Cycloheximide and 4-OH-TEMPO suppress chloramphenicol-induced apoptosis in RL-34 cells via the suppression of the formation of megamitochondria

Toxic effects of chloramphenicol, an antibiotic inhibitor of mitochondrial protein synthesis, on rat liver derived RL-34 cell line were completely blocked by a combined treatment with substances endowed with direct or indirect antioxidant properties. A stable, nitroxide free radical scavenger, 4-hydroxy-2,2,6, 6-tetramethylpiperidine-1-oxyl, and a protein synthesis inhibitor, cycloheximide, suppressed in a similar manner the following manifestations of the chloramphenicol cytotoxicity: (1) Oxidative stress state as evidenced by FACS analysis of cells loaded with carboxy-dichlorodihydrofluorescein diacetate and Mito Tracker CMTH2MRos; (2) megamitochondria formation detected by staining of mitochondria with MitoTracker CMXRos under a laser confocal microscopy and electron microscopy; (3) apoptotic changes of the cell detected by the phase contrast microscopy, DNA laddering analysis and cell cycle analysis. Since increases of ROS generation in chloramphenicol-treated cells were the first sign of the chloramphenicol toxicity, we assume that oxidative stress state is a mediator of above described alternations of RL-34 cells including MG formation. Pretreatment of cells with cycloheximide or 4-hydroxy-2,2, 6,6-tetramethylpiperidine-1-oxyl, which is known to be localized into mitochondria, inhibited the megamitochondria formation and succeeding apoptotic changes of the cell. Protective effects of cycloheximide, which enhances the expression of Bcl-2 protein, may further confirm our hypothesis that the megamitochondria formation is a cellular response to an increased ROS generation and raise a possibility that antiapoptotic action of the drug is exerted via the protection of the mitochondria functions.

Free radical-induced megamitochondria formation and apoptosis

Pathophysiological meaning and the mechanism of the formation of megamitochondria (MG) induced under physiological and pathological conditions remain obscure. We now provide evidence suggesting that the MG formation may be a prerequisite for free radical-mediated apoptosis. MG were detected in primary cultured rat hepatocytes, rat liver cell lines RL-34 and IAR-20 and kidney cell line Cos-1 treated for 22 h with various chemicals known to generate free radicals: hydrazine, chloramphenicol, methyl-glyoxal-bis-guanylhydrazone, indomethacin, H2O2, and erythromycin using a fluorescent dye Mito Tracker Red CMXRos (CMXRos) for confocal laser microscopy and also by electron microscopy. Remarkable elevations of the intracellular level of reactive oxygen species (ROS), monitored by staining of cells with a fluorescent dye carboxy-H2-DCFDA, were detected before MG were formed. Prolongation of the incubation time with various chemicals, specified above, for 36 h or longer has induced distinct structural changes of the cell, which characterize apoptosis: condensation of nuclei, the formation of apoptotic bodies, and the ladder formation. Cells treated with the chemicals for 22 h were arrested in G1 phase, and apoptotic sub-G1 populations then became gradually increased. The membrane potential of MG induced by chloramphenicol detected by CMXRos for flow cytometry was found to be decreased compared to that of mitochondria in control cells. Rates of the generation of H2O2 and O2- from MG isolated from the liver of rats treated with chloramphenicol or hydrazine were found to be lower than those of mitochondria of the liver of control animals. We suggest, based on the present results together with our previous findings, that the formation of MG may be an adaptive process at a subcellular level to unfavorable environments: when cells are exposed to excess amounts of free radicals mitochondria become enlarged decreasing the rate of oxygen consumption. Decreases in the oxygen consumption of MG may result in decreases in the rate of ROS production as shown in the present study. This will at the same time result in decreases in ATP production from MG. If cells are exposed to a large amount of free radicals beyond a certain period of time, lowered intracellular levels of ATP may result in apoptotic changes of the cell.

