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PubMed1984

Visible persistence as a function of viewing condition and eye-handedness relationship.

Duration of visible persistence was investigated as a function of spatial frequency, orientation and viewing condition (binocular, dominant eye and non-dominant eye). Persistence increased with increasing spatial frequency and was longer for oblique than vertical gratings. Viewing condition also influenced visible persistence such that binocular persistence was significantly shorter than for either monocular condition. A post-hoc analysis indicated that this was only true with subjects who were right-handed and right-eyed. Subjects mixed on this relationship showed no differences in persistence across viewing conditions. A second experiment which selected subjects on the basis of this relationship confirmed the results of Experiment 1. The results for the right-right group broaden the generality of the rule showing an inverse relationship between response strength and persistence duration. The results for the Mixed group indicate a lack of binocular summation.

Dominance, Cerebral↗
PubMed1988

Persistent ovarian cysts following administration of human menopausal and chorionic gonadotropins: an attenuated form of ovarian hyperstimulation syndrome.

Ovarian cysts persisting after the onset of menses were demonstrated by ultrasound (US) in 40 of 71 (56%) nonconception cycles following ovulation induction with human menopausal gonadotropins (hMG) and human chorionic gonadotropin (hCG). Persistent cysts were self-limited and all resolved spontaneously within two cycles. They developed more frequently during stimulation cycles with (1) higher mean pre-hCG serum estradiol (E2), (2) a greater number of medium and large follicles at peak pre-hCG E2, and (3) a larger leading follicle diameter at peak pre-hCG E2. Persistent ovarian cysts frequently occurred despite a peak pre-hCG E2 lower than 1000 pg/ml. Although ovarian enlargement in the presence of cysts exceeded 5 X 5 cm in 25% of cases, no patient developed clinical symptoms of ovarian hyperstimulation syndrome (OHSS). Repeated induction of ovulation with hMG/hCG in the presence of nonfunctional, persistent cysts resulted in pregnancies in 6 of 15 cases (40%). Asymptomatic persistent ovarian cysts frequently follow an hMG/hCG regimen and, when nonfunctional, are not a contraindication to repeated ovarian stimulation. Persistent ovarian cysts appear to be an attenuated form of OHSS.

Adult↗
PubMed2000

A dendritic cable model for the amplification of synaptic potentials by an ensemble average of persistent sodium channels.

The persistent sodium current density (I(NaP)) at the soma measured with the 'whole-cell' patch-clamp recording method is linearized about the resting state and used as a current source along the dendritic cable (depicting the spatial distribution of voltage-dependent persistent sodium ionic channels). This procedure allows time-dependent analytical solutions to be obtained for the membrane depolarization. Computer simulated response to a dendritic current injection in the form of synaptically-induced voltage change located at a distance from the recording site in a cable with unequally distributed persistent sodium ion channel densities per unit length of cable (the so-called 'hot-spots') is used to obtain conclusions on the density and distribution of persistent sodium ion channels. It is shown that the excitatory postsynaptic potentials (EPSPs) are amplified if hot-spots of persistent sodium ion channels are spatially distributed along the dendritic cable, with the local density of I(NaP) with respect to the recording site shown to specifically increase the peak amplitude of the EPSP for a proximally placed synaptic input, while the spatial distribution of I(NaP) serves to broaden the time course of the amplified EPSP. However, in the case of a distally positioned synaptic input, both local and nonlocal densities yield an approximately identical enhancement of EPSPs in contradiction to the computer simulations performed by Lipowsky et al. [J. Neurophysiol. 76 (1996) 2181]. The results indicate that persistent sodium channels produce EPSP amplification even when their distribution is relatively sparse (i.e. , approximately 1-2% of the transient sodium channels are found in dendrites of CA1 hippocampal pyramidal neurons). This gives a strong impetus for the use of the theory as a novel approach in the investigation of synaptic integration of signals in active dendrites represented as ionic cables.

Animals↗
PubMed1998

Intrapartum sonography and persistent occiput posterior position: a study of 408 deliveries.

