Temporary placement of fully covered self-expandable metal stents in biliary complications after liver transplantation.

In the present study we prospectively evaluated the safety and efficacy of temporary fully covered, self-expandable metal stents (fcSEMS) to treat biliary strictures (n = 9), leaks (n = 9), and combined lesions (n = 1) occurring after liver transplantation, when standard endoscopic attempts had failed. Placement of fcSEMS and their removal in scheduled patients were successful and without complications. Resolution of the biliary lesion was confirmed in 15 of 19 patients (79 %). Treatment was not successful in two patients and not evaluable in 2 other patients. Complications occurred in 9 /19 patients (47 %): stent migration in 6, stent occlusion in 1, and de novo stricture after successful treatment of a biliary leak in 2. After a median follow-up of 12 months, one recurrent anastomotic stricture was noted. Temporary placement of fcSEMS in biliary strictures and leaks after liver transplantation provides satisfactory results even in patients who have undergone multiple previous conventional endoscopic attempts, and offers an alternative approach to surgical intervention.

SCPP gene evolution and the dental mineralization continuum.

Many genes critical to vertebrate skeletal mineralization are members of the secretory calcium-binding phosphoprotein (SCPP) gene family, which has evolved by gene duplication from a single ancestral gene. In humans, mutations in some of these SCPP genes have been associated with various diseases related to dentin or enamel hypoplasia. Recently, systematic searches for SCPP genes of various species have allowed us to investigate the history of phylogenetically variable dental tissues as a whole. One important conclusion is that not all disease-associated SCPP genes are present in tetrapods, and teleost fish probably have none, even in toothed species, having acquired their complement of SCPP genes through an independent duplication history. Here, we review comparative analyses of mineralized dental tissues, with particular emphasis on the use of SCPPs, within and between tetrapods and teleosts. Current knowledge suggests a close relationship among bone, dentin, teleost fish enameloid (enamel-like hard tissue), and tetrapod enamel. These tissues thus form a mineralized-tissue continuum. Contemporary dental tissues have evolved from an ancestral continuum through lineage-specific modifications.

Multiple roles of a histaminergic afferent neuron in the feeding behavior of Aplysia.

The cellular and circuit properties of individual identified neurons in invertebrates can be readily studied; hence it is possible to determine how the complex properties of nerve cells function in the generation of behavior. Recent studies of the cellular basis of feeding behavior in the marine mollusc Aplysia have focused on a neuron, C2, that has a variety of complex properties that determine the behavioral functions of the neuron. C2 conveys mechanosensory information from the mouth of the animal. It receives a complex pattern of inputs during feeding behavior, and generates diverse outputs that may shape behavior. It can act to filter out slow or sporadic sensory inputs, and its own outputs can be 'gated' by synaptic input. C2 uses histamine as its transmitter, and some of its synaptic outputs are modulatory and contribute to the expression of an arousal state induced by food. Other outputs shape feeding behavior directly by affecting motor neurons, as well as presynaptically inhibiting the outputs of feeding motor programs. Thus, the complex properties of this neuron may contribute to the flexibility and adaptability of feeding in Aplysia. Studies of C2 have expanded our concepts of the properties of sensory neurons.

Cranial and cervical nerve injuries: local complications of carotid artery surgery.

Injury to the nervous structures extending through the operative field or in areas adjacent to it constitutes a local complication in surgery of the carotid artery. These lesions may become, after an otherwise well-tolerated reconstruction, the source of severe and, occasionally even permanent, complaints. In a series of 536 operations of the carotid artery, 14.4% of transient and 6% of permanent injuries to some of the distal cranial and cervical nerves occurred. The highest injury rate was observed in the hypoglossal nerve (8.6%), followed by the marginal mandibular branch of the facial nerve (6.2%) and the vagus nerve with its superior and recurrent laryngeal branches (3.7% of cases). Injury to the glossopharyngeal nerve and the greater auricular nerve occurs very rarely. A thorough knowledge of the topographic and anatomical situation combined with a cautious operation technique may lower the frequency of these lesions. That is why the essential data on the anatomy, function and the most frequent causes of injury to the individual nerves sustained during surgery within the trigonum caroticum are presented in this article.

