Bleeding ears: a case of Munchausen syndrome by proxy

A case is presented of a child who initially presented with genuine aural symptoms and pathology. Over a period of time it became apparent that the persistent aural bleeding, which is an uncommon feature of Chronic Suppurative Otitis Media, was the result of trauma inflicted by its mother; a case of Munchausen syndrome by proxy (MSBP).

A numerical model for magnetic induction tomographic measurements in biological tissues

A finite-difference model has been developed for simulating measurements in magnetic induction tomography (MIT) for biological tissues. The model has three stages: (1) computation of the distribution of current induced in a volume of dielectric due to the magnetic field from an excitation coil; both the electrical conductivity and permittivity of the dielectric are taken into account: (2) computation of the e.m.f. induced in the sensing coil directly from the excitation coil; (3) computation of the e.m.f. induced in a sensing coil due to the current distribution in the dielectric. From the results of stages (2) and (3), the change in signal in the sensing coil due to the dielectric can be obtained, in magnitude and phase, as a fraction of the signal received in the absence of the dielectric. The peak values in the modelled curves agreed to within 14% of practical measurements at 10 MHz on volumes of saline solution with conductivities in the range 0.7 to 6 S m(-1).

Longitudinal evaluation of cognitive disorder in Huntington's disease

The study investigated longitudinal change in cognitive function in 87 patients with Huntington's disease (HD), using a range of neuropsychological tests, which tap mental manipulative abilities, memory, and frontal executive skills. Over a 1-year period the largest changes were noted in letter fluency, object recall, and Stroop Test performance, whereas no changes were noted over more than 3 years on the modified Wisconsin Card Sorting Test. Contrary to expectation, greater change was evident over 1 year for tasks with low compared to high cognitive demands. The differential sensitivity of tasks was attributed in part to inherent characteristics of the tests themselves: their capacity to detect minor gradations of change and their vulnerability to practice effects. However, the greater change for relatively automatic, speed-based tasks with low cognitive demands was interpreted as reflecting the evolution of HD, with a greater magnitude of change occurring in basal ganglia than cortical function. One purpose of the study was to identify tasks sensitive to the progression of HD and hence most suitable for the evaluation of therapies. Despite reaching statistical significance by virtue of the large group size, numerical differences in test scores over 1 year were very small, suggesting that the use of such tests to evaluate change in individuals or small groups of subjects would be problematic. The data highlight the slow progression of HD, the limitations of standard cognitive tests in detecting change over short periods, and the need for therapeutic studies that encompass a relatively prolonged time frame.

Cholesteatoma: an unusual presentation

A case is described of an extensive cholesteatoma presenting as a lump on the side of a patient's head overlying the squamous temporal bone, with erosion of the underlying bone and intracranial extension. The patient was otherwise asymptomatic. This case highlights the bone-eroding capacity of cholesteatoma and the vigilance required in assessing lumps on the head.

Antibody concentration and clinical protection after Hib conjugate vaccination in the United Kingdom

CONTEXT

The schedule for Haemophilus influenzae type b (Hib) vaccination of infants in the United Kingdom consists of 3 doses given at 2, 3, and 4 months of age. Many countries include a fourth dose (booster) of Hib vaccine in the second year of life on the basis of declining Hib antibody concentrations after the primary series. Few data are available to show that this fourth dose is actually necessary.

OBJECTIVE

To evaluate long-term clinical protection against Hib disease and Hib antibody concentrations following primary Hib vaccination without a booster dose.

DESIGN, SETTING, AND SUBJECTS

Clinical protection study conducted between October 1992 and March 1999 in the United Kingdom, in which children developing invasive Hib disease despite vaccination in infancy with 3 doses of Hib conjugate vaccine were reported by pediatricians through an active, prospective, national survey. Separate antibody studies were conducted among 2 cohorts of children (n = 153 and n = 107) vaccinated at 2, 3, and 4 months of age with Hib conjugate vaccine and followed up to 43 and 72 months of age.

MAIN OUTCOME MEASURES

Age-specific vaccine effectiveness, derived from the observed number of true vaccine failures after 3 Hib vaccine doses compared with the number of cases expected based on the age-specific rates of invasive Hib disease obtained prior to the introduction of Hib vaccines; and proportion of children in the 2 cohorts with Hib antibody concentrations of less than 0.15 and less than 1.0 microg/mL.

