Characterization of metformin transport system in NIH 3T3 cells

The biochemical properties of the metformin transport system were studied in NIH 3T3 cells. 14C-metformin uptake appeared to be a sodium dependent process. Iso-osmotical replacement of Na+ by choline chloride in the assay medium resulted in a decrease of metformin uptake. Amiloride (200 microM) inhibited the metformin transport by 35% in these cells. Gramicidin, a channel ionophore, was the most effective in inhibiting the metformin transport as compared to valinomycin, a mobile ion carrier, and Ca2+ ionophore (A 23187). Loading of cells with asparagine, ornithine, or polylysine did not influence the uptake process. However, the addition of lysine or arginine significantly stimulated the metformin uptake by NIH 3T3 cells. Similarly, the addition of metformin stimulated the arginine uptake by these cells, suggesting that metformin shares the y+ transport system. Metformin inhibited competitively the uptake of 14C-spermidine, a molecule of the polyamine family, by NIH 3T3 cells, whereas the latter failed to influence the uptake of the former significantly by these cells. Incubation of NIH 3T3 cells in the presence of difluoromethyl-ornithine (a suicidal inhibitor of polyamine biosynthesis) stimulated the spermidine, but not the metformin, uptake by these cells. Interestingly, a prolonged incubation of these cells in the presence of metformin failed to down-regulate the spermidine transport process. The spermidine- and methylglyoxal-bis(guanylhydrazone), MGBG-transport deficient (3T3MG) cells which do not accumulate exogeneous spermidine or MGBG, took up 14C-metformin. However, 14C-metformin uptake by 3T3MG cells was lower than that by normal NIH 3T3 cells.

Protein kinase C inhibitor (H-7) potentiates antiproliferative effects of a polyamine biosynthesis inhibitor

In this study, a protein kinase C inhibitor, H-7, was found to potentiate the antiproliferative effects of difluoromethyl ornithine (DFMO), inhibitor of the polyamine biosynthesis, on NIH 3T3 and 3T3/SV40 cells in culture. Incubation of the cells with DFMO inhibited the cell growth, whereas the addition of polyamine spermidine to these cells restored the normal rate of cell proliferation with the fact that these cells took up the polyamine from the extracellular medium to compensate the intracellular needs. The addition of H-7 to both the 3T3 and 3T3/SV40 cells, inhibited the cell proliferation, though the level of inhibition was always lower than in those treated with the DFMO alone. The addition of H-7 to the DFMO containing cells potentiated the antiproliferative effects of the latter with the fact that the former inhibited the uptake of the spermidine, though there might be additional targets, like the protein kinase C, involved in the inhibition process.

Phorbol esters augment polyamine transport by influencing Na(+)-K+ pump in murine leukemia cells

In this report, we elucidate the role of Na(+)-K+ pump in the regulation of polyamine spermidine (Spd) transport in murine leukemia (L 1210) cells in culture. Ouabain, known to bind extracellularly to the alpha-subunit of the Na(+)-K+ pump, inhibits the pump activity. The L 1210 cells were found to possess ouabain binding sites at 7.5 fmol/10(6) cells. Ouabain significantly inhibited the Spd uptake in a dose-dependent manner. The maximum inhibition of Spd uptake by ouabain was observed beyond 200 microM. Spd transport was inversely correlated with the [3H]ouabain binding to L 1210 cells: an increase in the saturation of ouabain binding to L 1210 cells resulted in a decrease of the Spd uptake process. Treatment of L 1210 cells with protein kinase C activator phorbol esters increased the Spd transport and, also, ouabain-sensitive 86Rb+ uptake, a measure of the activity of the Na(+)-K+ pump. H-7, a protein kinase C inhibitor, significantly inhibited the ouabain-sensitive 86Rb+ uptake by L 1210 cells. Phorbol esters stimulated the level, but not the rate, of 22Na+ influx. Addition of H-7 to L 1210 cells inhibited the 22Na+ influx process. A concomitant phorbol ester-induced increase in 22Na+ influx, [14C]Spd uptake, together with the functioning of Na(+)-K+ pump, indicates the role of the "Na+ cycle" in the regulation of the polyamine transport process.

