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At least 307 records · Page 17Linked to original sources
PubMed1985

Protein-mediated chloride-phosphate and lactate-lactate exchange in cytoskeleton-free vesicles budded from rabbit erythrocytes.

Spectrin-free budded vesicles from rabbit erythrocytes (Leonards, K.S. and Ohki, S. (1983) Biochim. Biophys. Acta 728, 383-393) exchange intravesicular L-[14C]lactate for extravesicular L-lactate and intravesicular [36C]chloride for extravesicular phosphate with inhibitor sensitivity consistent with what is seen in intact cells. The time-course of these fluxes is faster than for intact cells, but is somewhat slower than predicted from surface to volume ratios. Labelling with tritiated 4,4'-diisothiocyanyl-2,2'-dihydrostilbenedisulfonate (H2DIDS) at concentrations which selectively inhibit inorganic anion exchange or specific lactate exchange supports the involvement of a 93-110 kDa (band 3) polypeptide in anion transport and a 40-50 kDa polypeptide in lactate transport across these vesicle membranes. Since the budded vesicles have a markedly simplified protein profile on electrophoresis, their isolated membranes represent a preliminary stage in the purification of these transport proteins in which structure and function appear to be preserved.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

The effects of insulin and the pituitary peptide beta-cell tropin on the incorporation of D-3-3H-glucose into lipid in brown adipocytes from lactating and non-lactating rats.

Lactating and non-lactating rat brown adipocytes were used to study the dose-dependent stimulation of lipogenesis by Beta-cell tropin (BCT) and insulin. In non-lactating animals BCT increased lipogenesis approximately 2-fold compared to a 3-fold stimulation with insulin; however BCT was effective at a substantially lower molar concentration than insulin. In lactating animals resistance was observed to both BCT and insulin action.

Adipose Tissue, Brown↗
PubMed1987

Antipanic drug effects during lactate infusion in lactate-refractory panic patients.

In previous articles we have reported on the total Acute Panic Inventory (API) score during lactate-induced panic. Even patients with panic disorder who do not panic during lactate infusion have higher API scores during the infusion than normal controls. In this post hoc analysis, we wished to determine whether specific API items were more sensitive to the beneficial effects of antipanic medication, either at baseline or during the infusion, in these lactate-insensitive panic patients. Four of the 17 items showed specific drug blockade of baseline severity. Five additional items showed specific drug blockade of lactate exacerbation of symptom severity. Medication apparently had no effect on severity of the remaining eight items. We suggest that the nine symptoms that responded to drug therapy are associated with hyperventilation. The study indicates that antipanic drugs may have a specific effect in blunting hyperventilation.

Adult↗
PubMed1988

A comparative study of D-lactate, L-lactate and glycerol formation by four species of Leishmania and by Trypanosoma lewisi and Trypanosoma brucei gambiense.

Leishmania braziliensis panamensis, L. donovani, L. major, and L. mexicana amazonensis promastigotes, Trypanosoma lewisi bloodstream forms, and T. brucei gambiense procyclic forms were incubated with glucose as sole carbon source. All species consumed glucose more rapidly under aerobic than anaerobic conditions. All produced glycerol under anaerobic conditions, though the rate of glycerol production by T. lewisi was markedly lower than that by the other species. The four Leishmania species produced D-lactate, but not L-lactate, whereas T. b. gambiense procyclic forms produced L-lactate, but not D-lactate, and T. lewisi produced both isomers.

Animals↗
PubMed1991

Properties of D-lactate dehydrogenase from Lactobacillus bulgaricus: a possible different evolutionary origin for the D- and L-lactate dehydrogenases.

The NAD-dependent D-lactate dehydrogenase from Lactobacillus bulgaricus has been purified to homogeneity. This enzyme was a dimer made of two identical chains of molecular mass 37,000. Saturation by either substrate was hyperbolic, with Km values of 50 microM for NADH and 1 mM for pyruvate. The specific activity was 2200 units/mg and was not affected by the presence of fructose-1,6-bisphosphate, Mn2+ ions, ATP or ADP. The amino-terminal sequence determined on 50 residues showed no significant homology with known lactate dehydrogenases, suggesting that the D-lactate dehydrogenase from L. bulgaricus could not be evolutionarily related to the family of NAD-dependent L-lactate dehydrogenases.

Amino Acid Sequence↗
PubMed1994

An in situ electrosynthesized amperometric biosensor based on lactate oxidase immobilized in a poly-o-phenylenediamine film: determination of lactate in serum by flow injection analysis.

