Association of vancomycin plus piperacillin-tazobactam with early changes in creatinine versus cystatin C in critically ill adults: a prospective cohort study

PURPOSE

Although dozens of studies have associated vancomycin + piperacillin-tazobactam with increased acute kidney injury (AKI) risk, it is unclear whether the association represents true injury or a pseudotoxicity characterized by isolated effects on creatinine secretion. We tested this hypothesis by contrasting changes in creatinine concentration after antibiotic initiation with changes in cystatin C concentration, a kidney biomarker unaffected by tubular secretion.

METHODS

We included patients enrolled in the Molecular Epidemiology of SepsiS in the ICU (MESSI) prospective cohort who were treated for ≥ 48 h with vancomycin + piperacillin-tazobactam or vancomycin + cefepime. Kidney function biomarkers [creatinine, cystatin C, and blood urea nitrogen (BUN)] were measured before antibiotic treatment and at day two after initiation. Creatinine-defined AKI and dialysis were examined through day-14, and mortality through day-30. Inverse probability of treatment weighting was used to adjust for confounding. Multiple imputation was used to impute missing baseline covariates.

RESULTS

The study included 739 patients (vancomycin + piperacillin-tazobactam n = 297, vancomycin + cefepime n = 442), of whom 192 had cystatin C measurements. Vancomycin + piperacillin-tazobactam was associated with a higher percentage increase of creatinine at day-two 8.04% (95% CI 1.21, 15.34) and higher incidence of creatinine-defined AKI: rate ratio (RR) 1.34 (95% CI 1.01, 1.78). In contrast, vancomycin + piperacillin-tazobactam was not associated with change in alternative biomarkers: cystatin C: - 5.63% (95% CI - 18.19, 8.86); BUN: - 4.51% (95% CI - 12.83, 4.59); or clinical outcomes: dialysis: RR 0.63 (95% CI 0.31, 1.29); mortality: RR 1.05 (95%CI 0.79, 1.41).

CONCLUSIONS

Vancomycin + piperacillin-tazobactam was associated with creatinine-defined AKI, but not changes in alternative kidney biomarkers, dialysis, or mortality, supporting the hypothesis that vancomycin + piperacillin-tazobactam effects on creatinine represent pseudotoxicity.

Elevated Plasma Levels of Matrix Metalloproteinase-3 and Tissue-Inhibitor of Matrix Metalloproteinases-1 Associate With Organ Dysfunction and Mortality in Sepsis

BACKGROUND

Matrix Metalloproteinases (MMP) respond to tissue damage during sepsis. Higher plasma concentrations of MMPs and the tissue-inhibitor of matrix metalloproteinases (TIMP) have been reported in sepsis compared with healthy controls. The objective of this study was to examine if plasma levels of MMP-3, MMP-9, and TIMP-1 associate with mortality and organ dysfunction during sepsis.

METHODS

We conducted a prospective cohort study of critically ill patients with sepsis adjudicated per Sepsis-3 criteria at a tertiary academic medical center. We measured plasma concentrations of MMP-3, MMP-9, and TIMP-1 on intensive care unit admission. We phenotyped the subjects for shock, acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and mortality at 30 days. We used logistic regression to test the associations between the MMPs and TIMP-1 with shock, ARDS, AKI, and mortality.

RESULTS

Higher plasma TIMP-1 levels were associated with shock (odds ratio [OR] 1.51 per log increase [95% CI 1.25, 1.83]), ARDS (OR 1.24 [95% CI 1.05, 1.46]), AKI (OR 1.18 [95% CI 1.01, 1.38]), and mortality (OR 1.20 [95% CI 1.05, 1.46]. Higher plasma MMP-3 concentrations were associated with shock (OR 1.40 [95% CI 1.12, 1.75]) and mortality (OR 1.24 [95% CI 1.03, 1.48]) whereas MMP-9 levels were not associated with outcomes. Higher plasma TIMP-1 to MMP-3 ratios were associated with shock (OR 1.41 [95% CI 1.15, 1.72], P = 0.02).

CONCLUSION

Elevated plasma concentrations of TIMP-1 associate with organ dysfunction and mortality in sepsis. Higher plasma levels of MMP-3 associate with shock and mortality. Plasma MMP and TIMP-1 may warrant further investigation as emerging sepsis theragnostic biomarkers.

CD8+ T cells contribute to survival in patients with COVID-19 and hematologic cancer

Patients with cancer have high mortality from coronavirus disease 2019 (COVID-19), and the immune parameters that dictate clinical outcomes remain unknown. In a cohort of 100 patients with cancer who were hospitalized for COVID-19, patients with hematologic cancer had higher mortality relative to patients with solid cancer. In two additional cohorts, flow cytometric and serologic analyses demonstrated that patients with solid cancer and patients without cancer had a similar immune phenotype during acute COVID-19, whereas patients with hematologic cancer had impairment of B cells and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody responses. Despite the impaired humoral immunity and high mortality in patients with hematologic cancer who also have COVID-19, those with a greater number of CD8 T cells had improved survival, including those treated with anti-CD20 therapy. Furthermore, 77% of patients with hematologic cancer had detectable SARS-CoV-2-specific T cell responses. Thus, CD8 T cells might influence recovery from COVID-19 when humoral immunity is deficient. These observations suggest that CD8 T cell responses to vaccination might provide protection in patients with hematologic cancer even in the setting of limited humoral responses.

