Emerging Trends in Complications Associated with SARS-CoV-2 Infection

The coronavirus disease 2019 (COVID-19) pandemic has presented a remarkable challenge to global health, sparking a surge in research aimed at understanding the multifaceted impacts of the virus [...].

Chorea following SARS-CoV-2 infection and vaccination: a systematic review of reported cases

OBJECTIVES

Chorea following SARS-CoV-2 infection and vaccination, has been increasingly recognized. We aimed to synthesize clinical and paraclinical characteristics, treatment responses, and outcomes of this neurologic complication.

METHODS

We systematically reviewed LitCOVID, the World Health Organization database on COVID-19, and MedRxiv up to March 2023, following a published protocol.

RESULTS

We included 14 chorea cases in patients with SARS-CoV-2 infection and eight following COVID-19 vaccination. Acute or subacute chorea preceded COVID-19 symptoms within 1-3 days or developed up to 3 months after infection. Frequently it was generalized (85.7%), with associated neurological manifestations (encephalopathy 35.7%; other movement disorders 7.1%). After vaccination, chorea had a sudden onset (87.5%) within 2 weeks (75%); 87.5% of cases presented hemichorea, with hemiballismus (37.5%) or other movement disorders; 12.5% presented additional neurological findings. Cerebrospinal fluid was normal in 50% of infected individuals but abnormal in all vaccinated cases. Brain magnetic resonance imaging detected normal basal ganglia in 51.7% of infection cases and 87.5% following vaccination.

CONCLUSION

In SARS-CoV-2 infection, chorea may present several pathogenic mechanisms: autoimmune response to infection, direct infection-related injury, or an infection-related complication (i.e., acute disseminated encephalomyelitis, cerebral venous sinus thrombosis, hyperglycemia); also, previous Sydenham chorea may relapse. After COVID-19 vaccination, chorea could be due to an autoimmune reaction or other mechanisms (vaccine-induced hyperglycemia, stroke).

Assessment and Diagnosis of HIV-Associated Dementia

The modern combined antiretroviral treatment (cART) for human immunodeficiency virus (HIV) infection has substantially lowered the incidence of HIV-associated dementia (HAD). The dominant clinical features include deficits in cognitive processing speed, concentration, attention, and memory. As people living with HIV become older, with high rates of comorbidities and concomitant treatments, the prevalence and complexity of cognitive impairment are expected to increase. Currently, the management of HAD and milder forms of HAND is grounded on the best clinical practice, as there is no specific, evidence-based, proven intervention for managing cognitive impairment. The present article acknowledges the multifactorial nature of the cognitive impairments found in HIV patients, outlining the current concepts in the field of HAD. Major areas of interest include neuropsychological testing and neuroimaging to evaluate CNS status, focusing on greater reliability in the exclusion of associated diseases and allowing for earlier diagnosis. Additionally, we considered the evidence for neurological involvement in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the impact of the coronavirus (COVID-19) pandemic, with wider consequences to population health than can be attributed to the virus itself. The indirect effects of COVID-19, including the increased adoption of telehealth, decreased access to community resources, and social isolation, represent a significant health burden, disproportionately affecting older adults with dementia who have limited social networks and increased functional dependence on the community and health system. This synopsis reviews these aspects in greater detail, identifying key gaps and opportunities for researchers and clinicians; we provide an overview of the current concepts in the field of HAD, with suggestions for diagnosing and managing this important neurological complication, which is intended to be applicable across diverse populations, in line with clinical observations, and closely representative of HIV brain pathology.

