The cytoskeletal motor proteins Dynein and MyoV direct apical transport of Crumbs

Crumbs (Crb in Drosophila; CRB1-3 in mammals) is a transmembrane determinant of epithelial cell polarity and a regulator of Hippo signalling. Crb is normally localized to apical cell-cell contacts, just above adherens junctions, but how apical trafficking of Crb is regulated in epithelial cells remains unclear. We use the Drosophila follicular epithelium to demonstrate that polarized trafficking of Crb is mediated by transport along microtubules by the motor protein Dynein and along actin filaments by the motor protein Myosin-V (MyoV). Blocking transport of Crb-containing vesicles by Dynein or MyoV leads to accumulation of Crb within Rab11 endosomes, rather than apical delivery. The final steps of Crb delivery and stabilisation at the plasma membrane requires the exocyst complex and three apical FERM domain proteins - Merlin, Moesin and Expanded - whose simultaneous loss disrupts apical localization of Crb. Accordingly, a knock-in deletion of the Crb FERM-binding motif (FBM) also impairs apical localization. Finally, overexpression of Crb challenges this system, creating a sensitized background to identify components involved in cytoskeletal polarization, apical membrane trafficking and stabilisation of Crb at the apical domain.

The long-term effect of maternal dietary protein restriction on 5-HT1A receptor function and behavioral responses to stress in adulthood

Maternal nutrition impacts fetal development, and may play a role in determining resilience to stress and vulnerability to stress-precipitated psychiatric disorders, such as anxiety and depression. In this study, we examined the effect of a reduction in maternal dietary protein during pregnancy on the brain neurochemistry and behavior of offspring. We focused specifically on the serotonin system, the 5-HT_1A receptor and the responsivity of offspring as adults to stress. Dams were fed either a low protein diet (10% protein by weight) or isocaloric control diet (20% protein by weight). The low protein diet did not alter maternal food intake and body weight, or litter size and the average birth weight of male or female littermates. 5-HT_1A receptor function, as measured by quantitative autoradiography of 8-OH-DPAT (1 μM)-stimulated [³⁵S]GTPγS binding, was markedly reduced in hippocampus of weanling female, but not male offspring (postnatal day, PND 21) of dams fed the low protein diet. The number of serotonergic cell bodies in the rostral raphe, and 5-HT metabolism in the limbic system of weanling offspring was not altered by maternal low protein diet. The deficit in hippocampal 5-HT_1A receptor function observed in weanling female offspring persisted into adulthood (PND 112), and was accompanied by an increased sensitivity to stress, specifically increased immobility during a 15-minute forced swim challenge and increased anorexia following 30-minute restraint (PND 97-100). The present work begins to uncover important future directions for understanding the early developmental origins of resilience to stress, and factors that may put individuals at greater risk for stress-related psychiatric disorders.

Inhibition of the Serotonin Transporter Is Altered by Metabolites of Selective Serotonin and Norepinephrine Reuptake Inhibitors and Represents a Caution to Acute or Chronic Treatment Paradigms

Previous studies of transgenic mice carrying a single isoleucine to methionine substitution (I172M) in the serotonin transporter (SERT) demonstrated a loss of sensitivity to multiple antidepressants (ADs) at SERT. However, the ability of AD metabolites to antagonize SERT was not assessed. Here, we evaluated the selectivity and potency of these metabolites for inhibition of SERT in mouse brain-derived synaptosomes and blood platelets from wild-type (I172 mSERT) and the antidepressant-insensitive mouse M172 mSERT. The metabolites norfluoxetine and desmethylsertraline lost the selectivity demonstrated by the parent compounds for inhibition of wild-type mSERT over M172 mSERT, whereas desvenlafaxine and desmethylcitalopram retained selectivity. Furthermore, we show that the metabolite desmethylcitalopram accumulates in the brain and that the metabolites desmethylcitalopram, norfluoxetine, and desvenlafaxine inhibit serotonin uptake in wild-type mSERT at potencies similar to those of their parent compounds, suggesting that metabolites may play a role in effects observed following AD administration in wild-type and M172 mice.

