Macrophage-mediated angiogenic activation of outgrowth endothelial cells in co-culture with primary osteoblasts

The successful vascularisation of complex tissue engineered constructs for bone regeneration is still a major challenge in the field of tissue engineering. In this context, co-culture systems of endothelial cells and osteoblasts represent a promising approach to advance the formation of a stable vasculature as well as an excellent in vitro model to identify factors that positively influence bone healing processes, including angiogenesis. Under physiological conditions, the activation phase of angiogenesis is mainly induced by hypoxia or inflammation. Inflammatory cells such as macrophages secrete proinflammatory cytokines and proangiogenic growth factors, finally leading to the formation of new blood vessels. The aim of this study was to investigate if macrophages might positively influence the formation of microvessel-like structures via inflammatory mechanisms in a co-culture system consisting of human outgrowth endothelial cells (OECs) and primary osteoblasts. Treatment of co-cultures with macrophages (induced from THP-1) resulted in a higher number of microvessel-like structures formed by OECs compared to the co-culture. This change correlated with a significantly higher concentration of the proangiogenic VEGF in cell culture supernatants of triple-cultures and was accompanied by an increase in the expression of different proinflammatory cytokines, such as IL-6, IL-8 and TNFα. In addition, the expression of E-selectin and ICAM-1, adhesion molecules which are strongly involved in the interaction between leukocytes and endothelial cells during the process of inflammation was also found to be higher in triple-cultures compared to the double co-cultures, documenting an ongoing proinflammatory stimulus. These results raise the possibility of actively using pro-inflammatory stimuli in a tissue engineering context to accelerate healing mechanisms.

Mechanistic studies on the nucleophilic reaction of porphyrins with organolithium reagents

Porphyrins react readily with organolithium reagents under substitution of free meso positions. As this method has proven to be very versatile for the preparation of a wide range of meso substituted porphyrins, a mechanistic study of the reaction was undertaken using 5,15-diaryl- and dialkyl substituted porphyrins, 2,3,7,8,12,13,17,18-octaethylporphyrin, and the respective nickel(II) complexes. A combination of deuteration experiments, electronic absorption spectroscopy of the reactive intermediates, trapping of intermediates with organic electrophiles, and reaction at different pH values showed significant differences in the reaction pathways of free base porphyrins and metalloporphyrins. In both cases the reaction proceeds initially under formation of phlorin like intermediates which are stable in water. For the Ni(II)phlorins a mesomeric carbanionic form with a highly distorted structure exists that can react as a nucleophile with electrophiles such as RI, H+, or D+. In the latter case a protonation-deprotonation equilibrium involving porphodimethen intermediates has to be assumed. Free base phlorins do not react as nucleophiles but can undergo H/D exchange reactions in strongly acidic media.

The reaction of porphyrins with organolithium reagents

Porphyrins react readily with organolithium reagents, preferentially in the meso positions. The overall reaction is a nucleophilic substitution and proceeds via initial reaction of the organic nucleophile with a meso carbon yielding an anionic species which is hydrolyzed to a porphodimethene (5,15-dihydroporphyrin), formally constituting an addition reaction to two Cm positions. Subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yields meso-substituted porphyrins. The reaction is highly versatile as it is accomplished in high, often quantitative yields with various alkyl or aryl lithium reagents. In addition, LiR can be used for reaction with a variety of metal complexes (best with NiII, but also with ZnII, CuII, and CoII) and most useful with free base porphyrins. Similarly beneficial this reaction can be used in sequence for the introduction of 1, 2, 3, or 4 (different) meso substituents giving for the first time an entry into any desired meso-substituted porphyrin. If meso-substituted porphyrins are used, reaction with LiR can be used for either the preparation of phlorins (already known reaction), porphodimethenes (5,15-dihydroporphyrins, including those with exocyclic double bonds, for example, 5(1),5(2)-didehydroporphyrins) or chlorins (2,3-dihydroporphyrins) depending on the substituent type in the reactant porphyrins. Thus, this reaction presents a generally applicable method for the facile and versatile functionalization of porphyrins.

