Development of cellular absorptive tracers for quantitative characterization of microbial mass in flow systems.

We report a new cellular absorptive tracer (CAT) method for simple, nondestructive characterization of bacterial mass in flow systems. Results show that adsorption of a CAT molecule into the cellular mass results in its slowdown during flow, which is an accurate quantitative measurement of biomass quantity and distribution. No such methods are currently available for quantitative characterization of cell mass.

Microbial reduction of Fe(III) and sorption/precipitation of Fe(II) on Shewanella putrefaciens strain CN32.

The influence of Fe(II) on the dissimilatory bacterial reduction of an Fe(III) aqueous complex (Fe(III)-citrate(aq)) was investigated using Shewanella putrefaciens strain CN32. The sorption of Fe(II) on CN32 followed a Langmuir isotherm. Least-squares fitting gave a maximum sorption capacity of Qmax = 4.19 x 10(-3) mol/10(12) cells (1.19 mmol/m2 of cell surface area) and an affinity coefficient of log K = 3.29. The growth yield of CN32 with respect to Fe(III)aq reduction showed a linear trend with an average value of 5.24 (+/-0.12) x 10(9) cells/mmol of Fe(III). The reduction of Fe(III)aq by CN32 was described by Monod kinetics with respect to the electron acceptor concentration, Fe(III)aq, with a half-saturation constant (Ks) of 29 (+/-3) mM and maximum growth rate (micromax) of 0.32 (+/-0.02) h(-1). However, the pretreatment of CN32 with Fe(II)aq significantly inhibited the reduction of Fe(III)aq, resulting in a lag phase of about 3-30 h depending on initial cell concentrations. Lower initial cell concentration led to longer lag phase duration, and higher cell concentration led to a shorter one. Transmission electron microscopy and energy dispersive spectroscopy revealed that many cells carried surface precipitates of Fe mineral phases (valence unspecified) during the lag phase. These precipitates disappeared after the cells recovered from the lag phase. The cell inhibition and recovery mechanisms from Fe(II)-induced mineral precipitation were not identified by this study, but several alternatives were discussed. A modified Monod model incorporating a lag phase, Fe(II) adsorption, and aqueous complexation reactions was able to describe the experimental results of microbial Fe(III)aq reduction and cell growth when cells were pretreated with Fe(II)aq.

Biotransformation of Ni-substituted hydrous ferric oxide by an Fe(III)-reducing bacterium.

The reductive biotransformation of a Ni(2+)-substituted (5 mol %) hydrous ferric oxide (NiHFO) by Shewanella putrefaciens, strain CN32, was investigated under anoxic conditions at circumneutral pH. Our objectives were to define the influence of Ni2+ substitution on the bioreducibility of the HFO and the biomineralization products formed and to identify biogeochemical factors controlling the phase distribution of Ni2+ during bioreduction. Incubations with CN32 and NiHFO were sampled after 14 and 32 d, and both aqueous chemistry and solid phases were characterized. By comparison of these results with a previous study (Fredrickson, J. K.; Zachara, J. M.; Kennedy, D. W.; Dong, H.; Onstott, T. C.; Hinman, N. W.; Li, S. W. Geochim. Cosmochim. Acta 1998, 62, 3239-3257), it was concluded that coprecipitated/sorbed Ni2+ inhibited the bioreduction of HFO through an undefined chemical mechanism. Mössbauer spectroscopy allowed analysis of the residual HFO phase and the identity and approximate mass percent of biogenic mineral phases. The presence of AQDS, a soluble electron shuttle that obviates need for cell--oxide contact, was found to counteract the inhibiting effect of Ni2+. Nickel was generally mobilized during bioreduction in a trend that correlated with final pH, except in cases where PO4(3-) was present and vivianite precipitation occurred. CN32 promoted the formation of Ni(2+)-substituted magnetite (Fe2IIIFe(1-x)IINixIIO4) in media with AQDS but without PO4(3-). The formation of this biogenic coprecipitate, however, had little discernible impact on final aqueous Ni2+ concentrations. These results demonstrate that coprecipitated Ni can inhibit dissimilatory microbial reduction of amorphous iron oxide, but the presence of humic acids may facilitate the immobilization of Ni within the crystal structure of biogenic magnetite.

No excuses: televised pornography harms children.

