Effect of intake on fasting heat production, respiratory quotient and plasma metabolites measured using the washed rumen technique.

The objective was to investigate the effect of intake before fasting on concentrations of metabolites and hormones, respiratory quotient (RQ) and fasting heat production (HP) using the washed rumen technique and to compare these values with those from the fed state. Six Holstein steers (360±22 kg) were maintained at 21°C and fed three different energy intakes within a replicated 3×3 Latin square design with 21-day periods. Steers were fed alfalfa cubes to provide 1.0, 1.5 and 2.0×NEm during 19 days of each experimental period. Steers were placed in individual metabolism stalls fitted with indirect calorimetry head-boxes on day 20 of each experimental period (FED steers) and fed their normal meal. On day 21 of each period the reticulorumen was emptied, washed and refilled with ruminal buffer (NaCl=96; NaHCO3=24; KHCO3=30; K2HPO4=2; CaCl2=1.5; MgCl2=1.5 mmol/kg of buffer) aerated with 75% N2 and 25% CO2 before introduction to the rumen (steers were not fed; WASHED steers). Each gas exchange was measured over 24 h. HP for 1.0, 1.5 and 2.0×NEm were 479, 597 and 714 kJ/daykg0.75 (s.e.m. =16), respectively. The plateau RQ was 0.756, 0.824 and 0.860 for the 1.0, 1.5 and 2.0×NEm intakes for the FED steers, respectively. After rumen washing, fasting HP was 331, 359 and 400 kJ/daykg0.75 (s.e.m.=13) for 1.0, 1.5, and 2.0×NEm intakes before fasting, respectively. The RQ for WASHED rumen steers was 0.717, 0.710 and 0.719, respectively. Cortisol and ß-hydroxybutyrate concentrations in WASHED rumen steers did not exceed threshold levels for severe energy deficit and stress as can be induced from prolonged fasting. This study demonstrates that a fasting state can be emulated using the washed rumen technique, minimizing the time required as opposed to traditional fasting methodologies, without causing a severe energy deficit and stress.

Ergot alkaloids from endophyte-infected tall fescue decrease reticuloruminal epithelial blood flow and volatile fatty acid absorption from the washed reticulorumen.

An experiment was conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen. Steers (n=8) were pair-fed alfalfa cubes and received ground endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum; E+) seed (0.015 mg ergovaline·kg BW(-1)·d(-1)) or endophyte-free tall fescue (E-) seed via the rumen cannula 2x daily for 7 d at thermoneutral (TN; 22°C) and heat stress (HS; 32°C) conditions. On d 8, the rumen was emptied and rinsed. A buffer containing VFA was incubated in the following sequence: control (CON), 15 µg ergovaline·kg BW(-1) (1×EXT) from a tall fescue seed extract, and 45 µg ergovaline·kg BW(-1) (3×EXT). For each buffer treatment there were two 30-min incubations: a 30-min incubation of a treatment buffer with no sampling followed by an incubation of an identical sampling buffer with the addition of Cr-EDTA and deuterium oxide (D2O). Epithelial blood flow was calculated as ruminal clearance of D2O corrected for influx of physiological water and liquid outflow. Feed intake decreased with dosing E+ seed at HS but not at thermoneutral conditions (TN; P<0.02). Dosing E+ seed decreased serum prolactin (P<0.005) at TN. At HS, prolactin decreased in both groups over the 8-d experiment (P<0.0001), but there was no difference in E+ and E- steers (P=0.33). There was a seed treatment×buffer treatment interaction at TN (P=0.038), indicating that E+ seed treatment decreased reticuloruminal epithelial blood flow at TN during the CON incubation, but the two groups of steers were not different during 1×EXT and 3×EXT (P>0.05). Inclusion of the extract in the buffer caused at least a 50% reduction in epithelial blood flow at TN (P=0.004), but there was no difference between 1×EXT and 3×EXT. There was a seed × buffer treatment interaction at HS (P=0.005), indicating that the reduction of blood flow induced by incubating the extract was larger for steers receiving E- seed than E+ seed. Volatile fatty acid flux was reduced during the 1×EXT and 3×EXT treatments (P<0.01). An additional experiment was conducted to determine the effect of time on blood flow and VFA flux because buffer sequence could not be randomized. Time either increased (P=0.05) or did not affect blood flow (P=0.18) or VFA flux (P>0.80), indicating that observed differences are due to the presence of ergot alkaloids in the rumen. A decrease in VFA absorption could contribute to the signs of fescue toxicosis including depressed growth and performance.

