Inhibition of xanthine oxidase and xanthine dehydrogenase by nitric oxide. Nitric oxide converts reduced xanthine-oxidizing enzymes into the desulfo-type inactive form.
(9/4495)
Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) were inactivated by incubation with nitric oxide under anaerobic conditions in the presence of xanthine or allopurinol. The inactivation was not pronounced in the absence of an electron donor, indicating that only the reduced enzyme form was inactivated by nitric oxide. The second-order rate constant of the reaction between reduced XO and nitric oxide was determined to be 14.8 +/- 1.4 M-1 s-1 at 25 degrees C. The inactivated enzymes lacked xanthine-dichlorophenolindophenol activity, and the oxypurinol-bound form of XO was partly protected from the inactivation. The absorption spectrum of the inactivated enzyme was not markedly different from that of the normal enzyme. The flavin and iron-sulfur centers of inactivated XO were reduced by dithionite and reoxidized readily with oxygen, and inactivated XDH retained electron transfer activities from NADH to electron acceptors, consistent with the conclusion that the flavin and iron-sulfur centers of the inactivated enzyme both remained intact. Inactivated XO reduced with 6-methylpurine showed no "very rapid" spectra, indicating that the molybdopterin moiety was damaged. Furthermore, inactivated XO reduced by dithionite showed the same slow Mo(V) spectrum as that derived from the desulfo-type enzyme. On the other hand, inactivated XO reduced by dithionite exhibited the same signals for iron-sulfur centers as the normal enzyme. Inactivated XO recovered its activity in the presence of a sulfide-generating system. It is concluded that nitric oxide reacts with an essential sulfur of the reduced molybdenum center of XO and XDH to produce desulfo-type inactive enzymes. (+info)
The modified anaphylaxis hypothesis for cot death. Anaphylactic sensitization in guinea-pigs fed cow's milk.
(10/4495)
Guinea-pigs on a normal diet, but given cow's milk to drink instead of water, very soon became anaphylactically sensitive to cow's milk and may be fatally shocked following either i.v. injection or intratracheal inhalation of cow's milk. (+info)
Effects of milk yield on biological efficiency and profit of beef production from birth to slaughter.
(11/4495)
Effect of milk yield (MY) on biological efficiency and gross margin as an indicator of profit potential of beef production from birth to slaughter was determined. Data included 9 yr of spring-born single male calves. Biological efficiency was calculated as carcass weight/total feed energy intake, including nonlactating and lactating intakes of cow and creep and feedlot intakes of calf. Slaughter end point was finish constant at 9 mm of fat thickness. Gross margin was determined as returns minus feed costs. Three breeding systems were analyzed: purebred Hereford (HE), large rotational (LR), and small rotational (SR). Analyses were performed separately by breeding system when differences in the effect of MY among breeding systems were significant. Increased MY was associated with increased preweaning gain (P < .001), increased weight at start of feedlot trial (P < .001), and increased hot carcass weight (P < .05). No significant (P > .10) effect of MY on age at slaughter or on carcass weight per day of age at slaughter was found. Increased MY was associated with increased cow lactating energy intake (P < .10) and negatively associated with calf creep intake (P < .01). No effects of MY on intake of the cow during the nonlactating period, calf feedlot intake, or total feed intake were found. Increased MY was associated with a reduction in backfat thickness of the cow during the lactating period (P < .01) with no change in body weight. In the subsequent nonlactating period, increasing MY was associated with increased backfat thickness (P < .10) and body weight (P < .05). No effect of MY on change in backfat or weight of cow from calving to the end of the next nonlactating period was found. No effect of MY on biological efficiency to slaughter was detected. Milk yield was positively associated with gross margin from birth to slaughter (P < .05); results were similar when cow feed prices were reduced by 30%. Increased MY was associated with increased biological efficiency to weaning in HE (P < .01) and SR (P < .10), with no effect found in LR. When feeding cows to requirements, milk yield has a positive effect on the profit potential of beef production from birth to slaughter. (+info)
Role of calcium in activity and stability of the Lactococcus lactis cell envelope proteinase.
