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PubMed1986

Mechanism of renal peritubular extraction of plasma glutathione. The catalytic activity of contralumenal gamma-glutamyltransferase is prerequisite to the apparent peritubular extraction of plasma glutathione.

To clarify the peritubular mechanism for renal handling of plasma glutathione (GSH), variation of GSH levels in plasma, urine, kidney and liver was examined after intravenous administration of GSH to three groups of animals; control, acivicin-treated and rats treated with buthionine sulfoximine (BSO). Treatment of animals with BSO, a potent inhibitor of de novo GSH synthesis, markedly reduced hepatorenal GSH levels. Acivicin did not affect these levels. Upon intravenous injection of GSH (0.1 mmol/kg), renal GSH levels did not appreciably change in any of three animal groups. The rate of GSH disappearance from the circulation was rapid in control and BSO-treated rats, while it was markedly retarded in animals whose renal gamma-glutamyltransferase was extensively inactivated by acivicin. At 30 min after administration a significant amount of injected GSH was localized extracellularly (urine and plasma) in acivicin-treated animals. By contrast, most of the GSH rapidly disappeared from the extracellular space in control and BSO-treated animals. Together with the immunocytochemical evidence for the peritubular gamma-glutamyltransferase [Spater, H.W., Poruchynsky, M.S., Quintana, N., Inoue, M. & Novikoff, A.B. (1982) Proc. Natl Acad. Sci. USA 79, 3547-3550] the present results are fully consistent with the contention that the catalytic function of this enzyme is principally responsible for the peritubular mechanism for the renal handling of plasma GSH.

Animals↗
PubMed1987

Relations between plasma membrane and lysosomal membrane. 1. Fate of covalently labelled plasma membrane protein.

To quantify the kinetics of the plasma membrane flow into lysosomes, we covalently labelled at 4 degrees C the pericellular membrane of rat fibroblasts and followed label redistribution to the lysosomal membrane using purified lysosomal preparations. The polypeptides were, either labelled with 125I by the lactoperoxidase procedure, or conjugated to [3H]peroxidase using bisdiazobenzidine as a bifunctional reagent. Both labels were initially bound to plasma membrane, as indicated by their equilibrium density in sucrose or Percoll gradients and their displacement by digitonin, as well as by electron microscopy. Upon cell incubation at 37 degrees C, both covalent labels were lost from cells with diphasic kinetics: a minor component (35% of cell-associated labels) was rapidly released (half-life less than 1 h), and most label (65%) was released slowly (half-life was 20 h for incorporated 125I and 27 h for 3H). Immediately after labelling up to 30 h after incubation at 37 degrees C, the patterns of 125I-polypeptides quantified by autoradiography after SDS-PAGE were indistinguishable, indicating no preferential turnover for the major plasma membrane polypeptides. The redistribution of both labels to lysosomes was next quantified by cell fractionation. At equilibrium (between 6 and 25 h of cell incubation) 2-4% of cell-associated 125I label was recovered with the purified lysosomal membranes. By contrast, when 3H-labelled cells were incubated for 16 h, most of the label codistributed with lysosomes. However, only 6% of cell-associated 3H was bound to lysosomal membrane. These results indicate that in cultured rat fibroblasts, a minor fraction of plasma membrane polypeptides becomes associated with the lysosomal membrane and is constantly equilibrated by membrane traffic.

Acetylglucosaminidase↗
PubMedDate not supplied

Effect of calmodulin-like protein from buffalo (Bubalus bubalis) seminal plasma on Ca2+, Mg(2+)-ATPase of purified plasma membrane of buffalo spermatozoa.

