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Biomedical subjects

B Johnston

Publications and source records attributed to B Johnston.

At least 37 records · Page 2Linked to original sources
PubMed1999

Endothelin-1 causes P-selectin-dependent leukocyte rolling and adhesion within rat mesenteric microvessels.

Endothelin-1 (ET-1) is a potent vasoconstrictor postulated to play a role in hypertension, ischemia-reperfusion, and atherosclerosis. In addition to these contributions, it has been also proposed to induce leukocyte-endothelial cell interactions. The aim of the present study was to assess the mechanisms of action of ET-1 on leukocyte recruitment in vivo. Intravital microscopy of the rat mesenteric postcapillary venules was used. Ten minutes after 1 nM ET-1 superfusion, a significant increase in leukocyte rolling (77.5 +/- 22.6 vs. 20.5 +/- 4.5 cells/min) and adhesion (15.5 +/- 2.9 vs. 3.0 +/- 0.8 cells/100 micrometer) but not emigration was observed. These effects were found not to be mediated by mast cell activation. No platelet-endothelial cell interactions were detected in this in vivo system and furthermore, flow cytometry analysis revealed no increase of P-selectin expression in rat platelets on ET-1 stimulation. Pretreatment of animals with an anti-rat P-selectin monoclonal antibody (mAb) dramatically reduced leukocyte rolling and adhesion by 100 and 94% respectively when compared with control mAb-treated animals. At this dose of ET-1, a very transient decrease in shear rate was detected, arteriolar diameter was significantly reduced but venular diameter remained unchanged. A similar mechanical reduction in blood flow did not induce leukocyte recruitment. Thus this study demonstrates that ET-1 can directly cause significant leukocyte rolling and adhesion adding to its potential pathophysiological role in the development of disease states of the cardiovascular system.

Animals↗
PubMed1999

Chronic inflammation upregulates chemokine receptors and induces neutrophil migration to monocyte chemoattractant protein-1.

Monocyte chemoattractant protein-1 (MCP-1) is a CC chemokine that stimulates monocyte recruitment when injected into tissues of healthy animals. However, the function of this chemokine in models with preexisting inflammation is not known. Therefore, MCP-1 was superfused over the mesentery of naive rats or rats with chronic adjuvant-induced vasculitis. MCP-1 elicited increased leukocyte transendothelial migration in adjuvant-immunized rats compared with naive animals. Surprisingly, histology revealed that neutrophils constituted the majority of leukocytes recruited in adjuvant-immunized animals. In vitro, MCP-1 was also able to induce chemotaxis of neutrophils isolated from adjuvant-immunized rats but not from naive rats. Flow cytometry revealed novel expression of the CC chemokine receptors CCR1 and CCR2 on neutrophils from adjuvant-immunized animals. In naive animals, an antibody against CD18 blocked leukocyte adhesion and emigration in response to MCP-1. In adjuvant-immunized animals, leukocyte adhesion was reduced by antibodies against the alpha4-integrin but not by antibodies against CD18. However, the CD18 antibody did block emigration. To our knowledge, this study is the first to show increased sensitivity to a CC chemokine in a model with preexisting inflammation, and altered leukocyte recruitment profiles in response to MCP-1. It also demonstrates that CD18 is required for chemokine-induced leukocyte transendothelial migration, independent of its known role in mediating firm adhesion. J. Clin. Invest. 103:1269-1276 (1999).

Animals↗
PubMed1999

Observer variability in interpretation of abdominal radiographs of infants with suspected necrotizing enterocolitis.

