1324. Target Attainment of Exebacase, a First-In-Class Antibacterial Lysin, to Determine Optimal Doses for Adult Patients with Staphylococcus aureus (S. aureus) Bloodstream Infections (Bacteremia) Including Endocarditis

Background

Exebacase, a novel, antibacterial direct lytic agent for the treatment of S. aureus bacterimia and endocarditis, studied in Phase 1 and 2 trials, demonstrated potential to improve clinical outcomes when used in addition to conventional antibiotics. Objectives were to develop population PK (PPK) model and perform target attainment (TA) simulations to determine optimal clinical doses.

Methods

PPK model was developed with data from 72 patients receiving Exebacase, in addition to the standard of care, as single 2-hr infusion of 0.25 mg/kg (0.12 mg/kg for patients with creatinine clearance (CrCL) < 60 mL/min). PPK model was used for TA simulations of various IV regimens.

Results

3-compartment model best fit the data, parameters were well estimated (CL=4.2 L/hr (RSE=5.5%), Vc=4.5 L (RSE=8.2%)). Total volume of distribution (V_d) was 20.2 L. Values were lower than estimated previously in healthy subjects, CL=7.1 L/hr and V_d=27.7 L. CrCL was the only clinically meaningful covariate. Patients with moderate and severe renal impairment are expected to have 1.3 to 2-fold higher AUC_0-24 or C_max than patients with normal renal function. Age was statistically significant on peripheral clearance but was not clinically meaningful (≤4% effect on exposure).

TA simulations were stratified by renal function across a range of fixed as well as weight-based doses (all simulated as 2-hr infusion). In patients with normal renal function or mild impairment, 18 mg dose result in C_max and AUC_0-24 of 1254 ng/mL and 3026 ng*hr/mL, respectively. In patients with moderate or severe renal impairment, 12 mg dose result in C_max and AUC_0-24 of 1107 ng/mL and 3099 ng*hr/mL, respectively. In ESRD patients including hemodialysis, 8 mg dose result in C_max and AUC_0-24 of 910 ng/mL and 3109 ng*hr/mL, respectively. These exposures place >99% subjects above efficacious thresholds of AUC/MIC >0.2 established in animals.

Conclusion

PPK model described exebacase PK in patients adequately. CL and V_d were estimated to be 40% and 17% lower, respectively, than healthy subjects. CrCL was the only clinically meaningful covariate requiring dose adjustment. TA assessments identified doses that achieve minimum efficacy target (AUC/MIC≥0.2) in >99% of patients with S. aureus. Based on these simulations, fixed dosing schedule was recommended.

Disclosures

Parviz Ghahramani, PhD, PharmD, MSc, MBA, Consultant to ConatFect (Consultant) Tatiana Khariton, PhD, Consultant to ConatFect (Consultant) Joannellyn Chiu, PhD, Consultant to ConatFect (Consultant) Cara Cassino, MD, ContraFect Corporation (Employee)ContraFect Corporation (Employee)

Enumeration and Confirmation of Bacillus cereus in Foods: Collaborative Study

A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-polymyxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MFN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.

1550. PK-PD Relationship and PK Driver of Efficacy of the Novel Antibacterial Lysin Exebacase (CF-301) in Pre-Clinical Models

Background

Exebacase (CF-301) is a novel lysin with rapid bacteriolytic and anti-biofilm activity against S. aureus, pronounced synergy with antibiotics and low propensity for resistance. Exebacase has undergone Phase 1–2 trials. This work was to develop pharmacokinetic (PK) model in animal and determine the relationship between exebacase exposure and efficacy in animals.

Methods

PK data in 592 animals (4 species) included in population PK model. A range of linear and nonlinear mammillary models with allometric scaling fitted to the PK data using NONMEM and the most parsimonious model was selected by improvement in objective function value (P < 0.01). To evaluate efficacy, 349 animals with 177 mice (neutropenic thigh infection) and 172 rabbits (aortic valve infective endocarditis were treated with exebacase in addition to suboptimal doses of daptomycin (DAP). Full PK profiles were simulated for individual animals. Fifty-nine dosing regimens of exebacase in mice (0–90 mg/kg) and 18 regimens in rabbits (0–1.4 mg/kg) with q24h, q12h and q8h frequencies. Relationship between AUC/MIC, Cmax/MIC, T> MIC, and log-CFU was examined using a range of functions by comparing residual standard error (RSE).

