Showing papers by "University of Göttingen published in 1988"

Organic phosphorus compounds as a phosphorus source for higher plants through the activity of phosphatases produced by plant roots and microorganisms

Abstract: The efficiency of phosphatases produced by clover, barley, oats and wheat was investigated in soils treated with sodium glycerophosphate, lecithin and phytin. Root exudates of aseptically grown clover were also examined for the breakdown of different organic P compounds in order to test the efficiency of plant-produced phosphatases. In general, the plants were able to use P from all the organic sources used in the study almost as efficiently as inorganic sources. Dry-matter yield, P uptake, acid and alkaline phosphatase activity and microbial population were increased in all the P treatments. Organic P enhanced alkaline phosphatase activity. Lecithin increased fungal, and phytin bacterial growth. There was no alkaline phosphatase activity in the asepticallly grown clover root exudates. Phosphatase released in aseptic culture after 4 weeks of clover growth was able to efficiently hydrolyse sodium glycerophosphate, lecithin and phytin. The amount of organic P hydrolysed in this and in the soil experiment surpassed plant uptake by a factor of 20. This suggests that the limiting factor on plant utilization of organic P is the availability of hydrolysable organic P sources.

Cloning of the Alcaligenes eutrophus genes for synthesis of poly-beta-hydroxybutyric acid (PHB) and synthesis of PHB in Escherichia coli.

Abstract: Eight mutants of Alcaligenes eutrophus defective in the intracellular accumulation of poly-beta-hydroxybutyric acid (PHB) were isolated after transposon Tn5 mutagenesis with the suicide vector pSUP5011. EcoRI fragments which harbor Tn5-mob were isolated from pHC79 cosmid gene banks. One of them, PPT1, was used as a probe to detect the intact 12.5-kilobase-pair EcoRI fragment PP1 in a lambda L47 gene bank of A. eutrophus genomic DNA. In six of these mutants (PSI, API, GPI, GPIV, GPV, and GPVI) the insertion of Tn5-mob was physically mapped within a region of approximately 1.2 kilobase pairs in PP1; in mutant API, cointegration of vector DNA has occurred. In two other mutants (GPII and GPIII), most probably only the insertion element had inserted into PP1. All PHB-negative mutants were completely impaired in the formation of active PHB synthase, which was measured by a radiometric assay. In addition, activities of beta-ketothiolase and of NADPH-dependent acetoacetyl coenzyme A (acetoacetyl-CoA) reductase were diminished, whereas the activity of NADPH-dependent acetoacetyl-CoA reductase was unaffected. In all PHB-negative mutants the ability to accumulate PHB was restored upon complementation in trans with PP1. The PHB-synthetic pathway of A. eutrophus was heterologously expressed in Escherichia coli. Recombinant strains of E. coli JM83 and K-12, which harbor pUC9-1::PP1, pSUP202::PP1, or pVK101::PP1, accumulated PHB up to 30% of the cellular dry weight. Crude extracts of these cells had significant activities of the enzymes PHB synthase, beta-ketothiolase, and NADPH-dependent acetoacetyl-CoA reductase. Therefore, PP1 most probably encodes all three genes of the PHB-synthetic pathway in A. eutrophus. In addition to PHB-negative mutants, we isolated mutants which accumulate PHB at a much lower rate than the wild type does. These PHB-leaky mutants exhibited activities of all three PHB-synthetic enzymes; Tn5-mob had not inserted into PP1, and the phenotype of the wild type could not be restored with fragment PP1. The rationale for this mutant type remains unknown.

Histopathological classification of nonantral gastric endocrine growths in man.

Abstract: Recently, the gastric endocrine system has been recognized as the origin of benign and malignant tumors in pernicious anemia. It has also been found that the gastric endocrine cells respond to permanent elevation of serum gastrin levels induced by changes in acid secretion in response to surgical procedures, drug therapy and age. Therefore, a definition of nonantral gastric endocrine hyperplasia (simple or diffuse, linear or chain-forming, micronodular, adenomatoid), dysplasia (enlarging or fusing micronodules, microinvasion, nodular growth) and neoplasia (intramucosal carcinoid, invasive carcinoid) is presented. The individual entities are illustrated, together with the literature discussed and the techniques for their identification presented.

