[Establishment and characterization of a cell line derived from human ovarian mucinous cystadenocarcinoma]

OBJECTIVE

To establish a cell line of human ovarian cancer, and study its characterization.

METHODS

The cell line was established by the cultivation of subsides walls, and kept by freezing. The morphology was observed by microscope and electromicroscope. The authors studied its growth and propagation, the agglutination test of phytohemagglutinin (PHA), the chromosome analysis, heterotransplanting, immuno-histochemistry staining, the analysis of hormone, the pollution examination and the test of sensitivity to virus etc.

RESULTS

A new human ovarian carcinoma cell line, designated ovarian mucinous cystadenocarcinoma 685 (OMC685), was established from mucinous cystadenocarcinoma. This cell line had subcultured to 91 generations, and some had been frozen for 8 years and revived, still grew well. This cell line possessed the feature of glandular epithelium cancer cell. The cells grew exuberantly, and the agglutinating test of PHA was positive. Karyotype was subtriploid with distortion. Heterotransplantations, alcian blue periobic acid-schiff (AbPAS), mucicarmine, alcian blue stainings, estradiol (E2) and progesterone were all positive. Without being polluted, it was sensitive to polivirus-I, adenovirus 7 and measles virus.

CONCLUSIONS

OMC685 is a distinct human ovarian tumous cell line.

Enzyme replacement therapy in feline mucopolysaccharidosis I

Enzyme replacement therapy (ERT) has long been considered an approach to treating lysosomal storage disorders caused by deficiency of lysosomal enzymes. ERT is currently used to treat Gaucher disease and is being developed for several lysosomal storage disorders now that recombinant sources of the enzymes have become available. We have continued development of ERT for mucopolysaccharidosis I (MPS I) using the feline model. Recombinant alpha-L-iduronidase was administered intravenously at low dose (approximately 0.1 mg/kg or 25,000 units/kg) to four cats and high dose (0.5 mg/kg or 125,000 units/kg) to two cats on a weekly basis for 3- or 6-month terms. Clinical examinations showed distinct clearing of corneal clouding in one cat although clinical effects in the others were not evident. Biochemical studies of the cats showed that the enzyme was distributed to a variety of tissues although the liver and spleen contained the highest enzyme activities. Glycosaminoglycan storage was decreased in liver and spleen, and the histologic appearance improved in liver, spleen, and renal cortex. Enzyme was not consistently detected in cerebral cortex, brainstem, or cerebellum and the histologic appearance and ganglioside profiles did not improve. A variety of other tissues showed low variable uptake of enzyme and no distinct improvement. IgG antibodies to alpha-L-iduronidase were observed in five cats with higher titers noted when higher doses were administered. Mild complement activation occurred in three cats. Enzyme replacement therapy was effective in reversing storage in some tissues at the biochemical and histologic level in MPS I cats but an improved tissue distribution and prevention of a significant immune response could make the therapy more effective.

Distribution of a common methylenetetrahydrofolate mutation in six Chinese population groups

The distribution of the C677T polymorphism was analyzed by the PCR-RFLP technique in the Northeast Han, the Oroqen, the Ewenki, the Daur as well as in Koreans and Mongolians. The results were compared with each other. They revealed that the frequencies of the T allele are quite different (17-47%) among the tested groups and are much higher in Chinese population groups than in others.

Auricular-plaster therapy plus acupuncture at zusanli for postoperative recovery of intestinal function

In order to relieve the abdominal distension and other discomforts due to gastrointestinal dysfunction after abdominal operations, the patients were treated by auricular-plaster therapy plus acupuncture at Zusanli (ST 36). 12 (92.4%) of the 13 cases in the treatment group showed recovery of normal peristalsis within 72 hours after operations, while that in 13 cases of the control group was 46.1%, indicating that auricular-plaster therapy plus acupuncture at Zusanli (ST 36) may promote postoperative recovery of the intestinal function.

