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At least 307 records · Page 17Linked to original sources
PubMed1999

Muscle and bone-aging and space.

One of the major concerns of aging, but also during and after spaceflight, is loss of muscle and bone mass. In aging, this is associated with an increasing risk of fractures. Recently, the possibility of aged and aging astronauts has been arisen. Thus considering the perspectives of aging and space we want to discuss, in how far the adaptations during spaceflight and during aging interfere. In other words: does spaceflight push the astronauts along the irreversible axis of aging? And which of the spaceflight effects will be reversible? Bones adapt to their mechanical function. For convenience, a simple model has been proposed: Bone, as a 'mechanostat', keeps the strains within certain thresholds, namely one threshold for modeling, i.e. formation of new bone, and one for remodeling, i.e. repair and removal. These thresholds are usually expressed as strains. A crucial role in physiological strain detection is obviously played by the osteocytes. The largest forces in the musculo-skeletal systems arise from muscle contractions. The reason for this are the poor levers, against which the muscles pull. For example: during a one-leg vertical jump, a young subject (body weight 70 kg) exerts a vertical ground reaction force of 2500 N. Due to the lever ratio of os calcis and forefoot around the tibio-talar joint, the calf muscles must exert a force 3 times greater, so that together with the body weight the bones of the lower leg are loaded with 10000 N, i.e. 14 times the body weight. Accordingly, good correlations can be observed between muscle strength and bone strength, or muscle mass and bone mass. It is therefore reasonable to discuss the accumulated knowledge about loss of muscle and bone in a combined approach. In this respect, two points must be considered: (i) for structural adaptation of bone, the muscular variable of interest arc force and rate of force development, but not power, and (ii) women before menopause have a greater bone to muscle ratio than men.

Adaptation, Physiological↗
PubMed1995

[Not Available].

E. F. Geoffroy's table of different relations ("rapports") between different chemical substances is mainly based on empirical knowledge accumulated in 16th and 17th century metallurgy and pharmacy. The substances listed in the left half of the table were basic for the formation of salts which were produced for medical ends in the chemical-pharmaceutical practice of the 17th century. The right half of the table refers to substances and operations of metallurgy which had already been described in the metallurgical writings of the 16th century. Even Geoffroy's ordering of the substances within the columns of his table has its origin in metallurgical and pharmaceutical practice. The key concept of the conceptual framework underlying the table and its commentary is the concept of chemical compound which emerged at the end of the 17th century. Geoffroy extends the range of application of this concept, which was first limited to chemical artefacts, to include natural bodies. Eliminating the peripatetical distinction between natural bodies and chemical artefacts he formulates a new research program, consisting in the determination of the "laws" of the relations ("rapports") between different chemical substances.

Chemistry↗
PubMed2001

Developing an approach to evaluate the use of neoplastic cells as vaccine substrates.

Advances in technology, emerging infectious diseases and accumulating knowledge of the mechanisms of neoplastic development are stimulating the need to develop a regulatory management plan that can be used to evaluate different types of neoplastic cells as possible substrates for vaccine development. To address this challenge, CBER is developing an approach, based on issue identification, issue-based model development and validation, and, where possible, a quantitative risk evaluation, as a basis for regulatory guidance on the use of neoplastic cell substrates for the manufacture of viral vaccines. The issues or concerns that have been identified with the use of neoplastic cell substrates include vaccine contamination with viable human tumour cells or adventitious agents, the possible risks associated with residual cell-substrate DNA or proteins in the vaccine, possible vaccine virus interactions with the cell substrate, and possible uncertainties associated with the instability of the neoplastic cell genome.

Neoplasms↗
PubMed2002

Medical genetics: 2. The diagnostic approach to the child with dysmorphic signs.

