Biosynthesis of N-acetylsphingosine by platelet-activating factor: sphingosine CoA-independent transacetylase in HL-60 cels

We have previously identified a novel CoA-independent transacetylase in the membrane fraction of HL-60 cells that transfers the acetate group from platelet activating factor (PAF) to a variety of lysophospholipid acceptors (Lee, T.-c., Uemura, Y., and Snyder, F. (1992) J. Biol. Chem. 267, 19992-20001). In the present study, we demonstrate that a similar transacetylase can transfer the acetate group from PAF to sphingosine forming N-acetylsphingosine (C2-ceramide). The chemical structure of the reaction product, C3-ceramide, was established by its identical Rf value with authentic C2-ceramide standard on thin-layer plate, sensitivity to acid treatment, resistance to alkaline hydrolysis, and ability to form the C2-ceramide dibenzoate derivative. Nonspecific transfer of the acetate from PAF to sphingosine in the absence of enzyme and nonlinearity of the reaction rates were rectified by complexing sphingosine to bovine serum albumin in a 1:1 molar ratio. Under these conditions, the apparent Km for PAF is 5.4 microM, which is in the same range as the Km (12.0 microM) when lysoplasmalogen is the acetate acceptor. PAF:sphingosine transacetylase has a narrow substrate specificity and strict stereochemical configuration requirements. Ceramide, sphingosylphosphocholine, stearylamine, sphingosine 1-phosphate, or sphingomyelin are not substrates, whereas sphinganine has a limited capacity to accept the acetate from PAF. Also, only the naturally synthesized D-erythroisomer but not the synthetic L-erythro-, D-threo-, or L-threosiomers of sphingosine can serve as a substrate. PAF transacetylase activity is widely distributed among several tissues and may involve histidine and cysteine for its catalytic activity due to inhibitory effects to the enzyme by diethyl pyrocarbonate and N-ethylmaleimide, respectively. C2-ceramide is produced via PAF:sphingosine transacetylase, and physiological levels of C2-ceramide are detected in both undifferentiated and differentiated intact HL-60 cells. Collectively, because C2-ceramide has many biological activities that differ from that of PAF and sphingosine, the CoA-independent, PAF-dependent transacetylase serves as a modifier of PAF, and sphingosine functions by generating a variant lipid mediator, C2-ceramide.

Aneurysm of superior branch of anterior choroidal artery mimicking carotid bifurcation aneurysm--case report

Aneurysm of the superior branch of anterior choroidal artery is very rare. We report this rare case with unique angiographic findings mimicking an internal carotid bifurcation aneurysm. A 35-year-old woman was admitted to our hospital because of severe headache. Lumbar puncture disclosed numerous red blood cells. Computed tomography revealed an enhanced circular area in the left basal cistern with moderate hydrocephalus. Cerebral angiography showed a saccular aneurysm near the left internal carotid bifurcation. During operation, the aneurysm was not found at the internal carotid bifurcation, but located deeper budding from the superior branch of the anterior choroidal artery. The aneurysm was successfully clipped. The postoperative course was favourable without any neurological deficit. The postoperative angiogram showed that the aneurysm was clipped well with preservation of the main trunk of the anterior choroidal artery. Computed tomography of the brain did not show any infarction area, 3 months after the surgery. The uniqueness of this case is the favourable outcome after sacrificing the superior branch of the anterior choroidal artery. The role of collaterals of the anterior perforating substance is emphasized.

[Brain abscess as a complication of ear malignancy: a case report]

Ear infection is the most common cause of brain abscess. A suppurative process in the ear has access to the central nervous system by direct extension or through preformed pathways, either developmental, traumatic or pathologic, or by retrograde spread along the thromobophlebitic vein. Squamous cell carcinoma of middle ear or mastoid cavity is a rare disease and often associated with chronic otitis or chronic draining ear. Ear malignancy easily produces the destruction of temporal bone which may serve as a route for coexistent infection spreading into the brain. This paper reports a case of brain abscess occurring in a patient with temporal bone cancer. To the best of our knowledge, no more than three similar cases have been reported in the literature. The authors suggest that if an otogenic brain abscess is concomitant with infection and granulomatous mass in the ear, biopsy should be performed to rule out malignancy.

