Distribution of GABA-like immunoreactivity during post-metamorphic development and regeneration of the central nervous system in the ascidian Ciona intestinalis

During regeneration of the neural ganglion in Ciona intestinalis, the pattern of reappearance of some peptidergic cells is similar to the ontogenetic patterns exhibited by these cell types during normal post-metamorphic development. Using a specific antiserum to gamma-aminobutyric acid (GABA), we describe here the appearance of GABA-ergic cells in Ciona during both post-metamorphic development and regeneration of the neural ganglion following total ablation. Post-metamorphic animals were divided into the categories: 1, 3–5, 6–10, 11–15 and 23–27 mm in body length. Regeneration was monitored at 12, 15, 18, 21, 28 and 56 days post ablation. The first appearance of GABA-like immunoreactive cells during normal development were at the 3 to 5-mm stage where they were seen as discrete cells, without processes, evenly distributed in the cortical region throughout the ganglion. Fibres were first seen at the 6 to 10-mm stage. As development proceeded, GABA-like immunoreactive cells became more concentrated near the nerve root exits and along the dorsal rind of the ganglion. In regenerating ganglia, GABA was first detected at 18–21 days post ablation, in cells that lacked any obvious processes and that were distributed in all regions of the ganglion. At 28 days post ablation, processes could be detected in the neuropile, and after 56 days GABA cells were found predominantly in the same regions as in the normally developing adult ganglion. Although the overall pattern reflects that in a normal adult, a few differences were detectable. For example, rather more GABAergic cells were concentrated ventrally in the ganglion close to the neural gland.     

The properties of cultured fetal human and rat brain tissue and its use as grafts for the relief of the Parkinsonian syndrome

Primary cultures were derived from human fetal ventral mesencephalon and cerebral cortex at 7–11 weeks gestation, and from fetal rat mesencephalon and cortex at embryonic day 14–15. Immunohistochemical analysis of the mesencephalic cultures using antibodies to tyrosine hydroxylase (TH) showed between 0.1–0.5% of human cells to be TH positive and 0.1–1% of rat cells to be TH positive. HPLC analysis of extracts from the cultures showed that they had the ability to synthesise and store dopamine. Implantation of the cultured human and rat mesencephalic tissue into a 6-hydroxydopamine rat model of Parkinson's disease produced marked recovery from amphetamine induced rotational asymmetry in the recipient rats, but no such recovery was observed following implantation of cortical cultures. Histological examination demonstrated the presence of surviving human mesencephalic and cortical grafts at least 6 months after implantation. Implants of cultured fetal rat tissue were less obviously but still significantly effective in these experiments. These rat tissue grafts were detectable for periods of at least 6–8 weeks by histological staining.Abbreviations TH tyrosine hydroxylase - DA dopamine - DMEM Dulbecco's modified Eagle's medium - EBSS Earle's balanced salt solution - PBS phosphate buffered saline - DAB diaminobenzidine - 6-OHDA 6-hydroxydopamine - DIV days in vitro - HNF human neurofilaments Special issue dedicated to Dr. Alan N. Davison.     

Fine structure of the small,granule-containing cells in the superior cervical ganglia of hydrocortisone-treated early postnatal and adult rats

