Identification of two new nonclassical members of the rat prolactin family

The prolactin (PRL) family is comprised of a group of hormones/cytokines that are expressed in the anterior pituitary, uterus, and placenta. These proteins participate in the control of maternal and fetal adaptations to pregnancy. In this report, we have identified two new nonclassical members of the rat PRL family through a search of the National Center for Biotechnology Information dbEST database. The cDNAs were sequenced and their corresponding mRNAs characterized. Overall, the rat cDNAs showed considerable structural similarities with mouse proliferin-related protein (PLF-RP) and prolactin-like protein-F (PLP-F), consistent with their classification as rat homologs for PLF-RP and PLP-F. The expression of both cytokines/hormones was restricted to the placenta. The intraplacental sites of PLF-RP and PLP-F synthesis differed in the rat and the mouse. In the mouse, PLF-RP was expressed in the trophoblast giant cell layer of the midgestation chorioallantoic and choriovitelline placentas and, during later gestation, in the trophoblast giant cell and spongiotrophoblast layers within the junctional zone of the mouse chorioallantoic placenta. In contrast, in the rat, PLF-RP was first expressed in the primordium of the chorioallantoic placenta (ectoplacental cone region) and, later, exclusively within the labyrinth zone of the chorioallantoic placenta. In the mouse, PLP-F is an exclusive product of the spongiotrophoblast layer, whereas in the rat, trophoblast giant cells were found to be the major source of PLP-F, with a lesser contribution from spongiotrophoblast cells late in gestation. In summary, we have established the presence of PLF-RP and PLP-F in the rat.

Distribution of prolactin-releasing peptide mRNA in the rat brain

In order to identify the distribution of prolactin-releasing peptide (PrRP) mRNA in the rat brain, we independently cloned cDNA of PrRP. Brains were removed from three adult males, and brains from three females each at 0200 and 1400 h on day 7 of pregnancy were obtained. By the nonradioactive in situ hybridization method, the location of PrRP mRNA was detected in very restricted brain areas. The distribution of PrRP mRNA signals was very similar in both sexes. In the hypothalamus, only the ventral part of the caudal dorsomedial nucleus had PrRP mRNA signals. Other forebrain areas did not show any positive signals. In the medulla oblongata, two discrete areas contained PrRP mRNA signals. No positive signal was found in the rostral part of the medulla oblongata extending to the anterior part of the area postrema. The caudal part of the nucleus of the solitary tract (NTS) had neurons with very strong signals of PrRP mRNA. The reticular nucleus showed a few PrRP mRNA positive neurons. The number of PrRP mRNA positive cells in the NTS was not different between experimental groups, although plasma prolactin levels in these animals were different. This anatomical information on the location of PrRP mRNA in the brain provides the framework to understand the physiological functions of PrRP in vivo.

Distinct regulatory regions from the prolactin-like protein C variant promoter direct trophoblast giant cell versus spongiotrophoblast cell-specific expression

PRL-like protein C variant (PLP-Cv) is a newly identified member of the PRL family. PLP-Cv is specifically expressed in the chorioallantoic placenta by two distinct cell populations: trophoblast giant cells and spongiotrophoblast cells. To gain some insight regarding the control of PLP-Cv gene expression and the regulatory factors controlling trophoblast giant cell and spongiotrophoblast cell lineages, we have initiated a structural and functional analysis of the PLP-Cv promoter. The activities of a series of PLP-Cv promoter constructs, ranging in size from 4.5 kb to 50 bp, ligated to a luciferase reporter have been assessed in the Rcho-1 trophoblast cell line (restricted to trophoblast giant cell differentiation) and in a primary spongiotrophoblast cell culture system after transient transfection. PLP-Cv promoter constructs containing 4.5 kb to 149 bp of 5'-flanking DNA possessed full activity in the trophoblast giant cell model. A region located between -149 and -124 bp upstream of the PLP-Cv transcription start site was found to be essential for activation of the PLP-Cv promoter. Spongiotrophoblast cells required additional PLP-Cv 5'-flanking DNA for full activity. A region located between -2518 and -2242 bp upstream of the PLP-Cv transcription start site significantly enhanced PLP-Cv promoter in spongiotrophoblast cells. In conclusion, mechanisms underlying the activation of the PLP-Cv promoter are different in trophoblast giant cells vs. spongiotrophoblast cells.

Transcriptional activation of the decidual/trophoblast prolactin-related protein gene

The decidual/trophoblast PRL-related protein (d/tPRP) is dually expressed by decidual and trophoblast cells during pregnancy. We have characterized the proximal d/tPRP promoter responsible for directing d/tPRP expression in decidual and trophoblast cells. We have demonstrated that the proximal 93 bp of d/tPRP 5'-flanking DNA are sufficient to direct luciferase gene expression in primary decidual and Rcho-1 trophoblast cells, but not in fibroblast, undifferentiated uterine stromal cells or trophoblast cells of a labyrinthine lineage. The 93-bp d/tPRP promoter was also sufficient to direct differentiation-dependent expression in trophoblast giant cells. Mutational analysis demonstrated the differential importance of activating protein-1 and Ets regulatory elements (located within the proximal 93 bp of d/tPRP 5'-flanking DNA) for activation of the d/tPRP promoter in decidual vs. trophoblast cells. Disruption of the activating protein-1 regulatory element inhibited d/tPRP promoter activity by more than 95% in decidual cells, and approximately 80% trophoblast cells. Disruption of the Ets regulatory element reduced d/tPRP promoter activity by approximately 50% in decidual cells, while inactivating the d/tPRP promoter in trophoblast cells. Protein interactions with the trophoblast Ets regulatory element were shown to be cell type specific and to change during trophoblast giant cell formation. In conclusion, a 93-bp region of the d/tPRP promoter is shown to contain regulatory elements sufficient for gene activation in decidual and trophoblast cells.

Using consensus OPCRIT diagnoses. An efficient procedure for best-estimate lifetime diagnoses

BACKGROUND

The Operational Criteria Checklist (OPCRIT) generates diagnoses according to 12 operational diagnostic systems (e.g. DSM-III, DSM-III-R, Research Diagnostic Criteria, ICD-10).

AIMS

To examine the agreement between diagnoses generated by the OPCRIT, as completed by the interviewer, with a best-estimate lifetime procedure using the OPCRIT.

METHOD

Subjects came from large multi-generational bipolar or schizophrenia pedigrees (n = 100), and from a sample of unrelated subjects with schizophrenia (n = 40). We analysed the diagnostic agreement between OPCRIT diagnoses generated by the interviewer and our best-estimate OPCRIT diagnoses, according to DSM-III-R and ICD-10, using Cohen kappa statistics.

RESULTS

Excellent agreement was found between interviewer OPCRIT diagnoses and OPCRIT diagnoses made by the best-estimate lifetime consensus procedure for DSM-III-R (kappa = 0.83) and ICD-10 (kappa = 0.81).

CONCLUSIONS

Results suggest that this procedure for diagnostic assessment is an efficient alternative to classic best-estimate diagnosis procedures.

Biological effects of lithium chloride on Herpetomonas muscarum muscarum and Blastocrithidia culicis (kinetoplastida: trypanosomatidae)

Lithium is widely used in medicine as an antidepressive drug and for myelosuppression attenuation during chemotherapy. In spite of abundant literature, questions on the biological action of lithium ions are far from being answered. We have here examined the effects of lithium (10-200 mM) on culture forms of the trypanosomatid protozoa Herpetornonas muscarum muscarum and Blastocrithidia culicis. Incubation of these parasites with LiCl inhibited cell growth in a concentration-dependent manner, but growth could be restored when the drug was removed from the medium. Furthermore, Li+ induced cell differentiation in H. m. muscarum. Light microscopy examination of cell viability, using erythrosin B staining, showed that all treated parasites remained viable with all drug concentrations used. Ultrastructural analysis by transmission electron microscopy showed that the cells presented no signs of degeneration. However, in H. m. muscarum the nuclei lost their peripheral heterochromatin and appeared filled with a homogeneous matrix, whereas in B. culicis an increased amount of lipid droplets was present in the cytoplasm. Our data show that LiCl treatment arrested the cell division process, stimulated cell differentiation, and affected the metabolism of these parasites.