Aluminum toxicity and forest decline.

Abstract: The rate of root elongation in seedlings of Picea abies was drastically inhibited by exposure to AlCl3 at 800 or 1200 μmol/dm3 in nutrient solutions. A 35-day exposure to Al at 700 μmol/dm3 reduced Mg and Ca in roots and needles of the seedlings. The Mg content of needles was reduced to levels considered to be critical for Mg deficiency. In investigations of 45Ca uptake into roots, exposure to Al at 100-800 μmol/dm3 reduced 45Ca uptake by 77-92%, respectively. By using x-ray microanalysis, the distribution of Al, Mg, Ca, and K was found to be similar in roots of Picea abies seedlings grown in solution culture and in roots collected from declining spruce stands at Solling, F.R.G. In solution culture Al displaced Mg and Ca in the root cortex. A mechanism of Al toxicity for root growth and ion uptake is proposed, and its relevance to forest decline is discussed.

Coarse control of sucrose-phosphate synthase in leaves: Alterations of the kinetic properties in response to the rate of photosynthesis and the accumulation of sucrose

Abstract: It has been investigated whether diurnal rhythms of sucrose-phosphate synthase (SPS) are involved in controlling the rate of photosynthetic sucrose synthesis. Extracts were prepared from spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) leaves and assayed for enzyme activity. The activity of SPS increased in parallel with a rising rate of photosynthesis, and was increased by feeding mannose and decreased by supplying inorganic phosphate. In leaf material where sucrose had accumulated during the photoperiod or when sucrose was supplied exogenously, SPS activity decreased. During a diurnal rhythm, SPS activity increased after illumination, declined gradually during the light period, decreased further after darkening and then recovered gradually during the night. These changes did not involve an alteration of the maximal activity, but were caused by changes in the kinetic properties, revealed as a change in sensitivity to inhibition by inorganic phosphate. In experiments which modelled the response of SPS to changing metabolite concentrations, it was shown that these alterations of kinetic properties would strongly modify the activity of SPS in vivo. It is proposed that SPS can exist in kinetically distinct forms in vivo, and that the distribution between these forms can be rapidly altered. As the rate of photosynthesis increases there is an activation of SPS, which may be directly or indirectly linked to changes in the availability of Pi. This activation can be modified by factors related to the accumulation of sucrose. Under normal conditions there is a balance between these factors, and the leaf contains a mixture of the different forms of SPS.

Alloxan: history and mechanism of action.

Abstract: Revue sur l'alloxane synthetisee en 1838 et dont l'action diabetogene suspectee depuis 1926 a ete publiee en 1943

Expression of extracellular acid proteinase by proteolytic Candida spp. during experimental infection of oral mucosa.

Abstract: We traced an acid proteinase from Candida spp. in the initial stages of the pathogenesis of the mycosis. On infection of human buccal mucosa, proteinase antigens were detected by immuno-scanning electron microscopy on the surface of adhering blastoconidia and invading filamentous cells of C. albicans serotype A. Proteinase antigens were also present on blastoconidia of C. albicans serotype B, but were missing on filamentous cells of this serotype. Proteolytic isolates of C. tropicalis behaved like C. albicans serotype A. An isolate of C. parapsilosis did not express the proteinase antigen under conditions of this study. After infection of mucosa, culture medium of C. albicans or C. tropicalis showed a time-dependent accumulation of acid proteolytic activity, indicating that the visualized antigens represent active proteinase. No such activity was detected in the medium of C. parapsilosis. Preliminary experiments with the proteinase inhibitor pepstatin A revealed an 89% reduction of mucosal adherence of C. albicans (serotype A). These results suggest that Candida proteinase is involved in fungal attachment. The pattern of adherence reflects the differential expression of secretory proteinase by different candidal strains. Images

Effects of a protein phosphatase inhibitor, okadaic acid, on membrane currents of isolated guinea-pig cardiac myocytes

