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PubMed2000

Free radical scavenging and antioxidant effects of lactate ion: an in vitro study.

Divergent literature data are found concerning the effect of lactate on free radical production during exercise. To clarify this point, we tested the pro- or antioxidant effect of lactate ion in vitro at different concentrations using three methods: 1) electron paramagnetic resonance (EPR) was used to study the scavenging ability of lactate toward the superoxide aion (O(2)(-).) and hydroxyl radical (.OH); 2) linoleic acid micelles were employed to investigate the lipid radical scavenging capacity of lactate; and 3) primary rat hepatocyte culture was used to study the inhibition of membrane lipid peroxidation by lactate. EPR experiments exhibited scavenging activities of lactate toward both O(2)(-). and.OH; lactate was also able to inhibit lipid peroxidation of hepatocyte culture. Both effects of lactate were concentration dependent. However, no inhibition of lipid peroxidation by lactate was observed in the micelle model. These results suggested that lactate ion may prevent lipid peroxidation by scavenging free radicals such as O(2)(-). and.OH but not lipid radicals. Thus lactate ion might be considered as a potential antioxidant agent.

Animals↗
PubMed2004

Does exercise-induced hypoxemia modify lactate influx into erythrocytes and hemorheological parameters in athletes?

This study investigated 1) red blood cells (RBC) rigidity and 2) lactate influxes into RBCs in endurance-trained athletes with and without exercise-induced hypoxemia (EIH). Nine EIH and six non-EIH subjects performed a submaximal steady-state exercise on a cyclo-ergometer at 60% of maximal aerobic power for 10 min, followed by 15 min at 85% of maximal aerobic power. At rest and at the end of exercise, arterialized blood was sampled for analysis of arterialized pressure in oxygen, and venous blood was drawn for analysis of plasma lactate concentrations and hemorheological parameters. Lactate influxes into RBCs were measured at three labeled [U-14C]lactate concentrations (1.6, 8.1, and 41 mM) on venous blood sampled at rest. The EIH subjects had higher maximal oxygen uptake than non-EIH (P < 0.05). Total lactate influx was significantly higher in RBCs from EIH compared with non-EIH subjects at 8.1 mM (1,498.1 +/- 87.8 vs. 1,035.9 +/- 114.8 nmol.ml(-1).min(-1); P < 0.05) and 41 mM (2,562.0 +/- 145.0 vs. 1,618.1 +/- 149.4 nmol.ml(-1).min(-1); P < 0.01). Monocarboxylate transporter-1-mediated lactate influx was also higher in EIH at 8.1 mM (P < 0.05) and 41 mM (P < 0.01). The drop in arterial oxygen partial pressure was negatively correlated with total lactate influx measured at 8.1 mM (r = -0.82, P < 0.05) and 41 mM (r = -0.84, P < 0.05) in the two groups together. Plasma lactate concentrations and hemorheological data were similar in the two groups at rest and at the end of exercise. The results showed higher monocarboxylate transporter-1-mediated lactate influx in the EIH subjects and suggested that EIH could modify lactate influx into erythrocyte. However, higher lactate influx in EIH subjects was not accompanied by an increase in RBC rigidity.

Adaptation, Physiological↗
PubMed1997

Lactate-proton cotransport in skeletal muscle.

Skeletal muscle and most other tissues possess a membrane transport system mediating a coupled lactate and H+ translocation. Muscle possesses several lactate-proton transporter isoforms of which two have been cloned; however, the main isoform remains to be identified. The isoforms may have different properties and functional roles, but these have not been specifically characterized. The distribution of lactate-proton transport capacity in skeletal muscle is fiber type dependent, with a higher capacity in slow-twitch fibers compared with fast-twitch fibers. During intense muscle activity and in the recovery period, the lactate and H+ effluxes are mainly mediated by the lactate-proton transporter, which reduces the accumulation of lactate in muscle as well as the drop in internal pH suggested to be involved in muscle fatigue. Thus the lactate-proton transporter is of functional importance for pH regulation in association with muscle activity. This carrier is also important for lactate uptake into resting muscle and other tissues; therefore, the carrier distribution is important for the fate of lactate in the body. In addition, the capacity of the lactate-proton transporter can be increased by intense training and is reduced by inactivity; thus the lactate-proton transporter can undergo adaptive changes.

