Starting DNA Synthesis: Initiation Processes during the Replication of Chromosomal DNA in Humans.

The initiation reactions of DNA synthesis are central processes during human chromosomal DNA replication. They are separated into two main processes: the initiation events at replication origins, the start of the leading strand synthesis for each replicon, and the numerous initiation events taking place during lagging strand DNA synthesis. In addition, a third mechanism is the re-initiation of DNA synthesis after replication fork stalling, which takes place when DNA lesions hinder the progression of DNA synthesis. The initiation of leading strand synthesis at replication origins is regulated at multiple levels, from the origin recognition to the assembly and activation of replicative helicase, the Cdc45-MCM2-7-GINS (CMG) complex. In addition, the multiple interactions of the CMG complex with the eukaryotic replicative DNA polymerases, DNA polymerase α-primase, DNA polymerase δ and ε, at replication forks play pivotal roles in the mechanism of the initiation reactions of leading and lagging strand DNA synthesis. These interactions are also important for the initiation of signalling at unperturbed and stalled replication forks, "replication stress" events, via ATR (ATM-Rad 3-related protein kinase). These processes are essential for the accurate transfer of the cells' genetic information to their daughters. Thus, failures and dysfunctions in these processes give rise to genome instability causing genetic diseases, including cancer. In their influential review "Hallmarks of Cancer: New Dimensions", Hanahan and Weinberg (2022) therefore call genome instability a fundamental function in the development process of cancer cells. In recent years, the understanding of the initiation processes and mechanisms of human DNA replication has made substantial progress at all levels, which will be discussed in the review.

Replication Protein A, the Main Eukaryotic Single-Stranded DNA Binding Protein, a Focal Point in Cellular DNA Metabolism.

Replication protein A (RPA) is a heterotrimeric protein complex and the main single-stranded DNA (ssDNA)-binding protein in eukaryotes. RPA has key functions in most of the DNA-associated metabolic pathways and DNA damage signalling. Its high affinity for ssDNA helps to stabilise ssDNA structures and protect the DNA sequence from nuclease attacks. RPA consists of multiple DNA-binding domains which are oligonucleotide/oligosaccharide-binding (OB)-folds that are responsible for DNA binding and interactions with proteins. These RPA-ssDNA and RPA-protein interactions are crucial for DNA replication, DNA repair, DNA damage signalling, and the conservation of the genetic information of cells. Proteins such as ATR use RPA to locate to regions of DNA damage for DNA damage signalling. The recruitment of nucleases and DNA exchange factors to sites of double-strand breaks are also an important RPA function to ensure effective DNA recombination to correct these DNA lesions. Due to its high affinity to ssDNA, RPA's removal from ssDNA is of central importance to allow these metabolic pathways to proceed, and processes to exchange RPA against downstream factors are established in all eukaryotes. These faceted and multi-layered functions of RPA as well as its role in a variety of human diseases will be discussed.

Transitive inference after minimal training in rhesus macaques (Macaca mulatta).

Rhesus macaques, when trained for several hundred trials on adjacent items in an ordered list (e.g., A > B, B > C, C > D), are able to make accurate transitive inferences (TI) about previously untrained pairs (e.g., A > C, B > D). How that learning unfolds during training, however, is not well understood. We sought to measure the relationship between the amount of TI training and the resulting response accuracy in 4 rhesus macaques using seven-item lists. The training conditions included the absolute minimal case of presenting each of the six adjacent pairs only once prior to testing. We also tested transfer to nonadjacent pairs with 24 and 114 training trials. Because performance during and after small amounts of training is expected to be near chance levels, we developed a descriptive statistical model to estimate potentially subtle learning effects in the presence of much larger random response variability and systematic bias. These results suggest that subjects learned serial order in an incremental fashion. Thus, rather than performing transitive inference by a logical process, serial learning in rhesus macaques proceeds in a manner more akin to a statistical inference, with an initial uncertainty about list position that gradually becomes more accurate as evidence accumulates. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Safety evaluation of a clinical focused ultrasound system for neuronavigation guided blood-brain barrier opening in non-human primates.

