Survival of Vibrio parahaemolyticus at low temperatures under starvation conditions and subsequent resuscitation of viable, nonculturable cells.

Morphological changes of Vibrio parahaemolyticus from rods to spheres took place after a culture was subjected to starvation at a wide range of temperatures. Scanning electron micrographs revealed that starved spherical cells gradually developed a rippled cell surface with blebs and an extracellular filamentous substance adhesive to the cell surface. Cells starved at a low temperature for certain intervals were counted by various bacterial enumeration methods, including plate count, direct viable count, and total cell count for both Kanagawa-positive and -negative strains. The results indicated that this species could reach the nonculturable stage in 50 to approximately 80 days during starvation at 3.5 degrees C. Kanagawa-negative strain 38C6 lost culturability more slowly than Kanagawa-positive strain 38C1 at low temperature. As detected by thiosulfate-citrate-bile salts-sucrose plate count, a high percentage of the surviving cells at 3.5 degrees C in starvation medium were possibly injured by the low temperature rather than by starvation. Both addition of nalidixic acid to the starved cultures and the most-probable-number method demonstrated that the cells recovered after a temperature upshift probably represented the regrowth of a few surviving cells. These surviving cells were capable of growth and multiplication with limited nutrients at an extraordinary rate when the temperature was upshifted.     

Molecular cloning and sequence analysis of the mouse kallikrein-binding protein gene.

A genomic clone (MKBP-10) encoding the mouse kallikrein-binding protein (MKBP) was isolated from a mouse genomic DNA library by screening with a rat kallikrein-binding protein (RKBP) cDNA probe. The total sequenced region of the MKBP gene spans 8615 base pairs. The exon and intron locations of the RKBP gene were identified by similarity with the RKBP gene. The MKBP gene encodes a prepeptide of 417 amino acid residues which exhibits 71% homology with RKBP. A TATA box sequence was located in the 5' flanking region of the MKBP gene by similarity with the consensus sequence TATAAAA.     

中华血簇虫的生活史研究 Ⅰ.中华血簇虫在鳖穆蛭中的发育

中华血簇虫是湖北产的中华鳖体内发现的一种寄主虫。在其生活史发育中,存在着两种寄主的交替。本文只介绍它在无脊椎动物寄主——鳖穆蛭体中的发育情形。这一时期包括两个阶段:配子生殖和孢子生殖。配子生殖的特点是,两性配子母细胞先融合,然后才进行配子分化,产生4个雄配子核,其中1个核与雌配子核受精,形成合子核。孢子生殖以单核卵囊的核分裂开始,最后形成含8个裸子孢子的成熟卵囊,并解体释放出子孢子。整个过程都发生在蛭消化道内。脊椎动物寄主的感染,很可能是因为吃下含成熟子孢子的无脊椎动物寄主而引起的。     

Infection status of Sesarma dehaani collected from Sumjin river delta with the metacercariae of Paragonimus iloktsuenensis

This study was performed to observe the recent infection status of Sesarma dehaani with the metacercariae of P. iloktsuenensis in the well-known enzootic focus, Sumjin river delta. A total of 74 Sesarma dehaani were collected from a focus near the mouth of the Sumjin river in November, 1986 and February, 1987. The crabs were examined for P. iloktsuenensis metacercariae by the method of Seo and Kwak(1972). The metacercariae of P. iloktsuenensis were found in the liver of the crabs. Among the 74 crabs examined, 47(63.5%) were found infected with 1-102 metacercariae (18.2 per crab). The infection rate and metacercarial density increased as the size of the crab was increased. From the results, it is suggested that the life cycle of P. iloktsuenensis is actively maintained in the Sumjin river basin.     

A human case of Stellantchasmus falcatus infection

A human case infected with Stellantchasmus falcatus(Heterophyidae) is reported based on the adult worms collected after praziquantel treatment. The patient is a 33-year old male residing in Seoul. For several months he experienced vague abdominal discomfort and hunger pain. Praziquantel at a single dose of 600 mg was given followed by purgation with magnesium salt, and 17 adult S. falcatus specimens were collected from the diarrheal stools. He recalled he had eaten raw flesh of several kinds of brackish water fishes. This is the 4th human case of S. falcatus infection in Korea.     

