A vacuum-compatible cylindrical inertial rotation sensor with picoradian sensitivity

We describe an inertial rotation sensor with a 30-cm cylindrical proof-mass suspended from a pair of 14 μm thick BeCu flexures. The angle between the proof-mass and support structure is measured with a pair of homodyne interferometers, which achieve a noise level of ∼5prad/Hz. The sensor is entirely made of vacuum compatible materials, and the center of mass can be adjusted remotely.

A cryogenic torsion balance using a liquid-cryogen free, ultra-low vibration cryostat

We describe a liquid-cryogen free cryostat with ultra-low vibration levels, which allows for continuous operation of a torsion balance at cryogenic temperatures. The apparatus uses a commercially available two-stage pulse-tube cooler and passive vibration isolation. The torsion balance exhibits torque noise levels lower than room temperature thermal noise by a factor of about four in the frequency range of 3-10 mHz, limited by residual seismic motion and by radiative heating of the pendulum body. In addition to lowering thermal noise below room-temperature limits, the low-temperature environment enables novel torsion balance experiments. Currently, the maximum duration of a continuous measurement run is limited by accumulation of cryogenic surface contamination on the optical elements inside the cryostat.

A low-frequency torsion pendulum with interferometric readout

We describe a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz, whose angle is measured using a Michelson interferometer. The system achieved noise levels of ∼200prad/Hz between 0.2 and 30 Hz and ∼10prad/Hz above 100 Hz. Such a system can be applied to a broad range of fields from the study of rotational seismic motion and elastogravity signals to gravitational wave observation and tests of gravity.

Cytosolic expression, solution structures, and molecular dynamics simulation of genetically encodable disulfide-rich de novo designed peptides

Disulfide-rich peptides represent an important protein family with broad pharmacological potential. Recent advances in computational methods have made it possible to design new peptides which adopt a stable conformation de novo. Here, we describe a system to produce disulfide-rich de novo peptides using Escherichia coli as the expression host. The advantage of this system is that it enables production of uniformly ¹³ C- and ¹⁵ N-labeled peptides for solution nuclear magnetic resonance (NMR) studies. This expression system was used to isotopically label two previously reported de novo designed peptides, and to determine their solution structures using NMR. The ensemble of NMR structures calculated for both peptides agreed well with the design models, further confirming the accuracy of the design protocol. Collection of NMR data on the peptides under reducing conditions revealed a dependency on disulfide bonds to maintain stability. Furthermore, we performed long-time molecular dynamics (MD) simulations with tempering to assess the stability of two families of de novo designed peptides. Initial designs which exhibited a stable structure during simulations were more likely to adopt a stable structure in vitro, but attempts to utilize this method to redesign unstable peptides to fold into a stable state were unsuccessful. Further work is therefore needed to assess the utility of MD simulation techniques for de novo protein design.

Heterotopic ossification of the temporomandibular joint in juvenile idiopathic arthritis

OBJECTIVE

To describe the clinical, laboratory, pathologic, and radiographic imaging characteristics of a series of children with juvenile idiopathic arthritis (JIA) and radiographic imaging evidence of heterotopic ossification of their temporomandibular joint (TMJ).

METHODS

Children were identified through search of an administrative database of imaging results at Seattle Children's Hospital. Retrospective chart review was performed to collect data on each patient's clinical and laboratory characteristics, systemic therapies, timing and number of TMJ intraarticular corticosteroid injections (IAS), TMJ symptoms, and TMJ findings on physician examination. TMJ imaging studies for which heterotopic ossifications were reported were reviewed. Pathology specimens were reviewed for the 2 children who underwent synovial biopsy of their TMJ.

RESULTS

Twelve children were identified. The average duration between onset of JIA and detection of heterotopic ossification of TMJ on an imaging study was 36 months (range 19-94). Half the children had abnormal mouth-opening for age when the calcifications were first detected. In each case, the heterotopic ossification was first detected by computed tomography scan, and in 11 of the cases they were associated with synovial pannus formation as documented on an imaging study. Two children underwent synovial biopsy, which revealed reactive parosteal osteochondromatosis in one case and findings consistent with an intraarticular rheumatoid nodule in the other.

CONCLUSION

Heterotopic ossifications of the TMJ may be seen in children with JIA and are associated with particularly severe TMJ arthritis, joint destruction, and pannus formation. Pathology from these joints suggests that the heterotopic ossification may result from multiple pathological processes.

