Dietary intake of micronized avian eggshell membrane in aged mice reduces circulating inflammatory markers, increases microbiota diversity, and attenuates skeletal muscle aging

Introduction

Avian eggshell membrane (ESM) is a complex extracellular matrix comprising collagens, glycoproteins, proteoglycans, and hyaluronic acid. We have previously demonstrated that ESM possesses anti-inflammatory properties in vitro and regulates wound healing processes in vivo. The present study aimed to investigate if oral intake of micronized ESM could attenuate skeletal muscle aging associated with beneficial alterations in gut microbiota profile and reduced inflammation.

Methods

Elderly male C57BL/6 mice were fed an AIN93G diet supplemented with 0, 0.1, 1, or 8% ESM. Young mice were used as reference. The digestibility of ESM was investigated using the static in vitro digestion model INFOGEST for older people and adults, and the gut microbiota profile was analyzed in mice. In addition, we performed a small-scale pre-clinical human study with healthy home-dwelling elderly (>70 years) who received capsules with a placebo or 500 mg ESM every day for 4 weeks and studied the effect on circulating inflammatory markers.

Results and discussion

Intake of ESM in elderly mice impacted and attenuated several well-known hallmarks of aging, such as a reduction in the number of skeletal muscle fibers, the appearance of centronucleated fibers, a decrease in type IIa/IIx fiber type proportion, reduced gene expression of satellite cell markers Sdc3 and Pax7 and increased gene expression of the muscle atrophy marker Fbxo32. Similarly, a transition toward the phenotypic characteristics of young mice was observed for several proteins involved in cellular processes and metabolism. The digestibility of ESM was poor, especially for the elderly condition. Furthermore, our experiments showed that mice fed with 8% ESM had increased gut microbiota diversity and altered microbiota composition compared with the other groups. ESM in the diet also lowered the expression of the inflammation marker TNFA in mice and in vitro in THP-1 macrophages. In the human study, intake of ESM capsules significantly reduced the inflammatory marker CRP. Altogether, our results suggest that ESM, a natural extracellular biomaterial, may be attractive as a nutraceutical candidate with a possible effect on skeletal muscle aging possibly through its immunomodulating effect or gut microbiota.

Static in vitro digestion model adapted to the general older adult population: an INFOGEST international consensus

Understanding the mechanisms of food digestion is of paramount importance to determine the effect foods have on human health. Significant knowledge on the fate of food during digestion has been generated in healthy adults due to the development of physiologically-relevant in vitro digestion models. However, it appears that the performance of the oro-gastrointestinal tract is affected by ageing and that a model simulating the digestive conditions found in a younger adult (<65 years) is not relevant for an older adult (>65 years). The objectives of the present paper were: (1) to conduct an exhaustive literature search to find data on the physiological parameters of the older adult oro-gastrointestinal tract, (2) to define the parameters of an in vitro digestion model adapted to the older adult. International experts have discussed all the parameters during a dedicated workshop organized within the INFOGEST network. Data on food bolus properties collected in the older adult were gathered, including food particle size found in older adult boluses. In the stomach and small intestine, data suggest that significant physiological changes are observed between younger and older adults. In the latter, the rate of gastric emptying is slowed down, the pH of the stomach content is higher, the amount of secretions and thus the hydrolytic activities of gastric and intestinal digestive enzymes are reduced and the concentration of bile salts lower. The consensus in vitro digestion model of the older adult proposed here will allow significant progress to be made in understanding the fate of food in this specific population, facilitating the development of foods adapted to their nutritional needs. Nevertheless, better foundational data when available and further refinement of the parameters will be needed to implement the proposed model in the future.

Levels of nitrate, nitrite and nitrosamines in model sausages during heat treatment and in vitro digestion - The impact of adding nitrite and spinach (Spinacia oleracea L.)

Nitrite derivatives react with endogenous precursors forming N-nitrosamines associated with development of colorectal cancer. The present study aims to investigate the formation of N-nitrosamines in sausage during processing and in vitro gastrointestinal digestion after adding sodium nitrite and/or spinach emulsion. The INFOGEST digestion protocol was used to simulate the oral, gastric, and small intestinal phases of digestion, and sodium nitrite was added in the oral phase to mimic the input of nitrite from saliva as it has shown to affect the endogenous formation of N-nitrosamines. The results show that the addition of spinach emulsion, in spite of it being a source of nitrate, did not affect the nitrite content in either batter, sausage, or roasted sausage. The levels of N-nitrosamines increased with the added amount of sodium nitrite, and further formation of some volatile N-nitrosamines was observed during roasting and in vitro digestion. In general, N-nitrosamine levels in the intestinal phase followed the same trend as in the undigested products. The results further indicate that nitrite present in saliva may cause a significant increase in N-nitrosamine levels in the gastrointestinal tract and that bioactive components in spinach may protect against the formation of volatile N-nitrosamines both during roasting and digestion.

Improved estimation of in vitro protein digestibility of different foods using size exclusion chromatography

While the harmonized INFOGEST model provides a physiologically relevant platform for simulated digestion, it needs to be combined with adequate analytical methods to enable quantification and comparison of protein digestibility in different food matrices. We have shown that size exclusion chromatography (SEC) can be used to estimate the proportion of small peptides potentially available for uptake. Combined with determination of total dissolved protein, the % of small peptides per total protein was calculated as a physiologically relevant estimate of protein digestibility (D_SEC). Values for D_SEC differed for casein (87.6%), chicken mince (72.6%), heated pea protein concentrate (67.8%), bread (63%), beef entrecote (57.7%) and pea protein concentrate (57.8%). In contrast to existing methods (TCA soluble protein, free NH₂-groups), the proposed SEC based method gives separate insight into the two fundamental processes during protein digestion (solubilization and break-down), while maintaining the ability to rank digestibility of very different food proteins.

Direct contact ultrasound assisted freezing of chicken breast samples

Nowadays, rapid freezing is sought to favor the formation of small ice crystals. Several studies have shown that the application of ultrasounds (US) accelerates the processes of energy and mass transfer when they are applied through immersion systems. However, there are hardly any studies on its application in direct systems without the use of a liquid medium for its transmission. Therefore, the objective of this work was to evaluate the potential of the application of US for improving the freezing process of chicken breast samples. First, the application of intermittent US treatments at different net sonication times of 7, 17, 37, 50 and 67% during the freezing of distilled water samples in a conventional freezer was evaluated. It was observed that net sonication times of 37, 50 and 67% reduced the phase change period by 30.0, 21.4, 27.0%, respectively. The effective freezing time was also reduced by 12.4 and 12.8% by applying net sonication times of 37 and 50%. Considering these results, an intermittent US treatment with a net sonication time of 37% was chosen for chicken breast freezing in an air-forced cooling tunnel at ambient temperatures from -13 to -22 °C. The length of all the freezing phases was reduced upon application of US, leading to an overall process time reduction of approx. 11%. On the other hand, no significant differences were found either in the Water Holding Capacity (WHC) or Cooking Loss (CL) values between control and US assisted frozen chicken breast samples. Furthermore, in vitro experiments showed that US-assisted freezing did not influence protein digestibility of chicken meat samples. This study demonstrates the potential of the application of US by direct contact to favor energy transfer processes during freezing of water and chicken breasts samples. However, its effect on the quality of the frozen products should be further studied.

