PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Lactation, Prolonged”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed2001

Mechanisms of twinning. II. Laterality and intercellular bonding in monozygotic twinning.

OBJECTIVE: To utilize observations on laterality and handedness to gain insight into the initiating mechanism of monozygotic human quadruplets. STUDY DESIGN: In a study of thumbprints and handedness in sets of monozygotic quadruplets, homolateral and heterolateral comparisons were used to distinguish mirror-image from symmetric divisions. RESULTS: Data were consistent with a mechanism involving a mirror-image duplication in the first division and a subsequent symmetric separation of the daughters. In addition, these data failed to substantiate a genetic linkage between dermatoglyphics and handedness. CONCLUSION: Reported and reviewed data tend to support the analogy of monozygotic polyembryony in armadillos and humans. The plausible roles of delayed implantation and intercellular bonding are explored, especially as they relate to ambient calcium concentration. Factors tending to enhance the likelihood of monozygotic twinning include calcium channel blockers, lactation, ovulation induction and prolonged in vitro fertilization incubation.

Dermatoglyphics↗
PubMed1976

The immune mechanism which expels the intestinal stage of Trichinella spiralis from rats.

The immunological response of rats to the intestinal phase of Trichinella spiralis was assessed using criteria derived from pervious studies with the nematode Nippostrongylus brasiliensis in rats and mice. In adult rats, the duration of infection with either parasite is similar and both infections are prolonged in young and lactating rats. As previously shown with N. brasiliensis, immunity to T. spiralis was transferred to recipients with antiserum or mesenteric lymph node cells from immune donors and antisera and cells given in combination had an additive effect. Signs of damage similar to that caused by antibodies in N. brasiliensis appeared in T. spiralis adult worms as the infection progressed and this damage occurred earlier in animals given antiserum or cells. On the basis of these results, it is concluded that the immunological control of adult T. spiralis requires both antibodies and cells, but the relative importance of these components and the way in which they affect T. spiralis requires further analysis.

Animals↗
PubMed1992

Hydroxyurea and erythropoietin therapy in sickle cell anemia.

Hydroxyurea has been shown to increase fetal hemoglobin (Hb F) production in patients with sickle cell disease and therefore has the potential to alleviate both the hemolytic and vaso-occlusive manifestations of the disease. Preliminary evidence indicates that recombinant human erythropoietin (rhEpo) may also induce Hb F. Three sickle cell anemia patients were treated with escalating doses of intravenous rhEpo and, subsequently, with daily oral hydroxyurea. After the optimal hydroxyurea dose was attained, rhEpo was added again. Two additional patients were treated with hydroxyurea alone. Treatment with rhEp, either alone or in combination with hydroxyurea, had no significant effect on the percentage of F reticulocytes or F cells. In contrast, hydroxyurea treatment was associated with a 1.5-fold to sevenfold increase in F cells and a 2.3- to 27-fold increase in the percentage of Hb F. In the three patients whose response reached a plateau, hydroxyurea treatment was associated with lessened hemolysis, decreased serum bilirubin and lactate dehydrogenase levels, and prolonged 51chromium-labeled RBC survival. Hydroxyurea treatment also resulted in decreased numbers of irreversibly sickled cells and in decreased sickling at partial oxygen saturation, increased oxygen affinity, increased total RBC cation content, and diminished potassium:chloride co-transport. All five patients treated with hydroxyurea experienced a decrease in severity and frequency of painful sickle crises. This study confirms that hydroxyurea therapy increases Hb F production and provides objective evidence of a significant reduction in hemolytic rate and intracellular polymerization. In contrast, rhEpo, either alone or in combination with hydroxyurea, offered no measurable benefit. Based on these encouraging preliminary data, large-scale, controlled clinical trials are warranted to study the safety and efficacy of hydroxyurea in the treatment of sickle cell disease.

Administration, Oral↗
PubMed2004

Effect of lactate infusion on M-wave characteristics and force in the rat plantaris muscle during repeated stimulation in situ.

