Male reproductive health and environmental xenoestrogens

Male reproductive health has deteriorated in many countries during the last few decades. In the 1990s, declining semen quality has been reported from Belgium, Denmark, France, and Great Britain. The incidence of testicular cancer has increased during the same time incidences of hypospadias and cryptorchidism also appear to be increasing. Similar reproductive problems occur in many wildlife species. There are marked geographic differences in the prevalence of male reproductive disorders. While the reasons for these differences are currently unknown, both clinical and laboratory research suggest that the adverse changes may be inter-related and have a common origin in fetal life or childhood. Exposure of the male fetus to supranormal levels of estrogens, such as diethlylstilbestrol, can result in the above-mentioned reproductive defects. The growing number of reports demonstrating that common environmental contaminants and natural factors possess estrogenic activity presents the working hypothesis that the adverse trends in male reproductive health may be, at least in part, associated with exposure to estrogenic or other hormonally active (e.g., antiandrogenic) environmental chemicals during fetal and childhood development. An extensive research program is needed to understand the extent of the problem, its underlying etiology, and the development of a strategy for prevention and intervention.

Carcinoma-in-situ of the testis: possible origin from gonocytes and precursor of all types of germ cell tumours except spermatocytoma

Based on evidence from morphological and histochemical studies and from clinical experience, the following hypotheses are proposed: carcinoma-in-situ (CIS) germ cells are malignant gonocytes; these CIS gonocytes have some capacity to regress into more primitive, totipotent embryonic cells which can give rise to all types of nonseminomatous germ cell tumours; the tumour germ cells of classical seminomas are malignant gonocytes derived from CIS gonocytes which have lost their ability to regress into totipotent embryonic cells; the ability of CIS gonocytes to regress into totipotent embryonic cells decreases with age, whereas the capacity to form classical seminoma cells is preserved; the transformation of CIS gonocytes into invasive tumours is dependent on factors such as gonadotrophins and/or testicular steroids; the pathogenesis of classical and spermatocytic seminoma are unrelated. As a consequence of these hypotheses an alternative nomenclature for carcinoma-in-situ, seminoma and dysgerminoma is suggested.

Restless legs syndrome: A community-based study of prevalence, severity, and risk factors

OBJECTIVE

To assess the prevalence and severity of restless legs syndrome (RLS) in the general community and to investigate its potential relationship with iron metabolism and other potential risk factors.

METHODS

This was a cross-sectional study of a sex- and age-stratified random sample of the general population (50 to 89 years; n = 701). The diagnosis of RLS was established by face-to-face interviews; severity was graded on the RLS severity scale. Each subject underwent a thorough clinical examination and extensive laboratory testing.

RESULTS

The prevalence of RLS was 10.6% (14.2% in women, 6.6% in men); 33.8% of all patients with RLS had mild, 44.6% had moderate, and 21.6% had severe disease expression. None had been previously diagnosed or was on dopaminergic therapy. Free serum iron, transferrin, and ferritin concentrations were similar in subjects with and without RLS. However, soluble transferrin receptor (sTR) concentrations were different in subjects with and without RLS (1.48 vs 1.34 mg/L; p < 0.001). Female sex and high sTR independently predicted the risk of RLS.

CONCLUSION

This large survey confirms the high prevalence, female preponderance, and underrecognition of restless legs syndrome in the general community. Although two-thirds of patients had moderate to severe disease, none was on current dopaminergic therapy.

dMi-2, a hunchback-interacting protein that functions in polycomb repression

Early in Drosophila embryogenesis, gap gene products directly repress transcription of homeotic (HOX) genes and thereby delimit HOX expression domains. Subsequently, Polycomb-group proteins maintain this repression. Currently, there is no known molecular link between gap and Polycomb-group proteins. Here, dMi-2 is identified as a protein that binds to a domain in the gap protein Hunchback that is specifically required for the repression of HOX genes. Genetic analyses show that dMi-2 participates in both Hunchback and Polycomb repression in vivo. Hence, recruitment of dMi-2 may serve as a link between repression of HOX genes by Hunchback and Polycomb proteins.

