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Biomedical subjects

K E Stephens

Publications and source records attributed to K E Stephens.

At least 19 recordsLinked to original sources
PubMed2000

Alteration of pulmonary neuroendocrine cells during epithelial repair of naphthalene-induced airway injury.

Whole-mount airway preparations isolated from the lungs of mice treated by intraperitoneal injection of naphthalene and allowed to recover for 5 days were examined for the distribution and abundance of solitary pulmonary neuroendocrine cells (PNECs) and neuroepithelial bodies (NEBs) along the main axial pathway of the right middle lobe. Sham mice treated with corn oil vehicle were examined in a similar manner. An antibody to calcitonin gene-related peptide, a neuroendocrine cell marker, was used to identify the location, size, and number of PNECs and NEBs in the airways. After naphthalene treatment and epithelial repair, NEBs were significantly increased along the walls of the airways as well as on branch point ridges. The surface area covered by NEBs composed of 20 or fewer PNECs was significantly enlarged after naphthalene treatment compared with control NEBs of an equivalent cell number. The PNEC number per square millimeter was also increased more than threefold above control values after naphthalene treatment. These findings provide further support for a key role of neuroendocrine cells in the reparative process of airway epithelial cell renewal after injury.

Animals↗
PubMed2000

Pulmonary function after modified venovenous ultrafiltration in infants: a prospective, randomized trial.

OBJECTIVE: We sought to examine the effects of modified venovenous ultrafiltration after cardiopulmonary bypass on pulmonary compliance in infants. METHODS: We prospectively enrolled 38 infants undergoing their first operation for congenital heart disease. Infants were randomized to receive 20 minutes of modified ultrafiltration after bypass or control. Static and dynamic compliance was measured after induction of anesthesia, before and immediately after filtration in the operating theater, 1 hour after return to the pediatric intensive care unit, and 24 hours after the operation. Length of time on the ventilator, inotropic requirements, and length of stay in the intensive care unit were recorded. RESULTS: Modified ultrafiltration produced a significant immediate improvement in dynamic (pre-ultrafiltration 2.5 +/- 1.9 mL/cm H(2)O to post-ultrafiltration 2.9 +/- 2.7 mL/cm H(2)O, P =.03) and static (pre-ultrafiltration 2.1 +/- 0.9 mL/cm H(2)O to post-ultrafiltration 2.9 +/- 2.1 mL/cm H(2)O, P =.04) compliance. However, there was no significant difference in the change in dynamic (P =.3) or static (P =.7) compliance in the ultrafiltration and control groups when compared before the operation, after the operation, and at 24 hours. There was no significant difference in the time to extubation between patients and control subjects (140 +/- 91 hours vs 90 +/- 58 hours) or the length of intensive care unit stay (10.0 +/- 9.1 days vs 7.4 +/- 5.7 days). CONCLUSIONS: Modified ultrafiltration produces an improvement in pulmonary compliance after bypass in infants. However, these improvements are not sustained past the immediate post-ultrafiltration period and do not lead to a decreased length of intubation or intensive care unit stay.

Cardiopulmonary Bypass↗
PubMed2000

Bronchoscopic management of central airway obstruction.

OBJECTIVES: Patients with central airway obstruction are critically ill, with impending suffocation. They are seen with diverse anatomic and functional deficits caused by both benign and malignant obstructions. Such cases were reviewed to examine the indications, techniques, and outcomes of an algorithm approach to bronchoscopic management. METHODS: Between July 1992 and April 1996, 97 patients underwent bronchoscopic procedures for the management of central airway obstruction, and their cases were used for a retrospective review of the airway management. RESULTS: There were 48 male and 49 female patients, aged 13 to 85 years. There were 48 benign and 49 malignant pathologic conditions that gave rise to 108 stenoses. These were treated with 199 endoscopic procedures with an average of 1.7 interventions per endoscopy, including mechanical core-out (62), dilation (135), laser ablation (44), placement of brachytherapy catheters (9), and stent placement (88). Diagnoses included lung cancer, primary tracheobronchial tumors, tumors metastatic to the airway or mediastinum, and a variety of benign obstructions. In the group of 97 patients there were 2 (2%) perioperative deaths and 34 (34%) late deaths, 29 in the malignant group and 5 in the benign group. Median survival was 7.6 months (range 1 week-31 months). There were 7 (7%) complications among the group of 97, 4 in the malignant group, and 3 in the benign group. CONCLUSIONS: Endobronchial surgical techniques can be used safely and systematically for the relief of benign and malignant central airway obstructions; a diversity of approaches and interventions are required to produce and maintain palliation of airway symptoms.

