Developmental biology. Hedgehog keeps to the left.
Explore the source record for details and available documents.
Activins↗
Biomedical subjects
N A Brown
Publications and source records attributed to N A Brown.
Section directed cryosectioning of specimens for scanning electron microscopy: a new method to study cardiac development.
A new method to study the developing heart was developed. Using this "section directed" cryosectioning method, appropriate fixed embryos can be trimmed optimally to obtain sectional planes that, if necessary, can be matched with histologically treated sections. As a result, the morphological information obtained with the scanning electron microscope can be compared in detail with the information on the molecular phenotypes of the subpopulations of cells as deducted from staining patterns of the sections. This method allows combination of the specific advantages of sophisticated histological techniques, such as immunohistochemistry and in situ hybridisation, with those of the scanning electron microscope.
Animals↗
Opinions on left-right axis formation.
Explore the source record for details and available documents.
Animals↗
Phosphorylation- and voltage-dependent inhibition of neuronal calcium currents by activation of human D2(short) dopamine receptors.
1. Activation of human D2(s) dopamine receptors with quinpirole (10 nM) inhibits omega-conotoxin GVIa-sensitive, high-threshold calcium currents when expressed in differentiated NG108-15 cells (55% inhibition at +10 mV). This inhibition was made irreversible following intracellular dialysis with the non-hydrolysable guanosine triphosphate analogue GTP-gamma-S (100 microM), and was prevented by pretreatment with pertussis toxin (1 microgram ml-1 for 24 h). 2. Stimulation of protein kinase C with the diacylglycerol analogue, 1-oleoyl-2-acetyl-sn-glycerol (100 microM), also attenuated the inhibition of the sustained calcium current but did not affect the receptor-mediated decrease in rate of current activation. Similarly, okadaic acid (100 nM), a protein phosphatase 1/2A inhibitor, selectively occluded the inhibition of the sustained current. 3. The depression of calcium currents by quinpirole (10 nM) was enhanced following intracellular dialysis with 100 microM cyclic adenosine monophosphate (cyclic AMP, 72.8 +/- 9.8% depression), but was not mimicked by the membrane permeant cyclic GMP analogue, Sp-8-bromoguanosine-3',5':cyclic monophosphorothioate (100 microM). 4. Inhibition of calcium currents was only partly attenuated by 100 ms depolarizing prepulses to +100 mV immediately preceding the test pulse. However, following occlusion of the sustained depression with okadaic acid (100 nM) the residual kinetic slowing was reversed in a voltage-dependent manner (P < 0.05). 5. Thus pertussis toxin-sensitive G-proteins liberated upon activation of human D2(short) dopamine receptors inhibited high-threshold calcium currents in two distinct ways. The decrease in rate of calcium current activation involved a voltage-dependent pathway, whereas the sustained inhibition of calcium current involved, in part, the voltage-resistant phosphorylation by cyclic AMP-dependent protein kinases and subsequent dephosphorylation by protein phosphatases 1/2A.
Calcium↗
Morphology of the sinus node in human and mouse hearts with isomerism of the atrial appendages.
BACKGROUND: The location of the sinus node is known to be at best abnormal, or at worst unknown, in patients with isomerism of the morphologically left atrial appendage. In contrast, the sinus node is known to be an excellent histological marker of the morphologically right appendage, being duplicated in those with right isomerism. The aim of the study was to investigate this condition further in fetal human and mouse hearts. METHODS: Serial histological sections of the area anticipated to contain the sinus node were studied in hearts with isomerism of the atrial appendages taken from 14 human fetuses and 13 iv/iv mice, using 12 mouse hearts with normally arranged or mirror imaged atrial chambers for controls. RESULTS: All hearts with isomerism of the right appendages (two human and four mouse) had bilateral sinus nodes. The cases with isomerism of the left appendages (12 human and nine mouse) showed absence of a recognisable sinus node except in four cases (19%) in which a small remnant of the node was found. In three of these cases, it was related postero-inferiorly to the superior cavoatrial junction. CONCLUSIONS: The concept of isomerism of the atrial appendages is endorsed by findings on the morphology of the sinus node, this being the most reliable histological criterion for existence of a morphologically right atrium. A small proportion of hearts with left isomerism had a structure resembling the sinus node, but it was hypoplastic and displaced postero-inferiorly, distant from its expected position had the hearts possessed an incompletely formed morphologically right appendage.
