Toward a general analysis of endogenous Easterlin cycles

Easterlin believed that there were two features associated with the birth cycles he observed: the cycles were related to the labor market, and they might be self-generating. This paper tries to set up a model that contains both of these two features. The authors suppose that the welfare of various age-specific cohorts are determined by their respective marginal productivity, and that the underlying technology which puts together labor force of various age-specific cohorts can be characterized by a general production function. Under these weak assumptions, they show that the well-analyzed cohort and period models along the lines of Lee (1974) are restricted versions of the general setting. Given that both the cohort model and the period model were rejected by statistical tests, the authors adopt the coefficient values obtained from the estimation of the unrestricted version to perform the bifurcation analysis. They go beyond the previous study which focused upon the possible existence of limit cycles, and show that the US fertility limit cycle solution is unstable. Therefore the population trajectory will never converge to that limit cycle.

Blockage of the urokinase receptor on the cell surface: construction and characterization of a hybrid protein consisting of the N-terminal fragment of human urokinase and human albumin

Receptor-bound urokinase is likely to be a crucial determinant in both tumor invasion and angiogenesis. We report here that a yeast-derived genetic conjugate between human serum albumin and the 1-135 N-terminal residues of urokinase (u-PA) competitively inhibits the binding of exogenous and endogenous u-PA to its cell-anchored receptor (u-PAR). This hybrid molecule (ATF-HSA) also inhibits in vitro pro-urokinase-dependent plasminogen activation in the presence of u-PAR bearing cells. These effects are probably responsible for the observed in vitro inhibition of tumor cell invasion in a reconstituted basement membrane extract (Matrigel).

Differential tyrosine phosphorylation of JAK1, JAK2, and STAT1 by growth hormone and interferon-gamma in IM-9 cells

Both the growth hormone (GH) and interferon gamma (IFN gamma) receptors are members of the cytokine receptor family that activate tyrosine phosphorylation despite the lack of a tyrosine kinase domain. Recently, the Janus kinase (JAK) family of tyrosine kinases have been shown to play an integral role in intracellular signaling by the cytokine receptors. We demonstrate that, in the human IM-9 lymphocyte, both JAK1 and JAK2 are tyrosine-phosphorylated in response to IFN gamma, whereas only JAK2 is tyrosine-phosphorylated in response to GH. Furthermore, dimerization of the GH receptor appears to be necessary for GH stimulated tyrosine phosphorylation of JAK2. We provide two lines of evidence that the JAK2 kinases can be regulated independently by GH and IFN gamma in IM-9 cells: 1) desensitization of JAK2 to GH stimulation does not affect the IFN gamma stimulated tyrosine phosphorylation of JAK2; and 2) JAK2 tyrosine phosphorylation by GH and IFN gamma is additive to that seen with either hormone alone. Furthermore, we demonstrate that although IFN gamma activates the tyrosine phosphorylation of the p91 signal transducer and activator of transcription (STAT1) in IM-9 cells, GH does not. GH does activate the tyrosine phosphorylation of a 93-kDa protein that appears to be distinct from STAT1.

Activation energy of single-stranded DNA moving through cross-linked polyacrylamide gels at 300 V/cm. Effect of temperature on sequencing rate in high-electric-field capillary gel electrophoresis

In DNA sequencing, single-stranded DNA fragments are separated by gel electrophoresis. This separation is based on a sieving mechanism where DNA fragments are retarded as they pass through pores in the gel. In this paper, we present the mobility of DNA sequencing fragments as a function of temperature; mobility is determined in 4% T LongRanger gels at an electric field of 300 V/cm. The temperature dependence is compared with the predictions of the biased reptation model. The model predicts that the fragment length for the onset of biased reptation with stretching increases with the square of temperature; the data show that the onset of biased reptation with stretching decreases with temperature. Biased reptation fails to model accurately the temperature dependence of mobility. We analyzed the data and extracted the activation energy for passage of sequencing fragments through the gel. For fragments containing less than ca. 200 bases, the activation energy increases linearly with the number of bases at a rate of 25 J/mol per base; for longer fragments, the activation energy increases at a rate of 6.5 J/mol per base. This transition in the activation energy presumably reflects a change in conformation of the DNA fragments; small fragments exist in a random coil configuration and larger fragments migrate in an elongated configuration.