Characterization of the peripheral retinopathy in X-linked and autosomal recessive Alport syndrome

BACKGROUND

Alport syndrome is an inherited disease resulting in kidney failure, hearing loss and ocular abnormalities. Alport syndrome is however often unrecognized, and the aim of this study was to characterize the associated but rarely described peripheral retinopathy and determine whether its demonstration was diagnostically helpful.

METHODS

Index cases were diagnosed with Alport syndrome on renal biopsy in themselves or a family member. Inheritance and affected status were determined using microsatellite markers at the COL4A5 and COL4A3/COL4A4 loci, respectively. Participants' eyes were dilated, and examined with direct and indirect ophthalmoscopy, and slit lamp biomicroscopy by an expert ophthalmologist who was unaware of the patients' disease status.

RESULTS

Ten males and nine females with X-linked Alport syndrome and seven with autosomal recessive disease were studied. Of the 26 patients, 16 had central retinopathy (62%), and 19 patients had peripheral retinopathy (74%). The peripheral changes occurred in both males and females with X-linked and autosomal recessive Alport syndrome, and were more common when renal failure, hearing loss, lenticonus and the central changes were present, but were also noted in 3 X-linked carriers with normal renal function.

CONCLUSIONS

The peripheral retinopathy occurs in X-linked and autosomal recessive Alport syndrome even when the central retinopathy is absent. Careful retinal examination and photography that includes the periphery is a safe and inexpensive method that may help in the diagnosis of Alport syndrome especially in carriers of X-linked disease.

Access to colposcopy services for high-risk Canadian women: can we do better?

BACKGROUND

Despite overall decreasing mortality from cervical cancer, selected groups of Canadian women continue to have suboptimal access to diagnostic and treatment interventions for cervical cancer. In this paper, we present an evaluation of a colposcopy program developed to improve attendance for colposcopy in a lower socio-economic and immigrant population.

METHODS

All women attending the North Hamilton Community Health Centre (CHC) who required colposcopic assessment and were referred to a newly developed colposcopy program based at the CHC were evaluated. Attendance rates for consultation, follow up and treatment in women referred for colposcopy were compared retrospectively for the CHC-based colposcopy program and concurrently with the regional colposcopy clinic (RCC).

RESULTS

Women referred to the CHC colposcopy program had a significant reduction in their no-show rate after the introduction of the locally based colposcopy program (17.2% vs. 1.3%, p<0.01). Comparing the same time periods, there was no significant reduction in the default rate at the RCC (2.5% vs. 3.3%, p=0.21). Despite serving a population of women who were at higher risk for non-attendance, patients at the CHC had a default rate for appointments similar to that of the RCC (1.3% vs. 3.3%, p=0.55) after the introduction of the local colposcopy program.

CONCLUSIONS

Lower socio-economic status and immigrant women receiving care from a CHC-based colposcopy program had a significant decrease in their no-show rate for colposcopic evaluation after the introduction of the on-site program. Consideration must be given to locating diagnostic colposcopy programs in settings more accessible to women who require these services the most.

Access to colposcopy services for high-risk Canadian women: can we do better?

BACKGROUND

Despite overall decreasing mortality from cervical cancer, selected groups of Canadian women continue to have suboptimal access to diagnostic and treatment interventions for cervical cancer. In this paper, we present an evaluation of a colposcopy program developed to improve attendance for colposcopy in a lower socio-economic and immigrant population.

METHODS

All women attending the North Hamilton Community Health Centre (CHC) who required colposcopic assessment and were referred to a newly developed colposcopy program based at the CHC were evaluated. Attendance rates for consultation, follow up and treatment in women referred for colposcopy were compared retrospectively for the CHC-based colposcopy program and concurrently with the regional colposcopy clinic (RCC).

RESULTS

Women referred to the CHC colposcopy program had a significant reduction in their no-show rate after the introduction of the locally based colposcopy program (17.2% vs. 1.3%, p<0.01). Comparing the same time periods, there was no significant reduction in the default rate at the RCC (2.5% vs. 3.3%, p=0.21). Despite serving a population of women who were at higher risk for non-attendance, patients at the CHC had a default rate for appointments similar to that of the RCC (1.3% vs. 3.3%, p=0.55) after the introduction of the local colposcopy program.