Wernicke Encephalopathy Presenting with Dysphagia: A Case Report and Systematic Literature Review

Wernicke encephalopathy (WE) is a well-known neurological condition caused by thiamine (vitamin B1) deficiency that occurs in both alcoholic and non-alcoholic populations. We aimed to report a case of a patient with WE who presented with dysphagia and dysphonia and later developed typical symptoms of thiamine deficiency and to conduct a systematic review of the literature on this rare presentation of WE. We searched two databases (PubMed and Scopus) and included publications up to November 2022. We found 12 cases of WE and dysphagia, aged between 12 and 81 years; swallowing problems presented at the onset in nine patients (including the current case report). Our findings suggest that thiamine deficiency should be suspected in patients with dysphagia of unknown cause, even in the absence of alcohol abuse. In contrast to most WE patients, the majority of patients included in this review presented with dysphagia at the onset of their disease, even in the absence of the classic triad of cognitive impairment, ataxia, and oculomotor abnormalities, indicating that there could be varying susceptibilities to clinical manifestations of thiamine deficiency in different brain regions.

Montreal Cognitive Assessment for Evaluating Cognitive Impairment in Subarachnoid Hemorrhage: A Systematic Review

Subarachnoid hemorrhage (SAH) is a severe condition with high mortality and extensive long-term morbidity. Although research has focused mainly on physical signs and disability for decades, in recent years, it has been increasingly recognized that cognitive and psychological impairments may be present in many patients with SAH, negatively impacting their quality of life. We performed a systematic review aiming to provide a comprehensive report on the diagnostic accuracy of the Montreal Cognitive Assessment (MoCA) test for evaluating the presence of cognitive impairment in patients with SAH. Using appropriate search terms, we searched five databases (PubMed, Scopus, PsychINFO, Web of Sciences, and Latin American and Caribbean Health Sciences Literature) up to January 2022. Two cross-sectional studies investigated the accuracy of MoCA in SAH patients in the subacute and chronic phase. We appraised the quality of the included studies using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) criteria. The MoCA test provides information about general cognitive functioning disturbances. However, a lower threshold than the original cutoff might be needed as it improves diagnostic accuracy, lowering the false positive rates. Further research is necessary for an evidence-based decision to use the MoCA in SAH patients.

International HIV Dementia Scale for HIV-Associated Neurocognitive Disorders: A Systematic Review and Meta-Analysis

The present study aims to systematically review the evidence on the accuracy of the International HIV Dementia Scale (IHDS) test for diagnosing human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) and outline the quality and quantity of research evidence available on the accuracy of IHDS in people living with HIV. We conducted a systematic literature review, searching five databases from inception until July 2020. We extracted dichotomized positive and negative test results at various thresholds and calculated the sensitivity and specificity of IHDS. Quality assessment was performed according to the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) criteria. Fifteen cross-sectional studies, published between 2011 and 2018, met the inclusion criteria for meta-analysis. Overall, 3760 patients were included, but most studies recruited small samples. We assessed most studies as being applicable to the review question, though we had concerns about the selection of participants in three studies. The accuracy of IHDS was investigated at thirteen cut-off points (scores 6-12). The threshold of 10 is the most useful for optimal HAND screening (including asymptomatic neurocognitive disorder, symptomatic HAND, and HIV-associated dementia) with fair diagnostic accuracy.

Parkinson's Disease in Romania: A Scoping Review

Parkinson's disease (PD) is a significant cause of disability, with a fast-growing prevalence. This review summarizes the epidemiological and clinical data, research on the diagnostic approaches and the interventions available in the Eastern European country of Romania. This scoping review follows the recommendations on the scoping review methodology by Joanna Briggs Institute. We searched four databases (up to 27 January 2021). The data of eligible studies were extracted in standardized forms. We identified 149 unique studies from 1133 records, with 11 epidemiological studies, 52 studies investigating clinical aspects of PD, 35 studies on diagnostic tools, and 51 intervention studies. A narrative synthesis is provided and placed in a historical context. Our review revealed a considerable increase in the Romanian research on PD in the latest 15 years, which largely follows international trends. However, we also identified several research gaps that provide useful information for policymakers, public health specialists, and clinicians.

