Biomedical subjects

M F Lee

Publications and source records attributed to M F Lee.

At least 19 recordsLinked to original sources

PubMed2003

IgE-binding epitopes of the American cockroach Per a 3 allergen.

BACKGROUND: The Per a 3 is a species-specific allergen of the American cockroach (Periplaneta americana) related to insect hemolymph proteins and includes four known isoallergens. This study aimed to identify Per a 3 linear IgE-binding epitopes. METHODS: Per a 3 recombinant fragments were generated from the recombinant Per a 3.01 allergen (685 amino acid residues) by using existing restriction sites or by using polymerase chain reaction products, and expressed in Escherichia coli. Antigenicities were assessed by immunoblotting, enzyme-linked immunosorbent assay (ELISA), and binding inhibition with human IgE. RESULTS: Human IgE recognized recombinant fragments 340-425, 466-579, 502-595, and 595-636 as revealed by immunoblotting and ELISA. On the other hand, the N-terminal fragment 1-399, recombinants 410-443, 472-551, 502-579, 606-636, and the C-terminal fragment 636-685 were unable to bind human IgE. Amino acid sequences 400-409, 466-471, 580-595, and 595-605 were shown to be required for IgE binding to the Per a 3.01 allergen, suggesting that the C-terminus contains most of the IgE-binding sites. Four peptides corresponding to these IgE-binding amino acid sequences were synthesized. These peptides reacted with most sera (62.5-87.5%) tested as revealed by ELISA, demonstrating a heterogeneous IgE-binding response. Moreover, preincubation of IgE-positive recombinant proteins and synthetic peptides with atopic IgE resulted in marked inhibition of the IgE binding to Per a 3.01 allergen. Amino acid sequences 400TVLRDPVFYQ409, 466NNVDQI471, 580VDKGHNYCGYPENLLI595, and 595IPKGKKGGQAY605 of the major recombinant American cockroach Per a 3.01 allergen were involved in IgE binding. CONCLUSION: These findings will advance our understanding of the antigenic structures responsible for allergenicity to the American cockroach, thereby providing strategies for the development of immunotherapies.

Allergens↗

PubMed2001

Sex change in the protandrous black porgy, Acanthopagrus schlegeli: a review in gonadal development, estradiol, estrogen receptor, aromatase activity and gonadotropin.

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is functional male for the first two years of life but begins to sexually change to female after the third year. Testicular tissue and ovarian tissue was separated by connective tissue in the bisexual gonad. This sex pattern provides a very good model to study the endocrine mechanism of sex change in fish. The annual profiles of plasma estradiol, vitellogenin and 11-ketotestosterone concentrations in males were significantly different from those in the three-year-old females. Significantly high levels of plasma estradiol during the prespawning/spawning season and low levels of plasma 11-ketotestosterone during the spawning season were observed in the inversing females. No difference of plasma testosterone levels was observed in males and females. Oral administration of estradiol stimulated high levels of gonadal aromatase activity, plasma gonadotropin II levels and sex change in the two-year-old fish. Exogenous estradiol administered for 5-6 months induced a reversible sex change in one- and two-year-old fish. The sensitive period for estradiol treatment of sex change is from early prespawning to spawning season. Implantation with testosterone for more than a year could not block the natural sex change in three-year-old fish. Exogenous aromatase inhibitors (1,4,6-androstatriene-3,17-dione or fadrozole) suppressed aromatase activity in the brain. Oral administration with aromatase inhibitors for a year further inhibited the natural sex change in three-year-old black porgy and all fish became functional male with spermiation. Estrogen receptor alpha gene in the ovarian tissue of bisexual gonad is significantly less expressed than that in the vitellogenic ovary of female on the basis of reverse-transcription polymerase-chain reaction. There was no difference in the annual profiles of the plasma gonadotropin II levels in the males and natural inversing females. Plasma gonadotropin II levels were significantly higher in estradiol-treated group than those in the control. It is concluded that estradiol, aromatase activity and estrogen receptor in the ovarian tissue play an important role in the natural and controlled sex change in black porgy. The association of gonadotropin and sex change in black porgy is not clear.

