Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “persistent”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1999

The significance of the persistent presence of acid-fast bacilli in sputum smears in pulmonary tuberculosis.

STUDY OBJECTIVES: Identification of acid-fast bacilli (AFB) in the sputum smear at the completion of tuberculosis therapy is in some settings considered evidence of treatment failure. However, some patients with pulmonary tuberculosis (TB) will have positive smear results with negative sputum culture results at the end of therapy. The objectives of this study were to estimate the prevalence of persisting positive sputum smear results in patients with TB and to identify characteristics that distinguish patients with persistently positive sputum smear results who also had negative sputum culture results from patients identified as treatment failures. DESIGN: A population-based, historical cohort study with nested case control study. SETTING: British Columbia Division of Tuberculosis Control central case registry. PATIENTS: All 428 patients with culture-proven pulmonary TB in British Columbia over 7 years with sputum that was positive for AFB. METHODS: Review of laboratory data of all 428 patients, as well as clinical data of a subset of 30 patients with persistently positive smear results beyond 20 weeks. RESULTS: Sputum smears were positive for AFB in 205 patients (48%) at 4 weeks, in 30 patients (7%) at 20 weeks, and in 12 patients (3%) at 36 weeks. Of the patients with smear results that were persistently positive at 20 weeks, 23 (77%) had negative sputum culture results and 7 (23%) had positive sputum culture results (ie, they were treatment failures). Patients identified as treatment failures had more localized disease as shown on chest radiographs, had less radiographic improvement at follow-up, had a higher prevalence of drug resistance, and were less compliant with medications than patients with persistently positive smear results and negative culture results. No subject with a negative culture result relapsed over the 6- to 48-month observation period. CONCLUSION: Sputum that is persistently positive for AFB in patients in developed countries is more likely to be associated with negative culture results than with treatment failure.

Adult↗
PubMed2001

Symptomatic persistent post-coronary artery bypass graft pleural effusions requiring operative treatment : clinical and histologic features.

BACKGROUND: More than 85% of patients develop pleural effusions after coronary artery bypass grafting (CABG). Although the majority resolve spontaneously, post-CABG effusions can persist. The cause of these persistent effusions is unknown, and the histology of the pleural changes has seldom been reported. OBJECTIVES: To describe the patient characteristics and pathologic condition of the pleural tissues in patients with persistent post-CABG effusions. SUBJECTS: Eight patients with persistent post-CABG effusions who underwent thoracoscopy or thoracotomy over a 2-year period by one thoracic surgeon. These eight patients were selected as having undergone CABG > 2 months before their thoracic surgery and had no other identifiable causes of effusion. RESULTS: The median time from CABG to pleural surgery was 132 days (range, 74 to 2,258 days). The median left ventricular ejection fraction was 57% (range, 15 to 70%). All patients were dyspneic and had large (> or = 25% of the hemithorax) effusions on chest radiograph. All effusions persisted after two or more thoracenteses. Pleural effusion was left sided in three patients and bilateral in five patients. Pleural fluid was characterized by lymphocytosis (82 to 99%). Four of the eight patients had a visceral peel and trapped lung requiring decortication. Seven of the eight biopsy specimens showed pleural thickening characterized by dense fibrous tissues with associated mononuclear cell infiltration, while the eighth biopsy specimen showed only clotted blood. The degree of inflammation and fibrosis correlated with the interval between CABG and pleural surgery. Early post-CABG patients displayed more inflammation, with abundant lymphocytes in nodular configuration deep in the fibrous tissues away from the surface. Abundant keratin-positive, spindle-shaped cells were present in the fibrous tissues. Late cases showed predominantly mature fibrosis. CONCLUSIONS: Persistent post-CABG effusion can occur. Pleural fluids and pleural tissue in early-stage lesions were characterized by lymphocytosis. With time, the inflammatory changes were replaced by fibrosis that resulted in dyspnea and, at times, trapped lungs requiring surgical intervention.

