Effects of ovarian tissue reduction on the menstrual cycle: persistent normalcy after near-total oophorectomy

These experiments were designed to evaluate whether removal of approximately 95% visible ovarian tissue would interrupt the short- or long-term regulation of cyclic ovarian function. On cycle Days 2 4 (onset of menses = Day 1), the entire left ovary and approximately 90% of the right ovary were removed from three cycling cynomolgus monkeys. After approximately 95% ovariectomy, there was an acute elevation of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which lasted 11 +/- 2 days. A midcycle-like gonadotropin surge occurred 20 +/- 3 days following approximately 95% ovariectomy; the next menses occurred 19 +/- 1 days later. Follicular phase patterns of estradiol preceded the midcycle gonadotropin surge, and luteal phase progesterone levels indicated subsequent ovulation. Two of three monkeys resumed normal menstrual cyclicity in the following cycle with follicular phase, luteal phase, and menstrual cycle lengths similar to pretreatment levels. Histological examination of the ovarian remnant removed on Day 21 of the next cycle revealed a morphologically normal corpus luteum and many small follicles. A second group of 6 rhesus monkeys also underwent approximately 95% ovariectomy for long-term evaluation of menstrual cyclicity; typical 28-day menstrual cycle patterns were observed in 4 of the 6 monkeys for 5 mo, with 2 of these 3 animals maintaining regular menstrual cycles for 1 yr. In summary, our data suggest that normal ovarian function, i.e. recruitment, selection, and dominance of the ovulatory follicle, ovulation, and subsequent corpus luteum function, is maintained with only approximately 5% of functional ovarian tissue remaining.(ABSTRACT TRUNCATED AT 250 WORDS)     

Negative effects of pesticides on wild bee communities can be buffered by landscape context

Wild bee communities provide underappreciated but critical agricultural pollination services. Given predicted global shortages in pollination services, managing agroecosystems to support thriving wild bee communities is, therefore, central to ensuring sustainable food production. Benefits of natural (including semi-natural) habitat for wild bee abundance and diversity on farms are well documented. By contrast, few studies have examined toxicity of pesticides on wild bees, let alone effects of farm-level pesticide exposure on entire bee communities. Whether beneficial natural areas could mediate effects of harmful pesticides on wild bees is also unknown. Here, we assess the effect of conventional pesticide use on the wild bee community visiting apple (Malus domestica) within a gradient of percentage natural area in the landscape. Wild bee community abundance and species richness decreased linearly with increasing pesticide use in orchards one year after application; however, pesticide effects on wild bees were buffered by increasing proportion of natural habitat in the surrounding landscape. A significant contribution of fungicides to observed pesticide effects suggests deleterious properties of a class of pesticides that was, until recently, considered benign to bees. Our results demonstrate extended benefits of natural areas for wild pollinators and highlight the importance of considering the landscape context when weighing up the costs of pest management on crop pollination services.     

ORIGINS,EVOLUTION, AND DIVERSIFICATION OF CLEPTOPARASITIC LINEAGES IN LONG‐TONGUED BEES

The evolution of parasitic behavior may catalyze the exploitation of new ecological niches yet also binds the fate of a parasite to that of its host. It is thus not clear whether evolutionary transitions from free‐living organism to parasite lead to increased or decreased rates of diversification. We explore the evolution of brood parasitism in long‐tongued bees and find decreased rates of diversification in eight of 10 brood parasitic clades. We propose a pathway for the evolution of brood parasitic strategy and find that a strategy in which a closed host nest cell is parasitized and the host offspring is killed by the adult parasite represents an obligate first step in the appearance of a brood parasitic lineage; this ultimately evolves into a strategy in which an open host cell is parasitized and the host offspring is killed by a specialized larval instar. The transition to parasitizing open nest cells expanded the range of potential hosts for brood parasitic bees and played a fundamental role in the patterns of diversification seen in brood parasitic clades. We address the prevalence of brood parasitic lineages in certain families of bees and examine the evolution of brood parasitism in other groups of organisms.     

