Prenatal diagnosis of mucolipidosis II--electron microscopy and biochemical evaluation

Prenatal diagnosis of mucolipidosis type II (I-cell disease) can be performed quickly and reliably by electron microscopy of chorionic villus tissue. This study reports the results of studies in three prenatal assessments (two families) where the pregnancy was at one in four risk of the disorder. In all three cases, electron microscopy showed marked vacuolation in chorionic villus cells, consistent with the fetus being affected by the disorder. Further studies in cultured chorionic villus cells showed a marked deficiency of a number of lysosomal enzymes. All pregnancies were terminated. Follow-up studies in fetal tissue (where available) confirmed the prenatal diagnosis as correct.

Update of recent clinical trials in heart failure and myocardial infarction

BACKGROUND

There are currently many on-going clinical trials assessing therapies for the treatment of patients with heart failure.

AIMS

The purpose of this series of papers is to present concise summaries of current randomised trials in the field of heart failure and myocardial infarction (MI).

METHODS

Data from large double-blind, placebo-controlled trials, which are on-going or have only recently been published, are given in a format allowing easy comparison. Where appropriate, data from smaller studies are included.

RESULTS

Major studies which are examined in this issue include CIBIS II, MERIT-HF, RESOLVD, SPICE, VEST, MACH-1, ATLAS, RALES, CIDS and CASH. These trials assess the efficacy and safety of beta-blocker, angiotensin-II-receptor blocker, positive inotropic agent, calcium antagonist, angiotensin-converting enzyme (ACE) inhibitor, aldosterone receptor blocker, and antiarrhythmic interventions in the treatment of heart failure.

CONCLUSIONS

The presentation of data from these on-going trials should allow an up-to-date assessment, by physicians, of the most appropriate and effective treatment for patients with heart failure. It is evident that some therapies may play no further role in the treatment of heart failure, due to the increased risk of mortality associated with their administration, whilst others may convey significant benefits.

The symbolism and myth surrounding nurses' uniform

This article addresses nurses' uniform from the perspective of the symbolic, myth, legend and competing discourse. The analysis touches upon why nurses working with people who have learning disabilities discarded the nurses' uniform and why other nurses may consider doing so, particularly if suitable alternatives exist. The analysis draws from various areas of nursing practice, including the nursing of disabled people, elderly people and people with learning disabilities. Nurses' uniform is revealed as a totem of considerable potency such that to wear a uniform in just any setting or context has to be cautioned. The practicalities of protective clothing are addressed. A differentiation is drawn between uniform and protective clothing such that much of the undesirable symbolism associated with uniform may be discarded with a consequent enhancement of the image of the nurse.

Impact of social interactions in the community on the transmission of tuberculosis in a high incidence area

BACKGROUND

Tuberculosis (TB) is transmitted by close contact with an infectious person. It is assumed that close contact occurs amongst household members and that contact outside the house is "causal" and does not play a major role in the transmission of TB.

METHODS

This study was conducted in an impoverished area with a high incidence of TB and a low HIV seropositive prevalence. Thirty three households with 84 TB patients were identified between February 1993 and April 1996 and the transmission of TB was studied by combining Mycobacterium tuberculosis fingerprinting with in depth sociological interviews.

RESULTS

Forty two strain genotypes were identified in the 84 patients. In 15 households all the patients had identical strains, in nine households all the patients had different strains, and in nine households some patients had identical strains and one had a different strain. In 26 houses at least one patient had a strain which formed part of a larger community cluster and in 12 of these households the patient(s) had contact with a community member who had the identical strain. In 58% of the cases the contact took place while drinking in social groups.

CONCLUSION

In high incidence areas contact outside the household may be important for the transmission of TB. This contact often takes place during recreation which, in the case of this study of impoverished people, consisted of drinking in social groups. Social interaction patterns should be studied and understood for effective implementation of control strategies.

