Rest Of Gestation Research Articles

Events Leading to the Establishment of Pregnancy and Placental Formation: The Need to Fine-Tune the Nomenclature on Pregnancy and Gestation.

Today, there is strong and diversified evidence that in humans at least 50% of early embryos do not proceed beyond the pre-implantation period. This evidence comes from clinical investigations, demography, epidemiology, embryology, immunology, and molecular biology. The purpose of this article is to highlight the steps leading to the establishment of pregnancy and placenta formation. These early events document the existence of a clear distinction between embryonic losses during the first two weeks after conception and those occurring during the subsequent months. This review attempts to highlight the nature of the maternal-embryonic dialogue and the major mechanisms active during the pre-implantation period aimed at "selecting" embryos with the ability to proceed to the formation of the placenta and therefore to the completion of pregnancy. This intense molecular cross-talk between the early embryo and the endometrium starts even before the blastocyst reaches the uterine cavity, substantially initiating and conditioning the process of implantation and the formation of the placenta. Today, several factors involved in this dialogue have been identified, although the best-known and overall, the most important, still remains Chorionic Gonadotrophin, indispensable during the first 8 to 10 weeks after fertilization. In addition, there are other substances acting during the first days following fertilization, the Early Pregnancy Factor, believed to be involved in the suppression of the maternal response, thereby allowing the continued viability of the early embryo. The Pre-Implantation Factor, secreted between 2 and 4 days after fertilization. This linear peptide molecule exhibits a self-protective and antitoxic action, is present in maternal blood as early as 7 days after conception, and is absent in the presence of non-viable embryos. The Embryo-Derived Platelet-activating Factor, produced and released by embryos of all mammalian species studied seems to have a role in the ligand-mediated trophic support of the early embryo. The implantation process is also guided by signals from cells in the decidualized endometrium. Various types of cells are involved, among them epithelial, stromal, and trophoblastic, producing a number of cellular molecules, such as cytokines, chemokines, growth factors, and adhesion molecules. Immune cells are also involved, mainly uterine natural killer cells, macrophages, and T cells. In conclusion, events taking place during the first two weeks after fertilization determine whether pregnancy can proceed and therefore whether placenta's formation can proceed. These events represent the scientific basis for a clear distinction between the first two weeks following fertilization and the rest of gestation. For this reason, we propose that a new nomenclature be adopted specifically separating the two periods. In other words, the period from fertilization and birth should be named "gestation", whereas that from the completion of the process of implantation leading to the formation of the placenta, and birth should be named "pregnancy".

Proteção fetal contra o vírus da diarréia viral bovina (BVDV) em vacas prenhes previamente imunizadas com uma vacina experimental atenuada

Esse artigo relata a avaliação da resposta sorológica e proteção fetal conferida por uma vacina experimental contendo duas amostras atenuadas do vírus da diarréia viral bovina tipos 1 (BVDV-1) e 2 (BVDV-2). Vacas foram imunizadas com a vacina experimental (n=19) e juntamente com controles não-vacinadas (n=18) foram colocadas em cobertura e desafiadas, entre os dias 60 e 90 de gestação, pela inoculação intranasal de quatro amostras heterólogas de BVDV-1 e BVDV-2. A resposta sorológica foi avaliada por testes de soro-neutralização realizados a diferentes intervalos após a vacinação (dias 34, 78 e 138 pós-vacinação [pv]). A proteção fetal foi monitorada por exames ultra-sonográficos e clínicos realizados durante o restante da gestação; e pela pesquisa de vírus e anticorpos no sangue pré-colostral coletado dos fetos abortados e/ou dos bezerros recém nascidos. No dia do desafio (dia 138 pv), todas as vacas vacinadas apresentavam anticorpos neutralizantes em títulos altos contra o BVDV-1 (1.280- >10.240) e, com exceção de uma vaca (título 20), todas apresentavam títulos médios a altos contra o BVDV-2 (80-1.280). O monitoramento da gestação revelou que, dentre as 18 vacas não-vacinadas, apenas três (16,6%) pariram bezerros saudáveis e livres de vírus. As 15 restantes (83,3%) apresentaram indicativos de infecção fetal e/ou falhas reprodutivas. Sete dessas vacas (38,8%) pariram bezerros positivos para o vírus, sendo que cinco eram saudáveis e sobreviveram (27,7%); e dois apresentavam sinais de prematuridade ou fraqueza e morreram três e 15 dias após o nascimento, respectivamente. As oito vacas controle restantes (44,4%) abortaram entre o dia 30 pós-desafio e às proximidades do parto, ou deram à luz bezerros prematuros, inviáveis ou natimortos. Por outro lado, 17 de 19 (89,4%) vacas vacinadas deram à luz bezerros saudáveis e livres de vírus. Uma vaca vacinada abortou 130 dias pós-desafio, mas o produto não pôde ser examinado para a presença de vírus. Outra vaca vacinada pariu um bezerro positivo para o vírus (5,2%). Em resumo, a vacina experimental induziu títulos adequados de anticorpos na maioria dos animais; e a resposta imunológica induzida pela vacinação foi capaz de conferir proteção fetal e prevenir as perdas reprodutivas frente ao desafio com um pool de amostras heterólogas de BVDV. Assim, essa vacina experimental pode representar uma boa alternativa para a redução das perdas reprodutivas associadas com a infecção pelo BVDV.

