RESUMO
The records of the sterilization processes of 2 practices from the period 2012-2019 were analysed. The study evaluated whether sterilization processes with an additional steam penetration test gave a complete colour change. A total of 13,923 sterilization runs were evaluated. Reasons for unsuccessful sterilization runs were damp instruments (35%) or an error message on the sterilization apparatus display (35%). Of the 635 sterilization runs with the additional TST strip a complete colour change was observed in all cases. Of the 250 sterilization runs using an additional Helix Test, an incomplete colour change was observed in 2 cases. Based on this retrospective analysis, carrying out an additional test (TST strip or Helix Test) on a weekly basis did not appear to contribute to the detection of irregularities. Visual evaluation and checking the display following the sterilization process did do so.
Assuntos
Vapor , Esterilização , Humanos , Estudos RetrospectivosRESUMO
BACKGROUND: Mucopolysaccharidosis type IIIB (MPS IIIB) is a rare genetic disorder in which the deficiency of the lysosomal enzyme N-acetyl-α-glucosaminidase (NAGLU) results in the accumulation of heparan sulfate (HS), leading to progressive neurocognitive deterioration. In MPS IIIB a wide spectrum of disease severity is seen. Due to a large allelic heterogeneity, establishing genotype-phenotype correlations is difficult. However, reliable prediction of the natural course of the disease is needed, in particular for the assessment of the efficacy of potential therapies. METHODS: To identify markers that correlate with disease severity, all Dutch patients diagnosed with MPS IIIB were characterised as either rapid (RP; classical, severe phenotype) or slow progressors (SP; non-classical, less severe phenotype), based on clinical data. NAGLU activity and HS levels were measured in patients' fibroblasts after culturing at different temperatures. RESULTS: A small, though significant difference in NAGLU activity was measured between RP and SP patients after culturing at 37 °C (p < 0.01). Culturing at 30 °C resulted in more pronounced and significantly higher NAGLU activity levels in SP patients (p < 0.001) with a NAGLU activity of 0.58 nmol.mg-1.hr-1 calculated to be the optimal cut-off value to distinguish between the groups (sensitivity and specificity 100 %). A lower capacity of patients' fibroblasts to increase NAGLU activity at 30 °C could significantly predict for the loss of several disease specific functions. CONCLUSION: NAGLU activity in fibroblasts cultured at 30 °C can be used to discriminate between RP and SP MPS IIIB patients and the capacity of cells to increase NAGLU activity at lower temperatures correlates with disease symptoms.
Assuntos
Acetilglucosaminidase/metabolismo , Fibroblastos/metabolismo , Mucopolissacaridose III/metabolismo , Mucopolissacaridose III/patologia , Acetilglucosaminidase/genética , Adolescente , Adulto , Idoso , Biomarcadores/metabolismo , Células Cultivadas , Feminino , Fibroblastos/patologia , Estudos de Associação Genética , Heparitina Sulfato/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Mucopolissacaridose III/genética , Mutação/genética , Índice de Gravidade de Doença , Adulto JovemRESUMO
Many studies have used visual adaptation to investigate how recent experience with faces influences perception. While faces similar to those seen during adaptation phases are typically perceived as more 'normal' after adaptation, it is possible to induce aftereffects in one direction for one category (e.g. female) and simultaneously induce aftereffects in the opposite direction for another category (e.g. male). Such aftereffects could reflect 'category-contingent' adaptation of neurons selective for perceptual category (e.g. male or female) or 'structure-contingent' adaptation of lower-level neurons coding the physical characteristics of different face patterns. We compared these explanations by testing for simultaneous opposite after effects following adaptation to (a) two groups of faces from distinct sex categories (male and female) or (b) two groups of faces from the same sex category (female and hyper-female) where the structural differences between the female and hyper-female groups were mathematically identical to those between male and female groups. We were able to induce opposite aftereffects following adaptation between sex categories but not after adaptation within a sex category. These findings indicate the involvement of neurons coding perceptual category in sex-contingent face aftereffects and cannot be explained by neurons coding only the physical aspects of face patterns.
