Linguistic history of posterior reversible encephalopathy syndrome: mirror of developing knowledge

BACKGROUND

the term posterior reversible encephalopathy syndrome (PRES) was first proposed in 2000. Since then, the acronym PRES has become very popular in imaging and clinical literature as it is short, easy to say and remember, and neatly couples the frequent localization of neuroimaging findings along with the typical outcome of this syndrome. Another possible reason for the popularity of this acronym in clinical circles is the connotation of PRES with (elevated blood) PRESsure, as a majority of cases are believed to be associated with hypertension. However, problems exist with the interpretation and common understanding of PRES, questioning the appropriateness of "P" and "R" in the acronym. The linguistic issues related to the acronym of PRES are interesting.

OBJECTIVES

the aim of this work is to analyze the controversies related to the acronym of PRES.

RESULTS

in 2006, modifying the meaning of the acronym was suggested, renaming it Potentially Reversible Encephalopathy Syndrome in order to adjust to the cases when posterior involvement is not prominent and emphasize that the reversibility is not spontaneous. This meant the creation of a backronym, where the new phrase is constructed by starting with an existing acronym.

CONCLUSION

this new backronym indicates that the original acronym of PRES has become a misnomer.

Displacement of the temporomandibular joint disk: correlation between clinical findings and MRI characteristics

BACKGROUND AND OBJECTIVE

Disk displacement frequently causes dysfunction of the temporomandibular joint (TMJ). Magnetic resonance imaging (MRI) of the TMJ is 95% accurate in the assessment of disk position and form. Various restorative procedures are used for treatment of disk displacement. However, several authors have noted a lack of correlation between MRI findings of disk displacement and the extent of pain and dysfunction of the TMJ. The purpose of this study was to evaluate whether MRI findings of various degrees of disk displacement could be correlated with the presence of clinical signs and symptoms in patients with a clinical disorder of the TMJ.

MATERIALS AND METHODS

One hundred and forty-four TMJs (in 72 patients) were imaged. Displacement of the posterior band in relation to the condyle was quantified as mild or significant.

RESULTS

Disk displacement was found in 45 (54%) of the 84 symptomatic joints and 13 (22%) of the 60 asymptomatic joints. Among the 84 symptomatic joints, 31 (37%) had disk displacement with reduction and 14 (17%) had disk displacement without reduction. In the latter group, 11 (79%) of the 14 joints had significant displacement of the posterior band (8 or 9 o'clock) and 21% had mild displacement of the posterior band (10 o'clock). Of the 60 clinically asymptomatic joints, 47 (78%) had no signs of disk displacement on MRI, whereas 13 (22%) had disk displacement with reduction. None of the asymptomatic joints had disk displacement without reduction. The difference in occurrence of disk displacement between symptomatic and asymptomatic joints was statistically significant (54% vs. 22%; p < 0.001). However, the difference in occurrence of disk displacement with reduction of the disk on mouth opening was not statistically significant (37% vs. 22%; p = 0.06).

CONCLUSIONS

Disk displacement on MRI correlated well with clinical symptoms in cases of significant disk displacement and in cases of disk displacement without reduction. When disk displacement with reduction was mild, there was no statistically significant difference between symptomatic and asymptomatic joints, which suggests that other causes should be considered.

MR arthrography of the wrist: controversies and concepts

Magnetic resonance arthrography (MRA) has become the preferred modality for imaging patients with internal derangement of the wrist. However, several aspects of MRA use need to be clarified before a standardized approach to the imaging of internal derangement of the wrist can be developed. The objective of the study is to evaluate the efficiency of different magnetic resonance (MR) sequences in the detection of lesions of the triangular fibrocartilage complex (TFCC) and scapholunate and lunotriquetral ligaments on direct MRA. Thirty-one consecutive direct magnetic resonance arthrographic examinations of the wrist using a wrist surface coil were performed for the assessment of the TFCC and intrinsic ligaments on a 1.5-T MR imaging system (Signa; 16 channel, Excite, GE Healthcare, Milwaukee, WI, USA). All patients had wrist pain, and in six cases, there was associated clinical carpal instability. The presence, location, and extent of TFCC, scapholunate ligament (SLL), and lunotriquetral ligament (LTL) lesions on T1 fat-saturated, multiplanar gradient recalled (MPGR) and short tau inversion recovery (STIR) images were identified, compared, and analyzed. Forty-one lesions of the TFCC, SLL, and LTL were visualized on contrast-sensitive (T1 fat-saturated) images in 23/31 (74.2%) patients. Twenty-one lesions of the TFCC and intrinsic ligaments were visualized on noncontrast-sensitive (MPGR and STIR) images (15 tears of the TFCC and six tears of the SLL and LTL). All of these lesions were seen on T1 fat-saturated images; 48.8% (20/41) lesions seen on T1 fat-saturated images (eight tears of TFCC and 12 tears of SLL and LTT) were not seen on MPGR and/or STIR images. Superior contrast resolution, joint distention, and the flow of contrast facilitate the diagnosis of lesions of the TFCC and intrinsic ligaments on contrast-sensitive sequences making MRA the preferred modality for imaging internal derangements of the wrist. Little agreement exists regarding the value and location of perforations of the intrinsic ligaments given that both traumatic and degenerative perforations may be symptomatic. Noncommunicating defects of the ulnar attachments of the triangular fibrocartilage (TFC), tears of the dorsal segment of the SLL, and defects at the lunate attachment of the SLL have a higher likelihood of being symptomatic and caused by trauma rather than by degenerative perforation. Although no consensus exists, it would appear that most arthrographies should be started with a radiocarpal injection. Injection into the distal radioulnar joint should be added if no communicational defects are visualized following radiocarpal injection in patients with ulnar-sided wrist pain.

