Characterization of the work-time relationship during cross-country ski ergometry

The purpose of this study was to examine the validity and reliability of estimated parameters of the work-time relationship during cross-country ski ergometry using the traditional multi-trial critical power (CP) test and a 3 min 'all-out' test (3MT). Fourteen recreationally active male participants (mean ± SD; age: 22.14 ± 2.85 yrs; height: 177.09 ± 6.57 cm; weight: 85.68 ± 13.56 kg) completed three testing visits. All testing was conducted using an upper-body ergometer (SkiErg, Concept2, Inc., Morrisville, VT). A graded exercise test was used to determined maximal oxygen uptake (VO2peak). Two separate 3MT sessions were used to determine oxygen uptake (VO23MT), end-test power (EP), work above end-test power (WEP) and end stroke rate (ESR). Additionally, three time trials completed in a single day at simulated distances of 300 m, 650 m and 1000 m were used to estimate CP, W' and critical stroke rate (CSR). VO2peak (3.65 ± 0.50 l · min(-1)) and VO23MT (3.59 ± 0.4 l · min(-1)) were not significantly different (p = 0.162). Intraclass correlation coefficients for EP, WEP and ESR were 0.809, 0.611 and 0.783, respectively. EP (148 ± 33 W) and CP (157 ± 49 W), were not significantly different between the testing methodologies (p = 0.290) and were highly correlated (r = 0.780). WEP (8.4 ± 3.0 kJ) and W' (8.3 ± 3.0 kJ) were similar (p = 0.947) but not related (r = 0.119), while ESR (45 ± 7 spm) and CSR (47 ± 7 spm) values were not significantly different (p = 0.238) and moderately correlated (r = 0.498). The 3MT using ski ergometry was shown to produce concurrently valid results with the traditional multi-trial CP test for CP and CSR, but not W', and elicited similar maximal oxygen uptake values when compared to a graded exercise test.

Effects of natal male alliances on aggression and power dynamics in rhesus macaques

In the wild, male rhesus macaques disperse at sexual maturity. In captivity, however, males cannot disperse from their natal groups. Thus, the presence of natal males in captive rhesus social groups is unnatural and has the potential to negatively influence group dynamics and stability. A primary difference between natal males and non-natal (immigrant) males is that natal males have the opportunity to form long-term alliances with their maternal kin as well as nonkin. We investigated the factors associated with natal males' kin alliances and the impact of these alliances on measures of natal male behavior, group dynamics, and group stability. We found that natal males more frequently formed alliances with maternal kin when they were from high-ranking matrilines, had more siblings, and were younger. More frequent kin alliances were associated with more frequent use of intense aggression, higher individual rank, and higher degree of integration within the male displacement network. Thus, it seems that natal males use their alliances to be more active and influential in the social group, which may affect group stability. It appears that juvenile natal males from high-ranking matrilines, in particular, have the largest impact on group stability. Younger natal males from high-ranking matrilines formed alliances with kin more frequently and used intense aggression more frequently than older or lower ranking males. Furthermore, groups with a higher proportion of juvenile males from high-ranking matrilines also had higher rates of wounding. We suggest that the presence of natal males in rhesus groups may act in opposition to group stability.

A dose-response study with the feed enzyme beta-mannanase in broilers provided with corn-soybean meal based diets in the absence of antibiotic growth promoters

An experiment was designed to assess the effects of graded levels of beta-mannanase on performance and body weight uniformity of male broilers provided with diets based on corn and soybean meal and devoid of antibiotic growth promoters or coccidiostats. Four dietary treatments contained 0, 50, 80, and 110 MU of Hemicell/ ton (where 1 MU = 10(6) enzyme activity units, 100 MU/ton is manufacturer's recommendation). Each treatment contained 15 pens with 40 birds/pen. Individual bird weights were determined on d 0, 21, and 42. From 21 to 42 d of age, feed intake for the 80 MU/ton treatment was significantly greater than the 50 MU/ton treatment. beta-Mannanase inclusion at 80 or 110 MU/ton induced improvements (P < 0.05) in weight gain (3.9 to 4.8%) and feed efficiency (3.5 to 3.8%) over the control, whereas inclusion of 50 MU/ton resulted in no significant benefit. There were no significant differences between 80 or 110 MU/ton. The experiment demonstrated that dietary inclusion of beta-mannanase at approximately 50 MU/ton is not sufficient for maximum response. Inclusion at 80 MU/ ton improved broiler gains and feed conversion and increasing to 110 MU/ton resulted in no significant additional response.

Beneficial Effect of β-Mannanase Feed Enzyme on Performance of Chicks Challenged with Eimeria sp. and Clostridium perfringens

Two experiments were conducted to determine the effect of a beta-mannanase feed enzyme on the performance of broiler chicks subject to a necrotic enteritis disease challenge model involving oral inoculation of Eimeria sp. and Clostridium pefringens. Beta-mannanase is known to improve productive performance when added to poultry and swine diets. In both experiments, disease challenge in the absence of feed additives demonstrated significant reductions in performance as measured by weight gain, feed conversion, and the incidence of coccidial lesion scores. Significant mortality was also observed in challenged groups in Experiment 1. The disease challenge model was therefore judged as highly effective. Additions of a commonly used antibiotic, bacitracin methylene disalicilate (BMD), and coccidiostat, salinomycin, were highly effective in partially counteracting negative effects of the disease challenge. In both experiments, addition of beta-mannanase significantly improved performance and reduced lesion scores in disease-challenged groups. The degree of improvement was somewhat less than that afforded by a combination of BMD and salinomycin in Experiment 1 but was not different from that afforded by BMD alone in Experiment 2. We conclude that the beta-mannanase enzyme can play a role in circumstances where the use of antibiotics is not desired.

Analysis of the frequency response of the saccadic circuit: numerical simulations

Fundamental mechanisms of a brain circuit's operation can be revealed by quantitative analysis of the system's dynamic behavior. This approach is particularly useful for investigation of motor circuits, which generate machine-like outputs and where systems control techniques can be applied to reveal the circuit behavior outside the dynamic range of volitional activation. As an extension of our previous study of the step response of the saccadic motor system, this paper presents analytical and numerical considerations for the frequency response of the saccadic circuit-the system response to a steady-state sinusoidal input. Consideration of these responses provides mechanistic explanation for several aspects of the biological circuit and formalizes constraints for viable models of the saccadic circuit. Most importantly, these studies provide quantitative predictions for comparison with experimental data in vivo and make explicit hypotheses about biological mechanisms for experimental verification.

