Bounding Global Aerosol Radiative Forcing of Climate Change

Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable, and arguable lines of evidence, including modeling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of -1.6 to -0.6 W m-2, or -2.0 to -0.4 W m-2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted toward more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.

Quantifying the Importance of Rapid Adjustments for Global Precipitation Changes

Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2, CH4, solar irradiance, black carbon, and sulfate aerosols). The fast precipitation responses to a doubling of CO2 and a 10-fold increase in black carbon are found to be similar, despite very different instantaneous changes in the radiative cooling, individual rapid adjustments, and sensible heating. The model diversity in rapid adjustments is smaller for the experiment involving an increase in the solar irradiance compared to the other climate driver perturbations, and this is also seen in the precipitation changes.

A proposal for a new PhD level curriculum on quantitative methods for drug development

This paper provides an overview of "Improving Design, Evaluation and Analysis of early drug development Studies" (IDEAS), a European Commission-funded network bringing together leading academic institutions and small- to large-sized pharmaceutical companies to train a cohort of graduate-level medical statisticians. The network is composed of a diverse mix of public and private sector partners spread across Europe, which will host 14 early-stage researchers for 36 months. IDEAS training activities are composed of a well-rounded mixture of specialist methodological components and generic transferable skills. Particular attention is paid to fostering collaborations between researchers and supervisors, which span academia and the private sector. Within this paper, we review existing medical statistics programmes (MSc and PhD) and highlight the training they provide on skills relevant to drug development. Motivated by this review and our experiences with the IDEAS project, we propose a concept for a joint, harmonised European PhD programme to train statisticians in quantitative methods for drug development.

Genetic discontinuity between local hunter-gatherers and central Europe's first farmers

After the domestication of animals and crops in the Near East some 11,000 years ago, farming had reached much of central Europe by 7500 years before the present. The extent to which these early European farmers were immigrants or descendants of resident hunter-gatherers who had adopted farming has been widely debated. We compared new mitochondrial DNA (mtDNA) sequences from late European hunter-gatherer skeletons with those from early farmers and from modern Europeans. We find large genetic differences between all three groups that cannot be explained by population continuity alone. Most (82%) of the ancient hunter-gatherers share mtDNA types that are relatively rare in central Europeans today. Together, these analyses provide persuasive evidence that the first farmers were not the descendants of local hunter-gatherers but immigrated into central Europe at the onset of the Neolithic.

Airway management for tonsillectomy: a national survey of UK practice

BACKGROUND

The emergence of variant Creutzfeldt-Jakob disease (vCJD) prompted guidelines from the Department of Health that stress the use of disposable and protective equipment. This survey explores current methods of airway management for tonsillectomy in the UK and ascertains anaesthetists' current knowledge and opinions of the guidelines and of vCJD.

METHODS

Three hundred and five questionnaires were sent to all Royal College tutors across the UK to explore the current practice and adherence to the guidelines.

RESULTS

The tracheal tube was the most frequently used airway across all age groups: 87% for <3 yr old, 79% for 3-16 yr old, and 73% for adults. Of the respondents who intubated, 57% protected the laryngoscope blade with a disposable sheath or used a disposable blade, while others used a reusable laryngoscope blade without protection. Fourteen per cent protected the laryngoscope handle, as recommended. When a reusable classic or flexible laryngeal mask airway was used, 45% reused it after routine sterilization. Thirty-eight per cent of respondents were unaware that any recommendations existed, 55% disagreed with them, and 84% were not fully compliant with them. Compliance rates did not differ between the anaesthetists who agreed or disagreed with the recommendations. Overall full compliance was achieved by only 16% of respondents. The most common reason for non-compliance was the lack of protection of the laryngoscope handle.

CONCLUSIONS

The survey demonstrates widespread non-compliance with and lack of knowledge of, national guidelines.

