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Biomedical subjects

C J Nielsen

Publications and source records attributed to C J Nielsen.

At least 19 recordsLinked to original sources
PubMed2005

Optical constants of HNO3/H2O and H2SO4/HNO3/H2O at low temperatures in the infrared region.

The complex index of refraction of liquid HNO3/H2O and H2SO4/HNO3/H2O has been obtained at different temperatures and acid concentrations. FT-IR specular reflectance spectra were obtained for 30, 54, and 64 wt % aqueous HNO3 and for four different H2SO4/HNO3/H2O mixtures in the temperature region from 293 to 183 K. The complex index of refraction was obtained from the reflectance spectra with the Kramers-Kronig transformation. The optical constants of the binary and ternary mixtures vary with the acid concentration and the temperature. The results demonstrate that vibrational bands originating from the sulfate species are more sensitive to changes in temperature than the bands originating from vibrations in the nitrate species; only minor changes in the nitrate vibrational bands are observed as the temperature decreases below 248 K.

Journal Article↗
PubMed2003

Follow-up after cervical laminectomy, with special reference to instability and deformity.

Misalignment and instability after cervical laminectomy, performed to treat spondylotic myelopathy, has been described as possible adverse effects. Forty-six consecutively patients on whom laminectomy had been performed in a 4-year period were identified; 7.7 +/- 0.6 years after operation, 11 patients had died and 27 patients were available for follow-up. Postoperative static subluxation was observed in 26% of the patients with an average slip of 3.7 +/- 3.1 mm; 7% had abnormal intervertebral movement displaying 1-2 mm movement from full flexion to full extension. Seventy-four per cent of the patients showed abnormal spinal curvature as judged from radiographs. However, no correlation with outcome was observed. Seventy-four per cent of the patients thought of the result of the operation as either good or fair; objectively, the best long-term effect of the operation was upon arm function. Although some patients develop postural anomaly, laminectomy remains, in terms of instability, a justifiable procedure in the elderly patient with spondylosis.

Adult↗
PubMed2001

Effect of scenario and experience on interpretation of mach bands.

The creation of the radiographic illusion known as a mach band at the intersection of two images of differing radiopacities can be misinterpreted as pathosis in certain situations. After reviewing instances where misinterpretation may occur, this study asked 33 fourth-year dental students and 40 dentists to interpret the same radiograph involving a maxillary central incisor under two different hypothetical scenarios: first, in the case of a patient requesting vital bleaching, and second, where a patient has received recent trauma to the mouth. Results showed that dental students are more susceptible than dentists to misinterpreting as a horizontal root fracture (a mach band illusion) what is known to be the junction of alveolar crestal bone and root. Furthermore when presented with a scenario of trauma, both students and dentists are more likely to mistake what is being seen as being a fracture line.

Adolescent↗
PubMed2000

Evaluation of root reinforcement of endodontically treated teeth.

OBJECTIVES: The purpose of this study was to test the root reinforcing capabilities of a glass ionomer sealer and to test whether pretreatment of the instrumented canal to alter or remove the smear layer might enhance the reinforcement. STUDY DESIGN: Ninety single-canaled roots of standardized dimensions were instrumented to International Standards Organization size 45 and were analyzed for resistance to vertical fracture. Six groups were tested (n = 15). RESULTS: No significant difference in fracture resistance was observed between any of the groups. CONCLUSIONS: Under the conditions of this study, reinforcement of endodontically treated mature teeth by placement of adhesive materials in the root was not demonstrated.

Analysis of Variance↗
PubMed2000

Quality of root-end preparations using ultrasonic and rotary instrumentation in cadavers.

Prior investigations have demonstrated dentinal cracking and chipping during ultrasonic preparation of the root-end. This study compared the frequency of cracking and chipping in two groups, cadaver and extracted teeth, using an indirect resin technique. Preparations were performed using either a 33 1/2 inverted cone bur in a high-speed handpiece, or with ultrasonics using a CT-2 tip at either high or low intensity. After replication of the root-end in epoxy resin, all teeth were evaluated for cracking and chipping under scanning electron microscopy. Statistical analysis using a general contingency table or ANOVA with Scheffé post-hoc analysis (p = 0.05) revealed no significant difference between all groups in terms of root-end cracking. In extracted teeth (n = 15), rotary instrumentation produced less chipping than either ultrasonic technique. Varying the intensity was not significant. There was no significant difference between any instrumentation group in cadaver teeth (n = 10) related to the amount of chipping.

Analysis of Variance↗
PubMed1999

Comparison of the obturation of lateral canals by six techniques.

The following obturation techniques were compared on their ability to obturate lateral canals in vitro, lateral condensation (LC), continuous wave of condensation (CW), warm vertical condensation (WV), carrier-based thermoplasticized gutta-percha (CB), warm lateral condensation (WL), and vertically condensed high-temperature gutta-percha (HT). A root canal system with lateral canals in the coronal, middle, and apical thirds was prepared in resin blocks. Each block was obturated using each technique (n = 30, 15 each, with and without sealer). The length of gutta-percha and sealer in each of the lateral canals was measured with a measuring microscope and statistically compared. All techniques obturated all three levels of lateral canals with sealer. WV, CB, and CW were able to fill the lateral canals with gutta-percha significantly better when root canal sealer was used. WV, CB, CW, and HT filled the coronal and middle lateral canals significantly better with gutta-percha than LC or WL condensation. CB and CW filled the apical lateral canal significantly better with gutta-percha than HT, WV, WL, or LC.

