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Biomedical subjects

A Miller

Publications and source records attributed to A Miller.

At least 307 records · Page 17Linked to original sources
PubMed1993

Quantitative studies of human lung airspace wall in relation to collagen and elastin content.

Biochemical determinations of the collagen and elastin content in 50 mm3 samples of human lung are presented in relation to morphometric measurements of lung structure, as the amount of alveolar wall surface area per unit volume (AWUV), on adjacent slices. There were no differences in AWUV values, collagen content (determined as hydroxyproline) or elastin content (determined as isodesmosine) between upper and lower lobes within a single lung. In a study of 102 samples from 9 smokers lungs with no evidence of macro- or microscopic emphysema (as estimated by AWUV measurement), there was a negative correlation between AWUV and the amounts of collagen or elastin per unit volume of inflated lung. The correlation was stronger when collagen and elastin content were expressed per unit area of alveolar wall. The negative correlation is interpreted as representing either the anatomical variation within the complex hierarchy of normal lung structure or possibly low levels of fibrosis in response to cigarette smoking.

Aged↗
PubMed1993

Comparison of angioscopy and angiography for monitoring infrainguinal bypass vein grafts: results of a prospective randomized trial.

PURPOSE: This study was designed to determine whether, in primary infrainguinal bypass grafts in which only saphenous vein is used as the graft conduit, routine monitoring with intraoperative angioscopy can improve early graft patency as compared with standard monitoring with intraoperative completion angiography; and to delineate the advantages and disadvantages of these two modalities and their respective roles for the routine monitoring of the infrainguinal bypass graft. METHODS: A total of 293 patients undergoing primary saphenous vein infrainguinal bypass grafting were prospectively randomized and monitored with either completion angioscopy or completion angiography. Clinical parameters, indications for operation, graft anatomy, and configuration were evenly matched in both groups. Forty-three bypasses were excluded from the study after randomization, including 12 veins randomized to angiogram, deemed inferior, and prepared with angioscopy. RESULTS: In the 250 bypass grafts (angioscopy 128, angiography 122) there were 39 interventions (conduit, 29; anastomosis, 8; distal artery, 2), 32 with angioscopy and 7 with angiography (p < 0.0001). Twelve (4.8%) of the 250 grafts failed in less than 30 days, four (3.1%) of 128 in the angioscopy group and eight (6.6%) of 122 in the angiography group (p = 0.11 by one-sided hypothesis test). CONCLUSION: Although no statistical improvement in the proportions of failures in primary saphenous vein bypass grafts routinely monitored with completion angioscopy rather than the standard completion angiogram was demonstrated, the study delineates a trend that favors completion angioscopy for routine vein graft monitoring and demonstrates the advantages of angioscopy in preparing the optimal vein conduit.

Aged↗
PubMed1993

Angioscopically directed interventions improve arm vein bypass grafts.

PURPOSE: Our purpose was to determine the incidence and segmental distribution of intraluminal disease in the arm veins of patients in whom saphenous vein was unavailable or inadequate for bypass, determine whether angioscopic evaluation and directed interventions can upgrade the quality of arm vein conduit and improve early graft patency, and describe the angioscopic technique of in situ retrograde arm vein inspection. METHODS: Retrospective review of 109 infrainguinal arm vein bypass grafts in 104 patients performed with intraoperative angioscopic vein preparation and monitoring between August 1989 and March 1992 was undertaken. Four additional arm veins harvested were discarded because of diffuse disease. RESULTS: Intraluminal disease was noted in 71 (62.8%) of 113 arm veins, "webs" in 61 (54%), vein sclerosis in 25 (22.1%), localized stenosis in 11 (9.7%), and thrombus in 7 (6.2%). Intraluminal disease was most common in the cephalic (forearm 49.2%; arm 35.1%) and median cubital (33.3%) veins and least common in the basilic vein (11.7%). Eighty-three angioscopically directed interventions in 68 of 71 abnormal arm veins resulted in upgraded vein conduit quality in 47 (66.1%) of 71. Primary patency (< 30 days) was 99 (90.8%) of the 109 grafts, 85 (95.5%) of 89 grafts with normal or upgraded quality conduits, and 14 (70%) of 20 inferior-quality grafts (p = 0.0024). These differences persisted through 1 year by life-table analysis, (p < 0.001). CONCLUSIONS: Not only is the routine use of the angioscope in arm vein bypass grafting a sensitive technique to detect the intraluminal diseases so prevalent in arm veins but it can also direct endoluminal and surgical interventions that upgrade the quality of the vein conduit and improve early graft patency.