How do insect nuclear ribosomal genes compare to protein-coding genes in phylogenetic utility and nucleotide substitution patterns?

Abstract. The expanding data set on insect molecular systematics allows examination of phylogenetic performance and molecular evolution of different types of gene. Studies combining more than one gene in the same analysis allow examination of the relative contribution and performance of each gene partition and can help inform gene choice for resolving deep and/or problematic divergences. We compared results obtained from analyses of twelve insect data sets in which authors combined one or more nuclear ribosomal genes (28S and/or 18S) with one or more protein-coding genes [elongation factor-1α (EF-1α), histone H3, carbamoylphosphate synthetase domain (CPS domain of CAD, or rudimentary), long-wavelength rhodopsin (LW opsin), glucose-6-phosphate dehydrogenase (G₆pd), phosphoenolpyruvate carboxykinase (PEPCK), arginine kinase, and white]. Data sets examined spanned eight orders of insects (Odonata, Ephemeroptera, Hemiptera, Coleoptera, Trichoptera, Lepidoptera, Diptera and Hymenoptera), providing a broad range of divergence times and taxonomic levels. We estimated the phylogenetic utility of the individual genes (using parsimony methods) and characterized the nucleotide substitution patterns (using Bayesian methods) to ask which type of data is preferable for phylogenetic analysis in insects. Nuclear ribosomal and protein coding genes differed little in our measures of phylogenetic performance and patterns of nucleotide substitution. We recommend combining nuclear ribosomal gene data with nuclear protein-coding gene data because each data set has distinct advantages. We do not recommend using mitochondrial genes for higher-level studies of insect phylogeny because reviewed studies demonstrate substitution patterns that lead to high levels of homoplasy.     

Distribution of transfer RNA genes in thePisum sativum chloroplast DNA

Purified chloroplast tRNAs were isolated fromPisum sativum leaves and radioactively labeled at their 3′ end using tRNA nucleotidyl transferase and α³²P-labeled CTP. Pea ctDNA was fragmented using a number of restriction endonucleases and hybridized with thein vitro labeled chloroplast tRNAs by DNA transfer method. Genes for tRNAs have been found to be dispersed throughout the chloroplast genome. A closer analysis of the several hybrid regions using recombinant DNA plasmids have shown that tRNA genes are localized in the chloroplast genome in both single and multiple arrangements. Two dimensional gel electrophoresis of total ct tRNA have identified 36 spots. All of them have been found to hybridize withPisum sativum ctDNA. Using recombinant clones, 30 of the tRNA spots have been mapped inPisum sativum ctDNA.     

Localization of a low molecular weight antigen of Eimeria tenella by use of hybridoma antibodies.

Three monoclonal antibodies (Mabs), found by western blot analysis to recognize 10-kDa bands of Eimeria tenella sporozoite preparations, were used with immunoelectron (IE) microscopy, immunogold-silver staining (IGSS), and indirect immunofluorescent antibody (IFA) light microscopy to determine the location and distribution of the antigens in or on extra- and intracellular parasites. All 3 of the Mabs (designated C3, E5, and 1231) were found by IE microscopy to label amylopectin granules of extracellular sporozoites. Additionally, these Mabs extensively gold-labeled the sporocyst wall. In cultured primary chicken kidney cells inoculated with sporozoites of E. tenella, IGSS showed surface labeling of the parasite and intense labeling of the infected host cells by 6 hr postinoculation (PI). At 24 hr PI, host cell vacuoles in infected and uninfected cells were labeled by the 3 Mabs by IFA. The E5 and C3 Mabs also were seen to label the host cell membrane of newly infected cells. The C3 and 1231 Mabs showed little label of the host cells by 48 hr PI, but the parasites still were labeled up to 96 hr PI. The E5 Mab had intense IFA labeling of infected host cells at 48 hr PI. The results of this study indicate that parasites apparently release antigenic material during the early stages of parasite development and that this material is found internally and/or on the surface of the infected host cells.     