Stimulation of prefrontal cortex at physiologically relevant frequencies inhibits dopamine release in the nucleus accumbens

The prefrontal cortex (PFC) is thought to provide an excitatory influence on the output of mesoaccumbens dopamine neurons. The evidence for this influence primarily arises from findings in the rat that chemical or high-intensity and high-frequency (60-200 Hz) electrical stimulations of PFC increase burst activity of midbrain dopamine neurons, and augment terminal release of dopamine in the nucleus accumbens. However, PFC neurons in animals that are engaged in PFC-dependent cognitive tasks increase their firing frequency from a baseline of 1-3 Hz to 7-10 Hz, suggesting that the commonly used high-frequency stimulation parameters of the PFC may not be relevant to the behavioral states that are associated with PFC activation. We investigated the influence of PFC activation at lower physiologically relevant frequencies on the release of dopamine in the nucleus accumbens. Using rapid (5-min) microdialysis measures of extracellular dopamine in the nucleus accumbens, we found that although PFC stimulation at 60 Hz produces the expected increases in accumbal dopamine release, the same amplitude of PFC stimulation at 10 Hz significantly decreased these levels. These results indicate that activation of PFC, at frequencies that are associated with increased cognitive demand on this region, inhibits the mesoaccumbens dopamine system.

Analysis of the frequency response of the saccadic circuit: system behavior

To more thoroughly describe the system dynamics for the saccadic circuit in monkeys, we have determined the frequency response by applying a frequency modulated train of microstimulation pulses in the superior colliculus. The resulting eye movements reflect the transfer function of the saccadic circuit. Below input modulations of 5 cycles/s, the saccadic circuit increasingly oscillates with multiple high-frequency, low-amplitude movements reminiscent of the "staircase saccades" evoked during the sustained step response. Between 5 and 20 cycles/s, the circuit entrains well to the input, exhibiting one saccadic response to each sinusoidal input. Within this range there are systematic frequency-dependent changes in movement amplitudes, including super-normal saccades at some input frequencies. Above 20 cycles/s, the saccadic circuit increasingly exhibits periodic failures at rates of 1:2 or higher. In addition, the circuit exhibits predictable amplitude-modulated interference patterns in response to a combined step and frequency-modulated input. These experimental results provide insight into several biological mechanisms and serve as benchmark tests of viable models of the saccadic system. The data are consistent with negative feedback models of the saccadic system that operate as a displacement controller and inconsistent with theories that put the superior colliculus within the lowest-order, local feedback loop. The data support theories that the circuit feedback operates with dynamics that simulate a "leaky integrator." In addition, the results demonstrate how the temporal output of the superior colliculus interacts with recurrent inhibition to influence the eye movement dynamics.

British Society for Immunology: vaccines and mucosal immunity

The Annual Congress of the British Society for Immunology was well attended with over 1000 British scientists converging on the small Yorkshire town of Harrogate. Wide-ranging and varied, the topics covered included the biochemistry of signaling as well as sessions examining dietary influences upon mucosal immunity. The plenary session on the morning of Wednesday 6 December focused on immunology at the cell surface, where many speakers discussed the role of lipid rafts in immune cell signaling. A session of particular interest followed the plenary session, hosted by the Vaccine Immunology Group. Discussion centered around a number of novel vaccines currently under development, with the emphasis on finding alternatives to the use of hypodermic needles. A number of interesting posters affiliated to this session reflected the high quality of the research presented at the meeting in general.

Amygdala regulation of nucleus accumbens dopamine output is governed by the prefrontal cortex

A dynamic interaction between the prefrontal cortex (PFC), amygdala, and nucleus accumbens (NAc) may be fundamental to regulation of goal-directed behavior by affective and cognitive processes. This study demonstrates that a mechanism for this triadic relationship is an inhibitory control by prefrontal cortex on accumbal dopamine release during amygdala activation. In freely moving rats, microstimulation of basolateral amygdala at intensities that produced mild behavioral activation produced an expected rapid increase in glutamate efflux in the prefrontal cortex and the nucleus accumbens shell region of the ventral striatum. However, during the stimulation, dopamine release increased only in the prefrontal cortex, not in the nucleus accumbens. An increase in accumbal dopamine release was observed during the stimulation if glutamate activation in the prefrontal cortex was inhibited at either presynaptic or postsynaptic levels. Some behaviors expressed during the stimulation were intensified in animals in which prefrontal cortex glutamate activation was blocked. In addition, these animals continued to express stimulus-induced behaviors after the termination of stimulation, whereas normal poststimulus behaviors such as ambulation and grooming were not displayed as frequently. Considering that dopamine neurotransmission in the nucleus accumbens is thought to play an integral role in goal-directed motor behavior, these findings suggest that the prefrontal cortex influences the behavioral impact of amygdala activation via a concomitant active suppression of accumbal dopamine release. Absence of this cortical influence appears to result in an aberrant pattern of behavioral expression in response to amygdala activation, including behavioral perseveration after stimulus termination.

Shared responsibility in home birth practice: collaborating with clients

The home setting not only provides a special environment for birth and the practice of midwifery, but also has an impact on the processes used in clinical decision making. This article focuses on collaboration between the midwife and the birthing woman and also discusses the collaborative relationship between midwives and obstetric consultants. A home birth case study illustrates the interactions among the midwife, the woman, and the medical system. These critical relationships provide structure for safe, effective clinical practice in planned home birth when practice boundaries are not defined by institutional walls.

Effects of beta-mannanase in corn-soybean meal diets on laying hen performance

Recently, a patented enzyme product (beta-Mannanase, Hemicell) has been shown to improve feed conversion in corn-soybean diets fed to broilers and swine. The mechanism of beta-Mannanase is to degrade beta-mannan, which is an antinutritional factor existing in many legumes, including soybean and canola meals. The objective of this study was to determine whether or not performance can be improved by including beta-Mannanase in diets of commercial laying hens, 18 through 66 wk of age. A 2 x 2 x 2 factorial arrangement of treatments was employed. There were two energy sequences of 2,926-2,907-2,885 and 2,827-2,808-2,786 kcal ME/kg, which changed at 33 and 43 wk of age respectively; two dietary enzyme levels (0 and 110 units/g); and two Hy-Line strains (W36 and W77). Hen-day production, hen-housed production, BW, feed intake, mortality, egg weight, and specific gravity data were collected biweekly. Data were analyzed in four cycles (each with six 2-wk periods) and also for the whole experiment. beta-Mannanase increased egg weight from 51.4 to 51.7 g/egg (P < 0.05) in the first 12-wk cycle. This effect was consistent across energy levels. beta-Mannanase significantly improved hen-day and hen-housed production after the first cycle. Hen-day production of the beta-Mannanase group was 0.70, 1.07, and 1.5% greater than the control for cycles two, three, and four, respectively (P < 0.01). After 30 wk of age, average hen-day production of hens fed the low-energy diets with beta-Mannanase was similar or superior to that of hens fed the high-energy diets without the enzyme. The study indicates that beta-Mannanase is capable of increasing egg weight in commercial layers at early stages of production, and increasing egg production, particularly delaying the postpeak decline in productivity.