Adolescent↗
PubMed1998

Imaging of acute thoracic aortic injury due to blunt trauma: a review.

Much recent work on the use of computed tomography (CT) and transesophageal echocardiography in screening for and facilitating the diagnosis of acute thoracic aortic injury in the patient with blunt chest trauma has shown favorable results. This has led some physicians to question whether conventional thoracic aortography is still the reference standard. The purpose of this review article is to summarize the epidemiology and pathophysiology of acute thoracic aortic injury, the current status of the individual imaging modalities in use, and the surgeon's perspective. Despite a burgeoning literature and a confounding array of clinical and imaging advances, timely diagnosis of acute thoracic aortic injury remains a challenge. To overcome this problem, some trauma centers have used CT, transesophageal echocardiography, or both, in their diagnostic algorithm for acute thoracic aortic injury. These diagnostic algorithms are individually tailored by each institution and are still under investigation; therefore, no definite conclusions can be reached.

Acute Disease↗
PubMed1996

Transiently catecholaminergic cells in the fetal rat express mRNA for the glutamate NMDAR1 receptor.

The N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor has been shown to be vital to the development of the central nervous system. The purpose of this study was to determine if the neural crost-derived precursors which migrate to the primitive gut contain mRNA encoding for the NMDA receptor. Many of these enteric precursors briefly elaborate tyrosine hydroxylase (TH) and have been termed transiently catecholaminergic (TC) cells. TH-like immunoreactivity (TH-ir) serves as a marker for them. Immunocytochemistry combined with NMDAR1 in situ hybridization revealed that TH-ir cells in Day 14 rat embryos do express mRNA coding for the NMDAR1 receptor. However, the TC cells did not contain detectable levels of immunoreactivity for the NMDAR1 receptor peptide. The absence of detectable NMDAR1-like immunoreactivity might reflect some form of transcriptional or translational regulation, such that the onset of functional receptor activity is delayed until differentiation and/or synaptogenesis commence. Whether TC cell migration is glutamate-mediated remains unclear, since some of them successfully reached the gut without expressing NMDAR1 message. Characterizing TC cell NMDA receptor activity and determining exactly when it ensues will be of paramount importance to defining the role(s) of this receptor in ENS development. In conclusion, the expression of NMDAR1 mRNA by TH-ir cells suggests a possible developmental role for this receptor.

Animals↗
PubMed1995

Expression of mRNA for the N-methyl-D-aspartate (NMDAR1) receptor and vasoactive intestinal polypeptide (VIP) co-exist in enteric neurons of the rat.

Anatomical, physiological and pharmacological evidence suggests that vasoactive intestinal polypeptide neurons are important mediators of the descending inhibitory component of intestinal peristalsis. Pharmacological data also indicate that glutamate may modulate intestinal motility. Recently, we demonstrated that mRNA coding for the glutamate N-methyl-D-aspartate (NMDA) receptor is expressed by rat enteric neurons. In order to ascertain whether NMDA receptor message is expressed by vasoactive intestinal polypeptide (VIP) neurons, we employed a double in situ hybridization technique. We hybridized tissue sections from the stomach, ileum and descending colon of adult rats with an NMDAR1 oligoprobe and a VIP oligonucleotide. Enteric neurons expressing mRNA for both NMDA and VIP were found in the myenteric and submucosal ganglia at all of the sampling sites. These data suggest that the mechanism for glutamatergic excitation is present in VIP-containing enteric neurons.