The electrochemical immobilization of lactate oxidase in a poly-o-phenylenediamine film permits the one-step and all-chemical construction of a lactate amperometric biosensor. The sensor was prepared in situ i.e. in the flow injection analysis (FIA) system by simply injecting a plug of a solution containing the monomer and the enzyme. At a flow rate of 50 microL/min linearity was observed up to 0.2 mM lactate and detection limits of about 2 microM could be easily achieved. Faradaic interferences caused by ascorbate, urate, cysteine and acetaminophen were sufficiently minimized to permit lactate determination in diluted serum by FIA. Results obtained by FIA-amperometric detection compared well (according to a proper t-test at a 95% confidence level) with those obtained by a standard enzymatic colorimetric assay. At a flow rate of 1 ml/min a sample throughput higher than 70 sample h-1 was achieved. After one week of continuous use in the FIA system a 75% decrease in biosensor sensitivity was observed.

Animals↗
PubMed2006

Effectiveness of administration of gonadotropin-releasing hormone at Days 11, 14 or 15 after anticipated ovulation for increasing fertility of lactating dairy cows and non-lactating heifers.

One strategy for improving fertility in cattle is mid-cycle administration of GnRH to increase progesterone secretion and delay luteolysis. This strategy might be especially useful during hot weather because heat stress increases uterine prostaglandin release and reduces development of the elongating embryo. A series of experiments was conducted to test the efficacy of GnRH for increasing fertility. There was no effect of administration of 100 microg GnRH at Day 11 after anticipated ovulation on pregnancy rates in virgin heifers subjected to timed artificial insemination (TAI) during the summer. Similarly, there was no beneficial effect of administration of GnRH at Day 11 after anticipated ovulation on pregnancy rates of lactating cows subjected to TAI in summer and winter. Three experiments tested effects of injection of GnRH at Days 14 or 15 after anticipated ovulation on pregnancy rates of lactating cows. The first experiment used 477 lactating cows subjected to TAI. Cows receiving GnRH at Day 14 had higher pregnancy rates in both summer and winter than cows receiving vehicle (20.3 versus 12.7%, P<0.02). When this experiment was repeated during summer with 137 cows, there was a negative effect of GnRH treatment at Day 14 on pregnancy rate. In the third experiment, lactating cows during summer were inseminated at detected estrus and cows were assigned to treatment with either GnRH or vehicle at Days 14 or 15 after insemination. Pregnancy rates were 25.6% (32/125) for cows receiving vehicle, 20.7% (19/92) for cows receiving GnRH at Day 14, and 20.3% (16/79) for cows receiving GnRH at Day 15. In conclusion, GnRH administration at Days 11-15 after anticipated ovulation or estrus did not consistently increase pregnancy rates in either cool or warm seasons.

Animals↗
PubMed2002

Sol-gel encapsulation of lactate dehydrogenase for optical sensing of L-lactate.

Sol-gel encapsulation of lactate dehydrogenase and its cofactor can be employed as a disposable sensor for L-lactate. The sensor utilized the changes in absorbance or fluorescence from the reduced cofactor nicotinamide adenine dinucleotide (NADH) upon exposure to L-lactate. Although, problems such as diminished enzymatic activity and/or leaching of enzyme from the sol-gel matrix occurred, the sol-gel process is sufficiently mild to permit retention of enzymatic activity. The apparent activity of LDH in the sensor is at least 10% of that of the dissolved enzyme. The sensor has a linear dynamic range over the normal physiological L-lactate level and has a long-term storage stability of at least 3 weeks.

Biosensing Techniques↗
PubMed1971

Differences in the ribosomes prepared from lactating and non-lactating bovine mammary gland.

1. Ribosomes prepared from bovine lactating mammary gland are able to synthesize protein, whereas similar preparations from non-lactating glands are not. Washing the ribosome suspensions through a medium containing 0.5m-ammonium chloride enhanced their ability to incorporate phenylalanine into polyphenylalanine. 2. Ribosomes isolated from non-lactating bovine mammary gland, in contrast with those from rat liver and lactating mammary gland, contained significant amounts of extraneous nucleases. These enzymes could be removed by washing with a medium A buffer containing 0.5m-ammonium chloride. 3. Only those ribosomes from functionally active tissues were able to bind polyuridylic acid and phenylalanyl-tRNA.

