Recombinational error and deletion formation in Neisseria gonorrhoeae: a role for RecJ in the production of pilE (L) deletions

Genetic linkage within Neisseria gonorrhoeae populations is in equilibrium, yet the physical linkage map indicates a relatively stable chromosome structure, despite an apparently vast potential for mispairing between repeated sequences (e.g. between the multiple pil or opa alleles, or through mispairing of any of the numerous small repeated sequences that are liberally scattered throughout the chromosome). Therefore, the stability of the physical linkage map suggests that aberrant recombination between repeated sequences is a rare event. This study was undertaken to explore some of the parameters that may govern deletion events between short direct oligonucleotide repeats, using a chromosomal locus that appears to be especially prone to deletions (the pilin expression locus; pilE). In this report, we demonstrate that deletion formation at pilE occurs primarily through recombinational error following a pilE/pilS interaction; illegitimate (i.e. RecA-independent) events can occur, but they are infrequent. In contrast, when genetically engineered opa deletion substrates were constructed and placed in the chromosome, deletions at the opa loci were infrequent even under rec(+) conditions. A model is presented in which the gonococcal RecA and RecJ proteins promote pilE deletions through a recombination event that is templated or stabilised by a pilE/pilS interaction.

Microwave disinfection of dentures for the treatment of oral candidiasis

Thirty-four institutionalized subjects (mean age, 81 years) with a positive test for C. albicans pseudohyphae were randomly assigned to test (microwave) and control (soak) groups. All subjects received the same course of topical antifungal medication (Nystatin 300,000 IU lozenges 3x daily for 14 days). Subjects in the microwave treatment group had their maxillary denture scrubbed and then microwaved for one minute at 850 Watts. This procedure was repeated three times. For subjects receiving the standard denture soak treatment, the nursing staff was instructed to disinfect the maxillary dentures in 0.2% chlorhexidine digluconate solution overnight for 14 days, changing the solution every two days. Infestation of the tissue surface of the maxillary denture with C. albicans progressively took place over the three-month period following treatment such that 8 (53%) of the microwaved dentures and 16 (84%) of the soaked dentures demonstrated pseudohyphae as determined by Gram stain. Infection of the soft tissues with the hyphal form of C. albicans also increased with time. After three months, one (8%) patient in the microwave group and 12 (63%) patients in the denture soak group demonstrated pseudohyphae on the cytological smears. Re-infestation of the denture surface and infection of the adjacent soft tissue were delayed dramatically in patients whose dentures were microwaved compared with those whose dentures were disinfected by being soaked in a chlorhexidine solution. However, microwave treatment is not recommended for all dentures and should be used with caution.

Potent anti-metastatic activity of combretastatin-A4

The requirement for tumour vascularisation to permit the expansion of solid tumours beyond a threshold size of approximately 1 mm diameter has focussed attention on anti-vascular and anti-angiogenic agents for cancer therapy. Combretastatin-A4 (cis CA-4P) is a tubulin-binding agent that is cytotoxic for proliferating endothelial cells in vitro and causes anti-vascular effects in the established tumour vessels of some primary tumours. Preliminary data from Phase I clinical trials indicate that cis CA-4 may also be effective in targeting the vasculature of human tumours. As metastatic disease is the principal cause of mortality in cancer, we have investigated the effects of cis CA-4 on metastatic development using an in vivo model. We show that bolus or continuous administration of cis CA-4P results in potent inhibition of metastases derived from ectopic primary Lewis lung carcinomas in mice whereas the trans CA-4 isomer is without effect. These data further characterise the activity of CA-4 in vivo and suggest that the drug should be evaluated clinically as an anti-metastatic agent.

