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Biomedical subjects

E Jensen

Publications and source records attributed to E Jensen.

At least 19 recordsLinked to original sources
PubMed1992

Hydrolysis and reconjugation of gibberellin A20 glucosyl ester by seedlings of Zea mays L.

The [6-2H]glucosyl ester of [17-13C,3H]gibberellin A20 (GA20) was injected into light-grown 14-day-old seedlings of normal, dwarf-1, and dwarf-5 maize (Zea mays L.). The plant material was extracted 24 h later, and the extracts were purified by solvent partitioning, column chromatography, and HPLC. 13C-labeled metabolites were identified from the purified extracts by full-scan gas chromatography/mass spectrometry and selected ion current monitoring in conjunction with Kovats retention indices. The metabolites, [13C]GA20, [13C]GA29, [13C]GA20-13-O-glucoside, and [13C]GA29-2-O-glucoside, were identified from normal, dwarf-1, and dwarf-5 seedlings. [13C]GA8 and [13C]GA8-2-O-glucoside were also identified from normal and dwarf-5 seedlings but not from dwarf-1 seedlings. The data provide definitive evidence for the endogenous hydrolysis by the seedlings of the introduced conjugate and its reconjugation to three glucosides.

Esters↗
PubMed1992

Purification and crystallization of insecticidal delta-endotoxin CryIIIB2 from Bacillus thuringiensis.

CryIIIB2, an insecticidal protein from Bacillus thuringiensis has been crystallized from 0.6 M NaBr and HEPES buffer at pH 7.0 and X-ray diffraction data collected on a native crystal to 2.4 A. The insecticidal protein was obtained from a Bacillus thuringiensis (Bt) strain EG7231. Crystals of the endotoxin are orthorhombic, space group C2221, with unit cell dimensions of a = 122.44, b = 131.81, and c = 105.37 A. A unit cell contains one molecule of the 67,000 Da endotoxin per asymmetric unit.

Bacillus thuringiensis↗
PubMed1992

Influence of plasma cholinesterase activity on recovery from mivacurium-induced neuromuscular blockade in phenotypically normal patients.

The significance of plasma cholinesterase (pChe) activity for the duration of action of mivacurium in phenotypically normal patients was evaluated in 35 patients during neurolept anaesthesia. The response to train-of-four nerve stimulation was recorded using a Myograph 2000. Ten patients with normal pChe (Group I) and five patients with decreased pChe activity (Group 2) were given a small test dose of mivacurium 0.03 mg kg-1. Mivacurium 0.1 mg kg-1 was administered following spontaneous recovery from the first dose. The mean suppression of the height of the first (T1) of the train-of-four responses following mivacurium 0.03 mg kg-1 patients with normal and decreased enzyme activity was 40% and 56%, respectively, and the mean T1 suppression after mivacurium 0.1 mg kg-1 was 100% in both groups. The times to different levels of twitch height recovery following the 0.1 mg kg-1 dose did not differ between the two groups of patients. Another 20 patients with normal or decreased pChe activity (Group 3) were given mivacurium 0.2 mg kg-1. In this group the time to maximum block was 1.4 min (1.0-4.0) mean (range) and the time to reappearance of the T1 response was 15.0 min (7.4-22.7) (range). An inverse relationship was found between the patients' pChe activity and the time to first response. It is concluded that mivacurium is short-acting in patients with normal pChe phenotype and normal to low-normal pChe activity. No patient with very low pChe activity was included in the study. A prolonged response to mivacurium may, however, be expected in these patients.

Anesthesia Recovery Period↗
PubMed1992

Long-term Antabuse treatment: tolerance and reasons for withdrawal.

We studied 210 alcoholics, who were re-admitted to a disulfiram treatment programme after having voluntarily discontinued disulfiram therapy, primarily to ascertain whether illness, hospitalization, or serious adverse effects were the cause of the withdrawal. A simple 9-item questionnaire was used. About 70% of the patients gave either "a wish to drink again" or "no need for further treatment" as the reason. Withdrawal in the remaining patients was in no case related to adverse effects of disulfiram. The low incidence of adverse effects was confirmed in another group comprising 93 patients treated under supervision with disulfiram 600-800 mg twice a week for at least a year (i.e. total dose at least 70 g disulfiram). They were monitored by standard laboratory blood and urine tests. There were no clinically significant changes in the measures used. Indeed, many of the patients improved during the year of abstinence. These two studies add weight to the evidence that disulfiram is not a drug with a high incidence of adverse effects.