Numerical simulation of nonlinear feedback model of saccade generation circuit implemented in the LabView graphical programming language

The object-oriented graphical programming language LabView was used to implement the numerical solution to a computational model of saccade generation in primates. The computational model simulates the activity and connectivity of anatomical strictures known to be involved in saccadic eye movements. The LabView program provides a graphical user interface to the model that makes it easy to observe and modify the behavior of each element of the model. Essential elements of the source code of the LabView program are presented and explained. A copy of the model is available for download from the internet.

The KDEL retrieval system is exploited by Pseudomonas exotoxin A, but not by Shiga-like toxin-1, during retrograde transport from the Golgi complex to the endoplasmic reticulum

To investigate the role of the KDEL receptor in the retrieval of protein toxins to the mammalian cell endoplasmic reticulum (ER), lysozyme variants containing AARL or KDEL C-terminal tags, or the human KDEL receptor, have been expressed in toxin-treated COS 7 and HeLa cells. Expression of the lysozyme variants and the KDEL receptor was confirmed by immunofluorescence. When such cells were challenged with diphtheria toxin (DT) or Escherichia coli Shiga-like toxin 1 (SLT-1), there was no observable difference in their sensitivities as compared to cells which did not express these exogenous proteins. By contrast, the cytotoxicity of Pseudomonas exotoxin A (PE) is reduced by expressing lysozyme-KDEL, which causes a redistribution of the KDEL receptor from the Golgi complex to the ER, and cells are sensitised to this toxin when they express additional KDEL receptors. These data suggest that, in contrast to SLT-1, PE can exploit the KDEL receptor in order to reach the ER lumen where it is believed that membrane transfer to the cytosol occurs. This contention was confirmed by microinjecting into Vero cells antibodies raised against the cytoplasmically exposed tail of the KDEL receptor. Immunofluorescence confirmed that these antibodies prevented the retrograde transport of the KDEL receptor from the Golgi complex to the ER, and this in turn reduced the cytotoxicity of PE, but not that of SLT-1, to these cells.

Neural activity in SII modifies sensory evoked potentials in SI in awake rats

The function of the projection from the secondary somatosensory cortex (SII) to the primary somatosensory cortex (SI) in rats was investigated by recording sensory evoked potentials (SEP) in SI during glutamate activation and lidocaine blockade of SII. In anesthetized animals, glutamate stimulation of SII decreased SEP latency and increased SEP amplitude, whereas no changes were evident during lidocaine blockade of SII. In awake animals, a second, later component of the SEP appeared. This second component was almost completely eliminated during lidocaine blockade of SII. We conclude that the projection from SII to SI in rats slightly facilitates the SEP response in anesthetized animals and is responsible for a major portion of the late component of the SEP in awake animals.

The impact of female caregivers' employment status on patterns of formal and informal eldercare

This article uses data from the 1989 National Long-Term Care Survey and its companion Informal Caregivers Survey to investigate how the employment of female primary caregivers (FPCGs) affects hours of care received by disabled elderly care recipients (CRs). Multivariage analyses controlling for key FPCG and CR characteristics indicate that when FPCGs are employed they provide significantly fewer hours of care personally; however, their CRs also receive significantly more hours of help from other sources. When FPCGs work more than 17 hours per week, their CRs receive significantly fewer total weekly hours of care than would otherwise be the case.

The BPV-4 co-carcinogen quercetin induces cell cycle arrest and up-regulates transcription from the LCR of BPV-4

Bracken fern is the environmental co-carcinogen of BPV-4 in the induction of neoplasias of the upper alimentary canal of cattle. The flavonoid quercetin is one of the most potent and best characterised mutagens present in the fern. We have shown that transfection with BPV-4 DNA and exposure to a single dose of quercetin leads to tumorigenic transformation of primary bovine cells. We now show that quercetin induces cell cycle arrest and up-regulates transcription from the BPV-4 long control region (LCR). This up-regulation is mediated by a 21 nucleotide-long cis-element in the LCR, designated QRE-1, which is located immediately downstream of the TATA box. Cellular proteins bind to QRE-1 and removal or substitution of QRE-1 lead to the abrogation of the response to quercetin. As expression of the viral oncogenes is controlled by the LCR, perturbation in this control and increased oncoprotein expression are likely to contribute to fully malignant cell transformation by overcoming the cell cycle arrest induced by quercetin, thus forcing damaged cells to proliferate.

The role of exogenous p53 and E6 oncoproteins in in vitro transformation by bovine papillomavirus type 4 (BPV-4): significance of the absence of an E6 ORF in the BPV-4 genome

Bovine papillomavirus type 4 (BPV-4) does not possess an E6 ORF. The E6 oncoprotein of human papillomavirus (HPV) binds and degrades the tumour suppressor protein p53, thus contributing to tumour progression. Since BPV-4 lacks E6, it is unknown how the virus evades the tumour suppressor properties of p53 in the induction of tumours of the gastrointestinal tract. Mutations in the p53 gene have been detected both in papillomas and carcinomas, suggesting that p53 dysfunction plays a part in these neoplasias. BPV-4 can transform primary foetal bovine cells (PalFs) in cooperation with an activated ras gene, but the transformed cells are neither immortal nor tumorigenic. Co-transfection with the HPV-16 E6 (16E6) ORF confers immortality but not tumorigenicity. To investigate the role of p53 in BPV-4 cell transformation in vitro, we transfected PalFs and p53-null mouse fibroblasts with BPV-4 DNA in combinations with ras, 16E6 ORF and mutant (V143A) p53 cDNA. Transfection of PalFs with BPV-4 DNA, ras and mutant p53 led to cell immortalization, indicating that 16E6 and mutant p53 are functionally equivalent in conferring immortality. However, co-transfection of PalFs with BPV-4 DNA, ras, and both mutant p53 cDNA and 16E6 ORF resulted in cells which were fully transformed to tumorigenicity. In p53-null mouse fibroblasts, BPV-4 DNA induced transformation by itself, but the transformed cells were incapable of suspension growth. The co-transfection of BPV-4 DNA with 16E6 ORF produced many more transformed colonies and the cells were capable of growing in suspension. In this system, therefore, 16E6 confers anchorage-independence to BPV-4-transformed cells in a p53-independent fashion.

