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1.
J Dairy Sci ; 103(7): 6612-6626, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32307158

RESUMEN

Adrenal responsiveness was tested in nonpregnant, lactating Holstein dairy cows fed diets supplemented with OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ), an immune modulator, and in nonsupplemented control (CON) cows following bolus infusions of a combination of corticotropin-releasing hormone (CRH; 0.3 µg/kg of BW) and arginine vasopressin (VP; 1.0 µg/kg of BW) or ACTH (0.1 IU/kg of BW) in 2 environments: thermoneutral [TN; temperature-humidity index (THI) <60] for 24 h/d and heat stress (HS; THI >68 for 17 h/d). Cows (506) were initially fed OG (n = 254) or CON (n = 252) diets for 44 d before selection of a subgroup of cows (n = 12; 6 OG, 6 CON) for the study. The 2 subgroups were balanced for parity, milk yield, and days in milk. All cows were transported to and housed in 2 environmentally controlled rooms at the University of Arizona Agricultural Research Complex (Tucson). Cows were given 3 d to acclimate to the rooms and then underwent 12 d of TN conditions and then 8 d of HS conditions for a total of 24 d on experiment. Cows were infused with CRH-VP on d 9 of TN and on d 1 of HS and with ACTH on d 10 of TN and on d 2 of HS. Hormone infusions took place at 1000 h (0 h) on each infusion day. Blood samples, taken in 30-min intervals, were first collected at 0800 h (-2 h) and were drawn until 1800 h (8 h). Before infusion, serum progesterone was elevated in OG cows compared with CON cows. Infusion of releasing factors (CRH-VP or ACTH) caused increases in serum cortisol and progesterone, but cortisol release was greater in CON cows than in OG cows during HS, whereas progesterone did not differ between the 2 treatments. Serum ACTH increased following infusion of releasing factors, but this increase was greater following CRH-VP infusion than ACTH infusion. Serum bovine corticosteroid-binding globulin also increased following infusion of releasing factors in both treatment groups, but this increase was greater during HS in cows fed OG. The free cortisol index (FCI) increased following CRH-VP and ACTH and was higher in HS than in TN for both OG and CON cows. However, the FCI response was blunted in OG cows compared with CON cows during HS. Heat stress enhanced the adrenal response to releasing factors. Additionally, the adrenal cortisol and FCI response to releasing factors was reduced during acute heat stress in cows fed OG. Collectively, these data suggest that OG supplementation reduced the adrenal responsiveness to factors regulating cortisol secretion during acute HS.


Asunto(s)
Hormona Adrenocorticotrópica/farmacología , Bovinos/fisiología , Hormona Liberadora de Corticotropina/farmacología , Suplementos Dietéticos/análisis , Leche/metabolismo , Vasopresinas/farmacología , Animales , Dieta/veterinaria , Femenino , Respuesta al Choque Térmico , Humedad , Hidrocortisona/sangre , Lactancia , Paridad , Embarazo , Progesterona/sangre
2.
J Dairy Sci ; 100(5): 4025-4037, 2017 May.
Artículo en Inglés | MEDLINE | ID: mdl-28237583

