Caspase-2 is not required for thymocyte or neuronal apoptosis even though cleavage of caspase-2 is dependent on both Apaf-1 and caspase-9

We have generated rat monoclonal antibodies that specifically recognise caspase-2 from many species, including mouse, rat and humans. Using these antibodies, we have investigated caspase-2 expression, subcellular localisation and processing. We demonstrate that caspase-2 is expressed in most tissues and cell types. Cell fractionation and immunohistochemistry experiments show that caspase-2 is found in the nuclear and cytosolic fractions, including a significant portion present in the Golgi complex. We found that caspase-2 is processed in response to many apoptotic stimuli but experiments with caspase-2 deficient mice demonstrated that it is not required for apoptosis of thymocytes or dorsal root ganglia (DRG) neurons in response to a variety of cytotoxic stimuli. Caspase-2 processing does not occur in thymocytes lacking Apaf-1 or caspase-9, suggesting that in this cell type, activation of caspase-2 occurs downstream of apoptosome formation.

Standardising the descriptive epidemiology of osteoporosis: recommendations from the Epidemiology and Quality of Life Working Group of IOF

The Committee of Scientific Advisors of International Osteoporosis Foundation (IOF) recommends that papers describing the descriptive epidemiology of osteoporosis using bone mineral density (BMD) at the femoral neck include T-scores derived from an international reference standard.

INTRODUCTION

The prevalence of osteoporosis as defined by the T-score is inconsistently reported in the literature which makes comparisons between studies problematic.

METHODS

The Epidemiology and Quality of Life Working Group of IOF convened to make its recommendations and endorsement sought thereafter from the Committee of Scientific Advisors of IOF.

RESULTS

The Committee of Scientific Advisors of IOF recommends that papers describing the descriptive epidemiology of osteoporosis using BMD at the femoral neck include T-scores derived from the National Health and Nutrition Examination Survey III reference database for femoral neck measurements in Caucasian women aged 20-29 years.

CONCLUSIONS

It is expected that the use of the reference standard will help resolve difficulties in the comparison of results between studies and the comparative assessment of new technologies.

Does birthweight predict bone mass in adulthood? A systematic review and meta-analysis

SUMMARY

This systematic review and meta-analysis assessed the strength and magnitude of the association between birthweight and adult bone mass. Higher birthweight was associated with higher bone mineral content of the spine and hip in adult men and women at ages between 18 and 80 years across a range of settings.

INTRODUCTION

The aim of this review was to assess the strength and magnitude of the association between early size and adult bone mass.

METHODS

Systematic review and meta-analysis of studies that assessed the association between birthweight or weight at 1 year, and bone mineral content (BMC) or bone mineral density (BMD) in adulthood.

RESULTS

Fourteen studies met inclusion criteria. Nine assessed the relationship between birthweight and lumbar spine BMC, most showing that higher birthweight was associated with greater adult BMC. Meta-analysis demonstrated that a 1 kg increase in birthweight was associated with a 1.49 g increase in lumbar spine BMC (95% CI 0.77-2.21). Birthweight was not associated with lumbar spine BMD in 11 studies. In six studies, considering the relationship between birthweight and hip BMC, most found that higher birthweight was associated with greater BMC. Meta-analysis demonstrated that a 1 kg increase in birthweight was associated with a 1.41 g increase in hip BMC (95% CI 0.91-1.91). Seven studies considered the relationship between birthweight and hip BMD and, in most, birthweight was not a significant predictor of hip BMD. Three studies assessing the relationship between weight at 1 year and adult bone mass all reported that higher weight at one was associated with greater BMC of the lumbar spine and hip.

CONCLUSIONS

Higher birthweight is associated with greater BMC of the lumbar spine and hip in adulthood. The consistency of these associations, across a range of settings, provides compelling evidence for the intrauterine programming of skeletal development and tracking of skeletal size from infancy to adulthood.

