Enhanced responsiveness of endothelium in the growing/motile state to tumor necrosis factor/cachectin

Some in vivo observations have suggested that growing or perturbed endothelium, such as that which occurs during angiogenesis, is more sensitive to the action of cytokines (TNF/cachectin, TNF, or IL-1) than normal quiescent endothelial cells. This led us to examine the responsiveness of endothelium to TNF as a function of the growth/motile state of the cell. TNF-induced modulation of endothelial cell surface coagulant function was half-maximal at a concentration of approximately 0.1 nM in subconfluent cultures, whereas 1-2 nM was required for the same effect in postconfluent cultures. Perturbation of endothelial cell shape/cytoskeleton was similarly more sensitive to TNF in subconfluent cultures. Consistent with these results, radioligand binding studies demonstrated high affinity TNF binding sites, Kd approximately 0.1 nM on subconfluent cultures, whereas only lower affinity sites (Kd approximately 1.8 nM) were detected on postconfluent cultures. The mechanisms underlying this change in the affinity of endothelium for TNF were studied in four settings. Crosslinking experiments with 125I-TNF and endothelium showed additional bands corresponding to Mr approximately 66,000 and approximately 84,000 with subconfluent cultures that were not observed with postconfluent cultures. Experiments with X-irradiated endothelium, whose growth but not motility was blocked, indicated that proliferation was not required for induction of high affinity TNF sites. Postconfluent endothelium, triggered to enter the proliferative cycle by microbutuble poisons, expressed high affinity TNF binding sites together with changes in cell shape/cytoskeleton well before their entry into S phase. Using wounded postconfluent monolayers, cells that migrated into the wound and those close to the wound edge displayed enhanced TNF binding and modulation of coagulant properties. These results suggest a model for targetting TNF action within the vasculature; regulation of high affinity endothelial cell binding sites can direct TNF to activated cells in particular parts of the vascular tree.

Tumor necrosis factor/cachectin increases permeability of endothelial cell monolayers by a mechanism involving regulatory G proteins

Endothelium is an important target of tumor necrosis factor/cachectin (TNF), a central mediator of the host response in endotoxemia and Gram-negative sepsis. In this report, TNF is shown to increase the permeability of endothelial cell monolayers to macromolecules and lower molecular weight solutes by a mechanism involving a pertussis toxin-sensitive regulatory G protein. Within 1-3 h of exposure to TNF (5 nM), changes in cell shape/cytoskeleton occurred that led to disruption of monolayer continuity with the formation of intercellular gaps. Correlated with these structural changes was an increase in endothelial permeability to macromolecular and lower molecular weight tracers; time-dependent, reversible increases in passage of these tracers, evident by 1-3 h, were observed after addition of TNF to cultures. Perturbation of barrier function by TNF also depended on the dose of TNF added being half-maximal by approximately 0.4 nM. Only a brief exposure (15 min) of TNF to endothelium was required to induce an increase in permeability, and this was not prevented by the presence of cycloheximide or actinomycin D. Preincubation of monolayers with pertussis toxin blocked in parallel TNF-induced increased passage of solutes and cell shape/cytoskeletal perturbation, indicating the close correlation between these changes in endothelial cell function. In contrast, pertussis toxin did not alter TNF-induced modulation of two endothelial cell coagulant properties. These data provide evidence for two intracellular pathways of TNF action that are distinguishable by pertussis toxin and provide insight into a mechanism underlying loss of solute from the intravascular space mediated by TNF: alteration in endothelial cell barrier function.

Corneal ablation by nanosecond, picosecond, and femtosecond lasers at 532 and 625 nm

We produced corneal excisions with nanosecond (ns)-, picosecond-, and femtosecond (fs)-pulsed lasers at visible wavelengths. The threshold energy for ablation was proportional to the square root of the pulse duration and varied from 2.5 microjoules (microJ) at 100 fs to 500 microJ at 8 ns. Excisions made with picosecond and femtosecond lasers was ultrastructurally superior to those made with nanosecond lasers and, at pulse energies near threshold, showed almost as little tissue damage as excisions made with excimer lasers at 193 nm. We conclude that ultrashort-pulsed lasers at visible and near-infrared wavelengths are a possible alternative to excimer lasers for corneal surgery and might have advantages over conventional ophthalmic neodymium-YAG lasers for some intraocular applications.

