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  • 1
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Der Lebensraum und die Nestbiologie der Afrikanischen Honigbiene,Apis mellifera scutellata, wurden an Völkern im natürlichen Verbreitungsgebiet im Delta des Okavango Flusses, Botswana, untersucht. Beobachtungen der Vegetation zeigten, daß den Völkern im Delta das ganze Jahr über reichlich Nahrung zur Verfügung steht. Die Koloniedichte betrug 7.8 Nester/km2. Nesthöhlen fanden sich gleich häufig in Bäumen wie in Termitenhügeln, sie hatten ein Volumen von ca. 17 L, waren nicht propolisiert und hatten nach Süden gerichtete, oben liegende Eingänge. Die Völker im Delta waren klein (ca. 6,500 Arbeiterinnen), sie bauten wenig Waben (ca. 3,000 cm2), speicherten wenig Nahrung, verwendeten 78% der Waben für die Brut und sie verfteidigten ihr Nest nur schwach; die Verlustrate durch Räuber betrug 48%. Die charakteristischen Eigenschaften, die fürscutellata in dieser Untersuchung beobachtet wurden, werden als Anpassungen an das heisse Klima, an die lange Trachtperiode und an die im Delta auftretende hohe Verlustrate diskutiert. Die Ergebnisse, die an Völkern im Delta gewonnen wurden, werden verglichen mit Ergebnissen anscutellata in anderen tropischen Gebieten und mit Ergebnissen anscutellata in anderen tropischen Gebieten und mit Ergebnissen an Honigbienen in gemäßigten Klimazonen.
    Notes: Summary The habitat and nesting biology were studied for naturally occurring colonies of the African honey bee,Apis mellifera scutellata, in the Okavango River Delta, Botswana. Vegetational surveys revealed that the forage available to Delta colonies was abundant and potentially available year round. Colonies had a density of 7.8 nests/km2. Nest cavities occurred with equal frequency in trees and termite mounds, had a volume of approximately 17 L, were unpropolized, and had south-facing, top-located entrances. Delta colonies were small (ca. 6,500 workers), constructed small amounts of comb (ca. 3,000 cm2), stored little food, devoted 78% of comb space to brood production, exhibited little nest defense, and experienced a 48% predation rate during the 5 month study period. The characteristics observed forscutellata in this study are discussed as adaptations to the hot climate, long foraging season, and high predation rate experienced in the Delta. Data for the Delta colonies are compared to those forscutellata in other tropical areas, and to honey bees in temperate climate regions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9098
    Keywords: African honey bee ; scutellata ; swarming ; absconding ; migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relationship between the annual colony cycle and seasonal patterns of forage availability was investigated for the African honey bee,Apis mellifera scutellata, in the Okavango River Delta, Botswana. The annual cycle occurred in three distinct periods. The swarming season occurred from October-November, following two to three months of intense brood production, and coincided with the end of peak forage abundance. The migration season occurred from November-May and coincided with reduced and variable floral resources. During the migration season, brood production and food storage were generally low but quite variable from month to month, and swarms passing over the study area at this time traveled in an easterly direction. The migration season was followed by the establishment period (June-September), in which large numbers of new colonies traveling from the west moved into the study area. The establishment period coincided with, and slightly preceded, the period of peak forage abundance, and colonies devoted resources collected at this time almost entirely to brood rearing, which culminated in swarm production. The data suggest that honey bee colonies in the Okavango are mobile and gear their reproduction and movement to seasonally shifting resource pattern.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1420-9098
    Keywords: Apis mellifera scutellata ; African honey bee ; foraging ; brood rearing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal foraging patterns were investigated using six observation colonies maintained in the Okavango Delta, Botswana. Pollen collection, flight from the hive, and recruitment for pollen and nectar sources occurred throughout the 11 months of the study. However, the distribution of foraging activity throughout the day changed seasonally. Colonies emphasized recruitment for pollen sites throughout most of the year. Brood production occurred in all months except May, and there was a significant, positive correlation between the proportion of recruitment activity devoted to pollen sources and the amount of brood comb in the colonies. The seasonal foraging patterns ofscutellata in the Okavango were similar to those of Africanized honey bees in the neotropics. The extended foraging season and emphasis on pollen collection may be associated with the high swarming rates and migrational movements of tropical honey bees.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 18 (1980), S. 49-54 
    ISSN: 1432-0428
