[Canary in the Coal Mine: Reflections on the Current Global Wave of Nursing Strikes]

A worldwide wave of nurse strikes has erupted. Labor strikes represent a last resort measure and are a powerful means for nurses to fight back against adverse working conditions such as heavy workloads, unfair pay, and unsafe staffing conditions that not only affect patient care outcomes but also economic growth and social political stability. Despite the pandemic placing most nurses under extremely stressful conditions for an extended period of time, nurses remained on duty to cope with the changing circumstances while continuing to provide high-quality care. Overwhelmed nurses worldwide are the "canary in the coal mine", with the current strikes sounding the alarm about the urgent need to increase investments in our fragile health system. In this article, the concept underlying labor strikes is outlined, the potential impacts of strike actions are presented, the status quo of nursing practice in Taiwan is discussed, and the readiness of nursing professional organizations for industrial action is considered. We call on the government to invest further in healthcare to both stimulate economic growth and give more respect, value, protect and identity to nurses through fairer pay and better working conditions.

[From Invisible to Visible - Validating Media Presence: Forging a New Image of Nursing in the Post-Pandemic Era]

The COVID-19 pandemic has increased the exposure and attention given to nurses in the global media. Although media outlets have repeatedly praised them as "heroes" or "angels", nurses continue to be regular targets of stigmatization during infectious outbreaks. The lack of a strong public image may be an important reason behind why the general public has yet to adequately understand and acknowledge the nursing profession. Therefore, new branding is needed to improve the public image of nursing in the post-pandemic era. In this article, common stereotypes regarding nurses are reviewed, the heroic narrative is introduced, and suggestions regarding how to leverage social media to improve the image of nursing are provided. To give nurses a more respected voice, make the invisible visible, and validate a stronger media presence in line with International Council of Nurses tenets, nurses should be united together under a shared professional image to be a positive force for global health.

[Analytical performance verification protocols and performance specifications of platelet-dependent von Willebrand factor activity testing]

Objective: To investigate the analytical performance verification protocols and performance specifications of platelet-dependent von Willebrand factor (VWF) activity testing (VWF:GPIbM) for clinical laboratories. Methods: According to Clinical Laboratory Standards Institute (CLSI) documents and National Health Standard of China, the performance verification of VWF:GPIbM was designed and implemented using Sysmex CS-5100 instrument and its corresponding reagents. (1) Precision verification: Two commercial quality control samples (with normal and low activity levels) and three plasma pools (with activity range from 5.0% to 150.0%) were prepared. Each sample was tested five times daily for five consecutive days. The coefficient of variation (CV) of intra-and inter-run precisions were calculated, and the precision evaluation criterion was set according to package inserts. (2) Trueness verification: The calibrator was diluted to five reference materials with activity values of 5.2%, 31.2%, 62.4%, 104.0% and 138.7%, and each reference material was tested five times daily for five consecutive days. The bias between the measured value and the reference value was calculated, and the trueness evaluation criterion was set according to the total allowable error. (3) Linearity verification: Ten pooled plasmas with theoretical value range from 3.6% to 160.4% were prepared for the linearity verification of two calibration curves set by the manufacturer (i.e. low range and normal range calibration curve). Each pooled plasma was tested three times in a single run. The slope and R² of linear regression of mean of measured value and theoretical value, as well as bias, were calculated, and the linearity evaluation criterion was set according to National Health Standard of China and package inserts. (4) Limit of quantitation verification: The calibrator was diluted to two reference materials with activity values of 3.3% and 2.7%, and each material was tested twelve times. The limit of quantitation evaluation criterion was set according to CLSI document. Results: The CVs of intra-and inter-run were 1.0%-2.5% and 1.1%-2.6%, respectively. The biases of trueness verification were -0.4%, 1.0%, -2.6%, 0.3% and -2.7%, respectively. The linearity verification results of low range (3.6%-31.8%) and normal range (28.4%-160.4%) showed that the slopes of regression equation were 1.021 7 and 0.996 2, respectively, R² were 0.993 5 and 0.993 9, respectively, and the biases with 0-1.8% and -10.1%-0 of plasmas met the criterion. The biases ranged from -0.4% to 0.3% of test results in the verification of limit of quantitation met the criterion. Conclusion: The verification results of VWF:GPIbM assay for precision, trueness, linearity and limit of quantification meet the performance requirements indicated in the package inserts and the criteria set in this study, which can be taken as a reference of performance verification for the clinical laboratories.

[Beware of Wolves in Sheep`s Clothing: A Brief Introduction to Open Access and Predatory Journals]

The advance of information technology has led to the significant diversification of scholarly publishing. Over the past decade, the popularity of open access in scholarly publishing has led to an unintended rise in the number of predatory journals and the growth in predatory open access (POA) publishing practices. The main goal of POA publishing is to profit from article processing charges, and thus little or no attention is given to proper peer review or to editorial / publishing standards. Most articles published in predatory journals are tainted by examples of academic ethics violations such as falsification, deception, and fraud. Moreover, the risk of citation contamination is high, as articles published in POA publications may be cited and referenced in the legitimate scientific literature, with consequences including confounding subsequent research, negatively influencing public policies, and hindering social progress and public health. However, most nurses in Taiwan remain unfamiliar with this issue. This article provides a brief review of the open access movement and insights regarding how to assess the credentials of journals and publishers before submitting manuscripts to avoid predatory journals, promote academic integrity, and contribute to the sustainable development of the nursing profession.

[Current status of CD34+cell enumeration assay in clinical laboratories and its improvement]

Objective: To investigate the current status and problems of CD34⁺ cell enumeration in clinical laboratories and provide suggestions for the development of quality improvement programs. Methods: A total of 101 laboratories participating in the national external quality assessment program of CD34⁺cell enumeration were surveyed. Questionnaires and quality assessment materials were distributed to collect information on assay methodology and testing results. Quality control requirements for CD34⁺cell enumeration were determined according to the international guidelines, and the compliance of the surveyed laboratories was analyzed. Testing results were analyzed in groups and compared with the College of American Pathologists (CAP) quality assessment data. Results: A total of 97 laboratories returned the questionnaires and 99 laboratories returned the results of quality assessment materials. The questionnaire data showed high compliance rates of quality control requirements such as gating protocols, pipetting methods, and the number of cells acquired (92.8%, 83.9%, and 82.5% respectively). However, these laboratories had relatively low compliance rates such as the use of whole blood quality control materials for internal quality control, selection of erythrocyte lysing reagents, sample processing method, whether to report absolute count results, and quality control of equipment (5.2 %, 28.9%, 39.2%, 46.4%, and 55.7%, respectively). Testing results demonstrated that the coefficient of variation (CV) of percent counts was similar to the CAP quality assessment data, but the CV of absolute counts was greater than the CAP quality assessment data. Conclusions: Clinical laboratories have poor compliance with some quality control requirements and the variability of absolute count results between different laboratories is not satisfactory. Therefore, it is recommended that clinical laboratories should strengthen the training related to the quality control of CD34⁺cell enumeration, especially the absolute counting.