Ammonium Chloride↗
PubMed1999

Telemetric registration of heart rate and blood pressure in the same unrestrained goats during pregnancy, lactation and the non-pregnant, non-lactating period.

The purpose of this study was to investigate how changes in heart rate and arterial blood pressure relate to the time of day, reproductive period and feeding routines in dairy goats (Capra hircus). Registrations were made by radiotelemetry in the same four goats during pregnancy, lactation and the non-pregnant, non-lactating (dry) period. Heart rate rose around the morning and afternoon feedings, whereas blood pressure did not show any diurnal rhythm. Comparison between reproductive periods revealed that heart rate was higher during the fifth month of pregnancy than during lactation and the dry period, whereas for blood pressure no such differences between periods were found. Withholding three meals from lactating goats resulted in a continuous slowdown of the heart rate, whereas blood pressure fluctuated. Re-feeding temporarily increased the heart rate but had no effect on blood pressure which continued to fluctuate. After another 2 days, blood pressure (but not heart rate) had stabilized. Food-restriction, aimed at terminating milk production resulted in a consistently depressed heart rate and reduced the mean and systolic blood pressures at night. The results show that with this implantable telemetry device it is possible to measure both heart rate and blood pressure day and night in the same unrestrained animals over a length of time long enough to include all reproductive periods. Our results emphasize that when planning experiments it is important that the exact stage in each reproductive period, the act of feeding and the amount of food given be taken into account.

Animals↗
PubMed2002

A comparison of the lactate Pro, Accusport, Analox GM7 and Kodak Ektachem lactate analysers in normal, hot and humid conditions.

This study aimed to compare the performance of a new portable lactate analyser against other standard laboratory methods in three conditions, normal (20 +/- 1.3 degrees C; 40 +/- 5 % RH), hot (40 +/- 2.5 degrees C; 40 +/- 5 % RH), and humid (20 +/- 1.1 degrees C; 82 +/- 6 % RH) conditions. Seven healthy males, ([Mean +/- SE]: age, 26.3 +/- 1.3 yr; height, 177.7 +/- 1.6 cm; weight, 77.4 +/- 0.9 kg, .VO(2)max, 56.1 +/- 1.9 ml x kg x min(-1)) undertook a maximal cycle ergometry test to exhaustion in the three conditions. Blood was taken every 3 min at the end of each stage and was analysed using the Lactate Pro LT-1710, the Accusport, the Analox GM7 and the Kodak Ektachem systems. The MANOVA (Analyser Type x Condition x Workload) indicated no interaction effect (F(42,660), = 0.45, p > 0.99, Power = 0.53). The data across all workloads indicated that the machines measured significantly differently to each other (F(4,743) = 14.652, p < 0.0001, Power = 1.00). The data were moderately to highly correlated. We conclude that the Lactate Pro is a simple and effective measurement device for taking blood lactate in a field or laboratory setting. However, we would caution against using this machine to compare data from other machines.

Adult↗
PubMed1984

The action of various hormones and metabolites upon glucose production by isolated hepatocytes from lactating and non-lactating ewes.

Glucose production was measured from hepatocytes isolated from the livers of non-mated, 20- and 50-day lactating ewes (4 animals/group) in the presence and absence of various substrates and hormones. The output of glucose was reduced at peak lactation (20-day) compared to both the unmated (P less than 0.05) and 50-day lactating groups (P less than 0.05). There was no significant difference in glucose production between the unmated and 50-day lactating groups. In the presence of glucagon (1 uM), glucose production was stimulated above control levels (P less than 0.05). However, insulin (1 uM) did not reduce glucose production compared to controls, while the effect of insulin and glucagon combined (1:1 uM) was not significantly higher than control values. Propionate, acetate and butyrate (10 mM) significantly increased glucose output above control values (P less than 0.05), in all three groups of animals. Glucose output was relatively unchanged in the presence of alanine and glutamate (10 mM), while fructose supplementation (10 mM) resulted in a significantly reduced glucose output compared to the controls (P less than 0.05).

Animals↗
PubMed1995

Gonadotropins in lactating sows exposed to long or short days during pregnancy and lactation: serum concentrations and ovarian receptors.

