Quality of life and mental health in children and adolescents during the first year of the COVID-19 pandemic: results of a two-wave nationwide population-based study

BACKGROUND

The COVID-19 pandemic has disrupted the lives of children and adolescents worldwide. The German COPSY study is among the first population-based longitudinal studies to examine the mental health impact of the pandemic. The objective of the study was to assess changes in health-related quality of life (HRQoL) and mental health in children and adolescents and to identify the associated risk and resource factors during the pandemic.

METHODS

A nationwide longitudinal survey was conducted with two waves during the pandemic (May/June 2020 and December 2020/January 2021). In total, n = 1923 children and adolescents aged 7 to 17 years and their parents participated (retention rate from wave 1 to wave 2: 85%). The self-report and parent-proxy surveys assessed HRQoL (KIDSCREEN-10), mental health problems (SDQ with the subscales emotional problems, conduct problems, hyperactivity, and peer problems), anxiety (SCARED), depressive symptoms (CES-DC, PHQ-2) and psychosomatic complaints (HBSC-SCL). Mixed model panel regression analyses were conducted to examine longitudinal changes in mental health and to identify risk and resource factors.

RESULTS

The HRQoL of children and adolescents decreased during the pandemic, and emotional problems, peer-related mental health problems, anxiety, depressive and psychosomatic symptoms increased over time, however the change in global mental health problems from wave 1 to wave 2 was not significant, and some changes were negligible. Socially disadvantaged children and children of mentally burdened parents were at particular risk of impaired mental health, while female gender and older age were associated with fewer mental health problems. A positive family climate and social support supported the mental health of children and adolescents during the pandemic.

DISCUSSION

Health promotion, prevention and intervention strategies could support children and adolescents in coping with the pandemic and protect and maintain their mental health.

Abnormal lymphatic phenotype in a CRISPR mouse model of the human lymphedema-causing Connexin47 R260C point mutation

Connexin proteins form gap junctions controlling exchange of ions and small molecules between cells and play an important role in movement of lymph within lymphatic vessels. Connexin47 (CX47) is highly expressed in lymphatic endothelial cells and CX47 missense mutations, i.e., R260C, cosegregate with primary lymphedema in humans. However, studies utilizing CX47 knockout mice have failed to demonstrate any lymphatic anomalies. To unravel the lymphatic consequences of expressing a mutant CX47 protein, we used CRISPR technology to create a mouse carrying a Cx47 missense mutation (Cx47R259C) equivalent to the human CX47R260C missense mutation associated with human primary lymphedema. Intradermal Evans Blue dye injection identified a 2-fold increase in regional lymph nodes in homozygous Cx47R259C mice compared to wildtype, particularly in the jugular region (4.8 ± 0.4 and 2.0 ± 0.0, respectively, p<0.01). Associated lymphatic channels were increased in Cx47R259C mice and mesenteric lymph reflux occurred in homozygous Cx47R259C mice but not in wildtype. Contractility of superficial cervical lymphatics, assessed by pressure myography, was reduced in homozygous Cx47R259C mice compared to wildtype. In conclusion, our data are the first to demonstrate a role for the Cx47 protein in lymphatic anatomy and function. This phenotype is similar to that found with other valve deficient mouse mutants, e.g., in Foxc2. Of significance, this study is the first to use CRISPR technology to develop a pre-clinical model of primary lymphedema and demonstrates the importance of distinguishing between lack of and presence of mutant protein when developing clinically relevant animal models for translation of pre-clinical findings.

Online adaptive neural control of a robotic lower limb prosthesis

OBJECTIVE

The purpose of this study was to develop and evaluate an adaptive intent recognition algorithm that continuously learns to incorporate a lower limb amputee's neural information (acquired via electromyography (EMG)) as they ambulate with a robotic leg prosthesis.

APPROACH

We present a powered lower limb prosthesis that was configured to acquire the user's neural information and kinetic/kinematic information from embedded mechanical sensors, and identify and respond to the user's intent. We conducted an experiment with eight transfemoral amputees over multiple days. EMG and mechanical sensor data were collected while subjects using a powered knee/ankle prosthesis completed various ambulation activities such as walking on level ground, stairs, and ramps. Our adaptive intent recognition algorithm automatically transitioned the prosthesis into the different locomotion modes and continuously updated the user's model of neural data during ambulation.