[Frequently Asked Questions About the Seventh Edition APA Citation]

The Publication Manual of the American Psychological Association is an academic writing format reference manual commonly used in the field of social sciences. The current, seventh edition of this manual was published in October 2019. The two main issues spotlighted in this edition are the increasingly common citation of online material and the use of inclusive and bias-free language in academic writing. APA (American Psychological Association) style guidelines are widely used in nursing academia, in papers written for N3 and N4 nursing clinical ladder qualification, and in papers submitted to nursing journals. The lengthy and detailed content of the APA publication manual frequently overwhelms and confuses clinical nurses and students, and Taiwan Nursing Association members regularly submit APA-style-related questions to the Association. Thus, this article was written to address the origin and evolution of APA formatting guidelines and their importance in academic writing, highlight the major changes in the seventh edition, answer common questions about the APA citation format, and share APA online resources. It is hoped that the information in this article assists readers to improve the quality of their academic writing.

[The Key Role of Taiwanese Nurses in Combating COVID-19 Pandemic]

As the COVID-19 pandemic continues to rage worldwide, Taiwan has achieved outstanding performance in controlling the spread of the outbreak domestically, earning global appreciation. Nurses on the frontlines deserve much of the credit for the ongoing success in fighting against this outbreak in Taiwan. Taiwan's success to date is grounded in proactive preparedness and deployment by the government and effective teamwork among government agencies, medical institutions, enterprises, and the public. Comprehensive containment strategies and preparedness have allowed nurses to effectively perform their duties and combat the pandemic. Nurses safeguard the public's health a myriad of ways, including implementing quarantine measures at air and seaports, conducting fever screenings, delivering inpatient isolation treatments, performing case contact tracing, providing community care services, and operating special chartered-flight services. The Taiwan Nurses Association (TWNA) provides vital lead in this pandemic response, advocating for the safety, health and wellbeing of nurses; highlighting the contributions and value of nurses; and enhancing the professional image and status of nurses. Furthermore, through its global platform, TWNA shares with peer organizations worldwide the content and efficacy of actions taken by the national government, the contributions of healthcare workers, and the support and encouragement received from the public in COVID-19 containment to demonstrate values of Taiwan and nursing.

[Nurses: A Voice to Lead, Nursing the World to Health-Viewing COVID-19 Epidemic Prevention Efforts in Light of Nightingale's Perspective on Infection Control]

Florence Nightingale (1820-1910), extolled as the founder of modern nursing, contributed greatly to the advancement of modern public health. Written 150 years ago, Nightingale's advice on infection control, addressing the importance of hand washing, environmental sanitation, ventilation, sunshine, statistical data, and health literacy, remains highly relevant in today's global fight against the coronavirus. In honor of Florence Nightingale's 200th birthday, World Health Organization declared 2020 the International Year of the Nurse and Midwife. The era of "Nurses: A Voice to Lead - Nursing the World to Health" is drawing near. This article addresses the profound impact of Nightingale's infection control and public health perspectives on measures currently being taken to contain coronavirus disease 2019 (COVID-19). Furthermore, we call on governments throughout the world to invest proactively in nursing to assure the safety of patients and promote public health in order to achieve the pledge of the United Nations' sustainable development goals to leave no one behind.

[Study on commutability evaluation of reference materials for fibrinogen]

Objective: To discuss the commutability evaluation method of reference materials for fibrinogen measurement and evaluate the commutability of the Third WHO International Standard Fibrinogen Plasma (WHO 09/264), SSC/ISTH Secondary Coagulation Standard (SSC LOT4) and homemade reference materials (RM01, RM02) in order to provide suggestions on how to determine the suitable method of commutability evaluation and reliable traceability standard. Methods: The comparability of fibrinogen among different measurement systems were evaluated and WHO 09/264 was used to calibrate each system to improve the comparability if the comparability among different systems couldn't be accepted. Forty clinical samples and the reference materials randomly interspersed among the clinical samples were measured on Stago STA-R Evolution, Sysmex CS 5100, IL ACL TOP 700 simultaneously. Measurement results were pairwise analyzed by Deming regression and difference in bias approach according to the Clinical and Laboratory Standards Institute (CLSI) EP14-A3 protocol and the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) working group on commutability, respectively. Results: The comparability of fibrinogen measurement among common systems could not meet the criterion. WHO 09/264 could improve the agreement among different measurement systems. The prediction interval of Deming regression was affected by the comparability of measurement systems, resulting in unreliable results. The difference in bias approach was more suitable because its criterion was related to the medical requirements. WHO 09/264 was commutable between Stago and Sysmex, inconclusive between Stago and IL, Sysmex and IL (The calibration effectiveness of WHO 09/264 showed that it was commutable among the three measurement systems). SSC LOT4 was commutable between Stago and Sysmex, inconclusive between Stago and IL, Sysmex and IL. RM01 and RM02 were commutable between all systems pairs assessed by difference in bias approach. Conclusions: There are differences in the results of two commutability evaluation approaches. The difference in bias approach is recommended for commutability evaluation. WHO International Standard and homemade reference materials can be used as traceability standard for fibrinogen measurement.

[The Role of Nurses in Achieving Sustainable Development Goals]

The sustainable development goals (SDGs), announced by the United Nations in 2016, now help guide public policy in many nations around the world. The United Nations has appealed to all governments and citizens worldwide to align together, taking action in each of the SDG dimensions of people, planet, prosperity, peace, and partnership in order to eradicate extreme poverty, inequality, and injustice; to slow / stop climate change; and to ensure sustainable development for humanity and the earth. Nursing is critical to achieving SDG3 (Health and Welfare) and has a significant impact on each of the other 16 SDGs. However, many nurses are unfamiliar or inadequately acquainted with SDGs. Therefore, this article introduces the content of the SDGs and the role of nurses in achieving each. In addition, we encourage nurses to exert their professionalism and compassion in realizing the pledge of the SDGs -- No one is left behind.