The objective of this study was to determine the influence of day length on gonadotropin profiles and the expression of their ovarian receptors in lactating sows. Primiparous Large White gilts were exposed to either a gradual increase (from 12 to 16 h/day, LONG treatment, n = 13) or decrease (from 12 to 8 h/day, SHORT treatment, n = 12) in photoperiod during gestation. Weaning occurred at Day 21 of lactation. All 4 sows that were submitted to the SHORT light duration and checked for postpartum estrus demonstrated an estrus by 10 days postwearing in contrast to 2 of 5 sows submitted to the LONG light duration (p < 0.05). In the remaining 16 sows, day length had no significant effect on the number of LH pulses or on mean or basal concentrations of gonadotropins (FSH and LH) or estradiol-17 beta measured at Day 20 of lactation. Ovarian receptors for gonadotropins and prolactin (PRL) and their mRNA were measured through use of receptor-binding and slot-blot analyses, respectively, at Day 21 of lactation in these 16 sows. ALONG photoperiod duration had no influence on receptor number, binding or affinity, but it significantly increased LH receptor mRNA levels (p < 0.05). However, FSH receptor mRNA levels were similar in the two groups of sows. Plasma LH concentration was positively related to LH and FSH receptor content but not to their cognate mRNA levels. Plasma concentration of FSH was positively related to the level of its own receptor mRNA as well as to that of the PRL receptor mRNA. Although the LONG day length may have delayed the return to estrus, there was no effect on gonadotropin secretion. Our results show an effect of photoperiod only on the level of LH receptor mRNA. We suggest that not all transcripts of the LH receptor are translated and that nontranslatable mRNA accumulate in ovaries of sows exhibiting delayed estrus.

Animals↗
PubMed1992

Preparation and kinetic properties of 5-ethylphenazine-lactate-dehydrogenase-NAD+ conjugate, a semisynthetic lactate oxidase showing a hide-and-seek effect.

5-Ethylphenazine-lactate-dehydrogenase-NAD+ conjugate (EP(+)-LDH-NAD+) was prepared by linking poly(ethylene glycol)-bound 5-ethylphenazine and poly(ethylene glycol)-bound NAD+ to lactate dehydrogenase. The average number of the ethylphenazine moieties bound per molecule of enzyme subunit was 0.46, and that of the NAD+ moieties was 0.32. This conjugate is a semisynthetic enzyme having lactate oxidase activity using oxygen or 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) as an electron acceptor; to make such conjugates seems to be a general method for artificially converting a dehydrogenase into an oxidase. When the concentration of oxygen or MTT is varied, the oxidase activity fits the Michaelis-Menten equation with the following kinetic constants: for the reaction system with oxygen, the turnover number per subunit is 2.3 min-1 and Km for oxygen is 1.91 mM; and for the system with MTT, the turnover number is 0.25 min-1 and Km for MTT is 0.076 mM. At the initial steady state of the oxidase reaction, only 2.1% of the NAD+ moieties of the conjugate are in the free state (i.e. not bound in the coenzyme-binding site of the lactate dehydrogenase moiety) and the rest are hidden in the coenzyme site; almost all the NAD+ moieties are in the reduced state. The apparent intramolecular rate constant for the reaction between a free NADH moiety and an oxidized ethylphenazine moiety is 2.3 s-1 and 2.1 s-1 for the systems with oxygen and with MTT, respectively. The apparent effective concentration of the free NADH moiety for the ethylphenazine moiety is 5.5 microM and is much smaller than that (0.34 mM) of the ethylphenazine moiety for the free NADH moiety; this difference is due to the effect of hiding the NADH moiety in the binding site, as the hidden NADH moiety cannot react with the ethylphenazine moiety.

Animals↗
PubMed1983

Changes in plasma vitamin A in lactating and non-lactating oral contraceptive users.

Plasma vitamin A and retinol-binding protein (RBP) concentrations have been studied in women using oral contraceptives (OC) for up to 4 years. In eight women taking an oestrogenic OC(1 mg of norethisterone acetate + 50 micrograms of ethinyloestradiol) values almost doubled within 6 months, but diminished somewhat after 4 years. Saturation of RBP with retinol remained fairly constant. Five lactating women who took progestogen-only OC (30 micrograms of levonorgestrel or 350 micrograms of norethisterone) showed no significant alteration in plasma vitamin A or RBP concentrations as compared with nine lactating non-OC users. All lactating women showed significant differences between the highest and lowest plasma vitamin A (P less than 0.005) and RBP (P less than 0.05) concentrations during the first 6 months of lactation. Highest values occurred 11-12 weeks postpartum and the lowest at 15-17 weeks. Percentage saturation of RBP with retinol was significantly higher (P less than 0.005) when vitamin A concentration was highest.

