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PubMed2006

Yields and persistency of lactation in Friesian and Jersey cows milked once daily.

Effects of milking cows once daily throughout lactation at high stocking rates (17% more cows/ha than for those milked twice daily) were studied in 2 Friesian and 2 Jersey herds during 3 lactations. Cows were allocated to 2 herds within breed and were milked either once or twice daily, based on age, genetic merit, and previous performance. Cows remained in their original herd and were milked at the same milking frequency during all lactations. Culled cows (20% per year) were replaced by 2-yr-old heifers. Yields of milk, lactose, protein, and fat were measured every 2 wk by commercial herd test. Cubic splines (5 knots) were used to approximate the lactation curve for each cow-yr to provide estimates of performance for each day of lactation. Yields of milk were greater for Friesian and Jersey cows milked twice daily (4,751 +/- 89 and 3,067 +/- 81 kg/cow) than for cows milked once daily (3,329 +/- 80 and 2,431 +/- 75 kg/cow), respectively. Cows milked once daily had lesser total and peak yields of milk, lactose, protein, and fat than cows milked twice daily. Friesians had greater total and peak yields than Jerseys. Peak production for all milk components occurred earlier in lactation for cows milked once daily than twice daily (d 24 to 39 vs. 32 to 44). Three measures of persistency of lactation were considered for each cow with 2 measures (Pers1 and Pers2) indicating that cows milked twice daily had better persistency than those milked once daily. Ranking of herds in persistency tended to match the ranking based on total yields. Measures of persistency (Pers1 and Pers2) were positively related to total yield in the Jerseys milked once daily and negatively related to peak yield in the Friesians. The third persistency measure (Pers3) ranked once-daily Jerseys first and twice-daily Friesians last, and was negatively correlated with total yield in the Friesian herds and negatively correlated with peak yield in all herds. For most performance measures, cows milked twice daily had better total yields and persistency than cows milked once daily.

Animals↗
PubMed2006

Long-term persistence of specific genetic types of mastitis-causing Staphylococcus aureus on three dairies.

Pulsed-field gel electrophoresis (PFGE) after SmaI digestion was used to investigate the persistence of specific genotypes of bovine mammary gland isolates of Staphylococcus aureus on 3 dairy herds. A total of 341 isolates of Staph. aureus were available from cows in 3 herds, collected over a period of 15 yr. Pulsed-field gel electrophoresis band patterns of Staph. aureus isolates were analyzed visually and with gel analysis and comparison software. Based on this analysis, isolates were classified by PFGE type. Persistence was determined as the time period from the first to the last isolation of a particular PFGE type of Staph. aureus within a herd. Specific types of mastitis-causing Staph. aureus persisted long-term on these dairies. For example, PFGE type 3 isolates persisted on farms A, B, and C for 15, 15, and 13 yr, respectively. Type 6 was found to persist for 13 yr on farm C. Despite the application of standard mastitis control practices, mastitis-causing Staph. aureus types appeared to persist long-term, as detected by PFGE, and were isolated coincident with herd problems of increased milk somatic cell counts and decreased milk production.

Animals↗
PubMed1987

Effects of persistency and production on the genetic parameters of milk and fat yield in Israeli-Holsteins.

Herd-years of Israeli-Holsteins were stratified into three groups by two criteria: mean annualized milk yield [365 (total lactations yield/calving interval)] and mean persistency, estimated as the ratio of daily milk production at the 5th mo postpartum to daily production during the postpartum peak period. The latter was taken as an indication of the relative environmental stress on the cow. Primi- and multiparous cows were analyzed separately. Genetic parameters were estimated for annualized milk and fat production at each production and persistency group. Heritabilities increased with a rise in production for both primiparous and multiparous cows, but the effect was greater for multiparous cows. Even though persistency and production were correlated, no clear trends were evident for stratification by persistency; thus, a relationship between stress and heritability was not established. Genetic correlations among stratification groups were between .7 and .9 for persistency and between .6 and .86 for production; thus, sire x environmental interaction was greater for production than for persistency stratification. Production in a given year can be used as a criterion for selecting herds to test progeny of young sires in the following year.

Animals↗
PubMed1991

Duration of visible persistence in relation to stimulus complexity.

