A Multipronged Comparative Study of the Ultraviolet Photochemistry of 2-, 3-, and 4-Chlorophenol in the Gas Phase.

The S1((1)ππ*) state of the (dominant) syn-conformer of 2-chlorophenol (2-ClPhOH) in the gas phase has a subpicosecond lifetime, whereas the corresponding S1 states of 3- and 4-ClPhOH have lifetimes that are, respectively, ∼2 and ∼3-orders of magnitude longer. A range of experimental techniques-electronic spectroscopy, ultrafast time-resolved photoion and photoelectron spectroscopies, H Rydberg atom photofragment translational spectroscopy, velocity map imaging, and time-resolved Fourier transform infrared emission spectroscopy-as well as electronic structure calculations (of key regions of the multidimensional ground (S0) state potential energy surface (PES) and selected cuts through the first few excited singlet PESs) have been used in the quest to explain these striking differences in excited state lifetime. The intramolecular O-H···Cl hydrogen bond specific to syn-2-ClPhOH is key. It encourages partial charge transfer and preferential stabilization of the diabatic (1)πσ* potential (relative to that of the (1)ππ* state) upon stretching the C-Cl bond, with the result that initial C-Cl bond extension on the adiabatic S1 PES offers an essentially barrierless internal conversion pathway via regions of conical intersection with the S0 PES. Intramolecular hydrogen bonding is thus seen to facilitate the type of heterolytic dissociation more typically encountered in solution studies.

Breast cancer risk following Hodgkin lymphoma radiotherapy in relation to menstrual and reproductive factors.

BACKGROUND: Women treated with supradiaphragmatic radiotherapy (sRT) for Hodgkin lymphoma (HL) at young ages have a substantially increased breast cancer risk. Little is known about how menarcheal and reproductive factors modify this risk. METHODS: We examined the effects of menarcheal age, pregnancy, and menopausal age on breast cancer risk following sRT in case-control data from questionnaires completed by 2497 women from a cohort of 5002 treated with sRT for HL at ages <36 during 1956-2003. RESULTS: Two-hundred and sixty women had been diagnosed with breast cancer. Breast cancer risk was significantly increased in patients treated within 6 months of menarche (odds ratio (OR) 5.52, 95% confidence interval (CI) (1.97-15.46)), and increased significantly with proximity of sRT to menarche (Ptrend<0.001). It was greatest when sRT was close to a late menarche, but based on small numbers and needing reexamination elsewhere. Risk was not significantly affected by full-term pregnancies before or after treatment. Risk was significantly reduced by early menopause (OR 0.55, 95% CI (0.35-0.85)), and increased with number of premenopausal years after treatment (Ptrend=0.003). CONCLUSION: In summary, this paper shows for the first time that sRT close to menarche substantially increases breast cancer risk. Careful consideration should be given to follow-up of these women, and to measures that might reduce their future breast cancer risk.

Rare and declining bird species benefit most from designating protected areas for conservation in the UK.

There have been recent renewed commitments to increase the extent of protected areas to combat the growing biodiversity crisis but the underpinning evidence for their effectiveness is mixed and causal connections are rarely evaluated. We used data gathered by three large-scale citizen science programmes in the UK to provide the most comprehensive assessment to date of whether national (Sites of Special Scientific Interest) and European (Special Protection Areas/Special Areas of Conservation) designated areas are associated with improved state (occurrence, abundance), change (rates of colonization, persistence and trend in abundance), community structure and, uniquely, demography (productivity) on a national avifauna, while controlling for differences in land cover, elevation and climate. We found positive associations with state that suggest these areas are well targeted and that the greatest benefit accrued to the most conservation-dependent species since positive associations with change were largely restricted to rare and declining species and habitat specialists. We suggest that increased productivity provides a plausible demographic mechanism for positive effects of designation.

Estrogenic activity of o,p'-DDT in the mammalian uterus and avian oviduct.

When rats and birds were treated with o, p-DDT, their reproductive tissues exhibited the same response as when they were treated with estrogen. Weight, water content, glycogen, and RNA increased in uteri and oviducts of rats, chickens, and quail receiving o, p-DDT; p, p-DDT produced little if any response. The o, p-DDT did not accumulate in the reproductive or adipose tissues to a greater extent than p, p-DDT.

