Reconstitution into liposomes of the Na+-dependent transport systems for cyclacillin,an aminopenicillin,from brush border membranes of rat small intestine

Triton X-100 extract from brush border membranes of rat small intestine was recombined with egg phosphatidylcholine liposomes by the freeze-thaw sonication method. The treated liposomes showed a Na⁺-dependent uptake of cyclacillin, which was inhibited by a low concentration of mercuric ions and L-phenylalanylglycine, but not by glycine. These are consistent with the absorption characteristics of the antibiotic in situ and indicate that reconstitution of the Na⁺-dependent active cyclacillin transport system of rat small intestine has been achieved.     

Mineral nutrition, of cultured chlorophyllous cells of tobacco VII. Effects of the NH4/NO3 ratio and of Cl in the media on the growth and ionic balance of cells

NG, a strain of cultured tobacco cells of Nicotiana glutinosahad high growth rates and carboxylate contents (C—A) of100 to 130 meq/100 g of dry cells on media containing 42 meqNO₃/liter as the sole N source. (C—A) is the amount ofinorganic cations minus inorganic anions in meq per 100 g ofdry cells. NG, cultured on media containing NH₄ 10+NO₃ 42 in meq/liter,had lower growth rates and lower (C—A) values as comparedwith NG on media containing NO₃ as the sole N source. NG, cultured on media containing NH₄ 30+NO₃ 42 in meq/liter,had high growth rates and (A—C) values of 22 to 53 meq/100gof dry cells. In this case, the (A—C) content may correspondto organic cations, basic organic N compounds such as free asprotein-bound basic amino acids. The easily absorbed Cl mayhave been required maintain good growth conditions such as ionicbalance and a favorable pH in the cells. Thus cultured cells of Nicotiana glutinosa may have physiologicaladaptability against variations in a relatively wide range of|C—A| contents [|C—A| being the absolute valuesof (C—A)]. (Received May 15, 1980; )     

Effect of fatty acids and monoglycerides on permeability of lipid bilayer

The effect of fatty acids and monoglycerides on barrier properties of liposomal membranes prepared from egg phosphatidylcholine was investigated. The incorporation of these lipids as liposomal membrane components induced the alteration of the permeability to less permeable liposomally entrapped drugs, sulfanilic acid and procainamide ethobromide (PAEB). Monoolein caused greatly increased permeability of both drugs and unsaturated fatty acids markedly enhanced the release rate of PAEB, while saturated fatty acids caused a small increase in the release rate.Electron spin resonance (ESR) investigation with 5-nitroxide stearic acid showed that fatty acids disordered the hydrophobic region of the lipid bilayer and the disordering effect of unsaturated fatty acids was greater than that of saturated ones. It was demonstrated that the incorporated fatty acids and monoglycerides interacted with the polar region of the membranes by ESR study with cholestane label and ¹H-NMR study. These results indicated that the increase in the membrane permeability caused by fatty acids and monoglycerides associated with the disorder in the membranes' interior and the interaction of the incorporated lipid with the polar head group of phospholipid.     

Nitrate and nitrite in interstitial waters of eelgrass beds in relation to the rhizosphere

The distribution of nitrate and nitrite in the interstitial water of the sediment of eelgrass (Zostera marina) bed of Izembek Lagoon, Alaska, were investigated. Their concentrations were relatively high (0 to 9.8 μg-at.N·1^?1, average 4.8 for nitrate; 0 to 4.0 μ-at.N·1^?1, average 1.9 for nitrite) although the sediments were anoxic and contained hydrogen sulphide. The rates of bacterial denitrification measured by ¹⁵N tracer technique ranged from 0.49×10^?10 to 1.2 × 10^?9 g-atN·g^?1·h^?1. When a steady state is maintained, the loss of nitrate and nitrite must be balanced by their production by bacterial nitrification. Experimentally determined rate of nitrification in the sediment was of the same order. A model experiment demonstrated that oxygen is transported from leaves to rhizomes and roots of eelgrass and released into the sediment. The oxygen is used for nitrification in the rhizosphere in anoxic sediments.     

Mineral nutrition of cultured chlorophyllous cells of tobacco IV. Kinetic studies of K and Mg uptake by the cells

1. When applying the adsorption theory to the selectivity coefficient,K and Mg uptakes by cells in a K-Mg replacement series of mediaare not regulated only by a common mechanism, under the assumptionthat b values, which indicate the affinities between the ionand the adsorptive surface, do not change.
2. Regulation of Kand Mg uptakes by a common multiphasic mechanismin the cellsis possible when the selectivity coefficient b_K/b_Mgvaries inverselywith the M_K/M_Mg ratio in the external medium.
3. K and Mg uptakesare not regulated only by their respectivesingle specific mechanisms.
4. Another possibility is regulation of K and Mg uptakes bothbycommon and specific mechanisms. The common mechanism maybemultiphasic.

(Received December 2, 1975; )     

A Nosema species of the Egyptian cotton leafworm, Spodoptera litura (Lepidoptera): Its morphology,development, host range,and taxonomy

A microsporidian was isolated from the Egyptian cotton leafworm, Spodoptera litura, and was identified as a member of the genus Nosema since its sporont produced two spores. The size of the fresh spores was 3.3–4.5 × 1.7 – 2.2 μm. Mean length of the polar filaments was 90.7 μm. In addition to the Egyptian cotton leafworm, this microsporidian was also infectious to Pieris rapae crucivora, Hyphantria cunea, Chilo suppressalis, Agrotis ipsilon, and Adoxophyes orana. Although the parasite ultimately caused generalized infection in the Egyptian cotton leafworm larva, the main site of infection was the adipose tissue.     

l-2-Amino-4-methylpimelic acid: A new amino acid from Lactarius species

A PC survey revealed the occurrence of an unusual amino acid in fruit bodies of the mushroom Lactarius quietus Fr. and a related species. This was identified as l-2-amino-4-methylpimelic acid, which has not been previously reported as a naturally occurring compound.     

Integration mechanism of molecular rhythm in biological clock

Sleep and Biological Rhythms -     

Local caspase activation interacts with Slit-Robo signaling to restrict axonal arborization

In addition to being critical for apoptosis, components of the apoptotic pathway, such as caspases, are involved in other physiological processes in many types of cells, including neurons. However, very little is known about their role in dynamic, nonphysically destructive processes, such as axonal arborization and synaptogenesis. We show that caspases were locally active in vivo at the branch points of young, dynamic retinal ganglion cell axonal arbors but not in the cell body or in stable mature arbors. Caspase activation, dependent on Caspase-3, Caspase-9, and p38 mitogen-activated protein kinase (MAPK), rapidly increased at branch points corresponding with branch tip addition. Time-lapse imaging revealed that knockdown of Caspase-3 and Caspase-9 led to more stable arbors and presynaptic sites. Genetic analysis showed that Caspase-3, Caspase-9, and p38 MAPK interacted with Slit1a-Robo2 signaling, suggesting that localized activation of caspases lie downstream of a ligand receptor system, acting as key promoters of axonal branch tip and synaptic dynamics to restrict arbor growth in vivo in the central nervous system.