Summary Hydrocortisone injections into rats on postnatal days 3–9 caused an increase in the number of small granulecontaining cells in the superior cervical ganglia. These cells, corresponding to the small, intensely fluorescent cells, showed an extensive rough endoplasmic reticulum, a large Golgi apparatus and a very large number of granular vesicles. In addition to the granular vesicles, 70–160 nm in diameter, in which the dense core filled most of the vesicle, most cells of the hydrocortisone-injected rats contained also larger granular vesicles, up to 350 nm in diameter, in which the dense core was eccentrically located. A minority of the cells contained only granular vesicles 70–100 nm in diameter, which was the only type seen in the saline-treated control rats.Thirty days after discontinuation of the hydrocortisone treatment, most of the cells with large granular vesicles had disappeared, and only two profiles of such cells were seen on day 40. The other small cells contained only granular vesicles 70–160 nm in diameter, and these cells could not be distinguished from the small granule-containing cells of 40-day-old control rats treated early postnatally with saline.Hydrocortisone treatment, first on days 3–9 and subsequently on days 40–46, caused reappearance of the small granule-containing cells with large granular vesicles up to 350 nm in diameter, the dense core of which was eccentrically located. Hydrocortisone treatment on days 40–46 only was not followed by appearance of such cells in rats treated with saline on days 3–9.Abbreviations used in the Text PNMT phenylethanolamine-N-methyltransferase - SIF cell small intensely fluorescent cell - SGC cell small granule-containing cell The author is grateful to Professor Olavi Eränkö and Dr. Seppo Soinila for constructive criticism. Expert technical assistance by Miss Hanna-Liisa Alanen, Mrs. Marja-Leena Piironen and Mrs. Anne Reijula is gratefully acknowledged. This study has been supported by a grant from the Finnish Medical Foundation.     

Changes in the metabolism of PGE1 and PGF2α in rat placenta during pregnancy

The metabolism of PGE₁ and PGF_2α were studied in an in vitro system using placentae from 11-day pregnant rats. PGE₁ was metabolized faster than PGF_2α. The same system was employed to study the quantitative metabolism of these prostaglandins at various stages of pregnancy in the rat. Results of these investigations showed that metabolism became maximal between days 9–12 and between days 15–22 of gestation. On days 12–15 of pregnancy, metabolism decreased, and was at its lowest point on day 14. Maximum prostaglandin metabolism during the sensitive period of days 9–12 of gestation may act as a protective device against the detrimental effects of prostaglandin. Possible correlation of prostaglandin regulation with hormonal balance is discussed.     

Cell differentiation of the fetal rat anterior pituitary in vitro

Summary Adenohypophysial primordia of rat embryos at 13 to 15 days gestation were cultured in Parker 199 synthetic medium for 2 to 11 days. At the end of the culture period their fine structure and the presence of immunoreactive trophic hormones using the peroxidase-labeled antibody technique were investigated. The degree of differentiation in the glands depends largely on the age of the embryos furnishing the explants. Cultured pituitaries explanted on the 13th day of gestation contain only ACTH-positive cells and about 15% of the cells are granular. The granules are 50–100 nm in diameter in some cells, while in other cells they range from 50 to 200 nm. In cultivated adenohypophysial primordia of embryos on the 15th day of intrauterine life ACTH, prolactin, LH and TSH cells are evident, but only the same two kinds of granular cells can be observed with the electron microscope. The extent of cytodifferentiation in the glands explanted on the 14th day of gestation is intermediate between the two other groups. The data suggest that the fetal rat pituitary has the capacity of self-differentiation but to a lesser extent than that of the in situ hypophysis.Dedicated to Professor W. Bargmann on the occasion of his 70th birthday     

Studies on the rust,Maravalia cryptostegiae,a potential biological control agent of rubber-vine weed,Cryptostegia grandiflora (Asclepiadaceae: Periplocoideae), in Australia,II: Infection

The parameters which govern infection of rubber-vine weed by the rustMaravalia cryptostegiae were investigated. The infection process, from appressorial formation to sporulation, is described and illustrated. Uredinioid teliospores have an optimum temperature range for germination at 22–27 °C, both in vitro and in vivo. However, germination on the rubber-vine leaf was more than double (81–92%) that in the absence of the host, and appressoria were formed only in vivo. An optimum temperature of 20–22°C and a dew period of 12 hours or more gave the highest level of infection as measured by sporulation density. The latent period from inoculation to pustule formation decreased with increasing temperature; the shortest period (8–11 days) being recorded at 25–27°C. At the lower temperatures (18°C), this was significantly extended (19–21 days). Four successive inoculations significantly reduced plant height and dry weight, although a compensatory growth flush occurred after the third inoculation. The addition of cryoprotectants had a negative affect on spore viability and subsequent infectivity. Cooling dry spores to –196°C at the rate of 10°C min^–1 gave the best results, with high germination (93–65%) up to 8 days after thawing.     

