Genomic sequence of a Lyme disease spirochaete, Borrelia burgdorferi

The genome of the bacterium Borrelia burgdorferi B31, the aetiologic agent of Lyme disease, contains a linear chromosome of 910,725 base pairs and at least 17 linear and circular plasmids with a combined size of more than 533,000 base pairs. The chromosome contains 853 genes encoding a basic set of proteins for DNA replication, transcription, translation, solute transport and energy metabolism, but, like Mycoplasma genitalium, it contains no genes for cellular biosynthetic reactions. Because B. burgdorferi and M. genitalium are distantly related eubacteria, we suggest that their limited metabolic capacities reflect convergent evolution by gene loss from more metabolically competent progenitors. Of 430 genes on 11 plasmids, most have no known biological function; 39% of plasmid genes are paralogues that form 47 gene families. The biological significance of the multiple plasmid-encoded genes is not clear, although they may be involved in antigenic variation or immune evasion.

Basic principles of thermal dosimetry and thermal thresholds for tissue damage from hyperthermia

This paper is one of several in this Special Issue of the International Journal of Hyperthermia that discusses the current state of knowledge about the human health risks of hyperthermia. This special issue emanated from a workshop sponsored by the World Health Organization in the Spring of 2002 on this topic. It is anticipated that these papers will help to establish guidelines for human exposure to conditions leading to hyperthermia. This comprehensive review of the literature makes it clear that much more work needs to be done to clarify what the thresholds for thermal damage are in humans. This review summarizes the basic principles that govern the relationships between thermal exposure (temperature and time of exposure) and thermal damage, with an emphasis on normal tissue effects. Methods for converting one time-temperature combination to a time at a standardized temperature are provided as well as a detailed discussion about the underlying assumptions that go into these calculations. There are few in vivo papers examining the type and extent of damage that occurs in the lower temperature range for hyperthermic exposures (e.g. 39-42 degrees C). Therefore, it is clear that estimation of thermal dose to effect at these thermal exposures is less precise in that temperature range. In addition, there are virtually no data that directly relate to the thermal sensitivity of human tissues. Thus, establishment of guidelines for human exposure based on the data provided must be done with significant caution. There is detailed review and presentation of thermal thresholds for tissue damage (based on what is detectable in vivo). The data are normalized using thermal dosimetric concepts. Tables are included in an Appendix Database which compile published data for thresholds of thermal damage in a variety of tissues and species. This database is available by request (contact MWD or PJH), but not included in this manuscript for brevity. All of the studies reported are for single acute thermal exposures. Except for brain function and physiology (as detailed in this issue by Sharma et al) one notes the critical lack of publications examining effects of chronic thermal exposures as might be encountered in occupational hazards. This review also does not include information on the embryo, which is covered in detail elsewhere in this volume (see article by Edwards et al.) as well as in a recent review on this subject, which focuses on thermal dose.

Transgenerational effects of prenatal exposure to the Dutch famine on neonatal adiposity and health in later life

OBJECTIVE

Maternal undernutrition during gestation is associated with increased metabolic and cardiovascular disease in the offspring. We investigated whether these effects may persist in subsequent generations.

DESIGN

Historical cohort study.

SETTING

Interview during a clinic or home visit or by telephone.

POPULATION

Men and women born in the Wilhelmina Gasthuis in Amsterdam between November 1943 and February 1947.

METHODS

We interviewed cohort members (F1) born around the time of the 1944-45 Dutch famine, who were exposed or unexposed to famine in utero, about their offspring (F2).

MAIN OUTCOME MEASURES

Birthweight, birth length, ponderal index and health in later life (as reported by F1) of the offspring (F2) of 855 participating cohort members, according to F1 famine exposure in utero.