Dysmorphology is the branch of clinical genetics in which clinicians and researchers study and attempt to interpret the patterns of human growth and structural defects. Reaching an accurate diagnosis for children with dysmorphic signs is important to their families, because it makes available all the accumulated knowledge about the relevant condition and may provide the family with the opportunity for interaction with patient or parent support groups. I show in this review that reaching a diagnosis in dysmorphology involves an approach that is not fundamentally different from that of other medical disciplines. Cytogenetic and molecular techniques continue to improve our ability to make precise syndrome diagnoses; however, these tests are expensive and should be used selectively.

Adolescent↗
PubMed2002

Abiotic hydrolysis of pesticides in the aquatic environment.

Hydrolysis of a pesticide is basically a reaction with a water molecule involving specific catalysis by proton or hydroxide, and sometimes inorganic ions such as phosphate ion, present in the aquatic environment that play a role in general acid-base catalysis. In this review, the basic profiles of hydrolysis such as pH and temperature dependencies are clarified for each class of pesticides together with typical reaction mechanisms. Although these hydrolytic profiles depend on the chemical structure and functional group(s) of a pesticide molecule, they are not always consistent within a chemical class of pesticides. For example, organophosphorus pesticides are primarily susceptible to alkaline hydrolysis with less acidic catalysis, but some of phosphorodithioates are found to be acid labile. In the case of carbamates, the pKa value of a leaving group is known to control their hydrolysis mechanism, whether BAC2 or E1cB. As one of the predictive approaches, the linear free-energy relationship has been successfully applied to hydrolysis of a series of organophosphorus and carbamate pesticides under conditions in which the reaction mechanism does not change. However, it still seems advantageous to estimate a priori hydrolytic profiles of pesticides, either because there is insufficient precision in the methodology or the chemical class is limited, or because of pH and temperature dependencies of hydrolysis. Therefore, it would still be practical, for the present, when investigating abiotic hydrolysis of a new pesticide that a laboratory study be effectively designed on the basis of accumulated knowledge of hydrolytic profiles for the essential chemical structure and functional groups and conducted to obtain pH- and temperature-rate profiles. Various instrumental techniques have been applied to chemical identification of degradates, leading to clarification of the reaction mechanisms involved, but greater use of computational methods such as ab initio and semiempirical molecular orbital calculations would be highly recommended for better understanding at a molecular level by considering the solvent effect (hydration). The chemical identification of degradates is usually cumbersome and challenging, especially when these are unstable species. The recent progress of LC-MS allows unstable or polar degradates to be identified more efficiently, and such knowledge will help researchers to hydrolytic processes more easily understand. Although testing guidelines being harmonized throughout the world afford valuable information on the basic profiles of hydrolysis, recent investigations on interactions of pesticides with dissolved organic matter and catalytic or inhibitive effects caused by metal ions, metal oxides, and clay seem to raise the question as to what degree laboratory and field data differ and how laboratory data can be more precisely extrapolated to field data. Moreover, pesticides are usually applied as a suitable formulation, and thus the effects of surfactants and other formulation reagents on hydrolysis should be examined in more detail. To assess the fate and impact of pesticides and their degradates in real aquatic environments, these concerns should be further examined using the various analytical techniques together with simulation models.

Environmental Monitoring↗
PubMedDate not supplied

[Can an organism select new valuable information from environment].

The process of selecting new information by the organism ("learning") was studied. To take a decision, key patterns have to be set a priori, and so knowledge accumulation (learning) based on pattern recognition is impossible. It was shown that the only physical process that, takes place during the emergence of an external signal is the triggering of a priori programmes. An equivalent biophysical scheme of pattern recognition and taking the decisions by the organism was developed in which a signal received by the receptor leads to the synthesis of one of possible catalysts. The catalyst starts up the corresponding thermodynamic process. The information contained in the organism does not change during this process.

Animals↗
PubMed2002

An overview of vagal airway receptors.

Breathing is critically depending on a variety of sensory feedbacks from multiple sources for its optimal performance. The sensory information from the lung and airways probably provides one of the most important feedbacks to adjust the respiratory controller to generate optimal breathing movements. Since Breuer and Hering made the seminal report regarding role of the vagus nerve in control of breathing in 1868, airway sensory receptors have been a subject for intensive and extensive studies. After more than a century investigation, our knowledge accumulates immensely, however, our understanding of the nature of these sensory receptors is still far from complete. This brief review provides an overview on this topic.

