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Biomedical subjects

G Forbes

Publications and source records attributed to G Forbes.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1986

Magnetic resonance imaging, electroencephalogram, and selected neuropsychological testing in staged corpus callosotomy.

A 21-year-old man with medically intractable secondarily generalized atonic seizures underwent a corpus callosotomy on Nov 5, 1981. Though improved, the falling seizures persisted. In January 1984, magnetic resonance imaging (MRI) documented that the anterior quarter of the corpus callosum remained intact. In March, the patient underwent a completion of the callosotomy, at which time the MRI findings were corroborated. Since the second surgery, a further improvement in seizure control has been observed. Use of MRI can document both noninvasively and in vivo the extent of corpus callosotomy. The implications of selected neurophysiologic and neuropsychological findings are also discussed.

Adult↗
PubMed1986

Radiolabeled polyvinyl alcohol particles: a potential agent to monitor embolization procedures.

Polyvinyl alcohol sponge (PVA) is a widely used angiographic embolic agent. The radiolabeling of PVA can accurately identify particle localization and may decrease the possibility of patient morbidity from embolization to distal sites. We incorporated 99mTc sulfur colloid (SC) into PVA by heating. Animal experiments demonstrated the in vivo stability of the 99mTc SC-PVA complex and the efficacy of external imaging. 99mTc SC-PVA biodistribution data and external NaI(T1) scintillation probe counts were performed, to assess anatomic localization. Embolization with this complex was performed in a patient.

Angiography↗
PubMed1986

Therapeutic embolization angiography for extra-axial lesions in the head.

Percutaneous transcatheter arterial embolization has played an increasingly important role in the management of vascular lesions in the head. Embolization can promote thrombosis within vascular tumors and malformations, reduce bleeding and decrease the need for transfusion intraoperatively, and facilitate surgical approaches to otherwise unresectable lesions. It is important for the clinician to be aware of this interventional technique because many of the patients who are considered for embolization are triaged through several different clinical areas, and much can be gained from the collaboration of the clinician, the surgeon, and the angiographer. We performed 31 therapeutic particulate embolization procedures for extra-axial head lesions in 23 patients by using flow-directed techniques. Of these procedures, 11 resulted in vascular occlusion and 15 resulted in 80 to 95% obstruction, as demonstrated by angiography. In 14 patients, embolization was performed preoperatively both to decrease blood loss and to occlude inaccessible or unresectable portions of a lesion. In nine patients, embolization was the sole means of treatment for occluding an abnormal vascular shunt. Two patients (9%) experienced a minor transient neurologic change after the procedure.

Adolescent↗
PubMed1986

Emergency carotid endarterectomy for patients with acute carotid occlusion and profound neurological deficits.

Emergency revascularization procedures for patients with acute stroke are controversial. Thirty-four patients with acute internal carotid artery occlusion documented at the time of emergency endarterectomy were analyzed. Before operation, all these patients had profound neurological deficits including hemiplegia and aphasia. There was a 94% success rate in restoring patency. In follow-up, nine patients (26.5%) had a normal neurological exam, four (11.8%) had a minimal deficit, 10 (29.4%) had a moderate hemiparesis, which was improved over their preoperative deficit, 4 (11.8%) remained hemiplegic, and seven (20.6%) died. The natural history of patients with acute carotid occlusion and profound neurological deficits is dismal. In comparison, 13 patients (38%) made a dramatic recovery. The surgical mortality rate compares favorably with the natural history. Good collateral flow was a good prognostic factor, while a simultaneous middle cerebral artery embolus was associated with a poorer prognosis. An emergency carotid endarterectomy may be indicated in selected patients with acute internal carotid artery occlusion with profound neurological deficits. Full preoperative angiography may identify those patients who would benefit from surgical intervention and reduce the operative mortality rate.

Aged↗
PubMed1985

mRNA and apolipoprotein E synthesis abnormalities in peripheral blood monocyte macrophages in familial apolipoprotein E deficiency.

