Continuous-wave EPR at 275GHz: application to high-spin Fe(3+) systems.

The 275GHz electron-paramagnetic-resonance spectrometer we reported on in 2004 has been equipped with a new probe head, which contains a cavity especially designed for operation in continuous-wave mode. The sensitivity and signal stability that is achieved with this new probe head is illustrated with 275GHz continuous-wave spectra of a 1mM frozen solution of the complex Fe(III)-ethylenediamine tetra-acetic acid and of 10mM frozen solutions of the protein rubredoxin, which contains Fe(3+) in its active site, from three different organisms. The high quality of the spectra of the rubredoxins allows the determination of the zero-field-splitting parameters with an accuracy of 0.5GHz. The success of our approach results partially from the enhanced absolute sensitivity, which can be reached using a single-mode cavity. At least as important is the signal stability that we were able to achieve with the new probe head.

Residual inorganic soil nitrogen in grass and maize on sandy soil.

Nitrogen (N) remaining as inorganic ('mineral') soil N at crop harvest (N(minH)) contributes to nitrate leaching. N(minH) data from 20 (grass) and 78 (maize) experiments were examined to identify main determinants of N(minH). N-rate (A) explained 51% (grass) and 34% (maize) of the variance in N(minH). Best models included in addition crop N-offtake (U), offtake in unfertilised plots (U(0)), and N(minH) in unfertilised plots (N(minH,0)) and then explained up to 75% of variance. At low N-rates where apparent N recovery rho keeps to its initial value rho(ini), N(minH) keeps to its base level N(minH,0). At N-rates that exceed the value A(crit) where rho drops below rho(ini), N(minH) rises above N(minH,0) by an amount proportional to (rho(ini)-rho)A. About 80% of (rho(ini)-rho)A was found as N(minH,) in grass as well as in maize. The fraction (1-rho(ini))A does not appear to contribute to N(minH) at low N-rates (A< or =A(crit)) or at high N-rates (A>A(crit)).

ENDOR spectroscopy at 275 GHz.

A pulsed ENDOR spectrometer operating at a microwave frequency of 275 GHz is described. The results demonstrate that this type of spectroscopy can now be performed routinely at this high microwave frequency. The advantages compared to conventional EPR frequencies are the high spectral resolution, time resolution, and sensitivity.

Limits to nitrogen use on grassland.

Data from nitrogen (N) response experiments on grassland in Belgium and the Netherlands were analysed with the help of a descriptive crop N response model, to identify permissible doses below which no accumulation occurs of residual mineral soil N in autumn. N(min). Using different years as separate sets, a total of 29 data sets were obtained from eight locations on various soil types. A large variation was found in N(min) base levels (unfertilised) between locations and between years at a given location. For doses low enough not to affect crop N recovery, every 100 kg N applied was associated with 3-4 kg residual N(min) in autumn. This is considered very low compared to N(min) base levels, but values differed significantly from zero. After normalising N-doses from different sources (mineral fertiliser and cattle slurry) with the help of a coefficient expressing effectiveness based on crop N uptake, no difference was found between fertiliser and slurry in terms of their effect on residual Nmin. The above also holds for nitrate leaching as measured. The sources do differ, however, with respect to long-term effects and these are quantified with a first-order approximation. It it shown that, also after incorporation of long-term effects, much higher N-doses on grassland are justified than the 170 kg N per ha per year in animal manures currently proposed by the European Commission. On normal productive cut grassland as in the analysed experiments, total N doses in cattle slurry up to 400 kg per ha per year have very little effect on residual N(min), if not accompanied by high fertiliser doses. Introducing limits to the use of animal manures on grassland without limiting the input of mineral fertiliser-N lacks any scientific ground.

[Insufficient vaccination status of children with a chronic disease]. / Ontoereikende vaccinatiestatus van kinderen met een chronische ziekte.

OBJECTIVE: To determine whether the vaccination status of children with a chronic disease in adequate, what amount of delay occurs and whether vaccination opportunities are missed. DESIGN: Retrospective descriptive. SETTING: Department of Pediatrics, University Hospital, Groningen, the Netherlands. METHODS: Vaccination data of all 79 children with chronic diseases admitted to the infant and toddler ward of the Beatrix Children's Hospital between January 1 and December 31 1993 were obtained through review of hospital admission charts and local Vaccination Administration records, as well as through telephone contacts with the parents. The data of 71 children were complete; these were compared with the vaccination guidelines with respect to diphtheria-tetanus-pertussis-poliomyelitis (DTPP) vaccination and mumps-measles-rubella (MMR) vaccination. RESULTS: Vaccination coverage for DTPP reached over 90% although for DTPP 3 and 4 with a delay of more than 3 months. MMR vaccination coverage was 86%. Only 21% of the patients received all vaccinations within a period of 1 month after the recommended age. Among the remaining 79% of children 56 opportunities were missed to administer vaccines during admission. Twenty-one times the possibility to administer DTPP and MMR simultaneously was missed. CONCLUSION: Children with a chronic disease run a high risk of incomplete and delayed immunization.

Visual resolution during growth in a cichlid fish: a morphological and behavioural case study.

