Microbial degradation of benzene, toluene, ethylbenzene and xylene isomers (BTEX) contaminated groundwater in Korea

A mixed culture derived from a gasoline-contaminated aquifer in Korea was enriched on toluene at 25 degrees C. A study was conducted to characterize the substrate interaction of BTEX by toluene-enriched consortia and determine the effects of initial BTEX concentration on BTEX degradation. Substrate degradation patterns in individual aromatics were found to differ significantly from patterns for aromatics in mixtures. In the experiment of a single substrate, toluene was degraded fastest, followed by benzene, ethylbenzene, and the xylenes. In BTEX mixtures, degradation followed the order of toluene, ethylbenzene, benzene, and the xylenes. The studies conducting with toluene-enriched consortia evaluated substrate interactions by the concurrent presence of multiple BTEX compounds and revealed a range of substrate interaction patterns including no interaction, stimulation, inhibition, and cometabolism. The simultaneous presence of benzene and toluene were degraded with a slight inhibitory effect on each other. Ethylbenzene was shown to be the most potent inhibitor of BTEX degradation. p-xylene also inhibited the degradation of benzene, toluene, and ethylbenzene, whereas the presence of either benzene or toluene enhanced the degradation of ethylbenzene and the xylenes.

Construction of transgenic mice with tissue-specific acceleration of mitochondrial DNA mutagenesis

Transgenic mice having rapid accumulation of mitochondrial DNA (mtDNA) mutations specifically in the heart were created. These mice contained a transgene encoding a proofreading-deficient, mouse mitochondrial DNA polymerase (pol gamma) driven by the promoter for the cardiac-specific alpha-myosin heavy chain. Starting shortly after birth greater than 95% of all pol gamma mRNA in the heart was transgene derived; expression in other tissues was low or absent. Mutations in cardiac mtDNA began to accumulate by 7 days after birth. At 1 month of age the frequency of point mutations was 0.014% as determined by DNA sequencing of cloned mtDNA. By long-extension PCR multiple different deletion mutations that had removed several thousand basepairs of genomic sequence were also detected. Sequencing of two deletion molecules showed that one was flanked at the breakpoint by direct repeat sequences. The expression of proofreading-deficient pol gamma had no apparent deleterious effect on mitochondrial DNA and protein content, gene expression, or respiratory function. However, associated with the rise in mtDNA mutation levels was the development of cardiomyopathy as evidenced by enlarged hearts in the transgenic mice. These mice may prove to be useful models to study the pathogenic effects of elevated levels of mitochondrial DNA mutations in specific tissues.

Klebsiella pneumoniae renal abscess

BACKGROUND

The clinical characteristics of renal abscess caused by Klebsiella pneumoniae have not been previously reported in case-series studies. The purpose of this study is to demonstrate the clinical characteristics of K pneumoniae renal abscess for early diagnosis and to identify the clinical risk factors associating with poor prognosis.

METHODS

We retrospectively reviewed the medical records of 24 patients with K pneumoniae renal abscess, from April, 1982 through February, 1998. The clinical presentations, including the demographic characteristics, predisposing disorders, initial signs and symptoms, laboratory test results, diagnostic radiology studies, therapeutic modalities and risk factors associated with mortality were studied.

RESULTS

The mean age was 58.7 years and the male to female ratio was 10:14. The most common predisposing factors were diabetes mellitus (58%), urolithiasis (25%) and immunosuppression (17%). Fever, chills and flank pain were the most common symptoms and signs, whereas pyuria, elevation of leukocyte count, glucose, blood urea nitrogen and creatinine were the common laboratory features. The distinct complications of K pneumoniae renal abscess were bacteremia in 13 (54%), emphysematous pyelonephritis in five (21%), and metastatic septic infection in three (12.5%). The cure rate was 52% (11/21) in patients treated with a combination of antibiotics and percutaneous drainage; however, six (35%) patients who survived required another surgical procedure for complete recovery. The overall mortality rate was 25%. The clinical factors of elderly age (>65 years) at presentation, lethargy, elevation of serum blood urea nitrogen and pulmonary complications were associated with poor prognoses.

CONCLUSIONS

Focusing on the early diagnosis of K pneumoniae renal abscess and recognition of the prognostic factors for a poor prognosis, we highlight the specific clinical characteristics that include elderly age, lethargy, impairment of renal function, metastatic septic lesions and pulmonary complications. All patients with K pneumoniae renal abscesses should receive empiric antibiotics and percutaneous drainage or aspiration, and surgical intervention as necessary for patients with intractable disease.

Wound healing patterns following perforation sustained during laser in situ keratomileusis

BACKGROUND AND PURPOSE

Corneal perforation during laser in situ keratomileusis (LASIK) may interfere with flap adhesion and wound healing. The purpose of this study was to investigate wound healing patterns following corneal perforation sustained during LASIK in rabbits.

METHODS

Forty-two pigmented rabbit eyes underwent LASIK surgery with 5.0-mm excimer laser treatment under the corneal flap. Animals were divided into two groups: group I (n = 19) underwent the regular LASIK procedure with -10.0 D treatment, without perforation; in group II (n = 23), the cornea was perforated with the excimer laser. Treatment was discontinued once perforation was observed, and the corneal flap was replaced without sutures. Slit-lamp biomicroscopy, photography, and scatterometry were performed preoperatively and at 1 and 2 days, 1 week, and weekly up to 1 month, 2 months, and 3 months postoperatively. Animals were killed at 1 day, 1 week, 1 month, and 3 months postoperatively and processed for light microscopic, electron microscopic, and immunohistochemical examinations.

RESULTS

In group I, the corneas remained clear throughout the experiment. In all eyes, the interface was not readily discernable clinically or histologically. Corneal wound healing was accompanied by minimal cell infiltration. Epithelial hyperplasia at the flap edge was noted at 1 week. Myofibroblast activation was found at the epithelial wedge where there was an epithelial basement membrane break. In group II, the anterior chamber was shallow with no iris incarceration at the end of surgery. The corneas were clear (n = 6) or showed mild to moderate edema (n = 12). Corneal edema peaked at 3.6 +/- 5.0 days and subsided thereafter. Corneal wounds healed similarly to those in group I except at the perforation site. The break in Descemet's membrane and endothelium was covered with a fibrin plug on day 1, which resolved thereafter. There was no statistically significant difference in the incidence of postoperative infection (p = 1.0) or flap displacement (p = 0.69) rates between the two treatment groups. The scatterometry index peaked at 2 to 3 weeks postoperatively and was significantly higher in group II than in group I (p < 0.001).

CONCLUSIONS

Although corneal perforation during LASIK surgery may interfere with immediate postoperative flap adhesion, corneal wound healing following LASIK perforation may be similar to that after an uncomplicated LASIK procedure.

Benzalkonium chloride and gentamicin cause a leak in corneal epithelial cell membrane

The purposes of this study are to characterize the pathophysiological effects of benzalkonium chloride and gentamicin on corneal epithelial cells and to determine the concentration dependent effect of these agents on membrane currents of these cells. Rabbit corneal epithelial cells were isolated and subdivided into small, medium and large cells according to their cell capacitance. Using whole cell clamp technique, potassium current of corneal epithelial cells was recorded. Transmembrane current was measured again after bathing in benzalkonium chloride 1, 3, 10, 30 and 100 micrometer ml(-1)for 3 min. The effect of gentamicin was tested at concentrations of 0.4, 1.0, 2.0, 4.0 and 10 mg ml(-1). Synergistic effect of gentamicin of the above mentioned concentrations in the presence of benzalkonium chloride 1 microgram ml(-1)was also measured. We found that small corneal epithelial cells had the highest depolarization-gated, outward potassium current density and large cells had the lowest current density, while medium cells had a current density in between. Benzalkonium chloride induced a concentration dependent increase in the leak current with increasing concentration from 1 to 100 microgram ml(-1). The increase of leak current in medium and large cells was less than that in the small cells. Gentamicin also caused a concentration dependent increase in leak current density from 0.4 to 10.0 mg ml(-1). The increase in leak current density was statistically significant when the concentration was 2.0 mg ml(-1)or higher in small corneal epithelial cells and 1.0 mg ml(-1)or higher in the medium and large cells. Benzalkonium chloride 1.0 microgram ml(-1)augmented the effect of gentamicin on epithelial cell membrane. The extent of enhancement was more prominent in larger than smaller cells. Using whole-cell clamp technique, we were able to determine the threshold concentration of gentamicin and benzalkonium chloride on the integrity of corneal epithelial cell membrane. The toxic action of both agents is mediated by an increase in leak current. We propose that the whole-cell clamp technique is a sensitive and useful tool in determining cytotoxic effects of various agents.