Renal handling of drugs in the healthy elderly. Creatinine clearance underestimates renal function and pharmacokinetics remain virtually unchanged

OBJECTIVE

It is commonly assumed that renal function, and in parallel the excretion of drugs, is considerably reduced in the elderly. Endogenous creatinine clearance or indirect estimates of this parameter are generally recommended for adapting drug dosage. The present study evaluates the validity of both assumptions.

METHODS

We compared pharmacokinetics (and pharmacodynamics) of 50 mg atenolol, 800 mg piracetam and 25 mg hydrochlorothiazide plus 50 mg triamterene in ten healthy young [25 (2) years] and 11 healthy elderly subjects [68 (5) years]. Inulin (Cin) and para-aminohippurate [PAH (CPAH)] clearance (infusion clearance technique), endogenous (C(Cr)) and calculated (Cockroft-Gault) creatinine clearance, analysis of drugs and their metabolites (HPLC), were performed. Renal haemodynamics and the pharmacokinetics of beta-adrenergic blocking agent, diuretics and the nootropic agent piracetam, respectively, were measured on separate days.

RESULTS

Cin was significantly (P < 0.01) lower in the healthy elderly subjects [104 (12) vs 120 (14) ml x min(-2) x 1.73 m(-2) in the young], but remained within the normal range (> 90 ml x min(-2) x 1.73 m(-2)). In contrast, C(Cr) was even lower in healthy elderly subjects [95 (24) vs 121 (20) ml x min(-1) in the young], and the Cockroft-Gault clearance underestimated true glomerular filtration rate (GFR) even more seriously [74 (17) vs 122 (16) ml min(-1)]. For atenolol the mean area under the curve (AUC) was similar in both groups [3.16 (0.48) microg x h(-1) x ml(-1) in the elderly vs 3.01 (0.30) in the young], as was the mean maximal plasma concentration [0.42 (0.07) vs 0.44 (0.06) microg x ml(-1)], but the proportion of the drug excreted in urine was marginally (P < 0.025) lower in the elderly. Similar results were obtained for hydrochlorothiazide, whereas no marked differences between the groups were found for triamterene and its metabolite. Furthermore, the pharmacodynamic action of diuretics was not significantly altered in the elderly.

CONCLUSIONS

The true GFR of the healthy elderly remains within the normal range and is underestimated by creatinine clearance and more so by its surrogate (Cockroft-Gault clearance). In parallel, pharmacokinetics of renally excreted drugs are not affected in the healthy elderly to a clinically significant extent. For drugs with a narrow therapeutic window, indirect estimates of GFR appear to be an unreliable means for calculating correct dosage in the elderly.

Coadministration of albumin and furosemide in patients with the nephrotic syndrome

BACKGROUND

In patients with nephrotic syndrome, the natriuretic effect of furosemide (FU) is diminished. The effect of coadministration of FU and human albumin (HA) has remained controversial.

METHODS

In a double-blind, placebo-controlled study, nine nephrotic patients (six males, 48 +/- 4 years) on standardized sodium chloride intake, in random order on three separate days, received by intravenous administration for 60 minutes either (a) 60 mg FU plus a sham infusion, (b) 60 mg FU plus 200 ml of a 20% solution of HA, or (c) sham infusion plus 200 ml of a 20% solution of HA. Urinary volume, sodium, albumin and FU excretion, renal hemodynamics, and plasma atrial natriuretic factor concentration were assessed.

RESULTS

Administration of FU alone significantly (P < 0.01) increased mean cumulative urinary sodium (259 +/- 30 mmol) and volume excretion (2684 +/- 167 ml) in the first eight hours as compared with the HA infusion alone (118 +/- 12 mmol, 1827 +/- 141 ml). The coadministration of FU and HA caused an even more marked increase (P < 0.01 vs. HA alone) of urinary sodium (312 +/- 28 mmol) and volume excretion (3230 +/- 201 ml); the difference to FU administration alone was significant (P < 0.05). Plasma atrial natriuretic factor, serum albumin concentration, and urinary albumin excretion increased significantly on both HA infusion days, whereas urinary excretion of FU remained unchanged with HA coadministration. Glomerular filtration rate (CIn) was not significantly affected by any of the infusion protocols, but effective renal plasma flow (CPAH) increased significantly on both HA infusion days.

