Notochordal cells interact with nucleus pulposus cells: regulation of proteoglycan synthesis

The disappearance of notochordal cells is correlated with early degenerative changes in the intervertebral disc. With increased disc degeneration there is a marked decrease in proteoglycan synthesis, resulting in loss of mechanical function. One possible mechanism for the decrease in proteoglycan synthesis is the loss of notochordal cells from the tissue. In this study, nucleus pulposus cells cocultured with notochordal cells exhibit an increase in proteoglycan synthesis. Interestingly, purified notochordal cells synthesize little proteoglycan as observed by [35S]sulfate incorporation into proteoglycans. The observed increase in proteoglycan synthesis does not appear to be dependent on cell-cell contact; rather it is the result of soluble factor(s) produced by notochordal cells. Finally, no difference in chondroitin sulfate chain size in notochordal-stimulated nucleus pulposus cells was observed which is consistent with an up-regulation in aggrecan core protein synthesis. These results are consistent with canine breeds where notochordal cells persist into adult age and disc degeneration is not observed. This suggests notochordal cells play a vital role in maintaining disc integrity.

Effects of 14 d of covert substitution of olestra for conventional fat on spontaneous food intake

We conducted a double-blind, placebo-controlled, within-subject crossover study to investigate the effects of covert substitution of olestra, a non-energy-containing fat replacer, for conventional fat on food selection and energy intake in lean and obese men and women. Fifty-one subjects [BMI (kg/m2): 19-36; age: 25-63 y] were studied during two 14-d treatment periods (olestra and placebo), with a 7-d washout between feeding periods. During the intervention periods all foods were provided to the subjects. The aim was to produce a 10% dilution of total energy intake by replacing conventional triacylglycerol with olestra. To accomplish this, subjects were required to consume core foods providing 20-35 g olestra (depending on estimated energy needs) or the same foods containing placebo triacylglycerol. Additional items could be selected from foods that varied in macronutrient composition. When the two treatment periods were compared, total energy intake was 8% lower and fat intake 11% lower during the olestra period than during the placebo treatment period (P < 0.0001). Overall, subjects compensated for 15% of the fat and 20% of the total energy replaced by olestra. In absolute terms, subjects consumed 32% of total energy from fat during the placebo period and 27% of total energy from fat during the olestra period. Neither carbohydrate nor protein intake (g/d) differed between periods. The results did not differ as a function of BMI (lean compared with obese) or sex. Over a 2-wk period, covert substitution of olestra for conventional fat led to reductions in dietary fat intake and total energy intake in all subjects.

Vertebrate genome evolution and the zebrafish gene map

In chordate phylogeny, changes in the nervous system, jaws, and appendages transformed meek filter feeders into fearsome predators. Gene duplication is thought to promote such innovation. Vertebrate ancestors probably had single copies of genes now found in multiple copies in vertebrates and gene maps suggest that this occurred by polyploidization. It has been suggested that one genome duplication event occurred before, and one after the divergence of ray-finned and lobe-finned fishes. Holland et al., however, have argued that because various vertebrates have several HOX clusters, two rounds of duplication occurred before the origin of jawed fishes. Such gene-number data, however, do not distinguish between tandem duplications and polyploidization events, nor whether independent duplications occurred in different lineages. To investigate these matters, we mapped 144 zebrafish genes and compared the resulting map with mammalian maps. Comparison revealed large conserved chromosome segments. Because duplicated chromosome segments in zebrafish often correspond with specific chromosome segments in mammals, it is likely that two polyploidization events occurred prior to the divergence of fish and mammal lineages. This zebrafish gene map will facilitate molecular identification of mutated zebrafish genes, which can suggest functions for human genes known only by sequence.

Negative life events and time to recovery from episodes of bipolar disorder

The authors of the current study examined the impact of severe negative life events on time to recovery from episodes of bipolar disorder. Although negative life events have been shown to influence relapse in bipolar disorder, research has not focused on life events and recovery in bipolar disorder. The authors recruited 67 individuals with bipolar disorder during hospitalization and conducted monthly assessments for at least 1 year. Individuals with severe negative life events took more than 3 times as long to achieve recovery as those without severe life events, and the impact of life events was not mediated by medication compliance. These results reveal that the psychosocial environment may play a much larger role in the course of bipolar disorder than previous biological models have suggested.

