摘要:

Two NADP-specific "malic" enzymes have been found to be present inNeurospora crassa. They have different pH optima and are influenced differently by some metabolites and inhibitors. The pH 8.0 "malic" enzyme appears during the early stages of growth and is inhibited by fructose 1,6-diphosphate while the pH 10.0 "malic" enzyme appears during the later stages of growth and is inhibited by aspartate. Both enzymes are repressed by acetate and pyruvate and their activities are inhibited by glyoxylate and oxaloacetate. The metabolic function of the enzymes is discussed.

ISSN:0008-4166    

DOI:10.1139/m72-097

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A culture ofMortierella alpinaPeyroud isolated from soil and grown on Czapek-Dox medium was found to contain a high concentration of mycoferritin (MF). The MF was extracted from lyophilized mycelium by grinding with 0.1 M, pH 7.0, potassium-phosphate buffer and chloroform followed by differential centrifugation. Sucrose density-gradient centrifugation of the concentrated MF resulted in a brownish-yellow band in the region of 60–70 S. Following dialysis and concentration by high-speed centrifugation, the MF was compared to horse-spleen ferritin (HF). The ultraviolet (uv.) and infrared (i.r.) spectra of MF and HF were identical. Negatively stained preparations examined in the electron microscope showed particles of about 10 nm diameter. Sedimentation rates of S20,w = 66 for MF and S20,w = 56 for HF were obtained by analytical ultracentrifugation. The MF preparation contained 83% protein and 17% iron. The molecular weight of the protein subunit was determined by gel electrophoresis to be about 19 300 daltons.

ISSN:0008-4166    

DOI:10.1139/m72-098

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Isolated cell walls ofMicrococcus lysodeikticusandStaphylococcus aureuswere found to have relatively low densities in both the dried and hydrated states. Thus, it appears that the component polymers of these structures do not form crystallites or other highly condensed assemblies, but rather, that their distribution within the wall matrix is similar to that of the polymer chains in low-density, ion-exchange resins.Micrococcus lysodeikticuswalls, which are composed mainly of peptidoglycan, swelled significantly when they were heated or transferred to 8 Murea solution. This finding suggests that the compactness of walls and their component peptidoglycans is determined in part by weak interactions that can be disrupted by urea or by heat.

ISSN:0008-4166    

DOI:10.1139/m72-099

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Various strains of species belonging to theAspergillus ochraceusgroup (A.ochraceus,A.sclerotiorum,A.alliaceus,A.ostianus,A.melleus, andA.sulphureus) can produce two mycotoxins, ochratoxin A and penicillic acid, on liquid media and in cereal grains. The quantity of each toxin produced is influenced by temperature; low temperature (10 and 20C) favor penicillic acid synthesis and higher (28C), ochratoxin A production. Generally penicillic acid is produced in yields about one to three magnitudes greater than ochratoxin A. A simple fluorodensitometric method for concomitant quantitative analysis of the two toxins has been developed based on conversion of penicillic acid and ochratoxin A to fluorescent derivatives by treatment with ammonia fumes.

ISSN:0008-4166    

DOI:10.1139/m72-100

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Significant variations in the protein and carbohydrate contents of bacterial cells and of mycobacterial fractions occurred during the growth cycle of three strains of Mycobacteria (H37Rv, H37Ra, and BCG).In whole bacilli or their water-soluble extracts, a peak of proteins occurred early during the exponential phase of growth, whereas polysaccharides reached a maximum 2 to 3 weeks later. In culture filtrates, the amount of both proteins and carbohydrates increased with the aging of tubercle bacilli; the increase of carbohydrates, however, was larger. Few quantitative differences in the yield and chemical composition of mycobacterial fractions were noted between the three tubercle bacilli.

ISSN:0008-4166    

DOI:10.1139/m72-101

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The degradation of DNA in bacterial cells has been studied in two strains ofEscherichia coliafter exposure to X-radiation, ultraviolet (uv.), or methyl methanesulfonate. The degradative system functions differently in freshly harvested growing cells and in cells which have been aged by standing for 2 days at room temperature in saline-phosphate. Growing cells degrade their DNA most effectively at low doses of X-radiation and require a factor whose synthesis is inhibited by chloramphenicol; these cells also degrade DNA after exposure to uv. radiation. Aged cells degrade their DNA most effectively at high X-radiation doses, do not require the chloramphenicol-sensitive factor, and no longer respond to uv. irradiation. Together with data on effects of freezing, of cold-water, and of various inhibitors, the above results suggest that the system responsible for radiation-induced degradation of DNA is dependent on structural organization in the intact cell.

