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H J Sips

Publications and source records attributed to H J Sips.

29 records · Page 2Linked to original sources
PubMed1981

Mechanism of the bactericidal action of myeloperoxidase: increased permeability of the Escherichia coli cell envelope.

The killing of Escherichia coli by isolated human myeloperoxidase plus hydrogen peroxide plus chloride ions was shown to proceed via an increased permeability of the bacterial cell wall. A correlation between the extent of the increased permeability and the number of surviving colony-forming units was found (P less than 0.0005). The same phenomenon was observed with isolated human neutrophils. The permeability increase was shown to be limited, because low-molecular-weight substrate became freely permeant, but the bacteria retained their permeability barrier for protein. Furthermore, disruption of the permeability barrier was followed by destruction of cytoplasmic protein. The active antibacterial agent was probably hypochlorous acid, the direct product of the system, rather than singlet oxygen, the nonenzymic product of hypochlorous acid and hydrogen peroxide. This is concluded from the fact that the myeloperoxidase system could be mimicked by hypochlorous acid, whereas conditions that favor formation of singlet oxygen did not enhance this effect. The relevance of the system for killing of bacteria at neutral pH is discussed.

Cell Membrane Permeability↗
PubMed1980

Heterogeneous distribution of the sodium-dependent alanine transport activity in the rat hepatocyte plasma membrane.

The localization of the sodium-dependent alanine uptake activity in rat liver cells was studied. Fractions representative of the canalicular, the contiguous (lateral) and the blood-sinusoidal surface of the hepatocyte were isolated by means of centrifugal fractionation and density gradient centrifugation. The distribution of various marker-enzyme activities in conjunction with the occurrence of alanine transport activity was studied both in fractions obtained after zonal density gradient centrifugation, and in the subcellular fractions mentioned above. It is concluded that the sodium-dependent alanine transport activity is primarily located in the blood-sinusoidal plasma membrane of the hepatocyte.

Alanine↗
PubMed1980

Amino acid transport in plasma-membrane vesicles from rat liver. Characterization of L-alanine transport.

Plasma-membrane vesicles, isolated from rat liver, catalyze active transport of L-alanine. The transient accumulation of L-alanine requires the presence of Na+ concentration gradient (outside greater than inside). The alanine-Na+ symport is an electrogenic process, since it is stimulated under conditions that allow compensatory ion movements: both co-transported anions as well as counter-transported cations influence the rate of alanine-Na+ symport. However, no uptake is observed in the presence of a membrane potential, when no Na+ concentration gradient is present. Sodium-gradient-stimulated alanine uptake is dependent on temperature and pH, stereospecific, and is affected by the presence of other amino acids. The activity of the L-alanine transport system is influenced both by the Na+ and by the L-alanine concentration. In the presence of 100 mM Na+, an apparent Km for alanine of 2 mM is observed; lowering the Na+ concentration results in an increase in the apparent Km, and a decrease in the apparent V. The apparent Km for Na+ is 34 mM in the presence of 0.2 mM L-alanine. Increasing the L-alanine concentration also results in a lower apparent Km for Na+, and a higher V.

Alanine↗
PubMed1979

Uncoupling action of amytal in membrane vesicles from Escherichia coli.

The barbiturate amytal (5-ethyl-5-isopentylbarbituric acid) has been shown to inhibit amino acid transport in membrane vesicles from anaerobically grown Escherichia coli. Amytal has no effect on the activity of the enzymes of the nitrate respiration system, nor on electron transfer in this system. However, addition of amytal to the membrane vesicles results in a decrease of the membrane potential from -90 mV to -72 mV, and to a decrease of the pH-gradient of -61 mV to undetectable values. Furthermore, amytal causes an increase in the rate of ferricyanide reduction in liposomes, indicating that amytal increases the proton permeability of phospholipid membranes. These results demonstrate that amytal acts as an uncoupler in membrane vesicles from anaerobically grown E. coli.

Aerobiosis↗
PubMed1979

The amino acid sequence of hamster pancreatic ribonuclease.

The amino acid sequence of golden hamster pancreatic ribonuclease was determined by analysis of tryptic, chymotryptic, thermolytic, and CNBr peptides and by automatic sequence analysis of the intact protein. Like all RNases with an Asn-Met-Thr sequence at positions 34-36, hamster RNase is glycosylated at position 34 with a complex-type carbohydrated chain. Val-17, Ala-18, His-55, His-76 and Ala-90 have never been observed in other pancreatic RNases. Ala-90 replaces Ser-90, which had been invariant in all mammalian RNases studied so far. The amino acid sequence of hamster RNase differs at 15 positions from that of another Cricetidae rodent, the muskrat. The similarity between both ribonucleases was used to confirm a few less certain parts of the muskrat RNase sequence. The replacement rate of the RNases of the Cricetidae appeared to be higher than the average rate in the mammals, but much lower than the rate in another myomorph family, the Muridae (mouse and rat). Possibly, in many respects, the Cricetidae underwent less evolutionary change in recent times than the evolutionarily highly successful Muridae.

