Biomedical subjects

F Tang

Publications and source records attributed to F Tang.

At least 19 recordsLinked to original sources

PubMed1992

Decrease of enkephalins in cerebellum during Wobbler mouse motoneuron disease.

The Wobbler mouse possesses an inherited motoneuron disease, which expresses itself primarily at cervical spinal levels and in cranial motor nuclei. Cell degeneration is sporatic and negligible in other motor regions of the brain (e.g., cerebellum, corpus striatum). However, enkephalin concentrations are consistently lower in the Wobbler cerebellum throughout the motoneuron disease, whereas substance P concentrations are significantly higher late in the disease compared with the normal phenotype littermates. The data imply that early changes in enkephalin (also shown for leucine enkephalin in the spinal cord and brainstem) may be important to the etiology of the Wobbler disorder. Like the late increase of substance P, this may reflect a yet-to-be described response to parent cell degeneration in the raphe nuclei. TRH remained unchanged in Wobbler cerebellum and corpus striatum, wherein the other peptides studied herein also maintained similar concentrations to the normal phenotype littermates.

Aging↗

PubMed1992

Ultrastructural and cytochemical studies of the effects of prolactin on the lateral prostate and the seminal vesicle of the castrated guinea pig.

Administration of ovine prolactin to castrated guinea pigs for 2 weeks induced hypertrophy of secretory cells in the lateral prostate when compared with the castrated controls. This was accompanied by an apparent increase in the number of profiles of granular endoplasmic reticulum and well developed Golgi complexes with dilated cisternae. An increase in the number of low-contrast electron-dense secretory granules was observed 4 weeks after prolactin treatment. In the seminal vesicle, dilatation and degranulation of granular endoplasmic reticulum and an apparent decrease in the number of secretory granules were observed 4 weeks after prolactin administration. Following castration and 2 weeks after prolactin treatment, thiamine pyrophosphatase (TPPase)-reaction product was mainly confined to 1-2 trans cisternae of the Golgi complexes in secretory cells of the lateral prostate and the seminal vesicle. In both glands, a reduction of TPPase activity was observed 2 weeks following prolactin administration, and the reaction product was totally absent after prolonged treatment for 4 weeks. The present study has provided morphological evidence that prolactin is capable of stimulating the secretory function of the lateral prostate while exerting some inhibitory effects on the seminal vesicle of the castrated guinea pig. In both glands, TPPase activity, and hence the process of glycosylation was inhibited after prolactin administration. The results from radioimmunoassay indicated that the action of prolactin on these glands could be a direct effect and not mediated through testosterone.

Animals↗

PubMed1992

Alteration in the levels of thyrotropin releasing hormone, substance P and enkephalins in the spinal cord, brainstem, hypothalamus and midbrain of the Wobbler mouse at different stages of the motoneuron disease.

The present study was undertaken to quantify selected neuropeptides (thyrotropin releasing hormone, substance P, methionine and leucine enkephalin) in the cervical spinal cord and other regions of the central nervous system of Wobbler mice by radioimmunoassays during several stages of the motoneuron disease compared with age- and sex-matched normal phenotype littermates. In Wobbler spinal cord, thyrotropin releasing hormone is higher early in the disease, whereas in the brainstem it is higher at a later stage. Substance P in spinal cord is also higher late in the disease. Leucine enkephalin levels are greater at all stages in diseased spinal cord and brainstem, but methionine enkephalin increases only late in the disease. Highly significant increases of the peptides (except thyrotropin releasing hormone) appear in hypothalamus and midbrain only late in the motoneuron disease. Regression analyses show that thyrotropin releasing hormone in spinal cord and brainstem decreases normally with age in the control mice and at a faster rate related to the extent of motor impairment in Wobbler mice. Thyrotropin releasing hormone and methionine enkephalin in the Wobbler brainstem correlate (P less than 0.05) with the progress of the motoneuron disease. Methionine enkephalin increases faster in Wobbler brainstem and decreases faster in control spinal cord with age. The increase of leucine enkephalin in the Wobbler spinal cord correlates significantly with age and with the progress of the disease, but leucine enkephalin declines slightly with age in the controls. The changes of substance P in spinal cord and brainstem do not correlate significantly with the progress of the disease. In the hypothalamus, increasing values for substance P in control specimens and enkephalins in Wobbler specimens are significantly correlated with age. However, in the midbrain, higher methionine and leucine enkephalin levels are significantly associated with age only in the control mice. Alterations of neuropeptides in the Wobbler mouse spinal cord and brainstem may result from the degeneration of bulbospinal raphe neurons projecting to the ventral spinal cord, or from primary afferent or interneuronal nerve terminals. The data imply that the neuronal degeneration process in the Wobbler motoneuron disease is not limited to motoneurons. In the spinal cord, the data support our previous hypothesis that neuronal sprouting presynaptic to the motoneurons may account for increased neuropeptide concentrations. Alternatively, synthesis and/or degradation of these peptides may be altered. In addition, it is proposed that enkephalinergic neurons may develop abnormally in Wobbler mice. The early increase of leucine enkephalin in the Wobbler spinal cord possibly indicates its importance in the etiology of the motoneuron disease.

