Monte Carlo simulation of a LSC based on stacked layers of fiber arrays with core-coating different absorbing properties

In this work, a Monte Carlo ray-tracing model for the simulation and optimization of a fiber Luminescent Solar Concentrator (LSC) based on stacked layers of fiber arrays is developed and validated. The fiber LSC efficiency improvements are compared against a conventional planar LSC. We developed a new model to analyze the performance of different configurations of bulk-doped fibers and fibers constituted by a doped coating and a passive core. These configurations are analyzed also varying fiber packing geometry diameters, and length. Due to the exceptionally low absorption coefficient of the silica fibers (α_wg ≈ 10^-4 cm^-1), concentration factors of up to 1.9 are predicted when dimensions are scaled over 1 m², which improve more than twice the maximum concentration factor ever reported. These results serve as a preliminary theoretical study for the future development of a new LSC design based on flexible silica micro-fibers coated with Si-QDs doped poly(lauryl methacrylate) (PLMA) layers.

Continuous fiberizing by laser melting (Cofiblas): Production of highly flexible glass nanofibers with effectively unlimited length

The development of nanofibers is expected to foster the creation of outstanding lightweight nanocomposites and flexible and transparent composites for applications such as optoelectronics. However, the reduced length of existing nanofibers and nanotubes limits mechanical strengthening and effective manufacturing. Here, we present an innovative method that produces glass nanofibers with lengths that are, effectively, unlimited by the process. The method uses a combination of a high-power laser with a supersonic gas jet. We describe the experimental setup and the physical processes involved, and, with the aid of a mathematical simulation, identify and discuss the key parameters which determine its distinctive features and feasibility. This method enabled the production of virtually unlimited long, solid, and nonporous glass nanofibers that display outstanding flexibility and could be separately arranged and weaved.

Antimicrobial activity of submicron glass fibres incorporated as a filler to a dental sealer

Two types of antimicrobial glass fibers containing ZnO and CaO, with diameters ranging from tens of nanometers to 1 µm, were successfully fabricated by a laser spinning technique. The antimicrobial performance was corroborated according to ISO 20743:2013, by using gram-negative (Escherichia coli) and gram-positive (Streptococcus oralis, Streptococcus mutans and Staphylococcus aureus) bacteria, and yeast (Candida krusei) (more than 3 logs of reduction). The metabolic activity and endosomal system of eukaryotic cells were not altered by using eluents of CaO glass submicrometric fibers and ZnO fibers at 1 : 10 dilution as cellular media (viability rates over 70%). A dental material was functionalized by embedding ZnO nanofibers above the percolation threshold (20% wt), creating a three-dimensional (3D) fiber network that added an antimicrobial profile. This new ZnO glass fiber composite is proved non-cytotoxic and preserved the antimicrobial effect after immersion in human saliva. This is the first time that a fiber-reinforced liner with strong antimicrobial-activity has been created to prevent secondary caries. The potential of developing new fiber-reinforced composites (FRCs) with antimicrobial properties opens up an extensive field of dental applications where most important diseases have an infectious origin.

Antibacterial properties of laser spinning glass nanofibers

A laser-spinning technique has been used to produce amorphous, dense and flexible glass nanofibers of two different compositions with potential utility as reinforcement materials in composites, fillers in bone defects or scaffolds (3D structures) for tissue engineering. Morphological and microstructural analyses have been carried out using SEM-EDX, ATR-FTIR and TEM. Bioactivity studies allow the nanofibers with high proportion in SiO2 (S18/12) to be classified as a bioinert glass and the nanofibers with high proportion of calcium (ICIE16) as a bioactive glass. The cell viability tests (MTT) show high biocompatibility of the laser spinning glass nanofibers. Results from the antibacterial activity study carried out using dynamic conditions revealed that the bioactive glass nanofibers show a dose-dependent bactericidal effect on Sthaphylococcus aureus (S. aureus) while the bioinert glass nanofibers show a bacteriostatic effect also dose-dependent. The antibacterial activity has been related to the release of alkaline ions, the increase of pH of the medium and also the formation of needle-like aggregates of calcium phosphate at the surface of the bioactive glass nanofibers which act as a physical mechanism against bacteria. The antibacterial properties give an additional value to the laser-spinning glass nanofibers for different biomedical applications, such as treating or preventing surgery-associated infections.

