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Biomedical subjects

U Arnold

Publications and source records attributed to U Arnold.

At least 19 recordsLinked to original sources
PubMed2003

Influenza B pneumonia with Staphylococcus aureus superinfection associated with parvovirus B19 and concomitant agranulocytosis.

An 11-year-old patient with anamnestic fever for 3 days and signs of upper respiratory tract infection underwent fulminant Staphylococcus aureus pneumonia with concomitant agranulocytosis. From autopsia influenza B virus and parvovirus B19 were detected by nucleic acid amplification technique (NAT). Specific IgG but no IgM points to preexisting parvovirus B19 infection. Whether in this case agranulocytosis can be interpreted as early manifestation of reactivated parvovirus B19 infection is under discussion. Therefore, parvovirus B19 could have provoked a foudroyant course of influenza B pneumonia which was superinfected with S. aureus.

Agranulocytosis↗
PubMed2001

Proteolytic degradation of ribonuclease A in the pretransition region of thermally and urea-induced unfolding.

The method of limited proteolysis has proven to be appropriate for the determination of unfolding rate constants (k(U)) of ribonuclease A in the transition region of thermal denaturation [Arnold, U. & Ulbrich-Hofmann, R. (1997) Biochemistry 36, 2166-2172]. The aim of the present paper was to extend this procedure to the pretransition region of thermally and urea-induced denaturation where spectroscopic methods do not allow direct measurement of k(U). The results show that the approach can be applied successfully to denaturing (free energy of unfolding Delta G < 10 kJ.mol(-1)) and to marginally native conditions (Delta G = 10-25 kJ.mol(-1)). Under moderately (Delta G = 25-30 kJ.mol(-1)) and strongly native conditions (Delta G > 30 kJ.mol(-1)), however, the determination of kU was not possible in this way as the proteolytic degradation of ribonuclease A by thermolysin or trypsin was no longer determined by global unfolding. Here, proteolysis proceeds via the native RNase A. In the presence of low concentrations of urea, the rate constants of proteolysis were, surprisingly, smaller than in the absence of urea. As the protease activity has been taken into account, this result points to a local stabilization of the RNase A molecule.

Bacillus↗
PubMed2001

The use of fibrin beads for tissue engineering and subsequential transplantation.

New biological technologies such as tissue engineering procedures require the transplantation of functionally active cells within supportive carrier matrices. This paper describes a sequential culture procedure for different types of cells. The technique includes the initial preparation of a mixed alginate-fibrin vehicle that guaranteed an initial cell proliferation and differentiation to establish a stable matrix structure, and the subsequent removal of the alginate component prior to transplantation to circumvent the problem of missing bioresorbability. The resulting biodegradable carrier is mechanically stable and promotes further tissue maturation. Chondrocytes, periosteal-derived cells, as well as nucleus pulposus cells were entrapped in fibrin-alginate beads and in fibrin beads. The results indicate a promising technical approach to create stable transplants for reconstructive surgery of cartilage and bone.

Alginates↗
PubMed2001

Increased proteolytic resistance of ribonuclease A by protein engineering.

Although highly stable toward unfolding, native ribonuclease A is known to be cleaved by unspecific proteases in the flexible loop region near Ala20. With the aim to create a protease-resistant ribonuclease A, Ala20 was substituted for Pro by site-directed mutagenesis. The resulting mutant enzyme was nearly identical to the wild-type enzyme in the near-UV and far-UV circular dichroism spectra, in its activity to 2',3'-cCMP and in its thermodynamic stability. However, the proteolytic resistance to proteinase K and subtilisin Carlsberg was extremely increased. Pseudo-first-order rate constants of proteolysis, determined by densitometric analysis of the bands of intact protein in SDS-PAGE, decreased by two orders of magnitude. In contrast, the rate constant of proteolysis with elastase was similar to that of the wild-type enzyme. These differences can be explained by the analysis of the fragments occurring in proteolysis with elastase. Ser21-Ser22 was identified as the main primary cleavage site in the degradation of the mutant enzyme by elastase. Obviously, this bond is not cleavable by proteinase K or subtilisin Carlsberg. The results demonstrate the high potential of a single mutation in protein stabilization to proteolytic degradation.

