Restricted Ion Research Articles

Increasing the Power of the Test Through Pre-Test – A Robust Method

Robust test procedures are developed for testing the intercept of a simple regression model when the slope is (i) completely unspecified, (ii) specified to a fixed value, or (iii) suspected to be a fixed value. Defining (i) unrestricted (UT), (ii) restricted (RT), and (iii) pre-test test (PTT) functions for the intercept parameter under the three choices of the slope, tests are formulated using the M-estimation methodology. The asymptotic distributions of the test statistics and their asymptotic power functions are derived. The analytical and graphical comparisons of the tests reveal that the PTT achieves a reasonable dominance over the other tests.

Phosphorylation and Ubiquitination of Degron Proximal Residues Are Essential for Class II Transactivator (CIITA) Transactivation and Major Histocompatibility Class II Expression

Major histocompatibility (MHC) class II molecules are cell surface glycoproteins that present extracellular antigens to CD4(+) T cells and are essential for initiation of the adaptive immune response. MHC class II expression requires recruitment of a master regulator, the class II transactivator (CIITA), to the MHC class II promoter. Post-translational modifications to CIITA play important roles in modulating CIITA mediated transcription of various genes in different cell types. We have previously linked regulation of CIITA to the Ubiquitin Proteasome System (UPS), and we and others have demonstrated that mono-ubiquitination of CIITA dramatically increases its transactivity whereas poly-ubiquitination leads to CIITA degradation. Here we identify three degron proximal lysine residues, Lys-315, Lys-330, and Lys-333, and a phosphorylation site, Ser-280, located within the CIITA degron, that regulate CIITA ubiquitination, stability, and MHC class II expression. Together, these findings contribute to the developing post-translational modification code for CIITA.

Molecular methods forBacillus cereusandBacillus thuringiensisfrom humans, pesticides and foods, differentiation

B. cereus and B. thuringiensis strains have been associated with gastro-intestinal infections due to enterotoxins production. The possibility of differentiating between B. cereus and B. thuringiensis is a real need in preventing intoxication and in monitoring potentially contaminated foods. The use of DNA comparison provides clearer results than classical microbiological methods in distinguishing B. cereus from B. thuringiensis . The use of a Polymerase Chain Reaction (PCR) followed by Endonuclease Restriction (RE) made the distinction possible in spite of the huge similarity between the two closely related species.

Effect of environmental enrichment by providing trees as rubbing objects in grassland: Grazing cattle need tree‐grooming

ABSTRACTWe examined the role of trees as grooming objects in grazing pasture and investigated their necessity. Four grazing Japanese Black cows were used. Experimental pastures with restricted (RST) and released (RLS) grooming with trees were established. Examination was carried out for 24 h in each RST and RLS. The respective frequencies and duration of self‐grooming, allo‐grooming (social grooming) and grooming with trees was recorded by a continuous scan sampling method, and maintenance behavior was recorded by a 2‐min group animal scan sampling method. Grooming with trees in RLS occurred 29 ± 12 times/24 h and for 1342 ± 475 s/24 h. Total frequencies and duration of grooming in RLS tended to increase from that in RST (P = 0.08, P = 0.06, respectively). However, self‐grooming and allo‐grooming exhibited no differences. The results indicate that cattle may enrich their grooming through the use of trees if the latter are available. Furthermore, they may not substitute grooming with trees with other forms of grooming if no trees are available in the grassland. No difference was observed in the general proportion of their maintenance behavior. These results suggest that trees in grassland provide a good environmental enrichment object that satisfies cattle's potential needs of grooming and did not restrict their general behavior.

Abnormal Pulmonary Function in Adults and Children with Sickle Cell Disease.