The quinobenzoxazines: relationship between DNA binding and biological activity

The quinobenzoxazine compounds, derived from antibacterial quinolones, is active in vitro and in vivo against murine and human tumors. In this contribution, we show that the relative DNA binding affinity of the quinobenzoxazine compounds correlates with their cytotoxicity, their ability to inhibit gyrase-DNA complex formation, and the decatenation of kinetoplast DNA by human topoisomerase II. DNA binding studies with the descarboxy-A-62176 analogue indicate that the beta-keto acid moiety of the quinobenzoxazine compounds plays an important role in their interaction with DNA.

Production of brominated tiacumicin derivatives

Several novel tiacumicin derivatives containing bromine have been produced by the addition of inorganic bromine to the fermentation both of Dactylosporangium aurantiacum subsp, hamdenensis. Structures were elucidated employing mass spectrometry and NMR spectroscopy. Antibacterial activity of the bromotiacumicins is comparable to that of the parent compounds.

Novel triterpene sulfates from Fusarium compactum using a rhinovirus 3C protease inhibitor screen

Two novel triterpene sulfates have been isolated from Fusarium compactum by bioactivity-directed fractionation using an assay which measures the inhibition of proteolytic activity of rhinovirus 3C protease on a fluorogenic peptide substrate. The compounds were purified by countercurrent and reverse phase chromatographies. NMR, MS, UV and IR studies revealed two triterpene sulfates, uncommon metabolites of terrestrial fungi.

Preclinical in vivo efficacy of two 9-dihydrotaxane analogues against human and murine tumours

Two 9-dihydrotaxane analogues were synthesised and tested for in vitro potency and in vivo efficacy against murine and human tumour xenografts in mice. The in vitro potency of 9-dihydrotaxol (9-DH-t) and 10-deacetyl-9-dihydrotaxol (10-DeAc-9-DH-t) was generally less than that of paclitaxel against human and murine tumour cells. However, both analogues were at least 20-fold more soluble than paclitaxel in water. The analogues yielded cure rates > or = 60% against human MX-1 solid tumour xenografts in mice, compared with a cure rate of 10% for mice treated with paclitaxel. Both of the analogues were more effective than paclitaxel for treatment of murine M109 solid tumour in mice. 10-DeAc-9-DH-t was as effective as paclitaxel against murine B16 ascites tumour, while 9-DH-t was less effective. Both 10-DeAc-9-DH-t and 9-DH-t were demonstrably less toxic than paclitaxel. At equal dosages 9-DH-t produced serum concentrations greater than paclitaxel, while 10-DeAc-9-DH-t yielded serum concentrations less than paclitaxel. However, the decrease in toxicity of 9-DH-t and 10-DeAc-9-DH-t allowed a 4-fold increase in daily dosage. These two 9-dihydrotaxane analogues yielded favourable preclinical data and demonstrated good potential for further development.

Dibefurin, a novel fungal metabolite inhibiting calcineurin phosphatase activity

The novel calcineurin inhibitor, dibefurin, has been isolated from the fungal culture AB 1650I-759. The isolation was bioactivity-directed fractionation using an assay which measures the phosphatase activity of calcineurin. The compound was purified by countercurrent, reverse phase and gel filtration chromatographies. Several studies, including crystallographic, NMR and MS, revealed that dibefurin is a novel dimeric compound of a unique structural type.

In vitro evaluation of ABT-719, a novel DNA gyrase inhibitor

ABT-719 (A-86719.1) is the first compound of a new class of novel DNA gyrase inhibitors, the 2-pyridones, with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. ABT-719 was more active than ciprofloxacin, sparfloxacin, and clinafloxacin against gram-positive bacteria. ABT-719 was particularly active against Staphylococcus aureus (MIC at which 90% of the isolates were inhibited [MIC90] = 0.015 micrograms/ml) and Streptococcus pneumoniae (MIC90 = 0.03 micrograms/ml). ABT-719 was also the most active of the compounds tested against ciprofloxacin-resistant S. aureus isolates, with an MIC90 of 0.25 micrograms/ml, compared with 64 micrograms/ml for ciprofloxacin. Against gram-negative organisms, ABT-719 was as active as or slightly more active than ciprofloxacin and was the most active compound against ciprofloxacin-resistant Pseudomonas aeruginosa (MIC90 = 2.0 micrograms/ml). ABT-719 was also the most active compound against both gram-positive and gram-negative anaerobes, with MIC90s ranging from 0.12 to 0.25 micrograms/ml.

Biological characterization of a novel antitumor quinolone

A-84441, a potent new antitumor quinolone, was active in vitro and in vivo against murine and human tumors. A-84441, a prodrug, was comparable in potency to the parent compound with an IC50 range of 0.03-0.49 microgram/ml against a panel of murine and human tumor cell lines. The parent compound bound mammalian DNA in a magnesium-dependent manner and caused inhibition of DNA and RNA synthesis. A-84441 produced a significant increased life span and cures in three lines of i.p. implanted murine tumors. A-84441 was active against seven of nine solid tumors including s.c. murine tumors and human tumor xenografts. The compound appeared to be more active when administered i.v. compared to i.p. injection. Antitumor efficacy was little effected by treatment schedule, although multiple divided dosing was generally more effective than single dose treatment. A-84441 was over 10-fold-more active against murine leukemic cells than against normal murine bone marrow cells. The acute toxicity of A-84441 following single or multiple dosing ranged between 11 and 50 mg/kg dependent on schedule of administration when given by i.v. or i.p. route. The agent had no apparent toxicity or efficacy when administered p.o.