Buffalo sperm heads and tails were cleaved by sonication and isolated in relatively pure proportions i.e. 95% and 98% respectively, by discontinuous sucrose density-gradient centrifugation. Purified plasma membranes from the isolated sperm heads and tails were obtained by hypotonic treatment and brief sonication followed by discontinuous sucrose density-gradient centrifugation. Ca2+, Mg(2+)-ATPase activity was evident in plasma membrane from sperm heads and tails, although activity was greater in the latter. A calmodulin-like protein isolated from buffalo seminal plasma increased the Ca2+, Mg(2+)-ATPase of plasma membrane from the sperm heads and tails by 128 and 136% respectively. Based upon the data obtained here and elsewhere (Sidhu & Guraya, 1989a) a model is proposed which explains regulation of Ca2+ in buffalo spermatozoa and implicates calmodulin-like protein and Ca2+, Mg(2+)-ATPase in sperm acrosome reaction.

Animals↗
PubMed2006

IgG2 containing IgM-IgG immune complexes predominate in normal human plasma, but not in plasma of patients with warm autoimmune haemolytic anaemia.

The different physicochemical and sterical properties of IgG subclasses may favour a selective enrichment of defined IgG subclasses in IgM-IgG immune complexes (IC) of human plasma under physiological conditions. Such enrichment of IgG subclasses in IgM-IgG IC of plasma may differ from the normal IgG subclass distribution in plasma itself, and contribute to the physiological functions of IgM-IgG IC. Systematic studies on the IgG subclass distribution in IgM-IgG IC in humans are lacking. Using specific analytical techniques to characterise IgM-IgG IC in human plasma (i.e. fast protein liquid chromatography, enzyme-linked immunosorbent assay, affinity biosensor technology), and taking warm autoimmune haemolytic anaemia (WAIHA) of humans as a disease model, we here demonstrate that: (i) IgG2 is the predominant IgG subclass in IgM-IgG IC under physiological conditions, (ii) the predominance of IgG2 within IgM-IgG IC may get lost in polyclonal IgG-mediated autoimmune disease and (iii) the IgG subclass distribution in IgM-IgG IC influences the interaction between IC and blood cells involved in antigen presentation. The data presented here therefore extend the physiological function of IgG2, which is the protective immune response towards carbohydrate antigens in bacterial infections, and suggest IgG2-dependent regulation of immune responses to self-immunoglobulin in humans. The disturbed IgG subclass distribution in IgM-IgG IC of patients with WAIHA might influence activity of self-reactive B cells involved in the pathophysiology of the disease.

Adult↗
PubMed1983

Separation of plasma kallikrein and a kallikrein-like plasminogen activator generated by acetone in rat plasma.

Plasminogen activator (PGA), kininogenase (Kase) and benzoyl arginine ethyl ester (BAEe) activities generated in plasminogen-free rat plasma by incubation with acetone (23% v/v) at 22 degrees were purified. The activities passed unadsorbed through columns of DEAE-Sephadex A-50 (pH 7.8) and arginine methylester-Sepharose 4B (pH 8.5). Part of the activities (rat plasma kallikrein) was adsorbed onto a soybean trypsin inhibitor (SBTI)-Sepharose 4B column at pH 8.5. At pH 7.0 a fraction with higher ratios PGA/BAEe esterase and Kase/BAEe esterase was also adsorbed. Both fractions could be eluted with 5 mM sodium hydroxide. The fraction not adsorbed at pH 8.5, but adsorbed at pH 7.0 was designated low molecular weight plasminogen activator (LMr-PGA), a plasminogen activator fraction with higher molecular weight, but without esterase activity being also present (Berstad & Briseid 1982). LMr-PGA was strongly inhibited by tranexamic acid (AMCA) 0.10 mM, whereas the fraction designated rat plasma kallikrein was not. By polyacrylamide gel electrophoresis Mr-values in the range 120,000 to 130,000 were established for native samples of both rat plasma kallikrein and LMr-PGA, whereas Mr-values of 78,000 to 80,000 were established after treatment with SDS.

Acetone↗
PubMed1997

Plasma and tissue levels of lipids, fatty acids and plasma carnitine in neonates receiving a new fat emulsion.

