Variation in protein metabolism biomarkers during the transition period and associations with health, colostrum quality, reproduction, and milk production traits in Holstein cows

The aims of this study were to assess (1) the variation of protein metabolism biomarkers and factors affecting them during the transition period, (2) the association of each biomarker with skeletal muscle reserves and their changes, and (3) the association of these biomarkers with postpartum health, colostrum quality, reproduction, and milk production. For this purpose, 238 multiparous Holstein cows from 6 herds were used in a prospective cohort study. Plasma concentrations of 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH) and serum concentrations of total protein (TP), albumin (ALB), urea nitrogen (BUN), and creatinine (SCR) were determined for each cow at -21, -7, 7, 21, and 28 d relative to calving. Clinical diseases were recorded during the first 28 d postcalving, and presence of subclinical ketosis (scKET) was investigated at 7 and 21 d. Colostrum quality was estimated by Brix refractometry. Reproduction data by 150 d in milk (DIM) and milk production records were also available. Linear mixed models including the fixed effects of time point, herd, parity, body condition score (-21 d), duration of dry period and postparturient diseases were fitted to assess the variation in each biomarker's concentration. The association between the biomarkers' concentration during the prepartum period with the odds for each postparturient disease and for a combined trait (CD_1-28), defined as the presence of at least one clinical condition during the first 28 d after calving, were assessed with separate binary logistic models for time points -21 d and -7 d. The relationship of each biomarker's concentration with longissimus dorsi thickness (LDT) and the changes in LDT (ΔLDT) was assessed with pairwise correlations. Separate general linear models were used to assess the association of each biomarker with colostrum Brix values and milk production traits. Finally, the associated hazard for first artificial insemination (AI) and for pregnancy by 150 DIM (PREG_150DIM) was assessed with Cox proportional hazard models, whereas odds for pregnancy to the first AI (PREG_1stAI) were assessed with binary logistic models. The level of 3-MH was affected mainly by herd, time points, and their interaction. Higher 3-MH was associated with increased odds for metritis and CD_1-28, increased hazard for PREG_150 DIM and with increased milk production. 1-Methylhistidine was affected mainly by herd, scKET and occurrence of displaced abomasum. Higher 1-MH was associated with better colostrum quality, increased odds for scKET, increased hazard for first AI by 150 DIM and with decreased milk production. Both 3-MH and 1-MH were weakly to moderately negatively correlated with LDT and moderately to strongly negatively correlated with ΔLDT at the corresponding time periods. Additionally, higher TP was associated with increased odds for metritis and CD_1-28 and increased milk production, while higher ALB was associated with increased odds for scKET and increased milk production. Moreover, higher BUN was associated with decreased odds for scKET, increased odds for PREG_1stAI and increased milk production. Higher SCR was associated with decreased odds for retained fetal membranes, metritis, and CD_1-28. Periparturient protein metabolism is significantly associated with postpartum health, colostrum quality, reproduction, and milk production; mechanisms involved require further investigation.

A non-canonical nucleophile unlocks a new mechanistic pathway in a designed enzyme

Directed evolution of computationally designed enzymes has provided new insights into the emergence of sophisticated catalytic sites in proteins. In this regard, we have recently shown that a histidine nucleophile and a flexible arginine can work in synergy to accelerate the Morita-Baylis-Hillman (MBH) reaction with unrivalled efficiency. Here, we show that replacing the catalytic histidine with a non-canonical Nδ-methylhistidine (MeHis23) nucleophile leads to a substantially altered evolutionary outcome in which the catalytic Arg124 has been abandoned. Instead, Glu26 has emerged, which mediates a rate-limiting proton transfer step to deliver an enzyme (BHMeHis1.8) that is more than an order of magnitude more active than our earlier MBHase. Interestingly, although MeHis23 to His substitution in BHMeHis1.8 reduces activity by 4-fold, the resulting His containing variant is still a potent MBH biocatalyst. However, analysis of the BHMeHis1.8 evolutionary trajectory reveals that the MeHis nucleophile was crucial in the early stages of engineering to unlock the new mechanistic pathway. This study demonstrates how even subtle perturbations to key catalytic elements of designed enzymes can lead to vastly different evolutionary outcomes, resulting in new mechanistic solutions to complex chemical transformations.

