Growth and reproductive development from weaning through 20 months of age among breeds of bulls in subtropical Florida

To determine the effect of breed on growth and reproductive development, weaned bulls in each of 2 yr were managed as a single group for approximately a year. In Year 1, the study group consisted of 24 Angus, 24 Brahman, 20 Hereford and 14 Senepol bulls, while in Year 2, it contained 25 Angus, 17 Brahman. 13 Romosinuano and 9 Nellore x Brahman bulls. Body and testicular growth measurements were recorded at 6-wk intervals. At approximately 1 yr of age and quarterly thereafter (4 periods), bulls were evaluated for libido, pubertal status, and GnRH-induced LH and testosterone secretion. Significant breed-by-age interactions occurred for most growth measurements. Brahman bulls (Bos indicus ) were (P < 0.05) older and heavier at puberty than Angus, Hereford, Senepol and Romosinuano bulls (Bos taurus ). Libido scores were lowest for Brahman and Nell ore x Brahman bulls (Bos indicus ). highest for Angus and Hereford bulls (temperate Bos taurus breeds) and intermediate for Senepol and Romosinuano bulls (tropical Bos taurus breeds; P < 0.05). Differences were not consistent among breeds or between years for GnRH-induced LH secretion. In both years, basal testosterone concentrations and areas under the GnRH-induced testosterone curve were higher (P < 0.05) for Angus and Hereford bulls (temperate breeds) than for Brahman, Senepol, Romosinuano and Nellore x Brahman bulls (tropical breeds). In conclusion, reproductive development of Senepol and Romosinuano bulls (tropical Bos taurus breeds) was more similar to Angus and Hereford bulls (temperate Bos taurus breeds) than to Brahman and Nellore x Brahman bulls (Bos indicus ).     

Evolutionary potential of the extrinsic incubation period of dengue virus in Aedes aegypti

Dengue fever is the most common arboviral disease worldwide. It is caused by dengue viruses (DENV) and the mosquito Aedes aegypti is its primary vector. One of the most powerful determinants of a mosquito's ability to transmit DENV is the length of the extrinsic incubation period (EIP), the time it takes for a virus to be transmitted by a mosquito after consuming an infected blood meal. Here, we repeatedly measured DENV load in the saliva of individual mosquitoes over their lifetime and used this in combination with a breeding design to determine the extent to which EIP might respond to the evolutionary forces of drift and selection. We demonstrated that genetic variation among mosquitoes contributes significantly to transmission potential and length of EIP. We reveal that shorter EIP is genetically correlated with reduced mosquito lifespan, highlighting negative life‐history consequences for virus‐infected mosquitoes. This work highlights the capacity for local genetic variation in mosquito populations to evolve and to dramatically affect the nature of human outbreaks. It also provides the impetus for isolating mosquito genes that determine EIP. More broadly, our dual experimental approach offers new opportunities for studying the evolutionary potential of transmission traits in other vector/pathogen systems.     

Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.     

Efficiency of single-sire mating programs with beef bulls mated to estrus synchronized females

Efficiency in reference to pregnancy rates of breeding beef bulls with estrus synchronized cows and heifers was tested. Most bulls (104 of 112) were given a breeding soundness examination and two 10-min libido/serving capacity tests. Females received either Syncro-Mate-B (SMB) or two injections of Prostaglandin F(2)alpha (PGF) to synchronize estrus. They were assigned to single-sire breeding groups with bull-to-female ratios ranging from 1:7 to 1:51. Control groups consisted of untreated females maintained in single-sire breeding pastures with ratios from 1:24 to 1:37. Continuous observations of sexual activity were made for 30 h (SMB) and 48 h (PGF). After the 120-h posttreatment breeding period, females were placed in breeding pastures. During the synchronized breeding period the percentage of pregnant cattle of total treated was 43.5 +/- 1.7% compared (P < 0.01) with 58.9 +/- 3.3% for the control group after 23 d of breeding. At end of 28-d (treated) and 46-d (control) period, the percentage of pregnant females was 75.0 +/- 2.4 and 79.6 +/- 4.7, respectively (P > 0.05). In SMB trials, the percentages of females exhibiting estrus, those serviced at estrus and those pregnant following service during the synchronized breeding period were 90.8 +/- 1.5, 73.3 +/- 4.5 and 56.4 +/- 5.6%, respectively. In PGF trials, the means for these same factors were 78.3 +/- 2.4, 70.4 +/- 5.9 and 56.1 +/- 6.5%, respectively.     

Determination of synthesis, recycling and body mass of glucose in rats and rabbits in vivo with 3H- and 14C-labelled glucose

1. Glucose labelled with (3)H in position 2 and uniformly with (14)C was administered simultaneously to rabbits and rats either as a single injection or by continuous infusion. Plasma glucose specific radioactivity and the yield of (3)H in the plasma water were monitored. 2. The rates of synthesis, recycling of carbon and total body mass of glucose were calculated, without assuming a multicompartmental model and without fitting data by exponential expressions. 3. The rate of synthesis of glucose in starved-overnight rabbits was 4mg/min per kg (range 3-4.5mg/min per kg) and 25-35% of the glucose carbon was recycled. The mass of total body glucose in starved rabbits was 290mg/kg (range 220-390mg/kg). About one-third of the total body glucose equilibrates nearly instantaneously with plasma glucose. 4. In rats starved overnight, glucose synthesis was about 10mg/min per kg and recycling of carbon ranged from 30-40%. Total body mass (per kg body weight) is similar to that in rabbits. 5. The activity in plasma water after injection of [2-(3)H]glucose was determined. The initial rate of (3)H(2)O formation is rapid, indicating that the major site of glucose catabolism is in the rapidly mixing pool. The curve of total body glucose radioactivity was obtained from the (3)H(2)O yield, and total mass of glucose was calculated. This agrees with that obtained from the (3)H specific-radioactivity curve.     