Oatmeal particle size alters glycemic index but not as a function of gastric emptying rate

The aim of this study was to determine the extent to which oat particle size in a porridge could alter glucose absorption, gastric emptying, gastrointestinal hormone response, and subjective feelings of appetite and satiety. Porridge was prepared from either oat flakes or oat flour with the same protein, fat, carbohydrate, and mass. These were fed to eight volunteers on separate days in a crossover study, and subjective appetite ratings, gastric contents, and plasma glucose, insulin, and gastrointestinal hormones were determined over a period of 3 h. The flake porridge gave a lower glucose response than the flour porridge, and there were apparent differences in gastric emptying in both the early and late postprandial phases. The appetite ratings showed similar differences between early- and late-phase behavior. The structure of the oat flakes remained sufficiently intact to delay their gastric emptying, leading to a lower glycemic response, even though initial gastric emptying rates were similar for the flake and flour porridge. This highlights the need to take food structure into account when considering relatively simple physiological measures and offering nutritional guidance.NEW & NOTEWORTHY The impact of food structure on glycemic response even in simple foods such as porridge is dependent on both timing of gastric emptying and the composition of what is emptied as well as duodenal starch digestion. Thus structure should be accounted for when considering relatively simple physiological measures and offering nutritional guidance.

Effects of dietary beef, pork, chicken and salmon on intestinal carcinogenesis in A/J Min/+ mice

The International Agency for Research on Cancer has classified red meat as “probably carcinogenic to humans” (Group 2A). In mechanistic studies exploring the link between intake of red meat and CRC, heme iron, the pigment of red meat, is proposed to play a central role as a catalyzer of luminal lipid peroxidation and cytotoxicity. In the present work, the novel A/J Min/+ mouse was used to investigate the effects of dietary beef, pork, chicken, or salmon (40% muscle food (dry weight) and 60% powder diet) on Apc-driven intestinal carcinogenesis, from week 3–13 of age. Muscle food diets did not differentially affect carcinogenesis in the colon (flat ACF and tumors). In the small intestine, salmon intake resulted in a lower tumor size and load than did meat from terrestrial animals (beef, pork or chicken), while no differences were observed between the effects of white meat (chicken) and red meat (pork and beef). Additional results indicated that intestinal carcinogenesis was not related to dietary n-6 polyunsaturated fatty acids, intestinal formation of lipid peroxidation products (thiobarbituric acid reactive substances, TBARS), or cytotoxic effects of fecal water on Apc^-/+ cells. Notably, the amount of heme reaching the colon appeared to be relatively low in this study. The greatest tumor load was induced by the reference diet RM1, underlining the importance of the basic diets in experimental CRC. The present study in A/J Min/+ mice does not support the hypothesis of a role of red meat in intestinal carcinogenesis.

Formation of Malondialdehyde, 4-Hydroxynonenal, and 4-Hydroxyhexenal during in Vitro Digestion of Cooked Beef, Pork, Chicken, and Salmon

Red meat high in heme iron may promote the formation of potentially genotoxic aldehydes during lipid peroxidation in the gastrointestinal tract. In this study, the formation of malondialdehyde (MDA) equivalents measured by the thiobarbituric acid reactive substances (TBARS) method was determined during in vitro digestion of cooked red meat (beef and pork), as well as white meat (chicken) and fish (salmon), whereas analysis of 4-hydroxyhexenal (HHE) and 4-hydroxynonenal (HNE) was performed during in vitro digestion of cooked beef and salmon. Comparing products with similar fat contents indicated that the amount of unsaturated fat and not total iron content was the dominating factor influencing the formation of aldehydes. It was also shown that increasing fat content in beef products caused increasing concentrations of MDA equivalents. The highest levels, however, were found in minced beef with added fish oil high in unsaturated fat. This study indicates that when ingested alone, red meat products low in unsaturated fat and low in total fat content contribute to relatively low levels of potentially genotoxic aldehydes in the gastrointestinal tract.

A standardised static in vitro digestion method suitable for food - an international consensus

Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.

Effect of broccoli phytochemical extract on release of fatty acids from salmon muscle and salmon oil during in vitro digestion

The aim of the present work was to study the effect of a broccoli phytochemical extract (Br-ex) on the release of fatty acids (FA) from salmon muscle (SM) and salmon oil (SO) duringin vitrodigestion.

The impact of meal composition on the release of fatty acids from salmon during in vitro gastrointestinal digestion

We hypothesize that the rate of release of lipids from salmon muscle during in vitro digestion is altered by additional meal components. In vitro digestion of salmon was performed using a mixture of porcine gastrointestinal enzymes and bile salts. Broccoli and barley were also added to the digestion simulating a meal. The extent of lipolysis was determined by measuring the release of fatty acids (FAs) during sampling at the simulated gastric phase endpoint (60 minutes) and 20, 40, 60, 80, 110 and 140 minutes simulated small intestinal phase, using solid phase extraction and GC-FID. Adding barley resulted in a lower overall release of FA from salmon, whereas broccoli caused an initial delay followed by increased release from 80-140 min when lipid digestion of salmon alone plateaued. The impact of broccoli and barley on the release of peptides and digesta viscosity were also measured. The effect of different components in the meal shown by this in vitro study suggests that it would be possible to make dietary changes affecting the lipolysis, further triggering specific responses in the gastrointestinal tract. However, these observations need to be validated in vivo, and the mechanisms need to be further examined.

Effects of environmental factors on edible oil quality of organically grown Camelina sativa

The aim of the present study was to evaluate the potential for the production of edible oil from organically grown camelina ( Camelina sativa L. Crantz), focusing on the influence of environmental factors on nutritional quality parameters. Field experiments with precrop barley were conducted in Norway in the growing seasons 2007, 2008, and 2009. Trials were fully randomized with two levels of nitrogen (N) fertilization, 0 and 120 kg total N ha(-1), and two levels of sulfur (S) fertilization, 0 and 20 kg total S ha(-1). Weather conditions, that is, temperature and precipitation, were recorded. Additional experiments were performed in the years 2008 and 2009 to evaluate the effects of replacing precrop barley with precrop pea. Seed oil content was measured by near-infrared transmittance, and crude oil compositions of fatty acids, phytosterols, tocopherols, and phospholipids were analyzed by chromatography and mass spectrometry. Results showed significant seasonal variations in seed oil content and oil composition of fatty acids, tocopherols, phytosterols, and phospholipids that to a great extent could be explained by the variations in weather conditions. Furthermore, significant effects of N fertilization were observed. Seed oil content decreased at the highest level of N fertilization, whereas the oil concentrations of α-linolenic acid (18:3n-3), erucic acid (22:1n-9), tocopherols, and campesterol increased. Pea compared to barley as precrop also increased the 18:3n-3 content of oil. S fertilization had little impact on oil composition, but an increase in tocopherols and a decrease in brassicasterol were observed. In conclusion, organically grown camelina seems to be well suited for the production of edible oil. Variations in nutritional quality parameters were generally small, but significantly influenced by season and fertilization.

Phytosterol capsules and serum cholesterol in hypercholesterolemia: a randomized controlled trial

OBJECTIVE

Phytosterols are recommended in combination with diet therapy to reduce elevated LDL-cholesterol level. Meta-analyses indicate a 10% reduction in LDL-cholesterol from intake of approximately 2 g phytosterols/d incorporated into fat-based foods. However, the cholesterol lowering effect from capsules containing phytosterols is less documented. The pre-specified primary endpoint of the present study was to investigate the effect of capsules with phytosterols on circulating LDL-cholesterol in patients with mild to moderate hypercholesterolemia.