CONCLUSIONS

Lower socio-economic status and immigrant women receiving care from a CHC-based colposcopy program had a significant decrease in their no-show rate for colposcopic evaluation after the introduction of the on-site program. Consideration must be given to locating diagnostic colposcopy programs in settings more accessible to women who require these services the most.

Anaesthetic induction in children: the effects of maternal presence on mood and subsequent behaviour

Forty-nine children, aged from 1 to 9 years, undergoing elective surgery under general anaesthesia, were studied in two groups. In one group, each child's mother was present during induction of anaesthesia, whereas in the other group no parent was present. Children's moods and cooperation during waiting and induction periods did not differ significantly between the groups, neither was the incidence of technical difficulties with anaesthetic induction different. Induction took longer (P = 0.005) if the mother was present. Mothers, when present, were calm and supportive to their children, with one exception. No mother was critical or interfering. Each child's behaviour was assessed by questionnaire pre-operatively and 4 weeks post-operatively. There was a significant overall improvement in behaviour scores post-operatively. There were no significant differences in direction or magnitude of behaviour changes between the two groups.

Comparison of atracurium-induced neuromuscular blockade in neonates, infants and children

The potency of atracurium was determined in neonates, infants and children during thiopentone-fentanyl-nitrous oxide in oxygen anaesthesia using single dose-response curves. The effective doses producing 50% depression of the first twitch of the train-of-four were significantly lower in neonates and infants than in children (82 and 112 v. 135 micrograms kg-1). Following a standard dose of atracurium 0.5 mg kg-1, 95% depression of the first twitch occurred more rapidly in neonates than in children (0.9 v. 1.4 min), while recovery to 10% of the control twitch height occurred more rapidly in neonates than in the other two groups (22.7 v. 29.7 and 28.6 min). It is concluded that neonates and infants require less atracurium to produce a given degree of neuromuscular blockade compared with older children. However, prompt recovery can be expected in all healthy paediatric patients following a standard intubating dose of atracurium 0.5 mg kg-1.

Abnormal thyroid hormone binding to serum proteins in ob/ob and db/db genetically obese mice

Sera from ob/ob and db/db genetically obese mice exhibited abnormal nonspecific (no antibody present) binding measurements in T4 and T3 RIAs employing dextran-charcoal separations. They also showed decreased charcoal uptake compared to sera of lean controls in a conventional charcoal T4 uptake binding test. After correction for the abnormal nonspecific binding and after extraction of serum, mean serum T4 concentrations were similar in control and ob/ob mice. Mean serum T3 concentrations differed significantly (85 ng/dl in controls and 178 ng/dl in ob/ob) when a correction for altered binding in the T3 assay was made, but not when extracted serum was assayed (109 ng/dl in lean and 124 ng/dl in ob/ob). Dialyzable fractions of T4 and T3 were significantly reduced in both ob/ob and db/db mice. Free T4 concentrations were 0.82 +/- 0.05 (+/- SE) ng/dl in control and 0.61 +/- 0.05 ng/dl in ob/ob sera (P less than 0.01). Polyacrylamide gel electrophoresis showed increased binding of tracer T4 and T3 in ob/ob and db/db sera to a postalbumin with mobility similar to that of human T4-binding globulin. In ob/ob sera, this appeared to result from an increased binding capacity of the postalbumin. After in vivo iv injection of tracer T4 and T3 to ob/ob and lean control mice, analysis of tissue and plasma radioactivity showed that, except for T4 in cerebral cortex, tissue to plasma T4 and T3 ratios were lower in cerebral cortex, cerebellum, and liver of ob/ob mice. In summary, these data show increased binding of T4 and T3 to a postalbumin in two strains of genetically obese mice and, in the ob/ob strain, complex relationships between tissue and serum concentrations of thyroid hormones.