Fixation of pathological humeral fractures by the cemented plate technique.

Pathological fractures of the humerus are associated with pain, morbidity, loss of function and a diminished quality of life. We report our experience of stabilising these fractures using polymethylmethacrylate and non-locking plates. We undertook a retrospective review over 20 years of patients treated at a tertiary musculoskeletal oncology centre. Those who had undergone surgery for an impending or completed pathological humeral fracture with a diagnosis of metastatic disease or myeloma were identified from our database. There were 63 patients (43 men, 20 women) in the series with a mean age of 63 years (39 to 87). All had undergone intralesional curettage of the tumour followed by fixation with intramedullary polymethylmethacrylate and plating. Complications occurred in 14 patients (22.2%) and seven (11.1%) required re-operation. At the latest follow-up, 47 patients (74.6%) were deceased and 16 (25.4%) were living with a mean follow-up of 75 months (1 to 184). A total of 54 (86%) patients had no or mild pain and 50 (80%) required no or minimal assistance with activities of daily living. Of the 16 living patients none had pain and all could perform activities of daily living without assistance. Intralesional resection of the tumour, filling of the cavity with cement, and plate stabilisation of the pathological fracture gives immediate rigidity and allows an early return of function without the need for bony union. The patient's local disease burden is reduced, which may alleviate tumour-related pain and slow the progression of the disease. The cemented-plate technique provides a reliable option for the treatment of pathological fractures of the humerus.

Impact of modified acidic soft drinks on enamel erosion.

OBJECTIVE: To evaluate the enamel erosive potential of modified acidic soft drinks under controlled conditions in an artificial mouth. MATERIALS AND METHODS: From each of 144 bovine incisors one enamel sample was prepared. Labial surfaces of the samples were ground flat, polished and covered with adhesive tape, leaving an exposed area. The samples were distributed among four (A-D) groups for treatment with A: Coca-Cola, B: Sprite; C: Sprite light, D: orange juice. Either 1.0 mmol l(-1) calcium (Ca) or a combination (comb.) of 0.5 mmol l(-1) calcium plus 0.5 mmol l(-1) phosphate plus 0.031 mmol l(-1) fluoride was added to the beverages. Samples of each group were subdivided into three subgroups (-original; -Ca and -comb.) for treatment with original and modified drinks. De- and remineralization cycles were based on a standard protocol described earlier. Surface loss of the specimens was determined using profilometry after test procedure. RESULTS: In all subgroups, loss of enamel was observed. The enamel loss recorded for the samples rinsed with original Sprite and original orange juice was significantly higher compared with all other solutions (P = 0.001). Lowest enamel loss was recorded for the original Coca-Cola group (P = 0.001). With the exception of Coca-Cola, demineralization with the modified beverages led to significantly lower losses compared with the respective original solutions. CONCLUSION: Modification of the test soft drinks with low concentrations of calcium or a combination of calcium, phosphate and fluoride may exert a significant protective potential with respect to dental erosion.

Hepatitis C: what a dentist should know.

During the last two decades, the existence of a blood-borne virus responsible for non-A, non-B hepatitis was suspected but not identified. In the United States, an estimated 170,000 cases of post-transfusion hepatitis, many of which became chronic, were attributed to the unknown virus. Recently, however, the virus has been identified and more has been learned about the disease. This review will focus on recent advances regarding the virus and its implications for dental practice.

An identified histaminergic neuron can modulate the outputs of buccal-cerebral interneurons in Aplysia via presynaptic inhibition.

