The Brock procedure (closed infundibular resection) for Fallot's tetralogy: 43 years later

Innovative cardiac surgery ('blind' or indirect infundibular resection) for tetralogy of Fallot on a child of 4 years was followed by survival for 43 years without further surgery. The patient remained well until about one year before death, when he developed clinical features of progressive biventricular failure associated with pulmonary hypertension and incompetence of the pulmonary and tricuspid valves. Postmortem examination showed severe damage to one of the leaflets of the pulmonary valve, interpreted as due to inadvertent avulsion during the original surgical procedure. A large ventricular septal defect was present, but there was no residual subpulmonary infundibular obstruction.

Warming intravenous fluids reduces perioperative hypothermia in women undergoing ambulatory gynecological surgery

We evaluated whether warming i.v. fluids resulted in less hypothermia (core temperature < 35.5 degrees C) compared with room-temperature fluids. Thirty-eight adult outpatients undergoing elective gynecological surgery of > 30 min were randomized to two groups: fluid warming at 42 degrees C or control (room temperature fluids at approximately 21 degrees C). All patients received general anesthesia with isoflurane, tracheal intubation, standard operating room blankets and surgical drapes, and passive humidification of inspired gases. Tympanic membrane (core) temperatures were measured at baseline and at 15-min intervals after induction. The incidence of shivering and postoperative requirement for meperidine and/or radiant heat were evaluated. Core temperatures were lower in the control compared with the warm fluid group at the end of surgery (35.6 +/- 0.1 degrees C vs 36.2 +/- 0.1 degrees C; P < 0.05). More patients had final core temperature < 35.5 degrees C in the control compared with the warm fluid group (35% vs 0%; P < 0.05). There were no differences in time to discharge from the postanesthesia care unit or the incidence of shivering between the groups. We conclude that fluid warming, in conjunction with standard heat conservation measures, was effective in maintaining normothermia during outpatient gynecological surgery; however, there was no improvement in patient outcome.

IMPLICATIONS

Women who received i.v. fluid at body temperature had significantly higher core temperatures during and after outpatient gynecological surgery compared with women who received i.v. fluids at the temperature of the operating room.

Cellular and chemical events during enamel maturation

This review focuses on the process of enamel maturation, a series of events associated with slow, progressive growth in the width and thickness of apatitic crystals. This developmental step causes gradual physical hardening and transformation of soft, newly formed enamel into one of the most durable mineralized tissues produced biologically. Enamel is the secretory product of specialized epithelial cells, the ameloblasts, which make this covering on the crowns of teeth in two steps. First, they roughly "map out" the location and limits (overall thickness) of the entire extracellular layer as a protein-rich, acellular, and avascular matrix filled with thin, ribbon-like crystals of carbonated hydroxyapatite. These initial crystals are organized spatially into rod and interrod territories as they form, and rod crystals are lengthened by Tomes' processes in tandem with appositional movement of ameloblasts away from the dentin surface. Once the full thickness of enamel has been formed, ameloblasts initiate a series of repetitive morphological changes at the enamel surface in which tight junctions and deep membrane infoldings periodically appear (ruffle-ended), then disappear for short intervals (smooth-ended), from the apical ends of the cells. As this happens, the enamel covered by these cells changes rhythmically in net pH from mildly acidic (ruffle-ended) to near-physiologic (smooth-ended) as mineral crystals slowly expand into the "spaces" (volume) formerly occupied by matrix proteins and water. Matrix proteins are processed and degraded by proteinases throughout amelogenesis, but they undergo more rapid destruction once ameloblast modulation begins. Ruffle-ended ameloblasts appear to function primarily as a regulatory and transport epithelium for controlling the movement of calcium and other ions such as bicarbonate into enamel to maintain buffering capacity and driving forces optimized for surface crystal growth. The reason ruffle-ended ameloblasts become smooth-ended periodically is unknown, although this event seems to be crucial for sustaining long-term crystal growth.