(12/4495)
The mature lactococcal cell envelope proteinase (CEP) consists of an N-terminal subtilisin-like proteinase domain and a large C-terminal extension of unknown function whose far end anchors the molecule in the cell envelope. Different types of CEP can be distinguished on the basis of specificity and amino acid sequence. Removal of weakly bound Ca2+ from the native cell-bound CEP of Lactococcus lactis SK11 (type III specificity) is coupled with a significant reversible decrease in specific activity and a dramatic reversible reduction in thermal stability, as a result of which no activity at 25 degrees C (pH 6.5) can be measured. The consequences of Ca2+ removal are less dramatic for the CEP of strain Wg2 (mixed type I-type III specificity). Autoproteolytic release of CEP from cells concerns this so-called "Ca-free" form only and occurs most efficiently in the case of the Wg2 CEP. The results of a study of the relationship between the Ca2+ concentration and the stability and activity of the cell-bound SK11 CEP at 25 degrees C suggested that binding of at least two Ca2+ ions occurred. Similar studies performed with hybrid CEPs constructed from SK11 and Wg2 wild-type CEPs revealed that the C-terminal extension plays a determinative role with respect to the ultimate distinct Ca2+ dependence of the cell-bound CEP. The results are discussed in terms of predicted Ca2+ binding sites in the subtilisin-like proteinase domain and Ca-triggered structural rearrangements that influence both the conformational stability of the enzyme and the effectiveness of the catalytic site. We argue that distinctive primary folding of the proteinase domain is guided and maintained by the large C-terminal extension. (+info)
Antigenicity of purified glutaraldehyde-treated cholera toxoid administered orally.
(13/4495)
The antigenicity of orally administered glutaraldehyde-treated cholera toxoid was investigated in healthy volunteers. Fourteen volunteers ingested two or three 2-mg doses of toxoid with saline, with the doses spaced at 28-day intervals. Thirteen other volunteers received comparable toxoid doses with NaHCO3 and milk to neutralize gastric acid. Increments in circulating antitoxin levels were used to assay the antigenicity of oral toxoid. Antitoxin was measured by adrenal cell, rabbit skin permeability factor, and passive hemagglutination assays in sera collected on days 0, 28, 35, 56, 63, and 84 after primary immunization. Adrenal cell and rabbit skin assays exhibited identical sensitivity in detecting antitoxin rises in the 27 vaccinees (19/27) and were significantly more sensitive than passive hemagglutination (11/27) (P less than 0.03). Volunteers who ingested toxoid with NaHCO3 and milk had a higher rate of seroconversion (77%) than those who received toxoid with saline (64%); they also had earlier rises in antitoxin titer and consistently higher geometric mean titers on all days tested. These studies demonstrate that purified cholera toxoid is antigenic in humans after oral administration. The possible role of oral toxoid in enhancing the protective effect of killed whole-cell vaccines can now be investigated. (+info)
Ca2+-ATPases and their expression in the mammary gland of pregnant and lactating rats.