The origin and development of somatic embryos following cryopreservation of an embryogenic suspension culture ofPicea sitchensis

Summary The development of somatic embryos in an embryogenic suspension culture ofPicea sitchensis was followed every day for two weeks after thawing from liquid nitrogen (LN₂). Only a few cells, primarily located at the periphery of the embryonic region of the embryos, survived cryopreservation in LN₂. Surviving cells were classified into two groups: embryogenic cells (EC) and non-embryogenic cells (NEC), based on their morphology and embryogenic competence. The dense cytoplasmic EC underwent organized growth and differentiation with first divisions occurring after 24 h, and embryo formation 6–8 days after thawing from LN₂. No evidence of asymmetrical divisions or free-nuclear stages was found during somatic embryo formation. NEC had less dense cytoplasm with numerous small vacuoles. One to five days after thawing the NEC became progressively more vacuolated and elongated. Histological examination revealed no mitotic activity in NEC, and six days after thawing NECs were seen as single cells or unorganized cell aggregates. Two weeks after thawing the appearance of the cryopreserved cultures was comparable to that of the untreated cultures.Abbreviations EC embryogenic cells - ECC embryogenic cell clusters - FDA fluorescein diacetate - GMA glycol methacrylate - LN₂ liquid nitrogen (–196°C) - NEC non-embryogenic cells     

The appearance of surface H-2 antigens on fetal and postnatal murine hepatocytes in vivo and in vitro: A comparative study of MHC control

We have collected data on the kinetics of in vivo development of H-2^b antigens in fetal and postnatal hepatocytes from days 15–89 postcoitum (pc) in C57BL/10 mice using a sensitive immunoferritin labeling method combined with electron microscopy. We compared these data with data on the kinetic development of H-2^b antigens on fetal hepatocytes cultured from days 15, 16, and 17 pc onwards. Using the same techniques, we also compared the surface concentrations of H-2 antigens on the hepatocytes of pregnant and age-matched male and virgin female mice at day 110 pc. We found that the surface concentration of H-2 antigens on fetal and postnatal hepatocytes increased with time but that the birth event was associated with an increase in H-2 antigen expression from 60–80 ferritin grains per meter (F/m) to 190 F/m followed by a decrease to 115 F/m within 72 h of birth. The concentration of antigens on postnatal hepatocytes increased gradually and reached a maximum of 640 F/m on day 41 pc. By day 89 pc, however, this level had decreased 433 F/m, which was not significantly different from that found in day 110 pc males and virgin females. In contrast to previous findings, we found that hepatocytes cultured from days 15, 16, and 17 pc exhibited a large increase in H-2 surface antigen concentration within 48 h from 60–80 F/m to 1500–2200 F/m. After day 2, the H-2 concentration decreased and by days 14–17 in culture it was not significantly different from day 110 pc male and virgin female levels (485 F/m). Lastly, we found that the H-2 concentration on hepatocytes from pregnant mice was increased significantly (725 F/m) compared with the concentration of hepatocytes from day 110 pc males or virgin females. We postulate that the control of cell-surface major histocompatibility complex antigen concentration is achieved by a combination of intra and extracellular mechanisms and we discuss how this might be of benefit to the animal in vivo.     

Pinoresinol and matairesinol accumulation in a Forsythia × intermedia cell suspension culture

A newly established Forsythia × intermedia cell suspension culture was shown to accumulate (+)- and (–)-pinoresinol as well as matairesinol. The influence of the sucrose content of the culture medium and of the cultivation time on pinoresinol and matairesinol accumulation was evaluated. The highest pinoresinol yield was achieved from cells grown in medium containing 6% sucrose for 12 ± 2 days with levels of 0.6–0.8 mg g^–1 dry weight and an average enantiomeric composition of 75 ± 5% (+)-pinoresinol. The highest matairesinol amount was reached in the same medium at the 14th ± 2 culture day with levels of 1.0–2.7 mg g^–1 dry weight. To our knowledge, this is the first report on pinoresinol accumulation in Forsythia × intermedia plants or cell suspension cultures.     