Interleukin-6 gene expression in human endothelial cells: RNA start sites, multiple IL-6 proteins and inhibition of proliferation

Interleukin-6 (IL-6) is a cytokine which is not only produced by a wide variety of different cells but one which also affects the function of diverse tissues. We have studied the expression of the IL-6 gene in freshly explanted human umbilical vein endothelial cells (HUVEC) and have also evaluated the effect of IL-6 on HUVEC proliferation. Cytokines like interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor (TNF) as well as bacterial products such as the lipopolysaccharide (LPS) rapidly enhance production of biologically active IL-6 by HUVEC (IL-6 bioassay: increase in alpha 1-antichymotrypsin secretion by Hep3B2 cells and its neutralization by antiserum to E. coli-derived human IL-6). The two inducible RNA start sites in the IL-6 gene that are used in cytokine-induced fibroblasts (at +1 and -21) are also used in the same relative proportion (+1 greater than -21) in cytokine or LPS-induced HUVEC as determined by S1-nuclease protection assays for IL-6 transcripts. Immunoaffinity chromatography followed by Western blotting shows that IL-6 species secreted by IL-1 alpha-induced HUVEC are of molecular mass 23-25, 27-30 and 45 kDa as judged by SDS-PAGE under reducing conditions. Finally, rIL-6 inhibits [3H]-thymidine incorporation by HUVEC in a dose-dependent manner. Thus IL-6 is not only produced by HUVEC but may also affect its proliferation. The ability of the vascular endothelium to rapidly secrete IL-6 in response to inflammation-associated cytokines is of strategic value since it generates a circulatory signal which helps mobilize the acute phase plasma protein response and enlists the immune system in host defence.

Femtosecond optical ranging of corneal incision depth

Excimer laser ablation has been proposed as a technique for keratorefractive surgery. Clinical acceptance of linear-incision laser keratectomy may depend on the availability of a method for accurately and noninvasively monitoring incision depth during the ablation process. We have developed a femto-second optical ranging technique for measurement of corneal incision depth. This technique uses nonlinear optical cross-correlation to determine the time-of-flight of an ultrashort laser pulse between the anterior corneal surface and the bottom of the keratectomy incision. Longitudinal and transverse resolution are estimated to be 5 micron and 10 micron, respectively.

Staging cecal and ascending colon carcinoma with computed tomography

Operable subserosal and transserosal and inoperable cecal and ascending colon carcinomas can be differentiated by computed tomography (CT). Invasion of the posterior peritoneal reflection produces recognizable changes on CT, which, with or without adjacent muscle invasion, are indicative of tumor nonoperability.

Infrared laser surgery of the cornea. Studies with a Raman-shifted neodymium:YAG laser at 2.80 and 2.92 micron

Tissue absorption lengths for infrared radiation at 2.8 to 3.1 micron are very short due to strong absorption by water. Corneal ablation using pulsed lasers at these wavelengths can potentially produce incisions similar in quality to cuts produced by excimer lasers at 193 nm. The authors have used 8-ns pulses at 2.80 and 2.92 micron, generated by a Raman-shifted neodymium:YAG (Nd:YAG) laser, to make slit-like incisions in bovine and human corneas. At 2.8 micron, etch depth per pulse increases sigmoidally from 0.15 micron at 390 mJ/cm2 to 3.8 micron at 2200 mJ/cm2. No ablation occurs at fluences below 250 mJ/cm2. Light and transmission electron microscopy show smooth-walled incisions bordered by a thermally damaged region that varies in width from 1.5 micron at 600 mJ/cm2 to 10 micron at 2200 mJ/cm2. The small amount of tissue damage produced at low fluences suggests that infrared ablation may be useful in keratorefractive surgery.

Tumor necrosis factor/cachectin-induced intravascular fibrin formation in meth A fibrosarcomas

Recent studies have indicated that TNF can promote activation of the coagulation mechanism by modulating coagulant properties of endothelial cells. In this report, we demonstrate that infusion of low concentrations of TNF (3 micrograms/animal) into mice bearing meth A fibrosarcomas leads to localized fibrin deposition with formation of occlusive intravascular thrombi in close association with the endothelial cell surface. Studies with 125I-fibrinogen showed tenfold enhanced accumulation of radioactivity in tumor within 2 h after TNF infusion. Western blots of tumor extracts subjected to SDS-PAGE and visualized with a fibrin-specific mAb indicated that fibrin forms in the tumor after the TNF infusion. Electron microscopic studies demonstrated fibrin strands, based on the characteristic 21-nm periodicity, which appeared to be adherent to the endothelial cell surface. Further ultrastructural studies indicated that fibrin formation, first evident within 30 min of the TNF infusion, led to occlusive thrombi limited to the tumor vascular bed (i.e., not in the normal mouse vasculature) within 2 h and was associated with an 80% reduction in tumor perfusion based on studies with Evans blue. In view of previous work concerning TNF induction of endothelial cell procoagulant activity, the hypothesis that tumor cell products prime the response of endothelium to this cytokine was tested. Supernatants of cultured meth A fibrosarcomas obtained serum-free conditions, which had no intrinsic procoagulant activity, considerably enhanced tissue factor induction in endothelium in response to submaximal concentrations of TNF. The factor(s) in the tumor-conditioned medium appeared to be distinct from IL-1, fibroblast growth factor, IFN-gamma, TNF, endotoxin, TGF-alpha, and TGF-beta. These studies delineate a novel model of localized clot formation in which thrombosis is initiated by a pathophysiologic mediator, TNF, and provides an opportunity to examine mechanisms in the microenvironment directing clot formation to the tumor vascular bed.