Animals↗
PubMed1994

Expression of mRNA for the N-methyl-D-aspartate (NMDAR1) receptor by the enteric neurons of the rat.

In this study, in situ hybridization techniques were employed to map the distribution of enteric neurons which express mRNA for the glutamate N-methyl-D-aspartate receptor 1 (NMDAR1). We hybridized tissue sections from the stomach, duodenum, ileum and descending colon of adult rats with a 1.43-kB riboprobe cleaved from a clone of the NMDA receptor. Enteric neurons expressing the mRNA were found in both myenteric and submucosal ganglia at each of the sampling sites. Possible functions of NMDA receptors on enteric neurons are discussed.

Animals↗
PubMed1993

Bromodeoxyuridine induces chromosomal fragile sites in the canine genome.

Peripheral blood lymphocytes from 3 clinically normal domestic dogs were cultured for bromodeoxyuridine (BrdU) induction of fragile site expression. BrdU induced fragile site expression in cells from all 3 dogs. The mean percent of cells with fragile sites and the mean number of fragile sites per cell were significantly increased in all BrdU incubated cultures compared to control cultures. The frequency of BrdU fragile site expression did not vary significantly among the dogs. Lymphocytes from all 3 dogs expressed BrdU induced autosomal fragile sites. Two BrdU induced fragile sites were identified on the long arm of chromosome 1, one of which was close to or coincident with a previously identified folate sensitive fragile site on this canine chromosome. Lymphocytes from the 2 female dogs also expressed BrdU induced fragile sites on the X chromosome, but BrdU failed to induce fragile sites on the X chromosome from the one male dog in the study. The 2 BrdU-induced fragile sites identified on the long arm of the X chromosome were close to, or coincident with 2 previously described folate-sensitive common fragile sites on the canine X chromosome. This is the first report of induction of BrdU-inducible fragile sites in the genome of the domestic dog.

Animals↗
PubMed1993

Folate-sensitive and aphidicolin-inducible fragile sites are expressed in the genome of the domestic cat.

Peripheral blood lymphocytes from three clinically normal domestic cats were cultured for folate-sensitive and aphidicolin-inducible fragile site expression. Induction of folate-sensitive fragile sites was accomplished by culturing cells with trimethoprim plus caffeine. Chromosomes from all cats expressed both folate-sensitive and aphidicolin-inducible breaks and gaps. There were no significant differences between the two methods of fragile site induction in the percentage of cells expressing chromosome breaks and gaps or the mean number of breaks and gaps per cell. All three cats expressed specific chromosome breaks resembling fragile sites at A1q21-22, A1p22, and B1q32. All three sites were induced by aphidicolin. The sites at A1q21-22 and B1q32 were also induced in folate-deficient medium. This is the first report of the induction of chromosomal fragile sites in a feline species.

Animals↗
PubMed1990

Sequential assessment of pulmonary epithelial diethylene triamine penta-acetate clearance and intrapulmonary transferrin accumulation during Escherichia coli peritonitis.

