Lateral organization of GM1 in phase-separated monolayers visualized by scanning force microscopy

Phase separation of glycolipids in lipid mono- and bilayers is of great interest for the understanding of membrane function. The distribution of the ganglioside GM1 in sphingomyelin (SM)/1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC), SM/1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DOPC) and SM/cholesterol/POPC Langmuir-Blodgett (LB) monolayers transferred at 36 mN/m has been studied by scanning force microscopy. Besides lateral organization of the glycolipid in LB monolayers as deduced from topography, material properties have been investigated by phase imaging, pulsed force mode and force modulation microscopy. It was shown that GM1 preferentially clusters in an ordered lipid matrix, i.e. the SM phase in the case of the SM/POPC and SM/DOPC mixture or in the ordered phase of POPC/SM/cholesterol monolayers. At higher local concentrations, three-dimensional protrusions enriched in GM1 occur, which may represent a precursor for the formation of micelles budding into the aqueous subphase. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00249-002-0232-4.     

Long-term suppression of pituitary-gonadal function with three-month depot of leuprorelin acetate in a girl with central precocious puberty

OBJECTIVE: The efficacy of a 3-month depot preparation of the GnRH agonist leuprorelin acetate in central precocious puberty was studied. METHODS: Treatment with a 3-month depot of leuprorelin acetate was performed subcutaneously in a 7.3-year-old girl with central precocious puberty. RESULTS: During treatment the hormonal suppression was constant and complete as demonstrated by suppressed GnRH stimulation tests and prepubertal estradiol plasma levels. The size and volume of the uterus and ovaries returned to the normal range. The rate of bone maturation was significantly reduced with a ratio deltaBA/deltaCA of 0.58 for 3 treatment years. Thus, the effects of treatment were comparable to those reported for treatment with 1-month depot of GnRH agonists. CONCLUSION: Three-month depots have the advantage of a prolonged injection interval which is more convenient for the patients and reduces costs by necessitating fewer visits to the physician and being approximately 10% cheaper than the 1-month depot. We suggest that comparative and randomized studies be performed to make 3-month depots of GnRH agonists available for routine use in children with central precocious puberty.     

Structural investigation of proapoptotic peptide by CD and NMR spectroscopy

We have performed a systematic investigation of the structural features of the peptides Int (a sequence able to cross cell membranes) and Int-H1(S6A,F8A) (which shows interesting antitumoral properties). After screening in aqueous solution at different ionic strength and pH values, we analyzed the structures of the peptides in different water/trifluoroethanol mixtures by Circular Dichroism and Nuclear Magnetic Resonance techniques.     

Nucleoli undergo structural and molecular modifications during hibernation

The nucleolus is a very dynamic structure able rapidly to adapt its activity to the cellular metabolic state. An interesting physiological model characterized by drastic modifications of cellular metabolism is represented by hibernating animals. In the present study we investigated the hepatocyte nuclei of euthermic and hibernating edible dormice (Glis glis) with the aim of revealing, by means of ultrastructural and immunocytochemical analyses, possible modifications of nucleolar components during hibernation. Our observations demonstrate that, in deep hibernation, nucleoli undergo structural and molecular modifications: (a) they show numerous nucleoplasmic invaginations and clumps of dense fibrillar component extend from the nucleolar surface; (b) they are frequently in contact with coiled bodies and fibro-granular material, two nuclear bodies usually occurring in the nucleoplasm; (c) the dense fibrillar component contains significant amounts of small nuclear ribonucleoproteins, splicing factors usually distributed in the nucleoplasm. Taken together, these results suggest that during hibernation complex relationships are established between the nucleolus and nucleoplasm, probably related to functional activities peculiar to this physiological phase. However, since no evident nucleolar modification was found in early hibernating dormice, it seems likely that the particular structural and molecular arrangement of nucleoli establishes progressively during hibernation, becoming evident only in the deepest phase, and then disappears upon arousal.     

Litter in a first–order stream of a temperate deciduous forest (Margaraça Forest, central Portugal)

To evaluate the importance and fate of organic matter inputs in forested streams, we determined the litterfall inputs and the benthic coarse particulate organic matter (CPOM) in one headwater stream flowing through a mixed deciduous forest, during one year. Both vertical traps and the stream bottom were sampled monthly. The material collected was sorted into four main categories: leaves, fruits and flowers, twigs and debris. Litter production was 715 g m−2 y−1 and seasonal, with 73% of the annual total during October–December (autumn). Leaves comprised the largest litter component. Benthic organic matter was 1880 g m−2 y−1, and was also seasonal. Highest accumulation was attained in spring, and twigs and branches comprised the major component. This revised version was published online in July 2006 with corrections to the Cover Date.     

Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus)

The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations.     

Feline ocular chlamydiosis: clinical and microbiological effects of topical and systemic therapy

Conjunctival swabs taken from a two-month-old kitten showing ocular discharge were found to be positive for Chlamydophila felis by PCR and isolation. The cat was treated with topical 1% tetracycline ophthalmic ointment twice a day for 60 days. At the end of the treatment, the cat showed no ocular signs and conjunctival swabs resulted PCR and isolation negative for C. felis. Forty days later, the ocular discharge recurred and C. felis was isolated from conjunctival swabs taken from both the cat's eyes. Twenty days of doxycycline systemic treatment at 10 mg/kg once daily was started. The treatment resulted in a complete clinical recovery after a few days. C. felis was not isolated or amplified on the 10th day after beginning the treatment. The cat's conjunctival swabs were also PCR and isolation negative on the 10th, 30th, 60th, 90th, 120th and 240th days after the end of therapy.     

P2X7 pre-synaptic receptors in adult rat cerebrocortical nerve terminals: a role in ATP-induced glutamate release

Although growing evidence suggests that extracellular ATP might play roles in the control of astrocyte/neuron crosstalk in the CNS by acting on P2X₇ receptors, it is still unclear whether neuronal functions can be attributed to P2X₇ receptors. In the present paper, we investigate the location, pharmacological profile, and function of P2X₇ receptors on cerebrocortical nerve terminals freshly prepared from adult rats, by measuring glutamate release and calcium accumulation. The preparation chosen (purified synaptosomes) ensures negligible contamination of non-neuronal cells and allows exposure of 'nude' release-regulating pre-synaptic receptors. To confirm the results obtained, we also carried out specific experiments on human embryonic kidney 293 cells which had been stably transfected with rat P2X₇ receptors. Together, our findings suggest that (i) P2X₇ receptors are present in a subpopulation of adult rat cerebrocortical nerve terminals; (ii) P2X₇ receptors are localized on glutamatergic nerve terminals; (iii) P2X₇ receptors play a significant role in ATP-evoked glutamate efflux, which involves Ca²⁺-dependent vesicular release; and (iv) the P2X₇ receptor itself constitutes a significant Ca²⁺-independent mode of exit for glutamate.