Studies on gastric mucosal cell injury induced by Helicobacter pylori

The cause of gastric cell injury induced by Helicobacter pylori was investigated in vitro using gastric mucosal cells derived from male Japanese white rabbits. To evaluate the contribution of the potent urease activity of H. pylori to gastric mucosal cell injury, the supernatant of the H. pylori bacterial pellet, solubilized with N-octyl-glucoside, was added to the gastric mucosal cell suspension. Cell injury was assessed by lactate dehydrogenase (LDH) release into the extracellular fluid. Treatment of cells with H. pylori extracts together with urea resulted in high levels of LDH release, suggesting definite gastric mucosal cell injury, and elevation of ammonia concentration was also observed. In contrast, incubation with H. pylori extracts alone or urea solution alone did not result in increased LDH release or elevated ammonia concentrations. The degree of LDH release from gastric mucosal cells due to H. pylori extracts in the presence of urea was similar to that induced by administration of the same amount of exogenous ammonia. The addition of acetohydroxamic acid, a potent specific urease inhibitor, remarkably inhibited ammonia production, the elevation of pH of extracellular fluid, and LDH release in a dose-dependent manner. These results suggest that ammonia produced by potent urease activity of H. pylori in the presence of urea plays an important role in the pathogenesis of gastric mucosal cell injury.

Role of O-linked carbohydrate of human urinary trypsin inhibitor on its lysosomal membrane-stabilizing property

Human urinary trypsin inhibitor (UTI) was digested with various enzymes to obtain O-glycoside linked N-terminal glycopeptide (UTIm1), N-glycoside linked C-terminal tandem Kunitz-domains (domain I and II, UTIm2), UTI lacking O-glycoside (UTIc), asialo UTI (UTIa) and UTI lacking N-glycoside (UTIn). We investigated the membrane stabilizing effect of these UTI derivatives on rat renal lysosome by measurement of lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAG) release after hypotonic treatment. Intact UTI suppressed NAG release, but aprotinin, gabexate mesilate (FOY), nafamostat mesilate (FUT) and recombinant domain II of UTI (R-020) had no effect, indicating that inhibition of serine proteases was not involved and the carbohydrate moiety of UTI might be necessary for this property. Among UTI derivatives, UTIm1, UTIm2, UTIm1+ UTIm2, and UTIc had no effect. In contrast, UTIa or UTIn suppressed NAG release. From these results, we conclude that O-glycoside linked core protein without N-glycoside is essential to the lysosomal membrane-stabilizing property of UTI.

Review article: Long-term Helicobacter pylori infection--from gastritis to gastric cancer

An analysis carried out in 1994 by the WHO International Agency for Research on Cancer (IARC) resulted in Helicobacter pylori being designated as a Group 1 carcinogen and thus clearly having an association with the development of gastric cancer. In the case of H. pylori, the evaluation was made solely on the basis of epidemiological results. In Japan, in 1993, only 235,000 of the 60 million people with H. pylori had gastric cancer. This represents only 0.4% of the infected population. Each individual reacts in a unique way to H. pylori infection in terms of the inflammatory response. The probability of developing cancer will be determined by environmental factors such as diet, duration of or age at acquisition of H. pylori infection, the virulence of H. pylori strains, and host factors including genetic make-up.

Effects of i.v. anaesthetic agents and halothane on [3H]tetracaine binding to rat cerebrocortical membranes

In an attempt to determine if there is any overlap in local and general anaesthetic binding sites, we have examined the effects of thiopental, phenobarbital, pentobarbital, propofol, ketamine (racemic and R(+)/S(-)), alfaxalone, etomidate and halothane on [3H]tetracaine binding to rat cerebrocortical membranes. Membranes were prepared in Tris HCI 50 mmol litre-1, pH 7.4, by homogenization and centrifugation. Binding assays were performed in 1-ml volumes of Tris HCI buffer at room temperature or 37 degrees C for halothane. Binding of [3H]tetracaine was displaced dose-dependently by unlabelled tetracaine with a mean pIC50 value of 6.91 (SEM 0.07) (123 nmol litre-1). With the exception of propofol (at high concentrations), all i.v. anaesthetic agents failed to displace the binding of [3H]tetracaine. In contrast, halothane produced a dose-dependent and statistically significant reduction in total [3H]tetracaine binding at clinically achievable concentrations (0.289, 0.885 and 1.484 mmol litre-1 equivalent to 1.0, 3.1 and 5.1 rat MAC) without markedly affecting the pIC50. Collectively these data may suggest some overlap in the binding sites for [3H]tetracaine and volatile but not i.v. general anaesthetic agents.