The individual roles of pulmonary capillary endothelial and alveolar epithelial permeability in the pathogenesis of the adult respiratory distress syndrome (ARDS) are unclear. We developed a method for the sequential assessment of pulmonary macromolecule accumulation and small solute clearance in vivo using a gamma camera. We measured the exponential clearance coefficient of 111In-labeled diethylene triamine penta-acetate (111In-DTPA) to assess airway clearance of small solutes. We also calculated the exponential equilibration coefficient of 111In-labeled transferrin (111In-TF) to assess intrapulmonary accumulation of transferrin. We determined these parameters in guinea pigs with Escherichia coli peritonitis and compared them with a saline-treated control group, oleic-acid-treated groups, and a group treated with low molecular weight dextran Ringer solution. The pulmonary DTPA clearance and the intrapulmonary transferrin accumulation were significantly increased in the peritonitis group (29.4 +/- 8.2 x 10(-3) min-1, p less than 0.02, and 15.1 +/- 3.1 x 10(-3) min-1, p less than 0.02) when compared with the control group (3.1 +/- 0.8 x 10(-3) min-1 and 4.5 +/- 0.5 x 10(-3) min-1). These changes developed within 5.5 h of the initial insult. Neither increased extravascular lung water nor elevated pulmonary artery and left atrial pressures were detected in the peritonitis group. The low molecular weight dextran Ringer group did not show a significant increase in the pulmonary DTPA clearance and the intrapulmonary transferrin accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Multiple organ damage caused by tumor necrosis factor and prevented by prior neutrophil depletion.

The effect of TNF on nonpulmonary multiple organ damage (MOD) was studied. Since polymorphonuclear leukocytes (PMN) are thought to play an important role in septic or TNF-induced MOD, we investigated both neutrophil sufficient (PMN+) and neutropenic (PMN-) guinea pigs. Sepsis was induced by Escherichia coli administration (2 x 10(9)/kg) or recombinant human TNF (1.4 x 10(6) U/kg) was infused into PMN+ and PMN- guinea pigs. During necropsy, the PMN+/TNF and PMN+/E coli animals exhibited marked damage in the adrenal glands, kidneys and liver as evidenced by hemorrhage, congestion, and PMN sequestration on histopathologic examination. There was also increased tissue albumin accumulation in the adrenal glands, kidneys, spleen, heart, and liver as demonstrated by 125I-labeled albumin determinations. In contrast, the PMN-/TNF group did not reveal histopathologic damage in any organ system and there was no abnormal organ accumulation of 125I-albumin. However, in PMN-/E coli animals, marked histopathologic damage in the adrenal glands and liver was evident. Furthermore, there were marked accumulations of 125I-albumin in the adrenals, heart, kidneys, liver, and spleen. Moreover, the PMN-/E coli guinea pigs had a much greater accumulation (p less than 0.01) of 125I-albumin in the kidneys than any other group including the PMN+/E coli group. Thus, nonpulmonary MOD in guinea pigs is caused by TNF administration and can be prevented by PMN depletion. However, while E coli administration also caused marked nonpulmonary MOD in neutrophil sufficient guinea pigs, equivalent or greater damage was produced in neutropenic animals. This suggests that while TNF-induced MOD may be primarily mediated by PMN, E coli-induced MOD seems to be mediated by more than PMN.

Adrenal Glands↗
PubMed1989

Effects of tumor necrosis factor on PMN chemotaxis, chemiluminescence, and elastase activity.

Tumor necrosis factor (TNF) has been proposed as an important mediator of the inflammatory response in acute lung injury. To better understand polymorphonuclear leukocyte (PMN) activation during acute lung injury, we evaluated the effects of TNF on several in vitro PMN functions, including chemotaxis, chemiluminescence, and elastase activity. In the chemotaxis assay using a modified Boyden chamber, TNF alone or with N-formyl-methionyl-leucyl-phenylalanine (FMLP, 10(-8) mol/L) did not alter PMN migration. TNF suspended with 1% zymosan-activated serum (ZAS) increased PMN migration at low concentrations and decreased migration at high concentrations (control 99 +/- 4.8 microns, n = 9; TNF 0.1 ng/ml 135 +/- 9.4 microns, n = 5, p less than 0.01; TNF 1000 ng/ml 62 +/- 7.5 microns, n = 5, p less than 0.01). In the chemiluminescence assay, TNF (1000 ng/ml) induced a 3-fold increase in the PMN chemiluminescent response. However, TNF incubated with PMN did not cause an increase in supernatant elastase activity. These data reveal TNF induced the production of PMN reactive oxygen species as evidenced by an increased chemiluminescent response. Whereas TNF increased chemotaxis at low concentrations in the presence of 1% ZAS, high concentrations of TNF similar to levels detected in septic shock caused a decrease in chemotaxis that might contribute to retaining PMN in sites of inflammation. It is thus suggested that TNF may contribute to inflammation by stimulating the production of PMN-reactive oxygen species and modulating-PMN chemotaxis.

