Displacement of the contents of dentinal tubules and sensory transduction in intradental nerves of the cat

Experiments were performed on anaesthetized cats to test the hypothesis that fluid flow through dentinal tubules is part of the mechanism involved in the transduction of pain-producing stimuli in teeth. In 11 animals, fluid flow through dentine and single- and multi-unit activity in intradental nerves were recorded simultaneously during the application of changes in hydrostatic pressure (-500 to +500 mm Hg) to exposed dentine. Seventeen A-fibres (conduction velocity (CV), 10.6-55.1 m s(-1)) were isolated that were pressure sensitive. The thresholds of these units in terms of dentinal fluid flow were in the range 0.3-2.1 nl s(-1) mm(-2) during outward flow from the pulp and 2.0-3.5 nl s(-1) mm(-2) during inward flow. All the units were more sensitive to outward than inward flow. Twenty-eight units (CV, 0.6-48.8 m s-1) were not pressure sensitive, and 12 of these had conduction velocities in the C-fibre range (< 2.5 m s(-1)). The velocities of the tubular contents were calculated by estimating the number and diameters of dentinal tubules exposed. At the threshold of single-fibre responses these velocities were in the range 31.7-222.9 microm s(-1) during outward flow 211.4-369.6 microm s-1 during inward flow. Repetitive pressure stimulation of dentine resulted in a progressive reduction in the evoked discharge, which was probably due to pulp damage. In seven animals, 10 single intradental nerve fibres were selected that responded to hydrostatic pressure stimuli and their responses to the application of hot, cold, osmotic, mechanical and drying stimuli to exposed dentine were investigated. With these stimuli dentinal fluid flow could not be recorded in vivo for technical reasons and was therefore recorded in vitro after completion of the electrophysiological recordings. With each form of stimulus, the discharge evoked in vivo was closely related to the flow predicted from the in vitro measurements. The results were therefore consistent with the hypothesis that the stimuli act through a common transduction mechanism that involves fluid flow through dentine.

The permeability of the dentine and other tissues that are exposed at the tip of a rat incisor

The tissues that form the incisal surface of a rat incisor include dentine, an atubular calcified tissue which lines the last-formed dentine, and calcified pulp remnants. The permeability of these tissues was investigated in vitro and in vivo using Evans blue dye. The incisal surface was prepared by etching it with acid or removing 1 mm by fracturing or with a diamond disc followed by etching. In some cases, 1.5-3.0 mm was removed to expose the soft tissue of the pulp. The dye was applied for 30 min, then longitudinal sections of the crown were cut and examined microscopically to determine the extent to which the dye had diffused into the underlying tissues. In only those teeth in which the dye had been applied direct to the pulpal soft tissue could any be detected below the exposed tooth surface. In previous experiments, it was found that both cat and human dentines were freely permeable to Evans blue when they were tested in vitro. It is concluded that the dentine and other tissues that form the incisal surface of a rat incisor are less permeable than cat or human dentine.

Polyanionic (i.e., polysulfonate) dendrimers can inhibit the replication of human immunodeficiency virus by interfering with both virus adsorption and later steps (reverse transcriptase/integrase) in the virus replicative cycle

Polyanionic dendrimers were synthesized and evaluated for their antiviral effects. Phenyldicarboxylic acid (BRI6195) and naphthyldisulfonic acid (BRI2923) dendrimers were found to inhibit the replication of human immunodeficiency virus type 1 (HIV-1; strain III(B)) in MT-4 cells at a EC(50) of 0.1 and 0.3 microg/ml, respectively. The dendrimers were not toxic to MT-4 cells up to the highest concentrations tested (250 microg/ml). These compounds were also effective against various other HIV-1 strains, including clinical isolates, HIV-2 strains, simian immunodeficiency virus (SIV, strain MAC(251)), and HIV-1 strains that were resistant to reverse transcriptase inhibitors. HIV strains containing mutations in the envelope glycoprotein gp120 (engendering resistance to known adsorption inhibitors) displayed reduced sensitivity to the dendrimers. The compounds inhibited the binding of wild-type virus and recombinant virus (containing wild-type gp120) to MT-4 cells at concentrations comparable to those that inhibited the replication of HIV-1(III(B)) in these cells. Cellular uptake studies indicated that BRI2923, but not BRI6195, permeates into MT-4 and CEM cells. Accordingly, the naphtyldisulfonic acid dendrimer (BRI2923) proved able to inhibit later steps of the replication cycle of HIV, i.e., reverse transcriptase and integrase. NL4.3 strains resistant to BRI2923 were selected after passage of the virus in the presence of increasing concentrations of BRI2923. The virus mutants showed 15-fold reduced sensitivity to BRI2923 and cross-resistance to known adsorption inhibitors. However, these virus mutants were not cross-resistant to reverse transcriptase inhibitors or protease inhibitors. We identified several mutations in the envelope glycoprotein gp120 gene (i.e., V2, V3, and C3, V4, and C4 regions) of the BRI2923-resistant NL4.3 strains that were not present in the wild-type NL4.3 strain, whereas no mutations were found in the reverse transcriptase or integrase genes.

The permeability of human dentine in vitro and in vivo

Experiments in cats have shown that Evans blue dye diffuses at a greater rate into dentine in recently extracted teeth than in vivo. These experiments have now been repeated in man and similar results were obtained except that, after applications in vivo, visible concentrations of the dye were present in the dentine, and in a few cases, even in the pulp. It is concluded that, as in the cat, the diffusion in vivo was impaired by outward flow of fluid in the dentinal tubules but the mean velocity of flow in the human dentine was less than that in the cat.

