Using alternative forage species to reduce emissions of the greenhouse gas nitrous oxide from cattle urine deposited onto soil

Grazed pastures are a major contributor to emissions of the greenhouse gas nitrous oxide (N₂O), and urine deposition from grazing animals is the main source of the emissions. Incorporating alternative forages into grazing systems could be an approach for reducing N₂O emissions through mechanisms such as release of biological nitrification inhibitors from roots and increased root depth. Field plot and lysimeter (intact soil column) trials were conducted in a free draining Horotiu silt loam soil to test whether two alternative forage species, plantain (Plantago lanceolate L.) and lucerne (Medicago sativa L.), could reduce N₂O emissions relative to traditional pasture species, white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.). The amounts of N₂O emitted from the soil below each forage species, which all received the same cow urine at the same rates, was measured using an established static chamber method. Total N₂O emissions from the plantain, lucerne and perennial ryegrass controls (without urine application) were generally very low, but emissions from the white clover control were significantly higher. When urine was applied in autumn or winter N₂O emissions from plantain were lower compared with those from perennial ryegrass or white clover, but this difference was not found when urine was applied in summer. Lucerne had lower emissions in winter but not in other seasons. Incorporation of plantain into grazed pasture could be an approach to reduce N₂O emissions. However, further work is required to understand the mechanisms for the reduced emissions and the effects of environmental conditions in different seasons.

Dung and farm dairy effluent affect urine patch nitrous oxide emissions from a pasture

Urine patches in grazed pastures have been identified as important sources of nitrous oxide (N2O) emissions. An increase in N2O emissions is possible where urine patches coincide with dung patches and farm dairy effluent (FDE) applications. The aim of the present study was to quantify the effects of dung additions and fresh FDE applications on N2O emissions from urine patches. A field experiment was conducted on a pasture site at the AgResearch’s Ruakura dairy farm in Hamilton, New Zealand. A closed soil chamber technique was used to measure the N2O emissions from a free-draining volcanic soil that received urine (492 kg N/ha, simulated urine patches), with or without dung (1146 kg N/ha) and fresh FDE (100 kg N/ha) and to compare these with controls receiving no urine. The addition of dung delayed the peak N2O fluxes from the urine patches by ~30 days. This could be due to temporary nitrogen (N) immobilisation during decomposition of carbon from the dung. However, over the whole measurement period (271 days), dung addition increased the N2O emission factor (EF, % of applied N emitted as N2O) for the urine from 1.02% to 2.09%. The application of fresh FDE increased the EF to 1.40%. The effluent- or dung-induced increases in N2O emissions from the urine patches were possibly caused both by the direct input of N from effluent or dung and through the indirect priming effect of addition of dung or effluent on the availability of N from urine patches for N2O production. We conclude that when EFs are used in calculations of N2O emissions from urine, consideration should be given to the likelihood of coincidence with dung or FDE applications.

Effect of dicyandiamide (DCD) on nitrous oxide emissions from cow urine deposited on a pasture soil, as influenced by DCD application method and rate

Animal urine deposited on pastoral soils during grazing is recognised as a dominant source of nitrous oxide (N2O) emissions. The nitrification inhibitor, dicyandiamide (DCD), is a potential mitigation technology to control N2O emissions from urine patches on grazed pastures. One delivery option is to include DCD in animal feed so that the DCD is targeted directly in the urine patch when excreted in the animal urine. The hypothesis tested in the present study was that DCD in urine, excreted by cows that were orally administered with DCD, would have the same effect as DCD added to urine after the urine is excreted. The study also aimed to determine the most effective DCD rate for reducing N2O emissions. Fresh dairy cow urine (700 kg N per ha) was applied to a free-draining silt loam pastoral soil in Waikato, New Zealand, in May (late autumn) or July (winter) of 2014, and was mixed with DCD at rates of 0, 10, 30 and 60 kg/ha. In late autumn, there was an equivalent treatment of urine (containing 60 kg DCD per ha) from DCD-treated cows. A static chamber technique was used to determine gaseous N2O emissions. An annual emission factor (EF3; the percentage of applied urine N lost as N2O-N) of 0.23% or 0.21% was found following late-autumn or winter applications of urine without DCD. Late-autumn application of urine containing DCD from oral administration to cows had the same significant reduction effect on N2O emissions as did DCD that was mixed with urine after excretion, at the equivalent DCD application rate of 60 kg/ha. Application of urine with DCD mixed with the urine after excretion at varying DCD rates showed a significant (P < 0.05) linear decrease in both N2O emissions and EF3 values.

Excess vibrational modes and high thermoelectric performance of the quenched and slow-cooled two-phase alloy Cu0.2Ag2.8SbSeTe2

In this article we examine the low-temperature specific heat of slow-cooled Cu(0.2)Ag(2.8)SbSeTe(2) and the thermoelectric performance of quenched samples. We find that the low-temperature specific heat is dominated by two Einstein terms of approximate energies of 2.5 and 5 meV. The specific-heat behavior is consistent with the amorphous low-temperature thermal conductivity behavior and validates the glassy nature of the structure. We performed the synthesis of quenched samples in an attempt to eliminate the presence of micro-cracks, whose existence presumably enhances electronic scattering. We find that quenching eliminates the presence of micro-cracks but does not result in an improvement of the figure of merit. Specifically, the highest ZT obtained in the quenched samples (ZT = 1.5), though very competitive, is still significantly less that the ZT obtained in the slow-cooled samples (ZT = 1.75).