Susceptibility to periodic breathing with assisted ventilation during sleep in normal subjects

Assisted ventilation with pressure support (PSV) or proportional assist (PAV) ventilation has the potential to produce periodic breathing (PB) during sleep. We hypothesized that PB will develop when PSV level exceeds the product of spontaneous tidal volume (VT) and elastance (VTsp . E) but that the actual level at which PB will develop [PSV(PB)] will be influenced by the DeltaPCO2 (difference between eupneic PCO2 and CO2 apneic threshold) and by DeltaRR [response of respiratory rate (RR) to PSV]. We also wished to determine the PAV level at which PB develops to assess inherent ventilatory stability in normal subjects. Twelve normal subjects underwent polysomnography while connected to a PSV/PAV ventilator prototype. Level of assist with either mode was increased in small steps (2-5 min each) until PB developed or the subject awakened. End-tidal PCO2, VT, RR, and airway pressure (Paw) were continuously monitored, and the pressure generated by respiratory muscle (Pmus) was calculated. The pressure amplification factor (PAF) at the highest PAV level was calculated from [(DeltaPaw + Pmus)/Pmus], where DeltaPaw is peak Paw - continuous positive airway pressure. PB with central apneas developed in 11 of 12 subjects on PSV. DeltaPCO2 ranged from 1.5 to 5.8 Torr. Changes in RR with PSV were small and bidirectional (+1.1 to -3.5 min-1). With use of stepwise regression, PSV(PB) was significantly correlated with VTsp (P = 0.001), E (P = 0.00009), DeltaPCO2 (P = 0.007), and DeltaRR (P = 0.006). The final regression model was as follows: PSV(PB) = 11.1 VTsp + 0.3E - 0.4 DeltaPCO2 - 0.34 DeltaRR - 3.4 (r = 0.98). PB developed in five subjects on PAV at amplification factors of 1.5-3.4. It failed to occur in seven subjects, despite PAF of up to 7.6. We conclude that 1) a PCO2 apneic threshold exists during sleep at 1.5-5.8 Torr below eupneic PCO2, 2) the development of PB during PSV is entirely predictable during sleep, and 3) the inherent susceptibility to PB varies considerably among normal subjects.

CC-chemokines enhance the replication of T-tropic strains of HIV-1 in CD4(+) T cells: role of signal transduction

This study demonstrates that several CC-chemokines, including those that inhibit entry and replication of macrophage-tropic strains of HIV, increase the replication of T cell (T)-tropic strains in CD4(+) T cells. Enhancement of T-tropic HIV replication is observed at early stages of replication, requires signaling through inhibitory guanine nucleotide-binding regulatory (Gi) proteins, and is associated with increased cell surface colocalization of CD4 and the T-tropic HIV coreceptor CXCR4. These findings may further our understanding of the factors that influence the replication and spread of T-tropic strains of HIV in vivo and suggest that the use of cell signaling CC-chemokines as therapeutic agents for the purpose of limiting HIV replication in vivo should be approached with caution.

Dendritic cells express multiple chemokine receptors used as coreceptors for HIV entry

Cells of the dendritic lineage are thought to be among the first cells infected after mucosal exposure to HIV. In this study, we have identified the presence of multiple chemokine receptors on dendritic cells (DC) that may function as coreceptors for HIV entry. DC effectively used CCR5 for entry of macrophage (M)-tropic isolates. CCR3, the eotaxin receptor, initially identified on eosinophils, is expressed on DC and may be used as an entry coreceptor by certain dual-tropic strains. CXCR4 was not expressed on DC, although SDF-1 induced a calcium flux and DC could be infected by T cell line (T)-tropic HIV. Our findings provide evidence for the presence of a non-CXCR4 SDF-1 receptor on DC that is used mainly by T-tropic strains of HIV. DC from individuals homozygous for a 32-bp deletion of the CCR5 gene are also infectable with M-tropic strains of HIV-1, and this infection is inhibited by stromal cell-derived factor (SDF)1, suggesting that this receptor can also be used by M-tropic HIV for entry. Delineation of the spectrum of coreceptor usage on DC may offer new approaches to interfere with the initiation and propagation of HIV infection.

[Use of Hammer type external fixators for pelvic fractures--case report]

A case of comminuted pelvic fracture with marked displacement of the fragments complicated by extensive genitourinary injury is presented. Pelvic ring was reconstructed and stabilized with Hammer external fixator; the fracture united without complications.

