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Biomedical subjects

J P Fisher

Publications and source records attributed to J P Fisher.

17 recordsLinked to original sources
PubMed2001

Absent relative afferent pupillary defect in an asymptomatic case of lateral chiasmal syndrome from cerebral aneurysm.

INTRODUCTION: This report documents a case of an asymptomatic 34-year-old female who had right eye subtle temporal optic nerve pallor with absent clinically detectable relative afferent pupillary defect. CASE REPORT: This presentation was secondary to a fusiform paraclinoid aneurysm resulting in lateral chiasmal syndrome. Visual fields demonstrated a nasal depression OD. Neuroimaging studies revealed the presence of a fusiform paraclinoid aneurysm compressing the right optic nerve and optic chiasm. The lesion was treated surgically without additional visual loss nor systemic and neurological complications. CONCLUSIONS: A clinically detectable relative afferent pupillary defect may be absent in unilateral optic nerve pallor and/or visual field loss and does not preclude the need to attempt to identify an underlying etiology. Neuroradiological examination of orbital and cranial structures is an imperative protocol in the appropriate management of this potential life- and vision-threatening condition.

Adult↗
PubMed2001

Synthesis and properties of photocross-linked poly(propylene fumarate) scaffolds.

The photocross-linking of poly(propylene fumarate) (PPF) to form porous scaffolds for bone tissue engineering applications was investigated. PPF was cross-linked using the photoinitiator bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO) and exposure to 30 min of long wavelength ultraviolet (UV) light. The porous photocross-linked PPF scaffolds (6.5 mm diameter cylinders) were synthesized by including a NaCl porogen (70, 80, and 90 wt% at cross-linking) prior to photocross-linking. After UV exposure, the samples were placed in water to remove the soluble porogen, revealing the porous PPF scaffold. As porogen leaching has not been used often with cross-linked polymers, and even more rarely with photoinitiated cross-linking, a study of the efficacy of this strategy and the properties of the resulting material was required. Results show that the inclusion of a porogen does not significantly alter the photoinitiation process and the resulting scaffolds are homogeneously cross-linked throughout their diameter. It was also shown that porosity can be generally controlled by porogen content and that scaffolds synthesized with at least 80 wt% porogen possess an interconnected pore structure. Compressive mechanical testing showed scaffold strength to decrease with increasing porogen content. The strongest scaffolds with interconnected pores had an elastic modulus of 2.3+/-0.5 MPa and compressive strength at 1% yield of 0.11+/-0.02 MPa. This work has shown that a photocross-linking/porogen leaching technique is a viable method to form porous scaffolds from photoinitiated materials.

Biophysical Phenomena↗
PubMed2000

Wintering greater scaup as biomonitors of metal contamination in federal wildlife refuges in the Long Island region.

Tissues of greater scaup (Aythya marila mariloides) and components of their habitat (sediment, plankton, macroalgae, and invertebrates) were collected for heavy metal analysis in the winter of 1996-97 from US Department of the Interior wildlife refuges in the Long Island region. Geographic and temporal relationships between the concentration of nine metals in tissue and in habitat components were examined. In greater scaup tissues and habitat components, concentrations of As and Se were highest in Branford, Connecticut; Pb values were greatest in Oyster Bay, New York; and Hg concentrations were largest in Sandy Hook, New Jersey. Over the course of the winter, the concentration of Hg in liver increased, and concentrations of Cd, Cr, Cu, Hg, Pb, Se, and Zn in kidney decreased. Based on several criteria derived from geographic and temporal trends, metals were ranked using the apparent biomonitoring efficacy of greater scaup (As = Cr > Cu = Pb = Zn = Hg > Se = Cd > Ni). Although the seasonal migration and daily mobility of greater scaup are drawbacks to using this species as a sentinel for metal pollution, it was possible to demonstrate a relationship between geographic and temporal patterns of metals in habitat and greater scaup tissue. However, most metal concentrations in tissue were below thresholds known to adversely affect health of waterfowl.

Animals↗
PubMed1998

Maternal blood, egg and larval thiamin levels correlate with larval survival in landlocked Atlantic salmon.

