Variability in time delay between two models of pulse oximeters for deriving the photoplethysmographic signals

Pulse oximetry is commonly used as an arterial blood oxygen saturation (SaO(2)) measure. However, its other serial output, the photoplethysmography (PPG) signal, is not as well studied. Raw PPG signals can be used to estimate cardiovascular measures like pulse transit time (PTT) and possibly heart rate (HR). These timing-related measurements are heavily dependent on the minimal variability in phase delay of the PPG signals. Masimo SET (R) Rad-9 (TM) and Novametrix Oxypleth oximeters were investigated for their PPG phase characteristics on nine healthy adults. To facilitate comparison, PPG signals were acquired from fingers on the same hand in a random fashion. Results showed that mean PTT variations acquired from the Masimo oximeter (37.89 ms) were much greater than the Novametrix (5.66 ms). Documented evidence suggests that I ms variation in PTT is equivalent to I mmHg change in blood pressure. Moreover, the PTT trend derived from the Masimo oximeter can be mistaken as obstructive sleep apnoeas based on the known criteria. HR comparison was evaluated against estimates attained from an electrocardiogram (ECG). Novametrix differed from ECG by 0.71 +/- 0.58% (p < 0.05) while Masimo differed by 4.51 +/- 3.66% (p > 0.05). Modem oximeters can be attractive for their improved SaO(2) measurement. However, using raw PPG signals obtained directly from these oximeters for timing-related measurements warrants further investigations.

Influence of geomagnetic activity on the occurrence of midlatitude ionogram-recorded spread-F

Delayed spread-F occurrence as recorded by ionograms, following geomagnetic activity (GA) has been investigated using data from 88 stations located around the world. The spread-F occurrence is delayed progressively from one to three days, from subauroral to midlatitude regions. The equatorial latitudes show suppressed activity. An examination of daily spread-F occurrence values relative to the AE index reveals not only a main delay of one day, but also delays of two and three days. These delays involve principally GA occurring around 0600 hrs LT.

Degrees of freedom and motor planning in purposive movement

This paper presents empirical evidence suggesting that healthy humans can perform a two degree of freedom visuo-motor pursuit tracking task with the same response time delay as a one degree of freedom task. In contrast, the time delay of the response is influenced markedly by the nature of the motor synergy required to produce it. We suggest a conceptual account of this evidence based on adaptive model theory, which combines theories of intermittency from psychology and adaptive optimal control from engineering. The intermittent response planning stage has a fixed period. It possesses multiple optimal trajectory generators such that multiple degrees of freedom can be planned concurrently, without requiring an increase in the planning period. In tasks which require unfamiliar motor synergies, or are deemed to be incompatible, internal adaptive models representing movement dynamics are inaccurate. This means that the actual response which is produced will deviate from the one which is planned. For a given target-response discrepancy, corrective response trajectories of longer duration are planned, consistent with the principle of speed-accuracy trade-off. Compared to familiar or compatible tasks, this results in a longer response time delay and reduced accuracy. From the standpoint of the intermittency approach, the findings of this study help make possible a more integral and predictive account of purposive action. (c) 2005 Elsevier B.V. All rights reserved.

Comparison of gelation profile of yoghurts during fermentation measured by RVA and ultrasonic spectroscopy

The gelation profile of yoghurts from conventionally treated (85 degrees C/30 min) and UHT treated (143 degrees C/6s) milks at 16, 18, and 20% total solids was analyzed during fermentation for 4 hrs using the invasive Rapid Visco Analyzer (RVA) and the non-invasive ultrasonic spectroscope. The viscosity measured by the RVA and the ultrasonic velocity measured by the ultrasonic spectroscope exhibited similar sigmoid trends with respect to fermentation time. The ultrasonic spectroscope detected the onset of gelation of yoghurt milk earlier (by an average of 52 min) than did the RVA, indicating a higher sensitivity of ultrasonic spectroscopy. The delay of gelation time of UHT-treated yoghurt milk as compared to conventionally treated yoghurt milk was detected by both techniques. A non-significant ( P > 0.05) effect of solids content in the yoghurt milks on their gelation time was also observed by both instruments.