Assuntos
Cognição , Face , Percepção Visual , Feminino , Humanos , Masculino , Fatores SexuaisRESUMO
To study the physical properties of renal tubular basement membranes directly, the epithelial layer of single isolated perfused rabbit proximal convoluted, proximal straight, and cortical collecting tubules was removed with sodium desoxycholate. Tubular segments were perfused using micropipets. The distal end of each segment was occluded in order to simplify the measurement of transmembrane water flow. The relation between outer tubular diameter and applied transmural pressure was identical in intact tubules and their respective isolated tubular basement membranes indicating that the basement membrane determines tubular distensibility. Young's modulus for basement membranes from all tubular segments corresponded to that of tendon collagen. Membrane hydraulic conductivity was measured in two ways: (a) from the rate of transmural flow in response to an applied difference in hydrostatic pressure and, (b) from the rate of transmural flow in response to a difference in colloid osmotic pressure. The hydraulic conductivity of tubular basement membranes was 300-800 times greater than that of the intact epithelial layer. Basement membrane hydraulic conductance was similar to that of peritubular and glomerular capillaries in vivo. The hydrostatic conductance of tubular basement membranes exceeded the osmotic conductance by 3-10-fold owing largely to the fact that the membranes were moderately permeable to the osmotic solute (albumin). In view of these findings we suggest that oncotic and hydrostatic pressure may play an important role in the movement of tubular absorbate from the epithelial compartment into the renal interstitium.
Assuntos
Membrana Basal/fisiologia , Túbulos Renais/fisiologia , Albuminas/metabolismo , Animais , Transporte Biológico Ativo , Feminino , Pressão Osmótica , Perfusão , Coelhos , Soroalbumina Radioiodada , Trítio , Equilíbrio HidroeletrolíticoRESUMO
PURPOSE: The optimum response to the different stages of a major burns incident is still not established. The fire in a café in Volendam on New Year's Eve 2000 was the worst incident in recent Dutch history and resulted in mass burn casualties. The fire has been the subject of several investigations concerned with organisational and medical aspects. Based on the findings in these investigations, a multidisciplinary research group started a consensus study. The aim of this study was to further identify areas of improvement in the care after mass burns incidents. DESIGN/METHODOLOGY/APPROACH: The consensus process comprised three postal rounds (Delphi Method) and a consensus conference (modified nominal group technique). The multidisciplinary panel consisted of 26 Dutch-speaking experts, working in influential positions within the sphere of disaster management and healthcare. FINDINGS: In response to the postal questionnaires, consensus was reached for 66 per cent of the statements. Six topics were subsequently discussed during the consensus conference; three topics were discussed within the plenary session and three during subgroup meetings. During the conference, consensus was reached for seven statements (one subject generated two statements). In total, the panel agreed on 21 statements. These covered the following topics: registration and evaluation of disaster care, capacity planning for disasters, pre hospital care of victims of burns disasters, treatment and transportation priorities, distribution of casualties (including interhospital transports), diagnosis and treatment and education and training. ORIGINALITY/VALUE: In disaster medicine, the paper shows how a consensus process is a suitable tool to identify areas of improvement of care after mass burns incidents.
Assuntos
Queimaduras/terapia , Conferências de Consenso como Assunto , Planejamento em Desastres/normas , Serviços Médicos de Emergência/normas , Incêndios , Adulto , Queimaduras/epidemiologia , Técnica Delphi , Planejamento em Desastres/organização & administração , Serviços Médicos de Emergência/organização & administração , Humanos , Países Baixos/epidemiologia , Garantia da Qualidade dos Cuidados de Saúde , Sistema de Registros , Restaurantes , Transporte de Pacientes/normasRESUMO
UNLABELLED: Fires involving mass burn casualties require extreme efforts and flexibility from the regular health care system. The café fire in Volendam, which occurred shortly after midnight on the first of January 2001, resulted in the worst indoor mass burns incident in Dutch history. During the extensive medical evaluation of this disaster, it became obvious that information on similar incidents is relatively scarce in the literature. This article systematically reviews the existing information in the medical literature on indoor fires and provides findings and knowledge used in the evaluation of the medical management after indoor fires and for future mass burn casualty preparedness, mitigation and response. METHODS: A literature review was undertaken for burn disasters with characteristics similar to the indoor Volendam fire disaster. In all fires, the following aspects were investigated: characteristics of the fire; the initial emergency response; triage and on-site treatment; primary and secondary distribution; hospital admission; severity of the sustained injuries and mortality. RESULTS: A total of nine similar indoor fires were selected. The number of people involved was reported in seven fires (range 137-6000). All reports provided the mortality rate (range 1.4% to over 50%). Data regarding the emergency response could be collected in half of the studies. On-scene triage was performed in five fires. The number of hospitals participating in the primary distribution ranged from 1 to 19. Except for the Volendam fire, all patients were primarily distributed to general hospitals. CONCLUSION: Characteristics of indoor fires, which are relevant for disaster preparedness, mitigation and response are not frequently reported in medical literature. The current articles on indoor fires, mainly report on numbers of casualties and the mortality. Limited data are available to provide insight in the characteristics of management and medical treatment and to come up with suggestions for improvement of future burn incidents management. The evaluation of disasters should be based on uniform methods and structured reports and effective record keeping is essential to achieve this.