Alanine↗
PubMed2000

Differences in the denaturation behavior of ribonuclease A induced by temperature and guanidine hydrochloride.

Moderate temperatures or low concentrations of denaturants diminish the catalytic activity of some enzymes before spectroscopic methods indicate protein unfolding. To discriminate between possible reasons for the inactivation of ribonuclease A, we investigated the influence of temperature and guanidine hydrochloride on its proteolytic susceptibility to proteinase K by determining the proteolytic rate constants and fragment patterns. The results were related to changes of activity and spectroscopic properties of ribonuclease A. With thermal denaturation, the changes in activity and in the rate constants of proteolytic degradation coincide and occur slightly before the spectroscopically observable transition. In the case of guanidine hydrochloride-induced denaturation, however, proteolytic resistance of ribonuclease A initially increases accompanied by a drastic activity decrease far before unfolding of the protein is detected by spectroscopy or proteolysis. In addition to ionic effects, a tightening of the protein structure at low guanidine hydrochloride concentrations is suggested to be responsible for ribonuclease A inactivation.

Chromatography, High Pressure Liquid↗
PubMed2000

Influencing factors on perioperative morbidity in knee arthroplasty.

In an unselected, prospective case control study, the incidence of risk factors and perioperative complications was investigated in 237 knees (203 patients) undergoing implantation of cementless total knee endoprostheses. Intraoperative complications and postoperative complications occurred in 84 patients (99 knees), with 61 specific orthopaedic complications in 50 patients (57 knees) and 74 nonsurgical complications in 55 patients (65 knees). The presence of cardiac, neurologic, or psychiatric concomitant diseases, advanced age, male gender, high-risk anesthesia scores, number and extent of intraoperative blood pressure fluctuations, and surgery under intubation anesthesia are associated significantly with the incidence of nonsurgical perioperative complications. In contrast, body weight, concomitant metabolic and circulatory diseases, previous surgery on the joint, origin of the articular disease, and the duration of surgery and tourniquet time do not correlate with the probability of a nonsurgical perioperative complication. A significant correlation with the parameters investigated could not be found for the occurrence of specific orthopaedic complications. The current report identifies specific risk factors that define patients with risk of having perioperative complications according to objective criteria. These parameters must be given individual consideration when establishing the indication and planning of surgery.

Adult↗
PubMed1999

Modification of the unfolding region in bovine pancreatic ribonuclease and its influence on the thermal stability and proteolytic fragmentation.

Ribonuclease (RNase) A and the more stable glycosylated RNase B differ by a carbohydrate moiety (GlcNAc2Man5-9) attached to Asn34. As previously shown, the first proteolytic cleavage sites to appear on thermal denaturation of both enzymes are in the structural region around Asn34. To discriminate the contribution of the modifying moiety to the stabilization toward thermal unfolding, on the one hand, and proteolytic fragmentation, on the other hand, the carbohydrate chain of RNase B was shortened by treatment with glycosidases to obtain GlcNAc-RNase and (GlcNAc)2Man3 -RNase and extended by binding to concanavalin A or concanavalin A-agarose. The results show a saltatory increase of the thermal unfolding constants and transition temperatures of GlcNAc-RNase in comparison to RNase A, whereas the extension of the modification at Asn34 in the other RNase species does not further increase thermal stability. Therefore, the stability difference between RNase A and RNase B derivatives is attributed to the first carbohydrate unit. In contrast, the rate of proteolysis decreases gradually with increasing volume of the modifying moiety. As concluded from the analysis of the primary cleavage fragments, the main degradation pathway is shifted from the Asn34-Leu35 to the Thr45-Phe46 peptide bond due to increasing shielding effects.

Animals↗
PubMed1999

[Postnatal skeletal and body weight in beagles].

Growth of beagles is described on the basis of body weight and 14 bone measures. Eighteen male and 19 female dogs were investigated at 14 different ages from birth to the 13th month of life. Characteristics of the growth curves were evaluated using the modified Janoschek growth curve. For the classification into dwarfish, low, normal, big and gigantic growth, the growth curves are presented with percentiles. The arithmetic means and standard deviations for both sexes are presented in tables. Additionally, the degrees of maturity at birth (relative proportion of final weight or bone measure), the point of inflection for the growth curve, the times to grow to 50 and 95% of the final measures, and the asymptotic measures are also presented in tables. Sex differences in growth for the body weight and bone measures are discussed. Growth differences between large and small dog breeds are considered. The conclusion is drawn that the feeding of dogs has to be adapted to the growth course.

