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M F Kramer

Publications and source records attributed to M F Kramer.

At least 55 records · Page 3Linked to original sources
PubMed1982

Synthesis of a mucous glycoprotein in the human uterus.

Scrapings of endometrium and uterine contents of 10 women were analysed. In the uterine lumina of two women that used synthetic progestagens, a considerable amount of mucus was present. We fractionated the mucus by CsCl density equilibrium centrifugation into glycoprotein and protein fractions. With sugar and amino acid analysis the glycoprotein could be classified as a typical epithelial glycoprotein, resembling the cervical glycoprotein. It contains neuraminic acid (6.2%) and sulfate (8.4%). From the uteri of the other 8 women, who did not use hormones, a small amount of a similar glycoprotein could be isolated.

Adolescent↗
PubMed1982

Spermatogenesis in the boar.

In order to study kinetics of the spermatogenic epithelium in the adult boar, a method has been developed to prepare seminiferous tubules mounted as a whole, after which these tubules have been processed and studied as described previously only for rats, mice and hamsters. The tubules were fixed in Zenker for 24 hours and stained with periodic acid - Schiff - haematoxylin to identify the steps in spermatid development, or by Harris' hemalum to identify spermatogonia and spermatogonial divisions. Spermatid development in the boar is comparable with spermatid development in small laboratory rodents. The spermatogenic cycle was divided into 12 steps, each characterized by one step in the development of the acrosome or the shape of the nucleus of the spermatids. By studying whole mounts we could distinguish four classes of spermatogonia in the boar: undifferentiated A spermatogonia (A s, A pr, A al), differentiating A spermatogonia (A1, A2, A3, A4), intermediate and B spermatogonia. The boar demonstrates a striking similarity with small laboratory rodents.

Animals↗
PubMed1982

Spermatogenesis in the immature mouse proceeds faster than in the adult.

The first appearance of spermatogenic cell types related to the age of the animal was studied in sections and tubular whole mounts of testes of normal mice (Cpb-N strain) up to 34 days pp. The first intermediate spermatogonia and leptotene spermatocytes were seen at days 4 and 7 p.p., respectively. It was found that the subsequent types of spermatogenic cells appear earlier than could be expected if spermatogenesis was to proceed at adult speed. [3H]thymidine labelling studies revealed that within a given interval of time, spermatocytes and spermatids in immature mice develop into more advanced cell types than in adults. The labelling studies and the observation that the cellular associations are always identical to those in the adult, indicate that the rate of acceleration in young mice is the same for spermatogonia, spermatocytes and spermatids. The mean duration of the cycle of the seminiferous epithelium during the age interval of 10 to 30 days p.p. is 7.51 +/- 0.10 days, compared to 8.61 +/- 0.08 in the adult. It increases gradually towards the adult level, reaching the value of 8.45 +/- 0.17 days between days 33 and 56 p.p.

Aging↗
PubMed1981

Glycoprotein synthesis in the mucous cells of the vascularly perfused rat stomach. III. Mucous cells of the antrum and the duodenal glands.

Labeled leucine, serine, galactose, glucosamine, fucose, and sulfate were administered to rat stomachs in a vascular perfusion system. Sections of gastric fundus and antrum, and of the duodenal glands, were studied by light-microscopic autoradiography. The rate of incorporation of radioactive label in the various mucous cell types of the antrum and of the duodenal glands was measured by counting the silver grains over each cell type and comparing this rate with that of the surface mucous cells of the fundus. The following major observations were made: The patterns of incorporation in the mucous cells on the surface and in the pits of the antrum did not differ essentially from those of the surface mucous cells of the fundus. On the contrary, the incorporation patterns of the surface mucous cells of the fundus differed considerably from those of the mucous cells of the antral glands and from the mucous cells of the duodenal glands. The mucous cells of the antral glands showed a lower incorporation rate of amino acids and of (amino) sugars, especially of galactose and glucosamine, but a higher incorporation rate of sulfate. The mucous cells of the duodenal glands showed a considerably higher rate of incorporation for serine, but a lower rate for glucosamine. No differences were seen for leucine, galactose, and sulfate. The relatively low synthetic activity of the mucous cells of antral glands correlates well with the various amounts of RER, Golgi system, and secretory granules, found in these cells, and with the histochemical staining characteristics of their mucous granules. The mucous cells of the duodenal glands are characterized by typical parallel arrays of their numerous RER cisternae and by a low number of small secretory granules.