We examined (1) the observer variability (both interobserver and intraobserver) in interpretation of abdominal radiographs of infants with suspected necrotizing enterocolitis (NEC), (2) the interobserver variability for individual radiologic signs used to diagnose NEC, and (3) the influence of experience in determining the extent of observer variability. Our hypotheses were (1) there would be considerable observer variability in interpretation of abdominal radiographs of infants with suspected NEC; (2) the extent of observer variability would differ for individual radiologic signs of NEC; and (3) the extent of observer variability would be determined by the observer's experience. The participants included 12 observers: two pediatric radiologists, four attending neonatologists, three neonatal fellows, and three pediatric residents. The participating observers under similar interpretation conditions, twice independently, interpreted the same 40 pairs of abdominal radiographs from infants with suspected NEC. The interval between the two interpretations was 3 to 6 months. Intraobserver and interobserver variability was assessed by applying the Kappa statistic to the radiologic signs of NEC for the two separate interpretations. The observers were blinded to patient's identity and the clinical course. Each observer recorded the absence, suspicion, or presence of (1) intestinal distention, (2) air fluid levels, (3) bowel wall thickening, (4) pneumatosis intestinalis, (5) portal venous gas, (6) pneumoperitoneum, and (7) NEC. We found low intraobserver and interobserver agreements. There was considerable variation in observer variability for individual radiologic signs. Trained observers performed better than intraining observers. We conclude that the radiologic signs in isolation should not be considered reliable. We recommend studies to formulate more objective criteria for many of the radiographic features of NEC. Standardization and periodic enforcement of these criteria among observers could reduce observer variability. We suggest that, to decrease both false-negative and false-positive interpretation, an experienced observer should always review the radiographs of infants with suspected NEC.

Diagnosis, Differential↗
PubMed1999

Nitric oxide inhibits microvascular protein leakage induced by leukocyte adhesion-independent and adhesion-dependent inflammatory mediators.

OBJECTIVE: The purpose of this study was to determine whether exogenous nitric oxide could block permeability alterations induced by neutrophil-independent (histamine) and neutrophil-dependent (CINC/gro) inflammatory mediators. METHODS: Intravital microscopy was used in the rat mesentery to examine leukocyte adhesion, transvascular FITC-albumin leakage, and perivascular mast cell activation (ruthenium red uptake) in response to local superfusion with histamine or the chemokine CINC/gro. The effects of the nitric oxide donor spermine-NO, or the cGMP analog 8-Br-cGMP were examined. RESULTS: Histamine superfusion increased vascular protein leakage within minutes, but did not increase firm adhesion above that seen in control preparations. The increase in albumin leakage could be prevented by co-administration of spermine-NO, but was not affected by 8-Br-cGMP. CINC/gro elicited a linear increase in vascular protein leakage and a profound increase in leukocyte adhesion. Treatment with spermine-NO or 8-Br-cGMP significantly attenuated increases in both adhesion and albumin leakage. The actions of spermine-NO and 8-Br-cGMP were not due to mast cell stabilization as neither histamine nor CINC/gro elicited mast cell activation. CONCLUSIONS: This study demonstrates that exogenous nitric oxide and 8-Br-cGMP could block adhesion dependent alterations in vascular permeability induced by CINC/gro, while adhesion-independent alterations in permeability induced by histamine could be blocked by exogenous NO but not 8-Br-cGMP. This suggests that different NO-dependent signalling pathways are important in modulating these two types of vascular protein leakage.

Animals↗
PubMed1998

The functional paradox of CD43 in leukocyte recruitment: a study using CD43-deficient mice.

Although there is considerable evidence implicating a role for CD43 (leukosialin) in leukocyte cell-cell interactions, its precise function remains uncertain. Using CD43-deficient mice (CD43(-/-)) and intravital microscopy to directly visualize leukocyte interactions in vivo, we investigated the role of CD43 in leukocyte-endothelial cell interactions within the cremasteric microcirculation under flow conditions. Our studies demonstrated significantly enhanced leukocyte rolling and adhesion after chemotactic stimuli in CD43(-/-) mice compared with wild type mice. Using an in vitro flow chamber, we established that the enhanced rolling interactions of CD43(-/-) leukocytes, primarily neutrophils, were also observed using immobilized E-selectin as a substrate, suggesting that passive processes related to steric hindrance or charge repulsion were likely mechanisms. Despite increased adhesion and rolling interactions by CD43(-/-) leukocytes, we uncovered a previously unrecognized impairment of CD43(-/-) leukocytes to infiltrate tissues. Oyster glycogen-induced neutrophil and monocyte infiltration into the peritoneum was significantly reduced in CD43(-/-) mice. In response to platelet activating factor, CD43(-/-) leukocytes were impaired in their ability to emigrate out of the vasculature. These results suggest that leukocyte CD43 has a dual function in leukocyte-endothelial interactions. In addition to its role as a passive nonspecific functional barrier, CD43 also facilitates emigration of leukocytes into tissues.