Administration, Oral↗

PubMed2000

Expression of the American cockroach Per a 1 allergen in mammalian cells.

BACKGROUND: Cockroach allergens are one of the major etiologic risk factors for developing IgE-mediated allergic respiratory illness throughout the world. Per a 1 is a cross-reactive allergen of American and German cockroaches. This study aimed to investigate the expression of a recombinant American cockroach (Periplaneta americana) Per a 1, C42, allergen in mammalian COS-1 cells. METHODS: The COS-1 cells and Escherichia coli were used to express the P. americana C42 allergen. Recombinant proteins were purified with hydroxylapatite and DE52 chromatography. Biologic reactivities of recombinant proteins were examined by direct IgE binding and IgE inhibition studies with the enzyme-linked immunosorbent assay (ELISA). RESULTS: C42 was successfully expressed in the mammalian COS-1 cell as a 50-kDa secreted protein, and purified from the culture medium. The specific human IgE antibodies against recombinant C42 from either E. coli (C42-E. coli) or COS-1 (C42-COS-1) were compared by ELISA with 12 sera from Per a 1 and C42 skin-test-positive patients. All atopic sera contained specific IgE antibodies to C42 from either E. coli or COS-1. Moreover, recombinant C42-COS-1 bound higher levels of serum IgE than recombinant C42-E. coli among C42-sensitive atopic patients, and a statistically significant difference (P<0.01) was found between them. In addition, recombinant C42-COS-1 as an inhibitor revealed higher inhibition of IgE binding to natural Per a 1 than recombinant C42-E. coli. CONCLUSIONS: The biologically highly reactive recombinant C42 produced in the COS-1 cell provides an alternative expression system and will facilitate studies on the immune response of asthma patients to cockroach allergens.

Allergens↗

PubMed1999

Immunologic characterization of a recombinant American cockroach (Periplaneta americana) Per a 1 (Cr-PII) allergen.

BACKGROUND: Previously, we have identified several Per a 1 (Cr-PII) allergens from a deltagt22A cDNA library of Periplaneta americana. This study aimed to sequence clone C42 and determine its molecular and antigenic properties. METHODS: The cDNA of C42 was sequenced and ligated into a bacteria expression vector, pET21. The recombinant proteins were purified by ion-exchange and affinity chromatographies. Their antigenicities were analyzed by immunoblotting, ELISA, and binding inhibition with human IgE. RESULTS: The nucleotide of the cDNA has been sequenced and the deduced amino acid which encodes a 446-amino-acid protein (50kDa) determined. The recombinant C42 protein can bind both anti-Per a 1 monoclonal antibodies and human IgE and showed a 54.4% (12/22) skin reactivity in atopic patients. Sequence homology searches revealed a high degree of identity to two other members of the Per a 1 family, C17 and C6, and the German cockroach (Blattella germanica) Bla g Bd90K allergen. Interestingly, these allergens all contain internal repeats, and the crude B. germanica extract, Per a 1, and recombinant allergens share similar antigenic determinant(s) as defined by ELISA and IgE-binding inhibition studies. In IgE-binding epitope studies, an immunopositive C42 fragment was first identified from partial protease digestion. Overlapping peptides were then generated by expression of restriction enzyme fragments in E. coli. The shortest peptide, C42-P560, identified by monoclonal antibodies and human specific IgE, can inhibit IgE binding to C42. CONCLUSIONS: An additional Per a 1 allergen has been defined at the molecular level and characterized and preliminary results showed that a potential IgE-reactive region is located within amino-acid residue 358-446 of C42, which is an internal repeat. The results defined the boundaries of the antigenic site and will facilitate further epitope-mapping studies.

Allergens↗

PubMed1998

Detection of human papillomavirus types in cervical adenocarcinoma by the polymerase chain reaction.

