Effect of ageing upon warfarin dose requirements: a longitudinal study

This longitudinal study was designed to establish the rate of age-related change in warfarin dose requirements. Warfarin dosage was recorded retrospectively in 104 patients who had been stabilized on warfarin for a median period of 10 years (range 6-24 years) for prophylaxis of thromboembolic disease. There was a significant negative correlation between dosage and age at the start of therapy (p = 0.002, r = -0.30). Warfarin requirements fell over time, dosage difference being significantly correlated with age difference (p = 0.01, r = 0.25). Use of regression equation derived from these data suggests a 21% fall in warfarin requirements in this population over a 15-year period. The relationship between change in warfarin dose requirements and ageing established in this longitudinal study is in good agreement with that established by cross-sectional studies, suggesting that no major birth cohort effect is influencing requirements in our warfarin-treated population.

A gene map of the human genome

The human genome is thought to harbor 50,000 to 100,000 genes, of which about half have been sampled to date in the form of expressed sequence tags. An international consortium was organized to develop and map gene-based sequence tagged site markers on a set of two radiation hybrid panels and a yeast artificial chromosome library. More than 16,000 human genes have been mapped relative to a framework map that contains about 1000 polymorphic genetic markers. The gene map unifies the existing genetic and physical maps with the nucleotide and protein sequence databases in a fashion that should speed the discovery of genes underlying inherited human disease. The integrated resource is available through a site on the World Wide Web at http://www.ncbi.nlm.nih.gov/SCIENCE96/.

Patterns of expression of tumor necrosis factor alpha, tumor necrosis factor beta, and their receptors in synovia of patients with juvenile rheumatoid arthritis and juvenile spondylarthropathy

OBJECTIVE

To assess the expression of tumor necrosis factor alpha (TNF alpha), TNF beta, and their receptors in synovia of patients with juvenile rheumatoid arthritis (JRA) and juvenile spondylarthropathy (JSpA), and to determine similarities with and differences from adult RA.

METHODS

Twenty-eight synovial tissue samples from patients with JRA, 6 from patients with JSpA, and 6 from patients with RA, selected for the presence of inflammatory infiltrates, were analyzed for the expression of TNF alpha, TNF beta, and their receptors (p55 and p75 TNFR), utilizing the dual approach of reverse transcriptase-polymerase chain reaction and immunohistochemistry analysis.

RESULTS

The presence of both TNF alpha and TNF beta expression was demonstrated in most JRA and JSpA tissues, although samples from patients with pauciarticular JRA had somewhat lesser amounts of these cytokines. TNF beta expression correlated significantly with the occurrence of lymphocytic aggregates in tissues. Staining with monoclonal antibodies specific for the p55 and p75 receptors revealed that a diverse range of cell types expressed the receptors, with the most intense p55 staining on vascular endothelial cells. In the vast majority of synovial tissues, far greater numbers of cells expressed the p55 form of the receptor than the p75 form.

CONCLUSION

JRA and JSpA synovia are characterized by the presence of TNF alpha, TNF beta, and cells expressing TNFR. These findings provide further evidence that TNF, through autocrine/paracrine mechanisms, may amplify local inflammation, leading to joint destruction. The prominence of TNF beta in the synovium in particular subgroups of JRA patients and in JSpA patients may be a distinguishing feature of these diseases.

Survival of cells and DNA of Aeromonas salmonicida released into aquatic microcosms

The survival of the bacterial fish pathogen Aeromonas salmonicida, and persistence of its DNA, were monitored in aquatic microcosms using selective culture and most probable number PCR. Bacterial cells and naked DNA were released into natural non-sterile microcosms consisting of lake sediment overlayered with lake water. Two different types of surface sediment were used. One was sandy in character, taken from the shoreline whilst the other was a littoral loamy surface mud. Inoculated cells and naked DNA became undetectable from water overlayers within 4 weeks of release. Colony counts of Aer. salmonicida declined below detectable limits after 4 weeks in loamy sediment or 7 weeks in sandy sediment; however, naked DNA and DNA from released cells remained detectable for more than 13 weeks.

An association between maternal diet and colonic diverticulosis in an animal model

BACKGROUND/AIMS

Maternal diet may have an effect on the health of the offspring in middle and later life. This study used the laboratory rat as an animal model to examine whether the fibre content of the maternal diet during pregnancy affected subsequent development of colonic diverticula in the offspring fed lifelong fibre deficient or higher fibre diets.