Discrete cleavage motifs of constitutive and immunoproteasomes revealed by quantitative analysis of cleavage products

Proteasomes are the main proteases responsible for cytosolic protein degradation and the production of major histocompatibility complex class I ligands. Incorporation of the interferon gamma--inducible subunits low molecular weight protein (LMP)-2, LMP-7, and multicatalytic endopeptidase complex--like (MECL)-1 leads to the formation of immunoproteasomes which have been associated with more efficient class I antigen processing. Although differences in cleavage specificities of constitutive and immunoproteasomes have been observed frequently, cleavage motifs have not been described previously. We now report that cells expressing immunoproteasomes display a different peptide repertoire changing the overall cytotoxic T cell--specificity as indicated by the observation that LMP-7(-/-) mice react against cells of LMP-7 wild-type mice. Moreover, using the 436 amino acid protein enolase-1 as an unmodified model substrate in combination with a quantitative approach, we analyzed a large collection of peptides generated by either set of proteasomes. Inspection of the amino acids flanking proteasomal cleavage sites allowed the description of two different cleavage motifs. These motifs finally explain recent findings describing differential processing of epitopes by constitutive and immunoproteasomes and are important to the understanding of peripheral T cell tolerization/activation as well as for effective vaccine development.

Weaning from mechanical cardiac support in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Implantation of mechanical cardiac support systems (MCSS) in patients with idiopathic dilated cardiomyopathy (IDC) may improve cardiac function and allow explantation of the device. We report of long-term effects of ventricular unloading on cardiac function, humoral anti-beta1-adrenoceptor autoantibodies (A-beta1-AABs), and myocardial fibrosis.

METHODS AND RESULTS

Seventeen patients in New York Heart Association functional class IV with nonischemic IDC received MCSS. All had a cardiac index of < 1.6 L x min(-1) x m(-2) of body surface area, a left ventricular ejection fraction (LVEF) of <16%, and a left ventricular internal diameter in diastole (LVIDd) of >68 mm and tested positive for A-beta1-AABs. Echocardiographic evaluation, serum tests for A-beta1-AABs, and histological assessment of myocardial fibrosis were performed before and after MCSS implantation. The mean support duration was 230+/-201 days. Six patients died, four were transplanted, and two are still on MCSS. Five patients with significant cardiac recovery (mean LVIDd, 54+/-2.3 mm; LVEF, 47+/-3.7%) were weaned after 160 to 794 days and are now device free for 51 to 592 days. A-beta1-AABs disappeared gradually during MCSS without increase after weaning; cardiac function and volume density of fibrosis remained normal. Nine patients' cardiac function hardly improved during ventricular unloading.

CONCLUSIONS

Cardiac function can be normalized in selected patients with end-stage IDC by MCSS. The degree of preoperative myocardial fibrosis may be an indicator for outcome; A-beta1-AABs can be used to monitor myocyte recovery. Weaning from MCSS offers an alternative to cardiac transplantation in certain patients.

Progression of dysarthria and dysphagia in postmortem-confirmed parkinsonian disorders

BACKGROUND

Dysarthria and dysphagia are known to occur in parkinsonian syndromes such as Parkinson disease (PD), dementia with Lewy bodies (DLB), corticobasal degeneration (CBD), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). Differences in the evolution of these symptoms have not been studied systematically in postmortem-confirmed cases.

OBJECTIVE

To study differences in the evolution of dysarthria and dysphagia in postmortem-confirmed parkinsonian disorders.

PATIENTS AND METHODS

Eighty-three pathologically confirmed cases (PD, n = 17; MSA, n = 15; DLB, n = 14; PSP, n = 24; and CBD, n = 13) formed the basis for a multicenter clinicopathological study organized by the National Institute of Neurological Disorders and Stroke, Bethesda, Md. Cases with enough clinicopathological documentation for the purpose of the study were selected from research and neuropathological files of 7 medical centers in 4 countries (Austria, France, England, and the United States).

RESULTS

Median dysarthria latencies were short in PSP and MSA (24 months each), intermediate in CBD and DLB (40 and 42 months), and long in PD (84 months). Median dysphagia latencies were intermediate in PSP (42 months), DLB (43 months), CBD (64 months), and MSA (67 months), and long in PD (130 months). Dysarthria or dysphagia within 1 year of disease onset was a distinguishing feature for atypical parkinsonian disorders (APDs) (specificity, 100%) but failed to further distinguish among the APDs. Survival time after onset of a complaint of dysphagia was similar in PD, MSA, and PSP (15 to 24 months, P =.7) and latency to a complaint of dysphagia was highly correlated with total survival time (rho = 0.88; P<.001) in all disorders.

