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  • Analytical Chemistry and Spectroscopy  (9)
  • Magnetic resonance imaging  (2)
  • glucagon  (2)
  • 1
    ISSN: 1432-1920
    Keywords: Internal auditory canal ; Acoustic schwannoma ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prospective baseline MRI was obtained on 31 patients who had “total” removal of acoustic schwannoma 6 months to 9 years previously. Follow-up MRI was performed after 1–2 years on patients with questionable abnormalities. We found four patterns (1) internal auditory canals (IAC) with nonenhancing soft-tissue strands, possibly scars or distorted residual nerves (8); (2) IAC with marginal enhancement-reactive dura mater (16); (3) IAC with contrast-enhancing globular tissues suggesting residual or recurrent tumour (5); (4) high-signal intensity in the IAC before contrast medium administration, probably related to graft with fat/fascia/muscle (2). Prospective 1-to 2-year follow-up studies were available in 8, 5, and 1 patients in groups 2, 3, and 4 respectively. In group 2, dural enhancement remained unchanged in 5 patients and decreased in 3. In group 3 follow-up showed 1 tumor recurrence (surgically confirmed) and 4 stable abnormalities. In group 4, follow-up in 1 of the 2 patients was stable. In groups 1 and 2, the MRI features correlate well with complete tumor removal. Whether follow-up in these groups is indicated needs to be determined. In group 3 residual or recurrent tumor cannot be excluded. In group 4, grafts may prevent adequate visualization of the IAC.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1920
    Keywords: Key words Internal auditory canal ; Acoustic schwannoma ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prospective baseline MRI was obtained on 31 patients who had “total” removal of acoustic schwannoma 6 months to 9 years previously. Follow-up MRI was performed after 1–2 years on patients with questionable abnormalities. We found four patterns (1) internal auditory canals (IAC) with nonenhancing soft-tissue strands, possibly scars or distorted residual nerves (8); (2) IAC with marginal enhancement-reactive dura mater (16); (3) IAC with contrast-enhancing globular tissues suggesting residual or recurrent tumour (5); (4) high-signal intensity in the IAC before contrast medium administration, probably related to graft with fat/fascia/muscle (2). Prospective 1- to 2-year follow-up studies were available in 8, 5, and 1 patients in groups 2, 3, and 4 respectively. In group 2, dural enhancement remained unchanged in 5 patients and decreased in 3. In group 3 follow-up showed 1 tumor recurrence (surgically confirmed) and 4 stable abnormalities. In group 4, follow-up in 1 of the 2 patients was stable. In groups 1 and 2, the MRI features correlate well with complete tumor removal. Whether follow-up in these groups is indicated needs to be determined. In group 3 residual or recurrent tumor cannot be excluded. In group 4, grafts may prevent adequate visualization of the IAC.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0428
    Keywords: Growth hormone ; somatotrophic diabetes ; metasomatotrophic diabetes ; hyperinsulinaemia ; hypoinsulinaemia ; insulin content of pancreas ; insulin responses to glucose ; glucagon ; arginine ; meals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Growth hormone treatment produced somatotrophic diabetes, with hyperglycaemia, polyuria, glycosuria and elevation in serum non-esterified fatty acids (NEFA) in dogs. Early in this diabetes, fasting serum immunoreactive insulin (IRI) rose 20-fold, the insulin/glucose (I/G) ratio rose 10-fold and in response to glucose infusion, the rise in IRI was twice the normal. In the latter half of the continued growth hormone treatment, the intensity of the diabetes increased, serum IRI declined to the normal level and the I/G ratio became subnormal. Late in the treatment, following glucose infusion, there was no change in serum IRI, no fall in NEFA and further depression of glucose tolerance. In metasomatotrophic diabetes, in which hyperglycaemia, glycosuria and high NEFA level persisted, fasting serum IRI was normal during several months, then became subnormal and the I/G ratio was diminished further. Following glucose IV there was no change in serum IRI, no fall in NEFA and low glucose tolerance. The normally-occurring rises in serum IRI following arginine and glucagon IV and after the ingestion of a meal were absent. These permanently diabetic dogs were responsive to insulin IV. The insulin content of the pancreas was reduced to about 1.2% of the normal after 14 months of this diabetes. From the sequence of change it is concluded that growth hormone induced metasomatotrophic diabetes by causing excessive secretion of insulin under basal and stimulative conditions, leading to permanent loss of function of the beta cells of the pancreatic islets, to such an extent that basal insulin secretion was low and the ability to secrete extra insulin in response to stimuli was lost.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 15 (1978), S. 205-212 
    ISSN: 1432-0428
    Keywords: Growth hormone ; somatotrophic diabetes ; diabetes ; glucagon ; arginine ; serum insulin ; immunoreactive insulin ; hyperinsulinaemia ; insulin secretion ; insulin-secretory responses ; augmentation of insulin secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Growth hormone injected daily in 6 dogs for 6 days caused a 20-fold elevation in fasting serum immunoreactive insulin (IRI) without appreciable change in serum glucose in 1 day. In the somatotrophic diabetes that occurred after 2 days, the hyperinsulinaemia was maintained and the serum IRI/glucose (I/G) ratio declined from the early high level but remained elevated. During this treatment, in response to glucose infusion, the rise in serum IRI above the initially high fasting level was 16 times the normal. In response to glucagon, the rise in IRI was twice the normal and the rise in glucose was more prolonged, resulting in a decline in the I/G ratio. In response to arginine infusion, the rise in serum IRI was 8 times the normal and the rise in the I/G ratio was twice normal. Following a meal, the rise in serum IRI was 8 times the normal. Thus, with growth hormone treatment the insulin secretory responses to these stimulating factors were magnified over the already elevated fasting level of secretion. The insulin content of the pancreas was reduced to less than 10% of normal by growth hormone treatment for 6 days, due apparently to elevation of the rate of secretion over the rate of formation of insulin.