High power single-mode delivery of mid-infrared sources through chalcogenide fiber.

Mechanically robust and low loss single-mode arsenic sulfide fibers are used to deliver high power mid-infrared sources. Anti-reflection coatings were deposited on the fiber facets, enabling 90% transmission through 20 cm length fibers. 10.3 W was transmitted through an anti-reflection coated fiber at 2053 nm, and uncoated fibers sustained 12 MW/cm2 intensities on the facet without failure. A Cr:ZnSe laser transmitted >1 W at 2520 nm, and a Fe:ZnSe laser transmitted 0.5 W at 4102 nm. These results indicate that by improving the anti-reflection coatings and using a high beam quality mid-infrared source, chalcogenide fibers can reliably deliver ≥10 W in a single mode, potentially out to 6.5 µm.

Diffractive optical elements utilized for efficiency enhancement of photovoltaic modules.

Common solar cells used in photovoltaic modules feature metallic contacts which partially block the sunlight from reaching the semiconductor layer and reduce the overall efficiency of the modules. Diffractive optical elements were generated in the bulk glass of a photovoltaic module by ultrafast laser irradiation to direct light away from the contacts. Calculations of the planar electromagnetic wave diffraction and propagation were performed using the rigorous coupled wave analysis technique providing quantitative estimations for the potential efficiency enhancement of photovoltaic modules.

Lack of direct inhibitory action of oxytocin on progesterone production by dispersed cells from human corpus luteum.

Suspensions of luteal cells were prepared from samples of human corpora lutea obtained during the luteal phase of menstrual cycles. Addition of oxytocin (1 mumol/l) to the various cell preparations had no effect on either basal production of progesterone or on steroidogenic responses to a range of concentrations of gonadotrophin.

Stimulation by human chorionic gonadotrophin of oestradiol production by dispersed cells from human corpus luteum: comparison with progesterone production; utilization of exogenous testosterone.

Cell suspensions were prepared from tissue samples of human corpora lutea obtained during the mid- and late-luteal phase of the menstrual cycle. Both oestradiol and progesterone production by dispersed cells were stimulated by similar concentrations of human chorionic gonadotrophin (hCG). As the degree of stimulation of production by hCG was greater for progesterone than for oestradiol (five- to tenfold compared two- to threefold higher than basal production), the ratio of progesterone to oestradiol produced varied according to the level of trophic stimulation. A comparison of cell suspensions prepared form mid- to late-luteal phase corpora lutea, exposed to the same concentration of hCG (10 i.u./ml) in vitro, did not reveal a shift to oestradiol production in the late-luteal phase. Provision of additional testosterone during incubation raised the level of oestradiol production by dispersed luteal cells. At an optimum concentration of testosterone (l mumol/l), oestradiol synthesis was not raised further in the presence of hCG or N6, O2'-dibutyryl cyclic AMP, suggesting a lack of induction or activation of the aromatase system by gonadotrophin in short-term cultures. Basal and stimulated levels of progesterone production were not significantly impaired in the presence of testosterone.

Progesterone production by dispersed cells from human corpus luteum: stimulation by gonadotrophins and prostaglandin F 2 alpha; lack of response to adrenaline and isoprenaline.

Progesterone production was assessed following short-term incubations of luteal cell suspensions prepared from tissue samples of human corpora lutea obtained at specific times throughout the luteal phase of the menstrual cycle. Luteal cells responded rapidly and sensitively to human chorionic gonadotrophin (HCG: concentration required for 50% maximum response, 0.1--1.0 i.u./ml) with a maximum level of response (five- to tenfold higher than basal production) similar to that elicited by human LH or N6,O2'-dibutyryl cyclic AMP. In the absence of gonadotrophin or in the presence of sub-maximal (but not maximal) concentrations of HCG, progesterone production by mid-luteal phase cells was stimulated by prostaglandin F 2 alpha (1 mumol/l, an effect not observed during the late-luteal phase. L-Adrenaline and L-isoprenaline failed to elicit significant increases in the level of progesterone production.

Inhibitory action of chemically deglycosylated human chorionic gonadotrophin on hormone-induced steroid production by dispersed cells from human corpus luteum.