Auditory projections from the IC to the SCN by way of the LG in the mole, Mogera

To study morphological substrates for sensory specialization in subterranean mammals, we investigated both auditory and visual pathways in the mole. The inferior colliculus (IC), an auditory relay, projects not only to the medial geniculate, the major gateway to the auditory cortex, but also to the lateral geniculate (LG), the major gateway to visual cortex. Further evidence is that the LG does not send many fibers to the cortex in the mole. Instead, the auditory inputs to the LG are likely to be conveyed to the suprachiasmatic hypothalamic nucleus (SCN), which plays a role in photoperiodic functions in common mammals. Auditory inputs to the SCN may subserve periodic reproductive behaviors in the exclusively separated territorial domains of subterranean mammals.

Co-expression of defective luteinizing hormone receptor fragments partially reconstitutes ligand-induced signal generation

Gonadotropin receptors are unique members of the seven-transmembrane (TM), G protein-coupled receptor family with a large extracellular (EC) sequence forming the high-affinity ligand binding domain. In a patient with Leydig cell hypoplasia, we identified a mutant LH receptor that is truncated at TM5. This protein retains limited ligand binding ability but cannot mediate cAMP responses. To study interactions between receptor fragments defective in either ligand binding or signal transduction, we co-expressed this truncated receptor together with a chimeric receptor containing the EC region of the FSH receptor and the TM region of the LH receptor. Although the chimeric receptor could not respond to human chorionic gonadotropin in producing cAMP, co-expression with the truncated LH receptor allowed partial restoration of ligand signaling through intermolecular interactions. In addition, co-expression of the same truncated LH receptor with an N-terminally truncated LH receptor that lacked the EC ligand binding domain also partially restored ligand signaling. Further shortening of the TM region in the mutant receptor found in the patient indicated that the EC domain and TM1 were sufficient for interactions with the N terminally truncated receptor. In contrast, co-expression of the N terminally truncated receptor together with cell-associated or soluble EC region of the LH receptor did not allow ligand signaling. Unlike thrombin receptors, co-expression of the anchored EC region of the LH receptor together with the N-terminally truncated receptor did not allow ligand signaling despite moderate levels of human chorionic gonadotropin binding in transfected cells. These studies demonstrate that the co-expression of binding (+)/signaling (-) and binding (-)/signaling (+) receptor fragments partially restores ligand-induced signal generation and indicate the importance of TM1 of the LH receptor in the proper orientation of the EC ligand binding domain.

Development of the tecto-thalamic projection neurons and the differential expressions of calcium-binding proteins in the rat

We studied expression of calbindin-D 28 K and parvalbumin in tecto-thalamic projection neurons and during the formation of their tecto thalamic projections using a double-labeling with Fluoro-Gold. To discern the completion of these projections, Fluoro Gold, an opalescent fluorescent dye, was injected into the dorsal lateral geniculate and/or the lateral posterior nucleus in rats of various ages from neonates to adults. After one day's survival, the brains were removed and sections of the brain were immunohistochemically processed using Cy3, a red fluorescent dye, as a marker for calbindin-D 28 K or parvalbumin. The three types of tecto thalamic neurons, which have been described previously in the adult rats, were identified in the present study. The results revealed that in developing rats: 1) A population of medium-sized neurons (the presumed pyriform cells) express calbindin-D 28 K as early as the day of birth prior to the formation of their tecto thalamic projection that occured on postnatal day 4. Most (over 90%) of them project to the dorsal lateral geniculate nucleus; 2) A population of large neurons (the presumed wide-field vertical cells) express calbindin-D 28 K on postnatal day 7, and most of them (over 90%) project to the lateral posterior nucleus; 3) Another population of medium-sized neurons (the presumed narrow-field cells) express parvalbumin on post-natal day 17, but only a half (45%) of them project to the dorsal lateral geniculate nucleus. In the developing nervous system, calcium ions play important roles in the biological and molecular events underlying neural development. Changes in the free intracellular calcium ion level, indicating neuronal activity has been reported to be correlated with onset of calbindin-D 28 K or parvalbumin-immunoreactivity that participate in the regulation of intracellular calcium homeostasis in neurons. Therefore, the present findings may reflect distinct developmental events in the different classes of tectal relay neurons that form parallel visual pathways, but which have such different functions as the detection of luminance, discrimination of direction, and the detection of fast movements.

