Search PubMed⌕ Search

Biomedical subjects

B Herman

Publications and source records attributed to B Herman.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Inhibition of Na+/H+ exchange preserves viability, restores mechanical function, and prevents the pH paradox in reperfusion injury to rat neonatal myocytes.

Rat neonatal myocytes exposed to 2.5 mM CaCN and 20 mM 2-deoxyglucose at pH 6.2 (chemical hypoxia) quickly lose viability when pH is increased to 7.4, with or without washout of inhibitors--a 'pH paradox'. In this study, we evaluated the effect of two Na+/H+ exchange inhibitors (dimethylamiloride and HOE694) and a Na+/Ca2+ exchange inhibitor (dichlorobenzamil) on pH-dependent reperfusion injury. Intracellular free Ca2+ and electrical potential were monitored by laser scanning confocal microscopy of rat neonatal cardiac myocytes grown on coverslips and co-loaded with Fluo-3 and tetramethylrhodamine methylester. After 30-60 min of chemical hypoxia at pH 6.2, mitochondria depolarized and Ca2+ began to increase uniformly throughout the cell. Free Ca2+ reached levels estimated to exceed 2 microM by 4 h. Washout of inhibitors at pH 7.4 (reperfusion), with or without dichlorobenzamil, killed most cells within 60 min, despite a marked reduction of Ca2+ in dichlorobenzamil-treated cells. Reperfusion at pH 7.4 in the presence of 75 microM dimethylamiloride or 20 microM HOE694, or at pH 6.2, prevented cell death. HOE694-treated cells placed into culture medium recovered mitochondrial membrane potential. In most cells, this occurred before normal Ca2+ was restored. Contracted myocytes re-extended over a 24-h-period. By 48 hours, most cells contracted spontaneously and showed normal Ca2+ transients. Our results indicate that Na+/H+ exchange inhibition protects against pH-dependent reperfusion injury and facilitates full recovery of cell function.

Amiloride↗
PubMedDate not supplied

Assessment of Fura-2 for measurements of cytosolic free calcium.

Fura-2 has become the most popular fluorescent probe with which to monitor dynamic changes in cytosolic free calcium in intact living cells. In this paper, we describe many of the currently recognized limitations to the use of Fura-2 in living cells and certain approaches which can circumvent some of these problems. Many of these problems are cell type specific, and include: (a) incomplete hydrolysis of Fura-2 acetoxymethyl ester bonds by cytosolic esterases, and the potential presence of either esterase resistant methyl ester complexes on the Fura-2/AM molecule or other as yet unidentified contaminants in commercial preparations of Fura-2/AM; (b) sequestration of Fura-2 in non-cytoplasmic compartments (i.e. cytoplasmic organelles); (c) dye loss (either active or passive) from labeled cells; (d) quenching of Fura-2 fluorescence by heavy metals; (e) photobleaching and photochemical formation of fluorescent non-Ca2+ sensitive Fura-2 species; (f) shifts in the absorption and emission spectra, as well as the Kd for Ca2+ of Fura-2 as a function of either polarity, viscosity, ionic strength or temperature of the probe environment; and (g) accurate calibration of the Fura-2 signal inside cells. Solutions to these problems include: (a) labeling of cells with Fura-2 pentapotassium salt (by scrape loading, microinjection or ATP permeabilization) to circumvent the problems of ester hydrolysis; (b) labeling of cells at low temperatures or after a 4 degrees C pre-chill to prevent intracellular organelle sequestration; (c) performance of experiments at lower than physiological temperatures (i.e. 15-33 degrees C) and use of ratio quantitation to remedy inaccuracies caused by dye leakage; (d) addition of N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) to chelate heavy metals; (e) use of low levels of excitation energy and high sensitivity detectors to minimize photobleaching or formation of fluorescent non-Ca2+ sensitive forms of Fura-2; and (f) the use of 340 nm and 365 nm (instead of 340 nm and 380 nm) for ratio imaging, which diminishes the potential contributions of artifacts of polarity, viscosity and ionic strength on calculated calcium concentrations, provides a measure of dye leakage from the cells, rate of Fura-2 photobleaching, and can be used to perform in situ calibration of Fura-2 fluorescence in intact cells; however, use of this wavelength pair diminishes the dynamic range of the ratio and thus makes it more sensitive to noise involved in photon detection. Failure to consider these potential problems may result in erroneous estimates of cytosolic free calcium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Ligand-induced rapid redistribution of lysosomes is temporally distinct from endosome translocation.

When many ligands bind to cell-surface receptors, ligand-receptor complexes are internalized via clathrin coated pits by a process called receptor-mediated endocytosis. The cytoplasmic fate of ligands internalized within endocytic vesicles or endosomes is variable. For example, maternal immunoglobulins are transported through the cytoplasm of neonatal intestinal epithelial cells and are exocytosed at the basolateral surface. However, other ligands are degraded as a result of their delivery to the lysosomal compartment of cells. Although the translocation of endosomes to the Golgi region in the cell centre seems to be a general phenomenon presumably coupled to ligand degradation by lysosomes and endosomes and lysosomes undergo saltatory movements within the cytoplasm, the spatial control of interaction between the two structures is not understood. To address this problem we have begun to examine the spatial and temporal intracellular distribution of endosomes and lysosomes. Utilizing a new fluorescent microscopic approach, we have now been able simultaneously to visualize endosome and lysosome populations in living cells. Our results suggest that a specific relocation of lysosomes is rapidly induced upon binding of different types of ligands to the cell surface; this migration of lysosomes to the Golgi region of the cell precedes the translocation of endosomes into the same area.