OBJECTIVE: To determine the human papillomavirus (HPV) types in cervical adenocarcinoma of patients from Taiwan. METHODS: DNA was extracted from fixed tissues and polymerase chain reaction was performed in conjunction with a unique probe, pRSA I, allowing simultaneous detection of HPV types 6, 11, 16, 18, 31 and 33 from amplified HPV DNAs after endonuclease, RsaI, digestion. RESULTS: Of 69 tissues examined, 31.9% (22/69) were found to contain HPV DNA. Among 22 HPV-positive specimens, no HPV types 6, 11, 31 and 33 were detected. On the other hand, HPV 16 and HPV 18 were found in 11 (15.9%) and 10 (14.5%) of HPV-positive specimens, respectively. One specimen (1.5%) was found to contain both HPV 16 and 18 DNAs. CONCLUSIONS: Our findings support that HPV 18, along with HPV 16, may play a certain role in the adenocarcinoma pathogenesis of the uterine cervix.

Adenocarcinoma↗

PubMed1998

Cloning of the American cockroach Cr-PII allergens: evidence for the existence of cross-reactive allergens between species.

BACKGROUND: Previously, we have identified the 28 and 32 kd proteins as additional important allergens from the American cockroach (Periplaneta americana) Cr-PII allergenic fraction. OBJECTIVE: The aim of this study was the cloning of P. americana Cr-PII allergens. METHODS: A lambdagt22A cDNA library constructed from P. americana mRNA was packaged into Escherichia coli Y1090 (r-), and clones recognized by murine anti-Cr-PII monoclonal antibodies and human IgE antibodies were isolated, sequenced, and subcloned into pET 21 and expressed in E. coli BL21(DE3). RESULTS: Six Cr-PII-positive clones recognized by human IgE antibodies were isolated. Two clones, C6 and C17, were sequenced, and we found encoding proteins of 228 and 274 amino acids with no cysteine or any potential N-glycosylation site, with predicted masses of 25.8 and 31.14 kd, respectively. Both molecules contain internal repeated sequences with a 94% identity between them. C6 and C17 showed 59% and 77.3% skin reactivities, respectively, on 22 cockroach-sensitive atopic patients. Both clones were found to have 28.9% to 31.8% identities to ANG12 protein, a precursor of the African malaria mosquito (Anopheles gambiae) and 82.7% to 85.1% identity to a nucleotide sequence of the German cockroach (Blattella germanica) Bla g Bd90K allergen. The anti-C6 and anti-C17 antibodies were able to recognize Cr-PII, recombinant proteins, five commercial American extracts, and two German cockroach extracts. Moreover, the binding of anti-C6 and anti-C17 antibodies to recombinant protein can be inhibited by B. germanica crude extract. Furthermore, Northern blot analyses have shown that B. germanica mRNAs could be detected by both cDNA probes. CONCLUSION: Our findings provide the first evidence of antigenic cross-reactivity between P. americana and B. germanica allergens on molecular levels. The results will be a great aid in facilitating the epitope mapping and improving diagnostic and therapeutic reagents for both cockroach species.

Allergens↗

PubMed1998

Human adult-onset lactase decline: an update.

Human adult-onset lactase decline is a biologic feature characteristic of the maturing intestine in the majority of the world's population. The digestion and absorption of lactose, the major carbohydrate in milk and also the main substrate for lactase, is often variable, a consequence of lactase levels, gastric emptying rate, and colonic salvage. Although commercially available "lactase" products alleviate symptoms in many lactose-intolerant people, a greater understanding of this variability in lactose tolerance could lead to interventions that reduce the rate of gastric emptying and/or increase the proliferation of lactose-metabolizing bacteria in the colon, leading to more efficient lactose utilization. Adult-onset lactase decline appears to be a risk factor for developing osteoporosis, owing to avoidance of dairy products or interference of undigested lactose with calcium absorption. Elderly with both adult-onset lactase decline and atrophic gastritis or those undergoing anti-ulcer treatment may have an increased risk of low calcium absorption owing to the lack of gastric acid that facilitates calcium uptake. Thus, lactose-intolerant elders should monitor their calcium nutrition status carefully.

Animals↗

PubMed1997

The endocrine mechanism of sex reversal in the protandrous black porgy, Acanthopagrus schlegeli: a review.