[Unintentional drowning by immersion. Epidemiological profile of victims attended in 21 Spanish emergency departments]

OBJECTIVES

To determine the frequency of accidental drowning seen in paediatric emergency departments, to define the epidemiological profile of the victims, and to analyse the circumstances related to prognosis and survival.

PATIENTS AND METHODS

A multicentre, prospective and descriptive study was conducted on victims of accidental drowning seen in 21 paediatric emergency departments between June and September 2009 and 2010. We collected personal, environmental, safety, security data, as well as the need for cardiopulmonary resuscitation (CPR), hospitalisation rate, sequelae and mortality.

RESULTS

Out of 234,566 emergency department cases, 53 were due to accidental drowning (frequency: 2.2/10,000 consultations during the summer period, 64.2% males). The median age was 3.5 years (p25-75: 2.6-8.4), with 34 had less than 6 years. Thirty-two children were hospitalised. Most drowning occurred in the afternoon (40), in freshwater (49), in private pools (33) and unprotected (33). The victims, mostly healthy children (40), did not know how to swim (38) and were not wearing flotation systems (37/38). There was lack of supervision in 42 cases. Acidosis (20) and hypoxaemia (18) were the most frequent findings. Five children died, 4 were healthy, none knew how to swim or had a float device, and none were supervised. Thirty six children required CPR, mostly applied by family (15). In the children who died, CPR was started after 3 min. Two survivors had hemiparesis.

CONCLUSIONS

Accidental drowning was a rare cause of consultation in paediatric emergency departments. In children less than 6 years, who did not know how to swim, did not use flotation devices in unprotected private pools, and were not properly supervised, there is an increased of suffering from accidental drowning and its associated morbidity. An immersion time> 10 min, starting CPR > 3 min, acidosis, hyponatraemia, and hypothermia on arrival at the emergency department increases mortality. Training family members in cardiopulmonary resuscitation can be useful.

Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO(2) laser cladding

Three-dimensional bioactive glass implants were produced by rapid prototyping based on laser cladding without using moulds. CO(2) laser radiation was employed to melt 45S5 and S520 bioactive glass particles and to deposit the material layer by layer following a desired geometry. Controlled thermal input and cooling rate by fine tuning of the processing parameters allowed the production of crack-free fully dense implants. Microstructural characterization revealed chemical composition stability, but crystallization during processing was extensive when 45S5 bioactive glass was used. Improved results were obtained using the S520 bioactive glass, which showed limited surface crystallization due to an expanded sintering window (the difference between the glass transition temperature and crystallization onset temperature). Ion release from the S520 implants in Tris buffer was similar to that of amorphous 45S5 bioactive glass prepared by casting in graphite moulds. Laser processed S520 scaffolds were not cytotoxic in vitro when osteoblast-like MC3T3-E1 cells were cultured with the dissolution products of the glasses; and the MC3T3-E1 cells attached and spread well when cultured on the surface of the materials.

Laser-assisted production of spherical TiO2 nanoparticles in water

TiO(2) nanoparticles with controllable average diameter have been obtained by laser ablation in water. A monomode ytterbium doped fiber laser (YDFL) was used to ablate a metallic titanium target placed in deionized water. The resulting colloidal solutions were subjected to laser radiation to study the resizing effect. The crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. The colloidal suspensions produced consisting of titanium dioxide crystalline nanoparticles show almost perfect spherical shape with diameters ranging from 3 to 40 nm. The nanoparticles are polycrystalline and exhibit anatase as well as rutile phases.

