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Summary Emerging technologies in stem cell engineering have produced sophisticated organoid platforms by controlling stem cell fate via biomaterial instructive cues. By micropatterning and differentiating human induced pluripotent stem cells (hiPSCs), we have engineered spatially organized cardiac organoids with contracting cardiomyocytes in the center surrounded by stromal cells distributed along the pattern perimeter. We investigated how geometric confinement directed the structural morphology and contractile functions of the cardiac organoids and tailored the pattern geometry to optimize organoid production. Using modern data-mining techniques, we found that pattern sizes significantly affected contraction functions, particularly in the parameters related to contraction duration and diastolic functions. We applied cardiac organoids generated from 600 μm diameter circles as a developmental toxicity screening assay and quantified the embryotoxic potential of nine pharmaceutical compounds. These cardiac organoids have potential use as an in vitro platform for studying organoid structure-function relationships, developmental processes, and drug-induced cardiac developmental toxicity., Graphical abstract, Highlights • Micropattern-based geometric confinement directs cardiac organoid development • Cardiac organoid structure-function relationships are guided by organoid size • Cardiac organoids can be used as an in vitro embryotoxicity assessment tool, Advances in organoid engineering have produced sophisticated organoid platforms by controlling stem cell fate via biomaterial instructive cues. Ma and colleagues show that micropatterning is a versatile tool to engineer cardiac organoids with different architectures and cardiac functions. Furthermore, the cardiac organoid development was sensitive to numerous drug compounds and demonstrated potential as an embryotoxicity screening platform.

BACKGROUND AND PURPOSE: Computed tomography angiography offers a non-invasive alternative to DSA for the assessment of cerebral vasospasm following subarachnoid hemorrhage but there is limited evidence regarding its reliability. Our aim was to perform a systematic review (Part I) and to assess (Part II) the inter- and intraobserver reliability of CTA in the diagnosis of cerebral vasospasm. MATERIALS AND METHODS: In Part I, articles reporting the reliability of CTA up to May 2018 were systematically searched and evaluated. In Part II, 11 raters independently graded 17 arterial segments in each of 50 patients with SAH for the presence of vasospasm using a 4-category scale. Raters were additionally asked to judge the presence of any moderate/severe vasospasm (≥ 50% narrowing) and whether findings would justify augmentation of medical treatment or conventional angiography ± balloon angioplasty. Four raters took part in the intraobserver reliability study. RESULTS: In Part I, the systematic review revealed few studies with heterogeneous vasospasm definitions. In Part II, we found interrater reliability to be moderate at best (κ ≤ 0.6), even when results were stratified according to specialty and experience. Intrarater reliability was substantial (κ > 0.6) in 3/4 readers. In the per arterial segment analysis, substantial agreement was reached only for the middle cerebral arteries, and only when senior raters’ judgments were dichotomized (presence or absence of ≥50% narrowing). Agreement on the medical or angiographic management of vasospasm based on CTA alone was less than substantial (κ ≤ 0.6). CONCLUSIONS: The diagnosis of vasospasm using CTA alone was not sufficiently repeatable among observers to support its general use to guide decisions in the clinical management of patients with SAH.

Impaired temporal perception of multisensory cues is a common phenomenon observed in older adults that can lead to unreliable percepts of the external world. For instance, the sound induced flash illusion (SIFI) can induce an illusory percept of a second flash by presenting a beep close in time to an initial flash-beep pair. Older adults that have enhanced susceptibility to a fall demonstrate significantly stronger illusion percepts during the SIFI task compared to those older adults without any history of falling. We hypothesize that a global inhibitory deficit may be driving the impairments across both postural stability and multisensory function in older adults with a fall history (FH). We investigated oscillatory activity and perceptual performance during the SIFI task, to understand how active sensory processing, measured by gamma (30–80 Hz) power, was regulated by alpha activity (8–13 Hz), oscillations that reflect inhibitory control. Compared to young adults (YA), the FH and non-faller (NF) groups demonstrated enhanced susceptibility to the SIFI. Further, the FH group had significantly greater illusion strength compared to the NF group. The FH group also showed significantly impaired performance relative to YA during congruent trials (2 flash-beep pairs resulting in veridical perception of 2 flashes). In illusion compared to non-illusion trials, the NF group demonstrated reduced alpha power (or diminished inhibitory control). Relative to YA and NF, the FH group showed reduced phase-amplitude coupling between alpha and gamma activity in non-illusion trials. This loss of inhibitory capacity over sensory processing in FH compared to NF suggests a more severe change than that consequent of natural aging.