OBJECTIVE: To use intrapartum sonography as a tool to investigate the development of the persistent occiput posterior position during labor, as well as to identify parameters correlating with the outcome of labor. METHODS: A prospective study of 408 women in labor after 37 weeks' gestation with a singleton fetus in a vertex position using sonography at the onset of labor was performed. Fetal position, placental location, and maternal BMI (body mass index) were recorded. Outcome of labor was monitored for all relevant parameters. RESULTS: Most (68%) of persistent occiput posterior positions develop through a malrotation during labor from an initially occipitoanterior position. Only 32% of persistent cases were occipitoposterior (dorsoposterior) at the onset of labor; operative interventions were required in 87.5% of these. Of the 61 (15%) occipitoposterior positions at the onset of labor, 53 (87%) rotated into an occiput anterior position. Persistent occiput posterior position was more common in the initially occipitoposterior group (P < 0.01, Fisher exact test), and posterior placental locations were fewer (z test, P = 0.05). Also, operative deliveries were more common in the group remaining occipitoposterior throughout labor (P < .01, Fisher exact test). A higher maternal BMI correlated with neonatal weight (P < .01, Pearson correlation), an increase in operative deliveries (P = .032, Pearson correlation), lower Apgar scores at 1 minute (P = .02, Spearman correlation), and increase in posterior placental locations (P = .037, two-tailed t test). CONCLUSION: In most cases, persistent occiput posterior position develops through a malrotation and only in a little more than one-third of cases through absence of rotation from an initially occipitoposterior position. Higher maternal BMI correlates with higher fetal weight, increased operative deliveries, lower Apgar scores at 1 minute, and posterior placental locations. Intrapartum sonography proved to be useful in investigating the development of the persistent occipitoposterior position.

Adult↗
PubMed2001

The persistence of position.

I describe a signal coined position persistence that stores information about the last seen position of an object. Position persistence is not the same as visible persistence, although some of its properties are similar. The duration of position persistence is such that objects visible briefly always generate a position signal for at least 180 ms. The signal is not affected by the intensity of the object, nor of the background. Position persistence decreases with increasing speed, but does not depend on retinal eccentricity. Finally, the persisting signal is not tightly bound to the object that causes it. The signal contains no information on the colour of the object, whereas shape information may become represented after approximately 100 ms. The existence of this signal is interpreted as a psychophysical signature of the parallel processing of visual information.

Adult↗
PubMed1997

Surgical management of persistent müllerian duct syndrome.

OBJECTIVES: To describe the optimal surgical management of the testes and müllerian duct structures in patients with persistent müllerian duct syndrome. METHODS: We performed a comprehensive Medline literature search regarding the surgical management of persistent müllerian duct syndrome and extracted information regarding the etiology, pathogenesis, and treatment of this disorder. We specifically assessed the risks of retained müllerian structures versus surgical excision of the infantile uterus and fallopian tubes. Using this information, we formulated a comprehensive strategy for the management of patients with persistent müllerian duct syndrome. An illustrative case is described. RESULTS: No malignant degeneration of persistent müllerian structures has been reported. The risk of testicular neoplasia in persistent müllerian duct syndrome approximates the risk of neoplasia in other intra-abdominal gonads. Fertility has rarely been reported although virilization is unaffected. Surgical excision of the infantile uterus and fallopian tubes risks damage to vasa deferentia and the deferential blood supply to the testis. CONCLUSIONS: Surgical excision of persistent müllerian duct structure may result in ischemic and/or traumatic damage to the vasa deferentia and testes. Optimal surgical management is orchiopexy leaving the uterus and fallopian tubes in situ. Meticulous proximal salpingectomy and hysterectomy is indicated only in patients whose müllerian structures limit intrascrotal placement of the tests. Orchiectomy is indicated for testes that cannot be mobilized to a palpable location.

Congenital Abnormalities↗
PubMed1998

Differential immune responses to acute lower respiratory illness in early life and subsequent development of persistent wheezing and asthma.