Alteration of fasting heat production during fescue toxicosis in Holstein steers.

This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348 ± 13 kg) were BW-matched into pairs and used in a 2 period crossover design experiment. Each period consisted of 2 temperature segments, one each at 22 and 30°C. During each period, 1 steer per pair was ruminally dosed twice daily with 0.5 kg of ground endophyte-infected fescue seed (E+) and the other with ground endophyte-free fescue seed (E-) for 7 d. Steers on E- treatment were pair-fed to E+ steers offered alfalfa cubes at 1.5 × NEm. On d 8 of each segment, steers were moved to individual metabolism stalls fitted with indirect calorimetry head boxes. Ruminal contents were removed, weighed, and subsampled for DM determinations. The reticulorumen was washed and filled with a buffer (NaCl = 96; NaHCO3 = 24; KHCO3 = 30; K2HPO4 = 2; CaCl2 = 1.5; MgCl2 = 1.5 mmol·kg buffer(-1)) that was gassed with a 75% N2 and 25% CO2 mixture before rumen incubation. During buffer incubation, an E+ or E- fescue seed extract was added at 12 h intervals to maintain treatment presentation to the animal. After a 12-h wait, heart rate, O2 consumption, CO2 production, and urinary output were recorded for 16 h. There was no difference (P = 0.931) in DMI/kg(0.75) between endophyte treatments by design; however, intake decreased (P = 0.004) at 30°C. Increased temperature had no effect (P > 0.10) on other measurements and there were no significant interactions (P > 0.11) of temperature and endophyte treatment. Heart rate was unaffected by fescue treatment or environmental temperature. Percent DM of ruminal contents as well as total rumen DM/kg(0.75) was increased (P < 0.0001) in E+ steers. Respiratory quotient was elevated (P = 0.02) in E+ steers. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) during E+ treatment. Calculated FHP (kcal/kg BW(0.75)) was also less (P = 0.006) in steers receiving E+ treatment. These data suggest that consumption of endophyte-infected tall fescue by cattle results in a reduction in basal metabolic rate.

Evaluation of a rapid determination of fasting heat production and respiratory quotient in Holstein steers using the washed rumen technique.

