Headache at high altitude is not related to internal carotid arterial blood velocity

The cause of headache in persons going to high altitude is unknown. Relatively severe hypoxemia in susceptible subjects could induce large increases in cerebral blood flow that then could initiate the headache. Thus we measured noninvasively, by Doppler ultrasound, changes in internal carotid arterial blood velocity (velocity) in 12 subjects in Denver (1,600 m) and repeatedly up to 7 h at a simulated altitude of 4,800 m (barometric pressure = 430 Torr). Six subjects, selected because of prior history of high-altitude headache, developed comparatively severe headache at 4,800 m, and four subjects, without such history, remained well. Two subjects developed moderate headache. Velocity at 4,800 m did not correlate with symptom development, arterial O2 saturation, or end-tidal PCO2. Also, neither velocity nor blood pressure was consistently elevated above the Denver base-line values. During measurements of hypercapnic ventilatory response in Denver, velocity increased linearly with end-tidal PCO2, confirming that our Doppler method could demonstrate an increase. Also, 30 min of isocapnic or poikilocapnic hypoxia caused small increases in velocity (+8 and +6%) during the base-line measurement at low altitude. Although even a small increase in cerebral perfusion could contribute to headache symptoms at high altitude, cerebral blood flow does not appear to play a primary role.     

Emergence of some caddisflies (Trichoptera) from a wooded stream in southern Ontario

Twenty-eight species of nine families of caddisflies (Trichoptera) were identified in 170 samples taken over an 8-month period from five emergence traps placed on a second-order, forested, cold-stenothermal stream on the Niagara Escarpment, Ontario, Canada.A mean of 980.9 caddisflies m^–2 of streambed was obtained over the entire sampling period. Eleven common species accounted for 92.8% of the total emergence with specific proportions ranging from 23.8% (Wormaldia moesta) to 0.11 % (Rhyacophila sp.). The use of various kinds of traps in other studies and their effects on the detection of species composition and abundance are discussed and compared with the present study.Although the distributions of all the common species were invariant over time, four species showed low to high degrees of patchiness in the streambed; the other seven common species were uniformly distributed. However, a large residual variance suggested a subtle mechanism of microhabitat selection by the larvae and (or) pupae, not detectable by even the small emergence traps used.Both sexes of 15 species, only males of 4 and only females of 9 species were collected. Eight of the eleven common species showed significant departures from a balanced sex ratio and five exhibited a protandry of from 1 to 3 weeks. Neither this study nor others have been able to establish a predictable pattern of sex ratios in Trichoptera.The emergence periods and patterns of the eleven common species are described and compared with other studies. Of these common species, one emerged in the spring, seven during the summer and three during the late summer or early fall. Ten species had a short emergence period with a distinct peak and a significantly skewed pattern. One species,Parapsyche apicalis, exhibited a prolonged emergence period, no distinct peak and a significantly platykurtotic² pattern. With the exception ofLepidostoma sp. A, the emergence patterns of the common species were unimodal.     

Fetal bovine bone cells synthesize bone-specific matrix proteins

We isolated cells from both calvaria and the outer cortices of long bones from 3- to 5-mo bovine fetuses. The cells were identified as functional osteoblasts by indirect immunofluorescence using antibodies against three bone-specific, noncollagenous matrix proteins (osteonectin, the bone proteoglycan, and the bone sialoprotein) and against type 1 collagen. In separate experiments, confluent cultures of the cells were radiolabeled and shown to synthesize and secrete osteonectin, the bone proteoglycan and the bone sialoprotein by immunoprecipitation and fluorography of SDS polyacrylamide gels. Analysis of the radiolabeled collagens synthesized by the cultures showed that they produced predominantly (approximately 94%) type I collagen, with small amounts of types III and V collagens. In agreement with previous investigators who have employed the rodent bone cell system, we confirmed in bovine bone cells that (a) there was a typical cyclic AMP response to parathyroid hormone, (b) freshly isolated cells possessed high levels of alkaline phosphatase, which diminished during culture but returned to normal levels in mineralizing cultures, and (c) cells grown in the presence of ascorbic acid and beta-glycerophosphate rapidly produced and mineralized an extracellular matrix containing largely type I collagen. These results show that antibodies directed against bone-specific, noncollagenous proteins can be used to clearly identify bone cells in vitro.     

Flies as a source of enteric pathogens in a rural village in Thailand.

The village of Ban Pong in northeastern Thailand was studied from January through December 1981 to determine the importance of flies as a source of enteric pathogens. The number of flies (predominantly Musca domestica) increased in kitchens and animal pens in the hot dry spring, when the incidence of diarrhea was highest in the village. Enterotoxigenic Escherichia coli, Shigella spp., non-O1 Vibrio cholerae, and Vibrio fluvalis were isolated from fly pools in yards (69%), animal pens (38%), bathrooms (35%), and kitchens (8%). Enterotoxigenic E. coli was isolated from one fly pool in May and from another in June, when the incidence of such infections was highest in the village. Flies often carry and presumably disseminate enteric pathogens in rural Thailand.     

Structure of tomato busy stunt virus IV. The virus particle at 2.9 A resolution

The structure of tomato bushy stunt virus has been determined crystallographically to 2.9 A resolution. Details are presented of both the molecular structure and the methods by which it has been solved. The icosahedrally symmetric viral shell is composed of 180 protein subunits (Mr 43,000), with three similar but distinct modes of subunit bonding. This capacity for alternative packing is due to localized flexibility in the folded polypeptide (hinges between domains) and to multiple conformations for surface side-chains. The polypeptide backbone has an essentially invariant fold within a compact domain. A mechanism for correct positioning of the different modes of subunit interaction is evident from the structure of the TBSV particle. Thirty-five residues of the polypeptide chain fold in an ordered way on 60 of the 180 subunits, forming an internal framework. Interaction of folded domains with this framework permits accuracy of long-range geometry (correct curvature and closure) to be determined by unambiguous switching between alternative local contact angles. RNA packs tightly into the particle interior. Protein-RNA interactions occur through parts of the subunit that are flexibly linked to the well-ordered domains of the shell. This variable interaction imposes minimum restrictions on the folding of the RNA chain.     

Divalent cation sites in tomato bushy stunt virus. Difference maps at 2-9 A resolution

Difference electron density maps, using as few as four 1/2 degrees oscillation photographs, have been computed for tomato bushy stunt virus crystals soaked in EDTA. GdCl3 and silicotungstate. The maps define a double divalent cation site, responsible for regulating expansion of the virus particle, as well as sites for binding tungstate anions.