Presynaptic glutamate receptors facilitate release of norepinephrine and 5-hydroxytryptamine as well as dopamine in the normal and ischemic striatum

We investigated the effects of selective glutamate (Glu) agonists on the release of monoamine neurotransmitters and their implication in the enhanced monoamine release in cerebral ischemia. In the striatum of anesthetized Sprague-Dawley rats, in vivo microdialysis was performed and the release of excitatory amino acids (Glu and aspartate (Asp)) and monoamines (dopamine (DA), norepinephrine (NE) and 5-hydroxytryptamine (5-HT)) was measured by high-performance liquid chromatography with an electrochemical detector. (1) Forebrain ischemia by 4-vessel occlusion generated significant correlations between the Glu and Asp levels and the DA, NE and 5-HT levels (r = 0.922-0.967, P < 0.01, n = 6). (2) L-Glu and its selective agonists (N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and kainate (KA)) evoked a simultaneous release of striatal DA, NE and 5-HT in a dose-dependent manner (P < 0.01, ANOVA, n = 8). The maximal monoamine release evoked by the Glu agonists showed different magnitudes in the order of DA >> NE > 5-HT (118-, 16- and 9-fold from the baseline levels by 62.5 mM L-Glu, respectively). Each Glu agonist exerted a different magnitude of transmitter release and the order of agonist efficacy was different among NE, 5-HT and DA release: AMPA = KA > L-Glu = NMDA for DA release, AMPA > L-Glu = NMDA = KA for NE release, and L-Glu = NMDA = KA = AMPA for 5-HT release.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel in vivo assay system for consecutive measurement of brain nitric oxide production combined with the microdialysis technique

A novel spectrophotometric nitrite (NO2-)/nitrate (NO3-) assay system for a small quantity (5 microliter) of dialysate sample obtained by in vivo brain microdialysis was developed based on the diazotization reaction. The system has the advantage of in vivo consecutive measurement, high precision, good reproducibility, technical simplicity, relatively short resolution time (2.5-20 min), and wide availability. The NO3- level in the rat striatum was found to be 3 times higher than the NO2- level. A nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester, reduced striatal NO2-/citrulline formation in a dose-related manner and increased arginine, indicating that the tissue NO2- level detected by this assay system adequately reflects the striatal NO synthase activity.

Modification of striatal arginine and citrulline metabolism by nitric oxide synthase inhibitors

The effects of NG-substituted L-arginine (ARG) analogues on striatal ARG and citrulline (CIT) levels were investigated using in vivo microdialysis technique. A microdialysis probe was implanted into the striatum of anaesthesized Sprague-Dawley rats. Direct intrastriatal perfusion with 1 mM NG-nitro-L-arginine methyl ester (n = 8) increased striatal ARG release and decreased CIT release, suggesting suppressed NO synthase activity in the tissue. On the other hand, 1 mM NG-monomethyl-L-arginine (L-NMMA) (n = 6) evoked a persistent increase in both ARG and CIT. Considering that 4-320 microM L-ARG (n = 8) failed to increase CIT formation, CIT seems to be synthesized in the striatal tissue from L-NMMA by the enzyme that has been demonstrated in the kidney and aortic endothelium (NG,NG-dimethylarginine dimethyl-aminohydrolase).

[A case of interstitial pneumonia antedating rheumatoid arthritis--differentiation from idiopathic BOOP]

A 49-year-old female presented with productive cough, fever and chest pain, and was admitted to Nagoya University Hospital. Her chest X-rays, taken previously and on admission, showed infiltrative shadows in both upper lung fields and left-sided pleural effusion. Rheumatoid factors were positive in serum and the pleural effusion. Antibiotics were ineffective. Transbronchial lung biopsy revealed intraalveolar fibrosis as well as interstitial inflammation. Idiopathic BOOP was suspected on the basis of clinical findings together with the histological features. However, open lung biopsy revealed lymphoid hyperplasia with germinal center formation. The patient was diagnosed as having lung involvement antedating rheumatoid arthritis, despite the absence of joint symptoms at present.

