RESUMEN

Although archaea have a similar cellular organization as other prokaryotes, the lipid composition of their membranes and their cell surface is unique. Here we discuss recent developments in our understanding of the archaeal protein secretion mechanisms, the assembly of macromolecular cell surface structures, and the release of S-layer-coated vesicles from the archaeal membrane.

Asunto(s)

RESUMEN

BACKGROUND: Central obesity, diabetes mellitus, dyslipidaemia and chronic hypertension--features of the metabolic syndrome--have been individually associated with venous thromboembolism (VTE). However, whether each of these factors additively increases the risk of VTE is uncertain. AIM: To determine whether features of the metabolic syndrome independently increase the risk of VTE. DESIGN: Prospective cohort study derived from the Heart Outcomes Prevention Evaluation 2 (HOPE-2) randomized clinical trial. SETTING: One hundred and forty-five clinical centres in 13 countries. METHODS: We studied 5522 adults aged > or =55 years with cardiovascular disease or diabetes mellitus. At enrollment, 35% had 0-1 features of the metabolic syndrome, 30% had two, 24% had three and 11% had four. We defined symptomatic VTE as an objectively confirmed new episode of deep-vein thrombosis or pulmonary embolism. RESULTS: VTE occurred in 88 individuals during a median 5.0 years of follow-up. The incidence rate of VTE (per 100 person-years) was 0.30 with 0-1 features, 0.36 with two features, 0.38 with three features and 0.40 with four features of the metabolic syndrome (trend p = 0.43). Relative to the presence of 0-1 features of the metabolic syndrome, the adjusted hazard ratio (95%CI) for VTE was 1.22 (0.71-2.08) with two features, 1.25 (0.70-2.24) with three features, and 1.26 (0.59-2.69) with four features. DISCUSSION: The number of features of the metabolic syndrome present was not a clinically important risk factor for VTE in older adults with vascular arterial disease.

Asunto(s)

RESUMEN

PURPOSE: To measure selected parameters of energy metabolism and adenosine triphosphate (ATP) production in passaged monolayer cultures of human retinal glial (Müller) cells to assess the effects of varying substrate and oxygen availability on the biochemistry and histologic integrity of these cells. METHODS: Confluent Müller cell cultures were incubated for up to 4 hours at 37 degrees C in a modified minimal essential medium (no serum) under aerobic or mitochondrial-inhibited conditions in the presence and absence of 5 mM glucose or in the presence of lactate, pyruvate, glutamate, or glutamine. Cellular ATP levels, lactic acid production, and (14)CO(2) production from labeled glucose or glutamate were measured along with an examination of cellular morphology. Immunohistochemistry with antibodies to glial cell-specific proteins was also performed. Cells were positive for vimentin, but negative for glial fibrillary acidic protein and glutamine synthetase. RESULTS: Human Müller cells maintained ATP content aerobically at the same level for 4 hours in the presence and absence of glucose. ATP content was also maintained anaerobically at a value equal to that found aerobically, but only in the presence of glucose. ATP content in human Müller cells declined to a very low level when glycolysis was blocked by iodoacetate, and inclusion of lactate, pyruvate, glutamate, or glutamine did not restore the level of ATP. Aerobically, lactic acid production accounted for 99% of the total glucose used, whereas the oxidation of glucose by the mitochondria accounted for only 1%. When mitochondria were inhibited with antimycin A, there was only a modest (1.3-fold) increase in the rate of lactic acid production. No significant differences were found in the histologic appearance of the cells after mitochondrial blockade, but there was massive death of cells after inhibition of glycolysis with iodoacetate. CONCLUSIONS: These results suggest that, in the presence of glucose and oxygen, cultured Müller cells obtain their ATP principally from glycolysis and have a low rate of oxygen consumption. This metabolic pattern may spare oxygen for retinal neurons, particularly in the inner nuclear and ganglion cell layers under normal physiological conditions. Furthermore, retinal Müller cells in culture are resistant to anoxia or absence of glucose, which provides a basis for understanding why Müller cells are less susceptible than neurons to ischemia or hypoglycemia.

Asunto(s)

RESUMEN

The purpose of the present experiments was to evaluate the contribution of the glutamate-glutamine cycle in retinal glial (Müller) cells to photoreceptor cell synaptic transmission. Dark-adapted isolated rat retinas were superfused with oxygenated bicarbonate-buffered media. Recordings were made of the b-wave of the electroretinogram as a measure of light-induced photoreceptor to ON-bipolar neuron transmission. L-methionine sulfoximine (1-10 mM) was added to superfusion media to inhibit glutamine synthetase, a Müller cell specific enzyme, by more than 99% within 5-10 min, thereby disrupting the conversion of glutamate to glutamine in the Müller cells. Threo-hydroxyaspartic acid and D-aspartate were used to block glutamate transporters. The amplitude of the b-wave was well maintained for 1-2 h provided 0.25 mM glutamate or 0.25 mM glutamine was included in the media. Without exogenous glutamate or glutamine the amplitude of the b-wave declined by about 70% within 1 h. Inhibition of glutamate transporters led to a rapid (2-5 min) reversible loss of the b-wave in the presence and absence of the amino acids. In contrast, inhibition of glutamine synthetase did not alter significantly either the amplitude of the b-wave in the presence of glutamate or glutamine or the rate of decline of the b-wave found in the absence of these amino acids. Excellent recovery of the b-wave was found when 0.25 mM glutamate was resupplied to L-methionine sulfoximine-treated retinas. The results suggest that in the isolated rat retina uptake of released glutamate into photoreceptors plays a more important role in transmitter recycling than does uptake of glutamate into Müller cells and its subsequent conversion to glutamine.