METHODS

In a double-blinded, randomized, placebo-controlled crossover study, 41 men and women were randomized into two four-weeks intervention periods with softgel capsules containing either phytosterols (2.0 g/d) or sunflower oil. There was a three-weeks washout period between the intervention periods.

RESULTS

No significant difference in total- or LDL-cholesterol between the phytosterol and the placebo period were observed after four weeks intervention (0.0 mmol/L (95%CI: -0.3 to 0.2), P = 0.74 and -0.1 mmol/L (95%CI: -0.3 to 0.1), P = 0.32, respectively).

CONCLUSION

Daily intake of capsules containing 2 g phytosterols did not reduce total- or LDL-cholesterol significantly in a highly relevant target group for the use of phytosterol products. The present results may emphasize the importance of choosing a suitable dosage-delivery system in order to achieve optimal cholesterol lowering effect. The study was registered at www.clinicaltrials.gov, IDno:NCT00485095.

Oxidative Stability of Polyunsaturated Edible Oils Mixed With Microcrystalline Cellulose

The oxidative stability of mixtures of edible oils containing polyunsaturated fatty acids (PUFA) and microcrystalline cellulose (MCC) was investigated. The mixtures studied consisted of oils of either camelina (CAM), cod liver (CLO), or salmon (SO) mixed with either colloidal or powdered MCC. A 50:50 (w/w) ratio of oil:MCC resulted in an applicable mixture containing high levels of PUFA edible oil and dietary fiber. The oxidative stability of the formulated mixtures and the pure oils was investigated over a period of 28 days. The peroxide value (PV) was assessed as a parameter for primary oxidation products and dynamic headspace gas chromatography mass spectrometry (GC/MS) was used to analyze secondary volatile organic compounds (VOC). CAM and the respective mixtures were oxidatively stable at both 4 and 22 °C during the storage period. The marine oils and the respective mixtures were stable at 4 °C. At 22 °C, an increase in hydroperoxides was found, but no increase in VOC was detected during the time-frame investigated. At 42 °C, prominent increases in PV and VOC were found for all oils and mixtures. Hexanal, a common marker for the degradation of n-6 fatty acids, propanal and 2,4-heptadienal (E,E), common indicators for the degradation of n-3 fatty acids, were among the volatiles detected in the headspace of oils and mixtures. This study showed that a mixture containing a 50:50 ratio of oil:MCC can be obtained by a low-tech procedure that does not induce oxidation when stored at low temperatures during a period of 1 month.

Plant sterols from rapeseed and tall oils: effects on lipids, fat-soluble vitamins and plant sterol concentrations

BACKGROUND AND AIMS

Data comparing the impact of different sources of plant sterols on CVD risk factors and antioxidant levels is scarce. We evaluated the effects of plant sterols from rapeseed and tall oils on serum lipids, lipoproteins, fat-soluble vitamins and plant sterol concentrations.

METHODS AND RESULTS

This was a double-blinded, randomized, crossover trial in which 59 hypercholesterolemic subjects consumed 25 g/day of margarine for 4 weeks separated by 1 week washout periods. The two experimental margarines provided 2g/day of plant sterols from rapeseed or tall oil. The control margarine had no added plant sterols. The control margarine reduced LDL cholesterol by 4.5% (95% CI 1.4, 7.6%). The tall and rapeseed sterol margarines additionally reduced LDL cholesterol by 9.0% (95% CI 5.5, 12.4%) and 8.2% (95% CI 5.2, 11.4%) and apolipoprotein B by 5.3% (95% CI 1.0, 9.6%) and 6.9% (95% CI 3.6, 10.2%), respectively. Lipid-adjusted beta-carotene concentrations were reduced by both sterol margarines (P<0.017). alpha-Tocopherol concentrations were reduced by the tall sterol compared to the rapeseed sterol margarine (P=0.001). Campesterol concentrations increased more markedly with the rapeseed sterol versus tall sterol margarine (P<0.001). The rapeseed sterol margarine increased while the tall sterol margarine decreased brassicasterol concentrations (P<0.001).

CONCLUSIONS

Plant sterols from tall and rapeseed oils reduce atherogenic lipids and lipoproteins similarly. The rapeseed sterol margarine may have more favorable effects on serum alpha-tocopherol concentrations.

Palm oil versus hydrogenated soybean oil: effects on serum lipids and plasma haemostatic variables

The purpose of this study was to test if replacement of trans fatty acids by palmitic acid in an experimental margarine results in unfavourable effects on serum lipids and haemostatic factors. We have compared the effects of three different margarines, one based on palm oil (PALM-margarine), one based on partially hydrogenated soybean oil (TRANS- margarine) and one with a high content of polyunsaturated fatty acids (PUFA-margarine), on serum lipids in 27 young women. In nine of the participants fasting levels and diurnal postprandial levels of haemostatic variables on the 3 diets were compared. The sum of 12:0, 14:0, 16:0 provided 11% of energy (E%) in the PALM diet, the same as the sum of 12:0, 14:0, 16:0 and trans fatty acids in the TRANS-diet. Oleic acid provided 10-11E% in all three diets, while PUFA provided 5.7, 5.5 and 10.2 E%, respectively. Total fat provided 30-31% and the test margarines 26% of total energy in all three diets. Each of the diets was consumed for 17 days in a crossover design. There were no significant differences in total cholesterol, LDL-cholesterol and apoB between the TRANS- and the PALM-diet. HDL-cholesterol and apoA-I were significantly higher on the PALM-diet compared to the TRANS-diet while the ratio of LDL- to HDL-cholesterol was lower, although not significantly (P = 0.077) on the PALM-diet. Total cholesterol, LDL-cholesterol and apoB were significantly lower on the PUFA-diet compared to the two other diets. HDL-cholesterol was not different on the PALM- and the PUFA-diet while it was significantly lower on the TRANS-diet compared to the PUFA-diet. Triglycerides and Lp(a) were not different among the three diets. The diurnal postprandial state level of tissue plasminogen activator (t-PA) activity was significantly decreased on the TRANS-diet compared to the PALM-diet. t-PA activity was also decreased on the PUFA-diet compared to PALM-diet although not significantly (P=0.07). There were no significant differences in neither fasting levels or in circadian variation of t-PA antigen, PAI-1 activity, PAI-1 antigen, factor VII coagulant activity or fibrinogen between the three diets. Our results suggest that dietary palm oil may have a more favourable effect on the fibrinolytic system compared to partially hydrogenated soybean oil. We conclude that from a nutritional point of view, palmitic acid from palm oil may be a reasonable alternative to trans fatty acids from partially hydrogenated soybean oil in margarine if the aim is to avoid trans fatty acids. A palm oil based margarine is, however, less favourable than one based on a more polyunsaturated vegetable oil.

[Diet changes and the rise and fall of cardiovascular disease mortality in Norway]

BACKGROUND

Cardiovascular disease mortality in Norway during the last 50 years has been analysed and related to changes in dietary habits and serum cholesterol in the population.

MATERIAL AND METHODS

Mortality and dietary data have been collected from official statistics. Changes in serum cholesterol have been estimated from changes in intake of fatty acids based on published regression equations. Data on changes in serum cholesterol and blood pressure are from the former National Health Screening Service.