Epimorphin in embryonic pancreas induces epithelial morphogenesis

Abstract Introduction: Epimorphin is a membrane-associated mesenchymal protein postulated to regulate epithelial morphogenesis in several tissues such as hair follicles, mammary gland, lung and gastrointestinal tract. However, the role of epimorphin in the development and differentiation of the pancreas has not been studied. Methods: Embryonic pancreata of ICR mice were harvested at various gestational ages. The localization of epimorphin protein and mRNA expression was investigated by immunohistochemistry/western blotting and RT-PCR. Further, E (embryonic day) 11.5 dorsal pancreatic rudiments were cultured in Millipore filter-containing Matrigel. Epimorphin neutralizing antibody or recombinant epimorphin protein was added to modulate endogenous epimorphin activities. Results: Epimorphin mRNA was observed in pancreatic mesenchyme from E11.5 through the rest of gestation. Protein expression was seen in the mesenchymal cells as early as E12.5. The intensity and breadth of expression of epimorphin gradually increased during pancreas differentiation and maturation. In adult pancreas, epimorphin was expressed in mesenchymal cells, ducts, blood vessels and islets of Langerhans. Western blot analysis showed expression of both 32-kD and 150-kD isomers in developing pancreas. Treatment of cultured pancreatic epithelia with epimorphin neutralizing antibody prevented normal duct morphogenesis. However, when neutralizing antibody-treated cultures were incubated with recombinant epimorphin, ductal morphogenesis was rescued. Conclusions: The expression of epimorphin during the embryonic period, together with in-vitro culture results, suggest that epimorphin may play a role in mediating the mesenchymal induction of pancreatic epithelial differentiation. This role may be particularly important in duct formation.

Tracheal side effects of endoscopic balloon tracheal occlusion in the fetal lamb model

Objective: To evaluate effects of in-utero endoluminal balloon tracheal occlusion (TO) as suggested for the treatment of Congenital Diaphragmatic Hernia (CDH) on the higher airways of a fetal lamb model. Study design: Fetuses from time-dated pregnant ewes underwent at 94 days (term=145 days) in-utero tracheal occlusion. In study animals an endoluminal, detachable balloon was placed by tracheoscopy. For that purpose a 1.2 mm fibre-optic, semi-rigid endoscope and a medically graded latex balloon were used. In group I ( n=9) lambs were delivered after 2 weeks. In group II ( n=8) the tracheal occlusion was released after 2 weeks, to allow in-utero recovery until term. In positive control animals (group III; n=5) the trachea was clipped at 98 days and fetuses were harvested near term by cesarean section. A total of 17 contralateral littermates in multiple pregnancies served as negative controls. After macroscopic inspection of the trachea, sections were evaluated by light microscopy. Alterations were scored with an empirical interval score for each of the different anatomical elements in the fetal trachea (epithelium, submucosa, cartilage, pars membranacea). Results: For the animal experiments in group I, all balloons were found in place and according to the pulmonary response they were obstructive. Tracheas were macroscopically dilated by the plug mainly due to elongation of the pars membranacea. The total histologic score was correlated to the increase in circumference (mean increase: 3.0 mm). In nearly all cases, the tracheal epithelium at the level of the plug had lost its typical folding pattern. In 44% of cases, local epithelial defects were observed and in 33% of cases there was squamous metaplasia. A chronic inflammatory response was present in over half of the cases, sometimes with giant cell reaction. In group II (the in-utero recovery group) the total score was significantly lower than in group I, with much less prominent unfolding and absence of epithelial defects. Squamous metaplastia was still present in half of the cases; whereas inflammatory responses were less frequent. In group III the trachea expanded normally after removal of the clip. The epithelium had compacted folds, and cilia were well preserved. In two animals however, intraluminal synechia were observed. Below the level of occlusion animals of groups I and II all showed areas of unfolding, but without metaplasia or epithelial defects. Conclusion: Tracheal obstruction by means of endoluminal plugging has been suggested as an alternative in-utero treatment for congenital diagphragmatic hernia. The balloon causes mild epithelial changes, such as unfolding, limited epithelial defects (<25% of the exposure surface) and local inflammatory changes. These changes disappear nearly completely following in-utero unplugging during the rest of gestation. Unfolding of the epithelium is also seen in the trachea under the plug.

