Cryptic species in Diacyclops bicuspidatus (Copepoda:Cyclopoida): evidence from crossbreeding studies

The problem of cryptic species in Diacyclops bicuspidatus was examined using interpopulation crosses of four populations collected from a: (1) permanent flood lake in Kiev, Ukraine, (2) temporary pool in Kiev, (3) permanent pond in St. Petersburg, Russia (1200 km to north from Kiev) and (4) lake in Crimea (1100 km south of Kiev). The only interpopulation crosses to exhibit fertility were those between the St. Petersburg population and each of the two Kiev populations. The crosses between the Kiev and Crimea populations, between the St. Petersburg and Crimea populations, and between the two Kiev populations were sterile, as evidenced by either nonviable eggs, empty egg membranes or incomplete copulations. The F₁ hybrids resulting from the St. Petersburg permanent pond X Kiev flood lake cross were fertile and produced mature F₂ offspring. Some data on development times of parental and hybrid lines are presented. The St. Petersburg parental line showed development times almost twice as long as those of the Kiev flood lake population when reared at 10 °C and 20 °C in the laboratory. The F₁ offspring of the cross between St. Petersburg females and Kiev floodlake males showed similar development times to females of the St. Petersburg parental lines at both temperatures. The F₂ hybrids also showed development times that approximated those of the St. Petersburg parental line. These crossbreeding studies suggest the presence of cryptic species in the D. bicuspidatus inhabiting ecologically different populations in many parts of its large holarctic range.     

Dual role of osteoblastic proenkephalin derived peptides in skeletal tissues

Proenkephalin encodes a group of small peptides with opiate-like activity, the endogenous opioids, known to function as neurohormones, neuromodulators, and neurotransmitters. Recently, we have demonstrated that in addition to its abundance in fetal brain tissue, proenkephalin is highly expressed in nondifferentiated mesodermal cells of developing fetuses. We identified the skeletal tissues, bone, and cartilage as major sites of proenkephalin expression. To examine the possibility that proenkephalin is involved in bone development we have studied the expression of this gene in bone-derived cells, its modulation by bone active hormones, and the effects of enkephalin-derived peptides on osteoblastic phenotype. Our studies revealed that osteoblastic cells synthesize high levels of proenkephalin mRNA which are translated, and the derived peptides are secreted. Reciprocal interrelationships between osteoblast maturation and proenkephalin expression were established. These results together with our observations demonstrating inhibitory effects of proenkephalin-derived peptides on osteoblastic alkaline phosphatase activity, strongly support the notion that proenkephalin is involved in bone development. A different direction of research by other investigators has established the capability of the opioid system in the periphery to participate in the control of pain. On the basis of these two lines of observation, we would like to present the following hypothesis: The potential of embryonic skeletal tissue to synthesize proenkephalin-derived peptides is retained in the adult in small defined undifferentiated cell populations. This potential is realized in certain situations requiring rapid growth, such as remodeling or fracture repair. We suggest that in these processes, similarly to the situation in the embryo, the undifferentiated dividing cells produce the endogenous opioids. In the adult these peptides may have a dual function, namely participating in the control of tissue regeneration and in the control of pain. © 1994 Wiley-Liss, Inc.     

Response to drought among farmers and herders in southern Kajiado District,Kenya

From 1972 to 1976 rainfall in Kajiado District of Kenya was below normal. The capacity of the farming and herding systems to cope with the consequent reduction in production is discussed within a context of changing land-use patterns and altered resource availability. It is concluded that land-use planning to allocate the available land and water resources and to promote off-farm employment is required to reduce the vulnerability of the population to future drought conditions.     