Introduction: Chronic lung disease is a fatal complication in sickle cell disease (SCD) often undiagnosed until late stages. Early detection and treatment of risk factors may improve survival. Since asthma, pulmonary hypertension (PHT), and acute chest syndrome (ACS) are potential risk factors, in 1998, we began screening patients with history of ACS or wheezing with pulmonary function tests (PFT) and echocardiogram (echo).Methods: A chart review was completed on the 362 adults and children evaluating history of asthma, lung function (PFT) and PHT (echo, tricuspid regurgitant jet velocity ≥ 2.5).Results:PFT FindingsAll AgesAdultsChildrenPHT (All Ages)Study performed34% (124/362)41% (95/232)22% (29/130)Echo: 90% (111/124)Abnormal85% (106/124)87% (83/95)79% (23/29)51% (54/106)Obstructive (OBS) only31% (33/106)31% (26/83)30% (7/23)42% (14/33)Restrictive (REST) only30% (32/106)28% (23/83)39%(9/23)38% (12/32)Both OBS + REST pattern27% (29/106)29% (24/83)22% (5/23)69% (20/29)“Abnormal,” not specified11% (12/106)12% (10/83)9% (2/23)67% (8/12)DLCO < 65% predicted48% (45/94)53% (42/80)21% (3/14)54% (26/48)Diagnosis & TreatmentClinical asthma diagnosis13% (47/362)14% (33/232)11% (14/130)43% (20/47)Receiving asthma treatment51% (24/47)45% (15/33)64% (9/14)50% (12/24)Bronchodilator only23% (11/47)24% (8/33)21% (3/14)45% (5/11)Inhaled steroid23% (11/47)18% (6/33)36% (5/14)55% (6/11)Singulair4% (2/47)3% (1/33)7% (1/14)50% (1/2)PFT suggests asthma50% (62/124)53% (50/95)41% (12/29)53% (33/62)+PFT, + asthma treatment16% (10/62)14% (7/50)25% (3/12)80% (8/10)One hundred twenty-four patients underwent PFTs, of which 111 (85%) were abnormal. Obstructive and/or restrictive disease with abnormal diffusion capacity were widespread. Of patients with an obstructive pattern, only 16% were receiving any asthma treatment. Forty-seven patients (33 adults and 14 children) were diagnosed with asthma. However, only half were receiving any treatment: 23% bronchodilators, and 23% inhaled steroids. Echo was performed on 90% of patients with PFT data. Half of all patients with abnormal PFTs, and 69% of those with obstructive/restrictive patterns, had PHT.Conclusion: While a more severe population may have been tested, this data suggests abnormal lung function is prevalent in SCD and is associated with PHT. Recent data suggests abnormal NO metabolism may link asthma and PHT in SCD. In conclusion, our data suggests patient morbidity will be decreased by regular screening with PFT and echo followed by early treatment for asthma and PHT.

New Concept in Cavernous Sinus Dural Arteriovenous Fistula

An extradurally located cavernous sinus dural arteriovenous fistula (CSDAVF) exhibits different clinical behavior from other dural arteriovenous fistulas (DAVFs) located between 2 dural leaves. The aim of this study is to define angiographic types of CSDAVF associated with presenting symptom (Sx) and venous drainage patterns. CSDAVFs during a mean of 23-month follow-up period of 58 patients (17 to 73 years, male:female ratio=8:50) were retrospectively analyzed. The 3 types of CSDAF, ie, proliferative (PT), restrictive (RT), and late restrictive (LRT) types, were categorized by the degrees and patterns of prominent arteriovenous shunt as well as venous flow. The status of the venous connection with CS and the presenting Sx patterns classified as orbital (OrbSxP), ocular (OcuSxP), cavernous (CavSxP), and cerebral (CerSxP) were associated with angiographic types as well as symptom onset, age, and gender. Correlations of discrete and categorical variables were statistically analyzed using the chi2 or Fisher exact test. PT (n=23) and RT (n=23) of CSDAVF were more common than LRT (n=12) (P=0.016) in patients with younger than 65 years and were related to OrbSxP (P=0.015) and CavSxP (P=0.038) in contrast to LRT to OcuSxP (P=0.004). Early onset of Sxs was related to the OrbSxP (P=0.08) and CavSxP (P<0.001). CerSxP (5%) was noted in RT or LRT. OrbSxP was related to the superior ophthalmic venous drainage (P=0.026) and CavSxP to the inferior petrosal sinus (P=0.046) and posterior fossa venous drainages (P=0.014). Seven patients revealed chronological progression of CSDAVF from PT to LRT and even to complete healing. CSDAVF presents as 3 distinctive angiographic types and is associated with presenting Sxs and venous drainage patterns.

