The development of an aquatic bivalve model: evaluating the toxic effects on gametogenesis following 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) exposure in the eastern oyster (Crassostrea virginica).

The objective of this study is to develop a gametogenesis protocol to serve as a model for evaluating the toxic effects of chemicals on oogenesis and spermatogenesis in the eastern oyster (Crassostrea virginica). The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was selected as a "proof of principle" toxicant to examine developmental toxicity in this invertebrate system. The studies were designed to: (1) test the model using 2,3,7,8-TCDD and (2) to use histopathological evaluations to characterize the effects on oocyte and sperm development during stages of gametogenesis. 2,3,7,8-TCDD at 10 pg/g resulted in significant histopathological gonadal lesions by day 14 of gametogenesis in both female and male oysters. These lesions resulted in complete inhibition of gonadogenesis. Studies also showed that a total body dose of 2 and 10 pg/g 2,3,7,8-TCDD caused adverse responses resulting in abnormal gametogenesis in female and male oysters, respectively, such as: (1) incomplete oocyte division, (2) inhibition of oocyte growth and maturation, (3) unsynchronized sperm development, and (4) inhibition of spermatogenesis. The eastern oyster is one of the most responsive invertebrate models tested to date for reproductive effects of chemicals. Therefore, the eastern oyster can be used as a sensitive toxicological model for examining the effects of dioxin-like compounds and other xenobiotics on gametogenesis. The reported studies show that environmentally relevant concentrations of 2,3,7,8-TCDD (2-10 pg/g) have a significant adverse effect on oyster gametogenesis.

Sleep apnea in active acromegaly.

Previous case reports have shown an association between acromegaly and the sleep apnea syndrome (SAS). Some of the patients described had central SAS, raising the possibility that an elevation of the growth hormone (GH) level may cause a defect in respiratory drive. We determined the prevalence of SAS in 21 patients with a history of acromegaly. We separated them into two groups based on serum GH concentrations. Ten patients had active acromegaly (mean GH concentration, 62.2 ng/mL; range, 12.6 to 148 ng/mL), while 11 patients had inactive acromegaly (mean GH, 3.2 ng/mL; range, 0.7 to 6.4 ng/mL). Four of the ten patients with active acromegaly had SAS; none of the 11 patients with inactive acromegaly had SAS. Three patients with SAS had the purely obstructive type, and one had the mixed central and obstructive type. The hypercapnic ventilatory response was normal in all patients tested and was not influenced by the GH level. We conclude that SAS is associated with active acromegaly and that the GH level does not affect the hypercapnic ventilatory response. The absence of SAS in successfully treated patients suggests that it may resolve after a normal GH level is restored.

Benefit of nasal CPAP in obstructive sleep apnea is due to positive pharyngeal pressure.

The purpose of this study was to determine if the mechanism of nasal continuous positive airway pressure's (CPAP's) effectiveness is to act as a pneumatic splint or to increase functional residual capacity (FRC) and consequently, upper airway caliber. Four subjects with obstructive sleep apnea underwent 3 nights of polysomnography: night 1, control; night 2, nasal CPAP; night 3, external subatmospheric pressure (ESAP). ESAP, a negative pressure body suit, increases FRC. We measured the changes in FRC with nasal CPAP and ESAP using the weighted spirometer technique. The dose used for the ESAP night was the dose that produced the same FRC as the subject's prescribed nasal CPAP dose. The mean number of arousals and the respiratory events index were higher on ESAP and control nights. Less severe oxygen desaturation occurred during non-rapid-eye-movement sleep on the nasal CPAP and ESAP nights. These preliminary results show that increasing FRC alone does not account for the effectiveness of nasal CPAP, and splinting of the collapsible upper airway is necessary.

Effect of gestational and lactational 2,3,7, 8-tetrachlorodibenzo-p-dioxin exposure on the level and catalytic activities of hepatic microsomal CYP1A in prepubertal and adult rats.