A protein particle vaccine containing multiple malaria epitopes.

Ty virus-like particles consist of a single protein species that can be produced in yeast. Recombinant Ty-VLPs carrying a string of up to 15 defined cytotoxic T lymphocyte (CTL) epitopes from Plasmodium species prime protective CTL responses in mice following a single administration without adjuvant. Effective processing of epitopes from the string was demonstrated in vitro and in vivo and was not affected by flanking sequences.

Computer-assisted hip resurfacing surgery using the acrobot navigation system.

The authors have previously reported on the laboratory development of the Acrobot Navigation System for accurate computer-assisted hip resurfacing surgery. This paper describes the findings of using the system in the clinical setting and including the improvements that have been made to expedite the procedure. The aim of the present system is to allow accurate planning of the procedure and precise placement of the prosthesis in accordance with the plan, with a zero intraoperative time penalty in comparison to the standard non-navigated technique. At present the navigation system is undergoing final clinical evaluation prior to a clinical study designed to demonstrate the accuracy of outcome compared with the conventional technique. While full results are not yet available, this paper describes the techniques that will be used to evaluate accuracy by comparing pre-operative computed tomography (CT)-based plans with post-operative CT scans. Example qualitative clinical results are included based on visual comparison of the plan with post-operative X-rays.

Robotic control in knee joint replacement surgery.

A brief history of robotic systems in knee arthroplasty is provided. The place of autonomous robots is then discussed and compared to more recent 'hands-on' robotic systems that can be more cost effective. The case is made for robotic systems to have a clear justification, with improved benefits compared to those from cheaper navigation systems. A number of more recent, smaller, robot systems for knee arthroplasty are also described. A specific example is given of an active constraint medical robot, the ACROBOT system, used in a prospective randomized controlled trial of unicondylar robotic knee arthroplasty in which the robot was compared to conventional surgery. The results of the trial are presented together with a discussion of the need for measures of accuracy to be introduced so that the efficacy of the robotic surgery can be immediately identified, rather than have to wait for a number of years before long-term clinical improvements can be demonstrated.

Preoperative planning and intraoperative guidance for accurate computer-assisted minimally invasive hip resurfacing surgery.

Hip resurfacing is an alternative to total hip replacement (THR) and is particularly suitable for the younger, more active patient. However, it is a more demanding procedure. This paper describes a system that enables the surgeon to plan the surgery preoperatively with optimally sized and placed components, and then transfer this plan to an intraoperative system that registers computer models to the real patient and tracks surgical tools, allowing the surgeon to ensure that the bone is resected correctly and that the components are fitted in accordance with the plan. The paper describes a series of instruments used with the system which are locked to the bone. These instruments serve the dual purpose of soft tissue retraction and bone immobilization. The system will shortly be the subject of laboratory and clinical evaluation. Registration, a cornerstone of the tracked instrument system, has been tested, and accuracy measures are provided. Experimental results for the remainder of the system will be provided after clinical trials.

Effect of calcium ion on the interaction of aldolase with rabbit muscle myofibrils.

A partition equilibrium study has shown calcium ion to be a noncompetitive inhibitor of aldolase adsorption by rabbit muscle myofibrils. This inhibition is interpreted quantitatively in terms of a 10-fold decrease in the intrinsic association constant for the aldolase-myofibril interaction upon Ca2+ binding to either or both of the low-affinity troponin sites associated with regulation of muscle contraction.

Interactions of glycolytic enzymes with erythrocyte membranes.