Humans↗
PubMed2002

The role of tumor suppressor genes in esophageal cancer.

Esophageal cancer remains one of the 10 most common cancers worldwide. Although patients with early lesions have a reasonable prognosis, most patients present with advanced disease resulting in an overall 5-year survival of 5-10%. Therefore, the current challenges in the management of esophageal cancer are to obtain a better understanding of the underlying molecular biological alterations to provide new treatment options. During the development of esophageal cancer, there is progression from a premalignant epithelium to a neoplasm that frequently demonstrates a heterogeneous mix of genetic alterations. The vast majority of esophageal cancers have inactivation of the p53 and p16 genes at an early stage followed by defects in genes such as APC, Rb and cyclin D1 at later stages of progression. There is also mounting evidence that numerous, specific regions throughout the genome are frequently lost in these cancers. As a result, we will in the next decade, likely see the discovery and characterizations of novel tumor suppressor genes that may be important in the development of esophageal cancer. The accumulating knowledge about the inactivation of the tumor suppressor genes could ultimately provide us with objective diagnostic tools, more accurate markers for prediction of malignant transformation from premalignant epithelium and facilitate the introduction of novel therapeutic options for the management of esophageal cancer.

Esophageal Neoplasms↗
PubMed2002

"With much nausea, loathing, and foetor": William Harvey, dissection, and dispassion in early modern medicine.

In early modern England accumulating knowledge of normal and morbid anatomy through dissecting the human body not only led to a better understanding of nature, but also defined the identity of the people who engaged in this activity. This essay analyses the relationship between systemically dismembering the dead and how this pursuit shaped the attitudes and emotions of early modern medical men toward the living. I focus on the most famous anatomist in early modern Britain - the discoverer of the circulation of the blood, William Harvey (1578-1657).

Anatomy↗
PubMed2002

Reactive Oxygen and Nitrogen Oxide Species-induced Stress, a Major Intrinsic Factor Involved in Carcinogenic Processes and a Possible Target for Cancer Prevention.

Reactive oxygen and nitrogen oxide species and their inducing stress are involved in a variety of physiological and pathological phenomena in aerobes, including humans. For multistage carcinogenic processes, reactive oxygen and nitrogen oxide species-induced stress (RONOSS) serves as a major intrinsic factor and is involved in every step. This means that free radicals, RONOSS and their inducing downstream events may be targets for cancer prevention. It is therefore of importance to elucidate the mechanisms underlying the participation of RONOSS in carcinogenesis and to apply the obtained results for establishment of strategies to control cancer development. Despite the large body of accumulated knowledge due to worldwide efforts dealing with this research field, there still remain numerous uncertainties. In this mini-review, we introduce two examples of such efforts, one concerning a renal carcinogen KBrO(3) and the other dealing with hepatocarcinogenesis caused by a choline-deficient, L-amino acid-defined diet, in order to give some idea about the current understanding of the roles of RONOSS in carcinogenesis.

Journal Article↗
PubMed2003

Molecular diagnosis of dysmorphic syndromes and inherited metabolic disorders in Thailand.

While dysmorphic syndromes and inherited metabolic disorders are individually rare, they collectively account for a significant proportion of illnesses, especially in children. They present clinically in a wide variety of ways, involving virtually any organ or tissue of the body making them relatively difficult to diagnose. However, reaching an accurate diagnosis for children with dysmorphic features and suspected inherited metabolic disorders is important to them and their families both for treatment and for the prevention of disease in other family members. It also makes all the accumulated knowledge available about the relevant condition. Molecular techniques have kindled a revolution in the diagnosis of genetic disorders, including dysmorphic syndromes and inherited metabolic disorders. Molecular methods essentially avoid problems of other techniques. This review exemplifies some of the diseases that can be diagnosed by molecular tools available in Thailand and illustrates some of their benefits.

