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Biomedical subjects

A Nielsen

Publications and source records attributed to A Nielsen.

At least 19 recordsLinked to original sources
PubMed1992

Mechanism of killer gene activation. Antisense RNA-dependent RNase III cleavage ensures rapid turn-over of the stable hok, srnB and pndA effector messenger RNAs.

The hok/sok, srnB and pnd systems of plasmids R1, F and R438 mediate plasmid maintenance by killing plasmid-free segregants. The systems encode exceptionally stable full-length mRNAs that code for potent cell toxins that kill the cells from within. The systems also produce truncated mRNAs whose appearance is correlated with killing activity. The truncated mRNAs are shortened by 35 to 70 nucleotides in the 3' ends, but have the same 5' ends as the full-length transcripts. Translation of the stable killer mRNAs is regulated by unstable antisense RNAs that are complementary to the leader regions of the full-length and truncated mRNAs. We show here, that both the presence of the antisense RNA and of the host enzyme RNase III is required for rapid cleavage of the truncated mRNAs, and we map the cleavage point in the Hok mRNA in vitro and in vivo to be located between nucleotides +245 and +246. The RNase III cleavage products of the Hok mRNA were found to be very unstable in vivo. Thus, RNase III cleavage seems to be the initial event leading to decay of the killer mRNAs. In an rnc- strain, the truncated mRNA species were found in steady-state cells. This observation indicates that the truncated mRNAs are formed constitutively and independently of the presence of the antisense RNAs. Thus, the antisense RNAs prevent the accumulation of the truncated mRNAs solely by mediating their rapid hydrolysis by RNase III. Furthermore, the generation of the truncated killer mRNAs in the rnc- host indicate that RNase III is dispensable for induction of the killer gene systems. Based on these and on observations obtained previously, we present a molecular model that explains the activation of the killer mRNAs in plasmid-free segregants and after addition of rifampicin.

Base Sequence↗
PubMed1992

Permeation resistance of glove materials to agricultural pesticides.

The toxicities of many agricultural pesticides require that hand protection be used by persons who mix, load, and apply these products, as specified on the label and material safety data sheet. Selection of gloves for formulations that contain organic solvents is particularly problematic because a solvent that permeates the glove can carry with it the active ingredient of the pesticide formulation. With a test method that measures the simultaneous permeation of the carrier solvent(s) and active ingredient(s), in particular those active ingredients that have low solubility in water and low volatility, over 100 permeation tests (in triplicate) with approximately 20 pesticide formulations were conducted with 13 different glove materials. These results are summarized and generalizations are presented within the perspective of the large base of permeation data for neat chemicals and another large permeation study with pesticides. Key among the findings is that the carrier solvent generally permeates first and at a much higher rate than the active ingredient. Furthermore, the permeation behavior of formulations containing solvents generally mirrored that of neat carrier solvents alone. Thus, insight into the selection of the most appropriate glove material for a given pesticide formulation can be gained from permeation data for neat chemicals. For the types of solvents that may be present in pesticide formulations, preferred materials include nitrile rubber, butyl rubber, and plastic film laminates. Natural rubber and polyvinyl chloride materials generally are not recommended.

Agrochemicals↗
PubMed1992

A monthly cycle in the plasma concentration of GnRH and the glomerular filtered load of GnRH during second trimester pregnancy.

Six healthy women were examined three times a week during the second trimester. The aim of the study was to test the existence of a monthly cycle in plasma GnRH. Because the kidney plays a dominant part in the elimination of small peptides from the circulation by filtration, the filtered load (P-GnRH x GFR) of GnRH was estimated and tested for a cycle. A mathematical model (parabolas overlaid with a cosine curve and containing parameters for cycle length, cycle amplitude and phase) was used in a multivariate analysis of changes in plasma GnRH, creatinine clearance and GnRH filtered load. We found significant monthly cycles in plasma GnRH (p = 0.003) and in GnRH filtered load (p = 0.004), but no significance for a cycle in creatinine clearance. As an intermediate result we demonstrated that the tubular reabsorption of GnRH was unsaturated for all values of plasma GnRH and GnRH filtered load in question. The increased pregnancy level of plasma GnRH originates in part in the placenta, but we assume that the cycle generator is contained in the maternal neuroendocrine system.

Absorption↗
PubMed1992

Student evaluation of sex education programs advocating abstinence.

This research examined the attitudes of students who were enrolled in three different sex education programs that emphasize abstinence. Data were examined to determine whether secondary school students responded positively to the programs. The programs examined were Values and Choices, Teen Aid, and Sex Respect. Results of the study indicated that all three programs were rated positively, with female, younger (junior high school age), and virgin-naive students rating the programs more highly.

Adolescent↗
PubMed1991

A versatile method for integration of genes and gene fusions into the lambda attachment site of Escherichia coli.

We have developed a versatile method for integration of modified genes and gene fusions into the bacteriophage lambda attachment site (attB) of the Escherichia coli chromosome. The method relies on two components: (1) a DNA integration cassette, flanked by multiple restriction enzyme sites, which contains the lambda attP site and, as a selectable marker, the Tn5 aphA gene conferring kanamycin resistance (KmR); and (2) a plasmid with the lambda int gene transcribed from the tet promoter. A fragment carrying the gene in question is ligated to the integration cassette, resulting in a circular piece of DNA unable to replicate. The ligation product is then transformed into a strain that contains the int-carrying plasmid. Selection for KmR results in colonies with the cassette integrated into the attB site of the E. coli chromosome. This method was used for integration of several lacZ and phoA promoter fusions. The integration products were analyzed by Southern hybridization. In addition, we found, fortuitously, that the ligated DNA circles could also integrate by homologous recombination, although usually at a much lower frequency than the Int-mediated integration into attB.

