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Biomedical subjects

G Sorger

Publications and source records attributed to G Sorger.

6 recordsLinked to original sources
PubMed2004

Ascaridole-less infusions of Chenopodium ambrosioides contain a nematocide(s) that is(are) not toxic to mammalian smooth muscle.

Infusions of Chenopodium ambrosioides (L.) have been used for centuries in the Americas as a popular remedy against intestinal worm infections. The essential oil of Chenopodium ambrosioides contains high levels of ascaridole, which is a potent anthelmintic, but which has also been responsible for human fatalities, leading to its disuse. Almost 90% of the nematocidal activity of Chenopodium ambrosioides infusions was due to a hydrophilic component different from ascaridole. Synthetic ascaridole and the ascaridole from infusions, extracted into hexane, caused a reduction of carbachol-induced contractions in rat gastrointestinal smooth muscle at concentrations required to kill Caenorhabditis elegans (L.). The herbal infusion and the ascaridole-free hexane-extracted aqueous residue of the above infusion, at nematocidal concentrations, had no detectable effect on smooth muscle contraction in the above system. It would appear that the traditional form of usage of Chenopodium ambrosioides infusions as a vermifuge is safer than the use of the herb's essential oil.

Animals↗
PubMed1990

Capital accumulation, aspiration adjustment, and population growth: limit cycles in an Easterlin-type model.

"One of the recent interesting hypotheses of population growth is due to Easterlin who suggests the possibility of self-generating fluctuations in birth numbers. The present paper tries to answer the question whether feedback mechanisms produce persistent oscillations in population growth. A system of two nonlinear differential equations for the per capita capital stock and the aspiration level is studied by a phase portrait analysis. Using the Poincare-Bendixson theorem we derive sufficient conditions for the existence of a stable limit cycle." (SUMMARY IN FRE)

Demography↗
PubMed1989

Self-generated fertility waves in a non-linear continuous overlapping generations model.

In this paper, Samuelson's simplified version of the Easterlin theory is extended to a continuous-time model with 3 age groups. This approach enables one to apply the qualitative theory of nonlinear differential equations to show the existence of Easterlin-type cycles. In contrast to the discrete time model we obtain information about the period length of the cycle.

Age Factors↗
PubMed1986

NADH Nitrate Reductase and NAD(P)H Nitrate Reductase in Genetic Variants and Regenerating Callus of Maize.

Different organs of maize seedlings are known to contain different complements of NADH and NAD(P)H nitrate reductase (NR) activity. The study of the genetic programming that gives rise to such differences can be initiated by looking for genetic variants exhibiting different patterns of distribution of the above enzymes. We demonstrate in this work that scutella of very young maize seedlings contain NADH NR almost exclusively and that this activity is gradually replaced, as the seedling ages, with NAD(P)H NR. Leaves in the seedlings contain exclusively the NADH NR activity. A genetic variant is described that contains much reduced levels of NAD(P)H NR activity but not of NADH NR activity in the scutellum. This same variant exhibits a relatively low level of NAD(P)H NR but normal NADH NR activity in seedling root tips. These observations suggest that the genetic program used to specify the scutellar complement of NR activity shares some common components with the genetic program used to determine the young root tip complement of NR activities. Parts of regenerating callus at different stages of differentiation were examined to determine when the differences in NR complement begin to appear. The same pattern of NADH NR and NAD(P)H NR activities was found in unorganized as well as in organized callus, in recognizable root-like and even in green shoot-like material, both activities being present in all these tissues. An examination of the NR complement in different organs of a number of siblings originating from a cross involving transposon Mu-containing parents and having different levels of leaf NADH NR activity shows that the leaf NADH NR activity content and the scutellum NAD(P)H NR activity content are relatively independent of each other, indicating that the genetic programs specifying the NR content of these organs are not tightly coupled, if at all.

Journal Article↗