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Biomedical subjects

R A Erdman

Publications and source records attributed to R A Erdman.

At least 37 records · Page 2Linked to original sources
PubMed2000

The impact of somatotropin, milking frequency, and photoperiod on dairy farm nutrient flows.

Three technologies that increase milk production per cow and that are available to dairy producers are bovine somatotropin, three times daily milking, and extended daily photoperiod. Dairy herds fed according to National Research Council requirements were simulated to predict the impact of these technologies on N losses to manure and to water resources. Because Dairy Herd Improvement Association total lactation records (n = 93,080) revealed a positive linear relationship between 305-d milk production and calving interval, calving intervals were predicted to increase with the use of technologies and to result in a change in the ratio of lactating cows to growing heifers in a herd. Compared with a herd using no technologies, the use of bovine somatotropin, three times daily milking, or extended photoperiod were predicted to reduce herd N excretion per unit of milk by 7.8, 7.0, and 3.6%, respectively. When the use of all three technologies was simulated, N losses to manure were decreased by 15.7% when assuming calving interval increases from the technologies or 15.4% without accounting for calving interval increases. Reductions in feed N requirements and manure N losses with these three technologies were predicted to reduce environmental N loading by up to 16%.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Diets deficient in rumen undegraded protein did not depress milk production.

The objective of this study was to evaluate the National Research Council's recommendations for feeding levels of rumen undegraded protein (RUP) for cows fed a one-group total mixed ration. Sixty Holstein cows were paired by parity (1 to 6) and DIM (23 to 315) and were randomly assigned to one of two treatment sequences. Diets contained alfalfa silage (30% diet DM) and corn silage (26% diet DM), and were isonitrogenous (16% CP) and isocaloric (1.71 Mcal/kg). Soybean meal, protected soybean meal (Soy Best), and urea were used to make ration protein fractions that were predicted to be 35 or 29% RUP. The 35% RUP diet was formulated to provide 98 and 105% of the average requirement for RUP and rumen degraded protein (RDP), respectively. The ration containing 29% RUP provided 79 and 117% of average required RUP and RDP, respectively. All cows were group-fed the high RUP diet during a 2-wk pretreatment period, and then were fed one ration for 4 wk followed by the other for 4 wk according to their assigned treatment sequence. Data were collected in the last wk of each period. Mean milk production, milk fat, and milk protein were 32.6 kg/d, 4.35%, and 3.36%, respectively, with no treatment differences. Treatment response was not affected by degree of predicted RUP deficiency. National Research Council requirements for RUP may be too high for cows fed diets similar in energy to a one-group total mixed ration. Alternatively, estimates of RUP content of feedstuffs may be low.

Animal Feed↗
PubMed2000

Milk composition and apparent digestibilities of dietary fatty acids in lactating dairy cows abomasally infused with Cis or Trans fatty acids.

Fat supplementation of diets for dairy cows produces changes in nutrient supply and milk composition. The effect of abomasal infusion of either cis-C18:1 or trans-C18:1 fatty acid isomers on the digestibility of fatty acids and milk composition was determined in lactating dairy cows. Six multiparous midlactation Holstein cows were used and fed a control diet containing 50% forage and 50% concentrate. Treatments were (per day): no infusion, infusion of a 630-g fat mixture high in cis-C18:1 isomers, and infusion of a 623-g fat mixture high in trans-C18:1 isomers using two 3 x 3 Latin squares with 4-wk experimental periods. Fat infusion did not affect total dry matter intake and increased apparent digestibilities of total fatty acids. Apparent digestibilities of C18 fatty acids were directly related to the number of double bonds within isomers, and cis-C18:1 isomers were slightly more digestible than trans-C18:1 isomers. The lower yield of C12:0, C14:0, and C16:0 fatty acids in milk fat and higher milk citrate observed when cows were infused with trans-C18:1 suggests a depressed de novo milk fatty acid synthesis. Effects of trans infusion on milk fat were independent of ruminal fermentation, fatty acid apparent absorption, and fatty acid plasma concentrations. Lower milk protein yield in cows infused with fat may have been caused by a decrease in milk protein synthesis.

Abomasum↗
PubMed1999

Modification in Quetelet index five months after myocardial infarction: relevance of biographic and personality characteristics.