Uptake of heparin cofactor II and antithrombin into the aorta wall after a deendothelializing injury in vivo: comparison with the behaviors of prothrombin and fibrinogen

The initiation of a denuding injury to the vascular endothelium rapidly leads to a deposition of platelets and fibrin at the site of injury. We have measured previously the responses of rabbit fibrinogen, prothrombin, and antithrombin to a deendothelializing balloon-catheter injury to the rabbit aorta in vivo. In this study, rabbit iodine 125-labeled HCII and iodine 125-labeled AT were coinjected intravenously into anesthetized rabbits 5 minutes before deendothelialization of the thoracic aorta. The rabbit was exsanguinated at 5 to 60 minutes after injury, the aorta was excised, and the accumulation of each radiolabeled protein in each layer of aorta wall was determined relative to the concentration of the respective native protein in circulating blood at exsanguination. The maximum flux rates into the aorta wall (i.e., platelet layer and intima-media) in the first minute after injury were calculated from the uptake data; approximately 2.8 molecules of AT accumulated for each HCII molecule. By comparison with previous measurements, the maximum flux rate of AT was similar to that of prothrombin. Further, the molar ratio of accumulated prothrombin/AT + HCII) in the aorta wall was 0.75. Detergent extracts of the injured aorta intima-media contained unreacted HCII and HCII complexes; the uninjured aorta contained only unreacted HCII. By contrast, high molecular weight AT complexes and unreacted AT were extracted from the uninjured, and in greater quantity from the injured, aorta wall. We conclude that, of the plasma antithrombins, AT accumulated more rapidly than HCII in vivo and appeared to be the more active inhibitor at the site of vascular injury. HCII may play a relatively minor role as an antithrombin and possibly only after injury.

Direct ultrastructural imaging of macrophages using a novel x-ray contact microscopy

A compact, high-resolution, laser-plasma, x-ray contact microscopy method using a table-top Nd:glass laser system has been developed. This x-ray microscopy system was applied for the observation of macrophage ultrastructures. These images were produced using proximity imaging in which a 5-ns pulse of soft x-rays with wavelengths near and inside the water windows (23A-44A) produced by the laser-plasma were absorbed by the specimen and then registered on a photo resist. The x-ray images imprinted on the photo resist were then developed and analyzed with an atomic force microscope (AFM). Mouse thioglycollate-elicited peritoneal macrophages in suspension were examined by this new x-ray microscope. The x-ray images of the macrophages were compared with those observed by conventional transmission electron microscopy (TEM). The x-ray images showed no obvious organelles, including the nucleus and endoplasmic reticulum, as can be seen with TEM, but high- and low-contrast structures caused by mass distribution of carbon were observed. Thus, using the x-ray microscopy we visualized the first x-ray images of macrophage ultrastructures. The successful x-ray imaging of macrophage ultrastructure indicates that proximity x-ray microscopy may be of value in studying physiology linked to the dynamics of a cell.

Prospective randomized double-blind trial between laparoscopic Nissen fundoplication and anterior partial fundoplication

BACKGROUND

In the operative management of gastro-oesophageal reflux, a balance must be achieved between adequate control of reflux and excessive dysphagia. The ideal technique is not known. A randomized study was performed to determine whether laparoscopic anterior fundoplication is associated with a lower incidence of postoperative dysphagia than laparoscopic Nissen fundoplication, while achieving equivalent control of reflux.

METHODS

Patients presenting for laparoscopic antireflux surgery were randomized to undergo either a Nissen fundoplication (n = 53) or an anterior 180 degrees hemifundoplication (n = 54). Patients were blinded to which procedure had been performed, and follow-up was obtained by a blinded independent investigator. Standardized clinical grading systems were used to assess dysphagia, heartburn and patient satisfaction 1, 3 and 6 months after operation. Objective measurement of lower oesophageal sphincter pressure, oesophageal emptying time, distal oesophageal acid exposure and endoscopic healing of oesophagitis was also performed.

RESULTS

Operating time was similar for the two procedures (58 min for the Nissen procedure versus 60 min for anterior fundoplication). Resting and residual lower oesophageal sphincter pressures were lower following anterior fundoplication (29 versus 18 mmHg, and 13 versus 6 mmHg), and oesophageal emptying times were faster (92 versus 116 s). Acid exposure times and ability to heal oesophagitis were similar. At 3 months' follow-up clinical outcomes were similar for the two procedures. At 6 months, however, patients who had undergone anterior fundoplication experienced significantly less dysphagia for solid food and were more likely to be satisfied with the clinical outcome.

CONCLUSION

Laparoscopic anterior fundoplication achieved equivalent control of reflux, more physiological postoperative manometry parameters, and an improved clinical outcome at 6 months. Continued follow-up remains necessary to confirm the long-term efficacy of the partial fundoplication procedure.