Studies on the binding of [3H]amethocaine to rat cerebrocortical membranes

We have examined the binding of the local anaesthetic agent [3H]amethocaine to rat cerebrocortical membranes. All studies were performed in Tris buffer 50 mmol litre-1 at pH 7.4. Bound and free radioligand were separated by rapid vacuum filtration. [3H]Amethocaine binding at room temperature was dose-dependent and saturable, with mean Kd and Bmax values of 153 (SEM 18) nmol litre-1 and 9.4 (1.6) pmol/mg protein, respectively. [3H]Amethocaine binding was displaced in a dose-dependent manner (pIC50) by unlabelled amethocaine (6.89), procaine (5.20), lignocaine (3.46) and prilocaine (2.81). Ropivacaine and bupivacaine did not produce 50% displacement at the highest concentrations used (10(-4) and 10(-3) mol litre-1, respectively). We examined the nature of the binding site further with a range of ion channel antagonists (nifedipine, verapamil, diltiazem, omega-conotoxin, tetrodotoxin, tetraethylammonium and 4-aminopyridine) and ion channel coupled receptor ligands (L-glutamate, MK801, GABA, glycine and nicotine). With the exception of tetraethylammonium (pIC50 3.07) and 4-aminopyridine (pIC50 3.68), all non-anaesthetic agents failed to displace [3H]amethocaine. Collectively our data suggest that it is unlikely that there is a single target site for all local anaesthetic agents.

Derivation of functional antagonists using N-terminal extracellular domain of gonadotropin and thyrotropin receptors

Receptors for the glycoprotein hormones, LH/CG, FSH, and TSH, are a unique subclass of the seven-transmembrane, G protein-coupled proteins with a large N-terminal extracellular (ecto-) domain. Although ecto-domains of gonadotropin receptors confer ligand binding, expression of soluble binding proteins has been difficult. We fused the ecto-domains of LH or FSH receptors to the single-transmembrane domain of CD8 and found that hybrid proteins anchored on the cell surface retained high-affinity ligand binding. Inclusion of a junctional thrombin cleavage site in the hybrids allowed generation of soluble receptor fragments that interfered with gonadotropin binding to their receptors and blocked cAMP production stimulated by gonadotropins. Cross-linking analyses confirmed the formation of high molecular weight complexes between receptor ecto-domains and their specific ligands. A similar approach also generated a soluble TSH receptor fragment capable of blocking TSH-induced signal transduction. When administered to rats, the soluble FSH receptor fragment retarded testis growth and induced testis cell apoptosis. These findings demonstrate the feasibility of generating ligand-binding regions of glycoprotein hormone receptors to selectively neutralize actions of gonadotropins and TSH, thus allowing future design of novel contraceptives and management of different gonadal and thyroid dysfunction. The present study represents the first successful derivation of soluble, ligand-binding domains from glycoprotein hormone receptors as functional antagonists. Similar approaches could allow generation of ecto-domains of related receptors to neutralize actions of ligands or receptor antibodies and to facilitate structural-functional analysis.

Cystine knot of the gonadotropin alpha subunit is critical for intracellular behavior but not for in vitro biological activity

The common alpha subunit of glycoprotein hormones contains five disulfide bonds. Based on the published crystal structure, the assignments are 7-31, 59-87, 10-60, 28-82, and 32-84; the last three comprise the cystine knot, a structure also seen in a variety of growth factors. Previously, we demonstrated that the efficiency of secretion and the ability to form heterodimers by alpha subunits bearing single cysteine residue mutants in the cystine knot were significantly reduced. These results suggested that the cystine knot is critical for the intracellular integrity of the subunit. To assess if the presence of the free thiol affected the secretion kinetics, we constructed paired cysteine mutants of each disulfide bond of the alpha subunit. The secretion rate for these monomers was comparable with wild type except for the alpha-10-60 mutant, which was 40% lower. The recovery of the alpha7-31 and alpha59-87 mutants was greater than 95%, whereas for the cystine knot mutants, it was 20-40%. Co-expression of the wild-type chorionic gonadotropin beta subunit with double cysteine mutants did not enhance the recovery of alpha mutants in the media. Moreover, compared with wild-type, the efficiency of heterodimer formation of the alpha10-60 or alpha32-84 mutants was less than 5%. Because subunit assembly is required for biological activity, studies on the role of these disulfide bonds in signal transduction were not possible. To bypass the assembly step, we exploited the single chain model, where the alpha and beta subunits are genetically fused. The recovery of secreted tethered gonadotropins bearing mutations in the cystine knot was increased significantly. Although dimer-specific monoclonal antibodies discriminated the conformation of single chain alpha10-60 and alpha32-84 mutants from the native heterodimer, these mutants were nevertheless biologically active. Thus, individual bonds of cystine knot are important for secretion and heterodimer formation but not for in vitro bioactivity. Moreover, the data suggest that the native heterodimer configuration is not a prerequisite for receptor binding or signal transduction.