Animals↗
PubMedDate not supplied

(13)C MR spectroscopy study of lactate as substrate for rat brain.

In order to address the question whether lactate in blood can serve as a precursor for cerebral metabolites, fully awake rats were injected intravenously with [U-(13)C]lactate or [U-(13)C]glucose followed 15 min later by decapitation. Incorporation of label from [U-(13)C]glucose was seen mainly in glutamate, GABA, glutamine, aspartate, alanine and lactate. More label was found in glutamate than glutamine, underscoring the predominantly neuronal metabolism of pyruvate from [U-(13)C]glucose. It was estimated that the neuronal metabolism of acetyl CoA from glucose accounts for at least 66% and the glial for no more than 34% of the total glucose consumption. When [U-(13)C]lactate was the precursor, label incorporation was similar to that observed from [U-(13)C]glucose, but much reduced. Plasma analysis revealed the presence of approximately equal amounts of [1,2,3-(13)C]- and [1,2-(13)C]glucose, showing gluconeogenesis from [U-(13)C]lactate. It was thus possible that the labeling seen in the cerebral amino acids originated from labeled glucose, not [U-(13)C]lactate. However, the presence of significantly more label in [U-(13)C]- than in [2,3-(13)C]alanine demonstrated that [U-(13)C]lactate did indeed cross the blood-brain barrier, and was metabolized further in the brain. Furthermore, contributions from pyruvate carboxylase (glial enzyme) were detectable in glutamine, glutamate and GABA, and were comparatively more pronounced in the glucose group. This indicated that relatively more pyruvate from lactate than glucose was metabolized in neurons. Surprisingly, the same amount of lactate was synthesized via the tricarboxylic acid cycle in both groups, indicating transfer of neurotransmitters from the neuronal to the astrocytic compartment, as previous studies have shown that this lactate is synthesized primarily in astrocytes. Taking into consideration that astrocytes take up glutamate more avidly than GABA, it is conceivable that neuronal lactate metabolism was more prominent in glutamatergic neurons.

Acetyl Coenzyme A↗
PubMed1999

Effects of lactate on intracellular pH and hypercontracture during simulated ischemia and reperfusion in cardiac ventricular myocytes of the guinea pig.

Effects of lactate on changes in intracellular pH (pHi) and contractility during simulated ischemia and reperfusion were examined in single myocytes of the guinea pig cardiac ventricle. The conditions of simulated ischemia were produced by the exchange of perfusion medium from the standard one oxygenated with 95% O2-5% CO2 gas (pH 7.4) to one containing no glucose, 8 mM K+, and 0-30 mM sodium-D,L-lactate and was gassed with 90% argon - 10% CO2 (pH 6.6). The pHi was decreased by the simulated ischemia from approx. 7.3 to approx. 6.9 regardless of lactate concentration, while the rate of pHi decrease was increased by lactate in a concentration-dependent manner. The contraction induced by electrical stimulation disappeared faster in the presence of lactate. The incidence of irreversible hypercontracture of myocytes was significantly reduced by 20-30 mM lactate. The overshoot of pHi to approx. 7.7 and excess contractions were induced by withdrawal of lactate during the reperfusion, but not observed when lactate was continuously present. The recovery of normal contractility during reperfusion was facilitated by lactate. It can be concluded that lactate added to or removed from the perfusion medium increases the rate of pHi change under the simulated ischemia and reperfusion, respectively, and that the continuous presence of lactate reduces cell injury under these conditions.

Animals↗
PubMed2001

Lactate release, concentration in blood, and apparent distribution volume after intense bicycling.

