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Traditional N fertilizer guidelines were based on relationships between N application rates and yield response. These relationships varied greatly according to residual inorganic N content in the soil. The objective of this study was to establish inorganic N threshold values for maize production on a specific soil that could also be extrapolated to similar conditions. During the 1993/94 season a site situated near Viljoenskroon (27°10'S, 26°55'E) on a sandy Clovelly soil form was selected for a N×P fertilizer trial. Five N application rates (0, 40, 80, 120 and 180 kg N ha−1) and five P application rates (0, 10, 20, 40 and 60 kg P ha−1) were factorially combined and replicated thrice according to a randomised block design. Treatments were repeated for five consecutive seasons on the same plots. Over seasons 100% relative yield was obtained at an inorganic N threshold value of 74 kg N ha−1, 90% at 56 kg N ha−1, 80% at 45 kg N ha−1, 70% at 35 kg N ha−1, 60% at 27 kg N ha-1and 50% at 20 kg N ha−1, measured approximately six weeks after planting in the 0–600 mm soil layer for the total soil volume. Values for soil volumes over rows were very similar. An average N requirement factor of 2.3 kg N applied per kg N measured was calculated for soil volumes over rows, as well as for total soil volumes, in the top 600 mm soil according to linear models. Thus by taking the inorganic N threshold values, the N requirement factor and the measured inorganic N level in the soil into account, an actual N recommendation can be calculated in order to obtain a specific relative yield between 50 and 100%. Farmers should for economic reasons be encouraged to manage inorganic N levels in the soil to obtain a certain percentage of the expected yield. Inorganic N threshold values can be extrapolated to similar soils varying in inorganic N content.

South African analytical laboratories use different extractants for P in soils of which the most important are Bray 1, Ambic 1, Bray 2, Truog and Olsen. The fertilizer industry prefers to use Bray 1 extractions for fertilization recommendations and the ARC-Grain Crops Institute, Ambic 1 extractions for calibration research. Therefore it became necessary to establish relationships between the P extracted by the two methods in specific soils and if possible to relate differences in these relationships to soil properties. Soil samples collected to a depth of 150 mm from phosphorus fertilization trials at 12 localities were used for this study to ensure a large gradient in extractable P. The clay content of the 150 mm topsoil at these localities ranged between 8.4 and 47.0%. More than 3000 soil samples were analyzed for extractable P using both the Ambic 1 and Bray 1 methods. Relationships between Ambic 1 and Bray 1 extractable P for each locality and for 12 localities in total were determined. In addition, multiple and simple regression analyses were carried out to establish relationships between the slopes of Ambic 1 versus Bray 1 relationships and some soil properties of the different localities. Excellent relationships between Ambic 1 and Bray 1 extractable P with Revalues ranging from 92 to 98% have been established at nine localities. At the remaining three localities the Revalues ranged from 75 to 88%. Although the relationship between Ambic 1 and Bray 1 extractable P over all 12 localities was statistically significant with a R2-value of 91 %, the slopes of the different localities differed significantly from each other. Most of the variation between these slopes was attributed to exchangeable calcium (R2= 80 and 83%), degree of leaching based on clay content (R2= 80 and 71%), pH(KCI) (R2= 70 and 69%), effective cation exchange capacity (R2= 68 and 74%), degree of leaching based on silt-plus-clay content (R2= 68 and 63%), pH (H2O) (R2= 62 and 68%), Mn- oxides (R2= 60 and 72%) and the exchangeable Fe content (R2= 60 and 54%) of the soils. It is suggested that at least some of these soil properties should be considered in the development of an universal equation for the conversion of extractable P values from one to the other.