Perceptions of human cadaver dissection by medical students: a highly valued experience

Cadaver dissection remains a cornerstone in the study of anatomical sciences by medical students. However, this activity can cause emotions that may affect learning outcomes. This study, which involved medical students of various cultural backgrounds, assessed their responses to dissection. Medicine I year students (n = 100) at Oakland University William Beaumont School of Medicine were invited to complete a questionnaire after the first week of dissection, and again at the end of the course. The questionnaire asked for demographics, and assessed the students' appraisal of their dissection experience, cultural influences, coping activities and learning outcomes. After the first week of dissection, most of the students found the experience challenging, stimulating, exciting and informative, rather than nauseating or unbearable. Still, some students found the experience anxiety-provoking, especially when they thought about human mortality. Cultural background influenced the students' emotional development as they worked through the course. Most of the participants agreed that dissection promotes teamwork, familiarity with the human body, and integration of the theoretical knowledge with practical application. At the end of the course, dissection was significantly less anxiety-provoking, and, interestingly, the study found that culture and religious beliefs became more important to the students. Most students agreed that dissection is important, relevant, and necessary, and has the potential to improve learning outcomes that are essential to the development of physicians. The study suggests that an introductory course in social, behavioral and ethical considerations be presented at the beginning of the medical curriculum.

Sex comparisons of strength and coactivation following ten weeks of deadlift training

OBJECTIVES

To examine the effects of a ten week deadlift training program on peak torque and agonist-antagonist coactivation.

METHODS

Fifty-four untrained subjects (mean age=23 years) participated in this investigation, and were randomly assigned to a training (males, n=17; females, n=17) or control (males, n=9; females, n=11) group. The subjects in the training group performed deadlifts twice per week. Isometric peak torque for the leg extensors and flexors and surface electromyographic (EMG) amplitude for the superficial quadriceps and biceps femoris muscles were assessed.

RESULTS

Deadlift training increased leg extension peak torque for the males (P=.008, Cohen's d=0.43) and females (P=.003, d=0.48). Leg flexion peak torque improved for the females (P=.001, d=0.45). Increased EMG amplitude for the superficial quadriceps femoris muscles when they served as agonists was demonstrated for the females (P=.010, d=0.40), but not the males (P=.059, d=0.20). For both sexes, the effect sizes for the decline in biceps femoris coactivation were large.

CONCLUSION

Deadlift training elicited improvements in strength and agonist-antagonist coactivation in untrained subjects, and particularly, novice females.

The effects of a high-intensity free-weight back-squat exercise protocol on postural stability in resistance-trained males

The purpose of this study was to investigate the effects of a high-intensity free-weight back-squat exercise on postural stability characteristics in resistance-trained males. Eighteen college-aged (mean ± SD: age = 22.9 ± 2.9 years; height = 175.8 ± 6.4 cm; mass = 86.3 ± 9.3 kg), resistance-trained males performed postural stability testing before and after completing five sets of eight repetitions of back-squat exercises at 80% of one-repetition maximum. A commercial balance testing device was used to assess sway index at pre- and at 0, 5, 10, 15 and 20 min post-exercise. Each balance assessment consisted of four, 20-s static stance conditions: eyes-open firm surface, eyes-closed firm surface, eyes-open soft surface and eyes-closed soft surface. Sway index was greater (P = 0.001-0.020) at Post 0 than at all other time points. No differences (P > 0.05) were observed between any other time phases. Sway index was greater (P < 0.001) for eyes-closed soft surface than all other conditions. These findings revealed sway index for all conditions significantly increased following completion of the back-squat; however, sway index recovered within 5 min of exercise. Higher sway index values as a result of neuromuscular fatigue induced by a back-squat exercise may have performance and injury risk consequences to subsequent activities that rely on postural stability. However, these findings suggest balance impairments may recover in ~5 min following high-intensity lower body resistance exercise.

