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Biomedical subjects

C W Walker

Publications and source records attributed to C W Walker.

At least 19 recordsLinked to original sources
PubMed1992

The use of intravenous gadopentetate dimeglumine in magnetic resonance imaging of synovial lesions.

Spin echo T1- and T2-weighted images and intravenously administered gadopentetate dimeglumine-enhanced T1-weighted images were obtained in 4 normal volunteers and 11 patients (11 joints) with painful, intermittent, or persistent joint swelling of unknown etiology. These studies were retrospectively reviewed to assess the benefits of contrast-enhanced magnetic resonance imaging (MRI) in evaluating the synovium. Normal synovium and joint fluid showed no visually apparent enhancement on images obtained immediately after intravenous injection of gadopentetate dimeglumine. Abnormal synovium enhanced significantly, allowing the precise identification of equivocal or unsuspected synovial disease processes. These results suggest that, in selected cases, enhanced MRI can be a useful adjunct in the evaluation of suspected synovial disease processes.

Adult↗
PubMed1992

Sex steroid levels in the testes, ovaries, and pyloric caeca during gametogenesis in the sea star Asterias vulgaris.

The concentrations of progesterone, testosterone, and estradiol were determined via radioimmunoassay in testes, ovaries, and pyloric caeca of the sea star Asterias vulgaris during one complete and two partial gametogenic cycles. These compounds were found in all tissues examined and were present in quantities similar to those reported previously in other echinoderms and in vertebrates. Testes and ovaries exhibited annual growth cycles during which testicular and ovarian mass increased up to 100-fold as gametes were produced and stored until spawning. Pyloric caecal mass varied during the annual reproductive season; however, no seasonal trends were apparent. In the testes, sex steroid levels were highest at the onset of spermatogenesis. Transient increases in the levels of estradiol coincided with spermatogonial mitotic proliferation. Transient increases in the levels of testosterone and progesterone in the testes coincided with spermatogenic column formation and with spermiogenesis, respectively. In the ovaries, estradiol and testosterone levels were highest at the onset of oogenesis while progesterone levels did not change significantly throughout the annual gametogenic cycle. Male and female pyloric caeca exhibited similar seasonal variations in levels of sex steroids as compared with the gonads. It is hypothesized that transient increases in the levels of sex steroids during gametogenesis may serve as endogenous modulators of reproduction.

Animals↗
PubMed1992

Androgen metabolism in somatic and germinal tissues of the sea star Asterias vulgaris.

1. Cell-free homogenates of male and female pyloric caeca, body wall, testis and ovary were incubated with radiolabeled 3H-androstenedione. 2. Pyloric caeca had highest rates of androstenedione conversion. The predominant metabolites in the pyloric caeca were testosterone, 5 alpha-androstane-3 beta, 17 beta-diol and 5 beta-androstane-3 beta, 17 beta-diol. 3. In body wall, testicular and ovarian homogenates, androstenedione was converted primarily to testosterone and also to 5 alpha-androstanedione and epiandrosterone. 4. Qualitative and quantitative differences in androgen metabolism in somatic and germinal tissues may be related to tissue-specific regulation of cellular metabolism.

Androgens↗
PubMed1992

Occult fracture patterns of the knee associated with anterior cruciate ligament tears: assessment with MR imaging.

One hundred consecutive magnetic resonance (MR) images of the knee in patients with acute complete anterior cruciate ligament (ACL) tears were reviewed to evaluate the prevalence and patterns of associated occult fractures. Eighty-nine occult fractures were identified in 56 knees. All occult fractures were in the posterior aspect of the lateral tibial plateau. Of these, occult fractures were isolated in 24 cases (43%) and were in combination with fractures in the middle aspect of the lateral femoral condyle in 26 (46%), with fractures in the posterior aspect of the medial tibial plateau in four (7%), and with fractures involving all three areas in one (2%). Disruption of the ACL under valgus stress leads to anterior translation of the tibia and relative external rotation of the femur. This allows impaction of the posterior portion of the lateral tibial plateau against the middle of the lateral femoral condyle and accounts for the unique pattern of occult fractures associated with ACL tears. An occult fracture of the posterior lateral tibial plateau with or without an associated fracture in the lateral femoral condyle ("kissing contusion") is a relatively frequent finding in acute ACL tears and, when present, is highly suggestive of such an associated tear.