Faulty sternotomy and complications after median sternotomy

In 11 of 55 patients with complications of median sternotomy, a paramedian sternotomy has been detected by computed tomography or at reparative operation. The thin side of the sternum is easily broken by the closing wires, this being the cause of instability and probably dehiscence and consequent infection and osteomyelitis. Most of the 11 patients in this group had some other predisposing risk factors, such as obesity, prolonged aortic cross-clamp time, and prolonged respiratory assistance. We suggest that, if a paramedian sternotomy is diagnosed at the primary operation, special closure techniques should be undertaken. Each patient with early dehiscence of a median sternotomy should undergo a computed tomographic examination. If a paramedian sternotomy is proved, simple reclosure is inadvisable. Sternectomy and closure with muscle flaps are then indicated.

Sclerosing peritonitis. Possible early diagnosis by computerized tomography of the abdomen

Sclerosing peritonitis (SP) has come to be recognized as a serious complication of peritoneal dialysis (PD). However, diagnosis is often established at a late stage of the disease and at laparotomy. The use of computerized tomography (CT) of the abdomen in 2 patients, clinically suspected of suffering from SP, revealed loculated ascites, adherent bowel loops, bowel lumenal narrowing, and thickening of the peritoneal membrane. Such radiological changes in patients on PD seem highly consistent with a diagnosis of SP. We feel that CT of the abdomen may help in attaining an early, correct, and noninvasive diagnosis of SP. We recommend that CT of the abdomen be performed in any patient on chronic PD who has clinical manifestations suggestive of SP. Early diagnosis of SP can lead to early cessation of PD and hopeful recovery of the peritoneal membranes and space.

Computed tomographic demonstration of calcification of the ligamenta flava of the lumbosacral spine in ankylosing spondylitis

An axial computed tomographic (CT) scan of the lumbosacral regions was performed in 65 patients. The patient population was divided into two groups. The first (control) group included 40 elderly patients without calcification of the ligamenta flava. The second group included 25 patients with ankylosing spondylitis. More than 90% of those in the second group showed calcified lumbosacral ligamenta flava. In two patients these calcifications produced spinal stenosis. The diagnostic and practical importance of these findings are discussed.

[A combination of dihydroergotamine and acetylsalicylic acid--prevention of postoperative thromboembolic complications. Clinical study in orthopedics]

202 patients undergoing surgery involving the lower limbs were given antithrombotic treatment for at least 21 days, or until they had regained full mobility. Following subcutaneous prophylaxis with a combination of heparin and dihydroergotamine, two oral regimens were compared in a controlled and randomized prospective study. The first treatment consisted of a combination of acetylsalicylic acid (ASA) and dihydroergotamine (DHE), and the second of acenocoumarol. The radiofibrinogen uptake test was carried out in high-risk patients (i.e. those undergoing hip surgery) to detect deep-vein thrombosis. No statistically significant difference was found between the two groups. However, the ASA/DHE combination enjoyed better patient acceptance and was much easier to use.

Computed tomographic demonstration of intramural colonic air (pneumatosis coli) as a feature of severe ulcerative colitis

Fast rotational computed tomographic scanning techniques allow an accurate appreciation of the diameter of the colon, the presence of severe necrotizing mucosal change, and the detection of unsuspected intramural colonic air (pneumatosis coli) in cases of severe necrotizing ulcerative colitis.

High-speed photography of excimer laser ablation of the cornea

We have used laser-based high-speed photography to investigate excimer laser ablation of the cornea. Photographs of the ablation plume were obtained 500 ns to 150 microseconds after incidence of a 193- or 248-nm excimer laser pulse on the surface of the cornea. Ejection of material from the cornea begins on a time scale of nanoseconds and continues for 5 to 15 microseconds following the excimer pulse. At 193 nm the ablation plume resembles a burst of smoke, and individual particles are too small to be optically resolved with our apparatus. At 248 nm the plume resembles a spray of larger, discrete droplets. Material is ejected from the cornea at supersonic velocity but decelerates rapidly; the velocity for the first 500 ns following the excimer pulse averages 400 m/s at 193 nm. Plume size and velocity increase with increasing fluence.

