Week Of Embryonic Development Research Articles

Chicken folliculo-stellate cells express thyrotropin receptor mRNA

We investigated the presence of thyrotropin receptor (TSHR) mRNA in chicken pituitary and brain, and quantified the changes in its expression during the last week of embryonic development. We found that in the pituitary gland, TSHR mRNA co-localizes with folliculo-stellate cells but not with thyrotropic cells, suggesting the existence of a paracrine ultra-short thyrotropin feedback loop. TSHR mRNA was also present throughout the diencephalon and various other brain regions, which implies a more general function for thyrotropin in the avian brain. During late embryogenesis, when the activity of the hypothalamo-pituitary-thyroidal axis increases markedly, a significant rise in TSHR mRNA expression was observed in pituitary, which may signify an important change in pituitary ultra-short thyrotropin feedback regulation around the period of hatching.

Sex hormone concentrations and gonad histology in brown trout (Salmo trutta) exposed to 17β-estradiol and bisphenol A

The impact of 17beta-estradiol (E2) and bisphenol A (BPA) on steroid hormone levels and gonad development in brown trout (Salmo trutta) was determined. Exposure took place from 0 to 63 days post-fertilisation (dpf) and gonad development was followed till 400 dpf. The onset of xenoestrogen metabolism was examined by measurements of whole body concentrations of bisphenol A (BPA) and its conjugation product bisphenol A glucuronic acid (BPAGA). Exposure to 500 ng E2/l led to an increase in E2 levels in the embryos and fry while 10 ng E2/l did not. Metabolic conversion of BPA to BPAGA began during the first weeks of embryonic development. Few consistent effects were found on the sex differentiation of the brown trout. Only one intersex fish (4.5%) was found among male fish at 400 dpf exposed to 500 ng E2/l. Females with male germ cells among the normally developing oocytes were observed in all groups (in up to 50% of the female fish, independently of exposure regime). The fact that exposure to 500 ng E2/l only caused subtle effects in a small number of individuals indicates that exposure during early life stages results in little to no induction of endocrine disruption in brown trout.

Ontogenesis of the Expression of Prolactin Receptor Messenger Ribonucleic Acid During Late Embryogenesis in Turkeys and Chickens

Changes in circulating levels of prolactin (PRL) and tissue content of PRL receptor (PRLR) messenger RNA (mRNA) in the liver, pancreas, kidney, and gonads (testis/ovary) were measured in turkey and chicken embryos from embryonic day (ED) 21 or ED15, respectively, to 1 d after hatch by real-time PCR. There were no differences between the sexes in chickens or turkeys. Both species had very similar patterns of PRL release and expression of PRLR mRNA, and no major differences were observed between turkey or chicken embryos. Plasma levels of PRL increased from low levels during the last week of embryonic development and were at significantly higher levels (about 4-fold) by 1 d after hatch. Similarly, in all tissues the content of PRLR mRNA was minimal at the outset and increased to reach maxima about the time of hatch. In both species, the highest levels of transcript were observed in the kidney followed by the gonad, liver, and pancreas. The tissue content of PRLR was correlated (0.6 to 0.8 dependent on the tissue) to circulating levels of PRL, which suggested that PRL may be associated with an increase in its receptor number around the time of hatch. Because levels of PRL and tissue content of PRLR mRNA increased around the time of hatch, this suggests that these tissues may be targets for PRL and may be involved in the physiologic changes occurring in embryos around the time of hatching.

003 Génération de fibroblastes “like” cornéens issus de la différenciation de cellules souches mésenchymales humaines in vitro