Negative life events and time to recovery from episodes of bipolar disorder

The authors of the current study examined the impact of severe negative life events on time to recovery from episodes of bipolar disorder. Although negative life events have been shown to influence relapse in bipolar disorder, research has not focused on life events and recovery in bipolar disorder. The authors recruited 67 individuals with bipolar disorder during hospitalization and conducted monthly assessments for at least 1 year. Individuals with severe negative life events took more than 3 times as long to achieve recovery as those without severe life events, and the impact of life events was not mediated by medication compliance. These results reveal that the psychosocial environment may play a much larger role in the course of bipolar disorder than previous biological models have suggested.

Putting the behavior into the behavior genetics of obesity

Tremendous advances in the genetic underpinnings of obesity have emerged in recent years. Curiously, behavioral genetic methods have provided relatively less information on the environmental influences and intermediary behaviors which promote human obesity. This situation in unfortunate since human obesity is, in part, environmentally determined and the result of behaviors such as eating and physical (in)activity. This article has several goals. First, it outlines reasons why behavior qua behavior should be a specific focus of obesity-oriented behavioral genetic designs. Second, possible explanations for why behavior has been underinvestigated are explored. Third, data regarding the genetic/ environmental architecture of various obesity-related phenotypes (e.g., food intake, physical activity, etc.) are reviewed. Fourth, a commentary on the importance of gene-environment interactions is offered. Finally, suggestions for future research, including a list of possible "candidate environments" and "candidate intermediary behaviors," are offered.

Marital interactions of depressed men and women

This article examined marital interactions in 50 couples with a depressed husband, 41 couples with a depressed wife, and 50 nondepressed control couples. As expected, couples with a depressed partner evidenced more disturbed marital interaction than control couples. Furthermore, couples with a depressed wife demonstrated less positive communication than couples with a depressed husband, notwithstanding the fact the depressed husbands exhibited greater depression severity than depressed wives. Findings are integrated with recent research on gender differences in affective expression.

Marital interactions of depressed men and women

This article examined marital interactions in 50 couples with a depressed husband, 41 couples with a depressed wife, and 50 nondepressed control couples. As expected, couples with a depressed partner evidenced more disturbed marital interaction than control couples. Furthermore, couples with a depressed wife demonstrated less positive communication than couples with a depressed husband, notwithstanding the fact the depressed husbands exhibited greater depression severity than depressed wives. Findings are integrated with recent research on gender differences in affective expression.

Mapping of mhc class I and class II regions to different linkage groups in the zebrafish, Danio rerio

The mammalian major histocompatibility complex (Mhc) consists of three closely linked regions, I, II, and III, occupying a single chromosomal segment. The class I loci in region I and the class II loci in region II are related in their structure, function, and evolution. Region III, which is intercalated between regions I and II, contains loci unrelated to the class I and II loci, and to one another. There are indications that a similar Mhc organization exists in birds and amphibians. Here, we demonstrate that in the zebrafish (Danio rerio), a representative of the teleost fishes, the class II loci are divided between two linkage groups which are distinct from the linkage group containing the class I loci. The beta2-microglobulin-encoding gene is loosely linked to one of the class II loci. The gene coding for complement factor B, which is one of the region III genes in mammals, is linked neither to the class I nor to the class II loci in the zebrafish. These results, combined with preliminary data suggesting that the class I and class II regions in another order of teleost fish are also in different linkage groups, indicate that close linkage of the two regions is not necessary either for regulation of expression or for co-evolution of the class I and class II loci. They also raise the question of whether linkage of the class I and class II loci in tetrapods is a primitive or derived character.

Cdc53p acts in concert with Cdc4p and Cdc34p to control the G1-to-S-phase transition and identifies a conserved family of proteins

Regulation of cell cycle progression occurs in part through the targeted degradation of both activating and inhibitory subunits of the cyclin-dependent kinases. During G1, CDC4, encoding a WD-40 repeat protein, and CDC34, encoding a ubiquitin-conjugating enzyme, are involved in the destruction of these regulators. Here we describe evidence indicating that CDC53 also is involved in this process. Mutations in CDC53 cause a phenotype indistinguishable from those of cdc4 and cdc34 mutations, numerous genetic interactions are seen between these genes, and the encoded proteins are found physically associated in vivo. Cdc53p defines a large family of proteins found in yeasts, nematodes, and humans whose molecular functions are uncharacterized. These results suggest a role for this family of proteins in regulating cell cycle proliferation through protein degradation.