CONCLUSIONS

Latency to onset of dysarthria and dysphagia clearly differentiated PD from the APDs, but did not help distinguish different APDs. Survival after onset of dysphagia was similarly poor among all parkinsonian disorders. Evaluation and adequate treatment of patients with PD who complain of dysphagia might prevent or delay complications such as aspiration pneumonia, which in turn may improve quality of life and increase survival time.

C-TAK1 regulates Ras signaling by phosphorylating the MAPK scaffold, KSR1

Kinase suppressor of Ras (KSR) is a conserved component of the Ras pathway that interacts directly with MEK and MAPK. Here we show that KSR1 translocates from the cytoplasm to the cell surface in response to growth factor treatment and that this process is regulated by Cdc25C-associated kinase 1 (C-TAK1). C-TAK1 constitutively associates with mammalian KSR1 and phosphorylates serine 392 to confer 14-3-3 binding and cytoplasmic sequestration of KSR1 in unstimulated cells. In response to signal activation, the phosphorylation state of S392 is reduced, allowing the KSR1 complex to colocalize with activated Ras and Raf-1 at the plasma membrane, thereby facilitating the phosphorylation reactions required for the activation of MEK and MAPK.

Black TiO2 nanotubes: cocatalyst-free open-circuit hydrogen generation

Here we report that TiO2 nanotube (NT) arrays, converted by a high pressure H2 treatment to anatase-like "black titania", show a high open-circuit photocatalytic hydrogen production rate without the presence of a cocatalyst. Tubes converted to black titania using classic reduction treatments (e.g., atmospheric pressure H2/Ar annealing) do not show this effect. The main difference caused by the high H2 pressure annealing is the resulting room-temperature stable, isolated Ti(3+) defect-structure created in the anatase nanotubes, as evident from electron spin resonance (ESR) investigations. This feature, absent for conventional reduction, seems thus to be responsible for activating intrinsic, cocatalytic centers that enable the observed high open-circuit hydrogen generation.

Immunoglobulin adsorption in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Idiopathic dilated cardiomyopathy (IDC) frequently is a progressive disease without causative therapy options. Following the hypothesis that in certain patients autoantibodies against cardiac structures may induce, maintain, or promote the progression of the disease, we investigated whether the elimination of these autoantibodies through immunoadsorption would improve cardiac function.

METHODS AND RESULTS

This prospective case-control study included 34 patients with IDC. Each patient presented with moderate to severe heart failure and evidence of autoantibodies directed against beta(1)-adrenoceptors (beta(1)-AABs). Seventeen patients received standard medical therapy (control group), whereas 17 were also treated with immunoadsorption (treatment group) to eliminate beta(1)-AABs. A 1-year follow-up included echocardiographic assessment of left ventricular ejection fraction and internal diameters, beta(1)-AAB levels, and clinical status every 3 months. Within 1 year, the mean+/-SD left ventricular ejection fraction rose from 22.3+/-3.3% to 37.9+/-7.9% (P=0.0001) in the treatment group, with a relative increase of 69.9%. However, in the control group, no overall increase was seen (from 23.8+/-3.0% to 25.2+/-5.9%, P=0. 3154). Left ventricular diameter in diastole decreased by 14.5% from 74.5+/-7.1 to 63.7+/-6.0 mm in the treatment group (P=0.0001) and by 3.8% (P=0.2342) in the control group. In the treatment group, the NYHA functional rating improved after immunoadsorption (P=0.0001). beta(1)-AABs did not increase anew.

CONCLUSIONS

In IDC, the use of immunoadsorption is superior to the use of standard medical therapy. It significantly improves cardiac performance and clinical status.

Changes in blood hormone levels during the immune response

Injection of three different antigens into rats or mice led in the course of several days to about a threefold increase in serum corticosterone levels and concommitantly to a decrease in thyroxine (rats). In view of the known immuno-suppressive effect of the glucocorticoids the possibility is considered that the endocrine changes induced during the immune response could significantly modulate the subsequent character of the immune response, e.i. magnitude, duration and lymphoid cell proliferation, however, a more complete pattern of hormonal variations and their cause needs to be established. These findings while admittedly preliminary, suffice to provide an indication of a temporal pattern of hormonal change during the immune response which could be important in immunoregulation.