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic model for chemical events occurring within the high pressure electron capture mass spectrometer (HPECMS) ion source is developed which includes four different pathways by which unconventional negative ions can be produced. These routes to unusual ions include reactions of gas phase free radicals, surface-assisted reactions, ion-electron and ion-ion recombination reactions, and ion-wall neutralization. The model developed here provides a diagnostic tool useful for the elucidation of unusual HPEC spectra. Such spectra for two environmentally important classes of compounds are explained by use of the model. These compound classes include the trifluoroacetic derivatives of polycyclic aromatic amines, which have been shown to be present in materials derived from liquified coal, and the derivatives of hexachlorocyclopentadiene, which are used as pesticides. It is shown in this study that several processes, in addition to electron capture, can be operative in the typical HPECMS ion source, and that these processes can be used advantageously for the generation of informative and sensitive mass spectral signals.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 613-618 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several aminophenanthrenes have been examined with electron impact mass spectrometry. The trifluoroacetic anhydride (TFAA) and perfluoropropionic anhydride (PFPA) derivatives of 4-aminophenanthrene have been studied with electron impact as well as both positive and negative ion chemical ionization mass spectrometry utilizing methane as a reagent gas. The resulting mass spectra indicate a loss of water from the derivatives and a mechanism is proposed to account for this loss. The spectra also indicate unique fragmentation patterns associated with the position of the substituent, particularly the four position which is in the region of the molecule termed the bay region. Another interesting aspect is the spectral differences observed for the TFAA and PFPA derivatives of 4-aminophenanthrene. The positive ion chemical ionization mass spectrum of the TFAA derivative indicates an ion [M + H — H2O]+; however, the mass spectrum of the PFPA derivative of 4-aminophenanthrene indicates no water loss from the [M + H]+ ion. The negative ion chemical ionization mass spectra of the two derivatives are also very different. The mass spectrum of the TFAA derivative shows an [M — 18]- ion and the PFPA derivative shows successive losses of HF with no apparent loss of water.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 520-522 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Since the methylation of acids with diazomethane is widely used in trace analysis, it is extremely important for those using this technique to be alert to the analysis of compounds containing other functional groups which might become methylated with high concentrations of diazomethane. We have shown that by adding an excess of diazomethane to dansylated amino acids, not only is the methyl ester formed, but the products can be further methylated. The only remaining acidic hydrogen in the molecule is the hydrogen attached to the sulfonamide nitrogen, and the mass spectrometry results indicate that the methyl ester is formed first, and the N-methylated derivative is formed with excess diazomethane.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 191-197 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Accurate tail-to-peak intensity ratios are extracted from the spectra produced in a Si(Li) detector by x-rays of energies 2-10 keV. The widely used model of a surface layer of incomplete charge collection fails to explain the energy dependence of these data. The model is augmented to include loss of photoelectrons travelling back into the ICC layer from an interaction in the active silicon region; this gives excellent agreement with experiment. It is shown that the detection efficiency in the region of low x-ray energy may be deduced from the tail-to-peak ratios, together with measurement of the thicknesses of the beryllium window and the metal contact; a potential source of error in measuring the latter by the popular fluorescence technique is demonstrated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 21 (1992), S. 223-227 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: If the lineshape response of a Si(Li) detector is measured using monoenergetic x-rays provided by a monochromator, it must be convoluted by a Lorentzian of appropriate width in order to represent the lineshape encountered in directly measured x-ray spectra. It is shown that the Lorentzian component is responsible for a significant fraction of low-energy peak tailing, a phenomenon usually attributed to detector imperfections.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 18 (1989), S. 235-242 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Various semi-empirical schemes for generating x-ray attenuation coefficients, μ/ρ, devised primarily for use in electron probe microanalysis, are considered for application in the PIXE analysis of thick specimens where the relevant x-ray energy region is 1-40 keV. Using selected high-accuracy experimental data, it is shown that current theoretical values of μ/ρ agree better with the data than do the various schemes. The errors transmitted into PIXE analysis by use of the theoretical values are estimated, and a new parameterization of these values suitable for microcomputer use is justified and tested.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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