Assuntos
Queimaduras/terapia , Planejamento em Desastres/organização & administração , Desastres , Serviços Médicos de Emergência/organização & administração , Incêndios/estatística & dados numéricos , Queimaduras/mortalidade , Serviços Médicos de Emergência/estatística & dados numéricos , Hospitalização/estatística & dados numéricos , Humanos , Países Baixos/epidemiologia , Transporte de Pacientes/estatística & dados numéricos , TriagemRESUMO
AIM OF STUDY: The café fire at Volendam occurred shortly after midnight on the first of January 2001 and resulted in one of the worst mass burn incidents in recent Dutch history. The aim of this study was to provide insight into medical and organisational requirements of a major burns incident. METHODS: Shortly after the fire, two university hospitals and a burn center in the region of the accident developed a plan for evaluation of medical care given during and after this major burn incident. A multidisciplinary research group investigated the management of victims at the scene, in the emergency departments (ED) and during admission in the hospitals. All 245 casualties were included in this study. RESULTS: A brief severe fire occurred in a crowded cafe with around 350 young visitors on a small embankment of a relatively isolated town, resulting in a unusually high number of severely injured burn victims. Four died immediately. The ensuing rescue effort was hampered by poor access and chaotic circumstances. At the scene of the incident, mobile medical teams ensured orderly transport and treatment priority for the injured. There were 245 victims with a median total body surface area burned of 12%. Inhalation injury was present in 96 patients. A total of 182 victims were admitted, with 112 to intensive care. Ten patients died in the hospital. Seventy-eight patients were secondarily transported, many to specialised centers in the Netherlands and abroad. In total, 36 hospitals in three countries participated. CONCLUSION: An incident with high numbers of burn victims poses a challenge to any health care system. The difficult circumstances at the site demonstrated the need for robust organisational structures. The primary and secondary distribution of patients required coordination, general hospitals were able to provide initial medical care to these major burn casualties.
Assuntos
Queimaduras/terapia , Incêndios/estatística & dados numéricos , Adolescente , Adulto , Unidades de Queimados/estatística & dados numéricos , Queimaduras/epidemiologia , Serviços Médicos de Emergência/estatística & dados numéricos , Tratamento de Emergência , Feminino , Hospitais/estatística & dados numéricos , Humanos , Masculino , Países Baixos , Admissão do Paciente/estatística & dados numéricos , Lesão por Inalação de Fumaça/epidemiologia , Lesão por Inalação de Fumaça/terapia , Transporte de Pacientes/estatística & dados numéricos , Triagem/organização & administraçãoRESUMO
Intracellular calcium ([Ca2+]i) and hydrogen ion concentrations (pHi) are important regulators of cell function. Those ions also may interact and it is important, therefore, to measure their concentrations simultaneously. In the present studies we used a system developed for that purpose, a fluorescent emission ratio technique for simultaneous analysis of calcium (Indo-1) and pH (SNARF-1) in single cells at video rates, and determined if arginine vasopressin (AVP, 12.5 mumol/l) evoked [Ca2+]i and pHi signals interact in MDCK cells. We also employed a simple system for analysing the side specific (basolateral or apical) application of agonist to polarized cell layers on permeable membranes. AVP is found to evoke simultaneous changes in both pHi and [Ca2+]i. Basolateral application induced transient acidification, followed by partial recovery, and a [Ca2+]i transient with kinetic pattern similar to that of the pHi. Apical application also caused a mirror image pHi and [Ca2+]i pattern but of smaller magnitude (no peak). Selective removal of extracellular calcium ([Ca2+]e) or sodium ([Na+]e) dissociated the pHi and [Ca2+]i responses in both cases. Na+e removal abolished the pHi changes, but not the [Ca2+]i transients. [Ca2+]e removal abolished the [Ca2+]i changes and reduced, but did not abolish, the pHi responses. Thus, AVP induces pHi changes which are modified by calcium while calcium signalling is not modified by changes in pHi.