Adult↗
PubMed1993

Interstitial iodine 125 and concomitant cisplatin followed by hyperfractionated external beam irradiation for malignant supratentorial glioma. Preliminary experience at the University of Tennessee, Memphis.

Between November 1989 and October 1992, 28 consecutive patients with glioblastoma multiforme (n = 18) or anaplastic astrocytoma (n = 10; includes one patient with oligodendroglioma with anaplastic astrocytoma component) were treated with interstitial iodine 125 (60 Gy over 6 days) and with concomitant cisplatin (via infusion on days 2-6 of the implant), then followed by hyperfractionated external beam irradiation (110 cGy delivered twice daily; 66 Gy planned total dose). Of 26 patients (60%) who received both 125I and HEBI, 15 are alive with no evidence of recurrent disease at a median follow-up of 18 months post-125I (range: 11 to 34 months). Four other disease-free patients succumbed to nontumor-related events. Two patients with local control had distant failure outside the HEBI treatment fields. Overall local control is 77%. Local failure occurred in 6 patients (23%) 2 to 11 months post-125I. Time to disease progression ranged from 4 to 18 months (median: 10 months). Survival (measured from the date of diagnosis) has ranged from 6 to 26 months (median: 15 months). All patients have maintained Karnofsky Performance Status within 20 points of their preimplant status, with the exception of a single patient who, following diagnosis of radiation necrosis and surgical intervention for symptomatic relief, had a 30-point drop in KPS. Radiation necrosis or persistent mass effect were noted by neuroimaging in seven patients, four of whom required surgical intervention following failed medical management. Ototoxicity, nephrotoxicity, peripheral nerve dysfunction, or hematologic toxicities have not been observed. This new innovative treatment approach offers a promising alternative to the normally dismal prognosis for patients with malignant gliomas.

Adult↗
PubMed1993

Re-evaluation of the structural organization of neuritic plaques in Alzheimer's disease.

We re-examined the relationship among synaptic pathology, subcellular abnormalities within neurites in the plaques and beta-amyloid deposits of Alzheimer's disease (AD) using laser confocal imaging and computer-aided serial section reconstruction techniques. Analysis of serial optical sections of neuritic plaques double-immunolabeled for anti-beta-amyloid/anti-tau-2 revealed that 35% of this type of plaque contained a dense amyloid core with clusters of peripheral abnormal neurites. The other 65% were without a dense core and were mainly composed of abundant abnormal neuritic clusters with bundles of amyloid distributed throughout the neuritic plaque. While two-dimensional (2-D) analysis of the plaques has suggested that neurites are distributed in the plaque periphery with beta-amyloid localized in its center, serial section analysis showed the opposite arrangement can also be true. Three-dimensional (3-D) reconstructions of serial optical sections showed that the tau-positive tortuous axons clustered in the neuritic plaques were often continuous with synaptophysin-positive distended terminals. Analysis of electron micrographs from serial sections showed continuity among the different segments of the neurites. Further analysis of the computer generated 3-D reconstructed neuritic plaques (both from serial electron micrographs and serial optical sections), viewed as continuous rotating loops, confirmed that a great majority of the plaque volume was occupied by the clustered and continuous abnormal neurites, while the amyloid fibrils were compressed and displaced to the periphery of the plaque. The 3-D imaging of the neuritic plaques in AD suggests a more widespread and active neuritic damage than that predicted from 2-D observations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Physically damaged extracellular matrix induces TNF-alpha secretion by interacting resting CD4+ T cells and macrophages.

T lymphocytes and macrophages (Mø) are seen to accumulate at sites of lesions in blood vessel walls, suggesting that these cells may contribute to the initiation of the local inflammatory reaction. Tumour necrosis factor-alpha (TNF-alpha), a cytokine produced by both cell types, plays a major role in inflammatory reactions, in blood vessel formation, in thrombosis and in atherosclerosis. We now report that secretion of TNF-alpha by CD4+ T cells and Mø can be induced in vitro in the absence of antigen, in an MHC-II-independent manner by immobilized extracellular matrix (ECM). Moreover, the level of TNF secretion is greatly enhanced in the presence of physically damaged ECM (dECM). This mode of TNF secretion is regulated primarily by the fibronectin or laminin glycoprotein components of ECM. Thus, a multicellular interaction with ECM proteins exposed as a consequence of vascular wall injury can serve to signal the secretion of TNF-alpha by both cell types which induces the recruitment of additional immune cells to the developing lesion.

Animals↗
PubMed1993

Dominance and crypticity of T cell antigenic determinants.