Impaired development of fetal serotonergic neurons in intrauterine growth restricted baboons

We studied development of the fetal serotonergic central nervous system in a baboon, non-human primate model of intrauterine growth restriction (IUGR). Fetal (90% of full-term) IUGR brains were comparable in size to controls, but have reduced expression of serotonergic proteins and mRNAs, as well as having fewer serotonergic neurons.

Influence of acute eccentric exercise on the H:Q ratio

The purpose of the present study was to examine the effects of an acute bout of eccentric exercise on maximal isokinetic concentric peak torque (PT) of the leg flexors and extensors and the hamstrings-to-quadriceps (H:Q) strength ratio. Sixteen male (mean±SD: age=20.9±2 years; stature=177.0±4.4 cm; mass=76.8±10.0 kg) volunteers performed maximal, concentric isokinetic leg extension and flexion muscle actions at 60°·sec - 1 before and after (24-72 h) a bout of eccentric exercise. The eccentric exercise protocol consisted of 4 sets of 10 repetitions for the leg press, leg extension, and leg curl exercises at 120% of the concentric one repetition maximum (1-RM). The results indicated that the acute eccentric exercise protocol resulted in a significant (P<0.05) decrease in isokinetic leg flexion (13-19%) and leg extension (11-16%) PT 24-72 h post-exercise. However, the H:Q ratios were unaltered by the eccentric exercise protocol. These findings suggest that an acute bout of eccentric exercise utilizing both multi - and single - joint dynamic constant external resistance (DCER) exercises results in similar decreases in maximal isokinetic strength of the leg flexors and extensors, but does not alter the H:Q ratio.

Transgenic elimination of high-affinity antidepressant and cocaine sensitivity in the presynaptic serotonin transporter

Serotonin [i.e., 5-hydroxytryptamine (5-HT)]-targeted antidepressants are in wide use for the treatment of mood disorders, although many patients do not show a response or experience unpleasant side effects. Psychostimulants, such as cocaine and 3,4-methylenedioxymethamphetamine (i.e., "ecstasy"), also impact 5-HT signaling. To help dissect the contribution of 5-HT signaling to the actions of these and other agents, we developed transgenic mice in which high-affinity recognition of multiple antidepressants and cocaine is eliminated. Our animals possess a modified copy of the 5-HT transporter (i.e., SERT, slc6a4) that bears a single amino acid substitution, I172M, proximal to the 5-HT binding site. Although the M172 substitution does not impact the recognition of 5-HT, this mutation disrupts high-affinity binding of many competitive antagonists in transfected cells. Here, we demonstrate that, in M172 knock-in mice, basal SERT protein levels, 5-HT transport rates, and 5-HT levels are normal. However, SERT M172 mice display a substantial loss of sensitivity to the selective 5-HT reuptake inhibitors fluoxetine and citalopram, as well as to cocaine. Through a series of biochemical, electrophysiological, and behavioral assays, we demonstrate the unique properties of this model and establish directly that SERT is the sole protein responsible for selective 5-HT reuptake inhibitor-mediated alterations in 5-HT clearance, in 5-HT1A autoreceptor modulation of raphe neuron firing, and in behaviors used to predict the utility of antidepressants.

Modeling rare gene variation to gain insight into the oldest biomarker in autism: construction of the serotonin transporter Gly56Ala knock-in mouse

Alterations in peripheral and central indices of serotonin (5-hydroxytryptamine, 5-HT) production, storage and signaling have long been associated with autism. The 5-HT transporter gene (HTT, SERT, SLC6A4) has received considerable attention as a potential risk locus for autism-spectrum disorders, as well as disorders with overlapping symptoms, including obsessive-compulsive disorder (OCD). Here, we review our efforts to characterize rare, nonsynonymous polymorphisms in SERT derived from multiplex pedigrees carrying diagnoses of autism and OCD and present the initial stages of our effort to model one of these variants, Gly56Ala, in vivo. We generated a targeting vector to produce the Gly56Ala substitution in the Slc6a4 locus by homologous recombination. Following removal of a neomycin resistance selection cassette, animals exhibiting germline transmission of the Ala56 variant were bred to establish a breeding colony on a 129S6 background, suitable for initial evaluation of biochemical, physiological and behavioral alterations relative to SERT Gly56 (wild-type) animals. SERT Ala56 mice were achieved and exhibit a normal pattern of transmission. The initial growth and gross morphology of these animals is comparable to wildtype littermate controls. The SERT Ala56 variant can be propagated in 129S6 mice without apparent disruption of fertility and growth. We discuss both the opportunities and challenges that await the physiological/behavioral analysis of Gly56Ala transgenic mice, with particular reference to modeling autism-associated traits.