BACKGROUND: Obesity can be considered as a risk factor for (re-)occurrence of coronary heart disease. METHODS: The relationship between modification in quetelet index and personality characteristics was assessed in 166 survivors of a first myocardial infarction (MI). Quetelet index (weight/(height)2) was calculated a few days after first MI and again 5 months later. A multiple regression analysis was executed, with the quetelet index after 5 months as dependent variable and adjustment for gender, age, and quetelet index at baseline. RESULTS: It was found that strong feelings of vital exhaustion and lack of tension significantly contributed to the prediction of increased quetelet index 5 months after a first MI. CONCLUSIONS: It is recommended that individually tailored interventions be used based on these personality characteristics to accomplish body weight reduction in MI patients.

Anxiety↗
PubMed1999

A structural modeling analysis of anxiety and depression in patients undergoing coronary artery bypass graft surgery: a model generating approach.

The present study is a longitudinal study designed to explore structural relationships between anxiety, depression, personality, and background factors (e.g., gender, age, and complicated medical characteristics) in patients undergoing coronary artery bypass graft (CABG) surgery. At two timepoints before and two after CABG, 217 patients completed self-report questionnaires. To explore structural relationships, the structural equation modeling (SEM) method was applied. Using the model-generating approach, a model was developed, providing a good fit. The structural relationships revealed, in particular, the key position of neuroticism, which was related to both pre- and postoperative anxiety and depression. Relationships between anxiety and depression over time, both intra- and interrelationships, were relatively weak. Relationships between anxiety and depression at the same points in time were relatively strong, with preoperative depression leading to preoperative anxiety, and postoperative anxiety leading to postoperative depression. To provide a useful framework for development of intervention strategies, further research is needed to evaluate the plausibility of the final structural model.

Adult↗
PubMed1999

Safety and effects of physical training in chronic heart failure. Results of the Chronic Heart Failure and Graded Exercise study (CHANGE)

AIMS: Physical training is considered to be safe and beneficial as part of the treatment in heart failure patients. Prospective, sufficiently large studies are still needed to confirm this hypothesis. METHODS: In a prospective study, 80 patients with chronic heart failure class II and III (age, 56.6+/-8.3 years; left ventricular ejection fraction, 26.5+/-9.6%) were randomized to an endurance training group or to a control group with continuation of optimal pharmacological treatment. RESULTS: No training-related adverse event was reported, implying that the training programme was safe for these groups of chronic heart failure patients. Between-group comparison of changes revealed that training increased exercise time (from 608+/-35 to 738+/-40 s, P<0.0001), anaerobic threshold (from 10.5+/-0.4 to 11.8+/-0.3 ml x kg-1 min-1, P<0.05), and decreased the ventilatory equivalent for carbon dioxide at submaximal exercise level (from 2.8+/-0.1 to 2.7+/-0.1, P<0.05). Training did not increase peak oxygen consumption (15.2+/-0.5 to 16. 6+/-0.5 ml x kg-1 min-1, ns). An improvement in patients' assessment of quality of life was observed. There was a significant correlation between physiological and psychological improvements. Training was not effective in patients whose exercise test at entry had a duration of less than 7 min. None of the other baseline data could predict an effective training response. CONCLUSION: Physical training in chronic heart failure patients class II and III is safe and results in significant improvements in exercise time, anaerobic threshold, ventilatory equivalent for carbon dioxide at submaximal exercise level and quality of life.

Adult↗
PubMed1999

Effects of dietary crude protein concentration and degradability on milk production responses of early, mid, and late lactation diary cows.

Three experiments were conducted to investigate the effect of crude protein (CP) concentration and ruminally undegraded protein (RUP) concentration on milk production and composition of dairy cows at three different stages of lactation. Experiments 1, 2, and 3 using 39, 40, and 39 Holstein cows were conducted for cows in early (wk 4 to 14 postpartum), mid (wk 19 to 29), and late (wk 34 to 44) lactation, respectively. Cows were assigned to one of four corn-based diets: high CP, medium RUP (control); low CP, low RUP; low CP, medium RUP; and low CP, high RUP. Percentages of CP in the high and low CP diets were, respectively, 17.4 and 15.2 for Experiment 1, 15.3 and 13.3 for Experiment 2, and 14.2 and 12.6 for Experiment 3. The RUP concentrations (percentages of CP) for low, medium, and high diets averaged 35.5, 41.4, and 46.5%, respectively. For Experiment 1, production of milk, 4% fat-corrected milk, milk fat, and milk protein was increased by the high protein diets versus the low protein diets. Production of milk and fat-corrected milk increased linearly as RUP in the diet increased. During Experiment 2, lactational responses were not affected by treatment. During Experiment 3, dry matter intake, body weight, and body weight change increased for cows fed the high protein diets versus those same measurements for cows fed the low protein diets. Milk fat and milk protein percentage decreased linearly as RUP in the diet increased. Because there was no effect of diet on milk production, decreasing CP in diets fed to cows in mid or late lactation can reduce the cost of the diet and waste N excreted from the cow.