RESULTS

Ninety-six true vaccine failures occurring after 3 vaccine doses were detected. During the study period, an estimated 4,368,200 infants in the United Kingdom received 3 doses of vaccine; therefore, the vaccine failure rate was 2.2 per 100,000 vaccinees (95% confidence interval, 1.8-2.7 per 100,000). Although vaccine effectiveness declined significantly after the first year of life (P<.001), it remained high until the sixth year of life (99.4% in children aged 5-11 months vs 97.3% in those aged 12-71 months). The proportion of cohorts 1 and 2 with anti-PRP antibody levels of less than 0.15 microg/mL increased between 12 and 72 months of age (6% at 12 months, 8% at 43 months, and 32% at 72 months; chi(2)(1) = 18.25; P<.001 for trend).

CONCLUSIONS

Our results suggest that anti-PRP antibody levels and clinical protection against Hib disease wane over time after Hib vaccination at 2, 3, and 4 months of age without a booster dose at 2 years of age. The decline in clinical protection is minimal, however, suggesting that a booster dose of Hib vaccine following infant vaccination is not essential. JAMA. 2000;284:2334-2340.

Tracheomalacia and breath holding: a case report

A child with a long standing history of cyanotic breath holding attacks presented with acute respiratory distress. Subsequent investigation established that her clinical condition was caused by tracheomalacia. We hypothesise that tracheomalacia might be an under recognised contributor to cyanotic breath holding attacks, the pathogenesis of which is poorly understood.

Clinical and immunological risk factors associated with Haemophilus influenzae type b conjugate vaccine failure in childhood

Haemophilus influenzae type b (Hib) conjugate vaccines have proved extremely efficacious in healthy children. True Hib vaccine failures are rare. Hib conjugate vaccines were introduced for routine immunization in the United Kingdom and the Republic of Ireland in 1992. Coincident with this, active prospective and national surveillance via pediatricians, microbiologists, and public health physicians was commenced to assess the clinical and immunological factors associated with vaccine failure. During the 6 years of the study, 115 children with true vaccine failure were reported. Of the children who were vaccinated before 12 months of age, a clinical risk factor was detected in 20%, an immunological deficiency was detected in 30%, and one or both were detected in 44%. Children who were vaccinated after 12 months of age were more likely to have one or both factors (67%). Thirty percent (33 of 105) of children with true vaccine failure had a low Hib antibody response (concentration, <1.0 microg/mL) after disease, but the majority then responded to a further dose of Hib vaccine. Children who develop Hib disease despite vaccination deserve further clinical and immunological evaluation.

Safety, immunogenicity, and induction of immunologic memory by a serogroup C meningococcal conjugate vaccine in infants: A randomized controlled trial

CONTEXT

Neisseria meningitidis is a common cause of meningitis and septicemia in infants worldwide. Whether a meningococcal C conjugate vaccine protects infants against the serogroup C strain is unknown.

OBJECTIVES

To determine whether a meningococcal C conjugate vaccine is safe and immunogenic and induces immunologic memory in infants.

DESIGN

Single-center, double-blind, randomized controlled trial in 1995 and 1996.

SETTING

Community, Oxfordshire, England.

PARTICIPANTS

One hundred eighty-two healthy infants.

INTERVENTIONS

Participants were randomly assigned to receive vaccination with 0. 5-mL doses of 1 of 2 lots of meningococcal C conjugate vaccine (groups 1 and 2; n=60 in each group) or a hepatitis B control vaccine (group 3; n=62), administered with routine immunizations at 2, 3, and 4 months of age. Approximately half of each group received meningococcal C conjugate vaccine and half received plain meningococcal polysaccharide vaccine (MPS) at 12 months of age.

MAIN OUTCOME MEASURES

Serum antibodies to meningococcal C polysaccharide, assayed by enzyme-linked immunosorbent assay, and serum bactericidal activity (SBA), at 2, 3, 4, 5, 12, and 13 months of age; local and systemic reactions, recorded for 6 days after each vaccination, compared by intervention group.

RESULTS

Meningococcal C conjugate vaccine was well tolerated. After 3 doses, children in groups 1 and 2 achieved significantly higher meningococcal C IgG geometric mean concentrations (21 and 17 U/mL, respectively, vs 0.20 U/mL; P<.001) and SBA titers (629 and 420, respectively, vs 4.1; P<. 001) than controls. At 12 months, antibody concentrations had decreased in all groups but remained significantly higher in children vaccinated with meningococcal C conjugate vaccine (SBA, 24 and 16 in groups 1 and 2, respectively, vs 4.2 in group 3; P<.001). Following vaccination with MPS at 12 months of age, SBA in the meningococcal C conjugate vaccine group was significantly higher than in controls (SBA, 789 vs 4.5; P<.001).

CONCLUSIONS

Our data indicate that meningococcal C conjugate vaccine is safe and immunogenic and results in immunologic memory when given with other routinely administered vaccines to infants at 2, 3, and 4 months of age. JAMA. 2000;283:2795-2801

Plant-derived estrogens relax coronary arteries in vitro by a calcium antagonistic mechanism

OBJECTIVES

To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation.