Aim Tissue engineering (TE) offers considerable promise in damaged tissues repair or replacement. Corneal Fibroblasts (CF) result from mesodermal cell extension into optic cap. They participate in the genesis of corneal stroma during the 5th week of embryonic development. We used MSC to generate CF phenotype cells for corneal TE and clinical applications. Materials and Methods Genotype CF, obtained from 8 corneal grafts, were evaluated by genomic profiling of total RNA using microarray analysis (1300 genes). The MSC were isolated from 12 human bone marrows with the magnetic beads separation method. These cells were cultured in specific media. Three weeks later, capacity of CD34+ cells to differentiate into fibroblast like cells was analyzed. The resulting cells were renamed as mesenchymal stem cell “derivated corneal fibroblast-like” (DCFL) cells. Their phenotypes were analysed by imunocytochemistry (ICC) using specific antibodies against CD34, Von Willbrand factor (VWF), 3G5 (CF ganglioside being used as corneal keratocytes marker), stromal derived factor SDF-1 and its receptor CXCR4, VEGF receptors, Aqp 1, and α-SMA. These phenotypes were compared to CF microarray results. Results Microarray indicates corneal fibroblasts expression of SDF1, CXCR4, VEGF C, Flt1 and Flt4 mRNAs. Corresponding proteins were highlighted in corneal fibroblasts and DCFL cells by ICC. Indeed Aquaporin-1, SDF1alpha, CXCR4, VEGF and Flt1 and Flt4 were detected. 3G5 expression was detected on 0,2% DCFL. Both corneal fibroblasts and endothelial cells were stained with anti-alphaSMA antibody whereas only endothelial cells were positive for anti VWF staining. Interestingly, no corneal fibroblasts analysed by gene array (n = 2) and immunohistochemistry (n = 8) expressed CD34 + . Discussion 3G5 antigen is constitutively expressed by cultured human corneal fibroblast and is found in CD34 + BMDF cells which suggests the potential for bone marrow to generate CF like cells. Conclusion These cells, characterized by surface expression of CXCR4 + , SDF1- alpha + , Flt-4 + , VEGF-C + and 3G5 + should be considered as candidates for corneal tissue engineering.

Feedback control of thyrotropin secretion in the chicken: Thyroid hormones increase the expression of hypophyseal somatostatin receptor types 2 and 5

We have studied the involvement of the somatostatin receptor type 5 (SSTR5) in the control of thyrotropin (TSH) release in the chicken. Hypothalamic somatostatin (SS-14) is known to inhibit both thyrotropin-releasing hormone (TRH)- and corticotropin-releasing hormone (CRH)-induced TSH secretion. Studies using receptor-specific agonists have indicated that the inhibitory effect of SS-14 on TRH-induced TSH release is mediated by SSTR2 and SSTR5. Using the same agonists, we were able to demonstrate the involvement of SSTR5 in the inhibition of the in vitro CRH-induced TSH secretion by SS-14. Subsequently, we determined hypophyseal SSTR5 mRNA expression during the last week of embryonic development using real-time PCR. SSTR5 mRNA levels were low until day 19 of incubation, but between day 19 and hatching SSTR5 mRNA expression increased 3-fold. Since this increase coincides with the increasing plasma T 3 levels towards hatching, and a similar ontogenetic expression pattern was found for SSTR2, we quantified hypophyseal SSTR2 and SSTR5 mRNA expression levels in chicken embryos treated with thyroid hormones. Injection of thyroid hormones was indeed found to increase the expression of both mRNAs significantly. We hypothesize that the negative feedback exerted by the increasing plasma T 3 levels towards hatching is at least in part mediated by an increased expression of SSTR2 and SSTR5.