The susceptibility of tumors to the antivascular drug combretastatin A4 phosphate correlates with vascular permeability

The acute effects of the antivascular drug, combretastatin A4 phosphate, on tumor energy status and perfusion were assessed using magnetic resonance imaging (MRI) and spectroscopy. Localized (31)P magnetic resonance spectroscopy showed that LoVo and RIF-1 tumors responded well to drug treatment, with significant increases in the P(i)/nucleoside triphosphate ratio within 3 h, whereas SaS, SaF, and HT29 tumors did not respond to the same extent. This variable response was also seen in MRI experiments in which tumor perfusion was assessed by monitoring the kinetics of inflow of the contrast agent, gadolinium diethylenetriaminepentaacetate. These data were analyzed to give the initial rate and time constant for inflow of contrast agent and the integral under the inflow curve. The differential susceptibility of the tumors to combretastatin A4 phosphate showed a positive correlation with prior MRI measurements of tumor vascular permeability, which was determined by measuring the inflow of a macromolecular contrast agent, BSA-gadolinium diethylenetriaminepentaacetate.

Examining human T-lymphotropic virus type 1 infection and replication by cell-free infection with recombinant virus vectors

A sensitive and quantitative cell-free infection assay, utilizing recombinant human T-cell leukemia virus type 1 (HTLV-1)-based vectors, was developed in order to analyze early events in the virus replication cycle. Previous difficulties with the low infectivity and restricted expression of the virus have prevented a clear understanding of these events. Virus stocks were generated by transfecting cells with three plasmids: (i) a packaging plasmid encoding HTLV-1 structural and regulatory proteins, (ii) an HTLV-1 transfer vector containing either firefly luciferase or enhanced yellow fluorescent protein genes, and (iii) an envelope expression plasmid. Single-round infections were initiated by exposing target cells to filtered supernatants and quantified by assaying for luciferase activity in cell extracts or by enumerating transduced cells by flow cytometry. Transduction was dependent on reverse transcription and integration of the recombinant virus genome, as shown by the effects of the reverse transcriptase inhibitor 3'-azido-3'-deoxythymidine (AZT) and by mutation of the integrase gene in the packaging vector, respectively. The 50% inhibitory concentration of AZT was determined to be 30 nM in this HTLV-1 replication system. The stability of HTLV-1 particles, pseudotyped with either vesicular stomatitis virus G protein or HTLV-1 envelope, was typical of retroviruses, exhibiting a half-life of approximately 3.5 h at 37 degrees C. The specific infectivity of recombinant HTLV-1 virions was at least 3 orders of magnitude lower than that of analogous HIV-1 particles, though both were pseudotyped with the same envelope. Thus, the low infectivity of HTLV-1 is determined in large part by properties of the core particle and by the efficiency of postentry processes.

NAD malic enzyme and the control of carbohydrate metabolism in potato tubers

Potato (Solanum tuberosum) plants were transformed with a cDNA encoding the 59-kD subunit of the potato tuber NAD-dependent malic enzyme (NADME) in the antisense orientation. Measurements of the maximum catalytic activity of NADME in tubers revealed a range of reductions in the activity of this enzyme down to 40% of wild-type activity. There were no detrimental effects on plant growth or tuber yield. Biochemical analyses of developing tubers indicated that a reduction in NADME activity had no detectable effects on flux through the tricarboxylic acid cycle. However, there was an effect on glycolytic metabolism with significant increases in the concentration of 3-phosphoglycerate and phosphoenolpyruvate. These results suggest that alterations in the levels of intermediates toward the end of the glycolytic pathway may allow respiratory flux to continue at wild-type rates despite the reduction in NADME. There was also a statistically significant negative correlation between NADME activity and tuber starch content, with tubers containing reduced NADME having an increased starch content. The effect on plastid metabolism may result from the observed glycolytic perturbations.