Central Nervous System Involvement in Trichinellosis: A Systematic Review

We reviewed the evidence on features of central nervous system (CNS) involvement in trichinellosis, systematically searching five databases (to January 2021). We categorized clinical features based on their diagnostic value as warning signs for severe CNS infection (with outcome death) or non-specific signs (outcome improvement). They were suggestive of severe infection if they substantially raised death probability. The review included 87 papers published from 1906 through 2019, with data on 168 patients. Mydriasis, paraparesis, dysphagia, psychomotor seizures, or delirium present a 30-45% increased death likelihood. The best poor prognosis predictor is mydriasis (positive likelihood ratio 9.08). Slow/absent light reflex, diminished/absent knee reflexes, globally decreased tendon reflexes present a moderate increase (20-25%) of death risk. Anisocoria, acalculia, or seizures could also indicate an increased death risk. We provided a detailed presentation of clinical and paraclinical signs that alert physicians of a possible neurotrichinellosis, emphasizing signs that might indicate a poor prognosis.

Additional factors to corelate with a more than 30% NIHSS score improvement in patients 7 days after fibrinolytic and/or endovascular treatment for ischemic stroke

Background

Our objective was to find which additional factors can influence the favorable result in stroke patients after receiving fibrinolytic and/or endovascular treatment, quantified as a more than 30% improvement of the NIHSS score at 7 days.

Methods

This is a retrospective study to find factors that could influence a favorable evolution of patients with stroke that underwent fibrinolytic and or thrombectomy using the NIHSS score changes. At the admission in the hospital, blood glucose, blood count, coagulation time, INR, aPTT, PT, platelet count, NIHSS questionnaire and ASPECTS score were collected. NIHSS was assessed at the admission, after 1 h, after 2 h, after 24 h and after 7 days.

Results

As compared to the initial evaluation, at 7 days after admission 59% (72) of patients have improved with more than 30% the NIHSS. Higher levels of systolic blood pressure, glycemia and lower ASPECTS score at admission were observed in non-achievers. The value of INR contributed to model: for every unit increase of INR, the chance of better outcome decreases by 90,1%. High glycemia has also a negative impact: for every unit increase, the chance of better outcome decreases by 24%. Higher initial ASPECTS score is associated with better outcomes: each point increase of ASPECTS score at initial evaluation, increases the chance of better outcome by 154.2%.

Conclusion

Males, older age, diabetes, and hyperglycemia correlate with a worse outcome after cerebral stroke regardless of the benefit yielded fibrinolytic and/or thrombectomy therapy. In this study, patients with the above-mentioned factors did not improve more than 30% of baseline NIHSS score from admission to the 7th day.

Levodopa-Carbidopa Intestinal Gel Infusion Therapy Discontinuation: A Ten-Year Retrospective Analysis of 204 Treated Patients

BACKGROUND

Parkinson's disease (PD) is the second most common progressive neurodegenerative disease. In the advanced stages, the continuous delivery of levodopa (LD) as levodopa-carbidopa intestinal gel (LCIG) has demonstrated significant improvement of motor and nonmotor complications and improvement of the patients' quality of life (QoL). Despite the growing global experience with this treatment, anumber of unsolved practical issues remain, and currently, the data on the reasons that can lead to the discontinuation of LCIG are scarce.

OBJECTIVE

In the present study, we aimed to analyze the causes that led to the discontinuation of LCIG therapy.

METHODS

In this retrospective study, after 10 years of experience with LCIG as a therapeutic option in advanced PD, we analyzed the data of all dropout cases among the 204 patients that initiated LCIG therapy in two Romanian centers.

RESULTS

Of the 204 patients enrolled, 43 patients dropped out. Disease duration until LCIG infusion was significantly longer (11.67±4.98 vs 9.44±3.44) and the overall clinical picture more sever (both regarding motor symptoms and cognitive decline) in dropout patients (compared to patients who continued treatment). The dropout patients also presented significant differences regarding the incidence of polyneuropathy (32.5% vs 11.18%). The main cause of discontinuation was death.