Induction of macrophage growth by advanced glycation end products of the Maillard reaction

We previously showed that negatively-charged phospholipids, acetylated low density lipoprotein (LDL) and oxidized LDL, which are known to be taken up by macrophages via the scavenger receptor for modified LDLs, were able to induce the growth of peripheral macrophages in vitro. The present study demonstrated the macrophage growth-stimulating activity of the ligands for another macrophage receptor for advanced glycation end products (AGE) of the Maillard reaction. Experiments with murine macrophages showed that significant cell growth was induced by AGE-modified proteins such as bovine serum albumin (AGE-BSA) and AGE-human hemoglobin. The capacity of AGE-BSA to induce macrophage growth was completely blocked when cells were cultured with the mAb against granulocyte/macrophage CSF (GM-CSF). Moreover, PCR analysis revealed that AGE-BSA induced the expression of mRNA of GM-CSF. These data suggest that the macrophage AGE receptor may play an active role not only in phagocytic elimination of AGE-proteins but also induction of the growth of macrophages.

Induction of macrophage growth by advanced glycation end products of the Maillard reaction

We previously showed that negatively-charged phospholipids, acetylated low density lipoprotein (LDL) and oxidized LDL, which are known to be taken up by macrophages via the scavenger receptor for modified LDLs, were able to induce the growth of peripheral macrophages in vitro. The present study demonstrated the macrophage growth-stimulating activity of the ligands for another macrophage receptor for advanced glycation end products (AGE) of the Maillard reaction. Experiments with murine macrophages showed that significant cell growth was induced by AGE-modified proteins such as bovine serum albumin (AGE-BSA) and AGE-human hemoglobin. The capacity of AGE-BSA to induce macrophage growth was completely blocked when cells were cultured with the mAb against granulocyte/macrophage CSF (GM-CSF). Moreover, PCR analysis revealed that AGE-BSA induced the expression of mRNA of GM-CSF. These data suggest that the macrophage AGE receptor may play an active role not only in phagocytic elimination of AGE-proteins but also induction of the growth of macrophages.

Changes in Ca(++)-ATPase activity in smooth-muscle cell membranes of the canine basilar artery with experimental subarachnoid hemorrhage

Changes in Ca(++)-adenosine triphosphatase (ATPase) activity in the plasma membrane of smooth-muscle cells in the basilar arteries of dogs with experimental subarachnoid hemorrhage (SAH) were examined. The study methods included electron microscopic histochemistry and bioassay of the enzyme that exports cytoplasmic Ca++ to extracellular spaces. The Ca(++)-ATPase activity in the basilar artery increased significantly in response to the application of vasoconstrictive agents (prostaglandin F2 alpha and a phorbol ester), but decreased significantly 24 hours after experimental SAH, inversely with basilar artery contraction. Dogs that had undergone two arterial blood injections (double SAH) exhibited a further decrease in Ca(++)-ATPase activity as well as persistent contraction of the basilar artery for a longer period (at least 7 days) than was seen in animals with a single arterial blood injection. Bioassay of the enzyme also demonstrated a decrease in vascular Ca(++)-ATPase activity in dogs subjected to double SAH. These findings suggest that the early occurrence of and long-lasting decrease in Ca(++)-ATPase activity in dogs with experimental SAH induces a persistent disturbance of Ca++ homeostasis and indicates that damage to the plasma membrane in the cerebral arterial smooth-muscle cells proceeds to myonecrosis after SAH.

Advanced glycation end products of the Maillard reaction and their relation to aging

Long-term incubation of proteins with glucose leads to advanced glycation end products (AGE). Demonstration of AGE in vivo as well as determination of its main structure are crucial to elucidate its potential link to aging processes and diabetic complications. We prepared polyclonal and monoclonal anti-AGE antibodies and used them to identify and quantitate AGE in human lens proteins. Results suggest that there occurs a common AGE structure and provide the direct evidence for the presence of AGE in human lens crystallins and its age-related increase.