Dendrimers, a new class of candidate topical microbicides with activity against herpes simplex virus infection

Dendrimers are large highly branched macromolecules synthesized from a polyfunctional core. They have shown a variety of biological properties, including, in some instances, antiviral activity. In this study, five dendrimers were evaluated for in vitro activity against herpes simplex virus (HSV) types 1 and 2 by cytopathic effect (CPE) inhibition and plaque reduction (PR) assay in human foreskin fibroblast cells. All of the compounds were active against both virus types in the CPE inhibition assay, in which drug was added to the cells prior to the addition of virus. Antiviral activity was reduced or lost in the PR assays, in which the cells were incubated with the virus before the drug was added. The prophylactic efficacy suggested that the dendrimers might have potential as topical microbicides, products intended to be applied to the vaginal or rectal mucosa to protect against sexually transmitted infections. Three dendrimers were evaluated for this application against genital HSV infection in mice. Two of the compounds, BRI-2999 and BRI-6741, significantly reduced infection rates when 15 microl of a 100-mg/ml solution was administered immediately prior to intravaginal challenge, and the most effective compound, BRI-2999, provided significant protection even when applied 30 min before challenge. This is the first report of microbicidal activity by dendrimers in vivo.

Can 16-18-year-old elite ballet dancers improve their hip and ankle range of motion over a 12-month period?

OBJECTIVE

To determine the effect of a 12-month intensive ballet training regimen on hip and ankle range of motion in male and female, first- and second-year professional dancers.

DESIGN

12-month longitudinal follow-up.

SETTING

National classical ballet school in Australia.

PARTICIPANTS

28 female and 20 male full-time ballet students with a mean +/- 1 SD, ages 16.8 +/- 0.8 and 17.7 +/- 1.2 years, respectively.

MAIN OUTCOME MEASURES

Degrees of range of motion of left and right sides for the following movements: standing plié in parallel-passive ankle dorsiflexion (DF); standing turnout in the balletic first position--lower leg external rotation (LLER); supine hip external rotation (ER); supine hip internal rotation (IR). An additional range of motion was calculated: external rotation below the hip joint (BHER) derived by subtracting hip ER from LLER.

MAIN RESULTS

In all subjects combined, hip and ankle ranges increased statistically on the right. However, the amount was generally minimal and most at the borderline of the amount of error associated with the measurement tool. While there was no change in LLER, there was a decrease in BHER. There were no overall gender differences, and year differences existed only for left hip ER and total hip ER with first-year dancers showing significant improvements in these ranges. For DF and sum of hip IR, first-year males and second-year females had increases in range. There was a negative relationship between baseline range and the amount of change over the 12 months.

CONCLUSIONS

Dancers ages 16-18 years who enter full-time ballet training did not augment their ankle dorsiflexion to any appreciable degree. Some, but certainly not all, increased their hip active external rotation over 12 months without increasing their total lower limb turnout. Hip ER was more likely to improve in the first-year rather than second-year student in this elite full-time training school.

Pseudomembranous enteritis after proctocolectomy: report of a case

Intestinal pseudomembrane formation, sometimes a manifestation of antibiotic-associated diarrheal illnesses, is typically limited to the colon but rarely may affect the small bowel. A 56-year-old female taking antibiotics, who had undergone proctocolectomy for idiopathic inflammatory bowel disease, presented with septic shock and hypotension. A partial small-bowel resection revealed extensive mucosal pseudomembranes, which were cultured positive for Clostridium difficile. Intestinal drainage contents from an ileostomy were enzyme immunoassay positive for C. difficile toxin A. Gross and histopathologic features of the small-bowel resection specimen were similar to those characteristic of pseudomembranous colitis. The patient was treated successfully with metronidazole. These findings suggest a reservoir for C. difficile also exists in the small intestine and that conditions for enhanced mucosal susceptibility to C. difficile overgrowth may occur in the small-bowel environment of antibiotic-treated patients after colectomy. Pseudomembranous enteritis should be a consideration in those patients who present with purulent ostomy drainage, abdominal pain, fever, leukocytosis, or symptoms of septic shock.

Laparoscopic Nissen fundoplication: a technique for the easy and precise manufacture of a true fundoplication

Passing the stomach behind the esophagus during laparoscopic Nissen fundoplication is a common source of frustration for the laparoscopic surgeon. It often leads to an incorrect formation of the fundoplication, resulting in a wrapping or twisting of the fundus around the distal esophagus. The correct technique should result in the distal esophagus being enveloped inside the fundus without distorting the orientation of the greater curve. We have developed an easy, precise, and reproducible technique to perform this maneuver. The steps for performance of this maneuver are described.

Hernia at 5-mm laparoscopic port site presenting as early postoperative small bowel obstruction

A decade has passed since laparoscopy became a popular tool in general surgery. New technologies continue to surface, and surgeons are still trying to expand the applications of this technique. Parallel to the development of new techniques, we are also measuring the presentation of new complications. Incisional hernias are not new complications. Although their avoidance has been one of the proposed benefits of laparoscopy, several cases of port-site hernias have been reported. Current surgical wisdom suggests closure of 10-mm or larger port sites to avoid herniation. Most surgeons do not routinely close 5-mm port sites, believing that such fascial defects are not large enough to create a significant risk of hernia formation, thus not justifying the extra time and effort needed to close them. Although this practice may be reasonable for most cases, it should be reconsidered in lengthy procedures, particularly if the port has been used for active operative instruments. Under these circumstances, the repetitive motions in different directions may cause the 5-mm defect to enlarge significantly, allowing a hernia of considerable size to develop, with the obvious clinical implications of such a complication. We present a case of a hernia through a 5-mm port site presenting as small-bowel obstruction in the early postoperative period after a laparoscopic paraesophageal hernia repair.