The objective of this study was to validate use of the washed rumen (WR) technique for rapid measurement of fasting heat production (HP) and respiratory quotient (RQ). Sixteen Holstein steers were divided into 2 groups of 8 for a comparison of measurements made during feeding (both groups; 16 steers) and fasting (8 steers; BW = 237 ± 17 kg) and using the WR model (8 steers; BW = 322 ± 30 kg). Steers were maintained in a controlled temperature (21°C) environment and treated as follows: 10 d diet adaptation, 1 d measurement of respiratory gases at 1.5 × NEm (Fed state; all steers d 11), 1 d measurement of respiratory gases under fasting conditions (Fasted; 8 steers d 12) or using the WR technique (8 steers d 12), and 7 d to monitor the reestablishment of intake. Steers were offered alfalfa cubes top-dressed with a mineral premix at 1.5 × NEm. Using an indwelling probe, core temperature (CT) and heart rate (HR) were monitored continuously during the days respiratory gases were measured. For fasting measurements using the WR technique, the reticulorumen was washed and refilled with ruminal buffer (NaCl = 96, NaHCO3 = 24, KHCO3 = 30, K2HPO4 = 2, CaCl2 = 1.5, and MgCl2 = 1.5 mmol/kg of buffer) with Cr-EDTA aerated with 75% N2 and 25% CO2 before introduction to the rumen. Mean hourly CT, RQ, and daily HP between Fasted steers and WR steers were decreased for the WR steers on average from 8 to 24 h after removal of rumen contents (P = 0.049, P < 0.001, and P = 0.076, respectively). Fitting RQ data obtained during fasting to a 1-phase decay equation showed that plateau was achieved at 0.756 ± 0.003 and 0.719 ± 0.003 and time to plateau was 9 and 8 h for Fasted and WR steers, respectively. Mean RQ after WR were 0.778, 0.732, and 0.726 (SEM = 0.003) for time segments 0 to 8 h, 9 to 16 h, and 17 to 24 h, respectively. Mean fasting HP after WR was 18.8, 16.8, and 16.5 (SEM = 0.51) kJ/(h • kg(0.75)) for time segments 0 to 8 h, 9 to 16 h, and 17 to 24 h, respectively. There were no significant differences in RQ and fasting HP (P = 0.23 and P = 0.81, respectively) between the time segment of 9 to 16 h and 17 to 24 h after rumen washing. In contrast, both RQ and HP differed (P = 0.090 and P = 0.081, respectively) across these same time segments for the Fasted group. Therefore, an accurate measurement of fasting HP can be obtained using a shorter-term measurement with the WR technique. This approach provides an alternative to the traditional 48 h fasting time or measurements made during the third and fourth day after starvation.

Evaluation of a ruminally dosed tall fescue seed extract as a model for fescue toxicosis in steers.

Tall fescue (Lolium arundinaceum) toxicosis research is often complicated by a reduction in intake of infected forage or seed, making treatment comparisons difficult. This study was conducted to develop a fescue toxicosis model that would allow for variations in DMI without altering the quantity of alkaloids consumed over the course of the experiment. Ground tall fescue seed and a tall fescue seed extract were used in two 2-period crossover experiments to determine the effectiveness of ruminal dosing of a tall fescue seed extract to induce fescue toxicosis. This experiment used 4 growing Holstein steers (BW = 337 ± 24 kg) surgically fitted with ruminal cannulas. Steers were maintained on a diet of endophyte-free fescue hay fed ad libitum throughout the experiment. Endophyte-infected (E+; 4.1 mg/kg of ergovaline) and uninfected (E-; 0.0 mg/kg of ergovaline) KY-31 tall fescue seed was ground and dosed or extracted with ethanol, concentrated, and lyophilized before ruminal dosing. Ergovaline concentration of the final extract was 102 mg/kg. Animals were given a minimum of a 3-wk washout period between treatments. Physiological indicators were measured over 7 d at 22°C (d 1 to 3) and 32°C (d 4 to 7) during both seed and extract dosing. Seed and extract E+ dosing reduced serum prolactin concentrations such that they were not different from zero (P < 0.10). Treatment with E+ reduced feed intake (P < 0.05) and heart rate (P < 0.001), and increased respiration rate (P < 0.01) and core temperature (P < 0.05) during both seed and extract dosing. Increasing environmental temperature from 22 to 32°C reduced total intake (P < 0.05) and increased core temperature (P < 0.001) and respiration rate (P < 0.001) during both seed and extract dosing. Diastolic blood pressure tended (P < 0.09) to be increased during E+ extract dosing and reduced during heat stress. These physiological alterations are consistent with those reported for cattle grazing or consuming seed from endophyte-infected tall fescue. These data indicate that a ruminally dosed ethanol extract of tall fescue seed is efficacious in inducing fescue toxicosis in cattle.

Adult attachment: what are the underlying dimensions?