BACKGROUND: Recent epidemiologic evidence suggests that 2 wheezing syndromes coexist in early life: transient wheezing, limited to early childhood, and persistent wheezing, which starts in early childhood and persists beyond that age. OBJECTIVE: Whether the nature of the immune response occurring during acute lower respiratory illnesses (LRIs) in infancy differs between these 2 groups of wheezers has yet to be determined. METHODS: We compared total serum IgE levels and peripheral blood eosinophil counts obtained during the acute phase of the first LRI with those obtained during the convalescent phase or with well-baby samples in persistent (n = 49) and transient early wheezers (n = 88), as well as in children who had only nonwheezing LRIs (n = 43) during the first 3 years of life. RESULTS: Total serum IgE levels were significantly higher (P =.008) during the acute phase compared with the convalescent phase of the LRI in persistent wheezers, a response not observed in transient early wheezers (P =.7). Peripheral blood eosinophil counts were significantly reduced during the acute phase of the LRI (P =.009) in transient early wheezers, a response not observed among persistent wheezers (P =.7). Acute responses in children who had nonwheezing LRIs only were similar to those seen in transient early wheezers. CONCLUSION: Alterations in acute immune response to viral infection may be detected at the time of the first wheezing episode in subjects who will go on to have persistent wheezing symptoms.

Acute Disease↗
PubMed2002

Disconnection of speech-relevant brain areas in persistent developmental stuttering.

BACKGROUND: The neuronal basis of persistent developmental stuttering is unknown. The disorder could be related to a reduced left hemisphere dominance, which functional neuroimaging data suggest might lead to right hemispheric motor and premotor overactivation. Alternatively, the core deficit underlying stuttering might be located in the speech-dominant left hemisphere. Furthermore, magnetoencephalography study results show profound timing disturbances between areas involved in language preparation and execution in the left hemisphere, suggesting that persistent developmental stuttering might be related to impaired neuronal communication, possibly caused by a disruption of white matter fibre tracts. We aimed to establish whether disconnection between speech-related cortical areas was the structural basis of persistent developmental stuttering. METHODS: We analysed the speech of 15 people with persistent developmental stuttering and 15 closely matched controls for the percentage of syllables stuttered. We used diffusion tensor imaging to assess participants' brain tissue structure, and used and two-sample t test to compare diffusion characteristics between groups. FINDINGS: Diffusion characteristics of the group with persistent developmental stuttering and controls differed significantly immediately below the laryngeal and tongue representation in the left sensorimotor cortex (mean difference in fractional anisotropy 0.04 [95% CI 0.03-0.05]). INTERPRETATION: Our findings show that persistent developmental stuttering results from disturbed timing of activation in speech-relevant brain areas, and suggest that right hemisphere overactivation merely reflects a compensatory mechanism, analogous to right hemisphere activation in aphasia.

Adult↗
PubMed1996

Double-blind randomised trial of co-amoxiclav versus placebo for persistent otitis media with effusion in general practice.