RESUMEN

The objective of this study was to investigate the direct effects of feed supplements niacin and betaine on the heat shock responses of in vitro cultured cells derived from bovine mammary and uterine tissues. First, we determined the mRNA expression profiles of the niacin receptor (GPR109A) in bovine tissues (liver, skin, uterus, udder, and ovary) and in cells derived from bovine mammary epithelium (mammary alveolar cells, MAC-T; bovine mammary epithelial cells, BMEC) and endometrium (bovine endometrial cells, BEND). We found that GPR109A was distributed in all examined tissues and cells, and the highest expression was in cells from skin and udder. Second, we evaluated the effects of niacin treatment on the mRNA abundance of heat shock proteins 70 and 27 (HSP70 and HSP27) in MAC-T, BMEC, and BEND under thermoneutral conditions and heat stress, and whether these effects were associated with alterations in the mRNA expression of prostaglandin E2 synthesis-related genes, including cyclooxygenase 1 and 2 (COX-1 and COX-2) and microsomal prostaglandin E synthase 1 and 2 (mPGES-1 and mPGES-2). Quantitative PCR data indicated that niacin suppressed HSP70 mRNA expression in BMEC and both HSP70 and HSP27 in BEND under thermoneutral conditions. Only COX-2 expression was downregulated by niacin in BMEC; other prostaglandin E2 synthesis-related genes stayed unaltered in BMEC and BEND. The mRNA abundance of HSP70, COX-1, COX-2, and mPGES-1 were elevated in niacin-treated MAC-T. During heat stress, niacin increased mRNA levels of HSP70 and HSP27 in MAC-T and HSP27 in BEND, but decreased HSP70 in BMEC. Although mPGES-2 was stimulated by niacin in BEND, the mRNA expression of prostaglandin E2 synthesis-related genes were consistent with neither HSP70 nor HSP27 expression patterns in niacin-treated BMEC and MAC-T. These data suggest that the effects of niacin on heat shock protein expression and prostaglandin E2 synthesis were not well coupled in these cells. Finally, we tested the effects of betaine treatment on viability and apoptosis in BMEC. Compared with control cultures, viability was higher in betaine-treated cells at 8 h under thermoneutral conditions and at 16 h in heat stress, and apoptotic rates were lower at 8 h. Our data support a dual role for niacin in regulating heat shock protein expression in normal and heat-shocked cells derived from mammary and uterine tissues, and positive effects of betaine in regulating mammary cell viability during heat stress.


Asunto(s)
Betaína , Niacina , Animales , Bovinos , Proteínas HSP70 de Choque Térmico , Proteínas de Choque Térmico/genética , Respuesta al Choque Térmico , ARN Mensajero
3.
J Dairy Sci ; 97(8): 5023-34, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24881789

RESUMEN

Twenty-four multiparous high-producing dairy cows (40.0±1.4kg/d) were used in a factorial design to evaluate effects of 2 environments [thermoneutral (TN) and heat stress (HS)] and a dose range of dietary rumen-protected niacin (RPN; 0, 4, 8, or 12g/d) on body temperature, sweating rate, feed intake, water intake, production parameters, and blood niacin concentrations. Temperature-humidity index values during TN never exceeded 68 (stress threshold), whereas temperature-humidity index values during HS were above 68 for 24h/d. The HS environment increased hair coat and skin, rectal, and vaginal temperatures; respiration rate; skin and hair coat evaporative heat loss; and water intake and decreased DMI (3.5kg/d), milk yield (4.1kg/d), 4% fat-corrected milk (2.7kg/d), and milk protein yield (181.7g/d). Sweating rate increased during HS (12.7g/m(2) per h) compared with TN, but this increase was only 10% of that reported in summer-acclimated cattle. Niacin supplementation did not affect sweating rate, dry-matter intake, or milk yield in either environment. Rumen-protected niacin increased plasma and milk niacin concentrations in a linear manner. Heat stress reduced niacin concentration in whole blood (7.86 vs. 6.89µg/mL) but not in milk. Reduced blood niacin concentration was partially corrected by dietary RPN. An interaction existed between dietary RPN and environment; dietary RPN linearly increased water intake in both environments, but the increase was greater during HS conditions. Increasing dietary RPN did not influence skin temperatures. During TN, supplementing 12g/d of RPN increased hair coat (unshaved skin; 30.3 vs. 31.3°C at 1600h) but not shaved skin (32.8 vs. 32.9°C at 1600h) temperature when compared with 0g/d at all time points, whereas the maximum temperature (18°C) of the room was lower than skin temperature. These data suggest that dietary RPN increased water intake during both TN and HS and hair coat temperature during TN; however, core body temperature was unaffected. Thus, encapsulated niacin did not improve thermotolerance of winter-acclimated lactating dairy cows exposed to moderate thermal stress in Arizona.


