Leader cells mechanically respond to aligned collagen architecture to direct collective migration

Leader cells direct collective migration through sensing cues in their microenvironment to determine migration direction. The mechanism by which leader cells sense the mechanical cue of organized matrix architecture culminating in a mechanical response is not well defined. In this study, we investigated the effect of organized collagen matrix fibers on leader cell mechanics and demonstrate that leader cells protrude along aligned fibers resulting in an elongated phenotype of the entire cluster. Further, leader cells show increased mechanical interactions with their nearby matrix compared to follower cells, as evidenced by increased traction forces, increased and larger focal adhesions, and increased expression of integrin-α2. Together our results demonstrate changes in mechanical matrix cues drives changes in leader cell mechanoresponse that is required for directional collective migration. Our findings provide new insights into two fundamental components of carcinogenesis, namely invasion and metastasis.

Increased orbitofrontal cortex levels of choline in depressed adolescents as detected by in vivo proton magnetic resonance spectroscopy

BACKGROUND

The frontal lobe has been implicated in the pathology of depression in adults. Through the use of magnetic resonance spectroscopy, altered brain choline levels have also been linked to the pathophysiology of affective disorders.

METHODS

To identify possible alterations in orbitofrontal cortex levels of cytosolic choline in adolescents with and without depression, 22 depressed and 43 control adolescents were recruited. Of those recruited, usable proton magnetic resonance spectra were acquired from a voxel in the left anterior medial frontal lobe of 17 depressed (mean age 15.8+/-1.6) and 28 healthy adolescents (mean age 14.5+/-1.7).

RESULTS

Orbitofrontal cytosolic choline/creatine (Cho/Cr) ratios (p =.032) and cytosolic choline/N-acetyl aspartate (Cho/NAA) ratios (p =.043) were significantly higher in the depressed subjects than in the control subjects. There were no significant differences between depressed and control subjects in gray or white matter content within the voxel.

CONCLUSIONS

These findings suggest that brain cytosolic choline may be increased in depressed adolescents in comparison with control subjects and independent of a corresponding structural change. These results are consistent with similar, previously reported findings in adults and suggest that depression in adolescents is associated with alterations in orbitofrontal metabolism.

fMRI during affect discrimination in bipolar affective disorder

OBJECTIVE

It has been hypothesized that disturbances in affect may represent distinct etiologic factors for bipolar affective disorder. The neural mechanisms mediating affective processes and their relationship to brain development and the pathophysiology of bipolar affective disorder remain to be clarified. Recent advances in neuroimaging techniques have made possible the non-invasive examination of specific brain regions during cortical challenge paradigms. This study reports findings based on fMRI data acquired during fearful and happy affect recognition paradigms in patients with bipolar affective disorder and in healthy adult subjects.

METHODS

Prior to the scan, subjects were instructed to view the stimuli and to identify the type of facial expression presented. Echo planar scanning was performed on a 1.5 Tesla scanner which had been retrofitted with a whole body echo planar coil, using a head coil.

RESULTS

The data indicate that in adult subjects with bipolar affective disorder, there is a reduction in dorsolateral prefrontal cortex activation and an increase in amygdalar activation in response to fearful facial affect. In a healthy comparison group, signal intensity changes were not found in these regions. In addition, although the patients with bipolar affective disorder completed the task demands, they demonstrated an impaired ability to correctly identify fearful facial affect but not the happy facial affect displayed.

CONCLUSION

These findings are consistent with the hypothesis that in some patients with bipolar affective disorder, there may be a reduction of frontal cortical function which may be associated with affective as well as attentional processing deficits.

Adipyl crosslinked bovine hemoglobins as new models of allosteric systems

As indicated by peptide analyses and mass spectrometry estimations, intramolecular crosslink with bis(3,5-dibromosalicyl)adipate of bovine hemoglobin results in the formation of two main components covalently bridged across the beta-cleft. In one component the crosslink joins the beta(1)V1-beta(2)K81 residues (XL-Peak-1), in the other the bridge is between the beta(1)K81-beta(2)K81 residues (XL-Peak-2). Both components are tetrameric with a mass near MW = 67 kDa as estimated by gel filtration, and a hydrodynamic radius near 3. 20 nm, estimated by dynamic light scattering. They have very low oxygen affinity with Pm near 100 mmHg (XL-Peak-1) and near 70 mmHg (XL-Peak-2) respectively at 37 degrees C, at neutral pH. The Bohr effect is almost absent in XL-Peak-1, while in XL-Peak-2 it is very near normal. Both systems show oxygen binding cooperativity with an index near n = 2.0. Flash photolysis kinetics of the recombination with CO could be resolved into a fast and a slow component. The amplitude of the fast rates were not concentration-dependent. The stopped-flow kinetics were autoaccelerating, consistent with their ligand-binding cooperativity. All rates were very similar to those of normal hemoglobin, suggesting that the oxy- rather than the deoxy-forms of the systems were affected by the crosslink. Proteins 2000;39:166-169.

