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Biomedical subjects

H Sagara

Publications and source records attributed to H Sagara.

At least 91 records · Page 5Linked to original sources
PubMed1987

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli with special reference to plasmid profiles of Japanese clinical isolates.

A total of 111 clinical isolates of Campylobacter jejuni and 10 clinical isolates of Campylobacter coli were characterized by their susceptibility to nine antimicrobial agents and by their plasmid profiles on agarose gel electrophoresis. All of the C. jejuni isolates were susceptible to chloramphenicol, ciprofloxacin, erythromycin, kanamycin, and nalidixic acid, but 55% were tetracycline resistant. In the 10 C. coli isolates, a high prevalence of multiple-antibiotic resistance was noted. Plasmids were found in 82% of the tetracycline-resistant and 15% of the tetracycline-susceptible C. jejuni isolates. Tetracycline resistance in six randomly selected C. jejuni isolates, which contained 50- or 135-kilobase (kb) plasmids, was transferred by conjugation to a Campylobacter fetus subsp. fetus recipient with recovery of a 50- or a 45-kb plasmid from transconjugants. From one multiple-antibiotic-resistant C. coli isolate, resistance to tetracycline, kanamycin, and chloramphenicol was transferred concomitantly with a 58-kb plasmid, pNR9589. Nonconjugative 98-kb plasmids, pNR9131 and pNR9581, from C. coli isolates with resistance to tetracycline, kanamycin, and erythromycin were shown by cloning experiments to code for at least kanamycin resistance. Restriction digests revealed that 50-kb plasmids from tetracycline-resistant C. jejuni isolates were identical, although plasmids from multiple-antibiotic-resistant C. coli isolates shared partial DNA homology to each other. Cloning of the kanamycin and chloramphenicol resistance genes of pNR9589 into Escherichia coli showed that the two genes are closely linked or clustered. Double-digestion analysis of the fragments encoding the kanamycin resistance of pNR9131, pNR9581, and pNR9589 showed that these three plasmids contain a common fragment related to kanamycin resistance.

Anti-Bacterial Agents↗
PubMed1986

Formation of apical tubules from large endocytic vacuoles in kidney proximal tubule cells during absorption of horseradish peroxidase.

Using horseradish peroxidase (HRP) as a tracer, we have investigated if the so-called apical tubules (AT) in the kidney proximal tubule cells are directly involved in the endocytic process by carrying the tracer into the cells, or if they are derived from the intracellular membrane compartments. Rat kidney was fixed by vascular perfusion at different time intervals after intravenous injection of HRP and prepared for electron microscopy. An analysis revealed that 0.5 min after injection, invaginations of the plasma membrane and small apical endocytic vesicles, including coated vesicles, were labelled with reaction product, whereas almost all large apical endocytic vacuoles and the AT were negative. The endocytic vacuoles and about 18% of the AT were labelled 1 min after injection. The reaction product in the large endocytic vacuoles was usually seen along the luminal surface of the vacuoles. The AT with reaction product appeared as a branched network, and were frequently connected with the labelled endocytic vacuoles. Three min after injection, reaction product was detected in about 38% of the AT, and thereafter, the percentage increased to about 74% after 7 min. No reaction product was detected in the Golgi complex at any time after HRP-injection. These findings indicate that the AT are probably formed by budding off from the large endocytic vacuoles, rather than being directly involved in the endocytic process.

Absorption↗
PubMed1986

Helical structure in the apical tubules of several absorbing epithelia. Kidney proximal tubule, visceral yolk sac and ductuli efferentes.

Unique and highly ordered structures were discovered in the so-called apical tubules of several absorbing epithelia (kidney proximal tubule, visceral yolk sac and ductuli efferentes) fixed in situ with a mixture of formaldehyde, glutaraldehyde and osmium tetroxide. The apical tubules were especially numerous in the apical cytoplasm, in addition to the invaginations of the apical plasma membrane, newly formed endocytic vesicles and large endocytic vacuoles. They showed a cylindrical structure (approximately 80 nm in diameter) limited by a smooth membrane. Helically wound parallel rows of particles (approximately 11 nm in diameter) were found in the apical tubules in close proximity to their limiting membrane. The structure of the helix was determined by following the rows through serial sections and semithin sections, and was found to be a left-handed quadruple helix. These particles surround an electron-lucent cylinder (approximately 35 nm in diameter), containing at its center a single row of particles (approximately 9 nm in diameter). The apical tubules with the luminal specializations were not seen in continuity with the apical plasma membrane, but were frequently connected with the large endocytic vacuoles, which were present in the deeper levels of the apical cytoplasm. From these observations, it is suggested that the apical tubules are not derivatives of the apical plasma membrane; rather, they represent an intracellular compartment, which is morphologically related to the large endocytic vacuoles.

Absorption↗
PubMed1983

Ocellar system of the insect: comparison of dorsal ocellus and lateral ocellus.

The ocellar receptor and neuropil in the dorsal ocellar system of the cockroach and the lateral ocellar system of the swallowtail butterfly larva have been compared. In the dorsal ocellus of the cockroach more than 10,000 retinular cells each with a rhabdomere are piled up one upon another without a specific pattern in the ocellar capsule. Retinular axons synapse exclusively with branches of four thick second order neurons in the lower region of the capsule. Dark granule-containing neurons, originating in the brain, also synapse with the second order neurons in the ocellar neuropil. The ocellar nerve is comprised of four thick second order processes (ca. 6-16 micron) and 20-40 thin processes (ca. 1-5 micron), which include retinular axons, collaterals of thick processes, possible third order processes and unidentified processes. Synapses occur against these processes in the ocellar nerve and in the extreme proximal region of the ocellar neuropil. Six lateral ocelli occur on both sides of head in the butterfly larva. Each ocellus contains seven retinular cells, which are grouped into three distal cells and four proximal cells, or four distal cells, two peripheral cells and one central cell by the position of their rhabdomeres. Retinular axons extend to the brain, and enter the distal optic neuropil. There are six neuropils, each of which contains the seven axons from one ocellus and a dozen or so second order processes. Of seven retinular axons, four occur peripherally and the remaining three occur centrally in the neuropil. All axons synapse with fine branches of interneurons. Second order processes together with at least three central retinular axons extend to the second optic neuropil, but the peripheral axons could not be followed there. The highly organized receptors and the neuropil in the lateral ocellar system suggest a complexly integrated function. An ocellar nerve and proximal ocellar neuropil appear like an extension of the CNS, and direct connections of retinular axons with interneurons in the CNS appear characteristic of the dorsal ocellus. This difference may be related to the distribution of the two ocellar systems: the dorsal ocelli co-exist with the compound eyes of the adult, whereas the lateral ocelli are the only photoreceptor organs of the larval insect.

Animals↗