消息与动态

日本第四纪学会1988年大会于8月19—21日在仙台市举行,中国科学院古脊椎动物与古人类研究所黄慰文、祁国琴应邀出席。他们除参加由大会组织的宫城县江合川流域的地质旅行外,还与东道国、苏联、南朝鲜和香港的同行就“东亚更新世中期至晚期人类及其环境”专题开展热烈讨论。 此外,黄慰文还应日本国际交流基金会邀请和由奈良国立文化财研究所接待,于8月14日     

A neuroheptapeptide influence on cognitive functioning in the elderly

The heptapeptide core common to melanocyte-stimulating hormone (MSH) and adrenocorticotropin (ACTH) was administered as a single subcutaneous dose of 30 mg to 13 elderly human subjects (9 men, 4 women) in a double-blind, cross-over design. Significant improvement was found in the Benton Visual Retention Test after MSH/ACTH 4–10 as compared with administration of saline. This appeared to be greater in men than women. No side effects or laboratory abnormalities were observed. The behavioral results are consistent with our earlier findings in men and rats of improved visual attention after administration of MSH and extend them to the elderly population.     

Molecular evolutionary processes and conflicting gene trees: The hominoid case

Molecular evolutionary processes modify DNA over time, creating both newly derived substitutions shared by related descendant lineages (phylogenetic signal) and “false” similarities which confound phylogenetic reconstruction (homoplasy). However, some types of DNA regions, for example those containing tandem duplicate repeats, are preferentially subject to homoplasy-inducing processes such as sporadically occurring concerted evolution and DNA insertion/deletion. This added level of homoplasic “noise” can make DNA regions with repeats less reliable in phylogenetic reconstruction than those without repeats. Most molecular datasets which distinguish among African hominoids support a human-chimpanzee clade; the most notable exception is from the involucrin gene. However, phylogenetic resolution supporting a chimpanzee-gorilla clade is based entirely on involucrin DNA repeat regions. This is problematic because (1) involucrin repeats are difficult to align, and published alignments are contradictory; (2) involucrin repeats are subject to DNA insertion/deletion; (3) gorillas are polymorphic in that some do not have repeats reported to be synapomorphies linking chimpanzees and gorillas. Gene tree/species tree conflicts can occur due to the sorting of ancestrally polymorphic alleles during speciation. Because hominoid females transfer between groups, mitochondrial and nuclear gene flow occur to the same extent, and the probability of conflict between mitochondrial and nuclear gene trees is theoretically low. When hominoid intraspecific mitochondrial variability is taken into account [based on cytochrome oxidase subunit II (COII) gene sequences], humans and chimpanzees are most closely related, showing the same relative degree of separation from gorillas as when single individuals representing species are analyzed. Conflicting molecular phylogenies can be explained in terms of molecular evolutionary processes and sorting of ancient polymorphisms. This perspective can enhance our understanding of hominoid molecular phylogenies. © 1994 Wiley-Liss, Inc.     

Is chromium pharmacologically relevant?

Recent research, combined with reanalysis of previous results, has revealed that chromium can no longer be considered an essential trace element. Clinical studies are ambiguous at best as to whether Cr has a pharmacological effect in humans. Observed effects of Cr on rodent models of insulin resistance and diabetes are best interpreted in terms of a pharmacological role for Cr. Studies on the effects of Cr on rat models of diabetes are reviewed herein and suggest Cr increases insulin sensitivity in peripheral tissues of the rodent models. The lack of effects in human studies may stem from humans receiving a comparably smaller dose than the rodent models. However, given the different responses to Cr in the rodent models, humans could potentially have different responses to Cr.     

Subfossil mammalian tracks (Flandrian) in the Severn Estuary,S. W. Britain: mechanics of formation,preservation and distribution

