Frequency dependence of acoustic waves in marine sediments

In situ techniques provide the most reliable method of examining the geoacoustical properties of marine sediments. In the past, individual in situ surveys have only been able to examine compressional waves over a maximum frequency range of 100 Hz to 50 kHz. A new in situ acoustic device, the Sediment Probing Acoustic Detection Equipment, or SPADE, has been developed, which can emit a variety of pulses, e.g. tonal and swept-frequency, over a continuous frequency range of 10 - 100 kHz. Data from a recent field trial are analysed to obtain the in situ velocity and attenuation over frequency increments of 5 kHz between 10 - 75 kHz. Results imply that scattering is a dominant attenuation mechanism from 10-75 kHz and the media is dispersive for frequencies between 60 and 70 kHz and below 20 kHz. Biot theory cannot accurately model the observed velocity and attenuation

Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Effect of treatment on established osteoporosis in young women with amenorrhoea

Background and Objective - Amenorrhoea in women of reproductive age causes loss of bone mineral. This study assessed the effect of treatment of amenorrhoea on bone mineral density. Design - Serial measurements of bone mineral density were obtained in women receiving treatment for amenorrhoea. Patients - Eighty-five women aged 17-40 with a past or current history of amenorrhoea, from various causes, with median duration of 46.5 months (range 8 months-21 years). Measurements - Bone mineral density in the lumbar spine was measured by dual-energy X-ray absorptiometry. Results - Initial vertebral bone mineral density was low, mean 0.85 (SD 0.10) g/cm2. After an interval of 19.6 (SD 7.5) months on treatment there was a highly significant increase to 0.89 (SD 0.10) g/cm2 (P < 0.0005). This was equivalent to a gain in bone mass of 2.1% per year (95% confidence interval 1.5-2.8%). Improvement was seen in all diagnostic groups (except polycystic ovary syndrome) and with all types of therapy. We observed no difference in the response of previously untreated patients compared with those already on treatment, nor any change in response with increasing duration of treatment. No new fractures were reported during the study. Conclusions - Bone mineral density in young women with amenorrhoea is improved by appropriate treatment, but recovery is not substantial. Hence early diagnosis and therapy is essential to prevent bone loss

Thr-E11 regulates O2 affinity in Cerebratulus lacteus mini-hemoglobin

The mini-hemoglobin from Cerebratulus lacteus (CerHb) belongs to a class of globins containing the polar Tyr-B10/Gln-E7 amino acid pair that normally causes low rates of O2 dissociation and ultra-high O2 affinity, which suggest O2 sensing or NO scavenging functions. CerHb, however, has high rates of O2 dissociation (kO2 about 200\u2013600 s-1) and moderate O2 affinity (KO2 about 1 microM-1) as a result of a third polar amino acid in its active site, Thr- E11. When Thr-E11 is replaced by Val, kO2 decreases 1000-fold and KO2 increases 130-fold at pH 7.0, 20 \ub0C. The mutation also shifts the stretching frequencies of both heme-bound and photodissociated CO, indicating marked changes of the electrostatic field at the active site. The crystal structure of Thr-E11 3 Val CerHbO2 at 1.70 \uc5 resolution is almost identical to that of the wildtype protein (root mean square deviation of 0.12 \uc5). The dramatic functional and spectral effects of the Thr- E11 3 Val mutation are due exclusively to changes in the hydrogen bonding network in the active site. Replacing Thr-E11 with Val \u201cfrees\u201d the Tyr-B10 hydroxyl group to rotate toward and donate a strong hydrogen bond to the heme-bound ligand, causing a selective increase in O2 affinity, a decrease of the rate coefficient for O2 dissociation, a 40 cm-1 decrease in CO of hemebound CO, and an increase in ligand migration toward more remote intermediate sites

Effect of age on bone density and bone turnover in men

ObjectiveLittle is known about the pattern of age-related bone loss in men, and although androgens are required for optimum bone mass it is not clear whether the fall in bone mass with age in men is related to falling androgens.DesignCross-sectional measurement of bone density, at five sites, and markers of bone resorption and formation in 147 normal volunteers aged 20-83 years.SubjectsHealthy laboratory workers, hospital staff, their relatives, and husbands of women attending our osteoporosis clinic.MeasurementsForearm density (fat corrected), spine L2-L4, femoral neck, Ward's triangle and trochanter density; serum procollagen I C-terminal extension peptide, osteocalcin, bone alkaline phosphatase and collagen I C-terminal telopeptide; fasting urine hydroxyproline/creatinine, pyridinoline/creatinine and deoxy-pyridinoline/creatinine; and free androgen index (FAI), measured as serum testosterone/sex hormone binding globulin.ResultsBone loss accelerated at most sites after age 50. There was a significant fall in FAI from the third decade onwards. The levels of all bone markers fell with age.ConclusionsBone loss in men appears to accelerate from age 50 and is associated with decreased bone formation which may be associated with falling levels of free androgen