The frequency of point mutations in mitochondrial DNA is elevated in the Alzheimer's brain

Using a PCR-based strategy, we found that point mutation frequencies in mitochondrial DNA (mtDNA) were 2- to 3-fold higher in the parietal gyrus, hippocampus, and cerebellum from subjects with Alzheimer's disease (AD) compared to normal controls. In contrast, levels of a commonly studied deletion mutation, mtDNA(4977), were not elevated in AD. The frequency of point mutations did not vary significantly among the three brain areas, whereas the frequency of mtDNA(4977) was 15- to 25-fold lower in the cerebellum in comparison to the cortex; this regional variation was seen in both the normal and Alzheimer's brain. In blood mtDNA, point mutation frequencies were not elevated in AD patients. The elevated frequency of point mutations in all three brain regions is consistent with the idea that increased oxidant stress is associated with AD.

Absorption of rectally administered phenytoin: a pilot study

OBJECTIVE

To test the hypothesis that rectally administered phenytoin is absorbed in healthy volunteers.

DESIGN

This single-center, open-label crossover pilot study compared rectal absorption with intravenous administration of phenytoin injectable solution (7 mg/kg) in healthy volunteers. Twelve serial blood samples were taken from each volunteer beginning at time zero until 36 hours following administration. These were analyzed for presence of phenytoin by immunoassay.

SETTING

The study took place at St. Paul's Hospital, a tertiary care center.

PARTICIPANTS

Funding permitted for a sample size of five healthy participants, two men and three women, aged 21-45 years. Selection was by volunteer sample. Inclusion criteria were as follows: no known medical conditions, not receiving medication, no history of adverse drug reactions or allergies, not known to be pregnant, and normal liver function as determined per study protocol.

MAIN OUTCOME MEASURES

Signs of absorption as indicated by presence of phenytoin in blood samples, maximum concentrations (Cmax), time to Cmax (tmax), AUC, and apparent bioavailability.

RESULTS

Maximum mean concentrations of 2.4+/-1.1 mg/L (mean +/- SD) following rectal administration and 11.2+/-1.6 mg/L following intravenous administration were achieved during the first one to two hours (tmax in both treatment arms). Mean apparent bioavailability of the rectally administered phenytoin was 24.4+/-13.4% (15.8-44.1%).

CONCLUSIONS

Results from this pilot study demonstrate that rectal absorption of phenytoin begins within 30 minutes following single-dose administration and was reported by four out of five volunteers to be the preferred route. Further studies are required before extrapolation can be made to the patient population.

Outcomes of penetrating keratoplasty with imported donor corneas

PURPOSE

To analyze factors influencing the surgical success of penetrating keratoplasty and long-term graft survival when using imported donor corneas.

METHODS

Sixty-three donor corneas imported to Taipei from the Cincinnati Eye Bank from July 1992-June 1993 were used for penetrating keratoplasty. The corneal endothelium was examined using specular microscopy on arrival in Taiwan. The endothelial morphology and endothelial cell density (ECD) were compared with the photograph of the same cornea taken in the United States. The relationships of the surgical success rate with donor age, death to enucleation time, death to surgery time, and ECD were analyzed. The long-term graft survival and ECD of clear grafts were analyzed 4 years after surgery.

RESULTS

On specular microscopic examination. the imported corneas showed diminished endothelial reflection, blurred cellular borders, and increased dark areas, which were markedly different from the pictures of the corneal endothelium taken in the United States. The average ECD before transportation was 2,525+/-267/mm2 and decreased to 1,934+/-250/mm2 after transportation (p < 0.001), with an average endothelial cell loss of 590+/-247/mm2. The overall surgical success rate was 89% and did not correlate with any of the donor factors tested except death to surgery time. The surgical success rate decreased when the time from death to surgery was >7 days (p = 0.05), mainly because of poor reepithelialization. Four years after surgery, 24 grafts remained clear. The ECD had decreased by 72+/-5% in the clear grafts.

CONCLUSIONS

Our findings show that endothelial changes in imported donor corneas do occur after transportation, but the surgical success rate may not be influenced significantly if the penetrating keratoplasty is performed within 7 days after donor death. However, the ECD in the clear grafts 4 years after surgery is low.

Reducing financial barriers to HIV-related medical care: does the Ryan White CARE Act make a difference?

We evaluated whether the Ryan White CARE Act, which funds medical care and supportive services for low-income HIV-infected persons, equalizes health service use in San Francisco. Clients at nine CARE (n = 300) and four non-CARE (n = 172) funded sites completed self-administered questionnaires. There were no significant differences between CARE and non-CARE clients with respect to physician visits, hospitalization or emergency room use in the previous year after adjusting for sociodemographic characteristics and health status. Unemployment and poor health independently predicted higher medical service use. CARE appears to reduce financial barriers to medical services.

Corneal light scattering with stromal reformation after laser in situ keratomileusis and photorefractive keratectomy

OBJECTIVE

To correlate corneal light scattering with keratocyte and extracellular matrix reformation after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).

SETTING

Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, Maryland, USA.

METHODS

Sixteen pigmented rabbit eyes were randomly divided into 2 groups. Group 1 (n = 8) had a 5.0 mm, -10.0 diopter (D) LASIK treatment and Group 2 (n = 8), a 5.0 mm, -10.0 D surface PRK treatment after mechanical epithelial debridement. The stromal surface exposed at surgery was stained with dichlorotriazinylaminofluorescein (DTAF) solution. Slitlamp biomicroscopic and objective measurement of corneal light scattering using a scatterometer were performed 1 and 2 days and 1, 2, 3, 4, 8, and 12 weeks after surgery. In each group, 2 corneas were harvested at 1 week and 1 month and 4 corneas were harvested at 12 weeks. Tissue sections were examined by light and fluorescence microscopy. The percentage of newly formed stromal tissue was calculated and correlated with the scatterometry index.

RESULTS

In Group 1, corneas remained clear and healed without significant scarring throughout the study. In Group 2, subepithelial scarring was noted. Extracellular matrix reformation peaked at 1 month and showed a slight regression thereafter. The percentage of extracellular matrix reformation was strongly correlated with the scatterometry index (r = .86, P < .001).

CONCLUSIONS

In this study, significant subepithelial stromal tissue reformation followed PRK. The percentage of extracellular matrix reformation correlated well with the objective corneal light scattering measurements.

A vector DNA vaccine encoding pseudorabies virus immediate early protein demonstrates partial protection in mice against lethal virus challenge

An earlier study in our laboratory provided evidence that pseudorabies virus (PrV) immediate early protein (IE180) may contribute to the overall immune response against PrV. To examine the response by IE180 more closely, we initiated a vaccine trial in mice with a vector DNA construct that contains the gene encoding for IE180, designated pcDNAIE180. The DNA vaccine was delivered in gold microcarriers using a Helios Gene Gun, and 70% of BALB/c mice given the DNA vaccine (2 microg/mouse) seroconverted within 2 weeks. The remaining negative mice seroconverted after a single vaccine booster. Essentially similar results were obtained on vaccination of C57BL/6 mice, whereas C3H/HeJ mice remained negative after the first vaccination, but responded after a booster. Seven months after immunization with pcDNAIE180, an overall 25% of BALB/c, C3H/HeJ, and C57BL/6 mice receiving a lethal PrV challenge were protected. In addition, a significant passive transfer of IE180-specific antibodies to the offspring from pregnant mice vaccinated with pcDNAIE180 was observed. Interestingly, a moderate level of protection (27.6%) was also observed when these offspring received a lethal PrV challenge. Moreover, an enhancement of immune responses and a twofold increase in the level of protection were observed in mice that received a second vaccine booster by gene gun 8 months after the first vaccination. Together, these data support the theory that IE180 may indeed play a role in the overall protective immunity against PrV.