Abstract: The effects of a protein phosphatase inhibitor, okadaic acid (OA), were studied on membrane currents of isolated myocytes from guinea-pig cardiac ventricle. The whole-cell Ca2+ current (I Ca) was recorded as peak inward current in response to test pulse to O mV. Extracellular application of OA (5–100μM) produced an increase ofI Ca. The effect was markedly enhanced when the myocyte was pretreated with threshold concentrations of isoprenaline.I Ca was increased from 11.3±0.8μA cm−2 to 19.0±1.1μA cm−2 (n=4) by 5μM-OA in the presence of 1nM-isoprenaline. The delayed rectifier current was also slightly increased. Furthermore, the wash-out time of the β-adrenergic increase ofI Ca was markedly prolonged by OA. The β-adrenergic stimulation of cardiac Ca2+ current is thought to be mediated by cAMP-dependent phosphorylation. The present results strongly suggest that the effect of OA onI Ca is related to inhibition of endogenous protein phosphatase activity which is responsible for the dephosphorylation process. By the isotope method, the inhibitory effect of OA on different types of phosphatase was compared. OA had a relatively high specificity to type 1-, and type 2A-phosphatases.

Concentration-dependent effects of tolbutamide, meglitinide, glipizide, glibenclamide and diazoxide on ATP-regulated K+ currents in pancreatic B-cells.

Abstract: The influence of the hypoglycemic drugs tolbutamide, meglitinide, glipizide and glibenclamide on ATP-dependent K+ currents of mouse pancreatic B-cells was studied using the whole-cell configuration of the patch-clamp technique. In the absence of albumin, tolbutamide blocked the currents half maximally at 4.1 mumol/l. In the presence of 2 mg/ml albumin half maximal inhibition of the currents was observed at 2.1 mumol/l meglitinide, 6.4 nmol/l glipizide and 4.0 nmol/l glibenclamide. The hyperglycemic sulfonamide diazoxide opened ATP-dependent K+ channels. Half maximally effective concentrations of diazoxide were 20 mumol/l with 0.3 mmol/l ATP and 102 mumol/l with 1 mmol/l ATP in the recording pipette. Thus, the action of diazoxide was dependent on the presence of ATP in the recording pipette. The free concentrations of the drugs which influenced ATP-dependent K+ currents were comparable with the free plasma concentrations in humans and the free concentrations which affected insulin secretion in vitro. The results support the view that the target for the actions of sulfonylureas and of diazoxide is the ATP-dependent K+ channel of the pancreatic B-cell or a structure closely related to this channel.

Transcranial magnetic stimulation of the human brain: responses in muscles supplied by cranial nerves

Abstract: The present investigation demonstrates that time-varying magnetic fields induced over the skull elicit distinct types of responses in muscles supplied by the cranial nerves both on the ipsilateral and the contralateral side. When the center of the copper coil was positioned 4 cm lateral to the vertex on a line from the vertex to the external auditory meatus, bilateral responses in the masseter, orbicularis oculi, mentalis, and sternocleidomastoideus muscles with a delay of about 10 to 14 ms after the stimulus occurred. Similar to the transcranially evoked muscle responses in hand muscles, the responses in the cranial muscles can be influenced in latency and amplitude by background excitation. It is concluded that these responses are induced by excitation of the face-associated motor cortex followed by multiple I-waves in the corticonuclear tract with both ipsilateral and contralateral projections to the corresponding motoneurones. Additionally, at higher stimulation strengths "short-latency" ipsilateral responses in muscles supplied by the trigeminal, facial, and accessory nerves occurred which we suggest are induced by direct stimulation of the peripheral cranial nerves in their intracisternal course. The present study confirms the bilateral projection of corticonuclear tracts in awake unanesthetised human subjects which has been observed by electrical stimulation on the exposed cortex during surgical procedures already decades ago. The present investigation will serve as a basis for the assessment of pathophysiological mechanisms involving the corticonuclear system or the peripheral cranial nerves in their proximal parts in awake humans.