Asunto(s)
Respuesta al Choque Térmico , Niacina/farmacología , Rumen/efectos de los fármacos , Animales , Arizona , Regulación de la Temperatura Corporal/efectos de los fármacos , Bovinos , Dieta/veterinaria , Grasas de la Dieta/análisis , Suplementos Dietéticos , Relación Dosis-Respuesta a Droga , Femenino , Humedad , Lactancia , Modelos Lineales , Leche/química , Leche/metabolismo , Proteínas de la Leche/análisis , Niacina/sangre , Frecuencia Respiratoria/efectos de los fármacos , Rumen/metabolismo
4.
J Dairy Sci ; 96(1): 150-7, 2013 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-23141832

RESUMEN

The aim of this experiment was to localize the mRNA and protein of ghrelin and its active receptor, growth hormone secretagogue 1A (GHS-R1A), within the reproductive tract of dairy cattle. Ghrelin is an orexigenic hormone that has been identified as a potent regulator of energy homeostasis. Recent evidence suggests that ghrelin may also serve as a metabolic signal to the reproductive tract. Ghrelin and GHS-R1A have been identified in the reproductive tract of several species, including humans, mice, and rats. However, ghrelin and GHS-R1A expression have not been described within bovine reproductive tissues. Therefore, the ampulla, isthmus, uterine body, corpus luteum, and follicles were harvested from 3 Holstein heifers (15.91±0.07 mo of age) immediately following exsanguination. Duodenum and hypothalamus were collected as positive controls for ghrelin and GHS-R1A, respectively. Tissues were fixed in 10% formalin and embedded in paraffin for microscopy. Additional samples were stored at -80°C for detection of mRNA. Ghrelin and GHS-R1A mRNA and protein were observed in all tissue types within the reproductive tract of dairy heifers; however, expression appeared to be cell specific. Furthermore, ghrelin protein appeared to be localized to the cytoplasm, whereas GHS-R1A protein was found on the plasma membrane. Within the reproductive tissues, ghrelin mRNA and protein were most abundantly expressed in the ampulla of the oviduct. Concentrations of GHS-R1A were lower than those of ghrelin but differed between tissues. This is one of the first studies to provide molecular evidence for the presence of ghrelin and GHS-R1A within the entire reproductive tract. However, implications for fertility remain to be determined.


Asunto(s)
Genitales Femeninos/química , Ghrelina/fisiología , Receptores de Ghrelina/fisiología , Animales , Bovinos , Cuerpo Lúteo/química , Cuerpo Lúteo/fisiología , Duodeno/química , Femenino , Técnica del Anticuerpo Fluorescente/veterinaria , Genitales Femeninos/fisiología , Ghrelina/análisis , Hipotálamo/química , Folículo Ovárico/química , Folículo Ovárico/fisiología , Receptores de Ghrelina/análisis , Útero/química , Útero/fisiología
5.
Animal ; 6(3): 403-14, 2012 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-22436219

RESUMEN

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.


Asunto(s)
Bovinos/inmunología , Bovinos/fisiología , Industria Lechera , Hormona del Crecimiento/administración & dosificación , Lactancia , Glándulas Mamarias Animales/fisiología , Mastitis Bovina/inmunología , Animales , Apoptosis , Bovinos/anatomía & histología , Calostro/metabolismo , Industria Lechera/economía , Industria Lechera/métodos , Femenino , Glándulas Mamarias Animales/citología , Mastitis Bovina/terapia , Leche/química , Leche/metabolismo , Paridad , Periodo Posparto , Embarazo , Reproducción , Factores de Tiempo
6.
J Dairy Sci ; 90(1): 165-83, 2007 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17183085

