Low-density lipoprotein receptor-related protein-1 (LRP-1) expression in a rat model of oxygen-induced retinal neovascularization

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a high-molecular weight receptor of the LDL receptor gene family. Its ability to bind and internalize both proteinases and proteinase-inhibitor complexes from the extracellular space suggests that it has a major role in modulating uncontrolled retinal cell proliferation. In order to test this assumption, we investigated the expression of LRP-1 and receptor-associated ligands in a rat model of oxygen-induced retinal neovascularization. Wistar albino rats were placed into incubators at birth and exposed to an atmosphere alternating between 50% and 10% of oxygen every 24 h. After 14 days, the animals were allowed to recover in room air and sacrificed at postnatal day 20 (P20). The protein expression of LRP-1 and alpha2-macroglobulin (alpha2M) in the retina from unexposed and hyperoxia-exposed rats was investigated by Western blot. The localization of LRP-1 after neovascularization was assessed by immunohistochemical staining. The activity of metalloproteinases (MMPs) was determined by zymography. Histological analysis was done to quantitate the neovascular response in these animals. Western blot analysis showed that LRP-1 was expressed, along with alpha2M, in the retina of rats with oxygen-induced neovascularization at P20. By immunohistochemical analysis, positive staining for LRP-1 appeared in cells extending from the inner limiting membrane (ILM) to the outer limiting membrane (OLM). The cells of the retina that expressed LRP-1 were identified by immunofluorescence as Müller cells. Zymographic analysis demonstrated increased activity of MMP-2 and MMP-9 under neovascular conditions. This is the first demonstration of the involvement of LRP-1 in retinal neovascularization. In retinas of rats with oxygen-induced neovascularization, the expression of LRP-1 and alpha2M was increased along with an enhanced activity of MMPs, suggesting that LRP-1 expression may play a role in modulating retinal neovascularization by regulating proteolytic activity.     

Control of bacterial pneumonia during mechanical ventilation

Pneumonia complicates the course of 50% of patients on mechanical ventilation, requiring three or more days of mechanical ventilation and potentially increasing the relative risk of mortality by 20-40%. The predominant potentially pathogenic micro-organisms are Streptococcus pneumoniae, Staphylococcus aureus (sensitive to methicillin in the previously healthy host), Pseudomonas aeruginosa (aerobic gram-negative bacilli), and methicillin-resistant Staphylococcus aureus in the host with underlying disease. Approximately 85% of pneumonias are endogenous, caused by bacteria present in the patient's oropharyngeal flora. Bacteria present on admission cause primary endogenous pneumonia (55%), whereas bacteria acquired in the unit lead to supercarriage or secondary carriage and subsequently secondary endogenous pneumonia (30%). The remaining 15% are exogenous, ie the bacteria causing pneumonia are not carried by the patient. The diagnosis is usually based on clinical, radiological, and microbiological criteria, using the non-invasive method of tracheal aspirate, which yields >/=10(5) micro-organisms. Seven randomized trials have evaluated three non-antibiotic prophylactic maneuvers: hygiene (1 trial), subglottic drainage (4 trials), and semirecumbent position (2 trials). The impact on pneumonia was mixed, whereas mortality was unchanged. Selective digestive decontamination, using parenteral and enteral antimicrobials to control the three types of pneumonia, has been evaluated in 54 trials and showed an absolute mortality reduction of 8%. The therapy of pneumonia relies on six basic principles: (a) surveillance and diagnostic cultures to identify micro-organisms; (b) immediate and adequate antibiotic treatment to sterilize the lower airways, (c) the source of potential pathogens requires elimination for recovery of the original infection and prevention of relapses and/or superinfections; (d) aerosolized antimicrobials; (e) removal or replacement of the endotracheal tube; and (f) surveillance samples are indispensable to monitor efficacy of treatment. The aim of our review was to evaluate up to date facts regarding control of bacterial pneumonias during mechanical ventilation in intensive care unit settings.     