Asunto(s)

RESUMEN

PURPOSE: To measure glucose-dependent metabolic activities and selected parameters of the polyol pathway in retinas isolated from normal rats to test the hypothesis recently proposed by Van den Enden et al that incubation of whole retinas for 2 hours with elevated concentrations of glucose results in activation of the polyol pathway, which is the cause of a redox imbalance, as measured by an increase in the retinal cytosolic lactate-pyruvate ratio and a diabetic-like state. METHODS: Retinas obtained from nondiabetic rats and separated from other ocular tissues were incubated for several hours in incubation medium containing glucose at concentrations ranging from 5 to 30 mM. Measurements were made under aerobic and anaerobic conditions of lactic acid production, retinal adenosine triphosphate (ATP), lactic acid content, the hexose monophosphate shunt pathway, aldose reductase activity, and levels of sorbitol and galactitol. Morphology was examined by light microscopy at the end of the incubations. RESULTS: Incubation of isolated rat retinas with 20 mM glucose increased lactic acid production by approximately 25% in comparison to the rate observed in 5mM glucose under aerobic and anaerobic conditions. The content of ATP and lactate in the retinas after a 2-hour incubation in the presence of oxygen and 20 mM glucose was equal to the amounts found in fresh tissues, whereas these metabolites declined, respectively, by 25% and 45% when 5 mM glucose was used. The activity of the hexose monophosphate shunt pathway in isolated rat retinas was not increased increased significantly when the concentration of glucose was raised from 5 to 30 mM. Aldose reductase activity and polyols were below our limits of detection, 0.5 nmol/minute.mg protein and 3.5 nmol/retina, respectively, under all conditions tested. The morphologic appearance of the retina was similar in the presence of normal and high concentrations of glucose. CONCLUSIONS: These results show that incubation of isolated rat retinas, obtained from nondiabetic rats, with elevated concentrations of glucose for 2 hours leads to increases in glycolysis and a higher tissue content of lactic acid and ATP in comparison to values obtained with 5 mM glucose. However, the magnitude of the glucose-dependent increase in the retinal level of lactate in the current study and in that of Van den Enden et al is six to seven times greater than the calculated flux of glucose through the polyol pathway. These results, therefore, do not support the hypothesis of Van den Enden et al. Rather, it is suggested that supranormal concentrations of glucose yield more lactate and ATP in a whole retina because they optimize the supply of this essential nutrient to cells throughout the tissue by overcoming diffusional limitations that result when the retina is separated from its normal choroidal and intraretinal blood supplies.

Asunto(s)

RESUMEN

There has been significant improvement in breast health care in the United States over the past few decades primarily due to advances in health research by diverse teams of basic scientists, physicians, pharmacists, industries, nurses, and social workers. This research has involved inquiries about fundamental biological alterations in breast cancer, differences in diagnostic modalities, and treatment options and various outcome studies. Increase in public awareness of breast cancer, an interest in women's health issues, advances in radiologic imaging, development of new chemotherapeutic agents and the availability of molecular genetic testings have brought remarkable opportunities to a new insight in breast cancer. These efforts have resulted in earlier detection and prolonged disease-free intervals, however, the overall survival time has remained the same. This is mainly attributable to the wide range of individual therapy for breast cancer, which responds to a range of disease curable by surgery alone to one refractory to treatment and marked by rapid metastatic progression. Challenges remain in fostering adequate funding for biomedical, as well as behavioral and social research. Attempts should also be made to promote clinical and population-based studies and to emphasize the value of effective delivery of health-care services to all women with benign, high risk, premalignant and malignant breast disease.

Asunto(s)

RESUMEN

OBJECTIVES: The objective of the study was to establish the prevalence of hypertension and to assess determinants of blood pressure with special reference to socioeconomic status in a rural south Indian community. DESIGN: This was a door to door, cross sectional survey. SETTING: A rural south Indian community, KV Kuppam panchayat, North Arcot District, Tamil Nadu. SUBJECTS: The area has a total population of 3500 people. Those aged over 20 years who were available at the time of measurement were asked to participate (mean age 39.5 years). This convenience sample totalled 1027 (456 men, 571 women). Out of 697 families, 487 were visited; 15 people refused to participate. MEASUREMENTS AND MAIN RESULTS: The following potential determinants of blood pressure were assessed: age, body weight, pulse rate, salt intake, meat intake, and socioeconomic class. The prevalence of hypertension was 12.5%. Using multiple linear regression analysis, the most important positive determinants of high blood pressure seemed to be age, body weight, and pulse rate. Salt and meat intake were not significantly associated with hypertension. The prevalence of hypertension in the highest socioeconomic group (22.5%) was more than twice that in the lowest socioeconomic group (8.8%). When adjusted for body weight, the mean (SEM) difference in systolic blood pressure between the highest and lowest socioeconomic classes was 5.83 mmHg (1.63). CONCLUSION: Hypertension is not yet as important a health problem in rural southern India as it is in westernised societies. Those particularly at risk of hypertension, however, are the elderly and overweight people of high socioeconomic class.

