Quality, storability, and essential oil content of Ligularia fischeri during modified atmosphere packaging storage.

Modified atmosphere packaging (MAP) enhanced the quality and storability of Ligularia fischeri. Oxygen transmission rate (OTR) films were used as a MAP. MAP storage displayed lower fresh weight loss than perforated film. The oxygen, carbon dioxide, and ethylene concentration were properly maintained by a 10,000 cc OTR packaging film at 8 °C and 30,000 cc OTR packaging film at 24 °C. On the last day of storage, the off-odor, such as the acetaldehyde and ethanol concentration, was the lowest in the 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C treatments. The 10,000 cc OTR film treatment at 8 °C and 30,000 cc OTR film treatments at 24 °C had the highest chlorophyll content, total phenolic content, leaf toughness, antioxidant activity, vitamin C, and less off-flavor. The shelf life of 10,000 cc OTR film was 13 days, at 8 °C storage temperature. At 24 °C storage temperature, the shelf life of 30,000 cc OTR film was 4 days. The MAP storage of the Ligularia treated with 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C had the highest essential oil content. These results suggest that the best MAP film for cold-chain distribution was the 10,000 cc OTR film, and the 30,000 cc OTR film was a more suitable MAP film for local distribution without the cold-chain system of L. fischeri.

Steroid plus antiviral treatment for Bell's palsy.

OBJECTIVES: The effectiveness of antiviral agents for the treatment of Bell's palsy is uncertain. We evaluated whether a steroid with an antiviral agent (S + A group) provided better recovery outcomes than a steroid alone (S group) in patients with Bell's palsy. SUBJECTS AND DESIGN: A total of 1342 patients diagnosed with Bell's palsy who visited the Kyung Hee Medical Center in Seoul, Korea, from 2002 to 2012 were included in this study. Patients in the S + A group were treated with prednisolone and antiviral agents (n = 569) and those in the S group with prednisolone alone (n = 773). Outcomes were measured using the House-Brackmann (HB) scale according to age, initial disease severity, electroneurography (ENoG) findings and underlying comorbidities. RESULTS: The rate of recovery (HB grades I and II) with initially severe Bell's palsy (HB grades V and VI) was higher in the S + A than in the S group (P = 0.001). However, the rates of recovery were similar with initially moderate palsy (HB grades II-IV) (P = 0.502). In patients classified according to age and ENoG-determined severity of palsy, the overall recovery rate was higher in the S + A than in the S group, but the differences were not statistically significant (P > 0.05 for both). The recovery rate without diabetes mellitus (DM) and hypertension (HTN) was higher in the S + A group than in the S group (P = 0.031). But in the patients with HTN and DM, the difference in recovery rates between the S + A and S groups was not statistically significant (P = 0.805). CONCLUSIONS: Treatment with a steroid plus antiviral agent resulted in significantly higher recovery rates than steroid therapy alone in patients with initially severe Bell's palsy and without either HTN or DM, and a nonsignificant trend towards higher recovery rates in all patients with Bell's palsy in this study. Antiviral agents may therefore help in the treatment of Bell's palsy.

Influence of urban neighbourhood environment on physical activity and obesity-related diseases.

OBJECTIVES: The impact of characteristics of neighbourhood environment on physical activity and obesity-related diseases is still the subject of debate. This study aimed to explore the impact of urban neighbourhood environment on physical activity and obesity-related diseases. STUDY DESIGN: Cross-sectional study. METHODS: Individuals who participated in the 2009 national health-screening programme, submitted all necessary information, and had lived in Community 1 (Haengdang) or Community 2 (Ilsan) for at least 2 years (n = 16,178) were selected for inclusion in this study. Anthropometric measures were taken and physical activity was assessed using a short questionnaire. RESULTS: No significant difference in the trigger factors for walking, including the amount of neighbourhood park space, number of shopping malls, and distance between the community and shopping malls, was found between the two communities. However, Community 2 had a better street environment than Community 1. Participants who lived in Community 2 were more physically active [adjusted odds ratio (OR) 1.31, 95% confidence interval (CI) 1.16-1.48] and walked more regularly (adjusted OR 1.09, 95% CI 1.02-1.17) than participants who lived in Community 1, and were less likely to have abdominal obesity (adjusted OR 0.83, 95% CI 0.77-0.91), hypertension (adjusted OR 0.88, 95% CI 0.80-0.97) and diabetes (adjusted OR 0.86, 95% CI 0.75-0.99). However, the risk of dyslipidaemia, especially in terms of low-density lipoprotein cholesterol, was higher in Community 2. CONCLUSIONS: These results suggest that a walkable environment has a positive influence on hypertension and diabetes, and physical activity is the possible mechanism for this association. A walkable environment may function as an important tool for health promotion in urban areas.