Background and purpose Appropriate management of ruptured intracranial aneurysm (RIA) in patients eligible for surgical clipping but under-represented in or excluded from previous randomized trials remains undetermined. Methods The International Subarachnoid Aneurysm Trial-2 (ISAT-2) is a randomized care trial comparing surgical versus endovascular treatment (EVT) of RIA. All patients considered for surgical clipping but eligible for endovascular treatment can be included. The primary endpoint is death or dependency on modified Rankin score (mRS > 2) at 1 year. Secondary endpoints are 1 year angiographic results and length of hospital stay. Results An interim analysis was performed after 103 patients were treated from November 2012 to July 2017 in 4 active centers. Fifty-two of the 55 patients allocated to surgery were treated by clipping, and 45 of the 48 allocated to EVT were treated by coiling, with 3 crossovers in each arm. The main endpoint (1 year mRS > 2), available for 76 patients, was reached in 16/42 patients allocated to clipping (38%; 95%CI: 25%–53%), and 10/34 patients allocated to coiling (29%; 17%–46%). One year imaging results were available in 54 patients: complete aneurysm occlusion was found in 23/27 patients allocated to clipping (85%; 67%–94%), and 18/27 patients allocated to coiling (67%; 47%–81%). Hospital stay exceeding 20 days was more frequent in surgery (26/55 [47%; 34%–60%]) than EVT (9/48 [19%; 10%–31%]). Conclusion Ruptured aneurysm patients for whom surgical clipping may still be best can be managed in a randomized care trial, which is feasible in some centers. More participating centers are needed.

Introduction Palliative gastrojejunostomy is a surgical technique that allows restoration of oral intake among patients with gastric outlet obstruction (GOO) caused by unresectable neoplasms. Research suggests standard treatment for malignant GOO should be laparoscopic gastrojejunostomy (LGJ). This study presents the clinical outcomes of palliative gastrojejunostomy and compares results from LGJ and open gastrojejunostomy (OGJ) at our centre. Methods We performed a retrospective analysis on patients who underwent palliative gastrojejunostomy for GOO caused by unresectable neoplasms between 2008 and 2018. We included demographic variables, time to recover intestinal transit, time to recover oral intake, hospital stay, complications and global survival. Results A total of 39 patients underwent palliative gastrojejunostomy (20 OGJ, 19 LGJ). Patients in the LGJ group recovered oral intake and intestinal transit faster than those in the OGJ group (3 vs 5 days, pConclusions Palliative LGJ allows earlier restoration of oral intake and does not increase morbidity or mortality. Palliative LGJ should be considered the standard treatment for these patients.

Reliable duration perception is an integral aspect of daily life that impacts everyday perception, motor coordination, and subjective passage of time. The Scalar Expectancy Theory (SET) is a common model that explains how an internal pacemaker, gated by an external stimulus-driven switch, accumulates pulses during sensory events and compares these accumulated pulses to a reference memory duration for subsequent duration estimation. Second-order mechanisms, such as multisensory integration (MSI) and attention, can influence this model and affect duration perception. For instance, diverting attention away from temporal features could delay the switch closure or temporarily open the accumulator, altering pulse accumulation and distorting duration perception. In crossmodal duration perception, auditory signals of unequal duration can induce perceptual compression and expansion of durations of visual stimuli, presumably via auditory influence on the visual clock. The current project aimed to investigate the role of temporal (stimulus alignment) and nontemporal (stimulus complexity) features on crossmodal, specifically auditory over visual, duration perception. While temporal alignment revealed a larger impact on the strength of crossmodal duration percepts compared to stimulus complexity, both features showcase auditory dominance in processing visual duration.

In order to improve teaching skills and develop a medical educator community of practice within a supportive environment, we implemented a Teaching Squares methodology at Herbert Wertheim College o...