High-speed and high-accuracy DNA sequencing by capillary gel electrophoresis in a simple, low cost instrument. Two-color peak-height encoded sequencing at 40 degrees C

A low-cost DNA sequencer was constructed based on a single helium-neon laser. The two-color peak-height encoded sequencing protocol, based on the use of T7 DNA polymerase in a manganese buffer, was used to generate samples. Two termination reactions were performed. In the first, a TAMRA (applied Biosystems)-labeled primer was extended in the presence of ddATP and ddCTP. The amounts of dideoxynucleotides were adjusted to produce a 3:1 peak height ratio. Similarly, a ROX (Applied Biosystems)-labeled primer was extended in the presence of ddGTP and ddTTP; the amounts of dideoxynucleotides was adjusted to produce a 3:1 peak height ratio. The pooled fragments were separated on a 4% T LongRanger gel operated at 39 degrees C. Over 500 bases of sequence were generated in 50 min.

Pericardium-lined skeletal muscle ventricles in circulation up to 589 days

Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 15 beagles. The animals were divided into two groups based on modifications in the SMV construction: group I consisted of 5 animals and group II of 10 animals. After a 3-week vascular delay and 6 to 8 weeks of 2-Hz electrical conditioning, the SMVs were connected to the thoracic aorta. In group I, counterpulsation at 33 Hz resulted in an initial 24.4% augmentation of the mean diastolic pressure, a 27.1% decrease in the presystolic pressure, and a 15.9% increase in the endocardial viability ratio. In group II, the mean diastolic pressure rose by 24.7%, the presystolic pressure decreased by 14.3%, and the endocardial viability ratio increased by 24.5%. During propranolol-induced heart failure, the percentage increase in the mean diastolic pressure was improved (12.9% before propranolol infusion versus 27.6% during propranolol infusion), as was the percentage increase in the endocardial viability ratio (11.2% versus 28.7%). Under low cardiac output conditions, SMV contraction resulted in small but statistically significant increases in the total cardiac output (4.3% at 33 Hz, 7.6% at 85 Hz). One animal in group I survived for 589 days with a functioning SMV before progressive dilation of the SMV (impending rupture) developed. Delayed rupture of the SMV sewing ring anastomosis occurred in 2 dogs. Five animals in group II are all alive, with functioning SMVs in the circulation for 377 to 464 days. No animals in group II had rupture of their SMV or showed evidence of thrombus formation.

Development of cancer cachexia-like syndrome and adrenal tumors in inhibin-deficient mice

Activins and inhibins, members of the type beta transforming growth factor superfamily of growth regulatory proteins, are produced in multiple tissues and affect diverse physiologic processes. Using embryonic stem cell technology, we previously demonstrated that inhibin can function as a gonadal tumor suppressor. In this study, we show that development of gonadal tumors is rapidly followed by a cancer cachexia-like wasting syndrome. Cachectic inhibin-deficient mice develop hepatocellular necrosis around the central vein and parietal cell depletion and mucosal atrophy in the glandular stomach, are anemic, and demonstrate severe weight loss. The liver pathology is consistent with studies demonstrating an effect of elevated activins on rat hepatocytes. In inhibin-deficient mice with tumors, activins are > 10-fold elevated in the serum and are likely causing some of the cachexia symptoms. In contrast, inhibin-deficient mice gonadectomized at an early age do not develop this wasting syndrome. However, these gonadectomized, inhibin-deficient mice eventually develop adrenal cortical sex steroidogenic tumors with nearly 100% penetrance, demonstrating that inhibin is also a tumor suppressor for the adrenal gland.

