Chimeras vs X inactivation mosaics: significance of differences in pigment distribution

Cell cultures of cardiac, pectoral, and thigh muscle of chick embryos synthesized myoglobin, as measured by incorporation of radioactive lysine detected by radioimmunoprecipitation. Liver and skin cultures, although active in protein synthesis, failed to demonstrate myoglobin synthesis. Puromycin inhibited myoglobin synthesis by the cell cultures. The electrophoretic characteristics of the myoglobin antigen synthesized by thigh and pectoral muscle were identical. Myglobin synthesizing progenitor cells attached to plastic dishes in 1 hr, but not completely in 0.5 hr. Cells, unattached at 0.5 hr, were enriched in myoglobin synthesizing cells. Incorporation of lysine-U-¹⁴C into myoglobin was maximal in confluent cultures and its increase paralleled the increase of cell fusion in the cultures. The ability of pectoral, white muscle to synthesize myoglobin in a manner equivalent to that of cardiac tissue was unexpected because of its failure to synthesize myoglobin in vivo and may indicate that factors in the whole organism may regulate the expression of this muscle cell's capabilities.     

ADP-Glucose Pyrophosphorylase from Potato Tubers. Site-Directed Mutagenesis Studies of the Regulatory Sites

Several lysines (Lys) were determined to be involved in the regulation of the ADP-glucose (Glc) pyrophosphorylase from spinach leaf and the cyanobacterium Anabaena sp. PCC 7120 (K. Ball, J. Preiss [1994] J Biol Chem 269: 24706–24711; Y. Charng, A.A. Iglesias, J. Preiss [1994] J Biol Chem 269: 24107–24113). Site-directed mutagenesis was used to investigate the relative roles of the conserved Lys in the heterotetrameric enzyme from potato (Solanum tuberosum L.) tubers. Mutations to alanine of Lys-404 and Lys-441 on the small subunit decreased the apparent affinity for the activator, 3-phosphoglycerate, by 3090- and 54-fold, respectively. The apparent affinity for the inhibitor, phosphate, decreased greater than 400-fold. Mutation of Lys-441 to glutamic acid showed even larger effects. When Lys-417 and Lys-455 on the large subunit were mutated to alanine, the phosphate inhibition was not altered and the apparent affinity for the activator decreased only 9- and 3-fold, respectively. Mutations of these residues to glutamic acid only decreased the affinity for the activator 12- and 5-fold, respectively. No significant changes were observed on other kinetic constants for the substrates ADP-Glc, pyrophosphate, and Mg²⁺. These data indicate that Lys-404 and Lys-441 on the small subunit are more important for the regulation of the ADP-Glc pyrophosphorylase than their homologous residues in the large subunit.     

Factors influencing family physicians to continue providing obstetric care.

To determine the reasons some family physicians continue to practice obstetrics when most of their colleagues do not, we surveyed family physicians in 26 counties of northern California whose practices include obstetrics and those who have recently discontinued it. In all, 70% of family physicians practicing obstetrics cited enjoying it as a reason for continuing this practice. Over a third of family physicians practicing obstetrics thought that obstetric practice was a responsibility to the community. Only 1 in 6 reported obstetrics to be important in terms of financial implications. Despite this, family physicians practicing obstetrics had a mean gross income derived from obstetric practice of $30,000 above the cost of their total malpractice premium. In contrast, a comparison group of family physicians who had recently discontinued obstetrics cited malpractice insurance costs most frequently as the reason for discontinuing it. Nearly 40% of these physicians indicated that they would be willing to return to obstetrics if circumstances were to change substantially. The most frequently cited change necessary for these physicians to return to obstetrics was a reduction in malpractice insurance rates.     

Differential regulation of interleukin-6 receptor and gp130 gene expression in rat hepatocytes.

Interleukin-6 (IL-6) relays an important signal to hepatocytes during the early stages of an acute inflammatory response, causing an alteration in the expression of several major defense proteins. Additional regulation of this signal could occur either by altering the number of IL-6 receptors (IL-6-R) or of the signal transducing protein, gp130. We employed ribonuclease protection assays to measure the expression of IL-6-R and gp130 mRNA in primary rat hepatocytes in response to IL-6, interleukin-1, dexamethasone, and combinations thereof. Dexamethasone increases receptor mRNA levels 2.7-fold above controls but has no detectable effect on that of gp130. Such treatment increased surface expression of IL-6-R from 600 receptors per cell to greater than 6000, without a change in Kd (2.5-4.6 x 10(-10) M). In contrast to the stimulatory effect of the steroid signal, the inflammatory cytokines, individually and together, down-modulated both the mRNA and the cell surface expression of IL-6-R. These findings demonstrate for the first time that a sensitive control system exists between inflammatory mediators and IL-6-R.     