MAIN RESULTS

Our proposed algorithm accurately and consistently identified the user's intent over multiple days, despite changing neural signals. The algorithm incorporated 96.31% [0.91%] (mean, [standard error]) of neural information across multiple experimental sessions, and outperformed non-adaptive versions of our algorithm-with a 6.66% [3.16%] relative decrease in error rate.

SIGNIFICANCE

This study demonstrates that our adaptive intent recognition algorithm enables incorporation of neural information over long periods of use, allowing assistive robotic devices to accurately respond to the user's intent with low error rates.

Skull base tumor volume and surgical margins: a pilot study

The relationship between preoperative assessment of tumor volume and oncologic adequacy of surgical margins was studied retrospectively. Our hypothesis was that the risk of inadequate, or positive, margins would rise with increasing tumor volume and that this would adversely affect survival. We anticipated that limitations of surgical approaches used until 1988 would be reflected in an increasing proportion of positive margins with increasing tumor volume. We conducted a pilot study of 25 patients with malignant tumors of the anterolateral cranial base operated on at the University of Pittsburgh Center for Cranial Base Surgery between 1987 and 1988. Preoperative computed tomography assessment of tumor volume was performed in all patients, and correlation between tumor volume, surgical margins, and survival was examined. Follow-up interval averaged 31.7 months. Twelve histologic tumor types were represented, with squamous cell carcinoma the most common (eight patients [32%]). Tumor volume ranged from 0.9 to 390 cc, with a median of 48 cc. Based on a median split of tumor volumes, patients were classified as high volume (more than 48 cc) or low volume (less than 48 cc). Of patients in the high volume group, 92% were found to have positive surgical margins, whereas only 50% of patients in the low volume group had positive margins. Analysis of the effect of tumor volume and surgical margins on survival was limited by sample size constraints, but both high-tumor volume and positive margins tended to reduce patient survival (0.07 < p 0.10).

Male infertility: polymerase chain reaction-based deletion mapping of genes on the human chromosome

INTRODUCTION

Y chromosome microdeletions are common in about 10-15 percent of men with azoospermia or severe oligospermia. These microdeletions are too small to be detected by karyotyping. They can be easily identified using polymerase chain reaction (PCR). Most of the microdeletions that cause azoospermia or oligospermia occur in the non-overlapping regions of the long arm of the Y chromosome. These regions, also called azoospermia factor regions (AZF), are responsible for spermatogenesis. The loci are termed AZFa, AZFb and AZFc from proximal to distal Yq. Several genes located in AZF regions for spermatogenesis is viewed as "AZF candidate genes". This study aims at PCR-based rapid analysis of Y chromosome microdeletion, which is a cause for male infertility.

METHODS

PCR amplification using Y-specific STS (sequence tagged sites) of AZF regions for AZFa: DBY and sY84, AZFb: RBM1 and sY127, and AZFc: BPY2 and sY254, were conducted.

RESULTS

Of the 30 infertile men, 17 were azoospermic and 13 were severely oligospermic. Severe oligospermia was diagnosed in those patients who produced only one-third the concentrations of the sperm of that found in fertile men. Four patients showed a deletion of one or more STS. Two patients had complete deletion of AZFc loci, three patients had complete deletion of AZFa loci and two patients had complete deletion of AZFb loci.

CONCLUSION

The frequency involving the microdeletion in the AZF region was found in four out of 30 azoospermic and severely oligospermic infertile men, i.e. 13.3 percent of the total deletions.

The effect of epidural bupivacaine on maintenance requirements of sevoflurane evaluated by bispectral index in children

BACKGROUND AND OBJECTIVE

Combined (local and general) anaesthesia or Balanced (intravenous analgesics and inhalational hypnotics) anaesthesia are commonly used in paediatrics. The authors have investigated the influence of both types of anaesthesia on the requirements of sevoflurane to maintain an adequate level of hypnosis as measured by Bispectral index (at around 50) monitoring in paediatric orthopaedic patients.

METHODS

Twenty-six orthopaedic surgery patients aged 2-15 yr were randomized to receive, during general sevoflurane anaesthesia, 5 microg kg-1 of intravenous fentanyl (Balanced anaesthesia group) or 1 mL kg-1 of caudal-epidural bupivacaine 0.25% (Combined anaesthesia group). The end-tidal sevoflurane concentration was adjusted every 5 min in order to maintain Bispectral index values at around 50.