Animals↗
PubMed1998

Serum prolactin and dehydroepiandrosterone concentrations during the summer and winter hair growth cycles of mink (Mustela vison).

We investigated the relationship between serum concentrations of prolactin (PRL) and dehydroepiandrosterone (DHEA) during initiation and development of summer and winter hair growth (anagen) cycles in mink. In the spring, haloperidol (HAL) increased PRL concentrations and induced summer anagen earlier than controls, whereas melatonin (MEL) inhibited PRL secretion and completely blocked summer anagen. In the fall, HAL increased PRL concentrations, inducing anagen at an earlier time than controls, although the resulting fur was abnormal being almost devoid of underhair fibers. Exogenous MEL during the fall reduced PRL concentrations, initiating winter anagen 4 weeks earlier than controls. Adrenalectomy (ADX) induced earlier onset of summer and winter anagen and neutralized the inhibitory effects of HAL in the fall and MEL in the spring. No change in serum DHEA concentrations was observed during the onset of summer or winter anagen in any group although MEL increased DHEA levels from 27 March through 5 June relative to HAL-treated mink. We conclude that changes in serum levels of DHEA and PRL are not requisite to onset of summer or winter anagen in mink. It is possible that metabolites of DHEA and/or PRL may still affect other aspects of the hair growth cycle.

Adrenal Glands↗
PubMed1998

A role for mast cells in the development of adjuvant-induced vasculitis and arthritis.

The objective of this study was to characterize the role of mast cells in the development of vasculitis and joint swelling in adjuvant-immunized rats. Leukocyte trafficking within mesenteric venules (rolling and adhesion) and mast cell activation (ruthenium red uptake) were examined in vivo. Elevated leukocyte trafficking was observed by 4 days after immunization, whereas joint swelling developed between days 10 and 12. Perivascular mast cells took up ruthenium red and appeared activated by electron microscopy at 4 but not 12 days after immunization. Treatment with the mast cell stabilizer cromolyn on days 1 to 4 after immunization blocked ruthenium red uptake at day 4 and reduced leukocyte rolling and adhesion by approximately 50%. This treatment also reduced rolling, adhesion, and joint swelling at day 12 by approximately 50%. Cromolyn treatment over days 9 to 12 reduced joint swelling but increased leukocyte emigration into the mesentery. Peritoneal mast cells isolated 4 days after immunization elicited significant neutrophil chemotaxis in vitro, whereas day 12 mast cells did not. Mast cell activation and vasculitis were absent in adjuvant-resistant Fisher/344 rats. These data suggest that mast cells play an early role in the initiation of vasculitis and may function by day 12 to limit infiltration of leukocytes from the vasculature. In the joint, however, mast cells appear to contribute to inflammation at early as well as later time points.

Animals↗
PubMed1998

Positive biochemical effects of a bioartificial liver support system (BALSS) in a porcine fulminant hepatic failure (FHF) model.

