Heme regulation of HeLa cell transferrin receptor number

The number of diferic transferrin receptors on HeLa cells decreases when cells are grown in iron-supplemented media. The experiments reported here suggest that heme is the iron-containing compound which serves as the signal for receptor number regulation. When HeLa cells were grown in the presence of hemin, transferrin receptor number decreased to a greater degree than when cells were grown in equivalent amounts of iron supplied as ferric ammonium citrate. Incubation of cells in conditions which increased cellular heme content resulted in a decrease in cellular transferrin receptors. Incubating cells with 5-aminolevulinic acid (thus bypassing the rate-limiting step in heme biosynthesis, 5-aminolevulinic acid synthase) led to a decrease in transferrin receptor number. Incubation of cells with an inhibitor of heme oxygenase, Sn-protoporphyrin IX, also led to a decrease in transferrin receptor number. When cellular heme content was decreased by inhibiting heme synthesis with succinylacetone (an inhibitor of 5-aminolevulinic acid dehydratase), or by depriving cells of iron with deferoxamine, an increase in HeLa cell transferrin receptor number was seen. When HeLa cells were incubated with inducers of heme oxygenase (CoCl2, SnCl2, Co-protoporphyrin IX), transferrin receptor number also increased. The effects of all compounds which alter transferrin receptor number were dependent on the concentration of the supplement, as well as the duration of the supplementation. These experiments suggest that intracellular heme content may be an important signal controlling transferrin receptor number.     

Papovaviral sialoadenitis in athymic nude rats

A wasting disease was found in 32 athymic nude rats. The rats had parotid sialoadenitis with intranuclear inclusion bodies in ductal and acinar epithelial cells. Other common lesions included bronchitis, bronchiolitis and secondary bacterial pneumonia. Less commonly, rhinitis and Harderian adenitis were seen. Intranuclear inclusions were also seen in bronchial epithelium of 1 rat, Harderian gland acini of 1 rat and laryngeal glands of 2 rats. Viral particles, averaging 45 nm in diameter, sometimes in crystalline arrays, were found in the nucleus of parotid epithelial cells. By the use of the avidin-biotin-peroxidase complex (ABC) immunoperoxidase technique, antibodies to disrupted SV40 virus (the group specific antigen of the polyomavirus (miopapovavirus) genus of the papovavirus family) reacted with intranuclear inclusions and cytoplasm of parotid epithelium and inclusions in lung and Harderian gland. The viral antigen did not cross react with antibodies to mouse polyoma, mouse K or disrupted bovine papilloma viruses.     

Control mechanisms governing the infectivity of Chlamydia trachomatis for HeLa cells: mechanisms of endocytosis

The mechanism by which Chlamydia trachomatis is endocytosed by host cells is unclear. Studies of the kinetics of chlamydial attachment and uptake in the susceptible HeLa 229 cell line showed that chlamydial endocytosis was rapid and saturable but limited by the slow rate of chlamydial attachment. To overcome this limitation and to investigate the mechanism of endocytosis, chlamydiae were centrifuged onto the host cell surface in the cold to promote attachment. Endocytosis of the adherent chlamydiae was initiated synchronously by rapid warming to 36 degrees C. Electron micrographs of chlamydial uptake 5 min after onset showed that chlamydial ingestion involves movement of the host cell membrane, leading to interiorization in tight, endocytic vacuoles which were not clathrin coated. Chlamydial ingestion was not inhibited by monodansylcadaverine or amantadine, inhibitors of receptor-mediated endocytosis and chlamydiae failed to displace [3H]sucrose from micropinocytic vesicles. Chlamydial endocytosis was markedly inhibited by cytochalasin D, an inhibitor of host cell microfilament function, and by vincristine or vinblastine, inhibitors of host cell microtubules. Hyperimmune rabbit antibody prevented the ingestion of adherent chlamydiae, suggesting that endocytosis requires the circumferential binding of chlamydial and host cell surface ligands. These findings were incompatible with the suggestion that chlamydiae enter cells by taking advantage of the classic mechanism of receptor-mediated endocytosis into clathrin-coated vesicles, used by the host cell for the internalization of beta-lipoprotein and other macromolecules, but were consistent with the hypothesis that chlamydiae enter cells by a microfilament-dependent zipper mechanism.     

Natural killer activity in the rat. III. Characterization of transplantable large granular lymphocyte (LGL) leukemias in the F344 rat

Six transplantable large granular lymphocyte (LGL) tumor lines in F344 rats were examined for natural killer (NK) and antibody-dependent cell-mediated cytotoxicity. Tumor cells from all six lines were highly cytotoxic, even at low effector to target ratios, when tested against NK-susceptible targets, but were unreactive against an NK-resistant target (C58NT)D) and a macrophage-susceptible target (P815). Three lines showed significant levels of lysis against antibody-coated tumor cells. After in vivo transplantation, the levels of cytotoxicity steadily increased in three lines and decreased in one. The cytotoxic activity of one line (RNK-16) remained high through 12 transplant generations. Tumor cells injected i.p. spread via the lymphatics to regional lymph nodes, mediastinal nodes, blood, and eventually the bone marrow. Leukemia occurred concurrently with organ enlargement and increased levels of NK. Studies in (F344 X W/Fu)F1 rats clearly demonstrated that the cytotoxic cells from leukemic animals were the transplanted tumor cells themselves and not merely the activation of normal host LGL. These results demonstrate that naturally occurring, transplantable LGL leukemias are an easily obtainable and excellent source of materials for those studies requiring a large number of functionally active LGL.     