Starch synthesis in transgenic potato tubers with increased 3-phosphoglyceric acid content as a consequence of increased 6-phosphofructokinase activity

The aim of this work was to test the hypothesis that changes in cytosolic 3-phosphoglyceric acid (3-PGA) content can regulate the rate of starch synthesis in potato (Solanum tuberosum L.) tubers. The amount of 3-PGA was increased by expressing bacterial phosphofructokinase (PFK; EC 2.7.1.11) in transgenic potato tubers. The resultant 3-fold increase in PFK activity was accompanied by an increase in metabolites downstream of PFK, including a 3-fold increase in 3-PGA. There was also a decrease in metabolites upstream of PFK, most notably of glucose-6-phosphate. The increase in 3-PGA did not affect the amount of starch that accumulated in developing tubers, nor its rate of synthesis in tuber discs cut from developing tubers. This suggests that changes in cytosolic 3-PGA may not affect the rate of starch synthesis under all circumstances. We propose that in this case, a decrease in glucose-6-phosphate (which is transported into the amyloplast as a substrate for starch synthesis) may be sufficient to counteract the effect of increased 3-PGA.

Eradication of colorectal xenografts by combined radioimmunotherapy and combretastatin a-4 3-O-phosphate

Solid tumors have a heterogeneous pathophysiology, which has a major impact on therapy. Using SW1222 colorectal xenografts grown in nude mice, we have shown that antibody-targeted radioimmunotherapy (RIT) effectively treated the well-perfused tumor rim, producing regressions for approximately 35 days, but was less effective at the more hypoxic center. By 72 h after RIT, the number of apoptotic cells rose from an overall value of 1% in untreated tumors to 35% at the tumor periphery and 10% at the center. The antivascular agent disodium combretastatin A-4 3-O-phosphate (CA4-P) rapidly reduced tumor blood flow to 62% of control values by 1 h, 23% by 3 h, and between 32-36% from 6 to 24 h after administration. This created central hemorrhagic necrosis, but a peripheral rim of cells continued to grow, and survival was unaffected. Changes in the pattern of perfusion across the tumor over time were zonal. Untreated mice showed perfusion throughout the tumor, with greatest activity at the rim. There was an overall reduction at 1 h, and total cessation of central perfusion from 3 h onward. A narrow peripheral rim of perfusion was always present, which increased in intensity and extent between 6 and 24 h, either through reperfusion or new vessel growth. Combining these two complementary therapies (7.4 MBq (131)I-labeled anti-carcinoembryonic antigen IgG i.v. plus a single 200 mg/kg dose of CA4-P i.p.) produced complete cures in five of six mice for >9 months. Allowing maximal tumor localization of antibody (48 h) before blood flow inhibition by CA4-P increased tumor retention by two to three times control levels by 96 h without altering normal tissue levels, as confirmed by gamma counting and phosphor image analysis. The success of this combined, synergistic therapy was probably the result of several factors: (a) the killing of tumor cells in the outer, radiosensitive region by targeted radiotherapy; (b) enhancement of RIT by entrapment of additional radioantibody after combretastatin-induced vessel collapse; and (c) destruction of the central, more hypoxic and radioresistant region by CA4-P. This work demonstrates the need to consider cancer treatment in a biologically heterogeneous setting, if results are to be effectively translated to the clinic.

Tracheal agenesis: diagnosis and management

Tracheal agenesis (TA) is a rare congenital anomaly that typically has fatal consequences. Its rarity, lack of prenatal symptoms, and emergent presentation usually lead to a failure to arrive at the correct diagnosis and manage the airway properly before the onset of irreversible cerebral anoxia. We report the case history of an infant born with immediate respiratory failure who was diagnosed with tracheal agenesis. The clinical features, embryology, classification schemes and surgical management are discussed with the hope that increased awareness and earlier diagnosis may lead to better chances of survival for affected individuals.