CD8 T cells compensate for impaired humoral immunity in COVID-19 patients with hematologic cancer

Cancer patients have increased morbidity and mortality from Coronavirus Disease 2019 (COVID-19), but the underlying immune mechanisms are unknown. In a cohort of 100 cancer patients hospitalized for COVID-19 at the University of Pennsylvania Health System, we found that patients with hematologic cancers had a significantly higher mortality relative to patients with solid cancers after accounting for confounders including ECOG performance status and active cancer status. We performed flow cytometric and serologic analyses of 106 cancer patients and 113 non-cancer controls from two additional cohorts at Penn and Memorial Sloan Kettering Cancer Center. Patients with solid cancers exhibited an immune phenotype similar to non-cancer patients during acute COVID-19 whereas patients with hematologic cancers had significant impairment of B cells and SARS-CoV-2-specific antibody responses. High dimensional analysis of flow cytometric data revealed 5 distinct immune phenotypes. An immune phenotype characterized by CD8 T cell depletion was associated with a high viral load and the highest mortality of 71%, among all cancer patients. In contrast, despite impaired B cell responses, patients with hematologic cancers and preserved CD8 T cells had a lower viral load and mortality. These data highlight the importance of CD8 T cells in acute COVID-19, particularly in the setting of impaired humoral immunity. Further, depletion of B cells with anti-CD20 therapy resulted in almost complete abrogation of SARS-CoV-2-specific IgG and IgM antibodies, but was not associated with increased mortality compared to other hematologic cancers, when adequate CD8 T cells were present. Finally, higher CD8 T cell counts were associated with improved overall survival in patients with hematologic cancers. Thus, CD8 T cells likely compensate for deficient humoral immunity and influence clinical recovery of COVID-19. These observations have important implications for cancer and COVID-19-directed treatments, immunosuppressive therapies, and for understanding the role of B and T cells in acute COVID-19.

The ABO histo-blood group, endothelial activation, and acute respiratory distress syndrome risk in critical illness

BACKGROUNDThe ABO histo-blood group is defined by carbohydrate modifications and is associated with risk for multiple diseases, including acute respiratory distress syndrome (ARDS). We hypothesized that genetically determined blood subtype A1 is associated with increased risk of ARDS and markers of microvascular dysfunction and coagulation.METHODSWe conducted analyses in 3 cohorts of critically ill trauma and sepsis patients (n = 3710) genotyped on genome-wide platforms to determine the association of the A1 blood type genotype with ARDS risk. We subsequently determined whether associations were present in FUT2-defined nonsecretors who lack ABO antigens on epithelium, but not endothelium. In a patient subgroup, we determined the associations of blood type with plasma levels of endothelial glycoproteins and disseminated intravascular coagulation (DIC). Lastly, we tested whether blood type A was associated with less donor lung injury recovery during human ex vivo lung perfusion (EVLP).RESULTSThe A1 genotype was associated with a higher risk of moderate to severe ARDS relative to type O in all 3 populations. In sepsis, this relationship was strongest in nonpulmonary infections. The association persisted in nonsecretors, suggesting a vascular mechanism. The A1 genotype was also associated with higher DIC risk as well as concentrations of thrombomodulin and von Willebrand factor, which in turn were associated with ARDS risk. Blood type A was also associated with less lung injury recovery during EVLP.CONCLUSIONWe identified a replicable association between ABO blood type A1 and risk of ARDS among the critically ill, possibly mediated through microvascular dysfunction and coagulation.FUNDINGNIH HL122075, HL125723, HL137006, HL137915, DK097307, HL115354, HL101779, and the University of Pennsylvania McCabe Fund Fellowship Award.

Plasma sRAGE Acts as a Genetically Regulated Causal Intermediate in Sepsis-associated Acute Respiratory Distress Syndrome

Rationale: Acute respiratory distress syndrome (ARDS) lacks known causal biomarkers. Plasma concentrations of sRAGE (soluble receptor for advanced glycation end products) strongly associate with ARDS risk. However, whether plasma sRAGE contributes causally to ARDS remains unknown.Objectives: Evaluate plasma sRAGE as a causal intermediate in ARDS by Mendelian randomization (MR), a statistical method to infer causality using observational data.Methods: We measured early plasma sRAGE in two critically ill populations with sepsis. The cohorts were whole-genome genotyped and phenotyped for ARDS. To select validated genetic instruments for MR, we regressed plasma sRAGE on genome-wide genotypes in both cohorts. The causal effect of plasma sRAGE on ARDS was inferred using the top variants with significant associations in both populations (P < 0.01, R2 > 0.02). We applied the inverse variance-weighted method to obtain consistent estimates of the causal effect of plasma sRAGE on ARDS risk.Measurements and Main Results: There were 393 European and 266 African ancestry patients in the first cohort and 843 European ancestry patients in the second cohort. Plasma sRAGE was strongly associated with ARDS risk in both populations (odds ratio, 1.86; 95% confidence interval [1.54-2.25]; 2.56 [2.14-3.06] per log increase). Using genetic instruments common to both populations, plasma sRAGE had a consistent causal effect on ARDS risk with a β estimate of 0.50 (95% confidence interval [0.09-0.91] per log increase).Conclusions: Plasma sRAGE is genetically regulated during sepsis, and MR analysis indicates that increased plasma sRAGE leads to increased ARDS risk, suggesting plasma sRAGE acts as a causal intermediate in sepsis-related ARDS.

Plasma sTNFR1 and IL8 for prognostic enrichment in sepsis trials: a prospective cohort study

Background

Enrichment strategies improve therapeutic targeting and trial efficiency, but enrichment factors for sepsis trials are lacking. We determined whether concentrations of soluble tumor necrosis factor receptor-1 (sTNFR1), interleukin-8 (IL8), and angiopoietin-2 (Ang2) could identify sepsis patients at higher mortality risk and serve as prognostic enrichment factors.

Methods

In a multicenter prospective cohort study of 400 critically ill septic patients, we derived and validated thresholds for each marker and expressed prognostic enrichment using risk differences (RD) of 30-day mortality as predictive values. We then used decision curve analysis to simulate the prognostic enrichment of each marker and compare different prognostic enrichment strategies.

Measurements and main results

An admission sTNFR1 concentration > 8861 pg/ml identified patients with increased mortality in both the derivation (RD 21.6%) and validation (RD 17.8%) populations. Among immunocompetent patients, an IL8 concentration > 94 pg/ml identified patients with increased mortality in both the derivation (RD 17.7%) and validation (RD 27.0%) populations. An Ang2 level > 9761 pg/ml identified patients at 21.3% and 12.3% increased risk of mortality in the derivation and validation populations, respectively. Using sTNFR1 or IL8 to select high-risk patients improved clinical trial power and efficiency compared to selecting patients with septic shock. Ang2 did not outperform septic shock as an enrichment factor.