CONCLUSION

The causes of discontinuation from LCIG therapy in Romanian patients are similar to those from other centers; however, the rate of dropouts is somewhat lower. The clinician's experience in selecting and treating the patients in advanced stages of PD can increase therapeutic adherence. Also, the presence of a well-trained caregiver along with the availability of a proper aftercare system is mandatory for maintaining the long-term benefits of the therapy and the overall best outcome possible. Targeted prospective studies are needed to confirm whether a more severe stage of the disease and cognitive impairment at the time of initiation, respectively, the association of polyneuropathy can be considered as predictive factors for dropout.

Montreal Cognitive Assessment for evaluating the cognitive impairment in patients with schizophrenia: A systematic review

OBJECTIVE

This study aims to systematically review the evidence on the accuracy of the Montreal Cognitive Assessment (MoCA) test for evaluating the presence of cognitive impairment in patients with schizophrenia and to outline the quality and quantity of research evidence available about the accuracy of MoCA in this population.

METHODS

We conducted a systematic literature review, searching four databases from inception until April 2020.

RESULTS

We identified only three cross-sectional studies, two case - control studies, three studies comparing MoCA with Mini-Mental State Examination (MMSE) and four prevalence studies that met the inclusion criteria. Publication period ranged from 2012 to 2020.

CONCLUSIONS

In patients with schizophrenia, the MoCA test provides information about general cognitive functioning disturbances. A lower threshold than the original cut-off of 26 is probably more useful for optimal screening, as it lowers false positive rates and improves diagnostic accuracy. Nonetheless, more studies are necessary in this direction.

THE PREVALENCE AND CLINICAL PROFILE OF MULTIPLE SCLEROSIS IN TIMIS COUNTY, ROMANIA

Introduction. Multiple sclerosis is a neurodegenerative disease for which correct prevalence and incidence data are mandatory to assess the long term health policy in terms of social and economic burden. The present study aims to evaluate the prevalence of MS and the distribution of clinical MS forms in Timis County, a region inhabited by 3.39% of the Romanian stable population according to the 2011 Romanian census, and is meant as a sample of the national situation. There have been no previous attempts to assess the MS prevalence status in Timis County. Material and methods. This study was conducted in a well-defined geographical area (i.e. the Timis County which lies in the Western region of Romania) exploring the prevalence of MS and the patients’ clinical profile. The information regarding MS patients was obtained using hospital records and the files of the patients treated and followed up in the Romanian National MS Program for treatment of MS. Results. The crude calculated prevalence was 53.6 per 100,000 inhabitants. The F:M ratio was 1.7 corresponding to a number of 220 (65.4%) females and 116 (34.5%) males. Discussions. This study is the first attempt to estimate the prevalence of multiple sclerosis in Timis County as part of an ongoing project of the National Romanian Society of Neurology to build up the Romanian MS Registry and our results indicate higher prevalence values than expected, fact due to an increased diagnostic accuracy provided by clear cut diagnosis criteria and MRI standardized magnetic resonance imagery procedures currently available.