Aged↗
PubMed2005

Clinical factors associated with persistent pericardial effusion after successful primary coronary angioplasty.

STUDY OBJECTIVE: To evaluate the incidence and clinical factors related to the persistence of infarct-associated pericardial effusion (PE) after primary angioplasty. DESIGN: Consecutive case-series analysis. SETTING: Coronary care unit in a university hospital. PATIENTS: Three hundred ninety-one consecutive patients with acute myocardial infarction (AMI) who underwent successful primary percutaneous transluminal coronary angioplasty (PTCA) at hospital admission. INTERVENTIONS: Coronary angiography and primary PTCA on hospital admission and serial echocardiography. MEASUREMENTS AND RESULTS: The status of coronary flow before and after primary PTCA was evaluated by coronary angiography at hospital admission, while PE was studied by echocardiography within 24 h of admission and 1 month after the onset of AMI. PE was present in the acute phase in 76 patients (19%), and patients with PE had a significantly higher incidence of in-hospital death than those without PE (11% vs 2%, p < 0.001). Among 68 patients who had PE in the acute phase and underwent echocardiography 1 month later, PE persisted to 1 month after the onset of AMI (persistent PE) in 26 patients (38%). Patients with persistent PE had a significantly higher incidence of pericardial rub (p = 0.010), Killip class > 1 (p = 0.025), no reflow after PTCA (p = 0.026), lower incidence of collaterals (p = 0.024), and tended to have higher peak creatine kinase (CK) [p = 0.05] levels than those with transient PE. When five variables (peak CK, collaterals, no reflow, pericardial rub, and Killip class > 1) were used in the multivariate analysis, pericardial rub (p = 0.023; odds ratio [OR], 5.45), absence of collaterals (p = 0.011; OR, 0.16), and Killip class > 1 (p = 0.027; OR, 3.80) were the significant variables related to persistent PE. CONCLUSIONS: PE remains a relatively common complication of AMI even in the era of reperfusion therapy and is associated with increased mortality. Furthermore, the presence of a pericardial rub, Killip class > 1, and absence of collateral flow in the early phase of the infarct are associated with persistence of the PE to 1 month after the onset of AMI.

Angioplasty, Balloon, Coronary↗
PubMed2024

Molecular Analysis of Persistent and Recurrent Barrett's Esophagus in the Setting of Endoscopic Therapy.

INTRODUCTION: Early neoplastic progression of Barrett's esophagus (BE) is often treated with endoscopic therapy. Although effective, some patients are refractory to therapy or recur after apparent eradication of the BE. The goal of this study was to determine whether genomic alterations within the treated BE may be associated with persistent or recurrent disease. METHODS: We performed DNA sequencing on pre-treatment esophageal samples from 45 patients who were successfully treated by endoscopic therapy and did not recur as well as pre-treatment and post-treatment samples from 40 patients who had persistent neoplasia and 21 patients who had recurrent neoplasia. The genomic alterations were compared between groups. RESULTS: The genomic landscape was similar between all groups. Patients with persistent disease were more likely to have pre-treatment alterations involving the receptor tyrosine kinase pathway ( P = 0.01), amplifications of oncogenes ( P = 0.01), and deletions of tumor suppressor genes ( P = 0.02). These associations were no longer significant after adjusting for patient age and BE length. More than half of patients with persistent (52.5%) or recurrent (57.2%) disease showed pre-treatment and post-treatment samples that shared at least 50% of their driver mutations. DISCUSSION: Pre-treatment samples were genomically similar between those who responded to endoscopic therapy and those who had persistent or recurrent disease, suggesting there is not a strong genomic component to treatment response. Although it was expected to find shared driver mutations in pre-treatment and post-treatment samples in patients with persistent disease, the finding that an equal number of patients with recurrent disease also showed this relation suggests that many recurrences represent undetected minimal residual disease.

Humans↗
PubMed2004

Persistent accumulation of calcium/calmodulin-dependent protein kinase II in dendritic spines after induction of NMDA receptor-dependent chemical long-term potentiation.