Alcoholism↗
PubMed1992

N-substituted (aminomethyl)benzoate 21-esters of corticosteroids as water-soluble, solution-stable and biolabile prodrugs.

Various N-substituted 3- or 4-(aminomethyl)benzoate 21-esters of hydrocortisone, prednisolone and methylprednisolone were synthesized and evaluated as water-soluble prodrug forms, with the aim of developing improved preparations for parenteral or ophthalmic administration. All esters were readily hydrolyzed enzymatically by human plasma. The half lives of hydrolysis in 80% plasma ranged from 8 min to 342 min, the rate being dependent on the structure of the amino group and its position relative to the ester moiety, as well as on the structure of the steroid. The esters showed maximal stability in aqueous solution at pH 3-4. From temperature-accelerated studies of the 3-[(4-methylpiperazin-1-yl)methyl)]benzoate ester of hydrocortisone, the shelf life of an aqueous solution (pH 4.0) of this ester was predicted to be 6 years at 25 degrees C. This estimated shelf life is not reduced by precipitation of the slightly soluble parent drug since the ester was shown to be capable of solubilizing hydrocortisone, possibly by self-micelization.

Adrenal Cortex Hormones↗
PubMed1991

Insect immune response to bacterial infection is mediated by eicosanoids.

Inhibition of eicosanoid formation in larvae of the tobacco hornworm Manduca sexta, using specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase, severely weakened the ability of larvae to clear the bacterium Serratia marscescens from their hemolymph. The reduced capability to remove bacteria is associated with increased mortality due to these bacteria. There is a dose-dependent relationship between the phospholipase A2 inhibitor dexamethasone and both the reduced bacterial clearance and increased larval mortality. The dexamethasone effects on larval survival were reversed by treatment with arachidonic acid. Maleic acid, a nonspecific antioxidant, did not interfere with the insects' ability to remove bacterial cells from hemolymph. The larvae were shown to contain all of the C20 polyunsaturated fatty acids necessary for eicosanoid biosynthesis and to be capable of converting radioactive arachidonic acid into several primary prostaglandins. These results strongly suggest that eicosanoids mediate transduction of bacterial infection signals into the complex of cellular and humoral responses that comprise invertebrate immunity.

Animals↗
PubMed1991

Water-soluble, solution-stable, and biolabile N-substituted (aminomethyl)benzoate ester prodrugs of acyclovir.

Various N-substituted 3- or 4-(aminomethyl)benzoate esters of acyclovir were synthesized and evaluated as water-soluble prodrug forms with the aim of improving the delivery characteristics of acyclovir, in particular its parenteral administration. The esters showed a high solubility in weakly acidic solutions and, as demonstrated with the 3-(N,N-dipropylaminomethyl)benzoate ester, a high stability in such solutions, allowing storage for several years. The esters combine these properties with a high susceptibility to undergo enzymatic hydrolysis in plasma. The half-lives of hydrolysis in 80% human plasma ranged from 0.8 to 57 min, the rate being highly dependent on the position (3 or 4) of the aminomethyl group relative to the ester moiety. All esters were more lipophilic than acyclovir in terms of octanol-pH 7.4 buffer partition coefficients. These properties make N-substituted (aminomethyl)-benzoate esters a promising new prodrug type for acyclovir to enhance its delivery characteristics.

Acyclovir↗
PubMed1991

113Cd nuclear magnetic resonance (NMR) study of the inhibitory effect of methylvinylether/maleic acid (PVM/MA) copolymer on the alkaline phosphatase of Escherichia coli.

