High LF Research Articles

Associations between visceral fat and liver fat with insulin sensitivity and metabolic risk in obese adolescents.

We examined the joint and independent associations between VAT and LF with insulin sensitivity (IS) and lipids in seventy-one obese adolescents (BMI ≥ 95th, 14.9 ± 1.8 years). VAT was assessed by magnetic resonance imaging, and LF was quantified by proton magnetic resonance spectroscopy. IS was evaluated by a 3 -h hyperinsulinemic (80 mU·m(-2)·min(-1)) euglycemic clamp. Independent associations between VAT and LF on metabolic variables were assessed in mutually adjusted multivariate models. The joint association between VAT and LF on metabolic variables was assessed by categorizing participants into a low VAT + low LF group (n = 35), high VAT + low LF group (n = 26), or high VAT + high LF group (n = 10), based on a VAT median split (1.17 kg) and high (≥5%) and low (<5%) LF. Both VAT and LF were independently associated with fasting insulin, 2 h insulin, insulin AUC, IS, and triglycerides (P < 0.05). Adolescents with high VAT + high LF had higher 2 h glucose, glucose AUC, 2 h insulin, triglycerides, and lower insulin sensitivity compared to adolescents with high VAT only (P < 0.025 for all). In obese adolescents, VAT and LF were independently associated with insulin sensitivity and dyslipidemia, and the concomitant presence of VAT and LF is strongly associated with metabolic risk factors.

Ionic liquid‐based three phase partitioning (ILTPP) systems for whey protein recovery: ionic liquid selection

AbstractBACKGROUNDThe ionic liquid three phase partitioning (ILTPP) technique is a promising alternative to conventional processing technologies for protein separation and purification since it allows protein recovery at the liquid–liquid interface. In previous work, ILTPP has been developed with the BmimBF4/NaH2PO4 system for lactoferrin recovery, a bovine whey protein with important nutraceutical properties. However, BmimBF4 may suffer from hydrolysis when it is in contact with water, so the selection of an alternative ionic liquid with similar results regarding lactoferrin recovery should be sought.RESULTSThe system based on BmimTfO and phosphate is selected as the most suitable since it combines relatively high LF recoveries at the liquid–liquid interface (83–99%) and chemical stability. The highest LF recoveries occur at moderate acidic pH (3.1–4.0), which may also be improved at relatively low protein concentrations. The process selectivity with respect to bovine serum albumin (another whey protein) varies from 1.1 to 3.0, depending on experimental conditions.CONCLUSIONILTPP is a promising technique to recover the protein fraction from bovine whey or to enrich specific proteins such as lactoferrin, so ILTPP could replace alternative techniques such as membranes. The risk of hydrolysis associated with previous ionic liquid ILTPP systems has been successfully overcome. © 2014 Society of Chemical Industry

Lactoferrin up-regulates intestinal gene expression of brain-derived neurotrophic factors BDNF, UCHL1 and alkaline phosphatase activity to alleviate early weaning diarrhea in postnatal piglets

The molecular mechanisms underlying how dietary lactoferrin (Lf) impacts gut development and maturation and protects against early weaning diarrhea are not well understood. In this study, we supplemented postnatal piglets with an Lf at a dose level of 155 and 285 mg/kg/day from 3 to 38 days following birth. Our findings show that the high dose of Lf up-regulated messenger RNA expression levels of genes encoding brain-derived neurotrophic factor (BDNF) and ubiquitin carboxy-terminal hydrolase L1 (ubiquitin thiolesterase (UCHL1) and, to a lesser extent, glial cell line-derived neurotrophic factor, in the duodenum (P<.05). Piglets in the high and low Lf group had 30% and 7% larger jejunal crypts compared with the control group (P<.05). Escherichia coli 16S rRNA copy number per gram of ascending colon contents was significantly reduced (P=.001), while the copy number of Bifidobacteria and Lactobacillus spp. was not affected. In addition, Lf increased intestinal alkaline phosphatase activity (P<.05) and delayed the onset of food transitional diarrhea, reducing its frequency and duration (P<.05). The incidence of diarrhea in the high and low Lf groups was decreased 54% and 15%, respectively, compared with the control group (P=.035). In summary, these findings provide new evidence that dietary Lf supplementation up-regulated gene expression of BDNF and UCHL1, decreased the colon microbiota of E. coli, improved gut maturation and reduced early weaning diarrhea in piglets. The molecular basis underlying these findings suggests that Lf may enhance gut development and immune function by providing new insight into the gut–brain–microbe axis that has not been previously reported.