Effects of pre-slaughter fasting on antemortem skeletal muscle protein degradation levels and postmortem muscle free amino acid concentrations in broiler chickens

This study investigated the effects of pre-slaughter fasting time on the relationship between skeletal muscle protein degradation levels at slaughter and chicken meat quality after 48 h of postmortem aging. Twenty-four broiler chicks at 0 d of age were used in this study until 28 d of age. At 27 d of age, the chickens were assigned to 4 treatment groups: 0 h of fasting (0H), 8 h of fasting (8H), 16 h of fasting (16H), or 24 h of fasting (24H). They were slaughtered at 28 d of age. Blood samples were collected before fasting and immediately before slaughter. Plasma Nτ-methylhistidine concentration, an index of skeletal muscle protein degradation level, and muscle free amino acid concentration were analyzed. Antemortem changes in individual plasma Nτ-methylhistidine concentrations were significantly increased in 8H, 16H, and 24H compared to that in 0H (P < 0.05). After 48 h of postmortem storage, the glutamic acid content in the pectoralis major muscles increased with fasting time (P < 0.05), and the umami taste of chicken soup in the fasting groups (8H, 16H, 24H) was higher than that in the 0H group (P < 0.05). The antemortem changes in plasma Nτ-methylhistidine concentrations were correlated with glutamic acid content in the pectoralis major muscles (r = 0.57, P < 0.05) and umami taste (r = 0.66, P < 0.05). These results suggest that skeletal muscle protein degradation levels at slaughter are related to postmortem chicken meat quality, especially glutamic acid content and umami taste.

Ergothioneine, Ovothiol A, and Selenoneine-Histidine-Derived, Biologically Significant, Trace Global Alkaloids

The history, chemistry, biology, and biosynthesis of the globally occurring histidine-derived alkaloids ergothioneine (10), ovothiol A (11), and selenoneine (12) are reviewed comparatively and their significance to human well-being is discussed.

First evidence of ovothiol biosynthesis in marine diatoms

Ovothiols are histidine-derived thiols that are receiving a great interest for their biological activities in human model systems. Thanks to the position of the thiol group on the imidazole ring of histidine, these compounds exhibit unusual antioxidant properties. They have been revealing a very promising pharmacological potential due to their anti-proliferative and anti-inflammatory properties, as well as anti-fibrotic activities not always related to their antioxidant power. Ovothiols occur in three differentially methylated forms (A, B and C), isolated from ovary, eggs and biological fluids of many marine invertebrates, mollusks, microalgae, and pathogenic protozoa. These molecules are synthesized by two enzymes: the sulfoxide synthase OvoA and the sulfoxide lyase OvoB. OvoA catalyzes the insertion of the sulfur atom of cysteine on the imidazole ring of histidine, leading to the formation of a sulfoxide intermediate. This is then cleaved by OvoB, giving 5-thiohistidine, finally methylated on the imidazole ring thanks to the methyltransferase domain of OvoA. Recent studies have shown that OvoA homologs are encoded in a wide variety of genomes suggesting that ovothiol biosynthesis is much more widespread in nature than initially thought. Here we have investigated the OvoA occurrence in diatoms, one of the most abundant group of microalgae, dominating marine and freshwater environments. They are considered a very good model system for both biology/photophysiology studies and for biotechnological applications. We have performed comparative sequence and phylogenetic analyses of OvoA from diatoms, highlighting a high degree of conservation of the canonical domain architecture in the analyzed species, as well as a clear clustering of OvoA in the two different morphological groups, i.e. centric and pennate diatoms. The in silico analyses have also revealed that OvoA gene expression is modulated by growth conditions. More importantly, we have characterized the thiol fraction from cultures of the coastal centric diatom Skeletonema marinoi, providing the first evidence of ovothiol B biosynthesis in diatoms.

Characterization of aminoaciduria and hypoaminoacidemia in dogs with hepatocutaneous syndrome

OBJECTIVE To characterize aminoaciduria and plasma amino acid concentrations in dogs with hepatocutaneous syndrome (HCS). ANIMALS 20 client-owned dogs of various breeds and ages. PROCEDURES HCS was definitively diagnosed on the basis of liver biopsy specimens (n = 12), gross and histologic appearance of skin lesions (4), and examination of skin and liver biopsy specimens (2) and presumptively diagnosed on the basis of cutaneous lesions with compatible clinicopathologic and hepatic ultrasonographic (honeycomb or Swiss cheese pattern) findings (2). Amino acid concentrations in heparinized plasma and urine (samples obtained within 8 hours of each other) were measured by use of ion exchange chromatography. Urine creatinine concentration was used to normalize urine amino acid concentrations. Plasma amino acid values were compared relative to mean reference values; urine-corrected amino acid values were compared relative to maximal reference values. RESULTS All dogs had generalized hypoaminoacidemia, with numerous amino acid concentrations < 50% of mean reference values. The most consistent and severe abnormalities involved glutamine, proline, cysteine, and hydroxyproline, and all dogs had marked lysinuria. Urine amino acids exceeding maximum reference values (value > 1.0) included lysine, 1-methylhistidine, and proline. CONCLUSIONS AND CLINICAL RELEVANCE Hypoaminoacidemia in dogs with HCS prominently involved amino acids associated with the urea cycle and synthesis of glutathione and collagen. Marked lysinuria and prolinuria implicated dysfunction of specific amino acid transporters and wasting of amino acids essential for collagen synthesis. These findings may provide a means for tailoring nutritional support and for facilitating HCS diagnosis.