Mammalian tracks and trackways are widely preserved at all stratigraphical levels in the Flandrian sediments of tidal mudflat and marsh origins which formed over the last 8000–9000 years on the marginal wetlands of the inner Bristol Channel and Severn Estuary. The fauna recorded in this way, however, is less diverse than that known from the few, small assemblages of skeletal remains, including some from archaeological sites, so far assessed. Missing or rarely represented in terms of tracks are the smaller of the large mammals. Humans are represented by tracks throughout the Flandrian deposits. In the earlier Flandrian, they were accompanied by deer and aurochs which gave way, in the later Flandrian, to domesticated cattle and sheep/goat; there are sporadic indications of the presence of horse. Wolf/dog, represented by just two records, is the only smaller large mammal so far recorded as a track.The tracks were made, modified, and eventually preserved under a wide variety of sedimentological conditions on the margins of the estuary. Those environmental conditions constrained the quality of the anatomical evidence preserved in the tracks but can be inferred from the character of the tracks. Field experiments suggest that the moisture content of the sediment at the time was crucial to the general nature of the tracks. The mudflat–marsh silts which received the tracks varied from semi-liquid to firm, depending on tidal and seasonal factors and on the elevation of the sedimentary surface relative to the tidal frame. Some tracks were made in marsh peats which offered little resistance. Deep tracks preserving little detail were produced in weak sediments of high moisture content; tracks formed in strong, firm muds retained full anatomical detail. Referring to mechanical theory, and to a series of laboratory experiments using plasticine, the act of making a track is shown to be similar in character and effect to the indentation of an ideal elastic–plastic material by a punch. The punch represents the descending limb of the animal, the face of the punch the sole of the animal''s foot, and the elastic–plastic material the sediment which is pierced and deformed by the downward action of the limb. The character of the experimental tracks, and the range and relative size of the deformation structures they include, is qualitatively similar to what is recorded from the field. Many of the tracks recorded from the field were variously modified in a changeable and dynamic environment before final burial and preservation.     

Class III β-tubulin,a novel biomarker in the human melanocyte lineage

It is generally thought that class III β-tubulin expression is limited to cells of the neural lineage and is therefore often used to identify neurons amongst other cell types, both in vivo and in vitro. Melanocytes are derived from the neural crest and share both morphological features and functional characteristics with peripheral neurons. Here, we show that these similarities extend to class III β-tubulin (TUBB3) expression, and that human melanocytes express this protein both in vivo and in vitro. In addition, we studied the expression of class III β-tubulin in two murine melanogenic cell lines and show that expression of this protein starts as melanoblasts mature into melanocytes. Melanin bleaching experiments revealed close proximity between melanin and TUBB3 proteins. In vitro stimulation of primary human melanocytes by α-MSH indicated separate regulatory mechanisms for melanogenesis and to TUBB3 expression. Together, these observations imply that human melanocytes express TUBB3 and that this protein should be recognized as a wider marker for multiple neural crest-derived cells.     

Gas exchange between humans and multibiological life support system

To establish a Bioregenerative Life Support System (BLSS) in lunar or Mars bases in the future, manned stimulation experiments including several kinds of creatures are needed to be conducted first. Gas exchange relation, element transfer and transformation principles, etc. between humans and the multibiological system composed of plants, animals, microalgae and so on must be investigated in order to place different organisms with appropriate numbers and proportions in the BLSS. This research cultivated lettuce (Lactuca sativa L.) and silkworm (Bombyx mori L.) in the CICS (Closed Integrative Cultivating System) of the IES (Integrative Experimental System) with Chlorella vulgaris cultivated in the PPB (Plate Photo Bioreactor) of the IES. Conveyor-type cultivation method was implemented for harvesting the largest batch of lettuce and silkworms through the mass exchange chamber of the IES every four days and transferring the smallest batch of lettuce and silkworms into the system; carrying certain amounts of alga liquid out with nutrient liquid replenished every day. Gas exchange between testers and the IES including three phases was conducted periodically. Phase I involved one person participating in gas exchange with lettuce in plant chamber as primary means of air revitalization for 3 months. Phase II was gas exchange between one person and autotrophic creatures, which were lettuce and microalgae, for 1 month. In the Phase III test, silkworms were introduced into the animal chamber for 2 months. Mathematical modeling and experimental simulation for this system was done to study its gas robustness. Results show that CO₂/O₂ concentration fluctuated around normal levels, the system possessed relatively good gas robustness and there were no trace gas (CH₄, NH₃ and C₂H₄) contaminant problems in the system.     