Outpatient endoscopic thoracic sympathectomy using 2-mm instruments

BACKGROUND

For a long time it has been known that sympathectomy is an effective treatment for hyperhidrosis and other conditions. The surgical options available until recently usually have required thoracotomy or large posterior incisions, and physicians generally have been reluctant to recommend surgery for most patients with "benign" disorders. Recently, thoracoscopic techniques have allowed surgeons to offer these patients a permanent solution with minimal surgical trauma.

METHODS

In 20 patients, 30 endoscopic thoracic sympathectomies (ETS) were performed for several indications. Nine patients had bilateral sympathectomies. The procedures were performed on the day of admission, with the patient under general anesthesia using double lumen endotracheal intubation and hand temperature monitoring. Each lung was reinflated on completion of the sympathectomy, and residual pneumothorax aspirated before closure of the incisions. No placement of chest tubes was performed in the operating room.

RESULTS

All sympathectomies were completed thoracoscopically. There were no major complications, and 90% of the patients were discharged within 24 hours of admission. The average operative time was 69 min.

CONCLUSIONS

Findings from this study show that ETS is a safe and effective procedure that can be performed routinely on an outpatient basis. The use of miniendoscopic (2-mm) instrumentation is safe and effective in most patients and a helpful adjunct in providing these patients with minimally traumatic surgery. Long-term results should be evaluated on the basis of specific indications for sympathectomy.

Role of the actin cytoskeleton in insulin action

Insulin has diverse effects on cells, including stimulation of glucose transport, gene expression, and alterations of cell morphology. The hormone mediates these effects by activation of signaling pathways which utilize, 1) adaptor molecules such as the insulin receptor substrates (IRS), the Src and collagen homologs (Shc), and the growth factor receptor binding protein 2 (Grb2); 2) lipid kinases such as phosphatidylinositol 3-kinase (PI 3-Kinase); 3) small G proteins; and 4) serine, threonine, and tyrosine kinases. The activation of such signaling molecules by insulin is now well established, but we do not yet fully understand the mechanisms integrating these seemingly diverse pathways. Here, we discuss the involvement of the actin cytoskeleton in the propagation and regulation of insulin signals. In muscle cells in culture, insulin induces a rapid actin filament reorganization that coincides with plasma membrane ruffling and intense accumulation of pinocytotic vesicles. Initiation of these effects of insulin requires an intact actin cytoskeleton and activation of PI 3-kinase. We observed recruitment PI 3-kinase subunits and glucose transporter proteins to regions of reorganized actin. In both muscle and adipose cells, actin disassembly inhibited early insulin-induced events such as recruitment of glucose transporters to the cell surface and enhanced glucose transport. Additionally, actin disassembly inhibited more prolonged effects of insulin, including DNA synthesis and expression of immediate early genes such as c-fos. Intact actin filaments appear to be essential for mediation of early events such as association of Shc with Grb2 in response to insulin, which leads to stimulation of gene expression. Preliminary observations support a role for focal adhesion signaling complexes in insulin action. These observations suggest that the actin cytoskeleton facilitates propagation of the morphological, metabolic, and nuclear effects of insulin by regulating proper subcellular distribution of signaling molecules that participate in the insulin signaling pathway.

Hip and ankle range of motion and hip muscle strength in young female ballet dancers and controls

OBJECTIVES

To compare the hip and ankle range of motion and hip muscle strength in 8-11 year old novice female ballet dancers and controls.

METHODS

Subjects were 77 dancers and 49 controls (mean (SD) age 9.6 (0.8) and 9.6 (0.7) years respectively). Supine right active hip external rotation (ER) and internal rotation (IR) were measured using an inclinometer. A turnout protractor was used to assess standing active turnout range. The measure of ER achieved from below the hip during turnout (non-hip ER) was calculated by subtracting hip ER range from turnout range, and hip ER:IR was derived by dividing ER range by IR range. Range of right weight bearing ankle dorsiflexion was measured in a standing lunge using two methods: the distance from the foot to the wall (in centimetres) and the angle of the shank to the vertical via an inclinometer (in degrees). Right calf muscle range was measured in weight bearing using an inclinometer. A manual muscle tester was used to assess right isometric hip flexor, internal rotator, external rotator, abductor, and adductor strength.

RESULTS

Dancers had less ER (p<0.05) and IR (p<0.01) range than controls but greater ER:IR (p<0.01). Although there was no difference in turnout between groups, the dancers had greater non-hip ER. Dancers had greater range of ankle dorsiflexion than controls, measured in both centimetres (p<0.01) and degrees (p<0.05), but similar calf muscle range. After controlling for body weight, controls had stronger hip muscles than dancers except for hip abductor strength which was similar. Regression analyses disclosed a moderate relation between turnout and hip ER (r = 0.40). There were no significant correlations between range of motion and training years and weekly training hours.

CONCLUSIONS

Longitudinal follow up will assist in determining whether or not hip and ankle range in young dancers is genetically fixed and unable to be improved with further balletic training.

