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PubMed1993

Singlet-oxygen generation at gas-liquid interfaces: a significant artifact in the measurement of singlet-oxygen yields from ozone-biomolecule reactions.

Several ozone-biomolecule reactions have previously been shown to generate singlet oxygen in high yields. For some of these ozone-biomolecule reactions, we now show that the apparent singlet-oxygen yields determined from measurements of 1270 nm chemiluminescence were artifactually elevated by production of gas-phase singlet oxygen. The gas-phase singlet oxygen results from the reaction of gas-phase ozone with biomolecules near the surface of the solution. Through the use of a flow system that excludes air from the reaction chamber, accurate singlet-oxygen yields can be obtained. The revised singlet-oxygen yields (mol 1O2 per mol O3) for the reactions of ozone with cysteine, reduced glutathione, NADH, NADPH, human albumin, methionine, uric acid and oxidized glutathione are 0.23 +/- 0.02, 0.26 +/- 0.2, 0.48 +/- 0.04, 0.41 +/- 0.01, 0.53 +/- 0.06, 1.11 +/- 0.04, 0.73 +/- 0.05 and 0.75 +/- 0.01, respectively. These revised singlet-oxygen yields are still substantial.

Albumins↗
PubMed1967

The effect of very frequent milking and of oxytocin on the yield and composition of milk in fed and fasted goats.

1. The effect of milking goats 1-4 times an hour for 3-12 hr on the yield and composition of milk has been studied in fed and fasted animals at all stages of lactation.2. It was essential to inject oxytocin (50-400 m-u. I.V.) just before each milking to remove all the milk already in the udder and then the yield was similar to that obtained on twice daily milking (105 +/- 2.1 S.E.%). There were no significant differences between goats or between the two glands of one goat, even if one had been denervated by autotransplantation. However, the variation from hour to hour was 1.5 times greater than from day to day.3. The claim of Zaks (1964) and Zaks, Natochin, Sokolova, Tanasichuk & Tverskoy (1965) that milking every 15 min always produces a large rise in milk Na and a fall in K and lactose, which is characteristic of alveolar milk, is not substantiated. In high yielding goats milking gently by hand or with a cannula caused a small change in K only, but vigorous hand milking exacerbated this fall and also caused a fall in lactose and a rise in Na and Cl. Still larger changes were produced by using excessively large doses of oxytocin (2500 m-u.) when there was also a rise in citrate and total nitrogen. Hourly milking in goats fasted for 24 hr had the same effect.4. In fasted goats the milk yield fell to 90% within 8 hr and to 56 +/- 2.1% of the previous level by 24 hr. It remained at this level for a further 10-12 hr on twice daily or on hourly milking. The yields of autotransplanted glands usually fell slightly but significantly more than that of the glands in situ. In most goats mammary blood flow was halved but in all animals there were large falls in mammary uptake of glucose, acetate and amino acids and greatly increased uptake of free fatty acids. There were significant differences between fasted goats on hourly milking.5. It is concluded that, in spite of changes in milk composition, milking hourly can be a useful technique for studying milk secretion. The striking effects of a short fast in a lactating animal are emphasized.

Animals↗
PubMed1967

The effect of infusions of glucose, acetate and amino acids on hourly milk yield in fed, fasted and insulin-treated goats.