This study was undertaken to compare Intralipid with a new fat emulsion containing gamma-linolenic acid and carnitine, named Pediatric Fat Emulsion 4501, in neonates with regard to lipid and carnitine metabolism over a short period of total parenteral nutrition. There were 10 neonates in each group and they tolerated the total parenteral nutrition well. In spite of the gamma-linolenic acid supplementation in the new emulsion, arachidonic acid decreased significantly in plasma lipid esters and adipose tissue in both groups after 5 d of treatment. Also, there was a decrease in plasma docosahexaenoic acid which was more pronounced in the treatment group. The relative percentage values of linoleic and linolenic acids in adipose tissue were increased, indicating that newborns have a rapid accretion of fatty acids. Plasma-triglycerides were effectively cleared during the periods without fat infusion. In the group that received Pediatric Fat Emulsion 4501 the means of both free and total plasma carnitine concentrations increased significantly, whereas they tended to decrease in the Intralipid group.

Adipose Tissue↗
PubMed1988

Plasma pattern of growth hormone regulates sexual differentiation of phosphatidylcholine in rat plasma.

The effects of continuous and intermittent administration of human growth hormone (hGH) in the regulation of plasma phosphatidylcholine fatty acid composition was studied in adult hypophysectomized male and female Sprague-Dawley rats. Human GH was given for 7 days, either continuously by means of Alzet osmotic minipumps implanted s.c. or intermittently by means of s.c. injections at 12-h intervals. The 'masculinizing' effect of hypophysectomy on the fatty acid composition of plasma phosphatidylcholine in female rats, i.e. an increase in the proportions of palmitic and linoleic acids and a decrease in the proportions of stearic and arachidonic acids, was to a large extent reversed by continuous administration of hGH, while intermittent administration had no consistent effect. This effect of continuous hGH administration similar effect of continuous administration of hGH was also observed in hypophysectomized male rats. Prolactin had no effect on the fatty acid composition of phosphatidylcholine. Replacement therapy with thyroid hormones and glucocorticoids had a small effect on the proportions of palmitic and stearic acids in plasma phosphatidylcholine. It is concluded that the more continuous secretory pattern of GH in female rats is involved in the sexual differentiation of the fatty acid composition of plasma phosphatidylcholine.

Animals↗
PubMed1990

Alterations in plasma volume, plasma constituents, renin activity and aldosterone induced by maximal exercise in the horse.

Plasma volume (PV) decreased by 13 per cent following the completion of 1,000 m of maximal exercise in the horse. This study demonstrated that the critical reduction in PV following maximal exercise occurred within 10 mins of completion of exercise, as previously reported in man. Total plasma protein (TPP) increased by 23 per cent at 2 and 5 mins, and by 21 per cent at 10 mins post exercise. Therefore, it does not appear to be an accurate measurement to assess the degree of PV contraction in the horse. Protein was apparently added to the intravascular space either during or following exercise. The changes in osmolality correlated strongly with those in sodium, which is the primary determinant of alterations in plasma tonicity. The increase in osmolality (12 per cent) was similar to the reduction in PV (13 per cent) concluding that a transient hypotonic fluid loss had occurred. The increase in plasma renin activity (PRA) following maximal exercise was followed by an increase in aldosterone (ALD) concentration in both magnitude and time course. Alterations in PV should be considered when interpreting electrolyte and serum enzyme activity data collected following maximal exercise.

Aldosterone↗
PubMed1993

Increased plasma thyroid stimulating hormone in treated congenital hypothyroidism: relation to severity of hypothyroidism, plasma thyroid hormone status, and daily dose of thyroxine.