It is unclear whether accumulation of lactate in skeletal muscle during exercise contributes to muscle fatigue. The purpose of the present study was to examine the effect of lactate infusion on muscle fatigue during prolonged indirect stimulation in situ. For this purpose, the plantaris muscle was electrically stimulated (50 Hz, for 200 ms, every 2.7 s, 5 V) in situ through the sciatic nerve to perform concentric contractions for 60 min while either saline or lactate was infused intravenously (8 rats/group). Lactate infusion (lactate concentration approximately 12 mM) attenuated the reduction in submaximal dynamic force (-49 vs. -68% in rats infused with saline; P < 0.05). Maximum dynamic and isometric forces at the end of the period of stimulation were also higher (P < 0.05) in rats infused with lactate (3.8 +/- 0.3 and 4.4 +/- 0.3 N) compared with saline (3.1 +/- 0.2 and 3.6 +/- 0.2 N). The beneficial effect of lactate infusion on muscle force during prolonged stimulation was associated with a better maintenance of M-wave characteristics compared with control. In contrast, lactate infusion was not associated with any reduction in muscle glycogen utilization or with any reduction of fatigue at the neuromuscular junction (as assessed through maximal direct muscle stimulation: 200 Hz, 200 ms, 150 V).

Animals↗
PubMed1975

Mechanism for the paradoxical aciduria following alkali administration to prolonged-fasted patients.

Rapidly induced systemic alkalinization due to either sodium-lactate or sodium-bicarbonate infusion in prolonged-fasted subjects with steady-state ketoacidosis was associated with a decrease in urine pH. This decrease in urine pH from 5.50 to 5.20 was the result of a significant decrease in urinary ammonium excretion from 8.40 to 6.35 mEg/hr and was not accompanied by an increase in net acid excretion (11.3 vs. 10.6 mEg/hr). The decreased ammonium excretion is attributed to the raised pH of the proximal tubular fluid resulting in a less favorable pH gradient for gaseous ammonia entry. This would decrease gaseous ammonia generated in the loop of Henle for collecting duct buffering of secreted hydrogen ions.

Acidosis↗
PubMed2006

Nitric oxide production in the basal forebrain is required for recovery sleep.

Sleep homeostasis is the process by which recovery sleep is generated by prolonged wakefulness. The molecular mechanisms underlying this important phenomenon are poorly understood. Here, we assessed the role of the intercellular gaseous signaling agent NO in sleep homeostasis. We measured the concentration of nitrite and nitrate, indicative of NO production, in the basal forebrain (BF) of rats during sleep deprivation (SD), and found the level increased by 100 +/- 51%. To test whether an increase in NO production might play a causal role in recovery sleep, we administered compounds into the BF that increase or decrease concentrations of NO. Infusion of either a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, or a NO synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), completely abolished non-rapid eye movement (NREM) recovery sleep. Infusion of a NO donor, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2diolate (DETA/NO), produced an increase in NREM that closely resembled NREM recovery after prolonged wakefulness. The effects of inhibition of NO synthesis and the pharmacological induction of sleep were effective only in the BF area. Indicators of energy metabolism, adenosine, lactate and pyruvate increased during prolonged wakefulness and DETA/NO infusion, whereas L-NAME infusion during SD prevented the increases. We conclude that an increase in NO production in the BF is a causal event in the induction of recovery sleep.

Adenosine↗
PubMed2006

Ovarian activity and oestrous signs among group-housed, lactating sows: influence of behaviour, environment and production.

Animal welfare concerns require the development of housing systems that allow the animals to express their natural behaviour. One example of this is the group-housing system for lactating sows. The present study aimed at exploring ovarian activity in such a system. Thirty-eight sows farrowing individually outdoors during spring and summer, and indoors during autumn and winter, and group-housed in groups of four during weeks 3-7 of the lactation period, were monitored regarding reproductive functions, behaviour and production during their first to fourth lactation period. Average ovulation frequency during lactation was 47%. Only 50% of these ovulating cases were accompanied by a standing oestrus. Lactational ovulation frequency was higher in later parities (p < 0.001). Ovulation frequency was higher (p < 0.05) during winter (74%) and spring (69%), than during summer (10%) and autumn (23%). Occurrence of lactational ovulation was associated with some aspects of suckling behaviour and also with litter weight gain (p < 0.05). Forty-nine per cent of the lactational ovulations occurred during the seventh week of lactation. Timing of ovulation seemed positively (p = 0.08) associated with weight loss during lactation. Compared with the sows that were anoestrus during lactation, oestradiol-17beta values were higher (p < 0.05) only in the week before occurrence of lactational ovulation. Weaning-to-oestrous interval was prolonged (p < 0.05) among the sows that ovulated during lactation. The present study identifies several factors influencing ovarian activity among group-housed sows, thereby providing tools for the control of lactational ovulation in group-housing systems.

