Vagus nerve stimulation for depression: rationale, anatomical and physiological basis of efficacy and future prospects

Treatment-resistant depression (TRD) is a major public health concern due to its high costs to society. One of the novel approaches for the treatment of depression is the vagus nerve stimulation (VNS). Therapeutic brain stimulation through delivery of pulsed electrical impulses to the left cervical vagus nerve now has established safety and efficacy as an adjunct treatment for medication-resistant epilepsy and has recently been approved as an adjunct long-term treatment for chronic or recurrent depression. There is considerable evidence from both animal and human neurochemical and neuroimaging studies, that the vagus nerve and its stimulation influence limbic and higher cortical brain regions implicated in mood disorders, providing a rationale for its possible role in the treatment of psychiatric disorders. Clinical studies (open-label and comparator with treatment in naturalistic setting) in patients with TRD have produced promising results, especially when the response rates at longer-term (one- and two-year) follow-up time points are considered. Ongoing research efforts will help determine the place of VNS in the armament of therapeutic modalities available for major depression.

Biology of the X chromosome

The biology of the X chromosome is unique, as there are two Xs in females and only a single X in males, whereas the autosomes are present in duplicate in both sexes. The presence of only a single autosome, which can occur as a result of an error in meiotic segregation, is invariably an embryonic lethal event. Monosomy for the X chromosome is viable because of dosage compensation, a system found in all organisms with an X:Y form of sex determination, which brings about equality of expression of most X-linked genes in females and males. In mammals, the dosage compensation system involves silencing of most of the genes on one X chromosome; it is called X chromosome inactivation. In this review, we focus first on recent advances in our understanding of the molecular basis of the X inactivation mechanism. Then we consider an unusual feature of X inactivation, the mosaic nature of the female and subsequent exposure to somatic cell selection.

Comparative methylation analysis of murine transgenes that undergo or escape X-chromosome inactivation

We analyzed an X-linked metallothionein-vasopressin (MTVP) fusion transgene that undergoes X-chromosome inactivation (X inactivation) and an X-linked transferrin (TFN) transgene that escapes X inactivation with respect to methylation in the 5' regulatory regions. The MTVP transgene promoter region is unmethylated when the transgene is on the active X chromosome and methylated when on the inactive X chromosome. Interestingly, the MTVP transgene is not detectably transcribed from the male X chromosome, although it is unmethylated, consistent with its availability for transcription. The TFN transgene promoter region is hypomethylated on both the active and inactive X chromosomes, consistent with its expression from both chromosomes. The TFN and MTVP transgenes have been mapped to chromosomal regions D and C, respectively, by fluorescence in situ hybridization. These observations are discussed in the context of our understanding of the role of DNA methylation in the spread and maintenance of X-chromosome inactivation.

Isolation and characterization of radiation-reduced hybrids containing portions of the proximal long arm of the human X chromosome: identification of hybrids containing the Menkes' disease locus

The proximal long arm of the human X chromosome (Xcen----Xq13) encompasses an estimated 23 megabases of DNA and contains numerous identified genetic loci. In order to generate a highly enriched source of DNA from this region, radiation-reduced human-hamster hybrids were constructed and screened to identify those that contained at least part of proximal Xq. Eight such hybrids were identified and characterized by Southern blot and fluorescence in situ hybridization analyses to determine more precisely the human DNA complement in each. One hybrid contains the entire proximal long arm and will be useful for mapping Xcen----Xq13 in its entirety and for localizing genes within this region. Another hybrid contains a smaller portion of the proximal long arm that includes the region reported to contain the gene for Menkes' disease.

Fetal choroid plexus cysts: beware the smaller cyst

Current literature suggests that amniocentesis be performed on fetuses with simple choroid plexus cysts only when such cysts are 1.0 cm or greater in diameter and bilateral. At retrospective analysis of 3,769 patients, choroid plexus cysts were noted in 87 (2.3%), representing a rate three times greater than that of previous reports. Eight-three patients underwent amniocentesis. Six (7.2%) had abnormal karyotypes. Four patients had the commonly associated chromosomal abnormality trisomy 18. Two had karyotypes not usually associated with this problem: mosaic Turner syndrome and trisomy 21. Of the six patients with abnormal karyotypes, one had a 4-mm-diameter unilateral choroid plexus cyst and three had bilateral cysts of 3-5 mm. Only one patient with a 16-mm cyst had any associated structural abnormality discovered at rigorous ultrasound examination. Karyotyping may be necessary in fetuses with small choroid plexus cysts. Deciding which patients should be encouraged to undergo amniocentesis is made more complex by these data.