Plasma thyroid stimulating hormone (TSH) concentrations obtained during the first four years of treatment in 418 children with congenital hypothyroidism, identified by neonatal screening, were examined in relation to paired measurements of plasma thyroxine (n = 1945), free thyroxine (n = 836), triiodothyronine (n = 480), and free triiodothyronine (n = 231), and estimated daily dose of thyroxine at the time of blood sampling. Overall, plasma TSH was above 7 mU/l in 1280 out of 2960 samples (43%); the percentage was not related to severity of hypothyroidism at diagnosis. Mean values for thyroxine and free thyroxine, and to a lesser extent free triiodothyronine, were consistently lower in samples with TSH concentrations over 7 mU/l and this was the case in patients with either severe or less severe hypothyroidism. Raised TSH concentrations were also associated with lower mean doses of thyroxine (micrograms/kg/day) but here the mean doses of thyroxine in children with severe hypothyroidism were higher than in the children with less severe hypothyroidism. The mean dose of thyroxine associated with low/normal TSH values was highest in the first 6 months and fell progressively. Thyroxine dose was significantly related to thyroxine and free thyroxine concentrations but not to triiodothyronine and free triiodothyronine and the latter appeared to be of limited value as measures of plasma thyroid hormone status during treatment.

Child, Preschool↗
PubMed1987

The use of a bovine plasma progesterone ELISA kit to measure progesterone in equine, ovine and canine plasmas.

A commerical kit designed to measure the concentration of progesterone in bovine plasma using an enzyme-linked immunosorbent assay (ELISA) has been assessed for measuring progesterone in the plasma of horses, sheep and dogs. Without validation, an immunoassay developed for progesterone in one species should not be used to measure progesterone in the plasma of other species. The kit was assessed by using the criteria of parallelism to a standard curve, the recovery of added progesterone, the correlation with an established radioimmunoassay and the detection of physiological change for each of the species tested. The ELISA kit proved to be acceptable for the analysis of progesterone in the plasma of each species, and in particular for the detection of the low concentrations found during the follicular phase and of the subsequent rise during the luteal phase of the oestrous cycle.

Animals↗
PubMed1990

Infusion of iso-rANP(1-45) or (17-45) increases plasma immunoreactive ANP and lowers plasma renin activity and aldosterone.

We have reported that a second rat atrial natriuretic peptide, iso-rANP (1-45), as well as the putative ANP homologue, iso-rANP (17-45), elicited circulatory and renal responses in the rat similar to those found after administration of ANP. Iso-rANP also interacted with ANP to potentiate the observed biological activity in the rat. In the present studies in awake dogs, intravenous infusion of low doses (6.3-50 pmol.kg-1.min-1) of iso-rANP(1-45) and iso-rANP(17-45) increased plasma immunoreactive ANP and suppressed plasma renin activity (PRA) and aldosterone. Iso-rANP, like ring-deleted analogues of ANP, may have displaced ANP from ANP clearance receptors to increase plasma ANP concentration, since factors influencing myocardial ANP release were not changed. The effect of iso-rANP (1-45) and (17-45) in lowering PRA and plasma aldosterone may therefore have been indirect, via ANP stimulation of active guanylate cyclase-linked ANP receptors. However, an additional direct effect of iso-rANP on an active receptor cannot be excluded.

Aldosterone↗
PubMed2005

Vasopressin gene transcription increases in response to decreases in plasma volume, but not to increases in plasma osmolality, in chronically dehydrated rats.

The synthesis of arginine vasopressin (AVP) in the magnocellular neurons of the supraoptic (SON) and paraventricular nuclei (PVN) is physiologically regulated by plasma osmolality and volume. To clarify how the regulation of AVP gene transcription is affected by chronic dehydration, we examined changes in the transcriptional activities of AVP gene by plasma osmolality and volume in both euhydrated and dehydrated conditions. Euhydrated rats had free access to water, whereas dehydrated rats had been deprived of water for 3 days before experiments. Rats in both conditions were subjected to acute hypertonic stimuli or hypovolemia, and changes in AVP heteronuclear (hn)RNA levels, an indicator of gene transcription, in the SON and PVN were examined with in situ hybridization. The intraperitoneal (i.p.) injection (2% body wt) of hypertonic (1.5 M) saline increased plasma Na levels by approximately 40 meq/l in both euhydrated and dehydrated conditions. However, expression levels of AVP hnRNA in the SON and PVN were increased only in euhydrated, not dehydrated, rats. On the other hand, i.p. injection of polyethylene glycol decreased the plasma volume by approximately 16-20%, and AVP hnRNA levels in the SON and PVN were significantly increased in both conditions. Thus it is demonstrated that signaling pathways regulating AVP gene transcription in the magnocellular neurons were completely refractory to acute osmotic stimuli under the chronic dehydration and that AVP gene transcription could probably respond to acute hypovolemia through different intracellular signal transduction pathways from those for osmoregulation.