Screening of some Australian Flacourtiaceae species for in vitro antioxidant, cytotoxic and antimicrobial activity

A total of 27 methanol extracts obtained from different plant parts of 10 species of rain forest trees belonging to four genera of the Flacourtiaceae and originating from Australia were investigated. In vitro cytotoxicity was measured by an ATP Lite-M assay method against the mouse P388 lymphocytic leukemia cell line. The total antioxidant activity has been assessed based on scavenging activity of stable ABTS free radicals. The minimum inhibition concentration (MIC) was determined by the dilution method performed in 96 well plates against four different microbes. The leaf extract of Casearia sp. (RB 3051), mature stem extract of Casearia grayi and stem extract of Scolopia braunii were found to have most antioxidant activity (IC50 = 2.9 microg/ml), cytotoxic activity (LC50 = 0.89 microg/ml) and antimicrobial activity against all four different microbes, respectively. The results obtained suggested that among the four genera studied Casearia is the most promising in respect of finding significant antioxidant, cytotoxic and also antimicrobial activity.

DXYS156: a multi-purpose short tandem repeat locus for determination of sex, paternal and maternal geographic origins and DNA fingerprinting

In forensic science and in legal medicine Y chromosomal typing is indispensable for sex determination, for paternity testing in the absence of the father and for distinguishing males in multiple rape cases. Another potential application is the estimation of paternal geographic origin or family name from a crime stain to narrow down the range of suspects and thus reduce costs of mass screenings. However, Y typing alone cannot provide a sufficiently resolved DNA fingerprint as required for court convictions. Thus, there is a dilemma whether or not to sacrifice valuable material for the sake of extensive Y chromosomal investigations when stain DNA is limited (typically allowing only few PCR amplifications). We here describe a Y-chromosome-specific nucleotide insertion in the duplicate short tandem repeat (STR) locus DXYS156 which allows us to distinguish males from females as does the commonly used amelogenin system, but with the advantage that this locus is multi-allelic, thus substantially contributing towards DNA fingerprinting of a sample and furthermore enabling the detection of sample contamination. Yet another bonus is that both the X and the Y copies of DXYS156 have alleles specific to different parts of the world, offering separate estimates of maternal and paternal descent of that sample. We therefore recommend the inclusion of DXYS156 in standard multiplexing kits for forensic, archaeological and genealogical applications.

Phylogenetic star contraction applied to Asian and Papuan mtDNA evolution

In the past decade, mitochondrial DNA (mtDNA) of 826 representative East Asians and Papuans has been typed by high-resolution (14-enzyme) restriction fragment length polymorphism (RFLP) analysis. Compared with mtDNA control region sequencing, RFLP typing of the complete human mitochondrial DNA generally yields a cleaner phylogeny, the nodes of which can be dated assuming a molecular clock. We present here a novel star contraction algorithm which rigorously identifies starlike nodes (clusters) diagnostic of prehistoric demographic expansions. Applied to the Asian and Papuan data, we date the out-of-Africa migration of the ancestral mtDNA types that founded all Eurasian (including Papuan) lineages at 54,000 years. While the proto-Papuan mtDNA continued expanding at this time along a southern route to Papua New Guinea, the proto-Eurasian mtDNA appears to have drifted genetically and does not show any comparable demographic expansion until 30,000 years ago. By this time, the East Asian, Indian, and European mtDNA pools seem to have separated from each other, as postulated by the weak Garden of Eden model. The east Asian expansion entered America about 25,000 years ago, but was then restricted on both sides of the Pacific to more southerly latitudes during the Last Glacial Maximum around 20,000 years ago, coinciding with a chronological gap in our expansion dates. Repopulation of northern Asian latitudes occurred after the Last Glacial Maximum, obscuring the ancestral Asian gene pool of Amerinds.

