Spectroscopic gas detection using a Bragg grating - stabilized external cavity laser, custom written in planar integrated silica-on-silicon.

We present the development of an external cavity Bragg grating stabilized laser for tunable diode laser spectroscopy (TDLS). Our design uses a planar integrated silica-on-silicon platform incorporating a custom written Bragg grating as the wavelength-selective element of the laser cavity. We have developed a prototype singlemode laser at 1651 nm and performed a detailed characterization of its performance for the purpose of spectroscopic measurement of methane at this wavelength using a 25 cm path-length single-pass cell. Mode hop-free tuning of 0.13 nm has been demonstrated at frequencies of up to 10 kHz. A single-point limit of detection for TDLS of ΔI/I0 = 8.3 × 10-5 AU was achieved, which is consistent with the performance of standard distributed feedback lasers. The new device exhibits a side-mode suppression ratio of -40 dB and a low RIN of <-150 dB/Hz, and thus avoids the high levels of noise or instability normally associated with larger, mechanically driven external cavity lasers. The silica-on-silicon platform has the potential for low-volume manufacturing of special lasers at the custom wavelengths required for gas detection, without the need for investment in foundry solutions.

Multifaceted roles of GSK-3 and Wnt/ß-catenin in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention.

Glycogen synthase kinase-3 (GSK-3) is well documented to participate in a complex array of critical cellular processes. It was initially identified in rat skeletal muscle as a serine/threonine kinase that phosphorylated and inactivated glycogen synthase. This versatile protein is involved in numerous signaling pathways that influence metabolism, embryogenesis, differentiation, migration, cell cycle progression and survival. Recently, GSK-3 has been implicated in leukemia stem cell pathophysiology and may be an appropriate target for its eradication. In this review, we will discuss the roles that GSK-3 plays in hematopoiesis and leukemogenesis as how this pivotal kinase can interact with multiple signaling pathways such as: Wnt/ß-catenin, phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt/mammalian target of rapamycin (mTOR), Ras/Raf/MEK/extracellular signal-regulated kinase (ERK), Notch and others. Moreover, we will discuss how targeting GSK-3 and these other pathways can improve leukemia therapy and may overcome therapeutic resistance. In summary, GSK-3 is a crucial regulatory kinase interacting with multiple pathways to control various physiological processes, as well as leukemia stem cells, leukemia progression and therapeutic resistance. GSK-3 and Wnt are clearly intriguing therapeutic targets.

Cloning and expression of a novel cysteine-rich secreted protein family member expressed in thyroid and pancreatic mesoderm within the chicken embryo.

We have isolated a new chicken gene that is a member of the cysteine-rich secreted protein family (CRISP). The CRISP family is composed of over 70 members that are found in many phyla of organisms, including: vertebrates, plants, fungi, yeast, and insects. Here we describe the cloning of a novel member of this family, SugarCrisp, and its expression pattern throughout chicken embryogenesis. We also describe its utility as a marker of thyroid and pancreatic mesoderm in the developing chicken embryo and its expression within the human and mouse in glandular tissue.

Birth weight <1501 g and respiratory health at age 14.

AIMS: To determine the respiratory health in adolescence of children of birth weight <1501 g, and to compare the results with normal birthweight controls. METHODS: Prospective cohort study of children born in the Royal Women's Hospital, Melbourne. Two cohorts of preterm children (86 consecutive survivors 500-999 g birth weight, and 124 consecutive survivors 1000-1500 g birth weight) and a control group of 60 randomly selected children >2499 g birth weight were studied. Children were assessed at 14 years of age. A paediatrician determined the clinical respiratory status. Lung function was measured according to standard guidelines. RESULTS: Of 180 preterm children seen at age 14, 42 (23%) had bronchopulmonary dysplasia (BPD) in the newborn period. Readmission to hospital for respiratory ill health was infrequent in all groups and the rates of asthma were similar (15% in the 500-999 g birth weight group, 21% in the 1000-1500 g birth weight group, 21% in controls; 19% BPD, 18% no BPD). Overall, lung function was mostly within the normal range for all cohorts; few children had lung function abnormalities in clinically significant ranges. However, the preterm children had significantly lower values for variables reflecting flow. Lung function in children of 500-999 g birth weight was similar to children of 1000-1500 g birth weight. Preterm children with BPD had significantly lower values for variables reflecting flow than children without BPD. CONCLUSIONS: The respiratory health of children of birth weight <1501 g at 14 years of age is comparable to that of term controls.

Survival, cranial ultrasound and cerebral palsy in very low birthweight infants: 1980s versus 1990s.

OBJECTIVE: To determine the changes in the rates of survival, cranial ultrasound abnormalities and cerebral palsy in very low birthweight (VLBW) (birthweight 500-1499 g) infants between the early 1980s and the early 1990s. METHODOLOGY: A cohort study of consecutive VLBW live births in one tertiary perinatal hospital during two distinct eras was performed at The Royal Women's Hospital, Melbourne, a level-III perinatal centre. Consecutive VLBW infants born over the 18-month period from 1 October 1980 (n = 222), and over the 12-month period from 1 January 1992 (n = 202) were identified. The main outcome measures were the proportions of live births surviving to 5 years of age, rates of cranial ultrasound abnormalities, and rates of cerebral palsy at 5 years of age. RESULTS: Over the 18 months from 1 October 1980, 68% (150/222) VLBW live births survived to 5 years of age. The survival rate rose substantially to 82% (165/202) during 1992 (odds ratio 2.1, 95% confidence interval 1.4-3.2). The survival rate increased over time more for those of 500-999 g birthweight than for those of 1000-1499 g birthweight. The rates of cerebroventricular haemorrhage (CVH) were similar inlive births and survivors from both eras, as were the rates of cerebral palsy (7.5% in 1980-82; 7.8% in 1992) in survivors seen at 5 years of age. The positive predictive value of CVH for cerebral palsy was low, but cystic periventricular leucomalacia was followed by cerebral palsy in seven of eight survivors from the 1992 cohort. CONCLUSIONS: Despite the increasing survival rate with improvements in perinatal care, including more antenatal steroid therapy and the introduction of exogenous surfactant, the rates of CVH and of cerebral palsy in survivors have not diminished.

Axon tracts correlate with netrin-1a expression in the zebrafish embryo.

Netrins are secreted molecules that can attract or repel growth cones from a variety of organisms. In order to clarify the extent and scope of the effects of netrins for guiding growth cones, we have analyzed netrin-1a within the relatively simple and well-characterized nervous system of zebrafish embryos. netrin-1a is expressed in dynamic patterns that suggest that it guides the growth cones of a wide variety of neurons. The spatiotemporal relationship of netrin-1a expression and extending growth cones further suggests that netrins may act to delineate specific pathways and stimulate axonal outgrowth in addition to attracting and repelling growth cones. Furthermore, aberrant outgrowth by commissural growth cones in the spinal cords of floating head mutants, in which netrin-1a expression is altered, is consistent with an in vivo, chemoattractive action of netrin-1a. These data suggest that netrins act on many growth cones and influence their behavior in a variety of ways.