Risk of behavior problems among nursing home residents in the United States

This study identified personal risk factors associated with behavior problems among nursing home residents using data based on a national survey of nursing home residents. Data are based on the Institutional Population Component of the 1987 National Medical Expenditure Survey and include nursing home residents living in licensed facilities on January 1, 1987. Multiple regression analyses were conducted to examine characteristics of residents that place them at risk of behavior problems. Independent variables include physical functioning, sensory impairment, cognitive impairment, psychiatric diagnoses, and demographics. Eleven behavior problems grouped into four categories based on factor analysis serve as dependent variables: wandering/safety, aggressive behaviors, collecting behaviors, and delusions/hallucinations. Risk factors emerging as predictors included sex (male), cognitive impairment, ADL dependency, incontinence, psychiatric history, receptive communication, walking, and difficulty seeing. Risk factors differ by type of behavior problem. Results suggest a multiple etiology in which biological, psychological, and sociocultural factors all play a role in generating behavior problems in the long-term care setting.

Evaluation of simplified compartmental models of reconstructed neocortical neurons for use in large-scale simulations of biological neural networks

The electrotonic properties of the complex arborizations of neurons can be simulated by creating compartmental models based on the morphology of real neurons. These models can be very detailed with thousands of individual compartments and active channels. Large numbers of these models can be linked together into biologically realistic, large-scale neural networks with which to obtain a better understanding of the interactions among real neurons. However, the use of detailed compartmental models in such large networks is hindered by long computation times. Methods exist to reduce the complex morphology of detailed compartmental models to simpler reconstructions that retain many of the electrotonic properties of the original model yet are computationally efficient. However, little work exists that evaluates the limitations and performance of such reduced models with realistic active conductances modeled in both the soma and the dendrites to ensure that they are appropriate for use in biologically realistic network models. We have created detailed and reduced models of reconstructed dye-filled neurons from rat somatosensory neocortex and evaluated the ability of the reduced models to faithfully reproduce the input-output functions of the more detailed models. We find that the reduced models are not capable of perfectly reproducing the exact output of the detailed models using identical parameters. However, if the parameters are adjusted the reduced models are certainly capable of providing input-output patterns that are well within an acceptable range of known neural activity. The limitations and the benefits of such models are discussed.

Heterogeneity of colony stimulating factor-1 gene expression in the skeleton of four osteopetrotic mutations in rats and mice

Congenital osteopetrosis in mammals is an inherited bone disease caused by aberrations in osteoclast development and/or function. Colony-stimulating factor-1 (CSF-1) promotes formation of osteoclasts and is produced by osteoblasts. Recently, two osteopetrotic mutations (op mouse and tl rat) have been shown to have reductions in CSF-1 activity, and CSF-1 injections improve the skeletal manifestations in each. Several different CSF-1 transcripts have been described in mouse and human soft tissues, and differential expression of CSF-1 transcripts has been documented. Thus, we compared gene expression for CSF-1 as reflected by mRNA levels in the bones of tl rats and op mice, and also two other osteopetrotic rat mutations (ia and op). In op mouse calvaria the 4.6 kb transcript was reduced while the 2.3 kb transcript was absent. However, no differences were detected in the levels of these transcripts in mutant and normal calvaria of tl stock. In contrast, CSF-1 transcript levels were elevated in op rat mutants and variable in ia mutants compared to normal littermates. Osteoblast cultures derived from neonatal animals of tl and op rat stock showed the same differences seen in calvarial bone in vivo. The mRNA expression of another growth factor, TGF-beta 1, paralleled that of CSF-1 in vivo and in vitro in the rat mutations. These data demonstrate the emerging molecular heterogeneity among osteopetrotic mutations and underscore the need to evaluate the contributions of these and other cytokines to osteoclast differentiation and function in each mutation.

Use of bone cell cultures to study skeletal pathology

We describe procedures for the isolation, culture, and analysis of neonatal osteoblasts from osteopetrotic (toothless (tl) and osteopetrosis [op]) rats and normal littermates. Normal osteoblasts produce and mineralize an extracellular matrix indistinguishable from that of well-characterized fetal rat osteoblasts in vitro. Mutant (tl and op) cultures show an early abnormal pattern of cell proliferation and a later premature, extensive mineralization which mimic the mutant phenotype in vivo. In cocultures with normal osteoclasts, mutant (tl) osteoblasts also show a greatly reduced ability to orchestrate bone resorption, as revealed by pit formation in bone slices, in response to physiologic mediators. These phenomena in vitro are consistent with the behavior of mutant osteoblasts and osteoclasts in vivo and suggest that more definitive microscopic analyses of osteoblasts from each mutation in vitro will provide insights on the roles of osteoblasts in the compromised bone resorption which characterizes the osteopetroses as well as their role in osteoclast ontogeny. This study shows that when their behavior is confirmed in vivo, bone cell cultures offer rigorous systems for understanding skeletal cell dysfunction in normal and pathological development.

Home birth with certified nurse-midwife attendants in the United States. An overview

The move of the birth site from home to hospital in the United States from 1800 through the early part of the 20th Century is described. The reemergence of home birth in the United States since the early 1960s and the evolution of nurse-midwifery care in the home birth setting are discussed. Misconceptions regarding home birth and a review of international literature documenting the safety of home birth are included. The need for prospective research on home birth is supported. A Home Birth Curriculum Guide developed by the Home Birth Committee of the American College of Nurse-Midwives is provided.

Osteoblasts from the toothless (osteopetrotic) mutation in the rat are unable to direct bone resorption by normal osteoclasts in response to 1,25-dihydroxyvitamin D

Osteopetrosis describes a diversified group of metabolic bone disorders characterized by a generalized, skeletal sclerosis resulting from reduced osteoclast-mediated bone resorption. The toothless (tl) osteopetrotic mutation in the rat is characterized by few osteoclasts and the inability to be cured by transplants of hemopoietic stem cells. This implies that the defect(s) responsible for reduced osteoclast activity in tl rats is within the skeletal microenvironment (cells or matrices). Osteoblasts and their products are known to play a role in regulating bone resorption and abnormalities in the osteoblast population in tl rats have been reported. The purpose of this study was to determine whether osteoblasts isolated from tl mutant rats, when cultured with normal osteoclasts, could increase bone resorption (pit formation) in response to stimulation by 1,25 dihydroxyvitamin D (1,25(OH)2D). The addition of 1,25(OH)2D produced a highly significant response in normal osteoblast cocultures but no response in mutant cultures. A dose response study with 1,25(OH)2D (10(-6) to 10(-9)M) revealed that mutant osteoblasts are unable to increase osteoclast activity. These data indicate that the vitamin D receptor-signal transduction pathway in tl rats needs to be examined.