Exogeneous diacylglycerols downregulate the activity of Na(+)-K+ pump in Xenopus laevis oocytes

In this study, cell permeable diacylglycerols, sn-1,2-dioctanoglycerol (DiC8), and sn-1-oleoyl-2-acetylglycerol (OAG) were found to downregulate the activity of Na(+)-K+ pump in Xenopus laevis oocytes. Both DiC8 and OAG decreased the binding of [3H]ouabain to intact oocytes while phorbol esters did not appreciably influence the same. These diacylglycerols inhibited the amiloride-sensitive 22Na+ influx and ouabain-sensitive 86Rb+ uptake in the oocytes. Furthermore, DiC8 prevented the 22Na+ efflux from the oocytes preloaded with 22Na+. Addition of H-7 to DiC8- and OAG-treated oocytes stimulated the pump activity curtailed by the two latters. The impairment of Na(+)-K+ pump activity by diacylglycerols suggests that protein kinase C activators may stimulate endocytosis of membrane-coupled Na(+)-K+ ATPase.

Polyamine binding sites in the rat brain hippocampus plasma membranes: MK 801 does not influence the binding process

The study was undertaken to characterize the polyamine binding sites in rat brain hippocampus plasma membranes. There were two types of binding sites for putrescine, Bmax 650 and 100 pmol/mg protein, with Kd1 = 39.2 and Kd2 = 6.7 microM, respectively, while those for spermidine (Spd) and spermine (Spm) represented only one type of population with Bmax 2.55 and 15 nmol/mg protein, respectively. The Kd values for Spd and Spm were 34 and 30.3 microM, respectively. The maximum binding of polyamines was found at pH 8.0. The binding capacity of these molecules was curtailed at 4 degrees C, indicating that the binding is an energy-dependent phenomenon. The specific binding was not appreciably influenced by the addition of MK 801, an antagonist of NMDA receptor, indicating that there are polyamine-specific binding sites that are different from those for MK 801. Glycine also did not significantly influence the binding of these biogenic amines. Interestingly, the addition of polyamino acids (polylysine, polyornithine, and polyglutamic acid) inhibited the polyamine binding to their receptor sites, supporting the notion that positive charge of polyamines could be important factor in the binding process.

Gentamicin induced dose related alterations in lipid levels and lipid peroxidation in central auditory pathway of the rat

A study was carried out on the effect of gentamicin on the central auditory pathway in rats. Rats were administered graded doses of gentamicin (60 mg, 100 mg and 160 mg/kg b.wt., i.m.) daily for 21 days. Levels of total lipids, phospholipids and cholesterol showed dose related increment in the central auditory pathway. On the other hand, the rate of lipid peroxidation was inhibited in all regions of the central auditory pathway of the rat.

Inhibition of adenylate cyclase activity by polyamines in human erythrocyte plasma membranes

Polyamines (spermidine, spermine and putrescine) inhibited the adenylate cyclase activity in a concentration dependent manner in human erythrocyte plasma membranes. Spermidine (Spd) exhibited more inhibitory effect than spermine (Spm) and putrescine (Put). On the contrary, the addition of amino acids (arginine, glutamine and lysine) did not influence the basal enzyme activity. Other cations (polylysine, polyarginine and polyglutamine) also did not affect the enzyme activity. Addition of all the three polyamines (Spd, Spm and Put) in the reaction mixture exhibited moderate inhibitory effect on the adenylate cyclase activity whether it was basal or activated with sodium fluoride or with forskolin. Since the three polyamines exhibited maximum inhibitory effect at 10 microM concentration which is within physiological limit for mammalian tissues, we suggest that there may be a regulatory function of these molecules on adenylate cyclase activity in human erythrocytes.