To study the release of lactate from muscle and its relationship to the blood lactate concentration during and after intense bicycling, young men cycled at 5.5 W kg(-1) body mass for 2 min to exhaustion or stopped after 1 min (nonexhaustive ride). The leg's release of lactate during and after each ride was taken from the measured blood flow and lactate concentrations in arterial and femoral-venous blood. Muscle biopsies were taken in separate experiments and analyzed for lactate. During the bicycling, 6 to 10% of the lactate produced was released to the blood. During exercise and for the first few minutes after, the rate of lactate release did not differ between 2 min exhaustive and 1 min nonexhaustive bicycling. The integrated release (exercise plus recovery) for the 1 min bicycling was 60 to 80% of the corresponding value of the 2 min exhaustive bicycling. In the late recovery, the blood lactate concentration was 3 to 5 times higher after 2 min exhaustive bicycling than after the 1 min nonexhaustive bicycling. There was thus a mismatch between the amount of lactate released and measured concentration in blood, reflecting a smaller distribution volume after the exhaustive bicycling. The blood lactate concentration may therefore not be a good measure of the lactate production and anaerobic energy release during bicycling.

Adult↗
PubMed2005

Arterial lactate concentration, hospital survival, sepsis and SIRS in critically ill neonatal foals.

REASONS FOR PERFORMING STUDY: Blood lactate concentration has been shown to be a useful clinical indicator in human patients, but has not been formally investigated in critically ill foals. OBJECTIVE: To investigate the association of blood lactate with hospital survival, markers of cardiovascular status, metabolic acid base status, sepsis and systemic inflammatory response syndrome (SIRS). METHODS: A database containing clinical, haematological, plasma biochemical and hospital outcome data on neonatal foals referred to an intensive care unit in 2000-2001 was analysed. Seventy-two foals for which arterial lactate was measured at admission were included in the study. RESULTS: Sixty-one foals had an admission lactate concentration > 2.5 mmol/l. Admission lactate was statistically associated with hospital survival, mean arterial pressure, blood creatinine concentration, bacteraemia, anion gap, lactate concentration at 18-36 h after admission and evidence of SIRS, but not with packed cell volume or heart rate. Lactate at 18-36 h was also associated with survival and evidence of SIRS. Anion gap, base excess, base excess due to unidentified anions (BEua), simplified strong ion gap or bicarbonate correctly classified foals for presence of hyperlactaemia (> 5 mmol/l) in < or = 80% of animals. CONCLUSIONS: Admission blood lactate gives important prognostic information. Lactate should be measured rather than assumed from the anion gap, base excess, BEua, simplified strong ion gap or bicarbonate. POTENTIAL RELEVANCE: Blood lactate concentrations at admission are clinically relevant in neonatal foals and warrant further investigation. This should include the clinical value of measuring changes in lactate in response to treatment.

Acid-Base Equilibrium↗
PubMed2000

Effects of RGP lens extended wear on glucose-lactate metabolism and stromal swelling in the rabbit cornea.

PURPOSE: To assess the chronic effects of rigid gas-permeable (RGP) contact lenses on corneal swelling and glucose-lactate metabolism in the rabbit cornea during 1 month of continuous extended wear and to establish the relationship between these effects and the oxygen transmissibility (Dk/L) of the test lens polymer. METHODS: Four RGP lenses of varying Dk/L were tested in 8 rabbits per test group (left eyes served as controls). After 7 days and 1 month extended wear, the concentrations of lactate and glucose in the corneal epithelium, stroma and aqueous humor were determined by enzyme assay; and epithelial and stromal ATP concentrations were separately measured by bioluminescence techniques. Corneal thickness was measured at a standard morning time by ultrasonic pachymetry before and after 1, 7, 15 days and 1 month extended wear. RESULTS: After 7 days and 1 month extended wear, generalized decreases were found in aqueous humor lactate levels for all test lenses, while concomitant increased aqueous glucose concentrations were observed. Total epithelial lactate levels correlated inversely with decreasing Dk/L levels for lower oxygen transmissible lenses (R = 0.951, P = 0.0051); and remained unchanged after extended wear of the hyper-oxygen transmissible Dk/L 125 test lens. By contrast, stromal lactate levels consistently decreased at all time points measured forextended wear of all test lenses. As expected, both epithelial and stromal ATP concentrations simultaneously decreased in extended wear. Overnight corneal swelling values after 24 hours wear of Dk/L = 27, 43, 70 and 125 test lenses were increased by 9.8, 7.1, 5.5, and 5.2% while persistent (residual) stromal swelling after one month extended wear was 16.8, 10.1, 8.6, and 5.6% respectively, in excess of baseline values. CONCLUSIONS: Chronic RGP contact-lens induced hypoxia is associated with altered glucose-lactate metabolism in the cornea and aqueous humor with excess production of increased levels of lactate in the epithelium for lower Dk/L test lenses, but decreased lactate concentration in the stroma and aqueous humor. Extended wear of the hyper-oxygen transmissible test lens (Dk/L = 125) however, produced no increase in epithelial lactate levels. Expected lens-induced decreases in epithelial and stromal ATP were not dependent on lens-oxygen transmissibility. Despite the persistence of lower than normal stromal levels of lactate during 1 month of extended wear for all test lenses, residual corneal swelling values remained consistently elevated above baseline values. Taken together, these data establish that increased stromal lactate accumulation cannot account for persistent stromal edema in chronic extended wear of RGP lenses; and that this effect appears to be independent of lens-oxygen transmissibility and may thus represent the prolonged mechanical effect of lens wear itself.