Aging↗
PubMed1999

Basal forebrain amnesia: does the nucleus accumbens contribute to human memory?

OBJECTIVE: To analyse amnesia caused by basal forebrain lesions. METHODS: A single case study of a patient with amnesia after bleeding into the anterior portion of the left basal ganglia. Neuropsychological examination included tests of attention, executive function, working memory, recall, and recognition of verbal and non-verbal material, and recall from remote semantic and autobiographical memory. The patient's MRI and those of other published cases of basal forebrain amnesia were reviewed to specify which structures within the basal forebrain are crucial for amnesia. RESULTS: Attention and executive function were largely intact. There was anterograde amnesia for verbal material which affected free recall and recognition. With both modes of testing the patient produced many false positive responses and intrusions when lists of unrelated words had been memorised. However, he confabulated neither on story recall nor in day to day memory, nor in recall from remote memory. The lesion affected mainly the nucleus accumbens, but encroached on the inferior limb of the capsula interna and the most ventral portion of the nucleus caudatus and globus pallidus, and there was evidence of some atrophy of the head of the caudate nucleus. The lesion spared the nucleus basalis Meynert, the diagnonal band, and the septum, which are the sites of cholinergic cell concentrations. CONCLUSIONS: It seems unlikely that false positive responses were caused by insufficient strategic control of memory retrieval. This speaks against a major role of the capsular lesion which might disconnect the prefrontal cortex from the thalamus. It is proposed that the lesion of the nucleus accumbens caused amnesia.

Amnesia↗
PubMed1998

Influence of the carbohydrate moiety on the proteolytic cleavage sites in ribonuclease B.

The influence of glycosylation on proteolytic degradation was studied by comparing cleavage sites in ribonuclease A (RNase A) and ribonuclease B (RNase B), which only differ by a carbohydrate chain attached to Asn34 in RNase B. Primary cleavage sites in RNase B were determined by identifying complementary fragments using matrix-assisted laser desorption/ionization mass spectrometry and compared with those in RNase A [Arnold et al. (1996), Eur. J. Biochem. 237, 862-869]. RNase B was cleaved by subtilisin even at 25 degrees C at Ala2-Ser21 as known for RNase A. Under thermal unfolding, the peptide bonds Asn34-Leu35 and Thr45-Phe46 were identified as primary cleavage sites for thermolysin and Lys31-Ser32 for trypsin. These sites are widely identical with those in RNase A. Treatment of reduced and carbamidomethylated RNase A and RNase B with trypsin led to a fast degradation and revealed new primary cleavage sites. Therefore, the state of unfolding seems to determine the sequence of degradation steps more than steric hindrance by the carbohydrate moiety does.

Carbohydrate Metabolism↗
PubMed1997

Kinetic and thermodynamic thermal stabilities of ribonuclease A and ribonuclease B.

The thermal stabilities of ribonuclease A (RNase A) and ribonuclease B (RNase B), which possess identical protein structures but differ by the presence of a carbohydrate chain attached to Asn34 in RNase B, were studied by proteolysis and UV spectroscopy at pH 8.0. Proteolysis was quantified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and densitometry. Increasing protease concentrations led to a hyperbolic increase of the rate constants of proteolysis. With thermolysin, which attacks the unfolded molecules only, the thermal unfolding constants were determined by extrapolating the rate constants of proteolysis to infinite concentration of protease. With trypsin, the unfolding constants of RNase A could be confirmed. Subtilisin attacked even the native RNases, where RNase B was more stable toward proteolytic degradation. Kinetic stabilities (deltaG++) calculated from the unfolding constants for temperatures between 52.5 and 65 degrees C revealed a higher kinetic stability of RNase B, which results from enthalpic effects only, whereas entropic effects counteract stabilization. delta deltaG++ at the transition temperature of RNase A (60.4 degrees C) was 2.2 +/- 0.3 kJ mol(-1). Thermodynamic stabilities (deltaG) were estimated from the thermal transition curves at 287 nm for the temperature range from 55 to 70 degrees C. For 17.5-25 degrees C, deltaG values were determined from transition curves of unfolding induced by guanidine hydrochloride and extrapolation of the free energy values to those in the absence of denaturant. At all temperatures, RNase B proved to be more stable than RNase A with essentially the same enthalpy and entropy of unfolding. delta deltaG was 2.5 +/- 0.2 kJ mol(-1) at 60.4 degrees C and 2.3 kJ mol(-1) at 25 degrees C.