Spinal dermoid presenting with equinovarus deformity of the foot: A Case Report

Spinal dermoid tumors are relatively rare tumors especially in the adult age group. These slow growing benign tumors may become symptomatic at a later age leading to pain and neurological deficits due to involvement of the nerve roots and the cauda equina. We present here a case of a 36-year-old woman who presented with gradually progressive equinovarus deformity of the foot and scoliosis. Magnetic resonance imaging (MRI) revealed a large spinal dermoid tumor at the thoracolumbar junction. CASE REPORT A-36-year-old woman presented for evaluation of gradually progressive equinovarus deformity of the left foot and scoliosis (Fig 1). Figure 1 Figure 1: Equinovarus deformity of the left foot. She first noticed that her left foot was turning inwards about a year ago but at that time did not seek medical attention. There was no history of trauma to the back and she denied any back or leg pain. Neurological examination revealed an equinovarus deformity of left foot and a slightly broad based gait (Video). MRI lumbosacral spine revealed a large dermoid tumor in the spinal canal situated at the thoracolumbar junction (Fig 2). Figure 2 Figure 2: T weighted MRI of the thoracolumbar spine showing a large spinal dermoid with fat content. X-ray of the lumbar spine revealed scoliosis (Fig 3). Surgical excision of the tumor was deferred taking into account the absence of pain or difficulty walking and the possibility of bladder incontinence post surgery. As of this writing she remains in close follow up. Spinal dermoid presenting with equinovarus deformity of the foot: A Case Report 2 of 3 Figure 3 Figure 3: X-ray lumbar spine showing scoliosis. Video: Patient video showing equinovarus deformity of foot while walking. DISCUSSION Dermoid tumors or cysts are not true neoplasms. They along with epidermoid tumors represent inclusion cysts consisting of ectodermal elements 1. They can either be congenital where in during third to fifth week of embryonic development the ectoderm might get entrapped in the neural tube giving rise to epidermoid and dermoid cysts. Trauma has been implicated in the generation of these benign tumors later in life. Rarely skin tissue may be forced into the vertebral canal during lumbar puncture or surgery giving rise to these cystic tumors. Spinal dermoid tumors are most commonly situated near the thoracolumbar junction and may be either intradural intramedullary or intradural extramedullary. Extradural location is the least common for these slow growing tumors. They may involve the conus medullaris and cauda equina leading to back and leg pain as well as weakness. Terai et al reported a case of adult onset tethered cord syndrome due to an intradural dermoid cyst 2. Due to the pain and sensory deficits their patient underwent laminectomy with decompression of the canal and excision of the intradural cyst. We decided to withhold any active neurosurgical intervention in our patient due to the absence of pain or difficulty walking and also taking into consideration the possibility of bladder incontinence post surgery. CORRESPONDENCE TO NK Sethi, MD Department of Neurology NYP-Weill Cornell Medical Center 525 East, 68 Street New York, NY 10021 Email: sethinitinmd@hotmail.com Tel: +646-515-5168

Molecular Cloning, Tissue Distribution, and Ontogenic Thyroidal Expression of the Chicken Thyrotropin Receptor

TSH and the interaction with its receptor (TSHR) in the thyroid gland play a crucial role in the pituitary-thyroid axis of all vertebrates. Released upon stimulation by TSH, thyroid hormones influence numerous processes in the body and are extremely important during the last week of chicken embryonic development. In this study, we have cloned and functionally characterized the chicken TSHR (cTSHR), which was found to be a G protein-coupled receptor consisting of 10 exons. Besides the full-length cDNA, we detected two splice variants lacking either exon 3, or exons 2 and 3, both part of the extracellular domain of the receptor. Bovine TSH increased intracellular cAMP levels in HEK-239 cells transiently expressing the full-length cTSHR (EC50 = 1.43 nm). In situ hybridization showed the expression of cTSHR mRNA in the thyroidal follicular cells. cTSHR mRNA expression, as determined by real-time PCR, was also found in several other tissues such as brain, pituitary, pineal gland, and retina, suggesting that the TSH-TSHR interaction is not only important in regulating thyroid function. TSHR mRNA expression in the thyroid gland did not change significantly during the last week of embryonic development, which suggests that an increased thyroidal sensitivity is not part of the cause of the concomitant increasing T4 levels.

Increasing plasma thyroxine levels during late embryogenesis and hatching in the chicken are not caused by an increased sensitivity of the thyrotropes to hypothalamic stimulation