RESULTS

Patients showed very similar Bispectral index values (P > 0.05) in both the Combined and the Balanced groups before anaesthesia (96.7 +/- 2.7 vs. 96.9 +/- 1.8), after induction (48.5 +/- 2.9 vs. 49.8 +/- 3.6) and after administration of analgesia (50.9 +/- 3.8 vs. 50.3 +/- 4.3). The sevoflurane end-tidal concentration requirements were similar in both the Combined and Balanced groups before administration of analgesia (2.1 +/- 0.2 vs. 2.1 +/- 0.4, P = 0.9415), but lower end-tidal concentrations were required by the Combined group than by the Balanced group (0.81 +/- 0.4 vs. 1.5 +/- 0.5, P < 0.0001) in the first 20 min after administration of analgesia.

CONCLUSION

Combined anaesthesia with epidural bupivacaine maintains the same Bispectral index values as Balanced anaesthesia during orthopaedic surgery in children without fentanyl and with a lower sevoflurane requirement.

Mouse seminal vesicle secretory protein of 99 amino acids (MSVSP99): characterization and hormonal and developmental regulation

Polyclonal antibodies have been generated to investigate the localization, tissue and species distribution, androgen regulation, and ontogeny of a protein secreted by mouse seminal vesicle, designated as MSVSP99 (ie, mouse seminal vesicle secretory protein of 99 amino acids). MSVSP99 is a polymorphic compound with a molecular weight of around 14 kilodaltons and a positive immunoreactivity range of 5.23 to 5.70. Positive immunoreactivity was restricted to the epithelial cells of the seminal vesicle. Western blot analysis showed organ specificity for MSVSP99, which could not be detected in several organs in the mouse. Time course decrease of MSVSP99 after castration closely followed that of its mRNA. In contrast, the length of time required to restore control levels after testosterone treatment was higher for the protein than it was for its mRNA. Whereas the MSVSP99 gene is already active in 10-day-old males, MSVSP99 is first detected at 27 days. Then, we conclude that factors other than the accumulation of the mRNA regulate MSVSP99 expression.

High-resolution optical mapping of the right bundle branch in connexin40 knockout mice reveals slow conduction in the specialized conduction system

Connexin40 (Cx40) is a major gap junction protein that is expressed in the His-Purkinje system and thought to be a critical determinant of cell-to-cell communication and conduction of electrical impulses. Video maps of the ventricular epicardium and the proximal segment of the right bundle branch (RBB) were obtained using a high-speed CCD camera while simultaneously recording volume-conducted ECGs. In Cx40(-/-) mice, the PR interval was prolonged (47.4+/-1.4 in wild-type [WT] [n=6] and 57.5+/-2.8 in Cx40(-/-) [n=6]; P<0.01). WT ventricular epicardial activation was characterized by focused breakthroughs that originated first on the right ventricle (RV) and then the left ventricle (LV). In Cx40(-/-) hearts, the RV breakthrough occurred after the LV breakthrough. Additionally, Cx40(-/-) mice showed RV breakthrough times that were significantly delayed with respect to QRS complex onset (3.7+/-0.7 ms in WT [n=6] and 6.5+/-0.7 ms in Cx40(-/-) [n=6]; P<0.01), whereas LV breakthrough times did not change. Conduction velocity measurements from optical mapping of the RBB revealed slow conduction in Cx40(-/-) mice (74.5+/-3 cm/s in WT [n=7] and 43.7+/-6 cm/s in Cx40(-/-) [n=7]; P<0.01). In addition, simultaneous ECG records demonstrated significant delays in Cx40(-/-) RBB activation time with respect to P time (P-RBB time; 41.6+/-1.9 ms in WT [n=7] and 55.1+/-1.3 ms in [n=7]; P<0.01). These data represent the first direct demonstration of conduction defects in the specialized conduction system of Cx40(-/-) mice and provide new insight into the role of gap junctions in cardiac impulse propagation.