Cardiovascular disease in the JCR:LA-cp rat

The JCR:LA-cp rat is one of a number of strains that carry the mutant autosomal recessive cp gene. Animals, of all strains, that are homozygous, for the gene (cp/cp) become obese, insulin resistant, and hypertriglyceridemic. Heterozygotes or homozygous normal rats (+/+) are lean and metabolically normal. The JCR:LA-cp rat is unique in the development of a frank vasculopathy with atherosclerotic lesions and associated ischemic myocardial lesions. The cardiovascular disease is strongly correlated with the hyperinsulinemia, which develops as the animals mature from 4 to 8 weeks of age. The hyperinsulinemia can be decreased by marked food restriction, ethanol consumption, or reduction of the postprandial glucose and insulin responses through the use of alpha-glucosidase inhibitors. Any treatment that reduces plasma insulin levels is associated with a reduction in cardiovascular disease. In contrast, a reduction in plasma triglyceride concentrations, alone, has no effect on end-stage lesions. JCR:LA-cp rats, particularly those that are cp/cp, are, however, sensitive to cholesterol in the diet, unlike other strains that are highly resistant. Further, the rats have abnormal vascular smooth muscle cells that, especially in the cp/cp animals, are hyperplastic and activated and migrate into the intimal space. Our findings suggest that susceptibility to cardiovascular disease requires hypermsulinemic stress coupled with excessive dietary intake and the presence of one or more other necessary, but not sufficient, genetic factors. One of these may be a genetic abnormality of vascular smooth muscle cells. A similar situation may occur in humans.

Changes in the aortic endothelium and plasma von Willebrand factor levels during the onset and progression of insulin-dependent diabetes in BB rats

Endothelial injury has been implicated in the enhanced vascular disease associated with diabetes mellitus. In diabetic humans elevated plasma von Willebrand factor (vWF) levels have been interpreted as an indication of endothelial damage. Using the BB rat as a model of inherited insulin dependent-diabetes mellitus, plasma vWF and aortic endothelial ultrastructural alterations were examined during the first 7 months of diabetes. Total plasma vWF levels were determined by ELISA and vWF multimeric composition by electrophoresis. vWF was identified immunohistochemically. Following the onset of hyperglycemia, there were progressive alterations in aortic endothelial morphology, which were consistent with injury, and aortic intimal thickening was significantly greater in rats diabetic for 7 months compared to age-matched controls. Significant increases in the Weibel Palade (WP) body content of the endothelial cells were observed after 1 week and 2 months of diabetes, but not at later times. Endothelial alterations associated with the possible release of vWF appeared to involve fusion of WP bodies with other vacuoles rather than direct fusion with the cell membrane. Plasma vWF levels in diabetic rats were varied, but were not significantly different from those of control animals and did not correlate with either glucose or insulin levels. The multimeric composition of plasma vWF was also similar at all times in both diabetic and non-diabetic animals. From these observations, plasma vWF levels do not provide an indicator of the endothelial perturbations which occurs in diabetic rats.

Photo-neuroendocrine control of seasonal cycles in body weight, pelage growth and reproduction: lessons from the HPD sheep model

This chapter summarises the results of a recent study which investigated the role of the hypothalamo-pituitary relay system in mediating the effects of photoperiod on seasonal cycles in: (a) body weight; (b) pelage growth; and (c) reproduction in Soay rams. Hypothalamo-pituitary disconnected (HPD) and the control rams were housed indoors under an artificial lighting regimen of alternating 16-weekly periods. These periods consisted of long (16L:8D) and short days (8L:16D) and lasted for more than 2 years. The: (i) body weight; (ii) voluntary food intake; (iii) pelage and horn growth; and (iv) variations in testicular diameter were measured routinely every 2-4 weeks. Twice-weekly blood samples were collected to monitor long-term changes in the blood concentrations of: (1) pituitary; (2) metabolic; and (3) reproductive hormones (prolactin, GH, alpha-MSH, beta-endorphin, ACTH, TSH, LH, FSH, cortisol, insulin, IGF1 and testosterone). In control rams there were clearly defined photoperiod-induced cycles in blood concentrations of prolactin, alpha-MSH, beta-endorphin, LH, FSH, insulin and testosterone and associated morphological changes consistent with causal relationships (e.g. prolactin versus wool and horn growth, alpha-MSH, beta-endorphin and insulin versus body weight/food intake, LH and FSH versus testis size). In the HPD rams there were no photoperiod-induced cycles in the concentrations of any of the pituitary hormones with the exception of prolactin which varied as in controls (10-fold higher under long days). There was a permanent increase in blood concentrations of alpha-MSH, beta-endorphin and insulin in the HPD animals and a decrease in the concentrations of GH (loss of pulsatility) and IGF1. These changes were associated with the development of obesity. The reproductive axis was inactivated (basal LH, FSH and testosterone) although there was residual cyclicity in the size of the testis associated with the changes in prolactin secretion. Overall, the results support the view that the melatonin signal which encodes photoperiod, acts in the hypothalamus to regulate some photoperiodic responses (alpha-MSH and beta-endorphin-body weight axis, gonadotrophin-gonadal axis) but acts in the pituitary gland to regulate other responses (prolactin-pelage axis). However, a functional hypothalamus is required to generate normal seasonal cycles in: (a) body weight; (b) food intake; (c) growth; (d) fattening; and (e) reproduction, to provide the internal coordination between different systems and to facilitate the temporal entrainment to environmental cues.