Effects of short-term feed deprivation and melatonin implants on circadian patterns of leptin in the horse1

Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 +/- 0.41 vs. 7.29 +/- 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 +/- 0.31 vs. 1.08 +/- 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 +/- 0.58 ng/mL for morning vs. 19.00 +/- 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 +/- 1.7 vs. 22.07 +/- 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.

Low Carbohydrate Diet in Management of Obesity - A Short Review

There is a global rise in obesity in the form of epidemic .In view of obesity epidemic low carbohydrate diets are becoming popular. These diets claim to be effective at producing weight loss despite ad libitum consumption of fatty meat, butter, and other high-fat dairy products, restricting only the intake of carbohydrates. Low-carbohydrate diets have been regarded as fad diets, but recent research questions this view. A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restr ict ion of carbohydrates. Trials had showed better weight loss on the low-carbohydrate diet after 6 months, but no difference after 12 months. The apparent paradox that ad-libitum intake of high-fat foods produces weight loss might be due to severe restriction of carbohydrate depleting glycogen stores, leading to excretion of bound water, the ketogenic nature of the diet being appetite suppressant, the high protein-content being highly satiating and reducing spontaneous food intake, or limited food choices leading to decreased energy intake. Long-term studies are needed to measure changes in nutritional status and body composition during the low-carbohydrate diet, and assess fasting and postprandial cardio vascular risk factors and adverse effects. Without that information, lowcarbohydrate diets cannot be recommended.

Effects of different feeding strategies during the winter period on behaviour and performance in mink females ( Mustela vison)

Female mink used for breeding are slimmed during the winter to best prepare them for flushing immediately before the mating season. However, intensive and long-term slimming has a number of negative consequences e.g. a significant increase in stereotypies. The purpose of the study was to examine the effects of three different feeding strategies on the female’s body weight and behaviour during the winter as well as examine the effects of the feeding strategies on the reproduction results and physiological parameters. The three different feeding strategies were ad libitum (ADL) feeding from 16 October to 16 February, ad libitum feeding but with a substantial (SUB) diet from 22 December to 16 February, and restricted (RE) feeding from 16 October to 16 February. Thereafter, the three groups were fed according to the same feeding strategy. The study included a total of 180 female mink. Behavioural observations were made by focal sampling in December, January, February, and March. The females were weighed approximately every second week from August to March. During the lactation period, the females were weighed at parturition, and 2, 3, 4, and 7 weeks after parturition. Blood samples were collected in November, February, March, May, and June for clinical–chemical analysis. Fifty-three per cent of the females fed restrictively (RE) were observed carrying out stereotypies compared to 27% of the females fed ad libitum (ADL, SUB). The study has demonstrated that it was possible to reduce the body weight of the females by feeding them a low-energy feed, and that this treatment did not lead to an increase in the incidence of stereotypies in mink. The body weight was lower for stereotypic than for non-stereotypic females from the age of 4 months.

Effects of feeding level before and after calving, and restricted suckling frequency on postpartum reproductive and productive performance of Sarda and Charolais×Sarda beef cows

Two experiments were carried out on 48 Sarda (Sa) and 48 Charolais×Sarda (F1) grazing cows using a factorial design: 2 genotypes×2 feeding levels targeted to low (2, L) and high (3, H) body condition scores (BCS) at calving and in the following 3 months×2 suckling frequencies. These were ad libitum suckling (ADLIB) versus restricted (RESTR) to one suckling per day (45–90 days postpartum) in experiment 1 and ad libitum suckling (ADLIB) versus isolated (ISOL, one suckling daily between days 25 and 50 with no visual or auditory contacts between dams and calves outside the daily suckling period) in experiment 2. In experiment 1 postpartum anoestrus interval (PPI) was shorter in SaL than in F1L cows ( P<0.01). In experiment 2 BCS around calving exerted an overriding effect on PPI; Sa cows tended ( P<0.08) towards shorter PPI than F1 cows. Conception rate (CR) was higher in the 4th month postpartum in SaL than in F1L cows in experiment 1 (95 vs. 57%, P<0.01) and in H than in L cows (58 vs. 14%, P<0.001) in experiment 2. Suckling frequency affected CR of F1 cows by the 8th month postpartum in experiment 2: it was 90% in F1 ISOL cows and just 55% in F1 ADLIB cows ( P<0.02). It is concluded that in the less favoured areas of Sardinia, the Sarda breed gives better reproductive performance than F1 cows while maintained at low BCS during the calving period. Cross-bred, but not pure Sarda cows, can benefit from the implementation of suckling restriction with strict calf isolation.