    Keywords: Glipizide ; glucagon ; insulin ; insulin sensitivity ; maturity onset diabetes ; oral hypoglycaemic agents ; tolbutamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An open parallel trial with glipizide or tolbutamide was carried out in a cohort of 29 comparable maturity-onset diabetic patients. Eighteen of these individuals were studied in detail. During six months of active drug therapy the mean decrease in fasting serum glucose levels on glipizide was 25 ±2% versus 17±2% on tolbutamide (p〈0.025). Decreases in post prandial glucose levels were 12.2 and 10.4%. Glucose disappearance rates (Kg) during the sixth month of treatment with both drugs increased significantly: on glipizide from 0.47±0.04%/min to 0.85±0.08%/min (p〈0.005), and on tolbutamide from 0.47±0.08%/min to 0.70±0.11%/min (p〈0.01). Early and late insulin release (summed increases over basal for 2–10 min and 10–60 min) during intravenous glucose tolerance testing increased during glipizide, but not during tolbutamide therapy. Post prandial insulin increments over basal during an oral glucose tolerance test also increased during glipizide, but not tolbutamide therapy. Both drugs were comparable with regard to efficacy and safety; however, only glipizide had chronic effects upon insulin secretion.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0428
    Keywords: Exercise ; Type 2 diabetes ; physical training ; maximal oxygen uptake ; exertion ; insulin sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of 6 weeks of thrice weekly training on glycaemic control were assessed in 20 sedentary Type 2 (non-insulin-dependent) diabetic patients and 11 control subjects matched for previous physical activity. Maximal oxygen uptake was lower in the diabetic patients than in control subjects before training (26.2±1.1 versus 32.6±1.7 ml·kg-1·min-1; p〈0.001). Glycosylated haemoglobin levels decreased in the diabetic patients during the training programme (12.2±0.5 to 10.7±0.4%; p 〈 0.02). Oral and intravenous glucose tolerance determined 72 h after the last exercise period showed only minimal improvement. Plasma glucose levels were, however, significantly lower at 12 h than 72 h after exercise in eight subjects tested at both time points. These data suggest that an exercise programme can produce a significant decrease in glycosylated haemoglobin levels in Type 2 diabetic males probably due, in great measure, to the cumulative effect of transient improvements in glucose tolerance which follow each individual period of exercise.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Insectes sociaux 39 (1992), S. 403-423 
    ISSN: 1420-9098
    Keywords: Honey bee ; migration ; foraging ; Apis mellifera scutellata ; waggle dance ; absconding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study investigated the effects of colony growth and development, food storage, foraging activity and weather on the migration behavior of African honey bees in the Okavango River Delta, Botswana. Four observation colonies were studied during the honey bee migration season (November–May), at which time the availability of blooming species was reduced. Two of the colonies (colonies 1 & 2) migrated during the study period, while the remaining two (colonies 3 & 4) did not. During the 4–6 weeks preceding the onset of migration preparations, colonies 1 & 2 exhibited increasing population sizes, high levels of brood production with low brood mortality, relatively large stores of food, and increasing mass. In contrast, the populations of colonies 3 & 4 did not increase, brood-rearing activity was erratic and lower, brood mortality was higher, food stores became depleted and colony mass declined. Both colonies 3 & 4 ceased rearing brood, and colony 3 died of starvation. Colony foraging activity was examined by monitoring waggle-dance activity 2–3 days each week. For 4–6 weeks before the onset of migration in colonies 1 & 2, daily foraging areas and mean daily foraging distances became increasingly large and variable. Colonies 3 & 4 exhibited foraging patterns similar to those observed for colonies 1 & 2 preceding migration. There was no clear association between 7 weather parameters examined and migration behavior. These data suggest that migration is influenced by an interaction of intra-colony demographics, food reserves and foraging patterns. Migration may be feasible only for those colonies that possess (1) a population of appropriate size and age structure to compensate for the natural attrition of older workers during the emigration process, and (2) sufficient food reserves for long-distance travel and the establishment of a new nest. Changing foraging patterns may reflect a deteriorating foraging environment, which may trigger the onset of migration preparations, provided that colony demographics and food reserves are conducive. Colonies that show decreased brood production, higher brood mortality and reduced food stores may be incapable of migrating, even when experiencing deteriorating foraging conditions. Rather, such colonies may have a greater chance of survival if they attempt to persist in a given area.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1420-9098
    Keywords: Honey bee ; migration ; waggle dance ; absconding ; Apis mellifera scutellata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Waggle dance activity associated with seasonal absconding (migration) was investigated in two colonies of the African honey bee. Prior to absconding, waggle dances regularly communicated distances up to 10–20 km from the nests. However, compared to waggle dances observed during nonabsconding periods, those occurring prior to migration were less associated with food sources, occurred during periods of little or no flight activity, and exhibited great variability in the communication of distance by consecutive waggle runs of individual bees. It is therefore unlikely that “migration dances” communicated the locations of, or stimulated immediate recruitment for, specific foraging or nesting sites. Rather, the dances may have