MS TREATMENT OPTIMIZATION: FACTORS ASSOCIATED WITH POOR CLINICAL RESPONSE IN NAB POSITIVE PATIENTS

Background and purpose. Interferon beta (IFN beta) belongs to the first line of disease modifying therapy drugs in the treatment of relapsing-remitting multiple sclerosis being widely used in the chronic treatment of this pathology. The serum presence of the neutralizing antibodies (Nabs) has been shown to alter the treatment response, its routine applicability being still debated. In an observational study, we aimed to determine in the Nabs positive patients, correlations with other clinical factors which contribute to IFN beta decreased efficacy. Methods. We measured Nabs in 104 patients who were on IFN beta therapy (29.8% on IFN beta 1a s.c., 27.88% on IFN beta 1a i.m. and 42,3 on IFN beta 1b s.c.) for at least one year in our clinic. Serum was collected at 24 h after treatment injection to avoid transitory antibody peak (12-18 h post administration). We considered positive the patients with a titer higher than 20 TRU. Results. The prevalence of Nabs in our group of patients was 13.43% (42.85% IFN Beta 1b s.c., 50% IFN beta 1a s.c. and 7.14% IFN beta 1 a i.m.). Nabs positivity was associated with an increase in the relapse rate (for IFB beta 1a and 1b s.c. groups) and progression for IFN beta 1 b s.c. patient group. Conclusions. The routine clinical testing for Nabs should impact the clinical decision of switching therapy in multiple sclerosis patients that present with an increased number of relapses, EDSS progression or a higher number of MRI T2 lesions.

THE EPIDEMIOLOGY OF MULTIPLE SCLEROSIS IN ROMANIA AND ACROSS CENTRAL AND SOUTHEASTERN EUROPE – A HISTORICAL REVIEW

Background. Multiple sclerosis (MS) has a variable clinical and pathological course and pace, which eventually turns over years of that progression into a major source of disability especially among young adults. The regional incidence and prevalence data course are of utmost interest (i.e they tend to be higher in Europe within the last decade) mirroring diagnosis improvement, earlier and better treatment choices and an improved physio-pathological insight as shown by most recent studies. (1) The incidence and prevalence data tend to be higher in Europe within the last decade and are explained by diagnosis improvement and earlier and better treatment solutions for the patients mirrored by most recent studies. (1) The objective of the present study is to assess data available concerning the prevalence of multiple sclerosis in Romania and in Central and Southeastern Europe in a regional view. Material and method. A literature search has been performed in PubMed, DIMDI, Web of Science, and Google Scholar to retrieve population based studies in Central and Eastern Europe and epidemiological reviews through years 1960-2015. We searched the term “MS” combined with one of the following: “epidemiology” or “incidence” or “prevalence”. We also did a manual search of reference list of the relevant articles. Results. 38 studies met the inclusion criteria and were analyzed. The epidemiologic data available for Central and Eastern Europe during the period 1960-2015 support the heterogeneity both of this region’s resident population and of the studies design, making any global data assessment difficult, with a questionable reliability, therefore justifying a newer reappraisal.

Clinical, morphological and immunohistochemical characterization of a recurrent B1 type thymoma

Type B1 thymoma is widely accepted as a tumor with a non-aggressive behavior even in advanced stage. Most of these tumors are classified as Masaoka stage I or II. They rarely relapse or metastasize and the surgical treatment is considered curative. We have investigated a case of thymoma type B1, which relapsed 13 months after the primary tumor was excised. The patient was diagnosed with a local tumor recurrence after investigations due to the worsening of clinical symptoms of myasthenia gravis (MG). The therapy management of such cases is debatable and protocols not yet approved. For this reason, we have analyzed different clinical, morphological and immunohistochemical characteristics that may be considered as prognostic factors for a more aggressive behavior of such tumors. We have identified some morphologic characteristics rarely seen in this type of thymoma but none considered of prognostic value. In addition, we investigated some possible immunohistochemical markers that are generally associated with a more aggressive clinical outcome in different malignant tumors and thymic epithelial tumors. Among these markers, only p53 was positive and may be useful to predict a more aggressive evolution. In summary, probably the more appropriate approach of the patient is the clinical follow-up together with treatment of the clinical symptoms of myasthenia gravis.