Factors associated with women's adherence to mammography screening guidelines

OBJECTIVE

To examine individual and environmental factors associated with adherence to mammography screening guidelines.

DATA SOURCES

A unique data set that combines a national probability sample (1992 National Health Interview Survey); a national probability sample of mammography facility characteristics (1992 National Survey of Mammography Facilities); county-level data on 1990 HMO market share; and county-level data on the supply of primary care providers (1991 Area Resource File).

STUDY DESIGN

The design was cross-sectional. DATA EXTRACTION/ANALYSIS: Data sets were linked to create an individual-level sample of women ages 50-74 (weighted n = 2,026). We used multipart, sequential logistic regression models to examine the predictors of having ever had mammography, having had recent mammography, and adherence to guidelines. We categorized women as adherent if they reported a lifetime number of exams appropriate for their age (based on screening every two years) and they reported having had an exam in the past two years.

PRINCIPAL FINDINGS

Only 27 percent of women had the age-appropriate number of screening exams (range 16 percent-37 percent), while 59 percent of women had been screened within two years. Women were significantly more likely to adhere to screening guidelines if they reported participating with their doctor in the decision to be screened; were younger; had smaller families, higher education and income, and a recent Pap smear; reported breast problems; and lived in an area with a higher percentage of mammography facilities with reminder systems, no shortage of primary care providers, higher HMO market share, and higher screening charges.

CONCLUSIONS

A small percentage of women adhere to screening guidelines, suggesting that adherence needs to become a focus of clinical, programmatic, and policy efforts.

Analysis of corneal topography after excimer laser photorefractive keratectomy

Excimer laser photorefractive keratectomy (PRK) is an effective treatment for myopia. We investigated the magnitude of optical zone decentration and qualitative patterns of corneal topography after this treatment. We performed computer-assisted videokeratography on 44 myopic eyes (29 patients) that had undergone PRK before and 1, 6, and 12 months after the procedure. Associations of clinical outcomes with decentration and topographic patterns were assessed. The normalized scale of the topography 1 month postoperatively showed a mean decentration of 0.33 +/- 0.23 mm (range 0-0.9). Thirty-four eyes had decentration of less than 0.50 mm; 10 had an ablation zone decentered from 0.5 to 0.9 mm. Analysis of geometric mean visual acuities between eyes with less than 0.5 mm decentration and those with 0.5 to 0.9 mm decentration demonstrated minimal differences. No eye was decentered more than 1 mm. Four main ablation patterns were noted on subtraction analysis: homogeneous, semicircular, keyhole, and central island. Over time, the number of eyes with a homogeneous pattern increased. Eyes with a homogeneous ablation pattern had significantly better uncorrected visual acuity than those with other patterns. The mean visual acuity was 20/29.1 in the homogeneous group and 20/38.5 in the pooled irregular group 1 month postoperatively (p < 0.05). There was no significant difference among the four ablation patterns at 6 or 12 months after PRK. Topographic patterns were not significantly associated with best-corrected vision.

Bacterial toxin-induced pulmonary epithelial cytotoxicity and the protective effect of dibutyryl-cAMP

Bacterial infection is the most common cause of the adult respiratory distress syndrome which, in turn is associated with endothelial capillary permeability and alveolar oedema. Previously, we have demonstrated the direct cytotoxicity of the bacterial toxins Pseudomonas aeruginosa exotoxin A (Exo A) and Salmonella enteritidis lipopolysaccharide (LPS) on pulmonary endothelial cells. The purpose of this study was to investigate the effect of Exo A and LPS on pulmonary epithelial cells in vitro. We also tested the protective effect of dibutyryl cyclic adenosine monophosphate (db-cAMP) on Exo A-induced cytotoxicity. In cultured rat alveolar epithelial cells (RAEC) Exo A caused cytotoxicity as measured by 51Cr release from these cells. LPS did not injure RAEC's. Pretreatment of RAEC with db-cAMP (1 mM) attenuated Exo A induced cytotoxicity. We conclude that (1) Exo A directly injures epithelial lung cells and may contribute to lung injury in cases of bacterial infection; (2) db-cAMP protects alveolar epithelial cells against Exo A-induced cytotoxicity and (3) alveolar epithelial cells in this model are resistant to LPS induced injury.

Nitrous oxide synthase expression in placenta of preeclampsia

To compare the expression of endothelial nitrous oxide synthase (e-NOS), which plays a major role in vasoconstriction, in preeclampsia with that in the normotensive placenta and to identify whether or not e-NOS actually influences the pathogenesis of preeclampsia, we have studied the distribution and intensity of the endothelial isoform of NOS expression in preeclampsia (n = 121) and normal (n = 14) pregnancies. Archival paraffin-embedded tissues were immunostained with a polyclonal e-NOS antibody. E-NOS was stained predominantly in the endothelial cells of the umbilical cord and along the surface of the villi, especially within the cytoplasms of the syncytiotrophoblasts with a granular and punctuated pattern, but not in the trophoblastic island or in the intravillous capillaries. The degree of e-NOS expression in pregnancy-induced hypertension (PIH) was significantly lower than in normotensive placenta, and moreover in the patients lacking abruptio. The expression of e-NOS in preeclampsia has some correlation with patient age. In conclusion, the degree of e-NOS expression in cotyledon from PIH is far less than from control, it means a kind of hemodynamic alteration of the fetoplacental circulation in preeclampsia.

Lung capillary changes in hepatic cirrhosis in rats

The hypoxemia of the hepatopulmonary syndrome may result from dilated intrapulmonary vascular segments. Knowledge of the size, density, and branching frequency of the lung capillaries might confirm this hypothesis and suggest that the pathogenesis may involve vascular dilatation or angiogenesis. To investigate these changes, the common bile duct of rats was tied off to cause biliary cirrhosis. Later (4 wk), the pulmonary vasculature of these animals was cast, and the casts were studied with scanning electron microscopy. In the ligated animals, evidence for enhancement of the bronchial to pulmonary circulation was found: cast vasa vasorum of the pulmonary arteries and cast bronchial veins emptying into pulmonary veins. Ligated animals had more adherent intracapillary cells per alveolus than the sham-operated animals. The diameters of all capillary beds were larger in the ligated animals. The alveolar capillary density was increased, but the branching frequency was not. A few areas suggesting angiogenesis were found. Induction of biliary cirrhosis enhances the pulmonary-systemic circulation, increases intracapillary adherent cells, capillary diameter, and density, and may be associated with angiogenesis.

Racial differences in timeliness of follow-up after abnormal screening mammography

BACKGROUND

To determine whether patient race was associated with timeliness of follow-up after abnormal screening mammography, a retrospective record review of diagnostic tests for women with abnormal screening mammography from a Northern California mobile van program was conducted.

METHODS

The study included 317 women between the ages of 33 and 85 who were reported to have abnormal screening mammography between July 1993 and May 1994. Measurements included patient demographics, screening mammography interpretation, follow-up diagnostic tests, and dates of diagnostic evaluation.

RESULTS

Women with abnormal screening mammography underwent a wide variety of diagnostic evaluations. Nonwhite women had significantly longer time (median time, 19 days) from date of index abnormal screening mammography to final disposition compared with white women (median time, 12 days). This racial difference was primarily due to the longer interval between index abnormal screening mammography and first diagnostic test (median time, 15 days for nonwhite women versus 7 days for white women, P < 0.001). The difference persisted when adjusting for patient age, family history of breast cancer, report of palpable mass, and income. The racial difference was similarly significant for each nonwhite subgroup (African American, Latina, and Asian) when compared with white women (P < 0.01).

CONCLUSIONS

Reasons for less timely follow-up of abnormal mammography among nonwhite women need to be identified. Delays that may be instigated by the patient or be due to her physician or system of care need to be explored further.

Corneal epithelial recovery following photorefractive keratectomy

AIMS

To further understand the morphological and functional recovery of corneal epithelium following excimer laser photorefractive keratectomy (PRK).