Influence of feeding intensity on corporeal development, body composition and sexual maturity in female rabbits.

Twenty-six 6-week old female New Zealand White rabbits were divided into two groups: ad libitum (AL) and 70% restricted (RS) feeding. At the beginning of the experiment the liveweights were practically the same: 0.99 +/- 0.08 vs. 1.01 +/- 0.08 kg in group AL and RS, respectively. At 18 weeks of age the body weight of Group RS rabbits was 84.7% (3.14 +/- 0.24 kg) of the group AL (3.71 +/- 0.31 kg). The apparent digestibility of crude protein was significantly (p < 0.001) higher in Group RS than in Group AL (76.5 +/- 1.4 vs. 73.0 +/- 2.7%). The daily water consumption was significantly (p < 0.05) higher (3.5 ml/g DM intake) in Group RS as compared to Group AL (1.9 ml/g DM). Since the average body weight in Group RS at 18 weeks was the same as that of Group AL at 14 weeks of age (3.14 kg), the comparison of the live body measures and indices was based on these ages. Animals fed ad libitum or restricted show no differences at the defined age in most live body measurements except in heart girth and rump width, which were significantly (p < 0.05) shorter in Group AL than in Group RS (29.3 +/- 0.8, 5.7 +/- 0.5 and 30.7 +/- 1.0, 6.2 +/- 0.3 cm, respectively). Body capacity was significantly (p < 0.05) smaller in Group AL, as the head capacity-body capacity proportion was significantly (p < 0.05) higher in Group AL than in Group RS (1653.1 +/- 134.5, 22.0 +/- 2.5 and 1913.7 +/- 168.7, 17.7 +/- 1.9, respectively). Due to restricted feeding the growth of the head proved to be less intensive than that of the body at the same body weight. The body in these does tended to be wider. Since the head in comparison to length or capacity of the body was smaller in does fed 70% of ad libitum, it could be concluded that the development of body parts of restricted-fed does was unequal (allometric growth). The effect of feed restriction reflected in lower dry matter and fat, and a higher ash and protein content both in total body and in dry matter composition of rabbits at 18 weeks of age. Restricted feeding delayed sexual maturity (69 vs. 92% of rabbits) with later starting ovarian activity, weaker ovarian responsiveness, and a smaller number of tertiary follicles on the ovarian surface.

Sibutramine alters the central mechanisms regulating the defended body weight in diet-induced obese rats.

Chronic administration of sibutramine lowers body weight, presumably by altering brain monoamine metabolism. Here the effect of sibutramine on sympathoadrenal function (24-h urine norepinephrine and epinephrine levels) and arcuate nucleus (ARC) neuropeptide Y (NPY) and proopiomelanocortin (POMC) expression was assessed in diet-induced obese rats fed a low-fat diet. Chronic (10 wk) sibutramine [5 mg. kg(-1). day(-1) ip; rats fed ad libitum and injected with sibutramine (AS)] lowered body weight by 15% but only transiently (3-4 wk) reduced intake compared with vehicle-treated controls [rats fed chow ad libitum and injected with vehicle daily (AV)]. Other rats food restricted (RS) to 90% of the weight of AS rats and then given sibutramine restored their body weights to the level of AS rats when allowed libitum food intake. After reequilibration, RS rats were again energy restricted to reduce their weight to 90% of AS rats, and additional vehicle-treated rats (RV) were restricted to keep their body weights at the level of AS rats for 3 wk more. Terminally, total adipose depot weights and leptin levels paralleled body weights (AV > AS = RV > RS), although AS rats had heavier abdominal and lighter peripheral depots than RV rats of comparable body weights. Sibutramine treatment increased sympathetic activity, attenuated the increased ARC NPY, and decreased POMC mRNA levels induced by energy restriction in RV rats. Thus sibutramine lowered the defended body weight in association with compensatory changes in those central pathways involved in energy homeostasis.