Calcium/calmodulin-dependent protein kinase II (CaMKII) is a leading candidate for a synaptic memory molecule because it is persistently activated after long-term potentiation (LTP) induction and because mutations that block this persistent activity prevent LTP and learning. Previous work showed that synaptic stimulation causes a rapidly reversible translocation of CaMKII to the synaptic region. We have now measured green fluorescent protein (GFP)-CaMKIIalpha translocation into synaptic spines during NMDA receptor-dependent chemical LTP (cLTP) and find that under these conditions, translocation is persistent. Using red fluorescent protein as a cell morphology marker, we found that there are two components of the persistent accumulation. cLTP produces a persistent increase in spine volume, and some of the increase in GFP-CaMKIIalpha is secondary to this volume change. In addition, cLTP results in a dramatic increase in the bound fraction of GFP-CaMKIIalpha in spines. To further study the bound pool, immunogold electron microscopy was used to measure CaMKIIalpha in the postsynaptic density (PSD), an important regulator of synaptic function. cLTP produced a persistent increase in the PSD-associated pool of CaMKIIalpha. These results are consistent with the hypothesis that CaMKIIalpha accumulation at synapses is a memory trace of past synaptic activity.

Adenylyl Cyclases↗
PubMed2005

Directional persistence of EGF-induced cell migration is associated with stabilization of lamellipodial protrusions.

Migrating cells can sustain a relatively constant direction of lamellipodial protrusion and locomotion over timescales ranging from minutes to hours. However, individual waves of lamellipodial extension occur over much shorter characteristic times. Little understanding exists regarding how cells might integrate biophysical processes across these disparate timescales to control the directional persistence of locomotion. We address this issue by examining the effects of epidermal growth factor (EGF) stimulation on long-timescale directional persistence and short-timescale lamellipodial dynamics of EGF receptor-transfected Chinese hamster ovary cells migrating on fibronectin-coated substrata. Addition of EGF increased persistence, with the magnitude of increase correlating with fibronectin coating concentration. Kymographic analysis of EGF-stimulated lamellipodial dynamics revealed that the temporal stability of lamellipodial protrusions similarly increased with fibronectin concentration. A soluble RGD peptide competitor reduced both the persistence of long-timescale cell paths and the stability of short-timescale membrane protrusions, indicating that cell-substratum adhesion concomitantly influences lamellipodial dynamics and directional persistence. These results reveal the importance of adhesion strength in regulating the directional motility of cells and suggest that the short-timescale kinetics of adhesion complex formation may play a key role in modulating directional persistence over much longer timescales.

Animals↗
PubMed2006

A high-throughput migration assay reveals HER2-mediated cell migration arising from increased directional persistence.

Human epidermal growth factor receptor 2 (HER2) overexpression has been associated with increased invasiveness in mammalian breast cancer cell lines, but the effects of overexpression on key underlying cell migration properties such as translational speed and directional persistence are not understood. Moreover, the differential effect of HER2 activation through heterodimerization with epidermal growth factor receptor versus human epidermal growth factor receptor 3 (HER3) on cell speed and persistence has not been studied. To investigate these issues, we developed a high-throughput wound closure assay in which individual cell locomotion and wound closure kinetics were quantified in human mammary epithelial cells with varying levels of HER2 under epidermal growth factor or heregulin (a HER3 ligand) stimulation. Increasing levels of HER2 elevated wound closure with closure kinetics dependent on ligand treatment. Cell speed increased with HER2 levels under epidermal growth factor treatment, but decreased under heregulin treatment. In contrast, directional persistence increased with HER2 levels under both ligand treatments. Increasing persistence quantitatively accounted for observed elevated wound closure, as measured by the effective diffusion of the cells. Taken together, the data show that the HER2 overexpression mediates cell migration through differential control of translational speed and directional persistence dependent on epidermal growth factor receptor-HER2 versus HER2-HER3 heterodimerization. Observed consistent increases in persistence associated with HER2 overexpression indicate a prospective mechanism for invasiveness previously documented in HER2-overexpressing human breast tumors.