Effects of varying ruminally undegradable protein supplementation on forage digestion, nitrogen metabolism, and urea kinetics in Nellore cattle fed low-quality tropical forage

Effects of supplemental RDP and RUP on nutrient digestion, N metabolism, urea kinetics, and muscle protein degradation were evaluated in Nellore heifers () consuming low-quality signal grass hay (5% CP and 80% NDF, DM basis). Five ruminally and abomasally cannulated Nellore heifers (248 ± 9 kg) were used in a 5 × 5 Latin square. Treatments were the control (no supplement) and RDP supplementation to meet 100% of the RDP requirement plus RUP provision to supply 0, 50, 100, or 150% of the RUP requirement. Supplemental RDP (casein plus NPN) was ruminally dosed twice daily, and RUP supply (casein) was continuously infused abomasally. Jugular infusion of [NN]-urea with measurement of enrichment in urine was used to evaluate urea kinetics. The ratio of urinary 3-methylhistidine to creatinine was used to estimate skeletal muscle protein degradation. Forage NDF intake (2.48 kg/d) was not affected ( ≥ 0.37) by supplementation, but supplementation did increase ruminal NDF digestion ( < 0.01). Total N intake (by design) and N retention increased ( < 0.001) with supplementation and also linearly increased with RUP provision. Urea entry rate and gastrointestinal entry rate of urea were increased by supplementation ( < 0.001). Supplementation with RUP linearly increased ( = 0.02) urea entry rate and tended ( = 0.07) to linearly increase gastrointestinal entry rate of urea. Urea use for anabolic purposes tended ( = 0.07) to be increased by supplementation, and RUP provision also tended ( = 0.08) to linearly increase the amount of urea used for anabolism. The fraction of recycled urea N incorporated into microbial N was greater ( < 0.001) for control (22%) than for supplemented (9%) heifers. Urinary 3-methylhistidine:creatinine of control heifers was more than double that of supplemented heifers ( < 0.001). Control heifers reabsorbed a greater ( < 0.001) fraction of urea from the renal tubule than did supplemented heifers. Overall, unsupplemented heifers had greater mobilization of AA from myofibrillar protein, which provided N for urea synthesis and subsequent recycling. Supplemental RUP, when RDP was supplied, not only increased N retention but also supported increased urea N recycling and increased ruminal microbial protein synthesis.

Carnosine protects against NMDA-induced neurotoxicity in differentiated rat PC12 cells through carnosine-histidine-histamine pathway and H(1)/H(3) receptors

Since the histidine-containing dipeptide carnosine (beta-alanyl-L-histidine) is believed to have many physiological functions in the brain, we investigated the neuroprotective effects of carnosine and its mechanisms of action in an in vitro model of neurotoxicity induced by N-methyl-d-aspartate (NMDA) in differentiated PC12 cells. Pretreatment with carnosine increased the viability and decreased the number of apoptotic and necrotic cells measured by MTT and Hoechst 33342 and propidium iodide (PI) double staining assays. Carnosine also can inhibit the glutamate release and increase HDC activity and the intracellular and extracellular contents of carnosine, histidine and histamine detected by high-performance liquid chromatography (HPLC). The protection by carnosine was reversed by alpha- fluoromethylhistidine, a selective and irreversible inhibitor of histidine decarboxylase (HDC). Pyrilamine and thioperamide, selective central histamine H(1) and H(3) antagonists also significantly reversed the protection of carnosine. Further, the inhibition of glutamate release by carnosine was reversed by thioperamide. Therefore, the protective mechanism of carnosine may not only involve the carnosine-histidine-histamine pathway, but also H(1)/H(3) receptors and the effective inhibition of glutamate release. This study indicates that carnosine may be an endogenous protective factor and calls for its further study as a new antiexcitotoxic agent.

Identification of amino acids that promote specific and rigid TAR RNA-tat protein complex formation

The Tat protein and the transactivation responsive (TAR) RNA form an essential complex in the HIV lifecycle, and mutations in the basic region of the Tat protein alter this RNA-protein molecular recognition. Here, EPR spectroscopy was used to identify amino acids, flanking an essential arginine of the Tat protein, which contribute to specific and rigid TAR-Tat complex formation by monitoring changes in the mobility of nitroxide spin-labeled TAR RNA nucleotides upon binding. Arginine to lysine N-terminal mutations did not affect TAR RNA interfacial dynamics. In contrast, C-terminal point mutations, R56 in particular, affected the mobility of nucleotides U23 and U38, which are involved in a base-triple interaction in the complex. This report highlights the role of dynamics in specific molecular complex formation and demonstrates the ability of EPR spectroscopy to study interfacial dynamics of macromolecular complexes.

