Determinants of ovine compact bone viscoelastic properties: effects of architecture, mineralization, and remodeling

Significant decreases in ovine compact bone viscoelastic properties (specifically, stress-rate sensitivity, and damping efficiency) are associated with three years of ovariectomy and are particularly evident at higher frequencies [Proc. Orthop. Res. Soc. 27 (2002) 89]. It is unclear what materials or architectural features of bone are responsible for either the viscoelastic properties themselves, or for the changes in those properties that were observed with estrogen depletion. In this study, we examined the relationship between these viscoelastic mechanical properties and features involving bone architecture (BV/TV), materials parameters (ash density, %mineralization), and histologic evidence of remodeling (%remodeled, cement line interface). The extent of mineralization was inversely proportional to the material's efficiency in damping stress oscillations. The damping characteristics of bone material from ovariectomized animals were significantly more sensitive to variation in mineralization than was bone from control animals. At low frequencies (6 Hz or less), increased histologic evidence of remodeling was positively correlated with increased damping efficiency. However, the dramatic decreases in stress-rate sensitivity that accompanied 3-year ovariectomy were seen throughout the bone structure and occurred even in areas with little or no secondary Haversian remodeling as well as in areas of complete remodeling. Taken together, these data suggest that, while the mineral component may modify the viscoelastic behavior of bone, the basic mechanism underlying bone viscoelastic behavior, and of the changes in that behavior with estrogen depletion, reside in a non-mineral component of the bone that can be significantly altered in the absence of secondary remodeling.

Combined anterior and posterior inguinal hernia repair: Intermediate recurrence rates with three groups of surgeons

BACKGROUND

Use of a bilayer polypropylene mesh device (BPMD) for inguinal hernia repair began in 1998. Intermediate follow-up is now available for patients undergoing repair by three groups of surgeons.

METHODS

Surgeons whose practice is dedicated to hernia repair trained preceptors who, in turn, assisted in the training of other surgeons in this new technique. All three groups provided information regarding their recurrence rates with this technique.

RESULTS

Recurrence rates were similar for all three groups. Hernia specialists reported three recurrences out of 4,801 repairs. Preceptors reported one recurrence in 3,780 repairs. Other surgeons reported one failure in 3,369 repairs.

CONCLUSIONS

Use of the BPMD (Prolene Hernia System) provides reliable results in the hands of hernia specialists, as well as general surgeons whose practices are not concentrated on the management of hernias.

Outbreak of isoniazid resistant tuberculosis in north London

BACKGROUND

A description is given of a major outbreak of isoniazid monoresistant tuberculosis (TB) chiefly in north London, including prisons. The earliest case was diagnosed in 1995 with most cases appearing after 1999.

METHODS

Confirmation of a local cluster of cases was confirmed by restriction fragment length polymorphism (RFLP IS6110) typing or "rapid epidemiological typing" (RAPET). Further cases were found by retrospective analysis of existing databases, prospective screening of new isolates, and targeted epidemiological case detection including questionnaire analysis.

RESULTS

By the end of 2001, 70 confirmed cases in London had been linked with a further 13 clinical cases in contacts and nine epidemiologically linked cases outside London. The epidemic curve suggests that the peak of the outbreak has not yet been reached. Cases in the outbreak largely belong to a social group of young adults of mixed ethnic backgrounds including several individuals from professional/business backgrounds. Compared with other cases of TB reported to the enhanced surveillance scheme in London during 1999-2001, the cases are more likely to be of white (26/70 (37%) v 1308/7666 (17%)) or black Caribbean ethnicity (17/70 (24%) v 312/7666 (4%)), born in the UK (41/70 (59%) v 1335/7666 (17%)), and male (52/70 (74%) v 4195/7666 (55%)). Drug misuse and/or prison detention are factors common to many cases.

CONCLUSIONS

The investigation of the outbreak revealed significant problems on an individual patient and population based level including difficulties with contact tracing, compliance, and the risk of developing multidrug resistance. This incident has demonstrated the value of molecular strain typing in investigating an extensive outbreak of TB. This is the first documented outbreak involving a UK prison.