Aging selectively suppresses vasoactive intestinal peptide messenger RNA expression in the suprachiasmatic nucleus of the Syrian hamster

Aging leads to many changes in the expression of circadian rhythms, including reduced amplitude, altered relationship to the environmental illumination cycle, and reduced sensitivity to phase resetting signals. Neuropeptide synthesizing neurons in the suprachiasmatic nucleus (SCN), the principal circadian pacemaker in mammals, play a role in regulating pacemaker function and in coupling the pacemaker to overt circadian rhythms. Aging may alter the activity of neuropeptide neurons in the SCN, which could be reflected in changes in mRNA expression. Therefore, this study investigated whether aging alters the level or rhythm of expression of neuropeptide mRNAs in the SCN of male Syrian hamsters, a well established model for the study of age-related changes in circadian rhythms. Three age groups of hamsters (young [3--5 months old], middle-aged [12--15 months old] and old [19--22 months old] were sacrificed at five times of day. Their brains were dissected and sections through the suprachiasmatic nucleus were prepared and used for in situ hybridization for mRNAs for vasoactive intestinal peptide (VIP), arginine vasopressin (AVP) and somatostatin (SS). Aging selectively decreased the SCN expression of VIP mRNA without affecting AVP mRNA or SS mRNA. Also, only AVP mRNA expression exhibited a robust 24-h rhythm, in contrast to previous findings in other species that VIP mRNA and SS mRNA, as well as AVP mRNA, exhibit 24-h rhythms in the SCN. The present findings suggest that age-related reductions in VIP mRNA expression may contribute to the alterations in entrainment and attenuated sensitivity to phase resetting signals that are characteristic of aging. Furthermore, the results demonstrate that neuropeptide gene expression in the SCN is differentially regulated by aging and varies among species.

Nonlinear hydrodynamical approach to granular materials

We propose a nonlinear hydrodynamical model of granular materials. We show how this model describes the formation of a sandpile from a homogeneous distribution of material under gravity, and then discuss a simulation of a rotating sandpile which shows, in qualitative agreement with experiment, a static and dynamic angle of repose.

Proportion of infiltrating IgG-binding immune cells predict for tumour hypoxia

Macrophages can account for up to 50% of tumour mass and secrete many angiogenic factors. Furthermore, tumour hypoxia is thought to play a major role in the activation of macrophages and the regulation of angiogenesis. In this paper, we demonstrate a strong correlation between hypoxia and the recruitment of immune cells binding to IgG in 8 experimental tumours. We provide evidence that IgG binding immune cells in 3 tumour lines are predominately composed of macrophages. Reduced oxygenation may act as a stimulus for recruitment of immune cells to the tumour mass, and the detection of either IgG-positive host cells or macrophages may offer an alternative method for monitoring tumour hypoxia.

Reforming gendered health care: an assessment of change

Health policy in the United States has changed dramatically over the past three decades, with the main concern shifting from expanded health care coverage to containment of health care costs. The current focus on providing cost-effective health services, reflected in the growth of managed care initiatives, has elevated concern about the quality of health care. The authors contend that quality of health care has always been the key focus in the women's health movement, which evolved in the late 1960s as the first significant challenge to modern medicine. In this article, they apply the analytic lens of gender to develop a fresh perspective on U.S. health care organizations and policies, examining the six broad demands of the feminist consumer model of health care, all of which hinge on the issue of quality care for women, to determine whether women's health needs are now being better addressed. The authors conclude that, despite some notable gains in the roles of women as consumers and providers of health care, many of the new health reforms have replicated and solidified the historical inequities in the health care system.

