Early changes in water diffusion, perfusion, T1, and T2 during focal cerebral ischemia in the rat studied at 8.5 T

The time evolution of water diffusion, perfusion, T1, and T2 is investigated at high magnetic field (8.5 T) following permanent middle cerebral artery occlusion in the rat. Cerebral blood flow maps were obtained using arterial spin tagging. Although the quantitative perfusion measurements in ischemic tissue still pose difficulties, the combined perfusion and diffusion data nevertheless distinguish between a "moderately affected area," with reduced perfusion but normal diffusion; and a "severely affected area," in which both perfusion and diffusion are significantly reduced. Two novel magnetic resonance imaging observations are reported, namely, a decrease in T2 and an increase in T1, both within the first few minutes of ischemia. The rapid initial decrease in T2 is believed to be associated with an increase in deoxyhemoglobin levels, while the initial increase in T1 may be related to several factors, such as flow effects, an alteration in tissue oxygenation, and changes in water environment.

A prospective, community-based evaluation of liver enzymes in individuals with hepatitis C after drug use

Serum alanine transaminase (ALT) levels are used to select hepatitis C virus (HCV)-infected patients for treatment and liver biopsy. However, the natural history of these measurements is poorly understood. To examine the hypothesis that ALT levels vary over time in HCV-infected patients, serial serum ALT levels were prospectively measured in a cohort of 1,235 persons with a history of prior illicit drug use. Over 25 months of follow-up, there was a median of four evaluations per patient. ALT values were higher in 1,164 (94%) HCV-infected individuals than in 71 (6%) HCV-uninfected individuals. The remainder of the analysis focused on these HCV-infected individuals, 647 (62%) of whom had normal ALT values at their initial visit. However, 323 (49%) of these had at least one elevated ALT over the next 25 months. Of the 395 patients whose ALT was initially abnormal, 332 (84%) had at least one normal value over the next 25 months. Overall, among individuals with four or more visits, ALT values were persistently normal in 42%, persistently elevated in 15%, and intermittently elevated in 43%. Because serum ALT levels have high visit-to-visit variability, single assessments should not be used to manage HCV-infected individuals. Further investigation is needed to ascertain the correlation of serial ALT trends with important disease outcomes.

Rapid T2* mapping using interleaved echo planar imaging

Magnetic resonance imaging methods that are sensitive to T2* are widely used in the study of blood oxygenation changes, most notably in functional studies of the brain. In these studies the signal intensity change in T2*-weighted imaging is related to the coupling of cerebral blood flow and metabolism. Rapid measurement of T2* itself would offer a valuable method to quantify blood oxygenation changes indirectly and monitor their time course. An interleaved echoplanar imaging (EPI) sequence is presented here that allows maps of T2* to be generated in a few seconds. The sequence benefits from reduced geometric distortion and an improved point spread function compared with single-shot EPI. A comparison among a set of T2*-weighted interleaved EPI images, single-shot EPI, and conventional gradient-echo and spin-echo methods is made using a compartmentalized doped water phantom. The interleaved sequence yields accurate T2* values when compared with reference measurements made using the slower gradient-echo technique. Data acquired from the rat brain at 2.35 T prior to and during an anoxic challenge show, with high temporal resolution, the reduction in T2* associated with increased levels of deoxyhemoglobin.

Viral persistence, antibody to E1 and E2, and hypervariable region 1 sequence stability in hepatitis C virus-inoculated chimpanzees

The relationship of viral persistence, the immune response to hepatitis C virus (HCV) envelope proteins, and envelope sequence variability was examined in chimpanzees. Antibody reactivity to the HCV envelope proteins E1 or E2 was detected by enzyme-linked immunosorbent assay (ELISA) in more than 90% of a human serum panel. Although the ELISAs appeared to be sensitive indicators of HCV infection in human serum panels, the results of a cross-sectional study revealed that a low percentage of HCV-inoculated chimpanzees had detectable antibody to E1 (22%) and E2 (15%). Viral clearance, which was recognized in 28 (61%) of the chimpanzees, was not associated with an antibody response to E1 or E2. On the contrary, antibody to E2 was observed only in viremic chimpanzees. A longitudinal study of animals that cleared the viral infection or became chronically infected confirmed the low level of antibody to E1, E2, and the HVR-1. In 10 chronically infected animals, the sequence variation in the E2 hypervariable region (HVR-1) was minimal and did not coincide with antibody to E2 or to the HVR-1. In addition, low nucleotide and amino acid sequence variation was observed in the E1 and E2 regions from two chronically infected chimpanzees. These results suggest that mechanisms in addition to the emergence of HVR-1 antibody escape variants are involved in maintaining viral persistence. The significance of antibodies to E1 and E2 in the chimpanzee animal model is discussed.