BACKGROUND

Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens.

METHODS

Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension.

RESULTS

Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein.

CONCLUSIONS

This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.

Systematic errors in multi-frequency EIT

Systematic errors have been measured with a multi-frequency data-collection system operating between 10.24 and 81.92 kHz. The errors were present even though a conventional background measurement on a uniform saline phantom had already been subtracted. Errors due to changes in transimpedance between the calibration and the tissue measurements, cable movement and electrode-skin contact impedance were simulated giving a total systematic error estimate equivalent to a 9% change in tissue conductivity. It was shown that more than 89% of the image was above the total error magnitude, indicating that most of the image revealed true changes in tissue conductivity. In three human subjects, the largest conductivity changes were in two regions, located posteriorly on either side of the midline, and were interpreted as due to the erector spinae muscles. These regions showed increases in conductivity of 73-104%. Identification of other anatomical features was difficult because of the poor spatial resolution of the images.

Chloroplast acclimation in leaves of Guzmania monostachia in response to high light

Acclimation of leaves to high light (HL; 650 micromol m(-2) s(-1)) was investigated in the long-lived epiphytic bromeliad Guzmania monostachia and compared with plants maintained under low light (LL; 50 micromol m(-2) s(-1)). Despite a 60% decrease in total chlorophyll in HL-grown plants, the chlorophyll a/b ratio remained stable. Additionally, chloroplasts from HL-grown plants had a much lower thylakoid content and reduced granal stacking. Immunofluorescent labeling techniques were used to quantify the level of photosynthetic polypeptides. HL-grown plants had 30% to 40% of the content observed in LL-grown plants for the light-harvesting complex associated with photosystems I and II, the 33-kD photosystem II polypeptide, and Rubisco. These results were verified using conventional biochemical techniques, which revealed a comparable 60% decrease in Rubisco and total soluble protein. When expressed on a chlorophyll basis, the amount of protein and Rubisco was constant for HL- and LL-grown plants. Acclimation to HL involves a tightly coordinated adjustment of photosynthesis, indicating a highly regulated decrease in the number of photosynthetic units manifested at the level of the content of light-harvesting and electron transport components, the amount of Rubisco, and the induction of Crassulacean acid metabolism. This response occurs in mature leaves and may represent a strategy that is optimal for the resource-limited epiphytic niche.

Magnetic induction tomography. A measuring system for biological tissues

A single-channel magnetic induction system operating at 10 MHz has been constructed. The system consists of an excitation coil and a sensing coil, between which different objects can be scanned. The eddy currents induced in the object cause perturbations in the sensed magnetic field, which are measured with a phase-sensitive detector with backing off of the signal to improve sensitivity. Scans were obtained for saline solutions with conductivities ranging from 0.001 to 6 Sm-1, encompassing the range for biological tissues. The imaginary part of the perturbation in the sensed magnetic field was found to be proportional to saline conductivity, consistent with theoretical prediction, and had a constant of proportionality of -1.2% per Sm-1. A filtered back-projection algorithm was used to generate tomographic images from the scans.

Determinants of isotopic coupling of CO2 and water vapour within a Quercus petraea forest canopy

Concentration and isotopic composition (δ¹³C and δ¹⁸O) of ambient CO₂ and water vapour were determined within a Quercus petraea canopy, Northumberland, UK. From continuous measurements made across a 36-h period from three heights within the forest canopy, we generated mixing lines (Keeling plots) for δ_a¹³CO₂, δ_a C¹⁸O¹⁶O and δ_a H₂¹⁸O, to derive the isotopic composition of the signal being released from forest to atmosphere. These were compared directly with measurements of different respective pools within the forest system, i.e. δ¹³C of organic matter input for δ_a¹³CO₂, δ¹⁸O of exchangeable water for δ_a C¹⁸O¹⁶O and transpired water vapour for δ_a H₂¹⁸O. [CO₂] and δ_a¹³CO₂ showed strong coupling, where the released CO₂ was, on average, 4 per mil enriched compared to the organic matter of plant material in the system, suggesting either fractionation of organic material before eventual release as soil-respired CO₂, or temporal differences in ecosystem discrimination. δ_a C¹⁸O¹⁶O was less well coupled to [CO₂], probably due to the heterogeneity and transient nature of water pools (soil, leaf and moss) within the forest. Similarly, δ_a H₂¹⁸O was less coupled to [H₂O], again reflecting the transient nature of water transpired to the forest, seen as uncoupling during times of large changes in vapour pressure deficit. The δ¹⁸O of transpired water vapour, inferred from both mixing lines at the canopy scale and direct measurement at the leaf level, approximated that of source water, confirming that an isotopic steady state held for the forest integrated over the daily cycle. This demonstrates that isotopic coupling of CO₂ and water vapour within a forest canopy will depend on absolute differences in the isotopic composition of the respective pools involved in exchange and on the stability of each of these pools with time.