Quinobenoxazines: a class of novel antitumor quinolones and potent mammalian DNA topoisomerase II catalytic inhibitors

The antineoplastic quinobenoxazines A-62176 and A-74932 were shown to be potent inhibitors of mammalian DNA topoisomerase II in vivo. This was demonstrated by their selective inhibition of the SV40 DNA replication stages that require topoisomerase II. Neither drug stabilized a covalent complex of the enzyme with SV40 DNA, which suggests that they are not poisons of DNA topoisomerase II. A-77601, an analog having little antitumor activity, barely inhibited DNA topoisomerase II in vivo, even at high concentrations. These findings were supported by in vitro studies which showed that A-62176 and A-74932, but not A-77601, strongly inhibited the catalytic activity of mammalian DNA topoisomerase II. A-62176 did not cause topoisomerase II-mediated DNA strand breaks in vitro under conditions in which adriamycin produced extensive DNA breakage. The antineoplastic and topoisomerase inhibitory activities of the quinobenoxazines correlate with their ability to unwind DNA. A-62176 antagonized the poisoning of topoisomerase II by VM-26 in vivo and in vitro, but had no effect on DNA breakage induced by camptothecin, a DNA topoisomerase I poison. A-62176 and A-74932 thus inhibit DNA topoisomerase II reactions at a step prior to the formation of the "cleavable complex" intermediate. These findings indicate that stabilization of the DNA topoisomerase II-DNA cleavable complex is not necessary for the antitumor activity of this class of quinolones and that the catalytic inhibition of DNA topoisomerase II may contribute significantly to the anticancer activity of other DNA topoisomerase II inhibitors.

In vitro and in vivo evaluations of A-80556, a new fluoroquinolone

A-80556 is a novel fluoroquinolone with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. A-80556 was more active than ciprofloxacin, ofloxacin, lomefloxacin, and sparfloxacin against gram-positive bacteria. A-80556 was particularly active against Staphylococcus aureus (MIC for 90% of isolates [MIC90], 0.12 microgram/ml, relative to fluoroquinolone-susceptible strains) and Streptococcus pneumoniae (MIC90, 0.12 microgram/ml). A-80556 was also the most active of the quinolones tested against ciprofloxacin-resistant S. aureus, with an MIC90 of 4.0 micrograms/ml; that of ciprofloxacin was > 128 micrograms/ml. However, the significance of this activity is not known. A-80556 was slightly less active against Escherichia coli (MIC90, 0.06 microgram/ml) and other enteric organisms than ciprofloxacin (MIC90 for E. coli, < or = 0.03 microgram/ml). A-80556 was slightly less active against Pseudomonas aeruginosa (MIC90, 4.0 micrograms/ml) than ciprofloxacin (MIC90, 2.0 micrograms/ml) and more active against Acinetobacter spp. (respective MIC90s, 0.12 and 0.5 microgram/ml). A-80556 was also the most active compound against anaerobes. Against Bacteroides fragilis, the MIC90 of A-80556 was 2.0 micrograms/ml; that of ciprofloxacin was 16 micrograms/ml. The in vivo efficacy of A-80556 in experimental models with both gram-positive and gram-negative infections was consistent with the in vitro activity and pharmacokinetics and oral absorption in mice.

Pseudo-symmetrical difluoroketones. Highly potent and specific inhibitors of HIV-1 protease

A series of novel, pseudo-symmetrical difluoroketones which are highly potent inhibitors of the HIV-1 protease (IC50 = 1.55-0.02 nM) were synthesized. These compounds also possess good antiviral activity by inhibition of the cytopathic effect of HIV-13B in MT-4 cells in vitro.

Structure of the altromycin B (N7-guanine)-DNA adduct. A proposed prototypic DNA adduct structure for the pluramycin antitumor antibiotics

Altromycin B belongs to the pluramycin family of antitumor antibiotics, which also includes kidamycin, hedamycin, pluramycin, neopluramycin, DC92-B, and rubiflavin A. These potent antitumor compounds react with DNA in as yet imprecisely determined ways. In the present investigation, we have used gel electrophoresis methods in combination with nuclear magnetic resonance and mass spectrometry to determine the structure of the altromycin B-DNA adduct. High-resolution gel electrophoresis demonstrated that guanine was the reactive base, and N7 was implicated from experiments in which N7-deazaguanine was used in place of guanine in a strand breakage assay. Experiments using supercoiled DNA demonstrated that altromycin B and related drugs intercalated into DNA, which implicated this as a common mechanism for binding of the pluramycin antibiotics to DNA. The altromycin B-guanine adduct was isolated from calf thymus DNA after thermal depurination of the alkylated DNA. Mass spectrometry confirmed that altromycin alkylated DNA through guanine, and 1H- and 13C-NMR was used to confirm the covalent linkage sites between altromycin B and guanine. On the basis of these results, we propose that altromycin B first intercalates into DNA via a threading mechanism, reminiscent of nogalamycin, to insert the disaccharide into the minor groove and position the epoxide in the major groove in proximity to N7 of guanine. Nucleophilic attack from N7 of guanine leads to an acid-catalyzed opening of the epoxide, resulting in the altromycin B-DNA adduct. On the basis of these results, a general mechanism for the interaction of the pluramycin family of antibiotics with DNA is proposed.