[Analysis of internal quality control data of complete blood count from laboratories participating in national external quality assessment]

Objective: To investigate current status and problems of internal quality control (IQC) of complete blood count in China so as to perform IQC normally. Methods: The IQC data of complete blood count for five parameters were collected from laboratories participating in national external quality assessment during 2012-2017 (totally 12 times), including WBC, RBC, Hb, Hct and PLT. After confirmation of all data, data for the 12 times were analyzed as follows.The proportions of using different levels of quality control materials were calculated.The 25th, 50th, 75th, 90th percentiles CV of data collected for the 12 times were calculated respectively and the trends of CV were observed over time.The difference of CV among laboratories running three control levels was compared.The CV of each parameter in 2017 was compared with precision requirements based on biological variation, health standards and German Medical Association Directive; The proportions of laboratories using different control rules were calculated. Results: After invalid data was excluded from those IQC data of laboratories for the 12 times external quality assessment (up to 2 402, as low as 1 449) from 2012 to 2017, the residual data (up to 2 332, as low as 1 431, accounting for 96.0%-99.2%) was used for analysis. 61.9%-66.1%, 18.2%-23.6% and 14.3%-17.3% of laboratories ran one, two and three control levels respectively, and the proportions of laboratories running more than two control levels increased from 33.9% to 38.1%. The decrease trend of the 75th, 90th percentiles CV of WBC, RBC, Hb, Hct for three levels, PLT for normal level and the 90th percentiles CV of PLT low level had statistically significance over time (P<0.05); the decrease trend of the 75th percentiles CV of PLT low level and 75th, 90th percentiles CV of PLT high level had no statistically significance over time. The CV had significant difference between low and normal, low and high control level for WBC and PLT, while there were no difference between normal and high control levels. There were no significant difference of CV among three control levels for RBC, Hb, and Hct. Except for the CV of Hct low, normal level and PLT low level, 85% of laboratories for the other parameters could meet the minimum precision requirements based on biological variation; more than 85% laboratories met the requirements of health standards; except for the CV of PLT low level, more than 80% laboratories met the requirements of German Medical Association Directive. The proportion of laboratories using 1(3s)/2(2s) quality control rules increased from 59.2% to 76.0%. Conclusions: During the past 6 years, the CV for IQC has shown a decrease trend over time. However, the control level and quality control rules used by some laboratories do not meet management requirements. The CV of Hct and PLT in a few laboratories do not meet the minimum requirements of the health standards, and need to implement quality improvements fatherly.

[Study and analysis of national current status and problems of anticoagulant proteins assay]

Objective: To investigate current status and problems of anticoagulant proteins assay in domestic laboratories so as to provide suggestions for implementing the standardization and quality improvement. Methods: Two hundred and seventy-four laboratories those had developed or prepared to do anticoagulant proteins assay were selected from one thousand and five hundred participants in the national coagulation screening External Quality Assessment(EQA) program by an internet survey and then a questionnaire and quality control materials were sent to them to carry out a further survey. The questionnaire information was analyzed statistically. The results of quality control materials were grouped by the reagents and the average, median, standard deviation(s), coefficient variation(CV) of each group were calculated. The deviations or percentage deviations were determined by comparing the results of each laboratory to the target defined as the peer-group median after exclusion of outliers, and then the pass rates were calculated based on the criterion of RCPA, DGKL and the allowable total error based on biological variation. Results: Two hundred and thirty-five questionnaires were collected. The number of laboratories testing antithrombin(AT), protein C(PC) and protein S(PS) activity were 194, 63 and 50 respectively. The instruments and reagents were mainly from abroad (more than 96%), the matching rate of which were above 94%. For AT, PC and PS activity testing, there were 30.4%, 33.3%, 34.0% of laboratories did not perform verification assays respectively, and 8.8%, 7.9%, 14.0% of laboratories did not renew calibration curve when the reagent lots were changed. 11.3%, 17.5%, 16.0% of laboratories didn't run internal quality control, and 34.9%, 26.9%, 21.4% of laboratories only performed a single level of quality control. 4.1% of laboratories set the reference intervals of AT activity according to different age groups, and the percentage of that of PC and PS activity were 1.6% and 2.0%. 16.0% of laboratories set the reference interval of PS activity by sex. For normal control materials, the CV of AT, PC and PS activity results were 5.7%-12.9%, 4.2%-7.7% and 18.4%-33.1% while the CV for abnormal level were 13.3%-38.3%, 6.1%-14.4% and 31.5%-34.5% respectively. The pass rate was different when it was judged by different criteria. A suitable criterion for each item should be selected according to the concentration level of quality control materials. Conclusion: The comparability between laboratory results are not satisfactory and in order to promote quality improvement, it is necessary to develop guidelines, organize trainings and establish a national EQA scheme.

Standardization of haematology critical results management in adults: an International Council for Standardization in Haematology, ICSH, survey and recommendations

INTRODUCTION

These recommendations are intended to develop a consensus in the previously published papers as to which parameters and what values should be considered critical. A practical guide on the standardization of critical results management in haematology laboratories would be beneficial as part of good laboratory and clinical practice and for use by laboratory-accrediting agencies.

METHODS

A working group with members from Europe, America, Australasia and Asia was formed by International Council for Standardization in Haematology. A pattern of practice survey of 21 questions was distributed in 2014, and the data were collected electronically by Survey Monkey. The mode, or most commonly occurring value, was selected as the threshold for the upper and lower alert limits for critical results reporting.

RESULTS

A total of 666 laboratories submitted data to this study and, of these, 499 submitted complete responses. Full blood count critical results alert thresholds, morphology findings that trigger critical result notification, critical results alert list, notification process and maintenance of critical results management protocol are described. This international survey provided a snapshot of the current practice worldwide and has identified the existence of considerable heterogeneity of critical results management.

CONCLUSION

The recommendations in this study represent a consensus of good laboratory practice. They are intended to encourage the implementation of a standardized critical results management protocol in the laboratory.

[Evaluation and characterization of the certified reference materials for coagulation factor Ⅷ and Ⅸ activity testing]

OBJECTIVE

To evaluate and characterize the certified reference materials for coagulation factor Ⅷ (FⅧ) and factor Ⅸ (FⅨ) activity testing.

METHODS

The homogeneity and stability of three lots of certified reference materials (F01-F03) with different factor concentrations were evaluated according to guidelines"Reference materials-general and statistical principles for certification","Guidance on evaluating the homogeneity and stability of samples used for proficiency testing"and"Technical Norm of Primary Reference Material". The certified reference materials were characterized by eight laboratories using one-stage method, which were calibrated by the coagulation standard provided by the National Institute for Biological Standards and Control (NIBSC) in UK.