Efficacy of surgical wound drainage in orthopaedic trauma patients: a randomized prospective trial

OBJECTIVE

To study the efficacy of closed suction drainage in clean nonemergent surgical fracture fixation or bone grafting on the extremities or pelvis.

DESIGN

A prospective randomized trial.

SETTING

The orthopaedic trauma service of a Level I trauma hospital.

PATIENTS

Patients were older than age eighteen years and undergoing clean nonemergent surgical fracture fixation or bone grafting procedures on the extremities (excluding hands and feet) or pelvis.

INTERVENTION

The application of a surgical drain.

MAIN OUTCOME MEASUREMENTS

Wound drainage, edema, hematoma and erythema, dehiscence, infection, and need for surgery or readmission were followed for six weeks. A univariate analysis with Student's t test for continuous variables and chi-squared analysis for all categorical data were used, with a p value of < or = 0.05 considered statistically significant.

RESULTS

A total of 202 patients were randomized to 102 patients with no drain and 100 patients with a drain. There was no significant difference between the groups with regard to injury severity, systemic disease, age, body weight, physical status, or estimated blood loss. There was no significant difference between the drain and no-drain groups in any of the parameters evaluated.

CONCLUSION

There is no significant difference between drained and nondrained wounds in clean, nonurgent orthopaedic trauma surgery. It appears that drainage systems can be safely eliminated in this group.

Pretreatment of rabbits with either hirudin, ancrod, or warfarin significantly reduces the immediate uptake of fibrinogen and platelets by the deendothelialized aorta wall after balloon-catheter injury in vivo

Fibrinogen and platelets rapidly saturate the exposed subendothelium of a freshly deendothelialized aorta in vivo. As thrombin generated within the site of injury is largely responsible for fibrin(ogen) deposition, we questioned whether various anticoagulant treatments would inhibit uptake of both fibrinogen and platelets in vivo. Rabbits were anticoagulated by pretreatment with either Warfarin, Ancrod, or recombinant hirudin. Each anesthetized, anticoagulated (or saline-injected control) rabbit was injected i.v. with rabbit 51Cr-platelets and 125I-fibrinogen before a balloon-catheter deendothelializing (or sham) injury of the thoracic aorta. At 10 minutes after injury, the rabbit was exsanguinated and the aorta excised. Platelet adsorption by the deendothelialized aorta surface was substantially reduced in anticoagulated rabbits (controls, 2.2x10(5)/mm2; Warfarin-treated, 1.2x10(5)/mm2; Ancrod-treated, 5.3x10(4)/mm2; r-hirudin-treated [5 mg/kg], 5.3x10(4)/mm2), and a significant reduction of fibrinogen associated with the platelet layer (from 5.3 to 1 to 2 pmol/cm2) and within the underlying intima-media layer (from 16.9 to 5 to 6 pmol/cm2) was observed in the r-hirudin-and Warfarin-treated rabbits. The pattern of aorta-deposited 51Cr-platelets and 125I-fibrin in the anticoagulated rabbits corresponded well with an assessment by transmission electron microscopy of aortic tissue samples. We conclude that approximately 70% of fibrinogen uptake is thrombin dependent and that approximately 80% of platelet adsorption depends on codeposited fibrin(ogen) during the 10-minute interval after balloon injury. Pretreatment with an agent that interferes with either thrombin or fibrin production will inhibit the immediate interaction of fibrinogen and platelets with the freshly exposed subendothelium.