Partition equilibrium experiments have been used to characterize the interactions of erythrocyte ghosts with four glycolytic enzymes, namely aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphofructokinase and lactate dehydrogenase, in 5 mM sodium phosphate buffer (pH 7.4). For each of these tetrameric enzymes a single intrinsic association constant sufficed to describe its interaction with erythrocyte matrix sites, the membrane capacity for the first three enzymes coinciding with the band 3 protein content. For lactate dehydrogenase the erythrocyte membrane capacity was twice as great. The membrane interactions of aldolase and glyceraldehyde-3-phosphate dehydrogenase were mutually inhibitory, as were those involving either of these enzymes and lactate dehydrogenase. Although the binding of phosphofructokinase to erythrocyte membranes was inhibited by aldolase, there was a transient concentration range of aldolase for which its interaction with matrix sites was enhanced by the presence of phosphofructokinase. In the presence of a moderate concentration of bovine serum albumin (15 mg/ml) the binding of aldolase to erythrocyte ghosts was enhanced in accordance with the prediction of thermodynamic nonideality based on excluded volume. At higher concentrations of albumin, however, the measured association constant decreased due to very weak binding of the space-filling protein to either the enzyme or the erythrocyte membrane. The implications of these findings are discussed in relation to the likely subcellular distribution of glycolytic enzymes in the red blood cell.

Enzyme kinetic evidence of active-site involvement in the interaction between aldolase and muscle myofibrils.

The interaction of aldolase with the myofibrillar matrix of rabbit skeletal muscle has been investigated by means of its effect on kinetic parameters for the enzyme-catalyzed cleavage of fructose 1,6-bisphosphate. Involvement of the active site in the enzymic interaction with the thin filament of muscle is indicated, the association constant for competitive inhibition of catalysis (420,000 M-1) being in excellent agreement with the value of 410,000 M-1 obtained under the same conditions (pH 6.8, I 0.16) from partition equilibrium studies of the aldolase-myofibril interaction (Kuter, M.R., Masters, C.J. and Winzor, D.J. (1983) Arch. Biochem. Biophys. 225, 384-389). A second kinetic study, designed to take into greater account the inhibitory effects of substrate and other phosphate-containing metabolites on the interaction of enzyme with myofibrils, has substantiated further the concept of aldolase existing as an equilibrium mixture of cytoplasmic and filament-bound forms in muscle tissue.

Novel quorum-sensing-controlled genes in Erwinia carotovora subsp. carotovora: identification of a fungal elicitor homologue in a soft-rotting bacterium.

Seven new genes controlled by the quorum-sensing signal molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) have been identified in Erwinia carotovora subsp. carotovora. Using TnphoA as a mutagen, we enriched for mutants defective in proteins that could play a role in the interaction between E. carotovora subsp. carotovora and its plant hosts, and identified NipEcc and its counterpart in E. carotovora subsp. atroseptica. These are members of a growing family of proteins related to Nep1 from Fusarium oxysporum which can induce necrotic responses in a variety of dicotyledonous plants. NipEcc produced necrosis in tobacco, NipEca affected potato stem rot, and both affected virulence in potato tubers. In E. carotovora subsp. carotovora, nip was shown to be subject to weak repression by the LuxR family regulator, EccR, and may be regulated by the negative global regulator RsmA.

A correlation between versican and neurofilament expression patterns during the development and adult cycling of rat vibrissa follicles.

Versican, a proteoglycan recently implicated in hair follicle induction, has been shown to influence axon outgrowth in vitro and in vivo. We used immunohistochemistry to study the relationship between versican expression and innervation, during rat vibrissa follicle development and the adult hair cycle. During development, nerve fibres were commonly associated with areas of weak versican expression, and the path of axons appeared to be delineated by sharp boundaries of versican expression. Versican expression changed in the lower follicle dermis during the adult hair follicle cycle but remained strong around the follicle neck reflecting the constant innervation. Our observations show a correlation between versican expression and peripheral innervation indicating that versican may have a dual role in hair follicle biology.

Bidirectional interaction of valproate and lamotrigine in healthy subjects.

