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Biomedical subjects

A Steen

Publications and source records attributed to A Steen.

At least 19 recordsLinked to original sources
PubMed2006

Electron gyroharmonic effects in ionization and electron acceleration during high-frequency pumping in the ionosphere.

Optical emissions and incoherent scatter radar data obtained during high-frequency electromagnetic pumping of the ionospheric plasma from the ground give data on electron energization in an energy range from 2 to 100 eV. Optical emissions at 4278 A from N2+ that require electrons with energies above the 18 eV ionization energy give the first images ever of pump-induced ionization of the thermosphere. The intensity at 4278 A is asymmetric around the ionospheric electron gyroharmonic, being stronger above the gyroresonance. This contrasts with emissions at 6300 A from O(1D) and of electron temperature enhancements, which have minima at the gyroharmonic but have no apparent asymmetry. This direct evidence of pump-induced ionization contradicts previous indirect evidence, which indicated that ionization is most efficiently produced when the pump frequency was below the gyroharmonic.

Journal Article↗
PubMed2002

MTBE ambient water quality criteria development: a public/private partnership.

A public/private partnership was established in 1997, under the administrative oversight of the American Petroleum Institute (API), to develop aquatic toxicity data sufficient to calculate ambient water quality criteria for methyl tertiary-butyl ether (MTBE), a gasoline oxygenate. The MTBE Water Quality Criteria Work Group consisted of representatives from private companies, trade associations, and USEPA. Funding was provided by the private entities, while aquatic biological/toxicological expertise was provided by industry and USEPA scientists. This public/private partnership constituted a nonadversarial, cost-effective, and efficient process for generating the toxicity data necessary for deriving freshwater and marine ambient water quality criteria. Existing aquatic toxicity data were evaluated for acceptability, consistent with USEPA guidance, and nineteen freshwater and marine tests were conducted by commercial laboratories as part of this effort to satisfy the federal criteria database requirements. Definitive test data were developed and reported under the oversight of industry study monitors and Good Laboratory Practice standards auditors, and with USEPA scientists participating in advisory and critical review roles. Calculated, preliminary freshwater criteria for acute (Criterion Maximum Concentration) and chronic (Criterion Continuous Concentration) exposure effect protection are 151 and 51 mg MTBE/L, respectively. Calculated, preliminary marine criteria for acute and chronic exposure effect protection are 53 and 18 mg MTBE/L, respectively. These criteria values may be used for surface water quality management purposes, and they indicate that ambient MTBE concentrations documented in U. S. surface waters to date do not constitute a risk to aquatic organisms.

Animals↗
PubMed2001

Field study of dairy cows with reduced appetite in early lactation: clinical examinations, blood and rumen fluid analyses.

The study included 125 cows with reduced appetite and with clinical signs interpreted by the owner as indicating bovine ketosis 6 to 75 days postpartum. Almost all of the cows were given concentrates 2 to 3 times daily. With a practitioners view to treatment and prophylaxis the cows were divided into 5 diagnostic groups on the basis of thorough clinical examination, milk ketotest, decreased protozoal activity and concentrations, increased methylene blue reduction time, and increased liver parameters: ketosis (n = 32), indigestion (n = 26), combined ketosis and indigestion (n = 29), liver disease combined with ketosis, indigestion, or both (n = 15), and no specific diagnosis (n = 17). Three cows with traumatic reticuloperitonitis and 3 with abomasal displacement were not grouped. Nonparametric methods were used when groups were compared. Aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transferase and total bilirubin were elevated in the group with liver disease. Free fatty acids were significantly elevated in cows with ketosis, compared with cows with indigestion. Activity and concentrations of large and small protozoas were reduced, and methylene blue reduction time was increased in cows with indigestion. The rumen fluid pH was the same for groups of cows with and without indigestion. Prolonged reduced appetite before examination could have led to misclassification. Without careful interpretation of the milk ketotest, many cases with additional diagnoses would have been reported as primary ketosis. Thorough clinical examination together with feasible rumen fluid examination and economically reasonable blood biochemistry did not uncover the reason(s) for reduced appetite in 14% of the cows. More powerful diagnostic methods are needed.

Animals↗
PubMed1997

A double-blind six months comparative study of milnacipran and clomipramine in major depressive disorder.

