Botanische Gärten in der Zeit des Kolonialismus. Auf der Jagd nach dem “Grünen Gold”

Plant Transfer and Botanical Gardens in Colonial Times A constant of economic history is the need of natural resources – in the past often of vegetable origin and available only from the countries of natural distribution. These countries often tried to protect their interests against the traders or users by declaring monopoles. Between these both poles botanic gardens acted very successfully and by far not according to modern ethic standards. Results of their activities were the transcontinental movements of plants and the initiation of new agricultural based industries. These should be exemplified by the British botanical gardens and species as tea shrub, rubber tree, and cinchona tree.     

Mosaike bei monogenen Erkrankungen

Mosaicism is defined as the simultaneous presence of cells with different genotypes that originate from a common zygote. Mutations can either be present in germline or somatic cells. Monogenic disorders apparently caused by a de novo mutation may show a recurrence risk due to germline mosaicism in a parent. Duchenne muscular dystrophy is a well investigated example with a high frequency of germline mosaicism and the estimation for the risk of recurrence is based on theoretical models and empirical data. Recently, somatic mutations have been uncovered in various syndromic disorders, such as Proteus syndrome or hemimegalencephaly and respective mutations often show gain-of-function properties. Genetic testing is mainly based on next generation sequencing technologies but still remains challenging; however, detection of somatic mosaicism is expected to be of increasing relevance in the diagnosis of monogenic disorders. Somatic mosaicism may also play a hitherto underestimated role in common disorders.     

EVIDENCE FOR AN EXTREME BOTTLENECK IN A RARE MEXICAN PINYON: GENETIC DIVERSITY,DISEQUILIBRIUM, AND THE MATING SYSTEM IN PINUS MAXIMARTINEZII

Maxipiñon (Pinus maximartinezii Rzedowski), which is confined to a single population of approximately 2000 to 2500 mature trees, covers about 400 ha in southern Zacatecas, Mexico. Genetic diversity measured by expected heterozygosity was 0.122, which is moderate for pines. However, percentage polymorphic loci was low, 30.3%. The fixation index (F) of 0.081 indicated only slight heterozygote deficiency. Mating system analysis indicated a significant but low level of selling; the multilocus outcrossing rate, t_m, was 0.816. The mean of single locus estimates, t_s, was smaller (0.761), perhaps suggesting mating among relatives, although the difference between t_m and t_s was not statistically significant. The most striking features of maxipiñon's genetic structure were that no polymorphic locus had more than two alleles and most alleles at polymorphic loci were at intermediate frequencies. This is in contrast to other pines, which often have three to five or more alleles at some loci and in which the distribution of allele frequencies is U-shaped, most alleles being present at frequencies less than 10% or greater than 90%. A population with only two alleles per locus and at intermediate frequencies could occur if the population had been reduced to an extreme bottleneck and then expanded rapidly before random drift modified allele frequencies. A novel origin from a hybridization event would also explain the results. Significant gametic disequilibrium was detected at several pairs of loci in both maternal and paternal gametes. The presence of disequilibrium is in agreement with an origin from an extreme bottleneck, perhaps even a single seed. Furthermore, it demands that the event be relatively recent. The number of generations, as calculated from the observed mean disequilibrium, suggested that maxipiñon derived from an extreme bottleneck four to five generations ago, which is less than 1000 years in this species.     

Verlust des Sensibilitäts- und Schmerzempfindens

The sensory nervous system detects pressure, touch, stretching, heat, and cold and translates these stimuli into action potentials. To protect the body from tissue damage acute pain is felt when a stimulus gains a critical intensity. The combination of impaired nociception and autonomic dysfunction is the hallmark of hereditary sensory and autonomic neuropathies (HSAN). Sensory loss in HSAN patients results in ulcerations of hands and feet and may necessitate amputations. Congenital onset of HSAN leads to self-mutilating behavior in affected children. Degeneration of motor neurons can complicate the disease. HSAN is divided into five groups according to clinical symptoms. So far, nine genes have been identified as causative for the disorder. The present article reviews the clinical, genetic, and pathophysiological aspects of HSAN.     

Mitochondriale Erkrankungen

As outlined in other articles of this issue mitochondrial medicine is a complex area in clinical genetics. Due to the wide variability of clinical presentation in both pediatric and adult patients there are frequent constellations of symptoms that may suggest an underlying mitochondrial disorder. This is a challenge in genetic counseling because basically all patterns of inheritance have to be taken into account??including maternal transmission??but a straightforward genetic testing to confirm or exclude the suggested diagnosis is hampered by the immense genetic heterogeneity of the mitochondrial disease spectrum. This article focuses on a diagnostic strategy and specific aspects of genetic counseling in mitochondrial disorders.     

Evidence for long isolation among populations of a pacific cycad: genetic diversity and differentiation in Cycas seemannii A.Br. (Cycadaceae)

The genetic structure of Cycas seemannii A.Br. (Cycadaceae), sampled throughout its range in Vanuatu, New Caledonia, Fiji, and Tonga, was studied using starch-gel electrophoresis. Twenty enzyme loci in 13 enzyme systems were examined. Low genetic diversity within populations (A = 1.2, P = 21.3, Ho = 0.047, and He = 0.057) and a high degree of differentiation among populations (F(ST) = 0.594) were found. This, together with low gene flow estimates, suggests genetic drift by isolation to have been most critical to the current genetic structure of the species. Inbreeding may occur to some extent (F(IS) = 0.165). The decline in abundance of C. seemannii, coupled with the low level of genetic diversity, suggest that conservation strategies are urgently needed.     

Morphogenesis and fate of the residual body in human spermiogenesis

Summary In the human testis the formation of the residual body of the spermatid and its morphological changes during and after spermiation were studied by means of electron microscopy. The caudal cytoplasmic mass of the late spermatid contains a Golgi complex, mitochondria, annulate lamellae, a chromatoid body, flower-like structures, ribosomes, a few large vacuoles, myelin-like membrane profiles and sporadic lipid droplets. When, by detachment of the caudal cytoplasm from the free spermatozoon, the residual body is formed, the chromatoid body has disappeared; the mitochondria are clustered peripherally; the ribosomes appear as a single complex in contact with a large vacuole containing granular material; in place of the Golgi complex aggregations of vesicles are present. The lipid droplets remain unchanged. The residual bodies or their fragments are either extruded via the seminiferous tubular lumen into the excurrent ducts or they are engulfed by Sertoli cells where in the supranuclear region the successive steps of decomposition can be observed. The participation of the various constituents in the disintegration of the residual body is discussed. In contrast to other mammalian species, in man the sporadic lipid droplets seem to be of minor importance in the fate of the residual body.     

Giant cells fromSaccharomyces uvarum grown after X-irradiation

Yeast cells, Saccharomyces uvarum, were irradiated with X-rays and grown in liquid suspension. Glucose as the only carbon source was limited to 12.5 mM. Under these conditions giant cells are formed. Cell number, glucose utilization, ethanol production and oxygen consumption are measured during the time of growth. The mean weight of single cells in the stationary phase increases up to 75 krad and is not due to an uptake of water. In irradiated cultures oxygen consumption and glucose utilization per cell are higher than in control cells. The data demonstrate that synthesis- and energy-metabolism during the formation of non-dividing, radiation-induced giant cells is increased.