Animals↗
PubMed1999

Milk urea nitrogen target concentrations for lactating dairy cows fed according to National Research Council recommendations.

The objectives of this study were to develop and evaluate a mathematical model to predict milk urea N and to use this model to establish target concentrations. A mechanistic model to predict milk urea N was developed using raw data from 3 studies (10 diets, 40 cows, and 70 observations) and was evaluated with 18 independent studies (89 treatment means). For the independent literature data set, the model prediction error was approximately 35%; the majority of the error was due to variation among experiments. A mean of at least 25 cows was determined to be necessary for reliable model predictions. This model, which uses such data as protein intake and milk production, was used to predict milk urea N concentrations when cattle are fed according to National Research Council recommendations. Target values calculated in this manner for a typical lactation were 10 to 16 mg/dl, depending on days in milk. Target concentrations were sensitive to changes in milk production and amount of N intake and were relatively insensitive to body weight, parity, and grouping strategy. Analysis of data from the Lancaster Dairy Herd Improvement Association (n = 133,057) indicated that cows in the region were being fed diets containing approximately 17% crude protein, regardless of parity. A comparison to target milk urea N concentrations for this data indicated that cows were being fed 8 to 16% more protein than recommended by the National Research Council. Target milk urea N concentrations have been established, and dairy farmers now have a definitive way to interpret milk urea N concentrations.

Animal Nutritional Physiological Phenomena↗
PubMed1999

Effects of long daily photoperiod and bovine somatotropin (Trobest) on milk yield in cows.

Bovine somatotropin (bST) and exposure to long daily photoperiod increase milk yield of dairy cattle. We tested the hypothesis that long daily photoperiod and bST treatment would increase milk yield in an additive manner in lactating cows. At winter solstice, 40 lactating cows were started on a 140-d experiment; cows were greater than 70 d in milk (DIM) and were balanced for uniformity of DIM and milk yield within parity. Cows were randomly assigned to one of four treatments (10/treatment): 1) natural photoperiod, 2) natural photoperiod + bST (14 mg/d Trobest i.m.), 3) long daily photoperiod (18 h of light and 6 h of darkness/d), or 4) long daily photoperiod + bST. Long daily photoperiod increased fat-corrected milk (FCM) yield 1.9 kg/d versus natural photoperiod. Treatment with bST increased FCM 5.7 kg/d versus natural photoperiod, and long daily photoperiod + bST increased FCM 5.8 kg/d versus long daily photoperiod. Long daily photoperiod + bST was additive, increasing FCM 7.7 kg/d versus natural photoperiod. Serum somatotropin increased with bST, but not photoperiod, and bST increased serum insulin-like growth factor-I. Long daily photoperiod tended to increase prolactin; bST had no effect. Long daily photoperiod + bST increased dry matter intake (DMI) relative to natural photoperiod and natural photoperiod + bST; long daily photoperiod increased DMI relative to natural photoperiod + bST. Photoperiod had no effect on net energy balance; however, bST decreased net energy balance. Generally, body weight and milk composition did not differ among treatments. In conclusion, combination of bST with long-daily photoperiod tended to amplify the increases in milk yield observed with either treatment individually.

Animals↗
PubMed1998

Prenylation of Rab8 GTPase by type I and type II geranylgeranyl transferases.