BACKGROUND: The treatment of persistent otitis media with effusion (OME) remains controversial, but this condition is the commonest reason for children to require ear, nose, and throat (ENT) surgery. Trials of antibiotics are inconclusive, are often weak methodologically, and have not been done in general practice. Our aim was a trial of an antibiotic for OME in such a population. METHODS: 433 children, aged 6 months to 6 years, with OME from 57 general practices entered a 3-month watchful waiting period. Of 223 (52%) with persistent bilateral OME, 162 were randomised double-blind to receive co-amoxiclav suspension (20 mg/kg amoxicillin, 5 mg/kg clavulanate potassium) or matching placebo, orally three times a day for 14 days. All cases also received xylometazoline 0.25% decongestant nosedrops thrice daily. Of the 61 not randomised, 13 children were referred to an ENT surgeon and parents refused consent in 48 cases. The main outcome measures were persistent OME in both ears and in one or both ears, as assessed clinically and by tympanometry. Analysis was by intention-to-treat. FINDINGS: 79 children in the treatment group and 70 in the placebo group were analysed for efficacy. 3 withdrew in the co-amoxiclav group (2 lost to follow-up, 1 due to side-effects); 6 withdrew in the placebo group (5 and 1, respectively). In addition, 4 tympanograms were uninterpretable in the controls. Compliance was over 90% in both groups. Persistent OME in both ears and in one or both ears were found at significantly lower rates in the co-amoxiclav group than in the controls at the 2-week follow-up: 53 vs 84% and 77 vs 93%, respectively. Odds ratios adjusted for sex, history of adenoidectomy, and upper respiratory tract infection at follow-up were 0.25 (95% CI 0.11, 0.58, p = 0.001) and 0.30 (0.10, 0.89, p = 0.03), respectively. Parents of children in the co-amoxiclav group reported significantly more side-effects than those of control children (44 vs 22%, p = 0.03). Side-effects were mostly gastrointestinal and mild. INTERPRETATION: Our study in a general-practice setting confirmed the positive short-term effect of antibiotic treatment for persistent middle-ear infection. Before referral to an ENT surgeon, children with persistent OME presenting to general practitioners could be considered for such treatment, depending on the individual child and possible adverse sequelae.

Amoxicillin↗
PubMedDate not supplied

Does a coexisting anxiety disorder predict persistence of depressive illness in primary care patients with major depression?

We assessed whether a coexisting anxiety disorder predicts risk for persistent depression in primary care patients with major depression at baseline. Patients with major depression were identified in a 12-month prospective cohort study at a University-based family practice clinic. Presence of an anxiety disorder and other potential prognostic factors were measured at baseline. Persistent depressive illness (major depression, minor depression, or dysthymia) was determined at 12 months. Of 85 patients with major depression at baseline, 43 had coexisting anxiety disorder (38 with social phobia). The risk for persistent depression at 12 months was 44% greater [Risk Ratio (RR) = 1.44, 95% confidence interval (CI) 1.02-2.04] in those with coexisting anxiety. This risk persisted in stratified analysis controlling for other prognostic factors. Patients with coexisting anxiety had greater mean depressive severity [repeated measures analysis of variance (ANOVA), p < 0.04] and total disability days (54.9 vs 19.8, p < 0.02) over the 12-month study. Patients with social phobia had similar increased risk for persistent depression (RR = 1.40, 95% CI 0.98-2.00). A coexisting anxiety disorder indicates risk for persistent depression in primary care patients with major depression. Social phobia may be important to recognize in these patients. Identifying anxiety disorders can help primary care clinicians target patients needing more aggressive treatment for depression.

Adolescent↗
PubMed1999

Mechanisms and consequences of enterovirus persistence in cardiac myocytes and cells of the immune system.

In humans and experimental murine models enteroviruses, and in particular coxsackieviruses of group B (CVB), may induce chronic myocarditis associated with a persistent type of heart muscle infection. Persistent myocardial infection has been characterized by restricted viral replication and gene expression, which is capable of sustaining chronic inflammation. Altered replication and transcription of the virus, in addition to an immune response insufficient to recognize and clear infected cells entirely, are essential mechanisms for initiation and maintenance of persistent heart muscle infection. Viral cytotoxicity was found to be crucial for organ pathology both during acute and persistent infection, indicating that enterovirus myocarditis is a virus-induced rather than an immune-mediated disease. Notably, resistance to the development of persistent heart muscle infection is not linked to the H-2 haplotype of the host. In addition to persistently infected myocytes, detection of the replicative minus-strand RNA intermediate provided evidence for virus replication in lymphoid cells of the spleen, predominantly in splenic B lymphocytes, during the course of the disease. Whereas viral RNA was also detected in certain CD4+ helper T cells and Mac1+ macrophages, no enteroviral genomes were identified in CD8+ T cells. Detection of infected activated B lymphocytes both in heart tissue of CVB3-infected immunocompetent mice and syngenic SCID mice receiving splenocytes from CVB3-infected donors support the concept that B cell traffic may contribute to maintenance of chronic disease. Dissection of the diversity of viral and host-specific determinants in susceptible and resistant hosts will allow us to define the protective mechanisms that mediate resistance to the development of life-threatening acute and chronic enterovirus myocarditis.