METHODS

The parents of experimental animals were fed either a diet that was known to predispose to colonic diverticulosis or a control diet for one month prior to mating. The offspring were fed one of these diets for 18 months. The incidence of colonic diverticulosis, submucosal collagen content, collagen solubility in weak acid, and the composition of intestinal contents were then measured.

RESULTS

Offspring of rats fed a higher fibre diet from higher fibre diet fed parents had 0% incidence of colonic diverticulosis. When offspring (regardless of parental diet) were fed a low fibre diet for life the acid solubility was lowered compared with rats fed lifelong higher fibre diet mean (SD) (0.044 (0.0007) v 0.073 (0.0015) sigmoid colon (ratio of soluble:insoluble collagen)); 21.1% had diverticulosis and there was reduced fibre fermentation. However, when the diet of the parents of the fibre deficient diet fed rats was considered, the animals whose mothers had a fibre deficient diet had lower acid solubility (0.032 (0.0007)) and an increased incidence of colonic diverticulosis (42.1%) than the animals fed a fibre deficient diet from higher fibre diet fed parents (p < 0.01 in all instances).

CONCLUSION

Maternal diet and the subsequent nutrition of the progeny seem to be of importance in the development of colonic diverticulosis in the rat.

Expression of Aeromonas caviae bla genes in Escherichia coli

An isolate of Aeromonas caviae 035 carried a 55.5 kb self-transferable plasmid. Transfer of the plasmid to Escherichia coli K12 resulted in the expression of a TEM-like beta-lactamase that was not expressed in parental A. caviae. The bla gene sequence was detectable by DNA hybridization and PCR amplification of the plasmid when extracted from parental A. caviae or from E. coli K12 transconjugants. Sequence analysis of the bla genes revealed in each case an 858 bp open reading frame, differing from the TEM-1 sequence by five nucleotide substitutions. Only one of these resulted in amino acid substitution (at position 162 serine-->arginine). The sequence most closely resembles that of TEM-12.

Melanin content and distribution in the surface corneocyte with skin phototypes

An individual's sensitivity to sunlight is traditionally assessed by the Boston or Fitzpatrick classification of skin type. The ability to tan depends, to some degree, on the melanin content of the epidermis. In the study reported here, surface corneocytes in exposed skin and unexposed skin have been assessed using a surface stripping slide mounting technique and an Optomax V image analyser, with which the percentage of corneocyte area occupied by melanin granules has been taken as the melanin content index (MCI). There was a significantly different MCI between different skin types for both exposed (P < 0.0001) and unexposed (P < 0.0001) areas using the Kruskal-Wallis one-way ANOVA test. There was also a positive significant correlation between MCI and skin types II-VI in both exposed (r = 0.95, P < 0.001) and unexposed areas (r = 0.89, P < 0.005). Image analysis also demonstrated that the number of melanin granules in surface corneocytes was significantly higher in the exposed area compared with the unexposed area, for skin types II, III, IV, V and VI. Melanin cap-like structures were also observed in exposed corneocytes and heavily pigmented skin contained larger melanin particles than fairer skin. The results indicate that an individual's skin phototype and melanin content, assessed by image analysis, have a significant correlation.

Career preferences of doctors who qualified in the United Kingdom in 1993 compared with those of doctors qualifying in 1974, 1977, 1980, and 1983

OBJECTIVE

To report the career preferences of doctors who qualified in the United Kingdom in 1993 and to compare their choices with those of earlier cohorts of qualifiers.

DESIGN

Postal questionnaires with structured questions, including questions about choice of future long term career, were sent to doctors a year after qualification.

SETTING

United Kingdom.

SUBJECTS

All medical qualifiers of 1993, comparing their replies with those from earlier studies of the qualifiers of 1974, 1977, 1980, and 1983.

MAIN OUTCOME MEASURES

Choice of future long term career and certainty of choice expressed at the end of the first year after qualification.

RESULTS

Questionnaires were sent to 3657 doctors. 2621 (71.7%) replied. Of the 2621 respondents, 70.5% (1849) stated that their first preference was for a career in hospital practice, 25.8% (677) specified general practice, 1.0% (25) specified public health medicine or community health, 1.4% (36) specified careers outside medicine, and 1.3% (34) did not state a choice. By contrast, 44.7% (1416/3168) of the doctors in the 1983 cohort had specified that their first preference was general practice. Among the 1993 qualifiers, general practice was the first career choice of 17.5% of men (227/1297) and 34.0% of women (450/1324). Only 7.4% of men (96/1297) stated that they definitely wanted to enter general practice. Only 7.8% (103/1324) of women qualifiers in 1993 expressed a career preference for surgical specialties. Within hospital practice, comparing 1993 with 1983, choices for the medical specialties and for accident and emergency medicine rose and those for pathology fell. Women were less definite than men about their choice of future long term career.