The structure of the Golgi apparatus: a sperm's eye view in principal epithelial cells of the rat epididymis

The Golgi apparatus of epididymal principal cells shares many structural features with other cell types. Saccular regions are arranged in a cis-Golgi network, eight flattened saccules, and several trans-Golgi networks (TGNs). Dilated tubules form intersaccular connecting regions which joint together saccules at the same or different levels between adjacent stacks. Wells exist as large perforations in register with the four cis-most saccules and serve as areas of vesicular interactions. TGNs are variable and can appear to peel off the stack or to be detached from it in the form of an anastomotic tubular network with pale dilated areas corresponding to prosecretory granules connected by short narrow bridges. Elongated or discoid dilated cisternae of endoplasmic reticulum (ER) (sparsely granulated) lie over the cis face of the stack, from which they are separated by an intermediate compartment filled with vesicles and tubules. The ER is also closely juxtaposed to the TGNs and the eighth saccule but interconnections are never seen between them. Vesicles of the COP variety reside at all levels of the stack and appear to bud off the cis-located ER and the edges of the saccules, while clathrin-coated vesicles appear mainly on the trans face of the stack and next to lysosomes. In the supranuclear cytoplasm, clusters of vesicles and tubules, at times budding off enveloping ER, appear to radiate toward the Golgi stacks where they fuse with cis Golgi elements. Taken together, these observations suggest dynamic functions and interactions for the various Golgi elements, associated vesicles, ER, and vesicular tubular clusters.

A survey of computer technology utilization in school nursing

Computer technology offers a solution to problems associated with paper-based health records. The purposes of this descriptive study were to identify the utilization of and support for computer technology in managing student health data and documenting school nurse practice. Findings from a sample of school nurse respondents to the Computer Technology and School Nursing Survey (CTSNS) indicated that of the 65% that used computers, nearly two-third used computers for three years or less. Although there was an increase in computer use when compared with an earlier study, more training, financial support, and research are needed for optimal utilization of computer technology.

Biological monitoring standards for industrial toluene exposure recommended for South Africa

Coal combustion is used in many industrial processes in South Africa. The exposure of workers and the absence of international biological monitoring standards for toluene created a problem. A cross-sectional study on 100 workers indicated that the biological threshold for ortho-cresol:creatinine ratio reference value of < 1 mg/g could presently be used as a reference for non-industrial human exposure while the < 2 mg/g rate is for worker exposure in an industrial environment at a coal combustion plant.

Continuous positive airway pressure: patients' and caregivers' learning needs and barriers to use

OBJECTIVE

To identify learning needs and factors related to postdischarge use of continuous positive airway pressure (CPAP) ventilation.

DESIGN

Exploratory descriptive correlational.

SETTING

Metropolitan and rural clinics.

SUBJECTS

Adult patients (N = 21) and family caregivers, one half 60 years or older.

INSTRUMENTS

Family interviews, life satisfaction and quality, family function and relationship, depression and learning preparedness.

RESULTS

There were numerous learning needs related to CPAP machine management, monitoring illness severity, and recognizing depressive symptomology, oxygen deficits, and cardiovascular sequelae. Family members are involved in overcoming barriers interfering with nightly CPAP use. Interview and questionnaire data clearly indicate life satisfaction improves after CPAP treatment.

CONCLUSION

Predischarge and teaching programs coordinated by expert nurses are needed to address families' learning needs and support habitual long-term CPAP use. Family problem solving and depression interventions, instruction on recognizing symptoms of cardiovascular complications, and long-term follow-up programs are currently being studied.

Patients as peer preceptors for orthopedic oncology rehabilitation patients

This article describes a peer preceptor program that trains patients who have experienced limb preservation surgeries and managed long-term rehabilitative therapy to support and teach newly diagnosed patients through their rehabilitation. This preceptor program was designed to complement the professional counseling and support that rehabilitation staff provide to patients and their families. Training includes communication techniques, practice sessions using videotaped scenes of patients and their families, as well as role-playing. Experienced patients who became preceptors as a result of this program were orthopedic oncology patients who had completed limb preservation surgery, chemotherapy, grafting, and physical therapies. After their training, preceptors exhibited improved communication skills in terms of empathy, listening, and voice expressions. Initiatives designed to make the preceptor program self-sustaining by having staff nurses manage the training still have to be tested.