Establishment and evaluation of a preschool asthma programme: a pilot study

In New Zealand asthma has been recognised as a major health issue for preschool children and their families (Public Health Commission, 1995). While nurses have been involved with Asthma Self management programmes which have improved the outcomes for older children and adults (Garret, Kolbe, Richards, Whitlock & Rea, 1995: Mitchell, Ferguson & Norwood, 1986) self management programmes have rarely been used for preschool children. The aims of the study were to establish a Preschool Asthma Programme and evaluate whether it would enable parents and their children to increase their knowledge, confidence and skills in asthma management, while improving asthma control. Fifteen families with children aged between three and a half and five years with moderate and severe asthma participated; five families in each of the three programmes offered. The programmes were evaluated using both formative and outcome evaluation. Results indicated that the programme increased knowledge and changes in asthma management by parents and children and increased the confidence of parents in both their own ability, and that of their child, to manage asthma. Seven parents and seven children on the programme achieved positive change in all the self management criteria considered and six parents and two children made changes in most of them. Participation in the programme was associated with improved lung function, asthma control and preschool attendance. The programme was more successful if the child was over four years old and had suboptimal asthma control. It is concluded that, contrary to what has previously been thought, preschool children can be taught self management skills. There is evidence that a Preschool Asthma Programme is a useful addition to the conventional management and can result in improvements in asthma management.

Distribution of P2X3 receptors in the rat trigeminal ganglion after inferior alveolar nerve injury

The ATP-gated cation channel receptor P2X3 is associated with nociceptive primary sensory neurons. We have, using immunohistochemistry, examined the expression of P2X3 in rat trigeminal ganglia 4-22 days after ligation/section or chronic constriction of the mandibular inferior alveolar nerve. In the normal trigeminal ganglion the anti-P2X3 receptor antibody labeled 37-58% of all neurons. Double labeling demonstrated that about 70-95% of the small neurons that bind the isolectin I-B4 displayed P2X3-immunoreactivity, and that about 40% of larger RT97-positive nerve cells were P2X3 receptor-immunoreactive. At 4 and 10 days after inferior alveolar nerve injury, the proportion of P2X3-immunoreactive neurons had increased to about 65% (range 52-78%). Examinations at the injury sites showed an intense P2X3 receptor-immunoreactivity in nerve endings. At longer survival stages the proportion of P2X3 receptor-positive sensory neurons had returned to control values. These results show that the P2X3 receptor is transiently upregulated and anterogradely transported in trigeminal primary sensory neurons after nerve injury. Since the receptor is accumulated in injured nerve endings, it may be associated with abnormal impulse propagation from these sites.

A system for tracking dental readiness in the Air Force Reserve

The potential of dental emergencies to reduce combat effectiveness is a major concern of military planners. The dental fitness classification is teh primary measure of an airman's dental readiness. A dental class 3 identification means that the airman has a dental condition that is likely to cause a dental emergency within 12 months. With few exceptions, Air Force Reserve command units are using only nonstandardized, manual tracking systems to ensure that identified members get needed dental treatment completed in a timely manner. The reliability and effectiveness of this process has been questioned in recent years. The importance of accurately recording the dental class status and having a reliable means to track dental treatment compliance of members designated dental class 3 is essential to maintaining a high state of dental readiness. A computerized tracking system called the Reserve Dental Data System was designed and developed to address this problem.

Expression of an Aspartate Kinase Homoserine Dehydrogenase Gene Is Subject to Specific Spatial and Temporal Regulation in Vegetative Tissues, Flowers, and Developing Seeds

Although the regulation of amino acid synthesis has been studied extensively at the biochemical level, it is still not known how genes encoding amino acid biosynthesis enzymes are regulated during plant development. In the present report, we have used the [beta]-glucuronidase (GUS) reporter gene to study the regulation of expression of an Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase (AK/HSD) gene in transgenic tobacco plants. The polypeptide encoded by the AK/HSD gene comprises two linked key enzymes in the biosynthesis of aspartate-family amino acids. AK/HSD-GUS gene expression was highly stimulated in apical and lateral meristems, lateral buds, young leaves, trichomes, vascular and cortical tissues of growing stems, tapetum and other tissues of anthers, pollen grains, various parts of the developing gynoecium, developing seeds, and, in some transgenic plants, also in stem and leaf epidermal trichomes. AK/HSD-GUS gene expression gradually dimished upon maturation of leaves, stems, floral tissues, and embryos. GUS expression was relatively low in roots. During seed development, expression of the AK/HSD gene in the embryo was coordinated with the initiation and onset of storage protein synthesis, whereas in the endosperm it was coordinated with the onset of seed desiccation. Upon germination, AK/HSD-GUS gene expression in the hypocotyl and the cotyledons was significantly affected by light. The expression pattern of the A. thaliana AK/HSD-GUS reporter gene positively correlated with the levels of aspartate-family amino acids and was also very similar to the expression pattern of the endogenous tobacco AK/HSD mRNA as determined by in situ hybridization.

FlyBase: a Drosophila database. The FlyBase consortium

FlyBase is a database of genetic and molecular data concerning Drosophila. FlyBase is maintained as a relational database (in Sybase) and is made available as html documents and flat files. The scope of FlyBase includes: genes, alleles (and phenotypes), aberrations, transposons, pointers to sequence data, clones, stock lists, Drosophila workers and bibliographic references. The Encyclopedia of Drosophila is a joint effort between FlyBase and the Berkeley Drosophila Genome Project which integrates FlyBase data with those from the BDGP.