Contractile activity of the uterus prior to labor alters the temporal organization of spontaneous motor activity in the fetal sheep

Contractile activity of the uterus before the onset of labor (uterine contractures) has been described in a number of species and provides a powerful source of repeated stimulation for the fetus throughout much of gestation. To understand how fetal behavior responds to this dynamic aspect of the intrauterine environment, we investigated the effects of uterine contractures on the temporal organization of spontaneous motor activity in the fetal sheep during the last fifth of gestation. Eleven fetuses were instrumented on 113-116 days of gestation (dGA). Electromyogram (EMG) activity was recorded from flexor and extensor muscles in the fetal forelimbs and hindlimbs, and from the uterus. Pooled limb EMG activity from 2300 hr to 0700 hr on 118, 125, 132, and 139 dGA before, during, and after uterine contractures was spectral analyzed to detect and quantify the cyclic organization in fetal motor activity. There was strong evidence of cyclic organization in fetal motor activity (CM) at each gestational age, similar to what has been described in the fetal rat and human. There was no evidence of developmental changes in the baseline spectral measures of CM. The most prominent feature of the response of CM to uterine contractures was a transient decrease in irregularity at 118-132 dGA. The strength of CM increased during contractures at 125 and 132 dGA, and a slight acceleration of CM during contractures was detected at 118 and 139 dGA. The results demonstrate that the stimulation associated with contractures influences an important source of complexity in early behavioral organization. The results are consistent with speculation by others that uterine contractures might induce transient cerebral hypoxemia in the fetus, and suggest that conditions established in the first few minutes of sustained uterine activity constitute the effective perturbation of CM.

Centromere-linkage analysis and consolidation of the zebrafish genetic map

The ease of isolating mutations in zebrafish will contribute to an understanding of a variety of processes common to all vertebrates. To facilitate genetic analysis of such mutations, we have identified DNA polymorphisms closely linked to each of the 25 centromeres of zebrafish, placed centromeres on the linkage map, increased the number of mapped PCR-based markers to 652, and consolidated the number of linkage groups to the number of chromosomes. This work makes possible centromere-linkage analysis, a novel, rapid method to assign mutations to a specific linkage group using half-tetrads.

Temperature-sensitive mutations that cause stage-specific defects in Zebrafish fin regeneration

When amputated, the fins of adult zebrafish rapidly regenerate the missing tissue. Fin regeneration proceeds through several stages, including wound healing, establishment of the wound epithelium, recruitment of the blastema from mesenchymal cells underlying the wound epithelium, and differentiation and outgrowth of the regenerate. We screened for temperature-sensitive mutations that affect the regeneration of the fin. Seven mutations were identified, including five that fail to regenerate their fins, one that causes slow growth during regeneration, and one that causes dysmorphic bumps or tumors to develop in the regenerating fin. reg5 mutants fail to regenerate their caudal fins, whereas reg6 mutants develop dysmorphic bumps in their regenerates at the restrictive temperature. Temperature-shift experiments indicate that reg5 and reg6 affect different stages of regeneration. The critical period for reg5 occurs during the early stages of regeneration before or during establishment of the blastema, resulting in defects in subsequent growth of the blastema and failure to differentiate bone-forming cells. The critical period for reg6 occurs after the onset of bone differentiation and during early stages of regenerative outgrowth. Both reg5 and reg6 also show temperature-sensitive defects in embryonic development or in ontogenetic outgrowth of the juvenile fin.

Microsatellite-centromere mapping in the zebrafish (Danio rerio)

Ten (CA)n microsatellite simple sequence repeat (SSR) markers, 1, 2, 12, 14, 16, 18, 20, 22, 26, and 29, were used to show high chiasma interference and to determine centromere-marker map distances in the zebrafish (Danio rerio). Of these, SSR 12 exhibited no recombinant tetratypes among 175 half-tetrad embryos, placing this marker within 1 cM of the centromere of Linkage Group XVII. Fractions of heterozygous half-tetrads for the remaining nine markers ranged from 0.64 to 0.89. Of these, six recombinant fractions were more than 0.67 (P < 0.05), indicating strong chiasma interference during female meiosis in the zebrafish. Consistent with previous mapping data, SSRs 2 and 20 of Linkage Group VI were tightly linked. Half-tetrad analysis will allow the mapping of the remaining centromeres and may be useful in the mapping of new genes and mutations in the zebrafish.