Postoperative hemostasis and fibrinolysis in patients undergoing cardiopulmonary bypass with or without aprotinin therapy

Intra- and postoperative blood loss during open heart surgery is reduced by approximately 50% when aprotinin, a potent inhibitor for plasmin and kallikrein, is administered during surgery. But whether aprotinin increases the risk of thrombotic complications remains controversial. The aim of this study was to evaluate the effects of aprotinin administration on coagulation and fibrinolysis during and after cardiopulmonary bypass (CPB). Thirty patients undergoing CPB were randomly assigned to two comparable groups for a double-blind study (16 patients receiving high-dose aprotinin, 14 patients receiving placebo). Patients' plasma levels of ATM (thrombin-induced modified antithrombin III), FbDP (fibrin degradation products, D-Dimers), t-PA (tissue-type plasminogen activator) and PAI-1 (plasminogen activator inhibitor type 1) were measured at regular intervals. In both groups, ATM level increased during surgery (from less than 30 to 90-110 ng/ml) and returned to normal 24 h after surgery and remained unchanged thereafter. Aprotinin reduced this increase in ATM levels (p = 0.02 at 30 min after the start of CPB). The FbDP generated during surgery was greatly reduced in the aprotinin group (945 ng/ml) in comparison with the placebo group (1889 ng/ml, p = 0.004). After surgery, FbDP levels decreased in both groups with nadirs at 2nd day (placebo group: 940 ng/ml and aprotinin group: 865 ng/ml) indicating a hypofibrinolytic period. Then, the FbDP level in both groups started to increase up to the 9th day, in an identical manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of amino acid residues of Bacillus thuringiensis delta-endotoxin CryIAa associated with membrane binding and toxicity to Bombyx mori

Alanine substitution (A3) or deletion (D3) of residues 365 to 371 of Bacillus thuringiensis CryIAa insect toxin removed nearly all toxicity for Bombyx mori (> 1,000-fold less active than the wild type). The loss of larvicidal activity in the mutants was not caused by increased sensitivity to larval gut enzymes but could be attributed to significantly reduced binding to B. mori brush border membrane vesicles. Some or all of the affected amino acid residues may interact directly or indirectly with the B. mori membrane receptor(s). Such receptor binding appears to be directly correlated with insect toxicity.

Intrathoracic and extrathoracic skeletal muscle ventricles in circulation: left ventricular apex-to-aorta configuration

Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 12 dogs. In group I (n = 6), SMVs were placed intrathoracic, in the apex of the left hemithorax. In group II (n = 6), SMVs were positioned extrathoracic between the chest wall and subcutaneous tissue. After a 3-week vascular delay period, SMVs were electrically pre-conditioned with 2-Hz continuous stimulation for 6 weeks. At a second procedure, a valved conduit was placed between the left ventricular (LV) apex and the SMV, and a second valved conduit between the SMV and the thoracic aorta. The SMVs were stimulated to contract during diastole at a 1:2 ratio with the heart. In group I, SMVs generated peak pressures of 91 +/- 10 mmHg, pumped 47% of the systemic blood flow (0.73 +/- 0.25 vs 1.54 +/- 0.42 L/min; p < 0.05), and produced a 25% decrease in the LV systolic tension-time index (TTI) (16.9 +/- 2.7 vs 12.5 +/- 3.3 mmHg.sec; p < 0.05). In group II, SMV peak pressure was 93 +/- 10 mmHg, SMVs pumped 51% of the systemic blood flow (0.78 +/- 0.10 vs 1.53 +/- 0.42 L/min; p < 0.05), and the LV systolic TTI decreased 29% (14.0 +/- 0.8 vs 9.9 +/- 2.0 mmHg.sec; p < 0.05). There was no significant difference between group I and II. These data indicate that the SMV:LV apex-to-aorta configuration is the most effective method reported to date for skeletal muscle cardiac assist. Extrathoracic and intrathoracic SMVs functioned equally well after connection to the circulation.