An encyclopedia of mouse genes

The laboratory mouse is the premier model system for studies of mammalian development due to the powerful classical genetic analysis possible (see also the Jackson Laboratory web site, http://www.jax.org/) and the ever-expanding collection of molecular tools. To enhance the utility of the mouse system, we initiated a program to generate a large database of expressed sequence tags (ESTs) that can provide rapid access to genes. Of particular significance was the possibility that cDNA libraries could be prepared from very early stages of development, a situation unrealized in human EST projects. We report here the development of a comprehensive database of ESTs for the mouse. The project, initiated in March 1996, has focused on 5' end sequences from directionally cloned, oligo-dT primed cDNA libraries. As of 23 October 1998, 352,040 sequences had been generated, annotated and deposited in dbEST, where they comprised 93% of the total ESTs available for mouse. EST data are versatile and have been applied to gene identification, comparative sequence analysis, comparative gene mapping and candidate disease gene identification, genome sequence annotation, microarray development and the development of gene-based map resources.

Epigenetic influences in the developmental origins of osteoporosis

Osteoporosis is a major public health problem due to consequent fragility fractures; data from the UK suggest that up to 50% of women and 20% men aged 50 years will have an osteoporosis-related fracture in their remaining lifetime. Skeletal size and density increase from early embryogenesis through intrauterine, infant, childhood and adult life to reach a peak in the third to fourth decade. The peak bone mass achieved is a strong predictor of later osteoporosis risk. Epidemiological studies have demonstrated a positive relationship between early growth and later bone mass, both at peak and in later life, and also with reduced risk of hip fracture. Mother-offspring cohorts have allowed the elucidation of some of the specific factors in early life, such as maternal body build, lifestyle and 25(OH)-vitamin D status, which might be important. Most recently, the phenomenon of developmental plasticity, whereby a single genotype may give rise to different phenotypes depending on the prevailing environment, and the science of epigenetics have presented novel molecular mechanisms which may underlie previous observations. This review will give an overview of these latter developments in the context of the burden of osteoporosis and the wider data supporting the link between the early environment and bone health in later life.

The femoral head/neck offset and hip resurfacing

Because the femoral head/neck junction is preserved in hip resurfacing, patients may be at greater risk of impingement, leading to abnormal wear patterns and pain. We assessed femoral head/neck offset in 63 hips undergoing metal-on-metal hip resurfacing and in 56 hips presenting with non-arthritic pain secondary to femoroacetabular impingement. Most hips undergoing resurfacing (57%; 36) had an offset ratio ≤ 0.15 pre-operatively and required greater correction of offset at operation than the rest of the group. In the non-arthritic hips the mean offset ratio was 0.137 (0.04 to 0.23), with the offset ratio correlating negatively to an increasing α angle. An offset ratio ≤ 0.15 had a 9.5-fold increased relative risk of having an α angle ≥ 50.5°. Most hips undergoing resurfacing have an abnormal femoral head/neck offset, which is best assessed in the sagittal plane.

Using Advice and Assessing Its Quality

People received advice from four sources and used it to produce a judgment. They also assessed the quality of advice by estimating the probability that it would be correct. They were better at assessing than at using advice: combinations of advice based on their assessments were superior to their judgments. Order of assessing and using advice, superficial differences between advisors, and using other methods of advice assessment had no significant effects on this superiority of advice assessment over advice use. However, use but not assessment was improved when some advisors exhibited biases opposite to those that people typically show. It appears that using advice imposes a heavier processing load than assessing its quality and that this load can be lightened by including advisors who exhibit unusual behavior. Their salience may help people working under a heavy processing load make appropriate pairings between advisor weights and advice. Copyright 2000 Academic Press.

Confidence in judgment

Experiments have shown that, generally, people are overconfident about the correctness of their answers to questions. Cognitive psychologists have attributed this to biases in the way people generate and handle evidence for and against their views. The overconfidence phenomenon and cognitive psychologists' accounts of its origins have recently given rise to three debates. Firstly, ecological psychologists have proposed that overconfidence is an artefact that has arisen because experimenters have used question material not representative of the natural environment. However, it now appears that some overconfidence remains even after this problem has been remedied. Secondly, it has been proposed that overconfidence is an artefactual regression effect that arises because judgments contain an inherently random component. However, those claiming this appear to use the term overconfidence to refer to a phenomenon quite different from the one that the cognitive psychologists set out to explain. Finally, a debate has arisen about the status of perceptual judgments. Some claim that these evince only underconfidence and must, therefore, depend on mechanisms fundamentally different from those subserving other types of judgment. Others have obtained overconfidence with perceptual judgments and argue that a unitary theory is more appropriate. At present, however, no single theory provides an adequate account of the many diverse factors that influence confidence in judgment.