Red blood cell polyamine level changes following heart transplantation in man

Follow-up of orthotopic heart transplanted patients has revealed the existence of abnormally high red blood cell (RBC) spermidine (Spd) levels during the first two months after surgical procedure (A-period). From the third month after heart transplantation (B-period), RBC Spd concentrations went back to normal values in early cardiac rejection (ECR) patients. During A- and B-periods, significantly higher Spd levels and Spd/Spm ratios were observed in late cardiac rejecting (LCR) patients than in ECR ones. The lack of a direct relationship between the histological grade of rejection and RBC Spd levels leads us to consider these polyamine blood levels as a new biological instrument in the diagnosis of heart rejection.

Mechanism of spermidine uptake in cultured mammalian cells and its inhibition by some polyamine analogues

Transport pathways for spermidine (Spd) were characterized in mammalian cells in culture of different origin, i.e. L 1210, P 388, C 6, U 251, Balb/c 3T3 normal and transformed by virus SV40 (SV40/3T3). The kinetic constants (Km and Vmax) for 14C-Spd uptake were found to be different in these cells. Spd uptake was inhibited by spermine and putrescine in all cells. Preloading of these cells with system A and other amino acids, including ornithine, usually did not affect Spd uptake, except in L 1210 and C 6 cells, where Spd uptake was accelerated by 2-aminoisobutyric acid, demonstrating that in these two cell lines the polyamines share the system A pathway. Iso-osmotic replacement of Na+ by choline chloride in the assay medium resulted in a decrease in Spd uptake which suggests that Spd uptake is Na+ activated. In all cells, Spd uptake was inhibited by gramicidin and the Ca2+ ionophore A 23187. The degree of inhibition varied among the cells. Valinomycin (K+ ionophore) inhibited Spd uptake by C 6, P 388, Balb/c 3T3 and SV40/3T3 but not by L 1210 and U 251 cells. Treatment with N-ethylmaleimide or p-L 1210, C 6, Balb/c 3T3 and SV40/3T3 cells did not affect appreciably the uptake process. Some newly synthesized polyamine analogues inhibited the Spd uptake of all cells.

Effects of a series of homologous alpha,omega-dimethylaminoalkanes on cell proliferation: binding and uptake of putrescine by a human glioblastoma cell line (U251) in culture

The first step of polyamine uptake is the binding of polyamines to the cell membrane. In order to characterize the specificity of the putrescine binding sites at the surface of the glioblastoma cells (U251), we have carried out competition experiments between putrescine bound to latex microspheres and vizualized by scanning electron microscopy and a series of N,N'-tetramethyl-alpha,omega-diaminoalkanes. N,N'-tetramethyl-1,4-butanediamine (N,N'-tetramethylputrescine) and higher homologs inhibit the latex putrescine binding to the cell surface and concomitantly cell proliferation. [14C] putrescine uptake was mainly inhibited by the lower homologs, which were devoid of antiproliferative effects. Our results suggest that putrescine uptake by the human glioblastoma cell line U251, and putrescine binding to the surface of these cells are independent processes. The potential relationship between antitumor effect of N,N'-tetramethyl-alpha,omega-diaminoalkanes and its binding to a specific putrescine acceptor site is discussed.

