Biomedical subjects
Publications and source records attributed to S Weiss.
Stem cells are viewed from the perspectives of their function, evolution, development, and cause. Counterintuitively, most stem cells may arise late in development, to act principally in tissue renewal, thus ensuring an organism's long-term survival. Surprisingly, recent reports suggest that tissue-specific adult stem cells have the potential to contribute to replenishment of multiple adult tissues.
Hes1 is one of the basic helix-loop-helix transcription factors that regulate mammalian CNS development, and its loss- and gain-of-function phenotypes indicate that it negatively regulates neuronal differentiation. Here we report that Hes1(-/-) mice expressed both early (TuJ1 and Hu) and late (MAP2 and Neurofilament) neuronal markers prematurely, and that there were approximately twice the normal number of neurons in the Hes1(-/-) brain during early neural development. However, immunochemical analyses of sections and dissociated cells using neural progenitor markers, including nestin, failed to detect any changes in Hes1(-/-) progenitor population. Therefore, further characterization of neural progenitor cells that discriminated between multipotent and monopotent cells was performed using two culture methods, low-density culture, and a neurosphere assay. We demonstrate that the self-renewal activity of multipotent progenitor cells was reduced in the Hes1(-/-) brain, and that their subsequent commitment to the neuronal lineage was accelerated. The Hes1(-/-) neuronal progenitor cells were functionally abnormal, in that they divided, on average, only once, and then generated two neurons, (instead of one progenitor cell and one neuron), whereas wild-type progenitor cells divided more. In addition, some Hes1(-/-) progenitors followed an apoptotic fate. The overproduction of neurons in the early Hes1(-/-) brains may reflect this premature and immediate generation of neurons as well as a net increase in the number of neuronal progenitor cells. Taken together, we conclude that Hes1 is important for maintaining the self-renewing ability of progenitors and for repressing the commitment of multipotent progenitor cells to a neuronal fate, which is critical for the correct number of neurons to be produced and for the establishment of normal neuronal function.
OBJECTIVES: To describe the detailed auditory phenotype of DFNA15, genetic hearing loss associated with a mutation in the POU4F3 transcription factor, and to define genotype-phenotype correlations, namely, how specific mutations lead to particular clinical consequences. DESIGN: An analysis of clinical features of hearing-impaired members of an Israeli family, family H, with autosomal dominant-inherited hearing loss. SETTING: Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Audiology, Rabin Medical Center, Petah Tiqwa, Israel; and audiological centers. PARTICIPANTS: Clinical features of 11 affected and 5 unaffected individuals older than 40 years from family H were studied. Mutation analysis was performed in 6 presymptomatic individuals younger than 30 years; clinical features were analyzed in 4 of these family H members. INTERVENTIONS: Hearing was measured by pure-tone audiometry and speech audiometry on all participating relatives of family H. Immittance testing (tympanometry and acoustic reflexes), auditory brainstem response, and otoacoustic emissions were done in a selected patient population. RESULTS: The patients presented with progressive high-tone sensorineural hearing impairment, which became apparent between ages 18 and 30 years. The hearing impairment became more severe with time, eventually causing significant hearing loss across the spectrum at all frequencies. CONCLUSIONS: Our results indicate that POU4F3 mutation-associated deafness cannot be identified through clinical evaluation, but only through molecular analysis. Intrafamilial variability suggests that other genetic or environmental factors may modify the age at onset and rate of progression.
An important feature of microbial infections is the ability of the microorganisms to interfere with and modulate the induction of host immune reactions. However, little is known about the effects of broad host range pathogens such as Listeria monocytogenes on similar cell types in different hosts. Here we examine the effects of the human and animal pathogen L. monocytogenes on human dendritic cells (DC) since this type of cells is essential for the initiation of immune responses. Listeria are phagocytosed efficiently by immature human DC and the bacteria escape from the phagolysosome quickly. Lack of the pore-forming activity of listeriolysin, which was found to be essential for the vacuolar escape of this bacterium in other cell types, retarded but did not prevent egress from the vacuole. Treatment of cultures of immature DC with L. monocytogenes resulted in rapid changes in morphology and cellular constitution followed by maturation of the DC. This could be judged by the appearance of maturation-specific cell surface markers. Antigen presentation to CD4 T cells was apparently not impaired by the infection. These results are in clear contrast to results obtained previously in the mouse system (Guzman et al., Mol. Microbiol. 1996. 20: 119 - 126; Darji et al., Eur. J. Immunol. 1997. 27: 1696 - 1703.).