RESULTS

The Coefficient of Variation (CV) of homogeneity test of FⅧ activity of three lots of certified reference materials were 3.9%, 3.3% and 3.4%, respectively. While that of FⅨ activity were 3.7%, 3.0% and 1.8%, respectively. The results of one-way ANOVA showed that all certified reference materials had good homogeneity (P>0.05), and the between-bottle homogeneity uncertainties (ubb) of FⅧ and FⅨ activity were 0.5%-2.9% and 0.1%-3.9%, respectively. All certified reference materials stored in -80 ℃ remained stable in 9 months by trend analysis, and the long-term stability uncertainties(ults) of FⅧ and FⅨ activity were 0.5%-5.1% and 1.3%-4.4%, respectively. The characterization uncertainties (uchar) of FⅧ and FⅨ activity testing were 0.9%-2.4% and 1.1%-2.4%, respectively. The combined uncertainties and extended uncertainties (coverage factor k=2) were calculated. The assigned values of each lot of certified reference materials for FⅧ activity were (85±13)%, (36.0±3.4)% and (20.5±2.3)%, and that were (102±13)%, (47.8±6.9)% and (29.3±3.8)% for FⅨ activity, respectively.

CONCLUSIONS

The certified reference materials for FⅧ and FⅨ activity testing have good homogeneity and stability. The results of the characterization are accurate and reliable.

Enlarging effects of estradiol on the nuclear volume of neurons in the hypothalamus during aging

Neuronal nuclear volumes (NNVs) were measured in the medial preoptic nucleus (MPN), anterior hypothalamic area (AHA) and arcuate nucleus (ARN) of young adult, middle-aged, and old rats of both sexes. The NNVs in the darkly stained sexual-dimorphic nucleus of the preoptic area (SDN-POA) and the lighter staining surrounding area (non-SDN-POA) within the MPN were measured separately. Intact young and middle-aged female rats had larger NNVs than those of the males in SDN-POA, non-SDN-POA and AHA but not in ARN. During aging, only intact old female rats manifested significant NNV shrinkage in all the measured areas. Long-term treatment with estradiol benzoate (EB) caused a significant enlargement of the NNVs in non-SDN-POA and ARN of middle-aged and old male rats as well as the NNVs in SDN-POA, non-SDN-POA and ARN of old female rats. The enlarging effect of EB on NNVs in both SDN-POA and non-SDN-POA of female rats could be prevented by ovariectomy. Furthermore, NNVs in SDN-POA and non-SDN-POA of ovariectomized female rats were even smaller than those of the age-matched intact female rats. These results indicate that: (1) the NNVs of MPN and ARN in male and female rats were enlarged after long-term exposure of physiological dose of estradiol; (2) the enlarging effects of EB on NNV in MPN can explain why the NNV of intact female rats is larger than that of males, and (3) during aging, the sex-specific shrinkage of NNVs in MPN, AHA and ARN of female rats may be due to an intrinsic aging process rather than long-term effects of EB.

Male sexual behavior is associated with LHRH neuron number in middle-aged rats

LHRH administration is reported to facilitate male sexual behavior. The aim of the present study was to investigate whether male sexual behavior is associated with the number of LHRH neurons in the forebrain in middle-aged rats. Male Long-Evans rats (18-19 months) were assigned to three groups on the basis of sexual performance: (1) group MEI consisted of rats showing complete copulatory patterns, including mounts, intromissions and ejaculations, (2) group MI was composed of rats showing mounts and intromissions, but no ejaculation and (3) group NC were non-copulators, i.e. they did not show any copulatory behavior. Young adult rats (4-5 months), displaying sexual behavior, were used as controls. Following the sexual behavior tests, the number of LHRH neurons in the medial septum (MS), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA) and anterior hypothalamus (AH) was determined by immunocytochemistry. No difference was seen in the total number of LHRH neurons in these combined brain areas between group MIE and young controls. In the three middle-aged groups, the total number of LHRH neurons was greatest in group MIE, less in group MI, and lowest in group NC. In general, a similar trend was seen separately in the MS, OVLT and POA. These results suggest that changes in the number of LHRH neurons in the forebrain, in most cases, are age-related, at least in the middle-aged rats, but they also seem to be associated with male sexual performance.

Restoration of sexual behavior in aged male rats by intracerebral grafts of fetal preoptic area neurons

A decline in sexual arousal and copulatory activity has been observed in male rats with advancing age. Grafting of fetal hypothalamic tissue into the third ventricle of aged male rats restores sexual behavior. This study investigated the effects of grafting fetal preoptic area (POA) neurons into the POA of aged male rats exhibiting decreased sexual behavior. We grafted suspensions of fetal POA neurons into the POA of 20 aged (19 to 24 months old) male rats that displayed no ejaculation. From 2 weeks after grafting, one or more series of male copulatory activity and sexual motivation tests were performed at intervals of 3 to 4 weeks. Three behavioral tests given 5 days apart were repeated for each animal in each series. Among the 20 aged rats with the fetal grafts, 15 showed improved sexual motivation, and 14 of these had copulatory activity restored to levels comparable with those of young males. Among these 14 rats, eight ejaculated during copulation. Copulatory behavior was restored between 21 and 45 days after grafting and persisted until the end of observation (2-4.5 months). Sexual performance did not improve in control aged male rats grafted with either fetal cerebral cortex neurons into the POA or POA, neurons into the ventromedial hypothalamus. The rats that received grafts of fetal POA neurons into the POA and recovered sexual performance also showed improvement or recovery to levels comparable to those in young males of serum testosterone concentrations, serum luteinizing hormone levels after castration, and the post-castration rise in luteinizing hormone. These results indicate that decreases in copulatory activity, sexual motivation, and some neuroendocrine functions in aged male rats are at least partially due to dysfunction of the POA.

The neonatal neurotoxicity of monosodium L-glutamate on the sexually dimorphic nucleus of the preoptic area in rats

The neurotoxic effect of monosodium L-glutamate (MSG) on the morphologies in the darkly stained sexually dimorphic nucleus of the preoptic area (SDN-POA) and the lighter-staining surrounding area (non-SDN-POA) within the medial preoptic nucleus (MPN) was evaluated. Male and female Long-Evans rats were used. MSG (4 mg/g of body weight) was administered subcutaneously to pups on days 1 and 3 postnatally. Normal saline was used as the vehicle. At the age of 6 months, the rats were sacrificed and the brain tissues were fixed for histological examination. The morphological changes, i.e., total volume, density, total neuron number, neuronal nuclear volume (NNV) and ratio of pyknosis, of the SDN-POA and non-SDN-POA within the MPN, were estimated using the AMS VIDS III semiautomatic image-analytic system. The results indicate that neonatal MSG treatment caused significant neuronal loss and decreases in total volume of the SDN-POA and non-SDN-POA of male and female rats. However, only the SDN-POA of MSG-treated male rats showed a significant increase of pyknosis and decrease of neuronal density. A significant enlargement of NNV in the SDN-POA and non-SDN-POA was observed in the MSG-treated male rats. These results indicate that the MPN shows sex-specific and area-specific changes after neonatal neurotoxicity due to MSG.