Spermidine uptake by erythrocytes from normal and Lewis lung carcinoma (3LL) grafted mice: I. In vitro study

High red blood cell (RBC) spermidine levels have been observed in patients harboring various histological types of cancer. In an attempt to explain the mechanism of RBC spermidine uptake in the malignant cell growth process, erythrocytes from normal and (3LL) Lewis lung carcinoma grafted mice were incubated with [14C] spermidine in the presence of PBS or plasma from normal or 3LL grafted mice. Though RBC of cancer mice harbor abnormally elevated spermidine concentrations as compared with those of controls, when incubated with PBS, 3LL grafted mice exhibit [14C] spermidine uptake three times higher than that of normal mice erythrocytes in the same incubating conditions. Moreover, if plasma incubations always increase spermidine uptake in RBC from cancer mice compared with erythrocytes only incubated with PBS, plasma incubations are responsible for two opposite effects in RBC of normal mice: plasma increases spermidine uptake in PBS unwashed erythrocytes and lowers it in PBS washed RBC. One possible explanation for the observed plasma stimulating effect in RBC spermidine uptake might be the presence of a plasma component common to plasma from normal and cancer mice, able to interact with RBC membrane proteins. In erythrocytes from cancer mice, the high spermidine concentration would be responsible for the observed compactness in band 3 proteins involved in ionic transport through RBC stroma. In normal mice erythrocytes which exhibit low polyamine levels, the observed dissociation of band 3 proteins might explain the spermidine uptake in PBS washed normal RBC incubated with plasma. In vivo, this plasma component would participate in the stabilization of normal mice membrane proteins involved in RBC spermidine uptake.

Spermidine uptake by erythrocytes from normal and Lewis lung carcinoma (3LL) grafted mice: II. In vivo study

During Lewis lung carcinoma (3LL) growth, red blood cell (RBC) spermidine (Spd) level evolution was proportional to the increase in tumor volume and inversely correlated with the decrease in tumor Spd concentration. Similarly, in cancer mice i.p. injected with [14C] Spd, the increasing amount of erythrocyte [14C] Spd was in proportion with tumor volume enhancement and linked to decrease in tumor tissue [14C] Spd concentration. After i.p. injection of [14C] Spd putrescine or [14C] spermine, contrary to normal mice, cancer mice provided [14C] Spd in their erythrocytes. When injected with [14C] methionine, [14C] polyamines were never found in normal or cancer mice erythrocytes. As previously noted in vitro, increasing amounts of polyamines produced by tumor tissue and excreted into blood would modify erythrocyte stroma proteins involved in the RBC [14C] Spd uptake process. These data obtained in vivo demonstrate the tumor origin of polyamines carried by erythrocytes. Since RBC polyamine levels are directly correlated with tumor progression, these experimental results reinforce the clinical use of this index of cell proliferation in malignant diseases with a short doubling time.

Influence of in vitro lactic acidosis on central nervous system neurons

Central nervous system (CNS) cultured neurons while exposed to different concentrations and pH of L-lactic acid exhibited in general chromatin clumping, vacuolization in the cytoplasm, appearance of lipid bodies, accumulation of polyribosomes, cytoplasmic lucency and swollen and aggregation of mitochondria. These alterations progressed with lower pH and longer exposure to lactic acid. At pH 7.4, there was no considerable pathologic changes in cultured neurons irrespective to concentrations of lactic acid added. Comparable results were obtained with the use of other weak acid (citric acid) indicating that the observed changes were due to acidic pH rather than lactate per se.

Morphometric evaluation of the renal arterial system of Dahl salt-sensitive and salt-resistant rats on a high salt diet. II. Interlobular arteries and intralobular arterioles