Animals↗

PubMed1992

Cloning and characterization of a gene required for the secretion of extracellular enzymes across the outer membrane by Xanthomonas campestris pv. campestris.

Nonpathogenic mutants of Xanthomonas campestris pv. campestris, generated from transposon mutagenesis, accumulated extracellular polygalacturonate lyase, alpha-amylase, and endoglucanase in the periplasm. The transposon Tn5 was introduced by a mobilizable, suicidal plasmid, pSUP2021 or pEYDG1. Genomic banks of wild-type X. campestris pv. campestris, constructed on the broad-host-range, mobilizable cosmid pLAFR1 or pLAFR3, were conjugated with one of the mutants, designated XC1708. Recombinant plasmids isolated by their ability to complement XC1708 can be classified into two categories. One, represented by pLASC3, can complement some mutants, whereas the other, represented by a single plasmid, pLAHH2, can complement all of the other mutants. Restriction mapping showed that the two recombinant plasmids shared an EcoRI fragment of 8.9 kb. Results from subcloning, deletion mapping, and mini-Mu insertional mutation of the 8.9-kb EcoRI fragment suggested that a 4.2-kb fragment was sufficient to complement the mutant XC1708. Sequence analysis of this 4.2-kb fragment revealed three consecutive open reading frames (ORFs), ORF1, ORF2, and ORF3. Hybridization experiments showed that Tn5 in the genome of XC1708 and other mutants complemented by pLASC3 was located in ORF3, which could code for a protein of 83.5 kDa. A signal peptidase II processing site was identified at the N terminus of the predicted amino acid sequence. Sequence homology of 51% was observed between the amino acid sequences predicted from ORF3 and the pulD gene of Klebsiella species.

Amino Acid Sequence↗

PubMed1991

Alpha-bungarotoxin and the competing antibody WF6 interact with different amino acids within the same cholinergic subsite.

In the nicotinic acetylcholine receptors (AChRs), the sequence segment surrounding two invariant vicinal cysteinyl residues at positions 192 and 193 of the alpha subunit contains important structural component(s) of the binding site for acetylcholine and high molecular weight cholinergic antagonists, like snake alpha-neurotoxins. At least a second sequence region contributes to the formation of the cholinergic site. Studying the binding of alpha-bungarotoxin and three different monoclonal antibodies, able to compete with alpha-neurotoxins and cholinergic ligands, to a panel of synthetic peptides as representative structural elements of the AChR from Torpedo, we recently identified the sequence segments alpha 181-200 and alpha 55-74 as contributing to form the cholinergic site (Conti-Tronconi et al., 1990). As a first attempt to elucidate the structural requirements for ligand binding to the subsite formed by the sequence alpha 181-200, we have now studied the binding of alpha-bungarotoxin and of antibody WF6 to the synthetic peptide alpha 181-200, and to a panel of peptide analogues differing from the parental sequence alpha 181-200 by substitution of a single amino acid residue. CD spectral analysis of the synthetic peptide analogues indicated that they all have comparable structures in solution, and they can therefore be used to analyze the influence of single amino acid residues on ligand binding. Distinct clusters of amino acid residues, discontinuously positioned along the sequence 181-200, seem to serve as attachment points for the two ligands studied, and the residues necessary for binding of alpha-bungarotoxin are different from those crucial for binding of antibody WF6. In particular, residues at positions 188-190 (VYY) and 192-194 (CCP) were necessary for binding of alpha-bungarotoxin, while residues W187, T191, and Y198 and the three residues at positions 193-195 (CPD) were necessary for binding of WF6. Comparison of the CD spectra of the toxin/peptide complexes, and those obtained for the same peptides and alpha-bungarotoxin in solution, indicates that structural changes of the ligand(s) occur upon binding, with a net increase of the beta-structure component. The cholinergic binding site is therefore a complex surface area, formed by discontinuous clusters of amino acid residues from different sequence regions. Such complex structural arrangement is similar to the "discontinuous epitopes" observed by X-ray diffraction studies of antibody/antigen complexes [reviewed in Davies et al. (1988)]. Within this relatively large structure, cholinergic ligands bind with multiple points of attachment, and ligand-specific patterns of the attachment points exist.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1991