Protease-resistant form of insulin-like growth factor-binding protein 5 is an inhibitor of insulin-like growth factor-I actions on porcine smooth muscle cells in culture

IGFs are pleiotrophic mitogens for porcine smooth muscle cells (pSMC) in culture. The effects of IGFs on cells are modulated by various insulin-like growth factor-binding proteins (IGFBP). IGFBP-5 is synthesized by pSMC and binds to the extracellular matrix. However, IGFBP-5 is also secreted into conditioned medium of cultured cells and is cleaved into fragments by a concomitantly produced protease. These fragments have reduced affinity for the IGFs and cleavage makes it difficult to assess the role of intact IGFBP-5. To study the consequence of accumulation of intact IGFBP-5 in medium, we determined the cleavage site in IGFBP-5 and prepared a protease resistant mutant. Amino acid sequencing of purified IGFBP-5 fragments suggested Arg138-Arg139 as the primary cleavage site. Arg138-Arg139-->Asn138-Asn139 mutations were introduced to create protease-resistant IGFBP-5, which has the same affinity for IGF-I as the native protein. This mutant IGFBP-5 remained intact even after 24 h of incubation and it inhibited several IGF-I actions when added to pSMC culture medium. The mutant IGFBP-5 (500 ng/ml) decreased IGF-I stimulated cellular DNA synthesis by 84%, protein synthesis by 77%, and it inhibited IGF-I stimulated migration of pSMC by 77%. It also inhibited IGF-I stimulation of IRS-1 phosphorylation. In contrast, the same amount of native IGFBP-5 did not inhibit IGF-I actions. The significance of inhibitory effects of the protease resistant IGFBP-5 was further demonstrated in pSMC transfected with mutant or native IGFBP-5 cDNAs. The mutant IGFBP-5 accumulated in culture medium of transfected cells, while native IGFBP-5 was degraded into fragments, PSMC overexpressing the mutant IGFBP-5 also responded poorly to IGF-I compared with mock transfected cells. IGF-I (5 ng/ml) increased [35S]methionine incorporation into control cells by 36% above the basal level, but it did not significantly change (4%) in pSMC cultures that were producing the mutant IGFBP-5. In conclusion, the accumulation of protease-resistant IGFBP-5 in the medium was inhibitory to IGF-I actions on pSMC. This suggests that proteolysis can prevent IGFBP-5 from acting as an inhibitor of IGF-I-stimulated effects and that it serves as an important mechanism for regulating cellular responsiveness to IGF-I.

Structure and activity of uroguanylin and guanylin from the intestine and urine of rats

Uroguanylin and guanylin are related peptides that activate common guanylate cyclase signaling molecules in the intestine and kidney. Uroguanylin was isolated from urine and duodenum but was not detected in extracts from the colon of rats. Guanylin was identified in extracts from small and large intestine but was not detected in urine. Uroguanylin and guanylin have distinct biochemical and chromatographic properties that facilitated the separation, purification, and identification of these peptides. Northern assays revealed that mRNA transcripts for uroguanylin were more abundant in small intestine compared with large intestine, whereas guanylin mRNA levels were greater in large intestine relative to small intestine. Synthetic rat uroguanylin and guanylin had similar potencies in the activation of receptors in T84 intestinal cells. Production of uroguanylin and guanylin in the mucosa of duodenum is consistent with the postulate that both peptides influence the activity of an intracellular guanosine 3',5'-cyclic monophosphate signaling pathway that regulates the transepithelial secretion of chloride and bicarbonate in the intestinal epithelium.

A comparison of the infusion pharmacokinetics and pharmacodynamics of cisatracurium, the 1R-cis 1'R-cis isomer of atracurium, with atracurium besylate in healthy patients

We have compared the pharmacokinetics of cisatracurium with atracurium when given by bolus dose followed by continuous infusion. Twenty healthy patients were anaesthetised with thiopentone, midazolam, fentanyl and 70% nitrous oxide in oxygen. Ten patients (Group C) were randomly allocated to receive cisatracurium 0.1 mg.kg-1 and 10 patients (Group A) were given atracurium 0.5 mg.kg-1. Neuromuscular block was monitored using a mechanomyograph. When the first twitch of the train-of-four had recovered to 5% of control, an infusion of cisatracurium 3 micrograms.kg-1.min-1 was started in Group C and an infusion of atracurium 10 micrograms.kg-1.min-1 was started in Group A. The infusion rates were adjusted to maintain the first twitch of the train-of-four at 5% of control. The times to 90% and maximum depression of the first twitch of the train-of-four were significantly longer after cisatracurium than atracurium (2.2 and 3.4 min compared with 1.3 and 1.8 min, respectively; p < 0.01 in each instance). No significant differences were found in recovery parameters between the two groups. Blood samples were taken at regular intervals following the bolus, during the infusion and for 8 h thereafter. The plasma samples were analysed using high-performance liquid chromatography for cisatracurium and atracurium (using a method which distinguishes between the three geometric isomer groups), laudanosine and monoquaternary alcohol. The results were analysed using the Non-linear Mixed Effects Model program. A two-compartment model was fitted to the data. The different isomer groups of atracurium have different pharmacokinetics, the trans-trans group having the highest clearance (1440 ml.min-1) and the cis-cis group the lowest (499 ml.min-1). The clearance of cisatracurium (425 ml.min-1) is less than that of cis-cis atracurium and its elimination half-life is longer (34.9 min and 21.9 min, respectively). The plasma concentration of laudanosine after cisatracurium was one-fifth of that after atracurium.