Metformin activates AMPK and mTOR to Inhibit RANKL-stimulated osteoclast formation.

OBJECTIVE: Metformin is a medication used to treat type 2 diabetes by inhibiting hepatic glucose production through adenosine monophosphate-activated protein kinase (AMPK) activation. Autophagy is closely related to the homeostasis and stress mechanisms of the body. In recent years, much research has arisen on therapeutic methods utilizing autophagy mechanisms to treat diagnoses such as metabolic diseases, tumors, and Alzheimer's disease. This study thus aimed to investigate the effects of metformin treatment on the differentiation of osteoclasts and changes in AMPK mechanisms, which play an important role in regulating energy homeostasis, and mTOR, a highly conserved kinase that regulates autophagy. MATERIALS AND METHODS: Experimentation, including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, tartrate-resistant acid phosphate (TRAP) staining, pit formation assay, immunofluorescence, western blotting, and real-time polymerase chain reaction (PCR) was performed to investigate the effects of metformin on osteoclast differentiation. Additionally, to investigate its association with AMPK and pathways, the AMPK inhibitor compound C and mammalian targets of rapamycin (mTOR) activator leucine were used to examine the expression of osteoclast- or autophagy-related proteins, genes, and TRAP-positive cells. RESULTS: Metformin showed no cytotoxic effects on mouse osteoblastic cell lines (MC3T3-E1) and murine macrophage cell lines (RAW264.7) but did inhibit osteoclast differentiation. Furthermore, metformin was found to inhibit osteoclast differentiation through AMPK activation and mTOR inhibition. In turn, AMPK inhibition using compound C promoted osteoclast differentiation, and mTOR activation using leucine inhibited autophagy and osteoclast differentiation. CONCLUSIONS: Metformin activates the AMPK pathway while functioning as an activator of mTOR, thereby leading to the inhibition of autophagy and osteoclast differentiation.

Effect of precursor ratio on the structural properties of ZnO thin films deposited by low pressure MOCVD.

The effect of precursor ratio (H2O/DEZ) on the texture orientation, surface morphology, optical transparency and electrical resistivity of ZnO thin films deposited by MOCVD was investigated. Deposition temperature and pressure were fixed at 120 degrees C and 0.67 torr, respectively. The precursor ratio was varied between 0.1 and 4. It was found that the texture orientation changed from (0002) to (1120) with increase of the precursor ratio. (1120) textured film shows well facetted tetrapod like rough surface morphology, which scatters the incident light very effectively. The electrical resistivity was in the range of about 0.1 omega cm in the undoped state, which was found to decrease with increase of the film thickness and decrease of the precursor ratio.

Characterization of the low-pathogenic H5N1 avian influenza virus in South Korea.

The low-pathogenic avian influenza (LPAI) virus can serve as a progenitor of the highly pathogenic avian influenza virus, so it is important to monitor the LPAI virus as well as the highly pathogenic avian influenza virus. The Korean LPAI H5N1 virus, A/wild duck/Kr/CSM4-12/09 (H5N1) [Wd/CSM4-12/09], was first isolated from feces of the wild duck in South Korea. Genetic analysis showed that 7 genes of Wd/CSM 4-12/09 clustered in eastern Asia and that the neuraminidase (NA) gene of this isolate was closely related to European LPAI viruses. The Korean LPAI H5N1 virus has the highest similarity with the Japanese LPAI H5N1 virus, A/mallard/Hokkaido/24/09 (H5N1), in 6 genes [polymerase basic protein 2 (PB2), polymerase basic protein 1 (PB1), polymerase acidic protein (PA), hemagglutinin (HA), NA, and nonstructural (NS) genes]. The Korean LPAI H5N1 virus did not replicate in experimentally infected chickens, whereas it replicated in ducks and mice without preadaptation. This study shows that the first Korean LPAI H5N1 reassortment, which occurred between influenza viruses from wild migratory birds in Eurasia, has contributed to the increased diversity of the viral gene pool in eastern Asia; this has the potential to change the host range and to allow the virus to evolve into forms with increased pathogenicity.

