Control of ventilation in extreme-altitude climbers

Ten climbers who participated in the Nepal-Japan Kangchenjunga Expedition (altitude, 8,478-8,586 m) in 1984 were examined for their hypercapnic and isocapnic hypoxic ventilatory responses (HCVR and HVR) at sea level before and after the expedition. Five climbers who reached an altitude higher than 8,000 m, [designated high-performance climbers (HPC)] exhibited significantly higher HVR than five climbers who did not [low-performance climbers (LPC)]. On the other hand, no significant difference in HCVR was seen between HPC and LPC. Our results were in agreement with the findings reported by Schoene et al. (J. Appl. Physiol. 56: 1478-1483, 1984) obtained in the American Medical Research Expedition to Everest in 1981. Significant depression in HVR in five climbers was found even 35-40 days after the expedition, which was accompanied by decreased arterial partial pressure of CO2 and increased pH at rest. Hence, the effect of altitude acclimatization in the climbers exposed to extreme altitude may have still persisted at the time of the postexpedition study. Our results confirmed that HRV evaluated at sea level may be used as an indicator of a climber's capability at great high altitude.     

Fever in rats during normal and dehydrated conditions

The effect of endogenous pyrogen (EP, from rabbit) and endotoxin (Salmonella typhosa) on rectal temperature (Tre) was investigated in normal and dehydrated rats of both sexes. Intraperitoneal injection of either EP or endotoxin did not affect body temperature. In addition, no changes in Tre were observed when endotoxin was injected intravenously in normally hydrated male rats, but significant falls in Tre occurred in normal female rats. However, intravenous injection of EP produced fever in both sexes, but females generally showed smaller responses. A second intravenous injection of endotoxin, given 3 days after the first injection, always produced fever in normally hydrated rats. The pattern of this febrile response was monophasic. In contrast to the response in normal rats, intravenous endotoxin produced significant fevers with a biphasic pattern in dehydrated rats of either sex, but the febrile responses of male rats were greater than those of female rats. On the other hand, there were no significant differences between febrile responses to intravenous EP exhibited by normal and dehydrated animals. These results show that rats of both sexes possess physiological mechanisms capable of producing a fever following intravenous injections of EP.     

Cell-matrix interrelation and cell-to-cell connection in the secretory ameloblast layer of kitten teeth

To investigate the cell-matrix interrelation and the structure and permeability of the junctional complexes of secretory ameloblasts, molar tooth germs from kittens were examined by means of scanning electron microscopy, routine thin sections and freeze-fracture replication. Scanning electron microscopy showed remarkably dissolved growth fronts of enamel in materials that had been fixed with glutaraldehyde and then subjected to EDTA perfusion for 10 min. By the action of EDTA, intercrystallite spaces in rod and interrod enamel were prominently widened, and their longitudinal ends of crystallites displayed irregular and extremely sparse structures. In enamel rods surrounded entirely by interrod enamel, and in enamel rods of the typical key hole shape with successive interrod enamel participation, the most striking dissolution of crystallites occurred at the boundaries between rod and interrod enamel, where broad expanses of rod-sheath spaces were observed. In thin sections, the Tomes processes of secretory ameloblasts occupying the above rods were rectangular or variations of a rectangular shape, respectively; and interameloblast spaces opened to the enamel growth fronts, which corresponded to the junction between rod and interrod enamel. In enamel rods standing in regular rows and showing the typical arcade shape, the centers of the rods were drastically dissolved and exhibited single and deep slits, whereas the boundaries between rod and interrod enamel showed no wide furrows. The Tomes processes occupying such arcade-shaped rods were typically triangular, and the interameloblast space always joined the type-1 face of process, which is responsible for enamel rod formation. Secretory ameloblast possessed two sets of junctional complexes at the proximal and distal ends of the cell body. The distal one was situated proximally to the Tomes process. Freeze-fracture replication demonstrated the functional structures of these junctions: the proximal junction was fascia occludens, and the distal one incomplete zonula occludens with many free-ending tight junctional strands and interstrand spaces or a less developed irregular junction.     

Effects of Environmental Factors on Toxicity of a Cyanobacterium (Microcystis aeruginosa) under Culture Conditions

Effects of light intensity, temperature, and nutrients on the toxicity of Microcystis aeruginosa were investigated, using a toxic strain which kills mice. A marked change in toxicity was observed in the light intensity experiment, and slight changes were observed to be caused by temperature and phosphorus deficiency.     