We determined the inducibility, as well as the persistence of the induction, of hepatic microsomal CYP1A1 and CYP1A2 (by western blot analysis), and their catalytic activities (as measured by resorufin ether O-dealkylation) in prepubertal (25-day-old) and adult (120-day-old) offspring of timed-pregnant Sprague-Dawley rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD treatment was subcutaneous, at a low dose of 0.1 microg/kg, on gestational days 7, 14, and 20, and on lactational days 7 and 14. CYP1A1 protein was induced significantly (23-fold) in prepubertal but not in adult offspring of TCDD-exposed dams, whereas ethoxyresorufin O-deethylase (EROD) activity, which is CYP1A1-preferential, was induced less extensively (5-fold) and slightly (1.7-fold) in the prepubertal and adult offspring, respectively. Benzyloxyresorufin O-debenzylase (BROD) activity, which is CYP2B-preferential but has been reported to be catalyzed by CYP1A1, was also induced 5- and 6-fold in prepubertal and adult offspring, respectively, of TCDD-exposed dams. However, the induced BROD activity was neither inhibited by antibody against CYP1A1 nor accompanied by an elevated level of microsomal CYP2B. CYP1A2 was induced slightly only in prepubertal offspring of TCDD-treated dams. There was suggestive evidence of enhanced lipid peroxidation in hepatic microsomes from prepubertal but not adult offspring of TCDD-treated dams. These data showed that in utero plus lactational TCDD exposure effected transient induction of hepatic microsomal CYP1A1 but sustained induction of BROD activity, which may be catalyzed by enzymes other than CYP1A or CYP2B.

Hepatoma presenting as a single cavitary lung mass.

A patient who had had a lobectomy for a large cavitary lung mass died one month later. An autopsy was performed and pathologic review of surgical and postmortem specimens confirmed that the original lung lesion was metastatic hepatoma. Excavating solitary metastases from primary adenocarcinomas represent the rarest form of cavitary metastatic lesion, and this is the first report of hepatocellular carcinoma presenting as a single cavitary lung mass.

Reduced functional residual capacity and abnormal oxygenation in patients with severe head injury.

Severe head injury often results in hypoxemia, but the pathophysiology of this phenomenon is unclear. We studied 24 patients hospitalized after severe head injury to determine whether the abnormality of oxygen transfer as measured by venous admixture (Qs/Qt) was associated with a reduction in functional residual capacity (FRC) and also what changes in these variables could be induced by positive end-expiratory pressure (PEEP). Mean FRC was 68 percent of the value predicted for the upright position, and mean Qs/Qt was 0.196. The FRC and Qs/Qt were significantly related so that patients with the lowest FRC had the highest Qs/Qt (p less than 0.001). The FRC was small enough to expect closure of small airways in many of these patients. The addition of 10 cm H2O of PEEP resulted in an increase in FRC of 28 percent (+/- 15 percent [SD] of the value predicted for upright posture; Qs/Qt declined by 0.05 (+/- 0.05 [SD] ). Most of these patients had no spontaneous breathing due either to the severity of the brain injury or to the therapeutic hyperventilation and muscular paralysis employed to control intracranial pressure. We conclude that FRC is often reduced in patients hospitalized after severe head injury and that associated abnormalities of ventilation-perfusion matching often lead to an elevated Qs/Qt. Therapy with PEEP in the range of 10 to 15 cm H2O was well tolerated by our patients and can be used safely to reduce Qs/Qt.

Treatment of theophylline toxicity with oral activated charcoal.

We treated 14 patients who had an initial serum theophylline concentration greater than 30 micrograms/ml (48.3 +/- 19.4 micrograms/ml) and symptoms of theophylline toxicity with oral activated charcoal (OAC). Thirty-gram doses of OAC were administered approximately every two hours for two to four doses. Ten patients tolerated OAC and demonstrated a reduction in theophylline half-life to 5.6 +/- 2.5 hours with resolution of symptoms. Three of these ten patients were treated in the emergency department and discharged, making hospitalization unnecessary. The four patients with the highest initial theophylline concentrations (76.6 +/- 17.7 micrograms/ml) vomited all doses of OAC. Three of these four patients were treated with charcoal hemoperfusion with a reduction in the half-life to 5.2 +/- 1.0 hours. These data support the use of OAC as the primary therapeutic modality in the management of patients with theophylline toxicity. Patients with very high theophylline concentrations (greater than 50 micrograms/ml), however, usually vomit the OAC and may require charcoal hemoperfusion.

The effect of sleep loss on breathing in chronic obstructive pulmonary disease.