Results

3-compartment model with allometric scaling best described the PK data and was validated by bootstrap and Goodness of Fit. Maximum drop in log₁₀CFU/g in target tissues was at AUC/MIC< 0.2 for exebacase when added to DAP that was associated with CF reduction of -5 logs in rabbits (Figure (a)) with similar magnitudes in cardiac vegetations, kidney and spleen, and -4 logs in mice (Figure (b)). Treatment with DAP alone had log₁₀CFU reduction of -1 in mice; and -2 in rabbits. AUC/MIC was an appropriate predictor of CFU reductions.

Conclusion

PK model adequately described the data for 4 animal species. Exebacase addition to DAP has a synergistic effect on efficacy measured by CFU reductions in target tissues in the animal models. Results support previously presented determinations of AUC/MIC as predictor of efficacy. Maximum reductions in CFU in rabbits and mice were observed at AUC/MIC ratios <0.2. These results further indicate that rabbit is the most appropriate efficacy model with MICs and antibacterial activity reflective of previously reported observations in human serum.

Disclosures

All authors: No reported disclosures.

Ceftazidime-Avibactam Population Pharmacokinetic Modeling and Pharmacodynamic Target Attainment Across Adult Indications and Patient Subgroups

Ceftazidime‐avibactam is a novel β‐lactam/β‐lactamase inhibitor combination for the treatment of serious infections caused by resistant gram‐negative pathogens. Population pharmacokinetic (PopPK) models were built to incorporate pharmacokinetic (PK) data from five phase III trials in patients with complicated intra‐abdominal infection (cIAI), complicated urinary tract infection (cUTI), or nosocomial (including ventilator‐associated) pneumonia. Ceftazidime and avibactam pharmacokinetics were well‐described by two‐compartment disposition models, with creatinine clearance (CrCL) the key covariate determining clearance variability. Steady‐state ceftazidime and avibactam exposure for most patient subgroups differed by ≤ 20% vs. healthy volunteers. Probability of PK/pharmacodynamic (PD) target attainment (free plasma ceftazidime > 8 mg/L and avibactam > 1 mg/L for ≥ 50% of dosing interval) was ≥ 94.9% in simulations for all patient subgroups, including indication and renal function categories. No exposure‐microbiological response relationship was identified because target exposures were achieved in almost all patients. These modeling results support the approved ceftazidime‐avibactam dosage regimens (2000‐500 mg every 8 hours, adjusted for CrCL ≤ 50 mL/min).

Perceptions of Residents and Non-residents in Psychiatry on Training Needs and Care of Patients with Intellectual Disability and Mental Health Problems: A Study from Singapore

Background and Objective

Psychiatric assessment and care of people with Intellectual Disability (ID) is complex due to their cognitive and communication impairments. Demand for further training in this area by trainees in psychiatry has been well documented. The main of aims of this study were to explore the attitudes and perceptions of psychiatry residents and non-residents (non-trainees) with regards to care of patients with ID as well as their knowledge and training in this area.

Method

The study was conducted as an anonymous survey at the Institute of Mental Health, Singapore. A survey questionnaire developed by the study team was sent to residents and non-residents in psychiatry.

Results

Forty-eight out of the 76 questionnaires were returned with a response rate of 63.16%. Twenty-eight participants described themselves as non-residents and the rest were residents. All participants responded that postgraduate training was required in the area of ID and mental health and majority reported that available training was inadequate. Ninety percent of respondents believed that people with ID were vulnerable to exploitation by other patients in the inpatient unit and 94% of respondents believed that people with ID should be managed by a specialist team.

Conclusion

Currently residents and non-residents in psychiatry see that training in ID and mental health as well as services for people with ID as inadequate. Efforts should be made to include specialist training in psychiatry of ID in the Singapore psychiatry curriculum to enhance the confidence and expertise of psychiatrists in this field.