Laser cladding of bioactive glass coatings

Laser cladding by powder injection has been used to produce bioactive glass coatings on titanium alloy (Ti6Al4V) substrates. Bioactive glass compositions alternative to 45S5 Bioglass were demonstrated to exhibit a gradual wetting angle-temperature evolution and therefore a more homogeneous deposition of the coating over the substrate was achieved. Among the different compositions studied, the S520 bioactive glass showed smoother wetting angle-temperature behavior and was successfully used as precursor material to produce bioactive coatings. Coatings processed using a Nd:YAG laser presented calcium silicate crystallization at the surface, with a uniform composition along the coating cross-section, and no significant dilution of the titanium alloy was observed. These coatings maintain similar bioactivity to that of the precursor material as demonstrated by immersion in simulated body fluid.

Do retinal haemorrhages occur in infants with convulsions?

AIM

To determine the prevalence of retinal haemorrhages in infants presenting with convulsions and admitted to hospital, and to consider whether this finding indicates shaken baby syndrome.

METHODS

Prospective study of children aged 15 days to 2 years admitted with a diagnosis of first convulsion over a 2-year period (May 2004-May 2006). All infants were examined by an experienced ophthalmologist using indirect ophthalmoscopy within 72 h of admission.

RESULTS

182 of 389 children seen in the accident and emergency department were admitted and two were found to have retinal haemorrhages. Both children were eventually diagnosed as being abused.

CONCLUSIONS

Convulsions alone are unlikely to cause retinal haemorrhages in children under 2 years of age.

In vitro testing of Nd:YAG laser processed calcium phosphate coatings

Nd:YAG laser cladding is a new method for deposition of a calcium phosphate onto metallic surfaces of interest in implantology. The aim of this study was to compare the biologic response of MG-63 human osteoblast-like cells grown on Ti-6Al-4V substrates coated with a calcium phosphate layer applied using different methods: plasma spraying as reference material and Nd:YAG laser cladding as test material. Tissue culture polystyrene was used as negative control. The Nd:YAG laser clad material showed a behaviour similar to the reference material, plasma spray, respective to cell morphology (SEM observations), cell proliferation (AlamarBlue assay) and cytotoxicity of extracts (MTT assay). Proliferation, as measured by the AlamarBlue assay, showed little difference in the metabolic activity of the cells on the materials over an 18 day culture period. There were no significant differences in the cellular growth response on the test material when compared to the ones exhibited by the reference material. In the solvent extraction test all the extracts had some detrimental effect on cellular activity at 100% concentration, although cells incubated in the test material extract showed a proliferation rate similar to that of the reference material. To better understand the scope of these results it should be taken into account that the Nd:YAG clad coating has recently been developed. The fact that its in vitro performance is comparable to that produced by plasma spray, a material commercially available for more than ten years, indicates that this new laser based method could be of commercial interest in the near future.

Biological stability and osteoconductivity in rabbit tibia of pulsed laser deposited hydroxylapatite coatings

A comparative study of the biological stability and the osteoconductivity of hydroxylapatite (HA) coatings produced by pulsed laser deposition (PLD) and plasma spraying (PS) was conducted. Three different implant groups were used: grit-blasted titanium rods coated with HA-PLD (2-microm-thick), grit-blasted titanium rods coated with HA-PS (50-microm-thick), and uncoated. Implantation took place into the proximal tibia of 12 mature New Zealand White rabbits for 24 weeks. Samples were evaluated using descriptive histology and histomorphometry. While HA-PS implants showed considerable instability and reduction in thickness after 24 weeks, but no statistical difference to the titanium group, the HA-PLD group showed a significant higher amount of bone apposition (Scheffé test, p<0.05) than the other two groups, without signs of degradation or dissolution. Remarkably, after 6 months, the almost intact thin pulsed laser deposited coating could be observed by electron microscopy in extended areas.

Micro- and nano-testing of calcium phosphate coatings produced by pulsed laser deposition

Micro- and nano-testing methods have been explored to study the thin calcium phosphate coatings with high adhesive strength. The pulsed laser deposition (PLD) technique was utilised to produce calcium phosphate coatings on metal substrates, because this type of coatings exhibit much higher adhesive strength with substrates than conventional plasma-sprayed coatings. Due to the limitations of the conventional techniques to evaluate the mechanical properties of these thin coatings (1 microm thick), micro-scratch testing has been applied to evaluate the coating-to-substrate adhesion, and nano-indentation to determine the coating hardness and elastic modulus. The test results showed that the PLD produced amorphous and crystalline HA coatings are more ductile than titanium substrates, and the PLD coatings are not delaminated from the substrates by scratch. Also, the results showed that the crystalline HA coating is superior in internal cohesion to the amorphous one, even though the lower elastic modulus of amorphous coating could be more mechanically compatible with natural bone.