Direct protein-protein coupling enables cross-talk between dopamine D5 and gamma-aminobutyric acid A receptors

GABA(A) (gamma-aminobutyric-acid A) and dopamine D1 and D5 receptors represent two structurally and functionally divergent families of neurotransmitter receptors. The former comprises a class of multi-subunit ligand-gated channels mediating fast interneuronal synaptic transmission, whereas the latter belongs to the seven-transmembrane-domain single-polypeptide receptor superfamily that exerts its biological effects, including the modulation of GABA(A) receptor function, through the activation of second-messenger signalling cascades by G proteins. Here we show that GABA(A)-ligand-gated channels complex selectively with D5 receptors through the direct binding of the D5 carboxy-terminal domain with the second intracellular loop of the GABA(A) gamma2(short) receptor subunit. This physical association enables mutually inhibitory functional interactions between these receptor systems. The data highlight a previously unknown signal transduction mechanism whereby subtype-selective G-protein-coupled receptors dynamically regulate synaptic strength independently of classically defined second-messenger systems, and provide a heuristic framework in which to view these receptor systems in the maintenance of psychomotor disease states.

H2-E transgenic class II-negative mice can distinguish self from nonself in susceptibility to heterologous thyroglobulins in autoimmune thyroiditis

Susceptibility to experimental autoimmune thyroiditis (EAT) is linked to H2-A class II genes; k and s haplotypes are susceptible, while b and f are resistant. EAT is inducible with thyroglobulins (Tgs) from several mammalian species which share portions of identical sequences. But cross-activation and cross-tolerance studies with mouse (m), human (h), and porcine (p) Tg have indicated mTg-unique T-cell epitope(s), in addition to conserved, in EAT induction. The recent introduction of the HLA-DRB1*0301 (DR3) transgene rendered major histocompatibility complex (MHC) class II-negative (Ab(0)) mice susceptible to EAT induction by both hTg and mTg, suggesting usage of conserved epitopes. Here, we introduced the H2-Ea(k) transgene into resistant B10 (H2(b)) or Ab(0) mice with a defective Ea gene to provide functional surface H2E (b haplotype) expression. Surprisingly, both transgenic strains showed severe inflammation only after hTg, but not mTg, immunization, although the moderating influence of the A(b) gene in B10 was evident. In proliferative assays, hTg-primed cells did not respond to mTg, nor to conserved 12mer peptides from three primary hormonogenic sites, two of which can activate T cells for thyroiditis transfer and cytotoxicity. The vigorous response to hTg stimulation was reduced only by Ebeta(b)-specific monoclonal antibody. EAT induction with bovine and pTg showed responses similar to hTg, suggesting thyroiditogenic epitopes shared with hTg, but not mTg. This is the first demonstration of: (1) nonpermissiveness for EAT induction with mTg, normally the most thyroiditogenic Tg and the one with unique epitopes for susceptible mice, and (2) the separation of hTg from mTg in EAT induction in H2-E-transgenic mice.

Involvement of K(+) channels in the inhibitory effects of adenosine on anoxia-induced [Ca(2+) ](i) increase in cultured rat hippocampal CA1 neurons

Changes in intracellular free Ca(2+) concentration ([Ca(2+)](i)) in cultured hippocampal CA1 neurons isolated from newborn rats were measured by a confocal laser scanning microscope, using the Ca(2+) indicator Fluo-3. The results showed that exogenous adenosine (100 microM) significantly attenuated the increase of neuronal [Ca(2+)](i) induced by acute anoxia. This effect of adenosine could be suppressed by the adenosine A1 receptor antagonist 8-cyclopentyltheophylline. Moreover, potassium channel blockers, aminopyridine, and glipizide could also block the inhibitory role of adenosine, but tetraethylammonium had no effect. These results suggest that adenosine may activate 4-AP or ATP-sensitive potassium channels via an A1-receptor-mediated mechanism and consequently inhibit anoxia-induced [Ca(2+)](i) elevation in hippocampal neurons.

Identification and characterization of the molecular lesion causing mucopolysaccharidosis type I in cats