Primary repair without augmentation for early neglected Achilles tendon ruptures in the recreational athlete

From 1987 to 1994, the senior author performed 41 Achilles tendon repairs. We identified 11 patients during this period (age, 35.3 years; range, 26-60 years) who fit the criterion for neglected Achilles tendon rupture (repair > or = 4 weeks and < or = 12 weeks from injury). All patients underwent proximal release of the gastrocsoleus complex, imbrication of the early fibrous scar without excision of any local tissue, and primary repair of the tendinous ends with two No. 5 Ticron sutures (5R, 6L). Several (three to five) No. 0 Vicryl sutures were used to augment the repair. The ankle was placed in a 20 degree plantarflexion nonweightbearing short leg cast for 3 weeks. All skin closures were primary. At 3 weeks, weightbearing as tolerated was initiated in a short leg cast. The cast was discontinued at 6 weeks, and physical therapy was initiated, consisting of range of motion exercises and closed kinetic exercises, progressing to functional exercises as swelling, strength, and pain allowed. Minimal follow-up was 18 months (mean, 3.5 years; range, 1.5-5.8 years). There have been no subsequent ruptures to date. All patients returned to a preinjury level of activity at a mean of 5.8 months (range, 2.5-9 months). Total range of motion was not different (P > 0.05) between the involved (67 degree) and uninvolved (74 degree) ankle. Plantarflexion loss of strength in the involved ankle was the same (98.4%, 88.1%, and 87.6% respectively, involved to uninvolved) as that seen after acute repair at all speeds tested. Visual analog pain scale (0 to 10) revealed a mean score of 0.7 (range 0-2) during activities of daily living and 1.0 (range, 0-3) during sports activity. The subjective and objective outcome was similar (P > 0.05) to that seen after an acute repair by the same surgeon. There were no complications including skin sloughs or nerve damage. We believe this is the first article to report the results after primary repair without augmentation for the neglected Achilles tendon rupture. We conclude that this approach can result in excellent clinical and functional outcome, a low rate of subsequent rupture, and a high rate of return to sports in the recreational athlete whose repair is performed between 4 and 12 weeks after injury.

Neosartorya fischeri: an invasive fungal pathogen in an allogeneic bone marrow transplant patient

Invasive fungal infections are a complication of allogeneic BMT. We report the first case of a Neosartorya fischeri fungal infection in a patient following allogeneic BMT. Neosartorya fischeri is related to Aspergillus fumigatus, but it is a distinct fungal species. Despite granulocytic engraftment and aggressive anti-fungal therapy with amphotericin B, the patient died of overwhelming fungal infection on day 60 post-BMT. Neosartorya fischeri is a pathogen that grows slowly in culture which can delay or confuse identification. This case further supports the need for more effective prophylaxis and treatment of non-Candida fungal infections in the allogeneic BMT population.

Synthesis and HIV inhibition activity of 2',3'-dideoxy-3'-C-hydroxymethyl nucleosides

A series if 2',3'-dideoxy-3'-C-hydroxymethyl purine nucleosides were prepared based on the photochemical ring expansion of a chiral cyclobutanone precursor, (2S)-trans-2,3-bis[(benzoyloxy)methyl]cyclobutanone, in the presence of a 6-substituted purine. Both alpha- and beta-anomers are produced in this transformation. Deprotection was effected by reaction of the photoadducts with saturated methanolic ammonia. Nine purine nucleosides were tested for their inhibitory effect of HIV IIIB virus on H9 cells. The 6-hexyloxy and adenine derivatives 4e,c, respectively, appeared to be most effective at inhibiting viral reproduction with 4c comparable in activity to ddI and AZT.

HIV replication in CD4+ T cells of HIV-infected individuals is regulated by a balance between the viral suppressive effects of endogenous beta-chemokines and the viral inductive effects of other endogenous cytokines

This study demonstrates that the beta-chemokines macrophage inflammatory proteins 1 alpha and 1 beta (MIP-1 alpha and MIP-1 beta) and, RANTES (regulated on activation, normally T-cell expressed and secreted) inhibit human immunodeficiency virus (HIV) replication in anti-CD3 or recall antigen-stimulated peripheral blood mononuclear cells (PBMCs) of asymptomatic HIV-infected subjects. Significant levels of beta-chemokines were produced by both CD4+ and CD8+ PBMC subsets from HIV-infected individuals. Neutralization of endogenous MIP-1 alpha, MIP-1 beta, and RANTES did not rescue HIV replication in cultures to which greater than 10% CD8+ T cells had been added, indicating that the HIV suppressor activity of CD8+ T cells cannot be explained entirely by the beta-chemokines. However, significant enhancement of viral replication was observed upon neutralization of endogenous beta-chemokines in CD8-depleted or CD4+ PBMCs from most donors, particularly in cultures with low inducible levels of HIV production. In contrast, certain endogenous proinflammatory cytokines induced HIV replication in these same cells. These data suggest that the levels of HIV replication in CD4+ PBMC reflect the balance of the opposing effects of endogenous suppressive factors, such as the beta-chemokines, and HIV-inducing cytokines, such as tumor necrosis factor alpha and interleukin 1 beta.