A stem-loop "kissing" model for the initiation of recombination and the origin of introns

Mutations which improve the efficiency of recombination should affect either the proteins which mediate recombination or their substrate, DNA itself. The former mutations would be localized to a few sites. The latter would be dispersed. Studies of hybridization between RNA molecules have suggested that recombination may be initiated by a homology search involving the "kissing" of the tips of stem loops. This predicts that, in the absence of other constraints, mutations which assist the formation of stem loops would be favored. From comparisons of the folding of normal and shuffled DNA sequences, I present evidence for an evolutionary selection pressure to distribute stem loops generally throughout genomes. I propose that this early pressure came into conflict with later local pressures to impose information concerning specific function. The conflict was accommodated by permitting sections of DNA concerned with a specific function to evolve in dispersed segments. Traces of the conflict seem to be present in some modern intron-containing genes. Thus, introns may have allowed the interspersing of selectively advantageous stem loops in coding regions of DNA.      

A requirement for trypsin-sensitive cell-surface components for cell-cell interactions of embryonic neural retina cells

A quantitative assay was used to measure the rate of collection of a population of embryonic neural retina cells to the surface of cell aggregates. The rate of collection of freshly trysinized cells was limited in the initial stages by the rate of replacement of trypsin-sensitive cell- surface components. When cells were preincubated, or "recovered," and then added to cell aggregates, collection occurred at a linear rate and was independent of protein and glycoprotein synthesis. The adhesion of recovered cells was temperature and energy dependent, and was reversibly inhibited by cytochalasin B. Colchicine had little effect on collection of recovered cells. Antiserum directed against recovered cell membranes was shown to bind to recovered cells by indirect immunofluorescence. The antiserum also was shown to inhibit collection of recovered cells to aggregates, suggesting that at least some of the antigens identified might be involved in the adhesion process. The inhibitory effect of the antiserum was dose dependent . Freshly trypsinized cells absorbed neither the immunofluorescence activity nor the adhesion-inhibiting activity. Recovered cells absorbed away both activities. In specificity studies, dorsal neural retina cells adhered to aggregates of ventral optic tectum in preference to aggregates of dorsal optic tectum. The adhesive specificity of the dorsal retina cells was less sensitive to trypsin than the adhesive specificity of ventral retina cells which adhered preferentially to dorsal tectal aggregates only after a period of recovery.     

Characteristics of diet-induced brown adipose tissue growth and thermogenesis in rats

The characteristics of regional brown (BAT) and white adipose tissue (WAT) growth and of thermogenesis following experimental overfeeding were studied in groups of male Sprague-Dawley rats fed lab chow or cafeteria diets for 8 weeks postweaning. Regional BAT and WAT growth was determined by dissection and weighing, and thermogenesis was characterized by measurements of resting and norepinephrine (NE)-stimulated oxygen consumption, of serum thyroid hormone concentrations, and of 24-hour urinary NE excretion levels. Cafeteria feeding resulted in a 113% increase in total BAT, with the most prominent increases in the interscapular, thoracic, and perirenal regions. Retroperitoneal, epididymal, and omental WAT were significantly greater in cafeteria than in chow-fed rats. Resting oxygen consumption of cafeteria-fed rads increased by 10% and NE excretion by 64% compared to chow-fed controls, while serum T₃ concentrations were nearly doubled in the cafeteria-fed rats. The thermogenic response to NE injection in cafeteria-fed rats was 102% of their resting levels, compared to a 51% increase in the chow-fed controls. The results indicate that increased BAT growth occurs in all primary BAT depots following cafeteria-feeding in rats, and that the greater BAT mass is qualitatively proportional to their greater capacity for non-shivering thermogenesis. Also, the increased NE excretion and greater serum T₃ concentration are consistent with increased sympathetic and thyroidal activity and may in part explain the thermogenic response to diet in the rat.