Heat conservation vs convective warming in adults undergoing elective surgery

PURPOSE

To determine the relative efficacy of heat conservation and convective warming in maintaining perioperative normothermia, (central temperature > or = 36 degrees C).

METHODS

Thirty-seven patients undergoing elective gynaecological, orthopaedic, or general surgery scheduled to last two hours were prospectively studied. Patients were randomized to one of two groups. Group 1 patients received heat conservation with reflective blankets (Thermadrape, Vital Signs, Inc., Totowa, NJ) applied preoperatively and warmed i.v. fluids (Hotline SIMS Level I Technologies, Inc, Rockland, MA), Group 2 patients received convective warming (BairHugger, Augustine Medical Inc., Eden Prairie, MN) after induction of anaesthesia and i.v. fluids at room temperature. All patients received general anaesthesia with isoflurane. Tympanic membrane and forearm-fingertip skin temperature gradients were measured perioperatively at 15 min intervals.

RESULTS

Central temperature decreased after induction to a minimum level of 35.9 +/- 0.1 degrees C in group 1 and 36.0 +/- 0.1 degrees C in group 2 and then increased towards pre-induction values in group 2, and were higher (P < 0.05) than in group 1: 95% group 2 patients had central temperature > or = 36.0 degrees C at the end of surgery (vs 69% of group 1, P < 0.05). During the first 30 min in PACU, central temperatures were higher in group 1 than in group 2 (36.8 +/- 0.1 degrees C vs 36.2 +/- 0.2 degrees C, P < 0.05). After 60 min, central temperatures were similar (36.8 degrees C). The incidence of shivering and degree of peripheral cutaneous vasoconstriction were also similar.

CONCLUSION

Patients receiving convective warming were more likely to leave the operating room normothermic, and had higher central temperatures during the first 30 min in the recovery room. The intergroup temperature differences were small, and by 60 min, had disappeared.

Comparison of the postantibiotic and postantibiotic sub-MIC effects of levofloxacin and ciprofloxacin on Staphylococcus aureus and Streptococcus pneumoniae

The postantibiotic subminimum inhibitory concentration effect (PA SME) may simulate in vivo drug exposure more accurately than the postantibiotic effect (PAE) since subinhibitory concentrations of drug persist between antibiotic dosings. In this study, we compared the PAEs and PA SMEs of levofloxacin and ciprofloxacin for clinical isolates of fluoroquinolone-susceptible Staphylococcus aureus and Streptococcus pneumoniae. At two times the MIC, PAEs of levofloxacin were an average of 0.6 h longer than the PAEs obtained for ciprofloxacin for methicillin-susceptible and methicillin-resistant S. aureus strains. The PAEs of levofloxacin and ciprofloxacin ranged from 1.8 to 3.1 and 1.1 to 2.4 h, respectively. Continued exposure of the methicillin-resistant strain to 1/16, 1/8, and 1/4 the MIC resulted in PA SMEs of 6.5, 15.3, and >22.3 h, respectively, for levofloxacin and 3.8, 8.0, and 12.3 h, respectively, for ciprofloxacin. For isolates of S. pneumoniae, at two times the MIC of both fluoroquinolones, the average PAEs of levofloxacin and ciprofloxacin were equivalent: 1.3 h for the penicillin-susceptible isolate and 0.6 h for the penicillin-resistant isolate. Continued exposure of the penicillin-susceptible S. pneumoniae strain to 1/16, 1/8, and 1/4 the MIC resulted in average PA SMEs of 1.0, 1.4, and 2.8 h, respectively, for levofloxacin and 1.8, 2.0, and 2.5 h, respectively, for ciprofloxacin. Continued exposure of penicillin-resistant S. pneumoniae to 1/16, 1/8, and 1/4 the MIC of the same fluoroquinolones resulted in average PA SMEs of 0.6, 1.1, and 2.9 h, respectively, for levofloxacin and 0.6, 1.1, and 1.5 h, respectively, for ciprofloxacin. The PA SMEs observed demonstrate the superior activity of levofloxacin against methicillin-susceptible or methicillin-resistant S. aureus. Although PAEs were similar for the penicillin-susceptible and penicillin-resistant S. pneumoniae strains, the PA SME of levofloxacin at one-fourth the MIC was longer for penicillin-resistant S. pneumoniae.