Non-informative effects of stimuli functioning as cues

The category of a first stimulus (S1) serving as a cue may allow a subject to predict the category of a second stimulus (S2). However, a cue may have effects on RT to S2 that are independent of those derived from its intended role as a predictor. These non-informative effects of a cue may add to or subtract from the benefits associated with its predictive function. Two experiments demonstrate that when S1 is in the same category as S2 (as is frequently the case for valid cues in cueing experiments) but provides no information about S2, RT is slower than when S1 is in a different category from S2. It is suggested that this category relation effect arises because inhibition of a response to S1 is still present when S2 arrives and that, in some cueing experiments, it may subtract from the RT benefits derived from the cue as a predictor of S2. Also, RT to a visual but not to an auditory S2 was faster after an auditory S1 than after a visual S1. It is argued that this modality combination effect is consistent with the view that auditory signals are more alerting than visual ones and that this is another factor to be taken into account in the design of cueing and other experiments.

FRAX-based assessment and intervention thresholds--an exploration of thresholds in women aged 50 years and older in the UK

Under current guidelines, based on prior fracture probability thresholds, inequalities in access to therapy arise especially at older ages (≥70 years) depending on the presence or absence of a prior fracture. An alternative threshold (a fixed threshold from the age of 70 years) reduces this disparity, increases treatment access and decreases the need for bone densitometry.

INTRODUCTION

Several international guidelines set age-specific intervention thresholds at the 10-year probability of fracture equivalent to a woman of average BMI with a prior fracture. At older ages (≥70 years), women with prior fracture selected for treatment are at lower average absolute risk than those selected for treatment in the absence of prior fracture, prompting consideration of alternative thresholds in this age group.

METHODS

Using a simulated population of 50,633 women aged 50-90 years in the UK, with a distribution of risk factors similar to that in the European FRAX derivation cohorts and a UK-matched age distribution, the current NOGG intervention and assessment thresholds were compared to one where the thresholds remained constant from 70 years upwards.

RESULTS

Under current thresholds, 45.1% of women aged ≥70 years would be eligible for therapy, comprising 37.5% with prior fracture, 2.2% with high risk but no prior fracture and 5.4% selected for treatment after bone mineral density (BMD) measurement. Mean hip fracture probability was 11.3, 23.3 and 17.6%, respectively, in these groups. Under the alternative thresholds, the overall proportion of women treated increased from 45.1 to 52.9%, with 8.4% at high risk but no prior fracture and 7.0% selected for treatment after BMD measurement. In the latter group, the mean probability of hip fracture was identical to that observed in women with prior fracture (11.3%). The alternative threshold also reduced the need for BMD measurement, particularly at older ages (>80 years).

CONCLUSIONS

The alternative thresholds equilibrate fracture risk, particularly hip fracture risk, in those with or without prior fracture selected for treatment and reduce BMD usage at older ages.

Development of a binding assay for the B1 receptors for kinins

A novel binding assay to kinin B1 receptors was developed, based on the design of a high-affinity agonist ligand, [125I]Tyr-Gly-Lys-Aca-Lys-des-Arg9-BK. Binding to rabbit aortic smooth muscle cells is highly temperature-dependent (optimal at 37 degrees C); apparent binding equilibrium is reached within 30 min, and competition by kinin analogs reveals the expected correlation with the B1 receptor pharmacology. The dissociation constant (Kd) of the labeled ligand is approx. 0.2 nM and this value does not change significantly as a function of cytokine pretreatment. However, the receptor abundance (Bmax) is significantly increased (1.5-fold) by pretreating the cells with interleukin-1 (IL-1), while oncostatin M (OSM) produces a marginal increase of the Bmax. This assay may be useful in documenting the regulation of B1 receptors in pathology.

Isotonic vocalis contraction as a means of producing rapid decreases in Fo

In a first experiment, subjects were presented with frequency modulated tones and instructed to vary their own vocal pitch to match what they were hearing. It was found that the faster a subject modulated his voice, the higher the carrier frequency he produced became relative to that specified as his target. In a second experiment, subjects were presented with one or two target tones. After one was presented, they were required to reproduce its pitch with their own voice. They did so accurately. After two were presented, they were asked to oscillate the pitch of their voice as rapidly as possible between them. In this case, it was found that the tones which were produced were higher than those specified by the targets. It is argued that the results from both experiments indicate that fast decreases in voice pitch are produced by isotonic contraction of the vocalis muscles.