The progression of small vessel renal vascular disease was studied in inbred Dahl salt-sensitive (SS/Jr) and salt-resistant rats with acute hypertension induced by a high salt diet. Corrected cross-sectional areas of wall (WAC) and lumen were measured by planimetry and histologic staining for fibrin, hyalin deposition, and elastic lamellae was performed. In SS/Jr rats on the high salt diet, the hallmarks of malignant hypertension (fibrinoid necrosis, hyperplastic and necrotizing arteritis) appeared by week 2 and were intensified after 4 weeks on the high salt diet. Renal vascular lesions from SS/Jr rats were characterized by: hyperplasia and/or hypertrophy of medial smooth muscle cells; intimal proliferation; fibrin, basophilic mucoid, and hyalin deposition within the the subendothelial space and media; variable adventitial fibrosis; and accumulation of mononuclear inflammatory cells in the adventitia and media. Interlobular arteries from both rat strains exhibited significantly increased cross-sectional areas over time for all measured parameters. Intralobular arterioles from both rat strains exhibited significantly increased cross-sectional areas over time for all measured parameters except lumen from SS/Jr rats. For SS/Jr rats, increased WAC from both arterial divisions correlated positively with systolic blood pressure, but not body weight. In salt-resistant rats, increased WAC from both arterial divisions correlated positively with body weight, but not systolic blood pressure. We concluded that the rapid increase in WAC from SS/Jr rats could not be attributed solely to the normal growth of the rat. With the development of acute hypertension in the SS/Jr rat, these results demonstrate the potential usefulness of this model to investigate the pathogenesis of similar renal vascular alterations which are observed in man.

Clinicopathological profile of bronchogenic carcinoma in Bangladesh

This study reflects some of the basic facts and present status of bronchogenic carcinoma in Bangladesh. Of the total patients admitted in one surgical unit of IDCH during the period 1983 to 1986, 28.7 were clinically suspected to be suffering from bronchogenic carcinoma. Males largely dominated the females (82.4 percent as against 17.6 percent) giving a ratio of 4.6:1.0, and more than 90 percent of the victims were heavy smokers. All the suspected patients were then subjected to radiological examination of chest, bronchoscopic examination (73.0 percent), histopathological examination of the bronchial biopsy specimen and sputum cytological examination (63.2 percent) cases. Bronchoscopic examination revealed endobronchial tumor or suspicious lesion in 63.2 percent cases. The sputum cytological examination were positive for malignant cells in 35.6 percent cases. Histopathological gradation of the carcinoma in order of frequencies were squamous cell carcinoma (13.3 percent), large cell carcinoma (9.7 percent) and adenocarcinoma (4.2 percent) respectively. About one fourth of the cases (27.6 percent) were found to be clinically suitable for operation but on thoracotomy resectability was possible only in 20.6 percent cases. Inoperable cases were subsequently referred for radio or chemotherapy. Follow-up of the cases were rather difficult.

Efficacy of idiotypic vaccination in mice bearing B-cell lymphoma

Mice bearing B-cell lymphoma of BCL1 type were vaccinated with idiotype protein (IgM - Id) of IgM lambda type derived from BCL1 malignant cells. Mice were injected with different doses of BCL1 cells (10(3) and 10(6) cells) at the beginning of experimentation. The vaccination was started on days 5, 10 and 15. Mice were injected with either IgM - Id, IgM - Id conjugated with KLH, IgM - P (IgM lambda obtained from plasmacytoma) or were not immunized. Immunization with IgM - Id conjugated with KLH was more effective in preventing the death of mice injected with 10(3) and 10(6) cells than IgM - Id or IgM - P alone. There was a higher titre of anti-idiotype antibodies in mice immunized with IgM - Id - KLH than in those with IgM - Id only.

Dose-related neurochemical changes in the levels of gangliosides and glycogen in various regions of the rat brain and spinal cord following methyl parathion administration

The aim of the present study was to evaluate the neurochemical changes in the levels of gangliosides and glycogen of the cerebral hemisphere, cerebellum, brain stem and spinal cord following the intraperitoneal (ip) injection of the organophosphate pesticide methyl parathion (1.0 mg, 1.5 mg and 2.0 mg/kg) to each rat of the experimental group daily for 7 days. A remarkable dose-related depletion in the concentration of gangliosides was discernible in all the regions of the CNS. Also, the contents of glycogen exhibited a decrement in different parts of the brain with all the 3 dose-schedules following methyl parathion toxicosis. The results suggest that the levels of gangliosides and glycogen are affected dose-dependently in various regions of the rat brain and spinal cord.