Reported nitrogen fertilizer research results were inadequate to meet the needs of small-scale farmers in the Bushbuck Ridge area. The objectives of this study were to establish inorganic N optima for maize production and to calibrate soil responses to N applications under high rainfall plus supplemental flood irrigation conditions. During the 1998/99 season a site situated near Dingleydale (24°42'S, 31°07'E) on a Sepane soil form with 9 and 20% clay content in the 0–300 and 300–600 mm soil layers, respectively, was identified for the establishment of a N×K fertilizer trial. Five N application rates (0, 52,104, 156 and 208 kg N ha-1) and four K application rates (0, 63, 126 and 189 kg N ha-1) were factorially combined and replicated twice according to a randomised block design. Treatments were repeated for four successive seasons on the same plots. Over the seasons, relative yields of 100, 90, 80, 70, 60 and 50% respectively were obtained at inorganic N quantities of 139, 105, 85, 72, 61 and 52 kg N ha-1respectively six weeks after planting in the 0–600 mm soil layer. An average N requirement factor of 1.4 kg N applied per kg N measured was calculated for the top 600 mm soil according to a linear model, but a quadratic model explained more variation and should therefore be preferred. Farmers should preferably be encouraged to manage inorganic levels in the soil to obtain a certain percentage of the expected yield. Optimum soil N levels can be extrapolated to similar soils varying in inorganic N content. Farmers with difficulties in accessing analytical laboratories may also rely on the established relationship between N rates and relative grain yield, provided that inorganic N residues are near 40 kg N ha-1during the season, as was the case in this study, that soil and cultivation practices are comparable.

Early-onset group B streptococcal (GBS) infection can be prevented by intrapartum antibiotic prophylaxis. In the USA the effectiveness of this strategy was demonstrated after the introduction of formal guidelines in 1996. In Europe prevention strategies for early-onset GBS infection have not been implemented universally. In 1998 the Dutch Society of Paediatrics and the Dutch Society of Obstetrics and Gynaecology posted conjoint guidelines for the prevention of early-onset GBS disease based on currently available knowledge and the local situation. These guidelines will be discussed in this overview.

The prevalence of human papillomavirus (HPV) rises with increasing histological severity of neoplasia, more cigarettes smoked per day and higher lifetime number of sexual partners in women with cervical dyskaryosis. Recently, the highly sensitive SPF10 primers and Inno-LiPA (line probe assay) HPV prototype research assay became available for the detection and typing of HPV. Background: using this system, we challenged the previously reported findings. Study design: the study group comprised 304 women referred because of abnormal pap smears in whom a histological diagnosis was made. Data on the lifetime number of sexual partners and smoking behaviour were obtained by questionnaire. HPV analysis was performed on cervical scrapes obtained at the enrolment visit. Results: oncogenic HPV was found in 288 (95%) women. A total of 86 (30%) out of these 288 women disclosed multiple types. HPV 16 occurred significantly less often in multiple infections than was expected on the basis of chance alone. The grade of neoplasia was significantly associated with the presence of oncogenic HPV, and this association depended on the presence of HPV type 16. No association was found between grade of neoplasia and the presence of multiple HPV types. Neither the lifetime number of sexual partners nor smoking were associated with oncogenic HPV, the five most frequent HPV types separately or the presence of multiple types. Conclusion: we conclude that the association between the detection of HPV and the epidemiological risk factors, as found with the GP5/6 PCR in the past, could not be confirmed when using SPF10 PCR primers and LiPA HPV genotyping. We suggest that the number of sexual partners and smoking may be determinants of high HPV viral load rather than determinants of the presence of HPV per se.

ABSTRACTThe dynamics of active human cytomegalovirus (HCMV) infection was monitored by competitive nucleic acid sequence-based amplification (NASBA) assays for quantification of IE1 (UL123) and pp67 (UL65) mRNA expression levels in the blood of patients after lung transplantation. RNA was isolated from 339 samples of 13 lung transplant recipients and analyzed by the quantitative IE1 and pp67 NASBA in parallel with pp65 antigenemia and serology. Rapid increases in IE1 RNA exceeding 104copies per 100 µl of blood were associated with active infection, whereas lower levels were suggestive for abortive, subclinical viral activity. Any positive value for pp67 RNA was indicative for active infection, and quantification of pp67 mRNA did not give additional diagnostic information. The onset of IE1-positive NASBA preceded pp67 NASBA and was earlier than the pp65 antigenemia assay, confirming previous studies with qualitative NASBA. Effective antiviral treatment was reflected by a rapid disappearance of pp67 mRNA, whereas IE1 mRNA remained detectable for longer periods. Quantification of IE1 might be relevant to monitor progression of HCMV infection but should be validated in prospective studies.