1. Experiments have been carried out in lactating goats milked hourly to assess the value of this technique in studies of milk secretion.2. On refeeding 24 hr-fasted goats there was an increase in arterial concentration and mammary uptake of volatile fatty acids within an hour, but little increase in hourly milk and lactose yield until the mammary uptake of glucose had also increased (after 2-3 hr).3. Intravascular infusions of acetate had no effect on milk secretion in 24 hr-fasted goats but glucose infusions increased milk yield by 62 +/- 5% and lactose yield by 87 +/- 12% within 3 hr, with no effect on fat secretion. The addition of acetate or acetate plus amino acids had no more effect than glucose alone.4. The yield of milk and lactose could be reduced within an hour by insulin (2 u./kg I.V.) and this was prevented or reversed by injecting glucose. In one goat, where in spite of a fall in blood sugar, mammary arteriovenous difference and blood flow did not fall, there was little or no fall in milk yield.5. In fasted or insulin treated goats an increase in milk and lactose secretion could be obtained within an hour by infusing glucose into the artery of one gland autotransplanted to the neck, which responded before the control gland in situ, thus showing that the effect of glucose is directly on the mammary tissue.6. In two normally fed goats with a low blood sugar, glucose infusions increased the milk or lactose yield by 30% within 3 hr.7. It is concluded that frequent milking, using minimal doses of oxytocin, is a valid method of studying factors controlling milk secretion and that, in the lactating goat, the availability of glucose to the mammary gland can be a limiting factor for maximum milk secretion.

Acetates↗
PubMed1980

Milk yield, suckling behaviour and milk ejection in the lactating rat nursing litters of different sizes.

1. The quantitative relationship between the suckling stimulus and several suckling-dependent variables was studied in lactating rats. 2. The intensity of the suckling stimulus, measured as the product of duration and number of pups suckling was in proportion to litter size for litters of one, ten or twenty-two pups. 3. Pups in the litters of ten grew fastest. Single-pup litters grew most slowly, some not at all. Litter weight gain, corrected for inevitable losses, was used to estimate milk yield. Total milk yield was greater for litters of twenty-two to twenty-four pups than for litters of ten pups only in the first week. Milk yield for single pups was up to 7% of the yield for ten pups. Milk yield per mammary gland sucked was similar for the larger litters but less for single pups. 4. The number of milk ejections, measured as pup stretch reactions, in observation periods of 225 min, was similar for litters of ten and twenty-two to twenty-four pups, but less for single-pup litters. 5. The suckling stimulus applied by single-pup litters inhibited ovarian growth less effectively than did the stimulus applied by larger litters. 6. There was no change in serum osmolality during lactation. 7. It is concluded that litters of ten or twenty-two to twenty-four pups applied suckling stimuli of different intensities, but these had similar effects on the daily secretion rate of oxytocin, milk production and suppression of ovarian growth. Single-pup litters were less effective.

Animals↗
PubMed2007

Growth yields in bacterial denitrification and nitrate ammonification.

Denitrification and nitrate ammonification are considered the highest-energy-yielding respiration systems in anoxic environments after oxygen has been consumed. The corresponding free energy changes are 7 and 35% lower than that of aerobic respiration, respectively. Growth yield determinations with pure cultures of Paracoccus denitrificans and Pseudomonas stutzeri revealed that far less energy is converted via ATP into cell mass than expected from the above calculations. Denitrification with formate or hydrogen as electron donor yielded about 2.4 to 3.0 g dry matter per mol formate or hydrogen and 15 to 18 g dry matter per mol acetate. Similar yields with acetate were obtained with Pseudomonas stutzeri. Wolinella succinogenes and Sulfurospirillum deleyianum, which reduce nitrate to ammonia, both exhibited similar yield values with formate or H2 plus nitrate. The results indicate that ATP synthesis in denitrification is far lower than expected from the free energy changes and even lower than in nitrate ammonification. The results are discussed against the background of our present understanding of electron flow in denitrification and with respect to the importance of denitrification and nitrate ammonification in the environment.

Acetates↗
PubMed1976

Metabolism and growth yields in Bacteroides ruminicola strain b14.

Metabolism of D-glucose by Bacteroides ruminicola subsp. brevis, strain B14, has been examined. Growth yield studies gave molar growth yields, corrected for storage polysaccharide, of approximately 66 g (dry weight)/mol of glucose fermented. The storage polysaccharide amounted to about 14% of the total dry weight, or 55% of the total cellular carbohydrate, at full growth. After correcting glucose utilization for incorporation into cellular carbohydrate, measurement of product formation showed that 1.1 succinate, 0.8 acetate, and 0.35 formate are produced and 0.5 CO2 net is taken up during the fermentation of 1 glucose under the conditions used. The implication of these results with respect to adenosine 5'-triphosphate (ATP) molar growth yield calculations is discussed. If substrate-level phosphorylation reactions alone are responsible for ATP generation, then the ATP molar growth yield must be about 23 g (dry weight)/mol of ATP. Alternatively, if anaerobic electron transfer-linked phosphorylation also occurs, the ATP molar growth yield will be lower.

