Split phosphorus fertiliser applications as a strategy to reduce incidental phosphorus losses in surface runoff.

Organic soils have low sorption capacities for phosphorus (P), and may pose a risk of P loss to water if P applications to these soils coincide with runoff events. Little is known about the magnitude of exports of P in overland flow following application of P fertiliser onto these soils, or on the influence of the frequency on P losses and persistence. The number of P fertiliser applications was surveyed across 39 commercial farms to assess current practice and inform the design of a rainfall runoff experiment to evaluate the effect of frequency of P applications on losses and persistence across time. Superphosphate (16% P) was applied in single (equivalent to 30 and 55 kg P ha-1 applied at day 0) and split (equivalent to 15 and 27.5 kg P ha-1 applied in two doses at days 0 and 55) applications to an organic soil inclined at a slope of 6% in a rainfall simulator experiment. The surface runoff of dissolved reactive phosphorus (DRP) was measured in controlled 30-min rainfall simulations conducted intermittently over an 85-day period. The DRP losses in surface runoff after the first rainfall event were 44.6 and 97.8 mg L-1 for single applications of 30 and 55 kg ha-1, respectively, and 13.3 and 21.8 mg L-1 for the same rates split in two doses, indicating that single P applications had disproportionately bigger impacts on losses than split applications. This supports the idea that frequent, but smaller, P applications can minimise the impact of fertilisation on waters. Dissolved reactive P concentrations remained significantly higher than those from the control samples until the end the experiment for almost all the P treatments, highlighting the long-lasting effects of added P and the elevated risk of P losses on organic soils. For climates with frequent rainfall events, which are likely to coincide with fertiliser applications, smaller but more frequent P applications can reduce the risk of P transfer as opposed to one single application.

Magnetic resonance methods and applications in pharmaceutical research.

This review presents an overview of some recent magnetic resonance (MR) techniques for pharmaceutical research. MR is noninvasive, and does not expose subjects to ionizing radiation. Some methods that have been used in pharmaceutical research MR include magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods, among them, diffusion-weighted MRI, perfusion-weighted MRI, functional MRI, molecular imaging and contrast-enhance MRI. Some applications of MR in pharmaceutical research include MR in metabonomics, in vivo MRS, studies in cerebral ischemia and infarction, degenerative joint diseases, oncology, cardiovascular disorders, respiratory diseases and skin diseases. Some of these techniques, such as cardiac and joint imaging, or brain fMRI are standard, and are providing relevant data routinely. Skin MR and hyperpolarized gas lung MRI are still experimental. In conclusion, considering the importance of finding and characterizing biomarkers for improved drug evaluation, it can be expected that the use of MR techniques in pharmaceutical research is going to increase in the near future.

[Pseudoaneurysm in the radial artery after catheterization]. / Seudoaneurisma de arteria radial post-canulación.

Eleven days after surgery to remove an olfactory groove meningioma, a woman developed a pulsatile swelling and localized elevation of temperature in the radial artery catheterized to monitor arterial pressure. Pseudoaneurysm of the radial artery was diagnosed and the patient was returned to the operating room for ligation and biopsy of the vessel under regional anesthesia. Her condition worsened in spite of the resection and 48 hours after repair of the arterial pseudoaneurysm she was admitted to the intensive care unit with septic shock. Radial artery catheterization is a safe, frequently performed procedure but it is not free of risk. The most common complication is thrombosis. Much more rare are pseudoaneurysms, lesions that are observed late after catheterization (7-40 days) and are associated with vessel wall alterations, repeated puncture attempts, and catheter infection. The usual therapeutic approach involves surgical resection and ligature of the vessel, although other measures have been suggested.

Seudoaneurisma de arteria radial post-canulación / Pseudoaneurysm in the radial artery after catheterization

Una paciente intervenida de un meningioma del surcoolfatorio desarrolló once días después de la cirugía unatumoración pulsátil acompañada de fiebre en la zona dela arteria radial canulada para monitorizar la presiónarterial invasiva. Con el diagnóstico de seudoaneurismade la arteria radial fue conducida de nuevo a quirófanodonde se realizó ligadura y biopsia de dicho vaso bajoanestesia regional. A pesar de la resección sufrió un deterioroprogresivo de su situación clínica, precisando ingresoen la unidad de cuidados intensivos (UCI) 48 horasdespués de la reparación de la formación seudoaneurismáticaarterial con el diagnóstico de shock séptico.La canulación de la arteria radial es un procedimientohabitual y seguro, aunque no exento de complicaciones.La más frecuente es la trombosis, siendo mucho másrara la formación de seudoaneurismas, lesión que seobserva tardíamente (7-40 días) tras su cateterización yse asocia a alteración en la pared de los vasos, repetidosintentos de punción o infección del catéter. Aunque sehan propuesto otras opciones terapéuticas la más extendidaes la resección quirúrgica y ligadura del vaso