Development of the Human Fetal Testis

We describe the histological features of the fetal testis, utilizing 68 fetuses ranging in gestational age from 10 to 41 weeks. During fetal life, the tunica albuginea progressively increases in thickness, and between 29 and 32 weeks it develops two layers. Beyond 25 to 28 weeks, septa are invariably present. Tubules begin as straight structures and become maximally coiled by 30 weeks. Tubular diameter reaches its maximum by 16 weeks and remains constant throughout the rest of gestation. Germ cell and Sertoli cell numbers per tubular diameter have a wide range, but the median number for each cell type remains constant after 13 to 16 weeks. Leydig cells are most numerous between 17 and 19 weeks and decline thereafter. They are infrequent but still present at term. Interstitial lipochrome pigment accumulates during the latter half of gestation and may represent breakdown products from Leydig cell degeneration.

Spectral Edge Frequency as a Simple Quantitative Measure of the Maturation of Electrocortical Activity

The feasibility of using spectral edge frequency (SEF) as a single quantitative measure of the maturation of electrocortical activity is demonstrated in a large number of fetal lambs studied throughout the 3rd trimester. A total of 43 electrocortical recordings obtained from 23 fetal lambs ranging from 116-140 d were subjected to power spectral analysis using the fast Fourier transform. Spectral edge frequency was calculated as the frequency below which 90% of the power resides. The SEF was found to be highly sensitive in identifying the transition between high-voltage slow-activity and low-voltage fast-activity electrocortical activity. By 125 d, the distribution of SEF clearly showed two distinct populations, a low SEF with peak values ranging from 3-9 Hz; and a high SEF (SEFH) with values ranging from 13-23 Hz. Increase in gestational age was associated with a progressive increase in SEFH, which can be described by the linear function (SEF = 0.53GA-51.3). This progressive increase in SEFH reflects the gradual acquisition of faster frequencies. In contrast, low SEF declined with age before 130 d, but then stabilized at 4 Hz throughout the rest of gestation. As a result, there was a gradual increase in the separation between SEFH and low SEF as a function of gestational age.

The effects of insulin on the growth rate of the sheep fetus during late gestation.

The effects of insulin on fetal growth rates were investigated by measuring crown-rump length (CRL) chronically in sheep fetuses before and after pancreatectomy, sham operation or pancreatectomy accompanied by insulin-replacement treatment. Pancreatectomy of the fetus produced hypoinsulinaemia and reduced the daily and total increments in CRL by 40-50% over the last 20-30 days of gestation. The growth rate fell immediately after pancreatectomy and remained low throughout the rest of gestation. In contrast to the sham-operated fetus no pre-partum decline in the growth rate was observed in the pancreatectomized animal. The body weight, limb lengths and actual CRL at delivery were also significantly less after pancreatectomy than in the sham-operated animals. When fetal insulin levels were maintained after pancreatectomy by exogenous insulin infusion, the daily and total increments in CRL and the body size at delivery were restored to their normal values. Raising insulin levels above normal in the pancreatectomized fetus did not lead to additional fetal growth. When the data from all the fetuses were combined irrespective of treatment, there were significant positive correlations between the plasma insulin concentration in utero and the mean daily increment in CRL after treatment and between the former value and the body weight at delivery. These observations demonstrate that insulin is a major determinant of the growth rate in utero and that it is required throughout late gestation for the normal growth and development of the sheep fetus. They also indicate that insulin deficiency is probably the primary cause of the growth retardation observed after fetal pancreatectomy.

The ontogeny of fetal lamb electrocortical activity: A power spectral analysis

With the use of a relatively inexpensive microcomputer-based system for power spectral analysis, we have been able to provide quantitative information on maturational changes in electrocorticogram waveforms in the third-trimester fetal lamb. Twenty-six electrocorticogram recordings were obtained from nine fetal lambs, with gestational ages ranging from 114 to 139 days' gestation. The transition from disorganized to cyclic electrocorticogram activity (high-voltage slow activity and low-voltage fast activity) occurred at approximately 115 to 120 days' gestation. However, quantitative changes in waveform characteristics of the electrocorticogram continued throughout the rest of gestation. These maturational changes occurred primarily in the low-voltage fast activity periods, with a decrease in power density in the delta (0.3 to 3 Hz) band and an increase in the maximum frequencies detected in the beta (15 to 30 Hz) band. There were no significant changes in the power spectrum of the high-voltage slow activity periods as a function of gestational age.