Milnacipran is a new antidepressant with similar effects on the reuptake of noradrenaline and serotonin in vivo and in vitro. The present study was designed to study the efficacy and tolerability of long-term treatment of depressed patients with milnacipran in comparison with clomipramine. The study was designed as a double-blind, randomized parallel group comparison at 10 different hospitals in The Netherlands. The duration of treatment was 6 weeks, with an extension period of 20 weeks. The entire study period of 26 weeks was done under double-blind conditions. There was 1 week of dose escalation after which the patients received either treatment with milnacipran 200 mg/day or clomipramine 150 mg/day in fixed doses during weeks 2 to 10. This was followed by flexible dosing with 200, 150, or 100 mg/day milnacipran or 150, 100 or 75 mg/day clomipramine during weeks 11 to 26. Both milnacipran and clomipramine showed poor antidepressant activity in this patient sample. There were no significant differences between the two treatment groups with respect to antidepressant efficacy. Several methodological reasons might explain the lack of antidepressant efficacy in the present study. In 45% of the patients in the present study, the duration of the current episode of depression was longer than 6 months, whereas 48% of the patients used antidepressants before the study and 73% of these appeared to be non-responders. This raises the possibility that the present sample consisted of treatment-resistant depressive patients.

Adult↗
PubMed1997

Glucose and insulin responses to glucagon injection in dairy cows with ketosis and fatty liver.

The purpose of this investigation was to study the metabolic situation in clinical cases of bovine ketosis and to diagnose additional diseases. Extensive clinical examination, clinical biochemistry, haematology and fine-needle aspiration biopsy of liver was performed on 17 ketotic and eight control dairy cows in the field, and on seven hospitalized hyperketonaemic fatty liver patients. Additional findings in the ketotic group were heat (n = 7), indigestion (n = 5), endometritis (n = 2), cystic ovaries (n = 1), and mastitis (n = 1), and in the fatty liver group displaced abomasum (n = 4), abomasal ulcers (n = 3), mastitis (n = 2), laminitis (n = 1), bronchopneumonia (n = 1), and hypomagnesaemia (n = 2). There were no additional findings in the control group. Aspartate aminotransferase (AST) and creatine kinase (CK) were elevated in the ketosis and fatty liver groups. Total bilirubin, gamma-glutamyl transferase (GGT) and glutamate dehydrogenase (GD) were elevated in the fatty liver group and in some animals in the ketosis group. Total bile acid was not different between the groups. The free fatty acid/cholesterol ratio was higher in the fatty liver group compared with the control and ketosis groups. There was no or only slight fatty degeneration of the liver cells in the control and ketosis groups. Glucose and insulin preinjection concentrations and changes from basal values after glucagon injection were significantly lower in the ketosis group if compared with the control group. The responses in the fatty liver animals after glucagon injection were more heterogeneous than in the control and ketosis animals, a sign of disturbance in the metabolic adaptation, which together with high free fatty acid (FFA) levels can lead to fatty liver in cows with concurrent diseases.

Animals↗
PubMed1996

Evaluation of additional acetone and urea analyses, and of the fat-lactose-quotient in cow milk samples in the herd recording system in Norway.

The purpose of this study was to evaluate the use of additional acetone and urea analyses to the established herd recording system (protein, fat, lactose, and somatic cell count) in cow milk samples every second month. Samples were obtained from 43/82 herds (800/1368 cows) in a lowland/highland area. Acetone concentration (mmol/l) were classified into acetone classes 1 (<0.7); 2 (0.7-1.4); and 3 (>1.4). There was an association between increasing acetone class and increasing ketosis incidence in herd (Kendall's Tau-b = 0.13). The highest percentage frequencies of acetone classes 2 and 3 were in weeks 4-6 postpartum. Milk yield, urea, and lactose were significantly lower; milk protein not different, and milk fat was significantly higher in herds with high ketosis incidence and in cows in acetone classes 2 and 3. General linear models, obtained by backward elimination of non-significant variables, showed that milk protein was negatively associated to milk yield and positively associated to milk fat. Milk yield decreased, and milk fat concentration increased with increasing acetone level. Milk fat and milk lactose were negatively associated, and a fat-lactose-quotient might be promising in a model to rule out subclinical ketosis cows.