Seasonal changes in protein composition of whey from commercial manufacture of caprine and ovine specialty cheeses

Pooled whey from the production of one variety of ovine cheese and two varieties of caprine cheeses was studied for gross composition and individual whey protein composition over one production season. Individual proteins were quantified by sodium dodecyl sulfate-PAGE and digital imaging technology. The mean proportion of alpha-lactalbumin (LA) from caprine wheys from the manufacture of Chevre and Cheddar-type cheeses was higher than values previously reported for bovine whey from Cheddar cheese; proportions of serum albumin, immunoglobulin (Ig)G, and beta-lactoglobulin (LG) were lower. Ovine whey from Manchego-type cheese showed a higher proportion of beta-LG, about the same proportion of alpha-LA, and lower proportions of serum albumin and IgG than did the bovine whey. Relative amounts of alpha-LA decreased throughout the season, but beta-LG rose in midlactation and then gradually decreased toward the end of lactation. Relative proportions of serum albumin remained fairly stable throughout the year, and IgG decreased.

Assessment of hepatitis C virus sequence complexity by electrophoretic mobilities of both single-and double-stranded DNAs

To assess genetic variation in hepatitis C virus (HCV) sequences accurately, we optimized a method for identifying distinct viral clones without determining the nucleotide sequence of each clone. Twelve serum samples were obtained from seven individuals soon after they acquired HCV during a prospective study, and a 452-bp fragment from the E2 region was amplified by reverse transcriptase PCR and cloned. Thirty-three cloned cDNAs representing each specimen were assessed by a method that combined heteroduplex analysis (HDA) and a single-stranded conformational polymorphism (SSCP) method to determine the number of clonotypes (electrophoretically indistinguishable cloned cDNAs) as a measure of genetic complexity (this combined method is referred to herein as the HDA+SSCP method). We calculated Shannon entropy, incorporating the number and distribution of clonotypes into a single quantifier of complexity. These measures were evaluated for their correlation with nucleotide sequence diversity. Blinded analysis revealed that the sensitivity (ability to detect variants) and specificity (avoidance of false detection) of the HDA+SSCP method were very high. The genetic distance (mean +/- standard deviation) between indistinguishable cloned cDNAs (intraclonotype diversity) was 0.6% +/- 0.9%, and 98.7% of cDNAs differed by <2%, while the mean distance between cloned cDNAs with different patterns was 4.0% +/- 3.2%. The sensitivity of the HDA+SSCP method compared favorably with either HDA or the SSCP method alone, which resulted in intraclonotype diversities of 1.6% +/- 1.8% and 3.5% +/- 3.4%, respectively. The number of clonotypes correlated strongly with genetic diversity (R2, 0.93), but this correlation fell off sharply when fewer clones were assessed. This HDA+SSCP method accurately reflected nucleotide sequence diversity among a large number of viral cDNA clones, which should enhance analyses to determine the effects of viral diversity on HCV-associated disease. If sequence diversity becomes recognized as an important parameter for staging or monitoring of HCV infection, this method should be practical enough for use in laboratories that perform nucleic acid testing.

Advance directives in a correctional setting

Using advance directives to preconsent to mental health treatment is a promising approach to contending with the quandary posed by patients suffering from severe mental health illness, particularly those in a prison setting. The implementation of advance directives represents unfamiliar territory because it focuses on the patient's ability to preconsent to treatment rather than the commonly interpreted prerefusal of treatment. The challenge of consenting in the prison system generates a set of unique problems. The environment in which the instrument is signed can impose significant pressures and therefore result in a viable legal challenge. The prison setting is the most coercive environment in which a patient can be treated, particularly when the patient is mentally ill. Mentally ill prisoners signing preconsent for treatment advance directives have an opportunity for unprecedented relief yet may also experience pressure to select treatments desirable to the prison staff.

