Melatonin Does Not Modulate Testicular Responsiveness to Altered Photoperiods. A Study During Different Phases of the Annual Gonadal Cycle in Roseringed Parakeets (Psittacula krameri)

The roseringed parakeet has been shown to exhibit a variable testicular responsiveness to both altered photoperiodic regimens and to treatment with melatonin during different phases of the annual gonadal cycle. Adult male roseringed parakeets were held under either natural photoperiods (NP), or long photoperiods (LP; 16L 8D), or short photoperiods (SP; 8L 16D) for a total period of 90 days. From day 46 onward, half of the total birds in each group were administered with the vehicle of melatonin, and the other birds were injected daily in the afternoon with melatonin (25 µg/ 100 g body wt.) till the end of the experiment. An identical experimental schedule was followed during the four different (preparatory, progressive, pre-breeding, and breeding) phases of the annual testicular cycle. The testicular activities in various bird groups were evaluated by volumetric, gravimetric, histometric and karyometric measurements, and by quantitative histological studies. The findings revealed that exogenous melatonin may exert either a suppressive influence or none at all on the testicular functions in relation to the photoperiodic schedule as well as to the reproductive phase of the concerned bird, but in no case modulates gonadal responsiveness to artificially altered photoperiods.     

Cytodiagnosis of filarial infections from an endemic area

OBJECTIVE: To throw light on cytologic findings as a possible mode of diagnosis of lymphatic filariasis. STUDY DESIGN: Filariasis has worldwide distribution, but lymphatic filariasis predominantly affects tropical and subtropical regions. Demonstration of microfilaremia, the specific test for diagnosis of lymphatic filariasis, often shows false negative results in endemic areas. The present study, done in an endemic area, showed the presence of microfilariae or adult worms of Wuchereria bancrofti in fine needle aspirates collected from amicrofilariaemic cases. In a few cases the discovery was incidental. A total 4,534 cases undergoing cytologic evaluation were carefully screened for the presence of adult worms or larvae, irrespective of clinical diagnosis. Microfilariae were demonstrated in both clinically suspected cases of filariasis and asymptomatic cases. RESULTS: A total of 1 positive cases were found; in 4 cases the clinical diagnosis was lymphatic filariasis, and 7 cases were asymptomatic. All 11 cases were amicrofilariaemic. CONCLUSION: Various sophisticated investigations are used for diagnosis of lymphatic filariasis without microfilaremia. Fine needle aspiration cytology, being a cheap, simple and easy procedure, may have some role in this field, but further detailed studies are needed before any final claim.     

Steric Crowding of the Turn Region Alters the Tertiary Fold of Amyloid-β18–35 and Makes It Soluble

Aβ self-assembles into parallel cross-β fibrillar aggregates, which is associated with Alzheimer''s disease pathology. A central hairpin turn around residues 23–29 is a defining characteristic of Aβ in its aggregated state. Major biophysical properties of Aβ, including this turn, remain unaltered in the central fragment Aβ_18–35. Here, we synthesize a single deletion mutant, ΔG25, with the aim of sterically hindering the hairpin turn in Aβ_18–35. We find that the solubility of the peptide goes up by more than 20-fold. Although some oligomeric structures do form, solution state NMR spectroscopy shows that they have mostly random coil conformations. Fibrils ultimately form at a much higher concentration but have widths approximately twice that of Aβ_18–35, suggesting an opening of the hairpin bend. Surprisingly, two-dimensional solid state NMR shows that the contact between Phe¹⁹ and Leu³⁴ residues, observed in full-length Aβ and Aβ_18–35, is still intact in these fibrils. This is possible if the monomers in the fibril are arranged in an antiparallel β-sheet conformation. Indeed, IR measurements, supported by tyrosine cross-linking experiments, provide a characteristic signature of the antiparallel β-sheet. We conclude that the self-assembly of Aβ is critically dependent on the hairpin turn and on the contact between the Phe¹⁹ and Leu³⁴ regions, making them potentially sensitive targets for Alzheimer''s therapeutics. Our results show the importance of specific conformations in an aggregation process thought to be primarily driven by nonspecific hydrophobic interactions.     

Characterization of central nervous system structures by magnetic resonance diffusion anisotropy

Diffusion-weighted magnetic resonance imaging (MRI) provides information about tissue water diffusion. Diffusion anisotropy, which can be measured with diffusion tensor MRI, is a quantitative measure of the directional dependence of the diffusion restriction that is introduced by biological structures such as nerve fibers. Diffusion tensor MRI data was obtained in the brain, brain stem, and cervical spinal cord. For each region, scans were performed in four normal volunteers. Fractional anisotropy (FA), an index of diffusion anisotropy, was measured within regions of interest located in the corpus callosum, capsula interna, thalamus, caudate nucleus, putamen, brain cortex, pyramidal tract of the medulla, accessory olivary nucleus, dorsal olivary nucleus, inferior olivary nucleus, spinal white and gray matter. The highest FA value was measured in the corpus callosum (81 +/- 3%). The values of the other areas decreased in the following order: pyramidal tract in the medulla (72 +/- 1%), spinal white matter (65 +/- 4%), capsula interna (62 +/- 3%), accessory olivary nucleus (36 +/- 2%), spinal gray matter (35 +/- 5%), dorsal olivary nucleus in the medulla (29 +/- 2%), thalamus (28 +/- 2%), inferior olivary nucleus (15 +/- 2%), putamen (13 +/- 2%), caudate nucleus (13 +/- 2%), and brain cortex (9 +/- 1%). Our results indicate that the underlying fiber architecture, fiber density, and uniformity of nerve fiber direction affect anisotropy values of the various structures. Characterization of various central nervous system structures with diffusion anisotropy is possible and may be useful to monitor degenerative diseases in the central nervous system.     