METHODS

The right eyes (group 1) of 15 male, New Zealand white rabbits weighing 2-3 kg underwent PRK. The left eye of each rabbit (group 2) underwent simple mechanical de-epithelialisation and were examined as treated controls. Both eyes of another eight rabbits (group 3) served as untreated controls. All eyes underwent a corneal epithelial permeability study by fluorophotometry at 2, 4, and 8 weeks after surgery. Five animals in groups 1 and 2 were sacrificed at 9, 10, and 12 weeks after surgery. The animals in group 3 were sacrificed at the end of the 12 week experimental period. Both eyes of each sacrificed animal were enucleated immediately and processed for both haematoxylin and eosin stain and electron microscopic study. The electron micrograph was magnified to 14,000x and the extent of hemidesmosome formation was quantified and analysed.

RESULTS

The corneal epithelial barrier to sodium fluorescein was subnormal and returned to a normal barrier state 4 weeks after PRK in group 1 whereas it was normal in group 2 throughout the examination period. The extent of hemidesmosome formation was abundant yet subnormal in both groups 1 and 2 up to 12 weeks, when compared with that in group 3.

CONCLUSION

The corneal epithelium regained its functional barrier 4 weeks after PRK in rabbits while the extent of hemidesmosome formation was still subnormal 12 weeks after mechanical de-epithelialisation, with or without PRK.

Pulmonary intravascular phagocytosis in liver disease

Pulmonary intravascular phagocytosis, the uptake of circulating particles by lung cells, has been detected in rats with chronic biliary cirrhosis and in humans with malignancy and liver diseases. Clinical and experimental evidence supporting the association of pulmonary intravascular phagocytosis with liver cirrhosis is reviewed, and its relationship to pulmonary intravascular macrophage is discussed. A hypothesis is asserted that the induction of pulmonary intravascular macrophage in liver cirrhosis leads to increased susceptibility to adult respiratory distress syndrome in these patients.

Excimer laser photorefractive keratectomy for myopia

To evaluate the safety, effectiveness and stability of excimer laser photorefractive keratectomy (PRK) treatment, we studied its posttreatment results in 44 normal-sighted myopic eyes where a 193-nm emission wavelength excimer laser was used to correct myopia. The eyes were divided into three groups according to the preoperative refractive error and attempted correction: group I, preoperative myopia < or = 6.00 diopters (D), full correction; group II, preoperative myopia between 6.00 and 8.00 D, full correction; group III, preoperative myopia > 8.00 D, attempted correction of 8.00 D. Percentages of relative spherical equivalents (ie, observed spherical equivalent -- expected spherical equivalent) within +/- 1.0 D 3 months after treatment were 95% in group I, 64% in group II and 67% in group III. Uncorrected visual acuity of 20/40, or better, was achieved in 100% of eyes in group I, and 92% in group II at 6 months. Initial overcorrection followed by myopic regression was observed in all groups. The refractive outcome in our study was stable 3 months after surgery. Anterior stromal haze was mild and disappeared gradually 3 months postoperatively. The greater the diopter correction needed, the higher the grade of corneal haze (p < 0.01). There were no significant complications. The results of this study demonstrated that excimer laser PRK appears to be a reasonably predictable and stable procedure to correct low to moderate myopia.

Clinical evaluation of ciprofloxacin ophthalmic solution in the treatment of refractory bacterial keratitis

Ciprofloxacin is a fluoroquinolone antimicrobial agent inhibiting bacterial DNA gyrase, with good in vitro and in vivo activity against many Gram-positive and Gram-negative ocular pathogens. It has low toxicity, low resistance rate and low minimum inhibitory concentration. The purpose of this study was to evaluate the efficacy of ciprofloxacin in treating bacterial keratitis refractory to conventional therapy. Thirty patients with smear-proven bacterial ulcers were treated by conventional therapy. Of these, cultures were positive in 28 (93.3%) patients. Pseudomonas aeruginosa was isolated in 13 (46.4%) patients, nontuberculous mycobacteria in nine (32.1%) and other bacteria in six (21.4%). Fifteen patients (50%) were cured with conventional therapy. Four patients (13.3%) underwent surgery due to impending corneal perforation. Eleven patients were shifted to ciprofloxacin therapy because of poor results with conventional treatment. Of these, eight (72.7%) patients were treated successfully. No adverse events were encountered except a white crystalline precipitate in two cases which resolved spontaneously after discontinuation of therapy. In view of its effectiveness and low toxicity, ciprofloxacin should be considered in treating bacterial keratitis which is refractory to conventional therapy.

Endothelin-1 potentiates leukotoxin-induced edematous lung injury

We tested the hypothesis that leukotoxin (Lx), a cytochrome P-450-dependent linoleate product of leukocytes, can stimulate the release of endothelin-1 (ET-1) from the lung and further that exogenous ET-1 synergizes with Lx to produce edematous lung injury. In isolated rat lungs perfused with Earle's balanced salt solution, Lx (10 mumol) alone caused lung edema and increased the perfusate and lung tissue ET-1 levels. The combination of ET-1 (5 nM) and Lx (5 mumol), at concentrations that by themselves did not increase wet lung weight, significantly increased wet lung weight, wet-to-dry lung weight ratio, as well as the lung effluent lactate dehydrogenase activity. Pretreatment with BQ-123 (5 x 10(-6) M), an endothelin A receptor antagonist that significantly attenuated the ET-1 (5 nM)-induced increase in pulmonary arterial pressure (Ppa) and pulmonary capillary pressure (Ppc), suppressed the edematous lung injury generated by the combination of ET-1 and Lx, suggesting that the edema-enhancing effect of ET-1 in Lx-treated lungs occurred through endothelin A receptor-dependent elevation of Ppa and Ppc. Elevation of the pulmonary venous pressure in Lx-treated lungs (13.5 cmH2O) mimicked the effect of ET-1 on Ppa and Ppc and produced a degree of lung edema that was comparable to that after combined ET-1 + Lx treatment but without increase in the perfusate lactate dehydrogenase. These data support the idea that ET-1 and Lx promote lung edema in a synergistic fashion.

Effect of BQ123 on vasoconstriction as a result of either hypoxia or endothelin-1 in perfused rat lungs

A possible role of endothelin (ET)-1 in mediating hypoxic pulmonary vasoconstriction (HPV) was examined by comparing haemodynamic differences between ET-1-induced vasoconstriction and HPV in isolated perfused rat lungs. An ETA receptor antagonist (BQ123) was also employed to assess the effects of ET-1. The pulmonary arterial pressure (Ppa) was significantly increased by alveolar hypoxia (3% O2) and by ET-1 (5 nM). The pulmonary microvascular pressure was not changed by hypoxia, but increased more than two-fold by ET-1 (P < 0.01). Hypoxia significantly increased pulmonary arterial resistance (P < 0.01) while ET-1 significantly increased pulmonary venous resistance (P < 0.01), and slightly increased arterial resistance. Lung weight was increased by ET-1 and decreased by hypoxia, accompanied by similar Ppa responses in both cases. BQ123 (10(-6) M and 10(-5) M) did not influence the changes in Ppa and lung weight induced by hypoxia or angiotensin II (0.3 micrograms). BQ123 did, however, suppress (P < 0.05) the increase in Ppa and lung weight induced by 5 nM ET-1. Thus, it appears unlikely that ET-1 is involved in changes in pulmonary vascular tone during acute HPV.

Leukotoxin, 9,10-epoxy-12-octadecenoate causes edematous lung injury via activation of vascular nitric oxide synthase

We examined the mechanism of leukotoxin, 9,10-epoxy-12-octadecenoate (Lx)-induced lung injury in blood-free, physiological salt solution-perfused rat lungs under constant flow conditions. Mean pulmonary arterial (Ppa) and pulmonary capillary pressure (Pcap, estimated by the double-occlusion method), wet lung weight (WLW), pulmonary capillary filtration coefficient (Kfc), lung perfusate lactate dehydrogenase (LDH) activity, and nitrite levels were assessed. Bolus injection of Lx (200 microM) caused insidious and significant lung weight gain, which was not associated with remarkable elevation of Ppa or Pcap but was associated with an increase of perfusate LDH activity and nitrite levels. Lx (20 microM) elevated Kfc, indicating that Lx had affected pulmonary vascular permeability. Because Lx causes endothelium dependent pulmonary vasodilation, we studied the effect of NG-monomethyl-L-arginine (L-NMMA), NG-monomethyl-D-arginine (D-NMMA), superoxide dismutase (SOD), human oxyhemoglobin (oxyHb), and methylene blue (MB) on Lx-induced lung injury. L-NMMA, SOD, and oxyHb, but not MB or D-NMMA, protected the lungs against Lx (200 microM)-induced injury. Lx increased pulmonary vascular permeability and caused lung injury. Because both nitric oxide synthase inhibitors and SOD inhibited the Lx-induced lung injury, it is possible that peroxynitrite is involved in the mechanism whereby Lx causes lung injury.