Understanding the complexity of biological signals has been gaining widespread attention due to increasing knowledge on the nonlinearity that exists in these systems. Cardiac signals are known to exhibit highly complex dynamics, consisting of high degrees of interdependency that regulate the cardiac contractile functions. These regulatory mechanisms are important to understand for the development of novel in vitro cardiac systems, especially with the exponential growth in deriving cardiac tissue directly from human induced pluripotent stem cells (hiPSCs). This work describes a unique analytical approach that integrates linear amplitude and frequency analysis of physical cardiac contraction, with nonlinear analysis of the contraction signals to measure the signals’ complexity. We generated contraction motion waveforms reflecting the physical contraction of hiPSC-derived cardiomyocytes (hiPSC-CMs) and implemented these signals to nonlinear analysis to compute the capacity and correlation dimensions. These parameters allowed us to characterize the dynamics of the cardiac signals when reconstructed into a phase space and provided a measure of signal complexity to supplement contractile physiology data. Thus, we applied this approach to evaluate drug response and observed that relationships between contractile physiology and dynamic complexity were unique to each tested drug. This illustrated the applicability of this approach in not only characterization of cardiac signals, but also monitoring and diagnostics of cardiac health in response to external stress.

Results showed that 75% of the analyzed samples in a drinking water network were positive for fungi, in a range of 1–3,000 CFU/mL. Identification resulted in nine species of fungi and four species of yeasts being listed: Bjerkandera, Penicillium, Paraconiothyrium, Paecilomyces, Debaryomyces, Rhodotorula and Cryptococcus. Although yeasts showed higher traceability than filamentous fungi, the fungal genus Penicillium had relevance by both traceability (six species) and its role in mycotoxin generation. From volatile organic compound (VOC) mycotoxins and extracts analysis from P. ochrochloron and P. purpurogenum water–M9 culture, six groups were identified: phenols, alcohols, alkenes, monoterpenes, aldehydes and alkanes, phenols being the predominant group (2,4-bis(1,1-dimethyl)phenol 40–88%). P. ochrochloron water culture and M9 culture reported signals of toxicity: the first one as genotoxic for 0.5 y 1 mg/mL mycotoxin extract and the second one as cytotoxic. M9 media promoted a higher number of compounds in both species and a decrease in phenol predominance in P. ochrochloron but not in P. Purpurogenum. The results showed Penicillium and Debaryomyces as prevalent filamentous fungi and yeast in assessed networks, suggesting that these could be indicators of fungi and yeast presence in drinking water systems.

We evaluated the effect of cadmium (Cd) on the structure and function of the head kidney in the freshwater fish Colossoma macropomum (C. macropomum). Juveniles were exposed to 0.1 mg/L CdCl2 for 31 days. Blood samples were examined using hematological tests and head kidney histology was determined by light microscopy. The concentration of Cd in the head and trunk kidneys was measured using an atomic absorption spectrophotometer. Cd produced histopathological changes in the head kidney, the most evident of these being: the thickening of the vein wall, an increase in the number of basophils/mast cells close to blood vessels and a severe depletion of hematopoietic precursors especially the granulopoietic series. In the blood, a decrease in the total leucocytes and hemoglobin concentration was observed. Cd-exposed fish showed higher Cd concentrations in the trunk kidney than the head kidney. In conclusion, exposure to Cd affected precursor hematopoietic cells in C. macropomum.Keywords: Cadmium, Colossoma macropomum, Granulocytes, Head kidney, Histology.

The effects of boron content and preparation methods are studied in this present investigation. Three different methods are employed for the preparation of catalysts. The catalysts are characterized by pore size distribution (PSD), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Thiophene hydrodesulfurization (HDS), cumene hydrocracking (HC), gas oil HDS and Maya heavy crude oil HDS, and hydrodemetallization (HDM) activities are tested. The results show that the specific surface area and PSD are not changed with B loading. The enrichment of metal distribution on the alumina surface is observed from SEM experiments for the 0.6B–NiMo catalyst. More staging of MoS2 active phases is noticed in the B catalyst than the B-free catalyst. It can be stated that boron forms a monolayer on the alumina surface and reduces the metal–support interaction. It facilitates the formation of more staging of active phases. The thiophene HDS activity slightly increases wi...

