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71.
Rainer Roggenkamp 《Molecular & general genetics : MGG》1988,213(2-3):535-540
Summary A selection by glucosamine for mutants of Hansenula polymorpha insensitive to glucose repression of methanol assimilation is described. Constitutive synthesis of enzymes is established in standard batch cultures of glucosegrown cells. Upon prolonged glucose metabolism the phenotype is masked by catabolite inactivation and degradation of enzymes. Addition of the substrate methanol remarkably improves constitutive synthesis by preventing catabolite inactivation and delaying degradation. Regular peroxisomes of reduced number are formed in mutant cells under repressed conditions. No constitutive synthesis is detectable using ethanol as a carbon source. In addition, this alcohol is detrimental to growth of the mutants, indicating that H. polymorpha is constrained to repress synthesis of enzymes involved in the C1-metabolism when ethanol is present as a substrate. 相似文献
72.
Dominique Mouchiroud Christian Gautier Giorgio Bernardi 《Journal of molecular evolution》1988,27(4):311-320
Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole. 相似文献
73.
Luc Mejean Alena Bicakova-Rocher Marianne Kolopp Christian Villaume Francis Levi Gerard Debry Alain Reinberg Pierre Drouin 《Chronobiology international》1988,5(3):227-236
The circadian and ultradian variations of blood glucose and plasma insulin have been characterized individually and as a group phenomenon in five healthy young adults studied while adhering as closely as possible to their usual routine of sleep, activity, meal content and timing. Three complementary methods were used to analyze the data: displaying raw data as a function of time; cosinor method according to Nelson and Halberg; and time series analyses as proposed by De Prins and Malbecq. The subjects were studied in the laboratory and their life routine were controlled, but very close to that of their habitual routine. They had mainly ultradian rhythms of blood glucose (mainly about 6 hr) and circadian rhythms of immunoreactive insulin (I.R.I.). Blood glucose ultradian rhythms seem to be mainly but not exclusively mealtime dependent, while I.R.I, circadian rhythms appear to be primarily endogenous in origin. Therefore, the role played by insulin in the control of blood glucose levels seems to be programmed on a circadian basis rather than by a time independent feedback phenomenon as postulated by the conventional homeostatic hypothesis. The advantage of this chronophysiologic approach is to consider circadian rhythms of both I.R.I. and insulin effectiveness as an adaptive phenomenon able to maintain blood sugar changes in the ultradian domain of rhythms. 相似文献
74.
Markus Riederer Kathrin Kurbasik Rainer Steinbrecher Andreas Voss 《Trees - Structure and Function》1988,2(3):165-172
Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm2) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm3) by needle volume = 0.208 x projected needle area
1.353 (r = 0.969). 相似文献
75.
Päivi Heikkilä Arvi I. Kahri Christian Ehnholm Petri T. Kovanen 《In vitro cellular & developmental biology. Plant》1988,24(9):936-942
Summary To define the role of endogenously synthesized cholesterol in the differentiation of adrenocortical cells in primary culture,
fetal rat adrenal cells were cultured in the presence of exogenous cholesterol (serum-supplemented medium) or in the absence
of it (serum-free medium or lipoprotein-free medium). Ultrastructurally the cells had features of glomerulosa cells: mitochondria
were oval or rod shaped with lamellar inner membranes. The amount of smooth endoplasmic reticulum was small, and lipid droplets
were few. When the cells were cultured in serum-free medium some intracytoplasmic vacuoles were seen. The undifferentiated
zona glomerulosa-like cells secreted low amounts of corticosterone and 18-OH-deoxycorticosterone (18-OH-DOC) in all three
media (serum-supplemented medium, serum-free medium, and lipoprotein-free medium). Stimulation of the adrenocortical cells
with ACTH induced the ultrastructural features of differentiated zona fasciculata-like cells. Mitochondrial inner membranes
were well developed in lipoprotein-free medium, but not in serum-free medium. The amount of intracellular lipids was increased
in both media devoid of cholesterol. In the ACTH stimulated cultures the presence of exogenous cholesterol resulted in increased
secretions of corticosterone and 18-OH-DOC. In the absence of an exogenous source of cholesterol, the amounts of steroids
secreted were only half of that secreted in the presence of serum-supplemented medium. Endogenously synthesized cholesterol
is sufficient for the morphologic differentiation of fetal rat adrenocortical cells under ACTH stimulation. However, without
exogenously provided cholesterol, the steroid production accounts only for half of the maximal output achieved using serum-supplemented
medium.
This work was supported by Finnish Culture Foundation. 相似文献
76.
77.
