Evaluation of cardiovascular risk in a lung cancer screening cohort: what value does it bring?

There is a significant opportunity to improve cardiovascular disease (CVD) outcomes in lung cancer screening cohorts with a low-cost, noninvasive assessment of CVD risk, alongside existing assessments https://bit.ly/3a6Ha41.

Calcium Metabolism in Bone Disease: Effects of Treatment with Microcrystalline Calcium Hydroxy Apatite Compound and Dihydrotachysterol1

Microcrystalline calcium hydroxyapatite compound (MCHC) was given orally together with small doses of dihydrotachysterol (DHT) to a number of patients with osteogenesis imperfecta (OI). Serial calcium and phosphate balances in three patients representing wide variations in severity of OI are presented over periods from eight months to two years. The combination of MCHC and DHT resulted in an immediate positive calcium balance which was maintained throughout the period of assessment in 2 cases. However, no radiological improvement could be demonstrated. Substituting calcium gluconate for MCHC resulted in a reduction of positive balance. No adverse effects were noted. The reasons why MCHC with DHT should result in increased calcium retention are discussed. This combination of MCHC and DHT could be of benefit in many common situations of bone demineralization, such as osteoporosis.

Long-term ecosystem stress: the effects of years of experimental acidification on a small lake

Experimental acidification of a small lake from an original pH value of 6.8 to 5.0 over an 8-year period caused a number of dramatic changes in the lake's food web. Changes in phytoplankton species, cessation of fish reproduction, disappearance of the benthic crustaceans, and appearance of filamentous algae in the littoral zone were consistent with deductions from synoptic surveys of lakes in regions of high acid deposition. Contrary to what had been expected from synoptic surveys, acidification of Lake 223 did not cause decreases in primary production, rates of decomposition, or nutrient concentrations. Key organisms in the food web leading to lake trout, including Mysis relicta and Pimephales promelas, were eliminated from the lake at pH values as high as 5.8, an indication that irreversible stresses on aquatic ecosystems occur earlier in the acidification process than was heretofore believed. These changes are caused by hydrogen ion alone, and not by the secondary effect of aluminum toxicity. Since no species of fish reproduced at pH values below 5.4, the lake would become fishless within about a decade on the basis of the natural mortalities of the most long-lived species.

Stringent and growth-rate-dependent control of the gua operon of Escherichia coli K-12

The promoter of the gua operon has been located by transcript mapping using primer extension with reverse transcriptase. The surrounding nucleotide sequence has features characteristic of promoters under stringent and growth-rate-dependent regulation, namely a GC-rich discriminator next to the -10 hexamer, an upstream AT-rich sequence (the UP element) and potential FIS-binding sites. Transcriptional activity of the gua promoter was examined using transcriptional fusions to lacZ placed at a single chromosomal location. Expression from gua was reduced under stringent conditions in vivo, and varied with growth rate. Growth-rate control was independent of guanine-mediated repression. A fusion in which the GC-rich discriminator was mutated by insertion of an AT-rich oligonucleotide was used to demonstrate the importance of this region in control. Both stringent and growth-rate-dependent controls were abolished by the mutation. Other potential regulatory signals in the vicinity of the gua promoter are a pur operator (binding site for the PurR repressor), a gua operator, a DnaA-binding site and a CRP/FNR-binding sequence. The gua promoter lies back-to-back with the promoter for xseA (exonuclease VII), the two promoters being separated by only 20 bp.

Perceptual studies on ultrasonic B-scan textures

A pilot study of the perceptual characteristics of ultrasonic textured images is described. Scans of four models performed on four real-time machines optimised for display of a normal liver were used. A trial with 22 observers indicated that the model that gave images closest to the liver image varied between machines. A second, paired similarity test with five observers using all the model images was performed, with a cluster analysis of a multidimensional scaling procedure. This suggested that the prominent features of the textural images are often more closely related to the machines than to the models. Considerable further work is needed to confirm these pilot results and to identify the visual cues that are most significant in textured images.