Nutrient transport across the placenta

The placenta forms a selective barrier that functions to transport nutrients that are of critical use to the fetus. Nutrient transport across the placenta is regulated by many different active transporters found on the surface of both maternal and fetal facing membranes of the placenta. The presence of these transporters in the placenta has been implicated in the facilitation of nutrient diffusion and proper fetal growth. In this review, recent developments concerning nutrient transporters that regulate glucose, amino acid, fatty acid, and nucleoside transplacental movement are discussed.

Uterine natural killer cells are targets for a trophoblast cell-specific cytokine, prolactin-like protein A

PRL-like protein A (PLP-A) is a member of the PRL family expressed in trophoblast cells coincident with establishment of the chorioallantoic placenta. The purpose of this investigation was to identify targets for PLP-A. Using an alkaline phosphatase-tagging strategy, we show that PLP-A specifically interacts with a population of natural killer (NK) lymphocytes within the mesometrial compartment of decidua from pregnant and pseudopregnant rats. These observations are supported by the codistribution of PLP-A targets with cells expressing the rat NK cell surface marker, gp42, the absence of PLP-A binding in conceptuses from NK cell-deficient tg epsilon26 mice, and the specific interaction of PLP-A with a rat NK cell line, RNK-16. We have further demonstrated that PLP-A effectively suppresses RNK-16 cell cytolytic activities. Our results provide evidence for a new paradigm of embryonic-maternal communication involving a PLP-A signaling pathway between trophoblast cells and uterine NK lymphocytes.

Immunocytochemical mapping of the hemoglobin biosynthesis site in amphibian erythroid cells

During the past 25 years, several studies have attempted to determine the site of integration of the heme and the four globin chains in vertebrate erythroid cells that is important in the formation of the hemoglobin molecule. Mitochondrion-like organelles or hemosomes were pointed out as responsible for this task. We performed several experiments to investigate this hypothesis. The intracellular distribution of hemoglobin in amphibian erythroid cells was detected by post-embedding immuno-electron microscopy, using a polyclonal anti-human hemoglobin-proteinA-gold complex. Hemoglobin mapping showed an intense labeling in the cell cytoplasm, but none in cytoplasmic structures such as endoplasmic reticulum, mitochondria, mitochondrion-like organelles, Golgi complex, ribosomes or ferruginous inclusions. The mitochondrial fraction obtained according to the protocol described for some authors, showed by ultrastructural examination that this fraction has a heterogeneous content, also composed by microvesicles rich in cytoplasmic hemoglobin, an artifact generated by mechanical action during cell fractionation. Thus, when this fraction is lysed and its content submitted to electrophoresis, hemoglobin bands would be found inevitably, causing false-positive results, erroneously attributed to hemoglobin content of mitochondrion-like organelles. Our data do not confirm the hypothesis that the final hemoglobin biosynthesis occurs inside mitochondrion-like organelles. They suggest that the hemoglobin molecule be assembled in the erythrocyte cytoplasm outside of mitochondria or hemosomes.

Differentiation-dependent expression of gelatinase B/matrix metalloproteinase-9 in trophoblast cells

The purpose of this study was to evaluate the Rcho-1 trophoblast culture system as a model for studying trophoblast invasion and to examine stage-specific expression of enzyme(s) potentially participating in rat trophoblast giant cell invasive behavior. The invasive behavior of the differentiating Rcho-1 trophoblast cells was demonstrated using Matrigel invasion chambers. Gelatin zymography and Western blot analysis of conditioned medium from differentiating Rcho-1 trophoblast cell cultures and rat ectoplacental cone outgrowths revealed a differentiation-dependent increase in gelatinase B/matrix metalloproteinase (MMP-9). Nothern blot and reverse transcriptase polymerase chain reaction (RT-PCR) analyses of Rcho-1 trophoblast or ectoplacental cone cells also showed increasing expression of MMP-9 accompanying cell differentiation. Rcho-1 trophoblast cells stably transfected with MMP-9 promoter/luciferase reporter constructs exhibited a differentiation-dependent increase in MMP-9 promoter activation. In conclusion, trophoblast giant cell differentiation is characterized by transcriptional activation of the MMP-9 gene and appearance of the invasive phenotype.

Is there evidence for an age-related reduction in metabolic rate?

To determine whether the age-related reduction in basal metabolic rate (BMR) is explained by a quantitative and/or qualitative change in the components of lean tissue, we conducted a cross-sectional study in groups of young (n = 38, 18-35 yr) and older (n = 24, 50-77 yr) healthy individuals. BMR was measured by indirect calorimetry. Body composition was obtained by using dual-energy X-ray absorptiometry (DEXA), which permitted four compartments to be quantified [bone mineral mass, fat mass (FM), appendicular lean tissue mass (ALTM), and nonappendicular lean tissue mass (NALTM)]. Absolute BMR and ALTM were lower, whereas FM was significantly higher in the older, compared with young, subjects. BMR, adjusted for differences in FM, ALTM, and NALTM, was significantly lower in the older subjects by 644 kJ/day. In separate regression analyses of BMR on body compartments, older subjects had significantly lower regression coefficients for ALTM and NALTM, compared with young subjects. Hence, the age-related decline in BMR is partly explained by a reduction in the quantity, as well as the metabolic activity, of DEXA-derived lean tissue components.

A new member of the mouse prolactin (PRL)-like protein-C subfamily, PRL-like protein-C alpha: structure and expression

In this study, we establish the presence of a unique member of the PRL-like protein-C (PLP-C) subfamily in the mouse, PLP-C alpha, characterize its complementary DNA and gene, and map its chromosomal location and pattern of expression during pregnancy. Mouse PLP-C alpha encodes for a 239 amino acid protein and possesses from 69-71% identity with rat PLP-C, PLP-Cv, PLP-D, and PLP-H. Another feature characteristic of PLP-C subfamily members that is also present in mouse PLP-C alpha is a 6-exon/5-intron gene structure including an aromatic domain encoded by exon 3. Southern analysis with mouse and rat PLP-C subfamily probes suggested the existence of a single mouse PLP-C alpha gene. Mouse PLP-C alpha maps to chromosome 13 along with other members of the mouse PRL family. Expression of mouse PLP-C alpha increases dramatically as gestation advances and is restricted to spongiotrophoblast and trophoblast giant cells of the junctional zone. In summary, we have established the presence of a new PLP-C subfamily member in the mouse and demonstrated its similarity in structure and expression to rat PLP-C subfamily members. This level of conservation between species expands the biological significance of the PLP-C subfamily and provides additional opportunities for genetically evaluating its function.

Differential regulation of lipopolysaccharide (LPS) activation pathways in mouse macrophages by LPS-binding proteins

LPS binding to its receptor(s) on macrophages induces the synthesis of inflammatory mediators involved in septic shock. While the signaling mechanism(s) remains to be fully defined, the human LPS-binding protein (LBP) is known to regulate responses to LPS by facilitating its binding to CD14 on human monocytes. The structurally related bactericidal permeability increasing protein (BPI) differs from LBP by inhibiting LPS-induced human monocyte activation. We have demonstrated that, unlike the human monocyte response to LPS, both LBP and BPI inhibited LPS-stimulated TNF-alpha production in mouse peritoneal macrophages. In contrast, LPS-dependent nitric oxide release was not affected by LBP. LPS induces the phosphorylation of a number of proteins in a dose and time-dependent manner, however, the pattern of LPS-induced phosphorylation was not reduced by either LBP or BPI under conditions that result in selective TNF-alpha inhibition. Further, activation of the transcription factor NF-kappaB in response to LPS was also not modified by either LBP or BPI. Finally, no differences were detected in TNF-alpha or inducible nitric oxide synthase mRNA accumulations induced by LPS in the presence or absence of either protein, whereas a slight decreased mRNA stability was observed in the group with LPS treatment. These results would suggest that many of the early signaling events contribute to LPS-induced macrophage signaling at a point preceding the divergence of pathways that differentially regulate TNF-alpha and NO production.