Integrated palaeoecological and historical data in the service of fine-resolution land use and ecological change assessment during the last 1000 years in Rõuge, southern Estonia

Aims Our aim is to reconstruct decadal scale development of historical landscapes during the last 1000 years by means of fossil pollen analysis of annually laminated lake sediments, and detailed historical maps and documents. Location Lake Rõuge Tõugjärv (Estonia), a small lake with annually laminated lake sediments situated in a dense prehistoric setting. Methods The chronology of the palaeodata is based on the annual laminations supported by AMS ¹⁴C and ²¹⁰Pb dating and ¹³⁷Cs, ²⁴¹Am, and spheroidal carbonaceous particle marker horizons. The time‐scale and resolution allows fine sampling (the pollen samples generally comprise 3.5 years) and vegetation change reconstruction. Relevant source area of pollen (RSAP) of the lake was estimated, and the statistical zonation, rate of change, palynological richness, and DCA and PCA ordinations were generated on the basis of the pollen data. The historical calibration data set (maps, numerical information on population, domestic stock, farmland division, etc.) is based on archival material preserved in the Estonian Historical Archives. Results The topmost part (0–180 cm) of the sediment column of Lake Rõuge Tõugjärv, covering the last 1000 years, is visibly laminated carbonaceous gyttja. The varve chronology extends from ad 2000 to ad 1339, with a cumulative ± 9‐year error estimate. Beyond this the chronology is extrapolated using the ¹⁴C date and varve age–depth estimations. The simulation of the RSAP of Lake Tõugjärv shows that the major portion of the pollen loading originating from local vegetation is derived from plants growing within 2000 m of the sampling site. The pollen record divides into five statistically significant subgroups, which fall on the PCA plot into three clusters reflecting the general openness–closedness of the landscape. During the period between ad 1000 and 1200 (RT 1) the Rõuge area was generally wooded with birch, spruce and pine forests. The advancement of extensive farming gradually opened up the landscape between ad 1200 and 1650 (RT 2 and RT 3). The maximum openness of the landscape was reached between ad 1650 and 1875 (RT 4), with the most open period in the late eighteenth century. Historical maps from 1684 and 1870–99 and available quantitative data on population, domestic stock, farmland division, etc. show the same trend. The pollen data covering the last 125 years, and maps from 1935 and 1995, show the reduction of arable land in RSAP of the lake under investigation and the reduction of open land to an extent comparable with the end of the seventeenth century. Main conclusions The formation and development of the cultural landscape at Rõuge over the last 1000 years is characterized by rapid changes in floristic richness and rates of vegetation change attributed to certain historic processes in the RSAP. Five phases of landscape and social development are clearly distinguished during the last 1000 years. The decadal scale vegetation response to human‐induced forcing agrees with historical maps and documents and could be used for past landscapes prior to the period with solid historical data.     

Quantitative Development and Molecular Forms of Acetyl-and Butyrylcholinesterase During Morphogenesis and Synaptogenesis of Chick Brain and Retina

The embryonic development of total specific activities as well as of molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) and of butyrylcholinesterase (BChE, EC 3.1.1.8) have been studied in the chick brain. A comparison of the development in different brain parts shows that cholinesterases first develop in diencephalon, then in tectum and telencephalon; cholinesterase development in retina is delayed by about 2-3 days; and the development in rhombencephalon [not studied until embryonic day 6 (E6)] and cerebellum is last. Both enzymes show complex and independent developmental patterns. During the early period (E3-E7) first BChE expresses high specific activities that decline rapidly, but in contrast AChE increases more or less constantly with a short temporal delay. Thereafter the developmental courses approach a late phase (E14-E20), during which AChE reaches very high specific activities and BChE follows at much lower but about parallel levels. By extraction of tissues from brain and retina in high salt plus 1% Triton X-100, we find that both cholinesterases are present in two major molecular forms, AChE sedimenting at 5.9S and 11.6S (corresponding to G2 and G4 globular forms) and BChE at 2.9S and 10.3S (G1 and G4, globular). During development there is a continuous increase of G4 over G2 AChE, the G4 form reaching 80% in brain but only 30% in retina. The proportion of G1 BChE in brain remains almost constant at 55%, but in retina there is a drastic shift from 65% G1 before E5 to 70% G4 form at E7.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in Insulin Binding to Developing Embryonic Chick Neural Retina Cells

Specific cell surface insulin binding to embryonic chick neural retina cells has been demonstrated in vivo. Kinetics of insulin binding as well as hormonal specificity were similar to those reported for other vertebrate cells and tissues, both neural and nonneural. When surface insulin binding to retinal cells was studied as a function of embryonic age, a developmental relationship was observed. Scatchard analysis revealed that the number of cell surface insulin receptors decreased approximately 75% between days 10 and 16 of embryonic development. Receptor affinities remained fairly constant for this period.     