An annotated mtDNA database

We have compiled a database of mitochondrial DNA (mtDNA) control region, hypervariable regions 1 (HVR1) and 2 (HVR2) sequences of a total of 14,138 individuals compiled from 103 mtDNA publications before 1 January 2000, 13 data sets published in 2000 and 2001 and 2 unpublished data sets of Iraqi Kurds and Indians from Kerala. By contacting the authors and by other means, we have confirmed and corrected sequence errors, eliminated duplications and harmonised the sequence format. These changes affected all but 26 of the 116 publications. Furthermore, we have implemented a geographic information system ("mtradius") which searches for closest matches to a given mtDNA control region sequence and displays them on a geographic map. A potential application is to estimate a chance matching probability when a forensic stain and a suspect have an identical mtDNA sequence: we suggest that the geographic area with the highest frequency of closely related mtDNA sequence types may be used to define a reference population to give the suspect the maximum benefit of doubt in accordance with the ceiling principle.

The results of an mtDNA study of 1,200 inhabitants of a German village in comparison to other Caucasian databases and its relevance for forensic casework

Mitochondrial DNA control region sequences were determined in 1,200 male volunteers from one village area of Lower Saxony for the hypervariable region 1 (HV1). The 154 variable positions found resulted in 460 different haplotypes with a haplotype diversity value of 0.98165. The number of different haplotypes showed a nearly linear increase with the number of individuals typed. The haplotype diversity approached saturation level at a value of approximately 0.981 after typing 400 individuals. Furthermore, the number of different haplotypes and the haplotype diversity were calculated for four short amplicons of HV1 in order to establish the most variable section with a high efficiency for forensic casework.

Mutation rates at two human Y-chromosomal microsatellite loci using small pool PCR techniques

Polymorphic Y-chromosomal short tandem repeats (Y-STRs) are being employed for phylogenetic and evolutionary studies as well as for forensic applications. Precise knowledge of mutation types and rates is essential and has hitherto been obtained from computer simulation or small-sized father/son pairs, or derived from the more intensively studied autosomal STRs, respectively. To establish more accurate values we analysed about 18 000 DNA sequences isolated from sperm cells of three donors, representing highly validated offspring. Two loci were examined, i.e. DYS19 and DYS390. The methodology applied was small pool PCR with automated laser-induced fluorescence detection. The mutation rates for single repeat gains were determined as 0.18% [95% confidence interval (CI) 0.11--0.31%] for DYS390 and 0.21% (95% CI 0.13--0.33%) for DYS19, and two-repeat changes occurred in the order of 0.01%. Assuming a similar rate for the loss of repeats, which could not be detected with our approach, we predict an overall mutation rate of approximately 0.4% per gamete per generation for both Y tetranucleotide loci. Moreover, these results support the stepwise mutation mechanism based on replication slippage. We expect this approach to be useful for individual mutation risk determination, as well as for studies concerning male history.

Does the disbursement of income increase psychiatric emergencies involving drugs and alcohol?

OBJECTIVE

To determine if the incidence of psychiatric emergencies involving drugs or alcohol supports the argument that mentally ill persons contribute to elevated mortality during the days following disbursement of private earnings and public income transfers.

STUDY DESIGN

Interrupted time-series using Box-Jenkins methods.

DATA COLLECTION/EXTRACTION METHODS

Daily counts of adults admitted to psychiatric emergency services in San Francisco after using drugs or alcohol were derived from medical records for the period January 1 through June 30, 1997.

PRINCIPAL FINDINGS

Psychiatric emergencies among males who had used drugs or alcohol were elevated in the early days of the month. Such emergencies among females were not similarly elevated. Emergencies among females who had not used drugs or alcohol were elevated in the early days of the month.

CONCLUSION

Elevated mortality in the first week of the month may be attributable, in part, to the "check effect" or use of drugs and alcohol by mentally ill males in the days after they receive income. The contribution of women is more complex and may be induced by drug or alcohol abuse among persons in their social networks. The check effect suggests that persons with a history of substance abuse and mental illness should be offered the opportunity to have their income managed by someone who can monitor and influence how the money is being spent. The fact that drug- or alcohol-related admissions among males exhibit temporal patterns suggests that the provision of preventive as well as treatment services may be strategically scheduled.

