Screening method for colony-stimulating factor inducers using a human bone marrow stromal cell line, KM-102

A new screening method for inducers of colony-stimulating factors (CSFs) was established using KM-102, a human bone marrow stromal cell line as the producer. In this method, the assay system which uses CSF dependent cell lines is combined with the CSF production system. Interleukin-1 (IL-1), which is known to upregulate CSF production in many cell populations, was used as a positive control for production of granulocyte CSF (G-CSF) and granulocyte-macrophage CSF (GM-CSF). Induction in the positive controls was clearly detected within 24 hours. Activators of protein kinase C (PKC), protein phosphatase inhibitors and lipopolysaccharide (LPS) were positive in this assay system, but muramyl dipeptide (MDP) and Bestatin which are known macrophage activators, were negative. Inducers of CSFs were successfully detected using this assay method. Among 1,600 microbial strains tested, 2 actinomycete strains were found to produce active substances. One strain produces teleocidin-A, a strong activator of PKC, and the other strain produces a mixture of active compounds including three novel compounds. These three compounds do not induce terminal differentiation of HL-60 cells, suggesting that they are not teleocidin-like substances and form a new class of CSF inducers.

[Influence of cerebellopontine angle tumor on cerebellar circulation--possibility of remote effect to the cerebellum]

Nine cases (4 men and 5 women, ranging in age from 39 to 73 years with a mean age of 51 years) of cerebello-pontine angle tumors were evaluated by cerebral blood flow scintigraphy on the basis of clinico-functional anatomy. In the 4 of 5 cases in which the middle cerebellar peduncle was compressed by the mass, definite hypoperfusion was revealed in the ipsilateral cerebellar hemisphere. On the other hand, in the 3 of 4 cases without compression of the middle cerebellar peduncle, no asymmetric perfusion was seen in either the right or left cerebellar hemisphere. There were neither supratentorial lesions nor signs of increased intracranial pressure in any of the 9 cases. On the vertebral angiograms of the 4 cases with compression of the middle cerebellar peduncle, non-opacification of the ipsilateral anterior inferior cerebellar artery occurred in only one case. There were no definite signs of reduction of cerebellar blood flow in the other 3 cases. The middle cerebellar peduncle is one of the largest bundles of centripetal fibers in the cerebellar hemispheres. Secondary neuronal fibers of the corticopontocerebellar pathway are the most prominent among these fibers. The mass lesion in the cerebellopontine cistern has a tendency to compress the middle cerebellar peduncle and may deactivate the corticopontocerebellar pathway even if it is small.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of cell-mediated immunity in the resistance to experimental sporotrichosis in mice

Congenitally athymic nude (nu/nu) mice showed higher sensitivity to intratestical infection of Sporothrix schenckii than phenotypically normal littermates (nu/+). Active immunization with viable cells enhanced the resistance to intravenous (i.v.) infection of this fungus in BALB/c mice. Nu/nu mice transferred with immune spleen cells acquired the enhancement of resistance to the infection with S. schenckii, but not ones with normal spleen cells. Pre-treatment of OK-432 (Picibanil), one of the macrophage activating agents, enhanced resistance to i.v. infection of this fungus in BALB/c mice. On the other hand, pretreatment of carrageenan, one of the macrophage inhibitors, impaired the resistance. This fungus was intracellularly killed by peritoneal macrophage from OK-432 treated or immunized mice but not by those from normal mice in vitro. These results suggest that activated macrophage, that was mediated by T cells, play an important role in the resistance to S. schenckii in mice.

[Principle of treatment of intermittent claudication due to arteriosclerosis obliterans--reconstruction or conservative treatment]

MATERIALS AND METHODS

Two hundred and one patients of arteriosclerosis obliterans (ASO) with intermittent claudication (IC) were studied. Improvement of IC, score of return to social life, change of life condition and prognosis were compared between the two groups of reconstructive and conservative treatment.

RESULTS

Improvement of IC was seen in 88.0% of the patients in the group of reconstruction and only 30.4% in the conservative treatment group. In the reconstructive group, the score of return to social life improved from 2.10 to 1.31 and the score of life condition also improved from 2.71 to 1.66. However in the conservative treatment group these score showed no significant improvement. Moreover the long term mortality rate was lower in the treatment group of reconstruction.

CONCLUSION

The arterial reconstruction for IC is significant for improving the quality of life and exerts a favorable effect on life prognosis.

