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Biomedical subjects

C W Walker

Publications and source records attributed to C W Walker.

At least 37 records · Page 2Linked to original sources
PubMed1995

Translocation t(3;12)(q28;q14) in parosteal lipoma.

Parosteal lipoma is a rare primary benign bone tumor demonstrating histopathologic features similar to those seen in the commonly occurring lipoma of soft tissue. Cytogenetic studies of soft tissue lipoma have demonstrated frequent abnormalities of 12q13-15. To the best of our knowledge the cytogenetic findings in parosteal lipoma have not yet been described. Cytogenetic analysis of a parosteal lipoma of the femur of a 51-year-old female revealed a t(3;12)(q28;q14), indicating that bone and soft tissue lipomas are cytogenetically similar and likely share a common histopathogenesis.

Chromosome Mapping↗
PubMed1995

Effect of estradiol and progesterone on c-myc expression in the sea star testis and the seasonal regulation of spermatogenesis.

Analysis of the expression of cell cycle control genes provides a sensitive assay for mitotic and meiotic progression under experimental conditions. Transcription of the c-myc proto-oncogene and thymidine incorporation into DNA were both used to assay the mitogenic effects of estradiol and progesterone on the testicular germinal epithelium of the starfish Asterias vulgaris. Experimental in vitro studies during the annual spermatogenic cycle show that testes are not sensitive to mitotic stimulation by estradiol alone, whereas progesterone alone is mitotically inhibitory. The germinal epithelium can only be mitotically stimulated by estradiol after pretreatment with progesterone. The net increase in mitotic activity following a progesterone to estradiol transfer is dependent on the length of progesterone pretreatment. Overall, the seasonal pattern of testicular estradiol and progesterone levels evident in field populations of A. vulgaris (Hines et al., 1992a: Endocrinology 100:1468-1471) do not appear to be responsible for initiating spermatogonial mitosis at the onset of the annual spermatogenic cycle. Expression rates of the c-myc proto-oncogene are substantially more sensitive than thymidine incorporation in quantifying mitotic activity. Measuring proto-oncogene expression provides an ideal experimental approach to investigations of the regulatory mechanisms that control growth and reproduction in marine organisms.

Animals↗
PubMed1995

The third head of gastrocnemius in CT images.

A 17 year old male patient was undergoing a CT scan for pain and swelling of the left knee. The CT images of both legs, taken simultaneously, revealed an asymmetry of the musculature in the popliteal fossa of the right leg. Serial images indicated the presence of a third head joining the medial head of gastrocnemius.

Adolescent↗
PubMed1994

Unusual radiological features in Paget's disease of bone.

The radiological diagnosis of Paget's disease of bone is usually straightforward because most cases conform to well-established classic descriptions. Diagnosis becomes more difficult, however, when radiological appearances are not typical or other disease processes mask or alter the behavior of Paget's disease. Examples are presented to illustrate four categories of unusual radiological presentation of Paget's disease: (1) unusual disease progression, (2) massive post-immobilization lysis, (3) metastatic spread to pagetic bone, and (4) vertebral end-plate destruction that mimics infection.

Bone Diseases↗
PubMed1994

Parosteal lipoma: MR imaging characteristics.

OBJECTIVE: The purpose of this study was to determine the characteristics of parosteal lipomas on MR imaging. MATERIALS AND METHODS: We retrospectively reviewed the images and medical records of eight patients with surgically and pathologically confirmed parosteal lipomas. Radiologic studies performed included conventional radiography and MR imaging (n = 8), CT (n = 7), conventional tomography (n = 2), and scintigraphy (n = 5). RESULTS: Osseous reaction was present in all cases, manifesting as either mild cortical thickening best seen on magnification radiographs or larger osseous excrescences seen on all radiologic images. These osseous reactions were surrounded by the lipomatous component of the neoplasm and created a firm attachment of the neoplasm to the underlying bone. The lipomatous component showed typical features of adipose tissue on all images and was usually seen on radiographs (n = 7). However, CT or MR imaging was needed to determine the anatomic location and relationship to surrounding structures before surgery. MR imaging was considered superior to CT for preoperative assessment, primarily because of its multiplanar imaging capability. In addition, cartilage and fibrous tissue (n = 3) were identified adjacent to larger osseous excrescences. Associated muscle atrophy in three cases was caused by nerve impingement. These manifestations of parosteal lipoma were also better assessed with MR images because of improved contrast resolution. The distribution of muscle atrophy could be used to determine the site of nerve involvement preoperatively. CONCLUSION: We conclude that MR imaging is the most useful adjunct to conventional radiography in the presurgical evaluation of parosteal lipomas because of its multiplanar imaging capabilities and improved contrast resolution for detecting muscle atrophy and site of nerve involvement when present. These factors are important for preoperative assessment to help guide surgical intervention.

Adolescent↗
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↗