Repression of lac promoter as a function of distance, phase and quality of an auxiliary lac operator

The tetrameric Lac repressor can bind simultaneously to two lac operators on the same DNA molecule, thereby including the formation of a DNA loop. We investigated the phasing dependence of DNA loop formation between lac operator O1 and an auxiliary ideal lac operator (O(id)) on the bacterial chromosome, with inter-operator distances varying from 57.5 to 1493.5 bp. Repression of a CAP-independent lac UV5 promoter by O1 at its natural position increased up to 50-fold in the presence of an optimally positioned auxiliary O(id)). Repression values alternated between local maxima and minima with a periodicity of 11.0 to 11.3 bp, suggesting that the chromosomal helical repeat is in this range in vivo. Repression increased significantly with decreasing inter-operator DNA length, indicating that the local Lac repressor concentration at O1 is crucial for tight repression. Maximal repression, attributed to stable DNA loop formation, was obtained at an operator spacing of 70.5 bp. Other repression maxima occurred at operator distances of 92.5 and 115.5 bp, corresponding to natural operator spacings in the lac and in the gal operon, respectively. Substitution of the auxiliary O(id) with the weaker binding lac operator O3 lowered repression efficiency, presumably due to the reduced local concentration of Lac repressor.

Benefits of D2 lymph node dissection for patients with gastric cancer and pN0 and pN1 lymph node metastases

A retrospective immunohistological analysis of 100 patients with pT1-3 N0 and pT1-3 N1 gastric adenocarcinoma demonstrated a high frequency of micro-involvement in the removed lymph nodes. The presence of three or more tumour cells in more than 10 per cent of the lymph nodes was of significant prognostic value in the pN0 cases. Multivariate analysis identified micro-involvement as an independent prognostic factor. The results explain why patients benefit from lymphadenectomy even if the removed lymph nodes are not involved by tumour (pN0) in routine histological examination. The frequent occurrence of micro-involvement is a strong argument favouring routine D2 lymph node dissection in gastric cancer surgery in patients with lymph node metastasis.

Density and distribution of primordial follicles in single pieces of cortex from 21 patients and in individual pieces of cortex from three entire human ovaries

BACKGROUND

At the time of cryopreservation of ovarian tissue for fertility preservation a small biopsy of ovarian cortex is usually taken for histological evaluation of the follicular reserve. The purpose of this study was to evaluate the distribution and density of primordial follicles in single pieces of cortex from individual patients and in pieces of cortex comprising entire ovaries, all prepared for cryopreservation.

METHODS

Cortical biopsies from 21 patients and the whole cortex of one ovary were evaluated histologically prior to cryopreservation. In addition, the cortex of two whole ovaries was cryopreserved before histological evaluation. The volume of each cortical fragment was measured, all follicles counted and the follicular density calculated.

RESULTS

In individual pieces of cortex follicular density showed a significant inverse linear correlation with age. The follicular density per cortical fragment prepared from each of the three entire ovaries varied from 1.8 to 166, 0.007 to 140 and 0.04 to 4.48 follicles/mm(3) cortical tissue.

CONCLUSION

The density of primordial follicles varied more than two orders of magnitude in cortical fragments from each of the three ovaries. Primordial follicles were very unevenly distributed throughout the cortex of these ovaries, although a significant linear correlation between age and follicular density was found.

Germ cell cancer and disorders of spermatogenesis: an environmental connection?

Why is there a small peak of germ cell tumours in the postnatal period and a major peak in young age, starting at puberty? And, paradoxically, small risk in old age, although spermatogenesis is a lifelong process? Why is this type of cancer more common in individuals with maldeveloped gonads, including undescended testis, gonadal dysgenesis and androgen insensitivity syndrome? Why has there, during the past 50 years, been a quite dramatic increase in testicular cancer in many developed countries? These are just a few of many questions concerning testicular cancer. However, the recent progress in research in the early stages of testicular cancer (carcinoma in situ testis (CIS)) allows us to begin to answer some of these questions. There is more and more evidence that the CIS cell is a gonocyte with stem cell potential, which explains why an adult man can develop a non-seminoma, which is a neoplastic caricature of embryonic growth. We consider the possibility that CIS cells may loose their stem cell potential with ageing. Along these lines, a seminoma is regarded a gonocytoma where the single gonocytes have little or no stem cell potential. The Sertoli and Leydig cells, which are activated postnatally and during and after puberty, may play a crucial role for both the development of the CIS gonocyte and progression of the neoplasm to invasiveness. The reported increase in testicular cancer is not the only sign that male reproductive health is at risk. There are reports that undescended testis and hypospadias have become more common. Also semen quality has deteriorated, at least in some countries. The epidemiological evidence suggests that environmental factors may play a role. Are the environmental hormone disrupters (e.g. DDT, PCB, nonylphenol, bisphenol A) to be blamed for the apparently synchronised deterioration in these aspects of male reproductive health?