CONCLUSIONS

Coadministration of HA potentiates the action of FU in patients with the nephrotic syndrome, but only modestly. This effect is mediated by changes in renal hemodynamics.

Beta-blockade as an alternative to cardioplegic arrest during cardiopulmonary bypass

BACKGROUND

As an alternative to cardioplegic arrest, cardiac surgical conditions have been produced using beta-blocker-induced minimal myocardial contraction (MMC) during cardiopulmonary bypass. The technique of MMC involves the use of high-dose intravenous esmolol to suppress myocardial chronotropy and inotropy sufficiently to produce cardiac surgical conditions. The purpose of this study was to compare conventional crystalloid cardioplegic arrest with MMC in terms of ischemia avoidance, myocardial edema formation, and cardiac function.

METHODS

Twelve dogs were placed on cardiopulmonary bypass. Six dogs were subjected to crystalloid cardioplegic arrest for 2 hours. Surgical conditions were produced in the other 6 dogs for 2 hours using intravenous esmolol without aortic clamping or cardioplegia. Arterial and coronary sinus lactate concentrations were determined as a gauge of myocardial ischemia. Myocardial water content was determined using microgravimetry and preload recruitable stroke work was determined using sonomicrometry and micromanometry.

RESULTS

Significant lactate washout was demonstrated after cardioplegic arrest but not after MMC. Myocardial water content was significantly less during and after MMC compared with cardioplegic arrest (p < 0.05). Preload recruitable stroke work was decreased compared with baseline values in both groups (p < 0.05).

CONCLUSIONS

In contrast to a previous study that involved 1 hour of MMC, in this study, ventricular function was decreased to the same extent as with cardioplegic arrest after 2 hours of MMC. This was attributed to the accumulation of ASL-8123, the primary metabolite of esmolol, which possesses beta-antagonist properties. Although postbypass ventricular function is similar in both groups, MMC appears to be superior in terms of ischemia avoidance and myocardial edema formation.

A new genetic fibrinogen variant (fibrinogen Erfurt I). Structurally characterized by an abnormal B beta-chain and present both in plasma and platelets

An abnormal fibrinogen was discovered in the plasma of a clinically asymptomatic woman. This fibrinogen variant was analyzed by high resolution two-dimensional gel electrophoresis and its molecular abnormality established consisting in a slight decrease in molecular mass of the B beta-chains. Analysis of fibrin revealed that cleavage of fibrinopeptide B by thrombin is normal, the molecular defect being confined to the beta-portion of the B beta-chain. The same fibrinogen variant was detected in the blood platelets of the proposita. This finding supports the assumption of a common origin of plasma and platelet fibrinogen pools. Family studies revealed the presence of the abnormal fibrinogen in a brother of the proposita, thus confirming the genetic nature of the observed variant. The underlying mutant gene occurs in both carriers in heterozygous state.

A New Genetic Fibrinogen Variant (Fibrinogen Erfurt I) Structurally Characterized by an Abnormal Bβ-Chain and Present both in Plasma and Platelets

An abnormal fibrinogen was discovered in the plasma of a clinically asymptomatic woman. This fibrinogen variant was analyzed by high resolution two–dimensional gel electrophoresis and its molecular abnormality established consisting in a slight decrease in molecular mass of the Bβ–chains. Analysis of fibrin revealed that cleavage of fibrinopeptide B by thrombin is normal, the molecular defect being confined to the β–portion of the Bβ–chain. The same fibrinogen variant was detected in the blood platelets of the proposita. This finding supports the assumption of a common origin of plasma and platelet fibrinogen pools. Family studies revealed the presence of the abnormal fibrinogen in a brother of the proposita, thus confirming the genetic nature of the observed variant. The underlying mutant gene occurs in both carriers in heterozygous state.

[Frequency of lipid metabolism disorders in blood donors]

It is reported on a screening test examination for disturbances of the lipometabolism in 3,714 blood donors by means of the estimation of the beta-lipoproteins. In 240 blood donors (6.5%) increased values of beta-lipoproteins were found. 45 donors with values increased for several times underwent an after-examination by a specialist, by means of which among others in eight of them an asymptomatic diabetes mellitus was found. The estimation of the beta-lipoproteins as screening test examination is ingenious and serves the improved cure for the health of the donors.