Transient expression of a calcium-binding protein (spot 35-calbindin) and its mRNA in the immature pituicytes of embryonic rats

Summary Spot 35 protein is a Ca-binding protein originating from the rat cerebellum; it is now referred to spot 35-calbindin. This protein is expressed in immature pituicytes of the neurohypophyseal anlage in the E11–E18 rat embryo. The gene expression of spot 35-calbindin was detected by in-situ hybridization analysis only at stage E11–E12. Profiles of spot 35-positive nerve fibers of a neurosecretory nature were found in anlage at stage E16. At this stage, some immature pituicytes are partially immunopositive for spot 35-calbindin only in their peripheral cytoplasm; others are immunonegative. At birth and thereafter through adulthood, abundant nerve fibers are the sole structures immunoreactive for spot 35-calbindin; all the pituicytes are immunonegative, resulting in a light-microscopic appearance of numerous immunonegative round profiles, corresponding to pituicytes, and capillaries embedded in the granularly immunostained neurohypophysis. The present findings suggest that, during specific embryonic stages, immature pituicytes exert some as yet unidentified roles related to Ca-mediated functions involving the expression of spot 35-calbindin.     

Candida guilliermondii grows on rare pentoses – implications for production of pure xylitol

Feeding sucrose at 20 g l^–1 on day 16 gave maximum paclitaxel production at 10 mg l^–1 when Taxus chinensis in 5 l bioreactors. Paclitaxel accumulation was doubled by the cultivation of cells initially with dissolved O₂ tension at 60% for 20 days followed by being at 20% for another 12 days in the bioreactor. Combination of these two strategies gave maximum paclitaxel production of 19 mg l^–1 after 32 days.     

Quantitative fluorescence studies of the effects of catecholamines and hydrocortisone on endogenous amine levels in neurones and small intensely fluorescent cells of embryonic chick sympathetic ganglia in vivo and in vitro

Summary Chick embryo lumbar sympathetic ganglia (11 day) cultured for three days and uncultured (in vivo) ganglia of comparable age were freeze-dried and processed by the formaldehyde-induced fluorescence technique for the demonstration of biogenic monoamines. The catecholamine levels within principal neurone cell bodies and small intensely fluorescent (SIF) cells were then examined in plastic sections of the in vivo and in vitro ganglia by a quantitative fluorescence method under various experimental conditions. Culture of ganglia for three days in the presence of hydrocortisone acetate (10g/ml) resulted in an increased SIF cell fluorescence (P<0.001 compared to control) and a green to yellow colour shift in the fluorophore of SIF cells. No detectable alteration in the fluorescence level of neurones was observed. When neurones after three days in culture were incubated for 1 h in exogenous catecholamines, a significant increase in fluorescence levels (interpreted as an increase in catecholamine content) occurred with noradrenaline (2×10^–6 M; 2×10^–5 M). SIF cells in ganglia removed directly from 14-day old chicks similarly took up noradrenaline and dopamine, and also adrenaline (2×10^–5 M). Morphological results are presented which indicate that the cellular appearances and architecture of cultured ganglion explants are very similar to those in comparable ganglia in vivo.This work was supported by a grant from the Medical Research Council. We thank Mrs. G. O'Shea, Mr. T.T. Lee and Mr. P.F. Hire for their valuable technical assistance     