Lymphatic filariasis control in Tanga Region, Tanzania: status after eight rounds of mass drug administration

BackgroundLymphatic filariasis (LF) control started in Tanga Region of Tanzania in 2004, with annual ivermectin/albendazole mass drug administration (MDA). Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District. In 2013, after 8 rounds of MDA, spot check surveys were added in the other 7 districts of Tanga Region, to assess the regional LF status.MethodsLF vector and transmission surveillance, and human cross sectional surveys in communities and schools, continued in Tanga District as previously reported. In each of the other 7 districts, 2–3 spot check sites were selected and about 200 schoolchildren were examined for circulating filarial antigens (CFA). At 1–2 of the sites in each district, additional about 200 community volunteers were examined for CFA and chronic LF disease, and the CFA positives were re-examined for microfilariae (mf).ResultsThe downward trend in LF transmission and human infection previously reported for Tanga District continued, with prevalences after MDA 8 reaching 15.5% and 3.5% for CFA and mf in communities (decrease by 75.5% and 89.6% from baseline) and 2.3% for CFA in schoolchildren (decrease by 90.9% from baseline). Surprisingly, the prevalence of chronic LF morbidity after MDA 8 was less than half of baseline records. No infective vector mosquitoes were detected after MDA 7. Spot checks in the other districts after MDA 8 showed relatively high LF burdens in the coastal districts. LF burdens gradually decreased when moving to districts further inland and with higher altitudes.ConclusionLF was still widespread in many parts of Tanga Region after MDA 8, in particular in the coastal areas. This calls for intensified control, which should include increased MDA treatment coverage, strengthening of bed net usage, and more male focus in LF health information dissemination. The low LF burdens observed in some inland districts suggest that MDA in these could be stepped down to provide more resources for upscale of control in the coastal areas. Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination.

The use of laser flare photometry to assess therapeutical approaches for uveitis

AbstractLaser flare (LF) photometry is a standardized and reproducible method for grading the breakdown of the blood‐aqueous‐barrier by in‐vivo measurements of the protein content in the anterior chamber. Whereas anterior chamber cell‐grade directly correlates with the activity of anterior uveitis, high LF values may not only be observed during active inflammation but also as a remnant of chronic uveitis with irreversible damage of the blood‐aqueous barrier. The talk provides an overview of published and own data, analyzing the impact of LF photometry as a decision‐making tool for timing ocular surgery and selection of surgery techniques (e.g., lensectomy vs. phacoemulsification with primary IOL implantation; filtrating vs. non‐filtrating vs. drainage‐implants vs. cyclodestructive surgery). Furthermore, the role of LF in the context of secondary complications (CME, aphakia, glaucoma etc.) and in the management of drug therapy (topical treatment, classical immunosuppressives and biologicals) is elucidated. In this context, interesting LF topics (Do we treat cells, LF or both? Do high LF values necessarily demand for intensification of uveitis treatment? Does LF help us to decide when to stop our treatment?) are discussed.

Light fraction of soil organic matter under different management systems in Abeokuta, a derived Savanna, Nigeria

A study on light fraction organic matter was carried out on the soil from three different management systems namely; Gmelina arborea, Tectona grandis and Leucaena leucocephala plantations in the University of Agriculture, Abeokuta Nigeria. Soil samples were collected in each of the three management site at five auger points within the site at 0 – 10cm and 10 – 15cm depths with the aim of investigating the influence of soil management practices on the light fraction content of soil organic matter. The result showed that (Light fraction) LF nitrogen was highest in Leuceana stand (0.14g/kg) and lowest in Gmelina stand (0.12g/kg) at 0 – 10cm depth. Similar trend was recorded for LF carbon; Results showed no significant (P<0.05) difference in Total Carbon in the 10 – 15cm depth. High organic carbon in light fraction and microbial population of 0-10cm depth in all the three land management systems probably reflects the distribution of plants and microbial debris within the soil profile as reflected. High LF nitrogen and LF organic matter in Leuacaena stand was probably due to the ability Leuacaena to fix nitrogen to the soil and which could also be responsible for high microbial population (8.06 x 106). This is further enhanced by the significant positive correlation between organic matter and microbial population. Overall, the study revealed that light fraction contents provide a sensitive and reasonably precise measure of organic matter indices in the study area