Importance of vpr for infection of rhesus monkeys with simian immunodeficiency virus

The importance of the vpr gene for simian immunodeficiency virus (SIV) replication, persistence, and disease progression was examined by using the infectious pathogenic molecular clone called SIVmac239. The ATG start codon of the vpr gene was converted to TTG by site-specific mutagenesis. The constructed Vpr- mutant virus is identical with the parental SIVmac239/nef-stop virus with the exception of this one nucleotide. These viruses replicated with similar kinetics and to similar extents in rhesus monkey lymphocyte cultures and in the human CEMX174 cell line. Five rhesus monkeys were inoculated with the Vpr- variant of SIVmac239/nef-stop, and two monkeys received SIVmac239/nef-stop as controls. Both controls showed reversion of the TAA stop signal in nef by 2 weeks postinfection, as has been observed previously. Reversion of the TAA stop codon in nef also occurred in the five monkeys that received the Vpr- variant, but reversion was delayed on average to about 4 weeks. Thus, the mutation in vpr appeared to delay the rapidity with which reversion occurred in the nef gene. Reversion of the TTG sequence in vpr to ATG was observed in three of the five test animals. Reversion in vpr was first observed in these three animals 4 to 8 weeks postinfection. No vpr revertants were found over the entire 66 weeks of observation in the other two test animals that received the vpr mutant. Antibodies to vpr developed in those three animals in which reversion of vpr was documented, but antibodies to vpr were not observed in the two animals in which reversion of vpr was not detected. Antibody responses to gag and to whole virus antigens were of similar strength in all seven animals. Both control animals and two of the test animals in which vpr reverted maintained high virus loads and developed progressive disease. Low virus burden and no disease have been observed in the two animals in which vpr did not revert and in the one animal in which vpr reversion was first detected only at 8 weeks. The reversion of vpr in three of the five test animals indicates that there is significant selective pressure for functional forms of vpr in vivo. Furthermore, the results suggest that both vpr and nef are important for maximal SIV replication and persistence in vivo and for disease progression.

Comparative analysis of gait in Parkinson's disease, cerebellar ataxia and subcortical arteriosclerotic encephalopathy

Quantitative gait analysis has been used to elucidate characteristic features of neurological gait disturbances. Although a number of studies compared single patient groups with controls, there are only a few studies comparing gait parameters between patients with different neurological disorders affecting gait. In the present study, gait parameters were compared between control subjects, patients with parkinsonian gait due to idiopathic Parkinson's disease, subjects suffering from cerebellar ataxia and patients with gait disturbance due to subcortical arteriosclerotic encephalopathy. In addition to recording of baseline parameters during preferred walking velocity, subjects were required to vary velocity from very slow to very fast. Values of velocity and stride length from each subject were then used for linear regression analysis. Whereas all patient groups showed slower walking velocity and reduced step length compared with healthy controls when assessed during preferred walking, patients with ataxia and subcortical arteriosclerotic encephalopathy had, in addition, increased variability of amplitude and timing of steps. Regression analysis showed that with changing velocity, subjects with Parkinson's disease changed their stride length in the same proportion as that measured in controls. In contrast, patients with ataxia and subcortical arteriosclerotic encephalopathy had a disproportionate contribution of stride length when velocity was increased. Whereas the findings in patients with Parkinson's disease can be explained as a reduction of force gain, the observations for patients with ataxia and subcortical arteriosclerotic encephalopathy reflect an altered spatiotemporal gait strategy in order to compensate for instability. The similarity of gait disturbance in subcortical arteriosclerotic encephalopathy and cerebellar ataxia suggests common mechanisms.