All youngsters are at some risk from exposure to televised pornography, as described above. At particular risk for harm, however, are the most vulnerable children in our society--children in single-parent homes, children with mental and emotional disturbances, mentally challenged children, children who have been physically and/or sexually abused, and children in dysfunctional families. Youngsters for whom television serves as a babysitter or parental surrogate unfortunately are exposed to few competing influences to television viewing. In addition, parents in such homes are least likely to know what their children are viewing and to be able to pass on their own values about sex and sexual behavior. The main possible effects of televised pornography that must concern us as clinicians, educators, and parents are modeling and imitation of language heard and behaviors observed in televised pornography; negative interference with children's normal sexual development; emotional reactions such as nightmares and feelings of anxiety, guilt, confusion, and/or shame; stimulation of premature sexual activity; development of unrealistic, misleading, and/or harmful attitudes toward sex and adult male-female relationships; and undermining of family values with resultant conflict between parents and children. Much more research is clearly needed on this topic. Because of the ethical and procedural problems surrounding research on children exposed to pornography, ideal research designs may never be possible. Nonetheless, we hope that this article will stimulate further discussion and work. To devise public policy that protects children from potentially harmful material while at the same time respecting the media's First Amendment rights, such public discourse and responsible research are essential.

Expression and functional properties of transforming growth factor alpha and epidermal growth factor during mouse mammary gland ductal morphogenesis.

Primer-directed enzyme amplification was used to examine epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) mRNA transcripts in mammary glands of young virgin, mature virgin, midpregnant, and midlactating mice. Transcripts for both EGF and TGF-alpha mRNA were detected in virgin and pregnant mice, whereas transcripts for EGF mRNA but not TGF-alpha mRNA were expressed in 10-day lactating mice. TGF-alpha was localized in the epithelial cap-cell layer of the advancing terminal end bud and in the stromal fibroblasts at the base of the terminal end bud; EGF was localized in the inner layers of the terminal end bud and in ductal cells of mammary epithelium. Implantation of pellets containing EGF or TGF-alpha into the regressed mammary gland of ovariectomized mice stimulated the reappearance of end buds; contralateral glands implanted with pellets containing albumin or insulin were not affected. These results indicate that an EGF-receptor-mediated pathway remained intact in the mammary gland epithelium in the absence of ovarian steroids and that local availability of either EGF or TGF-alpha is sufficient to stimulate the pattern of normal ductal growth. The detection of EGF and TFF-alpha transcripts at different stages of mammary gland development and the different patterns of immunolocalization suggest that each polypeptide plays a different role in normal mammary gland morphogenesis.

Epidermal growth factor precursor in mouse lactating mammary gland alveolar cells.

Previous studies have demonstrated that high levels of epidermal growth factor (EGF) occur in human and rodent milk and that oral administration of this polypeptide stimulates rodent gastrointestinal development. It is not known whether EGF in milk originates from cells of the lactating mammary gland or is sequestered from an extramammary source. In the present study, prepro-EGF mRNA (approximately 4.7 kilobases) was detected in the CD-1 mouse mammary gland throughout the period of lactation; by comparison, negligible levels of this EGF transcript were found in the gland during pregnancy. Low levels of EGF immunoreactivity (4-5 ng/g wet wt tissue) were extracted from lactating (day 18) mammary glands with dilute acetic acid. Immunolocalization was evident with antisera to either EGF or two other regions of the EGF precursor in essentially all alveolar cells of the lactating gland. The most prominent staining with antiserum to EGF was observed along the luminal borders of cells; this pattern of cellular staining required proteolytic pretreatment of tissue sections. Western blot analyses of cell membranes isolated from the day 16 lactating mammary gland revealed an EGF-immunoreactive band at about 145K, which was equivalent in size to the EGF precursor found in mouse kidney cell membranes. Despite these findings, labeling of lactating mammary gland mince with L-[35S]methionine and cysteine for up to 4 h did not reveal any specific bands in immunoprecipitates. These cumulative findings suggest that the precursor form of EGF occurs in alveolar cells of lactating mammary gland and that this protein is translocated to the cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Topical fibronectin and corneal epithelial wound healing in the rabbit.

The effect of topically administered rabbit fibronectin on the rate of corneal epithelial wound healing was assessed in rabbits. Two types of epithelial defects were created, a "standard" 7-mm-diameter scraped central wound and a "persistent epithelial wound" secondary to postscraping application of alcian blue. In a masked fashion, eyes were treated with either fibronectin or balanced salt solution. Areas of the photographically documented fluorescein-stained defects were measured by computerized planimetry. The mean healing rate in fibronectin-treated eyes with standard wounds was linear but not significantly different from the rate in control eyes. The healing rate in persistent epithelial wounds treated with fibronectin was slower than that in standard wounds and was not linear, but it was not statistically significantly different from that of control eyes with persistent epithelial wounds. These results conflict with those of previous studies and indicate that the topical application of fibronectin in rabbits does not necessarily promote corneal epithelial wound healing.