Serum immunoglobulin G subclass concentrations in periodontally healthy and diseased individuals

Patients with localized juvenile periodontitis (LJP) often have high titers of antibody reactive with the serotype-specific immunodominant carbohydrate antigen of Actinobacillus actinomycetemcomitans serotype b. The vast majority of this A. actinomycetemcomitans serotype b-specific antibody is immunoglobulin G2 (IgG2). The present study was undertaken to determine whether the overall total levels of IgG2 in the sera of LJP patients are elevated. LJP patients and nonperiodontitis (NP) controls matched for age, race (black and white), and gender were studied. Additional controls included patients with adult periodontitis (AP) and patients similar in age to LJP patients but with the more-severe, generalized form of early-onset periodontitis (SP). Sera from over 700 periodontally characterized subjects were examined by using radial immunodiffusion to quantitate IgG2 as well as IgG1, -3, and -4, which were included for comparison. Serum IgG2 levels increased with age, and this was most dramatic around puberty. Black subjects in all periodontal groups had nearly 1 mg more IgG2 per ml than their white counterparts. Serum IgG2 levels were elevated (about 30 to 40%) in LJP patients of both races compared with their age- and race-matched NP controls (P < 0.01). In contrast, SP patients and AP patients had IgG2 levels comparable to their age- and race-matched NP controls. No other IgG subclass concentration correlated with periodontal diagnosis except for IgG3, which was elevated in white LJP patients. We reason that the high levels of serum IgG2 in LJP may be helpful in localizing periodontal destruction.

Chronic morphologic changes of skeletal muscle ventricles in circulation

Skeletal muscle ventricles (SMVs) were constructed either extrathoracically or intrathoracically in 44 dogs using the left latissimus dorsi muscle. These SMVs functioned as aortic counterpulsators for from several hours to 216 days. In this study, the relationship between the morphologic changes in the SMVs and their time course in the circulation was evaluated retrospectively. The average volume of the SMV chamber after it had been excised and fixed in formalin was 21.3 +/- 11.0 mL (mean +/- the standard deviation) for extrathoracic SMVs and 20.0 +/- 7.5 mL for intrathoracic SMVs. The volume of the SMV chamber did not correlate with the time course in the circulation. The SMV wall was mainly composed of three components: muscular, fibrous, and fatty aspects. The overall thickness of the wall appeared to be preserved over time in the circulation. However, the thickness of the muscular component tended to decrease over time. SMV rupture occurred in 15 dogs between postoperative days 4 and 39. All ruptures occurred at the suture line between the SMV and the vascular conduits. There was some degree of thrombus in 24 SMVs. Before SMVs can be applied clinically for the purpose of cardiac assist, problems with rupture and thrombus formation must be solved. A better understanding of the morphologic changes that take place in the SMV over time also is needed.

Experimental transfer of Paragonimus westermani from rodents to rodents following subcutaneous and intraperitoneal routes

In order to investigate the experimental transfer of Paragonimus westermani from rodents to rodents following subcutaneous and intraperitoneal routes, 13 rats and 23 mice were inoculated with a total of 115 (1 mature and 114 immature) worms of P. westermani subcutaneously and intraperitoneally. The age of worms before transfer was 25-193 days. The transfer was performed immediately after worm collection from rodents which were killed at various intervals from 4 to 144 days after infection. The location, development and size of worms were recorded. An infection rate of 58% (or 21/36) was demonstrated in rodents after experimental transfer of P. westermani by intraperitoneal and subcutaneous routes. Twenty-seven worms were recovered, giving a worm recovery rate of 23.5%. The rate was significantly higher by the subcutaneous route (34.8%) than by the intraperitoneal route (20.7%) but no difference was found between mice (23.9%) and rats (23.0%). The sizes of worms in the abdominal cavity, pleural cavity and thoracic muscles of mice, and in the leg muscles of rats were much less than in the pleural cavity and lung cysts of rats. A mature worm (7 x 5 mm) and numerous eggs were found in the uterus and pleural cavity of one rat. It is evidence that these rodents are unfavourable definitive hosts of P. westermani, because the worm size, infectivity, maturation and egg production are usually very low. However, the worms are usually widely distributed in their rodent hosts and remain small in size for a long period. Therefore, these rodents are good paratenic hosts for P. westermani and can play an important role in infecting cats and dogs with P. westermani in the laboratory.