Large-scale double-staining of rat fetal skeletons using Alizarin Red S and alcian blue

A critical component in the conduct of a prenatal developmental toxicity study is the evaluation of fetal skeletal development. As the developing rodent fetus is typically evaluated at gestation day 20, at a time when ossification of the skeleton is incomplete, a thorough assessment of skeletal development would include both ossified and cartilaginous structures. Current methods to double-stain the fetal skeleton using Alizarin Red S and Alcian Blue are typically described for small sample sizes or using time allotments for each processing step that are unsuitable for industry. In an industrial setting, there is a need for an effective means to double-stain fetal skeletons on a large scale (i.e., hundreds of fetuses simultaneously). This article describes a method used in our laboratory to stain both fetal bone and cartilage using solutions and procedures on an industrial scale.

Conduct and interpretation of a dermal developmental toxicity study with KBR 3023 (a prospective insect repellent) in the Sprague-Dawley rat and Himalayan rabbit

KBR 3023, 1-(1-methyl-propoxycarbonyl)-2-(2-hydroxyethyl)piperidine, a prospective insect repellent being developed by Bayer Corporation, was evaluated for developmental toxicity in the Sprague-Dawley rat and Himalayan rabbit. As the intended human usage of the test compound is topical, the test systems were exposed to the compound via the dermal route. Specifically, the animals were fitted with Elizabethan collars, to reduce the likelihood of oral ingestion, and dermally administered either 0, 50, 200, or 400 mg KBR 3023/kg (rat), and 0, 50, 100, or 200 mg KBR 3023/kg (rabbit) on gestation days 0-19 (rat) and 0-28 (rabbit). Maternal toxicity, as demonstrated by clinical signs and changes in body weight gain and food consumption during gestation, was characterized. Animals were sacrificed on gestation day 20 (rat) and 29 (rabbit), at which time fetuses were removed by cesarean section and a gross maternal necropsy was performed. All fetuses were evaluated for external anomalies. With rats, approximately half of each litter was examined for visceral effects; the other half underwent a skeletal examination. With rabbits, all fetuses underwent both visceral and skeletal examinations. No effects were observed on maternal body weight gain or food consumption in either the rat or rabbit. In the rat, dermal effects (scaling/sloughing), were observed at the dose site of all test substance-treated groups from approximately gestation day 7 until termination of the study. Also noted were an increase in both absolute and relative liver weights in rats in the 400-mg/kg dose group. In the rabbit, dermal effects (slight erythema, squamous and cracked skin) were noted at the dose site of virtually all does administered the test compound, from approximately gestation day 7 until termination. Also observed in the rabbits was a potentially compound-related increase in soft stool, particularly at the highest dose level. In both species, there were no statistically significant effects on any reproductive parameters, or any embryonic endpoints, including pre/post-implantation loss and resorptions. There were no statistically significant effects on litter size or fetal or placental weights. No test compound-related external, visceral, or skeletal findings were observed. No effect on the individual fetal or litter incidence of total malformations or variations was observed and there was no difference in the incidence of malformations between males and females. KBR 3023 Technical, administered as described in these studies, produced maternal effects in the rat (liver weight) at a dose of 400 mg/kg, and in the rabbit (soft stool) in the 200-mg/kg dose group. No developmental toxicity was observed at any dose level.