[Left atrial myxoma and isquemic stroke in a child]

The authors present a case of left atrial myxoma with stroke in an 8-year-old female child. The tumor was removed and two months after the surgery a left atrial septum mass was observed suggesting recurrence. The child was asymptomatic. Literature review emphasizes the rarity and clinically aggressive behavior of this tumor at this age group and demonstrates rare recurrence rates after surgery.

Placental lactogen-I (PL-I) target tissues identified with an alkaline phosphatase-PL-I fusion protein

The rat placenta expresses a family of genes related to prolactin (PRL). Target tissues and physiological roles for many members of the PRL family have yet to be determined. In this investigation we evaluated the use of an alkaline phosphatase (AP) tag for monitoring the behavior of a prototypical member of the PRL family, placental lactogen-I (PL-I). A probe was generated consisting of a fusion protein of human placental AP and rat PL-I (AP-PL-I). The AP-PL-I construct was stably expressed in 293 human fetal kidney cells, as was the unmodified AP vector that served as a control. AP activity was monitored with a colorimetric assay in conditioned medium from transfected cells. Immunoreactivity and PRL-like biological activities of the AP-PL-I fusion protein were demonstrated by immunoblotting and the Nb2 lymphoma cell proliferation assay, respectively. AP-PL-I specifically bound to tissue sections known to express the PRL receptor, including the ovary, liver, and choroid plexus. Binding of AP-PL-I to tissues was specific and could be competed with ovine PRL. The results indicate that AP is an effective tag for monitoring the behavior of PL-I and suggest that this labeling system may also be useful for monitoring the actions of other members of the PRL family.

No evidence for an ethnic influence on basal metabolism: an examination of data from India and Australia

A lower BMR of Indians, when compared with Westerners matched for age, sex and either surface area or body weight, has often been reported in the literature and has been interpreted to reflect an ethnic influence on BMR. To determine the contribution of body composition to these observed differences in BMR, we analysed the data on ninety-six Indians and eighty-one Caucasian Australians of both sexes, aged 18-30 years, studied in Bangalore, India and Melbourne, Australia. Absolute BMR and BMR adjusted for body weight were significantly lower in Indians when compared with Australians of the corresponding sex. However, BMR adjusted for fat-free mass (FFM) in men, and BMR adjusted for FFM and fat mass (FM) in women, were not significantly different between the two groups. Stepwise regression of FFM, FM, sex (0 = women; 1 = men) and ethnicity (0 = Indian; 1 = Australian) on BMR, resulted in the following relationship for the combined data on all subjects: BMR = 88.7 x FFM (kg) + 1713 (n 177; r 0.92; r2 0.85; SEE 425 kJ). The Indian equations of Hayter & Henry (1994), based on body weight, resulted in a significant bias (measured-predicted BMR) of 318 (SE 54) kJ/d in Indian men and -409 (SE 70) kJ/d in Indian women. The equation of Cunningham (1991), based on FFM, accurately predicted the BMR of Indian men, Indian women and Australian men. The small but significant bias of 185 (SE 61) kJ/d in Australian women, may be explained by the significant contribution of FM to BMR in this group. The present study does not provide any evidence for an ethnic influence on basal metabolism. The results strongly support the use of FFM, rather than body weight, for the prediction of BMR in population groups of varying body size and composition. This would allow an accurate estimation of BMR and hence energy requirements in population groups worldwide.

Identification of two new members of the mouse prolactin gene family

The prolactin (PRL) family consists of a collection of genes expressed in the uterus, placenta, and anterior pituitary. These cytokines/hormones participate in the control of maternal-fetal adaptations to pregnancy. In this report, we establish the presence of two new members of the mouse PRL family. Novel expressed sequence tags (ESTs) with significant homology to PRL were isolated from embryonic, ectoplacental cone, and placental cDNA libraries. The cDNAs were sequenced and compared to other members of the PRL family. The two new cDNAs were assigned to the PRL family based on sequence homology and were referred to as PRL-like protein-F (PLP-F) and PRL-like protein-G (PLP-G). PLP-F cDNA encodes for a predicted 267 amino acid protein containing a 30 amino acid signal peptide and three putative N-linked glycosylation sites. PLP-G cDNA encodes for a predicted 266 amino acid protein containing a 30 amino acid signal peptide and six putative N-linked glycosylation sites. Sequence alignments of these proteins with other members of the PRL family suggest some unique features. Both sequences contain an extra amino acid segment located between exons two and three of the prototypical PRL gene and a nine amino acid carboxy terminal extension. PLP-F contained an additional 15 amino acid region situated between exons four and five of the prototypical PRL gene. Both PLP-F and PLP-G mRNAs were expressed in the placenta but not in other tissues (uterus, brain, thymus, heart, lung, diaphragm, liver, kidney, and ovary). In summary, the two newly identified members share approximately 50% amino acid sequence identity, are specifically expressed in the placenta, and represent a new subfamily within the PRL family.

Mapping of bovine pericardium: physical and histopathologic tests

BACKGROUND AND AIMS OF THE STUDY

This study was performed to identify the physical and histopathologic characteristics of different sections of glutaraldehyde-tanned bovine pericardium.

METHODS

Ten pericardial sacs were obtained from animals aged from 18 to 36 months. Physical tests included shrinkage and mechanical resistance (rupture, elongation, tenacity index). Collagen and elastic fibers were evaluated in Gomori's trichrome-stained sections, hematoxylin and eosin, by PAS and Verhoeff's method. Studied areas were proximal to the great arteries, and the right atrial, right ventricular, left ventricular and left atrial regions.

RESULTS AND CONCLUSIONS

Results showed that bovine pericardium does not have enough regional differences to identify any single region for bioprosthesis manufacture. However, histopathology showed better preservation of collagen and elastic fibers in the right ventricular region, implying that this area is more adequate as bioprosthetic material.

Time-dependent physiological regulation of rodent and ovine placental glucose transporter (GLUT-1) protein

To examine the in vivo and in vitro time-dependent effects of glucose on placental glucose transporter (GLUT-1) protein levels, we employed Western blot analysis using placenta from the short-term streptozotocin-induced diabetic pregnancy (STZ-D), uterine artery ligation-intrauterine growth restriction (IUGR) rat models, pregnant sheep exposed to chronic maternal glucose and insulin infusions, and the HRP.1 rat trophoblastic cell line exposed to differing concentrations of glucose. In the rat, 6 days of STZ-D with maternal and fetal hyperglycemia caused no substantive change, whereas 72 h of IUGR with fetal hypoglycemia and ischemic hypoxia resulted in a 50% decline in placental GLUT-1 levels (P < 0.05). In late-gestation ewes, maternal and fetal hyperglycemia caused an initial threefold increase at 48 h (P < 0.05), with a persistent decline between 10 to 21 days, whereas maternal and fetal hypoglycemia led to a 30-50% decline in placental GLUT-1 levels (P < 0.05). Studies in vitro demonstrated no effect of 0 mM, whereas 100 mM glucose caused a 60% decline (P < 0.05; 48 h) in HRP.1 GLUT-1 levels compared with 5 mM of glucose. The added effect of hypoxia on 0 and 100 mM glucose concentrations appeared to increase GLUT-1 concentrations compared with normoxic cells (P < 0.05; 100 mM at 18 h). We conclude that abnormal glucose concentrations alter rodent and ovine placental GLUT-1 levels in a time- and concentration-dependent manner; hypoxia may upregulate this effect. The changes in placental GLUT-1 concentrations may contribute toward the process of altered maternoplacentofetal transport of glucose, thereby regulating placental and fetal growth.