Experiments in pigs on the sources of laser Doppler blood-flow signals recorded from teeth

A laser Doppler blood-flow meter (Moor Type MBF3D) was used to record from the crowns of eight deciduous mandibular incisors in three anaesthetized pigs. The flow-meter probe was attached to the crown either 2 or 6 mm from the gingival margin. Recordings were made from each tooth with the supporting tissues intact, after exposing the root pulp, after cutting the pulp, and after death of the animal. At each stage the effect of wrapping the crown in aluminium foil was determined. There was no significant change in the signals when the root pulp was exposed (p > 0.05, paired t-test). Without foil, cutting the pulp reduced the signal recorded 2 mm from the gingival margin by an average of 85.1 percent (n = 8, p < 0.001) and at 6 mm by 87.9 percent (n = 4, p < 0.001). There were further significant reductions (p < 0.01) equivalent to 12.9 percent and 9.0 percent, respectively, of the control values when the animal was killed. The foil increased the average blood-flow signals recorded from intact teeth at both 2 and 6 mm from the gingival margin by 77.8 percent and 98.3 percent (p < 0.05), respectively. It also had a similar effect after pulp exposure. With foil, cutting the pulp reduced the signal by 86.2 percent and 92.8 percent at the two sites, respectively, and post mortem there was a further reduction of 12.4 percent and 6.1 percent. Thus, under all conditions the major part of the signal recorded from an intact tooth was from the pulp but a significant component (an average of between 14.9 percent and 7.2 percent depending on the conditions) was from tissues outside the tooth. The best performance was obtained with foil and with the probe 6 mm from the gingival margin.

Microvascular architecture and exchange in teeth

Dental pulp is a low-compliance tissue surrounded by an avascular hard tissue case. Resin casts of the microvasculature in teeth of limited growth show arterioles and venules arranged axially in the pulp with capillary loops extending out toward the dentine. The capillary density is high. There is ultrastructural evidence for lymphatics in pulp. Pulpal blood flow has been estimated in intact teeth using radiolabeled microspheres and found to be in the range 20-60 ml/min per 100 g tissue. One of the difficulties of studying this tissue is that a cavity has to be cut into the tooth with the inherent risks that this may affect the parameters under study. Measurements from exposed pulp indicate that the tissue fluid pressure is high and pulsatile. Furthermore, micropuncture studies have shown that the arteriolar pressure is lower and the venular pressure higher than in other tissues. When dentine is exposed in vivo, fluid moves out through the dentinal tubules and this appears to be formed by a process of ultrafiltration from the pulpal interstitial fluid. The flow is sufficient to retard significantly the diffusion of chemicals into dentine from the oral cavity.

Interactions between neural and hydrodynamic mechanisms in dentine and pulp

Evidence is presented that the rate of inward diffusion of chemicals through exposed dentine is affected by the rate of outward flow of fluid through the dentinal tubules. Such a flow has been demonstrated in cats. The flow rate appears to depend upon the pulpal tissue-fluid pressure; flow increased during pulp vasodilatation and decreased, even reversing in direction, during vasoconstriction. Pulp vasodilatation can be produced by stimulating intradental afferent nerves, including some of those that seem to be excited by displacement of tubule contents (i.e. by a hydrodynamic mechanism). Thus, when dentine is exposed and these afferents are stimulated they will help to protect the pulp by producing reflex vasodilatation, which will decrease the rate of diffusion of toxins from the mouth into the pulp. The relation between the rate of flow through dentine and the discharge evoked in intradental nerves was investigated in cats. Single fibres were more sensitive to outward than to inward flow. The flow rates required to excite the pulp afferents were greater than those observed during even maximal pulpal vasodilatation.

Experiments on extracted teeth into the validity of using laser Doppler techniques for recording pulpal blood flow

The performances of two laser Doppler flow meters (Periflux model PF3 and Moor Blood Flow Monitor model MBF3D) were investigated. Recordings were made while diluted blood was pumped at different rates through the pulp cavities of extracted human or pig teeth. The probe of each instrument was fixed to the enamel surface 2 mm from the original position of the gingival margin. Both instruments performed similarly, although the Moor gave the better signal/noise ratios. Both were capable of detecting flow in the core of the pulp as well as the superficial part closest to the probe tip. With either instrument, and with any one dilution of blood (range 0.5-45% v/v red cells), there was a near-linear relationship between the blood-flow signal and the flow rate of blood through the tooth. However, when data obtained with different red-cell concentrations were compared, a good correlation between the blood-flow signal and red-cell flux (product of concentration and mean velocity) was obtained only with red-cell concentrations up to 1% v/v. Therefore these instruments would give an accurate indication of blood flow changes only under conditions in which either this value was not exceeded or if the red-cell volume fraction remained constant; neither of which can be assumed to apply when recording from teeth in situ. The signals representing the concentration of moving blood cells were unreliable in both instruments. It is concluded that the information provided by these laser Doppler flow meters can be ambiguous and must be interpreted with care.

Compartment syndrome and shin splints of the lower leg

OBJECTIVES

The objective of this article is to review and categorize the current knowledge on compartment syndromes (CS) and shin splints (SS), with specific importance relegated to the diagnosis, differential diagnosis and management of these conditions.

DATA SOURCES

The bibliographic data sources reviewed are limited to the English language and human content and are from medical and scientific journals, as well as chiropractic and medical texts. A mini-Medline version of Index Medicus was utilized. Terms for indexing included compartment syndromes, shin splints and stress fractures. The bibliographies of the journals selected were then evaluated and, where appropriate, the specific journal or text references regarding diagnosis and management were then reviewed. This information was then included in this article, where useful, to further clarify or reference statements made.