Mitochondrial biogenesis during germination in maize embryos

Mitochondrial biogenesis and metabolism were investigated during maize (Zea mays) seed germination. Mitochondria from dry and imbibed seed exhibited NADH-dependent O(2) uptake that was completely inhibited by KCN and antimycin A. Mitochondria in the dry seed had a lower rate of succinate-dependent O(2) uptake relative to that measured in imbibed and germinated seed. The activities of the tricarboxylic acid (TCA) cycle enzymes, pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase complex, NAD-malic enzyme, and citrate synthase, are similarly low in mitochondria from dry seed and this correlates with a lower relative abundance of the mitochondrial matrix-located citrate synthase and pyruvate dehydrogenase complex E1alpha-subunit polypeptides. Electron microscopy revealed that mitochondria in the dry seed have a poorly developed internal membrane structure with few cristae; following 24 h of germination the mitochondria developed a more normal structure with more developed cristae. The mitochondria from maize embryos could be fractionated into two subpopulations by Suc density gradient centrifugation: one subpopulation of buoyant density equivalent to 22% to 28% (w/w) Suc; the other equivalent to 37% to 42% (w/w) Suc. These two subpopulations had different activities of specific mitochondrial enzymes and contained different amounts of specific mitochondrial proteins as revealed by western-blot analysis. Both subpopulations from the dry embryo were comprised of poorly developed mitochondria. However, during imbibition mitochondria in the heavy fraction (37%-42% [w/w] Suc) progressively acquired characteristics of fully functional mitochondria found in the germinated seedling in terms of structure, enzymic activity, and protein complement. In contrast, mitochondria in the light fraction (22% to 28% [w/w] Suc) show no significant structural change during imbibition and the amounts of specific mitochondrial proteins decreased significantly during germination.

Effects of adhesive dressings on the stratum corneum of the skin

Two human models were developed to quantify the stratum corneum removed by different adhesive dressings and to measure the peel force of dressing removal and relate this to stratum corneum removal. The first was an open study designed to compare the effects of applying Mepiform Safetac, Tielle and Duoderm Extra Thin to the skin of 12 normal volunteers aged 19-53 years. Treatments were applied once (one 24-hour application) or three times (three x 24-hour applications) to forearm skin which had been prestained with methylene blue. After dressing removal the dye left on the skin was sampled using the skin surface biopsy method and measured spectrophotometrically. The results show that, after one and three applications, the Mepiform Safetac sites had a higher level of dye than those on which the other dressings had been applied (p < 0.05, after three applications). Based on the assumption that the more dye is left on the skin, the less damage is caused, this suggests that Mepiform Safetac is less damaging to the skin surface than the other products tested. In the second study the peel force needed to remove adhesive dressings from prestained skin was measured and related to the amount of stratum corneum removed. Mepilex Border Safetac, Duoderm Extra Thin, Allevyn Adhesive, Biatain Adhesive and Tielle Hydropolymer Dressing were compared in 20 normal volunteers aged 23-64 years. Three consecutive 24-hour applications of each product were made, with measurements of peel force at 24, 48 and 72 hours. The amount of dye remaining on the skin at 72 hours was assessed by the surface biopsy method. Statistically significant differences between products were observed in terms of both peak force and steady state force of removal. Differences in the level of damage to the superficial stratum corneum were also detected. However, low levels of peel force were not always associated with low damage and, therefore, other factors must contribute to stratum corneum removal in this model.

Age-related mitochondrial DNA mutations in the human larynx

OBJECTIVE

To determine whether age-related mitochondrial DNA mutations occur in the human larynx.

STUDY DESIGN

Genetic study of cadaveric larynx specimens.

METHODS

Vocal fold mucosa, thyroarytenoid muscle, and cricoarytenoidjoint tissue were harvested from 13 fresh postmortem larynges (age range, 2 d-82 y). DNA was extracted from each sample, and the polymerase chain reaction (PCR) was used to amplify a target DNA sequence resulting from the common age-associated, 4977-base-pair (bp) mitochondrial DNA deletion. PCR products were visualized by agarose gel electrophoresis. Automated sequencing determined the sequence of identified PCR products.

SUBJECTS

Thirteen cadaveric larynges were obtained through the University of Kentucky Medical Center (Lexington, KY). Specimens from patients with a history of head and neck cancer, previous laryngeal trauma, or surgery were excluded.

RESULTS

Strongly positive bands were identified in samples from three individuals. Weaker bands were seen in samples from four other samples. No band was noted from the two pediatric larynges. Different band patterns were seen among the three different tissue sites in the larynges with positive PCR products, but no consistent pattern was seen. Sequencing of the identified PCR products from selected samples confirmed that they were products of the age-associated, 4977-bp mitochondrial DNA deletion.