Estradiol modulation of neuron loss in the medial division of medial preoptic nucleus in rats during aging

The age-related morphological changes in the darkly stained sex-dimorphic nucleus (SDN-POA) and the lighter staining surrounding area (non-SDN-POA) within the medial division of preoptic nucleus of Long-Evans rats were studied. The long-term effects of estradiol benzoate (EB) on the changes were also assessed. During aging, the neuron loss in 14-(middle-age) and 22-month-old rats as well as increased pyknotic ratio of neurons in old male rats were observed in SDN-POA, but not in the non-SDN-POA. In female rats, significant neuron loss with advancing age was observed both in SDN-POA and the non-SDN-POA. Neuron loss in SDN-POA of EB-treated males was more severe than that of the intact males, while no significant difference of neuron loss was observed between EB-treated and age-matched intact female rats. However, neuron loss in SDN-POA of ovariectomized female rats was more severe than that of the age-matched intact females. These results indicate that age-related neuron loss in medial preoptic nucleus show sex-specific and area-specific features, and estradiol may play a important role in modulating neuron loss during aging.

Dopamine release in the nucleus accumbens during sexual behavior in prenatally stressed adult male rats

In vivo microdialysis experiments were performed on the nucleus accumbens (NAc) during observation of sexual behavior (including motivation and copulation) to determine if there were any changes in NAc dopamine (DA) transmission in prenatally stressed (PS) adult male rats. Approximate 37% of control males and 83% of PS males did not exhibit copulation during the sexual behavior tests and no significant changes in NAc DA release were seen during exposure to estrous females. In contrast, both control and PS males that displayed copulatory behavior showed a marked increase in NAc DA release when presented with a sexually receptive female behind a screen and this increased further during actual copulation. The increase in DA release in copulatory PS males was not significantly different from that in sexually active control males. In addition, a similar extent in DA release induced by high potassium perfusate was observed in all rats. These results suggest that prenatal stress may result in a deficit in DA neurotransmission in the NAc and this deficit may possibly cause impaired male sexual behavior in rats.

Effects of age on dopamine release in the nucleus accumbens and amphetamine-induced locomotor activity in rats

The effects of age on dopamine (DA) release in the nucleus accumbens (NAc) and on amphetamine (AMPH)-induced locomotor activity were studied by microdialysis in freely-moving young (5 month) and old (24 month) rats. Both basal extracellular DA and 3,4-dihydroxyphenylacetic acid (DOPAC) release and that following intra-accumbens perfusion of AMPH (1-10 microM) were significantly lower in old rats. After intraperitoneal injection of AMPH (1.5 mg/kg), no age-related change in DA release was seen in the NAc, but locomotor activity was found to increase much more in young rats than in old ones. These results indicate that (1) old rats show decreased extracellular DA and DOPAC release, both in the basal state and following intra-accumbens infusion of AMPH, and (2) the age-related locomotor activity induced by systemic injection of AMPH is not paralleled by changes in DA release in the NAc.

Effects of fetal brain grafting on adult behavioral masculinization and defeminization in neonatally androgenized female rats

Treatment of neonatal female rats with androgen results not only in decreased female sexual behavior but also in enhanced male sexual behavior examined in adulthood. The effects of grafting fetal preoptic area (POA) neurons into the POA, and fetal hypothalamic (HPT) neurons into the ventromedial hypothalamus (VMH), were tested in neonatally androgen-sterilized rats (ASR). The rats were injected subcutaneously with 80 micrograms testosterone propionate within the 24 hours after birth to see if sexual behavior could be normalized by fetal brain grafts. In repeated tests on ASR grafted with fetal HPT into the VMH, the lordotic response was seen to increase to the level seen in non-ASR controls, while the increase in mounting behavior in ASR was suppressed following grafting of fetal POA or cerebral cortex into the POA. These results suggest that there are dysfunctions of POA and VMH in ASR, and that the dysfunctions revealed by sexual behavior can be overcome by fetal POA or HPT grafting.

Effects of long-term estradiol exposure on the hypothalamic neuron number

Neuron density, volume of the area and total neuron number were measured in the medial preoptic area, anterior hypothalamic area and arcuate nucleus of the hypothalamus of young (6-month-old), middle age (14-month-old) and old (22-month-old) male and female rats. Intact male rats did not show neuron loss even in old age, while intact female rats manifested neuron loss in the medial preoptic area, anterior hypothalamic area and arcuate nucleus in old age. Long-term administration of estradiol benzoate to castrated male rats induced neuron loss in the anterior hypothalamic area and arcuate nucleus of the middle age group and in all three areas of the old age group. However, long-term ovariectomy could not prevent neuron loss in these hypothalamic areas in old age. The results suggested that estradiol can have a cumulative impact on the degree of neuron damage and simulate female-type age-related neuron loss in male rats and that there may be the possibility of an intrinsic aging process inducing neuron loss in female rats.

[The effects of neonatal monosodium glutamate treatment on sex-odor attractivity and approach behavior in rats]

The neurotoxic effects of monosodium glutamate (MSG) on certain parts of the central nervous system (CNS) and endocrine functions are well documented. MSG-treated rats exhibit stunted growth, obesity and decrease in sexual behavior. The present study was designed to evaluate how neonatal administration of MSG affects sex-odor attractivity and approach behavior, and to investigate factors limiting copulation in MSG-treated rats. In this experiment, subcutaneous injections of MSG (400 mg MSG/ml normal saline/0.1 Kg B.W.) were given to Long-Evans pups on days 1 and 3 after birth, whereas the control groups received normal saline injections of equal volume (1 ml/0.1 kg B.W.). When the rats were 3 months old, sex-odor attractivity and approach behavior were tested. Two points were displayed by MSG-treated rats: (a) attenuated the attractivity of sex-odor. (b) decreased performance of sexual approach to partners. From our results and those of a previous study, we suggest that the deterioration of sex-odor attractivity and approach behavior to partners is attributed to a decline in sexual hormones. Furthermore, we concluded that this decrease in behaviors is to some extent responsible for reduced copulatory behavior.