Both viral E2 protein and the cellular factor PEBP2 regulate transcription via E2 consensus sites within the bovine papillomavirus type 4 long control region

The bovine papillomavirus type 4 (BPV4) long control region (LCR) contains three consensus binding sites, E2(1), E2(2), and E2(3) (ACCN6GGT), for the viral E2 transcription factor and a fourth degenerate site, dE2 (ATCN6GGT), which lies 3 bp upstream of E2(3). The E2(2) site was found to bind the cellular transcription factor PEBP2, and mutations at this site reduced basal promoter activity by as much as 60%, indicating an important role for PEBP2 in LCR function. Mutation of the E2(3) or dE2 site slightly decreased basal promoter activity, but the cellular proteins binding these sites have not yet been characterized. E2 protein was found to have considerable influence upon LCR promoter activity in primary bovine palate keratinocytes. Thus, when high levels of BPV1 E2 were present, almost complete repression of the BPV4 LCR was observed, whereas smaller amounts of BPV1 or BPV4 E2 led to transactivation. Mutational analysis indicated that E2(1) and dE2 mediated transactivation by E2, whereas E2(2) and E2(3) were responsible for repression by E2. In vitro complexes of binding sites E2(1) and E2(2) with E2 protein demonstrated much greater stability than complexes formed by the E2(3) and dE2 sites. These data suggest that the four E2 sites in the BPV4 LCR each perform different functions in the control of transcription and that competition between cellular transcription factors and viral E2 proteins is essential in regulating the level of viral gene expression during papilloma development.

Normalization of mineral homeostasis after reversal of osteopetrosis

Whether a radiographic and histologic cure of osteopetrosis includes normalization of mineral homeostasis remains unknown. Thus, we explored the extent of defective mineral metabolism in the microphthalmic (mi/mi) mouse before and after cure. Under basal conditions mi mutants exhibit normocalcemia, hypophosphatemia, and elevated renal 25-hydroxyvitamin D-1-hydroxylase activity. However, administration of PTHrP (3 micrograms/h x 24 h) further stimulated enzyme activity in mi mutants with active disease, to a level no different than that in treated normals. Serum phosphorus levels also declined in mi/mi mice following PTHrP, suggesting a normal renal response to this hormone. In contrast, failure to suppress enzyme function in mi/mi mice following prolonged calcitriol infusion indicates that the observed enhancement of 1,25-dihydroxyvitamin D production occurred secondary to autonomous parathyroid function and/or nonparathyroid hormone-related stimuli. Although an increased fractional excretion and decreased tubular reabsorption of phosphate were demonstrated in mi/mi mice, serum PTH levels were no different in mi mutants compared with normal littermates. Following skeletal cure, the mi/mi mice surprisingly display normal serum phosphorus levels and renal enzyme activity. Moreover, treatment restored normal responsiveness to calcitriol suppression and maintained normal PTHrP responsiveness of enzyme activity. These data indicate that the cure of osteopetrosis in the mi mutant is universal and includes normalization of serum phosphorus and renal 25-hydroxyvitamin D-1-hydroxylase. Furthermore, these data suggest that phosphate depletion of unknown origin is the likely cause of elevated enzyme activity in this murine osteopetrotic mutant.

CSF-1 treatment promotes angiogenesis in the metaphysis of osteopetrotic (toothless, tl) rats

It has recently been shown that following treatment with colony-stimulating factor-1 (CSF-1) the osteopetrotic condition in toothless (tl) rats greatly improves and growth is accelerated. We have examined the effects of such treatment on the microvasculature of the distal femoral chondro-osseous junction, a site where bone growth in length is coordinated with angiogenesis. Vascular casts and ultrastructural analyses of this region showed that, compared to untreated normal rats, untreated mutants showed little bone growth or angiogenesis. When mutants were treated with CSF-1 angiogenesis was markedly accelerated. These data show a remarkable effect of this growth factor on angiogenesis in this osteopetrotic mutation. Whether this effect of CSF-1 on angiogenesis is direct or indirect is not known and indicates that its effects on the normal microvasculature deserve further study.

An element binding a C/EBP-related transcription factor contributes to negative regulation of the bovine papillomavirus type 4 long control region

Deletion of the NR2 element of the long control region (LCR) of bovine papillomavirus type 4 (BPV-4) was observed previously to lead to a fivefold increase in enhancer activity of a subfragment of the LCR. Further characterization of this element indicates that mutations in NR2 lead to increased enhancer activity in both mouse CT3 fibroblasts and in a transformed bovine epithelial cell line derived from an alimentary canal papilloma/in situ carcinoma, but not in primary bovine keratinocytes. Since similar oligonucleotide-nuclear factor complexes were obtained in electrophoretic mobility shift assays (EMSA) for all three cell types, the observed difference in negative activity may result from variation in the NR2-binding factor itself between primary and established/transformed cell lines, or from the involvement of other factors that vary between the lines. Characterization of the NR2-binding factor by heat stability and antibody supershifts in EMSA indicate that the factor is related to the CCAAT/enhancer-binding protein (C/EBP) family, and that one component of the complexes may be C/EBP beta.

Aberrant gene expression in cultured mammalian bone cells demonstrates an osteoblast defect in osteopetrosis

Osteopetrosis is a skeletal condition in which a generalized radioopacity of bone is caused by reduced resorption of bone by osteoclasts. However, it has recently been shown that during skeletal development in several osteopetrotic rat mutations specific aberrations occur in gene expression reflecting the activity of the bone forming cells, osteoblasts, and the development of tissue organization. To evaluate their pathogenetic significance, progressive osteoblast differentiation was studied in vitro. Primary cultures of normal osteoblasts undergo a sequential expression of cell growth and tissue-related genes associated with development of skeletal tissue. We report that osteoblast cultures can be established from one of these mutants, toothless; that these cells in vitro exhibit similar aberrations in gene expression during cell proliferation and extracellular matrix formation and mineralization observed in vivo; and that an accelerated maturation sequence by mutant osteoblasts mimics the characteristic skeletal sclerosis of this disease. These data are the first direct evidence for an intrinsic osteoblast defect in osteopetrosis and establish an in vitro model for the study of heritable skeletal disorders.