Influence of estrogens on mouse uterine epidermal growth factor precursor protein and messenger ribonucleic acid.

Estrogens stimulate the in vivo proliferation of epithelial cells of the mouse uterus. The cumulative evidence from several earlier studies suggests that the mitogenic effect of estrogens is mediated indirectly through a polypeptide growth factor. The primary focus of the present investigation was to determine whether an epidermal growth factor (EGF)-related polypeptide originates in the uterus of the immature or adult mouse under normal or altered estrogen status. Hybridization experiments revealed the presence of the 4.7-kilobase prepro-EGF mRNA in uteri of immature CD-1 mice. The level of this mRNA was augmented at least 2-fold in immature mice treated for 4 days with estrogen, but levels remained markedly low compared to those in submaxillary gland or kidney. Two preparations of pooled uterine luminal fluid from estrogen-treated immature mice contained EGF immunoreactivity (1.2 and 1.7 ng/ml) that was stable in response to acid (50 mM acetic acid) and heat. Negligible EGF (less than 20 pg/uterus) was detected in acid extracts of uteri from ovariectomized or cycling adult mice. After injection of 17 beta-estradiol (0.2 or 2.0 micrograms, ip), the levels of acid-extractable uterine EGF in ovariectomized adult mice up to 48 h after treatment were not different from those obtained with vehicle alone. Immunolocalization of EGF in the mouse uterus was demonstrated only after paraffin sections were first briefly treated with pronase. Staining was observed along the borders of luminal and glandular epithelial cells, especially at the apical region of the cells. Some staining was also observed in the myometrium; stromal cells were negative. Synthesis of the reactive material was apparently estrogen independent, since localization was retained in uteri of both ovariectomized and immature mice. Immunoblots of preparations of membranes from uterine homogenates or epithelial cells revealed a band at mol wt of about 130,000, which, along with other findings of the present study, suggests that EGF occurs predominantly as the membrane-bound precursor form in this organ, as has been previously shown for the kidney. Although the biological role of the precursor in the uterus is not known, we speculate that estrogens function in an autocrine circuit by stimulating processing of the membrane-bound EGF precursor. EGF elaborated by this mechanism might conceivably react with known complementary receptors on uterine epithelial cells to stimulate proliferation.

Hidradenitis suppurativa of the anogenital region: response to isotretinoin.

Hidradenitis suppurativa, a chronic relapsing disease of apocrine gland-bearing areas, most frequently occurs in the axillae, groin, perineal, and perianal regions. Hidradenitis of vulva is frequently misdiagnosed and inadequately treated. The case of a 15-year-old nulliparous black female adolescent referred for evaluation of multiple draining fistulas of the anogenital region is presented. Diagnostic studies for granulomatous disease were negative. Results of a barium enema were normal and biopsies were compatible with the diagnosis of hidradenitis suppurativa. She was treated for 22 weeks with isotretinoin, 1 mg/kg daily, with an excellent response. Side effects were minor and included cheilitis, mild xerosis, and a transient elevation of serum alkaline phosphatase levels. Few patients with severe hidradenitis have been responsive to this synthetic vitamin A derivative. A review of the literature indicates that the results of treatment with isotretinoin for hidradenitis have been at best equivocal. Isotretinoin should never be used during pregnancy because of known teratogenic effects. Women of childbearing age must use effective contraception during treatment.

Biochemical properties of tracheobronchial mucins from cystic fibrosis and non-cystic fibrosis individuals.

Tracheobronchial mucins from healthy individuals and from patients with bronchial asthma or cystic fibrosis (CF) were isolated from lung mucus, purified, and their chemical and physical properties compared. Normal and asthmatic mucins required both a dissociating and a reducing agent for solubilization and exhibited identical chromatographic behavior on Sepharose 4B, Sepharose 2B, and hydroxylapatite and similar amino acid and carbohydrate compositions. In contrast, 1) CF lung mucins were solubilized in the absence of dissociating and/or reducing agents and 2) the majority of the CF mucins analyzed was eluted in the included volume of Sepharose 4B with Kd values of 0.3 +/- 0.1 rather than in the void volume and thus appeared smaller than normal and asthmatic mucins. The lower molecular weight mucins in CF sputum apparently are produced by bacterial or inflammatory cell proteinases since radiolabelled asthmatic mucin was digested to smaller fragments when incubated with crude CF lung mucosal samples. Furthermore, mucins secreted by tracheal explants from CF and from non-CF individuals eluted in the void volume on Sepharose 4B, suggesting that CF tracheobronchial mucins were not inherently smaller than non-CF mucins.