Prevalence and incidence of hepatitis C virus infection among young adult injection drug users

Through community-based outreach, young adult injection drug users (IDUs) were enrolled in a prospective study of the prevalence, incidence, and risk factors for hepatitis C virus (HCV) infection. Demographics and information on sexual and injecting practices were collected during semiannual interviews, and HCV infection was evaluated using a second-generation antibody assay. Of the 229 participants, 86 (37.6%) were HCV-seropositive at baseline. After adjusting for injecting frequency and duration by logistic regression, HCV seroprevalence was independently associated with reusing syringes at least once in the past 6 months (odds ratio [OR]=3.81, 95% confidence interval [CI] 1.39-11.00), injecting the first time with someone > or =5 years older (OR=2.99; 95% CI, 1.43-6.23) or alone (OR=4.02; 95% CI, 1.12-14.43) versus with someone <5 years older, and injecting cocaine or speedball exclusively (OR=4.29; 95% CI, 1.53-12.01) or with other drugs (OR=5.27; 95% CI, 2.62-10.64) versus injecting no cocaine in the past 6 months. Of the 105 originally HCV-seronegative participants who returned for follow-up, 13 seroconverted (incidence rate=16.0/100 person-years). On bivariate analysis, HCV seroconversion was significantly associated with injecting for <2 years (relative risk [RR]=7.3; 95% CI, 1.6-32.8) and continuing to inject during follow-up (RR=4.4; 95% CI, 1.0-19.9). Young adult IDUs are at high risk for HCV infection. These data support the need for wider legal access to sterile syringes, as well as expanded community outreach education to this population to prevent transmission of HCV.

A quantitative method for fast diffusion imaging using magnetization-prepared TurboFLASH

For the in vivo measurement of the apparent diffusion coefficient (ADC), it is desirable for the total imaging time to be as short as possible. One technique is based on a TurboFLASH acquisition in which the diffusion gradients are inserted into a driven equilibrium Fourier transform (DEFT) combination of hard pulses. However, this sequence has the disadvantage that eddy current-induced inhomogeneities lead to incomplete refocusing of the magnetization during the diffusion preparation and to incorrect ADC values. A modification to the sequence is suggested that eliminates this error by phase-cycling the second 90 degrees pulse of the preparation. This study also investigates the effect of a reduced delay time between acquisitions on the accuracy of the measurement. The quality of the TurboFLASH sequence is demonstrated by experimental validation on an agar phantom and in vivo on the rat brain using a high-field (8.5 T) system. Reduction of the interexperiment delay time is shown to be achievable to a certain degree without compromising the measurement accuracy.

Perinatal transmission of hepatitis C virus from human immunodeficiency virus type 1-infected mothers. Women and Infants Transmission Study

Antepartum plasma hepatitis C virus (HCV) RNA was quantified in 155 mothers coinfected with HCV and human immunodeficiency virus type 1 (HIV-1), and HCV RNA was serially assessed in their infants. Of 155 singleton infants born to HCV antibody-positive mothers, 13 (8.4%) were HCV infected. The risk of HCV infection was 3.2-fold greater in HIV-1-infected infants compared with HIV-1-uninfected infants (17.1% of 41 vs. 5.4% of 112, P = .04). The median concentration of plasma HCV RNA was higher among the 13 mothers with HCV-infected infants (2.0 x 10(6) copies/mL) than among the 142 mothers with HCV-negative infants (3.5 x 10(5) copies/mL; P < .001), and there were no instances of HCV transmission from 40 mothers with HCV RNA concentrations of < 10(5) copies/mL. Women dually infected with HIV-1 and HCV but with little or no detectable HCV RNA should be reassured that the risk of perinatal transmission of HCV is exceedingly low.

Association of antibody to GB virus C (hepatitis G virus) with viral clearance and protection from reinfection

GB virus C (GBV-C) RNA and envelope antibody were assessed in a median of 4 samples collected over 6.5 years among injection drug users (IDUs). A marker of GBV-C infection was detected in 110 (94.8%) of 116 IDUs. GBV-C RNA was detected at all visits in 32, was never detected in 70, was acquired in 7, and was cleared in 8. The odds of detecting anti-GBV-C were 103-fold higher in participants without detectable RNA (64 of 70) than in IDUs with persistent RNA (3 of 32; P < 10(-7)). Anti-GBV-C was detected in all 8 instances of RNA clearance. GBV-C RNA never reappeared once it was cleared, and there were no new GBV-C infections among 61 anti-GBV-C-positive IDUs observed for 382 person-years, though all had ongoing drug use. Studies using RNA testing alone may significantly underestimate the occurrence of GBV-C infection. Anti-GBV-C is highly associated with viral clearance and protection from reinfection.