Adenosine Triphosphate↗
PubMedDate not supplied

Amniotic fluid volume responses to intra-amniotic infusion of lactate in fetal sheep.

OBJECTIVE: In human and ovine fetuses, severe anemia is associated with elevated fetal blood and amniotic lactate levels and polyhydramnios. In ovine fetuses, intravascular infusion of sodium lactate elevates fetal plasma and amniotic lactate levels and produces polyhydramnios. The present study tested the hypothesis that an elevated amniotic lactate concentration in the absence of an increased fetal plasma lactate would be associated with an increase in amniotic fluid volume (AFV). METHODS: Eight chronically catheterized, late-gestation fetal sheep were studied over 5 days. Twice each day, we measured blood gases and pH, electrolytes, glucose, lactate, and blood urea nitrogen (BUN) concentrations, as well as osmolality of fetal blood, maternal blood, amniotic fluid, and fetal urine. Amniotic fluid volume was measured once daily. During experimental days 2 to 4, lactic acid was infused into the amniotic compartment to achieve an amniotic lactate concentration of approximately 20 mmol/L. Statistical analysis was by analysis of variance and regression. RESULTS: Amniotic fluid lactate levels averaged 2.2 +/- 0.4 mmol/L (mean +/- standard error) before infusion and 18.9 +/- 3.3 mmol/L during the 72-hour infusion, falling to 5.8 +/- 1.2 mmol/L postinfusion (P < .001). Fetal plasma lactate averaged 1.8 +/- 0.1 mmol/L on day 1 and increased by 1.4 +/- 0.6 mmol/L on day 4 (P < .001). Fetal urine flow was unchanged and averaged 0.54 +/- 0.08 mL/min over the 5 days. Amniotic fetal volume was 821 +/- 186 mL on day 1, increased nonsignificantly by 99 +/- 95 mL on day 4, and remained unchanged on day 5. CONCLUSIONS: The present study suggests that if amniotic lactate acts osmotically to increase AFV, the effect is small. Thus, the primary site of action of elevated fetal lactate levels appears to be at the placenta rather than the intramembranous pathway.

Amniotic Fluid↗
PubMed2001

[Perioperative assessment of blood lactate levels in pediatric heart surgery].

Measuring arterial lactate concentration is a prompt, easy and relatively non-invasive way to estimate tissue oxygen metabolism. We evaluated whether perioperative levels of the arterial lactate concentrations can reflect the general severity of a pediatric patient's condition. A consecutive series of 112 patients, aged 5 days to 17 years (median age: 12 months), admitted to our pediatric intensive care unit (PICU) following cardiac surgery under cardiopulmonary bypass were studied. Arterial blood lactate concentration was measured preoperatively, immediately upon termination of the cardiopulmonary bypass (postCPB), immediately following the operation, and 16th hours postoperatively (D1). Trends within arterial lactate concentrations were examined in relation to mortality rates, the duration of PICU stays and the patient's ages. The studied population had a mortality rate of 5.7% (6 patients). Lactate levels increased significantly and exceeded 4.0 mmol.l-1 during postCPB measurements in a majority of the patients. The increases in lactate levels are affected by the changes in interorgan blood flow, blood glucose levels and/or blood pH in addition to the effects of the CPB-priming lactated Ringer's solution. Thus, higher cut off values have to be determined, and lower probabilities assigned, when using postCPB lactate levels to predict the severity of an outcome. Significantly and sustained increases in D1 lactate levels were noted in neonates, patients with longer PICU stays (> 15 days) and those died later. Hyperlactemia greater than 2.2 mmol.l-1 at D1 predicted death with a sensitivity of 82% and a specificity of 72%. The measurement of early postoperative lactate levels, reflecting postoperative ability to eliminate intraoperative hyperlactemia, is a better way of assessing the severity of a pediatric patient's condition following cardiac surgery. The ideal time to measure early postoperative lactate levels should be determined by further research.