Comparative chemotherapeutic activity of temafloxacin, cefoxitin, clindamycin, imipenem and ampicillin/sulbactam against Bacteroides fragilis in a mouse subcutaneous abscess model

The new fluorinated 4-quinolone temafloxacin was compared with cefoxitin, clindamycin, imipenem (with or without cilastatin) and ampicillin/sulbactam in a mouse subcutaneous abscess model of Bacteroides fragilis infection. Based upon in-vitro susceptibility data, temafloxacin may represent an effective oral and parenteral alternative to standard oral and parenteral anti-anaerobic agents currently in use. Temafloxacin therapy with dosage regimens of < 200 mg/kg/day typically yielded 2-3 x log10 reductions in cfu/abscess, similar to ampicillin/sulbactam, while cefoxitin and clindamycin were generally unable to produce similar reductions at doses up to 400 mg/kg/day. Imipenem (with or without cilastatin) was unable to produce a 1 x log10 reduction at doses of 400 mg/kg/day. This study suggests that temafloxacin has potential for the treatment of anaerobic or mixed aerobic-anaerobic infections in man.

Synthesis and activity of C-21 alkylamino derivatives of (9R)-erythromycylamine

Novel analogs of (9R)-9-deoxo-9-(N,N-dimethylamino)erythromycin A bearing N-alkylamino substituents at the C-21 position were synthesized. These compounds retained antibacterial activity. The C-21, N,N-dimethylamino analog showed a modest improvement in activity against some Gram-negative bacteria.

Synthesis and antibacterial activities of C-21 functionalized derivatives of (9R)-9-amino-9-deoxoerythromycins A and B

Selective protection of (9R)-9-amino-9-deoxoerythromycin A allowed for elimination of the 12-hydroxyl group to afford a versatile 12,21-olefin intermediate. Further modifications of the intermediate led to the syntheses of (9R)-9-deoxo-9-(N,N-dimethylamino)-12,21-epoxyerythromycin B, (9R)-9-deoxo-9-(N,N-dimethylamino)-21-hydroxyerythromycin A, and (9R)-9-deoxo-9-(N,N-dimethylamino)-21-hydroxyerythromycin B. All three compounds retained antibacterial activity against several organisms normally susceptible to (9R)-9-deoxo-9-(N,N-dimethylamino)erythromycin A. However, the 21-hydroxylated erythromycin A analogue was weaker in potency than the corresponding erythromycin B congener and much weaker than the epoxy derivative. This suggests that while substitution of a polar functionality at C-21 does not abolish antibacterial activity, introduction of vicinal polar groups at both C-12 and C-21 may lead to reduction in potency. Nevertheless, these 21-functionalized derivatives of (9R)-erythromycylamine provide an entry into novel analogues of the important macrolide antibiotic erythromycin.

Antitumor activity and biochemical effects of topsentin

Topsentin, a bis(indolyl)imidazole marine natural product, inhibited the proliferation of cultured human and murine tumor cells at micromolar concentrations (IC50 values ranged from 4 to 40 microM) and was active against in vivo P388 leukemia (%T/C = 137, 150 mg/kg, QD1-5) and B16 melanoma (%T/C = 144, 37.5 mg/kg, QD1-9) tumors. Effects of 30 microM topsentin (1-hr exposures) on incorporation of radiolabeled precursors by P388 cells indicated inhibition of DNA synthesis (91%) and to a lesser extent RNA synthesis (57%), whereas synthesis of protein was unaffected (0%). Fluorescence spectral changes and competitive binding experiments with ethidium bromide indicated that topsentin interacted with DNA. No evidence for intercalation was observed in DNA unwinding studies, but competitive binding experiments with Hoechst 33342 and CC-1065 indicated that topsentin bound to DNA in the minor groove.

In vitro and in vivo evaluation of tiacumicins B and C against Clostridium difficile

Tiacumicins B and C are members of a novel group of 18-membered macrolide antibiotics with in vitro activity against Clostridium difficile. The MICs against 15 strains of C. difficile were 0.12 to 0.25 microgram/ml for tiacumicin B, 0.25 to 1 microgram/ml for tiacumicin C, and 0.5 to 1 microgram/ml for vancomycin. The resistance frequency for both compounds against C. difficile was less than 2.8 x 10(-8) at four and eight times the MIC. The in vivo activities of the tiacumicins against two strains of C. difficile were compared with that of vancomycin in a hamster model of antibiotic-associated colitis. Oral therapy with 0.2, 1, or 5 mg of tiacumicin B or C per kg of body weight protected 100% of clindamycin-treated hamsters exposed to C. difficile ATCC 9689. Oral treatment with identical doses of vancomycin produced a prolonged, dose-dependent survival of hamsters, but it did not prevent the development of fatal colitis at doses of up to 5 mg/kg. When clindamycin-treated animals were exposed to another strain of C. difficile, both tiacumicin B and vancomycin were protective at 5 mg/kg, but not at lower doses. Tiacumicin C was not tested in vivo against the second strain of C. difficile. No tiacumicin B or C was detected in the sera of hamsters treated with single oral doses of 25 mg/kg, while antibiotic levels in the ceca of these hamsters reached 248 micrograms/ml and 285 mg/ml for tiacumicins B and C, respectively. The tiacumicins demonstrated in vitro and in vivo potencies against C. difficile and achieved high concentrations in the cecum, but not the serum, of hamsters after oral administration.