Prolonged effects of MK-801 in the cat during focal cerebral ischemia and recovery: survival, EEG activity and histopathology

Previously we reported an improvement in histological outcome in cats treated with MK-801 shortly after the induction of temporary middle cerebral artery occlusion, and examined after 2 h of ischemia followed by 4 h of reperfusion. This study investigates the prolonged effects of the same drug treatment. Focal cerebral ischemia was produced in 34 cats by temporary occlusion of the left middle cerebral artery for 2 h. Stroke severity was determined using the ratio of the EEG amplitude from the ipsilateral to that of the contralateral hemisphere. Thirty minutes after the onset of ischemia, cats were treated i.v. with either 1 mg/kg MK-801 or saline. Electrocortical activity of the animals who survived were followed for 6 days postocclusion at which point they were sacrificed for histopathological analysis. Twelve of the animals died during recovery, of which 4 were MK-801 treated, and 8 were saline controls. The EEG ratios in the non-surviving animals were more depressed than in the animals that survived, whereas the depression in the EEG amplitude in both the treated and the control surviving animals was equal. Among the survivors no reduction in infarct size with MK-801 treatment was observed. Thus treatment with MK-801 in the middle cerebral artery occlusion model in the cat leads to a significant increase in the rate of survival (P < 0.05), but no prolonged improvement in late histopathology, in contrast with acute histological findings using this model. MK-801 treatment may be shifting the stroke model towards the survival of animals with larger infarcts. Histological recovery during prolonged reperfusion may eliminate the early neuroprotective effects seen with MK-801 treatment.

Correlation between 99mTc-bicisate and regional CBF measured with iodo-[14C]antipyrine in a primate focal ischemia model

The need for an agent to quantitatively measure regional cerebral blood flow in humans using single photon emission computed tomography has led to the development of a new 99mTc-labeled agent: bicisate (ethyl cysteinate dimer). We have utilized an acute stroke model in the baboon to examine the ability of this agent to quantitatively measure regional cerebral blood flow in ischemic tissue. One hour after occlusion of either the left anterior cerebral or the middle cerebral artery, 99mTc-bicisate was administered intravenously, followed 20 min later by the measurement of local cerebral blood flow using iodo-[14C]antipyrine. With use of double-label autoradiography, the distribution of 99mTc-bicisate was correlated with the local cerebral blood flow images. A cerebral blood flow parameter was calculated from the 99mTc-bicisate tissue distribution and the arterial blood tracer concentration using an indicator fractionation model. For cerebral blood flows above approximately 40-50 ml 100 g-1 min-1, 99mTc-bicisate underestimates cerebral blood flow by as much as 20%, while for blood flows below approximately 15 ml 100 g-1 min-1, blood flow is overestimated by the 99mTc-bicisate distribution by an average of 3-4 ml 100 g-1 min-1. This apparent hyperfixation at very low blood flows may be related to a higher extraction of this tracer by ischemic tissue.

The shape and distribution of lysosomes and endocytosis in the ciliary epithelial cells of rats

The shape and distribution of lysosomes in the ciliary epithelium of rat eyes were examined by electron microscopy combined with acid phosphatase (ACPase) cytochemistry and three-dimensional observation of 2 microns-thick sections. ACPase activity was cytochemically localized in lysosomes and trans Golgi cisternae in the non-pigmented epithelial (NPE) and pigmented epithelial (PE) cells. In NPE cells, it was shown three-dimensionally, that most lysosomes had an elongate form, up to 5 microns in length, and a diameter of 70-100 nm. These elongate lysosomes (nematolysosomes) were predominantly located in the basal region of the cells. In contrast, PE cells had spherical lysosomes distributed at random throughout the cytoplasm. However, no nematolysosomes were seen in the PE cells. When the isolated ciliary processes were incubated in a medium containing horseradish peroxidase (HRP), HRP was incorporated into the nematolysosome-like structures by pinocytosis from the basal surface of the NPE cells. These findings suggest that nematolysosomes are associated with the pinocytotic activity of NPE cells. The pinocytosis-nematolysosomal route may be involved in the uptake and degradation of macromolecules from the aqueous humor in the posterior chamber.