Glassy thermal conductivity in the two-phase Cu(x)Ag(3-x)SbSeTe(2) alloy and high temperature thermoelectric behavior

We have measured the thermal transport properties over the temperature range 1.8 K<T<700 K of a two-phase alloy synthesized by reacting AgSbTe(2) and Ag(2)Se in a 1:1 molar ratio. Typical electrical resistivity values at 700 K are in the range ∼4 mΩ cm≤ρ≤20 mΩ cm, while low thermal conductivity values (κ<1 W m(-1) K(-1)) were obtained. We find that the thermal conductivity of this crystalline alloy has a temperature dependence strikingly similar to those of amorphous solids. In addition the thermal conductivity, thermopower, and electrical resistivity decouple. This result makes it possible to optimize thermoelectric performance by minimizing the electrical resistivity. It is therefore envisaged that this system has potential as a high performance bulk thermoelectric.

The use of pine bark and natural zeolite as biofilter media to remove animal rendering process odours

Studies of odour-control pilot-scale biofilters at a rendering plant were conducted for five years. The biofilters contained different sizes of crushed pine bark or a mixture of zeolite and crushed bark, and treated the exhaust gases from direct-fired meal dryers. The exhaust gases were odorous and contained significant smoke. The odour concentration of the rendering process air ranged between 50,000 and 307,200 OU m(-3). Odour-removal performance measurements of the biofilters were undertaken on five occasions using forced-choice dynamic-dilution olfactometry. Biofilter odour-removal efficiencies of between 80% and 99% were measured at various influent odour concentrations and air loading rates. There was no obvious deterioration in performance of these biofilters between various sampling times in the five year study period. The biofilters also reduced the "offensiveness" of the odour. The fine crushed bark biofilter generally reduced odour concentration more efficiently than the coarse bark biofilter. The additions of zeolite to the bark medium in the biofilter had little effect on the odour-removal performance. An increase in air loading rate produced only a very small decrease in odour-removal performance. The pilot-scale biofilters had smoke removal efficiencies between 71% and 100%. Finely crushed bark removed smoke more effectively than coarsely crushed bark. Drainage from the biofilters contained significant concentrations of pollutants, suggesting that controlled leaching has potential to remove accumulated substances in biofilter media from rendering gas emissions and increase the longevity of a biofilter system.

Medicine. Communicating statistical information

Most people, experts included, have difficulties understanding and combining statistical information effectively. Hoffrage et al. demonstrate that these difficulties can be considerably reduced by communicating the information in terms of natural frequencies rather than in terms of probabilities. Several applications in medicine, legal decision-making, and education are discussed.

A model of dual attitudes

When an attitude changes from A1 to A2, what happens to A1? Most theories assume, at least implicitly, that the new attitude replaces the former one. The authors argue that a new attitude can override, but not replace, the old one, resulting in dual attitudes. Dual attitudes are defined as different evaluations of the same attitude object: an automatic, implicit attitude and an explicit attitude. The attitude that people endorse depends on whether they have the cognitive capacity to retrieve the explicit attitude and whether this overrides their implicit attitude. A number of literatures consistent with these hypotheses are reviewed, and the implications of the dual-attitude model for attitude theory and measurement are discussed. For example, by including only explicit measures, previous studies may have exaggerated the ease with which people change their attitudes. Even if an explicit attitude changes, an implicit attitude can remain the same.

A model of dual attitudes

When an attitude changes from A1 to A2, what happens to A1? Most theories assume, at least implicitly, that the new attitude replaces the former one. The authors argue that a new attitude can override, but not replace, the old one, resulting in dual attitudes. Dual attitudes are defined as different evaluations of the same attitude object: an automatic, implicit attitude and an explicit attitude. The attitude that people endorse depends on whether they have the cognitive capacity to retrieve the explicit attitude and whether this overrides their implicit attitude. A number of literatures consistent with these hypotheses are reviewed, and the implications of the dual-attitude model for attitude theory and measurement are discussed. For example, by including only explicit measures, previous studies may have exaggerated the ease with which people change their attitudes. Even if an explicit attitude changes, an implicit attitude can remain the same.

Monocyte chemoattractant protein-1 accelerates atherosclerosis in apolipoprotein E-deficient mice

The pro-inflammatory chemokine, monocyte chemoattractant protein-1 (MCP-1), plays a fundamental role in monocyte recruitment and has been implicated as a contributing factor to atherosclerosis. The predominant cell types within the vessel wall--endothelial cells, smooth muscle cells, and macrophages--all contribute to overexpression of MCP-1 in atherosclerotic tissue. In this report we assess the role of MCP-1 expression by leukocytes on lesion progression in a murine model susceptible to atherosclerosis. Bone marrow cells from mice overexpressing a murine MCP-1 transgene on a background of apoE-deficiency or from control mice were transplanted into irradiated apoE-knockout mice. After repopulation of apoE-knockout mice with bone marrow containing the MCP-1 transgene, macrophages expressing the MCP-1 transgene were found in several tissues, including the aorta. Qualitative assessment of atherosclerosis in these mice revealed increased lipid staining, a 3-fold (P<0.001) increase in the amount of oxidized lipid, and increased immunostaining for macrophage cell surface markers with anti-F4/80 and anti-CD11b antibodies. There were no differences in plasma lipids, plasma lipoprotein profiles, or body weight between the 2 groups. These results provide the first direct evidence that MCP-1 expression by leukocytes, predominately macrophages, increases the progression of atherosclerosis by increasing both macrophage numbers and oxidized lipid accumulation.