Previous studies have shown the inhibitory effects of thiopentone on polymorphonuclear leucocyte (PML) function. However, major biochemical mechanisms which have been involved are still unknown. The aim of this study was therefore to investigate thiopentone's effects on intracellular amino acid metabolism in PML using both advanced PML separation- and HPLC techniques, especially developed for this purpose and precisely validated in our institute. Overall, our study indicates important dose-dependent alterations of free intracellular amino acid metabolism following thiopentone treatment and draw attention to the biochemical mechanisms which may be involved in both thiopentone-induced modulation in PML function and cellular immunocompetence.
Inhibition of cholesterol biosynthesis by hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors could, in theory, adversely affect male gonadal function because cholesterol is a precursor of steroid hormones. The objective of this randomized double-blind trial was to compare the effects of simvastatin, pravastatin, and placebo on gonadal testosterone production and spermatogenesis. After a 6-week placebo and lipid-lowering diet run-in period, 159 male patients aged 21 to 55 years with type IIa or IIb hypercholesterolemia, low-density lipoprotein (LDL) cholesterol between 145 and 240 mg/dL, and normal basal levels of testosterone were randomly assigned to treatment with simvastatin 20 mg (n = 40), simvastatin 40 mg (n = 41), pravastatin 40 mg (n = 39), or placebo (n = 39) once daily. After 24 weeks of treatment, mean total cholesterol levels were decreased 24% to 27% and mean LDL cholesterol was decreased 30% to 34% in the 3 active-treatment groups (P < .001 for all comparisons to placebo). At 24 weeks, there were no statistically significant differences between the placebo group and any of the active-treatment groups for the change from baseline in testosterone, human chorionic gonadotropin (hCG)stimulated testosterone, free testosterone index, follicle-stimulating hormone (FSH), luteinizing hormone (LH), or sex hormone-binding globulin (SHBG). Moreover, there were no statistically significant differences at week 12 or week 24 for the change from baseline in sperm concentration, ejaculate volume, or sperm motility for any active treatment relative to placebo. Both simvastatin and pravastatin were well tolerated. In summary, we found no evidence for clinically meaningful effects of simvastatin or pravastatin on gonadal testosterone production, testosterone reserve, or multiple parameters of semen quality.
Visual prostheses such as subretinal implants are intended for electrical multisite excitation of the retinal network. To investigate relevant issues like spatial resolution and operational range, we have developed an in vitro method using microelectrode arrays to stimulate isolated retinae. Ganglion cell activity in the chicken retina evoked by distally applied spatial voltage patterns consisted of fast bursts, transient inhibition and delayed discharges, and depended on the amount, location and spatial pattern of the injected charge. The response was altered or disappeared when synaptic transmission was blocked. Our results indicate that shape perception and object location can be partially achieved with subretinal electrical multisite stimulation.
We report the radiographic findings in three cases of hyperphosphatasemia. Often classified as a congenital bone dysplasia, the skeletal manifestations of this disorder are diagnostic. These features simulate Paget's disease both radiographically and with respect to salient biochemical markers. Typically, presentation is at early childhood with skull deformity, refusal to weight bear, and bowing of the extremities. Notable radiographic features include bowing of the long bones, thickening of the cortex, osteopenia, coarsened trabecular pattern, expansion of the medullary cavity, and thickening of the intramembranous portion of the calvarium. Histologic features include absence of lamellar bone and haversian systems, with thick osteoid seams and increased number of osteoclasts. An autosomal recessive pattern of inheritance has been suggested, although autosomal dominant varieties have been postulated.