Effects of energy intake, implantation, and subcutaneous fat end point on feedlot steer performance and carcass composition.

The purpose of this experiment was to evaluate the effects of energy intake, implantation, and fat end point on feedlot performance and carcass composition of steers. Three hundred eighty-four yearling crossbred steers (368 +/- 23.1 kg) were allotted in a completely randomized design. Treatments were arranged in a 2 x 3 x 2 factorial experiment. Main effect factors were two levels of intake, three implant strategies, and two compositional fat end points at slaughter. The levels of intake were ad libitum (AL) and restricted (RS) intake (90% ad libitum). The three implant strategies were Revalor-S (REV) (120 mg trenbolone acetate, 24 mg estradiol), Synovex-Plus (SYN) (200 mg trenbolone acetate, 28 mg estradiol benzoate), and no implant (control). The compositional target end points were 1.0 and 1.4 cm s.c. fat cover over the 12th and 13th rib. Restricted-intake steers consumed 9.2% less (P < .01) DM than AL steers. Ad libitum-intake steers gained weight 15.5% more rapidly (P < .01) than RS-intake steers. Steers implanted with REV tended (P < .07) to gain faster than SYN steers, who in turn gained 15.2% more (P < .01) than control steers. Ad libitum-intake steers were 4.8% more (P < .01) efficient than RS steers. Steers fed to a targeted 1.4 cm s.c. backfat cover were 2.9% less (P < .05) efficient than steers fed to 1.0 cm, and steers implanted with either REV or SYN had similar (P = .47) feed efficiencies, whereas control steers had lower (P < .01) feed efficiencies. Steers fed to a targeted compositional fat end point of 1.4 cm had 1.3% higher (P < .01) dressing percentage (DP) than steers fed to 1.0 cm. Control and SYN steers had similar (P = .13) DP; however, REV steers had 6.1% greater (P < .01) DP than SYN steers. Steers fed to 1.4 cm s.c. fat end point had higher (P < .01) numerical yield grades than steers fed to 1.0 cm (3.34 vs 2.71). There was an interaction (P < .01) for intake level and implant for marbling score. Marbling scores were lower (P < .05) for RS x SYN and AL x REV than in other treatments. Steers on the RS x REV treatment were intermediate in marbling to all treatments except AL control, which was higher (P < .01) than RS x SYN, AL x REV, and RS x REV. No interaction for dry matter intake level and anabolic implants was observed for growth performance. The depression in carcass quality resulting from implanting is reduced as backfat increases from 1.0 to 1.4 cm at slaughter.

Performance of Angora goat kids fed acidified milk replacer at two levels of intake

Daily milk intake, weekly BW and blood metabolites were monitored using Angora kids offered ad libitum (AL) or restricted (RES) intakes of acidified milk replacer (AMR) twice daily during an 11-week period. Solid feed was provided ad libitum starting in week 3. All kids were shorn at the end of the experiment and midside samples taken for fiber characteristics. Average daily gain during the experiment was 30% higher for kids fed AL compared with those fed RES (138 vs. 108 g/day; P<0.0001). Average daily milk intake was 0.97 l for RES and 1.37 l for AL ( P<0.001). Pre-treatment BW (2.8±0.1 kg) and blood metabolites were similar for both groups. No differences were found in clean mohair production (275 vs. 279 g; P<0.85) or in any other fiber quality characteristics. Plasma concentrations of glucose (84 mg/dl), non-esterified fatty acids (313 μequiv./l) and total protein (60 g/l) were not different ( P>0.05) between groups at the end of the experiment. In weeks 7 and 11 plasma urea nitrogen (PUN) concentrations were higher (10.1 vs. 8.5 mg/dl; P<0.01) for the kids in the RES treatment. No detrimental effects of feeding a restricted amount of AMR to Angora kids were noted on mohair production or blood metabolites although ADG was 28% lower and solid feed intake was three times higher (32.4 vs. 9.1 g/d; P<0.0001). Feed conversion efficiency for BW gain and mohair growth was greater in the RES group resulting in higher production per feed cost unit. Restricting milk intake decreases costs of kid rearing by decreasing milk costs and encourages faster adaptation to solid feed.