Adolescent↗
PubMed1993

Local blood flow is not linked to lactate within single rabbit skeletal muscles.

A marked regional distribution in blood flow within single skeletal muscles on a non-microvascular level, i.e. at the level of large arterioles or small arteries, is present in dog, cat and rabbit. The mechanism for this perfusion pattern is not known. The goal of the present study was to see if regional blood flow was correlated to regional lactate metabolism. Anesthetized rabbits were studied. Blood flow to 0.25 g muscle samples was measured with microspheres whereas lactate content and lactate dehydrogenase activity were determined in extracts of these samples. No correlation was detected between regional blood flow and regional lactate or lactate dehydrogenase either at rest or during exercise hyperemia. Expressed as the coefficient of variation (CVc), regional blood flow showed a marked scatter, the CVc ranged from 0.32 to 0.35. The corresponding CVc for both lactate and lactate dehydrogenase activity ranged from 0.16 to 0.19. It is concluded that regional blood flow is not correlated to regional lactate metabolism. The regional distribution in blood flow was markedly more uneven than that for lactate content and for lactate dehydrogenase activity.

Animals↗
PubMed1988

Onset of blood lactate accumulation exercise capacity, skeletal muscle fibers and metabolism before and after coronary artery bypass grafting.

Male patients with effort angina were studied before (n = 7), 1 week, and 1 and 6 months (n = 6) after coronary artery bypass grafting (CABG) with 2 to 7 grafts. The test battery included graded exercise, which was performed until unbearable leg exertion or chest pain, or both, was present. Onsets of blood lactate accumulation, anginal pain, leg exertion and dyspnea were interpolated for either the lactate concentration 2 mmol X 1-1 or the ratings 2 on the Borg subjective intensity scale. Onsets of blood lactate accumulation and symptom-limited exercise capacity before surgery amounted to 58 and 100 W, respectively. The corresponding figures 6 months later were the same for onset of blood lactate accumulation, whereas symptom-limited exercise capacity had increased by 58%. Blood lactate was the same at rest and mild exercise (congruent to onset of blood lactate accumulation) but more than doubled at symptom-limited exercise capacity (peak blood lactate concentration). Muscle fiber typing showed a low figure for the slow twitch fiber proportion (35%), which was unchanged after 6 months. Fast twitch subtype C was elevated before (7%) but disappeared after surgery, and fast twitch subtype A percent increased correspondingly. The major muscle biochemical changes were in the glycogenolytic pathway and the lactate dehydrogenase enzyme system, which appeared to increase in a quantitative manner, but with an unchanged relative lactate dehydrogenase isozyme pattern. The increased symptom-limited exercise capacity was related to the increased glycogenolytic activity and peak blood lactate (i.e., increased "anaerobic power"). Whether the causative explanation was the relief from chest pain, i.e., a psychophysiologic feature or the biochemical changes that took place in the muscle could only be speculated on.

Angina Pectoris↗
PubMed1994

Multiple lactate dehydrogenase activities of the rumen bacterium Selenomonas ruminantium.