Morphological and biochemical features affecting the antithrombotic properties of the aorta in adult rabbits and rabbit pups

We hypothesised that there are important physiologic differences in arterial wall structure and function with respect to antithrombotic activity in the very young (pre-puberty) compared to adults. Electron microscopy, gel electrophoresis, and activity assays were used to examine differences in aorta structure and function comparing prepubertal rabbits (pups) to adult rabbits. Differences in endothelial function, extracellular matrix structure, proteoglycan (PG) distribution and glycosaminoglycan (GAG) content and function were shown. In both intima and media, total PG, chondroitin sulfate (CS) PG and heparan sulfate (HS) PG content were significantly increased in pups compared to adult rabbits. These findings corresponded to increased concentrations by mass analyses of CS GAG and DS GAG in aortas from pups. There was also a significant increase in antithrombin activity in pups due to HS GAG. In conclusion, differences in both structure and antithrombin activity of aortas from pups compared to adult rabbits suggest that young arteries may have greater antithrombotic potential that is, at least in part, related to increased HS GAG.

Vasculopathy and insulin resistance in the JCR:LA-cp rat

The JCR:LA-cp rat is one of a number of strains incorporating the autosomal recessive cp gene that induces obesity. This strain is unique in the development of not only a profound insulin resistance, but an accompanying cardiovascular disease that correlates strongly with hyperinsulinemia. The hyperinsulinemia develops rapidly after 4 weeks of age, with an age at half-maximum of 5.5 weeks. This reflects postprandial plasma insulin levels that peak at 1000 mU/l in a standardized meal tolerance test. Defective acetylcholine-mediated vascular relaxation develops with a 1-week lag over the developing hyperinsulinemia. The frequency of staining for the vascular adhesion molecules, VCAM-1 and ICAM, does not show either age or genotype variation, although plasma levels do show an age variation. Treatment of the rats with the alpha-glucosidase inhibitor, miglitol (Bay m1099), obviates the exaggerated postprandial glucose and, especially, the insulin responses of the cp/cp rat. This causes an improvement in insulin sensitivity, prevention of the impaired vascular relaxation, and reduction in plasma levels of advanced glycated end-products. Arterial wall morphology, as visualized by both scanning and transmission electron microscopy, shows abnormal endothelium, adherent macrophages, and activated migrating smooth muscle cells in the intima. Oil-Red-O staining reveals lipid deposits in the intimal spaces, as confirmed by the presence of foam cells. The lesions resemble fatty streaks or modest atherosclerosis in man, rather than the extensive cholesterol-laden lesions seen in familial hypercholesterolemia or cholesterol-fed rabbit models. The lean rats of the strain show similar, but less marked, intimal abnormalities. The vasculopathy in this animal model appears to be precipitated by the developing hyperinsulinemia, but also requires an underlying abnormality of vascular smooth muscle and possibly also of the endothelium.

Antibodies to the HIV-1 Tat protein correlated with nonprogression to AIDS: a rationale for the use of Tat toxoid as an HIV-1 vaccine

OBJECTIVES

To investigate which immune parameters, such as antibodies against HIV-1 specificities, or viral parameters, such as p24 antigenemia, are predictive of disease progression.

STUDY DESIGN

We performed studies on serum collected from individuals exhibiting two extremes of disease evolution--67 fast progressors (FP) and 182 nonprogressors (NP)--at their enrollment. After a 1- to 2-year clinical follow-up of 104 nonprogressors after their enrollment, we could determine the best serologic predictors for disease progression.

METHODS

We investigated levels of antibodies to tetanus toxoid and to HIV antigens including Env, Gag, Nef, and Tat proteins, as well as p24 antigenemia, viremia, CD4 cell count, and interferon-alpha (IFN-alpha) titers in FPs and NPs, and we correlated these data with clinical and biologic signs of progression.

RESULTS

p24 Antigenemia, a marker of viral replication, and anti-Tat antibodies were highly and inversely correlated in both groups (P < .001). Furthermore, anti-p24 antibodies and low serum IFN-alpha levels were correlated to the NP versus the FP cohort. Finally, among NPs, only antibodies to Tat and not to the other HIV specificities (Env, Nef, Gag) were significantly predictive of clinical stability during their follow-up.

CONCLUSION

Antibodies toward HIV-1 Tat, which are inversely correlated to p24 antigenemia, appear as a critical marker for a lack of disease progression. This study strongly suggests that rising anti-Tat antibodies through active immunization may be beneficial in AIDS vaccine development to control viral replication.