Immunization against growth hormone releasing factor or chronic feed restriction initiated at 3.5 months of age reduces ovarian response to pulsatile administration of gonadotropin-releasing hormone at 6 months of age and delays onset of puberty in heifers.

A severe or moderate suppression of serum insulin-like growth factor I (IGF-I) was induced in heifers, beginning at 104 days of age, by active immunization against growth hormone-releasing factor (GRFi) or by chronic feed restriction (RES), respectively. We hypothesized that reduced serum IGF-I results in decreased serum estradiol-17 beta (E2), which in turn delays onset of puberty. The objectives of this experiment were to determine 1) whether GRFi and RES would alter follicular development and delay onset of puberty through similar mechanisms, and 2) whether GnRH would enhance follicular growth in control, GRFi, and RES heifers at 6 mo of age. Changes in IGF-I, somatotropin, LH, FSH, and E2 were evaluated. Serum IGF-I was greater in control than in RES heifers, and was greater in both these groups than in GRFi heifers by 169 days of age. Basal LH decreased in control and RES but not in GRFi heifers from 136 to 157 days of age. During the same period, a decrease in mean FSH was detected in control but not in GRFi and RES heifers. RES decreased mean serum E2 from 148 to 183 days of age. At 6 mo of age, pulsatile administration of GnRH (5 micrograms every 2 h for 42-46 h) increased serum LH and FSH similarly across treatments but had no effect on the number of follicles > or = 8 mm in GRFi and RES heifers relative to saline treatment. Serum E2 and IGF-I in follicular fluid from follicles > or = 8 mm were increased in all GnRH-treated heifers; however, concentrations of both hormones were lower in GRFi than in control or RES heifers. The main effect of treatments on serum IGF-I was reflected in follicles < or = 7 mm; follicular fluid IGF-I was greater in control than in RES heifers and was greater in both these groups than in GRFi heifers. Serum E2 was lower in RES than in control and GRFi heifers from 253 to 281 days of age. Because of an interaction, E2 was lower in GRFi-GnRH than in control-GnRH heifers but similar in GRFi-saline and control-saline heifers. By 393 days of age, 0% of RES and 32% of GRFi heifers had reached puberty compared to 71% of control heifers. These data support our hypothesis that decreased serum IGF-I results in decreased serum E2. GRFi appears to delay puberty in heifers because decreased serum IGF-I impairs the ovary's ability to synthesize preovulatory concentrations of E2, thereby delaying stimulation of an LH surge. In contrast, RES may delay puberty by delaying follicular development at two stages: a) decreased IGF-I in follicles < or = 7 mm may delay predominant follicular growth, and b) decreased LH may delay maturation of the preovulatory follicle.

Effect of dietary protein and estradiol-17β on growth and insulin-like growth factor I in cattle during realimentation

Forty-eight medium-framed, crossbred steers (average BW = 268 +/- 20 kg) were limit-fed a 35% concentrate diet to gain approximately .10 kg/d during a 66-d restriction (REST) period. This was followed by a 98-d realimentation (REAL) period in which steers were allotted to a 3 x 2 factorial arrangement of treatments. Treatments were 80% concentrate diets containing 9, 12, or 15% CP, and implantation of one-half of the steers with 24 mg/steer of estradiol-17 beta (E2; Compudose). The allotted steers were distributed across four pens (12 steers/pen) with each pen containing two replicates of each treatment combination. Individual feed intakes were monitored using a Calan gate system. Each steer had ad libitum access to its respective diet. Longissimus muscle area and fat thickness at the 12th rib were measured using real-time ultrasound. Dry matter intake was not affected by CP or E2 through d 56. Steers fed 9% CP weighed less (quadratic, P < .05) after d 14 than steers fed 12 or 15% CP due to slower (quadratic, P < .05) gains during this initial period. Implantation increased (P < .05) ADG from d 15 to 56 resulting in heavier BW (P < .05) on d 56 and 98. Increasing concentrations of dietary CP resulted in linear (P < .05) increases in longissimus muscle area on d 28 and 56, and fat thickness on d 98. Serum IGF-I concentrations were lowest on d -21 of REST and highest on d 28 of REAL (quadratic, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Endocrine responses and body composition changes during feed restriction and realimentation in young bulls2

