Two adjacent epitopes on a synthetic dodecapeptide induce lactate dehydrogenase B-specific helper and suppressor T cells

The outcome of an immune response to the enzyme lactate dehydrogenase B (LDH-B) is determined by the interplay between two types of regulatory T lymphocytes, T helper (Th) and T suppressor (Ts) cells. Most mouse strains are capable of generating Th but not Ts cells, and are therefore high responders to LDH-B in terms of both antibody production and antigen-specific T-cell proliferation. However, in strains expressing the b or k allele at the E beta locus of the major histocompatibility complex (Mhc), Ts cells are induced that partly or totally abrogate the proliferative response of Th cells to LDH-B. As a result, these strains are phenotypically medium (E beta b expressors) or low (E beta k expressors) responders. Because the suppression in the LDH-B system is antigen-specific (i.e. it only affects LDH-B-specific Th cells), it is conceivable that the Th and Ts cells use the antigen itself to communicate with each other. To investigate this possibility, we set out to determine which epitopes of the LDH-B molecule are recognized by Th and Ts cells. On the basis of previous studies, a loop structure extending from residue 211 to residue 224 of pig LDH-B appeared to be preferentially recognized by most Th-type (class II Mhc-restricted, proliferating) clones. By using a synthetic peptide, we demonstrate here that both Th and Ts cells are induced by the 211-222 stretch of LDH-B sequence. The use of two further dodecapeptides, each with a single amino-acid substitution in comparison with the pig 211-222 sequence, has revealed that Th and Ts cells have different fine specificities. Thus the loop appears to have two closely linked, if not overlapping, epitopes, one recognized by Th and the other by Ts cells. This finding is consistent with two possible mechanisms of suppression, namely bridging of Th and Ts cells by antigen and subsequent transmission of a suppressive signal, and competition for antigen between Th and Ts cells.     

Direct evidence for the existence of nominal antigen binding sites on T cell surface Ti alpha-beta heterodimers of MHC-restricted T cell clones

The binding of nominal antigen to Ti alpha-beta heterodimers on MHC-restricted human T cell clones specific for fluorescein-5-isothiocyanate (FL) was detected by flow cytometry and affinity chromatography. The FL-Ti interaction is of physiologic significance, since T cell activation is induced by cross-linked arrays of FL in the absence of the specific MHC recognition. High antigen valence is required to achieve stable binding to cells and subsequent activation, which is consistent with estimated Ti-FL association constants of less than 3 X 10(5) l/mol. In addition to providing direct evidence that the Ti alpha-beta heterodimer is the receptor for antigen, these data suggest that nominal antigen binding sites exist on the Ti molecules of at least some MHC-restricted clones.     

Intergeneric hybrids of Saccharomyces cerevisiae and Zygosaccharomyces fermentati obtained by protoplast fusion

To obtain strains that are able to efficiently produce ethanol from different carbohydrates, mainly cellulose hydrolysates, several species of the genus Candida and a Zygosaccharomyces fermentati strain were examined for their ability to utilize cellobiose and produce ethanol, as well as for their thermotolerance and the possibility of genetic manipulation. Candida obtusa and Zygosaccharomyces fermentati tolerated the maximal temperature for growth, possessed the highest cellobiase activity, and offered the possibility of genetic manipulation, although neither of them proved to be a good producer of ethanol. Intergeneric hybrids of Saccharomyces cerevisiae and Z. fermentati were obtained after protoplast fusion. They were selected as prototrophic strains, after isolation of auxotrophic mutants from Z. fermentati and fusion with an S. cerevisiae strain which was also auxotrophic. The hybrids, which appeared at a frequency of 2 X 10(-7), presented characteristics of both parents, such as resistance to certain drugs and the ability to grow with either cellobiose or lactic acid as the sole carbon source; they were very stable, even under nonselective conditions. These hybrids may have important industrial applications as good fermenting strains.     

A trial of cybernetic explanation of the development and regression of benign child epilepsy

Using as an example the verification of a hypothetic mechanism of the course of benign child epilepsy the authors demonstrate a method of simulation investigations of neuron-like networks. The structure and possibilities of a digital system for network modelling are discussed, including the properties of the neuron-like element used presently for the experiments. The results of the simulation investigations described in the second part of the paper confirm the hypothesis that an attack of benign child epilepsy is a result of transgressing of the stability border by a fragment of the neuronal network with development in it of a self-exciting activity of a neuronal group.     

Tyzzer's disease as a complication of canine distemper in a raccoon

Intercurrent canine distemper and Tyzzer's disease were diagnosed in a mature raccoon (Procyon lotor) submitted for necropsy. Clinical, gross and microscopic findings characteristic of canine distemper virus (CDV), included ataxia, dyspnea, suppurative conjunctivitis, interstitial pneumonitis and generalized lymphocytolysis. Inclusion bodies typical of CDV infection were present in many epithelial tissues. Acute multifocal hepatic necrosis and acute segmental necrotizing enteritis were attributed to the presence of Bacillus piliformis organisms in these lesions, confirmed by special stains and electron microscopy. This is apparently the first reported case of Tyzzer's disease in a raccoon.     