Assuntos
Arginina Vasopressina/farmacologia , Cálcio , Animais , Células Cultivadas , Concentração de Íons de Hidrogênio , Microscopia de FluorescênciaRESUMO
OBJECTIVE: To assess the efficacy and safety of clinafloxacin as a single agent for the empirical treatment of febrile episodes and bacterial infections in neutropenic cancer patients. METHODS: An open label, active-controlled, randomized, parallel treatment, multicenter study was conducted where clinafloxacin monotherapy was compared to the combination of ceftazidime plus amikacin (plus optional vancomycin or teicoplanin). Four hundred and nineteen patients were randomized to receive either intravenous clinafloxacin 200 mg every 12 h or intravenous ceftazidime (2 g) iv every 8 h plus intravenous amikacin (15 mg/kg) per day in divided doses. All randomized patients were to receive a minimum of 48 h of primary study drug treatment, after which the primary treatment could be modified. Clinical and microbiological responses were evaluated at 7-21 days post-treatment after study treatment and long term (maximum 28 days), in intent-to-treat and modified intent-to-treat populations. RESULTS: Clinafloxacin and ceftazidime-amikacin were statistically equivalent for the 72-h defervescence rate, overall defervescence rate, time to defervescence, clinical success rate, by-pathogen microbiological eradication rate, and survival rate. Clinical cure was achieved in 84% (59/70) of patients who received clinafloxacin monotherapy. There were no significant differences between treatments in rates of adverse events or treatment discontinuation rates due to adverse events. CONCLUSIONS: Clinafloxacin appears to be an appropriate agent for empirical treatment in febrile neutropenic cancer patients.
Assuntos
Amicacina/uso terapêutico , Anti-Infecciosos/uso terapêutico , Infecções Bacterianas/tratamento farmacológico , Ceftazidima/uso terapêutico , Fluoroquinolonas , Neoplasias/complicações , Neutropenia/tratamento farmacológico , Adolescente , Adulto , Idoso , Amicacina/efeitos adversos , Antibacterianos/efeitos adversos , Antibacterianos/uso terapêutico , Anti-Infecciosos/efeitos adversos , Infecções Bacterianas/etiologia , Ceftazidima/efeitos adversos , Cefalosporinas/efeitos adversos , Cefalosporinas/uso terapêutico , Farmacorresistência Bacteriana , Quimioterapia Combinada/efeitos adversos , Feminino , Febre/tratamento farmacológico , Febre/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Neutropenia/etiologia , Teicoplanina/efeitos adversos , Teicoplanina/uso terapêutico , Resultado do Tratamento , Vancomicina/efeitos adversos , Vancomicina/uso terapêuticoAssuntos
Proteínas de Arabidopsis , Doenças das Plantas , Plantas/imunologia , Adaptação Fisiológica , Animais , Proteínas da Membrana Bacteriana Externa/metabolismo , Carbono/metabolismo , Ciclopentanos/metabolismo , Proteínas de Ligação a DNA/metabolismo , Insetos/patogenicidade , Nitrogênio/metabolismo , Oxilipinas , Doenças das Plantas/etiologia , Plantas/parasitologia , Receptor Cross-Talk , Ácido Salicílico/metabolismo , Transdução de SinaisAssuntos
Corpos Estranhos/diagnóstico , Bexiga Urinária , Adulto , Cistite/diagnóstico , Diagnóstico Diferencial , Humanos , MasculinoRESUMO
Findings from previous studies of hormone-mediated behavior in women suggest that raised progesterone level increases the probability of behaviors that will reduce the likelihood of disruption to fetal development during pregnancy (e.g. increased avoidance of sources of contagion). Here, we tested women's (N=52) sensitivity to potential cues to nearby sources of contagion (disgusted facial expressions with averted gaze) and nearby physical threat (fearful facial expressions with averted gaze) at two points in the menstrual cycle differing in progesterone level. Women demonstrated a greater tendency to perceive fearful and disgusted expressions with averted gaze as more intense than those with direct gaze when their progesterone level was relatively high. By contrast, change in progesterone level was not associated with any change in perceptions of happy expressions with direct and averted gaze, indicating that our findings for disgusted and fearful expressions were not due to a general response bias. Collectively, our findings suggest women are more sensitive to facial cues signalling nearby contagion and physical threat when raised progesterone level prepares the body for pregnancy.
