Strain preservation of rats: vitrification of two-cell stage embryos for multiple inbred strains.

OBJECTIVE: We examined whether the vitrification method using P10 and PEPeS is suitable for the cryopreservation of two-cell stage embryos collected from multiple rat strains with the objective of strain preservation of inbred rat strains. RESULTS: The average numbers of two-cell stage embryos collected per female for F344/Jcl, ACI/N, BUF/N, and WKY/N strains were 7.0 to 12.0, and survival rates of the embryos after vitrification were 94.2 to 96.3 % The in vitro development rates of vitrified embryos transferred were 47.1 to 60.8 %. CONCLUSION: At least two offspring produced from the embryos collected from one female are required for strain preservation of inbred strain. Taken together, the results of the experiment indicated expected numbers of surviving fetuses for embryos collected from one female were 3.2 to 6.7, and all were usable for strain preservation. The results suggest that this vitrification method is suitable for strain preservation of multiple inbred rat strains.

Superovulatory response, oocyte spontaneous activation, and embryo development in WMN/Nrs inbred rats.

WMN/Nrs inbred rats have been widely used in radiation biology for years. However, their reproductive profile has never been examined. We examined various reproductive characteristics of WMN/Nrs inbred rats such as superovulatory response, oocytes spontaneous activation (OSA), and embryo development in vitro and in vivo. Superovulation was induced in 3- to 9-week-old females by injection of 150 IU/kg PMSG and 150 IU/Kg hCG by 48 h apart. Only 8- and 9-week-old animals superovulated averaging 31.4 and 43.9 oocytes, respectively, and superovulation did not depend on estrous cycle. Animals 3-7 weeks of age did not superovulate. Because Wistar strains have been known to show a high incidence of OSA, factors expected to affect OSA in WMN/Nrs, including the time interval of various steps from euthanasia to oocyte recovery, incubation media, estrous cycle, and anesthetic treatments, were examined. The time from animal euthanasia to oviduct excision was the only factor shown to affect OSA. We also compared in vitro and in vivo embryo developmental competence between embryos obtained by natural ovulation and superovulation. Although percent in vitro development of 2-cell embryos to blastocysts was similar for embryos obtained by natural ovulation (63.7%) and superovulation (69.7%), fetus development after oviductal transfer of 2-cell embryos was significantly lower in embryos obtained by superovulation than in those obtained by natural ovulation (60.2% vs. 87.5%, P=0.02). Our results provide important normative data regarding future applications of rat assisted reproductive technologies (ARTs) such as in vitro fertilization and cryopreservation in WMN/Nrs strain and may be applicable to other strains of laboratory rats.

Examination of the rat eye at the early stage of development with osmium tetroxide staining.

This communication describes the benefit of osmium tetroxide (OsO4) staining on the examination of the eye during the early stage of organogenesis of rat embryos. The embryos were obtained by laparotomy on embryonic day 12 (ED 12) and were stained with OsO4 for examination of the ocular tissues with a binocular stereo-microscope, light microscope and scanning electron microscope. At the binocular stereo-microscopic level, the invaginated lens placode, lens pit and optic cup were clearly distinguished. The osmium-stained lens placode and the optic cup were light brown and dark brown in color, respectively. Light microscopic examination revealed that OsO4 postfixation could provide superior paraffin-embedded embryonic sections. Scanning electron microscopic examination revealed the lens pit as a round opening between the lateral nasal prominence and maxillary prominence. Thus, a rapid technique by which the ocular tissues of rat embryos can be examined under a binocular stereo-microscope was developed. This OsO4 staining method will provide a useful tool for research on organogenesis and ocular development.

Distribution of two splice variants of the glutamate transporter GLT-1 in the developing rat retina.

The distributions of a carboxyl terminal splice variant of the glutamate transporter GLT-1, referred to as GLT-1B, and the carboxyl terminus of the originally described variant of GLT-1, referred to hereafter as GLT-1 alpha, were examined using specific antisera. GLT-1B was present in the retina at very early developmental stages. Labelling was demonstrable at embryonic day 14, and strong labelling was evident by embryonic day 18. Such labelling was initially restricted to populations of cone photoreceptors, the processes of which extended through the entire thickness of the retina and appeared to make contact with the retinal ganglion cells. During postnatal development the GLT-1B-positive photoreceptor processes retracted to form the outer plexiform layer, and around postnatal day 7, GLT-1B-immunoreactive bipolar cells appeared. The pattern of labelling of bipolar cell processes within the inner plexiform layer changed during postnatal development. Two strata of strongly immunoreactive terminals were initially evident in the inner plexiform layer, but by adulthood these two bands were no longer evident and labelling was restricted to the somata and processes (but not synaptic terminals) of the bipolar cells, as well as the somata, processes, and terminals of cone photoreceptors. By contrast, GLT-1 alpha appeared late in postnatal development and was restricted mainly to a population of amacrine cells, although transient labelling was also associated with punctate elements in the outer plexiform layer, which may represent photoreceptor terminals.