Gestational and smoking effects on peptidase activity in the placenta

Angiotensin converting enzyme (ACE) and leucine aminopeptidase (LAP) regulate fetally and maternally generated peptides in the placenta. In this study, ACE-like activity was found to be decreased and LAP-like activity increased with increasing days of gestation in rat placental tissues forming the fetal:maternal interface. Membrane-associated ACE-like and LAP-like activities in the placenta of smokers were also found to be significantly higher than their respective activities in placenta of nonsmokers. Our collective findings suggest that gestational and environmentally-induced changes in placental peptidase activities may account for variable peptide hormone and/or therapeutic peptide metabolism in the placenta.

Homologues for prolactin-like proteins A and B are present in the mouse

The prolactin (PRL) family consists of a collection of proteins expressed in the uterus, placenta, and anterior pituitary. These cytokines/hormones are hypothesized to control maternal-fetal adaptations to pregnancy. Establishment of mouse models for members of the PRL family expands the experimental repertoire available for investigations on their biological activities. In this report, we establish the presence of mouse homologues for two rat members, PRL-like protein-A (PLP-A) and PLP-B. We present data on their cDNAs and describe aspects of their expression in uteroplacental tissues. A mouse genomic DNA fragment was found to hybridize with a rat PLP-A cDNA. Perusal of the National Center for Biotechnology Information dbEST database resulted in the identification of several putative mouse PLP-A cDNAs and a single putative mouse PLP-B cDNA. The cDNAs were obtained from the IMAGE consortium and Research Genetics and sequenced, and their corresponding mRNAs and proteins were characterized. Overall, mouse PLP-A and PLP-B showed considerable similarities with rat PLP-A and PLP-B in both structure and expression. PLP-A was expressed in both trophoblast giant cells and spongiotrophoblast cells, whereas PLP-B was expressed in decidual and spongiotrophoblast cells. However, some notable exceptions were evident. Mouse PLP-A contained a single putative N-linked glycosylation site and consisted of a single 29-kDa protein species, whereas rat PLP-A contained two putative N-linked glycosylation sites and consisted of two protein species, of 29 and 33 kDa. Subtle differences in the expression patterns in the mouse and rat are also apparent. In summary, we have established the presence of PLP-A and PLP-B in the mouse. The findings expand our knowledge of these two cytokines/hormones and provide additional strategies for studying their function.

Identification and characterization of a mouse homolog for decidual/trophoblast prolactin-related protein

Decidual/trophoblast PRL-related protein (d/tPRP) is one member of a large placental PRL gene family composed of at least nine members in the rat and four in the mouse. Only placental lactogen I and II have been characterized in both rat and mouse. The identification of mouse homologs for rat placental PRL family members will facilitate gene manipulation studies aimed at identifying functions for these hormones. In this report, we establish the presence of d/tPRP in the mouse and characterize its complementary DNA, protein, and pattern of expression during mouse gestation. Evaluation of the National Center for Biotechnology Information database of expressed sequence tags resulted in the identification of several mouse complementary DNA clones exhibiting significant homology to rat d/tPRP. One of these clones was obtained from IMAGE Consortium and Research Genetics for further investigation. The full-length mouse clone was found to have an 81% nucleotide homology with rat d/tPRP and to encode a 239-amino acid protein. Like rat d/tPRP, the mouse protein contains two putative N-linked glycosylation sites and six homologously located cysteine residues. Mouse d/tPRP maps to chromosome 13 along with other members of the mouse PRL family. Like the rat, mouse d/tPRP messenger RNA and protein are expressed by antimesometrial decidual cells and spongiotrophoblast and trophoblast giant cells in the junctional zone of the placenta. In summary, we have established the presence of d/tPRP in the mouse and demonstrated its similarity in structure and pattern of expression to rat d/tPRP. This level of conservation between species expands the biological significance of d/tPRP during pregnancy and provides additional opportunities for evaluating its function.

Signaling pathways controlling trophoblast cell differentiation: Src family protein tyrosine kinases in the rat

Trophoblast giant cell differentiation is characterized by endoreduplication and expression of members of the prolactin (PRL) gene family and can be simulated in vitro via manipulations of the Rcho-1 trophoblast cell line. The regulation of trophoblast cell proliferation and differentiation involves tyrosine protein kinase signaling pathways. Treatment of Rcho-1 trophoblast cells with tyrosine kinase inhibitors disrupted differentiation-dependent expression of members of the PRL gene family and cytoskeletal organization. Activated p60c-src, p62c-yes, and p53/56lyn were present in the Rcho-1 rat trophoblast cell line and in differentiated trophoblast cells isolated from the developing rat placenta. p60c-src and p62c-yes were active in proliferating and differentiating trophoblast cells. During proliferation, p62c-yes exhibited distinct associations with other phosphoproteins (34, 66, 76, and 150 kDa). p53/56lyn was activated only in differentiating trophoblast cells. p53/56lyn showed a differentiation-dependent accumulation in cytoskeletal and membrane fractions, whereas p60c-src levels were virtually invariant in both fractions. Expression patterns of csk, a negative regulator of Src family kinase activities, were not consistent with its involvement in the differentiation-dependent activation of p53/56lyn; however, there was some indication of the participation of a tyrosine phosphatase in the regulation of p53/56lyn. In conclusion, p60c-src, p62c-yes, and p53/56lyn patterns of activation in trophoblast cells are consistent with their involvement in the control of trophoblast cell proliferation and differentiation.

Permeability properties of monolayers of the human trophoblast cell line BeWo

The BeWo cell line (b30 clone) has been examined as a potential in vitro system to study transplacental transport. At the light and electron microscope level, the cells were observed to form confluent monolayers on polycarbonate filters in approximately 5 days and morphologically resembled the typical human trophoblast. BeWo monolayers developed a modest transepithelial electrical resistance and a molecular size-dependent permeability to hydrophilic passive diffusion markers, fluorescein, and selected fluorescein-labeled dextrans. Linoleic acid permeation across BeWo monolayers was asymmetric, saturable, and inhibited by low temperature and excess competing fatty acid. Forskolin and 8-bromoadenosine 3',5'-cyclic monophosphate treatments stimulated morphological changes in BeWo cultures and enhanced the asymmetric passage of linoleic acid across the BeWo monolayers while having minimal effects on passive permeability, affirming that the differentiation state of the cells can influence membrane transporters and transmonolayer permeability. The basic permeability properties of the BeWo monolayers suggest that the cells grown on permeable supports may be examined as a convenient in vitro system to evaluate some transplacental transport mechanisms.