Animals↗
PubMedDate not supplied

Blebbing, free Ca2+ and mitochondrial membrane potential preceding cell death in hepatocytes.

Cell surface 'blebbing' is an early consequence of hypoxic and toxic injury to cells. A rise in cytosolic free Ca2+ has been suggested as the stimulus for bleb formation and the final common pathway to irreversible cell injury. Here, using digitized low-light video microscopy, we examine blebbing, cytosolic free Ca2+, mitochondrial membrane potential and loss of cell viability in individual cultured hepatocytes. Unexpectedly, we found that after 'chemical hypoxia' with cyanide and iodoacetate, cytosolic free Ca2+ does not change during bleb formation or before loss of cellular viability. Cell death was precipitated by a sudden breakdown of the plasma membrane permeability barrier, possibly caused by rupture of a cell surface bleb.

Adenosine Triphosphate↗
PubMedDate not supplied

A laboratory evaluation of standard leakage tests for surgical & examination gloves.

Analysis of leakage tests for surgical and examination gloves is reported. Six widely applicable tests were evaluated, using samples from 16 glove manufacturers. Various techniques for inducing sub-millimeter holes were developed and employed for creating test holes in a wide variety of gloves. The prescribed tests were performed and the results compared to calculations of expected sensitivities. In general, there was reasonable agreement between calculation and measurement (within about a factor of 2), although there were some exceptions. Minimum detectable hole sizes, before the holes were stretched by the tests, were generally in the range of 25-100 microns in diameter. Theoretical predictions of minimum detectable hole sizes for the various tests ranged from about 100-200 microns (in the stretched condition). Because of inherent limitations of the test protocols, it is clear that much larger holes can go undetected under certain circumstances, especially in examination gloves. Some test procedures had important procedural ambiguities; some tests were patently impossible to perform. All tests had inherent limitations resulting in sensitivities that varied from glove to glove or that were quite nonuniform over the surface of the glove being tested or both.

Equipment Design↗
PubMedDate not supplied

Epidemiology of stroke in Tilburg, The Netherlands. The population-based stroke incidence register: 1. Introduction and preliminary results.

We present the methodology and some preliminary findings of a population-based stroke incidence register operating in Tilburg (about 150,000 persons), The Netherlands. From October 1, 1978 to March 31, 1979, 152 new strokes occurred giving an estimated overall incidence (per 100,000 population) for total and first attacks of 202 and 162, respectively. No major sex difference in stroke risk (all ages) was noted, although males did have a significantly higher incidence at 55--64 years of age. Stroke incidence increased strikingly with age. Thromboembolic infarcts comprised 83% and intracranial hemorrhage 13% of attacks. Males and females differed little in distribution of stroke types. The proportion of cerebral infarction was higher among older than younger cases. The opposite was true regarding intracranial hemorrhage. Embolic infarcts constituted a significantly higher proportion of cases at 65--74 years of age than at other ages. Hemiplegia and speech deficits dominated the clinical picture at onset. The 3-week case fatality for all strokes was 26%. Both a lowering of consciousness (found among 38% of cases during the first 24 hours) and a history of prior stroke were found related to a reduction in survival. Of patients surviving 3 weeks 25% were completely dependent and 25% partially dependent upon others for personal care.

Activities of Daily Living↗
PubMedDate not supplied

An evaluation of risk factors for stroke in a Dutch community.

The objective of the present epidemiological study was to reevaluate the relationship of various suspect risk factors to stroke within a Dutch community. The Tilburg study lends support to findings in other countries concerning the greater stroke risk of persons with high blood pressure, heart disorders, and diabetes mellitus. Significant interactions of both age and a history of myocardial infarction with hypertension on stroke risk were noted. The presence of overweight and possible transient ischemic attacks (TIA) were found related to stroke onset. No increase in stroke risk was associated with cigarette smoking. The extent of leisure time physical activity during one's lifetime was found inversely related to one's chances for stroke.

Adult↗
PubMedDate not supplied

Epidemiology of stroke in Tilburg, the Netherlands. The population-based stroke incidence register: 2. Incidence, initial clinical picture and medical care, and three-week case fatality.

The results of a prospective population study of stroke in Tilburg are reported. The average annual over-all incidence (per 100,000 population) for the period October 1, 1978-September 30, 1980 was 174 for total cases, 145 for first-ever cases. Males and older persons were at greater risk for a stroke. The vast majority of strokes were thrombo-embolic infarctions. Hemiplegia was the predominant neurological deficit resulting from an insult. Patients with speech problems, as opposed to those without, demonstrated more extreme motor deficit when such occurred. Seventy-four per cent of stroke cases had hypertensive blood pressure readings shortly after onset. Most patients were under hospital care during the initial phase of their attacks. The presence of such handling was related to specific patient characteristics. Three-week stroke case fatality was 30% for all patients registered, and varied significantly by age, sex and diagnostic type.

Aged↗
PubMedDate not supplied

Histiocytoma; histiocytoma proliferans; histiocytoma malignum: (clinical and morphological observations).

In a group of 112 cases of histiocytic neoplasms treated 1960--1973 103 benign tumors (histiocytoma), 3 semimalignant tumors (histiocytoma proliferans), and 6 malignant ones (histiocytoma malignum) were diagnosed. Clinical and morphological examinations indicate that under the influence of stimuli histiocytoma may undergo a biological transformation developing into less mature forms such as histiocytoma proliferans and histiocytoma malignum. The treatment of malignant tumors consisted in their removal together with a wide margin or adjacent tissues. In 2 cases enlarged lymph nodes were removed but no metastases were found. In one case death occurred 3 years after operation as a result of distant metastases.

Adult↗