Depletion of brain histamine produces regionally selective protection against thiamine deficiency-induced lesions in the rat

Breakdown of the blood brain barrier and the subsequent accumulation of free radicals, lactate, and glutamate appear to be the immediate causes of thiamine deficiency (TD)-induced damage to thalamus. The mechanisms triggering these events are unknown but recent evidence suggests an important role of histamine. We therefore studied the effects of histamine depletion on thalamic lesions in the pyrithiamine-induced thiamine deficient (PTD) rat. Chronic intracerebroventricular (i.c.v., 7 days) infusion of alpha-fluoromethylhistidine (FMH), combined with bilateral ibotenate destruction of the histamine-containing neurons in the tuberomammillary (TM) nucleus and bolus i.c.v. infusion of 48/80, a potent mast cell degranulating agent, was used to deplete brain histamine levels. PTD rats receiving combined FMH + 48/80 + TM lesions developed acute neurological symptoms, including spontaneous seizures, approximately 1 day earlier than PTD rats treated with i.c.v. infusion of vehicle and sham lesions of the TM. When examined 1 week after restoration of thiamine, the PTD vehicle + sham lesion animals contained severe neuronal loss and gliosis in midline, intralaminar, ventral, lateral, and posterior nuclei. PTD animals treated with FMH + 48/80 + TM lesions had little evidence of neuronal loss or microglial proliferation in thalamus except in the gelatinosus and anteroventral nuclei, in which there was complete neuronal loss. These data demonstrate a significant and regionally selective role of histamine in the development of thalamic lesions in a rat model of Wernicke's encephalopathy. Furthermore, these data suggest either a dissociation between seizures and thalamic lesions or a significant role of histamine in seizure-related damage to the thalamus.

Imidazole aminoaciduria in cerebromacular degeneration

Three families in which there are five patients with cerebromacular degeneration have been studied, and preliminary findings show that both the patients and some of the members of their immediate families have generalized imidazole aminoaciduria. The patients excrete large amounts of carnosine and anserine as well as histidine and 1-methyl histidine. The urinary defect appears to be transmitted as a dominant trait and the cerebromacular degeneration as a recessive trait. The fact that the two traits have been found in three unrelated families makes it likely that the two are manifestations of the same gene.

Thioperamide, a histamine H3 receptor antagonist, increases GABA release from the rat hypothalamus

Using a microdialysis method and a new high performance liquid chromatography (HPLC)-fluorometric method for the detection of gamma-aminobutyric acid (GABA), we investigated the effect of thioperamide, an H3 receptor antagonist, on the GABA content in the dialysate from the anterior hypothalamic area of rats anesthetized with urethane. The addition of thioperamide to the perfusion fluid increased the release of GABA and histamine. Depleting neuronal histamine with alpha-fluoromethylhistidine, a specific inhibitor of histidine decarboxylase, and the administration of immepip, an H3 agonist, had no effect on basal- and thioperamide-induced GABA release. In addition, an infusion of clobenpropit, the most specific H3 receptor antagonist available, did not alter the basal release of GABA. On the other hand, histamine release was decreased by immepip and increased by thioperamide and clobenpropit. Removing Ca2+ from the perfusion fluid did not alter the effect of thioperamide on the GABA release, whereas that on histamine release was abrogated. These results suggest that the effect of thioperamide on GABA release is not mediated by histamine H3 receptors and that thioperamide acts on the transporter to cause an efflux of GABA from neurons and/or glia. Thioperamide is a popular H3 receptor antagonist which has been used applied to many studies. However, results using this compound should be interpreted in consideration of its effects on GABA release.

Denervation, but not decentralization, reduces nerve growth factor content of the mesenteric artery

In the present study we applied an improved nerve growth factor (NGF) extraction method to examine the effects of denervation and sympathetic decentralization on NGF levels in vascular tissue. Adult male Wistar Kyoto rats underwent mesenteric arterial denervation or splanchnic nerve transection. Four days after operation, animals were killed, and the mesenteric artery and coeliac-superior mesenteric ganglia were removed. The arterial adventitia was stripped from the media to measure NGF levels in nerve and smooth muscle separately. A high concentration of NGF was detected in the normal artery, 90% of which was in the adventitial layer. Surgical denervation significantly reduced the NGF levels in the artery and ganglia by 78 and 71%, respectively. However, within the artery the level of NGF was reduced in the adventitia but not in the media. Thus, the large reduction of NGF content resulted from the loss of nerve plexus from the artery. In contrast, decentralization did not alter the NGF content in the artery, in either the adventitia or media. Our results are in marked contrast to previous studies reporting elevated levels of NGF following denervation. This discrepancy is explained by the ability of our new procedure to extract much greater amounts of NGF from the tissue.