Transcriptionally active nuclei isolated from intact bone reflect modified levels of gene expression in skeletal development and pathology

Transcriptional regulation of gene expression in vivo in bone, associated with normal development or skeletal disorders, to date, has not been studied. We report the successful isolation of nuclei that are transcriptionally active from normal and osteopetrotic rat bone. Transcription rates of cell growth and bone-related genes (including histone H4, c-fos, c-jun, TGF beta 1, beta 2 macroglobulin, collagen, fibronectin, osteocalcin, osteopontin, and tartrate resistant acid phosphatase) change as a function of calvarial development from birth to 6 weeks and are selectively modified in osteopetrotic animals. Additionally, nuclei isolated from intact bone yield promoter binding factors. Bone nuclei, which transcribe faithfully and contain the normal complement of nuclear protein factors, offer a powerful approach for investigating in vivo gene regulation in skeletal development and pathology.

Correlates of disruptive behaviors in nursing homes. A reanalysis

This study reexamines factors associated with the occurrence of disruptive behaviors using a representative sample of nursing home residents in Rhode Island in 1984-1985. Four indicators of disruptive behaviors are examined using multivariate methods: evidence of any disruptive behaviors, abusive behavior, wandering, and noisiness. Results are compared with the 1989 study by Jackson et al., which was based on the same data. Findings indicate that the likelihood of exhibiting disruptive behaviors in nursing homes increases with the severity of cognitive impairment, ADL dysfunction, and incontinence, and decreases with immobility. Immobility not only is negatively associated with wandering behavior, but with other behaviors as well. Women are less likely to be abusive. In contrast to the earlier study, which did not use multivariate methods, age and communication problems are not related to disruptive behaviors.

Measurements of the growth and distribution of mammalian cells in a hollow-fiber bioreactor using nuclear magnetic resonance imaging

We have used diffusion-weighted 1H NMR micro-imaging and localized spectroscopy techniques to monitor the growth and distribution of mammalian cells in a hollow-fiber bioreactor. Non-invasive NMR measurements of this type should also allow investigation of metabolic heterogeneity and assist in future designs of hollow-fiber systems.

Abnormalities of phosphoprotein gene expression in three osteopetrotic rat mutations: elevated mRNA transcripts, protein synthesis, and accumulation in bone of mutant animals

Osteoclast abnormalities that characterize osteopetrosis, a disorder of bone resorption, may derive from aberrant signals from the osteoblast or the bone matrix. In the present studies, both synthesis and the bone matrix content of the major bone phosphoprotein component, osteopontin, were found to be elevated in three osteopetrotic rat mutations (ia, op, and tl). In whole bone, a twofold increase in the content of the characteristic amino acid O-phosphoserine for osteopontin occurred in op and tl mutant long bone, but a smaller (15%) and more variable increase was observed in ia mutant rat long bone. Extraction of the bone matrix components and partial purification by reverse phase chromatography showed a twofold increase in a phosphoprotein fraction relative to other noncollagenous components. Amino acid analysis and staining characteristics of SDS-PAGE fractionated proteins indicated this to be osteopontin. Organ cultures of calvarial bone from 4 day ia osteopetrotic mutant and normal rats in the presence of 3H-proline showed increased synthesis of this 60 kD protein, which was stimulated by vitamin D. Preparation of total cellular RNA from bone of 2- and 6-week-old mutants and normal rats supported increased synthesis of osteopontin as reflected by hybridization with osteopontin cDNA probe, showing significantly higher levels of mRNA transcripts in ia (3-5 fold), tl (1.4-2 fold), and op (6-25 fold) mutant bone compared to normal littermates. The changes in osteopontin mRNA levels in mutant bone were also examined in relation to other growth and phenotype-expressed genes. The findings of increased accumulation of osteopontin in osteopetrotic bone and increased synthesis by osteoblasts are interesting in light of the previously reported decrease in bone osteocalcin content (Endocrinology, 126:966, 1990), confirmed here by decreased osteocalcin mRNA transcripts. Such aberrations in the composition of skeletal extracellular matrix could be a reflection of or a contributing factor to the osteoclast abnormalities of some of these osteopetrotic disorders.

Experimental studies of osteopetrosis in laboratory animals

Osteopetrosis is a metabolic bone disease characterized by a systemic increase in skeletal mass. It results from a defect in the production or function of osteoclasts and is inherited in nine genetically distinct osteopetrotic animal mutations and man. Studies of these mutations have revealed that osteopetrosis is a complex, heterogeneous disorder in its expression, etiology, and response to treatment by bone marrow transplantation or by hormone/growth factor therapy. These animal mutations have been valuable tools for probing the pathogenesis and treatment of osteopetrosis, and information obtained from these studies has been used clinically for the treatment of humans with osteopetrosis. In addition, studies of these mutations have contributed significantly to understanding normal bone cell biology, including the origin of the osteoclast and the significance of colony-stimulating factor-1 in osteoclast development. The resistance of some of these mutations to cure by stem cell transplantation and hormone therapy, coupled with similar observations and experiences in the human condition, indicates that these animal mutations will continue to serve important roles in the development of alternative therapies to treat resistant forms of the disease. These studies are bound to improve the understanding of normal bone biology by providing additional insights into the regulation of osteoclasts by osteoblasts and their products or by other elements of the skeletal microenvironment.

The skeletal effects of colony-stimulating factor-1 in toothless (osteopetrotic) rats: persistent metaphyseal sclerosis and the failure to restore subepiphyseal osteoclasts

Toothless (tl), one of four osteopetrotic mutations in the rat, is characterized by few osteoclasts, undetectable bone resorption, and failure of correction by bone marrow transplantation. We recently reported that CSF-1 treatment improves these skeletal problems but that metaphyseal sclerosis persists. In the present study we demonstrate that optimal reduction of the skeletal sclerosis in tl rats following CSF-1 treatment has lower and upper dosage thresholds and that skeletal sclerosis returns after CSF-1 withdrawal. Osteoclasts increase significantly in tl rats after CSF-1 treatment, but compared to untreated normal littermates, histochemical staining for characteristic enzymes and osteoclast number is reduced and no osteoclasts appear in the subepiphyseal areas of long bones. These data are interpreted to mean that there are dosage limits to the beneficial skeletal effects of CSF-1, that persistent sclerosis is related to the failure to restore subepiphyseal osteoclasts, that osteoclast or progenitor populations may be deficient or differ in their responses to CSF-1, and that the defect in tl rats is not merely lack of a circulating, biologically active form of CSF-1.

Evaluating the predictive validity of nursing home pre-admission screens

This article demonstrates a method for evaluating the predictive validity of nursing home pre-admission screens (PAS) by using measures of predictive validity adapted from the field of epidemiology. Our approach estimates how well as PAS performs in identifying the "who but for" population of the Medicaid home and community-based services waiver programs for the frail elderly. The methodology's usefulness in screen revision is also illustrated.