Animals↗
PubMed2004

Leptin treatment markedly increased plasma adiponectin but barely decreased plasma resistin of ob/ob mice.

Adiponectin (ApN) and leptin are two adipocytokines that control fuel homeostasis, body weight, and insulin sensitivity. Their interplay is still poorly studied. These hormones are either undetectable or decreased in obese, diabetic ob/ob mice. We examined the effects of leptin treatment on ApN gene expression, protein production, secretion, and circulating levels of ob/ob mice. We also briefly tackled the influence of this treatment on resistin, another adipocytokine involved in obesity-related insulin resistance. Leptin-treated (T) obese mice (continuous sc infusion for 6 days) were compared with untreated lean (L), untreated obese (O), and untreated pair-fed obese (PF) mice. Blood was collected throughout the study. At day 3 or day 6, fat pads were either directly analyzed (mRNA, ApN content) or cultured for up to 24 h (ApN secretion). The direct effect of leptin was also studied in 3T3-F442A adipocytes. Compared with L mice, ApN content of visceral or subcutaneous fat and ApN secretion by adipose explants were blunted in obese mice. Accordingly, plasma ApN levels of O mice were decreased by 50%. Leptin treatment of ob/ob mice increased ApN mRNAs, ApN content, and secretion from the visceral depot by 50-80%. Leptin also directly stimulated ApN mRNAs and secretion from 3T3-F442A adipocytes. After 6 days of treatment, plasma ApN of ob/ob mice increased 2.5-fold, a rise that did not occur in PF mice. Plasma resistin of T mice was barely decreased. Leptin treatment, but not mere calorie restriction, corrects plasma ApN in obese mice by restoring adipose tissue ApN concentrations and secretion, at least in part, via a direct stimulation of ApN gene expression. Such a treatment only minimally affects circulating resistin. ApN restoration could, in concert with leptin, contribute to the metabolic effects classically observed during leptin administration.

3T3 Cells↗
PubMed1977

Log linear relationship between plasma arginine vasopressin and plasma osmolality.

The integrated plasma arginine vasopressin concentration (IpAVP) was determined by pooling the results of single samples collected every 3 min for 0.5 h in dehydrated, randomly hydrated, and water-loaded sheep. A linear relationship was observed between the log of the integrated AVP concentration and plasma osmolality. This relationship was tested by the bolus injection of 20 g/100 ml NaCl to both water-loaded and randomly hydrated sheep. The rise in the log of IpAVP divided by the rise in plasma osmolality was similar in both groups (P greater than 0.5) and was superimposable upon the regression line derived from steady-state observations. The data would suggest that AVP is released as an exponential function of plasma osmolality rather than as a threshold phenomenon.

Animals↗
PubMed2005

Severe encephalopathy induced by the first but not the second course of high-dose methotrexate mirrored by plasma homocysteine elevations and preceded by extreme differences in pretreatment plasma folate.