(14/4495)
The transcellular Ca2+ fluxes required for milk production must be rigorously regulated to maintain the low cytosolic Ca2+ concentrations critical to cell function. Ca2+-ATPases play a critical role in the maintenance of this cellular Ca2+ homeostasis. Using RT-PCR and sequencing, we identified six Ca2+ pumps in lactating mammary tissue. Three plasma membrane Ca2+-ATPases (PMCAs) were found (PMCA1b, PMCA2b, and PMCA4b). Two sarco (endo)plasmic reticulum Ca2+-ATPases (SERCAs) were identified (SERCA2 and SERCA3), and the rat homologue to the yeast Golgi Ca2+-ATPase RS-10 was also found. The pattern of mRNA expression of each of these pumps was examined in rat mammary tissue from the 7th day of pregnancy to the 21st day of lactation. Northern blots revealed increased mRNA expression for all Ca2+ pumps by the 14th day of lactation, and transcripts continued to increase through the 18th day of lactation. PMCA1b, PMCA4b, SERCA2, and SERCA3 showed the lowest levels of expression. RS-10 transcripts were more abundant than SERCA2, SERCA3, PMCA1b, and PMCA4b. RS-10 was the only pump to increase in expression before parturition. PMCA2b was the most abundant transcript found in lactating mammary tissue. At peak lactation, expression of PMCA2b approached that of actin. The high expression, high affinity for Ca2+, and high activity at low calmodulin concentrations exhibited by PMCA2b suggest that it is uniquely suited for maintenance of Ca2+ homeostasis in the lactating mammary gland. The pattern of expression and abundance of RS-10 suggest that it is a candidate for the Golgi Ca2+-ATPase shown to be important in maintaining the Golgi Ca2+ concentration required for casein synthesis and micelle formation. (+info)
Bovine colostrum is a health food supplement which prevents NSAID induced gut damage.
(15/4495)
BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) are effective for arthritis but cause gastrointestinal injury. Bovine colostrum is a rich source of growth factors and is marketed as a health food supplement. AIMS: To examine whether spray dried, defatted colostrum or milk preparations could reduce gastrointestinal injury caused by indomethacin. METHODS: Effects of test solutions, administered orally, were examined using an indomethacin restraint rat model of gastric damage and an indomethacin mouse model of small intestinal injury. Effects on migration of the human colonic carcinoma cell line HT-29 and rat small intestinal cell line RIE-1 were assessed using a wounded monolayer assay system (used as an in vitro model of wound repair) and effects on proliferation determined using [3H]thymidine incorporation. RESULTS: Pretreatment with 0.5 or 1 ml colostral preparation reduced gastric injury by 30% and 60% respectively in rats. A milk preparation was much less efficacious. Recombinant transforming growth factor beta added at a dose similar to that found in the colostrum preparation (12.5 ng/rat), reduced injury by about 60%. Addition of colostrum to drinking water (10% vol/vol) prevented villus shortening in the mouse model of small intestinal injury. Addition of milk preparation was ineffective. Colostrum increased proliferation and cell migration of RIE-1 and HT-29 cells. These effects were mainly due to constituents of the colostrum with molecular weights greater than 30 kDa. CONCLUSIONS: Bovine colostrum could provide a novel, inexpensive approach for the prevention and treatment of the injurious effects of NSAIDs on the gut and may also be of value for the treatment of other ulcerative conditions of the bowel. (+info)
Lactation-dependent down regulation of leptin production in mouse mammary gland.
(16/4495)
Lactation-dependent regulation of leptin expression in mouse mammary gland and parametrial adipose tissue was estimated by RT-PCR analysis for virgin, pregnant, lactating and post-lactating mice, and the serum and milk leptin levels of these mice were also determined by ELISA. Leptin gene expression in mammary gland as well as in adipose tissue was obviously detected before pregnancy, markedly decreased to 30-50% after parturition and kept at the low level during lactation period, and restored to the original level after weaning. The leptin concentration of milk collected just before weaning was about two-fold higher than that of the milk collected at mid-lactating stages. The serum leptin levels of the mid- and late-lactating mice were not significantly higher than those of non-pregnant mice. These results suggested that the lactation-induced down regulation of leptin was associated with autocrine/paracrine action of leptin in mammary and adipose tissues, and that the milk leptin, especially at the latter stages of lactation, was not only ascribed to diffusive transport from maternal blood stream, but also regional production and secretion by mammary epithelial cells. This possible production of leptin by mammary epithelial cells was further supported by the fact that leptin was expressed by cultured cells of mammary epithelial cell line, COMMA-1D, in a manner negatively dependent on the lactogenic hormones. (+info)