Cytological investigation of Triticale

Summary A cytological investigation of 15 different 56-chromosome Triticale and 16 Triticale with 42 chromosomes was carried out. 4 were primary Triticale and 12 were secondary Triticale. Chromosome pairing was not disturbed; 21 and 28 bivalents were found in the hexaploids and octoploids, respectively. Meiotic irregularities were established, however, in all the Triticale studied; in octoploids the frequency of the irregularities was 22–88% and in hexaploids it was 12–87%.In metaphase and anaphase asynchronous separation of chromosomes was noted. Incompatibility between wheat and rye genomes and the inactivation of single loci of rye chromosomes are suggested as the main causes of the irregularities in meiosis.Mitotic disturbances were found in all the amphidiploids. The frequency of anomalies in mitosis was considerably lower than in meiosis: in octoploids they made up 5%–11% and in hexaploids 6.2%–15.2%. In all the amphidiploids studied chimera plants were found containing pollen mother cells with different chromosome numbers. The chromosome number in the aneuploid cells varied from 8–48 in hexaploids and from 8–62 in octoploids. Octoploid Triticale had 29.4%–72.9% aneuploid pollen mother cells, while hexaploid Triticale had 5-2%–55-7%.     

Immunocytochemical and ultrastructural study of the frog (Rana pipiens) pars distalis with special reference to folliculo-stellate cell function during in vitro superfusion

Summary The colloidal gold immunocytochemical technique was used to determine the ultrastructural features of the glandular cells in the pituitaries of male frogs, Rana pipiens, both in vivo and after superfusion in vitro. Specific reactions to antisera against bullfrog gonadotropins, human prolactin, and synthetic 1–39 corticotropin allowed identification of the 3 corresponding types of glandular cells. No immunoreaction was obtained with antisera against human or ovine-growth hormone, human -thyrotropin hormone, and bovine S-100 protein. General morphological features of these immunocytochemically identified glandular cells were similar to those of equivalent cells previously described in other amphibian species. Non-glandular folliculo-stellate cells were distinctive. In freshly removed pituitaries, these folliculo-stellate cells contained lysosome-like structures, but did not show phagocytic vacuoles in the cytoplasm; they contained many mitochondria, and the Golgi complex and endoplasmic reticulum were relatively undeveloped. After 4 or 18 h of superfusion, some immunoreactive gonadotropic, prolactin, and corticotropic cells showed degeneration and destruction. In the same gland, folliculo-stellate cells retained a viable appearance, but showed phagocytic vacuoles containing secretory granule-like structures which were immunoreactive to gonadotropic, prolactin, and corticotropic antibodies. Some folliculo-stellate cells showed phagocytic vacuoles containing complete glandular cells. These results suggest that superfusion causes a destruction of some of the glandular cells, and that folliculo-stellate cells act as phagocytes when cellular debris or moribund cells are present in the intercellular space in the pituitary parenchyma.Supported by grant DCB 8710462 from the National Science Foundation, grant 2148-83 from the CAICYT (Spain) and the Junta de Andalucia (Spain)     

Evaluation of culture systems for attachment and proliferation of epithelial cells cultured from ovine semen

Different culture systems were evaluated for their ability to support attachment and proliferation of the somatic cells obtained from ovine semen. Ejaculates (n = 14) were collected from eight rams representing three breeds, Dorper, Suffolk and Hampshire. All samples were processed immediately and somatic cells were obtained from 11 of the 14 ejaculates. These cells had classic epithelial morphology and expressed cytokeratin, indicating they were of epithelial origin. Cells from four rams with the greatest growth rates were used for subsequent studies. Cells were cultured in four different media for 5 days and total numbers of attached cells vs. total numbers of seeded cells were counted and compared each day. Four media were evaluated: (1) a supplemented medium composed of DMEM/F12, 10% fetal bovine serum (FBS), 10 ng/ml epidermal growth factor, 30 μg/ml bovine pituitary extract, 5 μg/ml insulin, 10 ng/ml cholera toxin, and 50 μg/ml gentamycin; (2) sheep fetal fibroblast (SFF)-conditioned medium; (3) swiss 3T3 fibroblast-conditioned medium; and (4) basic medium composed of DMEM/F12, 10% FBS, and 50 μg/ml gentamycin. Cell proliferation was greater in the supplemented medium, SFF-conditioned medium, and 3T3 fibroblast-conditioned medium compared to the basic medium by day 2 of culture (p < 0.05, n = 24), and greater in supplemented medium compared to the SFF-conditioned medium and 3T3 fibroblast-conditioned medium by day 4 of culture (p < 0.05, n = 24). Three different surfaces: (1) Matrigel basement membrane matrix-coated plastic; (2) collagen I-coated plastic; and (3) uncoated plastic were evaluated for their ability to support proliferation and attachment of the cells obtained from semen. Cell proliferation was greater when cells were cultured on the Matrigel-coated compared to the collagen I-coated and uncoated plastic by day 2 of culture (p < 0.05, n = 16). Cell attachment was greater when cells were plated on the Matrigel-coated and collagen I-coated plastic compared to the uncoated plastic (p < 0.05, n = 16). These studies describe an effective system for the culture and proliferation of epithelial cells obtained from ovine semen samples. The system may increase the likelihood of obtaining cells from frozen semen, which could be used for cloning to recover animals of genetic value in which semen is the only material that is available.     