Adolescent↗
PubMed1992

First non-vertebrate member of the myc gene family is seasonally expressed in an invertebrate testis.

We have cloned and characterized the first non-vertebrate member of the myc gene family, pAv-myc, from testes of the Northern sea star, Asterias vulgaris (Echinodermata). We have used an oligonucleotide that is complementary to the virtually 100% conserved vertebrate c-myc box A in the second exon and a cDNA library constructed from spermatogenically active testes. Relatives of this echinoderm existed approximately 100 million years prior to the origin of the earliest known organism for which c-myc sequence is currently available (the trout). Nonetheless, our cDNA encodes a protein with approximately 30% amino acid identity and 46% overall conservation to human c-myc. Regions of substantially higher conservation (63-95%) correspond in order to the transcriptional activation (boxes A, B and C), casein kinase II phosphorylation, nuclear-targeting, basic DNA-binding and oligomerization domains in the second and third exons of human c-myc. Sea star c-myc cDNA detects a 2.7-kb transcript on Northern blots of monthly samples of testicular tissue from field-collected individuals (n = 6-8), indicating peak expression during active spermatogenesis. This is also the first example of seasonal variation in expression of c-myc during spermatogenesis in laboratory or natural populations of any animal. It is intriguing to speculate about the potential oncogenic character of c-myc in this invertebrate, in which tumors have not yet been observed, and about the possibility that c-myc is more widely present in eucaryotes than has been anticipated.

Amino Acid Sequence↗
PubMed1991

Arthrography of painful hips following arthroplasty: digital versus plain film subtraction.

Digital and manual subtraction images obtained during the arthrographic evaluation of 78 painful hip prostheses were reviewed retrospectively. Revision arthroplasty was performed in 53 of these cases, and the arthrographic and surgical findings were correlated. The digital and manual subtraction images were evaluated without knowledge of the surgical results using established criteria for component loosening. Digital subtraction arthrography of the femoral component demonstrated a 96% sensitivity and 100% specificity for the diagnosis of component loosening. Sensitivity and specificity for acetabular component loosening were 83% and 80%, respectively. Plain film subtraction of the femoral component demonstrated a 79% sensitivity and 100% specificity; the sensitivity and specificity for the acetabular component were 75% and 80%, respectively. The difference between detection of femoral component loosening on digital as opposed to manual subtraction images was statistically significant (P less than 0.05). This study demonstrate that digital subtraction improves the evaluation of femoral component loosening in painful hip prostheses.

Arthrography↗
PubMed1991

Case report 667. Fibrolipomatous hamartoma of the median nerve.

Fibrolipomatous hamartoma of a nerve represents an uncommon soft-tissue tumor which typically involves the median nerve distribution near the wrist. Macrodactyly may or may not be present. The application of MRI using routine T1- and T2-weighted spin echo imaging sequences reveals serpiginous structures with low signal intensity. These structures probably represent the neural elements and associated perineural fibrosis. Further experience may allow for an accurate preoperative diagnosis of this tumor.

Child, Preschool↗
PubMed1991

Curriculum for musculoskeletal radiology.

Although general suggestions have been made regarding a radiology residency curriculum, no specific list of entities has been offered. Over the past ten years, we have developed a resident-run morning conference in musculoskeletal radiology that is supervised by faculty and covers a specific curriculum. We offer our curriculum as an example that may assist other departments in developing their own curricula.

Curriculum↗
PubMed1991

The changing epidemiology of tuberculosis and other mycobacterial infections in the United States: implications for the radiologist.

Diseases consequent to infection with mycobacterial organisms, such as Mycobacterium tuberculosis and other mycobacterial species, remain a significant health problem in the United States. Over the past decade several new factors have amplified this problem, the most significant of which is the ongoing epidemic of infection with the human immunodeficiency virus. This review will discuss the changing epidemiology of mycobacterial disease and emphasize the significance of these changes to the radiologist.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Radiologic evaluation of limb-lengthening procedures.

Limb-lengthening procedures are being performed at an increasing rate in the United States. A successful outcome relies heavily on serial radiologic evaluation. Therefore, it is important for radiologists to become familiar with the various techniques, their normal radiologic appearance, and associated complications. Lengthening by the Wagner method, distraction epiphysiolysis, and the Ilizarov technique are illustrated. Chondrodiatasis and callotasis also are discussed.