Animals↗
PubMed1981

Effect of carbenoxolone on the synthesis of glycoproteins and DNA in rat gastric epithelial cells.

The influence of carbenoxolone on the synthesis of glycoproteins in the surface mucous cells and the production of new cells in the rat gastric mucosa was studied by means of a vascular perfusion system. The rate of incorporation of tritiated galactose, glucosamine, serine, and sulphate in surface mucous cells, studied by autoradiography, was not affected by the addition of carbenoxolone to the drinking water. The sugar composition (determined by gas-liquid chromatography) of the gastric glycoproteins (isolated by centrifugation in CsCl), was not changed in carbenoxolone-treated rats. Compared with untreated animals, the number of [3H]-thymidine labelled nuclei per fundic pit increased by 38% to 76% in carbenoxolone-treated rats, implying a higher number of mitotically active cells. This results in an increased supply of young mucous cells; if this also proves to be true in human gastric mucosa, it may be relevant to the therapeutic effect of carbenoxolone.

Animals↗
PubMed1981

Vascular perfusion of the isolated rat stomach with a fluorocarbon emulsion.

A constant-pressure system using a fluorocarbon (FC-75) containing artificial medium was used for vascular perfusion of the isolated rat stomach. A 10% emulsion of FC-75 in a modified Tyrode solution, containing 3.5% bovine serum albumin, amino acids, nucleosides, and beta-hydroxybutyrate appeared to allow an adequate perfusion for at least seven hours. The following criteria were used to estimate for functional state of the perfused stomach: (1) venous flow, (2) oxygen consumption, (3) leakage from the blood vessels to the gastric lumen, (4) ultrastructure, (5) secretion of H+ and pepsinogen after stimulation, and (6) transport of labelled macromolecules. During perfusion oxygen consumption and venous flow remained, after an initial high value, constant for at least seven hours. Leakage from the vascular bed was absent. Ultrastructure was preserved for at least seven hours. Administration of pilocarpine led to secretion of HCl ad pepsinogen. Pentagastrin and histamine stimulated HCl secretion in only some of the preparations. [3H]-galactose was incorporated into macromolecules and transported from the Golgi-region towards the apex of the cell. These observations led to the conclusion that the described vascular perfusion system in at least an appropriate model for studying glycoprotein synthesis.

Animals↗
PubMed1981

Maturation of energy metabolism in the lamb: changes in myosin ATPase and creatine kinase activities.

Studies have been carried out to assess maturation of myofibrillar and mitochondrial proteins in fetal (113 to 140 days gestation), neonatal (30 min to 21 days postpartum), and adult sheep hearts. Ca++-activated myosin ATPase activity was approximately 20% lower in fetal than in adult left ventricular myocardium (1.13 +/- 0.06, n = 12, versus 1.36 +/- 0.07, n = 9, mumoles P1 per g protein per sec; P less than 0.025). In fetal and neonatal hearts (but not in adult hearts), myosin ATPase activity was slightly higher (approximately 14%; P less than 0.001) in right ventricular tissue than in left ventricular tissue. In contrast to these small changes in myosin ATPase activity, large changes indicative of maturation of energy metabolism occurred in the creatine kinase system: between 115 days gestation and 21 days postpartum, total creatine kinase activity increased nearly 8-fold (0.2 to 1.6 IU/mg cardiac mass), the MM-creatine kinase isozyme increased 7-fold (0.2 to 1.5 IU/mg wet weight), and mitochondrial creatine kinase increased more than 25-fold (less than 0.01 to 0.27 IU/mg wet weight). The total creatine pool, but not the ATP pool, increased (from approximately 6 to approximately 15 nmoles/g tissue). Neither the concentration nor isozyme distribution of lactate dehydrogenase, a glycolytic enzyme, changed during this 7-wk period of development.