Mucopolysaccharidosis Type I (MPS I) is the lysosomal storage disease caused by the deficient activity of alpha-L-iduronidase (IDUA). In man, MPS I can occur in severe, mild, or intermediate forms known as the Hurler, Scheie, or Hurler/Scheie syndromes, respectively. MPS I also has been described in cats, dogs, and mice. This manuscript reports the identification and characterization of the mutation causing MPS I in cats. To obtain wild-type feline IDUA cDNAs, two PCR-based strategies were used. PCR primers were constructed from a conserved region of the published human and dog sequences and used to amplify a 224-bp IDUA fragment from normal cat genomic DNA. This fragment was then used to screen a feline uterus cDNA library. PCR also was used to directly amplify IDUA fragments from the same cDNA library. Two overlapping feline IDUA cDNAs encoding 466 amino acid residues of the feline IDUA polypeptide ( approximately 85% of the mature protein based on comparison to the human, dog, and mouse sequences) were obtained by these strategies. To identify the mutation causing MPS I in cats, DNA sequencing was carried out on the corresponding IDUA region from several affected animals. A 3-bp deletion was found on both IDUA alleles in each of the MPS I animals, predicting the deletion of a single aspartate residue from the feline IDUA polypeptide. To confirm the authenticity of this mutation, heteroduplex, SSCP, and transient expression studies were carried out. Over 100 animals from the MPS I colony were screened for the presence of the mutation by heteroduplex and SSCP analyses-in all cases the presence of the 3-bp deletion was 100% concordant with the disease phenotype. For transient expression studies, the two partial, overlapping feline cDNAs were combined and joined in-frame to the 5' end of the canine IDUA cDNA. This wild-type, hybrid cDNA expressed IDUA activity up to sixfold over endogenous levels after transfection into COS-1 cells. A modified full-length IDUA cDNA containing the 3-bp deletion did not express IDUA activity in a transient expression system, providing proof that this lesion was the cause of feline MPS I.

[The different responses to anoxia in cultured CA1 and DG neurons from newborn rats]

Tissue culture from hippocampal CA1 or dentate gyrus (DG) region was established on the basis of previous neuronal culture technique. The viability, intracellular calcium concentration and brain-derived neurotrophic factor (BDNF) mRNA expression of the two kinds of neurons after anoxia were observed in the counting in the confocal microscopic field and in situ hybridization. It is found that DG neurons are not only more resistant to anoxia, but also have a stronger ability to keep calcium homeostasis and to express BDNF mRNA than CA1 neurons.

Thyroglobulin peptides of specific primary hormonogenic sites can generate cytotoxic T cells and serve as target autoantigens in experimental autoimmune thyroiditis

Previously we demonstrated that thyroxine (T4)-containing, 12-mer peptides from positions 5 (1-12) and 2553 (2549-2560), as well as thyronine (T0)-substituted 2553 peptide, derived from human (H) thyroglobulin (Tg) are capable of activating T cells that infiltrate the thyroid (thyroiditogenic). In contrast, peptides T4(2567) and T0(2567) (2559-2570) are not. To determine if these thyroiditogenic peptides, T4(5), T4(2553), and T0(2553), activated cytotoxic T cells (Tc) and served as target autoantigens when loaded onto indicator cells (BW5147 lymphoma, H2k), lymph node cells from CBA mice immunized with mouse (M) Tg were cultured in vitro with MTg, HTg, or Tg peptide. After MTg or HTg activation, Tc were detected for both MTg- and HTg-loaded target cells in an 18-h, 51Cr-release assay at an effector:target cell ratio of 50:1. These Tc also killed target cells labeled with T4(5), T4(2553), or T0(2553), but not the control peptide T4(2567). When MTg-primed lymphocytes were cultured with T4(5), T4(2553), or T0(2553), specific Tc were also generated against target cells labeled with the respective peptide. The data suggest that one of the thyroiditogenic properties of these peptides previously shown by adoptive transfer of thyroiditis is related to the generation of Tc. In addition, these conserved autoepitopes of Tg also serve as target antigens for Tc.

[Anoxia-induced c-fos expression of cultured rat hippocampal neurons and effect of recombinant human interleukin-1 beta]

Effects of recombinant human interleukin-1 beta (rhIL-1 beta) on the c-fos expression of cultured rat hippocampal neurons in vitro induced by anoxia were studied by using an immunohistochemical method. The results showed that the percentage and the mean optical density of the Fos-positive neuronal nuclei in cultured hippocampal neurons increased markedly as anoxia prolonged, while those in hippocampal neurons pretreated with rhIL-1 beta were significantly lower than those of control. The results indicate that anoxia can induce c-fos expression of cultured rat hippocampal neurons in vitro and this can be inhibited by rhIL-1 beta, suggesting that rhIL-1 beta may protect neurons from damage in a certain degree during anoxia.