Forest canopy transformation of atmospheric deposition

Abstract: Solute fluxes to the ground in open plots and under the forest canopy of different species were investigated in a number of long-term ecosystem studies in West Germany. From the canopy flux balance, rates of interception deposition and canopy/deposition interactions were assessed. Chemically, both open precipitation and throughfall are dilute solutions of H2SO4 and HNO3 and their salts. For the sites investigated, mean pH in bulk precipitation ranged from 4.1 to 4.6, and in throughfall from 3.4 to 4.7. The increase in acidity after canopy passage at most sites indicates considerable interception deposition of strong acids to the forest stands, exceeding the rate of H+ buffering in the canopy.

The function of auditory neurons in cricket phonotaxis

Abstract: In order to examine the role of particular identified auditory neurons of the cricket,Gryllus bimaculatus, in orientation to a sound source, a method has been developed by which intracellular recordings can be made while the animal walks on an air-suspended sphere, which is rotated by the leg movements (Fig. 1). The angular velocities of sphere rotation were found to depend on the direction of incident sound, on its intensity and frequency and on the temporal pattern of the sound stimulus (Figs. 2, 3). While the cricket was walking, auditory neurons discharged extra action potentials, not correlated with the sound stimulus, and the neuronal response to the sound itself was reduced (Figs. 4, 5). Suppressing the spike activity by hyperpolarization of a local neuron in the prothoracic ganglion (ON1) reduced in some animals the tendency to turn toward the sound source on the side of the ear that excites the ON1 (Figs. 6–8). Hyperpolarization of a neuron that ascends from the prothoracic ganglion into the brain (AN1), while sound was presented to the ear that excites this neuron, caused all animals to reverse direction; that is, they turned away from the sound source and from the side of the inactivated AN1 (Figs. 9, 10). Hyperpolarization of another ascending neuron (AN2) caused a reduction in turning velocity in half of the animals; but this effect occurred only with high sound pressure levels, and the direction of walking was not reversed (Figs. 11, 12). From the influences on turning tendency observed in these experiments, it appears that the paired AN1s (and possibly the AN2s at high intensities) may provide inputs to a central comparator that dictates turning tendency in phonotaxis.

Neurotrophic effects of GABA in cultures of embryonic chick brain and retina.

Abstract: The present study examined whether GABA treatments would affect the growth and development of embryonic chick cortical and retinal neurons in culture. Incubation of these cells in the presence of 10(-5) M GABA produced several responses. It promoted the proliferation and the differentiation of the neurons studied by affecting the length and branching of the neurites as well as synaptogenesis, as revealed by morphometric measures. At the ultrastructural level, GABA treatment also led to an increased density of neurotubules, rough endoplasmic reticulum (RER), Golgi apparatus, coated vesicles, and other vesicles. These data support the hypothesis that GABA functions as a trophic or regulatory factor of at least certain neuron types.

Receptors for glucagon-like peptide-1(7–36) amide on rat insulinoma-derived cells

Abstract: Specific binding of 125I-labelled glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) to rat insulinoma-derived RINm5F cells was dependent upon time and temperature and was proportional to cell concentration. Binding of radioactivity was inhibited in a concentration-dependent manner by GLP-1(7-36) amide consistent with the presence of a single class of binding site with a dissociation constant (Kd) of 204 +/- 8 pmol/l (mean +/- S.E.M.). Binding of the peptide resulted in a dose-dependent increase in cyclic AMP concentrations (half maximal response at 250 +/- 20 pmol/l). GLP-1(1-36)amide was approximately 200 times less potent than GLP-1(7-36)amide in inhibiting the binding of 125I-labelled GLP-1(7-36)amide to the cells (Kd of 45 +/- 6 nmol/l). Binding sites for GLP-1 (7-36)amide were not present on dispersed enterocytes from porcine small intestine.