Cytologic variation in the pineal organ of roseringed parakeets (Psittacula krameri) with respect to artificial photoperiods and annual cyclicity in testicular functions

Abstract

Adult male roseringed parakeets were transferred to 16L: 8D (LP), or 8L: 16D (SP) for 45 or 90 days on four particular dates corresponding to the different phases of an annual testicular cycle and the cytological responses of the pineal were studied comparing them with the features in respective natural photoperiodic (NP) birds. Different cytological characteristics including the values of nuclear diameter in pinealocytes indicated that LP for 45 days during the pre‐breeding phase and for 90 days during each phase resulted in an increased pineal activity, while SP for 45 and 90 days induced inhibitory responses of the pineal during each, but not the progressive phase of the annual testicular cycle. During the latter phase, none of the artificial photoperiodic schedules, other than LP for 90 days, influenced the cytological features of the pineal. The results suggest that the photosensitivity of the pineal in these parakeets varies in relation to the testicular functions in an annual testicular cycle, but the seasonal pattern of photoperiodic response of the pineal and that of the previously studied testes in the same birds does not seem to be identical.     

Nature of the amyloid-beta monomer and the monomer-oligomer equilibrium

The monomer to oligomer transition initiates the aggregation and pathogenic transformation of Alzheimer amyloid-β (Aβ) peptide. However, the monomeric state of this aggregation-prone peptide has remained beyond the reach of most experimental techniques, and a quantitative understanding of this transition is yet to emerge. Here, we employ single-molecule level fluorescence tools to characterize the monomeric state and the monomer-oligomer transition at physiological concentrations in buffers mimicking the cerebrospinal fluid (CSF). Our measurements show that the monomer has a hydrodynamic radius of 0.9 ± 0.1 nm, which confirms the prediction made by some of the in silico studies. Surprisingly, at equilibrium, both Aβ(40) and Aβ(42) remain predominantly monomeric up to 3 μm, above which it forms large aggregates. This concentration is much higher than the estimated concentrations in the CSF of either normal or diseased brains. If Aβ oligomers are present in the CSF and are the key agents in Alzheimer pathology, as is generally believed, then these must be released in the CSF as preformed entities. Although the oligomers are thermodynamically unstable, we find that a large kinetic barrier, which is mostly entropic in origin, strongly impedes their dissociation. Thermodynamic principles therefore allow the development of a pharmacological agent that can catalytically convert metastable oligomers into nontoxic monomers.     

Staphylococcus aureus produces membrane-derived vesicles that induce host cell death

Gram-negative bacteria produce outer membrane vesicles that play a role in the delivery of virulence factors to host cells. However, little is known about the membrane-derived vesicles (MVs) produced by gram-positive bacteria. The present study examined the production of MVs from Staphylococcus aureus and investigated the delivery of MVs to host cells and subsequent cytotoxicity. Four S. aureus strains tested, two type strains and two clinical isolates, produced spherical nanovesicles during in vitro culture. MVs were also produced during in vivo infection of a clinical S. aureus isolate in a mouse pneumonia model. Proteomic analysis showed that 143 different proteins were identified in the S. aureus-derived MVs. S. aureus MVs were interacted with the plasma membrane of host cells via a cholesterol-rich membrane microdomain and then delivered their component protein A to host cells within 30 min. Intact S. aureus MVs induced apoptosis of HEp-2 cells in a dose-dependent manner, whereas lysed MVs neither delivered their component into the cytosol of host cells nor induced cytotoxicity. In conclusion, this study is the first report that S. aureus MVs are an important vehicle for delivery of bacterial effector molecules to host cells.     

Does prosthodontic rehabilitation change the eating patterns among completely edentulous patients?

doi: 10.1111/j.1741‐2358.2010.00404.x Does prosthodontic rehabilitation change the eating patterns among completely edentulous patients? Objective: Nutrition is compromised in completely edentulous individuals. As there is limited literature available on the nutritional health of the elderly in the Indian population, the present study was undertaken to assess these changes before and 1 month after placement of complete dentures in a dental hospital in Indore, Madhya Pradesh, India. Materials and methods: The 10‐item closed‐ended questionnaire was completed by the investigator who interviewed the subjects (n = 35) before placement of complete dentures and 1 month later. Results: A statistically significant difference was found for having an illness or condition that led to a change in the type and/or amount of food eaten (p = 0.013); eating few fruits, vegetables, or milk products (p = 0.005) and having oral problems that made it difficult to eat (p = 0.003). Conclusions: Prosthodontic rehabilitation improved the eating pattern with increased intake of fruits, vegetables and milk products.