An emerging approach with potential in improving the treatment of neurodegenerative diseases and brain tumors is the use of focused ultrasound (FUS) to bypass the blood-brain barrier (BBB) in a non-invasive and localized manner. A large body of pre-clinical work has paved the way for the gradual clinical implementation of FUS-induced BBB opening. Even though the safety profile of FUS treatments in rodents has been extensively studied, the histological and behavioral effects of clinically relevant BBB opening in large animals are relatively understudied. Here, we examine the histological and behavioral safety profile following localized BBB opening in non-human primates (NHPs), using a neuronavigation-guided clinical system prototype. We show that FUS treatment triggers a short-lived immune response within the targeted region without exacerbating the touch accuracy or reaction time in visual-motor cognitive tasks. Our experiments were designed using a multiple-case-study approach, in order to maximize the acquired data and support translation of the FUS system into human studies. Four NHPs underwent a single session of FUS-mediated BBB opening in the prefrontal cortex. Two NHPs were treated bilaterally at different pressures, sacrificed on day 2 and 18 post-FUS, respectively, and their brains were histologically processed. In separate experiments, two NHPs that were earlier trained in a behavioral task were exposed to FUS unilaterally, and their performance was tracked for at least 3 weeks after BBB opening. An increased microglia density around blood vessels was detected on day 2, but was resolved by day 18. We also detected signs of enhanced immature neuron presence within areas that underwent BBB opening, compared to regions with an intact BBB, confirming previous rodent studies. Logistic regression analysis showed that the NHP cognitive performance did not deteriorate following BBB opening. These preliminary results demonstrate that neuronavigation-guided FUS with a single-element transducer is a non-invasive method capable of reversibly opening the BBB, without substantial histological or behavioral impact in an animal model closely resembling humans. Future work should confirm the observations of this multiple-case-study work across animals, species and tasks.

Developing a guidance resource for managing delirium in patients with COVID-19.

As the COVID-19 pandemic escalates worldwide, it is apparent that many patients with more severe illness will also experience delirium. These patients pose a particular challenge in the application of optimal care due to issues with infectious risk, respiratory compromise and potential interactions between medications that can be used to manage delirium with antiviral and other treatments used for COVID-19. We describe a guidance resource adapted from existing guidelines for delirium management that has been tailored to the specific challenge of managing delirium in patients with COVID-19 infection. Issues around the assessment and treatment of these patients are examined and distilled into a simple (one-paged guidance resource that can assist clinicians in managing suspected delirium.

Comparison of cognitive and neuropsychiatric profiles in hospitalised elderly medical patients with delirium, dementia and comorbid delirium-dementia.

OBJECTIVES: Differentiation of delirium and dementia is a key diagnostic challenge but there has been limited study of features that distinguish these conditions. We examined neuropsychiatric and neuropsychological symptoms in elderly medical inpatients to identify features that distinguish major neurocognitive disorders. SETTING: University teaching hospital in Ireland. PARTICIPANTS AND MEASURES: 176 consecutive elderly medical inpatients (mean age 80.6 ± 7.0 years (range 60-96); 85 males (48%)) referred to a psychiatry for later life consultation-liaison service with Diagnostic and Statistical Manual of Mental Disorders (DSM) IV delirium, dementia, comorbid delirium-dementia and cognitively intact controls. Participants were assessed cross-sectionally with comparison of scores (including individual items) for the Revised Delirium Rating Scale (DRS-R98), Cognitive Test for Delirium (CTD) and Neuropsychiatric Inventory (NPI-Q). RESULTS: The frequency of neurocognitive diagnoses was delirium (n=50), dementia (n=32), comorbid delirium-dementia (n=62) and cognitively intact patients (n=32). Both delirium and comorbid delirium-dementia groups scored higher than the dementia group for DRS-R98 and CTD total scores, but all three neurocognitively impaired groups scored similarly in respect of total NPI-Q scores. For individual DRS-R98 items, delirium groups were distinguished from dementia groups by a range of non-cognitive symptoms, but only for impaired attention of the cognitive items. For the CTD, attention (p=0.002) and vigilance (p=0.01) distinguished between delirium and dementia. No individual CTD item distinguished between comorbid delirium-dementia and delirium. For the NPI-Q, there were no differences between the three neurocognitively impaired groups for any individual item severity. CONCLUSIONS: The neurocognitive profile of delirium is similar with or without comorbid dementia and differs from dementia without delirium. Simple tests of attention and vigilance can help to distinguish between delirium and other presentations. The NPI-Q does not readily distinguish between neuropsychiatric disturbances in delirium versus dementia. Cases of suspected behavioural and psychological symptoms of dementia should be carefully assessed for possible delirium.

