Heat tolerance of Salmonella typhimurium DT104 isolates attached to muscle tissue

Aerobic and anaerobic plate counts were compared for routine monitoring of the microflora, dominated by lactic acid bacteria, developing on vacuum- and carbon dioxide-packaged raw meat during chilled storage. No statistical differences were observed between aerobic and anaerobic enumerations, made on plate count and blood agar plates, of the microflora developing on beef striploins packaged under vacuum or carbon dioxide during 14 weeks' storage at 0°C. With both techniques the spoilage microflora development differed between the two packaging regimes. The results indicate that there is no necessity for aerobic plate counts to be replaced by anaerobic plate counts in the routine microbiological examination of the spoilage microflora developing on chilled meats packaged under anoxic modified atmospheres.     

Oxygenation properties of haemoglobins from the flatfish plaice (Pleuronectes platessa) and flounder (Platichthys flesus)

Summary The oxygen binding properties and some haematological data of haemoglobins of plaice (Pleuronectes platessa) and flounder (Platichthys flesus) were measured and compared, with the view of discerning their adaptations to the benthic habitat.Compared to plaice, flounders posses higher haematocrit and haemoglobin levels, and their haemoglobin has a higher oxygen affinity, smaller Bohr and Root effects and appears to have a greater ATP sensitivity. At pH 7.6, the half-saturation oxygen tensions,P ₅₀, of stripped plaice and flounder haemoglobins amount to about 5.9 and 4.2 torr, and the Bohr shifts (logP ₅₀/ pH) to –0.51 and –0.34, respectively. The species differences in the oxygen binding patterns occur after stripping the haemoglobin in solution, from dissolved ions and thus appear to be inherent in the pigment molecules. The differences suggest that the haemoglobin of flounder is better adapted to hypoxic and hypercarbic environments than plaice haemoglobin, in accordance with the more inshore occurrence of the former species.The molar ratios of ATP to haemoglobin tetramers are low in plaice and flounder (about 1.6); in plaice this ratio corresponds to that where the cofactor effect is most pronounced. In contrast to previous evidence for an adaptive reduction in the temperature dependence of the haemoglobin of flounder but not of plaice from the Baltic Sea (Friedrich, 1935), the same temperature effects were found in representatives of the two species both from the Dutch North Sea and the Danish Kattegat.     

THE PAROTID GLAND—A Reinterpretation of Its Anatomic Structure

The parotid gland does not have a constant size and shape and relationship to the facial nerve. It consists of two glandular masses, one lying on the masseter muscle and the other in the pterygoid space to a varying depth. These two masses are connected by a glandular bridge, either wide or narrow, which lies on the posterior border of the mandible. The course of the facial nerve may be through this connecting bridge or it may pass to one side or a branch may pass on either side. In passing forward, the nerve branches may lie wholly within the glandular mass on the masseter, wholly beneath it or partly within it and partly beneath it.     

Symbiotrophy of lignophytes and fungi: Its terminological and conceptual deficiencies

The authors suggest a replacement of the terms ectotrophic, endotrophic, and peritrophic mycorrhizae byectocellular, endocellular, andperipheral mycorrhizae. The termrhizoclena (root mantle) is advanced for superficial rootadherent fungal mycelia. The two principal varieties of rhizoclenae are:mycochlamydes, lanose fungal mantles enveloping the roots;mycoplasts, grumose fungal mantles consisting of sapropellous clusters of soil, root sloughings, and fungal hyphae agglutinated by microbial excretions. Emphasis is placed on nutritional importance of the epirhizal root auxiliaries. These constituents of the rhizosphere by virtue of their chelating processes convert raw organic and mineral sources of nutrients into available form. A tree or other lignophyte removed from the soil is only a part of the whole plant surgically separated from its rhizospheric digestive organ. In consequence, suggestion is made to recognize obvious orphanero-symbiosis, detectable by ocular or microtome examination, and concealed orcrypto-symbiosis, effected by juxtaposed mycelia. A scarcity or entire absence of ectocellular mycorrhizal short roots of seedlings naturally reproduced under the canopy of mother stands indicated the minor nutritional importance of these root-fungus organs. The abundance of short roots, common to greenhouse and nursery cultures, is attributed to the exposure of trees to full sunlight and excessive production of carbohydrates. Preservation of the termpseudomycorrhizae may be justified in application to mycelia-free forked short roots produced in sterile nutrient solutions, especially those enriched in growth-promoting hormones.     