Type II iodothyronine 5'-deiodination by human and rat placenta in vitro

T4 and rT3 5'-deiodination were measured in human and rat placental homogenates. rT3 5'-deiodination rates were reduced 5-40% by 1 mM 6-n-propylthiouracil (PTU), but T4 5'-deiodination was not affected by 1 mM PTU. In human tissue, homogenates of the chorionic membrane decidua had greater PTU-insensitive activity than homogenates of trophoblastic tissue or amnion. In the rat placenta, basal zone homogenates had greater activity than homogenates of placental labyrinth or amnion. The distribution of 5'-deiodinating activity in placental structures differed from that of T3 tyrosyl ring deiodinating activity in both species. PTU-insensitive rT3 5'-deiodinating activity was enriched in particulate subcellular fractions, but not in cytosol. Kinetic studies of T4 5'-deiodination using particulate fractions from human chorionic membrane decidua and rat basal zone showed a sequential kinetic pattern when the dithiothreitol concentration was varied, with apparent Michaelis constants (Km) and 50% inhibitory concentrations for T4 of 2.1-3.2 nM, and for rT3 of 9-15 nM. Thus, PTU-insensitive iodothyronine 5'-deiodination in rat and human placenta is very similar to, or the same as, that termed type II activity in rat anterior pituitary, central nervous system, and brown adipose tissue. These results extend the range of tissues in which type II iodothyronine 5'-deiodination has been identified, and strengthen the applicability to man of studies of iodothyronine deiodination in the rat.

Iodothyronine deiodination reaction types in several rat tissues: effects of age, thyroid status, and glucocorticoid treatment

Two types of iodothyronine 5'-deiodination have been characterized previously in rat tissues. They can be distinguished by inhibition of type I but not type II by 6-n-propylthiouracil, by the relative suitability of T4 and rT3 as substrates, rT3 much better than T4 for type I and T4 as good as, or better than, rT3 for type II, and by the concentration of T4 required to inhibit deiodination of rT3, 1-10 microM for type I and 1-10 nM for type II. Type I activity (6-n-propylthiouracil sensitive) is most abundant in liver and kidney. Type II activity has, to date, been identified only in the pituitary, central nervous system, and brown adipose tissue. Iodothyronine tyrosyl deiodination has also been identified in homogenates of rat brain, liver, and placenta. It is not clear how many different enzymes carry out this latter reaction. In the present studies, we have extended previous work by determining maturational patterns of the deiodinating pathways in several thyroid hormone-responsive rat tissues, possible modulation of those patterns by glucocorticoids, and the age of onset of responsivity of the deiodinases to hypothyroidism. Iodothyronine 5'-deiodinating activity was found in rat lung and eye, and the reaction was all or nearly all type I in both. Activity in the eye was virtually absent from the lens and vitreous humor. In immature rat cerebrum, pituitary, lung, and eye, between gestational day 17 and postnatal day 21, there was a uniform pattern of an increase in type I 5'-deiodination activity over time, until adult levels were attained. The ages at which adult activity levels were reached varied from tissue to tissue, however. Type II activity was present at the earliest ages tested in the cerebrum (gestational day 17), pituitary, and brown adipose tissue (day of birth). In cerebral cortex, type II activity was highest at day 21 postnatally and equal at birth and in adulthood, and in pituitary and brown adipose tissue it was higher in adulthood than at birth. T3 tyrosyl ring deiodinating activity was several times greater in homogenates of eye and placenta than in cerebral homogenates. In all three tissues, there was similar, dose-dependent inhibition of [125I]T3 tyrosyl deiodination by 5 nM and 20 nM nonradioactive T3. In the eye and brain, T3 tyrosyl deiodination rates decreased progressively with age from gestational day 17 to postnatal day 7.(ABSTRACT TRUNCATED AT 400 WORDS)

Estimation of acoustical energy reflectance at the eardrum from measurements of pressure distribution in the human ear canal

At frequencies greater than 2 kHz the acoustic impedance at the human eardrum is an unreliable indicator of the behavior of the middle ear system because of the complicated configuration of the ear canal and tympanic membrane. The energy reflectance at the eardrum, however, when obtained from measurement of the standing wave ratio (SWR) in the canal, is relatively insensitive to irregularities in the anatomical layout at the higher frequencies. Measurements of sound pressure distribution in 13 normal ear canals have been analyzed in a critical manner to provide new values of SWR, with estimates of error, between 5 and 10 kHz. At the higher frequencies these values tend to be appreciably greater than those previously reported. At 8 kHz, for example, the new values of SWR range between 18 and 24 dB as compared with earlier values which are in the vicinity of 13 dB. The correspondingly greater values of energy reflectance (60%-78%, as compared with 40%) are more consistent with known properties (mass, size, vibrational patterns) of the human eardrum. These results are applicable to the development of network models representing the middle ear system.

Performance of a shell-type heat exchanger in extracorporeal circulation

Tests were performed on a "shell" type heat exchanger used in a simulated extracorporeal circulation. The counter flow mode was the most efficient pattern and recommendations are made on which flow pattern should be employed with low water flow rates.

Acute upper respiratory tract obstruction complicating childhood leukaemia

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