The conduct of a two-generation reproductive toxicity study via dermal exposure in the Sprague-Dawley rat--a case study with KBR 3023 (a prospective insect repellent)

KBR 3023, 1-(1-methyl-propoxycarbonyl)-2-(2-hydroxyethyl)-piperidine, a prospective insect repellent being developed by the Bayer Corporation, was evaluated for reproductive toxicity in the Sprague-Dawley rat. As the intended human use of the test compound is topical, the test system was also exposed to the compound via the dermal route. Specifically, the adult rats (P generation) were fitted with Elizabethan collars, to reduce the likelihood of oral ingestion, and dermally administered either 0, 50, 100, or 200 mg KBR 3023/kg body weight throughout the study (5 d/week) beginning at the onset of the 10-week premating period and continuing through the mating, gestation, and lactation phases. Clinical signs and changes in body weight and food consumption were assessed throughout the study. All adults and neonates underwent a gross necropsy examination. Tissues retained for microscopic examination from all adult animals included the kidney, liver, pituitary, reproductive organs, and samples of skin from the shaved dose site. In addition to the parameters noted above, the animals were evaluated for the effect of the test compound on estrous cycling, mating, fertility, gestation length, litter size, pup sex ratio, and pup viability. There were no test compound-related clinical signs or effects on body weight or food consumption observed in either the adults or the pups during any phase of the study. There were no compound-related effects on any reproductive or litter parameters. Dermal findings at the dose site (acanthosis and hyperkeratosis) were noted in both generations. Other than the dermal findings, no compound-related necropsy findings were seen in either the adults or the pups. No compound-related histopathologic findings were noted in the reproductive tissues of either the males or females. Based on these results, KBR 3023, administered as described in this study at dose levels as high as 200 mg/kg body weight (the physical limit of dermal application for this compound), did not demonstrate any reproductive toxicity.

The relationship between maternal and fetal effects following maternal organophosphate exposure during gestation in the rat

Organophosphates, a widely used class of insecticidal compounds, have been shown to cross the placental barrier, and thus potentially affect the developing fetus. This study compared the maternal and fetal effects, including cholinesterase inhibition, following gestational exposure to six organophosphates: tribufos, oxydemeton-methyl, azinphos-methyl, fenamiphos, isofenphos, and fenthion in the Sprague-Dawley rat. All test compounds were administered via oral gavage on gestation days 6-15. Maternal cholinesterase activities (plasma, PChe; erythrocyte, RChe; and brain, BChe) were measured on gestation days 16 and 20, and fetal brain cholinesterase activity was measured on gestation day 20. Effects on gestational parameters (clinical signs, food consumption, and body weight) in adult rats, when observed, were only observed at the highest dose tested for each compound. The inhibition of maternal cholinesterase activities associated with these clinical findings was, for all compounds, always greater than 20%. Moreover, cholinesterase activities were inhibited at dose levels below that which elicited clinical effects. Statistically significant inhibition of at least two of the three cholinesterase enzymes (PChe, RChe, or BChe) was observed on gestation day 16, 24 h following exposure, with all of the organophosphates tested. By gestation day 20, the inhibition of cholinesterase activity was reduced; however, the high dose for all test compounds (except BChe in fenamiphos-treated dams) continued to demonstrate statistically significant inhibition of RChe and BChe. Despite significantly affected cholinesterase activity in the dams, no remarkable effects on fetal BChe were observed with any test compound. No embryotoxicity or teratogenicity were observed with any of the test compounds. These results demonstrate that for the six organophosphates tested: (1) inhibition of maternal cholinesterase activity was the most sensitive indicator of organophosphate exposure; (2) the level of cholinesterase inhibition associated with clinical findings was always greater than 20%; and (3) no effect on fetal cholinesterase activity (BChe) was observed, even at dose levels that continued to demonstrate significant inhibition of maternal cholinesterase activity.

Erythropoiesis in peripheral blood of tuatara (Sphenodon punctatus) and turtle (Malaclemys terrapin)

Erythropoiesis in peripheral blood of domestic birds was shown earlier to arise directly from the nucleus of mature erythrocytes as nuclear protuberations that later broke free. Three to seven percent of new red cells originated in this way from clone cells.Investigations of peripheral blood in reptiles has further demonstrated formation of nucleated red cells as clones from nuclear buds of mature erythrocytes. Clone cells plus new immature red cells constitute, in Sphenodon punctatus, 8–18% and, in turtle, Malaclemys terrapin, 18–25% of the total cell population. Some lymphocytes and granulocytes appear also to arise from nuclear buds. Thrombocytes were present in some animals, absent in others, but were not counted in the present work.

Erythropoiesis in peripheral blood of seven species of New Zealand and one species of Canadian birds

The development of clone cells as protuberations from nuclei of mature erythrocytes in peripheral blood has been described for seven native New Zealand birds. The percentage of new cells ranged from 38.95 in the kiwi to 11.35 in the yellow-eyed penguin. Blood from a native Canadian bird, the white-throated sparrow, had 29.75% and 25.00% new cells. These results support earlier work.