Protein kinase C is involved in resistance to myocardial infarction induced by heat stress

Heat stress (HS) is known to protect against mechanical dysfunction and myocardial necrosis in myocardial ischemia-reperfusion models both in vivo and in vitro. However, the mechanisms involved in this form of cardioprotection remain unclear. Protein kinase C (PKC) and tyrosine kinase activation have both been shown to be involved in the delayed phase of protection following ischemic preconditioning, a phenomenon which appears to be analogous to HS-induced protection. Therefore, we investigated the role of PKC and tyrosine kinase in HS-induced resistance to myocardial infarction, in the isolated rat heart. The selective inhibitors chelerythrine (Che) and genistein (Gen) were used to inhibit PKC and tyrosine kinase, respectively. Rats were treated with Che (5 mg/kg, i.p.) or Gen (5 mg/kg, i.p.) or vehicle before they were either heat stressed (42 degrees C for 15 min) or sham anesthetized. Twenty-four h later their hearts were isolated, retrogradely perfused, and subjected to 35-min occlusion of the left coronary artery followed by 120-min of reperfusion. Infarct-to-risk ratio was significantly reduced in HS (19.9+/-1.1%) compared to sham (43.1+/-1.1%) hearts. This reduction in infarct size was abolished in chelerythrine-treated groups (43.8+/-1.9% in HS+Che v 44.9+/-2.0% in sham+Che), but was conserved in genistein-treated groups (17.7+/-0.9% in HS+Gen v 36.4+/-2.8% in sham+Gen). In order to confirm that genistein at this dose was effectively inhibiting tyrosine kinase activity, we observed the ability of the agent to prevent the hypoglycemic responses to insulin in a separate group of anesthetised rats receiving an i.v. insulin infusion. Western blot analysis of the myocardial hsp72 showed a HS-induced increase of this protein, which was modified by neither the PKC inhibitor, chelerythrine, nor the tyrosine kinase inhibitor, genistein. We conclude that the activation of PKC, but not of tyrosine kinase, appears to play a role in the functional cardioprotection associated with the heat stress response. Although protection appears to be dissociated from induction of hsp72, further work is required to explore the importance of hsp72 phosphorylation to cytoprotective activity of the protein.

Incidence and risk factors for hepatitis C among injection drug users in Baltimore, Maryland

Between 1988 and 1996, the incidence of and risk factors for hepatitis C virus (HCV) infection were studied in a cohort of injection drug users in Baltimore, Maryland. By second-generation antibody testing of stored serum samples, 142 participants were found to be susceptible to HCV at the time they entered the study. After a median follow-up of 6.5 years, 43 participants (30.3%) developed antibodies to HCV (anti-HCV). The overall incidence was 6.4 cases per 100 person-years, but a substantial decline in the annual incidence rate was observed after the first 2 years (1988 to 1990, 13.4/100 person-years; 1991 to 1996, 2.3/100 person-years [P = 0.0001 for trend]). Participants who acknowledged active drug use, especially those who acknowledged frequent use and sharing of drug paraphernalia, were at increased risk of HCV infection. However, high-risk sexual practices were not associated with HCV seroconversion. Efforts to reduce HCV infection must be focused on curbing drug use and especially on the sharing of needles and drug paraphernalia.

Syphilis serology in human immunodeficiency virus infection: evidence for false-negative fluorescent treponemal testing

Injection drug users were assessed serologically for human immunodeficiency virus infection and syphilis every 6 months. Treatment histories were reviewed for any high-titer biologic false-positive (BFP) reactors, that is, persons with rapid plasma reagin (RPR) titers > or = 1:4 and negative results for fluorescent treponemal antibody absorption (FTA-ABS) tests. Selected sera were analyzed further by immunoblotting for the presence of antibodies reactive with specific Treponema pallidum antigens. Of 112 BFP reactors, 35 (31%) had at least one RPR test reactive at a dilution >1:8 while the FTA-ABS test remained nonreactive. Five reactors (4.5%) converted from nonreactive to reactive by FTA-ABS test; 4 (3.6%) were reactive by FTA-ABS tests but later became nonreactive. Antibodies to T. pallidum membrane antigens were detected in some samples that were persistently nonreactive by FTA-ABS test. Serologic patterns over time, along with very high-titer BFP reactions and reactivity with T. pallidum-specific antigens, suggest that some BFP reactions may represent FTA-negative syphilis.