Evidence for isoaspartyl (deamidated) forms of mouse epidermal growth factor.

A variant form of mouse submaxillary gland epidermal growth factor (EGF) was identified by isocratic reversed-phase HPLC of EGF obtained by Bio-Gel P-10 column chromatography ("culture grade"). The variant form was essentially absent in preparations of EGF further purified by chromatography on DEAE-cellulose ("receptor-grade" EGF). The spectral properties and amino acid composition of the variant form (EGF-I) could not be distinguished from those of the intact polypeptide isolated by HPLC (alpha-EGF). Receptor-binding and mitogenic properties of EGF-I were also equivalent to those of alpha-EGF. These data suggested that EGF-I was structurally very similar to EGF. However, the very low yield (less than 4%) obtained by Edman degradation indicated that the N-terminal (Asn1) of the polypeptide was modified. Isoelectric focusing of EGF-I revealed two major immunoreactive bands: one with a pI equivalent to that of alpha-EGF (pI 4.6) and another at pI 4.1. Alkaline treatment of alpha-EGF (0.1 M NH4OH) yielded peak material by HPLC that coeluted with EGF-I; the alkaline-generated EGF-I yielded bands that also focused at pH 4.6 and 4.1. Ammonium hydroxide treatment of [des-Asn1]-EGF (beta-EGF) did not produce conversion to EGF-I. On the basis of these data, we propose that EGF-I was formed by selective deamidation of the N-terminal Asn of intact EGF. This notion is also supported by liquid secondary ion mass spectrometry, which showed that EGF-I was approximately 1.5 mass units greater than alpha-EGF. The heterogeneity observed by isoelectric focusing supports previous studies which have shown that, following deamidation of N-terminal asparagine, a beta-aspartyl shift can occur, which in the present study might yield succinimido-aspartyl1-EGF and beta-aspartyl1-EGF. Low yields observed during Edman degradation indicate that negligible amounts occur as the alpha-aspartyl1-EGF isomer.

Retroperitoneal hematoma: an unusual complication of cold knife conization of the cervix.

A case of an unusual complication of cold knife conization and associated extensive retroperitoneal hematoma is presented. The contributing factors, prevention, and management of this complication are discussed.

Physical fitness effect on bone mass in postmenopausal women.

This study was conducted to determine if bone mineral mass is influenced by the level of physical fitness in active, healthy, postmenopausal women from 50 through 59 years of age. In vivo neutron activation analysis (NAA) was used to measure calcium or bone mineral in the trunk and proximal femurs. The NAA measurement is expressed as calcium bone index (CaBI), which relates the subject's Ca value to the estimated mean value for normal subjects of the same size based on height and arm span. The normal CaBI is 1.00 +/- 0.12 (ISD). The level of physical fitness was determined by calculating the maximum oxygen uptake (VO2max), attained by a graded exercise test on the treadmill, and evaluating the muscle strength in performing one repetition maximum in the bench press and leg press. The "above-average fit" group (VO2max greater than 29 ml/kg/min) when compared to the "average fit" group (VO2max 21-29 ml/kg/min) had significantly higher CaBI (p less than 0.001) and leg press (p less than 0.01). There was significant correlation between VO2max and CaBI (p less than 0.01). The findings suggest that level of physical activity may modify the amount of bone loss in postmenopausal women.

Exercise-induced angina in the cold.