Opinions of Clergy and Guidance Counselors about the Desirability of Irrational Beliefs in Children

About one-third of 102 clergy and none of 118 female high school guidance counselors regarded Ellis's Beliefs 3, 8, 9, and 10 as desirable for young children. More than one-fifth of male high school counselors judged Beliefs 3 and 9 to be desirable.

Directionality of dental trait frequency between human second deciduous and first permanent molars

Dental traits were scored for second deciduous molars (dm2) and first permanent molars (M1) on casts of the dental arches of children aged 7-11 years. The children were from four different ethnic groups. The overall frequency of traits differed between the groups but the relative frequency of expression of traits in the two teeth showed a similar pattern. Traits such as continuous oblique ridge, Carabelli cusp, Y pattern and 7th cusp, that appear in the early stages of development, were more frequent in dm2 than in M1. Wrinkling, occlusal tubercles and marginal ridge cusps were more frequent in M1; these appear later. Thus the relative frequency of traits in these teeth reflects their ontogenetic history.

Management of hypertension in twelve Oxfordshire general practices

The general practice records of 2371 hypertensive patients on drug therapy in 12 practices were reviewed retrospectively. It was found that the mean systolic blood pressure of the patients had fallen by 29 mmHg and the mean diastolic pressure by 16 mmHg after one year of treatment and that there was a further reduction of 5 mmHg in the systolic pressure and 5 mmHg in the diastolic pressure at the most recent recording of blood pressure. Half of the patients had only a single blood pressure reading recorded before treatment was started and for 56% of the patients there was no record of smoking habit and for 69% no record of weight. Twenty-seven per cent of the patients suffered from mild hypertension, that is blood pressure less than 180/110 mmHg, and 56% were over 65 years of age. These results indicate the need for policies for selection of patients for treatment and for standards of recording. It is suggested that practices should review their results and undertake to treat elderly hypertensive patients and those with mild hypertension only when they can demonstrate that their policies are effective for young hypertensive patients and for those with moderate or severe hypertension.

Regulation of growth hormone and somatomedin-C secretion in postmenopausal women: effect of physiological estrogen replacement

To determine the effects of estrogen deficiency and replacement on GH secretion, we measured the 22-h GH secretory pattern and response to 1 h of light exercise in 16 normal postmenopausal women before and after treatment replacement with ethinyl estradiol (20 micrograms/day for 15 days). To determine whether the changes found were due to pituitary sensitization by estrogen, the response to synthetic GH-releasing hormone (GHRH; 1.0 microgram/kg, iv) was measured. To assess the biological effectiveness of GH in estrogen-treated women, somatomedin-C (Sm-C) responses to GHRH were measured. Pre- and postestrogen GH secretion rates, expressed as mean areas circumscribed by plasma GH values, were as follows: 22-h study, 1.4 +/- 0.1 (+/- SEM) vs. 2.0 +/- 0.3 ng/ml X h (P = 0.04; n = 5); during 1 h of exercise, 2.3 +/- 0.4 vs. 3.2 +/- 0.4 ng/ml X h (P = 0.03; n = 16); after GHRH-(1-40), 6.7 +/- 1.7 vs. 8.5 +/- 1.5 ng/ml X h (P = 0.12; n = 16). There also was a modest but significant increase in resting plasma GH (1.5 +/- 0.2 vs. 2.3 +/- 0.5 ng/ml (P = 0.039). Pre- and postestrogen plasma Sm-C concentrations were 0.56 +/- 0.08 and 0.32 +/- 0.03 U/ml, respectively (P = 0.006; n = 16). Thus, estrogen therapy increased spontaneous and exercise-induced GH secretion in postmenopausal women and reduced Sm-C levels. The mechanisms of GH elevation by estrogen may include both central effects and a negative feedback linkage to reduced plasma Sm activity.