We have previously shown that one night of sleep deprivation results in significant deterioration of spirometric performance and ventilatory responsiveness to inhaled carbon dioxide in normal people. Since even a small decrease in pulmonary function may be clinically important in patients with chronic limitation of airflow, we undertook the present study to assess the effects of sleep loss on breathing in patients with chronic obstructive pulmonary disease (COPD). Criteria for inclusion in this study were a ratio of the forced expiratory volume in one second over the forced vital capacity (FEV1/FVC) of less than 60 percent, no hospital admission for pulmonary disease within two weeks of testing, stable (less than 30 percent variation) in tests of pulmonary function on two occasions within three months of testing, and no history of asthma. We studied 15 men (mean age, 57 +/- 3 years) on two consecutive mornings. Patients were studied with and without sleep deprivation in a randomized fashion. Patients were hospitalized for the study so that sleep deprivation, medications, smoking, and diet could be monitored and enforced. We found small but statistically significant falls in FEV1 (1.06 +/- 0.11 to 1.00 +/- 0.09 L; p less than 0.05) and in FVC (2.56 +/- 0.20 to 2.43 +/- 0.17 L; p less than 0.05) following sleep deprivation. Changes of similar magnitude which were not statistically significant occurred in maximal voluntary ventilation (MVV) and response to carbon dioxide. The arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions were not affected. Maximal expiratory pressure at the mouth increased slightly, but there was a fall in maximal inspiratory pressure (MIP) at the mouth. We conclude that sleep loss is associated with small but significant falls in FEV1 and FVC, as well as changes of similar magnitude in MVV, minute ventilation, and MIP in patients with severe COPD. Although the sleep loss which frequently accompanies exacerbations of COPD may be a slight additional stress of pulmonary reserve, a single night's loss of sleep in the patient with stable chronic airflow obstruction does not have major clinical consequences.

Pulmonary compliance: early assessment of evolving lung injury after onset of sepsis.

We compared the sensitivity of dynamic (Cdyn) and static lung compliance (CL) with indicators of permeability injury in a model of septic porcine adult respiratory distress syndrome. Two groups of anesthetized ventilated swine (15-25 kg) were studied. Septic animals (Ps, n = 13) received Pseudomonas aeruginosa intravenously for 1 h, which resulted in severe adult respiratory distress syndrome. Controls (C, n = 13) received 0.9% NaCl. Cdyn, CL, bronchoalveolar lavage for protein estimation, and thermal cardiogreen extravascular lung water (EVLW) measurements were performed in seven C and eight Ps animals. Six C and five Ps animals underwent gamma camera measurement of lung-to-heart ratio (slope index) of 99Tc-labeled human serum albumin. Both Cdyn and CL decreased significantly (P less than 0.01) at 30 min and thereafter in Ps vs. C. EVLW, slope index, and bronchoalveolar protein content increased significantly (P less than 0.05) in Ps vs. C at 120, 150, and 300 min, respectively. Cdyn and CL decreased well before onset of permeability injury. These early changes may be due to release of vasoactive mediators and sequestration of neutrophils in the pulmonary capillaries and later to increases in EVLW. Measurement of Cdyn and CL represents an early means of assessing evolving lung injury in this acute septic porcine model.

Safe use of PEEP in patients with severe head injury.

Thirty-three patients with severe head trauma were studied to determine whether the use of positive end-expiratory pressure (PEEP) would cause an increase in intracranial pressure (ICP). Changes in ICP induced by PEEP were then correlated with a panel of physiological variables to try to explain these changes. Mean ICP increased from 13.2 +/- 7.7 mm Hg (+/- standard deviation) to 14.5 +/- 7.5 mm Hg (p less than 0.005) due to 10 cm H2O PEEP, but the eight patients with elevated baseline ICP experienced no significant increase. Cardiac output and venous admixture (Qs/Qt) declined significantly, while central venous pressure, peak inspiratory pressure, functional residual capacity, and arterial pCO2 increased significantly due to PEEP. Blood pressure and cerebral perfusion pressure were unchanged. The change in ICP due to PEEP correlated significantly with a combination of cardiac output, peak inspiratory pressure, Qs/Qt, and changes in blood pressure and arterial pCO2 due to PEEP, indicating that the effect of PEEP on ICP could be largely explained by its effect on hemodynamic and respiratory variables. No patient deteriorated clinically due to PEEP. It is concluded that 10 cm H2O PEEP increases ICP slightly via its effect on other physiological variables, but that this small increase in ICP is clinically inconsequential.

Profound pulmonary shunting without edema following stereotaxic biopsy of hypothalamic germinoma. Case report.