Development of insulin resistance in the JCR:LA-cp rat: role of triacylglycerols and effects of MEDICA 16

The JCR:LA-cp rat develops an extreme obese/insulin-resistant syndrome such that by 12 weeks of age, there is no longer any insulin-mediated glucose turnover. At 4 weeks of age, obese and lean rats have essentially identical basal and insulin-mediated glucose uptake in skeletal muscle. By 8 weeks of age, however, the obese rats no longer exhibit such intake. Plasma insulin concentrations in the normal fed state show only small increases up to 4 weeks, with a rapid rise to a marked hyperinsulinemia thereafter, with an age at half-development of 5.5 weeks. Plasma triacylglycerol concentrations in fed obese rats are elevated at 3 weeks and rise rapidly thereafter. The triacylglycerol content of skeletal muscle is significantly elevated in the obese rats at 4 weeks of age. Histological examination of Oil Red O-stained muscle tissue and transmission electron microscopy shows the presence of intracellular lipid droplets. Treatment with the potent triacylglycerol-lowering agent MEDICA 16 (beta,beta'-tetramethylhexadecanedioic acid) from 6 weeks of age reduces plasma lipids markedly, but it reduces body weight and insulin resistance only modestly. In contrast, treatment with MEDICA 16 from the time of weaning at 3 weeks of age results in the normalization of food intake and body weight to over 8 weeks of age. The development of hyperinsulinemia is also delayed until 8.5 weeks of age, and insulin levels remain strongly reduced. Plasma triacylglycerol concentrations remain at the same level as in lean rats, and neither an elevated muscle triacylglycerol content nor intracellular lipid droplets are found at 4 weeks of age. The results indicate that insulin resistance develops in the young animals and is not directly due to a genetically determined defect in insulin metabolism. The mechanism of induction instead appears to be related to an exaggerated triacylglycerol metabolism.

Significance of an echogenic intracardiac focus in fetuses at high and low risk for aneuploidy

Our objective was to evaluate the significance of an echogenic intracardiac focus in a mixed population of fetuses at high and low risk for aneuploidy. Over a 1 year period, we prospectively identified all fetuses with an echogenic intracardiac focus seen during prenatal sonography. A detailed structural evaluation was performed on each fetus as permitted by gestational age. The location and number of foci were tabulated prospectively, as were associated abnormalities. Follow-up was obtained by review of the medical record. Of the 290 fetuses who had an echogenic intracardiac focus, 14 of them were aneuploid (4.8%). Of the 290 mothers, 125 women were aged 35 years or older and 165 women were younger than 35 years old. Among the 125 fetuses born to women 35 years or older, eight were aneuploid fetuses (6.4%), while among the 165 fetuses of younger mothers, six were aneuploid fetuses (3.6%) (rate ratio = 1.8; 95% confidence interval [extremes] = 0.6, 4.9). Only one of the 14 aneuploid fetuses had an echogenic intracardiac focus as the only sonographic finding, and this occurred in a woman aged 41 years. The majority of the echogenic intracardiac foci (87.6%) were located in the left ventricle, while 4.8% of the foci were right-sided and 7.6% were bilateral. Among the 14 aneuploid fetuses, 14% had bilateral echogenic intracardiac foci and 7% had right-sided foci. Among the euploid fetuses, 7.3% had bilateral echogenic intracardiac foci and 4.7% had right-sided foci. In conclusion, we have shown that the presence of an echogenic intracardiac focus does raise the risk that the fetus has a chromosomal abnormality, most commonly Down syndrome, although all but one aneuploid fetus in our study had other sonographic findings.

Morphologic and biochemical features affecting the antithrombotic properties of the inferior vena cava of rabbit pups and adult rabbits