Conclusions

Thresholds for sTNFR1 and IL8 consistently identified sepsis patients with higher mortality risk and may have utility for prognostic enrichment in sepsis trials.

Neutropenic sepsis is associated with distinct clinical and biological characteristics: a cohort study of severe sepsis

Background

Immunocompromised patients who develop sepsis while neutropenic are at high risk for morbidity and mortality; however, it is unknown if neutropenic sepsis is associated with distinct clinical and biological characteristics.

Methods

We conducted a prospective cohort study of patients admitted to the medical intensive care unit of an academic medical center with severe sepsis. Patients were followed for the development of acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and mortality. Plasma proteins, representing the host inflammatory response, anti-inflammatory response, and endothelial leak were measured in 30 % of subjects. Clinical characteristics and plasma protein concentrations of patients with neutropenia at enrollment were compared to patients without neutropenia.

Results

Of 797 subjects enrolled, 103 (13 %) were neutropenic at ICU admission. The neutropenic subjects were more often in shock, admitted from the hospital ward, had higher APACHE III scores, and more likely bacteremic. Neutropenia was an independent risk factor for AKI (RR 1.28; 95 % CI 1.04, 1.57; p = 0.03), but not ARDS (RR 0.90; 95 % CI 0.70, 1.17; p = 0.42) or 30-day mortality (RR 1.05; 95 % CI 0.85, 1.31; p = 0.65). Neutropenic subjects had higher plasma interleukin (IL)-6 (457 vs. 249 pg/ml; p = 0.03), IL-8 (581 vs. 94 pg/ml; p <0.001), and granulocyte colony-stimulating factor (G-CSF) (3624 vs. 99 pg/ml; p <0.001). Angiopoietin-2 and IL-1 receptor antagonist concentrations did not differ between groups.

Conclusions

Neutropenic sepsis is associated with a higher AKI risk and concentrations of inflammatory mediators IL-6, IL-8, and G-CSF relative to non-neutropenic patients. These differences may have implications for future therapies targeting neutropenic sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1398-y) contains supplementary material, which is available to authorized users.

Admission plasma levels of the neuronal injury marker neuron-specific enolase are associated with mortality and delirium in sepsis

PURPOSE

Neuron-specific enolase (NSE) concentrations are prognostic following traumatic and anoxic brain injury and may provide a method to quantify neuronal injury in other populations. We determined the association of admission plasma NSE concentrations with mortality and delirium in critically ill septic patients.

METHODS

We performed a retrospective analysis of 124 patients from a larger sepsis cohort. Plasma NSE was measured in the earliest blood draw at intensive care unit admission. Primary outcomes were 30-day mortality and intensive care unit delirium determined by chart review.

RESULTS

Sixty-one patients (49.2%) died within 30 days, and delirium developed in 34 (31.5%) of the 108 patients who survived at least 24 hours and were not persistently comatose. Each doubling of the NSE concentration was associated with a 7.3% (95% confidence interval [CI] 2.5-12.0, P= .003) increased risk of 30-day mortality and a 5.2% (95% CI 3.2-7.2, P< .001) increased risk of delirium. An NSE concentration >12.5 μg/L was independently associated with a 23.3% (95% CI 6.7-39.9, P= .006) increased risk of 30-day mortality and a 29.3% (95% CI 8.8-49.8, P= .005) increased risk of delirium.

CONCLUSIONS

Higher plasma NSE concentrations were associated with mortality and delirium in critically ill septic patients, suggesting that NSE may have utility as a marker of neuronal injury in sepsis.

Low Plasma Levels of Adiponectin Do Not Explain Acute Respiratory Distress Syndrome Risk: a Prospective Cohort Study of Patients with Severe Sepsis

BACKGROUND

Obesity is associated with the development of acute respiratory distress syndrome (ARDS) in at-risk patients. Low plasma levels of adiponectin, a circulating hormone-like molecule, have been implicated as a possible mechanism for this association. The objective of this study was to determine the association of plasma adiponectin level at ICU admission with ARDS and 30-day mortality in patients with severe sepsis and septic shock.

METHODS

This is a prospective cohort study of patients admitted to the medical ICU at the Hospital of the University of Pennsylvania. Plasma adiponectin was measured at the time of ICU admission. ARDS was defined by Berlin criteria. Multivariable logistic regression was used to determine the association of plasma adiponectin with the development of ARDS and mortality at 30 days.

RESULTS

The study included 164 patients. The incidence of ARDS within 5 days of admission was 45%. The median initial plasma adiponectin level was 7.62 mcg/ml (IQR: 3.87, 14.90) in those without ARDS compared to 8.93 mcg/ml (IQR: 4.60, 18.85) in those developing ARDS. The adjusted odds ratio for ARDS associated with each 5 mcg increase in adiponectin was 1.12 (95% CI 1.01, 1.25), p-value 0.025). A total of 82 patients (51%) of the cohort died within 30 days of ICU admission. There was a statistically significant association between adiponectin and mortality in the unadjusted model (OR 1.11, 95% CI 1.00, 1.23, p-value 0.04) that was no longer significant after adjusting for potential confounders.

CONCLUSIONS

In this study, low levels of adiponectin were not associated with an increased risk of ARDS in patients with severe sepsis and septic shock. This argues against low levels of adiponectin as a mechanism explaining the association of obesity with ARDS. At present, it is unclear whether circulating adiponectin is involved in the pathogenesis of ARDS or simply represents an epiphenomenon of other unknown functions of adipose tissue or metabolic alterations in sepsis.