Cercarial shedding of Echinostoma cinetorchis and experimental infection of the cercariae to several kinds of snails

The development of Echinostoma cinetorchis in several snail species reared in laboratory aquaria was observed. The eggs from adult flukes collected from the intestine of rats were cultivated to miracidia, and exposed to Hippeutis sp. snails. Observations were made for cercarial shedding from the exposed snails. The cercariae shed from the snails were again exposed to several species of fresh water snails in order to observe metacercarial formation in the snails and their infectivity to final hosts. The results obtained in this study were as follows: 1. Twenty miracidia were exposed to each snail of Hippeutis sp. About 58.3% of the above snails (7 out of 12) were dead before shedding the cercariae, and the remainder shed the cercariae for a period of 7 to 9 days before death. 2. Cercarial shedding from the infected snails started from the 25th day after the exposure to miracidia, and the total number of cercariae shed per snail was 684 in average (range; 482-904). 3. The size of rediae developed in the infected Hippeutis sp. snails was 1,242 x 214 microns in average, and the number of rediae per snail was 350 in average (range; 120-510). 4. About 40 to 50 cercariae shed from the Hippeutis sp. snails were each exposed to several species of snails reared in the laboratory. The metacercarial formation was confirmed by dissecting the infected snails, 12 to 16 days after the infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Colicin A receptor: role of two Escherichia coli outer membrane proteins (OmpF protein and btuB gene product) and lipopolysaccharide.

ompF cells were completely resistant to colicin A, whereas btuB cells were partially resistant. The OmpF protein, in the presence of added lipopolysaccharide, inactivated colicin A. This inactivation was enhanced by added btuB gene product, btuB gene product with lipopolysaccharide did not inactivate colicin A. These data, together with the observation that vitamin B12 protected btuB+ cells from the killing effect of colicin A, suggest that the colicin A receptor in Escherichia coli K-12 is composed of the OmpF protein, the btuB gene product, and lipopolysaccharide.     

Surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae).

The surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae) was studied by scanning electron microscopy(SEM). The adult worms were recovered from experimentally infected cats and from a naturally infected patient. They were leaf-like, ventrally concave, and ovoid or pyriform in shape. Ciliated knob-like sensory papillae (type I) were observed in single or grouped forms on and around the oral sucker, whereas non-ciliated round swellings (type II papillae) were seen on the lip of the ventral sucker. The tegumental spines around the oral sucker were 5-9 pointed, whereas those between the two suckers were 12-17 pointed. Ventrolaterally, three groups of 5-6 type I papillae were located between the oral and ventral suckers, with single ones alternating between them. The genital sucker was protruded or depressed, depending on the contraction state of the flukes, and the gonotyl spine number ranged 50-60. The number of tip points of tegumental spines was decreased posteriorly; finally they became 1-3 pointed. On the dorsal surface, 4 groups of 4-5 type I papillae were symmetrically located on both lateral sides, and the shape and distribution of tegumental spines were similar to those of the ventral surface. Although the tegumental ultrastructure of H. nocens was generally similar to those of other heterophyids, the genital sucker morphology including the number of gonotyl spines and/or the distribution pattern of tegumental spines and sensory papillae were suggested to be the characteristic features of H. nocens.     

Demonstration of a missing outer membrane protein in tolG mutants of Escherichia cell

A class of Escherichia coli mutants called tolG are specifically tolerant to bacteriocin JF246. Cell envelopes were prepared from three independent spontaneous E. coli. tolG mutants and the parental strain (tolG⁺). Electrophoresis of these preparations in polyacrylamide gels containing sodium dodecyl sulfate showed that the tolG strains lacked a cell envelope protein found in the tolG⁺ strain. It was estimated that this protein accounted for 10% of the total cell envelope proteins by densitometer tracings of gels stained with Fast Green. Membrane fractionation by isopycnic centrifugation in a sucrose density gradient showed that this protein was located in the outer membrane of tolG⁺ cells. Genetic studies using conjugation, transduction and reversion showed that, in the limited number of recombinants or revertants studied, strains exhibiting the tolerant phenotype lacked the outer membrane protein, whereas the protein was present in bacteriocin-sensitive strains.     

PROPHASING OF INTERPHASE NUCLEI AND INDUCTION OF NUCLEAR ENVELOPES AROUND METAPHASE CHROMOSOMES IN HELA AND CHINESE HAMSTER HOMO- AND HETEROKARYONS

Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6–8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.