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At least 577 records · Page 32Linked to original sources
PubMed2006

Diagnostic protocol in cases of congenitally missing maxillary lateral incisors.

Patients with congenitally missing maxillary lateral incisors may seek treatment from an orthodontist for several reasons; unpleasant smile, dental arch disharmony, and midline deviations are among the most frequent complaints. Orthodontists and prosthodontists have raised important questions about the esthetics, occlusion, periodontal health, and psychological conditions noted in these patients. The decision to open lateral incisor spaces for prosthetics or close spaces by mesial movement of the canines requires a careful diagnosis and comprehensive multidisciplinary treatment planning. The purpose of this article is to present a diagnostic protocol to assist in the decision-making process, while analyzing patients with absent maxillary lateral incisors. The basis for a sound diagnosis and an effective treatment plan resides in careful consideration of the facial and dental characteristics of each patient. All information gathered during the clinical examination should be added to data obtained with other diagnostic tools, such as cephalometric analysis and orthodontic waxups, to achieve the treatment option that best suits the patient's expectations.

Anodontia↗
PubMed1982

Do neuronal signals regulate potassium flow in glial cells? Evidence from an invertebrate central nervous system.

Experiments were conducted with the aid of intracellular microelectrodes to study physiological properties of neuropile glial cells in the central nervous system of the medicinal leech. The results showed significant contributions of both K+ and Cl- ions to the membrane potential. The transmitter substance 5-hydroxytryptamine increased the K+ conductance of the cell membrane. On the basis of these experiments, a model for potassium homeostasis in leech neuropile is suggested, according to which excess K+ ions in the extracellular space lead to passive KCl fluxes across the glial cell membrane and the transmitter 5-hydroxytryptamine induces a K+ release from glial cells into the extracellular space. Since 5-hydroxytryptamine is known to be an inhibitory transmitter in the leech central nervous system, this release will occur in regions with inactive neurons, which may be specially well suited for neuronal reaccumulation of K+ ions.

Animals↗
PubMed1992

Radial scanning technique for volume selective 31P spectroscopy.

An interlaced radial scanning method that is ideally suited for 31P spectroscopy with short T2 components and a wide spectral range is presented. The proposed method, which uses an additional radial gradient and radial scans in the k-space, minimizes T2 decay during the selection time and also optimizes the volume selectivity in a given gradient field strength. Simulation and experimental results with a short selection time of 2 ms demonstrate that the proposed method is suitable for volume selective 31P spectroscopy.

Adenosine Triphosphate↗
PubMed1997

[Tolerance of +Gx-loads by females before and after a 120-day hypokinesia].

The goal of the work was to study female tolerance of g-loads before and after simulated weightlessness, and evaluate the effectiveness of countermeasures and anti-g means proposed for space flight. Centrifuge with a 7.25 m arm was used for 29 runs of 8 female subjects. The subjects were exposed to the transverse loads (+GX) at 8.2 g on a special regimen with the total run time of 9 min to simulate the ballistic descent from orbit in a SOYUZ-TM vehicle. Baseline tolerance of the females to transverse loads up to +8GX was good and satisfactory. Following 120 days of bed rest without the countermeasures or the anti-g suit g-tolerance was significantly lowered as evidenced by visual disorders in 67% of cases and exaggerated, if compared with the pre-hypokinesia levels, heart and respiration rates, i.e. 20% and 23.5%, respectively. The countermeasures and anti-g suit Centaur maintained g-tolerance at essentially the baseline level and precluded visual disorders. Results of the study speak in favor of the countermeasures and anti-g means used by the females in simulated long-duration weightlessness which can be recommended for the final phase of extended space mission.

Adaptation, Physiological↗
PubMed2000

Development and growth of several strains of Arabidopsis seedlings in microgravity.