Human lactoferrin increases Helicobacter pylori internalisation into AGS cells

Helicobacter pylori has high global infection rates and can cause other undesirable clinical manifestations such as duodenal ulcer (DU) and gastric cancer (GC). Frequencies of re-infection after therapeutic clearance and rates of DU versus GC vary geographically and differ markedly between developed and developing countries, which suggests additional factors may be involved. The possibility that, in vivo, lactoferrin (Lf) may play a subtle role in modulating micronutrient availability or bacterial internalisation with implications for disease etiology is considered. Lf is an iron binding protein produced in mammals that has antimicrobial and immunomodulatory properties. Some bacteria that regularly colonise mammalian hosts have adapted to living in high Lf environments and we investigated if this included the gastric pathogen H. pylori. We found that H. pylori was able to use iron from fully iron-saturated human Lf (hLf) whereas partially iron-saturated hLf (apo) did not increase H. pylori growth. Instead, apo-hLf increased adherence to and internalisation of bacteria into cultured epithelial cells. By increasing internalisation, we speculate that apo-human lactoferrin may contribute to H. pylori's ability to persistence in the human stomach, an observation that potentially has implications for the risk of H. pylori-associated disease.

Dairy calcium intake modifies responsiveness of fat metabolism and blood lipids to a high-fat diet

Intervention studies have demonstrated that saturated fat increases total and LDL-cholesterol concentrations, and it is therefore recommended that the intake of high-fat dairy products be limited. However, observational studies have found an inverse relationship between the intake of dairy products and incidence of CVD. We aimed to study whether the Ca content of dairy products influences the effect of dairy fat on the lipid profile. The study had a randomised cross-over design. Subjects (n 9) were randomised to one of the sequence of four isoenergetic 10d diets: low Ca and low fat (LC/LF: approximately 700mg Ca/d, 25% of energy (fat); high Ca and LF (HC/LF: approximately 2800mg Ca/d, 25% of energy fat); LC and high fat (LC/HF: approximately 700 mg Ca/d, 49E% fat); or HC and HF (approximately 2800mg Ca/d, 49E% fat). Blood variables were measured before and after each diet period, and faeces and urine were collected at the end of each diet period. A two-way ANOVA was used to examine the effect of Ca and fat intake. Independent of Ca intake, the HF diet increased the concentrations of total (9%; P<0·0001), LDL (14%; P<0·0001)- and HDL (13%; P=0·0002)-cholesterol compared with the LF diet. However, independent of fat intake, the HC diet decreased the concentrations of total (4%; P=0·0051) and LDL-cholesterol (10%; P<0·0001) but not HDL-cholesterol compared with the LC diet. In addition, total:HDL-cholesterol was decreased (5%; P=0·0299), and HDL:LDL was increased (12%; P=0·0097) by the HC diet compared with the LC diet. Faecal fat excretion was increased by both the HC (P<0·0001) and HF (P=0·0052) diets. In conclusion, we observed that dairy Ca seems to partly counteract the raising effect of dairy fat on total and LDL-cholesterol, without reducing HDL-cholesterol.

Efficient Mobility Enhancement Engineering on 65 nm Fully Silicide Complementary Metal–Oxide–Semiconductor Field-Effect-Transistors Using Second Contect Etch Stop Layer Process

In this study, we have applied a second high-stress contect etch stop layer (CESL) in nickel fully silicide complementary metal–oxide–semiconductor field-effect-transistors (Ni FUSI CMOSFETs) and investigated performance characteristics, such as driving capacity, leakages, low-frequency noise (LF noise), and capacitance–voltage (C–V) characteristics. In Ni FUSI nMOSFETs, the effect of the second CESL on the improvement of carrier mobility is apparent. However, the second CESL also induces defects and junction leakages, resulting in a high LF noise and a low accumulation capacitance. Since we adopted the tensile-stressed second CESL, which is profitless improving the performance of pMOSFETs (should be compress-stressed) and apparently degrades the devices' driving capability, leakages, and LF noise of the devices. Furthermore, the FUSI process does not induce apparent damage that increases the gate leakages of both Ni-FUSI nMOSFETs and pMOSFETs.