In vitro activity and in vivo efficacy of a new series of 9-deoxo-12-deoxy-9,12-epoxyerythromycin A derivatives

Analogs of 9-deoxo-12-deoxy-9,12-epoxyerythromycin A with an epimeric hydroxy, amino, or ketone substitution at the 11 position of the macrolide ring and an amino or epimeric hydroxy substitution at the 4" position of the cladinose sugar were synthesized in an attempt to produce acid-stable derivatives of erythromycin with improved bioavailability and activity against gram-negative bacteria. These modifications produced compounds with in vitro activities which were generally similar to that of erythromycin. In mice, however, selected analogs were more active than was erythromycin against staphylococci, streptococci, Haemophilus influenzae, and Legionella pneumophila. In mice, the 11-keto (A-63881), 11-epiamino (A-69334), 11-epiamino-4"-amino (A-71671), and 11-epiamino-4"-epiamino (A-73020) analogs achieved peak concentrations in serum and lung, serum half-lives, and/or areas under the serum curve which were greater than those of erythromycin. Improved pharmacokinetics, as compared with those of erythromycin, may explain the increased in vivo antibacterial activities of these compounds.

Potent HIV-1 protease inhibitors with antiviral activities in vitro

A series of novel difluoroketones with low molecular weight (less than 600 m.u.) and which are potent inhibitors of the HIV-1 protease (IC50 = 1.0 to 21 nM) were synthesized. These compounds also exhibited antiviral activity by inhibition of the cytopathic effect of HIV-1(3)B in MT-4 cells in vitro.

Activity of temafloxacin against respiratory pathogens

The activity of the quinolone temafloxacin against respiratory pathogens was compared with those of ciprofloxacin and ofloxacin. MICs for 90% of strains tested indicated that temafloxacin was at least two- to fourfold more potent than the other two quinolones against Staphylococcus aureus, Streptococcus pneumoniae, and Legionella pneumophila. Temafloxacin had potency equal to that of ciprofloxacin and was twofold more active than ofloxacin against Streptococcus pyogenes. Moraxella catarrhalis, and Bordetella pertussis. Against Haemophilus influenzae and Klebsiella pneumoniae, temafloxacin was four- and twofold less potent than ciprofloxacin, respectively. When administered orally in mouse protection tests against S. aureus, S. pneumoniae, and S. pyogenes, temafloxacin was at least eight times more potent than ciprofloxacin and was two to four times more active than ofloxacin. Against H. influenzae, temafloxacin was as active as ofloxacin and was two times less active than ciprofloxacin following oral administration in mice. In treating L. pneumophila in guinea pigs and H. influenzae otitis media in gerbils, temafloxacin and ofloxacin were more effective than ciprofloxacin. Against S. pneumoniae otitis media in gerbils, temafloxacin and ciprofloxacin were more active than ofloxacin. Following subcutaneous administration in mice, temafloxacin achieved higher lung levels than ciprofloxacin or ofloxacin did.

Synthesis and antitumor activity of structural analogues of the epipodophyllotoxins

Several ring-contracted analogues of the antitumor agent etoposide have been prepared. The synthesis of the simple indanyl system 3 is described along with two bicyclic systems of general structure 4 prepared through a stereoselective allylation of the keto-ester 6. A cis-fused lactone analogue 5, which is isomeric with the etoposide aglycone, has been synthesized via a dialkylation of the indene-2-carboxylate anion. Regiochemical and stereochemical results of these alkylations are described. The cytotoxicity of these derivatives toward several tumor cell lines is described and generally follows the structure-activity relationships known for the agent podophyllotoxin (2).

Enhancement of the in vitro and in vivo activities of clarithromycin against Haemophilus influenzae by 14-hydroxy-clarithromycin, its major metabolite in humans

MICs of clarithromycin and its major human metabolite, 14-hydroxy-clarithromycin, for Haemophilus influenzae in combination were reduced two- to fourfold compared with the MICs of each compound alone. Serum reduced the MICs of the parent compound and metabolite two- to fourfold compared with the MICs in medium without serum. In serum spiked with clinically relevant concentrations of clarithromycin and 14-hydroxy-clarithromycin at a fixed ratio of 4:1, 15 of 16 strains (94%) were inhibited and killed by combinations containing 1.2 and 0.3 micrograms/ml, respectively. In time kill experiments, the combination of parent compound and metabolite at one-fourth and one-half of their individual MICs, respectively, reduced bacterial counts by greater than 5 log CFU. The postantibiotic effect of clarithromycin combined with 14-hydroxy-clarithromycin was twice that of clarithromycin when tested alone. When orally administered to gerbils with H. influenzae otitis media, the 14-hydroxy metabolite was significantly more active than clarithromycin in reducing bacterial counts from the middle ear. The in vivo activity of the two compounds in combination was synergistic or additive, depending on the level of H. influenzae present at the time treatment was initiated. Significant reductions in bacterial counts and increases in cure rates were observed when clarithromycin at 50 or 100 mg/kg of body weight was combined with 14-hydroxy-clarithromycin at 12 mg/kg or higher. Results from in vitro and in vivo combinations suggest that routine susceptibility tests and animal efficacy studies with clarithromycin alone may underestimate its potential efficacy against H. influenzae.