Non-temperature related effects of osmotic pressure on inward sodium current in the membrane of isolated rat spinal ganglia neurons

The effects of osmotic pressure on inward sodium current during a change in temperature were investigated during experiments on isolated rat spinal ganglia neurons using techniques of intracellular perfusion and voltage clamping. It was found that the effect of osmotic pressure on the kinetic parameters of sodium current does not depend on temperature over a wide range of 8–40°C; the apparent values of activation energies for the activation and inactivation processes do not dependent on degree of osmolality. Overall findings would appear to indicate that the osmotic pressure effect is actually initiated by association with aqueous transmembrane flux. Opinions are expressed as to the location of the structures through which this aqueous flux passes and of the sodium channel gating mechanism, together which the molecular mechanisms of interaction between these two elements.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 518–525, July–August, 1986.     

Effects of external NaCl on the growth of Atriplex amnicola and the ion relations and carbohydrate status of the leaves

Abstract Atriplex amnicola, was grown in nutrient solution cultures with concentrations of NaCl up to 750 mol m^?3. The growth optimum was at 25–50 mol m^?3 NaCl and growth was 10–15% of that value at 750 mol m^?3 NaCl. Sodium chloride at 200 mol m^?3 and higher reduced the rate of leaf extension and increased the time taken for a leaf to reach its maximal length. Concentrations of Na⁺, K⁺ and Mg²⁺ in leaves of different ages were investigated for plants grown at 25, 200 and 400 mol m^?3 NaCl. Although leaves of plants grown at 200 and 400 mol m^?3 NaCl had high Na⁺ concentrations at young developmental stages, much of this Na⁺ was located in the salt bladders. Leaves excluding bladders had low Na⁺ concentrations when young, but very high in Na⁺ when old. In contrast to Na⁺, K⁺ concentrations were similar in bladders and leaves excluding bladders. Concentrations of K⁺ were higher in the rapidly expanding than in the old leaves. At 400 mol m^?3 NaCl, the K⁺:Na⁺ ratios of the leaves excluding bladders were 0.4–0.6 and 0.1 for rapidly expanding and oldest leaves, respectively. The Na⁺ content in moles per leaf, excluding bladders, increased linearly with the age of the leaves; concurrent increases in succulence were closely correlated with the Na ⁺ concentration in the leaves excluding the bladders. Soluble sugars and starch in leaves, stems and buds were determined at dusk and dawn. There was a pronounced diurnal fluctation in concentrations of carbohydrates. During the night, most plant parts showed large decreases in starch and sugar. Concentrations of carbohydrates in most plant organs were similar for plants grown at 25 and 400 mol m^?3 NaCl. One notable exception was buds at dusk, where sugar and starch concentrations were 30–35% less in plants grown at 400 mol m^?3 NaCl than in plants grown at 25 mol m^?3 NaCl. The data indicate that the growth of A. amnicola at 400 mol m^?3 NaCl is not limited by the availability of photosynthate in the plant as a whole. However, there could have been a growth limitation due to inadequate organic solutes for osmotic regulation.     

Effects of membrane depolarization and divalent cations on anaphylactic histamine secretion

The effects of membrane depolarization and divalent cations on histamine release have been studied in sensitized mast cells. Membrane potential of these cells has been measured with intracellular microelectrodes. Our results show that mast cells have a large resting potential (-61 +/- 12 mV) however they do not generate active membrane electrical responses when are depolarized by passing current through the recording microelectrode. High external K+ does not increase histamine release. Histamine secretion is supported by alkali-earth divalent cations (Ca2+ greater than Sr2+ greater than Ba2+) but strongly inhibited by transition metals. Ca2+ concentrations above 1 mM inhibit histamine release, however, this effect is not mimicked by Sr2+ and Ba2+.     

Postnatal development of amino acid metabolism enzymes in the liver and muscle of 'cafeteria' rats

The effect of feeding a high-energy highly palatable cafeteria diet on the liver and muscle ontogenesis of serine dehydratase, alanine transaminase, glutamine synthetase and adenylate deaminase during postnatal development of the rat has been studied. The results are in agreement with the lower amino acid utilization in cafeteria rats, both adults and during postnatal development. The feeding of excess energy coupled with high-quality protein resulted in changes in the ontogenesis of the studied enzymes that coincide with the development of protein synthesis and overall pup growth even before they had direct access to this rich diet, suggesting that cafeteria feeding already affects the amino acid metabolism of the pup through the dam's milk.