Neuropsychiatric and cognitive profile of patients with DSM-IV delirium referred to an old age psychiatry consultation-liaison service.

BACKGROUND: The phenomenology of delirium is understudied, including how the symptom profile varies across populations. The aim of this study was to explore phenomenology occurring in patients with delirium referred to an old age psychiatry consultation-liaison setting and compare with delirium occurring in palliative care patients. METHODS: Consecutive cases of DSM-IV delirium were assessed with the Delirium Rating scale Revised-98 (DRS-R98) and Cognitive Test for Delirium (CTD). RESULTS: Eighty patients (mean age 79.3 ± 7.7 years; mean DRS-R98 total score 21.7 ± 4.9 and total CTD score 10.2 ± 6.3) were included. Forty patients (50%) with comorbid dementia were older, had a longer duration of symptoms at referral, and more severe delirium due to greater cognitive impairments. Inattention (100%) was the most prominent cognitive disturbance, while sleep-wake cycle disturbance (98%), altered motor activity (97%), and thought process abnormality (96%) were the most frequent DRS-R98 non-cognitive features. Inattention was associated with severity of other cognitive disturbances on both the DRS-R98 and CTD, but not with DRS-R98 non-cognitive items. The phenomenological profile was similar to palliative care but with more severe delirium due to greater cognitive and non-cognitive disturbance. CONCLUSION: Delirium is a complex neuropsychiatric syndrome with generalized cognitive impairment and disproportionate inattention. Sleep-wake cycle and motor-activity disturbances are also common. Comorbid dementia results in a similar phenomenological pattern but with greater cognitive impairment and later referral.

Bone mineral density and its relationship to prolactin levels in patients taking antipsychotic treatment.

Antipsychotic treatment is frequently associated with elevated prolactin levels. Raised prolactin levels have been linked with osteoporosis. The objective of this study is to determine whether patients taking antipsychotics show reduced bone mineral density (BMD), and whether this is associated with prolactin levels. BMD (standardized as z scores) was compared using dual x-ray absorptiometry of the lumbar spine and hip in patients taking antipsychotics (n = 102, mean age: 46.0, SD: 13.1, 47% male, median treatment duration: 3.0 years) to matched reference controls. Levels of prolactin, markers of bone metabolism, and risk factors for osteoporosis were measured. Mean BMD was not significantly reduced, other than the total spine score for black males (mean z score: -0.88, P = 0.00001). BMD was correlated with body mass index but there was no correlation with prolactin. BMD was not correlated with prolactin levels and showed no clinically significant reduction. The low BMD in black males warrants further investigation.

Antipsychotic drugs: a new risk factor for osteoporosis in young women with schizophrenia?

Schizophrenic illness is associated with high rates of osteoporosis, the etiology of which remains obscure, but which may be at least partly explained by the prolactin-raising properties of antipsychotic medication. Conventional antipsychotics all cause hyperprolactinemia, whereas a limited number of atypical antipsychotic drugs do not. To investigate this further, we designed a cross-sectional comparison study between groups taking either prolactin-raising or prolactin-sparing antipsychotic medication. Participants were required to be premenopausal women with a diagnosis of schizophrenia, and to have received exclusively either prolactin-raising (n = 26), or olanzapine (n = 12) antipsychotic medication. Half of the subjects in the prolactin-raising group were being treated with conventional (n = 13), and half with newer "atypical," antipsychotic drugs (n = 13). Subjects had lumbar spine and hip bone mineral density (BMD) evaluated by a dual-energy x-ray absorptiometer (DEXA) scan. A blood sample was taken to measure prolactin and sex hormone axis measures. The results demonstrated that the group taking prolactin-raising medication had higher rates of bone pathology, compared with the olanzapine group. High prolactin levels were related to measures of hypogonadism and low BMD values. Within the prolactin-raising group, those taking newer atypical compounds had higher levels of prolactin, lower levels of sex hormones, and lower BMD values than the group taking conventional antipsychotic medication. These findings suggest that the high rates of osteoporosis associated with schizophrenia may result from hypogonadism secondary to antipsychotic-induced hyperprolactinemia, and that the prolactin-raising profile of antipsychotic drugs should be considered when choosing an antipsychotic drug.