Histochemically demonstrable monoamines in the pituitary gland and median eminence of the female rat during the postnatal development

Summary The postnatal development of formaldehyde induced fluorescence (FIF) was studied in the pituitary glands of female rats. The effects of 3,4-dihydroxyphenylalanine (L-dopa), D,L-5-hydroxytryptophan (DL-5-HTP) and dopamine (DA) treatments on the FIF were followed during the postnatal period.The appearance of specifically fluorescing monoamines into the cells of the pars intermedia occurred postnatally and the level of the adult fluorescence was reached at 4–5 weeks' age. The intensity of the fluorescence was independent on the density of the fluorescing nerves. Among the fluorescing nerves droplet fibres were regularly observed from the age of 3 weeks, which confirms the theory that these fibres are caused by toxic factors when the blood-brain barrier is not functioning.There was no change postnatally in the number of fluorescing cells in the pars distalis.The fluorescing innervation of the median eminence, developed most rapidly at the age of 1–3 weeks and the level of the adult fluorescence was reached at the age of 4–5 weeks.The first specifically fluorescing cells after L-dopa treatment were observed at 6 days age. A remarkable increase in the number of fluorescing cells was seen between 12 and 18 days. After DL-5-HTP treatment fluorescent cells were seen but at later stages. These observations suggest that the cells in the pituitary gland, which store amine-precursors and monoamines developmentally differ from the APUD-cells. The rapid increase of the fluorescing cells between 12 and 18 days and the simultaneous development of the fluorescing innervation of the median eminence suggest the following correlations: the development of dopaminergic innervation of the median eminence — the secretion of releasing hormones — the activity of PAS-positive cells (FSH, LH and TSH secretion) — the uptake of L-dopa and DL-5-HTP into the PAS-positive cells.Dopamine was not uptaken into the cells of pars distalis. The walls of the blood vessels began to show fluorescence suggesting a barrier mechanism, which prevents the DA-uptake into the PAS-positive cells.This work was supported by the Grant for Young Research Workers, University of Helsinki.     

Translocation and multiplication ofSpiroplasma citri in turnip (Brassica rapa)

Following inoculation of designated leaves of turnip plants withSpiroplasma citri byCirculifer tenellus, spiroplasmas were cultured first from roots (four days) and then from youngest leaves (eight days), but almost never from oldest leaves. In experiments using enzyme-linked immunosorbent assay to monitor changes in titer in turnip leaves during the course of plant infection,S. citri was detected seven days after inoculation and reached peak titers of 10¹⁰–10¹¹ colony-forming units/g 12–20 days after inoculation, declining thereafter. Spiroplasmas were detected 5–9 days before symptoms appeared.     