Animal Husbandry↗
PubMed1998

Breastfeeding provides passive and likely long-lasting active immunity.

OBJECTIVES: The reader of this review will learn about the mechanisms through which breastfeeding protects against infections during and most likely after lactation, as well as possibly against certain immunologic diseases, including allergy. DATA SOURCES: I have followed the literature in the area closely for the last 30 to 40 years and have made repeated literature searches through MEDLINE, most recently in 1998. Textbooks and peer-reviewed journals have been sought for, as well as books representing meeting reports in English, French, German, and Spanish. RESULTS: Human milk protects against infections in the breastfed offspring mainly via the secretory IgA antibodies, but also most likely via several other factors like the bactericidal lactoferrin. It is striking that the defense factors of human milk function without causing inflammation, some components are even directly anti-inflammatory. Protection against infections has been well evidenced during lactation against, e.g., acute and prolonged diarrhea, respiratory tract infections, otitis media, urinary tract infection, neonatal septicemia, and necrotizing enterocolitis. There is also interesting evidence for an enhanced protection remaining for years after lactation against diarrhea, respiratory tract infections, otitis media, Haemophilus influenzae type b infections, and wheezing illness. In several instances the protection seems to improve with the duration of breastfeeding. Some, but not all studies have shown better vaccine responses among breastfed than non-breastfed infants. A few factors in milk like anti-antibodies (anti-idiotypic antibodies) and T and B lymphocytes have in some experimental models been able to transfer priming of the breastfed offspring. This together with transfer of numerous cytokines and growth factors via milk may add to an active stimulation of the infant's immune system. Consequently, the infant might respond better to both infections and vaccines. Such an enhanced function could also explain why breastfeeding may protect against immunologic diseases like coeliac disease and possibly allergy. Suggestions of protection against autoimmune diseases and tumors have also been published, but need confirmation. CONCLUSIONS: Breastfeeding may, in addition to the well-known passive protection against infections during lactation, have a unique capacity to stimulate the immune system of the offspring possibly with several long-term positive effects.

Breast Feeding↗
PubMed1990

Lack of changes in cytosolic ionized calcium in primary cultures of rat kidney cortical cells exposed to cytotoxic concentrations of gentamicin.

Gentamicin nephrotoxicity in vivo has a delayed onset. Our assessment of gentamicin-induced cell death in vitro, by measuring the release of cytosolic lactate dehydrogenase (LDH), indicated a prolonged onset as well. A recent study, which showed that gentamicin caused an abrupt increase in the concentration of cytosolic free calcium ([Ca2+]i) in a trypsin-harvested kidney cell line, suggested that immediate changes in calcium homeostasis may initiate the pathogenesis of gentamicin nephrotoxicity. To study the immediate effect of gentamicin on [Ca2+]i, gentamicin was perfused for 1 hr over primary monolayer cultures of renal cortical epithelial cells, and suspensions of trypsin-harvested renal cells (from primary cultures and a cell line) were treated with gentamicin for 30 min. [Ca2+]i was determined using the fluorescent probe fura-2. Positive controls (ionomycin and mercury) reliably increased [Ca2+]i in each experimental model, but no increase in [Ca2+]i was observed with gentamicin. Because enzyme release data indicated that significant cytotoxicity did not occur until 48 hr of exposure to 2 mM gentamicin, primary cultures were exposed to gentamicin (1-2 mM) for 24-48 hr and [Ca2+]i was measured. No gentamicin-induced increase in [Ca2+]i was observed in these longer exposures, whether or not significant LDH release occurred. These results do not support a role for elevated [Ca2+]i in the cytotoxicity of gentamicin in cultured kidney cells, either immediately after exposure or following prolonged exposures.