Usefulness of fecal lactoferrin and hemoglobin in diagnosis of colorectal diseases

To evaluate prospectively usefulness of fecal lactoferrin (Lf) and fecal hemoglobin (Hb) in the diagnosis of colorectal diseases. Fecal Lf and Hb were measured using ELISA in 872 patients before they underwent colorectal endoscopy. Lf was positive in 18 (50%) of 36 patients with colorectal cancer, 25 (15.9%) of 157 with colorectal polyps, 29 (46.8%) of 62 with ulcerative colitis, and 25 (62.5%) of 40 (62.5%) with Crohn's disease. The Hb-positive rates were 50%, 12.1%, 41.9% and 32.5%, respectively. Of the 318 patients free of abnormalities by colorectal endoscopy, Lf was positive in 29 (9.1%) and Hb was positive in 15 (4.7%). Among patients with Crohn's disease, the Lf-positive rate was significantly higher than the Hb-positive rate. If either high Lf or Hb levels were considered positive, the positive rates rose to 61.1%, 51.6%, and 67.5% in the colorectal cancer group, ulcerative colitis group, and Crohn's disease group, respectively. If both high Lf and Hb levels were rated positive, the positive predictive values (PPV) were 21% for colorectal cancer, 33% for ulcerative colitis, and 17% for Crohn's disease, and PPV of high Hb level alone was 18%, 25% and 13%, respectively. Fecal Lf and Hb were found useful in the detection of colorectal diseases, and the combination of the two measurements appears to increase the sensitivity and efficacy of diagnosis.

Transgenic cows that produce recombinant human lactoferrin in milk are not protected from experimental Escherichia coli intramammary infection.

This is the first study describing an experimental mastitis model using transgenic cows expressing recombinant human lactoferrin (rhLf) in their milk. The aim of the study was to investigate the concentrations in milk and protective effects of bovine and recombinant human lactoferrin in experimental Escherichia coli mastitis. Experimental intramammary infection was induced in one udder quarter of seven first-lactating rhLf-transgenic cows and six normal cows, using an E. coli strain isolated from cows with clinical mastitis and known to be susceptible to Lf in vitro. Clinical signs were recorded during the experimental period, concentrations of human and bovine Lf and indicators of inflammation and bacterial counts were determined for milk, and concentrations of acute-phase proteins and tumor necrosis factor alpha were determined for sera and milk. Serum cortisol and blood hematological and biochemical parameters were also determined. Expression levels of rhLf in the milk of transgenic cows remained constant throughout the experiment (mean, 2.9 mg/ml). The high Lf concentrations in the milk of transgenic cows did not protect them from intramammary infection. All cows became infected and developed clinical mastitis. The rhLf-transgenic cows showed milder systemic signs and lower serum cortisol and haptoglobin concentrations than did controls. This may be explained by lipopolysaccharide-neutralizing and immunomodulatory effects of the high Lf concentrations in their milk. However, Lf does not seem to be a very efficient protein for genetic engineering to enhance the mastitis resistance of dairy cows.

Lactoferrin (Lf): Retinoid interactions in the mammary glands of transgenic mice overexpressing human Lf

Induction of protein expression in a tissue-specific manner by gene transfer over-expression techniques has been one means to define the function of a protein in a biological paradigm. Studies with retinoid reporter constructs transfected in mammary cell lines suggests that lactoferrin (Lf) affects retinoid signaling pathways and alters apoptosis. We tested the effects and interactions of over-expressed mammary-specific human lactoferrin (hLf) and dietary retinol palmitate on lactation and mammary gland development in mice. Increased retinol palmitate in the diet increased daily retinol equivalents (RE) to 2.6-fold over the normal mouse control diet. Transgene (Tg) expression in the dam fed control diet depressed pup weight gain. Severe depression of pup weight gain was observed when homozygote TgTg dams were fed the RE diet. Normal weight gain was restored when pups were placed with a wild type dam fed the RE diet; conversely, normal growing pups from the wild type dams showed declining weight gains when fostered to the TgTg RE-fed dams. Northern analysis of mammary tissue extracts showed a reduction in WAP and an increase in IGFBP-3 mRNA that was associated with the presence of the transgene. Histological evaluation of 3 days lactating mammary tissue showed mammary epithelial cells from TgTg animals contained excessive secretory products, suggesting a block in cellular secretion mechanisms. In addition, the mammary cells displayed a cellular apical membrane puckering that extended into the alveoli lumens. These studies demonstrate an in vivo interaction of Tg-hLf expression and dietary retinoids in mouse mammary glands. While normal mammary gland physiology may not be representative by these experiments because high Lf concentrations during early lactation are abnormal, the demonstrated biological interaction suggests that typical periods of high Lf concentrations may have impact upon developing and involuting mammary glands.