Evaluation of intracranial pressure from transcranial Doppler studies in cerebral disease

Abstract: The extent to which estimations of intracranial pressure can be derived from intracranial flow patterns was studied. The blood flow velocity in the middle cerebral artery was recorded with the EME TC 2–64 transcranial Doppler (TCD) device in 26 patients suffering from various severe cerebral diseases. Simultaneously the mean intracranial pressure (ICP) was measured by means of an epidural device. Arterial carbon-dioxide tensions were monitored by blood gas analysis. In all patients it was observed that the middle cerebral artery flow patterns changed distinctly when the ICP increased; these changes were distinguished by a decrease of the mean flow velocity and an increase of the Pourcelot index. A good correlation between the ICP and the flow parameters (especially the product mean systemic arterial pressure × Pourcelot index/mean flow velocity) was found in a select group of 13 patients, in whom comparable initial conditions existed and in whom additional parameters influencing the TCD recordings could be kept constant (r=0.873; P<0.001).

Long-term omeprazole treatment in man: effects on gastric endocrine cell populations.

Abstract: 36 patients with chronic gastric or oesophageal peptic ulceration (including 6 with antrectomy), resistant to high-dose ranitidine treatment for at least 3 months, were successfully treated with 40-60 mg of omeprazole daily for periods between 1 and 2 years. Fasting serum gastrin levels were monitored at regular intervals during therapy and multiple gastric mucosal biopsies were taken during gastroscopy every 3-6 months. Gastrin levels increased significantly during the first 6 months of therapy from a medium level of 81.5 to 206 pg/ml, a slight decrease was seen thereafter. In 10 patients investigated before the start of the treatment and after 1 and 2 years, the volume density of argyrophilic cells in the oxyntic mucosa increased from 0.43 +/- 0.08 to 0.91 +/- 0.14% during the first year; this change was statistically significant. No further increase was observed thereafter. No such difference could be demonstrated between a larger group of 18 patients investigated before and after 1 year of treatment with omeprazole (0.806 +/- 0.1 vs. 0.93 +/- 0.08%) and between a larger group of 22 untreated patients and 17 patients treated for 17-24 months with omeprazole (0.73 +/- 0.1 vs. 0.86 +/- 0.09%). The volume density of argyrophilic cells found in 8 patients with gastrinoma amounted to 1.37 +/- 0.22%. No clusters of endocrine cells were found in omeprazole-treated patients. The D cell volume density in the antral mucosa decreased significantly during the first months of treatment, but steadily increased thereafter to reach pretreatment values after 17 months. There was no change in G cell volume density under therapy. No changes in gastrin levels or oxyntic argyrophilic cells were observed in the antrectomized patients. It is concluded that the hyperplasia of argyrophilic cells observed in some patients during long-term omeprazole treatment is mediated by hypergastrinaemia.

Neuropeptide-gamma: a peptide isolated from rabbit intestine that is derived from gamma-preprotachykinin.

Abstract: The neurokinin A-like immunoreactivity in an extract of rabbit small intestine was resolved into two molecular forms by gel permeation chromatography. These components were purified to apparent homogeneity by reverse-phase HPLC. The primary structure of the larger component was established as the following: Asp-Ala-Gly-His-Gly-Gln-Ile-Ser-His-Lys-Arg-His-Lys-Thr-Asp-Ser-Phe-Val- Gly-Leu - Met.NH2. This amino acid sequence represents residues (72-92) of gamma-preprotachykinin, as predicted from the nucleotide sequence of a cloned cDNA from the rat. The peptide, termed neuropeptide-gamma, lacks residues (3-17) of neuropeptide K, and this segment is specified exactly by exon 4 in the preprotachykinin gene. The smaller form of neurokinin A-like immunoreactivity was identical to neurokinin A. Neuropeptide K was not present in the extract, demonstrating that the pathways of post-translational processing of beta- and gamma-preprotachykinins in the rabbit gut are different.