RESULTS

Mortality from ischemic heart disease (IHD) peaked in 1966-70 when it was 100% higher than in 1951-55 for men and 50% higher for women. For age group 40-69 years mortality has been reduced by more than one half during the last 30 years. For the period 1996-2000 and for all age groups, 30,903 fewer deaths occurred than expected, had the mortality remained the same as during 1971-75, that is 6180 per year. Mortality from sudden death has followed the same pattern as for IHD. Cerebrovascular disease mortality has shown a declining tendency during the entire period. Since 1960 the proportion of total fat in the diet has been reduced from 41 to 34% of energy and the proportion of unsaturated to saturated plus trans fatty acids has increased. Cholesterol in the diet has been reduced by almost one half. Based on changes in consumption in milk fat, fat from meat and margarine, and taken into consideration the change from boiled to filtered coffee the estimated reduction in serum cholesterol in the population is in the order of 0.8 mmol/l. This corresponds closely to the observed 0.5 to 1 mmol/l. Most of the reduction is due to changes in milk fat and margarine consumption and composition.

INTERPRETATION

Based on the established relation between serum cholesterol and risk of IHD we conclude that reduction in serum cholesterol may explain most of the decline in mortality since 1970. Other factors that may have contributed are reduced smoking (in men), a small reduction in blood pressure, increased consumption of fruit, vegetables, cod liver - and fish oil and better means of treatment.

Serum cholesterol predictive equations in product development

The aim of the study was to incorporate trans fatty acids into predictive equations for serum cholesterol and compare their effects with the effects of the individual saturated fatty acids 12:0, 14:0 and 16:0. We have introduced trans fatty acids from partially hydrogenated soybean oil (TransV) and fish oil (TransF) into previously published equations by constrained regression analysis. Prior knowledge about the signs and ordering of existing regression coefficients were incorporated into the regression modelling by adding lower and upper bounds to the coefficients. Oleic acid (18:1) and polyunsaturated fatty acids (18:2, 18:3) were not sufficiently varied in the studies and the respective regression coefficients therefore set equal to those found by Yu et al. (Am J Clin Nutr 1995;61:1129-39). Stearic acid (18:0) considered to be neutral was not included in the equations. The regression analyses were based on results from four controlled dietary studies with a total of 95 participants and including 10 diets differing in fatty acid composition. The analyses resulted in the following equations where the change in cholesterol is expressed in mmol/L and the change in intake of fatty acids is expressed in E%: Delta Total cholesterol = 0.01 delta(12:0) + 0.12 Delta(14:0) + 0.057 delta(16:0) + 0.039 delta(TransF) + 0.031 delta(TransV)- 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3) and deltaLDL cholesterol = 0.01 delta(12:0) + 0.071 delta(14:0) + 0.047 delta(16:0) + 0.043 delta(TransF) + 0.025 delta(TransV) - 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3). The test set used for validation consisted of 22 data points from seven recently published dietary studies. The equation for total cholesterol showed good prediction ability with a correlation coefficient of 0.981 between observed and predicted values. The equation has been used to reformulate margarines into "trans free" products all with more favourable effects on serum cholesterol than previous products. Also a cholesterol reducing margarine has been produced. When tested against butter in an open clinical trial among subjects with mild hypercholesterolemia the observed cholesterol-lowering effect of this margarine corresponded reasonably well with the predicted (0.77 vs. 0.64 mmol/L). We conclude that the equation has practical applicability and can be used to formulate and nutritionally optimise fat products as well as to evaluate already existing products on the market.

Serum cholesterol predictive equations with special emphasis on trans and saturated fatty acids. an analysis from designed controlled studies

The effects of dietary trans fatty acids on serum total and low density lipoprotein (LDL) cholesterol have been evaluated by incorporating trans fatty acids into predictive equations and comparing their effects with the effects of the individual saturated fatty acids 12:0, 14:0, and 16:0. Trans fatty acids from partially hydrogenated soybean oil (TRANS V) and fish oil (TRANS F) were included in previously published equations by constrained regression analysis, allowing slight adjustments of existing coefficients. Prior knowledge about the signs and ordering of the regression coefficients was explicitly incorporated into the regression modeling by adding lower and upper bounds to the coefficients. The amounts of oleic acid (18:1) and polyunsaturated fatty acids (18:2, 18:3) were not sufficiently varied in the studies, and the respective regression coefficients were therefore set equal to those found by Yu et al. [Yu, S., Derr, J., Etherton, T.D., and Kris-Etherton, P.M. (1995) Plasma Cholesterol-Predictive Equations Demonstrate That Stearic Acid Is Neutral and Monounsaturated Fatty Acids Are Hypocholesterolemic, Am. J. Clin. Nutr. 61, 1129-1139]. Stearic acid (18:0), considered to be neutral, was not included in the equations. The regression analyses were based on results from four controlled dietary studies with a total of 95 participants and including 10 diets differing in fatty acid composition and with 30-38% of energy (E%) as fat. The analyses resulted in the following equations, where the change in cholesterol is expressed in mmol/L and the change in intake of fatty acids is expressed in E%: delta Total cholesterol = 0.01 delta(12:0) + 0.12 delta(14:0) + 0.057 delta(16:0) + 0.039 delta(TRANS F) + 0.031 delta(TRANS V) - 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3) and deltaLDL cholesterol = 0.01 delta(12:0) + 0.071 delta(14:0) + 0.047 delta(16:0) + 0.043 delta(TRANS F) + 0.025 delta(TRANS V) - 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3). The regression analyses confirm previous findings that 14:0 is the most hypercholesterolemic fatty acid and indicate that trans fatty acids are less hypercholesterolemic than the saturated fatty acids 14:0 and 16:0. TRANS F may be slightly more hypercholesterolemic than TRANS V or there may be other hypercholesterolemic fatty acids in partially hydrogenated fish oil than those included in the equations. The test set used for validation consisted of 22 data points from seven recently published dietary studies. The equation for total cholesterol showed good prediction ability with a correlation coefficient of 0.981 between observed and predicted values. The equation has been used by the Norwegian food industry in reformulating margarines into more healthful products with reduced content of cholesterol-raising fatty acids.

Effect on plasma lipids and lipoproteins of replacing partially hydrogenated fish oil with vegetable fat in margarine

We have compared the effects on lipoproteins and haemostatic variables of two hard margarines with similar functional properties, one traditional margarine containing partially hydrogenated fish oil (PHFO), and one experimental margarine based on vegetable oil (VO). Both were all-purpose cooking margarines with nearly identical functional properties. Trans fatty acids from PHFO in the traditional margarine were replaced mostly by saturated, monounsaturated and trans fatty acids of vegetable origin in the new formulation. Both test margarines contained approximately the same amount of cis polyunsaturated fatty acids. Sixteen female normolipidaemic students consumed each diet with the two test margarines for 14 d in random order (crossover design). The amount of fat was 31% energy in the PHFO diet and 32% energy in the VO diet. The test margarines provided approximately 26% energy in both diets. In the PHFO diet 7.8% of the energy was derived from trans fatty acids and 9.2% from saturated fatty acids (12:0, 14:0 and 16:0) while in the VO diet, 1.1% energy was derived from trans fatty acids and 13.3% from saturated fatty acids (12:0, 14:0 and 16:0). The natural content of cholesterol in PHFO was deliberately not balanced by addition of cholesterol to the VO diet, thus the PHFO diet contained 215 mg and the VO diet 86 mg cholesterol per 8.5 MJ. LDL-cholesterol concentration was 19% higher in subjects on the PHFO diet compared with the VO diet (P < 0.01). The ratio LDL-cholesterol:HDL-cholesterol was 12.6% higher in subjects on the PHFO diet compared with the VO diet (P < 0.01). The level of apolipoprotein (apo)A-I was 6% lower in subjects on the PHFO diet compared with the VO diet (P < 0.01). The ratio apoB:apoA-I was 10.4% higher in subjects on the PHFO diet than on the VO diet (P < 0.01). There were no significant differences in total cholesterol, HDL-cholesterol, triacylglycerols, apoB, lipoprotein(a) and haemostatic variables between the diets. Our results demonstrate that PHFO, with its unfavourable effects on plasma lipids, can be replaced by vegetable oils in margarine without appreciable loss of functional properties but with significant improvement in the effects on plasma lipoproteins.