Pax9 and Jagged1 act downstream of Gli3 in vertabrate limb development

From early in limb development the transcription factor Gli3 acts to define boundaries of gene expression along the anterior-posterior (AP) axis, establishing asymmetric patterns required to provide positional information. As limb development proceeds, posterior mesenchyme expression of Sonic hedgehog (Shh) regulates Gli3 transcription and post-translational processing to specify digit number and identity. The molecular cascades dependent on Gli3 at later stages of limb development, which link early patterning events with final digit morphogenesis, remain poorly characterised. By analysing the transcriptional consequences of loss of Gli3 in the anterior margin of the E11.5 and E12.5 limb bud in the polydactylous mouse mutant extra-toes (Gli3(Xt/Xt)), we have identified a number of known and novel transcripts dependent on Gli3 in the limb. In particular, we demonstrated that the genes encoding the paired box transcription factor Pax9, the Notch ligand Jagged1 and the cell surface receptor Cdo are dependent on Gli3 for correct expression in the anterior limb mesenchyme. Analysis of expression in compound Shh;Gli3 mutant mouse embryos and in both in vitro and in vivo Shh signaling assays, further defined the importance of Shh regulated processing of Gli3 in controlling gene expression. In particular Pax9 regulation by Shh and Gli3 was shown to be context dependent, with major differences between the limb and somite revealed by Shh bead implantation experiments in the chick. Jagged1 was shown to be induced by Shh in the chick limb and in a C3H10T1/2 cell based signaling assay, with Shh;Gli3 mutant analysis indicating that expression is dependent on Gli3 derepression. Our data have also revealed that perturbation of early patterning events within the Gli3(Xt/Xt), limb culminates in a specific delay of anterior chondrogenesis which is subsequently realised as extra digits. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

The effect of larval age on morphology and gene expression during ascidian metamorphosis

Metamorphosis is both an ecological and a developmental genetic transition that an organism undergoes as a normal part of ontogeny. Many organisms have the ability to delay metamorphosis when conditions are unsuitable. This strategy carries obvious benefits, but may also result in severe consequences for older larvae that run low on energy. In the marine environment, some lecithotrophic larvae that have prolonged periods in the plankton may begin forming postlarval and juvenile structures that normally do not appear until after settlement and the initiation of metamorphosis. This precocious activation of the postlarval developmental program may reflect an adaptation to increase the survival of older, energy-depleted larvae by allowing them to metamorphose more quickly. In the present study, we investigate morphological and genetic consequences of delay of metamorphosis in larvae of Herdmania momus (a solitary stolidobranch ascidian). We observe significant morphological and genetic changes during prolonged larval life, with older larvae displaying significant changes in RNA levels, precocious migration of mesenchyme cells, and changes in larval shape including shortening of the tail. While these observations suggest that the older H. momus larvae are functionally different from younger larvae and possibly becoming more predisposed to undergo metamorphosis, we did not find any significant differences in gene expression levels between postlarvae arising from larvae that metamorphosed as soon as they were competent and postlarvae developing from larvae that postponed metamorphosis. This recalibration, or convergence, of transcript levels in the early postlarva suggests that changes that occur during prolonged larval life of H. momus are not necessarily associated with early activation of adult organ differentiation. Instead, it suggests that an autonomous developmental program is activated in H. momus upon the induction of metamorphosis regardless of the history of the larva.

Treatment delays in paediatric dento-alveolar trauma at a tertiary referral hospital

Background: Paediatric dento-alveolar trauma is a common event. Delays in treatment can have adverse effects on long term outcomes and the aim of this study was to quantify the treatment delays in paediatric dento-alveolar trauma in a tertiary referral hospital. Methods: All cases of paediatric dento-alveolar trauma over a two-year period from July 2000 to June 2002 were identified and the charts were reviewed retrospectively. All children presenting the emergency department with dento-alveolar trauma within 48 hours of injury during the time period were included. Results: Forty-three patients were identified. The average age was 5.51 years, though there was a bias towards one and two year olds. Males were injured 1.5 times more frequently than females. There was an average delay of 9.6 hours between injury and treatment for all patients. Transit time from outside practitioners to hospital and waiting times in hospital made up the greatest delays. Children injured an average of 2.37 teeth and only 14 per cent were uncomplicated crown fractures. Conclusions: Children who present to children's hospitals for treatment of dento-alveolar trauma have more severe injuries than those treated elsewhere. They have large but potentially reducible delays between injury and treatment.