Using a community sample of 115 young adults, this study applied a range of statistical techniques to five measures of adult attachment to gain a better understanding of what they assess. First, we determined comparability of measures, using both categorical and dimensional approaches to model the association. Agreement among classifications was modest. Next, we examined the relation of attachment classifications and attachment measure subscale scores to criterion variables (i.e. dyadic adjustment, interpersonal sensitivity and severity of psychiatric symptoms). Classification predicted severity of psychological symptoms better than it predicted other measures of adjustment. Finally, using a principal components analysis, we mapped the relationship among underlying constructs, the subscales of the five measures and three criterion measures of psychological adjustment. We discuss our findings from the perspective of underlying constructs of attachment insecurity and strategy for coping with insecurity in relationships, noting implications for further research.

Comparison of three different models to represent the wrist during wheelchair propulsion.

Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasis has been placed on the investigation of wheelchair propulsion biomechanics. Accurate representation of wrist activity during wheelchair propulsion may help to elucidate the mechanisms contributing to the development of wrist injuries. Unfortunately, no consensual wrist biomechanical model has been established. In order to determine if different methodologies obtain similar results, this investigation created and compared three different wrist models: 1) a fixed joint center placed between the styloids (midstyloid joint center); 2) a joint center with 2 degrees of freedom computed from de Leva's joint center data; and 3) a floating joint center. Results indicate that wrist flexion and extension angles are highly consistent between models, however, radial and ulnar deviation angles vary considerably. Mean maximum right flexion angles were found to be 3.5 degrees, 2.2 degrees, and 5.0 degrees for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3 degrees, 23.6 degrees, and 23.6 degrees, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0 degrees, 26.9 degrees, and 45.1 degrees, respectively, and ulnar deviation angles were found to be 30.5 degrees, 38.8 degrees, and 10.2 degrees, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.

An autoregressive modeling approach to analyzing wheelchair propulsion forces.

Biomechanical signals collected during wheelchair propulsion are often analyzed by computing averages and/or peak values over several strokes. Due to the complex nature of the signals, this type of analysis may not be specific to identifying factors that may predispose a wheelchair user to joint pain/injury. Hence, a new technique is introduced that uses a system identification approach, autoregressive (AR) modeling, to analyze wheelchair propulsion force waveforms. In this application an AR method was used to create a model force waveform based on current and past values of digital pushrim force data. The feasibility of the AR modeling method over point-wise methods to detect asymmetry among force waveforms was tested with a group of 20 wheelchair users. Subjects propelled at a constant 0.9 m/s on a roller system during which 20 s of force data were collected from the SMART(Wheel)s, force and torque sensing pushrims. Both methods showed that the wheelchair users as a group propelled evenly, however, individual analysis using the AR model error estimates indicated that twenty-five percent demonstrated significant asymmetry in their force waveforms. If only point-wise means and variances of the applied bilateral forces were considered, most subjects would have appeared symmetrical. Thus, the AR modeling approach is more sensitive to detecting anomalies in propulsion technique.

Serving women in need: nurse-midwifery practice in the United States.

OBJECTIVE: Nurse-midwifery practices in the United States were examined to study the relationship between certified nurse-midwives' (CNMs) demographic, work setting, and practice characteristics in terms of clientele, practice size, and practice type. Factors that might influence the ability of CNMs to serve populations at risk for poor outcomes were given particular attention. METHODOLOGY: A total of 2,405 responses to a 1998 mailed survey of 6,365 nurse-midwives ever-certified by the American College of Nurse-Midwives were analyzed. RESULTS: Study results indicated that CNMs continue to serve a population who are, based on a social risk profile, disproportionately at risk for poor pregnancy outcomes, including women who are uninsured (16%), immigrant (27%), adolescent (29%), and women of color (50%). It was also found that clientele varied according to practice settings: CNMs working in non-hospital, nonprofit settings served a clientele that was 65% nonwhite, 44% immigrant, 40% adolescent, and 29% uninsured; these CNMs received 61% of their client payments from Medicaid. CNMs working in private offices or for managed care organizations were less likely to serve women with these characteristics. CONCLUSION: Study results, taken in conjunction with research that documents the safety of nurse-midwifery practice, reinforce policy recommendations that support expanded access to nurse-midwifery services. Findings also indicate a need for further research in the areas of CNM workload and productivity in managed care settings and the association between CNM race and ethnicity and the race and ethnicity of their clients.