RESULTS

F1 famine exposure in utero did not affect F2 (n = 1496) birthweight, but, among the offspring of famine-exposed F1 women, F2 birth length was decreased (-0.6 cm, P adjusted for F2 gender and birth order = 0.01) and F2 ponderal index was increased (+1.2 kg/m(3), P adjusted for F2 gender and birth order = 0.001). The association remained unaltered after adjusting for possible confounders. The offspring of F1 women who were exposed to famine in utero also had poor health 1.8 (95% CI 1.1-2.7) times more frequently in later life (due to miscellaneous causes) than that of F1 unexposed women.

CONCLUSIONS

We did not find transgenerational effects of prenatal exposure to famine on birthweight nor on cardiovascular and metabolic disease rates. F1 famine exposure in utero was, however, associated with increased F2 neonatal adiposity and poor health in later life. Our findings may imply that the increase in chronic disease after famine exposure in utero is not limited to the F1 generation but persists in the F2 generation.

Dating the origin of the CCR5-Delta32 AIDS-resistance allele by the coalescence of haplotypes

The CCR5-Delta32 deletion obliterates the CCR5 chemokine and the human immunodeficiency virus (HIV)-1 coreceptor on lymphoid cells, leading to strong resistance against HIV-1 infection and AIDS. A genotype survey of 4,166 individuals revealed a cline of CCR5-Delta32 allele frequencies of 0%-14% across Eurasia, whereas the variant is absent among native African, American Indian, and East Asian ethnic groups. Haplotype analysis of 192 Caucasian chromosomes revealed strong linkage disequilibrium between CCR5 and two microsatellite loci. By use of coalescence theory to interpret modern haplotype genealogy, we estimate the origin of the CCR5-Delta32-containing ancestral haplotype to be approximately 700 years ago, with an estimated range of 275-1,875 years. The geographic cline of CCR5-Delta32 frequencies and its recent emergence are consistent with a historic strong selective event (e.g. , an epidemic of a pathogen that, like HIV-1, utilizes CCR5), driving its frequency upward in ancestral Caucasian populations.

Use of a whole genome approach to identify vaccine molecules affording protection against Streptococcus pneumoniae infection

Microbial targets for protective humoral immunity are typically surface-localized proteins and contain common sequence motifs related to their secretion or surface binding. Exploiting the whole genome sequence of the human bacterial pathogen Streptococcus pneumoniae, we identified 130 open reading frames encoding proteins with secretion motifs or similarity to predicted virulence factors. Mice were immunized with 108 of these proteins, and 6 conferred protection against disseminated S. pneumoniae infection. Flow cytometry confirmed the surface localization of several of these targets. Each of the six protective antigens showed broad strain distribution and immunogenicity during human infection. Our results validate the use of a genomic approach for the identification of novel microbial targets that elicit a protective immune response. These new antigens may play a role in the development of improved vaccines against S. pneumoniae.

Chloroquine neuromyotoxicity. Clinical and pathologic perspective

Six cases of toxic myopathy and/or neuropathy with chloroquine and/or hydroxychloroquine therapy are described. Two patients had unique clinical and pathologic evidence of cardiomyopathy secondary to chloroquine or hydroxychloroquine therapy. One patient had polyneuropathy secondary to chloroquine toxicity. This may be the first documentation of several features of chloroquine/hydroxychloroquine toxicity: morphologic changes in human peripheral nerve in chloroquine toxicity; chloroquine/hydroxychloroquine cardiomyopathy diagnosed by endomyocardial biopsy; and hydroxychloroquine myotoxicity. Chloroquine is a neuromyotoxin that affects nerves and cardiac and skeletal muscles. Discontinuation of chloroquine and hydroxychloroquine resulted in marked improvement in most cases. The reversibility of the symptoms emphasizes the importance of recognizing potential signs of nerve, muscle, and cardiac toxicity in patients being treated with chloroquine or hydroxychloroquine.

OSCE checklists do not capture increasing levels of expertise

PURPOSE

To evaluate the effectiveness of binary content checklists in measuring increasing levels of clinical competence.

