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Biomedical subjects

G S Bassi

Publications and source records attributed to G S Bassi.

11 recordsLinked to original sources
PubMed2004

The etiology and management of gagging: a review of the literature.

Gagging in dental patients can be disruptive to dental treatment and may be a barrier to patient care, preventing the provision of treatment and the wearing of prostheses. This article reviews the literature on the gagging problem from English-language peer-reviewed articles from the years 1940 to 2002 found by conducting an electronic search of PubMed, coupled with additional references from citations within the articles. Dentally relevant articles have been cited wherever evidence exists, and a balanced view given in situations where there is controversy. The first section considers the normal gag reflex and factors that may be associated with the etiology of gagging, including anatomical and iatrogenic factors, systemic disorders, and psychological conditions. A review of the management of patients with an exaggerated gag reflex follows and includes strategies to assist clinicians.

Behavior Therapy↗
PubMed2002

Improved resuscitation training of senior house officers in oral and maxillofacial surgery.

All healthcare professionals are expected to be competent at cardiopulmonary resuscitation. In a previous study [Br J Oral Maxillofac Surg 1999; 37: 1], senior house officers in oral and maxillofacial surgery (OMFS) expressed dissatisfaction about their training in resuscitation, and we now report the results of a follow-up survey. The amount of training in resuscitation has increased in the 5 years since the initial questionnaire, and 77% of the 73 respondents (n=56) been given such training in the 12 months before the present survey, compared to 48% in the previous study. Fifty-one (70%) now think that they would feel confident if required to resuscitate a patient who had a cardiorespiratory arrest, and this has increased from 47%. Despite this, 70 (96%) of senior house officers in OMFS stated that they wanted further training in cardiopulmonary resuscitation.

Cardiopulmonary Resuscitation↗
PubMed2001

An unusual presentation of non-Hodgkin's lymphoma in the head and neck.

The lymphomas are a group of lymphoproliferative disorders that can be divided histologically in the two main groups of Hodgkin's and non-Hodgkin's lymphoma. They sometimes present in the head and neck, and the diagnosis and management require a multidisciplinary approach. An unusual case is described presenting at an advanced stage because of patient delay in seeking medical help.

Actinomycosis↗
PubMed2000

Medical emergencies.

Explore the source record for details and available documents.

Cardiopulmonary Resuscitation↗
PubMed2000

An alternative putty/wash impression technique.

Conventionally, custom trays have been made in the laboratory on casts constructed from preliminary impressions. A spaced tray made in this way allows a uniform thickness of impression material of approximately 2 mm which is said to enhance the accuracy of the impression-taking procedure. A technique is described to fulfill this criterion without the need for a primary impression, by constructing a spaced putty custom tray inside the mouth.

Dental Impression Materials↗
PubMed1999

RNA folding and misfolding of the hammerhead ribozyme.

The hammerhead ribozyme undergoes a well-defined two-stage folding process induced by the sequential binding of two magnesium ions. These probably correspond to the formation of domain 2 (0-500 microM magnesium ions) and domain 1 (1-20 mM magnesium ions), respectively. In this study we have used fluorescence resonance energy transfer (FRET) to analyze the ion-induced folding of a number of variants of the hammerhead ribozyme. We find that both A14G and G8U mutations are highly destabilizing, such that these species are essentially unfolded under all conditions. Thus they appear to be blocked in the first stage of the folding process, and using uranyl-induced photocleavage we show that the core is completely accessible to this probe under these conditions. Changes at G5 do not affect the first transition but appear to provide a blockage at the second stage of folding; this is true of changes in the sugar (removal of the 2'-hydroxyl group) and base (G5C mutation, previously studied by comparative gel electrophoresis). Arrest of folding at this intermediate stage leads to a pattern of uranyl-induced photocleavage that is changed from the wild-type, but suggests a structure less open than the A14G mutant. Specific photocleavage at G5 is found only in the wild-type sequence, suggesting that this ion-binding site is formed late in the folding process. In addition to folding that is blocked at selected stages, we have also observed misfolding. Thus the A13G mutation appears to result in the ion-induced formation of a novel tertiary structure.