Knocking-down the NMDAR1 subunit in a limited amount of neurons in the rat hippocampus impairs learning

Amplicon vectors derived from herpes simplex virus type 1 were built to modify NMDA receptors by expressing antisense RNA for the essential NR1 subunit. Their ability to modify endogenous levels of NR1 was tested in cultures of rat embryo neocortical neurons. We studied behaviour and tested for expression in adult rats injected with those vectors into the dorsal hippocampus to find out which cells and how many appear involved in memory formation. Rats injected with vectors expressing NR1 antisense performed significantly worse than control rats in an inhibitory avoidance task. Immunohistochemistry was performed in brain slices from the same animals. The transduced cells represented 6-7% of pyramidal neurons in CA1, showing that a single gene knockdown of NR1 in a small number of neurons significantly impaired memory formation. Perhaps neurons undergoing synaptic plasticity are more susceptible to NR1 knockdown, and hence NMDAR are particularly required in those neurons undergoing synaptic plasticity during learning, or perhaps, and more likely, there is not a high level of redundancy in the hippocampal circuits involved, leading to the idea that a certain level of NR1 expression/availability appears necessary for memory formation in most of CA1 pyramidal neurons.

Femtosecond Ti:Sapphire Oscillator Electro-Optically Cavity Dumped at 50 kHz

Use of a transverse KD?P Pockels cell and novel low-loss sapphire Rochon polarizer to cavity dump a hard-aperture, Kerr-lens mode-locked, Ti:sapphire oscillator is demonstrated. High-quality 90-fs pulses with energies of ~50 nJ at repetition rates of up to 50 kHz were obtained.

Gonadotropin-releasing hormone receptor microaggregation. Rate monitored by fluorescence resonance energy transfer

Gonadotropin-releasing hormone (GnRH) regulates pituitary gonadotropin release and is a therapeutic target for human and animal reproductive diseases. In the present study we have utilized the technique of fluorescence resonance energy transfer to monitor the rate of GnRH receptor-receptor interactions. This technique relies on the observation that the degree of physical intimacy of molecules can be assessed by the tendency of proximal fluorophores to exchange energy. Our data indicate that GnRH agonist, but not antagonist, occupancy of the GnRH receptor promotes physical intimacy (microaggregation) between receptors. The time course indicates that this occurs promptly (<1 min) after occupancy and persists for at least 80 min and within the physiologically relevant range of the releasing hormone. The process measured is not inhibited by 0.1 mm vinblastin, 2 microm cytochalasin D, or 3 mm EGTA, an observation that distinguishes it from macroaggregation (patching, capping, and internalization). These observations, along with reports from other laboratories, are consonant with a growing body of evidence that indicates that microaggregation is an early event following agonist occupancy of the receptor and part of the mechanism by which effector regulation occurs.

Some hypothalamic hamartomas contain transforming growth factor alpha, a puberty-inducing growth factor, but not luteinizing hormone-releasing hormone neurons

Activation of LH-releasing hormone (LHRH) secretion, essential for the initiation of puberty, is brought about by the interaction of neurotransmitters and astroglia-derived substances. One of these substances, transforming growth factor alpha (TGFalpha), has been implicated as a facilitatory component of the glia-to-neuron signaling process controlling the onset of female puberty in rodents and nonhuman primates. Hypothalamic hamartomas (HH) are tumors frequently associated with precocious puberty in humans. The detection of LHRH-containing neurons in some hamartomas has led to the concept that hamartomas advance puberty because they contain an ectopic LHRH pulse generator. Examination of two HH associated with female sexual precocity revealed that neither tumor had LHRH neurons, but both contained astroglial cells expressing TGFalpha and its receptor. Thus, some HH may induce precocious puberty, not by secreting LHRH, but via the production of trophic factors--such as TGFalpha--able to activate the normal LHRH neuronal network in the patient's hypothalamus.