Nucleotide sequence of the 3' nuclease-sensitive region of the human phosphoglycerate kinase 1 (PGK1) gene

Many genes are known to have nuclease-sensitive sites and/or control sequences in their 3' flanking regions, but for very few genes has this region been sequenced. Previously, we mapped specific, gene activity-dependent DNAase I- and MspI-sensitive sites at the 3' end of the human X-linked housekeeping gene phosphoglycerate kinase (PGK1). Sequence information presented here shows that the 3' nuclease-sensitive site maps precisely to an Alu sequence and near a "BKM" repeat. This is the first report of an Alu sequence that has alternative chromatin configurations depending on gene activity.

Normal length of fetal kidneys: sonographic study in 397 obstetric patients

This study was done to measure normal lengths of fetal kidneys sonographically during pregnancy. Knowledge of these measurements may allow earlier diagnosis of a variety of abnormalities. The greatest length of each of 498 kidneys in 397 consecutive fetuses between 18 and 41 weeks gestation was measured on sonograms. Gestational ages were determined by last menstrual period and biometry; significant discrepancies led to case exclusion. Abnormal fetuses, twins, offspring of diabetic mothers, and fetuses with renal pelvic dilatation of 4 mm or greater were excluded to avoid any questionable measurements. The results show that mean lengths are greater and confidence intervals are wider than previously reported. Renal lengths are similar to those reported in premature and full-term neonates. Strong correlation exists between renal length and gestational age, determined by biparietal diameter, femoral length, and abdominal circumference, and an average of the three. No significant difference was found between right and left renal lengths in fetuses in whom both kidneys were imaged. Average renal lengths are significantly different when compared across the range of gestational ages (p less than .001). No correlation is seen (r = .00) between parental height or weight and fetal renal length. Our results show that fetal renal lengths are longer than previously reported.

Rapid diagnosis of thoracic aortic transection using intravenous digital subtraction angiography

Rupture of the thoracic aorta associated with blunt trauma remains a frequently lethal injury. Although increasing numbers of patients with ruptured aortas are surviving to reach the hospital, the in-hospital mortality attending this injury remains high. Death due to transected aorta has been related to a delay in diagnosis. In an attempt to decrease the time necessary for diagnosis of this injury, we studied 50 patients using intravenous digital subtraction angiography (IVDSA) and conventional biplane angiography. We found that IVDSA was significantly faster than conventional biplane angiography, and that when IVDSA films are of diagnostic quality, they are sufficient to reliably demonstrate the presence of traumatic aortic transection. Our study was too small to establish whether IVDSA is a sufficiently sensitive test to exclude aortic injury. Further studies in this area need to be performed.

A chicken transferrin gene in transgenic mice escapes X-chromosome inactivation

Mammalian X-chromosome inactivation involves a coordinate shutting down of physically linked genes. Several proposed models require the presence of specific sequences near genes to permit the spread of inactivation into these regions. If such models are correct, one might predict that heterologous genes transferred onto the X chromosome might lack the appropriate signal sequences and therefore escape inactivation. To determine whether a foreign gene inserted into the X chromosome is subject to inactivation, transgenic mice harboring 11 copies of the complete, 17-kilobase chicken transferrin gene on the X chromosome were used. Male mice hemizygous for this insert were bred with females bearing Searle's translocation, an X-chromosome rearrangement that is always active in heterozygous females (the unrearranged X chromosome is inactive). Female offspring bearing the Searle's translocation and the chicken transferrin gene had the same amount of chicken transferrin messenger RNA in liver as did transgenic male mice or transgenic female mice lacking the Searle's chromosome. This result shows that the inserted gene is not subject to X-chromosome inactivation and suggests that the inactivation process cannot spread over 187 kilobases of DNA in the absence of specific signal sequences required for inactivation.

Congenital intracardiac rhabdomyoma: prenatal detection by echocardiography, perinatal management, and surgical treatment

A case of a newborn infant with an intracardiac tumor, detected in utero by fetal echocardiography at 30 weeks gestation, is presented. The prenatal evaluation by serial fetal echocardiograms and nonstress tests is described. In the perinatal period, ventricular tachycardia occurred and was successfully managed with antiarrhythmic medications. At 20 months of age, a right ventricular rhabdomyoma was removed at open heart surgery. The patient represents the earliest in utero detection of a fetal intracardiac tumor with successful postnatal outcome.