Identification of the female sex pheromones of the moth, Chilo suppressalis

The female sex pheromone complex of the striped rice borer, Chilo suppressalis, has been shown to consist of two compounds: (Z)-11-hexadecenal (I) and (Z)-13-octadecenal (II). The pheromones were identified by gas chromatographic analysis, electroantennogram recording, ozonolysis, and comparison with synthetic material.     

Obstetric care,Medicaid, and family physicians. How policy changes affect physicians' attitudes.

Recent expansion of Medicaid eligibility for pregnant women and increased reimbursement to physicians who provide perinatal services were designed to improve access to care. Family physicians provide a relatively high proportion of care to pregnant women on Medicaid, especially in rural areas. We surveyed all family physicians who provide obstetric services in 26 northern California counties regarding these changes and perceived barriers to providing obstetric care to women on Medicaid. Of surveyed physicians who limited the number of their Medicaid obstetric patients, 58% stated that recent Medicaid policy changes had increased their willingness to accept new Medicaid obstetric patients. Despite these policy changes, administrative issues and poor reimbursement were cited as the two most notable barriers to providing obstetric care to women on Medicaid. Fear of being sued by Medicaid patients is still seen as a barrier by physicians who have recently discontinued practicing obstetrics and by those who continue to care for a large number of Medicaid obstetric patients.     

(Z)-8-dodecenyl acetate: the major component of the female sex pheromone of Cryptophlebia batrachopa, a Tortricid pest of macadamia in Malawi

Ovipositor washings from virgin female Cryptophlebia batrachopa (Meyrick) (Lepidoptera: Tortricidae) were analysed by gas chromatography (GC) linked to electroantennography (EAG) and by high-resolution GC. The major EAG-active component in ovipositor washings was shown to be (Z)-8-dodecenyl acetate with less than 0.5% of the E isomer. GC analysis of ovipositor washings from C. leucotreta confirmed the presence of approximately equal amounts of (Z)- and (E)-8-dodecenyl acetates (Persoons et al., 1977). When pure (Z)-8-dodecenyl acetate and mixtures containing up to 50% of the E isomer were tested in the field in Malawi where both Cryptophlebia species occurred, C. batrachopa male moths were caught only in traps baited with 10% or less of the E isomer and highest catches were recorded for the pure Z isomer. By contrast C. leucotretra males were caught predominantly by traps baited with more than 10% E isomer and no catches were recorded for the pure Z isomer. (Z)-8-dodecenyl acetate containing 1% of the E isomer was found to attract male moths of Opogona spp.

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Résumé Les produits recueillis par lavages de l'ovipositeur de Cryptophlebia batrachopa Meyr. (Lep. Tortricidae) ont été analysés par chromatographie gazeuse (GC) associée à l'électroantennographie (EAG) et la GC à haute résolution. Le principal constituant actif en EAG provenant des lavages s'est révélé être le (Z)-8-dodécényl acétate avec moins de 0,5% de l'isomère E. L'analyse GC de ces produits de lavage de C. leucotreta ont confirmé la présence d'à peu près les mêmes quantités de (Z) et (E)-8-dodécényl acétates (Persoons et al., 1977). Quand des essais sur le terrain ont été effectués au Malawi, où existent les deux espèces de Cryptophlebia, avec du (Z)-8-dodécényl acétate et des mélanges comprenant jusqu'à 50% de l'isomère E, des mâles de C. batrachopa ont seuls été capturés dans des pièges contenant 10% ou moins de l'isomère E; les captures les plus élevées ont été obtenues avec l'isomère Z pur. A l'opposé, surtout des mâles de C. leucotreta ont été capturés dans des pièges garnis avec plus de 10% d'isomère E, et aucune capture n'a été obtenue avec l'isomère Z pur. Des mâles d'Opogona spp. ont été attirés par du (Z)-8-dodécényl acétate contenant 1% de l'isomère E.

     

Avian pox in Florida sandhill cranes.

Cutaneous elevations were present on the feet, legs and heads of four Florida sandhill cranes, Grus canadensis pratensis, (one free-living, three penreared birds). As a result of examination of the elevations by light- and electron microscopy, it was determined that the lesions were caused by poxvirus. This is the first record of pox in cranes in North America.