Manual wheelchair pushrim biomechanics and axle position.

OBJECTIVE: The biomechanics of wheelchair propulsion have been linked to upper extremity injury. Specifically, prior studies have correlated increased median nerve dysfunction with increasing propulsion frequency and a higher rate of rise of the resultant, or total, pushrim force. Despite this link, there is little research on the effect of wheelchair setup on propulsion biomechanics. The objective of this study was to determine the effect of rear axle position relative to the shoulder on pushrim biomechanics. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Forty individuals with paraplegia who use manual wheelchairs for mobility. INTERVENTION: Subjects propelled their own wheelchairs on a dynamometer at two different steady-state speeds and going from a dead stop to maximum speed. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. MAIN OUTCOME MEASURES: Position of the axle relative to the shoulder at rest both horizontal (XPOS) and vertical (YPOS), and pushrim biomechanical variables including frequency of propulsion, peak and rate of rise of the resultant force, planar moment, and push angle. Partial correlation coefficients between relative axle position and propulsion biomechanics variables were calculated. RESULTS: After controlling for subject characteristics, XPOS was significantly correlated with the frequency of propulsion (p < .01) and the rate of rise of the resultant force (p < .05). In addition, both XPOS and YPOS were significantly correlated with the push angle at multiple speeds (p < .05). CONCLUSION: Specific biomechanical parameters known to correlate with median nerve injuries were found to be related to axle position relative to the shoulder. Providing wheelchair users with adjustable axle position and then fitting the user to the wheelchair can improve propulsion biomechanics and likely reduce the risk of injury.

Wheelchair pushrim kinetics: body weight and median nerve function.

OBJECTIVES: Individuals who use manual wheelchairs are at high risk for median nerve injury and subsequent carpal tunnel syndrome (CTS). To gain a better understanding of the mechanism behind CTS in manual wheelchair users, this study examined the relation between (1) pushrim biomechanics and function of the median nerve, (2) pushrim biomechanics and subject characteristics, and (3) median nerve function and subject characteristics. DESIGN: Case series. SETTING: Biomechanics laboratory and an electromyography laboratory. PARTICIPANTS: Thirty-four randomly recruited individuals with paraplegia who use a manual wheelchair for mobility. INTERVENTION: Subjects propelled their own wheelchair on a dynamometer at 0.9m/sec and 1.8m/sec. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. Bilateral nerve conduction studies focusing on the median nerve were also completed. MAIN OUTCOME MEASURES: Pearson's correlation coefficients between subject characteristics, median nerve conduction studies, and propulsion biomechanics; a regression model of nerve conduction studies incorporating subject characteristics and pushrim biomechanics. RESULTS: Subject weight was significantly related to median nerve latency (r = .36, p = .03) and median sensory amplitude (r = -.43, p = .01). Height was also significantly related to median sensory amplitude (r = -.58, p = .01). Subject weight was significantly related to the peak resultant force applied to the pushrim (r = .59, p < .001). Height, weight, and weight-normalized pushrim forces were successfully incorporated into a linear regression model predicting median sensory amplitude (r = .63, p < .05) and mean median latency (r = .54, p < .05). CONCLUSION: This study found subject weight to be related to pushrim forces and median nerve function. Independent of subject weight, pushrim biomechanics were also related to median nerve function. Through weight loss and changes in pushrim biomechanics, it may be possible to prevent median nerve injury in manual wheelchair users.

Involvement of two distinct regulatory T cell populations in the antigen-specific suppression of cytolytic T cell generation.