Adenosine Triphosphatases↗
PubMed1981

The proportion of ribosomes engaged in rat pancreatic polysomal structures as influenced by pilocarpine injection.

Rats intravenously injected with pilocarpine at a concentration of 4 mg per 100 g body weight were killed after various time intervals and the relative numbers of ribosomes per cell active in protein synthesis were determined. It was found that until 1 h after pilocarpine injection there is a significant decrease in the number of ribosomes engaged in protein synthesis, whereas 2--3 h after pilocarpine injection, the number of active ribosomes equals that of control animals. After a short incubation in vitro, the same relative number of active ribosomes is always found, independent of the value determined in the pancreas directly after the death of the animal.

Animals↗
PubMed1980

Role of galactosyl-transferases in rat gastric epithelial glycoprotein synthesis.

Two galactosyl-transferases have been found in the Golgi-enriched subcellular fractions derived from rat gastric mucosa. One incorporates galactose into ovomucoid at optimal pH 6.8. The reaction can be completely inhibited by acetylglucosamine. The apparent Km for UDPgalactose is 0.024 mM. The other galactosyl-transferase incorporates galactose into desialated ovine submaxillary mucin at optimal pH 7.5 and the transfer cannot be inhibited by acetylglucosamine. The apparent Km for UDPgalactose is 0.191 mM. Both enzymes require Mn2+ and Triton X-100 for optimal galactose incorporation. The enzymes could be separated by polyacrylamide gel electrophoresis. Incorporation into endogenous glycoprotein was studied in conditions optimal for the two galactosyl-transferases: (1) at pH 6.8, using Mes as buffer system, and (2) at pH 7.5, using Tris-HCl in the presence of an inhibitory excess of acetylglucosamine. In both cases, most radioactive galactose is incorporated into macromolecules, which could be identified as epithelial glycoprotein. Endogenous incorporation in the presence of excess acetylglucosamine results in the formation of a substantial amount of a disaccharide (probably galactose-beta-(1-3)acetylgalactosamine), whereas upon incorporation at pH 6.8 almost no disaccharide is formed. Quantitative immunoprecipitation experiments with specific antibodies to the endogenous product, labelled by [3H]galactose in the presence of varying amounts of desialated ovine submaxillary mucin and/or acetylglucosamine, indicated that other galactosyl-transferases are involved in the biosynthesis of epithelial glycoprotein.

Animals↗
PubMed1980

Isolation and partial characterization of rat gastric mucous glycoprotein.

Mucus glycoproteins from the rat stomach were characterized after their isolation from homogenates of the superficial gastric mucosa by equilibrium centrifugation in CsCl density gradients. Water-soluble as well as water-insoluble glycoproteins were studied. The latter were solubilized by 2-mercaptoethanol reduction of the homogenate. From both homogenate fractions the sames two glycoproteins 1 and 2 were purified, glycoprotein 1 being present in considerably higher amount than glycoprotein 2. Their respective buoyant densities in a CsCl gradient were 1.47--1.50 g/ml and 1.56--1.58 g/ml. The two glycoproteins expressed slight differences in gel electrophoresis and gel filtration. The results from column chromatographic comparisons between reduced and unreduced glycoproteins indicated strongly that both glycoproteins 1 and 2 were built from subunits kept together by S-S bonds. The s20,w values of the reduced glycoproteins 1 and 2 were 15.7 S and 11.6 S. Glycoprotein 1 contained 5% protein, 70% carbohydrate and 1--2% sulphate, whereas these percentages for glycoprotein 2 were 10% protein, 65% carbohydrate and 10% sulphate. The molar proportions of the main sugar components galactose, fucose, glucosamine and galactosamine were 4 :2 : 4 : 1 (glycoprotein 1) and 3 : 2 : 3 : 1 (glycoprotein 2). Blood-group activity A was expressed by glycoprotein 1, whereas glycoprotein 2 showed mainly blood-group activity Leb, some B activity and also some A activity, but to a lesser extent than glycoprotein 1.