Onset of the release of spermatozoa (spermarche) in boys in relation to age, testicular growth, pubic hair, and height

The onset of production of spermatozoa (spermarche) is the basis for achievement of reproductive capacity in men. We collected 24-h urine samples every 3 months in a 7-yr longitudinal study of 40 normal boys initially aged 8.6-11.7 yr. After centrifugation, the urine was analyzed for the presence of spermatozoa by microscopic examination, and spermarche was estimated on the basis of age at first observed spermaturia. The results were corrected for the intermittent occurrence of spermatozoa in the urine after first observed spermaturia and the fact that the urine samples were collected quarterly. In addition, physical examination, including determination of testicular size by orchidometer measurement, pubic hair distribution (Tanner stage), and height, was carried out every 6 months. Spermarche occurred at a median age of 13.4 yr (range, 11.7-15.3 yr), at a time when testicular size was 4.7-19.6 ml (median, 11.5 ml), and pubic hair distribution was 1-5 (median, 2.5). In most boys, spermarche preceded the age of peak height velocity (median, 13.8 yr; range, 12.2-15.2 yr); at the time of spermarche, median peak height growth velocity was 9.9 cm/yr (range, 7.5-13.4 cm/yr), and median height was 160.4 cm (range, 151.7-175.9 cm). We conclude that spermarche is an early pubertal event and that a wide variation in testicular size and secondary sex characteristics is found at that time. In particular, spermarche may occur when little or no pubic hair has developed, and the testes have grown only slightly.

Nifedipine in hypertensive emergencies

The effects and safety of using oral nifedipine 10-20 mg as acute antihypertensive treatment were studied in a single-blind placebo-controlled study of 25 consecutive patients with very high blood pressure requiring emergency reduction. In addition the effect of this treatment on cerebral blood flow was investigated using xenon-133 in 10 patients randomly allocated to receive oral nifedipine or intravenous clonidine. Whereas placebo did not alter the blood pressure, oral nifedipine significantly reduced the systolic and diastolic blood pressures in all 25 patients (from 221 +/- 22/126 +/- 14 mm Hg to 152 +/- 20/89 +/- 12 mm Hg after 30 minutes, p less than 0.001). Heart rate increased from 74 +/- 11 to 84 +/- 11 beats/minute (p less than 0.01); this effect was inversely related to age (r = -0.65, p less than 0.01). The falls in systolic and diastolic blood pressures were closely related to the blood pressures before treatment ) r = 0.67, p less than 0.001 for systolic, and r = -0.58, p less than 0.01 for diastolic values). No serious unwanted effects were observed. Measurement of cerebral blood flow after nifedipine showed an increase in flow in four out of five patients. Clonidine, by contrast, reduced cerebral blood flow in all patients by up to 28%. Nifedipine is a simple, effective, and safe alternative drug for managing hypertensive emergencies, especially when continuous monitoring of the patient cannot be guaranteed.

Polycomb group proteins and heritable silencing of Drosophila Hox genes

Early in Drosophila embryogenesis, transcriptional repressors encoded by Gap genes prevent the expression of particular combinations of Hox genes in each segment. During subsequent development, those Hox genes that were initially repressed in each segment remain off in all the descendent cells, even though the Gap repressors are no longer present. This phenomenon of heritable silencing depends on proteins of the Polycomb Group (PcG) and on cis-acting Polycomb response elements (PREs) in the Hox gene loci. We have removed individual PcG proteins from proliferating cells and then resupplied these proteins after a few or several cell generations. We show that most PcG proteins are required throughout development: when these proteins are removed, Hox genes become derepressed. However, we find that resupply of at least some PcG proteins can cause re-repression of Hox genes, provided that it occurs within a few cell generations of the loss of repression. These results suggest a functional distinction between transcriptional repression and heritable silencing: in at least some contexts, Hox genes can retain the capacity to be heritably silenced, despite being transcribed and replicated. We propose that silenced Hox genes bear a heritable, molecular mark that targets them for transcriptional repression. Some PcG proteins may be required to define and propagate this mark; others may function to repress the transcription of Hox genes that bear the mark.