Exercise-induced angina (AP) is a common complaint of cardiac patients, particularly when exercising in the cold. To investigate the effects of environmental and inspired air temperature on AP, 9 patients with a history of cold-induced AP underwent progressive cycle ergometry tests in a climatic chamber on 4 separate occasions: (1) room environment (RE) (24 degrees C), and room inspired air (RA) (22.5 degrees C); (2) RE and cold inspired air (CA) (0.7 degrees C); (3) cold environment (CE) (-7.5 degrees C) and RA; and (4) CE and CA. Measurements of oxygen consumption, heart rate, blood pressure, and ventilation were made every minute and at test endpoint, which was either AP (85%) or fatigue (15% of all tests). Expired air temperature and skin temperature at 5 sites were also recorded. Results indicated that angina occurred sooner, and mean exercise time was significantly reduced in both RA/CE (-24%) and CA/CE (-15%) when compared with the RA/RE. Breathing CA in the RE did not significantly reduce exercise tolerance. Skin temperature was lower in both CE's compared to the RE's at all sites. Submaximal systolic blood pressure and calculated rate-pressure product were significantly higher in the CE's vs RE's. The adverse effects of cold on exercising angina patients are due to the earlier onset of angina, which appears to be induced more by the effects of exposure to the cold environment (-7.5 degrees C) than by cold air inhalation (0.7 degrees).

Intercellular relationships in the synthesis of macromolecules by organ cultures of corneas.

Sepharose CL-4B chromatography of guanidine hydrochloride and aqueous extracts of 3H-glucosamine labeled intact corneal tissue reveals four peaks representing proteoglycans and glycoproteins. To evaluate the universality of the 4th peak, hereafter designated as Sepharose CL-4B (IV), its presence was investigated in rabbit, bovine, cat, rhesus monkey, and human corneal preparations. Following incubation in isotopically labeled medium, corneas were extracted with aqueous and/or 4M guanidine hydrochloride and subjected to Sepharose CL-4B chromatography. Sepharose CL-4B (IV) was detected in all species studied; 3H-glucosamine and 14C-amino acids, but not 35SO4, were incorporated into this peak which eluted in the range consistent with an apparent molecular weight of approximately 30,000 D. To determine which layers were involved in the synthesis of Sepharose CL-4B (IV) the layers of the rabbit cornea were incubated separately (stroma scraped of endothelium and/or epithelium, epithelium only, endothelium only). A distinct Sepharose CL-4B (IV) peak was not identified in the chromatographs obtained from organ cultures of corneal epithelium, endothelium, or from corneal stroma scraped of epithelium and/or endothelium. This decrease in Sepharose CL-4B (IV) synthesis occurred even if the scraped cornea was not allowed to expand in volume by compressing it beneath a membrane porous to the incubation medium. Thus, Sepharose CL-4B (IV) synthesis was enhanced significantly by the stroma being in conjunction with other corneal cells as they exist in vivo.

The effect of sleep loss on high intensity exercise and recovery.

The cardiovascular and metabolic responses of five male subjects during submaximal exercise (80% Vo2 max) were examined after 24 h of wakefulness. The protocol consisted of two sets of two trials separated by 7-10 days: first, a 20 min exercise bout, then a normal night's sleep, followed by another 20 minutes of exercise; second, a 20-min exercise bout, 24 h of wakefulness, then another 20 min exercise trial. Exercise ventilation, heart rate, and oxygen uptake were not affected by sleep loss. However, sleep loss caused the recovery ventilation and oxygen uptake to remain higher than normal during the slow phase of recovery. Blood glucose levels were found to be greater during the sleep deprived trials compared to controls, but were similar to controls 15 min after exercise. Blood lactates were lower at the end of exercise after sleep deprivation and remained lower during the recovery period. Changes in plasma volume were not affected by sleep loss. These results suggest that although sleep loss may not overtly affect acute submaximal exercise performance, it attenuates the recovery process.

Structural features of human tracheobronchial mucus glycoprotein.

Electron microscopy of platinum-shadowed preparations of human tracheobronchial mucins showed very flexible filamentous structures that frequently occurred in an intricate random-coiled pattern of filament(s) surrounding a dense core-like domain. The filament(s) associated with cores accounted for 70-80% of the mass of the mucin preparation, the remainder being accounted for by free filaments. On aggregation, the molecules formed a large interwoven network quite different from the massive rope-like structures characteristic of sheep submaxillary mucin aggregates [Rose, Voter, Sage, Brown & Kaufman (1984) J. Biol. Chem. 259, 3167-3172]. Mild sonication resulted in extensive fragmentation of the tracheobronchial mucin molecules and yielded short filaments of various lengths, free cores and some cores associated with short filaments. Mucin glycopeptide fragments obtained by proteolytic digestion were flexible, core-free, filaments. The glycopeptides obtained by Pronase digestion were shorter than those obtained by tryptic digestion. The intricate structures of human tracheobronchial mucin differ markedly from the extended filaments reported for sheep submaxillary and human ovarian-cyst mucins but agree with the roughly spherical expanded model proposed for mucins by Creeth & Knight [(1967) Biochem. J. 105, 1135-1145] on the basis of hydrodynamic measurements.