Antitumor activity and nucleic acid binding properties of dercitin, a new acridine alkaloid isolated from a marine Dercitus species sponge

A new cytotoxic acridine alkaloid that exhibited antitumor activity in vivo was isolated from a marine Dercitus species sponge collected at a depth of 160 m in the Bahamas. This violet alkaloid, designated dercitin, inhibited the proliferation of cultured murine and human leukemia, lung, and colon tumor cells at nM concentrations (IC50 values of 63-150 nM) and prolonged the life of mice bearing ascitic P388 tumors (%T/C = 170, 5 mg/kg, i.p., QD1-9). Dercitin was also active against i.p. B16 melanoma and modestly inhibited the growth of s.c. Lewis lung carcinoma on the same schedule. DNA blocked the antiproliferative effects of the agent in culture, and incorporation studies indicated that dercitin disrupted DNA and RNA synthesis with less effects on protein synthesis, similar to the effects of known DNA intercalators. After 1-h exposure to 400 nM dercitin, the rates of incorporation of [3H]uridine, [3H]thymidine, and [3H]leucine by cultured P388 cells were inhibited 83, 61, and 23%, respectively. Equilibrium dialysis indicated that dercitin bound calf thymus DNA with an affinity of 3.1 microM and maximal binding of 0.20 mol dercitin/mol base pair. Binding involved intercalation as evidenced by ability to relax supercoiled phi X174 DNA (half maximal concentration for dercitin relaxation was 36 nM). The effects of dercitin on DNA mobility were reversible, and complete relaxation of DNA with topoisomerase I in the presence of dercitin followed by phenol extraction resulted in the appearance of supercoiled DNA. Dercitin, at microM concentrations, had a small effect in the K+-sodium dodecyl sulfate assay using cultured P388 cells, suggesting minimal inhibition of topoisomerase activity. But, dercitin completely inhibited DNA polymerase I/DNase nick translation of DNA at 1 microM. Relaxation of DNA at a given concentration was greater than inhibition of nick translation suggesting that the effects of dercitin on enzyme activity were secondary to changes in DNA conformation. Results indicate that dercitin is a new marine natural product that probably exerts its biological effects through intercalation into nucleic acids.

Antitumor activity and mechanism of action of the novel marine natural products mycalamide-A and -B and onnamide

Three novel heterocyclic compounds, mycalamide-A and -B and onnamide, were isolated from Mycale sp. and Theonella sp. sponges collected in New Zealand and Okinawan waters. Each exhibited potent in vitro toxicity and in vivo efficacy against murine and human tumor cells. Concentrations of each that inhibited replication of cultured murine lymphoma P388 cells by 50% were 5 nM or less. Mycalamide-A and -B were also potent inhibitors of HL-60, HT-29, and A549 human tumor cell replication (50% inhibitory concentration less than 5 nM), while values for onnamide were greater (50% inhibitory concentrations between 25 and 200 nM). Mycalamide-A (10 micrograms/kg) and -B (2.5 micrograms/kg) were moderately active against P388 leukemia (increase in life span, approximately 50%), while onnamide was inactive (40 micrograms/kg; increase in life span, 15%). Mycalamide-A was also active against B16 melanoma, Lewis lung carcinoma, M5076 ovarian sarcoma, colon 26 carcinoma, and the human MX-1, CX-1, and Burkitt's lymphoma tumor xenografts. Mechanism of action studies indicate that the three agents inhibited protein synthesis. For example, after 1-h exposures to 20 nM mycalamide-A and -B, the rates of [3H]leucine incorporation into acid-precipitable material of cultured P388 cells were inhibited 54 and 99%, while the effects on incorporation of [3H]uridine and [3H]thymidine were less. The relative effects of 20 to 2000 nM mycalamide-A on protein, RNA, and DNA synthesis were consistent with those observed during exposure of P388 cells to 1 microM emetine, a known inhibitor of protein synthesis. Also, the three agents inhibited translation of RNA into protein in a cell-free lysate of rabbit reticulocytes. Although mycalamide-A disrupted DNA metabolism, the agent apparently did not intercalate into DNA, and a mixture of four deoxynucleosides (250 microM each) did not decrease the antiproliferative effects of the agent. Collectively, these data indicate that this class of compounds represents novel antitumor agents which should be further evaluated to define their potential.

Potential antiradiation drugs containing no nitrogen, and related compounds

Capabilities are reported of di- and higher sulfides (RSnR') terminated by sulfinate functions [-S(O)O-] for protecting mice against otherwise lethal effects of ionizing radiation. With the use of congeners, structure-activity correlations are developed for the effects of esterification of the sulfinate function, of changing the length of the chain of sulfur atoms, of reduction to a mercapto sulfinate, and of changing the substituents R and R' to chiral and other types of groups. Neither a trisulfide nor a sulfinate by itself was significantly radioprotective. The key requirement for radio-protection in the series appears to be the presence of a sulfur function (-Sn-) from which a thiol can be engendered by a neighboring-group effect of an electron-donating group; sulfoxide functions may afford alternatives to sulfinate functions as such neighboring groups. The relevance of structure-activity relations to the chemical and biological mechanisms involved in the radioprotective activities is discussed.

Skin radioprotection by 5-thio-D-glucose

The radioprotective effect of 5-thio-D-glucose on mouse skin was studied. Intraperitoneal injection of A/J mice with 1.5 g/kg of 5-thio-D-glucose 2 hr prior to X irradiation of the foot reduced early foot skin damage through Day 40 postirradiation by a dose modification factor of 1.3 +/- 0.1. Similarly, late foot deformity during Days 60-90 postirradiation was reduced by a factor of 1.2 +/- 0.1. The radioprotective effect of 5-thio-D-glucose was also compared with that of WR-2721, an aminothiol radioprotector, in CDF1 mice. An intraperitoneal injection of 1.5 g/kg of 5-thio-D-glucose reduced early radiation-induced skin damage by a dose modification factor of 1.2 +/- 0.1 as compared to that of 1.5 +/- 0.2 by 0.65 g/kg of WR-2721 in this strain of mice. 5-Thio-D-glucose is also known to specifically kill and radiosensitize hypoxic tumor cells. Consequently, this drug may be a useful radiotherapy adjuvant, reducing normal tissue damage and enhancing tumor control by minimizing hypoxic protection.