Establishment of the hereditary cataract rat strain (SCR) and genetic analysis.

The Shumiya cataract rat (SCR) and normal control rat strains of NC1 and NC2 were established. Mean cataract appearance in adult SCR rats was 66.7%, and embryo death rate was 25%. Genetic analysis of cataract formation in the SCR was studied by breeding experiments with strains such as NC1, BUF, ACI, AD3, and normal SCR rats. No sex-based differences in cataract appearance were observed in any of the progeny. These results confirmed our hypotheses that two autosomal genes, a recessive cataract gene (ctr1), and a normal allele of a dominant cataract gene with a recessive lethal trait (Ctr2(1)) for provisional designations participated in cataract genesis in SCR (ctr1/ctr1, Ctr2(1)/Ctr2) rats. One recessive cataract gene was maintained in normal SCR, NC1 and NC2 (ctr1/ctr1, Ctr2/Ctr2) rats. The same recessive cataract gene was retained in the albumin-deficient brown hooded rat strain AD3 (ctr1/ctr1, Ctr2/Ctr2).

Developmental time course of acidic and basic fibroblast growth factors' expression in distinct cellular populations of the rat central nervous system.

Acidic and basic fibroblast growth factors (aFGF and bFGF, respectively) are expressed in high levels in adult central nervous system (CNS). We report the time course of developmental appearance and distribution of these factors and of two FGF receptors, FGFR-1 and FGFR-2, in the CNS of rats ranging in age from embryonic day 16 to adult. Immunohistochemical analysis showed that sensory neurons in the midbrain were the first cells to contain detectable aFGF immunoreactivity at embryonic day 18. The next cell group to contain aFGF were motor neurons, which were found to be aFGF-positive at the day of birth. A number of other subcortical neuronal populations were observed to contain aFGF immunoreactivity after postnatal day 7. Adult levels and distribution patterns of aFGF were reached in all CNS areas by postnatal day 28. Basic FGF immunoreactivity was observed at postnatal day 0 in neurons in the CA2 subfield of hippocampus. Astrocytes contained detectable bFGF immunoreactivity, starting at postnatal day 7. Adult levels and patterns of distribution of bFGF were reached in all CNS areas by postnatal day 28. These immunohistochemical observations were confirmed by using bioassay and Western blot techniques. FGFR-1 and FGFR-2 mRNA were expressed in significant levels in all CNS areas at all time points analyzed. The observation that aFGF and bFGF appear in specific and distinct cellular populations at relatively late developmental times suggests that these FGFs may be involved in specific mechanisms of CNS maturation, maintenance, and repair.

Neuronal colocalization of mRNAs for neurotrophins and their receptors in the developing central nervous system suggests a potential for autocrine interactions.

Development and survival of neurons in the central nervous system are dependent on the activity of a variety of endogenous neurotrophic agents. Using combined isotopic and nonisotopic in situ hybridization histochemistry, we have found that subsets of neurons within the developing forebrain coexpress the mRNAs for both neurotrophins (nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3) and their receptors (p75NGFR, TrkA, and TrkB). The colocalization of mRNA for neurotrophin receptors and their ligands in presumptive neurotrophin target neurons suggests the potential for autocrine and paracrine mechanisms of action during development. Such mechanisms may ensure the onset of differentiation and survival of specific subsets of neurons prior to and following target innervation.

Action of an extract of Stryphnodendron obovatum benth seed on rat bone marrow and on human lymphocytes

O Brasil é um país rico em plantas medicinais e o Stryphnodendron obovatum Benth (Barbatimäo), é uma importante fonte de tanino usado em indústrias. Esta planta tem diferentes atividades biológicas causando inibiçäo do desenvolvimento embrionário em ratos, toxicidade ao gado que a ingere e é usada também, na cura de diversas doenças do homen. Devido a sua ampla distribuiçäo e uso estudamos o efeito do extrato de sementes de Barbatimäo em células de medula óssea de ratos Wistar (in vivo) e em linfócitos de sangue periférico humano (in vitro), avaliando o seu efeito ao nível mutagênico e na induçäo de metáfases-colchicínicas. Os tratamentos näo causaram um aumento estatisticamente significativo no número de alteraçöes cromossômicas e de SCEs nos dois sistemas-testes avaliados. Nos testes em ratos houve pequena induçäo de metáfases-colchícinicas e nas culturas de linfócitos esta induçäo foi dependente do tempo e da forma do tratamento. Nas culturas de linfócitos ocorreu um efeito citotóxico dependente do aumento da concentraçäo e do tempo de exposiçäo ao extrato. Algumas metáfases tratadas apresentaram cromossomos bandados