A targeted disruption in connexin40 leads to distinct atrioventricular conduction defects

INTRODUCTION

Gap junctions consist of connexin (Cx) proteins that enable electrical coupling of adjacent cells and propagation of action potentials. Cx40 is solely expressed in the atrium and His-Purkinje system. The purpose of this study was to evaluate atrioventricular (AV) conduction in mice with a homozygous deletion of Connexin40 (Cx40(-/-)).

METHODS

Surface ECGs, intracardiac electrophysiology (EP) studies, and ambulatory telemetry were performed in Cx40(-/-) mutant mice and wild-type (WT) controls. Atrioventricular (AV) conduction parameters and arrhythmia inducibility were evaluated using programmed stimulation. Analysis of heart rate variability was based on results of ambulatory monitoring.

RESULTS

Significant findings included prolonged measures of AV refractoriness and conduction in connexin40-deficient mice, including longer PR, AH, and HV intervals, increased AV refractory periods, and increased AV Wenckebach and 2:1 block cycle lengths. Connexin40-deficient mice also had an increased incidence of inducible ventricular tachycardia, decreased basal heart rates, and increased heart rate variability.

CONCLUSION

A homozygous disruption of Cx40 results in prolonged AV conduction parameters due to abnormal electrical coupling in the specialized conduction system, which may also predispose to arrhythmia vulnerability.

Isolated infarction of the cecum: CT findings in two patients

Colonic ischemia isolated to the cecum is a rare entity. The authors evaluated two patients who underwent computed tomography (CT) because appendicitis was suspected at clinical examination. CT findings were suggestive of isolated cecal ischemia or infarction. Surgical-histopathologic findings helped confirm the presumptive CT diagnoses. Isolated cecal infarction should be included in the differential diagnosis of acute right lower quadrant pain.

Fatigue in cancer patients

The interest in fatigue seems to be growing. A Medline search combining the key words fatigue and cancer yielded 248 entries compared with 72 entries 10 years previously. The studies published are mainly descriptive, augmenting the knowledge about the extent of fatigue associated with cancer, as well as during and after the various treatments used to fight it. New measurement instruments integrating the multidimensional concept of fatigue are being proposed. In 1998, the first study describing fatigue in children and adolescents with cancer was published. The knowledge of the causes of fatigue related to cancer remains extremely limited. In only a few studies are interventions and treatment possibilities for fatigue discussed. Hopefully, the refined knowledge about the characteristics of fatigue and its epidemiology will provide new etiologic understanding, resulting in effective treatment. This article provides a survey on the literature published in 1998.

Gap junctional intercellular communication in the mouse ovarian follicle

A targeted disruption of the gene encoding the gap junction protein connexin37 (Cx37; alpha 4) results in female infertility. Mutant follicles are not observed to develop beyond early antral stages, and there is a lack of both observable mature Graafian follicles and ovulation. The oocytes are unable to acquire meiotic competence. Following oocyte failure, the residual follicular cells do not undergo atresia but rather transdifferentiate into luteal cells, resulting in a mutant ovary populated with numerous, inappropriate corpora lutea. These results indicate that the Cx37-containing gap junctions formed between oocyte and follicular cells permit bidirectional signalling between the two cell types. These junctions are required for oocyte growth and development during preantral stages of the follicle, and for the inhibition of follicle cell luteinization. An additional role for these junctions may be to permit transfer of cytoplasmic signals required to hold oocytes in meiotic arrest. Since the mutant follicles never acquire meiotic competence, this latter role for gap junctional communication cannot be tested in this model.

Diverse functions of vertebrate gap junctions

Gap junctions are clusters of intercellular channels between adjacent cells. The channels are formed by the direct apposition of oligomeric transmembrane proteins, permitting the direct exchange of ions and small molecules (< 1 kDa) between cells without involvement of the extracellular space. Vertebrate gap junction channels are composed of oligomers of connexins, an enlarging family of proteins consisting of perhaps > 20 members. This article reviews recent advances in understanding the structure of intercellular channels and describes the diverse functions attributable to gap junctions as a result of insights gained from targeted gene disruptions in mice and genetic disease in humans.