Evaluation of radiosensitizers in combination with chemotherapeutic agents in solid tumors

The electron-affinic compounds misonidazole (MISO), metronidazole (MET), desmethylmisonidazole (DMM), and CB1954 were shown to enhance the activity of alkylating agents in M5076 ovarian tumor. MISO, MET, and DMM enhanced the antitumor activity of cyclophosphamide by factors of 1.7, 1.5, and 1.7, respectively. MIS, MET, and CB1954 enhanced the antitumor activity of melphalan by factors of 2.2, 2.4, and 1.8, respectively. MISO also enhanced the antitumor activity of mitomycin C by a factor of 2.0. MISO did not enhance the activity of chlorozotocin given as a single dose and only slightly enhanced the antitumor activity of this agent when the combination was given on a q4D x 3 schedule. MISO administered 1 hr prior to the antimetabolite 5-FU on a q7D x 3 schedule was no more effective than 5-FU alone against colon carcinoma 38. MISO given simultaneously with or 1 hr after 5-FU strongly inhibited the antitumor activity of 5-FU in this tumor. Data obtained in this study indicate that several radiation sensitizers including three nitroimidazoles and a dinitrobenzamide can enhance the antineoplastic activity of alkylating agents. The degree of enhancement in the M5076 tumor appears to be independent of the electron affinity of the sensitizer. Enhancement was observed with relatively ineffective as well as highly active alkylating agents.

Influence of WR 2721 on the efficacy of radiotherapy and chemotherapy of murine tumors

The effect of WR 2721 on the response of tumors to radiation, antineoplastic alkylating drugs, and DNA binding agents was evaluated and compared to the degree of normal tissue protection provided by WR 2721 against these agents. WR 2721 administered to mice bearing P388 leukemia or Lewis lung carcinoma was found to reduce the radiosensitivity of the leukemia and lung tumor by dose modifying factors of 1.4 and 1.3, respectively. WR 2721 protected bone marrow, intestine, and skin from radiation by factors of 1.9, 1.5, and 1.8. WR 2721 protected mice from the lethality of cyclophosphamide by a factor of only 1.2 whereas protection from melphalan toxicity was more dramatic with a dose modifying factor of 1.6. In chemotherapy studies of established M5076 ovarian tumor, the combination of WR 2721 plus cyclophosphamide was equivalent in activity to cyclophosphamide alone. WR 2721 did not modify the antitumor activity of melphalan in early Lewis lung carcinoma but did decrease the antileukemic effects of this agent by a factor of 2.6 indicating tumor protection greater than host protection in the leukemia. The antitumor activity of the DNA binding agents etoposide (VP16--213) and mitoxantrone against systemic P388 leukemia was not diminished by WR 2721, while a substantial increase in host toxicity was noted for the combinations. The protective effects of WR 2721 against radiation and drug damage were, therefore, not entirely selective for normal tissues. In some cases the degree of tumor protection can be similar to, or greater than, normal tissue protection.

Enhancement of antitumor activity of alkylating agents by the radiation sensitizer misonidazole

The influence of the radiosensitizer misonidazole on the effectiveness of several alkylating agents and cis-platinum against advanced solid murine tumors was investigated. Tumor regrowth delay, frequency of tumor regressions, and animal life span were used to evaluate misonidazole in combination with cyclophosphamide, L-phenylalanine mustard, 1-(2-chloroethyl)-3-trans-4-methylcyclohexyl)-1-nitrosourea, aziridinyl-benzoquinone, and cis-platinum. In the advanced M5076 ovarian carcinoma, misonidazole enhanced the activity of cyclophosphamide, L-phenylalanine mustard, 1-(2-chloroethyl)-3-trans-4-methylcyclohexyl)-1-nitrosourea, and aziridinyl benzoquinone, but not cis-platinum. In early B16 melanoma, misonidazole plus cyclophosphamide was no more effective than cyclophosphamide alone. In advanced Lewis lung carcinoma, misonidazole enhanced the antitumor activity of cyclophosphamide but not 1-(2-chloroethyl)-3-trans-4-methylcyclohexyl)-1-nitrosourea. Misonidazole, at 1000 mg/kg, increased the antitumor effectiveness of L-phenylalanine mustard and cyclophosphamide in M5076 tumors by factors of 2.2 and 1.8, but caused only a 1.2- and 1.3-fold increase in the myelotoxicity of these agents as determined by spleen colony assay of normal bone marrow. Misonidazole also increased the toxicity of cyclophosphamide and L-phenylalanine mustard in non-tumor-bearing mice but to a lesser degree than it enhanced antitumor activity. These results indicate that misonidazole is capable of enhancing the effects not only of ionizing radiation but of alkylating agents as well.