Acetates↗
PubMed1979

Comparison of maintenance energy expenditures and growth yields among several rumen bacteria grown on continuous culture.

Maintenance energy expenditures were mesured for five rumen bacteria, Selenomonas ruminantium, Butyrivibrio fibrisolvens, Bacteroides ruminicola, Megasphaera elsdenii, and Streptococcus bovis, by using a complex medium with glucose as the carbon source. Large differences (as high as 8.5-fold) in maintenance energy expenditures were seen among these bacteria. The suggestion is made that maintenance requirements could be a significant determinant of bacterial competition in the rumen. Theoretical maximum growth yields, calculated from double reciprocal plots of yield versus dilution rate, were compared to theoretical Y(ATP) values in order to estimate minimum molar adenosine 5'-triphosphate yields from glucose for each bacterium. Results showed that relative yield among the bacteria was growth rate dependent. At high dilution rates, both S. ruminantium and S. bovis produced lactate as their principal fermentation product. At lower dilution rates very little lactate was formed and growth yields increased. Acetate and ethanol were the predominant fermentation products of S. bovis at low dilution rates. Other workers have shown that S. ruminantium produces acetate and propionate at low growth rates.

Journal Article↗
PubMed1994

Alfalfa yield response to inoculation with recombinant strains of Rhizobium meliloti with an extra copy of dctABD and/or modified nifA expression.

The construction of rhizobial strains which increase plant biomass under controlled conditions has been previously reported. However, there is no evidence that these newly constructed strains increase legume yield under agricultural conditions. This work tested the hypothesis that carefully manipulating expression of additional copies of nifA and dctABD in strains of Rhizobium meliloti would increase alfalfa yield in the field. The rationale for this hypothesis is based on the positive regulatory role that nifA plays in the expression of the nif regulon and the fact that a supply of dicarboxylic acids from the plant is required as a carbon and energy source for nitrogen fixation by the Rhizobium bacteroids in the nodule. These recombinant strains, as well as the wild-type strains from which they were derived, are ideal tools to examine the effects of modifying or increasing the expression of these genes on alfalfa biomass. The experimental design comprised seven recombinant strains, two wild-type strains, and an uninoculated control. Each treatment was replicated eight times and was conducted at four field sites in Wisconsin. Recombinant strain RMBPC-2, which has an additional copy of both nifA and dctABD, increased alfalfa biomass by 12.9% compared with the yield with the wild-type strain RMBPC and 17.9% over that in the uninoculated control plot at the site where soil nitrogen and organic matter content was lowest. These increases were statistically significant at the 5% confidence interval for each of the three harvests made during the growing season. Strain RMBPC-2 did increase alfalfa biomass at the Hancock site; however, no other significant increases or decreases in alfalfa biomass were observed with the seven other recombinant strains at that site. At three sites where this experiment was conducted, either native rhizobial populations or soil nitrogen concentrations were high. At these sites, none of the recombinant strains affected yield. We conclude that RMBPC -2 can increase alfalfa yields under field conditions of nitrogen limitation, low endogenous rhizobial competitors, and sufficient moisture.

Base Sequence↗
PubMed2001

Cosecretion of chaperones and low-molecular-size medium additives increases the yield of recombinant disulfide-bridged proteins.