Genetic analyses of avian influenza viruses in Mongolia, 2007 to 2009, and their relationships with Korean isolates from domestic poultry and wild birds.

The present study was conducted to monitor wild birds based on the concern that they could disseminate avian influenza virus (AIV) between Mongolia and Korea, which shares the same migratory flyway. Of 1,528 fecal samples analyzed, 21 low-pathogenic AIV were isolated from 2007 to 2009. Nineteen AIV-positive fecal samples were identified as Anseriformes by DNA bar coding. The most frequently isolated subtype was H3 (61.9%), and the most prevalent hemagglutinin/neuraminidase combination was H3N8 (52.4%). Phylogenetic analysis was performed to assess their genetic relationships with those of domestic poultry and wild birds in Korea. The H3 and H7 surface genes belonged to the Eurasian lineage and clustered together in a group with Korean wild birds and poultry. Most N8 genes clustered phylogenetically with viruses isolated in Eurasia, whereas 1 of the Mongolian viruses and some Korean viruses belonged to the North American lineage. The polymerase acidic protein of the internal gene was not distinguishable from the H5N1 highly pathogenic AIV of the goose/Guangdong/1/1996 (Gs/Gd)-like virus. Our study suggests that Mongolian AIV isolates have evolved with genetically multiple genotypes and are closely related to those of AIV in poultry as well as in wild birds in Korea.

Genome-wide analysis in 756,646 individuals provides first genetic evidence that ACE2 expression influences COVID-19 risk and yields genetic risk scores predictive of severe disease.

SARS-CoV-2 enters host cells by binding angiotensin-converting enzyme 2 (ACE2). Through a genome-wide association study, we show that a rare variant (MAF = 0.3%, odds ratio 0.60, P=4.5×10-13) that down-regulates ACE2 expression reduces risk of COVID-19 disease, providing human genetics support for the hypothesis that ACE2 levels influence COVID-19 risk. Further, we show that common genetic variants define a risk score that predicts severe disease among COVID-19 cases.

A catalog of associations between rare coding variants and COVID-19 outcomes.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes coronavirus disease-19 (COVID-19), a respiratory illness that can result in hospitalization or death. We investigated associations between rare genetic variants and seven COVID-19 outcomes in 543,213 individuals, including 8,248 with COVID-19. After accounting for multiple testing, we did not identify any clear associations with rare variants either exome-wide or when specifically focusing on (i) 14 interferon pathway genes in which rare deleterious variants have been reported in severe COVID-19 patients; (ii) 167 genes located in COVID-19 GWAS risk loci; or (iii) 32 additional genes of immunologic relevance and/or therapeutic potential. Our analyses indicate there are no significant associations with rare protein-coding variants with detectable effect sizes at our current sample sizes. Analyses will be updated as additional data become available, with results publicly browsable at https://rgc-covid19.regeneron.com.

Antimicrobial susceptibility of coagulase-negative staphylococci isolated from bovine mastitis between 2003 and 2008 in Korea.

A total of 1,444 coagulase-negative staphylococci (CNS) isolates from bovine mastitic milk samples collected during 2003-2008 in Korea were identified to the species level. Of 14 species identified, S. simulans, S. haemolyticus, and S. sciuri accounted for over 60% of the isolates. All the CNS isolates were tested for susceptibility to eight antimicrobials commonly used in dairy cattle. With a few exceptions, similar resistance patterns were observed among the CNS species: penicillin and ampicillin showed the lowest activity while amikacin, cephalothin, and gentamycin were highly effective. About 39% (557/1,444) of the CNS isolates were pan-susceptible, while 12% (175/1,444) showed resistance to four or more antimicrobials tested.

Survival rate of H5N1 highly pathogenic avian influenza viruses at different temperatures.

The survival rate of Korean H5N1 highly pathogenic avian influenza (HPAI) viruses was investigated at different temperatures under the laboratory conditions. The estimated survival days for a starting viral concentration of 10(6.5) 50% egg infectious dose/0.1 mL were 930, 1,042, and 3,213 d at 4 degrees C; 226, 232, and 293 d at 20 degrees C; and 51, 55, and 58 d at 30 degrees C for A/chicken/Korea/ES/03, A/chicken/Korea/IS/06, and A/chicken/Korea/Gimje/08 (Gimje/08) viruses, respectively. The stability of the Gimje/08 virus was statistically significant compared with the other 2 viruses except for the data between Gimje/08 and A/chicken/Korea/IS/06 virus at 30 degrees C. This result indicated that the survival rate of 3 Korean HPAI viruses is different at various temperatures, which might have partially influenced the large scale of HPAI outbreak in Korea in 2008.