1,2,3-Cyclohexanetrione-1,2-dioxime-3-thiosemicarbazone (CTDT), produces coloured complexes with zinc and cadmium ions in basic medium. The yellow colour obtained has been used to develop spectrophotometric methods for zinc and cadmium in the concentration range 1.30-8.50 μg ml−1 of zinc and 1.20-6.50 μg ml−1 of cadmium. A new method for the determination of zinc and cadmium in mixtures is proposed for concentrations between 0.5-6.0 μg ml−1 and 0.8-5.5 μg ml−1 by first derivative spectrophotometry and between 0.5-6.0 μg ml−1 and 0.8-5.5 μg ml−1 by second derivative spectrophotometry.

Glutamate, released from central terminals of glossopharyngeal nerve, is a major excitatory neurotransmitter of commissural nucleus tractus solitarii (cNTS) afferent terminals, and brain derived neurotrophic factor (BDNF) has been shown to attenuate glutamatergic AMPA currents in NTS neurons. To test the hypothesis that AMPA contributes to glucose regulation in vivo modulating the hyperglycemic reflex with brain glucose retention (BGR), we microinjected AMPA and NBQX (AMPA antagonist) into the cNTS before carotid chemoreceptor stimulation in anesthetized normal Wistar rats, while hyperglycemic reflex an brain glucose retention (BGR) were analyzed. To investigate the underlying mechanisms, GluR2/3 receptor and c-Fos protein expressions in cNTS neurons were determined. We showed that AMPA in the cNTS before CChr stimulation inhibited BGR observed in aCSF group. In contrast, NBQX in similar conditions, did not modify the effects on glucose variables observed in aCSF control group. These experiments suggest that glutamatergic pathways, via AMPA receptors, in the cNTS may play a role in glucose homeostasis.

A new, rapid and simple method is described and applied to resolve and quantify mixtures of prednisolone, Zn-bacitracin and phenylephrine. The determination was accomplished by MEKC. The separation was carried out at 25 °C and 30 kV, using a 5 mM phosphate-5 mM borate buffer (pH=8.2), 40 mM SDS as background electrolyte. Under these conditions, the run time was 6.6 min and the limits of quantification were about 1.0 mg L−1 for every component. Repeatability and reproducibility studies were achieved showing no significant differences at 95% confidence level. The MEKC method has been applied for quantifying these compounds in different commercials pharmaceuticals products, without separations steps.

A new, rapid and simple method is described and applied to resolve and quantify mixtures of prednisolone acetate, sulfacetamide and phenylefrine. The determination was accomplished by micellar electrokinetic capillary chromatography (MEKC) using a fused silica capillary (57 cm x 75 microm ID). The separation was carried out at 25 degrees C and 30 kV, using a 5 mM phosphate-5 mM borate buffer adjusted to pH 8.2, 40 mM sodium dodecylsulfate (SDS) as background electrolyte. Under these conditions, the run time was 6.5 min and the limits of quantification were about 0.5 mg l(-1) for every component. Repeatability and reproducibility studies achieved were showing no significant differences at 95% confidence level. Then, multivariate calibration regression spectrophotometric methods (PLS-1, PLS-2 and PCR) were applied providing, especially PLS-1, a clear example of the high resolving power of these techniques. The MEKC method has been applied for quantifying these compounds in different commercial pharmaceuticals products and the method gave good results when it is compared with the spectrophotometric method. The pharmaceutical preparations do not require any separation step by the two described procedures.

A method for quantifying hydrocortisone (HYD), hydrocortisone acetate (HYDA), oxytetracycline (OXY), Zn‐bacitracin (BAC), and polymyxin B (PLX) in pharmaceutical products by micellar electrokinetic chromatography (MEKC) is described. The separation was carried out at 25°C and 25 kV, using a 15 mM phosphate–15 mM borate buffer (pH = 8.2), 60 mM sodium dodecyl sulfate (SDS), and 10% methanol–water (v/v) as a background electrolyte. Under these conditions, the analysis takes about 23 min. The method has been applied for quantifying these compounds in four different commercial pharmaceutical products, and the method gave good results when compared with a reference spectrophotometric method.