Rab GTPases are post-translationally modified by addition of geranylgeranyl moieties to carboxyl-terminal cysteine residues. For Rab proteins ending with xxCC xCxC and CCxx motifs this modification is catalysed by geranylgeranyltransferase type II (GGTaseII), and is entirely dependent on the Rab substrate being bound to Rab escort protein (REP). Several Rab proteins contain carboxyl-terminal CaaL prenylation motifs typical of members of the Rho family, which are modified in a REP-independent manner by geranylgeranyltransferase type I (GGTaseI). The present studies show that one such Rab protein (Rab8), which ends with a CVLL motif, is uniquely able to serve as a substrate for either REP/GGTaseII or GGTaseI in cell-free assays. The modification of Rab8 by GGTaseI did not require REP, indicating that a REP-induced conformational change is not essential for exposure of the Rab carboxyl-terminal cysteine prenylation site. To determine whether one enzyme plays a predominant role in Rab8 prenylation in vivo, the incorporation of [3H]mevalonate into Rab8 was measured in human embryonal kidney 293 cells under conditions where the activity of GGTaseI, but not GGTaseII, was blocked by the peptidomimetic inhibitor GGTI-298. The GGTaseI inhibitor did not prevent prenylation of either overexpressed Myc-tagged Rab8 or endogenous Rab8, whereas prenylation of a known GGTaseI substrate with the same carboxyl-terminal motif, Cdc42Hs, was completely blocked. To rule out the possibility that the apparent prenylation of Rab8 by GGTaseII occurs only when GGTaseI activity is eliminated, metabolic labelling studies were carried out in the absence of the GGTaseI inhibitor, using a REP-binding-deficient Rab8 construct (Y78D) that cannot serve as a substrate for GGTaseII, but is indistinguishable from wild-type Rab8 as a substrate for GGTaseI. Prenylation of the Y78D mutant was reduced by 60-70% in intact cells, consistent with the conclusion that the majority of Rab8 is prenylated by the REP/GGTaseII system in vivo.

Adaptor Proteins, Signal Transducing↗
PubMed1998

The course of anxiety and depression in patients undergoing coronary artery bypass graft surgery.

A semilongitudinal study was designed to follow-up the course of anxiety and depression in patients undergoing coronary artery bypass graft (CABG) surgery. The focus was on possible effects of gender and age on variations in both mean level and interindividual differences over time. At two timepoints before and two after surgery, 217 patients completed self-report questionnaires. Multivariate testing revealed an overall decrease in mean levels of anxiety and depression in the postoperative period but different trends for men and women. Compared with men, women reported more anxiety and depression, both pre- and postoperatively, but showed a relatively stronger decrease in the early postoperative period. Regarding variations in interindividual differences over time, multivariate testing revealed different trends of depression for men and women. Women appeared to be most homogeneous in the early days after surgery, whereas interindividual differences for men showed a stable trend.

Adult↗
PubMed1998

Effect of exercise training on quality of life in patients with chronic heart failure.

The effect of exercise training on quality of life and exercise capacity was studied in 67 patients with mild to moderate chronic heart failure (CHF; age: 65.6+/-8.3 years; left ventricular ejection fraction: 26.5+/-9.6%). Patients were randomly allocated to either a training group or to a control group. After intervention a significantly larger decrease in Feelings of Being Disabled (a subscale of the Heart Patients Psychological Questionnaire) and a significantly larger increase in the Self-Assessment of General Well-Being (SAGWB) were observed in the training group. Exercise time and anaerobic threshold were increased in the training group only. The increase in exercise time was related to both Feelings of Being Disabled and SAGWB. We conclude that supervised exercise training improves both quality of life and exercise capacity and can be safely performed by chronic heart failure patients.

Aged↗
PubMed1998

Psychopathology in young adults with congenital heart disease. Follow-up results.

AIMS: The aim of the present study was to assess the occurrence of a wide range of behavioural and emotional problems long-term (> 9 years) after surgical correction for congenital heart disease in infancy and childhood. METHODS: The problem scores on the Young Adult Self-Report of 166 19-25-year-old adults with congenital heart disease were compared with those of subjects of similar age from the general population. RESULTS: On most Young Adult Self-Report scales no differences were found between the mean problem scores of the congenital heart disease-adults and reference peers. On only two Young Adult Self-Report scales (i.e. Somatic Complaints and Strange) and the total problem score were significant though small differences found between the mean problem scores of the congenital heart disease adults and reference peers. No significant relationship was found between cardiac diagnosis and problem behaviours in congenital heart disease adults. No relationship was found between IQ scores and problem behaviours in congenital heart disease adults. CONCLUSION: Overall, it can be concluded that the results of the congenital heart disease adults were not unfavourable, since the differences in mean (total) problem scores between the congenital heart disease sample and reference group were small and limited to only two specific problem areas.