Population pharmacokinetics and exposure-response of trametinib, a MEK inhibitor, in patients with BRAF V600 mutation-positive melanoma

PURPOSE

To characterize the pharmacokinetics of oral trametinib, a first in class MEK inhibitor, identify covariates, and describe the relationship between exposure and clinical effects in patients with BRAF V600 metastatic melanoma.

EXPERIMENTAL DESIGN

Trametinib concentrations obtained in three clinical studies were included in the population pharmacokinetic analysis. Trametinib 2 mg once daily was administered in the Phase 2 and 3 studies. The impact of exposure [trough (C min) or average concentration] on response rates and progression-free survival (PFS) was examined.

RESULTS

Plasma concentrations (n = 3120) obtained in 493 patients were described using a two-compartment model. Trametinib oral clearance was lower in women relative to men (1.26-fold) and increased with body weight. There was no significant effect of age, mild or moderate renal impairment, or mild hepatic impairment on oral clearance. Between-subject variability was low (24 %). The number of responders was consistent across median exposure range, although tended to be lower at trough concentration <10 ng/mL. Disease stage was found to be a significant predictor of response with a lower response rate in patients with disease stage of M1c. Lactate dehydrogenase was significant in the analysis of PFS. Patients with observed C min above the median had longer PFS than those below median based on Phase 2 study (median 10.6 ng/mL), while the effect of exposure was not statistically significant in the Phase 3 study (median 13.6 ng/mL).

CONCLUSIONS

No dosage adjustments are required with any of the covariates tested. Clinical efficacy was associated with trametinib trough concentrations greater than 10 ng/mL.

Endoscopic versus open radial artery harvesting for coronary artery bypass grafting

AIM

The radial artery has become the artery of choice after the internal thoracic artery for coronary artery bypass grafting (CABG). This study compares wound healing and arm complications after endoscopic versus open radial artery harvesting for CABG.

METHODS

From January 2002 to July 2004, 509 patients underwent CABG in which a radial artery conduit was used. Thirty-nine had endoscopic and 470 had conventional open radial artery harvesting. A propensity score was used to obtain 1:3 matching of all endoscopic to 117 open-harvesting patients. Postoperative wound healing using the Hollander scale, local neurologic deficits, wound infection, and pain scores were compared.

RESULTS

Wound healing: 34 of 39 endoscopic wounds exhibited a perfect Hollander score versus 339 of 470 open-harvest wounds (P=0.01). Wound appearance in particular was better than for open harvesting (P=0.004), with no abnormal step-off borders, irregular contours, or abnormal scar width observed. Neurologic deficits. Three incomplete neurologic deficits were observed after open harvesting (two being distal sensitivity localized in the interspace between the first and second metacarpals); one complete neurologic deficit occurred after endoscopic harvesting, but improved remarkably prior to hospital discharge. Wound infection. Occurrence of wound infection was similar in the two groups (P=0.7), although infection was more severe with open harvesting. Pain: pain score was lower (P=0.006) with endoscopic harvesting.

CONCLUSION

Compared with conventional open harvesting, endoscopic radial artery harvesting was associated with better wound appearance and less pain. Occurrence of neurologic deficits and wound infection was infrequent in both groups.

Metabolic and hormonal effects of oral DHEA in premenopausal women with HIV infection: a randomized, prospective, placebo-controlled pilot study

Women with HIV infection use dehydroepiandrosterone (DHEA) because of its potential effects on mood and energy. We examined the effects of DHEA on the hypothalamic-pituitary-adrenal and gonadal axes and on insulin sensitivity. Fifteen HIV-positive women were randomized to receive placebo (6 subjects) or oral DHEA (9 subjects). ACTH-, CRF-, and GnRH-stimulation tests were performed before and after 8 weeks of treatment. DHEA, DHEA-S, dihydrotestosterone, total testosterone, free testosterone, sex hormone-binding globulin, estrone, estradiol, cortisol, insulin, IGF-1, IGFBP-1, IGFBP-3, and adiponectin in plasma or serum were measured. There was a significant increase in DHEA (p<0.004), DHEA-S (p<0.008), total testosterone (p<0.008), dihydrotestosterone (p<0.004), androstenedione (p<0.04), and estrone (p<0.03) from baseline within the DHEA group but not within the placebo group. There was a significant increase in DHEA (p<0.0006), DHEA-S (p<0.032), total testosterone (p<0.01), and dihydrotestosterone (p<0.005) in the DHEA group compared with the placebo group. Oral DHEA produces significant increases in circulating DHEA, DHEA-S, testosterone, DHT, and, possibly, androstenedione and estrone levels in premenopausal women with HIV infection. In the current pilot study these hormone changes did not affect the pituitary or adrenal axis or insulin/IGF indices. Long-term studies with larger groups of patients are needed to confirm these data and to determine their clinical significance.