Amino Acid Sequence↗
PubMed1978

Sodium-dependent alanine transport in plasma-membrane vesicles from rat liver.

L-Alanine transport was studied in plasma-membrane vesicles from rat liver. A gradient of NaSCN, but not of KSCN, stimulated alanine uptake. Monensin plus carbonyl cyanide p-trifluoromethoxyphenylhydrazone abolished the observed overshoot in uptake. After equilibration of alanine, NaSCN induced uphill transport.

Alanine↗
PubMed1976

Active transport by membrane vesicles from anaerobically grown Escherichia coli energized by electron transfer to ferricyanide and chlorate.

Active transport of amino acids by membrane vesicles from Escherichia coli, grown anaerobically on glucose in the presence of nitrate, can be energized under anaerobic conditions by electron transfer in the nitrate respiration system with formate as electron donor and nitrate as acceptor. A high rate of amino acid transport is also obtained under anaerobic conditions by electron transfer from formate to the nitrate analogue chlorate or to the membrane-impermeable electron acceptor ferricyanide. Electron transfer from formate to nitrate results in the generation of an electrical potential as is indicated by the uptake of the lipophilic cation triphenylmethylphosphonium. Ferricyanide accpets electrons from at least two sites of the nitrate respiration system. One of these sites appears to be nitrate reductase, because cytochrome b, reduced by formate, is completely reoxidized by ferricyanide and glutamate transport energized by formate plus ferricyanide and formate plus nitrate are affected by the same electron transfer inhibitors. A second site of electron transfer to ferricyanide appears to be located prior to nitrate reductase in the nitrate respiration system, since formate is oxidized at a higher rate in the presence of ferricyanide than with nitrate while formate/ferricyanide energizes transport of amino acids at a lower rate than formate/nitrate. Moreover, electron transfer inhibitors block electron transfer from formate to nitrate to a significantly higher extent than from formate to ferricyanide. The effects of irradiation of the membrane vesicles with near ultra-violet light suggest that quinones play an essential role in the electron transfer from formate to nitrate or ferricyanide. Irradiation blocks completely formate-dependent nitrate and ferricyanide reduction and active transport driven by formate/nitrate and formate/ferricyanide, but has hardly any effect on the activity of formate dehydrogenase and on ascorbate/phenazine methosulphate/oxygen-driven transport. Similar effects of ferricyanide have been observed in membrane vesicles from E. coli, grown anaerobically in the presence of fumarate. In these membrane vesicles a high rate of lactose and triphenylmethylphosphonium uptake under anaerobic conditions is obtained by electron transfer from glycerol 1-phosphate to fumarate and also to ferricyanide and evidence has been presented for the involvement of cytochromes in these electron transfers.

Amino Acids↗
PubMedDate not supplied

Prenatal detection of cystic fibrosis; comparative study of maltase and alkaline phosphatase activities in amniotic fluid.

The potential value of microvillar enzymes in the prenatal diagnosis of cystic fibrosis (CF) has previously been demonstrated and is corroborated in the present comparative study. Maltase and alkaline phosphatase (ALP) activities were studied in the amniotic fluids of 57 pregnancies with a 1 in 4 risk for CF or with a known CF outcome and in 489 controls. A simple assay for maltase activity (MU-maltase) with the fluorogenic substate 4-methylumbelliferyl alpha-glucoside, offers great technical advantages and an at least equal detection rate of CF, when compared to the previously used test with maltose as substrate. Intestinal ALP was estimated either as phenylalanine inhibitable activity (PI-ALP) or as the proportions of residual activity in the presence of the inhibitors phenylalanine or homoarginine. MU-maltase and PI-ALP appeared the most successful methods: both tests were able to detect 14 of the 16 (88 per cent) pregnancies with fetal CF. Each of the two tests alone also allowed a correct prediction in 24 of the 25 pregnancies at risk but with normal outcome; however all 25 cases could be correctly predicted by a combined evaluation. It is suggested that more than one intestinal enzyme activity should be evaluated to allow optimal results in the prenatal monitoring of pregnancies at high risk for CF.

Alkaline Phosphatase↗