Asunto(s)

RESUMEN

The quadriceps femoral angle (Q angle) has been linked with several knee disorders, but Q-angle measurement procedures have not been standardized. The purpose of this study was to examine the effects of isometric quadriceps contraction in the standing and supine positions on the Q angle. The Q angles of the right knees of 30 men and 30 women were measured goniometrically during four test conditions: 1) quadriceps relaxed in standing, 2) quadriceps contracted in standing, 3) quadriceps relaxed in supine, and 4) quadriceps contracted in supine. The pelvic widths were also measured as the distance between the anterior superior iliac spines in standing and supine. A two-way multivariate analysis of variance showed a significant difference between genders (p < 0.001) and among the four test conditions (p < 0.001) (N = 60). Separate one-way analyses of variance (ANOVAs) with two grouping factors (contraction and position) showed significant effects of contraction (p < 0.001) for both men and women, but no significant effect of positions. A dependent t-test showed that the pelvic width differed between standing and supine for both men and women (p < 0.001). The results showed that isometric quadriceps contraction affects the Q angle with the subjects standing or supine, even though the pelvic width differed significantly between the two positions. Clinicians and researchers should consider the results of this study in order to standardize procedures for measuring the Q angle.

Asunto(s)

RESUMEN

Transvaginal sonographic localization of the placenta was performed in 100 patients suspected of having placenta previa. Except in one patient, the diagnosis was confirmed at cesarean delivery in all cases of placenta previa found by sonography before delivery, resulting in a 93.3% predictive value of a positive test. The predictive value of a negative test was 97.6%; in two patients a low-insertion placenta diagnosed by sonography was found to be a placenta previa at delivery. The sensitivity and specificity of the technique were 87.5 and 98.8%, respectively. Although in some instances transvaginal sonography was performed during vaginal hemorrhage, aggravation of bleeding was never observed. Transvaginal sonographic localization of the placenta proved to be an accurate and safe diagnostic procedure.

Asunto(s)

Asunto(s)

RESUMEN

An increased occurrence of salivary tumors was observed in 1922 patients who received radiation to the tonsils and nasopharynx. Twenty-seven tumors, 19 benign and eight malignant, were found in this group as compared with an expected 0.2 malignant and less than 1 benign tumor. The latent period between the initial radiation treatment and diagnosis ranged from 7 to 32 years. After the first 15 years the incidence (77 cases/10(5) subjects/year) has remained constant and shows no indication of declining. Continued observation for salivary gland tumors is therefore indicated for subjects who received childhood irradiation.

Asunto(s)

RESUMEN

The level of thyroglobulin in plasma was measured in 904 subjects with a history of head and neck irradiation during childhood to evaluate its potential value in screening for and differentiating thyroid neoplasms. Mean plasma thyroglobulin level was significantly elevated in subjects with nodular thyroid disease versus those without evidence of nodules (49.8 versus 27.0 ng/ml). However, the overlap with normal subjects does not allow thyroglobulin assays to serve as the only screening procedure. The mean levels in subjects with benign and malignant thyroid nodules were indistinguishable (48.8 versus 53.9 ng/ml). Thirteen percent of otherwise normal-appearing subjects had elevated values that may represent clinically inapparent thyroid disease. It is concluded that in screening large numbers of persons at risk for thyroid neoplasia, thyroglobulin assays are useful in combination with other modes of evaluation. The assay is without value in distinguishing benign from malignant disease.

Asunto(s)

RESUMEN

From January 1 to September 30, 1974, we examined 1056 of 5266 subjects (20.1%) who had received therapeutic irradiation primarily for infections and inflammatory disease of the upper respiratory tract at our institution during the 1940's and 1950's. The tonsillar and nasopharyngeal region was the treatment site in 85% of those examined. Palpable nodular thyroid disease was found in 16.5%, and nonpalpable lesions were detected by 99m Tc pertechnetate thyroid imaging in an additional 10.7%, for a prevalence of nodular disease of 27.2%. Operation on 71% with nodular disease revealed thyroid cancer in 33% (60 of 182). Preliminary analysis for potential risk factors suggests a correlation between radiation exposure and the presence of thyroid nodules (P less than 0.001). These findings indicate that nodular thyroid disease, both benign and malignant, continues as a major health problem for at least 35 years in exposed subjects.

Asunto(s)