Growth and development of dark-grown Arabidopsis thaliana seedlings were studied in microgravity during space shuttle mission STS-84. The major purpose of this project was to determine if there were developmental differences among the four ecotypes studied--Wassilewskija (Ws), Columbia (Col), Landsberg erecta (Ler), and C24--and to evaluate whether particular ecotypes are better suited for spaceflight experimentation compared with others. A secondary goal was to study the growth of three starch-deficient strains of Arabidopsis by extending the observations made in a previously published report. For all strains, seed germination was not affected by microgravity, but seedlings were smaller in the spaceflight samples compared with the ground controls. The starch-deficient strains continued to exhibit vigorous growth until the termination of the experiment at 121 h after imbibition of seeds. However, ethylene effects, i.e., reduced growth and exaggerated hypocotyl hooks, were observed in all strains studied. Nevertheless, the Ler and C24 ecotypes seem to be more suitable for spaceflight research, compared with the other two ecotypes, based on measurements of their relative and absolute growth. This type of information should aid in the design of plant experiments for the International Space Station.

Arabidopsis↗
PubMed2001

[Tolerance of +Gx by MIR 22 -- 27 main crew in space flights].

Data on +Gx tolerance by 16 cosmonauts-members of the Mir 22-27 main crews in missions from 8 up to 380 days in duration are reported. All cosmonauts showed good tolerance of g-loads during insertion into orbit. Owing to the use of anti-g suit Centaur and water-salt supplements prior to deorbiting, tolerance of +Gx in the course of descent was satisfactory in the majority of the cosmonauts and low only in one person. As compared with short missions (8 to 21 days), strain of the physiological systems exposed to the deorbit +Gx loads following an extended period in microgravity (186 to 380 days) was greater and manifested by more often arrhythmias, hard breathing and speech, vestibulo-autonomous reactions, petechial hematomas into the back tegmentum, and more severe sinus tachycardia. As a rule, there were no symptoms indicative of poor g-tolerance (visual disorders etc.) which speaks for effectiveness of the anti-g measures in most of the cosmonauts. However, prognostically bad cardiac rhythm disturbances (multitude of single, group and systemic polytope ventricular extrasystoles) registered in one cosmonaut on the deorbit phase mean that efforts should be redoubled to improve countermeasures against the deconditioning of organism by microgravity, particularly the cardiac rhythm disturbances.

Adult↗
PubMed2002

MR angiography with a new rapid-clearance blood pool agent: Initial experience in rabbits.

The purpose of this study was to assess a new Gd-based macromolecular intravascular contrast agent (P792, Vistarem(R); Laboratoire Guerbet, Aulnay sous Bois, France) for MR angiography (MRA). P792 is a macrocyclic gadolinium compound based on a gadoterate meglumine structure substituted by hydrophilic arms. In vitro imaging of phantoms containing varying concentrations of P792 and gadoterate meglumine (Gd-DOTA) was performed. In rabbits (N = 5), arterial concentrations for P792 and Gd-DOTA were determined, and in vivo 3D MRA was performed. For gadolinium concentrations ranging from 200 to 3000 micromol/l, in vitro imaging showed higher SNR values for P792 compared to Gd-DOTA. Determination of arterial Gd concentration showed comparable bolus phase curves for P792 and Gd-DOTA. With P792, higher concentrations were obtained due to a restricted diffusion into the interstitial space. P792 allowed acquisition of high-quality MR angiograms. Image quality was rated as superior for P792 in the post-bolus phase images. In conclusion, P792 appears to be well suited for high-quality first-pass and equilibrium-phase MRA. The intravascular properties lead to an excellent signal in the vasculature, with limited background enhancement. Since the agent is rapidly renally excreted, it should be well suited for perfusion and permeability imaging.

Animals↗
PubMedDate not supplied

A comparison of neural computations underlying stereo vision and sound localization.

Stereo vision and sound localization are behaviors that help organisms to orient in space. Stereo vision provides information about the distance of an object. In sound localization mainly directional signals are analyzed. Two specific cues, binocular disparities underlying stereo vision, and the interaural time difference, suited to represent azimuth in sound localization, have many computational problems in common, although they are generated in two different modalities. The extraction of both cues requires a comparison of signals that arise from two independent sensors, called two-sensor comparison here. This two-sensor comparison is achieved by algorithms similar to summation, half-wave rectification and multiplication. Since the underlying neurons are band-pass filters, the two-sensor comparison results in ambiguities. These are removed in a hierarchical way in several computational steps, involving squaring, inhibition and across-frequency integration.

Animals↗
PubMed2000

Delayed diagnosis of vascular injuries during lumbar discectomy.