Peter Schlag Maria Manasterski Thomas Gerneth Peter Hohenberger Margret Dueck Christian Herfarth Winfrid Liebrich Volker Schirrmacher 《Cancer immunology, immunotherapy : CII》1992,35(5):325-330
Summary A group of 23 colorectal cancer patients were treated by a new type of active specific immunotherapy (ASI) following complete surgical resection of liver metastases (R0 resection). For ASI treatment we used a vaccine consisting of 1 × 107 autologous, irradiated (200 Gy) metastases-derived tumor cells incubated with 32 hemagglutination units (HU) of Newcastle disease virus (NDV). The adjuvant vaccine therapy was started 2 weeks after surgery and was repeated five times at 14-days intervals followed by one boost 3 months later. The delayed-type hypersensitivity (DTH) skin reactions to the vaccine were measured as well as the DTH reactions to a challenge test of 1 × 107 non-virus-modified autologous tumor cells from liver metastases or 1 × 107 autologous normal liver cells. In addition 32 HU NDV alone and a standard antigen test (Merieux test) were applied pre- and post-vaccination. The vaccination was well tolerated. In 13 of 23 patients an increasing reactivity against the vaccine was observed during the vaccination procedure. Nine patients (40%) experienced an increased DTH reactivity against autologous tumor cells following vaccination, while 17% or fewer showed an increased reactivity to Merieux test antigens, NDV, or normal liver cells. The increased antitumor response was not correlated to responsiveness to NDV alone, autologous liver cells, enzymes and culture medium used for vaccine preparation or standard antigens (Merieux test). After a follow-up of at least 18 months 61% of the vaccinated patients developed tumor recurrence in comparison to 87% of a matched control groups from the same institution that had been only surgically treated. The results of this phase II trial are encouraging and should stimulate further prospective randomized studies. 相似文献
78.
Rainer Voigt Jelle Atema 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,171(5):673-683
1. | We determined the spectral tuning properties of 47 chemoreceptor cells of the antenna of Homarus americanus to amino acids and other compounds. Tests with 17 single compounds at 10-4 M showed 40 of 47 cells responded best to hydroxyproline, 4 cells to taurine and 3 cells to betaine. Mean tuning breadth (H-metric) doubled with 10 fold increase in concentration. |
2. | In hydroxyproline-best cells the mean threshold for hydroxyproline (Hyp) was found between 10-7 M and 10-8 M. An equimolar mixture of the 17 compounds generated a shallower stimulus-response function with thresholds similar to Hyp function (mixture suppression). Hyp-best cells were relatively narrowly tuned, often with arginine or leucine as second best stimuli. |
3. | Thus, physiologically the second antenna of H. americanus is a major chemoreceptor organ. It is more than any of the 5 chemoreceptor organs studied so far dominated by a single best-cell type (Hyp). Receptor cell composition of antennae resembles that of antennules more than legs or maxillipeds. Hyp-best cells in antennae and lateral antennules have similar tuning spectra. |
4. | Our cell tuning studies argue for independent receptors for all amino acids tested. We conclude that diversity of receptor cell tuning is created by cell-specific blends of receptors. At the organ level, differences in organ tuning result from different blends of receptor cells. |
79.
Christian Bry Edgar Basset Xavier Rognon François Bonamy 《Environmental Biology of Fishes》1992,35(1):75-84
Synopsis Sibling cannibalism in pike, Esox lucius, larvae and juveniles living in outdoor rearing ponds was studied using stomach contents analysis. For the two initial densities tested (6 and 18 larvae m–2, equivalent to 12 and 36 larvae m–3), cannibalism was non-existent during the larval period (13 to 35 mm total length) and was observed only during the juvenile stages. Initial density of larvae influenced both the date of first detection of cannibalistic individuals and the rate of development of cannibalism in the population. At initial stocking densities of 18 larvae m–2 (36 larvae m–3), cannibalism was observed from 21 days after the start of exogenous feeding (mean total length: 60 mm) onwards. At a mean total length of 100 mm and for initial stocking densities of 6 and 18 larvae m–2, (12 and 36 larvae m–3), the average proportions of cannibals in the populations of juveniles were 7.8% and 41.3% and the cannibals accounted for 15.5% and 65.9% of the total pike biomass, respectively. In stomachs of cannibals, young pike were the dominant prey in terms of weight. Dry weights of invertebrate-prey were lower in cannibals than in non-cannibals of similar size. Cannibalism among pike juveniles was characterized by the prey being swallowed whole and head first in the vast majority of cases. There was a strong positive correlation between predator and prey size and the mouth size of a cannibal was found to be an important constraint determining maximum victim size. The overall mean ratio of pike prey length to pike cannibal length was 66.2% and the average ratio of prey head depth to predator mouth width amounted to 87.6%. Prey size selection could be demonstrated for several length-groups of cannibals. These results are compared with the characteristics of early cannibalism in other fish species. 相似文献
80.
Ecophysiology of Aufwuchs-eating cichlids in Lake Tanganyika: niche separation by trophic specialization 总被引:1,自引:0,他引:1
Christian Sturmbauer Wolfgang Mark Reinhard Dallinger 《Environmental Biology of Fishes》1992,35(3):283-290
Synopsis The Aufwuchs-eating cichlids of Lake Tanganyika show clear trophic differences that are correlated to their morphology, physiology and foraging behaviour. The species are grouped into three categories of relative intestinal length according to their feeding habits. A correlation between the intestinal length and the diet could be demonstrated, ranging from around 2.5 for species ingesting more animal food, to 7.8 for detritivorous and microalgivorous species. The relative intestinal length of domesticTropheus moorii, raised in aquaria was significantly lower than that of wild individuals by a factor of 1.7, demonstrating a wide range of phenotypic adaptability. The activities of trypsin and amylase were at an equal level in four Aufwuchseating species, but the activity of laminarinase of a detritivorous-microalgivorous species (Petrochromis orthognathus) was 2.6 times higher than that of an algivorous species (Tropheus moorii). The laminarinase seems to be an excellent marker enzyme for detritivorous or microalgivorous feeding. 相似文献