Spore coat protein and enterotoxin synthesis in Clostridium perfringens.

Polyacrylamide gel profiles of Clostridium perfringens spore coat protein revealed four and occasionally five components. Pulse-chase experiments indicated that synthesis of coat protein polypeptide and enterotoxin was an early sporulation event. However, maximum synthesis occurred coincident with the onset of heat resistance.     

Analysis of the major histocompatibility complex in Syrian hamsters. III. Cellular and humoral immunity to alloantigens.

Among the genetic loci incorporated into the major histocompatibility complex in every species studied to date have been prominent genes encoding for strong histocompatibility determinants that elicit detectable alloantibody responses and which are the chief antigenic targets of cell-mediated cytotoxicity reactions. The K and D regions of the H-2 complex in the mouse and the A, B, and C regions of the HLA complex in man are representative examples. Syrian hamsters, as described in this report, do not make alloantibodies to antigens of this type and only very poorly do they carry out in vitro cell-mediated cytotoxicity to target cells putatively bearing these antigens. Since hamsters are quite capable of discriminating analogous antigenic differences in xenogeneic species, and xenogeneic sources cannot distinguish immunologically between the antigens encoded by the two hamster major histocompatibility alleles. Hm-1a and Hm-1b, we conclude that the hamster strains we work with are serologically indistinguishable by the methods used here. However, they obviously differ for determinants which elicit T cell-mediated responses, as evidenced by their ability to express acute skin graft rejection, mixed lymphocyte reactivity, graft-vs-host reactions, and cell-mediated cytotoxicity reactions. Such alloreactivity may reflect a mutation at an SD locus, affecting antigenic sites recognized only by T cells, or that the available hamster strains are SD identical, but differ at loci similar to the I region loci in mice. Alternatively, we cannot exclude the possibility that Syrian hamsters somehow fail to express properly the genes coding for SD determinants.     

Sweat tests to diagnose cystic fibrosis in adults.

Twenty five patients with cystic fibrosis and 25 controls were studied to define a sweat sodium concentration in adults that could be taken as diagnostic of cystic fibrosis. Some of the controls had a sweat sodium concentration of over 50 mmol(mEq)/l, and thus cystic fibrosis should be diagnosed in an adult only when two measurements of sweat sodium concentration are above 70 mmol/l. In cases in which the sweat sodium concentration was borderline a suppression test using fludrocortisone improved the accuracy of diagnosis; this test entails recording the lowest concentration reached after administration of the drug. A scatter diagram of the baseline sweat sodium concentrations plotted against the lowest concentration attained after suppression with fludrocortisone may aid the diagnosis further.     

Glucocorticoid modulation of lymphokine-induced macrophage proliferation

The ability of glucocorticoids to modify lymphokine-induced macrophage proliferation, an in vitro correlate of cellular immunity in the guinea pig, was investigated. Lymphocyte production of macrophage mitogenic factor (MMF) was decreased in the presence of physiological concentrations of glucocorticoids. Inhibition was concentration dependent (IC₅₀ of triamcinolone acetonide (TA): 2 × 10^?9M), glucocorticoid specific, and reversed by cortexolone. In contrast, pharmacological concentrations of glucocorticoids were necessary to inhibit macrophage proliferation induced by suboptimal dilutions of MMF. This inhibition was concentration dependent (IC₅₀ of TA: 4 × 10^?7M), glucocorticoid specific, and reversed by cortexolone. At supraoptimal dilutions of MMF, glucocorticoids caused a twofold potentiation of MMF-induced macrophage proliferation. Potentiation was concentration dependent (EC₅₀ of TA: 3 × 10^?8M), glucocorticoid specific, reversed by glucocorticoid antagonists, and occurred in the presence of indomethacin. Thus, glucocorticoids regulate both the initiation and effector phases of this in vitro model of delayed hypersensitivity. However, the results indicate that the major mechanism of glucocorticoid-mediated anti-inflammatory action occurs at the level of the MMF-producing lymphocyte rather than at the effector macrophage, as MMF-induced proliferation is likely controlled by opposing glucocorticoid-sensitive mechanisms.     

Prevention of fungal colonization and digestion of cellulose by the addition of methylcellulose

When the attachment of cellulolytic rumen fungi to cellulose is blocked by the addition of methylcellulose, cellulose digestion is entirely inhibited. Even after these fungi have colonized and penetrated the cellulosic fibers of filter paper, the addition of methylcellulose effectively halts cellulose digestion. This effect of methylcellulose is accompanied by the complete inhibition of fungal attachment to cellulose fibers; the addition of methylcellulose does not affect the growth of these organisms on soluble substrates. We conclude that fungal cellulose digestion, like bacterial cellulose digestion, requires the spatial juxtaposition of the cellulolytic organism and its insoluble substrate. The simultaneous inhibition of both attachment and digestion by the same inhibitor suggests that these two processes are functionally linked in the fungi.     

Stage-specific cuticular proteins of Ostertagia circumcincta and Ostertagia ostertagi

In this study we have shown that NHS-biotin and I¹²⁵-streptavidin can detect cuticular polypeptides of Ostertagia spp. The labelled polypeptide profile of intact nematodes is simple compared to the profile obtained by labelling homogenates. None of the major internal polypeptides are labelled and the subset of proteins labelled in intact nematodes appears to be mainly surface associated. The results presented here demonstrate that NHS-biotin may be used as a reagent for the analysis of surface polypeptides. The surface polypeptide profiles of the five major developmental stages (L1, L2, L3, L4 and adult) of Ostertagia circumcincta show a series of stage-specific molecules with no polypeptides common to all stages, indicating that the cuticle is a dynamic structure which changes throughout the life cycle. Similarity comparison of Ostertagia ostertagi L3 and L4 stage surface profiles showed that each stage is clearly distinct; comparison of these stages between the two species shows an overall similarity.     

Central nervous system actions of 2, 5-bis (3,4-dimethoxybenzyl) cyclopentyl amine,a peripheral dopamine blocking agent

The behavioral and brain catecholamine effects of 2,5-bis (3,4-dimethoxybenzyl) cyclopentyl amine were investigated in mice. It rapidly depleted norepinephrine. Chronic dosing also depleted dopamine, but to a lesser degree. As indicated by a lack of effect on amphetamine induced stereotypy and apomorphine induced emesis and failure to induce catalepsy, the compound does not block brain dopamine receptors. It has no effect on brain catecholamine synthesis or dopamine-β-hydroxylase activity.     

A portable pump sampler for lotic periphyton

A sampling technique for collecting lotic periphyton on sedimentary substrates using a peristaltic pump is described. Quantitative samples of periphyton standing crop and colonization rate are collected by the same procedure. The technique eliminates human disturbance problems associated with floating artificial samplers by establishing permanent sampling sites directly on submerged substances.