HMG-CoA reductase regulation: use of structurally diverse first half-reaction squalene synthetase inhibitors to characterize the site of mevalonate-derived nonsterol regulator production in cultured IM-9 cells

The activity of HMG-CoA reductase (HMGR) is tightly regulated, in part through post-transcriptional mechanisms that are mediated by nonsterol products of mevalonate metabolism. Previous reports have suggested that these mediators are derived from farnesyl pyrophosphate (FPP). Recent studies have implicated FPP hydrolysis products (e.g., farnesol), the squalene synthetase (SQS) reaction products presqualene pyrophosphate (PSQPP) and squalene, or their metabolites. To distinguish among these possible mediators, we evaluated the ability of HMGR and SQS inhibitors to induce compensatory increases in HMGR activity in cultured IM-9 cells. Mevinolin (HMGR inhibitor) produced predicted increases in HMGR activity that were related to the degree of cholesterolgenesis inhibition (e.g., 4-fold, 9-fold, and 17-fold increases relative to 50%, 76%, and 90% inhibition, respectively). By contrast, a variety of structurally distinct reversible, competitive, first half-reaction SQS inhibitors all reduced cholesterolgenesis by up to 90% with no appreciable increases in HMGR activity. These observations strongly suggest that nonsterol-mediated post-transcriptional mechanisms regulating HMGR activity remain intact after SQS first half-reaction inhibition, indicating that nonsterol regulator production is independent of SQS action and ruling out PSQPP, squalene and their metabolites as possible mediators. Unexpectedly, the SQS mechanism-based irreversible inactivator, zaragozic acid A (ZGA) exhibited the greatest degree of HMGR modulation, producing 5-fold, 11-fold, and 40-fold increases in HMGR activity at concentrations that produced 25%, 50%, and 75% cholesterolgenesis inhibition, respectively. The markedly greater magnitude of HMGR stimulation by ZGA versus mevinolin at similar levels of cholesterolgenesis inhibition suggests that ZGA may directly interfere with the production or action of the nonsterol regulator.

Electron tomography of large, multicomponent biological structures

Electron tomography is an extremely useful method for deriving three-dimensional structure from electron microscope images. The application of this technique to the reconstruction of large, complex structures such as mitochondria is described in conjunction with several tools for segmentation, measurement, classification, and visualization. In addition, the use of massively parallel computers to perform the tomographic reconstruction efficiently using R-weighted backprojection or iterative techniques is described.

3-(4-chlorophenyl)-2-(4-diethylaminoethoxyphenyl)-A-pentenonitrile monohydrogen citrate and related analogs. Reversible, competitive, first half-reaction squalene synthetase inhibitors

Squalene synthetase (SQS) catalyzes the head-to-head condensation of two molecules of farnesyl pyrophosphate (FPP) to form squalene. The reaction is unique when compared with those of other FPP-utilizing enzymes, and proceeds in two distinct steps, both of which involve carbocationic reaction intermediates. In this report, we describe the mechanism of action of, and structure-activity relationships within, a series of substituted diethylaminoethoxystilbenes that mimic these reaction intermediates, through characterization of the biochemical properties of 3-(4-chlorophenyl)-2-(4-diethylaminoethoxyphenyl)-A- pentenonitrile monohydrogen citrate (P-3622) and related analogs. As a representative member of this series, P-3622 inhibited SQS reversibly and competitively with respect to FPP (Ki = 0.7 microM), inhibited the enzymatic first half-reaction to the same extent as the overall reaction, exhibited a 300-fold specificity for SQS inhibition relative to protein farnesyltransferase inhibition, inhibited cholesterol synthesis in rat primary hepatocytes (IC50 = 0.8 microM), in cultured human cells (Hep-G2, CaCo-2, and IM-9; IC50 = 0.2, 1.2, and 1.0 microM), and in chow-fed hamsters (62% at 100 mg/kg) without accumulation of post-squalene sterol precursors, and reduced plasma cholesterol in experimental animals. Structure-activity relationships among 72 related analogs suggest that the phenyl residues and central trans-olefin of the stilbene moiety serve as mimics of the three isoprene units of the donor FPP, that substitutions across the central olefin and para-substitutions on the terminal phenyl residue mimic the branching methyl groups of the donor FPP, and that the diethylaminoethoxy moiety of these molecules mimics the various carbocations that develop in the C1-C3 region of the acceptor FPP during reaction. Members of this series of reversible, competitive, first half-reaction SQS inhibitors that show a high degree of specificity for SQS inhibition relative to inhibition of other FPP-utilizing enzymes and other cholesterol synthesis pathway enzymes may serve as useful tools for probing the unique catalytic mechanisms of this important enzyme.

CP-225,917 and CP-263,114, novel Ras farnesylation inhibitors from an unidentified fungus. I. Taxonomy, fermentation, isolation, and biochemical properties

During the course of our screening for squalene synthase inhibitors and Ras farnesylation inhibitors, a novel fungal culture was discovered to produce two structurally unique compounds, CP-225,917 and CP-263,114, as well as zaragozic acid A (squalestatin I). The two compounds are characterized by a bicyclo[4.3.1]dec-1,6-diene core plus two extended alkyl chains. CP-225,917 and CP-263,114 inhibit Ras farnesyl transferase from rat brain with IC50 values of 6 microM and 20 microM, respectively. CP-225,917 inhibits squalene synthase with an IC50 value of 43 microM and CP-263,114 with an IC50 of 160 microM. The producing organism, though not fully classified, exhibits the characteristics of a sterile Phoma species.