Mice lacking connexin40 have cardiac conduction abnormalities characteristic of atrioventricular block and bundle branch block

Activation of cardiac muscle is mediated by the His-Purkinje system, a discrete pathway containing fast-conducting cells (Purkinje fibers) which coordinate the spread of excitation from the atrioventricular node (AV node) to ventricular myocardium [1]. Although pathologies of this specialized conduction system are common in humans, especially among the elderly [2], their molecular bases have not been defined. Gap junctions are present at appositions between Purkinje fibers and could provide a mechanism for propagating impulses between these cells [3]. Studies of the expression of connexins - the family of proteins from which gap junctions are formed - reveal that connexin40 (Cx40) is prominent in the conduction system [4]. In order to study the role of gap junction communication in cardiac conduction, we generated mice that lack Cx40. Using electrocardiographic analysis, we show that Cx40 null mice have cardiac conduction abnormalities characteristic of first-degree atrioventricular block with associated bundle branch block. Thus, gap junctions are essential for the rapid conduction of impulses in the His-Purkinje system.

The androgen-dependent mouse seminal vesicle secretory protein of 99 amino acids (MSVSP99): regulation of the mRNA and preliminary characterization of the promoter

MSVSP99 (mouse seminal vesicle secretory protein of 99 amino acids) is a member of the rat and mouse seminal vesicle secretory protein (SVS) family. In order to characterize its androgenic regulation, the cloned cDNA and gene encoding MSVSP99 have been used. At adulthood, the MSVSP99 mRNA represents from 3 to 7% of the total mRNA population. This mRNA accumulation is under androgenic control because it is abolished by castration and restored in castrated mice by heptylate testosterone injection. During ontogenesis, MSVSP99 mRNA is just detectable in 10-day-old mice, and reaches adult levels at 30 days. Neonatal castration abolishes MSVSP99 mRNA accumulation in 20-day-old mice. Transcription elongation assays show that androgens act mainly on the MSVSP99 gene transcription. In an attempt to obtain information about the mechanism of androgen action on transcription, preliminary transient transfection experiments in CV-1 cells permitted us to define a promoter region (-387/ + 16), the activity of which is enhanced by dihydrotestosterone.

Female infertility in mice lacking connexin 37

The signals regulating ovarian follicle development and the mechanisms by which they are communicated are largely undefined. At birth, the ovary contains primordial follicles consisting of meiotically arrested oocytes surrounded by a single layer of supporting (granulosa) cells. Periodically, subsets of primordial follicles undergo further development during which the oocyte increases in size and the granulosa cells proliferate, stratify and develop a fluid-filled antrum. After ovulation, oocytes resume meiosis and granulosa cells retained in the follicle differentiate into steroidogenic cells, forming the corpus luteum. It has been proposed that intercellular signalling through gap junction channels may influence aspects of follicular development. Gap junctions are aggregations of intercellular channels composed of connexins, a family of at least 13 related proteins that directly connect adjacent cells allowing the diffusional movement of ions, metabolites, and other potential signalling molecules. Here we show that connexin 37 is present in gap junctions between oocyte and granulosa cells and that connexin 37-deficient mice lack mature (Graafian) follicles, fail to ovulate and develop numerous inappropriate corpora lutea. In addition, oocyte development arrests before meiotic competence is achieved. Thus, cell-cell signalling through intercellular channels critically regulates the highly coordinated set of cellular interactions required for successful oogenesis and ovulation.

Structure and sequence of a mouse gene encoding an androgen-regulated protein: a new member of the seminal vesicle secretory protein family

The gene encoding MSVSP99 (mouse seminal vesicle secretory protein of 99 amino acids), an androgen-dependent protein specifically expressed in the mouse seminal vesicle, was isolated and sequenced. A mouse genomic library constructed in the lambda EMBL12 vector was screened using a full length cDNA probe. One genomic clone was selected, 7.4 kb of which were shown to contain the whole MSVSP99 gene. The complete sequence of the MSVSP99 gene (1.7 kb), plus 0.8 and 0.3 kb of the 5' and 3' flanking regions respectively, has been determined. The gene is composed of four exons interrupted by three introns. The size range for the four exons is 47-217 bp, while that of introns is 87-615 bp. The transcription start site was identified as an adenine residue located 21 nucleotides upstream from the ATG start codon. Putative TATA and CAAT boxes were identified, along with a number of regions that shared homologies with known regulatory sequences. These included androgen-responsive elements located in the promoter as well as in the gene sequence. Sequence comparisons with other androgen-responsive genes showed strong homologies between the MSVSP99 gene and the seminal vesicle secretory protein (SVS) family genes (rat SVS II, IV, V and VI). Moreover, some regions were found to be conserved between the MSVSP99 gene and the human semenogelin I and II genes.