Complications of transpedicular reduction and stabilization of the thoracolumbar spine

Between July 1990 and January 1994, 160 patients underwent transpedicular reduction and stabilization using an AO internal fixator. In this series, most of the patients (101 cases) had degenerative spondylolisthesis. The follow-up period ranged from 12 to 36 months. One hundred and thirty one patients (82%) had a good or excellent postoperative outcome. Sixteen (10%) had fair outcomes and 13 (8%) had poor outcomes. There were 26 complications (16%) secondary to this treatment. Improper screw placement was found in five patients, wound infection in four patients and dural tear with cerebrospinal fluid leakage in two patients. Two patients were suspected of having an iatrogenic root injury during the insertion of the pedicle screws. One patient with advanced spondylosis developed a postoperative neurologic deficit (foot drop). In the follow-up period, there was loss of correction of the alignment in five patients, screw breakages in three patients, screw pull-out in two patients and loosening of the clamps in another two patients. As most of the complications were preventable or treatable, pedicle fixation system is still highly recommended for the treatment of spondylolisthesis or spinal instability.

Differential cytotoxicity of cadmium to rat embryonic fibroblasts and human skin fibroblasts

In order to identify why cadmium is differentially toxic to humans and rats, we compared cadmium-induced cytotoxic responses in rat embryonic fibroblasts (REF) and human skin fibroblasts (HFW). According to the values of the lethal concentration 50% for cadmium, REF were about 13-fold more sensitive than HFW to cadmium acetate (1.5 vs 25 microM). Furthermore, progression of S phase cells was more severely delayed by cadmium in REF than in HFW. At doses that killed 90% of REF or HFW (5 or 50 microM, respectively), 50% of DNA synthesis was inhibited in REF, whereas DNA synthesis was not apparently inhibited in HFW. The differential sensitivity to cadmium could not be simply due to different basal levels of metallothionein, since the cellular metallothionein content in HFW was only 1.6 times that in REF, and metallothionein was apparently induced by cadmium in both cells with similar synthesis rates. Furthermore, elevation of cellular metallothionein levels by zinc sulfate pretreatment decreased cadmium toxicity in both cell types, but did not alter their relative sensitivity to cadmium. The differential sensitivity was also not due to differences in cadmium accumulation, since HFW accumulated more cadmium than REF after a 24-hr exposure to 1 or 5 microM cadmium acetate. Although most of the cadmium remained in the cytoplasm, the nuclei of REF contained 12-fold more cadmium than nuclei of HFW (1.31 vs 0.11 micrograms Cd/mg nuclear protein). Therefore, our results indicate that a high level of cadmium accumulation in nuclei of REF may be responsible for cell killing through breakdown of nuclear functions.

Modulation of cellular antioxidant defense activities by sodium arsenite in human fibroblasts

Many studies have shown that oxygen radicals can be produced during arsenic metabolism. We report here that in human fibroblasts (HFW cells) sodium arsenite exposure caused increased formation of fluorescent dichlorofluorescein (DCF) by oxidation of the nonfluorescent form. The enhanced DCF fluorescence was inhibited by a radical scavenger, butylated hydroxytoluene. The effects of sodium arsenite treatment on cellular antioxidant activities were then examined. Treatment of HFW cells with sodium arsenite resulted in a significant increase in heme oxygenase activity and ferritin level. Sodium arsenite-enhanced heme oxygenase synthesis was inhibited by co-treatment of cells with the antioxidants sodium azide and dimethyl sulfoxide. Furthermore, sodium arsenite treatment did not apparently affect glucose-6-phosphate dehydrogenase activity, but resulted in significantly increased glutathione levels and superoxide dismutase activity, slightly decreased glutathione peroxidase activity, and significantly decreased catalase activity. Sodium arsenite toxicity was partly reduced by addition of catalase to the culture medium. These results imply that arsenite can enhance oxidative stress in HFW cells.

Light exposure decreases IOP in rabbits during the night

Elevated IOP observed in rabbits during the dark phase of the circadian cycle decreased rapidly and reversibly when rabbits were exposed to light during the dark phase. The decrease of IOP does not result from decreased aqueous flow and only part of the decrease requires intact ocular sympathetic innervation.

The optimal management of hairy cell leukaemia

Hairy cell leukaemia is an uncommon B cell chronic lymphoproliferative disorder characterised by circulating lymphocytes displaying prominent cytoplasmic projections. Therapy is initiated for severe cytopenias or recurrent infections. Splenectomy, the first standard treatment, is now less commonly used as primary treatment. Interferon-alpha (IFN alpha) induces partial responses in most patients but complete responses in only a few. Adverse effects from IFN alpha are common but not life-threatening. The ability of two newer purine analogues, pentostatin (2'-deoxycoformycin) and cladribine (2-chlorodeoxyadenosine), to induce long-lasting complete remissions in the majority of patients has revolutionised the treatment of this disease. Cladribine is emerging as the treatment of choice because of its favourable toxicity profile, brief duration of treatment, high percentage of unmaintained complete remissions and low incidence of relapse.