Isolation and characterization of cDNA and genomic sequences for mouse O6-methylguanine-DNA methyltransferase

An enzyme, O6-methylguanine-DNA methyltransferase, is present in various organisms and plays an important role in repair of DNA damaged by alkylating agents. The enzyme transfers methyl groups from O6-methylguanine and other methylated moieties of the DNA to its own molecule. As a first step to construct animal models with altered levels of the enzyme activity, we cloned cDNA and genomic DNA sequences for mouse methyltransferase and elucidated their structures. The nucleotide sequence of the cDNA revealed an open reading frame comprising 211 amino acid residues. The mol. wt of mouse O6-methylguanine-DNA methyltransferase, calculated from the predicted amino acid sequence, was 22,400, and the methyltransferase protein of this size was present when the cDNA was expressed in methyltransferase-deficient human cells. The predicted amino acid sequence of the mouse methyltransferase exhibits an intense homology with those of human and bacterial counterparts. Using the cDNA as a probe, part of the mouse gene for methyltransferase was isolated. The gene consisted of at least four exons and spanned greater than 145 kb. Sequences around the exon/intron junctions for the mouse gene are almost the same as those for the human species.

Local motion processing in the optic tectum of the Japanese toad, Bufo japonicus

The results of previous behavioral studies can be so interpreted that the prey-catching behavior in the toad is elicited if there is a 'local' motion restricted within a small part of the visual field, while it is suppressed if there is a 'global' motion over a large part of the visual field. This has led us to design experiments to answer a specific question (yet a very essential one for understanding neural processes underlying this behavior): Are there 'local motion detectors' in the toad's visual system that are not activated by 'global' motion over a large part of the visual field but are activated by 'local' motion confined within a smaller part of it? The present study showed that (1) the majority of the toad's tectal neurons exhibit properties of the 'local motion detectors' as defined above, and (2) these properties can be explained from the receptive field structure revealed in the present experiments. Based on these results, we suggest that the tectal 'local motion detectors' are essential for the detection and localization of small moving prey-objects in the natural environment while ignoring the large moving objects or the self-induced motion of the visual field.

Cloning and expresion of cDNA for rat O6-methylguanine-DNA methyltransferase

cDNA for O6-methylguanine-DNA methyltransferase was isolated by screening rat liver cDNA libraries, using as a probe the human cDNA sequence for methyltransferase. The rat cDNA encodes a protein with 209 amino acid residues. The predicted amino acid sequence of the rat methyltransferase exhibits considerable homology with those of the human, yeast and bacterial enzymes, especially around putative methyl acceptor sites. When the cDNA was placed under control of the lac promoter and expressed in methyltransferase-deficient Escherichia coli (ada-, ogt-) cells, a characteristic methyltransferase protein was produced. The rat DNA methyltransferase thus expressed could complement the biological defects of the E. coli cell caused by lack of its own DNA methyltransferases; e.g. increased sensitivity to alkylating agents in terms of both cell death and mutation induction.

New noninvasive assessment of regional left ventricular function by digital subtraction angiography without the use of contrast medium

We have developed a new noninvasive method to evaluate regional left ventricular (LV) function by digital subtraction angiography (DSA) without the use of contrast medium. DSA images of the left ventricle with and without contrast medium were obtained from 35 patients with anterior myocardial infarction (MI) and from 35 control subjects. Using an image-processing computer, regional LV time-density curves were constructed for one cardiac cycle. Regional LV time-density curves obtained from DSA without the use of contrast medium presented a pattern similar to those from intravenous DSA. The amplitude of regional LV time-density curves in patients with MI decreased along with increasing severity of regional wall motion abnormality assessed by conventional left ventriculography. In attempting semi-quantitative evaluation by DSA without the use of contrast medium, the regional wall motion index (RWI) in the 6 segments of the left ventricle was calculated by normalizing segmental density changes to the maximal segmental density changes. When compared with control subjects, patients with MI have significantly lower RWIs in the anterolateral and apical regions. RWI showed a good correlation with the regional ejection fraction (REF) obtained from intravenous contrast DSA (r = 0.83). RWI decreased with increasing severity of regional wall motion abnormality by qualitative analysis in conventional left ventriculography, being consistent with REF. The diagnostic accuracy of RWI therefore seemed to be comparable to that of REF derived from intravenous contrast DSA. These results indicate that computerized analysis of DSA without the use of contrast medium is a valuable noninvasive method for semi-quantitative assessment of regional LV function.