beta 2-Microglobulin modified with advanced glycation end products is a major component of hemodialysis-associated amyloidosis

beta 2-Microglobulin (beta 2M) is a major constituent of amyloid fibrils in hemodialysis-associated amyloidosis, a complication of long-term hemodialysis patients. Amyloid fibril proteins were isolated from connective tissues forming carpal tunnels in hemodialysis patients with carpal tunnel syndrome. Two-dimensional polyacrylamide gel electrophoresis and Western blotting demonstrated that most of the beta 2M forming amyloid fibrils exhibited a more acidic pI value than normal beta 2M. This acidic beta 2M was also found in a small fraction of beta 2M in sera and urine from these patients, whereas heterogeneity was not observed in healthy individuals. We purified acidic and normal beta 2M from the urine of long-term hemodialysis patients and compared their physicochemical and immunochemical properties. Acidic beta 2M, but not normal beta 2M, was brown in color and fluoresced, both of which are characteristics of advanced glycation end products (AGEs) of the Maillard reaction. Immunochemical studies showed that acidic beta 2M reacted with anti-AGE antibody and also with an antibody against an Amadori product, an early product of the Maillard reaction, but normal beta 2M did not react with either antibody. Incubating normal beta 2M with glucose in vitro resulted in a shift to a more acidic pI, generation of fluorescence, and immunoreactivity to the anti-AGE antibody. The beta 2M forming amyloid fibrils also reacted with anti-AGE antibody. These data provided evidence that AGE-modified beta 2M is a dominant constituent of the amyloid deposits in hemodialysis-associated amyloidosis.

[A case of drug induced pneumonitis caused by oral etoposide]

We report a case of drug induced pneumonitis caused by oral etoposide. A 63-year-old man was admitted to our hospital in August 1991 because of low grade fever and dyspnea. He underwent right upper lobectomy on Nov. 27th, 1990 for lung cancer (squamous cell carcinoma), and courses of adjuvant chemotherapy (CBDCA, IFX, etoposide) during the following admission period. He was discharged on Feb. 14th, 1991, and as an outpatient, oral etoposide (25 mg/day) was administered for about 7 months (6,125 mg in total). Chest X-ray film on admission showed reticulonodular shadows in bilateral lung fields, and computed tomography showed diffuse interstitial shadows. Blood gas analysis showed marked hypoxemia (PaO2 breathing room air was 48.4 Torr). Transbronchial lung biopsy revealed edema of the alveolar walls and marked proliferation of type II alveolar epithelial cells, suggesting cytotoxic reaction. After termination of etoposide administration and following steroid pulse therapy, both clinical symptoms and hypoxemia were ameliorated. To our knowledge, this is the first report of etoposide-induced pneumonitis.

Angiogenic effects of advanced glycation end products of the Maillard reaction on cultured human umbilical cord vein endothelial cells

The effects of advanced glycation end products (AGE) of the Maillard reaction on proliferation, migration and angiogenesis of cultured human umbilical vein endothelial cells (HUVEC) were studied. In an in vitro angiogenesis system, tube formation of HUVEC was dose-dependently stimulated by AGE at 0.5-50 micrograms/ml. Migration of HUVEC was also stimulated by AGE in a similar concentration range, and checkerboard analysis revealed that AGE were chemotactic but not chemokinetic. Proliferation of HUVEC was not affected by AGE. These data provide evidence that AGE are angiogenic.

Relaxant effects of brain natriuretic peptide on guinea-pig tracheal smooth muscle

1. The relaxant effects of brain natriuretic peptide (BNP) were investigated on guinea-pig tracheal smooth muscle. 2. Various amounts of BNP (10(-9)-10(-6) mol/L) showed concentration-dependent relaxant effects on resting tone, leukotriene D4 (LTD4; 10(-8) mol/L) and endothelin-1 (ET-1; 10(-8) mol/L) induced contraction of tracheal smooth muscle with EC50 values of 3.1 +/- 0.7 x 10(-8), 3.9 +/- 1.0 x 10(-8) and 3.5 +/- 1.0 x 10(-8) mol/L, respectively. 3. BNP increased tissue cyclic GMP levels in tracheal smooth muscle concentration dependently (187 +/- 26 fmol/mg protein in control, 334 +/- 77 fmol/mg protein at 10(-8) mol/L, 680 +/- 54 fmol/mg protein at 10(-7) mol/L, 2162 +/- 133 fmol/mg protein at 10(-6) mol/L). 4. With the addition of BNP, tissue cyclic GMP levels reached a maximum at 1-3 min. The relaxation of tracheal smooth muscle began at 1 min and reached a maximum level at 5 min after the superfusion of BNP (10(-6) mol/L). The elevation of cyclic GMP preceded the relaxation of tracheal smooth muscle. 5. These results suggest that BNP may have a potent relaxant effect on tracheal smooth muscle and this effect may be mediated by cyclic GMP level.