CONCLUSIONS

If the 1993 cohort is typical of the current generation of young doctors, there has been a substantial shift away from general practice as a career choice expressed at the end of the preregistration year. General practice was much more popular among women than men. Few women opted for surgery. The sex imbalance in the percentage of doctors who choose different mainstreams of medical practice seems set to continue.

Laboratory-scale purification of microcystins using flash chromatography and reversed-phase high-performance liquid chromatography

Microcystins were extracted from 7 l (equivalent to 313 g dry weight) of cyanobacterial scum collected from Rutland Water in Leicestershire, UK in 1989. The resulting aqueous extract was rapidly concentrated on a C18 flash chromatography cartridge and microcystins were eluted using a step gradient. Fractions were collected manually and monitored by UV spectrophotometer and analytical HPLC. Fractions containing microcystins of similar polarity were pooled to give three fractions. Simple isocratic methods for separating each fraction were developed on an analytical column and scaled up to a 15 x 7.5 cm I.D. column. Closed-loop recycling was used to maximise yield and purity of two hydrophobic microcystins.

Career destinations in 1994 of United Kingdom medical graduates of 1983: results of a questionnaire survey

Cohort studies of doctors' career choices and career progression since the mid-1970s have shown important changes in the medical workforce, in specialist training, and in employment. Examples of these changes are the increasing proportion of women doctors and of doctors who wish to work part time, the emigration patterns of doctors, and the development of vocational training for general practice. Studies enable the effects of longer term changes to be assessed, and sometimes they inform current debate.

Isolation and identification of methanogen-specific DNA from blanket bog peat by PCR amplification and sequence analysis

The presence of methanogenic bacteria was assessed in peat and soil cores taken from upland moors. The sampling area was largely covered by blanket bog peat together with small areas of red-brown limestone and peaty gley. A 30-cm-deep core of each soil type was taken, and DNA was extracted from 5-cm transverse sections. Purified DNA was subjected to PCR amplification with primers IAf and 1100Ar, which specifically amplify 1.1 kb of the archaeal 16S rRNA gene, and ME1 and ME2, which were designed to amplify a 0.75-kb region of the alpha-subunit gene for methyl coenzyme M reductase (MCR). Amplification with both primer pairs was obtained only with DNA extracted from the two deepest sections of the blanket bog peat core. This is consistent with the notion that anaerobiosis is required for activity and survival of the methanogen population. PCR products from both amplifications were cloned, and the resulting transformants were screened with specific oligonucleotide probes internal to the MCR or archaeal 16S rRNA PCR product. Plasmid DNA was extracted from probe-positive clones of both types and the insert was sequenced. The DNA sequences of 8 MCR clones were identical, as were those of 16 of the 17 16S rRNA clones. One clone showed marked variation from the remainder in specific regions of the sequence. From a comparison of these two different 16S rRNA sequences, an oligonucleotide was synthesized that was 100% homologous to a sequence region of the first 16 clones but had six mismatches with the variant. This probe was used to screen primary populations of PCR clones, and all of those that were probe negative were checked for the presence of inserts, which were then sequenced. By using this strategy, further novel methanogen 16S rRNA variants were identified and analyzed. The sequences recovered from the peat formed two clusters on the end of long branches within the methanogen radiation that are distinct from each other. These cannot be placed directly with sequences from any cultured taxa for which sequence information is available.

Isolation and identification of methanogen-specific DNA from blanket bog peat by PCR amplification and sequence analysis