METHOD

Fourteen clinical clerks, 14 family practice residents, and 14 family physicians participated in two 15-minute standardized patient interviews. An examiner rated each participant's performance using a binary content checklist and a global process rating. The participants provided a diagnosis two minutes into and at the end of the interview.

RESULTS

On global scales, the experienced clinicians scored significantly better than did the residents and clerks, but on checklists, the experienced clinicians scored significantly worse than did the residents and clerks. Diagnostic accuracy increased for all groups between the two-minute and 15-minute marks without significant differences between the groups.

CONCLUSION

These findings are consistent with the hypothesis that binary checklists may not be valid measures of increasing clinical competence.

Therapeutic implications of patterns of recurrence in cancer of the uterine cervix

Five hundred twenty-six patients with invasive cervical cancer, treated at the University of Kentucky from 1964 to 1976, were followed 2--12 years after therapy. One hundred and sixty patients (31%) developed tumor recurrence. Recurrent cancer was noted with 1 year after therapy in 58% of patients and within 2 years of treatment in 76% of patients. Only 6% of patients with recurrent cervical cancer survived 3 or more years. Stage of disease, cell type, lesion size, and the presence of lymph vascular space invasion by tumor cells were all shown to be prognostically significant. The addition of extrafascial hysterectomy to radiation therapy significantly decreased the incidence of recurrence in stage IB cervical tumors 5 cm or more in diameter. Analysis of this data suggests that radical hysterectomy and pelvic lymphadenectomy is as effective as irradiation only in the treatment of large cell squamous carcinomas 2 cm or less in diameter.

Risk factors for lack of detectable antibody following hepatitis B vaccination of Minnesota health care workers

OBJECTIVE

To assess the presence of antibody to hepatitis B surface antigen (anti-HBs) at postvaccination testing in Minnesota health care workers receiving recombinant hepatitis B vaccines, and to identify risk factors for lacking anti-HBs following hepatitis B vaccination.

DESIGN

Retrospective cohort study.

SETTING

Ten acute care hospitals in Minnesota.

PARTICIPANTS

A total of 595 health care workers who had received hepatitis B vaccine (Recombivax HB or Engerix-B) between June 1987 and December 1991 and who underwent postvaccination testing for anti-HBs within 6 months after receiving the third dose of vaccine.

MAIN OUTCOME MEASURE

Presence or absence of anti-HBs following hepatitis B vaccination.

RESULTS

Five variables were independently associated with lacking anti-HBs by multivariate analysis: vaccine brand, smoking status, gender, age, and body mass index. Stratifying by vaccine brand demonstrated that age (P = .01), body mass index (P < .01), and smoking status (P < .01) were associated with lacking anti-HBs only for Recombivax HB recipients; and gender (P = .03) was associated with lacking anti-HBs only for Engerix-B recipients. After controlling for smoking status, age, gender, and body mass index, recipients of Recombivax HB were more likely to lack anti-HBs than recipients of Engerix-B (relative risk, 2.3; 95% confidence interval, 1.1 to 4.7; P = .02).

CONCLUSIONS

Results indicate that certain populations of health care workers are at increased risk of not responding to hepatitis B vaccination. Further studies evaluating immunogenicity of currently available recombinant hepatitis B vaccines in persons at high risk for primary vaccine failure are needed.

Mental stress-induced ischemia in the laboratory and ambulatory ischemia during daily life. Association and hemodynamic features

BACKGROUND

The purpose of this study was to determine the correspondence of mental stress-induced ischemia in the laboratory with ambulatory ischemia and to assess the relationship between hemodynamic responses to mental stress and the occurrence of ischemia. Although exercise testing is usually used to elicit myocardial ischemia, ischemia during daily life usually occurs at relatively low heart rates and in the absence of strenuous physical exercise. Mental stress has been shown to trigger ischemic events in the laboratory at lower heart rates but at blood pressures comparable to exercise. We therefore compared the extent to which mental stress and exercise testing identify patients who develop ischemia out of hospital.