Complexation Behavior of Cu2+ in the Presence of Iminodiacetic Acid and Poly(ethyleneimine)

Summary: Multicomponent aqueous systems containing Cu²⁺ as metal ion, iminodiacetic acid (IDAA) as a low‐molecular‐weight chelating molecule, and branched poly(ethyleneimine) (BPEI) as a polychelatogen are analyzed at different pH by UV‐Vis spectroscopy and diafiltration. It was found that at pH 4, saturation of BPEI with Cu²⁺ takes place at a Cu²⁺:BPEI ratio of 1:5.7, probably indicating a stoichiometry for the complex of 1:4. At the same conditions the Cu²⁺‐IDAA complex has a stoichiometry of 1:1. The ability of BPEI to bind the metal ion is higher than that of IDAA in mixtures of both chelating molecules. Lowering the pH between 2 and 3.5, protonation of BPEI allows increasing the amounts of Cu²⁺‐IDAA complex so that Cu²⁺ is transferred from the polychelatogen to IDAA. Good correlations are found comparing the results obtained by diafiltration and by UV‐Vis spectroscopy. Moreover, diafiltration results indicate that in the absence of Cu²⁺, IDAA interacts with BPEI with apparent dissociation constants of 2.88 at pH 2.7 and 0.96 at pH 4. These interactions may be responsible for the appearance of an apparent dissociation constant of 3.60 for the interactions between BPEI and the Cu²⁺‐IDAA complex at pH 4.

The binding of Cu²⁺ to branched poly(ethyleneimine) and iminodiacetic acid in water.     

Prefrontal cortical cell firing during maintenance, extinction, and reinstatement of goal-directed behavior for natural reward

The prefrontal cortex (PFC) is important for higher cognitive functioning and the processing of reward-related information. Here, electrophysiological recording procedures were used to examine cell firing in the PFC in rats (n = 12) during water reinforcement sessions consisting of three phases. In phase one (maintenance), animals pressed a lever (fixed ratio 1) for water reinforcement (0.05 ml/press) paired with an auditory stimulus. Of 62 neurons recorded during maintenance, 39 (63%) exhibited one of three types of patterned discharges relative to the reinforced response for water. Specifically, PFC neurons exhibited increases in firing rate within seconds preceding the response (type PR; n = 9 cells) or increases (type RFe; n = 16 cells) or decreases (type RFi; n = 14 cells) in firing rate immediately following response completion. The remaining neurons did not alter their firing profiles relative to the reinforced response (type nonphasic cells; n = 23 cells). In phase two (extinction), lever press responses had no programmed consequences (i.e., water reinforcement and the auditory stimulus were not presented). After 30 min of no responding, phase three (reinstatement) began, during which each lever press response was again associated with water reinforcement paired with the stimulus. Results indicate differential effects of extinction/reinstatement on cell firing rates and patterns dependent on cell type. These findings are discussed with respect to the adaptive nature of PFC activity during goal-directed behaviors for "natural" rewards, and are considered relative to prior studies that examined nucleus accumbens cell firing during a similar behavioral task.     

Glycinergic and GABAergic synaptic transmission are differentially affected by gephyrin in spinal neurons

In the present study, we have examined the physiological properties of synaptic currents mediated by GlyRs and GABAARs after culturing spinal neurons with a gephyrin antisense oligonucleotide. Application of gephyrin antisense, but not the sense, reduced the glycinergic mIPSC amplitude ( approximately 50%) and frequency ( approximately 85%), indicating the importance of gephyrin for GlyR anchoring at postsynaptic sites. On the other hand, the glycine-evoked current amplitude was unchanged indicating that functional GlyRs were still located in the extrasynaptic membrane. The analysis of the GABAergic transmission in the same neurons revealed approximately 70% reduction in the frequency of the GABAergic mIPSCs, without changes in the amplitude. Interestingly, the modulation of remaining GABAAR-mediated synaptic events by zinc and diazepam was significantly altered by the antisense. These results indicate that gephyrin is required for the membrane insertion/stabilization of the GABAAR gamma2 subunit as well as for its subsequent localization in the postsynaptic membrane.     

Umbilical endometriosis. A case report

The Authors present a case of umbilical endometriosis. A 38-year-old female presented with a nodule in her umbilical region. The nodule was brownish in colour and had enlarged slowly, reaching a size of 2 cm in diameter over the previous 7 months. The patient had no symptoms and there was no bleeding or pain during menstruation. The nodule was removed under local anaesthesia and histological examination was diagnostic for umbilical endometriosis. No recurrence occurred over a follow-up period of 7 months and the patient is in good general condition. Umbilical endometriosis is a very rare disease, but should be borne in mind in the differential diagnosis of umbilical lesions.