Influence of Androgenicity on Adipocytes and Precursor Cells in Female Rats

We examined the effects of overexposure of testosterone (T) on fat cell morphology and adipocyte precursor pools in inguinal and retroperitoneal fat depots of ovariectomized rats. In both tissues peripubertal T decreased weights without affecting adipocyte mean cell size or the size distribution profiles, but adipocyte number was decreased by 65% in the inguinal and by 38% in the retroperitoneal depots. Immunofluorescent flow cytometry utilizing a specific antibody to rat adipose tissue lipoprotein lipase was used to quantify regional precursor cell populations. T sharply reduced the percentages of differentiated and undifferentiated preadipocytes in the inguinal depot, from 43.2 ± 5.3 to 23.5 ± 2.1% and from 57.7 ± 4.0 to 43.6 ± 5.3%, respectively, with a concomitant increase in fibroblasts from 1.6 to 32.9%. On the other hand, T had no effect on retroperitoneal preadipocyte pools. Perinatal andro-genization exacerbated the decline in the inguinal weight (1.4 ± 0.1 vs. 2.2 ± 0.1g) but otherwise did not influence the actions of peripubertal T. Androgens may thus act in a tissue-specific manner to regulate fat cell growth potential in the femoral region in the female.     

Local helix content in an alanine-rich peptide as determined by the complete set of 3JHNα coupling constants

Summary Alanine-rich peptides serve as models for exploring the factors that control helix structure in peptides and proteins. Scalar CH-NH couplings (³J_HN) are an extremely useful measure of local helix content; however, the large alanine content in these peptides leads to significant signal overlap in the CH region of ¹H 2D NMR spectra. Quantitative determination of all possible ³J_HN values is, therefore, very challenging. Szyperski and co-workers [(1992) J. Magn. Reson., 99, 552–560] have recently developed a method for determining ³J_HN from NOESY spectra. Because ³J_HN may be determined from 2D peaks outside of the CH region, there is a much greater likelihood of identifying resolved resonances and measuring the associated coupling constants. It is demonstrated here that ³J_HN can be obtained for every residue in the helical peptide Ac-(AAAAK)₃A-NH₂. The resulting ³J_HN profile clearly identifies a helical structure in the middle of the peptide and further suggests that the respective helix termini unfold via distinct pathways.Abbreviations ³J_HN three-bond CH-NH scalar coupling constant - NOE nuclear Overhauser enhancement - NOESY two-dimensional nuclear Overhauser spectroscopy - COSY two-dimensional correlated spectroscopy - DQF-COSY two-dimensional double-quantum-filtered correlated spectroscopy - TOCSY two-dimensional total correlation spectroscopy To whom correspondence should be addressed.Deceased March 5, 1996.     

Photoperiodic responses of a northern and southern ecotype of black cottonwood

Photoperiod is an important signal controlling the onset of dormancy in perennial plants. Short days typically induce growth cessation, the initiation of cold acclimation, the formation of a terminal bud. bud dormancy and other adaptive responses. Photoperiodic ecotypes have evolved in many species with large latitudinal distributions. The photoperiodic responses of two northern (53°35′ and 53°50′N) and two southern (34°10′ and 40°32′N) genotypes of black cottonwood (Populus trichocarpa Torr. & Gray) were characterized by growing trees under a range of photoperiods in the greenhouse and growth chamber. Short days induced bud set in both ecotypes. resulting in trees with fewer leaves and less height growth than trees grown under long days. Short days also enhanced anthocyanin accumulation in the northern ecotype and decreased branching of the southernmost genotype. Two aspects of the photoperiodic response were evaluated for each trail: critical photoperiod. which was defined as the longest photoperiod that elicited a short-day response, and photoperiodic sensitivity, which was defined as the change in response per unit change in photoperiod. For each of the traits analyzed, the northern ecotype had a longer critical photoperiod and greater photoperiodic sensitivity than did the southern ecotype. The short critical photoperiod and reduced photoperiodic sensitivity of the southern ecotype resulted in a significant delay in bud set compared to that of the northern ecotype, even under a 9-h photoperiod. Typically, photoperiodic ecotypes have been characterized as having different critical photoperiods. Ecotypic differences in photoperiodic sensitivity, however, indicate that differences in the photoperiodic response curves cannot be completely described by the critical photoperiod alone. These results also suggest that the critical photoperiod. photoperiodic sensitivity and speed of bud set have a common physiological basis. Bud set occurred earlier hi the northern ecotype primarily because bud scale leaves were initiated earlier. For one of the northern genotypes, leaf primordia that were initialed under long days subsequently differentiated into bud scale leaves after the trees were transferred to a 9-h photoperiod. This demonstrates that primordia initiated under long days are not necessarily committed to becoming foliage leaves. The response to photoperiod did not differ appreciably between the greenhouse and growth chamber conditions that were tested.     