Animals↗
PubMedDate not supplied

Characteristics of a macrophage culture persistently infected with herpes simplex virus type 1.

BACKGROUND: Persistence of herpes simplex type 1 (HSV-1) has been reported in sensory neurons, corneal epithelium, and lymphocytes, although other cell types such as macrophages should also be considered as hosts for HSV-1 persistence. Here we report the establishment and characterization of HSV-1 persistence in an immortalized murine macrophage-like cell line (P388D1). METHODS: The persistently HSV-1 infected culture (P388D1per) was obtained from surviving P388D1 macrophages infected with HSV-1 MP strain at multiplicity of 0.001. P388D1per was characterized by [corrected] extracellular production of viruses, cells expressing viral antigens, and cells releasing infectious viruses. Viral plaque size and cytophatic effect were determined in viruses (HSVA and HSVB) obtained from two different P388D1per passages. Host and viral proteins were detected in P388D1per and in P388D1 cells infected with HSV-1 by metabolic [35S]-methionine labeling assays. RESULTS: P388D1per culture was characterized [corrected] by cyclic production of infectious viruses from non-detectable to 10(6) TCID50/mL, [corrected] from 1.0 to 15.0% cells expressing viral antigens and macrophages released infectious viruses from 0.008 to 12.5%. Differences in viral plaque size and cytopathic effect morphology between HSVA, HSVB and HSV-1 were observed. Similar patterns of viral proteins were observed in P388D1per and in P388D1 infected with HSV-1. Nonetheless, the characteristic interference effect of HSV-1 on host protein synthesis was not observed in P388D1per culture. CONCLUSIONS: An HSV-1 persistently infected immortalized macrophage culture was established and characterized. Virus produced during persistence showed phenotypic alterations with respect to the original virus. P388D1per cell protein synthesis was not affected by the presence of HSV-1.

Animals↗
PubMed1997

Non-specific musculoskeletal pain in preadolescents. Prevalence and 1-year persistence.

A 1-year follow-up study of 1756 third- and fifth-grade schoolchildren was conducted with a structured pain questionnaire to assess the prevalence and persistence of self-reported musculoskeletal pain symptoms and disability caused by pain. At follow-up, 1626 (92.7%) children participated in the study. Pain at least once a week persisted in 270 (52.4%) of the 564 children who reported musculoskeletal pain at least once a week in at least one part of the body at baseline. Of the regional pain symptoms, neck pain had highest persistence and, in girls, significantly more than in boys. Persistence of pain was not related to school grade. Widespread pain, determined as in the criteria for fibromyalgia, was found in 132 children (7.5%) and persisted in 35 children (29.7%, 95% CI 21.9-38.4) at follow-up. Disability was more severe in children with pain symptoms in more than one area. This study showed that about half of the preadolescents complaining of musculoskeletal pain at least once a week at baseline had persistent pain symptoms at follow-up. The prognosis of widespread pain in preadolescents was almost the same as the previous findings in adults.

Child↗
PubMed2001

Persistent sodium channel activity mediates subthreshold membrane potential oscillations and low-threshold spikes in rat entorhinal cortex layer V neurons.