Leg blood flow during slow head-down tilt with and without leg venous congestion

The effects of slow changes in body position on leg blood flow (LBF) were studied in nine healthy male subjects. Using a tilt table, sitting volunteers were tilted about 60° backwards to a supine position within 40 s. To modify the venous filling in the legs, the tilt manoeuvre was repeated with congestion of the leg veins induced by two thigh cuffs inflated to a subdiastolic pressure of 60 mmHg. Doppler measurements in the femoral artery were used to estimate LBF. Additional Doppler measurements at the aortic root in five of the subjects were taken for the determination of cardiac output. The LBF was influenced by body position. In the control experiment it increased from 500 ml · min⁻¹ in the upright to 780 ml · min^–1 after 15 min in the supine position. A mean maximal value of 950 ml · min⁻¹ was observed 20 s after the tilt. Heart rate remained almost constant during the tilt phase, whereas stroke volume increased from 90 ml to 120 ml and it remained at that level after the cessation of the tilt. Congestion of the leg veins had no significant effect on heart rate, stroke volume and mean blood pressure. However, it increased vascular resistance of the leg during and after the tilt. After 15 min in the tilted position LBF amounted to 600 ml · min⁻¹. The results suggest that the filling of the leg veins is inversely related to leg blood flow. The most likely mechanism underlying this observation is a local effect of venous filling on vasomotor tone. Accepted: 20 May 1998     

Physiological changes induced by pre-adaptation to high altitude

To study the physiological effects of pre-adaptation to high altitude, seven subjects were submitted to acclimatization at 4350 m followed by intermittent acclimation in a low barometric pressure chamber (5000 m to 8500 m). The subjects then spent 25 days in the Himalayas. Ventilatory and cardiac responses were studied during a hypobaric poikilocapnic hypoxic test performed both at rest and during exercise (100 W) in normoxia and in hypoxia (barometric pressure: 589 hPa, altitude: 4500 m). Haemoglobin, erythrocytes, reticulocytes, packed cell volume, 2,3-diphosphoglycerate (2,3-DPG) and erythropoietin (EPO) were measured. All variables were studied before pre-adaptation to high altitude (A), after the acclimatization period (B), after the acclimation period (C) and after the expedition (D). The ventilatory and cardiac responses were characterized by an increased tidal volume in hypoxia (+ 33% during exercise in B,P < 0.05; + 100% at rest and + 33% during exercise in C,P < 0.05) without any change in respiratory frequency, whereas an increased systolic blood pressure was only observed in C during exercise in hypoxia [+23 mmHg (3.07 kPa),P<0.01]. Arterial O2 saturation was higher in hypoxia in C and D, both at rest (+8.2% and +4.7%,P<0.01, respectively), and during exercise (+6.3% and +6.3%,P<0.01, respectively). Erythrocytes, haemoglobin and packed cell volume did not vary significantly. The number of reticulocytes was higher in B (+172%,P<0.05) and in C (+249%,P<0.05). EPO and 2,3-DPG increased only in C (+ 770%,P<0.01 and +23%,P<0.05, respectively). These results showed that a combination of continuous pre-acclimatization on Mont Blanc and intermittent acclimation in the hypobaric chamber triggered efficient pre-adaptation mechanisms allowing climbers to save 1 to 2 weeks of acclimatization on the mountain without clinical inconvenience.     

Nut-like oil seeds: food for monkeys, chimpanzees, humans, and probably ape-men

The hypothetical hyperrobust australopithecine gnathic nutcracker adaptation is reexamined in light of ecobotanical information on edible wild nuts provided by the flora of tropical and subtropical Africa. The nut producing species are tree-forms. Those of the forest region do not as a rule produce fruits with edible mesocarps. In contrast, the woodland savanna species (particularly in the Zambezian region) characteristically provide an important whole fruit, i.e., a nutritious mesocarp in addition to edible oil-rich nut seeds. These fruits drop from the tree before they are fully mature and go through the final ripening phase on the ground. They are important seasonal foods for a variety of vertebrates, including primates, elephants, and antelope. Altogether the nuts exhibit a broad range of toughness values, measured here as strength under compression. The woodland nuts are not as tough (177-934 kg force, breaking load) as those of the tropical forest (192-1,673 kg force). The seed-predators of the woodland species include squirrels, baboons, warthogs, and parrots. Paleoecological analyses indicate that it was the woodland nuts that were probably available to Australopithecus boisei and A. robustus. Preliminary estimates of adult male gnathic nut-cracking capabilities suggest that A. boisei could have orally cracked a significant portion of the woodland nuts. In spite of this, ecobotanical data indicate that we can probably reject the hypothesis that these hominids were year-round gnathic nut-cracking specialists. Both the indirect and direct evidence support this conclusion.