Hydroxyl Radical-Mediated Oxidation of Serotonin: Potential Insights into the Neurotoxicity of Methamphetamine

Abstract: When incubated with a hydroxyl radical (HO^?)-generating system (ascorbic acid/Fe²⁺-EDTA/O₂/H₂O₂), 5-hydroxytryptamine (5-HT; serotonin) is rapidly oxidized initially to a mixture of 2,5-, 4,5-, and 5,6-dihydroxytryptamine (DHT). The major reaction product is 2,5-DHT, which at physiological pH exists as its keto tautomer, 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). Rapid autoxidation of 4,5-DHT gives tryptamine-4,5-dione (T-4,5-D), which reacts with the C(3)-centered carbanion of 5-HEO to give 3,3′-bis(2-aminoethyl)-5-hydroxy-[3,7′-bi-1H-indole]-2,4′,5′-3H-trione (7). The latter slowly cyclizes to 3′-(2-aminoethyl)-1′,6′,7′,8′-tetrahydro-5-hydroxyspiro[3H-indole-3,9′-[9H]pyrrolo[2,3-f]quinoline]-2,4′,5′(1H)- trione (9). A minor amount of T-4,5-D dimerizes to give 7,7′-bi-(5-hydroxytryptamine-4-one) (7,7′-D). In the presence of GSH, the reaction of T-4,5-D with 5-HEO is diverted and, in the presence of sufficient concentrations of this tripeptide, completely blocked. This is because GSH preferentially reacts with T-4,5-D to give 7-S-glutathionyltryptamine-4,5-dione (11). The results of this investigation suggest that 5,6-DHT, 5-HEO, 7, and 9 are products unique to the HO^?-mediated oxidation of 5-HT. Thus, the observation of other investigators that 5,6-DHT is formed in the brains of rats following a large dose of methamphetamine (MA) suggests that this drug might evoke HO^? formation. However, the present in vitro study indicates that 5,6-DHT is a rather minor, unstable product of the HO^?-mediated oxidation of 5-HT and suggests that detection of 5-HEO, 7/9, and 11 in rat brain following MA administration could provide additional support for HO^? formation. Furthermore, one or more of the intermediates and major products of oxidation of 5-HT by HO^? might, in addition to 5,6-DHT, contribute to the MA-induced degeneration of serotonergic neurons.     

Goats and garbage in Khartoum,Sudan: A study of the urban ecology of animal keeping

Waste management in developing world urban areas is an acute problem which is linked to high growth rates and abatement methods less advanced than in the developed world. Existing neighborhood waste management practices often include the use of organic waste as a feed supplement for urban livestock (mainly goats, but also sheep and cattle). These urban animals bring economic benefits to less affluent residents, who would suffer an economic loss if their supply of urban waste was reduced or eliminated by an organized waste collection and disposal strategy. This paper employs a survey of 319 Greater Khartoum households to derive an estimate of waste intake per urban animal, and illustrate demographic factors (e.g., rural or urban roots, income, education, number of children) which influence animal keeping. A loglinear/logit model is developed to predict animal-keeping households. This model can be applied by waste management planners to estimate the frequency of urban animals in developing world urban areas.     