Stimulation of the P-450 side chain cleavage enzyme (CYP11A1) promoter through ras- and Ets-2-signaling pathways

Expression of the ovine P-450 side-chain cleavage enzyme gene (CYP11A1) is stimulated by epidermal growth factor (EGF) through a pathway that involves c-Jun in JEG-3 placental cells. Growth factor signaling involves ras-dependent and ras-independent signaling pathways, which in turn regulate gene transcription through related but distinct mitogen-activated protein kinase pathways (MAPKs) including the extracellular signal-regulated kinases (ERKs) and the stress-activated protein kinases (SAPKs). We investigated the intracellular signaling pathways governing EGF induction of the CYP11A1 promoter. EGF stimulation of the CYP11A1 promoter (4-fold) was reduced 60% by a dominant negative mutant of ras (N17), and 30-40% by antisense ras. EGF induced both ERK and SAPK activity in JEG-3 cells. EGF-induced CYP11A1 promoter activity was reduced 60% by the MEK1 inhibitor PD098059 and 50% by a dominant negative mutant of the ERK-specific regulator MEK1. In contrast, dominant negative mutants of the SAPK-specific activator, SEK1, induced a further increase in EGF-induced CYP11A1 promoter activity. Constitutively active mutants of ras (V12 or L61) increased CYP11A1 promoter activity 6- to 8-fold. Deletion of the EGF response element (EGF-RE) between -92 and -77 bp reduced ras induction by 60%; however, a residual 3-fold induction remained through the proximal -77 bp. Mutation of the EGF-RE AP-1-like sequence in the context of the native promoter reduced CYP11A1 promoter activation by ras 60%. The EGF-RE sequence was sufficient for 6-fold activation by ras in the context of an heterologous thymidine kinase promoter. Candidate transcription factor targets (c-Jun, c-Ets-2) for the ras-signaling cascade were examined for their effects on CYP11A1 promoter activity. Overexpression of c-Jun induced the CYP11A1 promoter through the EGF-RE; however, c-Ets-2 activation of the CYP11A1 promoter (12-fold) required the proximal ras-responsive promoter sequences that are distinct from the EGF/MEK/c-Jun-responsive element. Induction of the CYP11A1 promoter by EGF involves a ras/MEK1/AP-1-dependent pathway that is distinct from induction by ras/c-Ets-2.

Relationship between spatial pattern of basal bodies and membrane skeleton (epiplasm) during the cell cycle of Tetrahymena: cdaA mutant and anti-membrane skeleton immunostaining

Microtubular basal bodies and epiplasm (membrane skeleton) are the main components of the cortical skeleton of Tetrahymena. The aim of this report was to study functional interactions of basal bodies and epiplasm during the cell cycle. The cortex of Tetrahymena cells was stained with anti-epiplasm antibody. This staining produced a bright epiplasmic layer with a dark pattern of unstained microtubular structures. The fluorescence of the anti-epiplasm antibody disappeared at sites of newly formed microtubular structures, so the new basal body domains and epiplasmic layer could be followed throughout the cell cycle. Different patterns of deployment of new basal bodies were observed in early and advanced dividers. In advanced dividers the fluorescence of the epiplasmic layer diminished locally within the forming fission line where the polymerization of new basal bodies largely extincted. In wild type Tetrahymena, the completion of the micronuclear metaphase/anaphase transition was associated with a transition from the pattern of new basal body deployment and epiplasm staining of the early divider to the pattern of the advanced dividers. The signal for the fission line formation in Tetrahymena (absent in cdaA1 Tetrahymena mutationally arrested in cytokinesis) brings about 1) transition of patterns of deployment of basal bodies and epiplasmic layer on both sides of the fission line; and 2) coordination of cortical divisional morphogenesis with the micronuclear mitotic cycle.