Study on mutagenicity and identification of organic pollutants in wastewater of industrial area.

In this study, wastewater samples from three industrial wastewater channels and 12 related factories were collected. Nonvolatile organic chemicals were concentrated on H-103 resin and analysed by GC/MS/DS techniques. The mutagenicity of organic extracts from the samples was examined by using S. typhimurium assay (Ames test). The results of both Ames test and chemical analysis showed that the mutagenic compounds in the Loujia Channel mainly come from Dyestuff Factory, and that Pharmaceutical Factory is a main pollution source of mutagenic compounds for the Xindun Channel. Our experimental results also showed that it is necessary to examine the mutagenicity of industrial wastewater by using short term bioassay for evaluating long-term effect of industrial wastewater on human health.

Coloring Agents↗

PubMed1991

The regional distribution of thyrotropin releasing hormone, leu-enkephalin, met-enkephalin, substance P, somatostatin and cholecystokinin in the rat brain and pituitary.

There was no apparent difference in the regional distribution of neuropeptides in the brain of male and female rats. The highest levels of immunoreactive leu-enkephalin, TRH, substance P and somatostatin were found in the hypothalamus, while the striatum and the cerebral cortex had the highest concentrations of met-enkephalin and cholecystokinin respectively. The lowest concentrations of these were found in the cerebellum. Enkephalins (cerebral cortex), substance P (cerebral cortex and brain stem), and somatostatin (brain stem and striatum) showed higher level in the female while enkephalin and substance P contents in the anterior pituitary were higher in the male.

Animals↗

PubMed1991

Effect of reserpine on catecholamine contents and met-enkephalin and beta-endorphin levels in the hypothalamus and the pituitary.

1. The effects of reserpine treatment on the contents of catecholamines and opioid peptides have been studied in the rat hypothalamus and pituitary. 2. Hypothalamic and pituitary catecholamines were drastically depleted following acute reserpine treatment. 3. Reserpine treatment also resulted in a significant decrease in immunoactive met-enkephalin content in both the hypothalamus (25%) and the anterior lobe (50%), but not in the neurointermediate lobe of the pituitary. 4. No changes were observed in immunoactive beta-endorphin levels. 5. These findings suggest that the met-enkephalin contents in the hypothalamus and the anterior pituitary may be under catecholaminergic control. 6. The lack of effect of acute reserpine treatment on immunoactive beta-endorphin contents might be due to the opposing effects of adrenergic and dopaminergic mechanisms.

Animals↗

PubMed1991

Endocrine control of hypothalamic and pituitary met-enkephalin and beta-endorphin contents.

This review summarizes the recent findings on the effects of endocrine manipulation on the hypothalamic and pituitary contents of met-enkephalin and beta-endorphin. In the pituitary, gonadectomy decreases beta-endorphin content in both the anterior lobe and neuro-intermediate lobe. Orchidectomy results in a decrease while ovariectomy leads to an increase in anterior lobe met-enkephalin contents. Adrenalectomy only lead to an increase in beta-endorphin contents in the anterior pituitary lobe. Hypothyroidism induced by propylthiouracil treatment is accompanied by a decrease of beta-endorphin in the neuro-intermediate lobe and a decrease in met-enkephalin in the anterior lobe while thyroidectomy entails a decrease in met-enkephalin in the anterior lobe only. Chemically induced diabetes mellitus results in a decrease in beta-endorphin content in the hypothalamus and the neuro-intermediate lobe, and a reduction in met-enkephalin level in the anterior and neuro-intermediate lobes. All these changes are reversible with appropriate hormone treatments. These results indicate the importance of hormones in the regulation of the synthesis and/or release of the opioid peptides in the hypothalamus and the pituitary.