Worldwide ethnic distribution of the G protein beta3 subunit 825T allele and its association with obesity in Caucasian, Chinese, and Black African individuals

Recently, it was demonstrated that one allele (825T) of the gene encoding the G protein beta3 subunit (GNB3) is associated with hypertension in Germans. This study investigates a possible association with obesity in young male Germans, Chinese, and black South Africans with low, intermediate, and high 825T allele frequencies, respectively. In each of these three distinct cohorts, the 825T allele frequency was increased significantly in overweight (body mass index [BMI] > or =25 kg/m2) and obese individuals (BMI >27 kg/m2) compared to those with normal weight. The 825T allele frequencies in these three BMI groups were, respectively, 29.5, 39.3, and 47.7% in Germans, 46.8, 53.9, and 58.6% in Chinese, and 83.1, 87.7, and 90.9% in South Africans. In each of these three distinct groups, the 825T allele was significantly associated with obesity with odds ratios between 2 and 3. More urban than rural black Africans were overweight despite similar 825T allele frequencies in both populations, which underscores the role of both genetic and environmental factors. BP values in young male whites increased significantly with increasing BMI values but were independent of the C825T polymorphism, suggesting that hypertension associated with the 825T allele could be a consequence of obesity. Genotyping of 5254 individuals from 55 native population samples from Africa, the Americas, Europe, Asia, Australia, and New Guinea demonstrated highest 825T allele frequencies in black Africans (82%) and intermediate values in east Asians (47%). It is anticipated that high frequencies of the 825T allele in Africans and Asians may contribute to an obesity and hypertension epidemic if Westernization of lifestyles continues.

Expanding the forensic German mitochondrial DNA control region database: genetic diversity as a function of sample size and microgeography

Mitochondrial DNA control region sequences were determined in 109 unrelated German Caucasoid individuals from north west Germany for both hypervariable regions 1 (HV1) and 2 (HV2) and 100 polymorphic nucleotide positions (nps) were found, 63 in HV1 and 37 in HV2. A total of 100 different mtDNA lineages was revealed, of which 7 were shared by 2 individuals and 1 by 3 individuals. The probability of drawing a HV1 sequence match within the north west Germans or within published sets of south Germans and west Austrians is similar (within a factor of 2) to drawing a sequence match between any two of these three population samples. Furthermore, HV1 sequences of 700 male inhabitants of one village in Lower Saxony were generated and these showed a nearly linear increase of the number of different haplotypes with increasing number of individuals, demonstrating that the commonly used haplotype diversity measure (Nei 1987) for population samples tends to underestimate mtDNA diversity in the actual population.

Human Y-chromosomal STR haplotypes in a Kurdish population sample

In an Iraqi Kurdish population sample (n = 101), seven polymorphic STR loci of the Y-chromosome (DYS19, 389, 390, 391, 392, 393, and DXYS156-Y) were typed, with DYS389 being subtyped for its four segments. The haplotype diversity was 97.83% and 82 different haplotypes were observed. The Kurds shared some Y-types with neighbouring south Turks but strikingly few with Germans: it is 20-30 times more likely to find a sequence match in a random pair of Kurds than in a random Kurd-German pair.

Median-joining networks for inferring intraspecific phylogenies

Reconstructing phylogenies from intraspecific data (such as human mitochondrial DNA variation) is often a challenging task because of large sample sizes and small genetic distances between individuals. The resulting multitude of plausible trees is best expressed by a network which displays alternative potential evolutionary paths in the form of cycles. We present a method ("median joining" [MJ]) for constructing networks from recombination-free population data that combines features of Kruskal's algorithm for finding minimum spanning trees by favoring short connections, and Farris's maximum-parsimony (MP) heuristic algorithm, which sequentially adds new vertices called "median vectors", except that our MJ method does not resolve ties. The MJ method is hence closely related to the earlier approach of Foulds, Hendy, and Penny for estimating MP trees but can be adjusted to the level of homoplasy by setting a parameter epsilon. Unlike our earlier reduced median (RM) network method, MJ is applicable to multistate characters (e.g., amino acid sequences). An additional feature is the speed of the implemented algorithm: a sample of 800 worldwide mtDNA hypervariable segment I sequences requires less than 3 h on a Pentium 120 PC. The MJ method is demonstrated on a Tibetan mitochondrial DNA RFLP data set.