CONCLUSION

Differential diagnosis of the acute CS from chronic CS and SS requires clinical methods and imaging procedures. The pathogenesis of the acute CS of the lower leg is associated with external pressure or internal hemorrhage. If the tissue pressure were to rise above 30-40 mm Hg for 4-12 h, irreversible muscular damage would result. Emergency surgical intervention is the only appropriate form of treatment in acute CS. In chronic CS, where elevated pressures exist on a transient basis, influenced by activity, conservative management procedures are felt to be effective. However, if these methods are not helpful, surgical intervention may be necessary. The etiology of pain associated with SS is not associated with compartmental pressure elevations, but rather, results from periostitis occurring along the tibia caused by muscular and tendinous strain associated with inflammation. Conservative management is most appropriate for this disorder, with surgical intervention being an uncommon treatment approach. Although clinical findings are useful in the diagnosis of these disorders, fluid pressure findings may be necessary to fully differentiate acute CS from other disorders. Up until recently, common methods of obtaining pressure measurements of compartments included the use of a needle manometer. More recently, however, a hand-held miniature fluid pressure monitor has been developed that produces reproducible measurements of interstitial fluid, making testing potentially practical for the clinician.

Some aspects of the use of laser Doppler flow meters for recording tissue blood flow

Laser Doppler flow meters are used to provide continuous records of blood flow in tissues. An account is given of their principles of operation and of the differences between two of the commercially available instruments: the Periflux model PF3 and the Moor blood flow monitor model MBF3D. The Periflux tended to have higher noise levels and to drift more than the Moor. The principal disadvantage of these instruments is that they cannot be calibrated in absolute units of blood flow. It is suggested that the method of standardization adopted for the Periflux be used with other machines, based on the signal produced by the Brownian motion of a 0.5% suspension of 0.48 micron diameter polystyrene microspheres at 20 degrees C. The signal representing zero flow in a tissue can be obtained by recording with the same light intensity from a stationary reflector. In model systems the instruments are linear with red cell volume fractions up to only 1%, which is below that likely to be encountered in many tissues. The effects of ambient light and the origin of movement artifacts are also considered.

Responses of trigeminal brain stem neurons and the digastric muscle to tooth-pulp stimulation in awake cats

1. Cats were prepared for chronic recording from neurons in pars oralis and pars interpolaris of the trigeminal spinal nucleus. Electrodes were implanted into canine teeth for electrical stimulation and the digastric muscle for recording electromyograms. 2. Recordings were made from the animals when they were awake and unrestrained as well as when they were lightly anesthetized. Some neurons were studied under both conditions. 3. In an awake animal, single tooth-pulp stimuli of 0.1 ms duration and < or = 1 mA intensity produced no aversive behavior. 4. The response of trigeminal brain stem neurons in the awake animal to such stimuli consisted of short (approximately 3 ms)- and long (approximately 25 ms)-latency discharges whose thresholds suggested that they were both due to inputs from fast conducting primary afferent fibers. 5. Light anesthesia reduced the number of impulses in both components and in most cases completely abolished the long-latency component evoked by low-intensity stimuli. The threshold of the short-latency component was little affected by light anesthesia. It is postulated that the short-latency component is mediated by a monosynaptic input from primary afferent fibers and the long-latency component by a polysynaptic input from these same fibers. 6. All neurons that responded to tooth-pulp stimulation had inputs from other orofacial sites both in the awake and lightly anesthetized states. After light anesthesia, these receptive fields were altered in only 3 out of 15 neurons. 7. The majority of neurons (18 out of 20) were not spontaneously active in the awake animal. Spontaneous activity in the other two was reduced by light anesthesia. 8. The threshold of the digastric reflex evoked by tooth-pulp stimulation was not altered by light anesthesia, but the size of the response was reduced. 9. The effects of changing the level of anesthesia from deep to light (i.e., without and with reflex withdrawal to squeezing a paw) on the responses to tooth-pulp stimulation were also studied. Decreasing the anesthetic depth tended to decrease the thresholds and increase the magnitude of both the short- and long-latency neuronal responses and the short-latency digastric response.

A technique for recording the activity of brain-stem neurones in awake, unrestrained cats using microwires and an implantable micromanipulator

A new technique is described which is suitable for long-term recording of the activity of neurones in the brain of an awake, unrestrained cat. By using telescopic electrodes, neurones up to 39 mm from the cranial surface can be reached with a miniature micromanipulator which is small enough to be left in place between recording sessions. The most stable recordings have been obtained with electrodes made from microwire, with which units have been held for up to 8 h.

The vascularity of dental pulp in cats

The fraction of the volume of the coronal pulp of cat canines that is occupied by blood vessels was estimated by measurement of the cross-sectional areas of all the vessels in a complete transverse section of the pulp from each of four teeth. The sections were taken 0.5 mm from the pulp cornu. Overall, 14.4% of the area of the pulp was occupied by vessels. In the core of the pulp, the average value was 42.9%, and superficially, near the odontoblast layer, it was between 5 and 10%. The average capillary density was 1402/mm2, which is higher than in most other tissues. Laser Doppler flow meters can be used for recording blood flow from the coronal pulp of intact teeth, but these instruments are linear only if the moving blood cells occupy no more than 1% of the tissue volume. The present results suggest that this figure is exceeded in pulp.

