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Biomedical subjects

S S Nielsen

Publications and source records attributed to S S Nielsen.

At least 19 recordsLinked to original sources
PubMed1998

Phage display selection can differentiate insecticidal activity of soybean cystatins.

Plant cysteine proteinase inhibitors (phytocystatins) have been implicated as defensive molecules against Coleopteran and Hemipteran insect pests. Two soybean cystatins, soyacystatin N (scN) and soyacystatin L (scL), have 70% sequence identity but scN is a much more potent inhibitor of papain, vicilin peptidohydrolase and insect gut proteinases. When these cystatins were displayed on phage particles, papain-binding affinity and CPI activity of scN were substantially greater than those of scL, in direct correlation with their relative CPI activity as soluble recombinant proteins. Furthermore, scN substantially delayed cowpea weevil (Callosobruchus maculatus (F.)) growth and development in insect feeding bioassays, whereas scL was essentially inactive as an insecticide. Papain biopanning selection of phage-displayed soyacystatins resulted in a 200-1000-fold greater enrichment for scN relative to scL. These results establish that binding affinity of cystatins can be used in phage display biopanning procedures to select variants with greater insecticidal activity, illustrating the potential of phage display and biopanning selection for directed molecular evolution of biological activity of these plant defensive proteins.

Amino Acid Sequence↗
PubMed1998

Effect of psychrotrophic microorganisms on the plasmin system in milk.

The psychrotrophic bacteria that are present in raw milk produce heat-stable proteases that affect the plasmin system and, in turn, the quality of the processed milk and other dairy products. Three bacterial strains, Pseudomonas spp. SRM21A and SRM28A and Pseudomonas fluorescens M3/6, were inoculated at a level of approximately 10(3) cfu/ml into reconstituted nonfat dry milk and incubated at 4 degrees C for up to 9 d. From each sample, casein and whey fractions were obtained and electrophoresed to visualize protein hydrolysis and plasmin activity. Colorimetric assays were used to quantify plasmin-related activities. The casein SDS-PAGE gels showed that, by 5 d of incubation, caseinolytic activity was visible in whey fractions of all three strains at the same molecular mass range as commercial bovine plasmin, which was used as a control. Colorimetric assays indicated that plasmin activity in the casein samples decreased as incubation time increased; plasmin activity in the whey samples increased, peaking at 5 to 7 d. Plasminogen activity decreased over time in the casein fraction and increased in the whey fraction. Protein immunodetection indicated crossreactivity between anti-bovine plasminogen and the plasmin and plasminogen from whey samples collected at 5 and 7 d from the incubated milk. The growth of the Pseudomonas strains tested and their concomitant production of proteases caused the release of plasmin and plasminogen from the casein micelle into the whey fraction.

Animals↗
PubMed1997

Presence in bovine milk of two protease inhibitors of the plasmin system.

Proteolysis, caused by the serine proteinase plasmin (EC 3.4.21.7) that is present in milk, influences the quality of dairy products. Within the plasmin system, activators and inhibitors control plasmin activity. This study investigated the presence in bovine milk of two serine proteinase inhibitors of the plasmin system, alpha(2)-antiplasmin and plasminogen activator inhibitor-1, and an isolation procedure used for partial purification of them from milk. Two colorimetric assays were used to detect either plasmin inhibitor activity or plasminogen activator inhibitor activity. Two inhibitors were partially purified from milk using a combination of ammonium sulfate fractionation and concanavalin A affinity chromatography. Plasminogen activator inhibitor-1 and alpha(2)-antiplasmin antigens, which were associated with the inhibitory activities from bovine milk, were visualized by Western blot using commercial polyclonal antibodies raised against the corresponding human inhibitors. Both inhibitors were present in milk as several forms, possibly from the formation of complexes with other milk proteins. The predominant forms of the inhibitors in milk exhibited an approximate molecular mass of 60 kDa for alpha(2)-antiplasmin and 55 kDa for plasminogen activator inhibitor-1.

Animals↗
PubMed1996

Two wound-inducible soybean cysteine proteinase inhibitors have greater insect digestive proteinase inhibitory activities than a constitutive homolog.

Diverse functions for three soybean (Glycine max L. Merr.) cysteine proteinase inhibitors (CysPIs) are inferred from unique characteristics of differential regulation of gene expression and inhibitory activities against specific Cys proteinases. Based on northern blot analyses, we found that the expression in leaves of one soybean CysPI gene (L1) was constitutive and the other two (N2 and R1) were induced by wounding or methyl jasmonate treatment. Induction of N2 and R1 transcript levels in leaves occurred coincidentally with increased papain inhibitory activity. Analyses of kinetic data from bacterial recombinant CysPI proteins indicated that soybean CysPIs are noncompetitive inhibitors of papain. The inhibition constants against papain of the CysPIs encoded by the wound and methyl jasmonate-inducible genes (57 and 21 nM for N2 and R1, respectively) were 500 to 1000 times lower than the inhibition constant of L1 (19,000 nM). N2 and R1 had substantially greater inhibitory activities than L1 against gut cysteine proteinases of the third-instar larvae of western corn rootworm and Colorado potato beetle. Cysteine proteinases were the predominant digestive proteolytic enzymes in the guts of these insects at this developmental stage. N2 and R1 were more inhibitory than the epoxide trans-epoxysuccinyl-L-leucylamide-(4-guanidino)butane (E-64) against western corn rootworm gut proteinases (50% inhibition concentration = 50, 200, and 7000 nM for N2, R1, and E-64, respectively). However, N2 and R1 were less effective than E-64 against the gut proteinases of Colorado potato beetle. These results indicate that the wound-inducible soybean CysPIs, N2 and R1, function in host plant defense against insect predation, and that substantial variation in CysPI activity against insect digestive proteinases exists among plant CysPI proteins.