RESUMEN

Objectives were to determine effects of continuous milking (CM) and bovine somatotropin (bST) administration on 1) mammary epithelial cell (MEC) proliferation, apoptosis, and ultrastructure during late gestation and early lactation, 2) expression of genes associated with proliferation, and apoptosis in mammary epithelial cells, and 3) milk yield and composition. Second-gestation, first dry-period cows were randomly assigned to either continuous bST throughout late gestation and early lactation (+bST; n = 4) or no bST (-bST; n = 4) administration. Within each animal, udder halves were randomly assigned to CM or a 60-d dry period (control) treatment. Daily milk yield and weekly milk composition were measured during the last 60 d of gestation in CM halves and from 1 to 30 d postpartum for both halves. Mammary biopsies were obtained at -20 +/- 7, -8 +/- 3, +1 +/- 0, +7 +/- 0, and +20 +/- 0 d (mean +/- standard error) relative to parturition. Prepartum half-udder milk yield was greater in +bST cows than in -bST cows (9.9 vs. 8.2 kg/d) and postpartum half-udder milk yields were dramatically reduced in CM halves compared with control halves (10.6 vs. 22.2 kg/d), regardless of bST treatment. Proliferation of MEC was reduced in CM halves at -8 d (2.7 vs. 5.4%). Apoptosis of MEC was elevated during early lactation for d +1 and +7 in control halves, but was only increased at d +1 in CM halves. Turnover of MEC was not affected by bST. Ultrastructure data indicated complete involution of the control half and lactation maintenance in CM glands (d -20). By d -8, control tissue contained alveoli in an immature secretory state, but CM tissue contained both lactating and immature alveoli. Postpartum ultrastructure parameters were similar between halves until d 20 when control tissue was composed of a homogeneous population of lactating alveoli, but CM tissue contained lactating, engorged, and resting alveoli. Expression of CCAAT/enhancer binding protein-beta (CEBP-beta), cyclin D1, and bcl(2) were up-regulated during late gestation, but did not differ between control and CM halves. Expression of alpha-lactalbumin was increased in CM halves during late gestation, but was not different in CM and control tissue after parturition. Other genes evaluated (bax, insulin-like growth factor binding protein 5, ATP-binding cassette 1, and p27) were not differentially expressed at any timepoints evaluated. Results indicate that CM reduced subsequent half-udder milk yield in primiparous cows through altered MEC turnover and secretory capacity. Negative effects of CM on the subsequent lactation were not alleviated by bST supplementation.


Asunto(s)
Bovinos/fisiología , Suplementos Dietéticos , Células Epiteliales/citología , Hormona del Crecimiento/administración & dosificación , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/fisiología , Animales , Apoptosis/fisiología , Proliferación Celular , Industria Lechera/métodos , Ingestión de Alimentos , Células Epiteliales/fisiología , Células Epiteliales/ultraestructura , Femenino , Regulación de la Expresión Génica/fisiología , Lactancia/fisiología , Glándulas Mamarias Animales/ultraestructura , Leche/química , Leche/metabolismo , Periodo Posparto , Embarazo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Tiempo
7.
J Dairy Sci ; 88(5): 1732-40, 2005 May.
Artículo en Inglés | MEDLINE | ID: mdl-15829665

RESUMEN

Heat-stressed dairy cattle are bioenergetically similar to early-lactation cows in that dietary energy may be inadequate to support maximum milk and milk component synthesis. Study objectives were to evaluate whether conjugated linoleic acids- (CLA-) induced milk fat depression (MFD) during heat stress would allow for increased milk and milk component synthesis. In addition, CLA effects on production variables and its ability to induce MFD were compared between Holstein and Brown Swiss cows. Multiparous cows (n = 8, Holstein; n = 5, Brown Swiss) averaging 97 +/- 17 d in milk were used in a crossover design during the summer (mean temperature-humidity index = 75.7). Treatment periods were 21 d with a 7-d adaptation period before and between periods. During adaptation periods, all cows received a supplement of palm fatty acid distillate (242 g/d). Dietary treatment consisted of 250 g/d of CLA supplement (78.9 g/d of CLA) or 242 g/d of palm fatty acid distillate to provide equal amounts of fatty acids. The CLA supplement contained a variety of CLA isomers (3.0% trans-8, cis-10; 3.4% cis-9, trans-11; 4.5% trans-10, cis-12; and 4.8% cis-11, trans-13 CLA). Treatments were applied 2 x/d with half of the supplement top-dressed at 0600 h and the remainder top-dressed at 1800 h. There was no overall treatment effect on dry matter intake (23.9 kg/d), milk yield (40.0 kg/d), somatic cell count (305,000), protein (2.86%), or lactose content (4.51%) or yields of these milk components. Supplementation with CLA decreased overall milk fat content and yield by 26 and 30%, irrespective of breed. The reduction of milk fat content and yield was greatest on d 21 (28 and 37%, respectively). Energy availability predicted by energy balance was improved with CLA supplementation compared with controls (3.7 vs. 7.1 Mcal/d, respectively). Respiration rate (78 breaths/min) and skin temperature (35.4 degrees C) during maximum heat load were not affected by treatment. The group receiving CLA had higher total milk fat CLA concentration (9.3 vs. 4.9 mg/g). Supplementation with CLA induced MFD and altered milk fat composition similarly between breeds and improved calculated energy balance during heat stress, but had no effect on production measures under these conditions.