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is a functional male for the first 2 years of life but begin to sexually reverse to female after the third year. This sex pattern provides a very good model to study the mechanism of sex reversal in fish. The gonad at 5 month of age consisted of testicular tissue with few primary oocytes at 5 month of age. The ovarian tissue became dominant at 18 months of age during the non-spawning season. Testicular and ovarian tissues were separated by connective tissue. Plasma estradiol-17 beta(E2), vitellogenin and 11-ketotestosterone (11-KT) profiles in males were significantly different from those in the 3-year-old reversing females. Peak levels of plasma E2 in the reversing females occurred during the early prespawning season (in October). Lower levels of plasma E2 were, however, observed in the males. Plasma 11-KT levels significant decreased but no changes of plasma testosterone were detected in the reversing females. Exogenous E2 suppressed the testicular development but induced the gonadal aromatase activity, ovarian development and sex reversal in 2-year-old black porgy. Exogenous T and LHRH analog did not have effects on the sex reversal. Higher concentrations of pituitary GtH II and mRNA of GtH II-beta subunit were detected in the reversed females. These data suggested that E2 and gonadal aromatase closely associated to the occurrence of sex reversal. A working model of the sex reversal in black porgy is proposed.

Animals↗

PubMed1997

Sequencing and immunochemical characterization of the American cockroach per a 3 (Cr-PI) isoallergenic variants.

Two additional members of the American cockroach (Periplaneta americana) Per a 3 (Cr-PI) allergen, C13 and C28, were isolated and sequenced. They encoded proteins of 470 and 393 amino acids with two and no potential N-glycosylation sites, respectively. The molecular weights for C13 and C28 cloned proteins are 56,200 and 46,7000, with PI values of 7.06 and 6.54. C13 and C28 display 95.4% identity with several overlapping predicted central antigenic determinants. Both allergens were also found to have a 95% sequence homology with previously cloned C20 and share similar antigenic determinants, as defined by the structural prediction and ELISA analysis. However, the recombinant C13 and C28 allergens showed 26.3 and 94.7% skin reactivities on asthmatic patients while C20 elicited 47.4%. While no sequence similarity was found to other known allergens, these two aromatic amino acid-rich allergens were highly related to insect hemolymph proteins (28.7-36.5%), as with C20 cloned protein. Results suggest that these two are isoallergenic variants of C20. Sequence variations among isoforms, resulting a significant difference in skin reactivities, will be useful in elucidating the allergenic determinants.

Adolescent↗

PubMed1997

Total intestinal lactase and sucrase activities are reduced in aged rats.

Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestinal microvillus membrane hydrolases that play important roles in carbohydrate digestion. Although the expression of these enzymes during postnatal development has been characterized, the effect of old age on disaccharidase activity is poorly understood. In the present investigation, we examined the effect of aging on lactase and sucrase activities and their mRNA levels in the small intestines of 3-, 12- and 24- mo-old rats by sampling from nine equidistant segments of small intestine. Total intestinal disaccharidase activity or mRNA abundance was determined from areas under the proximal-to-distal curves. Rats 24 mo of age had total intestinal lactase and sucrase activities that were 12 and 38% lower, respectively, than the 3-mo-old animals (P < 0.05). In contrast, total LPH and SI mRNA abundance did not change significantly. Thus, total intestinal lactase and sucrase activities decrease with age in a manner that likely involves a posttranscriptional process. The age-related decline in disaccharidase activity, if extrapolated to humans, may have important implications for the digestion of carbohydrate contained in the diet of the elderly.

Aging↗

PubMed1997

Distribution of hepatitis C virus genotypes among blood donors in Taiwan.