Viridans streptococcal endocarditis: clinical, microbiological, and echocardiographic correlations

Infections caused by species within the viridans streptococci have been associated with different clinical characteristics. We studied 36 patients with viridans streptococcal endocarditis. Complications were seen in 10 (32%) of 31 patients with native valve endocarditis and four (80%) of five with prosthetic valve endocarditis and included death in two, valve replacement in six, persistent infection in three, emboli in two, and congestive heart failure in nine. Two-dimensional echocardiograms demonstrated vegetations in 26 (72%) of 36, flail mitral valves in seven, disruption of aortic valve prosthesis in one, and perivalvular abscesses in three (two Streptococcus sanguis I and one Streptococcus intermedius I). All twelve patients with native valve endocarditis who suffered complications had vegetations detected by two-dimensional echocardiography, whereas seven patients with native valve endocarditis without vegetations, as detected by two-dimensional echocardiography, had no complications (P = .03). We found no significant correlation between streptococcal species and clinical outcome. To confirm our identifications, we sent 16 identical viridans streptococcal endocarditis isolates to five institutions; only three of 16 were identified as the same species by all five institutions. We conclude that viridans streptococcal endocarditis can be associated with a virulent clinical course and that there is marked variability in species designations of individual strains by different laboratories.

Chromatin structure of active and inactive human X-linked phosphoglycerate kinase gene

We have carried out a comparative analysis of DNase I sensitivity of the active and inactive X-linked phosphoglycerate kinase (Pgk) genes in human lymphoblast and fibroblast cultured cells. Three DNase I-sensitive regions were detected: a 5' hypersensitive site, a sensitive region in the interior of the gene and a 3' slightly sensitive site which we previously reported and have now mapped with some precision. A comparison of these sensitive sites in single and multiple X cell lines indicates that the sensitive sites are unique to the active X chromosome. A similar study of an X-linked Pgk pseudogene shows no difference in DNase I sensitivity between the pseudogenes on the active and inactive X chromosomes. These latter results imply that sex chromatin does not confer a unique level of DNase I resistance to DNA on the inactive X chromosome. The exact role of sex chromatin in differential DNase I sensitivity of genes on the inactive and active X chromosomes is discussed.

Tumor of the heart diagnosed by magnetic resonance imaging

A case of liposarcoma metastatic to the heart is presented. This is a very rare entity and only three prior case reports could be found. Magnetic resonance imaging was successfully used to visualize the tumor. These images compared favorably with a two-dimensional echocardiographic study and postmortem examination.

Clinical and echocardiographic features of isolated severe pure mitral regurgitation

Recent studies have shown that rheumatic heart disease is no longer the main cause of isolated severe pure mitral regurgitation. In this study, we evaluated various clinical and echocardiographic features found in the syndrome of mitral regurgitation. Our data is consistent with recent reports that mitral valve prolapse and coronary artery disease are now the predominant causes of mitral regurgitation and that rheumatic heart disease is a much less common etiology. In addition, our data suggest that clinical evaluation alone is usually very accurate in identifying the correct etiology. Various clinical and echocardiographic features found in the subsets of acute and chronic mitral regurgitation are described. Specifically, patients with acute mitral regurgitation were more likely to have echocardiographic evidence of segmental left ventricular dysfunction and flail mitral valve leaflet. In chronic mitral regurgitation, atrial fibrillation and left atrial dilatation were more commonly present. Echocardiography was found to be more useful in the detection of the complications of coronary artery disease rather than in identifying its presence. Patients with a New York Heart Association classification of IV and those with echocardiographic evidence of an increased left ventricular endsystolic dimension or left ventricular hypertrophy had a worse prognosis.

Replication timing of genes and middle repetitive sequences

DNA replication in mammals is temporally bimodal. "Housekeeping" genes, which are active in all cells, replicate during the first half of the S phase of cell growth. Tissue-specific genes replicate early in those cells in which they are potentially expressed, and they usually replicate late in tissues in which they are not expressed. Replication during the first half of the S phase is, therefore, a necessary but not sufficient condition for gene transcription. A change in the replication timing of a tissue-specific gene appears to reflect the commitment of that gene to transcriptional competence or to quiescence during ontogeny. Most families of middle repetitive sequences replicate either early or late. These data are consistent with a model in which two functionally distinct genomes coexist in the nucleus.