Hepatitis A among homosexual men and injection drug users: more evidence for vaccination

As agencies develop guidelines for administering the newly developed hepatitis A virus (HAV) vaccine, information is needed regarding the occurrence of HAV infection in groups putatively at risk for the infection. We tested serum samples from 300 injection drug users (IDUs), 300 homosexual males, and 300 blood donors for the presence of total antibody to HAV (anti-HAV). Anti-HAV was detected in 66% of IDUs, 32% of homosexual males, and 14% of blood donors. Anti-HAV was not significantly associated (P > .10) with high-risk drug-using behaviors but was more prevalent among IDUs with annual incomes of <$5,000 (P = .018). The occurrence of anti-HAV increased among homosexual males as the number of sexual partners increased (P < .001) but was similar to the age-adjusted prevalence (30.6%) estimated for the general United States population. IDUs are at increased risk for HAV infection; however, our data suggest that factors related to low socioeconomic status contribute more to the occurrence of HAV infection among IDUs than does injection drug use. IDUs and persons at risk for injection drug use should receive HAV vaccine.

Evaluation of electronic technology to assess lamb carcass composition

Accurate price signals are essential for producers of American lamb to ensure production of uniformly lean animals. Development of carcass merit-pricing systems will require the use of objective technology for assessing carcass composition or lean distribution. The objective of this study was to evaluate electronic technologies for accurate determination of lamb carcass composition. Lambs (n = 106) were selected as a representation of U.S. market lambs that transcended geographic location, sex, breed, carcass weight, yield grade, and production system. The independent variables used to predict lamb composition varied with the technology. The electronic technologies tested included realtime ultrasound, optical reflectance probe, bioelectrical impedance analysis, and electromagnetic scanning (TOBEC). All technologies, except realtime ultrasound, were tested on warm (prerigor) carcasses and repeated after a 24-h chill. Longitudinal ultrasonic scans of fat and muscle tissue depth and grading probe fat depths were marginal predictors of proportional carcass yield. The TOBEC measurements often accounted for more variability associated with kilograms of dissected lean and percentage of carcass lean than did carcass weight. Equations from TOBEC measurements were the most accurate predictors of weight and percentage of dissected and fat-free lean. Bioelectrical impedance measurements of resistance and reactance combined with carcass weight were also good predictors of carcass composition. Prediction of carcass lean distribution by measures of TOBEC were the most accurate for prediction of leg lean. The implications of usefulness of these technologies will depend on the commitment of the U. S. sheep industry in development of a lamb price discovery system based on carcass composition.

Persistence and clinical significance of hepatitis G virus infections in injecting drug users

To assess the persistence of hepatitis G virus (HGV) infection and its association with liver disease, HGV RNA was assessed in the most recent serum sample for 246 long-term injecting drug users (IDUs) and in prior specimens for those found HGV RNA-positive. HGV RNA was detected at the most recent visit in 38 (15.4%). For 31 (82%), HGV RNA was also found at all prior visits occurring a median of 6.1 years earlier. HGV-positive IDUs were younger and had fewer years of drug use, suggesting that HGV RNA had previously been cleared. Serial samples from 29 short-term IDUs were then assessed. HGV RNA was detected in 9 (31%) of 29 short-term IDUs, and 5 (56%) of the 9 HGV infections cleared. No differences were detected in serum levels of liver-related enzymes among HGV RNA-positive and -negative participants (P > .20). HGV infection is not associated with hepatic inflammation. HGV clearance occurs after many acute infections but uncommonly in persons who remain RNA-positive years after exposure.

Increased vertical transmission of human immunodeficiency virus from hepatitis C virus-coinfected mothers. Women and Infants Transmission Study

To determine if hepatitis C virus (HCV) infection affects vertical transmission of human immunodeficiency virus (HIV), 487 HIV-infected pregnant women in the prospective, multicenter, Women and Infants Transmission Study had HCV antibody (anti-HCV by second-generation ELISA) and HCV RNA (by quantitative polymerase chain reaction) measured in peripartum maternal plasma; 161 (33%) were anti-HCV-positive. HIV vertical transmission occurred from 42 HCV-infected mothers (26.1%) versus 53 HCV-uninfected mothers (16.3%; odds radio [OR], 1.82; P = .01). In a logistic regression model that included maternal drug use, a potential confounder, HCV infection was marginally associated with perinatal HIV transmission (OR, 1.64; P = .05), whereas drug use was not. Women who transmitted HIV had higher levels of HCV RNA (median, 721,254 copies/mL) than those who did not (337,561 copies/mL; P = .01). Maternal HCV infection is associated with increased HIV vertical transmission. Further studies are needed to ascertain if HCV directly affects perinatal HIV transmission or is a marker for another factor, such as maternal drug use.