Structural requirements and mechanism of the pressor activity of Leu-Val-Val-hemorphin-7, a fragment of hemoglobin beta-chain in rats

A rat blood pressure assay was used to perform a structure-activity relationship study (SAR) of Leu-Val-Val-hemorphin-7 (LVV-H7), a fragment of hemoglobin (Hb) beta-chain, elucidate the mechanisms of its cardiovascular effects, and test its potential involvement in the pressor activity of diaspirin crosslinked Hb (DCLHb), a recently developed Hb-based oxygen carrier. The SAR study revealed that the C-terminal-Arg-Phe-amino acid sequence of LVV-H7 contained the main determinants of the pressor activity of this peptide. Drug interaction studies using various inhibitory drugs (e.g., phentolamine, clonidine, etc.) and LVV-H7 showed that the pressor effect and tachycardia elicited by LVV-H7 involved the activation of the sympathetic nervous system (SNS). Additional studies using phenytoin (sodium channel blocker), [Tic7]H7(5-7)-NH2 (putative antagonist of receptors for LVV-H7) and H7(5-7)-NH2, an amidated C-terminal fragment of LVV-H7, suggested that LVV-H7 activated the SNS by interacting with specific receptors functionally coupled with phenytoin-sensitive sodium channels. The pressor effect and tachycardia caused by LVV-H7 were potentiated by captopril, suggesting that the angiotensin converting enzyme may contribute to the inactivation of LVV-H7 in rats. The pressor activity of DCLHb, in contrast to that elicited by LVV-H7, was not affected by animal pretreatment with LVV-H7 fragments shown to inhibit the pressor effect of LVV-H7. We conclude that: 1) LVV-H7 is unlikely to mediate the pressor activity of DCLHb in rats; 2) the pressor and tachycardic activities of LVV-H7 are mediated by the SNS; 3) the C-terminal-Arg-Phe-amino acid sequence of LVV-H7 contains the chemical groups responsible for the pressor effect of this peptide in rats; 4) LVV-H7 and FMRF amide-related peptides may share the same mechanism of pressor activity in rats.

No phospholipid monolayer-sugar interactions

Studies by a number of workers using the Langmuir film balance have shown that when carbohydrates, such as sucrose or glycerol, are dissolved in a subphase on which a phospholipid is spread, film expansion occurs (Cadenhead & Demchak, 1969; Cadenhead & Bean, 1972; Maggio et al., 1976; Maggio & Lucy, 1978). Recently such effects have been observed again, particularly with the carbohydrates galactose and trehalose (Johnston et al., 1984). The origin of these film expansions was uncertain, and various suggestions have been made to explain them. One idea was that they might be due to interactions which these carbohydrates have with the water molecules close to the polar head groups of the lipids. Recent studies in our two laboratories, described here, show that the magnitude of the expansion effects is variable and that in general they arise from surfactant impurities in the sugars. These impurities are observed in carbohydrates which are reputedly of high grade; the amount of impurity present can vary from batch to batch, and sometimes they can be difficult to remove. Film balance techniques or subphase preparation can mask the detection of minor impurities. The presence of surfactant impurities in reputedly pure carbohydrates needs to be considered in other biochemical and biophysical studies of lipids and cell membranes.

Post-fracture management of patients with hip fracture: a perspective

BACKGROUND

Hip fracture creates a worldwide morbidity, mortality and economic burden. After surgery, many patients experience long-term disability or die as a consequence of the fracture. A fracture is a major risk factor for a subsequent fracture, which may occur within a short interval.

METHODS

A literature search on post-fracture management of patients with hip fracture was performed on the Medline database. Key experts convened to develop a consensus document.

FINDINGS

Management of hip-fracture patients to optimize outcome after hospital discharge requires several stages of care co-ordinated by a multidisciplinary team from before admission through to discharge. Further studies that specifically assess prevention and post-fracture management of hip fracture are needed, as only one study to date has assessed an osteoporosis medication in patients with a recent hip fracture. Proper nutrition is vital to assist bone repair and prevent further falls, particularly in malnourished patients. Vitamin D, calcium and protein supplementation is associated with an increase in hip BMD and reduction in falls. Rehabilitation is essential to improve functional disabilities and survival rates. Fall prevention and functional recovery strategies should include patient education and training to improve balance and increase muscle strength and mobility. Appropriate management can prevent further fractures and it is critical that high-risk patients are identified and treated. To foster this process, clinical pathways have been established to support orthopaedic surgeons.