Circulating levels of steroids and chorionic gonadotropin during pregnancy in the rhesus monkey, with special attention to the rescue of the corpus luteum in early pregnancy.

Circulating levels of progesterone and estrogen in the pregnant rhesus monkey are indistinguishable from those of the nonpregnant animal until 12 days after the LH peak, when the first significant rise in chorionic gonadotropin (RhCG) levels is noted concomitant with an abrupt elevation in progesterone levels (the corpus Iuteum rescue). Serum RhCG concentration rises rapidly (doubling time = 2 days) to a peak at about day 23 of pregnancy, then falls to undetectable levels at day 35, and remains undetectable throughout the rest of gestation. Serum estrone and estradiol levels rise and fall with RhCG titers in early pregnancy, reaching a nadir on day 35 of gestation before placental estrogen secretion (largely estradiol) supervenes. Circulating estrogens reach a high and variable plateau at about day 80 of pregnancy and rise to maxima on the day prior to parturition. Serum progesterone levels in early pregnancy, while rising abruptly at the outset of RhCG secretion, fall in the face of waxing RhCG titers and increase again only as RhCG levels fall. Ovariectomy on day 23 of pregnancy causes a sharp fall in circulating levels of estrogens and no compromise of the continuation of pregnancy. These data suggest that the order of hormone production by the placenta is RhCG. first discernable at about 10-I I days after ovulation, followed by progesterone, whose secretion by the placenta is initiated prior to day 23 of pregnancy since ovariectomy at this time causes no fall in circulating progesterone levels, and lastly, estradiol and estrone. which rise rapidly in peripheral serum after day 35 of pregnancy. These data support the hypothesis that the shortlived stimulation of progesterone secretion by the corpus luteum in early pregnancy is caused by the initiation of placental RhCG secretion and that the failure of Iuteal progesterone secretion to be maintained in the face of rising RhCG titers may be an expression of the luteolytic effect of the increased luteal estrogen production also stimulated by this gonadotropin.

Progesterone studies in the Macaca fascicularis.

Plasma progesterone levels were determined in the crab—eating macaque (Macaca fascicularis) during the menstrual cycle and pregnancy, including parturition. Menstrual cycles averaged 31 days in duration. Progesterone levels rose above 1 ng/ml plasma about 15 days prior to the onset of menstruation with peak values (7.8 ng/ml) observed on day 7 prior to menstruation. Progesterone levels declined to > 1 ng/ml 1–4 days before menstruation. Two animals studied daily for the first 30 days postbreeding, and then 2 times weekly, had 2 distinct progesterone peaks, one about IS days postbreeding and another at about 34 days with a low point in progesterone levels observed between these peaks at about days 23 to 25. The progesterone decline which followed the second peak reached minimal levels (1 to 2 ng/ml) by about day 45 of gestation. Progesterone levels increased gradually throughout the rest of gestation with average values of about 4 ng/ml observed the last 2 weeks prior to parturition. No significant changes...

Immune Lysis of Thymus and Spleen Cells of Embryonic and Neonatal Mice

Summary The cytotoxic effect of H-2 isoantibodies and complement on thymus and spleen cells of embryonic and neonatal C3H mice was investigated. The sensitivity of the cytotoxic test employed was increased by using small numbers of cells and by washing the antibody-sensitized cells prior to the addition of complement. Spleen cells showed a low though definite sensitivity to the cytotoxic effect of isoantibodies and complement as early as on the 15½ day of gestation and throughout the rest of gestation. During the first days of life the sensitivity of the spleen cells increased rapidly, and thereafter it gradually increased further to adult levels. The thymus of 15½-day-old embryos was almost completely refractory to the cytotoxic effect of isoantibodies and complement. In the 17½-day-old embryo the thymus cells had already developed a high sensitivity. The sensitivity of the thymus cells showed only minor fluctuations throughout the gestation period and remained unchanged during the 1st month of life. A higher sensitivity was found in thymus cells of 6-month-old mice. Fresh guinea pig serum had a distinctive toxicity for mouse thymus cells, probably due to the action of heat-labile naturally occuring antibodies in the presence of complement. Sensitivity of the thymus cells to the toxic effect of guinea pig serum appeared between the 15½ and 17½ day of gestation.