Modulation by peripheral conditioning stimuli of the responses of trigeminal brain stem neurones and of the jaw opening reflex to tooth pulp stimulation in chronically prepared, anaesthetized cats

The effects of peripheral conditioning stimuli on the thresholds of the jaw opening reflex (JOR) and of trigeminal brain stem neurones to tooth pulp stimulation were examined in chronically prepared, anaesthetized cats. High intensity electrical conditioning stimuli applied to the ipsilateral forepaw produced an increase in the thresholds of both responses, with the JOR thresholds being elevated significantly more, and remaining elevated for significantly longer, than those of the neurones. These findings suggest that the elevation of the JOR cannot be explained just by inhibitory effects on the brain stem neurones.

Fluid flow through cat dentine in vivo

An outward flow of fluid through exposed dentine was demonstrated in anaesthetized cats. The flow was measured by observing the movement of the fat droplets of dilute milk in a glass capillary (i.d. 30 microns) with a microscope. The capillary was sealed to the dentine with a plastic cap. The resting flow rate through dentine exposed by fracturing off the tip of a cat's canine ranged from 2.8 to 50.9 pl.s-1.mm-2 (mean 18.1, SD 15.9, n = 12). Raising the pressure at the dentine surface to about 15 cmH2O stopped the flow. Immediately after cutting the pulp at the root apex, in 11 of 12 preparations, the flow reversed. The average flow rate was then 3.8 pl.s-1.mm-2 inward (range 8.4 outward to 15.9 inward, SD 5.4, n = 12). The inward flow after pulp section suggests that an osmotic effect may contribute to the net pressure causing flow. The average hydraulic conductance of the exposed dentine was 1.6 x 10(-8) m.s-1.kPa-1 (range 0.5-2.9, SD 0.8) before pulp section. After pulp section, it increased to an average of 2.5 x 10(-8) m.s-1.kPa-1 (range 0.8-5.2, SD 1.3).

Drosophila single-minded gene and the molecular genetics of CNS midline development

Our goal is to understand the molecular mechanisms that govern the formation of the central nervous system. In particular, we have focused on the development of a small group of neurons and glia that lie along the midline of the Drosophila CNS. These midline cells possess a number of unique attributes which make them particularly amenable to molecular, cellular, and genetic examinations of nervous system formation and function. In addition, the midline cells exhibit distinctive ontogeny, morphology, anatomical position, and patterns of gene expression which suggest that they may provide unique functions to the developing CNS. The single-minded gene encodes a nuclear protein which is specifically expressed in the midline cells and has been shown to play a crucial role in midline cell development and CNS formation. Genetic experiments reveal that sim is required for the expression of many CNS midline genes which are thought to be involved in the proper differentiation of these cells. In order to identify additional genes which are expressed in some or all of the midline cells at different developmental stages, a technique known as enhancer trap screening was employed. This screen led to the identification of a large number of potential genes which exhibit various midline expression patterns and may be involved in discrete aspects of midline cell development. Further molecular, genetic, and biochemical analyses of sim and several of the enhancer trap lines are being pursued. This should permit elucidation of the genetic hierarchy which acts in the specification, differentiation, and function of these CNS midline cells.

Methods for recording the jaw-opening reflex to tooth-pulp stimulation in awake cats

Techniques are described for use in awake, unrestrained cats which enable recordings to be made from the digastric muscle, electrical stimuli to be applied to the teeth, and intravenous injections to be made via an indwelling cannula. A headpiece was fixed to the skull of the animal and leads were passed subcutaneously from it to electrodes in the muscle and the teeth. A silicone rubber cannula was inserted into the external jugular vein and connected to an injection port in the headpiece. The headpiece incorporated a miniature 9-way connector which was connected to the electrode leads.

A technique for recording from brain-stem neurones in awake, unrestrained cats

A method is described which enables single unit recordings to be made from neurones over a wide area of the brain-stem of awake, unrestrained cats. A small headpiece, made from titanium and acrylic, was fixed to the skull over a craniotomy at pre-set stereotaxic co-ordinates. Between recording sessions the craniotomy was sealed. During recording, a miniature micro-manipulator and adjustable titanium support was screwed into the headpiece and recordings were made with tungsten electrodes.

Section 136 and African/Afro-Caribbean minorities

Social, demographic and clinical information was collected retrospectively on all 99 people referred to a South London hospital in 1986 under Section 136 of the Mental Health Act (1983), this being the last complete year before local changes in the procedure for assessment of Section 136 cases were initiated. An over-representation of Afro-Caribbeans was confirmed and this seemed to be accounted for largely by young men under the age of 30 who with Africans had very high rates of previous Section 136 referral, were more likely to be perceived as threatening, incoherent and disturbed but less clearly diagnosed with a mental illness, and were more likely than the Caucasian sample to be living in stable accommodation. The implications of these results are discussed.

The permeability of cat dentine in vivo and in vitro

The apparent impermeability of dentinal tubules to chemicals applied to exposed dentine in vivo was investigated. It was shown that whereas Evans' blue diffused readily into dentine in extracted teeth, it did not do so in visible amounts when it was applied in vivo. In the in vitro experiments, decreasing the pressure of the Evans' blue solution to 20 cmH2O below atmospheric apparently prevented the dye entering the tubules, while increasing the pressure of the solution to 15 cmH2O or more above atmospheric in vivo resulted in the dye penetrating the dentine in high concentrations. It is concluded that, in cat dentine in vivo, there is an outward flow of fluid through exposed dentinal tubules, and that this flow is sufficient to substantially reduce diffusion into the tubules of chemicals such as Evans' blue.

