Endothelin B receptors contribute to retinal ganglion cell loss in a rat model of glaucoma

Glaucoma is an optic neuropathy, commonly associated with elevated intraocular pressure (IOP) characterized by optic nerve degeneration, cupping of the optic disc, and loss of retinal ganglion cells which could lead to loss of vision. Endothelin-1 (ET-1) is a 21-amino acid vasoactive peptide that plays a key role in the pathogenesis of glaucoma; however, the receptors mediating these effects have not been defined. In the current study, endothelin B (ET_B) receptor expression was assessed in vivo, in the Morrison's ocular hypertension model of glaucoma in rats. Elevation of IOP in Brown Norway rats produced increased expression of ET_B receptors in the retina, mainly in retinal ganglion cells (RGCs), nerve fiber layer (NFL), and also in the inner plexiform layer (IPL) and inner nuclear layer (INL). To determine the role of ET_B receptors in neurodegeneration, Wistar-Kyoto wild type (WT) and ET_B receptor-deficient (KO) rats were subjected to retrograde labeling with Fluoro-Gold (FG), following which IOP was elevated in one eye while the contralateral eye served as control. IOP elevation for 4 weeks in WT rats caused an appreciable loss of RGCs, which was significantly attenuated in KO rats. In addition, degenerative changes in the optic nerve were greatly reduced in KO rats compared to those in WT rats. Taken together, elevated intraocular pressure mediated increase in ET_B receptor expression and its activation may contribute to a decrease in RGC survival as seen in glaucoma. These findings raise the possibility of using endothelin receptor antagonists as neuroprotective agents for the treatment of glaucoma.

Dissociation of Striatal Dopamine and Tyrosine Hydroxylase Expression from Aging-Related Motor Decline: Evidence from Calorie Restriction Intervention

The escalating increase in retirees living beyond their eighth decade brings increased prevalence of aging-related impairments, including locomotor impairment (Parkinsonism) that may affect ~50% of those reaching age 80, but has no confirmed neurobiological mechanism. Lifestyle strategies that attenuate motor decline, and its allied mechanisms, must be identified. Aging studies report little to moderate loss of striatal dopamine (DA) or tyrosine hydroxylase (TH) in nigrostriatal terminals, in contrast to ~70%-80% loss associated with bradykinesia onset in Parkinson's disease. These studies evaluated the effect of ~6 months 30% calorie restriction (CR) on nigrostriatal DA regulation and aging-related locomotor decline initiated at 12 months of age in Brown-Norway Fischer F1 hybrid rats. The aging-related decline in locomotor activity was prevented by CR. However, striatal DA or TH expression was decreased in the CR group, but increased in substantia nigra versus the ad libitum group or 12-month-old cohort. In a 4- to 6-month-old cohort, pharmacological TH inhibition reduced striatal DA ~30%, comparable with decreases reported in aged rats and the CR group, without affecting locomotor activity. The dissociation of moderate striatal DA reduction from locomotor activity seen in both studies suggests that aging-related decreases in striatal DA are dissociated from locomotor decline.

Proximity of antibody binding sites studied by fluorescence energy transfer

Fluorescence energy transfer experiments by steady-state and nanosecond monophoton techniques were carried out with a covalently linked hybrid rabbit IgG antibody containing one antilactose site and one anti-Dns [5-(dimethylamino)-1-naphthalenesulfonyl] site. The hybrid antibody was prepared from antilactose and anti-Dns antibody by mild reduction, dissociation into half-molecules in acid, and random reassociation with re-formation, to the extent of 80%, of the single disulfide bond between the heavy chains. Fractionation with an antilactose-specific immunoadsorbent yielded a population in which each IgG molecule contained no more than one anti-Dns site per antibody. The acceptor molecules used for intramolecular energy transfer were derivatives of p-aminophenyl beta-lactoside (PAPL): (dimethyl-amino)benzeneazo-PAPL and N-fluorescyl-PAPL. The fluorescence lifetime (24 ns) and quantum yield (0.57) of the bound Dns group were unaffected by the presence of the acceptor in the adjacent site. Three models were used to calculate the minimum distance between the adjacent sites of the IgG antibody based on the overlap in the emission and absorption spectra of the donor-acceptor pairs and the segmental flexibility of the immunoglobulin molecule. The calculations yielded values in the range of 5.5-7.0 nm for the minimum distance of separation between the antibody sites in solution and demonstrated a substantial energy barrier to the closer approach of the sites.

Structural basis for the preferential association of autologous immunoglobulin subunits: role of the J region of the light chain

We have used a series of sequenced V kappa 21 L-chains produced from murine myelomas to determine whether the V or J segment of the V region is responsible for dictating preferential recombination. In each competitive recombination, equimolar amounts of two different L-chains, selected on the basis of common V or J segments, were allowed to compete for a limiting amount of H-chain. It was found that the J segment of the L-chain was primarily responsible for dictating the ability of a chain to compete and that the nature of residue 96, the first residue of the J segment, was particularly important. Specifically, charged residues caused the L-chain to compete poorly against L-chains with hydrophobic side chains at this position. Furthermore, if Phe or, to a lesser extent, Tyr were present at position 96, the L-chain competed more successfully than chains with Trp-96 or Leu-96. This suggests that both the aromaticity and size of this residue were important factors in determining preferential recombination. It was also found that all other residues in VL were secondary to residue 96 in contributing to the ability of a chain to compete. Finally, unlike all previous studies, we observed a substantial number (64%) of preferred heterologous recombinations. These results are consistent with the hypothesis that the VL and VH gene rearrangements occur independently, thus resulting in random pairing of VH and VL domains.