Effects of anterior roof deafferentation on lordosis behavior and estrogen receptors in various brain regions of female rats

This study investigated whether the estrogen receptors (ER), located at different brain areas and anterior pituitary (AP), changed after anterior roof deafferentation (ARD), and on the effects of facilitating the lordosis reflex in female rats. Female rats were ovariectomized and implanted with estradiol capsules. ARD or sham operation was performed with a Halász knife. All animals were tested for lordosis both before and after surgery. One day after the last test they were sacrificed. Cytosol and nuclear ER in the AP, medial preoptic area (MPOA), basal medial hypothalamus (BMH), amygdala (AMYG), septum (SEP), hippocampus (HPC), and cortex (CTX) were measured using an in vitro exchange assay. Rats with ARD showed significantly higher mean levels of lordosis quotient than the control and the sham groups before ARD surgery. An increase of both cytosol and nuclear ER in the BMH area compared to the control was observed, whereas the ER, in the SEP was reduced. ER in other areas were not affected by ARD. Serum estradiol and progesterone levels were not altered by the operation. These data suggest that the dorsal inhibitory pathway from the extrahypothalamus to the preoptic area and hypothalamus may modulate the estrogen receptor and the display of lordosis in female rats. Change of ER level in the BMH area may influence the hormonal sensitivity of lordosis in female rats.

Improvement of sexual behavior in aged rats by p-chlorophenylalanine and methysergide

The effects of methysergide, a serotonin antagonist, and p-chlorophenylalanine (PCPA), a serotonin synthesis blocker on the sexual behavior of intact old male rats at 19-23 months of age and female rats at 17-18 months of age were studied. Female rats with prolonged vaginal cornification and a lordosis quotient (LQ) of less than 50%, and male rats displaying no ejaculation were selected as experimental animals. The receptivity of aged female rats, but not the approach behavior to males nor proceptivity was improved by PCPA or methysergide. The LQ of intact aged female rats in non-exit tests was improved by the i.p. administration of 50 mg/kg B.W. of PCPA 2 to 4 hours prior to the sexual behavior test or 3 mg/kg B.W. of methysergide 4 hours prior to the test. Total mount frequency and mount latency of intact aged male rats were improved by the administration of methysergide (3 mg/kg B.W.), while total mount frequency and intromission latency were improved by the administration of PCPA (20 mg/kg B.W. for 4 days). The present results together with the finding from our previous study suggest that the increase of serotonin (5-HT) activity per se plays an important role in the decline of receptivity of aged female rats and the copulatory activity of aged male rats.

Sex-specific impairment in sexual and ingestive behaviors of monosodium glutamate-treated rats

L-monosodium glutamate (MSG) (4 mg/g b.wt.) was injected subcutaneously to pups on days 1 and 3. At age 3.5 months, sexual and ingestive behaviors were observed. Neonatal MSG treatment resulted in severe and widespread neuron destruction in the basomedial hypothalamus of both sexes, but only super-chiasmatic nucleus in male rats. A decline in sexual behavior was also observed. Serum levels of testosterone and dihydrotestosterone in male rats as well as serum level of progesterone in female rats were decreased. Ovariectomized MSG-treated female rats injected with estradiol benzoate followed by progesterone showed a dramatic improvement in sexual behavior, whereas castrated MSG-treated male rats injected with testosterone propionate did not meliorate the decline of sexual behavior. Neonatal MSG treatment also induced reductions of body weight in male rats, higher diurnal percentages of food and water intake in male rats than in female rats, and a decline of water-to-food ratio. These observations suggest that neonatal male rats show higher susceptibility to glutamate-induced dysfunction of sexual and ingestive behaviors than females. Our findings also suggest a sex difference in the mechanism of dysfunction of sexual behavior, i.e., decreased copulatory activity in male rats is mainly due to CNS damage, in contrast to decreased blood progesterone level in female rats.

Decreased inhibitory influences from forebrain on proceptivity and receptivity in old female rats

Female rats of Long-Evans strain were divided into a young group (3 to 4 months of age, mo) and an aged group (over 19 mo). Rats were ovariectomized and implanted subcutaneously with 14%, 20% or 33% estradiol benzoate (E2)-cholesterol mixture-filled Silastic capsules. Proceptivity and receptivity were compared between young rats and aged rats. There was no age difference in the lordosis quotient (LQ) or in the incidence of lordosis, but the incidence of solicitation was lower in aged rats than in young rats. Proceptivity and receptivity were examined again after anterior roof deafferentation (ARD) of the brain. ARD enhanced LQ in young rats and old prolonged vaginal cornification (PVC) rats but not in old anestrous (ANE) rats. ARD also increased the incidence of solicitation in both young and aged rats. However, the extent of enhancement of these two behaviors was smaller in the aged rats than in the young rats. These results demonstrate that there is decreased inhibitory influence from the forebrain on solicitation and lordosis following induction by exogenous estradiol in advancing age and that the disinhibition of lordosis is more prominent in ANE rats than in PVC rats.

Circadian rhythms of feeding and drinking behavior of rats aged from 3 to 21 months

Circadian rhythms and patterns of feeding and drinking behavior of 8 male and 8 female Long-Evans rats were followed from 3 months of age (mo) to 21 mo at 3 month intervals. Meal number, draft number and feeding events/min/meal of female rats were greater than those of male rats of the same age, while intermeal intervals, interdraft intervals and licking events/min/draft of male rats were greater than those of female rats. Sex differences of meal number, intermeal intervals and feeding events/min/meal as a group disappeared by 21 mo. Light/dark differences of meal number of both sexes, intermeal intervals of females and licking events/min/draft of males as a group also disappeared by 21 mo and difference of feeding events/min/meal disappeared by 15 and 18 mo in males and females, respectively. Occurrence of age-related change varied from 6 to 21 mo depending upon the parameter of the behavior and period (light or dark). Meal number and feeding events/min/meal showed the most clear-cut age-related changes and the decline occurred earlier and was more remarkable in males than in females. The age-related decline of patterns and the power spectrum of drinking behavior was less prominent than that of feeding behavior. These results indicate that feeding behavior is more affected by the aging process than is the drinking behavior of rats, and that male rats show more prominent aging changes than females.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of pinealectomy on sexual behavior of normal and monosodium L-glutamate-treated rats

Subcutaneous injections of monosodium L-glutamate (MSG) were administered, as a neurotoxin, at a dose of 4 mg/g body weight to rat pups on days 1 and 3 postnatally. Pinealectomy was performed at 6 weeks of age, and animals were allowed to mature. The intact MSG-treated rats showed a decrease of lordosis quotient in females and a reduction of ejaculation frequency and an increase in mount frequency in males. Pinealectomy caused no significant improvement on sexual behavior of the saline-treated normal rats, but it caused a marked improvement of the sexual receptivity in MSG-treated female rats and reinstated ejaculation in MSG-treated males. The circulatory sex steroid levels, estrogen in females and androgen in males, were not significantly different between the intact and pinealectomized MSG-treated groups in the respective sexes, whereas the progesterone level in females was significantly elevated in the pinealectomized MSG-treated group compared with the intact MSG-treated group. These findings suggest that the pineal gland plays an inhibitory role on the sexual behavior of MSG-treated rats and the improvement of sexual behavior following pinealectomy may be dependent on certain mechanisms other than the actions of circulatory androgens or estrogens.