A new, simple and accurate micellar electrokinetic chromatography (MEKC) method is established for quantification of hydrocortisone, polymyxin B and Zn-bacitracin in local pharmaceutical preparations. The separation was carried out at 25 degrees C and 25 kV, using a 15 mmol L(-1) phosphate-15 mmol L(-1) borate buffer (pH 8.2), 60 mmol L(-1) sodium dodecylsulfate (SDS), and 10% methanol-water (v/v) as background electrolyte. Under these conditions the analysis takes about 23 min. The method has been applied for quantifying these compounds in two different commercial pharmaceutical products and the method gave good results when compared with a reference spectrophotometric multivariate calibration method.

A reverse phase high performance liquid chromatographic (HPLC) method to determine Hydrocortisone (HYD), Oxytetracycline (OXY) and Nystain (NYS) has been developed. The separation was made on a LichrCARTŖ C18 column using methanol-NaH2PO4/Na2HPO4 gradient elution and a diode-array detector measuring at the maximum absorption wavelength for each compound. Quantification limits ranging from 0.19 to 0.85 μg L−1 were obtained. The method was applied to synthetic mixtures and pharmaceutical formations. Analyses were made from the stock solutions and by means of standard addition. Both methods showed similar results, and the claimed levels of pharmaceutical preparations were sown to be in agreement with the results from our analytical method.

Two spectrophotometric methods are described and applied to resolve ternary mixtures of the corticosteroid hydrocortisone (HYD) and the antibiotics nystatin (NYS) and oxytetracycline (OXY). The simultaneous determination of these three compounds was firstly accomplished by a derivative method using the “ratio spectrum-zero crossing derivative” and then by multivariate methods partial least squares (PLS)-1, -2 and principal component regression (PCR). Multivariate calibration methods provide, specially PLS-2 in this case, a clear example of the high resolving powder of these techniques. The two described procedures do not require any separation step. Repeatability and reproducibility studies were achieved over two series of 10 standards for each compound showing no significant differences at 95% confidence level in the four spectrophotometric methods. A comparison of the derivative and multivariate calibration results obtained in pharmaceutical formulations was performed resulting in agreement of the values obtained and the results was confirm by a high-pressure liquid chromatography (HPLC) method.

A capillary zone electrophoresis method is presented to separate hydrocortisone 21-hemisuccinate, oxytetracycline HCl and nystatin by using a fused-silica capillary (57 cm × 75 µm I.D.). The separation was carried out at 30 kV and 25°C in a 10 mM phosphate buffer adjusted to pH = 11 as electrolyte. Under these conditions, the run time was 4 min and the limits of quantification were about 2 mg/L for every component. The new method was applied to two pharmaceutical preparations and the results provided recoveries close to 100%. These results compared well with a reference HPLC method.

Four spectrophotometric methods are described and applied to resolve ternary mixtures of the corticosteroid Dexamethasone (DEX), the antibiotic Polymyxin B (PLX) and its encouraging Trimethoprim (TMP). The simultaneous determination of these three compounds was firstly accomplished by a derivative method using the “ratio spectrum-zero crossing derivative” (satisfactory results in synthetic mixtures in different ratios and pharmaceutical formulations for DEX and TMP) and then by multivariate methods (satisfactory results in synthetic mixtures in different ratios and pharmaceutical formulations for DEX, PLX and TMP). Absorption spectra of compounds were used to optimise the spectral data set performs the calibration by partial least squares (PLS) 1 and 2 and principal component regression (PCR) algorithms. These calibration models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over synthetic and pharmaceutical mixtures. The four described procedures do not require any separation step. Repeatability and reproducibility studies were achieved over two series of 10 standards for each compound showing no significant differences at 95% confidence level in the four spectrophotometric methods. A comparison of the derivative and multivariate calibration results obtained in pharmaceutical formulations was performed resulting in agreement of the values obtained. © 2001 Elsevier Science B.V. All rights reserved.

Five spectrophotometric methods are described and applied to resolve binary mixtures of the corticosteroid Dexamethasone and the antibiotic Polymyxin B. The simultaneous determination of the two compounds was firstly accomplished by two derivative methods using the “first derivative” and the “ratio spectrum-zero crossing derivative”, which were satisfactory used to determine synthetic mixtures of these compounds in different ratios. Absorption spectra of compounds were used to optimise the spectral data set by performing the calibration by partial least squares-1 and 2 and principal component regression algorithms. These calibration models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over synthetic mixtures. The five described procedures do not require any separation step. Repeatability and reproducibility...