Preparation and characteristics of standard reference samples of fibrous minerals for biological experiments

Standard reference samples of fibrous minerals to be used for in vitro and in vivo (injection) biological experiments were prepared. Ten samples were selected from among the fibrous minerals currently used in industry: man-made mineral fibers (MMMF); glass wool (GW1), rock wool (RW1), micro glass fiber (MG1), refractory ceramic fibers (RF1, RF2), and mullite fibers (RF3), whiskers; potassium titanate (PT1), silicon carbide (SC1) and rutile (TlO2)(TO1), and a natural fibrous mineral; wollastonite (WO1). The MMMF samples were prepared by using the size-selective press method. The whisker samples and WO1 were all commercial products. The prepared samples were examined by X-ray diffraction and X-ray fluorescence analyses, and no impurities were identified in any of the samples at a level of 1%, although WO1 was found to have about 5% calcite and a trace amount of quartz (< 1%). The fiber sizes were measured by TEM. The geometric-mean length (micron), width (micron) and SD (in parenthesis) are: GW1 20.0 (2.58), 0.88 (3.10); RW1 16.5 (2.51), 1.80 (2.32); MG1 3.0 (2.22), 0.24 (2.35); RF1 12.0 (2.36), 0.77 (2.53); RF2 11.0 (1.96), 1.10 (2.00); RF3 11.0 (1.75), 2.40 (1.37); PT1 6.0 (2.04), 0.35 (1.51); SC1 6.40 (2.45), 0.30 (1.58); TO1 2.1 (2.00), 0.14 (1.53); WO1 10.5 (2.03), 1.00 (1.72). We concluded that these prepared fiber samples can be safely used for biological experiments. Sample sets containing about one gram of each sample known as JFM standard reference samples are provided by the Japan Fibrous Material Research Association (JFMRA).

[An autopsy case of multiple myeloma with pineal body and spinal cord dura mater infiltration]

An autopsy case of multiple myeloma (IgD lambda type) with pineal body and spinal cord dura mater infiltration is reported. The 63-year-old man was diagnosed as multiple myeloma (IgD lambda type). He was treated with melphalan and prednisolone. Extra bone marrow masses developed 1 year after the onset. He died with renal failure. At autopsy there were many extra bone marrow masses including pineal body and dura mater of the thoracic cord. Microscopic examination revealed that those mass lesions consisted of neoplastic plasma cells. Myeloma cells also infiltrated perivascular space near the pineal body, subdural space of the cerebrum and brain stem. The cells were labeled VS 38 c immunohistochemically. We discussed routes of the metastasis to the central nervous system of the multiple myeloma. This case suggests that the way of myeloma cells infiltration to the pineal body is hematogenous metastasis, because pineal body have no blood brain barrier.

Percutaneous transluminal coronary angioplasty for morphologic left anterior descending artery lesion in a patient with dextrocardia. A case report and literature review

A case report of percutaneous transluminal coronary angioplasty (PTCA) to treat coronary atherosclerotic lesions in a patient with dextrocardia associated with situs inversus totalis is presented. The patient was a sixty-two-year-old man who was admitted with a diagnosis of congestive heart failure. Cardiac catheterization was performed. Left ventriculography showed mild hypokinesis in segments 2 and 3 with ejection fraction of 63%. Coronary arteriography revealed 74% stenosis in segment 7 of the left anterior descending (LAD) artery. PTCA for this lesion was performed. Successful dilation was achieved with the residual stenosis in the LAD reduced from 74% to 34%. Performance of PTCA in patients with dextrocardia is extremely rare, and only 8 cases have been reported to date. However, by visualizing the procedure as a mirror image and choosing a guide catheter that permits good engagement, it appears possible to perform it like ordinary PTCA.