The human alpha-fetoprotein gene. Sequence organization and the 5' flanking region

The human alpha-fetoprotein (AFP) gene was isolated into three overlapping clones in bacteriophage lambda vectors and its sequence organization analyzed by restriction endonuclease mapping and nucleotide sequencing. The human AFP gene is about 20 kilobase pairs long and contains 15 exons and 14 introns. The overall organization of the human AFP gene is similar to that of the mouse AFP gene, with all but two exons showing identical sizes. Nucleotide sequences at all exon/intron junctions display similarity to the consensus boundary sequence (Breathnach, R., and Chambon, P. (1981) Annu. Rev. Biochem. 50, 349-383), with the GT-AG rule applied to the splicing point. The cap site maps 44 nucleotides upstream from the translation initiation site. The "TATA box" is located 27 nucleotides upstream from the putative cap site and is flanked by sequences with dyad symmetry. The TATA box can thus be placed in the loop portion of a possible stem-loop structure formed by intrastrand base-pairing. Other characteristic nucleotide sequences in the 5' flanking region include a CCAAC pentamer, a 14-base pair (bp) enhancer-like sequence, and a 9-bp sequence homologous to the glucocorticoid responsive element. A long (90 bp) direct repeat and several alternating purine/pyrimidine sequences are also present in the 5' flanking region. A 736-bp sequence of the 5' flanking region adjacent to the cap site of the human AFP gene shows a 61% similarity with the corresponding region of the mouse AFP gene. There are two Alu family sequences and two poly(dT-dG) repeats in the human AFP gene that show different distribution patterns from those in the mouse AFP gene.     

Effects of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) on cardiac function in perfused guinea-pig heart

The direct cardiac action of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) was studied in isolated perfused guinea-pig heart preparations. PAF produced a fall in left ventricular pressure, decreases in the rate of rise of the left ventricular pressure (dp/dt) and coronary flow, but had no effect on heart rate. These results indicate that PAF is a cardiodepressant with inotropic selectivity and this effect on heart is blocked by CV-3988, a specific PAF antagonist.     

Radiation-induced formation of apoptotic bodies in rat thymus

The process of interphase death of thymocytes in whole-body X-irradiated rats were studied. Cell size distribution analysis indicates that cell fragments (= apoptotic bodies) appeared in the thymus and increased in number depending on dose (200-1000 R) and time (2-6 hr) after irradiation with corresponding decrease in normal-size thymocytes. Occurrence of nuclear fragmentation in association with the cellular fragmentation was proved with cytofluorometric determination of DNA content in individual cells. Scanning electron microscopic observations also revealed extensive fragmentation of cells in the irradiated rat thymus. The results show clearly that cells as well as nuclei fragment rapidly into smaller pieces of various sizes in the irradiated rat thymus as commonly observed with apoptosis.     

Effects of brain and mesenchyme upon the cytogenesis of rat adenohypophysis in vitro

Summary The objective of this in-vitro study was to examine whether the diencephalic floor or the mesenchyme is involved in differentiation of LH cells in the developing rat adenohypophysis. Overall growth of the adenohypophysial tissue was retarded when the adenohypophysial primordium was cultivated after enzymatic removal of the diencephalic floor on days 11.5 and 12.5 of gestation. This malgrowth was more marked when the brain was separated on day 11.5; most expiants retained a simple cystiform structure that consisted of a few layers of undifferentiated cells. Removal of the brain also caused a highly significant decrease (P < 0.001) in the number of immunoreactive LH cells, if it was performed on day 11.5 but not day 12.5. Mesenchyme had little effect on the adenohypophysial growth or the number of immunopositive cells. Cultivation of the adenohypophysial primordium with the diencephalic floor resulted in the appearance of many immunoreactive LH cells. The number of LH cells significantly decreased, however, when the co-cultivated brain completely surrounded the adenohypophysial tissue.These results indicate that in 11.5-day-old fetal rats the diencephalic floor is indispensable for the initial proliferation of adenohypophysial primordial cells and for the early determinating process of LH cells. Once determined, the development of LH cells may proceed without the surrounding tissues. The cytodifferentiation seems to be rather inhibited when in contact with the brain. The significance of the intimate spatial relationship between developing LH cells and the surrounding mesenchyme is also discussed.