Animals↗
PubMed1989

Effects of lactic acidosis on the function of cerebral cortical synaptosomes.

Synaptosomes exposed to anoxic insult produce lactate at a slow rate (measured over 60 min). No measurable damaging effects were produced by prolonged depolarisation, anoxic insult, or exogenous lactate (2-32 mM) either on the synaptic plasma membrane (as judged by release of lactate dehydrogenase and soluble proteins), or on synaptosomal phospholipases (as judged by choline release from membrane phospholipids). Potassium-stimulated acetylcholine release was decreased by incubation in the presence of lactate (2-32 mM), as was potassium- and veratrine-stimulated calcium uptake and the calcium content of depolarised synaptosomes. The intrasynaptosomal pH was also reduced but there was no stimulation of oxygen radical production (as judged by H2O2 generation) by exogenous lactate. The role that lactic acidosis may play in giving rise to the altered calcium homeostasis and decreased acetylcholine release from synaptosomes exposed to anoxic insult is discussed.

Acetylcholine↗
PubMed2000

Effects of beta-hydroxy-beta-methylbutyrate on muscle damage after a prolonged run.

This study examined the effects of supplemental beta-hydroxy-beta-methylbutyrate (HMB) on muscle damage as a result of intense endurance exercise. Subjects (n = 13) were paired according to their 2-mile run times and past running experience. Each pair was randomly assigned a treatment of either HMB (3 g/day) or a placebo. After 6 wk of daily training and supplementation, all subjects participated in a prolonged run (20-km course). Creatine phosphokinase and lactate dehydrogenase (LDH) activities were measured before and after a prolonged run to assess muscle damage. The placebo-supplemented group exhibited a significantly greater (treatment main effect, P = 0.05) increase in creatine phosphokinase activity after a prolonged run than did the HMB-supplemented group. In addition, LDH activity was significantly lower (treatment main effect, P = 0.003) with HMB supplementation compared with the placebo-supplemented group. In conclusion, supplementation with 3.0 g of HMB results in a decreased creatine phosphokinase and LDH response after a prolonged run. These findings support the hypothesis that HMB supplementation helps prevent exercise-induced muscle damage.

Adult↗
PubMed1999

Effects of ebselen on cerebral ischemia and reperfusion evaluated by microdialysis.

Since ebselen is known to have glutathione peroxidase-like activity and inhibitory effects on lipoxygenase and cyclo-oxygenase, we investigated its protective effects against cerebral ischemia in the rat using microdialysis. Ebselen was given through a gastric tube 30 min before occlusion in the experimental groups. Ischemia was induced using 4-vessel occlusion either transiently (20-min occlusion of the arteries followed by reperfusion), or over a prolonged period (120-min occlusion). Extracellular lactate, pyruvate and purine catabolites were sampled using microdialysis and measured by high performance liquid chromatography. During ischemia, the level of lactate, adenosine, inosine and hypoxanthine in the control group increased markedly. The lactate: pyruvate ratio increased during ischemia and decreased after reperfusion. Although the level of lactate and adenosine decreased immediately after reperfusion, those of inosine and hypoxanthine showed delayed decrease. Ebselen reduced the maximum values of lactate and purine catabolites significantly and markedly in transient ischemia. Although it reduced the values significantly in prolonged ischemia, the decrements were less marked than those in transient ischemia. Based on these results we consider ebselen to protect against ischemic metabolic changes and to accelerate the recovery during reperfusion.

Animals↗
PubMed1993

Interstitial lactate and glucose concentrations of the isolated perfused rat heart before, during and after anoxia.

