Effect of acid and salt concentration in fresh-pack pickles on the growth of Clostridium botulinum spores.

The addition of various amounts of acetic acid to pureed cucumbers inoculated with Clostridium botulinum spores has shown that outgrowth is inhibited at pH 4.8 but not at pH 5.0. Inoculation experiments with whole cucumbers showed that as little as 0.9% acetic acid in the brine was sufficient to prevent outgrowth from spore inocula as high as 10(6)/cucumber. It was further shown that the rapid rate of acetic acid penetration into fresh-pack pickles prevents the growth of any C. botulinum spores that may be present.     

Differentiation of channel models by noise analysis.

Differentiation of membrane channel models based on fluctuation (or noise) analysis is discussed. The theory is particularly useful in distinguishing a single-conductance model (Hodgkin-Huxley formalism) from a multiconductance model. When applied to the frog node of Ranvier, it seems likely that the potassium channels of the membrane may have multiconductance states.     

OLIGOSACCHARIDE STORAGE IN BRAINS FROM PATIENTS WITH FUCOSIDOSIS,GM1-GANGLIOSIDOSIS AND GM2-GANGLIOSIDOSIS (SANDHOFF'S DISEASE)1

Abstract— Analysis of whole autopsy brain from a patient with fucosidosis (α-fucosidase deficiency) revealed minor storage of H-antigen glycolipid [Fuc (α, 1→2) Gal-GlcNAc-Gal-Glc-Ceramide] and a slightly abnormal ganglioside composition in the form of a two-fold elevation of G_M1 and the presence of a fucose-containing glycolipid (a minor component) which co-migrated with G_D1a. The major storage materials in fucosidosis brain were an oligosaccharide (Fuc-Gal-GlcNAc-Man[Fuc-Gal-GlcNAc-Man]-ManGlcNAc) and a disaccharide [Fuc(α, 1→6)-GlcNAc] in the approximate ratio of 5:1. Lesser amounts of a related oligosaccharide (Gal-GlcNAc-Man[Gal-GlcNAc-Man]-Man-GlcNAc) were isolated from the brain of patients with G_M1-gangliosidosis (Types I and II) where the major storage material is known to be G_M1-ganglioside (Gal (β, 1→3)GalNAc(β, 1→4) [NeuNAcf(α, 2→3) Gal(β, 1→4)Glc-Ceramide). Similarly, a related oligosaccharide (GlcNAc-Man [GlcNAc-Man]-Man-GlcNAc) was isolated from the brain of a patient with a total deficiency of N-acetyl-β-d -hexosaminidase (Sandhoff variant of G_M2-gangliosidosis) where the major storage products are known to be G_M2-ganglioside (GalNAc (β 1→4) [NeuNAc (α, 2→3)Gal(β, 1→4)Glc-Ceramine) and its asialo derivative. These studies indicate that glycoproteins containing at least 2 mol of l -fucose per oligosaccharide unit are normally catabolized in human brain. Further, it appears that such glycoproteins are initially catabolized by an endo-N-acetylglucosaminidase to release an oligosaccharide which is then degraded by the sequential action of exo-glycosidases.     

Some self-consistent two-state sliding filament models of muscle contraction.

The general formalism required to treat two-state sliding filament models of muscle contraction, including free energy considerations, is first reviewed and amplified. This formalism is then used to examine, and modify as needed, three models studied previously by Podolsky and Nolan, in which cross-bridge attachment-detachment and ATP turnover are not tightly coupled. No attempt is made here to establish an optimal, self-consistent model of this type because our interest is primarily in methadology rather than in fitting experimental results. But it appears from this preliminary study that such a model, with satisfactory mechanical and thermodynamic properties, could be found. An extremely simple but unrealistic two-state model is also studied which is of interest because it demonstrates the fact that it is possible, in principle at least, for sliding filament models to work with very high thermodynamic efficiencies (50-100 percent). An appendix is included that is concerned with the form of the dependence of certain first-order rate constants on the concentrations of ATP, ADP, and P.     

Fungi isolated from asthmatic homes in the Taipei area.