Pharyngoesophageal dysfunctions. The role of cricopharyngeal myotomy

Eighteen patients were evaluated for primary symptoms of cervical dysphagia and/or laryngeal aspiration and subsequently had a cricopharyngeal myotomy. Twelve patients had a neurologic lesion as the cause of the symptoms. Four patients had a Zenker's diverticulum as demonstrated by barium contrast roentgenograms. Two patients complained of persistent suprasternal dysphagia following one or more antireflux repairs for gastroesophageal reflux disease. Esophageal manometry identified a pharyngoesophageal motor disorder in all but four patients, two of the four with Zenker's diverticulum and the two who had an antireflux procedure. The results show that cricopharyngeal myotomy should be reserved for patients with an identifiable motor disorder confined to the pharyngeal phase of swallowing, ie, failure of the pharyngeal pump or cricopharyngeal incoordination and/or incomplete relaxation. Exceptions to this rule are as follows: Zenker's diverticulum, in which an abnormality may not always be detected but of which the results of surgery demonstrate the effectiveness of this procedure; and pharyngoesophageal complaints associated with reflux, most of which resolve with the restoration of distal esophageal sphincter competence. In those few patients in whom these conditions persist, a cricopharyngeal myotomy may be beneficial. Caution should be used in applying the procedure to individuals who have had multiple antireflux repairs.

Technique and clinical importance of eustachian tube radiography

The intact eustachian tube is essential for a successful tympanoplasty. Since clinical function tests do not provide satisfactory results in every case, radiologic examination of the tube becomes very significant. The technique, which we have employed since 1966 in sixty-seven cases of transtympanic radiography of the eustachian tube, is described. The most important indications for this examination are discussed (cases of chronic middle ear suppuration, post-traumatic tube stenosis, and early diagnosis and clarification of tumors of the nasopharynx and middle ear). The transtympanic method is physiologic, simple to perform, and essential for hearing improvement.

Mitochondrial integrity and maltose utilization in yeast

Strains of the yeast Saccharomyces cerevisiae able to utilize maltose only in the presence of functional mitochondria have been described. Two such strains Z104-4B and Z109-1C were isolated as revertants from parental strains unable to utilize maltose. These strains are unique in the sense that although they produce inducible maltase for normal growth on maltose agar plates in the presence of functional mitochondria, they are very poor fermenters of maltose under anaerobic condition. Glycerol negative mutants isolated from these strains simultaneously lose the ability to utilize maltose. One of the manganese induced glycerol negative mit- mutants Z104-4B-Mn1, reverts concomitantly to growth on glycerol and maltose agar plates. On the basis of results presented in this paper, we propose the possibility of existence of two alternate mechanisms for maltose utilization in yeast. An oxidative mechanism for which mitochondrial functions are indispensable, and a fermentative pathway for which mitochondrial integrity is not required.

Effect of a mild dose of X-irradiation on rats under stress

This investigation was apt at studying the effect of a mild dose of X-rays on the normal and shock administered rats. Administration of stress brought about a marked depression in the contents of DNA, RNA and protein in the brain. On the other hand, total body exposure to X-rays was found to increase the levels of DNA, RNA and protein in the brain. Thus, the use of a mild dose of X-rays in stressed animals seems to be stimulatory to the diminished levels of DNA, RNA and protein in the brain. There were rising levels of 5-hydroxy indol acetic acid and Vinyl mandelic acid in the urine of stress administered rats and the enhanced levels of these urinary metabolites appeared to be refractory to the application of X-rays.