This study describes biochemical changes in the plasma and blood of pigs with devascularised livers treated in a bioartificial liver support system (BALSS). Porcine hepatic cells were incubated with collagen-coated dextran microspheres (CDM) for 3 hours and the medium tested to determine cellular metabolic activity. Incubation continued for a further 18 hours during which the hepatic cells attach to the CDM. The CDM-attached cells were inoculated into a hollow fibre bioreactor which was part of an extracorporeal support system. Hepatic cell content of the bioreactor was 6 x 10(9) cells. The system was tested in a controlled trial in pigs prepared in a surgical model of fulminant hepatic failure (FHF). When plasma from FHF pigs was circulated through the device containing hepatic cells, there was significantly less increase in the accumulation of ammonia and most amino acids, together with a decrease in plasma lactate and of one amino acid, compared to control experiments when hepatic cells were excluded. We conclude that primary porcine hepatocytes can contribute beneficial metabolic function in a BALSS.

Adenosine Triphosphate↗
PubMed1998

Cardiac sarcoidosis--an occult cause of sudden death: a case report and literature review.

Sarcoidosis is a multi-systemic granulomatous disease of unknown cause. It commonly involves lymph nodes, lungs, eyes, and skin. Cardiac sarcoid may be isolated, or associated with systemic involvement. Cardiac involvement is found in 20-50% of autopsied patients with sarcoidosis. However, it only gives rise to clinical manifestations in about 5% of patients. Cardiac involvement by sarcoid has been reported to manifest as complete heart block, papillary muscle dysfunction, congestive heart failure, pericarditis and/or effusion, conduction abnormality or arrhythmia, chest pain, and sudden death. The most common site of involvement is the interventricular septum base, which when involved may lead to heart block or arrhythmia. We report a case of sudden death in a 33-year-old male with a history of surgically repaired congenital heart disease. Although his congenital heart disease was originally postulated to be important in his death, autopsy examination revealed cardiac sarcoid with prominent involvement of the conduction system.

Adult↗
PubMed1998

Transurethral radiofrequency hot balloon thermal therapy in chronic nonbacterial prostatitis.

There is no universally successful therapy for chronic nonbacterial prostatitis. Successful outcomes of treatment have been independently reported with transurethral heat therapy and balloon dilation. The THERP transurethral "hot balloon" uses balloon dilation of the prostatic urethra and radiofrequency heating of the prostate. Patients with refractory chronic nonbacterial prostatitis were assessed with validated prostatitis-specific symptom indices prior to, 3, and 6 months after 900 seconds of THERP treatment. Although early results appeared promising the long-term results in four patients led to early termination of the study. Although one patient did have improvement at 6 months, no patient reported improvement at 9 months, and the adverse events (urinary retention, retrograde ejaculation, hematuria, urethral stricture, worsening of symptoms) of this treatment in prostatitis patients was significant. This study demonstrated no sustainable efficacy and substantial adverse effects for the use of combination balloon dilation and heat therapy for patients with chronic nonbacterial prostatitis.

Adult↗
PubMed1997

Differential roles of selectins and the alpha4-integrin in acute, subacute, and chronic leukocyte recruitment in vivo.

Adhesion blocking mAbs specific for rat P-, E-, and L-selectin and the alpha4-integrin were used to characterize leukocyte recruitment mechanisms in models of LTC4 (acute), LPS (subacute), and adjuvant-induced (chronic) inflammation. Intravital microscopy was employed to measure leukocyte rolling and adhesion in rat mesenteric venules. Superfusing the mesentery with 20 nM LTC4 elicited an increase in leukocyte rolling (66.8 +/- 3.8 vs 18.2 +/- 3.2 cells/min control) that was completely eliminated by an anti-rat P-selectin mAb. Superfusion with 1 microg/ml LPS induced a significant increase in leukocyte rolling within 15 min (73 +/- 8 vs 33 +/- 6 cells/min control). Rolling increased further starting at 105 min and peaked by 150 min (141 +/- 23 cells/min). LPS-induced leukocyte rolling was eliminated during the first 90 min by the P-selectin mAb. The later increase in leukocyte rolling was not prevented by a second treatment with P-selectin mAb or a function-blocking mAb against rat E-selectin. This later phase of leukocyte rolling was blocked by treatments with mAbs against either the alpha4-integrin or L-selectin. Twelve days following Mycobacterium butyricum immunization, 300 to 500 rolling cells/min were observed. This could be reduced approximately 50 to 60% by mAb against either the alpha4-integrin or L-selectin. The combination of both mAbs eliminated approximately 90% of rolling. Neither the P- nor E-selectin mAbs reduced rolling in this chronic inflammatory model. This study highlights differences in leukocyte adhesive mechanisms elicited by different stimuli and at different time points within the same vascular bed.