Entorhinal cortex layer V occupies a critical position in temporal lobe circuitry since, on the one hand, it serves as the main conduit for the flow of information out of the hippocampal formation back to the neocortex and, on the other, it closes a hippocampal-entorhinal loop by projecting upon the superficial cell layers that give rise to the perforant path. Recent in vitro electrophysiological studies have shown that rat entorhinal cortex layer V cells are endowed with the ability to generate subthreshold oscillations and all-or-none, low-threshold depolarizing potentials. In the present study, by applying current-clamp, voltage-clamp and single-channel recording techniques in rat slices and dissociated neurons, we investigated whether entorhinal cortex layer V cells express a persistent sodium current and sustained sodium channel activity to evaluate the contribution of this activity to the subthreshold behavior of the cells. Sharp-electrode recording in slices demonstrated that layer V cells display tetrodotoxin-sensitive inward rectification in the depolarizing direction, suggesting that a persistent sodium current is present in the cells. Subthreshold oscillations and low-threshold regenerative events were also abolished by tetrodotoxin, suggesting that their generation also requires the activation of such a low-threshold sodium current. The presence of a persistent sodium current was confirmed in whole-cell voltage-clamp experiments, which revealed that its activation "threshold" was negative by about 10mV to that of the transient sodium current. Furthermore, stationary noise analysis and cell-attached, patch-clamp recordings indicated that whole-cell persistent sodium currents were mediated by persistent sodium channel activity, consisting of relatively high-conductance ( approximately 18pS) sustained openings. The presence of a persistent sodium current in entorhinal cortex layer V cells can cause the generation of oscillatory behavior, bursting activity and sustained discharge; this might be implicated in the encoding of memories in which the entorhinal cortex participates but, under pathological situations, may also contribute to epileptogenesis and neurodegeneration.

Action Potentials↗
PubMed2003

Linear accelerator-based stereotactic radiosurgery for limited, locally persistent, and recurrent nasopharyngeal carcinoma: efficacy and complications.

PURPOSE: To evaluate the efficacy and complication of linear accelerator-based stereotactic radiosurgery (SRS) when used as salvage treatment for early-stage persistent and recurrent nasopharyngeal carcinoma (NPC) after primary radiotherapy (RT). MATERIALS AND METHODS: Between March 1998 and June 2001, 18 patients (15 men and 3 women; median age 46 years, range 32-84) with locally persistent or recurrent NPC confined to the nasopharynx (rT1) or with limited extension to the nasal fossa or parapharyngeal space (rT2) were treated by SRS. Thirteen patients had rT1 disease and 5 had rT2 disease. Most patients had disease not amenable to surgery or brachytherapy. All patients had undergone previous radical RT. Persistent disease was defined as tumor relapse within 4 months of completion of primary RT, and recurrence as tumor relapse beyond 4 months. Seven patients were treated for persistent disease, eight for a first recurrence, and three for a second recurrence. SRS was performed using multiple noncoplanar arcs of photons delivered to the target volume, which was defined by axial CT at a 3 mm thickness, supplemented by MRI in selected patients (67%). The median target volume was 5.3 cm(3) (range 2.2-16.9). The median SRS dose was 12.5 Gy (range 11-14) delivered to the 80% isodose line. All patients underwent serial nasopharyngoscopy and imaging after SRS. The median follow-up was 26 months (range 11-48). RESULTS: After SRS, 16 (89%) of 18 patients had complete regression of tumor as assessed by nasopharyngoscopy and biopsy. Four patients with an initial complete response to SRS subsequently developed local relapse again, with one recurrence developing outside the target volume 8 months after SRS and three within the target volume at 6-26 months after SRS. Two patients with local disease controlled by SRS developed relapse in other sites (neck node and liver metastases). The actuarial 2-year local control rate after SRS was 72%. Patients treated for persistent disease had a better local control rate (100%; 7 of 7) than those treated for recurrent disease (46%; 5 of 11). Patients with rT1 disease also had a better outcome after SRS compared with those with rT2 disease, with a control rate of 77% (10 of 13) for rT1 disease and 40% (2 of 5) for rT2 disease. Treatments were well tolerated, with no acute side effects. One patient had radiologic evidence of temporal lobe necrosis, although the right temporal lobe had already received a high dose during prior RT. That patient also developed additional local recurrence and liver metastases and died. The actuarial 2-year survival rate was 86%. CONCLUSIONS: Our preliminary results indicate that SRS is an effective treatment modality for persistent and recurrent early-stage NPC, with early control rates comparable to other salvage treatments such as brachytherapy and nasopharyngectomy. A modest SRS dose at 12.5 Gy also appears to be effective and is associated with minimal morbidities. More clinical experience and longer follow-up are needed to validate our results and to address fully the role of SRS in salvaging local failures of NPC.