Calcium phosphate coatings obtained by Nd:YAG laser cladding: physicochemical and biologic properties

The plasma spray (PS) technique is the most popular method commercially in use to produce calcium phosphate (CaP) coatings to promote fixation and osteointegration of the cementless prosthesis. Nevertheless, PS has some disadvantages, such as the poor coating-to-substrate adhesion, low mechanical strength, and brittleness of the coating. In order to overcome the drawbacks of plasma spraying, we introduce in this work a new method to apply a CaP coating on a Ti alloy using a well-known technique in the metallurgical field: laser surface cladding. The physicochemical characterization of the coatings has been carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The biologic properties of the coatings have been assessed in vitro with human osteoblast-like MG-63 cells. The overall results of this study affirm that the Nd:YAG laser cladding technique is a promising method in the biomedical field.

Alloying of hydroxyapatite onto Ti6Al-4V by high power laser irradiation

In the biomedical field, the synthetic hydroxyapatite [Ca(10)(PO)(4)(OH)(2)], with similarity to the inorganic component of bone but brittle, has been considered as the appropriate coating on stronger implant materials, such as metallic implants, for presenting a surface which is conductive to bone formation. Many industrial and laboratory techniques were developed to apply hydroxyapatite onto metallic substrates, such as electrophoretic deposition, ion sputtering, hot isostatic pressing, pulsed laser deposition and the only widely used method commercially available: plasma spraying. This work presents a new approach on how to bind calcium phosphate (CaP) to the Ti alloy with a well-known technique in the metallurgical field: laser surface alloying, in order to overcome the drawbacks of plasma spraying. The analysis of the results obtained and the description of the phenomena that take place in the coating process will complete this explorative study.

Diagnostic approach to inborn errors of metabolism in an emergency unit

OBJECTIVES

Our aim was to review the patients with a final diagnosis of inborn error of metabolism (IEM) who had previously required clinical attention at the emergency unit of our hospital over the last 9 years.

METHODS

From the 184 patients with IEM, we selected 53 patients who required clinical attention at the EU as a prior step that led to a definitive diagnosis. We analyzed the frequency of the various IEM, their clinical presentations, and basic biochemical abnormalities in decompensation.

RESULTS

We detected a predominance of neurologic signs (in 85% of our patients), followed by digestive symptoms (58.5%). Both were associated in 51% of patients. Vomiting and other digestive signs were observed in the same proportion as described in other series, but dehydration was only seen in three of our patients, probably because of early attention and fluid correction.

CONCLUSIONS

1) the diagnosis of an IEM has often been made after the first consultation at the EU, leading to hospitalization; 2) we should suspect an IEM in patients with neurologic abnormalities (eg, developmental delay, hypotonus or feeding difficulties), especially in those patients with multisystem involvement who appear with acute symptoms; 3) it is of the greatest importance that the appropriate sample collection be made before starting any treatment, because abnormal biochemical data can yield a first approach and allow the definitive diagnosis; and 4) the diagnosis of a patient with an IEM is not based on a single clinical or biochemical data but rather on all abnormal features taken together.

Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings

Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 degrees C. They were heated in air at different temperatures: 300, 450, 525 and 650 degrees C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM, XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some beta-tricalcium phosphate in the coatings heated at 525 and 600 degrees C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 degrees C and almost solely for phosphate at 525 and 600 degrees C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600 degrees C. At 450 degrees C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600 degrees C, probably due to a transformation into calcium oxide.