METHODS AND RESULTS

One hundred thirty-two patients with documented coronary disease and recent evidence of exercise-induced myocardial ischemia underwent 48-hour ambulatory monitoring and radionuclide ventriculography during exercise and mental stress testing. Patients who displayed mental stress-induced ischemia in the laboratory were more likely to exhibit ischemia during daily life (P < .021). Furthermore, patients who exhibited ischemia during ambulatory monitoring displayed larger diastolic blood pressure (P < .006), heart rate (P < .039), and rate-pressure product responses (P < .018) during mental stress.

CONCLUSIONS

Among patients with prior positive exercise stress tests, mental stress-induced ischemia, defined by new wall motion abnormalities, predicts daily ischemia independent of exercise-induced ischemia. Exaggerated hemodynamic responses during mental stress testing also identify individuals who are more likely to exhibit myocardial ischemia during daily life and mental stress.

Absence of HIV infection in blood donors with indeterminate western blot tests for antibody to HIV-1

To determine whether apparently healthy persons who have had repeatedly reactive enzyme immunoassays and an indeterminate Western blot assay for antibody to the human immunodeficiency virus type 1 (HIV-1) are infected with HIV-1 or HIV-2, we studied 99 such volunteer blood donors in a low-risk area of the country. The subjects were interviewed about HIV risk factors. Coded blood specimens were tested again for HIV-1 antibody (by two different enzyme immunoassays, a Western blot assay and a radioimmunoprecipitation assay) and for HIV-2 antibody by enzyme immunoassay, for HIV-1 by the serum antigen test, for HIV-1 by culture, for human T-cell leukemia virus Type I or II antibody by enzyme immunoassay, and for sequences of HIV DNA by the polymerase chain reaction. Of the 99 blood donors, 98 reported no risk factors for HIV-1 infection; 1 donor had used intravenous drugs. After a median of 14 months (range, 1 to 30) from the time of the initial test, 65 subjects (66 percent) were still repeatedly reactive for HIV-1 antibody on at least one immunoassay. In 91 subjects (92 percent) the Western blot results were still indeterminate, whereas in 8 they were negative. No donor met the criteria for a positive Western blot assay for HIV-1, and none had evidence of HIV-1 or HIV-2 infection on culture or by any other test. We conclude that persons at low risk for HIV infection who have persistent indeterminate HIV-1 Western blots are rarely if ever infected with HIV-1 or HIV-2.

Ferromagnetic imprinting of nuclear spins in semiconductors

We examine how a ferromagnetic layer affects the coherent electron spin dynamics in a neighboring gallium arsenide semiconductor. Ultrafast optical pump-probe measurements reveal that the spin dynamics are unexpectedly dominated by hyperpolarized nuclear spins that align along the ferromagnet's magnetization. We find evidence that photoexcited carriers acquire spin-polarization from the ferromagnet, and dynamically polarize these nuclear spins. The resulting hyperfine fields are as high as 9000 gauss in small external fields (less than 1000 gauss), enabling ferromagnetic control of local electron spin coherence.

Glucose tolerance and smoking: a population study of oral and intravenous glucose tolerance tests in middle-aged men

The oral and intravenous glucose tolerance tests have been compared in middle-aged, normal-weight male non-smokers, ex-smokers and smokers who participated in a general health screening programme in Malmö, Sweden. Subjects with diabetes, previous gastric resection and/or present medication with diuretic agents were excluded. No difference was found when comparing fasting glucose in non-smokers, ex-smokers and smokers. In the oral glucose tolerance test, plasma glucose at 40 and 60 min increased stepwise from non-smokers (8.7 and 7.4 mmol/l) to ex-smokers (8.9 and 7.5 mmol/l), smokers (9.2 and 7.9 mmol/l) and heavy smokers (9.7 and 8.2 mmol/l). Blood glucose levels at 120 min were inversely arranged. Plasma insulin at 120 min was lower in heavy smokers (16.2 mU/l) than in non-smokers (24.8 mU/l). The mean intravenous glucose tolerance test k-value was lower in smokers than in non-smokers. K-values below 1.0 were twice as common in smokers (30%) as in non-smokers. It is concluded that smoking has a clinically significant influence on both the oral and intravenous glucose tolerance tests.