Assuntos
Emoções/fisiologia , Expressão Facial , Ciclo Menstrual/psicologia , Reconhecimento Visual de Modelos/fisiologia , Progesterona/metabolismo , Adolescente , Adulto , Análise de Variância , Sinais (Psicologia) , Feminino , Humanos , Ciclo Menstrual/metabolismo , Comunicação não Verbal/psicologia , Comunicação Persuasiva , Estimulação Luminosa , Valores de Referência , Saliva/metabolismo , Percepção Visual/fisiologiaRESUMO
Women's preferences for masculinity in men's faces, voices and behavioral displays change during the menstrual cycle and are strongest around ovulation. While previous findings suggest that change in progesterone level is an important hormonal mechanism for such variation, it is likely that changes in the levels of other hormones will also contribute to cyclic variation in masculinity preferences. Here we compared women's preferences for masculine faces at two points in the menstrual cycle where women differed in salivary testosterone, but not in salivary progesterone or estrogen. Preferences for masculinity were strongest when women's testosterone levels were relatively high. Our findings complement those from previous studies that show systematic variation in masculinity preferences during the menstrual cycle and suggest that change in testosterone level may play an important role in cyclic shifts in women's preferences for masculine traits.
Assuntos
Beleza , Face , Saliva/química , Comportamento Sexual/fisiologia , Testosterona/metabolismo , Adolescente , Adulto , Feminino , Humanos , Masculino , Projetos Piloto , Desejabilidade SocialRESUMO
BACKGROUND: We have compared the use of alizapride, propofol, droperidol and promethazine for the prevention of spinal morphine-induced pruritus. METHODS: Three hundred ASA I or II women undergoing Caesarean section under spinal anaesthesia, in which morphine 0.2 mg was added to a local anaesthetic, were assigned randomly to receive i.v., in the operating room, just after delivery of the baby, alizapride 100 mg, propofol 20 mg, droperidol 1.25 mg, promethazine 50 mg or saline 2 ml (control group). In the postoperative period, the women were assessed for pruritus (absent, mild, moderate or severe) or other untoward symptoms by blinded observers. We used 95% confidence limits (95% CI) for the cumulative incidence of moderate and severe pruritus to compare the groups, and the NNT and 95% CI to compare droperidol, propofol and alizapride as for their effectiveness in preventing pruritus. For other untoward effects, the chi(2)-test was used, results being considered significant when P<0.05. RESULTS: The droperidol, propofol and alizapride groups had significantly lower incidences of pruritus compared with the control and promethazine groups, while the incidence of pruritus was similar among the patients assigned to the promethazine and control groups. As for the prevention of moderate and severe pruritus, droperidol had the lowest NNT (3.52; 95% CI: 3.37-3.67), followed by propofol (4.61; 95% CI: 4.45-4.77) and alizapride (5.43; 95% CI: 5.27-5.59). As for untoward effects, droperidol and promethazine increased the incidence of somnolence, which seemed more severe with promethazine. Otherwise, there were no differences between the groups. CONCLUSION: Droperidol, propofol and alizapride, in a decreasing order of effectiveness in the doses used in this study, reduced the incidence of pruritus induced by the use of morphine 0.2 mg intrathecally. On the other hand, promethazine 50 mg was shown to be ineffective.