Acridines↗
PubMed1989

Effects of anti-C5a antibodies on human polymorphonuclear leukocyte function: chemotaxis, chemiluminescence, and lysosomal enzyme release.

Previous investigation has demonstrated that in vivo complement activation can produce acute lung injury. Complement component C5a has been implicated as a key factor in this damage. In addition, C5a is thought to play a central role in mediating polymorphonuclear leukocyte (PMN) function. Studies suggest that administering antibodies to C5a might play a role in attenuating lung injury in animal models of sepsis. To evaluate further the effects of anti-C5a antibodies, we compared the effects of anti-human C5a des-Arg monoclonal (MAb) and polyclonal (PAb) antibodies on PMN functions including chemotaxis, chemiluminescence, and lysosomal release. PMN chemotaxis was assayed in Boyden chambers using 0.5% zymosan-activated serum (ZAS) as a source of C5a and 0.5% normal human serum (NHS) as a control. PMN chemiluminescence was measured by scintillation counting using ZAS as a stimulant and NHS as control. In addition, the lysosomal marker enzyme beta-D-glucuronidase was spectrophotometrically determined to assess lysosomal release. The PMN chemotactic response to ZAS was completely abolished with MAb and PAb anti-C5a antibodies (p less than 0.01). Control antibodies had no effect on ZAS-stimulated chemotaxis. The anti-C5a MAb markedly inhibited PMN chemotaxis at concentrations ranging from 20 to 0.2 microgram/ml, and was approximately 30 times more potent than the PAb. ZAS-stimulated PMN chemiluminescence was markedly decreased in response to monoclonal antibodies to C5a. In contrast, the control antibody did not inhibit ZAS-stimulated PMN chemiluminescence. Anti-C5a antibodies also significantly attenuated the release of the lysosomal enzyme beta-D-glucuronidase from ZAS-stimulated PMN. Anti-C5a antibody treatment did not cause a significant lytic effect when incubated with PMN, as demonstrated by the absence of the cytoplasmic marker lactate dehydrogenase in the supernatant. These studies suggest that in states of complement activation, MAbs and PAbs may decrease PMN functions including chemotaxis, chemiluminescence, and lysosomal enzyme release.

Antibodies↗
PubMed1988

Pulmonary edema after Escherichia coli peritonitis correlates with thiobarbituric-acid-reactive materials in bronchoalveolar lavage fluid.

We developed a new model of acute lung injury caused by live Escherichia coli peritonitis in guinea pigs. Arterial blood gas determinations, arterial blood pressure, and white blood cell counts were monitored serially for 12 h after the injection of either 2 x 10(9) E. coli J96 or saline. Lung water, albumin concentration in bronchoalveolar lavage fluid (BALF) and in lung tissue, WBC counts in BALF, and thiobarbituric-acid-reactive materials (TBARM) in plasma, lung tissue, and BALF were examined. Increased TBARM might be associated with pulmonary injury and are produced either by the generation of lipoperoxides secondary to oxygen-free radicals or as metabolic byproducts of prostanoid metabolism. Lung tissue sections were studied by light microscopy. E. coli peritonitis, as compared with control animals, caused significant peripheral neutropenia, histopathologic evidence of lung inflammation, acidosis, and hypotension. The wet-to-dry lung ratio was increased in the peritonitis group when compared with that in the control group (p less than 0.01). Pulmonary edema in the peritonitis group was associated with significantly increased albumin concentrations in BALF and lung tissue. We report the new finding of increased TBARM concentrations in BALF after E. coli peritonitis (p less than 0.01 and p less than 0.05, respectively). In contrast, plasma TBARM concentrations were unchanged. The levels of TBARM in the BALF correlated significantly with both lung water (p less than 0.01) and lung tissue albumin concentration (p less than 0.01). The measurement of elevated TBARM in BALF may allow acute lung injury to be detected. We conclude that this model may be useful for further studies of acute lung injury caused by E. coli peritonitis.

