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Biomedical subjects

G Forbes

Publications and source records attributed to G Forbes.

At least 19 recordsLinked to original sources
PubMed2005

Virtual colonoscopy: issues in implementation.

The following issues and requirements related to the implementation of a CT colonography (CTC) service are important: (i) policies are needed regarding the indications for CTC. Concomitant with this is the need for education of potential referrers and patients. Expectations of the procedure, particularly by general practitioners, may be unrealistic and indications for referral may otherwise be inappropriate. At present there is not general acceptance of CTC for screening asymptomatic persons; (ii) a flexible approach to CT protocols is useful, dependent on the indication for and clinical context of referral, the age and body habitus of the patient; (iii) attention to the issues related to the special skills required by the reporting radiologist. While there is a temptation to regard CTC interpretation as an extension of skills used in interpreting other cross-sectional images, there is a need to realise that there are skills required specific to CTC and there should be adequate provision for training; (iv) matters related to reporting, such as reporting format, and lesions that will be reported/not reported; and (v) informed consent from the patient. Information should be provided with regard to the limitations of CTC, the implications of a positive finding and radiation dosage.

Colonic Diseases↗
PubMed2000

Apical microsurgery for failed endodontics.

The operating microscope allows the surgeon unparalleled visualization of the root end structures for periapical surgery. The ultrasonic root end preparation tips enable debridement of the resected root end 2 to 4 mm in the long axis of the root. These advances have allowed periapical surgery to be performed at a new level of excellence with, we believe, more predictable healing.

Apicoectomy↗
PubMed1998

Characterization of siglec-5, a novel glycoprotein expressed on myeloid cells related to CD33.

We describe the characterization of siglec-5 (sialic acid-binding Ig-like lectin-5), a novel transmembrane member of the immunoglobulin superfamily, highly related to the myeloid antigen, CD33. A full-length cDNA encoding siglec-5 was isolated from a human activated monocyte cDNA library. Sequencing predicted that siglec-5 contains four extracellular immunoglobulin-like domains, the N-terminal two of which are 57% identical to the corresponding region of CD33. The cytoplasmic tail is also related to that of CD33, containing two tyrosine residues embodied in immunoreceptor tyrosine-based inhibitory motif-like motifs. The siglec-5 gene was shown to map to chromosome 19q13.41-43, closely linked to the CD33 gene. When siglec-5 was expressed on COS cells or as a recombinant protein fused to the Fc region of human IgG1, it was able to mediate sialic acid-dependent binding to human erythrocytes and soluble glycoconjugates, suggesting that it may be involved in cell-cell interactions. By using specific antibodies, siglec-5 was found to have an expression pattern distinct from that of CD33, being present at relatively high levels on neutrophils but absent from leukemic cell lines representing early stages of myelomonocytic differentiation. Western blot analysis of neutrophil lysates indicated that siglec-5 exists as a disulfide-linked dimer of approximately 140 kD.

Amino Acid Sequence↗
PubMed1996

Utility of creatinine excretion in body-composition studies of healthy men and women older than 60 y.

This study evaluated whether aging alters the usefulness of creatinine excretion as an index of lean body mass (LBM) or muscle mass in healthy men and women. Creatinine excretion was determined while 24 young (15 men and 9 women aged < 32 y) and 38 older (23 men and 15 women aged > 60 y) healthy volunteers stayed at a clinical research center for 3 d. Total LBM was determined by 40K counting in all subjects, and cross-sectional areas of upper arm and thigh muscles were determined in some subjects (10 young, 20 old) by magnetic resonance imaging. The slopes and intercepts of the regression equations relating LBM to average daily creatinine excretion were the same in the younger and older groups, and the precision with which LBM could be determined from creatinine excretion was not diminished by aging. Creatinine excretion was closely correlated with cross-sectional areas of upper arm (r = 0.85) and thigh (r = 0.88) muscles, and the slopes and intercepts of the regression equations were not significantly affected by age. The older group had a mean LBM smaller than that of the younger group, which was accounted for entirely by a smaller muscle mass. Mean resting metabolic rate (RMR), whole-body protein turnover rate, and thigh strength were lower in the older group than in the young group. Adjustment of RMR and protein turnover for creatinine excretion or LBM eliminated the age effects. Strength was lower in the older group even after adjustment for creatinine excretion or LBM. This study indicates that creatinine excretion is useful for evaluating body composition in both young and old subjects.