Adverse effects and sero-responses to an acellular pertussis/diphtheria/tetanus vaccine when combined with Haemophilus influenzae type b vaccine in an accelerated schedule

Acellular pertussis vaccines provide protection against pertussis with few adverse effects. Differences in the reactogenicity and immunogenicity of available pertussis vaccines may be influenced by the immunisation schedule employed. We assessed responses to an acellular pertussis, diphtheria, tetanus vaccine mixed with Haemophilus influenzae type b (Hib) vaccine, (PRP-T) given at age 2, 3 and 4 months. Parents kept a symptom diary for 3 days after each immunisation. Antibodies to diphtheria, tetanus, pertussis toxin and filamentous haemagglutinin were measured by enzyme immunoassay at 2 and 5 months. Results were compared with historical controls who received a combination whole-cell pertussis, diphtheria, tetanus/PRP-T vaccine in the same schedule. A total of 262 infants were recruited, of whom 251 were fully evaluated after three doses of vaccine. Systemic and most local reactions were less frequent following the acellular combination. Fever > or = 38 degrees C was reported after only 0.6% of doses. Redness or swelling > or = 2.5 cm were unusual after the first two doses (2-5%), but rates rose to 13% after the third dose. Antibody responses to diphtheria and tetanus toxoids were lower, while those to pertussis antigens were higher, more uniform and less attenuated by pre-immunisation antibody than in infants who received the whole-cell combination. All infants achieved protective antibody titres of at least 0.1 IU/ml for diphtheria and 0.01 IU/ml for tetanus.

CONCLUSION

The acellular combination vaccine was immunogenic for diphtheria, tetanus and pertussis components and was associated with low rates of fever following immunisation.

Radiologic case study. Primary lymphoma of bone

Distinguishing primary lymphoma of bone from disseminated lymphoma and similar appearing bone malignancies is important because of its better prognosis. It is also important to remember how indolent the process can be even in the face of massive bone involvement. Early recognition of this rare entity can increase patient survival.

Thinking of the future and walking back to normal: an exploratory study of patients' experiences during recovery from lower limb fracture

Admission to hospital following a traumatic lower limb fracture is undoubtedly a stressful life event; however, few studies have detailed this from the patient's perspective. By exploring patients' experiences of hospitalization with lower limb trauma, this study aimed to explicate some of the factors impinging on the recovery trajectory. Patients' perceptions of the events influencing their strategies for coping with stress, hospitalization and temporary incapacity were investigated using a qualitative methodology. A convenience sample of nine patients was recruited from an orthopaedic ward in a district general hospital in Wales. The respondents used health diaries to document their recovery for up to 6 weeks after emergency surgery. These diaries were validated and supplemented by semi-structured interviews. Following their traumatic injuries, our respondents were subjected to a variety of stressors and uncertainties. They coped with this period of uncertainty by positive attempts to gain control over their situations, guided by an over-riding desire to 'return to normal' and assisted by the caring attributes of their nurses. From the experiences and events documented, this study was able to identify several stressors which could have been mitigated by optimization of the technical aspects of care, including the management of pain.

Chemiluminescence determination of hydroperoxides following radiolysis and photolysis of free amino acids

Hydroperoxides were determined in selected amino acids using three free radical generating systems by a sensitive (50 pmol limit of detection) and specific high performance liquid chromatography (HPLC)/chemiluminescence method. UVB and gamma radiation produced significant hydroperoxide formation, particularly in the aromatic amino acids tyrosine and tryptophan. Hydroperoxide yield was found to be dependent on both amino acid and irradiation source. Generation of hydrogen peroxide as a by-product of irradiation caused interference with chemiluminescence detection demonstrating the need for catalase addition. Hydroperoxides were not detectable following metal-catalysed H2O2 breakdown. We suggest that metal ions could interfere with the detection of hydroperoxides by causing preferential decomposition.