[Imported malaria in children (1993-1998)]

Malaria is the world's most important parasitic infection, accounting for an estimated 300 million cases and 1.5 to 3 million deaths annually. Although it has been eradicated from temperate countries, increasing numbers of travellers visit each year tropical countries, where malaria remains a major cause of morbidity and mortality. Children are particularly at risk from malaria since symptoms can be especially severe and can develop rapidly. Symptoms may differ from those in adults and, as children often have febrile illnesses, malaria could not be suspected. Eleven cases of imported mala-na in children which ages was between 15 month until 13 years, were seen in the Sant Joan de D|u Hospital, Barcelona (Spain) since August 1993 until August 1998. The aetiology was in 7 cases Plasmodium falciparum and in 4 cases Plasmodium vivax, in one case we found also with the P. falciparum some forms of P. malariae. All of them experience fever and anaemia at admission and nine had splenomegaly; the evolution after the treatment was fine. Cases of imported malaria in children are increasing and it is timely to review the prevention and the management.

Acute overdose due to benzydamine

Benzydamine is a nonsteroidal anti-inflammatory drug, currently available as mouthwash, aerosol, dermal cream, vaginal douche preparation, pills and otic drops. Up to now no cases of poisoning due to this drug have been reported. A 6-year-old girl with an accidental poisoning with benzydamine is described. The episode consisted of hallucinosis without other symptoms and resolved spontaneously in 17 h.

Physicochemical properties of calcium phosphate coatings produced by pulsed laser deposition at different water vapour pressures

Calcium phosphate coatings were produced by pulsed laser deposition from targets of non-stoichiometric hydroxyapatite (Ca/P = 1.70) at a substrate temperature of 485 degrees C and different processing pressures of water vapour: 0.15, 0.30, 0.45, 0.60 and 0.80 mbar. The physicochemical properties of these coatings were studied using Fourier-transform IR spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX). A minimum pressure of water vapour was necessary in order to obtain a crystalline coating, as deduced from the FT-IR spectroscopy of these coatings. This analysis also revealed that when the deposition pressure of water vapour was further increased, the coatings were less crystalline and the content of hydroxyl groups, the carbonate substitution for phosphate, and the Ca/P ratio, as measured by EDX, were lower. These effects can be explained by a combined substitution of carbonate and HPO4(2-) for phosphate, being predominant the carbonate substitution at low pressures and the HPO4(2-) substitution at high pressures.

Structural analysis of calcium phosphate coatings produced by pulsed laser deposition at different water-vapour pressures

Calcium phosphate coatings have been produced by pulsed laser deposition (PLD) at different water-vapour pressures. Rietveld refinement of X-ray diffraction (XRD) data allows us to determine that the structure of these coatings is apatitic with carbonate substitution for phosphate. The carbonate substitution decreases when the chamber pressure is raised, a fact that has been corroborated by Fourier transform-infrared (FT-IR) spectroscopy. Carbonate concentrations between 5 and 17 wt% have been calculated for the crystalline samples. Amorphous coatings are produced at the lowest and highest pressures due to the high carbonate concentration in the first case, and possibly to another type of substitution (Mg(2+), HPO(2-)4, P2O(4-)7) or the inherent kinetics of the PLD process, in the second case.

Hydroxyapatite coatings: a comparative study between plasma-spray and pulsed laser deposition techniques

A comparative study between hydroxyapatite coatings produced by two different techniques, plasma spray (PS) and pulsed-laser deposition (PLD) was carried out. Plasma spray is currently commercially used for coating dental and orthopaedical implant devices, and pulsed-laser deposition (or laser-ablation deposition) gave good results in the field of high critical temperature superconductive thin films, and is being applied to produce calcium phosphate coatings for biomedical purposes. X-ray diffraction was used to control the crystallinity of the coatings, scanning electron microscopy for the surface and cross-sectional morphology, and the pull test to determine the tensile strength of the coatings. This study reveals that the pulsed-laser deposition technique appears to be a very good candidate to replace the plasma spray in many biomedical applications, because it overcomes most of the drawbacks of the plasma spray.

[The evaluation of an incentive system for the primary care professionals of Mallorca]

OBJECTIVE

To describe the assessment made by Mallorca's primary care professionals of the economic incentives system set up in 1994 and find their opinions of financial incentives and other motivating mechanisms.