Epidemiology of HIV in young people in England, Wales and Northern Ireland

We describe the epidemiology of HIV among young people (15-24 years) in England, Wales and Northern Ireland (E, W&NI) between 1997 and 2001 inclusive. Rising rates of sexually transmitted infections (STIs) and 'risk' behaviours suggest that they are at increased risk of acquiring HIV. Data from three national surveillance systems are reviewed. Over the period, 1,624 young people were diagnosed with HIV (10% of all new diagnoses). In 1997 there were 254 new diagnoses, rising to 493 in 2001, a 1.9-fold increase. Of the total, 890 (55%) were heterosexually infected (81% female), 631 through sex between men, and the remainder via other routes. Where probable country of infection was reported (1,139), 618 (54%) were infected in Africa and 362 (32%) in the UK. In 1997, 675 young people accessed HIV-related services, rising to 975 in 2001: an increase of 1.4 fold. In 2001, for 34 of those accessing services the likely route of infection was perinatal. Between 1997 and 2001 inclusive, HIV prevalence among young heterosexual genitourinary medicine (GUM) clinic attendees was 0.17% (193/116,443), and for young homo/bisexual males, 3.4% (174/5,086). Sixty-five percent (104/159) of previously undiagnosed HIV-infected heterosexuals and 47% (51/108) of previously undiagnosed HIV-infected homo/bisexual males left the clinic unaware of their infection. In 2000 and 2001, overall prevalence was 0.11% (77/70,455) among young women giving birth. HIV diagnoses in young people have increased in recent years, while HIV prevalence among young people attending GUM clinics and giving birth has remained low. However, with dramatic increases in chlamydia rates among young women over the past decade, and the highest rates of gonorrhoea and concurrent partnerships among young people, concern about the potential for HIV transmission remains.

Urethral retro-resistance pressure: A new clinical measure of urethral function

AIMS

The urethral retro-resistance pressure (URP) is a new retrograde measurement of urethral function. URP is the pressure required to achieve and maintain an open sphincter. The assessment of any potential diagnostic measure must include an evaluation in individuals both with and without disease. In this study, we examined URP values in women without urinary incontinence.

METHODS

Four centers enrolled 61 women who did not report symptoms of urinary incontinence, and who had negative standing stress tests (SST). Each center was to perform three consecutive URP measurements on each subject. At two centers, 32 subjects returned in 3-7 days for three additional URP measurements. We compared the average URP in this asymptomatic population to the average URP from women symptomatic of stress urinary incontinence (SUI) derived from a previous study. We evaluated the within-subject variation of the URP measurement at a single visit and the within-subject change in URP over time using test and retest values.

RESULTS

The mean age was 33 +/- 9 years and the mean body mass index (BMI) was 24 +/- 6. URP values were normally distributed. The mean URP at visit 1 was 112.6 +/- 39.2 cm H2O (n = 60). This was statistically significantly different from the mean URP of symptomatic women (69.9 cm H2O, P < 0.0001). The within-subject standard deviation of URP at visit 1 was 12.6 +/- 12.6 cm H2O (n = 60) and at retest visit was 9.3 +/- 6.2 cm H2O (n = 32). For the retest cases, the mean URP at visit 1 was 113.9 +/- 39.9 cm H2O (n = 32) and at retest visit was 125.5 +/- 33.9 cm H2O (n = 32) (Wilcoxon Signed Rank test, P = 0.145).

CONCLUSIONS

The mean URP measurement obtained in this study of asymptomatic women showed significantly higher values when compared to our study in women with SUI. The URP measurements were consistent within the same subject. Furthermore, there was no statistically significant difference in the URP measurement from visit 1 to retest visit. The data suggest that URP shows promise as a physiological urethral pressure measurement.

Relationship of urethral retro-resistance pressure to urodynamic measurements and incontinence severity

AIMS

The urethral retro-resistance pressure (URP) is a retrograde urethral pressure profile measured by a new urodynamic measurement system.1GYNECARE MoniTorr Urodynamic Measurement System (ETHICON, Inc., Somerville, NJ). URP is the pressure required to achieve and maintain an open sphincter. This clinical investigation focused on a comparison of URP to standard urodynamic measurements and an examination of their relationship to incontinence severity.

METHODS

Twenty-two centers enrolled 258 stress incontinent women in a randomized, crossover study of two groups: (1) test procedure followed by multichannel urodynamics, (2) multichannel urodynamics followed by test procedure. We defined incontinence severity categories using 24 hr urine loss and assessed these categories using incontinence quality of life (I-QOL), urinary incontinence severity score (UISS), incontinence visual analogue score (VAS), URP, maximum urethral closure pressure (MUCP), and leak point pressure (LPP).

RESULTS

The mean age was 56.2 (+/-12) years. No order effect was present. The correlation coefficient between URP and MUCP was 0.31 (95% CI 0.19-1, P < 0.0001); between URP and LPP was 0.28 (95% CI 0.12-1, P = 0.003); and between MUCP and LPP was 0.14 (95% CI-0.04-1, P = 0.101). The mean values for URP across symptom severity categories were significantly different (P = 0.028) and decreased with increasing severity. The mean values for MUCP and LPP did not decrease with increasing severity.