Comparison of transendocardial and retrograde coronary venous intramyocardial catheter delivery systems in healthy and infarcted pigs

We compared two routes for myocardial delivery of therapeutics, transendocardial (TE) delivery with an intramyocardial injection catheter, and retrograde coronary venous (RCV) delivery with a balloon occlusion catheter in the interventricular vein.

METHODS

TE and RCV injection of 15 microM, neutron-activatable microspheres was compared in healthy pigs (Group I, n = 3), pigs with a 1-week-old myocardial infarction (MI; group II, n = 5), and pigs with a 2-weeks-old MI (group III, n = 4). The MI was induced by a 1-hr balloon occlusion in the LAD. Both methods were compared in the same animal using different microspheres. The RCV catheter allowed for continuous measurement of distal pressure and 2.5 x 10(6) microspheres were injected in 10 ml at 300 mmHg above balloon occlusion pressure. The TE injections were targeted to the infarct zone and 2.5 x 10(6) microspheres were distributed over 10 injections of 200 microl.

RESULTS

The retention of microspheres decreased with increase in MI age, but was comparable between devices within the groups. RCV delivery resulted in (14.3 +/- 0.9)% microsphere retention in Group I, (10.3 +/- 0.2)% in Group II, and (6.4 +/- 0.1)% in group III (P < 0.05 versus group I). Microsphere retention after TE was (15.1 +/- 0.7)% in group I, (18.9 +/- 0.6)% in group II, (4.1 +/- 0.1)% in Group III (P < 0.05 versus groups I and II). The RCV catheter delivered primarily to midventricular, antero-septal segments, whereas TE targeted apical areas predominantly.

CONCLUSIONS

Delivery efficacy was comparable between devices in each group however RCV targeted midventricular areas whereas TE targeted apical areas.

Duration-dependent response of SI to vibrotactile stimulation in squirrel monkey

In previous studies, we showed that the spatial and intensive aspects of the SI response to skin flutter stimulation are modified systematically as stimulus amplitude is increased. In this study, we examined the effects of duration of skin flutter stimulation on the spatiotemporal characteristics of the response of SI cortex. Optical intrinsic signal (OIS) imaging was used to study the evoked response in SI of anesthetized squirrel monkeys to 25-Hz sinusoidal vertical skin displacement stimulation. Four stimulus durations were tested (0.5, 1.0, 2.0, and 5.0 s); all stimuli were delivered to a discrete site on the glabrous skin of the contralateral forelimb. Skin stimulation evoked a prominent increase in absorbance within the forelimb regions in SI of the contralateral hemisphere. Responses to brief (0.5 s) stimuli were weaker and spatially more extensive than responses to longer duration stimuli (1.0, 2.0, and 5.0 s). Stimuli >or=1 s in duration suppressed responses to below background levels (decreased absorbance) in regions that surrounded the maximally activated region. The magnitude of the suppression in the surrounding regions was nonuniform and usually was strongest medial and posterior to the maximally activated region. The results show that sustained (>or=1.0 s) stimulation decreases the spatial extent of the responding SI cortical population. Registration of the optical responses with the previously documented SI topographical organization strongly suggests that the cortical regions that undergo the strongest suppression represent skin sites that are normally co-stimulated during tactile exploration.

Amplitude-dependency of response of SI cortex to flutter stimulation

Background

It is established that increasing the amplitude of a flutter stimulus increases its perceived intensity. Although many studies have examined this phenomenon with regard to the responding afferent population, the way in which the intensity of a stimulus is coded in primary somatosensory cortex (SI) remains unclear.