CONCLUSIONS

An age-associated mitochondrial DNA deletion was detected in several post-mortem human larynges. Its presence seemed to increase in appearance with age. In the larynges in which the deletion occurred, there were individual regional differences in the occurrence of the deletion, but no consistent pattern was noted across all individuals who carried the deletion.

Neisseria gonorrhoeae recJ mutants show defects in recombinational repair of alkylated bases and UV-induced pyrimidine dimers

Neisseria gonorrhoeae lacks several common DNA repair pathways found in other organisms. As recent evidence had indicated that gonococci use recombinational repair to repair UV-induced DNA lesions, this study examined whether the gonococcal RecJ homologue contributes in this repair capacity. The recJ gene from strain MS11 was cloned and sequenced and was found to show a considerable degree of identity to its Escherichia coli homologue. A N. gonorrhoeae delta recJ mutant was constructed and tested for recombinational proficiency as well as for defects in DNA repair. In the absence of the RecJ exonuclease, DNA transformation and pilin switching occurred at wild type levels, indicating that the efficiency of recombination remained unimpaired. In contrast, N. gonorrhoeae delta recJ mutants showed extreme sensitivity to low levels of UV irradiation and to exposure to DNA-alkylating reagents [e.g. ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS)]. Complementation of the gonococcal recJ mutant in cis restored resistance to low-level UV, indicating that the gonococcal RecJ protein is involved in recombinational repair, and can act independently of other single-strand-specific exonucleases. Furthermore, transformation competence was not required for RecJ-dependent DNA repair. Overall, the data show that N. gonorrhoeae recJ mutants present a unique phenotype when compared to their E. coli recJ counterparts, and further support the contention that RecORJ-dependent recombinational repair is a major DNA repair pathway in the genus Neisseria.

Determinants of anti-vascular action by combretastatin A-4 phosphate: role of nitric oxide

The anti-vascular action of the tubulin binding agent combretastatin A-4 phosphate (CA-4-P) has been quantified in two types of murine tumour, the breast adenocarcinoma CaNT and the round cell sarcoma SaS. The functional vascular volume, assessed using a fluorescent carbocyanine dye, was significantly reduced at 18 h after CA-4-P treatment in both tumour types, although the degree of reduction was very different in the two tumours. The SaS tumour, which has a higher nitric oxide synthase (NOS) activity than the CaNT tumour, showed approximately 10-fold greater resistance to vascular damage by CA-4-P. This is consistent with our previous findings, which showed that NO exerts a protective action against this drug. Simultaneous administration of CA-4-P with a NOS inhibitor, N(omega)-nitro-L-arginine (L-NNA), resulted in enhanced vascular damage and cytotoxicity in both tumour types. Administration of diethylamine NO, an NO donor, conferred protection against the vascular damaging effects. Following treatment with CA-4-P, neutrophil infiltration into the tumours, measured by myeloperoxidase (MPO) activity, was significantly increased. Levels of MPO activity also correlated with the levels of vascular injury and cytotoxicity measured in both tumour types. Neutrophilic MPO generates free radicals and may therefore contribute to the vascular damage associated with CA-4-P treatment. MPO activity was significantly increased in the presence of L-NNA, suggesting that the protective effect of NO against CA-4-P-induced vascular injury may be, at least partially, mediated by limiting neutrophil infiltration. The data are consistent with the hypothesis that neutrophil action contributes to vascular injury by CA-4-P and that NO generation acts to protect the tumour vasculature against CA4-P-induced injury. The protective effect of NO is probably associated with an anti-neutrophil action.