Homeobox genes and male reproductive development

PURPOSE

Homeobox genes encode transcription factors that dictate developmental events in philogenetically diverse organisms. In comparison to what is known about their role in embryogenesis, we know very little concerning homeobox gene function in neonates or adults. In this communication, we review studies that address the possible role of homeobox genes in male reproductive development, a system active in neonate and adult animals.

METHODS

Studies have shown that many homeobox genes are expressed in germ cells of the testis, while less is known about the identity of homeobox genes expressed in somatic cells of the testis or epididymis. Hox homeobox genes display a pattern of expression in testis that is dependent on their paralogous and orthologous position within the Hox gene chromosome clusters. Other homeobox genes are expressed in the male reproductive system, including many POU and Prd/Pax homeobox gene family members. More recently, it has been shown that the orphan homeobox gene, Pem, originally isolated by subtraction hybridization on the basis of its differential expression in tumor cell lines, is selectively expressed in reproductive tissue. Alternatively spliced Pem transcripts accumulate in testis and epididymis that differ from those expressed in tumors and placenta. Pem transcripts accumulate postnatally in the epididymis in a developmentally regulated manner.

CONCLUSIONS

The highly regulated pattern of expression exhibited by many homeobox genes in the male reproductive system suggests that homeobox transcription factors may dictate developmental events in this system. However, future studies are needed to determine the specific functional roles homeobox genes in male reproductive development and spermatogenesis.

Inhibition of mammalian squalene synthetase activity by zaragozic acid A is a result of competitive inhibition followed by mechanism-based irreversible inactivation

Squalene synthetase (SQS, EC 2.5.1.21) catalyzes the first committed step in the formation of cholesterol and thus represents an ideal site for selectively inhibiting sterol formation. Previous studies have demonstrated that the fungal metabolite, zaragozic acid A (ZGA-A), inhibits SQS activity by mimicking the substrate farnesyl pyrophosphate, the reaction intermediate presqualene pyrophosphate, or both, through a process that confers increased apparent potency in the presence of reduced enzyme concentrations, an observation consistent with either tight binding reversible competitive inhibition or mechanism-based irreversible inactivation. The studies outlined in this report provide multiple lines of evidence indicating that ZGA-A acts as a mechanism-based irreversible inactivator of SQS. 1) Inhibition of SQS by ZGA-A is dependent on the [SQS] present in the incubation reaction, and this inhibition is time-dependent and follows pseudo-first order reaction kinetics, exhibiting kobs values that range between 2 x 10(-4)/s and 23 x 10(-4)/s for [ZGA-A] within the log-linear range of the inhibition curve, and a bimolecular rate constant of 2.3 x 10(5) M-1s-1.2) SQS activity is titratable by ZGA-A, such that for each [ZGA-A] evaluated, inactivation exhibits a threshold [SQS] whereby enzyme activity at lower [SQS] is totally inhibited. 3) Time-dependent inactivation exhibits saturation kinetics with a Km for the process of 2.5 nM, which is approximately equal to the IC50 for SQS inhibition under these conditions, suggesting that inactivation results from selective modification of a functional group of the enzyme active center rather than from a nonspecific bimolecular reaction mechanism and that most, if not all of the inhibition results from irreversible inactivation. 4) Saturable, time-dependent inactivation occurs with similar inactivation kinetics for both the microsomal and trypsin-solubilized forms of the enzyme, indicating that irreversible inactivation by ZGA-A is not a consequence of membrane modification but is a direct effect of the inhibitor on the enzyme. 5) Inactivation is biphasic, exhibiting a rapid ("burst") phase followed by a second, pseudo-first order phase, similar to that previously noted for irreversible inactivators in other enzyme systems, and occurs even in the presence of 5 mM concentrations of the nucleophylic scavenger dithiothreitol, suggesting that the reaction between ZGA-A and SQS occurs at or near the active center prior to diffusion of reactive species out of the catalytic cleft. 6) Inactivation can be prevented through competition with the substrate, farnesyl pyrophosphate, further identifying the active center as the site of modification.(ABSTRACT TRUNCATED AT 400 WORDS)

The hostel outreach program: assertive case management for homeless mentally ill persons

OBJECTIVE

This study measured the impact of an assertive case management program for psychiatrically disabled homeless persons in metropolitan Toronto. It was hypothesized that the program would improve residential stability, reduce psychiatric symptoms, improve social functioning, improve social networks, and increase use of appropriate services.

METHOD

For 59 clients admitted to the program, assessments for the nine-month period before program entry were completed and were repeated nine months later. The Brief Psychiatric Rating Scale and a version of the Scale for Level of Functioning were the main measures of outcome.

RESULTS

At follow-up significant improvements in residential stability and reductions in psychopathology were demonstrated. Improvements in social functioning and increases in social network size were significant. Although no baseline data about service use were collected, clients used basic support services during their first nine months in the program.

CONCLUSIONS

The success of the program demonstrates that a difficult-to-treat patient population can be helped in a humane fashion if trained personnel are available.