In this review, we first consider the inherent structural constraints for binding of a peptide to MHC class II molecules. Such parameters at the site of TCR recognition are dependent upon the efficient generation of the antigenic determinant during natural processing of the whole protein antigen. Strikingly, only a minor fraction of such potential determinants on an antigen are presented in an immunodominant manner, while the remaining peptides are silent (cryptic). Why one determinant is selected while the majority are neglected is still unresolved, but we review the experimental evidence pertaining to this choice. Thus, features of the antigen remote from the actual determinant can either steer processing toward disclosure or revelation of a determinant, or interfere with the binding of peptides to MHC (hinderotopy). The evidence is reviewed for "MHC-guided processing," where the unfolding antigen binds at an early stage to an MHC molecule through its most available and affine agretope and then is trimmed down to final size, while the rest of the molecule, including cryptic determinants, is discarded. Different MHC molecules can compete for determinants at an early stage of processing when the antigen is close to its original length. There are shifts in the hierarchy of display of dominant and cryptic determinants, and these shifts relate to local inflammatory states, to changes in the state or composition of the APC population, and to aspects of exogenous vs endogenous processing. The impact of this differential display of determinants on tolerance and autoimmunity is discussed.

Animals↗
PubMed1993

Executive impairment among the functionally dependent: comparisons between schizophrenic and elderly subjects.

OBJECTIVE: Executive deficits have traditionally been associated with frontal lobe brain damage. They are relevant to a variety of disabling mental conditions, including schizophrenia and Alzheimer's disease. To measure these deficits, the authors developed the Executive Interview, a 25-item, 15-minute interview. It has been validated among elderly subjects across a wide range of functional impairment. METHODS: Forty young, chronically ill schizophrenic residents of a state mental health facility and 104 elderly residents, representing three levels of care, of a comprehensive retirement community were tested with the Executive Interview and the Mini-Mental State. RESULTS: When age, gender, education, and number of prescribed medications were controlled, cognitive impairment on the Executive Interview and Mini-Mental State rose with level of care. The Executive Interview alone discriminated between subjects at each level of care, and it was more sensitive to cognitive impairment than the Mini-Mental State. Executive Interview scores correlated the strongest with level of care. Mini-Mental State scores, number of prescribed medications, and age also correlated significantly. Schizophrenic patients showed as much executive impairment on the Executive Interview as elderly subjects at the same level of care despite significant differences in age, sex, and neuroleptic use. Executive Interview and Mini-Mental State scores were highly correlated among the elderly but less so among the schizophrenic patients. Cross-group differences were also found in the pattern of failure on selected Executive Interview items despite similar total Executive Interview scores. CONCLUSIONS: Increasing executive dyscontrol is associated with the need for increasing levels of care and supervision. This finding is neither age nor disease specific. Cross-group differences on selected Executive Interview items suggest the existence of disease-specific patterns of failure. Their recognition could prove useful in the identification of anatomically or pathophysiologically distinct subgroups among patients with executive dyscontrol.

Activities of Daily Living↗
PubMed1993

Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function.

An increasing number of patients with asbestos exposure are being identified with pleural thickening (PT) alone, with little or no impairment in standard tests of lung function despite their frequent complaint of dyspnea. We have employed incremental cardiorespiratory exercise testing to evaluate the types and mechanisms of impairment in 23 such patients. All had normal lung fields on radiographic examinations and normal (group 1, n = 12) or minimally reduced (group 2A slight restriction, n = 5, group 2B, slight obstruction, n = 6), lung function. Excessive ventilation was common in all groups, but especially in group 2B. Abnormal dead space ventilation (VD/VT) was more frequent in groups 2A (4/5) and 2B (4/6) than in group 1 (3/12). It was associated with O2 desaturation in three patients in groups 2A and B. Cardiovascular abnormalities were rare (1/23). Excessive ventilation and dead space provide a basis for the symptom of dyspnea in these patients.

Adult↗
PubMed1993

Evaluation and treatment of diastematomyelia.

We reviewed the results for forty-three patients who had a diastematomyelia. All of the patients had been skeletally immature when the diagnosis was made, the mean age being six years (range, birth to thirteen years), and were skeletally mature by the time that they were evaluated by us. When they were first seen at our institution, twenty-four patients (56 per cent) had a cutaneous lesion, such as hairy patch, dimple, hemangioma, subcutaneous mass, or teratoma at or near the level of the diastematomyelia; thirty-four patients (79 per cent) had congenital scoliosis; and forty-two patients (98 per cent) had at least one associated musculoskeletal anomaly, such as spinal dysraphism, asymmetry of the lower extremities, club foot, or a cavus foot. In twenty-seven patients (63 per cent), the diastematomyelia was located in the lumbar spine. Thirty-six patients had eighty-four neurological manifestations. Resection of the spur was performed in thirty-three patients at a mean age of seven years (range, three months to seventeen years). Twenty-two patients who had a resection had no change in neurological condition, nine patients had improvement, and one patient had one symptom improve and another symptom worsen after the operation. We believe that resection of the spur should be performed in patients who have progressive neurological manifestations. Patients who do not have progressive neurological manifestations should be observed; if progression is noted, a resection should then be performed.