The aim of this study was to investigate the prevalence and distribution of hepatitis C virus (HCV) genotypes of blood donors in Taiwan. RNA was extracted from the serum of anti-hepatitis C virus-positive carriers and this was followed by reverse transcriptase-polymerase chain reaction (RT-PCR) using type-specific primers for the presence of HCV genotypes, 1a, 1b, 2a, 2b, 3a and 6a. Of the 604 anti-HCV-positive specimens, the PCR demonstrated that 93.0% (562/604) were positive for at least one HCV genotype. The remaining 42 specimens (7%) were HCV negative. Among the 562 HCV-positive specimens, 505 (89.8%) contained HCV 1a, 1b, 2a, 2b and 3a as the only genotype, with a prevalence of 0.4% (2/562), 60.1% (338/562), 15.5% (87/562), 11.9% (67/562), and 2.0% (11/562), respectively. No HCV genotype 6a was found. Thirty-seven specimens (6.6%) exhibited mixed infections with multiple HCV genotypes that included types 1b, 2a and 2b, while 20 (3.5%) HCV RNA-positive sera remained unclassified. These results confirm that the predominant HCV genotype in Taiwan is 1b. In addition, genotypes 1a and 3a can also be found in Taiwan at low frequency.

Adolescent↗

PubMed1996

Sequencing analysis of cDNA clones encoding the American cockroach Cr-PI allergens. Homology with insect hemolymph proteins.

A previous article described the isolation of several lambdagt22A cDNA clones expressing the American cockroach (Periplaneta americana) Cr-PI allergens recognized by both human atopic IgE antibodies and anti-Cr-PI monoclonal antibodies (Wu, C. H., Lee, M. F., and Liao, S. C.(1995) J. Allergy Clin. Immunol. 96, 352-359). This article presents the nucleotide and deduced amino acid sequences of two cDNA clones encoding major allergens of P. americana. Clones C12 and C20 encode proteins of 685 and 631 amino acids with two potential N-glycosylation sites each. The predicted molecular weights for C12 and C20 cloned proteins are 79,300 and 75, 500 with isoelectric point values of 6.26 and 6.63, which are compatible with the determined sizes (Mr 78,000 and 72,000) and isoelectric point value (6.2) of the Cr-PI allergens of P. americana. A high degree of identity (69.1%), including several overlapped predicted central antigenic determinant residues, was found between two allergens. The anti-fusion protein antibody-based enzyme-linked immunosorbent assay was able to detect crude American cockroach extract, Cr-PI, recombinant proteins, and commercial cockroach extracts, which provides further evidence that two allergens share common antigen determinants. Recombinant allergens of clones C12 and C20 both showed 47.4% skin reactivities on 19 cockroach-sensitive asthmatic patients. Unexpectedly, although no sequence similarity was found to other known allergens, two aromatic amino acid-rich allergens were found to have a striking sequence identity to insect storage proteins (20.1-33.9%), insect juvenile hormone-suppressible proteins (30.9-36.4%), and arthropod hemocyanins (29.7-34.6%). Results suggested that two prominent allergens of P. americana are ancestrally related to these insect hemolymph proteins and represent a new group of proteins in the hemocyanin superfamily. These data will now facilitate epitope-mapping studies, and the recombinant allergens may be valuable for diagnostic and therapeutic purposes.

Adolescent↗

PubMed1996

Gene expression of the receptor for growth-hormone-releasing hormone is physiologically regulated by glucocorticoids and estrogen.

We investigated the effects of glucocorticoids and estrogen on the gene expression of growth hormone (GH) and the receptor for growth-hormone-releasing hormone (GHRH) by measuring the mRNA levels of GH and GHRH receptor in pituitary tissues of Sprague-Dawley rats using Northern blot hybridization and specific cDNA probes. Male rats, 6 weeks of age, were either adrenalectomized (or sham-operated) or treated with varying doses of dexamethasone (40, 200, 500 or 1,000 micrograms/kg/day, i.p.) for 3 days. Female rats, 4 weeks of age, were oophorectomized or sham-operated, and treated with 17 beta-estradiol benzoate 25 micrograms/kg/day (or vehicle) s.c. for 5 days starting 10 days after oophorectomy. Adrenalectomy was associated with a reduction in weight gain and decreased GHRH receptor mRNA levels (p < 0.05 and p < 0.0001 versus sham-operated, respectively). Dexamethasone treatment, however, was associated with a dose-dependent reduction in weight gain (p < 0.0001) but dose-dependent increases in GHRH receptor mRNA and GH mRNA levels (p < 0.0001 and p < 0.05, respectively). In the female rats, weight gain was increased by oophorectomy (p < 0.005 vs. sham-operated) and decreased by estrogen treatment (p < 0.05 vs. vehicle-treated). Pituitary GHRH receptor mRNA levels were also increased by oophorectomy (p < 0.05) and decreased by estrogen (p < 0.005). GH mRNA levels were unchanged by oophorectomy but decreased after estrogen treatment (p < 0.05). In conclusion, our findings suggest that endogenous glucocorticoids and estrogen are physiological regulators of pituitary GHRH receptor gene expression. Glucocorticoids and estrogen also regulate GH secretion via effects on GH gene expression. Changes in GHRH receptor and GH mRNA levels cannot explain the growth retardation in dexamethasone-treated rats.