Protective roles of alpha-calcitonin and beta-calcitonin gene-related peptide in spontaneous and experimentally induced colitis

Calcitonin gene-related peptide (CGRP) is thought to be involved in the regulation of gastric and mesenteric blood flow, in the control of gastric acid secretion and in the modulation of intestinal motility, yet the precise physiological roles of CGRP remain to be elucidated. To further examine the role(s) of CGRP in gastrointestinal function, we examined mutant mice lacking alphaCGRP or betaCGRP expression. Mutant mice did not demonstrate any overt phenotypic changes, yet exhibited a spontaneous, adult-onset colitis and increased colonic damage using a dextran sulfate sodium model of experimental colitis. Surprisingly, mice lacking betaCGRP show no obvious alterations in CGRP immunoreactivity in the gut, accompanied by an increase in alphaCGRP messenger RNA expression, suggesting an adaptive mechanism to compensate for the lack of betaCGRP. These data demonstrate that both alphaCGRP and betaCGRP play a protective role in the generation of spontaneous colitis, supporting a role for both extrinsic and intrinsic CGRP-containing neurons.

Temperature alters lipopolysaccharide-induced cytokine secretion by RAW 264.7 cells

Local and systemic temperature change is associated with the immune response to infection, but the role of temperature remains poorly understood. To study the effect of temperature on macrophage activation by lipopolysaccharide (LPS), RAW 264.7 cells were incubated with LPS at different temperatures and secretion of three cytokines was measured. Incubation at 31 degrees C increased tumour necrosis factor (TNF) secretion when compared with 37 degrees C, while cells exposed at 39 degrees C secreted less TNF. Interleukin-6 (IL-6) secretion was less at 31 degrees C than at 37 degrees C and remained unchanged at 39 degrees C. Interleukin-10 secretion was depressed on either side of 37 degrees C. Only IL-6 secretion was sensitive to preincubation temperature effects. The kinetics of cytokine secretion and steady-state mRNA analysis indicated potentially different mechanisms of temperature regulation for TNF and IL-6.

Identification of genes induced by growth hormone in rat liver using cDNA arrays

Growth hormone (GH) is a pleiotropic cytokine that acts upon its target cells to regulate their growth, differentiation and metabolism. GH is thought to act by altering gene expression in target cells, but few GH-regulated genes are known. In this study, we used cDNA array analysis to identify genes rapidly induced in the liver of GH-deficient dwarf rats following a single systemic injection of GH. Eight genes were found to upregulate their mRNA expression within 1-3 hours of GH administration, results which were confirmed by northern analysis. The identity of these genes suggests GH may influence a diversity of cellular processes. A role for GH in regulating cytokine and growth factor signalling is suggested by upregulation of mRNAs encoding three signal transducers: a subunit of the receptor for IL-6-type cytokines (gp130), STAT3 (signal transducer and activator of transcription) and p38MAPK (mitogen activated protein kinase). Two genes involved in DNA repair and cell cycle control, APEN (apurinic endonuclease) and GADD45 (growth arrest and DNA damage 45) were upregulated. Other induced genes include those encoding a lactate transporter (MCT-1), an extracellular matrix remodelling enzyme, MTI-MMP (membrane type 1 matrix metalloproteinase) and an acute phase protein (fibrinogen beta). In summary, this work is the first to apply cDNA arrays to the study of peptide hormone action in vivo and has identified 8 novel GH target genes.