The assessment of continuing medical education

There is a close link between audit of clinical competence and audit of continuing medical education. Some of the earlier assumptions about the organisation of continuing medical education need to be reviewed. The increasing provision of resources for continuing medical education by the NHS means that added safeguards are necessary to ensure that professional standards are not subordinated to service exigencies. The introduction of higher educational methodology into continuing medical education should be critically examined with awareness of the limitations and controversies concerning many methods of teaching and assessing educational outcome. The methodology of higher education may need to be substantially modified to suit the uniqueness of the clinical process and the problems of altering the behaviour of experienced and practising doctors. Criticism of behaviourist educational methods should be based on an understanding and knowledge of these methods. A new functional clinical educational domain is proposed which links educational methods with the clinical application of new learning.

Progesterone receptor in the hypothalamic cytosol of female rats

A progesterone (P)-binding component with a sedimentation coefficient of 8S has been demonstrated in hypothalamic cytosol from ovariectomized, estrogen-primed rats using both [H]P-containing sucrose-glycerol gradient analysis and dextran-coated charcoal adsorption of the preisolated 8S component. The association rate constant (K+1) was determined to be 1.90 +/- 0.38 (SD) X 10(6) M-1 min-1 at 0-2 C. The dissociation rate constant (K-1) was 1.86 x 10(-2) min-1, as calculated from the half-dissociation time [37.0 +/- 7.3 (SD) min]. The apparent dissociation constant (Kd) at 0-2 C was determined to be 6-10 nM by Scatchard plot analysis of data obtained from either direct [3HA]P binding or competition of the [3H]P binding by nonradioactive P and by calculating from K-1/K+1. The 8S binding component was protein in nature, and the concentration of binding sites was 12 fmol/mg cytosol protein. On a per U cytosol protein basis, the relative capacities of the specific 8S binding components were: uterus greater than pituitary greater than hypothalamus greater than hippocampus/amygdala greater than cerebral cortex. Competition studies showed a high specificity for P and 5 alpha-dihydroprogesterone. Corticosterone (C), although competing for the binding, had an affinity 8-fold less than P. Implantation of C in adrenalectomized, ovariectomized, estrogen-implanted rats suppressed the 8S binding of [3H]C without affecting the [3H]P binding. The binding of [3H]P to the cytoplasmic 8S component of hypothalamus was greater than that of combined hippocampus and amygdala, while the reverse was observed for the binding of [3H]dexamethasone. These results demonstrate in rat hypothalamic cytosol a tissue and hormone-specific, high affinity, 8S progesterone-binding protein which has many of the properties expected of a hormone receptor.

Lower levels of thyrotropin-releasing hormone-degrading activity in human cord and in maternal sera than in the serum of euthyroid, nonpregnant adults

Thyrotropin-releasing hormone (TRH)-degrading activity was investigated in human cord, maternal, and euthyroid adult sera by measuring (a) the rate of disappearance of TRH and (b) the rate of formation of degradation products. The rate of TRH degradation in cord and maternal sera was 25-33% of that in euthyroid adult serum. Concomitantly, in cord and maternal sera, the rate of formation of proline, a major TRH degradation product in serum, was one-quarter to one-third that in euthyroid adult sera. The differences were highly significant (P less than 0.001). The decreased levels of TRH-degrading activity in cord and maternal sera cannot be explained by (a) the presence of a dialyzable inhibitor, (b) the absence of an activator of TRH degradation, or (c) a reversal of the degradation process. There was no difference in the types of radioactive degradation products formed by cord, maternal, and euthyroid adult sera. The low level of TRH-degrading activity and its possible relationship to high thyrotropin-stimulating hormone levels in cord serum suggest that TRH-degrading activity may be a factor to consider in investigations of the perinatal pituitary-thyroid axis, but further studies are needed to determine the role of serum degradation of TRH in regulating physiological levels of TRH.