Heterocyclic thiols as antioxidants: why ovothiol C is a better antioxidant than ergothioneine

Spectral, acid-base, and redox properties of 4-mercaptoimidazoles were investigated by pulse radiolysis in aqueous solutions. Thiyl radicals of 1-methyl-5-ethyl-4-mercaptoimidazole (MEMI) have weak absorption band at 330 nm, epsilon = 300 +/- 60 M-1 cm-1. Because the ionic strength variation from 0.01 to 0.1 M in the pH range from 3 to 14 does not influence the rate constant of the radical decay, it is concluded that the MEMI thiyl radical is neutral. At pH 7, the reduction potential of the MEMI radical, E7 = 0.45 V, is lower than E7 = 0.48 V of the Trolox C radical, which means that MEMI may restitute vitamin E under physiological conditions (assuming similar reduction potentials of Trolox C and vitamin E radicals). Because pKa = 10.3 of the SH group in MEMI is lower than pKa = 11.9 of the OH group of Trolox C, the redox equilibrium with Trolox C is reversed at pH 13, and E13(MEMI-radical) = 0.29 +/- 0.04 V is determined against E13(Trolox C--radical) = 0.19 V. In contrast to extraordinary electron donating properties, MEMI is only a moderately good H-atom donor. k(.CH3 + MEMI) = (1.5 +/- 0.3) x 10(5) M-1 s-1 in neutral media is considerably lower than k(.CH3 + GSH) = 5 x 10(7) M-1 s-1, which is explained by the zwitterionic structure of MEMI. The ability of MEMI to act as antioxidant in biological systems is further demonstrated by its ability to efficiently scavenge superoxide and linoleate peroxyl radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

A highly sensitive assay for histamine using ion-pair HPLC coupled with postcolumn fluorescent derivatization: its application to biological specimens

A simple and highly sensitive method for the determination of histamine (HA) was developed using ion-pair, reversed-phase HPLC coupled with postcolumn o-phthalaldehyde derivatization fluorometry, and it was applied to the unpurified extracts of human and rat plasma, and brains of rats and mice. The HA concentrations both in the plasma and brains determined by the present method were well consistent with the values obtained by cation-exchange HPLC with postcolumn fluorescent derivatization currently in use. The present method was more advantageous than the assay using cation-exchange HPLC: (1) it was three to four times more sensitive (the detection limit was 0.5 pg of HA), and (2) it enabled the measurement of HA in samples containing (R)alpha-methylhistamine, a potent and specific H3-receptor agonist, which could not be separated from HA by cation-exchange chromatography. Using the present method coupled with intracerebral microdialysis, we found in the rat hypothalamus that (R)alpha-methylhistamine (5 mg/kg i.p.) markedly decreased the extracellular concentration of HA with a maximal effect (83% reduction) during 30-60 min after injection, suggesting that most of HA in the microdialysate fraction is neuronal in origin.

The control of oxidant stress at fertilization

Metazoan eggs alter their coats after fertilization to protect the early embryo. In sea urchins, this modification consists of a rapid, coordinated set of noncovalent macromolecular assembly steps that are stabilized by protein cross-linking. The sea urchin egg uses an oxidative cross-linking reaction that requires hydrogen peroxide and a secreted peroxidase and thus faces the challenge of oxidant stress at the beginning of its development. Protection from the deleterious effects of this oxidative mechanism is afforded by regulation of the production and utilization of oxidizing species. This regulation requires a specific protein kinase C-activated oxidase and ovothiol, an intracellular antioxidant.

Highly site-specific oxygenation of 1-methylhistidine and its analogue with a copper (II)/ascorbate-dependent redox system

The reaction of histidine-related materials with copper(II) and ascorbate under physiological conditions has been studied chemically. We discovered that 1-methylimidazole and its analogues, including biological metabolites L-1-methylhistidine and anserine (beta-alanyl-L-1-methylhistidine), exhibited dramatic reactivity with copper(II)/ascorbate. Reaction of copper(II) and ascorbate occurs specifically at the C-2 position of the imidazole ring of L-1-methylhistidine and anserine derivatives with mono-oxygenation to give the 1-methyl-2-imidazolones in good to excellent yields (70-80%). The occurrence of an oxocopper(III) intermediate in the oxidation process of ascorbate is postulated.

Ovothiols as free-radical scavengers and the mechanism of ovothiol-promoted NAD(P)H-O2 oxidoreductase activity

Racemic ovothiol A [(+/-)-1a] and the ovothiol model compound 1,5-dimethyl-4-mercaptoimidazole (DMI, 2) were found to scavange the free radicals Fremy's salt (4) and Banfield' radical (5) much more rapidly than did the thiol antioxidant glutathione. Ovothiol A also scavenges the tyrosyl radical, with efficiency comparable to that of ascorbic acid and the tocopherol analogue trolox (3). The ovothiol model compound DMI was found to scavenge superoxide with a rate constant comparable to that of the reaction between superoxide and glutathione. These results suggest both a free-radical scavenging role for the ovothiols and a mechanism by which the ovothiols confer NAD(P)H-O2 oxidoreductase activity upon the enzyme ovoperoxidase. Investigation of this mechanism implicates the ovothiol thiyl radical and the NAD radical as key intermediates. The ovothiyl radical appears to be unreactive toward oxygen but highly reactive toward NADH. An estimate of the one-electron oxidation potential of the ovothiol anion is presented. The physical basis for the stability of the ovothiol free radical is discussed.

