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At least 145 records · Page 8Linked to original sources
PubMed1998

Neurotransmitter involvement in development and maintenance of the auditory space map in the guinea pig superior colliculus.

Neurotransmitter involvement in development and maintenance of the auditory space map in the guinea pig superior colliculus. J. Neurophysiol. 80: 2941-2953, 1998. The mammalian superior colliculus (SC) is a complex area of the midbrain in terms of anatomy, physiology, and neurochemistry. The SC bears representations of the major sensory modalites integrated with a motor output system. It is implicated with saccade generation, in behavioral responses to novel sensory stimuli and receives innervation from diverse regions of the brain using many neurotransmitter classes. Ethylene-vinyl acetate copolymer (Elvax-40W polymer) was used here to deliver chronically neurotransmitter receptor antagonists to the SC of the guinea pig to investigate the potential role played by the major neurotransmitter systems in the collicular representation of auditory space. Slices of polymer containing different drugs were implanted onto the SC of guinea pigs before the development of the SC azimuthal auditory space map, at approximately 20 days after birth (DAB). A further group of animals was exposed to aminophosphonopentanoic acid (AP5) at approximately 250 DAB. Azimuthal spatial tuning properties of deep layer multiunits of anesthetized guinea pigs were examined approximately 20 days after implantation of the Elvax polymer. Broadband noise bursts were presented to the animals under anechoic, free-field conditions. Neuronal responses were used to construct polar plots representative of the auditory spatial multiunit receptive fields (MURFs). Animals exposed to control polymer could develop a map of auditory space in the SC comparable with that seen in unimplanted normal animals. Exposure of the SC of young animals to AP5, 6-cyano-7-nitroquinoxaline-2,3-dione, or atropine, resulted in a reduction in the proportion of spatially tuned responses with an increase in the proportion of broadly tuned responses and a degradation in topographic order. Thus N-methyl--aspartate (NMDA) and non-NMDA glutamate receptors and muscarinic acetylcholine receptors appear to play vital roles in the development of the SC auditory space map. A group of animals exposed to AP5 beginning at approximately 250 DAB produced results very similar to those obtained in the young group exposed to AP5. Thus NMDA glutamate receptors also seem to be involved in the maintenance of the SC representation of auditory space in the adult guinea pig. Exposure of the SC of young guinea pigs to gamma-aminobutyric acid (GABA) receptor blocking agents produced some but not total disruption of the spatial tuning of auditory MURFs. Receptive fields were large compared with controls, but a significant degree of topographical organization was maintained. GABA receptors may play a role in the development of fine tuning and sharpening of auditory spatial responses in the SC but not necessarily in the generation of topographical order of the these responses.

Acoustic Stimulation↗
PubMed1999

Endosteal implants for posterior single tooth replacement: alternatives, indications, contraindications, and limitations.

Patients frequently need treatment to replace single teeth in the posterior regions. A number of different kinds of therapy have been used to treat this problem, including (1) removable partial denture, (2) acid-etched resin-retained prosthesis, (3) maintenance of the missing space, (4) a fixed partial denture, or (5) an implant-supported prosthesis. The purpose of this article is to assess the strengths and weaknesses of each of these treatments. The author concludes that single tooth implants are generally the best choice for dealing with a missing single tooth in the posterior regions of the mouth.

Adolescent↗
PubMed1971

Immune states in long-term space flights.

Maintenance of health, as contrasted to illness induced by infectious agents, reflects a tenuous balance between the host's resistance and the number and genetic characteristics of the infectious organisms present. Nature has evolved both nonspecific defense mechanisms and specific immune systems to protect the body against invasion by exogenous organisms or the numerous agents which may reside dormant within the host. Long-term space flights with their accompanying prolonged weightlessness, unaccustomed environmental factors, emotional disturbances, and unforeseen influences may alter the host's natural or specific immune states. The non-specific and specific host defenses will be discussed, and the particular effects which their alteration might have on provocation of latent viral infections will be considered. Viruses which classically may be induced to cause recurrent infections such as herpes simplex and herpes zoster will be described, but in addition the effect that altered host defenses might have on slow virus infections such as kuru and virus-induced malignancies will be emphasized.

Aerospace Medicine↗
PubMed1987

Psychiatric components of a health maintenance facility (HMF) on Space Station.

The operation of a permanently manned space station brings a special challenge to psychiatry due to the combined physiological, emotional, and social stresses which will affect its occupants. Psychiatric diagnostic and therapeutic techniques will be a part of the Space Station's general medical support, known as the Health Maintenance Facility (HMF). The psychiatric component of HMF will promote psychological health throughout the mission and permit treatment, if necessary, of those psychiatric disorders which could impact mission success. This paper will discuss these emotional disorders and propose methods of management in the microgravity environment.

Adjustment Disorders↗
PubMed2000

The dynamin-related GTPase, Mgm1p, is an intermembrane space protein required for maintenance of fusion competent mitochondria.