Homeobox genes in axolotl lateral line placodes and neuromasts

 Gene expression has been studied in considerable detail in the developing vertebrate brain, neural crest, and some placode-derived organs. As a further investigation of vertebrate head morphogenesis, expression patterns of several homeobox-containing genes were examined using whole-mount in situ hybridization in a sensory system primitive for the vertebrate subphylum: the axolotl lateral lines and the placodes from which they develop. Axolotl Msx-2 and Dlx-3 are expressed in all of the lateral line placodes. Both genes are expressed throughout development of the lateral line system and their expression continues in the fully developed neuromasts. Expression within support cells is highly polarized. In contrast to most other observations of Msx genes in vertebrate organogenesis, expression of Msx-2 in developing lateral line organs is exclusively epithelial and is not associated with epithelial-mesenchymal interactions. A Hox-complex gene, Hoxb-3, is shown to be expressed in the embryonic hindbrain and in a lateral line placode at the same rostrocaudal level, but not in other placodes nor in mature lateral line organs. A Hox gene of a separate paralog group, Hoxa-4, is expressed in a more posterior hindbrain domain in the embryo, but is not expressed in the lateral line placode at that rostrocaudal level. These data provide the first test of the hypothesis that the neurogenic placodes develop in two rostrocaudal series aligned with the rhombomeric segments and patterned by combinations of Hox genes in parallel with the central nervous system. Received: 2 April 1997 / Accepted: 2 July 1997     

Studies on the factors influencing larval settlement in Balanus amphitrite and Mytilus galloprovincialis

Understanding of factors influencing settlement(attachment and metamorphosis) of marine invertebratelarvae is of great importance in aquaculture andcontrol of biofouling. The influence of two factors onsettlement of larvae was assessed from two separateinvestigations: 1, the influence of age (endogenousfactor) on cyprids of the barnacle Balanusamphitrite; and 2, the influence of a microbial film(exogenous factor) on pediveligers of the mussel Mytilus galloprovincialis.The settlement response of cypris larvae of B.amphitrite was found to be age-dependent. Oldercyprids responded more readily to settlement factorsthan newly molted ones. In M.galloprovincialis, competent pediveligers settled inresponse to a microbial filmed surface but not toan unfilmed surface. Moreover, a factor with MW of lessthan 5000 dalton, derived from culture medium of abacterial strain C1.1 (Pseudomonas-Alteromonasgroup), induced the settlement of M. galloprovincialis larvae.Thus, marine invertebrate larvae may require a periodof competence acquisition, during which they arepoorly responsive to settlement inducers. Uponacquisition of competence, larvae readily respondto external cues (e.g. microbial film, bacterialextracellular products).     

5-Hydroxy-3-Ethylamino-2-Oxindole Is Not Formed in Rat Brain Following a Neurotoxic Dose of Methamphetamine: Evidence that Methamphetamine Does Not Induce the Hydroxyl Radical-Mediated Oxidation of Serotonin