Influence of fetal death and fetectomy on gestation and the initiation of parturition in the ewe

Depressed function of the fetal hypothalamic-pituitary-adrenal axis results in prolonged gestation, and fetal death causes premature parturition. The objective of this experiment was to determine effects of death in utero of a sibling, or its removal, on the duration of gestation and concomitant changes in maternal serum concentrations of oestradiol (E) and progesterone (P). Ovine placental lactogen (oPL) was also determined as an index of placental viability. Blood samples were collected in the morning, beginning 3 days prior to surgery on Day 115 +/- 3 of gestation and continuing daily until 3 days post partum. Surgeries were performed via mid-ventral laparotomy to induce fetal death or to remove the fetus. Fetal death was induced by ligating the umbilicus. Duration of gestation was similar (P > 0.05) in control (C, n = 6) and sham-operated (S, n = 3) ewes (148 +/- 1.0 and 148.6 +/- 0.7 days, respectively). On the day of parturition, concentrations of P, E and oPL were 5.2 +/- 1.9 ng mL-1, 135 +/- 22 pg mL-1 and 153 +/- 54 ng mL-1, respectively, in ewes from combined C and S groups. Total fetectomy (n = 3) resulted in a rapid decrease (P < 0.05) in maternal serum concentrations of P, E, and oPL. Ligation of the umbilicus of both fetus(es) in utero (n = 4) induced fetal death, decreased (P < 0.05) length of gestation to 118.8 +/- 1.8 days and decreased (P < 0.05) serum concentrations of P and oPL prior to parturition and oPL on the day of parturition. In addition, maternal serum concentrations of E failed (P > 0.05) to increase at parturition. Length of gestation and concentrations of P, E and oPL at parturition were not affected (P > 0.05) by removal of one fetus when its sibling was undisturbed (n = 4) compared to control ewes. In contrast, death of one fetus with its sibling undisturbed (n = 5) decreased (P < 0.01) length of gestation (139.2 +/- 2.8 days), but did not affect P, E and oPL (P > 0.05) on all days tested. In conclusion, death of one fetus reduced the duration of gestation, but changes prepartum in maternal serum concentrations of P and oPL were similar to ewes delivering only live fetuses. The increase in maternal concentrations of E that normally occur at parturition was absent in ewes giving birth to only dead fetuses and, therefore, was not a prerequisite to parturition.

Extent to which guided-discovery teaching strategies were used by 20 preceptors in family medicine

BACKGROUND

Learners learn more and are able to categorize problems at higher levels when their teachers use guided-discovery strategies (e.g., questions and advice to investigate relationships between concepts), as opposed to directly telling learners the answers. This study examines the extent to which clinician preceptors of residents use guided-discovery strategies when faced with a diagnostic problem-solving situation.

METHOD

Twenty family medicine preceptors from four residencies volunteered in 1991-92 to role-play with a simulated first-year resident on a single standardized case. Judges coded the preceptors' verbal behaviors by type (question, statement, or advice) and by category. The categories were teacher, i.e., behaviors relating to more than the present case (hence exemplifying guided-discovery strategies), and consultant, i.e., behaviors relating to the successful disposition of the case (without overt concern for the education of the resident).

RESULTS

Of the preceptors' 846 verbal behaviors, 602 (71%) were coded as teacher behaviors, but only 329 (39%) were teacher behaviors that were of the specific types (high-level advice or questions promoting reflectivity, i.e., mindfulness) described in the literature as being most likely to promote learners' reflectivity and transfer of knowledge and skills from a lower level of abstraction to a higher level.

CONCLUSION

The results suggest that the 20 perceptors were aware of the importance of "getting residents to think" and did use teaching strategies known to promote transfer. However, their repertoire of strategies was limited.

Effects of nutrient deficiencies and excesses on reproductive efficiency of livestock

Successful reproduction is dependent on a host of macro- and micronutrients and ceases well before an animal expires from deficiency of a particular nutrient. This review focuses on the functional roles phosphorus, vitamin A and beta-carotene, protein, and energy play in reproductive processes. Although it is not known whether deficiencies of these nutrients limit reproduction through common or discrete mechanisms, appropriate quantities of these nutrients are required for optimal reproduction. Mechanisms through which nutritional status is perceived by the hypothalamic-pituitary-gonadal axis remain unclear but seem to impinge on hypothalamic regions that selectively regulate production and release of pituitary trophic hormones. Body condition, or degree of fatness, seems to be the most reliable indicator of well-being of an animal, and, when coupled with changes in BW, provides a useful method to assess reproductive potential.

Effect of implantation of dexamethasone adjacent to the paraventricular nucleus on messenger ribonucleic acid for corticotropin-releasing hormone and proopiomelanocortin during late gestation in fetal sheep

Glucocorticoids act upon the hypothalamic paraventricular nucleus (PVN) and anterior pituitary in a classic negative feedback loop to regulate ACTH biosynthesis and secretion. Evidence exists to indicate that glucocorticoid feedback may be attenuated during late gestation in the sheep fetus to allow the preterm rise in fetal plasma cortisol necessary for parturition in this species. The present studies were undertaken to determine the effect of glucocorticoids placed adjacent to the fetal PVN on messenger RNA (mRNA) for CRH in the PVN and mRNA for POMC in the anterior pituitary during late gestation. We performed our studies at two critical stages during late gestation to determine if gestational age related changes occur in the efficacy of negative feedback regulation of expression of CRH and subsequently POMC. Dexamethasone (DEX) implants were placed bilaterally 2 mm lateral to the fetal PVN at 105 to 107 days gestational age (dGA; group I, n = 4) and 121-123 dGA (group II; n = 4). Gestational-age matched, sham implanted fetuses were used as controls (CONT) for both groups (n = 4 per group). Fetuses were recovered at 126-128 (group I) and 136 dGA (group II). Fetal PVN were isolated by micropunching, and the anterior pituitary was separated from neurointermediate and posterior lobes after necropsy. Total RNA was subjected to Northern analysis using specific complementary DNA probes to CRH and POMC, and specific message was normalized to actin mRNA content in each individual sample. Anterior pituitary POMC mRNA was not different in DEX fetuses compared to CONT for either group I (78 +/- 26% of CONT; mean +/- SEM) or group II (84 +/- 17% of CONT). PVN CRH mRNA content was lower in DEX fetuses in group I (28 +/- 14% of CONT; P less than or equal to 0.01) and group II (65 +/- 12% of CONT; P less than or equal to 0.01). The degree to which DEX suppressed mRNA for CRH was greater in group I compared to group II (P less than or equal to 0.05). We conclude that 1) CRH expression in the PVN of fetal sheep is suppressible by glucocorticoids; 2) suppression can occur directly at the level of the PVN and 3) that the efficacy of negative feedback decreases with increasing gestational age. Furthermore, the lack of effect of hypothalamic administration of DEX on anterior pituitary POMC mRNA indicates that basal expression of POMC in fetal sheep may be independent from support from the PVN at this stage of gestation.