Plasma homocysteine has recently been associated with the occurrence of methotrexate-related neurotoxicity. We observed extreme elevations of homocysteine in a 9-year-old boy presenting with leukemia treated with the ALL-BFM 95 protocol. Coma occurred at about the 71st hour from the first methotrexate administration, and lasted for 30 h but MRI and CT studies showed no intracranial pathology. The second course of high-dose methotrexate was administered with no complications. Homocysteine areas under the curve (AUC) were calculated as the sum of areas of rectangles during the 6-hour intervals from T(0) to T(72) hours (AUC(0--72)) and methotrexate AUCs were evaluated using MW/PHARM 3.3 software. The AUC of homocysteine during the first, toxic course was 5.2 times higher than AUC during the second administration, whereas AUC of methotrexate also differed by a factor of 5. Plasma concentrations of folate prior to the first and the second courses, respectively, were 4.4 versus 45 micromol/l making this difference the most striking discriminator between the two courses. Mutation analysis showed that the patient was heterozygous for the C 677 T mutation in the MTHFR gene. We suggest that plasma homocysteine, pretreatment plasma folate and possibly the presence of MTHFR mutations may be biomarkers of methotrexate toxicity and possibly its antifolate effect targeted towards the tumor as well.

Antimetabolites, Antineoplastic↗
PubMed1978

Red blood cell Li+ to plasma Li+ ratios. Are they related to plasma Li+ concentrations?

The relationship between the lithium ratio (ratio of lithium in blood cells to that in plasma) and plasma lithium concentration was examined in a group of male inpatients taking lithium carbonate for affective disorders. The lithium ratio was found to increase in the majority of these patients as plasma lithium concentration increased. However, the magnitude of variation of the lithium ratio with plasma lithium concentration observed in these patients is not sufficient to seriously affect the value of determining the lithium ratio in the clinical situation.

Erythrocytes↗
PubMed1980

Melatonin concentration in cerebrospinal fluid, peripheral plasma and plasma of the confluens sinuum of the rat.

A procedure is described for collection of blood from the confluens sinuum of the rat. Melatonin concentration, measured by RIA, in plasma of the confluens was found to be significantly higher than that in peripheral plasma. Melatonin levels in cerebrospinal fluid of the cisterna magna were always lower than those in plasma and exhibited no significant changes which paralleled those occurring in plasma with darkness. It is concluded that, in the rat, the major route of secretion of melatonin by the pineal gland is into the blood of the confluens sinuum.

Anesthesia↗
PubMed1978

Binding of hippurate in normal plasma and in uremic plasma pre- and postdialysis.

The protein binding of 14C-hippurate has been measured by conventional ultrafiltration techniques in the plasma of normal subjects and in uremic subjects pre- and postdialysis. In addition, the clearance of 14C-hippurate was determined in vitro in both isotonic saline and plasma to assess binding limitations on hippurate removal during dialysis. Binding levels of hippurate in normal subjects of 68+/-1.8% (n = 5) were significantly higher than either postdialysis (48.3+/-15.4%; n = 7) or predialysis (36.6+/-11.7%; n = 7) levels in the same uremic subjects. Actual levels of plasma hippurate were, however, considerably greater in uremics (24.7+/-11.2 mg/dl' n = 7) than in normal subjects (congruent to 0.5 mg%). The difference in hippurate binding between pre- and postdialysis samples in uremics was significantly different from zero (p less than 0.01, t = 5.36), indicating depletion of competitive site-binding species during dialysis. The saline clearance of hippuric acid (99.1 +/-0.5 ml/min; n = 6) under standard conditions in a capillary dialyzer (CDAK-4) was consistent with the expected clearance of a solute of its molecular weight. Hippurate clearance in citrated plasma, where binding was determined as 50+/-3%, was 65+/-0.7 ml/min (n = 6), in good agreement with a theoretically predicted clearance of 60 ml/min for this level of binding. High serum levels of hippurate and its derivatives, may depress effective function of various organs. In addition to the normal dietary intake of hippurate and its precursors, patients on dialysis receive a further burden of hippurate precursor in the form of benzyl alcohol, the common preservative in heparin solutions. The large body burdens of hippurate in dialysis patients, coupled with its impaired removal on dialysis due to binding, point to the necessity for a through investigation of the potential toxicity of this compound.

Carbon Radioisotopes↗