Replacement of partially hydrogenated soybean oil by palm oil in margarine without unfavorable effects on serum lipoproteins

We have compared the effects of three different margarines, one based on palm oil (PALM-margarine), one based on partially hydrogenated soybean oil (TRANS-margarine) and one with a high content of polyunsaturated fatty acids (PUFA-margarine), on serum lipids in 27 young women. The main purpose of the study was to test if replacement of trans fatty acids in margarine by palmitic acid results in unfavorable effects on serum lipids. The sum of saturated fatty acids (12:0, 14:0, 16:0) was 36.3% of total fatty acids in the PALM-diet, the same as the sum of saturated (12:0, 14:0, 16:0) (12.5%) and trans (23.1%) fatty acids in the TRANS-diet. This sum was 20.7% in the PUFA-diet. The content of oleic acid was 37.9, 35.2, and 38.6%, respectively, in the three diets, whereas linoleic acid amounted to 16, 13.5, and 27.3%, respectively. Total fat provided 30-31% and the test margarines 26% of total energy in all three diets. The subjects consumed each of the diets for 17 d in a Latin-square crossover design. There were no significant differences in total cholesterol, low density lipoprotein (LDL)-cholesterol and apolipoprotein B (apoB) between the TRANS- and the PALM-diets. High density lipoprotein (HDL)-cholesterol and apoA-1 were significantly higher on the PALM-diet compared to the TRANS-diet whereas the ratio of LDL-cholesterol to HDL-cholesterol was lower, although not significantly (P = 0.077) on the PALM-diet. Total cholesterol, LDL-cholesterol, and apoB were significantly lower on the PUFA-diet compared to the two other diets. HDL-cholesterol was not different on the PALM- and the PUFA-diets but it was significantly lower on the TRANS-diet compared to the PUFA diet. Compared to the PUFA-diet the ratio of LDL- to HDL-cholesterol was higher on both the PALM- and the TRANS-diets whereas apoA-1 was not different. Triglycerides and lipoprotein (a) were not significantly different among the three diets. We concluded that nutritionally, palmitic acid from palm oil may be a reasonable alternative to trans fatty acids from partially hydrogenated soybean oil in margarine if the aim is to avoid trans fatty acids. A palm oil-based margarine is, however, less favorable than one based on a more polyunsaturated vegetable oil.

Heterogeneity in the mouse epidermal cell cycle analysed by computer simulations

Different sets of cell kinetic data obtained over many years from hairless mouse epidermis have been simulated by a mathematical model including circadian variations. Simulating several independent sets of data with the same mathematical model strengthens the validity of the results obtained. The data simulated in this investigation were all obtained with the experimental system in a state of natural synchrony. The data include cell cycle phase distributions measured by DNA flow cytometry of isolated epidermal basal cells, fractions of tritiated thymidine ([3H]TdR) labelled cells within the cell cycle phases measured by cell sorting at intervals after [3H]TdR pulse labelling, bivariate bromodeoxyuridine (BrdUrd)/DNA data from epidermal basal cells isolated at intervals after pulse labelling with BrdUrd, mitotic rate and per cent labelled mitosis (PLM) data from histologic sections. The following main new findings were made from the simulations: the second PLM peak observed at about 35 h after pulse labelling is hardly influenced by circadian variations; the peak is mainly determined by persisting synchrony of a rapidly cycling population with a G1-duration (TG1) of 20 h to 30 h; and there is a highly significant population of slowly cycling G1-cells (G1 sigma). However, no significant circadian variations were found in the number of these cells.

BrdUrd incorporation studies for evaluation of spermatogenesis in the blue fox

The utility of BrdUrd incorporation techniques for studies of spermatogenesis was investigated in the blue fox. BrdUrd was injected intraperitoneally followed by collection of testicular tissue by castration/hemicastration at intervals up to 35 days after pulse labelling. Fluorescent tagged monoclonal antibodies against BrdUrd allowed detection of cells with incorporated tracer in histological sections by fluorescent light microscopy as well as in isolated testicular cells by bivariate BrdUrd/DNA flow cytometry. The duration of the spermatogenic cycle was estimated by following the labelled cohort of preleptotene spermatocytes by immunofluorescence in sections through the various stages of maturation to the late spermatid stage. These data were confirmed by bivariate BrdUrd/DNA flow cytometry of testicular cells in suspensions. Furthermore, estimations of the S phase durations and length of the spermatogonial cell cycle were possible. A consistent and satisfactory fluorescence intensity of incorporated label throughout the study shows that degradation of the incorporated label is no practical problem for this type of study, and suggests that the method is an excellent tool for studying aspects of proliferation and maturation during normal as well as perturbed spermatogenesis. Advantages of the described method include avoidance of potential radiation influence on spermatogenesis from commonly used radiolabelled tracers, e.g., 3H-TdR, and that both large and small animals can be investigated at modest cost since the unlabelled BrdUrd is considerably less expensive than labelled tracers.

Circadian variations in cell cycle phase progression of mouse epidermal cells measured directly by bivariate BrdUrd/DNA flow cytometry

Circadian stage-dependent variations in cell cycle traverse of mouse epidermal cells in vivo were investigated. The fate of cohorts of basal cells pulse-labelled with bromodeoxyuridine (BrdUrd) at different times of the day were studied by bivariate BrdUrd/DNA flow cytometry of isolated epidermal basal cells. Basal cells were tracked through the cell cycle up to 96 h after intraperitoneal injection of BrdUrd at 0800 and 2000, or followed for 6 h after BrdUrd injection at 0400, 1200, 1600 and 2400. The results confirmed our previous assumption that the cell cycle progression through S phase and G2 phase is considerably delayed at night, i.e. from 1600 to 0400, compared with daytime. The results indicate variations in G1 phase as well. The data strongly support the hypothesis that the main parameters responsible for circadian fluctuations in mitotic activity are variations in the S and G2 phase durations. The data are also consistent with the notion of proliferative heterogeneity among basal cells as described by a hierarchical proliferation model.