Prevalence and antimicrobial susceptibility of gram-negative bacteria isolated from bovine mastitis between 2003 and 2008 in Korea.

The objective of this study was to assess trends in the prevalence and distribution of gram-negative bacteria isolated from bovine mastitis and their antimicrobial susceptibilities during a 6-yr period between 2003 and 2008 in Korea. Escherichia coli, Pseudomonas fluorescens, Klebsiella pneumoniae, Enterobacter cloacae, Acinetobacter lwoffi/junii, Pseudomonas aeruginosa, and Serratia marcescens were the most commonly observed pathogens during this period. Generally, gram-negative bacteria showed low susceptibilities to most of the antimicrobials tested in this study, except amikacin and gentamicin. Although these 2 aminoglycosides were broadly active against gram-negative bacteria, less than half of those bacteria showed susceptibilities to streptomycin. The beta-lactams, except piperacillin, had the lowest activity among antimicrobials tested in this study. Susceptibilities to chloramphenicol and trimethoprim were fairy high in all genera of gram-negative bacteria, except Acinetobacter spp. and Pseudomonas spp., whereas relatively high resistance to tetracycline was observed uniformly among gram-negative bacteria. There was no significant change in the prevalence of bacterial and the proportion of antimicrobial resistance among gram-negative bacteria isolates during a 6-yr period.

Efficient association study design via power-optimized tag SNP selection.

Discovering statistical correlation between causal genetic variation and clinical traits through association studies is an important method for identifying the genetic basis of human diseases. Since fully resequencing a cohort is prohibitively costly, genetic association studies take advantage of local correlation structure (or linkage disequilibrium) between single nucleotide polymorphisms (SNPs) by selecting a subset of SNPs to be genotyped (tag SNPs). While many current association studies are performed using commercially available high-throughput genotyping products that define a set of tag SNPs, choosing tag SNPs remains an important problem for both custom follow-up studies as well as designing the high-throughput genotyping products themselves. The most widely used tag SNP selection method optimizes the correlation between SNPs (r(2)). However, tag SNPs chosen based on an r(2) criterion do not necessarily maximize the statistical power of an association study. We propose a study design framework that chooses SNPs to maximize power and efficiently measures the power through empirical simulation. Empirical results based on the HapMap data show that our method gains considerable power over a widely used r(2)-based method, or equivalently reduces the number of tag SNPs required to attain the desired power of a study. Our power-optimized 100k whole genome tag set provides equivalent power to the Affymetrix 500k chip for the CEU population. For the design of custom follow-up studies, our method provides up to twice the power increase using the same number of tag SNPs as r(2)-based methods. Our method is publicly available via web server at http://design.cs.ucla.edu.

Construction of a bifunctional mRNA in the mouse by using the internal ribosomal entry site of the encephalomyocarditis virus.

Picornaviral mRNAs have been shown to possess special structures in their 5' nontranslated regions (5'NTRs) that provide sites for internal binding of ribosomes and thus direct cap-independent translation. The translational cis-acting elements for ribosomal internal entry into the 5'NTR of encephalomyocarditis virus (EMCV), a member of family Picornaviridae, have been named the internal ribosomal entry site (IRES). All of the published experiments regarding the IRES function of the picornavirus 5'NTR, however, were performed with cell extracts in vitro or with tissue culture cells in transient assay systems. In this study, we examined the IRES function of the EMCV 5'NTR in chimeric mouse embryos and demonstrated that this element does in fact work stably in mouse embryos as well as in embryonic stem (ES) cells. By using a dicistronic vector, pWH8, consisting of a promoter-driven neomycin resistance gene (neo) followed by the EMCV 5'NTR-lacZ sequence, we showed that more than half of the ES cells made G418 resistant by the vector stained positive for beta-galactosidase (beta-gal). On Northern (RNA) blots, all of the clones analyzed revealed a transcript of the expected size containing both the beta-gal and the neo cistrons. These results indicate that dicistronic mRNAs are produced from the stably integrated vector in those ES clones and that both of the cistrons are translated to produce functional proteins. The chimeric embryos derived from these ES clones also stained positive for beta-gal, suggesting that the bifunctional mRNAs are active in the embryos. This dicistronic vector system provides a novel tool by which to obtain temporally and spatially coordinated expression of two different genes driven by a single promoter in a single cell in mice.

