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Biomedical subjects

G Forbes

Publications and source records attributed to G Forbes.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1991

Epidemiology, bacteriology and control of an outbreak of Nocardia asteroides infection on a liver unit.

An outbreak of Nocardia asteroides infection affecting seven patients is described. Over a 5-week period, five patients with liver disease admitted to a ward developed clinical and laboratory evidence of nocardiosis, and two further cases were diagnosed 3 and 5 months later. Three out of the five patients who received specific antimicrobial therapy responded to treatment; in three patients nocardia infection was considered to have contributed to death. In six out of the seven patients, nocardiosis followed immunosuppression. A common-source outbreak was considered to be responsible for infection in the first five patients. In two patients, presentation of infection 5 and 7 months after the first case may have been due to prolonged colonization or subclinical infection with Nocardia. Biotyping of the seven isolates using a fluorogenic biochemical method identified three distinct strains of N. asteroides. The most probable source of Nocardia was contaminated brick and plaster dust arising from building work in an area adjacent to the ward. However, samples of air, dust and water failed to yield N. asteroides. Infection control measures included ward closure followed by thorough cleaning, and formaldehyde fumigation.

Adult↗
PubMed1990

Nocardia infection in patients with liver transplants or chronic liver disease: radiologic findings.

The radiologic findings in eight patients with nocardiosis were reviewed. Infection followed liver transplantation in six cases and was associated with chronic liver disease in two. Abnormalities of the chest radiograph predominated and included pleural effusions (n = 6), consolidation (n = 5), cavitating lesions (n = 1), and intrapulmonary nodules (n = 3), but there were no diagnostic features. The diagnosis was made on the basis of bronchial washings (n = 3), skin aspiration (n = 3), pleural fluid (n = 1), and aspiration biopsy of a pulmonary nodule (n = 1). Computed tomography (CT) was helpful in evaluating chest disease in three cases and allowed guided biopsy to obtain material for a definitive diagnosis. In three patients skin lesions in disseminated disease were associated with cerebral lesions seen at CT. A definitive tissue diagnosis is especially important in patients who have received transplants because of malignancy, since the radiologic manifestations of this unusual infection may mimic metastatic recurrence. Conventional radiography and CT are nonspecific but will enable determination of disease extent and selection of the most suitable site for tissue sampling, which is required to confirm the diagnosis.

Adult↗
PubMed1990

Optic nerve sheath meningoceles. Clinical and radiographic features in 13 cases with a review of the literature.

Thirteen patients with dilated intraorbital optic nerve sheaths with an expanded, patulous cerebrospinal fluid (CSF) space were studied with high-resolution computed tomography (CT) or magnetic resonance imaging (MRI). Eleven patients had bilateral findings. Headache or visual complaints, or both, were present in all patients. Signs of optic nerve dysfunction were present in eight patients. Three patients had visual acuity worse than 20/200. Cerebrospinal fluid pressure was mildly elevated in two patients. Three patients underwent a surgical procedure; visual acuity improved in one. The authors propose the term meningocele for this condition and suggest MRI with fat-suppression techniques and off-axis sagittal views as the radiographic procedure of choice.

Adolescent↗
PubMed1989

Effect of testosterone on muscle mass and muscle protein synthesis.

We have studied the effect of a pharmacological dose of testosterone enanthate (3 mg.kg-1.wk-1 for 12 wk) on muscle mass and total-body potassium and on whole-body and muscle protein synthesis in normal male subjects. Muscle mass estimated by creatinine excretion increased in all nine subjects (20% mean increase, P less than 0.02); total body potassium mass estimated by 40K counting increased in all subjects (12% mean increase, P less than 0.0001). In four subjects, a primed continuous infusion protocol with L-[1-13C]leucine was used to determine whole-body leucine flux and oxidation. Whole-body protein synthesis was estimated from nonoxidative flux. Muscle protein synthesis rate was determined by measuring [13C]leucine incorporation into muscle samples obtained by needle biopsy. Testosterone increased muscle protein synthesis in all subjects (27% mean increase, P less than 0.05). Leucine oxidation decreased slightly (17% mean decrease, P less than 0.01), but whole-body protein synthesis did not change significantly. Muscle morphometry showed no significant increase in muscle fiber diameter. These studies suggest that testosterone increases muscle mass by increasing muscle protein synthesis.