Inguinal lymphadenopathy due to metal release from a prosthesis. A case report

We report the case of a 19-year-old man with inguinal lymphadenopathy caused by metallic debris from the loosening of a prosthesis inserted after tumour resection. Large amounts of wear debris may be released from such massive replacements, and surgeons should be aware of the range of possible adverse effects.

Rapid and sensitive method of quantitation of bone gla protein mRNA using competitive polymerase chain reaction

A method for sensitive quantitation of bone gla protein (BGP, osteocalcin) mRNA has been developed using competitive polymerase chain reaction after reverse transcription (competitive RT-PCR). The complementary DNA (cDNA) were transcribed from sample RNA was co-amplified in a PCR with a known amount of mutant BGP cDNA (competitor) using the identical oligonucleotide primers. The mutant cDNA with its unique restriction site allowed quantitation of sample and mutant PCR products after densitometric analysis of ethidium bromide-stained agarose gels. A linear relationship between initial sample BGP amount and the ratio of BGP to mutant BGP band intensity was obtained and used to make a standard curve to determine the initial BGP mRNA of unknown samples. These standard curves were made with known amounts of recombinant BGP cDNA. The competitive RT-PCR for BGP allows measurement of twofold differences in 1 and 2 micrograms total RNA and requires at least 10 times less sample RNA than usual Northern blotting. Moreover, heteroduplexes with one BGP strand and one mutant BGP strand formed as a result of high PCR cycles were quantifiable. This provided the advantages of rapid quantitation from ethidium bromide-stained gels without blotting, hybridization, or autoradiography. Multiple samples could be assayed for greater confidence in the results. The sensitivity, accuracy, and ease of the assay will facilitate analysis of BGP mRNA from a small amount of sample. The assay has been used to confirm the BGP mRNA changes with hormonal treatment in cultured cells and the age-related changes in whole tibia in vivo.

Nematolysosomes (elongate lysosomes) in rat hepatocytes: their distribution, microtubule dependence, and role in endocytic transport pathway

The distribution of lysosomes in rat hepatocytes was examined by three-dimensional electron microscopy combined with acid phosphatase (ACPase) cytochemistry. In the 2-microns-thick sections observed under 200- or 1000-kV TEM, it was apparent that ACPase activity localized on elongate lysosomes (we refer to them as nematolysosomes) with a diameter of 70-100 nm and lengths of several micrometers, as well as spherical lysosomes and trans-Golgi cisternae. Though most spherical lysosomes were located within the pericanalicular region, nematolysosomes were widely distributed throughout the hepatocytes. Typically, it appeared that the nematolysosomes elongated from the subsinusoidal region to the pericanalicular-Golgi complex area and they frequently formed a network at the cell periphery along the sinusoidal front. Furthermore, the formation of nematolysosomes was independent of new protein synthesis, but highly dependent on the integrity of microtubules. After a 6-8 h colchicine treatment, nematolysosomes were shrunk and/or fragmented, becoming roughly spherical lysosomes scattered throughout the cells. Nematolysosomes recovered their normal profiles after 24 h due to the reversible effect of the drug on microtubules. When the hepatocytes were exposed to horseradish peroxidase (HRP) in vitro or in vivo, HRP was quickly sequestered in nematolysosome-like structures via pinocytosis from the sinusoidal surface and transported to an area near the Golgi complex. These findings raise the possibility that the nematolysosomes engage in microtubule-dependent transport of macromolecules from the sinusoidal circulation to the Golgi complex area.

An improved technique for observing both membranous organelles and cytoskeleton in saponin-extracted cells

Detergent-extraction of soluble cytoplasmic proteins under low osmotic pressure induces severe morphological damage, particularly on membranous organelles, although this processing is often required to observe cytoskeletal elements in the cells. In the present study, the osmotic adjustment of the rinsing solution and fixative, which were used after the detergent-extraction using saponin, has greatly improved the ultrastructure of membranous organelles. This improved method allowed us to observe both cytoskeletal elements and the fine structure of membranous organelles by electron microscopy.