Bone mineral density in patients undergoing bone marrow transplantation for myeloid malignancies

Bone mineral density (BMD) was measured in 23 patients who had undergone bone marrow transplantation (BMT) at the University of Minnesota for myeloid leukemia. The median age at BMT was 22 years (range 3-53) and the median age at assessment of BMD was 27 years (range 4-56). Total body BMD was measured a median of 2 years (range 1-10) after BMT using Dual Photon X-ray Absorptiometry (DEXA). BMD was measured in g/cm2, with results expressed as percent of normal values and as Z (standard deviation) scores. Patients were categorized into two groups (pediatric and adult) according to age at BMT (< or = 18 years vs > 18 years). Total body BMD of patients in the pediatric age group was significantly decreased (median Z-score -0.5) compared to the adult population (median Z-score 0.0, P = 0.03). No association was observed between BMD and time elapsed since BMT, type of conditioning regimen, gonadal function, steroid intake or graft-versus-host disease. Investigation of decreased BMD in children with AML following BMT is needed to determine the metabolic basis, long-term implications, appropriate preventive measures and potential interventions.

Evaluating blood loss in children's orthopaedic surgery: a simplified method of photometric analysis of eluted swabs

Assessment of intraoperative blood loss by the traditional method of weighing swabs (4 x 4-in. gauze) is propounded to estimate approximately 75% of total loss, although many believe this still underestimates actual loss. The various components of this technique were studied by using the method of colorimetric analysis of eluted swabs, but utilising a modern spectrophotometer. We modified and simplified the technique, resulting in > 95% accuracy in all instances, and by so doing, created a potential technique for use in children's orthopaedic surgery. Weighing swabs was found to estimate only approximately 50% of total loss, and this was supported in the pilot clinical study by a postoperative decrease in haemoglobin of 8-17%, despite transfusion, when transfusion was based on the traditional "75%" rule. Because it is impractical to elute theatre apparel and instruments to increase the accuracy of the elution method in the perioperative time scale necessary, a compromise may be to use the new "50%" rule as a better estimate of total blood loss when calculating transfusion requirements.

Nucleoprotein architecture and ColE1 dimer resolution: a hypothesis

Dimers of plasmid ColE1 are converted to monomers by site-specific recombination, a process that requires 240 bp of DNA (cer) and four host-encoded proteins (XerC, XerD, ArgR and PepA). Here, we propose structures for nucleoprotein complexes involved in cer-Xer recombination based upon existing knowledge of the structures of component proteins and computational analyses of protein structure and DNA curvature. We propose that, in the nucleoprotein complex at a single cer site, a PepA hexamer acts as an adaptor, connecting the heterodimeric recombinase (XerCD) to an ArgR hexamer. This provides a protein core around which the cer site wraps, its exact path being defined by strong sequence-specific interactions with ArgR and XerCD, weak interactions with PepA and sequence-dependent flexibility of cer. The initial association of single-site complexes (pairing) is proposed to occur via an ArgR-PepA interaction. Pairing between sites in a plasmid dimer is stabilized by DNA supercoiling and is followed by a structural isomerization to form a recombination-proficient synaptic complex. We propose that paired structures formed between sites in trans are too short-lived to permit synaptic complex formation. There is thus an energetic barrier to inappropriate recombination reactions. Our proposals are consistent with a wide range of experimental observations.

Effect of combination with an acellular pertussis, diphtheria, tetanus vaccine on antibody response to Hib vaccine (PRP-T)

Acellular pertussis vaccines provide protection against whooping cough with few adverse effects. Their introduction to routine immunisation programmes would be facilitated by their incorporation with other routinely administered vaccines. 262 infants were immunised with an acellular pertussis vaccine containing pertussis toxin and filamentous haemagglutinin, combined with diphtheria and tetanus toxoids. This vaccine was mixed with Haemophilus influenzae type b tetanus toxoid vaccine (PRP-T) so that infants received a single injection at age 2, 3 and 4 months. One month after the third dose the geometric mean titre of Hib IgG antibody was 0.48 microgram ml-1. Eighty-two percent of infants achieved a titre of 0.15 microgram ml-1, with only 27% achieving 1.0 microgram ml-1. This combination vaccine induced low Hib antibody responses when compared to other studies in which PRP-T was mixed with acellular or whole-cell pertussis vaccines. The combined vaccine did, however, appear to prime a subset of 35 infants for response to a fourth dose of PRP-T at 13 months of age, with a rise in GMT from 0.21 microgram ml-1 to 36.6 micrograms ml-1. These data have important implications for the introduction of combination acellular pertussis vaccines.