Genetic Diseases, Inborn↗
PubMedDate not supplied

[Memory disorders in schizophrenia].

The current interest in memory disorders in schizophrenia results from the way perceptions of schizophrenia--whose organic origin is becoming increasingly evident--and memory--according to which there exist not one, but several memories--have developed. Memory disorders in the schizophrenic cannot be considered in isolation from knowledge accumulated in other areas of the cognitive and neuro-sciences; a more detailed understanding of these disorders requires a comparison of the different cognitive approaches, both with each other and with the neurobiological and clinical approaches, so that they can be integrated. Despite numerous methodological and conceptual difficulties, it now appears to have been established that the schizophrenic's memory deficit should be seen in the context of a wider cognitive deficit, that the memory tasks are not all disturbed and that the memory deficit cannot be identified with one specific form of memory. Thus, iconic formation, short-term memory in the traditionally accepted sense and implicit memory are hardly, if at all, affected; in contrast, the early processing of information, working memory and explicit memory are disturbed, probably to the extent that they require the implementation of strategies to organise the information to be memorized. Finally, in certain tasks, such as those evaluating latent inhibition or negative priming, schizophrenics perform better than normal subjects, suggesting that schizophrenics' cognitive deficit is localised. This profile of memory disorders is compatible with a dysfunction predominating in the frontal and temporo-hippocampal regions. Neuroleptics and anticholinergics have opposite effects on cognitive and mnesic performance, which is improved by the former and aggravated by the latter. The influence of clinical symptoms, positive or negative, institutionalisation of patients and chronic tardive dyskinesia is unclear. Among the theoretical proposals put forward to account for the observed disorders, those relating to a disturbance of the action planning process and to that of the internal representation of context are compatible with the observed memory disorders. All the clinically derived data and those produced by the cognitive and neurosciences indicate a need to reformulate the links between memory, selective attention and evaluation of the relevance of a stimulus, to develop a general model of the reciprocal interactions between cognition and affectivity and to look for the origin of a pathology as complex as schizophrenia, not in a local lesion in an isolated cerebral structure but in a disturbance of the dynamic interactions within a functional, parallel and distributed network of broadly interconnected regions.

Antipsychotic Agents↗
PubMed2003

Reasonable choice of surgical procedures for patients with portal hypertension.

OBJECTIVE: To assess individualized therapeutic protocol for patients with portal hypertension on the basis of accumulated knowledge about the mechanism of portal hypertension. DATA SOURCES: Patients data on shunt and other surgical procedures from Ruijin Hospital, Shanghai, China and the published papers. RESULTS: The direction of blood flow of the collateral vessels in the gastro-splenic region is an important factor in deciding surgical strategy because there is a close relationship between surgical risk and the classification of liver function. Clinically it is confirmed that each patient needs an individualized surgical procedure and that prophylactic operation is suitable for patients with splenomegaly, splenism associated with serious esophageal varices and hemorrhagic tendency under endoscopy but acceptable liver function. The shunt diameter (SD) (SD = 0.67 x PVD) is determined in our patients according to individualized hemodynamics. The rehemorrhagic rate after shunt being higher than that in others may be related to lesioned gastric mucosa caused by portal hypertension or bleeding and temporary melena. This finding is good for prevention of hepatic encephalopathy. The life quality and labor ability of patients will be improved because of hepatopetal flow in the portal vein. With strict indications for reoperation, selective operation is performed as soon as possible when hemorrhage is controlled conservatively and liver function improved. Once the patient with cirrhosis associated with portal hypertension is scheduled for liver transplantation, treatment of hemorrhage should aim to keep the patient in good condition and to avoid the protocol that may be disadvantageous to liver transplantation in the future. CONCLUSION: Surgical procedures for patients with portal hypertension should follow the principle of individualization. To obtain the best outcome, the choice of reasonable surgical procedure is expected.

Humans↗
PubMed1992

[Metabolism of trace elements in healthy and sick children. I. Health status].

