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Biomedical subjects

J K Fisher

Publications and source records attributed to J K Fisher.

At least 19 recordsLinked to original sources
PubMed2006

Thin-foil magnetic force system for high-numerical-aperture microscopy.

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 mum paramagnetic particle and 13 nN on a 4.5 mum paramagnetic particle, forces over the full 4pi sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 mum xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function.

Journal Article↗
PubMed1999

Significance of retroperitoneal air after endoscopic retrograde cholangiopancreatography with sphincterotomy.

OBJECTIVE: We designed a prospective study to determine the frequency of retroperitoneal air after endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy. We sought to elucidate the relationship of retroperitoneal air with endoscopic maneuvers, clinical findings, the length of sphincterotomy, and the time spent during the procedure. We also endeavored to determine the importance of retroperitoneal air and its most appropriate clinical management. METHODS: Twenty-one consecutive patients who had undergone ERCP with sphincterotomy had abdominal computed tomography (CT) examinations within 24 h after completion of the procedure. The CT findings were unknown to the clinicians, and none of the patients received postprocedural antibiotics. RESULTS: Six (29%) of 21 patients exhibited CT findings of retroperitoneal air. All six patients had uneventful postprocedural courses, and none had abnormal clinical signs or symptoms. The occurrence of retroperitoneal air was not influenced by the presence of hyperamylasemia, the duration of the procedure, or the length of the sphincterotomy. CONCLUSIONS: Retroperitoneal air is not an uncommon finding after ERCP with sphincterotomy. Moreover, the finding of retroperitoneal air in the absence of physical findings, is not a cause for alarm and does not require surgical intervention.

Adult↗
PubMed1998

Giant sigmoid diverticulum: a rare manifestation of diverticular disease.

We report two unusual cases of giant sigmoid diverticulum, which is a rare manifestation of diverticular disease. Giant diverticula are 3 to 4 cm or greater in size and are produced by gradual enlargement of an acquired pseudodiverticulum that has had superimposed infection, abscess formation, and healing. For more than 3 years, we have observed and managed the first case conservatively, without surgery. The second case represents the largest recorded giant sigmoid diverticulum (33 cm) in the literature. We review the pathogenesis, clinical features, differential diagnosis, and management of this condition.

Aged↗
PubMed1996

TNF-alpha and the pathophysiology of endotoxin-induced acute respiratory failure in sheep.

We studied changes in cardiovascular and pulmonary function during prolonged endotoxemia in conscious sheep. Sheep with chronic lung lymph fistulas received a 12-h infusion of Escherichia coli endotoxin (10 ng x kg-1 x min-1) and allowed to recover for 12 h. Supportive therapies were withheld. Prolonged endotoxemia without volume support caused systemic hypotension associated with reduced cardiac output and increased systemic vascular resistance, pulmonary hypertension, and acute lung injury with progressive respiratory failure. Plasma tumor necrosis factor-alpha (TNF-alpha) concentrations increased transiently. Sustained pulmonary hypertension and increased pulmonary and systemic vascular resistances contributed to a poor outcome in 9 of 34 sheep (26%). Plasma TNF-alpha concentrations were significantly greater in survivors with sustained pulmonary hypertension and in nonsurviving sheep than in surviving sheep without pulmonary hypertension. Endotoxin (1 ng/ml) increased neutrophil expression of TNF-alpha in vitro. Addition of interleukin-6 prevented this response. Synthesis and release of TNF-alpha may be an important proximal event influencing the development of sustained pulmonary hypertension and progressive respiratory failure with endotoxemia. Interleukin-6 may contribute to the phasic nature of the TNF-alpha response.

Acute Disease↗
PubMed1996

Pneumothorax detection in patients with apical pleural caps.

The usual small apical pneumothorax has been previously described as being typified on chest radiographs by a pencil-thin white line that represents the retracted visceral pleura. Occasionally the apical visceral pleura can become thickened, known as the apical cap, which leads to a variant presentation of apical pneumothorax. To our knowledge, this variant presentation has never been described in the literature, and should improve the detection of apical pneumothorax.

Diagnosis, Differential↗
PubMed1996

What kind of general practitioner for the twenty-first century?

In this article a recently qualified physician, now in family practice in the USA, gives expression to the widely held view that a new breed of general practitioner with expanded roles and skills is required if the health-for-all targets are to be attained.

Community Health Services↗
PubMed1995

Endotoxin infusion in anesthetized sheep is associated with intrapulmonary sequestration of leukocytes that immunohistochemically express tumor necrosis factor-alpha.

Plasma levels of tumor necrosis factor-alpha (TNF-alpha) peak between 2 and 4 h during a 12-h continuous infusion of endotoxin in awake sheep. We hypothesized that a source of this TNF-alpha is the pool of leukocytes that accumulate in the pulmonary circulation. To test this hypothesis, we physiologically monitored six anesthetized sheep during baseline and 4-h endotoxin infusion periods (10 ng/kg x min). We obtained open-lung biopsies at baseline and at 20 min and 2 and 4 h during the endotoxin infusion period for immunohistochemical localization of TNF-alpha. The plasma concentration of TNF-alpha increased from an average baseline concentration of 0.06 +/- 0.03 ng/ml (mean +/- SD) to a peak of 1.40 +/- 0.28 ng/ml at 2 h of the endotoxin infusion. We observed increased cytoplasmic TNF-alpha immunoreactivity in situ among neutrophils and intravascular mononuclear phagocytes during the endotoxin infusion compared with baseline. Also, the number of immunopositive leukocytes increased in the pulmonary circulation during the continuous infusion of endotoxin. We conclude that TNF-alpha-producing leukocytes accumulate in the pulmonary circulation during endotoxemia. These cells probably contribute to both the rise in the circulating levels of TNF-alpha and the development of acute lung injury.

Anesthesia↗
PubMed1983

Abnormal colonic wall thickening on computed tomography.

There are many disease processes, both inflammatory and neoplastic, which can alter the colonic bowel wall. A retrospective study was done on surgically proven cases of colonic disease in which colonic bowel wall abnormalities were identified by computed tomography. Colonic bowel wall thickening was the most common finding, but was nonspecific. Finger-like projections extending from the bowel wall into the surrounding mesentery did help distinguish inflammatory change from neoplastic change. Examples of diverticulitis, appendicitis, Crohn's disease, carcinoma, lymphoma, and metastatic disease are presented.

Barium Sulfate↗
PubMed1982

Angled view of the distal small bowel.

The distal small-bowel loops in the pelvis do not always lend themselves to palpation of easy visualization during conventional small-bowel examinations. When this occurs, an angled view of the pelvis, such as that used to uncoil the sigmoid colon during barium-enema examinations, can separate these overlapping segments for better visualization.

Barium Sulfate↗