OBJECTIVE: To evaluate the steady-state pharmacokinetics of lamotrigine and valproate at three dosing levels of lamotrigine in normal volunteers receiving steady-state therapeutic doses of valproate. METHODS: This was an open-label, randomized, three-way crossover study of 18 normal male volunteers. Subjects received oral valproate (500 mg Depakote twice a day) throughout the study. Each subject subsequently received three oral dosage regimens of lamotrigine (50, 100, or 150 mg/day) for 1 week each, with a 2-week washout period between lamotrigine treatment periods. Valproate and lamotrigine trough plasma samples were determined by a capillary gas chromatography method and immunofluorometric assay, respectively. Urine samples were assayed for 11 valproate metabolites by gas chromatography/mass spectrometry. RESULTS: When compared to other studies in which lamotrigine was administered with no concurrent antiepileptic drug, concomitant valproate markedly increased the half-life of lamotrigine and decreased lamotrigine clearance, without substantial alteration in the linear kinetics of the drug. The addition of lamotrigine was associated with a small but significant 25% decrease in steady-state valproate plasma concentration. Oral clearance of valproate was increased (from 7.2 +/- 1.1 ml/hr/kg before lamotrigine treatment to 9.0 +/- 2.0 ml/hr/kg on day 28; p < 0.05). The formation clearance of the hepatotoxic valproate metabolites, 2-n-propyl-4-pentenoic acid (4-ene-valproate) and 2-propyl-2,4-pentadienoic acid [2(E),4-diene-valproate], was unaffected by lamotrigine administration. CONCLUSIONS: As a consequence of the interaction between lamotrigine and sodium valproate, a dosage reduction of lamotrigine should be considered in patients taking a combination of valproate and lamotrigine.

Identification and characterization of kraken, a gene encoding a putative hydrolytic enzyme in Drosophila melanogaster.

Kraken, a novel Drosophila gene isolated from a 4-8-h-old Drosophila embryo cDNA library, shows homology to a family of serine hydrolases whose common feature is that they all catalyse breakage of substrates with a carbonyl-containing group. It is a single-copy gene with at least two introns and maps to position 21D on polytene chromosomes. kraken is a member of a conserved gene family. Messenger RNA of kraken is expressed ubiquitously in early embryogenesis. Later, it is concentrated in the foregut and the posterior midgut primordium. Towards the end of embryogenesis, expression of kraken is confined to the gastric caeca. During the third-instar larval stage, kraken is expressed at low levels in the gastric caeca and parts of the gut, and at higher levels in the fat body. We suggest a role for Kraken in detoxification and digestion during embryogenesis and larval development.

The effect of aluminum on neuronal lipofuscin.

Adult white rats were injected over a period of 33 days with aluminum hydrochloride, while a control group, matched for age, sex and weight, received water injections only. At the end of that period, it was found that the group of rats which had received aluminum had lost weight. The animals were killed and an attempt was made to measure the amount of lipofuscin in hypoglossal neurones using fluorescence microscopy. The aluminum treated group did not have a greater level of autofluorescence, indicative of no increase in lipofuscin level in this group. However, a problem of method is described which might have led to the lack of a positive result.

Parvalbumin-immunoreactive, fast-spiking neurons in the medial septum/diagonal band complex of the rat: intracellular recordings in vitro.

The medial septum/diagonal band complex is composed predominantly of cholinergic and GABAergic neurons, and it projects to the hippocampal formation. A proportion of the GABAergic neurons contain parvalbumin, a calcium-binding protein that has previously been localized in fast-spiking, non-accommodating GABAergic neurons in the cerebral cortex and neostriatum. The aim of the present study was to determine whether parvalbumin is localized preferentially in a similar electrophysiological class of neuron in the medial septum/diagonal band complex. The study was carried out using in vitro intracellular recording, intracellular biocytin filling and parvalbumin immunocytochemistry. Three main classes of neurons were identified according to standard criteria: burst-firing, slow-firing and fast-firing neuronal populations. The fast-firing neurons were subdivided into two subpopulations based on whether or not they displayed accommodation. The fast-spiking, non-accommodating cells were furthermore found to be spontaneously active at resting potentials, and to possess action potentials of significantly (P < 0.05) shorter duration (half width: 0.61 +/- 0.12 ms) than those of the regular-spiking, accommodating neurons (1.0 +/- 0.34 ms). Of the neurons that were successfully filled with biocytin and processed for parvalbumin immunoreactivity, 82% of the fast-spiking, non-accommodating cells possessed parvalbumin immunoreactivity, while none of the regular-spiking, accommodating neurons were found to be immunoreactive for parvalbumin. The slow-firing neurons, shown previously to be cholinergic, did not stain for parvalbumin immunoreactivity, in agreement with studies showing parvalbumin to be localized solely in GABAergic neurons in the medial septum/diagonal band complex. In conclusion, these findings suggest the presence of a previously uncharacterized population of neurons in the medial septum/diagonal band complex that generate high-frequency, non-adaptive discharge. This property correlates with the localization of parvalbumin in these neurons, which suggests that parvalbumin fulfils the same role in the medial septum/diagonal band complex that it does in other parts of the brain. The fast-spiking neurons in the medial septum/diagonal band complex may play an essential role in the GABAergic influence of the septum on the hippocampal formation.