Proliferation of Sertoli cells during development of the human testis assessed by stereological methods

Sertoli cells were studied using stereological methods in testes obtained from five children who were stillborn, and 31 individuals between 3 months and 40 years of age, who had suffered from sudden, unexpected death. The mean nuclear volume of the Sertoli cells, the numerical density of Sertoli cells, and the total number of Sertoli cells per individual were determined by point- and profile-counting of 0.5 micron sections. The nuclear volume of Sertoli cells increased from a median of 120 microns3 (range 53-130) during the period of 3 months to 10 years to 210 microns3 (170-260) in adults (greater than 25 years). The numerical density of Sertoli cells decreased from a median of 1200 X 10(6)/cm3 (870-1400) during childhood (3 months to 10 years) to 140 X 10(6)/cm3 (110-260) in adults (greater than 25 years). The total number of Sertoli cells per individual increased significantly from a median of 260 X 10(6) (130-520) during the late foetal period to 1500 X 10(6) (850-2900) in individuals from 3 months to 10 years of age. A further increase was found during puberty as the number of Sertoli cells in adults (greater than 25 years) was 3700 X 10(6) (2500-5600). These results indicate that significant qualitative and quantitative changes in the population of Sertoli cells take place after birth.

Cardiac recovery in dilated cardiomyopathy by unloading with a left ventricular assist device

BACKGROUND

Lasting recovery from intractable end-stage dilated cardiomyopathy, which occurs with ventricular unloading, has recently been demonstrated in 5 patients. Here our extended clinical experience with the "weaning" concept is presented.

METHODS

In 19 patients (23 to 65 years) with intractable end-stage dilated cardiomyopathy, ventricular assist devices were explanted after support periods of up to 26 months, when repeat off-pump studies had shown either restoration of cardiac function (left ventricular ejection fraction, > 45%) and dimensions (left ventricular internal diameter in diastole, < 55 mm) or partial recovery (left ventricular ejection fraction between 35% and 40%) with serious complications on the device. At the time of device placement left ventricular ejection fraction was below 20% and left ventricular internal diameter in diastole more than 64 mm and bridge-to-transplantation had been planned.

RESULTS

Seven patients with persistently restored cardiac function for more than 8 months and 5 patients for less than 5 months after weaning were studied. Five patients with recurrent heart failure died within 4 to 8 months after explantation. Four patients had to be transplanted and 2 died for reasons unrelated to cardiac function. An individual optimal left ventricular ejection fraction and left ventricular internal diameter in diastole was reached before pump removal was actually conducted in all patients. These parameters gradually deteriorated until pump removal.

CONCLUSIONS

Lasting recovery can be reached by ventricular unloading in a subset of patients with intractable end-stage dilated cardiomyopathy. Obviously, there is an individual optimum of recovery that cannot be further improved by prolonged unloading.

X-ray structure of motor and neck domains from rat brain kinesin

We have determined the X-ray structure of rat kinesin head and neck domains. The folding of the core motor domain resembles that of human kinesin reported recently [Kull, F. J., et al. (1996) Nature 380, 550-554]. Novel features of the structure include the N-terminal region, folded as a beta-strand, and the C-terminal transition from the motor to the rod domain, folded as two beta-strands plus an alpha-helix. This helix is the beginning of kinesin's neck responsible for dimerization of the motor complex and for force transduction. Although the folding of the motor domain core is similar to that of a domain of myosin (an actin-dependent motor), the position and angle of kinesin's neck are very different from those of myosin's stalk, suggesting that the two motors have different mechanisms of force transduction. The N- and C-terminal ends of the core motor, thought to be responsible for the directionality of the motors [Case, R. B., et al. (1997) Cell 90, 959-966], take the form of beta-strands attached to the central beta-sheet of the structure.

dMi-2 and ISWI chromatin remodelling factors have distinct nucleosome binding and mobilization properties

Mi-2 and ISWI, two members of the Snf2 superfamily of ATPases, reside in separate ATP-dependent chromatin remodelling complexes. These complexes differ in their biochemical properties and are believed to perform distinct functions in the cell. We have compared the remodelling activity of recombinant Drosophila Mi-2 (dMi-2) with that of recombinant ISWI. Both proteins are nucleosome-stimulated ATPases and promote nucleosome mobilization. However, dMi-2 and ISWI differ in their interaction with nucleosome core particles, in their substrate requirements and in the direction of nucleosome mobilization. We have used antibodies to immobilize a complex containing dMi-2 and the dRPD3 histone deacetylase from Drosophila embryo extracts. This complex shares the nucleosome-stimulated ATPase and nucleosome mobilization properties of recombinant dMi-2, demonstrating that these activities are maintained in a physiological context. Its functional properties distinguish dMi-2 from both SWI2/SNF2 and ISWI, defining a new family of ATP-dependent remodelling machines.