Animals↗
PubMed1988

Tumor necrosis factor causes increased pulmonary permeability and edema. Comparison to septic acute lung injury.

Tumor necrosis factor alpha (TNF), a monokine produced by mononuclear cells in response to bacterial endotoxin (LPS), creates a syndrome similar to septic shock in animal models. To study whether TNF could induce acute lung injury similar to that seen in gram-negative sepsis, we injected recombinant human TNF (rHuTNF alpha) into guinea pigs and monitored arterial blood gases, leukocyte counts, and left atrial (Pla), pulmonary artery (Ppa), and mean arterial pressures (MAP) serially for 8 h. Pulmonary histopathology was assessed microscopically, and cell counts and 125I-labeled albumin (125I-albumin) in bronchoalveolar lavage (BAL) fluid and lung wet/dry weight ratios were determined. Five groups of animals were studied; the 2 TNF groups received high (1.4 X 10(6) U/kg) or low (1.0 X 10(6) U/kg) doses of rHuTNF alpha, the sepsis group received 2 X 10(9) Escherichia coli/kg intravenously, and the control group received saline. An LPS control group receiving 40 ng/kg E. coli LPS was also included because the rHuTNF alpha contained a small amount of LPS as a contaminant. Pulmonary permeability was assessed by studying the Pla and the BAL fluid/plasma 125I-albumin ratio (permeability index). The permeability index was significantly increased in the high-dose TNF (0.0408 +/- 0.0041, p less than 0.05) and sepsis groups (0.0466 +/- 0.0068, p less than 0.01) relative to controls (0.0215 +/- 0.0028). The wet/dry lung weight ratios were also significantly increased in the high-dose TNF (6.07 +/- 0.29, p less than 0.05) and sepsis groups (6.22 +/- 0.30, p less than 0.05) relative to the control group (5.18 +/- 0.20).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Attenuation of acute lung injury in septic guinea pigs by pentoxifylline.

Pentoxifylline (PTXF), a drug demonstrated to improve intermittent claudication, is a methylxanthine that increases intracellular cyclic AMP (cAMP) and, unlike theophylline, has few side effects. Because increased cAMP levels have been associated with a decrease in lung injury, we examined the effects of PTXF on acute lung injury in a septic guinea pig model. Five groups of guinea pigs were studied over a period of 8 h. (Group I: saline control injected intravenously with 2 ml of saline; Group II: septic control injected intravenously with 2 x 10(9) Escherichia coli; Group III: E. coli septicemia plus PTXF bolus 20 mg/kg injected 5 min before E. coli injection; Group IV: E. coli septicemia plus PTXF continuous infusion, begun with bolus [20 mg/kg] followed by continuous infusion [20 mg/kg/h] started 60 min before injection of E. coli; Group V: PTXF continuous infusion [20 mg/kg/h] control). Arterial blood gases, arterial blood pressure, and blood WBC counts were monitored serially for 8 h. Lung water (wet-to-dry ratio), the concentration ratio of 125I-labeled albumin in bronchoalveolar lavage (BAL) fluid to that in plasma (albumin index; AI), total cell count in BAL fluid, thiobarbituric-acid-reactive material (TBARM), and the lysosomal enzyme beta-glucuronidase (beta-G) were examined. Lung tissue was studied histologically to assess neutrophil accumulation. Our results showed that E. coli septicemia caused significant peripheral neutropenia and histopathologic evidence of neutrophil alveolitis associated with an increased ratio of TBARM and beta-G in BAL fluid as compared with those in plasma (TBARM BAL ratio and beta-G BAL ratio).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