The hatching process in the chicken is accompanied by dramatic changes in plasma thyroid hormones. The cause of these changes, though crucial for hatching and the onset of endothermy, is not known. One hypothesis is that the pituitary gland becomes more sensitive to hypothalamic stimulation during this period. We have tested whether the responsiveness of the thyrotropes to hypothalamic stimuli changes throughout the last week of embryonic development and hatching by studying the mRNA expression of receptors involved in the control of the secretory activity of this cell type. We used a real-time PCR set-up to quantify whole pituitary mRNA expression of the beta subunit of thyrotrophin (TSH-beta), type 1 thyrotrophin-releasing hormone receptor (TRH-R1), corticotrophin-releasing hormone receptors (CRH-R1 and CRH-R2) and somatostatin subtype receptor 2 (SSTR2) on every day of the last week of embryonic development, including the day of hatch and the first day of posthatch life. The thyrotrope-specific expression was investigated by a combination of in situ hybridization with immunohistochemistry at selected ages. Although TSH-beta mRNA levels increased towards day 19 of incubation (E19), the expression of CRH-R2 and TRH-R1 mRNA by the thyrotropes tended to decrease during this period, suggesting a lower sensitivity of the thyrotropes to the stimulatory factors CRH and TRH. CRH-R1, which is not involved in the control of TSH secretion, increased steadily throughout the period tested. The expression of SSTR2 mRNA by the thyrotropes was low during embryonic development and increased just before hatching. We have concluded that the sensitivity of the pituitary thyrotropes to hypothalamic stimulation decreases throughout the last week of embryonic development, so that the higher expression of TSH-beta mRNA around E16-E19, and hence the increasing plasma thyroxine level, is unlikely to be the result of an increased stimulation by either TRH or CRH.

Blepharophimosis and bilateral Duane syndrome associated with a FOXL2 mutation

This case describes the novel coexistence of sporadic blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) and bilateral type I Duane syndrome in a female infant, with a FOXL2 mutation. Mutational analysis of FOXL2 demonstrated a 30-nucleotide duplication (c.672(-)701dup30) within the polyalanine tract of FOXL2. The association of BPES and Duane syndrome represents a novel phenotype which may suggest a greater pleiotropic effect of FOXL2 in development. During the period of the 4-8th week of embryonic development, the cranial nerves, their nuclei and the corresponding innervation to the extraocular muscles develop, the extraocular muscles undergo development and differentiation. This coincides with the period of time that FOXL2 is expressed strongly in the developing eyelids and the surrounding tissues. Forkhead genes are transcription factors and likely to be involved in signal transduction pathways. This case expands the spectrum of FOXL2 mutations associated with BPES.

The dioxin-like PCB 77 but not the ortho-substituted PCB 153 interferes with chicken embryo thyroid hormone homeostasis and delays hatching

The effects of the dioxin-like polychlorinated biphenyl (PCB) 77 and the ortho-substituted PCB 153 on thyroid hormone availability were investigated during the last week of embryonic development in chicken. High doses of these PCBs (1 μg PCB 77 and 20 μg PCB 153) were injected into chicken eggs at day 4 of incubation. Blood and tissue samples were collected from day 14 of incubation until 1 day after hatching. We did not observe influences of PCB 153 on thyroid hormone (TH) levels. Treatment with PCB 77, on the other hand, decreased plasma total T 4 concentrations but increased hepatic T 4 levels at day 14 of incubation. Later in development, at stages near the process of hatching, severe decreases of T 4 and T 3 levels were observed in the PCB 77 group, both in plasma and tissues. PCB 77 severely reduced the TH peak that normally coincides with the stage of internal pipping. This reduction was accompanied by a considerable delay in the moment of hatching. We conclude that the dioxin-like PCB 77, but not the ortho-substituted PCB 153, can decrease TH availability towards the end of embryonic development and hence disturb the process of hatching.

Uptake and tissue‐specific distribution of selected polychlorinated biphenyls in developing chicken embryos

Fertilized chicken eggs were injected with high doses of individual polychlorinated biphenyl (PCB) congeners (0.5 microg of PCB 77, 9.8 microg of PCB 153, or 10.9 microg of PCB 180) before incubation to investigate the structure-specific uptake of these compounds by the embryo and their accumulation in brain and liver tissue. In accordance with earlier publications, a gradual uptake and accumulation of these compounds was observed during the last week of embryonic development. The PCB uptake and distribution to the specific tissues did not appear to be structure dependent. Wet-weight liver PCB concentrations (18, 266, and 278 ng/g at hatching for PCB 77, PCB 153, and PCB 180, respectively) were consistently two- to fourfold higher than carcass levels (7 ng/g of PCB 77, 117 ng/g of PCB 153, and 81 ng/g of PCB 180 at hatching). Whereas liver and carcass concentrations increased exponentially between day 13 of incubation and hatching, PCB levels in brain tissue remained unaltered (range, 0.6-1.0 ng/g of PCB 77 and 8-12 ng/g of PCB 153 and PCB 180 throughout the last week of incubation). Lipid analysis of the organs suggested that the lipid composition of brain may be an important factor explaining the low PCB accumulation in this tissue.