Once it is decided that the patient in distress requires tracheal intubation, the primary goal is to secure the airway as quickly and safely as possible to assure adequate oxygenation and ventilation. The clinician should quickly review the patient's history, physical examination findings, and laboratory data to determine the presence of cardiovascular disease, assess intravascular volume status, and formulate a plan for induction of anesthesia. The stresses of hypoxia, hypercarbia, acidosis, and extreme fatigue result in near-maximal sympathetic outflow that is manifest as tachycardia, labile blood pressure, and increased myocardial contractility. The astute clinician should anticipate that the tachycardia and hypertension associated with laryngoscopy and tracheal intubation is followed by a period of hypotension. This postintubation hypotension results from the acute marked attenuation of the sympathetic tone associated with resolution of hypoxia and hypercarbia, direct drug-induced negative inotropic effect, and vasodilation. The decrease in sympathetic vascular tone may result in hypotension by exacerbating the decrease in cardiac preload and afterload from hypovolemia. In addition, the use of positive pressure ventilation and positive end-expiratory pressure (PEEP) in these hypovolemic patients will further decrease ventricular preload by impeding venous return, leading to profound hypotension. Several pharmacologic agents are required to treat effectively the hemodynamic perturbations associated with induction, laryngoscopy, and tracheal intubation. Most sedative hypnotic agents that are administered for induction provide minimal to no analgesia. Patients are most often given a combination of drugs to provide adequate sedation, analgesia to blunt the noxious stimuli, and muscle relaxation to facilitate the laryngoscopy. The major challenge is to choose a combination of drugs that at the appropriate doses, effectively blunt the responses to intubation without contributing to postlaryngoscopy hypotension. One can use several strategies to accomplish these goals; administration of a narcotic analgesic before induction decreases the dose of induction agent and can attenuate the sympathetic response to intubation. Because of the prevalence of cardiovascular disease and hypovolemia in this population of patients, all chosen drugs should have minimal negative effect on cardiac function and patients with hypovolemia should be hydrated. Most clinical studies have been performed in hemodynamically stable patients, so the routine dosages of sedative hypnotics should be reduced substantially and titrated to effect. An additional strategy is to treat significant hemodynamic perturbations with vasopressors, vasodilators, short-acting selective beta-1 blockers, and inotropic agents. The choice of vasoactive agent depends on the magnitude of the hemodynamic response and the presence of specific underlying cardiovascular pathology.
Distinct cortical activity during memory encoding of words, which were either recalled or not, was reported by a number of studies. This activity was mainly found at frontal and temporal/parietal brain regions. However, it was not clear if these regions interact with each other or work independently. In order to get a functional measure of the degree of neuronal large-scale cooperation, we calculated EEG coherence, which provides a statistical measure of synchronization between two EEG signals per frequency band. Therefore, coherence enables us to assess the functional interaction between cell assemblies of distant brain regions. The purpose of our study was to investigate if successfully recalled words show enhanced cortical synchronization compared with not recalled ones. Additionally, the influence of stimulus modality and the way different EEG frequencies participate in this process was examined. The EEG of 25 participants was recorded during memory encoding of concrete German nouns, either presented auditorily or visually and stimuli were separated according to the participant's memory performance. Recalled nouns exhibited overall enhanced synchronization but showed typical patterns, especially between anterior and posterior brain regions in all frequency bands except the alpha-1 band (8-10 Hz). Recalling nouns was accompanied by increased synchronization between more distant electrodes in relation to an increase of synchronization between adjacent electrodes. Moreover, the degree of intrahemispheric synchronization was higher for recalled nouns. The pattern of EEG coherence and amplitude changes during verbal memory encoding allowed us to assess the probability that nouns would be recalled or not.
Transient kinetic methods such as stopped flow and quenched flow have been used to elucidate many of the fundamental features of the molecular interactions which underlie muscle contraction. However, these methods traditionally require relatively large amounts of protein (10(-3) g) and so have been used most effectively for the proteins purified from bulk muscle tissue of large animals or where the proteins can be expressed in large amounts (e.g.. Dictyostelium). We have investigated the use of flash photolysis of an inert precursor of ATP (cATP) to initiate the dissociation of acto.S1 and acto.myosin and the subsequent ATP turnover reaction. Using a sample volume of 10 microl we show that a significant amount of information on the transient and steady-state kinetics of the system can be obtained from a sample containing just 50 nM of acto.myosin or acto.S1 complex in solution. Therefore in presence of excess of one protein component the measurements require only 250 ng myosin, 62 ng S1 or 25 ng actin. This is therefore the method of choice for kinetic analysis of acto.myosins which are only available in microgram quantities. We report for the first time the determination of the second order rate constant of ATP-induced dissociation of actin from the myosin extracted from a single fibre from a rabbit psoas muscle.