Enzyme Stability↗
PubMed1996

Thermal unfolding and proteolytic susceptibility of ribonuclease A.

With the aim to localize the structural region that becomes first accessible to proteolytic attack during thermal unfolding, the proteolysis of ribonuclease A was studied in the temperature range of 20-65 degrees C. Subtilisin, proteinase K, and elastase proved to be not appropriate as indicators of thermal unfolding, because even the native protein molecule was cleaved by these proteases. In contrast, chymotrypsin, trypsin, and thermolysin attacked ribonuclease A only after its thermal treatment. For thermolysin and trypsin, the first primary cleavage sites of ribonuclease A could be identified by blotting of the electrophoretic bands, partial N-terminal sequencing of the fragments and assignment according to their molecular masses. The results were confirmed by the separation of the proteolytic fragments by HPLC and subsequent matrix-assisted laser desorption ionization mass spectrometry. The first cleavage sites were determined to be Lys31-Ser32 and Arg33-Asn34 for trypsin and Asn34-Leu35 and Thr45-Phe46 for thermolysin. Hence the structural region from Lys31 to Leu35, together with the adjacent beta-structure containing Thr45-Phe46, is suggested to represent a labile region of the ribonuclease A molecule, which becomes exposed at thermal denaturation.

Amino Acid Sequence↗
PubMed1996

Analysis of free amino acids in green coffee beans. II. Changes of the amino acid content in arabica coffees in connection with post-harvest model treatment.

To investigate amino acid changes in green coffee beans in the post-harvest period, amino acid concentrations were determined in green beans and after modelled drying, fermentation and storage. After the drying at alternating temperatures up to maximally 40 degrees C, considerable changes in the concentrations of individual amino acids were identified. At the beginning of the storage period, significant changes in concentration were found to a minor extent. Under the condition of drying, it was mainly the concentration of glutamic acid that changed considerably. There was an increase in all the samples by 500 mg/kg dry matter on average, which corresponds to an increase of about 50% of the original value. In contrast, the concentration of aspartic acid in most of the samples decreased clearly due to drying. For the predominant part of the coffee samples, there was a significant increase in the hydrophobic amino acids Val, Phe, Ile and Leu. Changes of the quantities of other amino acids were non-uniform and only insignificant. Constant drying at 80 degrees C for most of the amino acids brought about only minor concentration changes compared to those values obtained at 40 degrees C. Modelled fermentation had no significant effect on the concentrations of the individual amino acids. After a 4-week storage of dried beans, amino acid concentrations did not change further. It is very possible that different post-harvest treatment parameters may influence the amount of aroma precursor compounds in the coffee beans.

Amino Acids↗
PubMed1995

The effect of dietary salt on insulin sensitivity.

Acute reduction of salt intake causes an increase in serum lipid and insulin levels in healthy volunteers and patients with essential hypertension, suggesting induction of insulin resistance by salt restriction. Direct measurements of insulin sensitivity using the euglycaemic clamp showed no significant change after 7 days of salt restriction. Our previous study showed a time dependent course of dyslipidaemia after institution of a low salt diet. We therefore assessed insulin sensitivity (M-value) under euglycaemic conditions (clamp technique) at discrete time points using a parallel group design. Two groups of healthy males were examined on high (200 mmol d-1) and low (20 mmol d-1) salt intake. One group (n = 7, 25 +/- 3 years, BMI 22.4 +/- 2.1 kg m-2) received high and low salt diet in random order each for 7 days. The other group (n = 7, 26 +/- 3 years, 22.1 +/- 1.9 kg m-2) received the respective diet in random order for 3 days. A significantly (P < 0.01) different mean M-value was noted in the group receiving the diets for 3 days, i.e. after low salt intake it was 7.4 +/- 1.2 mg kg-1 min-1 and after high salt intake 8.6 +/- 1.1 mg kg-1 min-1. In contrast, the mean M-value was similar after low and high salt periods in the group of individuals who had been studied after 7 days on either salt take (7.8 +/- 1.8 on low salt vs. 7.6 +/- 1.3 mg kg-1 min-1 on high salt).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Analysis of free amino acids in green coffee beans. I. Determination of amino acids after precolumn derivatization using 9-fluorenylmethylchloroformate.