Activation of coagulation releases endothelial cell mitogens

Recent studies have indicated that endothelial cell function includes elaboration of growth factors and regulation of coagulation. In this paper we demonstrate that activated coagulation Factor X (Factor Xa), a product of the coagulation mechanism generated before thrombin, induces enhanced release of endothelial cell mitogens, linking these two functions. Mitogenic activity generated by cultured bovine aortic endothelial cells in response to Factor Xa included platelet-derived growth-factor-like molecules based on a radioreceptor assay. Effective induction of mitogens by Factor Xa required the integrity of the enzyme's active center and the presence of the gamma-carboxyglutamic acid-containing domain of the molecule. Factor Xa-induced release of mitogens from endothelium occurred in serum-free medium and was not altered by hirudin or antibody to Factor V, indicating that it was a direct effect of Factor Xa and was not mediated by thrombin. Elaboration of mitogenic activity required only brief contact between Factor Xa and endothelium, and occurred in a time-dependent manner. Generation of enhanced mitogenic activity in response to Factor Xa was unaffected by the presence of actinomycin D and was not associated with increased hybridization of RNA from treated cells to a v-sis probe. Release of mitogenic activity was dependent on the dose of Factor Xa, being half-maximal at 0.5 nM and reaching a maximum by 5 nM. Radioligand binding studies demonstrated a class of endothelial cell sites half-maximally occupied at a Factor Xa concentration of 0.8 nM. The close correspondence between the parameters of Factor Xa-induced mitogen release and Factor Xa binding suggests these sites may be related. When Factor X was activated on the endothelial cell surface by Factors IXa and VIII, the Factor Xa formed resulted in the induction of enhanced release of mitogenic activity. These data suggest a mechanism by which the coagulation system can locally regulate endothelial cell function and vessel wall biology before thrombin-induced release of growth factors from platelets.

Cloned bovine aortic endothelial cells synthesize anticoagulantly active heparan sulfate proteoglycan

Cloned bovine aortic endothelial cells were cultured with [35S]Na2SO4 and proteolyzed extensively with papain. Radiolabeled heparan sulfate was isolated by DEAE-Sephacel chromatography. The mucopolysaccharide was then affinity fractionated into two separate populations utilizing immobilized antithrombin. The heparan sulfate, which bound tightly to the protease inhibitor, represented 0.84% of the mucopolysaccharide mass, accounted for greater than 99% of the initial anticoagulant activity, and exhibited a specific activity of 1.16 USP units/10(6) 35S-cpm. However, the heparan sulfate that interacted minimally with the protease inhibitor constituted greater than 99% of the mucopolysaccharide mass, represented less than 1% of the starting biologic activity, and possessed a specific anticoagulant potency of less than 0.0002 USP unit/10(6) 35S-cpm. An examination of the disaccharide composition of the two populations revealed that the high-affinity heparan sulfate contained a 4-fold or greater amount of GlcA----GlcN-SO3-3-O-SO3 (where GlcA is glucuronic acid), which is a marker for the antithrombin-binding domain of commercial heparin, as compared with the depleted material. Cloned bovine aortic endothelial cells were incubated with [35S]Na2SO4 as well as tritiated amino acids and completely solubilized with 4 M guanidine hydrochloride and detergents. The double-labeled proteoglycans were isolated by DEAE-Sephacel, Sepharose CL-4B, and octyl-Sepharose chromatography. These hydrophobic macromolecules were then affinity fractionated into two separate populations utilizing immobilized antithrombin. The heparan sulfate proteoglycans which bound tightly to the protease inhibitor represented less than 1% of the starting material and exhibited a specific anticoagulant activity as high as 21 USP units/10(6) 35S-cpm, whereas the heparan sulfate proteoglycan that interacted weakly with the protease inhibitor constituted greater than 99% of the starting material and possessed a specific anticoagulant potency as high as 0.02 USP unit/10(6) 35S-cpm. The high-affinity heparan sulfate proteoglycan is responsible for more than 85% of the anticoagulant activity of the cloned bovine aortic endothelial cells. Binding studies conducted with 125I-labeled antithrombin demonstrated that these biologically active proteoglycans are located on the surface of cloned bovine aortic endothelial cells.

Tumor necrosis factor/cachectin interacts with endothelial cell receptors to induce release of interleukin 1

Tumor necrosis factor/cachectin (TNF) has been implicated as a mediator of the host response in sepsis and neoplasia. Recent work has shown that TNF can modulate endothelial cell hemostatic properties, suggesting that endothelium is a target tissue for TNF. This led us to examine whether endothelial cells have specific binding sites for TNF and augment the biological response to TNF by elaborating the inflammatory mediator, IL-1. Incubation of 125I-recombinant human TNF with confluent, cultured human umbilical vein endothelial cells resulted in time-dependent, reversible, and saturable binding. Binding was half-maximal at a TNF concentration of 105 +/- 40 pM, and at saturation 1,500 molecules were bound per cell. Heat-treated TNF, which is biologically inactive, did not bind to endothelium. In addition to surface binding, TNF induced the elaboration of IL-1 activity by endothelial cells in a time-dependent manner. Generation of IL-1 activity required protein synthesis and was half-maximal at a TNF concentration of 50 +/- 20 pM. IL-1 activity from TNF-treated endothelium could be adsorbed by an immobilized antibody to IL-1. Heat-treated TNF was ineffective in eliciting endothelial cell IL-1. These data indicate that TNF can bind specifically to endothelium and initiate a cascade of inflammatory and coagulant events on the vessel surface potentially central to the host response to neoplasia and sepsis.