We report an accidental perforation of the left iliac artery and vein during lumbar discectomy in the kneeling position. During the surgical procedure, a brief and transient hypotension occurred, although the surgeon did not observe any abnormal bleeding in the operating field. In the recovery room, arterial blood pressure decreased, and tachycardia, pallor, and abdominal pain occurred. Retroperitoneal bleeding was suspected. Immediate fluid resuscitation was initiated, anesthesia was continued, and red blood cells were ordered. The use of medical antishock trousers enabled temporization until vascular surgeons were ready. An emergent laparotomy was performed to repair vascular injuries. The delayed symptoms, use of medical antishock trousers, and implications for anesthetists are discussed.

Abdominal Pain↗
PubMed1991

AIDS, older people, and social work.

The acquired immune deficiency syndrome (AIDS) epidemic is significantly affecting older people. Older people themselves may be HIV positive, or they may be the caregiving spouse, partner, parent, or grandparent of a person with AIDS. In addition, older people may share housing or institutional space with people with AIDS. Concerns about the allocation of long-term care resources may create conflict between the needs of older people and people with AIDS. Social workers are particularly suited to lead the discussion of the impact of AIDS on older people, a role the profession has not yet embraced. Four areas of social work leadership are discussed: education, direct service, research, and advocacy.

Acquired Immunodeficiency Syndrome↗
PubMed1981

Theory on prospect of population evolution processes.

This paper is aimed at investigating the dynamic process of population growth applied to population of the People's Republic of China. The discrete and continuous models of population evolution process are revised and adjusted to suit the social conditions of China. The relationship between two kinds of models is established. A series of new formulae of demographic indices are studied and defined as functions on the negative space of generalized solutions of the population equation. Based on survey data collected in China for recent years, the prospect of population growth according to different projections is offered for a one-hundred-year period from now on.

Demography↗
PubMed1986

Cellular sodium transport in arterial wall--summary of studies by digital computer simulation.

The distribution of electrolytes between extracellular and intracellular compartments is of greater functional significance in biological tissues than the total amount. A method commonly employed for the study of a substance distribution among different spaces is the continuous outflow and radioisotope counting of a fragment of tissue previously incubated with a radioactive tracer (here 22Na+). The experimental data can be analyzed within the frame of a compartmental analysis system which is defined by transport rate constants (kij) and solved when all kij are numerically determined. In practical applications the direct solution requires measurements in different compartments or knowledge of the initial condition for each compartment, but this is not possible in most biological tissues where the experimentally observable data represent the summation of tracer in all compartments at each point in time. The availability of the SAAM (Simulation, Analysis And Modelling) computer program allows for a powerful simulation procedure to arrive at values for kij. Experimental data and specifications for a chosen model are entered in the SAAM format. A simulated 'inflow' experiment is made by the computer by assigning to kij some estimate values. All initial conditions are now zero, since at the beginning there is no radioactive tracer in any compartment. After a time equivalent in the experimental realm to achieving constant specific activity, a 'time change' programmed into the computer takes place so that the outflow part of the experiment is developed with the same kij as for the inflow part, the final conditions for the inflow before the time change being the initial conditions for the outflow. An iterative procedure modifies the initial estimates of kij to seek the best fit. By coupling a powerful simulation procedure to an advanced radionuclide tracer biological methodology, we have been able to find effects of the hormone aldosterone and of experimental hypertension on Na+ distribution in arterial wall years before such effects were demonstrated by purely conventional experimental techniques. This computer simulation procedure may be suited to other experimental situations in which outflow data are the only available.

Aldosterone↗
PubMedDate not supplied

MR imaging of blood vessels with an intravascular coil.

A method for producing high-resolution magnetic resonance (MR) images of blood vessel walls is described. The authors review a theoretical analysis of receiver-coil design and present a coil well suited for intravascular MR imaging. The design is based on two coaxial solenoids separated by a gap region and with current driven in opposite directions. Placement of this receiver coil within the vascular space is shown to provide a substantial increase in sensitivity over that external surface coils. Experimental verification of these predictions was obtained in a vessel phantom in which a 13-cm surface coil was compared with a 3.5-mm-diameter opposed-solenoid intravascular coil. This intravascular coil had a cylindric region of high sensitivity that offered a 10-fold improvement in signal-to-noise ratio over that of an external coil near the vessel wall. The performance of this coil was also tested in the jugular vein of a swine.