Hypoxemia is a nearly constant accompaniment of head injury. Diverse theories have been proposed to explain this relationship. The authors report the case of a patient who suffered an episode of severe, transient, arterial oxygen desaturation during "controlled" brain trauma: an otherwise uneventful stereotaxic biopsy of a small germinoma of the hypothalamus. Evidence is provided that pure ventilation-perfusion mismatching, without pulmonary edema, underlay the hypoxemia. The hypothalamus is intimately involved in matching pulmonary ventilation to perfusion; the hypoxemia of various brain injuries may be mediated by perturbation of this structure.

Using capillary electrophoresis to study the chemical conditions within cracks in aluminum alloys.

The environment-assisted cracking (EAC) susceptibility of some aluminum alloys used for airplane structural components currently limits their use in the peak strength condition. Understanding the mechanism of EAC will facilitate the development of crack-resistant alloys with optimum mechanical properties. One component towards understanding the fundamental processes responsible for EAC is a comprehensive knowledge of the chemical conditions within cracks. The present work uses capillary electrophoresis (CE) to quantify the crack chemistry in order to provide insight into the nature of the mechanism controlling cracking. The highly restricted geometry of cracks in metals means that a crack typically contains less than 10 microliters of solution. The high mass sensitivity combined with the inherently robust nature of CE makes it an ideal analytical technique for this application. Complicating factors in the accurate determination of the crack environment include high levels of sodium present from the test solution. Low sample volume and analyte matrix complexity necessitated the development of specific sampling, extraction and analysis methods. Analysis of the crack solutions in EAC-susceptible material revealed high levels of Al3+, Mg2+, Zn2+, and Cl- near the crack tip. Cations arise from the anodic dissolution of the alloy, whereas chloride ingress from the external environment occurs to maintain solution electroneutrality within the crack. In contrast, EAC-resistant material exhibited significantly lower concentrations of dissolution products.

Interactive inhibition of erythroid 59Fe utilization by benzene metabolites in female mice.

Using radioiron uptake into erythrocytes as a measure of hematopoiesis, it was demonstrated that benzene inhibited bone marrow function in female mice. Hydroquinone was marginally effective, but the inhibition occurred only at the highest dose tested (100 mg/kg). The combination of phenol and hydroquinone was more effective in reducing erythrocyte production than either chemical given alone. Catechol given alone was not inhibitory but when phenol was added to catechol, erythropoiesis was suppressed, as observed for the phenol and hydroquinone combination. It appears that benzene toxicity may be the result of cooperative inhibitory effects produced by its metabolites.

Learning effect of repeated hypercapneic ventilatory response testing.

To determine whether hypercapneic ventilatory response (HCVR) is affected by repeated testing, the HCVR of 22 healthy subjects was determined daily for 4 consecutive days. The slope (S) of the HCVR increased to a maximum on Day 3, which was 14% greater than S on Day 1 (p less than 0.05). The increase in airway occlusion pressure during progressive hypercapnea (delta P0.1/delta PCO2) showed no significant change, indicating that although S and delta P0.1/delta PCO2 are both good measurements of ventilatory response, they are not totally interchangeable in normal subjects. A subgroup of 12 subjects (termed "increasers") was responsible for the overall increase in S. For this subgroup, S was significantly smaller on Day 1 than on each subsequent day. Increasers also had a significantly greater value of S on each day of the study than subjects who did not increase ("decreasers"). On Day 1, increasers' S was 3.77 +/- 1.31 L min-1 mm Hg-1, while decreasers' S was 2.46 +/- 1.00 (p less than 0.001). Some normal subjects demonstrate a learning effect during repeated daily testing of HCVR by the rebreathing technique, and those subjects whose S increases are those with large initial values of S.

A proposed multigeneration protocol for Japanese medaka (Oryzias latipes) to evaluate effects of endocrine disruptors.

Definitive data on reproductive impairment of chronically exposed populations may be required to assess the appropriateness of the existing test methods for hazard identification and prioritization of endocrine modulators. Multigeneration toxicity testing protocols for wildlife receptors are lacking. To help address this gap we describe a multigeneration fish assay using the freshwater fish, Japanese medake (Oryzias latipes). This test species has been used for the evaluation of carcinogenic, teratogenic and reproductive effects and is sensitive to estrogen exposure producing ovo-testis, altered biochemical parameters and phenotypic characteristics. Due to the short life cycle, a multigeneration test with medaka can be conducted in 1 year. Endpoints evaluated include: survival, growth, sex ratio, fecundity, embryonic lesion occurrence, embryonic stage development, gonadal and hepatic somatic indices, histopathology and biochemical parameters. As new endpoints are developed they can be incorporated into the protocol. Results of a positive control (17 beta-estradiol) study are presented to give an indication of the baseline associated with various test endpoints and to highlight the importance of nutrition in the experimental design. 17 beta-Estradiol treatment induced vitellogenin production in male and female medaka, feminized males, and disrupted egg production. The proposed protocol provides researchers with an effective multigeneration fish test that can be used to examine potential effects of stressors at the population, individual, cellular and subcellular level.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in food samples collected in southern Mississippi, USA.