Biological Assay↗
PubMed1987

Prostaglandin F2 alpha and oxytocin release during persistence of the corpus luteum in sheep.

Oxytocin (OT), progesterone and prostaglandin F2 alpha (PGF2 alpha) concentrations were measured in the utero-ovarian vein (UOV) of ewes which displayed persistence of the corpus luteum (CL). During the period of expected luteolysis, the frequency of OT and PGF2 alpha pulses in the UOV was significantly (P less than 0.005 for both) lower in ewes with persistent CLs, compared with ewes that underwent normal luteal regression. In contrast, the amplitude of both OT and PGF2 alpha pulses was similar in both groups of animals. It is suggested that persistence of the CL resulted from a decreased PGF2 alpha pulse frequency, which may have arisen from a decreased frequency of stimulation by OT. In two persistent CL ewes, however, it appeared that a failure at the level of the uterus may have contributed to the observed decrease in PGF2 alpha release. Although a PGF2 alpha analogue (Lutalyse) infusion into the uterine vein of two ewes with persistent CLs failed to induced luteolysis, it did stimulate a large release of OT into the UOV. This suggests that persistent CLs maybe more resistant to PGF2 alpha and, that at day 22 post-oestrus, these CLs are capable of releasing large quantities of OT into the UOV.

Animals↗
PubMed2003

Persistent insomnia is a predictor of hypertension in Japanese male workers.

Insomnia is one of the most common complaints at worksites, as well as in the general population. This study aims to assess the effect of insomnia on the development of hypertension in Japanese male workers. Using the annual health examination database of a Japanese telecommunication company, eligible middle-aged male participants in the 1994 health examination were followed up until 1998 or the development of hypertension (either initiation of antihypertensive therapy or a systolic blood pressure > or = 140 mmHg and/or a diastolic blood pressure > or = 90 mmHg). The effect of difficulty initiating sleep (DIS) was assessed with a DIS dataset (n=4,794), which included non-DIS (n=4,602) and persistent-DIS (n=192) subjects. That of difficulty maintaining sleep (DMS) was assessed with a DMS dataset (n=4,443), which included non-DMS (n=4,157) and persistent-DMS (n=286) subjects. The incidence of hypertension among persistent-DIS (40.1%; 130.7 per 1,000 person-yr) was significantly higher than that among non-DIS (30.6%; 89.9 per 1,000 person-yr). The incidence of hypertension among persistent-DMS (42.3%; 136.7 per 1,000 person-yr) was significantly higher than that among non-DMS (30.7%; 90.8 per 1,000 person-yr). After adjusting for potential confounding factors (i.e. age, body mass index, smoking, alcohol drinking, and job stress), persistent complaints of DIS and DMS were significantly associated with an increased risk of hypertension (OR=1.96; 95%CI: 1.42-2.70 and OR=1.88; 95%CI: 1.45-2.45, respectively). Persistent insomnia may be a useful predictor of hypertension in Japanese male workers.

Adult↗
PubMed2004

[Risk factors for persistent diarrhea in infants].

BACKGROUND: Persistent diarrhea is a multicausal disease. The analysis of risk factors for persistent diarrhea includes environmental and biological variables as well as therapeutical management. AIM: To identify risk factors for persistent diarrhea among children hospitalized with acute diarrhea. PATIENT AND METHODS: This is a case-control study. The sample consisted of 212 infants under 24 months, hospitalized with acute diarrhea, at the "Instituto Materno-Infantil de Pernambuco", Recife, PE, Brazil. Cases were infants with persistent diarrhea and controls those with acute diarrhea. Cases and controls were compared to a series of socio-economic, biological and clinical variables, previous morbidities and therapeutic management prior to hospital admission. Unadjusted and adjusted odds ratio were used with the respective 95% confidence intervals. It was adopted the level of significance of 5%. Logistic regression analysis was conducted to control for potential confounding factors. RESULTS: The risk of persistent diarrhea was higher for infants with: dysentery, fever at the onset of diarrhea, fasting and taking antibiotics prior to hospital admission. The variables that showed the highest adjusted odds ratios for persistent diarrhea were infants living in households without refrigerator and perianal hyperemia at hospital admission. CONCLUSIONS: The improvement of environmental conditions and an adequate clinical management of diarrhea for hospitalized infants may contribute to the reduction of diarrhea morbidity.