Primary hormonogenic sites as conserved autoepitopes on thyroglobulin in murine autoimmune thyroiditis: role of MHC class II

A few synthetic peptides corresponding to amino acid sequences on human thyroglobulin (Tg) have been reported to induce moderate thyroiditis or activate mouse Tg (MTg)-primed T cells to transfer thyroiditis in mice susceptible to experimental autoimmune thyroiditis. Using three pairs of 12-mer peptides (1-12, 2549-2560, 2559-2570), with thyroxine (T4) or noniodinated thyronine (T0) at the conserved, hormonogenic site 5, 2553, or 2567 respectively, we reported that iodination was not required for a Tg hormonogenic site to be a thyroiditogenic autoepitope. To determine the relative importance of MHC class II and T cell receptor (TCR) repertoire, we compared two EAT-susceptible k and s (CBA and A.SW) haplotypes and their respective MHC-identical strain (C57BR and SJL) with approximately 50% genomic deletion of TCR Vbeta genes. Whereas k and s strains develop MTg-induced EAT, vigorous immunization with peptides containing T4 or T0 at either 5 or 2553, but not at 2567, led to mild (10-20%) thyroiditis only in some mice of either k strain. TCR Vbeta gene differences played a minor role. T cell responses to all peptide pairs were quite similar in CBA and C57BR mice, and both hT0(2553) and hT4(2553) reciprocally primed and stimulated their T cells. In adoptive transfer, SJL mice were somewhat more responsive to peptide activation than A.SW but much weaker than k strains. By comparing T4- and T0-containing peptides in different haplotypes, we show further that antigenicity of conserved hormonogenic sites is intrinsic, dependent more on amino acid sequence and binding to appropriate class II molecules and less on TCR repertoire or iodination of T0.

[Study on the permeability of the infiltration glass of GI- I slip casting aluminous ceramic core]

In order to explore the infiltration condition of GI- I slip casting aluminous ceramic core glass material to aluminous ceramic substratum and provide reference for clinical use, the linear change relationship between the minimal infiltration depth and infiltration time was determined by measuring the minimal depth of glass material infiltrated to aluminous ceramic substratum from one to six hours. The result showed: there is a high linear relationship between the minimal infiltration depth for GI- I infiltration glass and the infiltration time. For clinical use, the minimal infiltration time for GI- I slip casting aluminous ceramic core at least 2.5 hrs and 5 hrs for bridge framework.

[Effect of adenosine on intracellular free calcium in cultured rat hippocampal CA1 neurons during anoxia]

Intracellular free Ca2+ concentration ([Ca2+]i) was measured by laser scanning confocal microscope, using Ca2+ indicator Fluo-3 in cultured hippocampal CA1 neurons isolated from newborn rat. The results showed that acute anoxia induced a rapid increase of [Ca2+]i in hippocampal CA1 neurons, and this increase could be attenuated by 100 mumol/L adenosine significantly. This effect of adenosine could be suppressed by adenosine A1 receptor antagonist CPT or potassium channel blockers, 4-AP and glipizide. These results suggest that adenosine activates 4-AP- or ATP-sensitive potassium channels through A1 receptors, and consequently inhibits the [Ca2+]i elevation in hippocampal neurons during anoxia.

Recruitment of functional GABA(A) receptors to postsynaptic domains by insulin

Modification of synaptic strength in the mammalian central nervous system (CNS) occurs at both pre- and postsynaptic sites. However, because postsynaptic receptors are likely to be saturated by released transmitter, an increase in the number of active postsynaptic receptors may be a more efficient way of strengthening synaptic efficacy. But there has been no evidence for a rapid recruitment of neurotransmitter receptors to the postsynaptic membrane in the CNS. Here we report that insulin causes the type A gamma-aminobutyric acid (GABA[A]) receptor, the principal receptor that mediates synaptic inhibition in the CNS, to translocate rapidly from the intracellular compartment to the plasma membrane in transfected HEK 293 cells, and that this relocation requires the beta2 subunit of the GABA(A) receptor. In CNS neurons, insulin increases the expression of GABA(A) receptors on the postsynaptic and dendritic membranes. We found that insulin increases the number of functional postsynaptic GABA(A) receptors, thereby increasing the amplitude of the GABA(A)-receptor-mediated miniature inhibitory postsynaptic currents (mIPSCs) without altering their time course. These results provide evidence for a rapid recruitment of functional receptors to the postsynaptic plasma membrane, suggesting a fundamental mechanism for the generation of synaptic plasticity.