CONCLUSION

Although hip fracture is generally associated with poor outcomes, appropriate management can ensure optimal recovery and survival, and should be prioritized after a hip fracture to avoid deterioration of health and prevent subsequent fracture.

The timed up and go test predicts fracture risk in older women independently of clinical risk factors and bone mineral density

The timed up and go (TUG) test measures physical performance and predicts falls in the elderly. In older women, TUG time predicts the risk of major osteoporotic fracture and hip fracture independently of clinical risk factors and bone mineral density, and has a substantial impact on fracture probabilities.

INTRODUCTION

The timed up and go (TUG) test measures physical performance and predicts falls in the elderly. A slow TUG has been associated with an increased fracture risk, but it is unclear whether the association is independent of clinical risk factors and bone mineral density (BMD). The aim of this study was to investigate if TUG time was associated with fracture risk independently of clinical risk factors and BMD and to determine its impact on fracture probabilities in older women.

METHODS

A standardized questionnaire was used to assess information regarding clinical risk factors in the large population-based SUPERB study of 3028 older women (75-80 years). At baseline, the TUG test was performed and BMD measured with DXA. The association between TUG time and the risk of hip fracture and major osteoporotic fracture (MOF) was examined using an extension of Poisson regression.

RESULTS

Fracture incidence increased steeply with increasing TUG time up to 12 s and subsequently started to level off. A slow TUG time was therefore defined as TUG > 12 s, a cutoff level then used in Cox models to study the association between slow TUG and fracture risk. A slow TUG time was associated with an increased risk of fracture (MOF 2.39 [1.80-3.18] and hip fracture 2.96 [1.62-5.40]). These associations were slightly attenuated but remained significant after adjustment for clinical risk factors and femoral neck BMD. Depending on BMD, the 4-year fracture probability of MOF increased by a factor of 1.5-1.9 in a 75-year-old woman with slow TUG (> 12 s).

CONCLUSION

The TUG time predicts the risk of MOF and hip fracture independently of clinical risk factors and BMD and has a substantial impact on fracture probabilities, indicating that inclusion of the TUG test in patient evaluation should be considered in order to improve fracture prediction in older women.

Systematic screening using FRAX® leads to increased use of, and adherence to, anti-osteoporosis medications: an analysis of the UK SCOOP trial

In the large community-based SCOOP trial, systematic fracture risk screening using FRAX^® led to greater use of AOM and greater adherence, in women at high fracture risk, compared with usual care.

INTRODUCTION

In the SCreening of Older wOmen for Prevention of fracture (SCOOP) trial, we investigated the effect of the screening intervention on subsequent long-term self-reported adherence to anti-osteoporosis medications (AOM).

METHODS

SCOOP was a primary care-based UK multicentre trial of screening for fracture risk. A total of 12,483 women (70-85 years) were randomised to either usual NHS care, or assessment using the FRAX^® tool ± dual-energy X-ray absorptiometry (DXA), with medication recommended for those found to be at high risk of hip fracture. Self-reported AOM use was obtained by postal questionnaires at 6, 12, 24, 36, 48 and 60 months. Analysis was limited to those who initiated AOM during follow-up. Logistic regression was used to explore baseline determinants of adherence (good ≥ 80%; poor < 80%).

RESULTS

The mean (SD) age of participants was 75.6 (4.2) years, with 6233 randomised to screening and 6250 to the control group. Of those participants identified at high fracture risk in the screening group, 38.2% of those on treatment at 6 months were still treated at 60 months, whereas the corresponding figure for the control group was 21.6%. Older age was associated with poorer adherence (OR per year increase in age 0.96 [95% CI 0.93, 0.99], p = 0.01), whereas history of parental hip fracture was associated with greater rate adherence (OR 1.67 [95% CI 1.23, 2.26], p < 0.01).

CONCLUSIONS

Systematic fracture risk screening using FRAX^® leads to greater use of AOM and greater adherence, in women at high fracture risk, compared with usual care.

