Biomedical subjects
Publications and source records attributed to C A Hansen.
The most difficult aspect of retrofitting a new crown to an existing removable partial denture clasp assembly is maintaining an accurate relationship of the prepared abutment tooth to the clasp assembly while making an impression. A procedure is presented that helps to ensure that the framework is not displaced during this critical step of the process.
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The procedure described is used to reproduce, in gold, the occlusal morphology of complete and removable partial denture teeth or those of an implant-supported prosthesis. The gold occlusal surfaces are made after all adjustments are completed and the occlusion is harmonious. An acrylic resin strut reinforces the wax patterns, and a reline jig is used to accurately stamp out the occlusal anatomy in wax. Careful adherence to the step-by-step procedure is required to achieve an excellent result.
Signal transducing heterotrimeric G proteins are responsible for coupling a large number of cell surface receptors to the appropriate effector(s). Of the three subunits, 16 alpha, 4 beta, and 5 gamma subunits have been characterized, indicating a potential for over 300 unique combinations of heterotrimeric G proteins. To begin deciphering the unique G protein combinations that couple specific receptors with effectors, we examined the subcellular localization of the gamma subunits. Using anti-peptide antibodies specific for each of the known gamma subunits, neonatal cardiac fibroblasts were screened by standard immunocytochemistry. The anti-gamma 5 subunit antibody yielded a highly distinctive pattern of intensely fluorescent regions near the periphery of the cell that tended to protrude into the cell in a fibrous pattern. Dual staining with anti-vinculin antibody showed co-localization of the gamma 5 subunit with vinculin. In addition, the gamma 5 subunit staining extended a short distance out from the vinculin pattern along the protruding stress fiber, as revealed by double staining with phalloidin. These data indicated that the gamma 5 subunit was localized to areas of focal adhesion. Dual staining of rat aortic smooth muscle cells and Schwann cells also indicated co-localization of the gamma 5 subunit and vinculin, suggesting that the association of the gamma 5 subunit with areas of focal adhesion was wide-spread.
A technique is described for the fabrication of a full arch maxillary passive-fitting, screw-retained, rigid ceramometal prosthesis. The two posterior segments containing Screw-Bloc attachments are cast initially. The waxed anterior segment with its attachments is then aligned to the cast posterior segments and cast. Porcelain is fired to the individual segments in an attempt to reduce deformation, which occurs when large ceramometal restorations are constructed. When the prosthesis is completely fabricated, the segments are assembled on the master cast and the attachments on the posterior segments are tapped to receive the screws, which rigidly attach them to the anterior segment. The Screw-Bloc attachment has an irregular configuration that resists rotation of the individual segments. The segments are united once the passively aligned screws are tightened. A clinical report is presented.
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A checklist is described that is designed to permit a systematic evaluation of the factors involved in the trial insertion appointment. The checklist aids both the student and the instructor in assuring that items are not overlooked during this important appointment. More equitable grading of the student's preparation and knowledge is facilitated. The checklist also serves as an excellent patient approval form.
In a nationwide survey, all orthopaedic clinics were surveyed via a questionnaire about the use of bone allografts and how they managed their bone banks. Thirty-two clinics (100 per cent) responded to the questionnaire (mid 1991). Seventeen clinics had established bone banks on the basis of femoral heads obtained from donors during primary hip replacement. Only five used bone substitutes. The mean consumption was 30 capita per year (10-132) and ten clinics estimated an increasing demand for allografts. The storage method was by freezing at temperatures varying from minus 20 to minus 80 degrees Celsius. Contraindications to procurement comprised history of infection and malignancy, all clinics tested donors for HIV antibodies and all but one for hepatitis B. Testing for hepatitis C was about to be introduced. All but one clinic developed cultures from the procured bone. Informed consent was employed by nearly all clinics, but very few obtained written consent. Since this survey, revised recommendations have been directed from the Danish National Board of Health, these listing that an HIV-test should be performed with a 90-day interval, and that testing should also be done for hepatitis B and C. International experience and this survey show that the establishment of more specific and general national recommendations would be preferable to present practice.