The biological activity of deglycosylated human chorionic gonadotrophin (hCG) prepared by treatment of the native hormone with anhydrous hydrogen fluoride was evaluated using suspensions of dispersed cells from biopsies of human corpus luteum obtained during the luteal phase of normal menstrual cycles. A reproducible pattern of response to hCG in terms of progesterone production by luteal cells was established for a range of luteal ages. Deglycosylation of hCG led to a diminished level of maximum response to the hormone. Co-incubation of luteal cells with a level of hCG just sufficient to elicit a maximum response and increasing concentrations of deglycosylated hCG led to a progressive inhibition of the hormonal response; at a concentration of 10(3) ng deglycosylated hCG/ml (a tenfold excess of deglycosylated hCG over the native hormone), hCG-induced progesterone production was reduced by about 50%. Deglycosylated hCG therefore acts as a partial antagonist for the action of hCG on human luteal cells.

Augmentation by epidermal growth factor of basal and stimulated progesterone production by human luteinized granulosa cells.

Human granulosa cells were prepared from follicular aspirates obtained during oocyte collection for in vitro fertilization. Following several days in culture, cells were washed and then progesterone output was measured in 2-h incubations. After culture for 3 days, incubated cells responded well to human chorionic gonadotrophin (hCG) and prostaglandin (PG) E2 with similar levels of maximum response. Exposure of cultured cells to epidermal growth factor (EGF) for 2 days (days 3-5) led to substantial increases both in basal production and in responses to hCG and PGE2 during subsequent incubations. These effects of EGF were not accompanied by measurable increases in DNA levels in cultures over this time. Results may point to a possible paracrine role for EGF-like factors modulating the activity of cells forming the early corpus luteum.

Effects of a long-acting analogue of LH releasing hormone on human and rat corpora lutea.

Dispersed luteal cells were prepared both from samples of human corpora lutea obtained during normal menstrual cycles and from luteinized rat ovaries of animals pretreated with pregnant mare's serum gonadotrophin and human chorionic gonadotrophin (hCG). Addition of the long-acting analogue, D-Ala6-des-Gly10-LH releasing hormone ethylamide (D-Ala6-LHRH), to rat luteal cells caused a small but significant increase in progesterone production. An inhibitory action of the analogue on hCG-stimulated steroidogenesis by rat luteal cells was confirmed. Addition of D-Ala6-LHRH to suspensions of human luteal cells had no effect on either basal or hCG-stimulated progesterone production. Studies on the interaction of 125I-labelled D-Ala6-LHRH with the dispersed cell preparations, while confirming the presence of displaceable binding to rat luteal cells, failed to detect any equivalent binding to human luteal cells. Low levels of displaceable binding observed using homogenates of human corpora lutea are interpreted as being of doubtful physiological significance in view of the negative findings obtained with the intact cell system.

Actively mode-locked and Q-controlled Nd:glass laser.

A Q-controlled Nd:glass ring laser system has been developed which is actively mode-locked by means of either KD *P or LiNbO(3) electro-optic modulators and is capable of producing 1.5 mJ, 100 ps, 1.06 mum pulses synchronized to better than 400 ps to an external event. By using prelase methods or saturable absorbers shorter pulses from 37 to 15 ps duration can be generated with poorer synchronization.

Environmental and developmental origins of ovarian reserve.