Acyclovir treatment for linear endotheliitis on grafted corneas

Two patients with previous corneal transplants developed unusual rejection-like episodes of the grafted cornea. Both had a migrating line of keratic precipitates and stromal edema involving both the donor and recipient corneas. Intensive steroid treatment attained little effect, but oral acyclovir treatment dramatically suppressed the disease process. The facts suggest that a virus-related immune mechanism against both the donor and recipient endothelia, rather than simple allograft rejection, may have been responsible for the clinical presentations. Oral acyclovir therapy might be considered in patients with steroid-nonresponsive corneal endotheliitis mimicking allograft rejection.

Early change of vascular permeability in hypercholesterolemic rabbits

To study the effect of hyperlipidemia on vascular permeability, serial anterior chamber fluorophotometric examinations were carried out on 33 control rabbits (group 1) and 32 diet-induced hypercholesterolemic (group 2) rabbits. Changes in the blood-aqueous barrier function associated with total serum cholesterol (CHO) and triglyceride (TG) levels were studied at the beginning of the study and every 2 weeks thereafter for up to 16 weeks following 0.5% cholesterol-enriched diet feeding. Concurrently, a slit-lamp biomicroscope was used to examine the iris for evidence of atheromatous plaque. In group 1, the CHO level decreased slightly during the first 6 weeks and remained rather steady thereafter. The status of the blood-aqueous barrier correlated significantly with serum CHO and TG levels (r = .46, P < .001; r = .23, P = .01, respectively). In group 2, CHO and TG levels increased significantly after 2 and 8 weeks of cholesterol-enriched diet feeding, respectively. The blood-aqueous barrier also became more permeable than that in group 1 after 2 weeks' and increased above its baseline level after 6 weeks' feeding. Both CHO and TG levels correlated well with the degree of blood-aqueous barrier breakdown (r = .51, P < .001; r = .25, P < .001, respectively). The first evidence of iridic lipid-streak deposition was noted at 7.6 +/- 0.7 weeks, while definite iridic atheromatous plaque appeared 11.2 +/- 0.7 weeks after feeding. The change in the blood-aqueous barrier also correlated well with the semiquantitative score of iridic plaque (r = .58, P < .001) and usually preceded visual evidence of plaque formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Corneal autofluorescence and epithelial barrier function in diabetic patients

Corneal autofluorescence and corneal epithelial barrier function of 146 diabetic patients and 121 controls were examined using anterior segment fluorophotometry. Corneal autofluorescence in diabetic patients was significantly higher when compared with that of controls (14.6 +/- 3.7 vs. 10.9 +/- 2.7 ng/ml, p < 0.001), and was increased in patients with more severe diabetic retinopathy (r = 0.23, p = 0.005), higher postprandial blood glucose level (r = 0.25, p = 0.009), and higher glycosylated hemoglobin (r = 0.21, p = 0.047). No correlation existed between corneal autofluorescence and the duration of diabetes mellitus. The corneal fluorescein concentration 45 min after topical application of 20 microliters of 2% sodium fluorescein was also significantly higher in diabetics than in controls (1,373.2 +/- 1,081.5 vs. 363.0 +/- 308.3 ng/ml, p < 0.001). No correlation existed with postprandial blood sugar (r = -0.19, p = 0.056) nor with glycosylated hemoglobin (r = -0.13, p = 0.20). The corneas in diabetics became more hypesthetic with longer duration of diabetes mellitus (r = -0.19, p = 0.02), although the mean corneal sensitivity threshold was not statistically higher in the diabetic group (p = 0.57). There was no correlation of the epithelial barrier function with the duration of diabetes (r = -0.07, p = 0.38), the severity of diabetic retinopathy (r = 0.07, p = 0.38), and the corneal sensitivity threshold (r = -0.06, p = 0.43).

Health insurance and use of medical services by men infected with HIV

Among 178 HIV-infected men from the San Francisco City Clinic Cohort (SFCCC), we examined the association between health insurance and use of outpatient services and treatment. For men with private insurance, we also assessed the frequency of avoiding the use of health insurance. Men without private insurance reported fewer outpatient visits than men with fee-for-service or managed-care plans. Use of zidovudine for eligible men was similar for those with fee-for-service plans (74%), managed-care plans (77%), or no insurance (61%). Use of Pneumocytstis carinii pneumonia prophylaxis was similar for those with fee-for-service (93%) and managed-care plans (83%) but lower for those with no insurance (63%). Of 149 men with private insurance, 31 (21%) reported that they had avoided using their health insurance for medical expenses in the previous year. In multivariate analysis, the independent predictors of avoiding the use of insurance were working for a small company and living outside the San Francisco Bay Area. Having private insurance resulted in higher use of outpatient services, but the type of private insurance did not appear to affect the use of service or treatment. Fears of loss of coverage and confidentiality may negate some benefits of health insurance for HIV-infected persons.

Leukotoxin, 9,10-epoxy-12-octadecenoate causes pulmonary vasodilation in rats

Leukotoxin (Lx), a cytochrome P-450-dependent metabolite of linoleate synthesized by neutrophils or synthesized by OH- and linoleate in neutrophil cell membranes, has been recovered in lung lavages of patients with the adult respiratory distress syndrome. We studied the direct vasoactive effects of Lx and linoleate, its parent compound, in the rat pulmonary circulation. In isolated rat lungs perfused at constant flow with a physiological salt solution, Lx (but not linoleate) caused a biphasic response, an initial transient vasoconstriction followed by a more prolonged vasodilation. The latter response was only evident when the pulmonary vascular tone was increased with either alveolar hypoxia (0% O2) or KCl (20 mM). The pressor response to angiotensin II was also attenuated in the presence of Lx. The vasodilatory response in perfused lungs was attenuated by methylene blue (2 x 10(-5) M), a putative inhibitor of the soluble guanylate cyclase but not by pretreatment with meclofenamate (10(-5) M), a cyclooxygenase inhibitor. In isolated pulmonary arterial (PA) rings preconstricted either with phenylephrine (5 x 10(-9) M), endothelin-1 (10(-8) M), or KCl (30 mM), Lx (but not linoleate) caused dose-dependent relaxation. The relaxing effect of Lx on endothelium-intact rings was attenuated by NG-monomethyl-L-arginine or methylene blue. The magnitude of the hypoxic contraction of PA rings was attenuated in the presence of Lx. Whereas the mechanism of Lx-induced vasoconstriction is not clear, we conclude that Lx causes vasodilation in rat lungs and that the vasodilatory component is to a large degree endothelium-derived relaxing factor-dependent.

TNF potentiates PAF-induced pulmonary vasoconstriction in the rat: role of neutrophils and thromboxane A2

Both tumor necrosis factor (TNF) and platelet-activating factor (PAF) are released during sepsis and are important mediators of septic lung injury. I investigated the interactions of TNF and PAF on vasoactive responses in the pulmonary circulation. In isolated rat lungs perfused with a cell- and plasma-free physiological salt solution, PAF (0.01- and 0.1-micrograms boluses) caused transient dose-dependent pulmonary arterial and venous constrictions. In vivo pretreatment of the rats with TNF (0.02 or 0.2 mg/kg i.v.) 1 h before lung isolation increased lung myeloperoxidase activity and markedly enhanced PAF-induced pulmonary vasoconstriction without affecting the pressor responses to angiotensin II or hypoxia. In contrast, pretreatment with lipopolysaccharide (10 mg/kg), which increased lung myeloperoxidase to the same extent as TNF, caused only a modest enhancement of PAF-induced vasoconstriction associated with reduced pressor responses to angiotensin II and hypoxia. Ex vivo perfusion of isolated lungs with TNF for 1 h did not affect PAF vasoconstriction. The TNF-induced potentiation of PAF vasoconstriction was not altered by depletion of circulating neutrophils with vinblastine but was blocked by Dazmegrel, a thromboxane synthase inhibitor. Thus, TNF potentiates PAF-induced pulmonary vasoconstriction by an in vivo mechanism that is neutrophil independent but thromboxane dependent. This TNF-PAF interaction likely contributes to the development of pulmonary hypertension during sepsis.