OBJECTIVES: To identify the neurologic complications of critical medical illnesses, and to assess their effect on mortality rates and on medical ICU and hospital lengths of stay. DESIGN: Prospective clinical evaluation of all medical ICU admissions for 2 yrs. SETTING: A 14-bed, general medical intensive and coronary care unit in a large university hospital. PATIENTS: Patients (n = 1,850) admitted to the hospital, of whom 92 were admitted for primarily neurologic problems. Of the remaining 1,758 patients, 217 (12.3%) experienced a neurologic complication. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients developing a neurologic complication while in the medical ICU demonstrated an increased risk of inhospital mortality when compared with patients who did not suffer such problems (45.7% vs. 26.6%; p < .00001). Patients with neurologic complications experienced 2.5-fold longer medical ICU stay times (p < .001) and almost two-fold longer hospital stay times (p < .001). Metabolic encephalopathy, seizures, hypoxic-ischemic encephalopathy, and stroke were the most common complications. Sepsis was the most frequent cause of encephalopathy, and cerebrovascular lesions were the most common cause of seizures. Formal neurologic consultations were requested in only 36% of these patients. CONCLUSIONS: Neurologic complications are associated with increased mortality rates and longer medical ICU and hospital lengths of stay. These conditions are probably underrecognized at present. ICUs have the potential to serve as environments for neurologic teaching and research.
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BACKGROUND AND PURPOSE: Early thrombolytic therapy with recombinant tissue-type plasminogen activator is a theoretically attractive approach to the treatment of acute focal cerebral ischemia. In preparation for a larger multicenter trial, three centers piloted a protocol for a randomized, double-blind, placebo-controlled trial of intravenous recombinant tissue-type plasminogen activator begun within 3 hours of the onset of symptoms of acute stroke to test its feasibility and to explore trends. METHODS: Eligible patients had pretreatment computed tomographic scanning, gave informed consent, and began treatment with either 0.85 mg/kg recombinant tissue-type plasminogen activator or placebo as soon as possible, but no later than 180 minutes after stroke onset. Patients were stratified by whether treatment was begun within 90 minutes or 91 to 180 minutes from onset. The primary end point was the proportion of patients in each group who improved by 4 or more points on the National Institutes of Health Stroke Scale at 24 hours, as determined by a separate blinded evaluator. RESULTS: Twenty-seven patients were randomized: 20 (10 recombinant tissue-type plasminogen activator, 10 placebo) within 90 minutes, and 7 (4 recombinant tissue-type plasminogen activator, 3 placebo) from 91 to 180 minutes. Median baseline Stroke Scale scores were 16 (minimum = 5, maximum = 26) for the recombinant tissue-type plasminogen activator-treated group and 11 (minimum = 3, maximum = 21) for the control subjects in the group treated within 90 minutes. Six patients treated with recombinant tissue-type plasminogen activator within 90 minutes improved by 4 or more points at 24 hours compared with 1 patient in the placebo group (P < .05, Fisher's Exact Test). Two patients in each group in the 91- to 180-minute arm improved. One fatal intracerebral hemorrhage occurred in the placebo group. CONCLUSIONS: A randomized, double-blind, placebo-controlled trial of recombinant tissue-type plasminogen activator very early in acute stroke is feasible. Preliminary observations suggest that recombinant tissue-type plasminogen activator treatment within 90 minutes may be associated with early neurological improvement. Larger studies are needed so that the potentially serious short-term risks of this treatment can be assessed in relation to meaningful long-term benefit.
OBJECTIVES: We sought to determine the effects of intrauterine cocaine exposure in newborns, in an inner-city population in which cocaine use during pregnancy was common. METHODS: During a 1-year period, 12.8% (361 of 2810) of all live singleton infants at Harlem Hospital in New York were identified as cocaine exposed, either by universal urine toxicologic screening or by maternal history. Cocaine-exposed infants were compared with a control group of 387 infants not known to be exposed to cocaine or other illicit drugs. RESULTS: Low birthweight (< 2500 g) was more common among cocaine-exposed infants (31% vs 10%), as was preterm birth (< 37 completed weeks of gestation) (32% vs 14%). In multivariate analyses controlled for demographic and life-style factors and duration of gestation, cocaine was associated with decreased birthweight (154 g), length (1.02 cm), head circumference (0.69 cm), and duration of gestation (0.74 weeks). The birthweight deficits were larger for infants born to mothers who used cocaine in combination with other drugs (195 g) and for infants born to mothers who specifically admitted using crack (200 g). CONCLUSIONS: Intrauterine cocaine exposure is linked with fetal growth retardation and shortened gestation in this population.
When five to six implants are used in a fixed reconstruction, it is desirable to place the most distal implant as close to the mental nerve as possible. This allows the cantilever of the fixed prosthesis to be extended posteriorly as much as is biomechanically feasible. Forty-seven mental nerve regions were dissected on cadavers to determine the exact relationship between the mental foramen, the inferior alveolar nerve, and its two terminal branches--the incisive and mental nerves. The most anterior position in which the mental nerve was encountered was 1 mm forward or mesial to the most anterior aspect of the mental foramen. Based upon this finding, it is likely that damage to the mental nerve can be avoided if the distal surface of the most posterior implant is 1 mm anterior to the anterior border of the mental foramen.