Seroreactivity to hepatitis E virus in areas where the disease is not endemic

If the occurrence of hepatitis E virus antibody (anti-HEV) in regions where the disease is not endemic represents infection, rates may be greater in high-risk populations and behavioral correlates may reflect recognized transmission modes. Serum samples from 300 homosexual males, 300 injection drug users (IDUs), and 300 blood donors from Baltimore, Md., were tested for anti-HEV by enzyme immunoassay. Anti-HEV was found in an unexpectedly high percentage of homosexual men (15.9%) and IDUs (23.0%). However, anti-HEV was present in a similar proportion of blood donors (21.3%) (P > 0.05), while hepatitis A, B, and C virus antibodies were more prevalent in the high-risk groups (P < 0.001). Among homosexual men, anti-HEV was not significantly correlated with a history of hepatitis, high-risk sexual practices, or sexually transmitted infections, in contrast to hepatitis A and B antibodies. Among IDUs, anti-HEV was not significantly associated with a history of hepatitis or high-risk drug-using practices, as was found with hepatitis C antibodies. In a setting without endemic hepatitis E disease, there was no evidence that anti-HEV reflected subclinical infection. Until the basis for HEV seroreactivity in such areas is elucidated, anti-HEV results should be interpreted with caution.

Genetic analysis of discrete reproductive traits in sheep using linear and nonlinear models: II. Goodness of fit and predictive ability

The performance of linear and nonlinear sire and animal models in the analyses of reproductive traits (fertility, litter size, and ovulation rate) in two sheep populations (Rambouillet and Finnsheep) was compared in terms of goodness of fit and predictive ability. Linear sire (LSM) and animal (LAM) models were used with all traits. Nonlinear models were the threshold, Poisson, and negative binomial. Threshold sire (TSM) and animal (TAM) models were also used with all traits. Litter size and ovulation rate were analyzed also with Poisson and negative binomial sire (PSM and NBSM, respectively) and animal (PAM and NBAM, respectively) models. Variance components were those reported in the companion article. For PAM a new set of variance components derived from estimates found with the linear animal model also was used (PAM-L). Mean squares error (MSE) and correlations between fitted and observed values were used to assess goodness of fit. Predictive ability was assessed by partitioning the data sets for the different traits into two subsets with the restriction that all levels of fixed effects were represented in each subset. Parameters from one subset were employed to predict observations in the other, and then MSE and correlations between observed and predicted values were used as criteria for model comparison. Within estimation procedure, breed, and trait, goodness of fit of sire and animal models was similar. Linear and threshold models resulted in similar fit, and both outperformed Poisson and negative binomial models. In terms of predictive ability, linear and threshold models performed only slightly better than Poisson and negative binomial models. Goodness of fit and predictive ability generally were better when models included permanent environmental effects.

Genetic analysis of discrete reproductive traits in sheep using linear and nonlinear models: I. Estimation of genetic parameters

Repeated records on fertility, litter size, and ovulation rate of Rambouillet ewes and on fertility and litter size of Finnsheep ewes were used to estimate heritabilities and repeatabilities with linear and nonlinear sire and animal models. Linear sire (LSM) and animal models were used with all traits. Nonlinear models were the threshold, Poisson, and negative binomial. Threshold sire (TSM) and animal models were used with all traits. Litter size and ovulation rate were analyzed also with Poisson sire and animal models and with negative binomial sire and animal models. Variance components for linear models were estimated using REML; in the threshold, Poisson, and negative binomial, they were estimated using approximate marginal maximum likelihood. Poisson and negative binomial analyses yielded results difficult to interpret due to problems in variance component estimation. Animal models resulted in slightly greater estimates of heritability for fertility than did sire models, but ovulation rate heritability estimates from sire models were much greater than estimates form animal models. Differences between sire and animal models for heritability estimates for litter size were not consistent. Threshold models resulted in higher heritability estimates for all traits in both breeds and with both sire and animal models. In general, repeatabilities were consistent across models. For example, LSM (TSM) repeatabilities were .10 (.14) for fertility, .20 (.25) for litter size, and .25 (.29) for ovulation rate in the Rambouillet, and .17 (.17) for fertility and .11 (.13 for litter size in the Finnsheep.