The spatial resolution of the visual system during growth of the cichlid fish Haplochromis argens was deduced from the cone density according to two models of possible connectivity patterns. The models include a convergency type of 5 cones per visual unit and a divergency type of 1.25 cones per visual unit. The minimum separable angle in this species was measured during ontogeny using operant conditioning in a two choice discrete trial situation. As a consequence of the moderate performances of the juveniles, the behavioural study showed a greater change of visual resolution than was predicted by the morphology. The minimum separable angle of the adult fishes was accurately predicted by the 'divergency model', which led to rejection of the other morphological model. It is argued that the high resolution as found in some other fish species by authors using the same technique may be due to imperfect calculations.

Interspecific variation of photoreceptors in four co-existing haplochromine cichlid fishes.

The photoreceptors of four co-existing haplochromine cichlids have been studied morphometrically and microspectrophotometrically, and the results were interpreted in terms of resolution and sensitivity. Among the three species, Haplochromis argens, H. piceatus and H. ishmaeli, the cone dimensions and the visual pigments differed only slightly, in spite of differences in vertical distribution and feeding behaviour between these species. The fourth species H. pyrrhocephalus showed distinctly different visual properties, with very large double cones at low densities, and its spectral sensitivity shifted to significantly longer wavelengths. To some degree, the photoreceptor morphometrics and visual pigments appeared to be attuned to the photic conditions of the specific habitats. The two species H. piceatus and H. pyrrhocephalus, occupying a dimmer habitat with less penetrating blue light, had reduced blue sensitive single cones, whereas the surface dwelling species H. argens had relatively small red/green sensitive double cones. Also an attempt has been made to relate the visual capacity of the cichlids to their behavioural patterns, focussing on prey detection. The greatest visual differences were observed in the two species H. argens and H. pyrrhocephalus, with resources coincidence and with the highest encounter frequency, which may indicate that visual segregation contributes towards reducing interference competition among co-existing species with a similar diet.

Ontogenetic change of visual thresholds in the cichlid fish Haplochromis sauvagei.

The ontogenetic alterations of visual sensitivity thresholds and acuity of the cichlid Haplochromis sauvagei were quantitatively predicted from the developmental change of size and convergence of the photoreceptors and measured behaviourally using optomotor response. The observed enlargement of the cone-photoreceptors was considered to improve their photon catching ability. Accordingly, the ontogenetic change of the photopic threshold was accurately predicted by the increase of the cone size during growth. The measured scotopic threshold decreased to a greater degree during growth than was predicted by the increasing number of rods connected to a ganglion cell. Additionally, the resolution and the flicker fusion frequency were derived from histological and behavioural measurements, respectively. The behaviourally measured resolution was much higher than expected, which was probably due to the method used. In conclusion, the ontogenetic addition and enlargement of photoreceptors in the eyes of fishes lead to improved visual properties in general, which enable a fish to perform new visual tasks.

Inappropriate antidiuretic state in long-term psychiatric inpatients.

To investigate the occurrence of an inappropriate antidiuretic state in a long-term psychiatric inpatient population, 690 patients underwent serum sodium determination. Forty-four patients (6.4%) had levels less than 133 mmol/l. Fifteen of these patients could be investigated further and the biochemical findings in all were consistent with an inappropriate antidiuretic state. Evidence of previous episodes of water intoxication was found in 80% of these patients. Although more than one possible cause was present in most patients, the two factors most strongly incriminated in the pathogenesis of the inappropriate antidiuretic state were the drugs carbamazepine and hydrochlorothiazide.

Significance of in vitro cultures in myelodysplastic syndromes.

Bone marrow samples from 20 controls, 41 patients suffering from various types of myelodysplasia and 19 suffering from ANLL were investigated by in vitro cultures. The cultures were stimulated by various concentrations of leucocyte conditioned medium (LCM) and PHA-stimulated conditioned medium (PCM) and were examined after 7 and 14 d. We found that, in clinically stable MDS, growth patterns and dose-response to CM's were mostly within the normal range. With progressive blastic transformation, these features became abnormal with an increase in cluster growth. Clusters responding to a high dose of LCM, persisting after 14 d and enhanced by PCM may represent 'early' clonogenic cells. These clusters were found in progressive MDS with increased numbers of blast cells. Clusters formed by 'late' clonogenic cells were found in normal bone marrow and stable MDS. In ANLL the disturbance of proliferation and maturation seems to be much more pronounced than in progressive MDS with blastic transformation. We conclude that the interpretation of in vitro bone marrow culture data in terms of a disorderly arrangement of clonogenic cells in MDS and ANLL is facilitated by comparing different conditioned medium stimulations and by scoring after different time intervals.

Morphological studies on the binding of low-density lipoproteins and acetylated low-density lipoproteins to the plasma membrane of cultured monocytes.

Binding of low density lipoproteins (LDL) and acetyl-LDL to the plasma membrane of cultured swine monocytes was investigated by immunofluorescent and immunoelectron microscopy. Binding sites for native LDL, visualized on both the light microscopical and the ultrastructural level, were found to be comparable to those of cultured human fibroblasts. These techniques, however, failed to reveal binding of acetyl-LDL to the cell surface. Biochemical experiments showed that both LDL and acetyl-LDL have specific receptors, the acetyl-LDL receptor being distinctly different from the LDL receptor. It is concluded that there are morphological differences in the binding of LDL and acetyl-LDL to cultured monocytes. These differences are supported by biochemical data.