Comparison of external jugular and central venous pressures in mechanically ventilated patient

We compared central venous pressures, measured via a 150 mm triple lumen catheter in the internal jugular vein with simultaneous external jugular venous pressures, measured with a 5 mm cannula in the external jugular vein, in 24 patients undergoing major surgery. Patients were mechanically ventilated in the supine position. Six sets of paired measurements of mean central venous pressure and mean external jugular venous pressure were taken by a blinded observer, in random order and at end-expiration at 30-min intervals during surgery. Four patients were not studied because of a failure to cannulate the external jugular vein. The remaining 20 patients yielded 111 sets of paired measurements. The mean difference between external jugular venous pressure and central venous pressure was 0.3 mmHg over a range of central venous pressure of 0-22 mmHg. Limits of agreement were 3.6 to +3.0 mmHg (95% CI 4.1 to +3.5 mmHg). We conclude that external jugular venous pressure is an accurate estimate of central venous pressure in surgical patients undergoing mechanical ventilation.

Taking advice, using information and knowing what you are doing

Subjective descriptions of judgment policies have been found to be imperfect. This could be because subjective weights are obtained on just a single occasion after all judgments have been completed. It could also be because people have tended to state their perception of an ideal way of responding rather than their perception of how they actually responded. Finally, it could be because they experience difficulty in relating variation in stimulus dimensions to variation in quite different response dimensions. In our task, people made sales forecasts on the basis of four pieces of information. They also stated the weight they placed on each one and the weight they should have placed on it. The means of weights stated on each trial were more appropriate than those stated at the end of all trials. Stated actual weights were very similar to stated ideal weights. Weights were more appropriate when forecasts and cues varied along the same dimension than when they did not. Thus, our results are consistent with the view that all three factors affect people's ability to provide subjective descriptions of their judgment policies.

Normal molecular size of the Na(+)-phosphate cotransporter and normal Na(+)-dependent binding of phosphonoformic acid in renal brush border membranes of X-linked Hyp mice

X-linked Hyp mice have a specific defect in Na(+)-dependent phosphate (Pi) transport at the renal brush border membrane (BBM). In the present study we examined the effect of the Hyp mutation on the molecular size of the Pi transporting unit and on Na(+)-dependent 14C-phosphonoformic (PFA) binding in renal BBM vesicles. By radiation inactivation analysis, we demonstrated that the molecular size of the Na(+)-Pi cotransporter is similar in normal (242 +/- 16 kDa) and Hyp mice (227 +/- 39 kDa). Moreover, while BBM Na(+)-dependent Pi transport is significantly reduced in Hyp mice (249 +/- 54 vs 465 +/- 82 pmol/mg protein/6s), genotype differences in (1) Na(+)-dependent PFA binding (1020 +/- 115 vs 1009 +/- 97 pmol/mg protein/30 min), (2) Pi-displaceable Na(+)-dependent PFA binding (605 +/- 82 vs 624 +/- 65 pmol/mg protein/6s), and (3) phosphate uptake at Na(+)-equilibrium (67 +/- 10 vs 54 +/- 7 pmol/mg protein/6s) are not apparent. The present data demonstrate that the molecular size of the renal BBM Na(+)-Pi cotransporter is normal in Hyp mice and suggest that the number of Na(+)-Pi cotransporters may not be reduced in the mutant strain.

Renal Na(+)-phosphate cotransport in X-linked Hyp mice responds appropriately to Na+ gradient, membrane potential, and pH