Eligibility for publicly financed home care

OBJECTIVES

Proposals for publicly financed home care for the elderly now tend to include cognitive impairment criteria as well as activities of daily living (ADL) criteria. The numbers of elderly deemed eligible for services will depend on the definitions of ADL and cognitive impairment used.

METHODS

Data from the 1984 National Long-Term Care Survey were used to generate a series of estimates of the community-dwelling elderly with ADL disabilities and cognitive impairment.

RESULTS

When only ADL criteria are used, estimates of disability range from 472,000 to over 3 million (1.6% to 12.5% of the community-dwelling elderly). These estimates increase to approximately 1 million to 4.2 million (3.5% to 14.0% of the community-dwelling elderly) when cognitive impairment criteria are added.

CONCLUSIONS

The use of more stringent or more liberal eligibility criteria will have dramatic effects on the number of elders who qualify for services. The nature of the eligibility criteria employed in any expansion of federally financed home care benefits will be a major factor in determining the costs of such a program.

Performance of growing pullets and laying hens fed low-protein, amino acid-supplemented diets

An experiment was conducted to determine the effect of feeding low-protein, amino acid-supplemented diets during growing and laying periods on performance of a commercial strain of White Leghorn chickens. The birds of the positive control were fed diets in a sequence of 20, 16, and 14% protein during 0 to 6, 6 to 12, and 12 to 18 wk (growing period) and of 18, 16.5 and 15% protein during 18 to 34, 34 to 50, and 50 to 66 wk of age (laying period). The birds of the negative control were fed protein levels of 16, 13.5, and 11.5% in the growing period and 14, 13, and 12% in the laying period. Other groups were fed the negative control series supplemented with methionine, methionine plus lysine, or methionine plus lysine plus other deficient essential amino acids. An additional group was fed the negative control supplemented with methionine plus lysine during the growing period and a protein sequence of 15, 14, and 13% supplemented with methionine and lysine during the laying period. At 18 wk of age, birds fed the negative control supplemented with methionine plus lysine or methionine plus lysine plus other deficient essential amino acids had comparable body weight to those fed the positive control despite significantly lower protein and lysine intake. Overall egg production and egg weight of birds fed the sequence of 14, 13, and 12% protein supplemented with combination of methionine, lysine, and extra levels of tryptophan and isoleucine or of the birds fed the sequence of 15, 14, and 13% protein supplemented with methionine and lysine were not different from those fed the positive control. However, egg mass and body weight were inferior to those of birds fed the positive control.

Technology management: a perspective on system support, procurement, and replacement planning

The escalating costs associated with medical technology present a host of challenges for the hospital clinical engineering department. As service and support costs comprise ever larger portions of a system's life cycle cost, innovative management of service provider mix and mechanisms can provide substantial savings in operating expenses. In addition to full-service contracts, the use of demand service and independents has become commonplace. Medical equipment maintenance insurance programs provide yet another service alternative, combining the flexibility of demand service with the safety of a capped budget. These programs have gained acceptance among hospitals as their providers have become more focused on the healthcare market and its many needs. In view of the long-term cost impact surrounding technology procurement, the authors recommend that hospitals refine system evaluation methodologies and develop more comprehensive techniques directed at capital equipment replacement planning. One replacement planning approach, based on an estimation of system value changes, is described and illustrated using data collected through client consultations. Although the validity of this method has not been demonstrated, it represents a simplified approach to life cycle cost analysis and is intended to provide a standard method by which system replacement planning may be quantified. As a departure from system devaluation based solely on depreciation, this method estimates prospective system values derived from anticipated operations and maintenance costs, projected revenue, and the availability of new technology.

Efficacy of nursing home preadmission screening

This study evaluates the efficacy of four state nursing home preadmission screening instruments. Using data from three community-based services demonstration experiments, the screens were compared on measures of sensitivity, specificity, and proportions of false negatives and false positives. Results indicate that the more restrictive screens tended to have lower sensitivity but higher specificity, and to generate a higher proportion of false negative decisions than the more liberal screens. Overall rates of correct prediction were higher for the more restrictive screens. Results highlight differences in eligibility restrictiveness across states as well as possible tradeoffs of cost containment and access in designing a preadmission screen.

Myoelectric activity and sequencing of selected trunk muscles during isokinetic lifting

Trained weight lifters lift heavy loads without a concomitant degree of acute low-back injuries. To study the process by which large loads are lifted with minimal injury, integrated electromyographic signals were recorded from four large muscle groups: gluteus maximus, quadriceps, latissimus dorsi, and erector spinae in 4 weight lifters and 11 asymptomatic control subjects. These signals were recorded during a floor-to-knuckle-height isokinetic lift (dead lift) at 30.5 and 45.7 cm/sec. The signals were normalized for the height of the lift and the maximal isokinetic integrated electromyographic activity. The weight lifters achieved maximal force at 50% of maximal lift height, whereas the control subjects achieved it at 67%. Although not statistically significant, the weight lifters used the gluteus maximus more during the early stages of the lift, perhaps contributing to earlier development of force. This process would stabilize the pelvis and permit the erector spinae to extend the trunk more efficiently. The weight lifter then completed the lift with prolonged and increasing activity in the quadriceps. This technique may minimize the required force in the erector spinae and the forces on the low-back structures. Clinical implications include more effective strength training of lifting muscle groups other than spinal extensors and the teaching of lifting strategies employed by weight lifters in low-back rehabilitation and work-hardening programs.

Gene expression during skeletal development in three osteopetrotic rat mutations. Evidence for osteoblast abnormalities

Osteopetrosis is a group of metabolic bone diseases characterized by reductions in osteoclast development and/or function. These aspects of osteoclast biology are known to be influenced by osteoblasts and their products. To ascertain whether osteoblast dysfunction contributes to aberrations in the structural and functional properties of osteoclasts in osteopetrosis, we systematically examined gene expression as reflected by mRNA levels for a series of cell growth- and tissue-related genes associated with the osteoblast phenotype during skeletal development in normal and mutant rats of three different osteopetrotic stocks. We show that the methods used permit the reproducible isolation of undegraded total cellular RNA from bone and that mRNA levels can be reliably quantitated in these preparations. Each osteopetrotic mutation exhibits a distinct aberrant pattern of osteoblast gene expression that may be correlated with and explain some abnormalities in extracellular matrix composition, mineralization, osteoclast development, and effects of elevated serum levels of 1 alpha,25-dihydroxyvitamin D3, depending upon the mutation. Normal rats show minor variations in gene expression that reflect the genetic background (stock). This, the first comprehensive molecular analysis of osteoblast gene expression in osteopetrosis, suggests that some osteopetroses, particularly in the toothless rat, are associated with and potentially related to mechanisms associated with aberrations in osteoblast function. More generally, the present studies demonstrate alterations in gene expression as reflected by mRNA levels that are associated with functional properties of the osteoblast, particularly those contributing to the recruitment and/or differentiation of osteoclasts, thereby influencing skeletal modeling.