The incidence of venous thromboembolic disease is reduced in children compared with adults. Thromboprotective mechanisms, some of which have already been identified in plasma, must be present in children. Blood vessel walls have important antithrombotic properties that maintain blood fluidity. This is in part due to proteoglycan (PG)-related glycosaminoglycan (GAG) molecules within vessel walls. PGs are macromolecules with covalently attached GAG chains, either chondroitin, dermatan, heparan, or keratan sulfate. The influence of age on the concentration and anticoagulant activities of PGs and GAGs, within vein walls before puberty has not been previously investigated. We hypothesized that developmental differences in vein walls may contribute to the reduced risk of thrombosis in children. We used a rabbit model to examine morphologic and biochemical features of inferior venae cavae (IVCs). We assessed IVC wall morphology, PG distribution, GAG mass, and GAG antithrombin activity. Morphologically, there were only minor differences between pups and adult rabbits' IVCs. However, there was a significant increase in GAGs by mass in IVCs from pups compared with adult rabbits (p = 0.012). In addition the total antithrombin activity (p = 0.04), and especially that of heparan sulfate (p = 0.01) was significantly increased in pups compared with adult rabbits. These results demonstrate important differences in the antithrombotic properties of IVC walls in pups and adult rabbits. In summary, developmental differences in vein wall PG content and activity exist which may contribute to the reduced risk of venous thromboembolism in children. Further characterization of these differences is required.

Comparative catabolism of prothrombin and antithrombin in normal and alloxan-diabetic rabbits

Previous studies have shown that alloxan-induced diabetes in rabbits effects a slower release of plasma proteins from the liver, a slower synthesis of 35S-glycosaminoglycan in the extracellular matrix of the arterial wall, and a concurrent reduction in the fractional catabolic rates of several plasma proteins. In the present study, the catabolism of two hemostatic proteins, prothrombin and antithrombin, are compared in alloxan-induced diabetic rabbits (of 6 months' duration) and age-matched control rabbits. Differentially radiolabeled prothrombin and antithrombin were injected intravenously, and arterial blood was sampled over a 7-day period to measure the clearance from plasma. A three-compartment model was used to determine the fractional catabolic rate and compartmental distribution of the two proteins. As observed for other plasma proteins, the whole-body fractional catabolic rates (jt) for prothrombin and antithrombin were significantly less in diabetic rabbits (prothrombin, 0.33 d-1; antithrombin, 0.27 d-1) than in control rabbits (prothrombin, 0.37 d-1; antithrombin, 0.30 d-1; P < .001 and P < .005, respectively). In absolute terms, the catabolism of antithrombin and prothrombin in diabetic rabbits was 5.1 and 6.2 mg.kg-1.d-1, respectively, equivalent to a molar ratio for antithrombin to prothrombin of 0.94. For the control rabbits, catabolism accounted for 6.3 mg.kg-1.d-1 of antithrombin and 7.3 mg.kg-1.d-1 of prothrombin, equivalent to a molar ratio of 1.01. The fractional distribution of these proteins was not significantly different within the intravascular and extravascular spaces in diabetic and control rabbits. The decreased catabolic rates observed for prothrombin and antithrombin in diabetic rabbits conform with results obtained previously for other plasma proteins, and probably reflect a generally decreased rate of plasma protein production by diabetic rabbit liver compared with control liver.

X-ray microscopy and imaging of Escherichia coli, LPS and DNA

Ultrastructural examination by transmission and scanning electron microscopy involves a series of specialized preparation steps which may introduce artefacts in the micrographs. X-ray microscopy can take instant images of specimens but is mostly restricted to a few synchrotron X-ray sources. We have utilized a bench-top nanosecond laser-plasma to produce a single-shot source of nanosecond X-rays tuned for maximum contrast with carbon-rich material. To examine the ultrastructure by absorption profiles, we utilized a laser-produced plasma generated by a single-shot laser (1.06 microns wavelength, 5 x 10(12) W cm-2 intensity) focused on to a silicon target as an X-ray source for high-resolution X-ray microscopy. This approach eliminates the specimen preparation steps. Whole hydrated cells of Escherichia coli and purified preparations of lipopolysaccharide (LPS) and chromosomal DNA (cDNA) were streaked onto poly(methyl methacrylate) (PMMA)-coated grids (resist). This resist was exposed to X-rays under vacuum at a distance of 2.5 cm from the target disc. The silicon plasma produced by a 10-ns burst of laser energy (at 20J) radiates strong emission lines in the region of 300 eV. The X-rays penetrate the sample and their absorption profile is transferred on to the resist where PMMA acts as a negative to generate an image. By atomic force microscopy imaging of this photoresist we have visualized layers around cells of E.coli, darker areas inside the cell probably corresponding to cDNA, and preliminary images of LPS and DNA molecules. This technique has resolution at the 100 A level, produces images similar to the space-filling models of macromolecules and may be of great value in the study of the ultrastructure of hydrated live biological specimens.