Positive and negative selection of antigen-specific B cells in transgenic mice expressing variant forms of the V(H)1 (T15) heavy chain

Four variant forms of the V1 (T15-H chain) gene are synthesized in mice. Each V1 variant pairs with a distinct L chain to produce a binding site having specificity for phosphocholine (PC). Transgenic mice expressing variant forms of the V1 gene were analyzed to elucidate the factors driving B cell selection into the peripheral repertoire. In all four lines of H chain transgenic mice analyzed, transgene expression caused complete allelic exclusion of endogenous H chains in the bone marrow (BM), whereas most splenic B cells expressed endogenous H chains. The number of sIgM(+) BM B cells and their sIg receptor number was reduced compared to that of normal transgene-negative controls, suggesting that B cells expressing transgene-encoded H chains were being negatively selected in the BM. Mice expressing autoreactive forms of the V1 transgene with lower affinity for PC (M603H and M167H) exhibit positive selection of PC-specific B cells into the spleen, whereas mice expressing the higher affinity T15H variant exhibited elevated PC-specific B cells in the peritoneal cavity but few V(H)1(+) splenic B cells. These data suggest that the higher affinity T15-id(+) B cells preferentially survive in the peritoneal cavity. When these H chain transgenes were crossed into the mu MT knockout mouse in which surface expression of endogenous H chains is blocked, the percent of splenic V(H)1(+) PC-specific B cells increased up to 5-fold and T15-id(+) B cells were detectable in the spleen of T15H mice. This implies that T15-id(+) PC-specific B cells can be selected into the periphery, but they compete poorly with follicular B cells expressing endogenous Ig.

Reappraisal of filter effects on P300 voltage and latency

The selection of which high-pass filter cutoff to use in P300 studies continues to be a serious methodological consideration. To determine whether there was an optimal range of bandpass widths-a range in which P300 voltage and latency would not show statistically significant differences-the authors recorded P300 responses to the auditory "oddball" paradigm from Cz and Pz electrodes in a group of eight healthy males. The authors used high-pass filter cutoffs of 0.01, 0.1, 0.3, and 1.0 Hz with low-pass filter cutoffs of 30 and 100 Hz and measured both P300 peak voltages and P300 integrated mean voltages at 12 bandpass settings. There were statistically significant differences in 7 out of 12 bandpass comparisons for P300 peak voltages and in 7 out of 12 bandwidth comparisons for P300 integrated mean voltages. For P300 latencies, there were statistically significant differences in 9 out of 12 bandwidth comparisons. Based on these results, the best recommendation, therefore, is that the high-pass filter be set no higher than 0.3 Hz.

The man who claimed to be a paedophile

A psychiatrist recounts a case of a man presenting with severe depression who claimed to have abused children and his pet dog. Clinical management of the case hinged on whether this claim was true, a lie or delusional. The uncertainty over this raised complex ethical dilemmas regarding confidentiality and protection of the public (and animals).

The 4-pregnene and 5alpha-pregnane progesterone metabolites formed in nontumorous and tumorous breast tissue have opposite effects on breast cell proliferation and adhesion