Enhanced insulin-like growth factor molecules in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by activated alveolar macrophages (AM), alveolar epithelial cell proliferation and interstitial matrix, and immune complex deposition. Spontaneous release of competence and progression-type growth factors and their associated binding proteins may contribute to the pathologic features of IPF. To study the role of insulin-like growth factor (IGF) molecules in IPF we evaluated spontaneous release of IGF-I and IGFBP-3 in bronchoalveolar lavage cells from control subjects and from patients with IPF. IGF-I levels were similar compared with those in control subjects. In contrast, IGFBP-3 was significantly increased in IPF. In situ hybridization of open lung biopsies showed IGF-I to be abundant in IPF lung tissue in alveolar macrophages, interstitial mesenchymal cells, and epithelial cells. Northern, Western ligand blotting, reverse transcription PCR, and radioimmunoassay suggested that immune complexes stimulate expression of IGFBP-3 in mononuclear phagocytes in a time- and dose-dependent manner bearing strong similarities to stimulation by LPS. These data are compatible with the hypothesis that IGFBP-3 increases the bioactivity of IGF-I derived from a variety of lung tissues contributing to the fibrosis and remodeling seen in IPF.

Quantitative arteriography of apparently normal coronary segments with nearby or distant disease suggests presence of occult, nonvisualized atherosclerosis

OBJECTIVES

The aim of this study was to evaluate, using quantitative arteriography, whether the diameter of visually normal coronary segments might be influenced by the relative proximity of visually apparent disease.

BACKGROUND

Severity of coronary artery lesions is commonly referenced against a presumed normal nearby coronary segment with the presumption that visually smooth segments are relatively free of atherosclerotic disease.

METHODS

Angiograms from 136 male patients with focal coronary disease were examined, and visually normal segments in the proximal portions of the major vessels were identified for measurement of mean segment diameters. Normal segments with immediately adjacent disease were compared with normal segments with distal disease in the same vessel and compared with normal segments in vessels for which the only other visible disease was in distant vessels. Angiograms with entirely normal findings from 26 age-matched men with atypical chest pain were used as controls. Segments were measured after nitroglycerin administration by means of computer-assisted quantitation.

RESULTS

Mean diameters of visually normal segments with distant disease were smaller than those of control segments (p < 0.05). Normal left main and proximal left anterior descending coronary artery segments in patients with disease within the same vessel were significantly smaller than normal segments in patients with distant disease (p < 0.05). Normal segments with immediately adjacent disease had smaller mean diameters than normal segments with distal disease in the same vessel (p < 0.05).

CONCLUSIONS

Visually normal coronary segments have progressively smaller lumen diameters, depending on the relative proximity of visible disease. Measurement of percent stenosis on the basis of the diameter of apparently normal adjacent reference segments can result in underestimation of coronary lesion severity.

Sodium arsenite induces chromosome endoreduplication and inhibits protein phosphatase activity in human fibroblasts

Arsenic, strongly associated with increased risks of human cancers, is a potent clastogen in a variety of mammalian cell systems. The effect of sodium arsenite (a trivalent arsenic compound) on chromatid separation was studied in human skin fibroblasts (HFW). Human fibroblasts were arrested in S phase by the aid of serum starvation and aphidicolin blocking and then these cells were allowed to synchronously progress into G2 phase. Treatment of the G2-enriched HFW cells with sodium arsenite (0-200 microM) resulted in arrest of cells in the G2 phase, interference with mitotic division, inhibition of spindle assembly, and induction of chromosome endoreduplication in their second mitosis. Sodium arsenite treatment also inhibited the activities of serine/threonine protein phosphatases and enhanced phosphorylation levels of a small heat shock protein (HSP27). These results suggest that sodium arsenite may mimic okadaic acid to induce chromosome endoreduplication through its inhibitory effect on protein phosphatase activity.