VOIDING PATTERN AND ACQUISITION OF BLADDER CONTROL FROM BIRTH TO AGE 6 YEARS—A LONGITUDINAL STUDY

PURPOSE

We describe the voiding pattern and acquisition of bladder control in healthy children up to age 6 years.

MATERIALS AND METHODS

We determined age for daytime and nighttime dryness, voiding patterns, voiding volumes and post-void residual volume per 4 hours individually and noninvasively every 3 months up to age 3 years and every 6 months up to age 6 years in 36 female and 23 male patients using 4-hour voiding observation and uroflowmetry/ultrasound.

RESULTS

Median age for attaining daytime and nighttime dryness was 3.5 and 4 years, respectively. No significant difference was found between girls and boys. All but 1 child attained daytime dryness an average of 10 months before attaining nighttime dryness. Bladder sensation was reported in 31%, 79% and 100% of patients at ages 2, 3 and 4 years, respectively. Median bladder capacity was 67 ml, 123 ml and 140 ml at years 1, 3 and 6, respectively. Median post-void residual volume was 5.5 ml, 0 ml and 2 ml at ages 1, 3 and 6 years, respectively.

CONCLUSIONS

Today bladder control is acquired at a later stage despite earlier awareness of bladder function. The occurrence of bladder sensation from age 1.5 years motivates an earlier start with toilet training. Infants with small post-void residual volume at age 6 months or large bladder capacity will probably attain daytime dryness earlier than those with large post-void residual volume at age 6 months or small bladder capacity.

Portal and umbilical venous blood supply to the liver in the human fetus near term

OBJECTIVES

To determine the contribution of the umbilical (UV) and portal (PV) veins to blood supply to the human fetal liver in a low-risk population near term, and to assess the distribution between the left and right lobes.

METHODS

In 91 low-risk pregnancies with normally grown fetuses at 36 weeks of gestation we measured the distribution of blood in the UV and PV to the right and left hepatic lobes using ultrasound imaging and Doppler techniques.

RESULTS

The median (10(th), 90(th) centile) total UV return was 205 (127, 294) mL/min, of which 25% (13, 47%) was shunted through the ductus venosus, 55% (35, 66%) was distributed to the left hepatic lobe, and 20% (11, 30%) was distributed to the right hepatic lobe. While the left lobe was supplied exclusively by the UV, the right lobe received 50% (20, 70%; 37 (16, 65) mL/min) of its venous blood supply from the PV. The total venous blood supply to the liver parenchyma was 185 (114, 277) mL/min; 21% (8, 34%) came from the PV supply to the right lobe and the remainder came from the UV supply to both lobes.

CONCLUSIONS

The venous supply to the left lobe is from nutrient-rich UV blood; for the right lobe, half is from UV blood and half from nutrient-poor PV blood. This watershed between the portal and umbilical venous flows to the fetal liver suggests a corresponding functional dichotomy; this may be modified by hemodynamic influences, with long-term consequences.

Characteristics of the major internal protein and RNA-dependent DNA polymerase of bovine leukaemia virus

A virus designated bovine leukaemia virus (BLV), associated with leukaemia in cattle and previously demonstrated to induce the disease in sheep, was purified from chronically infected sheep cell cultures. Electrophoretic analysis showed a major protein of mol. wt. about 24,000 (p24) which reacted in gel diffusion and complement-fixation tests with sera from naturally infected cattle, experimentally infected sheep, and guinea pigs immunized with p24. BLV p24 has an isoelectric point of 8-6. Interspecies antigenic reactivities characteristic of mammalian Type C virus p30s were not detected in disrupted BLV or on p24. Sheep and guinea pig antisera to BLV, reactive with p24, also did not precipitate several Type C virus p30s in radioimmunoassays. BLV is also distinguished from Type C viruses and resembles mouse mammary tumour virus and Mason-Pfezer virus in having an RNA-dependent DNA polymerase which is preferentially active in the presence of Mg++ when synthetic templates are used. Along with previously published morphological data, the above indicates that BLV is not a Type C virus as classically defined. Four hundred and forty one human sera from cancer patients and matched controls were non-reactive with disruped BLV, BLV infected cells, and BLV p24 in complement-fixation tests.