Histamine turnover in the rat hypothalamic nuclei estimated from alpha-fluoromethylhistidine-induced histamine decrease

The turnover rates, rate constants and half-life values of neuronal histamine (HA) in 10 nuclei of the rat hypothalamus were estimated from the depletion of HA induced by alpha-fluoromethylhistidine (alpha-FMH: 100 mg/kg, i.p.), a specific inhibitor of histidine decarboxylase, on the presumption that alpha-FMH depletable HA pools represent neuronal ones. Marked variation in the HA turnover rates were observed among the hypothalamic nuclei, ranging from 5.7 to 19.5 pmole/mg protein/hr.

Biochemical and physiological evidence that histamine is the transmitter of barnacle photoreceptors

We tested the hypothesis that histamine is the transmitter released by barnacle photoreceptors. Median and lateral ocelli were incubated with 3H-histidine and found to synthesize 3H-histamine, identified by high-voltage electrophoresis. Synthesis could be blocked by the histidine decarboxylase inhibitor (S)-alpha-fluoromethylhistidine. Histamine was applied to I-cells either by superfusion or by pressure ejection from a pipette (100 microM or 1 mM histamine) positioned close to the I-cell's soma. When bath-applied at concentrations ranging from 5-100 microM, histamine hyperpolarized the I-cell in a dose-dependent fashion and increased its conductance. At 100 microM, histamine abolished the I-cell's response to light. The response to a pulse of pressure-applied histamine was a hyperpolarization whose amplitude was graded with dose (determined by the duration of the pulse). This response persisted in concentrations of Co2+ and Cd2+ that blocked synaptic transmission from the photoreceptors. Cimetidine, an antagonist of mammalian H2 receptors, markedly decreased the cell's responses both to HA and to light at 100 microM and blocked both responses at 1 mM. Pyrilamine and triprolidine, H1 antagonists, had a complex effect on the I-cell's responses to histamine and to light. Neither H1 nor H2 antagonists, nor histamine itself, affected the voltage or light responses recorded in the presynaptic terminal region, or any phase of calcium-dependent action potentials induced in the terminal in the presence of tetraethylammonium ion. Thus, biochemical, immunocytochemical, and physiological evidence suggests that HA is the transmitter from these photoreceptors to the I-cells. Although gamma-aminobutyric acid (GABA) is also present in the photoreceptors, it did not affect the I-cell's responses to light or to histamine when bath-applied at 100 microM. Thus, GABA does not appear to modulate transmission from the photoreceptor to the I-cell.

Effect of peroperative normothermia on postoperative protein metabolism in elderly patients undergoing hip arthroplasty

We have examined in elderly patients the effect of maintenance of normothermia during hip surgery on postoperative protein metabolism. In one group of six patients (warmed group) heat loss was minimized during surgery and in the recovery period by warming fresh gases, i.v. fluids and wrapping the exposed parts of the body with a warming blanket. In a second group of six patients (cold group), routine care was provided. General anaesthesia consisted of thiopentone, tubocurarine and halothane in both groups. Urinary excretion of urea nitrogen and 3-methylhistidine (3-MeH) after surgery was significantly lower in the warmed group compared with the cold group (P less than 0.05). There was little effect of normothermia on amino acid concentrations in plasma after surgery. Muscle glutamine concentration 4 days after surgery decreased by 50% in the cold group and 18% in the warmed group. Total body potassium (TBK), measured as an index of body cell mass, decreased significantly after surgery in both groups. However, 7 days after surgery the reduction in TBK in the cold group remained significantly lower than that of the warmed group (P less than 0.05). Maintenance of normothermia during hip surgery appeared to attenuate, but not eliminate, protein breakdown and nitrogen loss after surgery.

[A study on amino acid solutions for postoperative parenteral nutrition--evaluation in terms of surgical stress, amino acid composition and its doses]

A newly composed amino acid solution, which contained a 30% branched-chain amino acid (BCAA), and a standard amino acid solution containing 22.6% BCAA were used for total parenteral nutrition following operation of the digestive organs. Their nutritional effects were evaluated by surgical stress (thoracotomy group or non-thoracotomy group) according to the two steps of amino acid doses (1.2g/kg/day administration group or 1.6g/kg/day group). 1. No significant differences could be recognized in an improvement in the serum proteins following administration of BCAA-enriched solution either in the thoracotomy or in the non-thoracotomy group. 2. An improvement in BCAA/AAA molar ratio was seen on the plasma aminogram following administration of BCAA-enriched solution both in the thoracotomy and in the non-thoracotomy groups. 3. No improvement in nitrogen balance following administration of BCAA-enriched solution could be found in the thoracotomy group, while its improving trend was recognized in the non-thoracotomy group treated with 1.6g/kg/day of the amino acid. 4. Neither in the thoracotomy nor in the non-thoracotomy group any significant inhibition of the excreted volumes of urinary 3-methylhistidine could be recognized.