Gene expression signatures associated with the resistance to imatinib.

Imatinib (imatinib mesylate, STI-571, Gleevec) is a selective BCR-ABL tyrosine kinase inhibitor that has been used as a highly effective chemoagent for treating chronic myelogenous leukemia. However, the initial response to imatinib is often followed by the recurrence of a resistant form of the disease, which is major obstacle to many therapeutic modalities. The aim of this study was to identify the gene expression signatures that confer resistance to imatinib. A series of four resistant K562 sublines was established with different imatinib dosage (200, 400, 600 and 800 nM) and analyzed using microarray technology. The transcripts of the genes showing universal or dose-dependent expression changes across the resistant sublines were identified. The gene sets associated with the imatinib-resistance were also identified using gene set enrichment analysis. In the resistant K562 sublines, the transcription- and apoptosis-related expression signatures were upregulated, whereas those related to the protein and energy metabolism were downregulated. Several genes identified in this study such as IGF1 and RAB11A have the potential to become surrogate markers useful in a clinical evaluation of imatinib-resistant patients without BCR-ABL mutation. The expression signatures identified in this study provide insights into the mechanism of imatinib-resistance and are expected to facilitate the development of an effective diagnostic and therapeutic strategy.

Phenotypic and genetic antibiogram of methicillin-resistant staphylococci isolated from bovine mastitis in Korea.

Staphylococcus aureus belongs to the group of major contagious mastitis pathogens, whereas the coagulase-negative staphylococci (CNS) are also capable of causing opportunistic bovine mastitis. Many of these strains are resistant to penicillin or ampicillin because of the long-term use of beta-lactam antibiotics in agricultural and healthcare settings. Based on the simple and highly specific coagulase genotyping by PCR-RFLP used for discriminating among Staph. aureus strains, the relationship between phenotypic antibiogram and the polymorphism of coagulase gene was determined in this study. The staphylococci strains (835 Staph. aureus and 763 CNS) were isolated from 3,047 bovine mastitic milk samples from 153 dairy farms in 8 provinces from 1997 to 2004 in the Republic of Korea. Twenty-one (2.5%) Staph. aureus and 19 (2.4%) CNS strains were resistant to methicillin [oxacillin minimum inhibitory concentration (MIC) > or = 4 microg/mL]. The mecA gene was also found in 13 methicillin-resistant Staph. aureus (MRSA) and 12 methicillin-resistant CNS (MRCNS) isolates with a significantly higher detection rate of the mecA gene in MRSA with high MIC (> or = 16 microg/mL) compared with those with MIC < or = 8 microg/mL. Methicillin-resistant Staph. aureus and MRCNS were also more resistant to other antibiotics (ampicillin, cephalothin, kanamycin, and gentamicin) than methicillin-susceptible staphylococci. Among 10 different coa PCR-RFLP patterns (A to J) in 706 Staph. aureus strains, the main types were A (26.9%), B (17.0%), G (10.5%), and H (15.4%), with the frequent observation of the A and H types (6 and 10 isolates) in MRSA. This study indicates that major epidemic Staph. aureus clones may be spread between different dairy farms, and the profile of coa genotype can be applied for epidemiological investigations and control of bovine mastitis, particularly one caused by MRSA with specific prevalent coa types.

Antibiogram and coagulase diversity in staphylococcal enterotoxin-producing Staphylococcus aureus from bovine mastitis.

We investigated antibiogram and coagulase gene diversity in staphylococcal enterotoxin (StE)-producing Staphylococcus aureus isolated from raw milk samples of cows infected with mastitis from 140 dairy farms in Korea between 1997 and 2004. Of the 696 Staph. aureus isolates collected in this study, 164 isolates (23.6%) produced one or more staphylococcal enterotoxins (A to D), and 19 isolates (2.7%) were methicillin-resistant. The percentage of StE-producing Staph. aureus (SES) isolates resistant to methicillin, kanamycin, neomycin, amikacin, and tetracycline was greater than that of non-SES. Ten coagulase genotype patterns were observed, including 4 main types comprising I (25.4%), II (13.9%), VII (13.2%), and VIII (17.8%). More than 4 Staph. aureus types were isolated from each of 82 dairy farms in different geographic locations, and only 1 coagulase genotype pattern was observed in 39 of the herds (47.6%). There was no significant correlation between coagulase genotypes harbored by Staph. aureus and their specific StE type. The percentage of isolates producing major StE types (A, B, AC, and ABCD) and being resistant to cephalothin and methicillin was greater among the Staph. aureus isolates with the 4 predominant coagulase genotypes (I, II, VII, and VIII) than among the isolates harboring the 6 rare coagulase types (III, IV, V, VI, IX, and X). Based on coagulase gene polymorphisms, our data indicate that a broad distribution of identical or closely related enterotoxin-producing Staph. aureus strains seem to contribute to bovine mastitis in the Republic of Korea.