We have identified 2 buccal-cerebral interneurons (BCIs), B17 and B18, that appear to be involved in the coordination of feeding behavior in Aplysia. The BCIs have their cell bodies in the buccal ganglion, but send axons to the cerebral ganglion via the cerebral-buccal connectives. The BCIs appear to make monosynaptic connections with neurons in the cerebral ganglion that modulate extrinsic muscles involved in feeding behavior. B17 and B18 are activated antiphasically during a motor program induced by stimulating the esophageal nerve and appear to "read out" different phases of the buccal program to different cells in the cerebral ganglion. B17 and B18 are not necessary, and probably not sufficient, to generate the buccal program. These BCIs, and other cells like them in the buccal ganglion, may be capable of coordinating the activity of the intrinsic muscles of the buccal mass with the activity of its extrinsic muscles, and perhaps with those of the lips, mouth, and tentacles. Identified histaminergic neuron, C2, can modulate the outputs of the BCIs onto their synaptic followers in the cerebral ganglion. Firing of C2 inhibits spiking of the BCIs, probably via cerebral-buccal interneurons. C2 also decreases the size of the EPSP that B17 and B18 evoke in cerebral neuron C4. C2 appears to do so monosynaptically, and it decreases the conductance of C4, ruling out one possible postsynaptic mechanism of action. Variance analysis of the EPSPs evoked by B18 supports the hypothesis that C2 acts presynaptically to decrease the release of transmitter. Applications of histamine to the solution bathing the neuron mimic the effect of firing C2 and reduce the size of the EPSPs B18 induces in C4. The bath-applied histamine appears to act directly on B18, since it elicits a voltage-dependent increased conductance hyperpolarization recorded in the soma of B18, and the hyperpolarization persists in a solution in which synaptic transmission has been blocked. Histamine did not produce any marked changes of the duration of a TEA-broadened somatic action potential of B18. To the extent that the soma of B18 reflects the membrane properties of its synaptic terminal region, the data suggest that histamine may produce presynaptic inhibition by hyperpolarizing the synaptic terminal region.

Appetitive feeding behavior of Aplysia: behavioral and neural analysis of directed head turning.

The appetitive phase of feeding behavior in Aplysia consists of a behavioral sequence in which the quiescent animal starts to locomote and then assumes a characteristic feeding posture. In this position, head-turning responses can be elicited by a localized food stimulus (seaweed) delivered to the lips or tentacles. In response to brief (open loop) stimulation with seaweed, the animal turns toward the stimulus but greatly overshoots the target. However, the angular velocity and the final turning angle are a function of the eccentricity of the stimulus, progressively increasing with greater eccentricities. In a food-aroused animal, a brief tactile stimulus evokes turning and biting responses similar to those triggered by seaweed, which provides both tactile and chemical stimulation. Upon repeated tactile stimulation, however, the response magnitude decrements rapidly, whereas the magnitude remains high when turning responses are repeatedly elicited by food stimuli. A purely chemical stimulus sometimes can elicit a turning response, but chemical stimuli alone are much less efficacious than tactile stimuli alone. When the stimulus is maintained in a stationary position (closed loop), the animal turns until its mouth is oriented over the food. A turning response to a lateral stimulus can be reduced by an immediately following medial stimulus. To explain the above findings, we propose a form of response substitution, in which the response to the first, lateral stimulus is substituted by a weaker response to a more medial stimulus. No turning response is evoked when the animal is stimulated while performing spontaneous or evoked bites, though biting per se does not interrupt ongoing turning movements. In animals with lesions of the cerebral-buccal connectives, a food stimulus on the mouth is also followed by a reduction of the capacity of stimuli to elicit turning responses. In these lesioned animals, the food stimulus appears to elicit a bite command, though the biting behavior itself does not occur. Thus, it appears that the bite-related gating of stimuli is of cerebral origin, rather than due to the generation of the buccal motor program. The force necessary to power the turning movements was calculated from the trajectories of the movements. The results indicate that a power phase during the first half of the duration of the total movement is sufficient to generate a turn. The power phase can be followed by a brief gliding phase, and finally the movement appears to be actively terminated.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of Dlx genes during the development of the murine dentition.