Low density lipoprotein from humans supplemented with n-3 fatty acids depresses both LDL receptor activity and LDLr mRNA abundance in HepG2 cells

Fish oil supplementation in humans is often associated with an expanded low density lipoprotein (LDL) pool that is not thought to reflect increased production. Since data on clearance of LDL after fish oil supplementation (FO-LDL) are equivocal, normal volunteers (four men and three women) received ten capsules containing 3.6 g eicosapentaenoic acid and 2.9 g docosahexaenoic acid (approximately 2.5% total calories as methyl esters) for 2 weeks. Total plasma cholesterol was unchanged, but triglycerides decreased 30%. Low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) were unchanged. Analysis of the LDL particles revealed that increased esterified cholesterol caused the FO-LDL core/surface ratio to be greater than baseline LDL (BL-LDL), resulting in a shift in mean LDL density from 1.060 to 1.056. N-3 fatty acids in FO-LDL were also increased greater than 40% at the expense of n-6 and n-9 fatty acids. Human hepatoma HepG2 cells were used to study the effects of FO-LDL on LDL receptor activity and mRNA abundance for the LDL receptor, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and various apolipoproteins associated with cholesterol metabolism. In this system FO-LDL reduced LDL receptor activity compared to BL-LDL. Scatchard analysis revealed that LDL receptor number (Bmax) was reduced to one-third normal (P less than 0.001) whereas particle binding affinity was unchanged. The mRNA abundance for the LDL receptor and apoA-I were also depressed, even by low concentrations (10 micrograms/ml and 20 micrograms/ml LDL protein) of FO-LDL as compared to BL-LDL. HepG2 cells incubated with FO-LDL had decreased cellular free cholesterol but increased cholesteryl esters. Thus, moderate supplementation with fish oil n-3 fatty acids in normal humans enriches their LDL particles in cholesteryl esters and n-3 fatty acids. These particles depress both LDL receptor activity and LDL receptor mRNA abundance in HepG2 cells.

The American College of Rheumatology 1991 revised criteria for the classification of global functional status in rheumatoid arthritis

OBJECTIVE

To develop and validate revised criteria for global functional status in rheumatoid arthritis (RA).

METHODS

Revised criteria were formulated and tested for criterion and discriminant validity in 325 patients with RA.

RESULTS

The revised criteria developed are as follows: class I = able to perform usual activities of daily living (self-care, vocational, and avocational); class II = able to perform usual self-care and vocational activities, but limited in avocational activities; class III = able to perform usual self-care activities but limited in vocational and avocational activities; class IV = limited in ability to perform usual self-care, vocational, and avocational activities. Usual self-care activities include dressing, feeding, bathing, grooming, and toileting; vocational and avocational activities are both patient-desired and age-, and sex-specific. The distribution properties of this classification schema were superior to those of the original Steinbrocker criteria. Mean Health Assessment Questionnaire scores were significantly (P less than 0.0001) different between, and increased across, the 4 classes.

CONCLUSION

Although there are limitations inherent in the use of global ordinal scales, the American College of Rheumatology revised criteria will be useful in describing the functional consequences of RA. A more detailed quantitative measure of physical disability should be used, however, for optimal monitoring of patients' clinical status in office practice and clinical research.

RNA blots: staining procedures and optimization of conditions

Images

Dietary saturated fatty acids (12:0, 14:0, 16:0) differ in their impact on plasma cholesterol and lipoproteins in nonhuman primates

Three species of monkey (rhesus, cebus, and squirrel) were rotated through five purified diets containing 31% energy as various fat blends (P:S between 0.1 and 1.0) for 12-wk periods to compare the impact of specific dietary fatty acids on plasma lipids and lipoproteins. As 12:0 + 14:0 was replaced by 16:0, a significant decrease occurred in total and LDL cholesterol, whereas slight increases in total cholesterol and the LDL-HDL ratio occurred when 16:0 replaced 18:2. Hegsted and Keys regression equations provided a good fit for the observed data, but the predicted total cholesterol response was perfect (r = 0.995) for both equations when 16:0 was considered neutral. Thus, under these conditions 16:0 was less cholesterolemic than 12:0 + 14:0 and only slightly cholesterolemic compared with 18:2.

Dietary palmitic acid (16:0) enhances high density lipoprotein cholesterol and low density lipoprotein receptor mRNA abundance in hamsters

In order to examine the qualitative effect of different fats and specific fatty acids on plasma lipids and lipoprotein metabolism, six low fat, cholesterol-free diets were fed to young male hamsters (10/group) for a 4-week period. Fat blends were formulated with coconut oil, palm oil, soybean oil, high oleic acid safflower oil, butter, corn oil, and canola oil. Diets contained 13% energy as fat and dietary polyunsaturate/saturate ratios ranged from 0.12 to 1.04, one of which incorporated the American Heart Association-recommended concentrations of saturates, monoenes, and polyenes and another reflected the current American Fat Blend. In three diets the polyunsaturate/monounsaturate/saturate ratio was held constant while only the 12:0, 14:0, and 16:0 were varied. Plasma lipoproteins and apoproteins were assessed in conjunction with the abundance of specific hepatic and intestinal mRNA for the low density lipoproteins (LDL) receptor and various apolipoproteins associated with cholesterol metabolism. The plasma cholesterol response was lowest with the American Heart Association blend and equally elevated by the more saturated, low polyene diets (polyunsaturate/saturate, 0.12-0.38). Replacing 12:0 plus 14:0 from coconut oil with 16:0 as palm oil induced a significant increase in high density lipoprotein (HDL) cholesterol with a trend toward decreased LDL. These shifts in lipoprotein cholesterol were corroborated by measures of the LDL/HDL ratio, the plasma apolipoprotein B/apolipoprotein A1 ratio, and differences in the synthesis of apolipoproteins and the LDL receptor based on estimates of the mRNA for these proteins in the liver and gut, using specific cDNA probes for apolipoprotein A1, apolipoprotein B, apolipoprotein E, and the LDL receptor. Although it has been suggested that dietary polyenes lower total plasma cholesterol, including HDL, and that saturated fat increases both these pools of cholesterol, the current data represents the first evidence that a specific saturated fatty acid, i.e., palmitic acid, may enhance HDL production.