Aladapcin, a new microbial metabolite that enhances host resistance against bacterial infection. Production, isolation, physico-chemical properties and biological activities

We have constructed a new screening system for detecting microbial products that enhance host resistance against bacterial infection. It was found that a new compound with such activity is produced by a soil isolate classified as Nocardia sp. SANK 60484. The compound was isolated from the culture filtrate of the organism and named aladapcin after its amino acid composition. Aladapcin was obtained as an amphoteric white amorphous powder with the molecular formula, C13H25N5O5. It consists of 2 mol of D-alanine and 1 mol of meso-diaminopimelic acid. From the analysis of IR, 1H NMR and FAB-MS spectra, the structure was assigned to be a tripeptide. Aladapcin enhanced host resistance against an experimental Escherichia coli infection in mice at doses ranging between 1 and 100 micrograms/kg.

Relationship between coronary risk factor and arteriographic feature of coronary atherosclerosis

Coronary arteriography was performed in 1,029 consecutive patients with ischemic heart disease and the relationship between the arteriographic features of coronary atherosclerosis and coronary risk factors was analyzed by case control studies. Patients were divided into four groups according to coronary arteriographic findings. Patients with normal or near normal coronary arteriograms (Group I) showed a high prevalence of smoking habit and a higher value of serum uric acid compared with the control group, so smoking and hyperuricemia were considered to be the risk factors for coronary atherosclerosis in patients of group. Four selected variables: smoking, hyperuricemia, hypertension and hyperlipidemia, were identified to be risk factors for the patients with minor plaques in the coronary arteries (Group II). As in Group I, smoking and hyperuricemia had a close relationship to solitary tight plaque in a branch of the coronary artery (Group III). Multiple tight stenoses in the coronary arteries (Group IV) correlated closely with smoking, hyperuricemia, hypertension, hyperlipidemia and diabetes mellitus. Thus, there were many strong risk factors for patients with diffuse, extended coronary atherosclerosis (Group II and Group IV), while only two factors, smoking and hyperuricemia, were considered to be risk factors for the patients with near normal coronary arteries ies or a solitary plaque in a branch of the coronary artery. These findings suggest that the role of the coronary risk factors on the pathogenesis of coronary atherosclerosis is not uniform but variable depending on the morphologic variability of the coronary atherosclerosis and on the pathophysiology of the ischemic heart disease.

[A case of alcoholic cirrhosis demonstrating long-term poor-visualization of the hepatic image on 99mTc-phytate scintigraphy]

A 27-year-old female patient with alcoholic cirrhosis was reported. She was admitted to the hospital because of jaundice and ascites after heavy drinking. She had a history of drinking Japanese Sake in quantities of more than 5 go/day (900 ml/day) for 7 years. On admission, she was icteric, and had both hepatosplenomegaly and ascites. Laboratory data showed an elevation of serum transaminase and bilirubin, and a decrease in the albumin and prothrombin values. A biopsy specimen of the liver showed pericellular fibrosis, fatty change, Mallory bodies and regenerative nodules, and revealed findings compatible with alcoholic cirrhosis. A 99mTc-N-pyridoxyl-5-methyltryptophan scintigram showed hepatomegaly. On the 99mTc-phytate scintigram, the uptake of radioisotope to the liver was markedly decreased with the increased uptake to the spleen and bone marrow. Even 6 months after the onset, poor visualization of the hepatic image on 99mTc-phytate scintigram continued. This is the first report of alcoholic cirrhosis demonstrating a long-term poor visualization of the hepatic image on 99mTc-phytate scintigraphy.

Behavioral sensitization to beta-phenylethylamine (PEA): enduring modifications of specific dopaminergic neuron systems in the rat