Adult↗
Teledermatology: one application of telemedicine.
Telemedicine can be defined as the use of telecommunications technologies to provide medical information and services. This field has recently begun a period of explosive growth. Oregon's teledermatology program within the National Library of Medicine's high-performance computing and communications initiative is designed to generate much-needed basic and clinical research information about one specific telemedicine application. The background of this program is discussed, and the research objectives are described.
Academies and Institutes↗
Block of human voltage-sensitive Na+ currents in differentiated SH-SY5Y cells by lifarizine.
1. The ability of lifarizine (RS-87476) to block human voltage-sensitive Na+ channel currents was studied by use of whole cell patch clamp recording from differentiated neuroblastoma cells (SH-SY5Y). 2. The Na+ conductance in differentiated SH-SY5Y cells (24.0 +/- 2.4 nS, n = 11) was half-maximally activated by 10 ms depolarizations to -37 +/- 2 mV and was half-maximally inactivated by predepolarizing pulses of 200 ms duration to -86 +/- 3 mV (n = 11). 3. At low stimulus frequencies (0.1 to 0.33 Hz) voltage-dependent sodium currents were completely blocked, in a concentration-dependent manner, by extracellular application of either tetrodotoxin (EC50 = 4 +/- 1 nM, n = 12) or by lifarizine (EC50 = 783 +/- 67 nM, n = 9). The onset of block by lifarizine (tau = 91 +/- 14 s at 10 microM) was considerably slower than that of tetrodotoxin (tau = 16 +/- 3 s at 100 nM). 4. Lifarizine (1 microM) reduced the peak sodium conductance in each cell (from 26.4 +/- 2.0 nS to 15.1 +/- 2.7 nS, n = 4) without changing the macroscopic kinetics of sodium current activation or inactivation (V1/2 = -35 1 mV and -87 +/- 4 mV respectively, n = 4). Similarly, lifarizine (1 microM) did not affect the reversal potential of the macroscopic sodium current (+14 +/- 5 mV in control and +16 +/- 2 mV in 1 microM lifarizine; n = 4) or reactivation time-constant (tau = 14.0 +/- 4.4 ms). 5. Block of the sodium channel open state by tetrodotoxin (30 nM) did not prevent the inhibition caused by a subsequent application of lifarizine (3 micro M). In contrast the depression caused by lifarizinewas readily reversible after pretreatment of cells with the local anaesthetic, lignocaine (1O mM).6. These data demonstrate that lifarizine is a use- and voltage-dependent antagonist of human voltage sensitive sodium currents. The slow kinetics and pharmacology of the block by lifarizine indicate that access of this drug to the channel is more restricted than that of tetrodotoxin and may involve an allosteric site or state of the channel that is also regulated by local anaesthetics.
Cell Differentiation↗
Antibodies against highly conserved sites in the epidermal growth factor receptor tyrosine kinase domain as probes for structure and function.
We generated anti-peptide antibodies against four highly conserved sequences in the kinase domain and against two nonconserved sequences surrounding autophosphorylation sites in the carboxyl-terminal domain of the epidermal growth factor receptor (EGFR). These antibodies were used to examine topology and function in catalysis of specific sequences. Two of the highly conserved sites, HRD (residues 811-818) and DFG (residues 827-838), appeared to participate in catalysis since alpha HRD and alpha DFG but not the other anti-peptide antibodies inhibited EGFR kinase activity. Examination of the topology of the six sites revealed that epitopes in all except the HRD site appeared to be exposed to antibody binding in the EGFR. The conditions that caused increased exposure of the HRD site to interaction with antibody included autophosphorylation, addition of the ionic detergent sodium dodecyl sulfate (SDS), and elevation in temperature from 4 to 34 degrees C.
Adenosine Triphosphate↗
The lens in diabetes.