Luteinizing hormone in nutrient-restricted ovariectomized ewes

This study was designed to evaluate profiles of serum concentrations of LH, pituitary content of LH and GnRH receptors, and hypothalamic content of GnRH in undernourished, ovariectomized ewes. In earlier studies, pulsatile secretion of LH diminished as duration of undernutrition progressed in prepubertal or adult ovariectomized ewes. Ewes having similar body condition scores (CS) of 5 to 9 (1 = extremely thin, 5 = moderate, 9 = obese) were fed maintenance or low-energy diets (100% and 60% of NRC requirements, respectively). Blood samples for analysis of LH were collected at 15-min intervals for 4 h at initiation of the project and immediately prior to slaughter. Serum concentrations of LH did not differ (P greater than .05) among groups at the initial sampling period. At slaughter, ewes with CS less than or equal to 2 (n = 7) had lost 26.8 kg (42% of initial weight). Ewes with CS greater than or equal to 3 (n = 12) had lost an average of 13.7 kg (18% of initial weight). Concentrations of LH in ewes with final CS greater than or equal to 3 was similar (P greater than .05) to that observed during the initial sampling period. However, release of LH was reduced (P less than .01) in ewes with CS less than or equal to 2 compared with ewes with CS greater than or equal to 3 (2.6 vs 9.5 and 3.2 vs 10.5 ng/ml for basal and mean concentrations, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The learning process in biofeedback: is it feed-forward or feedback?

Twenty participants responded to inquiries about strategies used, and thoughts during, each of three electromyograph biofeedback sessions. The purpose of the study was to learn more about what individuals report doing during biofeedback and, specifically, to determine if individuals construct a response using feedback to sense subtle differences in muscle tension (feedback processes), or select a response from an existing repertoire using feedback primarily for confirmation (feed-forward processes). Protocol analyses found considerable support for feed-forward processes and little support for feedback processes. Such results are important because early reliance on feed-forward processes may result in limited control and limited transfer.

Fetal growth of beef calves. I. Effect of prepartum dietary crude protein on birth weight, blood metabolites and steroid hormone concentrations

Fifty-nine crossbred heifers (427 kg) bred to one Hereford sire were randomly assigned at 75 d prepartum to two diets. Heifers were individually fed, and diets were isocaloric but contained either a low (LP = 81% NRC, .56 kg/d) or high (HP = 141% NRC, .98 kg/d) level of crude protein. Jugular vein cannulae were inserted into 16 LP and 16 HP heifers at 10 prepartum. Daily preprandial blood samples that were collected until parturition were analyzed for serum estradiol-17 beta (E2), progesterone (P4), glucose (G) and urea nitrogen (UN). Heifers fed LP gained slower than HP-fed heifers before calving (.73 vs 1.02 kg/d; P less than .01); immediate post-calving weights and condition scores were 418 vs 444 kg (P less than .01) and 5.4 vs 6.1 (P less than .01; LP vs HP, respectively). Calf birth weights (35.3 vs 36.1 kg), average calving difficulty score (1.6 vs 1.6) and percent assisted births (35.5 vs 35.7%) did not differ (P greater than .10; LP vs HP, respectively). Prepartum concentrations of UN (6.2 vs 13.5 mg/dl) and G (52.9 vs 58.2 mg/dl) were lower (P less than .05) and P4 (5.94 vs 4.26 ng/ml) was higher (P approximately equal to .07) in LP heifers. Prepartum concentration profiles were related to calving difficulty score (CD, 1 = no assistance to 3 = hard pull) for E2 (CD1 vs CD2 + CD3, P less than .01; CD2 vs CD3, P approximately equal to .01), P4 (CD1 vs CD2 + CD3, P less than .05), G (CD1 vs CD2 + CD3, P less than .05) and UN (CD2 vs CD3, P less than .05). After calving, all dams were maintained together on pasture and supplemented with alfalfa hay and grain mix until adequate range forage was available to maintain weight gains. Dams that were fed LP prepartum gained faster than HP dams during this period (.49 vs .15 kg/d; P less than .01). Prebreeding weights (443 vs 453 kg; LP vs HP) and condition scores (5.1 vs 5.1) did not differ, nor was the postpartum interval affected (44 vs 40 d; LP vs HP). There was no effect of dietary protein on dystocia or postpartum interval, although there were diet-induced differences in body weight and condition of the dams at calving. Results indicate that differences in prepartum profiles of serum steroid hormones and metabolites may be related to dystocia, in addition to relative fetal oversize.