Multivariate flow cytometry of epidermal regeneration provoked by a skin irritant and a tumor promoter

The DNA content and the changes in cellular and nuclear size of isolated regenerating mouse epidermal basal cells were studied after topical application of the skin irritant cantharidin and the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) to the back skin of hairless mice. The DNA and protein contents of isolated basal cells were stained with propidium iodide and fluorescein isothiocyanate, respectively, and analysed by flow cytometry using the total protein fluorescence as an estimate of cell size and the DNA fluorescence pulse width as an estimate of nuclear size. Transmission electron microscopy was used to identify cells sorted from regions in the bivariate DNA/protein distributions. The results showed that both chemicals induced an increase in cellular as well as nuclear size of the basal cells. The increase in size was higher in TPA treated than in cantharidin treated animals, and the bivariate DNA/protein distributions of TPA treated cells differed from those of cantharidin treated cells in that two subpopulations of cycling keratinocytes could be identified. These deviations are probably related to the higher proliferative response observed after TPA treatment and the possibility that proliferative subpopulations in epidermis respond differently to TPA. It may reflect mechanisms providing for a growth advantage of initiated cells, important in tumor promotion. About 8% of the cells in the suspensions from treated animals were non-cycling non-keratinocytes, probably infiltrating leukocytes. The results indicate a strong correlation between rapid regenerative cell cycle progression, i.e., reduced G1 transit time and increased cellular and nuclear size.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison between the epidermal regenerative responses provoked by a skin irritant and a tumor promoter using anti-BrdUrd/DNA flow cytometry

The proliferative responses induced in hairless mouse epidermis after application of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and the skin irritant cantharidin were investigated. Doses known to give the same degree of hyperplasia were chosen. Mice were pulse-labeled with bromodeoxyuridine (BrdUrd) 30 min prior to or 24 h after a single application of either cantharidin or TPA, and thereafter killed at various time intervals. The basal cells were isolated from epidermis, fixed in 70% ethanol and prepared for bivariate BrdUrd/DNA flow cytometric analysis. Cells pulse-labeled in S phase 30 min prior to treatment with cantharidin or TPA were slightly delayed in their progression through S phase and temporarily blocked in G2 phase. However, they were still able to re-enter S phase 18 h later, indicating a shortening of the G1 phase. Cells pulse-labeled 24 h after treatment had a considerably reduced cell cycle time, i.e. reduced G1 transit time. Hence, the wave of cells entering S phase from 16 h after injury could be explained by an immediate reduction in G1 transit time, without assuming recruitment of temporarily resting G0/G1 cells. Although cantharidin caused the longest initial delay in cell cycle progression, the subsequent proliferative response was less pronounced than that provoked by TPA. Rapid proliferation may allow for clonal expansion of initiated cells. The higher ability of TPA to induce rapid proliferation, apparently without causing any severe initial cell damage, may thus be related to its higher tumor promoting ability.

Mathematical model analysis of mouse epidermal cell kinetics measured by bivariate DNA/anti-bromodeoxyuridine flow cytometry and continuous [3H]-thymidine labelling

In a previous study the epidermal cell kinetics of hairless mice were investigated with bivariate DNA/anti-bromodeoxyuridine (BrdU) flow cytometry of isolated basal cells after BrdU pulse labelling. The results confirmed our previous observations of two kinetically distinct sub-populations in the G2 phase. However, the results also showed that almost all BrdU-positive cells had left S phase 6-12 h after pulse labelling, contradicting our previous assumption of a distinct, slowly cycling, major sub-population in S phase. The latter study was based on an experiment combining continuous tritiated thymidine [( 3H]TdR) labelling and cell sorting. The purpose of the present study was to use a mathematical model to analyse epidermal cell kinetics by simulating bivariate DNA/BrdU data in order to get more details about the kinetic organization and cell cycle parameter values. We also wanted to re-evaluate our assumption of slowly cycling cells in S phase. The mathematical model shows a good fit to the experimental BrdU data initiated either at 08.00 hours or 20.00 hours. Simultaneously, it was also possible to obtain a good fit to our previous continuous labelling data without including a sub-population of slowly cycling cells in S phase. This was achieved by improving the way in which the continuous [3H]TdR labelling was simulated. The presence of two distinct subpopulations in G2 phase was confirmed and a similar kinetic organization with rapidly and slowly cycling cells in G1 phase is suggested. The sizes of the slowly cycling fractions in G1 and G2 showed the same distinct circadian dependency. The model analysis indicates that a small fraction of BrdU labelled cells (3-5%) was arrested in G2 phase due to BrdU toxicity. This is insignificant compared with the total number of labelled cells and has a negligible effect on the average cell cycle data. However, it comprises 1/3 to 1/2 of the BrdU positive G2 cells after the pulse labelled cells have been distributed among the cell cycle compartments.

Cell kinetics in mouse epidermis studied by bivariate DNA/bromodeoxyuridine and DNA/keratin flow cytometry

Hairless mice were injected intraperitoneally with bromodeoxyuridine (Brd-Urd). Basal cells were isolated from epidermis, fixed in 70% ethanol, and prepared for bivariate BrdUrd/DNA flow cytometric (FCM) analysis. Optimum detection of incorporated BrdUrd in DNA was obtained by combining pepsin digestion and acid denaturation. The cell loss was reduced to a minimum by using phosphate-buffered saline containing Ca2+ and Mg2+ to neutralize the acid. The percentage of cells in S phase and the average uptake of BrdUrd per labelled cell in eight consecutive windows throughout the S phase were measured after pulse labelling at intervals during a 24 h period. Furthermore, the cell cycle progression of a pulse-labelled cohort of cells was followed up to 96 h after BrdUrd injection. In general the results from both experiments were in good agreement with previous data from 3H-thymidine labelling studies. The percentage of cells in S phase was highest at night and lowest in the afternoon, whereas the average uptake of BrdUrd per labelled cell showed only minor circadian variations. There were no indications that BrdUrd significantly perturbed normal epidermal growth kinetics. A cell cycle time of about 36 h was observed for the labelled cohort. Indications of heterogeneity in traverse through G1 phase were found, and the existence of slowly cycling or temporarily resting cells in G2 phase was confirmed. There was, however, no evidence of a significant population of temporarily resting cells in the S phase. Bivariate DNA/keratin FCM analysis revealed a high purity of basal cells in the suspensions and indicated that the synthesis of the differentiation-keratin K10 was turned on only in G1 phase and after the last division.

The epidermal cell kinetic response to ultraviolet B irradiation combines regenerative proliferation and carcinogen associated cell cycle delay

The cell cycle traverse of epidermal basal cells 24 h after in vivo exposure of ultraviolet B (UVB) irradiation was studied by immunochemical staining of incorporated bromodeoxyuridine (BrdU) and bivariate BrdU/DNA flow cytometric analysis. The results were compared with the cell kinetic patterns following topical application of the skin carcinogen methylnitrosourea (MNU) as well as the skin irritant cantharidin. Hairless mice were injected intraperitoneally with BrdU 24 h after treatment of their back skin with either a minimal erythema dose of UVB, or a single application of MNU or cantharidin dissolved in acetone. The cell cycle traverse of the BrdU-labelled cohorts of epidermal basal cells were then followed for the subsequent 12 h. At 6 h after BrdU-injection, when all labelled cells in the control group as well as in the cantharidin group had left the S phase, the bivariate distributions of the UVB-exposed and the MNU group showed that BrdU-positive cells were still present in S phase. Hence, UVB irradiation, similar to the carcinogen MNU, prolonged the S phase duration in some of the basal cells. At 12 h after pulse labelling, however, BrdU-positive cells from UVB-exposed mice were re-entering S phase from G1 phase, indicating that UVB irradiation induced a shortening of the cell cycle time as well, similar to the response observed after cantharidin. The present data can not tell whether these cells also were delayed in S phase. Thus, the cell cycle traverse in hairless mouse epidermis 24 h after in vivo exposure to UVB seemed to be a combination of the cell kinetic effects following chemical skin carcinogens and skin irritants. UVB irradiation induced both a delay in transit time through S phase, probably due to DNA damage and subsequent repair, as well as a reduction in the total cell cycle time consistent with rapid regenerative proliferation.