Desenvolvimento embrionário de ratas Wistar: padröes do 16§, 18§ e 20§ dias de gestaçäo / Embryogenic development of Wistar rats: patterns of 16th, 18th and 20th gestational days

Estudos visando a analisar efeitos teratogênicos e abortivos envolvem, entre outros parâmetros o desenvolvimento de fetos e placentas. A fim de verificar se a colônia de ratas do biotério do Centro de Biologia da Reproduçäo - UFJF apresenta padröes reprodutivos e de desenvolvimento comparáveis aos citados pela literatura e indicativos de boa qualidade da colônia, foi feito o acompanhamento da gestaçäo de 30 animais, observando-se dados de reproduçäo e desenvolvimento embrionário nos dias 16, 18 e 20. O índice de implantaçäo maior que 90 por cento; de reabsorçäo menor que 5 por cento e o de natimortalidade nulo sugerem que esta colônia apresenta padröes de reproduçäo e desenvolvimento de bom nível de qualidade. O crescimento e desenvolvimento dos embriöes foi compatível com dados obtidos da literatura.

A rat cytotrophoblast antigen defined by a monoclonal antibody.

A monoclonal antibody that recognizes specifically a cytotrophoblast antigen was obtained. The monoclonal antibody 22H6 was tested on rat choriocarcinoma (in vivo, in vitro), normal placenta, ectoplacental cone, blastocysts, and several normal organs. The antigen was detected on frozen sections and on tissue culture by indirect immunofluorescence. The monoclonal antibody 22H6 reacts with the cytotrophoblasts of rat choriocarcinoma. The giant cells do not display a positive reaction. It is not expressed on other tumors than choriocarcinoma. In adult rats the only cells revealing a positive reaction are the hepatocytes and the epithelial cells lining the small intestine. In the pregnant rat, the antigen is expressed on the cytotrophoblasts of the junctional zone in the placenta, but not on the giant cells. The mab reacts only with the small trophoblast cells of the ectoplacental cone, but not with trophectoderm of blastocyst. The mab has an IgG2b isotype and is not cytotoxic for choriocarcinoma cells in a complement-dependent cytotoxicity test. The described monoclonal antibody is to our knowledge the only known marker of rat benign and malignant cytotrophoblast.

Ultrastructure of the basement membrane and its precursor in developing rat submandibular gland as shown by alcian blue staining.

The ultrastructure of the epithelial basement membrane and membrane precursor was studied in rat submandibular rudiment and a model system of the reconstructed basement membrane, by transmission electron microscopy following alcian blue staining. Directly beneath the epithelial plasma membrane, a meshwork layer was found to consist of anastomosing thin fibers arranged as a three-dimensional meshwork (100-400 nm in thickness). Straight strands (5-10 nm in diameter) could sometimes be seen to pass through the meshwork. Adjacent to this layer, a coarse network composed of threads (20-40 nm in diameter) connected the meshwork layer with collagen fibers of the underlying connective tissue. The earliest precursors recognized in the reconstruction-model system were part of the fine-meshwork structure, and showed this structure to be a fundamental component of the basement membrane.

Migration of cranial neural crest cells to the pharyngeal arches and heart in rat embryos.

The existence of a neural crest cell migration pathway from occipital levels of the hindbrain into the heart was suspected in mammalian embryos because it had previously been identified in avian embryos and because the Di George anomaly, an association between craniofacial and cardiac malformations, is most easily explained on the basis of abnormal neural crest cell migration to all of the affected structures. In order to demonstrate the existence of this pathway, neural crest cells were labelled in situ in rat embryos with the fluorescent dye DiI, and the embryos cultured for up to 48 h. Cells labelled between occipital somites 1 and 2 or 3 and 4 migrated within and dorsal to the third and fourth pharyngeal arches and into the outflow tract of the heart (conus cordis and truncus arteriosus). The cardiac labelling was in individually visible cells, in contrast to the mass of fluorescence seen in the pharyngeal and dorsal mesenchyme. Within the outflow tract wall, the labelled cells were enmeshed by strands of alcian blue-stained extracellular matrix. There was no labelling of cardiac cells following injections just rostral to, or just caudal to, somites one and four. This study establishes the existence and precise levels of origin of the 'cardiac' neural crest in a mammalian embryo.