Further analysis of maize C(4) pyruvate,orthophosphate dikinase phosphorylation by its bifunctional regulatory protein using selective substitutions of the regulatory Thr-456 and catalytic His-458 residues

In C(4) plants such as maize, pyruvate,orthophosphate dikinase (PPDK) catalyzes the regeneration of the initial carboxylation substrate during C(4) photosynthesis. The primary catalytic residue, His-458 (maize C(4) PPDK), is involved in the ultimate transfer of the beta-phosphate from ATP to pyruvate. C(4) PPDK activity undergoes light-dark regulation in vivo by reversible phosphorylation of a nearby active-site residue (Thr-456) by a single bifunctional regulatory protein (RP). Using site-directed mutagenesis of maize recombinant C(4) dikinase, we made substitutions at the catalytic His residue (H458N) and at this regulatory target Thr (T456E, T456Y, T456F). Each of these affinity-purified mutant enzymes was assayed for changes in dikinase activity. As expected, substituting His-458 with Asn results in a catalytically incompetent enzyme. Substitutions of the Thr-456 residue with Tyr and Phe reduced activity by about 94 and 99%, respectively. Insertion of Glu at this position completely abolished activity, presumably by the introduction of negative charge proximal to the catalytic His. Furthermore, neither the T456Y nor inactive H458N mutant enzyme was phosphorylated in vitro by RP. The inability of the former to serve as a phosphorylation substrate indicates that RP is functionally a member of the Ser/Thr family of protein kinases rather than a "dual-specificity" Ser-Thr/Tyr kinase, since our previous work showed that RP effectively phosphorylated Ser inserted at position 456. The inability of RP to phosphorylate its native target Thr residue when Asn is substituted for His-458 documents that RP requires the His-P catalytic intermediate form of PPDK as its protein substrate. For these latter studies, synthetic phosphopeptide-directed antibodies specific for the Thr(456)-P form of maize C(4) PPDK were developed and characterized.

Lessons from the front: implementing outcomes projects

These issues are representative of the challenges facing those wishing to implement outcomes evaluations in the dramatically different settings of today's behavioral healthcare. To maintain acceptable levels of credibility, difficult issues such as these need to be addressed openly and assertively. We remain optimistic about the value of measuring the effects of behavioral healthcare interventions. Such measurement facilitates the development of communication across service providers and creates accountability where once there was none. When standards of quality research are applied, outcomes management offers great potential benefit to consumers, providers, and behavioral healthcare organizations.

Maize recombinant C4-pyruvate,orthophosphate dikinase: Expression in Escherichia coli, partial purification, and characterization of the phosphorylatable protein

The gene for C4-pyruvate,orthophosphate dikinase (PPDK) from maize (Zea mays) was cloned into an Escherichia coli expression vector and recombinant PPDK produced in E. coli cells. Recombinant enzyme was found to be expressed in high amounts (5.3 U purified enzyme-activity liter(-1) of induced cells) as a predominantly soluble and active protein. Biochemical analysis of partially purified recombinant PPDK showed this enzyme to be equivalent to enzyme extracted from illuminated maize leaves with respect to (i) molecular mass, (ii) specific activity, (iii) substrate requirements, and (iv) phosphorylation/inactivation by its bifunctional regulatory protein.

Biosynthesis of fatty acids by lactating human breast epithelial cells: an evaluation of the contribution to the overall composition of human milk fat

The objective of this study was to characterize the fatty acid biosynthetic pathway of the lactating human breast. Mixed cell populations, obtained by centrifugation of human milk, were enriched in breast epithelial cells by a selective adsorption procedure. Confirmation of the identity of the breast epithelial cells was obtained immunohistochemically. These viable breast epithelial cells incorporated radioactively labeled acetate predominantly into fatty acids with less than 16C atoms. The presence of the two key enzymes characteristic of the medium-chain fatty acid biosynthetic pathway of nonruminants, fatty acid synthetase, and thioesterase II, was demonstrated both qualitatively, by immunohistochemistry, and quantitatively, by enzyme assay. The results indicate that the lipogenic system of the human breast is qualitatively very similar to that of rats, mice, and rabbits, which also secrete milk fats containing medium-chain fatty acids. Quantitatively, however, the mammary fatty acid biosynthetic pathway appears to be less active in humans than in these other species.