In 1994, we analyzed 43 foodstuff samples from local supermarkets in southern Mississippi, USA, for PCDD/PCDF. 2,3,7,8-Cl4DD could be quantified in 31 of these samples. On a lipid basis, levels in meat (0.53-1.10 pg I-TEQ/g) and dairy products (0.42-1.10 pg I-TEQ/g) were slightly lower than those reported from other industrialized countries. While levels in dairy samples from the United States and Europe are comparable, there is a difference in the contribution of individual congeners to the I-TEQ: for example, in milk samples from Germany approximately 40% of the I-TEQ is due to the presence of 2,3, 4,7,8-Cl5DF while in the Mississippi samples this congener only contributes 16%. The highest concentrations of PCDD/PCDF in our study were detected in the farm-raised catfish (10.2-27.8 pg I-TEQ/g). A unique finding was that in addition to the 2,3,7,8-substituted PCDD/PCDF the catfish samples contained many non-2,3,7,8-substituted congeners. This is unusual because vertebrate animals selectively eliminate or metabolize the non-2,3,7,8-substituted congeners.

PCDD and PCDF contamination in catfish feed from Arkansas, USA.

One combined catfish feed sample from Arkansas, USA, and its eight ingredients were analyzed for PCDDs and PCDFs. One of the ingredients, soybean meal, was highly contaminated by PCDDs, especially the toxic 2,3,7,8-substituted congeners, e.g., 7.3 pg/g dry weight or 370 pg/g lipid for the 2,3,7,8-tetra CDD. The I-TEQ value for the soybean meal was 11.4 pg/g dry weight or 576 pg/g fat. The corresponding values for the combined catfish feed concentrations were approximately 3 times lower. The congener pattern, the congener profile and the ratio sigma PCDDs/sigma PCDFs for the soybean meal were quite unique. We are not aware of any environmental sample or technical product with similar characteristics. As a result, natural formation of the PCDDs found in the soybean meal cannot be ruled out.

The effect of levenogesterol (Norplant) contraception on coagulation as measured by antithrombin-III levels.

PURPOSE: To determine the effect of contraception given immediately postpartum on coagulation as measured by antithrombin III. STUDY DESIGN: In this prospective study, parturients (n = 85) self selected three means of postpartum contraception: levenorgesterol implants, oral contraceptives, or a barrier method. RESULTS: Baseline coagulation was assessed by antithrombin-III levels in each of the 85 women within 48 hours of delivery (100.35 +/- 1.61%) and at one (109.1 +/- 1.89%) and six (105.51 +/- 1.71%) weeks postpartum. There was a rise in antithrombin-III after delivery but there were no significant differences between the groups. CONCLUSION: The levenorgesterol implant system did not cause a decrease in antithrombin-III in normal parturients.

PIP: The effect of postpartum Norplant implant use on coagulation factors was investigated in a prospective study conducted in Mississippi, US. 85 postpartum women were given a choice of 3 contraceptive methods: levonorgestrel implants (n = 25), oral contraceptives (n = 38), or a barrier method (n = 22). Antithrombin-III (AT-III) levels were measured on the day of discharge from the hospital after delivery, 7 days after delivery, and 6 weeks after delivery. There was no significant difference between groups in the initial AT-III level (mean, 100.35 +or- 1.61%). At the end of the first postpartum week, AT-III levels rose significantly to 109.1 +or- 1.89%, but again, there were no significant differences according to contraceptive method. By the 6-week follow-up, AT-III levels had stabilized at a mean of 105.51 +or- 1.71%, with no significant between-group differences. AT-III levels in pill users declined more markedly between the first and sixth postpartum weeks than those in the 2 other groups. These findings indicate that subdermal implant use does not affect coagulation, and these devices can be inserted safely during the postpartum period.