Decalcification of teeth in a microwave oven

The effects of microwave radiation in reducing decalcification time were evaluated by measuring rates of calcium removal from samples of rat and cat teeth in 0.1 mol l-1 EDTA. In some cases, 3% glutaraldehyde was added to the decalcifying solution. Test specimens were placed in a microwave oven at 39 +/- 2 degrees C for repeated periods of 1-2 h. Control specimens were placed in a conventional oven at 39 degrees C for the same times or held at room temperature. The calcium removed during each treatment was measured using an atomic absorption spectrophotometer. There was no consistent difference between the results obtained with microwave radiation as compared with heating in a conventional oven, although in both cases decalcification was slightly faster than at room temperature. These results are attributed to thermal effects. No evidence for non-thermal effects of micro-radiation was found.

The effect of bacterial products on human fibroblast and keratinocyte detachment and viability

An in vitro model has been developed to study the effect of soluble bacterial products on the viability and detachment of skin cell types utilized cultured grafts. Microbial products prepared from clinical isolates of bacterial species which most commonly colonize burn lesions showed marked variation in their ability to detach and kill both keratinocytes and fibroblasts. All three isolates of Acinetobacter spp. tested were effective in causing detachment and death of keratinocytes and fibroblasts, whereas Escherichia coli, Proteus mirabilis and Enterobacter spp. tested had little, or no, effect on detachment or viability for either skin cell type. Four Staphylococcus aureus isolates elicited variable strain-dependent results with regard to detachment and viability. One isolate possessed activity specific for keratinocyte detachment and death. These results indicate the possible undesirable effects such bacterial species may have on graft success in colonized burn wounds.

The thresholds of the jaw-opening reflex and trigeminal brainstem neurons to tooth-pulp stimulation in acutely and chronically prepared cats

Electrical stimuli were applied to tooth-pulp in cats and the thresholds of the jaw-opening reflex and of neurons in the trigeminal sensory nuclei were determined. The effects of the method of preparation of the animal for stereotaxic recording were determined by making observations on animals set up in one of three ways: acutely in the usual manner; chronically, three to five days before recording; and acutely with precautions to minimize nociceptive input to the central nervous system. The threshold of the jaw-opening reflex increased progressively during the setting up of the normal, acute preparations and at the time brainstem recording began was significantly higher in these than in either the chronic or low-trauma acute preparations. Previous studies have shown that the increase in threshold is maintained for several hours and is not due to the effects of the anaesthetic. In normal acute preparations, few units (27/154) were found that had thresholds below 50 microA, 0.1 ms, whereas many units were encountered that responded to such a stimulus in chronic (147/152) and low-trauma acute (99/127) animals. In the chronic and in low-trauma acute preparations, there was no significant difference between the thresholds of the units in the main sensory trigeminal nucleus and spinal subnucleus oralis compared with those in subnucleus caudalis. Thus the preparation of an animal for stereotaxic recording can cause a severe and long-lasting depression in the excitability of neurons in the trigeminal sensory nuclei and an increase in the threshold of the jaw-opening reflex. This effect will have influenced the results of previous studies on the responses evoked in central neurons by stimulation of tooth-pulp, and may have similarly affected recordings from other regions.

Genetic transfer systems in Bacteroides: cloning and mapping of the transferable tetracycline-resistance locus

Conjugation systems that transfer antibiotic resistance in the absence of detectable plasmids are common in Bacteroides, but the mechanism of transfer is poorly understood. We found that linked transfer of tetracycline (TcR) and clindamycin (ClR) resistance by Bacteroides fragilis strain 1126 is induced by growth in either Tc or Cl. We cloned the transferable TcR locus as a 13 kb fragment on the shuttle vector pPH6 in Escherichia coli and showed that this region expresses TcR in Bacteroides but not E. coli. The TcR gene was mapped to a 3 kb region and the ClR gene was shown not to be present in the 13 kb insert. Homologous TcR genes are found in B. fragilis V479 and 1792. Using pulsed-field electrophoresis, the transferable TcR gene was shown to be physically associated with high molecular-weight DNA, suggesting that it is located on the chromosome. A new TcR shuttle vector, pPH7 delta 1.1, was constructed to facilitate use of this selective marker in Bacteroides genetics.

myc-related proteins and DNA sequences in Trypanosoma brucei

The cAMP content of Trypanosoma brucei increases in parallel with ascending mammalian parasitemia to very high levels just before differentiation of the long-slender to the short-stumpy bloodstream form. Because expression of myc oncogenes is required for vertebrate cells to interpret proliferation signals and declines in response to cAMP mediated differentiation, we investigated whether T. brucei also harbored myc-like proteins and genes. Accordingly, we probed lysates of long-slenders, short-stumpies and procyclics (insect midgut stage) with antibody to myc proteins and also hybridized myc gene family sequences to procyclic DNA. We found that antibody to myc-family proteins of mammals reacts with 40 kDa and 55 kDa proteins in all three life cycle stages, and that procyclic DNA contains three EcoRI fragments that are homologous to a v-myc probe. One of these fragments also hybridizes to a synthetic 25-mer oligonucleotide deduced from a consensus sequence in the second exon of the myc family and expresses a 3.2 kb mRNA transcript in Northern blots of procyclic RNA. The conservation of myc-family homologous across the broad phylogenetic gap between mammals and trypanosomes illustrates ancient evolutionary relationships and raises the possibility of stage-specific expression of myc genes during the life cycle of T. brucei.