Physical activity and energy requirements

Differences in physical activity represent the largest source of variability in energy requirements, both within and between individuals. Chronic changes in physical activity can produce chronic changes in energy requirements that, if not compensated for, can lead to changes in the level at which body weight and body composition are maintained over time. We present a model that can serve as a framework for understanding how energy and macronutrient balance are maintained in steady state conditions, and for illustrating the potential effect of a change in physical activity on these steady state conditions and on energy requirements. According to the model, a chronic change in physical activity forces changes in other aspects of energy and substrate utilization so that a steady state condition can be reestablished. The net effects of the change in physical activity on energy requirements will depend on how and over what period of time these new steady states are reached. Although we cannot at present predict, for any individual, the precise effect of changes in physical activity on energy requirements and on body weight and composition, our model provides a framework for further study of the factors that can influence energy requirements.

Effects of reduced exposure on computed radiography: comparison of nodule detection accuracy with conventional and asymmetric screen-film radiographs of a chest phantom

OBJECTIVE

Radiographic exposure has been thought to have little impact on the diagnostic quality of chest computed radiography because of automatic digital control of global optical density. The objectives of this study were to compare images obtained with two different exposures in computed radiography with conventional and asymmetric screen-film images of the chest for the detection of simulated lung nodules by use of receiver operating characteristic analysis and to relate differences in observer performance to parameters of image noise measured for each receptor condition.

MATERIALS AND METHODS

At 110 kVp (fixed), exposures for the two screen-film systems were those necessary to achieve adequate optical densities over the lung and mediastinal regions of an anthropomorphic phantom. The two exposures used for the computed radiographs corresponded to the exposure used for the conventional chest screen-film system and an exposure 22% lower. An anthropomorphic phantom constructed of materials matched to the muscle, lung, and bone attenuation of a muscular adult man was used. Soft-tissue-equivalent plastic nodules of various sizes were secured at multiple sites on the phantom to simulate lung nodules. The chest phantom was imaged in 50 configurations with a total of 70 superimposed nodules. The perceptual performances of five radiologists were compared by use of receiver operating characteristic analysis. The signal-to-noise ratio in the mediastinum and the coefficient of variation of noise were measured for all four image conditions by use of a step wedge technique to provide an explanation for differences in diagnostic accuracy.

RESULTS

We found no significant differences in the detection of lung nodules between the two screen-film systems or between the conventional screen-film images and the standard-exposure computed radiographs. However, there was a significant decrease in nodule detection on computed radiographs obtained at a reduced exposure; this result was associated with a 21% decrease in the signal-to-noise ratio.

CONCLUSION

Our results show that underexposure of computed radiographs decreases the detection of low-contrast objects such as lung nodules. Although consistent global optical density on computed radiographs is achieved over a wide range of exposures, the alterations in signal-to-noise ratio that result from underexposure can reduce the diagnostic quality of computed radiographs.

Life events and bipolar disorder: implications from biological theories

Although a number of studies suggest that stressful life events play a role in bipolar disorder, methodological flaws impose serious limitations on this literature. Nonetheless, better designed studies indicate that life events influence the course of bipolar disorder. Little is known, however, about the nature of events that are of particular importance to this disorder. Given the strong biological vulnerability and the unique clinical aspects of bipolar disorder, certain forms of stress may have stronger interactions with vulnerability characteristics. Three major biological theories of bipolar disorder are discussed, with particular attention to their implications for investigations of life events. Although tenuous, these models suggest that greater attention needs to be paid to particular dimensions of life events and the course of disorder.

Half-tetrad analysis in zebrafish: mapping the ros mutation and the centromere of linkage group I

Analysis of meiotic tetrads is routinely used to determine genetic linkage in various fungi. Here we apply tetrad analysis to the study of genetic linkage in a vertebrate. The half-tetrad genotypes of gynogenetic diploid zebrafish produced by early-pressure (EP) treatment were used to investigate the linkage relationships of two recessive pigment pattern mutations, leopard (leo) and rose (ros). The results showed that ros is tightly linked to its centromere and leo maps 31 cM from its centromere. Analysis of half-tetrads segregating for ros and leo in repulsion revealed no homozygous ros individuals among 32 homozygous leo half-tetrads--i.e., a parental ditype (PD) to nonparental ditype (NPD) ratio of 32:0. This result shows that ros is linked to leo, a mutation previously mapped to Linkage Group I. Investigation of PCR-based DNA polymorphisms on Linkage Group I confirmed the location of ros near the centromere of this linkage group. We propose an efficient, generally useful method to assign new mutations to a linkage group in zebrafish by determining which of 25 polymerase chain reaction (PCR)-based centromere markers shows a significant excess of PD to NPD in half-tetrad fish.