Alkaline Phosphatase↗
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

[Whooping cough epidemiology in Denmark prior to and after the introduction of whooping cough vaccination. Protective effect of the vaccine and herd immunity].

The epidemiology of whooping cough in Denmark is described on the basis of the notified cases of the disease. The frequency of whooping cough has decreased to approximately one sixteenth of the previous level in children following the introduction of vaccination for whooping cough in 1961. Following change to a programme with only three vaccinations with a weaker, non-aluminium-adsorbed pure whooping cough vaccine in 1970, whooping cough became again slightly more frequent in the nineteen seventies and eighties. No definite reduction in the proportion of cases of whooping cough among infants could be detected although this was what the 1970 programme was particularly aimed at. Isolated deaths from whooping cough still occurred in the eighties, all of these among unvaccinated infants. The risk of whooping cough in an unvaccinated child is approximately one sixth of the risk prior to introduction of vaccination. In a vaccinated child, the risk, as judged from the notified cases, is one twentieth of the risk during the time prior to introduction of vaccination. In all age groups "herd immunity" is considered to have contributed considerably to the reduced incidence. The incidence in Denmark is, however, high compared with the incidence in some other industrialized countries. A vaccination programme with more numerous whooping cough vaccinations and possibly with a more immunogenic vaccine may be recommended on the basis of the strategy aimed at keeping the incidence of whooping cough, and thus the risk of exposure, as low as possible.

Cross-Sectional Studies↗
PubMed1990

A monthly cycle in the adrenocortical function during third trimester pregnancy.

Eleven healthy women were examined three times a week during the third trimester. The possibility of monthly cyclical changes in the serum concentrations of cortisol, placental hCG and fetoplacental estradiol was tested because of previous findings of highly significant monthly cycles in aldosterone and progesterone. A semiparametric statistical model was used and a highly significant monthly cycle in serum cortisol was found, whereas the amplitude for a cycle in hCG was barely significant and non-significant for estradiol. The previous findings of monthly cycles in aldosterone and progesterone, using a parametric multivariate model, were retested by the semiparametric method employed for the present publication. The findings of highly significant cycles in aldosterone and progesterone were corroborated. We think that the results indicate the existence of an adrenocortical cycle. We think that the monthly ovarian cycle in the non-pregnant state is paralleled by an adrenocortical cycle, where changes in aldosterone are "linked" with changes in progesterone and changes in cortisol with changes in estrogens. During pregnancy the adrenocortical cycle persists, probably controlled by the maternal hypothalamus. The physiological background for this monthly endocrine cycle during pregnancy is enigmatic.

Adrenal Cortex↗
PubMed1989

Isolation, characterization, and nucleotide sequence of appY, a regulatory gene for growth-phase-dependent gene expression in Escherichia coli.

A plasmid carrying a regulator gene, designated appY, was found in the screening of an Escherichia coli gene library for clones overproducing AppA, an acid phosphatase which is induced as a culture approaches the stationary phase. In cells containing multicopy plasmids carrying the appY gene, the expression of the chromosomal appY gene was stimulated 10- to 40-fold in the stationary phase and more than 100-fold during exponential growth. The appA plasmid also changed the rate of synthesis of more than 30 other proteins in a growth-phase-dependent way. The appY gene was mapped to 13 min on the E. coli genetic map. The position of the appY gene on the 4.9-kilobase HindIII fragment of the original clone was located by Tn5 mutagenesis and deletion analysis, and the nucleotide sequence of a 1.9-kilobase region containing the gene was determined. The appY gene product was identified as a weakly expressed 243-amino-acid polypeptide which contains a stretch of 20 amino acids showing very good similarity to the conserved DNA-binding domain of repressors and transcriptional activators.

Amino Acid Sequence↗
PubMed1989

A monthly cycle during third trimester pregnancy in the serum concentrations of progesterone and aldosterone and the urinary excretion rate of potassium.

Eleven healthy women were examined three times a week during the third trimester. A mathematical model (parabolas overlaid with a cosine curve and containing parameters for cycle length, cycle amplitude and phase) was used in a multivariate analysis of changes in serum progesterone, serum aldosterone, serum osmolality and urinary potassium. A highly significant monthly cycle in progesterone and aldosterone and a significant cycle in the urinary excretion rate of potassium were found. The individual rates of increase in serum progesterone and serum aldosterone were different and uncorrelated, and in the monthly cycle there was a phase difference between them. We think that the changes in serum progesterone and serum aldosterone are controlled by different stimuli and that the control of the cyclical component originates in the maternal neuro-endocrine system.

Aldosterone↗
PubMed1988

Cyclical changes in endogenous overnight creatinine clearance during the third trimester of pregnancy.

To investigate the pattern of change in endogenous overnight creatinine clearance during the third trimester, 12 healthy women with uncomplicated pregnancies were examined three times a week. Urine was collected overnight from 22.00 to 08.00 hours and analysed for creatinine. Serum was sampled in the morning and analysed for creatinine, beta 2-microglobulin, progesterone and estradiol. The general trend of creatinine clearance was parabolic with a declining level during the last month before term. A sinusoid pattern with minimum values around the time when the women would have had menstruation had they not become pregnant was superimposed on the parabolic trend. A mathematical model (parabolas overlaid with a cosine curve) was constructed and fitted to the data. The cyclical pattern was significant. Serum creatinine showed a pattern with increasing values during the last 4-6 weeks before term and cyclical changes which were also significant. In the individual case the monthly and preterm clearance decrement sometimes was over 50%. Monthly and preterm decreases in creatinine clearance may be quite normal and serial measurements of creatinine clearance are therefore necessary to determine if declining values indicate pathological falls in the glomerular filtration rate.

Adult↗