Adenine↗
PubMed1997

Ion-induced folding of the hammerhead ribozyme: a fluorescence resonance energy transfer study.

The ion-induced folding transitions of the hammerhead ribozyme have been analysed by fluorescence resonance energy transfer. The hammerhead ribozyme may be regarded as a special example of a three-way RNA junction, the global structure of which has been studied by comparing the distances (as energy transfer efficiencies) between the ends of pairs of labelled arms for the three possible end-to-end vectors as a function of magnesium ion concentration. The data support two sequential ion-dependent transitions, which can be interpreted in the light of the crystal structures of the hammerhead ribozyme. The first transition corresponds to the formation of a coaxial stacking between helices II and III; the data can be fully explained by a model in which the transition is induced by a single magnesium ion which binds with an apparent association constant of 8000-10 000 M-1. The second structural transition corresponds to the formation of the catalytic domain of the ribozyme, induced by a single magnesium ion with an apparent association constant of approximately 1100 M-1. The hammerhead ribozyme provides a well-defined example of ion-dependent folding in RNA.

Base Sequence↗
PubMed1997

Nucleic acid structure and recognition.

We review the global structures adopted by branched nucleic acids, including three- and four-way helical junctions in DNA and RNA. We find that some general folding principles emerge. First, all the structures exhibit a tendency to undergo pairwise coaxial helical stacking when permitted by the local stereochemistry of strand exchange. Second, metal ions generally play an important role in facilitating folding of branched nucleic acids. These principles can be applied to functionally important branched nucleic acids, such as the Holliday DNA junction of genetic recombination, and the hammerhead ribozyme in RNA.

Journal Article↗
PubMed1996

The ion-induced folding of the hammerhead ribozyme: core sequence changes that perturb folding into the active conformation.

The hammerhead ribozyme undergoes an ion-dependent folding process into the active conformation. We find that the folding can be blocked at specific stages by changes of sequence or functionality within the core. In the the absence of added metal ions, the global structure of the hammerhead is extended, with a large angle subtended between stems I and II. No core sequence changes appear to alter this geometry, consistent with an unstructured core under these conditions. Upon addition of low concentrations of magnesium ions, the hammerhead folds by an association of stems II and III, to include a large angle between them. This stage is inhibited or altered by mutations within the oligopurine sequence lying between stems II and III, and folding is completely prevented by an A14G mutation. Further increase in magnesium ion concentration brings about a second stage of folding in the natural sequence hammerhead, involving a reorientation of stem I, which rotates around into the same direction of stem II. Because this transition occurs over the same range of magnesium ion concentration over which the hammerhead ribozyme becomes active, it is likely that the final conformation is most closely related to the active form of the structure. Magnesium ion-dependent folding into this conformation is prevented by changes at G5, notably removal of the 2'-hydroxyl group and replacement of the base by cytidine. The ability to dissect the folding process by means of sequence changes suggests that two separate ion-dependent stages are involved in the folding of the hammerhead ribozyme into the active conformation.

Base Sequence↗
PubMed1995

Ionic interactions and the global conformations of the hammerhead ribozyme.

Here we investigate the global conformation of the hammerhead ribozyme. Electrophoretic studies demonstrate that the structure is folded in response to the concentration and type of ions present. Folding based on colinear alignment of arms II and III is suggested, with a variable angle subtended by the remaining helix I. In the probable active conformation, a small angle is subtended between helices I and II. Using uranyl photocleavage, an ion binding site has been detected in the long single-stranded region. The folded conformation could generate a preactivation of the scissile bond to permit in-line attack of the 2'-hydroxyl group, with a bound metal ion playing an integral role in the chemistry.

Base Sequence↗