The inhibitory effect of PVM/MA copolymer on the alkaline phosphatase (AP) of E. coli was investigated. Kinetic studies indicated that enzyme inhibition was characterized by a reduction in both the Vmax and the Km. Addition of 1 mM zinc or magnesium ions to the reaction prevented inhibition of the enzyme by the copolymer. The inhibitory effect of the copolymer on alkaline phosphatase was also investigated using 113Cd NMR after exchange of the active center metal ions with 113Cd. The resulting Cd(II)6AP exhibited characteristic 113Cd resonances reflecting the environment of the A, B, and C metal binding sites of the enzyme's active center. Addition of copolymer resulted in a 113Cd NMR spectrum which indicated removal of 113Cd from the C site and formation of two distinct forms of the enzyme. Possible explanations for the 113Cd NMR results are discussed.

Alkaline Phosphatase↗
PubMed1991

Twitch tension and train-of-four ratio during prolonged neuromuscular monitoring at different peripheral temperatures.

In eight healthy patients, the influence of the train-of-four (TOF) response of prolonged neuromuscular monitoring and of different peripheral temperatures was studied during normal core temperature. Anaesthesia was induced and maintained with midazolam-fentanyl and a 70/30% mixture of nitrous oxide and oxygen. The mechanical TOF response of the adductor pollicis muscle (twitch tension and TOF ratio), was recorded simultaneously in both hands using supramaximal TOF stimulation of the ulnar nerve at the wrist. One arm was kept normothermic. The other arm was cooled using cold infusions and cold packings. Skin, muscle and core temperatures were continuously measured. In the normothermic arm (skin temperature greater than 32.0 degrees C), the twitch tension and TOF ratio were unchanged following 130-230 min of continuous nerve stimulation. In the hypothermic arm the twitch tension and TOF ratio showed only minor variations above a skin temperature of 32.0 degrees C (corresponding to a mean muscle temperature of 34.5 +/- 0.3 degrees C). Below a skin temperature of 32.0 degrees C a progressive decrease in TOF response was recorded. A linear relationship was found between skin temperature and TOF response as well as between muscle temperature and TOF response. At a skin temperature of 27.0 degrees C (corresponding to a mean muscle temperature of 30.8 +/- 0.4 degrees C), an approximate 20% reduction in twitch tension and a 10% decrease in TOF ratio were recorded with a considerable interindividual variation. We conclude that prolonged TOF nerve stimulation does not change the mechanical twitch response in patients with a normal central and peripheral temperature. A peripheral skin temperature below 32.0 degrees C with sustained and normal body temperature is, however, associated with changes in both twitch tension and TOF ratio that may be a source of error when evaluating neuromuscular function.

Aged↗
PubMed1991

Synthesis, enzymatic hydrolysis and physico-chemical properties of N-substituted 4-(aminomethyl)benzoate diester prodrugs of ganciclovir.

Various N-substituted 4-(aminomethyl)benzoate diesters of ganciclovir were synthesized and evaluated as prodrug forms with the aim of improving the delivery characteristics of ganciclovir. The esters were hydrolyzed enzymatically by human plasma to the parent drug, the hydrolysis proceeding through formation of the corresponding monoester. The nature of the amino substituents had a marked influence on the rate of enzymatic hydrolysis, the most enzymatically labile ester being the 4-(morpholinomethyl)benzoate derivative. All esters were more lipophilic than ganciclovir in terms of octanol-pH 7.4 buffer partition coefficients. These properties combined with good aqueous solubility and high chemical stability in weakly acidic solutions make the N-substituted 4-(aminomethyl)benzoate diesters a promising prodrug type for ganciclovir to enhance its delivery characteristics for e.g. parenteral administration.

Drug Stability↗
PubMed1991

Kinetics of the acid-catalyzed hydrolysis of acyclovir and an ester prodrug in aqueous solution.

The kinetics of hydrolysis of acyclovir was studied in 0.01-0.5 M hydrochloric acid solutions (pH 0.5-2.2) at 80 degrees C. The hydrolytic cleavage of the 9-C-N bond in acyclovir to give guanine was found to proceed almost quantitatively (greater than 90%) as evidenced by HPLC analysis. The rate of hydrolysis was subject to apparent specific acid catalysis, the specific hydrogen ion catalytic rate constant being 4.9 x 10(-2) M-1 min-1 at 80 degrees C and mu = 0.5. The possible significance of acid-catalyzed hydrolysis for the stability of acyclovir during its transit through the stomach after peroral administration was found to be negligible. A novel 4-(morpholinomethyl)benzoate ester prodrug of acyclovir was found to be three times more stable in acidic solutions than acyclovir itself despite the ester group being an additional site of degradation. The dominating degradation reaction of the ester was found to be cleavage of the 9-C-N bond. The higher stability of the ester was ascribed to the greater electron-withdrawing effect of the ester group relative to the hydroxyl group which decreases the tendency of the 9-C-N bond to be ruptured by an A-1 mechanism.