This paper reviews the changes which occur in the human lens in diabetes. They include refractive changes and cataract and age-related increases in thickness, curvatures, light scattering, autofluorescence and yellowing. The incidence of cataract is greatly increased over the age of 50 years, slightly more so in women, compared with non-diabetics. Experimental models of sugar cataract provide some evidence for the mechanism of the uncommon, but morphologically distinct, juvenile form of human diabetic cataract, where an osmotic mechanism due to sugar alcohol accumulation has been thoroughly studied in diabetic or galactose-fed rats. The discrepancy between the ready accumulation of sugar alcohol in the lens in model systems and the very slow kinetics of aldose reductase (AR) has not been satisfactorily explained and suggests that the mechanism of polyol formation is not yet fully understood in mammalian systems. The activity of AR in the human lens lies mainly in the epithelium and there appears to be a marginal expectation that sufficient sorbitol accumulates in cortical lens fibres to explain the lens swelling and cataract on an osmotic basis. This is even more so in the cataracts of adult diabetics, which resemble those of age-related non-diabetic cataracts in appearance. The very low levels of sorbitol in adult diabetic lenses make an osmotic mechanism for the increased risk of cataract even less likely. Other mechanisms, including glycation and oxidative stress, are discussed. The occurrence of cataract is a predictor for increased mortality in the diabetic.
Adolescent↗
Development of the left-right axis.
Left-right is not an axis in the conventional sense but rather two mirror-image proximodistal axes, upon which a quantal piece of positional information (leftness or rightness) is superimposed for laterally asymmetric organ development. We are attempting to establish the stages at which left-right is specified and determined, but this is complicated by the apparent loss of normal handed development in embryos that are cultured from pre-neural plate stages. Experiments suggest that left-right is determined by the first somite stage. The loss of normal left-right development in early cultures is probably not due to removal of some maternal signal, even though embryos do develop in vivo with their axes in a specific orientation relative to the uterus. The fact that there are two random embryonic axis orientations, 180 degrees opposed to one another, and that the axes of the two uterine horns are mirror-images of each other make it unlikely that the uterus could impart a sense of left-right to the embryo. The right ovary produces more eggs than the left one; this is reversed in iv/iv situs inversus mice. Analysis of iv/iv mice shows a correlation of left-right abnormalities with sex and close relationships between the abnormal left-right development of some organs, for example the heart and spleen, that have no obvious developmental connection.
Animals↗
Distribution of p21ras in postimplantation rat embryos.
Expression of ras cellular oncogenes during the early postimplantation period in the rat was investigated using immunohistochemistry to p21ras. A broad spectrum polyclonal antibody recognizing N-, Ha- and Ki- forms of p21ras was used in an indirect avidin-biotin-peroxidase (ABC) technique. Positive staining indicating the presence of p21ras was found in embryos from 6.5 to 12 days embryonic age. In early egg cylinders (6.5 days), positive staining for p21ras was observed on the ectoplacental cone, primitive ectoderm and trophectoderm, while primitive endoderm and parietal endoderm appeared paler. In later egg cylinder stages (7.5 days), strong positive staining was observed in the primitive embryonic ectoderm and ectoplacental cone, but parietal and visceral endoderm still appeared to be devoid of positive staining. As development proceeded during primitive streak stages, the visceral and parietal endoderm became positively stained. By 10 days, all tissues appeared to be positive for p21ras, with strong staining appearing in the heart and neural elements. Therefore, p21ras does not appear to be ubiquitous in the rat conceptus prior to gastrulation, but shows differential distribution, appearing later in endodermal derivatives. Possibly p21ras is involved in determination of the ectodermal and endodermal lineages.
Animals↗
Comparison of staging systems for the gastrulation and early neurulation period in rodents: a proposed new system.
Because there is no standard developmental staging system for the early postimplantation period of rodent embryos, investigators must now choose between a variety of systems that differ significantly. We have reviewed many of these staging systems and have summarized the ambiguities within them and the inconsistencies among them. In order to compare systems, we first obtained a consensus of the order of developmental events from the literature, and then attempted to fit existing systems into this order taking into account inconsistencies in terminology and blurred borderlines between stages. We were able to do this for most systems but not all because some were too divergent. We found that inconsistencies in definition of some terms, such as "primitive streak stage" and those used to describe the early neurulation process (neural plate, neural groove, neural folds, and head fold) cause much confusion. In order to develop an unambiguous system which can be used by all investigators, we propose to modify Theiler's system, which is one of the most commonly used systems but is not defined precisely during the early postimplantation period. We suggest making subdivisions of the original stages as follows: 1) stage 8 into 8a and 8b, by the degree of extension of the proamniotic cavity into the extraembryonic region; 2) stage 10 into 10a and 10b, by the completion of amnion formation; 3) stage 11 into 11a, 11b, and 11c, by the appearance of neural folds and foregut pocket. After Stage 12, the number of somite pairs can be used to precisely stage embryos.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Human herpesvirus-6: clinical implications of a recently discovered, ubiquitous agent.