Lactose protects against estrogen-induced pigment gallstones in hamsters fed nutritionally adequate purified diets

To evaluate the impact of dietary factors on gallstone induction in hamsters, male Syrian hamsters were fed for 2-8 wk purified diets that varied in type and amount of simple sugar (glucose vs. lactose, 17.5-72%), fat (2-5%), fiber (0-15%) and estrogen (0 or 300 micrograms/kg diet). Plasma and liver cholesterol and plasma triglycerides were measured, daily weight gain was determined, cecal weights were obtained, and gallbladder bile was scored by light microscopy and analyzed chemically for its lithogenicity and gallstone incidence. Lactose reduced plasma lipids, especially triglycerides, and hepatic cholesterol accumulation, and maintained a lower biliary cholesterol concentration. When fed at 30% or more, lactose reduced weight gain, increased cecal volume 2- to 4-fold and prevented gallstone formation. Diarrhea and death from 'wet tail' was associated with gallstones and was frequent in hamsters fed glucose without fiber, but its incidence was essentially eliminated by rice flour plus fiber or lactose. Under these experimental conditions of time and diet, estrogen supplementation was required for the formation of gallstones. These appeared to be pigment stones containing a minimal amount of cholesterol. In summary, pigment gallstones were induced in less than 8 wk in hamsters fed estrogen-supplemented purified diets. Lactose feeding improved lipid metabolism and reduced gallstone formation, apparently through its impact on large bowel metabolism.

Retinal pigment epithelium possesses both LDL and scavenger receptor activity

The lipid metabolism of photoreceptors depends in part on the retinal pigment epithelium (RPE). One aspect of cholesterol homeostasis in cultured bovine RPE was evaluated by measuring low-density lipoprotein (LDL) and scavenger receptor activity with [125I]-LDL and [125I]Ac-LDL, respectively. Incubation of RPE cells in the presence of increasing concentrations of LDL or Ac-LDL resulted in down-regulation of the LDL receptor but not the scavenger receptor, patterns consistent with the presence of both receptors on these cells. This receptor profile distinguishes the RPE cell from fibroblasts and indicates its similarity to macrophages and arterial endothelial cells.

Taurine enhances low density lipoprotein binding. Internalization and degradation by cultured Hep G2 cells

To evaluate the impact of taurine on hepatic cholesterol catabolism low density lipoprotein (LDL) binding, internalization and degradation were measured in cultured Hep G2 cells. Preincubation of cells with 0.1-10 mM taurine for 24 h stimulated LDL receptor activity by as much as 100%. Only the high affinity LDL receptor activity (specific) was increased by taurine preincubation, whereas the low affinity receptor activity (nonspecific) remained unchanged. Scatchard analysis of the binding data revealed that taurine doubled the number of LDL receptors without affecting receptor affinity. Taurine-enhanced LDL receptor activity was most pronounced when LDL concentrations exceeded 100 micrograms/ml, but was noted at taurine concentrations as low as 0.1 mM (plasma level). Interestingly, taurine had no effect on LDL receptor activity when it was added simultaneously with 125I-LDL to Hep G2 cells, or when non-bile acid-producing human skin fibroblasts were tested. Stimulation of LDL receptor activity was also obtained with 10 mM cysteine, a taurine precursor, but not with glycine. Increased cellular concentrations of taurine and cysteine were associated with an elevated rate of bile acid synthesis and a reduced cellular free cholesterol concentration. The data suggest that taurine enhanced LDL receptor activity by sparing cysteine, a known sulfhydryl group donor and stimulator of 7 alpha-hydroxylase activity, and that the latter stimulated bile acid production leading to increased utilization of cellular free cholesterol and enhanced LDL uptake.

Monocyte adherence to endothelial cells in vitro is increased by beta-VLDL

The adherence of blood monocytes to the arterial endothelium is an early event in the development of atherosclerotic lesions. The possibility was investigated that alterations in the level and composition of plasma lipoproteins may contribute to this phenomenon. The adherence of human mononuclear cells to primary bovine aortic endothelial cells was measured in an in vitro monolayer collection assay. Preincubation of endothelial cells with beta-very low density lipoprotein (beta-VLDL) from cholesterol-fed rabbits or with very low density lipoprotein (VLDL) from cholesterol/saturated fat-fed cebus monkeys resulted in a significant increase in the subsequent adherence of monocytes to the endothelial cells. The effect of beta-VLDL was maximal at 100 micrograms protein/ml. The response increased with time when endothelial cells were incubated with beta-VLDL for 0-120 minutes, then remained maximal for up to 4 hours. The adherence of a human monocytic cell line (U937) to endothelial cells was also increased by beta-VLDL. These results suggest that diet-induced alterations in lipoprotein composition may contribute to the development of atherosclerotic lesions by affecting the adherence of monocytes to the arterial endothelium.