Use of the ultrasound aspiration transducer in midtrimester amniocentesis

Midtrimester amniocentesis was performed on 2,100 consecutive patients over a four-year period. A specially designed ultrasonic aspiration transducer was used to guide the needle into the amniotic cavity under direct vision by following the path of the needle tip ultrasonically as it entered the fluid. This technique has made the aspiration of amniotic fluid relatively simple and safe. We obtained an adequate amount of amniotic fluid in 99.2% of the patients at their initial visits. The incidence of grossly bloody taps was 0.8%, and the total number of bloody amniotic fluid specimens was 2.37%. The rate of primary culture failure was 0.53%. The total fetal loss within eight weeks after amniocentesis was 0.9% as compared with 0.52% in a control population composed of pregnant women between 16 and 24 weeks of gestation. The estimated amniocentesis-related fetal loss was 0.38%.

Aortic dilatation resulting in chronic aortic regurgitation and complicated by aortic dissection in a patient with Turner's syndrome

A patient with XO Turner's syndrome with a 12-year history of progressive aortic root dilatation resulting in chronic aortic regurgitation is presented. Her case is unique in that it occurred in the absence of coarctation of the aorta, bicuspid aortic valve, or hypertension. Idiopathic dilatation of the aorta may be an additional risk factor to the development of aortic dissection in the setting of Turner's syndrome.

Left atrial size, pressure, and V wave height in patients with isolated, severe, pure mitral regurgitation

In recent years, some concepts regarding the etiology and hemodynamics present in the syndrome of mitral regurgitation have changed. Coronary artery disease and mitral valve prolapse have replaced rheumatic heart disease as the most frequent cause of mitral regurgitation. Hemodynamic studies have shown that tall V waves in the pulmonary capillary wedge tracings are neither specific nor sensitive in detecting the presence of mitral regurgitation. In this study, we evaluated the role of various clinical, echocardiographic, and hemodynamic findings with regard to left atrial (LA) size, pressure, and V wave height. We found that the mean pulmonary capillary wedge pressure (PCW) and V wave height for the subset of patients with acute mitral regurgitation (PCW = 24.1 +/- 10.9; V = 41.2 +/- 20.7 mm Hg) was similar to the subset with chronic mitral regurgitation (PCW = 17.9 +/- 7.5; V = 32.0 +/- 18.2 mm Hg). In addition, we found that there was a significant logarithmic relationship between the LA size and the duration of the mitral regurgitation (y = 1.404 [log X] + 3.948; R = 0.678; p less than 0.0005). Lastly, we found that LA size, compliance, regurgitant volume, and regurgitant valve orifice area all increase with time.

Klippel-Trenaunay-Weber syndrome: appearance in utero

We were able to detect hemihypertrophy of a fetus in a routine prenatal ultrasound examination. The presence of hemangiomas and varicose veins in the hypertrophied left lower extremity at birth enabled us to diagnose the Klippel-Trenaunay-Weber syndrome. The possibility of a congenital arteriovenous fistula causing the constellation of findings was ruled out by a nuclear flow study and a thorough physical examination. A computerized tomographic scan revealed that the hemangiomas were superficial in the hypertrophied left lower extremity and did not interrupt the deep muscle bundles.

Testing for hepatitis B virus in patients with chronic urticaria and angioedema

Serologic markers of hepatitis B virus (HBV) infection were sought in serum from 85 (75%) of 114 consecutive patients with chronic urticaria and angioedema (CUA). Markers of HBV infection were detected in 15 (17.6%) patients. Of these 13 (15.3%) were found to have anti-hepatitis B surface antibody (anti-HBs) and 2 (2.4%) had hepatitis B surface antigen (HBsAg). The frequency of current and previous HBV infection is thus several times greater than that reported in the general population. No patient was found to have anti-HBs and HBsAg detectable in the same sample of blood. A diagnosis of chronic persistent hepatitis was established in the two patients with HBsAg in their circulation. The possibility that CUA was causally related to HBV infection in these two cases, as well as those with anti-HBs, was considered and it was suggested that further exploration of the relationship between CUA and HBV infection is warranted.