Animals↗
PubMed1997

A minimal role for selectins in the recruitment of leukocytes into the inflamed liver microvasculature.

A two-step paradigm for leukocyte recruitment has been established in a number of tissues including the mesentery, skin, and muscle, and necessitates an initial rolling step via the selectins before firm leukocyte adhesion via the integrins. In view of the many inflammatory diseases that involve the liver, we investigated the importance of rolling and the selectins in the hepatic microvasculature and compared the responses to that of the commonly used mesentery or cremaster microvasculature. We visualized the liver microvasculature using intravital microscopy and we determined that within the liver the majority of leukocytes adhere within the sinusoids (80%) in response to a chemotactic stimulus such as FMLP (20% in postsinusoidal venules) whereas leukocytes adhere exclusively within postcapillary venules in tissue like the mouse cremaster. In the sinusoids, the adhesive response to FMLP is not dependent upon selectins inasmuch as adhesion was not reduced in the sinusoidal vessels of P-selectin-deficient mice or E-selectin/P-selectin- deficient animals in the presence or absence of L-selectin antibody. No rolling or adhesion was detected in response to FMLP in the selectin-deficient cremaster microvasculature. Immunoneutralization of selectins with fucoidan in wildtype mice eliminated rolling and adhesion in the cremaster but failed to affect adhesion in the liver sinusoids in response to FMLP. More long-term leukocyte recruitment with lipopolysaccharide (4 h) was also impaired in the cremaster but not the liver microvasculature in selectin-deficient animals. Leukocyte adhesion in the sinusoids was reduced in P-selectin-deficient mice also lacking intercellular adhesion molecule-1 (ICAM-1). This study for the first time demonstrates that selectins are not an essential step for leukocyte recruitment into the inflamed liver microvasculature.

Animals↗
PubMed1997

Testosterone supplementation for hypogonadal impotence: assessment of biochemical measures and therapeutic outcomes.

PURPOSE: Although hypogonadism is a rare cause of erectile failure, impotent men are frequently treated with supplemental androgens. The results of such treatment and the individual merits of available formulations remain controversial. A series of hypogonadal men participated in a trial of oral testosterone undecanoate to assess the effectiveness of the medication, and use of biochemical and clinical outcome measures. MATERIALS AND METHODS: A consecutive sample of 23 hypogonadal impotent men received testosterone undecanoate orally for no less than 60 days. Serum levels of gonadotropins, testosterone, estrogens and sex hormone-binding globulin were measured before, during and after the trial. Sexual response and feeling of well-being were measured by daily diaries and visual analogue scales. RESULTS: Testosterone undecanoate produced restoration of plasma testosterone levels in all patients but a measurable improvement in sexual attitudes and performance in only 61%. Visual analogue scores were effective discriminants of the therapeutic response but none of the conventional biochemical measures predicted or correlated with clinical outcome. CONCLUSIONS: Testosterone undecanoate is an effective agent for treating hypogonadism. In hypogonadal impotent patients the most appropriate outcome measure for androgen supplementation is individual response to therapy, while conventional biochemical hormone determinations lack predictive value and fail to correlate with response.

Adult↗
PubMed1997

Rapid detection of bladder cancer: a comparative study of point of care tests.