Ovothiol replaces glutathione peroxidase as a hydrogen peroxide scavenger in sea urchin eggs

Despite its potential toxicity, H2O2 is used as an extracellular oxidant by Stronglylocentrotus purpuratus eggs to cross-link their fertilization envelopes. These eggs contain 5 mM 1-methyl-N alpha,N alpha-dimethyl-4-mercaptohistidine (ovothiol C), which reacts with H2O2. In consuming H2O2 and being reduced by glutathione, ovothiol acts as a glutathione peroxidase and replaces the function of the enzyme in eggs. The ovothiol system is more effective than egg catalase in destroying H2O2 at concentrations produced during fertilization and constitutes a principal mechanism for preventing oxidative damage at fertilization.

Oxidative stress and the role of novel thiol compounds at fertilization

A new class of thiols, the 1-methyl-4-mercaptohistidines, has been found in high concentrations in invertebrate eggs. This family, called the ovothiols, has unusual redox properties, including the ability to confer a CN- -resistant NAD(P)H oxidase activity on ovoperoxidase, the enzyme that catalyzes the physiological crosslinking of the fertilization envelope with dityrosine residues. Ovothiol has a redox potential of 44 mV positive to glutathione and thus is maintained in the reduced state in eggs by reduced glutathione, without the need for an ovothiol reductase. We propose that high concentrations of reduced ovothiol are present in eggs to protect them from the oxidative stress caused by the respiratory burst of fertilization.

Studies on the role of actin's N tau-methylhistidine using oligodeoxynucleotide-directed site-specific mutagenesis

The primary structure of all actins except that isolated from Naegleria gruberi contains a unique N tau-methylhistidine (MeHis) at position 73. This modified residue has been implicated as possibly being important for the post-translational processing of actin's amino terminus, the binding of actin to DNase I, and in the polymerization of G-actin. We have investigated the potential role of MeHis in each of these processes by utilizing site-directed mutagenesis to change His-73 of skeletal muscle actin to Arg and Tyr. Wild type and mutant actins were synthesized in vivo, using non-muscle cells transfected with mutant cDNAs, and in vitro by translating mutant RNAs synthesized using SP6 RNA polymerase in a rabbit reticulocyte lysate. We have found that actins containing Arg or Tyr at position 73 undergo amino-terminal processing, bind to DNase I-agarose, and become incorporated into the cytoskeleton of a nonmuscle cell as efficiently as wild type actin. Furthermore, using an in vitro copolymerization assay we have found that although there is no difference between the Arg mutant and the wild type actins, the Tyr mutant has a slightly greater critical concentration for polymerization. These results show that MeHis is not absolutely required for any of these processes.

Ovothiols, a family of redox-active mercaptohistidine compounds from marine invertebrate eggs

We have previously reported a novel thiol compound, 1-methyl-N alpha,N alpha-dimethyl-4-mercaptohistidine, or ovothiol, present at high concentration in the eggs of the sea urchin Strongylocentrotus purpuratus [Turner, E., Klevit, R., Hopkins, P. B., & Shapiro, B. M. (1986) J. Biol. Chem. 261, 13056-13063]. Here we report two related compounds, 1-methyl-N alpha-methyl-4-mercaptohistidine, or ovothiol B, from the scallop Chlamys hastata, and 1-methyl-4-mercaptohistidine, or ovothiol A, from the starfish Evasterias troschelii. These two compounds, as well as the S. purpuratus compound now designated ovothiol C, were isolated from eggs or ovarian tissue by S-carboxymethylation with [3H]iodoacetic acid, ion-exchange chromatography and ion-pairing high-pressure liquid chromatography. The structures of S-(carboxymethyl)ovothiols A and B were determined by 1H NMR, and that of ovothiol A was confirmed by comparison with authentic methylhistidine samples after desulfuration with Raney nickel. In the ovary of each species, the predominant methylation form of ovothiol accounts for at least 80% of the total 4-mercaptohistidine. The ovothiol concentration of the ovary far exceeds that of the testis or somatic tissues. The ovothiol C content of unfertilized S. purpuratus eggs is 1.14 mumol/10(6) eggs, equivalent to approximately 4.3 mM average concentration; the glutathione (GSH + GSSG) content is 0.9 mumol/10(6) eggs. In this species, high ovothiol levels persisted for the first 2 weeks of embryonic development. Ovothiol and glutathione account for virtually all of the trichloroacetic acid soluble-SH groups in the egg; these results are compared to several previous studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovothiol: a novel thiohistidine compound from sea urchin eggs that confers NAD(P)H-O2 oxidoreductase activity on ovoperoxidase