Dimensional analysis of nonlinear oscillations in brain, heart, and muscle

Abstract: We present some numerical studies on the dimensional analysis of temporal oscillations observed in human electroencephalograms (EEG), heart rates, and muscle tremors. We show that it is insufficient to characterize the individual system by a single dimension value alone. We also present some detailed numerical analysis of the scaling structure of the attractors reconstructed from the time signal. Our methods are based on the concept of local gauge functions, which we derive from the raw signals and from transformed signals obtained through singular value decomposition. We are able to confirm and improve earlier results on the change of dimensionality of EEG signals. For heart rates we observe an increase of the dimensional complexity during sleep, and for muscle tremor data we find significant changes in the dimensionality depending on the isometrical contraction of the muscle. We attempt to indicate which factors are important in determining dimension estimates and where specific problems lie in each of the examples.

Eubacterium acidaminophilum sp. nov., a versatile amino acid-degrading anaerobe producing or utilizing H2 or formate: description and enzymatic studies

Abstract: An obligately anaerobic, rod-shaped bacterium was isolated on alanine in co-culture with H2-scavenging Desulfovibrio and obtained in pure culture with glycine as sole fermentation substrate. The isolated strain, al-2, was motile by a polar to subpolar flagellum and stained Gram-positive. The guanine plus cytosine content of the DNA was 44.0 mol%. Strain al-2 grew in defined, reduced glycine media supplemented with biotin. The pure culture fermented 4 mol glycine to 3 mol acetate, 4 mol ammonia and 2 mol CO2. Under optimum conditions (34°C, pH 7.3), the doubling time on glycine was 60 min and the molar growth yield 7.6 g cell dry mass. Serine was fermented to acetate, ethanol, CO2, H2 and ammonia. In addition, betaine, sarcosine or creatine served as substrates for growth and acetate production if H2, formate or e.g. valine were added as H-donors. In pure culture on alanine under N2, strain al-2 grew very poorly and produced H2 up to a partial pressure of 3.6 kPa (0.035 atm). Desulfovibrio species, Methanospirillum hungatei and Acetobacterium woodii served as H2-scavengers that allowed good syntrophic growth on alanine. The co-cultures also grew on aspartate, leucine, valine or malate. Alanine and aspartate were stoichiometrically degraded to acetate and ammonia, whereas the reducing equivalents were recovered as H2S, CH4 or newly synthetized acetate, respectively. Growth of strain al-2 in co-culture with the hydrogenase-negative, formate-utilizing Desulfovibrio baarsii indicated that a syntrophy was also possible by interspecies formate transfer. Growth on glycine, or on betaine, sarcosine or creatine (plus H-donors) depended strictly on the addition of selenite (≥0.1 μM); selenite was not required for fermentation of serine, or for degradation of alanine, aspartate or valine by the co-cultures. Cell-free extracts of glycine-grown cells contained active glycine reductase, glycine decarboxylase and reversible methyl viologen-dependent formate dehydrogenase in addition to the other enzymes necessary for an oxidation to CO2. In all reactions NADP was the preferred H-carrier. Both formate and glycine could be synthesized from bicarbonate. Serine-grown cells did not contain serine hydroxymethyl transferase but serine dehydratase and other enzymes commonly involved in pyruvate metabolism to acetate, CO2 and H2. The enzymes involved in glycine metabolism were repressed during growth on serine. By its morphology and physiology, strain al-2 did not resemble described amino acid-degrading species. Therefore, the new isolate is proposed as type strain of a new species, Eubacterium acidaminophilum.

Metabolic zonation of liver parenchyma.

Abstract: Periportal and perivenous hepatocytes differ in their content of enzymes and subcellular structures and thus in their metabolic capacities. Therefore, the model of metabolic zonation proposes that: (1) periportal hepatocytes catalyze predominantly oxidative energy metabolism with beta-oxidation and amino acid catabolism as well as ureagenesis for glycogen synthesis and glucose release, bile formation with cholesterol synthesis and protective metabolism; and (2) perivenous hepatocytes mediate preferentially glucose uptake for glycogen synthesis, glycolysis, and liponeogenesis as well as ketogenesis, glutamine formation, and xenobiotic metabolism. Periportal and perivenous hepatocytes are under the control of a different input of humoral and nervous signals, because concentration gradients of oxygen, substrates, and hormones are established during passage of blood through the liver and because gradients of nerve densities seem to exist. In periportal and perivenous hepatocytes gene expression can be different due to the zonal gradients in oxygen and hormone concentrations as well as nerve densities. The functional specialization of periportal and perivenous hepatocytes has been demonstrated especially well for carbohydrate, amino acid and ammonia, and xenobiotic metabolism as well as for bile formation by different techniques: Calculation of metabolic rates based on the zonal distributions of enzymes and metabolites, measurements of rates in periportal-like and perivenous-like hepatocytes in cell culture and in hepatocyte populations enriched in periportal and perivenous cells as well as in perfused livers during orthograde and retrograde flow using standard methods and noninvasive techniques with surface microlight guides and miniature oxygen electrodes.