Participation of endothelial cells in the protein C-protein S anticoagulant pathway: the synthesis and release of protein S

The protein C-protein S anticoagulant pathway is closely linked to the endothelium. In this paper the synthesis and release of the vitamin K-dependent coagulation factor protein S is demonstrated. Western blotting, after SDS PAGE of Triton X-100 extracts of bovine aortic endothelial cells grown in serum-free medium, demonstrated the presence of protein S. A single major band was observed at Mr approximately 75,000, closely migrating with protein S purified from plasma absent from cells treated with cycloheximide. Metabolic labeling of endothelial cells with [35S]methionine confirmed de novo synthesis of protein S. Using a radioimmunoassay, endothelium was found to release 180 fmol/10(5) cells per 24 h and contain 44 fmol/10(5) cells of protein S antigen. Protein S released from endothelium was functionally active and could promote activated protein C-mediated factor Va inactivation on the endothelial cell surface. Warfarin decreased secretion of protein S antigen by greater than 90% and increased intracellular accumulation by almost twofold. Morphological studies demonstrated intracellular protein S was in the Golgi complex, concentrated at the trans face, rough endoplasmic reticulum, lysosomes, and in vesicles at the periphery. In contrast, protein S was not found in vascular fibroblasts or smooth muscle cells. A pool of intracellular protein S could be released rapidly by the calcium ionophore A23187 (5 microM). This effect was dependent on the presence of calcium in the culture medium and could be blocked by LaCl3, which suggests that cytosolic calcium flux may be responsible for protein S release. These results demonstrate that endothelial cells, but not the subendothelial cells of the vessel wall, can synthesize and release protein S, which indicates a new mechanism by which the inner lining of the vessel wall can contribute to the prevention of thrombotic events.

Individual variation in enamel structure of human mandibular first premolars

Nine human mandibular first premolars were examined to assess variation in external morphology and enamel structural organization within a tooth type. The relationship of enamel ultrastructure to gross dental morphology was also studied. The teeth were cut in the mesiodistal direction just lingual to the buccal cusp, and etched. Montages were constructed of the cut enamel surface photographed in the scanning electron microscope at 100 X magnification. Parameters were measured and correlation coefficients were calculated for the comparison of various odontometric features. The mesiodistal and buccolingual dimensions were highly correlated and the occlusal thickness of enamel was significantly correlated to crown height but not crown width. Hunter-Schreger bands were less pronounced in fossa areas than at lateral aspects, cusps, or ridges; these bands were directly related to the geometry of the tooth. It was concluded that within this tooth type, there is a large amount of individual variation not only in gross morphology but also in enamel ultrastructure. This result underscores the fact that interspecific comparisons must be made with care.

Calcified subdural haematomas associated with arrested hydrocephalus--late sequelae of shunt operation in infancy

Calcified chronic subdural haematomas (SDH) and features of arrested (compensated) hydrocephalus were demonstrated by skull radiography and cranial computed tomography (CT) in two children who had no neurological deficit. Ventricular surgical drainage had been performed 8 and 11 years prior to admission and the haematomas remained subsequently undetected. The following presentation will serve to illustrate the characteristic radiological features of this entity, the issue of management, and includes a review of the literature.

The role of endothelium in the homeostatic balance of haemostasis

As the cells forming the luminal vascular surface, endothelial cells are strategically positioned to play an important role in the regulation of coagulation. They cannot be regarded as an inert surface lining the vessel wall since they possess multiple activities. Anticoagulant properties include provision of a cell surface with heparin-like molecules (which can serve as binding sites for antithrombin III), synthesis of thrombomodulin (which alters the substrate specificity of thrombin), maintenance of a low level of tissue factor and generation of prostacyclin. In addition to these anticoagulant properties, endothelial cells can play a role in procoagulant reactions. Studies which have examined mechanisms underlying the localization of thrombotic processes have suggested the possible involvement of endothelial cells in procoagulant events. Endothelial cells have been found to propagate factor X and prothrombin activation once factor IXa and factor Xa have been formed. Factors regulating the balance of plasminogen activator and inhibitor synthesis are also under study. Perturbation of endothelial cells with induction of tissue factor and production of platelet-activating factor and thromboxane provides a model of the thrombotic state in which endothelium can promote coagulation. The multiple properties of endothelial cells indicate that a continuous blood flow in an unperturbed region of the vessel wall results from a complex interplay of anticoagulant and procoagulant activities. In a perturbed region, endothelial cells might initiate coagulation and the thrombin formed on the surface of endothelial cells might then lead to recruitment of platelets.