Longitudinal studies showing alterations in the levels and functional response of T and B lymphocytes in human pregnancy

Altered blood levels of T and B lymphocytes were found in the first half of human pregnancy. A total of twenty-two women were tested, using direct or indirect rosetting assays or the fluorescence-activated cell sorter, to determine the levels of peripheral blood T and B cells. In all cases, an inversion of T- and B-cell levels was observed, i.e. T-cell levels were decreased and B-cell levels (as measured by the presence of surface immunoglobulin or the presence of B-cell surface antigens) were increased. This inversion was exhibited as early as 1 week post-implantation. Lymphocytes from two fo the women were also examined for stimulation with phytohaemagglutinin (PHA) and pokeweed mitogen (PWM) at intervals during gestation, and the amount of [3H]thymidine uptake was compared to that of two non-pregnant women tested at each interval. The values obtained for the pregnant women with PHA were markedly lower, and with pokeweed mitogen slightly lower, than those of non-pregnant controls. However, the PHA and PWM values in the pregnant women returned to levels similar to those of the nonpregnant women shortly after the T- and B-cell levels returned to normal. Thus the decrease in the response of the lymphocytes to mitogens during early pregnancy appears to parallel the numerical deficiency of T cells.

Pituitary gonadotropin responsiveness with danazol

Danazol (17alpha-pregn-4-en-20-yno-[2,3-d]isoxazol-17-ol) was administered daily for 4 days to castrated female rats. As previously demonstrated, danazol lowered serum levels of luteinizing hormone (LH) in an apparent dose-dependent fashion. Animals which received danazol in a dose sufficient to lower serum LH responded to administered LH-releasing hormone (LHRH) with increases in serum LH levels which were not diminished as compared with those of control animals. Although these experiments do not preclude an effect of danazol directly on the pituitary, the results indicate that this agent probably lowers serum LH primarily by inhibition of hypothalamic LHRH secretion.

Danazol inhibits steroidogenesis

Danazol was found to inhibit multiple enzymes of steroidogenesis directly in the pregnant mare serum (PMS)-treated hamster ovary and the rat testis and adrenal in vitro. In the PMS-treated hamster ovary, danazol inhibited 17alpha-hydroxylase, 17,20-lyase, and 3beta-hydroxysteroid dehydrogenase. In the rat testis, danazol inhibited 17alpha-hydroxylase, 17,20-lyase, 3beta-hydroxysteroid dehydrogenase, and 17beta-hydroxysteroid dehydrogenase. In the rat adrenal, danazol inhibited 3beta-hydroxysteroid dehydrogenase, 21-hydroxylase, and 11beta-hydroxylase. Two hours after a subcutaneous injection of 5 mg/kg of danazol to adult male rats, serum luteinizing hormone levels were significantly increased and serum testosterone levels were significantly suppressed. These findings suggest that in the rodent one of danazol's major pharmacologic effects is the direct inhibition of steroidogenesis.

Catechol estrogen formation by the human fetal brain and pituitary

Homogenates of central neuroendocrine tissues from 2 male and 1 female midtrimester fetuses were incubated with (23H) estradiol-17beta. Metabolism at the C-2 position was monitored by measuring the tritium incorporated into water in the incubate. Liberation of tritium from the substrate by hypothalamus, limbic tissues, parietal cortex and pituitary occurred to the extent of 5.1-12.7%, 1.6-8.5%, 4.7-10.8%, and 0.9-4.1% of starting radioactivity, respectively. The nature of the product was confirmed by the isolation of 14C labelled 2-hydroxyestrone derivative from separate incubations with 14C-estrone as the substrate. With or without correction for weight of tissue incubated, catechol estrogen formation under these conditions occurs at levels similar to those seen in rat brain homogenates except that in contrast to the rat, the human cortex is also highly active.