Adult↗
PubMed2001

Doxorubicin-induced persistent oxidative stress to cardiac myocytes.

We recently reported a cardioselective and cumulative oxidation of cardiac mitochondrial DNA (mtDNA) following subchronic administration of doxorubicin to rats. The mtDNA adducts persist for up to 5 weeks after cessation of doxorubicin treatment. Since the evidence suggests that this persistence of mtDNA adducts cannot be attributed to a lack of repair and replication, we investigated whether it might reflect a long-lasting stimulation of free radical-mediated adduct formation. Male Sprague-Dawley rats received weekly s.c. injections of either doxorubicin (2 mg/kg) or an equivalent volume of saline. Cardiac myocytes isolated from rats following 6 weekly injections of doxorubicin expressed a much higher rate of reactive oxygen species (ROS) formation compared to saline controls. This higher rate of ROS formation persisted for 5 weeks following the last injection. Associated with this was a persistent depression of GSH in heart tissue, while protein-thiol content was not markedly altered. These data suggest that the accumulation and persistence of oxidized mtDNA may be due, not to the stability of the adducts, but to some as yet undefined toxic lesion that causes long-lasting stimulation of ROS generation by doxorubicin. This persistent generation of ROS may contribute to the cumulative and irreversible cardiotoxicity observed clinically with the drug.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2002

Endocrine profiles of cows undergoing extended lactation in relation to the control of lactation persistency.

We conducted an experiment in dairy cows investigating the effects of calving season, milking frequency and nutrition on lactation persistency. Cows calved in the Spring (n=12) or Winter (n=12). Commencing in lactation week 9 one udder-half of each cow was milked thrice-daily and half of each calving group received additional concentrate at a fixed rate of 3kg per day above that of the control cows. As reported elsewhere, between lactation weeks 9 and 33 persistency (measured as the slope of decline in milk yield) was significantly improved by frequent milking (P<0.001), by calving in the Winter (P<0.001) and by additional concentrate (P<0.05). The cows were rebred after week 33. When analysis of persistency was extended up to week 20 of the recurring pregnancy only the frequency effect remained significant. Persistency was unaffected by the pregnancy up until pregnancy week 20 but was then greatly reduced (P<0.001). In this paper we report hormone concentrations. GH was unaffected by nutrition but was consistently elevated in the Winter calving group relative to the Spring. IGF1 and prolactin were both unaffected by nutrition and calving season, IGF1 tended to increase as lactation progressed but changes in prolactin were related to time of year more than stage of lactation. Insulin was not affected by nutrition and was lower in Winter calvers, but only during early lactation. Prior to rebreeding, lactation persistency was correlated (slightly) with [GH] but not with [IGF1] or [insulin] and was correlated significantly with changes in GH, IGF1 (both positive) and insulin (negative). In conclusion, whilst bovine lactation persistency is plastic and amenable to beneficial manipulation, the details of its endocrine control remain to be elucidated.

Animals↗
PubMed2002

Molecular bases of long-term memories: a question of persistence.

The most distinctive attribute of long-term memory is persistence over time. New studies have uncovered many aspects of the molecular and cellular biology of synaptic plasticity, and the acquisition and consolidation of memory, which are thought to depend on synaptic plasticity. Much less, however, is known about the molecular and cellular biology of long-term memory persistence. Recent findings in the field are construed within the conceptual framework that proposes that consolidation and persistence of long-term memories require modulation of gene expression, which can culminate in synaptic remodeling. Whether modulation of gene expression, and particularly the ensuing morphological plasticity of the synapse, is permissive, causal or sufficient for the materialization and persistence of the long-term trace is, as yet, undetermined. How persistent is persistence? Renewed interest is focused on the possibility that some long-term memories consolidate anew with retrieval, and could, under certain conditions, become transiently shaky in this period of reconsolidation.

Animals↗