Automatic message handling for a national counselling service

An automatic email handling system (AutoRouter) was introduced at a national counselling service in Australia. In 2003, counsellors responded to a total of 7421 email messages. Over nine days in early May 2004 the administrator responsible for the management of the manual email counselling service recorded the time spent on managing email messages. The AutoRouter was then introduced. Since the implementation of the AutoRouter the administrator's management role has become redundant, an average of 12 h 5 min per week of staff time has been saved. There have been further savings in supervisor time. Counsellors were taking an average of 6.2 days to respond to email messages (n=4307), with an average delay of 1.2 days from the time counsellors wrote the email to when the email was sent. Thus the response was sent on average 7.4 days after receipt of the original client email message. A significant decrease in response time has been noted since implementation of the AutoRouter, with client responses now taking an average of 5.4 days, a decrease of 2.0 days. Automatic message handling appears to be a promising method of managing the administration of a steadily increasing email counselling service.

Delayed Sry and Sox9 expression in developing mouse gonads underlies B6-Y-DOM sex reversal

The phenomenon of B6-Y-DOM sex reversal arises when certain variants of the Mus domesticus Y chromosome are crossed onto the genetic background of the C57BL/6J (136) inbred mouse strain, which normally carries a Mus musculus-derived Y chromosome. While the sex reversal has been assumed to involve strain-specific variations in structure or expression of Sry, the actual cause has not been identified. Here we used in situ hybridization to study expression of Sry, and the critical downstream gene Sox9, in strains containing different chromosome combinations to investigate the cause of B6-Y-DOM sex reversal. Our findings establish that a delay of expression of Sry(DOM) relative to Sry(B6) underlies B6-Y-DOM sex reversal and provide the first molecular confirmation that Sry must act during a critical time window to appropriately activate Sox9 and effect male testis determination before the onset of the ovarian-determining pathway. (C) 2004 Elsevier Inc. All rights reserved.

Are the changes in postural control associated with low back pain caused by pain interference?

Background: Voluntary limb movements are associated with involuntary and automatic postural adjustments of the trunk muscles. These postural adjustments occur prior to movement and prevent unwanted perturbation of the trunk. In low back pain, postural adjustments of the trunk muscles are altered such that the deep trunk muscles are consistently delayed and the superficial trunk muscles are sometimes augmented. This alteration of postural adjustments may reflect disruption of normal postural control imparted by reduced central nervous system resources available during pain, so-called pain interference, or reflect adoption of an alternate postural adjustment strategy. Methods: We aimed to clarify this by recording electromyographic activity of the upper (obliquus extemus) and lower (transversus abdominis/obliquus internus) abdominal muscles during voluntary arm movements that were coupled with painful cutaneous stimulation at the low back. If the effect of pain on postural adjustments is caused by pain interference, it should be greatest at the onset of the stimulus, should habituate with repeated exposure, and be absent immediately when the threat of pain is removed. Sixteen patients performed 30 forward movements of the right arm in response to a visual cue (control). Seventy trials were then conducted in which arm movement was coupled with pain (pain trials) and then a further 70 trials were conducted without the pain stimulus (no pain trials). Results: There was a gradual and increasing delay of transversus abdominis/obliquus internus electromyograph and augmentation of obliquus externus during the pain trials, both of which gradually returned to control values during the no pain trials. Conclusion: The results suggest that altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy, which may serve to limit the amplitude and velocity of trunk excursion caused by arm movement.

Oscillatory regulation of hes1: Discrete stochastic delay modelling and simulation

Discrete stochastic simulations are a powerful tool for understanding the dynamics of chemical kinetics when there are small-to-moderate numbers of certain molecular species. In this paper we introduce delays into the stochastic simulation algorithm, thus mimicking delays associated with transcription and translation. We then show that this process may well explain more faithfully than continuous deterministic models the observed sustained oscillations in expression levels of hes1 mRNA and Hes1 protein.