Differential induction of four msx homeobox genes during fin development and regeneration in zebrafish

To study the genetic regulation of growth control and pattern formation during fin development and regeneration, we have analysed the expression of four homeobox genes, msxA, msxB, msxC and msxD in zebrafish fins. The median fin fold, which gives rise to the unpaired fins, expresses these four msx genes during development. Transcripts of the genes are also present in cells of the presumptive pectoral fin buds. The most distal cells, the apical ectodermal ridge of the paired fins and the cleft and flanking cells of the median fin fold express all these msx genes with the exception of msxC. Mesenchymal cells underlying the most distal cells express all four genes. Expression of the msx genes in the fin fold and fin buds is transient and, by 3 days after fertilization, msx expression in the median fin fold falls below levels detectable by in situ hybridization. Although the fins of adult zebrafish normally have levels of msx transcripts undetectable by in situ hybridization, expression of all four genes is strongly reinduced during regeneration of both paired and unpaired fins. Induction of msx gene expression in regenerating caudal fins occurs as early as 30 hours postamputation. As the blastema forms, the levels of expression increase and reach a maximum between the third and fifth days. Then, msx expression progressively declines and disappears by day 12 when the caudal fin has grown back to its normal size. In the regenerating fin, the blastema cells that develop at the tip of each fin ray express msxB and msxC. Cells of the overlying epithelium express msxA and msxD, but do not express msxB or msxC. Amputations at various levels along the proximodistal axis of the fin suggest that msxB expression depends upon the position of the blastema, with cells of the rapidly proliferating proximal blastema expressing higher levels than the cells of the less rapidly proliferating distal blastema. Expression of msxC and msxD is independent of the position of the blastema cell along this axis. Our results suggest distinct roles for each of the four msx genes during fin development and regeneration and differential regulation of their expression.

Genetic control of adult pigment stripe development in zebrafish

Adult zebrafish stripes are formed from stripes of gold iridophores alternating with stripes of black melanocytes lying beneath silver stripes. Analysis of defects in pigment pattern development caused by sparse (spa, rose (ros), and leopard (leo) single and double mutant combinations suggests that spa+ and ros+ functions are required for development of separate populations of pigment cells in the adult and that leo+ functions to control assembly of melanocytes into stripes. Thus, between 2 and 3 weeks of zebrafish development, spa-dependent melanocytes differentiate throughout the flank, followed by leo-dependent assembly of these cells into stripes. Beginning at 3 weeks of development, a distinct ros-dependent population of melanocytes differentiates in the stripe. Both early and late differentiating melanocytes then affect the formation of the silver stripes, ensuring registration of melanocyte and iridophore stripes.

Clinical characteristics associated with interpersonal depression: symptoms, course and treatment response

A range of theories, including environmental, personality and cognitive theories, have suggested that loss may be a particularly critical form of stress in the etiology and expression of depression. The current study examines whether interpersonal depression predicted a unique clinical presentation and course in subjects with major depression. Subjects who became depressed following a severe interpersonal event were contrasted with two control groups: patients without antecedent stressors and patients with major non-interpersonal stressors. The hypothesized interpersonal subgroup was differentiated from the control groups only in the speed of treatment response. Proposals for future research are discussed.

A genetic linkage map for the zebrafish

To facilitate molecular genetic analysis of vertebrate development, haploid genetics was used to construct a recombination map for the zebrafish Danio (Brachydanio) rerio. The map consists of 401 random amplified polymorphic DNAs (RAPDs) and 13 simple sequence repeats spaced at an average interval of 5.8 centimorgans. Strategies that exploit the advantages of haploid genetics and RAPD markers were developed that quickly mapped lethal and visible mutations and that placed cloned genes on the map. This map is useful for the position-based cloning of mutant genes, the characterization of chromosome rearrangements, and the investigation of evolution in vertebrate genomes.

Identification of RAPD primers that reveal extensive polymorphisms between laboratory strains of zebrafish

The zebrafish has recently emerged as a useful system for understanding vertebrate developmental genetics, despite the lack of a linkage map. To identify DNA-based genetic polymorphisms for constructing a genetic map, we have screened a collection of RAPD primers for their utility in identifying genetic polymorphisms between two laboratory strains of zebrafish. Here, we report 116 primers that identify 721 strain-specific genetic markers and show how they can be used in haploid genetics of zebrafish.