Alloantigen-specific, radiation-resistant T cells generated in mixed-lymphocyte cultures inhibited the generation of allospecific CTL responses in vitro. This regulatory T cell population was studied using mAb generated to Ag-specific suppressor factors that regulate the response to the synthetic terpolymer L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT). Both monoclonal 984 D4.6.5 and a pool of four mAb 2441, when added in the presence of complement, eliminated alloantigen-specific inhibition of the CTL response. When separate cell cultures treated with mAb 984 or 2441 plus complement were recombined, inhibition was reestablished, suggesting that two or more populations of cells are required for active inhibition. Furthermore, neither the mAb 984 nor the mAb 2441 plus complement had any effect on any stage of CTL development. This suggests that the inhibition of the CTL response was not the result of cytolytic activity via the regulatory T cells. Experiments in which these antibodies were added without complement treatment showed that the mAb 2441 neutralized the inhibitory activity, whereas mAb 984 augmented inhibition. It is concluded from these studies that regulatory T cells originally identified in humoral immune responses also regulate cell-mediated immune responses. Suppressor epitopes are displayed on the surface of these cells that allow them to be distinguished from other T cells. These data also show the utility of the mAb 984 and 2441 raised against specific suppressor T cell products in different experimental models of immunity. These studies suggest that phenotypically distinct Ts cell populations can play a normal regulatory role in both cell-mediated and humoral immunity.

Cytokine effects on the down regulation of cytolytic T cell responses in vitro.

Lymphocytes from mouse and men can be stimulated by a variety of cellular signals including concanavalin A and the interferons to generate cells capable of non-specific down regulation of the generation of immune responses. The studies reported here extend this finding to show that such regulatory cells are also generated during the course of a mixed lymphocyte response and following stimulation of the CD3 component of the T cell receptor with anti-CD3 antibody. Regulatory activity was assessed by the addition of putative regulatory cells to mixed lymphocyte cultures and measuring the generation of cytolytic T cell activity in these cultures. The action of such non-specific regulatory cells was blocked by antiserum to the N-terminal sequence of soluble immune response suppressor (SIRS). In addition, generation of the regulatory cell population was inhibited by antiserum to the 55 kd subunit of the IL-2 receptor. A survey of cytokines showed that while IL-2 was able to stimulate the generation of non-specific regulatory cell activity, IL-1,3,6,7, and 10 as well as TNF alpha and TGF beta were unable to generate such activity. IL-2 was unable to generate non-specific suppressive activity in the presence of anti-IL-2 receptor antibody. The regulatory activity of cells generated by IL-2 was inhibited by the anti-SIRS antiserum.

Putative N-terminal sequence of murine soluble immune response suppressor (SIRS): significant homology with short neurotoxin 1.

Soluble immune response suppressor (SIRS) is a low-molecular-weight protein (approximately 10,000 daltons) produced by mitogen- or interferon-activated T lymphocytes that can block development of humoral or cell-mediated immune responses in vivo or in vitro. As previously reported, murine SIRS is heterogeneous, eluting in two broad peaks on high performance reverse phase chromatography as well as displaying several broad isoelectric point forms. A putative N-terminal 21 amino acid sequence has been obtained for one of the less hydrophobic isoforms, SIRS-alpha 7. The sequence of SIRS-alpha 7 is unique in mammals but shows a remarkable homology to the family of short neurotoxins (short neurotoxin 1) found in sea snake, adder, and cobra species. A degenerate oligonucleotide probe based on the protein sequence was synthesized and was shown to hybridize to SIRS messenger RNA as measured by SIRS synthesis in a rabbit reticulocyte lysate system. A synthetic polypeptide based on the 21-residue sequence was also prepared and coupled to thyroglobulin or keyhole limpet hemocyanin. These were used to prepare rabbit antisera that neutralize SIRS bioactivity and precipitate authentic SIRS.

Racial differences in pregnancy outcomes.

Black mothers in the United States are twice as likely as their white counterparts to experience a wide variety of adverse pregnancy outcomes, including prematurity, low birth weight, and infant and fetal death. Although blacks have higher proportions of births with maternal risk factors such as young age, high birth order, low education, and unmarried mothers, these differences do not account for their higher rates of adverse outcomes; the reasons for the excess remain largely unknown. To develop effective interventions to reduce the racial disparities in pregnancy outcome, we must further our understanding of the mechanisms underlying premature onset of labor and intrauterine growth.