The Relationship Between Sperm Hydrolysis of the Perivitelline Layer and Embryonic Livability

The hypothesis was proposed that altered sperm hydrolysis of the germinal disc area of the ovum affects embryonic survival. Genetics and damaged spermatozoa were the 2 factors tested. Both factors affect embryonic livability. The mechanism of sperm selection was proposed to be in the oviduct or at the ovum during fertilization. To test the hypothesis, sperm hydrolysis from the creation of holes in the perivitelline layer and embryonic mortality were compared in 3 lines of turkeys representing the past 50 yr of turkey genetics. In the newer lines compared with older, sperm hydrolysis decreased and embryo livability at the first week of embryonic development declined, but embryo livability during the fourth week improved. The same lines were inseminated with 0- or 24-h-stored semen. Although penetration of the perivitelline layer by fresh sperm cells declined in modern lines, penetration of 24-h-stored sperm cells did not. When inseminated with 24-h-stored semen, all 3 lines showed depressed embryo livability compared with fresh semen at wk 1 of embryo development but improved embryo livability at wk 4 of development. In experiment 2, specific comparisons of single-trait selected lines with unselected control lines indicated that selection for rapid growth has increased sperm hydrolysis of the perivitelline layer by 24-h-stored sperm, but selection for increased egg production has not. In vitro sperm hydrolysis of the perivitelline layer was examined only for the growth-selected line in experiment 3. The in vitro technique was used to examine perivitelline layer hydrolysis without oviduct effects. The data indicated no differences in holes in the perivitelline layer for lines or sperm storage. Thus, the data suggest that a reduction in the penetration of sperm through the perivitelline layer results in improved embryo livability at wk 4 of development, but we saw no association with wk 1 embryo livability.

Molecular cloning and developmental expression of corticotropin-releasing factor in the chicken.

We have characterized the structure of the chicken corticotropin-releasing factor (CRF) gene through cDNA cloning and genomic sequence analysis, and we analyzed the expression of CRF mRNA and peptide in the diencephalon of the chick throughout embryonic development. The structure of the chicken CRF gene is similar to other vertebrate CRF genes and contains two exons and a single intron. The primary structure of the mature chicken CRF peptide is identical to human and rat CRF. This is the first archosaurian CRF gene to be characterized. We used RIAs to analyze CRF peptide content in the diencephalon and the median eminence and plasma corticosterone during the last week of embryonic development. We also developed a semiquantitative RT-PCR method to analyze the expression of CRF mRNA during the same period. CRF peptide content in the diencephalon increased, whereas peptide content in the ME decreased just before hatching, suggesting that release and biosynthesis are coupled. Plasma corticosterone concentration significantly increased between embryonic d 20 and the first day post hatch. By contrast, CRF mRNA levels in the diencephalon decreased just before hatching. Changes in CRF production just before hatching may be causally related to the regulation of the thyroid and interrenal axes at this stage of chicken development.

Lung growth and development.

The organogenesis of lung involves several complex mechanisms, including interactions between cells originating from two germ layers--endoderm and mesoderm. Regulation of lung branching morphogenesis with reference to its architecture, growth pattern, differentiation, interactions between epithelium and mesenchyme and / or endothelium, as well as genes regulating these processes have been addressed by the pulmonary biologists through careful molecular biology and genetic experimental approaches. The mammalian lung develops by outpouching from the foregut endoderm as two lung buds into the surrounding splanchnic mesenchyme. Several different regions of the foregut are specified to develop into different thoracic and visceral organs. The lung-buds further elongate and branch, and the foregut longitudinally gets separated into esophagus and trachea. In rodents (mice and rats), this occurs around embryonic day 11, where the right lung bud develops into four different lobes and left lung develops as a single lobe. In humans, these processes occur by 3-4 weeks of embryonic development, where the right lung is a trilobar lung and the left lung is a bilobar lung. Several generations of dichotomous branching occur during embryonic development, followed by secularization and alveolarization pre- and post-natally, which transform a fluid-filled lung into an air-breathing lung able to sustain the newborn. During these different developmental stages from embryonic to newborn stage, the lung architecture undergoes profound changes, which are marked by a series of programmed events regulated by master genes (e.g., homeobox genes), nuclear transcription factors, hormones, growth factors and other factors. These programmed events can be altered by undesirable exposure to overdoses of hormones/vitamins/growth factors, synthetic drugs, environmental toxins, radiation and other agents. In the recent years molecular techniques have opened avenues to study specific functions of genes or their products (proteins) in vivo or in vitro at a cellular or an organelle level, some of these include targeted disruption, knock-in / knock-out genes, in vitro mutagenesis, use of sense and anti-sense oligonucleotides. Some of these aspects with reference to regulation of normal lung development and growth and a specific example of pulmonary hypoplasia as an abnormal lung formation are discussed in this review.