The presence of methanogenic bacteria was assessed in peat and soil cores taken from upland moors. The sampling area was largely covered by blanket bog peat together with small areas of red-brown limestone and peaty gley. A 30-cm-deep core of each soil type was taken, and DNA was extracted from 5-cm transverse sections. Purified DNA was subjected to PCR amplification with primers IAf and 1100Ar, which specifically amplify 1.1 kb of the archaeal 16S rRNA gene, and ME1 and ME2, which were designed to amplify a 0.75-kb region of the alpha-subunit gene for methyl coenzyme M reductase (MCR). Amplification with both primer pairs was obtained only with DNA extracted from the two deepest sections of the blanket bog peat core. This is consistent with the notion that anaerobiosis is required for activity and survival of the methanogen population. PCR products from both amplifications were cloned, and the resulting transformants were screened with specific oligonucleotide probes internal to the MCR or archaeal 16S rRNA PCR product. Plasmid DNA was extracted from probe-positive clones of both types and the insert was sequenced. The DNA sequences of 8 MCR clones were identical, as were those of 16 of the 17 16S rRNA clones. One clone showed marked variation from the remainder in specific regions of the sequence. From a comparison of these two different 16S rRNA sequences, an oligonucleotide was synthesized that was 100% homologous to a sequence region of the first 16 clones but had six mismatches with the variant. This probe was used to screen primary populations of PCR clones, and all of those that were probe negative were checked for the presence of inserts, which were then sequenced. By using this strategy, further novel methanogen 16S rRNA variants were identified and analyzed. The sequences recovered from the peat formed two clusters on the end of long branches within the methanogen radiation that are distinct from each other. These cannot be placed directly with sequences from any cultured taxa for which sequence information is available.

A study of white dermographism in atopic dermatitis

Vascular responses of 15 adults with atopic dermatitis (AD), 15 with psoriasis and 15 with normal skin were studied using an automated dermographometer we have designed. The type of colour change, time to onset and the duration of responses were recorded after a constant stroking force was applied to the skin of each subject. Of the 15 patients with atopic dermatitis, 11 had white dermographism (WD) with abnormal looking skin and four had red dermographism (RD) with normal looking skin. All the control subjects had RD. WD in AD had a significantly longer time to onset and shorter duration of response than RD in controls (P < 0.01), whereas RD in AD had a significantly shorter duration of response than RD in controls (P < 0.01). WD in AD changed to RD after topical corticosteroid treatment and this post-treatment RD was quantitatively similar to the RD in AD. We have quantified, for the first time, a subnormal form of RD in clinically normal skin of patients with AD, which is different from that of the RD in normal subjects. We have also shown that WD in AD is altered to this subnormal form of RD after treatment with topical coricosteroids.

Fluorescent probes and flow cytometry: new insights into environmental bacteriology

Recent trends in flow cytometry have established new techniques in bacteriology. Advances in fluorescent dye technology complement these improvements, offering probes for a variety of cellular functions. Bacterial ecology requires the application of new techniques to help answer questions unanswerable by traditional methods alone. Here we review some aspects of how coupling the two technologies has enabled researchers to directly study individual bacterial cells, and revealed the complexity and heterogeneity present in both laboratory cultures and in environmental samples. Results are discussed with respect to viability analysis, stress induced changes, specific cell detection and cell sorting.

Flow cytometric detection of specific genes in genetically modified bacteria using in situ polymerase chain reaction

Use of the polymerase chain reaction, coupled with flow cytometry, to detect a plasmid encoded xylE gene sequence in intact cells of Escherichia coli and Pseudomonas putida was investigated. Optimal incorporation of fluorescently labelled dUTP into a full length PCR product required substitution at a level of 2:3 dUTP:dTTP. Formaldehyde fixed cells of both species were counted before and after thermal cycling. Sufficient numbers of cells remained intact for subsequent detection using microscopy and flow cytometry but light scatter properties were altered. Intact cell suspensions of both species containing plasmid pLV1013 were subjected to thermal cycling with fluorescent dUTP in the reaction mix. Subsequent analysis by flow cytometry allowed detection of a fluorescent PCR product associated with cells. Control samples (without the plasmid) showed only background fluorescence. This method demonstrates the potential for applying DNA amplification methods for sensitive detection of specific sequences localized inside intact bacterial cells.

Membrane hyperpolarisation by valinomycin and its limitations for bacterial viability assessment using rhodamine 123 and flow cytometry

The ionophore, valinomycin, was investigated as a possible means of bacterial viability assessment using the fluorescent membrane potential dye rhodamine 123. Membrane hyperpolarisation in Escherichia coli, Pseudomonas fluorescens, Enterobacter aerogenes and Arthrobacter globiformis was examined during exponential growth and during stress by brief starvation in a high sodium, low potassium buffer using flow cytometric analysis of rhodamine 123 uptake. Dye uptake was variable both between species and amongst cells from the same culture. Exponential phase cells showed no increase in dye uptake due to valinomycin treatment. Stressed P. fluorescens cells responded to valinomycin treatment by increased dye uptake, while stressed E. coli and A. globiformis cells showed no response. Approximately 50% of stressed Eb. aerogenes cells responded to valinomycin. The results demonstrate the limitations of rhodamine dye for viability analysing the viability of diverse bacterial communities and underline the degree of cell heterogeneity in batch cultures.