Comparison of the incidence and case fatality of early-onset group B streptococcus sepsis and sepsis caused by other pathogens in neonates after change of management of intrauterine infection. All infants delivered from 1988 through 1997 at a gestational age ≥ 24 weeks with a birth weight ≥ 500 gram without lethal congenital abnormalities were eligible for inclusion. Infants delivered by cesarean section before the onset of labor or rupture of membranes were excluded. During the first period (1988–1991) intrauterine infection was diagnosed by a temperature > 38°C, during the second period (1992–1997) this diagnosis was made at a lower temperature (≥ 37.8°C) or by fetal tachycardia ≥ 160/min. Treatment of intrauterine infection was similar during both periods with 3 × 2 gram amoxicillin and 1 × 240 mg gentamicin every 24 hours intravenously during labor. Prophylactic treatment during labor was only given to women with a history of an earlier infant with early-onset group B streptococcus sepsis. During the first period 6,103 infants were included, during the second period 8,504. Intrauterine infection was diagnosed and treated more often in the second period (7.1% vs. 2.6%). The incidence of early-onset group B streptococcus sepsis was significantly lower in the second period than in the first period [0.2% vs. 0.4%; OR 0.5 (0.3–0.9)] and survival without disability higher [80% vs. 52%; OR 4.5 (1.4–16.5)]. However, in both periods the overall incidence of neonatal sepsis (3.6% vs. 3.5%) and overall mortality because of sepsis (14.3% vs.13.1%) were similar. Although the early detection of clinical signs of intrauterine infection might have been effective for the prevention of serious sequelae of early-onset group B streptococcus sepsis the overall incidence and mortality from neonatal sepsis remained unchanged. Evaluation of preventive measures for early-onset group B streptococcus sepsis should always take the incidence of neonatal sepsis caused by other pathogens into account. Infect. Dis. Obstet. Gynecol. 8:143–150, 2000. © 2000 Wiley-Liss, Inc.

Parasitoid females are known to preferentially allocate female eggs to hosts with the higher resource value, usually leading to oviposition of female eggs in larger hosts and male eggs in smaller hosts. For koinobiont parasitoids, if male and female hosts are of equal size at time of oviposition, but differ in size in later developmental stages, the sex of the host could be used to indicate future resource value. Using parasitoids of the braconid genus Asobara, which are larval parasitoids of Drosophila, it is shown that parasitoids emerging from female hosts are larger than those from male hosts. Given this difference in resource value, ovipositing females should preferentially allocate female eggs to female hosts. An alternative strategy would be to decrease the difference in resource value between male and female hosts by castrating male hosts. The primary sex ratio of A. tabidain their two main host species does not differ between male and female hosts. In contrast to A. tabida, A. citriis known to partially castrate male hosts, but this does not decrease the size difference between male and female hosts. As in A. tabida, there is no difference in sex allocation to male and female hosts in A. citri. Despite the clear difference between the resource value of male and female hosts, these parasitoid species do not seem to make optimal use of this difference. They may not be able to discriminate between host sexes or, alternatively, there is a presently unknown fitness disadvantage to ovipositing in female hosts.

Background.The objective of this study was to gain insight into the determinants of dietary fat and fiber consumption in American rural energy workers. Main determinants in this study were knowledge, efficacy expectations, and outcome expectations. The determinants will be ordered in a model, assuming that efficacy and outcome expectations predict intention.Methods.The study consisted of a cross-sectional survey. The questionnaires on food behavior and the determinants of fat and fiber consumption were administered to the subjects at the same time. Models of determinants of fat and fiber consumption were derived from the correlation and regression analyses.Results.There were 211 questionnaires analyzed. The scales were shown to be valid and reliable. In the models of determinants of fat and fiber consumption the following determinants were generated: gender, education, knowledge, interest, efficacy expectations, outcome expectations, and intention. In this study efficacy expectations were important to determine fat and fiber consumption.Conclusions.Efficacy expectations can be considered an important variable of an intervention program aiming at the decrease of fat consumption and at the increase of fiber consumption in rural energy workers.

