Spontaneous phrenic nerve activity in the exteriorized fetal lamb.

Phrenic nerve activity and tracheal pressure changes were recorded in four exteriorized fetal lambs (120-135 days gestation) from lightly anesthetized ewes to study possible mechanisms involved in the establishment of rhythmical breathing patterns. Two types of spontaneous neural activity were found. The first consisted of high-frequency multiunit bursts (mean duration 820 ms; range 450-2,500 ms) that preceded a gasp. Individual units within these bursts reached peak discharge frequencies as high as 40 impulses/s. The second type of neural activity consisted of single-unit, low-frequency (1-14 impulses/s), irregular background discharges lasting up to several seconds without changes in tracheal pressure. Occasionally, higher frequency bursts of single-unit activity were detected that were also unassociated with tracheal pressure changes. The data indicate that the neural correlate of a fetal gasp includes high-frequency synchronized bursting activity in the phrenic nerve. In addition, background phrenic activity can be detected in the exteriorized fetal lamb that reflects central nervous activity in the absence of tracheal pressure changes.     

Aldosterone dynamics during graded exercise at sea level and high altitude.

Hormonal responses to graded exercise of eight low altitude residents were examined at sea level (SL) and after 1 (acute) and 11 (chronic) days at 4,300 m (HA). Caloric, water, and electrolyte intakes were controlled, as were temperature and humidity. Blood was sampled at rest and during light and moderate upright bicycle exercise (20 min at 40% and 75% of maximal O2 uptake, respectively). Mean VO2 max at HA was 27% lower than at SL. Resting plasma levels of aldosterone (Aldo), renin, and angiotensin II (A II) were significantly lower (P smaller than 0.05) on day 1 at HA compared to SL, but returned to SL values by day 11. Plasma cortisol values at rest were similar at SL and HA and were not significantly altered by light or moderate exercise. Renin, A II, and Aldo rose progressively with increasing workload in each environment. With acute HA, renin and Aldo were lower than at either SL or chronic HA. The chronic HA levels tended to approximate SL findings, implying adaptation. The data suggest that aldosterone is predominantly under the control of the renin-angiotensin system during graded exercise at sea level and that the response of this system is altered on acute high-altitude exposure.     

Isolation and identification of the conidial germination factor of Neurospora crassa.

The germination-essential substance (germination factor [GF]) that is lost from conidia of Neurospora crassa on exposure to solutions of low water activity has been isolated and identified as a group of iron-transport compounds, or siderochromes. The principal siderochrome of conidia is ferricrocin, a cyclic hexapeptide. A closely related substance, ferrichrome C, is tentatively identified as a minor constituent. The same substances are also present in extracts of mycelium along with small amounts of a third siderochrome, which has not been identified. The GF activity of culture filtrates is due to coprogen, the only siderochrome previously identified with N. crassa.     

Ubiquity of plasmids in coding for toluene and xylene metabolism in soil bacteria: evidence for the existence of new TOL plasmids.

Thirteen bacteria have been isolated from nine different soil samples by selective enrichment culture on m-toluate (m-methylbenzoate) minimal medium. Eight of these were classified as Pseudomonas putida, one as a fluorescent Pseudomonas sp., and four as nonfluorescent Pseudomonas sp. All 13 strains appeared to carry TOL plasmids superficially similar to that previously described in P. putida mt-2 in that: (i) all the wild-type strains could utilize toluene, m-xylene, and p-xylene as sole carbon and energy sources, (ii) these growth substrates were metabolized through the corresponding alcohols and aldehydes to benzoate, m-toluate, and p-toluate, respectively, and thence by the divergent meta (or alpha-ketoacid) pathway, and (iii) the isolates could simultaneously and spontaneously lose their ability to utilize the hydrocarbons, alcohols, aldehydes, and acids, particularly during growth on benzoate, giving rise to cured strains which could grow only on benzaldehyde and benzoate of the aromatic substrates by the alternative ortho (or beta-ketoadipate) pathway. Eight of the isolates were able to transfer their TOL plasmids into their own cured strains, but only five were able to transfer them in interstrain conjugation into the cured strains, but only five were able to transfer them in interstrain conjugation into the cured derivative of P. putida mt-2. However, P. putida mt-2 was able to transfer its TOL plasmid into 11 of the cured isolates, and eight of these were able to retransmit this foreign plasmid in intrastrain conjugation with their own cured derivatives. Three of the isolates, MT 14, MT 15, and MT 20, differed significantly from the others in that the wild-type strains dissimilated the p-methyl-substituted substrates poorly, and also, during growth on benzoate, in addition to the cured derivatives, they gave rise to derivatives with a phenotype intermediate between the cured and wild-type strains, the biochemical and genetic nature of which has not been elucidated.     

Complementation of human adenovirus type 5 ts mutants by human adenovirus type 12.

Temperature-sensitive mutants of type 5 adenovirus belonging to eight complementation groups were complemented in mixed infection by type 12 adenovirus, whereas mutants of 7 other groups were not enhanced. In some crosses, phenotypic mixing took place. No evidence of recombination between type 5 ts mutants and type 12 was found.     

The metabolism of synthetic estrogens in non-users and users of oral contraceptives

Using both pulse injections and constant infusions of ³H-mestranol (³H-ME) (1) and ³H-ethinyl estradiol (³H-EE) we have studied the metabolism of these compounds in non-users and users of oral contraceptives. Following pulse injection of ³H-ME the disappearance of radioactivity could be described as a function which was the sum of two exponentials. Studied by both types of administration there was no difference in the metabolism of ³H-ME in the two groups; the overall mean ± SE metabolic clearance rate (MCR) was 690 ± 45 1/day/m², the mean ratio of the concentrations of radioactivity as EE following administration of ME (CR_BB^{M, E}) was 0. 23 ± 0. 02 and the mean [ρ]_BB^{M, E} (fraction of administered ME measured in blood as EE) was 0. 19 (95% confidence limits = 0.15 – 0. 23).Following pulse injection of ³H-EE the disappearance of radioactivity was best described as a function which is the sum of three exponentials. Results from both types of administration revealed no difference in the metabolism of ³H-EE between non-users. The overall mean ± SE MCR^EE was 630 ± 30 I/day/m². The MCR^EE is significantly (0. 02 > P > 0. 01) less than the mean MCR for estradiol reported previously, in both non-users and users of oral contraceptives. The use of oral contraceptives containing estrogens and progestins does not appear to influence the metabolism of the estrogen used. Approximately 20% of mestranol is converted to and appears in the blood as ethinyl estradiol.     

The location of the genes coding for hexon and fiber proteins in adenovirus DNA.

A serological analysis has been made of the capsid antigens hexon and fiber from 17 Ad5-Ad2+ND1 recombinants that enables us to determine the phenotype of the recombinants. By correlation of this data with the genetic and physical maps of the adenovirus genome, obtained by recombination and restriction endonuclease analysis, the genes coding for the hexon and fiber have been assigned to specific locations on the adenovirus DNA.