Acute Disease↗
PubMedDate not supplied

Molecular investigation of Escherichia coli strains associated with apparently persistent urinary tract infection in dogs.

Persistent Escherichia coli urinary tract infection (UTI) in dogs is a frustrating clinical problem. Affected dogs often appear to fail to respond to therapy or to reacquire infection shortly after therapy is completed. Urovirulence factors (UVFs) of the infecting E. coli, antibiotic resistance, and tissue colonization may be contributory but have not been evaluated in dogs with persistent E. coli UTI. In this study, the strain types of E. coli in dogs with persistent UTI were evaluated with pulsed-field gel electrophoresis (PFGE) to determine whether persistence was due to acquisition of new isolates or failure to eradicate existing isolates. UVFs in these isolates, assessed by polymerase chain reaction, and antibiograms were correlated with treatment outcome in these dogs. Results documented a mixed pattern: 9 dogs remained chronically infected with 1 or 2 strains, each with distinct reproducible UVFs, but 1 dog was infected with numerous unrelated E. coli strains over time. Two dogs had a mixed pattern, consisting of 1 or more episodes of persistent E. coli infection attributable to a single strain in addition to episodes caused by unrelated strains. Many isolates had no detectable UVFs, highlighting the likely importance of impaired colonization resistance in the affected dogs. Antibiotic resistance was common, often in response to previous treatments, especially with trimethoprim-sulfamethoxazole. Antibiotic resistance patterns differed significantly within PFGE strain types, suggesting lateral acquisition of resistance plasmids or integrons. These results can be used to help guide testing for and management of persistent E. coli UTI in dogs.

Animals↗
PubMed2004

Persistence of selected organophosphate and carbamate insecticides in waters from a coastal watershed.

Organophosphate and carbamate compounds are among the most widely used pesticides. Contamination of surface water by these compounds is of concern because of potential toxicity to aquatic organisms, especially those at lower trophic levels. In this study we evaluated the persistence of diazinon, chlorpyrifos, malathion, and carbaryl in waters from various sites in the Newport Bay-San Diego Creek watershed in southern California (USA). The persistence of diazinon and chlorpyrifos was much longer than that of malathion or carbaryl and was further prolonged in seawater. Microbial degradation contributed significantly to the dissipation of diazinon and chlorpyrifos in freshwater, but was inhibited in seawater, leading to increased persistence. In contrast, degradation of malathion and carbaryl was rapid and primarily abiotic. A greater temperature dependence was observed for carbaryl degradation in all waters and for diazinon degradation in freshwater. The interactions of pesticide persistence with water location, temperature, and type of pesticides suggest that site- and compound-specific information is needed when evaluating the overall ecotoxicological risks of pesticide pollution in a watershed. Because the persistence of diazinon and chlorpyrifos may increase significantly in seawater, mitigation should occur before the pesticides reach seawater. The relatively short persistence of these compounds in freshwater suggests that practices aimed at extending residence time (e.g., diversion to wetlands) may effectively reduce pesticide output to downstream water bodies.

Biodegradation, Environmental↗
PubMed2004

Effects of childhood socioeconomic circumstances on persistent smoking.