Mutations in the dynamin-related GTPase, Mgm1p, have been shown to cause mitochondrial aggregation and mitochondrial DNA loss in Saccharomyces cerevisiae cells, but Mgm1p's exact role in mitochondrial maintenance is unclear. To study the primary function of MGM1, we characterized new temperature sensitive MGM1 alleles. Examination of mitochondrial morphology in mgm1 cells indicates that fragmentation of mitochondrial reticuli is the primary phenotype associated with loss of MGM1 function, with secondary aggregation of mitochondrial fragments. This mgm1 phenotype is identical to that observed in cells with a conditional mutation in FZO1, which encodes a transmembrane GTPase required for mitochondrial fusion, raising the possibility that Mgm1p is also required for fusion. Consistent with this idea, mitochondrial fusion is blocked in mgm1 cells during mating, and deletion of DNM1, which encodes a dynamin-related GTPase required for mitochondrial fission, blocks mitochondrial fragmentation in mgm1 cells. However, in contrast to fzo1 cells, deletion of DNM1 in mgm1 cells restores mitochondrial fusion during mating. This last observation indicates that despite the phenotypic similarities observed between mgm1 and fzo1 cells, MGM1 does not play a direct role in mitochondrial fusion. Although Mgm1p was recently reported to localize to the mitochondrial outer membrane, our studies indicate that Mgm1p is localized to the mitochondrial intermembrane space. Based on our localization data and Mgm1p's structural homology to dynamin, we postulate that it functions in inner membrane remodeling events. In this context, the observed mgm1 phenotypes suggest that inner and outer membrane fission is coupled and that loss of MGM1 function may stimulate Dnm1p-dependent outer membrane fission, resulting in the formation of mitochondrial fragments that are structurally incompetent for fusion.

Cell Compartmentation↗
PubMed2006

Decision analysis in aerospace medicine: costs and benefits of a hyperbaric facility in space.

INTRODUCTION: Assembly and maintenance of the International Space Station (ISS) requires an unprecedented number of spacewalks, which expose astronauts to the risk of decompression sickness (DCS). We illustrate the use of decision analysis to compare a hyperbaric oxygen (HBO) chamber to currently available therapy for DCS treatment on the ISS. METHODS: A decision-analytic model that simulates events over the lifespan of the ISS was constructed. Inputs to the model for probabilities, costs, and measures of morbidity and mortality were derived from a variety of sources, including a systematic literature review and an iterative consultation process with personnel at the Canadian Space Agency and the National Aeronautics and Space Administration (NASA). The decision model was analyzed using the methods of Monte-Carlo simulation and expected value calculation. Main outcome measures included the present value of costs and quality adjusted life years (QALYs), and the cumulative probability of mission-related events over the life cycle of the ISS. Sensitivity analysis was performed. RESULTS: The HBO chamber strategy is associated with a mean cost of -12.5 million dollarsw (a net cost saving of 12.5 million dollars) with a 95% CI (-112.8 million dollars, 51.3 million dollars). An HBO chamber reduces the likelihood of a premature shuttle return and a premature Soyuz return by 8% and 3%, respectively. The result is sensitive to the lifespan of the ISS. CONCLUSIONS: At a 50 million dollars cost, an HBO chamber is likely, though not certain, to result in cost savings. Decision analysis is a useful tool for use in priority setting in aerospace medicine.

Cost-Benefit Analysis↗
PubMed1995

Low temperature preservation and space medicine.

Cold maintenance may be an option for compromised space-borne astronauts. Contemporary aneurysm surgery can involve cooling below 20 degrees C for nearly one hour. Dogs and baboons have survived blood-substituted hypothermia for 1-3 hours. Hamsters have recovered from partial-freezing below -1 degree C, and supercooling at -5 degrees C. Laboratory frogs have survived partial-freezing from -9 degrees C, while in nature, frogs may overwinter in these states. While some invertebrates can tolerate freezing to cryogenic temperatures, no vertebrate has survived complete freezing. The following studies (hypothermia and sub-zero experiments) were conducted to explore low temperature preservation of rodents, dogs and baboons.

Animals↗
PubMed2006

Towards a "crippled-mode" operation of an industrial wastewater treatment plant.

In house treatment of metal plating wastewater mainly involves chemical treatments performed in continuous flow stirred tank reactors (CFSTR). The inflow of these tanks is directly produced by the plating shops activity, and the storage capacity never exceeds a few hours of incoming flow. Thus, any fault on one of the CFSTR may impose a complete stop of the whole manufacturing process, which is unacceptable for the manufacturer. Another solution would be having "spare" CFSTRs ready to be used as alternative in case of any CFSTR fault or maintenance. The latter solution however implies additional costs in equipment, storage space and maintenance so as to keep this equipment fit and ready for operation. The paper presents the study of a "crippled-mode" wastewater treatment (WWT) operation which enables a sufficiently efficient working of the WWT plant during maintenance phases and failure repairing on any of the CFSTR, without any extra equipment needed. This survey has been performed on real industrial WWT plants, with a continuous influent and under industrial operation constraints. The performances of the detoxication have been analysed when a CFSTR is short-circuited and the corresponding chemical treatment is shunt in the upstream or downstream CSFTR. This work shows the possibility of satisfying the environmental regulations with a WWT plant functioning under subnormal conditions.

Electroplating↗
PubMed1991

Space dermatology: a specialty in evolution.

The last thirty years have demonstrated the ability of humans to survive both brief and prolonged durations of microgravity in the unique environment of space. The maintenance of health and well-being during spaceflight has been the focus of physicians and health care personnel involved in space medicine. It follows that dermatology will become a defined component of space medicine, as skin-related physiology and subsequent disorders are elucidated and as health maintenance protocols are developed. This information will become part of the core of what can be called space dermatology.

Aerospace Medicine↗