Role of annexin II tetramer in plasminogen activation.

The enzymatic cascade triggered by activation of plasminogen has been implicated in a variety of normal and pathologic events, such as fibrinolysis, wound healing, tissue remodeling, embryogenesis, and the invasion and spread of transformed tumor cells. Recent data established that the Ca(2+)- and phospholipid-binding protein, annexin II heterotetramer (AIIt) binds tissue-type plasminogen activator (tPA), plasminogen, and plasmin, and dramatically stimulates the tPA-dependent conversion of plasminogen to plasmin in vitro. Interestingly, the binding of plasmin to AIIt can inhibit the activity of the enzyme, suggesting that plasmin bound to the cell surface is regulated by AIIt. The existing experimental evidence suggests that AIIt is the key physiological receptor for plasminogen on the extracellular surface of endothelial cells.

Molecular cloning, distribution and pharmacological characterization of a novel gonadotropin-releasing hormone ([Trp8] GnRH) in frog brain.

To date nine structural variants of GnRH have been identified in vertebrates and two additional forms have been isolated from a tunicate. In amphibians only mammalian GnRH ([Arg8] GnRH) and type II GnRH (chicken GnRH II, [His5, Trp7, Tyr8] GnRH) have been identified. In the present study, a full-length cDNA encoding a novel type of GnRH was isolated from pituitary of Rana dybowskii. The GnRH gene encodes a GnRH peptide ([Trp8] GnRH) in which tryptophan is substituted for arginine of mammalian GnRH Northern blot analysis revealed the presence of a single 500 bp transcript for the [Trp8] GnRH precursor in forebrain but its absence in testis, ovary, kidney and liver. Restriction digests of genomic DNA demonstrated a single copy of the gene. The [Trp8] GnRH immunoreactive cells were identified in the preoptic area of the frog brain. Synthetic [Trp8] GnRH was tested for its ability to stimulate inositol phosphate production by COS-1 cells transfected with the cloned Xenopus pituitary GnRH receptor and the cloned human GnRH receptor. [Trp8] GnRH had a potency of about 60% compared with mammalian GnRH ([Arg8] GnRH) for the Xenopus receptor, whereas the potency of [Trp8] GnRH was approximately 5% compared with mammalian GnRH for the human receptor. Both mammalian GnRH and [Trp8] GnRH were 1000-fold less potent than type II GnRH for the Xenopus GnRH receptor. The similar potency of [Arg8] GnRH and the novel [Trp8] GnRH for the Xenopus pituitary receptor indicates that, unlike the human receptor, the Xenopus receptor does not discriminate between these amino acids in position eight thereby allowing substitution of the arginine in the mammalian GnRH.

Changes in mRNA levels of a pituitary-specific trans-acting factor, Pit-1, and prolactin during the rat estrous cycle.

The present study examined the changes in mRNA levels of a pituitary-specific trans-acting factor, Pit-1, and prolactin during the rat estrous cycle. Total cytoplasmic RNA was analyzed by Northern blot and slot-blot hybridization to examine the prolactin mRNA level. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to examine the Pit-1 mRNA level. Proestrous and estrous prolactin mRNA levels were significantly higher than the metestrous and diestrous levels, whereas Pit-1 mRNA levels of the estrous and metestrous stages were about two- to threefold higher than those of the proestrous and diestrous stages. Proestrous Pit-1 mRNA levels increased gradually from 10.00 h to 20.00 h, while prolactin mRNA levels slightly decreased until 14.00 h but increased later until 20.00 h. During the rat estrous cycle, especially in the afternoon of the proestrous day, changes of prolactin mRNA levels seem to follow a prior increase of Pit-1 mRNA. Therefore, Pit-1 may be partly involved in the regulation of prolactin gene expression according to the rat estrous cycle. Estradiol administration to ovariectomized rats significantly increased both the mRNA levels of prolactin and Pit-1, which suggests that the gene expression of Pit-1 is regulated by estrogen through indirect extracellular pathways.