Three-dimensional topographic analysis of spinal accessory motoneurons under chronic mechanical compression: an experimental study in the mouse

We investigated the effect of chronic mechanical compression of the cervical spinal cord on the number of spinal accessory motoneurons in 25 tiptoe-walking Yoshimura mice. The animals had calcified deposits in the atlantoaxial membrane at the C1-C2 vertebral level, compressing the spinal cord posterolaterally. Motoneurons of the spinal accessory nerve between C1 and C5 segments were labelled using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injected into the sternocleidomastoid muscles. The counted cells were processed into a three-dimensional computer display to analyse the cytoarchitectonic changes caused by external cord compression. The number of WGA-HRP-labelled spinal accessory motoneurons was significantly reduced on the affected side. The number of motoneurons in compromised C2 and C3 cord segments correlated linearly with the extent of mechanical compression, but no such relationship was present on the contralateral side. There was an increase in the number of WGA-HRP-labelled spinal accessory motoneurons in the medial cell pools of the anterior grey horn at a level most rostral to the compression, and in the ventrolateral cell pools at levels immediately rostral to the compression. Our findings suggest that the spinal accessory motoneurons translocate rostral to the area of external compression in order to avoid mechanical injury.

The biologic action of single-chain choriogonadotropin is not dependent on the individual disulfide bonds of the beta subunit

Disrupting disulfide loops in the human chorionic gonadotropin beta subunit (CGbeta) inhibits combination with the alpha subunit. Because the bioactivity requires a heterodimer, studies on the role of disulfide bonds on receptor binding/signal transduction have previously been precluded. To address this problem, we bypassed the assembly step and genetically fused CGbeta subunits bearing paired cysteine mutations to a wild-type alpha (WTalpha) subunit. The changes altered secretion of the single-chain mutants which parallel that seen for the CGbeta monomeric subunit. Despite conformational changes in CG disulfide bond mutants (assayed by gel electrophoresis and conformationally sensitive monoclonal antibodies), the variants bind to the lutropin/CG receptor and activated adenylate cyclase in vitro. The data show that the structural requirements for secretion and bioactivity are not the same. The results also suggest that the extensive native subunit interactions determined by the cystine bonds are not required for signal transduction. Moreover, these studies demonstrate that the single-chain model is an effective approach to structure-activity relationships of residues and structural domains associated with assembly of multisubunit ligands.

Compartmental analysis of asialoglycoprotein receptor scintigraphy for quantitative measurement of liver function: a multicentre study

A multicentre study on multicompartmental analysis of hepatic scintigraphy using technetium-99m labelled galactosyl serum albumin (GSA), which binds to the asialoglycoprotein receptor, was carried out at seven institutions in Japan. Seventy-four patients with liver disease received 3 mg (185 MBq) of 99mTc-GSA by intravenous injection. Sequential scanning was performed 30 min after injection to obtain anterior images of the heart and liver, followed by single-photon emission tomography (SPET). The indices included in this analysis were hepatic blood flow (Q) and maximal receptor binding rate (Rmax), which showed a good correlation with semiquantitative ratio indices for 99mTc-GSA, namely the retention rate in blood (HH15) and the hepatic uptake rate (LHL15). Q and Rmax also showed a significant correlation with other measures of hepatic function. When patients were grouped according to the severity of chronic liver damage (hepatocellular functional damage), Q was reduced in the moderate and severe groups, while Rmax was reduced in proportion to the functional stage. Both parameters showed no inter-institution difference using analysis of co-variance with the functional stage as a co-variant. With regard to the hepatic uptake rate, anterior planar images and SPET images gave similar results for Q and Rmax. Acquisition times of 15 or 30 min provided the same results. The multicompartmental model analysis permitted comparable results to be obtained at institutions using different gamma cameras, and is therefore considered a universally applicable method. These results indicate that Q and Rmax are useful general indices for evaluating the functional reserve capacity of the liver.

Different administration schedules of the same dose of 2,5-hexanedione influence the development of neuropathy and the toxicokinetics

The same total dose (1.2 g/kg/week) of 2,5-hexanedione (2,5-HD) was administered subcutaneously at 100 mg/kg/12 hr, 200 mg/kg/24 hr, and 400 mg/kg/48 hr to three groups of Donryu rats. The peripheral neuropathy induced by 2,5-HD was confirmed by clinical observation every day, and neurophysiological measurements every 4 weeks. During the 15th week of this experiment, 2,5-HD concentrations in plasma 0.5 to 24 hours after injection were determined. It was found that the greater the dose of 2,5-HD per treatment injected, the earlier peripheral neuropathy developed. Toxicokinetic analysis showed that both the values of the area under the plasma concentration versus time curve and the half life of 2,5-HD were increased, but the excretion parameters (Ke) were decreased, in animals treated with 200 mg/kg/24 hr and 400 mg/kg/48 hr 2,5-HD.

