Transient radiation myelopathy: spinal somatosensory evoked responses following incidental cord exposure during radiotherapy

Serial spinal somatosensory evoked potentials were recorded in six patients undergoing radiotherapy involving incidental spinal radiation. Two patients developed transient radiation myelopathy. No abnormality was found in the somatosensory evoked potentials throughout the study.

Histocompatibility-2 system in wild mice. X. Frequencies of H-2 and Ia antigens in wild mice from Europe and Africa

In this study, data are presented on serologic H-2 typing of 320 wild mice collected in several parts of Europe and Egypt. The sample was typed for 39 class I (K, D) and 16 class II (Ia) antigens. The phenotype frequencies of class I and class II antigens showed high variability in their distribution among different areas, ranging from absence or presence in low frequency in one area to presence in about one-half of the mice in another area. The average phenotypic frequency of class I private antigens was 6.3%; at least 60% of class I alleles (blanks) could not be identified with the available reagents. The data suggest that there might be more than 100 alleles for each class I locus, H-2K and H-2D. The average phenotypic frequencies of Ia-1 private antigens was 10.8%. About 75% of Ia-1 alleles (blanks) could not be identified. The number of Ia-1 alleles was estimated to be in the range of 20 to 50.

Histocompatibility-2 system in wild mice. X. Frequencies of H-2 and Ia antigens in wild mice from Europe and Africa

In this study, data are presented on serologic H-2 typing of 320 wild mice collected in several parts of Europe and Egypt. The sample was typed for 39 class I (K, D) and 16 class II (Ia) antigens. The phenotype frequencies of class I and class II antigens showed high variability in their distribution among different areas, ranging from absence or presence in low frequency in one area to presence in about one-half of the mice in another area. The average phenotypic frequency of class I private antigens was 6.3%; at least 60% of class I alleles (blanks) could not be identified with the available reagents. The data suggest that there might be more than 100 alleles for each class I locus, H-2K and H-2D. The average phenotypic frequencies of Ia-1 private antigens was 10.8%. About 75% of Ia-1 alleles (blanks) could not be identified. The number of Ia-1 alleles was estimated to be in the range of 20 to 50.

Dare we count the cost of cancer chemotherapy?

During 1972-1976, when the incidence of cancer rose only slightly in the United Kingdom and the number of cancer patients seen at a large metropolitan teaching hospital and oncological centre remained largely unchanged, the use of cytotoxic drugs rose from 5.1% to 14% of the hospital's total drug budget. Most of the rise in cost can be ascribed to the increased use and increased unit cost of four effective but expensive drugs. Although the cost of drugs is but a small proportion of the cost of care of the cancer patient, it is argued that cytotoxic chemotherapy cannot offer a "cheap alternative" to surgery and radiotherapy. In a health service with cash spending limits the use of the more expensive cytotoxic drugs should be limited to the treatment of patients in whom "cure" or long-term ablation of disease is being attempted or to protocol studies in which their effectiveness is compared with that of other, possibly less expensive, drugs. Further studies are required of the use of the less expensive cytotoxic drugs in order to maximise their usefulness in the palliative treatment of advanced disease.

High energy fast neutrons from the Harwell variable energy cyclotron. I. Physical characteristics

A high energy fast neutron beam potentially suitable for radiotherapy was built at the Harwell variable energy cyclotron. The beam line is described and results are given of physical measurements on the fast neutron beams produced by 42 MeV deuterons on thick (4 mm) and thin (2 mm) beryllium targets. With 20 muA beam current the entrance dose rate in a phantom 150 cm from the target was about 130 rad min-1 with the thick target and about 60 rad min-1 with the thin target. Therefore, it is possible to use both the thin target and the relatively large target-skin distance of 150 cm to improve depth dose for radiotherapy or radiobiology. With this arrangement the dose rate decreased to 50% at depths in the phantom of 11.3-15.4 cm, depending on the field size. The use of primarily hydrogenous materials for shielding and collimation provided beam edge definition similar to that of 60Co teletherapy units, and off-axis radiation levels of approximately 1% which compare favorably with 14 MeV deuteron-tritium generators. The copper backing of the thin target became highly radioactive and an alterative material may be preferable. Biologic characteristics of the beam are described in a companion paper.