Animals↗

PubMed1995

Complete genomic RNA sequences of cucumber mosaic virus strain NT9 from Taiwan.

The nucleotide sequences of the RNAs 1, 2, and 3 of the cucumber mosaic virus (CMV) Taiwan isolate NT9 were determined and compared at both the nucleotide and amino acid levels with those of CMV strains Fny, Y, O from subgroup I and strain Q from subgroup II. NT9-CMV has an unique feature at the C-terminus of the 3a protein which contains four extra-amino acids. All three RNAs and their encoded proteins, except 2b, of NT9-CMV share more than 90% identity with those of strains in subgroup I, and 72%-85% identity with Q-CMV. The results indicated the conservation of sequences of CMV derived from different geographical locations.

Amino Acid Sequence↗

PubMed1995

Isolation and preliminary characterization of cDNA encoding American cockroach allergens.

BACKGROUND: Two prominent proteins of 78 and 72 kd in Cr-PI have been found to be the major allergens of American cockroach (Periplaneta americana). METHODS: A lambda gt22A cDNA library generated from messenger RNA of American cockroach was packaged into Escherichia coli Y1090(r-) and initially screened with rabbit polyclonal antiserum raised to crude extract of American cockroach (CRa-A). RESULTS: Twenty-nine anti-CRa-A-positive clones were isolated, and 11 clones were recognized by rabbit anti-Cr-PI and reactive with IgE antibodies of atopic serum pool. Among these 11 clones, eight were recognized by murine anti-Cr-PI monoclonal antibodies. Four clones (C7, C8, C12, and C29) were found to contain inserts of 2.6 kilobases (kb), and clones C5 and C20 were found to contain inserts of 2.4 kb. The remaining clones (C13, C23, C25, C28, and C35) were found to contain inserts of 1.8, 1.6, 2.5, 1.7, and 0.9 kb, respectively. Clones C12, C20, C13, and C28 were selected, subcloned into the expression pET vectors, and used to transform, E. coli BL21(DE3). Immunoblot analyses of clones C12, C20, C13, and C28 with anti-Cr-PI monoclonal antibodies revealed fusion proteins with molecular weights of 78 and 50 kd, and 43 kd, 54 kd, and 46 kd, respectively. However, among those fusion proteins only those with molecular weights of 78, 72, 54, and 46 kd were able to bind human specific IgE antibodies. CONCLUSIONS: The cDNA clones are expected to code for the major and principal allergens of American cockroach, and recombinant allergens may therefore be valuable for diagnostic and therapeutic purposes.

Allergens↗

PubMed1995

A microencapsulated analog of LH-RH accelerates maturation but without stimulating sex reversal in the protandrous black porgy, Acanthopagrus schlegeli.