Repeated daily administration of an endogenous trace amine, beta-phenylethylamine (PEA), produces behavioral sensitization such that the intensity of PEA-induced stereotyped behaviors in rats increases gradually during the treatment, and a challenge injection with PEA reinstates the enhanced stereotypy even long after withdrawal. In the present study, we examined the neurochemical changes in the central dopaminergic neurons systems in the rat for 7 drug-free days after repeated treatment with PEA (50 mg/kg, IP day for 14 or 28 days). During withdrawal, a decrease in steady-state levels of tissue dopamine (DA) and its metabolite, dihydroxyphenylacetic acid (DOPAC), was found in the mesolimbic DA nerve terminal areas of the rat brain receiving repeated PEA treatment. Fifteen minutes after challenge administration of PEA at varying doses from 6.3 to 75 mg/kg, the rats with repeated PEA treatment required smaller doses of PEA challenge than the rats with acute PEA treatment in order to obtain a significant decrease in striatal DOPAC content compared to the saline control in each treatment group. These results imply that the behavioral sensitization to PEA is accompanied by enduring modifications of the specific dopaminergic neuron systems in the rat brain. This suggestion was strongly supported by the results of the study using in vivo intracerebral dialysis, which indicated that 25 mg/kg PEA challenge elicited a remarkable increase in the extracellular DA concentrations in striatal perfusates collected from the PEA-pretreated rats, in accordance with the intensity of stereotyped behaviors. These findings argue that the hyper-responsiveness to PEA of the striatal dopaminergic neuron systems persists long after withdrawal from repeated treatment with PEA.

After-effects of moving textured background in motion-sensitive neurons of anuran optic tectum

Motion-sensitive neurons in anuran optic tectum were shown to respond to a stationary object centered in the excitatory receptive field, if a textured background moved for a while and then stopped ('motion after-response'). This motion after-response was attributed to a post-inhibitory rebound activation derived from effects of masking the excitatory receptive field center surrounded by an antagonistic inhibitory region. It was suggested that a similar rebound activation mechanism may also be involved in a certain type of perceptual motion after-effects in humans.

[A case of esophageal diverticula in a child]

Esophageal diverticula in infants and children are rarely seen, even by the pediatric radiologist. This is a case report of an infant girl presenting with an esophageal diverticulum arising from the right anterior lateral aspect of the proximal third of the esophagus. The diverticulum included a metallic foreign body.

Determination of guanine by high-performance liquid chromatography with electrochemical detection: application to DNA and RNA assays

A highly sensitive assay for guanine was developed using high-performance liquid chromatography with electrochemical detection (ECD). Guanine was susceptible to the electrochemical oxidation, and ECD response was proportional to the amount of guanine in the range 0.25-4 pmol of guanine. The ECD of guanine was applicable to the analysis of nucleic acids. DNA and RNA were hydrolyzed in 0.03 and 3 M HCl, respectively, and guanine liberated from the nucleic acids was separated on a reverse-phase column and determined by ECD. The method allowed detection of 0.2 ng of calf thymus DNA or tRNA. An application of the method is shown for DNA and RNA assays in trichloroacetic acid extracts of rat adrenal and liver.

Humoral mediator-dependent activation of the Sarcophaga lectin gene

Sarcophaga lectin is a defence protein synthesized by the fat body and secreted into the hemolymph in response to injury of the body of third instar larvae of Sarcophaga peregrina (flesh-fly). In this paper, we demonstrate that the stimulus of body injury is first transmitted to a certain tissue present in the anterior part of the body, and from there a mediator molecule that interacts directly with fat body cells is secreted into the hemolymph. On interaction with this mediator molecule, the fat body begins to synthesize mRNA for Sarcophaga lectin.

Antimycobacterial activities in vitro and in vivo and pharmacokinetics of dihydromycoplanecin A

The in vitro activity of dihydromycoplanecin A (DHMP A), a new cyclic peptide antibiotic, was compared with those of antimycobacterial drugs such as streptomycin, isoniazid (INH), rifampin, and ofloxacin against several clinically isolated species of mycobacteria, including Mycobacterium tuberculosis, M. intracellulare, and M. kansasii. DHMP A demonstrated stronger activities than other drugs against all species of mycobacteria tested at concentrations of less than 0.0125 to 25 microgram/ml. A marked synergism between DHMP A and INH was demonstrated by the checkerboard technique against M. tuberculosis, M. intracellulare, and M. smegmatis, and the synergistic effect was observed by treatment of the culture of M. smegmatis with DHMP A for at least 3 h prior to treatment with INH. It was also shown that both absorption and excretion of INH in mice were faster than those of DHMP A. On the basis of these results, combination therapy with DHMP A and INH was successfully carried out in experimental tuberculosis in mice infected with M. bovis Ravenel. After a single intravenous administration of 10 mg of DHMP A per kg, its half-life in serum in mice was about 0.5 h and in dogs it was 5.5 h. A single oral administration to dogs of 12.5 mg/kg gave a peak of 5.0 micrograms/ml at 3 h. In these experiments, urinary recoveries within 48 h were 21.0% in mice and 25.2% in dogs. The tissue distribution level of DHMP A in mice after oral administration was in the order of liver greater than kidney greater than serum greater than spleen = lung. The 50% lethal doses of DHMP A for mice were more than 6,000 mg/kg orally and 1,840 mg/kg intraperitoneally.