Sea urchin eggs contain a small molecular weight heat-stable factor that confers cyanide-resistant NAD(P)H-O2 oxidoreductase activity on ovoperoxidase (Turner, E., Somers, C. E., and Shapiro, B. M. (1985) J. Biol. Chem. 260, 13163-13171), the enzyme responsible for cross-linking the extracellular protein coat (fertilization membrane) of the egg. Here we report the isolation of the active cofactor and its identification by ultraviolet, NMR, and mass spectroscopy as a new sulfur-containing amino acid derivative, 1-methyl-alpha N,alpha N-dimethyl-4-thiohistidine, or ovothiol. Ovothiol reacts slowly with atmospheric oxygen or rapidly with micromolar concentrations of H2O2 to form ovothiol disulfide, which is inactive as a cofactor for the ovoperoxidase NAD(P)H oxidase. Reduced active ovothiol is regenerated by treatment with disulfide reductants and shows significant differences in its ultraviolet and NMR spectra from oxidized ovothiol. The oxidoreductase activity of the ovoperoxidase/ovothiol system is similar to that previously characterized with crude cofactor preparations; it is greatly enhanced by Mn2+ and is relatively insensitive to CN-, compared to the peroxidase activity of ovoperoxidase. The ovothiol content of eggs is estimated as 1.8 pmol/egg or an intracellular concentration of 6.8 mM. This concentration exceeds the amount of reductant needed for the CN-(-)insensitive oxygen consumption following fertilization and used in the production of H2O2 for fertilization membrane cross-linking. Whether ovothiol is involved in the cross-linking reaction, protects the egg from damage from H2O2, or has another role in development remains unclear.

Restraint stress stimulation of prolactin and ACTH secretion: role of brain histamine

The possible role of brain histamine in the release of prolactin, ACTH and corticosterone following acute restraint, was pharmacologically evaluated in adult male rats. Fifteen min of restraint caused marked increases in the plasma levels of these hormones. alpha-Fluoromethyl histidine (FH), a histidine decarboxylase inhibitor which depleted hypothalamic histamine, inhibited the enhancement of plasma prolactin levels. In contrast, plasma ACTH levels were not modified. FH treatment decreased plasma corticosterone concentrations in animals submitted to stress or in rest; this suggests a direct action of FH on the adrenal. Intraventricular (IVT) injection of ranitidine (H2 antagonist) blunted the prolactin response to restraint stress whereas its systemic administration had no effect. On the contrary, pyrilamine (H1 antagonist) given systemically decreased slightly, but significantly, the prolactin rise but when injected IVT it was ineffective. Pyrilamine was also unable to affect the ranitidine action. ACTH and corticosterone levels in plasma of restrained rats were not modified by the histamine antagonists. It is concluded that histamine is involved, mainly through central H2 receptors, in the enhancement of plasma prolactin levels produced by an acute stress. The failure of both antihistaminic compounds and a histamine depletor to alter the ACTH stimulation suggest that histamine has no participation in the hypophysio-corticoadrenal response to acute restraint.

Reactions between peroxidizing lipids and histidyl residue analogues: enhancement of lipid oxidation and browning by 4-methylimidazole

As a part of our study on the interactions between peroxidizing lipids and the histidyl imidazole side-chain in simple, low-moisture model systems, 4-methylimidazole (4MI) was reacted with methyl linoleate (ML). This analogue was chosen to avoid interference from other functional groups in histidine (free base) or in proteins. Changes in the concentrations of lipid hydroperoxides, carbonyls, 4MI, and brown pigments were followed over a period of 24 days. The results indicate that 4MI exhibits significant prooxidative activity by reducing the induction period as well as by enhancing the formation of brown pigments. These effects are more pronounced at high 4MI/MI molar ratios and under basic pH's. Upon interactions with peroxidizing ML, as much as 44% of initially present 4MI was destroyed by the sixth day of incubation.

The isolation and partial characterization of ribonuclease A from Bison bison

1. Bison ribonuclease was isolated from pancreas glands of Bison bison by acid extraction, (NH(4))(2)SO(4) fractionation, affinity chromatography on Sepharose-5'-(4-aminophenylphosphoryl)uridine 2',3'-phosphate and ion-exchange chromatography on Bio-Rex-70. 2. The selectivity of the affinity column towards bison ribonuclease in heterogeneous protein solutions was greatly improved by employing piperazine buffers at pH5.3, which decreased non-specific interactions of other proteins. Rapid desorption from the affinity column was obtained with sodium phosphate buffer (pH3). 3. Bison ribonuclease has a total amino acid content very similar to ox ribonuclease. Inactivation of bison ribonuclease with iodoacetic acid leads to the formation of 0.62 residues of pi-carboxymethylhistidine and 0.36 residues of tau-carboxymethylhistidine. The amino acid composition of peptides isolated from diagonal peptide ;maps' and also of peptides isolated after pH1.6 and 2.4 two-dimensional high-voltage electrophoresis of a digest of bison ribonuclease labelled with pyridoxal 5-phosphate indicates that there is complete homology between ox and bison ribonucleases. 4. The Schiff-base attachment site of pyridoxal 5-phosphate was identified as lysine-41 by NaBH(4) reduction followed by peptide isolation.