The objective of this study was to regulate the reproduction and levels of gonadal steroids in 3-year-old protandrous black porgy (Acanthopagrus schlegeli) by treatment with microencapsulated D-Trp6-luteinizing hormone-releasing hormone (LH-RH analog) during the prespawning season. Twenty-four previously male black porgy were equally divided into 2 groups and injected with vehicle (control group) or with microencapsulated LH-RH analog (LH-RH analog group), respectively. Spermiation and plasma levels of testosterone (T), estradiol-17 beta (E2) and 17 alpha-hydroxyprogesterone (17 alpha-OH P) were measured, after treatment, at intervals of 1-2 weeks for 4 months. Oocyte diameters were also measured after 4, 10, 12, 14 and 16 weeks of treatment. The microencapsulated LH-RH analog accelerated the onset of spermiation by at least 5 weeks. Oocyte diameters were also significantly increased in the LH-RH analog group. The microencapsulated LH-RH analog did not increase the number of sex-reversing females compared with the number in the control group. High levels of plasma E2 were found in the sex-reversing females in the LH-RH analog and control groups during the prespawning and spawning season. Low levels of plasma E2 were observed in the non-reversed males in both the LH-RH analog and the control groups. Similar profiles of plasma T levels were detected in male and in reversing female black porgy in the LH-RH analog and control groups. Plasma 17 alpha-CH P levels were low and constant throughout the experimental period in fish in each group. These findings indicate that the microencapsulated LH-RH analog accelerated gonadal maturation in the black porgy during the prespawning season. Plasma levels of E2 seem to be closely related to the occurrence of natural sex reversal in the protandrous black porgy, A schlegeli.

17-alpha-Hydroxyprogesterone↗

PubMed1995

Decreased vascular contractile and inositol phosphate responses in portal hypertensive rats.

The purpose of this study was to investigate the vascular contractile and inositol phosphate responses in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation (PVL) in Sprague-Dawley rats. Sham-operated rats served as controls. Pressures, vasoconstrictor responses, and inositol phosphate responses were determined at 14 days after surgery. The portal venous pressure was significantly higher, while systemic arterial pressure and heart rate were lower, in PVL rats. Dose-dependent contractile responses were observed for both norepinephrine (1 x 10(-8) - 3 x 10(-6) M) and vasopressin (3 x 10(-10) - 3 x 10(-8) M) in the tail artery of both groups. The contractile response to norepinephrine was significantly decreased in PVL rats compared with controls at all doses. The contractile response to vasopressin was significantly decreased in PVL rats at higher doses. After myo-[3H]inositol incorporation in tail artery, the levels of 3H-labelled phosphatidylinositols (cpm/mg) were similar between the two groups. Norepinephrine (10(-7) - 10(-5) M) and vasopressin (10(-10) - 10(-8) M) dose dependently stimulated the 3H-labelled inositol phosphate production in the tail artery of both PVL and sham-operated rats. However, the response was significantly lower in PVL rats. The results suggested that the attenuation of vascular contractile responses in portal hypertension was reflected in the phosphoinositide messenger system.

Animals↗

PubMed1994

Structural genes, not the LTRs, are the primary determinants of reticuloendotheliosis virus A-induced runting and bursal atrophy.

Reticuloendotheliosis virus strain A (REV-A) and chicken syncytial virus (CSV), two replication competent avian retroviruses, differ in the extent to which they induce a runting syndrome that includes anemia, lymphoid organ atrophy, and reduced body size. We have isolated an infectious clone of CSV, the less pathogenic of the two viruses, and compared it to REV-A. Partial DNA sequence analysis suggests that it differs from REV-A by no more than 1 to 2% at the nucleotide level. Analysis of viral interference indicates that these two viruses use the same cell receptor for infection of both fibroblasts and hematopoietic cells, DNA sequence of the CSV and REV-A long terminal repeats (LTRs) reveals that these structures differ principally by two small insertions (5 and 19 bp) present in the U3 region of REV-A. The larger of these may encode enhancer sequences that have been reported to influence transcription rates in vitro. Measurement of steady-state levels of viral RNA in infected cells, however, as well as circulating virus in infected chicks indicates that the different pathogenic responses elicited by these two viruses are not due to large differences in viral transcription or replication. Chimeric viruses were constructed in which the LTRs from one virus were used to express the structural genes of the second virus. Infection of 1-day-old chicks by parental virus as well as the reciprocal chimeric constructs demonstrated that the ability to induce both runting and bursal atrophy segregated with the structural genes of REV-A. Infection of birds with additional chimeric viruses in which the env genes of REV-A and CSV were exchanged indicated that the pathogenic response resulting from REV-A infection was due to at least two regions of the viral genome encoding structural genes.

Anemia↗