Sulfation and sialylation requirements for a glycoform of CD34, a major endothelial ligand for L-selectin in porcine peripheral lymph nodes

Leukocyte recruitment from blood into peripheral lymph nodes is controlled in part by a specific interaction of lymphocyte-associated L-selectin with endothelial cell receptors known as peripheral addressins. In murine lymph nodes, two peripheral addressins have been identified, Gly-CAM-1, a 50 kDa molecule that also appears as a secreted form in plasma, and CD34, a 90 kDa membrane-associated sialomucin. A predominant 105 kDa CD34 mucin-like protein has also been identified in human tonsil as peripheral addressin. We have identified a 120 kDa sialomucin as the predominant peripheral addressin in porcine lymph nodes. Validation of the 120 kDa porcine molecule as a peripheral addressins was based on its ability to bind MECA-79, a monoclonal antibody previously used to isolate peripheral addressins from mouse and human tissues, and to bind an L-selectin-Fc chimera (LS-Fc). The binding with LS-Fc was abolished in the presence of fucoidin, a sulfated polysaccharide known to inhibit L-selectin-receptor interactions. To address the possibility that the 120 kDa ligand may contain common recognition determinants for MECA-79 and L-selectin, the requirements for sialylation and sulfation were compared. Whereas desialylation of 120 kDa ligand drastically reduced its binding to LS-Fc, this treatment appeared to enhance the binding of 120 kDa ligand to MECA-79. In contrast, the binding of both MECA-79 and LS-Fc to 120 kDa ligand was drastically reduced when de novo sulfation of this ligand was reduced by including chlorate, a metabolic inhibitor of sulfation, in the culture media. N-Terminal amino acid sequences of the porcine 120 kDa protein revealed homology with human CD34. Taken together, these findings suggest that the porcine 120 kDa peripheral addressin is an L-selectin-binding glycoform of CD34.

Assessment of the synergistic interactions of levofloxacin and ampicillin against Enterococcus faecium by the checkerboard agar dilution and time-kill methods

Multidrug-resistant enterococci have become increasingly difficult to eradicate in a growing number of nosocomial infections. With the emergence of vancomycin-resistant enterococci, the use of synergistic antibiotic combinations has become one of the only remaining therapeutic options. Levofloxacin, the active l-isomer of ofloxacin, is a new oral and intravenous fluoroquinolone with a broad spectrum of activity against numerous Gram-positive, Gram-negative, and atypical organisms. The in vitro activity of levofloxacin, alone and in combination with ampicillin, against recent clinical isolates of Enterococcus faecium was assessed for synergistic interactions using the checkerboard agar dilution technique and time-kill methodology. Against all strains, the static technique of checkerboard agar dilution demonstrated indifferent or additive effects for the ampicillin + levofloxacin combination. With the dynamic time-kill technique, synergy was demonstrated for ampicillin (16 micrograms/ml) + levofloxacin (2 micrograms/ml) combination against three levofloxacin-sensitive, ampicillin-resistant isolates. At 24 h, the combination yielded a > or = 2-log10 decrease in CFU/ml compared to levofloxacin alone, while ampicillin had negligible effects. Against both a levofloxacin-intermediate, ampicillin-resistant isolate, and a highly levofloxacin-resistant, ampicillin-resistant isolate, none of the ampicillin+levofloxacin combinations tested demonstrated a synergistic interaction. The time-kill method suggested synergy for the ampicillin+levofloxacin combination against some strains of E. faecium.