An E box mediates activation and repression of the acetylcholine receptor delta-subunit gene during myogenesis

The genes encoding the skeletal muscle acetylcholine receptor (AChR) are induced during muscle development and are regulated subsequently by innervation. Because both the initiation and the subsequent regulation of AChR expression are controlled by transcriptional mechanisms, an understanding of the steps that regulate AChR expression following innervation is likely to require knowledge of the pathway that activates AChR genes during myogenesis. Thus, we sought to identify the cis-acting sequences that regulate expression of the AChR delta-subunit gene during muscle differentiation. We transfected muscle and nonmuscle cell lines with gene fusions between 5'-flanking DNA from the AChR delta-subunit gene and the human growth hormone gene, and we show here that 148 bp of 5'-flanking DNA from the AChR delta-subunit gene contains two regulatory elements that control muscle-specific gene expression. One element is an E box, which is important both for activation of the delta-subunit gene in myotubes and for its repression in myoblasts and nonmuscle cells. Mutation of this E box, which prevents binding of MyoD-E2A and myogenin-E2A heterodimers, decreases expression in myotubes and increases expression in myoblasts and nonmuscle cells. An E-box binding activity, which does not contain MyoD, myogenin, or E2A proteins, is present in muscle and nonmuscle cells and may be responsible for repressing the delta-subunit gene in myoblasts and nonmuscle cells. An enhancer, which lacks E boxes, is also required for expression of the delta-subunit gene but does not confer muscle-specific expression.

Cloning and sequence analysis of a cDNA encoding an androgen-dependent mouse seminal vesicle secretory protein

We report the cloning and sequencing of a new cDNA sequence encoding a protein from the mouse seminal vesicle. An open reading frame of 297 nucleotides encoded a protein of 99 amino acids with a calculated molecular mass of 11.454 kDa. The first 21 amino acids constituted a signal peptide followed by 78 amino acids encoding the secreted protein. The cDNA sequence comprised a 3' untranslated region of 226 bp and the polyadenylation signal AATAAA, 19 bp upstream from the poly(A)+ tail. A high degree of homology was found between this protein and members of the family of seminal vesicle secretory (SVS) proteins, especially rat SVS VI. Northern blot analysis indicated the presence of a 0.7 kb mRNA species in the mRNAs of seminal vesicle tissue. Castration resulted in a marked decrease in the level of the 0.7 kb mRNA encoding the protein, whereas administration of testosterone to castrated males restored the 0.7 kb mRNA.

Electrical activity-dependent regulation of the acetylcholine receptor delta-subunit gene, MyoD, and myogenin in primary myotubes

Expression of the skeletal muscle acetylcholine receptor (AChR) is regulated by nerve-evoked muscle activity. Studies using transgenic mice have shown that this regulation is controlled largely by transcriptional mechanisms because responsiveness to electrical activity can be conferred by transgenes containing cis-acting sequences from the AChR subunit genes. The lack of a convenient muscle cell culture system for studying electrical activity-dependent gene regulation, however, has made it difficult to identify the important cis-acting sequences and to characterize an electrical activity-dependent signaling pathway. We developed a muscle culture system to study the mechanisms of electrical activity-dependent gene expression. Gene fusions between the murine AChR delta-subunit gene and the human growth hormone gene were transfected into primary myoblasts, and the amount of growth hormone secreted into the culture medium from either spontaneously electrically active or inactive myotube cultures was measured. We show that 181 bp of 5'-flanking DNA from the AChR delta-subunit gene are sufficient to confer electrical activity-dependent gene expression. In addition, we show that the rate of AChR delta-subunit gene expression differs among individual nuclei in a single myotube but that highly expressing nuclei are not necessarily colocalized with AChR clusters. We also show that expression of MyoD and myogenin are regulated by electrical activity in primary myotube cultures and that all nuclei within a myotube express similar levels of MyoD and similar levels of myogenin.