The lactate utilizing strain of Selenomonas ruminantium 5934e was found to contain three lactate dehydrogenase (LDH) activities in sonicated cell extracts. One activity, an NAD dependent L-LDH (L-nLDH) was measured at 15-fold greater levels in extracts of cells grown to mid-exponential phase on glucose compared to cells grown to the equivalent growth stage on DL-lactate. A second nLDH activity specific for D-lactate (D-nLDH) was detected at similar levels in both lactate-grown cell extracts and glucose-grown cell extracts. The third activity, an NAD independent DLDH (D-iLDH) was very low in cells grown on glucose but was induced more than 10-fold when DL-lactate was used as the carbon source. The three LDH activities could be separated by gel filtration. Recovery of the activities was low due to the apparent instability of the enzymes at 4 degrees C, which was most pronounced in the case of the D-iLDH. A Km for lactate of 0.5 mM was estimated for the D-iLDH and this was considerably lower than the values of 45 mM and 70 mM measured for L-nLDH and D-nLDH respectively. It is proposed that the D-iLDH may be largely responsible for the formation of pyruvate in lactate-grown cells of S. ruminantium strain 5934e. Three other lactate utilizing strains of S. ruminantium, HD4, 5521C1 and JW13 exhibited a similar profile of LDH activities to strain 5934e when grown on glucose and DL-lactate.

Animals↗
PubMed1978

Mechanism of autoenergized transport and nature of energy coupling for D-lactate in Escherichia coli.

To fully energize the active transport systems of Escherichia coli, it is common practice to preincubate the cells for 10 min with 10 or 20 mM concentration of a compound that can serve as an energy source. This paper shows that the active accumulation of D-lactate can be achieved within 1 min with only 50 micron D-lactate serving as an energy source for its own uptake in starved cells (autoenergization). The cells were strain DL54 which had been induced by growth in the presence of D-lactate. Uninduced cells were not able to show autoenergized D-lactate uptake under these conditions. The induced cells were also able to transport proline in the presence of 100 micron D-lactate as sole energy source. The D-lactate-dependent dehydrogenase activity in inverted French press vesicles was comparable for the induced and uninduced cells. The same was true for respiration of whole cells in the presence of 20 mM D-lactate. However, the Vmax for D-lactate transport of induced cells was six times higher than that of uninduced cells. It appears that a sufficient number of high-affinity carrier molecules in the cytoplasmic membrane are necessary for the autoenergized transport of D-lactate. A similar conclusion was reached for the autoenergized uptake of glycerol-3-phosphate by Escherichia coli strain 7. The active transport of D-lactate is driven by the protonmotive force.

Anaerobiosis↗
PubMed1991

Relationship of early lactation and bovine somatotropin on nutrient uptake by cow mammary glands.

Twenty-one multiparous lactating dairy cows with previous 305-d milk production records varying from 5900 to 13,600 kg were used to investigate effects of bST administration and stage of lactation on nutrient plasma arterial concentrations and arterial-venous differences across the mammary glands (uptake). On d 71 and continuing until d 126 of lactation, cows were injected with 40 mg of sometribove (bST group) or bicarbonate buffer (placebo group). Arterial and venous blood plasma samples were collected over a 12-h period on d 35, 70, 105, and 126 of lactation. Plasma concentration of glucose was 7% higher in midlactation compared with early lactation cows. Plasma concentration of acetate decreased from 2.11 to 1.87 mM in placebo versus bST-treated cows. Plasma arterial concentration and uptake of D-beta-hydroxybutyrate were .52 and .18 mM higher, respectively, in early versus midlactation cows. Concentration and uptake of NEFA were elevated in both early lactation and bST-treated cows. Triacylglyceride concentrations were 24 and 19% lower in early lactation and bST-treated cows compared with midlactation cows receiving placebo. Likewise, uptake of triacylglyceride was reduced in early lactation and with bST treatment compared with midlactation. The mediation of nutrient delivery and uptake by the mammary gland appears to be markedly similar between early lactation and bST-treated cows, suggesting a similarity between these physiological states and the homeostatic and homeorhetic mechanisms regulating nutrient partitioning in the lactating dairy cow. In early compared with midlactation cows receiving placebo, uptakes of D-beta-hydroxybutyrate and NEFA were reduced, and triacylglyceride uptake increased.

3-Hydroxybutyric Acid↗
PubMed1996

A study of the lactational amenorrhoea method of family planning in New Zealand women.