Acyclovir↗
PubMed1990

[The risk of silicosis from building site dust].

The quartz content of ordinary building materials such as concrete, mortar and bricks is 10-50%. The extension of concrete building which has occurred since 1960 and the subsequent repairs and preparation by means of mechanical tools result in increased concentrations of dust containing quartz. Measurements at various types of work in Danish building sites reveal that the quantity of respirable quartz constitutes 0.16-1.8 mg/m3 (limit 0.1 mg/m3). Corresponding figures are found in investigations from abroad. Cases of silicosis have been reported among builders abroad and, in Denmark, only few cases of occupational dust lung conditions have been notified to the Workers' Supervision Authorities. Whether or not quartz in dust at building sites also causes an increase in the occurrence of cancer of the lung, as is the case in sandstone workers exposed to pure quartz, has not yet been proved. The latent period of several decades for the development of silicosis is such that it may well be feared that the cases now reported are only the beginning of increased occurrence of the disease in coming years among particularly exposed concrete workers, bricklayers, unskilled workers, electricians, joiners and carpenters. Relevant technical methods have already been developed to limit exposure to quartz-containing dust at building sites. Prophylactic measures should be accelerated.

Construction Materials↗
PubMed1990

[Psychological stress before, during and after hospitalization for low back disease. Patients' experience illustrated by qualitative interviews].

Thirteen patients were interviewed 14 days after discharge for low back disease requiring hospitalization with the object of illustrating their experience of the period of waiting for admission, treatment in the primary and secondary health services, their relationships to children living at home during their illness and the effect of the low back disease on sexual life. The patients stated that the period of waiting was the worst, dominated by pain, uncertainty, loss of sleep and lowered self esteem. Treatment in the primary health sector was found to be unsatisfactory as regards relief of pain but satisfactory as regards contact with the general practitioner. In the secondary health sector, relief of pain was found to be satisfactory to varying extents while better contact with the doctor treating the case and the staff as a whole could be desired. Waiting and uncertainty while waiting for a diagnosis and result of treatment, inactivity and the poor contact with the staff were considered by the patients to be contributory causes to the increasing mental vulnerability. The relationship to children living at home was dominated by bad conscience prior to admission and by poor contact during hospitalization. Conditions improved after discharge. Practically no sexual activity occurred during the illness. This was not primarily experienced by the patients as a problem but they feared it might be so in the long run. Patients stated that they required mental support during hospitalization, better information and advice about practical problems after discharge.

Adult↗
PubMed1990

[The social and occupational situation of patients 2 1/2 years after hospitalization for low back pain].

Sixty-two of 84 patients hospitalized consecutively for low back pain completed a questionnaire during hospitalization and seven months and 30 months after hospitalization. Out of 43 patients who were occupationally active at the time of admission to hospital, only 23 were still occupied 2 1/2 years after. Fourteen had been granted disability pensions, two were under rehabilitation, two were unemployed and two were on sick leave and had lost their jobs. Patients who were under rehabilitation or on sick leave at the time of admission but had lost their jobs, had now been awarded disability pensions. Seven months after admission, twelve patients had been dismissed from work; of these two were now at work again and seven were disability pensioners. Significant associations were found between rejection from the labour force and the following variables: presence of pain, failure of resumption of work seven months after hospitalization, sick-leave longer than 120 days and dismissal from work after hospitalization. Low educational level and age over 45 years were also associated with rejection, and there was an almost significant trend for patients belonging to social classes 4 and 5. 72% of the patients still had low back pain at least once a week, slightly less than half the patients experienced sexual problems because of the back disease, and more than half had given up at least one leisure activity. 23% used analgesics or non-steroid-anti-inflammatory drugs every day. While 58% considered that the disease was caused by work, only six had applied for and two had been awarded compensation for occupational disease or injury.