Changes in serum metabolic hormones, carcass composition, and body weight gains were examined in 21 Angus bulls (9 mo old) subjected to feed restriction and realimentation. They were allotted to three feeding regimens: 1) control (CON); 2) restricted (REST); and 3) realimented (REAL). The CON group was fed 3.2% of their body weight; the REST group was fed 1.5%. The REAL group was fed the restricted diet (1.5% BW) for 84 d then fed the control diet (3.2% BW) until slaughter. The CON and REAL groups were slaughtered at approximately 400 kg and the REST group at 346 kg. For the experiment, average daily gains (kg/d) were different (P < .05) (CON = 1.60; REAL = 1.35; REST = .64). Bulls were bled every 20 min for 6 h on d 14, 70, 98, and 127 of the experiment. Overall carcass characteristics (yield grade, muscle area, marbling) and chemical analysis of 9-10-11 rib sections indicated changes in quantity and percentages of protein and fat commensurate with the dietary intake treatments. The REST group had the least lean and fat (P < .05); the REAL group had less fat than (P < .05) but the same amount of lean (P > .05) as the CON group. Serum GH was higher in the REST than in the CON group (P < .05). In the REAL group, serum GH values rose to a level similar to that of the REST group; realimentation lowered serum GH (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma growth hormone, insulin-like growth factor, insulin, and thyroid hormone association with body protein and fat accretion in steers undergoing compensatory gain after dietary energy restriction2

Eighteen Chianina crossbred steers were used to examine the interrelationship between hormonal status and empty body protein (EBPRT) and fat (EBFAT) accretion during an 88-d controlled realimentation (REAL; DMI was adjusted weekly on an individual BW basis) period. Body composition was determined by monitoring endogenous whole-body 40[K]. At the end of restriction (REST) and on d 31 and 59 of REAL blood samples were taken and analyzed for concentrations of growth hormone (GH), IGF-I, IGF-II, insulin (INS), thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), nonesterified fatty acids (NEFA), glucose, and urea nitrogen. Depositions of EBPRT and EBFAT were decreased (P < .001) in REST (92 d) animals compared with nonrestricted (NR) controls. During REST, plasma levels of glucose, IGF-I, INS, T4, T3, and rT3 were decreased (P < .05); plasma urea nitrogen (PUN), NEFA, and GH levels were increased (P < .05), and IGF-II concentrations were similar between REST and NR steers. A transient compensatory response in BW gain and protein deposition occurred in repleted steers between d 35 and 62 of REAL. During this period, PUN levels markedly declined (P < .01) in REAL steers and glucose concentration increased (P < .01) to levels similar to those in NR controls. This response prevailed even though apparent digestible nutrients were decreased in repleted animals. During energy repletion, plasma levels of T4, T3, rT3, IGF-I, and INS were positively, and of GH was negatively, correlated with EBPRT and EBFAT gain in repleted animals. Unlike IGF-I, IGF-II was not correlated with compensatory body growth. These results suggest that compensating steers are more metabolically efficient; rapid body tissue gain occurs during a period of reduced nutrient digestibility. Additionally, plasma levels of IGF-I, GH, INS, and thyroid hormones, but not of IGF-II, are markedly affected by alteration of energy intake and are highly correlated with empty body gain and protein deposition in compensating late-maturing steers.

Stimulatory effect of potassium glutamate in PCR.