Chronic biliary obstruction induces pulmonary intravascular phagocytosis and endotoxin sensitivity in rats

Endotoxin sensitivity varies among animal species and appears to correlate with the presence of pulmonary intravascular macrophage (PIM). In rats, which lack PIM, we investigated the hypothesis that chronic cholestatic liver injury leads to induction of PIM and endotoxin sensitivity. Rats were randomized to either common bile duct ligation (BDL) or sham-surgery and studied at 1 wk (acute cholestasis), 2 wk (cholestasis, early cirrhosis), and 4 wk (cholestasis, established cirrhosis) after surgery. Intravascularly injected fluorescent latex microspheres (1 micron diameter) were taken up by large phagocytic cells in lung parenchyma of BDL rats (at 2 and 4 wk), while no uptake was observed in lungs from control rats. Electronmicroscopy revealed accumulation of large, mononuclear, macrophage-like cells containing ingested latex particles within the pulmonary capillaries. Pulmonary intravascular phagocytosis, as reflected in lung uptake of 99mTc microaggregated albumin (Microlite, mean particle diameter = 1 micron), averaged 0.7 +/- 0.1% (mean +/- SEM) of total injected dose in 13 control rats and progressively increased with time after BDL (1 wk, 1.7 +/- 0.2%; 2 wk, 10.0 +/- 3.0%; 4 wk 35.1 +/- 5.9%). Rats with biliary cirrhosis were markedly sensitive to the lethal effects of low dose endotoxin and demonstrated marked lung edema at the time of death. Furthermore, the lung uptake of intravascular 125I-lipopolysaccharide was increased five-fold in cirrhotic rats. We conclude that chronic biliary obstruction leads to the induction of pulmonary intravascular phagocytes and enhances endotoxin sensitivity in rats. Pulmonary intravascular phagocytosis in patients with advanced cirrhosis may account for their increased susceptibility to sepsis-induced adult respiratory distress syndrome.

Evans blue dye in the assessment of permeability-surface area product in perfused rat lungs

Evans blue dye (EBD) has been used extensively as a marker of extravascular protein leakage. We assessed the utility of EBD as an albumin marker in the measurement of permeability-surface area product (PS) in perfused rat lungs and compared the results with PS values obtained using 125I-labeled albumin. In isolated perfused rat lungs, PS was measured by exposure to a perfusate containing EBD (600 micrograms/ml) and 125I-albumin (I microCi) for exactly 3 min, followed by washout of the intravascular space with fresh perfusate for 6 min. In lungs from normal rats, we found that PS obtained by EBD (PS-EBD) was fivefold higher than PS obtained by 125I-albumin (PS-125I) [1.92 +/- 0.32 (SE) vs. 0.42 +/- 0.03 x 10(-2) cm3.min-1.g-1, P < 0.05]. Similarly, in rats pretreated with Salmonella enteritidis lipopolysaccharide (2 mg/kg iv), PS-EBD was much higher than PS-125I (2.01 +/- 0.30 vs. 0.59 +/- 0.08 x 10(-2) cm3.min-1.g-1, P < 0.01). This discrepancy between PS-EBD and PS-125I was not explained by differences in the amount of free marker in perfusate, because the albumin-binding rate for both markers was very high. In addition, prolonged perfusion (40 min) with EBD did not significantly affect pulmonary vasoreactivity or water content in rat lungs. A detailed comparison of the kinetics of lung tissue uptake of EBD followed by parallel uptake of both markers up to 60 min of perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinicopathologic study of Gore-Tex patch graft in corneoscleral surgery

Three patients with corneal or scleral defects were treated with Gore-Tex grafting, including one case of corneal ulcer, one case of Mooren's ulcer, and one case of necrotizing scleritis. These eyes remained inflamed after Gore-Tex grafting. The interval between grafting and removal ranged from 2 months to 1 year. Pathologically, none of these grafts showed evident epithelial or fibrous tissue ingrowth of the Gore-Tex graft. Fungal inhabitation was noted in one graft, and fungal endophthalmitis developed 5 months after graft removal and penetrating keratoplasty. Although Gore-Tex offers some advantages, it has disadvantages when it is used without adequate conjunctival covering, including poor epithelialization, poor adhesion between graft and surrounding tissue, and potential infectious route.

Endotoxin-induced pulmonary leukostasis in the rat: role of platelet-activating factor and tumor necrosis factor

Injection of bacterial lipopolysaccharide (LPS) into experimental animals induces septic shock associated with the release of tumor necrosis factor (TNF) and platelet-activating factor (PAF). Because both TNF and PAF stimulate neutrophil adhesion to endothelial cells in vitro, and because neutrophils are important effector cells in sepsis-induced lung vascular injury, the role of TNF and PAF in LPS-induced lung neutrophil sequestration was investigated. Lung myeloperoxidase (MPO) activity was measured as a quantitative assessment of pulmonary leukostasis. Injection of Salmonella enteritidis LPS into rats caused dose-dependent increases in lung MPO that peaked at 2 hours and persisted for up to 24 hours. Injection of purified human recombinant TNF (2 to 200 micrograms/kg i.v.) mimicked the effect of LPS on lung MPO activity. Injection of synthetic PAF increased lung MPO only at the highest and lethal dose (10 micrograms/kg). Lower doses (0.1 and 1 microgram/kg) of PAF had no effect on lung MPO by itself and did not enhance LPS- or TNF-induced lung neutrophil sequestration. Furthermore, pretreatment of the rats with two different PAF receptor-antagonists, WEB 2086 (10 mg/kg IP) and SRI 63-441 (10 mg/kg IP), failed to block LPS-induced (1 mg/kg) increase in lung MPO. These data suggest that TNF, not PAF, mediates LPS-induced pulmonary neutrophil sequestration in the intact rat.

Platelet-activating factor potentiates protamine-induced lung edema. Role of eicosanoids

Platelet-activating factor (PAF) is a cell membrane-derived ether lipid that plays an important role in acute lung vascular injury. We recently reported that PAF potentiates protamine-induced lung edema by enhancing pulmonary venoconstriction. As PAF is known to stimulate lung eicosanoid synthesis, we investigated the role of peptidoleukotrienes and other eicosanoids in this priming effect of PAF. Addition of PAF (1.6 nM), followed 10 min later by protamine (50 micrograms/ml), to perfusate of salt solution-perfused rat lungs resulted in marked arterial and venous constrictions and severe lung edema. Lung tissue thromboxane B2, 6-ketoprostaglandin F1 alpha and leukotriene C4 (LTC4) were markedly elevated 20 min after PAF/protamine. Pretreatment of the lungs with AA-861, a specific 5-lipoxygenase inhibitor, blocked PAF/protamine-induced leukotriene synthesis, arterial and venous constrictions, and lung edema. In addition, injection of LTC4 (1 microgram) markedly potentiated protamine-induced arterial and venous constrictions and caused lung edema similar to PAF/protamine. Indomethacin, a specific cyclooxygenase inhibitor, also reduced the vasoconstrictive and edemagenic responses to PAF/protamine. However, the pulmonary edema after LTC4/protamine was not blocked by indomethacin. In separate experiments, infusion of this "priming" dose of PAF into isolated perfused lungs induced LTC4 synthesis and augmented lung thromboxane A2 synthesis after arachidonic acid infusion. We conclude that both cyclooxygenase and lipoxygenase products of arachidonic acid metabolism are involved in PAF-induced potentiation of protamine lung edema.

The epithelial barrier function in clear corneal grafts

We conducted a corneal epithelial permeability study using a fluorophotometer on 93 eyes of 79 patients with clear corneal grafts. There were 45 males and 34 females, aged 61.6 +/- 10.2 years. All eyes received penetrating keratoplasty at least 1 year (mean 40.4 +/- 31.3 months) before examination. The normal fellow eyes of 65 subjects were examined as controls. The averaged corneal epithelial permeability of grafted corneas was significantly higher than that of controls (p < 0.001). In the 65 individuals having an otherwise healthy fellow eye, the grafted corneas were significantly more permeable than their control fellow eyes verified by paired t test (n = 65, p = 0.006). Concomitant corneal sensitivity test revealed a significantly hypesthetic cornea. These results show that in spite of a clinically normal clear graft, there is usually a subnormal epithelial barrier function and reinnervation, even years after corneal transplantation.