OBJECTIVES: We investigated whether socioeconomic circumstances at different life stages influence persistent smoking. METHODS: We followed a British birth cohort (all births between March 3 and 9, 1958) for 41 years to examine the influence of childhood and adulthood socioeconomic position on persistent smoking in adulthood (n = 6541). RESULTS: Persistent smoking (19% of participants, n = 1216) showed strong social gradients with both childhood and adulthood socioeconomic measures. Among men, the association with childhood socioeconomic circumstances was no longer significant after we adjusted for adulthood socioeconomic circumstances; however, among women, the adjusted odds of persistent smoking increased by 8% for each unit increase across a 16-point childhood score. CONCLUSIONS: Childhood socioeconomic circumstances predicted persistent smoking among women in our cohort, a finding that highlights the importance of influences on the development of persistent smoking across the life course.

Adolescent↗
PubMed2000

[Persistent diarrhea]

INTRODUCTION: Persistent diarrhea has high impact on infantile morbidity and mortality rates in developing countries. Several studies have shown that 3 to 20% of acute diarrheal episodes in children under 5 years of age become persistent. DEFINITION: Persistent diarrhea is defined as an episode that lasts more than 14 days. ETIOLOGY: The most important agents isolated in persistent diarrhea are: Enteropathogenic E. coli (EPEC), Salmonella, Enteroaggregative E. coli (EAEC), Klebisiella and Cryptosporidium. CLINICAL ASPECTS: In general, the clinical characteristics of patients with persistent diarrhea do not change with the pathogenic agent. Persistent diarrhea seems to represent the final result of a several insults a infant suffers that predisposes to a more severe episode of diarrhea due to a combination of host factors and high rates of enviromental contamination. Therefore, efforts should be made to promptly treat all episodes of diarrhea with apropriate follow-up. THERAPY: The aim of the treatment is to restore hydroelectrolytic deficits and to replace losses until the diarrheal ceases. It is possible in the majority of the cases, using oral rehydration therapy and erly an appropriate type of diet. PREVENTION: It is imperative that management strategies also focus on preventive aspects. The most effective diarrheal prevention strategy in young infants worldwide is promotion of exclusive breast feeding.

Journal Article↗
PubMed1999

Persistence of depressive symptoms in diabetic adults.

OBJECTIVE: To determine the level and pattern of persistent depressive symptoms among adults with diabetes and identify factors associated with increased risk of being persistently depressed. RESEARCH DESIGN AND METHODS: A self-report depression symptom inventory was administered to 245 patients at two initial time points--the beginning and end of a comprehensive outpatient diabetes education program--and at 6-month follow-up. RESULTS: Only 13% of subjects were persistently depressed (i.e., exceeded the criterion for depression symptoms at all three time points). The rate of being depressed at follow-up was 10% for those negative for depression symptoms at either of the initial time points, 36% for those positive at one initial time point, and 73% for those positive at both initial time points (P < 0.0001). Those at increased risk for being persistently depressed were those who did not graduate from high school, had more than two complications of diabetes, and were not treated with insulin. CONCLUSIONS: Persistent depressive symptomatology is present in a substantial number of diabetic adults and can be effectively predicted using simple screening instruments during initial contacts. Risk factors for being persistently depressed only partly overlap those for transient depressive symptoms and represent a possible biological dimension.

Adult↗
PubMed2004

Evaluation of antiviral activity and toxicity of recombinant human interferon alfa-2a in calves persistently infected with type 1 bovine viral diarrhea virus.

OBJECTIVE: To evaluate antiviral activity and toxicity of recombinant human interferon alfa-2a in calves persistently infected with noncytopathic type 1 bovine viral diarrhea virus (BVDV). ANIMALS: 5 Holstein heifers, 4 to 12 months of age. PROCEDURES: Calves persistently infected with noncytopathic type 1 BVDV were treated with recombinant human interferon alfa-2a every other day for 12 weeks. Viral loads were measured during the treatment period and compared with pre- and post-treatment values. Complete physical examinations were performed weekly, and calves were observed daily for signs of systemic illness. Complete blood counts and serum biochemical analyses were performed before, during, and after the treatment period. Because calves developed anemia during the treatment period, bone marrow biopsy specimens were collected. Antirecombinant human interferon alfa-2a antibody concentrations in serum samples obtained before, during, and after the treatment period were measured by use of an ELISA. RESULTS: Recombinant human interferon alfa-2a had no antiviral activity against noncytopathic type 1 BVDV in persistently infected calves. All calves developed microcytic anemia during the treatment period that persisted for up to 13 weeks after cessation of treatment. Anti-interferon antibodies were detected during the treatment period and persisted for at least 2 weeks after cessation of treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Because of lack of in vivo antiviral activity against BVDV, recombinant human interferon alfa-2a has little promise as a therapeutic agent for the treatment of BVDV infection, at least in persistently infected cattle. Furthermore, treatment was associated with adverse immunologic and hematologic effects.