Indoor fungi in Taipei were surveyed during 1969-1974 using Sabouraud's agar plates. No remarkable yearly variation of fungal incidence was observed. The fungal population was found to be different from home to home. The dominant members were Aspergillus, Penicillium, Mycelia sterila, Oospora, Rhodotorula, Hormodendrum and yeasts. The order of frequency of fungi found indoors was quite different from that of outdoor fungi. The fungal spores were more numerous during summer months, and this trend was more apparent for Aspergillus, Oospora, Rhodotorula, and Hormodendrum. The kind and the incidence of fungi found in asthmatic homes were not different from those detected in non-asthmatic homes, except that in asthmatic homes there were greater numbers of fungi.     

Isolation and characterization of the plasma membrane of L-1210 cells. Iodination as a marker for the plasma membrane

Mouse leukemia L-1210 cells were iodinated with ¹²⁵I; this permitted the development of a method for the isolation of the plasma membranes. These show a 10- to 16-fold increase in the specific activity of ¹²⁵I over that of the cell homogenate and a 20-fold increase in the specific activities of 5′-nucleotidase and alkaline phosphate; no mitochondrial or microsomal marker enzyme activities were detected. Sodium dodecyl sulfate gel electrophoresis of the plasma membranes shows approx. 40 peptides with molecular weights ranging from 10 000 to over 200 000; a polypeptide ($\text{M}{}_{\mathrm{<mtext>m</mtext>}}$ 50 000) predominates. Of 13 iodinated surface membrane proteins, the major radioactive peptide has a molecular weight of 85 000. The importance of the selection of the appropriate gel sytem for the analysis of membrane proteins is emphasized.     

Photomonomerization of pyrimidine dimers by indoles and proteins.

Model systems for the study of photoreactivation have been developed that utilize a variety of indole derivatives. These systems can split uracil cis-syn cyclobutadipyrimidine, either free or in RNA, when irradiated at wave-lengths absorbed only by the indole moiety. The ability of indole compounds to split dimers is closely related to their electronic properties. Those of high electron-donor capacity such as indole, 3-methylindole, indole-3-acetic acid, 5-hydroxytryptophan and tryptophan are good photosensitizers, with efficacy in that order. Indoles with electron-withdrawing substituents such as indole-3-carboxylic acid, indole-3-aldehyde and oxindole are inactive in the monomerization reaction. These findings support the proposed mechanism that the photosensitized monomerization occurs as a result of electron transfer from the excited indole molecules to the pyrimidine bases.Proteins containing fully exposed tryptophan residues (chicken egg white lysozyme and bovine diisopropylphosphoryltrypsin) also cause the splitting of the ¹⁴C-labeled dimers under the same conditions. In the case of lysozyme the quantum yield of monomerization is similar to that of free tryptophan. Much of the monomerization ability of lysozyme was lost after the solvent-available tryptophan had been oxidized by treatment with N-bromosuccinimide. Bovine pancreatic ribonuclease A, a protein devoid of tryptophan, failed to exhibit photosensitized monomerization of uracil dimers. The biological implication of these reactions involving a protein with an exposed tryptophan residue is discussed.Although indoles are able to split the dimers in RNA, they fail to photo-reactivate u.v.-damaged TMV-RNA. Indole-3-acetic acid, 3-methylindole and 5-hydroxytryptophan rapidly inactivate viral RNA when irradiated at 313 nm, possibly because of side reactions.     

Effect of leaf water deficit on stomatal and nonstomatal regulation of net carbon dioxide assimilation

The effect of leaf water deficit on net CO₂ assimilation was studied under two conditions: in one, the stomata were allowed to contribute to the regulation of CO₂ assimilation; in the other, air was forced through the leaf at a constant rate to overcome the effects of change in stomatal resistance accompanying changes in leaf water deficit. When the stomata were allowed to regulate the gaseous diffusive resistance of the leaf, CO₂ assimilation decreased with increasing leaf water deficit. However, when air was forced through the leaf, the rate of assimilation was not inhibited by increasing leaf water deficit. The results indicate that the inhibition of net CO₂ assimilation with increasing leaf water deficit is a consequence of an increase in the diffusive resistance to gas exchange and not of a change in apparent mesophyll resistance.