PURPOSE: We assessed sensitivity, specificity, accuracy, positive predictive value and negative predictive value of the bladder tumor antigen (Bard BTA), fibrinogen/fibrin degradation products (AuraTek FDP), urinary cytology and hemoglobin dipstick tests in the urine of patients presenting to a urology clinic. MATERIALS AND METHODS: A total of 130 patients (60 with bladder cancer) provided a urine sample, which was divided into appropriate aliquots for each of the tests cited above. The endoscopist, pathologist, cytologist and the person performing the BTA/FDP/hemoglobin dipstick were blinded as to the results of the other tests, and the tests were read independently by a second blinded evaluator. RESULTS: Comparative results demonstrate a clear superiority of FDP in sensitivity (81%) and overall accuracy in bladder cancer detection (p = 0.0001) while cytology and BTA were marginally better than FDP in specificity. CONCLUSIONS: The anticipated lack of specificity of the hemoglobin dipstick was confirmed as well as the inadequacy of urinary cytology, particularly in the well differentiated tumors. Our findings with BTA were disappointing. The superiority of the FDP, first demonstrated here, was particularly striking in its ability to detect even well differentiated tumors. The simplicity and significantly better overall performance of FDP make it a reliable test for detection of transitional cell carcinoma of the bladder and a potential alternative to urinary cytology with important implications for clinical practice and health economics.

Aged↗
PubMed1997

Intralesional administration of biological response modifiers in the treatment of localized cancer of the prostate: a feasibility study.

OBJECTIVES: The primary aims of this pilot study were to establish the feasibility of intraprostatic administration of biological response modifiers (BRMs) and to investigate the toxicity and side effects of recombinant interferon (IFN)-alpha-2b injected into prostate glands harboring cancer. A secondary goal was to perform a preliminary assessment of the antitumor effect of this treatment. METHODS: Nine patients with histologically documented carcinoma of the prostate participated in the study. IFN was administered weekly for 5 weeks, under transrectal ultrasound visualization, with a modified gun that permitted the controlled injection of small volumes initially into the area of the tumor and later into the whole gland. Total doses of IFN ranged between 15 and 100 MU. RESULTS: The procedure resulted in minor local discomfort, comparable to a prostatic biopsy. Side effects from the drug were those anticipated from most BRMs (chills, fever, malaise, headache, fatigue), and in every case they were minor and self-limiting to several hours. Local adverse events were limited to gross hematuria (2 patients [22%]) and hematospermia (1 patient [11%]) and resolved spontaneously within 2 weeks. Antitumor activity, a secondary goal of the study, was noted in 3 (33%) patients with limited follow-up (mean 22.5 months). CONCLUSIONS: The results of this pilot study indicate that the intraprostatic administration of IFN-alpha-2b can be readily accomplished by the method described here and is associated with minor, self-limited toxicity. With the regimen and doses used, IFN demonstrated modest antineoplastic activity. Modifications of the schedule, routes, and amounts administered may result in enhanced therapeutic value.

Aged↗
PubMed1997

Combined videomanometric identification of abnormalities related to pharyngeal retention.

RATIONALE AND OBJECTIVES: The authors determined the usefulness of performing videoradiography and pharyngeal solid-state manometry during barium swallow in dysphagic patients with pharyngeal retention. METHODS: Results were retrospectively analyzed of simultaneous videoradiography and manometry examinations in 14 patients with retention of barium in the pharynx. Twelve age-matched patients without retention served as a control group. RESULTS: Patients with retention regularly had less opening of the upper esophageal sphincter than patients without retention (7.6 vs 10.3 mm, respectively; P = .003). In patients with retention, the laryngeal elevation was lower (17.1 vs 23.8 mm, respectively; P = .001), and the resting pressure of the upper esophageal sphincter was significantly lower (42.4 vs 54.0 mm Hg, respectively; P = .04). The duration of upper esophageal sphincter relaxation was also shorter in patients with retention (374 vs 603 msec, respectively; P = .003). The peak pharyngeal contraction pressure was not significantly different. CONCLUSION: The constrictors play a minor role in the conveyance of the bolus through the pharynx. Pharyngeal shortening could be the most important mechanism in bolus transport.

Adult↗