Attempts were made to engineer the periplasm of Escherichia coli to an expression compartment of heterologous proteins in their native conformation. As a first approach the low-molecular-size additive L-arginine and the redox compound glutathione (GSH) were added to the culture medium. Addition of 0.4 M L-arginine and 5 mM reduced GSH increased the yield of a native tissue-type plasminogen activator variant (rPA), consisting of the kringle-2 and the protease domain, and a single-chain antibody fragment (scFv) up to 10- and 37-fold, respectively. A variety of other medium additives also had positive effects on the yield of rPA. In a second set of experiments, the effects of cosecreted ATP-independent molecular chaperones on the yields of native therapeutic proteins were investigated. At optimized conditions, cosecretion of E. coli DnaJ or murine Hsp25 increased the yield of native rPA by a factor of 170 and 125, respectively. Cosecretion of DnaJ also dramatically increased the amount of a second model protein, native proinsulin, in the periplasm. The results of this study are anticipated to initiate a series of new approaches to increase the yields of native, disulfide-bridged, recombinant proteins in the periplasm of E. coli.

Culture Media↗
PubMed1983

Carbon monoxide yield of cigarettes and its relation to cardiorespiratory disease.

Estimates of the carbon monoxide yield of their cigarettes have been obtained for 4910 smokers (68% of all smokers) in the Whitehall study of men aged 40 to 64. In the 10 years after examination 635 men died. When men smoking cigarettes with high carbon monoxide yield were compared with those smoking cigarettes with a low yield, and after adjusting for age, employment grade, amount smoked, and tar yield, the risk of death was 32% lower for coronary heart disease, 49% higher for lung cancer, and 10% lower for total mortality; these differences were not statistically significant. Among men who said that they inhaled the risk of fatal coronary heart disease was 51% lower in the high carbon monoxide group (p less than 0.01), while the risk of lung cancer was 75% higher. These results provide no evidence that a smoker can reduce his risk of death by smoking a brand with a low carbon monoxide yield; he might even increase it. The complex interactions between characteristics of the smoker, smoking behaviour, constituents of tobacco smoke, and health are again demonstrated.

Adult↗
PubMed1988

Does measurement of yield pressure at the cardia during endoscopy provide information on the function of the lower oesophageal sphincter mechanism?

We describe a technique for measuring the yield pressure at the cardia during upper gastrointestinal endoscopy. The test was applied to 47 patients with macroscopic oesophagitis and nine patients with achalasia. Controls were 123 patients from the routine endoscopy list in whom no abnormality was found and 21 healthy volunteers. Yield pressure was similar in both control groups, but was significantly higher in achalasia (p less than 0.001) and lower in oesophagitis (p less than 0.001). Yield pressures fell dramatically after pneumatic dilatation in the achalasia patients. The test was reproducible and yield pressure was not affected by age, sex, weight, or sedation. Measurement of yield pressure during endoscopy provides information which may reflect the function of the whole antireflux mechanism, and not just the lower oesophageal sphincter.

Adolescent↗
PubMed1991

Tuberculous pleural effusions: increased culture yield with bedside inoculation of pleural fluid and poor diagnostic value of adenosine deaminase.

A prospective study of 111 adult patients with a pleural effusion was carried out in an area with a high prevalence of tuberculosis to compare the yield of bedside with laboratory inoculation of pleural fluid, and the yield and speed of a radiometric mycobacterial culture system (BACTEC) with that of conventional culture. The use of adenosine deaminase activity in pleural fluid as a diagnostic test for tuberculosis was also evaluated. In the 62 cases of tuberculosis confirmed histologically or by culture, or both, the BACTEC system had the same culture yield as conventional mycobacterial culture (positive in 14 cases-23%), but was significantly faster (18 versus 33 days). Bedside inoculation had a culture yield significantly higher than laboratory inoculation in the 24 patients tested (11 versus four). The remaining three diagnostic categories were malignant (28), miscellaneous (10), and undiagnosed (11). Median adenosine deaminase activity was significantly higher in tuberculous effusions than in any of the other categories, but there was considerable overlap between the groups. It is concluded that the BACTEC system is significantly faster than conventional mycobacterial culture and that bedside inoculation of pleural fluid substantially increases culture yield. Adenosine deaminase does not provide as valuable a diagnostic test of pleural tuberculosis as has been suggested.