Ontogeny of gene expression of adenosine A2 receptor in the striatum: early localization in the patch compartment.

The ontogeny of adenosine A2 receptor mRNA and adenosine A2 binding sites distributions was studied by in situ hybridization histochemistry and receptor autoradiography in pre- and post-natal rat striatum, postnatal dog striatum, and a human fetus striatum and compared to that of dopamine D1 and mu opiate receptors. The early postnatal striatum demonstrated heterogeneous distributions of adenosine A2 receptor mRNA and adenosine A2 binding sites with patches of dense labeling corresponding to dopamine D1 and mu opiate receptors enriched zones. This patchy pattern evolved to the homogeneous distribution observed in the adult. The higher intensity of adenosine A2 receptor mRNA enriched patches correspond at the microscopical level to a higher density of labeled neurons in the patches areas and also to a higher level of expression per labeled patches neuron than in the matrix ones. This demonstrates for the first time that differences in patch/matrix receptor density is at least partly linked to different levels of receptor gene expression.

Distribution of histamine in the rat kidney during pregnancy and development.

An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.

Ontogeny of histamine-immunoreactive cells in rat stomach.

An antiserum against hemocyanin-conjugated histamine was used to study the cellular stores of histamine in the stomach, especially the oxyntic mucosa, of fetal and early postnatal rats. Tissues were fixed in 4% 1-ethyl-3(3-dimethyl-aminopropyl) carbodiimide (EDC-DI) and standard immunofluorescence technique was used. Histamine was first detected on the 16th embryonic (E16) day when a few histamine-immunoreactive (HA-ir) cells and nerve fibers were observed in the muscular layer of the stomach wall. On day E18, HA-ir cells were visualized for the first time in the oxyntic mucosa of the stomach, and from that day on the number of such cells increased slowly initially and after day E20 more rapidly. At birth many of the HA-ir cells in the oxyntic mucosa possessed processes giving them a paracrine-like appearance typical of enterochromaffin-like cells (ECL cells). Only a very small number of the HA-ir cells represented metachromatically stained mast cells and were located in the submucosa. After birth, the number of HA-ir ECL cells increased steadily, until day 21 when the distribution and number was very similar to that of the adult. The results suggest that histamine-containing neurons and ECL cells appear in the stomach wall before birth, and that there are histamine-containing ECL cells in the mucosa and mast cells in the submucosa of the stomach wall at birth.

Postnatal development of von Ebner's glands: accumulation of a protein of the lipocalin superfamily in taste papillae of rat tongue.

Antibodies produced against rat von Ebner's gland (VEG) protein, a recently characterized member of a lipophilic ligand carrier protein family, detect this protein immunocytochemically in von Ebner's gland acini and show that it is present at high concentrations in the clefts of circumvallate and foliate papillae. During embryonic development, von Ebner's gland anlagen are innervated (as shown immunocytochemically using neuronal specific antibodies) as early as embryonic day 20, before lateral glandular outgrowth and VEG protein can be observed. Expression of the VEG protein as determined by in situ hybridization and immunocytochemistry begins at postnatal day-2 cells in differentiating and branching off from von Ebner's gland ducts, and sharply increases with further enlargement and maturation of the gland. The close temporal correlation of von Ebner's gland innervation and VEG protein expression with papilla innervation and taste-bud development suggests a functional relationship of both structures. VEG protein might control access of lipophilic sapid molecules, such as bitter substances, to the gustatory receptors.

Tobramycin-induced changes in renal histology of fetal and newborn Sprague-Dawley rats.

Effects on renal development were studied using tobramycin (TBM) as a model compound. Pregnant Sprague-Dawley rats were injected i.p. with TBM at 30 or 60 mg/kg body weight/day on gestational days (GD) 10-19. Kidneys from dams and conceptuses were examined on GD 20 and on postnatal day (PD) 9. The dosing regimen caused in dams moderate proximal tubular alterations and increased concentrations in serum creatinine. Fetal kidneys showed granularity and swelling of proximal tubule cells at the 30 mg/kg dose, poor glomerular differentiation at the 60 mg/kg dose, increased glomerular density at both doses, and no changes on macroscopic examination at either dose. In newborns were observed a moderate developmental delay and tubular lesions at the higher dose, and dose-related increases of glomerular density and relative medullary area at both doses. All findings were more pronounced in males. A maturational disruption of the tubular structures possibly leading to increased glomerular density was attributed to TBM exposure during renal organogenesis in the rat.