For the determination of free amino acids in green coffee beans, 9-fluorenylmethylchloroformate was applied successfully as the precolumn derivatization agent. The separation of the 27 free amino acids of green coffee as yet identified or quantitatively determined is almost complete. The paper describes in detail the conditions of extraction, derivatization and resolution and presents reproducible data of standard curves and of quantitative results. It has been demonstrated that by applying the extraction procedure described, 99.8% of the free amino acids detectable by this method are extracted. On principle, Arabica and Robusta coffees contain the same main and minor amino acids. It was possible for the first time to determine the free amino acids ornithine, beta-alanine and pipecolic acid quantitatively in Arabica and Robusta coffees as well as hydroxyproline in Arabica coffees.

Amino Acids↗
PubMed1993

Angiotensin II enhances insulin sensitivity in healthy volunteers under euglycemic conditions.

OBJECTIVE: It has been postulated that vasoconstrictors cause insulin resistance. This effect has been documented for epinephrine but not for angiotensin II (Ang II). The aim of this study was to investigate the effect of the latter on insulin sensitivity. DESIGN: In order to study the influence of subpressor doses of Ang II on insulin-mediated glucose uptake under euglycemic conditions, eight healthy volunteers were allocated in random order to sham infusion or infusion of Ang II (first 0.75 ng/kg per min and subsequently 1.5 ng/kg per min). In addition, in seven of the subjects Ang II was infused after 3 days of indomethacin pretreatment (150 mg/day). METHODS: Insulin-mediated glucose uptake (expressed as M value) was measured with the euglycemic clamp technique. Insulin levels were measured enzymatically, plasma renin activity, Ang II, aldosterone and C-peptide levels by radioimmunoassay, blood pressure by Dinamap and muscle blood flow by plethysmography. RESULTS: The M value after sham infusion was 7.81 +/- 1.52 mg/kg per min and after 1.5 ng/kg Ang II per min was 9.76 +/- 1.26 mg/kg per min (P < 0.001). Indomethacin pretreatment did not abolish the Ang II-induced rise in the M value. Mean arterial blood pressure during the euglycemic clamp was unchanged with sham infusion and the low dose of Ang II. It increased slightly with the higher dose of Ang II. Inferior limb muscle perfusion was higher after infusion of Ang II than after sham infusion; this effect was not obliterated by indomethacin pretreatment. CONCLUSIONS: Ang II increases insulin-mediated glucose uptake: that is, it enhances insulin sensitivity by mechanisms independent of prostaglandins. The observations are of potential relevance to the changes in insulin sensitivity in some forms of hypertension.

Adult↗
PubMed1991

[Serological diagnosis of cytomegalovirus-induced interstitial pneumonia in patients following bone marrow transplantation].

For diagnosis of the interstitial pneumonia conditioned by cytomegalovirus (CMV) an indirect immunofluorescence test was used to measure IgM and IgG antibodies to CMV in 369 serum specimens from 41 patients after bone marrow transplantation (BMT). An interstitial pneumonia conditioned by CMV was diagnosed in 5 patients either serological (4 patients) or by detection of cytomegaloviral infection typical inclusion bodies in lung cells (1 patient). The detection of antibodies to CMV for diagnosis of interstitial pneumonia conditioned by CMV is problematical in the phase immediately after BMT because bone marrow recipients are severely immunosuppressed by radiation and cytotoxic drugs received before transplantation. New method for detection of CMV-specific antigens are necessary.

Adolescent↗