Animals↗
PubMed1991

Battery-powered, electrocuting trap for stable flies (Diptera: Muscidae).

A solar-charged, battery-powered, electrocuting grid was combined with a white plywood base to make a portable, pulsed-current, pest-electrocuting device that attracted and killed stable flies, Stomoxys calcitrans (L.), outdoors. The grid was powered once every 1-2 s by a 0.016-s pulse of 60-Hz alternating current of 4 mA and 9,500 V. Power was turned off at night by a photoresistor. The trap functioned continuously for 14 d with an unrecharged 12-V, 18A/h lawn-tractor battery and killed as many as 4,000 flies per day. Solar cells were used to charge a single 12-V battery continuously that operated 12 grids for a period of 90 d. The grid did not short circuit for any length of time even during heavy rainstorms or when large insects were killed. The incorporation of moiré patterns and the utilization of the correct size, orientation, and placement of wires made the electrocuting grid itself attractive to stable flies. The traps were spaced at distances of up to 120 m from the battery and pulse circuit. The electrocuting traps were more effective than sticky traps and avoided the problems associated with chemicals. They are well suited for use around calf pens, dog kennels, or large animal shelters.

Animals↗
PubMed1993

Improved transdural exposure and temporary occlusion of the petrous internal carotid artery for cavernous sinus surgery. Technical note.

Safe surgery for vascular and neoplastic lesions involving the cavernous sinus requires adequate proximal control of the cavernous internal carotid artery (ICA). Classically, control of the cavernous ICA has necessitated dissection and isolation of the cervical vessels. The authors describe an alternative method for obtaining vascular control via transdural exposure of the petrous ICA and the use of the Fogarty balloon embolectomy catheter inserted extra-arterially into the carotid canal to provide temporary occlusion. This method is particularly well suited for proximal ICA occlusion during short-segment petrous-to-paraclinoid ICA bypass procedures as it eliminates the need for a temporary proximal ICA aneurysm clip and increases the available working space for completion of the anastomosis.

Carotid Artery, Internal↗
PubMed1991

[Hearing disorders following spinal anesthesia].

In the few case reports of hearing loss following spinal anesthesia, complete recovery of the hearing impairment has always been described. In nine cases with hearing loss following not only spinal anesthesia but also myelography and dural puncture, the hearing of three patients did not recover or only partly returned. Two cases went to court for malpractice. Their suits could be dismissed because it appears likely that this rare complication arises only in persons with a wholly or partially unobliterated aquaeductus cochleae due to loss of perilymphatic fluid into the cerebrospinal space. Hearing loss was seen in eight of nine patients in lower frequencies around 30-40 dB. In six patients there was impairment on both sides. Recovery of normal hearing occurred in six of the nine patients. Transient hearing loss may occur more often than is generally assumed, and the symptom may remain unnoticed when a severe post-dural puncture syndrome with headache, dizziness, and nausea dominates the attention of the patient. Not all cases of hearing loss proved to be fully reversible, but the individual risk for this complication is not predictable. The use of fine-gauge needles may reduce the leakage of cerebrospinal fluid through the dural puncture and thus lower the incidence.

Adult↗
PubMedDate not supplied

Amino acids and cell regulation.

Free amino play an important role in regulating cell volume in fishes. Four tissues/cells (skeletal muscle, RBC, brain, and myocardium) of the little skate, Raja erinacea, were selected for detailed study because of their special importance or unique advantage as experimental models. Three particular amino acids, beta-alanine, taurine, and sarcosine play a predominant role in all four tissues. As in higher vertebrates, amino acid uptake in skate brain, heart, and RBC is mediated via a Na+-dependent process. Amino acids leave the skate brain rapidly in response to a sudden decrease in plasma osmolality and/or to a simultaneous drop in extracellular Na+ concentration. However, although amino acids are important for volume regulation in normal brain cells, they do not appear to be likely candidates for the unidentified "idiogenic" osmolytes in mammalian brain cells. The high concentration of taurine in skate myocardium is of special interest because of the special role of this amino acid in myocardial contractility. Thus, unlike beta-alanine and sarcosine, taurine may play a dual role in regulating both cell volume and contractility of myocardial cells. The isolated skate atrium is well suited for in vitro studies of these two processes.

Amino Acids↗