[Role of Na+/Ca2+ exchange blocker in rat hippocampal injury during anoxia]

Effects of Na+/Ca2+ exchange blocker, Benzamil, on rat hippocampal slices and on cultured hippocampal neuronal [Ca2+]i (intracellular free Ca2+ concentration) during anoxia were investigated by means of microelectrode recording technique and laser scanning confocal microscope respectively. The results showed that the PV sustained time of hippocampal slices pretreated with Benzamil (50 mumol) after anoxia was markedly longer than that of control, suggesting that inhibition of Na+/Ca2+ exchange can delay the irreversible injury to hippocampal cells. Moreover, by using a confocal microscope we found that acute anoxia induced a rapid increase of [Ca2+]i in hippocampal neurons and this could be significantly attenuated by 20 mumol Benzamil. All these results indicate that Na+/Ca2+ exchanger is involved in the anoxic injury to rat hippocampus and it may be one of the major ways leading to the anoxia-induced [Ca2+]i increase of hippocampal neurons.

Modulation of GABAA receptor function by tyrosine phosphorylation of beta subunits

Protein tyrosine phosphorylation is a key event in diverse intracellular signaling pathways and has been implicated in modification of neuronal functioning. We investigated the role of tyrosine phosphorylation in regulating type A GABA (GABAA) receptors in cultured CNS neurons. Extracellular application of genistein (50 microM), a membrane-permeable inhibitor of protein tyrosine kinases (PTKs), produced a reversible reduction in the amplitude of GABAA receptor-mediated whole-cell currents, and this effect was not reproduced by daidzein (50 microM), an inactive analog of genistein. In contrast, intracellular application of the PTK pp60(c-src) (30 U/ml) resulted in a progressive increase in current amplitude, and this potentiation was prevented by pretreatment of the neurons with genistein. Immunoprecipitation and immunoblotting of cultured neuronal homogenates indicated that the beta2/beta3 subunit(s) of the GABAA receptor are tyrosine phosphorylated in situ. Moreover, genistein (50 microM) was found to be capable of decreasing GABAA currents in human embryonic kidney 293 cells transiently expressing functional GABAA receptors containing the beta2 subunit. Thus, the present work provides the first evidence that native GABAA receptors are phosphorylated and modulated in situ by endogenous PTKs in cultured CNS neurons and that phosphorylation of the beta subunits may be sufficient to support such a modulation. Given the prominent role of GABAA receptors in mediating many brain functions and dysfunctions, modulation of these receptors by PTKs may be important in a wide range of physiological and pathological processes in the CNS.

Melatonin receptors in the spinal cord

The pineal hormone, melatonin, plays an important role in the regulation of diurnal and seasonal rhythms in animals. In addition to the well established actions on the brain, the possibility of a direct melatonin action on the spinal cord has to be considered. In our laboratory, we have obtained data suggesting that melatonin receptors are present in the spinal cords of birds and mammals. Using radioreceptor binding and quantitative autoradiography assays with 2-[125I]iodomelatonin as the specific melatonin agonist, melatonin binding sites have been demonstrated in the rabbit and chicken spinal cords. These sites are saturable, reversible, specific, guanosine nucleotide-sensitive, of picomolar affinity and femtomolar density. The linearity of Scatchard plots of saturation data and the unity of Hill coefficients indicate that a single class of melatonin binding sites is present in the spinal cord membranes studied. The picomolar affinity of these sites is in line with the circulating levels of melatonin in these animals suggesting that these sites are physiologically relevant. Autoradiography studies in the rabbit spinal cord show that melatonin binding sites are localized in the central gray substance (lamina X). In the chicken spinal cord, these binding sites are localized in dorsal gray horns (laminae I-V) and lamina X. As lamina X and laminae I-II have similar functions, melatonin may have comparable roles in the chicken and rabbit spinal cords. Moreover, in the chicken spinal cord, the density of 2-[125I]iodomelatonin binding in the lumbar segment was significantly higher than those of the cervical and thoracic segments. The densities of these binding sites changed with environmental manipulations. When chickens were adapted to a 12L/12D photoperiod and sacrificed at mid-light and mid-dark, there was a significant diurnal variation in the density (maximum number of binding sites; Bmax) of melatonin binding sites in the spinal cord. After constant light treatment or pinealectomy, the Bmax of melatonin receptors in the chicken spinal cord increased significantly in the subjective mid-dark period. Moreover, there was an age-related decrease in the 2-[125I]iodomelatonin binding to the chicken spinal cord. Our results suggest that melatonin receptors in the chicken spinal cord are regulated by environmental lighting and change with development. These receptors may play an important role in the chronobiology of spinal cord function. The biological responses of melatonin on spinal cords have also been demonstrated in vitro. Melatonin decreased the forskolin-stimulated cAMP production in the chicken spinal cord explant. Preincubation with pertussis toxin blocked the melatonin effect. Our results suggest that melatonin receptors in the chicken spinal cord are linked to the adenylate cyclase via a pertussis toxin-sensitive G protein and that melatonin binding sites in spinal cords are melatonin receptors with biological functions. These receptors may be involved in the regulation of spinal cord functions related to sensory transmission, visceral reflexes and autonomic activities.

