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Biomedical subjects

J E Linder

Publications and source records attributed to J E Linder.

15 recordsLinked to original sources
PubMed2005

Natural selection and genetic variation for female resistance to harm from males.

The sexual conflict hypothesis predicts that males evolve traits that exploit the higher parental investment of females, which generates selection for females to counter-evolve resistance. In Drosophila melanogaster it is now established that males harm females and that there is genetic variation among males for the degree of this harm. Genetic variation among females for resistance to harm from males, and the corresponding strength of selection on this variation, however, have not been quantified previously. Here we carryout a genome-wide screen for female resistance to harm from males. We estimate that the cost of interactions with males depresses lifetime fecundity of females by 15% (95% CI: 8.2-22.0), that genetic variation for female resistance constitutes 17% of total genetic variation for female adult fitness, and that propensity to remate in response to persistent male courtship is a major factor contributing to genetic variation for female resistance.

Aggression↗
PubMed2005

Sexy sons from re-mating do not recoup the direct costs of harmful male interactions in the Drosophila melanogaster laboratory model system.

The empirical foundation for sexual conflict theory is the data from many different taxa demonstrating that females are harmed while interacting with males. However, the interpretation of this keystone evidence has been challenged because females may more than counterbalance the direct costs of interacting with males by the indirect benefits of obtaining higher quality genes for their offspring. A quantification of this trade-off is critical to resolve the controversy and is presented here. A multi-generation fitness assay in the Drosophila melanogaster laboratory model system was used to quantify both the direct costs to females due to interactions with males and indirect benefits via sexy sons. We specifically focus on the interactions that occur between males and nonvirgin females. In the laboratory environment of our base population, females mate soon after eclosion and store sufficient sperm for their entire lifetime, yet males persistently court these nonvirgin females and frequently succeed in re-mating them. Females may benefit from these interactions despite direct costs to their lifetime fecundity if re-mating allows them to trade-up to mates of higher genetic quality and thereby secure indirect benefits for their offspring. We found that direct costs of interactions between males and nonvirgin females substantially exceeded indirect benefits through sexy sons. These data, in combination with past studies of the good genes route of indirect benefits, demonstrate that inter-sexual interactions drive sexually antagonistic co-evolution in this model system.

Animals↗
PubMed1989

An assessment of emergency medicine residency graduates' perceptions of the adequacy of their residency training.

A study of emergency medicine residency training graduates was conducted to determine their perceptions of the quality of their graduate training. A sample of 300 individuals was randomly selected from a population of 1,000 persons graduating from 1982 through 1984. Respondents were asked to use a scale of 1 to 5 (with 1 being highest) to rate the adequacy of their residency training relative to 20 major core content areas. A 50% response rate (N = 151) was achieved. Mean ratings of residents' perceptions of the adequacy of their training relative to the core content ranged from 1.7 to 3.24. Training in resuscitation and stabilization, principles of emergency care, and general assessment were among the most highly rated, while training in physician interpersonal skills, disorders related to the immune system, and cutaneous disorders were rated the lowest. Overall, residents were quite positive in their perceptions regarding the quality of their training. They indicated plans to attend continuing medical education programs to reinforce some of their training and to address some of the deficiencies they perceived in residency training. Programs are encouraged to conduct similar surveys with their own graduates to assess particular strengths and weaknesses.

Adult↗
PubMed1983

Kinetics of osteoclast formation: the significance of blood monocytes as osteoclast precursors during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in the mouse.

The significance of blood monocytes as a source of osteoclast precursors was investigated during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in mice. Animals were given three injections of tritiated thymidine at 8 hourly intervals in order to label blood monocytes. The proportion of labelled monocytes was then compared with the proportion of labelled nuclei in osteoclasts, the formation of which was provoked by daily injections of 1 alpha-hydroxycholecalciferol, beginning 48 hours after the first injection of isotope. Although more than 60% of blood monocytes were labelled during the period of peak osteoclast formation, labelling of osteoclast nuclei in the metaphyseal endosteum of the femur never exceeded 8%. These results suggest strongly that the majority of osteoclast nuclei were derived from a source of unlabelled precursors, and that very few osteoclasts were derived directly from blood monocytes. Although few labelled osteoclasts were found, the proportion of labelled spindle shaped cells in the metaphyseal endosteum rose gradually to 16%. It is likely, therefore, that labelled mononuclear cells, possibly blood monocytes, were attracted to the endosteum where they formed a population of tissue macrophages. At this site they may participate in bone resorption, either individually or by providing a local pool of osteoclast precursors.

Animals↗
PubMed1982

A histological method for the visualization of the intercellular permeability barrier in mammalian stratified squamous epithelia.

Mammalian epidermis and oral epithelial possess an intercellular permeability barrier which is located in the superficial region of the tissue. This study reports a staining reaction which appears to demonstrate a histological correlate of this functional property. Specimens of ear skin, palate, buccal and oesophageal mucosa and of cornea and bladder were obtained from adult rabbits and rats, bisected and either incubated in vitro with 2.5% horseradish peroxidase as a tracer or fixed and processed for light microscopy and stained with a modification of Hart's elastin stain. Examination of specimens prepared by each procedure showed a complementary staining pattern in the intercellular spaces of the stratum corneum or in the superficial region of the non-keratinized tissue. In the epidermis and oral and oesophageal epithelia, the region which excluded the tracer stained with the modified elastin stain. In contrast, the corneal and bladder epithelia neither excluded the tracer nor showed intercellular staining. This relationship between staining of the intercellular space and the exclusion of tracer suggests that the intercellular material in the superficial region of epithelia may be chemically altered to form a barrier substance, possibly as the result of the discharge of the contents of the membrane-coating granules which are present in all the epithelia examined except the cornea and bladder.