Visible persistence refers to the phenomenal impression that a stimulus is still present after its offset. A dispute exists whether visible persistence is due to temporal sluggishness in the visual pathway (neural hypothesis) or whether it is a byproduct of information-extraction processes under cognitive control (process hypothesis). This was investigated by manipulating stimulus complexity in five temporal integration experiments and one recognition memory experiment. According to the process hypothesis, complex stimuli should persist longer than simple stimuli because they require more information extraction. This prediction was not confirmed; in all six experiments, complexity was found to have no reliable effect on the duration of visible persistence. By contrast, and in accordance with earlier findings, complexity was shown to have a significant effect on a short-lived, nonvisible form of memory known as schematic persistenc. This pattern of results supports two major conclusions: First, that the effects of complexity reported in earlier research were probably on schematic--rather than visible--persistence; and second, that visible persistence must be regarded as a residual neural trace of an extinguished stimulus, rather than as a byproduct of information-extraction processes.

Adult↗
PubMed2005

Telomere length of transferred lymphocytes correlates with in vivo persistence and tumor regression in melanoma patients receiving cell transfer therapy.

Recent studies have indicated that adoptive immunotherapy with autologous antitumor tumor-infiltrating lymphocytes (TILs) following nonmyeloablative chemotherapy mediates tumor regression in approximately 50% of treated patients with metastatic melanoma, and that tumor regression is correlated with the degree of persistence of adoptively transferred T cells in peripheral blood. These findings, which suggested that the proliferative potential of transferred T cells may play a role in clinical responses, led to the current studies in which telomere length as well as phenotypic markers expressed on the administered TILs were examined. TILs that were associated with objective clinical responses following adoptive transfer possessed a mean telomere length of 6.3 kb, whereas TILs that were not associated with significant clinical responses were significantly shorter, averaging 4.9 kb (p < 0.01). Furthermore, individual TIL-derived T cell clonotypes that persisted in vivo following adoptive cell transfer possessed telomeres that were longer than telomeres of T cell clonotypes that failed to persist (6.2 vs 4.5 kb, respectively; p < 0.001). Expression of the costimulatory molecule CD28 also appeared to be associated with long telomeres and T cell persistence. These results, indicating that the telomere length of transferred lymphocytes correlated with in vivo T cell persistence following adoptive transfer, and coupled with the previous observation that T cell persistence was associated with clinical responses in this adoptive immunotherapy trial, suggest that telomere length and the proliferative potential of the transferred T cells may play a significant role in mediating response to adoptive immunotherapy.

Base Sequence↗
PubMed2006

CD94/NKG2A expression is associated with proliferative potential of CD8 T cells during persistent polyoma virus infection.

Memory CD8 T cells comprise a critical component of durable immunity because of their capacity to rapidly proliferate and exert effector activity upon Ag rechallenge. During persistent viral infection, memory CD8 T cells repetitively encounter viral Ag and must maintain a delicate balance between limiting viral replication and minimizing immunopathology. In mice infected by polyoma virus, a natural mouse pathogen that establishes long-term persistent infection, the majority of persistence-phase antiviral CD8 T cells express the inhibitory NK cell receptor CD94/NKG2A. In this study, we asked whether CD94/NKG2A expression is associated with Ag-specific recall of polyoma virus-specific CD8 T cells. During the persistent phase of infection, polyoma virus-specific CD8 T cells that express CD94/NKG2A were found to preferentially proliferate; this proliferation was dependent on cognate Ag both in vitro and in vivo. In addition, CD94/NKG2A(+) polyoma-specific CD8 T cells have a markedly enhanced capacity to produce IL-2 upon ex vivo Ag stimulation compared with CD94/NKG2A(-) polyoma-specific CD8 T cells. Importantly, CD94/NKG2A(+) anti-polyoma virus CD8 T cells appear to be essential for Ag-specific recall responses in mice persistently infected by polyoma virus. Because of its higher proliferative potential and capacity to produce IL-2, we propose that the CD94/NKG2A(+) subpopulation represents a less differentiated state than the CD94/NKG2A(-) subpopulation. Identification of proliferation-competent subpopulations of memory CD8 T cells should prove valuable in designing therapeutic vaccination strategies for persistent viral infections.

Animals↗
PubMedDate not supplied

Toddlers' persistence in the emerging occupations of functional play and self-feeding.