Characterization of bladder tumours by multiparameter flow cytometry with special reference to grade II tumours

Sixty-three human transitional cell carcinomas of the urinary bladder were studied by multiparameter flow cytometry (FCM). The cellular DNA content, the cellular protein content, the fraction of cells in S phase, and the nuclear size were registered and correlated to histological grade (WHO) and histologically determined infiltration through the basement membrane. Aneuploidy was found in the great majority of grade III tumours, but in only 24% of grade II tumours. A new, combined variable, viz. the cellular DNA to protein ratio, indicated a possibility for further subdivision of the tumours. Grade II tumours, which constitute a rather heterogeneous group with regard to prognosis, could be classified in two subgroups: One group of diploid tumours with the FCM characteristics of grade I tumours, and another group of diploid and aneuploid tumours with the characteristics of grade III tumours. Infiltration was most frequently seen in the latter subgroup. The putative prognostic relevance of such a subdivision will be the subject of a future study. Compared to FCM measurement of DNA alone, multiparameter FCM, including measurement of the total cellular protein content, has given additional information that may be of prognostic value.

Carcinogenic doses of methylnitrosourea induce dose response related delay in transit through S and G2 phases in mouse epidermis: a cell kinetic study

The cell kinetic, tumorigenic and carcinogenic effects of the short acting, alkylating carcinogen N-methyl-N-nitrosourea (MNU) on hairless mouse epidermis were investigated. The epidermal mitotic rate, the mitotic index, and the number of basal and suprabasal cells were scored in histological sections. Incorporation of [3H]thymidine and flow cytometric analysis of cellular DNA and protein content were performed on isolated basal cells at intervals for up to 10 days after a single application of either 1 or 10 mg MNU. The ensuing tumor rates and yields were observed for up to 48 weeks after 1 mg MNU and 30 weeks after 10 mg MNU. Generally, MNU induced an initial delay in epidermal cell cycle progression with an accumulation of cells in the S and G2 phases. Some days after treatment the delayed cells were released and entered mitosis. One milligram MNU caused a moderate delay of cells in S and G2, lasting for 2-3 days, and this was followed by a release leading to an increased number of suprabasal cells on day 7. The highest dose of MNU caused a more pronounced delay in transit through S and G2 and seemed to be followed by rapid regenerative proliferation. The subsequent tumor crop after 10 mg was significantly higher than that seen after the lowest dose. The present cell kinetic results are consistent with previous data from the study of other carcinogens, all showing a carcinogen-induced initial reduction in DNA synthesis after appropriate doses. A delay in transit through G2 phase was found as well, indicating that a general delay in cell cycle progression may follow the application of most (or all) carcinogens.

Persisting long-term effects of a single carcinogenic dose of methylnitrosourea on epidermal growth in mice

The cell proliferation in hairless mouse epidermis was studied before tumor development following a single application of a carcinogenic dose (2 mg) of N-methyl-N-nitrosourea (MNU). The number of basal and suprabasal cells, the mitotic index (MI) and the mitotic rate (MR) were scored in histological sections. The [3H]thymidine labeling index (LI) and the mean grain count (MGC) were scored in histological sections or in smears of basal cells. Flow cytometric two-parameter analyses of cellular DNA and protein content were performed on isolated epidermal basal cells. An increased MR and a slight but consistent epidermal hyperplasia were found. A 24-h study performed 25 weeks after MNU application showed that the MR and MI were altered in a circadian stage-dependent manner with considerably increased values around noon when the circadian rhythms had their peaks, followed by normal values around midnight. The LI was generally increased, but showed a normal circadian rhythm with high values at night and low values during day. The MGC was reduced at night and in the morning when the LI values were high. The results show that a single carcinogenic dose of MNU caused alterations in the epidermal growth kinetics that persisted until tumor development. The altered growth parameters, however, had circadian rhythms that were in phase with control rhythms. Assuming a constant size of the proliferative compartment, the increased mitotic activity indicated a considerable shortening of the mean cell cycle time.

Cell cycle progression kinetics of regenerating mouse epidermal cells: an in vivo study combining DNA flow cytometry, cell sorting, and [3H]dThd autoradiography

Cantharidin application to mouse skin induces cell injury followed by a regenerative wave of cells entering S phase in partial synchrony about 16 h after application. After pulse labeling with [3H]dThd the synchronized cohort of cells was traced through subsequent cell cycles during regeneration. This was accomplished by DNA flow cytometry of isolated basal cells combined with sorting from G1, S, and G2 phases followed by autoradiography at intervals after pulse labeling. Successive peaks of labeled cells in S phase at about 12-h intervals, followed by subsequent peaks in G2 and G1 phases were seen. This shows that the peaks of S-phase cells seen at 16 and 28 h after cantharidin application represent mother and daughter cells, respectively, the latter still cycling in partial synchrony. These 2 peaks of S-phase cells, therefore, are not keratinocyte subpopulations with different time lags between the stimulus to regeneration and the subsequent response. It is further shown that the mean cell cycle time is reduced from about 55 h in normal epidermis to 12 h during early regeneration. This is mainly due to a considerably reduced G1 phase duration, but the S and G2 phase durations are also reduced, although still within the range of circadian variations seen in normal animals. It is reasonable to assume a causal relationship between the considerably reduced G1 duration and loss of growth restriction. Cells with a slow progression rate through G2 phase (70% of all G2 cells) in normal mouse epidermis seem to maintain a slow progression rate during regeneration. Normal growth homeostasis seems to be gradually reestablished during the second day of regeneration.

Evidence of mouse epidermal subpopulations with different cell cycle times

In order to obtain information on the distribution of total cell cycle times in hairless mouse epidermis, basal cells were isolated and prepared for DNA flow cytometry at intervals after a pulse labeling with 50 microCi of thymidine. The DNA distributions were recorded, and cells were sorted from windows in the S, G2, and G1 phases of the cell cycle, collected on glass slides, and subjected to autoradiography. The proportions of labeled cells were scored in each fraction, and the percentage of labeled mitoses was determined in histologic sections from the same animals. Grain count distributions were recorded at selected time points over labeled cells in sorted fractions and over labeled mitoses. The movement of the labeled S-phase cohort was thus followed through all cell cycle phases. Peaks in labeled cells were observed at about 36 h in S phase, G2 phase, and mitosis, and high levels of labeled G2 cells and mitoses were seen at about 80 h. These results indicate the existence of one rapidly cycling subpopulation of keratinocytes with a cell cycle time slightly less than 30 h, in addition to keratinocytes with considerably longer cell cycle times. The first peak of labeled G2 cells reached only about 30%. This is consistent with earlier findings of about 30% G2 cells with a rapid traverse, and 70% with a considerably delayed traverse through G2 phase. The proportion of labeled G1 cells reached a value corresponding to twice the initial labeling index at 8 h after pulse labeling. This is consistent with previously obtained phase durations, indicating an unperturbed cell cycle traverse of labeled cells from S phase through G2 and mitosis.

DNA synthesis rate changes during the S phase in mouse epidermis

The in vivo DNA synthesis rate throughout the S phase of mouse epidermal cells was investigated. Epidermal basal cells were isolated at various times of the day from normal animals injected with [3H]TdR 30 min before sacrifice, and from pulse-labelled animals with regenerating and growth-inhibited epidermis. The cells were analysed by DNA flow cytometry combined with cell sorting. Cells from successive fractions of the S phase were sorted on glass slides and subjected to quantitative [3H]TdR autoradiography. The results confirmed the presence of unlabelled (slowly replicating) cells in the S phase, the proportion of which was circadian stage-dependent with minimum values at midnight and in the early morning. The DNA synthesis rate throughout the S phase showed a general trend with high values in the mid-fractions, a pattern which was similar in normal and in growth perturbed epidermis. In the early morning the DNA synthesis rate pattern was bimodal with maxima both in the first and second half of the S phase, with a corresponding trough in mid-S. At this time of day the cell progression rate through S is at its maximum, indicating a relationship between the overall DNA synthesis rate and the rate distribution pattern through S.