A link was previously established between the Cayuga syndrome, a condition causing 100% mortality in larval landlocked Atlantic salmon, Salmo salar, in several of New York's Finger Lakes, and a maternal diet of alewife, Alosa pseudoharengus, a non-native thiaminase-rich Clupeid fish. We evaluated salmon larvae viability relative to maternal thiamin status, and investigated the putative link of the Cayuga syndrome to an alewife diet in fish from the geographic regions outside the Finger Lakes/lower Great Lakes watersheds. We identified Cayuga syndrome in Atlantic salmon from Otsego Lake in the Susquehanna River watershed and from Green Pond in New York's Adirondack Mountains. In both systems alewife represent the major component of the diet for the salmon. Thiamin levels in the maternal blood of Otsego salmon with syndrome-negative progeny were three- to four-fold greater than those Otsego females whose progeny exhibited 100% mortality. Thiamin levels in eggs and larvae were directly related to thiamin levels in maternal blood in both syndrome-positive and syndrome-negative stocks. Thiamin bath treatments of syndrome-afflicted larvae eliminated mortality regardless of their lake stock of origin. Maternal blood levels of approximately 0.31 nmol thiamin pyrophosphate/g or 0.44 nmol total thiamin/g appear necessary to achieve egg threshold levels of approximately 0.8 and 1.1 nmol/g unphosphorylated and total thiamin, respectively; these egg thiamin levels should prevent significant syndrome-related mortality in landlocked Atlantic salmon larvae. These results confirm the role of thiamin in the etiology of the Cayuga syndrome and support the dietary link of this naturally occurring thiamin deficiency to the thiaminase-rich alewife.

Animals↗
PubMed1997

Factors determining hydrogel permeability.

Developing hydrogel membranes and coatings of appropriate permeability characteristics is key to the success of a number bioartificial organ technologies. Key principles relevant to the design and application of hydrogels for such applications were reviewed. The first key point is that permeability is a function of both transport and thermodynamic properties, the diffusion coefficient and partition coefficient, respectively, and that these parameters can be evaluated separately. Although the aspect of partitioning often emphasized is size exclusion, this review points out that many other relevant interactions come into play, especially hydrophobic and electrostatic interactions, and that these phenomena can dominate size exclusion. Similarly, while the diffusion coefficient also is strongly dependent upon size, other interactions can also cause diffusivity to deviate from theories which consider only solute size and gel swelling. For example, the heterogeneity of hydrogel networks can result in permeabilities that fail to decline as much as might be anticipated if networks were uniform.

Animals↗
PubMed1995

Quantitation of myocardial dysfunction in ischemic heart disease by echocardiographic endocardial surface mapping: correlation with hemodynamic status.

Autopsy studies have suggested that infarction of > 35% of the myocardium is associated with cardiogenic shock. However, the relation between the extent of myocardial dysfunction and hemodynamic status has not been defined in patients in vivo. This study investigated, in patients with short-term and chronic left ventricular dysfunction, the relation between hemodynamic status and the extent of regional dyssynergia measured by two-dimensional echocardiography with quantitative endocardial surface mapping. Sixty patients were classified into hemodynamic groups by pulmonary capillary wedge pressure and cardiac index. Two-dimensional echocardiograms were used to calculate left ventricular endocardial surface area index (ESAi), abnormal wall motion index (AWMi), percentage myocardial dysfunction (%MD), and number of wall motion abnormalities. All patients in class 4 (high pulmonary capillary wedge pressure and low cardiac index had > or = 60% MD. With univariate analysis, hemodynamic class correlated with ESAi, AWMi, %MD, the number of wall motion abnormalities, and two clinical variables (number of infarctions and use of diuretic agents). By stepwise linear regression, only AWMi and the number of infarctions were independently predictive of hemodynamic status.

Aged↗
PubMed1994

Intracardiac ultrasound determination of left ventricular volumes: in vitro and in vivo validation.