Depar tmen t s of Or thoped ics and Biochemis t ry and Molecular Biology, Mayo Clinic and Foundat ion , Rochester, Minneso t a 55905 PCR (1~ has become one of the mos t wide ly used technologies in m a n y areas of research. PCR depends on a bacterial DNA polymerase and is quite specific and efficient in ampl i fy ing a target DNA. However, there are s i tuat ions w h e n the PCR can be subopt imal even t h o u g h the specifici ty is no t compromised . One exp l ana t ion ( among many) of a suboptimal PCR m i g h t be tha t the process is carried out in an e n v i r o n m e n t foreign to a bacteria. For example, there are a number of auxi l iary proteins tha t take part du r ing DNA repl icat ion in a bacteria tha t are absent in a test tube e n v i r o n m e n t . In addi t ion, the intracel lular ionic environm e n t in bacteria, such as Escherichia coli, ~2'3) is different f rom tha t used in a s tandard PCR. The mos t re levant physiological a n i o n in E. coli is g lutamate , (3~ whereas chlor ide is the rou t ine an ion of choice in a PCR. In accordance wi th this observat ion, it has been demons t r a t ed tha t r ep lacement of po tass ium chlor ide by po tass ium g lu tamate dramat ica l ly enhances p ro te in -DNA interac t ions in vitro. ~3~ The beneficial effect of such a salt r equ i r emen t has been fur ther suppor ted by the demons t r a t i on tha t virtually all of the restr ict ion enzymes tested work as well or bet ter in a buffer cont a in ing g lu tamate t han in a chloridec o n t a i n i n g buffer. (4~ Because AmpliTaq is a bacterial enzyme, we tested the effect of replacing chlor ide wi th g lu tamate in the buffer used for PCR. Our data demonstrate a cons i s ten t (but no t dramat ic) e n h a n c e m e n t of PCR eff ic iency wi th g lu tamate w h e n this e n z y m e is used. PCR as described and universa l ly pract iced is best carried ou t at 50 mM KC1. ~s~ Therefore, we compared the effic iency of po tass ium g lu tama te (KGM) in PCR agains t 50 mM KC1. The effect of KGM in PCR on the ampl i f i ca t ion of two segments of 291 and 492 bp f rom the h u m a n in ter leukin-5 (IL-5) gene is presented in Figure 1. It appears tha t for the 291-bp segment , KGM is a bet ter salt at all concen t ra t ions (50--200 mM, lanes 2-6) t h a n 50 mM KCl (lane 1). For the 492-bp segment , however , KGM is subop t imal at some concen t r a t ions (50 and 75 mM; lanes 8 and 9, respectively) and inh ib i to ry at 200 mM (lane 12) compared wi th PCR of this s egmen t at 50 mM KC1. The m a x i m u m increases in the PCR ampl i f icat ion of these bands are seen at 100 mM KGM (lanes 4,10). The ex ten t of the effect of KGM in PCR was t h e n d e t e r m i n e d in a semiquant i f i ed manne r . For this, a n u m b e r of segments were ampl i f ied in the presence of [~-32P]dCTP wi th KC1 and KGM. A por t ion of the PCR-amplif ied mater ia l was e lect rophoresed, the DNA bands

Inferential Conditions in the Statistical Detection of Measurement Bias

Measurement bias in an observed variable Y as a measure of an unobserved variable W exists when the relationship of Y to W varies among popula tions of interest. Bias is often studied by examin ing population differences in the relationship of Y to a second observed measure Z that serves as a substitute for W. Whether the results of such studies have implications for measurement bias is addressed by first defining two forms of invariance— one corresponding to the relationship of Y to the unmeasured W, and one corresponding to the rela tionship of Y to the observed Z. General theoreti cal conditions are provided that justify the inference of one form of invariance from the other. The implications of these conditions for bias detection in two broad areas of application are discussed: differential item functioning and predictive bias in employment and educational settings. It is con cluded that the conditions for inference are restric tive, and that bias investigations that rely strictly on observed measures are not, in general, diag nostic of measurement bias or the lack of bias. Some alternative approaches to bias detection are discussed. Index terms: differential item function ing, invariance, item bias, item response theory, measurement bias, predictive bias.