Fetal growth of beef calves. II. Effect of sire on prenatal development of the calf and related placental characteristics

Fifteen Hereford and 47 crossbred heifers were allotted by breed and body weight to be artificially inseminated to one of two Angus sires selected for progeny birth weights (L = low; H = high). Forty-two of the heifers were randomly assigned to be slaughtered at 200, 215, 230, 245 or 260 d of gestation for measurement of fetal and placental characteristics. Twenty heifers were allowed to go to term and five calves from each sire group were randomly assigned to be euthanized and dissected within 24 h after birth. Sire differences in birth weight (BW) and dystocia score (32.9 vs 35.4 kg; 1.8 vs 3.1, L vs H sires, respectively) existed (P less than .01), and there was a sire effect (P less than .01) for fetal calf weights (FW) and eviscerated calf weights (EW). However, there was a sire X calf sex interaction for BW (P less than .05), EW (P less than .01), FW (P less than .01), femur length (P less than .05), heart weight (P less than .05), kidney weight (P less than .01) and pituitary weight (P less than .01). Weight differences suggested these interactions were a result of the relationship of the organ weights to fetal body weights and the interaction effects on calf weights resulted from limitations in the maternal environment which restricted growth of H-sired male calves in utero. Sire X fetal age interaction effects were all nonsignificant (P greater than .10) except for cerebrum weight. This finding indicates that fetus and calf growth rates were parallel for the L and H sires. A sire effect was found for biceps (P less than .01) and liver weights (P less than .01), but not for cerebrum weights (P greater than .10). Increasing weight due to fetal age was attributed to hypertrophy for the cerebrum (P less than .05) and liver (P approximately equal to .01), while the biceps increased (P less than .05) by both hypertrophy and hyperplasia, as determined from deoxyribonucleic acid and protein analyses. All measured fetal organ weights except heart, when expressed as a ratio with EW, decreased (P less than .05) with increasing fetal age. Brain (cerebrum + cerebellum):liver weight ratios were higher (P less than .01) in L-sired calves (.32 vs. .28) than in H-sired calves. Total placentome weight (b' = 91; P less than .01) and placental fluid volume (b' = .32; P less than .01) were highly associated with FW, accounting for 84% of the variation in FW.(ABSTRACT TRUNCATED AT 400 WORDS)

Estrous response and pregnancy rates following calf removal in beef cows treated with prostaglandin F(2)alpha

Five hundred fifty-four suckled beef cows in three herds were allotted within postpartum interval to one of four treatments. All cows received two injections of prostaglandin F(2)alpha (PGF(2)alpha) 11 days apart. Treatment I served as a control. Calves were removed for 48 hr following the first injection of PGF(2)alpha in treatment II. Calves were removed similarly after the second injection of PGF(2)alpha in treatment III and after both injections of PGF(2)alpha in treatment IV. Pregnancy rates at the synchronized service, by 24 days and by 45 days of breeding were not (P>0.05) affected by treatment. Similarly, the treatments had no significant (P>0.05) effect on percentage of animals exhibiting estrus following the first and second injections of PGF(2)alpha.

Negative feedback control of luteinizing hormone secretion in prepubertal beef heifers at 60 and 200 days of age

Prepubertal beef heifers at 60 and 200 d of age, born in the fall or spring, were assigned randomly to one of three treatment groups: (1) intact = 1; (2) bilateral ovariectomy (OVX); or (3) OVX plus estradiol-17 beta(E2) administered in silastic implants (OVX + E2). Luteinizing hormone (LH) was measured in serum samples collected at 20-min intervals for 4 h from heifers on -1, +7, +21, +35 and +49 d after OVX. Luteinizing hormone concentrations increased in the serum by 7 d after OVX in heifers at both 60 and 200 d of age (P less than .001; time X treatment). Prior to OVX, the LH patterns were characterized by low levels and infrequent episodic pulses. By 49 d after OVX, the mean LH concentrations increased and the pattern changed to one of rhythmic LH pulses with a periodicity of 1 h (P less than .001; time X treatment). Estradiol-treated OVX heifers did not exhibit a postovariectomy rise in serum LH concentrations. Serum E2 concentration 49 d after OVX in OVX heifers was threefold greater than in 1 or OVX heifers, thus demonstrating that E2 exerted negative feedback on pituitary LH secretion in prepubertal heifers. There was no measurable difference in serum E2 concentrations between I and OVX heifers; however, the contrast in the concentration and pattern of serum LH between the two groups was dramatic and suggested gonadal factors in addition to E2 are involved in controlling LH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine and fetal growth following unilateral hysterectomy-ovariectomy in ewes

The left uterine horn and ovary (UHOX; n = 25) or just the left ovary (UOX; n = 18) were excised from mature ewes to investigate growth capabilities of the uterus and uterine capacity effects on fetal growth in sheep. The remaining right uterine horns were excised from 5 UHOX ewes on day 13 of the second successive estrous cycle following initial surgery and were compared to 11 left uterine horns previously obtained from UHOX ewes during the midluteal phase of the estrous cycle. Uterine and endometrial content of DNA, RNA, protein, and number of myometrial nuclei indicated that removal of the left uterine horns resulted in hypertrophy of the right uterine horns. The conception rate of the remaining 20 UHOX ewes was lower than of the 18 UOX ewes. However, at 140 days of gestation, there appeared to be no uterine capacity effects on fetal growth.

Luteal phase insufficiency in the ewe as a consequence of premature induction of ovulation by intrafollicular injection of gonadotropins

The largest ovarian follicle of ewes was injected on d 15 of the estrous cycle (2 to 3 d before the anticipated preovulatory surge of gonadotropins) with saline or either luteinizing hormone (LH) or follicle-stimulating hormone (FSH) in saline (5 micrograms). Ovulation was assumed based on the presence of an ovulation stigma at d 5 post-treatment. Control animals expressed estrus 2 to 3 d after treatment with saline, and during the estrous period ovulated from the treated follicle. Gonadotropin-treated animals ovulated from injected follicles prematurely and did not exhibit estrus. The stated observations with respect to time of ovulation were established by visual and hormonal criteria: (1) control follicles appeared to have ruptured within a day or two prior to relaparotomy (corpora hemorrhagica), whereas gonadotropin-treated follicles were in a more advanced stage of luteal development (corpora lutea); and (2) concentrations of systemic sera progesterone rose (P less than .05) in LH- and FSH-treated ewes 2d before such an increase in control animals. Luteal function was assessed by comparing sera concentrations of progesterone throughout the induced and spontaneous (vehicle controls) luteal phases. Premature stimulation of ovulation with either gonadotropin was followed by suppressed luteal function (maximum sera levels of progesterone in gonadotropin-treated animals and controls were slightly greater than 1 ng/ml and nearly 2.5 ng/ml, respectively; P less than .01). No differences in the level of luteal function due to treatment with LH or FSH were observed. The duration of the luteal phases of gonadotropin-treated animals were similar to controls (approximately 17 d).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum cortisol and progesterone after administration of adrenocorticotropin and(or) prolactin to sheep