OBJECTIVE: This descriptive study explores motivation of toddlers who are typically developing to persist with challenging occupations. METHOD: The persistence of 33 children, 12 to 19 months of age (M = 15.7 months), in functional play and self-feeding with a utensil was examined through videotape analysis of on-task behaviors. RESULTS: A modest correlation was demonstrated between the percentages of on-task time in the two conditions (r = .44, p < .01). Although chronological age was not associated with persistence, participants' age-equivalent fine motor scores were correlated with persistence with challenging toys (r = .39, p < .03) but not with self-feeding with a utensil. Having an older sibling was associated with longer periods of functional play, t(32) = 3.02, p < .005, but the amount the parent urged the child to eat with a utensil was not associated with persistence in self-feeding. CONCLUSION: The modest association between on-task time for functional play and self-feeding with a utensil reveals that factors other than urge to meet perceptual motor challenges lead to children's persistence. The results reinforce the importance of considering not only challenging activities, but also the experienced meaning that elicits optimal effort and, thus, learning.

Feeding Behavior↗
PubMed1999

Persistence and boosting of bacille Calmette-Guérin-induced delayed-type hypersensitivity.

BACKGROUND: Bacille Calmette-Guérin (BCG) vaccination may induce persistent and booster purified protein derivative (PPD) responses that complicate tuberculosis screening efforts. OBJECTIVES: To investigate the effects of BCG vaccination on serial PPD tests and to study correlations between persistent delayed-type hypersensitivity and other potential surrogate markers of protective immunity. DESIGN: Cohort study. SETTING: Midwestern urban university. PARTICIPANTS: 69 healthy adults. INTERVENTIONS: BCG vaccination, blood samples drawn for immunologic studies, and PPD tests done sequentially over 1 to 3 years. MEASUREMENTS: Serial PPD induration, lymphoproliferation, and interferon-gamma responses. RESULTS: 10% of participants (95% CI, 4% to 20%) had persistent PPD responses of 15 mm or greater, and 3% (CI, 0% to 10%) demonstrated PPD boosting of 15 mm or greater 1 to 3 years after BCG vaccination. Intradermal BCG vaccination induced a larger number of persistent responses that were 10 mm or greater than did percutaneous BCG vaccination (12 of 46 participants compared with 1 of 23 participants; P = 0.05). Persistent and boosted delayed-type hypersensitivity correlated with mycobacterial-specific lymphoproliferation and interferon-gamma responses. CONCLUSIONS: Previous BCG vaccination reduces the predictive value of serial PPD testing. The lowest PPD predictive values will occur in persons without known tuberculosis exposure who were vaccinated recently or many times with intradermal BCG. In addition, BCG-related persistence and boosting of delayed-type hypersensitivity responses correlate with other potential surrogate markers of protective mycobacterial immunity.

Adult↗
PubMedDate not supplied

[Strategy of persistence (facts, hypotheses)].

The universal phenomenon of virus persistence is considered to be a regular phenomenon primarily meeting the interests of the host. Examinations of 1112 patients with various diseases of the nervous system revealed a certain dependence of macroglobulin measles antibody upon the character of the disease and the intensity of demyelinization process. These data do not suggest the etiological role of the persisting measles virus in the genesis of multiple sclerosis and a large group of other nervous system diseases (SSPE). Similar results were obtained in analogous examinations of patients for macroglobulin mumps antibody. The results indicate the role of persisting viruses in the formation of solid specific immunity as well as their importance for nonspecific protection against other immunologically similar diseases. Virus persistence is considered to be a certain antiviral strategy of the body based on accumulation in the life course of a considerable number of persisting viruses on which both specific and nonspecific antiviral protection is founded. Congenital or acquired defects of immunity cause the development of the persisting infection and appearance of some chronic diseases of the nervous system.

Antibodies, Viral↗
PubMed1999

Immune response in patients with persistent candiduria and occult candidemia.