Ontogeny of pituitary responsiveness to corticotropin-releasing hormone in rat

The ontogeny of the pituitary's responsiveness to synthetic rat corticotropin-releasing hormone (CRH) in the late prenatal and early postnatal periods of rats was studied by a superfusion system using whole pituitaries. A significant increase of immunoreactive beta-endorphin (IR-beta-Ep) secretion in response to 10(-10) M CRH but not to 10(-11) M CRH was observed in pituitaries from the 15th day of gestation, the earliest day that we tested, whereas 10(-11) M CRH stimulated IR-beta-Ep release from the pituitaries of 17.5-day-old fetuses. Dose-related IR-beta-Ep secretions induced by 10(-12) M to 10(-10) M CRH were observed in pituitaries of 19.5- and 21.5-day-old fetuses, and 1-, 3- and 9-day-old newborn pups. CRH stimulated not only IR-beta-Ep and IR-adrenocorticotropic hormone (ACTH) but also IR-alpha-melanocyte-stimulating hormone (IR-alpha-MSH) secretions from fetal pituitaries. The content of IR-CRH in the hypothalamic extract from 15-day-old fetus was 6.6 +/- 3.6 pg/hypothalamus (mean +/- S.E.M.) and it gradually increased to reach 212.7 +/- 20.3 pg/hypothalamus on the 21.5th day of gestation. However, the content of IR-CRH in the hypothalamus dramatically decreased just after birth and then rapidly increased again from the 5th day after birth. These data indicate that the responsiveness of corticotrophs to CRH is already present on the 15th day of gestation, when the content of IR-CRH in the hypothalamus is extremely low and that the amount of hypothalamic IR-CRH dramatically dropped for several days just after birth in rats.     

Morphometric studies on lipoprotein particles in developing rat liver and their corticosteroid-induced changes during the late gestational period

Summary Changes in lipoprotein particles in hepatocytes of the fetal rat liver have been studied morphometrically from days 15–21 of gestation. On all these days, distinct lipoprotein particles are found within the cisternae of the RER, Golgi complexes and Golgi-derived secretory vesicles. Their mean diameter is 30–31 nm. The number of Golgi complexes per hepatocyte, the lipoprotein particle number per Golgi complex and the volume density of the latter remain unchanged within the developmental period examined. The volume density of lipid droplets, however, shows a significant decrease during this time.Following corticosteroid treatment, the mean diameter of lipoprotein particles, the number of lipoprotein particles per Golgi complex, the volume density of the Golgi complex, and that of the lipid droplets increase significantly within the examined period, whereas the number of Golgi complexes per hepatocyte is reduced. These data support the view that triglyceride production in the fetal liver is directly or indirectly stimulated by corticosteroids administered to the pregnant rat, thus giving rise to larger amounts of hepatic lipoproteins and lipids.Abbreviations LP lipoprotein - VLDL very low density lipoproteins (d< 1.006 g/ml) - RER rough endoplasmic reticulum - ER endoplasmic reticulum     

Ontogenetic development of neural responses in the olfactory bulb of laboratory mice

Summary In laboratory mice (strain NMRI) the ontogenetic development of single unit activity in the olfactory bulb was investigated. From postnatal day 10 on, spontaneously active neurons were recorded with glass-microelectrodes, and their responses to olfactory stimuli were tested (butyric acid, geraniol, grass- and nest-odour).From day 10 to 13 only very few neurons were recordable (and most of these elements were too weak and were lost before being stimulated). At day 14 the number of recordable neurons increased rapidly, and by day 15 spontaneously active neurons reached adult level in terms of incidence and electric properties.There were 3 types of neurons: 1. respiration synchronous elements; 2. bursting neurons not correlated with respiration; 3. continuously, but randomly, firing elements (about 60% of all neurons). Reactions to odour stimuli (excitation, ca. 50%; inhibition, ca. 34%; complex reactions, ca. 12%; change in activity pattern, ca. 4%) occurred as soon as the cells were stable enough for testing. The reaction patterns showed no age specific differences; the duration of the responses varied from 100 ms to 100 s.In younger animals (P11–P14) the percentage of responses was slightly smaller (47%) than in the older ones (P30–P50; 64% response to olfactory stimulation). For some of the odours tested the proportion of responding cells differed depending on age (for instance grass odour evoked a response in 40% of the cells in young ones, but in 65% in adults).Abbreviations AP action potential - In interneuron - MTc mitral or tufted cell - P10 postnatal day 10