Adult↗
PubMed1988

Complications of spinal cord arteriography: prospective assessment of risk for diagnostic procedures.

A prospective study was done of complications associated with 134 consecutive diagnostic spinal cord arteriograms in 96 patients (63 men and 33 women aged 17-78 years). Patients were examined for either arteriovenous malformation (n = 88) or tumor (n = 8), as indicated by myelography. Among the complications, 11 (8.2%) were local, five (3.7%) were systemic nonneurologic, and three (2.2%) were neurologic (two were associated with full recovery in less than 24 hours, and one was associated with full recovery in less than 1 week). No specific clinical or technical factors were significantly associated with the development of neurologic complications. Details of the clinical profile, angiographic technique, and pathologic findings for each patient were recorded and analyzed with respect to the potential risk for arteriographic complications. Diagnostic spinal cord arteriography had an acceptable risk within the range of other neuroangiographic diagnostic procedures.

Adult↗
PubMed1988

The natural history of unruptured intracranial arteriovenous malformations.

The authors conducted a long-term follow-up study of 168 patients to define the natural history of clinically unruptured intracranial arteriovenous malformations (AVM's). Charts of patients seen at the Mayo Clinic between 1974 and 1985 were reviewed. Follow-up information was obtained on 166 patients until death, surgery, or other intervention, or for at least 4 years after diagnosis (mean follow-up time 8.2 years). All available cerebral arteriograms and computerized tomography scans of the head were reviewed. Intracranial hemorrhage occurred in 31 patients (18%), due to AVM rupture in 29 and secondary to AVM or aneurysm rupture in two. The mean risk of hemorrhage was 2.2% per year, and the observed annual rates of hemorrhage increased over time. The risk of death from rupture was 29%, and 23% of survivors had significant long-term morbidity. The size of the AVM and the presence of treated or untreated hypertension were of no value in predicting rupture.

Adolescent↗
PubMed1987

Analysis of cranial neural crest distribution in the developing heart using quail-chick chimeras.

Previous studies have shown that ablation of cranial neural crest results in heart malformations in chick embryos. Cranial neural crest cells populate all of the pharyngeal arches and provide the mesenchymal walls of the aortic arch arteries. Neural crest cells migrate from the pharyngeal apparatus into the outflow region of the heart. However, it is not known which of the pharyngeal arches contribute ectomesenchyme to the developing heart nor has a pattern of distribution in the outflow region been established. In the present study, premigratory presumptive arch neural crest from quail embryos was grafted homotopically onto early chick embryos. On Day 6 of incubation, the chimeric embryos were fixed and processed for histological evaluation. The neural crest providing mesenchyme to pharyngeal arches 1 and 2 was not associated with the developing heart. Neural crest presumptive for arches 3, 4, and 6 was found distributed to the outflow region of the heart. Neural crest from arch 4 contributed the largest number of cells to the developing aorticopulmonary and conotruncal septa. This information indicates that ablations of neural crest presumptive for arches 3, 4, and 6 influence heart development directly while lesions of other areas of cranial neural crest probably influence heart development only secondarily with the primary effects occurring in the pharyngeal arches.

Animals↗
PubMed1987

Relationship of the optic nerve to the paranasal sinuses as shown by computed tomography.

Restricted exposure and inconsistencies in sinus pneumatization place the optic nerve at risk during operations on the sphenoid sinus and posterior ethmoid cells. In this study, computed tomography was used to examine these relationships. We reviewed 80 patients who underwent high-resolution computed tomographic scanning for ophthalmologic complaints in which the scan was negative. Forty-eight percent of posterior ethmoid cells are separated from the optic nerve by the thin bony lamina of the optic canal. Nearly 90% of sphenoid sinuses contact the ipsilateral optic nerve and 10% contact both nerves. Eight percent of posterior ethmoid cells override the ipsilateral sphenoid sinus and contact the optic nerve on that side. Paraxial reformatted displays allowed estimation of the degree of projection of the optic nerve into adjacent sinus cavities. Three percent of optic nerves have significant projection into the posterior ethmoid cell, and 23% project significantly into the sphenoid sinus. The width of the bony plate that separates the optic nerve from the sinus cavity was the same for sphenoid and ethmoid sinuses. Although sinus pneumatization varies among individuals, right and left sides are generally similar within one person.

Adolescent↗