OBJECTIVES: This study was designed to assess the feasibility of calculating left ventricular volumes using intracardiac ultrasound. BACKGROUND: Previous studies have validated transthoracic echocardiographic determinations of left ventricular volumes and have indicated the superiority of Simpson rule reconstruction algorithms. The feasibility of imaging the left ventricle with intracardiac ultrasound has also been demonstrated. METHODS: The determination of left ventricular volumes with Simpson rule reconstruction of intracardiac ultrasound images was evaluated in two phases. In vitro validation was performed in 29 animal hearts preserved in either a nondistended or distended state. Latex cast volumes were the reference standard. In vivo studies used 14 pigs, and compared intracardiac ultrasound volumes and ejection fraction with single-plane contrast angiographic values. A 12.5-MHz device was used to record short-axis images at 0.5-cm intervals. These were used to reconstruct the ventricle as a stack of cylindric elements using all imaged levels as well as sections recorded every 1 and 2 cm and at a single midventricular level. RESULTS: In the in vitro hearts, when all recorded sections were used, there was excellent agreement between intracardiac ultrasound and latex cast volumes (intracardiac ultrasound volume = 0.89 latex cast volume + 2.22, r = 0.95; intracardiac ultrasound volume = 0.97 latex cast volume + 0.91, r = 0.99) for nondistended and distended hearts, respectively. In vivo, there was again close correspondence between ultrasound and angiographic volumes (intracardiac ultrasound volume = 1.04 angiographic volume - 3.6, r = 0.91). The relation between intracardiac ultrasound and angiographic ejection fraction was fair (intracardiac ultrasound ejection fraction = 1.00 angiographic ejection fraction + 6.85, r = 0.69). Excellent correlations for the volumes were maintained as the number of cross sections was reduced to those recorded every 1 and 2 cm (r = 0.87 to 0.99). With a single midventricular site more variable but generally good correlations were obtained (r = 0.77 to 0.99). CONCLUSIONS: The application of Simpson rule reconstruction to short-axis images of the left ventricle obtained with intracardiac ultrasound provides accurate determination of left ventricular volumes in animal hearts. This technique may prove useful in the analysis of left ventricular structure and function.

Algorithms↗
PubMed1993

Low pressure radiofrequency balloon angioplasty: evaluation in porcine peripheral arteries.

OBJECTIVES: The purpose of this study was to evaluate the efficacy of radiofrequency-powered thermal balloon angioplasty in an in vivo porcine model. BACKGROUND: Various modes of thermal energy used adjunctively during balloon angioplasty have demonstrated the potential to enhance the results of acute lumen dilation. METHODS: In normal pigs, 75 peripheral arteries were dilated with a newly designed, radiofrequency-powered, thermal angioplasty balloon. All inflations were performed at 2-atm pressure for 85 s. Dilations were performed either with (hot) or without (cold) the application of heat. Lumen dimensions and vessel morphology were assessed with intravascular ultrasonography. At the end of each study, dilated arterial segments were harvested for histologic examination. RESULTS: Single cold balloon inflations resulted in a 12.7% increase in arterial cross-sectional area whereas single hot inflations resulted in a 22.9% increase (p < 0.03). Similarly, when multiple cold inflations were compared with multiple hot inflations, two, three and four sequential hot inflations resulted in a significantly greater increase in cross-sectional area than an equivalent number of cold inflations (p < 0.03). Histologic examination demonstrated a temperature-dependent effect on the depth of medial necrosis and extent of arterial wall thinning (p < 0.001) as well as evidence for uniform alteration of elastic tissue fibers at temperatures of > or = 60 degrees C (p < 0.03). CONCLUSIONS: Low pressure radiofrequency thermal balloon angioplasty results in a greater increase in cross-sectional area in porcine peripheral arteries than does nonheated conventional balloon angioplasty. The pathologic basis for this enhanced dilation may be a temperature-dependent effect on medial necrosis, thinning of the arterial wall or alteration of vascular elastic fibers, alone or in combination.

Angioplasty, Balloon↗
PubMed1993

Intracardiac echocardiography in humans using a small-sized (6F), low frequency (12.5 MHz) ultrasound catheter. Methods, imaging planes and clinical experience.

OBJECTIVES: This study was designed to determine the clinical utility and feasibility of using 12.5-MHz ultrasound catheters for intracardiac echocardiography. BACKGROUND: Intracardiac echocardiography is a potentially useful technique of cardiac imaging and monitoring in certain settings. The feasibility of intracardiac echocardiography using 20-MHz ultrasound catheters in patients has been demonstrated. High resolution images of normal cardiac structures as well as cardiac abnormalities have been obtained. However, imaging has been limited by the shallow depth of field inherent in high frequency ultrasound imaging. METHODS: Intracardiac echocardiography with 12.5-MHz catheters was performed in eight mongrel dogs and 92 patients. Catheters were introduced percutaneously in 80 patients studied in the catheterization laboratory and directly into the heart in 12 patients in the operating room. Right heart imaging was performed in 68 patients and arterial and left heart imaging in 35 patients. RESULTS: When these catheters were introduced into the venous system, the right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery were visualized. Pericardial effusion, intracardiac masses and atrial septal defects were correctly identified. The left ventricle, left atrium, mitral valve, aortic valve, aorta and coronary arteries could be imaged from the arterial circulation. Diseases identified included valvular aortic stenosis, subvalvular aortic stenosis and Kawasaki disease. Average imaging time was 10 min. No complications occurred as a result of intracardiac echocardiography. CONCLUSIONS: Intracardiac echocardiography with 12.5-MHz ultrasound catheters is safe and feasible; it also provides anatomic and physiologic information. This feasibility study provides a foundation for wider clinical use of intracardic echocardiography.