ABO Blood-Group System↗
PubMed1980

Human cervical mucus and its mucous glycoprotein during the menstrual cycle.

Human cervical mucus was collected serially during the menstrual cycles of each of 10 healthy women. After fractionation by equilibrium density centrifugation in CsCl, the sugar composition of the fractions containing mucous glycoprotein (MG) was examined by gas-liquid chromatography. No cyclic variations were detected in the sugar composition of MG (including sialic acid) or in its electrophoretic behavior. The composition of the mucus varied greatly during the cycle. Near ovulation the ratio of proteins to MG was minimal. During the luteal phase this ratio rose quickly. The secretion of MG was high during ovulation. The concentrations of the other proteins. The composition of cervical proteins was mapped by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

ABO Blood-Group System↗
PubMed1979

Glycoprotein synthesis in the mucous cells of the vascularly perfused rat stomach. I. Surface mucous cells.

We developed a constant-pressure vascular perfusion system of the isolated rat stomach, utilizing an artificial, fluorocarbon (FC-75)-containing medium. Perfusion could be maintained for at least six hours, as demonstrated by the ultrastructure of the mucosal cells and by the constant incorporation of [3H]-galactose in the surface mucous cells. Moreover all mucous cell types in tissue fixed after six hours of perfusion showed the same histochemical reactions for glycoproteins as in tissue fixed shortly after decapitation of the animal. The surface mucous cells of the antrum incorporated 30% less [3H]-galactose, [3H]-serine and [35S]-sulphate than those of the fundus. The amount of radioactivity incorporated per cell did not decrease during a subsequent 2 hour chase.

Animals↗
PubMed1979

Glycoprotein synthesis in the mucous cells of the vascularly perfused rat stomach. II. Differentiating mucous cells.

Labeled leucine, serine, galactose, glucosamine and sulphate were administered to rat stomachs in a perfusion system. Sections of the gastric fundus were studied by light microscopic autoradiography. Five categories of mucous cells were distinguished and their glycoprotein synthetic activity was measured in autoradiographs by counting silver grains over each category. During their differentiation, while migrating from the isthmus of the fundic glands to the free luminal surface, the surface mucous cells (SMC) showed an increase in incorporation of all precursors used. Differences between the incorporation patterns of the various precursors, in cells of different ages, suggest that structural development runs ahead of functional activity, and that the latter continues up to the very moment the cell is shed from the surface. Sulphate was incorporated at a considerably lower rate by the SMC of the free surface than by the foveolar SMC, in which by cytochemical staining strongly acidic glycoproteins were shown. Since the mucous neck cells incorporated all precursors at a low rate, these cells apparently do not play an important role in gastric mucus synthesis. They did not incorporate sulphate, which is consistent with histochemical observations.

Animals↗
PubMed1978

Site of synthesis, intracellular transport and secretion of glycoprotein in exocrine cells.

The site of attachment of the first sugar, N-acetylgalactosamine, to the seryl and threonyl residues of the protein chain is unknown in exocrine cells. The subsequent sugars of the carbohydrate side chains, galactose and N-acetylglucosamine alternately, and the end-group sugars, galactose, N-acetylgalactosamine and fucose, are attached in the Golgi complex. Sulphate too is attached in that structure. In the stomach, sulphate is probably transferred in the most mature cisterna of the Golgi stacks, galactose and fucose in other cisternae, suggesting a gradient in transferase activities along the stack. The possibilities of regulating the amount and relative sugar composition of the glycoproteins are discussed. The secretory product is stored in granules. Their polygonal, large and swollen appearance and complex formation by loss of bordering membranes, as observed in many kinds of glycoprotein-secreting cells ('mucous cells') might be caused by ineffective fixation techniques. Direct vascular perfusion results in a picture no different from what is found in non-mucous cells. Whether secretion is merely exocytotic, as in non-mucous cells, or whether it is accompanied by a loss of membrane and even cytoplasm needs thorough investigation, with the effects of various fixation techniques being compared.

Acetylgalactosamine↗