Results

Optical intrinsic signal (OIS) imaging was used to study the evoked responses in SI of anesthetized squirrel monkeys by 25 Hz sinusoidal vertical skin displacement stimulation. Stimuli were 10 sec duration with a 50 sec inter-stimulus interval. Stimulus amplitude ranged from 50 to 400 microns and different amplitudes were interleaved. Control levels of activity were measured in the absence of stimulation, and used to compare with activation levels evoked by the different stimulus amplitudes. Stimulation of a discrete skin site on the forelimb evoked a prominent increase in absorbance within the forelimb representational region in cytoarchitectonic areas 3b and 1 of the contralateral hemisphere. An increase in stimulus amplitude led to a proportional increase in the magnitude of the absorbance increase in this region of areas 3b and 1 while surrounding cortex underwent a decrease in absorbance. Correlation maps revealed that as stimulus amplitude is increased, the spatial extent of the activated region in SI remains relatively constant, and the activity within this region increases progressively. Additionally, as stimulus amplitude is increased to suprathreshold levels, activity in the surround of the activated SI territory decreases, suggesting an increase in inhibition of neuronal activity within these regions.

Conclusion

Increasing the amplitude of a flutter stimulus leads to a proportional increase in absorbance within the forelimb representational region of SI. This most likely reflects an increase in the firing rate of neurons in this region of SI. The relatively constant spatial extent of this stimulus-evoked increase in absorbance suggests that an increase in the amplitude of a 25 Hz skin stimulus does not evoke a larger area of SI neuronal activation due to an amplitude-dependent lateral inhibitory effect that spatially funnels the responding SI neuronal population.

Metabolite and light regulation of metabolism in plants: lessons from the study of a single biochemical pathway

We are using molecular, biochemical, and genetic approaches to study the structural and regulatory genes controlling the assimilation of inorganic nitrogen into the amino acids glutamine, glutamate, aspartate and asparagine. These amino acids serve as the principal nitrogen-transport amino acids in most crop and higher plants including Arabidopsis thaliana. We have begun to investigate the regulatory mechanisms controlling nitrogen assimilation into these amino acids in plants using molecular and genetic approaches in Arabidopsis. The synthesis of the amide amino acids glutamine and asparagine is subject to tight regulation in response to environmental factors such as light and to metabolic factors such as sucrose and amino acids. For instance, light induces the expression of glutamine synthetase (GLN2) and represses expression of asparagine synthetase (ASN1) genes. This reciprocal regulation of GLN2 and ASN1 genes by light is reflected at the level of transcription and at the level of glutamine and asparagine biosynthesis. Moreover, we have shown that the regulation of these genes is also reciprocally controlled by both organic nitrogen and carbon metabolites. We have recently used a reverse genetic approach to study putative components of such metabolic sensing mechanisms in plants that may be conserved in evolution. These components include an Arabidopsis homolog for a glutamate receptor gene originally found in animal systems and a plant PII gene, which is a homolog of a component of the bacterial Ntr system. Based on our observations on the biology of both structural and regulatory genes of the nitrogen assimilatory pathway, we have developed a model for metabolic control of the genes involved in the nitrogen assimilatory pathway in plants.

Nrg-1 belongs to the endothelial differentiation gene family of G protein-coupled sphingosine-1-phosphate receptors