Positive and negative E2-independent regulatory elements in the long control region of bovine papillomavirus type 4

The long control region (LCR) of bovine papilloma-virus type 4 demonstrated enhancer activity when cloned upstream of a bacterial chloramphenicol acetyltransferase reporter gene under thymidine kinase promoter control. Deletion analysis of the LCR revealed the presence of several positive and negative control elements, all of which could function independently of the viral E2 trans-activator. Each of the three positive elements present appeared to be paired with a negative element which modulated its activity. DNase I footprinting was used to identify protein binding sites within the LCR, which might represent these control elements. The results suggest a highly complex and finely tuned control of viral gene expression.

Coexistence of reduced function of natural killer cells and osteoclasts in two distinct osteopetrotic mutations in the rat

Recent evidence suggesting that immune cells and their products (cytokines) play an important role in the regulation of skeletal development and function, particularly of the osteoclast, implies that immune cell dysfunction may be involved in the pathogenesis of certain skeletal disorders. The mammalian osteopetroses are a pathogenetically heterogeneous group of skeletal disorders characterized by skeletal sclerosis resulting from reduced osteoclast-mediated bone resorption. Using a 51Cr-release microcytotoxicity assay we demonstrated that splenic natural killer (NK) cell activity was significantly reduced in two distinctly different osteopetrotic mutations in the rat, osteopetrosis (op) and toothless (tl). To determine whether this reduction in NK cell-mediated cytotoxicity is caused by decreased cell number and/or function in these osteopetrotic mutants, we quantitated NK cells by analyzing mononuclear cell suspensions labeled for two-color fluorescence with OX8 and OX19 monoclonal antibodies in a fluorescence-activated cell sorter. Flow cytometry of these double-labeled cells revealed that the percentage of NK cells (OX8+/OX19- subset) in op and tl spleens was not significantly different from that of normal spleens. These results suggest that NK cells in these osteopetrotic mutants are functionally defective. Thus aberrations in osteoclast and NK cell function coexist in these mutations, and their developmental relationships deserve further study.

The B subgroup bovine papillomaviruses lack an identifiable E6 open reading frame

Analysis of the corrected DNA sequence for the bovine papillomavirus type 4 (BPV4) genome revealed that there is no open reading frame (ORF) that might encode an E6 protein. The other two B subgroup bovine papillomaviruses, BPV3 and BPV6, were found to have the same arrangement of ORFs in this region as BPV4. Thus, we conclude that E6 functions are either not required by these viruses or are performed by another viral (or host) protein. Furthermore, the position that might be expected to be occupied by E6, between the long control region and the E7 ORF, contains the E8 ORF, which has the potential to encode a 42-residue polypeptide with considerable similarity to the E5 transforming protein of BPV1. Therefore, it appears that during the evolution of the B subgroup of BPVs, genomic rearrangements may have occurred resulting in the present layout of the early ORFs.

Cooperation between bovine papillomavirus type 4 and ras in the morphological transformation of primary bovine fibroblasts

Primary bovine fibroblasts derived from foetal palate can be transformed by bovine papillomavirus type 4 DNA only in the presence of an activated ras gene, indicating that the virus does not encode all the information required for morphological transformation of non-established cells. A subgenomic fragment containing the complete E8 and E7 open reading frames (ORFs) induces transformation in cooperation with activated ras but transformation is abolished when the E7 ORF is deleted at the 3' end, showing that this ORF encodes a necessary transforming function. Transformation is more aggressive when the E8 and E7 ORFs are placed under the transcriptional control of the long terminal repeat of the mouse Moloney leukaemia virus, suggesting that the degree of transformation is dependent on the level of expression of these genes.

Risk of functional decline among well elders

Active lifestyles may delay the onset of the functional consequences of chronic disease, potentially increasing active life expectancy. We analyzed the Longitudinal Study of Aging (LSOA) to test the hypothesis that elders participation in an active lifestyle prevents loss of function. Focusing on the cohort aged 70-74 who reported being able to carry 25 lb, walk 1/4 mile, climb 10 steps and do heavy housework without help and without difficulty at baseline, decline was defined as no longer being able to perform these tasks independently and without difficulty 2 years later. Using multivariate logistic regression, results reveal that those who did not report regularly exercising or walking a mile were 1.5 times more likely to decline than those who did, controlling for reported medical conditions and demographic factors. Similar findings (with different models) were observed for both men and women. Findings suggest the potential value of programs oriented toward the primary prevention of functional decline.

Analysis of the membrane-binding domain of penicillin-binding protein 5 of Escherichia coli

Internal deletions close to the C-terminus of the Escherichia coli penicillin binding protein 5 (PBP5, DacA) have defined the C-terminal 18 residues of the protein as essential for membrane binding. This C-terminal sequence is capable of forming a strongly amphiphilic alpha-helix. In this paper we show that the PBP5 amphiphilic helix is able to anchor the periplasmic TEM-beta-lactamase to the inner membrane. In addition, we have demonstrated that mature PBP5 (lacking the N-terminal signal sequence) possesses the ability to bind to the membrane from a soluble form of the protein, showing that translocation across the membrane is unnecessary for anchoring to be established.

Shell quality: potential for improvement by dietary means and relationship with egg size

Three experiments were conducted by sampling a total of 15,705 eggs from Leghorn hens fed diets varying in methionine, Na, and Ca content. In Experiment 1, birds of four different ages were housed in a common environment and fed diets containing between .233 and .383% methionine. In Experiment 2, birds of five different ages were housed in a common environment and fed diets containing .15, .30, and .45% Na and .25, .45, and .65% nonphytate phosphorus (NPP). In Experiment 3, eggs were sampled from 42 to 62 wk of age in 4-wk intervals from hens fed diets containing from 3 to 9% Ca in increments of 1.5%. Feeding lower levels of methionine (.233%) produced significantly lower egg weights and greater shell strength but at the expense of a decline in egg production at early ages. Reducing the NPP level from .65 to .25% produced lower egg weights and greater shell strength. A corresponding drop in production was not observed except at the .45%-Na level. No significant effects of Na on shell strength were observed. Higher Ca levels produced greater shell strength and had variable effects on egg weight. Increasing the Ca level beyond 6% resulted in a significant decline in production. Regression analyses indicated that within a population, the relationship between egg weight and shell strength is positive. In some instances, the relationship was curvilinear, where the positive association between egg weight and shell strength decreased with increasing egg weights.