Intra-specific variation in the photosynthetic responses of cyanobiont lichens from contrasting habitats

The photosynthetic properties of cyanobiont lichens from contrasting habitats were measured to identify whether the increased assimilation rates which characterized Peltigera membranacea (Ach.) Nyl. from an exposed habitat were correlated with increased carbon-concentrating mechanism (CCM) activity. The results were contrasted with data obtained from two populations of Peltigera praetextata (Flörke ex Sommerf.) Zopf collected from dry and damp microhabitats within a shaded woodland and Peltigera leucophlebia (Nyl.) Gyelnik, which has been shown to lack a carbon-concentrating mechanism. The differences in assimilation rates between the cyanobiont lichens were not accounted for by differences in chlorophyll content. Peltigera membranacea from the exposed habitat which had the highest assimilation rates had the lowest Gamma; and K_0·5 values and accumulated the greatest C_i -pool indicating that increased C_i accumulation contributed towards the higher assimilation rates shown by these species. The convexity of the light response curve for the cyanobiont lichens decreased with increasing assimilation rates. This might have indicated a diversion of electron transport to energize the carbon-concentrating mechanism. The apparent quantum efficiency of CO₂ assimilation (ΦCO₂ ) was correlated with the genus of lichen photobiont. All cyanobiont lichens had comparable values for ΦCO₂ which were greater than that of the tripartite Peltigera leucophlebia. Light compensation points reflected the exposure of the habitats with higher compensation points characterizing the cyanobiont population from the exposed crag and the tri-partite population from the open grassland. Carbon isotope discrimination values for organic matter and measured instantaneously were the same for all cyanobiont lichens and were comparable with values recorded for species with a carbon-concentrating mechanism. Carbon isotope measurements for P. leucophlebia were typical of those recorded for species without a carbon-concentrating mechanism. Variation in source isotope signature and refixation of respiratory CO₂ were considered to be significant factors in determining organic matter and instantaneous carbon-isotope discrimination. These factors might have masked any subtle variation in carbon-isotope discrimination which resulted from variable CCM activity. The functional significance of increased carbon-concentrating mechanism activity in cyanobiont lichens occupying exposed habitats is discussed.

Antibody persistence and Haemophilus influenzae type b carriage after infant immunisation with PRP-T

OBJECTIVES

To assess the persistence of serum Haemophilus influenzae type b antibodies and the prevalence of H influenzae type b carriage in a group of preschool age children previously vaccinated in infancy.

DESIGN

Names were randomly selected from immunisation records. Families were visited on five occasions over a period of 12 months and throat swabs were taken from all family members present, with blood obtained from children at the first and last visits.

RESULTS

One hundred and fifty three children at a median age of 3.6 years had a geometric mean titre (GMT) of 1.06 micrograms/ml (95% CI 0.80 to 1.38). Eight per cent had an undetectable antibody concentration, received a booster dose of plain PRP vaccine, and responded with concentrations > 2 micrograms/ml. GMT at 4.5 years of age was 0.89 microgram/ml (0.69 to 1.16). Twelve children who had been exposed to H influenzae had a GMT of 4.7 v 0.8 micrograms/ml for those without exposure.

CONCLUSIONS

Accelerated immunisation against H influenzae without a second year booster results in persistence of satisfactory serum concentrations of antibody to 4.5 years of age. In those with undetectable antibody, immunological memory may still be present.

A case-control investigation of the relation between hyperlipidaemia and calcific aortic valve stenosis

OBJECTIVE

To investigate the relation of hyperlipidaemia to calcific aortic valve stenosis.

DESIGN

A case-control study designed to detect a clinically relevant difference in the fasting plasma concentrations of total cholesterol between the groups at the 5% level with a power of 90%. Predefined subgroup analyses were based on presence of significant coronary disease and valve morphology (that is, bicuspid or tricuspid).

SETTING

A district general hospital.

SUBJECTS

20 patients with severe calcific aortic stenosis and 20 controls.

RESULTS

Mean (SD) fasting plasma total cholesterol in patients with aortic stenosis was 0.79 (1.50) mmol/l greater than in the controls (p = 0.029). The magnitude of differences between patients with aortic stenosis and controls was similar whether the patients had coronary artery disease (0.78 (1.73) mmol/l) or not (0.80 (1.37) mmol/l). The presence of a stenosed tricuspid aortic valve was associated with a significant increase in plasma cholesterol (1.70 (0.87) mmol/l, p = 0.012). For bicuspid valves the degree of elevation of plasma cholesterol was less and not statistically significant.

CONCLUSIONS

Calcific aortic stenosis is associated with hypercholesterolaemia, especially when the valve is tricuspid. Further studies are necessary to confirm that the relation is causal. This finding may have implications for measures to prevent the most common cause of cardiac valve replacement in the developed world.

Colleagues as a resource for learning

As a fairly recent newcomer to nursing and as someone who feels responsible for maintaining his competence to practice, Jamie Simpson has a lot of questions. To get the answers, he often turns to his nurse colleagues.