Assessment of acuity in human infants using face and grating stimuli.

In a variety of ocular disorders, square-wave gratings yield more optimistic estimates of visual acuity than more complex stimuli such as letters. However, for clinical vision testing of preverbal patients, square-wave gratings are usually employed in conjunction with preferential looking procedures. We developed a complex stimulus--a schematic face--for use in preferential looking procedures. Using the method of constant stimuli, the acuities of 1-, 3-, and 5-month-old infants with normal eyes were estimated using schematic faces and square-wave gratings. Within each age group, thresholds for face and grating stimuli were not significantly different, but psychometric functions obtained with faces were significantly steeper than those obtained with square-wave gratings. This suggests that complex stimuli such as the schematic face could yield more precise acuity estimates than gratings in some pediatric eye patients.

Assessment of acuity of amblyopic subjects using face, grating, and recognition stimuli.

For amblyopic subjects, square-wave gratings, such as those used in preferential looking tests of infants' vision, yield more optimistic estimates of visual acuity than complex stimuli such as letters. A complex stimulus--a schematic face pattern--has recently been shown (Harris et al, IOVS 25:782, 1984) to permit preferential looking estimates of acuity of infants with normal eyes. In the present study, older amblyopic subjects had acuities measured with the face stimulus as well as gratings and standard recognition tests. Acuities measured with the face stimulus agreed better with the results of the standard recognition tests than did those obtained with gratings. Thus, if amblyopia of infants and young children affects spatial vision in a manner similar to that of older children and adults, one would anticipate that complex stimuli, such as the face pattern, would complement current assessments of young pediatric patients.

Four radiation hypersensitivity cases and their implications for clinical radiotherapy.

BACKGROUND AND PURPOSE: Over a 20 year period, four out of 2000 paediatric radiotherapy patients, treated at St. Bartholomew's Hospital (three with lymphoma, one with angiosarcoma), have revealed extreme/fatal clinical hypersensitivity in normal tissues. PATIENTS AND METHODS: Cellular hypersensitivity was confirmed in vitro and attributed to the ataxia-telangiectasia (A-T) gene in cases I and II, a newly described defect in the DNA ligase 4 gene in case III, and a novel and as yet incompletely defined, molecular defect in case IV who presented with xeroderma pigmentosum (XP). RESULTS: The severe clinical hypersensitivity preceded the cellular and molecular analysis, but did not manifest as a clinically exaggerated normal tissue reaction until 3+ weeks after the start of a conventionally fractionated course of radiotherapy, by which time the latent damage had been inflicted. There were no clinical stigmata to alert the clinician to a predisposing syndrome in two patients (cases I and II). We point out that approximately 20% of A-T patients are classified as variants with delayed expression of clinical symptoms, and case II falls into this category. CONCLUSIONS: As lymphoma (incidence, one in 100000 children) constituted the majority of the diagnoses, questions arise as to: (1), the probability of other centres having experienced and being presented in the future with similar problems (particularly bearing in mind that other oncologically predisposing radiosensitivity syndromes have not been not represented in our experience); and (2), the appropriateness, efficiency and applicability of predictive assays. Unambiguous cellular radiosensitivity would have been apparent from clonal assays on fibroblast cultures from all four cases prior to treatment, but such assays take 4-6 weeks to produce results. While estimates of chromosome damage or clonal assays on pre-treatment blood derived cells would be faster, there is a health economics issue as to the general applicability of such 'screening' assays.