Somatotype and idiopathic mitral valve prolapse

Records from 18 subjects with angiographic idiopathic mitral valve prolapse, 28 subjects with merely exaggerated posterior mitral leaflet systolic bulging, and 100 subjects with normal hemodynamic and angiographic findings were compared with regard to age, sex, height, weight, ponderal index (height/3 square root weight), auscultatory and echocardiographic abnormalities. Chest x-ray films available for subjects with mitral valve prolapse were reviewed. The ponderal index of subjects with mitral valve prolapse (13.1 +/- 0.8) differed from that of subjects with merely exaggerated posterior mitral leaflet systolic bulging (12.6 +/- 0.7) (P less than 0.02) and from that of subjects without angiographic abnormality (12.3 +/- 0.8) (P less than 0.001). The three groups differed in ponderal index when equated statistically for age, height, weight, and sex (P less than 0.001). Among mitral valve prolapse patients, an asthenic habitus occurred independent of the presence of thoracic skeletal abnormalities.

Comparative karyology of the freshwater snails Bulinus tropicus and B. natalensis

Species of the subgenus Bulinus s.s. occur in a polyploid series which is of interest because of the rarity of polyploidy in animal species and because there appears to be a relation between ploidy level and ability to transmit Schistosoma haematobium, a parasite of major public health importance. We describe a technique for the preparation of standard karyotypes using cell suspensions from colchicine-treated embryos. The results for two diploid species, B. tropicus (Krauss) and B. natalensis (Küster), are presented. Both karyotypes consist of 15 metacentric and 3 submetacentric chromosomes. However, differences in centromere position are found in four pairs of chromosomes, and in the appearance of a secondary constriction. Because B. natalensis may represent a relict taxon involved in the origin of the polyploids, the results of significance for future work on the phylogeny of this group.

Echocardiographic identification of intrapericardial fibrous strands in acute pericarditis with pericardial effusion

In three cases of acute pericarditis with pericardial effusion, the presence of fibrous strands within the fluid-filled pericardial cavity was demonstrated by M-mode and cross-sectional echocardiography. Pericardiocentesis proved difficult in all three. No patient progressed to constrictive pericarditis.

Pneumomediastinum as a complication of asthma in teenage and young adult patients

The characteristics of 11 patients (age range, 13 to 31 yr) with asthma complicated by pneumomediastinum are presented. Nine of 11 patients were male. Cough and chest pain were prominent symptoms in the affected individuals. Subcutaneous emphysema was noted in all but 1 patient who presented with an unusual radiographic finding: a radiolucent rim surrounding the pulmonary artery. Hamman's sign was detected in 7 patients. None of the patients required specific therapy for pneumomediastinum. The pathophysiology of pneumomediastinum was reviewed.

The big rib sign: localization of basal pulmonary pathology in lateral projection utilizing differential magnification of the two hemithoraces

Basal pulmonary pathology which silhouettes the hemidiaphragm in lateral view may not be detectable in routine postero-anterior projection. In such cases, correct lateralization of pathology to the left or right hemithorax depends on accurate identification of the silhouetted left and right hemidiaphragm in lateral view. A prospective analysis of the sensitivity and accuracy of five techniques for identifying the left and right hemidiaphragms in more than 100 patients revealed that the most accurate method for lateralizing juxtadiaphragmatic pathology was the "big rib" sign, a technique based upon the relative difference in magnification between the left and right ribs. Techniques based upon the visceral gas bubble or upon obscuration of the anterior portion of the left hemidiaphragm by the heart proved less useful. Techniques based upon the position and configuration of the major fissures or upon higher and lower position of the two hemidiaphragms were ineffective.

A wet chemical method for rendering scanning electron microscopy samples conductive and observations on the surface morphology of human erythrocytes and Ehrlich ascites cells

An alternate method to the common technique of evaporating a metallic coating on cells to render them conductive for scanning electron microscopy is described. This wet chemical technique is less expensive and easier to use, but is not as widely applicable as the evaporative technique. It should prove invaluable in the identification of artifacts by comparison of micrographs of material prepared in both manners. The first step in our application of this wet chemical method is to use the Centrifugal Cytology bucket to deposit the cells onto conductive polyethylene. After centrifugation and fixation with 4% glutaraldehyde, the sample is placed in a 50% glutaraldehyde solution. After a rinse in distilled water it is treated with ammoniacal silver nitrate. The reduced silver renders the sample conductive and, thus, for erythrocytes, eliminates artifacts due to charging and reduces these artifacts to virtually acceptable levels for larger cells. The surfaces of erythrocytes appear smooth with this technique while those coated by conventional vapor deposition of Au-Pd alloys often appear slightly wrinkled. Ehrlich ascites cells apparently can be divided into two classes by surface morphology. The surface structure of Ehrlich ascites cells rendered conductive by the wet method appears to be finer than conventionally prepared ones.