Changes in corneal autofluorescence and corneal epithelial barrier function with aging

Corneal epithelial permeability studies using fluorophotometers were performed on 90 eyes of 51 normal subjects. After recording the autofluorescence of the cornea (AFC) and of the lens (AFL), we applied 20 microliters of 2% sodium fluorescein to the conjunctival sac. The corneal fluorescence 45 min later (F45), which paralleled the corneal epithelial permeability to fluorescein, was measured by fluorophotometer and analyzed. All parameters of the two eyes of each subject correlated well with each other. There was positive correlation between AFL and patient age and between AFC and patient age (r = 0.78, p < 0.001, and r = 0.74, p < 0.001, respectively). The F45 increased exponentially with advancing age (r = 0.67, p < 0.001). The strong correlation between AFC and AFL in each eye (r = 0.79, p < 0.001) indicated corresponding aging processes in both the cornea and the lens. The increase in epithelial permeability with age possibly represents a subclinical breakdown of barrier function, rendering the corneas more vulnerable to insults.

Tissue eicosanoids and vascular permeability in rats with chronic biliary obstruction

Advanced cirrhosis is known to be associated with extrahepatic organ dysfunction, but the mechanism for this cirrhosis complication is largely unknown. We measured tissue albumin leakage in rats with biliary cirrhosis or acute cholestasis and tested the hypothesis that arachidonic acid metabolites contribute to the vascular permeability change. Six weeks after bile duct ligation, rats with biliary cirrhosis exhibited increased extravascular leakage of 125I-albumin in lung (p < 0.001) and kidney (p < 0.01) but not in heart or brain. In contrast, in cholestatic rats 10 days after bile duct ligation, only the kidney albumin leak was significantly increased (p < 0.01). Tissue thromboxane B2 levels, measured with an enzyme immunoassay, were increased in lung, kidney and liver of cirrhotic and cholestatic rats. To determine whether thromboxane A2 contributes to the vascular permeability defects in cirrhosis, we pretreated cirrhotic rats with the thromboxane synthase inhibitor dazoxiben (10 mg/kg intraperitoneally every 8 hr) for 20 hr before assessment of vascular permeability. Dazoxiben blocked the increase in thromboxane B2 level in lung but not in kidney and lowered the lung but not the kidney albumin leak index. In cholestatic rats given a higher dose of dazoxiben (40 mg/kg intraperitoneally every 8 hr) for 20 hr, the kidney thromboxane B2 level but not albumin leak was significantly lowered. We conclude that chronic biliary obstruction in rats leads to increased vascular permeability in selected extrahepatic organs and that thromboxane A2 contributes to the vascular permeability increase in the lung. Whether thromboxane A2 plays a role in renal albumin leakage will require further study.

Endotoxin priming followed by high altitude causes pulmonary edema in rats

Rapid ascent to high altitude may be associated with the development of high-altitude pulmonary edema (HAPE) in susceptible individuals. Because lung lavage fluid obtained from such patients can be rich in protein and neutrophils, we considered that an element of lung injury and inflammation contributed to the pathogenesis of some forms of HAPE. On the basis of such a likely contribution of inflammatory mechanisms, we induced pulmonary lung injury and inflammation by priming rats with Salmonella enteritidis endotoxin (ETX) (0.1 or 0.5 mg/kg body wt ip) and examined the influence of added exposure to simulated hypobaric hypoxia (24 h, 4,300 m). The animals that were primed with ETX and exposed to hypoxia, but not those that received either ETX or hypoxia alone, developed lung vascular damage. This vascular damage manifested itself histologically and by increases in the lung vascular permeability-surface area product and the lung bloodless wet weight-to-dry weight ratio. The bronchoalveolar lavage fluid of ETX-primed hypoxia-exposed rats contained a greater number of white blood cells and a higher concentration of protein compared with that of the ETX-primed rats. Hearts of ETX + hypoxia-treated rats showed an increased ratio of right ventricular weight divided by body weight (RV/BW). Neutropenia prevented the development of pulmonary edema and the increase in ETX + hypoxia rats with a Ca2+ entry blocker inhibited lung injury and RV hypertrophy, these results indicate that ETX priming causes pulmonary edema at high altitude and suggest a role for neutrophils and Ca2+ in this rat model of lung injury.

Increased pulmonary vascular permeability in rats with biliary cirrhosis: role of thromboxane A2

Rats with liver cirrhosis exhibit arterial hypoxemia and loss of hypoxic pulmonary vasoconstriction similar to some patients with end-stage liver disease. We hypothesized that the pulmonary circulatory dysfunction in cirrhosis results from vascular endothelial cell injury and interstitial lung edema. To investigate this hypothesis, we compared the extravascular lung albumin leak, lung ultrastructural changes, and tissue eicosanoid levels in control and cirrhotic rats. In comparison to sham-operated controls, rats with biliary cirrhosis, 6 wk after ligation of the common bile duct, had increased lung albumin leak index (1.46 +/- 0.12 vs. 0.80 +/- 0.04, P < 0.001) and bloodless lung wet-to-dry weight ratio (4.94 +/- 0.05 vs. 4.78 +/- 0.03, P < 0.05). Electron-microscopic sections of lungs from cirrhotic rats demonstrated infiltration with intravascular macrophage-like cells, endothelial cell injury, and interstitial edema. In addition, lung tissue thromboxane B2 was significantly increased in cirrhotic rats, and pretreatment with a thromboxane synthase inhibitor, dazoxiben, reduced lung thromboxane B2 level and attenuated extravascular lung albumin leak (control 1.03 +/- 0.07, cirrhotic 2.29 +/- 0.06, cirrhotic plus dazoxiben, 1.57 +/- 0.17). In contrast, WEB 2086, a platelet-activating factor antagonist, had no effect on lung albumin leak. We conclude that pulmonary vascular permeability is increased in rats with biliary cirrhosis and that thromboxane A2 contributes to the pulmonary circulatory abnormalities in cirrhosis.

Hyperglucagonemia and hyperdynamic circulation in rats with biliary cirrhosis

Glucagon, a hormone with a potent vasodilatory action, has been suggested to play a role in the hyperkinetic circulation in animals with portocaval shunts and chronic portal venous stenosis; however, its role in cirrhosis has not been examined. We tested the hypothesis that increased levels of circulating glucagon contribute to the hyperdynamic circulatory state found in rats with biliary cirrhosis. Compared with plasma glucagon levels in sham-operated controls, glucagon levels, measured by radioimmunoassay, were significantly increased in chronic bile duct-ligated (5 to 6 weeks) cirrhotic rats (603 +/- 107 pg/ml vs 197 +/- 11 pg/ml, p < 0.001) but not in acute bile duct-ligated (10 days) cholestatic rats (310 +/- 55 pg/ml). Unanesthetized, catheter-implanted cirrhotic--but not cholestatic--rats exhibited a hyperdynamic circulatory state with increased cardiac index and decreased systemic vascular resistance. The plasma glucagon level correlated with cardiac index (r = 0.62, p < 0.01) and systemic vascular resistance (r = -0.54, p < 0.05). In addition, cirrhotic rats showed depressed hypoxic pulmonary vasoconstriction that was correlated with increased plasma glucagon level (r = -0.68, p < 0.01). We conclude that circulating glucagon is increased in rats with biliary cirrhosis and that hyperglucagonemia may contribute to the observed systemic hyperdynamic circulatory state and the loss of hypoxic pulmonary vasoconstriction in these rats.