AIM: To evaluate the acceptance and efficacy of the lactational amenorrhoea method of family planning in breastfeeding clients attending clinics of the NZ Association of Natural Family Planning. METHODS: Mothers who were fully breastfeeding their babies, were amenorrhoeic and were early postpartum were offered for the purpose of family planning either lactational amenorrhoea method or the usual fertility awareness charting method. The clients who chose lactational amenorrhoea method were contacted at monthly intervals to check if they continued to meet the lactational amenorrhoea method criteria of fully breastfeeding and amenorrhoea. The fertility awareness group followed the normal practice of clinic visits for instruction until they became autonomous users. The status of both groups were assessed at 6 months postpartum when lactational amenorrhoea method users were advised to adopt another family planning method. RESULTS: Of 149 breastfeeding clients, 110 met the lactational amenorrhoea method criteria. Seventy chose lactational amenorrhoea method, the majority (56.7%) because of its simplicity. Thirty (48.6%) of initial lactational amenorrhoea method users were able to use the method for the full 6 months postpartum period. None of the women conceived while using lactational amenorrhoea method. CONCLUSION: For mothers who choose to fully breastfeed and who maintain a state of amenorrhoea lactational amenorrhoea method is an effective means of avoiding pregnancy during the first 6 months postpartum.

Adult↗
PubMed1964

LACTATE-DEGRADING SYSTEM IN BUTYRIBACTERIUM RETTGERI SUBJECT TO GLUCOSE REPRESSION.

Wittenberger, Charles L. (National Institute of Dental Research, U.S. Public Health Service, Bethesda, Md.), and Ann S. Haaf. Lactate-degrading system in Butyribacterium rettgeri subject to glucose repression. J. Bacteriol. 88:896-903. 1964.-The ability of Butyribacterium rettgeri to utilize lactate as the main energy source for growth requires the formation of a lactate-degrading system. The precise nature of this system is unknown, but preliminary evidence suggests that cellular acquisition of lactate-decomposing activity involves the formation of a nonpyridine nucleotide-linked lactic dehydrogenase. This enzyme, which can couple lactate oxidation to the reduction of ferricyanide [K(3)Fe(CN)(6)-lactic de-hydrogenase (LDH)], is absent from glucose-grown cells; this observation appears to account for the inability of such cells to decompose lactate even though they may form lactate from glucose. The formation of K(3)Fe(CN)(6)-LDH in growing cultures requires the addition of lipoic acid to the medium, and is repressed by glucose, pyruvate, or fructose. When any of the latter substrates are included in the growth medium with lactate, nicotinamide adenine dinucleotide-linked LDH activity is present in cells at markedly higher levels than it is in cells grown on lactate alone.

Culture Media↗
PubMed1991

Biological response of multicellular EMT6 spheroids to exogenous lactate.

The influence of elevated lactate concentrations, as found in tumor microregions, on cellular growth, viability, and metabolic state was studied employing the multicellular spheroid model. Spheroids of EMT6/Ro cells were cultured at 37 degrees C in 5% or 20% (v/v) oxygen, using stirred media with various concentrations of exogenous lactate ranging from 0.0 mM (standard conditions) to 20.0 mM. Elevated concentrations of exogenous lactate led to a considerable decrease of the maximum spheroid diameter at growth saturation, e.g., for 20% O2 from around 1700 microns to 700 microns in 0.0 and 20.0 mM lactate respectively. Histological investigations showed that the thickness of the viable cell rim was increased by elevated lactate concentrations in 20% O2, whereas this correlation was reversed in 5% O2. Cultivation of spheroids in increasing lactate concentrations was associated with a shift of metabolic pathways from net production to increased utilization of lactate in both 20% and 5% O2, as determined by standard enzymatic assays. Oxygen tension (PO2) values measured with micro-electrodes were less in spheroids cultured in high lactate (9.0 and 20.0 mM) than under standard conditions, irrespective of the external oxygen concentration. This finding reflected a substantial increase in the cellular O2 consumption with elevated external lactate levels. At given lactate concentrations, respiration rates that were derived from measured PO2 distributions by theoretical considerations were significantly lower in 5% O2 than in 20% O2.

Animals↗