An experiment was conducted to determine the effect of iv administration of adrenocorticotropin (ACTH) and(or) prolactin on serum cortisol and progesterone concentrations in hypophysectomized, ovariectomized, adult ewes. Twenty-four hours after surgery (d 1), six sheep were used in a crossover design and were assigned randomly to receive iv one of four treatments: (I) 200 IU ACTH in 10 ml .15 M NaCl at 0700 h, (II) 2.5 mg prolactin in 10 ml .15 M NaCl at 0700 h and again at 0730 h, (III) 200 IU ACTH and 2.5 mg prolactin in 10 ml .15 M NaCl at 0700 h followed by 2.5 mg prolactin in 10 ml .15 M NaCl at 0730 h, or (IV) 10 ml .15 M NaCl (vehicle) at 0700 and 0730 h. Blood samples (5 ml) were collected via jugular cannulae at 15-min intervals from 0600 to 0700 h and starting at 0700 h at 5, 10, 15, 30, 35, 40, 45, 60, 75, 90 and 120 min. Samples were then collected at hourly intervals until 1300 h. Twenty-four hours after commencement of first sampling (d 2), treatments were crossed and samples were collected as on d 1. Administration of ACTH alone or in combination with prolactin increased (P less than .01) serum cortisol and progesterone concentrations. Serum cortisol or progesterone concentrations were unaffected (P greater than .05) by administration of prolactin.

Luteal function after ovulation blockade by intrafollicular injection of indomethacin in the ewe

The dominant follicle of oestrous ewes was injected with saline or indomethacin. Treated follicles were obtained at 2 and 10 days after treatment and examined histologically. Indomethacin-injected follicles were abnormally enlarged and remained unruptured. On Day 2 after treatment, these follicles appeared grossly hyperaemic. The follicular walls of control and indomethacin-treated groups had luteinized. Blood samples for the measurement of serum progesterone were collected from animals with their ovaries left intact. Systemic progesterone and oestrous cycle lengths were unaltered by drug administration. It appears that prostaglandins are essential for ovulation in the ewe. The occurrence of ovulation per se was not a prerequisite of ensuing luteal-phase normality.

Dynamics of ovarian blood supply to periovulatory follicles of the ewe

Radioactive microspheres were injected into the ovarian artery ipsilateral to the ovary containing the dominant (preovulatory) or postovulatory follicle of the ewe to estimate the distribution of ovarian blood to those follicles throughout the periovulatory period. The follicle of interest was excised from the ovary at the first sign of estrus (4-h heat checks), or 4, 8, 12, 16, 20, 24, 28 and 32 h later. Blood samples to be analyzed for serum luteinizing hormone (LH) were taken at each observation for estrus. Follicles were partitioned into basal tissue, apical tissue and fluid (preovulatory follicles) constituents. Radioactivity was determined within the residual ovary and in each follicular component. Follicular data were normalized to the ascending limb of the preovulatory surge of serum LH (first detected increase in LH = O h). The supply of ovarian blood to the wall (apex + base) of follicles was elevated after the rise in LH was initially ascertained (0-12 h). The distribution of blood to the follicular wall began to decline from 12 to 16 h, and subsequently continued to decrease (20 h) until after ovulation had occurred (greater than or equal to 24 h after the LH increase). Blood supply was less to the wall of follicles in the 20-h group and to ruptured follicles than that to the wall of follicles collected before the initiation of the surge of LH. There was no evidence that blood supply to either the basal or apical portion of the follicular wall was altered preferentially. Radioactivity was not detectable within follicular fluid.

Alterations in follicular steroid hormones during the preovulatory period in the ewe

Progesterone, testosterone and estradiol-17 beta were quantified within the thecal layer, granulosal layer and fluid of the preovulatory follicle and in ovarian and jugular venous sera of sheep. Prior to the preovulatory surge of luteinizing hormone (LH), the total content of estradiol-17 beta was elevated within each follicular constituent. These levels diminished rapidly to minimal values concurrent with the surge of LH. Follicular tissue and fluid contents of testosterone were low at all times, but were higher before the surge of LH and subsequently (like estradiol-17 beta) declined. The initial decrease in follicular estradiol-17 beta occurred before the first detected decline in testosterone. Changes in sera concentrations of estradiol-17 beta in the ovarian vein draining the ovary with the preovulatory follicle or in the jugular vein were similar to follicular variations in estradiol-17 beta. Likewise, changes in concentrations of testosterone in ovarian venous sera were indicative of follicular changes. Testosterone was undetectable in jugular venous sera. During the period leading up to the anticipated time of ovulation, and approximately 8 h after follicular testosterone and estradiol-17 beta had fallen, content of progesterone within thecal tissue, granulosal tissue and follicular fluid increased. Alterations in follicular progesterone were not reflected by hormone changes in either ovarian or peripheral sera.

Relationship of growth and puberty in beef heifers fed monensin

An experiment was designed to determine the effects of dietary monensin on age and weight at puberty in Bos taurus crossbred beef heifers. One hundred and forty heifers were allotted to two weight classes: heavy (H) and light (L) groups, consisting of heifers above and below the average weaning weight, respectively. Heifers within each weight class were assigned to one of three diets during a 203-d winter feeding period: (1) R, 80% roughage: 20% concentrate; (2) M1, R diet plus monensin (200 mg/head daily) with feed intake restricted to produce average daily gains (ADG) similar to R and (3) M2, R diet plus monensin (200 mg/head daily). ADG was higher (P less than .001) for M2 heifers than for R and M1 heifers, which performed similarly. Age and weight at puberty were similar across treatments in L heifers. However, in the H group, HM1 and HM2 heifers were younger (P less than .07) at puberty than HR heifers and this difference was not removed by covariate adjustment of either ADG or body weight. Weigh at puberty was greater (P less than .01) for HM2 heifers than for HM1 or HR heifers; however, this difference was removed by covariate adjustment of either ADG or body weight. Ninety-one percent of LM2 heifers and 100% of all other groups had reached puberty before the breeding season. Pregnancy rates did not differ significantly between treatment groups. Supplementation of a high roughage diet with monensin decreased age at puberty of heifers in the heavy weight class and this decrease was not due to increased body weight or ADG. Perhaps heifers with above average weaning weight possess a greater inherent growth potential than heifers below the average weaning weight and hence are more capable of utilizing monensin to an advantage.