The first survey on adolescent drinking in the European Community in 1990 showed that differences in the prevalences of weekly drinkers by country are large. Prevalences in Italy and Greece are more than twice the average on the one hand, and hardly any child drinks weekly in Ireland on the other. Explanatory variables from three scientific domains, i.e., drinking among friends, drinking by parents, alcohol permissiveness by parents, pocket money, weekly smoking, and disco visits, are related with weekly drinking, confirming the theory of different mechanisms.

A secondary analysis of thirty-eight investigations of teachers' tobacco consumption was carried out in nineteen countries during 1966–1983. Studies are analyzed in terms of smoking behavior, recognition of the non-smoking teacher as a role model, and the extent of their participation in smoking reduction among students and the general population. Non-smokers were found to be more likely to affirm the importance of non-smoking teachers as role models for students. Only a minority of smokers recognized the importance of this role.

We have studied the temperature (T) and frequency (ω/2π) dependence of the complex conductivity σ(ω, T) of several systems where hopping conduction is dominant: conducting carbon-black/polymer composites as a function of carbon-black (CB) concentration, aggregates of molecular cluster compounds as a function of the size and of the distance between the metal cores and polymers as a function of degree of doping. For all compounds the conductivity as a function of ω and T can be scaled onto single curves. Using an extension of the anomalous diffusion model the specific details of these curves for the CB composites are shown to be characteristic of the underlying fractal structure. The main features of the scaled dependence of σ(ω, T) of the randomly packed cluster compounds are well described by effective medium theories, except at low frequencies where percolation effects become important. Similar features are seen in polythiophene derivatives at doping levels above the percolation threshold.

The purpose is to describe smoking behaviour of physicians and of the general population in the Scandinavian countries. Data on smoking behaviour in physicians and in the population at large were collected from 14 surveys. The smoking prevalence dropped among male and female physicians in the period under study. Changes for the general male population were similar, but smoking among the general female population changed little. If the present changes continue, physicians could be a smokefree profession by the year 2000.

The nocturnal TSH surge was studied in controls, in 34 patients with hypothalamic/pituitary disease and in 21 patients with primary hypothyroidism. It was absent in 5/12 hypothyroid patients and in 5/22 euthyroid patients with hypothalamic/pituitary disease (42% vs 23%. NS). Central hypothyroidism relative to euthyroidism was associated with a lower absolute (0.3±0.4 vs 0.9±1.0 mU/l, p<0.05) and relative (24±31 vs 63±51%, p<0.05) nocturnal rise in TSH. In primary hypothyroidism, the nocturnal TSH surge was absent in eight often patients with overt, in one of five patients with mild and in none of six patients with subclinical hypothyroidism. The relative nocturnal rise in TSH was normal in mild (54±33%) and subclinical (92±69%), but decreased in overt hypothyroidism (2±10%). Plasma T4was positively and 09.00 plasma TSH negatively related to the relative nocturnal TSH surge in primary hypothyroidism, but not in central lesions. In both conditions, however, a positive relationship was observed between the relative nocturnal TSH surge and the relative increase of TSH to TRH. In conclusion: (a) The nocturnal TSH surge is usually absent in overt hypothyroidism but present in mild primary hypothyroidism and equivocal in central hypothyroidism. This limits its usefulness as an adjunct in the diagnosis of central hypothyroidism. (b) The magnitude of the nocturnal TSH surge in patients with hypothalamic/pituitary disease or primary hypothyroidism is directly related to the TSH response to TRH, and thus appears to be determined by the directly releasable TSH pool of the pituitary.