Experimental implant-related osteomyelitis treated by antibiotic-calcium hydroxyapatite ceramic composites

The efficacy of locally implanted antibiotic-calcium hydroxyapatite ceramic composites was investigated for the treatment of experimentally produced, implant-related osteomyelitis in rats. High concentrations of antibiotics were detected at the site of infection and bacteria were eradicated without removal of the metal implants. Parenteral antibiotics and surgical debridement, alone or in combination with antibiotic-impregnated acrylic bone cement, all failed to eradicate the infections.

Relaxant effect of C-type natriuretic peptide on guinea-pig tracheal smooth muscle

The relaxant effects of the C-type natriuretic peptide (CNP) on guinea-pig tracheal smooth muscle were investigated. CNP (10(-8)-10(-5) mol/l) induced dose-dependent relaxant effects on the resting tone of tracheal smooth muscle with EC50 of 3.6 +/- 0.8 x 10(-6) mol/l (mean +/- SE). CNP caused a dose dependent increase in the tissue cyclic GMP level in tracheal smooth muscle (191 +/- 10 fmol/mg protein in control, 583 +/- 33 fmol/mg protein at 10(-7) mol/l, 688 +/- 56 fmol/mg protein at 10(-6) mol/l, 1091 +/- 167 fmol/mg protein at 10(-5) mol/l). Tissue cyclic GMP levels showed a peak at 1 min. Relaxation of the tracheal smooth muscle began at 1 min, reaching peak value at 5 min after the perfusion of CNP (10(-5) mol/l). Elevations in cyclic GMP preceded the relaxation of tracheal smooth muscle. These results suggest that CNP may be a novel potent relaxant in tracheal smooth muscle and that its relaxant effect may be mediated by cyclic GMP levels.

Calcium hydroxyapatite ceramic used as a delivery system for antibiotics

Porous blocks of calcium hydroxyapatite ceramic were evaluated as delivery systems for the sustained release of antibiotics. We tested gentamicin sulphate, cefoperazone sodium, and flomoxef sodium in powder form placed in a cylindrical cavity in calcium hydroxyapatite blocks, using in vitro studies of elution and in vivo studies in rats. Gentamicin sulphate gave a maximum concentration within the first week, which gradually decreased but was still effective at 12 weeks, when 70% of the antibiotic had been released. Even at this stage the antibiotic concentration from a 75 mg dose was five times the minimum inhibitory concentration for staphylococci. In the in vivo studies the release of gentamicin sulphate into the normal bone of rats was at similar rates and levels. The bacteriocidal activity of the drugs was not affected by packing into calcium hydroxyapatite ceramic and the blocks were completely biocompatible on histology. This new system overcomes the disadvantages of other drug delivery systems, avoiding thermal damage to the antibiotics and a second operation for the removal of the carrier. Some mechanical strength is provided by the ceramic and healing may be accelerated by bone ingrowth into its micropores.

Discovery of bone gamma-carboxyglutamic acid protein in mineralized scales. The abundance and structure of Lepomis macrochirus bone gamma-carboxyglutamic acid protein

The mineralized scale of the freshwater sunfish Lepomis macrochirus (bluegill) contains a Gla protein. The protein was identified in extracts of scale by a new colorimetric assay for Gla-containing proteins. The protein was purified by gel filtration chromatography followed by reversed phase high performance liquid chromatography (HPLC). Several tests establish the identity of scale Gla protein and bone Gla protein (BGP). First, the proteins exhibit identical mobilities on electrophoresis and by reversed phase HPLC. Second, they have identical amino-terminal amino acid sequences. Finally, identical peptides are generated by proteolytic digestion. The 45-residue amino acid sequence of the bone Gla protein from L. macrochirus has a high sequence homology with swordfish, as well as homology to mammalian bone Gla protein. The BGP of bluegill shares with swordfish BGP a truncated NH2 terminus and an extended COOH terminus. These features may be unique to fish, as they have not been observed in terrestrial vertebrates. The bluegill BGP is the first vitamin K-dependent protein to contain a non-gamma-carboxylated residue to the NH2-terminal side of all of its Gla residues. In all other vitamin K-dependent proteins, Gla always appears to the NH2-terminal side of the first Glu. The implications of this result are discussed. The bluegill rib bone is curiously enriched in BGP, as are other mineralized tissues of this species. One hypothesis is that this may be due to the acellular nature of the bone in this species. The abundance of BGP in the bones of this fish may provide clues to the unknown function of this bone protein.