Antipolysaccharide antibodies in 450 children with otitis media

We have measured antibodies to pneumococcal and Haemophilus polysaccharides in a prospective study of 450 children aged 2-16 years with otitis media requiring grommets (ear tubes). Pneumococcal antibody levels were significantly higher in the 2-6 year (P < 0.004) and 7-10 year (P < 0.04) study groups in comparison with age-matched controls. There was no difference in Haemophilus antibody levels between the study and control group children for the age groups 2-6 years and 11-16 years. Haemophilus antibody levels were significantly lower in the 7-10 year (P < 0.003) group in comparison with age-matched controls. Eighty-eight out of 450 (19.6%) children had pneumococcal antibody levels below the 25th percentile. Nineteen out of 88 (21.6%) children with pneumococcal antibody levels below the 25th centile were test immunized with 23 valent Pneumococcal polysaccharide and unconjugated Haemophilus type b capsular polysaccharide. Of these 19 children (aged 4-11 years), five mounted suboptimal responses to both polysaccharide antigens, whilst one child failed to respond to Haemophilus polysaccharide alone. There was no significant difference in the prevalence of IgG subclass deficiency between the normal responders and poor responders to immunization (P = 0.12). We found no evidence of specific polysaccharide antibody deficiency in the vast majority of the 450 children studied. However, the significance of poor antibody responses to test immunization in a small minority of children with otitis media is unclear. Long-term follow up of these children is required to determine whether poor immunization responses herald the development of frank antibody deficiency.

Discrimination Processes and Shifts in Carboxylation during the Phases of Crassulacean Acid Metabolism

The magnitude and extent of Crassulacean acid metabolism (CAM) activity in two Clusia species was manipulated to investigate the regulation of the distinct CAM phases. First, in response to leaf-air vapor pressure deficit at night, changes in leaf conductance altered on-line carbon-isotope discrimination throughout the theoretical range for dark CO2 uptake during CAM. These ranged from the limit set by phosphoenolpyruvate carboxylase (PEPc) (-6[per mille (thousand) sign], [delta]13C equivalent of -2[per mille (thousand) sign]) to that imposed by diffusion limitation (+4[per mille (thousand) sign], [delta]13C equivalent of -12[per mille (thousand) sign]), but the lowest carbon-isotope discrimination occurred when P[square root]pa was only 0.7. Second, when the availability of external or internal sources of CO2 was reduced for both field- and greenhouse-grown plants, CO2 uptake by day via PEPc during phase II largely compensated. Third, by reducing the dark period, plants accumulated low levels of acidity, and CO2 uptake occurred throughout the subsequent light period. Discrimination switched from being dominated by PEPc (phase II) to ribulose 1,5-bisphosphate carboxylase/oxygenase (phase III), with both enzymes active during phase IV. Under natural conditions, photochemical stability is maintained by extended PEPc activity in phase II, which enhances acid accumulation and delays decarboxylation until temperature and light stress are maximal at midday.

On the Mechanism of Reinitiation of Endogenous Crassulacean Acid Metabolism Rhythm by Temperature Changes

Under continuous light the endogenous Crassulacean acid metabolism (CAM) rhythm of Kalanchoe daigremontiana Hamet et Perrier de la Bathie disappears at high (>29.0[deg]C) or low (<8.0[deg]C) temperatures. We investigated the reinitiation of rhythmicity when temperature was reduced from above the upper and increased from below the lower threshold level via measurements of (a) short-term changes in carbon-isotope discrimination to illustrate shifts between C3 and C4 carboxylation in vivo, and (b) the malate sensitivity of phosphoenolpyruvate carboxylase (PEPC) in vitro. When the net CO2-exchange rhythm disappears at both temperatures, the instantaneous discrimination indicates low PEPC activity. Leaf malate concentration and osmolarity attain high and low values at low and high temperatures, respectively. After small temperature increases or reductions from the low and high temperatures, respectively, the rhythm is reinitiated, with phases shifted by 180[deg] relative to each other. This can be related to the contrasting low and high leaf malate concentrations due to direct inhibition of PEPC and possibly also of the phosphorylation of PEPC by malate. The experimental results were satisfactorily simulated by a mathematical CAM-cycle model, with temperature acting only on the passive efflux of malate from the vacuole. We stress the important role of the tonoplast in malate compartmentation and of malate itself for the reinitiation and generation of endogenous CAM rhythmicity.