The previously cloned rat nerve growth factor-regulated G protein-coupled receptor NRG-1 (Glickman, M., Malek, R. L., Kwitek-Black, A. E., Jacob, H. J., and Lee N. H. (1999) Mol. Cell. Neurosci. 14, 141-52), also known as EDG-8, binds sphingosine-1-phosphate (S1P) with high affinity and specificity. In this paper we examined the signal transduction pathways regulated by the binding of S1P to EDG-8. In Chinese hamster ovary cells heterologously expressing EDG-8, S1P inhibited forskolin-induced cAMP accumulation and activated c-Jun NH2-terminal kinase. Surprisingly, S1P inhibited serum-induced activation of extracellular regulated protein kinase 1 and 2 (ERK1/2). Treatment with pertussis toxin, which ADP-ribosylates and inactivates G(i), blocked S1P-mediated inhibition of cAMP accumulation, but had no effect on c-Jun NH2-terminal kinase activation or inhibition of ERK1/2. The inhibitory effect of S1P on ERK1/2 activity was abolished by treatment with orthovanadate, suggesting the involvement of a tyrosine phosphatase. A subunit selective [35S] guanosine 5'-3-O-(thio)triphosphate binding assay demonstrates that EDG-8 activated G(i/o) and G12 but not Gs and G(q/11) in response to S1P. In agreement, EDG-8 did not stimulate phosphoinositide turnover or cAMP accumulation. The ability of S1P to induce mitogenesis in cells expressing the EDG-1 subfamily of G protein-coupled receptors is well characterized. In contrast, S1P inhibited proliferation in Chinese hamster ovary cells expressing EDG-8 but not empty vector. The antiproliferative effect, like S1P-mediated ERK1/2 inhibition, was orthovanadate-sensitive and pertussis toxin-insensitive. Our results indicate that EDG-8, a member of the EDG-1 subfamily, couples to unique signaling pathways.

Tyrosine phosphatase inhibitors selectively antagonize beta-adrenergic receptor-dependent regulation of cardiac ion channels

beta-Adrenergic receptor stimulation regulates the activity of several different cardiac ion channels through an adenylate cyclase/cAMP/protein kinase A-dependent mechanism. Previous work has suggested that basal tyrosine kinase activity attenuates the beta-adrenergic responsiveness of these cardiac ion channels, supporting the idea that tyrosine phosphorylation exerts an inhibitory effect at some point in the common signaling pathway. To determine which element in the beta-adrenergic pathway is regulated by tyrosine kinase activity, we studied the effects of various protein tyrosine phosphatase (PTP) inhibitors on the cAMP-dependent regulation of the L-type Ca(2+) current in guinea pig ventricular myocytes. Three such compounds, sodium orthovanadate, peroxovanadate, and bpV(phen), had no effect on the basal Ca(2+) current, yet each caused a pronounced inhibition of the Ca(2+) current stimulated by the beta-adrenergic receptor agonist isoproterenol. These observations are consistent with the idea that basal tyrosine kinase activity is capable of inhibiting beta-adrenergic responses. However, these PTP inhibitors had no effect on cAMP-dependent stimulation of the Ca(2+) current via activation of adenylate cyclase with forskolin or activation of H(2)-histaminergic receptors with histamine. These results are consistent with the idea that inhibition of PTP activity produces an inhibitory effect involving a tyrosine kinase-dependent mechanism acting selectively at the level of the beta-adrenergic receptor. This signaling mechanism does not seem to be linked to tyrosine kinase activity associated with insulin and insulin-like growth factor receptors, because acute exposure to agonists of these receptors did not inhibit isoproterenol regulation of the Ca(2+) current.

Stress-mediated inhibition of the classical nuclear protein import pathway and nuclear accumulation of the small GTPase Gsp1p

Stress modifies all aspects of cellular physiology, including the targeting of macromolecules to the nucleus. To determine how distinct types of stress affect classical nuclear protein import, we followed the distribution of NLS-GFP, a reporter protein containing a classical nuclear localization sequence (NLS) fused to green fluorescent protein GFP. Nuclear accumulation of NLS-GFP requires import to be constitutively active; inhibition of import redistributes NLS-GFP throughout the nucleus and cytoplasm. In the yeast Saccharomyces cerevisiae, starvation, heat shock, ethanol and hydrogen peroxide rapidly inhibited classical nuclear import, whereas osmotic stress had no effect. To define the mechanisms underlying the inhibition of classical nuclear import, we located soluble components of the nuclear transport apparatus. Failure to accumulate NLS-GFP in the nucleus always correlated with a redistribution of the small GTPase Gsp1p. Whereas predominantly nuclear under normal conditions, Gsp1p equilibrated between nucleus and cytoplasm in cells exposed to starvation, heat, ethanol or hydrogen peroxide. Furthermore, analysis of yeast strains carrying mutations in different nuclear transport factors demonstrated a role for NTF2, PRP20 and MOG1 in establishing a Gsp1p gradient, as conditional lethal alleles of NTF2 and PRP20 or a deletion of MOG1 prevented Gsp1p nuclear accumulation. On the basis of these results, we now propose that certain types of stress release Gsp1p from its nuclear anchors, thereby promoting a collapse of the nucleocytoplasmic Gsp1p gradient and inhibiting classical nuclear protein import.