Longitudinal reference ranges for ductus venosus flow velocities and waveform indices

OBJECTIVES

Serial Doppler measurements of the ductus venosus are used increasingly for monitoring fetuses at risk of hemodynamic compromise, but existing reference ranges are based on cross-sectional studies and thus are less suitable for comparison with serial measurements. We aimed to establish longitudinal reference ranges for ductus venosus flow velocities and waveform indices and to provide the necessary terms for calculating conditional reference ranges for serial measurements.

METHODS

This was a longitudinal study of 160 low-risk pregnancies. Pulsed Doppler ultrasound was used to record ductus venosus blood flow velocities at 4-week intervals from 20-22 weeks of gestation onwards.

RESULTS

With a success rate of 93%, 547 measurements (four or five in each fetus) were used to establish reference ranges. The time-averaged maximum velocity was 50 cm/s at 21 weeks of gestation, increased to 60 cm/s at 32 weeks, and remained so until term. Similarly, the peak systolic velocity increased from 59 cm/s at 21 weeks to 71 cm/s at 31 weeks and remained so until term. The end-diastolic velocity showed a continuous increase from 31 cm/s at 21 weeks to 43 cm/s at 40 weeks. The pulsatility index for veins decreased from 0.57 at 21 weeks to 0.44 at 40 weeks. When conditioned by a previous measurement, the reference ranges for the next observation became narrower and commonly shifted compared with those of the entire population.

CONCLUSION

The new longitudinal reference ranges presented here reflect the development of the ductus venosus flow velocities and velocity indices and are thus appropriate for serial measurements, particularly if conditional terms are included.

Interleukin 7 receptor ligation stimulates tyrosine phosphorylation, inositol phospholipid turnover, and clonal proliferation of human B-cell precursors

Functional interleukin 7 (IL-7) receptors are expressed on the surface of multiphenotypic, biphenotypic, and immature B-lineage human lymphoid precursor cells with germ-line immunoglobulin heavy-chain genes but not on more mature B-lineage lymphoid cells with rearranged and/or expressed immunoglobulin heavy-chain genes. Thus, IL-7 may have an important regulatory role during the earliest stages of human B-cell ontogeny. The engagement of the surface IL-7 receptors on immature B-cell precursor cells with recombinant human IL-7 (rhIL-7) results in enhanced tyrosine phosphorylation of multiple phosphoproteins, stimulates inositol phospholipid turnover and DNA synthesis, and promotes their clonal proliferation. These effects are (i) specific for rhIL-7, since rhIL-3, rhIL-4, rhIL-5, rhIL-6, and recombinant human granulocyte colony-stimulating factor do not elicit similar activities on IL-7 receptor-positive human pro-B cells; and (ii) mediated by IL-7 receptors, since they are not observed in IL-7 receptor-negative B-lineage lymphoid cell populations. rhIL-7-induced tyrosine phosphorylation on the 35-, 53-, 55-, 62-, 69-, 76-, 94-, 150-, 170-, and 190-kDa substrates as well as rhIL-7-induced stimulation of inositol phospholipid turnover are abrogated by the tyrosine kinase inhibitor genistein. These results demonstrate that the IL-7 receptor on immature human B-cell precursor populations is intimately linked to a functional tyrosine kinase pathway and tyrosine phosphorylation is an important and perhaps mandatory step in the generation of the IL-7 receptor-linked transmembrane signal.