BACKGROUND Oocyte number is established early in life before a gradual loss of this ovarian reserve during reproductive life until oocyte availability becomes limiting at the menopause. Although there is a large genetic component to the ovarian reserve achieved before birth, other influences including the maternal endocrine and nutritional milieu, and environmental factors may represent important developmental determinants. Environmental and nutritional factors may also modify the downward trajectory of ovarian reserve in adult life. The combination of these early and later life influences has the potential to lead to diminished ovarian reserve, compromising fertility in later reproductive years and altering age at natural menopause. METHODS Literature searches of the ISI Web of Knowledge database were carried out using the main terms 'ovarian reserve' and 'menopause AND age' in conjunction with a range of other terms encompassing a variety of factors with potential effects on ovarian reserve. The various searches were inspected manually and the relevant papers selected for critical analysis and interpretation. RESULTS Evidence was identified supporting the view that elevated prenatal androgens have an adverse effect on the early establishment of ovarian reserve, although the implications for ovarian reserve in the polycystic ovary syndrome (which may also be programmed through prenatal androgen exposure) remain uncertain. Recent evidence is cited suggesting that effects of maternal nutrient restriction on ovarian reserve may also involve changes in prenatal androgen exposure. A general rationale is developed through examination of evidence which emphasizes the roles of the aryl hydrocarbon receptor (AHR) and the estrogen receptor (ER) systems in ovarian reserve modulation. Because of their similarity to the natural ligands, many environmental compounds have the ability to bind to these receptors (albeit at lower affinities) and thereby have the potential to influence either the initial setting of ovarian reserve during development or the trajectory of ovarian reserve during adult life. For example, exposure to compounds in cigarette smoke may accelerate loss of ovarian reserve in smokers leading to diminished ovarian reserve, earlier age at last child and earlier menopause. Socioenocomic factors are clearly associated with age at natural menopause, with correlations with economic status and education level. However, such effects in western societies are in general small, and the underlying mechanisms remain unclear. CONCLUSIONS Exposure to many environmental compounds, particularly to those that leach from plastics and other synthetic materials, is commonplace in modern societies to the extent that many are found at measurable concentrations in body fluids within most of the population. Relating fluid levels of individual compounds to parameters reflecting ovarian reserve in selected populations appears to be an effective way forward and, indeed, some early-stage findings do show some cause for concern. There is a pressing need for the development of practical advice enabling women to minimize their intake of AHR/ER ligands, perhaps through dietary/cosmetic choices or improved food packaging.

A general method for quantitative measurement of molecular mass distribution by mass spectrometry.

A method is presented to test whether the conversion of the mass spectrum of a polydisperse analyte to its molecular mass distribution is quantitative. Mixtures of samples with different average molecular masses, coupled with a Taylor's expansion mathematical formalism, were used to ascertain the reliability of molecular mass distributions derived from mass spectra. Additionally, the method describes how the molecular mass distributions may be corrected if the degree of mass bias is within certain defined limits. This method was demonstrated on polydisperse samples of C(60) fullerenes functionalized with ethylpyrrolidine groups measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; however, it is applicable to any polydisperse analyte and mass spectrometric method as long as spectrum resolution allows individual oligomers to be identified. Mass spectra of the derivatized fullerenes taken in positive ion mode were shown to give an accurate measurement of the molecular mass distribution while those taken in negative ion mode were not. Differences in the mechanisms for ion formation are used to explain the discrepancy. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States of America.

The role of protein kinase activation in the control of steroidogenesis by adrenocorticotrophic hormone in the adrenal cortex.

A method has been developed for investigation of the effect of adrenocorticotrophic hormone (ACTH) on the state of activation of a cyclic AMP-dependent protein kinase within cells of the adrenal cortex. Enzyme activity was measured in terms of the quantity of (32)P transferred from [gamma-(32)P]ATP to histone under conditions in which bound cyclic AMP did not dissociate from the regulatory subunit of the protein kinase ACTH (1x10(-2)i.u./ml) caused a rapid and complete activation of the cyclic AMP-dependent protein kinase activity within 2min of hormone addition to the isolated cells. In response to a range of ACTH concentrations a sigmoid log dose-response curve for protein kinase activation was obtained, with half-maximal stimulation attained at about 1x10(-3)i.u./ml. However, some low doses of ACTH that elicited a marked (but submaximal) steroidogenic response failed to cause a clear stimulation of protein kinase activity in isolated adrenal cells. Theophylline (2mm) potentiated the effect of ACTH on protein kinase activity. The results implicate an important role for protein kinase in ACTH action on the adrenocortical cell.

Inhibitory effect of PGF-2 alpha on hCG-stimulated progesterone production in vitro by luteal cells from guinea-pigs at different stages of the oestrous cycle.