Animals↗

PubMed1991

Intracerebroventricular atrial natriuretic factor (ANF) antiserum inhibits volume-induced ANF in sheep: evidence for the brain's regulation of ANF secretion.

Plasma volume expansion stimulates cardiac secretion of atrial natriuretic factor (ANF) and also increases the ANF concentration in cerebrospinal fluid. In order to determine whether brain ANF is involved in the compensatory response to hypervolemia or the regulation of cardiac secretion of ANF, we have studied the integrated hemodynamic, renal, and hormonal response to acute volume expansion (15 ml/kg Dextran over 30 min) in five sheep given nonimmune serum (control) and ANF antiserum by intracerebroventricular (icv) injections on separate days. Dextran loading caused similar decreases in hematocrit and increases in central venous and mean arterial pressures on both study days. Heart rate was higher after antiserum injections (P less than 0.05). Dextran loading increased plasma ANF on the control (20 pmol/liter maximal mean increment above baseline) but not on the antiserum day (P less than 0.01). The diuresis (P less than 0.01) and natriuresis (P less than 0.05) observed on the control day was inhibited by icv antiserum. Plasma aldosterone and cortisol levels showed similar falls in response to the dextran load on both days. These experiments show that icv ANF antiserum inhibits both the increase in cardiac secretion of ANF and the renal response to plasma volume expansion without affecting hemodynamic status. These data support the hypothesis that the brain ANF system is important in the systemic responses to volume loading.

Aldosterone↗

PubMed1991

Anti-PPD antibodies in Chinese Behçet's disease.

Anti-PPD antibody determinations were carried out by the ELISA method using extracted PPD of tubercle bacillus H37RV as the target antigen. The positive rates of anti-PPD antibodies in patients with active tuberculosis, inactive tuberculosis, Behçet's disease, or non-tubercular disease and in a village population were 97.5%, 77.4%, 48.9%, 33.6% and 13.9%, respectively. Although the average titer of anti-PPD antibodies in Behçet's disease was lower (2.168 +/- 0.854) than that in active tuberculosis (3.126 +/- 1.182), it was about the same as that in inactive tuberculosis (2.336 +/- 1.250). In comparison with the village community population surveyed, the average titer of anti-PPD antibodies in Behçet's disease patients was distinctly higher (P less than 0.001). These results indicate that tuberculosis may be etiologically related to Behçet's disease.

Antibodies, Bacterial↗

PubMed1991

[Bilateral changes of nociceptive sensitivity in rats with one paw inflamed].

Following a significant decrease in pain threshold (PT) in the carrageenin injected paw of rat, the PT of the contralateral uninjected paw was usually increased but might also be significantly decreased or unchanged. These three directions of PT change in the contralateral non-inflamed paws were found to be correlated with the magnitude of decrease in PT in the inflamed sides.

Animals↗

PubMed1990

Mapping of a cholinergic binding site by means of synthetic peptides, monoclonal antibodies, and alpha-bungarotoxin.

Previous studies by several laboratories have identified a narrow sequence region of the nicotinic acetylcholine receptor (AChR) alpha subunit, flanking the cysteinyl residues at positions 192 and 193, as containing major elements of, if not all, the binding site for cholinergic ligands. In the present study, we used a panel of synthetic peptides as representative structural elements of the AChR to investigate whether additional segments of the AChR sequences are able to bind alpha-bungarotoxin (alpha-BTX) and several alpha-BTX-competitive monoclonal antibodies (mAbs). The mAbs used (WF6, WF5, and W2) were raised against native Torpedo AChR, specifically recognize the alpha subunit, and bind to AChR is inhibited by all cholinergic ligands. WF6 competes with agonists, but not with low mol. wt. antagonists, for AChR binding. The synthetic peptides used in this study were approximately 20 residue long, overlapped each other by 4-6 residues, and corresponded to the complete sequence of Torpedo AChR alpha subunit. Also, overlapping peptides, corresponding to the sequence segments of each Torpedo AChR subunit homologous to alpha 166-203, were synthesized. alpha-BTX bound to a peptide containing the sequence alpha 181-200 and also, albeit to a lesser extent, to a peptide containing the sequence alpha 55-74. WF6 bound to alpha 181-200 and to a lesser extent to alpha 55-74 and alpha 134-153. The two other mAbs predominantly bound to alpha 55-74, and to a lesser extent to alpha 181-200. Peptides alpha 181-200 and alpha 55-74 both inhibited binding of 125I-alpha-BTX to native Torpedo AChR. None of the peptides corresponding to sequence segments from other subunits bound alpha-BTX or WF6, or interfered with their binding. Therefore, the cholinergic binding site is not a single narrow sequence region, but rather two or more discontinuous sequence segments within the N-terminal extracellular region of the AChR alpha subunit, folded together in the native structure of the receptor, contribute to form a cholinergic binding region. Such a structural arrangement is similar to the "discontinuous epitopes" observed by X-ray diffraction studies of antibody-antigen complexes [reviewed in Davies et al. (1988)].