Lipopolysaccharide modulates receptors for leukotriene B4, C5a, and formyl-methionyl-leucyl-phenylalanine on rabbit polymorphonuclear leukocytes

Peripheral blood polymorphonuclear leukocytes (PMNL) isolated from rabbits after an i.v. injection of endotoxin exhibited decreased chemotactic migration in response to leukotriene B4 (LTB4) and C5a, but not N-formyl-methionyl-leucyl-phenylalanine (fMLP), after endotoxin treatment. The binding of radiolabeled LTB4, fMLP, and C5a to isolated PMNL was assessed in order to determine whether altered receptor expression could account for the observed functional changes. Control PMNL expressed binding sites for fMLP, LTB4, and C5a similar to those previously characterized from human PMNL. Control PMNL expressed a single class of 14,600 +/- 2700 receptors for fMLP with a mean dissociation constant (Kd) of 2.0 +/- 0.6 nM at 0 degrees C, whereas two subclasses of binding sites were expressed for LTB4: 10,300 +/- 6800 high-affinity and 85,600 +/- 53,000 low-affinity binding sites per PMNL with mean Kd for LTB4 of 0.75 +/- 0.43 nM and 70 +/- 58 nM (mean +/- SD, n = 5), respectively. Control PMNL bound [125I]-C5a in a dose-dependent and saturable manner at 24 degrees C. At saturating concentrations of C5a, PMNL obtained from control rabbits bound 270,000 +/- 50,000 molecules of [125I]-C5a with half-maximal binding occurring at [125I]-C5a concentrations of 5.5 +/- 1.9 nM. The binding of LTB4 and C5a to PMNL obtained 24 hr after an i.v. injection of endotoxin was markedly decreased compared with control PMNL. PMNL from endotoxin-treated rabbits exhibited 68% fewer high-affinity binding sites per PMNL for LTB4 and a 51% decrease in the amount of [125I]-C5a bound at saturating concentrations compared with control PMNL. There was no significant change in the Kd of the high-affinity binding sites for LTB4, no change in the Kd and number of the low-affinity binding sites for LTB4, and a small decrease in the apparent Kd for C5a to 3.3 +/- 1.1 nM. Even though the pretreatment with i.v. endotoxin did not alter chemotactic or degranulation responses elicited by fMLP, the endotoxin pretreatment induced an eightfold increase in the receptor density without altering the Kd for fMLP. Decreased receptor expression could account in large part for the decreased chemotactic responsiveness towards C5a and LTB4 induced by LPS. The finding that a substantial increase in receptors for fMLP need not be accompanied by a comparable functional change suggests that decreased efficiency in receptor coupling to intracellular biochemical events may also result from i.v. endotoxin.     

Tongue manipulation of the palate assists estrous detection in the bovine

To understand the mechanisms for introducing urine or vaginal secretions into the vomeronasal organ, we used 16 mm cinematography and a freeze frame/slow motion technique to analyze the mouth and tongue movements of Brahman bulls while they examined the vulvas of restrained, estrogen-primed cows. Prior to flehmen, the mouth slowly opened, the curled tip of the tongue compressed the hard palate and the body of the tongue protruded from the mouth. The tongue maintained this form and moved forward. Once the tip of the tongue reached the incisive papilla, the body of the tongue retracted and the tip of the tongue relaxed. This tongue compression stroke (TCS) of the hard palate occurred 2 to 6 times, lasting 1 4 to 1 2 sec/stroke. Pressure changes in the vomeronasal organ are assumed to occur during and following TCSs, resulting in aspiration of any liquid in the incisive pit into the incisive and vomeronasal ducts. Such aspiration probably does not occur during flehmen because the tongue is relaxed and on the floor of the mouth.     

Harderian gland porphyrin, lysosomal and type II 5'-deiodinase rhythms in Sprague-Dawley and Fischer-344 rats kept under chronic long- or short-photoperiod conditions.

1. Harderian gland porphyrin concentrations were 1.5-fold higher in Fischer-344 male rats than in Sprague-Dawley male rats and there were no differences due to exposure to LD 14:10 (LP) or LD 10:14 (SP) lighting conditions for 8 weeks in either strain. 2. 24-hr periodic regression analyses of porphyrin concentration detected a significant rhythm in both lighting conditions in both strains, with no differences in acrophase due to lighting conditions. 3. In both strains, porphyrin levels were highest in the late phase-early dark period and fell during the early part of the dark period. 4. Acid phosphatase activity did not vary with time (circadian rhythm), strain or photoperiodic lighting condition. 5. Circadian rhythms in beta-glucuronidase, alpha-mannosidase and hexosaminidase activity were present in some instances, but, probably due to the low amplitude to these rhythms, a consistent effect of strain or housing condition was not found. When 24-hr rhythms were observed in either strain, the acrophase occurred during the afternoon-early evening daylight period. 6. A significant effect of strain on mean values of type II 5'-deiodinase activity was noted in Fischer-344 rats. 7. Significant rhythms in type II 5'-deiodinase activity were found in both strains exposed to LD 10:14.