Unlicensed assistive personnel in the perioperative setting

The present climate in health care, including a tendency toward more managed care and capitation systems, has caused hospital administrators and perioperative managers to reexamine traditional work systems and their associated costs. Some decisions around work redesign may be financially driven or based on the decreased availability of qualified professionals in the job market. The use of an increased number of unlicensed assistive personnel (UAP) in hospital settings has become a common redesign strategy to address both issues. In the perioperative setting, some traditional roles are well established for UAP. Today, changes associated with downsizing, cost containment, and increasing technology have opened up new opportunities to explore ways to integrate UAP roles into the perioperative setting.

Taping methods and tape types for securing oral endotracheal tubes

PURPOSE

To evaluate tapes and taping methods with respect to the minimum force required to dislodge endotracheal tubes (ETTs).

METHODS

A simulated face model consisting of a section of PVC pipe was used. The ETT was attached to a piezo-electric force transducer and pullout force was manually applied in a vertical, right or left direction. Five tape types were tested: Curity, Leukosilk, Hy.tape, Leukopore, and Transpore, Seven taping methods were used to secure the ETT. The methods differed with respect to tape width and whether the tape was split along its longitudinal axis. Each taping condition was replicated 20 times (7 methods x 5 tapes x 3 directions) for a total of 2100 pullout tests.

RESULTS

Minimum forces to dislodge ETTs were higher (P < 0.05) with Curity tape (mean +/- SD; 135 +/- 75 N) than with the other tapes (Leukosilk: 93 +/- 51 N, Hy.tape: 78 +/- 34 N, Leukopore: 47 +/- 32, and Transpore: 37 +/- 23 N). The most secure taping method was achieved by taping the ETT, using 2.5 cm wide Curity tape, in a circumferential fashion to both the upper and lower borders of the simulated mouth opening, and reinforcing these tapes with two strips applied longitudinally across the borders of the mouth opening (method 7). Taping methods which involved splitting the tape along its longitudinal axis resulted in lower minimal pullout forces whenever the pullout force was directed towards the side of attachment (P < 0.05 vs right and vertical direction).

CONCLUSION

There are differences in ETT pullout forces and mechanisms of dislodgement depending on taping method and tape type.

Primary branchial cleft carcinoma--a case report

Primary branchial cleft carcinoma is a diagnostic challenge. The majority of cases have been shown, following the application of rigid criteria, to have developed from an occult metastasis elsewhere. We describe what we believe to be only the second reported case in a patient who fulfils all of the established criteria.

Cycle-time and residence-time density approximations in a stochastic model for circulatory transport

The concentration of a drug in the circulatory system is studied under two different elimination strategies. The first strategy--geometric elimination--is the classical one which assumes a constant elimination rate per cycle. The second strategy--Poisson elimination--assumes that the elimination rate changes during the process of elimination. The problem studied here is to find a relationship between the residence-time distribution and the cycle-time distribution for a given rule of elimination. While the presented model gives this relationship in terms of Laplace-Stieltjes transform., the aim here is to determine the shapes of the corresponding probability density functions. From experimental data, we expect positively skewed, gamma-like distributions for the residence time of the drug in the body. Also, as some elimination parameter in the model approaches a limit, the exponential distribution often arises. Therefore, we use Laguerre series expansions, which yield a parsimonious approximation of positively skewed probability densities that are close to a gamma distribution. The coefficients in the expansion are determined by the central moments, which can be obtained from experimental data or as a consequence of theoretical assumptions. The examples presented show that gamma-like densities arise for a diverse set of cycle-time distribution and under both elimination rules.

Intubating conditions and neuromuscular block after divided dose mivacurium or single dose rocuronium

PURPOSE

To evaluate the tracheal intubating conditions and neuromuscular blocking characteristics of divided dose mivacurium or single dose rocuronium.

METHODS

Thirty-two patients undergoing elective surgery were studied. Anaesthesia was with propofol 2 mg.kg-1, followed by an infusion of 150 micrograms.kg-1.min.1. Patients were randomized to receive either mivacurium-0.15 mg.kg-1 followed 30 sec later by 0.1 mg.kg-1, or rocuronium- 0.9 mg.kg-1, followed 30 sec later by placebo. Tracheal intubating conditions were assessed 90 sec after the initial dose of relaxant by an anaesthetists who was unaware of patient group. The electromyographic (EMG) response of the first dorsal interosseus muscle to ulnar nerve train-of-four was measured.