An audit of psychotropic prescribing practice of general adult psychiatrists in elderly demented patients.

OBJECTIVES: In Ireland elderly patients with behavioural and psychological symptoms of dementia (BPSD) are frequently prescribed anti-psychotic and other psychotropic agents. Elderly patients with dementia are more sensitive to adverse effects of medications. Despite this, little is known of the psychotropic prescribing practice of psychiatrists who treat this population. General adult psychiatrists in the Republic of Ireland continue to treat elderly patients with BPSD. The aim of this audit was to identify the prescribing practice of general adult psychiatrists in elderly patients with BPSD. We compare this practice to that of old age psychiatrists in the UK and that recommended by the American Psychiatric Association in 1997. METHODS: We devised a structured anonymous questionnaire, which was forwarded to all general adult psychiatrists in the Republic of Ireland. RESULTS: Atypical anti-psychotics are frequently prescribed by general adult psychiatrists to manage BPSD in elderly patients. The anti-psychotic agent of first preference chosen to treat psychotic symptoms in dementia is risperidone. Overall, sedative typical anti-psychotics are still the most frequently chosen anti-psychotic agents, chosen to manage behavioural symptoms in dementia. Benzodiazepines and trazadone are the most frequently prescribed other psychotropic agents chosen to manage agitated behaviour. In general the median doses of antipsychotics and other psychotropic medication used are in keeping with both the APA guidelines and practice of old age psychiatrists in the UK. A minority of practitioners (10%) specified at least one dosage regime that was grossly outside recommended ranges. CONCLUSIONS: Overall, prescribing practice in terms of choice of treatment and dosage regime, of general adult psychiatrists in BPSD is in keeping with the best practice guidelines. However, sedating typical anti-psychotics and on occasion extraordinarily high doses of anti-psychotics are still prescribed.

Reduced bone mineral density in patients with schizophrenia receiving prolactin raising anti-psychotic medication.

Patients with schizophrenia frequently develop drug-induced hyperprolactinaemia and consequent hypogonadism. Reduced bone mineral density as a consequence of hyperprolactinaemia-induced hypogonadism has been well documented in medical, but not psychiatric, disorders. Little attention has been given to the potential risk of developing osteoporosis secondary to anti-psychotic-induced hyperprolactinaemia. Three cases are presented that illustrate how this debilitating but silent disease may affect even those young individuals with schizophrenia.

Prolactin and schizophrenia: clinical consequences of hyperprolactinaemia.

Prolactin is a polypeptide hormone that is synthesized and secreted from specialised cells of the anterior pituitary gland, known as lactotrophs. The hormone was given it's name because extracts from the bovine pituitary gland caused growth of the crop sac and stimulated the elaboration of crop milk in pigeons, and promoted lactation in rabbits. Although prolactin is best known for the multiple effects it exerts on the mammary gland, it has over 300 separate biological activities not represented by its name. It sub serves multiple roles in reproduction other than lactation and is an important modulator of homeostasis in the mammalian organism. Hence Bern and Nicoll suggested renaming it "omnipotin or versatilin". Schizophrenia is a severe psychiatric disorder that affects approximately one percent of the population worldwide. It is well established that traditional typical anti-psychotics elevate prolactin levels. It is also agreed that the serum prolactin concentration is not elevated in patients with schizophrenia who are not receiving anti-psychotic medication. Hyperprolactinaemia has direct effects on the brain and on other organs. Direct consequences include galactorrhoea. Indirect consequences of hyperprolactinaemia include oligomenorrhoea and amenorrhoea, erratic or absent ovulation, sexual dysfunction, reduced bone mineral density and cardiovascular disease. With the advent of prolactin sparing anti-psychotics, ample consideration needs to be given to the physiological consequences of hyperprolactinaemia in schizophrenic patients. In this paper we will examine molecular biology, secretion and physiology of prolactin. The consequences of hyperprolactinaemia in humans including effects on fertility, sexual dysfunction, bone mineral density, cardiovascular disease, changes in psychopathology and movement disorders will be reviewed. The literature on the association between schizophrenia, anti-psychotic medication and hyperprolactinaemia and more specifically on the consequences of this hyperprolactinaemia in schizophrenic patients will also be reviewed.