Transient phase locking patterns among respiration, heart rate and blood pressure during cardiorespiratory synchronisation in humans.

The interactions between respiration, heart rate and blood pressure variability (HRV, BPV), are considered to be of paramount importance for the study of the functional organisation of the autonomic nervous system (ANS). The aim of the reported study is to detect and classify the intermittent phase locking (PL) phenomena between respiration, HRV and BPV during cardiorespiratory synchronisation experiments, by using the following time-domain techniques: Poincaré maps, recurrence plots, time-space separation plots and frequency tracking locus. The experimental protocol consists of three stages, with normal subjects in paced breathing at 15, 12 and 8 breaths min-1. Transient phenomena of coordination between respiration and the major rhythms of HRV and BPV (low and high frequency, LF and HF) have been detected and classified: no interaction between LF and HF rhythms at 15 breaths min-1; short time intervals of stable 1:2 frequency and phase synchronisation during the 12 breaths min-1 stage; 1:1 PL during the 8 breaths min-1 stage. 1:1 and 1:2 PL phenomena occurred when the respiration frequency was quite close to the LF frequency or when it was about twice the LF frequency, respectively. The complex organisation of the ANS seems to provoke transient rather than permanent PL phenomena between the co-ordinating components of respiration and cardiovascular variability series.

Response of Tall Fescue to Saline Water as Influenced by Leaching Fractions and Irrigation Uniformity Distributions

AbstractThe use of poor quality water for irrigation purposes in the urban landscape has the potential to save significant quantities of good quality water for higher priority uses. Research was conducted to determine the impact leaching fractions (LF = drainage volume/irrigation volume) and irrigation‐uniformity distributions have on the spatial distribution of water and salts and plant response when irrigating with saline water. Tall fescue (Festuca arundinacea Schreb. ‘Monarch’) was grown in 18 plots, each with a centrally located lysimeter that enabled estimates of evapotranspiration and irrigation requirements. Imposed treatments included setting LF at 0.05, 0.15, or 0.25 and manipulating plot irrigation systems such that the Christiansen uniformity coefficient (CUC) was set at 0.65, 0.75, or 0.85. Saline irrigation water (2.5 dS m−1) was applied for an 18‐mo period. Significant LF × CUC interactions were observed for depth‐weighted soil salinity, yield, evapotranspiration (ET), tissue moisture content, and canopy temperatures. Although the coefficient of variation increased with each measured parameter as the CUC decreased, only the depth‐weighted electrical conductivity (ECc) showed a coefficient of variation &gt; 20%. A 14% savings in irrigation water was obtained when the high CUC, low LF treatment was compared with the high LF, low CUC treatment. Ninety‐one percent of the variability in the average plot ECc could be accounted for if the actual LF, lysimeter ET, and average plot canopy temperatures at the end of the experiment were taken into consideration. Under the conditions of this experiment, irrigating tall fescue with 2.5 dS m−1 water would be an acceptable practice even at LFs as low as 0.05 if the CUC is optimized.

Reduced Leaching Fractions Improve Irrigation Use Efficiency and Nutrient Efficacy