CONCLUSIONS

The study demonstrated that URP had a consistent relationship with incontinence severity. The data suggested that URP is a physiological measure of urethral function and may have clinical utility as a diagnostic tool. Future outcomes-based research is necessary to establish the predictive value of URP, MUCP, and LPP measurements in terms of incontinence cure rates and diagnosis of sphincter dysfunction.

Core biopsy versus FNAC for palpable breast cancers. Is image guidance necessary?

The aim of this study was to assess the efficacy of free-hand percutaneous core biopsy (FHCB) and to determine the role of fine needle aspiration cytology (FNAC) as diagnostic tools for palpable radiologically-suspicious breast lumps. This retrospective study was based on reviewing the clinical records of all patients diagnosed as having breast cancer between January 1999 and December 2000 and patients who had benign lesions, but suspicious breast imaging at triple assessment. Absolute sensitivity of FHCB for diagnosing cancer in palpable lesions was 98.7% compared with 51.3% for FNAC. The difference in the sensitivity of FHCB and FNAC was statistically significant (P<0.005, Wilcoxon matched pair test). Since 94.8% of radiologically-suspicious lumps were shown to be cancers, we advocate FHCB for all patients presenting with radiologically suspicious palpable lumps to our breast clinic. We also conclude that the sensitivity of FHCB for the diagnosis of malignancy in palpable radiologically-suspicious breast lesions is so high that image-guidance is unnecessary.

Determination of Helicobacter pylori vacA allelic types by single-step multiplex PCR

AIMS

To develop and evaluate a novel multiplex PCR assay that enables definition of Helicobacter pylori vacA allelic type in a single reaction.

METHODS AND RESULTS

Application of the one-step system to DNA extracts from 22 cultures of known vacA genotype demonstrated that it was highly accurate. Analysis of 15 matched gastric biopsy/culture pairs generated exactly correlating genotype profiles. vacA genotypes were determined from an additional 62/70 gastric biopsies from dyspeptic patients of known H. pylori positive status by the one-step assay, compared with 63/70 by the original two-reaction test. Types s1/m1, s1/m2 and s2/m2 were identified in 51.9%, 31.2% and 16.9% of biopsies, respectively.

CONCLUSIONS

The multiplex PCR system developed enables rapid one-step vacA genotyping that is accurate, easy to interpret and more economical than the alternative multiple-reaction tests. Application of this system to gastric biopsies from patients in South-east England demonstrated that s1/m1 was the most common genotype, while s1/m2 and s2/m2 were less prevalent.

SIGNIFICANCE AND IMPACT OF THE STUDY

This simple one-step system can be applied direct to antral gastric biopsies without the need for culture, thereby facilitating rapid surveillance of vacA genotype in relation to geographical location and disease status.

Extended acclimatization is required to eliminate stress effects of periodic blood-sampling procedures on vasoactive hormones and blood volume in beagle dogs

Important in all experimental animal studies is the need to control stress stimuli associated with environmental change and experimental procedures. As the stress response involves alterations in levels of vasoactive hormones, ensuing changes in cardiovascular parameters may confound experimental outcomes. Accordingly, we evaluated the duration required for dogs (n = 4) to acclimatized to frequent blood sampling that involved different procedures. On each sampling occasion during a 6-week period, dogs were removed from their pen to a laboratory area and blood was collected either by venepuncture (days 2, 15, 34, 41) for plasma renin activity (PRA), epinephrine (EPI), norepinephrine, aldosterone, insulin, and atrial natriuretic peptide, or by cannulation (dogs restrained in slings; days 1, 8, 14, 22, 30, 33, 37, 40) for determination of haematocrit (HCT) alone (days 1 to 22) or HCT with plasma volume (PV; days 30 to 40). PRA was higher on days 2 and 15 compared with days 34 and 41 and had decreased by up to 48% by the end of the study (day 41 vs day 15; mean/SEM: 1.18/0.27 vs 2.88/0.79 ng ANG I/ml/h, respectively). EPI showed a time-related decrease from days 2 to 34, during which mean values had decreased by 51% (mean/SEM: 279/29 vs 134/20.9 pg/ml for days 2 and 34, respectively), but appeared stable from then on. None of the other hormones showed any significant variability throughout the course of the study. HCT was relatively variable between days 1 to 22 but stabilized from day 30, after which all mean values were approximately 6% lower than those between days 1 and 8. We conclude that an acclimatization period of at least 4 weeks is required to eliminate stress-related effects in dogs associated with periodic blood sampling.