[The role of adenosine in the early stage of anoxia of hippocampal slices and its mechanisms]

The role of adenosine in reversible inhibition of synaptic function during the early stage of anoxia and its mechanisms were investigated with extracellular recording technique in rat hippocampal slices. The results showed that acute anoxia led to the reversible inhibition of synaptic function, which is similar to the response to addition of high concentration of exogenous adenosine. The reversible inhibition could be suppressed by adenosine A1 receptor antagonist CPT and potassium channel blocker 4-AP, whereas TEA and ATP-sensitive potassium channel blocker glipzide had no effect. These results suggest that during the early stage of anoxia, the enhanced release of endogenous adenosine can inhibit the synaptic transmission by activating 4-AP-sensitive potassium channels via A1 receptors and thus play a role in protenction against anoxic injury. ATP-sensitive potassium channels may not be involved in the mechanisms of adenosine action.

Guanosine 5'-O-(3-thiotriphosphate) and cations regulate melatonin receptors, and melatonin inhibits cyclic AMP production in the spinal cord

Effects of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and cations on 2-[125I]iodomelatonin binding were investigated in membrane preparations of the chicken spinal cord. At concentrations of 10 and 50 mumol/l, GTP gamma S dose-dependently increased (p < 0.05) the equilibrium dissociation constant (Kd) and depressed (p < 0.05) the maximum number of binding sites (Bmax). Na+ at a concentration of 125 mmol/l significantly increased (p < 0.05) the Kd and decreased (p < 0.05) the Bmax, and Mg2+ (2.5 mmol/l) significantly increased (p < 0.05) the Bmax without changes in Kd. In addition, Na+ and Mg2+ affected the interactions of GTP gamma S with melatonin receptors. In the spinal cord explants, melatonin (10 nmol/l) attenuated forskolin-stimulated cyclic AMP production by 53.1%, and preincubation with pertussis toxin abolished this effect of melatonin. These results suggest that the melatonin receptors in the chicken spinal cord are linked to its second messenger via a pertussis-toxin-sensitive guanine-nucleotide-binding protein, and that cations modulate these receptors. Our studies further support a previous hypothesis that melatonin exerts a direct action on spinal cord functions.

The developmental and circadian variation of melatonin receptors in the chicken spinal cord

The developmental variation of 2-[125I]iodomelatonin binding sites in membrane preparations of the chicken spinal cords was investigated. In 19-day-old embryos, the maximum number of binding sites (Bmax) was the highest during the development. With the increase in age posthatch, the Bmax decreased gradually and significantly from 1-day-old to 4-month-old chickens. However, there were no significant changes in equilibrium dissociation constant (Kd) among all age-groups studied. To study the circadian variation, the 2-[125I]iodomelatonin binding sites in the spinal cords of 3-week-old chickens were determined at 4-hour intervals throughout a 24-hour period under a 12-hour light/12-hour dark cycle. There was a diurnal rhythm in both Bmax and Kd of [125I]iodomelatonin binding sites in which Bmax decreased and Kd increased in the dark period. The characteristics of developmental and circadian variation of melatonin receptors in the chicken spinal cord suggest that melatonin may exert a direct action on spinal cord functions and that it plays a more important role in the young animal.