ISSN:0008-4166    

DOI:10.1139/m72-102

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Hamsters injected subcutaneously with a single "low-dose" inoculum (10 mouse LD50) of Powassan virus developed viremia titering 106.2mouse LD50per milliliter of blood whereas hamsters receiving a "high-dose" inoculum of 105.0mouse LD50of virus developed a viremia of only 104.5mouse LD50per milliliter.Hemagglutination-inhibiting (HI) antibodies were first detected 7 days following the "low-dose" inoculation and attained maximum titers of 160. The HI antibody response to the "high-dose" virus inoculation began on the 5th day, at a time when viremia was present, and antibody titers did not exceed 40. Sucrose-density analysis and 2-mercaptoethanol treatment of sera revealed that IgM antibodies were induced by both inocula but animals receiving a low dose of virus produced higher IgG responses than did animals receiving a high dose of virus. Neutralizing antibodies, which did not appear until 30 days post inoculation, were present at a log neutralizing index (NI) of 2.0 at 60 days in animals receiving 10 mouse LD50of virus and at a log NI of 1.0 in those receiving 105.0mouse LD50. The NI of IgG was equal to the index for total gamma globulin in samples that contained both IgM and IgG as demonstrated by the HI test.Animals originally exposed to a "low-dose" inoculum produced a more prolonged anamnestic response when challenged 63 days later with 105.0mouse LD50of virus than did animals receiving a second inoculum containing only 103.0or 10 mouse LD50of virus. In contrast, poor secondary antibody responses were elicited by challenge doses of 105.0, 103.0, or 10 mouse LD50of virus in animals that originally had received a "high-dose" of virus. IgM and IgG classes of antibody were induced in all secondary responses and the log NI of each group of animals was elevated by about 1 during anamnesis.

ISSN:0008-4166    

DOI:10.1139/m72-103

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The course of somatic nuclear division was investigated in randomly and synchronously dividing populations ofUstilago violacea. Interphase nuclei with diffuse chromatin are found in the sporidia just before budding, but distinct chromatin granules form at the onset of bud formation. These granules become more condensed and appear to be connected by lightly staining fibers. When the bud cell reaches about half the size of the parent cell, the granules aggregate into two parallel 'bars' or 'tracks' of chromatin. This double structure migrates towards the isthmus between parent cell and bud cell and passes through completely, leaving the parent cell enucleate. The nucleus in the bud cell becomes highly condensed and is composed of two lobes which separate from each other to form two daughter nuclei in the bud cell. One nucleus returns to the parent cell and immediately enters interphase, while the other is retained in the bud cell in telophase. The nucleus in the bud cell remains in telophase until the cell reaches the full size of a parent cell, when it then enters interphase. Counts of the chromatin granules before the formation of the 'double-bar' stage show that the number of visible elements may be as many as 20 in both haploid and diploid strains, and it is suggested that previous claims thatn = 2 inU.violaceaare based on misinterpretation of aggregates of chromosomes. The similarity in the number of visible elements in haploid and diploid strains is considered to be a result of somatic association of homologous chromosomes in the diploid strain.

ISSN:0008-4166    

DOI:10.1139/m72-104

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Salmonella typhimuriumderepressed for the histidine biosynthetic enzymes form wrinkled colonies at 37 °C on media containing a high (2%) content of metabolizable carbon source. "Wrinkledness" reflects accumulation of multinucleate filamentous cells caused by impaired cell division. At 42 °C, DNA synthesis and nuclear division are impaired. Addition of methionine at 42 °C permits DNA synthesis, nuclear division, and, under some conditions, cell division. However, multinucleate filaments are formed both on high and on low carbon source at 42 °C. The filaments contain nuclei that are peculiarly hypersensitive to inactivation with ultraviolet (uv.) light.Overproduction of both thehisHandhisFgene products is required for these pleiotropic effects of derepression. ThehisHandhisFproteins, and even some of their enzymologically inactive forms, may cooperate to inhibit cell division by direct interaction with (a) sensitive cellular site(s).

ISSN:0008-4166    

DOI:10.1139/m72-105

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The effects of the antifungal agent, griseofulvin, on mitosis in a diploid strain ofAspergillus nidulanshas been studied. Helly-fixed preparations stained with acid fuchsin normally reveal densely staining, spherical nucleoli, lateral granules accompanying the nucleoli, and spindles in various stages of development. The development of this granule results in the formation of a small cigar-shaped spindle which increases in size in later stages of division and then becomes stretched out into a thin, long fiber at the termination of division.Cultures treated with griseofulvin reveal damaged and distorted spindles within 30 s to 1 min after treatment. After 1 min or more of drug treatment,nonormal spindles are seen but granules forming the polar regions of the spindle persist.The division of the chromatin during mitosis is also distorted by griseofulvin treatment. Cultures treated with this drug reveal abnormal chromatin configurations after 15–20 min. Individual chromosomes such as those seen at metaphase-like stages become distorted into a dense mass of chromatin. The further stages of division reveal abnormally stretched out lengths of chromatin which are, however, capable of division by a break in the constricted thread near the center.Spindles appear to recover from the griseofulvin treatment when treated cultures are transferred to fresh medium not containing griseofulvin at 35 °C for 90 min.

ISSN:0008-4166    

DOI:10.1139/m72-106

出版商:NRC Research Press    

年代:1972

数据来源: NRC