Adriaanse R, Brabant G, Endert E, Bemelman FJ, Wiersinga WM. Pulsatile thyrotropin and prolactin secretion in a patient with mixed thyrotropin- and prolactin-secreting pituitary adenoma. Eur J Endocrinol 1994;130:113–20. ISSN 0804–4643The circadian and pulsatile thyrotropin (TSH) and prolactin (PRL) release was investigated in a patient with slight hyperthyroidism due to a mixed TSH- and PRL-secreting pituitary adenoma. Blood was withdrawn every 10 min for 24 h (before and after medical treatment); pulse characteristics were analyzed by Desade and Cluster programs (values as mean±sd). The inappropriately high mean 24-h TSH concentration of 3.55 ±0.31 mU/l was associated with a higher mean 24-h TSH pulse amplitude but unaltered mean 24-h TSH pulse frequency relative to healthy controls. The nocturnal TSH surge (absolute surge 0.5 mU/l, relative surge 16%) was low, related to a loss of the usual nocturnal increase of TSH pulse amplitude and TSH pulse frequency. Chronic treatment with octreotide resulted in a modest clinical and biochemical improvement of the hyperthyroid state; addition of bromocriptine at a later stage had no further beneficial effect. At the end of the follow-up period the mean 24-h TSH paradoxically had increased to 5.33 ±0.81 mU/l. The nocturnal TSH surge also increased (absolute surge 1.9 mU/l, relative surge 42%), but circadian changes in TSH pulsatility remained absent. In the untreated period the increased mean 24-h PRL concentration of 234 ± 24 μg/l was associated with an increased mean 24-h PRL amplitude, whereas the 24-h PRL pulse frequency (N = 4) was lower relative to controls. No circadian PRL rhythm was present. After octreotide and bromocriptine treatment the mean 24-h PRL concentration and mean 24-h PRL pulse amplitude were unchanged, but a clear nocturnal increase of PRL now was observed. Analysis of the temporal coupling between TSH and PRL release by bivariate autoregressive modeling revealed significant cross-correlations in all three periods investigated (coefficients in the range 0.34–0.76, median 0.52; p<0.01) between TSH and PRL concentrations with a lag time of 10–20 min. We conclude that pulsatile TSH and PRL release in this mixed TSH- and PRL-secreting pituitary adenoma was autonomous in nature. The observed dampening of the nocturnal increase of TSH and PRL is putatively related to a lack of TRH receptors in these tumors. The observed co-secretion of TSH and PRL suggests synthesis of both hormones by the same cell.R Adriaanse, Department of Endocrinology F5-171, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands

Between 1977 and 1983 roughly half of the Dutch general practitioners were smokers. The percentage of smokers was decreasing, both among general practitioners and in the general Dutch population. The number of smoking male general practitioners was higher than for men in general and considerably higher than in the highest socioeconomic bracket. Among general practitioners the daily consumption of manufactured and handrolled cigarettes was lower while the cigar consumption was higher. In most countries physician smoking behaviour antedates that of the general population but in Holland general practitioners' smoking habits are about four years behind that of the general population. It seems that Dutch general practitioners attribute little value to the role of setting an example in health behaviour, especially where it concerns their own smoking habits.

Adriaanse H, van Reek J. Physicians'' Smoking and Its Exemplary Effect. Scand J Prim Health Care 1989; 7: 193-6.Data presented are based on more than one hundred surveys on physicians'' smoking, carried out in 31 countries since 1951. Prevalences by gender are shown in two figures. For 13 countries, it is possible to compare the trend in smoking prevalence among physicians with the trend among the general population. In ten countries, smoking prevalences decreased over time for male physicians and the general population. This suggests a positive influence of the physicians'' example in those countries.

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Zwaan: Daiichi Sankyo: Consultancy; Sanofi: Consultancy; Roche: Consultancy; Pfizer: Research Funding; BMS: Research Funding; Incyte: Consultancy; Celgene: Consultancy, Research Funding; Servier: Consultancy; Jazz Pharmaceuticals: Other: Travel support; Janssen: Consultancy. Gruber:Bristol-Myers Squibb: Consultancy.