Bone Lengthening↗
PubMed1991

The radiographic spectrum of renal osteodystrophy.

Chronic renal failure often results in bone changes, collectively known as renal osteodystrophy. These changes include osteitis fibrosa, osteosclerosis, soft tissue calcifications, osteomalacia (in adults) and rickets (in children). Early recognition of renal osteodystrophy allows more aggressive clinical control of serum calcium and phosphate levels. Intervention may spare the patient late complications such as fractures, pain and loss of skeletal function.

Aluminum Hydroxide↗
PubMed1990

Indium-111 leukocyte localization in infected prosthetic graft.

Infective endocarditis can be difficult to prove, even in the face of strong clinical suspicion. A case in which standard methods of diagnosis failed to demonstrate endocarditis in a patient with recurrent Staphylococcus aureus bacteremia and porcine aortic valve is reported. An In-111 labelled leukocyte SPECT study demonstrated uptake in the aortic root and leaflets, and autopsy demonstrated vegetations on the leaflets. In-111 may prove useful in demonstrating endocarditis in patients with prosthetic valve infection.

Aged↗
PubMed1990

Radiologic manifestations of adult tuberculosis.

Adult pulmonary tuberculosis commonly presents with radiographic findings of upper lobe cavitary opacities, in which case the correct diagnosis is usually suspected. However, other radiographic presentations of this disease in the adult include intrathoracic adenopathy, pleural effusion, lower lobe consolidation, a miliary pattern, and a solitary nodule. In these latter cases, tuberculosis may not be considered in the differential diagnosis. This article discusses the protean manifestations of adult pulmonary tuberculosis.

Adult↗
PubMed1990

A rapid technique for detection of resistance to chloramphenicol in Streptococcus pneumoniae and comparison with minimum inhibitory concentration and disk-diffusion methods.

Fifty-two strains of Streptococcus pneumoniae were examined for production of chloramphenicol acetyltransferase (CAT) by a rapid technique based upon induction of enzyme activity and chemical assay. This method was compared with one measuring the minimum inhibitory concentration (MIC) by agar dilution and a diffusion test with disks containing 10 micrograms, 30 micrograms and 50 micrograms of chloramphenicol. The MIC for 13 chloramphenicol-resistant strains was 16 mg/L and for 39 sensitive strains less than or equal to 4 mg/L. The chemical assay clearly distinguished resistant from sensitive strains; it was technically simple and provided results within 90 min. The distinction between sensitive and resistant bacteria in the disk diffusion assay was clearer with 10-micrograms than with 30-microgram and 50-micrograms disks. However, the chemical CAT assay, with enzyme induction, is recommended when a rapid result is required.

Bacteriological Techniques↗
PubMed1989

Pulmonary embolism: chest radiographic abnormalities.

The value of chest radiography in the diagnosis of pulmonary embolism has been investigated extensively. Although the chest radiograph seldom permits one to say whether embolism is or is not present, it is still an essential component in the evaluation of the patient with suspected pulmonary embolism. This article stresses the radiographic abnormalities that occur with pulmonary embolism and defines the role of the chest radiograph for evaluation of this disorder.

Humans↗
PubMed1989

Complications from extravasated retroperitoneal barium: case report and review of the literature.

Extravasation of barium into the retroperitoneum is an uncommon complication of radiologic examinations of the gastrointestinal tract. It may occur during evaluation of either the upper or lower tract. A case is presented in which the result was abscess formation, a potential delayed complication of duodenal perforation and retroperitoneal extravasation of barium. In this case, medical treatment was successful.

Abscess↗
PubMed1989

Bronchogenic cysts.

Bronchogenic cysts are relatively uncommon congenital lesions. They may be detected on routine radiography in asymptomatic patients or may present with various manifestations, some of which may be life-threatening. Age at diagnosis ranges from infancy to late adulthood, with asymptomatic lesions occurring more often in older children and adults. Cysts may be located in subcarinal, paratracheal, hilar, paraesophageal and intrapulmonary sites. The chest radiograph is the primary diagnostic study, with computed tomographic scans of the chest providing more definitive evaluation. Despite some controversy, surgery is considered the treatment of choice, even in the asymptomatic patient.

Bronchogenic Cyst↗