Changes in female sexual behavior of old female rats: comparison between exit method and non-exit method

The female sexual behavior including proceptivity, receptivity and sociosexual behavior of preferential approach to males was tested in 12 young adult female rats aged from 6 to 7 months and in 59 old female rats aged from 18 to 21 months with the exit method and the traditional non-exit method. The percentage of rats displaying a high lordosis quotient (LQ) and that of rats showing solicitation were lower in old females than in young females tested either with the non-exit method or the exit method. Only with the non-exit method were the mount frequency per minute of male rats toward old females of the high-LQ group and the solicitation score of old female rats lower as compared to young females. The incidence of preferential approach of the female rats, whether young or old, toward intact young males and their time spent in the compartment of intact young males were not different, however, the frequency of old female rats to visit the arena of intact young males was lower than that of young females. In summary, the major age-related changes in female sexual behavior, the low percentage of rats displaying high LQ and of rats showing solicitation, are quite robust and environmentally independent.

Difference in the responsiveness of old female rats to estrogen to secrete sex attractants as a function of different reproductive states

Two age groups of Long-Evans rats (young: 3.5-7 months of age and old: over 23 months of age) were ovariectomized and implanted subcutaneously with a 1:2 estradiol benzoate (E2)-cholestrol mixture-filled Silastic capsule. Olfactory preference of male partners to these female rats over ovariectomized young rats without E2 replacement was examined. Olfactory preference of adult male rats as indicated by investigation frequency and investigation time for old pseudopregnancy (PSP) rats and long-term ovariectomized rats was decreased but not that of prolonged-vaginal-cornification (PVC) rats when compared with young female rats. These results indicate that the responsiveness of old PVC rats to estrogen to secrete sex attractants is not decreased but that of PSP rats and long-term ovariectomized rats is decreased when compared with young female rats.

Effects of long-term testosterone replacement on copulatory activity in old male rats

Various parameters of copulatory behavior were examined in intact and castrated testosterone-(T-)treated male rats of various ages ranging from 3 to 27 months. Serum T levels were controlled by subcutaneous implantation of different sizes of T-filled Silastic capsules at the time of castration. In intact male rats, scores of various parameters of copulatory behavior declined gradually from middle age and no ejaculation was observed in any rats over 22 months of age. When serum T levels were maintained at 0.78-0.87 ng/ml for 6 months from 4 months of age, these rats showed the same copulatory activity as intact rats, except that fewer rats exhibited ejaculation at 8 and 10 months of age and showed decreased total mount frequency at 10 months of age. Even when serum T levels were maintained at 2.95-3.53 ng/ml for a period of 6 months from 18 months of age, copulatory activity still declined gradually and no rats over 22 months of age ejaculated. However, long-term elevation of serum T level could prevent further decline of intromission frequency in old age. These results indicate that the copulatory activity of male rats in response to circulatory T declined with advancing age and that prolonged low levels of serum T had only a minor role in the onset of decreased responsiveness of neural male sexual behavior.

Effects of septal lesion on lordosis response induced by estradiol in middle-aged and old female rats

Long-Evans female rats were divided into three age groups: 10 young rats (5 months of age), 7 middle-aged rats (10-13 months of age) and 6 old rats (21-27 months of age). The rats were ovariectomized and immediately implanted subcutaneously with a silastic capsule filled with estradiol benzoate (E2). Lordosis response was compared in each animal before and after the septal lesion. Serum E2 levels were 197 +/- 27 pg/ml (mean +/- SEM), 192 +/- 81 pg/ml and 405 +/- 83 pg/ml in young, middle-aged and old rats respectively. When serum E2 levels were adjusted by analysis of covariance, LQ (lordosis quotient) was 42, 36 and 61 in young, middle-aged and old rats respectively before the septal lesion and 98, 68 and 88 respectively after the septal lesion. The extent of potentiation of lordosis after the septal lesion was less in middle-aged and old rats than young rats. These results indicate that an enhanced lordosis response in aged rats is partly due to high circulating E2 levels and partly due to disinhibition of the septal region on lordosis.

Circadian organization of running-wheel activity, food intake and drinking of old male rats

Circadian rhythms of running-wheel activity, food intake and drinking were monitored in old male rats of Long-Evans strain over 22 months of age in both entrained (light:dark 12:12, LD) and free running condition (continuous illumination, LL) and were compared with those of young adult male rats of 3.5 to 6.5 months of age. Twenty-four hour distribution of running activity, feeding events and licking events of young rats as well as old rats showed bi- or tri-modal patterns during the 12 hr dark period of the LD schedule. In the light period, 2 out of 8 old rats, 6 out of 10 old rats and 1 out of 6 old rats had 1 or 2 medium or high peaks in running activity, feeding events and licking events, respectively, leading to equal distribution between the dark and light period. In the LD schedule, old rats showed a decrease in running-wheel activity, its patterns and power spectra, a decrease in feeding events and its power spectra in 6 rats which lost circadian rhythms and increase in feeding events and its power spectra in 4 rats which still showed circadian rhythms and increase in licking events. LL suppressed running-wheel activity, its patterns and power spectra, licking events and its power spectra and feeding events in young rats. However, LL could suppress only feeding events of 4 rats which still showed circadian rhythms and licking events and its spectral level in old rats. The possible causes of decreased response to LL in old rats and its implication are discussed.

Circadian rhythms and patterns of running-wheel activity, feeding and drinking behaviors of old male rats

Running-wheel activity of 7 young adult male rats (3 to 6.5 months of age) and 11 old male rats (22 to 34 months of age), feeding behavior of 10 each of young adult and old male rats and drinking behavior of 6 each of young adult and old male rats were recorded. Circadian rhythms were lost in 2, 6 and 1 old rats respectively in running activity, feeding and drinking behaviors. Loss of circadian rhythm of three behaviors seems not to occur concomitantly. Although the remaining old rats still showed as high a percentage of nocturnal activities in these three behaviors as young rats, the patterns of the behaviors revealed age-related changes. Old rats had decreased daily activity with small numbers and short duration of bursts of activity. Total frequencies of the head of rats interrupting the photobeam of a feeder during 24 hour period increased in old age with patterns of a small number of long meals with a rapid ingestion rate. Total numbers of licking the spout per day increased in old rats with patterns of a small number of short duration draft with a rapid licking rate. Old rats still maintained diurnal difference of drinking-to-feeding ratio. The similarity of the feeding and drinking patterns between old male rats and ventromedial hypothalamus lesioned rats was discussed.