Techniques for hand-rearing tree-shrews (Tupaia belangeri) from birth

In captivity, Tupaia belangeri (Thailand tree-shrew) frequently show aberrant patterns of maternal care which result in the death of offspring. In order to maximize the potential of the tree-shrew as an animal resource for experimental studies we have developed a program for hand-rearing tupaiidae from birth. Newborn tree-shrews were removed from mothers with a history of poor parental care to a nursery maintained under conditions of controlled relative humidity (70 ± 10%) and temperature (25 ± 1°C) on a 12 h dark: 12 h light cycle. The young tree-shrews were fed on a liquid formula until the eyes opened (Day 18–23) and for the subsequent 10 days on a transitional diet until they could feed themselves on solid food. Our hand-rearing protocol appears to conform to the natural weaning pattern of tupaiids. Food consumption during the liquid diet phase was linearly related to age and the increase in body weight in both sexes. The initial growth rate of male and female hand-reared tree-shrews was slower than that of maternally reared animals during the liquid diet phase. The growth rate accelerated subsequently and the body weight of hand-reared tree-shrews eventually reached that of maternally reared animals of the same sex. Various developmental changes occurred during the same period in artificially and naturally reared animals. In both hand-reared and maternally reared groups, the growth rate of male tree-shrews exceeded that of females from about Day 40 onward. The accelerated growth rate of male tree-shrews was in apparent association with an increase in androgen secretion at the onset of puberty. The high fecundity of tree-shrews in captivity reinforced with a program for hand-rearing the young make T belangeri a potential alternative to more conventional laboratory species in specific areas of biomedical research.     

Biosynthesis and distribution of ecdysone and 20-OH-ecdysone in Aedes aegypti

The distribution and biosynthesis of ecdysone and 20-hydroxyecdysone (20-OH-ecdysone) was followed in sugar- and blood-fed female Aedes aegypti. In both sugar- and early blood-fed animals most of the ecdysteroid determined by radioimmunoassay was found outside the ovary. Twenty-four to 40 h after blood feeding, however, ecdysteroid was distributed between ovary and carcass in the ratio of 1:1.5. Ecdysteroid titer reached a plateau between 18 to 40 h after the blood meal and decreased thereafter. Analysis of the ecdysteroid titer using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) revealed that both 20-OH-ecdysone and ecdysone were synthesized after the blood meal. The ratio of 20-OH-ecdysone to ecdysone remained essentially constant and fluctuated in parallel throughout egg development. Chromatography of the early ecdysteroid peak (8 h after feeding) using TLC and HPLC indicated that although it cross-reacted with ecdysteroid antibodies, it did not have the same elution times as ecdysone and 20-OH-ecdysone and is, therefore, probably a precursor of these ecdysteroids. Injections of egg development neurosecretory hormone (EDNH) preparation purified to near homogeneity, into ligated abdomens, induced ecdysteroid synthesis only if the abdomens were first treated with methoprene (12.5 pg). Methoprene at this concentration did not stimulate ecdysteroid synthesis in these abdomens. When blood-fed females were treated with [4-¹⁴C] cholesterol and analyzed using TLC and HPLC procedures, both [¹⁴C]labeled ecdysone and [¹⁴C]labeled 20-OH-ecdysone were synthesized in the ratio of 1:1.5. This report is the first to show that both ecdysone and 20-OH-ecdysone are synthesized in vivo in female A. aegypti.