An endothelial cell-dependent pathway of coagulation

Although the endothelial cell is considered antithrombogenic, endothelium has recently been shown to participate in procoagulant reactions. In this report cultured bovine aortic endothelial cells are shown to propagate a procoagulant pathway starting with factor XIa, leading to activation of factors IX, VIII, X, and prothrombin, culminating in fibrinopeptide A cleavage from fibrinogen and formation of a fibrin clot. Electron microscopic studies demonstrated that fibrin strands are closely associated with the endothelial cells. Endotoxin-treated endothelial cells, having acquired tissue factor activity, generated fibrinopeptide A in the presence of factors VIIa, IX, VIII, X, prothrombin, and fibrinogen. Factor X activation by factor VIIa and tissue factor expressed by endothelial cells is 10 times greater in the presence of factors IX and VIII than in their absence. This indicates that on the perturbed endothelial cell surface, factors IX and VIII do have an important role in the activation of factor X. Addition of platelets (10(8) per ml) augmented thrombin formation seen in the presence of endothelium alone by about 15-fold. Anti-human factor V IgG decreased this enhanced thrombin formation in the presence of platelets, indicating that factor V from platelets was playing an important role in thrombin formation. These data lead us to propose that endothelial cells can actively participate in procoagulant reactions. Although platelets can augment thrombin formation by these endothelial cell-dependent reactions, endothelial cells alone can lead to formation of a cell-associated fibrin clot. The endotoxin-treated endothelial cell provides a model of the thrombotic state supplying tissue factor to initiate coagulation and propagating the reactions leading to fibrin formation. This endothelial cell-dependent pathway suggests a central role for factors VIII and IX consistent with their importance in hemostasis.

Interaction of antithrombin III with bovine aortic segments. Role of heparin in binding and enhanced anticoagulant activity

Bovine antithrombin III (AT III) interaction with the luminal surface of bovine aortic segments with a continuous layer of endothelium was examined. Incubation of 125I-AT III with vessel segments, previously washed free of endogenous AT III, demonstrated specific, time-dependent binding to the protease inhibitor to the endothelium. Half-maximal binding was observed at an added AT III concentration of 14 nM. Binding of 125I-AT III to the vessel wall was reversible (50% dissociated in 4 min), and addition of either heparin or Factor Xa accelerated displacement of 125I-AT III from the vessel segment. Dissociation of 125I-AT III from the vessel segment in the presence of factor Xa coincided with the formation of a Factor Xa-125I-AT III complex. Inactivation of Factor IXa and Factor Xa by AT III was facilitated in the presence of vessel segments. Pretreatment of vessel segments with highly purified Flavobacterium heparinase precluded the vessel-dependent augmentation of AT III anticoagulant activity as well as specific binding of 125I-AT III to the vessel endothelium. In contrast, pretreatment of the vessel segments with chrondroitinases (ABC or AC) had no detectable effect on 125I-AT III binding or on AT III anticoagulant activity. AT III binding to vessel segments was competitively inhibited by increasing concentration of platelet factor 4. Binding of the protease inhibitor to vessel segments was inhibited by chemical modification of AT III lysyl or tryptophan residues. These AT III derivatives retained progressive inhibitory activity. These data suggest that heparin-like molecules are present on the aortic vessel wall and mediate binding of AT III to the vessel surface, as well as enhancing the anticoagulant activity of AT III at these sites.

Penetrating duodenal trauma

Ten cases of penetrating injuries to the duodenum are presented. Six injuries were treated with primary repair, retrograde decompressing jejunostomy, and feeding jejunostomy. There was no postoperative duodenal leak in any patient treated with primary repair and retrograde decompressing jejunostomy. In a review of 563 cases of penetrating duodenal trauma, the superiority of primary repair of duodenal injuries with decompression of the suture line by a tube inserted in a remote site of the bowel (stomach or jejunum) was demonstrated. This technique afforded the lowest mortality and incidence of postoperative duodenal fistulae. When applicable, primary repair with retrograde decompressing jejunostomy and feeding jejunostomy is a rapid, simple, and safe method for the treatment of penetrating duodenal injuries.

Computerized tomography in pericardial disease

In many patients conventional radiographic procedures aid the detection of pericardial pathology. Echocardiography is undoubtedly the most satisfactory investigation for assessing pericardial thickening and fluid. However, in special circumstances CT of the mediastinum is able to offer additional information. Small quantities of pericardial air, associated tumor masses, and the extent of a pericardial effusion or pericardial calcification can be displayed most advantageously by CT.

Infant intermodal speech perception is a left-hemisphere function

Prelinguistic infants recognized structural correspondences in acoustic and optic properties of synchronized, naturally spoken disyllables, but did so only when they were looking to their right sides. This result suggests that intermodal speech perception is facilitated by rightward orientation of attention and subserved by the left hemisphere.