DESIGN

A descriptive, crossover study.

SETTING

Primary care in Mallorca (INSALUD of the Balearics).

PARTICIPANTS

All the health professionals and ancillary workers (554) of Mallorca's 24 Health Centres.

MEASUREMENTS AND MAIN RESULTS

A self-filled questionnaire was used as a measuring instrument. There was a 74% reply rate. Their assessment of the incentives system used was that the distribution of the incentives was unjust and a cause of tension. However, expectations as to the amount received had been met to a reasonable extent. Self-management was a stronger motivating force than incentives (48.4% vs 13.6%).

CONCLUSIONS

The incentives system used displayed certain faults (in distribution and the work atmosphere generated). However, decentralization was shown to be a powerful motivating force. Monitoring professionals' expectations and the fulfillment of them should be integrated into management habits.

[Evaluation of the system of direct purchase and distribution of urinary incontinence pads in primary care centers]

OBJECTIVE

To evaluate the impact of the pilot experience of direct purchase and distribution of incontinence diapers in primary health care centres of the Balearic Islands after 10 months of implementation.

DESIGN

Comparison of diapers's public expenditures and use during 10 months of pilot experience (9/1/1994-6/30/1995: POSTC) to a same length period prior to pilot experience implementation (11/1/1993-8/31/1994: PREC).

SETTING

Primary health care centres of the Balearic Islands (Spain).

MEASUREMENTS AND RESULTS

Monthly mean of packages used in the PREC period was 3,246 packages/month, whereas monthly mean of packages used in POSTC period was 4,541 packages/month. It means an increase of 1,295 packages/month. The mean price per package got by public tender was 4,426 ptas., nearly half of mean unit price per package paid through the usual dispensing system of medical prescription (8,583 ptas.), thus producing a saving of 4,157 ptas. per package. A decreasing trend to the monthly mean of diapers use of the PREC period was observed in the last months of the experience. The monthly expenditures in diapers was 27,790 milions ptas. in the PREC period and 21,024 milions ptas. during the POSTC period.

CONCLUSIONS

The expected increase in diapers use during the first year of implementation of this measure was 34.86%. Of this increase, 70.5% is attributed to development of stock in centres and the undergoing trend of diapers demand increase observed throughout the country.

[The pharmaceutical prescription: a comparison between the old and the new model of primary health care]

The possible influence of the model of primary health care (PHC), the educational background of the physician and the type of contract on pharmaceutical prescription were evaluated. The information was obtained from a sample of 1799 prescriptions, which were representative of the overall prescription of the PHC physicians from the Health Service of Palma de Mallorca. The health center physicians (HC) prescribed less expensive drugs than the classical clinic physicians (CC). The mean prize for HC was 498.98, with SD 418.97, and for CC it was 589.65 with SD 750.25. This difference was significant (p less than 0.0001). There were other significant differences, such as a smaller use of preparations with fixed drug associations (p less than 0.01) and parenteral administration (p less than 0.05) by HC. There were no significant differences in the prescription of cerebral and peripheral vasodilators and drugs for the digestive tract and metabolism considered as doubtful indications.

[Induction of cellulases and xylanases in Aureobasidium pullulans]

The specificity or induction of wood-degrading enzymes using series of mono, di or polysaccharides as carbon source for the yeasts Geotrichum candidum and Trychosporon penicillatum and the yeast-like organism Aureobadidium pullulans were studied. The strain A. pullulans was the only one that when xylan or "steam exploded wood" were used as carbon source all the enzymes tested were found. This strain was unable to grow on carboxymethyl or Avicel cellulose. D-xylose was the nutritional inducer of beta-xylosidase and beta-xylanase but D-glucuronic acid induced CMCase activity and beta-glucosidase was produced with every carbon source. The 1,4 beta-xylobiose was not an inducer of beta-xylanase but with the structural 1,2-beta- and 1,3-beta-xylobiose isomers high levels of this enzyme were obtained.