Abstract: Oxygen radicals have been implicated in the neurodegenerative and other neurobiological effects evoked by methamphetamine (MA) in the brain. It has been reported that shortly after a single large subcutaneous dose of MA to the rat, the serotonergic neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) is formed in the cortex and hippocampus. This somewhat controversial finding suggests that MA potentiates formation of the hydroxyl radical (HO^?) that oxidizes 5-hydroxytryptamine (5-HT) to 5,6-DHT, which, in turn, mediates the degeneration of serotonergic terminals. A major and more stable product of the in vitro HO^?-mediated oxidation of 5-HT is 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). In this investigation, a method based on HPLC with electrochemical detection (HPLC-EC) has been developed that permits measurement of very low levels of 5-HEO in rat brain tissue in the presence of biogenic amine neurotransmitters/metabolites. After intracerebroventricular administration into rat brain, 5-HEO is transformed into a single major, but unknown, metabolite that can be detected by HPLC-EC. One hour after administration of MA (100 mg/kg s.c.) to the rat, massive decrements of 5-HT were observed in all regions of the brain examined (cortex, hippocampus, medulla and pons, midbrain, and striatum). However, 5-HEO, its unidentified metabolite, or 5,6-DHT were not detected as in vivo metabolites of 5-HT. MA administration, in particular to rats pretreated with pargyline, resulted in the formation of low levels of N-acetyl-5-hydroxytryptamine (NAc-5-HT) in all brain regions examined. These results suggest that MA does not potentiate the HO^?-mediated oxidation of 5-HT. Furthermore, the rapid MA-induced decrease of 5-HT might not only be related to oxidative deactivation of tryptophan hydroxylase, as demonstrated by other investigators, but also to the inhibition of tetrahydrobiopterin biosynthesis by NAc-5-HT. The massive decrements of 5-HT evoked by MA are accompanied by small or no corresponding increases in 5-hydroxyindole-3-acetic acid (5-HIAA) levels. This is due, in part, to the relatively rapid clearance of 5-HIAA from the brain and monoamine oxidase (MAO) inhibition by MA. However, the loss of 5-HT without corresponding increases in its metabolites point to other mechanisms that might deplete the neurotransmitter, such as oxidation by superoxide radical anion (O₂^??), a reaction that in vitro does not generate 5-HEO or 5,6-DHT but rather another putative neurotoxin, tryptamine-4,5-dione. One hour after administration, MA evokes large depletions of norepinephrine (NE) throughout the brain but somewhat smaller decrements of dopamine (DA) that are restricted to the nigrostriatal pathway. Furthermore, MA evokes a major shift in the metabolism of both NE and DA from the pathway mediated by MAO to that mediated by catechol-O-methyltransferase. The profound and widespread effects of MA on the noradrenergic system, but more anatomically localized influence on the dopaminergic system, suggests that NE in addition to DA, or unusual metabolites of these neurotransmitters, might play roles in the neurodegenerative effects evoked by this drug.     

Time- and order-dependent changes in functional and NO-mediated dilation during exercise training

Lash, Julia M., and H. Glenn Bohlen. Time- andorder-dependent changes in functional and NO-mediated dilation during exercise training. J. Appl. Physiol.82(2): 460-468, 1997.Arterial vessel responses to sodiumnitroprusside (SNP) and acetylcholine (ACh) were measured in thespinotrapezius muscle of sedentary (Sed) and treadmill-trained (Tr)rats to determine whether these endothelium-dependent (ACh) and-independent (SNP) mechanisms contribute to thetraining-induced increase in functional vasodilation previouslyobserved. Control and maximal vessel diameters were similar between Sedand Tr. After 8 wk of training, functional dilation (2-, 4-, and 8-Hzcontractions) was enhanced in all orders of vessels studied[terminal feed artery (FA), largest arterioles (1A), andintermediate-sized arterioles (2A)], but responses to SNP wereincreased only in FA. Responses to ACh were not significantly increasedin any vessel order. After 16 wk of training, functional dilation hadregressed in Tr such that only the FA response to 4 Hz wassignificantly elevated relative to Sed. However, the FA and 1Aresponses to SNP were significantly greater in Tr than in Sed, as werethe 1A and 2A responses to ACh. These results show a dissociation offunctional dilation and SNP- or ACh-mediated responses, as well asage-dependent interactions, a time-dependent progression, and vesselorder specificity in the adaptations to training.

     

Paleopediatrics: Or when did human infants really become human?

Modern human children take about twice as long as their closest biological relative, the chimpanzee, to mature. One standard explanation for the evolution of “delayed maturation” at an early stage of human evolution is that it provided the time necessary for immature individuals to learn complex skills, most notably those relating to tool-making abilities. However, after comparing dental maturational profiles of early hominids from South Africa (who apparently did make and use stone tools) (Susman [1994] Science 265:1570–1573) to those of extant humans and chimpanzees, we find no evidence to document an association between “delayed maturation” and tool-making abilities in the early stages of human evolution. This also suggests that the assumed association between prolonged childhood dependency and other behaviors often associated with the advent of tool-making such as cooperative hunting, food sharing, home bases, sexual division of labor, etc., is also suspect. Instead, we must look for other, or additional, selective pressures for the evolution of “delayed maturation,” which may postdate the australopithecine radiation. © 1995 Wiley-Liss, Inc.