Assuntos
Anestesia Obstétrica/efeitos adversos , Raquianestesia/efeitos adversos , Antipruriginosos/uso terapêutico , Toxidermias/prevenção & controle , Morfina/efeitos adversos , Prurido/prevenção & controle , Adolescente , Adulto , Analgésicos Opioides/efeitos adversos , Cesárea , Método Duplo-Cego , Droperidol/uso terapêutico , Feminino , Humanos , Pessoa de Meia-Idade , Gravidez , Prometazina/uso terapêutico , Propofol/uso terapêutico , Prurido/induzido quimicamente , Pirrolidinas/uso terapêuticoRESUMO
If the complex shape of cells and intercellular channels in the renal proximal tubule is determined in part by the forces of large transepithelial water flow, the cell and channel shapes might serve as indicators of the type and magnitude of the forces required for water flow and the routes of that flow. We review here the known morphologic and functional data from the convoluted and straight portions of the rabbit proximal tubule and test the hypothesis of structure-function correlation in that tissue by means of a mass balance equation. If the lateral cell walls are sufficiently deformable to communicate small transmembrane differences in hydrostatic pressure, the resulting phenomenological model suggests an important new role for peritubular serum proteins and can be used to compute reasonable values for cell wall hydraulic conductivity, intercellular protein diffusion constant, and a channel fluid osmolality not more than 1% greater than that of luminal fluid. We conclude that quantitative morphologic studies may serve as a powerful means for evaluating and understanding transport phenomenons in the nephron.
Assuntos
Túbulos Renais Proximais/citologia , Água/metabolismo , Animais , Transporte Biológico Ativo , Permeabilidade da Membrana Celular , Espaço Extracelular/metabolismo , Túbulos Renais Proximais/fisiologia , Túbulos Renais Proximais/ultraestrutura , Microscopia Eletrônica de Varredura , Concentração Osmolar , Proteínas/fisiologia , CoelhosRESUMO
The treatment of dyspepsia in the emergency department often consists of antacid in combination with viscous lidocaine, even though the specific etiology of the pain is frequently unknown. The efficacy of lidocaine as a component of symptomatic therapy was evaluated in a randomized, patient-blinded protocol. Patients presenting to the ED with dyspeptic symptoms were randomized to receive 30 mL of antacid (Mylanta II), or 30 mL of antacid plus 15 mL of 2% viscous lidocaine (GI cocktail). Patients recorded their pain score on an 11-cm linear analog scale prior to and 30 minutes after treatment. Seventy-six patients were enrolled; three were excluded from analysis due to incomplete data. Thirty-four patients were randomized to receive antacid and 39 to receive GI cocktail. Patients rated their baseline pain at 6.4 +/- 2.8 cm in the antacid group and 6.7 +/- 2.7 cm in the cocktail group (P greater than .50). Improvement in pain score with treatment was 0.9 +/- 2.9 cm in the antacid group compared with 4.0 +/- 3.4 cm in the GI cocktail group (P less than .0001). Assessment of pain relief using a five-point rating scale also indicated greater relief with GI cocktail therapy compared with antacid alone (P = .004). No adverse effects were noted with either treatment. We conclude that a single dose of antacid and viscous lidocaine provides a significantly greater degree of immediate pain relief than antacid alone in patients with dyspepsia.
Assuntos
Hidróxido de Alumínio/administração & dosagem , Antiácidos/administração & dosagem , Dispepsia/tratamento farmacológico , Serviço Hospitalar de Emergência , Lidocaína/administração & dosagem , Hidróxido de Magnésio/administração & dosagem , Magnésio/administração & dosagem , Silicones/administração & dosagem , Simeticone/administração & dosagem , Doença Aguda , Hidróxido de Alumínio/uso terapêutico , Antiácidos/uso terapêutico , Combinação de Medicamentos/administração & dosagem , Combinação de Medicamentos/uso terapêutico , Quimioterapia Combinada , Feminino , Humanos , Lidocaína/uso terapêutico , Hidróxido de Magnésio/uso terapêutico , Masculino , Pessoa de Meia-Idade , Ensaios Clínicos Controlados Aleatórios como Assunto , Simeticone/uso terapêuticoRESUMO
The concept of centrifugal renal development is based on renal embryogenesis. It implies a relationship between nephron age and nephron position along a cortical to medullary axis. In common usage, however, it often also implies a relationship between nephron age or position and nephron maturity. We consider here whether the ideas of centrifugal development and centrifugal maturation should in fact be considered as separate and distinct concepts. That is, we consider the possibility that nephron maturity does not necessarily correlate with nephron age. Unfortunately, pertinent reported data give no clear answer. We conclude only that further study will be required before definitive conclusions about renal developmental stages can be stated with certainty.