Phylogenetic resolution of complex mutational features at Y-STR DYS390 in aboriginal Australians and Papuans

Y-chromosomal short tandem repeats (STRs) are used for the study of male aspects of human evolution as well as for forensic applications and paternity testing. Both applications require an understanding of the underlying mutational mechanisms that create variability. We describe complex mutations at the substructured DYS390 STR locus in 97 natives of the New Guinea/Australian region. Sequencing of short alleles in these populations indicates multirepeat deletions. All samples are further characterized using the five additional Y-STR loci DYS19, DXYS156-Y, DYS391, DYS392, and DYS393. Phylogenetic analysis of the resulting haplotypes yields ethnically specific clusters predating the settlement of Australia and Papua New Guinea (although archaic Homo sapiens or Homo erectus lineages are absent). The phylogeny confirms that DYS390 violates the stepwise mutation model and demonstrates that the DYS390 locus mutates relatively rapidly and retains its variability after structural change.

mtDNA analysis reveals a major late Paleolithic population expansion from southwestern to northeastern Europe

mtDNA sequence variation was studied in 419 individuals from nine Eurasian populations, by high-resolution RFLP analysis, and it was followed by sequencing of the control region of a subset of these mtDNAs and a detailed survey of previously published data from numerous other European populations. This analysis revealed that a major Paleolithic population expansion from the "Atlantic zone" (southwestern Europe) occurred 10,000-15,000 years ago, after the Last Glacial Maximum. As an mtDNA marker for this expansion we identified haplogroup V, an autochthonous European haplogroup, which most likely originated in the northern Iberian peninsula or southwestern France at about the time of the Younger Dryas. Its sister haplogroup, H, which is distributed throughout the entire range of Caucasoid populations and which originated in the Near East approximately 25,000-30,000 years ago, also took part in this expansion, thus rendering it by far the most frequent (40%-60%) haplogroup in western Europe. Subsequent migrations after the Younger Dryas eventually carried those "Atlantic" mtDNAs into central and northern Europe. This scenario, already implied by archaeological records, is given overwhelming support from both the distribution of the autochthonous European Y chromosome type 15, as detected by the probes 49a/f, and the synthetic maps of nuclear data.

Mitochondrial footprints of human expansions in Africa

mtDNA studies support an African origin for modern Eurasians, but expansion events within Africa have not previously been investigated. We have therefore analyzed 407 mtDNA control-region sequences from 13 African ethnic groups. A number of sequences (13%) were highly divergent and coalesced on the "mitochondrial Eve" in Africans. The remaining sequences also ultimately coalesced on this sequence but fell into four major clusters whose starlike phylogenies testify to demographic expansions. The oldest of these African expansions dates to approximately 60,000-80,000 years ago. Eurasian sequences are derived from essentially one sequence within this ancient cluster, even though a diverse mitochondrial pool was present in Africa at the time.

Site 73 in hypervariable region II of the human mitochondrial genome and the origin of European populations

The majority of published human mitochondrial DNA sequence data are confined to hypervariable region I in the control region. By contrast, this paper focuses on a nucleotide site in hypervariable region II. Unlike most non-European populations whose mtDNA sequences have been studied in the literature, the British 'white Caucasian' population has a high level of variation at site 73 (following the site numbering by Anderson et al. 1981). This variation appears to have its origin largely in a mutation from guanine to adenine at that site with an estimated minimum age between 15,000 and 25,000 years. The data of Piercy et al. (1993) suggest that roughly half of the British 'white Caucasian' mitochondrial gene pool is descended from a common maternal ancestor who carried this mutation at site 73. This site also plays a central role in distinguishing the five major European mtDNA clusters identified in Richards et al. (1996). We suggest that the lineages carrying an A at site 73, together with some other lineages, may have their origins in a small founder population which expanded after the last glacial maximum about 20,000 years ago. We conclude that, in addition to region I sequences, site 73 is worth determining in studies of Caucasian populations.