Effects of a new antibiotic, isohematinic acid, on the resistance of mice to experimental infections

Isohematinic acid, an antibiotic newly isolated from the culture broth of Actinoplanes philippinensis SANK 61681, was assessed for its ability to enhance nonspecific resistance to bacterial infections against Escherichia coli and Pseudomonas aeruginosa in mice. This agent, as well as BM 12,531 (Azimexon), was found to prolong the survival of normal mice infected with E. coli and also of compromised mice infected with either E. coli or P. aeruginosa, whose defense system had been deteriorated by treatment with carboquone, an alkylating agent. Like BM 12,531, isohematinic acid administered to normal mice significantly increased the nitroblue tetrazolium reducing potency of polymorphonuclear leucocytes (PMN), indicating that the microbicidal activity of PMN was enhanced by these agents. In addition, in the compromised mice these agents were able to restore the number of peripheral blood leucocytes, which had been reduced to about 30% of the normal level by carboquone. These results suggest that isohematinic acid, like BM 12,531, enhances nonspecific resistance to these bacterial infections by stimulating the microbicidal activity of PMN and inducing leucocytosis.

The calcitonin-like sequence of the beta CGRP gene

We have identified a region within the beta CGRP gene which has the potential to encode a novel calcitonin-like peptide. The gene is located on the short arm of chromosome 11 (11p 12-14.2) and we suggest that it resulted from a local duplication of the alpha gene. We have been unable to detect the corresponding mRNA in a variety of tissues which express alpha-calcitonin. It is not clear whether this sequence can be expressed in man.

Preparation of tyrosine-O-[35S]sulfated cholecystokinin octapeptide from a nonsulfated precursor peptide

A rapid and simple one-pot method for O-sulfation of nonsulfated cholecystokinin octapeptide (CCK-8) was developed using sulfuric acid and dicyclohexylcarbodiimide (DCC) without protection of the amino acid side chains. The extent of sulfation was increased with increasing the amount of reactants, sulfuric acid, and DCC, and reached maximum (40%) with fourfold molar excess of sulfuric acid and 40-fold molar excess of DCC. The excess of nonsulfated peptide inhibited the sulfation. The sulfation product was purified by HPLC or TLC to give a pure sulfated substance which showed exactly the same behavior as that of an authentic O-sulfated CCK-8 on HPLC or TLC. The purified sulfated peptide was active in stimulating amylase secretion from rat pancreatic fragments, and amino acid analysis showed that the tyrosine residue in the peptide existed in O-sulfated form. Sulfation with [35S]sulfuric acid-DCC produced a radioactive substance, from which O-[35S]sulfated CCK-8 could be easily purified by two-dimensional TLC.

Analysis of the DNase I-hypersensitive site of a developmentally regulated 25-kDa protein gene of Sarcophaga peregrina

Change in chromatin structure of a developmentally regulated gene of Sarcophaga peregrina (flesh fly) during development was investigated. This gene (25-kDa protein gene) was specifically activated in the fat body, but not the hemocytes of larvae in the middle of the third instar. The mRNA level in the fat body decreased thereafter, reaching one-fifth of the maximum level in the late third instar to early pupal stage. In the chromatin of fat body nuclei, a DNase I-hypersensitive site was found about 300 base pairs upstream from the transcription initiation site of the 25-kDa protein gene. This DNase I-hypersensitive site appeared before activation of the 25-kDa protein gene, and it was conserved until the late third instar, but disappeared in the early pupal stage. Since activity of the 25-kDa protein gene decreases significantly in the early pupal stage, it is likely that disappearance of this DNase I-hypersensitive site coincides with inactivation of the 25-kDa protein gene.

Aculeximycin, a new antibiotic from Streptosporangium albidum. II. Isolation, physicochemical and biological properties

A new larvicidal antibiotic, aculeximycin, was found in the culture broth of an actinomycete identified as Streptosporangium albidum. Aculeximycin was isolated from the culture filtrate by adsorption on a Diaion HP-20 column and successive elution with acidic aqueous acetone. It was extracted from the concentrated active fraction with 1-butanol and subjected to column chromatography on a Sephadex LH-20 column. Aculeximycin exhibited strong larvicidal activity against mosquito larvae as well as antimicrobial activities against Gram-positive and Gram-negative bacteria, yeasts and molds.