Adult↗
PubMed1996

Interobserver variability in angiographic measurement and morphologic characterization of intracranial aneurysms: a report from the International Study of Unruptured Intracranial Aneurysms.

PURPOSE: To determine the variability in assessment of the principal inherent characteristics of intracranial aneurysms through the evaluation of interobserver variability for material with uniform quality. METHODS: Blinded interpretations of a single set of cerebral arteriograms of 55 aneurysms were evaluated by several statistical approaches. RESULTS: Excellent correlations were found for the detection and measurement of aneurysms after adjusting for geometric distortion caused by magnification. Progressively decreasing correspondence was found for factors that characterized morphology, including, in order, determination of margins, assessment of accessory appendages, and identification of a neck. DISCUSSION: Correction for geometric distortion was the most critical factor that influenced uniform measurement of size. Standards for measurement and morphologic characteristics were subsequently established for use in the International Study of Unruptured Intracranial Aneurysms.

Adult↗
PubMed1996

Vascular lesions in the orbit.

Vascular lesions in the postbulbar region of the orbit include hemangiomas, lymphangiomas, dural arteriovenous fistulae, aneurysms, varices, and hematic cysts. The heterogeneous nature of the group indicates the diverse origins of the different entities. Cross-sectional imaging, including computed tomography and magnetic resonance imaging, is used for the majority of these lesions, although special computed tomography and magnetic resonance techniques and selective arteriography occasionally are needed for specific indications.

Adult↗
PubMed1996

Fluids and electrolytes--clinical aspects.

Medical practice rests on the foundation of science. Clinicians are constantly making practical decisions and dealing with immediate situations that demand solutions. Time should be taken to focus on those scientific principles that underlie our diagnostic and therapuetic maneuvers. This section of Pediatrics in Review presents selected topics that are relevant to practice from the areas of physiology, pharmacology, biochemistry, and other disciplines; clarification of these will augment the pediatrician's understanding of clinical procedures.

Acidosis↗
PubMed1995

Pilocytic astrocytomas: well-demarcated magnetic resonance appearance despite frequent infiltration histologically.

OBJECTIVE: To determine the magnetic resonance imaging (MRI) characteristics of pilocytic astrocytomas and to correlate them with the histopathologic findings. MATERIAL AND METHODS: MRI examinations and histopathologic findings in 56 patients with pilocytic astrocytomas were retrospectively reviewed. In 38 patients, findings on MRI were compared with those on computed tomography. RESULTS: The tumors occurred at all levels of the central nervous system, including the spinal cord. The intracranial tumors were periventricular (73%) or periaqueductal (9%). All tumors were typical pilocytic astrocytomas and were grade 1 on the basis of the World Health Organization classification. At operation, they were often circumscribed and cystic. Radiologically, the tumors were well demarcated (96%), had benign morphologic features, and almost always showed enhancement (94%). CONCLUSION: MRI of pilocytic astrocytomas typically demonstrated a relatively large, sharply demarcated periventricular mass with pronounced contrast enhancement but minimal or no associated edema. Often, the tumors were cystic on MRI. Despite the well-demarcated appearance grossly and on MRI, pathologic review showed that many of these tumors (64%) infiltrated the surrounding parenchyma, particularly the white matter.

Adolescent↗
PubMed1993

Spontaneous midbrain hemorrhage: report of seven new cases.

Spontaneous midbrain hemorrhage is a unique brain-stem vascular lesion. Sixty-six cases have been reported in the literature, to which we add seven. Of the total of 73 patients reviewed, most presented acutely (66%), but subacute (22%) and chronic onsets (12%) also occurred. Neuro-ophthalmologic abnormalities were found in 88% of patients. Some alteration of consciousness and headache occurred in most patients. Hemiparesis, hemisensory loss, and ataxia were less frequent manifestations. Vascular malformations were suspected or proved in 37% of patients, hypertension was present in 21%, and a bleeding diathesis was noted in 5%. No underlying cause was apparent in 37%. Most patients improved with supportive care only. At follow-up, 23% of patients had no neurologic deficits. In 51% of patients, minor neurologic deficits persisted, related chiefly to cranial nerves III and IV. Moderate deficits persisted in 16% of patients, and 5% of patients died.

Adolescent↗
PubMed1993

The differential diagnosis of orbital calcification as detected on computed tomographic scans.