We have studied synthesis of apolipoprotein E (apo-E) and apo-E mRNA in cultures of peripheral blood human monocyte macrophages (M-M cultures) obtained from a patient with familial apolipoprotein E deficiency. We have found that the M-M cultures of the apo-E-deficient patients contained two apo-E mRNA species with slightly different molecular weight as compared to normal apo-E mRNA. The apo-E mRNA concentration of the apo-E-deficient cultures was approximately 50-fold reduced as compared to the normal cultures, whereas the actin mRNA concentrations were identical in both M-M cultures. Genomic blotting analysis using a full-length apo-E cDNA clone as hybridization probe did not show gross differences between the restriction patterns of the DNA obtained from the apo-E-deficient patient and two normal controls. When normal M-M cultures were grown in media containing [35S]methionine they synthesized and secreted apo-E into the culture media. In contrast we could not detect any intracellular or extracellular apo-E in the patient's M-M cultures grown under identical conditions. These observations are consistent with the hypothesis that familial apo-E deficiency results from structural apo-E gene mutation(s). The putative mutation(s) affect either the transcription of the apo-E gene or the processing of the primary apo-E mRNA transcript. These abnormalities are associated with low levels of synthesis of aberrant apo-E mRNA forms which are either very unstable or cannot be translated into protein.

Apolipoproteins E↗
PubMed1985

Lack of relationship of hypogonadism to muscle wasting in myotonic dystrophy.

Myotonic dystrophy is frequently associated with testicular atrophy. Since androgens may play a role in the maintenance of muscle mass, we have studied the levels of plasma testosterone and gonadotropins and of urinary 17-ketosteroids in 22 men with myotonic dystrophy, 36 normal men, and 16 men (control group) with muscle wasting. Results were correlated with muscle mass as estimated by creatinine excretion and total body potassium. Patients with myotonic dystrophy had significantly lower testosterone and higher gonadotropin levels than normal, and these changes were progressive in longitudinal studies. Testosterone levels were also lower than normal in disease control subjects. There was no correlation between low testosterone levels and diminished muscle mass in either myotonic dystrophy or disease control patients. The low plasma concentration of testosterone in men with myotonic dystrophy and other neuromuscular diseases does not appear to be directly related to their muscle wasting. This study does not exclude the possibility that an alteration in testosterone receptor or tissue effects may contribute to a loss of muscle tissue.

17-Ketosteroids↗
PubMed1985

Myotonic dystrophy: effect of testosterone on total body potassium and on creatinine excretion.

Muscle wasting in myotonic dystrophy appears to reflect impaired anabolism rather than accelerated catabolism. We therefore investigated the effects of testosterone, an anabolic hormone, on muscle mass as estimated by creatinine excretion and total body potassium in nine patients with myotonic dystrophy. Weekly injections of testosterone for 10 to 13 weeks increased both creatinine excretion (19%) and total body potassium (16%) in all patients. Metabolic balance data showed a confirmatory accretion of nitrogen, potassium, and phosphorus. Because testosterone increases indirect measures of muscle mass, it may deserve a therapeutic trial in myotonic dystrophy.

Adult↗
PubMed1985

Volume measurements of normal orbital structures by computed tomographic analysis.

Computed tomographic digital data and special off-line computer graphic analysis were used to measure volumes of normal orbital soft tissue, extraocular muscle, orbital fat, and total bony orbit in vivo in 29 patients (58 orbits). The upper limits of normal for adult bony orbit, soft tissue exclusive of the globe, orbital fat, and muscle are 30.1 cm3, 20.0 cm3, 14.4 cm3, and 6.5 cm3, respectively. There are small differences in men as a group compared with women but minimal difference between right and left orbits in the same person. The accuracy of the techniques was established at 7%-8% for these orbit structural volumes in physical phantoms and in simulated silicone orbit phantoms in dry skulls. Mean values and upper limits of normal for volumes were determined in adult orbital structures for future comparison with changes due to endocrine ophthalmopathy, trauma, and congenital deformity.

Adult↗