Human newborn autologous mixed lymphocyte response: frequency and phenotype of responders and xenoantigen specificity

The response of human newborn lymphocytes in autologous mixed lymphocyte culture was examined for specificity (by restimulation), responder cell phenotype, and responder cell frequency. When the newborn T cells were separated from non-T cells by rosetting with sheep erythrocytes (E) in fetal calf serum (FCS), approximately 1:20,000 T cells proliferated. These responders had specificity for E + FCS, were T4+, and were self-restricted. Significant numbers of responder T cells were not found when newborn T and non-T cells were separated by nylon wool. Responses in parallel autologous cultures of adult T cells showed that 1) adults had a higher frequency than newborns of E + FCS specific responders, 2) evidence for self specificity was lacking in restimulated cultures, and 3) occasional responses to antigen on the surface of monocytes could not be excluded.     

Genotoxicity of ptaquiloside, a bracken carcinogen, in the hepatocyte primary culture/DNA-repair test

The genotoxicity of ptaquiloside (PT), recently isolated from bracken fern and shown to be carcinogenic, was examined by means of the hepatocyte primary culture/DNA-repair test. PT elicited clear unscheduled DNA synthesis with a dose-response effect. The result indicates that PT is a genotoxic carcinogen.     

The Effects of Ethylene on the Coordinated Synthesis of Multiple Proteins: Accumulation of an Acidic Chitinase and a Basic Glycoprotein Induced by Ethylene in Leaves of Azuki Bean, Vigna angularis

The ethylene-induced synthesis and accumulation of proteinswere studied in the primary leaves of azuki bean (Vigna angularis).Seven different proteins, designated AZ17, 23, 27, 32, 35, 36,42 according to their molecular masses, were synthesized andaccumulated in response to ethylene. AZ27 and AZ42 were purifiedto homogeneity and characterized. AZ27 was identified as anacidic chitinase and accumulated in the extracellular space.The sequence of the 40 N-terminal amino acids of AZ27 showedno similarity to that of a basic chitinase from bean and tobacco,but it was highly homologous to that of a chitinase from virus-infectedcucumber leaves. AZ42 was identified as a glycoprotein thataccumulated intracellularly. A search for proteins with sequenceshomologous to an internal sequence of 18 amino acids in AZ42was unsuccessful. Immunochemical examination revealed that auxinand abscisic acid enhanced the ethylene-induced accumulationof AZ27 but not of AZ42. In contrast, levels of AZ42 were notaffected by auxin or abscisic acid, but cytokinin suppressedthe accumulation of one of the doublet bands of AZ42. TranslatablemRNAs coding for AZ27 and AZ42 were not present in leaves thathad not been treated with ethylene, but levels of these mRNAsincreased after such treatment. (Received March 1, 1991; Accepted May 8, 1991)     

Ultrastructural changes of the midgut epithelial cells in feeding and moulting nymphs of the tick Haemaphysalis longicornis

The midgut epithelial cells in nymphs fed on laboratory rabbits were examined during feeding and after detachment. The midgut epithelium at the unfed stage consisted of digestive cells of lower activity, containing such nutritive substances as protein, lipid and glycogen. As feeding proceeded, the cells became active in intracellular digestion. At the middle of the feeding stage, the spent digestive cells derived from the active digestive cells began to be replaced by the new digestive cells of lower activity. After detachment, the pinocytotic activity of the above cells increased greatly, and the digestive activity increased to some extent. As a result, many large endosomes were formed by fusion of numerous pinosomes. Thereafter, endosomes decreased in size as digestion proceeded and there was an increase of haematin granules. On day 7 after detachment, the new digestive cells of lower activity, belonging to the 'nutritional reserve' type, appeared adjacent to the spent digestive cells which had almost exhausted all endosomes, and these new cells had completely replaced the spent cells by day 3 after moulting.     

Fluctuation of algal alkaline phosphatase activity and the possible mechanisms of hydrolysis of dissolved organic phosphorus in Lake Barato

For freshwater cyanobacteria, the autofluorescence of phycocyanin is quite high while the in vivo fluorescence (IVF) yield of chlorophyll-a is relatively low, apparently because of low chlorophyll concentrations associated with photosystem II. In eucaryotic phytoplankton, even those with phycobili-protein accessory pigments (e.g. some cryptophytes), the opposite is true. Thus, an IVF ratio which relates phycocyanin to chlorophyll-a signals could be a good index of relative cyanobacterial abundance in the field. Spectrofluorometric scans of whole cells from laboratory cultures indicated that the ratio Em₆₆₀ @ Ex₆₃₀/Em₆₈₀ @ Ex₄₃₀ could be a very sensitive cyanobacterial indicator. Tandem flowthrough fluorometers were then fitted with the appropriate interference filters and their discriminatory power was evaluated with mixtures of cyanobacterial and eucaryotic phytoplankton. Although subject to many of the constraints of other IVF assays, tandem fluorometry should be particularly appropriate for real-time mapping of the relative spatial and temporal distributions of broad phytoplankton taxa in continuous vertical of horizontal profiles in lakes.     

Biochemistry and neurotoxicology of guanidino compounds. History and recent advances

Guanidino compounds are known to have important biological roles, such as the participation of arginine in ureagenesis, and of creatine in muscular contraction. On the other hand, the high toxicity of guanidino compounds, such as methylguanidine and guanidine, has been under study for quite a long time in the biochemical as well as clinical fields. In this review, the author summarizes the experimental results of neurophysiological and neurochemical studies on guanidino compound-induced seizures, conducted by his colleagues since 1966, and introduces several topics arising from their recent investigations on guanidino compounds and seizure mechanism, i.e., (1) alpha-guanidino-glutaric acid in the cobalt epileptic focus and its convulsive activity; (2) guanidino-ethanesulfonic acid and epilepsy; (3) delta-guanidinovaleric acid, and endogenous and specific GABA receptor antagonist; and (4) guanidino compounds as radical generators.     

Immunoregulatory abnormalities in autoimmune thyroid diseases

We have investigated the ability of lymphocytes from normal subjects and patients with autoimmune thyroid diseases to respond to a thyroidal antigen (human thyroglobulin, hTG) and a non-thyroidal antigen (Keyhole limpet hemocyanin, KLH) in vitro, using a hapten (trinitrophenol, TNP)-carrier system. This system is based on the concept that the T helper cells which respond to hTG or KLH should stimulate anti-TNP antibody producing B cells in the presence of TNP conjugated hTG (TNP-hTG) or KLH (TNP-KLH). After 5 or 6 days of culture of peripheral blood mononuclear cells with pokeweed mitogen (PWM), PWM and TNP-hTG, or PWM and TNP-KLH, IgM anti-TNP and IgM anti-sheep red blood cell (SRBC) plaque forming cells (PFC) were enumerated. The results showed that (1) in normal controls, hTG caused only suppression in both TNP and SRBC response, and KLH caused dose-related enhancement and suppression in TNP response without a change in SRBC response, and (2) in patients, both hTG and KLH resulted in dose-related enhancement in TNP response without a change in SRBC response. These data suggest that patients with autoimmune thyroid diseases have regulatory cell abnormalities confined to a thyroid antigen.     

Stereoselective total synthesis of ceramide Di-, Tri- and tetrahexosides of wheat flour

The first total synthesis of glycosphingolipids isolated from wheat flour has been achieved in a regio- and stereo-controlled manner.Abbreviations THF tetrahydrofuran - DMF dimethylformamide Part 53 in the series Synthetic Studies on Cell Surface Glycans