Isolated newborn rat calvarial bone cells grown in monolayer on polyurethane membranes in specially constructed culture chambers and subjected to a cyclical biaxial mechanical strain of 0.17% at a frequency of 1 Hz for 30 min demonstrated a 16% increase in DNA synthesis during the subsequent 24 h. The metabolites of the inositol phosphate pathway, shown to be an important second messenger in many cell types, were shown to be elevated using high-performance liquid chromatography to separate and quantitate the various inositol polyphosphates. Inositol 1,4,5-trisphosphate, inositol 1,4-bisphosphate, and inositol 1,3,4,5-tetrakisphosphate reached peak accumulations after 20 s of mechanical strain. Inositol 1,3,4-trisphosphate reached a peak accumulation after 2 min, and inositol 1,2,3,4,5,6 phosphate reached a peak accumulation after 60 min of mechanical strain. Neomycin, an inhibitor of phospholipase C, a membrane-bound enzyme that hydrolyzes phosphatidyl inositol 4,5-bisphosphate to start the inositol phosphate cascade, completely inhibited accumulation of the above inositol phosphates during mechanical straining of the bone cells. Neomycin also completely abolished the increase in DNA synthesis that was seen after a mechanical strain of 0.17%. It is concluded from this study that the inositol phosphate pathway is activated by mechanical strain in bone cells and that this pathway is an important and primary mediator in the transduction of mechanical strain into cellular proliferation in these cells.
This article describes a technique for constructing a nickel chromium alloy lingual casting that reinforces a removable partial denture against heavy anterior occlusion. The metal can be cast into a thin secondary casting, and it is easily etched and bonded to the resin anterior teeth and associated base. This type of lingual casting has the potential to provide a simple and effective solution to the problem of repeated fracture or displacement of anterior teeth in many restorations.
A mathematical model for describing the caloric response over time offers many important advantages over the commercially-available qualitatively-fitted curves that are now used by the clinician for evaluating caloric results. In this report advances in the development of a nonlinear least-squares mathematical model are discussed and the roles and derivations of fitting parameters and curve-derived indices are outlined. This model provides a rigorous and objective description of the caloric response in its entirety with four continuous parameters. These fitting parameters make it possible to 1) describe individual caloric responses precisely and uniquely, 2) compare pairs of individual caloric responses or groups of caloric responses statistically, 3) extract information not previously available, 4) quantify variability within the caloric response, and 5) model physical properties of the caloric stimulus and physiological variables affecting the caloric response. Results from this model are compared with the results from our earlier models and with traditional multiparameter caloric results.
The single-tooth implant-supported restoration can provide an outstanding service to many patients. It requires an understanding of the biomechanical principles involved and attention to the many details involved with the diagnosis and treatment planning for these restorations. The clinician should realize that this restorative approach is contraindicated in many circumstances. As Peter K. Thomas said, "Spend more time planning than doing and doing becomes easier."
Treatment of rat hepatocytes with epidermal growth factor (EGF) produced an enhanced tyrosine phosphorylation of the EGF receptor and phospholipase C-gamma (PLC-gamma) in conjunction with the mobilization of Ca2+. Approximately 30% of the total PLC-gamma was tyrosine-phosphorylated with a maximum being reached after 30 s of incubation with EGF. Pretreatment of the rats with pertussis toxin prior to isolation of the hepatocytes blocked EGF-induced tyrosine phosphorylation of PLC-gamma and Ca2+ mobilization but had no effect on autophosphorylation of the EGF receptor or Ca2+ responses elicited by angiotensin II or phenylephrine. Under these conditions Gi protein alpha subunits were fully ADP-ribosylated. A 41-kDa Gi protein alpha subunit was found to be present in the anti-PLC-gamma immune complex after EGF stimulation as shown by in vitro ADP-ribosylation using [32P]NAD+ and activated pertussis toxin. The kinetics of association between PLC-gamma with Gi alpha protein reached a maximum after 1 min of incubation with EGF. Antibodies specific for the EGF receptor also coimmunoprecipitated a Gi protein alpha subunit. Treatment of hepatocytes with EGF caused first an increase and then a decrease in the amount of Gi protein alpha subunit associated with the EGF receptor. In contrast, studies with cultured rat liver (WB) cells, a cell line in which EGF stimulation of phosphoinositide hydrolysis is not inhibited by pertussis toxin, showed that a stable complex of Gi alpha was not formed with either PLC-gamma or EGF receptor immunoprecipitates. These results indicate that a pertussis toxin-sensitive Gi protein is uniquely involved in the signal transduction pathway mediating EGF-induced activation of PLC-gamma and Ca2+ mobilization in hepatocytes.