Reduction and stabilization without laminectomy for unstable degenerative spondylolisthesis: a preliminary report

Fifty-two patients with unstable degenerative spondylolisthesis treated with the "AO internal fixator" and posterolateral fusion were reviewed. The major purpose of this study is to observe whether this pedicle fixation system could adequately decompress the nervous system tissue by the restoration of the spinal canal and, hence, replace the conventional decompressive laminectomy for the treatment of this disease entity. The results were satisfactory, showing that 92% of the patients with radicular pain, 89% of the patients with low back pain, and 86% of the patients with intermittent claudication improved postoperatively. Observing the results, only two groups of patients with unstable degenerative spondylolisthesis are not suitable for this treatment modality. The first group consists of those patients who have a spondylolisthesis with borderline instability. The second group consists of those patients who have a positive Lasèque's sign.

Formation mechanism of ring domains in a TbFCo magneto-optical medium

The formation mechanism of stable ring domains in a TbFeCo magneto-optical medium with compensation temperature below the ambient temperature is discussed. A ring-domain formation model is proposed.

Tuberous sclerosis associated with neurofibromatosis: report of a case

Neurofibromatosis and tuberous sclerosis are phakomatous syndrome diseases. They are both inherited as autosomal dominant diseases. Neurofibromatosis type 1 and tuberous sclerosis very seldom occur together. We report a 16-year-old male who had characteristics of these two diseases. This patient had all the criteria for a definitive diagnosis of tuberous sclerosis such as: classical shagreen patches, periungual fibroma, retinal hamartomata, facial angiofibroma, renal angiomyolipomata, and subependymal glial nodules on computed tomography. He also had the three presumptive diagnostic criteria: cardiac rhabdomyoma, seizure history and first degree relatives with tuberous sclerosis. The patient had more than six café-au-lait spots, the greatest diameter of which exceeded 15 mm in diameter. Multiple neurofibromas, one plexiform neurofibroma, axillary freckling and optic gliomas were also found on his body. These criteria are sufficient for a diagnosis of neurofibromatosis type 1 to be made. The skin biopsies were also consistent with the disease. Apart from the patient's mother and younger sister, who had tuberous sclerosis, there was no other person with neurofibromatosis type 1 in his immediate family. We believe that tuberous sclerosis was inherited from his mother and that neurofibromatosis type 1 may have resulted from mutation.

Differential cytotoxic effects of arsenic on human and animal cells

Human fibroblasts (HFW) were 10-fold more susceptible than Chinese hamster ovary (CHO-K1) cells to sodium arsenite. Comparison of cellular antioxidant enzyme activities showed that CHO-K1 cells contained 3- and 8-fold more glutathione-peroxidase and catalase activities, respectively, than HFW cells. Since vitamin E, methylamine, and benzyl alcohol could prevent, in part, the arsenite-induced killing of HFW cells, we suggest that arsenite can induce oxidative damage in HFW cells. We have also established arsenic-resistant cells, SA7 and CL3R, from CHO cells and from a human lung adenocarcinoma cell line (CL3), respectively. The arsenic resistance of SA7 cells was attributed mainly to elevation of glutathione S-transferase pi levels, and that of CL3R cells was possibly due to an increase in heme oxygenase activity. Since induction of heme oxygenase is a general response to oxidative stress, we suspect that the differential toxicity of arsenic to human and animal cells could be due to arsenic's more efficient induction of oxidative damage in human cells.

Binding of heparin and compound Y to endothelial cells stimulates the synthesis of an antithrombotic heparan sulfate proteoglycan

The mechanism by which heparin and antithrombotic agents, including a cyclic octaphenolsulfonic acid (compound Y), stimulate the synthesis of an antithrombotic heparan sulfate by endothelial cells in culture was investigated. Compound Y increases the amount of heparan sulfate from the cell surface and secreted to the medium by endothelial cells by three-fold. Binding experiments have shown saturation of the endothelial cell receptors at a concentration of 0.16 microM for heparin and 2.7 microM for compound Y. The kinetic binding constants (Ks) for compound Y and heparin were 1,333 nM and 42 nM, respectively. It was also shown that both compounds bind to the same receptors. The Scatchard plots indicated that 1,319 nmoles compound Y and 35 nmoles heparin bound per microgram cell protein, indicating that 40-fold more molecules of compound Y bound to the receptors when compared to heparin. No significant internalization of the compounds was observed.

A proteolytic activity enhanced by arsenite in Chinese hamster ovary cells: possible involvement in arsenite-induced cell killing

Treatment of Chinese hamster ovary (CHO-K1) cells with 10 microM sodium arsenite for 24 h resulted in enhancement of a proteolytic activity toward the chromogenic substrate CBZ-Phe-Arg-AMC. Presence of dithiothreitol and a pH between 4 and 6 were required for displaying its full hydrolytic activity. According to its substrate- and inhibitor-specificity, this arsenite-induced proteolytic activity was very similar to lysosomal cathepsin B. Arsenite cytotoxicity was further shown to be partially prevented by inhibitors that inhibited the arsenite-induced protease, such as antipain and chymostatin, but not by protease inhibitors without inhibitory effects on the arsenite-induced protease. Our present results suggest that the arsenite-induced protease activity may be involved in arsenite's killing effects.