Origin and evolution of Native American mtDNA variation: a reappraisal

The timing and number of prehistoric migrations involved in the settlement of the American continent is subject to intense debate. Here, we reanalyze Native American control region mtDNA data and demonstrate that only an appropriate phylogenetic analysis accompanied by an appreciation of demographic factors allows us to discern different migrations and to estimate their ages. Reappraising 574 mtDNA control region sequences from aboriginal Siberians and Native Americans, we confirm in agreement with linguistic, archaeological and climatic evidence that (i) the major wave of migration brought one population, ancestral to the Amerinds, from northeastern Siberia to America 20,000-25,000 years ago and (ii) a rapid expansion of a Beringian source population took place at the end of the Younger Dryas glacial phase approximately 11,300 years ago, ancestral to present Eskimo and Na-Dene populations.

Paleolithic and neolithic lineages in the European mitochondrial gene pool

Phylogenetic and diversity analysis of the mtDNA control region sequence variation of 821 individuals from Europe and the Middle East distinguishes five major lineage groups with different internal diversities and divergence times. Consideration of the diversities and geographic distribution of these groups within Europe and the Middle East leads to the conclusion that ancestors of the great majority of modern, extant lineages entered Europe during the Upper Paleolithic. A further set of lineages arrived from the Middle East much later, and their age and geographic distribution within Europe correlates well with archaeological evidence for two culturally and geographically distinct Neolithic colonization events that are associated with the spread of agriculture. It follows from this interpretation that the major extant lineages throughout Europe predate the Neolithic expansion and that the spread of agriculture was a substantially indigenous development accompanied by only a relatively minor component of contemporary Middle Eastern agriculturalists. There is no evidence of any surviving Neanderthal lineages among modern Europeans.

Mitochondrial portraits of human populations using median networks

Analysis of variation in the hypervariable region of mitochondrial DNA (mtDNA) has emerged as an important tool for studying human evolution and migration. However, attempts to reconstruct optimal intraspecific mtDNA phylogenies frequently fail because parallel mutation events partly obscure the true evolutionary pathways. This makes it inadvisable to present a single phylogenetic tree at the expense of neglecting equally acceptable ones. As an alternative, we propose a novel network approach for portraying mtDNA relationships. For small sample sizes (< approximately 50), an unmodified median network contains all most parsimonious trees, displays graphically the full information content of the sequence data, and can easily be generated by hand. For larger sample sizes, we reduce the complexity of the network by identifying parallelisms. This reduction procedure is guided by a compatibility argument and an additional source of phylogenetic information: the frequencies of the mitochondrial haplotypes. As a spin-off, our approach can also assist in identifying sequencing errors, which manifest themselves in implausible network substructures. We illustrate the advantages of our approach with several examples from existing data sets.

An optimized electroporation protocol applicable to a wide range of cell lines

A number of transfection methods for mammalian cells are available; however, many cell lines may appear resistant to efficient transfection, or at best, necessitate lengthy optimization procedures in recommended protocols. We describe here an electroporation protocol that yields highly efficient gene transfer (20%-100% of surviving cells) in all 19 cell lines tested so far, including lymphoid, myeloid, glial, fibroblast and COS cells. Unlike earlier electroporation protocols, adaptation of this protocol to a cell line of interest only requires the optimization of a single parameter, i.e., the voltage, and can be performed within a day. Furthermore, it is also superior to transfection protocols for other methods (calcium phosphate precipitation, lipofection, DEAE-dextran transfection and transferrinfection) in terms of reproducibility, economy and average transfection efficiency for a wide variety of cell lines.