Analysis of Variance↗
PubMed1997

Palindromic oligonucleotide-directed enzymatic determination of 2'-deoxythymidine 5'-triphosphate and 2'-deoxycytidine 5'-triphosphate in human cells.

A new method is presented for the determination of 2'-deoxythymidine 5'-triphosphate and 2'-deoxycytidine 5'-triphosphate concentrations within human cells based on a DNA polymerase reaction directed by a palindromic oligonucleotide precursor. Two 19-mer oligonucleotide precursors are employed that contain a common 8-mer palindromic sequence followed by a sequence-specific insertion site and a 5'-oligodeoxythymidylate tail. To conduct a measurement, two molecules of the 19-mer oligonucleotide precursor are first annealed to form a pair of symmetrical template-primer addition sites at their 3'-termini that are coded for the analyte of interest, present in limiting amounts. The Klenow fragment of Escherichia coli DNA polymerase I then elongates the template-primer by the addition of two molecules of the complementary deoxyribonucleotide analyte. Following the addition of the analyte molecules, the template-primer is extended with a 10-mer oligo(dA) tail in the presence of excess dATP and the Klenow fragment. The result is a 30-mer palindromic oligonucleotide that can be separated from any remaining 19-mer precursor and quantified by paired-ion HPLC using UV detection. Since the molar extinction coefficient of the 30-mer palindromic oligonucleotide is much larger than that of the nucleotide analyte alone, the UV signal is markedly enhanced, thereby increasing sensitivity. Details describing this method and the application of it to measure these analytes in as few as 2.5 x 10(6) human cells are presented.

Adult↗
PubMed1994

[Intensive back exercises 5 weeks after surgery of lumbar disk prolapse. A prospective, randomized multicenter trial with a historical control group].

An intensive, dynamic rehabilitation program applied to patients who had undergone first time lumbar discectomy was evaluated in a multicentre, clinical trial. Ninety-six patients between 18 and 70 years of age who had been operated within the period September 1989 to May 1990 at the Department of Neurosurgery, Copenhagen County Hospital, Glostrup were consecutively randomized into one of two rehabilitation programs: a) traditional mild, general mobility-improving exercises within pain limits; or b) intensive dynamic back extension and abdominal exercises without low back pain being the limiting factor. Both groups underwent 14 hours of treatment over a period of six weeks, starting five weeks after surgery. Seventy-six patients operated within the period January 1989 to September 1989 formed the historical control group. The results at follow-up at 26 weeks favoured intensive exercises with regard to the patients disability-index and working capabilities. The results are statistically significant. After one year a trend favouring intensive exercises can be observed. No differences in pain or objective measurements were found. A rehabilitation program using intensive exercises without back pain being the limiting factor appears to give the patients increased behavioural support, resulting in improvements in work capacity and reduction in patients' self-rated disability.

Adolescent↗
PubMed1994

Brain biopsy in AIDS. Diagnostic value and consequence.

Nineteen male patients with AIDS were investigated by biopsy of brain lesions. Six patients had progressive multiple leucoencephalopathy and no specific treatment was given. Toxoplasmosis (two patients), bacterial abscesses (two cases), viral encephalitis (two patients) and only gliosis (two cases) accounted for almost half of the cases. A fungal infection, a lymphoma and a sarcoma-like tumour were found in three patients. In two patients the biopsy was not diagnostic: one had only necrosis and one had normal findings. The biopsy findings gave reason for modifying the treatment in only three cases. The mean survival rate was relatively short, only 76 days with a range from 1 to 1041 days. Two patients were in a very bad clinical condition at the time of biopsy and one died of a haemorrhagic complication due to the biopsy. In ten cases an autopsy was carried out. In five cases there was agreement between the biopsy and autopsy findings. In the other five cases the autopsy findings differed widely. In our experience we can recommend cerebral biopsy in patients with AIDS only after treatment for toxoplasmosis and mainly to estimate the prognosis.

AIDS Dementia Complex↗
PubMed1994

Treatment of shunt-related cerebral ventriculitis due to Corynebacterium jeikeium with vancomycin administered intraventricularly. Case report.

A 52-year-old female with subarachnoid haemorrhage and hydrocephalus was treated with external and later internal drainage. She developed ventriculoperitoneal shunt-related ventriculitis caused by Corynebacterium jeikeium. The infection was unsuccessfully treated with intravenous vancomycin. It was controlled only after shunt removal and administration of intraventricular vancomycin as well as systemic vancomycin, rifampicin and fusidic acid. A review of the literature confirmed our experience that vancomycin given intraventricularly is well tolerated and doses can be individualized by measuring vancomycin levels in cerebrospinal fluid.