Transforming growth factor-beta response elements of the skeletal alpha-actin gene. Combinatorial action of serum response factor, YY1, and the SV40 enhancer-binding protein, TEF-1

Skeletal alpha-actin (SkA) is representative of the cardiac genes that are expressed at high levels in embryonic myocardium, down-regulated after birth, and reactivated by trophic signals including type beta-transforming growth factors (TGF beta). To investigate the molecular basis for cardiac-restricted and TGF beta-induced SkA transcription, we have undertaken a mutational analysis of the SkA promoter in ventricular myocytes, with emphasis on the role of three nominal serum response elements. Serum response factor (SRF) and the bifunctional factor YY1 are the predominant cardiac proteins contacting the proximal SRE (SRE1). Mutations of SRE1 that prevent recognition by SRF and YY1, or SRF alone, virtually abolish SkA transcription in both TGF beta- and vehicle-treated cells; mutation of distal SREs was ineffective. A mutation which selectively abrogates YY1 binding increases both basal and TGF beta-dependent expression, substantiating the predicted role of YY1 as an inhibitor of SRF effects. However, efficient SkA transcription requires combinatorial action of SRE1 with consensus sites for Sp1 and the SV40 enhancer-binding protein, TEF-1. As isolated motifs, either SRE1- or TEF-1-binding sites function as TGF beta response elements. Induction of the SkA promoter by TGF beta required SRF and TEF-1 in concert, unlike other pathways for TGF beta-dependent gene expression.

Differentiation induced increase of platelet-activating factor acetylhydrolase in HL-60 cells

Platelet-activating factor (PAF) acetylhydrolase catalyzes the conversion of PAF to lyso-PAF and acetate. In this study we show that induced cellular differentiation of HL-60 cells grown in chemically defined media by dimethylsulfoxide (DMSO) to granulocytic cells increases the acetylhydrolase activity with a concomitant increased secretion of the enzyme into the media. This increase in acetylhydrolase activity is blocked by the presence of actinomycin D (1 microM) or cycloheximide (1-2 microM) in the culture media. Acetylhydrolase is located both in the cytosolic and particulate fractions; the relative distribution of acetylhydrolase activity in the particulate fraction and cytosol increases and decreases respectively, as the differentiation progresses. The addition of an intracellular protein transport inhibitor, monensin, causes further accumulation of acetylhydrolase activity in the particulate fraction and a decrease in the media, with no effect on the acetylhydrolase activity in the cytosol. Acetylhydrolase in differentiated HL-60 cells acquires properties similar to those of the plasma acetylhydrolase in that it becomes less sensitive to 5,5'-dithiobis-2-nitrobenzoic acid and p-bromophenacylbromide inhibition than the acetylhydrolase in undifferentiated cells. The acetylhydrolase secreted into the media by the differentiated cells was almost totally insensitive to these inhibitors, whereas the acetylhydrolase from the particulate fraction gave an intermediate response; the cytosolic acetylhydrolase was sensitive to both inhibitors. However, the acetylhydrolase secreted by differentiated HL-60 cells has a different electrophoretic mobility, temperature sensitivity, and association with lipoproteins when compared to that of human plasma acetylhydrolase. Collectively, these results indicate cellular differentiation induces intracellular acetylhydrolase activity through a mechanism involving both transcriptional and translational events. Furthermore, the acetylhydrolase synthesized during the DMSO-induced differentiation of HL-60 cells is then secreted into the media via the intracellular membrane transport system for proteins. Based on results obtained with HL-60 cells as a cell model, it is likely that more than one isoform of acetylhydrolase exists in the extracellular milieu.