PURPOSE: We evaluated the immunological response in patients with persistent candiduria with or without occult candidemia. MATERIALS AND METHODS: Levels of Thl (pro-inflammatory interleukin [IL]-1, IL-2 and tumor necrosis factor-alpha) and Th2 (anti-inflammatory IL-4 and IL-10) cytokines were measured in the sera of patients with persistent candiduria. Polymerase chain reaction assessment of the 158 base pair candidal actin gene was used to detect Candida albicans in blood to identify occult candidemia. RESULTS: During a 14-month period 66 hospitalized patients with a mean age of 63 years (range 44 to 80) with persistent candiduria were evaluated. Occult candidemia developed in 27 patients (41%) as evidenced by detection of candidal actin gene in the sera by polymerase chain reaction. Risk factors included antibiotics in 27 patients (100%), central venous catheter in 22 (81%), urinary catheter in 21 (78%), total parenteral nutrition in 18 (66%), diabetes mellitus in 16 (59%) and abdominal surgery in 14 (52%). A total of 17 age matched patients with a mean age of 59 years hospitalized for elective general or vascular surgical procedures with no clinical or laboratory evidence of urinary or hematogenous fungal or bacterial infection served as controls. Serum levels of Th2 cytokines were elevated in 18 of 39 patients with persistent candiduria alone, and in 22 of 27 patients with candiduria and occult candidemia compared to controls (p<0.002). Th1 cytokines were within normal limits or slightly decreased in all patients with persistent candiduria with or without candidemia. CONCLUSIONS: These observations indicate that an abnormal immune response develops in patients with persistent candiduria with or without candidemia.

Adult↗
PubMed2000

Ultrasonography and hormone profiles of adrenocorticotrophic hormone (ACTH)-induced persistent ovarian follicles (cysts) in cattle.

The objective of this study was to develop a model for the study of abnormal ovarian follicles in cattle by treating heifers with adrenocorticotrophic hormone (ACTH) (100 iu at 12 h intervals for 7 days, beginning on day 15 of the oestrous cycle). Cortisol concentrations increased (P < 0.05) within 24 h after beginning ACTH treatment and cortisol and progesterone concentrations remained elevated after cessation of ACTH treatment for 8 and 4 days, respectively. The pulses and surges of LH decreased during ACTH treatment, but FSH profiles were similar to those in controls and persistent or prolonged follicles were eventually observed in all heifers. In five heifers, prolonged dominant follicles ovulated after 10 days, whereas in six heifers, persistent follicular structures were present for 20 days, but ceased to secrete oestradiol after approximately 12 days. In the heifers with persistent follicular structures, new follicles emerged when the persistent follicle became non-oestrogenic. During the last 2 days of normal follicular growth, the concentration of oestradiol was greater than it was during prolonged or persistent follicle development (P < 0.05). There were no differences in the growth rates or maximum diameters of abnormal follicles that had different outcomes, but oestradiol concentrations were greater in prolonged follicles that ovulated compared with those follicles that persisted (P = 0.06). In conclusion, stimulation with ACTH resulted in a marked deviance from normal follicular activity. The aberrations were probably caused by the interruption of pulsatile secretion of LH (but not FSH) leading to decreased but prolonged oestradiol secretion.

Adrenocorticotropic Hormone↗
PubMed2001

Persistent symptoms among survivors of Hodgkin's disease: an explanatory model based on classical conditioning.

Persistent symptoms of nausea, distress, and vomiting triggered by reminders of cancer treatment were examined among 273 Hodgkin's disease survivors, 1 to 20 years posttreatment. Prevalence rates were high for distress and nausea but low for vomiting. Retrospective report of anticipatory symptoms during treatment was the strongest predictor of persistent symptoms, suggesting that treatment-induced symptoms are less likely to persist if conditioning does not occur initially. Time since treatment was also a significant predictor, with patients more recently treated more likely to experience persistent symptoms. Thus, an explanatory model based on classical conditioning theory successfully predicted presence of persistent symptoms. Symptoms also were associated with ongoing psychological distress, suggesting that quality of life is diminished among survivors with persistent symptoms. Recommendations for prevention and treatment of symptoms are discussed.

Adolescent↗
PubMed2001

Prevalence of persistent asymptomatic proteinuria in HIV-infected outpatients and lack of correlation with viral load.