Animals↗
PubMed1982

An ultrastructural and enzyme cytochemical study of the response of the neutrophil series to a local inflammatory stimulus in the rat.

Changes in neutrophil precursor populations in the bone marrow and their alkaline phosphatase reactivity following an inflammatory stimulus were studied in the rat using an osmiophilic method. Seven groups each of 3 Sprague-Dawley rats received subcutaneous injections of turpentine, and femoral marrow was examined at intervals up to 72 hr. Depletion of mature neutrophils resulted in an increased first in the myeloblast-promyelocyte compartment and at 48-72 hr in the myelocyte-metamyelocyte population. By 72 hr replenishment of the mature neutrophil marrow population had begun. Within 6 hr marked acceleration of cytoplasmic maturation was evident, together with accelerated synthetic activity, manifested by marked dilatation of the rough endoplasmic reticulum and an enlarged Golgi. Together with these changes there was an increase in the number of alkaline phosphatase reactive cells, which was evident first in the myeloblast-promyelocyte population at 2 hr. An absolute increase in the amount of enzyme reaction product associated with individual cells was also seen.

Alkaline Phosphatase↗
PubMed1981

Staining of demineralized cartilage. I. Alcoholic versus aqueous demineralization at neutral and acidic pH.

Demineralization of cartilage with alcoholic EDTA provides cartilage staining that is no better, as measured by scanning microdensitometry, than that of adequately fixed specimens demineralized with aqueous EDTA. Aqueous EDTA is a faster demineralizing agent than alcoholic EDTA. Certain fixatives can preserve maximal proteoglycan staining in articular cartilage even with subsequent rapid demineralization in formate buffer at pH 3.3. Although alcoholic formalin fixation provided optimum quantitative cartilage staining, cetylpyridinium chloride (CPC) in aqueous buffered formalin improved cellular detail, but CPC partially suppressed matrix staining.

Animals↗
PubMed1981

Formation of osteoclasts from blood monocytes during 1 alpha-OH Vit D-stimulated bone resorption in mice.

In order to investigate a monocyte origin for osteoclasts, tritiated thymidine labelled blood monocytes, harvested from the blood of donor mice, were injected intravenously into syngeneic recipient animals in which osteoclast formation was being stimulated by concomitant intraperitoneal injections of 1 alpha-hydroxycholecalciferol. Labelled osteoclasts were found in autoradiographs prepared from the femurs of recipient mice, demonstrating for the first time that, during hormonally stimulated osteoclast formation, blood monocytes form one source of osteoclasts.

Animals↗
PubMed1979

Light microscope and electron microscope alkaline phosphatase cytochemistry of rat bone marrow leukocytes.

An enzyme cytochemical method yielding an osmiophilic reaction product, visible at both the light and electron microscope levels, has been applied to the study of alkaline phosphatase in rat bone marrow cells. The enzyme is present in both eosinophils and, in much smaller amounts, in neutrophils. In both cases it is present on the plasma membrane, and in eosinophils intracellular aggregations of reaction product are also seen. The specific granules in both cell types fail to react and the enzyme is first detectable at the promyelocyte stage. Thus the enzyme is demonstrable before specific granule formation begins in the neutrophil, indicating that they are not a significant site of alkaline phosphatase activity in the rat.

Alkaline Phosphatase↗
PubMed1978

Ultrastructural localization of alkaline phosphatase in rat eosinophil leucocytes.

The ultrastructural localization of alkaline phosphatase in eosinophil leucocytes, obtained from experimentally-induced peritoneal exudates in rats, has been studied using an osmiophilic technique with 2-naphthylthiolphosphoryl dichloride as substrate, fast Blue BBN as diazonium salt and postosmication with 1% aqueous osmium tetroxide. With this method identical incubation procedures could be used for both light and electron microscope examination. Eosinophils were the only cells which contained alkaline phosphatase. The enzyme was predominantly associated with the outer surface of the plasma membrane, being present in much lower concentrations in cytoplasmic cisternae. Eosinophil granules only rarely showed reaction product. The plasma membrane location of alkaline phosphatase in eosinophil leucocytes is identical to that recently demonstrated in the human neutrophil.

Alkaline Phosphatase↗
PubMed1977

Methyl green-pyronin with hematoxylin and orange G for the identification of inflammatory cells in tissue sections.

Methyl green-pyronin is a notoriously difficult stain to reproduce. Although very useful in detecting cells containing substantial amounts of RNA, it is of limited use in broader problems of cell identification. By careful standardization of the proportions of methyl green to pyronin and combination of these stains with hematoxylin to enhance nuclear contrast and with orange G to improve connective tissue staining, it was possible to produce a consistently reliable staining preparation in which it is possible to identify all the component cells of a mixed inflammatory infiltrate in routine paraffin sections.

Animals↗