Single-photon emission tomography with a 12-pinhole collimator

To assess the advantages of more complete angular sampling and of more views in the tomographic reconstruction process, tomographic imaging with a 12-pinhole (12PH) collimator has been compared with 7-pinhole tomography (7PH). The 12PH system gives a 50% increase in sensitivity but resolution degrades more rapidly with depth. The 7PH and 12PH systems provide similar accuracy of detection of lesions in a myocardial ring phantom. The 7PH images, however, demonstrated more noise and "ripple" artifacts. The 12PH system offers a larger reconstruction volume and generates fewer artifacts when the collimator is misaligned with the myocardial long-axis, thus making patient positioning less critical than with 7PH. A disadvantage is that individual views are minified by the 12PH collimator, and a 256 X 256 image matrix should be used during image acquisition to limit digital sampling errors.

Comparison of myocardial thallium-201 clearance after maximal and submaximal exercise: implications for diagnosis of coronary disease: concise communication

Recently the quantitation of regional thallium-201 clearance has been shown to increase the sensitivity of the scintigraphic detection of coronary disease. Although TI-201 clearance rates might be expected to vary with the degree of exercise, this relationship has not been explored. We therefore evaluated the rate of decrease in myocardial TI-201 activity following maximal and submaximal stress in seven normal subjects and 21 patients with chest pain, using the seven-pinhole tomographic reconstruction technique. In normals, the mean TI-201 clearance rate declined from 41% +/- 7 over a 3-hr period with maximal exercise to 25% +/- 5 after 3 hr at a submaximal level (p less than 0.001). Similar differences in clearance rates were found in the normally perfused regions of the left ventricle in patients with chest pain, depending on whether or not a maximal end point (defined as either the appearance of ischemia or reaching 85% of age-predicted heart rate) was achieved. In five patients who did not reach these end points, 3-hr clearance rates in uninvolved regions averaged 25% +/- 2, in contrast to a mean of 38% +/- 5 for such regions in 15 patients who exercised to ischemia or an adequate heart rate. These findings indicate that clearance criteria derived from normals can be applied to patients who are stressed maximally, even if the duration of exercise is limited, but that caution must be used in interpreting clearance rates in those who do not exercise to an accepted end point.

Single-composite image display of information from tomographic myocardial perfusion studies

Tomography has the general advantage of improving spatial resolution in a direction perpendicular to the tomographic sections. However, visualizing the size, shape, and relative position of a lesion depicted in multiple tomograms can be difficult. The authors have developed computer software which permits the single-composite display of information contained in multiple tomographic sections from a thallium-201 myocardial perfusion study. The display also allows identification of left ventricular myocardial areas as normal, reversibly ischemic, or irreversibly ischemic and quantitates the per cent of myocardium in each category.

Ultrastructure of secretory ameloblasts in a monkey Macaca mulatta

A 13-month-old animal was fixed by perfusion; the tooth buds of the permanent dentition were removed and prepared for transmission electron microscopy. Secretory ameloblasts were about 35 micrometers long and Tomes processes varied from 6 to 16 micrometers in length. The organelles included a basal nucleus, a Golgi apparatus concentrated in a spherical region about 4 micrometers in diameter in the supranuclear region, rough endoplasmic reticulum situated between the basal and apical terminal webs, and mitochondria dispersed throughout the cytoplasm, including Tomes processes. Many ameloblasts also contained a variety of granules, rosettes of small vesicles, and multivesicular bodies interpreted as parts of a lysosomal or GERL system. Stippled material was observed only at the distal end of the Tomes process of some ameloblasts. The results demonstrate that the Tomes process in the macaque was longer than reported in cats or man, otherwise the secretory ameloblast ultrastructure is similar among the three species.

Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition of Macaca mulatta and Macaca arctoides

Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in two Macaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 micrometers, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 micrometers long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis in Macaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.

A study of lower-limb mechanics during stair-climbing

The motions, forces, and moments at the major joints of the lower limbs of ten men ascending and descending stairs were analyzed using an optoelectronic system, a force-plate, and electromyography. The mean values for the maximum sagittalplane motions of the hip, knee, and ankle were 42, 88, and 27 degrees, respectively. The mean maximum net flexion-extension moments were: at the hip, 123.9 newton-meters going up and 112.5 newton-meters going down stairs; at the knee, 57.1 newton-meters going up and 146.6 newton-meters going down stairs; and at the ankle, 137.2 newton-meters going up and 107.5 newton-meters going down stairs. When going up and down stairs large moments are present about weight-bearing joints, but descending movements produce the largest moments. The magnitudes of these moments are considerably higher than those produced during level walking.