Asunto(s)
Bovinos/fisiología , Calor , Ácidos Linoleicos Conjugados/administración & dosificación , Animales , Enfermedades de los Bovinos/fisiopatología , Suplementos Dietéticos , Metabolismo Energético/efectos de los fármacos , Ácidos Grasos/análisis , Femenino , Trastornos de Estrés por Calor/veterinaria , Humedad , Lactancia/efectos de los fármacos , Lípidos/análisis , Leche/química , Proteínas de la Leche/análisis , Estaciones del Año , Especificidad de la Especie , Temperatura
8.
Adv Exp Med Biol ; 419: 45-52, 1997.
Artículo en Inglés | MEDLINE | ID: mdl-9193635

RESUMEN

Saccharomyces cerevisiae was transformed with expression plasmids carrying the DTA gene under control of the GAL1 promoter; colonies that formed under inducing conditions were selected; and plasmids from these colonies were screened for mutations in DTA that failed to block expression of the protein. Substitutions at three sites were identified, all of which are in the active-site cleft; and each of the substitutions reduced ADP-ribosyltransferase activity by > 10(5). The substitutions include a charge reversal mutation of a catalytically important residue (Glu148Lys) and replacements of either of two glycines (Gly22 and Gly52) with bulky residues. The fact that multiple mutations were identified in these same residues implies that there are relatively few sites at which substitutions ablate ADP-ribosyltransferase activity without blocking expression of the full-length protein. Incorporation of a primary attenuating mutation into the DTA gene allowed S. cerevisiae also to be used to select complementary secondary mutations which altered activity less drastically. Besides elucidating structure-activity relationships, mutations identified by these approaches may be useful in designing new vaccines.


Asunto(s)
Toxina Diftérica/genética , Ácido Glutámico , Mutación , Saccharomyces cerevisiae/genética , Sitios de Unión , Toxina Diftérica/química , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Vectores Genéticos , Estructura Molecular , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Saccharomyces cerevisiae/aislamiento & purificación
9.
J Dairy Sci ; 78(4): 863-71, 1995 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-7790577

RESUMEN

Effects of supplemental energy or protein on the milk production response to bST administration were examined in two separate trials. In trial 1, 40 cows were used in a 2 x 2 factorial, completely randomized design to determine the effects of bST and fat supplementation. The study consisted of a 7-d pretreatment period and a 42-d treatment period. Fat was top-dressed at 3.0 Mcal/d of NEL, and bST was administered. Supplemental fat had no effect on milk production, and NEL intakes were unaffected. Administration of bST increased milk production by 7.1 kg/d, and the milk production response was unaffected by supplemental fat. In trial 2, 4 cows were used in four periods with a 2 x 2 factorial arrangement in which water or casein was infused into the abomasum of cows fed for ad libitum intake or at 80% of their requirements. Diets and infusions were initiated simultaneously and continued for 11 d. All cows were given bST during the last 5 d. Infusion of water or casein did not alter the milk production response to bST, but restricted feeding reduced the bST response (3.2 vs. 7.2 kg/d). Concentrations of IGF-I in plasma were increased by bST administration, and the increase was greatest for cows fed for ad libitum intake. The milk production response to bST was not increased by additional energy or protein offered to cows fed well-balanced diets.