Studies on urinary bladder carcinoma by morphometry, flow cytometry, and light microscopic malignancy grading with special reference to grade II tumours

Biopsies from 28 patients with urinary bladder carcinoma were investigated by flow cytometry and morphometry. Histopathological grading on 1.5 microns thick glycol methacrylate sections was also performed. Nuclear profile areas, nuclear volume densities and mitotic indices were usually larger in the higher grades of malignancy. All grade I tumours were diploid and all grade III tumours were aneuploid. Out of 13 grade II tumours 8 were diploid and 5 aneuploid. In these latter five cases nuclear profile areas were at the high end of the spectrum. The data show that flow cytometry and morphometry could be a valuable tool in the diagnosis of urinary bladder carcinoma. Our data also suggest that a subdivision of the grade II tumours might be possible and meaningful in the assessment of prognosis.

Effects of pulse labelling with tritiated thymidine on the circadian rhythmicity in epidermal cell-cycle distribution in mice

The influence of pulse labelling with 50 microCi tritiated thymidine ( [3H]TdR) (2 microCi/g) on epidermal cell-cycle distribution in mice was investigated. Animals were injected intraperitoneally with the radioactive tracer or with saline at 08.00 hours, and groups of animals were sacrificed at intervals during the following 32 hr. Epidermal basal cells were isolated from the back skin of the animals and prepared for DNA flow cytometry, and the proportions of cells in the S and G2 phases of the cell cycle were estimated from the obtained DNA frequency distributions. The proportions of mitoses among basal cells were determined in histological sections from the same animals, as were the numbers of [3H]TdR-labelled cells per microscopic field by means of autoradiography. The results showed that the [3H]TdR activity did not affect the pattern of circadian rhythms in the proportions of cells in S, G2 and M phase during the first 32 hr after the injection. The number of labelled cells per vision field was approximately doubled between 8 and 12 hr after tracer injection, indicating an unperturbed cell-cycle progression of the labelled cohort. In agreement with previous reports, an increase in the mitotic index was seen during the first 2 hr. These data are in agreement with the assumption that 50 microCi [3H]TdR given as a pulse does not perturb cell-cycle progression in mouse epidermis in a way that invalidates percentage labelled mitosis (PLM) and double-labelling experiments.

Seasonal changes in spermatogenesis in the blue fox (Alopex lagopus), quantified by DNA flow cytometry and measurement of soluble Mn2+ -dependent adenylate cyclase activity

The testes of the blue fox (Alopex lagopus) showed marked seasonal variations in size. Testicular weight and volume increased rapidly during January and February to reach maximal values by the beginning of the breeding season (approximately 15 March). During May and June the weights and volumes of the testes declined gradually to the quiescent state which lasted from July until October. Quantitation by DNA flow cytometry of the seasonal changes in the relative numbers of haploid (1C), diploid (2C) and tetraploid (4C) cell numbers in the testis showed that the increase in testis size from December to February was associated with a rapid expansion of the haploid cell compartment as spermatogenesis resumed. In addition, an increase in number of more mature cell types within the haploid cell population was observed over a 2-month period before the breeding season. The decline in testicular size from the middle of April until October was associated with a reduction in both the absolute and relative sizes of the haploid and tetraploid cell populations and a concomitant increase in the relative numbers of diploid cells. Measurements of the activity of the soluble Mn2+ -dependent adenylate cyclase revealed seasonal variations that closely paralleled those of the haploid cell population, indicating that, as in other species, the enzyme may be associated with maturing germ cells.

Subpopulations of slowly cycling cells in S and G2 phase in mouse epidermis

Evidence has been presented supporting the existence of heterogeneity in cell-cycle progression in mouse epidermis, The present study was undertaken to characterize this heterogeneity in more detail. Hairless mice were continuously labelled with tritiated thymidine every 4 hr for 4 days. Basal cell suspensions were prepared from slices of mouse skin at intervals during the experiment and subjected to DNA flow cytometry. Cell-cycle analysis was combined with sorting of cells from windows in G1, S and G2 phase, and the proportion of labelled cells within each window was determined in autoradiographs. Reanalysis and resorting to control the purity of of sorted fractions were performed. Computer simulations of the data were made using a mathematical model assuming different S and G2 phase characteristics. A good fit to the data was only obtained when heterogeneity in mouse epidermal cell-cycle progression was assumed, indicating the existence of slowly traversing, distinct subpopulations of cells in G2 and S phase. These cells are assumed to contribute to about 40% of all cells in S phase and to about 70% of all in G2 phase. The estimated residence times in the resting states were 38 and 32 hr in S and G2 phase, respectively. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells were larger than the average. There is no evidence of significant subpopulations of permanently non-proliferating keratinocytes in any of the cell-cycle phases.

Human sperm characteristics during frequent ejaculation

Sperm concentration, morphology, DNA condensation and nuclear protein pattern as well as sperm adenylate cyclase were evaluated in semen samples provided by 7 volunteers every 8 h for 2 days. During the observation period, sperm concentration and total sperm number decreased but began to return towards normal after a 3-day abstinence period. No increase in the proportion of immature sperm cells was observed by light microscopy. Total adenylate cyclase (EC 4.6.1.1) increased significantly per cell, due to an increase in the soluble component while the particulate component remained relatively constant. Microflow fluorometry revealed no consistent alterations in the DNA or nuclear protein distribution. We conclude that although a high frequency of ejaculation does not disturb the conventional measures of sperm integrity, such as DNA condensation, there are major changes in at least one biochemical measurement, the activity of soluble adenylate cyclase.

DNA synthesis in mouse epidermis: S phase cells that remain unlabeled after pulse labeling with DNA precursors progress slowly through S

Epidermal basal cells from hairless mice were isolated after pulse labeling with tritiated DNA precursors and subjected to DNA flow cytometry combined with cell sorting. Cells were sorted from a window in the middle of the S phase, collected on glass slides, and subjected to autoradiography. Unlabeled cells in the middle of the S phase were found in normal mouse epidermis after optimal pulse labeling with tritiated thymidine [( 3H]dThd), in accordance with previous results. The proportion of unlabeled S phase cells was considerably increased among basal cells from mice treated with growth-inhibitory epidermal extracts. Reanalysis and re-sorting of cells previously sorted from mid S showed that unlabeled cells could not be accounted for by G1 contamination. Furthermore, labeling with precursors incorporated into DNA by "de novo" metabolic pathway [( 3H]Urd) did not reduce the proportion of unlabeled S phase cells, either when given alone or when given in combination with the precursor for DNA incorporated by the "salvage" pathway [( 3H]dThd). This strongly indicates that the unlabeled S phase cells do not synthesize DNA continuously, or are synthesizing DNA at a rate below the level of detection. A reduced proportion of unlabeled S phase cells was found in regenerating epidermis. This may be explained by a dilution effect caused by the 3-fold increase in the total number of cells within S phase at this condition. The observation that essentially all cells in mid S phase were labeled during 4 days of continuous labeling with [3H]dThd, indicates that cells in S phase that remain unlabeled after optimal pulse labeling are cycling, albeit slowly. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells are larger than the average. These cells may represent a subpopulation of basal cells going through their last division cycle before differentiation.