Protein kinase C dependent and independent mechanisms controlling rat trophoblast cell DNA synthesis and differentiation

Trophoblast giant cells are the steroidogenic cells of the rat placenta. In this study, the role of protein kinase C signalling pathways in the control of DNA synthesis and differentiation-dependent progesterone biosynthesis by trophoblast cells were investigated. Rcho-1 trophoblast cells, derived from a rat choriocarcinoma, can be experimentally manipulated to proliferate or differentiate and provide a useful model for studying trophoblast giant cell endocrine differentiation. The role of protein kinase C signal transduction was examined through the treatment of Rcho-1 trophoblast cells with isoquinolinesulfonamide derivatives (H7, a protein kinase C inhibitor; HA1004, a control compound), chelytherine (a protein kinase C inhibitor), and phorbol esters (protein kinase C activators). Treatment with H7 significantly attenuated DNA synthesis in proliferating and differentiating trophoblast cells and accelerated the acquisition of progesterone biosynthetic capabilities by trophoblast cells. Treatment with HA1004, the related but functionally distinct isoquinolone, did not significantly affect trophoblast DNA synthesis or proliferation and only weakly increased progesterone accumulation. Chelytherine significantly inhibited trophoblast cell proliferation but failed to influence trophoblast progesterone production significantly. The phorbol ester, 12-O-tetradecanoylphorbol acetate, did not significantly influence progesterone accumulation. H7 did not significantly influence the concentration of either P450scc or the mRNA encoding it in Rcho-1 trophoblast cells, or the transcriptional activity of the P450scc gene. The results indicate that signalling pathways sensitive to protein kinase C are involved in the control of trophoblast cell proliferation. Differentiation-dependent production of progesterone is sensitive to H7 but appears to be independent of protein kinase C and occurs at a stage other than P450scc expression.

Enrichment in urinary ammonia and urea with hourly oral doses of [15N]glycine: evidence for a step function and a circadian rhythm in protein turnover

1. The present study sought to determine the possible existence of a pool of proteins which turn over with life-time kinetics. The pattern of enrichment of ammonia and urea in hourly samples of urine was determined in normal adults to whom oral doses of [15N]glycine were given hourly for 36 h. The subjects received hourly meals throughout, and in six the study commenced at 06.00 hours, in five at 12.00 hours and in two at 18.00 h. 2. A plateau level of enrichment was achieved in urinary ammonia within 4-6 h. Regardless of the time at which the study started this plateau was held until about midnight, at which time there was an increase in enrichment, with a second higher plateau 5-6 h later. The second plateau was held to the end of the study. For urinary urea the rate of rise in enrichment was slower and smoother, because of the slow turnover of the urea pool. 3. Protein synthesis, derived from the first ammonia plateau, 179 mg h-1 kg-1, was significantly higher than that derived from the second plateau, 118 mg h-1 kg-1. Using the plateau in urea towards the end of the 36 h, the estimate of protein synthesis was 153 mg h-1 kg-1. 4. The results are considered to provide evidence of a pool of proteins for which degradation takes place in harmony with a circadian rhythm.

Permeability and metabolic properties of a trophoblast cell line (HRP-1) derived from normal rat placenta

The HRP-1 cell line is derived from normal rat placenta and appears morphologically similar to and retains characteristic expression of cellular markers of labyrinthine trophoblast cells. In this study, monolayers of HRP-1 cells grown on permeable supports were evaluated as a potential in vitro system to study trophoblast transport and metabolism. The cell line was shown to express and retain functional activity of the predominant placental cytochrome P450 isozyme, CYP1A1. Additionally, the HRP-1 cells retain functional activity of angiotensin I converting enzyme and carboxypeptidase N-like enzyme, peptidases characteristic of the trophoblast. The permeation of several hydrophilic, inert markers across the HRP-1 monolayers was observed to be dependent on effective molecular size and to be passive in nature. Functional asymmetry of the HRP-1 cells was illustrated by the predominant permeation of linoleic acid in the apical-to-basolateral direction across the monolayers. Transferrin passage across HRP-1 monolayers was concentration-dependent, was bidirectional, and could be inhibited by unlabeled transferrin, features typical of the trophoblast transport system for transferrin. Collectively, these properties suggest that the HRP-1 cell line may provide a useful tool for evaluating some of the permeability and metabolic properties of the trophoblast.

Effect of platelet-activating factor on the process of cellular differentiation of Herpetomonas muscarum muscarum

The effects of platelet-activating factor (PAF), at doses ranging from 10(-6) M to 10(-10) M, on cell growth and on cell differentiation of Herpetomonas muscarum muscarum were investigated. Cell differentiation was evaluated by both light and electron microscopy. At the concentrations used, PAF did not interfere with the protozoan growth. However, parasites grown in the presence of PAF (10(-6) M) were significantly more differentiated than those grown in the absence of PAF, since the first day of culture. On the first two days of culture, PAF doses ranging from 10(-10) M to 10(-7) M, did not significantly interfere with the differentiation of these parasites, although after the third day of culture, all PAF doses used significantly increased the protozoan differentiation. Specific PAF receptor antagonists totally abrogated (WEB 2086 and WEB 2170) or significantly decreased (BN 52021) PAF effect on cell differentiation. These findings indicate PAF triggers the process of cell differentiation in Herpetomonas muscarum muscarum and suggest these parasites have receptors for PAF.

The effect of oral contraceptive agents on the basal metabolic rate of young women

The use of oral contraceptive agents by women may be a factor that contributes to the observed inter-individual variability in the BMR. We, therefore, measured the BMR, body build and composition in two groups of young women and also assessed their self-reported level of physical activity. One group had been using oral contraceptive agents for a period of 6 months or more (OCA, n 24), while the other group had never used oral contraceptives (NOCA, n 22). There were no significant differences in age, body build or composition. The absolute BMR in the groups were not significantly different when compared using an unpaired t test (OCA: 5841 (SD 471) v. NOCA: 5633 (SD 615) kJ/d). However, using an analysis of covariance, with either body weight or a combination of fat and fat free mass as covariates, the OCA group had a BMR almost 5% higher than that of the NOCA group (OCA: 5871 v. NOCA: 5601 kJ/d; P = 0.002). When those subjects with high self-reported levels of physical activity were excluded, the difference in BMR between the two groups persisted (P = 0.001). An ANOVA of oral contraceptives use and phase of menstrual cycle showed significant differences in BMR with use of oral contraceptives (P = 0.004) but no difference in BMR between phases of the menstrual cycle. In conclusion, the use of oral contraceptive agents deserves consideration when conducting and analysing data from studies on energy metabolism in young women, as it results in a significantly higher BMR.

Decidual/trophoblast prolactin-related protein: characterization of gene structure and cell-specific expression

Decidual/trophoblast PRL-related protein (d/tPRP) is a member of the PRL gene family and is dually expressed in uterine and placental tissues in a highly coordinated pattern during pregnancy. In the present study, we describe the isolation and characterization of the d/tPRP gene. A lambda DASH II Wistar-Kyoto rat genomic library was screened with a labeled d/tPRP complementary DNA, resulting in the isolation of two phage clones, RGLd-41 [17.7 kilobases (kb)] and RGLd-42 (15.8 kb). RGLd-41 alone was found to contain the full-length d/tPRP gene and was used for subsequent analyses. The d/tPRP gene possesses a six-exon, five-intron organization. Relative to other highly conserved members of the PRL gene family, d/tPRP contains a single small additional exon (exon 3) situated between exons 2 and 3 of the prototypical PRL gene. The region corresponding to exon 3 of d/tPRP encodes for a unique amino acid region found in a subset of PRL family members. A reverse transcription-PCR (RT-PCR) tissue survey for d/tPRP messenger RNA revealed that d/tPRP expression was restricted to decidual and trophoblast tissues. A single transcription start site 65 bp upstream of the initiation codon was identified in decidual tissue, whereas multiple transcription start sites ranging from 61-66 bp upstream of the initiation codon were detected in placental tissue. Various tissue culture systems (primary cultures and cell lines) were evaluated for d/tPRP expression and activation of a 3.96-kb d/tPRP promoter-luciferase reporter construct. Decidual, spongiotrophoblast, and trophoblast giant cell populations expressed d/tPRP and were capable of activating the d/tPRP promoter-reporter construct, whereas other cell types were ineffective. Limited d/tPRP promoter activation was noted in uterine stromal cell lines. In summary, d/tPRP possesses a unique six-exon, five-intron gene structure and exhibits cell-specific expression that is regulated at least in part by a 3.96-kb 5'-flanking region.