Pulmonary vascular reactivity: effect of PAF and PAF antagonists

We investigated the effects of two different platelet-activating factor (PAF) antagonists, SRI 63-441 and WEB 2086, on PAF-, angiotensin II-, and hypoxia-induced vasoconstrictions in isolated rat lungs perfused with a physiological salt solution. Bolus injection of PAF (0.5 micrograms) increased pulmonary arterial and microvascular pressures and caused lung edema. Both SRI 63-441, a PAF-analogue antagonist, and WEB 2086, a thienotriazolodiazepine structurally unrelated to PAF, completely blocked PAF-induced vasoconstriction and lung edema at 10(-5) M. At a lower concentration (10(-6) M), WEB 2086 was more effective than SRI 63-441. WEB 2086 also blocked the pulmonary vasodilation induced by low-dose PAF (15 ng) in blood-perfused lungs preconstricted with hypoxia. SRI 63-441 and CV 3988 (another PAF analogue antagonist), but not WEB 2086, caused acute pulmonary vasoconstriction at 10(-5) M and severe lung edema at a higher concentration (10(-4) M). PAF-induced but not SRI- or CV-induced pulmonary vasoconstriction and edema were inhibited by WEB 2086. In addition, SRI 63-441 potentiated angiotensin II- and hypoxia-induced vasoconstrictions. This effect of SRI 63-441 is not due to PAF receptor blockade because 1) addition of PAF (1.6 nM) to the perfusate likewise potentiated angiotensin II-induced vasoconstriction and 2) WEB 2086 did not cause a similar response. We conclude that both SRI 63-441 and WEB 2086 are effective inhibitors of PAF actions in the rat pulmonary circulation. However, antagonists with structures analogous to PAF (SRI 63-441 and CV 3988) can have significant pulmonary vasoactive side effects.

Intact lung cytochrome P-450 is not required for hypoxic pulmonary vasoconstriction

Lung cytochrome P-450 has been suggested to play a role in hypoxic pulmonary vasoconstriction. We reexamined this hypothesis using specific suicide substrate inhibitors of cytochrome P-450, 1-aminobenzotriazole (1-ABT), and chloramphenicol. In isolated, blood-perfused rat lungs, 1-ABT (0.5 mg/ml) and chloramphenicol (1 mg/ml) inhibited lung microsomal cytochrome P-450 (ethoxycoumarin O-deethylase) activity to 24 and 44% of control, respectively, and blunted hypoxia and angiotensin II-induced vasoconstriction. The depression of vascular contraction by 1-ABT was not due to an effect on calcium channels, since similar concentrations of 1-ABT had no inhibitory activity on electrical field-stimulated contractile response in rabbit papillary muscle strips. However, when 1-ABT was washed out of the lung after preincubation, the vascular reactivity to hypoxia and angiotensin II was restored despite persistent depression of lung cytochrome P-450 activity to 26% of control values. In isolated rat aortic and pulmonary arterial rings, addition of 1-ABT or metyrapone to the organ bath acutely reversed norepinephrine-induced contraction but preincubation with 1-ABT, metyrapone, or chloramphenicol had no effect on subsequent norepinephrine contractions. We conclude that 1-ABT inhibited lung vascular reactivity by a mechanism independent of cytochrome P-450 inhibition or calcium channel blockade and that an intact lung cytochrome P-450 system is not required for hypoxic pulmonary vasoconstriction in rat lungs.

Pulmonary circulatory dysfunction in rats with biliary cirrhosis. An animal model of the hepatopulmonary syndrome

We studied hypoxic pulmonary vasoconstriction (HPV) and pulmonary gas exchange in unanesthetized rats with biliary cirrhosis induced by chronic bile duct ligation (BDL) (5 to 6 wk) and compared pulmonary vascular reactivity in perfused lungs isolated from BDL and control rats. Awake, catheter-implanted, cirrhotic rats exhibited increased cardiac output, normal systemic and pulmonary arterial pressures, and decreased total systemic (TSR) and pulmonary (TPR) vascular resistances in comparison with those in sham-operated control rats. HPV was markedly depressed in cirrhotic rats (percent increase in TPR while breathing 8% O2: 42.3 +/- 13.7% in control and 0.9 +/- 3.6% in cirrhotic rats, p less than 0.05), and this was associated with an increased AaPO2 (control rats, 15.7 +/- 1.1 mm Hg; cirrhotic rats, 23.1 +/- 1.9 mm Hg; p less than 0.05). In contrast, the pulmonary pressor response to angiotensin II was intact, and the depression of HPV in cirrhotic rats was ameliorated after angiotensin II infusion. These changes in cirrhotic rats were not due to the accompanying cholestasis since noncirrhotic rats with severe cholestasis had intact HPV and normal AaPO2. Lungs isolated from cirrhotic rats and perfused with blood from normal rats exhibited two patterns of response to hypoxia. In one group, HPV was blunted compared with that in control rats (change in pulmonary arterial perfusion pressure after 3% O2: control rats, 23.2 +/- 2.8 mm Hg; cirrhotic rats, 4.8 +/- 1.4 mm Hg; p less than 0.01). Similar to the result in intact rat, angiotensin-II-induced vasoconstriction was preserved in lungs from cirrhotic rats, and HPV increased significantly after angiotensin II infusion (to 17.3 +/- 4.8 mm Hg). In the second group, baseline pulmonary arterial pressure progressively increased during normoxia, and this increase was attenuated by hypoxic ventilation (hypoxic vasodilation).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of eicosanoids in staphylococcal alpha-toxin-induced lung injury in the rat

We investigated the role of arachidonic acid-derived eicosanoids in staphylococcal alpha-toxin (alpha-T)-induced lung injury. Bolus injection of 200 and 500 micrograms alpha-T into isolated perfused rat lungs resulted in increased pulmonary perfusion pressure followed by lung weight gain. Inhibition of pressure change with papaverine (10(-4) M) failed to abolish lung edema. Furthermore, alpha-T increased the permeability-surface area product in papaverine-treated lungs and caused marked endothelial cell injury and interstitial edema as documented by electron microscopy. alpha-T dose dependently increased lung tissue thromboxane B2 (TxB2) levels and leukotriene C4 levels. In lungs given 0, 200, and 500 micrograms of alpha-T, TxB2 (in micrograms/g wet lung) values were 16.3 +/- 2.8, 25.0 +/- 3.0, and 54.2 +/- 6.2; and leukotriene C4 values were 4.6 +/- 1.1, 6.7 +/- 1.2, and 22.1 +/- 3.8, respectively. Inhibition of cyclooxygenase enzyme with indomethacin (10(-5) M) or lipoxygenase enzyme with 2(12-hydroxydodeca-5,10-dinyl)-3,5,6-trimethyl-1,4-benzoq uin one (AA861, 10(-5) M) attenuated the vasoconstriction and prevented lung edema due to low dose (200 micrograms) but not high dose (500 micrograms) alpha-T. The protective effect of these inhibitors on lung edema is in part due to decreases in alpha-T-stimulated venoconstriction because alpha-T-induced increase in lung microvascular pressure was attenuated by indomethacin and AA861 pretreatment. We conclude that both eicosanoid-dependent and eicosanoid-independent mechanisms contribute to alpha-T-induced lung edema in the rat.

The impact of diuretic therapy on reported sexual function

BACKGROUND

--Thiazide diuretics are the most commonly prescribed antihypertensive agent in the treatment of hypertension. No studies to date have isolated conclusively the effect of diuretic therapy on patient quality of life, and particularly on sexual dysfunction.

METHODS

--We carried out a randomized placebo-controlled trial of the effect of thiazide diuretics on quality of life in mildly hypertensive men between the ages of 35 and 70 years. After a 1-month washout period off diuretic therapy, the men were randomized to a 2-month trial of a thiazide treatment or placebo. At the end of the trial, 176 men completed a confidential self-administered questionnaire assessing aspects of social performance, general well-being, and emotional and physiologic states.

RESULTS

--Patients taking diuretics reported significantly greater sexual dysfunction than control subjects, including decreased libido, difficulty in gaining and maintaining an erection, and difficulty with ejaculation. Multivariate analysis suggested that the findings were not mediated by low serum potassium levels or by low blood pressure. Sexual dysfunction was noted more often in the confidential self-report questionnaire than in response to direct questions from clinicians. We found no differences between diuretic and placebo groups in measures of mood, general sense of well-being, ability to work, alertness, and social/recreational activities.

CONCLUSIONS

--Thiazide diuretic use is associated with male sexual dysfunction but does not appear to adversely affect other aspects of quality of life.