Differential expression of iodothyronine deiodinases in chicken tissues during the last week of embryonic development

In the current study, the authors examined the type 1 (D1), type 2 (D2), and type 3 deiodinase (D3) activity and mRNA expression patterns in thyroid, lung, brain, pituitary, heart, liver, spleen, gonads, skin, muscle, intestine, Fabricius' bursa, and kidney during the last week of chicken embryonic development and the first 2 days posthatch. The D3 was the most widely expressed, occurring in all examined tissues. Also, the D1 knows a widespread distribution, although no D1 activity or mRNA expression could be detected in the brain, the thyroid, the muscle, and the skin. In contrast, the D2 has a much more restricted expression pattern, since the brain is the only organ where, prior to hatching, both in vitro D2 activity and D2 mRNA expression can be detected. Taken together, these results demonstrate that during the last week of chicken embryonic development, the majority of tissues express D3, together with either D1 or D2, indicating that each tissue possesses the necessary tools to regulate local thyroid hormone levels at least partly independent from T 3 and T 4 levels in plasma. In addition, the deiodinase expression data could be correlated to certain thyroid hormone dependent tissue-specific developmental events. This strongly suggests that in birds, as in mammals and amphibians, the correct spatial and temporal expression of iodothyronine deiodinases are essential for normal embryonic development.

Information on familial cases of syringomyelia, basilar impression, and Chiari malformation

The presence of familial cases of syringomyelia, basilar impression (intussusception) and Chiari malformation (MC) indicates the role of heredity in the occurrence of these diseases. Studies by a number of authors [32, 44] show that the primary pathology in this case is bone anomalies of the craniovertebral region (CVR), which contribute to the formation of the posterior cranial fossa (PCF) of reduced volume. As a result of this, the caudal parts of the cerebellum and the medulla oblongata descend through the foramen magnum (foramen magnum), i.e. formation of type I MC. In the presence of bone anomalies of KVO and MV type I, in some cases, a violation of CSF dynamics can occur at the level of the BVO, which will lead to the development and progression of syringomyelia. CVD abnormalities are, in turn, the result of defective development of the cartilaginous tissue of the bones of the skull and adjacent parts of the spine during the first weeks of embryonic development [34, 43]. Such dysembryogenesis may be due to dysfunction of genes that control the formation of the fifth occipital somite in the human body [49]. Literature data on familial cases of syringomyelia, basilar impression and MC confirm their common heredity basis.

The Role of Ultrasound in the Management of a Twin Gestation with One Fetus Affected with Anencephaly

Anencephaly is the most common type of neural tube defect seen during prenatal development. This condition results from a failure of the neural tube to close at its cephalad end between the second and third weeks of embryonic development.1 Sonographically, anencephaly presents as the absence of the cranial vault and cerebral hemispheres. It is believed to be multifactorial in origin but usually not associated with chromosomal abnormalities.2 The condition is invariably lethal; 50% are stillborn, and the remainder die in the newborn period.3 We present a case of a twin gestation, with one fetus affected with anencephaly and the other with no apparent abnormalities.