Expression of minute virus of mice structural proteins in murine cell lines transformed by bovine papillomavirus-minute virus of mice plasmid chimera.

Recombinant plasmids containing the genomes of both bovine papillomavirus type I and minute virus of mice (MVM) were constructed and used to transform mouse C127 cells. Transformed lines that express MVM gene products with high efficiency were isolated and characterized. These transformants synthesize large amounts of MVM structural polypeptides and spontaneously assemble them into empty virion particles that are released into the culture medium. These lines were, however, genetically unstable; they slowly generated subpopulations that failed to express MVM-specific proteins, and they possessed episomal DNA in which both MVM and bovine papillomavirus sequences were deleted or rearranged, or both. Clonal isolates of these transformants were also superinfectible by infectious MVM virus. Therefore, in spite of their instability, they should be useful host cell lines for transcomplementing mutations introduced into the MVM genome and for growing defective viruses as virions.     

The nutritional ecology of the ctenophore Bolinopsis vitrea: comparisons with Mnemiopsis mccradyi from the same region

Bolinopsis vitrea is a warm water lobate ctenophore which doesnot overlap in its distribution with Mnemiopsis mccradyi incontiguous waters. We examined its feeding ecology on a seriesof cruises. B. virrea ingested increasingly more prey at higherfood concentrations (2–100 prey l^–1) but feedingeffort (clearance rate) decreased with increasing food availability.On a dry weight basis, smaller tentaculate Bolinopsis ingestedseveral times more than larger lobates, but based on carbonweight, specific ingestion was fairly uniform over the entiresize range investigated (6–60 mm total length). Bolinopsiscollected during the daytime in the Bahamas rarely had morethan three prey items in their guts. These results and laboratorymeasurements of digestion times (av. = 1.9 h) allowed computationof daily rations, which could not account for the metabolicrequirement as measured on the same cruises. Results of feedingexperiments, however, implied that prey densities in excessof 11^–1 were sufficient to sustain a growing populationof Bolinopsis. Prey concentrations about an order of magnitudehigher were required for M. mccradyi based on similar experiments.These results were in general agreement with observed densitiesand distributions of ctenophores and their zooplankton preyin the Bahamas and coastal South Florida.     

Brain temperature measurements in rats: a comparison of microwave and ambient temperature exposures

In an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or "hot spots," in the brain of these animals. In the first study, after a 30-min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time-temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2 degrees C. In this study, the 30-min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.     

Evaluating pedigree data. II. Identifying the cause of error in families with inconsistencies

Pedigree data can be evaluated, and subsequently corrected, by analysis of the distribution of genetic markers, taking account of the possibility of mistyping . Using a model of pedigree error developed previously, we obtained the maximum likelihood estimates of error parameters in pedigree data from Tokelau. Posterior probabilities for the possible true relationships in each family are conditional on the putative relationships and the marker data are calculated using the parameter estimates. These probabilities are used as a basis for discriminating between pedigree error and genetic marker errors in families where inconsistencies have been observed. When applied to the Tokelau data and compared with the results of retyping inconsistent families, these statistical procedures are able to discriminate between pedigree and marker error, with approximately 90% accuracy, for families with two or more offspring. The large proportion of inconsistencies inferred to be due to marker error (61%) indicates the importance of discriminating between error sources when judging the reliability of putative relationship data. Application of our model of pedigree error has proved to be an efficient way of determining and subsequently correcting sources of error in extensive pedigree data collected in large surveys.     

Identification of a large multigene family encoding the major sperm protein of Caenorhabditis elegans

DNA fragments corresponding to genes encoding the MSP of Caenorhabditis elegans sperm have been isolated by recombinant DNA techniques. Analyses of individual genomic clones suggest that there are multiple MSP genes that are dispersed in the genome. From restriction enzyme digests of genomic DNA fractionated and hybridized with an MSP complementary DNA probe, there appear to be more than 30 MSP genes in the genome. Despite the occurrence of this large dispersed multigene family, the MSP messenger RNA from both males and hermaphrodites is homogene in size. There are at least three different proteins of identical molecular weight but different isoelectric point that cross-react with anti-MSP antisera. Each protein is a primary translation product with no detectable post-translational modifications, suggesting that at least three of the MSP genes are expressed.     

Cultural Aspects of Health and Illness Behavior in Hospitals

Health care attitudes reflect the basic world view and values of a culture, such as how we relate to nature, other people, time, being, society versus community, children versus elders and independence versus dependence. Illness behavior determines who is vulnerable to illness and who agrees to become a patient—since only about one third of the ill will see a physician. Cultural values determine how one will behave as a patient and what it means to be ill and especially to be a hospital patient. They affect decisions about a patient''s treatment and who makes the decisions. Cultural differences create problems in communication, rapport, physical examination and treatment compliance and follow through. The special meaning of medicines and diet requires particular attention. The perception of physical pain and psychologic distress varies from culture to culture and affects the attitudes and effectiveness of care-givers as much as of patients. Religious beliefs and attitudes about death, which have many cultural variations, are especially relevant to hospital-based treatment. Linguistic and cultural interpreters can be essential; they are more available than realized, though there are pitfalls in their use. Finally, one must recognize that individual characteristics may outweigh the ethnic and that a good caring relationship can compensate for many cultural missteps.