Thioesterase II, a new marker enzyme for human cells of breast epithelial origin

Metabolic, enzymologic, and immunohistochemical techniques have been used to show that a human cell line of breast epithelial origin synthesized medium chain fatty acids via the ubiquitous fatty acid synthetase and a mammary-specific chain-terminating enzyme, thioesterase II. Previous studies in our laboratory with rodents indicated that thioesterase II is expressed exclusively in mammary epithelial cells, an observation consistent with the physiologic role of the enzyme in milk fat synthesis. Results of the present study suggest that the enzyme exhibits a similar cell specificity in its expression in humans and that the specificity is maintained in normal and neoplastic tissues. Thus thioesterase II was detected immunohistochemically in normal human breast epithelia derived from both lactating and nonlactating breast tissue, in cultured cells derived from both primary breast epithelial tumors and from a metastatic tumor of breast origin, and in several human breast epithelial cell lines; the enzyme could not be detected in HeLa cells, in a colon carcinoma, or in a mammary myoepithelial cell line. These findings raise the possibility that thioesterase II may be of use as a diagnostic tool to identify human tumors of breast epithelial origin.

Localization of thioesterase II, the chain-length regulatory enzyme of milk fatty acid synthesis, in rat mammary gland epithelial cells

Two approaches were used to establish the intercellular distribution of fatty acid synthetase and thioesterase II in the lactating rat mammary gland. Thioesterase II is the chain-length regulatory enzyme in the biosynthesis of the medium-chain fatty acids characteristic of milk fat. Using immunohistochemical techniques, immunoreactive fatty acid synthetase was found in both mammary adipocytes and epithelial cells; in contrast, immunoreactive epithelial cells were isolated from lactating rat mammary glands after digestion with collagenase and thermolysin, and their lipogenic activity was studied using isotopically labelled acetate. Consistent with the immunohistochemical data, adipocytes synthesized exclusively long-chain fatty acids whereas epithelial cells synthesized predominantly chain fatty acids. The results indicate that the capacity for synthesis of medium-chain fatty acids is a unique property of the epithelial cell component of the mammary gland.

Lack of coordinated regulation of lipogenic enzymes in a human breast cell line, SKBr3

A human breast cell line has been identified which contains prodigious levels of fatty acid synthetase but has a very low capacity for lipogenesis from glucose, lactate or acetate. The fatty acid synthetase from this cell line appears to be structurally and functionally normal, and the low lipogenic capacity of the cells appears to be due to the low activities of other lipogenic enzymes, notably acetyl-CoA carboxylase. Thus, the SKBr3 cell line appears to lack the long-term coordinated control of acetyl-CoA carboxylase and fatty acid synthetase commonly observed in normal lipogenic tissues.

Far-field holography of ampule contaminants

Detection and measurement of contaminating particles in cylindrical ampules have been achieved using far-field holography. The degradation of the images caused by the cylindrical nature of the ampule was overcome by index matching and clear images of particles as small as 5 microm in diameter were obtained.

Purification and properties of fatty acid synthetase from a human breast cell line

A human mammary epithelial cell line (SKBr3) has been identified in which fatty acid synthetase constitutes up to 28%, by weight of the cytosolic proteins. The enzymes has been purified to near homogeneity from this cell line and some of its properties studied. In common with fatty acid synthetases from other animal tissues, the enzyme is a 480 000 dalton dimer of similar molecular weight subunits, it synthesizes predominantly palmitic acid and is inactive in the absence of free coenzyme A. The kinetic properties and amino acid composition of the enzyme are also similar to those of fatty acid synthetases from various tissues of other animals. Appreciable structural resemblance between human and rodent fatty acid synthetases is indicated by studies on the immunological cross-reactivities of these enzymes.