Cardiomyoplasty: probable mechanism of effectiveness using the pressure-volume relationship

The mechanism of effectiveness of cardiomyoplasty was evaluated in the setting of chronic left ventricular dysfunction in terms of the pressure-volume relationship. The distal branches of the left coronary artery were ligated in 12 sheep. Seven sheep died and the 5 survivors underwent cardiomyoplasty using a left latissimus dorsi graft 10 to 12 weeks later. These muscle grafts were then electrically conditioned for 2 months. The systemic pressure and cardiac output were not different between the postinfarction and postcardiomyoplasty period with the pacemaker off or on. However, the pressure-volume loops were altered by cardiomyoplasty in all 5 animals. Emax, which is an index of ventricular contractility, increased after cardiomyoplasty from 2.66 +/- 0.92 to 4.59 +/- 1.73 mm Hg/mL (mean +/- the standard deviation; p < 0.05), but did not change between the pacemaker off and on situations. The pressure-volume area, which strongly correlates with myocardial oxygen consumption, decreased after cardiomyoplasty (1,932 +/- 615 mm Hg.mL), compared with before cardiomyoplasty (3,776 +/- 1,201 mm Hg.mL) (p < 0.05), but did not change between pacemaker off and on. The probable mechanism responsible for the effectiveness of cardiomyoplasty is an "active" support or constraint of the damaged myocardium by the latissimus dorsi and the prevention of further ventricular dilation. This suggests that left ventricular systolic function can be augmented by cardiomyoplasty, but that it is a secondary mechanism of action.

[Effects of nifedipine on hepatic hyaluronic acid, hydroxyproline and glucosaminidase contents in rats with liver fibrosis]

In early stage treatment groups, Nifedipine (Nif) could significantly reduce hepatic hyaluronic acid (HA) and hydroxyproline (Hyp) contents in rats in which liver fibrosis had been induced by CCl4 treatment. N-acetyl-beta-glucosaminidase (beta-NAG) activity showed a similar change in the high dosage group. In late stage treatment groups, HA was reduced markedly, and decreased beta-NAG levels were noted in the high dosage group. These effects on HA, Hyp and beta-NAG were dependent on Nif dosage. The results suggest that Nif could inhibit the development of liver fibrosis in rats, and may even reverse it.

Developmental regulation of re-uptake of phosphatidylcholine by type II alveolar epithelium

Type II alveolar epithelia produce, store and secrete pulmonary surfactant, a phospholipid and protein mixture which stabilizes alveoli at low lung volumes and, thereby, prevents alveolar collapse. We determined the developmental changes in the uptake, metabolism and reutilization of surfactant-related phospholipid in primary cultures of type II cells derived from fetal rat lung. Primary cultures of fetal and neonatal type II cells were incubated in media containing labelled liposomes. After the incubation phospholipids were extracted from the cells and uptake of label was analyzed. Re-uptake of radiolabelled dipalmitoyl phosphatidylcholine (DPPC) was concentration-dependent in undifferentiated fetal cells, differentiated fetal cells and neonatal cells. Re-uptake of DPPC by undifferentiated fetal cells was lower than re-uptake by both differentiated fetal and neonatal cells at 15 and 75 microM PC. Binding of DPPC to the cell surface involved a protein interaction, since trypsin was able to dissociate this trypsin-releasable fraction from internalized label. Undifferentiated fetal, differentiated fetal and neonatal cells all exhibited approx. 50% metabolic degradation of internalized phospholipid. Degraded lipids were reutilized in the synthesis of phosphatidylglycerol, but neonatal cells resynthesized twice as much phosphatidylglycerol as did undifferentiated fetal cells. These are the first studies which show that morphologically undifferentiated fetal type II cells are capable of the uptake of surfactant phospholipid as well as the degradation and reutilization of internalized phospholipid. Re-uptake, degradation and reutilization of internalized phospholipid appear to be under developmental control.