Mycoplanecins, novel antimycobacterial antibiotics from Actinoplanes awajinensis subsp. mycoplanecinus subsp. nov. II. Isolation, physico-chemical characterization and biological activities of mycoplanecin A

New antibiotics, mycoplanecins, were found in the culture broth of an actinomycete identified as Actinoplanes awajinensis subsp. mycoplanecinus subsp. nov. Mycoplanecin complex was extracted with organic solvents both from the culture filtrate and mycelium and purified by column chromatography on silica gel and Florisil. Mycoplanecin A, a major component, was separated by high performance liquid chromatography on Prep PAK-500/C18 column. The physico-chemical characterization revealed that mycoplanecin A was a new cyclic peptide antibiotic. Mycoplanecins exhibited strong activities primarily against mycobacteria and related microorganisms.

Antifungal activity of transferrin

Inhibitory effects of transferrin on fungal growth were successfully estimated by measuring fungal ATP content. By this method, it was demonstrated that both human and rabbit transferrin possessed the inhibitory effect in the absence of any other factor on yeast-like and filamentous fungi. However, rabbit stimulation factor enhanced the inhibitory effect. The inhibitory effect of transferrin was nonspecific and correlated with unsaturated iron binding capacity (UIBC) of transferrin. Human transferrin was more inhibitory than rabbit transferrin.

The effects of amino acids on the labellar hair chemosensory cells of the fly

The effects of amino acids on the labellar hair chemosensory cells were examined with two kinds of flies (the fleshfly, Boettcherisca peregrina, and the blowfly, Phormia regina). As a result of this examination, the effects of amino acids were divided into four main classes. Amino acids in class 1 did not stimulate any chemoreceptor cell. Amino acids in class 2 inhibited nonspecifically the discharges from three kinds of chemosensory cells. Amino acids in class 3 stimulated the salt receptor cell. Amino acids in class 4 stimulated the sugar receptor cell. A possibility that a fourth neuron in the labellar hair chemosensory cell might be a protein or an amino acid receptor cell was eliminated.

The effects of pH on the labellar sugar receptor of the fleshfly

Reproducible results describing the effects of pH on the response of the labellar sugar receptor of the fleshfly, Boettcherisca peregrina, were obtained. The response to sucrose was independent over a wide range of pH (3.0 to 10.0 for sucrose stimulation), but was inhibited fairly sharply on both sides of this range. Similar results were obtained for monosaccharide stimulation. The receptor was excited on stimulation by water above pH 12.0. The effects of high pH, both inhibitory and excitatory, were affected by the presence of salts. In the presence of 0.5 molar NaCl, for example, the pH-inhibition curve was shifted toward lower pH's by about one pH unit. The effects of low pH, on the other hand, were not affected by salts. Following Dixon's theory, it was concluded that at least five ionizable groups (loosing positive charges above pH 10.5) were located at the receptor site.

Stimulation of the labellar sugar receptor of the fleshfly by mono- and disaccharides

Responses of the labellar sugar receptor of the fleshfly, Boettcherisca peregrina, were studied over a wide range of concentrations of several sugars (sucrose, maltose, glucose, fructose, and mannose) in single solutions and in mixtures. The results suggest (a) that the receptor sites are not completely differentiated for glucose and for fructose combination, (b) that the receptor site is composed of two subunits. Such suggestions are based on the classical model, where the response is proportional to the number of the sites, two subunits of each site being simultaneously occupied with one molecule of disaccharides or two molecules of monosaccharides. It is shown, however, that an allosteric model gives a somewhat better interpretation of the experimental results.

Stimulation of the labellar sugar receptor of the fleshfly by mono- and disaccharides

Responses of the labellar sugar receptor of the fleshfly, Boettcherisca peregrina, were studied over a wide range of concentrations of several sugars (sucrose, maltose, glucose, fructose, and mannose) in single solutions and in mixtures. The results suggest (a) that the receptor sites are not completely differentiated for glucose and for fructose combination, (b) that the receptor site is composed of two subunits. Such suggestions are based on the classical model, where the response is proportional to the number of the sites, two subunits of each site being simultaneously occupied with one molecule of disaccharides or two molecules of monosaccharides. It is shown, however, that an allosteric model gives a somewhat better interpretation of the experimental results.