Animals↗
PubMed2005

Economic costs associated with two testing strategies for screening feeder calves for persistent infection with bovine viral diarrhea virus.

OBJECTIVE: To develop partial budgets of the economic costs of 2 test strategies for screening cattle for persistent infection with bovine viral diarrhea virus (BVDV). DESIGN: Partial budget analysis. ANIMALS: 938 calves arriving at 2 stocker operations. PROCEDURE: Calves were tested to determine prevalence of persistent BVDV infection. Test strategies that were evaluated included a single-test strategy consisting of immunohistochemical staining of skin biopsy specimens from all animals and a 2-test strategy consisting of polymerase chain reaction (PCR) assaying of pooled blood samples followed by immunohistochemical staining of skin biopsy specimens from animals in pools for which assay results were positive. Break-even costs (i.e., cost of persistent BVDV infection per animal necessary to justify whole-herd diagnostic testing) associated with each test strategy were calculated as a function of disease prevalence and test cost. RESULTS: Apparent prevalence of persistent BVDV infection was 0.32%. Sensitivity and specificity of the PCR assay for pooled samples were 100% and 89.7%, respectively. Regardless of the prevalence of persistent BVDV infection, the break-even cost for the 2-test strategy was lower than the break-even cost for the single-test strategy. However, the economic advantage was greatest when prevalence was low. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that using a 2-test strategy to screen cattle for persistent BVDV infection, whereby the first test involves PCR assaying of pooled samples and the second involves immunohistochemical testing only of those animals represented in pooled samples with positive assay results, will reduce the cost of screening incoming feedlot cattle, compared with immunohistochemical testing of all animals.

Animals↗
PubMed2003

Lactation persistency: insights from mammary cell proliferation studies.

A persistent lactation is dependent on maintaining the number and activity of milk secreting cells with advancing lactation. When dairy cows are milked twice daily, the increase in milk yield from parturition to peak lactation is due to increased secretory activity per cell rather than to accretion of additional epithelial cells. After peak lactation, declining milk yield is due to loss of mammary epithelial cells by apoptosis. During lactation, only 0.3% of mammary cells proliferate in a 24-h period. Yet this proliferative rate is sufficient to replace most mammary epithelial cells by the end of lactation. Management practices can influence lactation persistency. Administration of bovine somatotropin may enhance persistency by increasing cell proliferation and turnover, or by reducing the rate of apoptosis. Increased photoperiod may also increase persistency of lactation by mechanisms that are as yet undefined. Increased milking frequency during the first weeks of lactation increases milk yield, even after return to less frequent milking, with increases of approximately 8% over the entire lactation. A mammary cell proliferation response to frequent milking during early lactation appears to be involved. Conversely, advanced pregnancy, infrequent milking, and mastitis increase death of epithelial cells by apoptosis. Regulation of mammary cell renewal provides a key to increasing persistency. Investigations to characterize epithelial cells that serve as the proliferative population in the bovine mammary gland have been initiated. Epithelial cells that stain lightly in histological sections are evident through all phases of mammary development and secretion and account for nearly all proliferation in the prepubertal gland. Characterization of these cells may provide a means to regulate mammary cell proliferation and thus to enhance persistency, reduce the effects of mastitis, and decrease the necessity for a dry period.

Animals↗