Adolescent↗
PubMed1989

Factors influencing the differentiation of embryonal carcinoma and embryo-derived stem cells.

The effects of aggregation, retinoic acid, and medium conditioned by Buffalo rat liver (BRL) cells, alone and in combination, on the differentiation of PSA4TG12 embryonal carcinoma and E14 embryonal stem cells are reported. The observations indicate that BRL-conditioned medium has more than one effect on the differentiation process, that retinoic acid has at least two effects which operate in different concentration ranges, and that both agents influence the choice of differentiation pathway as well as the extent of differentiation.

Animals↗
PubMed1987

Drug-induced left ventricular failure in patients with pulmonary disease. Endomyocardial biopsy demonstration of catecholamine myocarditis.

Three patients with severe chronic lung disease had left ventricular failure develop with marked impairment of cardiac function. Ejection fractions by radioactive blood pool ventriculography were 0.17, 0.24, and 0.20. Right ventricular endomyocardial biopsy specimens showed interstitial hemorrhage and foci of interstitial polymorphonuclear leukocytes, strongly suggestive of catecholamine myocarditis. These patients had used beta-adrenergic agonist inhalants and methylxanthines. One of them clearly abused the inhalant and had elevated levels of urinary catecholamines. Progressive deterioration of pulmonary and cardiac function occurred in two patients, with death within three months of the initial myocardial biopsy. Concomitant use of beta-adrenergic agonists and methylxanthines may cause myocarditis with left ventricular failure in susceptible patients.

Adrenergic beta-Agonists↗
PubMed1982

Toxicity, efficacy, and clearance of intravitreally injected of cefazolin.

The intravitreal injection of cefazolin sodium was evaluated with respect to its potential toxicity, efficacy, and clearance in the treatment of bacterial endophthalmitis in the rabbit model. Toxicity evaluation included indirect ophthalmoscopy, scotopic electroretinogram, and light microscopy of histopathologic specimens. Rabbits given doses up to and including 2.25 mg of cefazolin sodium showed no evidence of toxic reaction by these criteria after two weeks of observation. When injected within 24 hours of inoculation, 2.25 mg of cefazolin sodium sterilized five of six rabbit eyes infected with Staphylococcus aureus. Following intravitreal injection of 2.25 mg of cefazolin sodium, vitreous concentrations in excess of the minimum inhibitory concentration for S aureus were maintained for five days. A 2.25-mg dose of cefazolin sodium appears to be nontoxic, effective, and biologically active against susceptible organisms during a prolonged period, when injected into the vitreous cavity of the pigmented rabbit in vivo.

Animals↗
PubMed1982

The acute retinal necrosis syndrome. Part 1: Clinical manifestations.

The acute retinal necrosis syndrome is characterized by necrotizing retinitis, vitritis, and retinal vasculitis occurring in otherwise healthy patients. Experience with 11 cases and the review of 30 additional cases in the literature are presented. In this series, 50% of the affected eyes developed retinal detachments, and 64% had a final visual acuity of less than 20/200. The natural history, diagnosis, postulated etiology, and suggestions for management will be discussed.

Acute Disease↗
PubMedDate not supplied

Aroclors 1254 and 1260 reduce dopamine concentrations in rat striatal slices.

Striatal slices from adult male Wistar-derived rats were exposed to a 1:1 mixture of Aroclor 1254:1260 at concentrations in media of 10, 20, 40, 60 or 100 ppm for 6 hr. Following exposure, slices and media were analyzed by high-performance liquid chromatography for dopamine (DA) and its metabolites. PCBs caused a significant dose-dependent decrease in slice DA content at concentrations greater than 20 ppm. Media concentrations of DA and its metabolites were significantly increased by PCB exposure greater than 60 ppm, indicating that, in addition to their suggested role in inhibiting DA synthesis, PCBs may interfere with either vesicular storage or release of DA. These data suggest that in addition to the recognized action of PCBs in inhibiting tyrosine hydroxylase, PCBs may also interfere with the vesicular monoamine transporter, and thereby suggest an additional mechanism by which DA concentrations and metabolism may be altered by PCB exposure.

3,4-Dihydroxyphenylacetic Acid↗