Factor XII and prekallikrein-kallikrein-kinin in the cryoactivation of human plasma prorenin.

Cryoactivation of human plasma 'prorenin' was followed for 24 h at -4 degrees C. Chromogenic assays were used to determine factor XII (FXII), FXIIa, prekallikrein and kallikrein in relation to the observed cold-induced increase in plasma renin activity (PRA). Bradykinin activity was also determined using the rat uterus bioassay. PRA increased rapidly and became significantly higher after just 6 h of cryoactivation, by which time prekallikrein had almost disappeared, while kallikrein and kinin levels increased. In contrast, FXII did not change notably, but some FXIIa was indeed formed. The bacteriostat neomycin sulphate did not affect the course of cryoactivation, but did block the dextran sulphate- and kaolin-induced activation of prekallikrein and FXII respectively, and was therefore omitted. Thus cryoactivation of prorenin is accompanied by, and may depend upon, the activation of FXII and prekallikrein, supporting other evidence in favour of this hypothesis.

Effects of deglycosylation on the architecture of ovine submaxillary mucin glycoprotein.

The structural features of native and deglycosylated ovine submaxillary mucin (OSM) were determined by electron microscopy of platinum unidirectionally shadowed preparations and by ultracentrifugation. Thin filamentous molecules, of which 90% were 100-230 nm in length with estimated diameters of 1.0-1.4 nm, were observed with dilute samples of OSM in high ionic strength solvents (5-30 micrograms/ml in 0.8 M NaCl or NH4Ac). Ultracentrifugation studies indicated that these filamentous structures were monomers and/or dimers. At higher mucin concentrations or in lower ionic strength solvents, OSM molecules were oligomers that appeared as long rope-like strands. Removal of sialic acid residues by incubation with Clostridium perfringens neuraminidase yielded filamentous structures similar to those observed with OSM and some smaller less extended structures. Subsequent removal of the GalNAc residues of asialo-OSM with C. perfringens alpha-N-acetylgalactosaminidase resulted in a dramatic change in appearance, from an extended filament to a globular form. The frictional ratios of OSM and deglycosylated OSM were consistent with the marked structural differences of these molecules. Native OSM had a frictional ratio of 3.09, comparable to that of highly asymmetric tropomyosin (3.22); deglycosylated OSM had a frictional ratio of 1.11, comparable to that of globular ovalbumin (1.08).

Characterization of pulmonary cellular influx differentials to known toxic agents between species.

In this study, we have shown that chickens, frogs, and toads are resistant to acute pulmonary injury by a variety of toxic agents, (O2, hyperbaric O2, paraquat, and silica), that cause extensive acute injury in mammals. Acute pulmonary injury is defined as a massive influx of inflammatory cells, both interstitially and into the alveolar spaces, pulmonary edema, hemorrhage, and the presence of H2O2 and O-2 in the lavaged supernatant, occurring within 48 h. In some cases, chronic effects of the toxins were observed after 90 h., i.e., hemorrhage, fibrosis, and an accumulation of interstitial inflammatory cells. In all three nonmammal systems, isolated inflammatory cells failed to respond chemotactically in vitro to known mammalian chemotaxins. Pulmonary lavage of the exposed chickens, frogs, and toads also failed to produce inflammatory cells. Pulmonary edema was not detected in any of the animals by comparison of lung weight to total body weight. Intratracheal injections of silica for 2 weeks did produce chronic effects in chickens and frogs. Morphologically, the lungs showed signs of fibrosis and accumulation of interstitial inflammatory cells, but no intraalveolar cells. After 90 h of hyperbaric O2, frogs exhibited a massive infiltration of interstitial inflammatory cells and hemorrhage. Elevated O2 levels (100%) for 2 weeks under normal atmospheric conditions produced no changes in frog lungs or in the amount of inflammatory cells in the lungs. Intravenous injections of paraquat for up to 208 h failed to initiate an accumulation of pulmonary inflammatory cells or the development of pulmonary edema in chickens. There was also no detectable H2O2 or O-2 in the lavaged supernatant. It was not determined whether paraquat had a longer or more chronic effect on chickens. We suggest that the lack of an acute pulmonary inflammatory mechanism in chickens, frogs, and toads is in part responsible for the resistance of these animals to acute pulmonary injury by oxidizing mammalian toxins.