Amino Acid Sequence↗
PubMed1996

Differential expression of soybean cysteine proteinase inhibitor genes during development and in response to wounding and methyl jasmonate.

Three cysteine proteinase inhibitor cDNA clones (pL1, pR1, and pN2) have been isolated from a soybean (Glycine max L. Merr.) embryo library. The proteins encoded by the clones are between 60 and 70% identical and contain the consensus QxVxG motif and W residue in the appropriate spatial context for interaction with the cysteine proteinase papain. L1, R1, and N2 mRNAs were differentially expressed in different organs of plants (juvenile and mature) and seedlings, although N2 mRNA was constitutive only in flowers. R1 and N2 transcripts were induced by wounding or methyl jasmonate (M-JA) treatment in local and systemic leaves coincident with increased papain inhibitory activity, indicating a role for R1 and N2 in plant defense. The L1 transcript was constitutively expressed in leaves and was induced slightly by M-JA treatment in roots. Unlike the chymotrypsin/trypsin proteinase inhibitor II gene (H. Peña-Cortés, J. Fisahn, L. Willmitzer [1995] Proc Natl Acad Sci USA 92: 4106-4113), expression of the soybean genes was only marginally induced by abscisic acid and only in certain tissues. Norbornadiene, a competitive inhibitor of ethylene binding, abolished the wounding or M-JA induction of R1 and N2 mRNAs but not the accumulation of the wound-inducible vspA transcript. Presumably, ethylene binding to its receptor is involved in the wound inducibility of R1 and N2 but not vspA mRNAs. Bacterial recombinant L1 and R1 proteins, expressed as glutathione S-transferase fusion proteins, exhibited substantial inhibitory activities against vicilin peptidohydrolase, the major thiol endopeptidase in mung bean seedlings. Recombinant R1 protein had much greater cysteine proteinase inhibitor activity than recombinant L1 protein, consistent with the wound inducibility of the R1 gene and its presumed role in plant defense.

Acetates↗
PubMed1996

Diagnosing renal artery stenosis: a comparison between conventional renography, captopril renography and ultrasound Doppler in a large consecutive series of patients with arterial hypertension.

The purpose of the study was to compare the positive and negative predictive values of conventional renography (Reno-A), captopril renography (Reno-B) and ultrasound Doppler (UD) with regard to the diagnosis renal artery stenosis. These three tests, and in addition a renal angiography, were performed in consecutively admitted patients with arterial hypertension, owing to either suspicion of renovascular hypertension or refractoriness to treatment. Patients with occlusion of a renal artery or a serum creatinine level higher than 300 mumol/l, or a previous investigation for renovascular hypertension at another hospital, were excluded from the analysis. The European Multicenter Study (EMS) criteria and local criteria for abnormal renography were compared. Of 131 patients, 28 had a renal artery stenosis (RAS) exceeding 50% reduction in diameter of the artery and 19 exceeding 70%. Using the EMS criteria for renography the predictive values of a negative test for a RAS more than 50% were 0.88 for Reno-A, 0.90 for Reno-B, 0.86 for changes from Reno-A to Reno-B, 0.92 for abnormalities either in Reno-A, Reno-B or changes from Reno-A to Reno-B, and 0.91 for UD. The corresponding values for a RAS more than 70% were 0.94, 0.97, 0.93, 0.98 and 0.96, respectively. The predictive values of a positive test were clearly lower, ranging from 0.20 to 0.75, but best when changes from Reno-A to Reno-B were used, 0.69-0.75. Using local criteria for renography the predictive values of a negative test were almost equal to those obtained by using the EMS criteria, but the predictive values of a positive test were slightly lower. It is concluded that conventional renography, captopril renography and ultrasound Doppler all are very good screening tests for renal artery stenosis, but the positive predictive values are clearly highest when using changes from conventional renography to captopril renography. It is suggested that captopril renography always should be performed when conventional renography is abnormal and vice versa to obtain the highest positive predictive value, on the assumption that total renal function is normal or almost normal, and that renal function is not absent in the affected kidney.

Humans↗
PubMed1991

Partial purification and characterization of native plasminogen activators from bovine milk.