LDL enhances monocyte adhesion to endothelial cells in vitro

Monocyte adhesion to the arterial endothelium is an early event in diet-induced atherogenesis. The possibility that low-density lipoprotein (LDL) may influence this adhesion was investigated by using an in vitro monolayer collection assay. Postprandial and fasting LDL was isolated from 12 normal adult human donors (8 male and 4 female) and incubated with primary cultures of bovine aortic endothelial cells (BAEC) for 6 hours. 51Cr-labeled mononuclear leukocytes (MNLs) were then added and incubated an additional 30 minutes. When results were expressed as the ratio of adherent counts per minute in LDL-treated BAEC cultures to that in PBS-treated controls, 10 of the 16 LDL samples isolated from male donors induced a significant increase (P less than 0.05) in MNL adhesion (1.06-1.27) attributable to esterase-positive cells. This increase was dose-dependent and maximal at 100 micrograms LDL protein/ml. The magnitude of the response was significantly correlated with LDL composition (r = 0.857, P less than 0.01) such that LDL rich in cholesterol and triglyceride relative to protein enhanced MNL adhesion, whereas lipid-poor LDL (typically isolated from the women) reduced adhesion.

Regulation of low-density lipoprotein receptors in the human hepatoma cell line Hep G2

The human hepatoma cell line Hep G2 can be maintained in continuous culture and secretes numerous plasma proteins and lipoproteins into the medium. To better characterize cholesterol homeostasis in these cells we have examined the binding, internalization and degradation of [125I]LDL by cultured Hep G2 cells. Hep G2 cells express high-affinity low-density lipoprotein (LDL) receptors which facilitate the binding, internalization and degradation of [125I]LDL; these receptors can be induced by growth in LDL-depleted medium and repressed by further incubation in medium supplemented with LDL. The degradation of [125I]LDL by derepressed Hep G2 cells was inhibited by greater than 90% by monensin. Incubation of Hep G2 cells in the presence of increasing concentrations of LDL also inhibited cholesterol biosynthesis. Our results indicate that Hep G2 cells possess high affinity LDL receptors which are subject to metabolic regulation and suggest that this cell line affords a valuable model to further examine cholesterol and lipoprotein metabolism in human liver cells.

Will dietary omega-3 fatty acids change the composition of human milk?

The most abundant long-chain polyunsaturated fatty acid in brain and retinal lipids is docosahexaenoic acid (DHA, C22:6 omega 3). It becomes incorporated into nerve tissues mostly in utero and during the 1st yr of life. DHA is derived in humans either performed in the diet or by hepatic synthesis from dietary linolenic acid (C18:3 omega 3). Since human milk contains DHA, this study was designed to see if increased dietary DHA would be reflected in a higher DHA content in human milk. Eight lactating women were given supplements of a fish oil concentrate rich in omega-3 fatty acids, including DHA (11% of fatty acids). Six women took 5 g/day of fish oil for 28 days; five women consumed 10 g/day for 14 days; and one woman consumed 47 g/day for 8 days. Each intake level of fish oil produced significant dose-dependent increases in the DHA content of milk and plasma. Base-line DHA levels in milk were 0.1 +/- 0.06% of total fatty acids. Five g/day of fish oil raised the levels to 0.5 +/- 0.1% (p less than 0.001); 10 g/day raised DHA levels to 0.8 +/- 0.1% (p less than 0.001); and 47 g/day produced DHA levels of 4.8%. The results of this study indicated that relatively low intakes of dietary DHA significantly elevated milk DHA content. This would clearly elevate the infant's DHA intake and might have implications for brain and retinal development.

Similarities and differences in the ultrastructure of two hormone-dependent and one independent human breast carcinoma grown in athymic nude mice: comparison with the rat DMBA-induced tumor and normal secretory mammocytes

The human breast cancer cell lines MCF-7 (ER positive), ZR 75-1 (ER positive) and MDA-MB 231 (ER negative) form solid tumors within one week following inoculation into athymic nude mice. Tumor formation by MCF-7 and ZR 75-1 cells was dependent upon estrogen, whereas MDA-MB 231 cells formed tumors in ovariectomized mice with or without supplemental estrogen. Ultrastructural comparison of tumors formed by the three human breast carcinoma lines in athymic nude mice indicated that lactoperoxidase activity, milk protein and fat globule formation were virtually absent from all three tumors. The estrogen-dependent tumors (MCF-7, ZR 75-1), however, had more desmosomes, intermediate-sized microfilaments and collagen than the estrogen-independent tumor (MDA-MB 231). When the ultrastructure of the three human tumors was compared to the hormone-dependent, DMBA-induced rat mammary carcinoma and to the normal lactating rat mammocytes, the following observations were evident: a) the estrogen-dependent human tumors closely resembled the normal rat tissue in the distribution of desmosomes and collagen, b) the rat mammary carcinoma differed from both the estrogen-dependent and -independent human tumors, in having milk protein, milk fat globules and intense lactoperoxidase activity. The results indicate that these hormone-dependent and -independent human mammary tumors maintained in athymic nude mice differ markedly in their ultrastructure from the lactating rat mammocytes and the rat DMBA-induced mammary carcinoma.