Effects of passive immunization against inhibin-peptide on secretion of follicle-stimulating hormone and ovulation rate in ewes carrying the Booroola fecundity gene

Objectives of the study were to determine whether 1) inhibin negative feedback regulation of FSH secretion is diminished in ewes carrying a copy of the Booroola fecundity (FecB) gene and 2) differential FSH secretion is obligatory for expression of gene-specific differences in ovulation rate (OR). The approach was to compare FSH and ovulatory responses to passive immunoneutralization of inhibin in ewes with and without a copy of the FecB gene. Twenty-eight 2- to 3-yr-old ewes were assigned within genotype to antibody (alpha-IF-Ab) or control groups. Genotypes consisted of 3/4 Rambouillet x 1/4 Booroola ewes with one copy of the FecB gene (FecB+; 57 kg) and 3/4 Rambouillet x 1/4 Booroola ewes without the FecB gene (++; 59 kg). Estrus was synchronized during the breeding season using progesterone-releasing pessaries (CIDR-G). Pessaries were removed at 0 h. A single injection of alpha-IF-Ab or control solution was given at -48 h. Alpha-IF-Ab had been developed against a synthetic inhibin fragment matching the N-terminal region of ovine inhibin's alpha subunit. For injection, alpha-IF-Ab had been precipitated from ovine immune sera and concentrated. Blood samples were collected at 6-h intervals from -48 to 48 h, and laparoscopy was performed 14 days after CIDR-G withdrawal. All ewes exhibited estrus and ovulated. Genotype and alpha-IF-Ab treatment were without effect on intervals to estrus. Both factors affected OR (p < or = 0.001). Mean OR in control ++ and FecB+ ewes were 1.6 and 2.7, respectively; mean OR in alpha-IF-Ab-treated ++ and FecB+ ewes were 2.5 and 4.6, respectively. Following injection of alpha-IF-Ab, FSH concentrations increased within 6 h, peaked 12-18 h later, and then declined. Magnitude of FSH increases was similar in ++ and FecB+ ewes (70% and 85% over control values, respectively). Results demonstrate that 1) inhibin negative feedback regulation of FSH secretion is not a site of FecB gene action and 2) the mechanism by which the FecB gene increases OR does not necessarily involve increased FSH secretion during the period of preovulatory follicular development.

Assessment of lamb carcass composition from live animal measurement of bioelectrical impedance or ultrasonic tissue depths

Market weight lambs, average weight 52.5 kg (+/-6.1), were used to evaluate nontraditional live animal measurements as predictors of carcass composition. The sample population (n = 106) represented U.S. market lambs and transcended geographic location, breed, carcass weight, yield grade, and production system. Realtime ultrasonic (RU) measurements and bioelectrical impedance analysis (BIA) were used for development and evaluation of prediction equations for % boneless, closely trimmed primal cuts (BCTPC), weight or % of dissected lean tissue (TDL), and chemically derived weight or % fat-free lean (FFL). Longitudinal ultrasonic images were obtained parallel to the longissimus thoracis et lumborum (LTL), positioning the last costae in the center of the transducer head. Images were saved and fat and LTL depths were derived from printed images of the ultrasonic scans. Bioelectrical impedance analysis was administered via a four-terminal impedance plethysmograph operating at 800 microA at 50 kHz. Impedance measurements of whole-body resistance and reactance were recorded. Prediction equations including common linear measurements of live weight, heart girth, hindsaddle length, and shoulder height were also evaluated. All measurements were taken just before slaughter. Bioelectrical impedance measurements (as compared to RU and linear measurements) provided equations for %BCTPC, TDL, %TDL, FFL and %FFL with the highest R2 and lowest root mean square error. Even though BIA provided the best equations of the three methodologies tested, prediction of proportional yield (%BCTPC, %TDL, and %FFL) was marginal (R2 = .296, .551, and .551, respectively). Equations combining BIA, RU, and linear measurements greatly improved equations for prediction of proportional lean yield.