Utilization of three-dimensional culture for early morphometric and electrophysiological analyses of solitary cerebellar neurons.

When cells from the cerebellum of late-gestation rats were grown at low density (50-100 cells/mm2) in a three-dimensional culture system, they rapidly expressed morphological and electrophysiological properties of neurons. Growth and differentiation of the population of solitary neurons as a whole was statistically assessed at 6, 12, 18, 24, 48 and 72 h using data obtained from image analysis. Mean length of axons and dendrites increased 17- and 220-fold, respectively, from 6 to 72 h. Average number of branch points rose 35-fold. Other indices of complexity increased 2- to 3-fold. Whole-cell voltage clamp revealed that as early as 24-30 h the cells displayed a tetrodotoxin-sensitive Na+ current (INa), a nifedipine-sensitive high-threshold Ca2+ current, a Ni(2+)-sensitive low-threshold Ca2+ current, and two voltage-dependent K+ outward currents consisting of a 4-aminopyridine-sensitive fast transient outward current and a CsCl-sensitive slow delayed component. These observations correlate closely with voltage-activated currents previously recorded in neonatal or young rat cerebellum, and demonstrate that the culture model is useful for analyzing the early rapid growth, differentiation and intrinsic ionic currents of these neurons as single cells.

Immunolabelling patterns of gap junction connexins in the developing and mature rat heart.

The distribution of gap junctions in prenatal, postnatal, and adult rat hearts was studied by laser scanning confocal microscopy, using antiserum raised to a peptide (HJ) matching part of the sequence of connexin43 (a cardiac gap junction protein). Using digital reconstruction of optically-sectioned tissue volumes, a highly sensitive detection of immunolabelled gap junctions was achieved. The distribution of positive anti-HJ immunolabelling was regionalised in the prenatal heart from its first detection at 10 days post-coitus. High levels of immunopositive staining occurred in the trabeculae of the embryonic ventricles. Other zones of the early myocardium including early central conduction tissues had no detectable signal. The prenatal outflow tract, interventricular septum and a narrow zone of myocardium subjacent to the epicardial free wall also had low levels of immunopositive signal. During postnatal growth and in the adult rat heart, a marked distinction emerged between the central conducting tissues of the atria and ventricles. Whilst small immunostained gap junctions became detectable within the atrioventricular node on the atrial side of the junction, between the interatrial and interventricular septa, no immunolabelling was found within the ventricular branching bundle. This difference between the atrioventricular node and branching bundle is consistent with potential functional distinctions between these two structures, and is not consistent with the recent proposal that the His bundle and its branches act as an extended atrioventricular node in smaller mammals such as the rat. Ventricular Purkinje fibres, distal to the branching bundle, showed high levels of anti-HJ immunostaining. Organisation of gap junctions into intercalated disks within the ventricle proceeded late into intercalated disks within the ventricle proceeded late into the adolescent stages of heart growth. The distribution of a second connexin protein, MP70, not previously characterised in the heart, was studied using monoclonal antibodies. MP70 was transiently immunolabelled in the heart during the postnatal period, but only within valves. Previously, this protein has been reported only in the eye lens. MP70-containing gap junctions may represent a specialisation in avascular tissues, since blood vessels are not present in either the eye lens or the cusps of heart valves.

Liver peroxisomes in newborns from clofibrate-treated rats. I. A morphometric study of the recovery period.

Morphological and morphometric parameters (volume density (Vv), numerical density (NA) and mean diameter (D)) of newborn liver peroxisomes were measured throughout the first week of life in rats born to mothers treated with clofibrate (ethyl 2 p-chlorophenoxy isobutyrate) during the last five days of pregnancy. In control studies the same analyses were carried out in newborns from untreated rats. At birth (day 0), treated animals exhibited a proliferated, pleiomorphic peroxisomal population (higher Vv, NA and D, and a spread distribution of profile diameter with respect to the controls). In the subsequent two days, many peroxisomes disappeared (decrease of Vv and NA to values even lower than controls), with a persisting high pleiomorphism (no change of D and diameter distribution) in residual ones. Starting from day 3, and up to day 6, larger peroxisomes were no longer detectable in test animals, and a significant, not pleiomorphic proliferation took place (D and diameter distributions strictly comparable to the controls and progressively increasing Vv and NA). The correlation analysis validated these morphological results, from which it can be surmised that the postnatal peroxisome recovery period consists of a destructive phase followed by a proliferative one. The possible mechanism(s) of disposal of the excess of drug-induced peroxisomes are discussed.