Heptapeptide toxin production during the batch culture of two Microcystis species (Cyanobacteria)

Changes in the content of cyclic heptapeptide hepatotoxins called microcystins were investigated during batch culture of two Microcystis species using high performance liquid chromatography. After adsorption to ODS-silica gel cartridges and elution with methanol, the toxins were analyzed and quantified by HPLC. 35 μg per 100 mg dry cells of microcystin-RR, 34 μg of -YR and 43 μg of -LR were present at the beginning of the exponential growth phase of M. viridis. Microcystin-RR increased markedly towards the end of the exponential phase with the maximum content of 112 μg per 100 mg cells was measured at the late stage of the exponential phase. A remarkable increase of microcystin-YR from 130 μg per 100 mg cells to 1020 μg was observed during the exponential phase of a highly toxic strain of M. aeruginosa. However no clear differences were found in the pattern of change among the three toxins during the growth course.     

Close linkage of MEN2A with RBP3 locus in Japanese kindreds

Summary The gene responsible for multiple endocrine neoplasia type 2A (MEN2A) has recently been assigned to the pericentromeric region of chromsome 10 in European Caucasian kindreds by linkage analysis using a DNA marker, interstitial retinol-binding protein 3 (RBP3). We have found tight linkage between the MEN2A and RBP3 loci in Japanese MEN2A kindreds. The maximum lod score is 5.19 at a recombination fraction of 0.00. This result suggests that mutation of a certain gene close to RBP3 is responsible for MEN2A irrespective of ethnic backgrounds.     

Formation of segregated regions of feature detecting cells in self-organizing nerve field

This paper investigates the formation of a segregated region for a specific set of input signals in a nerve field. The segregated region is formed by a feature detecting cell group which fires only for a specific set of input signals. This firing region is called the region of feature detecting cells for the corresponding input set. First, a basic self-organizing model is given. The model is composed of the first input layer, the second nerve cell layer with lateral inhibitory interactions (it is called a lateral-inhibition type nerve field) and an inhibitory nerve cell. An input signal is an-dimensional vector whose components assume continuous values. Next, the condition which gurantees the formation of a segregated region for a specific set of input signals is derived, and the properties of the model are discussed based on the derived condition. In addition, the behavior of the model is examined through computer-simulated experiments. The following observations are made: When a certain condition is satisfied, a segregated region is formed in the nerve field according to a specific set of input signals. By varying the parameters of learning, the region is formed depending on the similarity between input signals. The regions for similar input signals are formed near each other in the nerve field. The region is created depending on the occurence probability of the input signal and its norm.     

Lectin histochemistry in rat thyroid tumours

The thyroid tumours and background goiterous and adenomatous lesions induced in rats with diisopropanolnitrosamine (DIPN) plus methylthiouracil (MTU), and regenerative thyroid tissues after wounding were studied by lectin histochemistry. Ten weeks after cessation of the carcinogen treatments, carcinomas invading the surrounding tissues and blood vessels (13/20) and papillary micronodules (11/20) were formed in the thyroid tissues. In general, the carcinoma lesion was solitary, and the papillary micronodules were multiple in a single thyroid gland. Among the lectins tested, Maclura pomifera (MPA) and Solanum tuberosum (STA) showed specific binding with both carcinoma and papillary micronodule lesions, but not with the background goiterous and adenomatous lesions and regenerative thyroid tissues. The former both lesions showed higher labelling indices with BUdR or 3H-thymidine and poorer thyroglobulin accumulation than the latters, thereby indicating their enhanced proliferative capability and depressed potency of cyto-differentiation. The common cytological and histochemical properties of carcinoma lesions and papillary micronodules allow us to regard the latter as pre-invading carcinoma lesions. The lectins MPA and STA may be, therefore, used as the specific markers of malignancy in rat thyroid carcinogenesis.     

Altered ganglioside expression in ras-oncogene-transformed cells

Alteration of ganglioside composition in mouse BALB/3T3 cells transformed either by DNA transfection with viral K-, H-, or cellular H-ras oncogene, or by infection with the K-ras oncogene-carrying murine sarcoma virus (Ki-KSV) was studied using a highly sensitive thin-layer chromatography/enzyme immunostaining method. Marked common decreases in the content of GD3 ganglioside and the increase of its metabolic precursor GM3 were bound in BALB/3T3 cell lines transformed by either K- or H-ras oncogenes. Moreover, a common decrease or loss in the contents of "A" series ganglio-tetraose gangliosides such as GM1a and GD1a was also found in all transformed cell lines, indicating that the alteration of cellular glycosphingolipids by ras oncogenes apparently does not depend on the type of ras-concogenes (K- and H-ras).     

Enhancement of the Division of Equisetum arvense Protoplasts in Culture by Activated Charcoal and Their Further Development

Protoplasts were isolated from subcultured gametophytes of Equisetumarvense by treatment with Driselase and then cultured in vitro.Addition of activated charcoal (AC) to the culture medium enhancedthe rate of cell division, as well as the survival of both protoplastsand regenerated protoplasts. However, subsequent division ofcells was not observed after one or two cycles of replicationin cultures supplemented with AC. When regenerated protoplastswere transferred to fresh medium without AC 3 to 5 weeks afterthe first plating, the transferred cells formed rhizoids anddeveloped into small, young gametophytes without the prior formationof cell clusters or calluses. Furthermore, sprophytic shootsdifferentiated from the protoplast-derived gametophytes whenthey were cultured on medium supplemented with 6-benzylaminopurine(BA). (Received April 5, 1990; Accepted July 30, 1990)     

Mother-infant interactions of wild-born,individually-caged cynomolgus monkeys (Macaca fascicularis) during the first 14 weeks of infant life

This study documents age-related changes in the interactions of wild-born cynomolgus macaque mothers and their infants living in individual cages during the first 14 weeks of infant life. Body contact between mother and infant, maternal holding, and infant sucking were found to decrease, and the mothers showed an increased frequency of aggression toward their infants with age. These results were broadly similar to those reported for mother-infant interactions in other macaques living in social groups. Nevertheless, a clear difference between the present cynomolgus macaques and other macaques in social groups was apparent. The cynomolgus macaque mothers tended to permit their infants to move about freely without displaying maternal protectiveness such as restraint or retrieval, unlike other macaque mothers in social groups. Such maternal behaviors might derive from the experience of living in individual cages for many years and the relative safety of living in individual cages. The lack of maternal restraint and retrieval could be responsible for the observed sex differences in behavior: male infants moved more actively, and broke, and made contact with their mothers more frequently than did female infants. Moreover, mothers of female infants held and groomed them more frequently and were less aggressive toward them.