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  • Demographic mechanisms  (1)
  • Insulin secretion  (1)
  • 1
    ISSN: 1432-1939
    Keywords: Key words Cyclic dynamics ; Suppressed reproduction ; Demographic mechanisms ; Microtines ; Lemmus sibiricus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The reproduction of female Siberian lemmings in the increase and peak phases of the lemming cycle was investigated in connection with a ship-borne expedition along the Siberian arctic tundra. The cycle phase of each studied lemming population was determined using demographic analyses, i.e. current density indices (captured lemmings per 100 traps per 24 h), information on previous density (frequency of old lemming faeces and runways), and information from dendrochronological analyses revealing the most recent winters with a high intensity of willow-stem scarring caused by lemmings. The cycle phase determination was corroborated with data on the age profiles of the populations. The reproductive behaviour of female lemmings differed markedly in relation to cycle phase. In increase-phase populations, all captured females (including young and winter born) were reproducing (had embryos or were lactating), and females started to reproduce early in life, i.e. when 〈2 months old. By contrast, in peak-phase populations, only 6% of the young females and 63% of the winter-born ones were reproducing, and females did not start to reproduce until they were 5–6 months old. The average number of embryos per reproducing female was significantly higher in increase-phase populations than in peak-phase ones. It is concluded that the rapid population growth in lemmings during the increase phase can largely be explained by the early (young age) reproductive start and, consequently, the shorter generation time, the high proportion of females taking part in reproduction, and the large litters produced. Similarly, a delay in the start of reproduction, a lower proportion of reproducing females, and smaller litter sizes produced by peak-phase lemming populations can contribute substantially to the deceleration in the population increase and possibly lead to a decline.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Glipizide ; Insulin secretion ; Diabetes mellitus ; NIDDM ; sulphonylurea treatment ; hypocaloric diet weight control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Of 23 patients with non-insulin-dependent diabetes mellitus (NIDDM), whose fasting blood glucose had not reached ≤6.0 mmol·l−1 after 10 weeks of dietary regulation, 15, who had had a weight reduction of −2.8 kg by dietary control, did achieve a fasting blood glucose ≤6.0 mmol·l−1 after addition of ≤20 mg glipizide daily. They had a sustained (≥2 years) increase in meal-induced insulin secretion (32% increase in postprandial C-peptide AUC), and a sustained reduction in postprandial hyperglycaemia (34% reduction in AUC). Ten of the patients took a mean daily dose 〈5mg (4.8 mg) and had a sustained increase in insulin secretion rate (increased C-peptide slope). The 15 patients had no elevation of basal insulin secretion and no impairment of weight reduction. The remaining 8 subjects, who showed little or no weight reduction on dietary control, had little or no reduction in fasting blood glucose despite long-term treatment with 20 mg glipizide daily, a less sustained increase in meal-induced insulin secretion, a smaller reduction of postprandial hyperglycaemia, and an increase in body weight. On diagnosis the 8 subjects did not differ from the other 15 subjects in age, body weight, blood glucose, HbA1c, C-peptide or insulin, nor in their glucose and insulin responses to a test dose of glipizide; the main reason for the apparent drug failure appeared to be deficient compliance with dietary regulation rather than a primary inability to respond to sulphonylurea treatment. The findings indicate that glipizide is able to promote and maintain increased meal-induced insulin secretion and near-normal fasting and non-fasting blood glucose levels without continuous B cell stimulation. However, these improvements prevail mainly in subjects who persist with hypocaloric dietary regulation.
    Type of Medium: Electronic Resource
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