Lau effect: theory and experiment

It was recently shown that coherence theory provides a simple and elegant means of interpreting and extending the Lau effect. The details of this analysis are presented along with experimental results which show good qualitative agreement with the predicted intensity distributions. In addition an unexpected intensity modulation is observed which is readily explained in terms of the present analysis.

Cyclopentadienyl-ruthenium and -osmium chemistry. XII. Some complexes containing cyclic carbene ligands

Reactions between ω-hydroxyalk-1-ynes, HC2(CH2)nOH (n = 2 or 3) or HC2CH2CHMeOH, and MX(PR3)2(η-C5H5) (M = Ru, X = Cl, R = Me or Ph; M = Os, X = Br, R = Ph) in the presence of NH4PF6 give cationic cyclic carbene complexes, presumably by rapid intramolecular cyclization of (undetected) intermediate ω-hydroxyvinylidene complexes. Further reactions of {Ru[C(CH2)3O]-(PPh3)2(η-C5H5)}+ include (a) base-catalysed H- D exchange of both H atoms of the β-CH2 group; (b) metallation and subsequent dimethylation of the β-CH2 group; (c) reduction by NaAlH2- (OCH2CH2OMe)2 to Ru[CH(CH2)3O](PPh3)2(η-C5H5).

Isolation of F-actin filaments. Comparison of F-actin filament preparations from normal and dystrophic mouse muscle

To investigate the dystrophic influence on the characteristics of actin, a method for the isolation of F-actin filaments from the skeletal muscle of small sizes, i.e., less than 0.5 g, was devised. In this method, minced muscle was treated with collagenase and hyaluronidase, and the isolated filaments were washed with adenosine triphosphate (ATP). Upon examination in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the ATP-washed filaments showed a protein component identical in mobility to actin in untreated myofibrils or to that prepared by the conventional method. Electron microscopic appearances of the filaments were similar to those of F-actin filaments described in the literature. The dimensions of the filaments were 0.5--2.5 micrometer in length and 60--70 A in diameter. The ability to activate the Mg-adenosine triphosphatase or myosin was found to be Ca2+ independent. In all aspects of the above characteristics, the filaments from leg muscles of 129/Re dydy dystrophic mice and their litter mates were observed to be identical.

Keratosis follicularis spinulosa decalvans. An infant with failure to thrive, deafness, and recurrent infections

A 10-month-old male infant had keratosis follicularis spinulosa decalvans, an X-linked dominant disorder. His cutaneous abnormalities consisted of generalized hyperkeratosis, spiny follicular papular lesions, universal alopecia, and hypoplastic nails. Ocular changes characteristic of the disease were also present. Unusual findings included deafness, failure to thrive, predisposition to bacterial infections without demonstrable immune defect, and transient hepatomegaly with abnormal liver function studies.

Kinetics of branch migration in double-stranded DNA

The rate of branch migration in double stranded DNA has been measured by the use of a unique substrate formed by the action of the EcoRI restriction endonuclease on the dimeric figure-8 configuration of the replicative form DNA of phage G4. The figure-8 and the X-form derived from it contain a junction of the kind postulated to occur in the Holliday structure and to be an essential feature of a number of models of recombination. In the X-form this junction can branch migrate to an irreversible terminal configuration consisting of two linear monomers. The disappearance of X-forms was measured by electron microscopy. A treatment of branch migration as a random walk process was developed to permit the determination of the rate of the intrinsic process, a step movement of the junction by a distance of one base pair. A value of about 6 kilobase pairs per sec at 37 degrees was obtained.

Linear phase microscopy

A technique is described for measuring the phase of complex transmitting objects. It consists of two basic parts. The first is an optical system that imposes the phase of an object onto a sinusoidal carrier in the form of a phase modulation. This is accomplished using interferometric and optical heterodyning techniques. The second is a phase detection system that converts this phase modulation into a signal that is directly proportional to the phase of the object. This technique measures phase variations from zero to 167pi, (2pi ambiguities are avoided) with a spatial resolution of 600 cycles/mm and a phase resolution of 2pi/100. Analysis of this technique and experimental results are given.