Bifunctional transcriptional properties of YY1 in regulating muscle actin and c-myc gene expression during myogenesis

Oncogene expression is generally incompatible with terminal cell differentiation as in myogenesis. We present evidence that this incompatibility can be caused in part by the dual activity of a Kruppel-related zinc finger, YY1 (formerly F-ACT1), in differentially regulating oncogene and muscle-specific gene expression. The c-myc and skeletal alpha-actin gene promoters contain YY1 binding sites thought to act either as positive or negative cis-acting elements. Through manipulating the intracellular level of YY1 by treating primary myoblasts with bromodeoxyuridine (BrdU), which inhibited myogenesis and increased the YY1 protein content, or by transfecting YY1 cDNA expression vector, we show that it can simultaneously inhibit and activate expression of the skeletal alpha-actin and c-myc genes, respectively. The transrepression activity of YY1 solely depends on its C-terminal zinc finger region (amino acids 297-407) while its transactivation function requires an additional N-terminal domain (amino acids 1-90) normally masked in the full-length protein. We propose that the high level of YY1 in proliferating myoblasts might serve to maintain c-myc expression and suppress muscle actin expression, which can then be gradually reversed by downregulating YY1 activity toward myogenesis.

Expression of heme oxygenase in arsenic-resistant human lung adenocarcinoma cells

We have established arsenic-resistant cells (CL3R) and their subclones from a human lung adenocarcinoma cell line (CL3). CL3R cells and their subclones were maintained in the presence of 4 microM sodium arsenite. They were 6-fold more resistant than CL3 cells to arsenite. Heme oxygenase was expressed in CL3R cells and their subclones, as demonstrated by electrophoretic analysis, Northern blotting, and enzyme activity assay. When CL3R15 cells were grown in arsenite-free medium, their arsenite resistance declined in parallel with their decreasing heme oxygenase activity. Tin-protoporphyrin, a heme oxygenase inhibitor, was found to increase the toxicity of arsenic to CL3R cells. Expression of heme oxygenase might therefore be involved in the mechanism of arsenic resistance. CL3R cells were also shown to be cross-resistant to oxygen-radical generating agents, such as menadione and Adriamycin. Furthermore, sodium arsenite treatment dose-dependently increased the dichlorofluorescein fluorescence in CL3 cells but not in CL3R15 cells. These results suggest that heme oxygenase plays an important role in reducing cellular oxidants that are enhanced by sodium arsenite treatment.

Severe exfoliative dermatitis associated with hand ischemia during cisplatin therapy

BACKGROUND

Platinum is one of the most widely used agents in clinical oncology today. Serious toxic effects are well recognized.

FINDINGS

To our knowledge, the current report describes the first case of severe allergic exfoliative dermatitis associated with ischemia and necrosis of the hands in a patient who had received multiple doses of this agent. We postulate that the tissue damage was caused by vasospasm of small vessels from the initial injury triggered by platinum or its associated immune complexes.

CONCLUSION

Platinum has become an integral part of combination chemotherapy for various solid tumors. Clinicians must recognize its toxic side effects and control them within tolerable limits.

Induction of chromatid breaks and tetraploidy in Chinese hamster ovary cells by treatment with sodium arsenite during the G2 phase

Treatment of Chinese hamster ovary (CHO) cells with sodium arsenite during the G2 phase induced poorly condensed chromosomes and chromatid breaks. The induction of chromatid breaks was confirmed by the appearance of micronucleated cells after arsenite-treated G2 cells were allowed to re-enter interphase. When the duration of the G2 phase was artificially divided into 4 periods, more chromatid breaks were induced by treatment with arsenite during the very early G2 phase (or G2/S boundary). In addition to the induction of chromatid breaks, arsenite treatment also remarkably retarded the re-entry of mitotic cells into interphase. By replating and incubating arsenite-treated G2 cells in drug-free medium, we subsequently observed the appearance of a population of cells whose DNA content was between 4C and 8C, and metaphase cells with near-tetraploid chromosome numbers in the next mitotic division.

Growth of 28 Legionella species on selective culture media: a comparative study

We compared the growth of 28 Legionella spp. on four manufacturers' buffered charcoal-yeast extract (BCYE) agar media and selective BCYE media that contained polymyxin B, anisomycin, and vancomycin or cefamandole. With BCYE as a "gold standard," growth for Legionella pneumophila was significantly better than for the nonpneumophila species on all media tested. L. pneumophila and 24 other Legionella spp. grew on vancomycin-containing media, while L. santicrucis, L. rubrilucens, and L. erythra grew poorly. In contrast, 11 of 28 species (notably L. micdadei and L. bozemanii) did not grow on cefamandole-containing media and 8 of 28 species only grew marginally. We demonstrated that selective BCYE media that contain vancomycin or cefamandole may not support the growth of all Legionella spp. One commercial manufacturer's media were consistently suboptimal. Laboratories should not rely on a manufacturer's quality control testing in lieu of their own.