Alkylation↗

PubMed1990

Measurement of neuropeptides in the brain and spinal cord of Wobbler mouse: a model for motoneuron disease.

The Wobbler mouse (wr) exhibits the loss of motoneurons especially in the cervical spinal cord, and thus has been studied as a model for human motoneuron diseases. Wobbler mice selected at various ages and stages during the disease process show increased levels of thyrotropin releasing hormone and substance P in spinal cord and brainstem (medulla). Enkephalins (methionine and leucine) also increase in the spinal cord and brainstem. Somatostatin increases in hypothalamus, perhaps accounting partly for the small size of this mutant mouse via its effect on growth hormone.

Aging↗

PubMed1990

Nonequivalence of alpha-bungarotoxin binding sites in the native nicotinic receptor molecule.

In the native, membrane-bound form of the nicotinic acetylcholine receptor (M-AcChR) the two sites for the cholinergic antagonist alpha-bungarotoxin (alpha-BGT) have different binding properties. One site has high affinity, and the M-AcChR/alpha-BGT complexes thus formed dissociate very slowly, similar to the complexes formed with detergent-solubilized AcChR (S-AcChR). The second site has much lower affinity (KD approximately 59 +/- 35 nM) and forms quickly reversible complexes. The nondenaturing detergent Triton X-100 is known to solubilize the AcChR in a form unable, upon binding of cholinergic ligands, to open the ion channel and to become desensitized. Solubilization of the AcChR in Triton X-100 affects the binding properties of this second site and converts it to a high-affinity, slowly reversible site. Prolonged incubation of M-AcChR at 4 degrees C converts the low-affinity site to a high-affinity site similar to those observed in the presence of Triton X-100. Although the two sites have similar properties when the AcChR is solubilized in Triton X-100, their nonequivalence can be demonstrated by the effect on alpha-BGT binding of concanavalin A, which strongly reduces the association rate of one site only. The Bmax of alpha-BGT to either Triton-solubilized AcChR or M-AcChR is not affected by the presence of concanavalin A. Occupancy of the high-affinity, slowly reversible site in M-AcChR inhibits the Triton X-100 induced conversion to irreversibility of the second site. At difference with alpha-BGT, the long alpha-neurotoxin from Naja naja siamensis venom (alpha-NTX) binds with high affinity and in a very slowly reversible fashion to two sites in the M-AcChR (Conti-Tronconi & Raftery, 1986). We confirm here that Triton-solubilized AcChR or M-AcChR binds in a very slowly reversible fashion the same amount of alpha-NTX.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Localization of sequence segments forming a kappa-bungarotoxin-binding site on the alpha 3 neuronal nicotinic receptor.

To identify the sequence segments of the alpha 3 subunit of the neuronal nicotinic acetylcholine receptor (N-nAChR) forming the binding site for the cholinergic antagonist kappa-bungarotoxin (kappa-BGT), overlapping peptides corresponding to the complete alpha 3 sequence were tested for their ability to bind 125I-labeled kappa-BGT. Two peptides located within the N-terminal extracellular domain specifically bound kappa-BGT in a solid phase assay, i.e. peptide N alpha(3)51-70 with a Kd approximately 300 nM and peptide N alpha(3)1-18 with slightly lower affinity (Kd approximately 500 nM). Preincubation of 125I-kappa-BGT with peptides N alpha(3)51-70 or N alpha(3)1-18 resulted in greater than 90% inhibition of kappa-125I-BGT binding to native N-nAChR expressed on the neuronal cell line PC12. Under the same conditions, two additional peptides, N alpha(3)180-199 and N alpha(3)183-201, were found to inhibit kappa-125I-BGT binding to PC12 by approximately 50%. These latter peptides represent sequences that are homologous to those shown previously to bind alpha-bungarotoxin. Peptide N alpha(3)51-70 (400 microM) also reduced by approximately 4-fold the observed rate of association of kappa-BGT to PC12 cells. The results of these experiments identify sequence segments of the alpha 3 subunit which are likely to interact with kappa-BGT and may indicate the relative contribution that these segments make in the formation of the high affinity kappa-BGT-binding site of this N-nAChR subtype.