Effects of tolbutamide pretreatment on the rate of conversion of newly synthesized proinsulin to insulin and the compartmental characteristics of insulin storage in isolated rat islets

Tolbutamide (1 g/kg body wt) was administered to male rats for 3 days to determine the effects of this pretreatment on subsequent insulin biosynthesis and compartmental storage characteristics of freshly isolated islets. Islets were isolated 16 h after the last tolbutamide administration, at a time when fed plasma glucose concentrations were normal. Islet glucagon was unchanged but insulin content was significantly reduced (38 +/- 1.2 ng IRI/islet from seven untreated rats versus 7.9 +/- 1.2 ng IRI/islet from eight treated rats). After tolbutamide pretreatment, the rate of incorporation of 3H-leucine into islet proinsulin was unchanged, but the t1/2 of labeled proinsulin-to-insulin conversion was significantly (P less than 0.001) decreased from 36 to 20 min. After treatment, actual rates of glucose-stimulated insulin secretion were 50% lower, however, because due to the proportionately greater depletion of islet insulin content, the fractional rate of secretion was increased two-fold. After treatment, there was evidence of compartmental, heterogeneous insulin storage, and glucose still marked newly synthesized insulin for preferential release; however, the differential release of new and old insulin converged rapidly with time. Mathematical integration of the data suggested dilution of the newly synthesized insulin compartment with unlabeled insulin during the chase period, but additionally indicated more rapid mixing of newly synthesized with previously stored, unlabeled insulin. Thus, tolbutamide-treated rats partially compensated for acute insulin depletion by increasing the rate of proinsulin-to-insulin conversion, but not increasing the rate of proinsulin biosynthesis; doubling the glucose-stimulated fractional secretory rate of the depleted cellular insulin storage compartment; and retaining compartmental storage characteristics but mixing newly synthesized insulin more rapidly with the compartment of previously stored, unlabeled insulin.

[Mediterranean boutonneuse fever in children. Study of 139 cases]

A prospective study of 139 children suffering mediterranean spotted fever, all of them hospitalized during the summer time of the last five years is presented. Clinical features were high fever, maculopapulous rash and black eschar ("tàche noire"). Among analytical findings, leucocyte count was decreased in a 38.8% of children during the first week of illness. Weil-Felix test was positive in 47.2% for OX-2 and 52.7% for OX-19 of cases. The indirect immunofluorescence for rickettsial conorii was positive in 100% of cases in the second determination. 74.1% of patients received antimicrobial therapy and 25.9% symptomatic treatment. All children cured without complications.

Effects of monensin on conversion of proinsulin to insulin and secretion of newly synthesized insulin in isolated rat islets

When isolated rat islets were incubated with 10(-10) - 10(-6) M monensin, a sodium and proton ionophore, glucose-stimulated insulin release was inhibited in a concentration- and time-dependent manner. After removal of monensin, inhibition of insulin secretion persisted during stimulation with a variety of secretagogues, including 5 mM glucose plus 15 mM arginine, 20 mM glucose, and 20 mM glucose plus 1 mM 3-isobutyl-1-methylxanthine. Within the same low range of monensin concentrations, proteolytic conversion of newly synthesized proinsulin to insulin was also blocked. At each concentration, prohormone-to-hormone conversion was inhibited to almost the same extent as inhibition of insulin secretion. Therefore, both processes may have equal or common dependency on a subcellular ionic gradient. Although monensin decreased total insulin secretion, the glucose-regulated marking process was unaffected. Regardless of the monensin concentration or the overall rate of insulin secretion, the percentage of secreted newly synthesized versus older insulin remained the same, and the threefold differences in the fractional secretory rates of newly synthesized versus total insulin also remained the same. Thus, rather than specifically blocking protein traffic through the Golgi apparatus of the beta cell, monensin probably first inhibited insulin secretion by disrupting proton gradients in secretory vesicles and, thereby, also inhibited other processes occurring within this organelle.

[Hematemesis in childhood. Use of the fiberscope in diagnosis]

Authors report the results of utilization of fiberscope (FEC) in pediatric patients with hematemesis. They emphasize the utility of this method, its high percentage of positivity in the diagnostic in relation to the precocity of the FEC and the high incidence of hemorrhage gastritis in relation to salycilates ingest.