase (azide, cyanide), degrade H(2)O(2) (catalase), chelate Mg(2+) (EDTA, but not EGTA), or inhibit platelet metabolic activity (dinitrophenol, deoxyglucose).These results suggest that the myeloperoxidase system initiates the release of platelet constituents primarily by a nonlytic process analogous to the platelet release reaction. Because components of the peroxidase system (myeloperoxidase, H(2)O(2)) are secreted by activated neutrophils, the reactions described here may have implications for neutrophilplatelet interaction in sites of thrombus formation.

Adenine↗
PubMed1979

Chemotactic factor inactivation by the myeloperoxidase-hydrogen peroxide-halide system.

Polymorphonuclear leukocytes may modulate the acute inflammatory response by the secretion of enzymes capable of inactivating mediators of inflammation. The ability of the myeloperoxidase-H(2)O(2)-halide system of the neutrophil to inactivate chemoattractants was examined using both a radioassay and a morphologic assay of chemotaxis. Incubation of either a complement-derived agent, C5a, or a synthetic formyl-methionyl peptide chemoattractant with the myeloperoxidase system for 15 min at 37 degrees C resulted in essentially complete loss of chemotactic activity. Inactivation was dependent on enzymatically active myeloperoxidase, H(2)O(2) or a peroxide-generating enzyme system, and a halide cofactor. It was blocked by agents which inhibit peroxidase (azide) or degrade H(2)O(2) (catalase). Inactivation of chemoattractants was time-dependent, reaching maximal levels within 1-5 min, and temperature-dependent with no significant inactivation occurring at 0 degrees C. H(2)O(2) alone had no significant inactivating ability at concentrations as high as 10 mM, whereas in the presence of myeloperoxidase and a halide, 0.1 muM H(2)O(2) showed significant activity and 10 muM H(2)O(2) caused complete inactivation. On a molar basis, the order of effectiveness of the halide cofactors was Br(-) > I(-) > Cl(-), although only chloride was fully active at physiologic concentrations. Neutrophils stimulated by phagocytosis or by membraneperturbing agents secrete enzymatic constituents, including myeloperoxidase, and metabolic products such as H(2)O(2). Thus, it is suggested that the myeloperoxidase system acting at an extracellular site serves as an inflammatory control mechanism by virtue of its ability to inactivate neutrophil chemoattractants.

Animals↗
PubMed1979

Intraarterial vasopressin infusion for treatment of Mallory-Weiss tears of the esophagogastric junction.

Five patients with refractory gastrointestinal bleeding from Mallory-Weiss tears of the esophagus were successfully treated with intraarterial infusions of vasopressin. Although transcatheter embolization has been shown to control the hemorrhage from these lesions, increased experience with and ease of vasopressin infusion suggest that infusion therapy should be the primary treatment method when more conservative measures are inadequate. Embolization techniques may be reserved for cases in which vasopressin therapy is contraindicated or unsuccessful.

Catheterization↗
PubMed1979

Complications of central venous catheterization.

The complications of central venous catheterization are discussed in a review of experience and of the literature. The anatomy surrounding the subclavian and internal jugular veins is described. Indications and contraindications of catheterization are reported. Common and unusual complications are discussed and illustrated. Laceration of pleura, subclavian artery puncture, hematoma, catheter malposition, fragment embolization, air embolism, venous thrombosis, and infection are included. The radiologist is responsible for recognizing immediate, as well as delayed, complications of central venous catheterization.

Blood Vessels↗
PubMed1979

Late complications at repair site of operated coarctation of aorta.

Late complications at the repair site of coarctation of the aorta include aneurysms and persistent coarctation. Aneurysms are usually due to failure of the surgical anastomosis and can occur many years after repair. Continued aortic coarctation may be due to either repair failure or failure of the anastomotic site to grow with the patient. Three cases are presented and the literature reviewed.

Aorta, Thoracic↗
PubMed1978

Combined therapy with salbutamol and beclomethasone inhalers in chronic asthma.

A double-blind cross-over trial was carried out to compare the effect of identical placebo with that of salbutamol inhalers used 30 min before inhalation of 100 microgram of beclomethasone dipropionate (B.D.P.) in 18 chronic asthmatics over two consecutive 4-week periods. The salbutamol and B.D.P. combination resulted in a significant improvement in the peak expiratory flow-rate and F.E.V.1, significantly less use of the rescue inhaler, and better control.

Adult↗
PubMed1978

Aspiration needle biopsy for solitary, peripheral lung lesions: a review of 50 examinations.

Percutaneous aspiration needle biopsy forms a simple method of obtaining histological material from solitary peripheral lung lesions. A new method for separating and preparing the material for histological examination is described. The results in 50 cases are recorded with a positive diagnosis in 46. The number of symptomatic complications with this technique is low. The clinical place of the biopsy in management is discussed.

Aged↗
PubMed1978

The influence of computed tomography on clinical decision making in the evaluation of a nonvisualizing kidney.

Nonvisualization of a kidney in an elderly man was investigated by computed tomography (CT). Simple low lying ureteral obstruction was excluded, multiple pathologic abnormalities were identified and causes for the nonvisualization are postulated. This case report demonstrates the important effect CT scanning produced on the clinical management of the patient in question.

Abdominal Neoplasms↗
PubMed1978

Radiology of needle biopsy of pulmonary lesions.

A technique for percutaneous aspiration needle biopsy is described and discussed. It is concluded that it forms a simple and easy way of obtaining histological material and it can be carried out in most radiological departments.

Aftercare↗
PubMed1978

Limitations of fibre-optic bronchoscopy under fluoroscopy in the investigation of peripheral lung lesions.

Transbronchial lung biopsy under fluoroscopic guidance was attempted in 14 patients with discrete peripheral lesions and histological evidence of pathology was obtained in five (37.7%). The difficulties and limitations of the procedure are discussed. The radiation hazard to both patient and bronchoscope are assessed. From this study it is concluded that aspiration needle biopsy is preferred in the investigation of patients with peripheral lung lesions.

Adult↗