Acetone↗
PubMed1996

Evaluation of bulk milk analyses of acetone, urea, and the fat-lactose-quotient as diagnostic aids in preventive veterinary medicine.

The purpose of this study was to evaluate the use of additional acetone and urea analyses to the established milk quality system (protein, fat, lactose, and somatic cell count) in bulk milk samples twice a month. Samples were obtained from 44/93 herds in a lowland/highland area. When ranging herds with most acetone values over 0.24mmol/1 (90th percentile), only two out of 10 herds would be on a corresponding list when ranged for highest ketosis treatment incidence. Most high acetone values occur after periods with concentrated calvings, but also in periods without calvings, presumably because of feeding with inferior silage high in butyric acid. Milk fat concentration, milk lactose concentration and the interaction term between these, the fat-lactose-quotient, show the largest absolute values in all three models with ketosis treatment incidence, milk protein concentration, and milk yield as dependent variables in general linear analyses on standardized variables. Acetone and urea concentrations in bulk milk show only small absolute values or are omitted from the models. The practical conclusion from these analyses on bulk milk samples to be used by advisory personnel is small, but it seems that high bulk milk fat concentrations and low lactose concentrations are unfavourable when it comes to ketosis treatment incidence, but favourable when it comes to milk protein concentration. Bulk milk acetone concentrations as a measure of the energy supply in herds must only be interpreted after calving intensity and silage quality are assessed.

Acetone↗
PubMed1987

Bacterial contamination in cerebrospinal fluid shunt surgery.

Infection is a major complication of cerebrospinal fluid (CSF) shunt treatment with a reported incidence of 8-27%. In the present study, comprising 64 patients operated under strictly defined preoperative and peroperative hygienic measures and without use of prophylactic antibiotics, the infection rate was 3.1%. Out of the 2 cases of shunt infection recorded, 1 was probably caused by peroperative contamination and 1 by postoperative, hematogenous spread. Bacterial cultures from the operation area before incision and during operation were negative in 95% and 78%, respectively, and when positive yielded low numbers of organisms. Specimens taken after skin closure revealed growth in 59% and high bacterial numbers in 20%, mostly of Staphylococcus epidermidis and other resident skin bacteria. In addition, cultures of irrigation solutions, kept in open bowls during operation, yielded bacterial growth in 65% with a predominance of S. epidermidis. Thus, the strict hygienic measures did not prevent bacterial recolonization of the wound during operation. It is conceivable that endogenous as well as exogenous spread may be of importance in this context. The contamination of irrigation solutions indicates that closed irrigation systems should be used in this type of surgery.

Adolescent↗
PubMed1985

Cannabinoids in blood and urine after passive inhalation of Cannabis smoke.

To test the possibility that cannabinoids are detectable following passive inhalation of Cannabis smoke the following study was performed. Five healthy volunteers who had previously never used Cannabis, passively inhaled Cannabis smoke for 30 min. Cannabis smoke was provided by other subjects smoking either marijuana or hashish cigarettes in a small closed car, containing approximately 1650 L of air. delta 9-Tetrahydrocannabinol (THC) could be detected in the blood of all passive smokers immediately after exposure in concentrations ranging from 1.3 to 6.3 ng/mL. At the same time total blood cannabinoid levels (assayed by radioimmunoassay [RIA] ) were higher than 13 ng/mL in four of the volunteers. Both THC and cannabinoid blood concentrations fell close to the cutoff limits of the respective assays during the following 2 h. Passive inhalation also resulted in the detection of cannabinoids in the urine by RIA and enzyme multiple immunoassay technique (EMIT) assays (above 13 and 20 ng/mL, respectively). It is concluded that the demonstration of cannabinoids in blood or urine is no unequivocal proof of active Cannabis smoking.

Adult↗
PubMed1984

Contamination of irrigation solutions in an operating theatre.

Sterile irrigation solution, used in open systems in a conventional orthopedic operating theatre, were examined for bacterial contamination. At the end of 13 of 21 operations (duration greater than or equal to one hour) the solution tested displayed the growth of Staphylococcus epidermidis and/or diphtheroid rods and/or other species. It is concluded that irrigation by solutions, kept in open bowls during an operation, is a potential source of contamination.

Acinetobacter↗