Heterogeneous heterozygosities in Mus musculus populations

Both chance and adaptation have effects in determining the genetical constitution of local populations of any organism, but opinions differ widely over their relative importance. This study describes the frequencies of electrophoretically detected alleles at 22 loci in 1538 house mice ( Mus musculus L.) from 27 population samples collected from the Faroe, Shetland and Orkney archipelagoes; the mainland of Great Britain plus three small off-shore islands; and a sub-Antarctic island (Macquarie) lying between Australia and the Antarctic Continent. Neither the average heterozygosities nor the distribution of allele frequencies in the different populations showed any discernible pattern, but at least three loci ( Hbb , Es -2, Dip -1) underwent seasonal changes in frequency which could only be due to selection. Moreover the overall variances of allele frequencies were significantly heterogeneous ( P ≈ 0.001), suggesting that different factors affect different loci. The key to understanding this apparent randomness of frequencies is recognizing that selection pressures are non-constant, and particular traits may affect fitness only spasmodically. The occurrence and frequency of an allele in any population may reflect only chance historical factors, but the trait(s) affected by it is potentially subject to selection at any time. For example, the proportion of heterozygotes at the Hbb locus in one population (Skokholm) living entirely independent of man, increased in five summers out of six. Winter death in mice is colddependent, and the exceptional summer followed a particularly mild winter when the usual decrease in heterozygotes did not take place. An r -selected species like the house mouse is more likely to reveal the interplay of genetical chance and purpose than a numerically less volatile one in which short-term genetical adjustment will be relatively uncommon.

Multilayer oxidation of polycrystalline platinum

The formation of a visible oxide film on polycrystalline Pt foil and wire is reported, and positively identified. The conditions for growth and dissociation of the oxide are outlined, and the energy of decomposition is estimated.

Skin response to X-irradiation in the guinea-pig

Skin reaction to X-irradiation has been studied in the albino guinea-pig; early response in limited-field irradiations of the flank is comparable to that commonly seen in rodents, swine and man, and is dose-dependent with a dynamic range from mild erythema to moist desquamation. The peak early skin reaction is seen between 14 and 21 days after irradiation, and declines before 30 days except at the highest doses used. Fractionation of the X-ray dose at 24 hours results in a 'sparing' of about 340 rad. Permanent partial epilation is detectable at doses in excess of 1400 rad, and complete epilation at 1 year occurs in 50 per cent of irradiated fields at 1740 rad. Twenty-four hour two-dose fractionation results in a 'sparing' of about 500 rad for epilation. Palpable dermal 'fibrosis' is detectable at 3 months after irradiation in fields given more than 2070 rad, and at 1 year after irradiation in fields given more than 1800 rad; 50 per cent of fields showed palpable 'fibrosis' at 1 year at 1930 rad. Unlike domestic swine and man, skin fields in the guinea-pig showed no dimensional contraction after X-ray doses which produced gross early skin damage.

Change in oxygen enhancement ratio with depth in tissue-equivalent material for a collimated beam of fast neutrons

Survival of reproductive capacity of murine leukaemia P-388 cells was assayed in vivo after the cells had been irradiated in vitro under aerobic or hypoxic conditions with collimated beams of X rays or 16 MeV D-Be fast neutrons at various depths in tissue-equivalent phantom material. The response to X-irradiation was the same in the absence of the phantom and at 8-7 cm depth. The response to fast neutrons under aerobic conditions was unchanged from 0 to 23 cm depth within the phantom. However, under hypoxic conditions, the dose-response curve for fast neutrons became significantly steeper with increasing depth in the phantom. The OER decreased from 2-0 in the absence of the phantom to 1-5 at 15 cm deep.

A comparison for use in radiotherapy of neutron beams generated with 16 and 42 MeV deuterons on beryllium

The physical and radiobiological properties of two neutron beams have been compared. The beams were generated by deuterons of 16 MeV at Hammersmith Hospital and 42 MeV at Harwell, in both cases falling on a Be/Cu target. The dose-rate and depth-dose characteristics at the higher energy were found to be superior to those at the lower energy. Collimation and shielding at the higher energy are facilitated by the greater degree of forward-peaking and by the fact that a higher dose-rate allows longer collimators to be used. Attenuation in iron was found to be similar at the two energies. The radiobiological properties of the two neutron beams are very similar. There is a difference of about 20 per cent in RBE for effects on mammalian tissues for doses between 300 and 2,000 rad of neutrons. The OER and the sparing effect of two large fractions are the same for the two beams.