Abstract An experiment with two leaching fractions (LF = volume of water leached ÷ volume of water applied) and two fertilizer rates was conducted to evaluate the effects of reduced irrigation volume in combination with reduced fertility on irrigation use efficiency, nutrient efficacy (retention), and plant growth. Rooted cuttings of Cotoneaster dammeri Schneid. ‘Skogholm’ were potted into 3.8 liter (#1) containers in a pine bark: sand substrate (8:1 by vol). Osmocote 24N-1.7P-5.8K (24-4-7) was topdressed at 3.5 g N or 1.75 g N per container at treatment initiation. The experiment, a RCBD with four replications was conducted for 100 days on a container-grown plant production area subdivided into 16 separate plots that allowed for the collection of all irrigation water leaving each plot. Twenty containers were placed in each plot. Irrigation water was applied daily to attain either a high LF of 0.4 to 0.6 or a low LF of 0.0 to 0.2. Irrigation water was applied in two cycles with a two hour rest interval between each application via pressure compensated spray stakes at a rate of 200 ml/min (0.28 in/min). Volume of effluent from each plot was measured daily and analyzed for NO3, NH4, and P. Low LF decreased irrigation volume and effluent volume by 44% and 63%, respectively, compared to high LF. Irrigation use efficiency [total plant dry weight (volume applied-volume leached)] by plants irrigated with low LF was 29% greater than high LF. Compared to high LF, low LF decreased cumulative NO3 and NH4 contents in effluent by 66% and 62%, respectively, for containers fertilized with 3.5 g N. Low LF also reduced cumulative P content in the effluent by 57% compared to high LF. Shoot and total plant dry weights produced with low LF were reduced 8% and 10%, respectively, compared to plants grown with high LF. Root dry weight was not effected by LF. Shoot, root, and total plant dry weights with 1.75 g N were reduced by 26%, 26%, and 28%, respectively compared to 3.5 g N. Nitrogen efficiency was higher when plants were fertilized with 3.5 g N regardless of LF. To maximize N absorption and minimize N losses requires a combination of maintaining an adequate N supply which is this study was 3.5 g N per 3.8 liter container in combination with a low LF.

Effects of high altitude acclimatization on heart rate variability in resting humans.

The sympatho-vagal nerve interaction at the heart was studied by means of power spectrum analysis of heart rate variability in seven Caucasians (aged 27-35 years) in resting supine and sitting positions before and during 35 days of a sojourn at 5050 m above sea level (asl) and in six Sherpas (aged 22-30 years) at high altitude only. A high frequency peak (HF)-central frequency between 0.20 and 0.33 Hz, a low frequency peak (LF)-central frequency between 0.08 and 0.14 Hz, and a very low frequency component (< 0.05 Hz), no peak observed, were found in the power spectrum in both positions and independent of altitude. The peak powers, as a percentage of the total power, were affected by both body position and altitude. At sea level the change from a supine to a sitting position yielded a decrease in percentage HF from 25 (SEM 1.9)% to 6.2 (SEM 1.5)% (P < 0.05) and a significant increase in the ratio between LF and HF powers (LF:HF) from 1.7 (SEM 0.4) to 6.9 (SEM 1.6). At altitude compared to sea level in the supine position, percentage HF decreased from 25% to 10.9 (SEM 1.0)% (P < 0.05) and the LF:HF ratio increased from 1.7 to 4.8 (SEM 0.7) (P < 0.05). No changes occurred at altitude in the sitting position either in the peak powers or in the LF:HF ratio, but the central frequency of HF peak increased significantly from 0.25 (SEM 0.02) Hz to 0.32 (SEM 0.01) Hz. In the Sherpas comparable results to the Caucasians were found in both body positions. The high LF:HF ratios observed at altitude in both body positions and groups would suggest that hypoxia caused a shift of sympatho-vagal nerve interaction at rest toward a dominance of the sympathetic system, which was found at sea level only in the sitting position. An acclimatization period of 10 days higher than 2850 m asl and 1 month at 5050 m asl did not modify the interactions of the autonomic systems.

Early and late effects of exercise and athletic training on neural mechanisms controlling heart rate.

This study addresses the long term and short term effects of heavy dynamic exercise on neural control of heart rate. A group of healthy controls was compared with (1) a group of trained athletes during a period of yearly rest (detrained) and (2) a group of trained athletes at the peak of their training routine. Additionally, a group of 10 controls was studied 1, 24, and 48 h after a single bout of maximal dynamic exercise. Spectral analysis of RR interval variability provided markers of sympathetic (low frequency, LF, 0.10 Hz) and vagal (high frequency, HF, 0.25 Hz) modulation of the sinoatrial node. (1) In detrained athletes resting bradycardia was accompanied by a predominant HF rhythmic component suggestive of a prevailing vagal tone. (2) Trained athletes showed a resting bradycardia together with high LF values, thus suggesting a more complex neural interaction modulating heart rate. An additional longitudinal part of the study, performed on a group of detrained athletes who were examined for the second time after resuming training, confirmed the finding of a prevailing LF component in resting conditions. (3) In the 10 control subjects maximal dynamic exercise induced an increase in LF which outlasted the cessation of exercise up to 24 h, suggesting a persistent sympathetic activation. (4) Passive tilt, a manoeuvre which enhances sympathetic drive, produced a greater enhancement of the LF component in trained athletes than in control subjects. The cardiac sympathetic excitation outlasting heavy dynamic exercise may explain the coexistence of training bradycardia with signs of enhanced sympathetic activity in trained champion athletes.