Assuntos
Túbulos Renais Proximais/embriologia , Animais , Membrana Celular/ultraestrutura , Humanos , Sistema Justaglomerular/embriologia , Sistema Justaglomerular/crescimento & desenvolvimento , Córtex Renal/embriologia , Córtex Renal/crescimento & desenvolvimento , Medula Renal/embriologia , Medula Renal/crescimento & desenvolvimento , Túbulos Renais Proximais/crescimento & desenvolvimento , Túbulos Renais Proximais/fisiologia , CoelhosRESUMO
Epithelia which support large transepithelial fluid movements are generally found to have histologic specializations which increase the surface areas of the cell membranes across which flows occur. A relationship between structure and function seems obvious in those cases. On the other hand, the area increasing specializations may also result in complicated shapes for the cells and their adjacent intercellular channels. In this paper we review the means for examining cell shape by quantitative stereologic techniques and the results obtained for the epithelium of the proximal renal tubule. We conclude that cell shape not only is a critical ingredient in any structure-function correlation for that tissue but also a "fingerprint" and a powerful tool with which one can predict and study epithelial absorptive flows and their driving forces.
Assuntos
Túbulos Renais Proximais/ultraestrutura , Animais , Túbulos Renais Proximais/citologia , Túbulos Renais Proximais/fisiologia , Membranas/ultraestrutura , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Coelhos , Propriedades de SuperfícieRESUMO
Isolated proximal renal tubules of rabbit reach a passive steady-state volume in isotonic medium after active transport is inhibited by ouabain or by inhibition of cellular metabolism or lack of metabolic substrates. If the tubules are then placed in a hypotonic NaCl medium they swell rapidly and then exhibit a volume regulatory decrease (VRD) similar to that seen when active transport is present. We have mathematically modeled these transient events by assuming that the basolateral cell membrane is permeated by pores having at least two distinct reflection coefficients with respect to sodium, potassium, and chloride. VRD depends on the difference of the values of the reflection coefficients of the pore types. As hydrostatic pressure is exerted by the stretching basement membrane, water and ions can be expelled from the cells across the lower reflection coefficient pores and cause VRD. When the hydrostatic pressure compliance is removed, the cells fail to volume decrease unless sufficient extracellular impermeant solute is present to provide an osmotic force for water and ion exit. We conclude that a heteroporous membrane may be an essential feature for cell volume regulation and maintenance.
Assuntos
Túbulos Renais Proximais/fisiologia , Animais , Transporte Biológico , Transporte Biológico Ativo , Membrana Celular/fisiologia , Homeostase , Soluções Hipotônicas , Técnicas In Vitro , Túbulos Renais Proximais/citologia , Túbulos Renais Proximais/efeitos dos fármacos , Cinética , Modelos Biológicos , Ouabaína/farmacologia , Coelhos , Cloreto de Sódio/farmacologiaRESUMO
Although the formation of fluid-filled, epithelial-lined cysts is a common event in a variety of tissues, the mechanisms involved are not well understood. Discussed here are means by which those mechanisms might be elucidated. In general, there are too few data available for complete analysis of in vivo disease processes. It can be suggested only that epithelial proliferation and basement membrane growth are probably absolute requirements. Whether the forces for fluid accumulation precede or follow the stimuli for cell growth cannot be stated with certainty. On the other hand, in certain in vitro model systems the forces required to keep cyst cavities filled with fluid may be so small that cell growth, rather than fluid accumulation, seems the more likely primary event.