In isolated rat hearts perfused according to the Langendorff technique lactate and glucose concentrations were determined in the interstitial transudate and the venous effluent before, during and after periods of 15 or 30 min anoxia. The interstitial transudate emerged at the surface of the heart as a result of albumin-free perfusion. During normoxic perfusion the interstitial lactate concentration was 0.144 +/- 0.025 mmol/l (n = 6); the venous lactate concentration was 0.033 +/- 0.005 mmol/l. From the interstitial and the mean vascular concentration, together with the lactate release and the glucose uptake, the apparent permeability surface area products (P.S product) were calculated using Fick's law. The apparent P.S products for lactate and glucose were 4.6 and 3.9 ml/(min x g), respectively. During anoxia we measured a four- to sixfold increase of the interstitial lactate concentration. At the end of the anoxic periods the apparent P.S product was two- to threefold higher than during normoxia; the apparent glucose P.S product increased about fourfold. After 15 min anoxia the increases of permeability were completely reversed in the reoxygenation period. However, after a period of 30 min anoxia the apparent P.S products for lactate and glucose remained raised, which means that there was a prolonged or even irreversible increase of capillary permeability. Besides the marked transcapillary concentration difference for lactate, these data show prolonged functional alteration of the capillary wall after 30 min anoxia.

Animals↗
PubMed2006

C5-blocking antibody reduces fluid requirements and improves responsiveness to fluid infusion in hemorrhagic shock managed with hypotensive resuscitation.

Hypotensive resuscitation strategies and inhibition of complement may both be of benefit in hemorrhagic shock. We asked if C5-blocking antibody (anti-C5) could diminish the amount of fluid required and improve responsiveness to resuscitation from hemorrhage. Awake, male Sprague-Dawley rats underwent controlled hemorrhage followed by prolonged (3 h) hypotensive resuscitation with lactated Ringer's or Hextend, with or without anti-C5. Anti-C5 treatment led to an estimated 62.3 and 58.5% reduction in the volume of Hextend and lactated Ringer's, respectively. In the subgroup of animals with a positive mean arterial pressure (MAP) response to fluid infusion following prolonged hypotension, anti-C5 treatment led to an estimated 4.7- and 4.1-fold increase in mean arterial pressure response per unit Hextend and lactated Ringer's infused, respectively. We observed no significant postresuscitation metabolic differences between the anti-C5 groups and controls. Whether anti-C5 could serve as a volume-sparing adjunct that improves responsiveness to fluid administration in humans deserves further study.

Animals↗
PubMed1996

-Myocardial protection by preconditioning. Experimental and clinical significance-.

Short periods of ischemia render the myocardium more resistant to a subsequent prolonged coronary occlusion resulting in a reduction of infarct size. This cardioprotective mechanism has been called ischemic preconditioning. Acute myocardial ischemia results in a rapid decline of high energy phosphates. After short periods of ischemia the high energy phosphate levels are better preserved and the increase of lactate is slower during the prolonged subsequent ischemia in the preconditioned group compared to control. The duration of ischemia needed for induction of the protective effect is 2.5 min in dogs and 20 min in our swine model. In porcine myocardium the protection is lost about 1 h after induction and a renewal is not possible at that time, but is 24 h later. For rabbits or dogs, but not in pigs, a late protection 24 h after induction or preconditioning has been shown ("second window of protection"). Adenosine or adenosine A1 receptor agonists, muscarinic M2 receptor agonists, alpha 1-receptor agonists and bradykinin B2 receptor agonists as well as opening of the K+ATP-channel substitute for ischemia in the induction of protection. Activation of protein kinase C results in protection in rats and rabbits, but not in dogs or pigs. Inhibition of protein kinase C translocation or kinase activity results in a loss of the protection induced by preceding ischemia. After blockade of the K+ATP-channel the protection induced by adenosine A1 receptor activation is lost. Therefore opening of the K+ATP-channel is a prerequisite for induction of the protective effect. Inhibition of the inhibitory G-protein by pertussis toxin has been shown to result in a loss of protection, therefore the Gi-protein seems to be involved in the evolution of protection. In humans during coronary angioplasty anginal pain and lactate production during a second balloon occlusion is diminished without any change in the regional myocardial perfusion. This adaptation is inhibited by blockade of the K+ATP-channel or of the adenosine A1 receptor. Intermittent cross-clamping before a longer occlusion during open-heart surgery results in a better preservation of high energy phosphates compared to controls without preceding short ischemia. These observations support the hypothesis that ischemic preconditioning also occurs in humans. Angina pectoris preceding the myocardial infarction may have preconditioned the human heart against the subsequent myocardial infarction, but studies concerning the influence of angina pectoris on short-term outcome after thrombolysis are conflicting. In the future, ischemic preconditioning or preconditioning with drugs may prolong the duration of ischemia tolerated without necrosis and improve the prognosis of patients by reducing the infarct size.

