[The cement free hollow hip prosthesis to reduce intramedullary pressure]. / Die zementfreie Hohlschaft-Hüftendoprothese zur Reduzierung des intramedullären Druckes.

PURPOSE: A hollow cementless femoral stem has been developed to reduce intramedullary pressure and fat embolism during implantation. METHODS: In a prospective randomized clinical study, cementless hip stems (ALPHA-FIT) were implanted in 42 patients (24 women, 18 men, mean age: 65.9 years). In Group I (n=21) a solid standard stem was used. In Group II (n=21) a modified hollow stem was implanted with vertical and longitudinal communicating drill holes opening at the implant surface. During surgery the intramedullary pressure was measured by a cannula fixed distally. RESULTS: During stem insertion the mean pressure was 82 mmHg (minimum-maximum, 12-259 mmHg) for Group I and 27 mmHg (minimum-maximum, 0-48 mmHg) for Group II. This difference was statistically significant (t-test, p < 0.00076). The pressure measured in Group II was similar to the base pressure before opening of the intramedullary canal (mean 35 mmHg; minimum-maximum, 4-72 mmHg). In both groups higher pressures were found for opening of the canal, drilling with the smallest drill size and rasping. CONCLUSION: Using the hollow prosthesis, the intramedullary pressure could be reduced significantly. The higher pressures during preparation of the femoral canal need further research.

Influence of the host on three sub-Arctic annual facultative root hemiparasites: II. Gas exchange characteristics and resource use-efficiency.

Light saturated rates of photosynthesis (Asat ), water use-efficiency (WUE) and photosynthetic nitrogen use-efficiency (PNUE) were measured for three sub-Arctic annual root hemiparasites (Rhinanthus minor L., Euphrasia frigida L. and Melampyrum sylvaticum L.) growing in the Torneträsk region of Swedish Lapland. Photosynthesis and resource use-efficiency of the hemiparasites were dependent on (i) attachment to a host and (ii) the nature of the host to which attachment was made. The highest rates of Asat were recorded in those hemiparasites attached to legumes and the lowest rates were recorded in those which were not attached to a host. Intermediate rates of Asat were recorded in hemiparasites attached to grasses. Asat and leaf conductance were more closely related in attached than in unattached hemiparasites, WUE was greatest in those hemiparasites attached to legumes, but was not a simple function of nitrogen supply. PNUE was greater in attached than in unattached plants, but was inversely related to the total-nitrogen concentration of the leaves. In an earlier paper we demonstrated that the growth of these hemiparasites is highly host dependent. Here we demonstrate that the carbon, nitrogen and water relations of these plants are also highly host dependent.

Gas exchange characteristics and nitrogen relations of two Mediterranean root hemiparasites:Bartsia trixago andParentucellia viscosa.

Plant height, light-saturated rates of photosynthesis (A max) and foliar nitrogen concentration (N 1) were measured forBartsia trixago under field conditions in Mallorca. All three variables were postively correlated, and were also positively related to the abundance of nitrogen-fixing legumes in the associated vegetation (putative host species).A max forB. trixago ranged from 7.7 to 18.8 µmol m-2 s-1; similar rates were measured for a second hemiparasiteParentucellia viscosa, and both species were within the range of rates measured for six putative hosts (10.6-19.2 µmol m-2 s-1). Fertilization of unattachedB. trixago plants with inorganic nitrogen (ammonium nitrate) elicited neither the growth nor the photosynthetic responses observed in plants considered to be parasitic on legumes and in receipt of an enriched organic nitrogen supply. Both hemiparasites had high diurnal leaf conductances (g s) (469-2291 mmol m-2 s-1) and were at the upper end of the range of those measured in putative hosts (409-879 mmol m-2 s-1). In contrast with the latter, high nocturnal rates ofg s were also recorded for the two hemiparasites (517-1862 mmol m-2 s-1). There was no clear relationship between eitherA max orN 1 and eitherg s, transpiration (E) or water use efficiency (A max/E) inB. trixago plants. The economics of water loss appear to be independent of both the supply of nitrogen from the host and autotrophic carbon fixation.

Do inorganic solutes limit growth of the facultative hemiparasite Rhinanthus minor L in the absence of a host?

The response of the facultative hemiparasitic angiosperm Rhinanthus minor to inorganic solutes was investigated by supplying plants not attached to a host with nitrogen, phosphorus and potassium. Solutes were supplied both individually (in pots) and in combination (under field conditions). Only phosphorus resulted in any significant stimulation of growth. The phosphorus treated plants also had higher rates of light saturated photosynthesis and higher water use efficiencies than control plants. In contrast to many autotrophic plants, nitrogen neither stimulated growth nor photosynthesis.

Influence of the host on three sub-Arctic annual facultative root hemiparasites: I. Growth, mineral accumulation and above-lground dry-matter partitioning.

Growth, mineral accumulation and above-ground dry-matter partitioning were measured in three sub-Arctic annual facultative root hemiparasites, Rhinanthus minor L., Euphrasia frigida L. and Melampyrum sylvaticum L., growing either unattached or attached to a host plant. Attached plants were at least an order of magnitude taller than unattached plants, and individuals produced a total above-ground biomass up to three orders of magnitude greater than that produced by unattached plants. Attached plants produced a greater number of branches, leaves, buds, flowers and ripe seed capsules. Leaf size was greater in attached than unattached plants. For two species, Rhinanthus minor and Euphrasia frigida, the response of individuals attached to a legume was compared to the response of those attached to a grass. Stimulation of parasite growth was greater with a legume host than with a grass. The architecture of parasites on legume hosts differed greatly from those either on grasses or unattached, with those on legumes often having a considerably greater number of second order branches. Above-ground biomass partitioning was affected by attachment to a host, and was a function of host type. Unattached plants of all three species of parasite accumulated foliar element concentrations within the same order of magnitude as their hosts. Element concentrations in attached plants were sometimes, but not always, greater than those of their hosts. Element concentrations, especially N, were greatest in those parasites attached to a legume.

Radical formation and accumulation in vivo, in desiccation tolerant and intolerant mosses.

Water loss in a desiccation-sensitive moss resulted in destruction of chlorophyll, loss of carotenoids and increased lipid peroxidation, indicating the presence of damaging forms of activated oxygen. These effects were exaggerated when the plants were desiccated at high light intensities. During water-deprivation there was a build up of a free radical, detected in vivo, with a close correlation between molecular damage and radical accumulation. In contrast, in a desiccation-tolerant moss there was almost no indication of molecular (oxidative) damage. However a stable radical similar in type and concentration to that found in the desiccation-sensitive species accumulated, particularly under high irradiances. The stable radical appears to be one of the end-products of a process initiated by environmental stress, desiccation and high irradiance: its association with molecular damage depending on the degree to which the species is tolerant of desiccation. Identification of the radical in intact tissue from EPR and ENDOR studies, suggests that this is not a short-lived peroxy-radical but instead is relatively stable and carbon-centred.