AIM: Human immunodeficiency virus-associated nephropathy (HIVAN) is projected to be a leading cause of end-stage renal disease (ESRD) in young African American men in the new millennium. Little is known about the early natural history of the disease, including the prevalence of asymptomatic nephropathy. The primary aim of this study was to define the prevalence of persistent asymptomatic proteinuria in a contemporary, ambulatory human immunodeficiency virus- (HIV) infected population. The secondary aim was to correlate the presence of persistent proteinuria with measures of HIV disease. METHODS: Using a readily available screening tool, the urine dipstick, we determined the prevalence of persistent asymptomatic proteinuria in the outpatient VA Connecticut (VA CT) Healthcare System West Haven HIV Clinic population. We compared the presence of persistent proteinuria with measures of HIV viral disease. RESULTS: The prevalence of persistent asymptomatic proteinuria was 14% (7 of 49 patients). The presence of persistent proteinuria was not correlated with viral load. CONCLUSIONS: A significant prevalence of occult renal disease exists in the asymptomatic HIV-seropositive outpatient population and is not correlated with viral load.

AIDS-Associated Nephropathy↗
PubMed2001

D1/D5 dopamine receptor activation differentially modulates rapidly inactivating and persistent sodium currents in prefrontal cortex pyramidal neurons.

Dopamine (DA) is a well established modulator of prefrontal cortex (PFC) function, yet the cellular mechanisms by which DA exerts its effects in this region are controversial. A major point of contention is the consequence of D(1) DA receptor activation. Several studies have argued that D(1) receptors enhance the excitability of PFC pyramidal neurons by augmenting voltage-dependent Na(+) currents, particularly persistent Na(+) currents. However, this conjecture is based on indirect evidence. To provide a direct test of this hypothesis, we combined voltage-clamp studies of acutely isolated layer V-VI prefrontal pyramidal neurons with single-cell RT-PCR profiling. Contrary to prediction, the activation of D(1) or D(5) DA receptors consistently suppressed rapidly inactivating Na(+) currents in identified corticostriatal pyramidal neurons. This modulation was attenuated by a D(1)/D(5) receptor antagonist, mimicked by a cAMP analog, and blocked by a protein kinase A (PKA) inhibitor. In the same cells the persistent component of the Na(+) current was unaffected by D(1)/D(5) receptor activation-suggesting that rapidly inactivating and persistent Na(+) currents arise in part from different channels. Single-cell RT-PCR profiling showed that pyramidal neurons coexpressed three alpha-subunit mRNAs (Nav1.1, 1.2, and 1.6) that code for the Na(+) channel pore. In neurons from Nav1.6 null mice the persistent Na(+) currents were significantly smaller than in wild-type neurons. Moreover, the residual persistent currents in these mutant neurons-which are attributable to Nav1.1/1.2 channels-were reduced significantly by PKA activation. These results argue that D(1)/D(5) DA receptor activation reduces the rapidly inactivating component of Na(+) current in PFC pyramidal neurons arising from Nav1.1/1.2 Na(+) channels but does not modulate effectively the persistent component of the Na(+) current that is attributable to Nav1.6 Na(+) channels.

Animals↗
PubMed2001

Long term results of radioactive gold grain implantation for the treatment of persistent and recurrent nasopharyngeal carcinoma.

BACKGROUND: Brachytherapy is useful for the reirradiation of nasopharyngeal carcinoma. In the current study, the long term treatment results of permanent radioactive gold(198) grain interstitial implantation in patients with persistent and recurrent nasopharyngeal carcinoma were reviewed. METHODS: Gold grain implantation was performed under direct vision with a split palate approach to provide 60 grays (Gy) 0.5 cm away from the plane of implantation. Between August 1986 and May 1999, 106 patients were treated with gold grain implantation (45 patients for persistent disease, 53 patients for first recurrence, and 8 patients for second recurrence in the nasopharynx). All patients had histologically proven disease by biopsy before undergoing implantation. RESULTS: Patients with persistent disease and those with first recurrence did well with the gold grain implantation. The 5-year local control rates for patients with persistent disease, first recurrence, and second recurrence in the nasopharynx were 87.2%, 62.7%, and 23.4%, respectively (P = 0.0004). The 5-year metastasis free survival rates were 68.1%, 60.3%, and 40%, respectively, for the 3 groups (P = 0.048). The overall survival rates at 5 years for the 3 groups were 79.1%, 53.6%, and 42.9%, respectively (P = 0.0047). Patients with computed tomography evidence of disease extension outside the nasopharynx had a lower local control rate compared with patients whose disease was confined to the nasopharynx (5-year local control rate of 52% vs. 72.3%; P = 0.031). The size of the lesion was not found to be an independent prognostic factor for local control after implantation. Multivariate analysis showed only an indication for implantation (persistent disease, first recurrence, and second recurrence) to be a significant prognostic factor for local control. Complications attributed to gold grain implantation included headache, palatal fistula, and mucosal radiation necrosis at the site of implantation, and were reported to occur in 28.3%, 18.9%, and 16%, respectively, of patients. CONCLUSIONS: For selected patients with disease confined to the nasopharynx, gold grain implantation is an effective salvage treatment for persistent and recurrent nasopharyngeal carcinoma.