Activation of the 92 kDa type IV collagenase by tissue kallikrein

Type IV collagenases are secreted as latent 92 and 72 kDa proenzymes which are then activated extracellularly. The mechanisms by which they are activated in vivo are not clear. We have studied the activation of porcine endothelial cell type IV collagenases by tissue and plasma kallikrein, and found that tissue kallikrein was a very efficient activator of the 92 kDa type IV collagenase. Enzyme cleavage was observed at concentrations of tissue kallikrein as low as 0.1 microgram/ml. Plasma kallikrein had no effect. By comparison, plasmin, which has been proposed to be the physiological activator of interstitial collagenase and stromelysin, and elastase were much less effective, and high concentrations (plasmin at 100-200 micrograms/ml and elastase at 20 micrograms/ml) were required to cause only a limited cleavage which was not associated with an increase in activity, as observed by the gelatin-gel lysis assay. In addition tissue kallikrein was found by immunohistochemistry to be present in the extracellular matrix of the intima of porcine aortic vessel wall. These findings suggest that tissue kallikrein can be a potential activator of the 92 kDa type IV collagenase in vivo.

Reversible translocation of glycoprotein Ib in plasmin-treated platelets: consequences for platelet function

Understanding the effect of fibrinolysis on platelet function is of clinical importance. Plasmin is recognized to affect platelet adhesive function by reducing the interaction of platelet glycoprotein (GP) Ib with von Willebrand factor (vWF) bound to the subendothelium. This platelet function is commonly explored in vitro by the ristocetin-induced agglutination test. Our previous study demonstrated a plasmin-induced redistribution of GP Ib molecules from the platelet surface to the linings of the surface-connected canalicular system (SCCS), a critical mechanism for understanding plasmin-induced GP Ib dysfunction. Here, we demonstrate that neutralization of plasmin by its inhibitors, aprotinin or tripeptide Val-Phe-Lys-CH2Cl, permits a time dependent recovery (within 30 min) of ristocetin-induced agglutination in the platelets which were stimulated by plasmin at < 1 CU ml-1. This functional recovery was accompanied with a restoration of a normal amount of GP Ib on the platelet surface, as measured by the binding of both monoclonal anti-GP Ib antibody SZ 2 and 125I-labelled vWF to the platelets. Cytochalasin D did not inhibit this recovery, suggesting that this process may be due to passive actin depolymerization. These findings were further confirmed by immunoelectron microscopic study. Utilizing the platelets pre-labelled with anti-GP Ib antibody prior to plasmin stimulation, it was demonstrated that the observed recovery is due to a reverse translocation from the SCCS to the plasma membrane of the same GP Ib molecules which were present initially at the cell surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversibility of thrombin-induced decrease in platelet glycoprotein Ib function

Thrombin induces a redistribution of glycoprotein (GP) Ib/GP IX complex from the platelet surface into the surface connected canalicular system (SCCS). This redistribution results in a reduced interaction of platelet GP Ib with von Willebrand factor (vWF) bound to subendothelium leading to impaired platelet adhesion. In this study we show that the platelet aggregation and degranulation require concentrations of thrombin above 0.05 U/ml, while the decrease in GP Ib function (about 50% of control value), as determined by ristocetin induced platelet agglutination, can be induced by lower concentrations (0.01-0.04 U/ml). Moreover, we show that when adding thrombin inhibitors to the platelets preincubated with < 0.04 U/ml thrombin for 5 min, their agglutinability by ristocetin was gradually recovered within 30 min, indicating that in these conditions the decrease in platelet adhesiveness is reversible. Immuno-electromicroscopic study showed that this restoration of platelet GP Ib function was associated with a reversed translocation of GP Ib from the SCCS to the plasma membrane. The data obtained from counting gold particles showed that the ratio of GP Ib immunolabelling on the external membrane versus that on the SCCS was 3.31 +/- 0.90 for resting platelets, down-regulated to 0.84 +/- 0.13 (P < 0.05 versus resting platelets) for the platelets treated with 0.04 U/ml thrombin and returned to 2.63 +/- 2.21 (P > 0.05 versus resting platelets) after incubation for 30 min with hirudin. However, the translocation of GP Ib was poorly reversed by thrombin inhibitors when higher concentrations of thrombin were used which induced platelet aggregation and large extent of degranulation. We conclude that thrombin affects platelets in a dose dependent manner, and that at low concentrations the decrease in platelet GP Ib related function is a reversible phenomenon.