The oligo-elements or trace elements have acquired a major importance in the knowledge concerning corporal composition and in the comprehension of their metabolic participation in organic processes. Today, thanks to the technological and scientific progress reached by modern pediatrics, the studies made at cellular level have advanced to a molecular level, which will in the future be, without doubt, the bridge that will lead into the atomic level. In addition, this review will briefly summarize several facts of the knowledge accumulated up to now, regarding: 1. The nutritional aspects of these oligo-elements; 2. Its biological functions in healthy condition, especially in children; 3. Their respective nutritional requirements.

Age Factors↗
PubMed2003

The Israel Penn International Transplant Tumor Registry.

The Israel Penn International Transplant Tumor Registry is literally the world's premier repository of information on patients who have developed malignancies after organ transplants. The administrators of the Registry not only collect information but also provide consulting services based on the accumulated knowledge that the Registry contains. By creating a secure Web-based front end, we have made it possible for the Registry to keep pace with its burgeoning international caseload.

Humans↗
PubMed1992

Molecular physiology of renal potassium channels.

The application of patch-clamp technique to the study of ion channels showed the enormous diversity of K channels. In the kidney, K channels play an major role in transepithelial K transport, in the regulation of vascular tone, and in cellular proliferation. In the last 5 years, the use of powerful genetic and molecular biological techniques has provided an understanding of the molecular structure of some types of K channels. Although much work remains to be done in this area, the greater challenge will be to integrate the molecular information with the extensive physiological data already available. Finally, the rapidly accumulating knowledge of K channel structure, and the recent appreciation of their possible role in important disease states, such as hypertension, make the study of K channels very exciting.

Animals↗
PubMed2004

[Passive smoking: an environmental health risk].

The supposed health risks of passive smoking are leading to increasingly restrictive legislation on smoking. Tobacco smoke is undoubtedly irritating to the eyes, nose and throat of non-smokers, but politicians wanted more spectacular facts. There is some evidence of fatal consequences of passive smoking, particularly increases in lung cancer and heart-disease mortality among non-smokers exposed to tobacco smoke. Most studies compare the non-smoking partners of smokers and non-smokers. The observed relative risks are too small to be ascertained reliably. The more than twentyfold increased risk of lung cancer among smokers and the presence of tobacco-related metabolites in non-smokers' body fluids lend support to the hypothesis that passive smoking causes lung cancer. The less than twofold increased risk of heart disease among smokers and the documented social-risk factors cast doubt on the validity of the increased risk of heart disease in non-smokers, associated with having a smoking partner. The precautionary principle regulates potential environmental health hazards: the suspicion and the hazard must be sufficiently serious to take legislative action. There is ample evidence of tobacco smoke's carcinogenicity and the accumulated knowledge strongly suggests that the legal threshold of an acceptable environmental health risk has been exceeded.

Cardiovascular Diseases↗
PubMed2004

[Genetic background of epilepsies].

In this article we review epilepsies with monogenic inheritance. Most of these diseases are caused by abnormal function of ligand- and voltage gated ion channels caused by a genetic defect, therefore belonging to the channelopathies. From the inherited epilepsies the genetics of the autosomal dominant partial epilepsies is clarified the best. Mutations of the nicotinic acetylcholine receptor subunits are found in familial nocturnal frontal lobe epilepsy, while defects in the voltage gated potassium channels (KCNQ2 and KCNQ3) have been identified in benign familial neonatal convulsions. Familial temporolateral epilepsy was associated with mutations of a tumor suppressor gene. From the generalized epilepsies, the syndrome of generalized epilepsy with febrile seizures plus (GEFS+) can be caused by mutations of the sodium channel subunits and of the GABAA receptor subunits. These important results would probably lead to new findings in the genetics of the more common forms of idiopathic generalized epilepsies, which have presumed polygenic origin. Although without definite conclusions, sodium channel and GABA receptor dysfunction is presumed. The accumulated knowledge about channelopathies enables insight to the cellular mechanism of epileptogenesis as well.

Chromosomes, Human, X↗