The "backdoor pathway" of androgen synthesis in human male sexual development.

Mammalian sex determination (male versus female) is largely controlled by genes, whereas sex differentiation (development of reproductive structures) is largely controlled by hormones. Work in the 20th century indicated that female external anatomy was a "default" pathway of development not requiring steroids, whereas male genital development required testicular testosterone plus dihydrotestosterone (DHT) made in genital skin according to a "classic" pathway. Recent work added the description of an alternative "backdoor" pathway of androgen synthesis discovered in marsupials. Unique "backdoor steroids" are found in human hyperandrogenic disorders, and genetic disruption of the pathway causes disordered male sexual development, suggesting it plays an essential role. O'Shaughnessy and colleagues now show that the principal human backdoor androgen is androsterone and provide strong evidence that it derives from placental progesterone that is metabolized to androsterone in nontesticular tissues. These studies are essential to understanding human sexual development and its disorders

Cassini: Mission to Saturn and Titan

The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission

Mitochondrial heat-shock protein hsp60 is essential for assembly of proteins imported into yeast mitochondria

A nuclear encoded mitochondrial heat-shock protein hsp60 is required for the assembly into oligomeric complexes of proteins imported into the mitochondrial matrix. hsp60 is a member of the 'chaperonin' class of protein factors, which include the Escherichia coli groEL protein and the Rubisco subunit-binding protein of chloroplast

Biology and management of river herring and shad in Virginia : Completion report, 1970-73

This report represents the final report for the 3-year segment 1970-1973 and the annual report for the contract period 1 October 1972 to 15 October 197 3. The projec.t has been active since 1965, thus relevant data has been carried forward, added to, and analyzed in this report. The analysis, however, remains subject to later refinement and possible reinterpretation, because many of the jobs and objectives will require several additional years of study before definitive conclusions can be generalized. The data presented here supercedes similar tables presented in previous annual reports because we have now standardized methods and solidified our attempts at presenting various yearly indices, The changes in any method of analysis are stated within each subsection. This report, therefore, contains earlier data adjusted with derived correction factors so all units have the same base and assumptions

Effect of Periodontal Therapy on Alveolar Bone as Measured by Subtraction Radiography

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141973/1/jper0633.pd

Tests of an alternate mobile transporter and extravehicular activity assembly procedure for the Space Station Freedom truss

Results are presented from a ground test program of an alternate mobile transporter (MT) concept and extravehicular activity (EVA) assembly procedure for the Space Station Freedom (SSF) truss keel. A three-bay orthogonal tetrahedral truss beam consisting of 44 2-in-diameter struts and 16 nodes was assembled repeatedly in neutral buoyancy by pairs of pressure-suited test subjects working from astronaut positioning devices (APD's) on the MT. The truss bays were cubic with edges 15 ft long. All the truss joint hardware was found to be EVA compatible. The average unit assembly time for a single pair of experienced test subjects was 27.6 sec/strut, which is about half the time derived from other SSF truss assembly tests. A concept for integration of utility trays during truss assembly is introduced and demonstrated in the assembly tests. The concept, which requires minimal EVA handling of the trays, is shown to have little impact on overall assembly time. The results of these tests indicate that by using an MT equipped with APD's, rapid EVA assembly of a space station-size truss structure can be expected

\u3csup\u3e1\u3c/sup\u3eH NMR Studies on the CuA Center of Nitrous Oxide Reductase from \u3cem\u3ePseudomonas stutzeri\u3c/em\u3e

1H NMR spectra of the CuA center of N2OR from Pseudomonas stutzeri, and a mutant enzyme that contains only CuA, were recorded in both H2O- and D2O-buffered solution at pH 7.5. Several sharp, well-resolved hyperfine-shifted 1H NMR signals were observed in the 60 to −10 ppm chemical shift range. Comparison of the native and mutant N2OR spectra recorded in H2O-buffered solutions indicated that several additional signals are present in the native protein spectrum. These signals are attributed to a dinuclear copper(II) center. At least two of the observed hyperfine-shifted signals associated with the dinuclear center, those at 23.0 and 13.2 ppm, are lost upon replacement of H2O buffer with D2O buffer. These data indicate that at least two histidine residues are ligands of a dinuclear Cu(II) center. Comparison of the mutant N2OR 1H NMR spectra recorded in H2O and D2O indicates that three signals, c (27.5 ppm), e (23.6 ppm), and i (12.4 ppm), are solvent exchangeable. The two most strongly downfield-shifted signals (c and e) are assigned to the two Nε2H (N-H) protons of the coordinated histidine residues, while the remaining exchangeable signal is assigned to a backbone N-H proton in close proximity to the CuA cluster. Signal e was found to decrease in intensity as the temperature was increased, indicating that proton e resides on a more solvent-exposed histidine residue. One-dimensional nOe studies at pH 7.5 allowed the histidine ring protons to be definitively assigned, while the remaining signals were assigned by comparison to previously reported spectra from CuA centers. The temperature dependence of the observed hyperfine-shifted 1H NMR signals of mutant N2OR were recorded over the temperature range of 276−315 K. Both Curie and anti-Curie temperature dependencies are observed for sets of hyperfine-shifted protons. Signals a and h (cysteine protons) follow anti-Curie behavior (contact shift increases with increasing temperatures), while signals b−g, i, and j (histidine protons) follow Curie behavior (contact shift decreases with increasing temperatures). Fits of the temperature dependence of the observed hyperfine-shifted signals provided the energy separation (ΔEL) between the ground (2B3u) and excited (2B2u) states. The temperature data obtained for all of the observed hyperfine-shifted histidine ligand protons provided a ΔEL value of 62 ± 35 cm-1. The temperature dependence of the observed cysteine CβH and CαH protons (a and h) were fit in a separate experiment providing a ΔEL value of 585 ± 125 cm-1. The differences between the ΔEL values determined by 1H NMR spectroscopy and those determined by EPR or MCD likely arise from coupling between relatively low-frequency vibrational states and the ground and excited electronic states