The validity of predicting the basal metabolic rate of young Australian men and women

OBJECTIVES

To assess the accuracy of the Schofield, Schofield & James (1985) equations and those of Hayter & Henry (1994) for the prediction of the basal metabolic rate (BMR), of young Australians.

DESIGN

BMR was measured by indirect calorimetry, while fat free mass (FFM) and fat mass (FM) were measured by bioelectric impendence analysis (BIA) in 128 volunteers (39 men and 89 women), aged between 18 and 30 y.

SETTING

Deakin Institute of Human Nutrition, Deakin University, Melbourne, Australia.

RESULTS

The measured BMR of Australian men and women were significantly lower (P < or = 0.001) than the predicted BMR using the Schofield et al (1985) equation, with a mean (s.d.) bias (bias = measured - predicted BMR) of -406(513) kj/d in men and -124(348) kj/d in women. The measured BMR of Australian men and women were similar to the predicted BMR using the equations of Hayter & Henry (1994) and bias was unrelated to body weight. BMR adjusted for FFM and FM was significantly higher by three percent in women on oral contraceptive agents (OCA) as compared to those not on OCA.

CONCLUSIONS

The Schofield et al (1985) equations are not valid for the prediction of BMR of young Australian men and women. The equations of Hayter & Henry (1994) for North Europeans and Americans, provide an accurate estimate of the BMR of Australian men and women at the group level. However, in young women not using OCA a correction factor of 0.97 applied to the predicted BMR provides a better estimate.

Ultrastructural and biochemical analysis of the relationship of Crithidia deanei with its endosymbiont

Some protozoa of the Trypanosomatidae family harbor in their cytoplasm bacterial endosymbionts that provide essential nutrients to and induce morphological alterations in the protozoa. In the present study, a close association between endosymbionts and glycosomes, a peroxisome-like organelle where most of the enzymes of the glycolytic pathway are compartmentalized, was identified by conventional transmission electron microscopy in Crithidia deanei. Such an association was further supported by the cytochemical localization of catalase in the glycosome and also confirmed by 3-D reconstruction of the protozoan. The enzymes cytochrome oxidase and succinate dehydrogenase were detected by ultrastructural cytochemistry. A positive reaction was observed in the protozoan mitochondrion but not in the endosymbiont envelope. Enzymatic assays for succinate cytochrome c reductase reinforced these results, as a low enzymatic activity was detected in an endosymbiont-enriched fraction, while high activity was observed in a purified protozoan mitochondrion fraction. We also demonstrated that a purified symbiont fraction was able to hydrolyze ATP. This activity was Mg+2 dependent, since it was highly stimulated by the presence of physiological concentrations of this ion. Taken together, these observations suggest that no electron transporting system is active in the symbionts of Crithidia deanei and that they might obtain energetic molecules derivated from the protozoan glycosomes.

Enterotoxin production by Staphylococcus aureus clones and detection of Brazilian epidemic MRSA clone (III::B:A) among isolates from food handlers

Staphylococcus aureus is a major bacterial pathogen involved in a wide range of diseases varying from infections to toxaemia. Staphylococcal food-poisoning syndrome is caused by ingestion of bacterial enterotoxins. These toxins are microbial superantigens and may also be virulence factors involved in staphylococcal infection. This study determined the enterotoxin types and pulsed-field gel patterns found among S. aureus isolates obtained from food handlers in community or hospital-located kitchens. Staphylococcal enterotoxin C was the most frequent enterotoxin produced. The data also suggested horizontal spread of ent genes among isolates belonging to the Brazilian epidemic MRSA clone III::B:A. A subclone of MRSA clone III::B:A was isolated from two hospital kitchen workers. This was the first report of this clone from a hospital in Teresina, Piaui State, although the presence of this MRSA clone has already been reported in six other Brazilian cities.

Dual expression of prolactin-related protein in decidua and trophoblast tissues during pregnancy in rats

Decidual prolactin-related protein (dPRP) is a member of the prolactin gene family and is abundantly expressed in the rat deciduum. Previously, dPRP was shown to associate with heparin-containing molecules and was found to reside, at least in part, within the decidual extracellular matrix, where it was postulated to influence decidual cells and other cell types. The purpose of this investigation was to identify the cellular origin and the temporal and regional characteristics of dPRP expression in the rat uterus during pregnancy. Protein expression was evaluated by Western blot analysis, immunoprecipitation, and immunocytochemistry; dPRP mRNA expression was assessed by reverse transcriptase polymerase chain reaction and in situ hybridization. Decidual PRP was first detected at Day 6 of pregnancy or pseudopregnancy. Expression increased with the growth of the deciduum and then declined coincident with regression of decidual tissue. Throughout the first half of pregnancy or pseudo-pregnancy, dPRP and mRNA were predominantly localized to the antimesometrial deciduum of the developing conceptus. During the second half of gestation, expression also appeared in the chorioallantoic placenta. Trophoblast giant cells and spongiotrophoblast cells within the junctional zone of the chorioallantoic placenta expressed dPRP, as did the Rcho-1 trophoblast cell line. In conclusion, dPRP production is elevated from implantation until parturition through the participation of decidual (early pregnancy) and trophoblastic (late pregnancy) tissues.

Developmental regulation of a pregnancy-specific oligosaccharide structure, NeuAcalpha2,6GalNAcbeta1,4GlcNAc, on select members of the rat placental prolactin family

Successful pregnancy is dependent upon an array of signaling proteins secreted by the trophoblast cells of the placenta. Among these is a group of proteins related to pituitary prolactin, known as the prolactin/growth hormone family. These proteins are expressed at specific times during gestation and synthesized in distinct trophoblast cell types in the rat placenta. We report here that select members of this family, prolactin-like protein (PLP-A), PLP-B, PLP-C, decidual/trophoblast PRP, and placental lactogen I variant, only which are expressed in the spongiotrophoblast, late in rat placental development bear Asn-linked oligosaccharides terminating with NeuAcalpha2,6GalNAcbeta1,4GlcNAcbeta-R. This reflects the concurrent expression of these prolactin/growth hormone family members with the peptide-specific beta1,4GalNAc-transferase and an alpha2,6-sialyltransferase, which can add sialic acid to terminal beta1,4-linked GalNAc. We have determined that at least one of the prolactin-like proteins, PLP-A, is recognized by the protein-specific GalNAc-transferase. The presence of NeuAcalpha2, 6GalNAcbeta1,4GlcNAcbeta-R on only a limited number of glycoproteins synthesized by the spongiotrophoblasts between mid gestation and birth reflects the need for both the GalNAc-transferase and the peptide recognition determinant for efficient addition of GalNAc. Thus, expression of the GalNAc-transferase and specific members of the prolactin/growth hormone family is developmentally regulated in the rat placenta, suggesting a physiological role for the terminal NeuAcalpha2,6GalNAcbeta1,4GlcNAcbeta-R sequence on Asn-linked oligosaccharides of these proteins.

Urea kinetics varies in Jamaican women and men in relation to adiposity, lean body mass and protein intake

OBJECTIVE

We have measured urea kinetics in normal adult men and women of different body composition to determine whether adiposity is associated with differences in the rate of urea production or endogenous urea hydrolysis.

DESIGN

Urea kinetics were determined from the excretion of [15N15N]urea in urine over a period of 48 h following a single oral dose of [15N15N]urea, in nine lean and nine obese women and in seven light and seven heavy males while they were consuming their habitual diets. Urinary 5-L-oxoproline was measured as an index of glycine metabolic status.

SETTING

The studies were carried out in the research ward of the Tropical Metabolism Research Unit, University of the West Indies.

RESULTS

Successful studies were completed in eight obese and five lean women and in six heavy and five light men. When compared with lean women, in obese women the rate of urea production and hydrolysis was significantly greater and this difference could not be accounted for by the greater fat-free mass alone, and was in part associated directly with the increase in fat mass. The rate of urea production and hydrolysis was greater in heavy men than in light men, a difference which was attributed to an increase in dietary protein. In obese women and heavy men there was a significantly higher rate of excretion of 5-L-oxoproline in urine when compared with lean women and lean men respectively.