functioned to establish a general route of travel. The majority of migration dances observed were oriented in an easterly direction, and upon departure both colonies traveled towards the E-SE. The orientation of migration dances occurred independently of the directions communicated by waggle dances associated with past foraging success or the sampling of alternate foraging areas. Migration dance orientation may have been affected by prevailing wind directions, because during the migration period winds blew primarily from the east. However, it is unlikely that wind direction was the only factor influencing migration dance orientation. The lack of immediate flight activity associated with migration dance performance suggests the dances may have gradually prepared colonies for migratory movement by conveying a message to fly for a long, but unspecified distance in a certain direction. Waggle dances associated with migration may therefore function differently from those associated with foraging and nest site selection, which convey both the distance and direction to specific locations.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0428
    Keywords: Keywords Proinsulin C-peptide ; erythrocyte deformability ; microcirculation ; laser diffractoscopy ; shear stress.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. In recent years, evidence has arisen that proinsulin C-peptide exerts biological effects especially on microcirculation, e. g. C-peptide has been shown to increase skin microcirculation in patients with Type I (insulin-dependent) diabetes mellitus and to activate endothelial nitric oxide synthase. This study aimed to investigate the influence of proinsulin C-peptide on erythrocyte deformability which was assessed by means of laser diffractoscopy. Methods. Blood samples from healthy control subjects (n = 10) and Type I diabetic patients (n = 15) completely deficient of C-peptide were analysed at shear stresses ranging from 0.3 to 30 Pa. Results. Erythrocyte deformability was lower in the group of Type I diabetic patients than in the control subjects. Preincubation of the diabetic blood samples with various concentrations of human proinsulin C-peptide for 8 h restored the deformability of erythrocytes, almost reaching the values of control samples. In contrast, proinsulin C-peptide did not modify the erythrocyte deformability of control subjects. Conclusion/interpretation. We conclude that proinsulin C-peptide is able to ameliorate the impaired deformability of erythrocytes in Type I diabetic patients and we hypothesise that this effect is mediated by restoration of Na+-K+-ATPase activity, which is known to be attenuated in diabetic patients. [Diabetologia (1999) 42: 465–471]
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0428
    Keywords: Forearm perfusion ; serum insulin ; plasma glucagon ; glucose ; plasma non-esterified fatty acids ; blood ketone bodies ; blood glycerol ; glucagon ; extrahepatic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The acute effects of glucagon (mol. wt. 3500) and its interactions with insulin were studied in the forearm during eight studies in seven normal, post-absorptive males. The protocol consisted of a 2 h baseline, 1 h glucagon perfusion (mean glucagon increment, 691±50 pg/ml), 1 h perfusion of both insulin and glucagon (mean insulin increment of 105 ±13 mU/l) and a 30 min recovery period. Simultaneous arterial (A), deep venous (DV), and superficial venous (SV) blood samples were obtained at 30 min intervals. Perfusion of glucagon resulted in a decrease in (A-DV) non-esterified fatty acids of-0.128±0.057 mmol/l (n=7, p〈0.05) and (A-SV) non-esterified fatty acids of -0.081±0.036 mmol/l (n=7, p〈0.05), as well as a change in deep compartment uptake of glycerol after 60 min of -0.044±0.019 μmol/min/100 ml of forearm tissue (n=6, p〈0.05), indicating increased lipolysis. There was also a decrease in net glucose uptake as reflected by a change in (A-DV) of -0.24±0.09 mmol/l (n=7, p〈0.025) and (A-SV) of 0.10± 0.05 mmol/l (n=7, p〈0.05). There was also a net decrease in deep arteriovenous differences of potassium in six of seven subjects. Insulin levels, similar to those found after a meal, rapidly reversed the effects of glucagon on non-esterified fatty acid, glucose and potassium. These effects persisted throughout the recovery period.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A human aniridia candidate (AN) gene on chromosome 11p13 has been cloned and characterized. The AN gene is the second cloned gene of the contiguous genes syndrome WAGR (Wilms' tumor, aniridia, genitourinary malformations, mental retardation) on chromosome 11p13, WT1 being the first gene cloned. Knowledge about the position of the AN and WT1 genes on the map of 11p13 makes the risk assessment for Wilms' tumor development in AN patients possible. In this study, we analyzed familial and sporadic aniridia patients for deletions in 11p13 by cytogenetic analyses, in situ hybridization, and pulsed field gel electrophoresis (PFGE). Cytogenetically visible deletions were found in 3/11 sporadic AN cases and in one AN/WT patient, and submicroscopic deletions were identified in two sporadic AN/WT patients and in 1/9 AN families. The exact extent of the deletions was determined with PFGE and, as a result, we could delineate the risk for Wilms' tumor development. Future analyses of specific deletion endpoints in individual AN cases with the 11p13 deletion should result in a more precise risk assessment for these patients.
    Type of Medium: Electronic Resource
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