Adolescent↗
PubMed1993

Dosimetry for quality assurance in electron-beam sterilization of medical devices.

During recent years, electron-beamed sterilization has quickly moved towards being able to compete with gamma-radiation sterilization, particularly now that several companies are offering high-power accelerators that can deliver electron beams with energies of 10 MeV; these beams are powerful enough to penetrate most medical devices. This article describes the role of dosimetry and the procedures used in the quality assurance and documentation required for electron-beam sterilization.

Electrons↗
PubMed1993

Heat-stressed CD4+ T lymphocytes: differential modulations of adhesiveness to extracellular matrix glycoproteins, proliferative responses and tumour necrosis factor-alpha secretion.

Although cells of the immune system often function under feverish conditions, the effects of elevated temperatures on T cells have not been fully elucidated. Herein, the effects of a 1-hr exposure to 41 degrees of CD4+ human T cell were studied. Heat-shock treatment of activated CD4+ T cells reduced their adhesion to fibronectin and laminin, the major adhesive glycoproteins of the extracellular matrix (ECM) by 25-40%. This decrease was partially due to a minor decrease in the surface expression of beta 1 integrins, which specifically interact with fibronectin and laminin. In contrast, the capacities of heat-stressed T cells to proliferate and to secrete tumour necrosis factor-alpha (TNF-alpha) were increased upon cell activation. In vivo, heat-treated antigen-primed murine T cells, injected directly into the antigen challenging site, induced a more severe delayed-type hypersensitivity (DTH) response than those not exposed to elevated temperatures. In contrast, the same heat-treated cells inoculated intravenously did not induce DTH, suggesting that these cells were impaired with respect to penetration of blood vessel walls. Thus, the effects of heat shock on key cellular functions are expressed in different manners: T-cell-ECM adhesiveness and subsequent extravasation are impaired, whereas their abilities to proliferate and to secrete TNF-alpha are augmented.

CD4-Positive T-Lymphocytes↗
PubMed1993

Accidental fires in clinical laboratories.

The National Fire Protection Association, Quincy, Mass, estimates that 169 fires have occurred annually in health care, medical, and chemical laboratories. On the average, there are 13 civilian injuries and $1.5 million per year in direct property damage. Most fires in which the cause or ignition source can be identified originate in malfunctioning electrical equipment (41.6%) or in the facility's electrical distribution system (14.7%). The prevalence of fire safety deficiencies was measured in the College of American Pathologists Laboratory Accreditation Program. Of the 1732 inspected laboratories, 5.5% lacked records of electrical receptacle polarity and ground checks in the preceding year. Of these inspected laboratories, 4.7% had no or incomplete documentation of electrical safety checks on laboratory instruments. There was no evidence of quarterly fire exit drills in 9% of the laboratories. Deficiencies were also found in precautionary labeling (6.8%), in periodic review of safe work practices (4.2%), in the use of safety cans (3.7%), and in venting of flammable liquid storage areas (2.8%). Fire preparedness would be improved if all clinical laboratories had smoke detectors and automatic fire-extinguishing systems. In-service training courses in fire safety should be targeted to the needs of specific service areas.

Fires↗
PubMed1993

Shade selection and laboratory communication.

This article reviews some of the factors involved in shade selection for prosthetic teeth and suggests simple techniques for accurately transmitting information about the desired color to the laboratory technician.

Color↗
PubMed1993

Primary antiphospholipid antibody syndrome, renal infarction and hypertension.

We describe a 22-year-old woman with renovascular hypertension, stroke, and left renal infarction. She had markedly elevated antiphospholipid antibodies without evidence of systemic lupus erythematosus, other autoimmune or rheumatic disorders. Selective renal angiogram revealed lack of perfusion to the lower pole of left kidney and her left renal vein renin level was elevated. She represents an example of primary antiphospholipid antibody syndrome resulting in renal infarction and hypertension.

Adult↗
PubMed1993

Acute arthritis of the hip in a child infected with the Lyme spirochete.

Acute Lyme arthritis may mimic acute pyogenic arthritis. Although the arthritis associated with infection with the spirochete, Borrelia burgdorferi, is more commonly seen in the chronic stage (Stage III) of the disease, occasionally it may present as the initial clinical manifestation. A five-year-old girl with acute arthritis of the hip is reported to discuss classification and management of arthritis associated with Lyme disease.

Acute Disease↗