Neuregulins signaling via a glial erbB-2-erbB-4 receptor complex contribute to the neuroendocrine control of mammalian sexual development

Activation of erbB-1 receptors by glial TGFalpha has been shown to be a component of the developmental program by which the neuroendocrine brain controls mammalian sexual development. The participation of other members of the erbB family may be required, however, for full signaling capacity. Here, we show that activation of astrocytic erbB-2/erbB-4 receptors plays a significant role in the process by which the hypothalamus controls the advent of mammalian sexual maturation. Hypothalamic astrocytes express both the erbB-2 and erbB-4 genes, but no erbB-3, and respond to neuregulins (NRGs) by releasing prostaglandin E(2) (PGE(2)), which acts on neurosecretory neurons to stimulate secretion of luteinizing hormone-releasing hormone (LHRH), the neuropeptide controlling sexual development. The actions of TGFalpha and NRGs in glia are synergistic and involve recruitment of erbB-2 as a coreceptor, via erbB-1 and erbB-4, respectively. Hypothalamic expression of both erbB-2 and erbB-4 increases first in a gonad-independent manner before the onset of puberty, and then, at the time of puberty, in a sex steroid-dependent manner. Disruption of erbB-2 synthesis in hypothalamic astrocytes by treatment with an antisense oligodeoxynucleotide inhibited the astrocytic response to NRGs and, to a lesser extent, that to TGFalpha and blocked the erbB-dependent, glia-mediated, stimulation of LHRH release. Intracerebral administration of the oligodeoxynucleotide to developing animals delayed the initiation of puberty. Thus, activation of the erbB-2-erbB-4 receptor complex appears to be a critical component of the signaling process by which astrocytes facilitate the acquisition of female reproductive capacity in mammals.

Simultaneous and independent visualization of the gonadotropin-releasing hormone receptor and its ligand: evidence for independent processing and recycling in living cells

The first step in GnRH signaling is binding by the peptide to its plasma membrane receptor (GnRHR). The receptor is a member of the seven transmembrane G protein-coupled class but lacks the characteristic C-terminal cytoplasmic tail, making it among the smallest receptors in this superfamily. It has been known since 1980 that agonist occupancy of the GnRHR results in patching, capping, and internalization, although it has not been possible to localize the unoccupied GnRHR, because elaboration of receptor antisera has not been easy to achieve. The recent production of a green fluorescent protein (GFP) conjugate of the GnRHR ("rGnRHR-C-tail-GFP") that is expressed in cells, targeted to the plasma membrane, binds GnRH analogs and couples to G proteins has made it possible to monitor movement of the unoccupied receptor by confocal microscopy. In the present study, we used this probe, along with Texas Red conjugates of a GnRH agonist, to examine simultaneous processing of the receptor and its ligands. The preparation of the GFP GnRHR chimera has been described. A Texas Red conjugate was made from the GnRH agonist D-Lys6-Pro9-des-Gly10EA-GnRH by standard procedures. Bioactivity of this conjugate was confirmed. Confocal fluorescence images of living GGH3 cells showed that the agonist binds the GFP-GnRH receptor construct on the cell membrane and causes the internalization of vesicles delimited by a membrane. Shortly after internalization, the agonist separates from receptor inside the vesicle, although it is still enclosed in membranes containing free receptor. As the vesicles approach the perinuclear space, the separation between receptor and agonist is more pronounced. Free receptor appears at the cell membrane after the internalization of agonist has been completed. The protein synthesis inhibitor, cycloheximide (1 mM) did not inhibit this process, suggesting that the free receptor results from the recycling of previously internalized vesicles rather than from newly synthesized receptor. These studies show visual evidence for recycling of the GnRH receptor in cultured cells.

The Oct-2 POU domain gene in the neuroendocrine brain: a transcriptional regulator of mammalian puberty