BACKGROUND: Previous studies have shown the inhibitory effects of etomidate on polymorphonuclear leucocyte (PMN) function. No reports exist, however, regarding free intracellular amino acid metabolism, although physiological cell metabolism and basic cell functions rely upon a balanced intracellular amino acid content and the cell membrane-mediated separation of cellular amino acids from the extracellular plasma amino acid pool. Thus, in the current study, we evaluated the effects of etomidate on free intracellular amino acid metabolism in PMN. METHODS: With ethics committee approval, blood was withdrawn from 35 healthy volunteers and incubated (1 h) either with 0 microg/ml, 0.0156 microg/ml, 0.0625 microg/ml or 0.5 microg/ml of etomidate as well as with its additives (propylene glycol and Lipofundin MCT 10%). The PMN were separated using standardized Percoll-gradient and centrifugation procedure before deep-freezing and lyophilization techniques were employed. All PMN samples were dissolved in methanol/H2O, and the concentrations of free intracellular amino acids were monitored using both novel advanced PMN-separation and high-performance liquid chromatography techniques. RESULTS: Etomidate influenced important free amino acid profiles in PMN in a dose-dependent manner, indicating complex changes of cellular amino acid turnover. Neither propylene glycol nor Lipofundin MCT 10% changed free amino acid concentrations in PMN. CONCLUSIONS: For the first time, the effects of etomidate on free intracellular amino acid metabolism in PMN have been investigated. Our results draw attention to the biochemical pathways which may be involved in etomidate-induced alterations in PMN function and cellular immunocompetence.
Dynamic structural changes of macromolecules undergoing biochemical reactions can be studied using novel single molecule spectroscopy tools. Recent advances in applying such distance and orientation molecular rulers to biological systems are reviewed, and future prospects and challenges are discussed.
AIMS: To examine the consistency and/or variability of gender differences in drinking behavior cross-culturally. DESIGN, SETTING, PARTICIPANTS: Women's and men's responses in 16 general population surveys from 10 countries, analyzed by members of the International Research Group on Gender and Alcohol. MEASUREMENTS: Comparable measures of drinking, versus abstention, typical drinking frequencies and quantities, heavy episodic drinking, intoxication, morning drinking, and alcohol-related family and occupational problems. FINDINGS: Women and men differed little in the probability of currently drinking versus abstaining, but men consistently exceeded women in typical drinking frequencies and quantities and in rates of heavy drinking episodes and adverse drinking consequences, while women were consistently more likely than men to be life-time abstainers. In older age groups, both men and women drank smaller quantities of alcohol and were more likely to stop drinking altogether, but drinking frequencies did not change consistently with age. CONCLUSIONS: A theoretical synthesis proposes that gender roles may amplify biological differences in reactions to alcohol, and that gender differences in drinking behavior may be modified by macrosocial factors that modify gender role contrasts.
Mitochondrial haplotype diversity in seven Portuguese populations of brown trout, Salmo trutta L., was investigated by sequencing the 5' end of the mitochondrial DNA (mtDNA) control region. Five new haplotypes were described for this species, each two to three mutational steps distant from the common north Atlantic haplotype. Significant population subdivision of mtDNA haplotypes was also apparent. Based on these results, as well as on published data describing the distribution of both mtDNA haplotypes and allozyme alleles throughout Europe, the postglacial recolonization of northern Europe was re-evaluated. It is argued that the available data do not support the contribution of two major glacial refugia (southwest Atlantic and Ponto-Caspian Basin) to this postglacial recolonization, as proposed in a recently published model. The unique genetic architecture of Portuguese brown trout within the Atlantic-basin clade of this species represents a highly valuable genetic resource that should be protected from introgression with nonendemic strains of hatchery fish.