Comparative gross and histological effects of the CO2 laser, Nd-YAG laser, scalpel, Shaw scalpel and cutting cautery on skin in rats

Surgical instruments capable of sealing blood vessels while incising skin were compared to standard scalpel incisions in rats and the resultant scars examined in the early stages of wound healing for both gross and histological appearances. Those instruments which provide for hemostasis appear to do so with a delay in the early phases of wound healing.

[Coexistence of WPW syndrome, coronary disease and segmental disorders of myocardial contraction. Diagnostic difficulties. Description of a case]

A 61 years old patient with Wolff-Parkinson-White's syndrome, and hypertension was admitted to the CCU, because of the first episode of substernal chest pain. ECG was deformed by Wolff-Parkinson-White's syndrome, type B, with accessory pathway located on the right side, without evolution. Serum enzymes remained low. Echocardiography showed akinesis of the posterior wall and hypokinesis of the lateral wall (the same contraction disorders were described in previous echocardiographical examination 5 years ago), it was observed that the first portion of myocardium to contract was the base of the right ventricle. To elucidate the etiology of the contraction disorders, scintigraphy of the heart, using Thallium 201, was performed, showing normal perfusion of the myocardium. To illustrate the dependence of the contraction disorders and abnormal depolarization pattern of the heart, echocardiographical examination was repeated, confirming the previous results, then 100 mg of Ajmaline was given to the patient intravenously, and echocardiographical examination was continued. Administration of the drug caused antidromic atrioventricular re-entrant tachycardia during which the lateral wall of the heart had been contracting properly. This case shows contraction disorders of the heart caused by the abnormal depolarization pattern, resulting from the presence of accessory pathway. It also illustrates the diagnostic difficulties in patients with Wolff-Parkinson-White's syndrome and suspected myocardial infarction, at the same time showing that scintigraphy of the heart might be very helpful in such patients. This case confirms the usefulness of echocardiography for localization of the accessory pathway.

Constitutive expression of C-myc in nih 3t3 cells which coexpress the colony stimulating factor-I receptor and the catalytic domain of the gtpase-activating protein restores colony stimulating factor-I dependent mitogenic growth

To begin to understand how ras p21 might be coupled to the human colony stimulating factor-1 receptor (CSF-IR), we compared the signaling properties of a CSF-IR containing a point mutation that converts the tyrosine at position 809 to a phenylalanine residue to signal transduction in cells that co-express the wild-type receptor and the catalytic domain of the GTPase activating protein (GAP(C)). We find that modulation of the immediate early gene c-myc and a delayed early response represented by the retrotransposon NVL3 were selectively impaired in both situations. Further, constitutive expression of c-myc in cells that contain GAP(C) restored CSF-1-dependent signal transduction. The data suggest a model in which information important for mitogenic cell.growth flows from the region of the receptor containing tyrosine 809, through ras p21, to c-myc in the nucleus.

What is the legal 'standard of medical care' when there is no standard medical care? A survey of the use of home apnea monitoring by neonatology fellowship training programs in the United States

In treating a patient, a doctor is obliged to use the skill and care that is ordinarily used by reasonably well-qualified doctors in similar cases. In addition, the only way in which a juror may decide whether the defendant used the skill and care which the law required of him or her is from evidence presented by doctors called as expert witnesses (cf Illinois Pattern Jury Instructions). However, what should be done if expert opinions differ concerning the care that is "ordinarily used"? Home apnea monitoring (HAM) is prescribed at times for graduates of neonatal intensive care units despite the fact that indications for its use are not well established and efficacy is completely unknown. The authors attempted to determine standards for HAM as it is currently practiced in neonatology training programs. The primary teaching hospital for each of the 99 neonatology training programs in the United States was identified. Both the medical director (MD) and a neonatal intensive care unit nurse manager (RN) were asked about the use of HAM in their own nursery for four clinical vignettes. Each vignette depicted a 1000-g birth weight infant, currently 7 weeks old and ready for discharge. In three vignettes, the infant had demonstrated no apnea, mild apnea (resolved by 2 weeks of age), or moderate apnea (requiring theophylline therapy at discharge) during the hospital course. In the fourth vignette, the infant had no apnea but was to be discharged home with supplemental oxygen. For 67 of 99 training programs, paired responses of RN managers and MD directors were obtained.(ABSTRACT TRUNCATED AT 250 WORDS)