RESULTS

Successful tracheal intubation was performed in all patients after both mivacurium and rocuronium. Intubating conditions (jaw relaxation, open visible vocal cords) were judged to be good-excellent in all but one patient before insertion of the tracheal tube. However, patients receiving mivacurium were more likely to experience coughing and bucking after tracheal tube insertion (10/16 patients) than those receiving rocuronium (3/16 patients, P < 0.05). No patient in the rocuronium group experienced moderately vigorous coughing and bucking after insertion of the tracheal tube vs six patients in the mivacurium group (P < 0.05). Time to 10 and 25% recovery of neuromuscular function was faster (P < 0.05) after divided dose mivacurium (20 +/- 1 and 23 +/- 1 min, respectively) than after rocuronium (45 +/- 5 and 57 +/- 8 min, respectively).

CONCLUSION

The results suggest that, during conditions of the study, divided dose mivacurium is not recommended for a 90-sec tracheal intubation in patients where moderate coughing and bucking is deemed unacceptable.

Transient accumulation of proteins at interrod and rod enamel growth sites

Conceptually, there should be a brief interval in time when newly secreted proteins "pile up" at secretory sites just outside the membrane of ameloblasts. Indeed, previous cytochemical studies have suggested that glycosylated and/or sulfated glycoproteins accumulate at enamel growth sites. Colloidal gold lectin cytochemistry and immunocytochemistry with antibodies to enamel proteins and phosphoserine, combined with cycloheximide and brefeldin A to inhibit protein synthesis and secretion, were applied to characterize the distribution of newly formed proteins at enamel interrod and rod growth sites. Although enamel growth sites show a "rarefied" appearance, the results indicate that one or more subclasses of enamel proteins accumulate near the cell surface at sites where elongation of enamel crystallites contributes to thickening of the enamel layer. These proteins are glycosylated and/or phosphorylated and, at least in the case of the glycosylated ones, are rapidly processed after they are released extracellularly. In contrast, immunolabeling for amelogenins is generally weaker near the cell surface and more intense at a short distance away from the site where crystallites elongate. The data suggest that the enamel proteins accumulating at growth sites likely belong to the non-amelogenin category and play a transient role in promoting the lengthening of crystallites. It is concluded that areas near the ameloblast membrane where certain enamel proteins accumulate in fact constitute the equivalent of a mineralization front.

Developmental changes in the pH of enamel fluid and its effects on matrix-resident proteinases

The objectives of this study were to measure pH in developing enamel at progressively older (more mature) stages of amelogenesis in vivo, and then to formulate synthetic enamel fluid mixtures that approximated these pH values for in vitro studies. The ultimate goal was to characterize the molecular weights of proteinases visualized by enzymograms incubated in synthetic enamel fluid using gelatin and casein as substrates. For most experiments, the proteinases were extracted en masse from small freeze-dried enamel strips directly into a non-reducing sample preparation buffer. In some experiments, we pre-treated the enamel strips with acetic acid to determine if this common method for demineralization and protein extraction caused any changes in the activity levels of the enamel proteinases. In other experiments, we first soaked enamel strips in synthetic enamel fluid to determine solubility of the proteinases within an aqueous phase. The results indicated that the pH of developing enamel remained fairly constant near pH 7.23 across the secretory stage, but it was generally more acidic (6.93) and fluctuated in focal areas between mildly acidic (6.2-6.8) and near-neutral (7.2) conditions across the maturation stage. The pH then slowly rose to near 7.35 when the enamel was almost mature (hard). The acidic conditions were generally inhibitory to most enamel proteinases, but there were some caseinase activities in mid-maturation-stage enamel near 23-30 kDa which appeared to be activated by weakly acidic conditions (pH 6.28). Pre-treatment of enamel samples with 0.5 M acetic acid markedly altered the overall profile of enamel proteinases, causing activation of some latent proteinase activities and permanent inhibition of other activities. Most proteinases in whole homogenates were insoluble in synthetic enamel fluid. This suggests that they may be tightly bound, directly or indirectly, to matrix proteins or mineral components in situ.