A Revision of the Genus Stenozygum Fieber (Pentatomidae: Strachini) From the Oriental and Australian Regions, With Reference to Zoogeography and Phylogeny

Three new species of the genus Stenozygum Fieber, viz. pakistanensis and woodwardi in the subgenus Stenozygum Fieber and constrictus in Setozygum Ghauri, are described from the Oriental (Pakistan) and the Australian-Melanesian (Fiji) regions, with special reference to their male and female genitalia. The new species are compared with the type-species S.(S.) coloratum (Klug), a Palaearctic and Ethiopian species, and S.(S.) gemmeum (Walker), S.(S.) lepida (Walker) [previously treated as a synonym of gemmeum (Walker) (Kirkaldy, 1909)], S.(S.) pseudospeciosum Ghauri and S.(S.) speciosum (Dallas) from the Oriental region, and S.(S.) meridionale Gross and S.(S.) miniatulum Distant from the Australian region. The last six are redescribed, a key to all these species is given, and their relationships briefly discussed.

Congenital pericardial defect associated with atrial and ventricular septal defects

Congenital pericardial defects are rare anomalies but in recent years improved diagnostic techniques have often led to a pre-operative diagnosis. The present communication describes a case of a partial pericardial defect with herniation of the lung into the pericardium associated with a lung cyst which is extremely rare. The sternum showed some deficiency in its lower portion. Atrial and ventricular septal defects with a small pericardio-peritoneal foramen were also present.

Suppression of maltose-negative phenotype by a specific nuclear gene (PMU1) in the petite cells of the yeast Saccharomyces cerevisiae

A small percentage of the primary petites isolated from strain 1403-7A-P1, constitutive for maltase synthesis, simultaneously lost the ability to utilize maltose and alpha-methylglucoside. Further studies showed that these primary petites were not stable with respect to maltose utilization. Approximately 30% of the secondary petites when isolated from the primary petites after vegetative growth were found to papillate on maltose plates. Tetrad analysis data revealed that a nuclear gene has reverted in these papillae, which is responsible for suppression of the maltose negative phenotype in primary petites. We have designated this nuclear gene as the PMU1 gene (petite maltose utilizer). The functional form of the PMU1 gene is required in addition to the MAL4 gene for both constitutive maltase synthesis and maltose utilization in cytoplasmic petite cells derived from strain 1403-7A-P1.

Genetic control of maltase synthesis in yeast. IV. Function of the MAL4 gene: extragenic suppression of a maltase negative mutant

A new series of maltase negative mutants have been isolated from yeast strains carrying the MAL4 gene. These mutants are allelic to the MAL4 gene and fail to ferment maltose, sucrose, and alpha-methylglucoside. Most revertants isolated from these mutants restore the ability to ferment above sugars, and also produce the same levels of maltase as the parental strains. One of the revertants (NA-520-R1), however, ferments maltose slowly, and produces 24 fold less enzyme than the parental strain. Genetic studies revealed that revertant (NA-520-R1), is not a true back mutation but is carrying an extra-genic suppressor, which suppresses the mal4 allele in mutant (NA-520). Since several lines of published evidence indicate that the MAL4 gene is a regulatory gene, it is suggested that the MAL4 gene codes for a regulatory protein, which acts as a positive regulatory element in maltase synthesis.

Genetic control of invertase formation in Saccharomyces cerevisiae. II. Isolation and characterization of mutants conferring invertase hyperproduction in strain EK-6B carrying the SUC3 gene

Invertase formation in the yeast Saccharomyces cerevisiae is subject to repression by hexoses in the growth medium. Mutagen-induced (ethyl methanesulfonate or N-methyl-N-nitro-nitrosoguanidine) invertase hyperproducer mutants have been derived from the SUC3 MAL3 strain EK-6B by selecting for their ability to grow on media containing the sugar raffinose plus 2-deoxy-D-glucose (2DG). Raffinose like sucrose is a betta-fructoside which can be hydrolyzed by yeast invertase (beta-fructoside which can be hydrolyzed by yeast invertase (beta-fructofuranoside fructohydrolase). These mutants, designated dgr, produce higher levels of invertase (pi-glucosidase levels are also elevated but to a lesser extent) under conditions normally repressing invertase biosynthesis in the parent. Invertases of mutants dgr2 and dgr3 are indistinguishable from that of EK-6B with respect to their Km's for sucrose and thermal labilities. Genetic studies revealed that dgr2 and dgr3 are recessive and unlinked to the SUC3 gene.