Adenosine Deaminase↗
PubMed1995

Needle-localization biopsy of the breast: impact of a selective core needle biopsy program on yield.

PURPOSE: To determine the effect of a selective core biopsy program on the yield at needle-localization biopsy (NLB) of nonpalpable lesions. MATERIALS AND METHODS: Two hundred consecutive core biopsy samples of the breast were evaluated in an ongoing consecutive series of 1,172 NLB samples. RESULTS: Before implementation of the core biopsy program, the yield at NLB improved from 21% at 100 cases to 35% just before the introduction of core biopsy. After implementation, the yield increased gradually to 55% at 200 cases. The yield in masses increased from 21% at 100 cases to 43% just before the initiation of the core biopsy program and then increased dramatically to 72% at 200 cases. The percentage of small lesions detected did not change with implementation: 88% of invasive cancers measured less than 1.5 cm and 60% measured less than 1 cm in the last 100 cases. CONCLUSION: Appropriate selection of cases for core biopsy can more than double the yield of cancer in NLB samples without a decrease in the percentage of small cancers detected.

Adolescent↗
PubMed2006

Cigarette yields and human exposure: a comparison of alternative testing regimens.

OBJECTIVE: There is general agreement that the testing protocol for measuring cigarette smoke constituents-the International Organization for Standardization regimen-is an inappropriate mechanism for evaluating human exposure. Alternative smoking regimens have been introduced in Canada and Massachusetts; however, these regimens have not been evaluated against human smoking behavior and biomeasures of exposure. The objective of this study was to compare measures of smoke volume and nicotine uptake among human smokers against the puffing variables and nicotine yields generated by five different machine smoking regimens: (a) International Organization for Standardization, (b) Massachusetts, (c) Canadian, (d) a Compensatory regimen, and (e) a Human Mimic regimen. METHODS: Measures of smoke volume and puffing behavior were recorded for 51 smokers who used a portable smoking topography device for three 1-week trials. Measures of salivary cotinine were taken at the completion of each week. The cigarette brands smoked by participants were then machine-smoked under five testing regimens, including a human mimic condition where brands were machine smoked using the puffing behavior recorded from human smokers. The total volume of smoke collected from each cigarette and the nicotine, tar, and carbon monoxide yields were recorded. RESULTS: None of the four machine smoking regimens adequately reflected Human Mimic Yields of tar, nicotine, and carbon monoxide. In addition, none of the four smoking regimens generated nicotine yields that were associated with actual nicotine uptake in humans. CONCLUSIONS: None of the existing smoking regimens adequately represents human smoking behavior nor do they generate yields associated with human measures of nicotine uptake.

Adult↗
PubMed1999

Economic impact of donor platelet count and platelet yield in apheresis products: relevance for emerging issues in platelet transfusion therapy.

INTRODUCTION: We analyzed donor platelet counts and platelet product yields in 708 consecutive platelet aphereses in our program in order to define the importance of this relationship for emerging issues in platelet transfusion therapy. METHODS: Aphereses performed on the Spectra 3.6 (COBE, Lakewood. Colo.) the CS-3000 Plus (Fenwall-Baxter, Deerfield, Ill.) were analyzed. RESULTS: Mean platelet count was 237+/-49x10(3)/mm3 (mean +/- SD), and mean yield was 4.24+/-1. 09x10(11) platelets. Eigthy-five (12%) procedures generated less that 3x10(11) platelets. Only thirty-eight (5.4%) procedures yielded >/=6x10(11) platelets, so that 'split products' could be obtained. Platelet yields were primarily related to the biologic contribution (baseline platelet count) of the donor. Procedure parameters selected for harvest, and the efficiency of the device also had a significant, but less important role in determining the final platelet yield. An increase in mean donor platelet count achieved with Mpl ligand therapy from 240,000 to 320,000/mm3 would reduce the cost from USD 378 to 267 for each apheresis product, since the fraction of split products would exceed 50% of apheresis procedures. CONCLUSION: Increasing the donor platelet count would have a significant economic impact on platelet apheresis programs, as well as important clinical consequences for the role of platelet apheresis products in future transfusion strategies.