Suspensions of luteal cells were prepared by collagenase dispersion of guinea-pig corpora lutea obtained at specific times during the oestrous cycle. Luteal cells incubated with hCG produced increased amounts of progesterone. For Days 3--13 of the oestrous cycle, the concentrations of hCG required for 50% of the maximum response were within the range, 1 x 10(-3) to 7 x 10(-3) i.u./ml, showing no marked loss of sensitivity to hCG with increasing luteal age. PGF-2 alpha (1 mumol/l), had no effect on basal production of progesterone but significantly inhibited hCG-stimulated progesterone production by luteal cells isolated on Days 7, 9, 10, 12 and 13 of the cycle. This concentration of PGF-2 alpha had no significant effect on progesterone production by luteal cells prepared earlier in the cycle (Days 3 and 5). It is concluded that (a) the luteolytic action of PGF-2 alpha in the guinea-pig is mediated, at least in part, by direct action on luteal cells, and (b) the cells from newly formed corpora lutea are resistant to the direct inhibitory action of PGF-2 alpha.

Calorimetric system for recording plasma blowoff and scattered light distributions from laser plasmas.

A complete system is described for the measurement of the distribution of energy emanating from laser-produced plasmas in the form of (1) plasma blowoff (ions, electrons, neutral particles, and x rays), and (2) scattered laser light. The detectors consist of small modules containing two differential calorimeters in one package, one for each form of energy. Modular autozeroing amplifiers enable the slowly varying signals to be measured by computer with the aid of CAMAC analog to digital converters. The computer is also capable of absolutely calibrating the units in situ. The programs used to record and display the data, and to calculate the fraction of laser energy absorbed, are described.

Incidence and nature of bile duct injuries following laparoscopic cholecystectomy: an audit of 5913 cases. West of Scotland Laparoscopic Cholecystectomy Audit Group.

The rapid introduction of laparoscopic cholecystectomy has been associated with an apparently increased incidence of bile duct injury which has provoked worldwide concern. The true incidence and mechanism of iatrogenic ductal injury during the development of this procedure remain unclear. To assess this, the introduction of laparoscopic cholecystectomy in the West of Scotland has been audited prospectively over a 5-year period. All cases of biliary ductal injury have been independently reviewed. Some 48 surgeons undertaking laparoscopic cholecystectomy in 19 hospitals submitted prospective data between September 1990 and September 1995. A total of 5913 laparoscopic cholecystectomies were attempted with 98.3 per cent completion of data collection. During this period 37 laparoscopic bile duct injuries occurred. The annual incidence peaked at 0.8 per cent and has fallen to 0.4 per cent in the final year of audit. Injuries occurred after a median personal experience of 51 (range 3-247) laparoscopic cholecystectomies in 22 surgeons. Major bile duct injuries occurred in 20 of 37 patients, giving an incidence of 0.3 per cent. Five mechanisms for laparoscopic ductal injury were identified, including tenting, confluence and diathermy injuries as well as the classical and variant classical types. Ductal injuries were discovered at operation in 18 patients with consequent repair giving a good clinical outcome in 17. Contributory factors (severe inflammation, aberrant anatomy and poor visualization) were present in only 13 of 37 cases. This audit suggests that, at least in the introductory period, laparoscopic cholecystectomy is associated with an overall bile duct injury rate higher than that reported previously after open cholecystectomy, although the incidence of major ductal injury is similar. The late downward trend in bile duct injury, however, suggests there may be a prolonged learning curve for this procedure. Improved understanding of the mechanism of injury may lead to yet further reductions in this complication.

Comparison of computed tomography and ultrasonographic imaging in the assessment of blunt abdominal trauma in children.

BACKGROUND: Computed tomography (CT) has become established in the assessment of paediatric blunt abdominal trauma. However, advances in diagnostic imaging necessitate reassessment of the role of available diagnostic modalities. METHODS: Experience at a paediatric teaching hospital over a 5-year period was reviewed, with direct comparison of CT against ultrasonographic imaging in 26 children presenting with acute blunt abdominal trauma. RESULTS: Intra-abdominal injury was diagnosed by CT in 23 of 24 patients compared with 21 on ultrasonography, although ultrasonography identified organ-specific injury in only 12 of 24 patients. CT was superior in the assessment of the multiply injured child, and identified spinal and pelvic injuries in three patients. CT augmented plain chest radiography in ten patients with associated thoracic injuries. CONCLUSION: CT is the imaging modality of choice in children with severe abdominal trauma but ultrasonography is a reasonable technique to arouse diagnostic suspicion in less severe injuries or where CT is unavailable or delayed.