Modified technique of tympanoplasty with functional results of 494 cases after 3 years

This paper gives the functional preliminary and final results of tympanoplasty as modified by Khan in types I--III in the form of a comparison. We examined 494 patients who were operated according to our modified technique. It is emphasized that in reconstruction of the middle ear, the use of a prepared fascial graft, homograft incus cartilage and external auditory meatal flap is sufficient. The preliminary and final results were documented with the aid of audiograms which were described and critically appraised according to two different types of evaluation. The evaluation did not only include the hearing results of tympanoplasty, but also the change in individual frequencies for all types. According to our appraisal of the operations with regard to social hearing the functional results of operations performed in our clinic may be considered above average. The hearing gain achieved from the preliminary postoperative control to the final examination is especially satisfying, since it also includes an improvement in bone conduction values.

Effect of the petite mutation on maltose and alpha-methylgucoside fermentation inSaccharomyces cerevisiae

Several hundred petite mutants were isolated from yeast strains of different genotype to examine the effect of the petite mutation on maltose and alpha-methylglucoside fermentation. In most cases petite mutants isolated retain the ability to ferment maltose and alpha-methylglucoside, although at a slower rate. In one strain (1403-7A), however, the ability to ferment alpha-methylglucoside is completely lost in all petite mutants isolated from this strain. It is suggested that mitochondrial factors may be involved in the utilization of alpha-methylglucoside in strain 1403-7A.

[Diagnosis and treatment of conductive deafness due to middle-ear effusion in childhood (author's transl)]

Results of follow-up examinations of 132 ears with serous or mucous middle ear effusions indicate that this disease is common in childhood and is also found in adults. In childhood adenoid growth as well as repeated catarrhal infection of the paranasal sinuses and the weakness of the levator palati play an important role in the development of middle ear effusions and deafness. With the aid of the operation microscope we were able to recognize this characteristic disease through the tympanic membrane. We perform regularly adenoidectomy together with paracentesis in this condition. In cases which had undergon several adenoidectomies we limit our treatment in the first instance to paracentesis. If cure is not so achieved we insert an inert tube into the tympanic membrane after the paracentesis. In persistent and difficult cases of glue ear radiation of the eustachion tube and antrotomy may be necessary.

[Histological study of otological homografts (incus, cartilage and fascia) (author's transl)]

To summarise our morphological findings of this study the following conclusions are drawn: In bone grafts growth of vital cells originating from the Haversian canals is clearly demonstrated. The growth of connective tissue in the Haversian system is understandable on general principles of pathology. The morphology of the change of osteocytes from fibrocytes through osteoblasts is photographically clearly shown and is in keeping with the findings of Steinbach and of Kerr and Smyth. New bone formation was detected at earliest nine months after implantation. Our investigations do not confirm whether this new bone formation occurs persistently in all cases or to what extent the original homograft material, preserves in cialit solution, takes part in this process. A similar mechanism of tissue regrowth should be accepted in homograft cartilage. We have studied two cases, one after 6 months and the other after 5 years following implant. The three fascial grafts examined compare with earlier publications, with oedema, slight inflammation and little shrinkage occurring. The suitability for grafting of homograft incus, cartilage and fascia we believe to have been demonstrated.

Genetic control of maltase formation in yeast

Temperature-sensitive mutants affecting maltose utilization in the yeast Saccharomyces cerevisiae have been isolated. Two such mutants although failing to ferment maltose at the restrictive temperature, have normal induced level of maltase. The third mutant (UNT-37) not only failed to ferment maltose but has 5-6 fold less induced level of maltase at the restrictive temperature than the parental strain. The genetic control mechanisms of maltase induction and maltose utilization have been discussed.