Cadmium-induced elevations in the gene expression of the regulatory subunit of gamma-glutamylcysteine synthetase in rat lung and alveolar epithelial cells

The controlled step in de novo glutathione (GSH) synthesis is catalyzed by gamma-glutamylcysteine synthetase (gamma-GCS), a dimeric enzyme consisting of a heavy catalytic subunit (gamma-GCS-HS) and a light regulatory subunit (gamma-GCS-LS). We have previously reported that exposure to cadmium (Cd) induces pulmonary gamma-GCS-HS mRNA and protein, and that these alterations are accompanied by increases in GSH synthesis and its steady-state level. The current study was designed to test the hypothesis that Cd exposure also up-regulates the expression of the regulatory gamma-GCS subunit. By using northern blotting, we have demonstrated that a single Cd aerosol exposure of adult male Lewis rats results in time- and dose-dependent increases in pulmonary levels of gamma-GCS-LS mRNA. Transcripts of gamma-GCS-LS in rat lung are maximally elevated (8-fold) 2 h following Cd inhalation exposure and remain significantly higher than air controls at 24 h. This response is highly correlated with Cd dose, ranging from 0.9 to 5 mg Cd per m(3), and with lung Cd burden. We also observed Cd-induced up-regulation of gamma-GCS-LS mRNA expression in alveolar epithelial cells exposed to Cd in vitro, either acutely or after repeated passaging in Cd-containing medium. The magnitude of the gamma-GCS regulatory subunit induction observed in Cd-treated cells was approximately five times greater than the induction of the catalytic subunit. These modifications in the expression of gamma-GCS subunits may offer protection from Cd toxicity.

Diffuse lamellar keratitis related to endotoxins released from sterilizer reservoir biofilms

OBJECTIVE

To investigate the risk factors and control mechanisms used to control the outbreak of diffuse lamellar keratitis (DLK) associated with laser in situ keratomileusis (LASIK) and examine the relationship between DLK and endotoxins released from sterilizer biofilm reservoirs.

DESIGN

Clinic-based cohort and laboratory study.

PARTICIPANTS

All patients undergoing LASIK at our clinic from October 7, 1998 through August 31, 1999. The case definition was a diffuse infiltrate in the interface developing within the first week after surgery.

INTERVENTIONS

Biofilm control in the sterilizer, changes in sterilizer, distilled water, instruments, and irrigating fluids.

MAIN OUTCOME MEASURES

The incidence of DLK after LASIK surgery.

RESULTS

There were 983 evaluable patients, with three whose DLK status was not recorded. There were 52 cases of DLK. Burkholderia pickettii was isolated from the sterilizer reservoir. Potential risk factors and associations, for which there was no significant difference, included age and sex of the patients, surgeon, operating suite temperature or humidity, drapes used, saline solutions used, time of day the surgery was performed, and microkeratome use. Sterilizers 1 and 2, before biofilm control, were compared with sterilizer 3, after control. The relative risk was 9.4 (confidence limits [CL], 7.5-11.8) for sterilizer 1 versus 3 and 18. 7 (CL, 11-32) for sterilizer 2 versus 3. Three cases occurred after biofilm control, but were sporadic in nature and associated with epithelial defects.

CONCLUSIONS

Clusters of DLK may be related to endotoxins released from gram-negative biofilms in sterilizer reservoirs. We experienced an outbreak of DLK affecting 52 patients and isolated B. pickettii from the sterilizer reservoir. Epidemiologic investigation showed that biofilm control in the sterilizer reservoirs was associated with a significant reduction in the development of DLK. We encourage any clinics that experience a cluster of DLK to consider microbiologic and epidemiologic investigation for the effectiveness of sterilizer biofilm control.