Explore the source record for details and available documents.
Age Factors↗
Changes in light scatter and width measurements from the human lens cortex with age.
Light scatter and width measurements of the anterior cortical layers of the human lens were made in 50 eyes of 50 subjects using computerised linear scanning densitometry of Scheimpflug images. It was demonstrated that the amount of light scatter increased with age in all of the three major zones and that zone C3 showed the most marked increase. Most lens growth occurs in zone C2 with C3 showing little increase in width once it has become established. Zone C1 showed a tendency to decrease in width with age. In addition it was shown that the C3 zone, which is not present at birth and during early childhood, appears as a distinct layer during the second decade of life. Its scattering properties continue to increase throughout life, exceeding all other zones after approximately 30 years of age, in the absence of cataract. Possible explanations for the lens zone pattern are discussed.
Adolescent↗
Autofluorescence of the crystalline lens in early and late onset diabetes.
Blue/green autofluorescence (excitation around 420 to 430 nm, emission around 520 nm) of the crystalline lens has been studied by an in vivo photographic method in two populations of diabetics and controls. The populations consisted of a geographically based survivor group of 161 mixed early and late onset diabetics (and 133 non-diabetic controls) and a second group of 104 early onset insulin dependent diabetics (and 138 non-diabetic controls), the latter all with non-cataractous lenses. Powerful associations (p less than 10(-6) were found between the presence of diabetes and increased lenticular autofluorescence in both populations. Among the mixed diabetics diabetic type was a significant factor after accounting for the effects of age and diabetic duration. In the early onset group (clear lenses) a powerful association existed between autofluorescence and diabetic duration (p = 0.000011) after allowing for the effect of age, while in a subgroup of late onset diabetics with clear lenses this effect was modest (p = 0.015). In the early onset diabetic group diabetic retinopathy (p = 0.0064) was associated with increased lenticular autofluorescence after allowing for the effects of age and diabetic duration. In addition a powerful interaction between diabetic duration and the presence of diabetic retinopathy (p less than 10(-6) was found in this subgroup. Among the geographically based population of diabetics, increased nuclear brunescence was powerfully associated (p less than 10(-6) with increased autofluorescence after allowing for the effects of age, diabetic duration, and type of diabetes. This association was not found in the non-diabetic population. Non-enzymatic glycosylation of lens proteins should be considered as a possible mechanism of production of the fluorogen with emission around 520 nm.
Adolescent↗
Capsular 'pits' in the human lens.
The lens capsule is an atypical basement membrane surrounding the lens epithelial cells and lens fibres which make up the remainder of the human lens. A seemingly unreported morphological change visible in the lens capsule with the biomicroscope is described.
Coronary Disease↗
Abnormal laterality and congenital cardiac anomalies. Relations of visceral and cardiac morphologies in the iv/iv mouse.
BACKGROUND: In the management of hearts with deranged laterality, it is essential that the left and right atrial chambers are correctly identified. There are two major approaches, which are based on venous connections or on the morphology of the atrial appendages, and there is no consensus as to which is the most useful. We used the iv/iv mouse mutant, which is known to be pertinent to this problem, to evaluate the relations of cardiac defects with atrial, venous, and other visceral morphologies. METHODS AND RESULTS: The morphology of the heart and other organs was examined in 275 iv/iv mice using criteria based on abnormal laterality in humans. The arrangement of the atrial appendages was determined by morphological examination of the junction between the appendage and the venous component of the atrium. On this basis, 45.1% of cases were shown to have usual atrial arrangement, 50.2% had mirror imagery, 1.5% had right isomerism, and 3.3% had left isomerism. Every case of atrial isomerism had a cardiac lesion; the morphological types were similar to those seen in human cases. Of cases with either usual or mirror-image arrangement of the appendages, 33.2% had abnormal spleens, but only 3.1% had cardiac defects. Similarly, venous abnormalities were much more common (30.1%) than cardiac defects. CONCLUSIONS: Study results endorse the importance of the morphology of atrial appendages in predicting cardiac abnormalities and point to the marked inconsistency of the arrangement of other organs, including the spleen and the connections of the systemic veins.
Animals↗