The affinity of catechol estrogens for estrogen receptors in the pituitary and anterior hypothalamus of the rat

The purpose of these experiments was to evaluate the potential for interaction between 2-hydroxyestrone and 2-hydroxyestradiol and estrogen receptors in rat pituitary and anterior hypothalamus. The 150,000 X g supernatant fractions of these tissues were prepared, the estrogen receptor-site concentration was measured, and the relative abilities of unlabelled estradiol, estrone, 2-hydroxyestradiol and 2-hydroxyestrone to compete with [3H]estradiol for estrogen binding sites was determined. From these results, and the previously determined association constant for [3H]estradiol, 10(10)M-1, the association constants of the other estrogens were calculated. The introduction of the 2-hydroxy group caused only a modest reduction in the affinity of these estrogens for the receptors. The association constants of the 2-hydroxy derivatives were within one order of magnitude of those of the parent compounds. These results demonstrate the potential for interaction between catechol estrogens and estrogen receptor in rat brain and pituitary of a magnitude which could be biologically significant.

The effects of dexamethasone and indomethacin on the outcome of pregnancy in the rabbit

Pregnant rabbits were treated with indomethacin (8-10 mg/kh/day) or dexamethasone (1-2-1-8 mg/kh/day) during late gestation. The effects of these treatments on the concentrations of progesterone and prostaglandin F (PGF) in the peripheral plasma, and the outcome of gestation was studied. Treatment with indomethacin significantly prolonged the length of gestation (P smaller than 0-01) compared iwth control, untreated animals. In these treated animals, the plasma progesterone levels declined at a similar time to that in control rabbits but the increase in systemic PGF normally seen during late pregnancy was reduced. Dexamethasone treatemnt reliably induced premature delivery within 3-6 days. The plasma progesterone concentration fell rapidly during the first 24 h of dexamethasone administration, but in no animal was this associated with a significant increase in the plasma levels of PGF. These results are consistent with the suggestion that prostaglandins are involved in the normal initiation of parturition in the rabbit. They do not support the hypothesis that the effect of dexamethasone on the length of gestation is mediated through an increase in the production of prostaglandin F.

The effects of dexamethasone on the peripheral plasma concentrations of androstenedione, testosterone and cortisol in the pregnant rhesus monkey

The concentrations of androstenedione, testosterone and cortisol have been measured in the maternal peripheral plasma of normal pregnant rhesus monkeys (Macaca mulatta), and in rhesus monkeys treated daily with dexamethasone during late pregnancy. During the last 30 days of pregnancy, the mean plasma concentrations of androstenedione, testosterone and cortisol were about 1400-2000 pg/m1375-425pg/ml and 300-400 ng/ml, respectively. None of these steroids increased significantly before parturition. As there was no rise in maternal androgens in late pregnancy when plasma estrogens increase sharply, it suggested that his elevation of plasma estrogens is related to an increase of fetal precursors Dexamethasone treatment resulted in 90% suppression of plasma cortisol and 40%-60% suppression of androstendione and testosterone. As the suppression of maternal androgens was of lesser magnitude than the decline of plasma estrogens, and as the androgens did not continue to fall with continuing dexamethasone treatment as did the estrogens, these findings also suggest that the decline in plasma estrogens is related in large part to suppression and atrophy of the fetal adrenals.

Glucocorticoid synthesis from pregnenolone by sheep foetal adrenals in vitro

[7-3H]Pregnenolone was incubated with homogenates of adrenal glands from two 100-day-old sheep foetuses. Cortisol and corticosterone were isolated and identified by reverse isotope dilution and recrystallization to constant specific activity. Together these two compounds accounted for 12% and 17% of the substrate with the two tissue preparations. Other C21 and C19 metabolites which were sought were not present in appreciable quantities. Additional incubations were done with the adrenals of lamb foetuses ranging in age from 110 days of gestation to the immediate newborn period. Glucocorticoidogenic capacity similar to that of the 100-day-old foetuses was demonstrated throughout this period and no age-related change was evident. These results demonstrate that the lamb foetal adrenal has a substantial enzymic capacity for glucocorticoid synthesis throughout at least the last third of gestation. In conjunction with the observations of others, these experiments support the hypothesis that during this period of gestation the lamb foetal adrenal is actively synthesizing glucocorticoids in a manner which is similar to the lamb at term and the adult sheep.