Amino Acid Sequence↗

PubMed1990

Main immunogenic region of Torpedo electroplax and human muscle acetylcholine receptor: localization and microheterogeneity revealed by the use of synthetic peptides.

Most anti-nicotinic acetylcholine receptor (AChR) antibodies in myasthenia gravis are directed against an immunodominant epitope or epitopes [main immunogenic region (MIR)] on the AChR alpha-subunit. Thirty-two synthetic peptides, corresponding to the complete Torpedo alpha-subunit sequence and to a segment of human muscle alpha-subunit, were used to map the epitopes for 11 monoclonal antibodies (mAbs) directed against the Torpedo and/or the human MIR and for a panel of anti-AChR mAbs directed against epitopes on the alpha-subunit other than the MIR. A main constituent loop of the MIR was localized within residues alpha 67-76. Residues 70 and 75, which are different in the Torpedo and human alpha-subunits, seem to be crucial in determining the binding profile for several mAbs whose binding to the peptides correlated very well with their binding pattern to native Torpedo and human AChRs. This strongly supports the identification of the peptide loop alpha 67-76 as the actual location of the MIR on the intact AChR molecule. Residues 75 and 76 were necessary for binding of some mAbs and irrelevant for others, in agreement with earlier suggestions that the MIR comprises overlapping epitopes. Structural predictions for the sequence segment alpha 67-76 indicate that this segment has a relatively high segmental mobility and a very strong turning potential centered around residues 68-71. The most stable structure predicted for this segment, in both the Torpedo and human alpha-subunits, is a hairpin loop, whose apex is a type I beta-turn and whose arms are beta-strands. This loop is highly hydrophilic, and its apex is negatively charged. All these structural properties have been proposed as characteristic of antibody binding sites. We also localized the epitopes for mAbs against non-MIR regions. Among these, the epitope for a monoclonal antibody (mAb 13) that noncompetitively inhibits channel function was localized within residues alpha 331-351.

Animals↗

PubMed1990

Binding characteristics, regional distribution and diurnal variation of [125I]-iodomelatonin binding sites in the chicken brain.

The [125I]-iodomelatonin binding sites in chicken brain membrane preparations were studied. The binding of [125I]-iodomelatonin to the membrane preparations of chicken brain was rapid, stable, saturable, and reversible. The order of pharmacological affinities of [125I]-iodomelatonin binding sites in the chicken brain membrane preparations was: melatonin greater than 6-chloromelatonin greater than N-acetylserotonin greater than 5-hydroxytryptamine greater than tryptamine greater than 5-methoxytryptophol, much greater than 1-acetylindole-3-carboxaldehyde, 5-hydroxyindole-3-acetic acid, L-tryptophan, 5-hydroxytryptophan, 3-acetylindole. Compounds known to act on the receptor of norepinephrine or acetylcholine were inactive as compared to melatonin. Among the various brain regions studied, melatonin binding had maximal level in the hypothalamus, intermediate levels in the mid-brain, ponsmedulla, and telencephalon, and minimum level in the cerebellum. Subcellular fraction studies indicated that 40% of the binding was located in the mitochondrial fraction, 27% in the nuclear, 26% in the microsomal, and 6% in the cytosol fraction. Scatchard analysis of the membrane preparations revealed a dissociation constant (Kd) of 199.6 +/- 17 pM and a total number of binding sites (Bmax) of 16.6 +/- 0.75 fmol/mg protein at midlight. Thus, our results showed the presence of specific melatonin binding sites in the chicken brain membrane preparations. Saturation studies demonstrated that [125I]-iodomelatonin binding capacity in chicken brain membrane preparations were 40% greater at midlight (16.6 +/- 0.75 fmol/mg protein) than at middark (10.6 +/- 0.56 fmol/mg protein), with no significant variation in their binding affinities.

Animals↗