Eleven days after surgery to remove an olfactory groovemeningioma, a woman developed a pulsatile swellingand localized elevation of temperature in the radialartery catheterized to monitor arterial pressure. Pseudoaneurysmof the radial artery was diagnosed and thepatient was returned to the operating room for ligationand biopsy of the vessel under regional anesthesia. Hercondition worsened in spite of the resection and 48 hoursafter repair of the arterial pseudoaneurysm she wasadmitted to the intensive care unit with septic shock.Radial artery catheterization is a safe, frequently performedprocedure but it is not free of risk. The mostcommon complication is thrombosis. Much more rareare pseudoaneurysms, lesions that are observed lateafter catheterization (7-40 days) and are associated withvessel wall alterations, repeated puncture attempts, andcatheter infection. The usual therapeutic approachinvolves surgical resection and ligature of the vessel, althoughother measures have been suggested

Interaction of acrylodan with human serum albumin. A fluorescence spectroscopic study.

The binding of the fluorescent probe acrylodan (AC) to human serum albumin (HSA) was studied by fluorescence spectroscopy. The binding isotherms could be fitted to two types of sites. Competition experiments using iodoacetamide suggested that AC binds tightly on HSA by the cysteine-34. Attempts were made to find the location of the second site using high concentrations of warfarin, phenylbutazone, diazepam, indomethacin, palmitic acid or bilirubin in order to displace the bound AC to the HSA. Bilirubin was the only ligand able to displace the bound AC. This result suggests that AC, which is a very hydrophobic molecule also capable of labeling lysine residues, should also bind the human albumin in the primary site of bilirubin, but with less affinity than to the cysteine-34.

Binding of the Promen fluorescent probe to human serum albumin: a fluorescence spectroscopic study.

The binding of Promen (6-propionyl-2-methoxynapthalene) to human serum albumin (HSA) was measured by fluorescence spectroscopy, finding only one class of binding sites on the protein. Hydrophobic interactions play an important role to stabilize the complex. Attempts were made to characterize its binding site using as competitors warfarin, phenylbutazone and diazepam, which bind in a specific site or region on the HSA. Fluorescence polarization measurements and spectrofluorimetric results suggest that diazepam and Promen bind at different but interacting binding sites on the HSA. The changes in the fluorescence emission of the bound Promen in the presence of these drugs, allow to use Promen to detect unspecific interactions with the site II on the HSA.

The fluorescent probe prodan characterizes the warfarin binding site on human serum albumin.

The fluorescent probe Prodan (6-propionyl-2-dimethyl-aminonaphthalene) binds with high affinity to human serum albumin (HSA). The spectral characteristics of the Prodan bound to the protein are very different from the free Prodan in solution. These differences allowed the spectra to be deconvoluted into log-normal bands in order to quantify the bound and unbound ligand and to calculate the binding constant at different temperatures. From such temperature dependence, we found the binding to be exothermic with a van't Hoff enthalpy of -22.8 kJ mol-1. Thermodynamic analysis suggests that the interaction may be mainly caused by hydrophobic forces and electrostatic interactions. The above analysis of the spectra and the measures of the fluorescence polarization during the successive presence of six specific drugs suggest that the Prodan binding site corresponds with the warfarin binding site on HSA, whereas under the present experimental conditions the other characteristic binding sites of HSA were not affected. Thus, this fluorescent probe provides a rapid and simple means for the characterization of a specific binding site on HSA and also for detecting potential or nonspecific drug-protein interactions.

Study of the interaction between xylazine and bovine serum albumin by fluorescence quenching measurements.

The binding of xylazine to bovine werum albumin (BSA) was studied by fluoresence quenching, as a function of temperature. The experimental data could be fitted to both the Stern-Volmer equation and the Stern-Volmer equation modified by Lehrer. The temperature dependence of the Stern-Volmer constant, Ksv suggests that the mechanism of the quenching process is mainly dynamic in origin. The thermodynamic parameters were estimated based on such temperature dependence. The positive values found for the enthalpy and entropy changes seem to indicate that the hydrophobic contribution is the predominant intermolecular force stabilizing the xylazine-BSA complex. Fluorescence quenching was also used to calculate the binding constants by the Scatchard procedure. The values of these constants are of the same order of magnitude as the Stern-Volmer constants. These results, together with the spectral changes in the fluorescence emission spectra of BSA induced by xylazine, suggest that the interaction may take place in subdomains IIA and IIIA since these subdomains have been proposed to bind drugs and other hydrophobic materials.