The mammalian Dlx homeobox gene family has been shown to play multiple roles in tooth development, but a detailed comparison of the expression pattern of all members throughout tooth development has been lacking. We provide such an analysis for the six known murine Dlx genes. The expression patterns for these genes allow a refinement of previously proposed models for the role of Dlx genes in tooth type specification and raise the possibility of roles for subsets of these genes in tooth initiation, morphogenesis (enamel navel formation, enamel knot induction, cervical loop growth), and enamel formation. The relationship of Dlx gene expression to their genomic organization suggests coordinate regulation of linked genes at early stages but regulatory differences at later stages.

Sensory function and gating of histaminergic neuron C2 in Aplysia.

This paper explores the possible sensory function of the identified histaminergic neuron C2. Mechanical stimulation of a narrow region around the mouth of the animal (perioral zone) elicits brief depolarizing potentials in C2. Extracellular recordings from the peripheral axons of C2 indicate that the depolarizing potentials are due to action potentials that are conveyed from the periphery but do not invade the cell body, since they fail at a region with a low safety factor within the cerebral ganglion. These blocked axonal spikes (A-spikes) function as if they were excitatory synaptic inputs to C2, since the synaptic output of C2 does not occur unless the A-spikes succeed in evoking full action potentials in the soma (or an electrically close initial segment) of C2. Furthermore, like synaptic potentials, the A-spikes exhibit temporal and spatial summation, and facilitation. C2 receives both tonic and phasic inhibitory synaptic potentials, which can decrease the summation of A-spikes and thereby alter the frequency-filtering properties of C2 or block its synaptic output. Thus, C2 appears to be an unusual proprioceptive afferent that has a high degree of integrative function and may provide critical gating that is dependent on a variety of external and internal conditions.

Patterning of the mammalian dentition in development and evolution.

The mammalian dentition is a segmented organ system with shape differences among its serially homologous elements (individual teeth). It is believed to have evolved from simpler precursors with greater similarities in shape among teeth, and a wealth of descriptive data exist on changes to the dentition that have occurred within mammals. Recent progress has been made in determining the genetic basis of the processes that form an individual tooth, but patterning of the dentition as a whole (i.e. the number, location and shape of the teeth) is less well understood. In contrast to similarly organized systems, such as the vertebral column and limb, Hox genes are not involved in specifying differences among elements. Nevertheless, recent work on a variety of systems is providing clues to the transcription factors and extracellular signalling molecules involved.

Dlx and other homeobox genes in the morphological development of the dentition.

The dentition is a segmental system whose evolution and morphology bears analogy to the evolution of segmentation in the vertebral column and limb. Combinatorial expression of members of the large "Hox" class of homeobox regulatory genes has been shown to play an important role in positional specification in these skeletal systems. This raises the possibility that homeobox genes are also used for positional specification in the dentition, and several homeobox genes are known to be expressed in developing teeth. To identify additional dentally expressed homeobox genes, cDNA from from murine tooth germs at 9.5, 14.5, and 17.5 days gestational age was amplified by PCR using sets of degenerate primers to the homeodomains of 18 different classes of homeobox genes. Amplification products were cloned and sequenced and compared to known gene sequences. To date this approach has confirmed the presence of Msx1, Msx2, Dlx1, and Dlx2, and identified several other homeobox genes not previously known to be expressed in teeth: Dbx, MHox, and Mox2A, plus an a additional Dlx gene, Dlx7. The Msx and Dlx genes are the best current candidates for a combinatorial mechanism that controls the differentiation of structures within and between teeth, and perhaps also the evolution of those structures.

Dynamic interactions and the evolutionary genetics of dental patterning.