Adenosine Triphosphate↗
PubMed2006

Discordance between lactate and base deficit in the surgical intensive care unit: which one do you trust?

PURPOSE: Both lactate and base deficit (BD) are used as predictors of injury severity and mortality. We examined the significance of these measures when used in combination, and particularly when they provide conflicting data. METHODS: We reviewed all intensive care unit patients with simultaneously obtained lactate and BD measurements. The ability to predict mortality and hospital stay was compared alone, in combination, and when there was disagreement between the measures. Receiver operating characteristic curves were generated to compare predictive abilities. RESULTS: There were 1,298 patients with 12,197 sets of paired laboratory data; 1,026 trauma patients and 272 surgical patients. Lactic acidosis was present in 41% and a significant BD level (> 2) was found in 52%. Nonsurvivors had higher admission lactate (6.2 vs. 3.3) and base deficit (6.1 vs. 3.2) levels than survivors (both P < .01), with a modest correlation (r = .52) between the measures. The admission lactate and BD levels had similar predictive ability for mortality, with areas under the receiver operating characteristic curve of .7 and .66, respectively (both P < .01). However, the predictive ability of the BD level decreased significantly during the intensive care unit stay (area, .5) compared with lactate level (area, .68). Lactate and BD levels disagreed in 44% of all laboratory sets. In patients with a normal lactate level (< 2.2), the BD level had no predictive ability for mortality (area, .48; P = .26). However, in patients with a normal BD level (< 2.0), the lactate level retained its predictive ability for mortality (area, .67; P < .01). Lengths of stay were longer among patients with an increased lactate level, even when the BD level was normal. There was no improvement in predictive ability using a combination of the 2 measures. CONCLUSIONS: Both lactate and BD levels may be used to identify lactic acidosis and predict mortality at admission. Increased lactate levels predict mortality and a prolonged course regardless of the associated BD level, whereas an increased BD level has no predictive value if the lactate level is normal.

Acid-Base Imbalance↗
PubMed1999

Comparison of the "nursing" and other parental behaviors of nulliparous and lactating female rats.

Virgin female rats display maternal behaviors after continuous exposure to pups (sensitization) that are in some respects similar to those of postpartum females. We herein provide a detailed comparison of the "nursing" and other parental behaviors of maternally sensitized virgin females and postpartum lactating dams. Ovariectomized and intact virgin females were exposed to pups until displaying maternal behavior. On the females' fourth day of maternal responsiveness, the pups were removed for 3 h and then returned, and subject-litter interactions were observed for 45 min. Behavior of maternal virgins was compared with that of lactating dams observed on day 4 postpartum interacting with either suckling pups or pups unable to suckle due to perioral anesthesia. Ovariectomy had no effect on behavior of virgins. Retrieval and licking of pups were deficient in virgins compared with lactating dams. Suckled dams showed prolonged kyphosis (upright crouched nursing), whereas nonsuckled dams displayed little kyphosis but rather were often in a hunched position over pups. Some aspects of quiescent "nursing" behaviors of virgins were surprisingly similar to those of suckled dams, including the latency to and duration of quiescence. Nonsuckling pup stimulation elicited more kyphosis in virgins than in lactating dams, which was still much less than in suckled dams. Virgins also "nursed" pups in hunched and prone postures. Differences between sensitized and postpartum females in their maternal behaviors likely reflect differences in motivation as well as sensory inputs they receive from pups. In particular, sensory regulation of "nursing" behaviors is influenced by reproductive state because nonsuckling pups elicit different postural responses in sensitized and lactating mothers.

Animals↗