Spatial restriction of AChR gene expression to subsynaptic nuclei

Acetylcholine receptors (AChRs) and the mRNAs encoding the four AChR subunits are highly concentrated in the synaptic region of skeletal myofibers. The initial localization of AChRs to synaptic sites is triggered by the nerve and is caused, in part, by post-translational mechanisms that involve a redistribution of AChR protein in the myotube membrane. We have used transgenic mice that harbor a gene fusion between the murine AChR delta subunit gene and the human growth hormone gene to show that innervation also activates two independent transcriptional pathways that are important for establishing and maintaining this non-uniform distribution of AChR mRNA and protein. One pathway is triggered by signal(s) that are associated with myofiber depolarization, and these signals act to repress delta subunit gene expression in nuclei throughout the myofiber. Denervation of muscle removes this repression and causes activation of delta subunit gene expression in nuclei in non-synaptic regions of the myofiber. A second pathway is triggered by an unknown signal that is associated with the synaptic site, and this signal acts locally to activate delta subunit gene expression only in nuclei within the synaptic region. Synapse-specific expression, however, does not depend upon the continuous presence of the nerve, since transcriptional activation of the delta subunit gene in subsynaptic nuclei persists after denervation. Thus, the nuclei in the synaptic region of multinucleated skeletal myofibers are transcriptionally distinct from nuclei elsewhere in the myofiber, and this spatially restricted transcription pattern is presumably imposed initially by the nerve.

Multiple forms of rat kidney L-arginine:glycine amidinotransferase

The relative amount of L-arginine:glycine amidinotransferase (transamidinase) protein in kidneys from rats fed a complete purified diet with and without the addition of creatine and/or glycine was determined by a monoclonal antibody-immunosorbent inhibition assay. Kidneys from the creatine-fed rats had 10% of the transamidinase activities and 78% of the monoclonal antibody immunoreactive transamidinase protein as kidneys from the control rats. An excellent correlation between transamidinase activities and protein was reported previously when the amounts of enzyme protein were determined by immunotitration with polyclonal antibodies. One possible explanation for the contrasting results was that multiple forms of transamidinase are present in rat kidneys. If so, the monoclonal antibody may have recognized forms of the enzyme that were not decreased in amounts commensurate with the decrease in enzyme activities as a result of creatine feeding. Evidence is presented in this report that multiple forms of transamidinase are present in rat kidneys. The distribution of the isoelectric points of the individual forms of transamidinase in kidneys of the control rats appeared to be dissimilar from that in the creatine-fed rats. Therefore, an alteration in the distribution of the individual forms of the enzyme may be a factor in the alteration of transamidinase activities in creatine-fed rats.

The purification and characterization of human kidney L-arginine:glycine amidinotransferase

Human kidney L-arginine:glycine amidinotransferase (transamidinase) has been purified to a homogeneous state as defined by native and sodium dodecyl sulfate gel electrophoresis and by ultracentrifugation (sedimentation equilibrium) experiments. The four steps in the isolation procedure were chromatography with DEAE-cellulose, gel filtration with Sephadex G-150, chromatography with phenyl Sepharose, and high-pressure liquid chromatography with hydroxylapatite. The final product represented a 90-fold purification of the enzyme. Human kidney transamidinase is a dimer with a molecular mass of 89,000 Da and subunit masses of 44,000 Da. The Km for arginine and glycine were both 2.5 mM and the Vmax was 0.5 mumol ornithine/min/mg protein. The ultraviolet absorption spectrum, specific activity, and isoelectric points were determined for human kidney transamidinase. Multiple forms of the enzyme were obtained by isoelectric focusing. Human kidney transamidinase cross-reacted with polyclonal antibodies raised to rat kidney transamidinase. All of the properties of human kidney transamidinase that we have examined were similar to those of rat kidney transamidinase. A close evolutionary relationship between the rat and human kidney transamidinase is suggested.

A study of drug abuse in a group of South African university students

Seventeen informal interviews and 1597 questionnarie responses provided an investigation of drug abuse in a group of South African students. Legal problems in South Africa make research of drug abuse (and indeed many other areas of social relations), particularly interviewing, extremely hazardous and therefore uncommon. Not surprisingly, in view of this, the interviews revealed findings inconsistent with the questionnaire data in many areas. Indeed, the informal technique demonstrated the need for more personal research in this field rather than grouped data questionnaires, the latter being seemingly responsible for the myth of the stereotypic drug taker.