Asunto(s)
Bovinos/fisiología , Grasas de la Dieta/administración & dosificación , Proteínas en la Dieta/administración & dosificación , Hormona del Crecimiento/farmacología , Lactancia/fisiología , Animales , Peso Corporal , Caseínas/administración & dosificación , Dieta , Ingestión de Alimentos , Metabolismo Energético , Femenino , Factor I del Crecimiento Similar a la Insulina/metabolismo , Lactancia/efectos de los fármacos
10.
Mol Microbiol ; 5(6): 1501-6, 1991 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-1787799

RESUMEN

To probe the role of the protective antigen (PA) component of anthrax toxin in toxin entry into animals cells, we examined the membrane channel-forming properties and hydrophobicity of intact and trypsin-cleaved forms of the protein at various pH values. At neutral pH neither form caused release of entrapped K+ from unilamellar lipid vesicles. At pH values below 6.0, however, K+ was rapidly released upon addition of either the nicked PA (PAN) or the 63 kDa tryptic fragment of PA (PA63), which has been implicated in the toxin entry process. Under the same conditions intact PA exhibited only weak channel-forming activity, and PA20, the complementary tryptic fragment, showed no such activity. Both PA and PA63 exhibited enhanced hydrophobicity at acidic pH values, but the enhancement was greater and the pH threshold higher with PA63. Our findings indicate that proteolytic removal of PA20 from intact PA enables the residual protein, PA63, to adopt a conformation at mildly acidic pH values that permits it to insert readily and form channels in membranes. Thus acidic conditions within endocytic vesicles may trigger membrane insertion of PA63, which in turn promotes translocation of ligated effector moieties, edema factor or lethal factor, across the vesicle membrane into the cytosol.


Asunto(s)
Antígenos Bacterianos , Bacillus anthracis/química , Toxinas Bacterianas/química , Carbunco/inmunología , Carbunco/metabolismo , Bacillus anthracis/inmunología , Bacillus anthracis/metabolismo , Toxinas Bacterianas/inmunología , Toxinas Bacterianas/metabolismo , Fluoresceínas/metabolismo , Fluorescencia , Concentración de Iones de Hidrógeno , Cinética , Liposomas/metabolismo , Sustancias Macromoleculares , Fosfatidilcolinas , Fosfolípidos/metabolismo , Potasio/metabolismo
11.
Infect Immun ; 55(7): 1647-51, 1987 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-3110068

RESUMEN

A mutant, full-length form of diphtheria toxin was cloned into Escherichia coli K-12 and expressed under BL-1 + EK-1 containment. A gene fragment encoding the catalytic domain of the toxin was subjected to oligonucleotide-directed mutagenesis to produce a three-base mutation of an active site residue; Glu-148 was thereby replaced by Ser. Ser-148 fragment A had less than 1% of the ADP-ribosyltransferase activity of wild-type fragment A. Next, the complementary portion of the toxin structural gene was spliced with the mutated DNA fragment downstream of codon 148 to produce a construct that encoded mutant whole toxin with Ser at position 148. The mutant toxin was indistinguishable from authentic diphtheria toxin by Western blot analysis, but was about 800-fold less cytotoxic than wild-type toxin for BS-C-1 cells. Evidence from subunit exchange experiments indicated that a substantial fraction of the mutant toxin contained a fully functional B moiety, capable of mediating the entry of wild-type fragment A into sensitive mammalian cells. This combination of approaches provides a means of applying recombinant DNA methods in E. coli to study structure-function relationships in whole diphtheria toxin.


Asunto(s)
Toxina Diftérica/genética , ADP Ribosa Transferasas , Secuencia de Aminoácidos , Células Cultivadas , Clonación Molecular , Toxina Diftérica/inmunología , Toxina Diftérica/toxicidad , Escherichia coli/genética , Técnicas Inmunológicas , Mutación , Pentosiltransferasa/genética , Pentosiltransferasa/metabolismo , Biosíntesis de Proteínas/efectos de los fármacos , Proteínas Recombinantes
12.
J Dairy Sci ; 69(3): 754-9, 1986 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-3711407

RESUMEN

Records from 2105 calves born over 2 yr on a large dairy in a subtropical climate were examined to delineate factors that influence passive transfer of colostral immunoglobulins and the effect of passive transfer of immunoglobulin on calf mortality. Seasonal effects on immunoglobulin absorption were detected with highest serum total protein occurring in February and March. Lower total protein concentrations were associated with elevated environmental temperatures in the summer months. Maternal antibody was highest in calves from second parity cows; and dystocia appeared to decrease the amount of immunoglobulin absorbed by the neonatal calf. Calves that died of infectious disease during the first 14 wk of life had significantly lower serum total protein concentrations than those that lived. Heritability of serum protein concentration in calves was .02 +/- .03.