CONCLUSION

This paper highlights the difficulty in identifying an appropriate reference with which to express results in people of different body composition. In obese women urea production and the hydrolysis of urea are increased, in part related to the increased fat-free mass, but also related to the increased fat mass itself. In obese women and men on high protein diets the greater rate of hydrolysis urea may be a reflection of an increased demand for the synthesis of non-essential amino acids, especially glycine.

Prolactin-like protein-B: heterologous expression and characterization of placental and decidual species

Prolactin-like protein-B (PLP-B) is a member of a family of proteins expressed by the rat placenta and/or decidua with characteristics similar to prolactin (PRL). In this report, we present the heterologous expression and characterization of PLP-B. Recombinant PLP-B heterologously expressed in Chinese hamster ovary cells exhibited similar immunoreactive and electrophoretic characteristics with PLP-B produced by rat placental and decidual tissues. N-terminal sequencing verified the identity and purity of the recombinant PLP-B species and the site of cleavage of the signal peptide from the mature secreted PLP-B species. Polyclonal antibodies were generated to the recombinant PLP-B and used for Western blot and immunocytochemical analyses. Recombinant and native PLP-B migrated as a doublet at 30-31 kDa in SDS-PAGE under reducing conditions. Treatment of recombinant and native PLP-B with N-glycanase accelerated their electrophoretic mobility, indicative of their glycoprotein nature. PLP-B was localized exclusively to decidual cells in the developing deciduum and spongiotrophoblast cells in the placental junctional zone. The level of PLP-B protein expression dramatically declined prior to parturition. Potential PRL-like biological actions of PLP-B were also investigated. PLP-B bound weakly to ovarian and liver PRL receptors and did not stimulate the proliferation of lactogen-dependent Nb2 lymphoma cells. In conclusion, recombinant PLP-B possesses characteristics similar to native decidual and placental PLP-B and may represent a hormone/cytokine that has important modulatory actions during the establishment of pregnancy and the initiation of parturition.

Decidual prolactin-related protein: heterologous expression and characterization

As a first step in understanding the role of decidual PRL-related protein (dPRP) during pregnancy, we have generated recombinant dPRP protein. In this report, we present data on the generation, purification, and characterization of recombinant dPRP protein. The dPRP complementary DNA was subcloned into the pMSXND vector, and the vector was transfected into Chinese hamster ovary (CHO) cells by electroporation. After appropriate selection, amplification, and induction procedures, recombinant dPRP was purified from conditioned medium of the CHO-dPRP cells using ultrafiltration, size-exclusion chromatography, and reverse phase HPLC. Recombinant dPRP was found to possess electrophoretic mobility, immunoreactivity, and N-terminal amino acid sequence identical to those of dPRP isolated from decidual tissue. Polyclonal antibodies were generated to the recombinant dPRP and used for Western blot analysis. dPRP is capable of binding heparin, and a significant fraction of synthesized dPRP resides within the decidual extracellular matrix. Recombinant dPRP failed to bind to PRL receptors and showed no stimulatory activity in the PRL-dependent rat Nb2 lymphoma cell proliferation assay. Additional studies have shown that heterologous expression of dPRP in CHO cells significantly increased the ability of CHO cells to form tumors in athymic mice. In conclusion, recombinant dPRP possesses characteristics similar to those of dPRP of decidual origin and is a heparin-binding protein that may facilitate the establishment of pregnancy.

Rcho-1 trophoblast cell placental lactogens: complementary deoxyribonucleic acids, heterologous expression, and biological activities

In this report, we have investigated placental lactogens (placental lactogen-I, PL-I; PL-I variant, PL-Iv; PL-II) expressed by differentiated Rcho-1 trophoblast cells. A complementary DNA (cDNA) library to differentiated Rcho-1 trophoblast cells was constructed and screened with probes to detect PL-I and PL-II. Sequence analysis of three independent Rcho-1 PL-I cDNAs indicated that they significantly differed from the previously reported PL-I sequence but more closely resembled a related cDNA referred to as PL-I mosaic (PL-Im). Upon further analysis, Rcho-1 PL-I/PL-Im transcripts could be detected in Rcho-1 trophoblast cells and normal developing placental tissue; however, the previously reported PL-I transcript could not be identified from the same sources. Given these results, we examined the original PL-I cDNA by PCR and nucleotide sequence analyses. The sequence differed from the original report and was found to be identical to the Rcho-1 PL-I and PL-Im cDNA clones. Thus, PL-I, Rcho-1 PL-I, and PL-Im are equivalent and should be referred to as PL-I. The PL-I gene was localized to chromosome 17 of the rat genome, similar to other PRL family members. Rcho-1 PL-II cDNAs were identical to the published PL-II sequence. PL-Iv cDNAs were isolated from differentiated Rcho-1 cells via an RT-PCR strategy and found to be identical to previously isolated PL-Iv cDNAs. Rcho-1 PL-I and PL-II cDNAs were subcloned into the pcDNA3 expression vector and recombinant protein produced in HRP-1 cells. Both recombinant Rcho-1 PL-I and PL-II proteins significantly stimulated the proliferation of lactogen-dependent rat Nb2 lymphoma cells and mouse mammary epithelial cells. In summary, we show that the Rcho-1 PL-I corresponds to PL-Im and Rcho-1 PL-Iv and PL-II are identical to their previously described placental counterparts. Additionally, both recombinant Rcho-1 PL-I and PL-II proteins are biologically active.

Prolactin-like protein-C variant: complementary deoxyribonucleic acid, unique six exon gene structure, and trophoblast cell-specific expression

The rat placental PRL family consists of proteins structurally related to pituitary PRL. As a consequence of attempting to characterize the gene for one of the members of the family, PRL-like protein-C (PLP-C), we identified a related gene that we have termed PLP-C variant (PLP-Cv). In this study, we present information on the PLP-Cv gene and its pattern of expression. Screening of a rat genomic library with a PLP-C cDNA resulted in the isolation of four phage clones. Nucleotide sequence analysis of the clones revealed a gene, PLP-Cv, closely related but distinct from PLP-C. The PLP-Cv gene possessed a six exon/five intron organization, unique among members of the PRL family, and was localized to chromosome 17 of the rat genome, similar to other PRL family members. A PCR strategy involving primers based on the PLP-Cv gene was used to isolate a placental PLP-Cv cDNA. PLP-Cv showed 90 and 78% sequence identity with PLP-C at nucleotide and amino acid levels, respectively. Expression of PLP-Cv was restricted to the trophoblast lineage and was coordinately activated with PLP-C beginning at day 11 of gestation and continuing until term. Primer extension analysis revealed multiple putative transcription start sites. A 2.1-kilobase pair PLP-Cv promoter-luciferase reporter construct was specifically activated in differentiating rat trophoblast cells but not in other cell types. In conclusion, we have identified a new member of the PRL family possessing considerable homology to PLP-C, a unique gene structure, and displaying a trophoblast-specific pattern of transcriptional activation.