The mammalian dentition is a segmental, or periodically arranged, organ system whose components are arrayed in specific number and in regionally differentiated locations along the linear axes of the jaws. This arrangement evolved from simpler dentitions comprised of many single-cusp teeth of relatively indeterminate number. The different types of mammalian teeth have subsequently evolved as largely independent units. The experimentally documented developmental autonomy of dental primordia shows that the basic dental pattern is established early in embryogenesis. An understanding of how genetic patterning processes may work must be consistent with the different modes of development, and partially independent evolution, of the upper and lower dentition in mammals. The periodic nature of the location, number, and morphological structure of teeth suggests that processes involving the quantitative interaction of diffusible signaling factors may be involved. Several extracellular signaling molecules and their interactions have been identified that may be responsible for locating teeth along the jaws and for the formation of the incisor field. Similarly, the wavelike expression of signaling factors within developing teeth suggests that dynamic interactions among those factors may be responsible for crown patterns. These factors seem to be similar among different tooth types, but the extent to which crown differences can be explained strictly in terms of variation in the parameters of interactions among the same genes, as opposed to tooth-type-specific combinatorial codes of gene expression, is not yet known. There is evidence that combinatorial expression of intracellular transcription factors, including homeobox gene families, may establish domains within the jaws in which different tooth types are able to develop. An evolutionary perspective can be important for our understanding of dental patterning and the designing of appropriate experimental approaches, but dental patterns also raise basic unresolved questions about the nature of the evolutionary assumptions made in developmental genetics.

Distal-less and other homeobox genes in the development of the dentition.

The mammalian tooth develops through an interaction between two tissue layers of different embryologic origin. A number of transcription factors and as well as two members of the Msx class of homeobox genes have been shown to be involved in the histogenesis of the mammalian tooth. This raised the possibility that other homeobox genes might be involved in dental morphogenesis. We have amplified mouse tooth germ cDNA from three different gestational ages by the polymerase chain reaction with degenerate primers for 18 classes of homeobox genes. Members of several classes have been isolated, including the Msx genes, two Dlx genes, and the Dbx, MHox, Mox2A genes. One of the Dlx genes, Dlx-7, had not previously been reported in mammals, and some details are presented of its cDNA sequence. This work plus that of other investigators has shown that at least six Dlx genes are expressed in developing teeth or in first branchial arches, suggesting the possibility that these genes are involved in specifying complexity within or between teeth. The screening approach with degenerate primers is a successful way to identify new as well as previously known regulatory genes expressed in developing tooth embryos.

Perspectives on genetic aspects of dental patterning.

Nearly a century of speculation and experimentation has gone into trying to understand the mechanisms that establish the pattern of the differentiated heterodont dentition. Regionally differing qualitative (combinatorial) expression of regulatory genes appears to be involved in this process. Work by our laboratory and others shows that the six members of the mammalian Dlx family of homeobox genes are expressed (a) at multiple times during dental development, (b) differently at different stages, (c) in a way that is related to their genomic organization as gene-pairs linked to three of the four Hox clusters of positional patterning genes. The expression appears to be involved in jaw regionalization, tooth initiation, and tooth development. However, this expression correlates with no single aspect of dental patterning or tooth development, involves redundant and complementary function, and developmental differences between the maxillary and mandibular dentition suggest that other elements remain to be identified. For example, the possibility that quantitative aspects of gene expression specify developmental fields in the dentition has not yet been investigated. Although the maxilla and mandible develop differently, indirect evidence suggests that, especially in the future midline (incisor) regions, both jaws may be patterned by a consistent process that occurs before neural crest migration takes place, and we hypothesize that signaling factors like Sonic hedgehog and Pax transcription factors may be involved.

Numerous members of the Sox family of HMG box-containing genes are expressed in developing mouse teeth.

We used RT-PCR to detect the expression in mouse molar and incisor tooth germs of 14 of the 19 known members of the Sox family of HMG box-containing transcription factors. These sequences fell into all 6 of the main subdivisions of the Sox family. In general, the relative transcript abundance of the different Sox genes is similar between molar and incisor tooth germs, although 3 low-abundance transcripts were found in only a single tooth type. The expression of Sox genes during tooth development has not been reported previously and further experiments will be required to determine their role in this process.