Reduction in energy consumption is known to inhibit development of a variety of spontaneous, carcinogen-induced, and hormone-dependent cancers, but the mechanism or mechanisms by which this occurs remain unknown. We hypothesize that energy consumption may modulate development of estrogen-dependent neoplasms by altering the manner in which target cells respond to estrogens. To test this hypothesis, ovariectomized female Fischer 344 rats were fed diets that allowed consumption of different amounts of energy, and the ability of 17beta-estradiol (E2), administered for 10 wk from subcutaneous Silastic implants, to promote development of prolactin-producing pituitary tumors was examined. A 40% restriction of energy consumption virtually abolished the ability of E2 to promote development of pituitary tumors and associated hyperprolactinemia. A 25% restriction of energy consumption appeared to slightly inhibit E2-induced pituitary growth and hyperprolactinemia, but the observed degree of inhibition was not statistically significant. Interestingly, dietary energy restriction did not inhibit induction by E2 of pituitary cell proliferation and lactotroph hyperplasia. Furthermore, E2 treatment inhibited expression of testosterone-repressed prostate message-2 mRNA, a cellular marker of apoptosis, and this inhibitory effect of E2 was blocked by 40% energy restriction. These data suggest that dietary energy restriction virtually abolished E2-induced development of prolactin-producing pituitary tumors, not by blocking the ability of E2 to induce cell proliferation but rather by blocking the ability of E2 to enhance cell survival. This study and the accompanying paper provide the first indication that dietary energy consumption may modulate estrogen action at the level of the target cell.

A stopped flow method for the determination of dopamine and methyldopa is proposed. The method is based on the aerial oxidation of these catecholamines in strong alkali medium. The method was optimized using a spectrophotometer (λ = 360 nm) as detector. Calibration graphs were linear up to 2 × 10−4 mol/L for dopamine and 3.0 × 10−4 mol/L for methyldopa with quantification limits of 3.5 × 10−6 mol/L and 4.3 × 10−7 mol/L for dopamine and methyldopa, respectively. The method was successfully applied to the determination of catecholamines in pharmaceutical formulations.

The voltammetric behavior of sulfadimetoxol (SDX) was studied by square-wave techniques, leading to two methods for its determination in aqueous samples and veterinary formulations. The application of the square-wave mode shows the determination of SDX between 1 × 10−7 M and 2 × 10−6 M at −0.60 V and for the stripping voltammetry of adsorbed SDX with an accumulation step of 15 s proved to be more sensitive, yielding signals five times larger than those obtained without the accumulation. The determination of SDX was done between 2 × 10−8 M and 5 × 10−7 M by stripping mode. The relative standard deviations obtained for concentration levels of SDX as low as 3 × 10−7 M with square-wave was 3.4 % (n = 8) and for 2 × 10−7 M with stripping square-wave was 3.1 % (n = 8). The methods were satisfactorily applied for determining SDX in four veterinary products.

The voltammetric behavior of pyrimethamine (PMT) was studied by square-wave (SW) and square-wave stripping (SWS) techniques, leading to two methods for its determination [in presence of sulfaquinoxaline (SQX)] in aqueous samples and veterinary formulations. Due to overlapping response of SQX and PMT the first derivative was used for the simultaneous determination of these two components. The relative standard deviations obtained for concentration levels of PMT as low as 3 × 10−6 M (SW) and 5 × 10−7 M (SWS) were 2.2% and 2.7% (n = 10), respectively.

Two-component mixtures of cefsulodin and clavulanic acid were analysed by a first-derivative spectrophotometric method using a zero-crossing technique of measurement. The relative ease offered by this derivative technique for the quantification of these drugs, with closely overlapping spectral bands, was clearly demonstrated. As the absorption band of clavulanic acid closely overlaps with that of cefsulodin, both direct and derivative spectrophotometric methods have been investigated and evaluated by an exhaustive statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more rapid, accurate and reproducible. The procedure does not require any separation step. The calibration graphs were linear in the range 2.0-56.0 micrograms ml-1 for cefsulodin and 2.0-28.0 micrograms ml-1 for clavulanic acid. The lower detection limits of cefsulodin and clavulinic acid (P 0.05 level) were calculated to be 0.16 and 0.24 microgram ml-1, respectively. Mixtures of cefsulodin and clavulanic acid in ratios of 1:4-7:2 were satisfactorily resolved. Both components were also determined in physiological solutions used to prepare intravenous infusions of these antibiotics.