Pattern of reproductive hormone secretion and disappearance rates of LH and FSH in senile male rats

Old Long-Evans male rats (24-33 months of age) do show postcastration rise in serum LH but do not have postcastration LH rise in the pituitary both as expressed in content and concentration. The serum LH levels of intact and castrated rats of old age show a tendency of decrease, though not to the level of statistical significance. The pituitary FSH content and concentration of intact old rats are not different from those of young adults (3.5-5 months of age), whereas serum FSH level of intact old male rats is significantly higher than that of intact young adults. There is a postcastration rise in the pituitary FSH content as well as concentration and serum FSH level in both age-groups. The half-lives of endogenous and exogenous LH and FSH are not different between old male rats (24- to 31-month-old) and young adults (3- to 5-month-old). Blood testosterone levels begin to decline between the age of 12 and 18 months and remained low from 18 months of age on. These results indicate: (1) deficiencies in the LH regulatory mechanism in response to removal of gonadal steroids are easier to manifest than those of FSH control mechanism in old age in male rats; (2) the ability of clearing circulating LH and FSH of old male rats is not different from that o young adult males, if their molecular sizes are similar, and (3) high serum FSH level of old male rats is not due to prolonged half-life in the circulation.

No neuron loss from hypothalamic nuclei of old male rats

Neuron density, volume of the area and total neuron number were measured in the medial preoptic area, supraoptic nucleus, paraventricular nucleus, anterior hypothalamic area, ventromedial nucleus, dorsomedial nucleus and arcuate nucleus of the hypothalamus in young adult male rats (3.5-5 months old) and in old male rats (26-27 months old) of the Sprague-Dawley strain. There is no neuron loss in all measured areas. The results correlate well with the sex difference in the functional changes of the feedback response to sex steroids in old rats.

Cytoplasmic and nuclear binding of estradiol in the brain and pituitary of old female rats

The subcellular distribution of estradiol following the in vivo administration of 3H-estradiol, cytosol and nuclear estrogen receptor after in vitro incubation with 3H-estradiol were studied in young adult female rats (3-6 months old) and old female rats (over 18 months old). After intravenous injection of 3H-estradiol, with or without deithylstilbestrol pretreatment, significantly higher cytosol uptake of estradiol in the pituitary, dorsal hypothalamus and corticomedial amygdala (AMYG) with concomitant significantly lower nuclear uptake in the preoptic area (POA) and basomedial hypothalamus (BMH) and a tendency of lower nuclear uptake in AMYG and pituitary of old noncyclic (NC) rats as compared with young adult female rats were observed. The uterus of NC rats had a low ratio of milligrams of protein per milligram wet weight as compared with young rats and the nuclear binding 1 h after the injection was significantly lower than that of young rats when the value was expressed as disintegrations per minute per milligram weight but not when expressed as disintegrations per minute per milligram protein. Assays of cytosol and nuclear estrogen receptor after in vitro incubation with 3H-estradiol revealed that old prolonged vaginal cornification (PVC) rats did not react estradiol priming with increased nuclear receptors in the pooled brain tissues of AMYG, POA and BMH, anterior pituitary and uterus. These results indicate that there seems to be an impaired translocation of estradiol from cytosol to nucleus in old PVC rats.

Some characteristics of the darkly stained area of the medial preoptic area of rats

Male rats have larger darkly stained area (DSA) within the medial preoptic area (MPOA) than female rats and this sex difference appears at the age of day 5 and continues to persist up to senescence. This sex dimorphism seems to be independent of gonadal hormones in the adult. In male rats the DSA has higher neuron density and larger neurons than the surrounding non-DSA. The total neuron number in MPOA is not different between young male rats and young female rats. In old age, neuron number of MPOA decreased in female rats but not in male rats.

Changes in running-wheel activity, eating and drinking and their day/night distributions throughout the life span of the rat

Running-wheel activity, eating and drinking of 39 male Long-Evans rats of various ages ranging from four to 33 months old, were recorded twice a day and total activity, and food and water intake per day and percentage nocturnal activity were studied. Running activity and food intake decrease as age advances and water intake first decreases from four months to 17 months of age and later increases proportionally with further increases in age. The percentage of nocturnal activity of the running-wheel decreases from 12 months of age proportionally with an increase of age; food and water intake also have this tendency. However, incidence of disappearance of diurnal difference in running activity, eating and drinking is quite low (7%, 32% and 25% respectively). Seven long-term ovariectomized Sprague-Dawley rats over 24 months of age show similar results to those with male Long-Evans rats. Reversal of the lighting schedule does not induce a phase shift of running activity, eating and drinking in two among 15 rats over 18 months of age, seven among 21 rats and four among 21 rats, respectively. Other rats over 18 months of age can recover their light/dark rhythm in a period not significantly different from rats below 13 months of age. The neuron number of the suprachiasmatic nucleus does not have significant correlations with percentage nocturnal activity in running activity, eating and drinking.

Regional differences of neuron loss of rat brain in old age

DNA content was measured in four areas of the brain (cerebral hemisphere, cerebellum, diencephalon, and lower brain stem) of young adult (5-month-old) and aged 24- to 30-month-old Long-Evans rats. There was no change in DNA content in all four areas in old age. The number of brain cells was counted in three areas of the brain (cerebral hemisphere, cerebellum and brain stem) with an ultrasonic separation method. In old age, there was significant loss in the total number of brain cells in the cerebellum but no cell loss in the cerebral hemisphere and the brain stem. The neuron number was significantly decreased and the glia/neuron ratio was increased in the cerebellum and cerebral hemisphere, but neither of them changed in the brain stem in old age. The cerebellum showed significantly more neuron loss than the cerebral hemisphere in old age. DNA content in individual brain cells in the cerebral hemisphere, cerebellum and brain stem does not change in old age; thus, calculation of brain cell number from DNA content in the brain of old rats is justified.

Hypothalamic neuron number of old female rats

Neuron density, volume of the area and total neuron number were measured in the medial preoptic area (MPOA), supraoptic nucleus (SO), paraventricular nucleus (PVN), anterior hypothalamic area (AHA), ventromedial nucleus (VMN), dorsomedial nucleus (DMN) and arcuate nucleus (ARN) of the hypothalamus in young adult female rats (3.5-5 months old) and in old female rats (over 24 months old). As age advances there is a tendency to increase in the volume of hypothalamic area and consequently decrease in the neuron density. However, loss of neuron due to aging occurs only in MPOA, AHA and ARN. The decrease in neuron number due to aging in these three areas ranged from 23 to 50%. No neuron loss due to aging was observed in SO, PVN, VMN and DMN. The physiological significance of neuron loss in MPOA, AHA and ARN is discussed.