Effect of mulch rates and tillage systems on infiltrability and other soil physical properties of an Oxisol in Paraná, Brazil☆

Abstract: A 7-year-old tillage trial, comprising conventional tillage (CT), minimum tillage (MT) and no-tillage (NT), was chosen to study the relative importance of controlled mulch rates and soil physical properties such as bulk density, pore volume and hydraulic conductivity upon infiltrability. Infiltration measurements were carried out with a portable rainfall simulator. Mulch consisted of soya bean residues. Soil physical analysis showed higher bulk densities in the top 20 cm under NT, whereas CT, and to a lesser extent MT, led to the development of a plough pan in 20–30 cm depth. At the same time, compaction brought about a decrease in macropores and an increase in micropores. Total porosity ranged between 56.6% and 66.4%. Hydraulic conductivity did not differ significantly between tillage systems, and overall conductivity values were very high. The main factor influencing infiltrability was the formation of a surface seal depending on the degree of soil cover by mulch, irrespective of tillage system. For all 3 tillage systems, a 100% soil cover led to the complete infiltration of a 60-mm rainfall, whereas only 20% of the applied rain infiltrated when the soil was bare and the surface completely sealed. Plant residues of 4–6 t ha −1 are proposed, as the minimum amount of mulch needed to reduce runoff and erosion effectively.

An Introduction to the Theory of the Riemann Zeta-Function

Abstract: 1. Historical introduction 2. The Poisson summation formula and the functional equation 3. The Hadamard product formula and 'explicit formulae' of prime number theory 4. The zeros of the zeta function and the prime number theorem 5. The Riemann hypothesis and the Lindelof hypothesis 6. The approximate functional equation Appendix 1. Fourier theory 2. The Mellin transform 3. An estimate for certain integrals 4. The gamma function 5. Integral functions of finite order 6. Borel-Caratheodory theorems 7. Littlewood's theorem.

Human lysosomal acid phosphatase is transported as a transmembrane protein to lysosomes in transfected baby hamster kidney cells.

Abstract: BHK cells transfected with human lysosomal acid phosphatase (LAP) cDNA (CT29) expressed 70-fold higher enzyme activities of acid phosphatase than non-transfected BHK cells. The CT29-LAP was synthesized in BHK cells as a heterogeneously glycosylated precursor that was tightly membrane associated. Transfer to the trans-Golgi was associated with a small increase in size (approximately 7 kd) and partial processing of the oligosaccharides to complex type structures. CT29-LAP was transferred into lysosomes as shown by subcellular fractionation, immunofluorescence and immunoelectron microscopy. Lack of mannose-6-phosphate residues suggested that transport does not involve mannose-6-phosphate receptors. Part of the membrane-associated CT29-LAP was processed to a soluble form. The mechanism that converts CT29-LAP into a soluble form was sensitive to NH4Cl, and reduced the size of the polypeptide by 7 kd. In vitro translation of CT29-derived cRNA in the presence of microsomal membranes yielded a CT29-LAP precursor that is protected from proteinase K except for a small peptide of approximately 2 kd. In combination with the sequence data available for LAP, these observations suggest that CT29-LAP is synthesized and transported to lysosomes as a transmembrane protein. In the lysosomes, CT29-LAP is released from the membrane by proteolytic cleavage, which removes a C-terminal peptide including the transmembrane domain and the cytosolic tail of 18 amino acids.