Elimination of hypoxic protection by 5-thio-D-glucose in multicell spheroids

The effect of 5-thio-D-glucose on oxic and hypoxic V79-171 Chinese hamster cells was studied in vitro with single cells and multicell spheroids. At concentrations that were not toxic to oxic cells, this compound killed hypoxic cells with a D0 of 1 hr with a 5 mM concentration and more rapidly at 10 mM beginning 2 hr after incubation at 37 degrees. 5-Thio-D-glucose also sensitized hypoxic cells to radiation and protected oxic cells from radiation damage. Multicell spheroids irradiated after incubation with the compound demonstrated increased radiosensitivity, although the relative contribution of cytotoxicity and hypoxic cell sensitization could not be evaluated. Spheroid reoxygenation by decreased cell respiration was determined not to be a contributing factor, suggesting that the spheroid-sensitizing effect was due to drug effects on hypoxic cells. The dramatic increase in multicell spheroid radiosensitivity that resulted from treatment with 5-thio-D-glucose suggests that this compound may be used to increase the effectiveness of radiotherapy by eliminating hypoxic protection.

Cytotoxic effect of 5-thio-D-glucose on chronically hypoxic cells in multicell spheroids

The effect of 5-thio-D-glucose on chronically hypoxic cells in the multicell spheroids of Chinese hamster V79 cells was investigated. The radiation survival curves of spheroid cells indicated that most of the chronically hypoxic cells in the spheroids could be eliminated by incubating the spheroids with 5-20 mM of 5-thio-D-glucose or 17 hours. Histological studies also demonstrated that 5-thio-D-glucose preferentially kills the hypoxic cells located in the inner part of the spheroids.

Tumor reoxygenation and postirradiation vascular changes

Postirradiation reoxygenation kinetics of the Walker 256 carcinoma were examined and related to radiation-induced changes in tumor vascular functions. Changes in the hypoxic cell component of irradiated Walker tumors may occur by two mechanisms. Reoxygenation of previously hypoxic cells may be due to an increased rate of blood flow in some parts of the tumor. Hypoxic tumor cells may also be eliminated by cell death due to prolonged or severe hypoxia in other parts of the tumor as a result of substantial damage to the tumor vasculature as seen in radiation-induced changes in vascular volume and blood vessel permeability. Reoxygenation of experimental tumors following single, massive doses of radiation may be different from that occurring in human tumors during the course of multifraction radiotherapy.

Tumor cell respiration following irradiation

Oxygen consumption rates for mouse mastocytoma cells examined from 3 to 4 hours after x-irradiation with 250-2000 rads were consistently higher than controls. Cyclic fluctuations in oxygen consumption per cell were dose-dependent; peaks in consumption were generally greater in magnitude and occurred later in time with increasing dose. The cyclic response in consumption is probably due to cell synchronization effects, while the overall higher respiration rates of irradiated cells may reflect increased metabolic activity in response to radiation damage. Oxygen consumption rates for the total cell population were cyclic after 250 and 500 rads, but declined steadily after 1000 or 2000 rads; oxygen consumption rates tended to be lower than controls, especially 12-24 hours postirradiation. Differences between cellular and population oxygen consumption rates reflect changes in cell number after irradiation. It is suggested that postirradiation reoxygenation kinetics in solid tumors may result from changes in tumor oxygen demand.

Cytotoxic and radiosensitizing effects of 5-thio-D-glucose on hypoxic cells

The effect of 5-thio-D-glucose on the viability and radiosensitivity of P815-X2 mouse mastocytoma cells was studied in vitro. By itself, this compound is specifically cytotoxic toward hypoxic cells; moreover, it sensitizes hypoxic cells to irradiation while it protects aerobic cells from radiation damage. These features, together with its low toxicity, suggest that 5- thio-D-glucose may be useful adjuvant to radiotherapy

Intracisternal A and bar-shaped particles in murine neuroblastoma C 1300

Transplantable murine neuroblastoma C 1300 was studied ultrastructurally at varying time intervals ranging from 2 hours to 40 days before and after X-irradiation. Following X-irradiation, 2000 and 4000 rads in a single dose, the uniformly small tumor cells became progressively enlarged multinucleated and degenerated, starting at one to two days. At five to seven days, the uni- and multinucleated giant cells predominated over the small tumor cells, while the giant cells progressively disappeared therafter and the small tumor cells predominated over the giant cells at 10 to 14 days. The giant cells contained abundant subcellular organelles and the X-irradiated tumor cells apparently continued to produce the organelles until they degenerated. Two types of cytoplasmic particles, intracisternal A and bar-shaped, were observed in the tumor cells. The intracisternal A particles occurred in almost all non-irradiated tumor cells though their number varied considerably from cell to cell, while they were observed less frequently in the radiation-induced giant cells probably due to a dilution effect rather than an actual numerical decrease. The bar-shaped particles, hitherto undescribed in the neuroblastoma, were 23 nm in diameter, variable in length and occasionally tubular. They occurred only in degenerating cells regardless of X-irradiation but were encountered more frequently in irradiated tumors than in non-irradiated ones. It is suggested that they may represent an unknown degenerative product of cytoplasm and/or nucleus rather than virus particles, despite their morphological resemblance to certain virus particles.

Preferential cytotoxicity of 5-thio-D-glucose against hypoxic tumor cells

5-Thio-D-glucose effectively killed hypoxic mastocytoma cells of DBA/2J mice, whereas it merely suppressed the growth of oxic cells. This specific toxicity suggested that 5-thio-D-glucose may be a useful adjuvant to radiotherapy by eliminating hypoxic protection.

Reserpine and the partial reinforcement effect in the fish Tilapia H. macrocephala

A strong partial reinforcement effect was produced in 20 fish trained to a free operant striking response by injection of reserpine before extinction of the response. This was interpreted as a result of inhibition of responding during extinction of 20 Ss trained on a consistent schedule of reinforcement rather than facilitation of responding in Ss trained on a .4 variable ratio schedule of reinforcement.