[31P magnetic resonance spectroscopy(MRS) study in basal ganglia of patients with Parkinson's disease]

We report 31P magnetic resonance spectroscopy(MRS) to study regional high energy phosphate and phospholipid metabolism in basal ganglia of patients with Parkinson's disease(PD) in comparison with normal controls. The ratio of phosphomonoester(PME)/phosphocreatine(PCr), phosphodiester(PDE)/PCr and total Adenosine triphosphate(ATP) tend to decrease and the ratio of PDE/PME tend to elevate compared with controls. Moreover these findings are correlated with the duration of illness. Our results suggest that neural elements in basal ganglia may be damaged in PD. In conclusion, 31P-MRS appears to be useful for the study of neural damage and degeneration in vivo.

Characterization of the major core structures of the alpha2-->8-linked polysialic acid-containing glycan chains present in neural cell adhesion molecule in embryonic chick brains

To gain more insight into the possible functional significance of the core glycan chain(s) on which polysialylation takes place in polysialic acid (poly-Sia)-containing glycoproteins, the structure of the core glycans in the embryonic form of chick brain neural cell adhesion molecule (N-CAM) were examined using chemical and instrumental techniques. The following new structural features, which had not been reported by the early pioneering study by Finne (Finne, J. (1982) J. Biol. Chem. 257, 11966-11970), were revealed (Structure I). (i) Two distinct types of multiantennary N-linked glycans, i.e. tri- and tetra-antennary structures, are present; (ii) an alpha1-->6-linked fucosyl residue is attached to the proximal GlcNAc residue of the di-N-acetylchitobiosyl unit; (iii) that the action of GlcNAc-transferase V, which catalyzes the attachment of the beta-(1-->6)-linked GlcNAc residue on the (1-->6)-alpha-linked mannose (Man) arm, appears to be essential for polysialylation to occur on the core glycan chain is suggested by the fact that the Man residue alpha1-->6-linked to the beta-linked Man residue is invariably 2,6-di-O-substituted by the GlcNAc residue; (iv) both type 1 (Galbeta1-->3GlcNAc) and type 2 (Galbeta1-->4 GlcNAc) sequences are present in the peripheral portion of the core glycan structure. An extended form of the type 2 chain, i.e. Galbeta1-->4GlcNAcbeta1-->3Galbeta1-->4GlcNAc, is also expressed on the (1-->3)- and (1-->6)-alpha-linked Man arms; (v) on average about 1.4 mol of sulfate is attached to the type 2 N-acetyllactosamine chain(s), where in the extended form the sulfate group is probably substituted at the O-3 position of the outmost GlcNAc residue, i.e. Galbeta1-->4(HSO3-->3)GlcNAcbeta1-->3Galbeta1--> 4GlcNAcbeta1-->Man. It is possible that the unusual structural features identified in this study might play a role in the initiation of polysialylation and our data should facilitate future research regarding the signals that control polysialylation.

Expression of biologically active fusion genes encoding the common alpha subunit and either the CG beta or FSH beta subunits: role of a linker sequence

The gonadotropin/thyrotropin hormone family is characterized by a heterodimeric structure composed of a common alpha subunit non-covalently linked to a hormone-specific beta subunit. The conformation of the heterodimer is essential for controlling secretion, hormone-specific post-translational modifications and signal transduction. Structure-function studies of FSH and the other glycoprotein hormones are often hampered by mutagenesis induced defects in subunit combination. Thus, the ability to overcome the limitation of subunit assembly would expand the range of structure activity relationships that can be performed on these hormones. Here we converted the FSH heterodimer to a single chain by genetically fusing the carboxyl end of the FSH beta subunit to the amino end of the alpha subunit in the presence or absence of a natural linker sequence. In the absence of the CTP linker, the secretion rate was decreased over three fold. (The CTP sequence is the last 28 amino acids of the CG beta sequence and contains four serine-linked oligosaccharides). Unexpectedly however receptor binding/signal transduction was unaffected by absence of the linker. Molecular modelling of the tethers lacking the linker sequence show that the alignment of the alpha/beta domains in the single chain differ substantially from that seen in the heterodimer. These data show that the single chain FSH was secreted efficiently and is biologically active and that the conformation determinants required for secretion and biologic activity are not the same.