To investigate the mechanism for the 50% decrease in Vmax of the high-affinity phosphate transport system in the renal brush-border membrane of X-linked Hyp mice, we compared the effects of external Na+ concentration, membrane potential, pH, phosphonoformic acid (PFA), and arsenate on Na(+)-Pi cotransport in brush-border membrane vesicles prepared from normal mice and Hyp littermates. The affinity of the Na(+)-Pi cotransport system for Na+ (apparent Km = 60 +/- 7 and 64 +/- 2 mM for normal and Hyp mice, respectively) and the Na(+)-Pi stoichiometry estimated from Hill plots (2.5 +/- 0.2 and 2.9 +/- 0.6 for normal and Hyp mice, respectively) were similar in brush-border membranes of both strains. Inside-negative membrane potential, generated by anions of different permeabilities, stimulated Na(+)-Pi cotransport and inside-positive membrane potential generated by valinomycin, and a K+ gradient (outside greater than inside) inhibited Na(+)-Pi cotransport to the same extent in brush-border membranes derived from normal mice and Hyp littermates. The pH dependence of Na(+)-Pi cotransport was similar in brush-border membrane vesicles of normal and Hyp mice. The ratio of Na(+)-Pi cotransport measured at pH 7.5 relative to that at pH 6.5 was 2.9 +/- 0.6 in normal mice and 2.9 +/- 0.7 in Hyp mice. PFA was a competitive inhibitor of Na(+)-Pi cotransport in brush-border membranes of both normal and Hyp mice. However, the apparent Ki for PFA was significantly lower in Hyp mice (0.31 +/- 0.01 and 0.19 +/- 0.02 mM in normal and Hyp mice, respectively, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The renal clearance and plasma binding of vasopressin in the dog

The isolated dog kidney was perfused with blood containing 1 m-u. arginine vasopressin/ml. In other experiments 40 or 50 m-u./min. were infused into three intact dogs. Antidiuretic activity was measured in renal venous blood, arterial blood, and in the urine. Renal blood flow was determined directly in the perfused dog kidney and by p-aminohippuric acid clearance in the intact dog; glomerular filtration rate was measured by either inulin or creatinine clearance.

About 38% of the hormone was extracted from the arterial blood in its passage through the kidney. Of the total amount of hormone infused, about 18% was eliminated by each kidney. The quantity of vasopressin extracted from the blood was greater than that excreted in the urine, indicating that the hormone is inactivated by the kidney. In intact dogs, the amount of hormone filtered by the kidney was less than that excreted, suggesting tubular secretion.

It was calculated that the release of endogenous arginine vasopressin induced by the stimuli of anaesthesia and surgery was between 3 and 7 m-u./min. and that approximately 15% of the endogenous hormone was excreted.

Ultrafiltration of dog plasma at three different concentrations of arginine vasopressin (30, 100 and 290 μ-u./ml.) showed that binding was reduced as the concentration was raised and that at the concentration of hormone in the experiments, less than 30% was bound.

The difficulties of relating these findings at artificially high blood concentrations to those at physiological blood concentrations of vasopressin are discussed.

Collecting information: optimizing outcomes, screening options, or facilitating discrimination?

Collection of information prior to a decision may be integrated into a compensatory choice process; if it is, the information packet that is collected should be the one that produces the highest net gain. Alternatively, information may be collected in order to screen out options that fail to meet minimum standards; if this is the case, people should not choose options on which they have not collected available information. We tested these and other predictions from the two approaches in four experiments. Participants were given specific information about three attributes of each choice option but only probabilistic information about a fourth one. They rated attractiveness of options, decided whether to collect specific information about the fourth attribute of each one, rated options again, and then selected one of them. Data were consistent with neither of the above approaches. Instead they suggested that people collect information in order to facilitate their ability to discriminate between the attractiveness of options.

Stereoselective recognition in phospholipid monolayers

During the past ten years we have investigated the stereochemistry of intermolecular interactions in monolayers at the air-water interface, a field which has never been developed explicitly before to our knowledge. Although we demonstrated clear enantiomeric and diastereomeric interactions for a number of chiral surfactants, we found no evidence whatsoever for stereoselective interaction in dipalmitoylphosphatidylcholine (DPPC) monolayers or vesicles by standard monolayer techniques, differential scanning calorimetry or ultra-highfield NMR. The present article extends these observations to dimyristoyl- and dilauroylphosphatidylcholine. Results from dynamic surface tension studies are also reported. In no case could chiral recognition be demonstrated using the 95% confidence limit as the criterion. In our previous study of DPPC mixtures with another chiral surfactant the question arose as to whether chiral interactions could be transmitted through intervening phospholipid molecules. This question is addressed by examining the force-area curves for a variety of mixed monolayers composed of chiral surfactants and phospholipids. We conclude that the chiral discrimination observed in some of these mixed monolayers is due to the direct interaction of chiral centers, and not due to the transmission of chirality from one stereocenter to the next through intermediate achiral molecules. Finally, we will consider the question of why phospholipids, the most ubiquitous of natural chiral surfactants, should show so little chiral discrimination in view of the wide occurrence of high stereoselectivity in many natural processes.