Progesterone is required for the full proliferative activity of the breasts and may be directly or indirectly involved in either stimulating or inhibiting breast cancer. To determine whether the effects on breast cancer are attributable to progesterone metabolites, we compared the capacity of nontumorous and tumorous breast tissue to convert progesterone and then tested the effects of these metabolites on breast cell proliferation and anchorage. Tissues from the operated breasts of six patients with infiltrating duct carcinomas were incubated with [14C]progesterone for 2, 4, and 8 h, and the metabolites were identified and quantified. The identified metabolites (equal to >95% of recovered radioactivity) can be divided into those that retain the double bond of progesterone in the carbon-4 position of ring A (4-pregnenes) and those that are 5alpha-reduced (5alpha-pregnanes). The results show that tumorous breast tissue has elevated 5alpha-reductase activity, which results in significantly higher total levels of 5alpha-pregnanes, especially 5alpha-pregnane-3,20-dione (5alphaP), whereas normal (nontumorous) breast tissue produces more 4-pregnenes, especially 3alpha-hydroxy-4-pregnen-20-one (3alphaHP). 5alphaP and 3alphaHP are each one enzymatic step removed from progesterone, resulting from the action of either 5alpha-reductase or 3alpha-hydroxysteroid oxidoreductase (3alpha-HSO), respectively. The ratio of 5alpha-pregnanes:4-pregnenes is >5-fold greater and the ratio of 5alphaP:3alphaHP is nearly 30-fold greater in tumorous than nontumorous breast tissue incubates. In vitro studies with three breast cell lines (MCF-7, MCF-10A, and ZR-75-1) show that 3alphaHP dose dependently inhibits, whereas 5alphaP significantly stimulates, proliferation. Additional studies with MCF-7 and MCF-10A cells indicate that each of the 4-pregnenes isolated from breast tissue suppresses, whereas each respective 5alpha-reduced product stimulates, cell proliferation. Studies of cell anchorage were conducted using MCF-7 cells and various concentrations of 5alphaP or 3alphaHP. The number of cells attached to the substrate was significantly (P<0.05) decreased by treatment with > or =30 nM 5alphaP and increased by treatment with > or =50 nM 3alphaHP. Conversely, the number of cells detached from the substrate after partial trypsin exposure was significantly increased by treatment with > or =40 nM 5alphaP and decreased by treatment with > or =30 nM 3alphaHP. The results suggest that a change in in situ progesterone metabolism, resulting in an increased 5alpha-pregnane:4-pregnene (especially 5alphaP:3alphaHP) ratio, may promote breast cancer by promoting increased cell proliferation and detachment, whereas increases in 4-pregnenes may retard these tumorigenic processes. These studies suggest that endogenous progesterone metabolites may provide a new hormonal basis for breast cancer.

Opa expression correlates with elevated transformation rates in Neisseria gonorrhoeae

Neisseria gonorrhoeae is naturally competent for DNA transformation. Under most conditions encountered in vivo, gonococci express one or more opacity (Opa) proteins on their surfaces. Recently, it was shown that DNA preferentially binds to the surfaces of Opa-expressing organisms compared to those of isogenic Opa-negative strains, presumably due to the numerous cationic residues in the predicted surface-exposed loops of the Opa protein. This study examined whether Opa-DNA interactions actually influence DNA transformation of the gonococcus. The data show that Opa-expressing gonococci are more efficient recipients of DNA for transformation and are more susceptible to exogenous DNase I treatment at early stages during the DNA transformation process than non-Opa expressors. Furthermore, inhibition of the transformation process was demonstrable for Opa(+) populations when either nonspecific DNA or the polyanion heparin was used. Overall, the data suggest that Opa expression, with its presumptive positive surface charge contribution, promotes DNA transformation by causing a more prolonged sequestration of donor DNA at the cell surface, which translates into more efficient transformation over time.

Cell to cell transmission of donor DNA overcomes differential incorporation of non-homologous and homologous markers in Neisseria gonorrhoeae

The neisseriae are naturally competent for DNA transformation. This genetic study examines whether the modification status of chromosomal donor DNA affects transformation of Neisseria gonorrhoeae to drug resistance. When a single modification system was inactivated, unmodified chromosomal donor DNA was not restricted when used to transform the cognate restriction+ host, irrespective of whether the donor DNA carried a point mutation (homologous marker) or a drug-resistance gene cassette (non-homologous marker). These observations contrasted transformations performed with unmodified plasmid donor DNAs, where the incoming DNA was excluded. However, during the study, it became apparent that certain strains of gonococci showed differential incorporation of non-homologous markers when compared with the incorporation of the homologous marker, even when the donor DNAs were prepared from parental strains. Differential incorporation of markers could be rescued either through cell to cell transmission of donor DNA, or by performing in vitro transformations with donor DNA preparations that were obtained from spent culture supernatants. Overall, the data indicate that, in addition to the exclusion of foreign DNA through the requirement for a genus-specific uptake sequence, gonococci appear capable of excluding DNA on the basis of homology.