Pituitary and ovarian function in postpartum beef cows. I. Effect of suckling on serum and follicular fluid hormones and follicular gonadotropin receptors

The effect of suckling on serum and follicular fluid hormones and on follicular gonadotropin receptors was studied. Sixteen anestrous postpartum cows were assigned to 1 of 2 groups: suckled (S) or weaned (W). All calves were allowed to suckle ad libitum from parturition to 21 days postpartum when calves from W cows were weaned. All cows were ovariectomized on Day 25 postpartum. W cows had more (P less than 0.01) pulses of LH during the 96-h period from weaning until ovariectomy than S cows (6.3 vs. 1.3 pulses). Serum concentrations of prolactin (Prl), estrone (E1), estradiol-17 beta (E2) and progesterone (P) were not different (P greater than 0.10) between groups. Furthermore, there were n differences (P greater than 0.10) in follicular in contents of luteinizing hormone (LH), E1, E2 and P between the treatment groups. However, follicular fluid content of Prl was greater (P less than 0.05) in the W cows than in the S cows (123 vs. 65.1 ng/cow). The number of follicular LH receptors was greater (P less than 0.05) in the W cows than in the S cows (71.1 vs. 48.3 fmoles/mg protein) although the number of follicular follicle-stimulating hormone (FSH) receptors was not different (P greater than 0.10) between W cows and S cows (1531 vs. 1862 fmoles/mg protein). There were no correlation between serum hormone concentrations and follicular fluid hormone content; however, the numbers of follicular LH receptors and follicular fluid Prl content were highly correlated in the W cows (r = 0.85; P less than 0.05). It is concluded that removal of the suckling stimulus increases pulsatile LH release and the accumulation of Prl in the follicular fluid. These factors, either together or separately, may at least in part be responsible for the increase in follicular LH receptor concentrations that were observed in the W cows.

Estriol- and estradiol-17 beta-induced luteinizing hormone release in ovariectomized cows and ewes

Two studies were conducted with ovariectomized animals to compare luteinizing hormone (LH) responses during the 24-hr period following an IM injection of either estriol or estradiol-17 beta. In Exp. 1, six long-term ovariectomized (6 months) beef cows were randomly assigned to be given 1 mg of estriol or estradiol 17 beta injected in 4 ml of corn oil. Two months later, the experiment was replicated in a switch back design. In Exp. 2, eight ewes that had been ovariectomized for 1 to 4 months were randomly assigned to be given 150 micrograms of estriol or estradiol-17 beta injected in 1.5 ml of corn oil. The initial increase in serum LH concentrations occurred earlier in both cows (P less than .01) and ewes (P less than .05) in response to estriol (8 to 9 hr) than in response to estradiol 17 beta (12 to 18 hr). In addition, duration of the decrease in LH release that occurred 1 hr after estrogen injection in ewes was 3 hr shorter (P less than .05) in response to estriol than in response to estradiol-17 beta. The total area under the LH response curve was greater for both cows (P less than .05) and ewes (P less than .01) given estradiol-17 beta than for those given estriol. Administration of estradiol-17 beta induced a 10-fold increase in serum estradiol-17 beta concentrations and a two to fourfold increase in serum estrone concentrations. Both estrogens returned to basal concentrations by 24 hr after administration. Peak serum estriol exceeded 300 pg/ml within 1 hr of estriol injection, but decreased to nondetectable levels within 12 hours. We concluded that estriol can stimulate LH release from the pituitary. Furthermore, the differential LH response to the two estrogens suggests that the positive effects of estriol are mediated earlier but that estradiol-17 beta is a more potent stimulus when administered as a single IM injection.

Effect of norgestomet on peripheral levels of progesterone and estradiol-17β in beef cows

Peripheral levels of progesterone and estradiol 17beta were quantified in 27 cycling cows following administration of a single Hydron ear implant (G. D. Searle and Co.) containing 2, 4 or 6 mg norgestomet or controls which received no implant. Implants were inserted subcutaneously in the ear on day 15 of the estrous cycle (day of estrus = day 0) and removed 9 days later. The 4 mg (seven of seven cows) and 6 mg (six of six cows) implants suppressed estrus; however, three of eight cows in the 2 mg group exhibited estrus prior to implant removal. The 6 mg implant group had a significantly longer interval from implant removal to estrus than either the 2 or 4 mg group. Failure to detect differences in the rate at which progesterone declined indicated norgestomet treatment did not affect normal corpus luteum regression. Estradiol levels rose at a similar rate approaching estrus in all treatments. There was no indication of increased endogenous estradiol levels due to norgestomet treatment.

Isolation and identification of metabolites of 14C-labeled estradiol in cattle

A total of six steers and six heifers received three daily injections containing either 200 muCi (1 mg) of [4-14C] estradiol-17beta or 312 muCi (2.16 mg) of [4-14C] estradiol 17beta 3-benzoate. Major metabolites of the administered estradiol-17beta and estradiol-17beta 3-benzoate were identified in muscle, fat, liver, and kidney samples obtained 3 hr after the final injection. Estradiol benzoate was nondetectable in the tissues analyzed, suggesting rapid hydrolysis of the benzoate ester. Consequently, the relative proportions of the various metabolites were similar for both the injected estrogens. Estradiol-17beta and estrone, which together accounted for 80-90% of the total extracted radioactivity, appear to be the major metabolites in both muscle and fats. In contrast, the major metabolites present in liver and kidney appear in the conjugate fraction. Most of the conjugated metabolites were glucuronates, which represent 85-95% of the total recovered conjugate radioactivity.