Catheterization↗
PubMed1989

Structure-activity relationship of the preservation and restoration of glucocorticoid receptors in rat hepatocytes and rat liver homogenates by sulfhydryl, phosphorothioate and disulfide compounds.

The purpose of this work was to examine whether the ability of dithiothreitol to preserve the steroid-binding capacity of glucocorticoid receptors in subcellular preparations is specific or a general property of sulfhydryl compounds and selected phosphorothioate and disulfide derivatives. A further goal was to see if this effect could be demonstrated in intact cells. The ability to preserve the steroid-binding capacity of the glucocorticoid receptor is not a universal property of all sulfhydryl compounds since many of the compounds tested were inactive. The steroid-binding capacity of the glucocorticoid receptor of the 100,000 g supernatant of rat liver homogenate is preserved/restored by sulfhydryl compounds containing a mercaptoethylamine or mercaptopropylamine subunit. However, small changes in the structure of the sulfhydryl compound such as the rearrangement of a methylene group significantly alter its effectiveness. All of the phosphorothioates examined are derivatives of active sulfhydryl compounds and are effective in preserving steroid-binding. The extent of metabolism of the phosphorothioates and their failure to restore steroid-binding capacity after short-time exposure to receptor preparations are consistent with the sulfhydryl form being the active form of the phosphorothioates. S-2-(3-Amino-propylamino)ethylphosphorothioic acid (WR 2721) preserved steroid-binding capacity in isolated intact rat hepatocytes down to 25 microM demonstrating that concentrations obtainable in whole animals are effective with intact cells. Disulfide derivatives of active sulfhydryl compounds are either immediately toxic or ineffective except for 1,18-diamino-6,13-diaza-9,10-dithiaoctadecane (WR 149,024) which is more effective than its corresponding sulfhydryl. The demonstration that some sulfhydryl-forming compounds preserve the steroid-binding capacity of glucocorticoid receptors in intact cells at potentially physiologically obtainable concentrations suggests a potential role for these or similar compounds to bolster the efficacy of conventional glucocorticoid therapy.

Adrenalectomy↗
PubMed1989

Photocarcinogenesis is retarded by a partly photodegraded solution of para-aminobenzoic acid.

A solution of para-aminobenzoic acid (PABA) was exposed to ultraviolet (UV) radiation emitted from a Philips TL 40 W/12 sunlamp and the degree of photodegradation following an exposure of 27 J/cm2 was estimated to be approximately 40%. The formation of the photoproducts was confirmed by mass spectroscopy and UV spectroscopy. The solution was painted on the backs of hairless light-pigmented mice prior to daily UV irradiation by the above sunlamp, and this procedure was continued for 30 weeks. The preirradiated solution of PABA significantly retarded the tumor induction time and reduced significantly the number of squamous cell carcinomas compared with nonprotected controls. This tumor-retarding ability did not differ significantly from the effect achieved when using nonirradiated PABA.

4-Aminobenzoic Acid↗
PubMed1988

Measurements of the photodegradation of PABA and some PABA derivatives.

The photodegradation of 4-aminobenzoic acid, 2-ethylhexyl N,N-dimethyl 4-aminobenzoate (Escalol 507) and 1-glyceryl 4-aminobenzoate (Escalol 106), resulting from irradiation by sun lamps, was examined by UV spectroscopy. 2-ethylhexyl N,N-dimethyl 4-aminobenzoate showed the longest half-life, indicating the highest photostability.

4-Aminobenzoic Acid↗
PubMed1985

Subsensitive pituitary cyclic AMP response to stress following adrenalectomy is not caused by loss of adrenal epinephrine.

We have previously reported that various stressors acutely elevate levels of pituitary cyclic AMP in vivo and that this stress response is not seen in animals tested 7 or 30 days post-adrenalectomy. In this report we present data that demonstrate that the loss of the pituitary cyclic AMP stress response following adrenalectomy is not the result of the loss of stress-induced adrenal epinephrine release. These data show that (1) although administration of epinephrine to intact rats does not elevate levels of pituitary cyclic AMP, administration of epinephrine to adrenalectomized animals does not elevate pituitary cyclic AMP levels in vivo; (2) splanchnic denervation prevents stress-induced adrenal epinephrine release but does not abolish stress-induced increases in pituitary cyclic AMP; and (3) the time course of the developing subsensitive pituitary cyclic AMP response to stress following adrenalectomy is much slower (2 to 3 days) than the loss of circulating epinephrine.

Adrenalectomy↗
PubMed1984

Adrenalectomy abolishes the stress-induced increase in pituitary cyclic AMP.

We have previously demonstrated that various stressors increase pituitary cyclic AMP in vivo in the rat. In the course of studying the mechanisms mediating this response, we examined the effect of bilateral adrenalectomy on footshock-induced increases in pituitary cyclic AMP. In unoperated rats, intermittent footshock markedly increased pituitary levels of cyclic AMP and plasma levels of corticosterone and prolactin. Adrenalectomy completely abolished the stress-induced increase in pituitary cyclic AMP. The marked increase in plasma prolactin following footshock was not affected by adrenalectomy. Our results indicate that adrenal factors are involved in the stress-induced increase in pituitary cyclic AMP.

Adrenalectomy↗