Resolution of symptomatic GERD and delayed gastric emptying after endoscopic ablation of antral diaphragm (web)

A prepyloric antral diaphragm is a rare anomaly of the gastric antrum that results from incomplete canalization of the foregut during the fifth and sixth weeks of embryonic development.1 Others believe that an antral diaphragm can be an acquired abnormality.2 About 150 cases have been reported since the initial description by Touroff et al.3 in 1940. Histologically, the antral diaphragm consists of normal gastric mucosa, submucosa, and muscularis mucosa.4 Symptoms depend on the size of the diaphragm’s aperture. If the aperture is less than 1 cm, obstructive symptoms are likely to be present. The usual treatment of these patients has been surgical resection of the diaphragm. Other treatments have included endoscopic resection with a snare,5 endoscopic transection with a papillotome,6 and endoscopic laser therapy.7 We report the case of a successful endoscopic ablation of an antral diaphragm.

Influence of Prenatal and Postnatal Acclimation on Nervous and Peripheral Thermoregulationa

The aim of the present study was to investigate whether prenatal and postnatal adaptation to different ambient temperatures affects the autonomic (heat production, heat loss, rectal or colonic temperature), behavioral (preferred ambient temperature) and nervous mechanisms (neuronal thermosensitivity of the preoptical area of the anterior hypothalamus) of thermoregulation. The experiments were carried out in postnatal, differently acclimated adult rabbits (60 days at 6-7, 20 and 30 degrees C) and adult rats (3 to 6 weeks at 5 and 21 degrees C) and in differently incubated 1- to 10-day-old Muscovy ducklings and turkeys (last week of incubation at 34.5, 37.5 and 38.5 degrees C). The results of the experiments are summarized as follows: (1) Postnatal acclimation changes the threshold ambient temperature of heat loss and heat production. For example, cold-acclimated rabbits have a lower threshold temperature for evaporative heat loss and thermoregulatory heat production than heat-acclimated ones. (2) Prenatal acclimation changes postnatal thermoregulatory behavior as well as autonomic thermoregulatory mechanisms. Birds incubated at higher (38.5 degrees C) or lower (34.5 degrees C) temperatures than the usual 37.5 degrees C for the last week of embryonic development have higher or lower preferred ambient temperatures during the first 10 days post hatching. Besides this, cold-incubated birds have a higher heat/ production and clonic temperature in the first days post hatching than normally/ incubated or heat-incubated ones. (3) Extracellular recordings from hypothalamic neurons in brain slices from differently acclimated rats have shown that adaptation to different ambient temperatures changes firstly the temperature sensitivity of the hypothalamic neurons and secondly the modulatory action of the neuropeptides bombesin and thyrotropin releasing hormone.

Primary Structure and Tissue Distribution of FRZB, a Novel Protein Related to Drosophila Frizzled, Suggest a Role in Skeletal Morphogenesis

Articular cartilage extracts were prepared to characterize protein fractions with in vivo chondrogenic activity (Chang, S., Hoang, B., Thomas, J. T., Vukicevic, S., Luyten, F. P., Ryba, N. J. P., Kozak, C. A., Reddi, A. H., and Moos, M. (1994) J. Biol. Chem. 269, 28227-28234). Trypsin digestion of highly purified chondrogenic protein fractions allowed the identification of several unique peptides by amino acid sequencing. We discovered a novel cDNA encoding a deduced 36-kDa protein by using degenerate oligonucleotide primers derived from a 30-residue peptide in reverse transcription polymerase chain reactions. Its N-terminal domain showed approximately 50% amino acid identity to the corresponding region of the Drosophila gene frizzled, which has been implicated in the specification of hair polarity during development. Hydropathy and structural analyses of the open reading frame revealed the presence of a signal peptide and a hydrophobic domain followed by multiple potential serine/threonine phosphorylation sites and a serine-rich C terminus. Cell fractionation studies of primary bovine articular chondrocytes and transfected COS cells suggested that the protein is membrane-associated. In situ hybridization and immunostaining of human embryonic sections demonstrated predominant expression surrounding the chondrifying bone primordia and subsequently in the chondrocytes of the epiphyses in a graded distribution that decreased toward the primary ossification center. Transcripts were present in the craniofacial structures but not in the vertebral bodies. Because it is expressed primarily in the cartilaginous cores of developing long bones during embryonic and fetal development (6-13 weeks) and is homologous to the polarity-determining gene frizzled, we believe that this gene, which we named frzb, is involved in morphogenesis of the mammalian skeleton.