Adult↗
PubMed1992

Effect of stage of lactation and milk accumulation on mammary cell differentiation in lactating bats.

Mammary cell differentiation was measured in lactating pipistrelle bats (Pipistrellus pipistrellus) by assay of key enzyme activities, and by determination of protein and lactose synthesis rates in short-term tissue cultures. By these criteria, mammary cell differentiation did not change significantly with stage of lactation, but depended on the extent to which the gland was filled with milk. Key enzyme activities and in vitro synthesis rates were significantly higher in glands suckled immediately before tissue collection, compared with contralateral glands that were engorged with milk. This indicates that mammary cell differentiation in the lactating bat is regulated locally within each gland by a mechanism sensitive to milk accumulation, to the extent that, unlike other species, this obscures any underlying effect of stage of lactation.

Animals↗
PubMed2003

IS981-mediated adaptive evolution recovers lactate production by ldhB transcription activation in a lactate dehydrogenase-deficient strain of Lactococcus lactis.

Lactococcus lactis NZ9010 in which the las operon-encoded ldh gene was replaced with an erythromycin resistance gene cassette displayed a stable phenotype when grown under aerobic conditions, and its main end products of fermentation under these conditions were acetate and acetoin. However, under anaerobic conditions, the growth of these cells was strongly retarded while the main end products of fermentation were acetate and ethanol. Upon prolonged subculturing of this strain under anaerobic conditions, both the growth rate and the ability to produce lactate were recovered after a variable number of generations. This recovery was shown to be due to the transcriptional activation of a silent ldhB gene coding for an Ldh protein (LdhB) with kinetic parameters different from those of the native las operon-encoded Ldh protein. Nevertheless, cells producing LdhB produced mainly lactate as the end product of fermentation. The mechanism underlying the ldhB gene activation was primarily studied in a single-colony isolate of the recovered culture, designated L. lactis NZ9015. Integration of IS981 in the upstream region of ldhB was responsible for transcription activation of the ldhB gene by generating an IS981-derived -35 promoter region at the correct spacing with a natively present -10 region. Subsequently, analysis of 10 independently isolated lactate-producing derivatives of L. lactis NZ9010 confirmed that the ldhB gene is transcribed in all of them. Moreover, characterization of the upstream region of the ldhB gene in these derivatives indicated that site-specific and directional IS981 insertion represents the predominant mechanism of the observed recovery of the ability to produce lactate.

Base Sequence↗
PubMed1991

Single dose cabergoline versus bromocriptine in inhibition of puerperal lactation: randomised, double blind, multicentre study. European Multicentre Study Group for Cabergoline in Lactation Inhibition.

OBJECTIVE: To compare the efficacy and safety of a single dose of 1 mg of cabergoline with that of bromocriptine 2.5 mg twice daily for 14 days in the inhibition of puerperal lactation. DESIGN: Prospective, randomised, double blind, parallel group, multicentre study. SETTING: University of hospital departments of obstetrics and gynaecology in different European countries. SUBJECTS: 272 puerperal women not wishing to lactate (136 randomised to each drug). INTERVENTIONS: Women randomised to cabergoline received two 0.5 mg tablets of cabergoline and one placebo tablet within 27 hours after delivery and then placebo twice daily for 14 days. Those randomised to bromocriptine received 2.5 mg of bromocriptine and two placebo tablets within 27 hours and then 2.5 mg of bromocriptine twice daily for 14 days. MAIN OUTCOME MEASURES: Success of treatment (complete or partial) according to milk secretion, breast engorgement, and breast pain; rebound symptomatology; serum prolactin concentrations; and number of adverse events. RESULTS: Complete success was achieved in 106 of 136 women randomised to cabergoline and in 94 of 136 randomised to bromocriptine and partial success in 21 and 33 women respectively. Rebound breast symptomatology occurred respectively in five and 23 women with complete success up to day 15 (p less than 0.0001). Serum prolactin concentrations dropped considerably with both drugs from day 2 to day 15; a prolactin secretion rebound effect was observed in women treated with bromocriptine. cabergoline and 36 receiving bromocriptine (p = 0.054), occurring most during the first treatment day. CONCLUSION: A single 1 mg dose of cabergoline is at least as effective as bromocriptine 2.5 mg twice daily for 14 days in preventing puerperal lactation. Because of the considerably lower rate of rebound breast activity and adverse events and the simpler administration schedule cabergoline should be the drug of choice for lactation inhibition.

Adult↗