Selective inactivation of viruses in the presence of human platelets: UV sensitization with psoralen derivatives

Inactivation of viruses in blood products requires that the method employed display selectivity in its action for viral elements while not affecting the biological entity of interest. Several methods have been developed for the treatment of human plasma or products derived from human plasma. An effective technique for the treatment of the cellular components of blood has been lacking, in part due to the inability to develop agents capable of selectively targeting viral agents in the milieu of cellular material. In this paper, we examine the behavior of a group of viral sensitizers designed to be added to cellular samples and be activated upon exposure to UVA light. Upon activation, these agents are capable of disrupting nucleic acids of the virus in a manner that renders them inactive for proliferation. The selectivity observed in this inactivation is determined by the chemical structure of the sensitizer, which can be varied to increase viral killing capacity while diminishing collateral damage to cellular and protein constituents.

The fortysomething barrier: medicine and age discrimination

Agism in the medical profession is mainly covert but it is not uncommon. It is widely believed that people become less productive as they get older. However, research has shown that older people have less absenteeism, more job stability, and greater output than younger workers. Job losses, which until recently were unheard of in the NHS, usually affect older people first, resulting in the loss of those with the most skill and experience. With an aging population it is important that the government takes steps to discourage age discrimination in the NHS and Britain as a whole.

Medicine in Europe. Equal opportunities: progress so far

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Actions of capsaicin on peripheral nociceptors of the neonatal rat spinal cord-tail in vitro: dependence of extracellular ions and independence of second messengers

1. We have tested the hypothesis that capsaicin-induced activation, desensitization and impairment of peripheral nociceptor function is mediated by separate mechanisms. This was investigated by use of an in vitro preparation of the neonatal rat spinal cord with the functionally attached tail in which the cord and tail were separately superfused with physiological solution. Activation of peripheral fibres by noxious (capsaicin, bradykinin, 5-hydroxytrptamine, heat, pinch) and innocuous (light brush) stimuli was assessed by recording the depolarization of a spinal ventral root (L3-L5). 2. Brief administration of capsaicin produced dose-related depolarizing responses (EC50 = 280 nM). These responses could be reproduced for many hours following the repeated application of capsaicin at a submaximal concentration. Prolonged application of 0.5-2.0 microM capsaicin induced a selective desensitization to subsequent brief administrations of capsaicin. Prolonged administration at 20-50 microM produced an additional non-selective reduction in responses to all noxious stimuli without changing innocuous brush responses. 3. Removal of extracellular calcium from the tail superfusate did not reduce the response to capsaicin or prevent capsaicin-induced desensitization. However, high concentrations of capsaicin no longer induced a non-specific reduction of responses to other noxious stimuli. The response to a brief administration of capsaicin was unaffected by calcium channel blocking drugs including nifedipine, cadmium or omega-conotoxin. On the other hand high extracellular calcium increased the incidence of the non-selective reduction of responses to all noxious stimuli produced by high concentrations of capsaicin. 4. Replacement of extracellular sodium with choline blocked peripheral nerve conduction but did not prevent the desensitization produced by capsaicin. In addition, high concentrations of capsaicin were less effective in reducing the responsiveness to other noxious stimuli. 5. Neither capsaicin-evoked responses nor capsaicin-induced desensitization were affected by the administration of forskolin, dibutyryl cyclic AMP, nitroprusside, dibutyryl cyclic GMP, beta-12,13 phorbol dibutyrate, trifluoperazine, indomethacin, staurosporine or mepacrine, in the tail superfusate. 6. These data suggest that capsaicin-induced activation, desensitization and impairment of peripheral nociceptors may be separable phenomena. Extracellular calcium is not required for capsaicin-induced activation or desensitization but calcium as well as sodium are important for capsaicin-induced impairment of nociceptive responses. Desensitization may occur independently of peripheral fibre activation and cannot be attributed to a central mechanism. Finally neither capsaicin-induced activation nor desensitization require the participation of a second messenger.