Adult↗
PubMedDate not supplied

Risk factors of persistent diarrhea in children below five years of age.

BACKGROUND/OBJECTIVE: Persistent diarrhea is a known cause of childhood mortality, morbidity and malnutrition in developing countries. This study was conducted to find out the host and environmental risk factors associated with persistent diarrhea in Bangladeshi children below 5 years of age. DESIGN: Prospective analytic case-control study. SETTING: Tertiary hospital in Dhaka, Bangladesh. METHODS: Fifty children with persistent diarrhea and 50 controls with acute diarrhea (matched for age and sex) comprised the study subjects. RESULTS: Most of the children (82%) were aged below 2 years. Among the risk factors, Grade III malnutrition (p<0.008), irrational antibiotic use during acute diarrheal episode (p<0.0000005), use of unsafe drinking water (p<0.004) and lack of exclusive breast-feeding up to the first four months of life (p<0.004) were significantly associated with persistent diarrhea. Logistic analysis showed irrational antibiotic use (p<0.0001) during an episode of acute diarrhea and lack of exclusive breast-feeding (p<0.05) during the first four months of life as independent risk factors associated with persistent diarrhea. CONCLUSION: Improvement of nutritional status, encouraging exclusive breast-feeding during the first four months of life, discouraging the irrational use of antibiotic for the treatment of acute diarrhea, and provision of safe drinking water may be important for the prevention of persistent diarrhea as these have been identified as risk factors in Bangladeshi children below five years of age.

Bangladesh↗
PubMed2001

Inhibition of poliovirus RNA synthesis as a molecular mechanism contributing to viral persistence in the mouse central nervous system.

Many survivors of poliomyelitis, several decades after the acute phase of the disease, develop a set of new muscle symptoms called post-polio syndrome. The persistence of poliovirus (PV) in the central nervous system (CNS) may be involved in the aetiology of this syndrome. By using a mouse model, we have shown that PV persists in the CNS of paralysed mice for over a year after the acute disease. Detection of PV plus- and minus-strand RNAs in the spinal cord of paralysed mice suggested continuous PV RNA replication in the CNS. However, infectious PV particles could not be recovered from homogenates of CNS from paralysed mice beyond 20 days post-paralysis, indicating that PV replication was restricted. In an attempt to identify the molecular mechanism by which PV replication was limited, PV plus- and minus-strand RNA levels were estimated in the CNS of persistently infected mice by a semi-quantitative RT-nested PCR method. Results revealed that RNA replication was inhibited at the level of plus-strand RNA synthesis during persistent infection. Similar results were obtained in neuroblastoma IMR-32 cell cultures persistently infected with PV Restriction of PV RNA synthesis could be involved in persistence by limiting PV replication.

Animals↗
PubMed2001

Poliovirus persistence in human cells in vitro.

Poliovirus (PV) can persist in vivo in the intestine of immunocompromised hosts for years. Moreover, immunocompetent individuals who have survived paralytic poliomyelitis sometimes develop the post-poliomyelitis syndrome (PPS), consisting of a variety of symptoms including new muscular atrophies. PPS may be due to PV persistence. We have developed models of PV persistence in neural cells and epidermoid cells. Cell determinants are of crucial importance for the establishment of persistent infections in human neuronal cells, whereas viral determinants play the primary role in human epidermoid HEp-2 cells. The results obtained with these in vitro models show the capacity of PV to persist and reveal a virus and cell co-evolution involving PV-receptor interactions. In addition, they suggest that several mechanisms are used by PV to establish and maintain persistent infections.

Animals↗