Proximity relationships within the Fc segment of rabbit immunoglobulin G analyzed by resonance energy transfer

Resonance energy transfer analysis has been carried out with a noncovalent rabbit hybrid of immunoglobulin G (IgG) composed of normal rabbit IgG and rabbit anti-lactose IgG. The hybrid IgG was prepared from proteins in which the single inter-heavy-chain disulfide linkage was specifically reduced and alkylated. Normal rabbit IgG was alkylated with the iodoacetyl derivative of N-(aminoethyl)-5-naphthylamine-1-sulfonic acid while the rabbit anti-lactose IgG was alkylated with either iodoacetamide or the iodoacetyl derivative of p-[[p-(dimethylamino)phenyl]azo]aniline. Fractionation with an anti-lactose-specific immunoadsorbent yielded a population in which each fluorescent donor [N-[(acetylamino)ethyl]-5-naphthylamine-1-sulfonic acid] was adjacent to a nonfluorescent acceptor [N-acetyl-p[[p-dimethylamino)phenyl]. Data on fluorescence quantum yield, excited-state lifetime, time-resolved emission anisotropy, and steady-state fluorescence polarization revealed a distribution of distances between the donor and acceptor. In the native molecule, the hinge regions are known to be covalently liked by a single disulfide bond. In the absence of this linkage, the hinge regions were separated such that for a majority of the molecules in solution (approximately 60%) the separation was 50-60 A. In the context of current knowledge of the IgG molecule, it is evident that the principle forces maintaining the integrity of the native, functional Fc segment are the strong noncovalent interactions of the CH3 domains and the single inter-heavy-chain disulfide bond.

A non-randomised pilot study to compare complementary and conventional treatments of acute sinusitis

BACKGROUND

It is still under discussion whether antibiotics are effective in the treatment of acute sinusitis. Moreover, they are known to have considerable side-effects. In contrast, complementary approaches are reported to have little side-effects and an equivalent efficiency.

OBJECTIVES

To assess the success of conventional and complementary treatments of acute sinusitis and to estimate the patient numbers needed to confirm therapeutic equivalence. Treatment success was measured by three different scores, assessed by both patients and physicians.

METHODS

Multicentre (2 complementary and 3 conventional ENT centres), non-randomised, controlled clinical trial with 63 patients (complementary group 30, conventional group 33 patients). To control for confounders treatment differences were estimated by propensity score techniques.

TREATMENTS

The choice of medication was entirely left to the physician. We recommended to use antibiotics, secretolytics and symptomimetics in the conventional group and a combination of the herbal remedy Sinupret((R)) and the homeopathic remedy Cinnabaris 3X in the complementary group.

RESULTS

Treatment differences varied substantially depending on the outcome measure, but they were always not clinically relevant. Conventional treatment was slightly better when the outcome was assessed by the physicians (1.8 score points) but slightly worse when it was assessed by patients (0.2 score points) or in terms of the HCG-5 quality of life score (0.8 score points). p values were always > 0.3.

CONCLUSIONS

Both treatments appear to be equally effective (or ineffective). Results might be biased because both treatment groups differed substantially. Randomised trials including at least 400 patients are needed to produce valid results.

Antibody interaction with a membrane-bound fluorescent ligand on synthetic lipid vesicles

The interaction of membrane-bound ligand with bivalent and monovalent fragments of monoclonal antibody was studied by fluorescence and precipitation analysis using synthetic lipid vesicles. The ligand N epsilon-[5-(dimethylamino)-naphthyl-1-sulfonyl]lysine was linked to the hydrophobic anchor dipalmitoylphosphatidylethanolamine and ranged between 0.01 and 1 mol% of the membrane components. The effects of cholesterol on the specific interaction were observed over the range of 0-50 mol%. A precipitation assay was developed to evaluate various factors related to the cross-linking of small unilamellar vesicles by bivalent antibody. The cholesterol content was critical for this process as demonstrated by the increased efficiency of precipitation over the range of 0-40 mol% of this component. Fluorescence analysis yielded the parallel finding of increased accessibility of the ligand to the antibody with greater cholesterol content. Increased surface density of the ligand also was found to enhance the intervesicle interaction. Finally, a comparison of the kinetics by fluorescence analysis of the binding of monovalent and bivalent fragments indicated that the bivalent interaction involved primarily the cross-linking of vesicles in accord with published findings of the interaction of monoclonal antibody with cell membrane antigens.

An example on the value of non-randomisation in clinical trials in complementary medicine

BACKGROUND

Randomised clinical trials may in principle show a small external validity. Non-randomised clinical trials therefore are sometimes regarded as an appropriate alternative when complementary and conventional treatments are compared.

OBJECTIVES

To assess the value of advanced statistical methods in the process of estimating differences between a complementary and a conventional treatment of acute sinusitis in a non-randomised clinical trial.

METHODS

Multicentre, non-randomised, controlled clinical trial comparing 2 complementary and 3 conventional ENT centres. Patients were free to choose the physician (and hence the therapy). Treatment differences were estimated by controlling for confounders in analyses of covariance or by propensity score techniques.

RESULTS

Most potential confounders (sex, age, life-style parameters) did not have significant effects on the choice of therapy. Disease severity and previous ENT surgery were the main confounding factors. At study onset they almost cause a defined separation of both treatment groups. As a result estimated treatment differences vary substantially depending on the chosen statistical model.

CONCLUSIONS

When comparing complementary and conventional treatments, non-randomised clinical trials may be misleading. Results may be strongly biased even when advanced statistical methods are used. Trials of complex statistical designs are needed to give valid results.