At least four native plasminogen activators were detected in bovine milk, and two partially purified plasminogen activators were characterized. The plasminogen activators were dissociated from casein proteins by treatments with sulfuric acid and dimethylformamide. The plasminogen activators in the resulting fractions were partially purified with size exclusion, affinity, or metal chelate chromatographic techniques. Molecular weights of the two partially purified plasminogen activators were 47.2 and 30.5 kDa by gel electrophoresis. Size exclusion chromatography gave a molecular weight of 43.2 kDa for the first plasminogen activator. The isoelectric points of the two plasminogen activators were in the pH range 6.2 to 6.7. Because activity was not enhanced by the presence of fibrinogen fragments in a plasminogen activator assay mixture and decreased when human anti-urokinase Ig were added, at least some bovine milk native plasminogen activators appear to be urokinase-type plasminogen activators.

Animals↗
PubMed1991

Production of proteases by psychrotrophic microorganisms.

Six milk-derived psychrotrophic microbial cultures were screened for the ability to grow at refrigerated temperatures and produce proteases in reconstituted skim milk. Of these, two cultures, Pseudomonas fluorescens M3/6 and Pseudomonas fragi K122, produced extracellular protease(s) beginning 7 d postinoculation when the cultures had entered late log or early stationary phases of growth. Further work with these two cultures showed that intracellular proteases were present after only 20-h incubation, before detection of the extracellular proteases. Using H-D-valyl-L-leucyl-L-lysyl-4-nitroanilide (S-2251), a sensitive substrate for plasmin activity, P. fluorescens was shown to have greater intracellular proteolytic activity than extracellular activity at 20 h of incubation. The intracellular enzyme activity remained constant while the extracellular and periplasmic activities increased over the remaining 6-d incubation period. The proteases in crude extracellular extracts from both cultures were characterized and were heat stable with broad temperature (7 to 52 degrees C) and pH (pH 5.5 to 8.5) ranges for activity and were inhibited by the metal chelator, EDTA, indicating that they were metalloproteases.

Animals↗
PubMed1991

Purification and characterization of an extracellular protease produced by Pseudomonas fluorescens M3/6.

Pseudomonas fluorescens strain M3/6 was inoculated into reconstituted NDM and incubated at 7 degrees C for 46 d. A significant amount of extracellular protease was produced, mainly during the latter part of the culture's life cycle. The protease was purified using ammonium sulfate fractionation, ion-exchange chromatography, and gel filtration. The isolated protease had activity on azocasein, alpha-, beta-, and kappa-caseins and a plasmin substrate but did not have plasminogen activator activity. The protease had a molecular weight of 45 kDa, an isoelectric point of pH 8.25, a broad temperature and pH range for activity, and was less heat stable in the isolated form than in the cell-free extract.

Animals↗
PubMed1986

Dynamic free-field headphone as hearing aid transducer. A preliminary report.

A comparison between a body-worn hearing aid with a conventional earphone/earmould system, and a free-field dynamic headphone demonstrated the significance of the coupling between the hearing aid earphone and the subject's ear. Measurement of the insertion gain revealed destruction of the ear-canal resonance with a conventional earmould, whereas the ear-canal resonance was preserved by the use of a dynamic headphone. The use of a body-worn hearing aid connected to a dynamic headphone showed a greater amplification at low as well as at high frequencies. Furthermore, a significantly better discrimination score and an improved sound quality were demonstrated with the dynamic headphone.

Acoustic Impedance Tests↗
PubMed1981

Food preferences of patients with cancer.

Cancer patients who experience food aversions generally rated foods less pleasant than healthy controls or cancer patients with no food aversions. Most high protein foods, cereal products, and sweet foods were generally less palatable to patients with food aversions. Most fruits, vegetables, and cultured dairy products were equally palatable to all three subject groups. Although the cause of these food aversions is not understood, they do not appear to be a generalized response to all foods.

Diet Surveys↗
PubMed1980

Influence of food odors on food aversions and preferences in patients with cancer.

One hundred thirty-three patients with cancer and 50 healthy controls judged the pleasantness of 10 common food odors and completed questionnaires on food likes or dislikes, recent smell or taste changes, development of food aversions, weight loss, decreased appetite, and early satiety. Chocolate, pork, roast beef, and chicken odors were significantly less pleasant for patients with food aversions (PA) than for controls. Ham, pork, and roast beef odors were significantly less pleasant for PA than for patients without food aversions (PNA). More PA than controls or PNA reported recent smell and taste changes for most of the 10 foods in the sample set. Roast beef was the only food on the questionnaire rated significantly less pleasant by PA than controls or PNA. There were no significant correlations between the odor hedonic scores and the questionnaire's hedonic scores for any of the 10 foods. More PA than PNA had weight loss, decreased appetite, and early satiety. Patients on chemotherapy did not have a significantly greater incidence of aversions, weight loss, decreased appetite, or early satiety than patients not receiving chemotherapy. The type of cancer appeared to have no relation to the development of food aversions.

Adolescent↗