Adult↗
PubMed2004

Comparison of viable cell yield from excised versus aspirated adipose tissue.

The correction of soft-tissue defects by adipose tissue transplantation often produces poor and unpredictable results. The implantation of isolated and cultured preadipocytes offers a solution to this problem since these cells differentiate into adipocytes when implanted in vivo. A field of major interest is to maximize the yield of preadipocytes isolated from adipose tissue showing only low contamination with other cell types. Aspiration and excision are two concurrent clinical ways of harvesting adipose tissue for the isolation of preadipocytes. This tissue is usually discarded after surgery. In this study, the yield of preadipocytes obtained from liposuction material was compared to that of excised adipose tissue. Furthermore, we determined the loss of precursor cells if isolation of preadipocytes was delayed for 24 h. Preadipocytes were isolated from the stromal cell fraction of human subcutaneous adipose tissue samples. Harvesting of adipose tissue by suction was performed according to the Coleman procedure (manually applied negative pressure using a 10-ml syringe with a blunt tip cannula). Isolation was either carried out within 60 min after extraction or after storage for 24 h in culture medium at 4 degrees C. Isolated preadipocytes were cultured for 24 h, trypsinized and counted in a Neubauer chamber. Our results show clearly that the yield of preadipocytes isolated from liposuction material (within 60 min after extraction and after 24 h of storage) is higher than the cell yield from excised adipose tissue. Overnight storage for 24 h leads to a significant loss of preadipocytes in excised tissue but not in liposuction material. The high yield of cells isolated from liposuction material proves that extraction by suction does not damage the stromal cell fraction in the adipose tissue. If cell isolation is not performed immediately after the operation, liposuction material is clearly the better alternative for storage.

Adipocytes↗
PubMed1989

Effects of low-yield cigarettes on electroencephalographic dynamics.

Previous research had indicated that the smoking of medium tar and nicotine (T/N) yield cigarettes produced a psychostimulant action on electroencephalographic (EEG) activity which was apparent after a single cigarette and was evident as early as the fourth puff. The present study adopted the identical smoking and recording procedure to examine whether low-T/N yield cigarettes produced qualitatively similar EEG profiles as previously observed with medium-yield cigarettes. Although the results indicated similarities in post-smoking EEG profiles of low- and medium-yield cigarettes, discrepancies with several EEG components and temporal (puff-by-puff) EEG features suggested that low-yield cigarettes may exert less impact on brain electric activity. The results are discussed in relation to motivational theories of smoking behavior.

Adolescent↗
PubMed1993

Cigarette yields of tar and nicotine and markers of exposure to tobacco smoke.

Although cigarette yields of tar and nicotine have been declining since the early 1970s, little information is available for the general population on the consequences of their use on exposure to tobacco combustion products. In a population-based sample of 298 smokers, the majority of whom were Hispanic, we examined the relationships between yields of cigarettes currently smoked and levels of salivary cotinine and end-expired carbon monoxide. Spearman correlation coefficients between the current number of cigarettes smoked and cotinine (r = 0.52) or carbon monoxide (r = 0.51) were higher than correlations between the Federal Trade Commission (FTC) nicotine data and these same markers, 0.12 and 0.05, respectively. Correlations between FTC tar and carbon monoxide yields and the biologic markers were similarly weak. In multiple linear regression models, the current number of cigarettes smoked was the most important predictor of cotinine and carbon monoxide levels (p < 0.0001). The addition of FTC tar, nicotine, or carbon monoxide to the models explained little of the variability in cotinine or carbon monoxide levels. Because FTC yields of tar and nicotine are poor predictors of exposure to tobacco combustion products, subjects' reports of cigarette brand should not be used as a primary marker of exposure in epidemiologic investigations. Furthermore, smokers need to be advised about the limitations of cigarette yield information for predicting the potential for adverse health effects of smoking.

Adult↗