We reviewed 350 orbital computed tomographic scans to determine the frequency, significance, and differential diagnosis of calcified lesions. Of 171 suitable scans that fulfilled the study criteria, 37 (22%) showed calcific densities. The most common intraocular lesion that contained calcium was retinoblastoma, and the most frequently calcified extraocular masses were vascular lesions (hemangioma, lymphangioma, and varix). We describe two orbital tumors--metastatic colonic carcinoma and primary orbital malignant melanoma--that previously have not been reported as having calcification. The presence of calcification within lesions of the lacrimal gland fossa usually, but not always, portends malignant disease.

Calcinosis↗
PubMed1993

Oligodendrocyte injury is an early event in lesions of multiple sclerosis.

The ultrastructural features of 11 stereotaxic brain biopsy specimens that demonstrated inflammatory primary demyelination consistent with acute multiple sclerosis were examined. Uniform widening of inner myelin lamellae (biphasic myelinopathy) and degeneration of inner glial loops ("dying-back" oligodendrogliopathy) were early pathologic abnormalities that antedated complete destruction of myelin sheaths. Perivascular inflammatory cells (lymphocytes, macrophages, and occasional plasma cells) were in intimate contact with degenerating myelin sheaths. The response of astrocytes was prominent, even in areas of minimal demyelination. Oligodendrocytes were morphologically preserved in early lesions but proliferated at the periphery of active lesions. Thinly myelinated axons indicative of central nervous system-type remyelination by oligodendrocytes were observed primarily at the edge of plaques. Disturbances of the myelinating function of oligodendrocytes--unaccompanied by death of these cells--may be among the earliest pathologic features in multiple sclerosis.

Adolescent↗
PubMed1992

Diffuse "fibrillary" astrocytomas: correlation of MRI features with histopathologic parameters and tumor grade.

MR images in 54 patients with biopsy-proven diffuse or "fibrillary" astrocytomas were analyzed and compared with the histopathologic features in order to determine which histopathologic characteristics underlie the radiographic findings in these gliomas and whether radiographic findings are more closely correlated with individual histopathologic characteristics than with histologically determined tumor grade. The MRI features studies included tumor heterogeneity, edema, mass effect, border sharpness, "anatomic invasion", contrast enhancement, hemorrhage, and the presence of flow voids, calcium and cyst formation. The histopathologic characteristics studied included cellular atypia, mitoses, cellularity, endothelial proliferation, necrosis and tumor grade. Edema (P less than 0.01), flow voids (P = 0.02) and contrast enhancement (P less than 0.01) demonstrated a direct correlation with tumor grade, but edema (P less than 0.01) and contrast enhancement (P less than 0.01) also demonstrated a significant correlation to tumor cellularity. Tumor heterogeneity was associated with the presence of necrosis (P = 0.01). Hemorrhage occurred only in high grade tumors, where it correlated with endothelial proliferation (P = 0.04).

Astrocytoma↗
PubMed1992

Effect of testosterone on metabolic rate and body composition in normal men and men with muscular dystrophy.

We have examined the effect of testosterone enanthate injections (3 mg/kg.week, im) on the basal metabolic rate (BMR) estimated by indirect calorimetry and on lean body mass (LBM) estimated by 40K counting in four normal men and nine men with muscular dystrophy. Testosterone treatment increased plasma testosterone levels in all subjects (3-fold mean elevation). BMR increased significantly after 3 months of testosterone treatment (mean, 10%; P less than 0.01; 13% mean increase in the men with muscular dystrophy and 7% mean increase in the normal subjects). BMR remained elevated (mean increase, 9%) after 12 months of testosterone treatment in four men with muscular dystrophy. LBM also was significantly higher after 3 months of treatment (mean, 10%; P less than 0.01) and remained elevated at 12 months. The percent increase in LBM was similar in men with muscular dystrophy (+10%) and normal men (+11%). When BMR was adjusted for the increase in LBM by linear regression, the men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment (mean increase, 7%), but not after 12 months. The normal men did not have an increase in adjusted BMR. Testosterone treatment for 12 months slightly reduced body fat, whereas there was an increase in body fat in subjects with muscular dystrophy who were treated with placebo for 12 months. We conclude that there is a significant increase in BMR associated with pharmacological testosterone treatment, which for the most part is explained by the increase in LBM. However, in men with muscular dystrophy, there is a small hypermetabolic effect of testosterone beyond that explained by increased LBM.

Adult↗