Influence of fixation and immunohistological technique on accuracy, precision and inter-observer reproducibility of plasma cell counting.

Recently two highly sensitive and specific diagnostic criteria for Sj?gren's syndrome based on percentages of IgA-, IgG-, and IgM-containing plasma cells measured in immunohistologically stained labial salivary gland tissue have been described. The reliability of such a criterion is dependent on the accuracy, precision and inter-observer reproducibility in plasma cell counting. The present study evaluates the effect of tissue fixation and immunohistological procedures on the aforementioned factors. Immunoglobulin (Ig)-containing plasma cells in sections of lamellated submandibular salivary gland tissue, alternately fixed in a 4% buffered formol solution or formol-sublimate solution and stained with an indirect immunoperoxidase and unlabelled peroxidase anti-peroxidase (PAP) method respectively, were enumerated by three independent observers. Relative numbers of Ig-containing plasma cells appeared to be less sensitive for systematic errors due to tissue fixation and immunohistological procedure than absolute numbers of Ig-containing plasma cells. The best inter-observer reproducibility of plasma cell counts was obtained in sections from formol sublimate-fixed specimens stained according to the PAP procedure.     

Comparison of collagen gels and mammary extracellular matrix as substrata for study of terminal differentiation in rabbit mammary epithelial cells

Mammary epithelial cells were prepared by collagenase digestion of tissue from mid-pregnant rabbits and cultured for up to 6 days on either collagen gels or an extracellular matrix prepared from the same tissue. The behaviour of the cells in serum-supplemented medium containing combinations of insulin, prolactin, hydrocortisone, estradiol and progesterone were monitored by measuring rates of casein synthesis, lactose synthesis, DNA synthesis and protein degradation. After 6 days, epithelial cells on floating collagen gels showed substantial increases in casein synthesis and DNA synthesis over freshly-prepared cells, following a decline during the first 3 days when the collagen gels are contracting. The optimum hormone combination for casein synthesis was insulin + prolactin + hydrocortisone, whereas for optimum DNA synthesis the additional presence of estradiol and progesterone was required. Cells on extracellular matrix showed increased rates of both casein synthesis and DNA synthesis by day 6 in the presence of insulin + prolactin + hydrocortisone, with additional estradiol + progesterone having an inhibitory effect. Whereas on day 2 rates of intracellular protein degradation were generally lower in cells on extracellular matrix, by day 6 rates of protein degradation were lowest in cells cultured on collagen gels with insulin + prolactin + hydrocortisone. In all cases, rates of lactose synthesis fell to low levels as the culture proceeded. Pulse-chase labelling of freshly-prepared cells with [32P]orthophosphate in medium containing serum and insulin + prolactin + hydrocortisone demonstrated that newly-synthesized casein was degraded during its passage through the epithelial cell. The influences of the collagen gels and extracellular matrix and of the hormone combinations on epithelial cell differentiation and secretory activity are discussed.     

The HIV-1 Gag precursor Pr55gag synthesized in yeast is myristoylated and targeted to the plasma membrane

Myristoylation of the Pr65gag protein from Moloney murine leukemia virus has been shown to be essential for virus particle formation [Rein et al., Proc. Natl. Acad. Sci. USA 83 (1986) 7246-7250], and by analogy, myristoylation of the human immunodeficiency virus (HIV) Gag precursor could possibly play a similar role. We have investigated the expression and myristoylation of the complete HIV Gag precursor Pr55gag in yeast, the subcellular localization of that protein, and the contribution of the myristoyl-glycine residue to this localization. Immunogold labelling of myristoylated Pr55gage with antibodies directed against HIV Gag products was apparent in the vicinity of the plasma membrane. On the contrary, non-myristoylated derivatives of Pr55gag were only detected in relatively well-defined regions of the cytoplasm. These results show that targeting and accumulation of the HIV Gag precursor, Pr55gag, at the plasma membrane occurs in yeast in the absence of other viral components and requires the N-myristoyl-glycine residue.