Adult↗
PubMed1990

Does perioperative tactile evaluation of the train-of-four response influence the frequency of postoperative residual neuromuscular blockade?

The authors conducted a randomized controlled clinical trial to evaluate the usefulness of perioperative manual evaluation of the response to train-of-four (TOF) nerve stimulation. A total of 80 patients were divided into four groups of 20 each. For two groups (one given vecuronium and one pancuronium), the anesthetists assessed the degree of neuromuscular blockade during operation and during recovery from neuromuscular blockade by manual evaluation of the response to TOF nerve stimulation. In the other two groups, one of which received vecuronium and the other pancuronium, the anesthetists evaluated the degree of neuromuscular blockade solely by clinical criteria. The use of a nerve stimulator was found to have no effect on the dose of relaxant given during anesthesia, on the need for supplementary doses of anticholinesterase in the recovery room, on the time from end of surgery to end of anesthesia, or on the incidence of postoperative residual neuromuscular blockade evaluated clinically. The median (and range of) TOF ratios recorded in the recovery room were 0.75 (0.33-0.96) and 0.79 (0.10-0.97) in the vecuronium groups monitored with and without a nerve stimulator, respectively. These ratios were significantly higher than those found in the pancuronium groups, which wre 0.66 (0.06-0.90) and 0.63 (0.29-0.95), respectively. However, no difference was found between the vecuronium and pancuronium groups in the number of patients showing clinical signs of residual neuromuscular blockade, as evaluated by the 5-s head-lift test.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

[Oxygen status of arterial blood including uncompensated mixed venous oxygen tension and cardial oxygen compensation factor. Reevaluation on the basis of 250 arterial punctures].

In arterial blood from 250 patients we measured pH, pco2, and po2 (electrochemically) together with total-hemoglobin concentration, oxygen saturation, carboxy- and methemoglobin fractions (spectrometrically). With a previously published algorithm we calculated the effective hemoglobin concentration, total-oxygen concentration, half saturation tension, erythrocyte 2,3-diphosphoglycerate concentration, and two new oxygen parameters: uncompensated mixed venous oxygen tension and cardiac oxygen compensation factor. 11% of the patients have normal arterial oxygen tension, but nevertheless risk of tissue hypoxia judged from the two new oxygen parameters. This is due to a low hemoglobin concentration and/or low half saturation tension (increased hemoglobin oxygen affinity). Some patients have decreased arterial oxygen tension but normal uncompensated mixed venous oxygen tension (15%) or normal cardiac oxygen compensation factor (9%). This is due to a high hemoglobin concentration and/or increased half saturation tension. The latter varies from 2.6 to 5.2 kPa (ref.: 3.3-3.9 kPa); 36% have decreased, 27% increased values. The 2,3-diphospho-glycerate concentration varies from 2.0 to 7.9 mmol/l (ref.: 3.6-5.1 mmol/l); 14% have decreased, 30% increased values. Uncompensated mixed venous oxygen tension varies from 1.8 to 5.7 kPa (ref.: 4.5-5.5 kPaf). The cardiac oxygen compensation factor varies from 0.9 to infinity (ref.: 0.8-1.6). We conclude that the variation in the different oxygen parameters is so significant that it justifies routine calculation for all arterial blood samples where the measurement on a conventional blood gas analyzer is supplemented with measurement on one of the new multi-wavelength hemoximeters. The calculation algorithm permits calculation of all the oxygen parameters for the majority of arterial samples (84%) where the oxygen saturation is less than or equal to 0.970.

Adult↗
PubMed1989

Cell-density-dependent release of hepatic lipase from cultured rat hepatocytes.

Cultured rat hepatocytes release the enzyme hepatic lipase. In this study we investigated the effect of cell density on this metabolic function under a variety of experimental conditions. The release of hepatic lipase from cultured rat hepatocytes exhibits a cell-density dependence, the secretion per mg cell protein being increased with increasing cell density. When cell density dependence was taken into consideration no significant effect of insulin on the release of hepatic lipase from cultured hepatocytes was observed, whereas glucagon suppressed the release. Glucose stimulating the release of the enzyme, especially in cultures with high cell density.

Animals↗