Effect of dietary tryptophan on muscle, liver and whole-body protein synthesis in weaned piglets: relationship to plasma insulin

Two experiments were carried out with piglets, 3-5 kg live weight, to evaluate the effects of feeding a tryptophan (TRP)-deficient diet for 2 weeks on protein synthesis rates measured in vivo 2 h after a meal. In the first experiment on twenty piglets fed on 250 g protein/kg diets, TRP deficiency (0.77 g/16 g nitrogen) as compared with adequacy (1.17 g/16 g N) significantly decreased feed intake, growth performance and fractional protein synthesis rates (FSR), without variation of RNA in longissimus dorsi (LD) and with parallel increases in RNA in semitendinosus (ST) muscle and liver. In the second experiment thirty-two piglets were tube-fed deficient and adequate diets at the two feeding levels (LF) previously achieved. Both TRP and LF significantly increased growth performance and FSR, but not RNA, in LD and ST muscle, with a trend to a synergy between the two factors (TRP x LF interaction). In another muscle, trapezius (TR), the same interaction was only apparent in RNA content. Among the three muscles it was in LD that FSR was the most responsive to dietary TRP (significant muscle x TRP interaction). In the liver the TRP x LF interaction on FSR and not RNA was the major significant effect, indicating that higher TRP and higher LF were both required to get the maximum protein synthesis rate. At 30 min after a meal the same significant interaction effect was shown on plasma glucose, whilst the higher LF increased plasma insulin with both diets. After a further 30 min the appearance of a similar significant effect of the TRP x LF interaction on plasma insulin resulted from its abatement when the deficient diet had been fed at high LF. These results suggest that dietary TRP deficiency decreased muscle and liver protein synthesis rates in relation to a decrease in the post-prandial release of insulin following a decreased rate of nutrient absorption.

A subnanoampere current generator circuit technique

The interconnection of a conventional type of current generator and a 'floating' current-divider network, based on the use of an FET op amp, facilitates the design of a variable subnanoampere direct current generator having a high LF incremental output resistance and a shielded output lead.

The Effect of Various Carbohydrates on Production of Diphtheria Toxin with Special Reference to its Flocculating Power.

Park and Williams, following the work of Spronck, reported that small amounts of glucose added to the broth aided in production of potent toxic filtrates from Corynebacterium diphtheriae. They warned at the same time that an excess of glucose sufficient to cause too great a degree of acidity would inhibit the development of the toxin. T. Smith also found that small quantities of dextrose were favorable to toxin production, provided the muscle sugar had been removed from the broth by fermentation. Recently Locke and Main and Ramon have again called attention to the use of glucose in the production of high-titred diphtheria toxin. We have studied the effect of a number of carbohydrates, fermentable by C. diphtheriae, on the production of toxic filtrates of high Lf unitage. We are reporting here only those experiments in which glucose and maltose have been used to enrich the culture medium. The culture filtrates (Park-Williams No. 8 strain of C. diphtheriae) were obtained after incubation from 48 hours to 5 days at 37.5°C., no preservative being added. The pellicles were grown in every case in one litre flasks containing 250-300 cc. of broth as used by Povitsky. The initial inoculum consisted of one large loopful of an actively growing pellicle, the seed culture having been maintained previously by rapid transfer, twice daily. Apparently little harm was done to the pellicles by manipulation of the flasks in adding the sugars and adjusting the pH of the culture fluid. Toxins were obtained within 48 hours from cultures grown in this basic medium which had 6.5 Lf units per cc. and approximately 500 M.L.D. per cc. The two sugars have been utilized as follows: (1) Fractional amounts of either glucose or maltose were added to the growing culture from one to 3 times daily for 48 to 72 hours, each addition of sugar being preceded by titration and adjustment of the culture fluid to pH 8.0.