Asunto(s)
Animales Recién Nacidos/inmunología , Bovinos/inmunología , Inmunidad Materno-Adquirida , Preñez , Animales , Proteínas Sanguíneas/análisis , Calostro/inmunología , Femenino , Masculino , Embarazo
13.
J Dairy Sci ; 68(6): 1479-87, 1985 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-4019886

RESUMEN

Objectives were to study influences of heat stress and dietary potassium content on production and physiological responses of 8 Jersey and 10 Holstein cows blocked by breed and assigned randomly to no shade or shade environments. Each cow received a different dietary potassium treatment (.66, 1.08, and 1.64% of dry matter) in each of three 30-day periods. Rates of potassium loss from skin were almost five times greater for no shade as for shade cows during the hottest part of the day (1300 to 1500 h). Overall, cows with no shade ate 56% less during the daytime (0800 to 1600 h), 19% more during nighttime (1600 to 0800 h), and 13% less total feed than cows with shade. Interactions of environment and breed with dietary potassium treatment suggest differences in feed intake and milk yield responses to increasing dietary potassium content. Total daily feed intake and milk yield of cows with no shade responded in curvilinear fashion to increasing dietary potassium, whereas responses in shade were small. Largest responses in no shade were as dietary potassium increased from .66 to 1.08%. Milk yield of Holsteins increased with increasing dietary potassium, but yield of Jerseys did not. Combined effects of elevated potassium loss from skin and reduced potassium and dry matter intake during heat stress suggested that lactating dairy cows may benefit from supplemental potassium.


Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Bovinos/fisiología , Calor , Lactancia , Potasio/metabolismo , Análisis de Varianza , Animales , Bovinos/metabolismo , Ingestión de Alimentos , Femenino , Alimentos Fortificados , Necesidades Nutricionales , Cloruro de Potasio/administración & dosificación , Embarazo , Piel/metabolismo , Sudoración
14.
J Dairy Sci ; 67(11): 2546-53, 1984 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-6097604

RESUMEN

Objectives were to study effects of heat stress, 0 or .85% sodium bicarbonate, 0 or 1.0% potassium bicarbonate, and 1.0 or 1.5% total dietary potassium on production and physiological responses of dairy cows. Eighteen lactating Holsteins were assigned to shade (control) or no shade (heat stress) lots continuously for three consecutive 35-day periods and to different dietary treatments each period. Basal diet was 25% cottonseed hulls and 75% concentrate. Daytime and nighttime feed intake and production were measured the last 2 wk of each period, and milk and blood were sampled the final day of each period. Black globe temperature, rectal temperature, respiration rate, and blood pH were higher in no shade. Daytime intake was 132% greater in shade, nighttime intake was not different between environments. Milk production was about 19% greater for evening and morning milkings in shade. Daytime intake, daytime and nighttime milk production were higher with sodium bicarbonate. Potassium bicarbonate reduced intake and production. Higher total dietary potassium increased total daily milk production. Lactating cows appear adept at withstanding environmental and dietary challenges to acid-base homeostasis. Supplementation of sodium bicarbonate and 1.5% dietary potassium, but not potassium bicarbonate, were beneficial to lactating dairy cows.


Asunto(s)
Bicarbonatos/farmacología , Enfermedades de los Bovinos/fisiopatología , Bovinos/fisiología , Calor , Lactancia , Compuestos de Potasio , Potasio/farmacología , Estrés Fisiológico/veterinaria , Animales , Análisis de los Gases de la Sangre/veterinaria , Temperatura Corporal , Femenino , Alimentos Fortificados , Leche/metabolismo , Embarazo , Recto , Respiración , Bicarbonato de Sodio , Estrés Fisiológico/fisiopatología
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