Adult↗
PubMed1998

Prediction of behavioural and emotional problems in children and adolescents with operated congenital heart disease.

AIMS: The aim of the present study was to determine which medical variables were predictors of long-term behavioural/emotional outcome after surgical correction for congenital heart disease in infancy and childhood. METHODS: The Child Behavior Checklist (CBCL) was used to predict parent-reported behavioural/emotional problems in 125 10-15 year-old congenital heart disease children from: (1) biographical status (2) medical history (3) heart surgery (4) short-term post-operative course and (5) number of heart operations and (6) extra cardiac concomitant anomalies. RESULTS: Higher CBCL total problem scores at follow-up were associated with a greater number of heart operations and deep hypothermic circulatory arrest (< 22 degrees). 'Internalizing problems' were associated with a greater number of heart operations, deep hypothermic circulatory arrest, a short gestational age, low systemic oxygen saturation, and older age at surgical repair. 'Externalizing problems' were associated with a greater number of heart operations only. CONCLUSION: Several medical variables were significant predictors and can be used to identify those congenital heart disease children who are at risk of long-term behavioural/emotional maladjustment.

Adolescent↗
PubMed1998

The putative "switch 2" domain of the Ras-related GTPase, Rab1B, plays an essential role in the interaction with Rab escort protein.

Posttranslational modification of Rab proteins by geranylgeranyltransferase type II requires that they first bind to Rab escort protein (REP). Following prenylation, REP is postulated to accompany the modified GTPase to its specific target membrane. REP binds preferentially to Rab proteins that are in the GDP state, but the specific structural domains involved in this interaction have not been defined. In p21 Ras, the alpha2 helix of the Switch 2 domain undergoes a major conformational change upon GTP hydrolysis. Therefore, we hypothesized that the corresponding region in Rab1B might play a key role in the interaction with REP. Introduction of amino acid substitutions (I73N, Y78D, and A81D) into the putative alpha2 helix of Myc-tagged Rab1B prevented prenylation of the recombinant protein in cell-free assays, whereas mutations in the alpha3 and alpha4 helices did not. Additionally, upon transient expression in transfected HEK-293 cells, the Myc-Rab1B alpha2 helix mutants were not efficiently prenylated as determined by incorporation of [3H]mevalonate. Metabolic labeling studies using [32P]orthophosphate indicated that the poor prenylation of the Rab1B alpha2 helix mutants was not directly correlated with major disruptions in guanine nucleotide binding or intrinsic GTPase activity. Finally, gel filtration analysis of cytosolic fractions from 293 cells that were coexpressing T7 epitope-tagged REP with various Myc-Rab1B constructs revealed that mutations in the alpha2 helix of Rab1B prevented the association of nascent (i.e., nonprenylated) Rab1B with REP. These data indicate that the Switch 2 domain of Rab1B is a key structural determinant for REP interaction and that nucleotide-dependent conformational changes in this region are largely responsible for the selective interaction of REP with the GDP-bound form of the Rab substrate.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Exercise training in elderly patients with chronic heart failure.

BACKGROUND: Physical training currently constitutes an important part of treatment of heart failure patients. So far, no data are available on the effects of regular exercise in elderly (aged > 65 years) heart failure patients. METHODS: In a prospective trial, patients with chronic heart failure (New York Heart Association class II and III) were randomly assigned to a training group and a control group. Patients in the training group performed additional exercises three times a week, while patients in the control group continued regular treatment. To analyse the influence of age, both groups were subdivided into subjects younger than and older than 65 years. The effect of training on exercise parameters was evaluated by means of a treadmill test. Quality of life aspects were evaluated with the help of the Heart Patients Psychological Questionnaire and a single-question Self Awareness of General Well-Being test. RESULTS: Comparison of changes between groups revealed that training increased the duration of the exercise test and improved aspects of quality of life in the trained patients aged both younger than and older than 65 years. CONCLUSION: Exercise training is equally effective in patients aged younger than and older than 65 years.

Adult↗