A comparative study on the regulation of C(3) and C (4) carboxylation processes in the constitutive crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana and the C(3)-CAM intermediate Clusia minor

A comparison of carbon metabolism in the constitutive crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perr. and the C(3)-CAM intermediate Clusia minor L. was undertaken under controlled environmental conditions where plants experience gradual changes in light intensity, temperature and humidity at the start and end of the photoperiod. The magnitude of CAM activity was manipulated by maintaining plants in ambient air or by enclosing leaves overnight in an atmosphere of N(2) to suppress C(4) carboxylation. Measurements of diel changes in carbonisotope discrimination and organic acid content were used to quantify the activities of C(3) and C(4) carboxylases in vivo and to indicate the extent to which the activities of phosphoenolpyruvate carboxylase (PEPCase), ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and decarboxylation processes overlap at the start and end of the photoperiod. These measurements in vivo were compared with measurements in vitro of changes in the diel sensitivity of PEPCase to malate inhibition. The results demonstrate fundamental differences in the down-regulation of PEPCase during the day in the two species. While PEPCase is inactivated within the first 30 min of the photoperiod in K. daigremontiana, the enzyme is active for 4 h at the start and 3 h at the end of the photoperiod in C. minor. Enclosing leaves in N(2) overnight resulted in a two-to threefold increase in PEPCase-mediated CO(2) uptake during Phase II of CAM in both species. However, futile cycling of CO(2) between malate synthesis and decarboxylation does not occur during Phase II in either species. In terms of overall carbon balance, C(4) carboxylation accounted for approximately 20% of net daytime assimilation in both species under control conditions, increasing to 30-34% after a night in N(2). Although N(2)-treated leaves of K. daigremontiana took up 25% more CO(2) than control leaves during the day this was insufficient to compensate for the loss of CO(2) taken up by CAM the previous night. In contrast, in N(2)-treated leaves of C. minor, the twofold increase in daytime PEPCase activity and the increase in net CO(2) uptake by Rubisco during Phase III compensated for the inhibition of C(4) carboxylation at night in terms of diel carbon balance.

Persistence of antibody responses to Haemophilus influenzae type b polysaccharide conjugate vaccine in children with vertically acquired human immunodeficiency virus infection

BACKGROUND

Recurrent bacterial sepsis is common in pediatric HIV infection and immunization against Haemophilus influenzae type b (Hib) is recommended. Long term persistence of anti-Hib antibody and the need for, or timing of, a booster dose has not been adequately studied.

METHODS

Immunogenicity during a 12-month period following immunization with Hib-tetanus conjugate vaccine (ACT-HIB; Merieux) was evaluated in 48 vertically HIV-infected children and 36 uninfected children, born to HIV-positive mothers. A titer of anti-Hib polysaccharide antibody of > or = 0.15 microgram/ml was considered to indicate short term and > or = 1 microgram/ml long term protection.

RESULTS

At 1 month postvaccination 36 (100%) uninfected and 42 (88%) HIV-infected children achieved titers of > or = 1 microgram/ml. However, by 1 year titers had dropped below this value in 18 (43%) infected compared with only 4 (11%) uninfected children (chi square, 9.7; P = 0.002). Although the rate of fall of antibody titer was greater in uninfected than in infected children, this was no longer the case after adjustment for the 1-month postimmunization titer. The rate of antibody titer decline was not significantly related to HIV disease status or to either the age-related CD4 count at the time of immunization or the change in age-adjusted CD4 count during the 12 months after immunization.

CONCLUSIONS

Not only was the initial antibody response to Hib conjugate vaccine decreased in children with HIV infection and AIDS but also 1 year later only 57% of the initial responders had persisting titers above the level associated with long term protection. The need for reimmunization of children with HIV infection against Hib requires further evaluation.

EITS changes following oleic acid induced lung water

We present the results of using electrical impedance tomographic spectroscopy (EITS) to follow the changes in lung water induced by oleic acid. Measurements were made on three goats before and after the injection of oleic acid. In addition to the EITs measurements, lung water was also measured using a double-indicator technique. Large falls in lung electrical impedance were seen as a result of the increase in lung water but the size of the fall was a function of the frequency at which the measurements were made. These changes have been modelled using the Cole equation. Four-electrode measurements were also made on two extracted porcine lungs and Cole equation modelling carried out following the introduction of saline into the lungs. Results were similar in the two sets of animal experiments.

An electrical impedance tomography microscope

A circular array of 16 electrodes has been constructed for use as an electrical impedance tomography (EIT) microscope. The electrodes were made from 60 microns diameter gold wires anchored to a printed circuit board. The internal diameter of the array was 0.9 mm giving a theoretical spatial resolution of about 100 microns. For EIT imaging, the array was connected to an imaging system operating at 82 kHz. Static images of conducting and insulating filaments (cooper wire and human hair) in saline solution were obtained as well as dynamic imaging sequences of glass microspheres migrating through the array. The interelectrode impedance was typically 5 k omega and the transimpedances ranged from 14 to 210 omega.