Regulation of connexin31 gene expression upon retinoic acid treatment in rat choriocarcinoma cells

The controlled invasiveness of the trophoblast is based on the balance between invasive properties at implantation and the differentiation program of the developing placenta. During placental development in rats a switch of connexin gene expression has been observed in parallel to the switch from the invasive to the differentiated phenotype of trophoblast cells. To investigate the role of connexin expression for trophoblast invasion, proliferation, and differentiation, we studied one rat trophoblast (HRP-1) and one rat choriocarcinoma cell line (Rcho-1). The choriocarcinoma cells were characterized by expression of cx31 and a lack of E-cadherin, corresponding to the invasive trophoblast in vivo, whereas HRP-1 cells expressed cx43, normally found in the spongiotrophoblast and in late giant cells, and E-cadherin. Upon retinoic acid treatment, Rcho-1 cells irreversibly lost cx31 expression, accompanied by a loss of functional coupling. No changes in regard to connexin expression and cell-cell communication could be observed in HRP-1 cells. In addition, treatment of Rcho-1 cells with retinoic acid for 7 days upregulated expression of cx43 transcript, but no protein could be found. Proliferation was clearly reduced and the mean volume of cells doubled from Day 4 to Day 7 of retinoic acid treatment in Rcho-1 cells, while both parameters were not affected in HRP-1 cells. Both cell lines showed a similar invasion rate using a Matrigel invasion assay, and invasion was equally suppressed upon retinoic acid treatment. Thus the different connexin expression appears more likely to play a role in regulating proliferation and differentiation along the multilineage pathway than invasiveness of rat trophoblast cells.

Effects of cadmium on Euglena gracilis membrane lipids

The toxic effects of cadmium (2 micrograms/ml) on membrane lipids and growth of Euglena gracilis were studied using autotrophic (AUTO), heterotrophic (DARK) and mixotrophic (LIGHT) cells. Cadmium caused inhibition of cellular proliferation (IC50 1.2 micrograms/ml) and morphological alterations which were most pronounced in chloroplasts. The chlorophyll content of LIGHT cadmium-treated cells was reduced 42.5%. Cadmium also caused an increase in protein and total lipid content per cell in all three cell types. Among the membrane lipids, cholesterol content was lower in cadmium-treated cells cultivated under illumination (AUTO: 0.40 +/- 0.02 vs 0.64 +/- 0.08 and LIGHT: 0.40 +/- 0.09 vs 0.53 +/- 0.01 microgram/10(5) cells). There were no changes in total phospholipid content, although cardiolipin content was altered in all three cell types, and in mixotrophic cells there was an increase in phosphatidylglycerol, a phospholipid typically found in chloroplasts. These results suggest that cadmium has an overall toxic effect on Euglena gracilis and that part of the effect can be ascribed to defects in the structure of chloroplasts and mitochondrial membranes.

Cytochrome P450 17 alpha-hydroxylase gene expression in differentiating rat trophoblast cells

Trophoblast giant cells of the rat placenta express cytochrome P450 17 alpha-hydroxylase (P450c17) and synthesize androgens. The purpose of this study was to investigate androgen production and expression of P450c17 in the Rcho-1 trophoblast cell line. These cells are capable of differentiating along the trophoblast giant cell lineage. Androstenedione production increased approximately 70-fold as Rcho-1 trophoblast cells progressed from the proliferation to the differentiation state. P450c17 enzyme activity and mRNA also showed significant increases associated with trophoblast giant cell differentiation. To study the transcriptional regulation of the P450c17 gene, the activities of a series of P450c17 promoter-luciferase reporter constructs were evaluated following transient transfection into Rcho-1 trophoblast cells. A DNA region located-98 bp upstream of the P450c17 gene transcriptional start site was the shortest promoter DNA construct consistently possessing activity in Rcho-1 trophoblast cells. Activities of longer constructs (-156 to -1560 bp) in this population of cells were significantly greater than the -98 bp promoter-reporter construct. The -476 bp P450c17 construct showed maximal promoter activity in transiently transfected Rcho-1 trophoblast cells and was developmentally activated in stably transfected Rcho-1 trophoblast cells. Activation of the cyclic AMP/protein kinase A pathway did not significantly affect P450c17 promoter activity in Rcho-1 trophoblast cells, in contrast to its effects in mouse MA-10 Leydig cells. In summary, Rcho-1 trophoblast cells are capable of endocrine differentiation and are a useful in vitro system for studying the regulation of trophoblast androgen production and P450c17 gene expression.

Ganglioside composition of the rat choriocarcinoma cell line, Rcho-1

The Rcho-1 cell line, originally established from a rat choriocarcinoma, shows differentiation into placental trophoblastic giant cell-like cells and has been used to study the mechanism of placental function control. In the present study, we analysed the ganglioside composition of Rcho-1 cells by HPTLC orcinol/H2So4, TLC/ immunostaining and immunohistochemistry. Rcho-1 cells expressed GM3 and GD3 as the major gangliosides and CTH as major neutral glycolipid when they were cultured in growth medium (20% FCS) or transplanted beneath the kidney capsule. The expression of these gangliosides was strong in the undifferentiated small cells, whereas the completely differentiated giant cells showed poor staining with antibodies against the gangliosides. Under culture conditions to induce cell differentiation using horse serum (1-20% HS), the expression of GD3 was suppressed and re-expressed when the medium was changed to growth medium, suggesting that a change of ganglioside components may trigger and define the direction of terminal differentiation. Thus the composition of glycolipids is conserved in Rcho-1 cells and is similar to that of the rat placenta, where GM3 is dominant in mid-pregnancy and decreased in late pregnancy, whereas GD3 is low in mid-pregnancy and increased in late pregnancy.

Rat placental lactogen-I abolishes nocturnal prolactin surges in the pregnant rat

The twice-daily surges of prolactin (PRL) present during the first half of pregnancy abruptly terminate at midpregnancy concurrent with the appearance of high levels of placental lactogen-I (PL-I) in the blood. This study addressed the role PL-I and other pituitary or placental hormones have in terminating PRL surges in pregnant rats. Implantation of rat PL-I (rPL-I) or ovine PRL into the arcuate-median eminence area of the hypothalamus of day 7 pregnant rats totally eliminated nocturnal PRL surges on days 8 and 9. To assess the specificity of the inhibitory effects of hormones from the PRL-growth hormone (GH) family, rat growth hormone (rGH), human growth hormone (hGH), and rat prolactin-like protein-A (PLP-A) were tested. Only the lactogenic hormone, hGH, had any effect. Since lactogenic hormones may inhibit PRL by stimulation of dopamine synthesis and release into the hypophysial portal blood vessels leading to the anterior pituitary, the effect of these hormones on tyrosine hydroxylase (TH), the rate-limiting enzyme for the synthesis of dopamine activity, was determined. In pregnant rats, both ovine prolactin (oPRL) and hGH significantly increased (64%) TH activity, whereas rPL-I was less effective. In ovariectomized, bromocriptine-treated rats, both rPL-I and oPRL increased TH activity 207 and 151%, respectively. This supports the concept that termination of PRL surges at midpregnancy are owing to secretion of placental lactogens (PLs) from the placenta. However, the mechanism for the inhibition cannot be entirely attributed to an increase in tuberoinfundibular dopaminergic neuronal activity.

Placental lactogen-I variant utilizes the prolactin receptor signaling pathway

Placenta lactogen-I variant (PL-Iv) is a member of a family of proteins expressed by the rat placenta with characteristics similar to prolactin (PRL). In this report, we present the molecular cloning, chromosomal localization, and heterologous expression of PL-Iv. Nucleotide sequence analysis of the PL-Iv cDNA clone predicted a precursor protein of 223 amino acids, including a 28-amino acid signal sequence. The PL-Iv gene was localized to chromosome 17 of the rat genome, which also carries other members of the PRL gene family. PL-Iv heterologously expressed in Chinese Hamster ovary (CHO) cells exhibited similar immunoreactive and electrophoretic characteristics with PL-Iv produced by the rat placenta. N-terminal sequencing verified the identity and purity of the recombinant PL-Iv species and the site of cleavage of the signal peptide from the mature secreted PL-Iv species. Recombinant PL-Iv was shown to bind to ovarian and liver PRL receptors, stimulate the proliferation of Nb2 lymphoma cells, and activate Jak2. Each of these actions is consistent with PL-Iv utilizing the PRL receptor signal transduction pathway.