[Postoperative cortical blindness after resection of a retroperitoneal teratoma]. / Ceguera cortical postoperatoria tras resección de teratocarcinoma retroperitoneal.

We present a rare case of cerebrovascular accident involving non-cardiac, non-neurological, non-carotid surgery in a 44-year-old man with no cardiovascular risk factors who underwent retroperitoneal resection of a teratocarcinoma, immediately after which he showed signs of confusion accompanied by cortical blindness. Neurological signs and symptoms remitted completely 5 days after surgery. Complementary tests and the patient's evolution confirmed a diagnosis of reversible ischemic neurological deficit.

Spectroscopic analysis of the binding of amylobarbitone, secbutobarbitone, pentobarbitone, phenobarbitone and quinalbarbitone to human serum albumin.

The binding of five barbiturates: amylobarbitone, secbutobarbitone, pentobarbitone, phenobarbitone and quinalbarbitone to human serum albumin (HSA) was studied by difference spectroscopy and spectrofluorimetric titrations. There were no changes in the HSA spectral properties. Our result suggest that there are two classes of binding sites on HSA for these barbiturates. A detailed investigation of the effect of their binding to HSA by deconvoluted spectra, suggests that the interaction of barbiturate-HSA takes place principally on the subdomain IIIA of HSA.

Analysis of the binding of chlorpheniramine to human serum albumin by spectroscopic techniques.

The binding of chlorpheniramine (CFA) to human serum albumin (HSA) has been studied by absorption and fluorescence techniques. By deconvolution of the UV-spectra into five Gaussian bands it can be observed that the band at 214 nm is the most sensitive for following the interaction CFA-HSA. Such interaction causes a redshift in the band at 227 nm to 235 nm, and an isosbestic point surges at 236 nm. Moreover, the fluorescence quenching depends on the excitation wavelength. By excitation at 278 nm, 25% of the native fluorescence is quenched, but only 6% is quenched by excitation at 290 nm. From these spectroscopic studies our results are compatible with the possibility that the interaction could take place mainly on the subdomain IIIA.

Fluorescence quenching studies on binding fluoreno-9-spiro-oxazolidinedione to human serum albumin.

Human serum albumin fluorescence quenching by fluorene-9-spiro-oxazolidinedione has been analyzed as a function of temperature. Such temperature dependence suggests that the mechanism of the quenching process is static in origin. This type of quenching implies that a non-fluorescent complex between oxazolidinedione and serum albumin has been formed and following the Stern-Volmer relationship we have calculated the binding constant. Thermodynamic parameters were also determined. The positive and large values of entropy and the negative value for enthalpy suggest that both hydrophobic and electrostatic interactions may play an important role in the stabilization of the complex. Finally, the irreversible changes in the spectral properties of HSA are interpreted in binding terms.

Fluorescence quenching of human serum albumin by xanthines.

A study of the fluorescence quenching of human serum albumin (HSA) by caffeine, theophylline and theobromine, based on temperature dependence, has shown that it is predominantly static. This quenching mechanism is due to the formation of a xanthine-HSA non-fluorescent complex. The Stern-Volmer equation let us determine the association constants. It seems that the quenching of the protein fluorescence depends on the number and position of the methyl groups. The temperature dependence of the association constant is used to estimate the values of the thermodynamic parameters involved in the interaction of the drugs with HSA. All three binding processes are exothermic and probably hydrophobic, and hydrogen bonds play a significant role in the stabilization of such complexes. The enthalpy and entropy changes observed appear to compensate each other to produce a relatively small Gibbs free energy.

Chlorpheniramine binding to human serum albumin by fluorescence quenching measurements.

The binding of chlorpheniramine to human serum albumin has been studied by fluorescence quenching, as a function of temperature; the experimental data could only be fitted to the Stern-Volmer modified equation. A statistical analysis of the results was performed in order to determine the significance of the constants calculated by this equation, as well as their thermodynamic parameters. The chlorpheniramine binding to human serum albumin accounts for almost half of the binding of this antihistaminic agent to human plasma proteins.