Adrenocortical response to adrenocorticotropin in heterozygous familial hypercholesterolemia

Receptor-mediated uptake of low density lipoproteins (LDL) provides an important source of cholesterol for corticosteroid synthesis by human adrenocortical cells grown in tissue culture. Recent studies have indicated an impaired adrenocortical response to prolonged ACTH stimulation in patients with abetalipoproteinemia (who lack plasma LDL) and in patients with homozygous familial hypercholesterolemia (FH), who have a virtual absence of high affinity LDL receptors. In the present study we examined parameters of adrenocortical function in four women with well characterized heterozygous FH to assess whether a 50% reduction in the number of LDL receptors measured in vitro influenced the response of the adrenal cortex to prolonged stimulation with ACTH. Biochemical studies of the binding, internalization, and degradation of [125I]LDL were undertaken in cultured skin fibroblasts from each patient, and all patients had reduced LDL receptor activity. The adrenocortical response to a 36-h iv infusion of alpha ACTH-(1-24) (Cortrosyn) was evaluated in the four patients with heterozygous FH and in five normal women. Stimulation with iv ACTH resulted in rapid increases in the serum concentrations of cortisol in both groups and plateau concentrations of 55-60 micrograms/dl. The rates of increase and the plateau concentrations were similar in the control and FH patients. Similarly, rates of excretion of 17-hydroxycorticosteroids and cortisol were similar in the normal subjects and FH patients. These results indicate that a 50% reduction in the number of high affinity LDL receptors due to the presence of one abnormal gene at the LDL receptor locus does not result in any impairment in the delivery of cholesterol to the adrenal cortex during conditions of maximal corticosteroid production.

Transcutaneous noninvasive monitoring of carbon dioxide tension

We evaluated the accuracy of a new device for continuous noninvasive measurement of cutaneous PCO2. The Hewlett-Packard capnometer (model 47210/HA) works by means of an infrared transducer applied to the forearm over an area of skin that has been stripped of the stratum corneum. Capnometer transcutaneous carbon dioxide pressure (CPCO2) was compared with arterial carbon dioxide pressure (PaCO2) during 60 simultaneously obtained measurements in 13 hemodynamically stable patients. Each patient was studied for 1 1/2 to 5 hours, and a wide range of PaCO2 values (21 to 82 mm Hg) was represented. The data show a clinically significant relationship whereby PaCO2 = CPCO2 - 4.13, with a SE of +/- 2.19 mm Hg. Clinical usefulness of noninvasive cutaneous CO2 monitoring can be foreseen in patients whose ventilatory support is being tapered, in those with respiratory depression caused by various neuromuscular disorders, and in patients with chronic obstructive pulmonary disease and acute respiratory failure. Our results indicate that continuous transcutaneous CPCO2 measurements are safe and accurate and strongly suggest that they can be of clinical usefulness in a select group of hemodynamically stable patients.

Organotypic culture of fetal rat lung: evaluation and comparison with organ culture

Monodispersed suspensions of 19-day fetal rat lung when plated onto gelatin sponges reaggregated to form alveolarlike structures. These structures consisted almost entirely of alveolar type II cells, whereas the whole cultures contained about 65% type II cells. The phospholipid content and composition of the organotypic cultures after 8 days of incubation was very similar to that of explants of 19-day fetal rat lung grown in organ culture of 48 h, as was the pattern of incorporation of choline and acetate into phospholipids. Very little phosphatidylcholine was secreted by the organotypic cultures into the culture medium. Initial observations suggested that the organ cultures are more responsive to hormones. Organotypic cultures do not appear to offer any major advantage over the simpler and quicker organ cultures for studies of hormonal influences on fetal lung maturation. They may be useful for examining the metabolism and sympathetic pathways of the type II cell.

Menopause, medroxyprogesterone and breathing during sleep

Twenty-one postmenopausal women were monitored for sleep-disordered breathing and nocturnal oxygen desaturation to evaluate the contribution of progestational hormones to the occurrence of these sleep events. For approximately one month 11 subjects received 30 mg of medroxyprogesterone (MPG) daily, and 10 received placebo tablets in a randomized, double-blind controlled study. Respiration, saturation and electroencephalography were monitored during one night of sleep before and one night after therapy. Contrasted with the low incidence of disordered breathing and desaturation in premenopausal women, 71 percent of the postmenopausal women had such events. In the placebo-treated group, all measured variables of sleep and breathing were identical on the two nights, which suggested that the findings of a single night of sleep monitoring may be representative of other nights of sleep. Although several subjects appeared to show improvement with MPG, only the maximum duration of apnea was significantly reduced the second night (p less than 0.03).

The effect of low flow oxygen on sleep-disordered breathing and oxygen desaturation. A study of patients with chronic obstructive lung disease

Oxygen desaturation occurs during sleep in many patients with chronic obstructive lung disease (COLD) and is often caused by sleep-disordered breathing (SDB). Nocturnal oxygen therapy should improve nighttime hypoxemia, but might also worsen SDB. Using standard polysomnographic techniques, we evaluated the frequency and duration of oxygen desaturation and SDB during sleep in 11 patients with stable COLD. During half of the night the patients breathed air through a nasal cannula and during the other half of the night they breathed oxygen at 2 liters per minute. Five patients had arterial lines inserted for determination of arterial blood gas levels during periods of SDB or desaturation. The ten men and one woman slept 70 minutes (52 percent of time in bed) while on air and 111 minutes (80 percent of time in bed) while on oxygen (p < 0.001). Oxygen therapy reduced the number of episodes of desaturation per hour and the time spent in desaturation. However, there was no difference between air and oxygen in episodes of SDB per hour, the duration of episodes of SDB, baseline sleeping PaCO2 or PaCO2 during episodes of desaturation or SDB. Therefore, in most patients with stable COLD, administration of oxygen at 2 liters per minute improves oxygenation, prolongs sleep, but does not adversely affect SDB.