Image-guided surgery for anal fistula in a 0.5T interventional MRI unit

PURPOSE

To determine whether MR-guided anorectal surgery is feasible, and to develop techniques for MR-guided anal fistula surgery.

MATERIALS AND METHODS

Six patients with pilonidal sinus (PNS), and 21 with suspected anal fistulae were operated on in the GE Signa SPIO 0.5T interventional MRI unit. Procedures were performed with magnet-safe Lockhart-Mummery fistula probes. Preprocedural and intra-operative MRI (IOMRI) techniques were used to identify the extent of the fistula tracts and septic foci, and to ensure the adequacy of the surgical procedure.

RESULTS

IOMRI demonstrated the PNS lesions and the adequacy of excision. Imaging failed to demonstrate a fistula in two patients, as confirmed by surgical examination. No images were obtained in one patient due to his size (weight in excess of 100 kg). In 18 patients a fistula tract or abscess was demonstrated and IOMRI was used to assess the adequacy of the surgical procedure. In three patients this demonstrated incomplete drainage of septic foci, which was not obvious on inspection of the surgical field. We believe that in these patients IOMRI prevented an incomplete procedure and the potential requirement for a second operation. Further surgery was performed to rectify this situation. The fistula tract was laid open in 13 patients, and a Seton drain was inserted in five.

CONCLUSION

MRI-guided surgery for anal fistula is feasible. IOMRI demonstrates the exact anatomy of the tracts and abscesses, and confirms that all have been adequately treated. We believe it may become particularly useful in surgery for recurrent and complex anal fistulae, and may lead to fewer recurrences.

Properties of neurotoxic peptides related to the BRI gene

Mutations in the BRI gene are thought to cause dementias in members of families. The clinical symptoms are similar to those of Alzheimer's disease, but with additional ocular and hearing deficits, and spasticity. The mutations lead to the release of the 34-residue peptides, ABri and ADan, in the brains of afflicted individuals. We have synthesized the peptides in their straight-chain and oxidized cyclic forms and shown that the oxidized form of ABri and reduced form of ADan are toxic to human neuronal cell lines in culture. Neurotoxicity correlates with the extent of formation of SDS-stable non-fibrillar low-molecular-mass oligomers (SSNFOs).

Combination vaccines: postlicensure safety evaluation

The success of immunizations in nearly eliminating many vaccine-preventable diseases has resulted in an increase in the need to study risks from vaccines, combination or otherwise. The well-known limitations associated with prelicensure trials have led many to hope that postlicensure studies can address safety issues. This article reviews measures that have been or should be taken to meet this expectation: establishment of clinical immunization safety assessment centers, standardization of case definitions for vaccine adverse events, use of the Vaccine Identification Standards Initiative to improve the accuracy and efficiency with which vaccination records are transferred, integration of vaccine safety monitoring into immunization registries, establishment (and enlargement) of the Vaccine Safety Datalink project, use of innovative analytic tools for better signal detection, and implementation of various methods to overcome confounding by contraindication. Only by investing in vaccine safety infrastructure at a level commensurate with investments in vaccine development can we hope to retain the public's confidence in immunization.

Development of a reading speed test for potential-vision measurements

PURPOSE

Previous studies suggest that optimal reading speed is unaffected by cataract, yet is significantly reduced in age-related macular degeneration (ARMD ). This raises the question of whether a reading speed test could be developed to assess potential vision after cataract surgery.

METHODS

Nineteen subjects with cataract, 15 with ARMD, and 13 control subjects with normal, healthy eyes read Bailey-Lovie word charts aloud, and subsequently, critical print size and optimal reading speed were calculated. Measurements were also taken with the charts in reversed-contrast polarity and after pupillary dilation.

RESULTS

Although the subjects with cataract had reduced word acuity and increased critical print size, optimal reading speed was similar to that of the control group at a mean of approximately 100 wpm. Optimal reading speed in the subjects with ARMD was substantially worse (mean of 39 wpm). Reversing the contrast polarity of the charts slightly increased the word acuity and optimal reading speed of the subjects with cataract.

CONCLUSIONS

The results suggest that optimal reading speed would be useful as a potential-vision test. The proposed test would use text size of at least 1.32 degrees (1.2 log minimum angle of resolution [logMAR]), and pupil dilation would be unnecessary. A reading test with black letters on a white background would be adequate, because charts with reversed-contrast polarity made minimal difference in reading speed.