A new spectrophotometric multicomponent analysis method, for resolving a ternary mixture of sulphaquinoxaline (SQX), sulphamethazine (SMT) and pyrimethamine (PMT) on the basis of the simultaneous use of the first derivative of ratio spectra and measurements of zero-crossing wavelengths is described. The procedure does not require any separation step. The optima conditions were established and the method was tested in synthetic mixtures (for SQX:SMT:PMT ratios from 1:1:4 to 1:4:1 and to 4:1:1). Finally, the method is applied for the quantification of the three compounds in a commercial product and the found results are compared with those ones obtained by PLS-2 and HPLC.

Derivative spectrophotometry, on the basis of the zero-crossing measurements in the first derivative spectra, is used for the resolution of the binary mixtures of cephradine (CED) and clavulanic acid (CA). Neither sample pretreatment nor any separation step were required. Linear calibration graphs of first derivative values at 277.0 and 235.5 nm for cephradine and clavulanic acid, respectively, with negligible intercept on the y-axis were obtained versus concentration in the range of 2.0-56.0 μg mL−1 for cephradine and 2.0-28.0 μg mL−1 for clavulanic acid. The detection limits for cephradine and clavulanic acid at a 0.05 level of significance, were 0.16 and 0.17 μg mL−1, respectively. The proposed method has been applied to determine these drugs in mixtures. Injectable dosages forms of cephradine and standard clavulanic acid were mixed and determined in saline physiological serum and physiological serum containing glucose.

First-derivative spectrophotometric method with a “zero-crossing” technique of measurement has been used for the quantification of two-components mixtures of cephalothin and clavulanic acid. As the absorption bands of these drugs overlap, both direct and derivative spectrophotometric methods have been investigated and evaluated by a rigorous statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more accurate, direct and reproducible.

A new spectrophotometric method has been applied for resolving binary mixtures of cephradine (CED) and clavulanic acid (CA). The method is based on the use of the first derivative of the ratio spectra obtained by dividing the amplitudes, at appropriate wavelengths, of the absorption spectra of the mixtures by those of a standard solution of clavulanic acid for determining cephradine and a standard solution of cephradine for determining clavulanic acid. Beer's law is obeyed for cephradine concentrations up to 56.0 mg/l and for clavulanic acid concentrations up to 32.0 mg/l. The recovery values of cephradine and clavulanic acid in their 6:1 and 1:4 (m/m) mixtures were satisfactory.

A new method is described for analysing the binary mixture of sulfamethoxazole and trimethoprim, using the ratio spectra derivative spectrophotometry. The procedure does not require any separation step. Calibration graphs were linear up to 25 mg/l of sulfamethoxazole and up to 50 mg/l of trimethoprim; their 1:5 and 5:1 (m/m) mixtures can be resolved with recoveries between 97 and 104%. The method was satisfactorily applied for determining sulfamethoxazole and trimethoprim in different pharmaceutical products.

We evaluate in rats the role of NO in the solitary tract nucleus (STn) after an anoxic stimulus to carotid body chemoreceptor cells (CChrc) with cyanide (NaCN), on the hyperglycemic reflex with glucose retention by the brain (BGR) and FOS expression (FOS-ir) in the STn. The results suggest that nitroxidergic pathways in the STn may play an important role in glucose homeostasis. A NO donor such as sodium nitroprusside (NPS) in the STn before CChrc stimulation increased arterial glucose level and significantly decreased BGR. NPS also induced a higher FOS-ir expression in STn neurons when compared to neurons in control rats that only received artificial cerebrospinal fluid (aCSF) before CChrc stimulation. In contrast, a selective NOS inhibitor such as Nomega-nitro-L-arginine methyl ester (L-NAME) in the STn before CChrc stimulation resulted in an increase of both, systemic glucose and BGR above control values. In this case, the number of FOS-ir positive neurons in the STn decreased when compared to control or to NPS experiments. FOS-ir expression in brainstem cells suggests that CChrc stimulation activates nitroxidergic pathways in the STn to regulate peripheral and central glucose homeostasis. The study of these functionally defined cells will be important to understand brain glucose homeostasis.