POU homeodomain genes are transcriptional regulators that control development of the mammalian forebrain. Although they are mostly active during embryonic life, some of them remain expressed in the postnatal hypothalamus, suggesting their involvement in regulating differentiated functions of the neuroendocrine brain. We show here that Oct-2, a POU domain gene originally described in cells of the immune system, is one of the controlling components of the cell-cell signaling process underlying the hypothalamic regulation of female puberty. Lesions of the anterior hypothalamus cause sexual precocity and recapitulate some of the events leading to the normal initiation of puberty. Prominent among these events is an increased astrocytic expression of the gene encoding transforming growth factor-alpha (TGF alpha), a tropic polypeptide involved in the stimulatory control of LHRH secretion. The present study shows that such lesions result in the rapid and selective increase in Oct-2 transcripts in TGF alpha-containing astrocytes surrounding the lesion site. In both lesion-induced and normal puberty, there is a preferential increase in hypothalamic expression of the Oct-2a and Oct-2c alternatively spliced messenger RNA forms of the Oct-2 gene, with an increase in 2a messenger RNA levels preceding that in 2c and antedating the peripubertal activation of gonadal steroid secretion. Both Oct-2a and 2c trans-activate the TGF alpha gene via recognition motifs contained in the TGF alpha gene promoter. Inhibition of Oct-2 synthesis reduces TGF alpha expression in astroglial cells and delays the initiation of puberty. These results suggest that the Oct-2 gene is one of the upstream components of the glia to neuron signaling process that controls the onset of female puberty in mammals.

Visualization of unoccupied and occupied gonadotropin-releasing hormone receptors in living cells

Three chimeras of the rat GnRH receptor (rGnRHR) and an enhanced green fluorescent protein (GFP) were assessed to examine their suitability as probes of the receptor in transfected GH3 cells. Direct fusion of GFP to the N or C terminus of the rGnRHR abolished the receptor ligand binding affinity and the chimeric receptors were intracellularly localized. In contrast, rGnRHR-Ctail-GFP, a fusion of the N-terminus of the GFP to the C-terminus of the rGnRHR with the intracellular C-terminal tail of the catfish GnRHR as an intermediate spacer, was functional in terms of plasma membrane localization, ligand binding ability, receptor-mediated signal transduction and pattern of homologous down-regulation. The functional chimera of GnRHR and GFP provided a useful model for observation of GnRHR distribution and agonist-stimulated trafficking in living cells.

Redistribution of G(q/11)alpha in the pituitary gonadotrope in response to a gonadotropin-releasing hormone agonist

In the present study, we took advantage of high-resolution multilaser confocal microscopy to examine the distribution of the alpha-subunit of the guanyl nucleotide binding protein subfamily G(q/11) (G(q/11)alpha). Dispersed cultures of pituitary cells were prepared from female weanling rats, fixed, permeabilized, and then stained with monoclonal antiserum (mouse) to the gonadotrope-specific form of secretogranin (SIIp), which was then tagged with Texas Red. Accordingly, the subpopulation of gonadotropes (approximately 15% of total cells) could be identified against a background of other pituitary cell types. G(q/11)alpha was localized with antiserum made in rabbit, then tagged with fluorescein. Hoechst 33258 nuclear stain was also used in some experiments for topological reference. The data indicate localization of the G(q/11)alpha in a cellular region near the plasma membrane and external to the border of the layer occupied by secretory granules. In the absence of activation, there were an average of six clusters of G(q/11)alpha in a section 1 microm thick and through the center of the cell. This corresponds to an average of 60 clusters per cell, assuming a mean gonadotrope diameter of 10 microm. Following continuous treatment with 0.1 microg/ml Buserelin, a metabolically stable GnRH agonist, the average number of clusters increased to 200/cell after 40 min and remained approximately constant for 120 min. This increase was blocked by the protein synthesis inhibitor, cycloheximide. In response to Buserelin, there was an additional increase in the number of clusters inside the cell in the area occupied by the secretory granules and in the perinuclear area. Prolonged (24 h) treatment with Buserelin, sufficient to provoke the onset of desensitization, did not significantly change total numbers of G(q/11)alpha clusters, although more were located in the peripheral compartment, an increase that occurred at the expense of the cytoplasmic compartment. Redistribution of the G(q/11)alpha family may be functionally significant, because this moiety may be rate limiting at the site of regulation of signal transduction.