PURPOSE: To depict the central and peripheral pulmonary vessel anatomy with real-time radial MR scanning without respiratory control. METHODS: Three healthy volunteers and one patient with pulmonary embolism proven by spiral CT angiography were studied with a 1.5 T MR imaging system. First, a breath-hold, contrast-enhanced MR angiography was performed for comparison of accuracy. Gradient echo images (TR 16 ms, TE 4 ms, flip angle 18 degrees) were obtained applying a combination of radial scanning and the sliding window reconstruction technique. A dedicated back-projector allowed data reconstruction in real-time with a frame rate of 20 images per second. Scanning was performed during free breathing. RESULTS: The described technique depicted the central and peripheral portions of the normal pulmonary anatomy with comparable image quality as the 3D contrast-enhanced angiography. Visualization of the pulmonary emboli as demonstrated by spiral CT was possible. CONCLUSION: Real-time radial scanning allows promising image acquisition of the pulmonary vasculature without respiratory control. Further technical improvements and clinical trials are required to evaluate its role in the diagnosis of vascular pathologies.
The role of tumor necrosis factor alpha (TNF alpha) and its type I receptor (TNFRI) in structural luteolysis was investigated. A semiquatitative reverse-transcription polymerase chain reaction (RT-PCR) was used to characterize the pattern of TNFRI mRNA expression within the corpus luteum (CL) throughout the estrous cycle and its cellular distribution. Increase in TNFRI mRNA levels was recorded both in regressed luteal tissue and in CL of cows injected with prostaglandin F(2 alpha). All three major cell types composing the CL, steroidogenic (large and small) and endothelial cells expressed the TNFRI gene. A densitometric analysis of TNFRI mRNA expression revealed that resident endothelial cells had significantly higher levels of TNFRI mRNA than steroidogenic luteal cells. The physiological effects associated with TNFRI expression were investigated in the various luteal cell types. TNF alpha-induced programmed cell death (PCD) in dose- and time-dependent manners of cultured luteal endothelial cells (LECs) but not of in vitro luteinized steroidogenic cells. Several lines of evidence are provided to show that progesterone regulates luteal cell survival: 1) CL and LECs express progesterone receptor mRNA, 2) physiological levels of the steroid abolished TNF alpha-induced PCD of LECs, and 3) progesterone-producing cells are protected from PCD. In conclusion, this study suggests that TNF alpha-induced PCD during structural luteolysis is mediated by TNFRI, primarily affects endothelial cells, and that the decline in progesterone, preceding structural luteolysis, is a prerequisite for the initiation of apoptosis in endothelial cells.
BACKGROUND: The authors applied an optimization model (direct search) to find the optimal combination of bupivacaine dose, fentanyl dose, clonidine dose, and infusion rate for continuous postoperative epidural analgesia. METHODS: One hundred ninety patients undergoing 48-h thoracic epidural analgesia after major abdominal surgery were studied. Combinations of the variables of bupivacaine dose, fentanyl dose, clonidine dose, and infusion rate were investigated to optimize the analgesic effect (monitored by verbal descriptor pain score) under restrictions dictated by the incidence and severity of side effects. Six combinations were empirically chosen and investigated. Then a stepwise optimization model was applied to determine subsequent combinations until no decrease in the pain score after three consecutive steps was obtained. RESULTS: Twenty combinations were analyzed. The optimization procedure led to a reduction in the incidence of side effects and in the mean pain scores. The three best combinations of bupivacaine dose (mg/h), fentanyl dose (microg/h), clonidine dose (microg/h), and infusion rate (ml/h) were: 9-21-5-7, 8-30-0-9, and 13-25-0-9, respectively. CONCLUSIONS: Given the variables investigated, the aforementioned combinations may be the optimal ones to provide postoperative analgesia after major abdominal surgery. Using the direct search method, the enormous number of possible combinations of a therapeutic strategy can be reduced to a small number of potentially useful ones. This is accomplished using a scientific rather than an arbitrary procedure.